Capacitor and method for manufacturing the same

Abstract

To provide a capacitor of decreased equivalent series resistance, and a manufacturing method thereof.SOLUTION: A capacitor (10) comprises: a positive electrode (11) composed of a valve metal porous body; a dielectric layer (12) made of oxide of the valve metal; a negative electrode (13) made of a conductive substance and provided on a side of the dielectric layer opposite to the positive electrode; and a solid electrolyte layer (14) formed between the dielectric layer and the negative electrode. The solid electrolyte layer contains a conductive complex including a π conjugate-based conductive polymer and a polyanion. The solid electrolyte layer is formed by a cured product of a particular coating material composition. The coating material composition contains a particular conductive polymer fluid dispersion including the conductive complex and a dispersion medium.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a capacitor provided with a solid electrolyte layer containing a π-conjugated conductive polymer and a method for manufacturing the same.

Background Art

[0002] A capacitor is known in which a solid electrolyte layer containing a conductive composite containing a π-conjugated conductive polymer and a polyanion is disposed between a dielectric layer and a cathode (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The solid electrolyte layer of the capacitor of Patent Document 1 contains a sulfide represented by a specific chemical formula in addition to the conductive composite, so that the equivalent series resistance (ESR) is reduced and the heat resistance is also improved. On the other hand, there may be a demand for a capacitor in which the equivalent series resistance is reduced regardless of the above sulfide. The present invention provides a capacitor with reduced equivalent series resistance and a method for manufacturing the same.

Means for Solving the Problems

[0005] [1] A capacitor comprising an anode made of a porous body of valve metal, a dielectric layer made of an oxide of the valve metal, a cathode made of a conductive material provided on the side opposite to the anode of the dielectric layer, and a solid electrolyte layer formed between the dielectric layer and the cathode, wherein the solid electrolyte layer contains a conductive composite containing a π-conjugated conductive polymer and a polyanion, the solid electrolyte layer is formed by a cured product of a paint composition, the paint composition contains a conductive polymer dispersion liquid composed of the conductive composite and a dispersion medium, the conductive polymer dispersion liquid shows a viscosity of 26 cp or less at 25 ° C when the conductive composite is contained at 1.0% by mass, and the conductive polymer dispersion liquid is such that when a mixed liquid composed of the conductive polymer dispersion liquid:propylene glycol:methanol = 95:5:200 by mass ratio is formed, the surface resistance value of the cured product of the coating film coated with the mixed liquid having a thickness of 17.5 μm or more and 18.4 μm or less is 1590 Ω / square or less. [2] The capacitor according to [1], wherein the paint composition further contains a basic compound. [3] The capacitor according to [2], wherein the basic compound is a nitrogen-containing aromatic compound. [4] The capacitor according to any one of [1] to [3], wherein the paint composition further contains a polyol compound containing two or more hydroxyl groups. [5] The capacitor according to [4], wherein the polyol compound is diethylene glycol. [6] The capacitor according to any one of [1] to [5], wherein the π-conjugated conductive polymer is poly(3,4-ethylenedioxythiophene). [7] The capacitor according to any one of [1] to [6], wherein the polyanion is polystyrene sulfonic acid. [8] The capacitor according to any one of [1] to [7], wherein the dispersion medium constituting the conductive polymer dispersion liquid is water. [9] The capacitor according to any one of [1] to [8], wherein the content of the π-conjugated conductive polymer and the polyanion with respect to the total mass of the paint composition is 1.0% by mass or more and 2.0% by mass or less. A method for manufacturing a capacitor, comprising a step of applying the coating composition according to any one of [1] to [9] onto the surface of a dielectric layer formed on the surface of an anode made of a porous body of valve metal and drying to form a solid electrolyte layer.

Advantages of the Invention

[0006] In the capacitor of the present invention, the equivalent series resistance is reduced because the solid electrolyte layer is a cured product of a specific coating composition. According to the method for manufacturing the capacitor of the present invention, the above capacitor can be easily manufactured.

[0007] The present invention is considered to contribute to SDGs Goal 12, "Responsibility for Production and Consumption".

[0008] In this specification and the claims, the lower limit value and the upper limit value of the numerical range indicated by "~" are included in the numerical range.

Brief Description of the Drawings

[0009]

Figure 1

Embodiments for Carrying Out the Invention

[0010] 《Capacitor》 The first aspect of the present invention is a capacitor. An example of its embodiment will be described. The capacitor 10 shown in FIG. 1 includes an anode 11 made of a porous body of valve metal, a dielectric layer 12 made of an oxide of valve metal, a solid electrolyte layer 14 formed on the surface of the dielectric layer 12, and a cathode 13 provided on the outermost side. The cathode 13 is provided on the side opposite to the anode 11 with the dielectric layer 12 and the solid electrolyte layer 14 interposed therebetween.

[0011] Examples of the valve metal constituting the anode 11 include aluminum, tantalum, niobium, titanium, hafnium, zirconium, zinc, tungsten, bismuth, antimony, etc. Among these, aluminum, tantalum, and niobium are preferable. As specific examples of the anode 11, there are those obtained by etching an aluminum foil to increase the surface area and then subjecting the surface to an oxidation treatment, and those obtained by subjecting the surface of a sintered body of tantalum particles or niobium particles to an oxidation treatment to form pellets. Those processed in this way become porous bodies with uneven surfaces formed thereon.

[0012] The dielectric layer 12 in the present embodiment is a layer formed by oxidizing the surface of the anode 11. For example, it is formed by anodizing the surface of the metal anode 11 in an electrolytic solution such as an ammonium adipate aqueous solution. Similar to the anode 11, unevenness is also formed in the dielectric layer 12.

[0013] As the cathode 13 in the present embodiment, a metal layer made of a conductive substance such as a conductive layer formed from a conductive paste or an aluminum foil can be used.

[0014] The solid electrolyte layer 14 in the present embodiment is formed on the surface of the dielectric layer 12. The solid electrolyte layer 14 covers at least a part of the surface of the dielectric layer 12 and may cover the entire surface of the dielectric layer 12. The thickness of the solid electrolyte layer 14 may be constant or may not be constant. For example, the thickness may be 1 μm or more and 100 μm or less.

[0015] <Conductive composite> The conductive composite contained in the solid electrolyte layer will be described. The conductive composite of this aspect contains a π-conjugated conductive polymer and a polyanion. The polyanion in the conductive composite dopes the π-conjugated conductive polymer to form a conductive composite having conductivity. In the polyanion, only some of the anion groups dope the π-conjugated conductive polymer, and it has surplus anion groups that do not participate in the doping. Since the surplus anion groups are hydrophilic groups, the conductive composite has water dispersibility.

[0016] (π-conjugated conductive polymer) As the π-conjugated conductive polymer, any organic polymer whose main chain is composed of a π-conjugated system may be used. 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 preferable, and from the viewpoint of transparency, polythiophene-based conductive polymers are more preferable.

[0017] Examples of polythiophene-based conductive polymers include polythiophene, poly(3-methylthiophene), poly(3-ethylthiophene), poly(3-propylthiophene), poly(3-butylthiophene), poly(3-hexylthiophene), poly(3-heptylthiophene), poly(3-octylthiophene), poly(3-decylthiophene), poly(3-dodecylthiophene), poly(3-octadecylthiophene), poly(3-bromothiophene), poly(3-chlorothiophene), poly(3-iodothiophene), poly(3-cyanothiophene), poly(3-phenylthiophene), poly(3,4-dimethylthiophene), poly(3,4-dibutylthiophene), poly(3-hydroxy-thiophene), poly(3-methoxythiophene), poly(3-ethoxythiophene), poly(3-butoxythiophene), poly(3-hexyloxythiophene), poly(3-heptyloxythiophene), poly(3-octyloxythiophene), poly(3-decyloxythiophene), poly(3-dodecyloxythiophene), poly(3-octadecyloxythiophene), poly(3,4-dihydroxy-thiophene), 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-didodecyloxythiophene), 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 π-conjugated conductive polymer contained in the conductive composite may be one type or two or more types.

[0018] (Polyanion) A polyanion is a polymer having two or more monomer units having anionic groups in the molecule. The anionic groups of this polyanion function as dopants for the π-conjugated conductive polymer and improve 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 polystyrene sulfonic acid, polyvinyl sulfonic acid, polyallyl sulfonic acid, polyacrylate esters having a sulfo group, polymethacrylate esters having a sulfo group (for example, poly(4-sulfobutyl methacrylate), polysulfoethyl methacrylate, polymethacryloyloxybenzene sulfonic acid), polymers having a sulfo group such as poly(2-acrylamido-2-methylpropanesulfonic acid), polyisoprene sulfonic acid, and polymers having a carboxy group such as polyvinyl carboxylic acid, polystyrene carboxylic acid, polyallyl carboxylic acid, polyacrylic acid, polymethacrylic acid, poly(2-acrylamido-2-methylpropane carboxylic acid), polyisoprene carboxylic acid. The polyanion may be a homopolymer obtained by polymerizing a single monomer, or may be a copolymer obtained by polymerizing two or more monomers. Among these polyanions, polymers having a sulfo group are preferred, and polystyrene sulfonic acid is more preferred because the conductivity can be made higher. The polyanion 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, and more preferably 100,000 or more and 500,000 or less. The mass average molecular weight is the average molecular weight on a mass basis measured by gel filtration chromatography and determined in terms of pullulan.

[0019] In the conductive composite, the content ratio of the polyanion is preferably in the range of, for example, 1 part by mass or more and 1000 parts by mass or less, more preferably 10 parts by mass or more and 700 parts by mass or less, and even more preferably 100 parts by mass or more and 500 parts by mass or less with respect to 100 parts by mass of the π-conjugated conductive polymer. If the content ratio of the polyanion is at least the above lower limit, the doping effect on the π-conjugated conductive polymer tends to be stronger and the conductivity becomes higher. On the other hand, if the content of the polyanion is at most the above upper limit, the π-conjugated conductive polymer can be sufficiently contained, so that sufficient conductivity can be ensured.

[0020] The content of the conductive composite with respect to the total mass of the solid electrolyte layer is preferably 1% by mass or more and 99% by mass or less, more preferably 50% by mass or more and 98% by mass or less, and even more preferably 70% by mass or more and 97% by mass or less. When it is within the above range, the equivalent series resistance of the capacitor is more likely to decrease, which is preferable.

[0021] <Basic compound> The solid electrolyte layer of this embodiment may further contain a basic compound different from the conductive composite and the polyanion. By containing the basic compound, the ESR of the capacitor can be further reduced.

[0022] The basic compound functions as a Bronsted base that extracts protons from the excess anion groups of the polyanion. To fulfill this function, the dissolution amount of the basic compound used in the present invention in water is preferably 0.001 g or more with respect to 100 g of water at 20°C. The upper limit value of the dissolution amount is not particularly limited, but for example, even if it is about 0.1 g, the above function can be sufficiently fulfilled.

[0023] As the basic compound, organic or inorganic basic compounds containing nitrogen, hydroxides of alkali metals or Group 2 metals, various carbonates and bicarbonates, etc. can be used. For example, hydroxides of alkali metals, quaternary ammonium hydroxides or their salts, ammonia, amines, etc. can be mentioned. Specific examples of the hydroxides of alkali metals include potassium hydroxide, sodium hydroxide, etc. Specific examples of the carbonates or bicarbonates include ammonium bicarbonate, ammonium carbonate, potassium bicarbonate, potassium carbonate, sodium bicarbonate, sodium carbonate, etc. Specific examples of the quaternary ammonium hydroxides or their salts include tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrabutylammonium hydroxide, etc.

[0024] Examples of the amines include aliphatic tertiary amines, nitrogen-containing aromatic compounds, etc. Examples of the aliphatic tertiary amine include triethanolamine, trimethylamine, triethylamine, tripropylamine, tributylamine, trihexylamine, trioctylamine, triphenylamine, tribenzylamine, trinaphthylamine, and the like.

[0025] Examples of the nitrogen-containing aromatic compound (aromatic compound 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, 1-cyanoethyl-2-ethyl-4-methylimidazole, 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 their alkyl-substituted products (e.g., products substituted with an alkyl group having 1 to 4 carbon atoms such as methyl, ethyl, propyl, butyl, etc.), halogen-substituted products (e.g., products substituted with a halogen group such as fluoro, chloro, bromo, etc.), and nitrile-substituted products. Among them, the nitrogen-containing aromatic compound is preferable, and imidazole is more preferable.

[0026] The basic compound contained in the solid electrolyte layer may be one kind or two or more kinds. The content ratio of the basic compound contained in the solid electrolyte layer is preferably, for example, 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 still more preferably 10 parts by mass or more and 50 parts by mass or less with respect to 100 parts by mass of the conductive composite. When it is within the above preferable range, the ESR of the capacitor can be further reduced.

[0027] <Polyol compound> The solid electrolyte layer of this aspect may further contain one or more compounds having two or more hydroxy groups (hereinafter sometimes referred to as polyol compounds), which are different from the conductive composite, the polyanion, and the basic compound. By containing a polyol compound, the ESR of the capacitor can be further reduced.

[0028] 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.

[0029] The total content of the polyol compound 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 with respect to 100 parts by mass in total of the π-conjugated system conductive polymer and the polyanion contained in the solid electrolyte layer (that is, 100 parts by mass of the conductive composite). It is preferable that the ESR of the capacitor is more likely to decrease within the above range. The type of the polyol compound contained in the solid electrolyte layer may be one type or two or more types.

[0030] [Electrolyte solution] The capacitor of this aspect may have an electrolyte solution that impregnates the solid electrolyte layer. Examples of the solvent constituting the electrolyte solution include alcohol solvents such as ethylene glycol, diethylene glycol, propylene glycol, 1,4-butanediol, and glycerin, lactone solvents such as γ-butyrolactone, γ-valerolactone, and δ-valerolactone, sulfur solvents such as sulfolane, dimethyl sulfoxide, and dimethyl sulfone, amide solvents such as N-methylformamide, N,N-dimethylformamide, N-methylacetamide, and N-methylpyrrolidinone, nitrile 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, 1,6-decanedicarboxylic acid, 5,6-decanedicarboxylic acid, octanedicarboxylic acids such as 1,7-octanedicarboxylic acid, azelaic acid, sebacic acid; or boric acid, a polyhydric alcohol complex compound of boric acid obtained from boric acid and a polyhydric alcohol; inorganic acids such as phosphoric acid, carbonic acid, silicic acid, etc. as the anion component, 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 the cation component; and the like.

[0031] 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. Examples of the capacitor having a separator provided between the dielectric layer and the cathode include a wound capacitor. Examples of the separator include sheets (including non-woven fabrics) made of cellulose, polyvinyl alcohol, polyester, polyethylene, polystyrene, polypropylene, polyimide, polyamide, polyvinylidene fluoride, etc., non-woven fabrics of glass fibers, and the like. The density of the separator is, for example, 0.1 g / cm 3 to 1.0 g / cm 3 are as follows. When providing a separator, a method of forming a cathode by impregnating the separator with a carbon paste or a silver paste can also be applied.

[0032] <Paint Composition> The solid electrolyte layer included in the capacitor of this aspect is formed by a cured product of a paint composition. The paint composition includes a conductive polymer dispersion liquid composed of the conductive composite and a dispersion medium. The paint composition may include optional components other than the conductive composite and the dispersion medium.

[0033] [Conductive Polymer Dispersion Liquid] When the conductive polymer dispersion liquid included in the paint composition contains 1.0 mass% (i.e., 0.95 mass% or more and 1.04 mass% or less) of the conductive composite (i.e., π-conjugated conductive polymer and polyanion), it shows a viscosity of 26 c P or less at 25°C as follows. Here, the viscosity of the conductive polymer dispersion liquid is the viscosity measured alone for the conductive polymer dispersion liquid before constituting the paint composition. When the viscosity is 26 cP or less, a solid electrolyte layer with high adhesion to the dielectric layer and reduced contact resistance can be formed. The lower limit value of the viscosity is not particularly limited, and 1 cP or more can be mentioned as a guideline. The viscosity is a value measured at 25°C using a tuning fork vibration viscometer in accordance with JIS Z8803:2011 (Viscosity Measurement Method by Vibration Viscometer).

[0034] The content ratio of the conductive polymer dispersion liquid to the total mass of the paint composition is preferably 80 mass% or more and 100 mass% or less, more preferably 85 mass% or more and 99 mass% or less, and even more preferably 90 mass% or more and 98 mass% or less. When it is within the above preferred range, the ESR of the capacitor having a solid electrolyte layer formed from the paint composition can be further reduced.

[0035] The content of the dispersion medium included in the conductive polymer dispersion liquid of the paint composition is preferably 95.0 mass% or more and 99.9 mass% or less, more preferably 97.5 mass% or more and 99.5 mass% or less, and even more preferably 98.0 mass% or more and 99.0 mass% or less with respect to the total mass of the conductive polymer dispersion liquid. When it is within the above preferable range, the ESR of the capacitor having the solid electrolyte layer formed from the paint composition can be further reduced.

[0036] The content of the conductive composite (i.e., π-conjugated conductive polymer and polyanion) contained in the conductive polymer dispersion of the paint composition is preferably 0.1% by mass or more and 5.0% by mass or less, more preferably 0.5% by mass or more and 2.5% by mass or less, and even more preferably 1.0% by mass or more and 2.0% by mass or less with respect to the total mass of the conductive polymer dispersion. When it is within the above preferable range, the ESR of the capacitor having the solid electrolyte layer formed from the paint composition can be further reduced.

[0037] The content of the conductive composite (i.e., π-conjugated conductive polymer and polyanion) contained in the paint composition is preferably 0.1% by mass or more and 5.0% by mass or less, more preferably 0.5% by mass or more and 2.5% by mass or less, and even more preferably 1.0% by mass or more and 2.0% by mass or less with respect to the total mass of the conductive polymer dispersion. When it is within the above preferable range, the ESR of the capacitor having the solid electrolyte layer formed from the paint composition can be further reduced.

[0038] The conductive polymer dispersion contained in the paint composition may contain optional components other than the conductive composite and the dispersion medium, but it is preferably free of optional components.

[0039] (Dispersion medium) The dispersion medium constituting the conductive polymer dispersion liquid contained in the coating composition is not particularly limited as long as it is a liquid capable of dispersing the conductive composite. For example, water, an organic solvent, or a mixture of water and an organic solvent can be mentioned. The conductive composite has an excess anion group derived from polyanion and has high dispersibility in water, so an aqueous dispersion medium is preferred. Here, the aqueous dispersion medium is water or a mixture of water and a water-soluble organic solvent. The water-soluble organic solvent is an organic solvent with a solubility of 1 g or more in 100 g of water at 20°C. For example, alcohol solvents, ketone solvents, and ester solvents can be mentioned. The water-soluble organic solvent contained in the aqueous dispersion medium may be one type or two or more types.

[0040] The water content with respect to the total mass of the aqueous dispersion medium is 50% by mass or more, preferably 60% by mass or more, more preferably 80% by mass or more, and may be 100% by mass.

[0041] Examples of the alcohol solvent include methanol, ethanol, isopropanol, n-butanol, t-butanol, allyl alcohol, and the like. Examples of the ketone solvent include diethyl ketone, methyl propyl ketone, methyl butyl ketone, methyl isopropyl ketone, methyl isobutyl ketone, methyl amyl ketone, diisopropyl ketone, methyl ethyl ketone, acetone, diacetone alcohol, and the like.

[0042] The conductive polymer dispersion (conductive composite concentration: 1.0% by mass, viscosity: 26 cP or less) that constitutes the coating composition, when separately forming a mixed liquid by mixing the conductive polymer dispersion: propylene glycol: methanol at a mass ratio of 95:5:200 independently of the coating composition, should have a surface resistance value of the cured product of the coating film coated with the mixed liquid of 1590 Ω / sq or less, where the coating film has a thickness of 17.5 μm or more and 18.4 μm or less. Here, the coating film is formed on the surface of an arbitrary insulating substrate. Examples of the insulating substrate include PET films. By applying the mixed liquid with a bar coater (e.g., #8 - 12), a coating film with a thickness of 18 μm can be formed. By drying the coating film, a cured product of the coating film is formed. The ESR of a capacitor having a solid electrolyte layer formed by a cured product of a coating composition based on the conductive polymer dispersion with a surface resistance value of 1590 Ω / sq or less is sufficiently reduced.

[0043] (Basic compound) The coating composition may contain the aforementioned basic compound. The content of the basic compound contained in the coating composition is preferably, for example, 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 with respect to a total of 100 parts by mass of the π-conjugated conductive polymer and polyanion (i.e., 100 parts by mass of the conductive composite). When within the above preferred range, the ESR of the capacitor can be further reduced.

[0044] The content of the basic compound contained in the coating composition preferably results in a pH of the conductive polymer dispersion (at 25 °C) of 2.0 - 8.0, more preferably 2.0 - 5.0, and even more preferably 2.0 - 3.0. When within the above preferred range, the ESR of the capacitor can be further reduced.

[0045] (Polyol compound) The paint composition may contain the aforementioned polyol compound. The content of the polyol compound contained in the paint composition is preferably, for example, 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 with respect to a total of 100 parts by mass of the π-conjugated conductive polymer and the polyanion (i.e., 100 parts by mass of the conductive composite). Within the above preferred range, the ESR of the capacitor can be further reduced.

[0046] The content of the polyol compound with respect to the total mass of the paint composition is preferably 1% by mass or more and 15% by mass or less, more preferably 3% by mass or more and 12% by mass or less, and even more preferably 5% by mass or more and 9% by mass or less. When within the above preferred range, the coating property of the paint composition is improved, and the ESR of the capacitor can be further reduced.

[0047] (Optional additive) The paint composition may contain an optional additive, and its content ratio can be appropriately determined according to the type of the additive. For example, it can be 1 to 1,000 parts by mass with respect to a total of 100 parts by mass of the π-conjugated conductive polymer and the polyanion (i.e., 100 parts by mass of the conductive composite). Here, the optional additive is a compound other than the conductive composite, the basic compound, the polyol compound, and the dispersion medium.

[0048] Examples of the optional additive include surfactants, inorganic conductive agents, defoamers, coupling agents, antioxidants, ultraviolet absorbers, and the like. Examples of the surfactant include nonionic, anionic, and cationic surfactants, and nonionic surfactants are preferred from the viewpoint of storage stability. Also, polymer surfactants such as polyvinyl alcohol and polyvinyl pyrrolidone may be added. Examples of the inorganic conductive agent include metal ions and conductive carbon. Metal ions can be generated by dissolving a metal salt in water. Examples of the defoaming agent include silicone resin, polydimethylsiloxane, silicone oil, and the like. Examples of the coupling agent include silane coupling agents having a vinyl group, an amino group, an epoxy group, and the like. Examples of the antioxidant include phenolic antioxidants, amine antioxidants, phosphorus antioxidants, sulfur antioxidants, saccharides, and the like. 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, benzoate-based ultraviolet absorbers, and the like.

[0049] <Method for producing conductive polymer dispersion> The conductive polymer dispersion is preferably produced by the following method. That is, in a reaction solution containing a polyanion and a dispersion medium, a monomer that forms a π-conjugated conductive polymer is polymerized to obtain a conductive polymer dispersion containing the π-conjugated conductive polymer, a conductive composite containing the polyanion, and the dispersion medium (polymerization step).

[0050] The synthesis of the conductive composite in the reaction solution can be carried out in the same manner as the synthesis of the conventional conductive composite.

[0051] The dispersion medium contained in the reaction solution is preferably the aqueous dispersion medium, and more preferably water. When the dispersion medium contains water, the polymerization reaction of the monomer proceeds stably, and the obtained conductive composite is obtained in a state of being stably dispersed in the dispersion medium.

[0052] The monomers can be polymerized by chemically oxidizing the monomers. Chemical oxidative polymerization can be carried out using known catalysts and oxidizing agents. Examples of the catalyst include transition metal compounds such as ferric chloride, ferric sulfate, ferric nitrate, and cupric chloride. Examples of the oxidizing agent include persulfates such as ammonium persulfate, sodium persulfate, and potassium persulfate.

[0053] As the content of the catalyst relative to the total mass of the reaction solution immediately before the start of the polymerization reaction, for example, 0.01% by mass or more and 0.50% by mass or less can be mentioned. When the concentration of the catalyst is lowered, the surface resistance value of the conductive layer made of the cured product obtained by coating the conductive polymer dispersion (conductive composite concentration 1.0% by mass, 25 ° C) with the predetermined thickness tends to be lowered. As the content of the oxidizing agent relative to the total mass of the reaction solution immediately before the start of the polymerization reaction, for example, 0.1% by mass or more and 1.0% by mass or less can be mentioned. When the concentration of the oxidizing agent is lowered, the viscosity of the conductive polymer dispersion (conductive composite concentration 1.0% by mass, 25 ° C) tends to be lowered.

[0054] The content of the monomer relative to the total mass of the reaction solution immediately before the start of the polymerization reaction is preferably, for example, 0.01% by mass or more and 5% by mass or less, more preferably 0.1% by mass or more and 2% by mass or less, and still more preferably 0.3% by mass or more and 1% by mass or less. The content of the polyanion relative to the total mass of the reaction solution immediately before the start of the polymerization reaction is preferably, for example, 0.02% by mass or more and 10% by mass or less, more preferably 0.3% by mass or more and 5% by mass or less, and still more preferably 1% by mass or more and 3% by mass or less. By setting the above-mentioned preferred range, a conductive polymer dispersion having a concentration of the conductive composite within the above-mentioned preferred content can be easily obtained.

[0055] In the conductive composite formed by the polymerization reaction, from the viewpoint of making the content ratios of the π-conjugated conductive polymer and the polyanion the above-described preferred ratios, the content ratio of the monomer and the polyanion contained in the reaction solution immediately before the start of the polymerization reaction is preferably in the range of 1 to 1000 parts by mass, more preferably 10 to 700 parts by mass, and even more preferably 100 to 500 parts by mass with respect to 100 parts by mass of the monomer.

[0056] The mass average molecular weight of the polyanion to be subjected to the polymerization reaction is preferably 20,000 or more and 1,000,000 or less, and more preferably 100,000 or more and 500,000 or less. The mass average molecular weight is the average molecular weight on a mass basis determined in terms of pullulan using gel filtration chromatography.

[0057] By synthesizing a π-conjugated conductive polymer by chemical oxidative polymerization of the monomer, a target conductive polymer dispersion can be obtained.

[0058] It is preferable to remove the catalyst and the oxidizing agent added to the reaction solution from the conductive polymer dispersion after the chemical oxidative polymerization of the monomer. Examples of the removal method include a method of bringing the conductive polymer dispersion into contact with an ion exchange resin to adsorb the catalyst and the oxidizing agent to the ion exchange resin, and a method of removing the conductive polymer dispersion by ultrafiltration to replace the dispersion medium and remove it. Among these, the method using an ion exchange resin is preferable because it is simple. It is preferable to use a combination of a cation exchange resin and an anion exchange resin as the ion exchange resin.

[0059] The paint composition is obtained by further adding a basic compound, a polyol compound, an arbitrary additive, etc. to the conductive polymer dispersion obtained above.

[0060] 《Method for manufacturing a capacitor》 The second aspect of the present invention is a method for manufacturing a capacitor, which includes a step of applying the coating composition described in the first aspect onto the surface of a dielectric layer formed on the surface of an anode made of a porous body of valve metal, and drying it to form a solid electrolyte layer. By the manufacturing method of this aspect, the capacitor of the first aspect can be easily manufactured.

[0061] The manufacturing method of this aspect preferably includes a step of oxidizing the surface of an anode made of a porous body of valve metal to form a dielectric layer (dielectric formation step), a step of arranging a cathode at a position facing the dielectric layer (cathode formation step), and a step of forming a solid electrolyte layer on at least a part of the surface of the dielectric layer (film formation step). Hereinafter, each step will be described with reference to FIG. 1.

[0062] [Dielectric Formation Step] In this step, the surface of the anode 11 made of a porous body of valve metal is oxidized to form a dielectric layer 12. The method for forming the dielectric layer 12 is not particularly limited. For example, a method of anodizing the surface of the anode 11 in an electrolytic solution for forming treatment such as an ammonium adipate aqueous solution, an ammonium borate aqueous solution, or an ammonium phosphate aqueous solution can be mentioned.

[0063] [Cathode Formation Step] In this step, the cathode 13 is arranged at a position facing the dielectric layer 12. The method for arranging the cathode 13 is not particularly limited. For example, a method of forming the cathode 13 using a conductive paste such as a carbon paste or a silver paste, a method of arranging a metal foil such as an aluminum foil facing the dielectric layer 12, etc. can be mentioned.

[0064] [Film Formation Step] In this step, the above-mentioned coating composition is applied to at least a part of the surface of the dielectric layer 12 and dried to form a solid electrolyte layer 14.

[0065] As a method for applying the coating composition, for example, dipping (dip coating), comma coating, reverse coating, lip coating, microgravure coating, etc. can be applied. Among these, a method of immersing the anode 11 in the coating composition under reduced pressure is preferable. In the case of the immersion method, the coating composition can be sufficiently applied to the inside of the porous structure on the surface of the dielectric layer 12. After immersion, it is taken out and the next drying process is carried out.

[0066] As drying methods, for example, room temperature drying, hot air drying, far-infrared drying, etc. can be mentioned. Among these, hot air drying is preferable. As the drying temperature, for example, 100 to 180 °C is preferable, and 120 to 150 °C is more preferable. As the drying time, for example, 0.2 to 1 hour is preferable. After the drying treatment, the capacitor may be assembled by a conventional method.

Examples

[0067] (Production Example 1) Production of Polystyrene Sulfonic Acid 1 206 g of sodium styrene sulfonate was dissolved in 1000 ml of ion-exchanged water, and while stirring at 80 °C, a solution of 1.14 g of ammonium persulfate oxidant previously dissolved in 10 ml of water was added dropwise over 20 minutes, and this solution was stirred for 12 hours. To the obtained sodium polystyrene sulfonate-containing solution, 1000 ml of sulfuric acid diluted to 10 mass% was added, and about 1000 ml of the solvent of the obtained polystyrene sulfonic acid-containing solution was removed by ultrafiltration. Next, 2000 ml of ion-exchanged water was added to the residue, and about 2000 ml of the solvent was removed by ultrafiltration to wash the polystyrene sulfonic acid with water. This water washing operation was repeated 3 times. The water in the obtained 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 solution of polystyrene sulfonic acid.

[0068] By gel permeation chromatography (GPC), using pullulan with a known weight average molecular weight as a standard substance, the weight average molecular weight (Mw) of the polystyrene sulfonic acid (PSS) obtained above was measured, and the result was 180,000. The measurement of the weight average molecular weight was performed using a high performance liquid chromatograph Prominence manufactured by Shimadzu Corporation. As the solvent, 0.1% NaNO 3 aqueous solution was used, Shodex OHpack SB-806M HQ was used as the column, RID-20A was used as the detector, the solvent temperature was set at 40 °C, the flow rate was set at 0.6 ml / min, the PSS concentration in the sample was set at 0.1 mass%, and 100 μl of the sample filtered through a membrane filter with a pore size of 0.2 μm was injected, and the analysis was performed using the analysis software Lab Solutions (manufactured by Shimadzu Corporation).

[0069] (Production Example 2) Production of Polystyrene Sulfonic Acid 2 206 g of sodium styrene sulfonate was dissolved in 1000 ml of ion-exchanged water, and while stirring at 80 °C, an oxidizing agent solution of 0.38 g of ammonium persulfate previously dissolved in 10 ml of water was added dropwise over 20 minutes, and this solution was stirred for 12 hours. To the obtained sodium polystyrene sulfonate-containing solution, 1000 ml of sulfuric acid diluted to 10 mass% was added, and about 1000 ml of the solvent of the obtained polystyrene sulfonic acid-containing solution was removed by ultrafiltration. Next, 2000 ml of ion-exchanged water was added to the residue, and about 2000 ml of the solvent was removed by ultrafiltration to wash the polystyrene sulfonic acid with water. This water washing operation was repeated 3 times. The water in the obtained solution was removed under reduced pressure to obtain a 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 solution of polystyrene sulfonic acid. The weight average molecular weight of the polystyrene sulfonic acid (PSS) obtained above, measured using GPC in the same manner as in Production Example 1, was 540,000.

[0070] (Production Example 3) Fabrication of an Element for a Capacitor After connecting an anode lead terminal to an etched aluminum foil (anode foil), a voltage of 40 V was applied in a 10 mass% aqueous solution of ammonium adipate, and chemical conversion (oxidation treatment) was performed to form dielectric layers on both sides of the aluminum foil, thereby obtaining an anode foil. Next, a counter aluminum cathode foil with cathode lead terminals welded to both sides of the anode foil was laminated via a cellulose separator, and this was wound into a cylindrical shape to obtain a capacitor element.

[0071] (Example 1) 3.0 g of 3,4-ethylenedioxythiophene (EDOT), 90 g of the aqueous polystyrene sulfonic acid solution (solid content: 10 mass%) of Production Example 1, and 325 g of ion-exchanged water were mixed at 20°C. While maintaining the obtained mixed solution at 20°C and stirring, 1.8 g of ferric sulfate was added. Next, a solution prepared by dissolving 4.4 g of sodium persulfate in 295.6 g of ion-exchanged water was slowly added, and the obtained reaction solution was stirred for 8 hours to cause a reaction. By the above reaction, a conductive polymer dispersion liquid containing a conductive composite (PEDOT-PSS) containing poly(3,4-ethylenedioxythiophene), which is a π-conjugated system conductive polymer, and polystyrene sulfonic acid, and water as a dispersion medium was obtained. To this conductive polymer dispersion liquid, 39 g of Duolite C255LFH (manufactured by Sumika Chemtex Corporation, cation exchange resin) and 39 g of Duolite A368S (manufactured by Sumika Chemtex Corporation, anion exchange resin) were added, and filtration was performed to remove the ion exchange resins, thereby obtaining 710 g of conductive polymer dispersion liquid A from which the oxidizing agent and the catalyst had been removed, and the non-volatile component was measured.

[0072] Next, a part of the obtained conductive polymer dispersion A was separated, water was added thereto, and the concentration of the non-volatile component was adjusted to 1.0% by mass to obtain a conductive polymer dispersion B. When the viscosity of the conductive polymer dispersion B was measured at 25 °C, it was 25 cP. Further, a mixed solution was obtained by mixing 95 g of the conductive polymer dispersion B, 5 g of propylene glycol, and 200 g of methanol. Using a #8 bar coater, a coating film with a thickness of 18 μm was formed on a PET film (manufactured by Toray Industries, Inc., Lumirror T60), and dried at 120 °C for 1 minute to obtain a conductive film having a conductive layer formed on the surface of the PET film. When the surface resistance value of the conductive layer was measured, it was 1033 Ω / sq.

[0073] On the other hand, water was distilled off under reduced pressure from the conductive polymer dispersion A using an evaporator to make the non-volatile component 1.6% by mass. To the obtained conductive polymer dispersion C (100 g), imidazole (0.3 g) was added to adjust the pH to 2.5, and diethylene glycol (8 g) was added to obtain a coating composition.

[0074] Next, the capacitor element obtained in Production Example 3 was immersed in the above coating composition under reduced pressure, and then dried with a hot air dryer at 125 °C for 30 minutes to form a solid electrolyte layer containing a conductive composite on the surface of the dielectric layer. Finally, the capacitor element having the above solid electrolyte layer formed thereon was loaded into an aluminum case and sealed with a sealing rubber to produce a capacitor.

[0075] (Example 2) Conductive polymer dispersions A to C and a coating composition were obtained in the same manner as in Example 1, except that the solution of "4.4 g of sodium persulfate dissolved in 295.6 g of ion-exchanged water" was changed to the solution of "2.2 g of sodium persulfate dissolved in 297.8 g of ion-exchanged water", and a conductive film and a capacitor were produced. Each measured value is also shown in Table 1.

[0076] (Example 3) Except for changing "1.8 g of ferric sulfate" to "1.2 g of ferric sulfate", conductive polymer dispersions A to C and a coating composition were obtained in the same manner as in Example 1, and a conductive film and a capacitor were produced. Each measured value is also shown in Table 1.

[0077] (Example 4) Except for changing "1.8 g of ferric sulfate" to "1.2 g of ferric sulfate" and changing "a solution prepared by dissolving 4.4 g of sodium persulfate in 295.6 g of ion-exchanged water" to "a solution prepared by dissolving 2.2 g of sodium persulfate in 297.8 g of ion-exchanged water", conductive polymer dispersions A to C and a coating composition were obtained in the same manner as in Example 1, and a conductive film and a capacitor were produced. Each measured value is also shown in Table 1.

[0078] (Example 5) Except for changing "1.8 g of ferric sulfate" to "0.6 g of ferric sulfate" and changing "a solution prepared by dissolving 4.4 g of sodium persulfate in 295.6 g of ion-exchanged water" to "a solution prepared by dissolving 6.6 g of sodium persulfate in 293.4 g of ion-exchanged water", conductive polymer dispersions A to C and a coating composition were obtained in the same manner as in Example 1, and a conductive film and a capacitor were produced. Each measured value is also shown in Table 1.

[0079] (Example 6) Except for changing "1.8 g of ferric sulfate" to "0.6 g of ferric sulfate", conductive polymer dispersions A to C and a coating composition were obtained in the same manner as in Example 1, and a conductive film and a capacitor were produced. Each measured value is also shown in Table 1.

[0080] (Example 7) Except for changing "1.8 g of ferric sulfate" to "0.3 g of ferric sulfate", conductive polymer dispersions A to C and a coating composition were obtained in the same manner as in Example 1, and a conductive film and a capacitor were produced. Each measured value is also shown in Table 1.

[0081] (Example 8) Conductive polymer dispersions A to C and coating compositions were obtained in the same manner as in Example 1, except that "1.8 g of ferric sulfate" was changed to "0.15 g of ferric sulfate", and conductive films and capacitors were produced. Each measured value is also shown in Table 1.

[0082] (Comparative Example 1) Conductive polymer dispersions A to C and coating compositions were obtained in the same manner as in Example 1, except that "a solution prepared by dissolving 4.4 g of sodium persulfate in 295.6 g of ion-exchanged water" was changed to "a solution prepared by dissolving 6.6 g of sodium persulfate in 293.4 g of ion-exchanged water", and conductive films and capacitors were produced. Each measured value is also shown in Table 1.

[0083] (Comparative Example 2) Conductive polymer dispersions A to C and coating compositions were obtained in the same manner as in Example 1, except that "1.8 g of ferric sulfate" was changed to "1.2 g of ferric sulfate", and "a solution prepared by dissolving 4.4 g of sodium persulfate in 295.6 g of ion-exchanged water" was changed to "a solution prepared by dissolving 6.6 g of sodium persulfate in 293.4 g of ion-exchanged water", and conductive films and capacitors were produced. Each measured value is also shown in Table 1.

[0084] (Comparative Example 3) Conductive polymer dispersions A to C and coating compositions were obtained in the same manner as in Example 1, except that "1.8 g of ferric sulfate" was changed to "0.6 g of ferric sulfate", and "a solution prepared by dissolving 4.4 g of sodium persulfate in 295.6 g of ion-exchanged water" was changed to "a solution prepared by dissolving 2.2 g of sodium persulfate in 297.8 g of ion-exchanged water", and conductive films and capacitors were produced. Each measured value is also shown in Table 1.

[0085] (Comparative Example 4) Except for changing "1.8 g of ferric sulfate" to "0.3 g of ferric sulfate" and changing "a solution prepared by dissolving 4.4 g of sodium persulfate in 295.6 g of ion-exchanged water" to "a solution prepared by dissolving 6.6 g of sodium persulfate in 293.4 g of ion-exchanged water", conductive polymer dispersions A to C and a coating composition were obtained in the same manner as in Example 1, and a conductive film and a capacitor were produced. Each measured value is also shown in Table 1.

[0086] (Comparative Example 5) Except for changing "1.8 g of ferric sulfate" to "0.3 g of ferric sulfate" and changing "a solution prepared by dissolving 4.4 g of sodium persulfate in 295.6 g of ion-exchanged water" to "a solution prepared by dissolving 2.2 g of sodium persulfate in 297.8 g of ion-exchanged water", conductive polymer dispersions A to C and a coating composition were obtained in the same manner as in Example 1, and a conductive film and a capacitor were produced. Each measured value is also shown in Table 1.

[0087] (Comparative Example 6) Except for changing "1.8 g of ferric sulfate" to "0.15 g of ferric sulfate" and changing "a solution prepared by dissolving 4.4 g of sodium persulfate in 295.6 g of ion-exchanged water" to "a solution prepared by dissolving 6.6 g of sodium persulfate in 293.4 g of ion-exchanged water", conductive polymer dispersions A to C and a coating composition were obtained in the same manner as in Example 1, and a conductive film and a capacitor were produced. Each measured value is also shown in Table 1.

[0088] (Comparative Example 7) Except for changing "1.8 g of ferric sulfate" to "0.15 g of ferric sulfate" and changing "a solution prepared by dissolving 4.4 g of sodium persulfate in 295.6 g of ion-exchanged water" to "a solution prepared by dissolving 2.2 g of sodium persulfate in 297.8 g of ion-exchanged water", conductive polymer dispersions A to C and a coating composition were obtained in the same manner as in Example 1, and a conductive film and a capacitor were produced. Each measured value is also shown in Table 1.

[0089] (Example 9) Conductive polymer dispersions A to C and a coating composition were obtained in the same manner as in Example 1, except that the "aqueous polystyrene sulfonic acid solution (solid content: 10% by mass) of Production Example 1" was changed to the "aqueous polystyrene sulfonic acid solution (solid content: 10% by mass) of Production Example 2", and a conductive film and a capacitor were produced. Each measured value is also shown in Table 1.

[0090] (Example 10) Conductive polymer dispersions A to C and a coating composition were obtained in the same manner as in Example 1, except that "90 g of the aqueous polystyrene sulfonic acid solution (solid content: 10% by mass) of Production Example 1 and 325 g of ion-exchanged water" was changed to "150 g of the aqueous polystyrene sulfonic acid solution (solid content: 10% by mass) of Production Example 1 and 265 g of ion-exchanged water", and a conductive film and a capacitor were produced. Each measured value is also shown in Table 1.

[0091] [Measurement of Viscosity] The viscosity at 25 °C of the conductive polymer dispersion B in each example was measured using a tuning fork vibration viscometer in accordance with JIS Z8803:2011 (Viscosity Measurement Method by Vibration Viscometer).

[0092] [Measurement of Surface Resistance Value] The surface resistance value (unit: Ω / sq.) of the conductive layer of the conductive film in each example was measured using a resistivity meter (Roresta manufactured by Nitto Seiko Analytic Co., Ltd.) under the condition of an applied voltage of 10 V.

[0093] [Measurement of pH] The pH at 25 °C was measured by a conventional method using a commercially available pH meter.

[0094] [Evaluation] [Capacitance and Equivalent Series Resistance] For the capacitor in each example, the capacitance (unit: μF) at 120 Hz and the equivalent series resistance (ESR) (unit: Ω) at 100 kHz were measured using an LCR meter ZM2376 (manufactured by NF Circuit Design Block Co., Ltd.). The measurement results are shown in Table 1.

[0095] [Table 1]

[0096] It was confirmed that the equivalent series resistance of the capacitor of the example according to the present invention provided with a solid electrolyte layer formed of a cured product of a specific paint composition was significantly reduced.

Description of Reference Numerals

[0097] 10 Capacitor 11 Anode 12 Dielectric layer 13 Cathode 14 Solid electrolyte layer

Claims

1. A capacitor comprising an anode made of a porous body of valve metal, a dielectric layer made of an oxide of the valve metal, a cathode made of a conductive material provided on the side opposite to the anode of the dielectric layer, and a solid electrolyte layer formed between the dielectric layer and the cathode, wherein the solid electrolyte layer contains a conductive composite containing a π-conjugated conductive polymer and a polyanion, the solid electrolyte layer is formed by curing a paint composition, the paint composition contains 80% by mass or more of a conductive polymer dispersion liquid composed of the conductive composite and a dispersion medium with respect to its total mass, the conductive polymer dispersion liquid exhibits a viscosity of 26 cP or less at 25 °C when the conductive composite is contained at 1.0% by mass, the conductive polymer dispersion liquid is such that when a mixed liquid composed of the conductive polymer dispersion liquid:propylene glycol:methanol = 95:5:200 by mass ratio is formed, the surface resistance value of the cured product of the coating film coated with the mixed liquid having a thickness of 17.5 μm or more and 18.4 μm or less is 1590 Ω / □ or less, a capacitor.

2. The capacitor according to claim 1, wherein the paint composition further contains a basic compound.

3. The capacitor according to claim 2, wherein the basic compound is a nitrogen-containing aromatic compound.

4. The capacitor according to any one of claims 1 to 3, wherein the paint composition further contains a polyol compound containing two or more hydroxyl groups.

5. The capacitor according to claim 4, wherein the polyol compound is diethylene glycol.

6. The capacitor according to any one of claims 1 to 5, wherein the π-conjugated conductive polymer is poly(3,4-ethylenedioxythiophene).

7. The capacitor according to any one of claims 1 to 6, wherein the polyanion is polystyrene sulfonic acid.

8. The capacitor according to any one of claims 1 to 7, wherein the dispersion medium constituting the conductive polymer dispersion liquid is water.

9. The capacitor according to any one of claims 1 to 8, wherein the content of the π-conjugated conductive polymer and the polyanion with respect to the total mass of the paint composition is 1.0% by mass or more and 2.0% by mass or less.

10. A method for manufacturing a capacitor, comprising a step of applying the coating composition according to any one of claims 1 to 9 onto the surface of a dielectric layer formed on the surface of an anode made of a porous body of valve metal, and drying to form a solid electrolyte layer.

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