Method for producing a conductive polymer dispersion, and method for producing a capacitor

Abstract

To provide a conductive polymer dispersion liquid of low viscosity suitable for manufacture of a capacitor, a method for manufacturing the same and a capacitor using the conductive polymer dispersion liquid.SOLUTION: There is produced a capacitor by using a conductive polymer dispersion liquid comprising a conductive composite containing a π-conjugated conductive polymer and a polyanion, a naphthalene monosulfonic acid and an aqueous dispersion medium, for example, by applying the conductive polymer dispersion liquid to the surface of a dielectric layer formed on the surface of a positive electrode composed of a porous body of a valve metal, followed by drying to form a solid electrolyte layer.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a conductive polymer dispersion containing a π-conjugated conductive polymer, a method for producing the conductive polymer dispersion, and a capacitor.

Background Art

[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 anion group, and exhibits dispersibility in water. A capacitor provided with a solid electrolyte layer formed using such a conductive polymer dispersion (conductive polymer-containing liquid) in which the conductive complex is dispersed is known (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 a capacitor such as Patent Document 1 is formed by applying a conductive polymer dispersion to a dielectric layer formed by a chemical conversion treatment on the surface of an anode and drying and solidifying the coating film. The conductive polymer dispersion to be applied is required to penetrate into the inside of the porous dielectric layer and the narrow gap between the anode and the cathode. Therefore, the viscosity of the conductive polymer dispersion used in the production of the capacitor is preferably low.

[0005] The present invention provides a low-viscosity conductive polymer dispersion suitable for the production of a capacitor, a method for producing the same, and a capacitor using the conductive polymer dispersion.

Means for Solving the Problems

[0006] [1] A conductive polymer dispersion comprising a conductive composite containing a π-conjugated conductive polymer and a polyanion, naphthalene monosulfonic acid, and an aqueous dispersion medium. [2] The conductive polymer dispersion according to [1], wherein the water content is 70% by mass or more relative to the total mass of the aqueous dispersion medium. [3] The conductive polymer dispersion according to [1] or [2], wherein the π-conjugated conductive polymer is poly(3,4-ethylenedioxythiophene), or the polyanion is polystyrene sulfonic acid, or the π-conjugated conductive polymer is poly(3,4-ethylenedioxythiophene) and the polyanion is polystyrene sulfonic acid. [4] A conductive polymer dispersion according to any one of [1] to [3], further comprising a basic compound. [5] A conductive polymer dispersion according to any one of [1] to [4], further comprising a polyol compound. [6] A conductive polymer dispersion according to any one of [1] to [5], wherein the viscosity at 25°C is 1 cP to 50 cP. [7] A method for producing a conductive polymer dispersion, comprising a polymerization step of polymerizing monomers that form a π-conjugated conductive polymer in a reaction solution containing a polyanion, naphthalene monosulfonic acid, and an aqueous dispersion medium, thereby forming a conductive composite containing the π-conjugated conductive polymer and the polyanion. [8] The method for producing a conductive polymer dispersion according to [7], wherein the mass-based mixing ratio of the amount of polyanion H1 and the amount of naphthalene monosulfonic acid H2 in the reaction solution, expressed as H1 / H2, is 0.1 to 3.0. [9] A method for producing a conductive polymer dispersion according to [7] or [8], wherein the mass-based blending ratio of the amount of monomers forming the π-conjugated conductive polymer H3 and the amount of naphthalene monosulfonic acid H2 in the reaction solution, expressed as H3 / H2, is 0.1 to 1.0.

[10] 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 dielectric layer opposite to the anode, and a solid electrolyte layer formed between the dielectric layer and the cathode, wherein the solid electrolyte layer is a cured product of a conductive polymer dispersion according to any one of [1] to [6].

[11] A method for manufacturing a capacitor, comprising the step of applying a conductive polymer dispersion according to any one of [1] to [6] to the surface of a dielectric layer formed on the surface of an anode made of a porous valve metal, and drying it to form a solid electrolyte layer. [Effects of the Invention]

[0007] The conductive polymer dispersion of the present invention has low viscosity, making it easy to impregnate the object to be coated, and is therefore suitable for the manufacture of capacitors. According to the method for producing a conductive polymer dispersion of the present invention, a conductive polymer dispersion with low viscosity can be prepared. A capacitor equipped with a cured conductive polymer dispersion of the present invention as a solid electrolyte layer exhibits reduced equivalent series resistance (ESR) and superior performance.

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

[0009] In this specification and the claims, the lower and upper limits of the numerical ranges indicated by "~" are included within those numerical ranges. [Brief explanation of the drawing]

[0010] [Figure 1] This is a cross-sectional view showing one embodiment of the capacitor of the present invention. [Modes for carrying out the invention]

[0011] <<Conductive polymer dispersion>> A first aspect of the present invention is a conductive polymer dispersion comprising a conductive composite containing a π-conjugated conductive polymer and a polyanion, naphthalene monosulfonic acid, and an aqueous dispersion medium.

[0012] <Conductive composite> The conductive composite according to this embodiment comprises a π-conjugated conductive polymer and a polyanion. The polyanion in the conductive composite dops the π-conjugated conductive polymer to form a conductive composite. In the polyanion, only some of the anionic groups dopate the π-conjugated conductive polymer, and there are excess anionic groups that do not participate in doping. Since the excess anionic groups are hydrophilic groups, the conductive composite is water-dispersible.

[0013] The conductive composite in this embodiment contains naphthalene monosulfonic acid. The sulfonic acid group of naphthalene monosulfonic acid can dope π-conjugated conductive polymers, similar to the anionic group of polyanions. Furthermore, naphthalene monosulfonic acid is a molecule possessing π electrons and can be stabilized in a stacked configuration by π-π interactions with π-conjugated conductive polymers. Thus, it is presumed that the presence of naphthalene monosulfonic acid in the conductive composite makes the molecular motion of the conductive composite in the dispersion rigid, resulting in a lower viscosity of the dispersion.

[0014] (π-conjugated conductive polymers) Any organic polymer whose main chain is composed of a π-conjugated system can be used as the π-conjugated conductive polymer. Examples 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.

[0015] Examples of polythiophene-based conductive polymers include polythiophene, poly(3-methylthiophene), poly(3-ethylthiophene), poly(3-propylthiophene), poly(3-butylthiophene), poly(3-hexylthiophene), poly(3-heptylthiophene), poly(3-octylthiophene), poly(3-decylthiophene), poly(3-dodecylthiophene), poly(3-octadecylthiophene), poly(3-bromothiophene), poly(3-chlorothiophene), and poly(3-iodine). Poly(3-Cyanothiophene), Poly(3-Phenylthiophene), Poly(3,4-Dimethylthiophene), Poly(3,4-Dibutylthiophene), Poly(3-Hydroxythiophene), Poly(3-Methoxythiophene), Poly(3-Ethoxythiophene), Poly(3-Butoxythiophene), Poly(3-Hexyloxythiophene), Poly(3-Heptyloxythiophene), Poly(3-Octyloxythiophene), Poly(3-Decyloxythiophene), Poly(3-Dodecyl 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 Examples include 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 π-conjugated conductive polymer contained in the conductive composite may be one type or two or more types.

[0016] (Polyanion) A polyanion is a polymer having two or more monomer units with 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, polymethacryloyloxybenzenesulfonic acid), polymers having a sulfo group such as poly(2-acrylamido-2-methylpropanesulfonic acid), polyisoprene sulfonic acid, etc., 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, etc. The polyanion may be a homopolymer obtained by polymerizing a single monomer, or a copolymer obtained by polymerizing two or more monomers. Among these polyanions, polymers having a sulfo group are preferable and polystyrene sulfonic acid is more preferable because the conductivity can be made higher.

[0017] The weight average molecular weight Mw of the polyanion is not particularly limited. For example, it is preferably from 10,000 to 100,000, more preferably from 50,000 to 800,000, and still more preferably from 100,000 to 600,000. When the weight average molecular weight Mw of the polyanion is within the above range, the viscosity of the conductive polymer dispersion of the present embodiment becomes moderately low, and a capacitor having a sufficiently low ESR can be easily manufactured. The weight average molecular weight Mw of the polyanion is the average molecular weight based on mass measured using gel filtration chromatography and determined in terms of pullulan.

[0018] The polyanion content in the conductive polymer dispersion of this embodiment 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, per 100 parts by mass of the π-conjugated conductive polymer. If the polyanion content is above 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 polyanion content is below the upper limit, the π-conjugated conductive polymer can be sufficiently contained, thus ensuring sufficient conductivity.

[0019] (Naphthalene monosulfonic acid) The naphthalene monosulfonic acid (hereinafter sometimes abbreviated as NS) in this embodiment is obtained in which one of the hydrogen atoms of naphthalene is substituted with a sulfonic acid group. 2-naphthalene sulfonic acid or 1-naphthalene sulfonic acid is preferred.

[0020] The naphthalene monosulfonic acid contained in the conductive polymer dispersion of this embodiment may be one type or two or more types. The total content is preferably in the range of 100 parts by mass or more and 5000 parts by mass or less, more preferably 300 parts by mass or more and 3000 parts by mass or less, and even more preferably 500 parts by mass or more and 1000 parts by mass or less, per 100 parts by mass of the π-conjugated conductive polymer. If the value is above the lower limit of the aforementioned range, the interaction with the π-conjugated conductive polymer tends to become stronger, the viscosity of the conductive polymer dispersion becomes lower, and the ESR of the capacitor is further reduced. If the value is below the upper limit of the aforementioned range, the relative content of the π-conjugated conductive polymer increases, so sufficient conductivity can be ensured.

[0021] The mass-based content ratio of the polyanion content G1 and the naphthalene monosulfonic acid content G2 in the conductive polymer dispersion of this embodiment, expressed as G1 / G2, is preferably 0.1 to 3.0, more preferably 0.1 to 0.7, even more preferably 0.1 to 0.6, particularly preferably 0.1 to 0.5, and most preferably 0.1 to 0.4. Within the most preferred range, any of the ranges 0.1 to 0.3, 0.1 to 0.2, 0.2 to 0.4, and 0.3 to 0.4 are acceptable. Within the above range, the viscosity of the conductive polymer dispersion is reduced, allowing for a reduction in ESR while maintaining the capacitance of the capacitor.

[0022] The mass-based content ratio of the π-conjugated conductive polymer (G3) and the naphthalene monosulfonic acid (G2) in the conductive polymer dispersion of this embodiment, expressed as G3 / G2, is preferably 0.1 to 1.0, more preferably 0.1 to 0.7, even more preferably 0.1 to 0.6, particularly preferably 0.1 to 0.5, and most preferably 0.1 to 0.4. Within the most preferred range, 0.1 to 0.4 is preferred, 0.1 to 0.3 is more preferred, and 0.1 to 0.2 is even more preferred. Within the above range, the viscosity of the conductive polymer dispersion is reduced, allowing for a reduction in ESR while maintaining the capacitance of the capacitor.

[0023] In this embodiment, the total content of π-conjugated conductive polymers and polyanions relative to the total mass of the conductive polymer dispersion is preferably 0.1% by mass or more and 5.0% by mass or less, and more preferably 0.5% by mass or more and 2.5% by mass or less. Within the above preferred range, the ESR of the capacitor having a solid electrolyte layer formed from the conductive polymer dispersion can be further reduced.

[0024] The content of naphthalene monosulfonic acid relative to the total mass of the conductive polymer dispersion in this embodiment is preferably 0.01% by mass or more and 10% by mass or less, more preferably 0.05% by mass or more and 5% by mass or less, and even more preferably 0.1% by mass or more and 1.0% by mass or less. Within the above preferred range, the ESR of the capacitor having a solid electrolyte layer formed from the conductive polymer dispersion can be further reduced.

[0025] (dispersion medium) The dispersion medium contained in the conductive polymer dispersion is preferably an aqueous dispersion medium containing water, given that the conductive composite is hydrophilic. However, a dispersion medium other than water may also be included. The dispersion medium other than water is not particularly limited, as long as it does not significantly impair the dispersibility of the conductive composite. The conductive composite has excess anionic groups derived from polyanions and exhibits high dispersibility in water; therefore, a water-soluble organic solvent is preferred as the dispersion medium other than water. Here, the water-soluble organic solvent is an organic solvent whose solubility in 100g of water at 20°C is 1g or more, and examples include alcohol-based solvents, ketone-based solvents, and ester-based solvents. The dispersion medium may consist of one or more water-soluble organic solvents.

[0026] 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% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and may also be 100% by mass. Including water at or above the lower limit of the above value increases the dispersibility of the conductive composite contained in the conductive polymer dispersion, and further reduces the ESR of the capacitor having a solid electrolyte layer formed from the conductive polymer dispersion.

[0027] (Basic compounds) The conductive polymer dispersion may contain one or more basic compounds. The basic compound functions as a Brønsted base, accepting protons from the excess anionic groups of the polyanion. To perform this function, the amount of basic compound 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 is sufficient to perform the above function.

[0028] Examples of basic compounds that can be used include nitrogen-containing organic or inorganic basic compounds, alkali metal or group 2 metal hydroxides, and various carbonates and bicarbonates. Specific examples of alkali metal hydroxides include potassium hydroxide and sodium hydroxide. Specific examples of carbonates or bicarbonates include ammonium bicarbonate, ammonium carbonate, potassium bicarbonate, potassium carbonate, sodium bicarbonate, and sodium carbonate. Specific examples of quaternary ammonium hydroxides or their salts include tetramethylammonium hydroxide, tetraethylammonium hydroxide, and tetrabutylammonium hydroxide.

[0029] Examples of amines include aliphatic tertiary amines and nitrogen-containing aromatic compounds. Examples of aliphatic tertiary amines include triethanolamine, trimethylamine, triethylamine, tripropylamine, tributylamine, trihexylamine, trioctylamine, triphenylamine, trynzylamine, and trinaphthylamine.

[0030] 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 derivatives include dazole, 2-phenyl-4,5-dihydroxymethylimidazole, 1-acetylimidazole, 2-aminobenzimidazole, 2-amino-1-methylbenzimidazole, 2-hydroxybenzimidazole, 2-(2-pyridyl)benzimidazole, pyridine, pyrimidine, pyrazine, and their alkyl-substituted derivatives (e.g., derivatives with C1-C4 alkyl groups such as methyl, ethyl, propyl, and butyl), halogen-substituted derivatives (e.g., derivatives with halogen groups such as fluoro, chloro, and brom), and nitrile-substituted derivatives. Among these, nitrogen-containing aromatic compounds are preferred, and imidazole is more preferred.

[0031] The content of the basic compound in the conductive polymer dispersion is preferably, for example, 1 to 1000 parts by mass, more preferably 5 to 100 parts by mass, and even more preferably 10 to 50 parts by mass, per 100 parts by mass of the total of the π-conjugated conductive polymer and polyanion. Within these preferred ranges, the ESR of the capacitor can be further reduced.

[0032] The content of basic compounds in the conductive polymer dispersion is preferably such that the pH of the conductive polymer dispersion (at 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.

[0033] (Polyol compounds) The conductive polymer dispersion may contain one or more polyol compounds. Here, the polyol compound refers to a compound having two or more hydroxyl groups, which is different from the π-conjugated conductive polymer, the polyanion, and the basic compound. By including a polyol compound, the ESR of the capacitor can be further reduced.

[0034] Examples of polyol compounds include one or more selected from ethylene glycol, diethylene glycol, propylene glycol, 1,4-butanediol, glycerin, pentaerythritol, trimethylolpropane, and trimethylolethane.

[0035] The content of the polyol compound in the conductive polymer dispersion 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, based on 100 parts by mass of the total of the π-conjugated conductive polymer and polyanion. Within the above preferred range, the ESR of the capacitor can be further reduced.

[0036] The content of the polyol compound relative to the total mass of the conductive polymer dispersion is preferably 1% to 15% by mass, more preferably 3% to 12% by mass, and even more preferably 5% to 9% by mass. Within the above preferred range, the coating properties of the conductive polymer dispersion are improved, and the ESR of the capacitor can be further reduced.

[0037] (Optional additives) The conductive polymer dispersion may contain any additives other than the conductive composite, the proportion of which can be appropriately determined depending on the type of additive, but can be, for example, 1 to 1000 parts by mass per 100 parts by mass of the total of the π-conjugated conductive polymer and polyanion. Here, the optional additives are compounds other than the basic compound, the polyol compound and the dispersion medium.

[0038] Optional additives include, for example, surfactants, inorganic conductive agents, defoamers, coupling agents, antioxidants, and UV absorbers. Examples of surfactants include nonionic, anionic, and cationic surfactants, but nonionic surfactants are preferred in terms of storage stability. Polymer-based surfactants such as polyvinyl alcohol and polyvinylpyrrolidone may also be added. Examples of inorganic conductive agents include metal ions and conductive carbon. Metal ions can be generated by dissolving metal salts in water. Examples of defoaming agents include silicone resins, polydimethylsiloxanes, and silicone oils. Examples of coupling agents include silane coupling agents having vinyl groups, amino groups, epoxy groups, etc. Examples of antioxidants include phenolic antioxidants, amine antioxidants, phosphorus antioxidants, sulfur antioxidants, and sugars. Examples of UV absorbers include benzotriazole-based UV absorbers, benzophenone-based UV absorbers, salicylate-based UV absorbers, cyanoacrylate-based UV absorbers, oxanilide-based UV absorbers, hindered amine-based UV absorbers, and benzoate-based UV absorbers.

[0039] The viscosity of the conductive polymer dispersion in this embodiment at 25°C is preferably 1 cP to 50 cP, more preferably 1 cP to 40 cP, even more preferably 1 cP to 30 cP, particularly preferably 1 cP to 20 cP, and most preferably 1 cP to 10 cP. If the value is above the lower limit of the above range, it becomes possible to secure the thickness of the coating applied on the dielectric layer, making it easy to form a solid electrolyte layer of appropriate thickness. If the value is below the upper limit of the above range, it becomes easier to permeate the conductive polymer dispersion into the fine porous structure pre-formed on the surface of the dielectric layer and to form a solid electrolyte layer inside it. The viscosity measurements described above were taken at 25°C using a tuning fork vibrating viscometer, in accordance with JIS Z8803:2011 (Viscosity measurement method using vibrating viscometer).

[0040] Method for producing conductive polymer dispersions A second aspect of the present invention is a method for producing a conductive polymer dispersion, comprising a polymerization step of polymerizing monomers that form a π-conjugated conductive polymer in a reaction solution containing a polyanion, naphthalene monosulfonic acid, and an aqueous dispersion medium, thereby forming a conductive composite containing the π-conjugated conductive polymer and the polyanion. The conductive polymer dispersion of the first embodiment can be produced by the manufacturing method of this embodiment.

[0041] A reaction solution is prepared containing the monomer, the polyanion, naphthalene monosulfonic acid, and water, and the monomer is polymerized to form a π-conjugated conductive polymer. In the reaction solution, the polyanion is spontaneously doped into the π-conjugated conductive polymer, forming a conductive composite consisting of the π-conjugated conductive polymer and the polyanion. In this case, the sulfonic acid group of naphthalene monosulfonic acid can dopine the π-conjugated conductive polymer in the same way as the anionic group of the polyanion. Furthermore, naphthalene monosulfonic acid is a molecule possessing π electrons and can be stabilized in a stacked configuration by π-π interaction with the π-conjugated conductive polymer. Thus, it is presumed that the presence of naphthalene monosulfonic acid in the conductive composite makes the molecular motion of the conductive composite in the dispersion rigid, resulting in a lower viscosity of the dispersion. From the above, it is concluded that the conductive composite obtained by the manufacturing method of this embodiment contains naphthalene monosulfonic acid.

[0042] The synthesis of the conductive composite in the reaction solution can be carried out in the same manner as the conventional synthesis of conductive composites, except that naphthalene monosulfonic acid is added to the reaction solution.

[0043] Since the aqueous dispersion medium contained in the reaction solution contains water, the polymerization reaction of the monomer proceeds stably, and the resulting conductive composite is obtained in a stably dispersed state in the aqueous dispersion medium. The aqueous dispersion medium may contain a dispersion medium other than water. The dispersion medium other than water does not need to inhibit polymerization, and a water-soluble organic solvent is preferred. Here, the water-soluble organic solvent is an organic solvent whose solubility in 100g of water at 20°C is 1g or more, and examples include alcohol-based solvents, ketone-based solvents, and ester-based solvents. The dispersion medium may contain one or more water-soluble organic solvents. The water content relative to the total mass of the aqueous dispersion medium is preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and may also be 100% by mass.

[0044] It is preferable to add a known catalyst and oxidizing agent to the reaction solution to promote the chemical oxidation of the monomer. 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.

[0045] The amount of catalyst blended with the total mass of the reaction solution (including the catalyst) is preferably, for example, 0.01% by mass or more and 0.50% by mass or less, and more preferably 0.01% by mass or more and 0.30% by mass or less.

[0046] The amount of oxidizing agent in relation to the total mass of the reaction solution (including the oxidizing agent) is preferably 0.10% by mass or more and 1.20% by mass or less, more preferably 0.50% by mass or more and 1.10% by mass or less, and even more preferably 0.70% by mass or more and 1.00% by mass or less.

[0047] The amount of monomer blended with respect to the total mass of the reaction solution is preferably, for example, 0.01% by mass or more and 2.0% by mass or less, more preferably 0.1% by mass or more and 1.0% by mass or less, and even more preferably 0.3% by mass or more and 0.5% by mass or less. The amount of the polyanion relative to the total mass of the reaction solution is preferably, for example, 0.1% by mass or more and 3.0% by mass or less, more preferably 0.5% by mass or more and 2.0% by mass or less, and even more preferably 1.0% by mass or more and 1.5% by mass or less. By setting the concentration of the conductive composite to the preferred content described above, a conductive polymer dispersion can be easily obtained.

[0048] In a conductive composite formed by a polymerization reaction, from the viewpoint of achieving the above-mentioned preferred ratio of the π-conjugated conductive polymer and the polyanion, the blending ratio of the monomer and the polyanion to be blended in the reaction solution 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, per 100 parts by mass of the monomer.

[0049] The mass-based content ratio of the amount of polyanion H1 and the amount of naphthalene monosulfonic acid H2 in the reaction solution, expressed as H1 / H2, is preferably 0.1 to 3.0, more preferably 0.1 to 0.7, even more preferably 0.1 to 0.6, particularly preferably 0.1 to 0.5, and most preferably 0.1 to 0.4. Within the most preferred range, any of the ranges 0.1 to 0.3, 0.1 to 0.2, 0.2 to 0.4, or 0.3 to 0.4 are acceptable. Within the above range, the viscosity of the resulting conductive polymer dispersion is reduced. Furthermore, it is possible to reduce the ESR while maintaining the capacitance of the capacitor manufactured using this conductive polymer dispersion.

[0050] The mass-based content ratio of the monomer H3 that forms the π-conjugated conductive polymer and the amount H2 of naphthalene monosulfonic acid blended into the reaction solution, expressed as H3 / H2, is preferably 0.1 to 1.0, more preferably 0.1 to 0.7, even more preferably 0.1 to 0.6, particularly preferably 0.1 to 0.5, and most preferably 0.1 to 0.4. Within the most preferred range, 0.1 to 0.4 is preferred, 0.1 to 0.3 is more preferred, and 0.1 to 0.2 is even more preferred. Within the above range, the viscosity of the resulting conductive polymer dispersion is reduced. Furthermore, it is possible to reduce the ESR while maintaining the capacitance of the capacitor manufactured using this conductive polymer dispersion.

[0051] The reaction temperature in the reaction solution can be, for example, 20-30°C. At this reaction temperature, the polymerization reaction is usually completed in about 4-12 hours. The completion of the polymerization reaction can be determined by measuring the amount of unreacted monomers in the reaction solution using gas chromatography or the like.

[0052] It is preferable to remove the catalyst and oxidizing agent added to the reaction solution from the conductive polymer dispersion after the chemical oxidative polymerization of the monomer. Methods for removal include, for example, contacting a conductive polymer dispersion with an ion exchange resin to adsorb the catalyst and oxidizing agent onto the ion exchange resin, and removing them along with the displacement of the dispersion medium by ultrafiltration of the conductive polymer dispersion. Of these, the method using an ion exchange resin is preferred because it is simple. It is preferable to use a combination of a cation exchange resin and an anion exchange resin.

[0053] The conductive polymer dispersion obtained above contains the target conductive composite. After removing the catalyst and oxidizing agent from the reaction solution, it can be used directly for the manufacture of capacitors described later. However, the dispersion medium may be replaced with a desired one, the concentration of the conductive composite may be adjusted, or basic compounds, polyol compounds, or other additives may be added.

[0054] Capacitor manufacturing method A third aspect of the present invention is a method for manufacturing a capacitor, comprising the step of applying the conductive polymer dispersion of the first aspect described above to the surface of a dielectric layer formed on the surface of an anode made of a porous valve metal, and drying it to form a solid electrolyte layer.

[0055] The method for manufacturing a capacitor according to 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 formation step); arranging a cathode at a position opposite the dielectric layer (cathode formation step); and forming a solid electrolyte layer on at least a part of the surface of the dielectric layer (film formation step). Each step will be described below with reference to Figure 1.

[0056] [Dielectric Formation Process] In this process, the surface of the anode 11, which is made of a porous valve metal, is oxidized to form a dielectric layer 12. The method for forming the dielectric layer 12 is not particularly limited, and examples include anodic oxidation of the surface of the anode 11 in an electrolyte solution for chemical treatment, such as an aqueous solution of ammonium adipate, an aqueous solution of ammonium borate, or an aqueous solution of ammonium phosphate.

[0057] [Cathode formation process] In this process, a cathode 13 is placed opposite the dielectric layer 12. The method of arranging the cathode 13 is not particularly limited, and examples include forming the cathode 13 using a conductive paste such as carbon paste or silver paste, or arranging a metal foil such as aluminum foil opposite the dielectric layer 12.

[0058] [Film forming process] In this process, the aforementioned conductive polymer dispersion is applied to at least a portion of the surface of the dielectric layer 12 and dried to form a solid electrolyte layer 14.

[0059] Methods for applying the conductive polymer dispersion include, for example, dip coating, comma coating, reverse coating, lip coating, and microgravure coating. Of these, the method of immersing the anode 11 in the conductive polymer dispersion under reduced pressure is preferred. With the dip method, the conductive polymer dispersion can be sufficiently applied to the interior of the porous structure on the surface of the dielectric layer 12. After immersion, it is removed and the drying process is carried out.

[0060] Drying methods include, for example, room temperature drying, hot air drying, and far-infrared drying. Among these, hot air drying is preferred. The drying temperature is preferably 100 to 180°C, and more preferably 120 to 150°C. The drying time is preferably 0.2 to 1 hour. After drying, the capacitor can be assembled using conventional methods.

[0061] Capacitor A fourth aspect of the present invention is 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 dielectric layer opposite to the anode, and a solid electrolyte layer formed between the dielectric layer and the cathode, wherein the solid electrolyte layer is a cured product of the conductive polymer dispersion of the first aspect described above. The capacitor of the fourth embodiment can be manufactured by the manufacturing method of the third embodiment.

[0062] An example of an embodiment of the fourth aspect will be described with reference to Figure 1. The capacitor 10 shown in Figure 1 comprises an anode 11 made of a porous valve metal, a dielectric layer 12 made of an oxide of the valve metal, a solid electrolyte layer 14 formed on the surface of the dielectric layer 12, and a cathode 13 provided on the outermost side. The cathode 13 is provided on the opposite side from the anode 11, with the dielectric layer 12 and the solid electrolyte layer 14 in between.

[0063] Examples of valve metals that constitute 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 anode 11 include aluminum foil that has been etched to increase its surface area and then oxidized, or sintered tantalum or niobium particles whose surface has been oxidized and formed into pellets. Materials treated in this way become porous bodies with irregularities formed on their surface.

[0064] In this embodiment, the dielectric layer 12 is a layer formed by oxidation of the surface of the anode 11. For example, it is formed by anodizing the surface of the metal anode 11 in an electrolyte such as an aqueous solution of ammonium adipate. Similar to the anode 11, the dielectric layer 12 also has irregularities formed on it.

[0065] In this embodiment, the cathode 13 can be a conductive layer formed from a conductive paste or a metal layer made of a conductive material such as aluminum foil.

[0066] In this embodiment, the solid electrolyte layer 14 is formed on the surface of the dielectric layer 12. The solid electrolyte layer 14 covers at least a portion of the surface of the dielectric layer 12, and may cover the entire surface of the dielectric layer 12. The thickness of the solid electrolyte layer 14 may be constant or not; for example, a thickness of 1 μm or more and 100 μm or less is possible.

[0067] <Conductive composite> The conductive composite contained in the solid electrolyte layer comprises at least a π-conjugated conductive polymer and polyanions. The polyanions in the conductive composite are doped into the π-conjugated conductive polymer.

[0068] The total content of the π-conjugated conductive polymer, polyanion, and naphthalene monosulfonic acid relative to the total mass of the solid electrolyte layer is preferably 1% to 99% by mass, more preferably 50% to 98% by mass, and even more preferably 70% to 97% by mass. This range is preferable because it makes it easier to lower the equivalent series resistance of the capacitor.

[0069] <Naphthalene monosulfonic acid> The solid electrolyte layer contains naphthalene monosulfonic acid, which reduces the ESR of the capacitor.

[0070] The mass-based content ratio of the polyanion content G1' and the naphthalene monosulfonic acid content G2' in the solid electrolyte layer, expressed as G1' / G2', is preferably 0.1 to 3.0, more preferably 0.1 to 0.7, even more preferably 0.1 to 0.6, particularly preferably 0.1 to 0.5, and most preferably 0.1 to 0.4. Within the most preferred range, any of the ranges 0.1 to 0.3, 0.1 to 0.2, 0.2 to 0.4, and 0.3 to 0.4 are acceptable. Within the above range, it is possible to reduce ESR while maintaining the capacitance of the capacitor.

[0071] The mass-based content ratio of the π-conjugated conductive polymer content G3' and the naphthalene monosulfonic acid content G2' in the solid electrolyte layer, expressed as G3' / G2', is preferably 0.1 to 1.0, more preferably 0.1 to 0.7, even more preferably 0.1 to 0.6, particularly preferably 0.1 to 0.5, and most preferably 0.1 to 0.4. Within the most preferred range, 0.1 to 0.4 is preferred, 0.1 to 0.3 is more preferred, and 0.1 to 0.2 is even more preferred. Within the above range, it is possible to reduce ESR while maintaining the capacitance of the capacitor.

[0072] <Basic compounds> The solid electrolyte layer may further contain one or more of the aforementioned basic compounds. The inclusion of basic compounds can further reduce the ESR of the capacitor.

[0073] The content ratio of the basic compound in the solid electrolyte layer is preferably, for example, 1 to 1000 parts by mass, more preferably 5 to 100 parts by mass, and even more preferably 10 to 50 parts by mass, per 100 parts by mass of the total of the π-conjugated conductive polymer and polyanion. Within the above preferred range, the ESR of the capacitor can be further reduced.

[0074] <Polyol compounds> The solid electrolyte layer may further contain one or more of the aforementioned polyols. The inclusion of polyols can further reduce the ESR of the capacitor.

[0075] The total content of polyol compounds in the solid electrolyte layer 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, based on 100 parts by mass of the total amount of π-conjugated conductive polymers and polyanions in the solid electrolyte layer. Within the above preferred range, the ESR of the capacitor can be further reduced.

[0076] [Electrolyte] The capacitor in this embodiment may have an electrolyte that impregnates a solid electrolyte layer. Examples of solvents that constitute the electrolyte 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. The electrolytes constituting the electrolyte solution include, for example, 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, organic acids such as azelaic acid and sebacic acid; or boric acid, polyhydric alcohol complex compounds of boric acid obtained from boric acid and polyhydric alcohols; and inorganic acids such as phosphoric acid, carbonic acid, and silicic acid as anionic components, with primary amines (methylamine, ethylamine, propylamine, Examples include electrolytes with cationic components such as butylamine, ethylenediamine, secondary amines (dimethylamine, diethylamine, dipropylamine, methylethylamine, diphenylamine, etc.), tertiary amines (trimethylamine, triethylamine, tripropylamine, triphenylamine, 1,8-diazabicyclo(5,4,0)-undecene-7, etc.), and tetraalkylammonium (tetramethylammonium, tetraethylammonium, tetrapropylammonium, tetrabutylammonium, methyltriethylammonium, dimethyldiethylammonium, etc.).

[0077] The capacitor in this embodiment is not limited to the configuration described above, and a separator may be provided between the dielectric layer and the cathode. An example of a capacitor with a separator between the dielectric layer and the cathode is a wound capacitor. Examples of separators include sheets (including nonwoven fabrics) made of cellulose, polyvinyl alcohol, polyester, polyethylene, polystyrene, polypropylene, polyimide, polyamide, polyvinylidene fluoride, etc., and glass fiber nonwoven fabrics. The density of the separator is, for example, 0.1 g / cm³. 3 More than 1.0g / cm 3 The following are listed: When a separator is provided, a method can be applied in which carbon paste or silver paste is impregnated into the separator to form the cathode. [Examples]

[0078] (Manufacturing Example 1) Production of Polystyrene Sulfonic Acid 1 206 g of sodium styrene sulfonate was dissolved in 1000 ml of deionized water, and while stirring at 80°C, 1.14 g of ammonium persulfate oxidizing agent solution, which had been previously dissolved in 10 ml of water, was added dropwise for 20 minutes, and this solution was stirred for 12 hours. To the obtained 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 sulfonate solution was removed by ultrafiltration. Next, 2000 ml of deionized water was added to the remaining solution, and approximately 2000 ml of solvent was removed by ultrafiltration to wash the polystyrene sulfonate with water. This washing procedure was repeated three times. The 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 deionized water to obtain a 10% by mass aqueous solution of polystyrene sulfonic acid.

[0079] Using gel permeation chromatography (GPC) with pullulan of known weight-average molecular weight as a standard substance, the weight-average molecular weight (Mw) of the polystyrene sulfonic acid aqueous solution obtained above was measured, and the weight-average molecular weight was found to be 200,000.

[0080] Weight-average molecular weight was measured using a Prominence high-performance liquid chromatograph manufactured by Shimadzu Corporation. A 0.1% NaNO3 aqueous solution was used as the solvent, a Shodex OHpack SB-806M HQ column was used, and a RID-20A detector was used. The solvent temperature was set to 40°C, the flow rate to 0.6 ml / min, and the PSS concentration in the sample was adjusted to 0.1% by mass. 100 μl of the sample, filtered through a 0.2 μm pore size membrane filter, was injected, and the analysis was performed using Lab Solutions software (Shimadzu Corporation).

[0081] (Manufacturing Example 2) Production of Polystyrene Sulfonic Acid 2 206 g of sodium styrene sulfonate was dissolved in 1000 ml of deionized water, and while stirring at 80°C, 0.38 g of ammonium persulfate oxidizing agent solution, which had been previously dissolved in 10 ml of water, was added dropwise for 20 minutes, and this solution was stirred for 12 hours. To the obtained 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 sulfonate solution was removed by ultrafiltration. Next, 2000 ml of deionized water was added to the remaining solution, and approximately 2000 ml of solvent was removed by ultrafiltration to wash the polystyrene sulfonate with water. This washing procedure was repeated three times. The 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 deionized water to obtain a 10% by mass aqueous solution of polystyrene sulfonic acid. The weight-average molecular weight of the polystyrene sulfonic acid (PSS) obtained above, measured using GPC as in Production Example 1, was 540,000.

[0082] (Manufacturing Example 3) Fabrication of capacitor elements After connecting anode lead terminals to etched aluminum foil (anodic foil), a voltage of 40V was applied in a 10% by mass aqueous solution of ammonium adipate to perform a chemical conversion (oxidation treatment) to form dielectric layers on both sides of the aluminum foil and obtain the anode foil. Next, opposing aluminum cathode foils, each with cathode lead terminals welded to both sides of an anode foil, were laminated with a cellulose separator in between, and this was wound into a cylindrical shape to obtain a capacitor element.

[0083] (Example 1) Preparation of conductive polymer dispersion 3.0 g of 3,4-ethylenedioxythiophene (EDOT), 90 g of polystyrene sulfonic acid (10% by mass aqueous solution) from Production Example 1, 4.5 g of 2-naphthalene sulfonic acid, and 325 g of deionized water were mixed at 20°C. The resulting mixed solution was kept at 20°C, and 0.3 g of ferric sulfate was added while stirring. Next, a solution of 6.6 g of sodium persulfate dissolved in 293.4 g of deionized water was slowly added, and the resulting reaction mixture was stirred for 8 hours to allow the reaction to proceed. The above reaction yielded a conductive polymer dispersion containing a conductive composite (PEDOT-PSS-NS) comprising poly(3,4-ethylenedioxythiophene), polystyrene sulfonic acid, and 2-naphthalene sulfonic acid, which are π-conjugated conductive polymers, and water as a dispersion medium.

[0084] Analysis of the obtained conductive polymer dispersion by GPC revealed that unpolymerized EDOT was below the detection limit, and free naphthalene monosulfonic acid (NS) was also below the detection limit. Therefore, it was determined that all of the blended EDOT, PSS, and NS complexed together to form PEDOT-PSS-NS.

[0085] 78g of Duolite C255LFH (manufactured by Sumika Chemtex, cation exchange resin) and 78g of Duolite A368S (manufactured by Sumika Chemtex, anion exchange resin) were added to this conductive polymer dispersion, and the dispersion was filtered to remove the ion exchange resins, obtaining 710g of conductive polymer dispersion from which the oxidizing agent and catalyst had been removed. The solid content (non-volatile components) was then measured. Next, water was removed from the obtained conductive polymer dispersion under reduced pressure using an evaporator to obtain a solid content of 1.6% by mass. Imidazole was added to 100 g of the obtained conductive polymer dispersion to adjust the pH to 2.5, and then 8 g of diethylene glycol was added.

[0086] The capacitor element obtained in Manufacturing Example 3 was immersed in the above-mentioned conductive polymer dispersion under reduced pressure, and then dried in 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. Next, the capacitor element with the solid electrolyte layer described above was loaded into an aluminum case, and the case was sealed with a rubber seal to create a capacitor.

[0087] (Example 2) A capacitor was fabricated in the same manner as in Example 1, except that 9 g of 2-naphthalenesulfonic acid was used.

[0088] (Example 3) A capacitor was fabricated in the same manner as in Example 1, except that 13.5 g of 2-naphthalenesulfonic acid was used.

[0089] (Example 4) A capacitor was fabricated in the same manner as in Example 1, except that 18.0 g of 2-naphthalenesulfonic acid was used.

[0090] (Example 5) A capacitor was fabricated in the same manner as in Example 1, except that 22.5 g of 2-naphthalenesulfonic acid was used.

[0091] (Example 6) A capacitor was fabricated in the same manner as in Example 1, except that 4.5 g of 1-naphthalenesulfonic acid was used instead of 2-naphthalenesulfonic acid.

[0092] (Example 7) The only difference from Example 6 is that 9 g of 1-naphthalenesulfonic acid was used. 6 A capacitor was fabricated in the same manner.

[0093] (Example 8) A capacitor was fabricated in the same manner as in Example 6, except that 13.5 g of 1-naphthalenesulfonic acid was used.

[0094] (Example 9) A capacitor was fabricated in the same manner as in Example 6, except that 18.0 g of 1-naphthalenesulfonic acid was used.

[0095] (Example 10) A capacitor was fabricated in the same manner as in Example 6, except that 22.5 g of 1-naphthalenesulfonic acid was used.

[0096] (Example 11) A capacitor was fabricated in the same manner as in Example 1, except that the 90g of polystyrene sulfonic acid (10% by mass aqueous solution) used in Production Example 1 was reduced to 60g.

[0097] (Example 12) A capacitor was fabricated in the same manner as in Example 1, except that 90 g of polystyrene sulfonic acid (10% by mass aqueous solution, Mw: 200,000) from Production Example 1 was replaced with 90 g of polystyrene sulfonic acid (10% by mass aqueous solution, Mw: 540,000) from Production Example 2.

[0098] (Comparative Example 1) A capacitor was fabricated in the same manner as in Example 1, except that 2-naphthalenesulfonic acid was not added.

[0099] (Comparative Example 2) A capacitor was fabricated in the same manner as in Example 1, except that 4.5 g of 2-naphthalenesulfonic acid was replaced with 4.5 g of 1,5-naphthalenedisulfonic acid.

[0100] (Comparative Example 3) In this study, the procedure was the same as in Example 1, except that polystyrene sulfonic acid was not added. However, particles precipitated and a conductive polymer dispersion could not be obtained, so the study was discontinued.

[0101] (Comparative Example 4) A conductive polymer dispersion was prepared in the same manner as in Example 1, except that 2-naphthalenesulfonic acid was not added. When 4.5 g of 2-naphthalenesulfonic acid was added to the obtained conductive polymer dispersion, the dispersion gelled, and the investigation was discontinued.

[0102] (Comparative Example 5) A conductive polymer dispersion was prepared in the same manner as in Example 1, except that 2-naphthalenesulfonic acid was not added. When 4.5 g of 1-naphthalenesulfonic acid was added to the obtained conductive polymer dispersion, the dispersion gelled, and the investigation was discontinued.

[0103] [Measuring pH] The pH was measured at 25°C using a commercially available pH meter and a standard method.

[0104] [Method 1 for measuring viscosity] As described in Example 1, a conductive polymer dispersion with a solid content of 1.6% by mass was obtained, dispersed in a high-pressure homogenizer, and measured at 25°C using a tuning fork vibrating viscometer (model: SV-10, manufactured by A&D Co., Ltd.) in accordance with JIS Z8803:2011 (Method for measuring viscosity by vibrating viscometer). The conversion was performed using 1 Pa·s (Pascal-second) = 1000 cP (centipoise).

[0105] <Rating> [Capacitance and equivalent series resistance] For each example capacitor, the capacitance (in μF) at 120 Hz and the equivalent series resistance (ESR) (in mΩ) 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.

[0106] [Table 1]

[0107] <Result> The conductive polymer dispersion in the examples contained naphthalene monosulfonic acid along with a π-conjugated conductive polymer and polyanion as a conductive composite, resulting in reduced viscosity. Furthermore, capacitors manufactured using the conductive polymer dispersion in the examples were able to maintain capacitance while reducing ESR. The higher the amount of naphthalene monosulfonic acid in the conductive polymer dispersion, the lower the viscosity tended to be, and the lower the ESR of the capacitor.

[0108] On the other hand, the conductive polymer dispersion of Comparative Example 1 did not contain naphthalene monosulfonic acid, so it had high viscosity and poor ESR of the capacitor. The conductive polymer dispersion of Comparative Example 2 did not contain naphthalene monosulfonic acid, but instead contained 1,5-naphthalenedisulfonic acid, but it also had high viscosity and poor ESR of the capacitor. In Comparative Example 3, since no polyanion was incorporated, a conductive composite that could be dispersed in an aqueous dispersion could not be obtained, and therefore a capacitor could not be manufactured. In Comparative Examples 4 and 5, when naphthalene monosulfonic acid (NS) was added to the PEDOT-PSS aqueous dispersion, gelation occurred. From these results, it can be understood that in each example, naphthalene monosulfonic acid is included in the conductive composite, forming PEDOT-PSS-NS and stably dispersed in the aqueous solvent. Examples 1-3, 6-8, and 11-12 are for reference only. [Explanation of Symbols]

[0109] 10 Capacitors 11 Anode 12 Dielectric layer 13 Cathode 14 Solid electrolyte layer

Claims

1. By polymerizing monomers that form a π-conjugated conductive polymer in a reaction solution containing a polyanion, naphthalene monosulfonic acid, and an aqueous dispersion medium, A method for producing a conductive composite dispersion, comprising a polymerization step to form a conductive composite containing the π-conjugated conductive polymer and the polyanion, A method for producing a conductive polymer dispersion, wherein the mass-based mixing ratio of the amount of polyanion H1 and the amount of naphthalene monosulfonic acid H2 in the reaction solution, expressed as H1 / H2, is 0.1 to 0.

5.

2. A method for producing a conductive polymer dispersion according to claim 1, wherein the mass-based blending ratio of the amount of monomer forming the π-conjugated conductive polymer H3 and the amount of naphthalene monosulfonic acid H2 in the reaction solution, expressed as H3 / H2, is 0.1 to 0.

4.

3. The method for producing a conductive polymer dispersion according to claim 1, wherein the water content is 70% by mass or more relative to the total mass of the aqueous dispersion medium.

4. The π-conjugated conductive polymer is poly(3,4-ethylenedioxythiophene), or the polyanion is polystyrene sulfonic acid, or A method for producing a conductive polymer dispersion according to claim 1, wherein the π-conjugated conductive polymer is poly(3,4-ethylenedioxythiophene) and the polyanion is polystyrene sulfonic acid.

5. The method for producing a conductive polymer dispersion according to claim 1, wherein a basic compound is added to the conductive polymer dispersion.

6. The method for producing a conductive polymer dispersion according to claim 1, wherein a polyol is added to the conductive polymer dispersion.

7. The method for producing a conductive polymer dispersion according to claim 1, wherein the viscosity of the conductive polymer dispersion at 25°C is 1 cP to 50 cP.

8. A step of obtaining the conductive polymer dispersion by a manufacturing method described in any one of Claims 1 to 7, A method for manufacturing a capacitor, comprising the step of applying the conductive polymer dispersion to the surface of a dielectric layer formed on the surface of an anode made of a porous valve metal, and drying it to form a solid electrolyte layer.

Images