JP2024015562A - Method for producing conductive polymer-containing liquid and method for producing capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a capacitor reduced in equivalent series resistance and a method for producing a conductive polymer-containing liquid.

SOLUTION: There is provided a method for producing a conductive polymer-containing liquid which comprises a polymerization step of polymerizing a monomer forming a π-conjugated conductive polymer with a reaction solution containing a polyanion and an aqueous dispersion medium to obtain a conductive polymer-containing liquid containing a conductive composite containing the π-conjugated conductive polymer and the polyanion, wherein the monomer is polymerized under an atmosphere in which the oxygen concentration of the gas in the reaction vessel containing the reaction solution is 0.9 vol.% or more and 5.0 vol.% or less to form the conductive composite.

SELECTED DRAWING: None

COPYRIGHT: (C)2024,JPO&INPIT

Description

The present invention relates to a method for manufacturing a conductive polymer-containing liquid containing a π-conjugated conductive polymer, and a method for manufacturing a capacitor.

A π-conjugated conductive polymer whose main chain is composed of a π-conjugated system forms a conductive composite by doping with a polyanion having an anion group, and becomes dispersible in water.
A capacitor including a solid electrolyte layer formed using a conductive polymer-containing liquid (also referred to as a conductive polymer dispersion) containing a conductive composite is known (for example, Patent Document 1).

Japanese Patent Application Publication No. 2020-100744

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, thereby reducing the equivalent series resistance (ESR) and improving heat resistance. On the other hand, there is a need for a capacitor with reduced equivalent series resistance, regardless of the sulfide described above.
The present invention provides a method for manufacturing a capacitor with reduced equivalent series resistance, and a method for manufacturing a liquid containing a conductive polymer.

[1] A conductive composite containing the π-conjugated conductive polymer and the polyanion is produced by polymerizing monomers forming the π-conjugated conductive polymer in a reaction solution containing the polyanion and an aqueous dispersion medium. A method for producing a conductive polymer-containing liquid, comprising a polymerization step to obtain a conductive polymer-containing liquid containing the reaction liquid, wherein the oxygen concentration of the gas in the reaction vessel containing the reaction liquid is 0.9% by volume or more. A method for producing a conductive polymer-containing liquid, comprising polymerizing the monomer in an atmosphere of 0% by volume or less to form the conductive composite.
[2] The conductive polymer-containing liquid according to [1], wherein the π-conjugated conductive polymer is poly(3,4-ethylenedioxythiophene) or the polyanion is polystyrene sulfonic acid. manufacturing method.
[3] After polymerizing the monomer by adding an oxidizing agent and a catalyst to the reaction liquid, removing the oxidizing agent and the catalyst from the conductive polymer-containing liquid, [1] or [2] A method for producing a conductive polymer-containing liquid according to .
[4] The conductive polymer-containing liquid according to [3], wherein the oxidizing agent and the catalyst are removed by bringing the conductive polymer-containing liquid into contact with at least one of a cation exchange resin and an anion exchange resin. Method of manufacturing liquid.
[5] The method for producing a conductive polymer-containing liquid according to [3] or [4], wherein a basic compound is further added to the conductive polymer-containing liquid from which the oxidizing agent and the catalyst have been removed.
[6] The method for producing a conductive polymer-containing liquid according to [5], wherein the basic compound is a nitrogen-containing aromatic compound.
[7] The conductive polymer according to [5] or [6], wherein the pH (25° C.) of the conductive polymer-containing liquid is adjusted to 2.0 to 8.0 by adding the basic compound. Method for producing a containing liquid.
[8] The method according to any one of [3] to [7], wherein a polyol compound containing two or more hydroxyl groups is further added to the conductive polymer-containing liquid from which the oxidizing agent and the catalyst have been removed. A method for producing a conductive polymer-containing liquid.
[9] The method for producing a conductive polymer-containing liquid according to [8], wherein the polyol compound is diethylene glycol.
[10] A step of obtaining a conductive polymer-containing liquid by the method for producing a conductive polymer-containing liquid according to any one of [1] to [9], and a step of producing an anode made of a porous body of valve metal. A method for manufacturing a capacitor, comprising the steps of applying the conductive polymer-containing liquid to the surface of a dielectric layer formed on the surface and drying the liquid to form a solid electrolyte layer.

According to the present invention, a capacitor with reduced equivalent series resistance can be easily manufactured. Further, a conductive polymer-containing liquid suitable for manufacturing the capacitor can be easily manufactured.

The present invention is considered to contribute to SDGs Goal 12, "Responsible Production and Responsible Consumption."

In this specification and claims, the lower and upper limits of the numerical range indicated by "~" are included in that numerical range.

1 is a sectional view showing one embodiment of a capacitor of the present invention.

≪Method for producing conductive polymer-containing liquid≫
In a first aspect of the present invention, the π-conjugated conductive polymer and the polyanion are formed by polymerizing monomers forming the π-conjugated conductive polymer in a reaction solution containing a polyanion and an aqueous dispersion medium. A method for producing a conductive polymer-containing liquid includes a polymerization step of obtaining a conductive polymer-containing liquid containing a conductive composite.

<Conductive composite>
The conductive composite of this embodiment includes a π-conjugated conductive polymer and a polyanion. The polyanion in the conductive composite is doped into a π-conjugated conductive polymer to form a conductive composite having conductivity.
In the polyanion, only some anion groups are doped into the π-conjugated conductive polymer, and there are surplus anion groups that do not participate in doping. Since the excess anion group is a hydrophilic group, the conductive composite has water dispersibility.

(π-conjugated conductive polymer)
The π-conjugated conductive polymer may be any organic polymer whose main chain is composed of a π-conjugated system, such as polypyrrole-based conductive polymers, polythiophene-based conductive polymers, and polyacetylene-based conductive polymers. Examples include polyphenylene conductive polymers, polyphenylene vinylene conductive polymers, polyaniline conductive polymers, polyacene conductive polymers, polythiophene vinylene 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.

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-hydroxythiophene), poly(3-methoxythiophene), poly(3-ethoxythiophene), poly(3-butoxythiophene), poly(3-hexyloxythiophene), poly(3-heptyloxythiophene) , poly(3-octyloxythiophene), poly(3-decyloxythiophene), poly(3-dodecyloxythiophene), poly(3-octadecyloxythiophene), poly(3,4-dihydroxythiophene), poly(3-decyloxythiophene) ,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), poly(3-methyl-4-carboxythiophene) butylthiophene).
Examples of polypyrrole-based conductive polymers include polypyrrole, poly(N-methylpyrrole), poly(3-methylpyrrole), poly(3-ethylpyrrole), poly(3-n-propylpyrrole), and poly(3-butylpyrrole). pyrrole), poly(3-octylpyrrole), poly(3-decylpyrrole), poly(3-dodecylpyrrole), poly(3,4-dimethylpyrrole), poly(3,4-dibutylpyrrole), poly(3-dibutylpyrrole) -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-aniline sulfonic acid), and poly(3-aniline sulfonic acid).
Among these π-conjugated conductive polymers, poly(3,4-ethylenedioxythiophene) is particularly preferred because it has excellent conductivity, transparency, and heat resistance.
The number of types of π-conjugated conductive polymers contained in the conductive composite may be one or two or more types.

(Polyanion)
A polyanion is a polymer having two or more monomer units having anionic groups in its molecule. The anion group of this polyanion functions as a dopant for the π-conjugated conductive polymer to improve the conductivity of the π-conjugated conductive polymer.
The anion 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, polyallylsulfonic acid, polyacrylic ester having a sulfo group, polymethacrylic ester having a sulfo group (for example, poly(4-sulfobutyl methacrylate) , polysulfoethyl methacrylate, polymethacryloyloxybenzenesulfonic acid), poly(2-acrylamido-2-methylpropanesulfonic acid), polyisoprene sulfonic acid, and other polymers with sulfo groups, polyvinylcarboxylic acid, polystyrenecarboxylic acid, Polymers having carboxyl groups such as polyarylcarboxylic acid, polyacrylic acid, polymethacrylic acid, poly(2-acrylamido-2-methylpropanecarboxylic acid), and polyisoprenecarboxylic acid are mentioned. may be a homopolymer obtained by polymerizing two or more types of monomers, or a copolymer obtained by polymerizing two or more types of monomers.
Among these polyanions, polymers having sulfo groups are preferred, and polystyrene sulfonic acid is more preferred, since it can further increase the conductivity.
The polyanions may be used alone or in combination of two or more.
The mass average molecular weight of the polyanion is preferably 20,000 or more and 1,000,000 or less, more preferably 100,000 or more and 500,000 or less. The mass average molecular weight is a mass-based average molecular weight measured using gel filtration chromatography and calculated in terms of pullulan.

The content ratio of the polyanion in the conductive composite is preferably in the range of 1 part by mass or more and 1000 parts by mass or less, for example, 10 parts by mass or more and 700 parts by mass, based on 100 parts by mass of the π-conjugated conductive polymer. It is more preferably 100 parts by mass or more and 500 parts by mass or less. If the content ratio of the polyanion is equal to or higher than the lower limit value, the doping effect on the π-conjugated conductive polymer tends to become stronger, and the conductivity becomes higher. On the other hand, if the content of the polyanion is below the upper limit value, the π-conjugated conductive polymer can be sufficiently contained, so that sufficient conductivity can be ensured.

<Polymerization process>
In this step, a polymerization reaction of the monomers is caused in a reaction vessel containing a reaction solution containing monomers forming the π-conjugated conductive polymer, a polyanion, and an aqueous dispersion medium, and Forms a conductive polymer. At this time, a conductive composite in which the polyanion is naturally doped into the π-conjugated conductive polymer and dispersed in the aqueous dispersion medium is obtained.

During the polymerization of the monomer, the desired conductive polymer-containing liquid can be obtained by maintaining the oxygen concentration of the gas in the reaction vessel at 0.9% by volume or more and 5.0% by volume or less. Although the detailed mechanism is not yet clear, in an atmosphere with an oxygen concentration within a certain range, the oxygen concentration dissolved in the reaction solution decreases, and the monomer polymerizes to form a π-conjugated conductive polymer and/or a conductive polymer. It is presumed that the three-dimensional structure of the composite is in an advantageous state when forming the solid electrolyte layer of the capacitor, and as a result, the ESR of the capacitor is reduced.

From the viewpoint of easily controlling the oxygen concentration of the gas within the reaction vessel, the reaction vessel is preferably a closed system rather than an open system. In a closed system, a reaction vessel that can be sealed or semi-closed is preferable. Here, the term "sealed" refers to a state in which no gas flows in or out between the reaction container and the outside. Semi-hermetic means a state in which the reaction vessel is incorporated into a reaction apparatus that can control gas flowing in from the outside and gas flowing out to the outside.

A method for controlling the oxygen concentration of the gas in the reaction vessel to a predetermined range lower than the oxygen concentration in the atmosphere includes a method of introducing a gas other than oxygen into the reaction vessel. As the gas other than oxygen, chemically inert gases such as nitrogen and argon are preferable. For example, an inert gas is introduced into the reaction container after the reaction liquid is put into the reaction container, and the atmosphere that previously filled the reaction container is expelled to remove the gas in the reaction container. An example is a method of substitution. When performing gas replacement in this way, an inert gas may be blown into the reaction solution.

The ratio (V1/V2) between the volume V1 of the gas introduced into the reaction vessel during gas replacement and the volume V2 of the reaction liquid is, for example, preferably 2 to 100, more preferably 10 to 100, and 30 to 100 is more preferable. When the ratio is at least the lower limit value, it is easy to keep the oxygen concentration in the reaction vessel within a predetermined range, and dissolved oxygen in the reaction solution can be sufficiently reduced. The upper limit of the ratio of 100 is a guideline.

The conductive composite in the reaction solution can be synthesized in the same manner as conventional conductive composite synthesis, except that the oxygen concentration in the reaction vessel is within a predetermined range.

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 state in which it is stably dispersed in the aqueous dispersion medium.
The aqueous dispersion medium may contain a dispersion medium other than water. The dispersion medium other than water may be one that does not inhibit polymerization, and water-soluble organic solvents are preferred. Here, the water-soluble organic solvent is an organic solvent having a dissolution amount of 1 g or more per 100 g of water at 20° C., and examples thereof include alcohol solvents, ketone solvents, and ester solvents. One type of water-soluble organic solvent may be included as a dispersion medium, or two or more types may be used.
The content of water based on the total mass of the aqueous dispersion medium is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 90% by mass or more, and may be 100% by mass.

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

The content of the catalyst relative to the total mass of the reaction solution during the polymerization reaction is, for example, preferably 0.01% by mass or more and 0.50% by mass or less, more preferably 0.01% by mass or more and 0.30% by mass or less. .

The content of the oxidizing agent relative to the total mass of the reaction solution during the polymerization reaction is, for example, preferably 0.10% by mass or more and 1.00% by mass or less, more preferably 0.30% by mass or more and 0.80% by mass or less. It is preferably at least 0.50% by mass and at most 0.70% by mass.

The content of the monomer relative to the total mass of the reaction solution immediately before the start of the polymerization reaction is, for example, preferably 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. It is preferably 0.3% by mass or more and 0.5% 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, for example, preferably 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. It is preferably 1.0% by mass or more and 1.5% by mass or less.
By setting the content within the above-mentioned suitable range, it is possible to easily obtain a conductive polymer-containing liquid in which the concentration of the conductive composite is set to the above-mentioned suitable content.

In the conductive composite formed by a polymerization reaction, from the viewpoint of adjusting the content ratio of the π-conjugated conductive polymer and the polyanion to the above-mentioned preferred ratio, the monomer contained in the reaction solution immediately before the start of the polymerization reaction. The content ratio of the polyanion to 100 parts by mass of the monomer is preferably 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 100 parts by mass or more and 500 parts by mass or less. The range is more preferred.

The mass average molecular weight of the polyanion used in the polymerization reaction is preferably 20,000 or more and 1,000,000 or less, more preferably 100,000 or more and 500,000 or less. The mass average molecular weight is a mass-based average molecular weight measured using gel filtration chromatography and calculated in terms of pullulan.

The temperature of the reaction solution during the polymerization reaction, that is, the reaction temperature, can be, for example, 20 to 30°C. At the above reaction temperature, the polymerization reaction is usually completed in about 4 to 12 hours. The completion of the polymerization reaction can be determined by measuring the amount of unreacted monomer in the reaction solution using gas chromatography or the like.

It is preferable that the catalyst and oxidizing agent added to the reaction solution are removed from the conductive polymer-containing solution after chemical oxidative polymerization of the monomer.
Methods for removing include, for example, bringing a conductive polymer-containing liquid into contact with an ion exchange resin and adsorbing the catalyst and oxidizing agent to the ion exchange resin, and ultrafiltrating the conductive polymer-containing liquid to remove the dispersion medium. Examples include a method of removing as well as replacing. Among these, the method using an ion exchange resin is preferred because it is simple. The ion exchange resin preferably includes a cation exchange resin and an anion exchange resin.

The conductive polymer-containing liquid obtained above contains the desired conductive composite. If the catalyst and oxidizing agent are removed from the reaction solution, it can be used as it is for manufacturing capacitors, which will be described later. However, it is necessary to replace the dispersion medium with a desired one, adjust the concentration of the conductive composite, Compounds, polyol compounds, arbitrary additives, etc. may be added.

[Conductive polymer-containing liquid]
The conductive polymer-containing liquid obtained by the manufacturing method of this embodiment includes the conductive composite and a dispersion medium. A conductive polymer-containing liquid suitable for the capacitor manufacturing method according to the second aspect of the present invention will be described below.

The content of the conductive composite (i.e., π-conjugated conductive polymer and polyanion) relative to the total mass of the conductive polymer-containing liquid is preferably 0.1% by mass or more and 5.0% by mass or less, and 0.1% by mass or more and 5.0% by mass or less. It is more preferably 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.
Within the above-mentioned suitable range, the ESR of a capacitor having a solid electrolyte layer formed from the conductive polymer-containing liquid can be further reduced.

(Dispersion medium)
The conductive polymer-containing liquid may contain a dispersion medium other than water. Such a dispersion medium is not particularly limited as long as it does not significantly impair the dispersibility of the conductive composite. Since the conductive composite has surplus anion groups derived from the polyanion and has high dispersibility in water, the dispersion medium other than water is preferably a water-soluble organic solvent. Here, the water-soluble organic solvent is an organic solvent having a dissolution amount of 1 g or more per 100 g of water at 20° C., and examples thereof include alcohol solvents, ketone solvents, and ester solvents. One type of water-soluble organic solvent may be included as a dispersion medium, or two or more types may be used.

The content of water relative to the total mass of the dispersion medium excluding nonvolatile components of the conductive polymer-containing liquid is preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and 100% by mass. It may be %. When water is contained above the above lower limit, the dispersibility of the conductive composite contained in the conductive polymer-containing liquid increases, further reducing the ESR of a capacitor having a solid electrolyte layer formed from the conductive polymer-containing liquid. can do.

(basic compound)
The conductive polymer-containing liquid may contain one or more basic compounds. The basic compound functions as a Brønsted base that receives protons from the excess anion groups of the polyanion. In order to fulfill this function, the amount of the basic compound dissolved in water is preferably 0.001 g or more per 100 g of water at 20°C. The upper limit of the dissolution amount is not particularly limited, but even if it is, for example, about 0.1 g, the above function can be sufficiently achieved.

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

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

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, and N-propyl. Imidazole, 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-hydroxy benzimidazole, 2-(2-pyridyl)benzimidazole, pyridine, pyrimidine, pyrazine and alkyl substituted products thereof (for example, substituted products with an alkyl group having 1 to 4 carbon atoms such as methyl, ethyl, propyl, butyl), Examples include derivatives such as halogen-substituted products (for example, substituted products with halogen groups such as fluoro, chloro, and bromine) and nitrile-substituted products.
Among these, nitrogen-containing aromatic compounds are preferred, and imidazole is more preferred.

The content of the basic compound contained in the conductive polymer-containing liquid is, for example, 1 mass part per 100 parts by mass of the π-conjugated conductive polymer and the polyanion (that is, 100 parts by mass of the conductive composite). Parts by weight or more and 1000 parts by weight or less, more preferably 5 parts by weight or more and 100 parts by weight or less, and still more preferably 10 parts by weight or more and 50 parts by weight or less. Within the above preferred range, the ESR of the capacitor can be further reduced.

The content of the basic compound contained in the conductive polymer-containing liquid is preferably such that the pH of the conductive polymer-containing liquid (25°C) is 2.0 to 8.0, and 2.0 to 8.0. The content is more preferably 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.

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

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.

The content of the polyol compound contained in the conductive polymer-containing liquid is, for example, 100 parts by mass with respect to a total of 100 parts by mass of the π-conjugated conductive polymer and the polyanion (that is, 100 parts by mass of the conductive composite). It is preferably at least 10,000 parts by mass, more preferably at least 200 parts by mass and at most 2,000 parts by mass, and even more preferably at least 300 parts by mass and at most 1,000 parts by mass.
Within the above preferred range, the ESR of the capacitor can be further reduced.

The content of the polyol compound relative to the total mass of the conductive polymer-containing liquid 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 5% by mass or more and 9% by mass or less. More preferred. Within the above preferred range, the coating properties of the conductive polymer-containing liquid can be improved, and the ESR of the capacitor can be further reduced.

(Optional additives)
The conductive polymer-containing liquid may contain any additive, and the content ratio is determined appropriately depending on the type of additive, but the total mass of the π-conjugated conductive polymer and the polyanion is 100. (ie, 100 parts by mass of the conductive composite), the amount can be, for example, 1 to 1000 parts by mass. Here, the optional additive is a compound other than the conductive composite, the basic compound, the polyol compound, and the dispersion medium.

Examples of optional additives include surfactants, inorganic conductive agents, antifoaming agents, coupling agents, antioxidants, and ultraviolet absorbers.
Examples of the surfactant include nonionic, anionic, and cationic surfactants, and nonionic surfactants are preferred from the viewpoint of storage stability. Additionally, polymeric surfactants such as polyvinyl alcohol and polyvinylpyrrolidone may be added.
Examples of the inorganic conductive agent include metal ions, conductive carbon, and the like. Metal ions can be generated by dissolving metal salts in water.
Examples of antifoaming agents include silicone resins, polydimethylsiloxanes, silicone oils, 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, sugars, and the like.
Examples of UV absorbers include benzotriazole UV absorbers, benzophenone UV absorbers, salicylate UV absorbers, cyanoacrylate UV absorbers, oxanilide UV absorbers, hindered amine UV absorbers, benzoate UV absorbers, etc. can be mentioned.

《Capacitor manufacturing method》
A second aspect of the present invention includes the step of obtaining a conductive polymer-containing liquid by the manufacturing method of the first aspect, and the step of obtaining the conductive polymer on the surface of the dielectric layer formed on the surface of the anode made of a porous body of valve metal. This method of manufacturing a capacitor includes the steps of applying a liquid containing a polymer and drying it to form a solid electrolyte layer.

The method for manufacturing a capacitor according to the present embodiment 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), and a step of forming a cathode at a position opposite to the dielectric layer. It is preferable to include a step of arranging (cathode forming step) and a step of forming a solid electrolyte layer on at least a portion of the surface of the dielectric layer (film forming step). Each step will be explained below with reference to FIG.

[Dielectric formation process]
In this step, the surface of the anode 11 made of a porous body of valve metal is oxidized to form the dielectric layer 12. The method for forming the dielectric layer 12 is not particularly limited, and for example, the surface of the anode 11 is anodized in an electrolytic solution for chemical conversion treatment such as an aqueous ammonium adipate solution, an aqueous ammonium borate solution, an aqueous ammonium phosphate solution, etc. There are several methods.

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

[Film forming process]
In this step, the solid electrolyte layer 14 is formed by applying the above-mentioned conductive polymer-containing liquid to at least a portion of the surface of the dielectric layer 12 and drying it.

As a method for applying the conductive polymer-containing liquid, for example, dipping (dip coating), comma coating, reverse coating, lip coating, microgravure coating, etc. can be applied. Among these methods, a method in which the anode 11 is immersed in a conductive polymer-containing liquid under reduced pressure is preferred. If the dipping method is used, the conductive polymer-containing liquid can be sufficiently applied to the inside of the porous structure on the surface of the dielectric layer 12. After soaking, take it out and proceed to the next drying process.

Examples of the drying method include room temperature drying, hot air drying, far infrared drying, and the like. Among these, hot air drying is preferred.
The drying temperature is preferably, for example, 100 to 180°C, more preferably 120 to 150°C. The drying time is preferably, for example, 0.2 to 1 hour.
After the drying process, the capacitor may be assembled by a conventional method.

<Capacitor>
An example of an embodiment of a capacitor that can be manufactured according to the second aspect 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 solid electrolyte layer 14 formed on the surface of the dielectric layer 12. The cathode 13 is provided on the front side. The cathode 13 is provided on the opposite side from the anode 11 with the dielectric layer 12 and solid electrolyte layer 14 interposed therebetween.

Examples of the valve metal constituting the anode 11 include aluminum, tantalum, niobium, titanium, hafnium, zirconium, zinc, tungsten, bismuth, and antimony. Among these, aluminum, tantalum, and niobium are preferred.
Specific examples of the anode 11 include aluminum foil that has been etched to increase its surface area and then its surface has been oxidized, and the surface of a sintered body of tantalum particles or niobium particles has been oxidized and made into pellets. Can be mentioned. The material treated in this manner becomes a porous material with irregularities formed on its surface.

The dielectric layer 12 in this embodiment is a layer formed by oxidizing the surface of the anode 11. For example, the surface of the anode 11, which is a metal body, is anodized in an electrolytic solution such as an aqueous ammonium adipate solution. It was formed by this. Similar to the anode 11, the dielectric layer 12 also has projections and depressions.

As the cathode 13 in this embodiment, a metal layer made of a conductive material, such as a conductive layer formed from a conductive paste or an aluminum foil, can be used.

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

<Conductive composite>
The conductive composite contained in the solid electrolyte layer includes a π-conjugated conductive polymer and a polyanion. The polyanion in the conductive composite is doped into a π-conjugated conductive polymer to form a conductive composite having conductivity.

The content of the conductive composite relative 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. . The above range is preferable because the equivalent series resistance of the capacitor is more likely to decrease.

<Basic compound>
The solid electrolyte layer may further contain one or more of the above-mentioned basic compounds. By containing a basic compound, the ESR of the capacitor can be further reduced.

The content ratio of the basic compound contained in the solid electrolyte layer is, for example, 1 part by mass or more and 1000 parts by mass with respect to a total of 100 parts by mass of the π-conjugated conductive polymer and the polyanion (that is, 100 parts by mass of the conductive composite). parts by weight or less, more preferably 5 parts by weight or more and 100 parts by weight or less, even more preferably 10 parts by weight or more and 50 parts by weight or less.
Within the above preferred range, the ESR of the capacitor can be further reduced.

<Polyol compound>
The solid electrolyte layer may further contain one or more of the aforementioned polyols. By containing polyol, the ESR of the capacitor can be further reduced.

The total content of the polyol compounds contained in the solid electrolyte layer is, for example, based on 100 parts by mass of the π-conjugated conductive polymer and polyanion contained in the solid electrolyte layer (that is, 100 parts by mass of the conductive composite). , preferably from 100 parts by mass to 10,000 parts by mass, more preferably from 200 parts by mass to 2,000 parts by mass, and even more preferably from 300 parts by mass to 1,000 parts by mass.
Within the above preferred range, the ESR of the capacitor can be further reduced.

[Electrolyte]
The capacitor of this embodiment may include an electrolytic solution that impregnates the solid electrolyte layer.
Examples of the solvent constituting the electrolytic solution include alcohol solvents such as ethylene glycol, diethylene glycol, propylene glycol, 1,4-butanediol, and glycerin, and lactone solvents such as γ-butyrolactone, γ-valerolactone, and δ-valerolactone. Solvents, sulfur-based solvents such as sulfolane, dimethylsulfoxide, dimethylsulfone, amide-based solvents such as N-methylformamide, N,N-dimethylformamide, N-methylacetamide, N-methylpyrrolidinone, acetonitrile, 3-methoxypropionitrile Examples include nitrile solvents such as nitrile solvents, water, and the like.
Examples of electrolytes constituting the electrolytic solution include adipic acid, glutaric acid, succinic acid, benzoic acid, isophthalic acid, phthalic acid, terephthalic acid, maleic acid, toluic acid, enanthic acid, malonic acid, formic acid, and 1,6- Decanedicarboxylic acid such as decanedicarboxylic acid, 5,6-decanedicarboxylic acid, octanedicarboxylic acid such as 1,7-octanedicarboxylic acid, organic acid such as azelaic acid, sebacic acid; or boric acid, boric acid and polyhydric alcohol. The resulting polyhydric alcohol complex compound of boric acid; contains inorganic acids such as phosphoric acid, carbonic acid, and silicic acid as an anion component, and contains primary amines (methylamine, ethylamine, propylamine, butylamine, ethylenediamine, etc.), secondary amines (dimethyl amines, diethylamine, dipropylamine, methylethylamine, diphenylamine, etc.), tertiary amines (trimethylamine, triethylamine, tripropylamine, triphenylamine, 1,8-diazabicyclo(5,4,0)-undecene-7, etc.), Electrolytes containing a cationic component such as tetraalkylammonium (tetramethylammonium, tetraethylammonium, tetrapropylammonium, tetrabutylammonium, methyltriethylammonium, dimethyldiethylammonium, etc.) may be mentioned.

The capacitor of this embodiment is not limited to the above configuration, and a separator may be provided between the dielectric layer and the cathode. An example of a capacitor in which a separator is provided between a dielectric layer and a cathode is a wound capacitor.
Examples of the separator include sheets (including nonwoven fabrics) made of cellulose, polyvinyl alcohol, polyester, polyethylene, polystyrene, polypropylene, polyimide, polyamide, polyvinylidene fluoride, etc., nonwoven fabrics of glass fiber, and the like.
The density of the separator is, for example, 0.1 g/cm ³ or more and 1.0 g/cm ³ or less.
When a separator is provided, a method of forming a cathode by impregnating the separator with carbon paste or silver paste can also be applied.

(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, 1.14 g of ammonium persulfate oxidizing agent solution previously dissolved in 10 ml of water was added dropwise for 20 minutes, and this solution was incubated for 12 hours. Stirred.
To the obtained sodium polystyrene sulfonate solution, 1000 ml of sulfuric acid diluted to 10% by mass was added, and about 1000 ml of the solvent in the obtained polystyrene sulfonic acid solution was removed by ultrafiltration. Next, 2000 ml of ion-exchanged water was added to the residual liquid, about 2000 ml of the solvent was removed by ultrafiltration, and the polystyrene sulfonic acid was washed with water. This water washing operation was repeated three times.
Water in the resulting solution was removed under reduced pressure to obtain colorless solid polystyrene sulfonic acid.
Next, 10 g of the obtained polystyrene sulfonic acid was dissolved in 90 g of ion-exchanged water to obtain a 10% by mass polystyrene sulfonic acid aqueous solution.

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

(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, 0.38 g of ammonium persulfate oxidizing agent solution previously dissolved in 10 ml of water was added dropwise for 20 minutes, and this solution was incubated for 12 hours. Stirred.
To the obtained sodium polystyrene sulfonate solution, 1000 ml of sulfuric acid diluted to 10% by mass was added, and about 1000 ml of the solvent in the obtained polystyrene sulfonic acid solution was removed by ultrafiltration. Next, 2000 ml of ion-exchanged water was added to the residual liquid, about 2000 ml of the solvent was removed by ultrafiltration, and the polystyrene sulfonic acid was washed with water. This water washing operation was repeated three times.
Water in the resulting solution was removed under reduced pressure to obtain colorless solid polystyrene sulfonic acid.
Next, 10 g of the obtained polystyrene sulfonic acid was dissolved in 90 g of ion-exchanged water to obtain a 10% by mass polystyrene sulfonic acid aqueous solution.
The weight average molecular weight of the polystyrene sulfonic acid (PSS) obtained above was measured using GPC in the same manner as in Production Example 1, and was 540,000.

(Manufacturing Example 3) Creation of a capacitor element After connecting an anode lead terminal to an etched aluminum foil (anode foil), a voltage of 40 V was applied in a 10% by mass ammonium adipate aqueous solution, and chemical conversion (oxidation treatment) was performed. A dielectric layer was formed on both sides of the aluminum foil to obtain an anode foil.
Next, opposing aluminum cathode foils with cathode lead terminals welded to both sides of the anode foil were laminated with a cellulose separator interposed therebetween, and this was wound into a cylindrical shape to obtain a capacitor element.

(Example 1)
3.0 g of 3,4-ethylenedioxythiophene (EDOT), 90 g of the 10% by mass PSS aqueous solution of Production Example 1, and 325 g of ion-exchanged water were mixed at 20° C. in a reaction vessel.
Next, after the gas in the reaction container was removed using a vacuum pump, nitrogen was blown into the reaction container to perform nitrogen substitution, and the oxygen concentration contained in the gas in the remaining space in the reaction container was set to 1.2% by volume. Note that the oxygen concentration was measured using an oxygen concentration meter (manufactured by Shin Cosmos Electric Co., Ltd., model XP-3380II).
The resulting mixed solution was maintained at 20° C. and sealed to maintain the oxygen concentration of the gas in the reaction vessel at 1.2% by volume, and 0.15 g of ferric sulfate was added while stirring. Next, a solution of 4.4 g of sodium persulfate dissolved in 295.6 g of ion-exchanged water was slowly added, and the resulting reaction solution was stirred for 8 hours and sealed tightly to increase the oxygen concentration of the gas in the reaction vessel. The reaction was carried out at 20° C. while maintaining the concentration at 1.2% by volume.
Through the above reaction, a conductive composite (PEDOT-PSS) containing poly(3,4-ethylenedioxythiophene), which is a π-conjugated conductive polymer, and polystyrene sulfonic acid, and water, which is a dispersion medium, is formed. A polymer-containing liquid was obtained.
39 g of Duolite C255LFH (manufactured by Sumika Chemtex Co., Ltd., cation exchange resin) and 39 g of Duolite A368MS (manufactured by Sumika Chemtex Co., Ltd., anion exchange resin) are added to this conductive polymer-containing liquid, and the ion exchange resin is filtered. 710 g of a conductive polymer-containing liquid from which the oxidizing agent and the catalyst had been removed was obtained, and the solid content was measured.
Next, water was distilled off under reduced pressure from the obtained conductive polymer-containing liquid using an evaporator to reduce the solid content to 1.6% by mass. Imidazole (0.3 g) was added to 100 g of the obtained conductive polymer-containing liquid to adjust the pH to 2.5, and 8 g of diethylene glycol was added.
Next, the capacitor element obtained in Production Example 3 was immersed in the above conductive polymer-containing liquid under reduced pressure, and then dried for 30 minutes in a hot air dryer at 125°C to form a conductive layer on the surface of the dielectric layer. A solid electrolyte layer containing the composite was formed.
Next, the capacitor element on which the solid electrolyte layer was formed was loaded into an aluminum case, and the capacitor element was sealed with a sealing rubber to produce a capacitor.

(Example 2)
A capacitor was produced in the same manner as in Example 1 except that the oxygen concentration of the gas in the reaction vessel was set to 3.0% by volume.

(Example 3)
A capacitor was produced in the same manner as in Example 1 except that the oxygen concentration of the gas in the reaction vessel was 4.7% by volume.

(Example 4)
A capacitor was produced in the same manner as in Example 1, except that the polystyrene sulfonic acid aqueous solution (PSS concentration 10% by mass) of Production Example 1 was replaced with the polystyrene sulfonic acid aqueous solution (PSS concentration 10% by mass) of Production Example 2. Created.

(Comparative example 1)
A capacitor was produced in the same manner as in Example 1 except that the oxygen concentration of the gas in the reaction vessel was 0.5% by volume.

(Comparative example 2)
A capacitor was produced in the same manner as in Example 1 except that the oxygen concentration of the gas in the reaction vessel was 0.1% by volume.

(Comparative example 3)
A capacitor was produced in the same manner as in Example 1, except that the gas in the reaction vessel was not replaced with nitrogen.

(Comparative example 4)
In Example 1, the oxygen concentration of the gas in the reaction vessel was set to 0.5% by volume, and the polystyrene sulfonic acid aqueous solution of Production Example 1 (PSS concentration 10% by mass) was replaced with the polystyrene sulfonic acid aqueous solution of Production Example 2 (PSS concentration 10% by mass). ) A capacitor was manufactured in the same manner as in Example 1 except that the capacitor was manufactured in the same manner as in Example 1.

(Comparative example 5)
Except that in Example 1, the gas in the reaction container was not replaced with nitrogen, and the polystyrene sulfonic acid aqueous solution (PSS concentration 10% by mass) of Production Example 1 was replaced with the polystyrene sulfonic acid aqueous solution (PSS concentration 10% by mass) of Production Example 2. A capacitor was manufactured in the same manner as in Example 1.

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

<Evaluation>
[Capacitance/Equivalent series resistance]
For each example capacitor, use LCR meter ZM2376 (manufactured by NF Circuit Design Block Co., Ltd.) to measure the capacitance at 120Hz (unit: μF) and the equivalent series resistance (ESR) at 100kHz (unit: Ω). was measured. The measurement results are shown in Table 1.

<Results>
When the oxygen concentration in the reaction vessel during chemical oxidative polymerization of a π-conjugated conductive polymer is within a predetermined range, a conductive polymer-containing liquid suitable for manufacturing a capacitor with reduced ESR can be obtained. was confirmed.

Claims (10)

By polymerizing a monomer that forms a π-conjugated conductive polymer with a reaction solution containing a polyanion and an aqueous dispersion medium,
A method for producing a conductive polymer-containing liquid, the method comprising a polymerization step of obtaining a conductive polymer-containing liquid containing a conductive composite containing the π-conjugated conductive polymer and the polyanion,
The monomer is polymerized in an atmosphere in which the oxygen concentration of the gas in the reaction container containing the reaction solution is 0.9% by volume or more and 5.0% by volume or less to form the conductive composite. Method for producing molecule-containing liquid. The method for producing a conductive polymer-containing liquid according to claim 1, wherein the π-conjugated conductive polymer is poly(3,4-ethylenedioxythiophene) or the polyanion is polystyrene sulfonic acid. . The conductive polymer according to claim 1, wherein the monomer is polymerized by adding an oxidizing agent and a catalyst to the reaction liquid, and then the oxidizing agent and the catalyst are removed from the conductive polymer-containing liquid. Method for producing a containing liquid. The production of the conductive polymer-containing liquid according to claim 3, wherein the oxidizing agent and the catalyst are removed by bringing the conductive polymer-containing liquid into contact with at least one of a cation exchange resin and an anion exchange resin. Method. 4. The method for producing a conductive polymer-containing liquid according to claim 3, wherein a basic compound is further added to the conductive polymer-containing liquid from which the oxidizing agent and the catalyst have been removed. The method for producing a conductive polymer-containing liquid according to claim 5, wherein the basic compound is a nitrogen-containing aromatic compound. The method for producing a conductive polymer-containing liquid according to claim 5, wherein the pH (25° C.) of the conductive polymer-containing liquid is adjusted to 2.0 to 8.0 by adding the basic compound. 4. The method for producing a conductive polymer-containing liquid according to claim 3, further comprising adding a polyol compound containing two or more hydroxyl groups to the conductive polymer-containing liquid from which the oxidizing agent and the catalyst have been removed. The method for producing a conductive polymer-containing liquid according to claim 8, wherein the polyol compound is diethylene glycol. Obtaining a conductive polymer-containing liquid by the method for producing a conductive polymer-containing liquid according to any one of claims 1 to 9;
applying the conductive polymer-containing liquid to the surface of the dielectric layer formed on the surface of the anode made of a porous body of valve metal and drying it to form a solid electrolyte layer. Production method.

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