WO2010147180A1 - Process for producing zinc sulfide-based blue fluorescent substance - Google Patents

Abstract

Provided is a process for producing a zinc sulfide-based blue fluorescent substance by burning a zinc sulfide-based fluorescent-substance precursor, characterized by comprising (a) a first burning step in which a flux is added to a zinc sulfide-based fluorescent-substance precursor and the mixture is heated to a certain temperature in the range of 1,000-1,200ºC, held at the temperature, and then rapidly cooled to a temperature of 700ºC or lower to form a primary burned object having a hexagonal crystal structure introduced thereinto, (b) an ultrasonic treatment step in which an ultrasonic wave is propagated to a dispersion obtained by dispersing the primary burned object in an aqueous liquid and some of the hexagonal crystal structure of the primary burned object is thereby transformed to a cubic crystal structure, and (c) a second burning step in which the primary burned object in which the hexagonal crystal structure and the cubic crystal structure coexist is heated in an inert gas atmosphere to a certain temperature in the range of 650-1,000ºC, held at the temperature, and then cooled.

Description

Method for producing zinc sulfide-based blue phosphor

The present invention relates to a method for producing a zinc sulfide blue phosphor.

An inorganic composition mainly composed of a compound semiconductor is used in the fields of light emitting materials such as fluorescence and phosphorescence, and phosphorescent materials. Among these, some zinc sulfide-based phosphors having EL characteristics that emit light by electric energy are partly used for display applications as light sources. Furthermore, in order to utilize these phosphors having EL characteristics for full-color display applications, it is desired to provide a high-luminance zinc sulfide-based blue phosphor.

As a method for producing a zinc sulfide phosphor, copper, manganese, zinc oxide, sulfur and a chloride-containing flux are added to zinc sulfide and fired at 1100 ° C. to 1250 ° C., and the fired material is ground and crystallized. A method has been proposed in which after defects are introduced into the structure, copper, manganese, and zinc oxide are added and fired at 750 ° C. to 950 ° C., and then rapidly cooled to less than 200 ° C. within 1 hour (Patent Document 1). . However, Patent Document 1 is a technique relating to the production of a yellow-orange phosphor, and a blue phosphor is not obtained.

The wavelength (color) of fluorescent color development depends on the type of activator added, and it is known that when copper is used as the activator, a blue-green color develops. In order to form a high-luminance EL phosphor element, as a method of doping an activator to zinc sulfide as a base material, a hydrothermal synthesis method (for example, Patent Document 2) or a liquid phase method (for example, Patent Document 3) is used. There has been proposed a method for firing the precursor. However, Patent Documents 2 and 3 differ from the method of introducing a metal that becomes an activator into the defects of the crystal structure proposed by Patent Document 1 and introduce metal ions that become the activator into the precursor before firing. Is the method.

JP 2004-99881 A JP 2005-264108 A JP 2007-106832 A

The solid-phase firing method is strongly influenced by the particle size of the precursor particles and the mixing method with the metal salt at the time of doping, and there is a problem that the emission color is not uniform due to the uneven distribution of the metal salt within and between the particles.

The hydrothermal synthesis method has problems such as corrosion of reaction equipment and difficulty in scaling up for industrialization because hydrogen sulfide is generated.

The liquid phase firing method has a problem that the deposition rate of the metal from the liquid phase is different and the homogeneity within the particles is lowered.

Therefore, an object of the present invention is to provide a method for producing a zinc sulfide-based blue phosphor that is industrially practical.

The present inventors examined each process in detail, paying attention to the fact that each processing condition of the manufacturing process of the zinc sulfide-based phosphor significantly affects the physical properties of the obtained zinc sulfide-based phosphor. The present inventors have found that the introduction of defects into the crystal structure performed between the primary firing step and the secondary firing step, and the cooling conditions in the secondary firing step contribute to blue light emission. It came to complete.

According to the present invention, a method for producing a zinc sulfide-based blue phosphor by firing a zinc sulfide-based phosphor precursor,
(A) A flux is added to the zinc sulfide-based phosphor precursor, and the temperature is raised to a constant temperature within a range of 1000 ° C. or higher and 1200 ° C. or lower and maintained at that temperature, and then rapidly cooled to a temperature of 700 ° C. or lower. A primary firing step for forming a primary fired product having a hexagonal crystal structure introduced;
(B) an ultrasonic treatment step of irradiating the dispersion obtained by dispersing the primary fired product in an aqueous liquid with ultrasonic waves to transfer a part of the hexagonal crystal structure of the primary fired product into a cubic structure;
(C) The primary fired product in which a hexagonal crystal structure and a cubic crystal structure are mixed is heated to a constant temperature within a range of 650 ° C. or higher and 1000 ° C. or lower in an inert gas atmosphere, and then cooled. A method is provided that includes a secondary firing step.

The present invention also provides the following aspects.

Before the (b) ultrasonic treatment step, the primary firing product is maintained at a constant temperature in the range of 100 ° C. or more and 500 ° C. or less in an inert atmosphere, and (c) 650 in the secondary firing step. At least one of cooling control for cooling the temperature range from 300 ° C. or less to room temperature at a cooling rate of 150 ° C./hr or less in the process of cooling to room temperature after maintaining a constant temperature in the range of ℃ to 1000 ° C. In addition.

(B) An annealing step for maintaining the primary fired product at a constant temperature within a range of 100 ° C. or higher and 500 ° C. or lower in an inert atmosphere before the ultrasonic treatment step, and (c) cooling in the secondary firing step. It further includes at least one of the controls.

In the (b) ultrasonic irradiation step, ultrasonic waves having an output of 1000 kW / m ³ or more and 6000 kW / m ³ or less are irradiated.

The (a) primary firing step includes a step of raising the temperature of the mixture of the zinc sulfide-based fluorescent precursor and the flux to a constant temperature within a range of 300 ° C. to 850 ° C. in an oxygen-containing atmosphere.

The (c) secondary firing step includes a step of switching to an oxygen-containing atmosphere after reaching a temperature of 650 ° C. or higher.

The (c) secondary firing step preferably includes adding a compound containing copper and a compound containing zinc to the primary fired product in which the hexagonal crystal structure and the cubic crystal structure are mixed to increase the temperature.

The zinc sulfide-based phosphor precursor is an inorganic composition containing at least one selected from zinc sulfide, a compound containing copper, silver, iridium and a rare earth element, and a combination thereof.

The zinc sulfide based phosphor precursor is obtained by adding a sulfurizing agent to an aqueous solution containing a zinc compound and at least one compound selected from compounds containing copper, silver, iridium and rare earth elements, and reacting them. It is an inorganic composition.

The zinc sulfide-based phosphor precursor is obtained by adding an aqueous solution containing a zinc compound, a sulfiding agent, and at least one compound selected from compounds containing copper, silver, iridium and rare earth elements to an organic solvent. It is an inorganic composition obtained by heating the reaction mixture and removing water by azeotroping water and an organic solvent.

The sulfurizing agent is thioacetamide and / or hydrogen sulfide.

Moreover, according to the present invention, there is provided a zinc sulfide-based blue phosphor having chromaticity coordinates (x, y) = (≦ 0.2, ≦ 0.2) obtained by the above production method.

The production method of the present invention makes it possible to industrially advantageously produce a zinc sulfide-based blue phosphor having practical and high brightness.

The method for producing the zinc sulfide blue phosphor of the present invention comprises:
(A) A flux is added to the zinc sulfide-based phosphor precursor, and the temperature is raised to a constant temperature within a range of 1000 ° C. or higher and 1200 ° C. or lower and maintained, and then rapidly cooled to a temperature of 700 ° C. or lower. A primary firing step for forming a primary fired product containing hexagonal crystals,
(B) The dispersion obtained by dispersing the primary fired product in an aqueous liquid is irradiated with ultrasonic waves, and a part of the hexagonal crystal of the primary fired product is converted into a cubic crystal so that a hexagonal structure and a cubic structure are mixed. An ultrasonic irradiation process for forming a primary fired product,
(C) The primary fired product in which the hexagonal crystal structure and the cubic crystal structure are mixed is heated to a constant temperature within a range of 650 ° C. or higher and 1000 ° C. or lower in an inert gas atmosphere, and then cooled. Including a secondary firing step.

In the claims and specification of the present application, “keep at a constant temperature” means to keep at a constant temperature within an error range of ± 5 ° C.

Hereinafter, the present invention will be described in detail for each process according to the processing procedure.

<Zinc sulfide based phosphor precursor>
The zinc sulfide-based phosphor precursor (hereinafter sometimes referred to as “precursor”) that can be used in the present invention is an inorganic composition mainly composed of zinc sulfide that does not exhibit fluorescence when excited by light absorption. Although it does not restrict | limit in particular, The inorganic composition containing at least 1 sort (s) chosen from zinc sulfide, the compound containing copper, silver, iridium, and rare earth elements, and these combinations can be mentioned as a suitable example.

Zinc sulfide is not particularly limited, but zinc sulfide not containing different metals such as iron, nickel, and chromium is preferable, and the purity is usually 99% or more. The crystal system of zinc sulfide may be either cubic or hexagonal. The particle size of zinc sulfide is preferably in the range of 10 nm to 20 μm as the particle size of primary particles, and the particle size of the aggregate is preferably in the range of 1 μm to 20 μm.

A compound containing copper, silver, iridium, and a rare earth element is doped into zinc sulfide, which is a base material, through a firing step described later, and acts as a light emission center of the zinc sulfide-based phosphor. The content of these metal elements is preferably in the range of 0.1 ppm to 150,000 ppm, more preferably in the range of 1 ppm to 50000 ppm, more preferably in the range of 2 ppm to 10,000 ppm, based on the weight of the obtained zinc sulfide-based phosphor precursor. A range is particularly preferred.

Preferred examples of compounds containing copper, silver, iridium and rare earth elements include compounds containing elements such as copper, silver, iridium and rare earth elements that act as acceptors and elements such as aluminum, gallium, and indium that act as donors. Can do. The compounds are used in the form of mineral salts with hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, etc., organic acid salts with formic acid, acetic acid, butyric acid, oxalic acid, etc., and complex salts with acetylacetonate as a ligand. be able to. Among these, mineral acid salts and organic acid salts can be preferably used from the viewpoints of stability and persistence.

The zinc sulfide-based phosphor precursor used in the present invention can be prepared by the following method.
(1) Zinc sulfide particles are mixed with a solid form compound containing copper, silver, iridium and a rare earth element while being crushed.
(2) A sulfurizing agent is added to an aqueous solution containing a zinc compound and at least one compound selected from compounds containing copper, silver, iridium and rare earth elements, and reacted.
(3) An aqueous solution containing a zinc compound, a sulfiding agent, and at least one compound selected from compounds containing copper, silver, iridium and rare earth elements is added to an organic solvent to form a reaction mixture, The reaction mixture is heated and water and organic solvent are azeotroped to remove water.

(1) Crushing and mixing can be performed using a commercially available crushing mixer.

The reactions (2) and (3) are methods for preparing a zinc sulfide-based phosphor precursor from a zinc compound and a sulfurizing agent. In the reaction (2), a sulfurizing agent is added to an aqueous solution containing a zinc compound, and in the reaction (3), an aqueous solution containing a zinc compound and a sulfurizing agent is used. The reaction (2) is particularly suitable when a sulfurizing agent is continuously added as a gas.

Zinc compounds that can be used in the reactions (2) and (3) include mineral acid salts with hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, etc., organic acid salts with formic acid, acetic acid, butyric acid, oxalic acid, etc., acetyl The complex salt which uses acetonate etc. as a ligand can be mentioned. Among these, organic acid salts can be preferably used from the viewpoint of stability and persistence. In addition, a zinc compound may be used individually by 1 type, or may be used in combination of multiple types. The concentration of the zinc compound in the aqueous solution is preferably 0.01 mol / L or more and 2 mol / L or less, and more preferably 0.1 mol / L or more and 1.5 mol / L or less. If the concentration of the zinc compound is too high, the reaction rate decreases with the precipitation of zinc sulfide produced by the reaction, and if the concentration is too low, the production amount per batch decreases and the volumetric efficiency decreases significantly.

The sulfurizing agent that can be used in the reactions (2) and (3) is not particularly limited, but includes alkali metal sulfides such as hydrogen sulfide, sodium sulfide, and potassium sulfide, thioacetamide, thioformamide, and the like. Thiamides, thioureas and the like can be used. Hydrogen sulfide, thioacetamide, and thiourea can be preferably used from the viewpoints of decomposition temperature, stability, and persistence of decomposition products. Among these, thioacetamide and hydrogen sulfide can be particularly preferably used. The sulfurizing agent is preferably used in an amount of 0.5 to 5 times the molar ratio to the zinc element, more preferably 1.1 to 4 times, and more preferably 1.1 to 2 times. It is particularly preferred to use in Outside the above range, the zinc compound may remain unreacted and adversely affect the reaction, leading to a decrease in color purity as a phosphor. The concentration of the sulfiding agent in the aqueous solution is preferably 0.01 mol / L or more and 2 mol / L or less, and more preferably 0.1 mol / L or more and 1.5 mol / L or less. Outside the above range, the sulfide and the zinc compound may be precipitated and remain unreacted.

In the reactions (2) and (3), the water used in the aqueous solution is preferably ion-exchanged water having an ash content of 100 ppm or less, preferably 10 ppm or less. Water containing metal ions as impurities is not preferable because it affects the emission color of the zinc sulfide phosphor.

The organic solvent that can be used in the reaction (3) is not particularly limited as long as it can remove water by azeotropic dehydration. Preferable examples include hexane, cyclohexane, heptane, octane, cyclooctane, nonane, decane, dodecane, cyclododecane, undecane and other saturated hydrocarbons, toluene, xylene, mesitylene and other aromatic hydrocarbons, carbon tetrachloride, 1, Halogenated hydrocarbons such as 2-dichloroethane and 1,1,2,2-tetrachloroethylene, halogenated aromatic hydrocarbons such as chlorobenzene and dichlorobenzene, dibutyl ether, diisobutyl ether, amyl ether, diisoamyl ether, dihexyl ether, dicyclohexyl Ethers such as ether, dioctyl ether, dicyclooctyl ether, anisole, phenylethyl ether, phenylpropyl ether, phenylbutyl ether, butyl alcohol, amyl alcohol , Alcohols such as isoamyl alcohol, hexyl alcohol, heptyl alcohol, octyl alcohol, cyclooctyl alcohol, esters such as butyl acetate, amyl acetate, isoamyl acetate, butyl butyrate, amyl butyrate, isoamyl butyrate, methyl benzoate, ethyl benzoate And the like. Among these, saturated hydrocarbon-based and aromatic hydrocarbon-based organic solvents are preferable from the viewpoints of stability and safety of organic solvents, water removal efficiency, and loss due to dissolution of sulfides and raw material salts to be generated. In particular, decane, dodecane and xylene are preferred from the viewpoint of the azeotropic temperature and azeotropic ratio with water. The amount of the organic solvent used may be larger than the amount of the aqueous solution in which the zinc compound is dissolved, as long as the generated zinc sulfide can be retained.

The temperature for heating the reaction mixture in the reaction of (3) is preferably in the range of 30 ° C. to 300 ° C., more preferably in the range of 40 ° C. to 230 ° C., and still more preferably in the range of 60 ° C. to 200 ° C. A range of 80 ° C. or higher and 180 ° C. or lower is particularly preferable. If it is a temperature range of 40 degreeC or more and 230 degrees C or less, since it is not necessary to use a special installation, it is advantageous practically. A temperature range of 60 ° C. or more and 200 ° C. or less is advantageous when thioacetamide is used as the sulfide.

The reactions (2) and (3) may be performed in the presence of hydrogen sulfide gas and / or an inert gas such as nitrogen and argon because there is a possibility that the oxidation of zinc sulfide may not be completely suppressed due to the presence of oxygen. preferable.

In the reactions (2) and (3), the deposited inorganic composition containing zinc sulfide and the metal element is subjected to washing such as water washing and drying under reduced pressure as necessary. The drying temperature can be 10 ° C. or more and 200 ° C. or less, but is preferably 10 ° C. or more and 150 ° C. or less, more preferably 50 ° C. or more and 120 ° C. or less in order to prevent oxidation due to the presence of moisture.

<Addition of flux>
In the production method of the present invention, a flux is added to the zinc sulfide-based phosphor precursor in the primary firing step.

As the flux, a halogen-containing flux, particularly a chlorine-containing flux can be preferably used. Preferable examples of the chlorine-containing flux include alkali metal chlorides such as lithium chloride, sodium chloride, potassium chloride, and cesium chloride, alkaline earth metal chlorides such as calcium chloride, magnesium chloride, barium chloride, and strontium chloride, and ammonium chloride. And zinc chloride. Preferable examples of the bromine-containing flux include alkali metal bromides such as lithium bromide, sodium bromide, potassium bromide and cesium bromide, alkaline earth such as calcium bromide, magnesium bromide, barium bromide and strontium bromide. Examples include metal bromides, ammonium bromides, zinc bromides and the like. Preferable examples of the iodine-containing flux include alkali metal iodides such as lithium iodide, sodium iodide, potassium iodide and cesium iodide, alkalis such as calcium iodide, magnesium iodide, barium iodide and strontium iodide. There may be mentioned earth metal iodide, ammonium iodide, zinc iodide and the like. It is preferable to mix a plurality of metal halides from the viewpoint of persistence and the melting temperature of the flux. More preferably, a mixture of potassium chloride, sodium chloride and magnesium chloride is used.

The amount of the flux used is not particularly limited, but usually the concentration in the zinc sulfide is preferably 0.1 wt% or more and 80 wt% or less. Considering the influence of the uniform dispersion of the flux, etc., 0.5 wt% or more and 60 wt% or less is more preferable, and 1 wt% or more and 40 wt% or less is particularly preferable.

The method of adding the flux is not particularly limited, and is a solid mixing method in which a solid flux and a zinc sulfide-based phosphor precursor are mixed. After the flux is dissolved in water, the zinc sulfide-based phosphor precursor is mixed. The solid mixing method and the aqueous solution mixing method may be combined in consideration of the aqueous solution mixing method of mixing with the body and drying, and the chemical stability of the flux used.

<Addition of sulfur>
In the production method of the present invention, sulfur may be added together with the flux to the zinc sulfide-based phosphor precursor in the primary firing step. By adding sulfur, the atmosphere in the firing furnace during firing can be maintained in a reducing atmosphere, and the oxidation of zinc sulfide by water and oxygen that may be present can be suppressed. The amount of sulfur added for the purpose of suppressing oxidation of zinc sulfide is preferably 0.01 times or more and 2 times or less, more preferably 0.02 times or more and 1 time or less, based on the weight of zinc sulfide.

<Primary firing>
In the primary firing step of the production method of the present invention, a flux and preferably sulfur is added to the zinc sulfide-based phosphor precursor, and the temperature is raised from room temperature to a constant temperature in the range of 1000 ° C. to 1200 ° C. Then, it is rapidly cooled to a temperature of 700 ° C. or lower to form a primary fired product having a hexagonal crystal structure.

From normal temperature to a temperature just before the start of crystal growth of zinc sulfide, preferably in the temperature range of 300 ° C. or higher and 850 ° C. or lower, more preferably in the temperature range of 300 ° C. or higher and 600 ° C. or lower, air is continuously introduced into the firing furnace. The temperature is increased in the presence of oxygen. During this temperature increase, the flux is melted and zinc sulfide is granulated. If the temperature is increased in the presence of oxygen to a temperature exceeding 850 ° C., the inside of the zinc sulfide particles is oxidized, and a portion not showing fluorescence is generated, which is not preferable.

Next, it is preferable to raise the temperature to a certain temperature within a range of 1000 ° C. or more and 1200 ° C. or less under an inert gas atmosphere such as nitrogen. The heating rate is preferably 50 ° C./hr or more and 1000 ° C./hr or less, more preferably 60 ° C./hr or more and 900 ° C./hr or less. If the rate of temperature rise is too fast, the equipment used will be overloaded, reducing the life of the equipment as well as promoting rapid decomposition of the flux and shortening the melt time, resulting in non-uniform dispersion of the flux. Cheap. If the rate of temperature rise is too slow, it is not economical, and in the case of a low-melting flux, the flux is localized and causes coarsening of zinc sulfide, which is not preferable.

After reaching a certain temperature in the range of 1000 ° C. or more and 1200 ° C. or less, the temperature is preferably maintained for about 1 hour or more and about 5 hours or less, and then rapidly cooled to a temperature of 700 ° C. or less. Here, rapid cooling means cooling with a cooling rate greater than that of natural cooling. The cooling rate is not particularly limited, and it is preferable to cool as quickly as possible, but considering the heat shock of the container, 600 ° C./hr or more and 30000 ° C./hr (that is, 10 ° C./min or more and 500 ° C./min or less) ), Preferably 720 ° C./hr or more and 18000 ° C./hr (that is, 12 ° C./min or more and 300 ° C./min or less).

A zinc sulfide-based phosphor precursor that has been transformed into a hexagonal crystal structure by raising the temperature to a constant temperature in the range of 1000 ° C. to 1200 ° C. in the primary firing step, maintaining the temperature, and rapidly cooling to a temperature of 700 ° C. or less. The crystal system can be stabilized. When the temperature exceeds about 800 ° C., the crystal system of the zinc sulfide-based phosphor precursor starts to change, and at about 1020 ° C., the crystal structure completely changes from a cubic structure to a hexagonal structure. This transition of the crystal system can be confirmed by the appearance of a (100) plane diffraction pattern by X-ray diffraction.

<Desalination treatment>
The primary fired product obtained by the primary firing process is then desalted. Desalting can be performed by washing with an acidic aqueous solution and then washing with ion exchange water until the washing becomes neutral. As the acidic aqueous solution, an organic acid aqueous solution such as formic acid or acetic acid, or a mineral acid aqueous solution such as hydrochloric acid, sulfuric acid or phosphoric acid can be used. Considering the permeability to zinc sulfide and the persistence on the surface, acetic acid and hydrochloric acid are preferably used.

<Annealing treatment>
In the production method of the present invention, ultrasonic treatment is performed after the primary firing step. However, prior to the ultrasonic treatment, it is more preferable to perform an annealing treatment immediately after the primary firing step or after the desalting treatment during the rapid cooling of the primary firing step.

The annealing treatment in the present invention is a heat treatment performed for stabilizing the hexagonal crystal structure of the primary fired product formed in the primary firing process. In the primary firing step, after the transition to the hexagonal crystal structure at a constant temperature within the range of 1000 ° C. or higher and 1200 ° C. or lower, rapid cooling is performed to a temperature of 700 ° C. or lower in order to maintain the hexagonal crystal structure. Since the hexagonal crystal structure formed at a high temperature is maintained, the hexagonal crystal structure is distorted. If ultrasonic treatment is performed with this distortion, the degree of distortion becomes irregular. This irregular distortion is difficult to alleviate during the secondary firing step, and the reproducibility of color development by final electroluminescence is lowered. Furthermore, when ultrasonic treatment is performed in a state having a large strain, the yield is reduced due to simultaneous breakage of zinc sulfide particles.

As the annealing treatment, a temperature range of 100 ° C. to 500 ° C., preferably 150 ° C. to 500 ° C., more preferably 200 ° C. to 480 ° C., which is a temperature range that does not re-transform into a cubic structure in an inert gas atmosphere such as a nitrogen gas atmosphere. It is preferable to hold the primary fired product at a constant temperature within a temperature range of 0 ° C. or lower for 0.1 hours to 30 hours, preferably 1 hour to 20 hours. Annealing treatment in an oxygen-containing atmosphere is not preferable because the zinc sulfide particles are oxidized and a non-light-emitting substance or a non-conductive substance is formed on the particle surface. In consideration of strain relaxation efficiency and economic efficiency for stabilizing the hexagonal crystal structure, it is preferable to maintain the temperature in the temperature range of 150 ° C. to 500 ° C. for 1 hour to 20 hours. In the case where the annealing process is performed during the rapid cooling in the first processing step, the film is rapidly cooled to 700 ° C. in order to maintain the hexagonal crystal structure, and then maintained in the above temperature range.

<Sonication>
The zinc sulfide particles, which are the primary fired product that has undergone the primary firing process and preferably the annealing treatment process, have a stabilized hexagonal crystal structure in a proportion of about 95% or more. In the present invention, in order to dope the zinc sulfide particles as the primary fired product with a metal element serving as a luminescent center, a part of the hexagonal crystal structure of the primary fired product is transferred to the cubic structure, and the hexagonal crystal structure and the cubic crystal are obtained. Mix with structure. The ratio of the hexagonal structure to the cubic structure is preferably in the range of 90:10 to 55:45 in the hexagonal structure: cubic structure.

In the present invention, ultrasonic waves are applied to a dispersion obtained by dispersing a primary fired product in an aqueous liquid, and the primary fired product is mixed with a hexagonal crystal structure and a cubic crystal structure.

Preferred examples of the aqueous liquid include water and a mixture of water and a water-soluble organic solvent, but are not particularly limited as long as they do not affect the reaction. The water-soluble organic solvent may be a mixture of two or more compounds, for example, alcohols such as methanol, ethanol, propanol, butanol, ethylene glycol, propylene glycol, 1,4-butanediol, methyl acetate, ethyl acetate, butyl acetate Esters such as methyl benzoate and dimethyl phthalate, and ethers such as tetrahydrofuran, tetrahydropyran, dipropyl ether, dibutyl ether, diethylene glycol, and tetraethylene glycol can be preferably used. Among these, alcohols are preferably used in consideration of low flammability and weak oxidizing power, and methanol and ethanol are particularly preferable.

It is desirable to adjust the concentration of the primary baked product in the dispersion to a range of 0.1 wt% to 50 wt%, preferably 0.5 wt% to 30 wt%, more preferably 0.7 wt% to 20 wt%. If the concentration is too high, it is not preferable because it promotes the polishing action between the particles, and if the concentration is too low, it is not preferable because the processing cost increases. Note that the temperature of the dispersion during ultrasonic irradiation is in the range of 1 ° C. to 90 ° C., preferably in the range of 2 ° C. to 80 ° C., more preferably 3 ° C. A range of 60 ° C. or lower is desirable.

In the present invention, the dispersion of the primary fired product, 15kHz or 50kHz, preferably 15kHz or more 40kHz or less, more preferably ultrasonic waves of frequencies below 37kHz or 18 kHz 800 kW / cm ³ or more 10000kW / cm ³ or less, preferably Irradiation is performed at a strength of 1000 kW / cm ^{3 to} 6000 kW / cm ^{3 for} 0.01 minutes to 102 minutes, preferably 0.05 minutes to 30 minutes. When the impact energy by ultrasonic irradiation is too strong, the crystal structure cannot be maintained and the particles are crushed, and when the impact energy is too weak, the transition to the cubic structure cannot be promoted.

<Secondary firing>
In the present invention, the primary fired product in which a hexagonal crystal structure and a cubic crystal structure obtained by ultrasonic treatment are mixed is heated in an inert gas atmosphere, and a constant temperature within a range of 650 ° C. to 1000 ° C. is maintained. Thereafter, it is subjected to secondary firing for cooling.

Prior to temperature increase, a primary fired product in which a hexagonal crystal structure and a cubic crystal structure are mixed, copper of 0.1 wt% or more and 5 wt% or less, zinc of 1 wt% or more and 45 wt% or less, and 0.1 wt% or more and 6 wt% or less of Contains sulfur.

In order to contain copper, it is preferably added as a solid or aqueous copper compound. Preferred examples of the copper compound include copper (I) chloride, copper (II) chloride, copper sulfate, and copper acetate. From the viewpoint of economy and operability, copper sulfate and copper acetate are preferred. The copper compound is added in the range of 0.01 wt% or more and 10 wt% or less, preferably 0.02 wt% or more and 5 wt% or less with respect to the primary fired product.

In order to contain zinc, it is preferably added as a solid or aqueous zinc compound. Preferred examples of the zinc compound include zinc oxide, zinc sulfide, zinc chloride, zinc bromide, zinc sulfate, zinc nitrate, zinc acetate, and zinc formate. From the viewpoints of economy and operability, zinc sulfate and zinc oxide are preferred. The zinc compound is added in the range of 0.1 wt% or more and 50 wt% or less, preferably 0.2 wt% or more and 30 wt% or less with respect to the primary fired product.

In order to contain sulfur, it is preferable to add sulfur or sulfur compounds such as thioacetamide and thiourea. From the viewpoint of economy and operability, use of sulfur is preferred. Sulfur is added in the range of 0.1 wt% or more and 40 wt% or less, preferably 0.5 wt% or more and 30 wt% or less with respect to the primary fired product.

A mixture of a primary fired product in which a hexagonal crystal structure and a cubic crystal structure are mixed, and copper, zinc and sulfur is 650 ° C. or higher and 1000 ° C. over 2 to 5 hours in an inert gas atmosphere such as nitrogen gas. The temperature is raised to a certain temperature within the following range, and after reaching that temperature, air is introduced to form an oxygen-containing atmosphere for 30 minutes to 2 hours, and a certain temperature within a range of 650 ° C. to 1000 ° C. And then cool. The oxygen concentration in the oxygen-containing atmosphere is not particularly limited, but is preferably 1 vol% or more and 30 vol% or less.

<Cooling control of secondary firing process>
In the present invention, since the primary fired product in which a hexagonal crystal structure and a cubic crystal structure are mixed is subjected to secondary treatment in a high temperature range, the cubic crystal structure is distorted. In order to alleviate this distortion and to obtain a stable cubic structure, it is particularly preferable to control the cooling rate in the secondary firing step.

As a control of the cooling rate in the secondary firing step in the present invention, in the process of cooling to room temperature after maintaining a constant temperature in the range of 650 ° C. to 1000 ° C., (1) the temperature from 300 ° C. to room temperature Cool at a cooling rate of 150 ° C./hr or less, preferably 10 ° C./hr or more and 150 ° C./hr or less (2) 0.5 hours or more to a constant temperature within a temperature range of 120 ° C. or more and 300 ° C. or less Preferably, it is maintained for 0.5 hours to 24 hours, more preferably 1 hour to 20 hours, and even more preferably 1.5 hours to 18 hours. In the claims and specification of the present application, “room temperature” means a temperature of 20 ° C. or more and 25 ° C. or less.

The cooling after maintaining a constant temperature in the range of 650 ° C. to 1000 ° C. is preferably performed at a cooling rate up to 300 ° C. in the range of 50 ° C./hr to 800 ° C./hr, More preferably, it is in the range of hr to 600 ° C./hr. When the cooling rate exceeds 800 ° C./hr, a container such as a crucible may be damaged or destroyed, and the broken pieces may become contaminated, resulting in deterioration of the phosphor quality. On the other hand, if the cooling rate is less than 50 ° C./hr, the cooling time becomes remarkably long and productivity is lowered, which is not preferable.

<Washing and drying>
The cooled secondary fired product is washed with extra zinc compounds that remain unreacted, compounds that contain extra unpublished central metal elements that have not been doped, and blackened metal compounds. To remove.

In the cleaning, a neutral aqueous solution, an acidic aqueous solution, an aqueous cyanide salt solution or the like can be used, but in any case, it is necessary to finally rinse thoroughly with ion-exchanged water.

As the acidic aqueous solution, a mineral acid aqueous solution such as hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid, and an organic acid aqueous solution such as acetic acid, propionic acid, and butyric acid can be preferably used. Particularly preferred. However, since the secondary fired product that is zinc sulfide particles may be decomposed when contacted with a high concentration acidic substance, in the case of an acidic aqueous solution, it is 0.1 wt% or more and 20 wt% or less, preferably 1 wt% or more and 10 wt%. The following concentration is desirable.

The aqueous cyanide salt solution is suitable for removing excess copper, silver, iridium and rare earth elements remaining on the surface of the secondary fired product. As the cyanide salt aqueous solution, a sodium cyanide aqueous solution and a potassium cyanide aqueous solution having a concentration of 0.1 wt% or more and 1 wt% or less can be preferably used. When an aqueous cyanide salt solution is used, it is used in an amount of 10 to 100 times by weight with respect to the secondary fired product.

After washing, drying by vacuum drying or hot air drying to obtain a zinc sulfide blue phosphor.

The fact that a zinc sulfide-based blue phosphor has been obtained can be confirmed by measuring quantum efficiency. Quantum efficiency is defined in JIS as the ratio of the number of quanta, such as electrons or photons generated by reacting molecules or interactions, to the number of incident photons absorbed when light radiation acts on a substance. Has been. A larger quantum efficiency means a higher doping effect. The quantum efficiency in this specification is a value measured by a spectrofluorophotometer, and is used as a ratio between the number of photons emitted by excitation by incident light and the number of photons of incident light absorbed by a substance.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

[Measurement item]
The measurement conditions of the measurement items in the examples and comparative examples in this specification are as follows.

<Measurement of quantum efficiency>
The quantum efficiency in this specification is set to an excitation wavelength of 350 nm and an excitation bandwidth of 5 nm using a spectrophotometer FP-6500 manufactured by JASCO Corporation, and the supplied Spectra Manager for Windows (registered trademark) manufactured by JASCO Corporation. ) Determined using 95 / NT Ver. 1.00.00 2005.

<Ratio between cubic structure and hexagonal structure>
The ratio of the cubic crystal structure and the hexagonal crystal structure in this specification is based on X-ray diffraction data obtained using RINT-2400 manufactured by Rigaku Corporation as an X-ray diffractometer. Was used to determine.

<Color analysis>
The manufactured EL element is sandwiched between the spectrophotometer FP-6500 spectrophotometer manufactured by JASCO Corporation, the excitation light shutter is closed, and a black screen is applied so that external light does not enter the sample holder. Then, the element was measured to emit light. At that time, light emission was detected without correcting the luminance. The emission color analysis was converted into chromaticity (x value, y value) using the emission color analysis of Spectra Manager for Windows (registered trademark) 95 / NT Ver. .

[Precursor production]
The zinc sulfide-based phosphor precursors used in the examples and comparative examples in this specification were produced according to the following Production Examples 1 to 3.

[Production Example 1] <Production of zinc sulfide-based phosphor precursor 1>
Zinc acetate dihydrate 65.9g, copper nitrate trihydrate 0.035g (equivalent to copper 500ppm), gallium nitrate octahydrate 0.008g (equivalent to gallium 50ppm), thioacetamide 45.0g, acetic acid 5g It was dissolved in 500 g of ion exchange water. Meanwhile, a 2 L three-necked flask was equipped with a Gene Stark, a reflux tube, a thermometer and a stirrer, charged with 800 ml of o-xylene, and the system was purged with nitrogen. Adjust the temperature of the oil bath to 150 ° C, raise the temperature of o-xylene in the reactor to 130 ° C, and then remove the distilled water with Gene Stark while adding a solution containing zinc acetate at 100 ml per hour. While reacting. All aqueous solutions were fed in about 6 hours, and water in the system was removed for another 30 minutes. After cooling to room temperature, the precipitated sulfide was precipitated, the supernatant was removed, and the target product was collected and dried at 100 ° C. for 12 hours in a vacuum dryer. The recovered amount was 28.9 g, and the yield was 98% of the theoretical yield.

[Production Example 2] <Production of zinc sulfide-based phosphor precursor 2>
A 3 L three-necked flask is equipped with a stirrer, thermometer, reflux tube and solid feeder, 297.6 g of zinc nitrate hexahydrate, 0.18 g of copper nitrate trihydrate (equivalent to 500 ppm copper), iridium hexachloride 0.022 g of diammonium (equivalent to 100 ppm of iridium) was charged, and 1000 g of ion-exchanged water was added and dissolved. 60% nitric acid was added thereto, and the inside of the system was adjusted to pH2. After replacing the system with nitrogen, the temperature was raised to 90 ° C., and 113.0 g of thioacetamide was charged from the solid feeder to start the reaction. The reaction was continued for 2 hours and then cooled to room temperature. The precipitated sulfide was precipitated, the supernatant was removed by decantation, and further, washing was performed using 3 L of ion exchange water until the pH in the system showed a neutral range. The target product was collected and dried in a vacuum dryer at 100 ° C. for 12 hours. The recovered amount was 94.16 g, and the yield was 96.6% of the theoretical yield.

[Production Example 3] <Production of zinc sulfide-based phosphor precursor 3>
A 100 ml container of THINKEY mixer (ARE-250) is charged with 100 g of zinc sulfide (RAK-N made by Sakai Chemical Industry Co., Ltd.) and 0.20 g of copper acetate trihydrate (equivalent to 500 ppm of copper) for 30 minutes. Crushed and mixed.

[Production Example 4] <Production of zinc sulfide-based phosphor precursor 4>
A zinc sulfide-based phosphor precursor was prepared in the same manner as in Production Example 1 except that the amount of copper nitrate trihydrate was 0.05 g (equivalent to 700 ppm of copper).

[Example 1]
<Primary firing>
To 27 g of the zinc sulfide-based phosphor precursor prepared in Production Example 1, 1.00 g of potassium chloride, 1.17 g of sodium chloride and 6.87 g of magnesium chloride hexahydrate were added and mixed with a ball mill. To the resulting mixture, 1.45 g of sulfur was added and placed in a crucible. The temperature of the crucible was increased at a rate of 400 ° C. per hour while introducing air into the firing furnace. When the furnace temperature reached 800 ° C., the air was switched to introduction of nitrogen, the temperature was raised to 1100 ° C. at a rate of 400 ° C. per hour, and held at 1100 ° C. for 3 hours. After holding for 3 hours, it was cooled to room temperature at 300 ° C. per hour.

<Desalination>
The obtained fired product was added to 200 g of a 15% acetic acid aqueous solution to disperse the fired product. The acetic acid aqueous solution was removed by decantation, and the mixture was washed with 500 g of ion exchange water until neutral, and a primary fired product was obtained. After removing the supernatant by decantation, it was dried at 100 ° C. for 12 hours in a vacuum dryer. The yield of the primary calcined product was 24 g, and the cubic / hexagonal ratio of the primary calcined product was determined by X-ray diffraction.

<Sonication>
200 g of ion-exchanged water was added to 20 g of the primary fired product to obtain a dispersion. Using an ultrasonic vibrator (manufactured by BRANSON, Digital Sonifier, frequency 20 kHz), a vibrator is set at a position of 25 mm from the dispersion, continuously irradiated for 5 minutes at 2000 kW / m ³ , and stopped for 5 minutes three times. Then, sonication was performed. Fine particles generated by crushing were removed using a 10 μm mesh. After removing the supernatant by decantation, it was dried at 100 ° C. for 12 hours in a vacuum dryer. The yield of the primary baked product after the ultrasonic treatment was 12.1 g, and the recovery rate was 60.5%. The cubic / hexagonal ratio of the primary fired product after sonication was determined by X-ray diffraction.

<Secondary firing>
0.25 g of copper sulfate pentahydrate and 2.5 g of zinc sulfate heptahydrate were mixed with 10 g of the primary fired product that had been subjected to ultrasonic treatment, and the mixture was placed in a crucible. The crucible was placed in a firing furnace, heated at a rate of 400 ° C. per hour in a nitrogen atmosphere, and when the temperature in the firing furnace reached 850 ° C., switching from nitrogen to air was introduced for 1 hour. Thereafter, the air was switched again to the introduction of nitrogen, and after holding for another 2 hours, it was cooled to room temperature at 500 ° C. per hour.

The obtained secondary fired product was washed with 100 g of 5% hydrochloric acid aqueous solution. The acidic aqueous solution was removed, and rinsing was repeated using 500 g of ion exchange water until neutrality was achieved. The supernatant was removed by decantation, and then washed with 200 g of a 1% aqueous sodium cyanide solution to remove excess sulfide. Furthermore, after rinsing repeatedly using ion-exchanged water until neutrality, it was dried in a vacuum dryer at 100 ° C. for 12 hours. The yield of the secondary fired product was 9.2 g. The photoexcitation fluorescence spectrum was measured for the obtained secondary fired product (phosphor) to determine the quantum efficiency.

<Production of EL element>
To 1.5 g of the obtained phosphor, 1.0 g of a fluorine-based binder (DuPont 7155) was added, mixed and degassed to prepare a light emitting layer paste. This light emitting layer paste was applied on a PET film with ITO to a film thickness of 40 μm using a 20 mm square screen plate (200 mesh, 25 μm). On the light emitting layer paste layer, a barium titanate paste (7153 manufactured by DuPont) was applied using a screen plate (150 mesh, 25 μm), dried at 100 ° C. for 10 minutes, and then a barium titanate paste was similarly applied. And dried at 100 ° C. for 10 minutes to form a 20 μm dielectric layer. On the upper surface, a silver paste (461 SS manufactured by Atchison) was applied using a screen plate (150 mesh, 25 μm), dried at 100 ° C. for 10 minutes, and an electrode was formed to form a printing EL device. About the obtained element, EL material evaluation was performed at 200 V and 1 kHz.

[Example 2]
The same processes as in Example 1 were performed until the primary firing step and the desalting step. The cubic / hexagonal ratio of the primary fired product was determined by X-ray diffraction.

24 g of vacuum-dried primary fired product was put in a crucible, heated to 400 ° C. over 1 hour in a nitrogen atmosphere, annealed at 400 ° C. for 8 hours in a nitrogen atmosphere, and after 8 hours had passed, At 400 ° C to 200 ° C per hour.

200 g of ion-exchanged water was added to 20 g of the annealed primary fired product to obtain a dispersion. Ultrasonic vibrator (BRANSON Ltd., DegitalSonifier) was used to set the oscillator from the dispersion at a position of 25 mm, continuously for 5 minutes irradiation at 2000 kW / ^{m 3,} ultrasonic performed 3 cycles of stopping 5 minutes Vibration was applied. Fine particles generated by crushing were removed using a 10 μm mesh. After removing ion-exchanged water from the obtained particles, the particles were dried in a vacuum dryer at 100 ° C. for 12 hours. The yield of the primary fired product after the ultrasonic treatment was 16.18 g, and the recovery rate was 80.9%. The cubic / hexagonal ratio of the primary fired product after ultrasonic treatment was determined by X-ray diffraction.

The secondary firing step was performed in the same manner as in Example 1. The photoexcitation fluorescence spectrum of the obtained secondary fired product (phosphor) was measured to determine the quantum efficiency of the phosphor.

EL element was produced in the same manner as in Example 1, and EL material evaluation was performed at 200 V and 1 kHz.

[Example 3]
The same procedure as in Example 2 was performed except that the zinc sulfide-based phosphor precursor prepared in Production Example 2 was used.

[Example 4]
The same operation as in Example 2 was performed except that the zinc sulfide-based phosphor precursor prepared in Production Example 3 was used.

[Example 5]
The same operation as in Example 2 was performed except that the output of the ultrasonic wave was set to 1000 kW / cm ³ .

[Example 6]
The same operation as in Example 2 was performed except that the output of the ultrasonic wave was 1800 kW / cm ³ .

[Example 7]
The same operation as in Example 2 was performed except that the output of the ultrasonic wave was 15800 kW / cm ³ .

[Example 8]
The same operation as in Example 2 was performed except that the output of the ultrasonic wave was set to 3000 kW / cm ³ .

[Example 9]
The same operation as in Example 2 was performed except that the output of the ultrasonic wave was 6000 kW / cm ³ .

[Example 10]
The same operation as in Example 2 was performed except that the annealing temperature was 350 ° C.

[Example 11]
The same operation as in Example 2 was performed except that the annealing temperature was set to 300 ° C.

[Example 12]
The same procedure as in Example 2 was performed, except that 27 g of the zinc sulfide-based phosphor precursor prepared in Production Example 1 was used, the rapid quenching in the primary firing step was set to 400 ° C., and annealing was performed while maintaining 400 ° C. for 8 hours.

[Example 13]
27 g of the zinc sulfide-based phosphor precursor prepared in Production Example 1 was used, and after the primary firing step, immediately heated to 400 ° C., annealed, and then desalted, the same as in Example 2. It was.

[Comparative Example 1]
The same operation as in Example 2 was performed except that the output of the ultrasonic wave was changed to 830 kW / cm ³ .

[Comparative Example 2]
The same operation as in Example 2 was performed except that the output of the ultrasonic wave was set to 560 kW / cm ³ .

[Comparative Example 3]
The same operation as in Example 2 was performed except that the output of the ultrasonic wave was 10500 kW / cm ³ . Since the particles were broken, the target product could not be recovered.

[Example 14]
To 27 g of the product obtained in Production Example 4, 1.00 g of potassium chloride, 1.17 g of sodium chloride and 6.87 g of magnesium chloride hexahydrate were added and mixed with a ball mill. To this mixture, 1.45 g of sulfur was added and placed in a crucible. This crucible was put in a firing furnace and heated in air at a rate of 400 ° C. per hour. When the furnace temperature reached 800 ° C, switching from introduction of air to introduction of nitrogen, raising the temperature to 1100 ° C at a rate of 400 ° C per hour, holding 1100 ° C for 3 hours, and then cooling to room temperature at 300 ° C per hour did.

The obtained fired product was added to 200 g of a 15% acetic acid aqueous solution to disperse the fired product. The supernatant is removed by decantation, washed with 500 g of ion-exchanged water until neutral, and after removing the ion-exchanged water, dried at 100 ° C. for 12 hours in a vacuum dryer to obtain 24 g of a primary fired product. It was.

200 g of ion-exchanged water was added to 20 g of the primary fired product to obtain a dispersion. Using an ultrasonic vibrator (manufactured by BRANSON, Digital Sonifier, frequency 20 kHz), a vibrator is set at a position of 25 mm from the dispersion, continuously irradiated for 5 minutes at 1000 KW / m ³ , and stopped for 5 minutes three times. Ultrasonic vibration was applied. Fine particles generated by crushing were removed using a 10 μm mesh. After removing the supernatant by decantation, it was dried at 100 ° C. for 12 hours in a vacuum dryer.

0.25 g of copper sulfate pentahydrate and 2.5 g of zinc sulfate heptahydrate were mixed with 10 g of the primary fired product after the ultrasonic treatment, and the mixture was put in a crucible. The crucible was placed in a firing furnace, heated at a rate of 400 ° C. per hour in a nitrogen atmosphere, and when the temperature in the firing furnace reached 850 ° C., switching from nitrogen introduction to air introduction was performed for 1 hour. . Thereafter, the introduction of air was switched again to the introduction of nitrogen, and the mixture was further maintained for 2 hours. After cooling to 300 ° C. at 500 ° C./hour, the cooling rate was changed to 50 ° C./hour to cool to room temperature.

After the obtained secondary fired product was washed in the same manner as in Example 1, the quantum efficiency was determined. Further, an EL element was produced in the same manner as in Example 1, and the EL material was evaluated.

[Example 15]
The same operation as in Example 14 was performed except that 8.2 g of the secondary fired product was obtained using 27 g of the zinc sulfide-based phosphor precursor prepared in Production Example 2.

[Example 16]
The same procedure as in Example 14 was performed, except that 7.7 g of the secondary fired product was obtained using 25 g of the zinc sulfide-based phosphor precursor prepared in Production Example 3.

[Example 17]
Using 27 g of the zinc sulfide-based phosphor precursor prepared in Production Example 4, 24.5 g of a primary fired product was obtained in the same manner as in Example 14, and cooling after the secondary firing was cooled to 300 ° C. at 500 ° C. per hour. Then, it was carried out in the same manner as in Example 14 except that baked product 9.2 g was obtained by holding at 300 ° C. for 3 hours and cooling to room temperature at 50 ° C. per hour.

[Example 18]
The cooling after the secondary firing was performed in the same manner as in Example 17 except that the cooling was performed at 500 ° C. per hour to 250 ° C., maintained at 250 ° C. for 3 hours, and cooled to 50 ° C. per hour to room temperature.

[Example 19]
Example 17 Except for cooling after secondary firing from 850 ° C to 300 ° C at 150 ° C per hour, from 300 ° C to 150 ° C at 20 ° C per hour, and from 150 ° C to 15 ° C per hour to room temperature. As well as.

[Comparative Example 4]
It was carried out in the same manner as in Example 14 except that the cooling after the secondary baking was cooled from 850 ° C. to room temperature at 500 ° C. per hour.

[Comparative Example 5]
The same procedure as in Example 15 was performed except that cooling after the secondary firing was performed from 850 ° C. to room temperature at 500 ° C. per hour.

[Comparative Example 6]
It was carried out in the same manner as in Example 16 except that cooling after the secondary firing was performed from 850 ° C. to room temperature at 500 ° C. per hour.

[Comparative Example 7]
The cooling after the secondary firing was performed in the same manner as in Example 14 except that the cooling was performed from 850 ° C. to 300 ° C. at 500 ° C. per hour and then at 200 ° C. per hour to room temperature.

[Comparative Example 8]
The cooling after the secondary firing was performed in the same manner as in Example 14 except that the cooling was performed from 850 ° C. to 300 ° C. at 500 ° C. per hour, then maintained at 300 ° C. for 10 minutes, and further cooled to room temperature at 200 ° C. per hour.

[Comparative Example 9]
The cooling after the secondary firing was performed in the same manner as in Example 14 except that the cooling was performed from 850 ° C. to 250 ° C. at 500 ° C. per hour and then cooled to 500 ° C. per hour to room temperature.

[Comparative Example 10]
Except for cooling after secondary firing from 850 ° C. to 350 ° C. at 500 ° C./hour, then holding at 300 ° C. for 0.5 hour, and further cooling to 200 ° C./hour to room temperature, the same as in Example 14. It was.

<Manufacturing conditions and measurement results>
For Examples 1 to 19 and Comparative Examples 1 to 10, annealing conditions, ultrasonic output, and cooling conditions during secondary firing were extracted as manufacturing conditions, and EL luminance and chromaticity (x value, y value) of EL elements were measured results. ) And the ratio of the cubic and hexagonal phosphors and the quantum efficiency are shown in Table 1. The EL device manufactured by the manufacturing method of the present invention showed blue light emission with both chromaticity (x value, y value) of 0.2 or less, but in the comparative example, the y value exceeded 0.2 and blue green Luminescence was shown.

According to the present invention, it is possible to industrially produce a high-luminance zinc sulfide-based blue phosphor that is practical and has great industrial utility.

Claims (12)

A method for producing a zinc sulfide-based blue phosphor by firing a zinc sulfide-based phosphor precursor,
(A) A flux is added to the zinc sulfide-based phosphor precursor, and the temperature is raised to a constant temperature within a range of 1000 ° C. or higher and 1200 ° C. or lower and maintained at that temperature, and then rapidly cooled to a temperature of 700 ° C. or lower. A primary firing step for forming a primary fired product having a hexagonal crystal structure introduced;
(B) an ultrasonic treatment step of irradiating the dispersion obtained by dispersing the primary fired product in an aqueous liquid with ultrasonic waves to transfer a part of the hexagonal crystal structure of the primary fired product into a cubic structure;
(C) The primary fired product in which a hexagonal crystal structure and a cubic crystal structure are mixed is heated to a constant temperature within a range of 650 ° C. or higher and 1000 ° C. or lower in an inert gas atmosphere, and then cooled. A method comprising a secondary firing step. Before the (b) ultrasonic treatment step, the primary firing product is maintained at a constant temperature in the range of 100 ° C. or more and 500 ° C. or less in an inert atmosphere, and (c) 650 in the secondary firing step. At least one of cooling control for cooling the temperature range from 300 ° C. or less to room temperature at a cooling rate of 150 ° C./hr or less in the process of cooling to room temperature after maintaining a constant temperature in the range of ℃ to 1000 ° C. The method of claim 1, further comprising: Before the (b) ultrasonic treatment step, the primary fired product is kept in an inert atmosphere at a constant temperature within a range of 100 ° C. or higher and 500 ° C. or lower, or (c) 650 in the secondary firing step. 2. The method according to claim 1, further comprising at least one of cooling control for holding at a constant temperature within a range of 120 ° C. or more and 300 ° C. or less for 0.5 hour or more after maintaining a constant temperature within a range of from 100 ° C. to 1000 ° C. the method of. The method according to any one of claims 1 to 3, wherein in the (b) ultrasonic irradiation step, ultrasonic waves having an output of 1000 kW / m ³ or more and 6000 kW / m ³ or less are irradiated. 5. The method of any one of claims 1 to 4, wherein the (a) primary firing step includes a step of raising the temperature of the mixture of the zinc sulfide-based fluorescent precursor and the flux from 300 ° C. to 850 ° C. in an oxygen-containing atmosphere. 2. The method according to item 1. The method according to any one of claims 1 to 5, wherein the (c) secondary firing step includes a step of switching to an oxygen-containing atmosphere after reaching a temperature of 650 ° C or higher. The (c) secondary firing step includes adding a compound containing copper and a compound containing zinc to a primary fired product in which the hexagonal crystal structure and the cubic crystal structure are mixed, and raising the temperature. 7. The method according to any one of items 6. The zinc sulfide-based phosphor precursor according to any one of claims 1 to 7, wherein the zinc sulfide-based phosphor precursor is a mixture containing zinc sulfide and at least one selected from a compound containing copper, silver, iridium and a rare earth element. The method described. The zinc sulfide-based phosphor precursor is a sulfide obtained by adding a sulfurizing agent to an aqueous solution containing at least one selected from a zinc compound and a compound containing copper, silver, iridium and a rare earth element, and reacting the same. The method according to any one of claims 1 to 7, which is a zinc phosphor precursor. The zinc sulfide-based phosphor precursor is obtained by adding an aqueous solution containing at least one selected from a zinc compound, a sulfurizing agent, and a compound containing copper, silver, iridium and a rare earth element to an organic solvent. The zinc sulfide-based phosphor precursor obtained by heating the reaction mixture and azeotropically distilling water and an organic solvent to remove the water. the method of. The method according to claim 9 or 10, wherein the sulfurizing agent is thioacetamide and / or hydrogen sulfide. A zinc sulfide blue phosphor obtained by the method according to any one of claims 1 to 11 and having chromaticity coordinates (x, y) = (≤ 0.2, ≤ 0.2).