Conductive composite dispersion, capacitor and conductive laminate

Abstract

To provide a conductive composite dispersion suitable for manufacturing a high-performance capacitor.SOLUTION: There are provided: (1) a conductive composite dispersion which comprises a conductive composite containing a π-conjugated conductive polymer and polyanions, water, a sugar alcohol having 4 to 7 carbon atoms and 3 to 7 hydroxyl groups and a polyvinyl alcohol and has a viscosity of less than 50 mPa s at 25°C; and (2) a capacitor which comprises an anode composed of a porous body of a valve metal, a dielectric layer composed of an oxide of the valve metal, a cathode made of a conductive material provided on the opposite side of the anode of the dielectric layer 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.SELECTED DRAWING: None

Description

[Technical Field]

[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. [Background technology]

[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, and becomes dispersible in water. A method for producing a capacitor has been disclosed (for example, Patent Document 1), in which a paint made from a conductive composite dispersion liquid containing a conductive composite is applied to a dielectric layer provided on the surface of an anode made of a valve metal, the paint is dried to form a solid electrolyte layer, and a cathode is placed opposite the solid electrolyte layer. According to this disclosure, the performance of the capacitor is improved by adding a specific unsaturated aliphatic alcohol compound to the paint. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-071400 Summary of the Invention [Problem to be solved by the invention]

[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. [Means for solving the problem]

[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 and 3 to 7 hydroxyl groups in the molecule, and polyvinyl alcohol, and having a viscosity of less than 50 mPa s at 25°C. [2] The conductive complex dispersion liquid according to [1], wherein the content of the polyvinyl alcohol is 0.01 parts by mass or more and less than 0.20 parts by mass per 100 parts by mass of the conductive complex and the water combined. [3] The conductive complex dispersion liquid 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 per 100 parts by mass of the total of the conductive complex and the water. [4] The conductive composite dispersion liquid according to any one of [1] to [3], wherein the content of the water relative to the total mass of the conductive composite dispersion liquid is 70 mass % or more and 99 mass % or less. [5] The conductive complex dispersion liquid according to any one of [1] to [4], wherein the sugar alcohol contains at least one of sorbitol, mannitol, erythritol, and pentaerythritol. [6] The conductive composite dispersion liquid according to any one of [1] to [5], further containing an organic solvent having a boiling point of 150° C. or higher at 1 atmosphere. [7] The conductive composite dispersion 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 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 [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]. [Effects of the Invention]

[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 when it dries after penetrating, making it suitable for the production of high-performance capacitors. This property makes it 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. A capacitor having a solid electrolyte layer made of a cured product of the conductive composite dispersion of the present invention has a stabilized conductive composite due to the coexistence of polyvinyl alcohol in the solid electrolyte, and further has a low equivalent series resistance (ESR) and high performance. The conductive laminate having a conductive layer made of a cured product of the conductive composite dispersion of the present invention has improved adhesion to the substrate and a stabilized conductive composite because polyvinyl alcohol coexists 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 numerical ranges indicated with "to" are included in the numerical range. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a cross-sectional view illustrating one embodiment of a capacitor. DETAILED DESCRIPTION OF THE INVENTION

[0011] ≪Conductive composite dispersion liquid≫ A first aspect of the present invention is a conductive complex dispersion comprising a conductive complex containing a π-conjugated conductive polymer and a polyanion, water, a specific sugar alcohol, and polyvinyl alcohol, and having a viscosity of less than 50 mPa s at 25°C.

[0012] <Conductive composite> The conductive composite of this embodiment includes 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 electrical 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 an 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] 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-dodecyloxythiophene) 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 because of its excellent conductivity, transparency, and heat resistance. The conductive composite may contain one type of π-conjugated conductive polymer, or two or more types of polymers.

[0015] (polyanion) A polyanion is a polymer having two or more monomer units with an anionic group in the molecule. The anionic group of this polyanion functions as a dopant for a 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 (for example, 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 types of monomers. Among these polyanions, polymers having sulfo groups are preferred, and polystyrene sulfonic acid is more preferred, since they can further increase the conductivity.

[0016] The weight average molecular weight Mw of the polyanion is not particularly limited, and is, for example, preferably from 10,000 to 1,000,000, more preferably from 50,000 to 800,000, and even more preferably from 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 measured by gel filtration chromatography and is the average molecular weight based on mass calculated as 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, a sufficient amount of the π-conjugated conductive polymer can be contained, thereby ensuring sufficient conductivity.

[0018] The content of the conductive complex in the conductive complex dispersion liquid 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, still 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 at least as large as the lower limit of the above range, the conductivity of the cured product of the conductive composite 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 composite 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 at least as large as the lower limit of the above range, the conductivity of the cured product of the conductive composite 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 composite dispersion can be easily reduced.

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

[0021] From the viewpoint of fully achieving 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 liquid of this embodiment is preferably 1.0 parts by mass or more and 20.0 parts by mass or less, more preferably 3.0 parts by mass or more and 15.0 parts by mass or less, and even more preferably 5.0 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 greater than the lower limit of the above range, the viscosity of the conductive complex dispersion can be sufficiently reduced, and 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, thereby increasing the conductivity of the cured product.

[0023] The content of the sugar alcohol relative to the total mass of the conductive composite dispersion of this embodiment is, for example, preferably 0.1 mass% or more and 20 mass% or less, more preferably 1.0 mass% or more and 18.0 mass% or less, even more preferably 3.0 mass% or more and 15.0 mass% or less, and most preferably 4.0 mass% or more and 10.0 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, and 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, thereby increasing the conductivity of the cured product.

[0024] (Polyvinyl alcohol) The conductive composite dispersion of this embodiment contains polyvinyl alcohol (PVA). The incorporation of PVA increases the viscosity of the conductive composite dispersion when it dries, thereby improving 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] The saponification degree of the PVA is preferably 70.0 mol % or more and 99.0 mol % or less, more preferably 80.0 mol % or more and 95.0 mol % or less, and even more preferably 85.0 mol % or more and 92.0 mol % or less. Within this range, the solubility in the conductive composite dispersion liquid is further increased. Here, the degree of saponification of PVA is a value measured in accordance with JIS K 6726-1994.

[0026] The viscosity of the PVA, when dissolved in water at 20°C at a concentration of 4% by mass, is preferably 3.0 mPa·s or more and 20.0 mPa·s or less, more preferably 5.0 mPa·s or more and 15.0 mPa·s or less, and even more preferably 6.0 mPa·s or more and 10.0 mPa·s or less. When the viscosity is within the above range, it becomes easy to adjust the viscosity of the conductive composite dispersion, and it becomes easy to improve the performance of the capacitor to be produced. Here, the viscosity of the PVA aqueous solution is a value measured in accordance with JIS K 6726-1994.

[0027] The content of PVA in the conductive composite dispersion liquid of this embodiment is preferably 0.001 parts by mass or more and 0.19 parts by mass or less, more preferably 0.005 parts by mass or more and 0.15 parts by mass or less, still more preferably 0.010 parts by mass or more and 0.120 parts by mass or less, particularly preferably 0.030 parts by mass or more and 0.120 parts by mass or less, and most preferably 0.060 parts by mass or more and 0.120 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, the adhesion of the cured product to the substrate can be further increased, and the performance of the produced capacitor can be further improved.When the content is equal to or less than the upper limit of the above range, the excess PVA contained in the conductive composite dispersion can be reduced, and the conductivity of the cured product can be improved.

[0028] The content of PVA relative to the total mass of the conductive composite dispersion of this embodiment is, for example, preferably 0.001 mass% or more and 0.15 mass% or less, more preferably 0.003 mass% or more and 0.12 mass% or less, even more preferably 0.005 mass% or more and 0.12 mass% or less, and most preferably 0.010 mass% or more and 0.10 mass% or less. 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, the adhesion of the cured product to the substrate can be further increased, and the performance of the produced capacitor can be further improved.When the content is equal to or less than the upper limit of the above range, the excess PVA contained in the conductive composite dispersion can be reduced, and the conductivity of the cured product can be improved.

[0029] (dispersion medium) The dispersion medium contained in the conductive composite dispersion liquid is preferably an aqueous dispersion medium containing water because the conductive composite is hydrophilic. Alternatively, 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 the polyanion 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. Note that the water-insoluble organic solvent is an organic solvent that dissolves in an amount of less than 1 g.

[0030] 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 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.

[0031] (Neutralizer) The conductive complex dispersion of this embodiment may further contain one or more neutralizing agents. When the polyanion has an acid group, the conductive complex dispersion tends to become strongly acidic, but this can be neutralized with a neutralizing agent. Examples of the neutralizing agent include basic compounds. The basic compound functions as a Bronsted base that accepts protons from excess anion 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 an amount of about 0.1 g can fully fulfill the above function.

[0032] Examples of the basic compound that can be used include organic or inorganic basic compounds containing nitrogen, hydroxides of alkali metals or Group 2 metals, various carbonates and hydrogen carbonates, etc. Examples include hydroxides of alkali metals, quaternary ammonium hydroxides or salts thereof, ammonia, and amines. Specific examples of alkali metal hydroxides include potassium hydroxide and sodium hydroxide. Specific examples of carbonates or hydrogen carbonates include ammonium hydrogen carbonate, ammonium carbonate, potassium hydrogen carbonate, potassium carbonate, sodium hydrogen carbonate, sodium carbonate, and the like. Specific examples of quaternary ammonium hydroxides or salts thereof include tetramethylammonium hydroxide, tetraethylammonium hydroxide, and tetrabutylammonium hydroxide.

[0033] Examples of the amine include aliphatic tertiary amines and nitrogen-containing aromatic compounds. Examples of the aliphatic tertiary amine include triethanolamine, trimethylamine, triethylamine, tripropylamine, tributylamine, trihexylamine, trioctylamine, triphenylamine, tribenzylamine, and trinaphthylamine.

[0034] 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 suitable hydroxybenzoates include benzotriazole, 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 products thereof (e.g., products substituted with an alkyl group having 1 to 4 carbon atoms, such as methyl, ethyl, propyl, or butyl), halogen-substituted products thereof (e.g., products substituted with a halogen group, such as fluoro, chloro, or bromine), and nitrile-substituted products. Of these, nitrogen-containing aromatic compounds are preferred, and imidazole is more preferred.

[0035] 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). Within 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.

[0036] 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. Within the above preferred range, the ESR of the capacitor can be further reduced.

[0037] (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 Pascals). The boiling point is preferably 250° C. or lower. The inclusion of a high boiling point solvent can provide effects such as improved conductivity of a cured product of the conductive composite dispersion.

[0038] 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.

[0039] Examples of high-boiling water-soluble organic solvents include alcohol-based solvents, ether-based solvents, ketone-based solvents, nitrogen-atom-containing solvents, and sulfur-atom-containing solvents. Examples of alcohol-based 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). An example of the sulfur atom-containing solvent is dimethyl sulfoxide (boiling point: 189° C.).

[0040] Examples of the high-boiling point water-insoluble organic solvent include hydrocarbon solvents, etc. Examples of the hydrocarbon solvent include aliphatic hydrocarbon solvents and aromatic hydrocarbon solvents. Examples of the aliphatic hydrocarbon solvent 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).

[0041] Among the above examples, alcohol-based high-boiling 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 effects in improving conductivity, etc.

[0042] 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, and the conductivity of the conductive layer formed from the conductive composite dispersion can be further increased.

[0043] 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 % or more and 20 mass % or less, more preferably 1.0 mass % or more and 18.0 mass % or less, even more preferably 3.0 mass % or more and 15.0 mass % or less, and most preferably 6.0 mass % or more and 12.0 mass % or less. When the content is at least the lower limit of the above range, the ESR and electrical 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.

[0044] (Optional additives) The conductive composite dispersion may contain other optional additives. The content ratio of the additives is determined appropriately depending on the type of additive, but can be, for example, 1 to 1,000 parts by mass per 100 parts by mass of the π-conjugated conductive polymer and polyanion combined. Here, the optional additives are compounds other than the basic compound, high-boiling point solvent, sugar alcohol, PVA, and dispersion medium.

[0045] Examples of optional additives include surfactants, inorganic conductive agents, antifoaming agents, coupling agents, antioxidants, and ultraviolet absorbers. The surfactant may be a nonionic, anionic, or cationic surfactant, with the nonionic surfactant being preferred from the standpoint of storage stability. A polymer surfactant such as polyvinyl alcohol may also be added. Examples of inorganic conductive agents include metal ions, conductive carbon, etc. Metal ions can be generated by dissolving a metal salt in water. Examples of the antifoaming agent include silicone resin, polydimethylsiloxane, and silicone oil. Examples of the coupling agent include silane coupling agents having a vinyl group, an amino group, an epoxy group, or the like. Examples of the antioxidant include phenol-based antioxidants, amine-based 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.

[0046] The viscosity of the conductive composite 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. There is no particular restriction on the lower limit of the viscosity, and a rough guideline is 1 mPa s or more. When measuring the viscosity, the conductive complex dispersion contains the conductive complex, water, the sugar alcohol, and PVA, 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).

[0047] <Method for producing conductive composite dispersion> An example of a method for producing the conductive composite dispersion of the first aspect of the present invention is a method in which PVA, a sugar alcohol, and, if necessary, a neutralizing agent and a high-boiling point solvent are added to an aqueous dispersion of a conductive composite. The aqueous dispersion of the conductive complex may be obtained by chemically oxidatively polymerizing a monomer that forms a π-conjugated conductive polymer in an aqueous solution of polyanion by a known method, or a commercially available product may be used.

[0048] <Capacitor manufacturing method> A capacitor can be produced by a production method including a step of applying the conductive composite dispersion of the first embodiment to the surface of a dielectric layer formed on the surface of an anode made of a porous valve metal, and drying the applied conductive composite dispersion to form a solid electrolyte layer.

[0049] 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 to the dielectric layer (cathode forming step), and forming a solid electrolyte layer on at least a part of the surface of the dielectric layer (film forming step). Each step will be described below with reference to FIG.

[0050] [Dielectric formation process] In this step, the surface of anode 11 made of a porous valve metal is oxidized to form dielectric layer 12. The method for forming dielectric layer 12 is not particularly limited, and examples thereof include a method of anodizing the surface of 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.

[0051] [Cathode formation process] 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.

[0052] [Film forming process] In this step, the conductive composite dispersion liquid is applied to at least a portion of the surface of the dielectric layer 12 and then dried to form the solid electrolyte layer 14.

[0053] 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 then subjected to the next drying process.

[0054] Drying methods include, for example, room temperature drying, hot air drying, far infrared drying, etc. Among these, hot air drying is preferred. The drying temperature is, for example, preferably 100 to 180° C., more preferably 120 to 150° C. The drying time is, for example, preferably 0.2 to 1 hour. After the drying process, the capacitor can be assembled in the usual manner.

[0055] The composition of the components contained in the solid electrolyte layer 14 reflects the composition of the applied conductive composite dispersion liquid. 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 range, the ESR of the capacitor is further reduced.

[0056] The content of PVA 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 0.10 parts by mass or more and 20 parts by mass or less, more preferably 0.50 parts by mass or more and 15 parts by mass or less, and even more preferably 1.0 parts by mass or more and 10 parts by mass or less. Within the above range, the ESR of the capacitor is further reduced.

[0057] <Capacitor> The capacitor comprises 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, and the solid electrolyte layer contains a cured product of the conductive composite dispersion of the first aspect.

[0058] An example of an embodiment of the capacitor will be described with reference to Fig. 1. 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 dielectric layer 12, and a cathode 13 provided on the outermost side. Cathode 13 is provided on the opposite side of anode 11, with dielectric layer 12 and solid electrolyte layer 14 sandwiched therebetween.

[0059] Examples of valve metals that can be used to form 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 an aluminum foil that has been etched to increase its surface area and then oxidized, and a tantalum or niobium particle sintered body whose surface has been oxidized and then pelletized. Such a processed body becomes a porous body with irregularities formed on the surface.

[0060] 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 such as an aqueous solution of ammonium adipate. Similar to the anode 11, the dielectric layer 12 also has projections and recesses.

[0061] 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.

[0062] 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 or may not be constant, and may be, for example, 1 μm or more and 100 μm or less.

[0063] [Electrolyte] The capacitor may have an electrolyte solution impregnating the solid electrolyte layer. Examples of the solvent that constitutes the electrolytic 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 cationic component;

[0064] The capacitor is not limited to the above configuration, and a separator may be provided between the dielectric layer and the cathode. An example of a capacitor having a separator provided between the dielectric layer and the cathode is a wound capacitor. Examples of the separator include sheets (including nonwoven fabrics) made of cellulose, polyvinyl alcohol, polyester, polyethylene, polystyrene, polypropylene, polyimide, polyamide, polyvinylidene fluoride, etc., and nonwoven fabrics of glass fibers. The density of the separator is, for example, 0.1 g / cm 3 More than 1.0g / cm 3 The following are included: 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.

[0065] <Method for manufacturing conductive laminate> The 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 part of the surface of a substrate to form a conductive layer.

[0066] Examples of a method for applying (coating) 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.

[0067] The amount of the conductive composite dispersion applied to the substrate is not particularly limited, but for example, it is 0.01 to 10.0 g / m as a non-volatile component. 2 The range is preferred.

[0068] The conductive layer can be formed by drying the coating film made of the conductive complex dispersion applied onto the substrate to remove at least a portion of the dispersion medium and curing the coating film. Methods for drying the coating film include heat drying, vacuum drying, etc. Heat drying can be performed using, for example, hot air heating or infrared heating. 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 temperature set in 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.

[0069] <Conductive laminate> The conductive laminate comprises a substrate and a conductive layer formed on at least a portion of the surface of the substrate, and the conductive layer contains a cured product of the conductive composite dispersion of the first aspect.

[0070] [Conductive layer] The conductive layer may be formed over the entire surface of the substrate or over only 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 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 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.

[0071] The average thickness of the conductive layer is, for example, preferably 10 nm or more and 100 μm or less, more preferably 20 nm or more and 50 μm or less, and even more preferably 30 nm or more and 30 μm or less. 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 adhesiveness of the conductive layer to the substrate is further improved.

[0072] The composition of the components contained in the conductive layer reflects the composition of the conductive composite dispersion liquid that is applied. 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 conductive layer 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 range, the conductive layer has good conductivity.

[0073] The content of PVA 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 0.10 parts by mass or more and 20 parts by mass or less, more preferably 0.50 parts by mass or more and 15 parts by mass or less, and even more preferably 1.0 parts by mass or more and 10 parts by mass or less. Within this range, the conductivity of the conductive layer is good.

[0074] [Base material] The substrate may be made of an insulating material or a conductive material. The shape of the substrate is not particularly limited, and examples thereof include a shape 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.

[0075] (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, such as 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 improving the 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.

[0076] 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 in order to further improve the adhesion of the conductive layer.

[0077] 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. When the average thickness of the film substrate is equal to or more than the lower limit, the film is less likely to break, and when the average thickness is equal to or less than the upper limit, the film can have sufficient flexibility. The average thickness of the film substrate is determined by measuring the thickness at 10 randomly selected locations and averaging the measured values.

[0078] (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. Therefore, among the glass substrates, an alkali-free glass is preferred. Here, alkali-free glass refers to a glass composition having an alkali component content of 0.1% by mass or less relative to the total mass of the glass composition.

[0079] 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. When 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 when the average thickness is equal to or less than the upper limit, the conductive laminate can be made thinner. The average thickness of the glass substrate is determined by measuring the thickness at 10 randomly selected locations and averaging the measured values. [Example]

[0080] (Production Example 1) Production of polystyrene sulfonic acid 206 g of sodium styrenesulfonate was dissolved in 1000 ml of ion-exchanged water, and while stirring at 80°C, 1.14 g of an oxidizing agent solution of ammonium persulfate, which had been dissolved in 10 ml of water in advance, was added dropwise over 20 minutes, and the solution was stirred for 12 hours. To the resulting sodium polystyrene sulfonate solution, 1000 ml of sulfuric acid diluted to 10% by mass was added, and approximately 1000 ml of the solvent from the resulting polystyrene sulfonic acid solution was removed by ultrafiltration. Next, 2000 ml of ion-exchanged water was added to the remaining solution, and approximately 2000 ml of the solvent was removed by ultrafiltration, and the polystyrene sulfonic acid was washed with water. This water washing procedure was repeated three times. Water in the resulting solution was removed under reduced pressure to obtain colorless solid polystyrene sulfonic acid (PSS).

[0081] (Production Example 2) Production of PEDOT-PSS aqueous dispersion 14.2 g of 3,4-ethylenedioxythiophene and a solution prepared by dissolving 36.7 g of polystyrene sulfonic acid in 2000 ml of ion-exchanged water were mixed at 20°C. The resulting mixed solution was kept at 20°C and, while stirring, an oxidation catalyst solution of 29.64 g of ammonium persulfate and 8.0 g of ferric sulfate dissolved in 200 ml of ion-exchanged water was slowly added, followed by stirring for 3 hours to allow the reaction to proceed. To the resulting reaction solution, 2000 ml of ion-exchanged water was added, and about 2000 ml of the solvent was removed by ultrafiltration. This procedure was repeated three times. Then, 200 ml of sulfuric acid diluted to 10% by mass and 2000 ml of ion-exchanged water were added to the obtained solution, and about 2000 ml of the solvent was removed by ultrafiltration. 2000 ml of ion-exchanged water was added to the remaining liquid, and about 2000 ml of the solution was removed by ultrafiltration. This procedure was repeated three times. 2000 ml of ion-exchanged water was added to the resulting solution, and approximately 2000 ml of solvent was removed by ultrafiltration. This process 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 yielded a 1.6% by mass aqueous dispersion of PEDOT-PSS.

[0082] (Production Example 3) A 1.2 mass% solution of polystyrene sulfonic acid-doped poly(3,4-ethylenedioxythiophene) (PEDOT-PSS aqueous dispersion) was obtained in the same manner as in Production Example 2. Then, ultrafiltration was further carried out to obtain a 2.0 mass% PEDOT-PSS aqueous dispersion.

[0083] (Manufacturing Example 4) Preparation of capacitor element After connecting an anode lead terminal to the 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), forming a dielectric layer on both sides of the aluminum foil to obtain an anode foil. Next, opposing aluminum cathode foils with cathode lead terminals welded thereto were laminated on both sides of the anode foil with a cellulose separator interposed therebetween, and the resultant was rolled up into a cylindrical shape to obtain a capacitor element.

[0084] (Production Example 5) A driving electrolyte solution was obtained by mixing 77 g of ethylene glycol, 23 g of polyethylene glycol #300, and 1 g of p-hydroxybenzoic acid.

[0085] Example 1 To 100 g of the PEDOT-PSS aqueous dispersion (concentration 1.6% by mass) obtained in Production Example 2, 0.35 g of imidazole, 10 g of diethylene glycol, 10 g of sorbitol, and 0.05 g of polyvinyl alcohol (Kuraray Co., Ltd., product name: Kuraray Poval PVA-217) were added and stirred for 30 minutes to obtain a conductive composite dispersion (hereinafter referred to as the coating composition). The coating composition had a pH of 2.4. 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 a conductive composite formed on the surface of the dielectric layer. Finally, the capacitor element having the above-described solid electrolyte layer formed thereon and the driving electrolyte solution obtained in Production Example 5 were loaded into an aluminum case, and the case was sealed with a sealing rubber, followed by treatment at 125°C for 30 minutes at an applied voltage of 40 V, thereby producing a capacitor.

[0086] Example 2 To 100 g of the PEDOT-PSS aqueous dispersion (concentration 2.0 mass%) obtained in Production Example 3, 0.40 g of imidazole, 10 g of diethylene glycol, 10 g of sorbitol, and 0.01 g of polyvinyl alcohol (Kuraray Co., Ltd., product name: Kuraray Poval PVA-217) were added and stirred for 30 minutes to obtain a conductive composite dispersion (hereinafter referred to as the coating composition). The coating composition had a pH of 2.4. 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 a conductive composite formed on the surface of the dielectric layer. Finally, the capacitor element with the above-mentioned solid electrolyte layer formed thereon and the driving electrolyte solution obtained in Production Example 5 were loaded into an aluminum case, sealed with a sealing rubber, and then treated at 125°C for 30 minutes with an applied voltage of 40 V to produce a capacitor.

[0087] Example 3 A capacitor was fabricated in the same manner as in Example 2, except that the amount of polyvinyl alcohol (manufactured by Kuraray Co., Ltd., product name: Kuraray Poval PVA-217) was changed from 0.01 g to 0.05 g.

[0088] Example 4 A capacitor was fabricated in the same manner as in Example 2, except that the amount of polyvinyl alcohol (manufactured by Kuraray Co., Ltd., product name: Kuraray Poval PVA-217) was changed from 0.01 g to 0.1 g.

[0089] Example 5 A capacitor was fabricated in the same manner as in Example 3, except that sorbitol was changed to mannitol.

[0090] Example 6 A capacitor was fabricated in the same manner as in Example 3, except that sorbitol was changed to erythritol.

[0091] Example 7 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 polyvinyl alcohol (manufactured by Kuraray Co., Ltd., product name: Kuraray Poval PVA-217) 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 polyvinyl alcohol (manufactured by Kuraray Co., Ltd., product name: Kuraray Poval PVA-217) was changed from 0.01 g to 0.2 g.

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

[0096] [Viscosity measurement method] Using the conductive composite dispersion (paint composition) obtained in each example as a sample, 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] [Table 1]

[0099] From the above, the conductive composite dispersion liquid produced in the examples according to the present invention contains PVA, a specific sugar alcohol, and a viscosity lower than a predetermined value, and therefore the capacitor produced using the conductive composite dispersion liquid has a low ESR and high performance. On the other hand, the conductive composite dispersion of Comparative Example 1 did not contain PVA, so the viscosity was low, but the ESR of the capacitor was high and the performance was poor. One of the reasons for this was thought to be the low conductivity of the solid electrolyte layer of Comparative Example 1. The conductive composite dispersion of Comparative Example 2 contained PVA but did not contain the specific sugar alcohol, so the viscosity was higher than that of Comparative Example 1, and the ESR of the capacitor was also higher than that of the Examples, resulting in inferior performance. The conductive composite of Comparative Example 3 contained PVA and a specific sugar alcohol, but because the viscosity exceeded 50 mPa·s, the ESR of the capacitor was high and the performance was poor. The conductive composite dispersion liquid of Example 1 has a lower content of the conductive composite than Examples 2 to 7, and therefore the ESR of the capacitor is higher than that of the other Examples. [Explanation of symbols]

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

Claims

1. A conductive complex dispersion liquid containing a conductive complex including 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 polyvinyl alcohol, and having a viscosity of less than 50 mPa s at 25°C.

2. 2. The conductive complex dispersion according to claim 1, wherein the content of the polyvinyl alcohol is 0.01 parts by mass or more and less than 0.20 parts by mass with respect to 100 parts by mass of the total of the conductive complex and the water.

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 with respect to 100 parts by mass of the total of the conductive complex and the water.

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% by mass or more and 99% by 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 atmosphere.

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

8. The π-conjugated conductive polymer is poly(3,4-ethylenedioxythiophene), or the polyanion is polystyrene sulfonic acid, or 8. The conductive composite dispersion according to claim 7, wherein the π-conjugated conductive polymer is poly(3,4-ethylenedioxythiophene) and the polyanion is polystyrenesulfonic acid.

9. a cathode made of a conductive material and provided on the dielectric layer opposite to the anode; and a solid electrolyte layer formed between the dielectric layer and the cathode. A capacitor, 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 substrate and a conductive layer formed on at least a portion of the surface of the substrate, A conductive laminate, wherein the conductive layer is a cured product of the conductive composite dispersion liquid according to any one of claims 1 to 8.

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