JP6325364B2 - Transparent conductive coating composition, transparent conductive sheet and method for producing the same, and transparent conductive pattern forming method - Google Patents

Description

  The present invention relates to a transparent conductive coating composition, a transparent conductive sheet and a method for producing the same, and a transparent conductive pattern forming method.

  In recent years, thiophene-based and aniline-based polymers have excellent stability and conductivity, and are expected to be used as organic conductive materials. As one of the applications, a coating composition in which a conductive polymer in which a dopant is added to the above polymer is dispersed in a solvent is used to form a transparent electrode used in various devices such as a liquid crystal display and a transparent touch panel. Yes. However, when the conductive polymer is used as a coating composition and a conductive film is formed on the substrate using the coating composition, the hardness of the conductive film and the adhesion of the conductive film to the substrate Is not enough. In particular, when the substrate is formed from a non-liquid-absorbing material such as glass, it is difficult to form a sufficiently hard conductive film without impairing the transparency of the substrate. For example, Patent Document 1 proposes a binder that can improve the hardness of the transparent conductive film and the adhesion of the transparent conductive film to the base material.

JP 2007-324143 A

  Patent Document 1 describes that the hardness of the conductive film and the adhesion to the substrate can be improved by using a resin such as polyvinyl alcohol (PVA) as the binder. However, the electrical properties, optical properties, heat resistance, and moisture resistance of the obtained conductive film are not sufficient, and there is still room for improvement.

  The present invention has been made to solve the above problems, and provides a transparent conductive coating composition capable of forming a transparent conductive film excellent in electrical characteristics, optical characteristics, heat resistance and moisture resistance. Furthermore, the present invention provides a transparent conductive sheet having a transparent conductive film excellent in electrical characteristics, optical characteristics, heat resistance and moisture resistance, a method for producing the same, and a method for forming a conductive pattern.

The transparent conductive coating composition of the present invention is a transparent conductive coating composition containing a conductive polymer, a resin, and a solvent, wherein the resin contains polyvinylidene fluoride, and the solvent is water, A solvent selected from ethanol and acetic acid, and a solvent selected from ethylene glycol, dimethyl sulfoxide, acetonitrile and acetone, and the dispersion particle size of the polyvinylidene fluoride in the coating composition is 0.3 μm or less. In addition, the content of the conductive polymer is 3% by mass or more and 45% by mass or less with respect to the mass of all solid components contained in the coating composition, and the content of the aprotic polar solvent is the solvent It is characterized by being 25% by mass or more and 50% by mass or less based on the total mass of

  The transparent conductive sheet of the present invention is a transparent conductive sheet comprising a transparent substrate and a transparent conductive film formed on at least one main surface of the substrate, and the transparent conductive film is It is formed using the transparent conductive coating composition of the present invention.

  The method for producing a transparent conductive sheet of the present invention includes a step of applying the transparent conductive coating composition of the present invention to at least one main surface of a transparent substrate, and heating the transparent conductive coating composition. And a step of forming a transparent conductive film.

  The conductive pattern forming method of the present invention is a conductive pattern forming method of forming a conductive pattern on a transparent substrate, and the transparent conductive coating composition of the present invention is applied to one main surface of the substrate. Forming a transparent conductive film, forming a resist film at a position where a conductive pattern is formed on the transparent conductive film, and using an inert agent to deactivate the conductive film, the resist film And a step of deactivating the conductivity of the exposed portion of the transparent conductive film.

  According to the transparent conductive coating composition of the present invention, a transparent conductive sheet having a transparent conductive film excellent in electrical properties, optical properties, heat resistance and moisture resistance can be provided.

(Transparent conductive coating composition)
The transparent conductive coating composition of the present invention contains a conductive polymer, a resin, and a solvent. The resin contains polyvinylidene fluoride, and the solvent contains a protic polar solvent and an aprotic polar solvent. Furthermore, the dispersed particle diameter of the polyvinylidene fluoride in the coating composition is 0.3 μm or less, and the content of the conductive polymer is based on the mass of all solid components contained in the coating composition. It is 3 mass% or more and 45 mass% or less, and content of the said aprotic polar solvent is 25 mass% or more and 50 mass% or less with respect to the total mass of the said solvent.

  By using the transparent conductive coating composition, a transparent conductive film excellent in electrical characteristics, optical characteristics, heat resistance and moisture resistance can be formed.

<Conductive polymer>
The conductive polymer is a polymer called Conductive Polymers (CPs), which exhibits conductivity in a state where a polyradical cationic salt or a polyradical anionic salt is formed by doping with a dopant. It refers to the polymer obtained.

  In the present invention, the conductive polymer containing a polythiophene compound and a dopant is used. As the conductive polymer in the present invention, a mixture (also referred to as PEDOT / PSS) containing poly (3,4-ethylenedioxythiophene) as a polythiophene compound and polystyrene sulfonic acid as a dopant can be used.

  Content of the said conductive polymer is set to 3 mass% or more and 45 mass% or less with respect to the mass of all the solid components contained in the said coating composition. When the content of the conductive polymer is less than 3% by mass with respect to the mass of all solid components contained in the coating composition, the conductivity of the transparent conductive film is reduced. The moisture resistance of the conductive film decreases.

<Resin>
The resin constituting the transparent conductive coating composition of the present invention includes polyvinylidene fluoride (PVDF). The PVDF plays a role as a binder, thereby improving the adhesion between the transparent conductive film and the substrate. Since the PVDF is uniformly dispersed in a transparent conductive film formed using the transparent conductive coating composition of the present invention to improve translucency, the dispersed particle size in the coating composition is 0.00. It is set to 3 μm or less. By forming the PVDF by emulsion polymerization, the dispersed particle diameter can be reduced to 0.3 μm or less. In the present invention, the dispersed particle size of PVDF can be measured by a particle size distribution system of a dynamic light scattering method. For example, measurement can be performed using a particle size distribution measuring device “N4 Plus” manufactured by Coulter, Inc. using distilled water as a diluent solvent.

  In addition to PVDF, the above resins include resins such as vinylidene fluoride-acrylic copolymer, vinylidene fluoride-hexafluoropropylene copolymer, hydroxyethyl cellulose, polyvinyl alcohol, polyethylene oxide, silane compound, polyester emulsion, and polyolefin emulsion. You may go out.

  The PVDF content is preferably 55% by mass or more and 97% by mass or less with respect to the mass of all solid components contained in the coating composition. When there is too little content of the said PVDF, it exists in the tendency for the adhesiveness to the base material of the formed transparent conductive film to fall, and to be easy to generate | occur | produce a crack in a transparent conductive film. Moreover, when there is too much content of the said PVDF, it exists in the tendency for an electrical property to deteriorate.

<Solvent>
The solvent constituting the transparent conductive coating composition of the present invention includes a protic polar solvent and an aprotic polar solvent. By using a protic polar solvent and an aprotic polar solvent in combination, a transparent conductive film excellent in transparency can be obtained at a relatively low drying temperature.

  Examples of the protic polar solvent include water, ethanol, acetic acid, and the like, and examples of the aprotic polar solvent include ethylene glycol, dimethyl sulfoxide, acetonitrile, acetone, and the like.

  The content of the aprotic polar solvent is set to 25% by mass or more and 50% by mass or less with respect to the total mass of the solvent. When the content of the aprotic polar solvent is less than 25% by mass with respect to the total mass of the solvent, the optical properties of the transparent conductive film are deteriorated, and when it exceeds 50% by mass, the moisture resistance of the transparent conductive film is decreased. descend.

  Although content of the said solvent is not specifically limited, What is necessary is just to be 70 mass% or more and 99.5 mass% or less with respect to the total mass of the transparent conductive coating composition of this invention. The solvent may contain a nonpolar solvent.

  The method for preparing the transparent conductive coating composition of the present invention is not particularly limited, and the conductive polymer, the resin, and the solvent may be appropriately mixed by a known method.

(Transparent conductive sheet)
The transparent conductive sheet of the present invention comprises a transparent substrate and a transparent conductive film formed on at least one main surface of the substrate, and the transparent conductive film is the transparent conductive film of the present invention. It is formed using a coating composition.

  By using the transparent conductive coating composition, it is possible to provide a transparent conductive sheet having a transparent conductive film excellent in electrical characteristics, optical characteristics, heat resistance and moisture resistance.

  As said base material, various things, such as a plastics, rubber | gum, glass, ceramics, can be used, for example.

  The surface resistance value of the transparent conductive film of the present invention is preferably 500 Ω / square or less. The smaller the surface resistance, the better the electrical characteristics.

  The total light transmittance in the wavelength range of 380 to 780 nm of the transparent conductive film is preferably 85% or more, and more preferably 88% or more. The higher the total light transmittance, the better the optical properties. The total light transmittance can be measured with a spectrophotometer, for example, “V-570” manufactured by JASCO Corporation.

  Although the film thickness of the transparent conductive film of this invention is suitably set according to a use, it is about 0.01-10 micrometers normally. If the film thickness is too thin or too thick, it becomes difficult to form a uniform transparent conductive film. Although depending on the proportion of the conductive polymer contained in the transparent conductive coating composition, the surface resistance tends to increase when the film thickness is thin, and the total light transmittance is increased when the film thickness is too thick. Tend to decrease.

(Transparent conductive sheet manufacturing method)
The method for producing a transparent conductive sheet of the present invention includes a step of applying the transparent conductive coating composition of the present invention to at least one main surface of a transparent substrate, and heating the transparent conductive coating composition. And a step of forming a transparent conductive film. Thereby, the transparent conductive sheet which has a transparent conductive film excellent in an electrical property, an optical characteristic, heat resistance, and moisture resistance can be manufactured.

  As a method for applying the transparent conductive coating composition, for example, a coating method such as a bar coating method, a reverse method, a gravure printing method, a micro gravure printing method, a dipping method, a spin coating method, or a spray method can be used. .

  The heating may be performed under the condition that the solvent component in the transparent conductive coating composition evaporates, and is preferably performed at 100 to 150 ° C. for 5 to 60 minutes. If the solvent remains in the transparent conductive film, the strength tends to be inferior. As the heating method, for example, a hot air drying method or the like can be used.

(Conductive pattern formation method)
The conductive pattern forming method of the present invention is a method of forming a conductive pattern on a transparent substrate, and the transparent conductive coating composition of the present invention is applied to one main surface of the substrate to form a transparent conductive layer. A step of forming a conductive film, a step of forming a resist film at a position where a conductive pattern on the transparent conductive film is formed, and an inert agent that deactivates the conductivity, using the resist film as a mask, And a step of deactivating the conductivity of the exposed portion of the transparent conductive film. Thereby, a highly accurate conductive pattern can be formed easily and inexpensively.

  The resist film can be formed, for example, by screen printing a resist agent on the transparent conductive film. The said resist agent is not specifically limited, It can select suitably.

  The inactive agent is not particularly limited as long as it can deactivate the conductive polymer, and examples thereof include an oxidizing compound and a basic compound.

  Examples of the oxidizing compound include hydrogen peroxide compounds, perchloric acid compounds, hypochlorous acid compounds, peracetic acid compounds, metachlorobenzoic acid compounds, sulfite compounds, and the like.

  Examples of the basic compound include ammonia, monomethylamine, dimethylamine, trimethylamine, monoethylamine, diethylamine, triethylamine, pyridine, 4-methylpyridine, and tetramethylammonium hydroxide.

  Hereinafter, the present invention will be described in detail using examples. However, the present invention is not limited to the following examples. Unless otherwise indicated, in the following, “part” means “part by mass”.

Example 1
<Preparation of transparent conductive coating solution>
First, the following components were added and mixed to prepare a transparent conductive coating solution. The dispersion particle diameter of PVDF contained in the prepared transparent conductive coating liquid below was 0.3 μm or less.
(1) Conductive polymer dispersion (manufactured by Heraeus, trade name “PH-500”, conductive polymer: PEDOT-PSS, solid content concentration: 1.0 mass%, solvent: water): 2.5 parts (2) Resin dispersion (resin: PVDF, PVDF average dispersion particle size: 0.2 μm, solid content concentration: 20 mass%, solvent: water): 2.4 parts (3) Protic polar solvent (ethanol): 1.2 parts (4) aprotic polar solvent (ethylene glycol): 3.9 parts

<Formation of transparent conductive sheet>
Next, a 10 cm square non-alkali glass (total light transmittance: 91.2%) having a thickness of 0.7 mm is used as a substrate, and the transparent conductive coating solution is rotated on one main surface of the substrate by a spin coating method. It was applied at a speed of 800 rpm for 30 seconds, and then heated at 100 ° C. for 5 minutes. This produced the transparent conductive sheet of Example 1 in which the transparent conductive film was formed on one main surface. The film thickness of the transparent conductive film was 0.5 μm.

(Example 2)
A transparent conductive sheet of Example 2 was produced in the same manner as in Example 1 except that the protic polar solvent of the transparent conductive coating solution was changed to a mixed solvent of 50:50 mass ratio of ethanol and water.

(Example 3)
A transparent conductive sheet of Example 3 was produced in the same manner as in Example 1 except that the aprotic polar solvent of the transparent conductive coating solution was changed to dimethyl sulfoxide.

Example 4
A transparent conductive sheet of Example 4 was produced in the same manner as in Example 1 except that the substrate was changed to a polyethylene terephthalate film having a thickness of 100 μm (trade name “Cosmo Shine A4300” manufactured by Toyobo Co., Ltd.).

(Example 5)
A transparent conductive sheet of Example 5 was produced in the same manner as in Example 1 except that the amount of each component of the transparent conductive coating liquid was changed as follows.
(1) Conductive polymer dispersion: 10.0 parts (2) Resin dispersion: 2.0 parts (3) Protic polar solvent: 3.0 parts (4) Aprotic polar solvent: 10.0 parts

(Example 6)
A transparent conductive sheet of Example 6 was produced in the same manner as in Example 1 except that the amount of the aprotic polar solvent in the transparent conductive coating liquid was changed to 2.2 parts.

(Comparative Example 1)
A transparent conductive sheet of Comparative Example 1 was produced in the same manner as in Example 1 except that the average dispersed particle size of PVDF contained in the resin dispersion of the transparent conductive coating liquid was changed to 0.5 μm. The dispersion particle diameter of PVDF contained in the transparent conductive coating liquid prepared in Comparative Example 1 exceeds 0.3 μm.

(Comparative Example 2)
A transparent conductive sheet of Comparative Example 2 was prepared in the same manner as in Example 1 except that the dispersion resin of the resin dispersion of the transparent conductive coating liquid was changed from PVDF to tetraethoxysilane.

(Comparative Example 3)
Comparative Example 3 was the same as Example 1 except that the dispersion resin of the transparent conductive coating liquid resin dispersion was changed from PVDF to polyethylene oxide (trade name “Alcox E-45” manufactured by Meisei Chemical Co., Ltd.). A transparent conductive sheet was produced.

(Comparative Example 4)
A transparent conductive sheet of Comparative Example 4 was produced in the same manner as in Example 1 except that the amount of each component of the transparent conductive coating liquid was changed as follows.
(1) Conductive polymer dispersion: 25.0 parts (2) Resin dispersion: 1.3 parts (3) Protic polar solvent: 6.6 parts (4) Aprotic polar solvent: 29.7 parts

(Comparative Example 5)
A transparent conductive sheet of Comparative Example 5 was produced in the same manner as in Example 1 except that the amount of the aprotic polar solvent in the transparent conductive coating liquid was changed to 1.0 part.

(Comparative Example 6)
A transparent conductive sheet of Comparative Example 6 was produced in the same manner as in Example 1 except that the amount of the aprotic polar solvent in the transparent conductive coating liquid was changed to 6.7 parts.

  In Table 1, the mass ratio (conductive polymer / total solid component) to the total solid component of the conductive polymer contained in the transparent conductive coating liquids used in Examples 1 to 6 and Comparative Examples 1 to 6 and the above transparent The mass ratio of the aprotic polar solvent contained in the solvent used for the conductive coating solution to the total solvent (aprotic polar solvent / total solvent) is shown.

  Next, each evaluation shown below was performed about the transparent conductive sheet obtained above.

<Electrical characteristics>
The electrical characteristics of the transparent conductive sheet were evaluated by measuring the surface resistance value of the transparent conductive film of the transparent conductive sheet as follows.

  The surface resistance value of the transparent conductive film of the transparent conductive sheet was measured using a resistivity measuring apparatus “Loresta-GP” (MCP-T610 type) manufactured by Mitsubishi Chemical Analytech Co., Ltd. and an LSP probe. As a result of the measurement, when the surface resistance value of the resistivity measuring device is displayed as “OVER”, the surface resistance value is set to the resistivity measuring device “Hiresta-UP” (manufactured by Mitsubishi Chemical Analytech Co., Ltd.). MCP-HT450 type) and URSP probe.

  As a result of the measurement, when the surface resistance value was 500 Ω / square or less, it was determined that the electrical characteristics were good, and when the surface resistance value was greater than 500 Ω / square, the electrical characteristics were determined to be poor.

<Optical characteristics>
The optical characteristics of the transparent conductive sheet were evaluated by measuring the haze of the transparent conductive sheet as follows.

  The haze of the transparent conductive sheet was measured using a spectrophotometer “V-570” manufactured by JASCO Corporation. Specifically, the integrating sphere “ILN-472” is combined, and in the haze value calculation mode, the response is Fast, the bandwidth is 2.0 nm, the near infrared bandwidth is 8.0 nm, and the scanning speed is 400 nm / min. Then, a light transmission spectrum in a wavelength range of 380 to 780 nm was measured, and using the measurement result of the light transmission spectrum, haze was calculated under the conditions of a C light source and a visual field of 2 degrees.

  As a result of the above measurement, when the haze was 1.0% or less, it was judged that the optical characteristics were good, and when the haze exceeded 1.0%, the optical characteristics were judged to be poor.

<Heat resistance>
The heat resistance of the transparent conductive sheet was evaluated by conducting a storage test of the transparent conductive sheet as follows.

First, the initial surface resistance value of the transparent conductive film of the transparent conductive sheet was measured in the same manner as in the evaluation of the electrical characteristics described above. Next, the transparent conductive sheet was placed in a thermostatic bath and stored at 85 ° C. for 240 hours. Subsequently, the surface resistance value of the transparent conductive film of the transparent conductive sheet after storage was measured in the same manner as described above. Finally, the degree of change in the surface resistance value was calculated by the following formula (1).
Change in surface resistance value = surface resistance value after storage / initial surface resistance value (1)

  As a result of the measurement, when the degree of change in the surface resistance value was 1.2 or less, the heat resistance was judged to be good, and when the degree of change in the surface resistance value exceeded 1.2, the heat resistance was judged to be poor.

<Moisture resistance>
The moisture resistance of the transparent conductive sheet was evaluated by conducting a storage test of the transparent conductive sheet as follows.

  First, the initial surface resistance value of the transparent conductive film of the transparent conductive sheet was measured in the same manner as in the evaluation of the electrical characteristics described above. Next, the transparent conductive sheet was placed in a constant temperature and humidity chamber and stored at 60 ° C. and a relative humidity of 90% for 240 hours. Subsequently, the surface resistance value of the transparent conductive film of the transparent conductive sheet after storage was measured in the same manner as described above. Finally, the degree of change in the surface resistance value was calculated by the above-described equation (1).

  As a result of the measurement, when the degree of change in the surface resistance value was 1.2 or less, it was judged that the moisture resistance was good, and when the degree of change in the surface resistance value exceeded 1.2, the moisture resistance was judged as poor.

  The results of the evaluation are shown in Table 2.

  From Table 2, the transparent conductive sheets of Examples 1 to 6 produced using the transparent conductive coating liquid of the present invention obtained evaluations that were good in all of electric characteristics, optical characteristics, heat resistance and moisture resistance. I understand that.

  On the other hand, in Comparative Example 1 where the dispersion particle diameter of PVDF contained in the transparent conductive coating liquid exceeds 0.3 μm, the optical properties are inferior, and the dispersion resin contained in the transparent conductive coating liquid is changed from PVDF to tetraethoxy. In Comparative Example 2 in which silane was changed, heat resistance was inferior, and in Comparative Example 3 in which the dispersion resin contained in the transparent conductive coating liquid was changed from PVDF to polyethylene oxide, heat resistance and moisture resistance were inferior and included in the transparent conductive coating liquid. In Comparative Example 4 in which the mass ratio of the conductive polymer to the total solid component exceeds 45 mass%, the moisture resistance is inferior, and the mass of the aprotic polar solvent contained in the solvent used in the transparent conductive coating liquid is based on the total solvent. In Comparative Example 5 in which the ratio was less than 25% by mass, the optical properties were inferior, and the non-contained solvent contained in the transparent conductive coating liquid was used. Weight percentage of the total solvent of protic polar solvents are poor electrical properties and moisture resistance in Comparative Example 6 exceeds 50 wt%.

Claims (6)

A transparent conductive coating composition comprising a conductive polymer, a resin, and a solvent,
The resin includes polyvinylidene fluoride,
The solvent includes a solvent selected from water, ethanol and acetic acid, and a solvent selected from ethylene glycol, dimethyl sulfoxide, acetonitrile and acetone ,
The dispersion particle diameter of the polyvinylidene fluoride in the coating composition is 0.3 μm or less,
The content of the conductive polymer is 3% by mass or more and 45% by mass or less with respect to the mass of all solid components contained in the coating composition,
Wherein the non-content of the protonic polar solvent, a transparent conductive coating composition, wherein the total mass with respect to at most 50 wt% to 25 wt% of said solvent.   The transparent conductive coating composition according to claim 1, wherein the conductive polymer includes a polythiophene compound and polystyrene sulfonic acid. A transparent conductive sheet comprising a transparent substrate and a transparent conductive film formed on at least one main surface of the substrate,
The said transparent conductive film is formed using the transparent conductive coating composition of Claim 1 or 2, The transparent conductive sheet characterized by the above-mentioned.   The transparent conductive sheet according to claim 3, wherein the base material is plastic, rubber, glass, or ceramics. Applying the transparent conductive coating composition according to claim 1 or 2 to at least one main surface of the transparent substrate;
And a step of forming a transparent conductive film by heating the transparent conductive coating composition. A conductive pattern forming method for forming a conductive pattern on a transparent substrate,
Applying the transparent conductive coating composition according to claim 1 or 2 to one main surface of the substrate to form a transparent conductive film;
Forming a resist film at a position to form a conductive pattern on the transparent conductive film;
And a step of deactivating the conductivity of the exposed portion of the transparent conductive film using an inert agent that deactivates the conductivity, using the resist film as a mask.