Paint composition, method for manufacturing a paint composition, method for manufacturing a coating film, and transparent conductive film

Abstract

To provide a technique to create a transparent conductive film containing carbon nanotubes with greater stability in surface resistivity.SOLUTION: Carbon nanotubes are combined with a triarylmethane-based dye and a polyacrylic acid.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a paint composition, a method for manufacturing a paint composition, a method for manufacturing a coating film, and a transparent conductive film. [Background technology]

[0002] In recent years, low-resistance transparent conductive films have been used in a variety of fields, including touch panels, organic EL displays, solar cells, and transparent electrodes. Various materials have been reported to be used as transparent conductive materials, including metallic materials such as ITO, conductive polymers such as PEDOT, and carbon materials such as carbon nanotubes. Currently, at the practical level, ITO is the most common transparent conductive material used in low-resistance transparent conductive films. However, ITO films have the disadvantage of being rigid and lacking flexibility.

[0003] Carbon nanotubes are less expensive and more durable than other transparent conductive materials, and are expected to be applied to products requiring flexibility. However, carbon nanotubes have relatively high resistance compared to other conductive materials, so when used in transparent conductive films, resistance reduction treatment is performed. For example, Patent Document 1 describes doping a carbon nanotube film by adding a water-dissolved halide and then performing heat calcination and light calcination to reduce the resistance of the coating film. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2019-151496 [Overview of the project] [Problems that the invention aims to solve]

[0005] The inventors of this invention focused on the fact that conventional carbon nanotube coatings, even those with reduced resistance, experience significant fluctuations (especially an increase) in surface resistivity during continued use, meaning that their surface resistivity is unstable.

[0006] Therefore, the object of the present invention is to provide a technology for obtaining a transparent conductive film containing carbon nanotubes with higher surface resistivity stability. [Means for solving the problem]

[0007] As a result of diligent research, the inventors have discovered that by combining carbon nanotubes with a triarylmethane-based dye and polyacrylic acid, a transparent conductive film containing carbon nanotubes with higher surface resistivity stability can be obtained. That is, the present invention encompasses the following aspects.

[0008] Item 1. A paint composition containing carbon nanotubes, a triarylmethane-based dye, and polyacrylic acid.

[0009] Item 2. The paint composition according to Item 1, wherein the triarylmethane-based dye has an amino group.

[0010] Item 3. The paint composition according to Item 1, wherein the weight-average molecular weight of the polyacrylic acid is 500 to 30000.

[0011] Item 4. The paint composition according to Item 1, wherein the carbon nanotube content is 0.4% by mass or less.

[0012] Item 5. The paint composition according to Item 1, wherein the content of the triarylmethane-based dye is 0.1 to 50 parts by weight per 100 parts by mass of the carbon nanotube.

[0013] Item 6. The paint composition according to Item 1, wherein the polyacrylic acid content is 1 to 300 parts by mass of the carbon nanotube.

[0014] Item 7. The paint composition according to any one of items 1 to 6, wherein the triarylmethane-based dye is held in the carbon nanotube.

[0015] Item 8. The coating composition according to any one of Items 1 to 6, which is for forming a transparent conductive film.

[0016] Item 9. A method for producing the coating composition according to any one of Items 1 to 6, comprising: (A) a step of bringing carbon nanotubes into contact with a triarylmethane-based dye in a liquid; (B) a step of adding a dispersant to the liquid containing the carbon nanotubes after the step (A); and (C) a step of adding polyacrylic acid to the liquid containing the carbon nanotubes after the step (B). Item 10. The method according to Item 9, wherein in the step (C), a binder is added to the liquid containing the carbon nanotubes.

[0017] Item 11. A method for producing a coating film, comprising: (a) a step of coating the coating composition according to any one of Items 1 to 6 on a substrate.

[0018] Item 12. A transparent conductive film comprising carbon nanotubes, a triarylmethane-based dye, and polyacrylic acid.

[0019] Item 13. The transparent conductive film according to Item 12, wherein the triarylmethane-based dye is held by the carbon nanotubes.

[0020] Item 14. The transparent conductive film according to Item 12, wherein the triarylmethane-based dye is held by the carbon nanotubes.

Advantages of the Invention

[0021] According to the present invention, it is possible to provide a technique for obtaining a carbon nanotube-containing transparent conductive film having higher surface resistivity stability.

Brief Description of the Drawings

[0022] [Figure 1] Shows the resistance change rates after each test of the coating films of Examples 1 to 6 and Comparative Examples 1 to 3.

Modes for Carrying Out the Invention

[0023] In this specification, the terms “contains” and “includes” include the concepts of “contains,” “includes,” “substantially consist of,” and “consist solely of.”

[0024] 1.Paint In one embodiment, the present invention relates to a coating composition (which may also be referred to as "the coating composition of the present invention" in this specification) containing carbon nanotubes, a triarylmethane-based dye, and polyacrylic acid. This is described below.

[0025] The carbon nanotubes are not particularly limited and can be manufactured by methods such as arc discharge, laser evaporation, or chemical vapor deposition (CVD). More specifically, single-walled carbon nanotubes, double-walled carbon nanotubes, multi-walled carbon nanotubes, and mixtures thereof can all be used. It is preferable to include at least single-walled carbon nanotubes due to their superior conductivity.

[0026] The length of the carbon nanotubes is preferably 1 to 2000 μm, more preferably 5 to 1000 μm, and even more preferably 5 to 500 μm. When the length of the carbon nanotubes is within the above range, the conductivity and transparency are excellent when used as a conductive layer.

[0027] The diameter of the carbon nanotube is preferably 0.5 to 20 nm, and more preferably 1 to 10 nm, in the case of single-walled carbon nanotubes. When the diameter of the carbon nanotube is within the above range, the conductivity and transparency are excellent when used as a conductive layer.

[0028] The BET specific surface area of ​​carbon nanotubes is, for example, 100 to 5000 m². 2 / g, preferably 500-3000 m 2 / g, more preferably 700-2000 m 2 It is / g.

[0029] The carbon nanotubes can be a single type or a combination of two or more types.

[0030] The content of carbon nanotubes in the coating composition of the present invention is not particularly limited as long as the dispersibility of the carbon nanotubes is not significantly impaired and a transparent conductive film can be formed. The content is, for example, 0.4% by mass or less, preferably 0.01 to 0.4% by mass, more preferably 0.02 to 0.3% by mass, still more preferably 0.04 to 0.2% by mass, and even more preferably 0.07 to 0.15% by mass.

[0031] A triarylmethane-based dye is a dye compound having a structure in which three aryl groups (preferably phenyl groups) are bonded to one carbon atom. The aryl groups may be bonded to each other via a divalent substituent such as an alkanediyl group or an ether bond. Generally, at least two aryl groups have an amino group, an ether group, or a hydroxy group.

[0032] Preferred examples of the amino group include -NR 1 R 2 where R 1 and R 2 are the same or different and are a hydrogen atom or a monovalent group. R 1 and R 2 may be bonded to each other to form a ring.

[0033] Examples of the monovalent group include an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, an alkylcarbonyl group having 1 to 20 carbon atoms, an alkylthio group having 1 to 20 carbon atoms, an aralkyl group having 1 to 20 carbon atoms, an alkenyl group having 1 to 20 carbon atoms, an alkynyl group having 1 to 20 carbon atoms, an ester group, an arylcarbonyl group, an arylthio group, an aryloxy group, an aromatic hydrocarbon group having 6 to 20 carbon atoms, or a heterocyclic group having 2 to 20 carbon atoms. These groups may be substituted with -SO3 - , an alkyl group, or the like. Preferred examples of the monovalent group include an alkyl group having 1 to 8 carbon atoms, an aryl group having 6 to 12 carbon atoms, an aralkyl group having 6 to 15 carbon atoms, and the like.

[0034] Examples of triarylmethane dyes include Brilliant Green, Brilliant Blue FCF, Malachite Green, Rhodamine B Base, Rhodamine B, Rhodamine 101, Victoria Blue R, Xylene Cyanol, Water Blue, Green S, Fast Green FCF, Coomassie Brilliant Blue, Crystal Violet Lactone, Crystal Violet, Simple Methyl Blue, Phenolphthalein, Cresol Red, Phenolsulfonphthalein, Thymol Blue, Phloxine, Bromothymol Blue, Bromophenol Blue, and others.

[0035] Triarylmethane dyes can be a single type or a combination of two or more types.

[0036] The content of the triarylmethane-based dye in the coating composition of the present invention is, for example, 0.1 to 50 parts by weight per 100 parts by weight of carbon nanotubes. From the viewpoint of the stability of the surface resistivity of the resulting carbon nanotube-containing transparent conductive film, the content is preferably 0.5 to 30 parts by weight, more preferably 1 to 25 parts by weight, even more preferably 2 to 20 parts by weight, and most preferably 4 to 17 parts by weight.

[0037] In the coating composition of the present invention, it is preferable that the triarylmethane-based dye is held in carbon nanotubes. This further enhances the stability of the surface resistivity of the resulting carbon nanotube-containing transparent conductive film. For example, the triarylmethane-based dye can be adsorbed on the surface of the carbon nanotubes.

[0038] Polyacrylic acid has the molecular formula: [-CH2CH(COOH)-] n The compound is represented by [formula], and is not particularly limited to that extent.

[0039] The weight-average molecular weight of polyacrylic acid is, for example, 500 to 30000. From the viewpoint of the stability of the surface resistivity of the resulting carbon nanotube-containing transparent conductive film, the molecular weight is preferably 1000 to 20000, more preferably 1000 to 15000, even more preferably 2000 to 10000, and particularly preferably 3000 to 7000.

[0040] Polyacrylic acid can be a single type or a combination of two or more types.

[0041] The polyacrylic acid content in the coating composition of the present invention is, for example, 1 to 300 parts by weight per 100 parts by weight of carbon nanotubes. From the viewpoint of the stability of the surface resistivity of the resulting carbon nanotube-containing transparent conductive film, the content is preferably 5 to 200 parts by weight, more preferably 10 to 150 parts by weight, even more preferably 20 to 100 parts by weight, and even more preferably 30 to 70 parts by weight. Furthermore, from the viewpoint of the adhesion of the resulting carbon nanotube-containing transparent conductive film to the substrate, the content is preferably 200 parts by weight or less, more preferably 150 parts by weight or less, even more preferably 100 parts by weight or less, and even more preferably 70 parts by weight or less.

[0042] The coating composition of the present invention preferably contains a dispersant. The dispersant is not particularly limited as long as it can improve the dispersibility of carbon nanotubes. As dispersants, anionic, cationic, nonionic, and amphoteric surfactants; polymeric dispersants can be used.

[0043] When selecting anionic surfactants, the type is not particularly limited. Specifically, examples include, but are not limited to, fatty acid salts, polysulfonates, polystyrene sulfonic acid, polycarboxylate salts, alkyl sulfate salts, alkylaryl sulfonates, alkylnaphthalene sulfonates, dialkyl sulfonates, dialkyl sulfosuccinates, alkyl phosphates, polyoxyethylene alkyl ether sulfates, polyoxyethylene alkylaryl ether sulfates, naphthalene sulfonic acid formalin condensates, polyoxyethylene alkyl phosphate sulfonates, glycerol borate fatty acid esters, and polyoxyethylene glycerol fatty acid esters. Furthermore, specifically, examples include, but are not limited to, sodium dodecylbenzenesulfonate, sodium lauryl sulfate, sodium polyoxyethylene lauryl ether sulfate, polyoxyethylene nonylphenyl ether sulfate salts, and sodium salts of β-naphthalene sulfonic acid formalin condensates.

[0044] Cationic surfactants include alkylamine salts and quaternary ammonium salts. Specifically, examples include, but are not limited to, stearylamine acetate, trimethyl coconut ammonium chloride, trimethyl beef tallow ammonium chloride, dimethyl dioleyl ammonium chloride, methyl oleyl diethanol chloride, tetramethyl ammonium chloride, laurylpyridinium chloride, laurylpyridinium bromide, laurylpyridinium disulfate, cetylpyridinium bromide, 4-alkyl mercaptopyridine, poly(vinylpyridine)-dodecyl bromide, and dodecylbenzyltriethylammonium chloride.

[0045] Nonionic surfactants include, but are not limited to, polyoxyethylene alkyl ethers, polyoxyalkylene derivatives, polyoxyethylene phenyl ethers, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, and alkyl allyl ethers. Specifically, they include, but are not limited to, polyoxyethylene lauryl ethers, sorbitan fatty acid esters, and polyoxyethylene octylphenyl ethers. Amphoteric surfactants include, but are not limited to, aminocarboxylate salts.

[0046] Examples of polymeric dispersants include cellulose derivatives (cellulose acetate, cellulose acetate butyrate, cellulose butyrate, cyanoethylcellulose, ethyl hydroxyethylcellulose, nitrocellulose, methylcellulose, ethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose, carboxymethylcellulose, etc.), polyvinyl alcohol, polyvinyl butyral, polyvinylpyrrolidone, and polyacrylonitrile polymers.

[0047] The dispersant can be a single type or a combination of two or more types.

[0048] If the coating composition of the present invention contains a dispersant, the amount of dispersant in the coating composition of the present invention is not particularly limited, as long as the dispersibility of carbon nanotubes is not significantly impaired and a transparent conductive film can be formed. The amount (in terms of solid content) is, for example, 50 to 2000 parts by mass, preferably 100 to 1500 parts by mass, more preferably 200 to 1000 parts by mass, even more preferably 300 to 700 parts by mass, and even more preferably 400 to 600 parts by mass, per 100 parts by mass of carbon nanotubes.

[0049] The paint composition of the present invention preferably contains a binder. The binder is not particularly limited as long as it can be used as a carbon nanotube-containing paint.

[0050] Examples of binders include silicon compound binders; polymers or copolymers containing ethylene, propylene, vinyl chloride, vinyl acetate, vinyl alcohol, maleic acid, acrylic acid, acrylic acid esters, methacrylic acid, methacrylic acid esters, acrylonitrile, styrene, vinyl butyral, vinyl acetal, vinylpyrrolidone, etc. as constituent units; polyurethane resins, polyester resins, phenolic resins, epoxy resins, phenoxy resins, urea resins, melamine resins, alkyd resins, acrylic resins, formaldehyde resins, silicone resins, fluororesins; cellulose resins such as carboxymethylcellulose; rubbers such as styrene-butadiene rubber and fluororubber; and conductive resins such as polyaniline and polyacetylene.

[0051] A silicon compound binder is a colloidal dispersion, solution, or emulsion of a silicon compound, comprising a solid or liquid silicon compound in an aqueous dispersion medium. Examples of silicon compound binders include silicates such as silicates; colloidal silica; silane and siloxane hydrolysate emulsions; silicone resin emulsions; and emulsions of copolymers of silicone resins with other resins, such as silicone-acrylic resin copolymers and silicone-urethane resin copolymers.

[0052] A binder can be a single type or a combination of two or more types.

[0053] If the coating composition of the present invention contains a binder, the amount of binder in the coating composition of the present invention is not particularly limited, as long as the dispersibility of carbon nanotubes is not significantly impaired and a transparent conductive film can be formed. The amount (in terms of solid content) is, for example, 10 to 1000 parts by mass, preferably 20 to 700 parts by mass, more preferably 50 to 500 parts by mass, even more preferably 100 to 400 parts by mass, and even more preferably 150 to 300 parts by mass, per 100 parts by mass of carbon nanotubes.

[0054] The paint composition of the present invention preferably contains an inorganic acid.

[0055] Inorganic acids are acids composed of inorganic compounds, and are not particularly limited in this respect. Examples of inorganic acids include strong acids such as nitric acid, sulfuric acid, and hydrochloric acid; and weak acids such as phosphoric acid and boric acid. Among these, strong acids are preferred, and nitric acid and sulfuric acid are particularly preferred. Sulfuric acid is particularly preferred from the viewpoint of the stability of the surface resistance of the coating film.

[0056] Inorganic acids can be a single type or a combination of two or more types.

[0057] When the coating composition of the present invention contains an inorganic acid, the content of the inorganic acid in the coating composition of the present invention is not particularly limited, as long as the dispersibility of carbon nanotubes is not significantly impaired and a transparent conductive film can be formed. The content is, for example, 0.1 to 5% by mass, preferably 0.2 to 4% by mass, more preferably 0.5 to 3% by mass, and even more preferably 1 to 2% by mass.

[0058] The paint composition of the present invention usually contains a solvent. The solvent is mainly water. Organic solvents, or mixed solvents of water and organic solvents, can also be used. Examples of organic solvents include: alcohols such as methanol, ethanol, 2-propanol, and 1-propanol; ethylene glycols such as ethylene glycol, diethylene glycol, triethylene glycol, and tetraethylene glycol; glycol ethers such as ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, ethylene glycol diethyl ether, and diethylene glycol dimethyl ether; glycol ether acetates such as ethylene glycol monoethyl ether acetate, diethylene glycol monoethyl ether acetate, and diethylene glycol monobutyl ether acetate; propylene glycols such as propylene glycol, dipropylene glycol, and tripropylene glycol; and propylene glycol monomethyl ether, propylene glycol monoethyl ether, dipropylene glycol monomethyl ether, propylene glycol dimethyl ether, and propylene glycol diethyl ether. Examples include: propylene glycol ethers; propylene glycol ether acetates 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; hydrocarbons such as toluene, xylene (o-, m-, or p-xylene), hexane, and heptane; esters such as ethyl acetate, butyl acetate, ethyl acetoacetate, methyl orthoacetate, and ethyl orthoformate; amide compounds such as N-methylformamide, N,N-dimethylformamide, γ-butyrolactone, and N-methylpyrrolidone; hydroxyl group-containing compounds such as trimethylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, catechol, cyclohexanediol, cyclohexanedimethanol, and glycerin; and compounds having a sulfo group such as dimethyl sulfoxide.

[0059] The paint composition of the present invention can be manufactured by mixing each component. From the viewpoint of the stability of the surface resistivity of the resulting carbon nanotube-containing transparent conductive film, the paint composition of the present invention is (A) A step of bringing carbon nanotubes into contact with a triarylmethane-based dye in a liquid. (B) After step (A), a step of adding a dispersant to the liquid containing the carbon nanotubes, and (C) After step (B), a step of adding polyacrylic acid to the liquid containing the carbon nanotubes, It is particularly preferable to manufacture it by a method that includes [the specified element].

[0060] The liquid contact in step (A) can be carried out, for example, by mixing the two in the aforementioned solvent such as water. Typically, this step causes the triarylmethane dye to adsorb onto the surface of the carbon nanotubes. This adsorption can be confirmed by the fact that the color of the solution derived from the triarylmethane dye approaches colorless and transparent. No dispersant is used in step (A).

[0061] Step (B) can be carried out by mixing a solution obtained by dissolving a dispersant in the aforementioned solvent, such as water, with the liquid obtained in step (A). If necessary, a dispersion device can be used to uniformly disperse the carbon nanotubes in the solvent.

[0062] Step (C) can be carried out by mixing a solution obtained by dissolving polyacrylic acid in the aforementioned solvent, such as water, with a liquid containing carbon nanotubes. In this process, a binder, a triarylmethane-based dye solution, etc., can be added as needed.

[0063] After step (C), aggregates and other materials can be removed by filtration or other means as needed to obtain the paint composition of the present invention.

[0064] The coating composition of the present invention makes it possible to obtain a transparent conductive film containing carbon nanotubes with higher surface resistivity stability.

[0065] 2. Method for manufacturing the coating film In one embodiment, the present invention relates to a method for manufacturing a coating film (which may be referred to as "the manufacturing method of the present invention" in this specification), comprising the step of (a) applying the coating composition of the present invention onto a substrate. This will be described below.

[0066] The substrate is not particularly limited, as long as it contains a resin that can be used as a substrate for a transparent conductive film (substrate resin).

[0067] The base material may contain components other than the base material resin, as long as the effects of the present invention are not significantly impaired. In that case, the total amount of base material resin in the base material is, for example, 80% by mass or more, preferably 90% by mass or more, more preferably 95% by mass or more, and even more preferably 99% by mass or more, and less than 100% by mass.

[0068] The resin used as the base material is not particularly limited and includes, for example, polyester resins such as polyethylene terephthalate (PET), polyethylene naphthalate, and modified polyester; polyolefin resins such as polyethylene (PE) resin, polypropylene (PP) resin, polystyrene resin, and cyclic olefin resin; vinyl resins such as polyvinyl chloride and polyvinylidene chloride; polyvinyl acetal resins such as polyvinyl butyral (PVB); polyetheretherketone (PEEK) resin, polysulfone (PSF) resin, polyethersulfone (PES) resin, polycarbonate (PC) resin, polyamide resin, polyimide resin, acrylic resin, and triacetylcellulose (TAC) resin. Among these, from the viewpoint of transparency and other factors, polyethylene terephthalate, polyethylene naphthalate, polyethersulfone, and polycarbonate are preferred, and polyethylene terephthalate is more preferred.

[0069] The base resin may be a single type or a combination of two or more types.

[0070] The thickness of the substrate is not particularly limited, as long as transparency and strength suitable for the application are ensured. The thickness of the substrate is, for example, 2 to 500 μm, preferably 10 to 400 μm, more preferably 20 to 300 μm, even more preferably 50 to 200 μm, and even more preferably 70 to 150 μm.

[0071] The layer structure of the substrate is not particularly limited. The substrate may consist of a single substrate, or it may be a combination of two or more substrates having the same or different compositions.

[0072] The substrate may be subjected to various surface treatments. Examples of surface treatments include surface activation treatments such as corona discharge treatment, flame treatment, ultraviolet treatment, high-frequency treatment, glow discharge treatment, activated plasma treatment, and laser treatment.

[0073] The coating method is not particularly limited. For example, conventionally known coating methods such as gravure coating, reverse roll coating, die coating, air doctor coating, blade coating, rod coating, bar coating, curtain coating, knife coating, transfer roll coating, squeeze coating, impregnation coating, kiss coating, spray coating, calender coating, and extrusion coating can be used.

[0074] After coating, it is preferable to allow it to dry. The drying temperature is, for example, 50 to 200°C, preferably 70 to 170°C, and more preferably 90 to 150°C. The drying time may also vary depending on the drying temperature, but is, for example, 30 seconds to 15 minutes, preferably 1 to 10 minutes, and more preferably 2 to 5 minutes.

[0075] The manufacturing method of the present invention preferably includes a step of washing the coating film obtained in step (a) with water. This further reduces the surface resistance of the coating film.

[0076] The cleaning method is not particularly limited, and various methods of bringing water into contact with the coating surface can be employed. Typically, cleaning can be done by directing running water onto the coating surface. The cleaning time can be, for example, 1 to 30 seconds.

[0077] After washing, drying is preferable. The drying temperature is, for example, 50 to 200°C, preferably 70 to 170°C, and more preferably 90 to 150°C. The drying time may also vary depending on the drying temperature, but is, for example, 30 seconds to 15 minutes, preferably 1 to 10 minutes, and more preferably 2 to 5 minutes.

[0078] The coating obtained by the manufacturing method of the present invention is a transparent conductive film containing carbon nanotubes with higher surface resistivity stability.

[0079] 3. Transparent conductive film In one embodiment, the present invention relates to a transparent conductive film (which may be referred to as "the transparent conductive film of the present invention" in this specification) comprising carbon nanotubes, a triarylmethane-based dye, and polyacrylic acid. This will be described below.

[0080] The content of triarylmethane-based dyes and polyacrylic acid in the transparent conductive film of the present invention is the same as the content of triarylmethane-based dyes and polyacrylic acid in the coating composition of the present invention. Alternatively, the content of triarylmethane-based dyes and polyacrylic acid in the transparent conductive film of the present invention is, for example, 40-100%, 50-100%, or 60-100% relative to 100% of the content of triarylmethane-based dyes and polyacrylic acid in the coating composition of the present invention.

[0081] In the transparent conductive film of the present invention, it is preferable that the triarylmethane-based dye is held by the carbon nanotube. This makes it possible to further improve the stability of the surface resistivity of the resulting carbon nanotube-containing transparent conductive film. For example, the triarylmethane-based dye can be adsorbed on the surface of the carbon nanotube. In this case, The surface resistivity of the transparent conductive film of the present invention is, for example, 500 Ω / □ or less, preferably 400 Ω / □ or less, and more preferably 300 Ω / □ or less. The lower limit of this surface resistivity is not particularly limited and may be, for example, 10 Ω / □, 20 Ω / □, or 40 Ω / □.

[0082] Surface resistivity is measured using a low resistivity meter (Loresta-GP MCP-T610, manufactured by Mitsubishi Chemical Analytec).

[0083] The transparent conductive film of the present invention exhibits higher stability in surface resistivity.

[0084] For example, the transparent conductive film of the present invention has a resistance change rate (= [(surface resistivity after 1500 hours - surface resistivity immediately after film formation) / surface resistivity immediately after film formation] × 100 (%)) after 1500 hours in an indoor ambient temperature environment (15°C to 25°C), which is preferably 20% or less (including negative values; the same applies hereinafter), more preferably 10% or less, and even more preferably 5% or less. More preferably, the absolute value of the resistance change rate is preferably 20% or less, more preferably 10% or less, and even more preferably 5% or less.

[0085] For example, the transparent conductive film of the present invention has a resistance change rate (= [(surface resistivity after 1500 hours - surface resistivity immediately after film formation) / surface resistivity immediately after film formation] × 100 (%)) after 1500 hours under light-shielding conditions and in a 100°C environment, preferably 20% or less (including negative values; the same applies hereinafter), more preferably 10% or less, and even more preferably 5% or less. More preferably, the absolute value of the resistance change rate is preferably 20% or less, more preferably 10% or less, and even more preferably 5% or less.

[0086] For example, the transparent conductive film of the present invention has a resistance change rate (= [(surface resistivity after 1500 hours - surface resistivity immediately after film formation) / surface resistivity immediately after film formation] × 100 (%)) after 1500 hours under light-shielding conditions and in a 50°C 95%RH environment, preferably 20% or less (including negative values; the same applies hereinafter), more preferably 10% or less, and even more preferably 5% or less. More preferably, the absolute value of the resistance change rate is preferably 20% or less, more preferably 10% or less, and even more preferably 5% or less.

[0087] For example, the transparent conductive film of the present invention is subjected to light irradiation (super xenon lamp, BPT (black panel temperature) = 63°C, illuminance = 180 W / m²). 2 The resistance change rate after 100 hours under the following conditions (=[(surface resistivity after 100 hours - surface resistivity immediately after film formation) / surface resistivity immediately after film formation] × 100 (%)) is preferably 20% or less (including negative values; the same applies hereinafter), more preferably 10% or less, and even more preferably 5% or less. More preferably, the absolute value of the resistance change rate is preferably 20% or less, more preferably 10% or less, and even more preferably 5% or less.

[0088] 4.Applications The transparent conductive film of the present invention can be used in various applications requiring transparency and conductivity, such as transparent electrodes in touch panels and display elements of various electronic devices such as televisions and mobile phones using various display methods such as liquid crystal, plasma, and field emission; transparent electrodes in solar cells, electromagnetic shielding materials, electronic paper, and electroluminescent dimming elements; electrolytic plating primers; and transparent surface heating elements. [Examples]

[0089] The present invention will be described in detail below based on examples, but the present invention is not limited to these examples.

[0090] (1) Preparation of paint (Example 1) Single-walled carbon nanotubes (CNTs) (OCSiAl Corporation, TUBALL PD0559, diameter: 1.6±0.4 nm, length: >5 μm, BET specific surface area: 1160 m²) 2 To 0.05 g of powder (1 / g), 10 mL of Brilliant Green (BRG) 0.06% solution (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added and stirred for approximately 15 minutes. During this stirring, the color of the solution changed from the color derived from BRG to colorless and transparent. A dispersant (ammonium polystyrene sulfonate, manufactured by Nouryon Surface Chemistry, VERSA-TL125, 30% solids) was dissolved in deionized water and added to the CNT solution obtained above. At this time, the solution was prepared so that the ratio of single-walled CNTs / dispersant was 100 / 500 (solids ratio) and the single-walled CNT ratio was 0.1%. The single-walled CNTs were uniformly dispersed in water using a dispersion apparatus. To 10 parts by weight of the obtained single-walled carbon nanotube dispersion, 0.1 parts by weight of binder (sodium silicate No. 3, manufactured by Fuji Chemical Co., Ltd.) and 0.3 parts by weight of 1 mol / L sulfuric acid were added and stirred for 5 minutes. Subsequently, 0.1 parts by weight of 5% polyacrylic acid (PAA) (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., weight-average molecular weight 5000) solution was added and stirred for 5 minutes. Subsequently, 0.3 parts by weight of IPA (isopropyl alcohol) was added and stirred for 5 minutes. The resulting liquid was filtered through a 200-mesh filter to obtain the paint.

[0091] (Example 2) The paint was obtained in the same manner as in Example 1, except that 0.2 parts by weight of a 0.1% BRG solution was added when adding PAA.

[0092] (Example 3) A paint was obtained in the same manner as in Example 1, except that Brilliant Blue (BRB) (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was used instead of BRG.

[0093] (Example 4) A paint was obtained in the same manner as in Example 2, except that BRB was used instead of BRG.

[0094] (Example 5) A paint was obtained in the same manner as in Example 1, except that malachite green oxalate (MG) (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was used instead of BRG.

[0095] (Example 6) The paint was obtained in the same manner as in Example 2, except that MG was used instead of BRG.

[0096] (Comparative Example 1) Dissolve the dispersant (ammonium polystyrene sulfonate, Nouryon Surface Chemistry, VERSA-TL125, 30% solids) in deionized water, and add single-walled carbon nanotubes (CNTs) (OCSiAl, TUBALL PD0559, diameter: 1.6±0.4 nm, length: >5 μm, BET specific surface area: 1160 m²). 2 It was added to 0.05 g of powder ( / g). At this time, the mixture was prepared so that the ratio of single-walled carbon nanotubes (WNTs) to dispersant was 100 / 500 (solid content ratio) and the proportion of WNTs was 0.1%. The WNTs were uniformly dispersed in water using a dispersion device. To 10 parts by weight of the obtained WNT dispersion, 0.1 parts by weight of binder (sodium silicate No. 3, manufactured by Fuji Chemical Co., Ltd.) and 0.3 parts by weight of 1 mol / L sulfuric acid were added and stirred for 5 minutes, and then 0.3 parts by weight of IPA (isopropyl alcohol) was added and stirred for 5 minutes. The resulting liquid was filtered through a 200-mesh filter to obtain the paint.

[0097] (Comparative Example 2) A paint was obtained in the same manner as in Comparative Example 1, except that 0.1 parts by weight of PAA solution was added between the addition of the binder and sulfuric acid and the addition of IPA, and the mixture was stirred for 5 minutes.

[0098] (Comparative Example 3) A coating was obtained in the same manner as in Example 1, except that 0.2 parts by weight of a 0.1% BRG solution was added instead of PAA.

[0099] Table 1 shows the differences in elements (content of triarylmethane-based dyes and content of polyacrylic acid) in the paints of Examples 1-6 and Comparative Examples 1-3.

[0100] [Table 1]

[0101] (2) Preparation of CNT coating CNT coatings were prepared using the paints of Examples 1-6 and Comparative Examples 1-3. The preparation methods are shown below.

[0102] A 100 μm thick PET film (visible light transmittance 90%) was coated using a coating bar with a bar diameter of 0.2 mm. The resulting coated film was dried in a hot air dryer at 120°C for 3 minutes. The coated surface of the dried film was washed with deionized water (running water). During this process, the entire coated surface was exposed to running water. The washing time was several seconds to about ten seconds. The washing water was lightly shaken off the coating film, and the film was dried in a hot air dryer at 120°C for 5 minutes until the washing water on the coating film was completely dry, thereby obtaining a CNT coating film. The CNT coating film was transparent, and the visible light transmittance measured using an ultraviolet-visible-near-infrared spectrophotometer (V-770 Spectrophotometer, JASCO Corporation) was approximately 70-73%.

[0103] Furthermore, the amount of triarylmethane-based dye adsorbed onto single-walled carbon nanotubes (WNTs) was measured. The coatings obtained using the paints of Examples 2, 4, and 6 were washed with a fixed amount of deionized water, and the amount of BRG contained in the washing solution was measured. The amount of adsorption was calculated from the difference between the amount of BRG added and the amount of BRG added. The ratio of the amount of adsorption to the amount of BRG added (adsorption rate) was as follows.

[0104] <Example 2> BRG adsorption amount: 9.12 × 10 ^-7 [mol] Adsorption rate: 69.18[%] <Example 4> BRB adsorption capacity: 7.23 × 10 ^-7 [mol] Adsorption rate: 90.06[%] <Example 6> MG adsorption capacity: 6.82 × 10 ^-7 [mol] Adsorption rate: 99.37[%].

[0105] (3) Evaluation of CNT coating The surface resistivity (initial surface resistivity S1) of the CNT coating films immediately after deposition, prepared using the paints of Examples 1-6 and Comparative Examples 1-3, was measured using a low resistivity meter (Loresta-GP MCP-T610, manufactured by Mitsubishi Chemical Analytec).

[0106] (3-A) Room temperature environment test After the CNT coating film is deposited, it is left to stand for approximately 1500 hours in an indoor room temperature environment (15°C to 25°C), and then the surface resistivity (S2) is determined in the same manner as above. A ) was measured.

[0107] (3-B) Heat resistance test After the CNT coating film was deposited, it was left to stand for approximately 1500 hours under light-shielding conditions and in a 100°C environment, and then the surface resistivity was measured in the same manner as above (S2 B )did.

[0108] (3-C) Heat and moisture resistance test After the CNT coating film is deposited, it is left to stand for approximately 1500 hours under light-shielding conditions and in a 50°C, 95% RH environment, and then the surface resistivity (S2) is determined in the same manner as above. C ) was measured.

[0109] (3-D) Lightfastness Test Light irradiation of the CNT coating immediately after deposition (super xenon lamp, BPT (black panel temperature) = 63°C, illuminance = 180 W / m²). 2 After performing the above procedure for 100 hours, the surface resistivity (S2) was determined in the same manner as above. D ) was measured.

[0110] Initial surface resistivity (S1) and surface resistivity after testing (S2:S2 A S2 B S2 C , or S2 DThe resistance change rate (=[(S2-S1) / S1]×100) was calculated from the above. The results are shown in Table 2 and Figure 1. As shown in Table 2 and Figure 1, it was found that the stability of the surface resistivity is further enhanced by including both triarylmethane-based dyes and polyacrylic acid.

[0111] [Table 2]

Claims

1. A coating composition for forming a transparent conductive film, containing carbon nanotubes, a triarylmethane-based dye, and polyacrylic acid.

2. The transparent conductive film-forming coating composition according to claim 1, wherein the triarylmethane-based dye has an amino group.

3. The transparent conductive film forming coating composition according to claim 1, wherein the weight-average molecular weight of the polyacrylic acid is 500 to 30000.

4. The transparent conductive film forming coating composition according to claim 1, wherein the carbon nanotube content is 0.4% by mass or less.

5. The transparent conductive film forming coating composition according to claim 1, wherein the content of the triarylmethane-based dye is 0.1 to 50 parts by weight per 100 parts by mass of the carbon nanotube.

6. The transparent conductive film forming coating composition according to claim 1, wherein the polyacrylic acid content is 1 to 300 parts by mass of the carbon nanotube.

7. The transparent conductive film forming coating composition according to any one of claims 1 to 6, wherein the triarylmethane-based dye is held in the carbon nanotube.

8. (A) A step of mixing carbon nanotubes and triarylmethane-based dyes in liquid, (B) After step (A), a step of adding a dispersant to the liquid containing the carbon nanotubes, and (C) After step (B), a step of adding polyacrylic acid to the liquid containing the carbon nanotubes, A method for producing a transparent conductive film-forming coating composition according to any one of claims 1 to 6, comprising:

9. The method according to claim 8, wherein in step (C), a binder is added to the liquid containing the carbon nanotubes.

10. (a) A method for manufacturing a coating film, comprising the step of applying a transparent conductive film-forming coating composition according to any one of claims 1 to 6 onto a substrate.

11. A transparent conductive film containing carbon nanotubes, a triarylmethane-based dye, and polyacrylic acid.

12. The transparent conductive film according to claim 11, wherein the triarylmethane-based dye is held in the carbon nanotube.

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