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WO2025197895A1 - Method for recovering metal component, method for regenerating molten salt, method for producing glass for chemical strengthening, and method for producing chemically strengthened glass - Google Patents

Method for recovering metal component, method for regenerating molten salt, method for producing glass for chemical strengthening, and method for producing chemically strengthened glass

Info

Publication number
WO2025197895A1
WO2025197895A1 PCT/JP2025/010397 JP2025010397W WO2025197895A1 WO 2025197895 A1 WO2025197895 A1 WO 2025197895A1 JP 2025010397 W JP2025010397 W JP 2025010397W WO 2025197895 A1 WO2025197895 A1 WO 2025197895A1
Authority
WO
WIPO (PCT)
Prior art keywords
molten salt
salt
specific metal
recovering
molten
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
PCT/JP2025/010397
Other languages
French (fr)
Japanese (ja)
Inventor
誠二 東
祐輔 藤原
裕介 片岡
要 関谷
篤典 橋本
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
AGC Inc
Original Assignee
Asahi Glass Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Asahi Glass Co Ltd filed Critical Asahi Glass Co Ltd
Publication of WO2025197895A1 publication Critical patent/WO2025197895A1/en
Pending legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D9/00—Crystallisation
    • B01D9/02—Crystallisation from solutions
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C21/00—Treatment of glass, not in the form of fibres or filaments, by diffusing ions or metals in the surface
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B26/00—Obtaining alkali, alkaline earth metals or magnesium
    • C22B26/10—Obtaining alkali metals

Definitions

  • the present invention relates to a method for recovering a metal component, and more particularly to a method for recovering a specific metal component from a molten salt.
  • the present invention also relates to a method for regenerating molten salt and a method for producing glass for chemical strengthening.
  • cover glass has been used to protect and enhance the appearance of display devices such as mobile phones, smartphones, and tablet devices.
  • Cover glass for these applications is required to have excellent strength to prevent breakage due to impacts, etc.
  • Patent Document 1 discloses lithium aluminosilicate glass that undergoes a two-stage chemical strengthening process to achieve a relatively large surface compressive stress layer and compressive stress layer depth. It describes how lithium aluminosilicate glass undergoes a two-stage chemical strengthening process, using sodium salts in the first stage and potassium salts in the second stage, which increases both the surface stress and the stress layer depth while suppressing the tensile stress generated within the chemically strengthened glass.
  • Patent Document 1 when glass such as lithium aluminosilicate glass is immersed in molten salt and chemically strengthened, the lithium content in the molten salt increases.
  • the inventors have conducted research and found that when a further chemical strengthening treatment is performed using molten salt in which the lithium content has increased after the chemical strengthening treatment, the chemical strengthening treatment does not proceed sufficiently. That is, there has been a demand for a method for recovering specific metal components (for example, components containing lithium) in molten salt. Furthermore, methods using molten salts are widely used, and for example, molten salts are used in the fields of extraction, refining, etc.
  • a method for recovering a metal component comprising cooling a molten salt containing a specific metal component, precipitating a specific metal salt containing the specific metal component while maintaining the molten state of the molten salt, and recovering the specific metal salt from the molten salt.
  • the molten salt contains two or more salts selected from the group consisting of lithium nitrate, sodium nitrate, and potassium nitrate, [5] The method for recovering a metal component according to any one of [1] to [4], wherein the molten salt further contains one or more salts selected from the group consisting of sodium sulfate and potassium sulfate. [6]
  • the specific metal component contains lithium, The specific metal salt includes lithium and sodium, [6] The method for recovering a metal component according to any one of [1] to [5], wherein the molten salt before cooling contains lithium atoms in an amount of 1,000 to 50,000 ppm by mass relative to the total mass of the molten salt.
  • the specific metal component contains sodium
  • the specific metal salts include sodium and potassium
  • [6] The method for recovering a metal component according to any one of [1] to [5], wherein the molten salt before cooling contains sodium atoms in an amount of 500 to 60,000 ppm by mass relative to the total mass of the molten salt.
  • [8] The method for recovering a metal component according to any one of [1] to [7], wherein the molten salt contains sodium nitrate, and the ratio of the potassium nitrate content to the sodium nitrate content is 0.00 to 24.00 in mass ratio.
  • a third jig having a temperature-controllable cooling section is used to change the temperature of the cooling section to cool the molten salt, thereby precipitating the specific metal salt on the surface of the cooling section;
  • a molten salt storage container in which the molten salt is stored; a circulation path connected to the molten salt storage container, through which the molten salt discharged from the molten salt storage container returns to the molten salt storage container; a filter disposed midway through the circulation path and capable of separating solids from the molten salt; introducing the molten salt containing the precipitated specific metal salt into the circulation path, and separating the specific metal salt from the molten salt using the filter;
  • the method for recovering a metal component according to any one of [1] to [12], wherein the specific metal salt is recovered from the filter.
  • the specific metal salt recovered by the method for recovering a metal component according to any one of [1] to [25] is dissolved in water to obtain a specific metal aqueous solution,
  • a method for recovering a metal component comprising adding a carbonate to the specific metal aqueous solution to form a precipitate, and recovering the precipitate, wherein the specific metal component includes lithium or sodium.
  • the method for recovering a metal component according to [26] wherein the aqueous solution of the specific metal containing a carbonate is heated to 80° C. or higher to form a precipitate.
  • a method for producing chemically strengthened glass comprising recovering the specific metal salt from the molten salt by the method for recovering a metal component according to any one of [1] to [27], and immersing glass containing silicon, aluminum, and lithium in the molten salt from which the specific metal salt has been recovered, A method for producing chemically strengthened glass, wherein the molten salt after recovering the specific metal salt does not substantially contain solid-state salt.
  • the chemical strengthening molten salt in which the chemical strengthening glass is immersed is used as the molten salt, and the specific metal salt is recovered by the metal component recovery method according to any one of [1] to [27].
  • the method for producing chemically strengthened glass according to [33] wherein a sulfate is added to the chemical strengthening molten salt in the molten salt regeneration treatment.
  • a method for recovering a metal component can be provided that allows a specific metal component to be recovered simply and easily from a molten salt. Furthermore, according to the present invention, it is possible to provide a method for regenerating molten salt, a method for producing glass for chemical strengthening, and a method for producing chemically strengthened glass.
  • FIG. 10 is a cross-sectional view showing a container for containing molten salt to explain a first embodiment of a recovery step, showing a state in which a first jig is installed in the container containing the molten salt.
  • FIG. 10 is a cross-sectional view showing a container for accommodating molten salt, illustrating a first embodiment of a recovery step, showing a state in which a first jig is pulled up from the container containing the molten salt.
  • FIG. 10 is a cross-sectional view showing a vessel for accommodating molten salt to explain a second embodiment of the recovery step.
  • FIG. 10 is a cross-sectional view showing a vessel for accommodating molten salt to explain a third embodiment of the recovery step.
  • FIG. 10 is a cross-sectional view showing a vessel for accommodating molten salt to explain a fourth embodiment of the recovery step.
  • substantially free means that it is not contained except for unavoidable impurities contained in the raw materials, etc., i.e., it is not intentionally contained.
  • it is preferably less than 0.1 mol%, more preferably 0.08 mol% or less, and even more preferably 0.05 mol% or less.
  • the molten salt to be subjected to the deposition step contains a specific metal component.
  • the specific metal component is preferably molten in the molten salt.
  • the specific metal component preferably contains lithium or sodium, more preferably lithium. That is, the specific metal salt precipitated in the precipitation step preferably contains lithium or sodium, more preferably lithium.
  • the molten salt preferably contains 1,000 mass ppm or more, more preferably 2,000 mass ppm or more, and even more preferably 3,000 mass ppm or more of lithium atoms relative to the total mass of the molten salt.
  • the molten salt preferably contains 50,000 mass ppm or less, more preferably 20,000 mass ppm or less, and even more preferably 10,000 mass ppm or less of lithium atoms relative to the total mass of the molten salt.
  • the specific metal component when the specific metal component contains lithium, the specific metal salt also preferably contains lithium and sodium.
  • the molten salt when the specific metal component contains sodium, the molten salt preferably contains 500 mass ppm or more, more preferably 2,000 mass ppm or more, and even more preferably 4,000 mass ppm or more of sodium atoms relative to the total mass of the molten salt.
  • a specific example of the composition of the molten salt is a first molten salt containing potassium nitrate, sodium nitrate, lithium nitrate, and sodium sulfate.
  • the content of potassium nitrate is preferably 10.0 to 96.0 mass %, more preferably 30.0 to 70.0 mass %.
  • the content of sodium nitrate is preferably 1.0 to 90.0 mass %, more preferably 30.0 to 70.0 mass %.
  • the content of lithium nitrate is preferably 1.0 to 50.0 mass %, more preferably 1.5 to 15.0 mass %.
  • the content of sodium sulfate is preferably 2.0 to 30.0 mass %, more preferably 4.0 to 20.0 mass %.
  • composition of the molten salt include a second molten salt containing potassium nitrate, sodium nitrate, and potassium carbonate.
  • the content of potassium nitrate is preferably 40.0 to 96.0 mass %, more preferably 30.0 to 92.0 mass %.
  • the content of sodium nitrate is preferably 0.2 to 30.0 mass %, more preferably 1.0 to 10.0 mass %.
  • the content of potassium carbonate is preferably 3.0 to 30.0 mass %, more preferably 4.0 to 20.0 mass %.
  • the type and use of the molten salt are not particularly limited, but preferred examples include molten salts used for chemical strengthening, as described below.
  • Other examples of the molten salt include molten salts used for metal smelting, heat transfer media, batteries, and electrorefining.
  • the molten salt is a molten salt used for chemical strengthening
  • the glass may be subjected to chemical strengthening, and components contained in the glass for chemical strengthening (e.g., lithium ions, sodium ions) may be exchanged for ions in the molten salt.
  • the molten salt is cooled, and the specific metal salt containing the specific metal component is precipitated while the molten salt is maintained in a molten state.
  • the method for cooling the molten salt in the precipitation step is not particularly limited, and any known method can be applied.
  • the molten salt may be cooled entirely or only partially.
  • the additive is a substance that reacts with the specific metal component to precipitate a specific metal salt, and specific examples thereof include the salts contained in the molten salt described above.
  • Examples of methods for cooling the entire molten salt include a method of bringing the molten salt or a container containing the molten salt into contact with a fluid having a temperature lower than that of the molten salt. More specifically, examples of the fluid include air, and a method of air-cooling the molten salt or a container containing the molten salt. When air-cooling the molten salt or a container containing the molten salt, air convection may be used. Another method for cooling the molten salt is to circulate a cooling medium through a container that contains the molten salt.
  • the container that contains the molten salt preferably includes a pipe through which the cooling medium circulates, and the method involves circulating the cooling medium between the container that contains the molten salt and the heat exchanger while exchanging heat with the cooling medium in a heat exchanger connected to the pipe.
  • a specific metal salt containing a specific metal component precipitates from the molten salt.
  • the specific metal salt may be dispersed in the molten salt and precipitate, or may precipitate on the wall surface of the container containing the molten salt. It may also precipitate on the surface of the jig, which will be described later.
  • a portion of the molten salt may be cooled.
  • One method for cooling a portion of the molten salt is to use a jig with a cooling part and bring the cooling part into contact with the molten salt.
  • the jig with the cooling part allows for free temperature control, and when the molten salt is cooled, the molten salt precipitates on the surface of the cooling part, etc.
  • the molten salt is cooled while maintaining the molten state.
  • the molten salt is cooled to a predetermined temperature and then maintained at that temperature for a holding time described below.
  • the cooling temperature is not particularly limited as long as the molten salt is maintained in a molten state and the specific metal salt is precipitated, but the temperature at which the molten salt is cooled is preferably 150° C. or higher, more preferably 200° C. or higher, and even more preferably 230° C. or higher.
  • the temperature at which the molten salt is cooled is preferably 500° C. or lower, more preferably 400° C. or lower, and even more preferably 350° C. or lower.
  • the temperature difference between the temperature of the molten salt before cooling and the temperature of the molten salt after cooling is preferably 20° C. or more, more preferably 50° C. or more, and even more preferably 100° C. or more.
  • the temperature difference is preferably 250° C. or less, and more preferably 180° C. or less.
  • the retention time is not particularly limited as long as the specific metal salt is precipitated, but may be, for example, 5 minutes or more, preferably 10 minutes or more, and more preferably 30 minutes or more, and may be, for example, 24 hours or less, preferably 12 hours or less, and more preferably 6 hours or less.
  • the temperature of the molten salt before cooling is preferably 370° C. or higher, more preferably 390° C.
  • the temperature of the molten salt after cooling is preferably 420° C. or lower, more preferably 410° C. or lower, even more preferably 360° C. or lower, particularly preferably 350° C. or lower, and most preferably 300° C. or lower.
  • the temperatures of the molten salt before cooling and the molten salt after cooling can be adjusted as appropriate depending on the composition of the molten salt, etc. For example, it is also preferable to cool a molten salt at 370° C. or higher to 360° C. or lower. It is also preferable that the specific metal component of the molten salt contains lithium, and that the molten salt contains at least a lithium salt and a sodium salt.
  • a molten salt it is also preferable to cool a molten salt at 420° C. or higher to 410° C. or lower. It is also preferable to cool a molten salt at 420° C. or higher by 20° C. or higher (the temperature difference between the temperature of the molten salt before cooling and the temperature of the molten salt after cooling is 20° C. or higher). It is also preferable that the specific metal component of the molten salt contains sodium, and the molten salt contains at least a sodium salt and a potassium salt. The temperature of the molten salt can be measured, for example, with a K thermocouple.
  • the molten salt is preferably cooled while generating convection in the molten salt.
  • a method for generating convection in the molten salt include stirring the molten salt with a stirring blade. By cooling the molten salt while generating convection, the molten salt can be cooled uniformly.
  • An example of an apparatus for carrying out the precipitation step is an apparatus having a container for containing molten salt, a temperature measuring means that is immersed in the molten salt and measures the temperature of the molten salt, a heating means that heats the container for containing the molten salt and heats the molten salt contained therein, and a stirring blade that stirs the molten salt.
  • the container for containing the molten salt is preferably made of a material that does not dissolve in the molten salt, such as metal materials such as stainless steel, ceramic materials such as quartz glass and alumina, and heat-resistant resin materials such as tetrafluoroethylene (PTFE).
  • the temperature measuring means is not particularly limited, but examples thereof include known thermocouples.
  • the heating means is not particularly limited, but may be, for example, a heater having an electric heating wire.
  • the molten salt can be cooled, for example, by controlling the output of the heating means while monitoring the temperature using a temperature measuring means so that the amount of heat input from the heating means is less than the amount of heat dissipated from the molten salt and the container containing the molten salt. Furthermore, by controlling the output of the heating means so that the amount of heat radiation and the amount of heat input are equal, the temperature of the molten salt can be kept constant.
  • the above-mentioned device may be equipped with a jig or the like used in the recovery step described below.
  • a recovery step is carried out in which the specific metal salt precipitated in the precipitating step is recovered from the molten salt in a molten state.
  • the solid specific metal salt is separated from the liquid molten salt, and the specific metal salt containing the specific metal component is recovered.
  • the method for carrying out the recovery step is not particularly limited, and known methods can be applied. A specific method for carrying out the recovery step will be described below, but the recovery step of the present invention is not limited to the following method, and various methods can be applied.
  • One aspect of the recovery process is a first embodiment in which, when recovering a specific metal salt from a molten salt in a molten state, a first jig having a mesh portion is used, the mesh portion is pulled up from the molten salt, and the precipitated specific metal salt is recovered from the molten salt in a molten state.
  • the specific metal salt precipitated as a solid is recovered by the mesh portion of the first jig and separated from the liquid molten salt. It is preferable that the first jig be placed in a container containing the molten salt and immersed in the molten salt before the above-mentioned precipitation step is carried out.
  • the first jig may have a handle for lifting the mesh part from the molten salt.
  • the handle is preferably connected directly or indirectly to the mesh part and protrudes above the liquid surface of the molten salt, allowing the mesh part to be lifted without coming into contact with the molten salt.
  • the first jig may be immersed in a molten salt to recover the specific metal salt.
  • Figures 1A and 1B are cross-sectional views showing a vessel 10 containing molten salt M, for explaining the first embodiment of the recovery step.
  • 1A shows a state in which a first jig 20a is placed in a container 10 containing molten salt M.
  • the first jig 20a is composed of a mesh portion 24a and a handle portion 22a connected to the mesh portion 24a.
  • the handle portion 22a protrudes from the liquid surface of the molten salt M.
  • the specific metal salt C1 is precipitated on the mesh portion 24a of the first jig 20a.
  • FIG. 1B shows a state in which the first jig 20a has been pulled up from the container 10 containing the molten salt M.
  • the specific metal salt C1 can be easily recovered by gripping the handle portion 22a of the first jig 20a and pulling the first jig 20a upward in the plane of the drawing (see FIG. 1B ).
  • the first jig is preferably made of a material that does not dissolve in the molten salt, such as a metal material such as stainless steel, a ceramic material such as quartz glass or alumina, or a heat-resistant resin material such as polytetrafluoroethylene (PTFE).
  • the mesh portion of the first jig is not particularly limited as long as it can recover the specific metal salt, and can be selected appropriately depending on the size of the precipitated particles of the specific metal salt.
  • the mesh opening of the mesh portion is preferably 0.05 to 0.2 mm. It is also preferable that the mesh portion of the first jig has a shape that conforms to the container that contains the molten salt.
  • One aspect of the recovery process is a second embodiment in which, when cooling a molten salt containing a specific metal component and precipitating a specific metal salt containing the specific metal component while maintaining the molten salt in a molten state, the specific metal salt is precipitated on the surface of a salt precipitating portion of a second jig having a salt precipitating portion, and the salt precipitating portion is pulled up from the molten salt to recover the specific metal salt from the molten molten salt.
  • the specific metal salt precipitated as a solid is separated from the liquid molten salt, and the specific metal salt containing the specific metal component is recovered.
  • the second jig is placed in a container containing the molten salt and is immersed in the molten salt.
  • the salt deposition portion of the second jig is not particularly limited, but preferably has a large surface area.
  • the structure of the salt deposition portion may be any known structure, such as a structure in which plate-like structures are arranged at predetermined intervals in a direction perpendicular to their main surfaces and connected to each other, or a structure in which a single plate is bent into a bellows shape.
  • the plate-like structure or plate may have holes.
  • the plate-like structure or plate is preferably a metal plate. That is, the plate-like structure or plate is preferably a punched metal.
  • the plate-like structure or plate may be subjected to a surface roughening treatment.
  • the plate-like structure or plate may be a mesh made of wire.
  • the mesh opening is preferably 0.5 mm or more.
  • the mesh opening is preferably 20.0 mm or less, and more preferably 2.0 mm or less.
  • the second jig may have a handle for pulling the mesh part out of the molten salt.
  • the handle is preferably connected directly or indirectly to the mesh part and protrudes above the liquid surface of the molten salt, allowing the mesh part to be pulled out without coming into contact with the molten salt.
  • the second jig is preferably made of a material that does not dissolve in the molten salt. Examples of the preferred material are the same as those of the first jig.
  • Fig. 2 is a cross-sectional view showing a vessel 10 containing molten salt M for explaining the second embodiment of the recovery step. 2 shows a state in which the second jig 20b is installed in the container 10 containing the molten salt M.
  • the first jig 20b is composed of a salt-precipitating portion 24b and a handle portion 22b connected to the salt-precipitating portion 24b.
  • the handle portion 22b protrudes from the liquid surface of the molten salt M.
  • the salt-precipitating portion 24b has a structure formed by bending a single plate into an accordion-like shape.
  • FIG. 2 is a cross-sectional view showing a vessel 10 containing molten salt M for explaining the second embodiment of the recovery step. 2 shows a state in which the second jig 20b is installed in the container 10 containing the molten salt M.
  • the first jig 20b is composed of a salt-precipitating portion 24b and
  • the specific metal salt C2 is precipitated on the surface of the salt precipitated portion 24b of the second jig 20b.
  • the specific metal salt C2 can be easily recovered by gripping the handle 22b of the second jig 20b and pulling the second jig 20b upward in the plane of the drawing.
  • the salt deposition portion 24b has only one structure formed by folding a single plate into an accordion shape, but the salt deposition portion may have a plurality of such structures.
  • the folding line direction of the structure formed by folding a single plate into an accordion shape is the front-to-back direction on the paper, but the folding line direction may be the up-to-down direction on the paper.
  • One aspect of the recovery process is a third embodiment in which, when cooling a molten salt containing a specific metal component and precipitating a specific metal salt containing the specific metal component while maintaining the molten salt in a molten state, a third jig having a temperature-controllable cooling section is used to cool the molten salt by changing the temperature of the cooling section, precipitating the specific metal salt on the surface of the cooling section, and then the cooling section is pulled up from the molten salt to recover the specific metal salt from the molten molten salt.
  • the cooling section of the third jig may have any configuration, including, for example, a structure having a pipe therein through which a refrigerant can flow.
  • the refrigerant is not particularly limited, and any known refrigerant can be used.
  • the cooling method for the refrigerant is also not particularly limited.
  • the cooling unit may be configured by connecting a metal plate or a mesh made of wire to a pipe through which the refrigerant can flow.
  • the specific metal salt tends to precipitate efficiently in that part.
  • the third jig is preferably made of a material that does not dissolve in the molten salt. Preferred examples of the material are the same as those of the first jig.
  • Fig. 3 is a cross-sectional view showing a vessel 10 containing molten salt M for explaining the third embodiment of the recovery step.
  • Fig. 3 shows a state in which a third jig 20c is installed in a container 10 containing molten salt M.
  • the third jig 20c has a cooling section 24c, which is the area surrounded by a dashed line in Fig. 3.
  • a pipe (not shown) through which a refrigerant can flow is provided inside the cooling section 24c, and the cooling section 24c can be cooled.
  • a specific metal salt C3 is precipitated on the surface of the cooling portion 24c of the third jig 20c.
  • the specific metal salt C3 can be easily recovered by lifting the third jig 20c upward in the plane of the drawing.
  • One embodiment of the recovery process is a fourth embodiment, in which, when recovering a specific metal salt from molten molten salt, a molten salt storage container in which the molten salt is stored, a circulation path connected to the molten salt storage container and through which the molten salt discharged from the molten salt storage container returns to the molten salt storage container, and a filter positioned midway along the circulation path and capable of separating solids from the molten salt are used, and the molten salt containing the precipitated specific metal salt is introduced into the circulation path, the specific metal salt is separated from the molten salt by the filter, and the specific metal salt is recovered from the filter.
  • a circulation path connected to a molten salt storage vessel includes a circulation means for circulating the molten salt, and the molten salt is sent from one end of the circulation path to the other end of the circulation path.
  • the filter is installed in this circulation path, the precipitated specific metal salt is captured by the filter.
  • a part or all of the molten salt is discharged from the circulation path, and the filter is removed from the circulation path, whereby the specific metal salt is recovered.
  • the circulation means is not particularly limited, and known means can be applied. Examples of the filter include a sintered metal filter, a ceramic filter, and a stainless steel mesh. The pore size of the filter can be adjusted appropriately depending on the specific metal salt precipitated.
  • the filter and the circulation path are preferably made of a material that does not dissolve in the molten salt. Examples of preferred materials are the same as those of the first jig.
  • Fig. 4 is a cross-sectional view showing a vessel 10 containing molten salt M for explaining the fourth embodiment of the recovery step. 4 shows a state in which a circulation path 32 is connected to a container 10 containing molten salt M, through which the molten salt M discharged from the container 10 returns to the container 10.
  • a filter 34 capable of separating solids from the molten salt is disposed midway along the circulation path 32.
  • a pump 36 capable of sending the molten salt M from one end of the circulation path 32 to the other end of the circulation path 32 is disposed between the filter 34 and the container 10.
  • the specific metal salt C4 precipitated in the molten salt M is introduced into the circulation path 32 together with the molten salt M and captured by the filter 34. By discharging a part or all of the molten salt M from the circulation path 32 and removing the filter 34 from the circulation path 32, the specific metal salt C4 can be easily recovered.
  • the specific metal salt recovered in the first to fourth embodiments may be heated at a temperature higher than the melting point of the molten salt.
  • the temperature is preferably higher than the temperature at which the specific metal salt is precipitated and lower than the temperature of the molten salt before the precipitation step, and is preferably 10 to 150° C. higher than the temperature at which the specific metal salt is precipitated.
  • the components of the molten salt that precipitate along with the specific metal salt are melted and removed from the specific metal salt, thereby increasing the content of the specific metal component contained in the specific metal salt.
  • the specific metal salt recovered in the recovery step contains the specific metal component, as described above.
  • the specific metal component preferably contains lithium or sodium, and more preferably contains lithium.
  • the specific metal salt is preferably a sulfate containing lithium, more preferably a sulfate containing lithium and sodium.
  • Specific examples of the specific metal salt include at least one selected from the group consisting of LiNaSO 4 , LiKSO 4 , and Li 2 NaK(SO 4 ) 2 .
  • the specific metal salt which is a lithium-containing sulfate, preferably contains crystals of a crystal structure of space group P31c, in which a diffraction peak appears in the range of 30.2 to 30.5° in an X-ray diffraction chart measured with Cu K ⁇ radiation.
  • the specific metal salt which is a lithium-containing sulfate, preferably contains crystals of at least one crystal structure selected from the group consisting of crystals having a crystal structure of space group P31c, which exhibits a diffraction peak in the range of 23.2 to 23.5° in an X-ray diffraction chart measured with Cu K ⁇ radiation, crystals having a crystal structure of space group Cmc2 1 , which exhibits a diffraction peak in the range of 22.4 to 22.7°, and crystals having a crystal structure of space group P2 1 2 1 2 1 , which exhibits a diffraction peak in the range of 22.8 to 23.1°.
  • An example of a crystal having a crystal structure of space group P31c in which a diffraction peak appears in the above-mentioned range of 23.2 to 23.5° is LiNaSO 4.
  • An example of a crystal having a crystal structure of space group Cmc2 1 in which a diffraction peak appears in the range of 22.4 to 22.7° is LiKSO 4.
  • An example of a crystal having a crystal structure of space group P2 1 2 1 2 1 in which a diffraction peak appears in the range of 22.8 to 23.1° is Li 2 NaK(SO 4 ) 2. It is also preferable that the peak showing the maximum diffraction intensity appears in each of the above-mentioned angle ranges in the X-ray diffraction chart.
  • the X-ray diffraction chart is measured by the so-called focusing method (also known as the ⁇ /2 ⁇ method), and the angle range is the range of 2 ⁇ .
  • the specific metal salt contains sodium
  • the specific metal salt is preferably a carbonate containing sodium, more preferably a carbonate containing sodium and potassium.
  • a specific salt contained in the specific metal salt is Na2CO3 .
  • the specific metal salt which is a lithium-containing sulfate, preferably contains crystals having a crystal structure of space group C2/m, in which a diffraction peak appears in the range of 28.4 to 28.7° in an X-ray diffraction chart measured with Cu K ⁇ radiation.
  • the specific metal salt thus obtained may be subjected to post-treatment to change its chemical bonding state, etc.
  • the post-treatment is not particularly limited and can be appropriately adjusted depending on the method of applying the specific metal component.
  • the post-treatment may involve dissolving the obtained specific metal salt in water to obtain a specific metal aqueous solution.
  • a predetermined salt to the specific metal aqueous solution to form a precipitate, and then recover the precipitate.
  • the specific metal component contains lithium.
  • the specific metal salt can be purified by the above procedure.
  • the precipitate is lithium carbonate (Li 2 CO 3 ).
  • the lithium-containing salt when dissolving the obtained lithium-containing salt in water, the lithium-containing salt may be brought into contact with water.
  • the lithium-containing salt may be brought into contact with water in a state where it is attached to the jig (first jig to third jig) or the filter used in the fourth embodiment.
  • the method for contacting the lithium-containing salt with water is not particularly limited, and for example, the lithium-containing salt (or the jig or filter having the lithium-containing salt attached thereto) may be immersed in water, or water may be supplied to the jig or filter having the lithium-containing salt attached thereto (for example, water may be supplied by showering).
  • the lithium-containing salt or the jig or filter having the lithium-containing salt attached thereto
  • the temperature of the water is not particularly limited, but may be, for example, 5°C or higher, preferably 15°C or higher, more preferably 30°C or higher, even more preferably 50°C or higher, and particularly preferably 70°C or higher.
  • the specific metal salt thus obtained and the specific metal salt obtained after the post-treatment can be used in a variety of applications.
  • the specific metal component is lithium
  • the specific metal salt can be used as a variety of raw materials, such as a glass raw material, an additive raw material for alloys, a raw material for battery materials, a raw material for chemical synthesis, and the like.
  • the method for recovering metal components of the present invention can be preferably applied to the regeneration of molten salt.
  • the specific metal component preferably contains lithium or sodium
  • the molten salt is a chemically strengthened molten salt obtained by immersing glass (glass for chemical strengthening) containing at least one selected from the group consisting of silicon, aluminum, lithium, and sodium. That is, the method for regenerating a molten salt of the present invention is a method in which the method for recovering a metal component of the present invention is applied to the chemically strengthened molten salt.
  • the chemically strengthened glass used to obtain the chemically strengthened molten salt is not particularly limited as long as it contains silicon, aluminum, and lithium or sodium, and chemically strengthened glasses of known compositions can be used.
  • the glass for chemical strengthening will be described in detail in the section on the method for producing chemically strengthened glass.
  • the preferred composition of the chemically strengthened molten salt used in the molten salt regeneration method of the present invention is the same as the composition of the molten salt described in the metal component recovery method above, so further explanation will be omitted.
  • the specific metal salt may contain components other than the specific metal component.
  • the method for regenerating a molten salt of the present invention may include a step of adding the components contained in the recovered specific metal salt to the molten salt to adjust the composition of the molten salt. That is, in the method for regenerating a molten salt of the present invention, after recovering a specific metal component from the chemically strengthened molten salt, the components of the molten salt may be further adjusted. When adjusting the components of the molten salt, it is preferable to add a sulfate.
  • a component containing a sodium salt it is more preferable to add a component containing sodium sulfate. It is preferable that the sulfate does not contain a specific metal component.
  • components other than the specific metal salts include nitrates. Therefore, it is also preferable to analyze the content of nitrate ions contained in the recovered specific metal salts. It is also preferable that the nitrates do not contain specific metal components.
  • the amount of nitrate ions contained in the recovered specific metal salts can be analyzed by measuring the nitrate ion concentration using naphthylethylenediamine absorptiometry, more specifically, by using a Digital Pack Test (DPM2-NO3) manufactured by Kyoritsu Chemical Research Institute.
  • the sulfate ion content in the recovered specific metal salt can be determined by measuring the sulfate ion concentration using barium chloride turbidimetry, for example, using a Digital Pack Test (DPM2-SO4) manufactured by Kyoritsu Chemical Research Institute.
  • Atomic absorption spectrometry can be used to measure the content of metal components contained in a molten salt. More specifically, a method can be used in which the molten salt is dissolved in a predetermined amount of pure water to dilute the solution, and the concentration of the metal components in the aqueous solution is measured using an atomic absorption spectrophotometer.
  • a polarized Zeeman atomic absorption spectrophotometer ZA3300 manufactured by Hitachi High-Tech Corporation is used for the atomic absorption spectrometry measurement.
  • the method for measuring the content of nitrate ions in the molten salt may be the same as the method for analyzing the content of nitrate ions in the recovered specific metal salt described above.
  • the method for measuring the content of sulfate ions in the molten salt may be the same as the method for analyzing the content of sulfate ions in the recovered specific metal salt described above.
  • one preferred aspect of adjusting the components of the molten salt is, for example, adding a component containing a sodium salt, and adding a component containing sodium sulfate is more preferred.
  • components other than sodium sulfate may be added depending on the components recovered as the specific metal salt. Examples of such components include nitrates, more specifically, one or more components selected from the group consisting of sodium nitrate, potassium nitrate, and potassium sulfate.
  • the composition of the molten salt can be maintained approximately constant.
  • chemically strengthened glass may contain sodium, and in a chemical strengthening process in which the chemically strengthened glass is obtained by immersing the chemically strengthened glass in molten salt, the sodium contained in the chemically strengthened glass may be exchanged with ions (e.g., potassium ions) in the molten salt by salt exchange.
  • ions e.g., potassium ions
  • the molten salt after chemical strengthening may contain sodium.
  • the salt exchange may not easily occur.
  • the mother glass composition preferably contains Li (lithium), and is preferably an aluminosilicate glass containing Li, Si (silicon), and Al (aluminum). More specifically, the first aspect of the mother glass composition is, in mole percent on an oxide basis, SiO2 52-75%, 8-20% Al 2 O 3 , It is preferable that Li 2 O is contained in an amount of 5 to 16%.
  • a first embodiment of a preferred mother glass composition will be described below. Note that, hereinafter, for example, the content of SiO 2 expressed as a mole percentage based on oxide may be expressed as "[SiO 2 ]".
  • SiO2 is a component that constitutes the skeleton of glass. It also increases chemical durability and reduces the occurrence of cracks when the glass surface is scratched.
  • the SiO2 content is preferably 52% or more, more preferably 55% or more, and particularly preferably 60% or more.
  • the SiO2 content is preferably 75% or less, more preferably 72% or less, even more preferably 70% or less, and particularly preferably 68% or less.
  • Al 2 O 3 is an effective component from the viewpoint of improving ion exchange performance during chemical strengthening and increasing the surface compressive stress after strengthening.
  • the Al2O3 content is preferably 8% or more, more preferably 9% or more, even more preferably 10% or more, particularly preferably 11% or more, and typically 12% or more.
  • the Al2O3 content is too high, crystals tend to grow during melting, which tends to reduce yield due to devitrification defects.
  • the viscosity of the glass increases and the melting property deteriorates.
  • the Al2O3 content is preferably 20% or less, more preferably 19% or less, and even more preferably 18% or less.
  • Both SiO2 and Al2O3 are components that stabilize the structure of glass, and in order to reduce brittleness, the total content is preferably 65% or more, more preferably 70% or more, and even more preferably 75% or more.
  • Li 2 O is a component that forms surface compressive stress by ion exchange and improves the meltability of glass.
  • surface compressive stress can be introduced by ion-exchanging lithium ions on the glass surface with sodium ions and then ion-exchanging the sodium ions with potassium ions.
  • the Li 2 O content is preferably 5% or more, more preferably 7% or more, even more preferably 9% or more, particularly preferably 10% or more, and most preferably 11% or more.
  • stress profile refers to a pattern that expresses compressive stress values with the depth from the glass surface as a variable.
  • a negative compressive stress value means tensile stress.
  • the "stress profile" can be measured by a method using an optical waveguide surface stress meter or a scattered light photoelastic stress meter.
  • the Li 2 O content is preferably 20% or less, more preferably 16% or less, even more preferably 14% or less, and particularly preferably 12% or less.
  • Na 2 O nor K 2 O are components that improve the meltability of the glass and reduce the crystal growth rate of the glass, and in order to improve the ion exchange performance, they are preferably contained in a total amount of 2% or more, and their total amount is preferably 10% or less, preferably 9% or less, more preferably 8% or less, even more preferably 7% or less, and particularly preferably 5% or less.
  • Na 2 O is a component that forms a surface compressive stress layer in a chemical strengthening treatment using a potassium salt and can also improve the meltability of glass.
  • the content of Na 2 O is preferably 1% or more, more preferably 2% or more, even more preferably 3% or more, and particularly preferably 4% or more.
  • the content is preferably 8% or less, more preferably 7% or less, even more preferably 6% or less, and particularly preferably 5% or less.
  • K 2 O may be contained for the purpose of improving ion exchange performance, etc.
  • the content is preferably 0.1% or more, more preferably 0.15% or more, particularly preferably 0.2% or more. In order to further prevent devitrification, 0.5% or more is preferable, and 1.2% or more is more preferable.
  • 5% or less is preferable, and 3% or less is more preferable.
  • the total content R of Li 2 O, Na 2 O, and K 2 O is preferably 5% or more, more preferably 8% or more, even more preferably 10% or more, and particularly preferably 12% or more.
  • the content R is preferably 25% or less, and more preferably 20% or less.
  • the ratio of the Li2O content to the R ([ Li2O ]/([ Li2O ]+[ Na2O ]+[ K2O ]), hereinafter also referred to as " Li2O / R2O ”) is more preferably 0.52 or more, and even more preferably 0.55 or more, from the viewpoint of further improving the chemical strengthening properties against compressive stress in the deep layer. From the viewpoint of further improving chemical durability, Li2O / R2O is more preferably 0.80 or less, even more preferably 0.78 or less, and particularly preferably 0.75 or less.
  • the ratio of the Na2O content to the R ([ Na2O ]/([ Li2O ]+[ Na2O ]+[ K2O ]), hereinafter also referred to as " Na2O / R2O ”) is preferably 0.05 or more, more preferably 0.08 or more, and even more preferably 0.10 or more, from the viewpoint of further improving the chemical strengthening properties against compressive stress in the deep layer. From the viewpoint of further improving chemical durability, Na2O / R2O is preferably 0.60 or less, more preferably 0.50 or less, even more preferably 0.40 or less, and particularly preferably 0.30 or less.
  • K 2 O/R 2 O The ratio of the content of K 2 O to the R ([K 2 O]/([Li 2 O] + [Na 2 O] + [K 2 O]), hereinafter also referred to as "K 2 O/R 2 O") is preferably 0.05 or more, more preferably 0.08 or more, and even more preferably 0.10 or more, from the viewpoint of further improving the electrical resistance of the glass. From the viewpoint of further improving the chemical strengthening properties against compressive stress near the surface, K 2 O/R 2 O is preferably 0.50 or less, more preferably 0.40 or less, even more preferably 0.30 or less, and particularly preferably 0.20 or less.
  • the product of Li2O / R2O , Na2O / R2O , and K2O / R2O is preferably 0.005 or more, more preferably 0.008 or more, and even more preferably 0.010 or more from the viewpoint of suppressing an increase in the devitrification temperature.
  • the product is preferably 0.030 or less, and more preferably 0.028 or less.
  • Al2O3 /R2O The ratio of the Al2O3 content to the R ([ Al2O3 ]/( [ Li2O ] + [ Na2O ] + [ K2O ]), hereinafter also referred to as " Al2O3 /R2O") is preferably 0.20 or more, more preferably 0.30 or more, even more preferably 0.40 or more, and still more preferably 0.50 or more.
  • Al2O3 / R2O is preferably 0.90 or less, more preferably 0.88 or less , and even more preferably 0.85 or less.
  • MgO may be included to reduce viscosity during dissolution, etc.
  • the MgO content is preferably 0.5% or more, more preferably 1% or more, even more preferably 2% or more, and particularly preferably 3% or more.
  • the MgO content is preferably 15% or less, more preferably 10% or less, even more preferably 8% or less, and particularly preferably 6% or less.
  • ZrO2 does not have to be contained, it is preferable to contain it from the viewpoint of increasing the surface compressive stress of chemically strengthened glass.
  • the content of ZrO2 is preferably 0.1% or more, more preferably 0.15% or more, even more preferably 0.2% or more, particularly preferably 0.25% or more, typically 0.3% or more.
  • the content of ZrO2 is preferably 2% or less, more preferably 1.5% or less, even more preferably 1% or less, and particularly preferably 0.8% or less.
  • Y 2 O 3 may be contained for the purpose of increasing the surface compressive stress of chemically strengthened glass while reducing the crystal growth rate.
  • the content is preferably 0.1% or more, more preferably 0.2% or more, even more preferably 0.5% or more, and particularly preferably 1% or more.
  • the content of Y 2 O 3 is preferably 5% or less, more preferably 3% or less, even more preferably 2% or less, and particularly preferably 1.5% or less.
  • a second embodiment of the mother glass composition which is different from the first embodiment of the mother glass composition, is as follows: SiO2 55-75% 3-18% Al 2 O 3 17-30% Li 2 O Na 2 O 0 to 3% K 2 O 0-1% MgO 0-10% CaO 0-10% SrO 0 to 5% ZnO 0-5% TiO2 0-3% ZrO2 0-3% SnO2 0-1% P2O5 0-3 % B2O3 0-10 % Contains 0 to 3% Y 2 O 3 ;
  • R which is the total of the Li 2 O content, the Na 2 O content, and the K 2 O content, is 8 to 35%
  • the Li 2 O content relative to R is 0.85 to 0.99
  • the product of the Li 2 O content relative to R, the Na 2 O content relative to R, and the K 2 O content relative to R is 0 to 0.003.
  • the second embodiment of the mother glass composition will be described below.
  • SiO2 is a component that constitutes the glass network. It also increases chemical durability and reduces the occurrence of cracks when the glass surface is scratched.
  • the SiO2 content is preferably 57.0% or more, even more preferably 58.0% or more, particularly preferably 59.0% or more, and most preferably 60.0% or more.
  • the SiO2 content is preferably 74.0% or less, even more preferably 72.0% or less, particularly preferably 69.0% or less, and most preferably 66.0% or less.
  • Al 2 O 3 is a component that improves ion exchange performance during chemical strengthening and increases the surface compressive stress after strengthening, and also contributes to the formation of crystals containing Al and Li.
  • the Al2O3 content is more preferably 3.5% or more, and even more preferably 4.0% or more and 4.5% or more, in the following order.
  • the Al2O3 content is more preferably 18.0% or less, and even more preferably 15.0% or less, 12.0% or less, 9.0% or less, 7.0% or less, and 6.0% or less, in the following order.
  • Both SiO2 and Al2O3 are components that stabilize the glass structure.
  • the total content of SiO2 and Al2O3 is preferably 60.0% or more, more preferably 62.0% or more, and even more preferably 64.0% or more.
  • both SiO 2 and Al 2 O 3 tend to increase the melting temperature of the glass. Therefore, in order to make the glass more easily meltable, the total content of SiO 2 and Al 2 O 3 is preferably 80.0% or less, more preferably 75.0% or less, even more preferably 70.0% or less, and particularly preferably 68.0% or less.
  • Li 2 O is an ion-exchangeable component that improves the meltability of glass.
  • glass contains Li 2 O
  • Li ions on the glass surface are ion-exchanged with external Na ions to be incorporated into the glass, and the incorporated Na ions are then ion-exchanged with external K ions, which makes it easy to obtain a stress profile with a large surface compressive stress and a thick compressive stress layer.
  • the Li 2 O content is more preferably 17% or more, and even more preferably 19% or more, 21% or more, and 22% or more, in the following order.
  • the content of Li 2 O is more preferably 30% or less, and further preferably 28% or less, 26% or less, 24% or less, and 23% or less, in that order.
  • Na 2 O and K 2 O are components that improve the meltability of the glass and reduce the crystal growth rate during glass forming, and are preferably contained in small amounts to improve ion exchange performance.
  • Na 2 O is a component that can be ion-exchanged in a chemical strengthening treatment using a potassium salt and also reduces the viscosity of glass.
  • the Na 2 O content is preferably 0.3% or more, more preferably 0.5% or more, 0.8% or more, 1.0% or more, 1.2% or more, 1.5% or more, and 1.8% or more, in the following order.
  • the Na 2 O content is preferably 3.0% or less, more preferably 2.5% or less, and even more preferably 2.3% or less.
  • K 2 O is a component that suppresses an increase in the devitrification temperature to suppress devitrification and improves ion exchange performance.
  • the content of K 2 O is more preferably 0.1% or more, even more preferably 0.15% or more, particularly preferably 0.2% or more, and most preferably 0.5% or more.
  • the content of K 2 O is preferably 1.0% or less, and more preferably 0.8% or less. It is not necessary for K 2 O to be substantially contained.
  • R which is the total of the Li 2 O content, the Na 2 O content, and the K 2 O content, is more preferably 10 to 30%, further preferably 15 to 28%, and particularly preferably 18 to 25%, from the viewpoint of suppressing an increase in the devitrification temperature and reducing the crystal growth rate.
  • Li 2 O/R 2 O The ratio of the Li 2 O content to the R ([Li 2 O]/([Li 2 O] + [Na 2 O] + [K 2 O]), hereinafter also referred to as "Li 2 O/R 2 O") is more preferably 0.88 or more, and even more preferably 0.90 or more, from the viewpoint of further improving deep layer stress in chemical strengthening characteristics. From the viewpoint of further increasing the electrical resistance and chemical resistance of the glass, Li 2 O/R 2 O is more preferably 0.98 or less, even more preferably 0.95 or less, and particularly preferably 0.93 or less.
  • the ratio of the Na 2 O content to the R ([Na 2 O]/([Li 2 O] + [Na 2 O] + [K 2 O]), hereinafter also referred to as "Na 2 O/R 2 O”) is preferably more than 0, more preferably 0.01 or more, even more preferably 0.03 or more, particularly preferably 0.05 or more, and most preferably 0.06 or more, from the viewpoint of further improving deep layer stress in chemical strengthening characteristics. From the viewpoint of further improving chemical resistance, Na 2 O/R 2 O is preferably 0.40 or less, more preferably 0.30 or less, even more preferably 0.20 or less, and particularly preferably 0.10 or less.
  • K 2 O/R 2 O The ratio of the content of K 2 O to the above R ([K 2 O]/([Li 2 O] + [Na 2 O] + [K 2 O]), hereinafter also referred to as "K 2 O/R 2 O") is preferably 0.05 or more, more preferably 0.08 or more, and even more preferably 0.10 or more, from the viewpoint of further increasing the electrical resistance of the glass. From the viewpoint of increasing the compressive stress near the surface in chemical strengthening characteristics, K 2 O/R 2 O is preferably 0.50 or less, more preferably 0.40 or less, even more preferably 0.30 or less, and particularly preferably 0.20 or less. The K 2 O/R 2 O ratio may be zero.
  • MgO may be contained to reduce viscosity during dissolution, etc.
  • the MgO content is more preferably 0.05% or more, and further preferably 0.5% or more, 1.0% or more, 2.0% or more, 3.0% or more, and 4.0% or more, in the following order.
  • the MgO content is more preferably 9.0% or less, and further preferably 8.0% or less, 7.0% or less, and 6.0% or less, in that order.
  • MgO it is possible to suppress the phase transition of the crystalline phase from ⁇ -quartz solid solution to ⁇ -spodumene, and to suppress the precipitation of ⁇ -spodumene crystals. Therefore, in embodiment 2, it is preferable to include MgO. From the above viewpoint, it is preferable to include more than 0.5% and not more than 7.0% of MgO. The more preferable range is as described above. MgO may not be substantially contained.
  • CaO is a component that improves the meltability of glass and may be contained.
  • the CaO content is more preferably 0.1% or more, and even more preferably 0.15% or more.
  • the CaO content is more preferably 2.0% or less, even more preferably 1.0% or less, particularly preferably 0.8% or less, and most preferably 0.5% or less. CaO may not be substantially contained.
  • MgO and CaO In order to increase the stability of the glass, it is more preferable to contain at least one of MgO and CaO, and it is even more preferable to contain MgO.
  • the total content of MgO and CaO is preferably over 1.0%, more preferably 2.0% or more, even more preferably 3.0% or more, and particularly preferably 4.0% or more.
  • the total content of MgO and CaO is preferably 10.0% or less, and more preferably 8.0% or less, 7.0% or less, and 6.0% or less, in that order.
  • SrO is a component that improves the meltability of glass and may be contained.
  • the content of SrO is more preferably 0.1% or more, further preferably 0.15% or more, and particularly preferably 0.5% or more.
  • the SrO content is more preferably 3.0% or less, even more preferably 2.0% or less, particularly preferably 1.0% or less, and most preferably 0.5% or less. SrO may not be substantially contained.
  • BaO is a component that improves the meltability of the glass and may be contained.
  • the content is preferably 0.1% or more, more preferably 0.15% or more, and even more preferably 0.5% or more.
  • the BaO content is preferably 3.0% or less, more preferably 2.0% or less, even more preferably 1.0% or less, and particularly preferably 0.5% or less. BaO may not be substantially contained.
  • ZnO is a component that improves the meltability of glass.
  • the ZnO content is more preferably 0.1% or more, further preferably 0.15% or more, and particularly preferably 0.5% or more.
  • the ZnO content is more preferably 3.0% or less, even more preferably 2.0% or less, particularly preferably 1.0% or less, and most preferably 0.5% or less. ZnO may not be substantially contained.
  • TiO2 is a component that is highly effective in suppressing solarization of glass and is a material that forms crystal nuclei, so it may be contained.
  • the content is preferably 0.05% or more, more preferably 0.1% or more, even more preferably 0.2% or more, particularly preferably 0.5% or more, and most preferably 0.8% or more.
  • the content of TiO2 is preferably 2.5% or less, more preferably 2.0% or less, even more preferably 1.5% or less, and particularly preferably 1.0% or less. TiO2 may be substantially absent.
  • ZrO2 is a component that facilitates increasing the surface compressive stress of chemically strengthened glass. Furthermore, since ZrO2 is a material that forms crystal nuclei, it may be contained. The ZrO2 content is more preferably greater than 0%, and even more preferably 0.5% or more, 1.0% or more, 1.5% or more, 2.0% or more, and 2.5% or more, in the following order.
  • the content of SnO2 is preferably 0.005% or more, and more preferably 0.01% or more.
  • the content of SnO2 is preferably 1% or less, and more preferably 0.50% or less.
  • P 2 O 5 tends to increase the compressive stress layer during chemical strengthening, and the content of P 2 O 5 is more preferably 0.5% or more, further preferably 1.0% or more, and particularly preferably 2.0% or more. On the other hand, from the viewpoint of increasing acid resistance, the content of P 2 O 5 is more preferably 2.0% or less. From the viewpoint of preventing the formation of striae during melting, it is also preferable that P 2 O 5 is substantially not contained.
  • the B 2 O 3 reduces the brittleness of the glass and improves the crack resistance, or improves the meltability of the glass.
  • the B 2 O 3 content is more preferably 0.5% or more, even more preferably 1.0% or more, and particularly preferably 2.0% or more.
  • the B2O3 content is preferably 8.0% or less.
  • the B2O3 content is more preferably 6.0% or less, even more preferably 4.0% or less, and particularly preferably 2.0% or less. In order to prevent the occurrence of striae during melting, it is also preferable that the B2O3 content be substantially zero.
  • Y 2 O 3 is a component that reduces the crystal growth rate while making it easier to increase the surface compressive stress of chemically strengthened glass.
  • the Y 2 O 3 content is more preferably more than 0%, and even more preferably 0.1% or more, 0.2% or more, 0.5% or more, and 0.8% or more, in that order.
  • the Y 2 O 3 content is more preferably 2.0% or less, and even more preferably 1.5% or less.
  • the total content of ZrO2 and Y2O3 is more preferably 5.0% or less. Although there is no particular lower limit for the total content of ZrO2 and Y2O3 , from the viewpoint of increasing the strength of the glass , it is more preferably 0.5% or more, and further preferably 1.0% or more, 1.5% or more, 2.0% or more, 2.5% or more, and 3.0% or more, in that order.
  • the ratio of the ZrO2 content to the total content of ZrO2 and Y2O3 , [ ZrO2 ]/([ ZrO2 ]+[ Y2O3 ]), is more preferably 0.50 or more, even more preferably 1.00 or more, and particularly preferably 2.00 or more.
  • [ ZrO2 ]/([ ZrO2 ]+ [ Y2O3 ]) is more preferably 8.00 or less, even more preferably 7.00 or less, and particularly preferably 6.00 or less.
  • La2O3 is not essential, but can be contained for the same reasons as Y2O3 .
  • La2O3 is preferably 0.1% or more, more preferably 0.2% or more, even more preferably 0.5% or more, and particularly preferably 0.8 % or more.
  • La2O3 is preferably 5.0% or less, more preferably 3.0% or less, even more preferably 2.0% or less, and particularly preferably 1.5% or less. It is also preferable that La 2 O 3 is substantially not contained.
  • the composition of the glass for chemical strengthening (mother glass composition) to be subjected to chemical strengthening is preferably as described above.
  • the method for obtaining a chemically strengthened glass having a mother glass composition is not particularly limited, and known methods can be applied.
  • glass raw materials are appropriately mixed, heated and melted in a glass melting furnace, and then the glass is homogenized by bubbling, stirring, adding a clarifier, etc., formed into a glass plate of a predetermined thickness, and slowly cooled.
  • the glass may be formed into a plate by forming it into a block, slowly cooling it, and then cutting it.
  • the specific metal salt recovered by the method for recovering metal components of the present invention is used as part of the raw material of the chemically strengthened glass.
  • the specific metal salt a specific metal salt containing lithium or sodium is preferred, and lithium carbonate ( Li2CO3 ) or sodium carbonate ( Na2CO3 ) is more preferred.
  • Methods for forming glass into sheets include, for example, the float method, press method, fusion method, and downdraw method.
  • the float method is particularly preferred when producing large glass sheets.
  • Continuous forming methods other than the float method, such as the fusion method and downdraw method, are also preferred.
  • the chemically strengthened glass may be glass-ceramics.
  • the chemically strengthened glass is glass-ceramics, it is preferably glass-ceramics containing one or more crystals selected from the group consisting of lithium silicate crystals, lithium aluminosilicate crystals, and lithium phosphate crystals.
  • Preferred lithium silicate crystals are lithium metasilicate crystals, lithium disilicate crystals, etc.
  • Preferred lithium phosphate crystals are lithium orthophosphate crystals, etc.
  • Preferred lithium aluminosilicate crystals are ⁇ -spodumene crystals, petalite crystals, etc.
  • the crystallization rate of crystallized glass is preferably 10% or more in terms of improving mechanical strength, more preferably 15% or more, even more preferably 20% or more, and particularly preferably 25% or more. To increase transparency, it is preferably 90% or less, more preferably 70% or less, even more preferably 60% or less, and particularly preferably 50% or less. A low crystallization rate is also advantageous in that it is easier to heat and bend.
  • the crystallization rate can be calculated from X-ray diffraction intensity using the Rietveld method. The Rietveld method is described in "Crystal Analysis Handbook," edited by the Editorial Committee of the Crystallographic Society of Japan (Kyoritsu Shuppan, 1999, pp. 492-499).
  • the average particle size of the precipitated crystals in the crystallized glass is preferably 300 nm or less, more preferably 200 nm or less, even more preferably 150 nm or less, and particularly preferably 100 nm or less.
  • the average particle size of the precipitated crystals can be determined from transmission electron microscope (TEM) images. It can also be estimated from scanning electron microscope (SEM) images.
  • a third embodiment of the mother glass composition which is different from the first and second embodiments of the mother glass composition, is, on an oxide basis, SiO2 50-85%, 4-25% Al 2 O 3 , B2O3 0-10% ; P2O5 0-10 % 0 to 10% Li 2 O, 5-20% Na 2 O, K 2 O 0.3 to 6%, ZnO 0 to 5%, MgO 1 to 20%, CaO 0 to 5%, SrO 0 to 5%, BaO 0 to 5%, TiO2 0-3%, ZrO2 0-3%, and It is preferable that Y 2 O 3 is contained in an amount of 0 to 3%.
  • a third embodiment of the mother glass composition will be described below.
  • the SiO2 content is more preferably 56% or more, and even more preferably 59% or more.
  • the SiO2 content is more preferably 80% or less, and even more preferably 70% or less.
  • the content of Al 2 O 3 is more preferably 5% or more, and further preferably 7% or more.
  • the content of Al 2 O 3 is more preferably 20% or less, and further preferably 15% or less.
  • the ratio of the SiO2 content to the Al2O3 content is preferably 3.4 or more, more preferably 5.1 or more. In many cases, the ratio is 17.0 or less, and preferably 10.2 or less.
  • the B2O3 content is more preferably 0.1% or more, and even more preferably 0.5% or more.
  • the B2O3 content is more preferably 6% or less , and even more preferably 4% or less.
  • the B2O3 content is also preferably 0%. That is, it is also preferable that the third embodiment of the mother glass composition does not contain B2O3 .
  • the Li 2 O content is more preferably 0.5% or more, and even more preferably 1% or more.
  • the Li 2 O content is more preferably 4% or less, and even more preferably 2% or less. It is also preferable that the Li 2 O content is 0%. That is, it is also preferable that the third embodiment of the mother glass composition does not contain Li 2 O.
  • the Na 2 O content is more preferably 10% or more, even more preferably 11% or more, particularly preferably 11.50% or more, and most preferably 12% or more.
  • the Na 2 O content is more preferably 18% or less, and even more preferably 16% or less, based on the oxide.
  • the content of K 2 O is more preferably 0.4% or more, and even more preferably 0.5% or more.
  • the content of K 2 O may be 1% or more, 2% or more, or 3% or more on an oxide basis. Moreover, the content of K 2 O is more preferably 5% or less, and even more preferably 4.5% or less.
  • the content of K 2 O may be 3% or less, 2% or less, or 1% or less.
  • the ratio of the content of K 2 O to the content of Na 2 O is preferably 0.91 or less, more preferably 0.76 or less. The ratio is often 0.01 or more, and preferably 0.04 or more.
  • the ZnO content is more preferably 0.1% or more, and even more preferably 0.5% or more. Furthermore, the ZnO content is more preferably 3% or less, and even more preferably 2% or less. It is also preferable that the ZnO content be 0%. In other words, it is also preferable that the third embodiment of the mother glass composition does not contain ZnO.
  • the MgO content is preferably 3% or more, and even more preferably 6% or more. Furthermore, the MgO content is preferably 18% or less, and even more preferably 12% or less.
  • the CaO content is preferably 0.01% or more, and even more preferably 0.02% or more.
  • the CaO content is preferably 3% or less, and even more preferably 1% or less.
  • the SrO content is more preferably 0.01% or more, and even more preferably 0.05% or more. Furthermore, the SrO content is more preferably 2% or less, and even more preferably 1% or less. The SrO content may be 0%. In other words, the third embodiment of the mother glass composition does not need to contain SrO.
  • the BaO content is more preferably 0.01% or more, and even more preferably 0.02% or more. Furthermore, the BaO content is more preferably 2% or less, and even more preferably 1% or less. The BaO content may be 0%. In other words, the third embodiment of the mother glass composition does not need to contain BaO.
  • the TiO2 content is more preferably 0.01% or more, and even more preferably 0.02% or more.
  • the TiO2 content is more preferably 1% or less, and even more preferably 0.5% or less.
  • the TiO2 content may be 0%. That is, the third embodiment of the mother glass composition does not need to contain TiO2 .
  • the ZrO2 content is more preferably 0.05% or more, and even more preferably 0.10% or more.
  • the ZrO2 content is more preferably 1.5% or less, and even more preferably 1% or less.
  • the Y2O3 content is more preferably 0.02% or more, and even more preferably 0.04% or more.
  • the Y2O3 content is more preferably 1% or less, and even more preferably 0.5% or less.
  • the Y2O3 content may be 0%. That is, the third embodiment of the mother glass composition does not need to contain Y2O3 .
  • a third embodiment of the mother glass composition may include HfO2 .
  • the content of HfO2 is preferably 0.02% or more, and more preferably 0.04% or more.
  • the content of HfO2 is preferably 1% or less, and more preferably 0.5% or less.
  • a third embodiment of the mother glass composition may include SnO2 .
  • the content of SnO2 is preferably 0.005% or more, and more preferably 0.01% or more.
  • the content of SnO2 is preferably 1% or less, and more preferably 0.50% or less.
  • the Young's modulus of the glass for chemical strengthening is preferably 70 GPa or more, more preferably 73 GPa or more, still more preferably 80 GPa or more, and particularly preferably 83 GPa or more.
  • the "Young's modulus” is measured using a cut glass piece by an ultrasonic pulse method in accordance with JIS R 1602.
  • the fracture toughness value (K IC ) of the chemically strengthened glass is preferably 0.70 MPa ⁇ m 1/2 or more, more preferably 0.75 MPa ⁇ m 1/2 or more, and even more preferably 0.80 MPa ⁇ m 1/2 or more.
  • the fracture toughness value K IC is often 2.00 MPa ⁇ m 1/2 or less, and preferably 1.80 MPa ⁇ m 1/2 or less.
  • the "fracture toughness value K IC" is measured with reference to the DCDC method [Reference: M. Y. He, M. R. Turner and A. G. Evans, Acta Metall. Mater. 43 (1995) 3453.].
  • the specific metal salt containing lithium is recovered from the molten salt subjected to chemical strengthening treatment by the method for recovering a metal component of the present invention, and the molten salt from which the specific metal salt has been recovered is again subjected to chemical strengthening treatment.
  • the chemical strengthening treatment and the molten salt regeneration treatment will be described in detail below.
  • a chemical strengthening treatment is carried out by immersing the glass for chemical strengthening in a chemical strengthening molten salt.
  • the preferred composition of the glass for chemical strengthening is as described in the section on the method for producing the glass for chemical strengthening.
  • the preferred composition of the chemical strengthening molten salt is as described in the section on the method for recovering metal components.
  • the chemical strengthening treatment may be repeatedly performed using a chemical strengthening molten salt. That is, the chemical strengthening treatment may be performed by immersing another chemically strengthened glass in the chemically strengthening molten salt in which the chemically strengthened glass has been immersed one or more times.
  • chemical strengthening treatment is repeatedly performed using a chemical strengthening molten salt, the concentration of components (e.g., lithium ions) that were contained in the chemically strengthened glass increases in the chemical strengthening molten salt. If the concentration of the components that were contained in the chemically strengthened glass increases in the chemical strengthening molten salt, the components in the chemically strengthened glass become less likely to be exchanged with ions contained in the chemical strengthening molten salt, and chemical strengthening may not proceed sufficiently.
  • a specific metal salt for example, a specific metal salt containing lithium
  • the chemical strengthening molten salt is regenerated. It is made into a state where it can be subjected to the chemical strengthening treatment again.
  • the method of chemical strengthening treatment is not particularly limited, and known methods can be applied.
  • the conditions of the chemical strengthening treatment can be appropriately adjusted depending on the chemical strengthening glass and chemical strengthening molten salt used.
  • chemical strengthening treatment can be performed by immersing the glass for chemical strengthening in a chemical strengthening molten salt heated to 360 to 600° C. for 0.1 to 500 hours.
  • the heating temperature of the chemical strengthening molten salt is preferably 375° C. or higher and 500° C. or lower.
  • the immersion time of the glass plate in the molten salt is preferably 0.3 hours or longer and 200 hours or shorter.
  • the chemical strengthening treatment may be performed only once, or may be performed multiple times under two or more different conditions (multi-stage strengthening).
  • the chemical strengthening treatment may be performed in one stage, but it is also preferable to perform chemical strengthening treatment in two or more stages. That is, the chemical strengthening treatment may use two or more chemical strengthening molten salts with different compositions.
  • the lithium ion content relative to the total mass of the chemical strengthening molten salt as the predetermined value is, for example, preferably 200 ppm by mass or more, more preferably 1,000 ppm by mass or more, even more preferably 2,000 ppm by mass or more, and particularly preferably 3,000 ppm by mass or more. Furthermore, the lithium ion content relative to the total mass of the chemical strengthening molten salt as the predetermined value is, for example, preferably 50,000 ppm by mass or less, more preferably 20,000 ppm by mass or less, and even more preferably 10,000 ppm by mass or less.
  • the content of a component (e.g., lithium ion) contained in the specific metal salt to be recovered in the chemical strengthening molten salt can be analyzed by, for example, atomic absorption spectrometry.
  • the predetermined standard is preferably set to a sodium ion content of a predetermined value or less relative to the total mass of the chemical strengthening molten salt.
  • the sodium ion content relative to the total mass of the chemical strengthening molten salt as the predetermined value is, for example, preferably 200 ppm by mass or more, more preferably 500 ppm by mass or more, even more preferably 2,000 ppm by mass or more, particularly preferably 4,000 ppm by mass or more, and most preferably 5,000 ppm by mass or more.
  • the lithium ion content relative to the total mass of the chemical strengthening molten salt as the predetermined value is, for example, preferably 60,000 ppm by mass or less, more preferably 40,000 ppm by mass or less, and even more preferably 20,000 ppm by mass or less.
  • the specific metal salt is recovered by the method for recovering metal components of the present invention, and a molten salt regeneration treatment is performed to regenerate the chemically strengthening molten salt. Note that in the method for producing chemically strengthened glass of the present invention, the chemical strengthening treatment and the molten salt regeneration treatment are performed alternately.
  • the specific method for the molten salt regeneration treatment is the same as the above-mentioned method for regenerating a molten salt of the present invention, and therefore, description thereof will be omitted.
  • the specific metal salt preferably contains lithium or sodium, and more preferably contains lithium.
  • the components of the chemical strengthening molten salt may be adjusted after recovering the specific metal salt from the chemical strengthening molten salt.
  • adding a sulfate may be used to adjust the components of the molten salt.
  • salts other than sulfate e.g., nitrates such as one or more components selected from the group consisting of sodium nitrate, potassium nitrate, and potassium sulfate
  • nitrates such as one or more components selected from the group consisting of sodium nitrate, potassium nitrate, and potassium sulfate
  • the composition of the molten salt may be adjusted by adding a carbonate, or by adding a salt other than the carbonate (for example, a nitrate such as potassium nitrate) simultaneously with the addition of the carbonate.
  • the molten salt regeneration treatment may be carried out once or twice or more times. It is also preferable to analyze the components of the chemical strengthening molten salt after the molten salt regeneration treatment has been carried out, and if the above-mentioned specified criteria are met, the chemical strengthening molten salt is subjected to the chemical strengthening treatment, but if the above-mentioned specified criteria are not met, the molten salt regeneration treatment is carried out again.
  • the above-mentioned chemical strengthening treatment and molten salt regeneration treatment are alternately performed.
  • the number of times that the alternation is performed may be one or more, and may be repeated two or more times.
  • chemically strengthened glass obtained by the above-mentioned method for producing chemically strengthened glass. That is, it is also preferable to produce chemically strengthened glass using the specific metal salt recovered by the molten salt regeneration treatment as a raw material, and then subject the chemically strengthened glass to the chemical strengthening treatment.
  • chemically strengthened glass is produced using the specific metal salt recovered by the molten salt regeneration treatment as a raw material, the components transferred to the chemically strengthening molten salt by the chemical strengthening treatment can be effectively utilized, which is preferable.
  • Another aspect of the method for producing chemically strengthened glass of the present invention is a method for producing chemically strengthened glass, which comprises recovering a specific metal salt from a molten salt and immersing a glass containing silicon, aluminum, and lithium in the molten salt after the specific metal salt has been recovered.
  • the specific metal component contained in the specific metal salt preferably includes lithium.
  • the molten salt obtained after recovering the specific metal salt is not particularly limited as long as it is a molten salt obtained by the above-mentioned method for recovering a metal salt of the present invention, and the molten salt obtained by the above-mentioned method for regenerating a molten salt can be preferably used.
  • the above-mentioned chemically strengthened glass can be preferably applied. It is also preferable to use the chemically strengthened glass obtained by the above-mentioned method for producing chemically strengthened glass.
  • the chemical strengthening treatment is carried out by immersing the glass containing silicon, aluminum, and lithium in the molten salt.
  • the chemical strengthening treatment is as described above, and the preferred embodiments are also as described above.
  • the molten salt after recovering the specific metal salt does not substantially contain solid-state salt.
  • the molten salt being substantially free of solid salt means that no precipitate is observed when the molten salt is visually observed. It is preferable that the molten salt does not contain a solid salt, since this results in excellent uniformity of strengthening within the glass surface.
  • the stress of the chemically strengthened glass was measured using a scattered light photoelastic stress meter (SLP: Scattered Light Photoelastic Stress Meter).
  • SLP Scattered Light Photoelastic Stress Meter
  • FSM optical waveguide surface stress meter
  • FSM-6000UV manufactured by Orihara Seisakusho
  • a molten salt A1 having the following composition was prepared.
  • the molten salt A1 was heated to 410° C. to be in a molten state.
  • the molten salt A1 was heated by placing a container containing the molten salt in a mantle heater. When heating with the mantle heater, a thermocouple was brought into contact with the molten salt A1 to measure the temperature. A K thermocouple was used as the thermocouple.
  • a jig having a mesh portion and a handle portion (corresponding to the first jig) was immersed in the molten salt A1.
  • the mesh portion had a mesh size of 0.09 mm.
  • the output of the mantle heater was controlled and the molten salt A1 was cooled to 280°C by air cooling.
  • the molten salt A1 was stirred for 30 minutes by rotating the stirring blade at 300 rpm (revolutions per minute) while the temperature of the molten salt A1 was maintained at 280° C. Thereafter, the molten salt A1 was allowed to stand for 60 minutes without stirring while the temperature of the molten salt A1 was maintained at 280° C.
  • the specific metal salt was precipitated in the molten salt A1.
  • molten salt A2 the molten salt A1 from which the specific metal salt has been recovered. It was confirmed that the recovered specific metal salt contained lithium.
  • the contents of lithium atoms in the molten salts A1 and A2 before the cooling are shown in Table 1 below.
  • Table 1 also shows the contents of lithium atoms contained in the recovered specific metal salts.
  • chemical strengthening treatment was performed under the following conditions using the molten salt A1 and molten salt A2 before the cooling to obtain chemically strengthened glass.
  • the stress profile of the obtained chemically strengthened glass was measured to obtain the compressive stress value at a depth of 50 ⁇ m from the surface.
  • the results are also shown in Table 1 below (the column "CS50 of chemically strengthened glass" in the table).
  • the methods for measuring the content of components in molten salts A1 and A2 were as described above.
  • the content of components in the specific metal salt was also analyzed by the same method.
  • Example 2 Molten salt A3, which had the same composition as molten salt A1 prepared in Example 1, was prepared in the same manner as in Example 1. Note that molten salt A1 and molten salt A3 were prepared separately, and therefore their compositions did not strictly match. With the molten salt A3 at 410°C, a jig (corresponding to the second jig described above) having a salt deposition portion and a handle portion, which had a structure formed by folding a plate (#20 mesh (opening size: 0.98 mm)) into an accordion-like shape, was immersed. The molten salt A3 was allowed to stand for 60 minutes without stirring while the temperature was maintained at 280°C. By the above procedure, the specific metal salt was precipitated in the molten salt A1. When the jig was checked, it was confirmed that the salt had precipitated on the surface of the salt precipitated portion.
  • the jig was lifted out of the molten salt A3, the specific metal salt was separated from the molten molten salt A1, and a portion of the specific metal salt adhering to the jig was recovered.
  • the molten salt A3 after the specific metal salt was recovered will be referred to as "molten salt A4" for convenience.
  • the specific metal salt adhering to the jig from which the portion was recovered will be referred to as "specific metal salt B1" for convenience. It was confirmed that the recovered specific metal salt B1 contained lithium.
  • the jig with the specific metal salt B1 attached was heated at 400°C for 3 hours.
  • the contents of lithium atoms in molten salts A3 and A4 before the cooling are shown in Table 2 below.
  • Table 2 also shows the contents of lithium atoms contained in specific metal salts B1, B2, and B3.
  • chemical strengthening treatment was performed under the same conditions as in Example 1 using the molten salts A3 and A4 before the cooling, to obtain chemically strengthened glass.
  • the stress profile of the obtained chemically strengthened glass was measured, and the compressive stress value at a depth of 50 ⁇ m from the surface was obtained.
  • the results are also shown in Table 2 below (the column "CS50 of chemically strengthened glass" in the table).
  • the content of each component in the molten salts A3 and A4 was measured by the same method as described above.
  • the content of each component in the specific metal salt was also analyzed by the same method.
  • Examples 1 and 2 chemically strengthened glasses having the following compositions were used. The compositions are expressed in mole percentages based on oxides. Some trace components may be added as an extra percentage. SiO2 : 66.2% Al2O3 : 11.2 % MgO: 3.1% CaO: 0.2% TiO2 : 0.1% ZrO2 : 1.3% Y2O3 : 0.5 % Li2O : 10.4% Na2O : 5.6% K2O : 1.5% In Examples 1 and 2, the chemically strengthened glass having the above composition was subjected to a chemical strengthening treatment under the following conditions. ⁇ Chemical strengthening temperature: 410°C Chemical strengthening time: 2 hours
  • Example 3 Molten salt A5, which had the same composition as molten salt A1 prepared in Example 1, was prepared in the same manner as in Example 1. Note that molten salt A1 and molten salt A5 were prepared separately, and therefore their compositions do not strictly match. With the molten salt A5 at 410°C, a jig (corresponding to the second jig described above) having a salt deposition portion and a handle portion, which had a structure formed by folding a plate (#20 mesh (opening size: 0.98 mm)) into an accordion-like shape, was immersed. The molten salt A5 was allowed to stand for 60 minutes without stirring while the temperature was maintained at 290°C. By the above procedure, the specific metal salt was precipitated in the molten salt A5. When the jig was checked, it was confirmed that the salt had precipitated on the surface of the salt precipitated portion.
  • Example 3 the molten salt A5 from which the specific metal salt was recovered will be referred to as "molten salt A6" for convenience.
  • specific metal salt adhered to the jig will be referred to as "specific metal salt C1" for convenience.
  • the jig with the specific metal salt C1 attached thereto was placed on top of a container containing molten salt A6, and the atmosphere in which the jig was placed was heated to 300°C and maintained for 30 minutes.
  • the sodium atom contents in the molten salts A10 and A11 before the cooling are shown in Table 5 below.
  • Table 5 also shows the sodium atom contents in the recovered specific metal salts.
  • chemical strengthening treatment was performed under the following conditions using the molten salt A10 and molten salt A11 before the cooling to obtain chemically strengthened glass.
  • the stress profile of the obtained chemically strengthened glass was measured to obtain the compressive stress value at the outermost surface.
  • the results are also shown in Table 5 below (the column "CS of chemically strengthened glass” in the table).
  • the methods for measuring the content of components in molten salts A12 and A13 were as described above.
  • the content of components in the specific metal salt was also analyzed by the same method.
  • a molten salt A12 having the following composition was prepared.
  • a jig (corresponding to the second jig described above) having a salt deposition portion and a handle portion, which had a structure formed by folding a plate (#20 mesh (opening size: 0.98 mm)) into an accordion-like shape, was immersed in molten salt A12 heated to 410°C.
  • the molten salt A12 was left to stand for 4 hours while the temperature thereof was maintained at 290°C.
  • the specific metal salt was precipitated in the molten salt A12.
  • the jig was checked, it was confirmed that the salt had precipitated on the surface of the salt precipitated portion.
  • Example 6 the molten salt A12 from which the specific metal salt was recovered will be referred to as "molten salt A13" for convenience.
  • specific metal salt F1 the specific metal salt adhered to the jig.
  • the jig with the specific metal salt F1 attached thereto was placed on top of a container containing molten salt A12, and the atmosphere in which the jig was placed was heated to 300°C and maintained for 30 minutes.
  • the content of lithium atoms in the molten salt A12 before the cooling is shown in Table 6 below.
  • Table 6 also shows the content of lithium atoms contained in the specific metal salt F2.
  • the methods for measuring the content of components in molten salts A12 and A13 were as described above.
  • the content of components in the specific metal salt was also analyzed by the same method.
  • molten salts (molten salts A14 to A17) having the compositions shown in Table 7 were prepared. Each of the obtained molten salts was heated to a molten state at the pre-cooling temperature shown in Table 7. The molten salt was heated by placing a container containing the molten salt in a mantle heater. When heating was performed using a mantle heater, a thermocouple was placed in contact with each molten salt to measure the temperature. A K thermocouple was used as the thermocouple.
  • a jig (corresponding to the second jig) having a salt deposition portion and a handle portion, which had a structure in which plates (#20 mesh (opening size: 0.98 mm)) were arranged at equal intervals, was immersed in each molten salt.
  • the plate was placed so that its in-plane direction was parallel to the direction of gravity.
  • the output of the mantle heater was controlled and each molten salt was cooled by air to the temperature (temperature after cooling) shown in Table 7. While the temperature of each molten salt was maintained at the above temperature, it was allowed to stand without stirring for the time shown in Table 7 (the holding time at the temperature after cooling).
  • the specific metal salt was precipitated in each molten salt.
  • each of the recovered specific metal salts contained sodium.
  • Table 7 shows the sodium atom content of the recovered specific metal salts.
  • Table 7 also shows the composition of the molten salt after cooling (after the specific metal salt was precipitated). Furthermore, potassium carbonate and potassium nitrate were added to the cooled molten salt so as to obtain the composition shown in Table 7 (molten salt after salt addition).
  • compositions of the chemically strengthened glasses used in the chemical strengthening using each molten salt are as follows. The compositions are expressed in mole percentages based on oxides.
  • Glass material 1 has the same composition as the chemically strengthened glass used in Example 5.
  • ⁇ Glass material 2 SiO2 : 64.45% Al2O3 : 10.5 % MgO: 8.3% ZrO2 : 0.15% Na2O : 16.0% K2O : 0.6%

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Abstract

The present invention addresses the problem of providing a method for recovering a metal component which easily recovers a specific metal component from a molten salt. Provided is a method for recovering a metal component, wherein a molten salt containing a specific metal component is cooled, a specific metal salt containing the specific metal component is precipitated while maintaining a molten state of the molten salt, and the specific metal salt is recovered from the molten salt that is in the molten state.

Description

金属成分の回収方法、溶融塩の再生方法、化学強化用ガラスの製造方法、化学強化ガラスの製造方法METHOD FOR RECOVERING METAL COMPONENTS, METHOD FOR REGENERATING MOLTEN SALT, METHOD FOR PRODUCING CHEMICALLY STRENGTHENED GLASS, AND METHOD FOR PRODUCING CHEMICALLY STRENGTHENED GLASS

　本発明は、金属成分の回収方法に関する。より具体的には、溶融塩から特定の金属成分を回収する金属成分の回収方法に関する。
　また、本発明は、溶融塩の再生方法、化学強化用ガラスの製造方法にも関する。 The present invention relates to a method for recovering a metal component, and more particularly to a method for recovering a specific metal component from a molten salt.
The present invention also relates to a method for regenerating molten salt and a method for producing glass for chemical strengthening.

　近年、携帯電話、スマートフォン、および、タブレット端末等のディスプレイ装置の保護ならびに美観を高める目的で、カバーガラスが用いられている。これらの用途のカバーガラスには、衝撃等による破損を抑制するため、優れた強度が求められている。 In recent years, cover glass has been used to protect and enhance the appearance of display devices such as mobile phones, smartphones, and tablet devices. Cover glass for these applications is required to have excellent strength to prevent breakage due to impacts, etc.

　従来から、硝酸カリウム溶融塩等にガラスを浸漬して化学強化処理をすることにより、ガラスの面強度を高める手法が知られている。例えば、特許文献１では、２段階の化学強化により、比較的大きい表面圧縮応力層と、圧縮応力層深さが得られるリチウムアルミノシリケートガラスが開示されている。リチウムアルミノシリケートガラスは、１段目の化学強化処理にナトリウム塩を用い、２段目の化学強化処理にカリウム塩を用いる２段階の化学強化処理によって、化学強化ガラスの内部に生じる引張応力を抑制しつつ、表面応力および応力層深さをともに大きくできることが記載されている。 A known method for increasing the surface strength of glass is to chemically strengthen the glass by immersing it in a molten salt such as potassium nitrate. For example, Patent Document 1 discloses lithium aluminosilicate glass that undergoes a two-stage chemical strengthening process to achieve a relatively large surface compressive stress layer and compressive stress layer depth. It describes how lithium aluminosilicate glass undergoes a two-stage chemical strengthening process, using sodium salts in the first stage and potassium salts in the second stage, which increases both the surface stress and the stress layer depth while suppressing the tensile stress generated within the chemically strengthened glass.

特表２０１３－５２０３８８号公報Special Publication No. 2013-520388

　特許文献１に記載の方法では、溶融塩にリチウムアルミノシリケートガラス等のガラスを浸漬して、化学強化処理を行うと、溶融塩中のリチウムの含有量が上昇していた。本発明者らが検討を行ったところ、化学強化処理を行った後のリチウムの含有量が上昇した溶融塩を用いて、更に別の化学強化処理を行った場合には、その化学強化処理が十分に進行しないことを知見した。
　すなわち、溶融塩中の特定の金属成分（例えば、リチウムを含む成分）を回収する方法が求められていた。
　また、溶融塩を用いる方法は、広く用いられており、例えば、抽出および精錬等の分野で溶融塩を用いる場合がある。つまり、化学強化処理を行うための溶融塩のみならず、特定の金属成分を溶融塩から回収する技術が求められていた。
　一方で、溶融塩から特定の金属成分を回収する方法は、簡便な方法が知られておらず、簡便に特定の金属成分を溶融塩から回収する技術が求められていた。 In the method described in Patent Document 1, when glass such as lithium aluminosilicate glass is immersed in molten salt and chemically strengthened, the lithium content in the molten salt increases. The inventors have conducted research and found that when a further chemical strengthening treatment is performed using molten salt in which the lithium content has increased after the chemical strengthening treatment, the chemical strengthening treatment does not proceed sufficiently.
That is, there has been a demand for a method for recovering specific metal components (for example, components containing lithium) in molten salt.
Furthermore, methods using molten salts are widely used, and for example, molten salts are used in the fields of extraction, refining, etc. In other words, there has been a demand for not only molten salts for chemical strengthening treatment but also technology for recovering specific metal components from molten salts.
On the other hand, there is no known simple method for recovering specific metal components from molten salt, and there has been a demand for a technology that can easily recover specific metal components from molten salt.

　本発明は、上記課題に鑑みてなされたものであり、特定の金属成分を溶融塩から簡便に回収する金属成分の回収方法の提供を課題とする。
　また、本発明は、溶融塩の再生方法、化学強化用ガラスの製造方法、および、化学強化ガラスの製造方法の提供も課題とする。 The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a method for recovering a metal component that allows a specific metal component to be recovered simply and easily from a molten salt.
Another object of the present invention is to provide a method for regenerating molten salt, a method for producing glass for chemical strengthening, and a method for producing chemically strengthened glass.

　本発明者らは、上記課題について鋭意検討した結果、溶融塩の溶融状態を保ったまま冷却し、特定の金属成分を含む塩を析出させると、特定の金属成分を溶融塩から回収可能なことを見出し、本発明に至った。 As a result of extensive research into the above-mentioned issues, the inventors discovered that by cooling a molten salt while maintaining its molten state and precipitating a salt containing a specific metal component, it is possible to recover the specific metal component from the molten salt, leading to the present invention.

　すなわち、発明者らは、以下の構成により上記課題が解決できることを見出した。
　〔１〕　特定金属成分を含む溶融塩を冷却し、上記溶融塩の溶融状態を保ったまま上記特定金属成分を含む特定金属塩を析出させ、上記特定金属塩を溶融状態の上記溶融塩から回収する、金属成分の回収方法。
　〔２〕　上記溶融塩が、硝酸塩、硫酸塩、亜硝酸塩、亜硫酸塩、炭酸塩、リン酸塩、および、ハロゲン化物塩からなる群から選択される１種以上を含む、〔１〕に記載の金属成分の回収方法。
　〔３〕　上記溶融塩が、硝酸塩と硫酸塩とを含む、または、硝酸塩と炭酸塩とを含む、〔２〕に記載の金属成分の回収方法。
　〔４〕　上記溶融塩が、リチウム塩、ナトリウム塩、および、カリウム塩からなる群から選択される２種以上の塩を含む、〔１〕～〔３〕のいずれか１つに記載の金属成分の回収方法。
　〔５〕　上記溶融塩が、硝酸リチウム、硝酸ナトリウム、および、硝酸カリウムからなる群から選択される２種以上の塩を含み、
　上記溶融塩が、さらに、硫酸ナトリウム、および、硫酸カリウムからなる群から選択される１種以上の塩を含む、〔１〕～〔４〕のいずれか１つに記載の金属成分の回収方法。
　〔６〕　上記特定金属成分が、リチウムを含み、
　上記特定金属塩が、リチウムおよびナトリウムを含み、
　冷却を行う前の上記溶融塩が、上記溶融塩の全質量に対して、リチウム原子を１,０００～５０,０００質量ｐｐｍ含む、〔１〕～〔５〕のいずれか１つに記載の金属成分の回収方法。
　〔７〕　上記特定金属成分が、ナトリウムを含み、
　上記特定金属塩が、ナトリウムおよびカリウムを含み、
　冷却を行う前の上記溶融塩が、上記溶融塩の全質量に対して、ナトリウム原子を５００～６０,０００質量ｐｐｍ含む、〔１〕～〔５〕のいずれか１つに記載の金属成分の回収方法。
　〔８〕　上記溶融塩が、硝酸ナトリウムを含み、硝酸ナトリウムの含有量に対する硝酸カリウムの含有量の比が、質量比で、０．００～２４．００である、〔１〕～〔７〕のいずれか１つに記載の金属成分の回収方法。
　〔９〕　上記溶融塩が、硝酸ナトリウムを含み、硝酸ナトリウムの含有量に対する硝酸カリウムの含有量の比が、質量比で、０．２５～４．００である、〔１〕～〔８〕のいずれか１つに記載の金属成分の回収方法。
　〔１０〕　上記溶融塩が、硫酸塩を含み、上記硫酸塩の含有量が、上記溶融塩の全質量に対して、２．０～５０．０質量％である、〔１〕～〔９〕のいずれか１つに記載の金属成分の回収方法。
　〔１１〕　上記溶融塩が、硫酸塩を含み、上記硫酸塩の含有量が、上記溶融塩の全質量に対して、３．０～２５．０質量％である、〔１〕～〔１０〕のいずれか１つに記載の金属成分の回収方法。
　〔１２〕　上記溶融塩が、炭酸塩を含み、上記炭酸塩の含有量が、上記溶融塩の全質量に対して、２．０～４０．０質量％である、〔１〕～〔１１〕のいずれか１つに記載の金属成分の回収方法。
　〔１３〕　上記特定金属塩を溶融状態の上記溶融塩から回収する際に、
　網状の網部を有する第１治具を用い、上記網部を上記溶融塩から引き上げ、析出した上記特定金属塩を溶融状態の上記溶融塩から回収する、〔１〕～〔１２〕のいずれか１つに記載の金属成分の回収方法。
　〔１４〕　上記特定金属成分を含む上記溶融塩を冷却し、上記溶融塩の溶融状態を保ったまま上記特定金属成分を含む上記特定金属塩を析出させる際に、
　塩析出部を有する第２治具の上記塩析出部の表面に、上記特定金属塩を析出させ、
　上記塩析出部を上記溶融塩から引き上げて、上記特定金属塩を溶融状態の上記溶融塩から回収する、〔１〕～〔１２〕のいずれか１つに記載の金属成分の回収方法。
　〔１５〕　上記特定金属成分を含む上記溶融塩を冷却し、上記溶融塩の溶融状態を保ったまま上記特定金属成分を含む上記特定金属塩を析出させる際に、
　温度制御自在な冷却部を有する第３治具を用い、上記冷却部の温度を変化させることによって上記溶融塩を冷却し、上記冷却部の表面に、上記特定金属塩を析出させ、
　上記冷却部を上記溶融塩から引き上げて、上記特定金属塩を溶融状態の上記溶融塩から回収する、〔１〕～〔１２〕のいずれか１つに記載の金属成分の回収方法。
　〔１６〕　上記特定金属塩を溶融状態の上記溶融塩から回収する際に、
　上記溶融塩が収容される溶融塩収容容器と、
　上記溶融塩収容容器に接続されて、上記溶融塩収容容器から排出された上記溶融塩が再び上記溶融塩収容容器に戻る循環路と、
　上記循環路の途中に配置されて固体を上記溶融塩から分離可能なフィルタと、を用い、
　析出した上記特定金属塩を含む上記溶融塩を、上記循環路に導入し、上記フィルタによって上記特定金属塩を上記溶融塩から分離し、
　上記フィルタから上記特定金属塩を回収する、〔１〕～〔１２〕のいずれか１つに記載の金属成分の回収方法。
　〔１７〕　上記特定金属塩を溶融状態の上記溶融塩から回収したあと、
　回収した上記特定金属塩を、上記溶融塩の融点以上の温度で加熱する、〔１〕～〔１６〕のいずれか１つに記載の金属成分の回収方法。
　〔１８〕　上記特定金属成分を含む３７０℃以上の上記溶融塩を３６０℃以下に冷却し、上記溶融塩の溶融状態を保ったまま上記特定金属成分を含む上記特定金属塩を析出させる、〔１〕～〔１７〕のいずれか１つに記載の金属成分の回収方法。
　〔１９〕　上記特定金属成分を含む４２０℃以上の上記溶融塩を４１０℃以下に冷却し、上記溶融塩の溶融状態を保ったまま上記特定金属成分を含む上記特定金属塩を析出させる、〔１〕～〔１８〕のいずれか１つに記載の金属成分の回収方法。
　〔２０〕　上記冷却前の上記溶融塩の温度と、上記冷却後の上記溶融塩の温度との差が、２０℃以上である、〔１〕～〔１９〕のいずれか１つに記載の金属成分の回収方法。
　〔２１〕　回収された上記特定金属塩が、Ｃｕ　Ｋα線で測定したＸ線回折チャートにおいて、３０．２～３０．５°の範囲に回折ピークが出現する結晶構造の結晶を含む、〔１〕～〔２０〕のいずれか１つに記載の金属成分の回収方法。
　〔２２〕　回収された上記特定金属塩が、Ｃｕ　Ｋα線で測定したＸ線回折チャートにおいて、２３．２～２３．５°の範囲に回折ピークが出現する結晶構造の結晶、２２．４～２２．７°の範囲に回折ピークが出現する結晶構造の結晶、および、２２．８～２３．１°の範囲に回折ピークが出現する結晶構造の結晶からなる群から選択される少なくとも１つの結晶構造の結晶を含む、〔１〕～〔２１〕のいずれか１つに記載の金属成分の回収方法。
　〔２３〕　回収された上記特定金属塩が、ＬｉＮａＳＯ４、ＬｉＫＳＯ４、および、Ｌｉ２ＮａＫ（ＳＯ４）２からなる群から選択される少なくとも１種を含む、〔２２〕に記載の金属成分の回収方法。
　〔２４〕　回収された上記特定金属塩が、Ｃｕ　Ｋα線で測定したＸ線回折チャートにおいて、２８．４～２８．７°の範囲に回折ピークが出現する結晶構造の結晶を含む、〔１〕～〔２１〕のいずれか１つに記載の金属成分の回収方法。
　〔２５〕　回収された上記特定金属塩が、Ｎａ２ＣＯ３を含む、〔２４〕に記載の金属成分の回収方法。
　〔２６〕　〔１〕～〔２５〕のいずれか１つに記載の金属成分の回収方法によって回収された上記特定金属塩を水に溶解して特定金属水溶液を得て、
　上記特定金属水溶液に対して炭酸塩を加え、沈殿物を生成させ、上記沈殿物を回収する、金属成分の回収方法であって、上記特定金属成分が、リチウムまたはナトリウムを含む、金属成分の回収方法。
　〔２７〕　炭酸塩を含む上記特定金属水溶液を８０℃以上として沈殿物を生成させる、〔２６〕に記載の金属成分の回収方法。
　〔２８〕　〔１〕～〔２７〕のいずれか１つに記載の金属成分の回収方法を適用する、溶融塩の再生方法であって、
　上記特定金属成分が、リチウムまたはナトリウムを含み、
　上記溶融塩が、ケイ素と、アルミニウムと、リチウムおよびナトリウムからなる群から選択される少なくとも１種とを含むガラスを浸漬して得られる化学強化後溶融塩である、溶融塩の再生方法。
　〔２９〕　〔１〕～〔２７〕のいずれか１つに記載の金属成分の回収方法によって回収された上記特定金属塩を、化学強化用ガラスの原料の一部として用い、化学強化用ガラスを製造する、化学強化用ガラスの製造方法。
　〔３０〕　〔２６〕に記載の上記沈殿物を、化学強化用ガラスの原料の一部として用い、化学強化用ガラスを製造する、化学強化用ガラスの製造方法。
　〔３１〕　〔１〕～〔２７〕のいずれか１つに記載の金属成分の回収方法によって上記溶融塩から上記特定金属塩を回収し、上記特定金属塩を回収した後の溶融塩に対して、ケイ素と、アルミニウムと、リチウムおよびナトリウムからなる群から選択される少なくとも１種とを含むガラスを浸漬する、化学強化ガラスの製造方法であって、
　上記特定金属成分が、リチウムまたはナトリウムを含む、化学強化ガラスの製造方法。
　〔３２〕　〔１〕～〔２７〕のいずれか１つに記載の金属成分の回収方法によって上記溶融塩から上記特定金属塩を回収し、上記特定金属塩を回収した後の溶融塩に対して、ケイ素、アルミニウムおよびリチウムを含むガラスを浸漬する、化学強化ガラスの製造方法であって、
　上記特定金属塩を回収した後の溶融塩が、実質的に固体状態の塩を含まない、化学強化ガラスの製造方法。
　〔３３〕　化学強化用溶融塩を用いる化学強化ガラスの製造方法であって、
　上記化学強化用溶融塩に対して化学強化用ガラスを浸漬する化学強化処理と、
　上記化学強化用ガラスを浸漬した上記化学強化用溶融塩を上記溶融塩として、〔１〕～〔２７〕のいずれか１つに記載の金属成分の回収方法によって上記特定金属塩を回収し、上記化学強化用溶融塩を再生する溶融塩再生処理とを、交互に行う、化学強化ガラスの製造方法。
　〔３４〕　上記溶融塩再生処理において、上記化学強化用溶融塩に対して硫酸塩を添加する、〔３３〕に記載の化学強化ガラスの製造方法。 That is, the inventors have found that the above problems can be solved by the following configuration.
[1] A method for recovering a metal component, comprising cooling a molten salt containing a specific metal component, precipitating a specific metal salt containing the specific metal component while maintaining the molten state of the molten salt, and recovering the specific metal salt from the molten salt.
[2] The method for recovering a metal component according to [1], wherein the molten salt contains at least one selected from the group consisting of nitrates, sulfates, nitrites, sulfites, carbonates, phosphates, and halide salts.
[3] The method for recovering a metal component according to [2], wherein the molten salt contains a nitrate and a sulfate, or a nitrate and a carbonate.
[4] The method for recovering a metal component according to any one of [1] to [3], wherein the molten salt contains two or more salts selected from the group consisting of lithium salts, sodium salts, and potassium salts.
[5] The molten salt contains two or more salts selected from the group consisting of lithium nitrate, sodium nitrate, and potassium nitrate,
[5] The method for recovering a metal component according to any one of [1] to [4], wherein the molten salt further contains one or more salts selected from the group consisting of sodium sulfate and potassium sulfate.
[6] The specific metal component contains lithium,
The specific metal salt includes lithium and sodium,
[6] The method for recovering a metal component according to any one of [1] to [5], wherein the molten salt before cooling contains lithium atoms in an amount of 1,000 to 50,000 ppm by mass relative to the total mass of the molten salt.
[7] The specific metal component contains sodium,
The specific metal salts include sodium and potassium,
[6] The method for recovering a metal component according to any one of [1] to [5], wherein the molten salt before cooling contains sodium atoms in an amount of 500 to 60,000 ppm by mass relative to the total mass of the molten salt.
[8] The method for recovering a metal component according to any one of [1] to [7], wherein the molten salt contains sodium nitrate, and the ratio of the potassium nitrate content to the sodium nitrate content is 0.00 to 24.00 in mass ratio.
[9] The method for recovering a metal component according to any one of [1] to [8], wherein the molten salt contains sodium nitrate, and the ratio of the potassium nitrate content to the sodium nitrate content is 0.25 to 4.00 in mass ratio.
[10] The method for recovering a metal component according to any one of [1] to [9], wherein the molten salt contains a sulfate, and the content of the sulfate is 2.0 to 50.0 mass% relative to the total mass of the molten salt.
[11] The method for recovering a metal component according to any one of [1] to [10], wherein the molten salt contains a sulfate, and the content of the sulfate is 3.0 to 25.0 mass% relative to the total mass of the molten salt.
[12] The method for recovering a metal component according to any one of [1] to [11], wherein the molten salt contains a carbonate, and the content of the carbonate is 2.0 to 40.0 mass% relative to the total mass of the molten salt.
[13] When recovering the specific metal salt from the molten salt in a molten state,
[13] The method for recovering a metal component according to any one of [1] to [12], wherein a first jig having a mesh portion is used to pull up the mesh portion from the molten salt, and the precipitated specific metal salt is recovered from the molten salt in a molten state.
[14] When the molten salt containing the specific metal component is cooled and the specific metal salt containing the specific metal component is precipitated while maintaining the molten state of the molten salt,
causing the specific metal salt to precipitate on a surface of the salt deposition portion of a second jig having the salt deposition portion;
The method for recovering a metal component according to any one of [1] to [12], wherein the salt precipitate portion is pulled up from the molten salt, and the specific metal salt is recovered from the molten salt in a molten state.
[15] When the molten salt containing the specific metal component is cooled and the specific metal salt containing the specific metal component is precipitated while maintaining the molten state of the molten salt,
a third jig having a temperature-controllable cooling section is used to change the temperature of the cooling section to cool the molten salt, thereby precipitating the specific metal salt on the surface of the cooling section;
The method for recovering a metal component according to any one of [1] to [12], wherein the cooling section is pulled out from the molten salt, and the specific metal salt is recovered from the molten salt in a molten state.
[16] When recovering the specific metal salt from the molten salt in a molten state,
a molten salt storage container in which the molten salt is stored;
a circulation path connected to the molten salt storage container, through which the molten salt discharged from the molten salt storage container returns to the molten salt storage container;
a filter disposed midway through the circulation path and capable of separating solids from the molten salt;
introducing the molten salt containing the precipitated specific metal salt into the circulation path, and separating the specific metal salt from the molten salt using the filter;
The method for recovering a metal component according to any one of [1] to [12], wherein the specific metal salt is recovered from the filter.
[17] After recovering the specific metal salt from the molten salt in a molten state,
The method for recovering a metal component according to any one of [1] to [16], wherein the recovered specific metal salt is heated at a temperature equal to or higher than the melting point of the molten salt.
[18] The method for recovering a metal component according to any one of [1] to [17], wherein the molten salt containing the specific metal component at a temperature of 370°C or higher is cooled to 360°C or lower, and the specific metal salt containing the specific metal component is precipitated while maintaining the molten state of the molten salt.
[19] The method for recovering a metal component according to any one of [1] to [18], wherein the molten salt containing the specific metal component at a temperature of 420°C or higher is cooled to 410°C or lower, and the specific metal salt containing the specific metal component is precipitated while maintaining the molten state of the molten salt.
[20] The method for recovering metal components according to any one of [1] to [19], wherein the difference between the temperature of the molten salt before the cooling and the temperature of the molten salt after the cooling is 20°C or more.
[21] The method for recovering a metal component according to any one of [1] to [20], wherein the recovered specific metal salt contains crystals having a crystal structure in which a diffraction peak appears in the range of 30.2 to 30.5° in an X-ray diffraction chart measured with Cu Kα radiation.
[22] The method for recovering a metal component according to any one of [1] to [21], wherein the recovered specific metal salt comprises crystals of at least one crystal structure selected from the group consisting of crystals having a crystal structure in which a diffraction peak appears in the range of 23.2 to 23.5° in an X-ray diffraction chart measured with Cu Kα rays, crystals having a crystal structure in which a diffraction peak appears in the range of 22.4 to 22.7°, and crystals having a crystal structure in which a diffraction peak appears in the range of 22.8 to 23.1°.
[23] The method for recovering a metal component according to [22], wherein the recovered specific metal salt comprises at least one selected from the group consisting of LiNaSO 4 , LiKSO 4 , and Li 2 NaK(SO 4 ) 2 .
[24] The method for recovering a metal component according to any one of [1] to [21], wherein the recovered specific metal salt contains crystals having a crystal structure in which a diffraction peak appears in the range of 28.4 to 28.7° in an X-ray diffraction chart measured with Cu Kα radiation.
[25] The method for recovering a metal component according to [24], wherein the recovered specific metal salt contains Na 2 CO 3 .
[26] The specific metal salt recovered by the method for recovering a metal component according to any one of [1] to [25] is dissolved in water to obtain a specific metal aqueous solution,
A method for recovering a metal component, comprising adding a carbonate to the specific metal aqueous solution to form a precipitate, and recovering the precipitate, wherein the specific metal component includes lithium or sodium.
[27] The method for recovering a metal component according to [26], wherein the aqueous solution of the specific metal containing a carbonate is heated to 80° C. or higher to form a precipitate.
[28] A method for regenerating a molten salt, which applies the method for recovering a metal component according to any one of [1] to [27],
the specific metal component includes lithium or sodium,
A method for regenerating a molten salt, wherein the molten salt is a chemically strengthened molten salt obtained by immersing glass containing silicon, aluminum, and at least one selected from the group consisting of lithium and sodium.
[29] The specific metal salt recovered by the method for recovering a metal component according to any one of [1] to [27] is used as part of a raw material for chemically strengthened glass, and chemically strengthened glass is produced. A method for producing chemically strengthened glass.
[30] A method for producing chemically strengthened glass, comprising using the precipitate according to [26] as part of a raw material for chemically strengthened glass to produce chemically strengthened glass.
[31] A method for producing chemically strengthened glass, comprising recovering the specific metal salt from the molten salt by the method for recovering a metal component according to any one of [1] to [27], and immersing glass containing silicon, aluminum, and at least one selected from the group consisting of lithium and sodium in the molten salt after the specific metal salt has been recovered.
The method for producing chemically strengthened glass, wherein the specific metal component contains lithium or sodium.
[32] A method for producing chemically strengthened glass, comprising recovering the specific metal salt from the molten salt by the method for recovering a metal component according to any one of [1] to [27], and immersing glass containing silicon, aluminum, and lithium in the molten salt from which the specific metal salt has been recovered,
A method for producing chemically strengthened glass, wherein the molten salt after recovering the specific metal salt does not substantially contain solid-state salt.
[33] A method for producing chemically strengthened glass using a chemically strengthening molten salt,
a chemical strengthening treatment in which the chemical strengthening glass is immersed in the chemical strengthening molten salt;
The chemical strengthening molten salt in which the chemical strengthening glass is immersed is used as the molten salt, and the specific metal salt is recovered by the metal component recovery method according to any one of [1] to [27]. A method for producing chemically strengthened glass, in which a molten salt regeneration treatment is alternately performed.
[34] The method for producing chemically strengthened glass according to [33], wherein a sulfate is added to the chemical strengthening molten salt in the molten salt regeneration treatment.

　本発明によれば、特定の金属成分を溶融塩から簡便に回収する金属成分の回収方法を提供できる。
　また、本発明によれば、溶融塩の再生方法、化学強化用ガラスの製造方法、および、化学強化ガラスの製造方法を提供できる。 According to the present invention, a method for recovering a metal component can be provided that allows a specific metal component to be recovered simply and easily from a molten salt.
Furthermore, according to the present invention, it is possible to provide a method for regenerating molten salt, a method for producing glass for chemical strengthening, and a method for producing chemically strengthened glass.

回収工程の第１実施態様を説明するための溶融塩を収容する容器を示す断面図であって、溶融塩が収容された容器に第１治具が設置されている状態を示す。FIG. 10 is a cross-sectional view showing a container for containing molten salt to explain a first embodiment of a recovery step, showing a state in which a first jig is installed in the container containing the molten salt. 回収工程の第１実施態様を説明するための溶融塩を収容する容器を示す断面図であって、溶融塩が収容された容器から第１治具を引き上げた状態を示す。FIG. 10 is a cross-sectional view showing a container for accommodating molten salt, illustrating a first embodiment of a recovery step, showing a state in which a first jig is pulled up from the container containing the molten salt. 回収工程の第２実施態様を説明するための溶融塩を収容する容器を示す断面図である。FIG. 10 is a cross-sectional view showing a vessel for accommodating molten salt to explain a second embodiment of the recovery step. 回収工程の第３実施態様を説明するための溶融塩を収容する容器を示す断面図である。FIG. 10 is a cross-sectional view showing a vessel for accommodating molten salt to explain a third embodiment of the recovery step. 回収工程の第４実施態様を説明するための溶融塩を収容する容器を示す断面図である。FIG. 10 is a cross-sectional view showing a vessel for accommodating molten salt to explain a fourth embodiment of the recovery step.

　以下に、本発明の金属成分の回収方法について詳細に説明するが、本発明は以下の実施形態に限定されるものではなく、本発明の要旨を逸脱しない範囲において、任意に変形して実施できる。　本明細書において、ガラス組成は酸化物基準のモル百分率表示で示し、モル％を単に％と記載することがある。また、数値範囲を示す「～」とは、その前後に記載された数値を下限値および上限値として含む意味で使用される。 The metal component recovery method of the present invention will be described in detail below, but the present invention is not limited to the following embodiments and can be modified as desired without departing from the spirit of the present invention. In this specification, glass compositions are expressed in mole percentage based on oxides, and mole % may be simply written as %. Furthermore, the symbol "to" indicating a numerical range is used to mean that the numerical values before and after it are included as the lower and upper limits.

　ガラス組成において「実質的に含有しない」とは、原材料等に含まれる不可避の不純物を除いて含有しない、すなわち、意図的に含有させたものではないことを意味する。具体的には、ガラス組成として記載した以外の成分については、たとえば、０．１モル％未満が好ましく、０．０８モル％以下がより好ましく、０．０５モル％以下がさらに好ましい。 In the glass composition, "substantially free" means that it is not contained except for unavoidable impurities contained in the raw materials, etc., i.e., it is not intentionally contained. Specifically, with regard to components other than those described as part of the glass composition, for example, it is preferably less than 0.1 mol%, more preferably 0.08 mol% or less, and even more preferably 0.05 mol% or less.

　本明細書において、「化学強化ガラス」は、化学強化処理を施した後のガラスを指す。また、「化学強化用ガラス」は、化学強化処理を施す前のガラスを指す。 In this specification, "chemically strengthened glass" refers to glass after chemical strengthening treatment. Also, "glass for chemical strengthening" refers to glass before chemical strengthening treatment.

　本明細書において、溶融塩が含む塩の例示は、特に断りがない場合、溶融塩を調製する際に用いる原料としての塩を示す。
　また、本明細書において、溶融塩における成分の含有量および比は、特に断りがない場合、溶融塩を調製する際に用いる原料としての成分の含有量および比についてそれぞれ示す。 In this specification, unless otherwise specified, examples of salts contained in the molten salt refer to salts used as raw materials when preparing the molten salt.
Furthermore, in this specification, unless otherwise specified, the contents and ratios of components in a molten salt refer to the contents and ratios of the components as raw materials used in preparing the molten salt.

＜金属成分の回収方法＞
　本発明の金属成分の回収方法は、特定金属成分を含む溶融塩を冷却し、上記溶融塩の溶融状態を保ったまま上記特定金属成分を含む特定金属塩を析出させ、上記特定金属塩を溶融状態の上記溶融塩から回収する方法である。
　すなわち、本発明の金属成分の回収方法は、特定金属成分を含む溶融塩を冷却し、上記溶融塩の溶融状態を保ったまま上記特定金属成分を含む特定金属塩を析出させる析出工程と、析出させた上記特定金属塩を溶融状態の上記溶融塩から回収する回収工程を有する。 <Method for recovering metal components>
The method for recovering a metal component of the present invention is a method for recovering a specific metal component by cooling a molten salt containing the specific metal component, precipitating a specific metal salt containing the specific metal component while maintaining the molten state of the molten salt, and recovering the specific metal salt from the molten salt.
That is, the method for recovering a metal component of the present invention includes a precipitation step of cooling a molten salt containing a specific metal component and precipitating a specific metal salt containing the specific metal component while maintaining the molten state of the molten salt, and a recovery step of recovering the precipitated specific metal salt from the molten salt in the molten state.

　本発明の金属成分の回収方法では、溶融塩の溶融状態を保ったまま、溶融塩を冷却し、特定金属塩を析出させるため、特定金属塩のみを溶融塩から分離することができ、特定金属成分を溶融塩から簡便に回収可能である。
　また、本発明の金属成分の回収方法によれば、他の溶媒を用いずに特定金属成分を溶融塩から回収するため、特定金属成分を回収した溶融塩は、そのまま溶融塩として利用可能である。 In the method for recovering metal components of the present invention, the molten salt is cooled while maintaining the molten state of the molten salt, causing the specific metal salt to precipitate, so that only the specific metal salt can be separated from the molten salt, and the specific metal component can be easily recovered from the molten salt.
Furthermore, according to the method for recovering a metal component of the present invention, the specific metal component is recovered from the molten salt without using any other solvent, and therefore the molten salt from which the specific metal component has been recovered can be used as the molten salt as is.

　以下、本発明の金属成分の回収方法について詳細に説明する。 The metal component recovery method of the present invention is described in detail below.

［析出工程］
　本発明の金属成分の回収方法では、特定金属成分を含む溶融塩を冷却し、上記溶融塩の溶融状態を保ったまま上記特定金属成分を含む特定金属塩を析出させる析出工程を実施する。
　析出工程によって、固体状の特定金属塩が溶融塩中に析出する。
　以下、析出工程に供する溶融塩、および、析出工程を実施する方法について詳細に説明する。 [Precipitation process]
In the method for recovering a metal component of the present invention, a precipitation step is carried out in which a molten salt containing a specific metal component is cooled and a specific metal salt containing the specific metal component is precipitated while maintaining the molten state of the molten salt.
The precipitation step causes the specific metal salt in a solid state to precipitate in the molten salt.
The molten salt to be subjected to the precipitation step and the method for carrying out the precipitation step will be described in detail below.

（溶融塩）
　析出工程に供する溶融塩は、通常、陰イオンおよび陽イオンからなる塩を含む。
　溶融塩に含まれる陰イオンとしては、例えば、硝酸イオン、硫酸イオン、亜硝酸イオン、亜硫酸イオン、炭酸イオン、リン酸イオン、および、ハロゲン化物イオンからなる群から選択される１種以上が挙げられる。
　すなわち、溶融塩は、硝酸塩、硫酸塩、亜硝酸塩、亜硫酸塩、炭酸塩、リン酸塩、および、ハロゲン化物塩からなる群から選択される１種以上の塩を含むことが好ましい。また、溶融塩は、硝酸塩と硫酸塩とを含む、または、硝酸塩と炭酸塩とを含むことが好ましく、硝酸塩と硫酸塩とを含むことがより好ましい。また、溶融塩は、硝酸塩と硫酸塩と炭酸塩とを同時に含んでもよい。
　溶融塩が硫酸塩を含む場合、硫酸塩の含有量は、溶融塩の全質量に対して、２．０質量％以上が好ましく、３．０質量％以上がより好ましく、５．０質量％以上がさらに好ましい。また、溶融塩が硫酸塩を含む場合、硫酸塩の含有量は、溶融塩の全質量に対して、５０．０質量％以下が好ましく、２５．０質量％以下がより好ましく、２０．０質量％以下がさらに好ましい。
　溶融塩が炭酸塩を含む場合、炭酸塩の含有量は、溶融塩の全質量に対して、２．０質量％以上が好ましく、３．０質量％以上がより好ましく、４．０質量％以上がさらに好ましい。また、溶融塩が炭酸塩を含む場合、炭酸塩の含有量は、溶融塩の全質量に対して、４０．０質量％以下が好ましく、３１．０質量％以下がより好ましく、２０．０質量％以下がさらに好ましい。
　なお、例えば、「硝酸塩」とは、陰イオンとして硝酸イオンを含む塩をいう。
　また、「炭酸塩」とは、陰イオンとして炭酸イオンを含む塩をいう。 (molten salt)
The molten salt used in the precipitation step usually contains a salt composed of anions and cations.
Examples of anions contained in the molten salt include one or more selected from the group consisting of nitrate ions, sulfate ions, nitrite ions, sulfite ions, carbonate ions, phosphate ions, and halide ions.
That is, the molten salt preferably contains one or more salts selected from the group consisting of nitrates, sulfates, nitrites, sulfites, carbonates, phosphates, and halides. The molten salt preferably contains a nitrate and a sulfate, or a nitrate and a carbonate, and more preferably a nitrate and a sulfate. The molten salt may also contain a nitrate, a sulfate, and a carbonate simultaneously.
When the molten salt contains a sulfate, the content of the sulfate is preferably 2.0 mass% or more, more preferably 3.0 mass% or more, and even more preferably 5.0 mass% or more, relative to the total mass of the molten salt. Also, when the molten salt contains a sulfate, the content of the sulfate is preferably 50.0 mass% or less, more preferably 25.0 mass% or less, and even more preferably 20.0 mass% or less, relative to the total mass of the molten salt.
When the molten salt contains a carbonate, the carbonate content is preferably 2.0 mass% or more, more preferably 3.0 mass% or more, and even more preferably 4.0 mass% or more, relative to the total mass of the molten salt. When the molten salt contains a carbonate, the carbonate content is preferably 40.0 mass% or less, more preferably 31.0 mass% or less, and even more preferably 20.0 mass% or less, relative to the total mass of the molten salt.
For example, "nitrate" refers to a salt containing nitrate ions as anions.
Furthermore, the term "carbonate" refers to a salt containing carbonate ions as an anion.

　上記溶融塩に含まれる陽イオンとしては、例えば、リチウム（Ｌｉ）イオン、ナトリウム（Ｎａ）イオン、および、カリウム（Ｋ）イオンからなる群から選択される１種以上が挙げられ、リチウムイオン、ナトリウムイオン、および、カリウムイオンからなる群から選択される２種以上が好ましい。
　すなわち、溶融塩は、リチウム塩、ナトリウム塩、および、カリウム塩からなる群から選択される１種以上の塩を含むことが好ましく、リチウム塩、ナトリウム塩、および、カリウム塩からなる群から選択される２種以上の塩を含むことがより好ましい。また、溶融塩は、リチウム塩、および、ナトリウム塩を含むことも好ましい。また、溶融塩は、ナトリウム塩、および、カリウム塩を含むことも好ましい。
　なお、例えば、「リチウム塩」とは、陽イオンとしてリチウムイオンを含む塩をいう。 Examples of the cation contained in the molten salt include one or more cations selected from the group consisting of lithium (Li) ions, sodium (Na) ions, and potassium (K) ions, and two or more cations selected from the group consisting of lithium ions, sodium ions, and potassium ions are preferred.
That is, the molten salt preferably contains one or more salts selected from the group consisting of lithium salts, sodium salts, and potassium salts, and more preferably contains two or more salts selected from the group consisting of lithium salts, sodium salts, and potassium salts. The molten salt also preferably contains a lithium salt and a sodium salt. The molten salt also preferably contains a sodium salt and a potassium salt.
For example, "lithium salt" refers to a salt containing lithium ions as cations.

　上記溶融塩に含まれる具体的な塩としては、硝酸リチウム（ＬｉＮＯ３）、硝酸ナトリウム（ＮａＮＯ３）、硝酸カリウム（ＫＮＯ３）、硫酸ナトリウム（Ｎａ２ＳＯ４）、および、硫酸カリウム（Ｋ２ＳＯ４）からなる群から選択される塩が挙げられる。
　なかでも、溶融塩は、硝酸リチウム、硝酸ナトリウム、および、硝酸カリウムからなる群から選択される２種以上の塩を含み、さらに、硫酸ナトリウム、および、硫酸カリウムからなる群から選択される１種以上の塩を含むことが好ましい。
　溶融塩の好ましい態様の一つは、硝酸リチウム、硝酸ナトリウム、硝酸カリウム、および、硫酸ナトリウムを含む溶融塩が挙げられる。
　また、溶融塩の好ましい態様の一つは、硝酸ナトリウム、硝酸カリウム、および、炭酸カリウムを含む溶融塩が挙げられる。 Specific examples of salts contained in the molten salt include salts selected from the group consisting of lithium nitrate (LiNO 3 ), sodium nitrate (NaNO 3 ), potassium nitrate (KNO 3 ), sodium sulfate (Na 2 SO 4 ), and potassium sulfate (K 2 SO 4 ).
In particular, it is preferable that the molten salt contains two or more salts selected from the group consisting of lithium nitrate, sodium nitrate, and potassium nitrate, and further contains one or more salts selected from the group consisting of sodium sulfate and potassium sulfate.
One preferred embodiment of the molten salt is a molten salt containing lithium nitrate, sodium nitrate, potassium nitrate, and sodium sulfate.
One preferred embodiment of the molten salt is a molten salt containing sodium nitrate, potassium nitrate, and potassium carbonate.

　また、上記溶融塩が、硝酸ナトリウムを含む場合、硝酸ナトリウムの含有量に対する硝酸カリウムの含有量の比（硝酸カリウム／硝酸ナトリウム）は、質量比で、０．００～２４．００が好ましく、０．２５～４．００がより好ましく、０．４２～２．３４がさらに好ましい。
　また、上記溶融塩が硫酸塩（好ましくは硫酸ナトリウム）を含み、上記の比を満たすことも好ましい。 Furthermore, when the molten salt contains sodium nitrate, the ratio of the potassium nitrate content to the sodium nitrate content (potassium nitrate/sodium nitrate) is preferably 0.00 to 24.00, more preferably 0.25 to 4.00, and even more preferably 0.42 to 2.34, in mass ratio.
It is also preferable that the molten salt contains a sulfate (preferably sodium sulfate) and satisfies the above ratio.

　また、析出工程に供する溶融塩は、特定金属成分を含む。
　特定金属成分は、溶融塩中において、溶融していることが好ましい。特定金属成分は、リチウムまたはナトリウムを含むことが好ましく、リチウムを含むことがより好ましい。すなわち、析出工程において析出する特定金属塩は、リチウムまたはナトリウムを含むことが好ましく、リチウムを含むことがより好ましい。
　特定金属成分がリチウムを含む場合、溶融塩は、溶融塩の全質量に対して、リチウム原子を１,０００質量ｐｐｍ以上含むことが好ましく、２,０００質量ｐｐｍ以上含むことがより好ましく、３,０００質量ｐｐｍ以上含むことがさらに好ましい。また、溶融塩は、溶融塩の全質量に対して、リチウム原子を５０,０００質量ｐｐｍ以下含むことが好ましく、２０,０００質量ｐｐｍ以下含むことがより好ましく、１０,０００質量ｐｐｍ以下含むことがさらに好ましい。また、特定金属成分がリチウムを含む場合、上記特定金属塩は、リチウムおよびナトリウムを含むことも好ましい。
　特定金属成分がナトリウムを含む場合、溶融塩は、溶融塩の全質量に対して、ナトリウム原子を５００質量ｐｐｍ以上含むことが好ましく、２,０００質量ｐｐｍ以上含むことがより好ましく、４,０００質量ｐｐｍ以上含むことがさらに好ましい。また、溶融塩は、溶融塩の全質量に対して、ナトリウム原子を６０,０００質量ｐｐｍ以下含むことが好ましく、４０,０００質量ｐｐｍ以下含むことがより好ましく、２０,０００質量ｐｐｍ以下含むことがさらに好ましい。また、特定金属成分がナトリウムを含む場合、上記特定金属塩は、ナトリウムおよびカリウムを含むことも好ましい。 The molten salt to be subjected to the deposition step contains a specific metal component.
The specific metal component is preferably molten in the molten salt. The specific metal component preferably contains lithium or sodium, more preferably lithium. That is, the specific metal salt precipitated in the precipitation step preferably contains lithium or sodium, more preferably lithium.
When the specific metal component contains lithium, the molten salt preferably contains 1,000 mass ppm or more, more preferably 2,000 mass ppm or more, and even more preferably 3,000 mass ppm or more of lithium atoms relative to the total mass of the molten salt. Furthermore, the molten salt preferably contains 50,000 mass ppm or less, more preferably 20,000 mass ppm or less, and even more preferably 10,000 mass ppm or less of lithium atoms relative to the total mass of the molten salt. Furthermore, when the specific metal component contains lithium, the specific metal salt also preferably contains lithium and sodium.
When the specific metal component contains sodium, the molten salt preferably contains 500 mass ppm or more, more preferably 2,000 mass ppm or more, and even more preferably 4,000 mass ppm or more of sodium atoms relative to the total mass of the molten salt. Furthermore, the molten salt preferably contains 60,000 mass ppm or less, more preferably 40,000 mass ppm or less, and even more preferably 20,000 mass ppm or less of sodium atoms relative to the total mass of the molten salt. Furthermore, when the specific metal component contains sodium, the specific metal salt also preferably contains sodium and potassium.

　溶融塩の具体的な組成としては、例えば、硝酸カリウム、硝酸ナトリウム、硝酸リチウム、および、硫酸ナトリウムを含む第１の溶融塩が挙げられる。
　第１の溶融塩において、硝酸カリウムの含有量は、１０．０～９６．０質量％が好ましく、３０．０～７０．０質量％がより好ましい。
　第１の溶融塩において、硝酸ナトリウムの含有量は、１．０～９０．０質量％が好ましく、３０．０～７０．０質量％がより好ましい。
　第１の溶融塩において、硝酸リチウムの含有量は、１．０～５０．０質量％が好ましく、１．５～１５．０質量％がより好ましい。
　第１の溶融塩において、硫酸ナトリウムの含有量は、２．０～３０．０質量％が好ましく、４．０～２０．０質量％がより好ましい。 A specific example of the composition of the molten salt is a first molten salt containing potassium nitrate, sodium nitrate, lithium nitrate, and sodium sulfate.
In the first molten salt, the content of potassium nitrate is preferably 10.0 to 96.0 mass %, more preferably 30.0 to 70.0 mass %.
In the first molten salt, the content of sodium nitrate is preferably 1.0 to 90.0 mass %, more preferably 30.0 to 70.0 mass %.
In the first molten salt, the content of lithium nitrate is preferably 1.0 to 50.0 mass %, more preferably 1.5 to 15.0 mass %.
In the first molten salt, the content of sodium sulfate is preferably 2.0 to 30.0 mass %, more preferably 4.0 to 20.0 mass %.

　溶融塩の具体的な組成としては、例えば、硝酸カリウム、硝酸ナトリウム、および、炭酸カリウムを含む第２の溶融塩も挙げられる。
　第２の溶融塩において、硝酸カリウムの含有量は、４０．０～９６．０質量％が好ましく、３０．０～９２．０質量％がより好ましい。
　第２の溶融塩において、硝酸ナトリウムの含有量は、０．２～３０．０質量％が好ましく、１．０～１０．０質量％がより好ましい。
　第２の溶融塩において、炭酸カリウムの含有量は、３．０～３０．０質量％が好ましく、４．０～２０．０質量％がより好ましい。 Specific examples of the composition of the molten salt include a second molten salt containing potassium nitrate, sodium nitrate, and potassium carbonate.
In the second molten salt, the content of potassium nitrate is preferably 40.0 to 96.0 mass %, more preferably 30.0 to 92.0 mass %.
In the second molten salt, the content of sodium nitrate is preferably 0.2 to 30.0 mass %, more preferably 1.0 to 10.0 mass %.
In the second molten salt, the content of potassium carbonate is preferably 3.0 to 30.0 mass %, more preferably 4.0 to 20.0 mass %.

　なお、溶融塩の種類および用途は特に制限されないが、後述するように、化学強化に用いる溶融塩が好ましく挙げられる。また、溶融塩としては、金属製錬、熱媒体、電池、電気精錬用の溶融塩も挙げられる。
　溶融塩が化学強化に用いられる溶融塩である場合、化学強化に供して、化学強化用ガラスに含まれる成分（例えばリチウムイオン、ナトリウムイオン）が溶融塩中のイオンと交換されたものであってもよい。 The type and use of the molten salt are not particularly limited, but preferred examples include molten salts used for chemical strengthening, as described below. Other examples of the molten salt include molten salts used for metal smelting, heat transfer media, batteries, and electrorefining.
When the molten salt is a molten salt used for chemical strengthening, the glass may be subjected to chemical strengthening, and components contained in the glass for chemical strengthening (e.g., lithium ions, sodium ions) may be exchanged for ions in the molten salt.

（析出方法）
　析出工程においては、溶融塩を冷却し、溶融塩の溶融状態を保ったまま、特定金属成分を含む特定金属塩を析出させる。
　析出工程における溶融塩の冷却方法は、特に制限されず、公知の方法を適用できる。また、溶融塩の冷却は、溶融塩全体を冷却してもよいし、溶融塩の一部のみを冷却してもよい。 (Precipitation method)
In the precipitation step, the molten salt is cooled, and the specific metal salt containing the specific metal component is precipitated while the molten salt is maintained in a molten state.
The method for cooling the molten salt in the precipitation step is not particularly limited, and any known method can be applied. The molten salt may be cooled entirely or only partially.

　このとき、溶融塩に添加物を添加することなく、溶融塩を冷却することが好ましい。
　添加物としては、特定金属成分と反応して特定金属塩を析出させる物質であり、具体的には、例えば、上述した溶融塩に含まれる塩が挙げられる。 At this time, it is preferable to cool the molten salt without adding any additives to the molten salt.
The additive is a substance that reacts with the specific metal component to precipitate a specific metal salt, and specific examples thereof include the salts contained in the molten salt described above.

　溶融塩全体を冷却する方法としては、例えば、溶融塩または溶融塩が収容される容器を、溶融塩よりも温度の低い流体等に接触させる方法が挙げられる。より具体的には、上記流体としては、例えば空気が挙げられ、溶融塩または溶融塩が収容される容器を空冷する方法が挙げられる。溶融塩または溶融塩が収容される容器を空冷する際には、その付近の空気を対流させて空冷してもよい。
　また、溶融塩を冷却する方法としては、溶融塩が収容される容器に冷却用媒体を流通させる方法も挙げられる。この場合、溶融塩が収容される容器は、冷却用媒体が流通する管を備えることが好ましく、上記方法としては、冷却用媒体をその管に接続された熱交換器で熱交換しながら、冷却用媒体を溶融塩が収容される容器と熱交換器との間を循環させればよい。 Examples of methods for cooling the entire molten salt include a method of bringing the molten salt or a container containing the molten salt into contact with a fluid having a temperature lower than that of the molten salt. More specifically, examples of the fluid include air, and a method of air-cooling the molten salt or a container containing the molten salt. When air-cooling the molten salt or a container containing the molten salt, air convection may be used.
Another method for cooling the molten salt is to circulate a cooling medium through a container that contains the molten salt. In this case, the container that contains the molten salt preferably includes a pipe through which the cooling medium circulates, and the method involves circulating the cooling medium between the container that contains the molten salt and the heat exchanger while exchanging heat with the cooling medium in a heat exchanger connected to the pipe.

　溶融塩全体を冷却すると、溶融塩から特定金属成分を含む特定金属塩が析出する。特定金属塩は、溶融塩に分散して析出してもよいし、溶融塩を収容する容器の壁面などに析出してもよい。また、後述する治具の表面に析出してもよい。 When the entire molten salt is cooled, a specific metal salt containing a specific metal component precipitates from the molten salt. The specific metal salt may be dispersed in the molten salt and precipitate, or may precipitate on the wall surface of the container containing the molten salt. It may also precipitate on the surface of the jig, which will be described later.

　また、溶融塩を冷却する際には、溶融塩の一部を冷却してもよい。溶融塩の一部を冷却する方法としては、冷却部を有する治具を用い、溶融塩に冷却部を接触させる方法が挙げられる。上記冷却部を有する治具は、温度制御を自在に行うことができ、溶融塩を冷却すると、冷却部の表面等に溶融塩が析出する。 Furthermore, when cooling the molten salt, a portion of the molten salt may be cooled. One method for cooling a portion of the molten salt is to use a jig with a cooling part and bring the cooling part into contact with the molten salt. The jig with the cooling part allows for free temperature control, and when the molten salt is cooled, the molten salt precipitates on the surface of the cooling part, etc.

　本発明において、溶融塩の冷却は、溶融塩の溶融状態を保ったまま行われる。また、溶融塩の冷却は、所定の温度まで溶融塩を冷却した後、後述する保持時間だけその温度を保持することが好ましい。
　冷却する温度は、溶融塩の溶融状態が保たれ、かつ、特定金属塩が析出すれば特に制限されないが、溶融塩を冷却する際の温度は、１５０℃以上が好ましく、２００℃以上がより好ましく、２３０℃以上がさらに好ましい。また、溶融塩を冷却する際の温度は、５００℃以下が好ましく、４００℃以下がより好ましく、３５０℃以下がさらに好ましい。
　また、冷却前の溶融塩の温度と、冷却後の溶融塩の温度との温度差は、２０℃以上が好ましく、５０℃以上がより好ましく、１００℃以上がさらに好ましい。また、上記温度差は、２５０℃以下が好ましく、１８０℃以下がより好ましい。
　保持時間は、特定金属塩が析出すれば特に制限されないが、例えば５分以上が挙げられ、１０分以上が好ましく、３０分以上がより好ましい。また、上記保持時間は、例えば２４時間以下が挙げられ、１２時間以下が好ましく、６時間以下がより好ましい。
　また、上記冷却前の溶融塩の温度は、３７０℃以上が好ましく、３９０℃以上がより好ましく、４２０℃以上がさらに好ましい。冷却後の溶融塩の温度は、４２０℃以下が好ましく、４１０℃以下がより好ましく、３６０℃以下がさらに好ましく、３５０℃以下が特に好ましく、３００℃以下が最も好ましい。上記冷却前の溶融塩の温度、および、上記冷却後の溶融塩の温度は、溶融塩の組成等によって適宜調整可能である。
　例えば、３７０℃以上の溶融塩を、３６０℃以下に冷却することも好ましい。上記溶融塩は、特定金属成分がリチウムを含み、溶融塩が少なくともリチウム塩およびナトリウム塩を含む態様であることも好ましい。
　また、４２０℃以上の溶融塩を、４１０℃以下に冷却することも好ましい。また、４２０℃以上の溶融塩を、２０℃以上冷却すること（冷却前の溶融塩の温度と、冷却後の溶融塩の温度との温度差が２０℃以上であること）も好ましい。上記溶融塩は、特定金属成分がナトリウムを含み、溶融塩が少なくともナトリウム塩およびカリウム塩を含む態様であることも好ましい。
　上記溶融塩の温度は、例えば、Ｋ熱電対で測定できる。 In the present invention, the molten salt is cooled while maintaining the molten state. Preferably, the molten salt is cooled to a predetermined temperature and then maintained at that temperature for a holding time described below.
The cooling temperature is not particularly limited as long as the molten salt is maintained in a molten state and the specific metal salt is precipitated, but the temperature at which the molten salt is cooled is preferably 150° C. or higher, more preferably 200° C. or higher, and even more preferably 230° C. or higher. The temperature at which the molten salt is cooled is preferably 500° C. or lower, more preferably 400° C. or lower, and even more preferably 350° C. or lower.
The temperature difference between the temperature of the molten salt before cooling and the temperature of the molten salt after cooling is preferably 20° C. or more, more preferably 50° C. or more, and even more preferably 100° C. or more. The temperature difference is preferably 250° C. or less, and more preferably 180° C. or less.
The retention time is not particularly limited as long as the specific metal salt is precipitated, but may be, for example, 5 minutes or more, preferably 10 minutes or more, and more preferably 30 minutes or more, and may be, for example, 24 hours or less, preferably 12 hours or less, and more preferably 6 hours or less.
The temperature of the molten salt before cooling is preferably 370° C. or higher, more preferably 390° C. or higher, and even more preferably 420° C. or higher. The temperature of the molten salt after cooling is preferably 420° C. or lower, more preferably 410° C. or lower, even more preferably 360° C. or lower, particularly preferably 350° C. or lower, and most preferably 300° C. or lower. The temperatures of the molten salt before cooling and the molten salt after cooling can be adjusted as appropriate depending on the composition of the molten salt, etc.
For example, it is also preferable to cool a molten salt at 370° C. or higher to 360° C. or lower. It is also preferable that the specific metal component of the molten salt contains lithium, and that the molten salt contains at least a lithium salt and a sodium salt.
It is also preferable to cool a molten salt at 420° C. or higher to 410° C. or lower. It is also preferable to cool a molten salt at 420° C. or higher by 20° C. or higher (the temperature difference between the temperature of the molten salt before cooling and the temperature of the molten salt after cooling is 20° C. or higher). It is also preferable that the specific metal component of the molten salt contains sodium, and the molten salt contains at least a sodium salt and a potassium salt.
The temperature of the molten salt can be measured, for example, with a K thermocouple.

　析出工程において、溶融塩の冷却は、溶融塩に対流を発生させながら実施することも好ましい。溶融塩に対流を発生させる方法としては、例えば、溶融塩を撹拌羽根で撹拌する方法が挙げられる。
　溶融塩に対流を発生させながら冷却することで、溶融塩を均一に冷却できる。 In the precipitation step, the molten salt is preferably cooled while generating convection in the molten salt. Examples of a method for generating convection in the molten salt include stirring the molten salt with a stirring blade.
By cooling the molten salt while generating convection, the molten salt can be cooled uniformly.

　析出工程を実施する装置としては、例えば、溶融塩を収容する容器と、溶融塩に浸漬され、溶融塩の温度を測定する温度測定手段と、溶融塩を収容する容器を加熱し、収容される溶融塩を加熱する加熱手段と、溶融塩を撹拌する撹拌羽根とを有する装置が挙げられる。
　溶融塩を収容する容器は、溶融塩に溶出しない材料で構成されることが好ましい。溶融塩に溶出しない材料としては、例えば、ステンレス鋼等の金属材料、石英ガラス、アルミナ等のセラミックス材料、テトラフルオロエチレン（ＰＴＦＥ）等の耐熱樹脂材料が挙げられる。
　上記温度測定手段は、特に制限されないが、例えば、公知の熱電対が挙げられる。
　上記加熱手段は、特に制限されないが、例えば、電熱線を有するヒーターが挙げられる。
　上記装置において、例えば、温度測定手段によって温度をモニタリングしながら、加熱手段の出力を制御し、溶融塩および溶融塩を収容する容器からの放熱量よりも加熱手段から供給される入熱量が少なくなるようにすると、溶融塩を冷却できる。
　また、上記放熱量および入熱量が等しくなるように加熱手段の出力を制御すると、溶融塩の温度を一定に保つことができる。
　なお、上記装置は、後述する回収工程で用いる治具等を備えていてもよい。 An example of an apparatus for carrying out the precipitation step is an apparatus having a container for containing molten salt, a temperature measuring means that is immersed in the molten salt and measures the temperature of the molten salt, a heating means that heats the container for containing the molten salt and heats the molten salt contained therein, and a stirring blade that stirs the molten salt.
The container for containing the molten salt is preferably made of a material that does not dissolve in the molten salt, such as metal materials such as stainless steel, ceramic materials such as quartz glass and alumina, and heat-resistant resin materials such as tetrafluoroethylene (PTFE).
The temperature measuring means is not particularly limited, but examples thereof include known thermocouples.
The heating means is not particularly limited, but may be, for example, a heater having an electric heating wire.
In the above-described device, the molten salt can be cooled, for example, by controlling the output of the heating means while monitoring the temperature using a temperature measuring means so that the amount of heat input from the heating means is less than the amount of heat dissipated from the molten salt and the container containing the molten salt.
Furthermore, by controlling the output of the heating means so that the amount of heat radiation and the amount of heat input are equal, the temperature of the molten salt can be kept constant.
The above-mentioned device may be equipped with a jig or the like used in the recovery step described below.

［回収工程］
　本発明の金属成分の回収方法では、上記析出工程で析出させた上記特定金属塩を溶融状態の上記溶融塩から回収する回収工程を実施する。
　回収工程によって、固体状の特定金属塩が、液体状の溶融塩から分離され、特定金属成分を含む特定金属塩が回収される。
　回収工程の実施方法は特に制限されず、公知の方法を適用できる。
　以下、回収工程の具体的な実施方法を説明するが、本発明の回収工程は、以下の方法に制限されず、種々の方法を適用できる。 [Recovery process]
In the method for recovering a metal component of the present invention, a recovery step is carried out in which the specific metal salt precipitated in the precipitating step is recovered from the molten salt in a molten state.
In the recovery step, the solid specific metal salt is separated from the liquid molten salt, and the specific metal salt containing the specific metal component is recovered.
The method for carrying out the recovery step is not particularly limited, and known methods can be applied.
A specific method for carrying out the recovery step will be described below, but the recovery step of the present invention is not limited to the following method, and various methods can be applied.

（回収工程の第１実施態様）
　回収工程の一態様としては、特定金属塩を溶融状態の溶融塩から回収する際に、網状の網部を有する第１治具を用い、網部を溶融塩から引き上げ、析出した特定金属塩を溶融状態の溶融塩から回収する、第１実施態様が挙げられる。
　第１治具が有する網部により、固体として析出した特定金属塩を回収し、液体状の溶融塩と分離される。
　上記第１治具は、上述した析出工程を実施する前に、溶融塩を収容する容器に設置し、溶融塩に浸漬しておくことが好ましい。第１治具を析出工程の実施前に溶融塩を収容する容器に設置しておけば、析出工程を行って特定金属塩を析出させた後、第１治具を引き上げて特定金属塩を回収することが簡便となる。
　上記第１治具は、網部を溶融塩から引き上げるための取手部を有していてもよい。取手部は、直接的ないし間接的に網部と接続され、溶融塩の液面から突出していて、溶融塩に接触することなく引き上げできることも好ましい。
　なお、上記第１治具は、析出工程を実施した後に溶融塩に浸漬して特定金属塩を回収してもよい。 (First embodiment of recovery step)
One aspect of the recovery process is a first embodiment in which, when recovering a specific metal salt from a molten salt in a molten state, a first jig having a mesh portion is used, the mesh portion is pulled up from the molten salt, and the precipitated specific metal salt is recovered from the molten salt in a molten state.
The specific metal salt precipitated as a solid is recovered by the mesh portion of the first jig and separated from the liquid molten salt.
It is preferable that the first jig be placed in a container containing the molten salt and immersed in the molten salt before the above-mentioned precipitation step is carried out. If the first jig is placed in the container containing the molten salt before the precipitation step is carried out, it becomes easy to collect the specific metal salt by pulling up the first jig after the precipitation step is carried out to precipitate the specific metal salt.
The first jig may have a handle for lifting the mesh part from the molten salt. The handle is preferably connected directly or indirectly to the mesh part and protrudes above the liquid surface of the molten salt, allowing the mesh part to be lifted without coming into contact with the molten salt.
After the precipitation step, the first jig may be immersed in a molten salt to recover the specific metal salt.

　回収工程の第１実施態様は、より具体的には、図１Ａおよび図１Ｂに示す構成で実施できる。図１Ａおよび図１Ｂは、回収工程の第１実施態様を説明するための溶融塩Ｍを収容する容器１０を示す断面図である。
　図１Ａは、溶融塩Ｍが収容された容器１０に第１治具２０ａが設置されている状態を示す。第１治具２０ａは、網部２４ａと、網部２４ａに接続される取手部２２ａから構成される。取手部２２ａは、溶融塩Ｍの液面から突出している。
　また、図１Ａにおいては、第１治具２０ａの網部２４ａ上に、特定金属塩Ｃ１が析出している。
　図１Ｂは、溶融塩Ｍが収容された容器１０から第１治具２０ａを引き上げた状態を示す。第１治具２０ａの取手部２２ａを把持し、第１治具２０ａを紙面上方向に引き上げれば（図１Ｂ参照）、特定金属塩Ｃ１を簡便に回収できる。 More specifically, the first embodiment of the recovery step can be carried out by the configuration shown in Figures 1A and 1B. Figures 1A and 1B are cross-sectional views showing a vessel 10 containing molten salt M, for explaining the first embodiment of the recovery step.
1A shows a state in which a first jig 20a is placed in a container 10 containing molten salt M. The first jig 20a is composed of a mesh portion 24a and a handle portion 22a connected to the mesh portion 24a. The handle portion 22a protrudes from the liquid surface of the molten salt M.
In addition, in FIG. 1A, the specific metal salt C1 is precipitated on the mesh portion 24a of the first jig 20a.
1B shows a state in which the first jig 20a has been pulled up from the container 10 containing the molten salt M. The specific metal salt C1 can be easily recovered by gripping the handle portion 22a of the first jig 20a and pulling the first jig 20a upward in the plane of the drawing (see FIG. 1B ).

　上記第１治具は、溶融塩に溶出しない材料で構成されることが好ましい。溶融塩に溶出しない材料としては、例えば、ステンレス鋼等の金属材料、石英ガラス、アルミナ等のセラミックス材料、ポリテトラフルオロエチレン（ＰＴＦＥ）等の耐熱樹脂材料が挙げられる。
　上記第１治具の網部は、特定金属塩を回収できれば特に制限されず、特定金属塩の析出した粒の大きさによって適宜選択し得るが、例えば、網部の目開きは、０．０５～０．２ｍｍが好ましい。
　上記第１治具の網部は、溶融塩を収容する容器に沿った形状であることも好ましい。 The first jig is preferably made of a material that does not dissolve in the molten salt, such as a metal material such as stainless steel, a ceramic material such as quartz glass or alumina, or a heat-resistant resin material such as polytetrafluoroethylene (PTFE).
The mesh portion of the first jig is not particularly limited as long as it can recover the specific metal salt, and can be selected appropriately depending on the size of the precipitated particles of the specific metal salt. For example, the mesh opening of the mesh portion is preferably 0.05 to 0.2 mm.
It is also preferable that the mesh portion of the first jig has a shape that conforms to the container that contains the molten salt.

（回収工程の第２実施態様）
　回収工程の一態様としては、特定金属成分を含む溶融塩を冷却し、溶融塩の溶融状態を保ったまま特定金属成分を含む特定金属塩を析出させる際に、塩析出部を有する第２治具の塩析出部の表面に、特定金属塩を析出させ、塩析出部を溶融塩から引き上げて、特定金属塩を溶融状態の溶融塩から回収する、第２実施態様が挙げられる。
　第２治具の塩析出部に特定金属塩を析出させるため、第２治具を溶融塩から引き揚げると、固体として析出した特定金属塩が液体状の溶融塩から分離され、特定金属成分を含む特定金属塩が回収される。
　上記第２治具は、上記析出工程を実施する際に、溶融塩を収容する容器内に設置し、溶融塩に浸漬しておく。
　第２治具が有する塩析出部は、特に制限されないが、大きな表面積を有することが好ましい。塩析出部の構造は、公知の構造を適用可能であるが、例えば、板状構造物をその主面と直交する方向に所定の間隔で配置し、板状構造物を互いに連結してなる構造、１枚の板をベローズ（蛇腹）状に折り曲げてなる構造等が挙げられる。
　上記板状構造物または板は、孔を有していてもよい。また、上記板状構造物または板は、金属板が好ましい。すなわち、上記板状構造物または板は、パンチングメタルであることが好ましい。他にも、上記板状構造物または板は、粗面化処理が施されていてもよい。
　また、上記板状構造物または板は、針金によって構成される網（メッシュ）であってもよい。網部の目開きは、０．５ｍｍ以上が好ましい。上記網部の目開きは、２０．０ｍｍ以下が好ましく、２．０ｍｍ以下がより好ましい。
　治具表面に微細な凹凸が存在する場合、塩の析出が促進され好ましい。
　上記第２治具は、網部を溶融塩から引き上げるための取手部を有していてもよい。取手部は、直接的ないし間接的に網部と接続され、溶融塩の液面から突出していて、溶融塩に接触することなく引き上げできることも好ましい。
　上記第２治具は、溶融塩に溶出しない材料で構成されることが好ましい。好ましい材料の例は、第１治具の好ましい材料と同様である。 (Second embodiment of recovery step)
One aspect of the recovery process is a second embodiment in which, when cooling a molten salt containing a specific metal component and precipitating a specific metal salt containing the specific metal component while maintaining the molten salt in a molten state, the specific metal salt is precipitated on the surface of a salt precipitating portion of a second jig having a salt precipitating portion, and the salt precipitating portion is pulled up from the molten salt to recover the specific metal salt from the molten molten salt.
In order to precipitate the specific metal salt in the salt precipitation portion of the second jig, when the second jig is pulled up from the molten salt, the specific metal salt precipitated as a solid is separated from the liquid molten salt, and the specific metal salt containing the specific metal component is recovered.
When the precipitation step is carried out, the second jig is placed in a container containing the molten salt and is immersed in the molten salt.
The salt deposition portion of the second jig is not particularly limited, but preferably has a large surface area. The structure of the salt deposition portion may be any known structure, such as a structure in which plate-like structures are arranged at predetermined intervals in a direction perpendicular to their main surfaces and connected to each other, or a structure in which a single plate is bent into a bellows shape.
The plate-like structure or plate may have holes. The plate-like structure or plate is preferably a metal plate. That is, the plate-like structure or plate is preferably a punched metal. In addition, the plate-like structure or plate may be subjected to a surface roughening treatment.
The plate-like structure or plate may be a mesh made of wire. The mesh opening is preferably 0.5 mm or more. The mesh opening is preferably 20.0 mm or less, and more preferably 2.0 mm or less.
The presence of minute irregularities on the surface of the jig is preferred as it promotes salt precipitation.
The second jig may have a handle for pulling the mesh part out of the molten salt. The handle is preferably connected directly or indirectly to the mesh part and protrudes above the liquid surface of the molten salt, allowing the mesh part to be pulled out without coming into contact with the molten salt.
The second jig is preferably made of a material that does not dissolve in the molten salt. Examples of the preferred material are the same as those of the first jig.

　回収工程の第２実施態様は、より具体的には、図２に示す構成で実施できる。図２は、回収工程の第２実施態様を説明するための溶融塩Ｍを収容する容器１０を示す断面図である。
　図２は、溶融塩Ｍが収容された容器１０に、第２治具２０ｂが設置されている状態を示す。第１治具２０ｂは、塩析出部２４ｂと、塩析出部２４ｂに接続される取手部２２ｂから構成される。取手部２２ｂは、溶融塩Ｍの液面から突出している。塩析出部２４ｂは、１枚の板を蛇腹状に折り曲げてなる構造を有している。
　また、図２においては、第２治具２０ｂの塩析出部２４ｂの表面に、特定金属塩Ｃ２が析出している。
　第２治具２０ｂの取手部２２ｂを把持し、第２治具２０ｂを紙面上方向に引き上げれば、特定金属塩Ｃ２を簡便に回収できる。
　なお、図２に示す態様においては、塩析出部２４ｂを構成する１枚の板を蛇腹状に折り曲げてなる構造は、１つのみであるが、塩析出部は、複数の上記構造を有していてもよい。また、図２に示す態様においては、１枚の板を蛇腹状に折り曲げてなる構造の折り曲げ線方向は、紙面奥手前方向であるが、上記折り曲げ線方向は、紙面上下方向となるように上記構造が配置されていてもよい。 More specifically, the second embodiment of the recovery step can be carried out by the configuration shown in Fig. 2. Fig. 2 is a cross-sectional view showing a vessel 10 containing molten salt M for explaining the second embodiment of the recovery step.
2 shows a state in which the second jig 20b is installed in the container 10 containing the molten salt M. The first jig 20b is composed of a salt-precipitating portion 24b and a handle portion 22b connected to the salt-precipitating portion 24b. The handle portion 22b protrudes from the liquid surface of the molten salt M. The salt-precipitating portion 24b has a structure formed by bending a single plate into an accordion-like shape.
In addition, in FIG. 2, the specific metal salt C2 is precipitated on the surface of the salt precipitated portion 24b of the second jig 20b.
The specific metal salt C2 can be easily recovered by gripping the handle 22b of the second jig 20b and pulling the second jig 20b upward in the plane of the drawing.
2, the salt deposition portion 24b has only one structure formed by folding a single plate into an accordion shape, but the salt deposition portion may have a plurality of such structures. Also, in the embodiment shown in FIG. 2, the folding line direction of the structure formed by folding a single plate into an accordion shape is the front-to-back direction on the paper, but the folding line direction may be the up-to-down direction on the paper.

（回収工程の第３実施態様）
　回収工程の一態様としては、特定金属成分を含む溶融塩を冷却し、溶融塩の溶融状態を保ったまま特定金属成分を含む特定金属塩を析出させる際に、温度制御自在な冷却部を有する第３治具を用い、冷却部の温度を変化させることによって溶融塩を冷却し、冷却部の表面に、特定金属塩を析出させ、冷却部を溶融塩から引き上げて、特定金属塩を溶融状態の溶融塩から回収する、第３実施態様が挙げられる。
　上記第３治具の冷却部によって溶融塩を冷却すると、冷却部の周囲の溶融塩は、より温度が低下しやすく、冷却部の表面において、特定金属塩が析出しやすい。特定金属塩が析出した第３治具を溶融塩から引き揚げると、固体として析出した特定金属塩が液体状の溶融塩から分離され、特定金属成分を含む特定金属塩が回収される。
　第３治具の冷却部の態様は特に制限されないが、例えば、冷媒が流通可能な管を内部に有する構造が挙げられる。冷媒は、特に制限されず、公知の冷媒を適用できる。また、冷媒の冷却方法も特に制限されない。
　冷却部は、冷媒が流通可能な管に対して、金属板または針金によって構成される網等が接続されて構成されていてもよい。冷却部が金属板または上記網等を有する場合、その部分に特定金属塩が効率的に析出しやすくなる。
　上記第３治具は、溶融塩に溶出しない材料で構成されることが好ましい。好ましい材料の例は、第１治具の好ましい材料と同様である。 (Third embodiment of recovery step)
One aspect of the recovery process is a third embodiment in which, when cooling a molten salt containing a specific metal component and precipitating a specific metal salt containing the specific metal component while maintaining the molten salt in a molten state, a third jig having a temperature-controllable cooling section is used to cool the molten salt by changing the temperature of the cooling section, precipitating the specific metal salt on the surface of the cooling section, and then the cooling section is pulled up from the molten salt to recover the specific metal salt from the molten molten salt.
When the molten salt is cooled by the cooling section of the third jig, the temperature of the molten salt around the cooling section is more likely to drop, and the specific metal salt is more likely to precipitate on the surface of the cooling section. When the third jig on which the specific metal salt has precipitated is lifted from the molten salt, the precipitated specific metal salt as a solid is separated from the liquid molten salt, and the specific metal salt containing the specific metal component is recovered.
The cooling section of the third jig may have any configuration, including, for example, a structure having a pipe therein through which a refrigerant can flow. The refrigerant is not particularly limited, and any known refrigerant can be used. The cooling method for the refrigerant is also not particularly limited.
The cooling unit may be configured by connecting a metal plate or a mesh made of wire to a pipe through which the refrigerant can flow. When the cooling unit has a metal plate or the mesh, the specific metal salt tends to precipitate efficiently in that part.
The third jig is preferably made of a material that does not dissolve in the molten salt. Preferred examples of the material are the same as those of the first jig.

　回収工程の第３実施態様は、より具体的には、図３に示す構成で実施できる。図３は、回収工程の第３実施態様を説明するための溶融塩Ｍを収容する容器１０を示す断面図である。
　図３は、溶融塩Ｍが収容された容器１０に、第３治具２０ｃが設置されている状態を示す。第３治具２０ｃは、図３中の破線で囲った部分である冷却部２４ｃを有する。冷却部２４ｃの内部には、冷媒が流通可能な管（図示せず）が設けられており、冷却部２４ｃを冷却可能である。
　また、図３においては、第３治具２０ｃの冷却部２４ｃの表面に、特定金属塩Ｃ３が析出している。
　第３治具２０ｃを紙面上方向に引き上げれば、特定金属塩Ｃ３を簡便に回収できる。 More specifically, the third embodiment of the recovery step can be carried out by the configuration shown in Fig. 3. Fig. 3 is a cross-sectional view showing a vessel 10 containing molten salt M for explaining the third embodiment of the recovery step.
Fig. 3 shows a state in which a third jig 20c is installed in a container 10 containing molten salt M. The third jig 20c has a cooling section 24c, which is the area surrounded by a dashed line in Fig. 3. A pipe (not shown) through which a refrigerant can flow is provided inside the cooling section 24c, and the cooling section 24c can be cooled.
In addition, in FIG. 3, a specific metal salt C3 is precipitated on the surface of the cooling portion 24c of the third jig 20c.
The specific metal salt C3 can be easily recovered by lifting the third jig 20c upward in the plane of the drawing.

（回収工程の第４実施態様）
　回収工程の一態様としては、特定金属塩を溶融状態の溶融塩から回収する際に、溶融塩が収容される溶融塩収容容器と、溶融塩収容容器に接続されて、溶融塩収容容器から排出された溶融塩が再び溶融塩収容容器に戻る循環路と、循環路の途中に配置されて固体を溶融塩から分離可能なフィルタと、を用い、析出した特定金属塩を含む溶融塩を、循環路に導入し、フィルタによって特定金属塩を溶融塩から分離し、フィルタから特定金属塩を回収する、第４実施態様が挙げられる。
　上記フィルタによって、溶融塩から特定金属塩を分離し、フィルタから特定金属塩を回収可能である。
　第４実施態様の実施態様としては、溶融塩収容容器に対して接続された循環路において、溶融塩を循環させる循環手段を有し、循環路の一端から、循環路の他端まで、溶融塩を送液する。この循環路において、上記フィルタを設置すると、析出した特定金属塩がフィルタに捕捉される。
　上記循環路から溶融塩の一部または全部を排出し、フィルタを循環路から取り出すと、特定金属塩が回収される。
　上記循環手段は、特に制限されず、公知の手段を適用できる。
　上記フィルタとしては、例えば、焼結金属フィルタ、セラミックフィルタ、ステンレス鋼製メッシュ等が挙げられる。フィルタの孔径等は、析出した特定金属塩によって適宜調整し得る。上記フィルタおよび循環路は、溶融塩に溶出しない材料で構成されることが好ましい。好ましい材料の例は、第１治具の好ましい材料と同様である。 (Fourth embodiment of recovery step)
One embodiment of the recovery process is a fourth embodiment, in which, when recovering a specific metal salt from molten molten salt, a molten salt storage container in which the molten salt is stored, a circulation path connected to the molten salt storage container and through which the molten salt discharged from the molten salt storage container returns to the molten salt storage container, and a filter positioned midway along the circulation path and capable of separating solids from the molten salt are used, and the molten salt containing the precipitated specific metal salt is introduced into the circulation path, the specific metal salt is separated from the molten salt by the filter, and the specific metal salt is recovered from the filter.
The filter separates the specific metal salt from the molten salt, and the specific metal salt can be recovered from the filter.
In one embodiment of the fourth aspect, a circulation path connected to a molten salt storage vessel includes a circulation means for circulating the molten salt, and the molten salt is sent from one end of the circulation path to the other end of the circulation path. When the filter is installed in this circulation path, the precipitated specific metal salt is captured by the filter.
A part or all of the molten salt is discharged from the circulation path, and the filter is removed from the circulation path, whereby the specific metal salt is recovered.
The circulation means is not particularly limited, and known means can be applied.
Examples of the filter include a sintered metal filter, a ceramic filter, and a stainless steel mesh. The pore size of the filter can be adjusted appropriately depending on the specific metal salt precipitated. The filter and the circulation path are preferably made of a material that does not dissolve in the molten salt. Examples of preferred materials are the same as those of the first jig.

　回収工程の第４実施態様は、より具体的には、図４に示す構成で実施できる。図４は、回収工程の第４実施態様を説明するための溶融塩Ｍを収容する容器１０を示す断面図である。
　図４は、溶融塩Ｍが収容された容器１０に、容器１０から排出された溶融塩Ｍが、再び容器１０に戻る循環路３２が接続されている状態を示す。循環路３２の途中には、固体を溶融塩から分離可能なフィルタ３４が配置される。さらに、循環路３２には、フィルタ３４と容器１０との間に、循環路３２の一端から、循環路３２の多端まで溶融塩Ｍを送液可能なポンプ３６が配置される。
　溶融塩Ｍ中に析出した特定金属塩Ｃ４は、溶融塩Ｍとともに循環路３２に導入され、フィルタ３４に捕捉される。
　循環路３２から溶融塩Ｍの一部または全部を排出し、フィルタ３４を循環路３２から取り出すと、特定金属塩Ｃ４を簡便に回収できる。 More specifically, the fourth embodiment of the recovery step can be carried out by the configuration shown in Fig. 4. Fig. 4 is a cross-sectional view showing a vessel 10 containing molten salt M for explaining the fourth embodiment of the recovery step.
4 shows a state in which a circulation path 32 is connected to a container 10 containing molten salt M, through which the molten salt M discharged from the container 10 returns to the container 10. A filter 34 capable of separating solids from the molten salt is disposed midway along the circulation path 32. Furthermore, a pump 36 capable of sending the molten salt M from one end of the circulation path 32 to the other end of the circulation path 32 is disposed between the filter 34 and the container 10.
The specific metal salt C4 precipitated in the molten salt M is introduced into the circulation path 32 together with the molten salt M and captured by the filter 34.
By discharging a part or all of the molten salt M from the circulation path 32 and removing the filter 34 from the circulation path 32, the specific metal salt C4 can be easily recovered.

　また、上記第１実施態様～第４実施態様で回収した特定金属塩を、溶融塩の融点よりも高い温度で加熱してもよい。
　上記の温度は、特定金属塩を析出させる温度よりも高く、かつ、析出工程を実施する前の溶融塩の温度よりも低い温度で行うことが好ましい。また、上記温度は、特定金属塩を析出させる温度よりも、１０～１５０℃高いことが好ましい。
　上記好ましい温度範囲で加熱すると、特定金属塩に付随して析出する溶融塩の構成成分を、特定金属塩から溶融して除去し、特定金属塩に含まれる特定金属成分の含有量を向上させることができる。 The specific metal salt recovered in the first to fourth embodiments may be heated at a temperature higher than the melting point of the molten salt.
The temperature is preferably higher than the temperature at which the specific metal salt is precipitated and lower than the temperature of the molten salt before the precipitation step, and is preferably 10 to 150° C. higher than the temperature at which the specific metal salt is precipitated.
When heated within the above preferred temperature range, the components of the molten salt that precipitate along with the specific metal salt are melted and removed from the specific metal salt, thereby increasing the content of the specific metal component contained in the specific metal salt.

　上記回収工程で回収された特定金属塩は、上述したように、特定金属成分を含む。
　特定金属成分は、上述したように、リチウムまたはナトリウムを含むことが好ましく、リチウムを含むことがより好ましい。
　特定金属塩がリチウムを含む場合、特定金属塩は、リチウムを含む硫酸塩が好ましく、リチウムおよびナトリウムを含む硫酸塩がより好ましい。上記特定金属塩に含まれる具体的な塩としては、ＬｉＮａＳＯ４、ＬｉＫＳＯ４、および、Ｌｉ２ＮａＫ（ＳＯ４）２からなる群から選択される少なくとも１種が挙げられる。
　リチウムを含む硫酸塩である特定金属塩は、Ｃｕ　Ｋα線で測定したＸ線回折チャートにおいて、３０．２～３０．５°の範囲に回折ピークが出現する空間群Ｐ３１ｃの結晶構造の結晶を含むことが好ましい。
　リチウムを含む硫酸塩である特定金属塩は、Ｃｕ　Ｋα線で測定したＸ線回折チャートにおいて、２３．２～２３．５°の範囲に回折ピークが出現する空間群Ｐ３１ｃの結晶構造の結晶、２２．４～２２．７°の範囲に回折ピークが出現する空間群Ｃｍｃ２１の結晶構造の結晶、および、２２．８～２３．１°の範囲に回折ピークが出現する空間群Ｐ２１２１２１の結晶構造の結晶からなる群から選択される少なくとも１つの結晶構造の結晶を含むことが好ましい。
　上記２３．２～２３．５°の範囲に回折ピークが出現する空間群Ｐ３１ｃの結晶構造の結晶としては、ＬｉＮａＳＯ４が挙げられる。２２．４～２２．７°の範囲に回折ピークが出現する空間群Ｃｍｃ２１の結晶構造の結晶としては、ＬｉＫＳＯ４が挙げられる。２２．８～２３．１°の範囲に回折ピークが出現する空間群Ｐ２１２１２１の結晶構造の結晶としては、Ｌｉ２ＮａＫ（ＳＯ４）２が挙げられる。また、Ｘ線回折チャートにおいて、最大の回折強度を示すピークが、上記各角度範囲に出現することも好ましい。
　上記Ｘ線回折チャートは、いわゆる集中法（θ／２θ法ともいわれる。）によって測定される。また、上記角度範囲は２θの範囲である。
　特定金属塩がナトリウムを含む場合、特定金属塩は、ナトリウムを含む炭酸塩が好ましく、ナトリウムおよびカリウムを含む炭酸塩がより好ましい。上記特定金属塩に含まれる具体的な塩としては、Ｎａ２ＣＯ３が挙げられる。
　リチウムを含む硫酸塩である特定金属塩は、Ｃｕ　Ｋα線で測定したＸ線回折チャートにおいて、２８．４～２８．７°の範囲に回折ピークが出現する空間群Ｃ２／ｍの結晶構造の結晶を含むことが好ましい。 The specific metal salt recovered in the recovery step contains the specific metal component, as described above.
As described above, the specific metal component preferably contains lithium or sodium, and more preferably contains lithium.
When the specific metal salt contains lithium, the specific metal salt is preferably a sulfate containing lithium, more preferably a sulfate containing lithium and sodium. Specific examples of the specific metal salt include at least one selected from the group consisting of LiNaSO 4 , LiKSO 4 , and Li 2 NaK(SO 4 ) 2 .
The specific metal salt, which is a lithium-containing sulfate, preferably contains crystals of a crystal structure of space group P31c, in which a diffraction peak appears in the range of 30.2 to 30.5° in an X-ray diffraction chart measured with Cu Kα radiation.
The specific metal salt, which is a lithium-containing sulfate, preferably contains crystals of at least one crystal structure selected from the group consisting of crystals having a crystal structure of space group P31c, which exhibits a diffraction peak in the range of 23.2 to 23.5° in an X-ray diffraction chart measured with Cu Kα radiation, crystals having a crystal structure of space group Cmc2 1 , which exhibits a diffraction peak in the range of 22.4 to 22.7°, and crystals having a crystal structure of space group P2 1 2 1 2 1 , which exhibits a diffraction peak in the range of 22.8 to 23.1°.
An example of a crystal having a crystal structure of space group P31c in which a diffraction peak appears in the above-mentioned range of 23.2 to 23.5° is LiNaSO 4. An example of a crystal having a crystal structure of space group Cmc2 1 in which a diffraction peak appears in the range of 22.4 to 22.7° is LiKSO 4. An example of a crystal having a crystal structure of space group P2 1 2 1 2 1 in which a diffraction peak appears in the range of 22.8 to 23.1° is Li 2 NaK(SO 4 ) 2. It is also preferable that the peak showing the maximum diffraction intensity appears in each of the above-mentioned angle ranges in the X-ray diffraction chart.
The X-ray diffraction chart is measured by the so-called focusing method (also known as the θ/2θ method), and the angle range is the range of 2θ.
When the specific metal salt contains sodium, the specific metal salt is preferably a carbonate containing sodium, more preferably a carbonate containing sodium and potassium. A specific salt contained in the specific metal salt is Na2CO3 .
The specific metal salt, which is a lithium-containing sulfate, preferably contains crystals having a crystal structure of space group C2/m, in which a diffraction peak appears in the range of 28.4 to 28.7° in an X-ray diffraction chart measured with Cu Kα radiation.

　得られた特定金属塩は、後処理を行って、その化学結合状態等を変化させてもよい。
　後処理としては、特に制限されず、特定金属成分の適用方法によって適宜調整可能である。 The specific metal salt thus obtained may be subjected to post-treatment to change its chemical bonding state, etc.
The post-treatment is not particularly limited and can be appropriately adjusted depending on the method of applying the specific metal component.

　例えば、上記後処理としては、得られた特定金属塩を、水に溶解して特定金属水溶液を得てもよい。さらに、上記特定金属水溶液に対して、所定の塩を添加し、沈殿物を生成させ、上記沈殿物を回収させることも好ましい。上記沈殿物を生成させる場合、上記特定金属成分がリチウムを含むことが好ましい。上記手順によって、特定金属塩を精製できる。
　上記沈殿物を生成させる手順の場合であって、特定金属成分がリチウムを含む場合、炭酸リチウム（Ｌｉ２ＣＯ３）が沈殿物であることが好ましい。
　また、上記手順において、炭酸塩を含む特定金属水溶液を８０℃以上として沈殿物を生成させることも好ましい。特定金属水溶液の温度を上記範囲に調整すると、炭酸リチウムの水への溶解度が低下しやすく、炭酸リチウムをより回収しやすくなる。
　また、上記手順において、得られたリチウム含有塩を水に溶解する際には、リチウム含有塩と水とを接触させればよい。リチウム含有塩は、上記治具（第１治具～第３治具）または第４実施態様に用いるフィルタに付着した状態で水と接触させてもよい。
　リチウム含有塩と水とを接触させる方法は特に制限されず、例えば、水にリチウム含有塩（またはリチウム含有塩が付着した上記治具またはフィルタ）を浸漬してもよいし、リチウム含有塩が付着した上記治具またはフィルタに対して水を供給（例えばシャワーにより水を供給）してもよい。水にリチウム含有塩（またはリチウム含有塩が付着した上記治具またはフィルタ）を浸漬する場合、水を撹拌することも好ましい。
　リチウム含有塩と水とを接触させる際、水の温度は、特に制限されないが、例えば、５℃以上が挙げられ、１５℃以上が好ましく、３０℃以上がより好ましく、５０℃以上がさらに好ましく、７０℃以上が特に好ましい。 For example, the post-treatment may involve dissolving the obtained specific metal salt in water to obtain a specific metal aqueous solution. Furthermore, it is also preferable to add a predetermined salt to the specific metal aqueous solution to form a precipitate, and then recover the precipitate. When forming the precipitate, it is preferable that the specific metal component contains lithium. The specific metal salt can be purified by the above procedure.
In the case of the above-mentioned procedure for producing a precipitate, when the specific metal component contains lithium, it is preferable that the precipitate is lithium carbonate (Li 2 CO 3 ).
In the above procedure, it is also preferable to generate a precipitate by heating the specific metal aqueous solution containing a carbonate to 80° C. or higher. When the temperature of the specific metal aqueous solution is adjusted to the above range, the solubility of lithium carbonate in water tends to decrease, making it easier to recover lithium carbonate.
In the above procedure, when dissolving the obtained lithium-containing salt in water, the lithium-containing salt may be brought into contact with water. The lithium-containing salt may be brought into contact with water in a state where it is attached to the jig (first jig to third jig) or the filter used in the fourth embodiment.
The method for contacting the lithium-containing salt with water is not particularly limited, and for example, the lithium-containing salt (or the jig or filter having the lithium-containing salt attached thereto) may be immersed in water, or water may be supplied to the jig or filter having the lithium-containing salt attached thereto (for example, water may be supplied by showering). When the lithium-containing salt (or the jig or filter having the lithium-containing salt attached thereto) is immersed in water, it is also preferable to stir the water.
When the lithium-containing salt is brought into contact with water, the temperature of the water is not particularly limited, but may be, for example, 5°C or higher, preferably 15°C or higher, more preferably 30°C or higher, even more preferably 50°C or higher, and particularly preferably 70°C or higher.

　得られた特定金属塩、および、後処理を行って得られた特定金属塩は、種々の用途に適用できる。
　例えば、特定金属成分がリチウムである場合、特定金属塩は、種々の原料として利用できる。例えば、特定金属塩は、ガラス原料、合金用の添加物原料、電池材料の原料、化学合成原料等に適用可能である。 The specific metal salt thus obtained and the specific metal salt obtained after the post-treatment can be used in a variety of applications.
For example, when the specific metal component is lithium, the specific metal salt can be used as a variety of raw materials, such as a glass raw material, an additive raw material for alloys, a raw material for battery materials, a raw material for chemical synthesis, and the like.

＜溶融塩の再生方法＞
　本発明の金属成分の回収方法は、溶融塩の再生に好ましく適用できる。
　より具体的には、特定金属成分がリチウムまたはナトリウムを含み、上記溶融塩が、ケイ素、アルミニウム、リチウムおよびナトリウムからなる群から選択される少なくとも１種とを含むガラス（化学強化用ガラス）を浸漬して得られる化学強化後溶融塩であることが好ましい。すなわち、本発明の溶融塩の再生方法は、上記化学強化後溶融塩に対して上記本発明の金属成分の回収方法を適用する方法である。
　化学強化用ガラスを溶融塩に浸漬して化学強化ガラスを得る化学強化処理では、化学強化用ガラスに含まれるリチウムまたはナトリウムが、塩交換によって溶融塩中のイオンと交換される。そうすると、化学強化後溶融塩は、リチウムまたはナトリウムを含む。上述したように、化学強化後溶融塩を再度、化学強化処理に供する場合には、上記塩交換が生じにくくなる場合がある。
　本発明の金属成分の回収方法では、特定金属成分（リチウムまたはナトリウム）を含む溶融塩から、特定金属塩を回収できるため、特定金属塩を回収した後の溶融塩においては、特定金属成分（リチウム）の濃度が低下する。
　よって、上記化学強化後溶融塩から特定金属塩を回収すると、特定金属成分（リチウムまたはナトリウム）の濃度が低下するため、化学強化後溶融塩を再生できる。 <Method for regenerating molten salt>
The method for recovering metal components of the present invention can be preferably applied to the regeneration of molten salt.
More specifically, the specific metal component preferably contains lithium or sodium, and the molten salt is a chemically strengthened molten salt obtained by immersing glass (glass for chemical strengthening) containing at least one selected from the group consisting of silicon, aluminum, lithium, and sodium. That is, the method for regenerating a molten salt of the present invention is a method in which the method for recovering a metal component of the present invention is applied to the chemically strengthened molten salt.
In a chemical strengthening process in which chemically strengthened glass is obtained by immersing the glass in molten salt, lithium or sodium contained in the glass is exchanged with ions in the molten salt through salt exchange. As a result, the molten salt after chemical strengthening contains lithium or sodium. As described above, if the molten salt after chemical strengthening is subjected to a chemical strengthening process again, the salt exchange may be less likely to occur.
In the method for recovering a metal component of the present invention, a specific metal salt can be recovered from a molten salt containing the specific metal component (lithium or sodium), and therefore the concentration of the specific metal component (lithium) is reduced in the molten salt after the specific metal salt has been recovered.
Therefore, when the specific metal salt is recovered from the chemically strengthened molten salt, the concentration of the specific metal component (lithium or sodium) decreases, and the chemically strengthened molten salt can be regenerated.

　上記化学強化後溶融塩を得る際に、用いる化学強化用ガラスは、ケイ素、アルミニウムおよびリチウムまたはナトリウムを含めば特に制限されず、公知の組成の化学強化用ガラスを適用できる。
　化学強化用ガラスについては、化学強化ガラスの製造方法の部分で詳述する。 The chemically strengthened glass used to obtain the chemically strengthened molten salt is not particularly limited as long as it contains silicon, aluminum, and lithium or sodium, and chemically strengthened glasses of known compositions can be used.
The glass for chemical strengthening will be described in detail in the section on the method for producing chemically strengthened glass.

　本発明の溶融塩の再生方法に供する化学強化後溶融塩の好ましい組成については、上記金属成分の回収方法で述べた溶融塩の組成と同様であるため、説明を省略する。 The preferred composition of the chemically strengthened molten salt used in the molten salt regeneration method of the present invention is the same as the composition of the molten salt described in the metal component recovery method above, so further explanation will be omitted.

　なお、上記本発明の金属成分の回収方法では、特定金属塩に、特定金属成分以外の成分が含まれる場合がある。その際には、本発明の溶融塩の再生方法には、回収された特定金属塩に含まれる成分を溶融塩に添加し、溶融塩の成分を調整する工程が含まれていてもよい。
　すなわち、本発明の溶融塩の再生方法においては、化学強化後溶融塩から特定金属成分を回収した後、さらに、溶融塩の成分を調整してもよい。
　溶融塩の成分を調整する際には、硫酸塩を添加することが好ましい。また、ナトリウム塩を含む成分を添加することが好ましく、硫酸ナトリウムを含む成分を添加することがより好ましい。上記硫酸塩は、特定金属成分を含まないことが好ましい。
　ここで、上記特定金属塩以外の成分としては、硝酸塩も挙げられる。よって、回収された特定金属塩に含まれる硝酸イオンの含有量を分析することも好ましい。上記硝酸塩は、特定金属成分を含まないことも好ましい。
　回収された特定金属塩に含まれる硝酸イオンの含有量を分析する方法としては、ナフチルエチレンジアミン吸光光度法を用いて硝酸イオン濃度の測定を行う方法が挙げられる。より具体的には、共立理化学研究所製デジタルパックテスト（ＤＰＭ２－ＮＯ３）を用いる方法が挙げられる。
　回収された特定金属塩に含まれる硫酸イオンの含有量を定量する方法としては、塩化バリウム比濁法を用いて硫酸イオン濃度の測定を行う方法が挙げられる。より具体的には、共立理化学研究所製デジタルパックテスト（ＤＰＭ２－ＳＯ４）を用いる方法が挙げられる。 In the method for recovering a metal component of the present invention, the specific metal salt may contain components other than the specific metal component. In such cases, the method for regenerating a molten salt of the present invention may include a step of adding the components contained in the recovered specific metal salt to the molten salt to adjust the composition of the molten salt.
That is, in the method for regenerating a molten salt of the present invention, after recovering a specific metal component from the chemically strengthened molten salt, the components of the molten salt may be further adjusted.
When adjusting the components of the molten salt, it is preferable to add a sulfate. It is also preferable to add a component containing a sodium salt, and it is more preferable to add a component containing sodium sulfate. It is preferable that the sulfate does not contain a specific metal component.
Here, components other than the specific metal salts include nitrates. Therefore, it is also preferable to analyze the content of nitrate ions contained in the recovered specific metal salts. It is also preferable that the nitrates do not contain specific metal components.
The amount of nitrate ions contained in the recovered specific metal salts can be analyzed by measuring the nitrate ion concentration using naphthylethylenediamine absorptiometry, more specifically, by using a Digital Pack Test (DPM2-NO3) manufactured by Kyoritsu Chemical Research Institute.
The sulfate ion content in the recovered specific metal salt can be determined by measuring the sulfate ion concentration using barium chloride turbidimetry, for example, using a Digital Pack Test (DPM2-SO4) manufactured by Kyoritsu Chemical Research Institute.

　また、溶融塩の成分の調整を行う際には、化学強化後溶融塩から特定金属成分を回収した後の溶融塩に含まれる成分を分析し、溶融塩に添加する各成分の量を決定し、溶融塩の成分を調整することも好ましい。
　溶融塩に含まれる金属成分の含有量の測定方法としては、原子吸光法が挙げられる。より具体的には、溶融塩を所定量の純水に溶解して希釈し、水溶液中の金属成分の濃度を原子吸光光度計で測定する方法が挙げられる。本明細書において、上記原子吸光法の測定には、日立ハイテク社製偏光ゼーマン原子吸光光度計　ＺＡ３３００を用いる。
　また、溶融塩に含まれる硝酸イオンの含有量の測定方法としては、上述した回収された特定金属塩に含まれる硝酸イオンの含有量を分析する方法と同様の方法が挙げられる。また、溶融塩に含まれる硫酸イオンの含有量の測定方法としては、上述した回収された特定金属塩に含まれる硫酸イオンの含有量を分析する方法と同様の方法が挙げられる。 Furthermore, when adjusting the components of the molten salt, it is also preferable to analyze the components contained in the molten salt after recovering specific metal components from the molten salt after chemical strengthening, determine the amount of each component to be added to the molten salt, and adjust the components of the molten salt.
Atomic absorption spectrometry can be used to measure the content of metal components contained in a molten salt. More specifically, a method can be used in which the molten salt is dissolved in a predetermined amount of pure water to dilute the solution, and the concentration of the metal components in the aqueous solution is measured using an atomic absorption spectrophotometer. In this specification, a polarized Zeeman atomic absorption spectrophotometer ZA3300 manufactured by Hitachi High-Tech Corporation is used for the atomic absorption spectrometry measurement.
The method for measuring the content of nitrate ions in the molten salt may be the same as the method for analyzing the content of nitrate ions in the recovered specific metal salt described above.The method for measuring the content of sulfate ions in the molten salt may be the same as the method for analyzing the content of sulfate ions in the recovered specific metal salt described above.

　化学強化後溶融塩がリチウムを含む場合、溶融塩の成分を調整する好ましい態様の１つとしては、例えば、ナトリウム塩を含む成分を添加することが好ましく、硫酸ナトリウムを含む成分を添加することがより好ましい。
　また、特定金属塩として回収される成分に応じて、硫酸ナトリウム以外の成分を添加してもよい。上記成分としては、硝酸塩が挙げられ、より具体的には、硝酸ナトリウム、硝酸カリウム、および、硫酸カリウムからなる群から選択される１種以上の成分が挙げられる。また、硫酸ナトリウムおよび上記成分の比率は、特定金属塩として回収される成分に応じて調整することで、溶融塩における組成を略一定に保つことができる。 When the molten salt after chemical strengthening contains lithium, one preferred aspect of adjusting the components of the molten salt is, for example, adding a component containing a sodium salt, and adding a component containing sodium sulfate is more preferred.
Furthermore, components other than sodium sulfate may be added depending on the components recovered as the specific metal salt. Examples of such components include nitrates, more specifically, one or more components selected from the group consisting of sodium nitrate, potassium nitrate, and potassium sulfate. Furthermore, by adjusting the ratio of sodium sulfate and the above components depending on the components recovered as the specific metal salt, the composition of the molten salt can be maintained approximately constant.

　また、化学強化用ガラスとしては、ナトリウムを含む場合があり、化学強化用ガラスを溶融塩に浸漬して化学強化ガラスを得る化学強化処理では、化学強化用ガラスに含まれるナトリウムが、塩交換によって溶融塩中のイオン（例えばカリウムイオン）と交換される場合もある。そうすると、化学強化後溶融塩は、ナトリウムを含む場合がある。
　上述したように、化学強化後溶融塩を再度、化学強化処理に供する場合には、上記塩交換が生じにくくなる場合がある。
　本発明の金属成分の回収方法では、特定金属成分（ナトリウム）を含む溶融塩から、特定金属塩を回収できるため、特定金属塩を回収した後の溶融塩においては、特定金属成分（ナトリウム）の濃度が低下する。
　よって、上記化学強化後溶融塩から特定金属塩を回収すると、特定金属成分（ナトリウム）の濃度が低下するため、化学強化後溶融塩を再生できる。
　また、上述したように、本発明の溶融塩の再生方法においては、化学強化後溶融塩から特定金属成分を回収した後、さらに、溶融塩の成分を調整してもよい。
　化学強化後溶融塩がナトリウムを含む場合、溶融塩の成分を調整する際には、炭酸塩または硫酸塩を添加することが好ましい。上記炭酸塩は、特定金属成分を含まないことが好ましい。
　ここで、上記特定金属塩以外の成分としては、硝酸塩も挙げられる。よって、回収された特定金属塩に含まれる硝酸イオンの含有量を分析することも好ましい。硝酸イオンの含有量の分析方法は上述した通りである。上記硝酸塩は、特定金属成分を含まないことも好ましい。 Furthermore, chemically strengthened glass may contain sodium, and in a chemical strengthening process in which the chemically strengthened glass is obtained by immersing the chemically strengthened glass in molten salt, the sodium contained in the chemically strengthened glass may be exchanged with ions (e.g., potassium ions) in the molten salt by salt exchange. As a result, the molten salt after chemical strengthening may contain sodium.
As described above, when the molten salt after chemical strengthening is subjected to a chemical strengthening treatment again, the salt exchange may not easily occur.
In the method for recovering a metal component of the present invention, a specific metal salt can be recovered from a molten salt containing the specific metal component (sodium), and therefore the concentration of the specific metal component (sodium) is reduced in the molten salt after the specific metal salt has been recovered.
Therefore, when the specific metal salt is recovered from the chemically strengthened molten salt, the concentration of the specific metal component (sodium) decreases, and the chemically strengthened molten salt can be regenerated.
As described above, in the method for regenerating a molten salt of the present invention, after recovering the specific metal component from the chemically strengthened molten salt, the components of the molten salt may be further adjusted.
When the molten salt after chemical strengthening contains sodium, it is preferable to add a carbonate or a sulfate when adjusting the components of the molten salt. The carbonate preferably does not contain a specific metal component.
Here, components other than the specific metal salts include nitrates. Therefore, it is also preferable to analyze the content of nitrate ions contained in the recovered specific metal salts. The method for analyzing the content of nitrate ions is as described above. It is also preferable that the nitrates do not contain specific metal components.

　また、溶融塩の成分の調整を行う際には、化学強化後溶融塩から特定金属成分を回収した後の溶融塩に含まれる成分を分析し、溶融塩に添加する各成分の量を決定し、溶融塩の成分を調整することも好ましい。
　溶融塩に含まれる金属成分の含有量および硝酸イオンの含有量の測定方法は上述した通りである。
　また、溶融塩に含まれる炭酸イオンの含有量の測定方法は、溶融塩の水溶液を調製し、水溶液においてイオンメータを用いて測定する方法が挙げられる。より具体的には、溶融塩の水溶液を、東興化学研究所社製イオンメータ（型番：ＴｉＮ－９００４ｉ）を用い、炭酸ガス電極（型番：９００４Ｋ－ＳＲ）で炭酸イオン濃度を測定できる。 Furthermore, when adjusting the components of the molten salt, it is also preferable to analyze the components contained in the molten salt after recovering specific metal components from the molten salt after chemical strengthening, determine the amount of each component to be added to the molten salt, and adjust the components of the molten salt.
The methods for measuring the content of metal components and the content of nitrate ions contained in the molten salt are as described above.
The carbonate ion content of the molten salt can be measured by preparing an aqueous solution of the molten salt and measuring the carbonate ion concentration in the aqueous solution using an ion meter. More specifically, the carbonate ion concentration in the aqueous solution of the molten salt can be measured using an ion meter (model number: TiN-9004i) manufactured by Toko Chemical Research Institute Co., Ltd. and a carbon dioxide electrode (model number: 9004K-SR).

　化学強化後溶融塩がナトリウムを含む場合、溶融塩の成分を調整する好ましい１つの態様としては、例えば、カリウム塩を含む成分を添加することが好ましく、炭酸カリウムを含む成分を添加することがより好ましい。
　また、特定金属塩として回収される成分に応じて、炭酸カリウム以外の成分を添加してもよい。上記成分としては、硝酸塩が挙げられ、より具体的には、硝酸カリウムが挙げられる。すなわち、溶融塩の成分を調整する好ましい１つの態様としては、炭酸カリウムおよび硝酸カリウムを含む成分を添加する態様が挙げられる。また、炭酸カリウムおよび上記成分の比率は、特定金属塩として回収される成分に応じて調整することで、溶融塩における組成を略一定に保つことができる。 When the molten salt after chemical strengthening contains sodium, one preferred embodiment of adjusting the components of the molten salt is, for example, adding a component containing a potassium salt, and adding a component containing potassium carbonate is more preferred.
Furthermore, components other than potassium carbonate may be added depending on the components recovered as the specific metal salt. Examples of such components include nitrates, more specifically potassium nitrate. That is, one preferred embodiment for adjusting the components of the molten salt is to add components containing potassium carbonate and potassium nitrate. Furthermore, by adjusting the ratio of potassium carbonate and the above components depending on the components recovered as the specific metal salt, the composition of the molten salt can be maintained approximately constant.

　上述したように、本発明の溶融塩の再生方法によれば、溶融塩における特定金属成分（例えば、リチウムまたはナトリウム）の含有量を低減しつつ、さらに、溶融塩の成分を調整する工程を含むことで、所定の組成を維持することができる。
　本発明の溶融塩の再生方法を適用すると、化学強化に供する溶融塩を交換することなく、溶融塩を繰り返し使用することができる。 As described above, according to the method for regenerating a molten salt of the present invention, it is possible to reduce the content of a specific metal component (e.g., lithium or sodium) in the molten salt, while also including a step of adjusting the components of the molten salt, thereby maintaining a predetermined composition.
By applying the method for regenerating molten salt of the present invention, the molten salt used for chemical strengthening can be reused repeatedly without replacing it.

＜化学強化用ガラスの製造方法＞
　本発明の金属成分の回収方法において回収された特定金属塩は、化学強化用ガラスの原料として用いることが好ましい。
　すなわち、本発明の化学強化用ガラスの製造方法は、本発明の金属成分の回収方法によって回収された特定金属塩を、化学強化用ガラスの原料の一部として用い、化学強化用ガラスを製造する方法である。
　例えば、特定金属成分としてリチウムを含む場合、化学強化ガラスの原料としてリチウムを含む特定金属塩を用いることができる。特定金属塩は、上述したように後処理を行い、金属成分の回収方法で回収した直後の特定金属塩とは、化学結合状態等が異なっていてもよい。
　以下、本発明の化学強化用ガラスの製造方法によって製造される化学強化用ガラスの好ましい態様について説明する。
　なお、以下、化学強化用ガラスの好ましい組成（以下、「母ガラス組成」ともいう。）について説明する。 <Method of manufacturing glass for chemical strengthening>
The specific metal salt recovered by the method for recovering metal components of the present invention is preferably used as a raw material for chemically strengthened glass.
That is, the method for producing chemically strengthened glass of the present invention uses the specific metal salt recovered by the metal component recovery method of the present invention as part of the raw materials for chemically strengthened glass. Is a method for producing chemically strengthened glass.
For example, when lithium is contained as the specific metal component, a specific metal salt containing lithium can be used as a raw material for chemically strengthened glass. The specific metal salt may be subjected to post-treatment as described above, and may have a different chemical bonding state, etc., from the specific metal salt immediately after recovery by the metal component recovery method.
Hereinafter, preferred embodiments of the chemically strengthened glass produced by the method for producing chemically strengthened glass of the present invention will be described.
A preferred composition of the glass for chemical strengthening (hereinafter also referred to as "mother glass composition") will be described below.

　母ガラス組成は、Ｌｉ（リチウム）を含むことが好ましく、ＬｉとＳｉ（ケイ素）とＡｌ（アルミニウム）とを含むアルミノシリケートガラスが好ましい。
　母ガラス組成の第１態様としては、より具体的には、酸化物基準のモル％表示で、
　ＳｉＯ２を５２～７５％、
　Ａｌ２Ｏ３を８～２０％、
　Ｌｉ２Ｏを５～１６％、含有することが好ましい。
　以下、好ましい母ガラス組成の第１態様について説明する。なお、以下、例えばＳｉＯ２の酸化物基準のモル百分率表示による含有量を「［ＳｉＯ２］」のように記載する場合がある。 The mother glass composition preferably contains Li (lithium), and is preferably an aluminosilicate glass containing Li, Si (silicon), and Al (aluminum).
More specifically, the first aspect of the mother glass composition is, in mole percent on an oxide basis,
SiO2 52-75%,
8-20% Al 2 O 3 ,
It is preferable that Li 2 O is contained in an amount of 5 to 16%.
A first embodiment of a preferred mother glass composition will be described below. Note that, hereinafter, for example, the content of SiO 2 expressed as a mole percentage based on oxide may be expressed as "[SiO 2 ]".

　ＳｉＯ２はガラスの骨格を構成する成分である。また、化学的耐久性を上げる成分であり、ガラス表面に傷がついた時のクラックの発生を低減させる成分である。
　ＳｉＯ２の含有量は、好ましくは５２％以上、さらに好ましくは５５％以上、特に好ましくは６０％以上である。一方、溶融性をよくする観点から、ＳｉＯ２の含有量は、好ましくは７５％以下、より好ましくは７２％以下、さらに好ましくは７０％以下、特に好ましくは６８％以下である。 SiO2 is a component that constitutes the skeleton of glass. It also increases chemical durability and reduces the occurrence of cracks when the glass surface is scratched.
The SiO2 content is preferably 52% or more, more preferably 55% or more, and particularly preferably 60% or more. On the other hand, from the viewpoint of improving melting property, the SiO2 content is preferably 75% or less, more preferably 72% or less, even more preferably 70% or less, and particularly preferably 68% or less.

　Ａｌ２Ｏ３は化学強化の際のイオン交換性能を向上させ、強化後の表面圧縮応力を大きくする観点から有効な成分である。
　Ａｌ２Ｏ３の含有量は好ましくは８％以上、より好ましくは９％以上、さらに好ましくは１０％以上、特に好ましくは１１％以上、典型的には１２％以上である。一方、Ａｌ２Ｏ３の含有量が多すぎると溶融中に結晶が成長しやすくなり、失透欠点による歩留まり低下が生じやすい。また、ガラスの粘性が増大し溶融性が低下する。Ａｌ２Ｏ３の含有量は、２０％以下が好ましく、より好ましくは１９％以下、さらに好ましくは１８％以下である。 Al 2 O 3 is an effective component from the viewpoint of improving ion exchange performance during chemical strengthening and increasing the surface compressive stress after strengthening.
The Al2O3 content is preferably 8% or more, more preferably 9% or more, even more preferably 10% or more, particularly preferably 11% or more, and typically 12% or more. On the other hand, if the Al2O3 content is too high, crystals tend to grow during melting, which tends to reduce yield due to devitrification defects. In addition, the viscosity of the glass increases and the melting property deteriorates. The Al2O3 content is preferably 20% or less, more preferably 19% or less, and even more preferably 18% or less.

　ＳｉＯ２とＡｌ２Ｏ３とは、いずれもガラスの構造を安定させる成分であり、脆性を低くするためには合計の含有量は好ましくは６５％以上、より好ましくは７０％以上、さらに好ましくは７５％以上である。 Both SiO2 and Al2O3 are components that stabilize the structure of glass, and in order to reduce brittleness, the total content is preferably 65% or more, more preferably 70% or more, and even more preferably 75% or more.

　Ｌｉ２Ｏは、イオン交換により表面圧縮応力を形成させる成分であり、ガラスの溶融性を向上させる成分である。母ガラス組成がＬｉ２Ｏを含有することにより、ガラス表面のリチウムイオンをナトリウムイオンにイオン交換し、さらにナトリウムイオンをカリウムイオンにイオン交換する方法で、表面圧縮応力を導入可能である。好ましい応力プロファイルを得やすい観点から、Ｌｉ２Ｏの含有量は、好ましくは５％以上、より好ましくは７％以上、さらに好ましくは９％以上、特に好ましくは１０％以上、最も好ましくは１１％以上である。
　なお、本明細書において「応力プロファイル」は、ガラス表面からの深さを変数として圧縮応力値を表したパターンである。負の圧縮応力値は、引張応力を意味する。
　本明細書において「応力プロファイル」の測定は、光導波表面応力計または散乱光光弾性応力計を用いる方法で測定できる。
　一方、Ｌｉ２Ｏの含有量が多すぎるとガラス成型時の結晶成長速度が大きくなり、失透欠点による歩留まり低下の問題が大きく場合がある。Ｌｉ２Ｏの含有量は、好ましくは２０％以下、より好ましくは１６％以下、さらに好ましくは１４％以下、特に好ましくは１２％以下である。 Li 2 O is a component that forms surface compressive stress by ion exchange and improves the meltability of glass. When the mother glass composition contains Li 2 O, surface compressive stress can be introduced by ion-exchanging lithium ions on the glass surface with sodium ions and then ion-exchanging the sodium ions with potassium ions. From the viewpoint of easily obtaining a preferable stress profile, the Li 2 O content is preferably 5% or more, more preferably 7% or more, even more preferably 9% or more, particularly preferably 10% or more, and most preferably 11% or more.
In this specification, the term "stress profile" refers to a pattern that expresses compressive stress values with the depth from the glass surface as a variable. A negative compressive stress value means tensile stress.
In this specification, the "stress profile" can be measured by a method using an optical waveguide surface stress meter or a scattered light photoelastic stress meter.
On the other hand, if the Li 2 O content is too high, the crystal growth rate during glass molding increases, and there may be a significant problem of reduced yield due to devitrification defects. The Li 2 O content is preferably 20% or less, more preferably 16% or less, even more preferably 14% or less, and particularly preferably 12% or less.

　Ｎａ２ＯおよびＫ２Ｏは、いずれも必須ではないが、ガラスの溶融性を向上させ、ガラスの結晶成長速度を小さくする成分であり、イオン交換性能を向上させるために合計で２％以上含有することが好ましい。また、合計で好ましくは１０％以下、好ましくは９％以下、より好ましくは８％以下、さらに好ましくは７％以下、特に好ましくは５％以下である。 Although neither Na 2 O nor K 2 O is essential, they are components that improve the meltability of the glass and reduce the crystal growth rate of the glass, and in order to improve the ion exchange performance, they are preferably contained in a total amount of 2% or more, and their total amount is preferably 10% or less, preferably 9% or less, more preferably 8% or less, even more preferably 7% or less, and particularly preferably 5% or less.

　Ｎａ２Ｏは、カリウム塩を用いる化学強化処理において表面圧縮応力層を形成させる成分であり、またガラスの溶融性を向上させ得る成分である。その効果を得るために、Ｎａ２Ｏの含有量は、１％以上が好ましく、より好ましくは２％以上、さらに好ましくは３％以上、特に好ましくは４％以上である。一方、ナトリウム塩による強化処理において表面圧縮応力（ＣＳ）が低下するのを避ける観点、また内部の圧縮応力を高くする観点から、８％以下が好ましく、７％以下がより好ましく、６％以下がさらに好ましく、５％以下が特に好ましい。 Na 2 O is a component that forms a surface compressive stress layer in a chemical strengthening treatment using a potassium salt and can also improve the meltability of glass. To achieve this effect, the content of Na 2 O is preferably 1% or more, more preferably 2% or more, even more preferably 3% or more, and particularly preferably 4% or more. On the other hand, from the viewpoint of avoiding a decrease in surface compressive stress (CS) in a strengthening treatment using a sodium salt and from the viewpoint of increasing internal compressive stress, the content is preferably 8% or less, more preferably 7% or less, even more preferably 6% or less, and particularly preferably 5% or less.

　Ｋ２Ｏは、イオン交換性能を向上させる等の目的で含有させてもよい。Ｋ２Ｏを含有させる場合の含有量は、０．１％以上が好ましく、より好ましくは０．１５％以上、特に好ましくは０．２％以上である。失透をより防止するためには０．５％以上が好ましく、１．２％以上がより好ましい。一方、Ｋを多く含むことで脆性や、強化時の逆交換によって表層応力の低下の要因となる場合があることから、５％以下が好ましく、３％以下がより好ましい。 K 2 O may be contained for the purpose of improving ion exchange performance, etc. When K 2 O is contained, the content is preferably 0.1% or more, more preferably 0.15% or more, particularly preferably 0.2% or more. In order to further prevent devitrification, 0.5% or more is preferable, and 1.2% or more is more preferable. On the other hand, since a large amount of K may cause brittleness or a decrease in surface stress due to back exchange during strengthening, 5% or less is preferable, and 3% or less is more preferable.

　Ｌｉ２Ｏの含有量、Ｎａ２Ｏの含有量、および、Ｋ２Ｏの含有量の合計であるＲは、好ましくは５％以上であり、より好ましくは８％以上であり、さらに好ましくは１０％以上であり、特に好ましくは１２％以上である。上記Ｒは、２５％以下が好ましく、２０％以下がより好ましい。 The total content R of Li 2 O, Na 2 O, and K 2 O is preferably 5% or more, more preferably 8% or more, even more preferably 10% or more, and particularly preferably 12% or more. The content R is preferably 25% or less, and more preferably 20% or less.

　上記Ｒに対するＬｉ２Ｏの含有量の比（［Ｌｉ２Ｏ］／（［Ｌｉ２Ｏ］＋［Ｎａ２Ｏ］＋［Ｋ２Ｏ］）、以下、「Ｌｉ２Ｏ／Ｒ２Ｏ」とも記載する）は、深層部の圧縮応力に対する化学強化特性をより向上する観点から、０．５２以上がより好ましく、０．５５以上がさらに好ましい。Ｌｉ２Ｏ／Ｒ２Ｏは、化学薬品耐久性をより高める観点から、０．８０以下がより好ましく、０．７８以下が更に好ましく、０．７５以下が特に好ましい。 The ratio of the Li2O content to the R ([ Li2O ]/([ Li2O ]+[ Na2O ]+[ K2O ]), hereinafter also referred to as " Li2O / R2O ") is more preferably 0.52 or more, and even more preferably 0.55 or more, from the viewpoint of further improving the chemical strengthening properties against compressive stress in the deep layer. From the viewpoint of further improving chemical durability, Li2O / R2O is more preferably 0.80 or less, even more preferably 0.78 or less, and particularly preferably 0.75 or less.

　上記Ｒに対するＮａ２Ｏの含有量の比（［Ｎａ２Ｏ］／（［Ｌｉ２Ｏ］＋［Ｎａ２Ｏ］＋［Ｋ２Ｏ］）、以下、「Ｎａ２Ｏ／Ｒ２Ｏ」とも記載する）は、深層部の圧縮応力に対する化学強化特性をより向上する観点から、０．０５以上が好ましく、０．０８以上がより好ましく、０．１０以上がさらに好ましい。Ｎａ２Ｏ／Ｒ２Ｏは、化学薬品耐久性をより高める観点から、０．６０以下が好ましく、０．５０以下がより好ましく、０．４０以下が更に好ましく、０．３０以下が特に好ましい。 The ratio of the Na2O content to the R ([ Na2O ]/([ Li2O ]+[ Na2O ]+[ K2O ]), hereinafter also referred to as " Na2O / R2O ") is preferably 0.05 or more, more preferably 0.08 or more, and even more preferably 0.10 or more, from the viewpoint of further improving the chemical strengthening properties against compressive stress in the deep layer. From the viewpoint of further improving chemical durability, Na2O / R2O is preferably 0.60 or less, more preferably 0.50 or less, even more preferably 0.40 or less, and particularly preferably 0.30 or less.

　上記Ｒに対するＫ２Ｏの含有量の比（［Ｋ２Ｏ］／（［Ｌｉ２Ｏ］＋［Ｎａ２Ｏ］＋［Ｋ２Ｏ］）、以下、「Ｋ２Ｏ／Ｒ２Ｏ」とも記載する）は、ガラスの電気抵抗をより向上する観点から、０．０５以上が好ましく、０．０８以上がより好ましく、０．１０以上がさらに好ましい。Ｋ２Ｏ／Ｒ２Ｏは、表面近傍の圧縮応力に対する化学強化特性をより高める　観点から、０．５０以下が好ましく、０．４０以下がより好ましく、０．３０以下が更に好ましく、０．２０以下が特に好ましい。 The ratio of the content of K 2 O to the R ([K 2 O]/([Li 2 O] + [Na 2 O] + [K 2 O]), hereinafter also referred to as "K 2 O/R 2 O") is preferably 0.05 or more, more preferably 0.08 or more, and even more preferably 0.10 or more, from the viewpoint of further improving the electrical resistance of the glass. From the viewpoint of further improving the chemical strengthening properties against compressive stress near the surface, K 2 O/R 2 O is preferably 0.50 or less, more preferably 0.40 or less, even more preferably 0.30 or less, and particularly preferably 0.20 or less.

　また、Ｌｉ２Ｏ／Ｒ２Ｏと、Ｎａ２Ｏ／Ｒ２Ｏと、Ｋ２Ｏ／Ｒ２Ｏとの積は、失透温度の上昇を抑制する耐観点から、０．００５以上が好ましく、０．００８以上がより好ましく、０．０１０以上がさらに好ましい。また、上記積は、耐薬品性を向上させる観点から、０．０３０以下が好ましく、０．０２８以下がより好ましい。 Moreover, the product of Li2O / R2O , Na2O / R2O , and K2O / R2O is preferably 0.005 or more, more preferably 0.008 or more, and even more preferably 0.010 or more from the viewpoint of suppressing an increase in the devitrification temperature. Moreover, from the viewpoint of improving chemical resistance, the product is preferably 0.030 or less, and more preferably 0.028 or less.

　上記Ｒに対するＡｌ２Ｏ３の含有量の比（［Ａｌ２Ｏ３］／（［Ｌｉ２Ｏ］＋［Ｎａ２Ｏ］＋［Ｋ２Ｏ］）、以下、「Ａｌ２Ｏ３／Ｒ２Ｏ」とも記載する）は、０．２０以上が好ましく、０．３０以上がより好ましく、０．４０以上がさらに好ましく、０．５０以上がより好ましい。Ａｌ２Ｏ３／Ｒ２Ｏは、０．９０以下が好ましく、０．８８以下がより好ましく、０．８５以下が更に好ましい。 The ratio of the Al2O3 content to the R ([ Al2O3 ]/( [ Li2O ] + [ Na2O ] + [ K2O ]), hereinafter also referred to as " Al2O3 /R2O") is preferably 0.20 or more, more preferably 0.30 or more, even more preferably 0.40 or more, and still more preferably 0.50 or more. Al2O3 / R2O is preferably 0.90 or less, more preferably 0.88 or less , and even more preferably 0.85 or less.

　ＭｇＯは、溶解時の粘性を下げる等のために含有してもよい。ＭｇＯの含有量は、好ましくは０．５％以上、より好ましくは１％以上、さらに好ましくは２％以上である、特に好ましくは３％以上である。一方、ＭｇＯの含有量が多すぎると化学強化処理時に圧縮応力層を大きくしにくくなる場合がある。ＭｇＯの含有量は好ましくは１５％以下であり、より好ましくは１０％以下であり、さらに好ましくは８％以下であり、特に好ましくは６％以下である。 MgO may be included to reduce viscosity during dissolution, etc. The MgO content is preferably 0.5% or more, more preferably 1% or more, even more preferably 2% or more, and particularly preferably 3% or more. On the other hand, if the MgO content is too high, it may be difficult to increase the compressive stress layer during chemical strengthening treatment. The MgO content is preferably 15% or less, more preferably 10% or less, even more preferably 8% or less, and particularly preferably 6% or less.

　ＺｒＯ２は含有させなくともよいが、化学強化ガラスの表面圧縮応力を増大させる観点から含有することが好ましい。ＺｒＯ２の含有量は、好ましくは０．１％以上、より好ましくは０．１５％以上、さらに好ましくは０．２％以上、特に好ましくは０．２５％以上、典型的には０．３％以上である。一方、ＺｒＯ２の含有量が多すぎると失透欠点が発生やすくなり、化学強化処理時に圧縮応力値を大きくしにくくなる場合がある。ＺｒＯ２の含有量は好ましくは２％以下であり、より好ましくは１．５％以下であり、さらに好ましくは１％以下であり、特に好ましくは０．８％以下である。 Although ZrO2 does not have to be contained, it is preferable to contain it from the viewpoint of increasing the surface compressive stress of chemically strengthened glass. The content of ZrO2 is preferably 0.1% or more, more preferably 0.15% or more, even more preferably 0.2% or more, particularly preferably 0.25% or more, typically 0.3% or more. On the other hand, if the content of ZrO2 is too high, devitrification defects are likely to occur, and it may be difficult to increase the compressive stress value during chemical strengthening treatment. The content of ZrO2 is preferably 2% or less, more preferably 1.5% or less, even more preferably 1% or less, and particularly preferably 0.8% or less.

　Ｙ２Ｏ３は化学強化ガラスの表面圧縮応力を増大させやすくしつつ、結晶成長速度を小さくする目的で含有させてもよい。Ｙ２Ｏ３を含有させる場合の含有量は、好ましくは０．１％以上、より好ましくは０．２％以上、さらに好ましくは０．５％以上、特に好ましくは１％以上である。一方、多すぎると化学強化処理時に圧縮応力層を大きくしにくくなる場合がある。Ｙ２Ｏ３の含有量は好ましくは５％以下、より好ましくは３％以下、さらに好ましくは２％以下、特に好ましくは１．５％以下である。 Y 2 O 3 may be contained for the purpose of increasing the surface compressive stress of chemically strengthened glass while reducing the crystal growth rate. When Y 2 O 3 is contained, the content is preferably 0.1% or more, more preferably 0.2% or more, even more preferably 0.5% or more, and particularly preferably 1% or more. On the other hand, if the content is too high, it may be difficult to increase the compressive stress layer during chemical strengthening treatment. The content of Y 2 O 3 is preferably 5% or less, more preferably 3% or less, even more preferably 2% or less, and particularly preferably 1.5% or less.

　上記母ガラス組成の第１態様とは異なる態様である、母ガラス組成の第２態様としては、
　ＳｉＯ２を５５～７５％
　Ａｌ２Ｏ３を３～１８％
　Ｌｉ２Ｏを１７～３０％
　Ｎａ２Ｏを０～３％
　Ｋ２Ｏを０～１％
　ＭｇＯを０～１０％
　ＣａＯを０～１０％
　ＳｒＯを０～５％
　ＺｎＯを０～５％
　ＴｉＯ２を０～３％
　ＺｒＯ２を０～３％
　ＳｎＯ２を０～１％
　Ｐ２Ｏ５を０～３％
　Ｂ２Ｏ３を０～１０％
　Ｙ２Ｏ３を０～３％含有し、
　Ｌｉ２Ｏの含有量、Ｎａ２Ｏの含有量、および、Ｋ２Ｏの含有量の合計であるＲが、８～３５％であり、Ｒに対するＬｉ２Ｏの含有量が０．８５～０．９９であり、Ｒに対するＬｉ２Ｏの含有量と、Ｒに対するＮａ２Ｏの含有量と、Ｒに対するＫ２Ｏの含有量との積の値が、０～０．００３である態様も挙げられる。
　以下、母ガラス組成の第２態様について説明する。 A second embodiment of the mother glass composition, which is different from the first embodiment of the mother glass composition, is as follows:
SiO2 55-75%
3-18% Al 2 O 3
17-30% Li 2 O
Na 2 O 0 to 3%
K 2 O 0-1%
MgO 0-10%
CaO 0-10%
SrO 0 to 5%
ZnO 0-5%
TiO2 0-3%
ZrO2 0-3%
SnO2 0-1%
P2O5 0-3 %
B2O3 0-10 %
Contains 0 to 3% Y 2 O 3 ;
In another embodiment, R, which is the total of the Li 2 O content, the Na 2 O content, and the K 2 O content, is 8 to 35%, the Li 2 O content relative to R is 0.85 to 0.99, and the product of the Li 2 O content relative to R, the Na 2 O content relative to R, and the K 2 O content relative to R is 0 to 0.003.
The second embodiment of the mother glass composition will be described below.

　ＳｉＯ２は、ガラスのネットワークを構成する成分である。また、化学的耐久性を上げる成分であり、ガラス表面に傷がついた時のクラックの発生を低減させる成分である。 SiO2 is a component that constitutes the glass network. It also increases chemical durability and reduces the occurrence of cracks when the glass surface is scratched.

　ＳｉＯ２の含有量は、化学的耐久性を向上させるために５７．０％以上がより好ましく、さらに好ましくは５８．０％以上、特に好ましくは５９．０％以上、最も好ましくは６０．０％以上である。一方、溶融性を良好にする観点から、ＳｉＯ２の含有量は７４．０％以下がより好ましく、さらに好ましくは７２．０％以下、特に好ましくは６９．０％以下、最も好ましくは６６．０％以下である。 In order to improve chemical durability, the SiO2 content is preferably 57.0% or more, even more preferably 58.0% or more, particularly preferably 59.0% or more, and most preferably 60.0% or more. On the other hand, in order to improve meltability, the SiO2 content is preferably 74.0% or less, even more preferably 72.0% or less, particularly preferably 69.0% or less, and most preferably 66.0% or less.

　Ａｌ２Ｏ３は化学強化の際のイオン交換性能を向上させ、強化後の表面圧縮応力を大きくする成分である。また、Ａｌ、Ｌｉを含有する結晶の生成に寄与する。
　上記効果を得る観点から、Ａｌ２Ｏ３の含有量は３．５％以上がより好ましく、さらに好ましくは、以下順に、４．０％以上、４．５％以上である。一方、溶融中に結晶が成長しにくくなること、失透欠点が生じにくく歩留まりがより高くなりやすいこと、また、ガラスの高温粘性を低下させて溶融しやすくすることが求められる場合もある。かかる観点から、Ａｌ２Ｏ３の含有量は、１８．０％以下がより好ましく、さらに好ましくは、以下順に、１５．０％以下、１２．０％以下、９．０％以下、７．０％以下、６．０％以下である。 Al 2 O 3 is a component that improves ion exchange performance during chemical strengthening and increases the surface compressive stress after strengthening, and also contributes to the formation of crystals containing Al and Li.
From the viewpoint of obtaining the above effects, the Al2O3 content is more preferably 3.5% or more, and even more preferably 4.0% or more and 4.5% or more, in the following order. On the other hand, there are also cases where it is required that crystals are less likely to grow during melting, that devitrification defects are less likely to occur, leading to a higher yield, and that the high-temperature viscosity of the glass is reduced to make it easier to melt. From these viewpoints, the Al2O3 content is more preferably 18.0% or less, and even more preferably 15.0% or less, 12.0% or less, 9.0% or less, 7.0% or less, and 6.0% or less, in the following order.

　ＳｉＯ２とＡｌ２Ｏ３とは、いずれもガラスの構造を安定にする成分である。脆性を低くするためには、ＳｉＯ２およびＡｌ２Ｏ３の合計の含有量は、好ましくは６０．０％以上、より好ましくは６２．０％以上、さらに好ましくは６４．０％以上である。
　また、ＳｉＯ２とＡｌ２Ｏ３とは、いずれもガラスの溶融温度を高くする傾向がある。そこで、より溶融しやすくするためには、ＳｉＯ２およびＡｌ２Ｏ３の合計の含有量は、好ましくは８０．０％以下、より好ましくは７５．０％以下、さらに好ましくは７０．０％以下、特に好ましくは６８．０％以下である。 Both SiO2 and Al2O3 are components that stabilize the glass structure. To reduce brittleness, the total content of SiO2 and Al2O3 is preferably 60.0% or more, more preferably 62.0% or more, and even more preferably 64.0% or more.
Furthermore, both SiO 2 and Al 2 O 3 tend to increase the melting temperature of the glass. Therefore, in order to make the glass more easily meltable, the total content of SiO 2 and Al 2 O 3 is preferably 80.0% or less, more preferably 75.0% or less, even more preferably 70.0% or less, and particularly preferably 68.0% or less.

　Ｌｉ２Ｏは、イオン交換が可能な成分であり、ガラスの溶融性を向上させる成分である。ガラスがＬｉ２Ｏを含有することにより、ガラス表面のＬｉイオンを外部のＮａイオンとイオン交換してガラス内部に取り込み、さらに取り込んだＮａイオンを外部のＫイオンとイオン交換する方法で、表面圧縮応力が大きく、圧縮応力層が厚い応力プロファイルが得られやすい。また、上記範囲でＬｉ２Ｏを含むことで、特定の熱処理を施した際に結晶化ガラスが得られやすい。上記観点から、Ｌｉ２Ｏの含有量は、１７％以上がより好ましく、さらに好ましくは、以下順に、１９％以上、２１％以上、２２％以上である。 Li 2 O is an ion-exchangeable component that improves the meltability of glass. When glass contains Li 2 O, Li ions on the glass surface are ion-exchanged with external Na ions to be incorporated into the glass, and the incorporated Na ions are then ion-exchanged with external K ions, which makes it easy to obtain a stress profile with a large surface compressive stress and a thick compressive stress layer. Furthermore, by including Li 2 O in the above range, it is easy to obtain crystallized glass when subjected to a specific heat treatment. From the above viewpoints, the Li 2 O content is more preferably 17% or more, and even more preferably 19% or more, 21% or more, and 22% or more, in the following order.

　一方、ガラス成形中の結晶成長速度を小さくし、失透による品質の低下を生じにくくする観点で、Ｌｉ２Ｏの含有量は、３０％以下がより好ましく、さらに好ましくは、以下順に、２８％以下、２６％以下、２４％以下、２３％以下である。 On the other hand, from the viewpoint of reducing the crystal growth rate during glass molding and making it difficult for quality degradation due to devitrification to occur, the content of Li 2 O is more preferably 30% or less, and further preferably 28% or less, 26% or less, 24% or less, and 23% or less, in that order.

　Ｎａ２ＯおよびＫ２Ｏは、ガラスの溶融性を向上させ、ガラス成形中の結晶成長速度を小さくする成分である。またイオン交換性能を向上させるためにも少量含有することが好ましい。 Na 2 O and K 2 O are components that improve the meltability of the glass and reduce the crystal growth rate during glass forming, and are preferably contained in small amounts to improve ion exchange performance.

　Ｎａ２Ｏは、カリウム塩を用いる化学強化処理においてイオン交換が可能な成分であり、またガラスの粘性を下げる成分である。上記効果を得るために、Ｎａ２Ｏの含有量は、０．３％以上が好ましく、より好ましくは、以下順に、０．５％以上、０．８％以上、１．０％以上、１．２％以上、１．５％以上、１．８％以上である。一方、ガラスネットワークを維持する観点、及びナトリウム塩による強化処理において表面圧縮応力（Ｎａ＿ＣＳ）が低下することを避ける観点から、Ｎａ２Ｏの含有量は、３．０％以下が好ましく、２．５％以下がより好ましく、２．３％以下がさらに好ましい。 Na 2 O is a component that can be ion-exchanged in a chemical strengthening treatment using a potassium salt and also reduces the viscosity of glass. To achieve the above effect, the Na 2 O content is preferably 0.3% or more, more preferably 0.5% or more, 0.8% or more, 1.0% or more, 1.2% or more, 1.5% or more, and 1.8% or more, in the following order. On the other hand, from the viewpoint of maintaining the glass network and avoiding a decrease in surface compressive stress (Na_CS) in a strengthening treatment using a sodium salt, the Na 2 O content is preferably 3.0% or less, more preferably 2.5% or less, and even more preferably 2.3% or less.

　Ｋ２Ｏは、失透温度の上昇を抑制して失透を抑制するとともに、イオン交換性能を向上する成分である。Ｋ２Ｏの含有量は、０．１％以上がより好ましく、さらに好ましくは０．１５％以上、特に好ましくは０．２％以上であり、最も好ましくは０．５％以上である。
　一方、ナトリウム塩による強化処理において表面圧縮応力が低下することを避ける観点から、Ｋ２Ｏの含有量は、１．０％以下が好ましく、０．８％以下がより好ましい。
　なお、Ｋ２Ｏは実質的に含まれなくてもよい。 K 2 O is a component that suppresses an increase in the devitrification temperature to suppress devitrification and improves ion exchange performance. The content of K 2 O is more preferably 0.1% or more, even more preferably 0.15% or more, particularly preferably 0.2% or more, and most preferably 0.5% or more.
On the other hand, from the viewpoint of avoiding a decrease in surface compressive stress during strengthening treatment with a sodium salt, the content of K 2 O is preferably 1.0% or less, and more preferably 0.8% or less.
It is not necessary for K 2 O to be substantially contained.

　Ｌｉ２Ｏの含有量、Ｎａ２Ｏの含有量およびＫ２Ｏの含有量の合計であるＲは、失透温度の上昇を抑制し、結晶成長速度を小さくする観点から、１０～３０％がより好ましく、１５～２８％が更に好ましく、１８～２５％が特に好ましい。 R, which is the total of the Li 2 O content, the Na 2 O content, and the K 2 O content, is more preferably 10 to 30%, further preferably 15 to 28%, and particularly preferably 18 to 25%, from the viewpoint of suppressing an increase in the devitrification temperature and reducing the crystal growth rate.

　上記Ｒに対するＬｉ２Ｏの含有量の比（［Ｌｉ２Ｏ］／（［Ｌｉ２Ｏ］＋［Ｎａ２Ｏ］＋［Ｋ２Ｏ］）、以下、「Ｌｉ２Ｏ／Ｒ２Ｏ」とも記載する）は、化学強化特性における深層部応力をより向上する観点から、０．８８以上がより好ましく、０．９０以上がさらに好ましい。Ｌｉ２Ｏ／Ｒ２Ｏは、ガラスの電気抵抗をより高め、耐薬品性をより高める観点から、０．９８以下がより好ましく、０．９５以下が更に好ましく、０．９３以下が特に好ましい。 The ratio of the Li 2 O content to the R ([Li 2 O]/([Li 2 O] + [Na 2 O] + [K 2 O]), hereinafter also referred to as "Li 2 O/R 2 O") is more preferably 0.88 or more, and even more preferably 0.90 or more, from the viewpoint of further improving deep layer stress in chemical strengthening characteristics. From the viewpoint of further increasing the electrical resistance and chemical resistance of the glass, Li 2 O/R 2 O is more preferably 0.98 or less, even more preferably 0.95 or less, and particularly preferably 0.93 or less.

　上記Ｒに対するＮａ２Ｏの含有量の比（［Ｎａ２Ｏ］／（［Ｌｉ２Ｏ］＋［Ｎａ２Ｏ］＋［Ｋ２Ｏ］）、以下、「Ｎａ２Ｏ／Ｒ２Ｏ」とも記載する）は、化学強化特性における深層部応力をより向上する観点から、０超が好ましく、０．０１以上がより好ましく、０．０３以上がさらに好ましく、０．０５以上が特に好ましく、０．０６以上が最も好ましい。Ｎａ２Ｏ／Ｒ２Ｏは、耐薬品性をより高める観点から、０．４０以下が好ましく、０．３０以下がより好ましく、０．２０以下が更に好ましく、０．１０以下が特に好ましい。 The ratio of the Na 2 O content to the R ([Na 2 O]/([Li 2 O] + [Na 2 O] + [K 2 O]), hereinafter also referred to as "Na 2 O/R 2 O") is preferably more than 0, more preferably 0.01 or more, even more preferably 0.03 or more, particularly preferably 0.05 or more, and most preferably 0.06 or more, from the viewpoint of further improving deep layer stress in chemical strengthening characteristics. From the viewpoint of further improving chemical resistance, Na 2 O/R 2 O is preferably 0.40 or less, more preferably 0.30 or less, even more preferably 0.20 or less, and particularly preferably 0.10 or less.

　上記Ｒに対するＫ２Ｏの含有量の比（［Ｋ２Ｏ］／（［Ｌｉ２Ｏ］＋［Ｎａ２Ｏ］＋［Ｋ２Ｏ］）、以下、「Ｋ２Ｏ／Ｒ２Ｏ」とも記載する）は、ガラスの電気抵抗をより高める観点から、０．０５以上が好ましく、０．０８以上がより好ましく、０．１０以上がさらに好ましい。Ｋ２Ｏ／Ｒ２Ｏは、化学強化特性における表面近傍の圧縮応力を高める観点から、０．５０以下が好ましく、０．４０以下がより好ましく、０．３０以下が更に好ましく、０．２０以下が特に好ましい。
　なお、Ｋ２Ｏ／Ｒ２Ｏは、０であってもよい。 The ratio of the content of K 2 O to the above R ([K 2 O]/([Li 2 O] + [Na 2 O] + [K 2 O]), hereinafter also referred to as "K 2 O/R 2 O") is preferably 0.05 or more, more preferably 0.08 or more, and even more preferably 0.10 or more, from the viewpoint of further increasing the electrical resistance of the glass. From the viewpoint of increasing the compressive stress near the surface in chemical strengthening characteristics, K 2 O/R 2 O is preferably 0.50 or less, more preferably 0.40 or less, even more preferably 0.30 or less, and particularly preferably 0.20 or less.
The K 2 O/R 2 O ratio may be zero.

　ＭｇＯは、溶解時の粘性を下げる等のために含有してもよい。ＭｇＯの含有量は、より好ましくは０．０５％以上、さらに好ましくは、以下順に、０．５％以上、１．０％以上、２．０％以上、３．０％以上、４．０％以上である。
　一方、化学強化処理時に圧縮応力層を大きくしやすい点で、ＭｇＯの含有量は、より好ましくは９．０％以下であり、さらに好ましくは、以下順に、８．０％以下、７．０％以下、６．０％以下である。 MgO may be contained to reduce viscosity during dissolution, etc. The MgO content is more preferably 0.05% or more, and further preferably 0.5% or more, 1.0% or more, 2.0% or more, 3.0% or more, and 4.0% or more, in the following order.
On the other hand, since the compressive stress layer is easily enlarged during chemical strengthening treatment, the MgO content is more preferably 9.0% or less, and further preferably 8.0% or less, 7.0% or less, and 6.0% or less, in that order.

　また、ＭｇＯを含有することによって、β石英固溶体からβスポジュメンへの結晶相の相転移を抑制することができ、βスポジュメン結晶の析出を抑制することができる。よって、実施形態２においては、ＭｇＯを含有することが好ましい。上記観点からは、ＭｇＯを０．５％超７．０％以下含有することが好ましい。さらに好ましい範囲は上記したとおりである。
　ＭｇＯは、実質的に含まれなくてもよい。 Furthermore, by including MgO, it is possible to suppress the phase transition of the crystalline phase from β-quartz solid solution to β-spodumene, and to suppress the precipitation of β-spodumene crystals. Therefore, in embodiment 2, it is preferable to include MgO. From the above viewpoint, it is preferable to include more than 0.5% and not more than 7.0% of MgO. The more preferable range is as described above.
MgO may not be substantially contained.

　ＣａＯは、ガラスの溶融性を向上させる成分であり、含有してもよい。ＣａＯの含有量は、より好ましくは０．１％以上であり、さらに好ましくは０．１５％以上である。一方、化学強化処理時に圧縮応力値を大きくしやすい点で、ＣａＯの含有量は、より好ましくは２．０％以下であり、さらに好ましくは１．０％以下であり、特に好ましくは０．８％以下であり、最も好ましくは０．５％以下である。
　ＣａＯは、実質的に含まれなくてもよい。 CaO is a component that improves the meltability of glass and may be contained. The CaO content is more preferably 0.1% or more, and even more preferably 0.15% or more. On the other hand, in terms of the tendency to increase the compressive stress value during chemical strengthening treatment, the CaO content is more preferably 2.0% or less, even more preferably 1.0% or less, particularly preferably 0.8% or less, and most preferably 0.5% or less.
CaO may not be substantially contained.

　ガラスの安定性を高くするためにはＭｇＯおよびＣａＯの少なくとも一方を含有することがより好ましく、ＭｇＯを含有することがさらに好ましい。ＭｇＯとＣａＯの合計の含有量は１．０％超が好ましく、２．０％以上がより好ましく、３．０％以上がさらに好ましく、４．０％以上が特に好ましい。化学強化特性をより向上する点で、ＭｇＯおよびＣａＯの合計の含有量は、１０．０％以下が好ましく、より好ましくは、以下順に、８．０％以下、７．０％以下、６．０％以下である。 In order to increase the stability of the glass, it is more preferable to contain at least one of MgO and CaO, and it is even more preferable to contain MgO. The total content of MgO and CaO is preferably over 1.0%, more preferably 2.0% or more, even more preferably 3.0% or more, and particularly preferably 4.0% or more. In terms of further improving chemical strengthening properties, the total content of MgO and CaO is preferably 10.0% or less, and more preferably 8.0% or less, 7.0% or less, and 6.0% or less, in that order.

　ＳｒＯは、ガラスの溶融性を向上させる成分であり、含有してもよい。ＳｒＯの含有量は、より好ましくは０．１％以上であり、さらに好ましくは０．１５％以上であり、特に好ましくは０．５％以上である。
　化学強化処理時に圧縮応力値を大きくしやすくする点で、ＳｒＯの含有量は、より好ましくは３．０％以下であり、さらに好ましくは２．０％以下であり、特に好ましくは１．０％以下であり、最も好ましくは０．５％以下である。
　ＳｒＯは、実質的に含まれなくてもよい。 SrO is a component that improves the meltability of glass and may be contained. The content of SrO is more preferably 0.1% or more, further preferably 0.15% or more, and particularly preferably 0.5% or more.
In order to make it easier to increase the compressive stress value during chemical strengthening treatment, the SrO content is more preferably 3.0% or less, even more preferably 2.0% or less, particularly preferably 1.0% or less, and most preferably 0.5% or less.
SrO may not be substantially contained.

　ＢａＯは、ガラスの溶融性を向上させる成分であり、含有させてもよい。ＢａＯを含有させる場合の含有量は、好ましくは０．１％以上であり、より好ましくは０．１５％以上であり、さらに好ましくは０．５％以上である。
　化学強化処理時に圧縮応力値を大きくしやすくする点で、ＢａＯの含有量は、好ましくは３．０％以下であり、より好ましくは２．０％以下であり、さらに好ましくは１．０％以下であり、特に好ましくは０．５％以下である。
　ＢａＯは、実質的に含まれなくてもよい。 BaO is a component that improves the meltability of the glass and may be contained. When BaO is contained, the content is preferably 0.1% or more, more preferably 0.15% or more, and even more preferably 0.5% or more.
In order to make it easier to increase the compressive stress value during chemical strengthening treatment, the BaO content is preferably 3.0% or less, more preferably 2.0% or less, even more preferably 1.0% or less, and particularly preferably 0.5% or less.
BaO may not be substantially contained.

　ＺｎＯは、ガラスの溶融性を向上させる成分である。ＺｎＯの含有量は、より好ましくは０．１％以上であり、さらに好ましくは０．１５％以上であり、特に好ましくは０．５％以上である。
　化学強化処理時に圧縮応力値を大きくしやすくする点で、ＺｎＯの含有量は、より好ましくは３．０％以下であり、さらに好ましくは２．０％以下であり、特に好ましくは１．０％以下であり、最も好ましくは０．５％以下である。
　ＺｎＯは、実質的に含まれなくてもよい。 ZnO is a component that improves the meltability of glass. The ZnO content is more preferably 0.1% or more, further preferably 0.15% or more, and particularly preferably 0.5% or more.
In order to make it easier to increase the compressive stress value during chemical strengthening treatment, the ZnO content is more preferably 3.0% or less, even more preferably 2.0% or less, particularly preferably 1.0% or less, and most preferably 0.5% or less.
ZnO may not be substantially contained.

　ＴｉＯ２は、ガラスのソラリゼーションを抑制する効果が高い成分であり、結晶の核を形成する材料であるため、含有させてもよい。ＴｉＯ２を含有させる場合の含有量は、好ましくは０．０５％以上であり、より好ましくは０．１％以上、さらに好ましくは０．２％以上であり、特に好ましくは０．５％以上であり、最も好ましくは０．８％以上である。
　一方、ＴｉＯ２は光吸収特性を持つため、ガラスの発色を防ぐ観点から、ＴｉＯ２の含有量は２．５％以下が好ましく、より好ましくは２．０％以下、さらに好ましくは１．５％以下であり、特に好ましくは１．０％以下である。
　ＴｉＯ２は、実質的に含まれなくてもよい。 TiO2 is a component that is highly effective in suppressing solarization of glass and is a material that forms crystal nuclei, so it may be contained. When TiO2 is contained, the content is preferably 0.05% or more, more preferably 0.1% or more, even more preferably 0.2% or more, particularly preferably 0.5% or more, and most preferably 0.8% or more.
On the other hand, since TiO2 has light absorption properties, from the viewpoint of preventing color development of the glass, the content of TiO2 is preferably 2.5% or less, more preferably 2.0% or less, even more preferably 1.5% or less, and particularly preferably 1.0% or less.
TiO2 may be substantially absent.

　ＺｒＯ２は、化学強化ガラスの表面圧縮応力を増大させやすくする成分である。また、結晶の核を形成する材料であるため、ＺｒＯ２を含有してもよい。ＺｒＯ２の含有量は、より好ましくは０％超であり、さらに好ましくは、以下順に、０．５％以上、１．０％以上、１．５％以上、２．０％以上、２．５％以上である。
　母ガラス組成の第２実施態様がＳｎＯ２を含む場合、ＳｎＯ２の含有量は、０．００５％以上がより好ましく、０．０１％以上がさらに好ましい。また、母ガラス組成の第２実施態様ＳｎＯ２を含む場合、ＳｎＯ２の含有量は、１％以下がより好ましく、０．５０％以下がさらに好ましい。 ZrO2 is a component that facilitates increasing the surface compressive stress of chemically strengthened glass. Furthermore, since ZrO2 is a material that forms crystal nuclei, it may be contained. The ZrO2 content is more preferably greater than 0%, and even more preferably 0.5% or more, 1.0% or more, 1.5% or more, 2.0% or more, and 2.5% or more, in the following order.
When the second embodiment of the mother glass composition contains SnO2 , the content of SnO2 is preferably 0.005% or more, and more preferably 0.01% or more. When the second embodiment of the mother glass composition contains SnO2 , the content of SnO2 is preferably 1% or less, and more preferably 0.50% or less.

　Ｐ２Ｏ５は、化学強化時の圧縮応力層を大きくしやすい。Ｐ２Ｏ５の含有量は、より好ましくは０．５％以上、さらに好ましくは１．０％以上、特に好ましくは２．０％以上である。
　一方、耐酸性を高くする観点から、Ｐ２Ｏ５の含有量は、２．０％以下がより好ましい。溶融時に脈理が発生することを防止する観点から、実質的に含有しないことも好ましい。 P 2 O 5 tends to increase the compressive stress layer during chemical strengthening, and the content of P 2 O 5 is more preferably 0.5% or more, further preferably 1.0% or more, and particularly preferably 2.0% or more.
On the other hand, from the viewpoint of increasing acid resistance, the content of P 2 O 5 is more preferably 2.0% or less. From the viewpoint of preventing the formation of striae during melting, it is also preferable that P 2 O 5 is substantially not contained.

　Ｂ２Ｏ３は、ガラスの脆性を小さくし耐クラック性を向上させる、または、ガラスの溶融性を向上させる。Ｂ２Ｏ３の含有量は、より好ましくは０．５％以上、さらに好ましくは１．０％以上、特に好ましくは２．０％以上である。
　一方、耐酸性を良好に保つ点で、Ｂ２Ｏ３の含有量は、８．０％以下が好ましい。Ｂ２Ｏ３の含有量は、より好ましくは６．０％以下、さらに好ましくは４．０％以下、特に好ましくは２．０％以下である。溶融時に脈理の発生を防止する観点から、実質的に含有しないことも好ましい。 B 2 O 3 reduces the brittleness of the glass and improves the crack resistance, or improves the meltability of the glass. The B 2 O 3 content is more preferably 0.5% or more, even more preferably 1.0% or more, and particularly preferably 2.0% or more.
On the other hand, in order to maintain good acid resistance, the B2O3 content is preferably 8.0% or less. The B2O3 content is more preferably 6.0% or less, even more preferably 4.0% or less, and particularly preferably 2.0% or less. In order to prevent the occurrence of striae during melting, it is also preferable that the B2O3 content be substantially zero.

　Ｙ２Ｏ３は、化学強化ガラスの表面圧縮応力を増大させやすくしつつ、結晶成長速度を小さくする成分である。Ｙ２Ｏ３の含有量は、より好ましくは０％超であり、さらに好ましくは、以下順に、０．１％以上、０．２％以上、０．５％以上、０．８％以上である。一方、化学強化処理時に圧縮応力層を大きくしやすい点で、Ｙ２Ｏ３の含有量は、２．０％以下がより好ましく、１．５％以下が更に好ましい。 Y 2 O 3 is a component that reduces the crystal growth rate while making it easier to increase the surface compressive stress of chemically strengthened glass. The Y 2 O 3 content is more preferably more than 0%, and even more preferably 0.1% or more, 0.2% or more, 0.5% or more, and 0.8% or more, in that order. On the other hand, in order to make it easier to increase the compressive stress layer during chemical strengthening treatment, the Y 2 O 3 content is more preferably 2.0% or less, and even more preferably 1.5% or less.

　初期溶解性を向上させる観点から、ＺｒＯ２およびＹ２Ｏ３の含有量の合計は、５．０％以下がより好ましい。ＺｒＯ２およびＹ２Ｏ３の含有量の合計の下限は特に制限されないが、ガラスの強度を高める観点から、０．５％以上がより好ましく、さらに好ましくは、以下順に、１．０％以上、１．５％以上、２．０％以上、２．５％以上、３．０％以上である。 From the viewpoint of improving the initial solubility, the total content of ZrO2 and Y2O3 is more preferably 5.0% or less. Although there is no particular lower limit for the total content of ZrO2 and Y2O3 , from the viewpoint of increasing the strength of the glass , it is more preferably 0.5% or more, and further preferably 1.0% or more, 1.5% or more, 2.0% or more, 2.5% or more, and 3.0% or more, in that order.

　ＺｒＯ２およびＹ２Ｏ３の含有量の合計に対するＺｒＯ２の含有量の比［ＺｒＯ２］／（［ＺｒＯ２］＋［Ｙ２Ｏ３］）は、０．５０以上がより好ましく、１．００以上がさらに好ましく、２．００以上が特に好ましい。［ＺｒＯ２］／（［ＺｒＯ２］＋［Ｙ２Ｏ３］）は、より好ましくは８．００以下、さらに好ましくは７．００以下、特に好ましくは６．００以下である。 The ratio of the ZrO2 content to the total content of ZrO2 and Y2O3 , [ ZrO2 ]/([ ZrO2 ]+[ Y2O3 ]), is more preferably 0.50 or more, even more preferably 1.00 or more, and particularly preferably 2.00 or more. [ ZrO2 ]/([ ZrO2 ]+ [ Y2O3 ]) is more preferably 8.00 or less, even more preferably 7.00 or less, and particularly preferably 6.00 or less.

　Ｌａ２Ｏ３は、必須ではないが、Ｙ２Ｏ３と同様の理由で含有できる。Ｌａ２Ｏ３は、好ましくは０．１％以上、より好ましくは０．２％以上、さらに好ましくは０．５％以上、特に好ましくは０．８％以上である。一方、多すぎると化学強化処理時に圧縮応力層を大きくしにくくなるので、Ｌａ２Ｏ３は好ましくは５．０％以下、より好ましくは３．０％以下、さらに好ましくは２．０％以下、特に好ましくは１．５％以下である。
　Ｌａ２Ｏ３は、実質的に含まないことも好ましい。 La2O3 is not essential, but can be contained for the same reasons as Y2O3 . La2O3 is preferably 0.1% or more, more preferably 0.2% or more, even more preferably 0.5% or more, and particularly preferably 0.8 % or more. On the other hand , if it is too much, it becomes difficult to increase the compressive stress layer during chemical strengthening treatment , so La2O3 is preferably 5.0% or less, more preferably 3.0% or less, even more preferably 2.0% or less, and particularly preferably 1.5% or less.
It is also preferable that La 2 O 3 is substantially not contained.

　化学強化に供される化学強化用ガラスの組成（母ガラス組成）は、以上のような組成が好ましい。
　母ガラス組成を有する化学強化用ガラスを得る方法は特に制限されず、公知の方法を適用できる。例えば、上記組成のガラスが得られるように、ガラス原料を適宜調合し、ガラス溶融窯で加熱溶融し、その後、バブリング、撹拌、清澄剤の添加等によりガラスを均質化し、所定の厚さのガラス板に成形し、徐冷すればよい。また、ブロック状に成形して徐冷した後に切断する方法で板状に成形してもよい。
　なお、本発明の化学強化用ガラスの製造方法においては、本発明の金属成分の回収方法によって回収された特定金属塩を、化学強化用ガラスの原料の一部として用いる。特定金属塩としては、リチウムまたはナトリウムを含む特定金属塩が好ましく、炭酸リチウム（Ｌｉ２ＣＯ３）または炭酸ナトリウム（Ｎａ２ＣＯ３）がより好ましい。 The composition of the glass for chemical strengthening (mother glass composition) to be subjected to chemical strengthening is preferably as described above.
The method for obtaining a chemically strengthened glass having a mother glass composition is not particularly limited, and known methods can be applied. For example, to obtain a glass of the above composition, glass raw materials are appropriately mixed, heated and melted in a glass melting furnace, and then the glass is homogenized by bubbling, stirring, adding a clarifier, etc., formed into a glass plate of a predetermined thickness, and slowly cooled. Alternatively, the glass may be formed into a plate by forming it into a block, slowly cooling it, and then cutting it.
In the method for producing chemically strengthened glass of the present invention, the specific metal salt recovered by the method for recovering metal components of the present invention is used as part of the raw material of the chemically strengthened glass. As the specific metal salt, a specific metal salt containing lithium or sodium is preferred, and lithium carbonate ( Li2CO3 ) or sodium carbonate ( Na2CO3 ) is more preferred.

　板状に成形する方法としては、例えば、フロート法、プレス法、フュージョン法及びダウンドロー法が挙げられる。特に、大型のガラス板を製造する場合は、フロート法が好ましい。また、フロート法以外の連続成形法、例えば、フュージョン法及びダウンドロー法も好ましい。 Methods for forming glass into sheets include, for example, the float method, press method, fusion method, and downdraw method. The float method is particularly preferred when producing large glass sheets. Continuous forming methods other than the float method, such as the fusion method and downdraw method, are also preferred.

　また、化学強化用ガラスは、結晶化ガラスであってもよい。化学強化用ガラスが結晶化ガラスである場合には、ケイ酸リチウム結晶、アルミノケイ酸リチウム結晶、リン酸リチウム結晶からなる群から選ばれる１以上の結晶を含有する結晶化ガラスが好ましい。ケイ酸リチウム結晶としては、メタケイ酸リチウム結晶、ジケイ酸リチウム結晶等が好ましい。リン酸リチウム結晶としては、オルトリン酸リチウム結晶等が好ましい。アルミノケイ酸リチウム結晶としては、β－スポジュメン結晶、ペタライト結晶等が好ましい。 Furthermore, the chemically strengthened glass may be glass-ceramics. When the chemically strengthened glass is glass-ceramics, it is preferably glass-ceramics containing one or more crystals selected from the group consisting of lithium silicate crystals, lithium aluminosilicate crystals, and lithium phosphate crystals. Preferred lithium silicate crystals are lithium metasilicate crystals, lithium disilicate crystals, etc. Preferred lithium phosphate crystals are lithium orthophosphate crystals, etc. Preferred lithium aluminosilicate crystals are β-spodumene crystals, petalite crystals, etc.

　結晶化ガラスの結晶化率は、機械的強度を向上する点で１０％以上が好ましく、１５％以上がより好ましく、２０％以上がさらに好ましく、２５％以上が特に好ましい。また、透明性を高くするために、９０％以下が好ましく、７０％以下がより好ましく、６０％以下がさらに好ましく、５０％以下が特に好ましい。結晶化率が小さいことは、加熱して曲げ成形等しやすい点でも優れている。結晶化率は、Ｘ線回折強度からリートベルト法で算出できる。リートベルト法については、日本結晶学会「結晶解析ハンドブック」編集委員会編、「結晶解析ハンドブック」（協立出版１９９９年刊、ｐ４９２～４９９）に記載されている。 The crystallization rate of crystallized glass is preferably 10% or more in terms of improving mechanical strength, more preferably 15% or more, even more preferably 20% or more, and particularly preferably 25% or more. To increase transparency, it is preferably 90% or less, more preferably 70% or less, even more preferably 60% or less, and particularly preferably 50% or less. A low crystallization rate is also advantageous in that it is easier to heat and bend. The crystallization rate can be calculated from X-ray diffraction intensity using the Rietveld method. The Rietveld method is described in "Crystal Analysis Handbook," edited by the Editorial Committee of the Crystallographic Society of Japan (Kyoritsu Shuppan, 1999, pp. 492-499).

　結晶化ガラスの析出結晶の平均粒径は、透明性を高くするために３００ｎｍ以下が好ましく、２００ｎｍ以下がより好ましく、１５０ｎｍ以下がさらに好ましく、１００ｎｍ以下が特に好ましい。析出結晶の平均粒径は、透過型電子顕微鏡（ＴＥＭ）像から求め得る。また、走査型電子顕微鏡（ＳＥＭ）像から推定できる。 To increase transparency, the average particle size of the precipitated crystals in the crystallized glass is preferably 300 nm or less, more preferably 200 nm or less, even more preferably 150 nm or less, and particularly preferably 100 nm or less. The average particle size of the precipitated crystals can be determined from transmission electron microscope (TEM) images. It can also be estimated from scanning electron microscope (SEM) images.

　上記母ガラス組成の第１態様および第２態様とは異なる態様である、母ガラス組成の第３態様としては、酸化物基準で、
　ＳｉＯ２を５０～８５％、
　Ａｌ２Ｏ３を４～２５％、
　Ｂ２Ｏ３を０～１０％、
　Ｐ２Ｏ５を０～１０％、
　Ｌｉ２Ｏを０～１０％、
　Ｎａ２Ｏを５～２０％、
　Ｋ２Ｏを０．３～６％、
　ＺｎＯを０～５％、
　ＭｇＯを１～２０％、
　ＣａＯを０～５％、
　ＳｒＯを０～５％、
　ＢａＯを０～５％、
　ＴｉＯ２を０～３％、
　ＺｒＯ２を０～３％、および、
　Ｙ２Ｏ３を０～３％含むことが好ましい。
　以下、母ガラス組成の第３実施態様について説明する。 A third embodiment of the mother glass composition, which is different from the first and second embodiments of the mother glass composition, is, on an oxide basis,
SiO2 50-85%,
4-25% Al 2 O 3 ,
B2O3 0-10% ;
P2O5 0-10 %
0 to 10% Li 2 O,
5-20% Na 2 O,
K 2 O 0.3 to 6%,
ZnO 0 to 5%,
MgO 1 to 20%,
CaO 0 to 5%,
SrO 0 to 5%,
BaO 0 to 5%,
TiO2 0-3%,
ZrO2 0-3%, and
It is preferable that Y 2 O 3 is contained in an amount of 0 to 3%.
A third embodiment of the mother glass composition will be described below.

　ＳｉＯ２の含有量は、５６％以上がより好ましく、５９％以上がさらに好ましい。また、ＳｉＯ２の含有量は、８０％以下がより好ましく、７０％以下がさらに好ましい。 The SiO2 content is more preferably 56% or more, and even more preferably 59% or more. The SiO2 content is more preferably 80% or less, and even more preferably 70% or less.

　Ａｌ２Ｏ３の含有量は、５％以上がより好ましく、７％以上がさらに好ましい。また、Ａｌ２Ｏ３の含有量は、２０％以下がより好ましく、１５％以下がさらに好ましい。
　Ａｌ２Ｏ３の含有量に対するＳｉＯ２の含有量の比（ＳｉＯ２／Ａｌ２Ｏ３）は、３．４以上が好ましく、５．１以上がより好ましい。また、上記含有量の比は、１７．０以下の場合が多く、１０．２以下が好ましい。 The content of Al 2 O 3 is more preferably 5% or more, and further preferably 7% or more. The content of Al 2 O 3 is more preferably 20% or less, and further preferably 15% or less.
The ratio of the SiO2 content to the Al2O3 content ( SiO2 / Al2O3 ) is preferably 3.4 or more, more preferably 5.1 or more. In many cases, the ratio is 17.0 or less, and preferably 10.2 or less.

　Ｂ２Ｏ３の含有量は、０．１％以上がより好ましく、０．５％以上がさらに好ましい。また、Ｂ２Ｏ３の含有量は、６％以下がより好ましく、４％以下がさらに好ましい。なお、Ｂ２Ｏ３含有量は、０％であることも好ましい。すなわち、母ガラス組成の第３実施態様は、Ｂ２Ｏ３を含まないことも好ましい。 The B2O3 content is more preferably 0.1% or more, and even more preferably 0.5% or more. The B2O3 content is more preferably 6% or less , and even more preferably 4% or less. The B2O3 content is also preferably 0%. That is, it is also preferable that the third embodiment of the mother glass composition does not contain B2O3 .

　Ｐ２Ｏ５の含有量は、０．５０％以上がより好ましく、１％以上がさらに好ましい。また、Ｐ２Ｏ５の含有量は、６％以下がより好ましく、４％以下がさらに好ましい。なお、Ｐ２Ｏ５の含有量は０％であることも好ましい。すなわち、母ガラス組成の第３実施態様は、Ｐ２Ｏ５を含まないことも好ましい。 The content of P2O5 is more preferably 0.50% or more, and even more preferably 1% or more. The content of P2O5 is more preferably 6% or less, and even more preferably 4% or less. It is also preferable that the content of P2O5 is 0%. That is, it is also preferable that the third embodiment of the mother glass composition does not contain P2O5 .

　Ｌｉ２Ｏの含有量は、０．５％以上がより好ましく、１％以上がさらに好ましい。また、Ｌｉ２Ｏの含有量は、４％以下がより好ましく、２％以下がさらに好ましい。なお、Ｌｉ２Ｏの含有量は０％であることも好ましい。すなわち、母ガラス組成の第３実施態様は、Ｌｉ２Ｏを含まないことも好ましい。 The Li 2 O content is more preferably 0.5% or more, and even more preferably 1% or more. The Li 2 O content is more preferably 4% or less, and even more preferably 2% or less. It is also preferable that the Li 2 O content is 0%. That is, it is also preferable that the third embodiment of the mother glass composition does not contain Li 2 O.

　Ｎａ２Ｏの含有量は、１０％以上がより好ましく、１１％以上がさらに好ましく、１１．５０％以上が特に好ましく、１２％以上が最も好ましい。Ｎａ２Ｏの含有量は、酸化物基準で１８％以下がより好ましく、１６％以下がさらに好ましい。 The Na 2 O content is more preferably 10% or more, even more preferably 11% or more, particularly preferably 11.50% or more, and most preferably 12% or more. The Na 2 O content is more preferably 18% or less, and even more preferably 16% or less, based on the oxide.

　Ｋ２Ｏの含有量は、０．４％以上がより好ましく、０．５％以上がさらに好ましい。Ｋ２Ｏの含有量は、酸化物基準で１％以上であってもよく、２％以上であってもよく、３％以上であってもよい。また、Ｋ２Ｏの含有量は、５％以下がより好ましく、４．５％以下がさらに好ましい。Ｋ２Ｏの含有量は、３％以下であってもよく、２％以下であってもよく、１％以下であってもよい。
　なお、Ｎａ２Ｏの含有量に対するＫ２Ｏの含有量の比は、０．９１以下が好ましく、０．７６以下がより好ましい。また、上記含有量の比は、０．０１以上の場合が多く、０．０４以上が好ましい。 The content of K 2 O is more preferably 0.4% or more, and even more preferably 0.5% or more. The content of K 2 O may be 1% or more, 2% or more, or 3% or more on an oxide basis. Moreover, the content of K 2 O is more preferably 5% or less, and even more preferably 4.5% or less. The content of K 2 O may be 3% or less, 2% or less, or 1% or less.
The ratio of the content of K 2 O to the content of Na 2 O is preferably 0.91 or less, more preferably 0.76 or less. The ratio is often 0.01 or more, and preferably 0.04 or more.

　ＺｎＯの含有量は、０．１％以上がより好ましく、０．５％以上がさらに好ましい。また、ＺｎＯの含有量は、３％以下がより好ましく、２％以下がさらに好ましい。なお、ＺｎＯの含有量は０％であることも好ましい。すなわち、母ガラス組成の第３実施態様は、ＺｎＯを含まないことも好ましい。 The ZnO content is more preferably 0.1% or more, and even more preferably 0.5% or more. Furthermore, the ZnO content is more preferably 3% or less, and even more preferably 2% or less. It is also preferable that the ZnO content be 0%. In other words, it is also preferable that the third embodiment of the mother glass composition does not contain ZnO.

　ＭｇＯの含有量は、３％以上がより好ましく、６％以上がさらに好ましい。また、ＭｇＯの含有量は、１８％以下がより好ましく、１２％以下がさらに好ましい。 The MgO content is preferably 3% or more, and even more preferably 6% or more. Furthermore, the MgO content is preferably 18% or less, and even more preferably 12% or less.

　ＣａＯの含有量は、０．０１％以上がより好ましく、０．０２％以上がさらに好ましい。また、ＣａＯの含有量は、３％以下がより好ましく、１％以下がさらに好ましい。 The CaO content is preferably 0.01% or more, and even more preferably 0.02% or more. The CaO content is preferably 3% or less, and even more preferably 1% or less.

　ＳｒＯの含有量は、０．０１％以上がより好ましく、０．０５％以上がさらに好ましい。また、ＳｒＯの含有量は、２％以下がより好ましく、１％以下がさらに好ましい。なお、ＳｒＯの含有量は０％であってもよい。すなわち、母ガラス組成の第３実施態様は、ＳｒＯを含まなくてもよい。 The SrO content is more preferably 0.01% or more, and even more preferably 0.05% or more. Furthermore, the SrO content is more preferably 2% or less, and even more preferably 1% or less. The SrO content may be 0%. In other words, the third embodiment of the mother glass composition does not need to contain SrO.

　ＢａＯの含有量は、０．０１％以上がより好ましく、０．０２％以上がさらに好ましい。また、ＢａＯの含有量は、２％以下がより好ましく、１％以下がさらに好ましい。なお、ＢａＯの含有量は０％であってもよい。すなわち、母ガラス組成の第３実施態様は、ＢａＯを含まなくてもよい。 The BaO content is more preferably 0.01% or more, and even more preferably 0.02% or more. Furthermore, the BaO content is more preferably 2% or less, and even more preferably 1% or less. The BaO content may be 0%. In other words, the third embodiment of the mother glass composition does not need to contain BaO.

　ＴｉＯ２の含有量は、０．０１％以上がより好ましく、０．０２％以上がさらに好ましい。また、ＴｉＯ２の含有量は、１％以下がより好ましく、０．５％以下がさらに好ましい。なお、ＴｉＯ２の含有量は０％であってもよい。すなわち、母ガラス組成の第３実施態様は、ＴｉＯ２を含まなくてもよい。 The TiO2 content is more preferably 0.01% or more, and even more preferably 0.02% or more. The TiO2 content is more preferably 1% or less, and even more preferably 0.5% or less. The TiO2 content may be 0%. That is, the third embodiment of the mother glass composition does not need to contain TiO2 .

　ＺｒＯ２の含有量は、０．０５％以上がより好ましく、０．１０％以上がさらに好ましい。また、ＺｒＯ２の含有量は、１．５％以下がより好ましく、１％以下がさらに好ましい。 The ZrO2 content is more preferably 0.05% or more, and even more preferably 0.10% or more. The ZrO2 content is more preferably 1.5% or less, and even more preferably 1% or less.

　Ｙ２Ｏ３の含有量は、０．０２％以上がより好ましく、０．０４％以上がさらに好ましい。また、Ｙ２Ｏ３の含有量は、１％以下がより好ましく、０．５％以下がさらに好ましい。なお、Ｙ２Ｏ３の含有量は０％であってもよい。すなわち、母ガラス組成の第３実施態様は、Ｙ２Ｏ３を含まなくてもよい。 The Y2O3 content is more preferably 0.02% or more, and even more preferably 0.04% or more. The Y2O3 content is more preferably 1% or less, and even more preferably 0.5% or less. The Y2O3 content may be 0%. That is, the third embodiment of the mother glass composition does not need to contain Y2O3 .

　母ガラス組成の第３実施態様は、ＨｆＯ２を含んでいてもよい。
　母ガラス組成の第３実施態様がＨｆＯ２を含む場合、ＨｆＯ２の含有量は、０．０２％以上がより好ましく、０．０４％以上がさらに好ましい。また、母ガラス組成の第３実施態様がＨｆＯ２を含む場合ＨｆＯ２の含有量は、１％以下がより好ましく、０．５％以下がさらに好ましい。 A third embodiment of the mother glass composition may include HfO2 .
When the third embodiment of the mother glass composition contains HfO2 , the content of HfO2 is preferably 0.02% or more, and more preferably 0.04% or more. When the third embodiment of the mother glass composition contains HfO2 , the content of HfO2 is preferably 1% or less, and more preferably 0.5% or less.

　母ガラス組成の第３実施態様は、ＳｎＯ２を含んでいてもよい。
　母ガラス組成の第３実施態様がＳｎＯ２を含む場合、ＳｎＯ２の含有量は、０．００５％以上がより好ましく、０．０１％以上がさらに好ましい。また、母ガラス組成の第３実施態様ＳｎＯ２を含む場合、ＳｎＯ２の含有量は、１％以下がより好ましく、０．５０％以下がさらに好ましい。 A third embodiment of the mother glass composition may include SnO2 .
When the third embodiment of the mother glass composition contains SnO2 , the content of SnO2 is preferably 0.005% or more, and more preferably 0.01% or more. When the third embodiment of the mother glass composition contains SnO2 , the content of SnO2 is preferably 1% or less, and more preferably 0.50% or less.

　また、母ガラス組成の第３実施態様は、ＣｅＯ２、Ｓｂ２Ｏ３、Ｆｅ２Ｏ３、ＣｏＯ、Ｃｒ２Ｏ３、ＣｕＯ、および、ＮｉＯからなる群から選択される１種以上の成分を含んでいてもよい。
　母ガラス組成の第３実施態様における上記成分の含有量は、適宜調整可能であるが、例えば、それぞれ、０．５０％以下が好ましい。また、母ガラス組成の第３実施態様は、上記成分を含まなくてもよい。 The third embodiment of the base glass composition may also contain one or more components selected from the group consisting of CeO2 , Sb2O3 , Fe2O3 , CoO , Cr2O3 , CuO, and NiO.
The contents of the above components in the third embodiment of the mother glass composition can be adjusted as appropriate, but are preferably, for example, 0.50% or less for each. Furthermore, the third embodiment of the mother glass composition does not necessarily need to contain the above components.

　化学強化用ガラスのヤング率は、７０ＧＰａ以上が好ましく、７３ＧＰａ以上がより好ましく、８０ＧＰａ以上がさらに好ましく、８３ＧＰａ以上が特に好ましい。
　本明細書において「ヤング率」は、切り出したガラス片を用いて、超音波パルス法により、ＪＩＳ　Ｒ　１６０２に準拠して測定する。
　また、化学強化用ガラスの破壊靭性値（ＫＩＣ）は、０．７０ＭＰａ・ｍ１／２以上が好ましく、０．７５ＭＰａ・ｍ１／２以上がより好ましく、０．８０ＭＰａ・ｍ１／２以上がさらに好ましい。破壊靱性値ＫＩＣは、２．００ＭＰａ・ｍ１／２以下の場合が多く、１．８０ＭＰａ・ｍ１／２以下が好ましい。
　本明細書において「破壊靱性値ＫＩＣ」は、ＤＣＤＣ法［参考文献：Ｍ．Ｙ．　Ｈｅ，　Ｍ．Ｒ．　Ｔｕｒｎｅｒ　ａｎｄ　Ａ．Ｇ．　Ｅｖａｎｓ，　Ａｃｔａ　Ｍｅｔａｌｌ．　Ｍａｔｅｒ．　４３　（１９９５）　３４５３．］を参考にして測定する。 The Young's modulus of the glass for chemical strengthening is preferably 70 GPa or more, more preferably 73 GPa or more, still more preferably 80 GPa or more, and particularly preferably 83 GPa or more.
In this specification, the "Young's modulus" is measured using a cut glass piece by an ultrasonic pulse method in accordance with JIS R 1602.
The fracture toughness value (K IC ) of the chemically strengthened glass is preferably 0.70 MPa·m 1/2 or more, more preferably 0.75 MPa·m 1/2 or more, and even more preferably 0.80 MPa·m 1/2 or more. The fracture toughness value K IC is often 2.00 MPa·m 1/2 or less, and preferably 1.80 MPa·m 1/2 or less.
In this specification, the "fracture toughness value K IC " is measured with reference to the DCDC method [Reference: M. Y. He, M. R. Turner and A. G. Evans, Acta Metall. Mater. 43 (1995) 3453.].

＜化学強化ガラスの製造方法＞
　本発明の化学強化ガラスの製造方法は、化学強化用溶融塩に対して化学強化用ガラスを浸漬する化学強化処理と、化学強化用ガラスを浸漬した化学強化用溶融塩を溶融塩として、上記本発明の金属成分の回収方法によって特定金属塩を回収し、化学強化用溶融塩を再生する溶融塩再生処理とを、交互に行う。
　本発明の化学強化ガラスの製造方法においては、特定金属塩に含まれる特定金属成分は、リチウムを含むことが好ましい。すなわち、本発明の化学強化ガラスの製造方法では、化学強化処理に供した溶融塩から、本発明の金属成分の回収方法によってリチウムを含む特定金属塩を回収し、特定金属塩を回収した溶融塩を再度、化学強化処理に供する。
　以下、化学強化処理、および、溶融塩再生処理について詳細に説明する。 <Method of manufacturing chemically strengthened glass>
The method for producing chemically strengthened glass of the present invention involves alternately performing a chemical strengthening treatment in which chemically strengthened glass is immersed in a chemically strengthening molten salt, and a molten salt regeneration treatment in which the chemically strengthened molten salt in which the chemically strengthened glass has been immersed is used as a molten salt, a specific metal salt is recovered by the metal component recovery method of the present invention, and the chemically strengthened molten salt is regenerated.
In the method for producing chemically strengthened glass of the present invention, the specific metal component contained in the specific metal salt preferably includes lithium. That is, in the method for producing chemically strengthened glass of the present invention, the specific metal salt containing lithium is recovered from the molten salt subjected to chemical strengthening treatment by the method for recovering a metal component of the present invention, and the molten salt from which the specific metal salt has been recovered is again subjected to chemical strengthening treatment.
The chemical strengthening treatment and the molten salt regeneration treatment will be described in detail below.

［化学強化処理］
　本発明の化学強化ガラスの製造方法では、化学強化用溶融塩に対して化学強化用ガラスを浸漬する、化学強化処理を行う。
　化学強化用ガラスの好ましい組成は、化学強化用ガラスの製造方法の部分で述べた通りである。
　化学強化用溶融塩の好ましい組成は、金属成分の回収方法の部分で述べた通りである。
　化学強化処理を実施すると、化学強化用ガラスにおける成分（例えば、リチウムイオンおよびナトリウムイオン等）が、化学強化用溶融塩に含まれるイオンと交換され、交換前のイオンのイオン半径と、交換されたイオンのイオン半径の差によって、圧縮応力を有する層が形成される。 [Chemical strengthening treatment]
In the method for producing chemically strengthened glass of the present invention, a chemical strengthening treatment is carried out by immersing the glass for chemical strengthening in a chemical strengthening molten salt.
The preferred composition of the glass for chemical strengthening is as described in the section on the method for producing the glass for chemical strengthening.
The preferred composition of the chemical strengthening molten salt is as described in the section on the method for recovering metal components.
When chemical strengthening treatment is performed, components in the chemically strengthened glass (e.g., lithium ions, sodium ions, etc.) are exchanged with ions contained in the chemically strengthened molten salt, and a layer having compressive stress is formed due to the difference between the ionic radius of the ions before the exchange and the ionic radius of the exchanged ions.

　化学強化処理は、化学強化用溶融塩を用いて繰り返し実施してもよい。すなわち、１回以上化学強化用ガラスを浸漬した化学強化用溶融塩を用いて、さらに別の化学強化用ガラスを浸漬して、化学強化処理を行ってもよい。
　化学強化用溶融塩を用いて繰り返し化学強化処理を実施すると、化学強化用ガラスに含まれていた成分（例えばリチウムイオン）の濃度が化学強化用溶融塩において上昇する。化学強化用溶融塩において化学強化用ガラスに含まれていた成分の濃度が上昇すると、化学強化用ガラスに含まれる成分が、化学強化用溶融塩に含まれるイオンと交換されにくくなり、化学強化が十分に進行しなくなる可能性がある。
　本発明の化学強化ガラスの製造方法では、後段で詳述する溶融塩再生処理によって、特定金属塩（例えばリチウムを含む特定金属塩）を回収し、化学強化用溶融塩を再生し、再度化学強化処理に供することができる状態とする。 The chemical strengthening treatment may be repeatedly performed using a chemical strengthening molten salt. That is, the chemical strengthening treatment may be performed by immersing another chemically strengthened glass in the chemically strengthening molten salt in which the chemically strengthened glass has been immersed one or more times.
When chemical strengthening treatment is repeatedly performed using a chemical strengthening molten salt, the concentration of components (e.g., lithium ions) that were contained in the chemically strengthened glass increases in the chemical strengthening molten salt. If the concentration of the components that were contained in the chemically strengthened glass increases in the chemical strengthening molten salt, the components in the chemically strengthened glass become less likely to be exchanged with ions contained in the chemical strengthening molten salt, and chemical strengthening may not proceed sufficiently.
In the method for producing chemically strengthened glass of the present invention, a specific metal salt (for example, a specific metal salt containing lithium) is recovered by a molten salt regeneration treatment described in detail later, and the chemical strengthening molten salt is regenerated. It is made into a state where it can be subjected to the chemical strengthening treatment again.

　化学強化処理の方法は、特に制限されず、公知の方法を適用できる。また、化学強化処理の条件等は、用いる化学強化用ガラス、および、化学強化用溶融塩等によって適宜調整できる。
　例えば、化学強化処理としては、３６０～６００℃に加熱された化学強化用溶融塩中に、化学強化用ガラスを０．１～５００時間浸漬することによって行える。なお、化学強化用溶融塩の加熱温度としては、３７５℃以上が好ましく、また、５００℃以下が好ましい。溶融塩中へのガラス板の浸漬時間は、０．３時間以上が好ましく、また、２００時間以下が好ましい。
　また、化学強化処理は、１回のみ行ってもよく、２以上の異なる条件で複数回の化学強化処理（多段強化）を行ってもよい。化学強化処理は１段階であってもよいが、２段階以上の化学強化処理を行うことも好ましい。すなわち、化学強化処理は、組成の異なる２以上の化学強化用溶融塩を用いてもよい。 The method of chemical strengthening treatment is not particularly limited, and known methods can be applied. The conditions of the chemical strengthening treatment can be appropriately adjusted depending on the chemical strengthening glass and chemical strengthening molten salt used.
For example, chemical strengthening treatment can be performed by immersing the glass for chemical strengthening in a chemical strengthening molten salt heated to 360 to 600° C. for 0.1 to 500 hours. The heating temperature of the chemical strengthening molten salt is preferably 375° C. or higher and 500° C. or lower. The immersion time of the glass plate in the molten salt is preferably 0.3 hours or longer and 200 hours or shorter.
The chemical strengthening treatment may be performed only once, or may be performed multiple times under two or more different conditions (multi-stage strengthening). The chemical strengthening treatment may be performed in one stage, but it is also preferable to perform chemical strengthening treatment in two or more stages. That is, the chemical strengthening treatment may use two or more chemical strengthening molten salts with different compositions.

　化学強化処理を繰り返し実施する際に、化学強化処理を行った後の化学強化用溶融塩の成分を分析し、所定の基準を満たす場合には、その化学強化用溶融塩を再度化学強化処理に供し、所定の基準を満たさない場合には、後段に記載する溶融塩再生処理を実施することも好ましい。上記所定の基準としては、化学強化用溶融塩における、後段の溶融塩再生処理において回収する特定金属塩に含まれる成分（例えばリチウムイオン）の含有量を分析した際の、その含有量が挙げられる。
　上記所定の基準としてリチウムイオンの含有量を分析する場合、上記所定の基準としては、リチウムイオンの含有量が、化学強化用溶融塩の全質量に対して所定の値以下であることを定めることが好ましい。上記所定の値としての化学強化用溶融塩の全質量に対するリチウムイオンの含有量は、例えば、２００質量ｐｐｍ以上が好ましく、１,０００質量ｐｐｍ以上がより好ましく、２,０００質量ｐｐｍ以上がさらに好ましく、３,０００質量ｐｐｍ以上が特に好ましい。また、上記所定の値としての化学強化用溶融塩の全質量に対するリチウムイオンの含有量は、例えば、５０,０００質量ｐｐｍ以下が好ましく、２０,０００質量ｐｐｍ以下がより好ましく、１０,０００質量ｐｐｍ以下がさらに好ましい。
　なお、化学強化用溶融塩における、回収する特定金属塩に含まれる成分（例えばリチウムイオン）の含有量は、例えば、原子吸光法で分析できる。
　また、上記所定の基準としてナトリウムイオンの含有量を分析する場合、上記所定の基準としては、ナトリウムイオンの含有量が、化学強化用溶融塩の全質量に対して所定の値以下であることを定めることが好ましい。上記所定の値としての化学強化用溶融塩の全質量に対するナトリウムイオンの含有量は、例えば、２００質量ｐｐｍ以上が好ましく、５００質量ｐｐｍ以上がより好ましく、２,０００質量ｐｐｍ以上がさらに好ましく、４,０００質量ｐｐｍ以上が特に好ましく、５,０００質量ｐｐｍ以上が最も好ましい。また、上記所定の値としての化学強化用溶融塩の全質量に対するリチウムイオンの含有量は、例えば、６０,０００質量ｐｐｍ以下が好ましく、４０,０００質量ｐｐｍ以下がより好ましく、２０,０００質量ｐｐｍ以下がさらに好ましい。 When chemical strengthening treatment is repeatedly performed, it is also preferable to analyze the components of the chemical strengthening molten salt after the chemical strengthening treatment, and if the components satisfy a predetermined standard, subject the chemical strengthening molten salt to the chemical strengthening treatment again, or if the predetermined standard is not satisfied, perform the molten salt regeneration treatment described below. The predetermined standard is the content of components (e.g., lithium ions) contained in the specific metal salt recovered in the subsequent molten salt regeneration treatment when the content of the components is analyzed in the chemical strengthening molten salt.
When analyzing the lithium ion content as the predetermined standard, the predetermined standard is preferably set to a lithium ion content of a predetermined value or less relative to the total mass of the chemical strengthening molten salt. The lithium ion content relative to the total mass of the chemical strengthening molten salt as the predetermined value is, for example, preferably 200 ppm by mass or more, more preferably 1,000 ppm by mass or more, even more preferably 2,000 ppm by mass or more, and particularly preferably 3,000 ppm by mass or more. Furthermore, the lithium ion content relative to the total mass of the chemical strengthening molten salt as the predetermined value is, for example, preferably 50,000 ppm by mass or less, more preferably 20,000 ppm by mass or less, and even more preferably 10,000 ppm by mass or less.
The content of a component (e.g., lithium ion) contained in the specific metal salt to be recovered in the chemical strengthening molten salt can be analyzed by, for example, atomic absorption spectrometry.
Furthermore, when analyzing the sodium ion content as the predetermined standard, the predetermined standard is preferably set to a sodium ion content of a predetermined value or less relative to the total mass of the chemical strengthening molten salt. The sodium ion content relative to the total mass of the chemical strengthening molten salt as the predetermined value is, for example, preferably 200 ppm by mass or more, more preferably 500 ppm by mass or more, even more preferably 2,000 ppm by mass or more, particularly preferably 4,000 ppm by mass or more, and most preferably 5,000 ppm by mass or more. The lithium ion content relative to the total mass of the chemical strengthening molten salt as the predetermined value is, for example, preferably 60,000 ppm by mass or less, more preferably 40,000 ppm by mass or less, and even more preferably 20,000 ppm by mass or less.

　なお、化学強化処理において、組成の異なる２以上の化学強化用溶融塩を用いる場合、それぞれ、上記所定の基準を満たすか否かを確認し、再度化学強化処理に供するか、溶融塩再生処理を実施するかを決定することも好ましい。 In addition, when two or more chemical strengthening molten salts with different compositions are used in the chemical strengthening process, it is preferable to check whether each of them meets the above-mentioned specified criteria and decide whether to subject the material to the chemical strengthening process again or to carry out a molten salt regeneration process.

［溶融塩再生処理］
　本発明の化学強化ガラスの製造方法では、上記化学強化処理を行った後、上記本発明の金属成分の回収方法によって特定金属塩を回収し、化学強化用溶融塩を再生する溶融塩再生処理を行う。なお、本発明の化学強化ガラスの製造方法では、化学強化処理と、溶融塩再生処理とを、交互に行う。
　溶融塩再生処理の具体的な方法については、上述した本発明の溶融塩の再生方法と同様であるため、説明を省略する。ここで、特定金属塩は、リチウムまたはナトリウムを含むことが好ましく、リチウムを含むことがより好ましい。
　なお、上述したように、化学強化用溶融塩から特定金属塩を回収した後、化学強化用溶融塩の成分を調整してもよい。溶融塩の成分を調整する方法としては、例えば、硫酸塩を添加することが挙げられる。また、硫酸塩の添加と同時に、硫酸塩以外の塩（例えば、硝酸ナトリウム、硝酸カリウム、および、硫酸カリウムからなる群から選択される１種以上の成分等の硝酸塩）を添加してもよい。溶融塩再生処理を実施すると、化学強化用溶融塩は、再度化学強化処理に供することができる。
　溶融塩の成分を調整する方法としては、炭酸塩を添加してもよい。また、炭酸塩の添加と同時に、炭酸塩以外の塩（例えば、硝酸カリウム等の硝酸塩）を添加してもよい。 [Molten salt regeneration process]
In the method for producing chemically strengthened glass of the present invention, after the chemical strengthening treatment, the specific metal salt is recovered by the method for recovering metal components of the present invention, and a molten salt regeneration treatment is performed to regenerate the chemically strengthening molten salt. Note that in the method for producing chemically strengthened glass of the present invention, the chemical strengthening treatment and the molten salt regeneration treatment are performed alternately.
The specific method for the molten salt regeneration treatment is the same as the above-mentioned method for regenerating a molten salt of the present invention, and therefore, description thereof will be omitted. Here, the specific metal salt preferably contains lithium or sodium, and more preferably contains lithium.
As described above, the components of the chemical strengthening molten salt may be adjusted after recovering the specific metal salt from the chemical strengthening molten salt. For example, adding a sulfate may be used to adjust the components of the molten salt. Furthermore, salts other than sulfate (e.g., nitrates such as one or more components selected from the group consisting of sodium nitrate, potassium nitrate, and potassium sulfate) may be added simultaneously with the addition of sulfate. After the molten salt regeneration process is performed, the chemical strengthening molten salt can be subjected to a chemical strengthening process again.
The composition of the molten salt may be adjusted by adding a carbonate, or by adding a salt other than the carbonate (for example, a nitrate such as potassium nitrate) simultaneously with the addition of the carbonate.

　溶融塩再生処理は、１回のみ行ってもよく、２回以上行ってもよい。また、溶融塩再生処理を実施した後の化学強化用溶融塩の成分を分析し、上記所定の基準を満たす場合には、その化学強化用溶融塩を化学強化処理に供し、上記所定の基準を満たさない場合には、再度溶融塩再生処理を行うことも好ましい。 The molten salt regeneration treatment may be carried out once or twice or more times. It is also preferable to analyze the components of the chemical strengthening molten salt after the molten salt regeneration treatment has been carried out, and if the above-mentioned specified criteria are met, the chemical strengthening molten salt is subjected to the chemical strengthening treatment, but if the above-mentioned specified criteria are not met, the molten salt regeneration treatment is carried out again.

　本発明の化学強化ガラスの製造方法では、上述した化学強化処理および溶融塩再生処理を交互に行う。交互に行う回数は、１回以上であればよく、２回以上繰り返してもよい。
　溶融塩再生処理により、化学強化用溶融塩を交換することなく、半永久的に使用することも可能である。 In the method for producing chemically strengthened glass of the present invention, the above-mentioned chemical strengthening treatment and molten salt regeneration treatment are alternately performed. The number of times that the alternation is performed may be one or more, and may be repeated two or more times.
By using the molten salt regeneration process, it is possible to use the chemical strengthening molten salt semi-permanently without replacing it.

　また、本発明の化学強化ガラスの製造方法においては、上記化学強化用ガラスの製造方法で得られた化学強化用ガラスを用いることも好ましい。
　すなわち、上記溶融塩再生処理で回収した特定金属塩を原料として化学強化用ガラスを製造し、その化学強化用ガラスを、化学強化処理に供することも好ましい。溶融塩再生処理で回収した特定金属塩を原料として化学強化用ガラスを製造すると、化学強化処理によって化学強化用溶融塩に移行した成分を有効利用することができ、好ましい。 In addition, in the method for producing chemically strengthened glass of the present invention, it is also preferable to use chemically strengthened glass obtained by the above-mentioned method for producing chemically strengthened glass.
That is, it is also preferable to produce chemically strengthened glass using the specific metal salt recovered by the molten salt regeneration treatment as a raw material, and then subject the chemically strengthened glass to the chemical strengthening treatment. When chemically strengthened glass is produced using the specific metal salt recovered by the molten salt regeneration treatment as a raw material, the components transferred to the chemically strengthening molten salt by the chemical strengthening treatment can be effectively utilized, which is preferable.

　また、本発明の化学強化ガラスの製造方法の別の態様としては、溶融塩から特定金属塩を回収し、特定金属塩を回収した後の溶融塩に対して、ケイ素、アルミニウムおよびリチウムを含むガラスを浸漬する、化学強化ガラスの製造方法も挙げられる。なお、上記化学強化ガラスの製造方法の別の態様においては、上記特定金属塩に含まれる特定金属成分は、リチウムを含むことが好ましい。
　特定金属塩を回収した後の溶融塩については、上記本発明の金属塩の回収方法を適用した溶融塩であれば特に制限されず、上記溶融塩の再生方法で得られる溶融塩を好ましく適用できる。
　また、ケイ素、アルミニウムおよびリチウムを含むガラスについては、上述した化学強化用ガラスを好ましく適用できる。また、上記化学強化用ガラスの製造方法で得られた化学強化用ガラスを用いることも好ましい。
　ケイ素、アルミニウムおよびリチウムを含むガラスを溶融塩に浸漬すると、化学強化処理が行われる。化学強化処理については、上述した通りであり、好ましい態様も上述した通りである。 Another aspect of the method for producing chemically strengthened glass of the present invention is a method for producing chemically strengthened glass, which comprises recovering a specific metal salt from a molten salt and immersing a glass containing silicon, aluminum, and lithium in the molten salt after the specific metal salt has been recovered. In this other aspect of the method for producing chemically strengthened glass, the specific metal component contained in the specific metal salt preferably includes lithium.
The molten salt obtained after recovering the specific metal salt is not particularly limited as long as it is a molten salt obtained by the above-mentioned method for recovering a metal salt of the present invention, and the molten salt obtained by the above-mentioned method for regenerating a molten salt can be preferably used.
Furthermore, for glass containing silicon, aluminum, and lithium, the above-mentioned chemically strengthened glass can be preferably applied. It is also preferable to use the chemically strengthened glass obtained by the above-mentioned method for producing chemically strengthened glass.
The chemical strengthening treatment is carried out by immersing the glass containing silicon, aluminum, and lithium in the molten salt. The chemical strengthening treatment is as described above, and the preferred embodiments are also as described above.

　上記本発明の化学強化ガラスの製造方法の別の態様において、上記特定金属塩を回収した後の溶融塩は、実質的に固体状態の塩を含まないことも好ましい。
　溶融塩が固体状態の塩を実質的に含まないとは、目視で溶融塩を観察した際に、析出物が観察されない状態をいう。
　溶融塩が固体状態の塩を含まない場合、ガラス面内の強化の均一性に優れるため、好ましい。 In another aspect of the method for producing chemically strengthened glass of the present invention, it is also preferable that the molten salt after recovering the specific metal salt does not substantially contain solid-state salt.
The molten salt being substantially free of solid salt means that no precipitate is observed when the molten salt is visually observed.
It is preferable that the molten salt does not contain a solid salt, since this results in excellent uniformity of strengthening within the glass surface.

　以下に実施例に基づいて本発明をさらに詳細に説明する。
　以下の実施例に示す材料、使用量、割合、処理内容、および、処理手順等は、本発明の趣旨を逸脱しない限り適宜変更できる。したがって、本発明の範囲は以下に示す実施例により限定的に解釈されるべきではない。
　なお、各例において、化学強化ガラスの応力は、散乱光光弾性応力計（ＳＬＰ：Ｓｃａｔｔｅｒｄ　Ｌｉｇｈｔ　Ｐｈｏｔｏｅｌａｓｔｉｃ　Ｓｔｒｅｓｓ　Ｍｅｔｅｒ）を用いて測定した。ＳＬＰとしては、折原製作所製ＳＬＰ－２０００を用いた。また、各例のうち、例５、例７においては、化学強化ガラスの応力は、光導波表面応力計（ＦＳＭ：Ｆｉｌｍ　Ｓｔｒｅｓｓ　Ｍｅａｓｕｒｍｅｎｔ）を用いて測定した。ＦＳＭとしては折原製作所製ＦＳＭ－６０００ＵＶを用いた。
　以下、例１～例６は実施例である。 The present invention will be described in more detail below with reference to examples.
The materials, amounts used, ratios, treatment details, treatment procedures, etc. shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the following examples.
In each example, the stress of the chemically strengthened glass was measured using a scattered light photoelastic stress meter (SLP: Scattered Light Photoelastic Stress Meter). As the SLP, SLP-2000 manufactured by Orihara Seisakusho was used. In addition, among the examples, in Examples 5 and 7, the stress of the chemically strengthened glass was measured using an optical waveguide surface stress meter (FSM: Film Stress Measurement). As the FSM, FSM-6000UV manufactured by Orihara Seisakusho was used.
The following Examples 1 to 6 are working examples.

＜例１＞
　まず、下記組成の溶融塩Ａ１を調製した。
　・硝酸カリウム：４２．６質量％
　・硝酸ナトリウム：４２．６質量％
　・硝酸リチウム：４．３質量％
　・硫酸ナトリウム：１０．５質量％
　上記溶融塩Ａ１を、４１０℃に加熱し、溶融状態とした。溶融塩Ａ１の加熱は、溶融塩を収容する容器をマントルヒーターに収め、マントルヒーターによって行った。
　また、マントルヒーターによる加熱を行う際には、溶融塩Ａ１に熱電対を接触させ、温度を測定した。上記熱電対としては、Ｋ熱電対を用いた。 <Example 1>
First, a molten salt A1 having the following composition was prepared.
・Potassium nitrate: 42.6% by mass
Sodium nitrate: 42.6% by mass
Lithium nitrate: 4.3% by mass
Sodium sulfate: 10.5% by mass
The molten salt A1 was heated to 410° C. to be in a molten state. The molten salt A1 was heated by placing a container containing the molten salt in a mantle heater.
When heating with the mantle heater, a thermocouple was brought into contact with the molten salt A1 to measure the temperature. A K thermocouple was used as the thermocouple.

　次いで、溶融塩Ａ１に対し、網部および取手部を有する治具（上記第１治具に相当）を浸漬した。上記網部は、目開きが０．０９ｍｍであった。
　上記治具を浸漬した状態で、マントルヒーターの出力を制御し、溶融塩Ａ１を空冷にて２８０℃まで冷却した。
　溶融塩Ａ１の温度を２８０℃に保持した状態で、撹拌羽根を３００ｒｐｍ（回転毎分）で回転させ、溶融塩Ａ１を３０分間撹拌した。その後、溶融塩Ａ１の温度を２８０℃に保持した状態で、撹拌せずに６０分静置した。
　上記手順により、溶融塩Ａ１中に特定金属塩を析出させた。 Next, a jig having a mesh portion and a handle portion (corresponding to the first jig) was immersed in the molten salt A1. The mesh portion had a mesh size of 0.09 mm.
With the jig immersed, the output of the mantle heater was controlled and the molten salt A1 was cooled to 280°C by air cooling.
The molten salt A1 was stirred for 30 minutes by rotating the stirring blade at 300 rpm (revolutions per minute) while the temperature of the molten salt A1 was maintained at 280° C. Thereafter, the molten salt A1 was allowed to stand for 60 minutes without stirring while the temperature of the molten salt A1 was maintained at 280° C.
By the above procedure, the specific metal salt was precipitated in the molten salt A1.

　静置した後、上記治具を溶融塩Ａ１から引き上げ、特定金属塩を溶融状態の溶融塩Ａ１から分離し、回収した。以下、特定金属塩を回収した後の溶融塩Ａ１を、便宜的に「溶融塩Ａ２」と記載する。
　回収した特定金属塩には、リチウムが含まれていることを確認した。 After being left to stand, the jig was pulled out from the molten salt A1, and the specific metal salt was separated and recovered from the molten molten salt A1. Hereinafter, the molten salt A1 from which the specific metal salt has been recovered will be referred to as "molten salt A2" for convenience.
It was confirmed that the recovered specific metal salt contained lithium.

　ここで、上記冷却を行う前の溶融塩Ａ１および溶融塩Ａ２におけるリチウム原子の含有量について、後段の表１に示す。また、回収した特定金属塩に含まれるリチウム原子の含有量についても表１に示す。
　さらに、上記冷却を行う前の溶融塩Ａ１および溶融塩Ａ２を用いて以下の条件で化学強化処理を実施し、化学強化ガラスを得た。得られた化学強化ガラスの応力プロファイルを測定し、表面からの深さ５０μｍにおける圧縮応力値を得た。この結果について、後段の表１に併せて示す（表中「化学強化ガラスのＣＳ５０」の欄）。
　なお、溶融塩Ａ１および溶融塩Ａ２における成分の含有量の測定方法は上述した通りである。また、特定金属塩中の成分の含有量も同様の方法で分析した。 The contents of lithium atoms in the molten salts A1 and A2 before the cooling are shown in Table 1 below. Table 1 also shows the contents of lithium atoms contained in the recovered specific metal salts.
Furthermore, chemical strengthening treatment was performed under the following conditions using the molten salt A1 and molten salt A2 before the cooling to obtain chemically strengthened glass. The stress profile of the obtained chemically strengthened glass was measured to obtain the compressive stress value at a depth of 50 μm from the surface. The results are also shown in Table 1 below (the column "CS50 of chemically strengthened glass" in the table).
The methods for measuring the content of components in molten salts A1 and A2 were as described above. The content of components in the specific metal salt was also analyzed by the same method.

　表１に示す結果から、本発明の金属成分の回収方法により、特定の金属成分（リチウム）を溶融塩から簡便に回収できることが確認された。また、本発明の金属成分の回収方法を適用すると、溶融塩を再生できることも確認された。 The results shown in Table 1 confirm that the metal component recovery method of the present invention makes it possible to easily recover a specific metal component (lithium) from molten salt. It was also confirmed that the molten salt can be regenerated by applying the metal component recovery method of the present invention.

＜例２＞
　例１で調製した溶融塩Ａ１と同様の組成の溶融塩Ａ３を、例１と同様に準備した。なお、溶融塩Ａ１および溶融塩Ａ３は、別個に準備したため、それぞれの組成は、厳密に一致しない。
　溶融塩Ａ３を４１０℃とした状態で、板（＃２０のメッシュ（目開き０．９８ｍｍ））を蛇腹状に折り曲げてなる構造を有する塩析出部および取手部を有する治具（上記第２治具に相当）を浸漬した。
　溶融塩Ａ３の温度を２８０℃に保持した状態で、撹拌せずに６０分静置した。
　上記手順により、溶融塩Ａ１中に特定金属塩を析出させた。ここで、上記治具を確認したところ、塩析出部の表面に塩が析出していることを確認した。 <Example 2>
Molten salt A3, which had the same composition as molten salt A1 prepared in Example 1, was prepared in the same manner as in Example 1. Note that molten salt A1 and molten salt A3 were prepared separately, and therefore their compositions did not strictly match.
With the molten salt A3 at 410°C, a jig (corresponding to the second jig described above) having a salt deposition portion and a handle portion, which had a structure formed by folding a plate (#20 mesh (opening size: 0.98 mm)) into an accordion-like shape, was immersed.
The molten salt A3 was allowed to stand for 60 minutes without stirring while the temperature was maintained at 280°C.
By the above procedure, the specific metal salt was precipitated in the molten salt A1. When the jig was checked, it was confirmed that the salt had precipitated on the surface of the salt precipitated portion.

　静置した後、上記治具を溶融塩Ａ３から引き揚げ、特定金属塩を溶融状態の溶融塩Ａ１から分離し、上記治具に付着した特定金属塩を一部回収した。以下、例２において、特定金属塩を回収した後の溶融塩Ａ３を、便宜的に「溶融塩Ａ４」と記載する。また、以下、上記一部を回収した治具に付着した特定金属塩を、便宜的に「特定金属塩Ｂ１」と記載する。
　回収した特定金属塩Ｂ１には、リチウムが含まれていることを確認した。
　さらに、特定金属塩Ｂ１が付着した治具を４００℃で３時間加熱した。そうすると、治具上に残る固体と、４００℃で溶融して治具から流れ落ちた成分とに分離された。上記加熱により、治具上に残った固体を、便宜的に「特定金属塩Ｂ２」と記載する。また、上記加熱により、４００℃で溶融して治具から流れ落ちた成分を固化した固体を、便宜的に「特定金属塩Ｂ３」と記載する。 After leaving the jig to stand, the jig was lifted out of the molten salt A3, the specific metal salt was separated from the molten molten salt A1, and a portion of the specific metal salt adhering to the jig was recovered. Hereinafter, in Example 2, the molten salt A3 after the specific metal salt was recovered will be referred to as "molten salt A4" for convenience. Furthermore, hereinafter, the specific metal salt adhering to the jig from which the portion was recovered will be referred to as "specific metal salt B1" for convenience.
It was confirmed that the recovered specific metal salt B1 contained lithium.
Furthermore, the jig with the specific metal salt B1 attached was heated at 400°C for 3 hours. This resulted in separation into a solid remaining on the jig and a component that melted at 400°C and flowed off the jig. The solid remaining on the jig after the heating is conveniently referred to as "specific metal salt B2." Furthermore, the solid resulting from solidifying the component that melted at 400°C and flowed off the jig after the heating is conveniently referred to as "specific metal salt B3."

　ここで、上記冷却を行う前の溶融塩Ａ３および溶融塩Ａ４におけるリチウム原子の含有量について、後段の表２に示す。また、特定金属塩Ｂ１、特定金属塩Ｂ２および特定金属塩Ｂ３のそれぞれに含まれるリチウム原子の含有量についても、表２に示す。
　さらに、上記冷却を行う前の溶融塩Ａ３および溶融塩Ａ４を用いて例１と同様の条件で化学強化処理を実施し、化学強化ガラスを得た。得られた化学強化ガラスの応力プロファイルを測定し、表面からの深さ５０μｍにおける圧縮応力値を得た。この結果について、後段の表２に併せて示す（表中「化学強化ガラスのＣＳ５０」の欄）。
　なお、溶融塩Ａ３および溶融塩Ａ４における成分の含有量の測定方法は上述した通りである。また、特定金属塩中の成分の含有量も同様の方法で分析した。 The contents of lithium atoms in molten salts A3 and A4 before the cooling are shown in Table 2 below. Table 2 also shows the contents of lithium atoms contained in specific metal salts B1, B2, and B3.
Furthermore, chemical strengthening treatment was performed under the same conditions as in Example 1 using the molten salts A3 and A4 before the cooling, to obtain chemically strengthened glass. The stress profile of the obtained chemically strengthened glass was measured, and the compressive stress value at a depth of 50 μm from the surface was obtained. The results are also shown in Table 2 below (the column "CS50 of chemically strengthened glass" in the table).
The content of each component in the molten salts A3 and A4 was measured by the same method as described above. The content of each component in the specific metal salt was also analyzed by the same method.

　なお、例１および例２においては、以下の組成の化学強化用ガラスを用いた。以下の組成は、酸化物基準のモル百分率表示である。なお、一部の微量成分については、外割で成分を添加している場合がある。
　ＳｉＯ２：６６．２％
　Ａｌ２Ｏ３：１１．２％
　ＭｇＯ：３．１％
　ＣａＯ：０．２％
　ＴｉＯ２：０．１％
　ＺｒＯ２：１．３％
　Ｙ２Ｏ３：０．５％
　Ｌｉ２Ｏ：１０．４％
　Ｎａ２Ｏ：５．６％
　Ｋ２Ｏ：１．５％
　例１および例２においては、上記組成の化学強化用ガラスに対し、以下の条件で化学強化処理を実施した。
　・化学強化温度：４１０℃
　・化学強化時間：２時間 In Examples 1 and 2, chemically strengthened glasses having the following compositions were used. The compositions are expressed in mole percentages based on oxides. Some trace components may be added as an extra percentage.
SiO2 : 66.2%
Al2O3 : 11.2 %
MgO: 3.1%
CaO: 0.2%
TiO2 : 0.1%
ZrO2 : 1.3%
Y2O3 : 0.5 %
Li2O : 10.4%
Na2O : 5.6%
K2O : 1.5%
In Examples 1 and 2, the chemically strengthened glass having the above composition was subjected to a chemical strengthening treatment under the following conditions.
・Chemical strengthening temperature: 410℃
Chemical strengthening time: 2 hours

　表２に示す結果から、本発明の金属成分の回収方法により、特定の金属成分（リチウム）を溶融塩から簡便に回収できることが確認された。また、本発明の金属成分の回収方法を適用すると、溶融塩を再生できることも確認された。
　さらに、回収した特定金属塩を、特定金属塩を析出させる溶融塩温度よりも高い温度で加熱した場合には、治具から流れ落ちる成分である特定金属塩Ｂ３では、硝酸塩の含有量が多くなり、治具に残存する成分である特定金属塩Ｂ２では硝酸塩の含有量が少なくなることが確認された。 The results shown in Table 2 confirm that the method for recovering metal components of the present invention allows a specific metal component (lithium) to be easily recovered from a molten salt. It was also confirmed that the application of the method for recovering metal components of the present invention allows the molten salt to be regenerated.
Furthermore, it was confirmed that when the recovered specific metal salt was heated at a temperature higher than the molten salt temperature at which the specific metal salt precipitated, the specific metal salt B3, which is the component that flows down from the jig, had a higher nitrate content, while the specific metal salt B2, which is the component that remained in the jig, had a lower nitrate content.

＜例３＞
　例１で調製した溶融塩Ａ１と同様の組成の溶融塩Ａ５を、例１と同様に準備した。なお、溶融塩Ａ１および溶融塩Ａ５は、別個に準備したため、それぞれの組成は、厳密に一致しない。
　溶融塩Ａ５を４１０℃とした状態で、板（＃２０のメッシュ（目開き０．９８ｍｍ））を蛇腹状に折り曲げてなる構造を有する塩析出部および取手部を有する治具（上記第２治具に相当）を浸漬した。
　溶融塩Ａ５の温度を２９０℃に保持した状態で、撹拌せずに６０分静置した。
　上記手順により、溶融塩Ａ５中に特定金属塩を析出させた。ここで、上記治具を確認したところ、塩析出部の表面に塩が析出していることを確認した。 <Example 3>
Molten salt A5, which had the same composition as molten salt A1 prepared in Example 1, was prepared in the same manner as in Example 1. Note that molten salt A1 and molten salt A5 were prepared separately, and therefore their compositions do not strictly match.
With the molten salt A5 at 410°C, a jig (corresponding to the second jig described above) having a salt deposition portion and a handle portion, which had a structure formed by folding a plate (#20 mesh (opening size: 0.98 mm)) into an accordion-like shape, was immersed.
The molten salt A5 was allowed to stand for 60 minutes without stirring while the temperature was maintained at 290°C.
By the above procedure, the specific metal salt was precipitated in the molten salt A5. When the jig was checked, it was confirmed that the salt had precipitated on the surface of the salt precipitated portion.

　静置した後、上記治具を溶融塩Ａ５から引き揚げ、特定金属塩を溶融状態の溶融塩Ａ１から分離した。以下、例３において、特定金属塩を回収した後の溶融塩Ａ５を、便宜的に「溶融塩Ａ６」と記載する。また、以下、上記治具に付着した特定金属塩を、便宜的に「特定金属塩Ｃ１」と記載する。
　上記特定金属塩Ｃ１が付着した治具を、溶融塩Ａ６を収容する容器の上部に設置し、治具が配置される雰囲気を３００℃に加熱し３０分間保持した。上記加熱により、特定金属塩Ｃ１に含まれる成分の一部が溶融し、溶融塩Ａ６に流れ落ちた。加熱後に上記治具に付着している特定金属塩は、便宜的に「特定金属塩Ｃ２」と記載する。
　回収した特定金属塩Ｃ２には、リチウムが含まれていることを確認した。 After standing, the jig was pulled out from the molten salt A5, and the specific metal salt was separated from the molten molten salt A1. Hereinafter, in Example 3, the molten salt A5 from which the specific metal salt was recovered will be referred to as "molten salt A6" for convenience. Hereinafter, the specific metal salt adhered to the jig will be referred to as "specific metal salt C1" for convenience.
The jig with the specific metal salt C1 attached thereto was placed on top of a container containing molten salt A6, and the atmosphere in which the jig was placed was heated to 300°C and maintained for 30 minutes. Due to the heating, some of the components contained in the specific metal salt C1 melted and flowed down into the molten salt A6. For convenience, the specific metal salt attached to the jig after heating is referred to as "specific metal salt C2."
It was confirmed that the recovered specific metal salt C2 contained lithium.

　ここで、上記冷却を行う前の溶融塩Ａ５および溶融塩Ａ６におけるリチウム原子の含有量について、後段の表３に示す。また、特定金属塩Ｃ２に含まれるリチウム原子の含有量についても、表３に示す。
　さらに、上記冷却を行う前の溶融塩Ａ５および溶融塩Ａ６を用いて例１と同様の条件で化学強化処理を実施し、化学強化ガラスを得た。得られた化学強化ガラスの応力プロファイルを測定し、表面からの深さ５０μｍにおける圧縮応力値を得た。この結果について、後段の表３に併せて示す（表中「化学強化ガラスのＣＳ５０」の欄）。 The contents of lithium atoms in molten salts A5 and A6 before the cooling are shown in Table 3 below. Table 3 also shows the content of lithium atoms contained in specific metal salt C2.
Furthermore, chemical strengthening treatment was performed under the same conditions as in Example 1 using molten salt A5 and molten salt A6 before the cooling, to obtain chemically strengthened glass. The stress profile of the obtained chemically strengthened glass was measured, and the compressive stress value at a depth of 50 μm from the surface was obtained. The results are also shown in Table 3 below (the column "CS50 of chemically strengthened glass" in the table).

　さらに、溶融塩Ａ６を用いて化学強化処理を行った後の溶融塩Ａ６に対して、例３で行った処理と同様の処理を行い、溶融塩Ａ６から特定金属塩の回収処理を行った。上記処理を行った後の溶融塩Ａ６を、便宜的に「溶融塩Ａ７」と記載する。また、上記溶融塩Ａ７を得る際に治具に付着した特定金属塩を便宜的に「特定金属塩Ｃ３」と記載する。
　さらに、溶融塩Ａ７を用いて例１と同様の条件で化学強化処理を実施し、化学強化ガラスを得た。得られた化学強化ガラスの応力プロファイルを測定し、表面からの深さ５０μｍにおける圧縮応力値を得た。この結果について、後段の表３に併せて示す（表中「化学強化ガラスのＣＳ５０」の欄）。
　なお、溶融塩Ａ５、溶融塩Ａ６および溶融塩Ａ７における成分の含有量の測定方法は上述した通りである。また、特定金属塩中の成分の含有量も同様の方法で分析した。 Furthermore, the molten salt A6 after the chemical strengthening treatment using the molten salt A6 was subjected to the same treatment as that performed in Example 3, and the specific metal salt was recovered from the molten salt A6. For convenience, the molten salt A6 after the above treatment is referred to as "molten salt A7." Furthermore, for convenience, the specific metal salt that adhered to the jig when obtaining the molten salt A7 is referred to as "specific metal salt C3."
Furthermore, chemical strengthening treatment was performed using molten salt A7 under the same conditions as in Example 1 to obtain chemically strengthened glass. The stress profile of the obtained chemically strengthened glass was measured to obtain a compressive stress value at a depth of 50 μm from the surface. The results are also shown in Table 3 below (the column "CS50 of chemically strengthened glass" in the table).
The methods for measuring the content of components in molten salts A5, A6, and A7 were as described above. The content of components in the specific metal salt was also analyzed by the same method.

　表３に示す結果から、本発明の金属成分の回収方法により、特定の金属成分（リチウム）を溶融塩から簡便に回収できることが確認された。また、本発明の金属成分の回収方法を適用すると、溶融塩を再生できることも確認された。
　さらに、表３に示す結果から、繰り返し溶融塩を使用して化学強化処理を行っても、得られる化学強化ガラスが同様の性質を有することが確認された。 The results shown in Table 3 confirm that the method for recovering metal components of the present invention allows a specific metal component (lithium) to be easily recovered from a molten salt. It was also confirmed that the application of the method for recovering metal components of the present invention allows the molten salt to be regenerated.
Furthermore, the results shown in Table 3 confirm that even if chemical strengthening treatment is repeatedly performed using a molten salt, the resulting chemically strengthened glass has similar properties.

＜例４＞
　まず、下記組成の溶融塩Ａ８を調製した。
　・硝酸カリウム：４０．９質量％
　・硝酸ナトリウム：４０．９質量％
　・硝酸リチウム：９．１質量％
　・硫酸ナトリウム：９．１質量％
　上記溶融塩Ａ８を、４１０℃に加熱し、溶融状態とした。溶融塩Ａ８の加熱は、溶融塩を収容する容器をマントルヒーターに収め、マントルヒーターによって行った。
　また、マントルヒーターによる加熱を行う際には、溶融塩Ａ８に熱電対を接触させ、温度を測定した。
　上記治具を浸漬した状態で、マントルヒーターの出力を制御し、溶融塩Ａ８を空冷にて２６０℃まで冷却した。
　溶融塩Ａ８の温度を２６０℃に保持した状態で、撹拌羽根を３０ｒｐｍ（回転毎分）で回転させ、溶融塩Ａ８を３０分間撹拌した。その後、溶融塩Ａ８の温度を２３０℃に保持した状態で、撹拌せずに３０分静置した。
　上記手順により、溶融塩Ａ８中に特定金属塩を析出させた。 <Example 4>
First, a molten salt A8 having the following composition was prepared.
・Potassium nitrate: 40.9% by mass
Sodium nitrate: 40.9% by mass
Lithium nitrate: 9.1% by mass
Sodium sulfate: 9.1% by mass
The molten salt A8 was heated to 410° C. to be in a molten state. The molten salt A8 was heated by placing a container containing the molten salt in a mantle heater.
When heating was performed using a mantle heater, a thermocouple was brought into contact with the molten salt A8 to measure the temperature.
With the jig immersed, the output of the mantle heater was controlled and the molten salt A8 was cooled to 260°C by air cooling.
Molten salt A8 was stirred for 30 minutes by rotating the stirring blade at 30 rpm (revolutions per minute) while the temperature of molten salt A8 was maintained at 260° C. Thereafter, molten salt A8 was allowed to stand for 30 minutes without stirring while the temperature of molten salt A8 was maintained at 230° C.
By the above procedure, the specific metal salt was precipitated in the molten salt A8.

　静置した後、容器を傾け溶融塩Ａ８から溶融状態の上澄み液をゆっくり容器から流し出し、溶融塩Ａ８と特定金属塩を分離して回収した。以下、流し出した溶融塩および回収した特定金属塩を、便宜的に「溶融塩Ａ９」および「特定金属塩Ｄ１」と記載する。
　回収した特定金属塩Ｄ１には、リチウムが含まれていることを確認した。
　また、回収した特定金属塩のＸ線回折チャートを上述した条件で得たところ、３０．２～３０．５°の範囲に回折ピークが出現していた。また、その回折ピークに帰属される結晶構造は、空間群Ｐ３１ｃのＬｉＮａＳＯ４であった。
　回収した特定金属塩には、硝酸ナトリウムおよび硝酸カリウムも含まれていることを確認した。
　回収した特定金属塩Ｄ１のうち、５．４ｇをステンレス製の容器に入れ、さらに４０ｇの純水を上記容器に加え、攪拌して溶解させ、特定金属水溶液を調製した。上記特定金属水溶液を、９０℃に加熱した。
　また、炭酸ナトリウム５ｇを別のステンレス製の容器に入れ、さらに２５ｇの純水を上記容器に加えて炭酸ナトリウム水溶液を調製し、９０℃に加熱した。
　加熱して特定金属水溶液と、炭酸ナトリウム水溶液とを混合したところ、白色の沈殿が生成した。この沈殿を濾過し、９０℃に加熱した純水３０ｇで洗浄後、１５０℃に加熱して乾燥させ白色の粉体を得た。上記粉体を便宜上、「特定金属塩Ｄ２」と呼ぶ。 After standing, the container was tilted and the molten supernatant liquid was slowly poured out of the container from the molten salt A8, and the molten salt A8 and the specific metal salt were separated and recovered. Hereinafter, for convenience, the poured-out molten salt and the recovered specific metal salt will be referred to as "molten salt A9" and "specific metal salt D1."
It was confirmed that the recovered specific metal salt D1 contained lithium.
Furthermore, when the X-ray diffraction chart of the recovered specific metal salt was obtained under the above-mentioned conditions, a diffraction peak appeared in the range of 30.2 to 30.5°. The crystalline structure assigned to the diffraction peak was LiNaSO4 of space group P31c.
It was confirmed that the recovered specific metal salts also contained sodium nitrate and potassium nitrate.
5.4 g of the recovered specific metal salt D1 was placed in a stainless steel container, and 40 g of pure water was added to the container and stirred to dissolve the salt, thereby preparing an aqueous solution of the specific metal. The aqueous solution of the specific metal was heated to 90°C.
Separately, 5 g of sodium carbonate was placed in another stainless steel container, and 25 g of pure water was added to the container to prepare an aqueous sodium carbonate solution, which was then heated to 90°C.
When the specific metal aqueous solution and the sodium carbonate aqueous solution were mixed under heating, a white precipitate was formed. This precipitate was filtered, washed with 30 g of pure water heated to 90°C, and then heated to 150°C and dried to obtain a white powder. For convenience, this powder is referred to as "specific metal salt D2."

　特定金属塩Ｄ２のＸ線回折チャートを上述した条件で得たところ、特定金属塩Ｄ２は炭酸リチウムであることが確認され、硝酸ナトリウムおよび硝酸カリウム等の硝酸塩のピークは確認されなかった。
　ここで、上記冷却を行う前の溶融塩Ａ８および溶融塩Ａ９における、リチウム原子の含有量について、後段の表４に示す。また、回収した特定金属塩Ｄ１および特定金属塩Ｄ２に含まれるリチウム原子の含有量についても表４に示す。
 When the X-ray diffraction chart of the specific metal salt D2 was obtained under the above-mentioned conditions, it was confirmed that the specific metal salt D2 was lithium carbonate, and no peaks of nitrates such as sodium nitrate and potassium nitrate were confirmed.
The contents of lithium atoms in the molten salts A8 and A9 before the cooling are shown in Table 4 below. Table 4 also shows the contents of lithium atoms contained in the recovered specific metal salts D1 and D2.

　表４に示す結果から、本発明の金属成分の回収方法により、特定の金属成分（リチウム）を溶融塩から簡便に回収できることが確認された。また、本発明の金属成分の回収方法を適用すると、回収したリチウム成分を炭酸リチウムとして回収できることが確認された。 The results shown in Table 4 confirm that the metal component recovery method of the present invention makes it possible to easily recover a specific metal component (lithium) from a molten salt. It was also confirmed that when the metal component recovery method of the present invention is applied, the recovered lithium component can be recovered as lithium carbonate.

＜例５＞
　まず、下記組成の溶融塩Ａ１０を調製した。
　・硝酸カリウム：８８．２質量％
　・硝酸ナトリウム：３．７質量％
　・炭酸カリウム：８．１質量％
　上記溶融塩Ａ１０を、４５０℃に加熱し、溶融状態とした。溶融塩Ａ１０の加熱は、溶融塩を収容する容器をマントルヒーターに収め、マントルヒーターによって行った。
　また、マントルヒーターによる加熱を行う際には、溶融塩Ａ１０に熱電対を接触させ、温度を測定した。上記熱電対としては、Ｋ熱電対を用いた。 <Example 5>
First, a molten salt A10 having the following composition was prepared.
・Potassium nitrate: 88.2% by mass
Sodium nitrate: 3.7% by mass
Potassium carbonate: 8.1% by mass
The molten salt A10 was heated to 450° C. to be in a molten state. The molten salt A10 was heated by placing a container containing the molten salt in a mantle heater.
When heating with a mantle heater, a thermocouple was brought into contact with the molten salt A10 to measure the temperature. A K thermocouple was used as the thermocouple.

　次いで、溶融塩Ａ１０に対し、板（＃２０のメッシュ（目開き０．９８ｍｍ））を蛇腹状に折り曲げてなる構造を有する塩析出部および取手部を有する治具（上記第２治具に相当）を浸漬した。
　上記治具を浸漬した状態で、マントルヒーターの出力を制御し、溶融塩Ａ１０を空冷にて３５０℃まで冷却した。
　溶融塩Ａ１０の温度を３５０℃に保持した状態で、撹拌せずに２４０分静置した。
　上記手順により、溶融塩Ａ１０中に特定金属塩を析出させた。 Next, a jig (corresponding to the second jig described above) having a salt deposition portion and a handle portion, which had a structure in which a plate (#20 mesh (opening size 0.98 mm)) was folded into an accordion shape, was immersed in the molten salt A10.
With the jig immersed, the output of the mantle heater was controlled and the molten salt A10 was cooled to 350°C by air cooling.
The molten salt A10 was allowed to stand for 240 minutes without stirring while the temperature was maintained at 350°C.
By the above procedure, the specific metal salt was precipitated in the molten salt A10.

　静置した後、上記治具を溶融塩Ａ１０から引き上げ、特定金属塩を溶融状態の溶融塩Ａ１０から分離し、回収した。以下、特定金属塩を「特定金属塩Ｅ」と記載し、特定金属塩Ｅを回収した後の溶融塩Ａ１０を、便宜的に「溶融塩Ａ１１」と記載する。
　回収した特定金属塩には、ナトリウムが含まれていることを確認した。 After being left to stand, the jig was pulled out from the molten salt A10, and the specific metal salt was separated and recovered from the molten molten salt A10. Hereinafter, the specific metal salt will be referred to as "specific metal salt E," and the molten salt A10 after recovery of specific metal salt E will be referred to as "molten salt A11" for convenience.
It was confirmed that the recovered specific metal salt contained sodium.

　ここで、上記冷却を行う前の溶融塩Ａ１０および溶融塩Ａ１１におけるナトリウム原子の含有量について、後段の表５に示す。また、回収した特定金属塩に含まれるナトリウム原子の含有量についても表５に示す。
　さらに、上記冷却を行う前の溶融塩Ａ１０および溶融塩Ａ１１を用いて以下の条件で化学強化処理を実施し、化学強化ガラスを得た。得られた化学強化ガラスの応力プロファイルを測定し、最表面における圧縮応力値を得た。この結果について、後段の表５に併せて示す（表中「化学強化ガラスのＣＳ」の欄）。
　なお、溶融塩Ａ１２および溶融塩Ａ１３における成分の含有量の測定方法は、上述した通りである。また、特定金属塩中の成分の含有量も同様の方法で分析した。 The sodium atom contents in the molten salts A10 and A11 before the cooling are shown in Table 5 below. Table 5 also shows the sodium atom contents in the recovered specific metal salts.
Furthermore, chemical strengthening treatment was performed under the following conditions using the molten salt A10 and molten salt A11 before the cooling to obtain chemically strengthened glass. The stress profile of the obtained chemically strengthened glass was measured to obtain the compressive stress value at the outermost surface. The results are also shown in Table 5 below (the column "CS of chemically strengthened glass" in the table).
The methods for measuring the content of components in molten salts A12 and A13 were as described above. The content of components in the specific metal salt was also analyzed by the same method.

　例５においては、以下の組成の化学強化用ガラスを用いた。以下の組成は、酸化物基準のモル百分率表示である。なお、一部の微量成分については、外割で成分を添加している場合がある。
　ＳｉＯ２：６４．４％
　Ａｌ２Ｏ３：８．０％
　ＭｇＯ：１０．５％
　ＣａＯ：０．１％
　ＳｒＯ：０．１％
　ＢａＯ：０．１％
　ＺｒＯ２：０．５％
　Ｎａ２Ｏ：１２．５％
　Ｋ２Ｏ：４．０％
　例５においては、上記組成の化学強化用ガラスに対し、以下の条件で化学強化処理を実施した。
　・化学強化温度：４５０℃
　・化学強化時間：９０分間 In Example 5, a chemically strengthened glass having the following composition was used. The following composition is expressed as a mole percentage based on oxides. Note that some trace components may be added as an extra percentage.
SiO2 : 64.4%
Al2O3 : 8.0 %
MgO: 10.5%
CaO: 0.1%
SrO: 0.1%
BaO: 0.1%
ZrO2 : 0.5%
Na2O : 12.5%
K2O : 4.0%
In Example 5, the glass for chemical strengthening having the above composition was subjected to a chemical strengthening treatment under the following conditions.
・Chemical strengthening temperature: 450℃
Chemical strengthening time: 90 minutes

　表５に示す結果から、本発明の金属成分の回収方法により、特定の金属成分（ナトリウム）を溶融塩から簡便に回収できることが確認された。また、本発明の金属成分の回収方法を適用すると、溶融塩を再生できることも確認された。 The results shown in Table 5 confirm that the metal component recovery method of the present invention makes it possible to easily recover a specific metal component (sodium) from molten salt. It was also confirmed that the molten salt can be regenerated by applying the metal component recovery method of the present invention.

＜例６＞
　まず、下記組成の溶融塩Ａ１２を調製した。
　・硝酸カリウム：５７．１質量％
　・硝酸ナトリウム：２４．５質量％
　・硝酸リチウム：４．１質量％
　・硫酸ナトリウム：１４．３質量％
　溶融塩Ａ１２を４１０℃とした状態で、板（＃２０のメッシュ（目開き０．９８ｍｍ））を蛇腹状に折り曲げてなる構造を有する塩析出部および取手部を有する治具（上記第２治具に相当）を浸漬した。
　溶融塩Ａ１２の温度を２９０℃に保持した状態で、４時間静置した。
　上記手順により、溶融塩Ａ１２中に特定金属塩を析出させた。ここで、上記治具を確認したところ、塩析出部の表面に塩が析出していることを確認した。 <Example 6>
First, a molten salt A12 having the following composition was prepared.
・Potassium nitrate: 57.1% by mass
Sodium nitrate: 24.5% by mass
Lithium nitrate: 4.1% by mass
Sodium sulfate: 14.3% by mass
A jig (corresponding to the second jig described above) having a salt deposition portion and a handle portion, which had a structure formed by folding a plate (#20 mesh (opening size: 0.98 mm)) into an accordion-like shape, was immersed in molten salt A12 heated to 410°C.
The molten salt A12 was left to stand for 4 hours while the temperature thereof was maintained at 290°C.
By the above procedure, the specific metal salt was precipitated in the molten salt A12. When the jig was checked, it was confirmed that the salt had precipitated on the surface of the salt precipitated portion.

　静置した後、上記治具を溶融塩Ａ１２から引き揚げ、特定金属塩を溶融状態の溶融塩Ａ１２から分離した。以下、例６において、特定金属塩を回収した後の溶融塩Ａ１２を、便宜的に「溶融塩Ａ１３」と記載する。また、以下、上記治具に付着した特定金属塩を、便宜的に「特定金属塩Ｆ１」と記載する。
　上記特定金属塩Ｆ１が付着した治具を、溶融塩Ａ１２を収容する容器の上部に設置し、治具が配置される雰囲気を３００℃に加熱し３０分間保持した。上記加熱により、特定金属塩Ｆ１に含まれる成分の一部が溶融し、溶融塩Ａ１２に流れ落ちた。加熱後に上記治具に付着している特定金属塩は、便宜的に「特定金属塩Ｆ２」と記載する。
　回収した特定金属塩Ｆ２には、リチウムが含まれていることを確認した。 After standing, the jig was pulled out from the molten salt A12, and the specific metal salt was separated from the molten molten salt A12. Hereinafter, in Example 6, the molten salt A12 from which the specific metal salt was recovered will be referred to as "molten salt A13" for convenience. Hereinafter, the specific metal salt adhered to the jig will be referred to as "specific metal salt F1" for convenience.
The jig with the specific metal salt F1 attached thereto was placed on top of a container containing molten salt A12, and the atmosphere in which the jig was placed was heated to 300°C and maintained for 30 minutes. Due to the heating, some of the components contained in the specific metal salt F1 melted and flowed down into the molten salt A12. For convenience, the specific metal salt attached to the jig after heating is referred to as "specific metal salt F2."
It was confirmed that the recovered specific metal salt F2 contained lithium.

　ここで、上記冷却を行う前の溶融塩Ａ１２におけるリチウム原子の含有量について、後段の表６に示す。また、特定金属塩Ｆ２に含まれるリチウム原子の含有量についても、表６に示す。
　なお、溶融塩Ａ１２、溶融塩Ａ１３における成分の含有量の測定方法は上述した通りである。また、特定金属塩中の成分の含有量も同様の方法で分析した。 The content of lithium atoms in the molten salt A12 before the cooling is shown in Table 6 below. Table 6 also shows the content of lithium atoms contained in the specific metal salt F2.
The methods for measuring the content of components in molten salts A12 and A13 were as described above. The content of components in the specific metal salt was also analyzed by the same method.

　表６に示す結果から、本発明の金属成分の回収方法により、特定の金属成分（リチウム）を溶融塩から簡便に回収できることが確認された。 The results shown in Table 6 confirm that the metal component recovery method of the present invention makes it possible to easily recover a specific metal component (lithium) from molten salt.

＜例７＞
　まず、表７に示す組成の溶融塩（溶融塩Ａ１４～溶融塩Ａ１７）をそれぞれ調製した。
　得られたそれぞれの溶融塩を、表７に示す冷却前温度にて加熱し、溶融状態とした。なお、溶融塩の加熱は、溶融塩を収容する容器をマントルヒーターに収め、マントルヒーターによって行った。
　また、マントルヒーターによる加熱を行う際には、それぞれの溶融塩に熱電対を接触させ、温度を測定した。上記熱電対としては、Ｋ熱電対を用いた。 <Example 7>
First, molten salts (molten salts A14 to A17) having the compositions shown in Table 7 were prepared.
Each of the obtained molten salts was heated to a molten state at the pre-cooling temperature shown in Table 7. The molten salt was heated by placing a container containing the molten salt in a mantle heater.
When heating was performed using a mantle heater, a thermocouple was placed in contact with each molten salt to measure the temperature. A K thermocouple was used as the thermocouple.

　次いで、それぞれの溶融塩に対し、板（＃２０のメッシュ（目開き０．９８ｍｍ））を等間隔に配置してなる構造を有する塩析出部および取手部を有する治具（上記第２治具に相当）を浸漬した。なお、上記板は、面内方向が重力の作用方向と平行になるように配置した。
　上記治具を浸漬した状態で、マントルヒーターの出力を制御し、それぞれの溶融塩を空冷にて表７に記載の温度（冷却後温度）まで冷却した。
　それぞれの溶融塩の温度を上記温度に保持した状態で、撹拌せずに表７に記載の時間（冷却後温度での保持時間）だけ静置した。
　上記手順により、それぞれの溶融塩中に特定金属塩を析出させた。 Next, a jig (corresponding to the second jig) having a salt deposition portion and a handle portion, which had a structure in which plates (#20 mesh (opening size: 0.98 mm)) were arranged at equal intervals, was immersed in each molten salt. The plate was placed so that its in-plane direction was parallel to the direction of gravity.
With the jig immersed, the output of the mantle heater was controlled and each molten salt was cooled by air to the temperature (temperature after cooling) shown in Table 7.
While the temperature of each molten salt was maintained at the above temperature, it was allowed to stand without stirring for the time shown in Table 7 (the holding time at the temperature after cooling).
By the above procedure, the specific metal salt was precipitated in each molten salt.

　静置した後、上記治具を溶融塩から引き上げ、特定金属塩を溶融状態の溶融塩から分離し、回収した。
　回収したそれぞれの特定金属塩には、ナトリウムが含まれていることを確認した。表７に、回収した特定金属塩に含まれるナトリウム原子の含有量を示す。
　また、冷却後（特定金属塩を析出させた後）の溶融塩の組成も表７に示す。
　さらに、表７に示す組成となるように、冷却後の溶融塩に対して炭酸カリウムおよび硝酸カリウムを添加した（塩添加後溶融塩）。 After being left to stand, the jig was pulled out of the molten salt, and the specific metal salt was separated from the molten salt in a molten state and recovered.
It was confirmed that each of the recovered specific metal salts contained sodium. Table 7 shows the sodium atom content of the recovered specific metal salts.
Table 7 also shows the composition of the molten salt after cooling (after the specific metal salt was precipitated).
Furthermore, potassium carbonate and potassium nitrate were added to the cooled molten salt so as to obtain the composition shown in Table 7 (molten salt after salt addition).

　さらに、上記冷却を行う前の溶融塩、冷却後の溶融塩、および、塩添加後溶融塩を用いて以下の条件で化学強化処理を実施し、化学強化ガラスを得た。得られた化学強化ガラスの応力プロファイルを測定し、最表面における圧縮応力値を得た。この結果について、後段の表７に併せて示す（表中「化学強化ガラスのＣＳ」の欄）。
　なお、それぞれの溶融塩における成分の含有量の測定方法は、上述した通りである。より具体的には、炭酸カリウムの含有量は、上記炭酸イオンの含有量の測定方法を併用して求めた。また、特定金属塩中の成分の含有量も同様の方法で分析した。なお、下記表においては、炭酸イオンは炭酸カリウムの形態で存在していると仮定して含有量を算出した。
　それぞれの溶融塩による化学強化に用いた化学強化用ガラスの組成は、以下の通りである。以下の組成は、酸化物基準のモル百分率表示である。なお、硝材１は、上記例５に用いた化学強化用ガラスの組成と同様である。
　・硝材２：
　ＳｉＯ２：６４．４５％
　Ａｌ２Ｏ３：１０．５％
　ＭｇＯ：８．３％
　ＺｒＯ２：０．１５％
　Ｎａ２Ｏ：１６．０％
　Ｋ２Ｏ：０．６％ Furthermore, chemical strengthening treatment was performed under the following conditions using the molten salt before cooling, the molten salt after cooling, and the molten salt after salt addition to obtain chemically strengthened glass. The stress profile of the obtained chemically strengthened glass was measured to obtain the compressive stress value at the outermost surface. The results are also shown in Table 7 below (the column "CS of chemically strengthened glass" in the table).
The method for measuring the content of components in each molten salt was as described above. More specifically, the content of potassium carbonate was determined by simultaneously using the method for measuring the content of carbonate ions described above. The content of components in the specific metal salts was also analyzed by the same method. In the table below, the content was calculated assuming that carbonate ions existed in the form of potassium carbonate.
The compositions of the chemically strengthened glasses used in the chemical strengthening using each molten salt are as follows. The compositions are expressed in mole percentages based on oxides. Glass material 1 has the same composition as the chemically strengthened glass used in Example 5.
・Glass material 2:
SiO2 : 64.45%
Al2O3 : 10.5 %
MgO: 8.3%
ZrO2 : 0.15%
Na2O : 16.0%
K2O : 0.6%

　表７に示す結果から、本発明の金属成分の回収方法により、特定の金属成分（ナトリウム）を溶融塩から簡便に回収できることが確認された。また、本発明の金属成分の回収方法を適用すると、溶融塩を再生できることが確認された（特に溶融塩Ａ１４および溶融塩Ａ１５）。加えて、本発明の金属成分の回収方法を適用した後、炭酸塩を溶融塩に添加すると、溶融塩を再生できることが確認された（特に溶融塩Ａ１６および溶融塩Ａ１７）。 The results shown in Table 7 confirm that a specific metal component (sodium) can be easily recovered from molten salt using the metal component recovery method of the present invention. It was also confirmed that applying the metal component recovery method of the present invention allows for the regeneration of molten salt (particularly molten salts A14 and A15). Additionally, it was confirmed that adding carbonate to the molten salt after applying the metal component recovery method of the present invention allows for the regeneration of molten salt (particularly molten salts A16 and A17).

　なお、２０２４年３月１９日に出願された日本特許出願２０２４－０４３０４６号の明細書、特許請求の範囲、図面および要約書の全内容をここに引用し、本発明の明細書の開示として、取り入れるものである。 The entire contents of the specification, claims, drawings, and abstract of Japanese Patent Application No. 2024-043046, filed on March 19, 2024, are hereby incorporated by reference as part of the disclosure of the present specification.

　１０　容器
　２０ａ，２０ｂ，２０ｃ　第１治具
　２２ａ，２２ｂ　取手部
　２４ａ　網部
　２４ｂ　塩析出部
　２４ｃ　冷却部
　３２　循環路
　３４　フィルタ
　３６　ポンプ 10 container 20a, 20b, 20c first jig 22a, 22b handle portion 24a mesh portion 24b salt precipitation portion 24c cooling portion 32 circulation path 34 filter 36 pump

Claims (34)

　特定金属成分を含む溶融塩を冷却し、前記溶融塩の溶融状態を保ったまま前記特定金属成分を含む特定金属塩を析出させ、前記特定金属塩を溶融状態の前記溶融塩から回収する、金属成分の回収方法。 A method for recovering metal components, comprising cooling a molten salt containing a specific metal component, precipitating a specific metal salt containing the specific metal component while maintaining the molten salt in a molten state, and recovering the specific metal salt from the molten salt. 　前記溶融塩が、硝酸塩、硫酸塩、亜硝酸塩、亜硫酸塩、炭酸塩、リン酸塩、および、ハロゲン化物塩からなる群から選択される１種以上を含む、請求項１に記載の金属成分の回収方法。 The method for recovering metal components according to claim 1, wherein the molten salt contains one or more salts selected from the group consisting of nitrates, sulfates, nitrites, sulfites, carbonates, phosphates, and halide salts. 　前記溶融塩が、硝酸塩と硫酸塩とを含む、または、硝酸塩と炭酸塩とを含む、請求項２に記載の金属成分の回収方法。 The method for recovering metal components described in claim 2, wherein the molten salt contains nitrate and sulfate, or nitrate and carbonate. 　前記溶融塩が、リチウム塩、ナトリウム塩、および、カリウム塩からなる群から選択される２種以上の塩を含む、請求項１～３のいずれか１項に記載の金属成分の回収方法。 The method for recovering metal components according to any one of claims 1 to 3, wherein the molten salt contains two or more salts selected from the group consisting of lithium salts, sodium salts, and potassium salts. 　前記溶融塩が、硝酸リチウム、硝酸ナトリウム、および、硝酸カリウムからなる群から選択される２種以上の塩を含み、
　前記溶融塩が、さらに、硫酸ナトリウム、および、硫酸カリウムからなる群から選択される１種以上の塩を含む、請求項１～３のいずれか１項に記載の金属成分の回収方法。 the molten salt contains two or more salts selected from the group consisting of lithium nitrate, sodium nitrate, and potassium nitrate;
4. The method for recovering a metal component according to claim 1, wherein the molten salt further contains one or more salts selected from the group consisting of sodium sulfate and potassium sulfate. 　前記特定金属成分が、リチウムを含み、
　前記特定金属塩が、リチウムおよびナトリウムを含み、
　冷却を行う前の前記溶融塩が、前記溶融塩の全質量に対して、リチウム原子を１,０００～５０,０００質量ｐｐｍ含む、請求項１～３のいずれか１項に記載の金属成分の回収方法。 the specific metal component includes lithium,
the specific metal salt includes lithium and sodium,
The method for recovering a metal component according to any one of claims 1 to 3, wherein the molten salt before cooling contains lithium atoms in an amount of 1,000 to 50,000 ppm by mass with respect to the total mass of the molten salt. 　前記特定金属成分が、ナトリウムを含み、
　前記特定金属塩が、ナトリウムおよびカリウムを含み、
　冷却を行う前の前記溶融塩が、前記溶融塩の全質量に対して、ナトリウム原子を５００～６０,０００質量ｐｐｍ含む、請求項１～３のいずれか１項に記載の金属成分の回収方法。 the specific metal component includes sodium,
the specific metal salts include sodium and potassium,
The method for recovering a metal component according to any one of claims 1 to 3, wherein the molten salt before cooling contains sodium atoms in an amount of 500 to 60,000 ppm by mass relative to the total mass of the molten salt. 　前記溶融塩が、硝酸ナトリウムを含み、硝酸ナトリウムの含有量に対する硝酸カリウムの含有量の比が、質量比で、０．００～２４．００である、請求項１～３のいずれか１項に記載の金属成分の回収方法。 The method for recovering metal components according to any one of claims 1 to 3, wherein the molten salt contains sodium nitrate, and the ratio of the potassium nitrate content to the sodium nitrate content is 0.00 to 24.00 by mass. 　前記溶融塩が、硝酸ナトリウムを含み、硝酸ナトリウムの含有量に対する硝酸カリウムの含有量の比が、質量比で、０．２５～４．００である、請求項１～３のいずれか１項に記載の金属成分の回収方法。 The method for recovering metal components described in any one of claims 1 to 3, wherein the molten salt contains sodium nitrate, and the ratio of the potassium nitrate content to the sodium nitrate content is 0.25 to 4.00 by mass. 　前記溶融塩が、硫酸塩を含み、前記硫酸塩の含有量が、前記溶融塩の全質量に対して、２．０～５０．０質量％である、請求項１～３のいずれか１項に記載の金属成分の回収方法。 The method for recovering metal components according to any one of claims 1 to 3, wherein the molten salt contains sulfate, and the content of the sulfate is 2.0 to 50.0 mass% relative to the total mass of the molten salt. 　前記溶融塩が、硫酸塩を含み、前記硫酸塩の含有量が、前記溶融塩の全質量に対して、３．０～２５．０質量％である、請求項１～３のいずれか１項に記載の金属成分の回収方法。 The method for recovering metal components according to any one of claims 1 to 3, wherein the molten salt contains sulfate, and the content of the sulfate is 3.0 to 25.0 mass% relative to the total mass of the molten salt. 　前記溶融塩が、炭酸塩を含み、前記炭酸塩の含有量が、前記溶融塩の全質量に対して、２．０～４０．０質量％である、請求項１～３のいずれか１項に記載の金属成分の回収方法。 The method for recovering metal components according to any one of claims 1 to 3, wherein the molten salt contains carbonate, and the carbonate content is 2.0 to 40.0 mass% relative to the total mass of the molten salt. 　前記特定金属塩を溶融状態の前記溶融塩から回収する際に、
　網状の網部を有する第１治具を用い、前記網部を前記溶融塩から引き上げ、析出した前記特定金属塩を溶融状態の前記溶融塩から回収する、請求項１～３のいずれか１項に記載の金属成分の回収方法。 When recovering the specific metal salt from the molten salt in a molten state,
The method for recovering a metal component according to any one of claims 1 to 3, further comprising using a first jig having a mesh portion, pulling the mesh portion out of the molten salt, and recovering the precipitated specific metal salt from the molten salt in a molten state. 　前記特定金属成分を含む前記溶融塩を冷却し、前記溶融塩の溶融状態を保ったまま前記特定金属成分を含む前記特定金属塩を析出させる際に、
　塩析出部を有する第２治具の前記塩析出部の表面に、前記特定金属塩を析出させ、
　前記塩析出部を前記溶融塩から引き上げて、前記特定金属塩を溶融状態の前記溶融塩から回収する、請求項１～３のいずれか１項に記載の金属成分の回収方法。 When the molten salt containing the specific metal component is cooled and the specific metal salt containing the specific metal component is precipitated while maintaining the molten state of the molten salt,
causing the specific metal salt to precipitate on a surface of a salt deposition portion of a second jig having the salt deposition portion;
4. The method for recovering a metal component according to claim 1, wherein the salt precipitate portion is pulled up from the molten salt, and the specific metal salt is recovered from the molten salt in a molten state. 　前記特定金属成分を含む前記溶融塩を冷却し、前記溶融塩の溶融状態を保ったまま前記特定金属成分を含む前記特定金属塩を析出させる際に、
　温度制御自在な冷却部を有する第３治具を用い、前記冷却部の温度を変化させることによって前記溶融塩を冷却し、前記冷却部の表面に、前記特定金属塩を析出させ、
　前記冷却部を前記溶融塩から引き上げて、前記特定金属塩を溶融状態の前記溶融塩から回収する、請求項１～３のいずれか１項に記載の金属成分の回収方法。 When the molten salt containing the specific metal component is cooled and the specific metal salt containing the specific metal component is precipitated while maintaining the molten state of the molten salt,
a third jig having a temperature-controllable cooling section is used to cool the molten salt by changing the temperature of the cooling section, thereby precipitating the specific metal salt on the surface of the cooling section;
4. The method for recovering a metal component according to claim 1, wherein the cooling section is lifted from the molten salt, and the specific metal salt is recovered from the molten salt in a molten state. 　前記特定金属塩を溶融状態の前記溶融塩から回収する際に、
　前記溶融塩が収容される溶融塩収容容器と、
　前記溶融塩収容容器に接続されて、前記溶融塩収容容器から排出された前記溶融塩が再び前記溶融塩収容容器に戻る循環路と、
　前記循環路の途中に配置されて固体を前記溶融塩から分離可能なフィルタと、を用い、
　析出した前記特定金属塩を含む前記溶融塩を、前記循環路に導入し、前記フィルタによって前記特定金属塩を前記溶融塩から分離し、
　前記フィルタから前記特定金属塩を回収する、請求項１～３のいずれか１項に記載の金属成分の回収方法。 When recovering the specific metal salt from the molten salt in a molten state,
a molten salt storage container in which the molten salt is stored;
a circulation path connected to the molten salt storage container, through which the molten salt discharged from the molten salt storage container returns to the molten salt storage container;
a filter disposed midway through the circulation path and capable of separating solids from the molten salt;
introducing the molten salt containing the precipitated specific metal salt into the circulation path, and separating the specific metal salt from the molten salt using the filter;
The method for recovering a metal component according to any one of claims 1 to 3, wherein the specific metal salt is recovered from the filter. 　前記特定金属塩を溶融状態の前記溶融塩から回収したあと、
　回収した前記特定金属塩を、前記溶融塩の融点以上の温度で加熱する、請求項１～３のいずれか１項に記載の金属成分の回収方法。 After recovering the specific metal salt from the molten salt in a molten state,
4. The method for recovering a metal component according to claim 1, wherein the recovered specific metal salt is heated at a temperature equal to or higher than the melting point of the molten salt. 　前記特定金属成分を含む３７０℃以上の前記溶融塩を３６０℃以下に冷却し、前記溶融塩の溶融状態を保ったまま前記特定金属成分を含む前記特定金属塩を析出させる、請求項１～３のいずれか１項に記載の金属成分の回収方法。 The method for recovering metal components described in any one of claims 1 to 3, wherein the molten salt containing the specific metal component at 370°C or higher is cooled to 360°C or lower, and the specific metal salt containing the specific metal component is precipitated while maintaining the molten state of the molten salt. 　前記特定金属成分を含む４２０℃以上の前記溶融塩を４１０℃以下に冷却し、前記溶融塩の溶融状態を保ったまま前記特定金属成分を含む前記特定金属塩を析出させる、請求項１～３のいずれか１項に記載の金属成分の回収方法。 The method for recovering metal components described in any one of claims 1 to 3, wherein the molten salt containing the specific metal component at 420°C or higher is cooled to 410°C or lower, and the specific metal salt containing the specific metal component is precipitated while maintaining the molten state of the molten salt. 　前記冷却前の前記溶融塩の温度と、前記冷却後の前記溶融塩の温度との差が、２０℃以上である、請求項１～３のいずれか１項に記載の金属成分の回収方法。 The method for recovering metal components described in any one of claims 1 to 3, wherein the difference between the temperature of the molten salt before cooling and the temperature of the molten salt after cooling is 20°C or more. 　回収された前記特定金属塩が、Ｃｕ　Ｋα線で測定したＸ線回折チャートにおいて、３０．２～３０．５°の範囲に回折ピークが出現する結晶構造の結晶を含む、請求項１～３のいずれか１項に記載の金属成分の回収方法。 The method for recovering metal components according to any one of claims 1 to 3, wherein the recovered specific metal salt contains crystals with a crystalline structure in which a diffraction peak appears in the range of 30.2 to 30.5° in an X-ray diffraction chart measured with Cu Kα radiation. 　回収された前記特定金属塩が、Ｃｕ　Ｋα線で測定したＸ線回折チャートにおいて、２３．２～２３．５°の範囲に回折ピークが出現する結晶構造の結晶、２２．４～２２．７°の範囲に回折ピークが出現する結晶構造の結晶、および、２２．８～２３．１°の範囲に回折ピークが出現する結晶構造の結晶からなる群から選択される少なくとも１つの結晶構造の結晶を含む、請求項１～３のいずれか１項に記載の金属成分の回収方法。 The method for recovering metal components according to any one of claims 1 to 3, wherein the recovered specific metal salt contains crystals of at least one crystal structure selected from the group consisting of crystals having a crystal structure in which a diffraction peak appears in the range of 23.2 to 23.5°, crystals having a crystal structure in which a diffraction peak appears in the range of 22.4 to 22.7°, and crystals having a crystal structure in which a diffraction peak appears in the range of 22.8 to 23.1° in an X-ray diffraction chart measured with Cu Kα radiation. 　回収された前記特定金属塩が、ＬｉＮａＳＯ４、ＬｉＫＳＯ４、および、Ｌｉ２ＮａＫ（ＳＯ４）２からなる群から選択される少なくとも１種を含む、請求項２２に記載の金属成分の回収方法。 23. The method for recovering a metal component according to claim 22, wherein the recovered specific metal salt comprises at least one selected from the group consisting of LiNaSO4 , LiKSO4 , and Li2NaK ( SO4 ) 2 . 　回収された前記特定金属塩が、Ｃｕ　Ｋα線で測定したＸ線回折チャートにおいて、２８．４～２８．７°の範囲に回折ピークが出現する結晶構造の結晶を含む、請求項１～３のいずれか１項に記載の金属成分の回収方法。 The method for recovering metal components according to any one of claims 1 to 3, wherein the recovered specific metal salt contains crystals with a crystalline structure in which a diffraction peak appears in the range of 28.4 to 28.7° in an X-ray diffraction chart measured with Cu Kα radiation. 　回収された前記特定金属塩が、Ｎａ２ＣＯ３を含む、請求項２４に記載の金属成分の回収方法。 25. The method for recovering metal components according to claim 24, wherein the recovered specific metal salt comprises Na2CO3 . 　請求項１～３のいずれか１項に記載の金属成分の回収方法によって回収された前記特定金属塩を水に溶解して特定金属水溶液を得て、
　前記特定金属水溶液に対して炭酸塩を加え、沈殿物を生成させ、前記沈殿物を回収する、金属成分の回収方法であって、前記特定金属成分が、リチウムまたはナトリウムを含む、金属成分の回収方法。 The specific metal salt recovered by the method for recovering a metal component according to any one of claims 1 to 3 is dissolved in water to obtain a specific metal aqueous solution,
A method for recovering a metal component, comprising adding a carbonate to the specific metal aqueous solution to form a precipitate, and recovering the precipitate, wherein the specific metal component includes lithium or sodium. 　炭酸塩を含む前記特定金属水溶液を８０℃以上として沈殿物を生成させる、請求項２６に記載の金属成分の回収方法。 The method for recovering metal components described in claim 26, wherein the specific metal aqueous solution containing carbonate is heated to 80°C or higher to produce a precipitate. 　請求項１～３のいずれか１項に記載の金属成分の回収方法を適用する、溶融塩の再生方法であって、
　前記特定金属成分が、リチウムまたはナトリウムを含み、
　前記溶融塩が、ケイ素と、アルミニウムと、リチウムおよびナトリウムからなる群から選択される少なくとも１種とを含むガラスを浸漬して得られる化学強化後溶融塩である、溶融塩の再生方法。 A method for regenerating molten salt, which applies the method for recovering metal components according to any one of claims 1 to 3,
the specific metal component includes lithium or sodium,
A method for regenerating molten salt, wherein the molten salt is a chemically strengthened molten salt obtained by immersing glass containing silicon, aluminum, and at least one selected from the group consisting of lithium and sodium. 　請求項１～３のいずれか１項に記載の金属成分の回収方法によって回収された前記特定金属塩を、化学強化用ガラスの原料の一部として用い、化学強化用ガラスを製造する、化学強化用ガラスの製造方法。 A method for producing chemically strengthened glass, in which the specific metal salt recovered by the metal component recovery method described in any one of claims 1 to 3 is used as part of the raw materials for chemically strengthened glass to produce chemically strengthened glass. 　請求項２６に記載の金属成分の回収方法において回収された前記沈殿物を、化学強化用ガラスの原料の一部として用い、化学強化用ガラスを製造する、化学強化用ガラスの製造方法。 A method for producing chemically strengthened glass, in which the precipitate recovered by the metal component recovery method described in claim 26 is used as part of the raw material for chemically strengthened glass to produce chemically strengthened glass. 　請求項１～３のいずれか１項に記載の金属成分の回収方法によって前記溶融塩から前記特定金属塩を回収し、前記特定金属塩を回収した後の溶融塩に対して、ケイ素と、アルミニウムと、リチウムおよびナトリウムからなる群から選択される少なくとも１種とを含むガラスを浸漬する、化学強化ガラスの製造方法であって、
　前記特定金属成分が、リチウムまたはナトリウムを含む、化学強化ガラスの製造方法。 A method for producing chemically strengthened glass, comprising recovering the specific metal salt from the molten salt by the method for recovering a metal component according to any one of claims 1 to 3, and immersing glass containing silicon, aluminum, and at least one selected from the group consisting of lithium and sodium in the molten salt after the specific metal salt has been recovered.
The method for producing chemically strengthened glass, wherein the specific metal component contains lithium or sodium. 　請求項１～３のいずれか１項に記載の金属成分の回収方法によって前記溶融塩から前記特定金属塩を回収し、前記特定金属塩を回収した後の溶融塩に対して、ケイ素、アルミニウムおよびリチウムを含むガラスを浸漬する、化学強化ガラスの製造方法であって、
　前記特定金属塩を回収した後の溶融塩が、実質的に固体状態の塩を含まない、化学強化ガラスの製造方法。 A method for producing chemically strengthened glass, comprising recovering the specific metal salt from the molten salt by the method for recovering a metal component according to any one of claims 1 to 3, and immersing glass containing silicon, aluminum, and lithium in the molten salt after the specific metal salt has been recovered.
A method for producing chemically strengthened glass, wherein the molten salt after recovering the specific metal salt does not substantially contain solid-state salt. 　化学強化用溶融塩を用いる化学強化ガラスの製造方法であって、
　前記化学強化用溶融塩に対して化学強化用ガラスを浸漬する化学強化処理と、
　前記化学強化用ガラスを浸漬した前記化学強化用溶融塩を前記溶融塩として、請求項１～３のいずれか１項に記載の金属成分の回収方法によって前記特定金属塩を回収し、前記化学強化用溶融塩を再生する溶融塩再生処理とを、交互に行う、化学強化ガラスの製造方法。 A method for producing chemically strengthened glass using a chemically strengthening molten salt,
A chemical strengthening treatment in which the chemical strengthening glass is immersed in the chemical strengthening molten salt;
The chemical strengthening molten salt in which the chemical strengthening glass is immersed is used as the molten salt, and the specific metal salt is recovered by the metal component recovery method according to any one of claims 1 to 3. A method for producing chemically strengthened glass, comprising alternately performing a molten salt regeneration process and a molten salt regeneration treatment for regenerating the chemical strengthening molten salt. 　前記溶融塩再生処理において、前記化学強化用溶融塩に対して硫酸塩を添加する、請求項３３に記載の化学強化ガラスの製造方法。 The method for producing chemically strengthened glass according to claim 33, wherein a sulfate is added to the chemical strengthening molten salt during the molten salt regeneration treatment.
PCT/JP2025/010397 2024-03-19 2025-03-18 Method for recovering metal component, method for regenerating molten salt, method for producing glass for chemical strengthening, and method for producing chemically strengthened glass Pending WO2025197895A1 (en)

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