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

Abstract

Provided are: a dispersion liquid containing a conductive polymer, which is capable of further reducing the equivalent series resistance (ESR) of a solid electrolytic capacitor; a method for producing the dispersion liquid; and a solid electrolytic capacitor having a lower ESR. A conductive polymer-containing dispersion liquid containing a conjugated conductive polymer (A), a polyanion (B), a hydroxyl group-containing cyclic ether compound (C), and a dispersion medium (D).

Description

Technical Field

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

[0002] Generally, a solid electrolytic capacitor has a structure in which a valve metal such as aluminum, tantalum, or niobium is used as an anode foil and a cathode foil, and a solid electrolyte is sandwiched between the anode foil and the cathode foil. In order to increase the electrostatic capacitance, the valve metal of the anode foil has its surface area increased by an etching process or the like, and a dielectric oxide film is formed on its surface. In addition, a conjugated system conductive polymer such as polypyrrole, polyaniline, or polythiophene is used in the solid electrolyte.

[0003] Since a solid electrolytic capacitor can reduce the equivalent series resistance (ESR) in a high-frequency region, it is used in electronic devices and the like. In addition, with the recent electrification of automobiles, the development of in-vehicle solid electrolytic capacitors has progressed. In particular, capacitors for vehicle electronic control devices are required to further reduce the ESR due to the high output of electronic control.

[0004] As a method for forming a solid electrolyte using a conductive polymer, for example, a method is known in which a monomer solution for obtaining a conductive polymer and an oxidizing agent solution are impregnated into an electrolytic capacitor assembly, and oxidative polymerization or electrolytic polymerization is performed inside the electrolytic capacitor assembly (for example, refer to Patent Document 1).

[0005] In addition, a method for forming a solid electrolyte in which a water dispersion liquid of a conductive polymer is impregnated into a dielectric oxide film of an anode body and dried is also known. When forming a solid electrolyte by such a method, by adding an additive for improving conductivity to the water dispersion liquid of the conductive polymer, the ESR of the solid electrolytic capacitor can be reduced. For example, Patent Document 2 proposes using a water-soluble compound such as ethylene glycol as an additive.

[0006] [Prior Art Documents]

[0007] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Laid-Open No. 63-173313

[0009] [Patent Document 2] Japanese Patent Laid-Open No. 2008-109068 Summary of the Invention

[0010] [Problems to be Solved by the Invention]

[0011] However, in the polymerization reaction within the electrolytic capacitor assembly described in Patent Document 1, since the conductive polymer forms in a condensed sponge state, the uniformity of the solid electrolyte deteriorates, and the conductivity is liable to decrease.

[0012] In addition, in the method using an aqueous dispersion of a conductive polymer, even when forming a solid electrolyte containing the water-soluble compound described in Patent Document 2, the ESR of the solid electrolytic capacitor cannot necessarily be said to be sufficiently low.

[0013] The present invention has been accomplished in view of such circumstances, and an object thereof is to provide a dispersion liquid containing a conductive polymer and a method for producing the same, which can further reduce the equivalent series resistance (ESR) of a solid electrolytic capacitor. In addition, the present invention aims to provide a solid electrolytic capacitor having a lower ESR.

[0014] [Means for Solving the Problem]

[0015] The present invention has found that by making the dispersion liquid containing a conductive polymer contain a cyclic ether compound having a specific structure, the ESR of the solid electrolytic capacitor produced using the dispersion liquid containing a conductive polymer can be reduced.

[0016] The present invention provides the following solutions.

[0017] [1]. A dispersion liquid containing a conductive polymer, comprising a conjugated conductive polymer A, a polyanion B, a hydroxyl group-containing cyclic ether compound C represented by any one of the following formulas (1) to (5), and a dispersion medium D,

[0018]

[0019] In the formulas (1) to (5), R 11 ~R 16 , R 21 ~R 28 , R 31 ~R 38 , R 41 ~R 44 , R 51 ~R 56 are each independently a hydrogen atom, a hydroxyl group, an alkyl group having 1 to 8 carbon atoms which may be substituted by a hydroxyl group, a cyano group or an amino group, a cycloalkenyl group having 5 or 6 carbon atoms, a phenyl group which may be substituted by a hydroxyl group, an amino group, a cyano group or a formyl group, an acetyl group, an acetoacetyl group, an allyl group, an acrylyl group, a pyridyl group, an alkylsulfonyl group which may be substituted by a hydroxyl group, or a formyl group.

[0020] [2]. The dispersion liquid containing a conductive polymer according to [1], wherein the content of the hydroxyl group-containing cyclic ether compound C is 1 to 50 parts by mass per 1 part by mass of the total amount of the conjugated conductive polymer A and the polyanion B.

[0021] [3]. The dispersion liquid containing a conductive polymer as described in [1] further contains polymer E, which neither belongs to the conjugated conductive polymer A nor to the polyanion B and is insoluble in the dispersion medium D.

[0022] [4]. The dispersion liquid containing a conductive polymer as described in [3], per 1 part by mass of the total amount of the conjugated conductive polymer A, the polyanion B, and the polymer E, contains 1 to 50 parts by mass of the hydroxy group-containing cyclic ether compound C.

[0023] [5]. The dispersion liquid containing a conductive polymer as described in any one of [1] to [4], the hydroxy group-containing cyclic ether compound C is at least one selected from 2,2-dimethyl-1,3-dioxolane-4-methanol, 4-hydroxymethyl-1,3-dioxolan-2-one, 2,2-dimethyl-1,3-dioxolane-4-ethanol, and 1,3-dioxane-5-ol.

[0024] [6]. The dispersion liquid containing a conductive polymer as described in any one of [1] to [5], the conjugated conductive polymer A is a polymer of a monomer containing one or more compounds selected from pyrrole-based, aniline-based, and thiophene-based compounds.

[0025] [7]. The dispersion liquid containing a conductive polymer as described in [6], the thiophene-based compound is represented by the following formula (6),

[0026]

[0027] In formula (6), R 61 and R 62 are each independently a hydrogen atom, a hydroxy group, a substituted or unsubstituted alkyl group having 1 to 18 carbon atoms, a substituted or unsubstituted alkoxy group having 1 to 18 carbon atoms, or a substituted or unsubstituted alkylthio group having 1 to 18 carbon atoms; or, R 61 and R 62 are combined with each other to form a substituted or unsubstituted alicyclic ring having 3 to 10 carbon atoms, a substituted or unsubstituted aromatic ring having 6 to 10 carbon atoms, a substituted or unsubstituted hetero ring containing an oxygen atom having 2 to 10 carbon atoms, a substituted or unsubstituted hetero ring containing a sulfur atom having 2 to 10 carbon atoms, or a substituted or unsubstituted hetero ring containing a sulfur atom and an oxygen atom having 2 to 10 carbon atoms.

[0028] [8]. The dispersion liquid containing a conductive polymer as described in any one of [1] to [7], the polyanion B is a polymer having two or more groups formed by a sulfonic acid or its salt.

[0029] [9]. The dispersion liquid containing a conductive polymer as described in any one of [1] to [8] further contains a basic compound F.

[0030]

[10] . In the dispersion liquid containing a conductive polymer as described in [9], the basic compound F is at least one selected from morpholine, 4-ethylmorpholine, and 4-(2-hydroxyethyl)morpholine.

[0031]

[11] . A method for manufacturing a solid electrolytic capacitor, comprising the following steps:

[0032] A step of attaching the dispersion liquid containing a conductive polymer according to any one of [1] to

[10] to a porous anode body formed of a valve metal having a dielectric film on its surface, and then removing the dispersion medium D to form a solid electrolyte layer.

[0033]

[12] . A solid electrolytic capacitor having a solid electrolyte layer on a porous anode body formed of a valve metal having a dielectric film on its surface,

[0034] The solid electrolyte layer contains a conjugated conductive polymer A, a polyanion B, and a hydroxyl group-containing cyclic ether compound C represented by any one of the following formulas (1) to (5),

[0035]

[0036] In the formulas (1) to (5), R 11 ~R 16 , R 21 ~R 28 , R 31 ~R 38 , R 41 ~R 44 , R 51 ~R 56 are each independently a hydrogen atom, a hydroxyl group, an alkyl group having 1 to 8 carbon atoms which may be substituted by a hydroxyl group, a cyano group or an amino group, a cycloalkenyl group having 5 or 6 carbon atoms, a phenyl group which may be substituted by a hydroxyl group, an amino group, a cyano group or a formyl group, an acetyl group, an acetoacetyl group, an allyl group, an acryloyl group, a pyridyl group, an alkylsulfonyl group which may be substituted by a hydroxyl group, or a formyl group.

[0037] [Advantages of the Invention]

[0038] According to the present invention, it is possible to provide a dispersion liquid containing a conductive polymer and a method for manufacturing the same, which can further reduce the ESR of a solid electrolytic capacitor. In addition, according to the present invention, a solid electrolytic capacitor with a lower ESR can be obtained. Detailed Embodiments

[0039] First, the definitions and meanings of the terms and symbols in this specification are shown below.

[0040] Regarding the group of a compound, the term "substitutable" means either the substituted case or the unsubstituted case (the case without substituents).

[0041] The "class" attached to the compound name refers to a group of compounds including the structure of the compound, and also includes the compound with substituents. For example, the so-called polypyrrole class refers to a group of compounds including the polypyrrole structure.

[0042] The so-called "(meth)acrylic acid" is a general term for acrylic acid and methacrylic acid. Similarly, the so-called "(meth)acrylate" is a general term for acrylate and methacrylate, and the so-called "(meth)acryloyl" is a general term for acryloyl and methacryloyl.

[0043] Unless otherwise specified, the so-called "ethylenically unsaturated bond" refers to an ethylenically unsaturated bond having radical polymerizability. In addition, the so-called "ethylenically unsaturated monomer" is a compound having an ethylenically unsaturated bond and used to form a polymer.

[0044] The so-called "polymer component" refers to a conjugated conductive polymer (A), a polyanion (B), and a polymer (E). When the dispersion liquid containing a conductive polymer does not contain the polymer (E), it refers to the conjugated conductive polymer (A) and the polyanion (B).

[0045] The numerical range indicated by "~" represents the range included when the numerical values described before and after "~" are taken as the minimum value and the maximum value respectively. In the numerical ranges described in this specification in stages, the upper limit value or the lower limit value of the numerical range at a certain stage can be arbitrarily combined with the upper limit value or the lower limit value of the numerical range at other stages. In the numerical ranges described in this specification, the upper limit value or the lower limit value of the numerical range can be replaced with the values shown in the examples.

[0046] [Dispersion liquid containing a conductive polymer]

[0047] The dispersion liquid containing a conductive polymer of an embodiment of the present invention (hereinafter referred to as "this embodiment") contains a conjugated conductive polymer (A), a polyanion (B), a hydroxyl group-containing cyclic ether compound (C) represented by any one of the following formulas (1) to (5), and a dispersion medium (D).

[0048] The dispersion liquid containing a conductive polymer of this embodiment is preferably a dispersion liquid containing a conductive polymer for manufacturing a solid electrolytic capacitor (a dispersion liquid containing a conductive polymer for a solid electrolytic capacitor).

[0049] [Chemical formula 4]

[0050]

[0051] (In formulas (1) to (5), R11 ~R 16 、R 21 ~R 28 、R 31 ~R 38 、R 41 ~R 44 、R 51 ~R 56 Each independently represents: a hydrogen atom; a hydroxyl group; an alkyl group having 1 to 8 carbon atoms which may be substituted with a hydroxyl group, a cyano group or an amino group; a cycloalkenyl group having 5 or 6 carbon atoms; a phenyl group which may be substituted with a hydroxyl group, an amino group, a cyano group or a formyl group; an acetyl group; an acetoacetyl group; an allyl group; an acryloyl group; a pyridyl group; an alkylsulfonyl group which may be substituted with a hydroxyl group; or a formyl group).

[0052] By using a dispersion of a conductive polymer containing a cyclic ether compound (C) having the specific structure as described above, a solid electrolytic capacitor with low ESR can be manufactured.

[0053] The dispersion of the conductive polymer of the present embodiment may further contain a polymer (E), a basic compound (F), and other additives described later.

[0054] In the first embodiment, in the dispersion of the conductive polymer, the total content of the conjugated conductive polymer (A), the polyanion (B), the cyclic ether compound (C) containing a hydroxyl group, and the dispersion medium (D) is preferably 80 to 100% by mass, more preferably 85 to 100% by mass, and still more preferably 90 to 100% by mass.

[0055] By having the total content within the above numerical range, the ESR of the solid electrolytic capacitor manufactured using the dispersion of the conductive polymer can be further reduced. In the first embodiment, it is preferably free of polymers other than the conjugated conductive polymer (A) and the polyanion (B).

[0056] In the first embodiment, it is preferable to form composite particles (1) containing the conjugated conductive polymer (A) and the polyanion (B).

[0057] In the first embodiment, in the dispersion of the conductive polymer, the total content of the conjugated conductive polymer (A) and the polyanion (B) is preferably 0.1 to 20% by mass, more preferably 0.5 to 15% by mass, and still more preferably 1 to 10% by mass, from the viewpoints of the ESR reduction effect of the solid electrolytic capacitor, the viscosity of the dispersion of the conductive polymer for easy handling, and the dispersibility of the composite particles (1).

[0058] In the second embodiment, the dispersion containing the conductive polymer may further contain a polymer (E) in addition to the conjugated conductive polymer (A), the polyanion (B), the hydroxyl group-containing cyclic ether compound (C), and the dispersion medium (D).

[0059] By using the dispersion containing the conductive polymer of the second embodiment, the ESR of the solid electrolytic capacitor can be further reduced.

[0060] In the second embodiment, the composite particles (2) containing the conjugated conductive polymer (A), the polyanion (B), and the polymer (E) may be contained in the dispersion containing the conductive polymer. Similar to the composite particles (2), the above-mentioned composite particles (1) may also be contained in the dispersion containing the conductive polymer.

[0061] In the second embodiment, the structure of the composite particles (2) contained in the dispersion containing the conductive polymer is not particularly limited, but it is preferably that the inner region of the composite particles (2) is formed by the polymer (E), the polyanion (B) coordinates on the polymer (E) to form the outer region of the composite particles (2), and a part or all of the region of the polymer (E) is coated with the conjugated conductive polymer (A) and the polyanion (B).

[0062] In the second embodiment, in the dispersion containing the conductive polymer, the total content of the conjugated conductive polymer (A), the polyanion (B), the hydroxyl group-containing cyclic ether compound (C), the dispersion medium (D), and the polymer (E) is preferably 80 to 100% by mass, more preferably 85 to 100% by mass, and still more preferably 90 to 100% by mass.

[0063] By having the total content within the above numerical range, the ESR of the solid electrolytic capacitor manufactured using the dispersion containing the conductive polymer can be further reduced.

[0064] In the second embodiment, in the dispersion containing the conductive polymer, the total content of the conjugated conductive polymer (A), the polyanion (B), and the polymer (E) is preferably 0.1 to 20% by mass, more preferably 0.5 to 15% by mass, and still more preferably 1 to 10% by mass from the viewpoints of the ESR reduction effect of the solid electrolytic capacitor, the viscosity for easy operation of the dispersion containing the conductive polymer, and the dispersibility of the composite particles (2).

[0065] (Conjugated conductive polymer (A))

[0066] The conjugated system 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 system conductive polymer can be used alone or in combination of two or more. In addition, it can be a homopolymer of the following monomers that are structural units of the conjugated system conductive polymer (A), or a copolymer of two or more monomers. Since the dispersion liquid containing a conductive polymer of the present embodiment contains a polyanion (B) used as a dopant, the conjugated system conductive polymer (A) may not have a self-doping function.

[0067] From the viewpoints of the dispersion stability of the dispersion liquid containing a conductive polymer and the reduction of the ESR of the solid electrolytic capacitor manufactured from the dispersion liquid containing a conductive polymer, the content of the conjugated system conductive polymer (A) in 100% by mass of the polymer components contained in the dispersion liquid containing a conductive polymer of the present embodiment is preferably 5 to 70% by mass, more preferably 10 to 60% by mass, and still more preferably 15 to 50% by mass.

[0068] Examples of the conjugated system conductive polymer (A) include polypyrroles, polythiophenes, polyisothianaphthenes, polyacetylenes, polyphenylenes, polyphenylenevinylenes, polyanilines, polyacenes, polythiophenylethylenes, and copolymers thereof. Among these, from the viewpoints of ease of operation or ease of acquisition, polypyrroles, polythiophenes, and polyanilines are preferred, and polythiophenes are more preferred.

[0069] In addition, from the viewpoint of high conductivity, the conjugated system conductive polymer (A) preferably has substituents such as alkyl, carboxyl, sulfo, alkoxy, hydroxyl, and cyano groups.

[0070] 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), poly(3-methyl-4-hexyloxypyrrole), etc.

[0071] 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), poly(3,4-dimethylthiophene), poly(3,4-dibutylthiophene), poly(3-hydroxythiophene), poly(3-methoxythiophene), poly(3-ethoxythiophene), poly(3-butoxythiophene), poly(3-hexoxythiophene), poly(3-heptoxythiophene), poly(3-octoxythiophene), poly(3-decoxythiophene), 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-dihexoxythiophene), poly(3,4-diheptoxythiophene), poly(3,4-dioctoxythiophene), poly(3,4-didecoxythiophene), poly(3,4-didodecyloxythiophene), poly(3,4-ethylenedioxythiophene), poly(3,4-propylenedioxythiophene), poly(3,4-butylenedioxythiophene), poly(3-methyl-4-methoxythiophene), poly(3-methyl-4-ethoxythiophene), poly(3-carboxythiophene), poly(3-methyl-4-carboxythiophene), poly(3-methyl-4-carboxyethylthiophene), poly(3-methyl-4-carboxybutylthiophene), poly(3,4-ethylenedioxybenzo[1,2-b:4,5-b']dithiophene), etc.

[0072] Examples of polyanilines include polyaniline, poly(2-methylaniline), poly(3-isobutylaniline), poly(2-anilinesulfonic acid), poly(3-anilinesulfonic acid), etc.

[0073] 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. Further, from the viewpoint of excellent heat resistance, poly(3,4-ethylenedioxythiophene) is more preferable.

[0074] The monomer for obtaining the conjugated conductive polymer (A), that is, the monomer that becomes the structural unit of the conjugated conductive polymer (A), is preferably a compound containing one or more selected from pyrrole compounds, aniline compounds, and thiophene compounds. The compound may have a substituent X, and 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 carboxyl group, a hydroxyl group, a halogen atom, a cyano group, etc. In addition, two or more of these substituents X may be bonded to each other by condensation or the like to form a ring. Further, these alkyl groups, aryl groups, heteroaryl groups, alkoxy groups, and alkylthio groups may have further substituents Y such as a carboxyl group, a hydroxyl group, a halogen atom, and a cyano group, for example.

[0075] As the monomer serving as the structural unit of the conjugated conductive polymer (A), for example, 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-carboxypyrrole, 3-methyl-4-carboxypyrrole, 3-methyl-4-carboxyethylpyrrole, 3-methyl-4-carboxybutylpyrrole, 3-hydroxypyrrole, 3-methoxypyrrole, 3-ethoxypyrrole, 3-butoxypyrrole, 3-hexyloxypyrrole, 3-methyl-4-hexyloxypyrrole, 3-methyl-4-hexyloxypyrrole and the like pyrroles can be mentioned; 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, 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-propyldioxythiophene, 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, 3,4-ethylenedioxythiathiophene and the like thiophenes; aniline, 2-methylaniline, 3-isobutylaniline, 2-anilinesulfonic acid, 3-anilinesulfonic acid and the like anilines and the like. These can be used alone or in combination of two or more.

[0076] Among these compounds, the monomer serving as the structural unit of the conjugated conductive polymer (A) is preferably a compound containing a thiophene represented by the following formula (6) from the viewpoint of obtaining a conjugated conductive polymer having high conductivity. The compound represented by the formula (6) can be used alone or in combination of two or more.

[0077] [Chemical formula 5]

[0078]

[0079] In formula (6), R 61 and R62 Each independently represents 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 61 and R 62 combine with 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 heterocyclic ring containing an oxygen atom having 2 to 10 carbon atoms, an optionally substituted heterocyclic ring containing a sulfur atom having 2 to 10 carbon atoms, or an optionally substituted heterocyclic ring containing a sulfur atom and an oxygen atom having 2 to 10 carbon atoms.

[0080] Examples of the substituent as the substitution may include a carboxyl group, a hydroxyl group, a halogen atom, a cyano group, etc.

[0081] As the heterocyclic ring containing an oxygen atom, it is preferably an oxygen atom number forming the ring is 1 to 3, and examples thereof may include an ethylene oxide ring, an oxetane ring, a furan ring, a tetrahydrofuran ring, a pyran ring, a pyrone ring, a dioxane ring, a trioxane ring, etc.

[0082] As the heterocyclic ring containing a sulfur atom, it is preferably a nitrogen atom number forming the ring is 1 to 3, and examples thereof may include a thiirane ring, a thietane ring, a thiophene ring, a tetrahydrothiopyran ring, a thiopyran ring, a thiopyrylium ring, a benzothiopyran ring, a dithiane ring, a dithiolane ring, a trithiane ring, etc.

[0083] As the heterocyclic ring containing a sulfur atom and an oxygen atom, it is preferably a total number of sulfur atoms and oxygen atoms forming the ring is 1 to 3, and examples thereof may include an oxathiacyclopentane ring, an oxathiacyclohexane ring, etc.

[0084] Among the monomers that are structural units of the conjugated conductive polymer (A), from the viewpoints of the uniformity and good conductivity of the conjugated conductive polymer (A), etc., the content of the compound represented by the formula (6) is preferably 90 to 100% by mass, more preferably 95 to 100% by mass, and still more preferably 100% by mass.

[0085] Among the monomers that are structural units of the conjugated conductive polymer (A), in the compound represented by the formula (6), it is more preferably to contain the compound represented by the following formula (7), and still more preferably to contain 3,4-ethylenedioxythiophene.

[0086] [Chemical formula 6]

[0087]

[0088] In the formula (7), R 71 and R 72Each independently represents a hydrogen atom, an optionally substituted alkyl group having 1 to 4 carbon atoms, or R 71 and R 72 combine with each other to form an oxygen-containing heterocycle having 3 to 6 carbon atoms which may be substituted.

[0089] R 71 and R 72 are preferably such that R 71 and R 72 combine with each other to form an oxygen-containing heterocycle having 3 to 6 carbon atoms which may be substituted.

[0090] As the oxygen-containing heterocycle, those having 1 to 3 oxygen atoms forming the ring are preferred, and examples thereof include dioxane, trioxane ring, etc., and dioxane is preferred. The oxygen-containing heterocycle is preferably unsubstituted.

[0091] The substituents for substitution herein are the same as the above-described substituent Y, and examples thereof include a carboxyl group, a hydroxyl group, a halogen atom, a cyano group, etc.

[0092] (Polyanion (B))

[0093] The polyanion (B) is a polymer having two or more anionic groups. It functions as a dopant for the conjugated conductive polymer (A). In addition, in the composite particle (2) of the second embodiment, it is considered that the polyanion (B) is coordinated on the inner side and outside the polymer (E) in the formation region, and is used as a protective colloid.

[0094] From the viewpoints of the stability in the dispersion liquid containing the conductive polymer and the reduction of the ESR of the solid electrolytic capacitor manufactured from the dispersion liquid containing the conductive polymer, the content of the polyanion (B) in 100% by mass of the polymer component contained in the dispersion liquid containing the conductive polymer of the present embodiment is preferably 30 to 95% by mass, more preferably 40 to 90% by mass, and still more preferably 50 to 85% by mass.

[0095] In addition, with respect to 100 parts by mass of the conjugated conductive polymer (A), the content of the polyanion (B) is preferably 45 to 1900 parts by mass, more preferably 70 to 900 parts by mass, and still more preferably 100 to 500 parts by mass.

[0096] Examples of the anionic group include a group formed from sulfonic acid or its salt, a group formed from phosphoric acid or its salt, a monosubstituted phosphate group, a group formed from carboxylic acid or its salt, a monosubstituted sulfate group, etc. Among these, a strongly acidic group is preferred, a group formed from sulfonic acid or its salt and a group formed from phosphoric acid or its salt are more preferred, and a group formed from sulfonic acid or its salt is still more preferred. That is, as the polyanion (B), a polymer having two or more groups formed from sulfonic acid or its salt is preferred.

[0097] As the salt, salts such as sodium, potassium, magnesium, calcium, ammonium and the like can be cited, for example.

[0098] The anionic group can be bonded to the main chain of the polymer constituting the polyanion (B), or can be bonded to the side chain. When the anionic group is bonded to the side chain, from the viewpoint of obtaining a high doping effect with respect to the conjugated conductive polymer (A), it is preferably bonded to the end of the side chain. Although the anionic group can also be directly bonded to the main chain, it can also be bonded through other structures. The anionic group is preferably bonded through a benzene ring, and in this case, it is more preferably bonded to the para position with respect to the main chain.

[0099] The polyanion (B) may have a substituent other than the anionic group.

[0100] The substituent can be bonded to the main chain of the polymer constituting the polyanion (B), or can be bonded to the side chain. When the substituent is bonded to the side chain, from the viewpoint of exerting the characteristics of the substituent, it is preferably bonded to the end of the side chain.

[0101] Although the main chain structure of the polymer constituting the polyanion (B) is not particularly limited, from the viewpoints of ease of synthesis or acquisition, etc., polyolefins such as polyethylene are preferred, for example.

[0102] As the polyanion (B), since the dispersibility in the dispersion medium (D) of the monomer which becomes the structural unit of the conjugated conductive polymer (A) can be improved, as described above, as the anionic group, a compound having a group formed from sulfonic acid or its salt is preferred.

[0103] The group formed from sulfonic acid, that is, the polyanion having a sulfo group (-SO2OH), can be cited, for example, polyvinylsulfonic acid, polystyrenesulfonic acid, polyallylsulfonic acid, polyethyl acrylate sulfonic acid, polybutyl acrylate sulfonic acid, poly(2-acrylamide-2-methylpropane sulfonic acid), polyisoprene sulfonic acid and their copolymers, etc. Among these, from the viewpoints of stability when used in the dispersion liquid containing the conductive polymer and reduction of the ESR of the solid electrolytic capacitor manufactured from the dispersion liquid containing the conductive polymer, etc., polystyrenesulfonic acid, polyisoprene sulfonic acid, polyethyl acrylate sulfonic acid, polybutyl acrylate sulfonic acid are preferred, and polystyrenesulfonic acid is more preferred.

[0104] In addition, the polyanion (B) contained in the dispersion liquid containing the conductive polymer and the polyanion used in the manufacturing step of the dispersion liquid containing the conductive polymer may have the same structure or different structures (for example, bonding different cations, etc.). For example, in the manufacturing step, from the viewpoints of water solubility, etc., sodium polystyrene sulfonate is suitably used as the polyanion, and it can be converted into polystyrenesulfonic acid by ion exchange, etc. in the subsequent desalting step.

[0105] The polyanion (B) can be produced by a known production method described in, for example, Japanese Patent Application Laid-Open No. 2005-76016, etc. In addition, commercially available products can also be used.

[0106] From the viewpoints of solubility in the dispersion medium (D) and doping effect on the conjugated conductive polymer (A), the weight-average molecular weight of the polyanion (B) is preferably 1,000 to 1,000,000, more preferably 5,000 to 500,000, and still more preferably 50,000 to 300,000.

[0107] In addition, the weight-average molecular weight referred to herein is the standard polystyrene-converted molecular weight measured by gel permeation chromatography. Specifically, it is measured by the method described in the examples.

[0108] (Hydroxy-containing cyclic ether compound (C))

[0109] In the present embodiment, the hydroxy-containing cyclic ether compound (C) is a hydroxy-containing compound represented by any one of the following formulas (1) to (5).

[0110] [Chemical formula 7]

[0111]

[0112] In formulas (1) to (5), R 11 to R 16 , R 21 to R 28 , R 31 to R 38 , R 41 to R 44 , R 51 to R 56 are each independently: a hydrogen atom; a hydroxyl group; an alkyl group having 1 to 8 carbon atoms which may be substituted by a hydroxyl group, a cyano group or an amino group; a cycloalkenyl group having 5 or 6 carbon atoms; a phenyl group which may be substituted by a hydroxyl group, an amino group, a cyano group or a formyl group; an acetyl group; an acetoacetyl group; an allyl group; an acryloyl group; a pyridyl group; an alkylsulfonyl group which may be substituted by a hydroxyl group; or a formyl group.

[0113] In formula (1), it is preferable that R 11 and R 12 are a hydrogen atom or an alkyl group, and at least any one of R 13 to R 16 is a hydroxyalkyl group, and the rest are hydrogen atoms.

[0114] In formula (2), it is preferable that R 21 and R 22 are a hydrogen atom or an alkyl group, and R 23 to R 28At least any one of them is a hydroxyalkyl group, and the rest are hydrogen atoms.

[0115] In formula (3), preferably R 31 and R 32 are hydrogen atoms or alkyl groups, and at least any one of R 33 ~R 38 is a hydroxyalkyl group, and the rest are hydrogen atoms.

[0116] In formula (4), preferably R 41 and R 42 are hydrogen atoms or alkyl groups, and at least any one of R 43 ~R 44 is a hydroxyalkyl group, and the rest are hydrogen atoms.

[0117] In formula (5), preferably R 51 and R 52 are hydrogen atoms or alkyl groups, and at least any one of R 53 ~R 56 is a hydroxyalkyl group, and the rest are hydrogen atoms.

[0118] The hydroxy-containing cyclic ether compound (C) functions to improve the conductivity of the dispersion of the conductive polymer-containing liquid and to reduce the ESR of the solid electrolytic capacitor manufactured using the dispersion of the conductive polymer-containing liquid. Although the reason for further reduction of the ESR of the solid electrolytic capacitor is not yet clear, it is speculated that the structure of the hydroxy-containing cyclic ether compound (C) not only further improves the conductivity of the conduction path formed by the dispersion of the conductive polymer-containing liquid containing the conjugated system conductive polymer (A) and the polyanion (B), but also brings some favorable effects and reduces the ESR of the solid electrolytic capacitor.

[0119] As the hydroxy-containing cyclic ether compound (C), from the viewpoint of reducing the ESR of the solid electrolytic capacitor, a compound having a carbonyl group is preferred, and a compound having a carbon atom forming a cyclic structure as a carbonyl group is more preferred.

[0120] Since the hydroxy-containing cyclic ether compound (C) has a higher boiling point and lower polarity than chain diol compounds such as ethylene glycol and propylene glycol, it is easy to maintain the dispersion stability of the dispersion of the conductive polymer-containing liquid. In addition, it is considered that the hydroxy-containing cyclic ether compound (C) having two oxygen atoms forming a cyclic structure has a higher boiling point than the cyclic ether compound having one oxygen atom forming a cyclic structure such as tetrahydrofuran and tetrahydropyran, and having a hydroxy group, and is easy to maintain the dispersion stability of the dispersion of the conductive polymer-containing liquid.

[0121] The hydroxy group of the hydroxy-containing cyclic ether compound (C) may be one or two or more. In addition, the hydroxy group may or may not be directly bonded to the carbon atom constituting the ring.

[0122] As the hydroxyl group-containing cyclic ether compound (C) represented by the formula (1), specifically, 1,3-dioxolan-2-ol, 1,3-dioxolan-2-methanol, 1,3-dioxolan-2-ethanol, 1,3-dioxolan-4-ol, 1,3-dioxolan-4-methanol, 1,3-dioxolan-4-ethanol, 2,2-dimethyl-1,3-dioxolan-4-ol, 2,2-dimethyl-1,3-dioxolan-4-methanol, 2,2-dimethyl-1,3-dioxolan-4-ethanol can be mentioned.

[0123] As the hydroxyl group-containing cyclic ether compound (C) represented by the formula (2), specifically, 1,3-dioxan-2-ol, 1,3-dioxan-4-ol, 1,3-dioxan-5-ol, 1,3-dioxan-2-methanol, 1,3-dioxan-4-methanol, 1,3-dioxan-5-methanol, 1,3-dioxan-2-ethanol, 1,3-dioxan-4-ethanol, 1,3-dioxan-5-ethanol, 2-phenyl-1,3-dioxan-5-ol can be mentioned.

[0124] As the hydroxyl group-containing cyclic ether compound (C) represented by the formula (3), specifically, 1,4-dioxan-2-ol, 1,4-dioxan-2-methanol, 1,4-dioxan-2-ethanol, 1,4-dioxan-2,3-diol, 1,4-dioxan-2,5-diol can be mentioned.

[0125] As the hydroxyl group-containing cyclic ether compound (C) represented by the formula (4), specifically, 4-hydroxy-1,3-dioxolan-2-one, 4-hydroxymethyl-1,3-dioxolan-2-one, 4-(2-hydroxyethyl)-1,3-dioxolan-2-one can be mentioned.

[0126] As the hydroxyl group-containing cyclic ether compound (C) represented by the formula (5), specifically, 5-hydroxy-1,3-dioxan-2-one, 5-hydroxymethyl-1,3-dioxan-2-one, 5-(2-hydroxyethyl)-1,3-dioxan-2-one can be mentioned.

[0127] As the hydroxyl group-containing cyclic ether compound (C), among the above specific compounds, at least one selected from 2,2-dimethyl-1,3-dioxolan-4-methanol, 4-hydroxymethyl-1,3-dioxolan-2-one, 2,2-dimethyl-1,3-dioxolan-4-ethanol and 1,3-dioxan-5-ol is preferred.

[0128] In the dispersion liquid containing a conductive polymer of the present embodiment, from the viewpoint of effectively reducing the stability of the dispersion liquid containing a conductive polymer and the ESR of the solid electrolytic capacitor, the content of the cyclic ether compound (C) having a hydroxyl group is preferably 1 to 50 parts by mass, more preferably 2 to 40 parts by mass, still more preferably 4 to 30 parts by mass, further more preferably 10 to 25 parts by mass, and particularly preferably 15 to 25 parts by mass, per 1 part by mass of the total amount of the polymer components contained in the dispersion liquid containing a polymer.

[0129] In addition, in the dispersion liquid containing a conductive polymer, the content of the cyclic ether compound (C) having a hydroxyl group is preferably 0.5 to 50% by mass, more preferably 3 to 40% by mass, still more preferably 6 to 30% by mass, further more preferably 12 to 30% by mass, and particularly preferably 20 to 30% by mass.

[0130] (Dispersion medium (D))

[0131] The dispersion medium (D) of the dispersion liquid containing a conductive polymer of the present embodiment is not particularly limited, but it is preferably one that can more effectively and maintain the high dispersion stability of the dispersion liquid containing a conductive polymer. In addition, the dispersion medium (D) is preferably one that can dissolve or disperse the cyclic ether compound (C) having a hydroxyl group, more preferably one that can dissolve, and still more preferably one that can dissolve all of the cyclic ether compound (C) having a hydroxyl group contained in the dispersion liquid containing a conductive polymer.

[0132] Examples of the dispersion medium (D) 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-butanediol, 1,4-butanediol, diglycerol, isopentylene 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, glutaronitrile, methoxyacetonitrile, propionitrile, and benzonitrile. The dispersion medium (D) can be used alone or in combination of two or more. Among these, from the viewpoints of good dispersion stability and ease of manufacture of the dispersion liquid containing a conductive polymer, it preferably contains 1 to 99% by mass of water, more preferably contains 50 to 99% by mass of water, and still more preferably contains only water.

[0133] In the dispersion liquid containing a conductive polymer, from the viewpoints of the desired viscosity and dispersion stability of the dispersion liquid containing a conductive polymer, the content of the dispersion medium (D) is preferably 30 to 98% by mass, more preferably 45 to 97% by mass, and still more preferably 60 to 94% by mass.

[0134] (Polymer (E))

[0135] The polymer (E) is a polymer other than the conjugated conductive polymer (A) and the polyanion (B), and is insoluble in the dispersion medium (D).

[0136] From the viewpoints of the dispersion stability of the conductive polymer-containing dispersion used and the reduction of the ESR of the solid electrolytic capacitor manufactured from the conductive polymer-containing dispersion, etc., the content of the polymer (E) in 100% by mass of the polymer components 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 still more preferably 0 to 25% by mass.

[0137] The polymer (E) is not particularly limited, but is preferably, for example, a polymer containing a structural unit derived from an ethylenically unsaturated monomer, and more preferably a polymer composed of a structural unit derived from an ethylenically unsaturated monomer. The polymer (E) is preferably a nonionic polymer, and more preferably composed of hydrocarbons. The polymer (E) may be either a single polymer (homopolymer) or a copolymer, or may contain both. The polymer (E) may be used alone as one kind, or two or more kinds may be used in combination. In addition, it may be either crystalline or amorphous, and is preferably amorphous. In addition, the polymer (E) may have a crosslinked structure.

[0138] Examples of the ethylenically unsaturated monomer that becomes the structural unit derived from the polymer (E) 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, butene and isobutene; conjugated dienes 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; cyanated vinyl compounds such as acrylonitrile; carbonyl-containing vinyl compounds such as acrolein and diacetone acrylamide, etc. The ethylenically unsaturated monomer may be used alone as one kind, or two or more kinds may be used in combination.

[0139] 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, the so-called plurality of independent ethylenically unsaturated bonds means a plurality of ethylenically unsaturated bonds that do not form a conjugated diene with each other.

[0140] The crosslinked structure can be formed, for example, by using a plurality of polymers having a first reactive functional group and a crosslinking agent having a second reactive functional group that reacts with the first reactive functional group. In addition, it can also be formed by reacting within or between molecules of a polymer having both a first reactive functional group and a second reactive functional group. By forming a crosslinked copolymer, it is easy to improve the water resistance, moisture resistance, heat resistance, etc. of the solid electrolyte using this.

[0141] When no crosslinking agent is used, the content of the structural unit forming the 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 still more preferably 15% by mass or less.

[0142] When a crosslinking agent is used, the total content of the structural unit forming the crosslinked structure and the constituent 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 still more preferably 15% by mass or less.

[0143] Examples of the compound for forming the crosslinked structure include epoxy group-containing α,β-ethylenically unsaturated compounds such as glycidyl (meth)acrylate; α,β-ethylenically unsaturated compounds containing a hydrolyzable alkoxysilyl group such as vinyltriethoxysilane and γ-methacryloxypropyltrimethoxysilane; polyfunctional vinyl compounds such as ethylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, allyl (meth)acrylate, divinylbenzene, and diallyl phthalate. In addition, a crosslinkable monomer such as a carbonyl group-containing α,β-ethylenically unsaturated compound (containing a ketone group) can be combined with a polyhydrazide compound (especially a compound having two or more hydrazide groups such as oxalic dihydrazide, succinic dihydrazide, adipic dihydrazide, and polyacrylic hydrazide) and crosslinked.

[0144] The polymer (E) is preferably obtained as a dispersion liquid containing the polymer (E) in a state of being dispersed in a dispersion medium, and more preferably obtained in a state of an emulsion.

[0145] Regarding the particles contained in the dispersion liquid containing the polymer (E), from the viewpoints of dispersion stability and sedimentation inhibition, etc., the 50% volume cumulative particle size (d 50 ) is preferably 0.01 to 10 μm, more preferably 0.05 to 1 μm, still more preferably 0.1 to 0.8 μm, and even more preferably 0.3 to 0.6 μm.

[0146] In addition, d 50 is obtained by the method described in the examples below.

[0147] The polymer (E) can be produced by a radical polymerization reaction in an atmospheric pressure or pressure-resistant reactor, and the production method can be any one of batch, semi-continuous, or continuous. Preferably, it is produced by emulsion polymerization in which a raw material liquid containing an ethylenically unsaturated monomer is continuously or intermittently added to a liquid containing a polyanion and polymerized. By emulsion polymerization, composite particles (2) having a structure in which the polyanion is coordinated to the polymer (E) and a polyanion region is formed outside the region of the polymer (E) can be effectively obtained.

[0148] The polyanion used herein may have the same structure as the polyanion (B) or may have a different structure (for example, bonded to different cations, etc.).

[0149] From the viewpoints of suppressing the viscosity increase of the dispersion liquid containing the polymer (E) and dispersion stability, the blending 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 still more preferably 30 to 80 parts by mass relative to 100 parts by mass of the polyanion.

[0150] 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% by mass or less from the viewpoint of the dispersion stability of the particles in the polymerization reaction. In addition, the dispersion medium used in the synthesis of the polymer (E) may have the same composition as the dispersion medium (D) contained in the dispersion liquid containing the conductive polymer, or may have a different composition.

[0151] Examples of the water-soluble solvent include alcohols such as methanol, ethanol, and isopropyl alcohol, ketones such as acetone, diols such as ethylene glycol and propylene glycol, and ethers such as ethylene glycol monomethyl ether and ethylene glycol monobutyl ether.

[0152] From the viewpoints of the dispersion stability of the dispersion liquid containing the polymer (E), etc., 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 still more preferably 70 to 90% by mass.

[0153] The polyanion contributes to the dispersion stability of the dispersion liquid containing the polymer (E). From the viewpoint of good dispersion stability, additives such as an emulsifier and an aliphatic amine may be added to the dispersion liquid containing the polymer (E) if necessary. The type and addition amount of the additive can be appropriately adjusted according to the content and composition of the ethylenically unsaturated monomer and the polyanion. The emulsifier and aliphatic amine contained in the dispersion liquid containing the polymer (E) may be a single type or two or more types.

[0154] Examples of the emulsifier include anionic surfactants such as alkyl sulfates, alkylbenzene 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.

[0155] Examples of the aliphatic amine 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.

[0156] In addition, from the viewpoint of the dispersion stability of the dispersion containing the polymer (E), water-soluble polymers such as polyvinyl alcohol, methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, and polyvinylpyrrolidone can be included within the range that does not impair the characteristics of the dispersion containing the conductive polymer of the present embodiment.

[0157] Examples of the polymerization initiator for the radical polymerization reaction for obtaining the 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-cyanopentanoic acid). These polymerization initiators can be combined with sodium formaldehyde sulfoxylate, ascorbic acids, sulfites, tartaric acid or its salts, iron(II) sulfate, etc. to perform redox polymerization. In addition, if necessary, chain transfer agents such as alcohols and thiols can be used.

[0158] In the radical polymerization reaction, the reaction temperature is preferably 10 to 100°C, more preferably 30 to 90°C. The reaction time is not particularly limited and can be appropriately adjusted according to the amount of the raw materials, the type of the polymerization initiator, and the reaction temperature.

[0159] Regarding the reaction product obtained by the radical polymerization reaction, from the viewpoint of the quality stability of the dispersion containing the polymer (E), it is preferably desalted. The desalting method is not particularly limited, and known methods can be used, such as dialysis, centrifugal separation and washing, and ion exchange using an ion exchange resin.

[0160] (Basic compound (F))

[0161] The dispersion liquid containing a conductive polymer may contain a basic compound (F) from the viewpoints of pH adjustment and corrosion inhibition of metals in contact therewith and the like.

[0162] The content of the basic compound (F) in the dispersion liquid containing a conductive polymer is preferably an amount that makes the pH of the dispersion liquid containing a conductive polymer 3 to 13, more preferably 3 to 8, and still more preferably 4 to 7, from the viewpoints of corrosion inhibition of metals in contact with the dispersion liquid containing a conductive polymer and inhibition of dedoping of the polyanion (B) from the conjugated conductive polymer (A) and the like. The content of the basic compound (F) in the dispersion liquid containing a conductive polymer is preferably 0 to 15% by mass, more preferably 0.05 to 10% by mass, and still more preferably 0.1 to 5% by mass.

[0163] There is no particular limitation on the basic compound, and organic or inorganic basic compounds can be used. The basic compound (F) can be used alone or in combination of two or more.

[0164] Examples of the organic basic compound include aromatic amines, aliphatic amines, heterocyclic amines, alkali metal alkoxides, and the like.

[0165] Examples of the aromatic amines include nitrogen-containing heteroaryl groups such as pyridines, imidazoles, pyrimidines, pyrazines, and triazines. Among these, pyridines, imidazoles, and pyrimidines are preferred from the viewpoints of solubility and the like.

[0166] Examples of the aliphatic amines include ethylamine, n-octylamine, diethylamine, diisobutylamine, methylethylamine, trimethylamine, triethylamine, allylamine, 2-ethylaminoethanol, 2,2'-iminodiethanol, N-ethylethylenediamine, and the like.

[0167] Examples of the heterocyclic amines include azetidines, pyrrolidines, piperidines, piperazines, morpholines, thiomorpholines, and the like. Among these, morpholines are preferred from the viewpoint of versatility.

[0168] As specific examples of morpholines, 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-morpholinocyclopentene, 4-phenylmorpholine, 4-(p-tolyl)morpholine, 4-(2-aminoethyl)morpholine, 4-(3-aminopropyl)morpholine, 2-morpholinoaniline, 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-acrylylmorpholine, 4-allylmorpholine, phenylmorpholine, ethyl 3-(morpholino)propionate, 4-formylmorpholine, 4-(4-formylphenyl)morpholine, and salts thereof can be mentioned. Among these, from the viewpoints of availability and operability, etc., morpholine, 4-ethylmorpholine, 4-n-butylmorpholine, 4-isobutylmorpholine, 4-phenylmorpholine, 4-(2-hydroxypropyl)morpholine, 4-(2-hydroxyethyl)morpholine, 4-(3-hydroxypropyl)morpholine are preferred, more preferably at least one selected from morpholine, 4-ethylmorpholine, and 4-(2-hydroxyethyl)morpholine, and particularly preferably morpholine.

[0169] As alkali metal alkoxides, for example, sodium alkoxides such as sodium methoxide and sodium ethoxide; potassium alkoxides; calcium alkoxides, etc. can be mentioned.

[0170] As inorganic basic compounds, for example, ammonia, sodium hydroxide, potassium hydroxide, calcium hydroxide, ammonia, etc. can be mentioned.

[0171] (Other additives)

[0172] The dispersion liquid containing a conductive polymer of the present embodiment may contain other additives from the viewpoint of imparting physical properties suitable for solid electrolytic capacitors, and these other additives neither belong to the conjugated conductive polymer (A), the polyanion (B), the hydroxyl group-containing cyclic ether compound (C), the dispersion medium (D), the polymer (E), nor the basic compound (F). There are no particular limitations on the types and contents of the other additives.

[0173] As other additives, for example, water-soluble polymer compounds, water-dispersible compounds, surfactants, defoaming agents, coupling agents, antioxidants, etc. can be mentioned. The other additives can be used alone or in combination of two or more.

[0174] Water-soluble polymer compounds and water-dispersible compounds can play a role in improving the viscosity adjustment and coating performance of a dispersion containing a conductive polymer.

[0175] When containing at least any one of a water-soluble polymer compound and a water-dispersible compound, per 1 part by mass of the polymer component contained in the dispersion containing a conductive polymer, 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 still more preferably 3 to 30 parts by mass.

[0176] Examples of the water-soluble polymer compound include polyoxyalkylene, water-soluble polyurethane, water-soluble polyester, water-soluble polyamide, water-soluble polyimide, water-soluble polyacrylic acid, water-soluble polyacrylamide, polyvinyl alcohol, polyacrylic acid, etc. Among these, polyoxyalkylene is preferred.

[0177] Examples of polyoxyalkylene include oligomeric ethylene glycol, triethylene glycol monochloroethyl ether, diethylene glycol monochloroethyl ether, oligomeric ethylene glycol monochloroethyl ether, triethylene glycol monobromoethyl ether, diethylene glycol monobromoethyl ether, oligomeric ethylene glycol monobromoethyl ether, 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 oxide, polyoxyethylene alkyl ether, polyoxyethylene glycerol fatty acid ester, polyoxyethylene fatty acid amide, etc.

[0178] The water-dispersible compound is preferably dispersed in water without precipitation, for example, by substituting a part of a compound with low hydrophilicity with a highly hydrophilic functional group.

[0179] Examples of the water-dispersible compound include polyester, polyurethane, acrylic resin, polysiloxane resin, and compounds obtained by modifying these with the introduction of functional groups, etc. In addition, block copolymers and graft copolymers of acrylic resin, polyester, or polyurethane can be cited.

[0180] Examples of the surfactant include anionic surfactants such as carboxylates, sulfonates, sulfate esters, and phosphate esters; cationic surfactants such as amine salts and quaternary ammonium salts; amphoteric surfactants such as carboxybetaine, amino carboxylates, and imidazolium betaine; nonionic surfactants such as polyoxyethylene alkyl ether, polyoxyethylene glycerol fatty acid ester, ethylene glycol fatty acid ester, and polyoxyethylene fatty acid amide.

[0181] Examples of the defoaming agent include polysiloxane resin, polydimethylsiloxane, and silicone oil.

[0182] Examples of antioxidants include phenolic antioxidants, amine antioxidants, phosphorus antioxidants, sulfur antioxidants, vitamins, and the like.

[0183] [Method for producing a dispersion liquid containing a conductive polymer]

[0184] The dispersion liquid containing a conductive polymer of the present embodiment can be produced, for example, by polymerizing a monomer having a structural unit that becomes a conjugated conductive polymer (A) in a raw material liquid (1) containing the monomer and a polyanion, and adding a hydroxy group-containing cyclic ether compound (C). The raw material liquid (1) may contain a polymer (E). A basic compound (F) and other additives can be optionally added. The polymer (E) can form a complex with the polyanion, or a complex in which the polyanion is coordinated can be formed outside the region of the polymer (E). In addition, the polymer (E) can also be added as the above-mentioned dispersion liquid containing the polymer (E).

[0185] In addition, as described above, the polyanion used in the production step of the dispersion liquid containing a conductive polymer may have the same structure as the polyanion (B) contained in the dispersion liquid containing a conductive polymer, or may have a different structure (such as a bonded cation, etc.).

[0186] From the viewpoint of suppressing the deviation of the polymerization reaction, the raw material liquid (1) is preferably a monomer having a structural unit that becomes a conjugated conductive polymer (A) dissolved, emulsified, or dispersed. The preparation of the raw material liquid (1) can be carried out, for example, by stirring with a stirrer such as a homogenizer or a homogenizing machine, or ultrasonic irradiation.

[0187] For the preparation of the raw material liquid (1), for example, even in the case of using a mixture containing a polyanion and a polymer (E) as in the dispersion liquid containing a polymer (E), from the viewpoint of suppressing the aggregation of particles in the raw material liquid (1), a polyanion can be further added. The raw material liquid (1) may contain composite particles (2) in which a polyanion is coordinated outside the region of the polymer (E) and the additionally added polyanion. The additionally added polyanion may be the same as the polyanion forming a complex with the polymer (E), or may be a different component, but is preferably the same.

[0188] The amount of the additionally added polyanion is preferably 99% by mass or less, more preferably 10 - 90% by mass, still more preferably 30 - 80% by mass, and even more preferably 40 - 70% by mass based on the total 100% by mass of the polyanion in the raw material liquid (1).

[0189] The total content of polyanions in the raw material liquid (1) is preferably such that the amount of anionic groups is 0.25 to 30 moles, more preferably 0.5 to 25 moles, and even more preferably 0.8 to 20 moles, per 1 mole of the monomer that forms the structural unit of the conjugated conductive polymer (A), from the viewpoints of the dispersion stability of the dispersion containing the conductive polymer and the reduction of the ESR of the solid electrolytic capacitor manufactured from the dispersion containing the conductive polymer.

[0190] 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-butanediol, 1,4-butanediol, diglycerol, isopentylene 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 can 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.

[0191] In addition, from the viewpoint of the ease of manufacturing the dispersion containing the conductive polymer, the dispersion medium of the raw material liquid (1) is preferably the same component as the dispersion medium (D) of the dispersion containing the conductive polymer.

[0192] From the viewpoints of the appropriate viscosity and reactivity during the polymerization reaction, 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.

[0193] The polymerization reaction for synthesizing the conjugated conductive polymer (A) is preferably carried out in the presence of an oxidizing agent.

[0194] Examples of the oxidizing agent include persulfates such as persulfuric acid, ammonium persulfate, sodium persulfate, and potassium persulfate; metal halides 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, persulfuric acid, persulfates, and transition metal compounds are preferred, and persulfates and transition metal compounds are more preferred. The oxidizing agent can be used alone or in combination of two or more.

[0195] From the viewpoint of moderately 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 still more preferably 100 to 500 parts by mass with respect to 100 parts by mass of the monomer that forms the structural unit of the conjugated system conductive polymer (A).

[0196] From the viewpoints of a moderate reaction rate and suppression of an increase in the viscosity of the reaction solution, the temperature of the polymerization reaction is preferably 5 to 80 °C, more preferably 10 to 60 °C, and still more preferably 15 to 40 °C. The temperature can be appropriately changed according to the progress of the reaction.

[0197] From the viewpoint of suppressing the aggregation of particles in the reaction solution, the polymerization reaction is preferably carried out with stirring. The stirring method is not particularly limited, and examples include a method of circulating and stirring the reaction solution using a high-shear mixer or the like.

[0198] [Method for manufacturing a solid electrolytic capacitor]

[0199] The method for manufacturing a solid electrolytic capacitor according to the present embodiment includes the following step: a step of forming a solid electrolyte layer by attaching the dispersion liquid containing a conductive polymer according to the present embodiment to a porous anode body formed of a valve metal having a dielectric film on its surface and then removing the dispersion medium (D) from the dispersion liquid attached to the porous anode body.

[0200] By using the dispersion liquid containing a conductive polymer according to the present embodiment and forming a solid electrolyte layer in such a step, a solid electrolytic capacitor with a low ESR can be well manufactured.

[0201] Examples of the valve metal include those containing at least one of aluminum, beryllium, bismuth, magnesium, germanium, hafnium, niobium, antimony, silicon, tin, tantalum, titanium, vanadium, tungsten, zirconium, and alloys or compounds of these metals. Among these, from the viewpoint of versatility, aluminum, niobium, and tantalum are preferred.

[0202] The porous anode body can be manufactured by forming a dielectric film on the surface of a porous valve metal.

[0203] A 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.

[0204] A dielectric film can be formed, for example, by anodizing in a phosphate solution of a porous valve metal as a dielectric oxide film on the surface of the porous valve metal. The forming voltage for anodization can be set according to the thickness of the dielectric oxide film, the withstand voltage of the capacitor, etc., preferably 1 - 800V, more preferably 1 - 500V, and even more preferably 1 - 300V.

[0205] The attachment of a conductive polymer-containing dispersion liquid to the porous anode body can be carried out, for example, by methods such as coating, spraying, and dipping. Among these methods, since the conductive polymer-containing dispersion liquid can be infiltrated into the porous anode body without deviation and uniformly, the method of dipping the porous anode body in the conductive polymer-containing dispersion liquid is preferred. In addition, in order to sufficiently infiltrate the conductive polymer-containing dispersion liquid into the details such as the pores of the porous anode body, impregnation can also be carried out under reduced pressure.

[0206] When impregnating and attaching a conductive polymer-containing dispersion liquid in the porous anode body, although it varies depending on the type and viscosity of the dispersion medium (D) of the conductive polymer-containing dispersion liquid, generally for the porous anode body, the conductive polymer-containing dispersion liquid at about 10 - 35°C is impregnated for about 10 seconds to 10 minutes.

[0207] From the viewpoint of removal efficiency, the removal of the dispersion medium (D) is preferably carried out by heating and drying the porous anode body with the conductive polymer-containing dispersion liquid attached. The heating conditions can be appropriately set considering the boiling point, volatility of the dispersion medium (D), and oxidative degradation of the polymer component, usually at room temperature - 300°C, preferably at 40 - 250°C, and even more preferably at 50 - 200°C, and heated for 5 seconds - several hours. As a heating device, for example, a hot plate, an oven, a hot air dryer, etc. can be used. From the viewpoint of improving the drying efficiency, drying can also be carried out under reduced pressure.

[0208] In addition, the so-called removal of the dispersion medium (D) here does not only refer to the state where there is no dispersion medium (D) at all. Within the range that does not hinder the manufacture of the solid electrolytic capacitor, a part of the dispersion medium can remain.

[0209] From the viewpoint of the uniformity of the thickness of the solid electrolyte layer, etc., the above steps can be repeated.

[0210] In addition, the solid electrolyte layer formed by the above steps can be impregnated with an arbitrary electrolyte solution. As the electrolyte solution impregnated in the solid electrolyte layer, for example, a polar organic solvent containing a salt can be cited.

[0211] As the polar organic solvent for the electrolyte, protic solvents can be used, such as monohydric alcohols like ethanol, propanol, butanol, pentanol, hexanol, cyclobutanol, cyclopentanol, cyclohexanol, benzyl alcohol, etc.; polyhydric alcohols and oxyalcohol compounds such as ethylene glycol, diethylene glycol, propylene glycol, glycerol, methyl cellosolve, ethyl cellosolve, methoxypropylene glycol, dimethoxypropanol, polyethylene glycol or ethylene oxide adducts of glycerol, etc.

[0212] In addition, as the polar organic solvent, aprotic solvents can also be used, and examples thereof include sulfones such as dimethyl sulfone, ethyl methyl sulfone, diethyl sulfone, sulfolane, 3 - methyl sulfolane, 2,4 - dimethyl sulfolane, etc.; amides such as N - methylformamide, N,N - dimethylformamide, N - ethylformamide, N,N - diethylformamide, N - methylacetamide, N,N - dimethylacetamide, N - ethylacetamide, N,N - diethylacetamide, hexamethylphosphoramide, etc.; lactones and cyclic amides such as γ - butyrolactone, γ - valerolactone, δ - valerolactone, N - methyl - 2 - pyrrolidone, ethylene carbonate, propylene carbonate, butylene carbonate, isobutyl carbonate, etc.; nitriles such as acetonitrile, 3 - methoxypropionitrile, glutaronitrile, etc.; oxides such as dimethyl sulfoxide, etc.

[0213] As the salt, examples thereof include ammonium salts; quaternary ammonium salts such as tetramethylammonium salt, triethylmethylammonium salt, tetraethylammonium salt, etc.; amidinium salts such as ethyldimethylimidazolium salt, tetramethylimidazolium salt, etc.; primary amine salts such as methylamine salt, ethylamine salt, propylamine salt, etc.; secondary amine salts such as dimethylamine salt, diethylamine salt, ethylmethylamine salt, dibutylamine salt, etc.; tertiary amine salts such as trimethylamine salt, triethylamine salt, tert - butylamine salt, ethyldimethylamine salt, ethyldiisopropylamine salt, etc.; sodium salts; potassium salts, etc.

[0214] Examples of the acid forming the salt 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, tolylformic acid, heptanoic acid, malonic acid, 1,6-decanedicarboxylic acid, 1,7-octanedicarboxylic acid, azelaic acid, m-hydroxybenzoic acid, trihydroxybenzoic acid, gallic acid, gentisic acid, protocatechuic acid, pyrocatechuic acid, trimellitic acid, pyromellitic acid, etc.; organic acids such as sulfonic acid. In addition, boric acid, phosphoric acid, phosphorous acid, hypophosphorous acid, carbonic acid, silicic acid, etc. can be cited. Further, boron-coordinated compounds such as boron-coordinated disalicylic acid, boron-coordinated dioxalic acid, boron-coordinated diglycolic acid, boron-coordinated dimalonic acid, boron-coordinated disuccinic acid, boron-coordinated diadipic acid, boron-coordinated diazelaic acid, boron-coordinated dibenzoic acid, boron-coordinated dimaleic acid, boron-coordinated dilactic acid, boron-coordinated dimalic acid, boron-coordinated ditartaric acid, boron-coordinated dicitric acid, boron-coordinated diphthalic acid, boron-coordinated bis(2-hydroxy)isobutyric acid, boron-coordinated bis(m-hydroxybenzoic acid), boron-coordinated dimethylsalicylic acid, boron-coordinated dinaphthoic acid, boron-coordinated dibenzalmandelic acid, boron-coordinated bis(3-hydroxy)propionic acid, etc. can be cited.

[0215] The electrolytic solution may contain an additive. Examples of the additive include coordination compounds of boric acid with polysaccharides such as mannose or sorbitol; coordination compounds of boric acid with polyhydric alcohols; borate esters; nitro compounds such as o-nitrobenzoic acid, m-nitrobenzoic acid, p-nitrobenzoic acid, o-nitrophenol, m-nitrophenol, p-nitrophenol, p-nitrobenzyl alcohol, etc.; phosphate esters, etc. These can be used alone or in combination of two or more.

[0216] In the method for manufacturing a solid electrolytic capacitor according to the present embodiment, the dispersion liquid containing a conductive polymer of the present embodiment can be used in the manufacturing steps of a conventional solid electrolytic capacitor, and the manufacturing conditions can be changed if necessary. Accordingly, according to the method for manufacturing a solid electrolytic capacitor of the present embodiment, compared with the manufacturing steps of a conventional solid electrolytic capacitor, significant equipment changes, etc. are not required, an increase in manufacturing cost can be suppressed, and a solid electrolytic capacitor having a lower ESR than that of the conventional one can be manufactured.

[0217] [Solid electrolytic capacitor]

[0218] The solid electrolytic capacitor of the present embodiment has a solid electrolyte layer on a porous anode body formed of a valve metal having a dielectric film on the surface, and the solid electrolyte layer contains: a conjugated conductive polymer (A), a polyanion (B), and a hydroxyl group-containing cyclic ether compound (C) represented by any one of the above formulas (1) to (5). The ESR of the solid electrolytic capacitor having such a configuration becomes low.

[0219] Such a solid electrolytic capacitor can be preferably manufactured by the method for manufacturing a solid electrolytic capacitor of the present embodiment described above. The solid electrolyte layer may contain the above-described electrolytic solution.

[0220] Example

[0221] Hereinafter, the present invention will be further specifically described by way of examples and comparative examples, but the present invention is not limited to the following examples.

[0222] [Measurement method]

[0223] The measurement methods for various physical properties in the examples and comparative examples are as follows.

[0224] (Weight-average molecular weight)

[0225] The weight-average molecular weight (Mw) of sodium polystyrene sulfonate was measured by a gel permeation chromatograph under the following measurement conditions, and the molecular weight was calculated in terms of standard polystyrene.

[0226] <Measurement conditions>

[0227] Measuring device: "Shodex (registered trademark) GPC101", manufactured by RESONAC Co., Ltd.

[0228] Column used: "OHpak SB-806M HQ", manufactured by RESONAC Co., Ltd.

[0229] Column temperature: 40 °C

[0230] Eluent: water

[0231] Elution rate: 1 mL / min

[0232] Standard sample: polystyrene

[0233] (50% volume cumulative particle size (d 50 ))

[0234] The 50% volume cumulative particle size (d 50 ) of the particles contained in the dispersion was measured by a particle size distribution measuring device (Microtrac (registered trademark) UPA type, manufactured by Nikkiso Co., Ltd.), and calculated using the attached software (Microtrac II) under the following set conditions.

[0235] <Set conditions>

[0236] Particles: transmission, spherical, refractive index 1.59, density 1.00 g / cm 3

[0237] Solvent: refractive index 1.333, viscosity 0.797 mPa·s (30 °C), 1.002 mPa·s (20 °C)

[0238] (Solid content concentration)

[0239] The solid component concentration is calculated by weighing approximately 10 g of the dispersion sample and heating it for 30 minutes at a temperature 10 °C higher than the boiling point of the dispersion medium with the highest boiling point among the contained dispersion media using an infrared moisture meter (“FD-720”, manufactured by KETT Scientific Research Institute Co., Ltd.), and taking the evaporation residue as the solid component. For example, when the dispersion medium is water, the heating condition is set at 110 °C for 30 minutes.

[0240] (pH)

[0241] The pH of the liquid containing composite particles is measured using a pH meter (“HM-30G”, manufactured by DKK-TOA Corporation; 25 °C).

[0242] [Manufacture of Dispersion Liquid Containing Conductive Polymer]

[0243] (Example 1)

[0244] <Manufacture of Dispersion Liquid Containing Polymer (E1)>

[0245] 86 g of styrene, 49 g of 2-ethylhexyl acrylate, 15 g of divinylbenzene, and 500 g of a 22 mass% aqueous solution of sodium polystyrenesulfonate (“Polynas (registered trademark) PS-5”, manufactured by TOSOH FINECHEM CORPORATION; Mw of about 120,000; the same applies hereinafter) (110 g of sodium polystyrenesulfonate) are stirred and mixed to prepare a raw material liquid (a).

[0246] In addition, while stirring 1000 g of a 22 mass% aqueous solution of sodium polystyrenesulfonate (220 g of sodium polystyrenesulfonate), the temperature is raised to 80 °C, and 2 g of potassium persulfate is added thereto to prepare a raw material liquid (b).

[0247] The raw material liquid (a) is added dropwise to the raw material liquid (b) over 2 hours, and further, 40 g of a 2.5 mass% aqueous solution of potassium persulfate is added dropwise over 2.5 hours, and after reacting at 80 °C for 2 hours, it is cooled to room temperature (25 °C).

[0248] 1500 mL of a cation exchange resin (“Amberlite (registered trademark) IR120B-H”, manufactured by ORGANO CORPORATION; the same applies hereinafter) and 1500 mL of an anion exchange resin (“Amberlite (registered trademark) IRA410-OH”, manufactured by ORGANO CORPORATION; the same applies hereinafter) are added to the reaction product, stirred for 12 hours, and then the ion exchange resin is filtered out. Pure water is added to obtain a dispersion liquid containing polyanion (B1) and polymer (E1), i.e., a dispersion liquid containing polymer (E1). The d of the particles contained in the dispersion liquid containing polymer (E1) (solid component concentration: 15.0 mass%) 50 is 0.46 μm.

[0249] <Preparation of starting liquid (1-1)>

[0250] In a 1 L polyethylene container, 34.0 g of a dispersion containing polymer (E1), 31.5 g of a 12 mass% aqueous solution of sodium polystyrenesulfonate (3.78 g of sodium polystyrenesulfonate), and 223.2 g of pure water were stirred and mixed at 32°C. 2.80 g of 3,4-ethylenedioxythiophene was added thereto, and emulsification mixing was performed for 30 minutes using a homogenizer (“Robomix (registered trademark)”, manufactured by Primix Corporation; 4000 rpm; the same applies hereinafter) to prepare starting liquid (1-1) (total content of sodium polystyrenesulfonate: 1.9 moles of sulfonate groups per 1 mole of 3,4-ethylenedioxythiophene).

[0251] <Production of conjugated conductive polymer (A1)>

[0252] 291.5 g of starting liquid (1-1) was put into a stainless steel container connected to a high-shear mixer (“MildeR (registered trademark) MDN303V”, manufactured by Taiheiyo Kiko Co., Ltd.; 5000 rpm, 32°C) and a circulation pump, and while circulating and stirring with a stirring blade and the high-shear mixer, 5.89 g of sodium persulfate and 6.88 g of a 1 mass% aqueous solution of iron(III) sulfate hexahydrate were added, and a polymerization reaction was carried out for 24 hours to obtain an intermediate product liquid (2) containing a conductive polymer (solid content concentration: 5.80 mass%).

[0253] The steps of preparing starting liquid (1-1) and producing conjugated conductive polymer (A1) were repeated, and a total of 1223.3 g of intermediate product liquid (2) containing a conductive polymer was recovered.

[0254] <Dispersion and desalting treatment>

[0255] 1223.3 g of intermediate product liquid (2) was diluted with pure water to 1500 mL (solid content concentration: 4.73 mass%), and a dispersion treatment was carried out for 45 minutes in a high-pressure homogenizer (“TwinPanda 600”, manufactured by Niro Soavi; 400 bar (40 MPa); the same applies hereinafter). Further, after diluting with pure water to a solid content concentration of 3.99 mass%, 1500 mL was taken out, and a dispersion treatment was carried out for 135 minutes in the high-pressure homogenizer to obtain a dispersion (3) containing a conductive polymer.

[0256] The dispersion (3) was subjected to ion exchange for 3 hours using 125.6 mL of a cation exchange resin and 109.9 mL of an anion exchange resin, and desalted to obtain a dispersion (4) containing a conductive polymer (pH 1.9, solid content concentration: 1.65 mass%).

[0257] <Manufacture of Dispersions Containing Conductive Polymers>

[0258] To 1000 g of the dispersion (4), 7.5 g of morpholine and 22.5 g of pure water were added, and the pH was adjusted to 4.7 (solid content concentration: 1.60 mass %). Further, 103 g of 2,2-dimethyl-1,3-dioxolane-4-methanol (6.3 parts by mass relative to 1 part by mass of the solid content in the desalted dispersion) was added to produce a dispersion containing a conductive polymer (content of 2,2-dimethyl-1,3-dioxolane-4-methanol: 9 mass %).

[0259] (Examples 2 to 6, Comparative Examples 1 and 2)

[0260] The 2,2-dimethyl-1,3-dioxolane-4-methanol used in Example 1 was changed to the (cyclic) ether compounds or amounts described in Examples 2 to 6, Comparative Examples 1 and 2 of Table 1, and otherwise the same procedure as in Example 1 was carried out to produce dispersions containing conductive polymers, respectively.

[0261] (Example 7)

[0262] In a 1 L polyethylene container, 63.0 g (7.56 g of sodium polystyrenesulfonate) of a 12 mass % aqueous solution of sodium polystyrenesulfonate and 225.7 g of pure water were stirred and mixed at 32°C. To this, 2.80 g of 3,4-ethylenedioxythiophene was added, and emulsification mixing was carried out in a homogenizer for 30 minutes to prepare a raw material liquid (1-2) (total content of sodium polystyrenesulfonate: 2.0 moles of sulfonate groups per 1 mole of 3,4-ethylenedioxythiophene).

[0263] Except that in Example 1, the raw material liquid (1-1) was changed to the raw material liquid (1-2), the steps for manufacturing the conjugated conductive polymer (A1) were carried out in the same manner as in Example 1 thereafter to produce a dispersion containing a conductive polymer.

[0264] (Examples 8 to 12, Comparative Examples 3 and 4)

[0265] The 2,2-dimethyl-1,3-dioxolane-4-methanol used in Example 7 was changed to the (cyclic) ether compounds or amounts described in Examples 8 to 12, Comparative Examples 3 and 4 of Table 1, and otherwise the same procedure as in Example 7 was carried out to produce dispersions containing conductive polymers, respectively.

[0266] In addition, the hydroxyl group-containing cyclic ether compounds used in Examples 1 to 12 are as follows.

[0267] 2,2-Dimethyl-1,3-dioxolane-4-methanol is in formula (1) where R 11 and R 12 are methyl, R 13 is hydroxymethyl, R14 ~R 16 a compound in which R is a hydrogen atom.

[0268] 4-Hydroxymethyl-1,3-dioxolan-2-one is a compound in which R in formula (4) 41 is hydroxymethyl and R 42 ~R 44 is a hydrogen atom.

[0269] 2,2-Dimethyl-1,3-dioxolan-4-ethanol is a compound in which R and R in formula (1) 11 and R 12 are methyl groups, R 13 is 2-hydroxyethyl, and R 14 ~R 16 is a hydrogen atom.

[0270] 1,3-Dioxan-5-ol is a compound in which R and R in formula (2) 21 and R 22 are hydrogen atoms, R 23 , R 24 , R 26 ~R 28 are hydrogen atoms, and R 25 is a hydroxyl group.

[0271] [Manufacture of Solid Electrolytic Capacitor]

[0272] Using the dispersion liquids containing conductive polymers manufactured in the above Examples and Comparative Examples, solid electrolytic capacitors were manufactured in the following manner.

[0273] A porous anode body of an aluminum electrolytic capacitor assembly (with a withstand voltage of 35 V and a designed capacitance of 400 μF) was impregnated in a dispersion liquid containing a conductive polymer for 5 minutes at 25°C in an atmospheric environment, and then dried at 120°C for 30 minutes using a hot air dryer (“ST-110”, manufactured by ESPEC Corporation), 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.

[0274] Regarding each solid electrolytic capacitor, the equivalent series resistance (ESR) [mΩ] at 100 kHz was measured using a precision LCR meter (“E4980A”, manufactured by Agilent Technologies, Inc.).

[0275] These measurement results are shown in Table 1.

[0276] Table 1

[0277]

[0278] It can be clearly confirmed from the results shown in Table 1 that by adding the hydroxyl group-containing cyclic ether compound (C) (Examples 1 to 12), a solid electrolytic capacitor with a lower ESR can be manufactured as compared with the case of adding ethylene glycol (Comparative Examples 1 and 3).

Claims

1. A dispersion containing a conductive polymer, comprising a conjugated conductive polymer A, a polyanion B, a hydroxyl group-containing cyclic ether compound C represented by any one of the following formulas (1) to (5), and a dispersion medium D. In formulas (1) to (5), R 11 ~R 16 , R 21 ~R 28 , R 31 ~R 38 , R 41 ~R 44 , R 51 ~R 56 each independently represents a hydrogen atom, a hydroxyl group, an alkyl group having 1 to 8 carbon atoms which may be substituted by a hydroxyl group, a cyano group or an amino group, a cycloalkenyl group having 5 or 6 carbon atoms, a phenyl group which may be substituted by a hydroxyl group, an amino group, a cyano group or a formyl group, an acetyl group, an acetoacetyl group, an allyl group, an acrylyl group, a pyridyl group, an alkylsulfonyl group which may be substituted by a hydroxyl group, or a formyl group.

2. The dispersion containing a conductive polymer according to claim 1, wherein the content of the hydroxyl group-containing cyclic ether compound C is 1 to 50 parts by mass per 1 part by mass of the total amount of the conjugated conductive polymer A and the polyanion B.

3. The dispersion containing a conductive polymer according to claim 1, further comprising a polymer E that neither belongs to the conjugated conductive polymer A nor to the polyanion B and is insoluble in the dispersion medium D.

4. The dispersion containing a conductive polymer according to claim 3, wherein the content of the hydroxyl group-containing cyclic ether compound C is 1 to 50 parts by mass per 1 part by mass of the total amount of the conjugated conductive polymer A, the polyanion B, and the polymer E.

5. The dispersion containing a conductive polymer according to claim 1, wherein the hydroxyl group-containing cyclic ether compound C is at least one selected from 2,2-dimethyl-1,3-dioxolane-4-methanol, 4-hydroxymethyl-1,3-dioxolan-2-one, 2,2-dimethyl-1,3-dioxolane-4-ethanol, and 1,3-dioxane-5-ol.

6. The dispersion containing a conductive polymer according to claim 1, wherein the conjugated conductive polymer A is a polymer of a monomer containing one or more compounds selected from pyrrole-based, aniline-based, and thiophene-based compounds.

7. The dispersion containing a conductive polymer according to claim 6, wherein the thiophene-based compound is represented by the following formula (6). In formula (6), R 61 and R 62 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 61 and R 62 combine with 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 heterocyclic ring having 2 to 10 carbon atoms and containing an oxygen atom, an optionally substituted heterocyclic ring having 2 to 10 carbon atoms and containing a sulfur atom, or an optionally substituted heterocyclic ring having 2 to 10 carbon atoms and containing a sulfur atom and an oxygen atom.

8. The dispersion containing a conductive polymer according to claim 1, wherein the polyanion B is a polymer having two or more groups formed by a sulfonic acid or its salt.

9. The dispersion containing a conductive polymer according to claim 1, further comprising a basic compound F.

10. The dispersion containing a conductive polymer according to claim 9, wherein the basic compound F is at least one selected from morpholine, 4-ethylmorpholine, and 4-(2-hydroxyethyl)morpholine.

11. A method for manufacturing a solid electrolytic capacitor, having the following steps: A step of attaching the dispersion containing a conductive polymer according to any one of claims 1 to 10 to a porous anode body made of a valve metal having a dielectric film on its surface, and then removing the dispersion medium D to form a solid electrolyte layer.

12. A solid electrolytic capacitor having a solid electrolyte layer on a porous anode body made of a valve metal having a dielectric film on its surface. The solid electrolyte layer contains a conjugated conductive polymer A, a polyanion B, and a hydroxyl group-containing cyclic ether compound C represented by any one of the following formulas (1) to (5). In Formulas (1) to (5), R 11 ~R 16 , R 21 ~R 28 , R 31 ~R 38 , R 41 ~R 44 , R 51 ~R 56 are each independently a hydrogen atom, a hydroxyl group, an alkyl group having 1 to 8 carbon atoms which may be substituted by a hydroxyl group, a cyano group or an amino group, a cycloalkenyl group having 5 or 6 carbon atoms, a phenyl group which may be substituted by a hydroxyl group, an amino group, a cyano group or a formyl group, an acetyl group, an acetoacetyl group, an allyl group, an acryloyl group, a pyridyl group, an alkylsulfonyl group which may be substituted by a hydroxyl group, or a formyl group.

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