JP7359588B2 - Transparent conductive laminate and method for producing transparent conductive laminate - Google Patents

Description

The present invention relates to a transparent conductive laminate and a method for manufacturing the transparent conductive laminate.

Carbon materials are known to exhibit high chemical stability in addition to excellent electrical conductivity and thermal conductivity, and are expected to be excellent conductive materials in fields such as optical applications. However, since carbon materials have a large aspect ratio and a coordinately unsaturated structure, they have strong intermolecular interactions and tend to aggregate. Since carbon materials cannot exhibit sufficient characteristics such as conductivity and transparency in an aggregated state, it is required to improve the dispersibility of carbon materials in conductive paints. In order to improve the dispersibility of carbon materials, it is known to perform dispersion treatment using, for example, ultrasonic waves.

However, even the above-mentioned dispersion treatment has not been sufficient to meet the recent market demand for high transparency. Currently, in response to this demand for high transparency, there are methods for reducing carbon materials to make them highly conductive (Patent Document 1) and methods for separating and using only highly conductive carbon nanomaterials (Patent Document 2). have been proposed, but each requires special equipment and processes, and there are still challenges in commercial production.

JP2016-60646A Patent No. 6237967

An object of the present invention is to provide a transparent conductive laminate having high conductivity and transparency.

The present inventors have discovered that the number of carbon materials (in this specification, including aggregates containing carbon materials as described later) per unit area has a large influence on conductivity and transparency. A transparent conductive laminate having a conductive layer on a base material containing a carbon material and having a surface resistivity of 1×10 ² to 1×10 ¹¹ Ω/sq, the major axis of which is 10 μm. A new discovery has been made that a transparent conductive laminate characterized by having carbon materials with a width of 2 μm or more and a short diameter of 10 pieces/cm ² or less can have high conductivity and transparency. , completed the present invention.

That is, the present invention relates to:
[1] A transparent conductive laminate having, on a base material, a conductive layer containing a carbon material and having a surface resistivity of 1×10 ² to 1× ¹⁰ Ω/sq,
A transparent conductive laminate characterized in that the content of carbon materials having a major axis of 10 μm or more and a minor axis of 2 μm or more is 10 pieces/cm ² or less.
[2] The transparent conductive laminate of [1], which has a haze value of 3% or less.
[3] The transparent conductive laminate of [1] or [2], wherein the carbon material is at least one selected from the group consisting of graphene, fullerene, and carbon nanotubes.
[4] The transparent conductive laminate according to any one of [1] to [3], wherein the content of carbon material in the conductive layer is 50 mg/m ² or less.
[5] A conductive paint for forming a conductive layer in the transparent conductive laminate according to any one of [1] to [4].
[6] A display device comprising the transparent conductive laminate according to any one of [1] to [4].
[7] A light control device comprising the transparent conductive laminate according to any one of [1] to [4].
[8] The method for producing a transparent conductive laminate according to any one of [1] to [4], which includes a step of forming a conductive layer on the base material using a conductive paint containing a carbon material.
[9] The method for producing a transparent conductive laminate according to [8], which includes a step of filtering the conductive paint containing a carbon material using a filter with a pore size of 1 to 20 μm before the step of forming the conductive layer.
[10] The method for producing a transparent conductive laminate according to [9], wherein the material of the filter is polyolefin.
[11] A method for producing a conductive paint containing a carbon material, comprising:
When a conductive layer is formed by coating the conductive paint on the base material so that the carbon material content is 50 mg/m ² , the conductive layer meets the following conditions (a) to (c):
(a) Surface resistivity is 10 ² to 10 ¹¹ Ω/sq;
(b) The haze value is 3% or less; and (c) The content of carbon materials having a major axis of 10 μm or more and a minor axis of 2 μm or more is 10 pieces/cm ² or less.
[12] The method for producing a conductive paint according to [11], wherein the carbon material is at least one selected from the group consisting of graphene, fullerene, and carbon nanotubes.
[13] The method for producing a conductive paint according to [11] or [12], which includes the step of filtering the conductive paint using a filter with a pore size of 1 to 20 μm.
[14] The method for producing a conductive paint according to [13], wherein the material of the filter is polyolefin.
[15] The method for producing a conductive paint according to any one of [11] to [14], which includes a step of dispersing the carbon material beyond the minimum point of surface resistivity.

According to the present invention, a transparent conductive laminate having high conductivity and transparency can be obtained.

<<Transparent conductive laminate>>
First, the transparent conductive laminate of the present invention will be explained.
The transparent conductive laminate of the present invention has, on a base material, a conductive layer containing a carbon material and having a surface resistivity of 1×10 ² to 1×10 ¹¹ Ω/sq, and has a major axis of 10 μm or more and a minor axis. The content of carbon materials having a diameter of 2 μm or more is 10 pieces/cm ² or less.

<Base material>
The material of the base material is not particularly limited, and may be either an inorganic base material or an organic base material. Among these, inorganic base materials are preferred because they are less affected by the solvent contained in the conductive paint and any solvent can be used. As the inorganic base material, alkali-free glass, borosilicate glass, aluminosilicate glass, etc. are preferable, and alkali-free glass is more preferable. Organic base materials include cycloolefin polymer (COP), acrylic resin, polyethylene terephthalate (PET), amorphous PET, polyethylene naphthalate, polyester resins such as modified polyester, polyethylene resin (PE), and polypropylene resin (PP). , polyolefin resins such as polystyrene resins and cyclic olefin resins, vinyl resins such as polyvinyl chloride and polyvinylidene chloride, polyetheretherketone resins (PEEK), polysulfone resins (PSF), and polyethersulfone resins (PES). , polycarbonate resin (PC), polyamide resin, polyimide resin, acrylic resin, triacetyl cellulose resin (TAC), and the like. Among these, cycloolefin polymers (COP), acrylic resins, polyethylene terephthalate (PET), polyvinyl alcohol resins, triacetyl cellulose resins (TAC), and the like are preferably used. These may be used alone or in combination of two or more.

The surface of the base material is subjected to various surface treatments such as corona treatment, plasma treatment, alkali treatment, excimer treatment, primer coating, degreasing treatment, and surface roughening treatment for the purpose of facilitating adhesion and improving wettability. You can. In particular, the inorganic base material is preferably one that has undergone an etching process or a cleaning process with an alkaline solution in order to make the film thinner and lighter, and to improve the wettability of the conductive paint to the base material.

In the case of an inorganic base material, the thickness of the base material is not particularly limited, but is preferably 10 mm or less, more preferably 0.01 to 50 mm, and even more preferably 0.01 to 1 mm.

In the case of an organic base material, its shape may be, for example, a film shape or a sheet shape. In the case of a film shape, the thickness is not particularly limited, but is preferably, for example, 10 to 200 μm, more preferably 50 to 150 μm. Further, in the case of a sheet shape, the thickness is not particularly limited, but is preferably 0.1 to 5 mm, and more preferably 0.2 to 1 mm.

<Conductive layer>
The conductive layer in the transparent conductive laminate of the present invention contains a carbon material and has a surface resistivity of 1×10 ² to 1×10 ¹¹ Ω/sq. By providing such a conductive layer, a transparent conductive laminate having excellent conductivity can be provided.

The conductive layer can be formed, for example, by applying a conductive paint containing a carbon material onto a base material and then subjecting it to heat treatment. The conductive paint may be applied directly onto at least one surface of the base material, or may be applied onto the functional layer after another functional layer such as a primer layer is previously provided on the base material. good.
Examples of the resin used for the functional layer include polyurethane resins, polyester resins, acrylic resins, epoxy resins, and other general-purpose resins.

(carbon material)
Examples of carbon materials include carbon nanotubes, graphene, and fullerene. These may be used alone or in combination of two or more.

The carbon nanotubes are not particularly limited, and carbon nanotubes manufactured by arc discharge method, laser evaporation method, chemical vapor deposition method (CVD method), etc. can be used, and more specifically, single-walled carbon nanotubes, Double-walled carbon nanotubes, multi-walled carbon nanotubes, and mixtures thereof can all be used. From the viewpoint of excellent conductivity, it is preferable that at least single-walled carbon nanotubes are included.

The length of the carbon nanotube is preferably 1 to 2000 μm, more preferably 5 to 1000 μm, and still more preferably 5 to 500 μm. When the length of the carbon nanotube is within the above range, when used as a conductive layer, the conductivity and transparency are excellent.

In the case of single-walled carbon nanotubes, the diameter of the carbon nanotube is preferably 0.5 to 20 nm, more preferably 1 to 10 nm. When the diameter of the carbon nanotube is within the above range, when used as a conductive layer, the conductivity and transparency are excellent.

The content of the carbon material in the conductive paint is not particularly limited, but it is preferably 0.1 to 40 parts by weight, more preferably 0.5 to 30 parts by weight, based on 100 parts by weight of the solid content of the conductive paint. , more preferably 1 to 20 parts by weight. When the content of the carbon material is within the above range, conductivity and transparency are both achieved when used as a conductive layer, which is preferable.

(dispersant)
The carbon material may be one that has been previously dispersed in water or the like using a dispersant. Examples of the dispersant include cationic dispersants, anionic dispersants, amphoteric dispersants, nonionic dispersants, and polymeric dispersants. These may be used alone or in combination of two or more. Furthermore, the dispersant preferably has an HLB value of 12 or more, more preferably 14 or more. Note that the HLB value in this specification can be calculated using the following formula:
Griffin method: HLB value = [(molecular weight of hydrophilic part) ÷ (total molecular weight)] x 20

Examples of the cationic dispersant include alkylamine salts having an alkyl group having 8 to 22 carbon atoms such as stearylamine acetate, and quaternary ammonium salts such as lauryltrimethylammonium chloride and hexadecyltrimethylammonium bromide. It will be done.

Examples of the anionic dispersant include sodium alkyl sulfate having 8 to 18 carbon atoms such as sodium lauryl sulfate, and polyoxyethylene alkyl ether sulfate having an alkyl group having 8 to 18 carbon atoms such as sodium polyoxyethylene lauryl ether sulfate. Naphthalene sulfonic acid formalin such as ester salt, sodium deoxycholate, alkylbenzene sulfonate having an alkyl group of 8 to 18 carbon atoms such as sodium dodecylbenzene sulfonate, fatty acid salt, sodium salt of β-naphthalene sulfonic acid formalin condensate Examples include condensates.

Examples of the amphoteric dispersant include alkyl betaines having an alkyl group having 8 to 22 carbon atoms, and alkylamine oxides having an alkyl group having 8 to 18 carbon atoms.

Examples of nonionic dispersants include polyoxyethylene alkyl ethers having alkyl groups having 1 to 20 carbon atoms, block copolymers composed of ethylene oxide and propylene oxide, and alkylphenols having alkyl groups having 1 to 20 carbon atoms. Examples include polyoxyalkylene derivatives such as polyethylene glycol ether, polycarboxylate ether having an alkylene group having 2 to 4 carbon atoms, and sorbitan fatty acid esters such as sorbitan tristearate.

Examples of polymeric dispersants include polyvinylpyrrolidone, polyvinyl alcohol, hydroxycellulose, hydroxyalkylcellulose having an alkyl group having 1 to 8 carbon atoms, cellulose derivatives such as carboxymethylcellulose and carboxypropylcellulose, starch, gelatin, and acrylic. Examples include polymeric dispersants such as copolymers, polycarboxylic acids or derivatives thereof, and polystyrene sulfonic acids or salts thereof.

Among these, polyvinylpyrrolidone, polyoxyalkylene derivatives, polystyrene sulfonic acid, cellulose derivatives, polycarboxylic acids, acrylic copolymers, and alkylbenzene sulfonates are preferred; polyvinylpyrrolidone, polyoxyalkylene derivatives, polycarboxylic acids, and acrylic copolymers are preferred. is preferable because the dispersibility of the carbon material becomes better. Further, a dispersant having one or more branched chains and a branched chain having a molecular weight of 15 or more is preferable because the molecular chains spread in all directions and the dispersibility of the carbon material becomes higher.

The amount of the dispersant added is preferably 0.01 to 100 parts by weight, and preferably 0.2 to 40 parts by weight, based on 1 part by weight of the carbon material, from the viewpoint of achieving both dispersibility and transparency. is more preferable, and even more preferably 0.5 to 10 parts by weight.

By dispersing the carbon material in water in the presence of a dispersant, the carbon material and the dispersant interact, and a conductive paint in which the carbon material is well dispersed in water can be obtained.

<Binder resin>
The conductive paint may contain a binder resin in order to increase the strength when used as a conductive layer. Examples of the binder resin include, but are not limited to, acrylic resin, polyester resin, urethane resin, melamine, silicate resin, titanate resin, aluminate resin, and the like. These may be used alone or in combination of two or more. In particular, from the viewpoint of strength, transparency, and durability, it is preferable to contain at least a silicate resin or a melamine resin.

The acrylic resin is not particularly limited, but may be a polymer containing as a constituent monomer a polymerizable monomer having an acid group such as a carboxyl group, an acid anhydride group, a sulfonic acid group, or a phosphoric acid group. , a single or copolymer of a polymerizable monomer having an acid group, a copolymer of a polymerizable monomer having an acid group and a copolymerizable monomer, etc. More specifically, ( Examples include meth)acrylic resins.

The (meth)acrylic resin may be polymerized with a copolymerizable monomer as long as it contains a (meth)acrylic monomer as the main constituent monomer (for example, 50 mol% or more); in this case, It is sufficient that at least one of the (meth)acrylic monomer and the copolymerizable monomer has an acid group.

Examples of (meth)acrylic resins include (meth)acrylic monomers having acid groups [(meth)acrylic acid, sulfoalkyl (meth)acrylate, sulfonic acid group-containing (meth)acrylamide, etc.] or their co-resins. A polymer, a (meth)acrylic monomer that may have an acid group, and other polymerizable monomers that have an acid group [other polymerizable carboxylic acids, polymerizable polycarboxylic acids, or anhydrides] , vinyl aromatic sulfonic acid, etc.] and/or copolymerizable monomers [e.g., (meth)acrylic acid alkyl ester, glycidyl (meth)acrylate, (meth)acrylonitrile, aromatic vinyl monomer, etc.] Polymers, other polymer monomers having acid groups and (meth)acrylic copolymerizable monomers [for example, (meth)acrylic acid alkyl esters, hydroxyalkyl (meth)acrylates, glycidyl (meth)acrylates, (meth)acrylonitrile, etc.], rosin-modified urethane acrylate, special modified acrylic resin, urethane acrylate, epoxy acrylate, urethane acrylate emulsion, and the like.

Among these (meth)acrylic resins, (meth)acrylic acid-(meth)acrylic acid ester polymers (acrylic acid-methyl methacrylate copolymer, etc.), (meth)acrylic acid-(meth)acrylic acid Ester-styrene copolymers (acrylic acid-methyl methacrylate-styrene copolymers, etc.) are preferred.

The polyester resin is not particularly limited as long as it is a polymer compound obtained by polycondensation of a compound having two or more carboxyl groups in the molecule and a compound having two or more hydroxyl groups, such as polyethylene. Examples include terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, and polybutylene naphthalate.

The urethane resin is not particularly limited as long as it is a polymer compound obtained by copolymerizing a compound having an isocyanate group and a compound having a hydroxyl group, such as ester/ether polyurethane, ether polyurethane, and polyester polyurethane. , carbonate polyurethane, acrylic polyurethane, and the like.

The silicate resin is, for example, an alkoxysilane in which alkoxysilane monomers represented by the following general formula (1) are condensed together, and has one or more siloxane bonds (Si-O-Si) in one molecule. Examples include oligomers:
_SiR4 (1)
[In the formula, R is hydrogen, a hydroxyl group, an alkoxy group having 1 to 4 carbon atoms, an alkyl group that may have a substituent, a phenyl group that may have a substituent, but among the four R At least one is an alkoxy group or hydroxyl group having 1 to 4 carbon atoms].
The silicate resin is preferably one in which two or more molecules of alkoxysilane represented by general formula (1) are condensed.
The structure of the alkoxysilane oligomer is not particularly limited, and may be linear or branched.

As the silicate resin, silicon alkoxide acrylic resin, silicon alkoxide epoxy resin, silicon alkoxide vinyl resin, silicon alkoxide methacrylic resin, silicon alkoxide thiol resin, silicon alkoxide amino resin, silicon alkoxide isocyanate resin, silicon alkoxide alkyl Examples include silicon alkoxide resins such as silicon alkoxide resins having no functional groups other than silicon alkoxide groups.

The content of the binder resin is not particularly limited, but for example, it is preferably 20 to 99 parts by weight, more preferably 50 to 98 parts by weight, and 60 to 95 parts by weight based on 100 parts by weight of the solid content of the conductive paint. It is more preferably 70 to 90 parts by weight, even more preferably 70 to 90 parts by weight. When the content of the binder resin is within the above range, the film strength and conductivity when used as a conductive layer will be good.

(Leveling agent)
The conductive paint preferably contains a leveling agent in order to increase its affinity for the base material. By adding a leveling agent, it is possible to suppress repelling and unevenness when forming a conductive layer. Furthermore, the leveling agent also contributes to improving the dispersion stability of the conductive paint, and a conductive layer formed from the conductive paint containing the leveling agent has good transparency and conductivity. As a leveling agent, one having an HLB value of 10 or more is preferable, and one having an HLB value of 12 or more is more preferable, since the higher the hydrophilicity, the less the dispersion of the carbon material will be inhibited. Further, it is preferable that the carbon material has a higher affinity than the dispersant for the hydrophobic carbon material, and therefore, it is preferable that the hydrophobicity is higher than that of the dispersant.

Specific examples of leveling agents include polyether leveling agents, siloxane leveling agents, fluorine leveling agents, polyester leveling agents, silicone leveling agents, and acrylic leveling agents. These may be used alone or in combination. Among these, polyester leveling agents having an ester bond and polyether leveling agents having an ether bond are preferred because they easily interact with the carbon material and do not inhibit the dispersion of the carbon material in water-alcohol.

Examples of the polyester leveling agent include polyester-modified acrylic group-containing polydimethylsiloxane, polyester-modified polydimethylsiloxane, and polyester polyol.

Polyether leveling agents include cellulose ether; pullulan; polyethylene glycol; silicones such as polyether-modified polydimethylsiloxane, polyether-modified siloxane, polyetherester-modified hydroxyl group-containing polydimethylsiloxane, and polyether-modified acrylic group-containing polydimethylsiloxane. Examples include modified polyether; polyglycerin; polyether polyol, polyoxyethylene-polyoxypropylene condensate, polyoxyethylene alkylphenyl ether, alkyl ether derivatives such as lauryl alcohol alkoxylate, and alkyl ether sulfate.

Examples of fluorine-based leveling agents include perfluoropolyether-modified polydimethylsiloxane, perfluoropolyester-modified polydimethylsiloxane, perfluorobutanesulfonic acid, oligomers containing fluorine-containing groups, hydrophilic groups, and lipophilic groups, and carvone containing perfluoroalkyl groups. Examples include acid salts, phosphoric acid esters containing perfluoroalkyl groups and phosphoric acid groups, and the like.

Silicone leveling agents include polysiloxanes, reactive polysiloxanes with reactive groups such as amino groups, epoxy groups, hydroxyl groups, and carboxyl groups, as well as alkyl groups, ester groups, aralkyl groups, and phenyl groups. , non-reactive polysiloxanes into which non-reactivity such as polyether groups are introduced.

Examples of the acrylic leveling agent include acrylic copolymers made of silicone and acrylic.

The content of the leveling agent is not particularly limited, but it is preferably 0.01 to 40 parts by weight, more preferably 0.1 to 20 parts by weight, and 1 to 20 parts by weight based on the entire solid content of the conductive paint. More preferably, the amount is 10 parts by weight. When the content of the conductive paint is within the above range, the coating properties on the substrate, the dispersion stability, and the film strength when formed into a conductive layer will be good.

(solvent)
The conductive paint may contain a solvent to increase its affinity for the base material. The solvent is not particularly limited, and includes, for example, alcohols such as methanol, ethanol, 2-propanol, and 1-propanol; ethylene glycols such as ethylene glycol, diethylene glycol, triethylene glycol, and tetraethylene glycol; ethylene glycol monomethyl ether; Glycol ethers such as diethylene glycol monomethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether; Glycol ether acetates such as ethylene glycol monoethyl ether acetate, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate; propylene glycol, dipropylene glycol, tripropylene Propylene glycols such as glycol; Propylene glycol ethers such as propylene glycol monomethyl ether, propylene glycol monoethyl ether, dipropylene glycol monomethyl ether, propylene glycol dimethyl ether, and propylene glycol diethyl ether; Propylene glycol ether acetate such as propylene glycol monomethyl ether acetate Ethers such as diethyl ether, diisopropyl ether, methyl-t-butyl ether, and tetrahydrofuran; Ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; toluene, xylene (o-, m-, or p-xylene), Hydrocarbons such as hexane and heptane: Esters such as ethyl acetate, butyl acetate, ethyl acetoacetate, methyl orthoacetate, and ethyl orthoformate: N-methylformamide, N,N-dimethylformamide, γ-butyrolactone, N-methyl Amide compounds such as pyrrolidone; hydroxyl groups such as trimethylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, catechol, cyclohexanediol, cyclohexanedimethanol, glycerin, etc. Containing compounds: Compounds with sulfo groups such as dimethyl sulfoxide; In addition to organic solvents such as halogens, isophorone, propylene carbonate, acetylacetone, and acetonitrile, mixed solvents of water and these organic solvents (water-containing organic solvents), two or more types Examples include mixed solvents of organic solvents.

When using an inorganic base material, among the above solvents, alcohols, ethers, acetates, ketones, alcohols and ethers are recommended from the viewpoint of dispersion stability of the carbon material and applicability to the base material. Mixed solvents with alcohols, mixed solvents with alcohols and acetates, mixed solvents with alcohols and ketones, mixed solvents with water and organic solvents are preferred; More preferred are mixed solvents with ethers, mixed solvents with water and acetates, mixed solvents with water, alcohol and ether, mixed solvents with water, alcohol and acetate, and mixed solvents with water, alcohol and ketones. Further preferred are mixed solvents of water and alcohols, mixed solvents of water and ethers, and mixed solvents of water and acetates. By using these solvents, a highly hydrophobic binder resin can be blended into the conductive layer. It is also effective to add ethylene glycols, propylene glycols, amide compounds, etc. to improve coating properties.

When using an organic base material, among the above solvents, water and organic solvents are preferred from the viewpoints of dispersion stability of the carbon material, applicability to the base material, and prevention of reduction in transparency due to swelling and discoloration of the base material. Mixed solvents of water and alcohols, mixed solvents of water and ethers, mixed solvents of water and acetates are more preferred, and mixed solvents of water and alcohols are even more preferred. The alcohol used in the mixed solvent of water and alcohols is preferably methanol, ethanol, or 2-propanol. When water and alcohol are combined, the alcohol ratio is preferably 20 to 99%, more preferably 30 to 97%, even more preferably 40 to 96%. Further, as with inorganic base materials, it is also effective to add ethylene glycols, propylene glycols, amide compounds, etc. to improve coating properties.

The content of the solvent is not particularly limited, but it is preferably added so that the solid content of the conductive paint is 3% by weight or less, and more preferably 0.1 to 2% by weight. . Furthermore, when adding a solvent to the conductive paint, it is preferable to make the proportion of water in the solvent contained in the conductive paint 1 to 70% by weight, preferably 3 to 65% by weight by combining water and another solvent. More preferably, the amount is 4 to 60% by weight.

In this specification, there is no particular distinction between what completely dissolves all the components of the conductive paint (i.e., "solvent") and what disperses the insoluble components (i.e., "dispersion medium"). , both are referred to as "solvent".

(Other ingredients)
The conductive paint may further contain a conductive polymer, a crosslinking agent, a catalyst, an antioxidant, an antifoaming agent, a rheology control agent, a neutralizing agent, a thickening agent, and the like.

Examples of the conductive polymer include polythiophene, polypyrrole, polyaniline, polyacetylene, polyphenylene vinylene, polynaphthalene, and derivatives thereof. These may be used alone or in combination of two or more. Among these, conductive polymers containing at least one thiophene ring in the molecule are preferred, since molecules with high conductivity can easily be produced. The conductive polymer may form a complex with a dopant such as a polyanion.
As a complex of a conductive polymer and a polyanion, a complex of poly(3,4-ethylenedioxythiophene) and polystyrene sulfonic acid is preferable because it has particularly excellent conductivity.

Examples of the crosslinking agent include, but are not limited to, melamine-based, polycarbodiimide-based, polyoxazoline-based, polyepoxy-based, polyisocyanate-based, and polyacrylate-based crosslinking agents. These may be used alone or in combination of two or more.

The catalyst is not particularly limited, and examples thereof include photopolymerization initiators, thermal polymerization initiators, acids, bases, and the like. These may be used alone or in combination of two or more.

The thickness of the conductive layer is preferably 1 to 500 nm, more preferably 10 to 300 nm, and even more preferably 20 to 200 nm.

The surface resistivity of the conductive layer is preferably 1×10 ² to 1×10 ¹¹ Ω/sq, more preferably 1×10 ² to 5×10 ¹⁰ Ω/sq, and 1×10 ² to 1×10 Ω/sq. More preferably, it is 1×10 ¹⁰ Ω/sq.

The content of the carbon material in the conductive layer is preferably 50 mg/m ² or less, more preferably 0.1 to 50 mg/m ² , and even more preferably 0.5 to 45 mg/m ² Preferably, it is even more preferably 1 to 45 mg/m ² .

As described above, the conductive layer can be formed by applying a conductive paint to at least one surface of the base material and then heat-treating the coated material. The coating method is not particularly limited, and examples include roll coating, bar coating, dip coating, spin coating, casting, die coating, blade coating, bar coating, gravure coating, curtain coating, and spraying. Coat method, doctor coat method, slit coat method, letterpress printing method, stencil (screen) printing method, planographic (offset) printing method, intaglio (gravure) printing method, spray printing method, inkjet printing method, tampo printing method etc. can be used.

When applying conductive paint to a large-area substrate, for example, a conductive layer is formed using coating equipment consisting of a tank, a pump for liquid delivery, a filter for removing foreign matter, and a coating device. It is advantageous in terms of production efficiency to do so.

The filter constituting the coating equipment is not particularly limited, but preferably has a pore size of 1 to 20 μm, more preferably 2 to 10 μm, and even more preferably 2 to 5 μm.

The material of the filter is not particularly limited, and examples include nylon, cellulose, a mixture of cellulose acetate and nitrocellulose, cellulose derivatives such as cellulose ester, fluororesins such as polytetrafluoroethylene, polyvinylidene fluoride, Teflon, and polyvinyl fluoride. , polyolefins such as polypropylene and polyethylene, ceramics, metals, polycarbonates, glass, polyesters, polyamides, polysulfones, polyimides, polyvinyl chloride, polystyrene, and perfluorosulfonic (carboxylic) acids. Among these, polyolefins are preferred. Depending on the material of the filter, the carbon material may be adsorbed to the filter and the surface resistivity may become too high when a conductive layer is formed using conductive paint, but if the filter is made of polyolefin, the carbon material and the Because it is difficult to act, a conductive coating material that can still exhibit sufficient surface resistivity even after filtration through a filter may be obtained.

By forming a conductive layer using coating equipment equipped with such a filter, it is possible to perform a process of filtering the conductive paint with a filter before performing the process of forming the conductive layer, improving conductivity and transparency. A conductive layer with excellent properties can be obtained.

The heat treatment when forming the conductive layer is not particularly limited, and can be performed using, for example, a blower oven, an infrared oven, a vacuum oven, or the like. When the conductive paint contains a solvent, the solvent is preferably removed by heat treatment.

The temperature conditions for the heat treatment when forming the conductive layer are preferably 200°C or less, more preferably 60 to 180°C, and even more preferably 80 to 150°C.

The heat treatment time is preferably 0.1 to 60 minutes, more preferably 0.5 to 30 minutes.

The transparent conductive laminate of the present invention is characterized in that the content of carbon materials having a major axis of 10 μm or more and a minor axis of 2 μm or more is 10 pieces/cm ² or less (10 pieces per square centimeter or less), preferably The number is 4 pieces/cm ² or less, more preferably 3 pieces/cm ² or less. Here, the carbon material whose major axis is 10 μm or more and the minor axis is 2 μm or more refers to carbon materials that have the above-mentioned size in one molecule, as well as carbon materials that aggregate with each other or with components in other conductive paints. This includes those that have become lumpy and have the size listed above. In addition, if the carbon material is in the shape of a plate, needle, bundle, etc., the long side (the length where the distance between two points is maximum) when the laminate is observed from the stacking direction is the major axis. One side shall be the short axis.
In this specification, the major axis, minor axis, and number of carbon materials are those measured and evaluated using an optical microscope, as described in Examples below.

The haze value of the transparent conductive laminate of the present invention is not particularly limited, but is preferably 3% or less, more preferably 2% or less, and even more preferably 0.6% or less. . When the haze value is 3% or less, the transparency of the laminate will be good. Note that the lower limit of the haze value is not particularly limited, but is preferably 0.01%, for example.
The haze value in the present invention is measured in accordance with JIS K 7136.

<<Conductive paint>>
The conductive paint described above is also one of the aspects of the present invention, and the transparent conductive laminate of the present invention can be manufactured by using the conductive paint of the present invention.
A conductive coating material can be manufactured, for example, through a process of dispersing a carbon material in water or an organic solvent in the presence of a dispersant. The dispersion treatment can be carried out using, for example, a vibration mill, a planetary mill, a ball mill, a bead mill, a sand mill, a jet mill, a roll mill, a homogenizer, an ultrasonic homogenizer, a high-pressure homogenizer, an ultrasonic device, or the like. In order to obtain a conductive paint that can exhibit high conductivity and transparency, it is preferable to carry out the dispersion treatment using at least one of an ultrasonic homogenizer or a high-pressure homogenizer.

Normally, carbon materials can be subjected to dispersion treatment without adding any optional components other than a dispersant, and under conditions that give the lowest surface resistivity when forming a conductive layer immediately after dispersion treatment (surface resistivity (minimum point of In some cases, transparency and conductivity decrease. Considering these factors that reduce transparency and conductivity, when dispersing carbon materials, we set high strength conditions that exceed the minimum point of surface resistivity. Even if a certain storage period occurs after production, a conductive paint that still has excellent transparency and conductivity when used as a conductive layer can be obtained.
Here, the dispersion treatment under conditions exceeding the minimum point of the surface resistivity can be appropriately set based on common technical knowledge in the field, depending on the processing method and processing amount of the apparatus used.

Before performing the dispersion treatment step, the carbon material may be subjected to high-speed stirring treatment as a pretreatment. The high-speed stirring process is a dispersion process under relatively lower intensity conditions than the dispersion process using an ultrasonic homogenizer or the like, and the high-speed rotation of the stirring body has the effect of loosening the agglomeration of the carbon material. By performing the high-speed stirring process before the dispersion process, the dispersion process of the carbon material can be performed more efficiently.

If aggregates, etc. (including aggregates formed by agglomeration of carbon materials or carbon materials and other components) remain after dispersion of carbon materials, perform centrifugation to remove these aggregates. Aggregates etc. may be removed, or these aggregates etc. may be removed using a filter. When removing these aggregates using a filter, the above-mentioned filter can be used.

As described above, the conductive paint may contain other optional components in addition to the carbon material, and each optional component may be added during the process of dispersing the carbon material, or the conductive paint may contain other optional components. You can add it after.

<<Applications>>
The transparent conductive laminate of the present invention can be applied to applications that require high conductivity and transparency, and is particularly suitable for use in display devices and light control devices.

The present invention will be described below with reference to Examples, but the present invention is not limited to these Examples. Note that "parts" and "%" mean "parts by weight" and "% by weight", respectively, unless otherwise specified.

1. Materials used 1-1. Base material: alkali-free glass plate (manufactured by Corning, EAGLE XG, haze 0.1%)
The alkali-free glass plate used was one that had been subjected to etching treatment and alkali treatment. In the etching process, the glass substrate was washed with water and then immersed in an etching solution consisting of 1% hydrofluoric acid, 5% hydrochloric acid, 2% sulfuric acid, and water, and the glass surface was chemically polished. Thereafter, it was washed with water and dried with a hair dryer. In the alkali treatment, a potassium hydroxide aqueous solution was used to clean the surface of the glass substrate. Thereafter, the glass substrate was washed with water and dried with a dryer.
・PET film (manufactured by Toray Industries, Inc., Lumirror T60, haze 2.1%)
・Acrylic resin (PMMA) film (manufactured by Sumitomo Chemical Co., Ltd., Technoloy S001G, haze 0.9%)
・Triacetyl cellulose film (manufactured by Fuji Film, Fujitac TJ25UL)

1-2. conductive material
・Single-walled carbon nanotube (SWCNT) water dispersion 1 (manufactured by Meijo Nano Carbon Co., Ltd., SWNT dispersion liquid, carbon nanotube concentration 0.1%, solid content rate 0.5%)
・Single-walled carbon nanotube (SWCNT) aqueous dispersion 2 (produced in Production Example 1, carbon nanotube concentration 0.1%, solid content 0.5%)
・Single-walled carbon nanotube (SWCNT) aqueous dispersion 3 (produced in Production Example 2, carbon nanotube concentration 0.1%, solid content 0.5%)
・Double-walled carbon nanotube (DWCNT) aqueous dispersion (produced in Production Example 3, carbon nanotube concentration 0.1%, solid content 1.1%)
・Multi-walled carbon nanotubes (MWCNT) (manufactured by Fuji Shiki Co., Ltd., MWNT dispersion, carbon nanotube concentration 5%, solid content 8%)
・Graphene (manufactured by XG Science, H-5 aqueous dispersion, solid content 15%)

1-3. Leveling agent/polyether type (manufactured by Clariant, product name: Emulsogen LCN070, HLB: 13)
・Fluorine-based (manufactured by DuPont, CAPSTONE FS-3100, 100% non-volatile content)
・Siloxane type (manufactured by Toray Dow Corning, 8029Additive)

1-4. Binder resin/tetraethoxysilicate (manufactured by Tokyo Chemical Industry Co., Ltd.)
・Polycondensate of tetraethoxysilicate (manufactured by Colcoat Co., Ltd., ethyl silicate 40)
・Melamine (manufactured by DIC Corporation, Beckamine M-3, solid content 77%)
・Acrylic resin (manufactured by Toagosei Co., Ltd., Julimar FC-80, solid content 30%, glass transition temperature 50°C)
・Urethane acrylate (urethane acrylate 8965, manufactured by Nippon U-Pica Co., Ltd.)

1-5. Catalyst/Nitric acid (manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.)
・Sulfuric acid (manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.)
・Formic acid (manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.)
・Dodecylbenzenesulfonic acid (DBS) (manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.)
・Cumensulfonic acid (CS) (manufactured by Teika, product name: Teikatox 500)
・T-Butyl peroxy 2-ethylhexanoate (TBPO) (Mitsubishi Chemical Corporation: Luperox 26)

1-6. Filter - Polyolefin (PO) filter (manufactured by 3M Corporation, Betapure AU0911120, pore size 1 μm)
・Polyolefin (PO) filter (manufactured by Nippon Entegris Co., Ltd., pore size 2.5 μm)
・Polyolefin (PO) filter (manufactured by Taiwan Grace Co., Ltd., pore size 5 μm)
・Polyolefin (PO) filter (manufactured by 3M Corporation, Micro-Klean DPPPC-2-A, pore size 10 μm)
・Teflon (registered trademark) (PTFE) filter (manufactured by Wintech Co., Ltd., FPF-500, pore size 5 μm)
・Teflon (registered trademark) (PTFE) filter (manufactured by Wintech Co., Ltd., FPF-045, pore size 0.45 μm)

(Production example 1) Preparation of single-walled carbon nanotube water dispersion 2 After adjusting the single-walled carbon nanotube (SWCNT) water dispersion 1 to 20°C, it was dispersed at 80 Mpa using a high-pressure homogenizer (Starburst Mini manufactured by Sugino Machine Co., Ltd.) After the treatment, it was immediately cooled down to 20° C. using a cooling tube. This dispersion step and cooling step were repeated 20 times to obtain a single-walled carbon nanotube aqueous dispersion 2 with a solid content of 0.5%. After each cooling process, a small amount is extracted and wire bar No. When the surface resistivity of the coating film was measured by coating the dispersion on glass using No. 16 and drying it on a hot plate at 120°C for 2 minutes, the surface resistivity decreased the most after the third cooling step ( conditions for the minimum point of surface resistivity), and then it was confirmed that the surface resistivity gradually increased.

(Manufacturing Example 2) Preparation of Single-Walled Carbon Nanotube Water Dispersion 3 Place the single-walled carbon nanotube (SWCNT) water dispersion 1 in a glass beaker and use an ultrasonic homogenizer (HP50H manufactured by Hielscher) at 50W and a frequency of 30kHz for 200 minutes. A single-walled carbon nanotube aqueous dispersion 3 having a solid content of 0.5% was obtained by carrying out a dispersion treatment while maintaining the liquid temperature at 25°C.
During the dispersion process, a small amount was taken out every 10 minutes and wire bar No. When the surface resistivity of the coating film was measured by coating the dispersion on glass using No. 16 and drying it on a hot plate at 120°C for 2 minutes, it was found that the surface resistivity was the highest when the dispersion process was performed for 30 minutes. It was confirmed that the surface resistivity became lower (conditions for reaching the minimum point of surface resistivity), and that the surface resistivity gradually increased when the dispersion process time was further extended.

(Production Example 3) Preparation of double-walled carbon nanotube aqueous dispersion 1 Double-walled carbon nanotubes with an average length of 10 μm and a diameter of about 4 nm (manufactured by Aldrich Co., Ltd., product number 755168) 1 part by weight, sodium dodecylbenzenesulfonate as a dispersant (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) and 989 parts by weight of pure water were placed in a glass beaker, and dispersion treatment was performed for 30 minutes at 50 W and a frequency of 30 kHz using an ultrasonic homogenizer (HP50H manufactured by Hielscher). A double-walled carbon nanotube aqueous dispersion 1 having a solid content of 1.1% was obtained.
During the dispersion process, a small amount was taken out every 5 minutes and wire bar No. When the surface resistivity of the coating film was measured by applying the dispersion on glass using No. It was confirmed that the value was low (conditions for the minimum point of surface resistivity), and the value was slightly higher after 30 minutes.

2. Examples (Examples 1 to 16, Comparative Examples 1 to 5)
The carbon material dispersion, binder resin, and leveling agent were mixed at the weight ratio (solid content ratio) shown in Table 1. A conductive paint was prepared by diluting with a diluent consisting of water and/or various solvents shown in Table 1 so as to have the solid content percentage shown in Table 1. The conductive paint was used after being filtered through the filter shown in Table 1, and applied using a wire bar. The obtained coating film was dried at 120° C. for 5 minutes using a blow dryer to form a conductive layer, thereby obtaining a transparent conductive laminate. The thickness of the conductive layer was adjusted to the thickness listed in Table 1 by appropriately selecting the wire bar count. The performance of the conductive layer was evaluated by the method described below, and the results are shown in Table 1.

3. Evaluation method (size and number of carbon materials)
Ten 5 cm x 5 cm square test pieces were each made from the transparent conductive laminates obtained in Examples 1 to 16 and Comparative Examples 1 to 5. Using an optical microscope, the size and number of carbon materials were observed in a 1 cm ² center area of this test piece, and the average value of the 10 test pieces was determined.

(Surface resistivity (SR))
For the 10 test pieces described above, the surface resistivity of the conductive layer was selected from the following methods depending on the surface resistivity and the measurable range of the device, and after measurement, the average value of the 10 test pieces was determined.
When the surface resistivity is 1×10 ⁶ Ω/sq to 1×10 ⁸ Ω/sq: Measured at an applied voltage of 10 V using a UA probe of Hiresta UP (MCP-HT450 type) manufactured by Mitsubishi Chemical Corporation.
When the surface resistivity exceeds 1×10 ⁸ Ω/sq: Measurement was performed at an applied voltage of 250 V using a UA probe of Hiresta UP (MCP-HT450 type) manufactured by Mitsubishi Chemical Corporation.

(Haze value)
The 10 test pieces described above were measured in accordance with JIS K 7150 using a haze computer HGM-2B manufactured by Suga Test Instruments, and then the average value of the 10 test pieces was determined.

(film thickness)
After measuring the 10 test pieces described above using an atomic force microscope (SPM-9600, manufactured by Shimadzu Corporation), the average value of the 10 test pieces was determined.

(Theoretical carbon material content)
The content of carbon material in the conductive layer was calculated using the following formula:
Theoretical carbon material content (mg/m ² ) = film thickness (μm) x weight percent of carbon material in conductive paint (solid content ratio)

As a result of the example, the haze value of the laminate increased and the transparency deteriorated as more carbon materials having a major axis of 10 μm or more and a minor axis of 2 μm or more were present in the conductive layer. A similar trend was also observed for surface resistivity.

Claims (15)

A transparent conductive laminate having, on a base material, a conductive layer containing a carbon material and a binder resin such as a silicate resin or a melamine resin , and having a surface resistivity of 1×10 ² to 1×10 ¹¹ Ω/sq. hand,
characterized in that the content of carbon materials having a major axis of 10 μm or more and a minor axis of 2 μm or more is 10 pieces/cm ² or less ,
Transparent conductive laminate for display devices or light control devices . The transparent conductive laminate according to claim 1, having a haze value of 3% or less. The transparent conductive laminate according to claim 1 or 2, wherein the carbon material is at least one selected from the group consisting of graphene, fullerene, and carbon nanotubes. The transparent conductive laminate according to any one of claims 1 to 3, wherein the content of carbon material in the conductive layer is 50 mg/m ² or less. A conductive paint for forming a conductive layer in the transparent conductive laminate according to any one of claims 1 to 4. A display device comprising the transparent conductive laminate according to any one of claims 1 to 4. A light control device comprising the transparent conductive laminate according to any one of claims 1 to 4. Including the step of forming a conductive layer on the base material with a conductive paint containing a carbon material,
A method for producing a transparent conductive laminate according to any one of claims 1 to 4. 9. The method for producing a transparent conductive laminate according to claim 8, comprising the step of filtering the conductive paint containing the carbon material using a filter having a pore size of 1 to 20 μm before the step of forming the conductive layer. The method for producing a transparent conductive laminate according to claim 9, wherein the material of the filter is polyolefin. A method for producing a conductive paint containing a carbon material and a binder resin that is a silicate resin or a melamine resin, the method comprising:
When a conductive layer is formed by coating the conductive paint on the base material so that the carbon material content is 50 mg/m ² , the conductive layer meets the following conditions (a) to (c):
(a) Surface resistivity is 10 ² to 10 ¹¹ Ω/sq;
(b) the haze value is 3% or less; and (c) the content of carbon materials having a major axis of 10 μm or more and a minor axis of 2 μm or more is 10 pieces/cm ² or less ,
The conductive layer is a conductive layer in a transparent conductive laminate for a display device or a light control device,
Method of manufacturing conductive paint. The method for producing a conductive paint according to claim 11, wherein the carbon material is at least one selected from the group consisting of graphene, fullerene, and carbon nanotubes. The method for producing a conductive paint according to claim 11 or 12, comprising the step of filtering the conductive paint using a filter having a pore size of 1 to 20 μm. The method for producing a conductive paint according to claim 13, wherein the material of the filter is polyolefin. The method for producing a conductive paint according to any one of claims 11 to 14, comprising a step of dispersing the carbon material beyond the minimum point of surface resistivity.