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WO2020090689A1 - Assemblage de nanofils d'argent, encre renfermant des nanofils d'argent, film conducteur transparent, procédé pour la production d'un assemblage de nanofils d'argent, procédé pour la production d'encre renfermant des nanofils d'argent et procédé pour la production d'un film conducteur transparent - Google Patents

Assemblage de nanofils d'argent, encre renfermant des nanofils d'argent, film conducteur transparent, procédé pour la production d'un assemblage de nanofils d'argent, procédé pour la production d'encre renfermant des nanofils d'argent et procédé pour la production d'un film conducteur transparent Download PDF

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WO2020090689A1
WO2020090689A1 PCT/JP2019/042054 JP2019042054W WO2020090689A1 WO 2020090689 A1 WO2020090689 A1 WO 2020090689A1 JP 2019042054 W JP2019042054 W JP 2019042054W WO 2020090689 A1 WO2020090689 A1 WO 2020090689A1
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silver
silver nanowires
silver nanowire
transparent conductive
conductive film
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Japanese (ja)
Inventor
王高 佐藤
哲 栗田
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Dowa Electronics Materials Co Ltd
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Dowa Electronics Materials Co Ltd
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F9/00—Making metallic powder or suspensions thereof
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B1/00—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B1/00—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors
    • H01B1/20—Conductive material dispersed in non-conductive organic material
    • H01B1/22—Conductive material dispersed in non-conductive organic material the conductive material comprising metals or alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B13/00—Apparatus or processes specially adapted for manufacturing conductors or cables
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B5/00—Non-insulated conductors or conductive bodies characterised by their form
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B5/00—Non-insulated conductors or conductive bodies characterised by their form
    • H01B5/14—Non-insulated conductors or conductive bodies characterised by their form comprising conductive layers or films on insulating-supports
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F9/00—Making metallic powder or suspensions thereof
    • B22F9/16—Making metallic powder or suspensions thereof using chemical processes
    • B22F9/18—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds
    • B22F9/24—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds starting from liquid metal compounds, e.g. solutions

Definitions

  • the present invention relates to an assembly of silver nanowires, a silver nanowire ink, a transparent conductive film, and a method for producing them.
  • metal nanowire a fine metal wire having an average diameter of about 50 nm or less
  • metal nanowire (s)) a fine metal wire having an average diameter of about 50 nm or less
  • silver nanowires are regarded as promising.
  • a coating liquid silver nanowire ink
  • a transparent substrate such as glass, PET (polyethylene terephthalate), PC (polycarbonate), etc.
  • a liquid component When the silver nanowires are removed, the silver nanowires form a conductive network by contacting each other on the transparent substrate, and a transparent conductive film is obtained.
  • the silver nanowires are oriented in the longitudinal direction (Machine Direction: MD) of the film of the transparent substrate, that is, the direction parallel to the coating direction.
  • MD Machine Direction
  • the ratio RTD / RMD of the sheet resistance RTD (Resistance of TD) in the width direction (Transverse Direction: TD) perpendicular to the longitudinal direction on the transparent substrate is large with respect to the sheet resistance RMD (Resistance of MD) in the longitudinal direction. Therefore, there is a problem that the sheet resistance becomes anisotropic.
  • the present invention can reduce the anisotropy of the sheet resistance of the transparent conductive film, and can achieve both low haze and low sheet resistance of the transparent conductive film, an aggregate of silver nanowires, a silver nanowire ink, A transparent conductive film and an assembly of silver nanowires capable of reducing anisotropy of sheet resistance of the transparent conductive film, and achieving both low haze and low sheet resistance of the transparent conductive film, silver nanowire ink, It is an object to provide a method for manufacturing a transparent conductive film.
  • the inventors of the present invention can advantageously solve the above problems by setting the length distribution of the aggregate of silver nanowires to a predetermined value. With the knowledge obtained, the present invention has been completed.
  • the gist of the present invention is as follows.
  • the aggregate of silver nanowires of the present invention is an aggregate of silver nanowires having an average diameter of 50 nm or less, and the number of the silver nanowires in the aggregate having a length of less than 10 ⁇ m is 15 to 40%, 10 ⁇ m. It is characterized in that the number of particles less than 25 ⁇ m is distributed in 30 to 74% and the number of particles more than 25 ⁇ m is distributed in 11 to 30%.
  • the “average diameter” of the silver nanowire is defined as follows. On the bright-field observation image by a transmission electron microscope (TEM), the distance between the contours on one side in the thickness direction of one silver nanowire is defined as the diameter of the wire.
  • TEM transmission electron microscope
  • each silver nanowire can be considered to have a substantially uniform diameter over its entire length. Therefore, the diameter can be measured by selecting a portion that does not overlap with other silver nanowires. In a TEM image of one field of view, measure the diameters of all the silver nanowires observed in the image, except for the silver nanowires that completely overlap with other silver nanowires and it is difficult to measure the diameter. Is performed for a plurality of randomly selected visual fields, the diameters of 300 or more different silver nanowires are obtained in total, the average value of the diameters of the individual silver nanowires is calculated, and the value is defined as the average diameter D M. Define.
  • the “length” of a silver nanowire means a trace length from one end to the other end of a certain silver nanowire on an image observed by a field emission scanning electron microscope (FE-SEM). Define.
  • the number of the silver nanowires having a length of less than 10 ⁇ m is 26 to 35%, the number of the silver nanowires having a length of 10 ⁇ m or more and less than 25 ⁇ m is 45 to 63%, or 25 ⁇ m or more. It is preferable that the number is distributed from 11 to 20%.
  • the silver nanowire ink of the present invention is characterized in that the above-mentioned aggregate of silver nanowires is dispersed in a liquid medium.
  • the transparent conductive film of the present invention is characterized by having the above-mentioned aggregate of silver nanowires on a transparent substrate.
  • the method for producing a silver nanowire of the present invention comprises a step of synthesizing a silver nanowire, In the tubular channel having a filter on the channel wall surface, the silver nanowires are introduced along with the flow of the liquid medium, and a part of the inflowed silver nanowires is passed through the filter together with a part of the liquid medium to form the tubular channel.
  • the "thin film swirl method” is a gap between a wall surface that rotates at a high speed and another wall surface that exists near the outer periphery of the wall surface. It means the technology to disperse.
  • the method for producing a silver nanowire ink of the present invention comprises a step of synthesizing a silver nanowire, In the tubular channel having a filter on the channel wall surface, the silver nanowires are introduced along with the flow of the liquid medium, and a part of the inflowed silver nanowires is passed through the filter together with a part of the liquid medium to form the tubular channel.
  • the method for producing a transparent conductive film of the present invention comprises a step of synthesizing silver nanowires, In the tubular channel having a filter on the channel wall surface, the silver nanowires are introduced along with the flow of the liquid medium, and a part of the inflowed silver nanowires is passed through the filter together with a part of the liquid medium to form the tubular channel.
  • a step of subjecting the dispersion liquid in which the silver nanowires recovered by the cross-flow filtration step are dispersed in a liquid medium to a further dispersion treatment by a thin film swirling method It is characterized by including the step of applying the silver nanowire in the form of ink, which has been further subjected to the dispersion treatment by the thin film turning method, on the transparent substrate.
  • the anisotropy of the sheet resistance of a transparent conductive film can be reduced, and the low haze and low sheet resistance of a transparent conductive film can be made compatible, a silver nanowire, a silver nanowire ink, a transparent conductive film. And, it is possible to reduce the anisotropy of the sheet resistance of the transparent conductive film and to achieve both low haze and low sheet resistance of the transparent conductive film, a silver nanowire, a silver nanowire ink, and a method for producing a transparent conductive film. Can be provided.
  • FIG. 6 is a diagram showing the relationship between the ratio of the number of silver nanowires having a length of less than 10 ⁇ m and the ratio RTD / RMD as a result of Examples. It is a figure which shows the relationship between the number ratio whose length of a silver nanowire is 10 micrometers or more and less than 25 micrometers, and ratio RTD / RMD as a result of an Example. It is a figure which shows the relationship between the ratio of the number of silver nanowires whose length is 25 ⁇ m or more, and the ratio RTD / RMD as a result of an example.
  • the aggregate of silver nanowires according to one embodiment of the present invention is an aggregate of silver nanowires having an average diameter of 50 nm or less.
  • the silver nanowires are preferably as thin and long as possible.
  • the average diameter of silver nanowires is preferably 40 nm or less, and more preferably 30 nm or less.
  • the number of silver nanowires in the aggregate is 15 to 40% when the length is less than 10 ⁇ m, 30 to 74% when the length is 10 ⁇ m or more and less than 25 ⁇ m, and 11 when the length is 25 ⁇ m or more. It is distributed at ⁇ 30%.
  • the function and effect when the aggregate of silver nanowires of the present embodiment is used for the transparent conductive film will be described.
  • the number of silver nanowires having a length of less than 10 ⁇ m is less than 15%, the number of links in the width direction of the transparent conductive film is reduced and the RTD is increased, so that the ratio RTD / RMD is increased and the sheet resistance is increased. Will end up.
  • the number of silver nanowires having a length of less than 10 ⁇ m exceeds 40%, the haze value and the sheet resistance increase.
  • the silver nanowires having a length of 25 ⁇ m or more have a role of increasing longitudinal links in the transparent conductive film and reducing sheet resistance. Therefore, if the number of silver nanowires having a length of 25 ⁇ m or more is less than 11%, the sheet resistance increases.
  • the RMD becomes low and the number of links in the width direction decreases, so that the anisotropy of the sheet resistance of the transparent conductive film increases. Will end up.
  • the reason why the number of particles having a size of 10 ⁇ m or more and less than 25 ⁇ m is set to 30 to 74% is that the number ratio of an intermediate length is also necessary to reduce the anisotropy of sheet resistance.
  • the number of the silver nanowires in the aggregate is 26 to 35% in the number of less than 10 ⁇ m, 45 to 63% in the number of 10 ⁇ m to less than 25 ⁇ m, and the number of 11 to 25 ⁇ m in the length.
  • the distribution is preferably 20%.
  • the widthwise links of the transparent conductive film can be increased and the anisotropy of the sheet resistance of the transparent conductive film can be reduced. Further, by setting the number of silver nanowires having a length of less than 10 ⁇ m to 35% or less, the haze value and the sheet resistance can be reduced. Further, when the number of silver nanowires having a length of 25 ⁇ m or more is less than 11%, the sheet resistance increases.
  • the number of silver nanowires having a length of 25 ⁇ m or more By setting the number of silver nanowires having a length of 25 ⁇ m or more to 20% or more, it is possible to prevent the silver nanowires from being oriented in the longitudinal direction of the transparent conductive film, and to suppress the anisotropy of the sheet resistance of the transparent conductive film. This is because it can be reduced.
  • the reason why the number of particles having a size of 10 ⁇ m or more and less than 25 ⁇ m is 45 to 63% is that the ratio of the number of intermediate lengths is also necessary for reducing the anisotropy of sheet resistance.
  • the average length of the silver nanowires a value obtained by averaging the lengths of the individual silver nanowires present on the above-described microscope image is defined as the average length L M.
  • the total number of wires to be measured is set to 300 or more.
  • the average length of the silver nanowires is preferably 10 ⁇ m or more. This is because it is preferable that the shape is as thin and long as possible from the viewpoint of forming a transparent conductive film having excellent conductivity and visibility.
  • the average aspect ratio A M can be calculated by substituting the average diameter D M and the average length L M into the following (Formula 1).
  • both D M and L M substituted in (Equation 1) are values expressed in units of nm.
  • a M L M / D M
  • the silver nanowires aggregate of the present invention, average aspect ratio A M is preferably 400 or more 875 or less, more preferably 500 to 850 or less.
  • the average aspect ratio A M is more preferably 550 or more 800 or less.
  • the aggregate of silver nanowires may be aggregated, for example, in a state of being dispersed in a liquid medium, and may be aggregated in the state of, for example, an ink. It may be applied thinly.
  • a silver nanowire ink in which a predetermined mass% of silver nanowires are dispersed in a water solvent or alcohol may be used.
  • the aggregate of silver nanowires may not be dispersed in the liquid medium.
  • the silver nanowire ink of the present embodiment is one in which the aggregate of the silver nanowires of the above embodiment is dispersed in a liquid medium. Since the aggregate of silver nanowires has already been described, the description is omitted.
  • the silver nanowire ink of the present embodiment it is desirable to use a water solvent or a mixed solvent of water and alcohol as a medium forming the liquid medium of the silver nanowire ink.
  • the alcohol used as the solvent one having a solubility parameter (SP value) of 10 or more is preferable.
  • SP value solubility parameter
  • low boiling point alcohols such as methanol, ethanol, 2-propanol (isopropyl alcohol), 1-butanol and the like can be preferably used.
  • the SP value is assumed to be 23.4 for water, 14.5 for methanol, 12.7 for ethanol, 11.5 for 2-propanol, and 11.4 for 1-butanol.
  • the SP value described here is a value defined by the regular solution theory introduced by Hildebrand.
  • the alcohol content in the silver nanowire ink is preferably in the range of 1.0 to 30.0% by mass.
  • the solvent used for the silver nanowire ink of the present embodiment may be alcohol, and the alcohol used may have a solubility parameter (SP value) of 10 or more in polarity as exemplified above. ..
  • a viscosity increasing substance is added to appropriately adjust the viscosity. This is because it is suitable for use in coating a transparent conductive film.
  • the viscosity of the silver nanowire ink at 25 ° C. can be set in the range of 1 to 40 mPa ⁇ s, for example.
  • As the viscosity value a value when the shear rate is 604.2 (1 / s) can be adopted.
  • thickening substances suitable for viscosity adjustment include water-soluble cellulose ethers such as HPMC (hydroxypropylmethylcellulose) and HEMC (hydroxyethylmethylcellulose).
  • the weight average molecular weight of HPMC used may be in the range of 100,000 to 2,000,000, and the weight average molecular weight of HEMC may be in the range of 100,000 to 2,000,000. These weight average molecular weights can be confirmed by, for example, the GPC-MALS method.
  • the thickening substance may be used in combination of two or more kinds. When one or two types of HPMC and HEMC are used, the total content of HPMC and HEMC in the ink, including those remaining as gel particles, is, for example, 0.01 to 2.0% by mass. can do.
  • a binder component can be contained in the silver nanowire ink, if necessary. It functions as a binder without impairing the dispersibility of the silver nanowires and is excellent in conductivity, light transmission, and adhesion, and for example, contains at least one of a water-soluble acrylic-urethane copolymer resin and a water-soluble urethane resin. You can The total content of the water-soluble acrylic-urethane copolymer resin and the water-soluble urethane resin (mass ratio to the total mass of the ink including silver nanowires) in the silver nanowire ink is in the range of 0.01 to 2.00% by mass. Preferably.
  • a binder containing a water-soluble acrylic-urethane copolymer resin as a component for example, Alberdingk Boley, Inc.
  • a binder containing a water-soluble acrylic-urethane copolymer resin as a component for example, Alberdingk Boley, Inc.
  • examples thereof include “UC90” manufactured by ADEKA, “ADEKA BON TITER HUX-401” manufactured by ADEKA Co., Ltd., “NeoPac TM E-125” manufactured by DSM Coating Resins, LLC.
  • urethane resin colloid or urethane resin dispersion As the binder containing a water-soluble urethane resin as a component, it is preferable to apply urethane resin colloid or urethane resin dispersion.
  • urethane resin colloid or urethane resin dispersion For example, Dai-ichi Kogyo Seiyaku Super-Flex 130, Super-Flex 150HS, Super-Flex 170, Super-Flex 210, Super-Flex 300, Super-Flex 500M, Super-Flex 420, Super- Perflex 820, Superflex E-2000, Superflex R-5002, DIC made Hydran AP-30, Hydran WLS-213, Bondic 1980NE, Hydran WLS-602, Hydran WLS-615, ADEKA made Adekabon Titer HUX-561S, Adekabon Titer HUX-350, Adekabon Titer HUX-282, Adekabon Titer HUX-830, Ad
  • the content of silver nanowires in the silver nanowire ink is in the range of 0.02 to 5.00 mass% in the mass ratio of metallic silver in the total mass of the silver nanowire ink.
  • the content of silver nanowires in the silver nanowire ink is in the range of 0.02 to 5.00 mass% in the mass ratio of metallic silver in the total mass of the silver nanowire ink.
  • the number of silver nanowires having a length of less than 10 ⁇ m is 15 to 40%, the number of silver nanowires having a length of 10 ⁇ m or more and less than 25 ⁇ m is 30 to 74%, and the number of 25 ⁇ m or more.
  • the distribution of 11 to 30% reduces the anisotropy of the sheet resistance of the transparent conductive film and reduces the anisotropy of the transparent conductive film for the same reason as described above in the embodiment of the aggregate of silver nanowires. It is possible to achieve both low haze and low sheet resistance.
  • the length of silver nanowires in the silver nanowire ink is 26-35% for numbers less than 10 ⁇ m, 45-63% for numbers 10 ⁇ m or more and less than 25 ⁇ m, and 11-20% for numbers 25 ⁇ m or more.
  • the anisotropy of the sheet resistance of the transparent conductive film is further reduced, and the low haze and the low sheet resistance of the transparent conductive film are reduced. This is because both can be made compatible.
  • the transparent conductive film of this embodiment has the aggregate of the silver nanowires of the above embodiment on a transparent substrate. Since the aggregate of silver nanowires is the same as that described in the above embodiment, description thereof will be omitted.
  • the transparent substrate can be, for example, a film of glass, PET (polyethylene terephthalate), PC (polycarbonate), COP (cycloolefin polymer), or the like.
  • a transparent conductive film is patterned by a method such as laser etching or a combination of resist and wet development, a transparent conductive circuit can be obtained.
  • the number of silver nanowires in the aggregate of silver nanowires on the transparent substrate is 15 to 40% when the length is less than 10 ⁇ m, and 30 to 74% when the number is 10 ⁇ m or more and less than 25 ⁇ m. Since the number of particles having a size of 25 ⁇ m or more is distributed at 11 to 30%, the anisotropy of the sheet resistance of the transparent conductive film is reduced for the same reason as already described in the embodiment of the aggregate of silver nanowires, and It is possible to achieve both low haze and low sheet resistance of the transparent conductive film.
  • the length of the silver nanowires in the aggregate of silver nanowires on the transparent substrate is 26 to 35% when the number is less than 10 ⁇ m and 45 to 63% when the number is from 10 ⁇ m to less than 25 ⁇ m. It is preferable that the number of particles having a size of 25 ⁇ m or more is distributed at 11 to 20%.
  • the anisotropy of the sheet resistance of the transparent conductive film is further reduced, and the low haze and the low sheet resistance of the transparent conductive film are reduced. This is because both can be made compatible.
  • Method for producing aggregate of silver nanowires (method for producing silver nanowire ink)>
  • two types of solutions are prepared.
  • solution A the solution stored in the reaction container will be described.
  • This solution is called "solution A”.
  • Alcohol solvent a method in which a silver-containing liquid is added to an alcohol solvent in which an organic protective agent is dissolved and silver is reduced and deposited in a wire shape in the alcohol solvent by utilizing the reducing power of the alcohol is applied. can do.
  • the type of alcohol one having an appropriate reducing power for silver and capable of depositing metallic silver in the form of a wire is suitably selected.
  • polyols represented by ethylene glycol are considered to be relatively suitable for producing silver nanowires, but future studies will identify many applicable alcohols.
  • an alcohol solvent composed of one or more of ethylene glycol, propylene glycol (1,2-propanediol), 1,3-propanediol, 1,3 butanediol, 1,4-butanediol and glycerin, Thin and long silver nanowires can be synthesized with industrially practical yields. These alcohols may be used alone or in combination of two or more.
  • chloride In order to reduce and precipitate metallic silver in the form of a wire in an alcohol solvent, for example, the presence of chloride ions having an action of giving anisotropy to the growth direction of precipitation is effective. It is considered that chloride ions have the effect of rapidly etching a specific crystal plane of nucleated metallic silver to promote the generation of multiple twins, thereby increasing the abundance ratio of the nuclei forming a wire.
  • chloride ion source various chloride ion sources are applicable as long as they are chlorides that are soluble in alcohol as a solvent.
  • An organic chlorine compound TBAC; etc. tetrabutylammonium chloride (CH 3 CH 2 CH 2 CH 2) 4 NCl) also of interest.
  • bromide ions are also known to have an action of giving anisotropy to the precipitation growth direction of metallic silver.
  • it is extremely effective to allow bromide ions to be present in the alcohol solvent in addition to the above chloride ions, in order to obtain thin and long silver nanowires.
  • the bromide ion source various kinds of bromide ion sources can be applied as long as they are bromide soluble in alcohol as a solvent.
  • An organic bromine compound CTAB cetyltrimethylammonium bromide; (C 16 H 33) N (CH 3) 3 Br) , etc. is also of interest.
  • the amount of bromide added with respect to the total amount of the alcohol solvent used is preferably in the range of 0.000001 (1 ⁇ 10 ⁇ 6 ) to 0.001 (1 ⁇ 10 ⁇ 3 ) mol per 1 L of the solvent. More preferably, it is in the range of 0.000000 (5 ⁇ 10 ⁇ 6 ) to 0.001 (1 ⁇ 10 ⁇ 3 ) mol.
  • a silver nanowire having a large aspect ratio can be effectively synthesized by dissolving an aluminum salt and an alkali metal hydroxide at a predetermined ratio in a solvent for depositing silver. It is speculated that aluminum ions may have a function of activating the crystal plane for silver to grow in a wire shape and a function of improving the reduction rate. It is thought to be demonstrated below. The presence of Al is confirmed in the silver nanowire synthesized in the solvent containing the aluminum salt.
  • metal nanowires containing Al in an amount of 100 to 1000 ppm have high diameter uniformity and tend to cause local bending or bending even though they are thin and long.
  • Such a silver nanowire is excellent in handleability in an operation of forming an ink or an operation of coating a substrate.
  • a silver nanowire containing 150 ppm or more of Al is more preferable, and a silver nanowire having 200 to 800 ppm is more preferable.
  • the molar ratio of the total amount of aluminum of the aluminum salt to be dissolved in the solvent and the total amount of hydroxide ions of the alkali metal hydroxide is referred to as “Al / OH”, and hereinafter, this molar ratio is simply referred to as “Al / OH”.
  • Al / OH the total amount of aluminum of the aluminum salt to be dissolved in the solvent and the total amount of hydroxide ions of the alkali metal hydroxide
  • Al / OH the molar ratio of the total amount of aluminum of the aluminum salt to be dissolved in the solvent and the total amount of hydroxide ions of the alkali metal hydroxide
  • Al / OH the molar ratio of the total amount of aluminum of the aluminum salt to be dissolved in the solvent and the total amount of hydroxide ions of the alkali metal hydroxide
  • OH molar ratio Sometimes referred to as "OH molar ratio”.
  • the Al / OH molar ratio is 0.01 to 0.40
  • the Al / OH molar ratio By setting the Al / OH molar ratio to 0.40 or less, it is possible to prevent the reducing power of the alcohol solvent from decreasing and reduce the silver ion or silver complex dissolved in the solvent to metallic silver. it can.
  • the Al / OH molar ratio is 0.01 or more, it becomes easy to synthesize a long wire having a large average aspect ratio.
  • the Al / OH molar ratio is in the proper range, if the amount of alkali hydroxide to silver is too large, a large amount of a compound mainly composed of silver oxide is formed, which makes wire synthesis difficult, which is not preferable. There are cases.
  • the molar ratio of the total hydroxide ion of the alkali metal hydroxide to be dissolved in the solvent and the total Ag of the silver compound is expressed as "OH / Ag", and hereinafter, this molar ratio is simply referred to as "OH / Ag”.
  • OH / Ag the molar ratio of the total hydroxide ion of the alkali metal hydroxide to be dissolved in the solvent and the total Ag of the silver compound.
  • Ag molar ratio Sometimes referred to as "Ag molar ratio”.
  • alkali metal hydroxide industrially, for example, it is desirable to use one or more of lithium hydroxide, sodium hydroxide and potassium hydroxide.
  • Aluminum nitrate and aluminum chloride are applicable as the aluminum salt.
  • Aluminum nitrate may be added as aluminum nitrate nonahydrate Al (NO 3) 3 ⁇ 9H 2 O.
  • Organic protective agent When synthesizing silver nanowires by the alcohol solvent reduction method, the reduction reaction proceeds in the presence of an organic protective agent.
  • the organic protective agent present in the solvent has a function of covering the surface of the silver nanowire deposited in the reduction reaction and suppressing coarse growth. Due to this action, it becomes possible to obtain a deposited shape as a nanowire.
  • the organic protective agent attached to the surface of the synthesized silver nanowire has the functions of ensuring the dispersibility of the wire in the liquid and preventing the oxidation of silver.
  • PVP polyvinylpyrrolidone
  • a copolymer having a polymerization composition of vinylpyrrolidone and another monomer are known.
  • the silver nanowire coated with PVP has good dispersibility in water.
  • a mixed solvent of water and alcohol it is preferable to use a mixed solvent of water and alcohol as the liquid medium.
  • a mixed solvent containing alcohol it is difficult to obtain the dispersion stability of the silver nanowire coated with PVP. That is, when the silver nanowires are made into ink, they tend to precipitate. In that case, it is advantageous to apply a silver nanowire on the surface of which a copolymer having a polymerization composition of vinylpyrrolidone and another monomer is attached.
  • Copolymers of this type have a moderately hydrophilic vinylpyrrolidone structural unit and thus exhibit moderate hydrophilicity and tend to be more hydrophobic than PVP. Therefore, it is presumed that excellent dispersion stability is exhibited in a mixed solvent of water and alcohol.
  • the alcohol it is preferable to use a monohydric alcohol having 1 to 4 carbon atoms. However, it is not limited to these.
  • the weight average molecular weight of the polymer used as the organic protective agent is preferably 30,000 to 3,000,000.
  • the “other monomer” examples include cationic monomers such as diallyldimethylammonium salt (a specific example of the salt includes nitrate), vinyl esters such as vinyl acetate, diethylaminoethyl methacrylate, acrylic acid, ethyl. (Meth) acrylic compounds such as acrylate, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 4-hydroxybutyl acrylate, N-methylmaleimide, N-ethylmaleimide, N-propylmaleimide, N-tert-butylmaleimide, etc.
  • cationic monomers such as diallyldimethylammonium salt (a specific example of the salt includes nitrate)
  • vinyl esters such as vinyl acetate, diethylaminoethyl methacrylate, acrylic acid, ethyl.
  • acrylic compounds such as acrylate, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 4-
  • Copolymers of vinylpyrrolidone and a diallyldimethylammonium salt monomer can be mentioned as a particularly advantageous copolymer for obtaining the excellent dispersion stability.
  • the polymerization composition of the copolymer is preferably 0.1 to 10% by mass of the other monomer and the balance vinylpyrrolidone. If the content of other monomers is less than 0.1% by mass, the hydrophilicity is too high, dispersibility in a mixed solvent of water and alcohol is poor, and if it is more than 10% by mass, the hydrophobicity is too strong and water and alcohol are contained.
  • Dispersibility in a mixed solvent of and becomes poor As described above, the silver nanowire coated with the copolymer having a composition of 0.1 to 10% by mass of other monomers and the balance of vinylpyrrolidone as the balance is superior in dispersion stability to PVP in a liquid medium of a mixture of water and alcohol. Shows sex. Then, when a solvent substance having a small polarity is added to the liquid medium exhibiting the excellent dispersibility, the silver nanowires rapidly aggregate.
  • this property is utilized, for example, by adding a liquid with a small polarity such as acetone, toluene, hexane, or kerosene to the alcohol solvent after synthesizing the silver nanowires to lower the polarity of the solvent, the agglomerates quickly, so that cleaning / It has excellent industrial properties, such as extremely simple recovery. It was also confirmed that when water, a mixed solvent of water and alcohol, or a solvent having a large polarity such as alcohol was added to this aggregated product, good dispersibility was exhibited.
  • a liquid with a small polarity such as acetone, toluene, hexane, or kerosene
  • Silver compound As a silver source for reducing and depositing the silver nanowires, a silver compound soluble in the solvent of the solution A and the solvent of the solution B is used.
  • silver nitrate, silver acetate, silver oxide, silver chloride and the like can be mentioned, but silver nitrate (AgNO 3 ) is easy to use in view of solubility in a solvent and cost.
  • solvent for silver-containing liquid As the solvent of the solution B, any of an alcohol solvent, a mixed solvent of alcohol and water, or a water solvent can be adopted.
  • the alcohol used for this solvent is preferably composed of one or more alcohols including the same kind as the alcohol used for the solvent of the solution A.
  • the silver concentration of the solution B (silver-containing solution) added to the solution A the higher the silver concentration of the solution B (silver-containing solution) added to the solution A, the more the total amount of the solution B can be reduced. It is preferable to set the silver concentration to 3.5 mol / L or more because the total amount of the silver-containing liquid can be significantly reduced as compared with the method generally used conventionally. Further, the higher the silver concentration of the solution B (silver-containing solution) added to the solution A, the more advantageous it is that the temperature change when the solution B is put into the solution A is small. It is more effective to set the silver concentration to 3.9 mol / L or more. When it is desired to significantly reduce the total amount of the silver-containing liquid, the silver concentration is preferably 5.0 mol / L or more, more preferably 10.0 mol / L or more.
  • a solution containing silver nitrate is heated to about 40 ° C. and stirred for about 1 hour to obtain a silver-containing solution having a silver concentration of 3.5 to 4.5 mol / L. be able to.
  • coloring is observed in the silver-containing liquid during the dissolution process.
  • UV-Vis spectroscopy Ultraviolet-Visible Absorption Spectroscopy
  • a solvent in which the mass ratio of water to the total amount of alcohol and water is 5.0% or more. is preferably used.
  • water functions as a “reduction inhibitor”.
  • the solubility is further increased by using a solvent containing 100% water (water solvent). For example, by raising the temperature of the water solvent to about 80 ° C. to dissolve silver nitrate, a silver-containing solution having a silver concentration of about 32.0 mol / L can be obtained.
  • the molar ratio Al / OH between the total amount of Al of the aluminum salt to be dissolved in the solvent and the total amount of hydroxide ions of the alkali metal hydroxide can be set to, for example, 0.01 to 0.40. Further, the molar ratio OH / Ag of the total hydroxide ion of the alkali metal hydroxide to be dissolved in the solvent and the total Ag amount of the silver compound may be, for example, 0.005 to 0.50.
  • the holding temperature for advancing the reduction and precipitation reaction of silver can be set within the range of preferably 60 ° C. or higher and 90 ° C. or lower, more preferably 85 ° C. or lower and the boiling point of the solvent or lower.
  • the boiling point is the boiling point at the pressure of the gas phase space where the liquid surface of the solvent in the reaction vessel contacts.
  • the temperature may be lower than the boiling point of the alcohol having the lowest boiling point.
  • the boiling point of propylene glycol is about 188 ° C, preferably the reaction is allowed to proceed at 60 to 95 ° C, more preferably 80 to 85 ° C.
  • each substance other than the silver compound is dissolved in an alcohol solvent, and after the temperature of the solvent (“solution A”) reaches a predetermined reaction temperature, the silver compound is added to the solution A. It is desirable to add.
  • the silver compound can be added, for example, by previously dissolving it in an alcohol solvent of the same type as the solvent in another container and mixing the silver-containing solution (“solution B”) in the solution A.
  • the solution B before being mixed with the solution A is preferably at a temperature near room temperature (for example, 15 to 40 ° C.).
  • the temperature of the solution B is too low, it takes time to dissolve the silver compound, and if it is too high, the reducing power of the alcohol solvent in the solution B easily causes the reduction reaction of silver in the stage before mixing with the solution A.
  • a silver compound such as silver nitrate which is easily dissolved in an alcohol solvent may be added to the solution A as a solid.
  • a method of adding the entire amount at once or a method of adding intermittently or continuously within a certain time can be adopted.
  • the liquid is continuously stirred while the reaction is in progress. Further, the atmosphere of the gas phase with which the liquid surface of the solution A is in contact during the progress of the reaction can be air or nitrogen.
  • a method may be employed in which after the silver precipitation reaction is completed, the slurry containing silver nanowires is subjected to solid-liquid separation using a means such as centrifugation or decantation to recover the solid content. Decantation may be carried out for about 1 to 2 weeks while still standing, or at least one or more polar solvents such as acetone, toluene, hexane, kerosene, and xylene may be added to the slurry to set the sedimentation rate. May be accelerated and concentrated.
  • polar solvents such as acetone, toluene, hexane, kerosene, and xylene
  • the slurry after the reaction may be directly applied to the centrifuge to concentrate the silver nanowires, or it may be diluted with a solvent or water having a lower viscosity and then applied to the centrifuge. In this embodiment, the supernatant can be removed after concentration.
  • the silver nanowires are redispersed, and further solid-liquid separation is performed using a means such as centrifugation or decantation to recover the solid content. It is preferable to repeat the redispersion and concentration steps (washing). ⁇ Washing and removal of supernatant>
  • the washing is performed by, for example, dispersing the concentrate in pure water or a predetermined liquid medium (water containing a copolymer of PVP or vinylpyrrolidone and another monomer), and performing solid-liquid separation operations such as centrifugation and decantation.
  • the operation can be performed by a method of repeating the operation.
  • the concentrate after washing contains useful long silver nanowires as well as impurities such as granular products and short wire-like products. Therefore, it is preferable to remove the supernatant. Therefore, the concentrate can be obtained by repeating the operations of dispersing pure water, adding a solvent of small polarity such as toluene or acetone, allowing to stand, and removing the supernatant.
  • the concentrate after the washing can be subjected to a redispersion treatment.
  • a redispersion treatment an aqueous solvent in which PVP (polyvinylpyrrolidone) is dissolved in pure water is used, and the aqueous solvent and the concentrate after the washing are mixed to obtain a predetermined metal silver concentration (silver nanowire and impurity silver nanowire).
  • a silver nanowire dispersion liquid having a particle-containing liquid silver concentration) is prepared.
  • the obtained silver nanowire dispersion liquid is diluted with pure water so as to have a predetermined silver concentration to obtain a silver nanowire dispersion liquid. This dispersion is referred to as a "crossflow original liquid".
  • FIG. 1 is a cross-sectional view schematically showing an example of the cross-sectional structure of a flow path portion using a porous ceramic filter.
  • FIG. 2 is a diagram schematically showing a purification image by cross-flow filtration using a porous ceramic filter.
  • FIG. 3 is a diagram schematically showing an example of a conduit configuration for purifying silver nanowires.
  • an upstream flow passage pipe 2 is connected to one end of a porous ceramic pipe 1, and a downstream flow passage pipe 3 is connected to the other end.
  • the silver nanowires flowing together with the liquid medium in the direction of the arrow A in the upstream flow tube 2 are introduced into the porous ceramic tube 1.
  • the ceramic of the porous ceramic tube 1 has a porous structure having an average pore diameter of 1.0 ⁇ m or more, preferably more than 2.0 ⁇ m, and more preferably more than 5.0 ⁇ m, and has voids connected in the thickness direction. Material transfer is possible through. That is, the tube wall of the porous ceramic tube 1 constitutes a "porous ceramic filter" that allows substances to pass therethrough.
  • the portion of the “tubular channel having a porous ceramic filter on the channel wall surface” that functions as a filter is indicated by reference numeral 10 in the figure.
  • the silver nanowires proceed in the direction of the arrow B along with the flow of the liquid medium, but some of the flowing silver nanowires together with some of the liquid medium form the tube of the porous ceramic tube 1. After passing through the wall, it is discharged to the outside of the tubular flow channel 10 as shown by an arrow C, and cross-flow filtration is realized.
  • the shortest wire out of the silver nanowires flowing in the tubular channel 10 is preferentially ejected to the outside, so that the tubular channel 10 is not ejected to the outside in the direction of the arrow D.
  • the abundance of long wires is improved.
  • the silver nanowires are recovered to produce silver nanowires with improved length distribution uniformity (ie, longer average length than the silver nanowires before reaching the tubular channel with the ceramic filter). ..
  • Fig. 2 schematically shows the image of purification by cross-flow filtration using a porous ceramic filter. Not only particulate impurities but also relatively short nanowires are discharged to the outside through the pores (actually continuous voids) of the porous ceramic filter together with some liquid medium. The probability that a wire whose length is significantly longer than the hole diameter will be discharged through the hole to the outside is extremely low. The liquid discharged to the outside is called "filtrate".
  • FIG. 3 schematically shows an example of a conduit structure for purifying silver nanowires.
  • the original cross-flow solution before purification is prepared in a tank, and flows into a tubular flow path having a porous ceramic filter on the wall surface of the flow path by the power of the pump, where cross-flow filtration is performed.
  • the short wire is discharged as a filtrate to the outside of the pipe, and the silver nanowire that has flowed through the flow path without being discharged to the outside of the tubular flow path is collected.
  • the “circulation method” in which the silver nanowires to be recovered are returned to the original tank is illustrated, but they may be recovered in another tank for batch processing.
  • the liquid feed pump can be used without particular limitation as long as it can feed a liquid containing silver nanowires, but wire breakage (breakage, breakage, entanglement, etc.) is unlikely to occur, and liquid feed is also possible at relatively high pressure. It is preferable to use a pump that can. Examples include hose pumps, tube pumps, rotary pumps, mohno pumps, screw pumps, piston pumps, syringe pumps, plunger pumps, heart pumps, and the like.
  • the pore diameter of the porous ceramic filter used in the cross-flow filtration is preferably 1.0 to 15.0 ⁇ m, more preferably 1.0 to 10.50, as the average pore diameter determined by the pore distribution measurement by the mercury penetration method. It is 0 ⁇ m, more preferably 2.0 to 8.0 ⁇ m.
  • the average pore diameter here is the median diameter.
  • the pressure of the liquid introduced into the tubular channel having the porous ceramic filter on the channel wall surface can be adjusted, for example, in the range of 0.005 to 0.2 MPa. Further, the flow velocity of the liquid introduced into the tubular channel having the porous ceramic filter on the channel wall surface should be adjusted within the range of, for example, 10 to 10000 mm / sec at the upstream end of the filter (the position corresponding to reference numeral 20 in FIG. 1). Good. In the present invention, since a ceramic filter having a very large pore diameter is adopted, if the purification is performed at a relatively high flow rate, clogging is reduced and good results are easily obtained.
  • the silver nanowire dispersion liquid often contains a salt, a low molecular weight dispersant, a high molecular weight dispersant, or the like through a wire synthesis step and a subsequent treatment step. It is preferable to select, as the liquid medium, a solvent in which one of the substances to be removed is dissolved. Generally, methyl alcohol, ethyl alcohol, 1-propanol, 2-propanol, 1-butanol, water, a mixed solvent thereof or the like can be used.
  • a liquid medium (solvent B) of a different type from the liquid medium (solvent A) of the original silver nanoparticle dispersion liquid is additionally added.
  • solvent B a liquid medium of a different type from the liquid medium (solvent A) of the original silver nanoparticle dispersion liquid
  • Cross-flow filtration removes part of the liquid medium as filtrate, so if you perform cross-flow filtration in the circulation route, the amount of liquid medium in the route will gradually decrease. Therefore, in the continuous operation of cross-flow filtration, it is usually necessary to replenish the circulation medium with the liquid medium. However, it is possible to increase the concentration of silver nanowires in the liquid by making good use of this decrease in the liquid medium. That is, the step of cross-flow filtration can be used as the step of concentrating the silver nanowire dispersion liquid. At that time, the replenishment amount of the liquid medium may be controlled to be smaller than the amount discharged by filtration. A method may be adopted in which the replenishment of the liquid medium is stopped after the cross-flow filtration is performed for a certain period of time.
  • the polymer used during synthesis is adsorbed on the surface of the silver nanowire linear particles.
  • an organic compound of a different type to the polymer used at the time of synthesis into the liquid medium, and by adding a dispersant and a surfactant as necessary. It is also possible to replace the adsorbed substance on the wire surface with the above organic compound.
  • the purification using this cross-flow filtration can be used as a washing step.
  • the silver nanowires are washed by subjecting the slurry after synthesis to solid-liquid separation means such as centrifugation or decantation.
  • solid-liquid separation means such as centrifugation or decantation.
  • decantation the method of concentrating over 2 to 3 weeks while still standing, or adding at least one solvent with small polarity such as acetone, toluene, hexane, kerosene, xylene to the slurry to accelerate the sedimentation rate A method of concentrating by using such a method is adopted.
  • the decantation is preferably performed in a glass container coated with a fluororesin.
  • the fluororesin coating has the effect of preventing hydrophilic nanowires from adhering to the container surface and increasing the yield.
  • centrifugation for example, the slurry after the reaction can be directly applied to a centrifuge to concentrate the silver nanowires. After concentration, remove the supernatant, then add a highly polar solvent such as water or alcohol to redisperse the silver nanowires, and then perform solid-liquid separation using a means such as centrifugation or decantation to recover the solid content. By doing so, the silver nanowires are carefully washed. Purification using the cross-flow filtration according to the present invention also exerts a cleaning effect, so that it becomes possible to reduce the burden in the conventional general cleaning process as described above.
  • the conductivity of the silver nanowire dispersion becomes 10 mS / m or less. Is preferable, and it is more preferable that it is 5 mS / m or less, and further preferable that it is 1 mS / m or less.
  • the silver nanowires used for cross-flow filtration can be controlled to the desired length distribution.
  • short wires are preferentially excluded, and the existence ratio of long wires to be collected can be significantly improved.
  • the method of synthesizing the silver nanowires does not have to be particular, but at present, a method of synthesizing in a wet process is known.
  • the reduction precipitation method shown in US2005 / 0056118 and JP2013-234341A is known.
  • the present applicant disclosed in Japanese Patent Application No. 2014-045754 a method of adding a predetermined amount of aluminum salt to an alcohol solvent as an advantageous method for synthesizing a thin and long silver nanowire.
  • the present applicant has disclosed in Japanese Patent Application No. 2014-036073 as a method for synthesizing a copper nanowire.
  • the silver nanowire in which the amount of the organic protective agent attached has been reduced to a predetermined range by the above cross-flow filtration is subjected to a treatment (concentration) for increasing the concentration of the wire in the liquid, if necessary. It is efficient to perform the concentration treatment by, for example, “cross-flow concentration” using the device after the above-mentioned cross-flow filtration.
  • concentration treatment by, for example, “cross-flow concentration” using the device after the above-mentioned cross-flow filtration.
  • cross-flow concentration in the above-mentioned cross-flow filtration, by stopping the replenishment of the liquid medium, or by circulating for a while with the amount of replenished liquid being less than the discharge amount of the filtrate discharged from the cross-flow filtration filter. Can be implemented.
  • a silver nanowire ink intermediate product in which the silver nanowires in which the amount of organic protective agent attached and the size and shape thereof are adjusted to the above-mentioned appropriate ranges are dispersed in a liquid medium.
  • the amount of the organic protective agent attached can be measured by the following procedure. From the silver nanowire ink intermediate product, an amount of a liquid containing silver nanowires equivalent to 20 mg of silver was collected, and a high speed centrifugal cooling centrifuge CR21N (rotor: R8S, centrifuge tube: 50 mL) manufactured by Hitachi Koki Co., Ltd. was used.
  • Centrifugation was performed at 8000 rpm for 45 minutes, the supernatant was removed, and the product was dried at 120 ° C. for 12 hours to obtain a dried product of silver nanowires.
  • a 15 mg sample of this dried product was subjected to TG-DTA measurement in the atmosphere using STA7200 manufactured by Hitachi High-Tech Science Co., Ltd. The temperature was raised at a rate of 10 ° C / min, and the change in weight from 40 ° C to 700 ° C was measured.
  • a platinum sample pan ( ⁇ 5.2 mm, height 5 mm) was used for the measurement.
  • the weight loss at 150 ° C is regarded as the amount Ws (mass%) of the components of the liquid medium (specifically, water and alcohol having 1 to 4 carbon atoms) remaining in the dried sample, and the temperature is changed from 150 ° C to 600 ° C.
  • the change in weight was defined as the amount Wp (mass%) of the organic protective agent attached to the silver nanowire.
  • the mass ratio P (mass%) of the organic protective agent to the total amount of the organic protective agent and silver was calculated by the following (formula 2).
  • This silver nanowire ink intermediate product can be stored as a dispersion liquid dispersed in a suitable liquid medium according to the purpose.
  • a thickening substance may be added to the silver nanowire ink intermediate product obtained through the above-described cross-flow filtration step.
  • a binder component can be added if necessary.
  • Dispersion processing by the thin film swirl method is a high-speed rotation of the intermediate product of silver nanowire ink pressed against the inner wall surface of the container in a thin film cylindrical shape by centrifugal force, and shear generated by the centrifugal force and the speed difference between the inner wall surface and the container.
  • This is a dispersion method in which silver nanowires are dispersed by applying stress to the silver nanowire ink intermediate product.
  • the silver nanowire ink of the present embodiment is obtained by the dispersion treatment by the thin film turning method.
  • the dispersion treatment by the thin film swirling method includes, for example, a tubular container having a circular cross section, a tubular stirring blade rotatably arranged concentrically with the tubular container in the tubular container, and an injection pipe opened below the stirring blade. It can be carried out using the equipment provided.
  • the stirring blade has an outer peripheral surface facing the inner peripheral surface of the tubular container with a slight gap, and a large number of through holes penetrating the tubular wall of the stirring blade in the thickness direction.
  • the distance between the inner peripheral surface of the tubular container and the outer peripheral surface of the stirring blade is appropriately adjusted depending on the amount of the silver nanowire ink intermediate product to be processed, the desired degree of dispersion, and the like, but is not particularly limited.
  • a mediumless disperser “Zeromill” (registered trademark) series manufactured by Asada Iron Works Co., Ltd.
  • Zeromill registered trademark
  • ⁇ Method of manufacturing transparent conductive film> By the dispersion treatment by the above-mentioned thin film turning method, only long wires can be cut, and the ratio RTD / RMD can be lowered.
  • the silver nanowire ink obtained by the dispersion treatment by the above-mentioned thin film rotation method is used as a coating liquid, and is applied to a PET film, PC, glass or the like which is a transparent substrate by a bar coater method, a die coater method, etc. Is removed by evaporation or the like and dried to obtain a transparent conductive film.
  • this transparent conductive film is patterned by a method such as laser etching or a combination of resist and wet development, a transparent conductive circuit is formed.
  • the silver nanowires are put on the flow of the liquid medium and circulated in the circulation channel having the filter, and filtration (cross flow filtration) is performed by the filter, so that the length is 10 ⁇ m or less.
  • An aggregate of silver nanowires having a small amount of silver nanowires and a wide length distribution can be obtained.
  • the silver nanowires collected by cross-flow filtration are dispersed in a liquid medium, and the dispersion liquid is subjected to a further dispersion treatment by a thin film swirling method to selectively cut the long silver nanowires. it can.
  • the number of silver nanowires having a length of less than 10 ⁇ m is 15 to 40%, the number of silver nanowires having a length of 10 ⁇ m or more and less than 25 ⁇ m is 30 to 74%, the number of silver nanowires having a length of 25 ⁇ m or more is 11 to 30%, and preferably the number of silver nanowires having a length of less than 10 ⁇ m is less than 10 ⁇ m.
  • the length of the silver nanowires in the aggregate of silver nanowires (silver nanowire ink) is 26-35%, the number of 10 ⁇ m or more and less than 25 ⁇ m is 45-63%, and the number of 25 ⁇ m or more is 11-20%. A distribution can be achieved.
  • the above embodiment is merely an example, and the present invention is not limited to the above embodiment.
  • the synthesis of silver nanowires was performed using “solution A” and “solution B”, but the synthesis of silver nanowires can be performed by any known method. Examples of the present invention will be described below, but the present invention is not limited to the following examples.
  • Example 1 (Synthesis of silver nanowires) As an organic protective agent, the following copolymers of vinylpyrrolidone and diallyldimethylammonium nitrate were prepared. Polymerization ratio: vinylpyrrolidone 99% by mass, diallyldimethylammonium nitrate 1% by mass, weight average molecular weight: 75,000 In this Example 1, the above copolymer was used as the organic protective agent. At room temperature, propylene glycol 816.3 g contained propylene glycol solution with a lithium chloride content of 10% by mass 4.838 g, potassium bromide 0.10337 g, lithium hydroxide 0.4024 g, and aluminum nitrate nonahydrate.
  • a solution A was prepared by dissolving 4.994 g of a propylene glycol solution having an amount of 20% by mass and 83.87 g of the powder of the above-mentioned copolymer as an organic protective agent.
  • 67.96 g of silver nitrate was added to a mixed solution of 95.70 g of propylene glycol and 8.00 g of pure water, and the mixture was stirred and dissolved at 35 ° C. to prepare a solution B containing silver. Obtained.
  • the above solution A was placed in a reaction vessel, heated from room temperature to 90 ° C. with stirring at a rotation speed of 175 rpm, and then the total amount of solution B was added into solution A from two addition ports over 1 minute. .. After the addition of the solution B was completed, the stirring state was further maintained and maintained at 90 ° C. for 24 hours. Then, the reaction solution was cooled to room temperature to synthesize silver nanowires.
  • a redispersion treatment was performed using a water solvent in which PVP (polyvinylpyrrolidone) having a weight average molecular weight of 55,000 was dissolved in pure water. That is, an aqueous solvent having a PVP concentration of 0.5% by mass was prepared, and the aqueous solvent and the concentrated product after washing were mixed to obtain a metallic silver concentration (silver concentration in a liquid containing silver nanowires and silver nanoparticles as impurities). ) was 0.8 mass% and the silver nanowire dispersion liquid was prepared. The obtained silver nanowire dispersion liquid was diluted with pure water so that the silver concentration was 0.08% by mass to obtain about 52 kg of silver nanowire dispersion liquid. This dispersion is called a "crossflow original liquid".
  • PVP polyvinylpyrrolidone
  • the cross-flow original liquid subjected to the above-mentioned pretreatment was stored in a tank of an apparatus having a conduit structure shown in FIG. 3 and then subjected to cross-flow filtration by a method of continuously circulating the conduit.
  • nine tubular filters were arranged in parallel, and the liquid was branched into each tubular filter for processing.
  • a tubular filter having a length of 500 mm, a tube wall made of porous ceramics, an outer diameter of 12 mm, and an inner diameter of 9 mm was used as the cross-flow filtration filter.
  • the material of the ceramic was SiC (silicon carbide), and the average pore diameter was 5.9 ⁇ m by the mercury injection method using a mercury porosimeter manufactured by Micromeritics.
  • the detailed conditions for the pore distribution measurement by the mercury porosimetry method are as follows.
  • ⁇ Measuring device Autopore IV9510 type
  • ⁇ Measuring range ⁇ 440-0.003 ⁇ m
  • ⁇ Mercury contact angle 130 ° -Mercury surface tension: 485 dynes / cm
  • Pretreatment 300 °C ⁇ 1h (in air)
  • Measurement sample mass 3.5g
  • 80 points of measurement data were collected in the measurement range of 1 to 100 ⁇ m.
  • the average pore diameter here is the median diameter.
  • the initial PVP concentration of the liquid medium to be circulated (mass ratio of PVP in the water solvent constituting the cross flow source liquid) is 250 ppm. Circulation was performed while replenishing the tank with fresh liquid medium.
  • the above-mentioned 9 tubular filters were installed in parallel in the circulation channel.
  • the flow rate of the liquid introduced per one tubular filter was 13 L / min and circulation was performed.
  • the flow rate of the liquid introduced into the tubular filter was 3495 mm / s.
  • the pressure in the conduit on the inlet side of the tubular filter was 0.025 MPa.
  • the liquid medium to be replenished was a PVP aqueous solution having a PVP concentration (mass ratio of PVP in the water solvent) of 50 ppm.
  • the tank was a tank with a jacket, and cooling water was caused to flow through the jacket to suppress an increase in the liquid temperature during circulation. Further, the pure water to be replenished was cooled and used at a temperature of 10 to 15 ° C. As a result, the liquid temperature during circulation was in the range of 17 to 30 ° C. In this way, cross flow circulation cleaning was performed for 5 hours.
  • the ink composition was 10% by mass of 2-propanol, 0.100% by mass of HPMC, 0.10% by mass of silver nanowires (silver + organic protective agent), and the balance being water.
  • the obtained HPMC-containing silver nanowire ink intermediate product was subjected to the following dispersion treatment to obtain a silver nanowire ink in which an aggregate of silver nanowires was dispersed in a liquid medium for application on a transparent substrate. ..
  • the mill peripheral speed was 24 m / s, and the treatment was performed at 50 g / min.
  • the average diameter and the average length of the silver nanowires contained in the silver nanowire ink obtained by the dispersion treatment were measured. 4 g of the silver nanowire ink was collected and diluted 40 times with pure water.
  • the silver nanowire ink diluted with pure water was treated with a centrifuge (BECKMAN COULTER X-30R) at 3000 rpm for 20 minutes, the supernatant was removed, and the solid content of silver nanowire was adjusted to 0.05% by mass. So that it was dispersed in methanol.
  • a methanol dispersion of silver nanowires was placed on a grid with a support film for a transmission electron microscope (Cu 150 mesh, manufactured by JEOL Ltd.), and an acceleration voltage of 100 kV was obtained with a transmission electron microscope (JEM-1011, produced by JEOL Ltd.).
  • a bright field image was observed at a magnification of 40,000 times to collect an observation image, and the original image collected to accurately measure the diameter was magnified to a size of 2 times, and then the software (MoticImage Plus 2.1S was used. ) was used to determine the diameter of a total of 300 or more different silver nanowires, and the average diameter was measured according to the above definition.
  • the sample solution is placed on a silicon substrate observation table of SEM thickness of 200 ⁇ m, 3 mm square, and water is volatilized on the observation table.
  • the average length and the length distribution were measured according to the above definition using software (Doctor Canvas) for all the wires whose total lengths could be confirmed in the visual fields. In the measurement, the total number of wires to be measured was set to 300 or more. Further, the average aspect ratio was obtained by substituting the values of the average diameter and the average length into the above (formula 1).
  • the resistance x haze was measured using a bar coater.
  • a PET film base material (Cosmoshine (registered trademark) A4100 manufactured by Toyobo Co., Ltd.) having a thickness of 100 ⁇ m and dimensions of 150 mm ⁇ 200 mm was prepared.
  • the above silver nanowire ink was adjusted to 0.09% and applied using a bar coater coater (PI-1210 manufactured by Tester Sangyo Co., Ltd.).
  • the bar coater's count is 3, 4, 5, 6, 7, 8, 9, 10, 12, 14 and 10 types of different thickness are prepared. It was applied to form a coating film. These were dried in air at 120 ° C. for 1 minute to obtain a transparent conductive film.
  • the ratio RTD / RMD was measured using a die coater.
  • a PET film substrate (Cosmoshine (registered trademark) A4100 manufactured by Toyobo Co., Ltd.) having a thickness of 100 ⁇ m and dimensions of 150 mm ⁇ 200 mm was prepared.
  • the silver nanowire ink described above was applied to the bare surface of the PET film base material using a die coater coating machine (manufactured by Daimonsha Co., Ltd., New Desk Die S, roll-to-roll type) to form a coating film having a width of 100 mm. Formed.
  • the coating conditions were: wet thickness: 11 ⁇ m, gap: 21 ⁇ m, speed: 20 m / min.
  • the drying part installed before the winding roll, it was dried at a drying temperature of 120 ° C. and a residence time in the drying part of 20 seconds to obtain a transparent conductive film.
  • the haze value of the base material + the transparent conductive film is the haze value (%) of the object formed of the base material film and the transparent conductive film formed thereon, and the "haze value of the base material only” is transparent. It is a haze value (%) of the base material film before forming a conductive film.
  • a transparent conductive film produced by using the above die coater was used as a longitudinal direction (MD direction) measurement sample, and a strip-shaped sample (width 10 mm in the direction perpendicular to the longitudinal direction (TD direction) and length 150 mm in the MD direction (
  • MD direction longitudinal direction
  • TD resistance sample a strip-shaped sample having a width of 10 mm in the MD direction and a length of 150 mm in the TD direction
  • both end portions in the longitudinal direction of the MD direction resistance sample were respectively made of aluminum plate electrodes from the upper surface and the lower surface to the upper surface side and the lower surface side.
  • the two aluminum plate electrodes are vertically overlapped with each other, and the aluminum plate is clipped so that the longitudinal direction of the MD resistance sample and the longitudinal direction of the aluminum plate electrode are orthogonal to each other on a plane orthogonal to the vertical direction.
  • the distance between the aluminum plate electrodes sandwiched between the longitudinal ends of the electrodes and measured in the longitudinal direction of the MD resistance sample (a plan view of the aluminum plate electrode at one end of the MD resistance sample in the longitudinal direction).
  • the distance from the long side closer to the aluminum plate electrode at the one end in the longitudinal direction of the MD direction resistance sample is 100 mm.
  • four aluminum plate electrodes having a width of 30 mm, a length of 20 mm, and a thickness of 3 mm are prepared, and both end portions in the longitudinal direction of the TD direction resistance sample are respectively made of aluminum plate electrodes from the upper surface and the lower surface to the upper surface side and the lower surface side.
  • the two aluminum plate electrodes are vertically overlapped, and the aluminum plate is clipped so that the longitudinal direction of the TD direction resistance sample and the longitudinal direction of the aluminum plate electrode are orthogonal to each other in a plane orthogonal to the vertical direction.
  • the distance between the aluminum plate electrodes when sandwiched between the longitudinal ends of the electrodes and measured in the longitudinal direction of the TD-direction resistance sample (a plan view of the aluminum plate electrode at one end of the TD-direction resistance sample in the longitudinal direction).
  • a plan view of the aluminum plate electrode at one end of the TD-direction resistance sample in the longitudinal direction Of the two long sides of one of the two long sides closer to the aluminum plate electrode at the other end in the longitudinal direction of the TD direction resistance sample and the other side in the longitudinal direction of the TD direction resistance sample.
  • the distance from the long side closer to the aluminum plate electrode at the one end in the longitudinal direction of the TD direction resistance sample is 100 mm.
  • the resistance value between the aluminum plate electrodes was measured by a resistance meter RM3544 manufactured by HIOKI using a clip-type lead L2101 as a probe.
  • the ratio rTD / rMD of the resistance value rTD ( ⁇ ) of the TD direction resistance sample to the resistance value rMD ( ⁇ ) of the MD direction resistance sample was used as the ratio RTD / RMD.
  • Example 2 An experiment was conducted under the same conditions as in Example 1 except that the tubular filter used as the cross-flow filtration filter in the cross-flow circulation washing and the cross-flow concentration step had an average pore diameter of 4.4 ⁇ m.
  • Example 3 Except that the average pore diameter of the tubular filter as the cross-flow filtration filter used in the cross-flow circulation washing and the cross-flow concentration step was 4.4 ⁇ m and the mill peripheral speed was 40 m / s in the dispersion treatment. The experiment was conducted under the same conditions as in Example 1.
  • Example 4 An experiment was performed under the same conditions as in Example 1 except that the tubular filter used as the cross-flow filtration filter in the cross-flow circulation washing and the cross-flow concentration step had an average pore diameter of 3.5 ⁇ m.
  • Example 5 Except that the average pore diameter of the tubular filter as the cross-flow filtration filter used in the cross-flow circulation cleaning and cross-flow concentration step was 3.5 ⁇ m, and the mill peripheral speed was 40 m / s in the dispersion treatment. The experiment was conducted under the same conditions as in Example 1.
  • the ratio RTD / RMD was close to 1 as compared with Comparative examples 1 and 2, and the anisotropy of the sheet resistance of the transparent conductive material was reduced.
  • a TD / MD of 1.5 or less and a haze of 0.6% or less are desirable characteristics for smartphone samples.
  • the sheet resistance at a haze of 0.6% is as low as 60 ⁇ / sq or less, and it can be seen that both low haze and low sheet resistance of the transparent conductive film can be achieved.
  • sheet resistance when haze is 0.6% means measuring the relationship between sheet resistance ( ⁇ / sq) and haze (%) at 10 points, performing power approximation to the measurement points, and using the power approximation formula to calculate haze. The sheet resistance at 0.6% is calculated. When the value of R 2 is lower than 0.95, 10 points having different film thicknesses are applied again, and the haze is calculated using the power approximation formula when the value of R 2 is 0.95 or more. The sheet resistance at 0.6% was calculated.

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  • Dispersion Chemistry (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Manufacture Of Metal Powder And Suspensions Thereof (AREA)
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Abstract

La présente invention concerne un assemblage de nanofils d'argent qui a un diamètre moyen et une distribution de longueur des nanofils d'argent dans des plages prédéterminées. La présente invention concerne également une encre renfermant des nanofils d'argent qui est obtenue par dispersion de l'assemblage de nanofils d'argent dans un milieu liquide. La présente invention concerne également un film conducteur transparent qui comprend l'assemblage de nanofils d'argent sur un matériau de base transparent. La présente invention concerne également un procédé pour la production d'un assemblage de nanofils d'argent et un procédé pour la production d'une encre renfermant des nanofils d'argent comprenant une étape consistant à synthétiser des nanofils d'argent et une étape consistant à effectuer en outre un processus de dispersion au moyen d'un procédé de dépôt de couche mince par rotation. La présente invention concerne également un procédé pour la production d'un film conducteur transparent comprenant, en plus des étapes décrites ci-dessus, une étape consistant à appliquer des nanofils d'argent dans un état d'encre sur le matériau de base transparent.
PCT/JP2019/042054 2018-10-29 2019-10-25 Assemblage de nanofils d'argent, encre renfermant des nanofils d'argent, film conducteur transparent, procédé pour la production d'un assemblage de nanofils d'argent, procédé pour la production d'encre renfermant des nanofils d'argent et procédé pour la production d'un film conducteur transparent Ceased WO2020090689A1 (fr)

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WO2014157259A1 (fr) * 2013-03-28 2014-10-02 富士フイルム株式会社 Procédé de fabrication d'élément de conversion thermoélectrique et procédé de production de dispersion pour couches de conversion thermoélectrique
WO2016035856A1 (fr) * 2014-09-05 2016-03-10 Ｄｏｗａホールディングス株式会社 Procédé de fabrication de nanofils métalliques ayant une uniformité de distribution de longueur améliorée

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2014157259A1 (fr) * 2013-03-28 2014-10-02 富士フイルム株式会社 Procédé de fabrication d'élément de conversion thermoélectrique et procédé de production de dispersion pour couches de conversion thermoélectrique
WO2016035856A1 (fr) * 2014-09-05 2016-03-10 Ｄｏｗａホールディングス株式会社 Procédé de fabrication de nanofils métalliques ayant une uniformité de distribution de longueur améliorée

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