Capacitor and method for manufacturing the same

Abstract

To provide a capacitor and a method for manufacturing the capacitor having excellent performance related to equivalent series resistance.SOLUTION: The capacitor includes: an anode made of a porous body of a valve metal; a dielectric layer formed on a surface of the anode; a solid electrolyte layer on a surface of the dielectric layer; and a cathode, the positive electrode and the negative electrode holding the solid electrolyte layer in between, the solid electrolyte layer containing a conductive complex including a π-conjugated conductive polymer and a polyanion, and an acetylene-based surfactant.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a capacitor using a π-conjugated conductive polymer and a polyanion, and a method for producing the same. [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 (e.g., Patent Document 1), in which a coating material made from a conductive polymer dispersion liquid containing a conductive complex is applied to a dielectric layer provided on the surface of an anode made of a valve metal, the coating material is dried to form a solid electrolyte layer, and a cathode is then placed opposite the solid electrolyte layer. According to this disclosure, the capacitor performance is improved by including a linear unsaturated aliphatic alcohol in 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] Capacitors with a solid electrolyte layer containing conductive polymers are required to have good capacitance and low equivalent series resistance (ESR). Furthermore, since capacitors may be exposed to high-temperature environments depending on their application, it is also required to suppress the increase in ESR due to heating.

[0005] The present invention provides a capacitor with excellent ESR performance and a method for manufacturing the same. [Means for solving the problem]

[0006] [1] A capacitor comprising an anode made of a porous valve metal body, a dielectric layer formed on the surface of the anode, a solid electrolyte layer formed on the surface of the dielectric layer, and a cathode sandwiching the solid electrolyte layer between the anode and the cathode, wherein the solid electrolyte layer contains a conductive complex including a π-conjugated conductive polymer and a polyanion, and an acetylene-based surfactant. [2] The capacitor according to [1], wherein the acetylene surfactant has one or more hydroxyl groups in the molecule. [3] The capacitor according to [1] or [2], wherein the acetylene surfactant is an ethoxylated product in which one or more of the hydroxyl groups have reacted with ethylene oxide. [4] The capacitor according to any one of [1] to [3], wherein the acetylene surfactant is a compound represented by formula (2) or formula (3) described below. [5] The capacitor according to any one of [1] to [4], wherein the content of the acetylene surfactant relative to the total mass of the π-conjugated conductive polymer, the polyanion, and the acetylene surfactant contained in the solid electrolyte layer is 1 mass % or more and 50 mass % or less. [6] The capacitor according to any one of [1] to [5], wherein the content of the π-conjugated conductive polymer is 5% by mass or more and 30% by mass or less, and the content of the polyanion is 30% by mass or more and 80% by mass or less, relative to the total mass of the π-conjugated conductive polymer, the polyanion, and the acetylene surfactant contained in the solid electrolyte layer. [7] The capacitor according to any one of [1] to [6], 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. [8] The capacitor according to any one of [1] to [7], wherein the solid electrolyte layer contains imidazole. [9] The capacitor according to any one of [1] to [8], wherein the solid electrolyte layer contains diethylene glycol.

[10] A method for manufacturing a capacitor, comprising the steps of applying a conductive polymer dispersion containing a π-conjugated conductive polymer, a polyanion, an acetylene-based surfactant, and an aqueous dispersion medium 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 polymer dispersion to form a solid electrolyte layer. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a capacitor that has a good capacitance, a low initial ESR, and a suppressed increase in ESR after heat treatment.

[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] Capacitor A first aspect of the present invention is a capacitor. An example of an embodiment thereof will be described. 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.

[0012] 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.

[0013] 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.

[0014] 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.

[0015] 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.

[0016] <Conductive composite> The conductive composite contained in the solid electrolyte layer will now be described. 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 electrical conductivity. In polyanions, only some of the anionic groups are 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.

[0017] (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.

[0018] 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.

[0019] (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. The polyanions may be used alone or in combination of two or more. The mass average molecular weight of the polyanion is preferably 20,000 or more and 1,000,000 or less, more preferably 100,000 or more and 500,000 or less, and even more preferably 100,000 to 300,000. When the weight average molecular weight Mw of the polyanion is within the above range, the resulting capacitor tends to have better ESR performance. The mass average molecular weight of the polyanion is measured by gel filtration chromatography and is the mass average molecular weight calculated as pullulan.

[0020] The content of the polyanion in the conductive composite 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.

[0021] The total content of the π-conjugated conductive polymer, polyanion, and acetylene surfactant relative to the total mass of the solid electrolyte layer is preferably 1% by mass to 99% by mass, more preferably 50% by mass to 98% by mass, and even more preferably 70% by mass to 97% by mass. This range is preferable because it makes it easier to reduce the equivalent series resistance of the capacitor.

[0022] With respect to the total mass of the π-conjugated conductive polymer, polyanion, and acetylene surfactant contained in the solid electrolyte, The content of the π-conjugated conductive polymer is preferably 5.0% by mass or more and 30.0% by mass or less, more preferably 10.0% by mass or more and 25.5% by mass or less, and even more preferably 18.0% by mass or more and 23.5% by mass or less. The content of the polyanion is preferably 30.0% by mass to 80.0% by mass, more preferably 40.0% by mass to 65.0% by mass, and even more preferably 45.0% by mass to 60.0% by mass. Within this range, the ESR performance of the capacitor can be further improved.

[0023] <Acetylene-based surfactants> The solid electrolyte layer of this embodiment contains an acetylene-based surfactant, which results in a capacitor with excellent ESR performance. Acetylenic surfactants are organic compounds having one carbon-carbon triple bond in the molecule. In order to enhance the ESR performance and further enhance the surfactant function, the following embodiments are preferred. That is, the acetylene surfactant preferably has one or more branched alkyl groups in the molecule. It also preferably has one or more hydroxyl groups in the molecule. It is also preferred that the hydroxyl groups are ethoxylated (EO adducts) in which ethylene oxide has reacted with the hydroxyl groups.

[0024] The acetylene surfactant is preferably a compound represented by formula (2) or formula (3).

[0025] [ka]

[0026] In formula (2), R 3 , R 4 , R 5 , R 6 each independently represents an alkyl group having 1 to 5 carbon atoms. R 3 and R 6 are each independently preferably a branched alkyl group, and more preferably have a branched chain in which a methyl group or an ethyl group is bonded to the second alkylene group from the end. R 4 and R 5 are each independently preferably a linear alkyl group, more preferably a methyl group or an ethyl group. In formula (2), l and m are each independently an integer of 0 to 25, and l+m is 0 to 40. When it is 0, it is a hydroxyl group, and when it is other than 0, it is an ethoxylated product formed by the reaction of a hydroxyl group with ethylene oxide. l and m are not particularly limited and may, for example, each independently be any of 1 to 20, 3 to 15, or 5 to 10. l+m is not particularly limited and may, for example, be any of 1 to 30, 3 to 20, or 5 to 10.

[0027] In formula (3), R 7 , R 8each independently represents an alkyl group having 1 to 5 carbon atoms. R 7 is preferably a branched alkyl group, and more preferably has a branched chain in which a methyl group or an ethyl group is bonded to the second alkylene group from the end. R 8 is preferably a linear alkyl group, more preferably a methyl group or an ethyl group. In formula (3), n is an integer of 0 to 25. When it is 0, it is a hydroxyl group, and when it is other than 0, it is an ethoxylated product formed by the reaction of a hydroxyl group with ethylene oxide. n is not particularly limited and may be, for example, any of 1 to 20, 3 to 15, and 5 to 10.

[0028] Specific examples of the acetylene surfactant include 2,4,7,9-tetramethyl-5-decyne-4,7-diol and its ethoxylated derivatives, 3,5-dimethyl-1-hexyn-3-ol and its ethoxylated derivatives, and 3,6-dimethyl-4-octyne-3,6-diol and its ethoxylated derivatives. Commercially available products of these acetylene surfactants can be used.

[0029] The solid electrolyte layer may contain one type of acetylene-based surfactant, or two or more types of surfactants. The content of the acetylene surfactant in the solid electrolyte is preferably 1.0% by mass to 50.0% by mass, more preferably 5.0% by mass to 40.0% by mass, even more preferably 10.0% by mass to 30.0% by mass, and most preferably 16.0% by mass to 25.0% by mass, based on the total mass of the π-conjugated conductive polymer, the polyanion, and the acetylene surfactant. Within this range, a capacitor with superior ESR performance is likely to be obtained.

[0030] <Basic compounds> The solid electrolyte layer of this embodiment may further contain a basic compound different from the conductive composite, the polyanion, and the acetylene surfactant. By containing the basic compound, the ESR of the capacitor can be further reduced.

[0031] 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 used in the present invention that dissolves 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 of dissolution, but even an amount of about 0.1 g can sufficiently 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 solid electrolyte layer may contain one kind of basic compound or two or more kinds of basic compounds. The content of the basic compound in the solid electrolyte layer is, for example, preferably 1 part by mass or more and 1000 parts by mass or less, more preferably 5 parts by mass or more and 100 parts by mass or less, and even more preferably 10 parts by mass or more and 50 parts by mass or less, relative to 100 parts by mass of the conductive composite. Within the above preferred range, the ESR of the capacitor can be further reduced.

[0036] <Polyol compounds> The solid electrolyte layer of this embodiment may further contain one or more compounds having two or more hydroxy groups (hereinafter, sometimes referred to as polyol compounds) different from the conductive complex, the polyanion, the acetylene surfactant, and the basic compound. By including a polyol compound, the ESR of the capacitor can be further reduced.

[0037] Examples of the polyol compound include one or more selected from ethylene glycol, diethylene glycol, propylene glycol, 1,4-butanediol, glycerin, pentaerythritol, trimethylolpropane, and trimethylolethane.

[0038] The total content of the polyol compounds contained in the solid electrolyte layer is, for example, preferably 100 parts by mass or more and 10,000 parts by mass or less, more preferably 200 parts by mass or more and 2,000 parts by mass or less, and even more preferably 300 parts by mass or more and 1,000 parts by mass or less, relative to 100 parts by mass of the total of the π-conjugated conductive polymer and polyanion contained in the solid electrolyte layer (i.e., 100 parts by mass of the conductive composite). The above range is preferable because it is easier to reduce the ESR of the capacitor. The solid electrolyte layer may contain one type of polyol compound or two or more types of polyol compounds.

[0039] [Electrolyte] The capacitor of this embodiment may have an electrolyte solution that impregnates 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;

[0040] The capacitor of this embodiment 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.

[0041] <Capacitor manufacturing method> A second aspect of the present invention is a method for producing a capacitor, which comprises the steps of applying a conductive polymer dispersion containing a π-conjugated conductive polymer, a polyanion, an acetylene-based surfactant, and an aqueous dispersion medium 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 polymer dispersion to form a solid electrolyte layer.

[0042] The manufacturing method of this embodiment 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), disposing 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.

[0043] [Dielectric formation process] 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.

[0044] [Cathode formation process] 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 in which the cathode 13 is formed using a conductive paste such as a carbon paste or a silver paste, and a method in which a metal foil such as an aluminum foil is disposed opposite the dielectric layer 12.

[0045] [Film forming process] A conductive polymer dispersion 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 .

[0046] Examples of methods that can be used to apply the conductive polymer dispersion include immersion (dip coating), comma coating, reverse coating, lip coating, and microgravure coating. Of these, a method in which the anode 11 is immersed in the conductive polymer dispersion under reduced pressure is preferred. The immersion method allows the conductive polymer dispersion to be applied thoroughly, 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.

[0047] 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.

[0048] <Conductive polymer dispersion> The conductive polymer dispersion used for film formation and fixation contains a conductive complex containing a π-conjugated conductive polymer and a polyanion, an acetylene-based surfactant, and an aqueous surfactant. The composition of the conductive polymer dispersion applied to the dielectric layer is reflected in the composition of the solid electrolyte to be formed.

[0049] Specific descriptions of the π-conjugated conductive polymer and polyanion are as described in the first embodiment. The content of the π-conjugated conductive polymer and polyanion (i.e., the conductive complex) relative to the total mass of the conductive polymer dispersion is preferably 0.1 mass% or more and 10.0 mass% or less, more preferably 0.5 mass% or more and 5.0 mass% or less, and even more preferably 1.0 mass% or more and 2.0 mass% or less. Within these ranges, the viscosity of the conductive polymer dispersion becomes appropriate, making it easy to form a solid electrolyte layer with excellent ESR performance.

[0050] The content of the polyanion contained in the conductive composite in the conductive polymer dispersion 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 content of the π-conjugated conductive polymer is sufficient, ensuring sufficient conductivity and allowing the production of a capacitor with higher ESR performance.

[0051] relative to the total mass of the π-conjugated conductive polymer, polyanion, and acetylene surfactant contained in the conductive polymer dispersion, The content of the π-conjugated conductive polymer is preferably 5.0% by mass or more and 30.0% by mass or less, more preferably 10.0% by mass or more and 25.5% by mass or less, and even more preferably 18.0% by mass or more and 23.5% by mass or less. The content of the polyanion is preferably 30.0% by mass to 80.0% by mass, more preferably 40.0% by mass to 65.0% by mass, and even more preferably 45.0% by mass to 60.0% by mass. Within this range, the ESR performance of the capacitor can be further improved.

[0052] The content of the acetylene surfactant in the conductive polymer dispersion is preferably 1.0% by mass to 50.0% by mass, more preferably 5.0% by mass to 40.0% by mass, even more preferably 10.0% by mass to 30.0% by mass, and most preferably 16.0% by mass to 25.0% by mass, based on the total mass of the π-conjugated conductive polymer, the polyanion, and the acetylene surfactant. Within this range, a capacitor with superior ESR performance is likely to be obtained.

[0053] The content of the acetylene surfactant relative to the total mass of the conductive polymer dispersion is, for example, 0.01% by mass to 5.0% by mass, preferably 0.10% by mass to 2.0% by mass, more preferably 0.20% by mass to 1.0% by mass, and even more preferably 0.30% by mass to 0.70% by mass. Within this range, the ESR performance of the capacitor can be further improved.

[0054] (aqueous dispersion medium) The dispersion medium contained in the conductive polymer dispersion is an aqueous dispersion medium containing water, since the conductive complex is hydrophilic. The aqueous dispersion medium may contain one or more water-soluble organic solvents, as long as the dispersion of the conductive complex is not hindered. Here, the water-soluble organic solvent is an organic solvent that dissolves at a rate of 1 g or more in 100 g of water (20°C). Examples of water-soluble organic solvents include alcohol-based solvents, ether-based solvents, ketone-based solvents, and nitrogen-atom-containing solvents.

[0055] Examples of alcohol-based solvents include methanol, ethanol, 1-propanol, 2-propanol (isopropanol), 2-methyl-2-propanol, 1-butanol, 2-butanol, 2-methyl-1-propanol, allyl alcohol, ethylene glycol, propylene glycol, propylene glycol monomethyl ether, and ethylene glycol monomethyl ether. Examples of the ether solvent include diethyl ether, dimethyl ether, propylene glycol dialkyl ether, and diethylene glycol diethyl ether. Examples of ketone solvents include diethyl ketone, methyl propyl ketone, methyl butyl ketone, methyl isopropyl ketone, methyl isobutyl ketone, methyl amyl ketone, diisopropyl ketone, methyl ethyl ketone, acetone, and diacetone alcohol. Examples of nitrogen atom-containing solvents include N-methylpyrrolidone, dimethylacetamide, and dimethylformamide. As the water-soluble organic solvent, an alcohol-based solvent or a ketone-based solvent is preferred, and an alcohol-based solvent is more preferred, since this improves the wettability of the conductive polymer dispersion liquid with respect to the substrate.

[0056] The water content relative to the total mass of the dispersion medium excluding the solid content (non-volatile components) of the conductive polymer dispersion is preferably 70 mass% or more, more preferably 80 mass% or more, even more preferably 90 mass% or more, and may be 100 mass%. When the water content is equal to or greater than the lower limit, the dispersibility of the conductive composite contained in the conductive polymer dispersion is increased, improving coatability. In addition, the ESR performance of a capacitor having a solid electrolyte layer formed from the conductive polymer dispersion can be further improved.

[0057] The viscosity of the conductive polymer dispersion at 25°C, when the concentration of the conductive complex relative to the total mass of the conductive polymer dispersion is adjusted to 1.6 mass%, is preferably 45 mPa s or less, more preferably 40 mPa s or less, even more preferably 38 mPa s or less, particularly preferably 36 mPa s or less, and most preferably 34 mPa s or less. There is no particular restriction on the lower limit of the viscosity, and a guideline is 1 mPa s or more. When measuring the viscosity, the dispersion medium contained in the conductive polymer dispersion is preferably ion-exchanged water alone. Furthermore, the conductive polymer dispersion for which the viscosity is measured contains an acetylene-based surfactant, but preferably does not contain any other additives. 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).

[0058] (Polyol compound) The conductive polymer dispersion applied to the dielectric layer may contain one or more polyol compounds, the specific details of which are as described in the first embodiment.

[0059] The content of the polyol compound in the conductive polymer dispersion is, for example, preferably 100 parts by mass or more and 10,000 parts by mass or less, more preferably 200 parts by mass or more and 2,000 parts by mass or less, and even more preferably 300 parts by mass or more and 1,000 parts by mass or less, relative to 100 parts by mass of the total of the π-conjugated conductive polymer and polyanion. Within the above preferred range, the coatability of the conductive polymer dispersion is improved, and the ESR performance of the capacitor can be further improved.

[0060] The content of the polyol compound relative to the total mass of the conductive polymer dispersion is preferably from 1 to 20% by mass, more preferably from 1 to 15% by mass, and even more preferably from 1 to 10% by mass. Within this preferred range, the ESR performance of the capacitor can be further improved while suppressing an increase in the viscosity of the conductive polymer dispersion.

[0061] (basic compounds) The conductive polymer dispersion to be applied to the dielectric layer may contain one or more basic compounds. Specific examples of the basic compounds are as described in the first embodiment.

[0062] The content of the basic compound in the conductive polymer dispersion is, for example, preferably 1 part by mass to 100 parts by mass, more preferably 10 parts by mass to 50 parts by mass, and even more preferably 15 parts by mass to 30 parts by mass, relative to 100 parts by mass of the total of the π-conjugated conductive polymer and polyanion. Within the above preferred range, the ESR performance of the capacitor can be further improved.

[0063] The content of the basic compound relative to the total mass of the conductive polymer dispersion is preferably 0.01% by mass to 1.0% by mass, more preferably 0.10% by mass to 0.60% by mass, and even more preferably 0.15% by mass to 0.40% by mass. Within these preferred ranges, the ESR of the capacitor can be further reduced.

[0064] The content of the basic compound contained in the conductive polymer dispersion is preferably such that the pH of the conductive polymer 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.

[0065] (Optional additives) The conductive polymer dispersion to be applied to the dielectric layer may contain any additive other than those described above, provided that the gist of the present invention is not impaired. The content ratio 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 total of the π-conjugated conductive polymer and polyanion. Here, the optional additive is a compound other than the acetylene surfactant, the polyol compound, the basic compound, and the dispersion medium.

[0066] Examples of optional additives include other surfactants, inorganic conductive agents, antifoaming agents, coupling agents, antioxidants, and ultraviolet absorbers. Other surfactants include nonionic, anionic, and cationic surfactants, with nonionic surfactants being preferred from the standpoint of storage stability. Polymer surfactants such as polyvinyl alcohol and polyvinylpyrrolidone 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.

[0067] <Method of manufacturing conductive polymer dispersion> The conductive polymer dispersion can be obtained by mixing the components by a conventional method. For example, a conductive composite containing a π-conjugated conductive polymer and a polyanion can be formed by polymerizing a monomer that forms the π-conjugated conductive polymer in a reaction solution containing a polyanion and an aqueous dispersion medium. The monomer can be polymerized, for example, by chemical oxidation. Chemical oxidative polymerization can be carried out using a known catalyst and oxidizing agent. Examples of catalysts include transition metal compounds such as ferric chloride, ferric sulfate, ferric nitrate, and cupric chloride. Examples of oxidizing agents include persulfates such as ammonium persulfate, sodium persulfate, and potassium persulfate.

[0068] The catalyst and oxidizing agent added to the reaction liquid are preferably removed from the conductive polymer dispersion after the chemical oxidative polymerization of the monomer. Examples of removal methods include a method of bringing the conductive polymer dispersion into contact with an ion exchange resin to adsorb the catalyst and oxidant onto the ion exchange resin, and a method of ultrafiltrating the conductive polymer dispersion to replace the dispersion medium and remove the catalyst and oxidant. Of these, the method using an ion exchange resin is preferred because it is simple. It is preferable to use a cation exchange resin and an anion exchange resin in combination as the ion exchange resin.

[0069] A basic compound, a polyol compound, any additives, etc. can be further added to the conductive polymer dispersion obtained above by any method. [Example]

[0070] (Production Example 1) Production of polystyrene sulfonic acid 1 206 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 obtained solution was removed under reduced pressure to obtain colorless solid polystyrene sulfonic acid (PSS). 10 g of this polystyrene sulfonic acid was dissolved in 90 g of ion-exchanged water to obtain a 10 mass % aqueous polystyrene sulfonic acid solution.

[0071] The weight-average molecular weight (Mw) of the polystyrene sulfonic acid aqueous solution obtained above was measured by gel permeation chromatography (GPC) using pullulan of known weight-average molecular weight as the standard substance, and the weight-average molecular weight was found to be 200,000.

[0072] The weight-average molecular weight was measured using a Prominence high-performance liquid chromatograph manufactured by Shimadzu Corporation, using 0.1% aqueous NaNO3 solution as the solvent, a Shodex OHpack SB-806M HQ column, and a RID-20A detector. The solvent temperature was set to 40°C, the flow rate was set to 0.6 ml / min, the PSS concentration in the sample was set to 0.1% by mass, and 100 μl of the sample filtered through a membrane filter with a pore size of 0.2 μm was injected, and the measurement was performed using the Lab Solutions analysis software (Shimadzu Corporation).

[0073] (Production Example 2) Production of polystyrene sulfonic acid 2 206 g of sodium styrenesulfonate was dissolved in 1000 ml of ion-exchanged water, and while stirring at 80°C, 0.38 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. Next, 10 g of the obtained polystyrene sulfonic acid was dissolved in 90 g of ion-exchanged water to obtain a 10 mass % aqueous polystyrene sulfonic acid solution. The weight average molecular weight of the polystyrene sulfonic acid (PSS) obtained above, measured by GPC in the same manner as in Production Example 1, was 540,000.

[0074] (Manufacturing Example 3) 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.

[0075] Example 1: Preparation of conductive polymer dispersion 5.7 g of 3,4-ethylenedioxythiophene (EDOT), 144.7 g of polystyrene sulfonic acid (10% by mass aqueous solution) of Production Example 1, and 773.6 g of ion-exchanged water were mixed at 25°C. The resulting mixed solution was kept at 25°C and 19.2 g of a 6% aqueous solution of ferric sulfate was added while stirring. Next, 56.8 g of an 11% aqueous solution of sodium persulfate was added, and the resulting reaction solution was stirred for 8 hours to react. Through the above reaction, a conductive polymer dispersion was obtained containing poly(3,4-ethylenedioxythiophene), a π-conjugated conductive polymer, a conductive complex (PEDOT-PSS) containing polystyrene sulfonic acid, and water, which is a dispersion medium.

[0076] When the obtained conductive polymer dispersion was analyzed by GPC, the amount of unpolymerized EDOT was below the detection limit.

[0077] To this conductive polymer dispersion, 132 g of Duolite C255LFH (a cation exchange resin manufactured by Sumika Chemtex Corporation) and 132 g of Duolite A368MS (an anion exchange resin manufactured by Sumika Chemtex Corporation) were added, and the mixture was filtered to remove the ion exchange resin, yielding 850 g of a conductive polymer dispersion from which the oxidizing agent and the catalyst had been removed, and the solid content (non-volatile components) was measured. Next, water was distilled off under reduced pressure from the obtained conductive polymer dispersion using an evaporator to make the solid content 1.6% by mass. Imidazole was added to 100 g of the obtained conductive polymer dispersion to adjust the pH to 2.5, and 8 g of diethylene glycol and 0.14 g of an ethoxylated acetylene surfactant, 2,4,7,9-tetramethyl-5-decyne-4,7-diol (average number of moles of EO added: 4), were added. The breakdown of each component in the conductive polymer dispersion liquid obtained here (to be used for subsequent immersion) relative to a total of 100 parts by mass of PEDOT, PSS, and acetylene-based surfactant is 26.0 parts by mass of PEDOT, 65.9 parts by mass of PSS, and 8.1 parts by mass of the acetylene-based surfactant.

[0078] The capacitor element obtained in Production Example 3 was immersed in the above conductive polymer dispersion under reduced pressure, and then dried for 30 minutes in a hot air dryer at 125°C to form a solid electrolyte layer containing a conductive composite on the surface of the dielectric layer. Next, the capacitor element having the solid electrolyte layer formed thereon was loaded into an aluminum case and sealed with a sealing rubber to prepare a capacitor.

[0079] Example 2 A capacitor was produced in the same manner as in Example 1, except that the amount of ethoxylated 2,4,7,9-tetramethyl-5-decyne-4,7-diol (average number of moles of EO added: 4) was changed to 0.28 g. The breakdown of each component relative to a total of 100 parts by mass of PEDOT, PSS, and acetylene-based surfactant contained in the conductive polymer dispersion obtained in this example is 24.1 parts by mass of PEDOT, 61.0 parts by mass of PSS, and 14.9 parts by mass of the acetylene-based surfactant.

[0080] Example 3 A capacitor was produced in the same manner as in Example 1, except that the amount of ethoxylated 2,4,7,9-tetramethyl-5-decyne-4,7-diol (average number of moles of EO added: 4) was changed to 0.42 g. The breakdown of each component relative to a total of 100 parts by mass of PEDOT, PSS, and acetylene-based surfactant contained in the conductive polymer dispersion obtained in this example is 22.4 parts by mass of PEDOT, 56.8 parts by mass of PSS, and 20.8 parts by mass of the acetylene-based surfactant.

[0081] Example 4 A capacitor was prepared in the same manner as in Example 1, except that the ethoxylated 2,4,7,9-tetramethyl-5-decyne-4,7-diol (average number of moles of EO added: 4) in Example 1 was replaced with the ethoxylated 2,4,7,9-tetramethyl-5-decyne-4,7-diol (average number of moles of EO added: 2).

[0082] Example 5 A capacitor was prepared in the same manner as in Example 1, except that the ethoxylated 2,4,7,9-tetramethyl-5-decyne-4,7-diol (average number of moles of EO added: 4) in Example 1 was replaced with an ethoxylated 2,4,7,9-tetramethyl-5-decyne-4,7-diol (average number of moles of EO added: 10).

[0083] Example 6 A capacitor was prepared in the same manner as in Example 1, except that the ethoxylated 2,4,7,9-tetramethyl-5-decyne-4,7-diol (average number of moles of EO added: 4) in Example 1 was replaced with an ethoxylated 2,4,7,9-tetramethyl-5-decyne-4,7-diol (average number of moles of EO added: 22).

[0084] Example 7 A capacitor was produced in the same manner as in Example 1, except that the ethoxylated product of 2,4,7,9-tetramethyl-5-decyne-4,7-diol (average number of moles of EO added: 4) was replaced with 3,5-dimethyl-1-hexyn-3-ol.

[0085] Example 8 A capacitor was produced in the same manner as in Example 1, except that the ethoxylated product of 2,4,7,9-tetramethyl-5-decyne-4,7-diol (average number of moles of EO added: 4) was replaced with 3,6-dimethyl-4-octyne-3,6-diol.

[0086] Example 9 A capacitor was fabricated in the same manner as in Example 1, except that the polystyrene sulfonic acid (10 mass % aqueous solution) in Production Example 1 was changed from 144.7 g to 91.3 g, and the water was changed to 813.0 g. The breakdown of each component relative to a total of 100 parts by mass of PEDOT, PSS, and acetylene-based surfactant contained in the conductive polymer dispersion obtained in this example is 35.3 parts by mass of PEDOT, 56.7 parts by mass of PSS, and 8.0 parts by mass of the acetylene-based surfactant.

[0087] Example 10 A capacitor was fabricated in the same manner as in Example 1, except that 130.7 g of polystyrene sulfonic acid (10% by mass aqueous solution, Mw: 200,000) of Production Example 1 was replaced with 130.7 g of polystyrene sulfonic acid (10% by mass aqueous solution, Mw: 540,000) of Production Example 2.

[0088] (Comparative Example 1) A capacitor was produced in the same manner as in Example 1, except that the ethoxylated 2,4,7,9-tetramethyl-5-decyne-4,7-diol (average number of moles of EO added: 4) was not added.

[0089] (Comparative Example 2) A capacitor was produced in the same manner as in Example 9, except that the ethoxylated 2,4,7,9-tetramethyl-5-decyne-4,7-diol (average number of moles of EO added: 4) was not added.

[0090] (Comparative Example 3) A capacitor was produced in the same manner as in Example 10, except that the ethoxylated 2,4,7,9-tetramethyl-5-decyne-4,7-diol (average number of moles of EO added: 4) was not added.

[0091] [pH measurement] The pH was measured at 25°C by a conventional method using a commercially available pH meter.

[0092] [Viscosity measurement method] A conductive polymer dispersion liquid prepared to a solids content of 1.6% by mass was obtained as described in Example 1, and this was dispersed using a high-pressure homogenizer. The viscosity of the sample 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 converted to 1000 cP (centipoise).

[0093] <Evaluation> [Capacitance / Equivalent Series Resistance] For each capacitor, 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 (NF Corporation). After measuring the initial ESR, the capacitor was subjected to a heat treatment by leaving it in a thermostatic chamber at 145°C for 300 hours, and then the ESR was measured again. The measurement results are shown in Table 1.

[0094] [Table 1]

[0095] From the above, in the examples of the present invention, the solid electrolyte layer of the capacitor contained an acetylene-based surfactant together with the PEDOT-PSS composite, which reduced the initial ESR of the capacitor and suppressed the increase in ESR after heat treatment. Furthermore, Example 1, which used an ethoxylated acetylene surfactant, had a better ESR rating than Examples 7 and 8, which used a non-ethoxylated surfactant in the same blending amount. [Explanation of symbols]

[0096] 10 Capacitors 11 Anode 12 Dielectric layer 13 Cathode 14 Solid electrolyte layer

Claims

1. A capacitor comprising: an anode made of a porous valve metal body; a dielectric layer formed on a surface of the anode; a solid electrolyte layer formed on the surface of the dielectric layer; and a cathode sandwiching the solid electrolyte layer between the anode and the cathode, The capacitor, wherein the solid electrolyte layer contains a conductive complex containing a π-conjugated conductive polymer and a polyanion, and an acetylene-based surfactant.

2. The capacitor according to claim 1 , wherein the acetylene-based surfactant has one or more hydroxyl groups in the molecule.

3. The capacitor according to claim 2 , wherein the acetylene surfactant is an ethoxylated product in which one or more of the hydroxyl groups have been reacted with ethylene oxide.

4. The capacitor according to claim 1 , wherein the acetylene-based surfactant is a compound represented by formula (2) or formula (3). 【Chemical 1】 [In formula (2), R ３ , R ４ , R ５ , R ６ each independently represents an alkyl group having 1 to 5 carbon atoms, l and m each independently represents an integer of 0 to 25, and l+m is 0 to 40. ７ , R ８ each independently represents an alkyl group having 1 to 5 carbon atoms, and n is an integer of 0 to 25.

5. 5. The capacitor according to claim 4, wherein a content of the acetylene-based surfactant relative to a total mass of the π-conjugated conductive polymer, the polyanion, and the acetylene-based surfactant contained in the solid electrolyte layer is 1 mass % or more and 50 mass % or less.

6. 6. The capacitor according to claim 5, wherein a content of the π-conjugated conductive polymer is 5% by mass or more and 30% by mass or less, and a content of the polyanion is 30% by mass or more and 80% by mass or less, relative to a total mass of the π-conjugated conductive polymer, the polyanion, and the acetylene surfactant contained in the solid electrolyte layer.

7. The π-conjugated conductive polymer is poly(3,4-ethylenedioxythiophene), or the polyanion is polystyrene sulfonic acid, or 7. The capacitor according to claim 6, wherein the π-conjugated conductive polymer is poly(3,4-ethylenedioxythiophene) and the polyanion is polystyrene sulfonic acid.

8. The capacitor of claim 7 , wherein the solid electrolyte layer comprises imidazole.

9. The capacitor of claim 8 , wherein the solid electrolyte layer comprises diethylene glycol.

10. A method for manufacturing a capacitor, comprising the steps of applying a conductive polymer dispersion containing a π-conjugated conductive polymer, a polyanion, an acetylene-based surfactant, and an aqueous dispersion medium 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 polymer dispersion to form a solid electrolyte layer.

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