JP2017088695A - Conductive coating liquid and conductive coating film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a conductive coating liquid for obtaining a transparent conductive coating film improved in hardness.SOLUTION: Provided is the conductive coating liquid containing: a conductive polymer; a binder; and a solvent, the main component of the binder being silica. Preferably, this silica is a water-soluble silica oligomer, water-dispersible silica particles or their mixture. From this conductive coating liquid, a conductive coating film including the conductive polymer and the binder, in which the main component of the binder is silica can be obtained. The method for producing the conductive coating film includes: a first step where the conductive polymer and the binder are blended to obtain the conductive coating liquid; a second step where this conductive coating liquid is applied to the surface of a base material; and a third step where the conductive coating liquid applied to the base material is dried to form the conductive coating film. The drying temperature in the third step is 50 to 200°C.SELECTED DRAWING: None

Description

  The present invention relates to a conductive material. Specifically, the present invention relates to a conductive material that can be used as a substitute for an inorganic conductive film material typified by indium-tin oxide (ITO).

  In recent years, a transparent base material provided with a transparent conductive film has been used as an electrode application or antistatic application such as a display, a touch panel, and a solar battery. A typical transparent conductive film material is an inorganic conductive film material such as indium-tin oxide (ITO). With the widespread use of devices equipped with displays and the like, demand for ITO, which is a transparent conductive film material, has increased, while problems such as a shortage of production of indium, a so-called rare metal, and resource depletion have been pointed out. There is a need for a transparent conductive film material that can replace ITO.

  A transparent conductive film made of an inorganic conductive film material such as ITO is formed on the surface of the transparent substrate using a vacuum deposition method, a sputtering method, or the like. In the vacuum deposition method or the like, since the substrate is heated at a high temperature when forming the transparent conductive film, the types of transparent substrates that can be used are limited. In addition, it has been pointed out that a manufacturing facility including an expensive vacuum deposition apparatus or the like is indispensable, which increases manufacturing costs and maintenance costs.

  Organic conductive film paints containing conductive polymers have been proposed as transparent conductive film materials that do not require expensive and special manufacturing equipment. However, a transparent conductive film made of a conventional organic conductive film paint is flexible but has a low hardness and does not satisfy market demands.

  Transparent conductive film materials examined as an alternative to inorganic conductive film materials such as ITO are disclosed in, for example, Japanese Patent Application Laid-Open Nos. 2007-324143 and 2012-102304.

JP 2007-324143 A JP2012-102304A

  In Japanese Patent Application Laid-Open Nos. 2007-324143 and 2012-102304, a method of forming a flexible transparent conductive film from a conductive coating composition containing a conductive polymer and an organosilane compound is attempted. The transparent conductive film includes a transparent film made of an organic silane compound and a conductive polymer dispersed in the film. The transparent conductive film proposed in Japanese Patent Application Laid-Open Nos. 2007-324143 and 2012-102304 is flexible but inferior in hardness, and therefore cannot be replaced with an inorganic conductive material such as ITO.

  As described above, a transparent conductive film material that can be practically substituted for an inorganic conductive film material such as ITO has not been proposed yet. An object of the present invention is to provide a conductive coating liquid that can easily form a transparent conductive film having the same degree of hardness and transparency as an inorganic conductive film material such as ITO under mild conditions.

  As a result of intensive studies in order to solve the above-mentioned problems, the inventors of the present invention include a conductive polymer, a binder, and a solvent, and a conductive coating liquid in which the main component of the binder is silica. It came to complete.

  Preferably, the silica is a water soluble silica oligomer, water dispersible silica particles or a mixture thereof.

  Preferably, the average particle diameter of the water-dispersible silica particles is 100 nm or less. Preferably, the primary particle diameter of the water-dispersible silica particles is 60 nm or less.

  Preferably, the conductive polymer is at least one selected from a polythiophene polymer and a polypyrrole polymer. Preferably, the main component of the solvent is water.

  Preferably, the amount of silica with respect to the total solid content contained in the conductive coating liquid is 10% by mass or more and 99% by mass or less. Preferably, the content of silica in the binder is 50% by mass or more.

  The conductive coating film according to the present invention includes a conductive polymer and a binder, and the main component of the binder is silica.

  Preferably, the pencil hardness of the conductive coating film measured on an alkali-free glass according to JIS K5600-5-4 is H or more.

The method for producing a conductive coating film according to the present invention is as follows.
(1) A first step of blending a conductive polymer, a binder, and a solvent to obtain a conductive coating liquid,
(2) a second step of applying this conductive coating liquid to the surface of the substrate;
And (3) a third step of forming a conductive coating film by drying the conductive coating liquid applied to the base. The main component of this binder is silica. The drying temperature in the third step is 50 ° C. or higher and 200 ° C. or lower.

  The conductive coating film obtained using the conductive coating liquid according to the present invention is excellent in hardness and transparency. This conductive coating film is easily formed by applying a conductive coating liquid to a substrate and drying it. Expensive and special equipment is not necessary for forming the conductive coating film. The conductive coating liquid and the conductive coating film according to the present invention satisfy market demand as an alternative material for the inorganic conductive film material.

  Hereinafter, the present invention will be described in detail based on preferred embodiments, but the present invention should not be construed in a limited manner based on these embodiments.

  The conductive coating liquid according to the present invention contains a conductive polymer, a binder, and a solvent. When this conductive coating solution is applied to the substrate and dried, the binder fixes the conductive polymer to the substrate. The main component of this binder is silica.

In the specification of the present application, “silica” is defined as a generic term of substances substantially composed of silicon (Si) and oxygen (O) and expressed as SiO ₂ . Silica includes oligomers and polymers composed of siloxane bonds (—O—Si—O—). The concept of “silica” in the present specification does not include an organosilane compound having a carbon-silicon bond. As long as the object of the present invention is achieved, the method for producing silica is not particularly limited. For example, a known method such as a condensation reaction using silicate as a monomer can be used.

  When the binder contains a plurality of components, the component with the highest content is referred to as the “main component”. In the conductive coating liquid according to the present invention, the main component of the binder is silica. 50 mass% or more is preferable, as for content of the silica in a binder, 60 mass% or more is more preferable, 80 mass% or more is further more preferable, and 90 mass% or more is especially preferable. The binder may be composed only of silica. As long as the object of the present invention is achieved, the binder may contain other components in addition to silica. Examples of other components include resins such as polyester, polyurethane and polyacrylic acid, and organic silane compounds.

  Examples of the organic silane compound include amino silane, ureido silane, epoxy silane, sulfide silane, mercapto silane, ketimino silane, alkyl silane, alkoxy silane, phenyl silane, fluoro silane, and isocyanate group-containing silane. Specifically, trade names “KBM303”, “KBM403”, “KBE402”, “KBM602”, “KBM603”, “KBE603”, “KBM903”, “KBE903”, “KBM573”, manufactured by Shin-Etsu Chemical Co., Ltd., “KBM703”, “KBM803”, “KBE9007”, “KBM5103”, “X-12-817H” and trade names “Z-6011”, “Z-6020”, “Z-6023” manufactured by Toray Dow Corning Co., Ltd. ”,“ Z-6026 ”,“ Z-6032 ”,“ Z-6050 ”,“ Z-6094 ”,“ Z-6610 ”,“ Z-6683 ”,“ AX-720 ”,“ Z-6675 ”, “Z-6676”, “Z-6040”, “Z-6041”, “Z-6042”, “Z-6044”, “Z-6043”, “Z-692” ”,“ Z-6940 ”,“ Z-6948 ”,“ Z-6062 ”,“ Z-6911 ”,“ Z-6860 ”,“ DC-5700 ”,“ Z-6806 ”,“ ACS-8 ”, “Z-2306”, “Z-6013”, “Z-6187”, “Z-6210”, “Z-6258”, “Z-6265”, “Z-6275”, “Z-6288”, “Z -6321 "," Z-6329 "," Z-6341 "," Z-6366 "," Z-6383 "," Z-6582 "," Z-6586 "," Z-6721 "," Z-6597 " ”,“ Z-6830 ”,“ Z-6047 ”,“ Z-6800 ”,“ Z-6333 ”,“ Z-1211 ”,“ Z-1219 ”,“ Z-1224 ”and“ Z-6079 ” Can be mentioned.

  By applying the conductive coating liquid according to the present invention to a substrate and drying it, liquid components such as a solvent are removed from the conductive coating liquid. A conductive coating film is formed from the solid content in the conductive coating liquid remaining on the substrate. The conductive coating film formed on the surface of the substrate contains a conductive polymer and a binder. As described above, the main component of this binder is silica. Although the details of the mechanism have not yet been elucidated, it is considered that the siloxane bond formed between the silicas contributes to the improvement of mechanical properties such as hardness in this conductive coating film. From this viewpoint, silica having one or two or more silanol groups (—Si—OH) is preferable, and silica having three or more silanol groups is more preferable. Furthermore, when silica has a silanol group, it is estimated that the adhesion between the conductive coating film and the substrate is improved by the interaction between the silanol group and the substrate surface.

  The amount of silica relative to the total solid content in the conductive coating solution affects the hardness of the resulting conductive coating film. In the present specification, the hardness of the conductive coating film is evaluated using pencil hardness as an index. The pencil hardness required as a substitute for the inorganic conductive film material made of ITO or the like is at least H. In this respect, the pencil hardness of the conductive coating film is preferably H or higher, more preferably 3H or higher, further preferably 5H or higher, and particularly preferably 8H or higher. The upper limit of pencil hardness is not particularly limited. In the present specification, the pencil hardness of the conductive coating film is measured according to JIS K5600-5-4. The upper limit of pencil hardness that can be measured by this measuring method is 8H.

Specifically, the pencil hardness of the conductive coating film (200 g / m ² ) formed on the surface of alkali-free glass having a length of 100 mm, a width of 100 mm, and a thickness of 0.5 mm is measured by a mechanical method. The hardest hardness at which the coating film is not damaged is defined as pencil hardness.

  As described above, the pencil hardness of the conductive coating film is adjusted by the amount of silica relative to the total solid content in the conductive coating liquid. From the viewpoint of obtaining a conductive coating film having an appropriate pencil hardness, the amount of silica is preferably 10% by mass or more, more preferably 50% by mass or more, and 70% by mass with respect to the total solid content in the conductive coating liquid. The above is particularly preferable. From the viewpoint of the stability of the conductive coating solution, the preferred amount of silica is 99% by mass or less, and more preferably 95% by mass or less.

  In the conductive coating liquid according to one embodiment of the present invention, preferred silica is a water-soluble silica oligomer. In the present specification, a silica oligomer in which particulate matter is not detected when the particle size is measured under the following measurement conditions is referred to as a “water-soluble silica oligomer”.

[Particle size measurement]
In general, when the particle size of the particles in the test solution is measured at 20 ° C. by a light scattering method using a dense particle size analyzer FPAR-1000 manufactured by Otsuka Electronics Co., Ltd., the degree of opening of the neutral density filter (ND value) ) Adjust the concentration of the test solution so that it is 50% or less and the appropriate light quantity (15000-30000 cps). Even if the concentration of the test solution is adjusted and an ND value of 50% or more is not obtained, it is determined that the substance in the test solution does not exhibit a particulate form. In the water-soluble silica oligomer (TOYO HC) described later, no particulate matter was observed in this particle size measurement.

  Preferably, the water-soluble silica oligomer contains silanol groups. When the main component of the binder is a silica oligomer containing a silanol group, it is presumed that the silanols react with each other during the drying of the conductive coating liquid to form a network structure by siloxane bonds. The conductive coating film obtained from this conductive coating liquid is considered to be a composite of a conductive polymer and a reaction product of silica oligomer.

  From the viewpoint of the hardness of the obtained conductive coating film, the amount of the water-soluble silica oligomer with respect to the total solid content in the conductive coating liquid is preferably 10% by mass or more. In this conductive coating film, it is presumed that an appropriate hardness can be obtained by forming a so-called “sea-island structure” in which a conductive polymer is dispersed in a matrix mainly composed of a silica oligomer. From this viewpoint, the amount of the silica oligomer with respect to the total solid content is more preferably 50% by mass or more, and further preferably 70% by mass or more. From the viewpoint of the stability of the conductive coating liquid, the amount of the silica oligomer relative to the total solid content is preferably 99% by mass or less, and more preferably 95% by mass or less.

  In the conductive coating liquid according to another embodiment of the present invention, preferred silica is silica particles. In the present specification, “silica particle” means a silica polymer having a network structure composed of siloxane bonds. This silica polymer is uniformly dispersed in water. In other words, the silica particles are water dispersible. In addition, as will be described later in [Examples], the silica particles in the present specification are different in physical properties from a substance known as so-called colloidal silica. Although details have not yet been elucidated, it is assumed that the structure of the silica particles in the present specification is different from so-called colloidal silica.

  The water-dispersible silica particles are considered to have silanol groups. When the silica particles are dispersed in water, silanol groups that are hydrophilic groups are localized on the surface of the silica particles. In the case where the main component of the binder is silica particles containing silanol groups, it is considered that silanols on the surface of the silica particles react with each other to form siloxane bonds during drying of the conductive coating liquid. The conductive coating film obtained from this conductive coating solution is a composite of a laminate of a plurality of silica particles bonded by siloxane bonds and a conductive polymer.

  In light of the hardness of the resulting conductive coating film, the primary particle diameter of the water-dispersible silica particles is preferably 60 nm or less, more preferably 40 nm or less, and even more preferably 20 nm or less. From the viewpoint of the stability of the conductive coating solution, the primary particle diameter of the silica particles is preferably 3 nm or more, and more preferably 10 nm or more. In the present specification, primary particles mean a minimum unit before forming secondary particles described later. A transmission electron microscope JEM-2010 manufactured by JEOL Ltd. is used for measuring the primary particle diameter of the silica particles. Specifically, a coating film obtained by drying a test liquid containing 2.0% by mass of water-dispersible silica particles in a solid content concentration is subjected to observation with a transmission electron microscope (TEM) as a sample piece. In the obtained TEM image, after measuring the diameter of all particles included in a randomly selected 150 nm square region, the minimum value D (max) and the maximum value D (min) excluding the upper limit and the lower limit 5% each Is expressed as primary particle diameter D (min) −D (max). In the present specification, “primary particle diameter of 60 nm or less” means that the diameter of primary particles excluding the upper limit and the lower limit of 5% each is 60 nm or less.

  In some cases, silica particles (that is, primary particles) dispersed in water or a conductive coating liquid aggregate over time to form secondary particles having different particle sizes. The particle size and particle size distribution of the secondary particles affect the hardness of the conductive coating film. From the viewpoint of obtaining a conductive coating film having an appropriate hardness, the weight average particle diameter of the secondary particles of the water-dispersible silica particles (hereinafter also referred to as “average particle diameter”) is preferably 100 nm or less. 50 nm or less is more preferable, and 20 nm or less is more preferable. Ideally, a conductive coating liquid containing no secondary particles is preferable. The weight average particle diameter of the silica particles in this ideal conductive coating liquid is substantially the same as the average particle diameter of the primary particle diameter. In the present specification, a concentrated particle size analyzer FPAR-1000 manufactured by Otsuka Electronics Co., Ltd. is used for measuring the weight average particle size of silica particles. Specifically, an aqueous dispersion of silica particles, whose solid content concentration is adjusted so as to obtain an appropriate light amount at an ND value of 50% or less, is measured at 20 ° C. by a light scattering method (wavelength 660 nm).

  From the viewpoint of the hardness of the obtained conductive coating film, the amount of the water-dispersible silica particles with respect to the total solid content in the conductive coating liquid is preferably 10% by mass or more. In this conductive coating film, it is estimated that an appropriate hardness can be obtained by forming a so-called “sea-island structure” in which a conductive polymer is dispersed in a matrix mainly composed of silica particles. In this respect, the amount of silica particles with respect to the total solid content is more preferably 50% by mass or more, and further preferably 70% by mass or more. From the viewpoint of the stability of the conductive coating liquid, the amount of silica particles relative to the total solid content is preferably 99% by mass or less, and more preferably 95% by mass or less.

  In still another embodiment of the present invention, the silica may be a mixture of water-soluble silica oligomer and water-dispersible silica particles. The mixing ratio of the water-soluble silica oligomer and the water-dispersible silica particles is not particularly limited, and can be appropriately adjusted according to the use and physical properties of the obtained conductive coating film.

  From the viewpoint of the hardness of the conductive coating film, the content of the water-soluble silica oligomer in the silica is preferably 50% by mass or more, and more preferably 90% by mass or more. Silica consisting only of water-soluble silica oligomer is particularly preferred.

  In the present specification, the type of the conductive polymer is not particularly limited. Examples include π-conjugated polymers such as polythiophene polymers, polypyrrole polymers, polyaniline polymers, polyacetylene polymers, and polyphenylene polymers doped with dopants. Two or more kinds of conductive polymers may be used in combination.

  From the viewpoint of conductivity, at least one kind of conductive polymer selected from the group consisting of a polythiophene polymer, a polypyrrole polymer, and a polyaniline polymer is more preferable. From the viewpoint of stability and availability, polythiophene polymers and polypyrrole polymers are more preferable.

  Specific examples of the polythiophene polymer include polythiophene, poly (3-methylthiophene), poly (3-ethylthiophene), poly (3-propylthiophene), poly (3-methoxythiophene), and poly (3,4-dimethyl). Thiophene), poly (3,4-diethylthiophene), poly (3,4-ethylenedioxythiophene) and the like.

  Specific examples of the polypyrrole polymer include polypyrrole, poly (3-methylpyrrole), poly (3-ethylpyrrole), poly (N-methylpyrrole), poly (3,4-dimethylpyrrole), and poly (3-carboxyl. Pyrrole) and the like.

  Specific examples of the polyaniline polymer include polyaniline, poly (2-methylaniline), poly (2-ethylaniline) and the like. Specific examples of the polyacetylene polymer include polyacetylene, polymethylacetylene, polyphenylacetylene and the like. Specific examples of the polyphenylene polymer include polyorthophenylene, polymetaphenylene, polyparaphenylene, and the like.

  A typical dopant is a polyanion. Specific examples of the polyanion include polystyrene sulfonate ion, polyacrylate ion, polyvinyl sulfonate ion, and poly (2-acrylamido-2-methylpropane sulfonate) ion. From the viewpoint that high conductivity is obtained, polystyrene sulfonate ions can be preferably used. Two or more dopants may be used in combination.

  When the dopant is coordinated to the π-conjugated polymer, the conductivity is improved. The blending amount of the dopant with respect to the π-conjugated polymer is appropriately selected according to the use of the conductive coating film. From the viewpoint that the effect of the dopant is exhibited, the preferable amount of the dopant is 0.2 parts by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the π-conjugated polymer.

  In the conductive coating liquid according to the present invention, a preferred solvent is water or a mixed solvent containing water. Water or a mixed solvent containing water dissolves or disperses the conductive polymer and the binder. From the viewpoint of obtaining a uniform conductive coating liquid, a mixed solvent containing water is preferable. The amount of water in the mixed solvent is preferably 20% by mass or more, more preferably 30% by mass, and further preferably 50% by mass or more. A mixed solvent containing water as a main component is particularly preferable.

  The mixed solvent containing water may contain an organic solvent miscible with water. Examples of such organic solvents include alcohols such as methanol, ethanol, n-propanol, isopropanol, ethylene glycol, diethylene glycol, and glycerin, ketones such as acetone, methyl ethyl ketone, and methyl isobutyl ketone, N, N-dimethylformamide, acetamide, N Amides such as N-dimethylacetamide, sulfoxides such as dimethyl sulfoxide and diethyl sulfoxide, and pyrrolidones such as N-methyl-2-pyrrolidone, 2-pyrrolidone and N-vinyl-2-pyrrolidone. Two or more organic solvents may be used in combination. From the viewpoint of the stability of the conductive coating liquid and the drying efficiency, methanol, ethanol, n-propanol, isopropanol, and methyl ethyl ketone are preferably used.

  Unless the object of the present invention is hindered, the conductive coating liquid may contain a metal oxide such as titanium oxide, an inorganic filler such as colloidal silica, and an organic filler such as polystyrene beads and polyethylene beads. Additives such as thixotropic agents, antifoaming agents, flame retardants, tackifiers, hydrolysis inhibitors, leveling agents, plasticizers, antioxidants, UV absorbers, pigments and dyes are added to the conductive coating liquid May be.

  As long as the object of the present invention is achieved, the conductive coating liquid may contain an inorganic or organic cation. Examples of inorganic cations include metal ions such as lithium ions, sodium ions, potassium ions, magnesium ions, aluminum ions, and ammonium ions. As organic cations, primary ammonium ions such as stearyl ammonium ion, hexyl ammonium ion, octyl ammonium ion and 2-ethylhexyl ammonium ion, 2 such as dibutyl ammonium ion, dihexyl ammonium ion, dioctyl ammonium ion and distearyl ammonium ion Examples include tertiary ammonium ions, tertiary ammonium ions such as trioctyl ammonium ion, and quaternary ammonium ions such as dioctyl dimethyl ammonium ion and distearyl dimethyl ammonium ion. The organic cation may be a derivative of amines such as primary amine, secondary amine, and tertiary amine. The conductive coating liquid can contain two or more kinds of cations.

  As long as the object of the present invention is achieved, the conductive coating liquid may contain a curing accelerator. Examples of curing accelerators include, for example, tetrabutoxyzirconium, zirconyl octylate, zirconyl naphthenate, zirconium acetylacetone complex, dibutyltin diacetate, bisacetyltin acetate, bis (acetoxydibutyltin) oxide, bis (lauroxydibutyltin) oxide And organic tin compounds such as dibutyltin bisacetylacetonate, dibutyltin bismaleic acid monobutyl ester, and dioctyl bismaleic acid monobutyl ester. The conductive coating liquid may contain two or more curing accelerators.

  The conductive coating film concerning this invention is manufactured by the manufacturing method containing a 1st process, a 2nd process, and a 3rd process. Details of each step will be described below.

  In the first step, the conductive coating liquid is adjusted by blending the conductive polymer, the binder, and the solvent. The main component of this binder is silica. This silica is a water-soluble silica oligomer, water-dispersible silica particles, or a mixture thereof. The first step may further include a step of filtering a blended liquid obtained by blending the conductive polymer, the binder and the solvent. In this case, the filtrate obtained by filtration is used as the conductive coating liquid.

  The method for blending the conductive polymer, the binder and the solvent is not particularly limited, and a known method can be used. For example, by preparing a conductive polymer / solvent dispersion having a known concentration and adding a binder / solvent dispersion having a known concentration prepared in advance to the conductive polymer / solvent dispersion under stirring. A conductive coating solution is prepared. From the viewpoint of the stability of the conductive coating liquid, it is preferably prepared at a temperature of 5 ° C. or higher and 40 ° C. or lower.

  In the second step, the conductive coating liquid adjusted in the first step is applied to the surface of the substrate.

  The kind and magnitude | size of the base material used are not specifically limited, According to a use, it selects suitably. Examples thereof include glass, crystalline or amorphous polyethylene terephthalate, polycarbonate, polyvinyl chloride, polyethylene, polypropylene, polyimide, polyurethane, polydimethylsiloxane, nitrile rubber, butadiene rubber, and styrene-butadiene rubber. A transparent substrate is preferred.

  In the second step, the method for applying the conductive coating liquid to the surface of the substrate is not particularly limited, and a known method is selected and used. For example, a coating method, a printing method, etc. are mentioned. Examples of the printing method include a screen printing method, a lithographic offset printing method, an ink jet method, a flexographic printing method, a gravure printing method, a gravure offset printing method, a stamping method, a dispensing method, and a squeegee printing method. Examples of the coating method include a bar coating method, a spin coating method, a flow coating method, a comma coating method, a die coating method, and a knife coating method. A dipping method or a spray method may be used.

  The second step may further include a substrate pretreatment step. In the pretreatment step, the surface of the substrate to be coated is surface-treated before the conductive coating liquid is applied. The surface treatment improves the adhesion between the conductive coating and the substrate. The surface treatment method is not particularly limited, and known methods such as plasma discharge and corona discharge can be used.

  In the third step, a conductive coating film is formed by drying the conductive coating liquid applied to the substrate in the second step. Although the drying method of a conductive coating liquid is not specifically limited, From a viewpoint of the hardness and drying efficiency of the conductive film obtained, a heat drying method is used suitably.

  The drying conditions for the conductive coating liquid are appropriately selected depending on the amount of the conductive coating liquid and the type of the substrate. From the viewpoint of the hardness of the resulting conductive coating film, the drying temperature is preferably 50 ° C. or higher, more preferably 100 ° C. or higher, and particularly preferably 115 ° C. or higher. From the viewpoint of the heat resistance of the conductive coating film and the substrate, the preferred drying temperature is 250 ° C. or lower. The conductive coating liquid may be dried in the air, in a vacuum atmosphere, in an inert gas atmosphere, in a reducing gas atmosphere, or the like.

  In the second step, the conductive coating liquid applied to the substrate includes a conductive polymer, a binder, and a solvent. In the third step, the conductive coating liquid is heated to evaporate the solvent and concentrate the conductive coating liquid. In a heated and concentrated conductive coating solution, a siloxane bond is formed between the silica, which is the main component of the binder, thereby forming a conductive coating film with high hardness and excellent adhesion to the substrate. Presumed to be.

  From the viewpoint of hardness and adhesion of the conductive coating film, the silica content in the conductive coating film is preferably 10% by mass or more, more preferably 50% by mass or more, and particularly preferably 70% by mass or more. From the viewpoint of conductivity, the preferred silica content is 95% by mass or less.

  The film thickness of the conductive coating film obtained by the production method according to the present invention is appropriately selected according to the application. In the second step, it can be adjusted by the area of the application target surface of the substrate, the solid content concentration of the conductive coating liquid, the coating amount of the conductive coating liquid with respect to the area of the coating target surface, and the like.

  Since the conductive coating liquid according to the present invention does not require a special device or equipment for forming the conductive coating film, the manufacturing cost is reduced. This conductive coating liquid does not require high-temperature processing exceeding 250 ° C. for forming a conductive coating film. Therefore, a resin composition that has not been adopted in terms of heat resistance can be selected as a material for the transparent substrate. Furthermore, the electroconductive coating film obtained from the electroconductive coating liquid which concerns on this invention adheres to a base material. This conductive coating film has the same transparency and hardness as a conventional conductive coating film made of ITO.

  Moreover, the conductive coating liquid and the conductive coating film according to the present invention can be applied to various uses depending on the kind of the selected conductive polymer and the blending amount of the binder. For example, in the case of a low resistance application requiring high conductivity (low resistance value) such as an electrode, a conductive polymer having a conductivity of about 500 S / cm to 1000 S / cm is selected. On the other hand, a conductive polymer having a lower conductivity can be selected for an antistatic application that requires high resistance (low conductivity). When the amount of the binder with respect to the conductive polymer increases, a conductive coating film having high resistance (low conductivity) can be obtained. When the amount of the binder with respect to the conductive polymer decreases, a conductive coating film having low resistance (high conductivity) can be obtained.

  Hereinafter, the effects of the present invention will be clarified by examples. However, the present invention should not be construed in a limited manner based on the description of the examples.

[Example 1]
5 parts by mass of an aqueous dispersion of poly (3,4-ethylenedioxythiophene) / polystyrene sulfonic acid (PEDOT / PSS) (manufactured by Heraeus, trade name “Clevious P”, solid content concentration 1.3% by mass) , 95 parts by mass of an aqueous silica oligomer solution (trade name “TOYO HC”, manufactured by Toyo Chemical Co., Ltd., solid content concentration: 3.0%), and stirred at room temperature for 60 minutes to obtain the conductivity of Example 1. A coating solution was obtained. The conductive coating liquid of Example 1 contains a water-soluble silica oligomer as a binder. In this conductive coating liquid, the silica content in the binder is 100% by mass. The amount of silica with respect to the total solid content contained in the conductive coating liquid is 98% by mass.

Subsequently, the alkali-free glass (width 100mm, length 100mm, thickness 0.5mm) which is a base material was installed. The conductive coating liquid of Example 1 was applied to the surface of this base material with a bar coater (manufactured by Daiichi Rika Co., Ltd.) and dried at 115 ° C. for 10 minutes to have a thickness of 200 g / m ² . A coating film was formed.

[Example 2-7]
Example 1 except that the composition of the aqueous dispersion of PEDOT / PSS (the above-mentioned “Clevious P”) and the silica oligomer aqueous solution (the above-mentioned “TOYO HC”) was as shown in Table 1-2 below. Similarly, the conductive coating liquid of Example 2-7 was obtained. The amount of silica relative to the total solid content contained in the conductive coating liquid of Example 2-7 is shown in Table 1-2 below as “silica content in the solid content”. A conductive coating film was formed in the same manner as in Example 1 using the conductive coating liquid of Example 2-7. The film thicknesses of the obtained conductive coating films are all 200 g / m ² .

[Example 8-10]
The conductive coating liquid of Examples 8-10 was obtained in the same manner as in Example 1 except that the aqueous dispersion of silica particles shown in Table 2 below was used as the binder. The amount of silica relative to the total solid content contained in the conductive coating liquid of Examples 8-10 is shown in Table 2 below as “silica content in the solid content”. A conductive coating film was formed in the same manner as in Example 1 using the conductive coating liquid of Example 8-10. The film thicknesses of the obtained conductive coating films are all 200 g / m ² .

[Examples 11-14]
The conductive coating liquids of Examples 11-14 were obtained in the same manner as in Example 1 except that the types and blends of the conductive polymers were as shown in Table 3 below. The amount of silica with respect to the total solid content contained in the conductive coating liquids of Examples 11-14 is shown in Table 3 below as “silica content in the solid content”. A conductive coating film was formed in the same manner as in Example 1 using the conductive coating liquid of Examples 11-14. The film thicknesses of the obtained conductive coating films are all 200 g / m ² .

[Examples 15-20]
The conductive coating liquid of Examples 15-20 was obtained like Example 1 except having made the kind and mixing | blending of a binder as having shown in the following Table 4-5. The amount of silica with respect to the total solid content contained in the conductive coating liquid of Examples 15-20 is shown in the following Table 4-5 as “silica content in solid content”. The amount of water-soluble silica oligomer relative to the total amount of silica in the conductive coating liquids of Examples 18-20 is shown in Table 5 below as “oligomer content in silica”. A conductive coating film was formed in the same manner as in Example 1 using the conductive coating liquid of Examples 15-20. The film thicknesses of the obtained conductive coating films are all 200 g / m ² .

[Comparative Example 1]
10 parts by mass of an aqueous dispersion of poly (3,4-ethylenedioxythiophene) / polystyrene sulfonic acid (PEDOT / PSS) (the above-mentioned “Clevious P”) was added to 0.8 parts by mass of polyester (manufactured by Toyo Chemical Co., Ltd.). , Trade name "Plus Coat Z446", solid content concentration 25% by mass) was added and mixed to obtain a conductive coating liquid of Comparative Example 1. The conductive coating liquid of Comparative Example 1 does not contain a water-soluble silica oligomer and water-dispersible silica particles. The amount of silica based on the total solid content contained in the conductive coating solution is 0% by mass. A conductive coating film was formed on the substrate in the same manner as in Example 1 except that the conductive coating liquid of Comparative Example 1 was used.

[Comparative Example 2]
10 parts by mass of an aqueous dispersion of poly (3,4-ethylenedioxythiophene) / polystyrene sulfonic acid (PEDOT / PSS) (the above-mentioned “Clevious P”) was added to 0.8 parts by mass of polyester (manufactured by Toyo Chemical Co., Ltd.). , Trade name “Plus Coat Z561”, solid content concentration 25% by mass) was added and mixed to obtain a conductive coating liquid of Comparative Example 2. The conductive coating liquid of Comparative Example 2 does not contain water-soluble silica oligomer and water-dispersible silica particles. The amount of silica based on the total solid content contained in the conductive coating solution is 0% by mass. A conductive coating film was formed on the substrate in the same manner as in Example 1 except that the conductive coating liquid of Comparative Example 2 was used.

[Comparative Example 3]
10 parts by mass of an aqueous dispersion of poly (3,4-ethylenedioxythiophene) / polystyrene sulfonic acid (PEDOT / PSS) (the aforementioned “Clevious P”) and 6 parts by mass of colloidal silica (manufactured by Nissan Chemical Industries, Ltd.) , Trade name “ST30”, solid content concentration 30%), and the mixture was stirred at room temperature for 60 minutes to obtain a conductive coating liquid of Comparative Example 3. The conductive coating liquid of Comparative Example 3 does not contain a water-soluble silica oligomer and water-dispersible silica particles. The amount of silica based on the total solid content contained in the conductive coating solution is 0% by mass. A conductive coating film was formed on the substrate in the same manner as in Example 1 except that the conductive coating liquid of Comparative Example 3 was used.

[Example 21]
10 parts by mass of an aqueous dispersion of poly (3,4-ethylenedioxythiophene) / polystyrene sulfonic acid (PEDOT / PSS) (the above-mentioned “Clevious P”) as a binder and 26 parts by mass of a water-soluble silica oligomer aqueous solution (The above-mentioned “TOYO HC”) and 2 parts by mass of polyester (the above-mentioned “Plus Coat Z446”) were added and mixed to obtain a conductive coating liquid of Example 21. The silica content in the binder of this conductive coating liquid is 61% by mass. The amount of silica with respect to the total solid content contained in this conductive coating liquid is 55% by mass. A conductive coating film was formed on the substrate in the same manner as in Example 1 except that the conductive coating liquid of Example 21 was used.

[Comparative Example 4]
10 parts by weight of a water-soluble silica oligomer aqueous solution as a binder in 10 parts by weight of an aqueous dispersion of poly (3,4-ethylenedioxythiophene) / polystyrene sulfonic acid (PEDOT / PSS) (the above-mentioned “Clevious P”). (The above-mentioned “TOYO HC”) and 3 parts by mass of polyester (the above-mentioned “Plus Coat Z446”) were added and mixed to obtain a conductive coating liquid of Comparative Example 4. The silica content in the binder of this conductive coating liquid is 39% by mass. The amount of silica with respect to the total solid content contained in this conductive coating liquid is 35% by mass. A conductive coating film was formed on the substrate in the same manner as in Example 1 except that the conductive coating liquid of Comparative Example 4 was used.

Details of the compounds described in Table 1-7 are as follows.
Clevious P: Heraeus conductive polymer, poly (3,4-ethylenedioxythiophene) / polystyrene sulfonic acid (PEDOT / PSS) aqueous dispersion, solid content 1.3 mass%
Clevious PH500: Heraeus conductive polymer, poly (3,4-ethylenedioxythiophene) / polystyrene sulfonic acid (PEDOT / PSS) aqueous dispersion, solid content 1.3 mass%
TOYO HC: Silica oligomer aqueous solution manufactured by Toyo Chemical Co., Ltd., solid content concentration of 3.0% by mass, no silica particles are observed in the particle size measurement.
TOYO HC10: aqueous dispersion of silica particles from Toyo Chemical Co., Ltd., solid content concentration 3.0 mass%, weight average particle size 10 nm, primary particle size 3-14 nm
TOYO HC60: aqueous dispersion of silica particles from Toyo Chemical Co., Ltd., solid content concentration 3.0 mass%, weight average particle size 60 nm, primary particle size 20-40 nm
TOYO HC100: aqueous dispersion of silica particles from Toyo Chemical Co., Ltd., solid content concentration 3.0 mass%, weight average particle size 100 nm, primary particle size 20-40 nm
TOYO PY: Toyo Chemical Co., Ltd. conductive polymer, polypyrrole aqueous dispersion, solid content of 9.0% by mass
Z446: Polyester aqueous solution manufactured by Kyodo Chemical Co., Ltd.
Z561: Polyester aqueous solution of Kyoyo Chemical Co., Ltd., solid content concentration 25% by mass, molecular weight about 27000
ST30: Na-stabilized silica sol manufactured by Nissan Chemical Industries, Ltd., solid content concentration 30% by mass, particle size 10-15 nm

[Stability of conductive coating liquid]
The conductive coating liquids of Example 1-21 and Comparative Example 1-4 were allowed to stand in a thermostat set to 25 ° C. ± 5 ° C. After one week, each conductive coating liquid taken out from the thermostatic device was filtered. The mass of the gel remaining on the filter paper was measured, and the ratio of the mass of the gel to the mass of the conductive coating liquid was calculated. Based on the following criteria, the stability of the conductive coating liquid was evaluated.
A: 0% by mass (no change)
B: Less than 5% by mass C: 5% by mass or more

[Measurement of pencil hardness]
According to the measuring method described in JIS K5600-5-4, the pencil hardness of the conductive coating film obtained for Example 1-21 and Comparative Example 1-4 was measured. For the hardness measurement, a pencil hardness tester (manufactured by TQC, weight 750 ± 10 g) was used. Table 1-7 shows the hardest pencil hardness at which the coating film is not damaged.

[Measurement of resistivity]
About Example 1-21 and Comparative Example 1-4 using high resistivity meter Hiresta UP (Mitsubishi Chemical Analytech Co., Ltd.) and low resistivity meter Loresta AXMCP-T370 (Mitsubishi Chemical Analytech Co., Ltd.) The resistance value of the obtained conductive coating film was measured. The obtained evaluation results are shown in Table 1-7.

[Measurement of transmittance]
According to the measuring method described in JIS R 1635, the wavelength of 550 nm of the conductive coating film obtained for Example 1-21 and Comparative Example 1-4 using a spectrophotometer 1U-4000 type manufactured by Hitachi, Ltd. The transmittance (%) was measured. The obtained evaluation results are shown in Table 1-7.

  As shown in Table 1-7, the evaluation of the conductive coating film obtained from the conductive coating liquid of the example is superior to the evaluation of the conductive coating film obtained from the conductive coating liquid of the comparative example. From this evaluation result, the superiority of the present invention is clear.

  The conductive coating liquid and the conductive coating film described above can be applied to various products such as an electromagnetic wave absorber, a sensor, and a capacitor electrode.

Claims (11)

  A conductive coating liquid containing a conductive polymer, a binder, and a solvent, and the main component of the binder is silica.   The conductive coating liquid according to claim 1, wherein the silica is a water-soluble silica oligomer, water-dispersible silica particles, or a mixture thereof.   The conductive coating liquid according to claim 2, wherein the water-dispersible silica particles have an average particle size of 100 nm or less.   The conductive coating liquid according to claim 2 or 3, wherein a primary particle diameter of the water-dispersible silica particles is 60 nm or less.   5. The conductive coating solution according to claim 1, wherein the conductive polymer is at least one selected from a polythiophene polymer and a polypyrrole polymer.   The conductive coating liquid according to claim 1, wherein a main component of the solvent is water.   The conductive coating liquid according to any one of claims 1 to 6, wherein an amount of the silica with respect to the total solid content contained in the conductive coating liquid is 10% by mass or more and 99% by mass or less.   The conductive coating liquid according to claim 1, wherein the content of the silica in the binder is 50% by mass or more.   A conductive coating film comprising a conductive polymer and a binder, the main component of which is silica.   The conductive coating film according to claim 9, wherein the conductive coating film has a pencil hardness of H or more, and the pencil hardness is measured on an alkali-free glass according to JIS K5600-5-4. A first step of blending a conductive polymer, a binder, and a solvent to obtain a conductive coating liquid;
A second step of applying the conductive coating liquid to the surface of the substrate;
Having a third step of forming a conductive coating by drying the conductive coating liquid applied to the base,
The main component of the binder is silica,
The manufacturing method of the electroconductive coating film whose drying temperature in the said 3rd process is 50 to 200 degreeC.