Conductive composition

Abstract

An objective of the present invention is to provide a conductive composition useful for manufacturing a conductive laminate that undergoes a small change in conductivity over time. The conductive composition contains a carbon nanotube (A), a dispersant (B), and a phenol (C), wherein the phenol (C) has a carboxyl group or an alkoxycarbonyl group that may have a hetero atom, and the molecular weight thereof is 100-1000.

Description

conductive composition

[0001] The present invention relates to an electrically conductive composition.

[0002] Conductive laminates such as transparent conductive films and antistatic films are manufactured by applying a coating agent containing a conductive material to a substrate and drying it. Carbon nanotubes are used as a conductive material because of their excellent conductivity, durability, and stretchability.

[0003] On the other hand, components in the atmosphere act as dopants on carbon nanotubes, which tends to improve the conductivity of conductive laminates containing carbon nanotubes over time. If the conductivity is too high, unintended conduction can cause malfunctions. Therefore, in applications requiring a certain level of quality, such as image display devices, it is necessary to stabilize the conductivity of conductive laminates over time. Patent Document 1 describes a method for suppressing changes in conductivity over time caused by atmospheric substances by depositing donors such as alkaline earth metal elements and acceptors such as fullerenes in the vapor phase on the outer surface of carbon nanotubes. However, these carbon nanotubes are formed by vapor-phase growth starting from a catalyst film, making it difficult to create a coating agent that is easy to use and industrially productive using wet processes such as roll coating or printing.

[0004] Japanese Patent Application Laid-Open No. 2006-190815

[0005] An object of the present invention is to provide a conductive composition that is useful for producing a conductive laminate that exhibits little change in conductivity over time.

[0006] The present inventors have discovered that a conductive laminate with little change in conductivity over time can be produced by using a conductive composition containing carbon nanotubes and a specific phenol, and have completed the present invention.

[0007] That is, the present invention includes the following aspects: <1> A conductive composition comprising carbon nanotubes (A), a dispersant (B), and a phenol (C), wherein the phenol (C) has a carboxyl group or an alkoxycarbonyl group which may have a heteroatom, and has a molecular weight of 100 to 1,000.

[0008] <2> The conductive composition according to item 1, further comprising 20 to 2500 parts by weight of a phenol (C) per 100 parts by weight of the total amount of the carbon nanotubes (A) and the dispersant (B).

[0009] <3> The conductive composition according to item 1 or 2, wherein the phenol (C) is a compound containing one aromatic ring.

[0010] <4> The conductive composition according to any one of items 1 to 3, further comprising a binder (D).

[0011] <5> A conductive film comprising the conductive composition according to any one of items 1 to 4.

[0012] <6> A conductive laminate comprising a substrate and the conductive film according to item 5 formed on the substrate.

[0013] By using the conductive composition of the present invention, a conductive laminate with little change in conductivity over time can be produced.

[0014] <<Conductive Composition>> The conductive composition of the present invention comprises carbon nanotubes (A), a dispersant (B), and a phenol (C), wherein the phenol (C) has a carboxyl group or an alkoxycarbonyl group that may have a heteroatom, and has a molecular weight of 100 to 1000. Note that, unless otherwise specified, the molecular weight in this specification is a weight average molecular weight.

[0015] <Carbon Nanotubes (A)> Carbon nanotubes are conductive materials with excellent conductivity, durability, and stretchability. The type of carbon nanotube is not particularly limited, and single-walled carbon nanotubes, double-walled carbon nanotubes, multi-walled carbon nanotubes, and mixtures containing these in any proportion can be used. Single-walled carbon nanotubes and double-walled carbon nanotubes are preferred because they are easy to use to obtain a conductive film with excellent heat resistance and / or moist heat resistance, and single-walled carbon nanotubes are more preferred because they have excellent conductivity. The method for producing carbon nanotubes is not particularly limited, and carbon nanotubes produced by known methods such as arc discharge, laser evaporation, and chemical vapor deposition (CVD) can be appropriately selected and used.

[0016] The length of the carbon nanotubes is preferably 0.1 to 2000 μm, more preferably 0.5 to 1000 μm, and even more preferably 0.5 to 500 μm. If the length exceeds 2000 μm, the carbon nanotubes tend to aggregate. If the length is less than 0.1 μm, the formation of conductive paths tends to be insufficient.

[0017] The diameter of the carbon nanotubes is preferably 0.1 to 50 nm, more preferably 0.3 to 20 nm, even more preferably 0.5 to 10 nm, and particularly preferably 0.5 to 5 nm. If the diameter exceeds 50 nm, the conductivity tends to decrease. Carbon nanotubes less than 0.1 nm are difficult to produce. Within the range of 0.5 to 5 nm, the conductivity can be maximized while maintaining dispersibility.

[0018] The content of carbon nanotubes in the conductive composition is preferably 0.1 to 60 wt %, more preferably 1 to 50 wt %, and even more preferably 5 to 40 wt %, based on the solid content. The content of carbon nanotubes (A) in the carbon nanotube dispersion is also preferably within the above range. Furthermore, when the conductive composition contains a binder, a crosslinking agent, or the like, the content of carbon nanotubes is preferably 0.1 to 40 wt %, preferably 0.1 to 30 wt %, and even more preferably 0.1 to 20 wt %, based on the solid content.

[0019] <Dispersant (B)> The dispersant has the function of suppressing aggregation of carbon nanotubes in the conductive composition and stably dispersing them. The dispersant may be any of cationic dispersants, anionic dispersants, amphoteric dispersants, nonionic dispersants, and polymeric dispersants, as long as it can suppress aggregation of carbon nanotubes. 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. The HLB value can be calculated using the following formula: Griffin method: HLB value = [(molecular weight of hydrophilic portion) ÷ (total molecular weight)] × 20

[0020] Examples of cationic dispersants 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.

[0021] Examples of the anionic dispersant include sodium alkyl sulfates having 8 to 18 carbon atoms, such as sodium lauryl sulfate; polyoxyethylene alkyl ether sulfates having 8 to 18 carbon atoms, such as sodium polyoxyethylene lauryl ether sulfate; alkylbenzenesulfonates having an alkyl group having 8 to 18 carbon atoms, such as sodium deoxycholate and sodium dodecylbenzenesulfonate; fatty acid salts; and naphthalenesulfonate-formalin condensates, such as the sodium salt of β-naphthalenesulfonate-formalin condensate.

[0022] Examples of amphoteric dispersants include alkylbetaines having an alkyl group with 8 to 22 carbon atoms, and alkylamine oxides having an alkyl group with 8 to 18 carbon atoms.

[0023] Examples of nonionic dispersants include polyoxyethylene alkyl ethers having an alkyl group with 1 to 20 carbon atoms, block copolymers composed of ethylene oxide and propylene oxide, alkylphenol polyethylene glycol ethers having an alkyl group with 1 to 20 carbon atoms, polyoxyalkylene derivatives such as polycarboxylate ethers having an alkylene group with 2 to 4 carbon atoms, and sorbitan fatty acid esters such as sorbitan tristearate.

[0024] 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, acrylic copolymers, sulfonic acid group-containing polymers, and carboxylic acid group-containing polymers.

[0025] Among polymeric dispersants, sulfonic acid group-containing polymers are polymeric compounds having sulfonic acid in the side chain of the main skeleton, such as fluorine-based polymers having sulfonic acid and hydrocarbon-based polymers having sulfonic acid. Fluorine-based polymers having sulfonic acid include perfluorosulfonic acid polymers and partially fluorinated sulfonic acid polymers. Hydrocarbon-based polymers having sulfonic acid include polystyrene sulfonic acid, polyvinyl sulfonic acid, polyisoprene sulfonic acid, sulfoethylated corn starch, polyester sulfonic acid, polyimide sulfonic acid, polyvinylidene fluoride sulfonic acid, polyether sulfonic acid, polyphenylene sulfide sulfonic acid, polyphenylene oxide sulfonic acid, polyethylene naphthalate sulfonic acid, polypyrrole sulfonic acid, aromatic sulfonic acid polymers, and bisphenol fluorene sulfonic acid. Among these, perfluorosulfonic acid polymers and polystyrene sulfonic acid are preferred, with Nafion (NAFION (registered trademark), manufactured by DuPont), Aquivion (AQUIVION (registered trademark), manufactured by Solvay Specialty Polymers), and polystyrene sulfonic acid being more preferred. The weight-average molecular weight of the polymeric sulfonic acid is preferably 1,000 to 200,000, and more preferably 75,000 to 100,000.

[0026] The content of the dispersant is preferably 1 to 10,000 parts by weight, more preferably 20 to 4,000 parts by weight, and even more preferably 50 to 2,000 parts by weight, per 100 parts by weight of the solid content of the carbon nanotubes. Within this range, the coating film tends to have excellent conductivity.

[0027] <Phenols (C)> Generally, phenols refer to aromatic compounds in which hydrogen atoms on the aromatic ring are substituted with hydroxyl groups (—OH). In the present invention, phenols having a carboxyl group or an alkoxycarbonyl group which may have a heteroatom and a molecular weight of 100 to 1,000 are used.

[0028] A carboxyl group or an alkoxycarbonyl group, which may have a heteroatom, has high electron-withdrawing properties and easily destabilizes the O-H bond of a hydroxyl group bonded to an aromatic ring. When a hydrogen atom dissociates from the destabilized O-H bond and is replaced by a free radical, the number of free radicals in the system decreases. As a result, it is presumed that oxidation of carbon nanotubes by free radicals and the resulting doping are suppressed. However, the present invention is not limited to this mechanism.

[0029] The number of aromatic rings contained in the phenols of the present invention is preferably 1 to 3, more preferably 1 to 2, and even more preferably 1. It is also preferable that the phenols do not contain a structure in which two or more aromatic rings are fused. The number of phenolic hydroxyl groups contained in the phenols of the present invention is preferably 1 to 5, and more preferably 2 to 3. The number of carboxyl groups or alkoxycarbonyl groups which may have a heteroatom contained in the phenols of the present invention is preferably 1 to 3, more preferably 1 to 2, and even more preferably 1. If the structure of the phenols is outside the above range, the change over time in the conductivity of a conductive laminate obtained using the conductive composition tends to be significant.

[0030] When there are two hydroxyl groups bonded to the aromatic ring, the positions of the hydroxyl groups may be any of positions 1 and 2, positions 1 and 3, or positions 1 and 4, with positions 1 and 2 being preferred.When there are three hydroxyl groups bonded to the aromatic ring, the positions may be any of positions 1, 2, and 3; positions 1, 2, and 4; or positions 1, 2, and 5, with positions 1, 2, and 3 being preferred.

[0031] The phenols in the present invention may have a structure bonded to the aromatic ring other than a hydroxyl group, a carboxyl group, or an alkoxycarbonyl group which may have a heteroatom, such as an alkoxy group having 1 to 4 carbon atoms and a sulfonyl group.

[0032] In the phenols of the present invention, the position of the carboxyl group or the alkoxycarbonyl group which may have a heteroatom is not particularly limited, and may be directly bonded to the aromatic ring or may be bonded to the aromatic ring via a linker structure. When bonded to the aromatic ring via a linker structure, the linker structure is preferably a hydrocarbon, more preferably a hydrocarbon which forms a conjugated system with the aromatic ring, and even more preferably a hydrocarbon which contains a carbon-carbon double bond. The number of carbon atoms in the linker structure is preferably 2 to 4, more preferably 2.

[0033] In the alkoxycarbonyl group (-(C=O)OR), the number of carbon atoms in the alkyl group (R) bonded to the oxygen atom is preferably 1 to 10, and more preferably 1 to 6. The alkyl group bonded to the oxygen atom may be linear or branched, or may have a cyclic structure. In addition, the alkyl group bonded to the oxygen atom may have a heteroatom such as O, S, N, P, or Cl. Examples of such alkyl groups include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, and a cyclohexyl group. In these alkyl groups, the hydrogen atom may be substituted with a hydroxyl group, a carboxyl group, a sulfonyl group, or the like.

[0034] The molecular weight of the phenol in the present invention is 100 to 1,000, preferably 100 to 500, and more preferably 150 to 250. When the molecular weight of the phenol is less than 100 or exceeds 1,000, the conductivity of a conductive laminate produced using the conductive composition tends to change significantly over time. Unless otherwise specified, the molecular weight of the phenol in the present invention is a weight average molecular weight.

[0035] The phenol in the present invention preferably has a pKa of 10 or less, more preferably 8 or less, and even more preferably 5 or less at 25° C. The lower limit of the pKa is not particularly limited, but is generally 3 or more. If the pKa exceeds 10, the conductivity of a conductive laminate obtained using the conductive composition tends to change significantly over time.

[0036] Specific examples of phenols include caffeic acid, 3,4-dihydroxybenzoic acid, chlorogenic acid, ferulic acid, gallic acid monohydrate, propyl gallate, and epigallocatechin gallate.

[0037] In the conductive composition, the content of the phenol (C) is preferably 20 to 2500 parts by weight, more preferably 50 to 2000 parts by weight, even more preferably 60 to 1000 parts by weight, and particularly preferably 70 to 500 parts by weight, per 100 parts by weight of the total amount of the carbon nanotubes (A) and the dispersant (B). Note that these parts by weight are parts by weight of the solid content.

[0038] <Optional Components> In addition to the carbon nanotubes (A), the dispersant (B), and the phenols (C), the conductive composition may contain a solvent, a binder, a crosslinking agent, a catalyst, a leveling agent, a conductive polymer, a water-soluble antioxidant, an inorganic filler, an antifoaming agent, a rheology control agent, a neutralizing agent, a thickener, or the like.

[0039] <Solvent> Examples of the solvent include water; alcohols such as methanol, ethanol, isopropanol, 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; 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; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, etc.; hydrocarbons such as toluene, xylene (o-, m-, or p-xylene), hexane, heptane, etc.; esters such as ethyl acetate, butyl acetate, ethyl acetoacetate, methyl orthoacetate, ethyl orthoformate, etc.; amide compounds such as N-methylformamide, N,N-dimethylformamide, γ-butyrolactone, N-methylpyrrolidone, etc.; hydroxyl group-containing compounds such as trimethylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, catechol, cyclohexanediol, cyclohexanedimethanol, glycerin, etc.; compounds having a sulfo group such as dimethyl sulfoxide, etc.; and organic solvents such as isophorone, propylene carbonate, acetylacetone, acetonitrile, etc. Furthermore, a mixed solvent of water and a water-miscible organic solvent (a water-containing organic solvent) or a mixed solvent of two or more organic solvents may be used.When a mixed solvent of water and a water-miscible organic solvent is used, the amount of the organic solvent in the mixed solvent is preferably 10 to 95 wt %, more preferably 20 to 80 wt %, and even more preferably 30 to 70 wt %. In this specification, there is no particular distinction between a solvent that completely dissolves all components of the conductive composition (i.e., a "solvent") and a solvent that disperses insoluble components (i.e., a "dispersion medium"), and both are referred to as a "solvent."

[0040] When an organic solvent or a mixed solvent of water and an organic solvent is used as the solvent, in order to facilitate removal of the solvent by heating after application of the conductive composition, the boiling point of the organic solvent is preferably 150° C. or lower, more preferably 120° C. or lower, and even more preferably 100° C. or lower. The lower limit of the boiling point of the organic solvent is not particularly limited, and is generally 60° C. or higher.

[0041] From the viewpoints of dispersion stability of carbon nanotubes and applicability to a substrate, the solvent is preferably water or a mixed solvent of water and an organic solvent, more preferably water or a mixed solvent of water and ethanol. In the mixed solvent of water and ethanol, the proportion of ethanol is preferably 5 to 95% by volume, more preferably 20 to 80% by volume.

[0042] The solid content of the conductive composition can be adjusted by the content of the solvent, and is preferably 0.1 to 50 wt %, more preferably 0.2 to 30 wt %, even more preferably 0.3 to 20 wt %, and even more preferably 0.3 to 10 wt %.

[0043] <Binder> The binder is not particularly limited as long as it is a resin binder, and thermoplastic resins or thermosetting resins can be used. Examples of thermoplastic resins include acrylic resins, polyurethane resins, polyester resins, polyolefin resins, styrene resins, vinyl acetate resins, vinyl chloride resins, and fluorine-based resins. Examples of thermosetting resins include silicone resins, epoxy resins, phenolic resins, amino resins, and polyimide resins, as well as thermoplastic resins having reactive functional groups. Conductive films made of conductive compositions containing these binders have good affinity for substrates. Furthermore, the binder may be a water-dispersible resin or a curable resin that hardens after application to a substrate. When the binder is a water-dispersible resin, the water-dispersible resin may be dispersed as a result of the addition of hydrophilic functional groups to the resin, or may be forcibly dispersed using an emulsifier. These binders may be used alone or in combination of two or more.

[0044] Examples of acrylic resins include (meth)acrylic resins, vinyl ester resins, etc. These acrylic resins may be polymers containing, as constituent monomers, polymerizable monomers having an acid group such as a carboxyl group, an acid anhydride group, a sulfonic acid group, or a phosphoric acid group, and examples thereof include homopolymers or copolymers of polymerizable monomers having an acid group, and copolymers of polymerizable monomers having an acid group and copolymerizable monomers.

[0045] The (meth)acrylic resin may be polymerized with a copolymerizable monomer as long as it contains a (meth)acrylic monomer as a main constituent monomer (e.g., 50 mol% or more), and 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 the (meth)acrylic resin include (meth)acrylic monomers having an acid group [such as (meth)acrylic acid, sulfoalkyl (meth)acrylates, and sulfonic acid group-containing (meth)acrylamides] or copolymers thereof; copolymers of (meth)acrylic monomers that may have an acid group with other polymerizable monomers having an acid group [such as other polymerizable carboxylic acids, polymerizable polycarboxylic acids or anhydrides, and vinyl aromatic sulfonic acids] and / or copolymerizable monomers [such as (meth)acrylic acid alkyl esters, glycidyl (meth)acrylate, (meth)acrylonitrile, and aromatic vinyl monomers]; copolymers of other polymer monomers having an acid group with (meth)acrylic copolymerizable monomers [such as (meth)acrylic acid alkyl esters, hydroxyalkyl (meth)acrylates, glycidyl (meth)acrylate, and (meth)acrylonitrile]; rosin-modified urethane acrylates; specially modified acrylic resins; urethane acrylates; epoxy acrylates; and urethane acrylate emulsions.

[0046] 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 copolymer, etc.), and the like are preferred.

[0047] The polyurethane 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, and examples thereof include ester-ether polyurethane, ether polyurethane, polyester polyurethane, carbonate polyurethane, and acrylic polyurethane.

[0048] 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, and examples thereof include polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, and polybutylene naphthalate.

[0049] The polyolefin resin is not particularly limited, but examples thereof include polyethylene, polypropylene, chlorinated polypropylene, maleic anhydride-modified polypropylene, maleic anhydride-modified chlorinated polypropylene, and ethylene-vinyl acetate copolymer.

[0050] The styrene-based resin is not particularly limited as long as it is a resin containing styrene as a main component, and examples thereof include polystyrene, acrylonitrile-styrene copolymer (AS), and acrylonitrile-butadiene-styrene copolymer (ABS).

[0051] The vinyl acetate resin is not particularly limited as long as it is a resin obtained by polymerization of vinyl acetate, and examples thereof include polyvinyl acetate and ethylene-vinyl acetate copolymer.

[0052] The vinyl chloride resin is not particularly limited as long as it is a resin obtained by polymerization of vinyl chloride, and examples thereof include polyvinyl chloride, ethylene vinyl chloride copolymer, vinyl chloride-vinyl acetate copolymer, and the like.

[0053] Examples of the fluorine-based resin include polytetrafluoroethylene, polyvinylidene fluoride, Teflon (registered trademark), and polyvinyl fluoride.

[0054] Examples of silicone-based resins include oligomers of alkoxysilanes formed by condensation of alkoxysilane monomers represented by the following formula (I), which have one or more siloxane bonds (Si—O—Si) in each molecule: SiR １ ４ (I) (wherein, R １is hydrogen, a hydroxyl group, an alkoxy group having 1 to 4 carbon atoms, an alkyl group having 1 to 12 carbon atoms which may have a substituent, or an aryl group having 6 to 20 carbon atoms which may have a substituent. １ at least one of which is an alkoxy group having 1 to 4 carbon atoms or a hydroxyl group)

[0055] In formula (I), R １ Examples of the alkoxy group of R include a methoxy group, an ethoxy group, a propoxy group, and a butoxy group. １ Examples of the alkyl group of R include a methyl group, an ethyl group, a propyl group, a normal butyl group, a tertiary butyl group, a pentyl group, and a hexyl group. １ The aryl group includes a phenyl group, a tolyl group, and a benzyl group.

[0056] Specific examples of the monomer represented by formula (I) include 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane,

[0033] Examples of suitable silanes include 3-isocyanatepropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N-(1,3-dimethylbutylidene)propylamine, N-phenyl-3-aminopropyltrimethoxysilane, 3-isocyanatepropyltriethoxysilane, methyltrimethoxysilane, phenyltrimethoxysilane, dimethyldimethoxysilane, methyltriethoxysilane, n-propyltrimethoxysilane, diisopropyldimethoxysilane, isobutyltrimethoxysilane, diisobutyldimethoxysilane, isobutyltriethoxysilane, n-hexyltrimethoxysilane, n-hexyltriethoxysilane, cyclohexylmethyldimethoxysilane, n-octyltriethoxysilane, n-decyltrimethoxysilane, tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, and tetrabutoxysilane. Among these, tetramethoxysilane and tetraethoxysilane are preferred.

[0057] The structure of the silicone-based resin is not particularly limited, and may be linear or branched. The silicone-based resin may be a condensate of one type of monomer represented by formula (I), or may be a condensate of two or more types of monomers. Specific examples of silicone-based resins include methyl silicate oligomer and ethyl silicate oligomer. The weight-average molecular weight of the silicone-based resin is not particularly limited, but is preferably 200 to 10,000, and more preferably 400 to 5,000.

[0058] Examples of epoxy resins include bisphenol A type, bisphenol F type, phenol novolac type, polyfunctional types having many benzene rings, such as tetrakis(hydroxyphenyl)ethane type or tris(hydroxyphenyl)methane type, biphenyl type, triphenolmethane type, naphthalene type, ortho novolac type, dicyclopentadiene type, aminophenol type, alicyclic epoxy resins, silicone epoxy resins, and the like.

[0059] Examples of the reactive functional group of the thermoplastic resin having a reactive functional group include a hydroxyl group, a carboxyl group, an acid anhydride group, a sulfonic acid group, a phosphoric acid group, and a glycidyl group.

[0060] Among the binders listed above, acrylic resins, polyester resins, polyurethane resins, polyolefin resins, and silicone resins are preferred.

[0061] The binder content in the conductive composition is preferably 20 to 98 wt %, more preferably 30 to 90 wt %, and even more preferably 35 to 85 wt %, based on the total solid content of the conductive composition. The binder content is preferably 10 to 10,000 wt %, more preferably 100 to 5,000 wt %, based on 100 wt % of the total amount of carbon nanotubes and dispersant. Within this range, the conductive film can have sufficient strength and conductivity.

[0062] <Crosslinking Agent, Catalyst> The crosslinking agent may be appropriately selected depending on the type of binder, and examples thereof include melamine-based, carbodiimide-based, oxazoline-based, epoxy-based, isocyanate-based, and acrylate-based crosslinking agents. The content of the crosslinking agent in the conductive composition is preferably 0.1 to 70 wt % of the total solid content of the conductive composition, and more preferably 1 to 50 wt %. Furthermore, when the conductive composition contains a curable binder and a crosslinking agent, an acid catalyst, a base catalyst, a photopolymerization initiator, a thermal polymerization initiator, or the like may be added as a catalyst for crosslinking the curable binder.

[0063] <Leveling Agent> By including a leveling agent in the conductive composition, it is possible to suppress the occurrence of repelling or unevenness when forming a conductive film. As a leveling agent, a leveling agent with high hydrophilicity is preferred because it has excellent dispersing power, and an HLB value of 9 or more is preferred, more preferably 10 or more, and even more preferably 12 or more. Furthermore, since it has a higher affinity than the dispersant for the hydrophobic carbon nanofibers, it is preferred that the HLB value be higher than that of the dispersant. The HLB value can be calculated using the following calculation method. Griffin method: [(molecular weight of hydrophilic portion) ÷ (total molecular weight)] × 20

[0064] Examples of the leveling agent include silicone-based leveling agents, fluorine-based leveling agents, polyether-based leveling agents, polyester-based leveling agents, and acrylic-based leveling agents.

[0065] Examples of silicone leveling agents include polysiloxanes; reactive polysiloxanes into which reactive groups such as amino groups, epoxy groups, hydroxyl groups, and carboxyl groups have been introduced; and non-reactive polysiloxanes into which non-reactive groups such as alkyl groups, ester groups, aralkyl groups, phenyl groups, and polyether groups have been introduced.

[0066] Examples of fluorine-based leveling agents include perfluoropolyether-modified polydimethylsiloxane, perfluoropolyester-modified polydimethylsiloxane, perfluorobutanesulfonic acid, oligomers containing a fluorine-containing group, a hydrophilic group, and a lipophilic group, perfluoroalkyl group-containing carboxylates, and perfluoroalkyl group- and phosphate group-containing phosphate esters.

[0067] Examples of polyether-based leveling agents include cellulose ether; pullulan; polyethylene glycol; silicone-modified polyethers such as polyether-modified polydimethylsiloxane, polyether-modified siloxane, polyetherester-modified hydroxyl group-containing polydimethylsiloxane, and polyether-modified acrylic group-containing polydimethylsiloxane; polyglycerin; polyether polyol, polyoxyethylene-polyoxypropylene condensate, polyoxyethylene alkylphenyl ether, alkyl ether derivatives such as lauryl alcohol alkoxylate, and alkyl ether sulfates.

[0068] Examples of polyester-based leveling agents include polyester-modified acrylic group-containing polydimethylsiloxane, polyester-modified polydimethylsiloxane, and polyester polyol.

[0069] Examples of the acrylic leveling agent include acrylic copolymers made of silicone and acrylic.

[0070] The content of the leveling agent in the conductive composition is preferably 0.01 to 40 wt %, more preferably 0.1 to 30 wt %, based on the total solid content of the conductive composition. When the content of the leveling agent is within the above range, the substrate coatability, dispersion stability, and film strength of the conductive film tend to be good.

[0071] <Conductive Polymer> Examples of conductive polymers include polythiophene, polypyrrole, polyaniline, polyacetylene, polyphenylene vinylene, polynaphthalene, and derivatives thereof. These may be used alone or in combination of two or more. Among them, conductive polymers containing at least one thiophene ring in the molecule are preferred because of their excellent conductivity. 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 preferred because of its particularly excellent conductivity. When a conductive polymer is incorporated, the amount added is preferably 1 to 10,000 parts by weight, more preferably 1 to 100 parts by weight, in terms of solid content, per 100 parts by weight of the solid content of the carbon nanotubes.

[0072] <Inorganic Filler> Examples of inorganic fillers include silica such as colloidal silica, hollow silica, and fumed silica, and metal oxides such as titania and zirconia, as well as organic-inorganic composites such as a core-shell type acrylic-silica composite in which a thermoplastic or thermosetting acrylic resin is coated with silica, a core-shell type melamine-silica composite in which a melamine resin is coated with silica, a core-shell type acrylic-silica composite in which silica is coated with a thermoplastic or thermosetting acrylic resin, a core-shell type melamine-silica composite in which silica is coated with a melamine resin, and an acrylic-silica composite in which small silica particles are supported by a thermoplastic or thermosetting acrylic resin. The content of the inorganic filler is preferably 0.1 to 30 wt %, and more preferably 0.2 to 10 wt %, of the total solid content of the conductive composition.

[0073] <<Method for Producing Conductive Composition>> In the method for producing the conductive composition of the present invention, the order of adding the components and the method for mixing are not particularly limited as long as a mixture of carbon nanotubes (A), dispersant (B), and phenols (C) can be obtained. Specific examples of the production method include a production method including a dispersion step of dispersing a mixture of carbon nanotubes (A) and dispersant (B), and a step of adding phenols (C) to the carbon nanotube dispersion.

[0074] <Dispersion Step> In the step of dispersing the mixture of carbon nanotubes and a dispersant, the carbon nanotubes and the dispersant interact to obtain a carbon nanotube dispersion in which the carbon nanotubes are well dispersed in the solvent. As the solvent for dispersion, the substances described above as solvents contained in the conductive composition can be used, and among these, water, alcohol, or a mixture thereof is preferred. The solids concentration of the mixture during dispersion is preferably 0.1 to 5 wt %.

[0075] Dispersion methods using a dispersing device include batch, pass, and circulation methods. Any of these methods may be used, or two or more methods may be combined. Batch dispersion is a method in which dispersion is performed using only the dispersing device itself without using piping or the like, making it easy to handle. Pass dispersion is a dispersion method in which the dispersing device itself is equipped with a tank that supplies the dispersion liquid via piping and a tank that receives the dispersion liquid, and the dispersion passes through the dispersing device itself. Circulation dispersion is a method in which the dispersion liquid that has passed through the dispersing device itself is returned to the tank that supplies the dispersion liquid and dispersed while circulating. In both pass dispersion and circulation dispersion, the longer the processing time, the more advanced the dispersion becomes; therefore, passing or circulation can be repeated until the desired dispersion state is achieved, and the processing volume can be increased by changing the tank size or processing time. Pass dispersion is preferable to circulation dispersion because it is easier to homogenize the dispersion state. Circulation dispersion is preferable to pass dispersion because the operation and manufacturing equipment are simpler. Among dispersion methods, batch dispersion and circulation dispersion are preferred because they allow for efficient overall dispersion.

[0076] Dispersion of the mixture of carbon nanotubes and a dispersant can be performed using a dispersing device such as a high-pressure homogenizer, 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, etc. Among these, it is preferable to use a high-pressure homogenizer in order to disperse the carbon nanotubes well.

[0077] The pH condition during dispersion is preferably 0.5 to 11, more preferably 3 to 9. The temperature condition is preferably 0 to 40° C., more preferably 5 to 30° C. The dispersion time can be appropriately set depending on the amount of the mixture during dispersion, but for example, when the amount is 500 to 1000 mL, it is preferably 1 to 600 minutes, more preferably 60 to 180 minutes.

[0078] The dispersion step is preferably repeated multiple times. The number of repetitions is preferably 3 to 300 times, more preferably 10 to 200 times. When the dispersion step is repeated, cooling of the mixture, scraping off of the dispersion liquid adhering to the tank wall, etc. may be performed between each dispersion step. When the dispersion step is repeated using a high-pressure homogenizer, it is preferable to discharge the dispersed mixture from the high-pressure homogenizer and inject it into the high-pressure homogenizer again.

[0079] <Pre-dispersion step> Before the dispersion step, a pre-dispersion step may be performed as a pretreatment step, in which a mixture of carbon nanotubes and a dispersant is subjected to high-speed stirring. The high-speed stirring in the pre-dispersion step is preferably performed under milder conditions than in a dispersion step using an ultrasonic homogenizer or the like. By performing the pre-dispersion step, the aggregation of carbon nanotubes can be loosened, thereby improving the dispersion efficiency of the carbon nanotubes in the subsequent dispersion step. The time for high-speed stirring in the pre-dispersion step can be appropriately set depending on the amount of the mixture to be treated. For example, in the case of 500 to 1000 mL, it is preferably within 1 hour, more preferably within 30 minutes, even more preferably within 10 minutes, and particularly preferably within 5 minutes.

[0080] <Step of adding phenols (C)> In this step, a conductive composition is obtained by adding phenols (C) to the dispersion of carbon nanotubes obtained in the dispersion step. The method of adding the phenols (C) is not particularly limited. In addition to the phenols (C), optional components such as a binder, a leveling agent, and a solvent may also be added in this step. The order of adding the phenols (C) and optional components is not particularly limited.

[0081] <Filtering Process> Filtering is preferably performed after the process of adding the phenol (C). Filtering can remove aggregates remaining in the carbon nanotube dispersion and aggregates resulting from the binder, etc. The pore size of the filter is not particularly limited, but is preferably 0.5 to 100 μm, more preferably 1 to 50 μm. The material of the filter medium is not particularly limited, but examples thereof include nylon, cellulose, a mixture of cellulose acetate and nitrocellulose, cellulose derivatives such as cellulose ester, polytetrafluoroethylene, polyvinylidene fluoride, Teflon (registered trademark), fluororesins such as polyvinyl fluoride, polyolefins such as polypropylene and polyethylene, ceramics, metals, polycarbonate, glass, polyester, polyamide, polysulfone, polyimide, polyvinyl chloride, polystyrene, or perfluorosulfonic (carboxylic) acid, among which polyolefins are preferred.

[0082] <<Conductive Laminate>> The conductive laminate of the present invention is characterized by having a substrate and a conductive film made of a conductive composition formed on the substrate.

[0083] The thickness of the conductive film is preferably 1 to 1000 nm, more preferably 2 to 500 nm, and even more preferably 5 to 100 nm. If the film thickness is less than 1 nm, the conductivity tends to be insufficient, and if it exceeds 1000 nm, the transparency tends to be insufficient. The film thickness of the conductive film can be calculated from the solid content of the conductive composition and the amount applied to the substrate.

[0084] <Substrate> Examples of materials for the substrate include 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; polyether ether ketone (PEEK) resin, polysulfone (PSF) resin, polyethersulfone (PES) resin, polycarbonate (PC) resin, polyamide resin, polyimide resin, acrylic resin, triacetyl cellulose (TAC) resin, glass, and metals such as copper and aluminum.

[0085] The shape of the substrate is not particularly limited, but when the conductive laminate is used in an electronic device or an optical component, the substrate is preferably in the form of a film. The thickness of the substrate film is preferably 10 to 10,000 μm, more preferably 25 to 5,000 μm. The total light transmittance of the substrate film is preferably 60% or more, more preferably 70% or more, and even more preferably 80% or more.

[0086] <Coating Method> The method for producing the conductive laminate is not particularly limited, but it is preferable to produce it by a method including a step of applying the above-mentioned conductive composition to a substrate to form a coating film, and a step of drying the coating film.

[0087] In the step of applying the conductive composition to a substrate to form a coating film, the conductive composition may be applied directly to the substrate to form a coating film, or a separate layer such as a primer layer may be provided on the substrate in advance, and then the conductive composition may be applied onto that layer to form a coating film. Furthermore, before applying the conductive composition to the substrate, the surface of the substrate may be subjected to a surface treatment such as a corona treatment, a plasma treatment, or an itro treatment.

[0088] Methods that can be used to apply the conductive composition to a substrate include bar coating, roll coating, dip coating, spin coating, casting, die coating, blade coating, gravure coating, curtain coating, spray coating, doctor coating, slit coating, relief (letterpress) printing, stencil (screen) printing, lithographic (offset) printing, intaglio (gravure) printing, spray printing, inkjet printing, and pad printing.

[0089] In the step of drying the coating film, it is preferable to dry the coating film by heating. The heat treatment can be carried out using a blast oven, an infrared oven, a vacuum oven, or the like. The heating temperature is preferably 60 to 200°C, more preferably 80 to 180°C. The heating time is not particularly limited, but is preferably 0.1 to 20 minutes, more preferably 0.5 to 15 minutes. When the conductive composition contains a solvent, it is preferable to remove the solvent by heat treatment.

[0090] The content of carbon nanotubes in the conductive film is 0.5 to 50 mg / m ２ is preferred, and 1 to 25 mg / m ２ By setting the content of carbon nanotubes in the conductive film within the above range, it is possible to impart sufficient conductivity to the conductive film, and also to maintain the strength and film-forming properties of the coating film.

[0091] The haze value of the conductive laminate is preferably 10% or less, more preferably 6% or less, and even more preferably 3% or less. Since a smaller haze value is preferable, the lower limit is not particularly limited, but is, for example, 0.01% or more. The haze value can be measured in accordance with JIS K 7150.

[0092] The total light transmittance of the transparent laminate is preferably 75% or more, more preferably 80% or more, and even more preferably 85% or more. The total light transmittance can be measured in accordance with JIS K 7150.

[0093] The conductive film has excellent conductivity. The surface resistivity of the conductive film is 1×10 ２ ~1 x 10 １０ Ω / □ is preferred, and 1×10３ ~1 x 10 ９ Ω / □ is more preferable, and 1×10 ５ ~1 x 10 ８ The surface resistivity is more preferably Ω / □. The surface resistivity can be measured by the method described in the Examples.

[0094] The conductive laminate has little change in conductivity over time. The change in conductivity over time can be evaluated by a heat resistance test of the conductive laminate. In the heat resistance test, the surface resistivity (SR2 (Ω / □)) after keeping the conductive laminate at 95°C for 72 hours and the surface resistivity (SR1 (Ω / □)) before keeping the heat are measured. Then, the increase / decrease rate (%) of the surface resistivity after the heat resistance test is calculated using the following formula (1): Increase / decrease rate (%) of surface resistivity after heat resistance test = (SR2 - SR1) / SR1 × 100 (1) The increase / decrease rate of the surface resistivity in the heat resistance test is preferably -80 to 40%, more preferably -50 to 20%, and even more preferably -50 to 10%.

[0095] Furthermore, the change in the conductivity of the conductive laminate over time can be evaluated by a moist heat resistance test of the conductive laminate. In the moist heat resistance test, the surface resistivity (SR4 (Ω / □)) after storing the conductive laminate for 72 hours under conditions of 85°C and 85% relative humidity, and the surface resistivity (SR3 (Ω / □)) before storage are measured. Then, the increase / decrease rate (%) of the surface resistivity after the moist heat resistance test is calculated using the following formula (2): Increase / decrease rate (%) of surface resistivity after moist heat resistance test = (SR4 - SR3) / SR3 × 100 (2) The increase / decrease rate of the surface resistivity after the moist heat resistance test is preferably -80 to 40%, more preferably -50 to 20%, and even more preferably -50 to 10%.

[0096] The conductive laminate has high durability and exhibits little change in conductivity over time, making it suitable for use in applications requiring these properties, such as optical films, batteries, electromagnetic wave shielding, solar power generation, transparent electrodes, and automotive parts.

[0097] The present invention will be described below with reference to examples, but is not limited to the following examples. In the following, "%" means "% by weight" unless otherwise specified.

[0098] (1) Materials Used (1-1) Base Material: PET film (Lumirror T60, manufactured by Toray Industries, Inc.)

[0099] (1-2) Carbon nanotubes (A) Single-walled carbon nanotubes (ZEON NANO SG101 manufactured by Zeon Nanotechnology Co., Ltd., average length 300 μm, diameter approximately 4 nm) Double-walled carbon nanotubes (755168 manufactured by Aldrich Co., Ltd., average length 10 μm, diameter approximately 4 nm) Multi-walled carbon nanotubes (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., product name: carbon nanotube, diameter 20 to 30 nm)

[0100] (1-3) Dispersant (B) Nonionic dispersant (Clariant, Genapol PF80, HLB: 19)

[0101] (1-4) Binder and crosslinking agent Polyester resin aqueous dispersion (manufactured by GOO Chemical Co., Ltd., PLASCOAT RZ-105, solid content 30%) Polyurethane resin aqueous dispersion (manufactured by ADEKA Corporation, ADEKA BONTITAR HUX-895, solid content 48% by weight) Acrylic resin (manufactured by TOAGOSEI Co., Ltd., JURYMER FC-80, solid content 30% by weight) Polyolefin resin aqueous dispersion (manufactured by TOYOBO Corporation, HARDLEN EW-5303, solid content 30% by weight) Tetraethoxysilicate (manufactured by Tokyo Chemical Industry Co., Ltd.)

[0102] (1-5) Organic solvent: Ethanol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.)

[0103] (2) Preparation of Carbon Nanotube Dispersion (Production Examples 1 to 3) Carbon nanotubes and a dispersant were mixed with pure water in the weight ratios shown in Table 1. The mixture was pre-dispersed by stirring at 500 rpm for 5 minutes using a stirrer. Following pre-dispersion, a main dispersion was carried out. For the main dispersion, a dispersion treatment was carried out at 80 MPa using a high-pressure homogenizer (Starburst Mini manufactured by Sugino Machine Co., Ltd.), followed by immediate cooling to 20°C using a cooling tube. This dispersion process and cooling process were repeated 50 times to prepare a carbon nanotube dispersion (total solids content 0.7% by weight).

[0104]

[0105] (3) Preparation of Conductive Compositions (Examples 1 to 19, Comparative Examples 1 to 4) The carbon nanotube dispersions (solid content 0.7 wt %) of Production Examples 1 to 3, phenols, and binders were mixed to give the total solid content (%) shown in Table 2. Furthermore, the mixture was diluted with a solvent to give the solid content shown in Table 2, thereby obtaining conductive compositions.

[0106] This conductive composition was diluted 5 times with a 50% aqueous ethanol solution and applied to a substrate made of PET film by bar coating. A No. 4 wire bar was used, and the theoretical coating thickness was adjusted to 4 μm. The conductive film was then dried at 130°C for 1 minute using a blower dryer to form a conductive film. The resulting conductive laminate was evaluated using the methods described below. The results are shown in Table 2.

[0107]

[0108] In Comparative Examples 1 to 4, since the phenol (C) of the present invention was not contained, the rate of increase or decrease in surface resistivity after the heat resistance test and / or moist heat resistance test was large. In Examples 1 to 19, the surface resistivity after both the heat resistance test and the moist heat resistance test was within the range of -80% to 10%.

[0109] (4) Evaluation Method of Conductive Laminate (4-1) Optical Properties The total light transmittance (%) and haze (%) of the conductive laminate were measured using a haze meter HZ-2 manufactured by Suga Test Instruments Co., Ltd.

[0110] (4-2) Surface Resistivity The surface resistivity of the conductive film was measured using a UA probe of a resistivity meter (Hilester UP (MCP-HT450 model) manufactured by Mitsubishi Chemical Corporation). The probe was pressed against the surface of the conductive film, and the surface resistivity was determined when an applied voltage of 10 V was maintained for 10 seconds (SR1).

[0111] (4-3) Heat Resistance Test, Moisture and Heat Resistance Test In the heat resistance test, the conductive laminate was kept at 95°C for 72 hours, and then the surface resistivity was measured by the method in (4-2) (SR2). In the moisture and heat resistance test, the conductive laminate was kept at 85°C and a relative humidity of 85% for 72 hours, and then the surface resistivity was measured by the method in (4-2) (SR2). The percentage change in surface resistivity after the heat resistance test and the moisture and heat resistance test was calculated using the following formula: Percent change in surface resistivity after the heat resistance test and the moisture and heat resistance test = (SR2 - SR1) / SR1 x 100

Claims

1. A conductive composition comprising carbon nanotubes (A), a dispersant (B), and a phenol (C), wherein the phenol (C) has a carboxyl group or an alkoxycarbonyl group which may have a heteroatom, and has a molecular weight of 100 to 1,000.

2. The conductive composition according to claim 1, which contains 20 to 2,500 parts by weight of a phenol (C) per 100 parts by weight of the total amount of the carbon nanotubes (A) and the dispersant (B).

3. The conductive composition according to claim 1 or 2, wherein the phenol (C) is a compound containing one aromatic ring.

4. The conductive composition according to any one of claims 1 to 3, further comprising a binder (D).

5. A conductive film comprising the conductive composition according to any one of claims 1 to 4.

6. A conductive laminate comprising a substrate and the conductive film according to claim 5 formed on said substrate.

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