JP7558130B2 - Capacitor and manufacturing method thereof - Google Patents

Description

The present invention relates to a capacitor having a solid electrolyte layer containing a π-conjugated conductive polymer and a method for manufacturing the same.

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

JP 2020-100744 A

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 the heat resistance. On the other hand, there is a demand for a capacitor with reduced equivalent series resistance without relying on the sulfide.
The present invention provides a capacitor with reduced equivalent series resistance and a method for manufacturing the same.

[1] A capacitor comprising: an anode made of a porous body of a valve metal; a dielectric layer made of an oxide of the valve metal; a cathode made of a conductive material provided on the dielectric layer opposite to the anode; and at least one solid electrolyte layer formed between the dielectric layer and the cathode, wherein the solid electrolyte layer contains a conductive complex including a π-conjugated conductive polymer and an anionic polymer having a monomer unit derived from compound 1 represented by the following formula (1):
[2] The capacitor according to [1], wherein the anionic polymer is a homopolymer of the compound 1.
[3] The capacitor according to [1], wherein the anionic polymer is a copolymer of styrenesulfonic acid and the compound 1.
[4] The capacitor according to any one of [1] to [3], wherein the solid electrolyte layer further contains a conductive complex containing a π-conjugated conductive polymer and a polyanion not corresponding to the anionic polymer.
[5] The capacitor according to [4], wherein the polyanion is polystyrene sulfonic acid.
[6] The capacitor according to any one of [1] to [5], wherein the solid electrolyte layer further contains a nitrogen-containing compound.
[7] The capacitor according to any one of [1] to [6], wherein the π-conjugated conductive polymer is poly(3,4-ethylenedioxythiophene).
[8] A method for producing a capacitor, comprising: a dielectric forming step of oxidizing a surface of an anode made of a porous valve metal to form a dielectric layer; a cathode forming step of arranging a cathode at a position facing the dielectric layer; and a lamination step of forming at least one solid electrolyte layer on the surface of the dielectric layer, wherein in the lamination step, the solid electrolyte layer is formed by applying a first conductive polymer dispersion to the surface of the dielectric layer and drying it, and the first conductive polymer dispersion contains a π-conjugated conductive polymer and an anionic polymer having a monomer unit derived from Compound 1 represented by the following formula (1):
[9] The method for producing a capacitor according to [8], wherein after the first conductive polymer dispersion is applied and dried, a second conductive polymer dispersion is further applied and dried to form the solid electrolyte layer, and the second conductive polymer dispersion contains a conductive complex including a π-conjugated conductive polymer and a polyanion not corresponding to the anionic polymer.
[10] A method for producing a capacitor, comprising: a dielectric forming step of oxidizing a surface of an anode made of a porous valve metal to form a dielectric layer; a cathode forming step of arranging a cathode at a position facing the dielectric layer; and a lamination step of forming at least one solid electrolyte layer on the surface of the dielectric layer, wherein in the lamination step, a second conductive polymer dispersion containing a π-conjugated conductive polymer and a conductive complex containing a polyanion not corresponding to the anionic polymer described below is applied to the surface of the dielectric layer and dried, and then a first conductive polymer dispersion is further applied and dried to form the solid electrolyte layer, and the first conductive polymer dispersion contains a conductive complex containing a π-conjugated conductive polymer and an anionic polymer having a monomer unit derived from Compound 1 represented by the following Formula (1):

［式中、Ｒは炭素数４～２０の直鎖状又は分岐鎖状アルキル基であり、ｎは４～１００の整数である。］

[In the formula, R is a linear or branched alkyl group having 4 to 20 carbon atoms, and n is an integer from 4 to 100.]

The capacitor of the present invention has a reduced equivalent series resistance due to the inclusion of a specific anionic polymer in the solid electrolyte layer. The capacitor can be easily manufactured by the manufacturing method of the present invention.

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

In this specification and claims, the lower and upper limits of the numerical ranges indicated with "~" are considered to be included in the numerical range.

1 is a cross-sectional view showing an embodiment of a capacitor of the present invention.

Capacitor
A first aspect of the present invention is a capacitor. An example of an embodiment of the capacitor will be described. A capacitor 10 shown in Fig. 1 includes an anode 11 made of a porous body of a 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 to the anode 11, with the dielectric layer 12 and the solid electrolyte layer 14 sandwiched therebetween.

Examples of valve metals constituting the anode 11 include aluminum, tantalum, niobium, titanium, hafnium, zirconium, zinc, tungsten, bismuth, and antimony. Among these, aluminum, tantalum, and niobium are preferable.
Specific examples of the anode 11 include an aluminum foil that has been etched to increase its surface area and then oxidized, and a sintered body of tantalum particles or niobium particles that has been oxidized and formed into pellets. Such a treatment results in a porous body with irregularities formed on the surface.

The dielectric layer 12 in this embodiment is a layer formed by oxidizing the surface of the anode 11, for example, by anodizing the surface of the metallic anode 11 in an electrolyte such as an aqueous solution of ammonium adipate. As with the anode 11, the dielectric layer 12 also has projections and recesses (see FIG. 1).

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.

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

In the illustrated example, the solid electrolyte layer 14 is depicted as a single layer, but the solid electrolyte layer 14 may be a laminate of two or more layers. The composition of each solid electrolyte layer may be the same or different. When the application and drying of the conductive polymer dispersion liquid described below is repeated multiple times during the manufacture of the solid electrolyte layer 14, the solid electrolyte layers may be laminated one by one after each application and drying. However, since it is not necessarily easy to strictly analyze whether the solid electrolyte layer 14 is a single layer or multiple layers, unless otherwise specified, the solid electrolyte layer 14 may be a single layer or multiple layers, and may be considered to be a single solid electrolyte layer 14 as a whole.

[Conductive composite]
The following describes the conductive complex contained in the solid electrolyte layer 14. The conductive complex of this embodiment contains a π-conjugated conductive polymer and an anionic polymer having a monomer unit derived from Compound 1 represented by Formula (1) described below.
The anionic polymer may be a homopolymer or a copolymer.
The homopolymer is a homopolymer formed by polymerizing only compound 1.
The copolymer is a copolymer of compound 1 and an anionic compound having a polymerizable functional group and an anionic group (excluding compound 1).

The mass average molecular weight Mw of the homopolymer is preferably from 1,000 to 1,000,000, more preferably from 5,000 to 100,000, and even more preferably from 10,000 to 50,000, from the viewpoint of improving the doping effect on the π-conjugated conductive polymer and the dispersibility of the conductive composite.
The mass average molecular weight herein refers to an average molecular weight based on mass measured by gel permeation chromatography (GPC) using pullulan as a standard substance.

The polymerizable functional group of the anionic compound is not particularly limited as long as it is copolymerizable with the vinyl group of compound 1, and examples thereof include a vinyl group and a vinylidene group.
The anionic group of the anionic compound is preferably one that can dissociate in water and be doped into a π-conjugated conductive polymer, and examples of the anionic group include a sulfo group and a carboxy group.
The counter cation of the anionic group may be a proton, an alkali metal cation such as a sodium ion or a potassium ion, or an alkaline earth metal cation, etc. However, the counter cation of the anionic group is preferably a proton, since this makes it easier for the anionic polymer to be doped into the π-conjugated conductive polymer.
Specific examples of the anionic compound include known compounds that form monomer units of polyanions, which will be described later.

In the copolymer, when the total number of monomer units in the copolymer is taken as 100 mol %, the ratio of the content a of the monomer unit derived from compound 1 to the content b of the other monomer unit is, for example, 10:90 to 90:10, preferably 20:80 to 80:20, more preferably 30:70 to 70:30, and even more preferably 40:60 to 60:40, based on mol %.
When the particle size falls within the above preferred range, the particle size of the conductive complex is appropriately small, and the equivalent series resistance of the capacitor of this embodiment is sufficiently reduced.

The mass average molecular weight Mw of the copolymer is preferably from 5,000 to 2,000,000, more preferably from 10,000 to 1,000,000, and even more preferably from 100,000 to 500,000, from the viewpoint of improving the doping effect on the π-conjugated conductive polymer and the dispersibility of the conductive composite.
The mass average molecular weight herein refers to an average molecular weight based on mass measured by gel permeation chromatography (GPC) using pullulan as a standard substance.

The other monomer units constituting the copolymer include, for example, monomer units constituting a polyanion, which will be described later.

The conductive complex may further contain a polyanion that does not have a monomer unit derived from compound 1. Specific examples of the polyanion will be described later.
By further including the polyanion in the conductive complex, the equivalent series resistance of the capacitor of this embodiment becomes lower.

The content of the anionic polymer in the conductive complex is preferably 1 part by mass or more and 1,000 parts by mass or less, more preferably 10 parts by mass or more and 700 parts by mass or less, and even more preferably 100 parts by mass or more and 500 parts by mass or less, relative to 100 parts by mass of the π-conjugated conductive polymer.
When the content is equal to or greater than the lower limit of the above range, the doping effect of the anionic polymer on the π-conjugated conductive polymer becomes stronger, the dispersibility of the conductive complex improves, the particle size of the conductive complex becomes sufficiently small, and the equivalent series resistance of the capacitor becomes lower.
When the content is equal to or less than the upper limit of the above range, a decrease in electrical conductivity due to a decrease in the content ratio of the π-conjugated conductive polymer can be suppressed.

When the conductive complex contains the polyanion, the content of the polyanion is preferably 1 part by mass or more and 1,000 parts by mass or less, more preferably 10 parts by mass or more and 500 parts by mass or less, and even more preferably 50 parts by mass or more and 200 parts by mass or less, relative to 100 parts by mass of the anionic polymer.
When the content is at least the lower limit of the above range, the conductivity of the conductive layer becomes higher.
When the content is equal to or less than the upper limit of the above range, the effect of reducing the particle size of the conductive composite can be sufficiently obtained.

The solid electrolyte layer of the capacitor of this embodiment may contain one type of conductive composite, or two or more types of conductive composites.
When two or more kinds of conductive complexes are contained, in addition to the conductive complex (A) containing the anionic polymer, the conductive complex (B) not containing the anionic polymer may be contained. The conductive complex (B) may be a conventional conductive complex, that is, a conductive complex containing a π-conjugated conductive polymer and a polyanion described later.

From the viewpoint of reducing the equivalent series resistance of the capacitor of this embodiment while ensuring a capacitance equal to or greater than that of conventional capacitors, it is preferable that the solid electrolyte layer of the capacitor of this embodiment contains both the conductive complex (A) and the conductive complex (B) described above.

The mass ratio (Ma/Mb) of the content Ma of the conductive complex (A) to the content Mb of the conductive complex (B) contained in the entire solid electrolyte layer 14 is preferably 0.1 to 2, more preferably 0.2 to 1, and even more preferably 0.3 to 0.8.
When the content is within the above range, it becomes easy to reduce the equivalent series resistance while maintaining the capacitance of the capacitor of this embodiment.

The content of the polyanion contained in the conductive complex (B) is preferably 1 part by mass or more and 1,000 parts by mass or less, more preferably 10 parts by mass or more and 700 parts by mass or less, and even more preferably 100 parts by mass or more and 500 parts by mass or less, relative to 100 parts by mass of the π-conjugated conductive polymer.
When the content is equal to or greater than the lower limit of the above range, the doping effect of the polyanion on the π-conjugated conductive polymer becomes stronger, the dispersibility of the conductive composite improves, and the equivalent series resistance of the capacitor becomes lower.
When the content is equal to or less than the upper limit of the above range, a decrease in electrical conductivity due to a decrease in the content ratio of the π-conjugated conductive polymer can be suppressed.

<π-conjugated conductive polymer>
The π-conjugated conductive polymer may be an organic polymer whose main chain is composed of a π-conjugated system, and examples thereof include polypyrrole-based conductive polymers, polythiophene-based conductive polymers, polyacetylene-based conductive polymers, polyphenylene-based conductive polymers, polyphenylenevinylene-based conductive polymers, polyaniline-based conductive polymers, polyacene-based conductive polymers, polythiophenevinylene-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.

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-iodothiophene). thiophene), poly(3-cyanothiophene), poly(3-phenylthiophene), poly(3,4-dimethylthiophene), poly(3,4-dibutylthiophene), poly(3-hydroxythiophene), poly(3-methoxythiophene), poly(3-ethoxythiophene), poly(3-butoxythiophene), poly(3-hexyloxythiophene), poly(3-heptyloxythiophene), poly(3-octyloxythiophene), poly(3-decyloxythiophene), poly(3-dodecyloxythiophene), oxythiophene), poly(3-octadecyloxythiophene), poly(3,4-dihydroxythiophene), poly(3,4-dimethoxythiophene), poly(3,4-diethoxythiophene), poly(3,4-dipropoxythiophene), poly(3,4-dibutoxythiophene), poly(3,4-dihexyloxythiophene), poly(3,4-diheptyloxythiophene), poly(3,4-dioctyloxythiophene), poly(3,4-didecyloxythiophene), poly(3,4-di dodecyloxythiophene), poly(3,4-ethylenedioxythiophene), poly(3,4-propylenedioxythiophene), poly(3,4-butylenedioxythiophene), poly(3-methyl-4-methoxythiophene), poly(3-methyl-4-ethoxythiophene), poly(3-carboxythiophene), poly(3-methyl-4-carboxythiophene), poly(3-methyl-4-carboxyethylthiophene), and poly(3-methyl-4-carboxybutylthiophene).
Examples of polypyrrole-based conductive polymers include polypyrrole, poly(N-methylpyrrole), poly(3-methylpyrrole), poly(3-ethylpyrrole), poly(3-n-propylpyrrole), poly(3-butylpyrrole), poly(3-octylpyrrole), poly(3-decylpyrrole), poly(3-dodecylpyrrole), poly(3,4-dimethylpyrrole), poly(3,4-dibutylpyrrole), poly(3-carboxypyrrole), poly(3-methyl-4-carboxypyrrole), poly(3-methyl-4-carboxyethylpyrrole), poly(3-methyl-4-carboxybutylpyrrole), poly(3-hydroxypyrrole), poly(3-methoxypyrrole), poly(3-ethoxypyrrole), poly(3-butoxypyrrole), poly(3-hexyloxypyrrole), and poly(3-methyl-4-hexyloxypyrrole).
Examples of polyaniline-based conductive polymers include polyaniline, poly(2-methylaniline), poly(3-isobutylaniline), poly(2-anilinesulfonic acid), and poly(3-anilinesulfonic acid).
Among these π-conjugated conductive polymers, poly(3,4-ethylenedioxythiophene) is particularly preferred because of its excellent conductivity, transparency and heat resistance.
The conductive composite may contain one type of π-conjugated conductive polymer, or two or more types of polymers.

<Anionic Polymer>
Compound 1 represented by the following formula (1), which is a monomer material for the anionic polymer, is a compound in which a sulfonic acid group and a vinyl group are linked by a polyoxyethylene chain (CH ₂ CH ₂ O) _n .
The compound 1 constituting the anionic polymer may be one type or two or more types.

［式中、Ｒは炭素数４～２０の直鎖状又は分岐鎖状アルキル基であり、ｎは４～１００の整数である。］

[In the formula, R is a linear or branched alkyl group having 4 to 20 carbon atoms, and n is an integer from 4 to 100.]

The anionic polymer can be bonded to the π-conjugated conductive polymer as a dopant, similar to conventional polyanions. When functioning as a dopant, it is believed that the sulfonic acid group is doped as an anionic group. Doping the anionic polymer into the π-conjugated conductive polymer improves the conductivity of the π-conjugated conductive polymer and contributes to reducing the particle size, which will be described later.

The anionic polymer may be simply included in the conductive polymer dispersion as an additive without being doped into the π-conjugated conductive polymer, but in order for a π-conjugated conductive polymer (e.g., PEDOT), which is inherently poorly dispersible in water, to exhibit dispersibility in an aqueous dispersion medium, it is preferable that the anionic polymer be doped into the π-conjugated conductive polymer.

The alkyl group represented by R in the formula (1) is preferably linear.
The alkyl group has 4 to 20 carbon atoms, preferably 6 to 18 carbon atoms, more preferably 8 to 16 carbon atoms, further preferably 10 to 14 carbon atoms, and particularly preferably 10 to 12 carbon atoms.
When the number of carbon atoms is within the above preferred range, the particle size of the conductive composite can be made smaller.

The degree of polymerization n of the polyoxyethylene chain is in the range of 4 to 100, preferably 5 to 80, more preferably 6 to 50, further preferably 7 to 30, and particularly preferably 8 to 20.
When the particle size is within the above preferred range, the particle size of the conductive composite can be made smaller, and the equivalent series resistance of the capacitor of this embodiment can be further reduced.

Specific preferred examples of compound 1 include a sulfonate in which the ammonium of ammonium α-[1-(allyloxy)dodecan-2-yl]-ω-(sulfonatooxy)poly(oxyethylene) registered under CAS No. 352661-91-7 is replaced with a proton; and a sulfonate in which the ammonium of ammonium α-[1-(allyloxy)tetradecan-2-yl]-ω-(sulfonatooxy)poly(oxyethylene) registered under CAS No. 224646-44-0 is replaced with a proton.
These ammonium salts are available as AQUALON KH-05 (n=8-11, R=straight-chain alkyl group having 10 or 12 carbon atoms), AQUALON KH-10 (n=22-25, R=straight-chain alkyl group having 10 or 12 carbon atoms), and AQUALON KH-1025 (n=68-71, R=straight-chain alkyl group having 10 or 12 carbon atoms), manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.

When an anionic polymer is doped into a π-conjugated conductive polymer to form a conductive complex, some anionic groups in the anionic polymer are not doped into the π-conjugated conductive polymer, and the anionic polymer has excess anionic groups that are not involved in the doping. Since these excess anionic groups are hydrophilic groups, the conductive complex has high water dispersibility and low organic solvent dispersibility.
When the number of all anionic groups in the anionic polymer is taken as 100 mol %, the excess anionic groups are preferably from 30 mol % to 90 mol %, more preferably from 45 mol % to 75 mol %.

<Polyanion>
The conductive complex (A) and the conductive complex (B) may contain a polyanion that does not have a monomer unit derived from compound 1. However, when the conductive complex (A) contains a polyanion, the particle size tends to become large, and therefore, if a smaller particle size is given priority, it is preferable that the conductive complex (A) does not contain a polyanion.
A polyanion is a polymer having two or more, preferably ten or more, monomer units having an anionic group in the molecule. The anionic group of the polyanion functions as a dopant for a π-conjugated conductive polymer, and can improve the conductivity of the π-conjugated conductive polymer.

The anion group of the polyanion is preferably a sulfo group or a carboxy group, since these groups have an excellent doping effect on the π-conjugated conductive polymer.
Specific examples of such polyanions include polymers having a sulfo group, such as polystyrene sulfonic acid, polyvinyl sulfonic acid, polyallyl sulfonic acid, polyacrylic acid esters having a sulfo group, polymethacrylic acid esters having a sulfo group (e.g., poly(4-sulfobutyl methacrylate, polysulfoethyl methacrylate, polymethacryloyloxybenzenesulfonic acid), poly(2-acrylamido-2-methylpropanesulfonic acid), and polyisoprene sulfonic acid; and polymers having a carboxy group, such as polyvinyl carboxylic acid, polystyrene carboxylic acid, polyallyl carboxylic acid, polyacrylic acid, polymethacrylic acid, poly(2-acrylamido-2-methylpropanecarboxylic acid), and polyisoprene carboxylic acid. These may be homopolymers or copolymers consisting of two or more monomers.
Among these polyanions, polymers having a sulfo group are preferred, and polystyrene sulfonic acid is more preferred, since they can provide higher electrical conductivity.
The conductive complex may be composed of one type of polyanion or two or more types of polyanions.
The mass average molecular weight of the polyanion is preferably 20,000 or more and 1,000,000 or less, and more preferably 100,000 or more and 500,000 or less.
The mass average molecular weight herein refers to an average molecular weight based on mass measured by gel filtration chromatography using pullulan as a standard substance.

When the polyanion is doped into a π-conjugated conductive polymer to form a conductive composite (B), some anion groups in the polyanion are not doped into the π-conjugated conductive polymer and have excess anion groups that are not involved in the doping. Since these excess anion groups are hydrophilic groups, the conductive composite has high water dispersibility and low organic solvent dispersibility before modification, as described below.
When the number of all anionic groups in the polyanion is taken as 100 mol %, the excess anionic groups are preferably from 30 mol % to 90 mol %, more preferably from 45 mol % to 75 mol %.

[Nitrogen-containing compounds]
One or more nitrogen-containing compounds may be contained in the solid electrolyte layer 14. By containing a nitrogen-containing compound in the solid electrolyte layer 14, the equivalent series resistance of the capacitor can be further reduced.

Examples of the nitrogen-containing compound include the following amine compounds, nitrogen-containing aromatic compounds, and quaternary ammonium salts. When one or more selected from these are contained in the solid electrolyte layer 14, the equivalent series resistance of the capacitor can be further reduced.

The amine compound is a compound having an amino group, and the amino group may react with the anion group of the polyanion.
The amine compound may be any of primary amines, secondary amines, and tertiary amines. The amine compound may have a substituent selected from a linear or branched alkyl group having from 2 to 12 carbon atoms, an aryl group having from 6 to 12 carbon atoms, an aralkyl group having from 7 to 12 carbon atoms, an alkylene group having from 2 to 12 carbon atoms, an arylene group having from 6 to 12 carbon atoms, an aralkylene group having from 7 to 12 carbon atoms, and an oxyalkylene group having from 2 to 12 carbon atoms.
Specific examples of primary amines include aniline, toluidine, benzylamine, and ethanolamine.
Specific examples of secondary amines include diethanolamine, dimethylamine, diethylamine, dipropylamine, diphenylamine, dibenzylamine, and dinaphthylamine.
Specific examples of the tertiary amine include triethanolamine, trimethylamine, triethylamine, tripropylamine, tributylamine, trioctylamine, triphenylamine, tribenzylamine, and trinaphthylamine.
Of these amine compounds, tertiary amines are preferred, and triethylamine and tripropylamine are more preferred.

Examples of nitrogen-containing aromatic compounds (aromatic compounds in which at least one nitrogen atom forms a ring structure) include pyrrole, imidazole, 2-methylimidazole, 2-propylimidazole, N-methylimidazole, N-propylimidazole, N-butylimidazole, 1-(2-hydroxyethyl)imidazole, 2-ethyl-4-methylimidazole, 1,2-dimethylimidazole, 1-benzyl-2-methylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 2-phenyl-4,5-dihydroxymethylimidazole, 1-acetylimidazole, 2-aminobenzimidazole, 2-amino-1-methylbenzimidazole, 2-hydroxybenzimidazole, 2-(2-pyridyl)benzimidazole, and pyridine.
Of these nitrogen-containing aromatic compounds, imidazole is more preferred.

Specific examples of quaternary ammonium salts include tetramethylammonium salts, tetraethylammonium salts, tetrapropylammonium salts, tetraphenylammonium salts, tetrabenzylammonium salts, and tetranaphthylammonium salts. Examples of an anion that pairs with ammonium include hydroxide ions.

The total content of the nitrogen-containing compounds contained in the solid electrolyte layer 14 is, for example, preferably 1 part by mass or more and 1,000 parts by mass or less, more preferably 5 parts by mass or more and 100 parts by mass or less, and even more preferably 10 parts by mass or more and 50 parts by mass or less, relative to 100 parts by mass of the conductive composite contained in the solid electrolyte layer 14.
The above range is preferable because it makes it easier to reduce the equivalent series resistance of the capacitor.
The number of types of the nitrogen-containing compound contained in the solid electrolyte layer 14 may be one or two or more.

[Polyol compound]
The solid electrolyte layer 14 may further contain one or more compounds having two or more hydroxyl groups (hereinafter, sometimes referred to as polyol compounds) different from the conductive complex and the nitrogen-containing compound. By containing a polyol compound, the equivalent series resistance of the capacitor may 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 polyol compound may be contained as a solvent for the electrolyte described below.

The total content of the polyol compounds contained in the solid electrolyte layer 14 is, for example, preferably 100 parts by mass or more and 10,000 parts by mass or less, more preferably 200 parts by mass or more and 2,000 parts by mass or less, and even more preferably 300 parts by mass or more and 1,000 parts by mass or less, relative to 100 parts by mass of the conductive composite contained in the solid electrolyte layer 14.
Within the above range, the equivalent series resistance of the capacitor is more easily reduced and the capacitance is more easily improved, which is preferable.
The number of types of the polyol compound contained in the solid electrolyte layer 14 may be one or two or more.

[Electrolyte]
The solid electrolyte layer 14 may contain an electrolyte solution in which an electrolyte is dissolved in a solvent for the electrolyte solution. The higher the electrical conductivity of the electrolyte solution, the more preferable it is.
Examples of the solvent for the electrolyte solution include alcohol-based solvents such as ethylene glycol, diethylene glycol, propylene glycol, 1,4-butanediol, and glycerin; lactone-based solvents such as γ-butyrolactone, γ-valerolactone, and δ-valerolactone; sulfur-based solvents such as sulfolane, dimethyl sulfoxide, and dimethyl sulfone; amide-based solvents such as N-methylformamide, N,N-dimethylformamide, N-methylacetamide, and N-methylpyrrolidinone; nitrile-based solvents such as acetonitrile and 3-methoxypropionitrile; and water.
Examples of the electrolyte include organic acids such as adipic acid, glutaric acid, succinic acid, benzoic acid, isophthalic acid, phthalic acid, terephthalic acid, maleic acid, toluic acid, enanthic acid, malonic acid, formic acid, decanedicarboxylic acids such as 1,6-decanedicarboxylic acid and 5,6-decanedicarboxylic acid, octanedicarboxylic acids such as 1,7-octanedicarboxylic acid, azelaic acid, and sebacic acid; or boric acid, polyhydric alcohol complex compounds of boric acid obtained from boric acid and polyhydric alcohol; inorganic acids such as phosphoric acid, carbonic acid, and silicic acid as anion components, and primary amines (methylamine, ethylamine, propylamine, butylamine, etc.). and the like), secondary amines (dimethylamine, diethylamine, dipropylamine, methylethylamine, diphenylamine, etc.), tertiary amines (trimethylamine, triethylamine, tripropylamine, triphenylamine, 1,8-diazabicyclo(5,4,0)-undecene-7, etc.), tetraalkylammonium (tetramethylammonium, tetraethylammonium, tetrapropylammonium, tetrabutylammonium, methyltriethylammonium, dimethyldiethylammonium, etc.), etc., as a cationic component.

<<Method of manufacturing a capacitor>>
The second aspect of the present invention is a method for producing a capacitor, which can easily produce the capacitor of the first aspect. This production method preferably includes a step of oxidizing the surface of an anode made of a porous valve metal to form a dielectric layer (dielectric forming step), a step of arranging a cathode at a position facing the dielectric layer (cathode forming step), and a step of forming at least one solid electrolyte layer on at least a part of the surface of the dielectric layer (lamination step).

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

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

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

First Embodiment
In a first embodiment of the lamination step, a first conductive polymer dispersion is applied to the surface of the dielectric layer and then dried to form a solid electrolyte layer.
The first conductive polymer dispersion contains a conductive complex (A) containing a π-conjugated conductive polymer and the anionic polymer, and a dispersion medium.

After the coating and drying are performed once on the surface of the dielectric layer to form a first solid electrolyte layer, the coating and drying of the conductive polymer dispersion may be repeated one or more times. By performing the second or subsequent coating and drying, second or subsequent solid electrolyte layers can be formed on the first solid electrolyte layer. However, due to the nature of the coating and drying, it is not necessary that the boundary between the first solid electrolyte layer and the second or subsequent solid electrolyte layers is clear.

In the first embodiment, the conductive polymer dispersion used for the second or subsequent coating and drying may be a first conductive polymer dispersion containing a conductive complex (A), or a second conductive polymer dispersion containing a conductive complex (B) containing a π-conjugated conductive polymer and a polyanion that does not fall under the category of the anionic polymer.

According to the first embodiment, the first conductive polymer dispersion is used in the first application and drying, so that the concentration of the conductive complex (A) near the surface of the dielectric layer can be increased.

Second Embodiment
In a second embodiment of the lamination step, a second conductive polymer dispersion is applied to the surface of the dielectric layer and dried, and then the first conductive polymer dispersion is further applied to the surface and dried to form a solid electrolyte layer.

In the second embodiment, by performing the above-mentioned two successive coating and drying operations, a first solid electrolyte layer containing the conductive complex (B) is formed on the surface of the dielectric layer, and a second solid electrolyte layer containing the conductive complex (A) is further formed on the surface of the first solid electrolyte layer. However, due to the nature of the coating and drying, it is not necessary that the boundary between the first solid electrolyte layer and the second solid electrolyte layer is clear.

After the second solid electrolyte layer is formed, the application and drying of the conductive polymer dispersion may be repeated one or more times. By applying and drying a third or subsequent time, a third or subsequent solid electrolyte layer can be formed on the second solid electrolyte layer. However, due to the nature of the application and drying, it is not necessary that the boundary between the second solid electrolyte layer and the third or subsequent solid electrolyte layers is clear.

In the second embodiment, the conductive polymer dispersion used for the third or subsequent application and drying may be a first conductive polymer dispersion containing a conductive complex (A), or a second conductive polymer dispersion containing a conductive complex (B) containing a π-conjugated conductive polymer and a polyanion that does not fall under the category of the anionic polymer.

According to the second embodiment, the second conductive polymer dispersion is used in the first application and drying, so that the concentration of the conductive complex (B) near the surface of the dielectric layer can be increased.

The first and second conductive polymer dispersion liquids used in the first and second embodiments may contain the nitrogen-containing compound, the polyol compound, additives described below, and the like.
The conductive polymer dispersion will be described below.

The dispersion medium constituting the conductive polymer dispersion is not particularly limited as long as it is a liquid capable of dispersing the conductive complex, and examples thereof include water, an organic solvent, and a mixture of water and an organic solvent.
Examples of the organic solvent include alcohol-based solvents, ether-based solvents, ketone-based solvents, ester-based solvents, aromatic hydrocarbon-based solvents, etc. These organic solvents may be used alone or in combination of two or more.
Examples of the alcohol solvent include methanol, ethanol, isopropanol, n-butanol, t-butanol, and allyl alcohol.
Examples of the ether solvent include diethyl ether, dimethyl ether, ethylene glycol, propylene glycol, propylene glycol monoalkyl ethers such as propylene glycol monomethyl ether, and propylene glycol dialkyl ethers.
Examples of the ketone solvent include diethyl ketone, methyl propyl ketone, methyl butyl ketone, methyl isopropyl ketone, methyl isobutyl ketone, methyl amyl ketone, diisopropyl ketone, methyl ethyl ketone, acetone, and diacetone alcohol.
Examples of the ester solvent include ethyl acetate, propyl acetate, and butyl acetate.
Examples of aromatic hydrocarbon solvents include benzene, toluene, xylene, ethylbenzene, propylbenzene, and isopropylbenzene.

Examples of the additives include a surfactant, an inorganic conductive agent, an antifoaming agent, a coupling agent, an antioxidant, an ultraviolet absorbing agent, etc. However, the additives are compounds other than the conductive complex, the nitrogen-containing compound, the polyol compound, and the dispersion medium (solvent).
The surfactant may be a nonionic, anionic or cationic surfactant, with the nonionic surfactant being preferred from the standpoint of storage stability. Polymer surfactants such as polyvinyl alcohol and polyvinylpyrrolidone may also be added.
Examples of the inorganic conductive agent include metal ions, conductive carbon, etc. Metal ions can be generated by dissolving a metal salt in water.
The antifoaming agent includes silicone resin, polydimethylsiloxane, silicone oil, and the like.
The coupling agent may be a silane coupling agent having a vinyl group, an amino group, an epoxy group, or the like.
Examples of the antioxidant include phenol-based antioxidants, amine-based antioxidants, phosphorus-based antioxidants, sulfur-based antioxidants, and sugars.
Examples of the ultraviolet absorber include benzotriazole-based ultraviolet absorbers, benzophenone-based ultraviolet absorbers, salicylate-based ultraviolet absorbers, cyanoacrylate-based ultraviolet absorbers, oxanilide-based ultraviolet absorbers, hindered amine-based ultraviolet absorbers, and benzoate-based ultraviolet absorbers.

The content of the conductive complex relative to the total mass of the conductive polymer dispersion is, for example, preferably 0.1 mass % or more and 10 mass % or less, more preferably 0.2 mass % or more and 5 mass % or less, and even more preferably 0.3 mass % or more and 2 mass % or less.
When the content is within the above preferred range, the dispersibility of the conductive composite in the conductive polymer dispersion can be further improved.

When the conductive polymer dispersion contains the nitrogen-containing compound, the content ratio thereof is appropriately determined depending on the type of the nitrogen-containing compound, but for example, it is preferably 1 part by mass or more and 1,000 parts by mass or less, more preferably 5 parts by mass or more and 100 parts by mass or less, and even more preferably 10 parts by mass or more and 50 parts by mass or less, relative to 100 parts by mass of the conductive composite.
Within this range, the equivalent series resistance of the capacitor is more likely to decrease.

When the conductive polymer dispersion contains the polyol compound, the content is appropriately determined depending on the type of polyol compound, but for example, it is preferably 100 parts by mass or more and 10,000 parts by mass or less, more preferably 200 parts by mass or more and 2,000 parts by mass or less, and even more preferably 300 parts by mass or more and 1,000 parts by mass or less, relative to 100 parts by mass of the solid content of the conductive composite.

When the conductive polymer dispersion contains the additive, the content ratio is appropriately determined depending on the type of additive, but can be, for example, within the range of 1 part by mass to 1,000 parts by mass per 100 parts by mass of the solid content of the conductive composite.

The pH of the conductive polymer dispersion (25°C) is preferably 1 to 5, more preferably 1.5 to 4, and even more preferably 2 to 4, from the viewpoint of suppressing corrosion of the dielectric layer 12 and the cathode 13 while fully obtaining the effect of improving the conductivity by doping with the anionic polymer or polyanion. The pH can be adjusted by adding the nitrogen-containing compound.

Examples of the method for applying the conductive polymer dispersion include immersion (dip coating), comma coating, reverse coating, lip coating, microgravure coating, etc. Among these, immersion is preferred from the viewpoint of easily forming the solid electrolyte layer 14 between the dielectric layer 12 and the cathode 13.
Examples of the drying method include room temperature drying, hot air drying, and far infrared drying.

<Method for producing anionic polymer>
The anionic polymer can be obtained by polymerizing the compound 1 in a reaction solution containing the compound 1 and a dispersion medium. A known method for polymerizing a vinyl compound can be applied as a method for polymerizing the compound 1. For example, a radical polymerization method using an oxidizing agent or a catalyst described later can be used.
The compound 1 contained in the reaction solution may be a salt containing a sodium ion or an ammonium ion as a counter cation of the sulfonic acid group.

The dispersion medium contained in the reaction liquid is preferably an aqueous dispersion medium, and more preferably water.
The aqueous dispersion medium is water or a mixture of water and a water-soluble organic solvent. Here, the water-soluble organic solvent is an organic solvent that dissolves in an amount of 1 g or more per 100 g of water at 20° C. Examples of the water-soluble organic solvent include alcohol-based solvents, ketone-based solvents, and ester-based solvents. The water-soluble organic solvents may be used alone or in combination of two or more.
The content of water relative to the total mass of the aqueous dispersion medium is 50% by mass or more, preferably 60% by mass or more, more preferably 80% by mass or more, and may be 100% by mass.

When the dispersion medium contains water, the polymerization reaction of compound 1 proceeds stably, and the anionic polymer is easily obtained in a stably dispersed state in the dispersion medium.
It is preferable to remove the counter cations bonded to the sulfonic acid groups of the compound 1 polymerized in the reaction solution, and the catalyst and oxidizing agent added to the reaction solution, from the reaction solution after polymerization of the compound 1. Removal of the counter cations means removing the counter cations bonded to the sulfonic acid groups of the anionic polymer obtained by polymerization and replacing them with protons.

Methods for removing the counter cations and the like from the reaction solution include, for example, a method in which the reaction solution is brought into contact with an ion exchange resin to be adsorbed onto the ion exchange resin, and a method in which the reaction solution is ultrafiltered while adding ion exchange water, and the counter cations and the like are removed together with the replacement of the dispersion medium. Among these, the method using an ion exchange resin is preferred because it is simple. It is preferred to use a cation exchange resin and an anion exchange resin in combination as the ion exchange resin.

<Method for producing conductive polymer dispersion>
<Synthesis of π-conjugated conductive polymer in the presence of anionic polymer>
By polymerizing the monomer in a reaction liquid containing a monomer that forms a π-conjugated conductive polymer, an anionic polymer having a monomer unit derived from Compound 1 represented by Formula (1), and an aqueous dispersion medium, it is possible to obtain a conductive polymer dispersion liquid containing a conductive complex containing the π-conjugated conductive polymer and the anionic polymer, and the aqueous dispersion medium.

The synthesis of the π-conjugated conductive polymer in the reaction solution can be carried out in the same manner as the synthesis of a conventional π-conjugated conductive polymer (the synthesis of a conventional conductive complex (B)), except that the reaction solution contains the anionic polymer.

The monomers can be polymerized by chemically oxidizing the monomers. Chemical oxidative polymerization can be carried out using a known catalyst and oxidizing agent. Examples of catalysts include transition metal compounds such as ferric chloride, ferric sulfate, ferric nitrate, and cupric chloride. Examples of oxidizing agents include persulfates such as ammonium persulfate, sodium persulfate, and potassium persulfate. The oxidizing agent can return the reduced catalyst to its original oxidized state.

The content of the anionic polymer relative to the total mass of the reaction liquid is, for example, preferably 0.1% by mass to 10% by mass, more preferably 0.5% by mass to 5% by mass, and even more preferably 0.75% by mass to 2% by mass.
When the content is within the above preferred range, it becomes easy to adjust the content ratio of the π-conjugated conductive polymer and the anionic polymer in the target conductive polymer dispersion to the preferred range described above.

The content of the monomer relative to the total mass of the reaction liquid immediately before the start of the polymerization reaction is, for example, preferably 0.1% by mass or more and 10% by mass or less, more preferably 0.2% by mass or more and 5% by mass or less, and even more preferably 0.3% by mass or more and 2% by mass or less.

In the reaction liquid, from the viewpoint of forming a conductive complex with excellent water dispersibility by binding an anionic polymer to a π-conjugated conductive polymer, the content of the anionic polymer contained in the reaction liquid immediately before the start of the polymerization reaction is preferably 50 parts by mass or more and 5,000 parts by mass or less, more preferably 100 parts by mass or more and 1,000 parts by mass or less, and even more preferably 150 parts by mass or more and 500 parts by mass or less, relative to 100 parts by mass of the monomer.

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

When produced by the method described above, an anionic polymer is present during the chemical oxidative polymerization of the π-conjugated conductive polymer, and the anionic polymer bonds to or dopes the π-conjugated conductive polymer, resulting in a conductive composite (A) that is water-dispersible and has a small particle size.

Addition of polyanions
The polyanion (a polyanion having no monomer unit derived from Compound 1) may be further added to the reaction solution before polymerization, and then the monomer may be polymerized. By polymerizing a π-conjugated conductive polymer in the presence of an anionic polymer and the polyanion, a conductive complex (A) in which at least one of the anionic polymer and the polyanion is bound to or doped with the π-conjugated conductive polymer can be formed.

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 mass % or more and 10 mass % or less, more preferably 0.5 mass % or more and 5 mass % or less, and even more preferably 0.75 mass % or more and 2 mass % or less.
By setting the content within the above preferred range, an increase in the particle size of the π-conjugated conductive polymer can be suppressed.

From the viewpoint of forming a conductive composite (A) having excellent water dispersibility and conductivity by binding the polyanion to the π-conjugated conductive polymer in the reaction liquid, the content of the polyanion contained in the reaction liquid immediately before the start of the polymerization reaction is preferably 50 parts by mass or more and 5,000 parts by mass or less, more preferably 100 parts by mass or more and 1,000 parts by mass or less, and even more preferably 150 parts by mass or more and 500 parts by mass or less, relative to 100 parts by mass of the monomer.

Nitrogen-containing compounds, polyol compounds, additives, etc. may be optionally added to the conductive polymer dispersion liquid obtained above. It is preferable to adjust the amount of these optional components added so that they fall within the suitable range described in the first embodiment.

In order to improve the dispersibility of each material contained in the conductive polymer dispersion, it is preferable to subject the conductive polymer dispersion to a known high dispersion treatment in which the material is dispersed while applying a shear force before application.

The capacitor and the method for manufacturing the same of the present invention are not limited to the above-mentioned embodiment.
In the capacitor of the present invention, 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 type capacitor.
Examples of the separator include sheets (including nonwoven fabrics) made of cellulose, polyvinyl alcohol, polyester, polyethylene, polystyrene, polypropylene, polyimide, polyamide, polyvinylidene fluoride, etc., and nonwoven fabrics of glass fibers.
The density of the separator is preferably in the range of 0.1 g/cm ³ or more and 1.0 g/cm ³ or less, and more preferably in the range of 0.2 g/cm ³ or more and 0.8 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) Synthesis of Anionic Polymer To 10 g of AQUALON KH-05 (manufactured by Daiichi Kogyo Seiyaku Co., Ltd., the above formula (1) n = 8 to 11, R = a linear alkyl group having 10 or 12 carbon atoms, ammonium salt), 90 g of ion-exchanged water and 0.1 g of ammonium persulfate were added and reacted at 80°C for 8 hours.
Next, 10 g of Duolite C255LFH (a cation exchange resin manufactured by Sumika Chemtex Co., Ltd.) was added and stirred for 16 hours. The resulting solution was filtered to remove the Duolite C255LFH, and 100 g of a sulfonic acid form (10% by weight aqueous solution) of the anionic polymer Aqualon KH-05 polymer was obtained. The weight average molecular weight Mw of this polymer was 12,000.

(Production Example 2) Preparation of a conductive composite (A) containing PEDOT and an anionic polymer 0.5 g of 3,4-ethylenedioxythiophene, 15 g of the sulfonic acid form (10% by mass aqueous solution) of the AQUALON KH-05 polymer of Production Example 1, and 84.5 g of ion-exchanged water were mixed to obtain a reaction liquid.
The resulting reaction liquid was kept at 20° C. and, while being stirred, a catalyst solution prepared by dissolving 0.03 g of ferric sulfate in 4.97 g of ion-exchanged water and an oxidant solution prepared by dissolving 1.1 g of ammonium persulfate in 8.9 g of ion-exchanged water were slowly added, and the resulting reaction liquid was reacted by stirring for 24 hours.
By the above reaction, a conductive composite containing poly(3,4-ethylenedioxythiophene) which is a π-conjugated conductive polymer and a sulfonic acid form of Aqualon KH-05 polymer, water which is a dispersion medium, and a conductive polymer dispersion liquid containing an oxidizing agent and a catalyst were obtained.
To this conductive polymer dispersion, 13.2 g of Duolite C255LFH (Sumika Chemtex Corporation, cation exchange resin) and 13.2 g of Duolite A368S (Sumika Chemtex Corporation, anion exchange resin) were added, and the ion exchange resin was removed by filtration to obtain a conductive polymer dispersion from which the oxidizing agent and the catalyst had been removed. The solid content (non-volatile component) concentration of the obtained conductive polymer dispersion was 2.0 mass %, and the pH was 1.6.

(Production Example 3) Synthesis of PSS 206 g of sodium styrenesulfonate was dissolved in 1000 ml of ion-exchanged water, and while stirring at 80° C., 1.14 g of an oxidizing agent solution of ammonium persulfate previously dissolved in 10 ml of water was added dropwise for 20 minutes, and the solution was stirred for 12 hours.
1000ml of sulfuric acid diluted to 10% by mass was added to the obtained sodium styrene sulfonate-containing solution to obtain a polystyrene sulfonic acid-containing solution, and about 1000ml of the solvent was removed from the polystyrene sulfonic acid-containing solution by ultrafiltration. 2000ml of ion-exchanged water was added to the remaining solution, and about 2000ml of the solvent was removed by ultrafiltration, and the polystyrene sulfonic acid was washed with water. This ultrafiltration operation was repeated three times.
Water in the resulting solution was removed under reduced pressure to obtain colorless solid polystyrene sulfonic acid.

(Production Example 4) Preparation of a conductive composite (B) containing PEDOT and PSS 14.2 g of 3,4-ethylenedioxythiophene and a solution in which 36.7 g of the polystyrene sulfonic acid obtained in Production Example 3 was dissolved in 2000 ml of ion-exchanged water were mixed at 20°C.
The resulting mixed solution was kept at 20° C., and while stirring, 29.64 g of ammonium persulfate and 8.0 g of an oxidation catalyst solution of ferric sulfate dissolved in 200 ml of ion-exchanged water were slowly added, followed by stirring for 3 hours to carry out the reaction.
To the reaction solution obtained, 2000 ml of ion-exchanged water was added, and about 2000 ml of the solution was removed by ultrafiltration. This operation was repeated three times.
200 ml of sulfuric acid diluted to 10% by mass and 2000 ml of ion-exchanged water were added to the obtained solution, and about 2000 ml of the solvent was removed by ultrafiltration. 2000 ml of ion-exchanged water was added to the remaining liquid, and about 2000 ml of the solvent was removed by ultrafiltration, and the polystyrene sulfonate-doped poly(3,4-ethylenedioxythiophene) (PEDOT-PSS) contained in the solution was washed with water. This operation was repeated eight times to obtain a 2.0% by mass aqueous dispersion of PEDOT-PSS.

(Production Example 5) Preparation of Capacitor Element An anode lead terminal was connected to an etched aluminum foil (anode foil), and then a voltage of 60 V was applied in a 10 mass % aqueous solution of ammonium adipate to perform chemical conversion (oxidation treatment). A dielectric layer was formed on both sides of the aluminum foil, thereby obtaining an anode foil.
Next, opposing aluminum cathode foils to which cathode lead terminals were welded were laminated on both sides of the anode foil via a cellulose separator, and the resultant was rolled up into a cylindrical shape to obtain a capacitor element.

Production Example 6 Preparation of Driving Electrolyte Solution 50 parts by mass of γ-butyrolactone, 50 parts by mass of ethylene glycol, 10 parts by mass of sulfolane, and 25 parts by mass of tetramethylammonium hydrogen phthalate were mixed and dissolved to obtain a driving electrolyte solution.

(Preparation Example 1) Conductive Composite (A)
The conductive polymer dispersion containing the conductive complex made of PEDOT and anionic polymer obtained in Production Example 2 was dispersed using a high-pressure disperser, and the particle size of the conductive complex was measured to be 250 nm.

(Preparation Example 2) Conductive Composite (A)
0.26 parts by mass of imidazole (13.0 parts by mass with respect to 100 parts by mass of the conductive polymer dispersion obtained in Preparation Example 1) was added to 100 parts by mass of the conductive polymer dispersion obtained in Preparation Example 1, and the mixture was stirred at room temperature to obtain a conductive polymer dispersion having a pH adjusted to 3.3.

(Preparation Example 3) Conductive Composite (B)
The conductive polymer dispersion (PEDOT-PSS aqueous dispersion) obtained in Production Example 4 was subjected to a dispersion treatment using a high-pressure disperser, and the particle size of the conductive composite was measured to be 1110 nm. 0.32 parts by mass of imidazole (16.0 parts by mass relative to 100 parts by mass of the conductive composite) was added to 100 parts by mass of this conductive polymer dispersion, and the mixture was stirred at room temperature to obtain a conductive polymer dispersion whose pH was adjusted to 2.3.

[Method of measuring particle size]
The conductive polymer dispersion prepared in each example was diluted with distilled water to adjust the conductive composite concentration to 0.1 mass %. The cumulant average particle size was measured at 25° C. by dynamic light scattering using a zeta potential/particle size/molecular weight measurement system (ELSZ-2000ZS, manufactured by Otsuka Electronics Co., Ltd.) and the measured value was used as the particle size.

[pH Measurement]
For the conductive polymer dispersion liquid prepared in each example, the pH was measured at a temperature of 25° C. by a conventional method using a commercially available pH meter.

Example 1
The capacitor element obtained in Production Example 5 was immersed under reduced pressure in the conductive polymer dispersion obtained in any one of Preparation Examples 1 to 3, and then dried for 15 minutes in a hot air dryer at 150° C. for three times to form a solid electrolyte layer containing a conductive complex on the surface of the dielectric layer. At this time, the conductive polymer dispersions used for immersion were used in the order shown in Table 1.
Next, the capacitor element was immersed in the driving electrolyte solution obtained in Production Example 6, and then loaded into an aluminum case, sealed with a sealing rubber, and a direct current voltage of 35 V was applied for 20 minutes in an atmosphere at 105° C. to obtain a capacitor.

(Examples 2 to 5)
A capacitor was obtained in the same manner as in Example 1. At this time, the conductive polymer dispersions in which the capacitor elements were immersed were used in the order shown in Table 1.

Example 6
A capacitor was obtained in the same manner as in Example 1, except that a step of immersing the capacitor in the conductive polymer dispersion obtained in Preparation Example 2 or Preparation Example 3 under reduced pressure, and then drying for 15 minutes in a hot air dryer at 150° C. was carried out five times. In this case, the conductive polymer dispersions used for immersion were used in the order shown in Table 1.

(Comparative Example 1)
A capacitor was obtained in the same manner as in Example 1, except that the conductive polymers in which the capacitor element was immersed were used in the order shown in Table 1.

<Evaluation>
[Capacitance/Equivalent Series Resistance]
The capacitance (C) at 120 Hz and the equivalent series resistance (ESR) at 100 kHz were measured using an LCR meter ZM2376 (manufactured by NF Corporation) for the capacitors of Examples 1 to 6 and Comparative Example 1. The measurement results are shown in Table 2.

The capacitors of the examples, which have a conductive complex containing an anionic polymer, have capacitance equal to or greater than that of the comparative example capacitor, and the equivalent series resistance is significantly reduced. The details of the reason for this are unclear, but one of the factors is thought to be that the particle size of the conductive complex in the examples is much smaller than that of the comparative example, and therefore the solid electrolyte layer in the examples is denser than that of the comparative example.

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

Claims (7)

A capacitor comprising an anode made of a porous body of a valve metal, a dielectric layer made of an oxide of the valve metal, a cathode made of a conductive material provided on the dielectric layer on the side opposite to the anode, and at least one solid electrolyte layer formed between the dielectric layer and the cathode,
the solid electrolyte layer contains a conductive complex including a π-conjugated conductive polymer and an anionic polymer having a monomer unit derived from Compound 1 represented by the following formula (1) ,
The capacitor further comprises a conductive complex including a π-conjugated conductive polymer and a polyanion not included in the anionic polymer .

[In the formula, R is a linear or branched alkyl group having 4 to 20 carbon atoms, and n is an integer from 4 to 100.] The capacitor of claim 1, wherein the anionic polymer is a homopolymer of compound 1. The capacitor of claim 1 or 2 , wherein the polyanion is polystyrene sulfonic acid. The capacitor according to claim 1 , wherein the solid electrolyte layer further contains a nitrogen-containing compound. The capacitor according to any one of claims 1 to 4 , wherein the π-conjugated conductive polymer is poly(3,4-ethylenedioxythiophene). a dielectric forming step of forming a dielectric layer by oxidizing the surface of an anode made of a porous valve metal;
a cathode forming step of disposing a cathode at a position facing the dielectric layer;
and forming at least one solid electrolyte layer on a surface of the dielectric layer,
In the lamination step,
a first conductive polymer dispersion liquid is applied to a surface of the dielectric layer and then dried to form the solid electrolyte layer;
The first conductive polymer dispersion contains a π-conjugated conductive polymer and an anionic polymer having a monomer unit derived from Compound 1 represented by the following formula (1):
After the first conductive polymer dispersion liquid is applied and dried, a second conductive polymer dispersion liquid is further applied and dried to form the solid electrolyte layer;
The method for producing a capacitor , wherein the second conductive polymer dispersion contains a conductive complex including a π-conjugated conductive polymer and a polyanion not corresponding to the anionic polymer .

[In the formula, R is a linear or branched alkyl group having 4 to 20 carbon atoms, and n is an integer from 4 to 100.] a dielectric forming step of forming a dielectric layer by oxidizing the surface of an anode made of a porous valve metal;
a cathode forming step of disposing a cathode at a position facing the dielectric layer;
and forming at least one solid electrolyte layer on a surface of the dielectric layer,
a second conductive polymer dispersion liquid containing a π-conjugated conductive polymer and a conductive complex containing a polyanion not corresponding to the anionic polymer described below is applied to the surface of the dielectric layer and dried, and then a first conductive polymer dispersion liquid is further applied and dried to form the solid electrolyte layer;
The first conductive polymer dispersion contains a conductive complex including a π-conjugated conductive polymer and an anionic polymer having a monomer unit derived from compound 1 represented by formula (1):

[In the formula, R is a linear or branched alkyl group having 4 to 20 carbon atoms, and n is an integer from 4 to 100.]

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