JP2009035619A - Conductive composition and conductive film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve problems not solved by the conventional technology, and to provide a conductive composition having good dispersibility of contained components and excellent in transparency and conductivity when a film is formed, additionally a conductive composition capable of forming a conductive film with less variation in conductivity, and a conductive film using the composition. <P>SOLUTION: The conductive composition contains a conductive polymer, an ionic liquid and carbon nanotubes, wherein an abundance ratio of the carbon nanotubes in the form of primary particles is ≥80% by number. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a conductive composition and a conductive film, and in particular, has good dispersibility of contained components, has excellent transparency and conductivity when a conductive film is formed, and further has a small variation in conductivity. It is related with the electrically conductive composition which can form.

  The conductive film is used for coating of a substrate such as a liquid crystal display, a plasma display, an electroluminescence display, an electrochromic display, a transparent electrode such as a solar battery or a touch panel, or an electromagnetic shielding material.

  The most widely applied transparent conductive film is a vapor-deposited film of indium-tin composite oxide (ITO), but there is a problem that it is necessary to form a film at a high temperature and the film formation cost is high.

  The ITO film formed by the coating film forming method also needs to be formed at a high temperature, its conductivity depends on the degree of dispersion of ITO, and the haze value is not necessarily low.

  In addition, an inorganic oxide film such as ITO is likely to crack due to the bending of the base material, and therefore the conductivity tends to decrease.

  As a transparent conductive film using an organic material, one using a conductive polymer that can be formed at low temperature and low cost has been proposed. As the conductive polymer, many synthesized by chemical oxidative polymerization or electrolytic oxidative polymerization of thiophene, pyrrole, aniline, or derivatives thereof have been disclosed, and among them, poly (3,4-ethylenedioxythiophene) is particularly preferable. ) Polymers of 3- and 4-position substituted thiophenes centered on (PEDOT) and the like are excellent in electrical conductivity and are being put into practical use.

As a technique using a conductive polymer containing the PEDOT or the like, a technique in which a conductive carbon material such as a carbon nanotube is dispersed in a conductive polymer is disclosed (for example, Patent Documents 1 and 2).
In particular, Patent Document 1 discloses that an ionic liquid may be further used as a solvent for swelling a conductive polymer. However, there is a description of a specific degree of dispersion of carbon nanotubes, a concentration in a composition, and the like. Absent. Patent Document 2 focuses on improving the dispersibility and solubility of carbon nanotubes, and improves conductivity and film formability, as well as the film physical properties of the coating film. However, the dispersibility is not always satisfactory. It is not a thing, and nothing is mentioned about the dispersion | variation in electroconductivity at the time of setting it as a coating film.

  As a conductive material containing carbon nanotubes, a technique of mixing carbon nanotubes in an ionic liquid is disclosed in addition to the above technique (for example, Patent Document 3). Patent Document 3 is a conductive film intended for application to an actuator element, and although it is described that it is important to uniformly mix each component, the conductivity is not necessarily sufficient, and further regarding transparency. This is not a practical level for applications requiring transparency.

On the other hand, a technique combining a conductive polymer and an ionic liquid for the purpose of improving conductivity is also disclosed (for example, Patent Documents 4 and 5). Patent Document 4 is intended to obtain a gel-like composition having conductivity, and is not suitable from the viewpoint of handling with the intention of forming a conductive film on a substrate by coating. Patent Document 5 is a technique in which a conductive polymer coating film is formed in advance and both are brought into contact with each other by a method such as immersing in an ionic liquid or spraying an ionic liquid. This also has a high conductivity by a simple method. It is not sufficient for the purpose of obtaining a coating film.
International Publication No. 2005/14693 Pamphlet JP-A-2005-97499 JP 2007-126624 A JP 2006-257148 A JP 2006-306957 A

  The present invention solves the problems that could not be solved by the prior art as described above, and its purpose is that the dispersibility of the contained components is good, and when the film is formed, it is excellent in transparency and conductivity. Another object of the present invention is to provide a conductive composition, a conductive composition capable of forming a conductive film with little variation in conductivity, and a conductive film using the same.

  The present invention relates to a conductive composition containing a conductive polymer, an ionic liquid, and a carbon nanotube, wherein the carbon nanotube is present in a highly dispersible manner with respect to the conductive polymer and the ionic liquid, and thereby carbon at a relatively high concentration. Realizing the inclusion of nanotubes, leading to the achievement of a conductive composition that is remarkably excellent in both conductivity and transparency, as well as a conductive composition that can form a conductive film with little variation in conductivity. Solved.

  Specifically, it is as shown below.

  1. A conductive composition comprising a conductive polymer, an ionic liquid, and carbon nanotubes, wherein the abundance ratio of primary particles of the carbon nanotubes is 80% by number or more.

  2. 2. The conductive composition as described in 1 above, wherein the carbon nanotube is surface-treated with an organic compound.

  3. 3. A conductive film obtained by forming the conductive composition according to any one of 1 or 2 on a substrate, wherein the content of carbon nanotubes in the conductive film is 30% by mass or more A conductive film having a content of 50% by mass or less.

  According to the present invention, it is possible to obtain a conductive film which is excellent in transparency and conductivity and has a small variation in conductivity.

  Next, the present invention will be described in more detail, but the present invention is not limited to this.

<Conductive polymer>
The conductive polymer contained in the conductive composition of the present invention is not particularly limited as long as it is a π-conjugated polymer compound, and various known polymers can be used. Specific examples include polypyrrole, polythiophene, polyaniline, polyquinone, polyvinylene, polyphenylenevinylene, polythienylene, polypyrrolylene, polyphenylene, polyiminophenylene, polyisothianaphthene, polyfurylene, polycarbazolylene, and derivatives thereof. . Among these, it is preferable to use polypyrrole or polythiophene. These conductive polymers can be synthesized by methods such as chemical oxidative polymerization and electrolytic oxidative polymerization.

  In the present invention, it may be advantageous to use a conductive polymer that can be dissolved or dispersed in an aqueous solvent when forming a conductive film, which will be described later. Specifically, a conductive polymer that is polymerized in the presence of a dopant that will be described later. It is preferable to use a conductive polymer in which sulfonic acid groups and / or carboxyl groups are substituted. Specifically, the latter includes a sulfonic acid group and / or a carboxyl group, or a sulfonic acid group and / or a carboxyl group on the skeleton of an unsubstituted and substituted π-conjugated polymer or a nitrogen atom in the polymer. A conductive polymer having an alkyl group substituted with or an alkyl group containing an ether bond.

(Dopant)
The conductive composition of the present invention preferably contains a dopant for the purpose of improving solubility and conductivity. The dopant is not particularly limited as long as the conductivity can be improved by oxidation-reduction of the conductive polymer in the present invention, and various known electron withdrawing (accepting) substances and electron donating substances are appropriately used. Although it is possible to use an electron withdrawing substance.

  There is no restriction | limiting in particular as an electron withdrawing (accepting) substance, According to the objective, it can select suitably, For example, a Lewis acid etc. can be mentioned. Examples of Lewis acids include sulfonic acid compounds, boric acid compounds, phosphoric acid compounds, and chloric acid compounds.

  Examples of the sulfonic acid compound include polystyrene sulfonic acid, alkyl naphthalene sulfonic acid, methane sulfonic acid, paratoluene sulfonic acid, naphthalene sulfonic acid, trifluoromethane sulfonic acid, show brain sulfonic acid, polyvinyl naphthalene sulfonic acid, and the like. Examples of the boric acid compound include tetrafluoroboric acid. Examples of the phosphoric acid compound include hexafluorophosphoric acid. Examples of chloric acid compounds include perchloric acid, chloric acid, chlorous acid, and hypochlorous acid. For example, when polythiophene is used as the conductive polymer, among these, polystyrene sulfonic acid and alkylnaphthalene sulfonic acid are particularly preferable. These may be used alone or in combination of two or more.

  There is no restriction | limiting in particular as content of the dopant in the electrically conductive composition of this invention, Although it can select arbitrarily, For example, 5-50 mass% is preferable, and 5-30 mass% is still more preferable. As a method of using the dopant, an embodiment in which the above-described conductive polymer is present during polymerization is preferable, and the dopant present during polymerization may be brought into the conductive composition as it is, or may be an ion exchange resin or various other types. The content may be appropriately adjusted by a filtration method or the like. For the purpose of controlling the final electric resistance value of the conductive film to a desired level, it is a preferable embodiment to appropriately control the content of the dopant in the conductive composition.

(Water-soluble organic compounds)
The conductive composition of the present invention can further contain a water-soluble organic compound. The water-soluble organic compound is not particularly limited as long as it is a water-soluble organic compound, and can be appropriately selected from known ones. For example, the water solubility is preferably 1% by mass or more, more preferably 5% by mass or more, with respect to 25 ° C. water. Among these water-soluble organic compounds, when the conductive composition is made into a conductive film, the surface resistivity is remarkably lowered, so that an oxygen-containing compound can be particularly preferably used.

  The oxygen-containing compound is not particularly limited as long as it contains oxygen, and examples thereof include a hydroxyl group-containing compound, a carbonyl group-containing compound, an ether group-containing compound, and a sulfoxide group-containing compound.

  Examples of the hydroxyl group-containing compound include ethylene glycol, diethylene glycol, propylene glycol, trimethylene glycol, 1,4-butanediol, glycerin and the like. Among these, ethylene glycol and diethylene glycol are preferable. Examples of the carbonyl group-containing compound include isophorone, propylene carbonate, cyclohexanone, and γ-butyrolactone. Examples of the ether group-containing compound include diethylene glycol monoethyl ether. Examples of the sulfoxide group-containing compound include dimethyl sulfoxide.

  When polythiophene is used as the conductive polymer, for example, dimethyl sulfoxide, ethylene glycol, diethylene glycol and the like are particularly preferable. These may be used alone or in combination of two or more.

  The boiling point of the water-soluble organic compound is not particularly limited and can be arbitrarily selected. However, the water-soluble organic compound is less likely to volatilize, and from the viewpoint of sufficiently reducing the electrical resistivity of the conductive composition, for example, 120 ° C. The above is preferable.

  There is no restriction | limiting in particular as content of the water-soluble organic compound in the electrically conductive composition of this invention, Although it can select arbitrarily, For example, 0.1-50 mass% is preferable, and 1-10 mass% is still more preferable. .

  The temperature and stirring conditions when mixing the water-soluble organic compound can be arbitrarily selected and controlled.

<Ionic liquid>
The ionic liquid contained in the conductive composition of the present invention is also called a room temperature molten salt or simply a molten salt, and is a salt that exhibits a molten state in a wide temperature range including room temperature (room temperature).

  In the present invention, conventionally known various ionic liquids can be used, but those that exhibit liquid at room temperature and are stable are preferable. Those having compatibility with various solvents to be used are preferred. Some ionic liquids are insoluble in water (hydrophobic ionic liquids). When used in applications where instability to humidity and corrosiveness of metals around the element are concerned, hydrophobic ionic liquids Is preferably used.

As an ionic liquid suitable for use in the present invention, a compound comprising a cation (preferably a quaternary ammonium ion) represented by the following general formulas (I) to (IV) and an anion (X ⁻ ) Can be mentioned.

General formula (III)
[NR _x H _4-x ] ⁺
Formula (IV)
[PR _x H _4-x ] ⁺
In the above general formulas (I) to (IV), R is a straight chain or branched chain having a linear or branched alkyl group having 10 or less carbon atoms or an ether bond, and the total number of carbon and oxygen is 3 to 12. In general formula (I), R ¹ represents a linear or branched alkyl group having 1 to 4 carbon atoms or a hydrogen atom, and a methyl group having 1 carbon atom is particularly preferable. In the general formula (I), R and R ¹ are preferably not the same. In the general formulas (III) and (IV), x is an integer of 1 to 4.

Examples of the alkyl group having an ether bond and having a straight chain or a branch having a total number of carbon and oxygen of 3 to 12 include —CH ₂ OCH ₃ , — (CH ₂ ) _p (OCH ₂ CH ₂ ) _q OR ² (here And p is an integer of 1 to 4, q is an integer of 1 to 4, and R ² represents a methyl group (CH ₃ ) or an ethyl group (C ₂ H ₅ ).

  Specific compounds of general formula (I) include 1-ethyl-3-methylimidazolium, 1-hexyl-3-methylimidazolium, 1-butyl-3-methylimidazolium and the like.

  Specific compounds of the general formula (II) include 1-ethylpyridinium, 1-butylpyridinium, 1-hexylpyridinium and the like.

  Specific examples of the general formula (III) include N, N, N-trimethyl-N-propylammonium and N-methyl-N-propylpiperidinium.

  Specific examples of the general formula (IV) include N, N, N-trimethyl-N-propylphosphonium.

Examples of the anion (X ⁻ ) include tetrafluoroboric acid, hexafluorophosphoric acid, bis (trifluoromethylsulfonyl) imidic acid, perchloric acid, tris (trifluoromethylsulfonyl) carbon acid, trifluoromethanesulfonic acid, Ions such as dicyanamide, trifluoroacetic acid, organic carboxylic acid or halogen atom can be mentioned.

However, the present invention is not limited to these combinations, and any ionic liquid that has a conductivity of 0.1 Sm ⁻¹ or more can be used.

  The ionic liquid of the present invention is a substance combining a cation and an anion as exemplified above, and can be synthesized by a known method. Specifically, a method such as an anion exchange method, an acid ester method, or a neutralization method can be used.

<carbon nanotube>
The carbon nanotubes contained in the conductive composition of the present invention are not particularly limited as long as the abundance ratio of primary particles is 80% by number or more, and more preferably 90% by number or more.

  As a method for measuring the abundance ratio of primary particles of carbon nanotubes, a dispersion of 5% by mass or less is prepared as a measurement sample, taken with a transmission electron microscope, and 1000 carbon nanotubes are observed in an arbitrary field of view. Then, it is obtained by calculating the abundance of primary particles.

  The carbon nanotubes contained in the conductive composition of the present invention are generally known, and are carbon having a shape in which a graphitic carbon atomic surface (graphene sheet) having a thickness of several atomic layers is wound into a cylindrical shape. This is a fiber material, and is roughly divided into single-walled nanotubes (SWNT) and multi-walled nanotubes (MWNT) based on the number of peripheral walls, and chiral, helical, zigzag, and armchairs due to the difference in the structure of graphene sheets Divided into molds, various types are known. Any type of carbon nanotube can be used in the present invention as long as it is referred to as such a carbon nanotube.

The carbon nanotubes used in the present invention are preferably single-walled nanotubes having a large aspect ratio, that is, thin and long. For example, carbon nanotubes having an aspect ratio of 10 ³ or more, preferably 10 ⁴ or more can be mentioned. The length of the carbon nanotube is usually 1 μm or more, preferably 50 μm or more, more preferably 500 μm or more, and the upper limit of the length is not particularly limited, but is, for example, about 10 mm. As the outer diameter, extremely minute carbon nanotubes on the order of nm are known.

  In the present invention, SWNT or MWNT is used alone, but both can be used simultaneously.

  The method for producing the carbon nanotube used in the present invention is not particularly limited. Specifically, catalytic hydrogen reduction of carbon dioxide, arc discharge method, laser evaporation method, CVD method, vapor phase growth method, carbon monoxide is reacted with an iron catalyst at high temperature and high pressure, and is grown in the vapor phase HiPco (High Pressure carbon monoxide) method and the like. Moreover, in order to remove residues such as by-products and catalytic metals, carbon nanotubes that have been further purified by various purification methods such as washing methods, centrifugal separation methods, filtration methods, oxidation methods, chromatographic methods, etc. Is more preferable because various functions are sufficiently exhibited.

<Surfactant>
In the conductive composition of the present invention, when the abundance of primary particles of carbon nanotubes is controlled to 80% by number or more, the carbon nanotubes are preferably surface-treated and coated with an organic compound, for example, a surfactant. Specifically, it is preferable to improve the dispersibility of each primary particle of carbon nanotubes by using a surfactant as an organic compound and dispersing the carbon nanotubes in the presence thereof.

  Examples of the surfactant that can be used in the present invention include generally known anionic surfactants, cationic surfactants, amphoteric surfactants, and nonionic surfactants. May be used arbitrarily.

  In the present invention, it may be advantageous to use an aqueous solvent for forming a conductive film, which will be described later. In this case, in particular, a polycondensation type aromatic surfactant, a polymerization type aromatic interface, and the like. It is also one of preferred embodiments to use an activator, an aromatic nonionic surfactant, a combination of an aromatic nonionic surfactant and an ionic surfactant, and the like.

  Next, specific examples of these surfactants are shown, but the present invention is not limited thereto.

  Examples of the anionic surfactant include alkyl sulfonic acid, alkyl benzene sulfonic acid, alkyl carboxylic acid, alkyl naphthalene sulfonic acid, α-olefin sulfonic acid, dialkyl sulfosuccinic acid, α-sulfonated fatty acid, N-methyl-N-oleyl taurine, Petroleum sulfonic acid, alkyl sulfuric acid, sulfated oil and fat, polyoxyethylene alkyl ether sulfuric acid, polyoxyethylene styrenated phenyl ether sulfuric acid, alkyl phosphoric acid, polyoxyethylene alkyl ether phosphoric acid, polyoxyethylene alkyl phenyl ether phosphoric acid, naphthalene sulfone Acid formalin condensate, methyl naphthalene sulfonic acid formalin condensate, butyl naphthalene / naphthalene sulfonic acid formalin condensate, naphthol methylene sulfonic acid formalin condensate, Creoso Examples thereof include tart oil sulfonic acid formalin condensate, naphthalene sulfonic acid formaldehyde condensate, polystyrene sulfonic acid, and salts thereof.

  Cationic surfactants include primary to tertiary fatty amines, quaternary ammonium, tetraalkylammonium, trialkylbenzylammonium alkylpyridinium, 2-alkyl-1-alkyl-1-hydroxyethylimidazolinium, N, N -Dialkylmorpholinium, polyethylene polyamine fatty acid amide, urea condensate of polyethylene polyamine fatty acid amide, quaternary ammonium of urea condensate of polyethylene polyamine fatty acid amide, and salts thereof.

  Examples of amphoteric surfactants include N, N-dimethyl-N-alkyl-N-carboxymethyl ammonium betaine, N, N, N-trialkyl-N-sulfoalkylene ammonium betaine, N, N-dialkyl-N, N-bispolyoxyethylene ammonium sulfate betaine, betaines such as 2-alkyl-1-carboxymethyl-1-hydroxyethylimidazolinium betaine, aminocarboxylic acids such as N, N-dialkylaminoalkylenecarboxylate, etc. Can be mentioned.

  Nonionic surfactants include polyoxyethylene alkyl ether, polyoxyethylene alkylphenyl ether, polyoxyethylene polystyryl phenyl ether, polyoxyethylene-polyoxypropylene glycol, polyoxyethylene-polyoxypropylene alkyl ether, many Polyhydric alcohol fatty acid partial ester, polyoxyethylene polyhydric alcohol fatty acid partial ester, polyoxyethylene fatty acid ester, polyglycerin fatty acid ester, polyoxyethylenated castor oil, fatty acid diethanolamide, polyoxyethylene alkylamine, triethanolamine fatty acid partial ester And trialkylamine oxide.

  Further, a fluorosurfactant such as fluoroalkyl carboxylic acid, perfluoroalkyl carboxylic acid, perfluoroalkyl benzene sulfonic acid, perfluoroalkyl polyoxyethylene ethanol may be used.

  Here, the alkyl group preferably has 1 to 24 carbon atoms, and more preferably 3 to 18 carbon atoms. The salt counter ion may be any alkali metal, alkaline earth metal, amine, etc., but Na salt is preferred from the viewpoint of availability.

  The content of the surfactant is not uniform because it depends on the molecular weight and ability of the surfactant used, but is generally preferably 0.5 to 500% by mass with respect to the carbon nanotube. -100 mass% is more preferable, and 1-50 mass% is still more preferable.

  In addition, the above polycondensation aromatic surfactant and / or polymerization aromatic surfactant (A), aromatic nonionic surfactant, and / or aromatic nonionic surfactant It is also preferable to use the agent and the ionic surfactant (B) in combination, and the mixing ratio (A) and (B) in that case is not particularly limited, The mass ratio is preferably 99.9 / 0.1 to 70/30. The mixing ratio of the aromatic nonionic surfactant and the ionic surfactant (aromatic nonionic surfactant / ionic surfactant) is not particularly limited, but is preferably 99.1 / by mass ratio. 0.1-50 / 50.

<solvent>
In the conductive composition of the present invention, although it is not an essential component, it may be advantageous to use a solvent when producing a conductive composition or when forming a conductive film using the conductive composition, In that case, you may contain a solvent arbitrarily. Use of a solvent is preferable in that a more homogeneous conductive composition can be produced, and a low-cost coating method can be easily used in film formation. As the type of solvent, a hydrophilic solvent or a hydrophobic solvent can be used arbitrarily, but it is hydrophilic in terms of the solubility of the conductive polymer, the handleability of the conductive composition, and the water-based coating method can be applied in film formation. It is preferable to use a solvent.

  Hydrophilic solvents include water, methanol, ethanol, isopropyl alcohol, propyl alcohol, butanol and other alcohols; acetone, methyl ethyl ketone, ethyl isobutyl ketone, methyl isobutyl ketone and other ketones; ethylene glycol, ethylene glycol methyl ether, ethylene glycol Ethylene glycols such as mono-n-propyl ether; propylene glycols such as propylene glycol, propylene glycol methyl ether, propylene glycol ethyl ether, propylene glycol butyl ether, propylene glycol propyl ether; ethers such as tetrahydrofuran; dimethylformamide, dimethylacetamide Amides such as N-methylpyrrolidone, N-ethylpyrrolidone, etc. Lorridones; esters such as methyl acetate, ethyl acetate, isopropyl acetate, butyl acetate, methyl propionate; dimethyl sulfoxide, γ-butyrolactone, methyl lactate, ethyl lactate, methyl β-methoxyisobutyrate, methyl α-hydroxyisobutyrate Hydroxy esters such as aniline, anilines such as N-methylaniline, and carbonates such as ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, propylene carbonate, and butylene carbonate.

  Examples of the hydrophobic solvent include ketones having 5 to 10 carbon atoms such as 4-methylpentan-2-one, halogenated hydrocarbons such as chloroform and methylene chloride, aromatic hydrocarbons such as toluene, benzene and xylene, Aliphatic or alicyclic hydrocarbons such as hexane and cyclohexane are exemplified.

<Other additives>
In addition to the various components described above, the conductive composition of the present invention can optionally contain additives as necessary. Specific examples include ultraviolet absorbers, antioxidants, deterioration inhibitors, pH adjusters, polymerization inhibitors, surface modifiers, defoamers, plasticizers, and antibacterial agents. These may be used individually by 1 type and may use 2 or more types together.

<Conductive composition and production method thereof>
The conductive composition of the present invention contains, as an essential component, a conductive polymer, an ionic liquid, and carbon nanotubes having an abundance ratio of primary particles of 80% by number or more, and optionally contains the above-described solvent or additive. You may do it. Although there is no restriction | limiting in particular in these content, As content rate at the time of converting into 100 mass% only with three types of essential components, it is preferable that content of a carbon nanotube is 30 to 50 mass% 40 mass% or more and 50 mass% or less is still more preferable. The content of the conductive polymer or the ionic liquid is not particularly limited, but the content of the conductive polymer is preferably 10% by mass to 50% by mass, and the ionic liquid is 20% by mass to 60% by mass. It is preferable.

  The content ratio of each of these essential components in the conductive composition is approximately equal to the content ratio in the film when the conductive film is finally formed. The conductive composition can contain a solvent or an appropriate amount of additives as necessary, but the solvent is removed in the drying step after film formation, so that the conductive composition has a final conductivity. It is preferable to prepare by mixing in advance according to the content ratio of the essential components in the film.

  Next, the manufacturing method of the electrically conductive composition of this invention is demonstrated.

The method for producing the conductive composition of the present invention is not particularly limited as long as the conductive polymer, the ionic liquid, and the carbon nanotubes having an abundance of primary particles of 80% by number or more are finally mixed. It can be manufactured by various manufacturing methods, and examples of the basic process include the following methods (1), (2), and (3).
(1) Disperse carbon nanotubes in ionic liquid and mix conductive polymer in dispersion liquid (2) Dissolve conductive polymer in ionic liquid and mix carbon nanotubes in solution (3) Aqueous solvent The carbon nanotubes are dispersed in the ionic liquid, while the conductive polymer is dissolved in the ionic liquid, and the dispersion and the solution are mixed. In particular, the abundance of the carbon nanotubes in the primary particles is further improved, and the carbon nanotubes are concentrated at a high concentration. In order to produce a conductive composition that maintains high dispersibility, it is preferable to produce it by the production method (3). In order to solve the problems of the present invention, it is preferable to disperse carbon nanotubes in advance in a simple system in which a conductive polymer and an ionic liquid do not coexist, and then mix them with the conductive polymer and the ionic liquid.

  Next, the manufacturing method (3) will be described in detail.

  The aqueous solvent is a solvent in which the above-mentioned hydrophilic solvents are used alone or arbitrarily in combination of two or more, and can be arbitrarily mixed and used, but a higher ratio of water is preferable. Carbon nanotubes are mixed with this, and dispersion treatment is preferably performed at this stage. In the dispersion treatment, ultrasonic irradiation may be performed, or pulverization may be performed using a ball kneader such as a ball mill, a vibration mill, a sand mill, or a roll mill. In addition, carbon nanotubes that have been cut short by ultrasonic irradiation together with acid treatment with nitric acid, sulfuric acid, or the like may be used. It is also preferable to use carbon nanotubes that have been fractionated by electrophoresis and have uniform fiber lengths. It is.

  Furthermore, it is preferable to perform surface treatment with an organic compound at this time. Specifically, the above-described various surfactants are used as the organic compound, and in the presence of this, the carbon nanotubes are dispersed in an aqueous solvent.

  On the other hand, a method for preparing a solution in which a conductive polymer is dissolved in an ionic liquid is not particularly limited and can be arbitrarily mixed. At this time, a solvent compatible with both may be mixed, or the solvent used at the time of polymerization of the conductive polymer may be brought in and mixed with the ionic liquid.

  Next, as a method of mixing the dispersion of carbon nanotubes and the ionic liquid solution of the conductive polymer, mixing can be performed by any method. While stirring the ionic liquid solution of the conductive polymer, the carbon A method of adding a nanotube dispersion is preferred. In this case, the addition time, the addition temperature, and the stirring conditions after mixing may be arbitrarily adjusted.

<Conductive film and manufacturing method thereof>
A transparent conductive film can be formed by forming the conductive composition of the present invention on a transparent substrate.

  The conductive film of the present invention contains a conductive polymer, an ionic liquid, and carbon nanotubes having an abundance of primary particles of 80% by number or more, and the carbon nanotubes are surface-treated with an organic compound. Is preferred. Although there is no restriction | limiting in particular in content of these each essential component, It is preferable that content of a carbon nanotube is 30 to 50 mass%, and it is still more preferable that it is 40 to 50 mass%. The content of the conductive polymer or ionic liquid is not particularly limited, but the conductive polymer is preferably 10% by mass to 50% by mass, and the ionic liquid is preferably 20% by mass to 60% by mass. . The above additives and the like can also be contained in any amount.

  There is no restriction | limiting in particular as a transparent base material, About the material, a shape, thickness, etc., it can select arbitrarily from well-known things, and can mention the resin film which consists of a glass plate and various resin materials. Among these, it is preferable to use a resin film having flexibility in consideration of applicability to various applications, convenience, or manufacturing aptitude.

  The resin material used as the resin film can be arbitrarily selected from known materials. For example, polyethylene terephthalate resin, polybutylene terephthalate resin, polyethylene naphthalate resin, polyvinyl chloride resin, polyethersulfone Resin, polycarbonate resin, polystyrene resin, polyimide resin, polyetherimide resin, polyvinyl acetate resin, polyvinylidene chloride resin, polyvinylidene fluoride resin, polyvinyl alcohol resin, polyvinyl acetal resin, polyvinyl butyral resin, polyacrylonitrile resin, polyolefin polystyrene resin , Polyamide resin, polybutadiene resin, cellulose acetate, cellulose nitrate, acrylonitrile-butadiene-styrene copolymer resin, and the like. Among these, polyethylene terephthalate resin is preferable in terms of excellent transparency and flexibility. These may be used individually by 1 type and may use 2 or more types together. Moreover, there is no limitation in particular also as the manufacturing method of a resin film.

  The thickness of the conductive film of the present invention is not particularly limited and can be arbitrarily selected. However, considering conductivity, transparency, adhesion to a substrate, and the like, for example, 0.01 to 10 μm. Is preferable, and 0.1-1 micrometer is still more preferable.

  The electrical resistance value of the conductive film of the present invention is preferably 10,000 Ω / □ or less, more preferably 1000 Ω / □ or less, and most preferably 100 Ω / □ or less as the surface resistivity. The surface resistivity can be measured based on, for example, JIS K6911, ASTM D257, etc., and can be easily measured using a commercially available surface resistivity meter.

  The visible light transmittance of the conductive film of the present invention is preferably 70% or more, more preferably 80% or more, and most preferably 90% or more.

  Next, a method for forming a conductive film using the conductive composition of the present invention will be described.

  There is no restriction | limiting in particular as a formation method of an electroconductive film, It can select suitably from well-known methods, For example, the coating method, the printing method, etc. are mentioned suitably. These may be used alone or in combination of two or more.

  There is no restriction | limiting in particular as a coating method, It can select suitably from well-known methods, for example, a roll coat method, a bar coat method, a dip coating method, a gravure coat method, a curtain coat method, a die coat method, a spray coat method And doctor coating method. There is no restriction | limiting in particular as a printing method, It can select suitably from well-known methods, For example, screen printing method, spray printing method, inkjet printing method, letterpress printing method, intaglio printing method, planographic printing method etc. are mentioned, for example. be able to.

  After forming the conductive film on the transparent substrate, it is preferable to perform drying by a known method such as a hot air drying method or a vacuum drying method in order to mainly remove the solvent.

  As the conductive film, the conductive film of the conductive composition of the present invention may be formed on the entire surface of the transparent substrate, or may be partially formed such as forming an electrode or a wiring pattern. good.

  Examples of the use of the transparent conductive film obtained by using the conductive composition of the present invention include, for example, a liquid crystal display, a plasma display, an electroluminescence display, an electrochromic display, a solar cell, a transparent electrode such as a touch panel, a capacitor, Secondary battery, connecting member, polymer semiconductor element, antistatic material such as antistatic coating, antistatic packaging material, electromagnetic shielding material, and electrophotographic equipment parts such as transfer belt, developing roll, charging roll, transfer roll Etc. can be used.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited thereto.

Example 1
(Carbon nanotube dispersion; production of CNT-1)
10 parts by mass of high-purity single-walled carbon nanotubes (manufactured by Carbon Nanotechnology Inc .; hereinafter referred to as “SWNT”) was added to 90 parts by mass of water with stirring at 100 rpm, followed by stirring for 1 hour. A mass% carbon nanotube dispersion was prepared and designated as CNT-1.

(Carbon nanotube dispersion; production of CNT-2)
10 parts by weight of SWNTs were added to 90 parts by weight of a 20% aqueous solution of sodium dodecylbenzenesulfonate with stirring at 100 rpm, followed by dispersion treatment for 1 hour with a sand mill using zirconia beads having a diameter of 0.1 mm. A 10% by mass carbon nanotube dispersion was prepared and designated as CNT-2.

(Carbon nanotube dispersion; production of CNT-3)
CNT-2 was prepared in the same manner as CNT-2 except that sodium dodecylbenzene sulfonate was changed to sodium polystyrene sulfonate to obtain CNT-3.

(Carbon nanotube dispersion; production of CNT-4)
In the production of CNT-3, it was produced in the same manner as CNT-3 except that the concentration of carbon nanotubes was changed to 20% by mass, and designated as CNT-4.

(Carbon nanotube dispersion; production of CNT-5)
13 parts by mass of SWNTs were added to 87 parts by mass of a 20% aqueous solution of sodium dodecylbenzenesulfonate under stirring at 100 rpm, followed by sonication for 1 hour. Next, using acrylamide gel, the pH of the electrophoresis buffer was adjusted to 8, and gel electrophoresis was performed under the conditions of an electrophoresis temperature of 20 ° C. and an applied voltage of 200 V to fractionate carbon nanotubes. Subsequently, a voltage was applied in a direction perpendicular to the migration direction to collect only carbon nanotubes having a fiber length of about 1 μm or more from the gel, and a 10% by mass carbon nanotube dispersion was prepared to obtain CNT-5.

(Carbon nanotube dispersion; production of CNT-6)
10 parts by mass of SWNTs and 10 parts by mass of 1-ethyl-3-methylimidazolium.BF ₄ (hereinafter “EMIBF4”) as an ionic liquid were stirred at 80 rpm in 20% aqueous solution of sodium dodecylbenzenesulfonate at 100 rpm. Then, stirring was continued for 1 hour to prepare a 10% by mass carbon nanotube dispersion, which was designated as CNT-6.

(Conductive polymer solution; production of CP-1)
3,4-Ethylenedioxythiophene (PEDOT) is oxidized and polymerized in an aqueous medium by a known method in the presence of polystyrene sulfonic acid (PSS), and further subjected to ultrafiltration treatment. As a conductive polymer, PEDOT / PSS 20 % Aqueous dispersion was obtained. At this stage, the aqueous dispersion contains 50% PSS and 20% ethylene glycol. On the other hand, EMIBF4 was added to a 20% aqueous solution of sodium dodecylbenzenesulfonate to obtain a 40% aqueous solution of EMIBF4. Next, 50 parts by mass of a 20% aqueous dispersion of PEDOT / PSS was added to 50 parts by mass of this 40% aqueous solution of EMIBF4 with stirring to prepare a 10% by mass conductive polymer solution, which was designated as CP-1.

<Conductive Composition; Preparation of Sample 1>
10 parts by mass of PEDOT / PSS powder was added to 100 parts by mass of the carbon nanotube dispersion CNT-6 with stirring, and then the stirring was continued for 1 hour to prepare a conductive composition sample 1.

<Conductive Composition; Preparation of Sample 2>
Conductive polymer solution CP-1 was added to 100 parts by mass and SWNTs were added to 10 parts by mass under stirring, and then the stirring was continued for 1 hour to prepare conductive composition sample 2.

<Conductive Composition; Preparation of Sample 3>
100 parts by mass of the conductive polymer solution CP-1 and 100 parts by mass of the carbon nanotube dispersion liquid CNT-1 were added with stirring, and then the stirring was continued for 1 hour to prepare a conductive composition sample 3.

<Conductive composition; Preparation of samples 4 to 7>
The conductive composition sample 3 was prepared in the same manner as the conductive composition sample 3 except that the carbon nanotube dispersion liquid CNT-1 was changed to CNT-2 to CNT-5. It was set as the physical samples 4-7.

  The primary particle abundance of carbon nanotubes in each conductive composition was measured and calculated as shown below, and is shown in Table 1.

<Preparation of conductive film>
Polyethylene terephthalate resin (thickness: 188 μm, manufactured by Toray Industries, Inc.) was used as the transparent substrate, and the conductive composition samples 1 to 7 were each bar coater (No. 9, wet film pressure 20 μm) on the transparent substrate. Was applied by a bar coating method. Then, the conductive film of this invention (thickness: about 0.2 micrometer) was produced by heat-drying for 10 minutes in 120 degreeC environment. Conductive films were similarly prepared for each of the conductive compositions 1 to 7, and samples 1 to 7 were prepared as shown in Table 1, respectively.

  The measurement results of the surface resistivity of each sample are shown in Table 1.

<Measurement and evaluation method>
1. Primary particle abundance ratio of carbon nanotubes in conductive composition A 1% by mass dispersion was prepared as a composition sample for measurement, photographed with a transmission electron microscope, and 1000 carbon nanotubes were observed in an arbitrary field of view. Observation was performed to calculate the abundance of primary particles.
2. Transparency of Conductive Film The light transmittance at a wavelength of 550 nm was measured using a spectrophotometer U-4000 type manufactured by Hitachi, Ltd. according to JIS-R-1635.
3. Conductivity of film (surface resistivity)
The surface resistivity was measured at room temperature (about 25 ° C.) using [MCP-T600 (trade name) manufactured by Mitsubishi Chemical Corporation] according to JIS-K-6911.
4). Variation in conductivity of conductive film Using [MCP-T610 (trade name) manufactured by Mitsubishi Chemical Corporation] according to JIS-K-7194, the surface resistivity at 100 locations is arbitrarily determined at room temperature (about 25 ° C). Measurements were made, and the resistance variation was calculated by the number of fluctuation digits. If the number of fluctuation digits is within 1.2 digits, the variation in conductivity is good.

  From Table 1, in the conductive film using the conductive composition in which the primary particle abundance ratio of the carbon nanotubes of the present invention is 80% by number or more, the transparency and conductivity are improved, and the type of the surfactant is changed. It has been found that by increasing the concentration of carbon nanotubes and adding a fractionation step, the abundance of primary particles increases, and the variation in conductivity is reduced accordingly.

Claims (3)

A conductive composition comprising a conductive polymer, an ionic liquid, and carbon nanotubes, wherein the abundance ratio of primary particles of the carbon nanotubes is 80% by number or more. The conductive composition according to claim 1, wherein the carbon nanotube is surface-treated with an organic compound. A conductive film obtained by forming the conductive composition according to claim 1 or 2 on a substrate, wherein the content of carbon nanotubes in the conductive film is 30% by mass. The conductive film is characterized by being 50% by mass or less.