Conductive composite dispersion liquid and method for producing same, capacitor and method for producing same, and conductive multilayer body and method for producing same

Abstract

Disclosed is a conductive composite dispersion liquid which comprises: a conductive composite body that contains a π-conjugated conductive polymer and a polyanion; water; a sugar alcohol that has 4 to 7 carbon atoms and 3 to 7 hydroxyl groups in each molecule, and a polyvinylpyrrolidone. This conductive composite dispersion liquid has a viscosity of less than 50 mPa∙s at 25°C.

Description

Conductive composite dispersion and manufacturing method thereof, capacitor and manufacturing method thereof, and conductive laminate and manufacturing method thereof

[0001] The present invention relates to a conductive composite dispersion containing a π-conjugated conductive polymer and a polyanion, a capacitor, and a conductive laminate. This application claims priority to Japanese Patent Application No. 2023-108090, filed on June 30, 2023, the contents of which are incorporated herein by reference.

[0002] A π-conjugated conductive polymer whose main chain is composed of a π-conjugated system forms a conductive complex by doping with a polyanion having an anionic group, resulting in dispersibility in water. A method for producing a capacitor has been disclosed (see, for example, Patent Document 1), in which a paint containing a conductive complex dispersion liquid containing the conductive complex is applied to a dielectric layer provided on the surface of an anode made of a valve metal, and then dried to form a solid electrolyte layer, which is then placed opposite a cathode. According to this disclosure, the performance of the capacitor is improved by adding a specific unsaturated aliphatic alcohol compound to the paint.

[0003] Japanese Patent Application Laid-Open No. 2022-071400

[0004] Conductive composite dispersions used in the manufacture of capacitors are required to have low viscosity so that they can penetrate into the porous structure of the dielectric layer. However, after penetrating, the viscosity must increase as the dispersion dries and solidifies, and the dispersion must remain stable within the porous structure. Adding a thickener is one way to ensure stable retention within the porous structure, but thickeners increase the viscosity of the conductive composite dispersion. Therefore, a conductive composite dispersion that has a low viscosity enough to penetrate into the porous structure and that increases in viscosity upon drying after penetrating has been desired.

[0005] The present invention provides a conductive composite dispersion suitable for producing high performance capacitors.

[0006] [1] A conductive complex dispersion comprising a conductive complex containing a π-conjugated conductive polymer and a polyanion, water, a sugar alcohol having 4 to 7 carbon atoms in the molecule and 3 to 7 hydroxyl groups, and polyvinylpyrrolidone, the conductive complex dispersion having a viscosity of less than 50 mPa·s at 25°C. [2] The conductive complex dispersion according to [1], wherein the content of the polyvinylpyrrolidone is 0.01 parts by mass or more and less than 0.30 parts by mass, relative to 100 parts by mass of the conductive complex and the water combined. [3] The conductive complex dispersion according to [1] or [2], wherein the content of the conductive complex is 0.1 parts by mass or more and 3.0 parts by mass or less, relative to 100 parts by mass of the conductive complex and the water combined. [4] The conductive complex dispersion according to any one of [1] to [3], wherein the content of the water relative to the total mass of the conductive complex dispersion is 70% by mass or more and 99% by mass or less. [5] The conductive composite dispersion liquid according to any one of [1] to [4], wherein the sugar alcohol comprises at least one of sorbitol, mannitol, erythritol, and pentaerythritol. [6] The conductive composite dispersion liquid according to any one of [1] to [5], further comprising an organic solvent having a boiling point of 150°C or higher at 1 atmosphere. [7] The conductive composite dispersion liquid according to any one of [1] to [6], further comprising a neutralizing agent. [8] The conductive composite dispersion liquid according to any one of [1] to [7], wherein the π-conjugated conductive polymer is poly(3,4-ethylenedioxythiophene), or the polyanion is polystyrenesulfonic acid, or the π-conjugated conductive polymer is poly(3,4-ethylenedioxythiophene) and the polyanion is polystyrenesulfonic acid. [9] A capacitor comprising an anode made of a porous body of a valve metal, a dielectric layer made of an oxide of the valve metal, a cathode made of a conductive material provided on the side of the dielectric layer opposite to the anode, and a solid electrolyte layer formed between the dielectric layer and the cathode, wherein the solid electrolyte layer is a cured product of the conductive composite dispersion liquid according to any one of [1] to [8].

[10] A conductive laminate comprising a substrate and a conductive layer formed on at least a part of the surface of the substrate, wherein the conductive layer is a cured product of the conductive composite dispersion liquid according to any one of [1] to [8].

[11] A method for producing a conductive composite dispersion, comprising the step of mixing a conductive composite comprising a π-conjugated conductive polymer and a polyanion, a dispersion medium, a sugar alcohol, and a sugar alcohol having 4 to 7 carbon atoms and 3 to 7 hydroxyl groups in the molecule to obtain a conductive composite dispersion having a viscosity of less than 50 mPa s at 25°C.

[12] A method for producing the conductive composite dispersion according to

[11] , comprising obtaining a dispersion in which the conductive composite is dispersed in the dispersion medium, concentrating the dispersion, and then mixing the sugar alcohol.

[13] A method for producing a capacitor, comprising the step of applying the conductive composite dispersion according to any one of [1] to [8] to a surface of a dielectric layer formed on the surface of an anode made of a porous valve metal body, and drying the applied dispersion to form a solid electrolyte.

[14] A method for producing a conductive laminate, comprising the step of applying the conductive composite dispersion according to any one of [1] to [8] to at least one surface of a substrate, and drying the applied dispersion to form a conductive layer.

[0007] The conductive composite dispersion of the present invention has a low viscosity that allows it to penetrate into a porous structure, and the viscosity increases upon drying after penetration, making it suitable for the production of high-performance capacitors. This property is suitable not only for the production of capacitors, but also for the production of conductive laminates in which a conductive layer is laminated on a substrate. Capacitors having a solid electrolyte layer made of a cured product of the conductive composite dispersion of the present invention have a stabilized conductive composite due to the coexistence of polyvinylpyrrolidone in the solid electrolyte, and further have a low equivalent series resistance (ESR) and high performance. Conductive laminates having a conductive layer made of a cured product of the conductive composite dispersion of the present invention have improved adhesion to the substrate and a stabilized conductive composite due to the coexistence of polyvinylpyrrolidone in the conductive layer.

[0008] This invention is believed to contribute to SDG Goal 12, "Responsible Consumption and Production."

[0009] In this specification and claims, the lower and upper limits of a range of values ​​indicated by "to" are included in the range.

[0010] FIG. 1 is a cross-sectional view illustrating one embodiment of a capacitor.

[0011] <Conductive Composite Dispersion> A first aspect of the present invention is a conductive composite dispersion that includes a conductive composite containing a π-conjugated conductive polymer and a polyanion, water, a specific sugar alcohol, and polyvinylpyrrolidone, and has a viscosity at 25°C of less than 50 mPa s.

[0012] <Conductive Composite> The conductive composite of this embodiment contains a π-conjugated conductive polymer and a polyanion. The polyanion in the conductive composite is doped into the π-conjugated conductive polymer to form a conductive composite having conductivity. In the polyanion, only a portion of the anionic groups is doped into the π-conjugated conductive polymer, and there are excess anionic groups that are not involved in the doping. Because the excess anionic groups are hydrophilic groups, the conductive composite has water dispersibility.

[0013] (π-conjugated conductive polymer) The π-conjugated conductive polymer may be any organic polymer whose main chain is composed of a π-conjugated system, and examples thereof include polypyrrole-based conductive polymers, polythiophene-based conductive polymers, polyacetylene-based conductive polymers, polyphenylene-based conductive polymers, polyphenylene vinylene-based conductive polymers, polyaniline-based conductive polymers, polyacene-based conductive polymers, polythiophene vinylene-based conductive polymers, and copolymers thereof. From the viewpoint of stability in air, polypyrrole-based conductive polymers, polythiophenes, and polyaniline-based conductive polymers are preferred, and from the viewpoint of transparency, polythiophene-based conductive polymers are more preferred.

[0014] Examples of polythiophene-based conductive polymers include polythiophene, poly(3-methylthiophene), poly(3-ethylthiophene), poly(3-propylthiophene), poly(3-butylthiophene), poly(3-hexylthiophene), poly(3-heptylthiophene), poly(3-octylthiophene), poly(3-decylthiophene), poly(3-dodecylthiophene), poly(3-octadecylthiophene), poly(3-bromothiophene), poly(3-chlorothiophene), and poly(3-iodothiophene). thiophene), poly(3-cyanothiophene), poly(3-phenylthiophene), poly(3,4-dimethylthiophene), poly(3,4-dibutylthiophene), poly(3-hydroxythiophene), poly(3-methoxythiophene), poly(3-ethoxythiophene), poly(3-butoxythiophene), poly(3-hexyloxythiophene), poly(3-heptyloxythiophene), poly(3-octyloxythiophene), poly(3-decyloxythiophene), poly(3-dodecyl oxythiophene), poly(3-octadecyloxythiophene), poly(3,4-dihydroxythiophene), poly(3,4-dimethoxythiophene), poly(3,4-diethoxythiophene), poly(3,4-dipropoxythiophene), poly(3,4-dibutoxythiophene), poly(3,4-dihexyloxythiophene), poly(3,4-diheptyloxythiophene), poly(3,4-dioctyloxythiophene), poly(3,4-didecyloxythiophene), poly(3,4-di dodecyloxythiophene), poly(3,4-ethylenedioxythiophene), poly(3,4-propylenedioxythiophene), poly(3,4-butylenedioxythiophene), poly(3-methyl-4-methoxythiophene), poly(3-methyl-4-ethoxythiophene), poly(3-carboxythiophene), poly(3-methyl-4-carboxythiophene), poly(3-methyl-4-carboxyethylthiophene), and poly(3-methyl-4-carboxybutylthiophene).Examples of polypyrrole-based conductive polymers include polypyrrole, poly(N-methylpyrrole), poly(3-methylpyrrole), poly(3-ethylpyrrole), poly(3-n-propylpyrrole), poly(3-butylpyrrole), poly(3-octylpyrrole), poly(3-decylpyrrole), poly(3-dodecylpyrrole), poly(3,4-dimethylpyrrole), poly(3,4-dibutylpyrrole), poly(3-carboxypyrrole), poly(3-methyl-4-carboxypyrrole), poly(3-methyl-4-carboxyethylpyrrole), poly(3-methyl-4-carboxybutylpyrrole), poly(3-hydroxypyrrole), poly(3-methoxypyrrole), poly(3-ethoxypyrrole), poly(3-butoxypyrrole), poly(3-hexyloxypyrrole), and poly(3-methyl-4-hexyloxypyrrole). Examples of polyaniline-based conductive polymers include polyaniline, poly(2-methylaniline), poly(3-isobutylaniline), poly(2-anilinesulfonic acid), and poly(3-anilinesulfonic acid). Among these π-conjugated conductive polymers, poly(3,4-ethylenedioxythiophene) is particularly preferred due to its excellent conductivity, transparency, and heat resistance. The π-conjugated conductive polymer contained in the conductive composite may be one type or two or more types.

[0015] (Polyanion) A polyanion is a polymer having two or more monomer units having an anionic group in the molecule. The anionic group of this polyanion functions as a dopant for the π-conjugated conductive polymer, improving the conductivity of the π-conjugated conductive polymer. The anionic group of the polyanion is preferably a sulfo group or a carboxy group. Specific examples of such polyanions include polymers having sulfo groups, such as polystyrene sulfonic acid, polyvinyl sulfonic acid, polyallyl sulfonic acid, polyacrylic acid esters having sulfo groups, polymethacrylic acid esters having sulfo groups (e.g., poly(4-sulfobutyl methacrylate, polysulfoethyl methacrylate, polymethacryloyloxybenzenesulfonic acid), poly(2-acrylamido-2-methylpropanesulfonic acid), and polyisoprene sulfonic acid; and polymers having carboxy groups, such as polyvinyl carboxylic acid, polystyrene carboxylic acid, polyallyl carboxylic acid, polyacrylic acid, polymethacrylic acid, poly(2-acrylamido-2-methylpropanecarboxylic acid), and polyisoprene carboxylic acid. The polyanion may be a homopolymer formed by polymerizing a single monomer, or a copolymer formed by polymerizing two or more monomers. Among these polyanions, polymers having sulfo groups are preferred because they can achieve higher conductivity, and polystyrene sulfonic acid is more preferred.

[0016] The weight-average molecular weight Mw of the polyanion is not particularly limited, and is, for example, preferably 10,000 to 1,000,000, more preferably 50,000 to 800,000, and even more preferably 100,000 to 600,000. When the weight-average molecular weight Mw of the polyanion is within the above range, the viscosity of the conductive composite dispersion of this embodiment becomes appropriately low, and a capacitor with a sufficiently low ESR can be easily produced. The weight-average molecular weight Mw of the polyanion is the average molecular weight on a mass basis measured using gel filtration chromatography and calculated in terms of pullulan.

[0017] The content of the polyanion contained in the conductive composite dispersion of this embodiment is, for example, preferably in the range of 1 part by mass to 1,000 parts by mass, more preferably 10 parts by mass to 700 parts by mass, and even more preferably 100 parts by mass to 500 parts by mass, relative to 100 parts by mass of the π-conjugated conductive polymer. If the content of the polyanion is equal to or greater than the lower limit, the doping effect on the π-conjugated conductive polymer tends to be stronger, resulting in higher conductivity. On the other hand, if the content of the polyanion is equal to or less than the upper limit, the π-conjugated conductive polymer can be sufficiently contained, thereby ensuring sufficient conductivity.

[0018] The content of the conductive complex in the conductive complex dispersion of this embodiment is preferably 0.1 parts by mass or more and 3.0 parts by mass or less, more preferably 0.5 parts by mass or more and 2.5 parts by mass or less, even more preferably 1.0 parts by mass or more and 2.3 parts by mass or less, and most preferably 1.3 parts by mass or more and 2.1 parts by mass or less, relative to 100 parts by mass of the conductive complex (total of the π-conjugated conductive polymer and the polyanion) and water combined. When the content is equal to or more than the lower limit of the above range, the conductivity of the cured product of the conductive complex dispersion is further increased. When the content is equal to or less than the upper limit of the above range, the viscosity of the conductive complex dispersion can be easily reduced.

[0019] The content of the conductive complex (total content of the π-conjugated conductive polymer and the polyanion) relative to the total mass of the conductive complex dispersion of this embodiment is, for example, preferably 0.1 mass% or more and 3.0 mass% or less, more preferably 0.5 mass% or more and 2.5 mass% or less, and even more preferably 1.0 mass% or more and 2.0 mass% or less. When the content is equal to or more than the lower limit of the above range, the conductivity of the cured product of the conductive complex dispersion is further increased. When the content is equal to or less than the upper limit of the above range, the viscosity of the conductive complex dispersion can be easily reduced.

[0020] (Sugar Alcohol) The conductive composite dispersion of this embodiment contains a specific sugar alcohol. By containing the specific sugar alcohol together with polyvinylpyrrolidone, the conductivity after curing can be improved, and the capacitor performance can be improved (ESR can be reduced).

[0021] From the viewpoint of fully obtaining the above-mentioned effects, the sugar alcohol preferably has 4 to 7 carbon atoms and 3 to 7 hydroxyl groups in the sugar alcohol molecule, and is more preferably one or more selected from pentaerythritol, sorbitol, mannitol, and erythritol.

[0022] The content of the sugar alcohol in the conductive complex dispersion of this embodiment is preferably 1.0 part by mass or more and 20.0 parts by mass or less, more preferably 3.0 parts by mass or more and 16.0 parts by mass or less, still more preferably 6.0 parts by mass or more and 14.0 parts by mass or less, and most preferably 8.0 parts by mass or more and 12.0 parts by mass or less, relative to 100 parts by mass of the conductive complex (total of the π-conjugated conductive polymer and the polyanion) and water. When the content is equal to or more than the lower limit of the above range, the viscosity of the conductive complex dispersion can be sufficiently reduced. When the content is equal to or less than the upper limit of the above range, the excess sugar alcohol contained in the conductive complex dispersion can be reduced, and the conductivity of the cured product can be increased.

[0023] The content of the sugar alcohol relative to the total mass of the conductive complex dispersion of this embodiment is, for example, preferably 0.1 mass% to 20 mass% or less, more preferably 1.0 mass% to 18.0 mass% or less, even more preferably 3.0 mass% to 15.0 mass% or less, and most preferably 6.0 mass% to 12.0 mass% or less. When the content is equal to or greater than the lower limit of the above range, the viscosity of the conductive complex dispersion can be sufficiently reduced. When the content is equal to or less than the upper limit of the above range, the excess sugar alcohol contained in the conductive complex dispersion can be reduced, and the conductivity of the cured product can be increased.

[0024] (Polyvinylpyrrolidone) The conductive composite dispersion of this embodiment contains polyvinylpyrrolidone (PVP). The incorporation of PVP increases the viscosity of the conductive composite dispersion when it dries, and this can improve the adhesion of the solid electrolyte layer formed by drying and solidifying to the dielectric layer (similarly, the adhesion of the conductive layer to the substrate).

[0025] From the viewpoint of further enhancing the above-mentioned effects, the K value of the PVP contained in this embodiment is preferably 50 or more, more preferably 80 or more, and even more preferably 90 or more. The upper limit of the K value is usually 200 or less, and preferably 160 or less. The K value is generally known as a viscosity characteristic value that correlates with molecular weight, and is calculated by applying the relative viscosity value (25°C) to water measured with a capillary viscometer to the Fikentscher formula. The formula and measurement method are specified in ISO 1628-1:1998(E).

[0026] The content of PVP in the conductive composite dispersion of this embodiment is preferably 0.01 parts by mass or more and 0.30 parts by mass or less, more preferably 0.01 parts by mass or more and 0.20 parts by mass or less, and even more preferably 0.01 parts by mass or more and 0.10 parts by mass or less, relative to 100 parts by mass of the conductive composite (total of the π-conjugated conductive polymer and the polyanion) and water combined. When the content is equal to or greater than the lower limit of the above range, the viscosity of the conductive composite dispersion when dried can be increased, and the adhesion of the cured product to the substrate can be further improved. When the content is equal to or less than the upper limit of the above range, the excess PVP contained in the conductive composite dispersion can be reduced, and the conductivity of the cured product can be increased.

[0027] The content of PVP relative to the total mass of the conductive composite dispersion of this embodiment is, for example, preferably 0.001 mass% or more and 0.50 mass% or less, more preferably 0.003 mass% or more and 0.35 mass% or less, and even more preferably 0.005 mass% or more and 0.20 mass% or less. When the content is equal to or more than the lower limit of the above range, the viscosity of the conductive composite dispersion when dried can be increased, and the adhesion of the cured product to the substrate can be further improved. When the content is equal to or less than the upper limit of the above range, the excess PVP contained in the conductive composite dispersion can be reduced, and the conductivity of the cured product can be increased.

[0028] (Dispersion medium) The dispersion medium contained in the conductive composite dispersion liquid is preferably an aqueous dispersion medium containing water, since the conductive composite is hydrophilic. Furthermore, a dispersion medium other than water may be contained. The dispersion medium other than water is not particularly limited as long as it does not significantly impair the dispersibility of the conductive composite. Since the conductive composite has excess anionic groups derived from polyanions and has high dispersibility in water, the dispersion medium other than water is preferably a water-soluble organic solvent. Here, the water-soluble organic solvent is an organic solvent that dissolves in an amount of 1 g or more in 100 g of water at 20°C, and examples thereof include alcohol-based solvents, ketone-based solvents, and ester-based solvents. The water-soluble organic solvent contained as the dispersion medium may be one type or two or more types. The non-water-soluble organic solvent is an organic solvent that dissolves in an amount of less than 1 g.

[0029] The content of water relative to the total mass of the conductive composite dispersion is preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more. It is also preferably 99% by mass or less. When the water content is equal to or greater than the above-mentioned lower limit, the dispersibility of the conductive composite contained in the conductive composite dispersion is increased, the viscosity is reduced, and the ESR of a capacitor having a solid electrolyte layer formed from the conductive composite dispersion can be further reduced. Furthermore, the conductivity of the conductive layer formed from the conductive composite dispersion can be further increased.

[0030] (Neutralizing Agent) The conductive composite dispersion of this embodiment may further contain one or more neutralizing agents. When the polyanion has acid groups, the conductive composite dispersion tends to become strongly acidic, but this can be neutralized with a neutralizing agent. Examples of neutralizing agents include basic compounds. The basic compound functions as a Brønsted base that accepts protons from excess anionic groups of the polyanion. To fulfill this function, the amount of the basic compound dissolved in water is preferably 0.001 g or more per 100 g of water at 20°C. There is no particular upper limit to the amount dissolved, but even if it is about 0.1 g, for example, the function can be fulfilled sufficiently.

[0031] Examples of basic compounds that can be used include nitrogen-containing organic or inorganic basic compounds, hydroxides of alkali metals or Group 2 metals, various carbonates and bicarbonates, etc. Examples include alkali metal hydroxides, quaternary ammonium hydroxides or salts thereof, ammonia, amines, etc. Specific examples of alkali metal hydroxides include potassium hydroxide and sodium hydroxide. Specific examples of carbonates or bicarbonates include ammonium bicarbonate, ammonium carbonate, potassium bicarbonate, potassium carbonate, sodium bicarbonate, sodium carbonate, etc. Specific examples of quaternary ammonium hydroxides or salts thereof include tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrabutylammonium hydroxide, etc.

[0032] Examples of the amine include aliphatic tertiary amines, nitrogen-containing aromatic compounds, etc. Examples of the aliphatic tertiary amine include triethanolamine, trimethylamine, triethylamine, tripropylamine, tributylamine, trihexylamine, trioctylamine, triphenylamine, tribenzylamine, and trinaphthylamine.

[0033] Examples of nitrogen-containing aromatic compounds (aromatic compounds in which at least one nitrogen atom forms a ring structure) include pyrrole, indole, imidazole, 2-methylimidazole, 2-propylimidazole, N-methylimidazole, N-propylimidazole, N-butylimidazole, 1-(2-hydroxyethyl)imidazole, 2-ethyl-4-methylimidazole, 1,2-dimethylimidazole, 1-benzyl-2-methylimidazole, 1-cyanoethyl-2-methylimidazole, and 1-cyanoethyl-2-ethyl-4-methylimidazole. Examples of the aromatic hydrocarbon derivative include imidazole, 2-phenyl-4,5-dihydroxymethylimidazole, 1-acetylimidazole, 2-aminobenzimidazole, 2-amino-1-methylbenzimidazole, 2-hydroxybenzimidazole, 2-(2-pyridyl)benzimidazole, pyridine, pyrimidine, pyrazine, and derivatives thereof such as alkyl-substituted derivatives thereof (e.g., those substituted with an alkyl group having 1 to 4 carbon atoms such as methyl, ethyl, propyl, or butyl), halogen-substituted derivatives thereof (e.g., those substituted with a halogen group such as fluoro, chloro, or bromine), and nitrile-substituted derivatives. Of these, nitrogen-containing aromatic compounds are preferred, and imidazole is more preferred.

[0034] The content of the basic compound contained in the conductive complex dispersion is, for example, preferably 1 part by mass or more and 100 parts by mass or less, more preferably 5 parts by mass or more and 60 parts by mass or less, and even more preferably 10 parts by mass or more and 30 parts by mass or less, relative to 100 parts by mass of the conductive complex (total of the π-conjugated conductive polymer and the polyanion). When the content is in the above preferred range, the acidity of the conductive complex dispersion is weakened, the corrosiveness to the substrate is reduced, and the ESR of the capacitor can be further reduced.

[0035] The content of the basic compound contained in the conductive composite dispersion is preferably such that the pH of the conductive composite dispersion (25° C.) is 2.0 to 8.0, more preferably 2.0 to 5.0, and even more preferably 2.0 to 3.0. When the content is within the above preferred range, the ESR of the capacitor can be further reduced.

[0036] (High-boiling point solvent) The conductive composite dispersion of this embodiment may further contain one or more organic solvents (high-boiling point solvents) having a boiling point of 150° C. or higher at 1 atmosphere (101,325 Pa). The boiling point is preferably 250° C. or lower. By including a high-boiling point solvent, effects such as improved conductivity of a cured product of the conductive composite dispersion can be obtained.

[0037] Examples of high-boiling point solvents include water-soluble organic solvents and water-insoluble organic solvents, where the definitions of water-soluble organic solvents and water-insoluble organic solvents are the same as those described above.

[0038] Examples of high-boiling water-soluble organic solvents include alcohol solvents, ether solvents, ketone solvents, nitrogen-containing solvents, and sulfur-containing solvents. Examples of alcohol solvents include polyhydric alcohols such as ethylene glycol (boiling point 198°C), 1,2-propanediol (also known as propylene glycol, boiling point 188°C), 1,3-propanediol (boiling point 214°C), 1,2-butanediol (boiling point 194°C), 1,3-butanediol (boiling point 207°C), 1,4-butanediol (boiling point 228°C), dipropylene glycol (boiling point 232°C, mixture of isomers), and diethylene glycol (boiling point 245°C). Examples of ether solvents include diethylene glycol dimethyl ether (boiling point 162°C) and diethylene glycol diethyl ether (boiling point 188°C). Examples of ketone solvents include methyl amyl ketone (boiling point 151°C) and diacetone alcohol (boiling point 168°C). Examples of nitrogen atom-containing solvents include N-methylpyrrolidone (boiling point 202°C), N-methylacetamide (boiling point 206°C), dimethylacetamide (boiling point 165°C), and N,N-dimethylformamide (boiling point 153°C). Examples of sulfur atom-containing solvents include dimethyl sulfoxide (boiling point 189°C).

[0039] Examples of high-boiling point water-insoluble organic solvents include hydrocarbon solvents. Examples of hydrocarbon solvents include aliphatic hydrocarbon solvents and aromatic hydrocarbon solvents. Examples of aliphatic hydrocarbon solvents include nonane (boiling point 151°C), decane (boiling point 174°C), and dodecane (boiling point 216°C). Examples of aromatic hydrocarbon solvents include propylbenzene (boiling point 159°C) and isopropylbenzene (boiling point 152°C).

[0040] Among the above examples, alcohol-based high-boiling point solvents are preferred because they provide a greater effect of improving conductivity. Among alcohol-based high-boiling point solvents, ethylene glycol (boiling point 198°C), 1,2-propanediol (boiling point 188°C), 1,3-propanediol (boiling point 214°C), diethylene glycol (boiling point 245°C), and dimethyl sulfoxide (boiling point 189°C) are preferred because of their excellent effect of improving conductivity.

[0041] The content of the high-boiling point solvent contained in the conductive composite dispersion is, for example, preferably 10 parts by mass or more and 2000 parts by mass or less, more preferably 100 parts by mass or more and 1000 parts by mass or less, and even more preferably 400 parts by mass or more and 800 parts by mass or less, relative to 100 parts by mass of the conductive composite (total of the π-conjugated conductive polymer and the polyanion). Within the above range, the ESR of a capacitor having a solid electrolyte layer formed from the conductive composite dispersion can be further reduced. Furthermore, the conductivity of the conductive layer formed from the conductive composite dispersion can be further increased.

[0042] The content of the high-boiling point solvent relative to the total mass of the conductive polymer-containing liquid of this embodiment is, for example, preferably 0.1 mass% to 20 mass% or less, more preferably 1.0 mass% to 18.0 mass% or less, even more preferably 3.0 mass% to 15.0 mass% or less, and most preferably 6.0 mass% to 12.0 mass% or less. When the content is equal to or greater than the lower limit of the above range, the ESR and conductivity can be further improved. When the content is equal to or less than the upper limit of the above range, an increase in viscosity of the conductive composite dispersion can be suppressed.

[0043] (Optional Additives) The conductive composite dispersion may contain other optional additives. The content ratio thereof is determined appropriately depending on the type of additive, but may be, for example, 1 to 1,000 parts by mass per 100 parts by mass of the total of the π-conjugated conductive polymer and polyanion. Here, the optional additives are compounds other than the basic compound, the high-boiling point solvent, the sugar alcohol, PVP, and the dispersion medium.

[0044] Examples of optional additives include surfactants, inorganic conductive agents, antifoaming agents, coupling agents, antioxidants, and ultraviolet absorbers. Examples of surfactants include nonionic, anionic, and cationic surfactants, with nonionic surfactants being preferred in terms of storage stability. Polymer surfactants such as polyvinyl alcohol may also be added. Examples of inorganic conductive agents include metal ions and conductive carbon. Metal ions can be generated by dissolving metal salts in water. Examples of antifoaming agents include silicone resins, polydimethylsiloxanes, and silicone oils. Examples of coupling agents include silane coupling agents having vinyl groups, amino groups, epoxy groups, and the like. Examples of antioxidants include phenolic antioxidants, amine antioxidants, phosphorus-based antioxidants, sulfur-based antioxidants, and sugars. Examples of the ultraviolet absorber include benzotriazole-based ultraviolet absorbers, benzophenone-based ultraviolet absorbers, salicylate-based ultraviolet absorbers, cyanoacrylate-based ultraviolet absorbers, oxanilide-based ultraviolet absorbers, hindered amine-based ultraviolet absorbers, and benzoate-based ultraviolet absorbers.

[0045] The viscosity of the conductive complex dispersion of this embodiment at 25°C is desirably low, preferably 50 mPa·s or less, more preferably 45 mPa·s or less, and even more preferably 40 mPa·s or less. The lower limit of the viscosity is not particularly limited, and a guideline is 1 mPa·s or more. When measuring the viscosity, the conductive complex dispersion contains the conductive complex, water, the sugar alcohol, and PVP, and may further contain a neutralizing agent and a high-boiling point solvent. The viscosity is measured at 25°C using a tuning fork vibration viscometer in accordance with JIS Z8803:2011 (Viscosity measurement method using a vibration viscometer).

[0046] <<Method for Producing Conductive Composite Dispersion>> Examples of a method for producing the conductive composite dispersion of the first aspect of the present invention include a method of adding PVP, a sugar alcohol, and, if necessary, a neutralizing agent and a high-boiling point solvent to an aqueous dispersion of a conductive composite. The aqueous dispersion of the conductive composite may be obtained by chemical oxidative polymerization of a monomer that forms a π-conjugated conductive polymer in an aqueous solution of a polyanion by a known method, or a commercially available one may be used.

[0047] <<Method for Producing Capacitor>> A capacitor can be produced by a production method including the steps of applying the conductive composite dispersion of the first aspect to the surface of a dielectric layer formed on the surface of an anode made of a porous valve metal body, and drying the applied conductive composite dispersion to form a solid electrolyte layer.

[0048] The method for manufacturing a capacitor preferably includes the steps of: oxidizing the surface of an anode made of a porous valve metal to form a dielectric layer (dielectric forming step); arranging a cathode in a position opposite the dielectric layer (cathode forming step); and forming a solid electrolyte layer on at least a portion of the surface of the dielectric layer (film forming step). Each step will be described below with reference to FIG.

[0049] [Dielectric Forming Step] In this step, the surface of the anode 11 made of a porous valve metal body is oxidized to form the dielectric layer 12. The method for forming the dielectric layer 12 is not particularly limited, and examples thereof include a method of anodizing the surface of the anode 11 in a chemical conversion treatment electrolyte such as an aqueous solution of ammonium adipate, an aqueous solution of ammonium borate, or an aqueous solution of ammonium phosphate.

[0050] [Cathode Formation Step] In this step, the cathode 13 is disposed at a position facing the dielectric layer 12. The method for disposing the cathode 13 is not particularly limited, and examples thereof include a method of forming the cathode 13 using a conductive paste such as a carbon paste or a silver paste, and a method of disposing a metal foil such as an aluminum foil facing the dielectric layer 12.

[0051] [Film Forming Step] In this step, the conductive composite dispersion liquid is applied to at least a part of the surface of the dielectric layer 12 and then dried to form the solid electrolyte layer 14 .

[0052] Examples of methods that can be used to apply the conductive composite dispersion include immersion (dip coating), comma coating, reverse coating, lip coating, and microgravure coating. Among these, a method in which the anode 11 is immersed in the conductive composite dispersion under reduced pressure is preferred. The immersion method allows the conductive composite dispersion to be sufficiently applied even to the interior of the porous structure on the surface of the dielectric layer 12. After immersion, the anode is removed and subjected to the next drying treatment.

[0053] Drying methods include, for example, room temperature drying, hot air drying, and far-infrared drying. Of these, hot air drying is preferred. The drying temperature is preferably, for example, 100 to 180°C, and more preferably 120 to 150°C. The drying time is preferably, for example, 0.2 to 1 hour. After the drying process, the capacitor can be assembled using standard methods.

[0054] The composition of the components contained in the solid electrolyte layer 14 reflects the composition of the applied conductive complex dispersion. The content of the sugar alcohol relative to 100 parts by mass of the conductive complex (total of the π-conjugated conductive polymer and the polyanion) contained in the solid electrolyte layer 14 is, for example, preferably 100 parts by mass or more and 5000 parts by mass or less, more preferably 200 parts by mass or more and 2000 parts by mass or less, and even more preferably 300 parts by mass or more and 1000 parts by mass or less. Within the above ranges, the ESR of the capacitor is reduced and its heat resistance is sufficiently improved.

[0055] The content of PVP relative to 100 parts by mass of the conductive complex (total of the π-conjugated conductive polymer and the polyanion) contained in the solid electrolyte layer 14 is, for example, preferably 0.01 parts by mass or more and 50 parts by mass or less, more preferably 0.10 parts by mass or more and 30 parts by mass or less, and even more preferably 0.30 parts by mass or more and 20 parts by mass or less. Within the above ranges, the ESR of the capacitor is reduced and its heat resistance is sufficiently improved.

[0056] <<Capacitor>> The capacitor includes an anode made of a porous body of a valve metal, a dielectric layer made of an oxide of the valve metal, a cathode made of a conductive material provided on the dielectric layer opposite to the anode, and a solid electrolyte layer formed between the dielectric layer and the cathode, wherein the solid electrolyte layer contains a cured product of the conductive composite dispersion of the first aspect.

[0057] An example of an embodiment of the capacitor will be described with reference to Fig. 1. The capacitor 10 shown in Fig. 1 includes an anode 11 made of a porous valve metal, a dielectric layer 12 made of an oxide of the valve metal, a solid electrolyte layer 14 formed on the surface of the dielectric layer 12, and a cathode 13 provided on the outermost side. The cathode 13 is provided on the opposite side of the anode 11, with the dielectric layer 12 and the solid electrolyte layer 14 sandwiched therebetween.

[0058] Examples of valve metals constituting the anode 11 include aluminum, tantalum, niobium, titanium, hafnium, zirconium, zinc, tungsten, bismuth, and antimony. Of these, aluminum, tantalum, and niobium are preferred. Specific examples of the anode 11 include aluminum foil etched to increase its surface area and then oxidized, and tantalum particles or niobium particles sintered and then pelletized. Products treated in this manner are porous bodies with irregularities formed on the surface.

[0059] The dielectric layer 12 in this embodiment is a layer formed by oxidizing the surface of the anode 11, for example, by anodizing the surface of the metallic anode 11 in an electrolyte solution such as an aqueous solution of ammonium adipate. Similar to the anode 11, the dielectric layer 12 also has irregularities formed thereon.

[0060] The cathode 13 in this embodiment may be a conductive layer formed from a conductive paste or a metal layer made of a conductive material such as aluminum foil.

[0061] The solid electrolyte layer 14 in this embodiment is formed on the surface of the dielectric layer 12. The solid electrolyte layer 14 covers at least a portion of the surface of the dielectric layer 12, and may cover the entire surface of the dielectric layer 12. The thickness of the solid electrolyte layer 14 may be constant or may not be constant, and may be, for example, 1 μm or more and 100 μm or less.

[0062] The capacitor may have an electrolyte solution impregnated into the solid electrolyte layer. Examples of the solvent constituting the electrolyte solution include alcohol-based solvents such as ethylene glycol, diethylene glycol, propylene glycol, 1,4-butanediol, and glycerin, lactone-based solvents such as γ-butyrolactone, γ-valerolactone, and δ-valerolactone, sulfur-based solvents such as sulfolane, dimethyl sulfoxide, and dimethyl sulfone, amide-based solvents such as N-methylformamide, N,N-dimethylformamide, N-methylacetamide, and N-methylpyrrolidinone, nitrile-based solvents such as acetonitrile and 3-methoxypropionitrile, and water. Examples of the electrolyte constituting the electrolytic solution include organic acids such as adipic acid, glutaric acid, succinic acid, benzoic acid, isophthalic acid, phthalic acid, terephthalic acid, maleic acid, toluic acid, enanthic acid, malonic acid, formic acid, decanedicarboxylic acids such as 1,6-decanedicarboxylic acid and 5,6-decanedicarboxylic acid, octanedicarboxylic acids such as 1,7-octanedicarboxylic acid, azelaic acid, and sebacic acid; or boric acid, polyhydric alcohol complex compounds of boric acid obtained from boric acid and polyhydric alcohols; inorganic acids such as phosphoric acid, carbonic acid, and silicic acid, and primary amines (methylamine, ethylamine, propylamine, butylamine, ethylenediamine, etc.), secondary amines (dimethylamine, diethylamine, dipropylamine, methylethylamine, diphenylamine, etc.), tertiary amines (trimethylamine, triethylamine, tripropylamine, triphenylamine, 1,8-diazabicyclo(5,4,0)-undecene-7, etc.), tetraalkylammonium (tetramethylammonium, tetraethylammonium, tetrapropylammonium, tetrabutylammonium, methyltriethylammonium, dimethyldiethylammonium, etc.), etc. as a cation component.

[0063] The capacitor is not limited to the above configuration, and a separator may be provided between the dielectric layer and the cathode. Examples of capacitors having a separator provided between the dielectric layer and the cathode include wound capacitors. Examples of separators include sheets (including nonwoven fabrics) made of cellulose, polyvinyl alcohol, polyester, polyethylene, polystyrene, polypropylene, polyimide, polyamide, polyvinylidene fluoride, and the like, and nonwoven fabrics of glass fibers. The density of the separator is, for example, 0.1 g / cm. ３ 1.0g / cm or more ３ The following can be mentioned: When a separator is provided, a method of forming a cathode by impregnating the separator with carbon paste or silver paste can also be applied.

[0064] <<Method for producing conductive laminate>> A conductive laminate can be produced by a production method including a step of applying the conductive composite dispersion of the first aspect of the present invention to at least a partial surface of a substrate to form a conductive layer.

[0065] Examples of a method for coating (applying) the conductive composite dispersion onto any surface of a substrate include a method using a coater such as a gravure coater, roll coater, curtain flow coater, spin coater, bar coater, reverse coater, kiss coater, fountain coater, rod coater, air doctor coater, knife coater, blade coater, cast coater, or screen coater; a method using a sprayer such as an air spray, airless spray, or rotor dampening; and an immersion method such as dipping.

[0066] The amount of the conductive composite dispersion applied to the substrate is not particularly limited, but for example, the amount of the non-volatile component is 0.01 to 10.0 g / m ２ The range is preferred.

[0067] A conductive layer can be formed by drying a coating film made of a conductive complex dispersion liquid applied to a substrate to remove at least a portion of the dispersion medium and hardening the coating film. Methods for drying the coating film include heat drying and vacuum drying. For example, methods such as hot air heating and infrared heating can be used for heat drying. When heat drying is applied, the heating temperature is appropriately set depending on the dispersion medium used, but is usually within the range of 50°C to 200°C. Here, the heating temperature is the set temperature of the drying device. A suitable drying time within the above heating temperature range is preferably 0.5 minutes to 30 minutes, more preferably 1 minute to 15 minutes.

[0068] <Conductive Laminate> The conductive laminate includes a substrate and a conductive layer formed on at least a portion of the surface of the substrate, and the conductive layer includes a cured product of the conductive composite dispersion of the first aspect.

[0069] [Conductive Layer] The conductive layer may be formed over the entire surface of any surface of the substrate, or only over a portion of the surface. In a conductive film, it is preferable that a conductive layer of substantially uniform thickness is formed over substantially the entire surface of one or the other surface of the film substrate. When a conductive layer is formed over only a portion of the surface of the substrate, the conductive layer may be, for example, a fine conductive pattern such as a circuit or an electrode, or may be simply roughly divided into a region where the conductive layer is provided and a region where the conductive layer is not provided, both present on the same surface.

[0070] The average thickness of the conductive layer is, for example, preferably 10 nm to 100 μm, more preferably 20 nm to 50 μm, and even more preferably 30 nm to 30 μm. When the average thickness of the conductive layer is equal to or greater than the lower limit, high conductivity can be exhibited, and when the average thickness is equal to or less than the upper limit, the adhesion of the conductive layer to the substrate is further improved.

[0071] The composition of the components contained in the conductive layer reflects the composition of the applied conductive complex dispersion. The content of the sugar alcohol relative to 100 parts by mass of the conductive complex (the total of the π-conjugated conductive polymer and the polyanion) contained in the conductive layer is, for example, preferably 1 part by mass or more and 50 parts by mass or less, more preferably 5 parts by mass or more and 40 parts by mass or less, and even more preferably 10 parts by mass or more and 30 parts by mass or less. Within the above range, the conductivity of the conductive layer is good.

[0072] The content of PVP relative to 100 parts by mass of the conductive complex (total of the π-conjugated conductive polymer and the polyanion) contained in the conductive layer is, for example, preferably 0.01 parts by mass or more and 50 parts by mass or less, more preferably 0.10 parts by mass or more and 30 parts by mass or less, and even more preferably 0.30 parts by mass or more and 20 parts by mass or less. When the content is within this range, the conductivity of the conductive layer becomes good.

[0073] [Substrate] The substrate may be a substrate made of an insulating material or a substrate made of a conductive material. The shape of the substrate is not particularly limited, and examples thereof include shapes mainly having a flat surface, such as a film or a substrate. Examples of insulating materials include glass, synthetic resin, and ceramics. Examples of conductive materials include metals, conductive metal oxides, and carbon.

[0074] (Film Substrate) When a film substrate is used as the substrate, the conductive laminate becomes a conductive film. Examples of the film substrate include plastic films made of synthetic resins. Examples of the synthetic resin include ethylene-methyl methacrylate copolymer resin, ethylene-vinyl acetate copolymer resin, polyethylene, polypropylene, polystyrene, polyvinyl chloride, polyvinyl alcohol, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyacrylate, polycarbonate, polyvinylidene fluoride, polyarylate, styrene-based elastomers, polyester-based elastomers, polyethersulfone, polyetherimide, polyetheretherketone, polyphenylene sulfide, polyimide, cellulose triacetate, and cellulose acetate propionate. From the viewpoint of enhancing adhesion between the film substrate and the conductive layer, the synthetic resin for the film substrate is preferably a polyester resin, and among these, polyethylene terephthalate is preferred.

[0075] The synthetic resin for the film substrate may be amorphous or crystalline. The film substrate may be unstretched or stretched. The film substrate may be subjected to a surface treatment such as corona discharge treatment, plasma treatment, or flame treatment to further improve the adhesion of the conductive layer.

[0076] The average thickness of the film substrate is preferably 5 μm or more and 500 μm or less, and more preferably 20 μm or more and 200 μm or less. If the average thickness of the film substrate is equal to or more than the lower limit, the film is less likely to break, and if it is equal to or less than the upper limit, the film can have sufficient flexibility. The average thickness of the film substrate is measured at 10 randomly selected locations and the average of the measured values.

[0077] (Glass substrate) Examples of the glass substrate include an alkali-free glass substrate, a soda-lime glass substrate, a borosilicate glass substrate, and a quartz glass substrate. If the substrate contains an alkali component, the conductivity of the conductive layer tends to decrease, so alkali-free glass is preferred among the glass substrates. Here, alkali-free glass refers to a glass composition in which the content of alkali components is 0.1 mass % or less relative to the total mass of the glass composition.

[0078] The average thickness of the glass substrate is preferably 100 μm or more and 3000 μm or less, and more preferably 100 μm or more and 1000 μm or less. If the average thickness of the glass substrate is equal to or more than the lower limit, the glass substrate is less likely to break, and if it is equal to or less than the upper limit, it can contribute to making the conductive laminate thinner. The average thickness of the glass substrate is a value obtained by measuring the thickness at 10 randomly selected locations and averaging the measured values.

[0079] (Production Example 1) Production of Polystyrene Sulfonic Acid 206 g of sodium styrene sulfonate was dissolved in 1000 ml of ion-exchanged water. While stirring at 80°C, 1.14 g of ammonium persulfate oxidant solution, previously dissolved in 10 ml of water, was added dropwise over 20 minutes, and the solution was stirred for 12 hours. 1000 ml of sulfuric acid diluted to 10% by mass was added to the resulting sodium polystyrene sulfonate solution, and approximately 1000 ml of solvent from the resulting polystyrene sulfonic acid solution was removed by ultrafiltration. Next, 2000 ml of ion-exchanged water was added to the residual solution, and approximately 2000 ml of solvent was removed by ultrafiltration to wash the polystyrene sulfonic acid with water. This water-washing procedure was repeated three times. The water in the resulting solution was removed under reduced pressure to obtain colorless solid polystyrene sulfonic acid (PSS).

[0080] (Preparation Example 2) Preparation of PEDOT-PSS Aqueous Dispersion: 14.2 g of 3,4-ethylenedioxythiophene and 36.7 g of polystyrene sulfonic acid dissolved in 2000 ml of ion-exchanged water were mixed at 20°C. The resulting mixture was maintained at 20°C and, while stirring, 29.64 g of ammonium persulfate and 8.0 g of an oxidation catalyst solution of ferric sulfate dissolved in 200 ml of ion-exchanged water were slowly added and allowed to react for 3 hours with stirring. 2000 ml of ion-exchanged water was added to the resulting reaction solution, and approximately 2000 ml of solvent was removed by ultrafiltration. This procedure was repeated three times. 200 ml of 10% diluted sulfuric acid and 2000 ml of ion-exchanged water were then added to the resulting solution, and approximately 2000 ml of solvent was removed by ultrafiltration. 2000 ml of ion-exchanged water was added to the remaining solution, and approximately 2000 ml of the solution was removed by ultrafiltration. This procedure was repeated three times. 2000 ml of ion-exchanged water was then added to the resulting solution, and approximately 2000 ml of the solvent was removed by ultrafiltration. This procedure was repeated five times to obtain a 1.2% by mass solution of polystyrene sulfonate-doped poly(3,4-ethylenedioxythiophene) (PEDOT-PSS aqueous dispersion). Further ultrafiltration was performed to obtain a 1.6% by mass aqueous dispersion of PEDOT-PSS.

[0081] (Production Example 3) A 1.2 mass% polystyrene sulfonic acid-doped poly(3,4-ethylenedioxythiophene) (PEDOT-PSS aqueous dispersion) solution was obtained in the same manner as in Production Example 2. Then, by further performing ultrafiltration, a 2.0 mass% PEDOT-PSS aqueous dispersion was obtained.

[0082] (Production Example 4) Preparation of Capacitor Element After connecting an anode lead terminal to an etched aluminum foil (anode foil), a voltage of 40 V was applied in a 10% by mass aqueous solution of ammonium adipate to perform chemical conversion (oxidation treatment) to form dielectric layers on both sides of the aluminum foil, thereby obtaining an anode foil. Next, opposing aluminum cathode foils with cathode lead terminals welded to both sides of the anode foil were laminated via a cellulose separator, and the resulting laminate was rolled up into a cylindrical shape to obtain a capacitor element.

[0083] (Production Example 5) 77 g of ethylene glycol, 23 g of polyethylene glycol #300, and 1 g of p-hydroxybenzoic acid were mixed together to obtain a driving electrolyte.

[0084] Example 1: 0.35 g of imidazole, 10 g of diethylene glycol, 10 g of sorbitol, and 0.05 g of polyvinylpyrrolidone (manufactured by Nippon Shokubai Co., Ltd., product name: PVP K-90) were added to 100 g of the PEDOT-PSS aqueous dispersion (1.6% by mass) obtained in Production Example 2, and the mixture was stirred for 30 minutes to obtain a conductive composite dispersion (hereinafter referred to as a coating composition). The coating composition had a pH of 2.5. Next, the capacitor element obtained in Production Example 4 was immersed in the coating composition under reduced pressure and then dried in a hot air dryer at 125°C for 30 minutes to obtain a capacitor element having a solid electrolyte containing the conductive composite formed on the dielectric layer surface. Finally, the capacitor element with the solid electrolyte layer formed thereon and the driving electrolyte solution obtained in Production Example 5 were loaded into an aluminum case, sealed with a rubber seal, and then treated at 125°C for 30 minutes at an applied voltage of 40 V. This produced a capacitor.

[0085] Example 2 0.40 g of imidazole, 10 g of diethylene glycol, 10 g of sorbitol, and 0.01 g of polyvinylpyrrolidone (manufactured by Nippon Shokubai Co., Ltd., product name: PVP K-90) were added to 100 g of the PEDOT-PSS aqueous dispersion (2.0 mass %) obtained in Production Example 3, and the mixture was stirred for 30 minutes to obtain a conductive composite dispersion (hereinafter referred to as a coating composition). The coating composition had a pH of 2.5. Next, a capacitor was fabricated using the coating composition in the same manner as in Example 1.

[0086] Example 3 A capacitor was fabricated in the same manner as in Example 2, except that the amount of polyvinylpyrrolidone (manufactured by Nippon Shokubai Co., Ltd., product name: PVP K-90) was changed from 0.01 g to 0.05 g.

[0087] Example 4 A capacitor was fabricated in the same manner as in Example 2, except that the amount of polyvinylpyrrolidone (manufactured by Nippon Shokubai Co., Ltd., product name: PVP K-90) was changed from 0.01 g to 0.10 g.

[0088] Example 5 A capacitor was fabricated in the same manner as in Example 2, except that the amount of polyvinylpyrrolidone (manufactured by Nippon Shokubai Co., Ltd., product name: PVP K-90) was changed from 0.01 g to 0.20 g.

[0089] Example 6 A capacitor was fabricated in the same manner as in Example 3, except that sorbitol was changed to mannitol.

[0090] Example 7 A capacitor was fabricated in the same manner as in Example 3, except that sorbitol was changed to erythritol.

[0091] Example 8 A capacitor was fabricated in the same manner as in Example 3, except that 10 g of sorbitol was changed to 5 g of pentaerythritol.

[0092] Comparative Example 1 A capacitor was fabricated in the same manner as in Example 2, except that polyvinylpyrrolidone (manufactured by Nippon Shokubai Co., Ltd., product name: PVP K-90) was not added.

[0093] Comparative Example 2 A capacitor was fabricated in the same manner as in Example 2, except that 10 g of sorbitol was replaced with 10 g of ion-exchanged water.

[0094] Comparative Example 3 A capacitor was fabricated in the same manner as in Example 2, except that the amount of polyvinylpyrrolidone (manufactured by Nippon Shokubai Co., Ltd., product name: PVP K-90) was changed from 0.01 g to 0.3 g.

[0095] [Measurement of pH] The pH was measured at a temperature of 25°C by a conventional method using a commercially available pH meter.

[0096] [Viscosity Measurement Method] The conductive composite dispersion (coating composition) obtained in each example was used as a sample and the viscosity of the conductive composite dispersion was measured at 25°C using a tuning fork vibration viscometer (model number: SV-10, manufactured by A&D Corporation) in accordance with JIS Z8803:2011 (Viscosity measurement method using a vibration viscometer). 1 Pa s (Pascal second) was calculated as 1000 cP (centipoise).

[0097] [Measurement of Equivalent Series Resistance] For the capacitors prepared using the conductive composite dispersions of each example, the capacitance (unit: μF) at 120 Hz and the equivalent series resistance (ESR) (unit: mΩ) at 100 kHz were measured using an LCR meter ZM2376 (manufactured by NF Corporation). The ESR measurement results are shown in Table 1.

[0098]

[0099] From the above, the conductive composite dispersions produced in the examples according to the present invention contained PVP and a specific sugar alcohol, and therefore showed a small increase in viscosity. Capacitors produced using these conductive composite dispersions had low ESR and high performance. On the other hand, the conductive composite dispersion of Comparative Example 1 did not contain PVP, so it had a low viscosity, but the capacitor ESR was high and performance was poor. This was thought to be due in part to the low conductivity of the solid electrolyte layer of Comparative Example 1. The conductive composite dispersion of Comparative Example 2 contained PVP but did not contain the specific sugar alcohol, so it had a higher viscosity than Comparative Example 1, and the capacitor ESR was also higher than in the examples, resulting in poor performance. The conductive composite of Comparative Example 3 contained PVP and a specific sugar alcohol, but its viscosity exceeded 50 mPa·s, so the capacitor ESR was high and performance was poor.

[0100] 10 Capacitor 11 Anode 12 Dielectric layer 13 Cathode 14 Solid electrolyte layer

Claims

1. A conductive complex dispersion liquid comprising a conductive complex containing a π-conjugated conductive polymer and a polyanion, water, a sugar alcohol having 4 to 7 carbon atoms and 3 to 7 hydroxyl groups in the molecule, and polyvinylpyrrolidone, and having a viscosity of less than 50 mPa·s at 25°C.

2. The conductive complex dispersion according to claim 1, wherein the content of the polyvinylpyrrolidone is 0.01 parts by mass or more and less than 0.30 parts by mass per 100 parts by mass of the conductive complex and the water combined.

3. The conductive complex dispersion according to claim 2, wherein the content of the conductive complex is 0.1 parts by mass or more and 3.0 parts by mass or less per 100 parts by mass of the conductive complex and the water combined.

4. The conductive complex dispersion according to claim 3, wherein the content of the water relative to the total mass of the conductive complex dispersion is 70 mass % or more and 99 mass % or less.

5. The conductive complex dispersion according to claim 4, wherein the sugar alcohol comprises at least one of sorbitol, mannitol, erythritol, and pentaerythritol.

6. The conductive composite dispersion according to claim 5, further comprising an organic solvent having a boiling point of 150° C. or higher at 1 atmospheric pressure.

7. The conductive composite dispersion of claim 6, further comprising a neutralizing agent.

8. The conductive composite dispersion according to claim 5, wherein the π-conjugated conductive polymer is poly(3,4-ethylenedioxythiophene), or the polyanion is polystyrenesulfonic acid, or the π-conjugated conductive polymer is poly(3,4-ethylenedioxythiophene) and the polyanion is polystyrenesulfonic acid.

9. A capacitor comprising an anode made of a porous body of a valve metal, a dielectric layer made of an oxide of the valve metal, a cathode made of a conductive material provided on the dielectric layer opposite the anode, and a solid electrolyte layer formed between the dielectric layer and the cathode, wherein the solid electrolyte layer is a cured product of the conductive composite dispersion liquid according to any one of claims 1 to 8.

10. A conductive laminate comprising a substrate and a conductive layer formed on at least a portion of the surface of the substrate, the conductive layer being a cured product of the conductive composite dispersion liquid according to any one of claims 1 to 8.

11. A method for producing a conductive complex dispersion, comprising the step of mixing a conductive complex consisting of a π-conjugated conductive polymer and a polyanion, a dispersion medium, a sugar alcohol, and a sugar alcohol having 4 to 7 carbon atoms and 3 to 7 hydroxyl groups in the molecule, to obtain a conductive complex dispersion having a viscosity of less than 50 mPa s at 25°C.

12. The method for producing a conductive complex dispersion liquid according to claim 11, comprising obtaining a dispersion liquid in which the conductive complex is dispersed in the dispersion medium, concentrating the dispersion liquid, and then mixing the sugar alcohol therewith.

13. A method for producing a capacitor, comprising the steps of applying the conductive composite dispersion liquid according to any one of claims 1 to 8 to the surface of a dielectric layer formed on the surface of an anode made of a porous valve metal body, and drying the applied liquid to form a solid electrolyte.

14. A method for producing a conductive laminate, comprising the steps of applying the conductive composite dispersion liquid according to any one of claims 1 to 8 to at least one surface of a substrate and drying the applied coating to form a conductive layer.

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