JP2014152296A - Carbon nanotube-containing acidic aqueous dispersion, conductive film, touch panel, electrode for solar battery, and solar battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a carbon nanotube-containing acidic aqueous dispersion useful for production of a conductive film which is excellent in conductivity and transparency and is excellent in adhesion between a conductive coating and a substrate, and to provide the conductive film obtained by using the aqueous dispersion, a touch panel and an electrode for a solar battery obtained by using the conductive film, and a solar battery including the electrode for the solar battery.SOLUTION: The carbon nanotube-containing acidic aqueous dispersion contains: a specific carbon nanotube (A); and a polymer compound (B) that has an acidic group in a side chain, the conductive film is obtained by using the aqueous dispersion, the touch panel and the electrode for the solar battery are obtained using the conductive film, and the solar battery is obtained by using the electrode for the solar battery.

Description

  The present invention provides a carbon nanotube-containing acidic aqueous dispersion useful for the production of a conductive film having excellent conductivity and transparency, and excellent adhesion between the conductive film and the substrate, and obtained using this aqueous dispersion. The present invention relates to a conductive film, a touch panel and a solar cell electrode obtained by using the conductive film, and a solar cell including the solar cell electrode.

In recent years, conductive films containing carbon nanotubes as conductors have been proposed.
For example, Patent Document 1 describes a conductive composition containing carbon nanotubes, a non-conjugated dispersant and a nonvolatile organic acid, a conductive composite obtained using this conductive composition, and the like. Yes.
Patent Document 2 describes an aqueous dispersion containing specific carbon nanotubes and a dispersant, a conductive composite obtained using the aqueous dispersion, and the like.

JP 2010-163568 A JP 2010-254546 A

As described in Patent Documents 1 and 2, a conductive film having excellent conductivity and transparency can be formed by highly dispersing carbon nanotubes in the conductive film. However, the conductive films described in these documents tend to have poor adhesion between the conductive film and the substrate, and are not satisfactory in terms of performance as materials for touch panels and solar cell electrodes.
Therefore, there has been a demand for a conductive film that is excellent in adhesion between the conductive film and the substrate in addition to excellent conductivity and transparency.

  The present invention has been made in view of such circumstances, and has carbon nanotube-containing acidic water useful for the production of a conductive film that is excellent in conductivity and transparency, and also excellent in adhesion between the conductive film and the substrate. Dispersion, conductive film obtained using this aqueous dispersion, touch panel and solar cell electrode obtained using this conductive film, and a solar cell comprising this solar cell electrode To do.

  The present inventors have intensively studied to solve the above problems. As a result, in the conductive film having the base material and the conductive film formed on the base material, the conductive film satisfies a specific relational expression in terms of average diameter (Av) and standard deviation of diameter (σ). A conductive film obtained by using an acidic aqueous dispersion containing a carbon nanotube and a polymer compound having an acidic group in a side chain is a conductive film and a substrate in addition to excellent conductivity and transparency. As a result, the present invention was completed.

  Thus, according to the present invention, the following (1) to (3) carbon nanotube-containing acidic aqueous dispersion, the following (4) conductive film, the following (5) touch panel, the following (6) solar cell electrode, The solar cell of the following (7) is provided.

(1) Carbon nanotube (A) in which the average diameter (Av) and the standard deviation (σ) of the diameter satisfy the relational expression: 0.60> 3σ / Av> 0.20, and a polymer having an acidic group in the side chain A carbon nanotube-containing acidic aqueous dispersion containing the compound (B).
(2) The carbon nanotube-containing acidic aqueous dispersion according to (1), containing 20 to 250 parts by mass of the polymer compound (B) with respect to 100 parts by mass of the carbon nanotubes (A).
(3) The carbon nanotube-containing acidic aqueous dispersion according to (1) or (2), further containing a nonvolatile organic acid.
(4) A conductive film having a base material and a conductive film formed on the base material, wherein the conductive film contains the carbon nanotube-containing acidic water according to any one of (1) to (3). A conductive film obtained by using a dispersion.
(5) A touch panel obtained using the conductive film according to (4).
(6) A solar cell electrode obtained using the conductive film according to (4).
(7) A solar cell comprising the electrode according to (6).

  According to the present invention, a carbon nanotube-containing acidic aqueous dispersion that is useful for the production of a conductive film that is excellent in conductivity and transparency, and that also has excellent adhesion between a conductive film and a substrate, and using this aqueous dispersion There are provided a conductive film obtained in this manner, a touch panel and a solar cell electrode obtained using the conductive film, and a solar cell including the solar cell electrode.

  Hereinafter, the present invention will be described in detail by dividing into 1) a carbon nanotube-containing acidic aqueous dispersion, 2) a conductive film, 3) a touch panel, and 4) a solar cell electrode and a solar cell.

1) Carbon nanotube-containing acidic aqueous dispersion The carbon nanotube-containing acidic aqueous dispersion of the present invention (hereinafter sometimes referred to as “aqueous dispersion of the present invention”) has an average diameter (Av) and a standard deviation of diameter (σ ) Contains a carbon nanotube (A) satisfying the relational expression: 0.60> 3σ / Av> 0.20 and a polymer compound (B) having an acidic group in the side chain.

[Carbon nanotube (A)]
The carbon nanotube (A) used in the present invention has an average diameter (Av) and a standard deviation (σ) of the diameter satisfying a relational expression: 0.60> 3σ / Av> 0.20.
In the present invention, “carbon nanotube (A)” is a general term for a set of predetermined carbon nanotubes constituting the carbon nanotube, and “diameter” means an outer diameter of the predetermined carbon nanotube.

In the present invention, the average diameter (Av) and the standard deviation (σ) of the diameter of the carbon nanotube (A) are a sample average value and a sample standard deviation, respectively. They are obtained as an average value and a standard deviation when measuring the diameter of 100 randomly selected carbon nanotubes under observation with a transmission electron microscope. In the above relational expression, 3σ is obtained by multiplying the obtained standard deviation (σ) by 3.
By using the carbon nanotube (A) in which the average diameter (Av) and the standard deviation (σ) satisfy the relational expression: 0.60> 3σ / Av> 0.20, a conductive film having the desired characteristics is obtained. be able to.

Here, 3σ / Av represents the diameter distribution of the carbon nanotube (A), and the larger the value, the wider the diameter distribution. In the present invention, the diameter distribution is preferably a normal distribution.
The diameter distribution of the carbon nanotube (A) can be calculated by observing with a transmission electron microscope. That is, under observation with a transmission electron microscope, the diameter of 100 randomly selected carbon nanotubes was measured, and the results were used to obtain the diameter on the horizontal axis and the frequency on the vertical axis. It is obtained by plotting the data and approximating with Gaussian. A combination of a plurality of types of carbon nanotubes obtained by different production methods can also increase the value of 3σ / Av, but in that case, it is difficult to obtain a normal distribution of diameters. In the present invention, the carbon nanotube (A) is composed of carbon nanotubes obtained by a single production method, or carbon nanotubes obtained by another production method in an amount that does not affect the diameter distribution of the carbon nanotubes. May be blended.

  The average diameter (Av) of the carbon nanotube (A) is preferably 0.5 nm or more and 15 nm or less from the viewpoint of obtaining a conductive film having the desired characteristics.

The average length of the carbon nanotube (A) is preferably 0.1 μm to 1 cm. When the average length of the carbon nanotube (A) is within the above range, it becomes easy to form a conductive film having desired characteristics.
The average length of the carbon nanotube (A) can be calculated, for example, by measuring 100 randomly selected carbon nanotubes using a transmission electron microscope.

The specific surface area of the carbon nanotube (A) is preferably 100 to 2500 m ² / g. It becomes easy to form the electroconductive film which has the target characteristic because the specific surface area of a carbon nanotube (A) exists in the said range.
The specific surface area of the carbon nanotube (A) can be determined by a nitrogen gas adsorption method.

  The carbon nanotubes constituting the carbon nanotube (A) may be single-walled or multi-layered.

  The carbon nanotube constituting the carbon nanotube (A) may be one having a functional group such as a carboxyl group introduced on the surface. The functional group can be introduced by a known oxidation treatment method using hydrogen peroxide, nitric acid or the like.

  The carbon nanotube (A) is a known method, for example, a substrate having a catalyst layer for producing carbon nanotubes (hereinafter sometimes referred to as a “CNT producing catalyst layer”) on the surface (hereinafter, referred to as “CNT producing substrate”). In addition, when a raw material compound and a carrier gas are supplied and carbon nanotubes are synthesized by chemical vapor deposition (CVD), a small amount of oxidant is present in the system. Thus, it can be obtained by a method (super growth method) of dramatically improving the catalytic activity of the catalyst layer for CNT production (WO 2006/011655 pamphlet).

The support for supporting the CNT production catalyst layer in the CNT production substrate is not particularly limited as long as it can carry the CNT production catalyst layer on the surface thereof.
Examples of the material of the support include metals such as iron, nickel, chromium, molybdenum, tungsten, titanium, aluminum, manganese, cobalt, copper, silver, gold, and platinum; alloys containing these metals; oxides containing the metals A semiconductor such as silicon; a non-metal such as quartz, glass, mica, graphite, diamond; and the like.
Examples of the shape of the support include a flat plate shape, a thin film shape, and a block shape.

  A conventionally known carbon nanotube production catalyst can be used as the catalyst constituting the CNT production catalyst layer. Examples of such a catalyst include metal catalysts such as iron chloride, iron, iron-molybdenum, alumina-iron, alumina-cobalt, and alumina-iron-molybdenum.

  Examples of the raw material compound include hydrocarbon compounds such as methane, ethane, propane, ethylene, propylene, and acetylene; alcohol compounds such as methanol and ethanol; ketone compounds such as acetone; carbon monoxide;

Examples of the carrier gas include helium, argon, hydrogen, nitrogen, neon, krypton, carbon dioxide, and chlorine.
Examples of the oxidizing agent include water vapor, oxygen, ozone, hydrogen sulfide and the like. The content of the oxidizing agent in the gas phase is usually 10 ppm or more and 10,000 ppm or less.

The pressure in the reaction system is preferably 10 ² Pa to 10 ⁷ Pa (100 atmospheric pressure).
The temperature in the reaction system during the production of the carbon nanotube (A) can be appropriately determined according to the catalyst, the raw material compound, and the oxidizing agent. Usually, it is 400-1200 degreeC.

[Polymer Compound (B)]
The polymer compound (B) is a polymer compound having an acidic group in the side chain. In this specification, an acidic group refers to a substituent having a dissociable proton.
By containing the polymer compound (B), the dispersibility of the carbon nanotube (A) in the aqueous dispersion is improved. And the conductive film which is excellent in electroconductivity and transparency and excellent in the adhesiveness of an electrically conductive film and a base material by using the aqueous dispersion containing a carbon nanotube (A) and a high molecular compound (B). It can be formed efficiently.

Examples of the acidic group contained in the polymer compound (B) include a carboxyl group, a sulfonic acid group, and a phosphoric acid group. Among these, a carboxyl group is preferable from the viewpoint that the carbon nanotube (A) can be highly dispersed in the aqueous dispersion or the conductive film, and the adhesion between the conductive film and the substrate can be improved. .
The number of acidic groups contained in the repeating unit of the polymer compound (B) is not particularly limited, but is an average number, preferably 0.1 to 5.

Although the weight average molecular weight (Mw) of a high molecular compound (B) is not specifically limited, Preferably it is 10,000-10,000,000.
The weight average molecular weight (Mw) is a polystyrene equivalent value obtained by performing gel permeation chromatography using a 0.1 M NaCl solution as a solvent.

  The polymer compound (B) is not particularly limited as long as it is a polymer compound having an acidic group in the side chain. Examples thereof include a polymer compound obtained by polymerizing a monomer having an acidic group, a polymer compound in which an acidic group is introduced into a side chain by modifying a synthetic polymer compound or a natural polymer compound, and the like. .

Specific examples of the polymer compound (B) include poly (meth) acrylic acid, copolymers of (meth) acrylic acid and other copolymerizable monomers, polymers having a carboxyl group such as carboxymethyl cellulose, alginic acid, and the like. Compound; Polymer compound having sulfonic acid group such as polystyrene sulfonic acid, copolymer of styrene and styrene sulfonic acid, chondroitin sulfate; Polymer compound having phosphoric acid group such as poly {(meth) acryloyloxyethyl phosphate} And the like. The polymer compound (B) may have at least an acidic group in its side chain in the aqueous dispersion of the present invention.
These polymer compounds (B) can be used singly or in combination of two or more.

[Acid compound (C)]
The aqueous dispersion of the present invention further contains a low molecular weight acidic compound (hereinafter sometimes referred to as “acidic compound (C)”) in addition to the carbon nanotube (A) and the polymer compound (B). Also good. By using the acidic compound (C), the pH of the aqueous dispersion can be adjusted efficiently.
The molecular weight of the acidic compound (C) is usually 2,000 or less.

Examples of the acidic compound (C) include inorganic acids and organic acids.
Examples of inorganic acids include nitric acid, phosphoric acid, sulfuric acid and the like.
Organic acids include aliphatic sulfonic acids such as octyl sulfonic acid, decyl sulfonic acid, dodecyl sulfonic acid, myristyl sulfonic acid, cetyl sulfonic acid, stearyl sulfonic acid, bromoethane sulfonic acid; benzene sulfonic acid, toluene sulfonic acid, xylene sulfone Aromatic sulfonic acids such as acid, dodecylbenzenesulfonic acid, eicosylbenzenesulfonic acid, naphthalenesulfonic acid, methylnaphthalenesulfonic acid, dodecylnaphthalenesulfonic acid, eicosylnaphthalenesulfonic acid; valeric acid, caproic acid, enanthic acid, caprylic acid , Aliphatic monocarboxylic acids such as capric acid, oleic acid, stearic acid, undecanoic acid, tridecanoic acid, myristic acid; oxalic acid, maleic acid, citric acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, Aliphatic polycarboxylic acids such as beryl acid, azelaic acid, and sebacic acid; aromatic monocarboxylic acids such as benzoic acid, toluic acid, and ethyl benzoic acid; phthalic acid, isophthalic acid, terephthalic acid, nitrophthalic acid, trimellitic acid, etc. Aromatic polycarboxylic acid; and the like.
These acidic compounds (C) can be used alone or in combination of two or more.

Among these acidic compounds (C), an organic acid is preferable and a non-volatile organic acid is more preferable because an aqueous dispersion in which pH is hardly changed can be efficiently prepared.
The “nonvolatile organic acid” refers to an organic acid having a mass reduction rate of 1% or less after being left for 24 hours at 25 ° C. and 1 atm.
Typical examples of the non-volatile organic acid include phthalic acid, oxalic acid, maleic acid, citric acid, malonic acid, succinic acid, benzoic acid, oleic acid, stearic acid and the like.

[Carbon nanotube-containing acidic aqueous dispersion]
The aqueous dispersion of the present invention may further contain other components as long as the effects of the present invention are not hindered.
Examples of other components include a binder, a conductive aid, a dispersant (excluding the polymer compound (B)), a surfactant (excluding the acidic compound (C)), and the like. These may be appropriately known ones.

The aqueous dispersion of the present invention may be water containing 50% by mass or more of the entire solvent, and may contain a hydrophilic organic solvent.
Examples of hydrophilic organic solvents include alcohols such as methyl alcohol, ethyl alcohol and propyl alcohol; ketones such as acetone and methyl ethyl ketone; ethers such as tetrahydrofuran, dioxane and diglyme; N, N-dimethylformamide and N, N-dimethyl. And amides such as acetamide, N-methyl-2-pyrrolidone and 1,3-dimethyl-2-imidazolidinone; sulfur-containing solvents such as dimethyl sulfoxide and sulfolane; and the like. These solvents can be used alone or in combination of two or more.

  In the aqueous dispersion of the present invention, for example, the carbon nanotube (A), the polymer compound (B), and if necessary, the acidic compound (C) and other components are mixed in water or a water-containing mixed solvent, It can be obtained by dispersing carbon nanotubes.

  A known method can be used for the mixing process and the dispersion process. Examples thereof include a method using a nanomizer, an optimizer, an ultrasonic disperser, a ball mill, a sand grinder, a dyno mill, a spike mill, a DCP mill, a basket mill, a paint conditioner, a high-speed stirring device, and the like.

Although content of a carbon nanotube (A) is not specifically limited, Preferably it is 0.001-10 mass% in the whole aqueous dispersion.
By setting the content of the carbon nanotube (A) within the above range, an aqueous dispersion in which the carbon nanotube (A) is highly dispersed can be efficiently prepared. And the electroconductive film which has the target characteristic can be efficiently formed by using this aqueous dispersion.

The content of the polymer compound (B) is preferably 20 to 250 parts by mass with respect to 100 parts by mass of the carbon nanotube (A).
By setting the content of the polymer compound (B) within the above range, an aqueous dispersion in which the carbon nanotubes (A) are highly dispersed can be efficiently prepared. In addition, if the content of the polymer compound (B) is within the above range, it is difficult to adversely affect the conductivity of the conductive film. Therefore, by using this aqueous dispersion, a conductive film having desired characteristics can be obtained. It can be formed efficiently.

When the acidic compound (C) is contained, the content can be appropriately determined according to the pH of the aqueous dispersion.
The pH of the aqueous dispersion of the present invention is less than 7.0. When the pH is less than 7, the dispersibility of the carbon nanotube (A) is improved, and a conductive film having desired characteristics can be efficiently formed.

  By using the aqueous dispersion of the present invention, it is possible to efficiently form a conductive film in which the carbon nanotubes (A) are highly dispersed and have excellent adhesion to the substrate.

2) Conductive film The conductive film of the present invention is a conductive film having a base material and a conductive film formed on the base material, and the conductive film uses the aqueous dispersion of the present invention. It is obtained.

〔Base material〕
The base material constituting the conductive film of the present invention is not particularly limited as long as it can support the conductive film. Examples of the substrate include a sheet made of synthetic resin or glass. Especially, since it is lightweight and excellent in flexibility and light transmittance, what consists of transparent resin is preferable.
As transparent resin to be used, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), syndiotactic polystyrene (SPS), polyphenylene sulfide (PPS), polycarbonate (PC), polyarylate (PAr), polysulfone (PSF), polyester Synthetic resins such as (PE), polyethersulfone (PES), polyetherimide (PEI), cycloolefin polymer (COP), and transparent polyimide (PI).

Although the thickness of a base material should just be determined suitably according to a use, it is 10-10000 micrometers normally.
The light transmittance (measurement wavelength: 500 nm) of the substrate is preferably 60% or more.

[Conductive film]
The conductive film constituting the conductive film of the present invention is obtained using the aqueous dispersion of the present invention. Details of the method for forming the conductive film will be described later.

The thickness of the conductive film may be appropriately determined according to the application, but is usually 0.1 nm to 100 μm.
The content of the carbon nanotube (A) contained in the conductive film may be appropriately determined according to the use, but is usually 1.0 × 10 ^{−6 to} 15 mg / cm ² .

[Conductive film]
The conductive film of the present invention can be obtained, for example, by applying the aqueous dispersion of the present invention on a substrate and drying the obtained coating film to form a conductive film.

  When applying the aqueous dispersion onto the substrate, a known application method can be employed. Examples of the coating method include a dipping method, a roll coating method, a gravure coating method, a knife coating method, an air knife coating method, a roll knife coating method, a die coating method, a screen printing method, a spray coating method, and a gravure offset method.

When drying a coating film, a well-known drying method is employable. Examples of the drying method include a hot air drying method, a hot roll drying method, and an infrared irradiation method.
The drying temperature is not particularly limited, but is usually room temperature to 200 ° C., and the drying time is not particularly limited, but is usually 0.1 to 150 minutes.

The conductive film of the present invention may have other layers in addition to the base material and the conductive film as long as the effects of the present invention are not hindered. Examples of other layers include a hard coat layer, a gas barrier layer, and an adhesive layer.
Other layers can be formed by a conventionally known method.

  The conductive film of the present invention is excellent in conductivity and transparency and excellent in adhesion between the conductive film and the substrate.

It is shown by measuring sheet resistance that the conductive film of this invention is excellent in electroconductivity.
The sheet resistance of the conductive film of the present invention is usually 100 to 5000 Ω / □.

The fact that the conductive film of the present invention is excellent in transparency is shown by measuring the total light transmittance.
The total light transmittance of the conductive film of the present invention is usually 70% or more.

That the electroconductive film of this invention is excellent in the adhesiveness of an electrically conductive film and a base material is shown because an electrically conductive film cannot peel easily when an electrically conductive film is wash | cleaned with organic solvents, such as toluene.
Measurement of sheet resistance and total light transmittance, and adhesion test can be performed by the methods described in the examples.

  Since the conductive film of the present invention is excellent in conductivity and transparency and excellent in adhesion between the conductive film and the substrate, it is suitably used as a material for a touch panel or a solar cell electrode.

3) Touch panel The touch panel of the present invention is obtained using the conductive film of the present invention.
Examples of the touch panel include a surface capacitive touch panel, a projected capacitive touch panel, and a resistive touch panel.
The conductive film of the present invention is suitably used as a conductive transparent substrate for these touch panels.
Since the touch panel of the present invention uses the conductive film of the present invention, the touch panel is excellent in visibility and durability.

4) Solar Cell Electrode and Solar Cell The solar cell electrode of the present invention is obtained using the conductive film of the present invention.
Since the electrode for solar cells of the present invention uses the conductive film of the present invention, the conversion efficiency is high and the durability is excellent.

Examples of the solar battery include a silicon solar battery, a compound solar battery, and an organic solar battery.
The solar cell electrode of the present invention is used as an electrode of these solar cells.

A dye-sensitized solar cell, which is a kind of organic solar cell, will be described as an example. A dye-sensitized solar cell usually has a structure in which a photoelectrode, an electrolyte layer, and a counter electrode are arranged in this order.
The photoelectrode is an electrode that can emit electrons to an external circuit by receiving light. The photoelectrode is usually a photoelectrode substrate in which a conductive film is formed on a base material, a porous semiconductor fine particle layer formed on the photoelectrode substrate, and a sensitizing dye on the surface of the porous semiconductor fine particle layer. And a sensitizing dye layer formed by adsorption.
The electrolyte layer is a layer for separating the photoelectrode and the counter electrode and efficiently performing charge transfer.
The counter electrode is an electrode for efficiently passing electrons entering from an external circuit to the electrolyte layer. The counter electrode usually has a counter electrode substrate in which a conductive film is formed on a base material and a catalyst layer formed on the counter electrode substrate.
The conductive film of the present invention is suitably used, for example, as the above-described photoelectrode substrate or counter electrode substrate.

The solar cell of this invention is equipped with the electrode for solar cells of this invention mentioned above. The solar cell of this invention will not be specifically limited if it is provided with the electrode for solar cells of this invention. For example, depending on the type of semiconductor substrate, a crystalline silicon solar cell such as a single crystal silicon solar cell, a polycrystalline silicon solar cell, a microcrystalline silicon solar cell, or a multi-bonded silicon solar cell; an amorphous silicon solar cell; Examples include those classified into compound solar cells such as GaAs solar cells, CIS solar cells, and CdTe solar cells; organic solar cells such as dye-sensitized solar cells and organic thin film solar cells.
Moreover, the solar cell of this invention is not limited to what uses the sun as a light source, For example, you may use indoor illumination as a light source.
Since the solar cell of the present invention comprises the solar cell electrode of the present invention, the conversion efficiency is high and the durability is excellent.
The solar cell of the present invention is preferably used as a portable solar cell or an indoor solar cell because the above characteristics are particularly utilized.

[Example 1]
In a 30 mL glass container, 4 g of water, 1 g of ethanol, 0.0025 g of carbon nanotubes, carboxymethylcellulose (Mw: 300,000, acidic group number: 0.8; hereinafter referred to as CMC) aqueous solution (diluted 100 times) 0.25 g, And 0.10 g of 0.05M aqueous phthalic acid solution was added.
The carbon nanotubes had the following characteristic values:
Average diameter (Av): 3.3 nm, diameter standard deviation (σ): 0.64 nm, 3σ / Av: 0.58, average length: 100 μm, specific surface area: 800 m ² / g, mainly monolayer.
The contents of this glass container are subjected to a dispersion treatment for 2 hours at room temperature using a bath-type ultrasonic cleaner [manufactured by BRANSON, 5510J-MT (42 kHz, 180 W)], and water dispersion having a pH of 5 is performed. Liquid 1 was obtained.
On a polyester film (Toyobo Co., Ltd., Cosmo Shine (registered trademark) A4100, film thickness 100 μm), the aqueous dispersion 1 was applied using a bar coater (Tester Sangyo Co., Ltd., SA-203, No. 10). It applied so that it might become thickness 22.9 micrometers. The obtained coating film was dried at 23 ° C. and 60% (relative humidity) for 2 hours to obtain a conductive film 1.

[Comparative Example 1]
An aqueous dispersion 2 was prepared in the same manner as in Example 1, except that 0.1 g of 0.01 mg / L sodium borate aqueous solution was added to adjust the pH of the aqueous dispersion to 9. This aqueous dispersion 2 was used to obtain a conductive film 2.

[Comparative Example 2]
An aqueous dispersion 3 having a pH of 5 was prepared in the same manner as in Example 1 except that 2 g of a hydroxyethyl cellulose (HEC) aqueous solution (100-fold dilution) was used instead of the CMC aqueous solution. 3 was used to obtain a conductive film 3.

The following measurements and tests were performed using the conductive films 1 to 3 obtained in Examples and Comparative Examples. The results are shown in Table 1.
(1) Sheet resistance In accordance with JIS K 7194, the sheet resistance was measured by a four-terminal four-probe method using a resistivity meter (manufactured by Mitsubishi Chemical Corporation, Loresta (registered trademark) GP).
(2) Total light transmittance Based on JIS K7361, the total light transmittance was measured using the spectrophotometer (the JASCO make, V-570).
(3) Adhesiveness After washing an electroconductive film with toluene, the adhesiveness of an electrically conductive film and a base material was evaluated by visually observing the state of the surface. The evaluation criteria are shown below.
〔Evaluation criteria〕
○: There is no change in the state of the conductive film.
Δ: Part of the conductive film is peeled off.
X: The conductive film is all peeled off.

Table 1 shows the following.
The electroconductive film 1 of Example 1 is excellent in electroconductivity and transparency, and is excellent in the adhesiveness of an electroconductive film and a base material.
On the other hand, the conductive film 2 of Comparative Example 1 uses the aqueous dispersion 2 having a high pH, and has a high sheet resistance.
Moreover, the conductive film 3 of Comparative Example 2 uses a polymer compound having a hydroxyl group instead of the polymer compound having an acidic group. All of the adhesion is inferior.

Claims (7)

  The carbon nanotube (A) in which the average diameter (Av) and the standard deviation (σ) of the diameter satisfy the relational expression: 0.60> 3σ / Av> 0.20, and the polymer compound having an acidic group in the side chain (B ) -Containing acidic aqueous dispersion containing carbon nanotubes.   The carbon nanotube-containing acidic aqueous dispersion according to claim 1, wherein the polymer compound (B) is contained in an amount of 20 to 250 parts by mass with respect to 100 parts by mass of the carbon nanotube (A).   The carbon nanotube-containing acidic aqueous dispersion according to claim 1 or 2, further comprising a nonvolatile organic acid.   It is a conductive film which has a base material and the electrically conductive film formed on the said base material, Comprising: The said electrically conductive film is obtained using the carbon nanotube containing acidic water dispersion liquid in any one of Claims 1-3. A conductive film.   A touch panel obtained using the conductive film according to claim 4.   The electrode for solar cells obtained using the electroconductive film of Claim 4.   A solar cell comprising the electrode according to claim 6.