Electrically conductive polymer-containing dispersion liquid, solid electrolytic capacitor, and method for producing same

Abstract

This electrically conductive polymer-containing dispersion liquid contains a conjugated electrically conductive polymer (A), a polyanion (B), a compound (C) having a group represented by formula (1), and a dispersion medium (D). (In formula (1), R1 and R2 are each independently an alkyl group having 1-6 carbon atoms, an alkenyl group having 2-6 carbon atoms, an aryl group or an aralkyl group. X is an oxygen atom or a sulfur atom.)

Description

Conductive polymer-containing dispersion, solid electrolytic capacitor, and method for producing the same

[0001] The present invention relates to a dispersion containing a conjugated conductive polymer, a solid electrolytic capacitor using the same, and a method for producing the same.

[0002] A solid electrolytic capacitor typically has a structure in which a valve metal, such as aluminum, tantalum, or niobium, is used as an anode foil and a cathode foil, with a solid electrolyte sandwiched between them. To increase the capacitance, the surface area of ​​the valve metal in the anode foil is increased by etching or other processes, and a dielectric oxide film is formed on the surface. The solid electrolyte is typically a conjugated conductive polymer, such as polypyrrole, polyaniline, or polythiophene.

[0003] Solid electrolytic capacitors are used in electronic devices because they can reduce equivalent series resistance (ESR) in the high-frequency range. In addition, with the recent trend toward electrification of cars, development of solid electrolytic capacitors for automotive use is progressing.

[0004] A known method for forming a solid electrolyte using a conductive polymer is, for example, to impregnate an electrolytic capacitor element with a monomer solution for obtaining the conductive polymer and an oxidant solution, and then perform oxidative polymerization or electrolytic polymerization within the electrolytic capacitor element (see, for example, Patent Document 1).

[0005] Another known method for forming a solid electrolyte involves permeating an aqueous dispersion of a conductive polymer into a dielectric oxide film on an anode body (anode foil) and then drying the resulting solution. When forming a solid electrolyte using this method, the ESR of the solid electrolytic capacitor can be reduced by adding an additive to the aqueous dispersion of the conductive polymer to improve conductivity. For example, the use of a water-soluble compound such as ethylene glycol or an unsaturated aliphatic alcohol compound as an additive has been proposed (see, for example, Patent Documents 2 and 3).

[0006] JP 63-173313 A JP 2008-109068 A JP 2022-69939 A

[0007] However, in the polymerization reaction within the electrolytic capacitor element as described in Patent Document 1, the conductive polymer aggregates and forms in a spongy state, which makes the solid electrolyte less uniform and prone to lowering of conductivity.

[0008] Furthermore, in the method using an aqueous dispersion of a conductive polymer, even when a solid electrolyte containing a water-soluble compound or an unsaturated aliphatic alcohol compound as an additive as described in Patent Documents 2 and 3 is formed, the ESR of the solid electrolytic capacitor is not necessarily sufficiently low.

[0009] In recent years, capacitors for vehicle electronic control devices in particular are required to have a lower ESR and an increased capacitance in order to achieve higher output power due to electronic control.

[0010] The present invention has been made in view of the above circumstances, and aims to provide a conductive polymer-containing dispersion that can produce a solid electrolytic capacitor having a lower ESR and a larger capacitance, as well as a solid electrolytic capacitor using the same and a method for producing the same.

[0011] The present invention is based on the finding that when a conductive polymer-containing dispersion contains a compound having a specific structure, the ESR of a solid electrolytic capacitor produced using the conductive polymer-containing dispersion is reduced and the capacitance is increased.

[0012] The present invention provides the following means: [1] A conductive polymer-containing dispersion comprising a conjugated conductive polymer (A), a polyanion (B), a compound (C) containing a group represented by the following formula (1), and a dispersion medium (D): (In formula (1), R １ and R ２ are each independently an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an aryl group, or an aralkyl group. X is an oxygen atom or a sulfur atom. [2] R １ and R ２are each independently an alkyl group having 1 to 4 carbon atoms. [3] The conductive polymer-containing dispersion of [1] or [2], wherein X is an oxygen atom. [4] The conductive polymer-containing dispersion of any of [1] to [3], wherein the group represented by formula (1) is a prenyloxy group. [5] The conductive polymer-containing dispersion of any of [1] to [4], wherein compound (C) is a compound having two or more prenyloxy groups. [6] The conductive polymer-containing dispersion of any of [1] to [3], wherein compound (C) is a compound represented by the following formula (2): (In formula (2), R １ ~R ４ are each independently an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an aryl group, or an aralkyl group. ５ and R ６ are each independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an aryl group, or an aralkyl group. ７ is a hydrogen atom or a methyl group. ８ is a hydroxyl group, a (meth)acryloyloxy group, a 4-vinylphenoxy group, or an alkenyloxy group having 2 to 6 carbon atoms.) [7] The conductive polymer-containing dispersion of any of [1] to [6], wherein the content of compound (C) is 0.001 to 1.0 part by mass per part by mass of the solid content of the conductive polymer-containing dispersion. [8] The conductive polymer-containing dispersion of any of [1] to [7], further comprising a polymer (E) that does not fall under either the conjugated conductive polymer (A) or the polyanion (B) and is insoluble in the dispersion medium (D). [9] The conductive polymer-containing dispersion of any of [1] to [8], wherein the conjugated conductive polymer (A) is a polymer of a monomer containing one or more compounds selected from the group consisting of pyrroles, anilines, and thiophenes.

[10] The conductive polymer-containing dispersion of [9], wherein the thiophene compound is represented by the following formula (3): (In formula (3), R １１ and R １２are each independently a hydrogen atom, a hydroxyl group, an optionally substituted alkyl group having 1 to 18 carbon atoms, an optionally substituted alkoxy group having 1 to 18 carbon atoms, or an optionally substituted alkylthio group having 1 to 18 carbon atoms; or R １１ and R １２ and (b) are bonded to each other to form an optionally substituted alicyclic ring having 3 to 10 carbon atoms, an optionally substituted aromatic ring having 6 to 10 carbon atoms, an optionally substituted oxygen-atom-containing heterocyclic ring having 2 to 10 carbon atoms, an optionally substituted sulfur-atom-containing heterocyclic ring having 2 to 10 carbon atoms, or an optionally substituted sulfur- and oxygen-atom-containing heterocyclic ring having 2 to 10 carbon atoms.)

[11] The conductive polymer-containing dispersion of any of [1] to

[10] , wherein the polyanion (B) is a polymer having two or more groups formed of sulfonic acid or a salt thereof.

[12] The conductive polymer-containing dispersion of any of [1] to

[11] , further comprising an alkaline compound (F).

[13] The conductive polymer-containing dispersion of

[12] , wherein the alkaline compound (F) is one or more selected from the group consisting of morpholine, 4-ethylmorpholine, and 4-(2-hydroxyethyl)morpholine.

[0013]

[14] A method for producing a solid electrolytic capacitor, comprising the steps of depositing the conductive polymer-containing dispersion according to any one of [1] to

[13] onto a porous anode body made of a valve metal having a dielectric coating on its surface, and then removing the dispersion medium (D) to form a solid electrolyte layer.

[15] A solid electrolytic capacitor comprising a porous anode body having a solid electrolyte layer, the porous anode body being a valve metal having a dielectric coating on its surface, and the solid electrolyte layer comprising a conjugated conductive polymer (A), a polyanion (B), and a compound (C) represented by the following formula (1): (In formula (1), R １ and R ２ are each independently an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an aryl group, or an aralkyl group; and X is an oxygen atom or a sulfur atom.

[0014] According to the present invention, a conductive polymer-containing dispersion capable of producing a solid electrolytic capacitor having a lower ESR and a larger capacitance can be provided. Also, according to the present invention, a solid electrolytic capacitor having a lower ESR and a larger capacitance can be obtained.

[0015] The definitions and meanings of terms and notations used in this specification are as follows. Regarding a compound group, "optionally substituted" means that the group may be substituted or unsubstituted. The term "class" attached to a compound name refers to a group of compounds containing the compound structure, including those compounds having a substituent. For example, "polypyrroles" refers to a group of compounds containing a polypyrrole structure. "(Meth)acrylic acid" is a general term for acrylic acid and methacrylic acid. Similarly, "(meth)acrylate" is a general term for acrylate and methacrylate, and "(meth)acryloyl" is a general term for acryloyl and methacryloyl. Unless otherwise specified, "ethylenically unsaturated bond" refers to an ethylenically unsaturated bond having radical polymerizability. Furthermore, "ethylenically unsaturated monomer" refers to a compound having an ethylenically unsaturated bond and is a compound from which a structural unit of a polymer is derived. "Polymer component" refers to a conjugated conductive polymer (A) and a polyanion (B). When the conductive polymer dispersion contains a polymer (E) described below, "polymer (E)" is also included. The solid content is determined based on the actual measurement of the evaporation residue in the solid content concentration measurement method described in the Examples. The notation "X to Y" (X and Y are numerical values) means a numerical range with X as the lower limit and Y as the upper limit. In a numerical range (e.g., a range of content, etc.), the lower limit and upper limit values ​​described in stages may be combined independently. The lower limit and upper limit values ​​of the numerical range may be replaced with numerical values ​​described in the Examples.

[0016] [Conductive Polymer-Containing Dispersion] A conductive polymer-containing dispersion according to an embodiment of the present invention (hereinafter referred to as "the present embodiment") comprises a conjugated conductive polymer (A), a polyanion (B), a compound (C) having a group represented by the following formula (1), and a dispersion medium (D). The conductive polymer-containing dispersion according to the present embodiment is preferably a conductive polymer-containing dispersion used in the production of a solid electrolytic capacitor (a conductive polymer-containing dispersion for a solid electrolytic capacitor).

[0017]

[0018] In formula (1), R １ and R ２ are each independently an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an aryl group, or an aralkyl group. X is an oxygen atom or a sulfur atom.

[0019] By using a conductive polymer-containing dispersion containing the compound (C) having the specific structure as described above, a solid electrolytic capacitor having a low ESR and a large capacitance can be produced.

[0020] The conductive polymer-containing dispersion of the present embodiment may further contain a polymer (E), an alkaline compound (F), and other additives, which will be described later.

[0021] As a first embodiment, there is mentioned a conductive polymer-containing dispersion that does not contain the polymer (E). In the first embodiment, it is preferable that the dispersion does not contain any polymer other than the conjugated conductive polymer (A) and the polyanion (B).

[0022] In the first embodiment, the total content of the conjugated conductive polymer (A), polyanion (B), compound (C), and dispersion medium (D) in the conductive polymer-containing dispersion is preferably 80 to 100 mass%, more preferably 85 to 100 mass%, and even more preferably 90 to 100 mass%. By having the total content within the above numerical range, the ESR of the solid electrolytic capacitor produced using the conductive polymer-containing dispersion can be further reduced and the capacitance can be further increased.

[0023] In the first embodiment, it is preferable that composite particles (1) containing a conjugated conductive polymer (A) and a polyanion (B) are formed.

[0024] In the first embodiment, the total content of the conjugated conductive polymer (A) and the polyanion (B) in the conductive polymer-containing dispersion is preferably 0.1 to 20% by mass, more preferably 0.5 to 15% by mass, and even more preferably 1 to 10% by mass, from the viewpoints of the effect of reducing the ESR and the effect of increasing the capacitance of the solid electrolytic capacitor, the viscosity of the conductive polymer-containing dispersion that is easy to handle, the dispersibility of the composite particles (1), and the like.

[0025] A second embodiment is a conductive polymer-containing dispersion that further contains, in addition to the conjugated conductive polymer (A), the polyanion (B), the compound (C), and the dispersion medium (D), a polymer (E) that is insoluble in the dispersion medium (D). By using the conductive polymer-containing dispersion of the second embodiment, the ESR of the solid electrolytic capacitor can be further reduced and the capacitance can be further increased.

[0026] In the second embodiment, the conductive polymer-containing dispersion may contain composite particles (2) containing a conjugated conductive polymer (A), a polyanion (B), and a polymer (E). The conductive polymer-containing dispersion may contain the above-described composite particles (1) together with the composite particles (2).

[0027] In the second embodiment, the structure of the composite particle (2) contained in the conductive polymer-containing dispersion is not particularly limited, but it is preferable that the polymer (E) forms an inner domain of the composite particle (2) and the polyanion (B) coordinates to the polymer (E) to form an outer domain of the composite particle (2), so that part or all of the domain of the polymer (E) is covered with the conjugated conductive polymer (A) and the polyanion (B).

[0028] In the second embodiment, the total content of the conjugated conductive polymer (A), polyanion (B), compound (C), dispersion medium (D), and polymer (E) in the conductive polymer-containing dispersion is preferably 80 to 100 mass%, more preferably 85 to 100 mass%, and even more preferably 90 to 100 mass%. By having the total content within the above numerical range, the ESR of the solid electrolytic capacitor produced using the conductive polymer-containing dispersion can be further reduced and the capacitance can be increased.

[0029] In the second embodiment, the total content of the conjugated conductive polymer (A), the polyanion (B), and the polymer (E) in the conductive polymer-containing dispersion is preferably 0.1 to 20% by mass, more preferably 0.5 to 15% by mass, and even more preferably 1 to 10% by mass, from the viewpoints of the effect of reducing the ESR and the effect of increasing the capacitance of the solid electrolytic capacitor, the viscosity of the conductive polymer-containing dispersion that is easy to handle, the dispersibility of the composite particles (2), and the like.

[0030] (Conjugated conductive polymer (A)) The conjugated conductive polymer (A) is not particularly limited as long as it is an organic polymer compound having a π-conjugated system in the main chain. The conjugated conductive polymer may be used alone or in combination of two or more types. Furthermore, the conjugated conductive polymer (A) may be a homopolymer of a monomer described below, which serves as a structural unit of the conjugated conductive polymer (A), or a copolymer of two or more types of monomers. Since the conductive polymer-containing dispersion of this embodiment contains a polyanion (B) that functions as a dopant, the conjugated conductive polymer (A) does not need to have a self-doping function.

[0031] The content of the conjugated conductive polymer (A) in 100% by mass of the polymer component contained in the conductive polymer-containing dispersion of this embodiment is preferably 5 to 70% by mass, more preferably 10 to 60% by mass, and even more preferably 15 to 50% by mass, from the viewpoints of the dispersion stability of the conductive polymer-containing dispersion, the effect of reducing the ESR of the solid electrolytic capacitor produced using the conductive polymer-containing dispersion, and the effect of increasing the capacitance.

[0032] Examples of the conjugated conductive polymer (A) include polypyrroles, polythiophenes, polyisothianaphthenes, polyacetylenes, polyphenylenes, polyphenylene vinylenes, polyanilines, polyacenes, polythiophene vinylenes, and copolymers thereof. Among these, from the viewpoints of ease of handling and availability, polypyrroles, polythiophenes, and polyanilines are preferred, and polythiophenes are more preferred. Furthermore, from the viewpoint of high conductivity, the conjugated conductive polymer (A) preferably has a substituent such as an alkyl group, a carboxy group, a sulfo group, an alkoxy group, a hydroxyl group, or a cyano group.

[0033] Examples of polypyrroles 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), poly(3-methyl-4-hexyloxypyrrole), and poly(3-methyl-4-hexyloxypyrrole).

[0034] Examples of polythiophenes include polythiophene, poly(3-methylthiophene), 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), and 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(3,4-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), thiophene), 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-carboxybutylthiophene), poly(3,4-ethyleneoxythiathiophene), and the like.

[0035] Examples of polyanilines include polyaniline, poly(2-methylaniline), poly(3-isobutylaniline), poly(2-anilinesulfonic acid), and poly(3-anilinesulfonic acid).

[0036] Among these compounds, the conjugated conductive polymer (A) is preferably polypyrrole, polythiophene, poly(N-methylpyrrole), poly(3-methylthiophene), poly(3-methoxythiophene), or poly(3,4-ethylenedioxythiophene) from the viewpoint of high conductivity, and more preferably poly(3,4-ethylenedioxythiophene) from the viewpoint of excellent heat resistance.

[0037] The monomer for obtaining the conjugated conductive polymer (A), i.e., the monomer that serves as a constituent unit of the conjugated conductive polymer (A), preferably contains one or more compounds selected from the group consisting of pyrroles, anilines, and thiophenes. The compound may have a substituent X. Examples of the substituent X include an alkyl group having 1 to 18 carbon atoms, an aryl group having 6 to 10 carbon atoms, a heteroaryl group having 5 to 10 carbon atoms, an alkoxy group having 1 to 18 carbon atoms, an alkylthio group having 1 to 18 carbon atoms, a carboxy group, a hydroxyl group, a halogen atom, and a cyano group. Two or more of these substituents X may be bonded to each other by condensation or the like to form a ring. These alkyl groups, aryl groups, heteroaryl groups, alkoxy groups, and alkylthio groups may also have a further substituent Y, such as a carboxy group, a hydroxyl group, a halogen atom, or a cyano group.

[0038] Examples of the monomer that serves as a constituent unit of the conjugated conductive polymer (A) include pyrroles such as pyrrole, N-methylpyrrole, 3-methylpyrrole, 3-ethylpyrrole, 3-n-propylpyrrole, 3-butylpyrrole, 3-octylpyrrole, 3-decylpyrrole, 3-dodecylpyrrole, 3,4-dimethylpyrrole, 3,4-dibutylpyrrole, 3-carboxylpyrrole, 3-methyl-4-carboxylpyrrole, 3-methyl-4-carboxyethylpyrrole, 3-methyl-4-carboxybutylpyrrole, 3-hydroxypyrrole, 3-methoxypyrrole, 3-ethoxypyrrole, 3-butoxypyrrole, 3-hexyloxypyrrole, 3-methyl-4-hexyloxypyrrole, and 3-methyl-4-hexyloxypyrrole;Thiophene, 3-methylthiophene, 3-ethylthiophene, 3-propylthiophene, 3-butylthiophene, 3-hexylthiophene, 3-heptylthiophene, 3-octylthiophene, 3-decylthiophene, 3-dodecylthiophene, 3-octadecylthiophene, 3-bromothiophene, 3-chlorothiophene, 3-iodothiophene, 3-cyanothiophene, 3-phenylthiophene, 3,4-dimethylthiophene, 3,4-dibutylthiophene, 3-hydroxythiophene, 3-methoxythiophene, 3-ethoxythiophene, 3-butoxythiophene, 3-hexyloxythiophene, 3-heptyloxythiophene, 3-octyloxythiophene, 3-decyloxythiophene, 3-dodecyloxythiophene, 3-octadecyloxythiophene, 3,4-dihydroxythiophene, 3,4-dimethoxythiophene, 3,4-diethoxythiophene Examples of suitable thiophenes include thiophenes such as 3,4-dipropoxythiophene, 3,4-dibutoxythiophene, 3,4-dihexyloxythiophene, 3,4-diheptyloxythiophene, 3,4-dioctyloxythiophene, 3,4-didecyloxythiophene, 3,4-didodecyloxythiophene, 3,4-ethylenedioxythiophene, 3,4-propylenedioxythiophene, 3,4-butylenedioxythiophene, 3-methyl-4-methoxythiophene, 3-methyl-4-ethoxythiophene, 3-carboxythiophene, 3-methyl-4-carboxythiophene, 3-methyl-4-carboxyethylthiophene, 3-methyl-4-carboxybutylthiophene, and 3,4-ethyleneoxythiathiophene; and anilines such as aniline, 2-methylaniline, 3-isobutylaniline, 2-anilinesulfonic acid, and 3-anilinesulfonic acid. These may be used alone or in combination of two or more.

[0039] Among these compounds, the monomer serving as a constituent unit of the conjugated conductive polymer (A) preferably contains a thiophene compound represented by the following formula (3), from the viewpoint of obtaining a conjugated conductive polymer having high conductivity. The compound represented by formula (3) may be used alone or in combination of two or more.

[0040]

[0041] In formula (3), R １１ and R １２ are each independently a hydrogen atom, a hydroxyl group, an optionally substituted alkyl group having 1 to 18 carbon atoms, an optionally substituted alkoxy group having 1 to 18 carbon atoms, or an optionally substituted alkylthio group having 1 to 18 carbon atoms; or R １１ and R １２ and are bonded to each other to form an optionally substituted alicyclic ring having 3 to 10 carbon atoms, an optionally substituted aromatic ring having 6 to 10 carbon atoms, an optionally substituted oxygen atom-containing heterocyclic ring having 2 to 10 carbon atoms, an optionally substituted sulfur atom-containing heterocyclic ring having 2 to 10 carbon atoms, or an optionally substituted sulfur atom- and oxygen atom-containing heterocyclic ring having 2 to 10 carbon atoms.

[0042] Examples of the substituent include a carboxy group, a hydroxyl group, a halogen atom, and a cyano group. The oxygen-atom-containing heterocycle preferably contains 1 to 3 oxygen atoms constituting the ring, and examples thereof include an oxirane ring, an oxetane ring, a furan ring, a hydrofuran ring, a pyran ring, a pyrone ring, a dioxane ring, and a trioxane ring. The sulfur-atom-containing heterocycle preferably contains 1 to 3 nitrogen atoms constituting the ring, and examples thereof include a thiirane ring, a thietane ring, a thiophene ring, a thiane ring, a thiopyran ring, a thiopyrylium ring, a benzothiopyran ring, a dithiane ring, a dithiolane ring, and a trithiane ring. The sulfur-atom- and oxygen-atom-containing heterocycle preferably contains 1 to 3 sulfur and oxygen atoms constituting the ring in total, and examples thereof include an oxathiolane ring and an oxathiane ring.

[0043] The content of the compound represented by formula (3) in the monomers that constitute the structural units of the conjugated conductive polymer (A) is preferably 90 to 100 mass%, more preferably 95 to 100 mass%, and even more preferably 100 mass%, from the viewpoints of uniformity and good conductivity of the conjugated conductive polymer (A).

[0044] The monomer serving as a constituent unit of the conjugated conductive polymer (A) preferably contains a compound represented by the following formula (4) among the compounds represented by formula (3), and more preferably contains 3,4-ethylenedioxythiophene:

[0045]

[0046] In formula (4), R １３ and R １４ are each independently a hydrogen atom, an optionally substituted alkyl group having 1 to 4 carbon atoms, or R １３ and R １４ and are bonded to each other to form an optionally substituted oxygen atom-containing heterocycle having 3 to 6 carbon atoms.

[0047] R １３ and R １４ is R １３ and R １４ and are bonded to each other, and are preferably oxygen atom-containing heterocycles having 3 to 6 carbon atoms, which may be substituted. The oxygen atom-containing heterocycle preferably has 1 to 3 oxygen atoms constituting the ring, and examples thereof include a dioxane ring and a trioxane ring, with a dioxane ring being preferred. The oxygen atom-containing heterocycle is preferably unsubstituted. The substituent to be substituted here is the same as the above-mentioned substituent Y, and examples thereof include a carboxy group, a hydroxyl group, a halogen atom, and a cyano group.

[0048] (Polyanion (B)) The polyanion (B) is a polymer having two or more anionic groups. It functions as a dopant for the conjugated conductive polymer (A). In the composite particle (2) of the second embodiment, the polyanion (B) is thought to be coordinated to the outside of the polymer (E) that forms a domain inside, and to act as a protective colloid.

[0049] The content of the polyanion (B) in 100% by mass of the polymer component contained in the conductive polymer-containing dispersion of this embodiment is preferably 30 to 95% by mass, more preferably 40 to 90% by mass, and even more preferably 50 to 85% by mass, from the viewpoints of stability in the conductive polymer-containing dispersion, the effect of reducing the ESR of a solid electrolytic capacitor produced using the conductive polymer-containing dispersion, and the effect of increasing the capacitance. The content of the polyanion (B) is preferably 45 to 1,900 parts by mass, more preferably 70 to 900 parts by mass, and even more preferably 100 to 500 parts by mass, relative to 100 parts by mass of the conjugated conductive polymer (A).

[0050] Examples of anionic groups include sulfonic acid or its salt groups, phosphoric acid or its salt groups, mono-substituted phosphate ester groups, carboxylic acid or its salt groups, and mono-substituted sulfate ester groups. Among these, strongly acidic groups are preferred, sulfonic acid or its salt groups, phosphoric acid or its salt groups are more preferred, and sulfonic acid or its salt groups are even more preferred. That is, the polyanion (B) is preferably a polymer having two or more sulfonic acid or its salt groups. Examples of salts include sodium, potassium, magnesium, calcium, and ammonium salts.

[0051] The anionic group may be bonded to the main chain or side chain of the polymer constituting the polyanion (B). When the anionic group is bonded to the side chain, it is preferable that the anionic group be bonded to the side chain terminal from the viewpoint of obtaining a high doping effect on the conjugated conductive polymer (A). The anionic group may be bonded directly to the main chain or via another structure. The anionic group is preferably bonded via a benzene ring, and in this case, it is more preferable that the anionic group be bonded at the para position relative to the main chain.

[0052] The polyanion (B) may have a substituent other than an anionic group. The substituent may be bonded to the main chain or to a side chain of the polymer constituting the polyanion (B). When the substituent is bonded to the side chain, it is preferable that the substituent is bonded to the end of the side chain in order to exhibit the properties of the substituent.

[0053] The main chain structure of the polymer constituting the polyanion (B) is not particularly limited, but from the viewpoints of synthesis and availability, for example, polyalkylene such as polyethylene is preferred.

[0054] As the polyanion (B), a compound having a group consisting of sulfonic acid or a salt thereof as an anionic group is preferred, as described above, in order to improve the dispersibility of the monomer that is the constituent unit of the conjugated conductive polymer (A) in the dispersion medium (D). A group consisting of sulfonic acid, i.e., a sulfo group (-SO ２ Examples of polyanions having a hydroxyl group (OH) include polyvinyl sulfonic acid, polystyrene sulfonic acid, polyallyl sulfonic acid, polyethyl acrylate sulfonic acid, polybutyl acrylate sulfonic acid, poly(2-acrylamido-2-methylpropane sulfonic acid), polyisoprene sulfonic acid, and copolymers thereof. Among these, from the viewpoints of stability in the conductive polymer-containing dispersion and the effect of reducing the ESR and increasing the capacitance of a solid electrolytic capacitor produced using the conductive polymer-containing dispersion, polystyrene sulfonic acid, polyisoprene sulfonic acid, polyethyl acrylate sulfonic acid, and polybutyl acrylate sulfonic acid are preferred, with polystyrene sulfonic acid being more preferred.

[0055] Furthermore, the polyanion (B) contained in the conductive polymer-containing dispersion and the polyanion added during the production stage of the conductive polymer-containing dispersion may have the same structure, or may have different structures, such as those in which different cations are bound. For example, in the production stage, sodium polystyrene sulfonate is preferably used as the polyanion from the standpoint of water solubility, but it may be converted to polystyrene sulfonic acid in a process such as ion exchange. The polyanion (B) can be produced, for example, by the production method described in JP 2005-76016 A, or a commercially available product can also be used.

[0056] From the viewpoints of solubility in the dispersion medium (D) and doping effect on the conjugated conductive polymer (A), the polyanion (B) preferably has a weight-average molecular weight of 1,000 to 1,000,000, more preferably 5,000 to 500,000, and even more preferably 50,000 to 300,000. The weight-average molecular weight referred to here is a standard polystyrene-equivalent molecular weight measured by gel permeation chromatography. Specifically, it is measured by the method described in the Examples.

[0057] (Compound (C)) The compound (C) in this embodiment is a compound containing a group represented by the following formula (1).

[0058]

[0059] In formula (1), R １ and R ２ are each independently an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an aryl group, or an aralkyl group. X is an oxygen atom or a sulfur atom.

[0060] It is believed that the addition of compound (C) is effective in reducing the ESR and increasing the capacitance of solid electrolytic capacitors manufactured using the conductive polymer-containing dispersion. Although the reason for this is unclear, it is presumed that compound (C) having a specific structure inhibits the deterioration of the conductive polymer in the conductive path of the solid electrolyte layer formed using the conductive polymer-containing dispersion, which is caused by the intrusion of oxygen from outside the capacitor element and the generation of peroxide compounds inside the capacitor element. This reduces the ESR of the solid electrolytic capacitor and increases the capacitance.

[0061] R １ and R ２ Specific examples of the alkyl group having 1 to 6 carbon atoms in the formula (I) include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a neopentyl group, an n-hexyl group, a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, and a cyclohexyl group. Specific examples of the alkenyl group having 2 to 6 carbon atoms include a vinyl group, an allyl group, a propenyl group, an isopropenyl group, a butenyl group, an isobutenyl group, a pentenyl group, a prenyl group, a hexenyl group (such as a cis-3-hexenyl group), and a cyclohexenyl group. The aryl group preferably has 6 to 20 carbon atoms, and specific examples thereof include a phenyl group, a tolyl group, a xylyl group, and a naphthyl group. The aralkyl group preferably has 7 to 20 carbon atoms, and specific examples include a benzyl group, a 2-phenylethyl group, a 2-naphthylethyl group, and a diphenylmethyl group.

[0062] Among these, from the viewpoints of the effect of reducing the ESR of the solid electrolytic capacitor and the effect of increasing the capacitance, and the ease of obtaining the compound (C), R １ and R ２ are each independently preferably an alkyl group having 1 to 6 carbon atoms or an alkenyl group having 2 to 6 carbon atoms, more preferably an alkyl group having 1 to 4 carbon atoms, and even more preferably a methyl group.

[0063] X is preferably an oxygen atom from the viewpoints of the effect of reducing the ESR and increasing the capacitance of the solid electrolytic capacitor, and ease of availability of the compound (C).

[0064] The group represented by formula (1) is preferably a prenyloxy group (3-methyl-2-butenoxy group ((CH ３ ) ２ C=CHCH ２ O-)). In compound (C), the number of groups represented by formula (1) may be one or more. Compound (C) is more preferably a compound having two or more prenyloxy groups.

[0065] The compound (C) is preferably a compound represented by the following formula (2):

[0066] In formula (2), R １ ~R ４ are each independently an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an aryl group, or an aralkyl group. ５ and R ６ are each independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an aryl group, or an aralkyl group. ７ is a hydrogen atom or a methyl group. ８ is a hydroxyl group, a (meth)acryloyloxy group, a 4-vinylphenoxy group, or an alkenyloxy group having 2 to 6 carbon atoms.

[0067] In the compound represented by formula (2), for example, during the polymerization reaction of the polymer component, a radical is generated at the allylic position (the carbon atom between the carbon-carbon double bond and the oxygen atom), which captures oxygen to generate a peroxy radical, which then abstracts hydrogen from another molecule to regenerate the radical, thus progressing the oxygen absorption cycle. As a result, it is presumed that compound (C) can suppress the deterioration of the conductive polymer, reduce the ESR of the solid electrolytic capacitor, and increase the capacitance.

[0068] R in formula (2) １ ~R ４ Specific and preferred groups in the above formula (1) are １and R ２ It is the same as R ５ and R ６ are each independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an aryl group, or an aralkyl group. Of these, specific examples and preferred groups of the alkyl group having 1 to 6 carbon atoms, the alkenyl group having 2 to 6 carbon atoms, the aryl group, or the aralkyl group are R １ and R ２ It is the same as R ７ is preferably a hydrogen atom. ８ is a hydroxyl group, a (meth)acryloyloxy group, a 4-vinylphenoxy group, or an alkenyloxy group having 2 to 6 carbon atoms, preferably a hydroxyl group or a (meth)acryloyloxy group, more preferably a hydroxyl group. The alkenyl group having 2 to 6 carbon atoms may be a vinyloxy group having 2 to 6 carbon atoms.

[0069] As the compound (C), 1,3-bis(3-methyl-2-butenoxy)-2-hydroxypropane (also known as diprenyl glycerin ether, abbreviated as DPNG) is preferred.

[0070] The method for producing the compound (C) is not particularly limited, and a commercially available product can be used as the compound (C).

[0071] In the conductive polymer-containing dispersion of this embodiment, the content of compound (C) is preferably 0.001 to 1.0 parts by mass, more preferably 0.01 to 0.9 parts by mass, and even more preferably 0.1 to 0.8 parts by mass per part by mass of the solid content in the conductive polymer-containing dispersion, from the viewpoints of the stability of the conductive polymer-containing dispersion and the effect of reducing the ESR and increasing the capacitance of the solid electrolytic capacitor. Furthermore, the content of compound (C) in the conductive polymer-containing dispersion is preferably 0.010 to 5.0% by mass, more preferably 0.10 to 3.0% by mass, and even more preferably 0.50 to 1.5% by mass.

[0072] (Dispersion medium (D)) The dispersion medium (D) of the conductive polymer-containing dispersion of this embodiment is not particularly limited, but it is preferable that the dispersion medium (D) can more efficiently maintain high dispersion stability of the conductive polymer-containing dispersion. Furthermore, the dispersion medium (D) is preferably capable of dissolving or dispersing the compound (C), more preferably capable of dissolving, and even more preferably capable of dissolving all of the compound (C) contained in the conductive polymer-containing dispersion. The dispersion medium (D) does not fall under the category of compound (C), and preferably has a melting point of 15°C or less and a boiling point of less than 150°C.

[0073] Examples of the dispersion medium (D) include water; amides such as N-vinylpyrrolidone, hexamethylphosphortriamide, N-vinylformamide, and N-vinylacetamide; phenols such as cresol, phenol, and xylenol; polyhydric alcohols such as dipropylene glycol, 1,3-butylene glycol, 1,4-butylene glycol, diglycerin, isoprene glycol, butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,9-nonanediol, and neopentyl glycol; carbonate compounds such as ethylene carbonate and propylene carbonate; ethers such as dioxane, diethyl ether, propylene glycol dialkyl ether, polyethylene glycol dialkyl ether, and polypropylene glycol dialkyl ether; heterocyclic compounds such as 3-methyl-2-oxazolidinone; and nitriles such as acetonitrile, glutarodinitrile, methoxyacetonitrile, propionitrile, and benzonitrile. The dispersion medium (D) may be used alone or in combination of two or more. Among these, from the viewpoints of good dispersion stability and ease of production of the conductive polymer-containing dispersion, it is preferable that the conductive polymer-containing dispersion contains 1 to 99 mass % of water, more preferably 50 to 99 mass % of water, and even more preferably contains only water.

[0074] The content of the dispersion medium (D) in the conductive polymer-containing dispersion is preferably 30 to 98 mass %, more preferably 45 to 97 mass %, and even more preferably 60 to 94 mass %, from the viewpoint of appropriate viscosity and dispersion stability of the conductive polymer-containing dispersion.

[0075] (Polymer (E)) It is preferable that the polymer (E) does not fall under either the conjugated conductive polymer (A) or the polyanion (B) and is insoluble in the dispersion medium (D). The polymer (E) exists in the form of particles in the conductive polymer-containing dispersion, and is thought to contribute to suppressing dedoping of the polyanion (B) from the conjugated conductive polymer (A) and suppressing oxidative degradation of the polymer component.

[0076] The content of the polymer (E) in 100% by mass of the polymer component contained in the conductive polymer-containing dispersion of the present embodiment is preferably 0 to 50% by mass, more preferably 0 to 40% by mass, and even more preferably 0 to 25% by mass, from the viewpoints of the dispersion stability of the conductive polymer-containing dispersion and the effect of reducing the ESR and increasing the capacitance of a solid electrolytic capacitor produced using the conductive polymer-containing dispersion.

[0077] The polymer (E) is not particularly limited, but for example, a polymer containing a structural unit derived from an ethylenically unsaturated monomer is preferred, and a polymer consisting of a structural unit derived from an ethylenically unsaturated monomer is more preferred. The polymer (E) is preferably a nonionic polymer, and more preferably composed of a hydrocarbon. The polymer (E) may contain either a homopolymer or a copolymer, or both. The polymer (E) may be used alone or in combination of two or more types. The polymer (E) may also have a crosslinked structure.

[0078] Examples of ethylenically unsaturated monomers from which the structural units of polymer (E) are derived include (meth)acrylates having a linear, branched, or cyclic alkyl group; aromatic vinyl compounds such as styrene and α-methylstyrene; heterocyclic vinyl compounds such as vinylpyrrolidone; hydroxyalkyl (meth)acrylates; dialkylaminoalkyl (meth)acrylates such as 2-ethylhexyl (meth)acrylate; vinyl esters such as vinyl acetate and vinyl alkanoate; monoolefins such as ethylene, propylene, butylene, and isobutylene; conjugated diolefins such as butadiene, isoprene, and chloroprene; α,β-unsaturated mono- or dicarboxylic acids such as (meth)acrylic acid, crotonic acid, itaconic acid, maleic acid, and fumaric acid; vinyl cyanide compounds such as acrylonitrile; and carbonyl group-containing vinyl compounds such as acrolein and diacetone acrylamide. The ethylenically unsaturated monomers may be used alone or in combination of two or more.

[0079] The polymer (E) may have a crosslinked structure. Examples of the crosslinked structure include a structure derived from a compound having a plurality of independent ethylenically unsaturated bonds. Here, "a plurality of independent ethylenically unsaturated bonds" refers to a plurality of ethylenically unsaturated bonds that do not form a conjugated diene with each other. The crosslinked structure may be formed, for example, by a polymer having a first reactive functional group and a crosslinking agent having a plurality of second reactive functional groups that react with the first reactive functional group, or by reacting a polymer having both a first reactive functional group and a second reactive functional group intramolecularly or intermolecularly. By forming a crosslinked copolymer, the water resistance, moisture resistance, heat resistance, etc. of a solid electrolyte using the same are likely to be improved.

[0080] When a crosslinking agent is not used, the content of the structural units forming a crosslinked structure in 100% by mass of the polymer (E) is preferably 50% by mass or less, more preferably 30% by mass or less, and even more preferably 15% by mass or less. When a crosslinking agent is used, the total content of the structural units forming a crosslinked structure and the components derived from the crosslinking agent in 100% by mass of the polymer (E) is preferably 50% by mass or less, more preferably 30% by mass or less, and even more preferably 15% by mass or less.

[0081] Examples of compounds that form crosslinked structures include epoxy group-containing α,β-ethylenically unsaturated compounds such as glycidyl (meth)acrylate; hydrolyzable alkoxysilyl group-containing α,β-ethylenically unsaturated compounds such as vinyltriethoxysilane and γ-methacryloxypropyltrimethoxysilane; and polyfunctional vinyl compounds such as ethylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, allyl (meth)acrylate, divinylbenzene, and diallyl phthalate. Furthermore, crosslinkable monomers such as carbonyl group-containing α,β-ethylenically unsaturated compounds (those containing ketone groups) may be crosslinked in combination with polyhydrazine compounds (particularly those having two or more hydrazide groups such as oxalic acid dihydrazide, succinic acid dihydrazide, adipic acid dihydrazide, and polyacrylic acid hydrazide).

[0082] The polymer (E) is preferably obtained as a dispersion containing the polymer (E) in a state of being dispersed in a dispersion medium, and more preferably obtained in the state of an emulsion.

[0083] From the viewpoints of dispersion stability and suppression of sedimentation, the particles contained in the dispersion containing the polymer (E) have a 50% volume cumulative particle diameter (d ５０ ) is preferably 0.01 to 10 μm, more preferably 0.05 to 1 μm, even more preferably 0.1 to 0.8 μm, and even more preferably 0.3 to 0.6 μm. ５０ is determined by the method described in the Examples below.

[0084] The polymer (E) can be produced by radical polymerization reaction in a normal pressure or pressure-resistant reactor, and the production method may be batchwise, semi-continuous, or continuous. It is preferably produced by emulsion polymerization, in which a raw material solution containing an ethylenically unsaturated monomer is continuously or intermittently added to a polyanion-containing solution and polymerized. Emulsion polymerization efficiently produces composite particles (2) in which the polyanion is coordinated to the polymer (E), forming a polyanion domain outside the domain of the polymer (E). The polyanion used here contributes to the dispersion stability of the polymer (E)-containing dispersion. The polyanion in the polymer (Z)-containing dispersion may be the same as or different from the polyanion (B) (e.g., different cations may be bonded to the polyanion).

[0085] The amount of the ethylenically unsaturated monomer used in the synthesis of the polymer (E) is preferably 10 to 100 parts by mass, more preferably 20 to 90 parts by mass, and even more preferably 30 to 80 parts by mass, per 100 parts by mass of the polyanion, from the viewpoints of suppressing thickening of the dispersion containing the polymer (E) and improving dispersion stability.

[0086] The dispersion medium used in the synthesis of the polymer (E) is preferably an aqueous medium, more preferably water or a mixed solvent of water and a water-soluble solvent. The proportion of the water-soluble solvent in the mixed solvent is preferably 30 mass% or less from the viewpoint of dispersion stability of the particles during the polymerization reaction. The dispersion medium used in the synthesis of the polymer (E) may be the same component as the dispersion medium (D) contained in the conductive polymer-containing dispersion liquid, or may be a different component. Examples of the water-soluble solvent include alcohols such as methanol, ethanol, and isopropanol, ketones such as acetone, glycols such as ethylene glycol and propylene glycol, and ethers such as ethylene glycol monomethyl ether and ethylene glycol monobutyl ether.

[0087] The content of the dispersion medium in the dispersion liquid containing the polymer (E) is preferably 30 to 99% by mass, more preferably 50 to 95% by mass, and even more preferably 70 to 90% by mass, from the viewpoint of the dispersion stability of the dispersion liquid containing the polymer (E).

[0088] From the viewpoint of good dispersion stability, additives such as emulsifiers and aliphatic amines may be added to the dispersion containing polymer (E) as needed. The type and amount of additives are appropriately adjusted depending on the content and composition of the ethylenically unsaturated monomer and polyanion. The emulsifier and aliphatic amine contained in the dispersion containing polymer (E) may be one type alone or two or more types.

[0089] Examples of the emulsifier include anionic surfactants such as alkyl sulfates, alkyl benzene sulfonates, alkyl sulfosuccinates, alkyl diphenyl ether disulfonates, polyoxyalkylene alkyl sulfates, and polyoxyalkylene alkyl phosphates; and nonionic surfactants such as polyoxyalkylene alkyl ethers, polyoxyalkylene alkylphenol ethers, polyoxyalkylene fatty acid esters, and polyoxyalkylene sorbitan fatty acid esters.

[0090] Examples of aliphatic amines include primary amines such as octylamine, laurylamine, myristylamine, stearylamine, and oleylamine; secondary amines such as dioctylamine, dilaurylamine, distearylamine, and dioleylamine; and tertiary amines such as N,N-dimethyllaurylamine, N,N-dimethylmyristylamine, N,N-dimethylpalmitylamine, N,N-dimethylstearylamine, N,N-dimethylbehenylamine, N,N-dimethyloleylamine, N-methyldidecylamine, and N-methyldioleylamine.

[0091] Furthermore, from the viewpoint of dispersion stability of the dispersion containing polymer (E), a water-soluble polymer such as polyvinyl alcohol, methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, or polyvinylpyrrolidone may be contained within a range that does not impair the properties of the conductive polymer-containing dispersion of this embodiment.

[0092] Examples of polymerization initiators for the radical polymerization reaction to obtain polymer (E) include inorganic peroxides such as hydrogen peroxide, persulfuric acid, ammonium persulfate, potassium persulfate, and sodium persulfate; organic peroxides such as benzoyl peroxide and tert-butyl hydroperoxide; and azo compounds such as 2,2'-azobisisobutyronitrile and 4,4'-azobis(4-cyanovaleric acid). These polymerization initiators may be combined with sodium sulfoxylate formaldehyde, ascorbic acids, sulfites, tartaric acid or its salts, iron(II) sulfate, or the like to carry out redox polymerization. Chain transfer agents such as alcohols and mercaptans may also be used as needed. The reaction temperature in the radical polymerization reaction is preferably 10 to 100°C, more preferably 30 to 90°C. The reaction time is not particularly limited and can be adjusted appropriately depending on the amount of raw materials, the type of polymerization initiator, the reaction temperature, and other factors.

[0093] From the viewpoint of the quality stability of the dispersion containing polymer (E), it is preferable to desalt the reaction product obtained by the radical polymerization reaction. The desalting method is not particularly limited, and examples thereof include dialysis, centrifugation washing, and ion exchange using an ion exchange resin.

[0094] (Alkaline Compound (F)) The conductive polymer-containing dispersion of this embodiment may contain an alkaline compound (F) from the viewpoints of pH adjustment and corrosion inhibition of metals and the like with which it comes into contact. The content of the alkaline compound (F) in the conductive polymer-containing dispersion is an amount such that the pH of the conductive polymer-containing dispersion becomes preferably 3 to 13, more preferably 3 to 8, and even more preferably 4 to 7, from the viewpoints of corrosion inhibition of metals and the like with which the conductive polymer-containing dispersion comes into contact and inhibition of undoping of the polyanion (B) from the conjugated conductive polymer (A). The content of the alkaline compound (F) in the conductive polymer-containing dispersion is preferably 0 to 15% by mass, more preferably 0.05 to 10% by mass, and even more preferably 0.1 to 5% by mass.

[0095] The alkaline compound (F) is not particularly limited, and organic or inorganic alkaline compounds can be used. The alkaline compound (F) may be used alone or in combination of two or more.

[0096] Examples of organic alkaline compounds include aromatic amines, aliphatic amines, heterocyclic amines, and alkali metal alkoxides. Examples of aromatic amines include nitrogen-containing heteroaryls such as pyridines, imidazoles, pyrimidines, pyrazines, and triazines. Among these, pyridines, imidazoles, and pyrimidines are preferred from the viewpoint of solubility and the like. Examples of aliphatic amines include ethylamine, n-octylamine, diethylamine, diisobutylamine, methylethylamine, trimethylamine, triethylamine, allylamine, 2-ethylaminoethanol, 2,2'-iminodiethanol, and N-ethylethylenediamine. Examples of heterocyclic amines include azetidines, pyrrolidines, piperidines, piperazines, morpholines, and thiomorpholines. Among these, morpholines are preferred from the viewpoint of versatility.

[0097] Specific examples of morpholines include morpholine, 4-methylmorpholine, 4-ethylmorpholine, 4-n-propylmorpholine, 4-isopropylmorpholine, 4-n-butylmorpholine, 4-isobutylmorpholine, 4-pentylmorpholine, 4-hexylmorpholine, (R)-3-methylmorpholine, (S)-3-methylmorpholine, cis-2,6-dimethylmorpholine, 4-(1-cyclohexenyl)morpholine, 1-morpholino-1-cyclopentene, 4-phenylmorpholine, 4-(p-tolyl)morpholine, 4-(2-aminoethyl)morpholine, 4-(3-aminopropyl)morpholine, 2-morpholinoaniline, and 4-morpholinoaniline. , 4-(2-morpholinoethoxy)aniline, 4-(4-pyridyl)morpholine, 4-aminomorpholine, 4-(2-hydroxypropyl)morpholine, 4-(2-hydroxyethyl)morpholine, 4-(3-hydroxypropyl)morpholine, 2-hydroxy-3-morpholinopropanesulfonic acid, 2-morpholinoethanesulfonic acid, 3-morpholinopropanesulfonic acid, 4-acetylmorpholine, 4-acetoacetylmorpholine, 4-acryloylmorpholine, 4-allylmorpholine, phenylmorpholine, ethyl 3-(morpholino)propionate, 4-formylmorpholine, 4-(4-formylphenyl)morpholine, and salts thereof. Among these, from the viewpoints of availability and ease of handling, morpholine, 4-ethylmorpholine, 4-n-butylmorpholine, 4-isobutylmorpholine, 4-phenylmorpholine, 4-(2-hydroxypropyl)morpholine, 4-(2-hydroxyethyl)morpholine, and 4-(3-hydroxypropyl)morpholine are preferred, and at least one selected from the group consisting of morpholine, 4-ethylmorpholine, and 4-(2-hydroxyethyl)morpholine is more preferred, with morpholine being particularly preferred.

[0098] Examples of alkali metal alkoxides include sodium alkoxides such as sodium methoxide and sodium ethoxide; potassium alkoxides; and calcium alkoxides.

[0099] Examples of inorganic alkaline compounds include ammonia, sodium hydroxide, potassium hydroxide, calcium hydroxide, and ammonia.

[0100] (Electrical Conductivity Enhancer) The conductive polymer-containing dispersion of the present embodiment may contain an electrical conductivity enhancer in order to further improve the conductivity of the solid electrolyte layer of the solid electrolytic capacitor. It is believed that the electrical conductivity enhancer improves the conductivity by making the polymer sequence of the conjugated conductive polymer (A) more likely to form a good conductive path when volatilized together with the dispersion medium (D) during the formation of the solid electrolyte layer using the conductive polymer-containing dispersion.

[0101] Examples of the electrical conductivity improver include ethers such as tetrahydrofuran; lactones such as γ-butyrolactone and γ-valerolactone; amides or lactams such as caprolactam, N-methylcaprolactam, N,N-dimethylacetamide, N-methylacetamide, N,N-dimethylformamide, N-methylformamide, N-methylformanilide, N-methylpyrrolidone, N-octylpyrrolidone, and pyrrolidone; sulfones or sulfoxides such as tetramethylene sulfone and dimethyl sulfoxide; sugars and derivatives thereof such as sucrose, glucose, fructose, and lactose; sugar alcohols such as sorbitol and mannitol; imides such as succinimide and maleimide; furans such as 2-furancarboxylic acid and 3-furancarboxylic acid; and polyalcohols such as ethylene glycol, propylene glycol, glycerin, diethylene glycol, and triethylene glycol. Among these, ethers, lactones, amides or lactams, sugar alcohols, and polyalcohols are preferred, with polyalcohols being particularly preferred. Specific compounds, from the viewpoint of improving electrical conductivity, include tetrahydrofuran, γ-butyrolactone, N-methylformamide, N-methylpyrrolidone, ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, glycerin, diglycerin, polyglycerin, dimethyl sulfoxide, and sorbitol, with ethylene glycol, diethylene glycol, and triethylene glycol being more preferred. The electrical conductivity improvers may be used alone or in combination of two or more.

[0102] (Other Additives) From the viewpoint of imparting properties suitable for solid electrolytic capacitors, the conductive polymer-containing dispersion of this embodiment may contain other additives that do not fall under any of the conjugated conductive polymer (A), polyanion (B), compound (C), dispersion medium (D), polymer (E), alkaline compound (F), and electrical conductivity enhancer. The type and content of the other additives are not particularly limited. Examples of the other additives include water-soluble polymer compounds, water-dispersible compounds, surfactants, antifoaming agents, coupling agents, and antioxidants. The other additives may be used alone or in combination of two or more.

[0103] The water-soluble polymer compound and the water-dispersible compound can adjust the viscosity of the conductive polymer-containing dispersion and improve the coating performance. When at least one of a water-soluble polymer compound and a water-dispersible compound is contained, the total content of the water-soluble polymer compound and the water-dispersible compound is preferably 1 to 50 parts by mass, more preferably 2 to 40 parts by mass, and even more preferably 3 to 30 parts by mass per part by mass of the polymer component contained in the conductive polymer-containing dispersion.

[0104] Examples of water-soluble polymer compounds include polyoxyalkylenes, water-soluble polyurethanes, water-soluble polyesters, water-soluble polyamides, water-soluble polyimides, water-soluble polyacrylics, water-soluble polyacrylamides, polyvinyl alcohols, and polyacrylic acids. Among these, polyoxyalkylenes are preferred. Examples of polyoxyalkylenes include oligopolyethylene glycol, triethylene glycol monochlorhydrin, diethylene glycol monochlorhydrin, oligoethylene glycol monochlorhydrin, triethylene glycol monobromohydrin, diethylene glycol monobromohydrin, oligoethylene glycol monobromohydrin, polyethylene glycol, glycidyl ethers, polyethylene glycol glycidyl ethers, polyethylene oxide, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, dipropylene glycol, tripropylene glycol, polypropylene glycol, polypropylene dioxide, polyoxyethylene alkyl ethers, polyoxyethylene glycerin fatty acid esters, and polyoxyethylene fatty acid amides.

[0105] The water-dispersible compound is preferably dispersed in water without precipitating, for example, by substituting a portion of a less hydrophilic compound with a more hydrophilic functional group. Examples of the water-dispersible compound include polyester, polyurethane, acrylic resin, silicone resin, and compounds obtained by modifying these by introducing a functional group or the like. Other examples include block copolymers and graft copolymers of acrylic resin and polyester or polyurethane.

[0106] Examples of surfactants include anionic surfactants such as carboxylates, sulfonates, sulfates, and phosphates; cationic surfactants such as amine salts and quaternary ammonium salts; amphoteric surfactants such as carboxybetaine, aminocarboxylates, and imidazolium betaine; and nonionic surfactants such as polyoxyethylene alkyl ethers, polyoxyethylene glycerin fatty acid esters, ethylene glycol fatty acid esters, and polyoxyethylene fatty acid amides. Examples of antifoaming agents include silicone resins, polydimethylsiloxanes, and silicone oils. Examples of antioxidants include phenolic antioxidants, amine antioxidants, phosphorus antioxidants, sulfur antioxidants, and vitamins.

[0107] [Method for Producing Conductive Polymer-Containing Dispersion] The conductive polymer-containing dispersion of this embodiment can be produced, for example, by polymerizing the monomer that will become the constituent unit of the conjugated conductive polymer (A) in a raw material solution (1) containing the monomer that will become the constituent unit of the conjugated conductive polymer (A) and a polyanion, and then adding compound (C). The raw material solution (1) may contain polymer (E). Optionally, an alkaline compound (F) and other additives may be added. The polymer (E) may form a complex with the polyanion, or may form a complex in which the polyanion is coordinated outside the domain of the polymer (E). Furthermore, the polymer (E) may be added as the above-mentioned dispersion containing the polymer (E). As described above, the polyanion used in the production process of the conductive polymer-containing dispersion may have the same structure as the polyanion (B) contained in the conductive polymer-containing dispersion, or may have a different structure (e.g., a cation is bound thereto).

[0108] From the viewpoint of suppressing uneven progress of the polymerization reaction, it is preferable that the monomers that become the constituent units of the conjugated conductive polymer (A) are dissolved, emulsified, or dispersed in the raw material liquid (1). The raw material liquid (1) can be prepared, for example, by stirring with a stirrer such as a homomixer or a homogenizer, or by ultrasonic irradiation.

[0109] In preparing the raw material solution (1), even when a mixture containing a polyanion and a polymer (E) is used, such as a dispersion containing a polymer (E), a polyanion may be added to suppress particle aggregation in the raw material solution (1). The raw material solution (1) may contain a composite particle (2), which is a complex in which a polyanion is coordinated outside the domain of the polymer (E), and an additional polyanion. The additional polyanion may be the same as or a different component from the polyanion that forms the complex with the polymer (E), but is preferably the same. The amount of the additional polyanion is preferably 99% by mass or less, more preferably 10 to 90% by mass, even more preferably 30 to 80% by mass, and even more preferably 40 to 70% by mass, based on 100% by mass of the total polyanions in the raw material solution (1).

[0110] From the viewpoints of dispersion stability of the conductive polymer-containing dispersion and the effect of reducing the ESR and increasing the capacitance of a solid electrolytic capacitor produced using the conductive polymer-containing dispersion, the total content of polyanions in the raw material liquid (1) is preferably an amount such that the number of anionic groups is 0.25 to 30 mol, more preferably 0.5 to 25 mol, and even more preferably 0.8 to 20 mol per mol of the monomer that serves as a constituent unit of the conjugated conductive polymer (A).

[0111] Examples of the dispersion medium in the raw material liquid (1) include water; amides such as N-vinylpyrrolidone, hexamethylphosphoramide, N-vinylformamide, and N-vinylacetamide; phenols such as cresol, phenol, and xylenol; polyhydric alcohols such as dipropylene glycol, 1,3-butylene glycol, 1,4-butylene glycol, diglycerin, isoprene glycol, butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,9-nonanediol, and neopentyl glycol; carbonates such as ethylene carbonate and propylene carbonate; ethers such as dioxane, diethyl ether, propylene glycol dialkyl ether, polyethylene glycol dialkyl ether, and polypropylene glycol dialkyl ether; heterocyclic compounds such as 3-methyl-2-oxazolidinone; and nitriles such as acetonitrile, glutarodinitrile, methoxyacetonitrile, propionitrile, and benzonitrile. The dispersion medium may be used alone or in combination of two or more. The dispersion medium preferably contains water, and in this case, the content of water in 100% by mass of the dispersion medium is preferably 1% by mass or more, more preferably 50% by mass or more, and even more preferably 100% by mass. From the viewpoint of ease of production of the conductive polymer-containing dispersion, the dispersion medium in the raw material liquid (1) is preferably the same component as the dispersion medium (D) of the conductive polymer-containing dispersion.

[0112] The content of the dispersion medium in the raw material liquid (1) is preferably 1 to 99.9% by mass, more preferably 10 to 99% by mass, and even more preferably 30 to 98% by mass, from the viewpoint of appropriate viscosity and reactivity during the polymerization reaction.

[0113] The polymerization reaction for synthesizing the conjugated conductive polymer (A) is preferably carried out in the presence of an oxidizing agent. Examples of the oxidizing agent include peroxodisulfuric acid, peroxodisulfate salts such as ammonium peroxodisulfate, sodium peroxodisulfate, and potassium peroxodisulfate; metal halide compounds such as boron trifluoride; transition metal compounds such as iron (III) chloride, iron (III) sulfate, and copper (II) chloride; metal oxides such as silver oxide and cesium oxide; peroxides such as hydrogen peroxide and ozone; organic peroxides such as benzoyl peroxide; and oxygen. Among these, peroxodisulfuric acid, peroxodisulfate salts, and transition metal compounds are preferred, and peroxodisulfate salts and transition metal compounds are more preferred. The oxidizing agent may be used alone or in combination of two or more. From the viewpoint of appropriately promoting the polymerization reaction, the amount of the oxidizing agent used is preferably 50 to 1500 parts by mass, more preferably 70 to 1000 parts by mass, and even more preferably 100 to 500 parts by mass, relative to 100 parts by mass of the monomer that becomes a constituent unit of the conjugated conductive polymer (A).

[0114] The temperature in the polymerization reaction is preferably 5 to 80° C., more preferably 10 to 60° C., and even more preferably 15 to 40° C., from the viewpoint of achieving an appropriate reaction rate and suppressing an increase in the viscosity of the reaction solution. The temperature may be changed as appropriate depending on the progress of the reaction.

[0115] The polymerization reaction is preferably carried out with stirring from the viewpoint of homogenizing the reaction system and suppressing aggregation of particles in the reaction solution. The stirring method is not particularly limited, and examples thereof include a method of circulating and stirring the reaction solution using a high-shear mixer or the like.

[0116] [Method for manufacturing a solid electrolytic capacitor] The method for manufacturing a solid electrolytic capacitor of this embodiment includes the steps of: depositing the conductive polymer-containing dispersion of this embodiment described above on a porous anode body made of a valve metal having a dielectric coating on its surface; and then removing the dispersion medium (D) from the dispersion liquid deposited on the porous anode body to form a solid electrolyte layer. By forming a solid electrolyte layer using the conductive polymer-containing dispersion of this embodiment in this step, a solid electrolytic capacitor having a low ESR and a large capacitance can be suitably manufactured.

[0117] Examples of valve metals include aluminum, beryllium, bismuth, magnesium, germanium, hafnium, niobium, antimony, silicon, tin, tantalum, titanium, vanadium, tungsten, zirconium, and alloys or compounds containing at least one of these metals. Among these, aluminum, niobium, and tantalum are preferred from the viewpoint of versatility.

[0118] The porous anode body can be produced by forming a dielectric coating on the surface of a porous valve metal. The porous valve metal can be obtained, for example, by sintering a valve metal powder with a high specific surface area or etching a valve metal foil. The dielectric coating can be formed as a dielectric oxide coating on the surface of the porous valve metal, for example, by anodizing the porous valve metal in a phosphate solution. The formation voltage in the anodization is set depending on the thickness of the dielectric oxide coating, the withstand voltage of the capacitor, and the like, and is preferably 1 to 800 V, more preferably 1 to 500 V, and even more preferably 1 to 300 V.

[0119] The conductive polymer-containing dispersion can be applied to the porous anode body by, for example, coating, spraying, immersion, etc. Among these methods, the method of immersing the porous anode body in the conductive polymer-containing dispersion is preferred because it allows the conductive polymer-containing dispersion to penetrate evenly and uniformly into the porous anode body and adhere to it. Furthermore, impregnation may be performed under reduced pressure in order to allow the conductive polymer-containing dispersion to fully penetrate into the pores and other details of the porous anode body.

[0120] When the conductive polymer-containing dispersion is attached to the porous anode body by immersion, the conductive polymer-containing dispersion is usually impregnated into the porous anode body for about 10 seconds to 10 minutes, although the temperature varies depending on the type and viscosity of the dispersion medium (D) of the conductive polymer-containing dispersion.

[0121] From the viewpoint of removal efficiency, the dispersion medium (D) is preferably removed by heating and drying the porous anode body to which the conductive polymer-containing dispersion liquid has been applied. Heating conditions are appropriately set taking into consideration the boiling point and volatility of the dispersion medium (D), oxidative degradation of the polymer component, and the like. Heating is typically performed at room temperature to 300°C, preferably 40 to 250°C, and more preferably 50 to 200°C, for 5 seconds to 10 hours. Examples of heating devices that can be used include a hot plate, oven, and hot air dryer. From the viewpoint of drying efficiency, drying may be performed under reduced pressure. Note that the removal of the dispersion medium (D) here does not necessarily mean achieving a state in which the dispersion medium (D) is completely absent; some dispersion medium may remain within a range that does not interfere with the production of the solid electrolytic capacitor.

[0122] From the viewpoint of achieving a uniform thickness of the solid electrolyte layer, the above steps may be repeated. The solid electrolyte layer formed in the above steps may be impregnated with an arbitrary electrolytic solution. Examples of the electrolytic solution to be impregnated into the solid electrolyte layer include polar organic solvents that may contain salts.

[0123] As the polar organic solvent for the electrolytic solution, a protic solvent can be used, and examples thereof include monohydric alcohols such as ethanol, propanol, butanol, pentanol, hexanol, cyclobutanol, cyclopentanol, cyclohexanol, and benzyl alcohol; and polyhydric alcohols such as alkylene oxide adducts of ethylene glycol, diethylene glycol, propylene glycol, glycerin, methyl cellosolve, ethyl cellosolve, methoxypropylene glycol, dimethoxypropanol, polyethylene glycol, and polyoxyethylene glycerin, and oxyalcohol compounds. In addition, an aprotic solvent can also be used as the polar organic solvent, and examples thereof include sulfones such as dimethyl sulfone, ethyl methyl sulfone, diethyl sulfone, sulfolane, 3-methyl sulfolane, and 2,4-dimethyl sulfolane; amides such as N-methylformamide, N,N-dimethylformamide, N-ethylformamide, N,N-diethylformamide, N-methylacetamide, N,N-dimethylacetamide, N-ethylacetamide, N,N-diethylacetamide, and hexamethylphosphoric amide; lactones and cyclic amides such as γ-butyrolactone, γ-valerolactone, δ-valerolactone, N-methyl-2-pyrrolidone, ethylene carbonate, propylene carbonate, butylene carbonate, and isobutylene carbonate; nitriles such as acetonitrile, 3-methoxypropionitrile, and glutaronitrile; and oxides such as dimethyl sulfoxide.

[0124] Examples of salts include ammonium salts; quaternary ammonium salts such as tetramethylammonium salt, triethylmethylammonium salt, and tetraethylammonium salt; amidinium salts such as ethyldimethylimidazolinium salt and tetramethylimidazolinium salt; primary amine salts such as methylamine salt, ethylamine salt, and propylamine salt; secondary amine salts such as dimethylamine salt, diethylamine salt, ethylmethylamine salt, and dibutylamine salt; tertiary amine salts such as trimethylamine salt, triethylamine salt, tributylamine salt, ethyldimethylamine salt, and ethyldiisopropylamine salt; sodium salts; and potassium salts.

[0125] Examples of acids that can form salts include carboxylic acids such as oxalic acid, succinic acid, glutaric acid, pimelic acid, suberic acid, sebacic acid, phthalic acid, isophthalic acid, terephthalic acid, maleic acid, adipic acid, benzoic acid, toluic acid, enanthic acid, malonic acid, 1,6-decanedicarboxylic acid, 1,7-octanedicarboxylic acid, azelaic acid, resorcylic acid, phloroglucinic acid, gallic acid, gentisic acid, protocatechuic acid, pyrocatechuic acid, trimellitic acid, and pyromellitic acid; and organic acids such as sulfonic acids. Further examples include boric acid, phosphoric acid, phosphorous acid, hypophosphorous acid, carbonic acid, and silicic acid. Further examples include boron complexes such as borodisalicylic acid, borodisalic acid, borodiglycolic acid, borodimalonic acid, borodisuccinic acid, borodiadipic acid, borodiazelaic acid, borodibenzoic acid, borodimaleic acid, borodilactic acid, borodimalic acid, boroditartaric acid, borodicitric acid, borodiphthalic acid, borodi(2-hydroxy)isobutyric acid, borodiresorcylic acid, borodimethylsalicylic acid, borodinaphthoic acid, borodimandelic acid, and borodi(3-hydroxy)propionic acid.

[0126] The electrolytic solution may contain an additive. Examples of the additive include complex compounds of boric acid and polysaccharides such as mannitol and sorbitol; complex compounds of boric acid and polyhydric alcohols; boric acid esters; nitro compounds such as o-nitrobenzoic acid, m-nitrobenzoic acid, p-nitrobenzoic acid, o-nitrophenol, m-nitrophenol, p-nitrophenol, and p-nitrobenzyl alcohol; and phosphate esters. These may be used alone or in combination of two or more.

[0127] [Solid Electrolytic Capacitor] The solid electrolytic capacitor of this embodiment includes a porous anode body having a solid electrolyte layer, the porous anode body being a valve metal having a dielectric coating on its surface, and the solid electrolyte layer including a conjugated conductive polymer (A), a polyanion (B), and the compound (C) represented by the above-described formula (1). A solid electrolytic capacitor having such a configuration has a low ESR and a high capacitance. Such a solid electrolytic capacitor can be suitably manufactured by the above-described method for manufacturing a solid electrolytic capacitor of this embodiment. The solid electrolyte layer may include the above-described electrolytic solution.

[0128] The present invention will be described in detail below with reference to examples. The present invention is not limited to the following examples, and various modifications are possible within the scope of the present invention.

[0129] [Measurement Methods] The methods for measuring various physical properties in the Examples and Comparative Examples are as follows. (Weight Average Molecular Weight) The weight average molecular weight (Mw) of sodium polystyrene sulfonate was determined as a standard polystyrene-equivalent molecular weight measured by gel permeation chromatography under the following measurement conditions. <Measurement Conditions> Measurement device: "Shodex GPC 101", manufactured by Resonac Co., Ltd. Column used: "OHpak SB-806M HQ", manufactured by Resonac Co., Ltd. Column temperature: 40°C Eluent: water Elution rate: 1 mL / min Standard sample: polystyrene

[0130] (50% volume cumulative particle diameter (d ５０ )) 50% volume cumulative particle diameter (d ５０ The particle size distribution was measured using a particle size distribution analyzer (Microtrac UPA type, manufactured by Nikkiso Co., Ltd.) and calculated using the accompanying software (Microtrac II) under the following conditions: <Setting conditions> Particles: transparent, spherical, refractive index 1.59, density 1.00 g / cm ３ Solvent: refractive index 1.333, viscosity 0.797 mPa·s (30°C), 1.002 mPa·s (20°C)

[0131] (Solid content concentration) The solid content concentration was calculated by weighing 10 g of a dispersion sample and heating it for 30 minutes using an infrared moisture meter (FD-720, manufactured by Kett Electric Laboratory) at a temperature 10°C higher than the boiling point of the dispersion medium with the highest boiling point among the dispersion mediums contained (110°C when the dispersion medium is water), and then estimating the evaporation residue (excluding morpholine) as the solid content.

[0132] (pH) The pH was measured using a pH meter ("HM-30G", manufactured by DKK-TOA Corporation; 25°C).

[0133] [Production of Conductive Polymer-Containing Dispersion] (Example 1) <Production of Dispersion Containing Polymer (E)> 86 g of styrene, 49 g of 2-ethylhexyl acrylate, 15 g of divinylbenzene, and 500 g of a 22% by mass aqueous solution of sodium polystyrene sulfonate (polyanion (B): "Polinas PS-5", manufactured by Tosoh Finechem Corporation; Mw 120,000; the same applies hereinafter) (110 g of sodium polystyrene sulfonate) were mixed with stirring to prepare raw material solution (a). Furthermore, 1,000 g of a 22% by mass aqueous solution of sodium polystyrene sulfonate (220 g of sodium polystyrene sulfonate) was heated to 80°C with stirring, and 2 g of potassium persulfate was added to the mixture to prepare raw material solution (b). To the raw material solution (b), the raw material solution (a) was added dropwise over 2 hours, and then 40 g of a 2.5 mass % aqueous solution of potassium persulfate was added dropwise over 2.5 hours. The mixture was allowed to react at 80°C for 2 hours, and then cooled to room temperature (25°C). 1500 mL of a cation exchange resin ("Amberlite IR120B-H", manufactured by Organo Corporation; the same applies hereinafter) and 1500 mL of anion exchange resin ("Amberlite IRA410-OH", manufactured by Organo Corporation; the same applies hereinafter) were added to the reaction product, and the mixture was stirred for 12 hours. The ion exchange resin was then filtered off. Pure water was added to obtain a dispersion containing polyanion (B) and polymer (E). The d of particles contained in this polymer (E)-containing dispersion (solids concentration 15.0 mass%) was ５０ was 0.46 μm.

[0134] <Preparation of Raw Material Solution (1)> In a 1 L polyethylene container, 34.0 g of the dispersion containing polymer (E) obtained above, 31.5 g of a 12 mass % aqueous solution of sodium polystyrene sulfonate (3.78 g of sodium polystyrene sulfonate), and 223.2 g of pure water were mixed with stirring at 32°C. 2.80 g of 3,4-ethylenedioxythiophene was added thereto, and the mixture was mixed in a homomixer ("Robomix", manufactured by Primix Corporation; 4000 min －１ ; the same applies hereinafter.) was emulsified and mixed for 30 minutes to prepare a raw material solution (1) (total amount of sodium polystyrene sulfonate: 1.9 moles of sodium sulfonate groups per mole of 3,4-ethylenedioxythiophene).

[0135] <Production of intermediate product solution (2)> 291.5 g of the raw material solution (1) was mixed in a high-shear mixer (Milder MDN303V, manufactured by Pacific Machinery Works, Ltd.; 5000 min －１ The mixture was placed in a stainless steel vessel connected to a circulating pump (32°C) and stirred while circulating with a stirring blade and a high-shear mixer. 5.89 g of sodium peroxodisulfate and 6.88 g of a 1 mass % aqueous solution of iron (III) sulfate hexahydrate were added, and the polymerization reaction was carried out for 24 hours to obtain an intermediate product liquid (2) (solids concentration 5.80 mass %) containing a conjugated conductive polymer (A). The procedures for preparing the raw material liquid (1) and producing the intermediate product liquid (2) were repeated, and a total of 1223.3 g of an intermediate product liquid (2) containing a conjugated conductive polymer (A) was obtained.

[0136] <Dispersion and desalination treatment> 1223.3 g of the intermediate product solution (2) was diluted with pure water to 1500 mL (solid content concentration 4.73 mass%) and then subjected to a dispersion treatment for 45 minutes using a high-pressure homogenizer ("TwinPanda 600", manufactured by Niro Soavi; 400 bar (40 MPa); the same applies hereinafter). Further, pure water was added to dilute the solution to a solid content concentration of 3.99 mass%, and 1500 mL was taken out and subjected to a dispersion treatment for 135 minutes using a high-pressure homogenizer to obtain a dispersion solution (3) containing a conjugated conductive polymer (A). The dispersion solution (3) was desalted by ion exchange using 125.6 mL of cation exchange resin and 109.9 mL of anion exchange resin for 3 hours to obtain a dispersion solution (4) containing a conjugated conductive polymer (A) (pH 1.9, solid content concentration 1.65 mass%).

[0137] <Preparation of conductive polymer-containing dispersion> 7.5 g of morpholine and 22.5 g of pure water were added to 1,000 g of dispersion (4), and the pH was adjusted to 4.7 to obtain dispersion (5) with a solids concentration of 1.60 mass %. 1.0 g of 1,3-bis(3-methyl-2-butenoxy)-2-hydroxypropane (DPNG) was added to 100 g of dispersion (5), and further 20 g of ethylene glycol was added as an electrical conductivity improver.

[0138] Example 2 A conductive polymer-containing dispersion was produced in the same manner as in Example 1, except that the 20 g of ethylene glycol used in Example 1 was changed to 10 g of triethylene glycol and 30 g of glycerin.

[0139] Comparative Examples 1 and 2 Each conductive polymer-containing dispersion was produced in the same manner as in Examples 1 and 2, except that the DPNG used in Examples 1 and 2 was not added.

[0140] [Production of Solid Electrolytic Capacitor] Using each of the conductive polymer-containing dispersions produced in the above Examples and Comparative Examples, solid electrolytic capacitors were produced as follows: A porous anode body of an aluminum electrolytic capacitor element (withstand voltage 35 V, design capacity 400 μF) was impregnated in the conductive polymer-containing dispersion under reduced pressure at 20 kPa and 25° C. for 5 minutes, and then dried in a hot air dryer ("ST-110", manufactured by Espec Corporation) at 150° C. for 30 minutes to obtain a solid electrolytic capacitor in which a solid electrolyte layer was formed on the surface of the dielectric oxide film of the porous anode body.

[0141] For each solid electrolytic capacitor, the capacitance at 120 Hz and the equivalent series resistance (ESR) [mΩ] at 120 Hz and 100 kHz were measured using a precision LCR meter ("E4980A", manufactured by Agilent Technologies, Inc.). The measurement results are shown in Table 1.

[0142]

[0143] As can be seen from the results shown in Table 1, it was found that by adding DPNG to the conductive polymer-containing dispersion (Examples 1 and 2), solid electrolytic capacitors with lower ESR and larger capacitance could be produced compared to the case where DPNG was not added (Comparative Examples 1 and 2).

Claims

1. A conductive polymer-containing dispersion comprising a conjugated conductive polymer (A), a polyanion (B), a compound (C) having a group represented by the following formula (1), and a dispersion medium (D): (In formula (1), R １ and R ２ are each independently an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an aryl group, or an aralkyl group; and X is an oxygen atom or a sulfur atom.

2. R １ and R ２ and each independently represent an alkyl group having 1 to 4 carbon atoms.

3. The conductive polymer-containing dispersion according to claim 1, wherein X is an oxygen atom.

4. The conductive polymer-containing dispersion according to claim 1, wherein the group represented by formula (1) is a prenyloxy group.

5. The conductive polymer-containing dispersion according to claim 1, wherein the compound (C) is a compound having two or more prenyloxy groups.

6. The conductive polymer-containing dispersion according to claim 1, wherein the compound (C) is a compound represented by the following formula (2): (In formula (2), R １ ~R ４ are each independently an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an aryl group, or an aralkyl group. ５ and R ６ are each independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an aryl group, or an aralkyl group. ７ is a hydrogen atom or a methyl group. ８ is a hydroxyl group, a (meth)acryloyloxy group, a 4-vinylphenoxy group, or an alkenyloxy group having 2 to 6 carbon atoms.

7. The conductive polymer-containing dispersion according to claim 1, wherein the content of compound (C) is 0.001 to 1.0 part by mass per part by mass of the solid content in the conductive polymer-containing dispersion.

8. The conductive polymer-containing dispersion according to claim 1, further comprising a polymer (E) which does not fall under either the conjugated conductive polymer (A) or the polyanion (B) and which is insoluble in the dispersion medium (D).

9. The conductive polymer-containing dispersion according to claim 1, wherein the conjugated conductive polymer (A) is a polymer of a monomer containing one or more compounds selected from the group consisting of pyrroles, anilines, and thiophenes.

10. The conductive polymer-containing dispersion according to claim 9, wherein the thiophene compound is represented by the following formula (3): (In formula (3), R １１ and R １２ are each independently a hydrogen atom, a hydroxyl group, an optionally substituted alkyl group having 1 to 18 carbon atoms, an optionally substituted alkoxy group having 1 to 18 carbon atoms, or an optionally substituted alkylthio group having 1 to 18 carbon atoms; or R １１ and R １２ and are bonded to each other to form an optionally substituted alicyclic ring having 3 to 10 carbon atoms, an optionally substituted aromatic ring having 6 to 10 carbon atoms, an optionally substituted oxygen atom-containing heterocyclic ring having 2 to 10 carbon atoms, an optionally substituted sulfur atom-containing heterocyclic ring having 2 to 10 carbon atoms, or an optionally substituted sulfur atom- and oxygen atom-containing heterocyclic ring having 2 to 10 carbon atoms.

11. The conductive polymer-containing dispersion according to claim 1, wherein the polyanion (B) is a polymer having two or more groups consisting of sulfonic acid or a salt thereof.

12. The conductive polymer-containing dispersion according to claim 1, further comprising an alkaline compound (F).

13. The conductive polymer-containing dispersion according to claim 12, wherein the alkaline compound (F) is at least one selected from the group consisting of morpholine, 4-ethylmorpholine, and 4-(2-hydroxyethyl)morpholine.

14. A method for producing a solid electrolytic capacitor, comprising the steps of: applying the conductive polymer-containing dispersion liquid according to any one of claims 1 to 13 to a porous anode body made of a valve metal having a dielectric coating on its surface; and then removing the dispersion medium (D) to form a solid electrolyte layer.

15. A solid electrolytic capacitor comprising a porous anode body having a solid electrolyte layer, wherein the porous anode body is a valve metal having a dielectric coating on its surface, and the solid electrolyte layer comprises a conjugated conductive polymer (A), a polyanion (B), and a compound (C) represented by the following formula (1): (In formula (1), R １ and R ２ are each independently an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an aryl group, or an aralkyl group; and X is an oxygen atom or a sulfur atom.

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