Solid electrolytic capacitor and method for producing solid electrolytic capacitor

Abstract

This solid electrolytic capacitor comprises an anode, a dielectric coating provided on the surface of the anode, and a solid electrolyte layer in contact with the dielectric coating, the solid electrolyte layer containing a conjugated conductive polymer, a polyanion, and an electrical conductivity improving agent, wherein the content of the electrical conductivity improving agent is 76.5-92.5 mass% in 100 mass% of the solid electrolyte layer.

Description

Solid electrolytic capacitor and method for manufacturing a solid electrolytic capacitor

[0001] This disclosure relates to a solid electrolytic capacitor and a method for manufacturing a solid electrolytic capacitor, and more particularly to a solid electrolytic capacitor with excellent equivalent series resistance (ESR) in the high-frequency range and a method for manufacturing a solid electrolytic capacitor.

[0002] Solid electrolytic capacitors are widely used throughout the electronics industry. A typical solid electrolytic capacitor has a structure in which valve metals such as aluminum, tantalum, and niobium are used as the anode and cathode foils, with a solid electrolyte layer interposed between them. To increase capacitance, the surface area of ​​the anode foil valve metal is increased through etching or other processes, and a dielectric film is formed on its surface. By using conjugated conductive polymers such as polypyrrole, polyaniline, and polythiophene in the solid electrolyte layer, solid electrolytic capacitors with high conductivity and low equivalent series resistance (ESR) can be obtained.

[0003] Solid electrolytic capacitors are used in electronic devices and other applications because they can lower the equivalent series resistance (ESR) in the high-frequency range. Furthermore, with the increasing electrification of vehicles in recent years, development of solid electrolytic capacitors for automotive use is progressing. In particular, for capacitors used in vehicle electronic control systems, further reduction of the equivalent series resistance (ESR) in the high-frequency range is required to achieve higher output power through electronic control.

[0004] As a method for forming a solid electrolyte layer containing a conjugated conductive polymer, for example, a method is known in which an electrolytic capacitor element is impregnated with a monomer solution constituting the conjugated conductive polymer and an oxidizing agent solution, and an oxidative polymerization or electrolytic polymerization is carried out within the electrolytic capacitor element to form a solid electrolyte layer (see, for example, Patent Document 1).

[0005] Furthermore, a method for forming a solid electrolyte layer containing a conjugated conductive polymer is also known, which involves impregnating and drying a dispersion containing the conjugated conductive polymer onto the dielectric film of the anode. For example, Patent Document 2 describes that a solid electrolytic capacitor with high capacitance and low equivalent series resistance (ESR) can be obtained by micronizing aggregates of a conductive polymer (conjugated conductive polymer) in an aqueous dispersion using ultrasonic irradiation and then dispersing them.

[0006] Japanese Patent Publication No. 2005-123630 Japanese Patent Publication No. 2013-55308

[0007] However, in the polymerization reaction within an electrolytic capacitor element as described in Patent Document 1, the conjugated conductive polymer is formed in an aggregated, spongy state, resulting in poor uniformity of the solid electrolyte layer, a tendency for conductivity to decrease, and a tendency for the equivalent series resistance (ESR) to increase.

[0008] Furthermore, even with solid electrolytic capacitors manufactured using a dispersion of fine particles of conductive polymers (conjugated conductive polymers) as described in Patent Document 2, it could not necessarily be said that the equivalent series resistance (ESR) could be sufficiently low.

[0009] This embodiment was made in view of the above circumstances, and aims to provide a solid electrolytic capacitor with excellent equivalent series resistance (ESR) in the high-frequency range, and a method for manufacturing a solid electrolytic capacitor.

[0010] This embodiment is based on the finding that the equivalent series resistance (ESR) in the high-frequency range can be reduced when the solid electrolyte layer contains a predetermined amount of an electrical conductivity enhancer.

[0011] This embodiment provides the following means: [1] A solid electrolytic capacitor comprising an anode, a dielectric film provided on the surface of the anode, and a solid electrolyte layer in contact with the dielectric film, wherein the solid electrolyte layer comprises a conjugated conductive polymer, a polyanion, and an electrical conductivity improver, and the content of the electrical conductivity improver is 76.5 to 92.5% by mass of 100% by mass of the solid electrolyte layer. [2] The solid electrolytic capacitor according to [1], wherein the electrical conductivity improver comprises an organic solvent having two or more oxygen atoms in one molecule. [3] The solid electrolytic capacitor according to [1] or [2], wherein the electrical conductivity improver comprises an organic solvent having three or more oxygen atoms in one molecule. [4] The solid electrolytic capacitor according to any one of [1] to [3], wherein the electrical conductivity improver comprises an organic solvent having a boiling point of 200°C or higher. [5] A method for manufacturing a solid electrolytic capacitor according to any one of [1] to [4] above, comprising an anode, a dielectric film provided on the surface of the anode, and a solid electrolyte layer in contact with the dielectric film, the method comprising: attaching a conductive polymer-containing dispersion to the surface of the dielectric film; and drying the conductive polymer-containing dispersion to form a solid electrolyte layer containing a conjugated conductive polymer, a polyanion, and an electrical conductivity improver, wherein the content of the electrical conductivity improver is 76.5 to 92.5% by mass of 100% by mass of the solid electrolyte layer.

[0012] According to this embodiment, it is possible to provide a solid electrolytic capacitor with excellent equivalent series resistance (ESR) in the high-frequency range, and a method for manufacturing a solid electrolytic capacitor.

[0013] The definitions and meanings of terms and notations used herein are as follows: Regarding the groups of a compound, "may be substituted" means that the group may be either substituted or unsubstituted (unsubstituted). The term "class" attached to a compound name refers to a group of compounds containing the compound structure in question, including compounds with substituents; for example, "polypyrroles" refers to a group of compounds containing the polypyrrole structure. "(meth)acrylic acid" is a general term for acrylic acid and methacrylic acid. Similarly, "(meth)acrylate" is a general term for acrylate and methacrylate, and "(meth)acryloyl" is a general term for acryloyl and methacryloyl. Unless otherwise specified, "ethylenically unsaturated bond" refers to an ethylenically unsaturated bond that exhibits radical polymerization. Furthermore, "ethylenically unsaturated monomer" refers to a compound having an ethylenically unsaturated bond, which is the origin of the polymer's constituent units. The solid content concentration is determined based on the actual measurement of the evaporation residue (solid content) using the measurement method described in the examples. In this specification, preferred provisions can be adopted at will, and combinations of preferred provisions are considered more preferred. In this specification, the notation "XX to YY" for a numerical range means "XX or more and YY or less". In this specification, the lower and upper limits of preferred numerical ranges (for example, ranges of content, etc.) described in steps can be combined independently. For example, from the notation "preferably 10 to 90, more preferably 30 to 60", the "preferred lower limit (10)" and the "more preferred upper limit (60)" can be combined to get "10 to 60". Also, in numerical ranges described in this specification, the upper or lower limit of that numerical range may be replaced with the values ​​shown in the examples. In this specification, "high frequency region" means 100 kHz or higher. In this specification, "boiling point" means the boiling point at 1 atmosphere (0.1 MPa).

[0014] [Solid Electrolytic Capacitor] The solid electrolytic capacitor of this embodiment comprises an anode, a dielectric film on the surface of the anode, and a solid electrolyte layer in contact with the dielectric film, wherein the solid electrolyte layer contains a conjugated conductive polymer, a polyanion, and an electrical conductivity improver, and the content of the electrical conductivity improver is 76.5 to 92.5% by mass of 100% by mass of the solid electrolyte layer. With such a configuration, a solid electrolytic capacitor with excellent equivalent series resistance (ESR) in the high-frequency range can be obtained. That is, the solid electrolytic capacitor of this embodiment is not particularly limited as long as it has at least the above configuration, and may or may not contain the electrolyte solution described later, as needed.

[0015] <Anode> The anode of the solid electrolytic capacitor of this embodiment is not particularly limited, but for example, a valve metal formed into any shape can be used. The material of the valve metal is not particularly limited, and for example, aluminum, beryllium, bismuth, magnesium, germanium, hafnium, niobium, antimony, silicon, tin, tantalum, titanium, vanadium, tungsten, zirconium, alloys thereof, compounds made from these metals, etc. These may be used individually or in combination of two or more. Among these, aluminum, niobium, and tantalum are preferred from the viewpoint of versatility.

[0016] There are no particular restrictions on the properties of the valve metal; it may be porous or not. Among these, a porous material is preferable from the viewpoint of increasing capacity. Hereinafter, when the valve metal is porous, it may simply be referred to as "porous valve metal." Hereinafter, an anode manufactured using a porous valve metal may simply be referred to as "porous anode."

[0017] There are no particular limitations on the method for manufacturing porous valve metal, and existing manufacturing methods can be used. Examples include a method of obtaining porous valve metal by sintering valve metal powder with a high specific surface area, and a method of obtaining porous valve metal by etching valve metal foil.

[0018] <Dielectric Coating> The dielectric coating provided by the solid electrolytic capacitor of this embodiment is not particularly limited, and examples include a coating formed by anodizing the surface of the anode. The method of anodizing is not particularly limited, and existing methods can be used, for example, a method in which the anode is immersed in a phosphate solution and a voltage (formation voltage) is applied to form a dielectric coating. The formation voltage in the anodizing is not particularly limited, and is set according to the thickness of the dielectric oxide coating and the withstand voltage of the capacitor, and is preferably 1 to 800V, more preferably 1 to 500V, and particularly preferably 1 to 300V.

[0019] <Solid Electrolyte Layer> The solid electrolyte layer of the solid electrolytic capacitor of this embodiment comprises a conjugated conductive polymer, a polyanion, and an electrical conductivity improver, wherein the content of the electrical conductivity improver is 76.5 to 92.5% by mass relative to 100% by mass of the solid electrolyte layer. In other words, the solid electrolyte layer is not particularly limited as long as it has at least the above configuration, and may or may not contain other polymers other than the conjugated conductive polymer and polyanion, alkaline compounds, and other additives as needed, as described later. Furthermore, the solid electrolyte layer may or may not be impregnated with an electrolyte solution as needed.

[0020] The conductivity enhancer is contained in the conductive polymer-containing dispersion described later, and when a solid electrolyte layer is manufactured using the conductive polymer-containing dispersion, it has the function of improving the conductivity of the solid electrolyte layer. Although the detailed mechanism by which the conductivity of the solid electrolyte layer is improved in the above case is unknown, it is presumed that when the conductive polymer-containing dispersion containing the conductivity enhancer is dried to form a solid electrolyte layer, the conductivity enhancer volatilizes together with the dispersion medium described later, making it easier for the polymer arrangement of the conjugated conductive polymer to form better conductive paths, and as a result, the conductivity is improved. In this embodiment, it was found that when the solid electrolyte layer contains a predetermined amount of the conductivity enhancer (when the content of the conductivity enhancer is 76.5 to 92.5% by mass of 100% by mass of the solid electrolyte layer), the equivalent series resistance (ESR) in the high-frequency range can be reduced. The detailed mechanism by which the equivalent series resistance (ESR) in the high-frequency range can decrease when a solid electrolyte layer contains a predetermined amount of conductivity enhancer is unknown. However, it is presumed that the predetermined amount of conductivity enhancer present in the solid electrolyte layer inhibits the aggregation of conjugated conductive polymers in the solid electrolyte layer, making it easier for the conjugated conductive polymers to form conductive paths.

[0021] The content of the electrical conductivity improver is not particularly limited as long as it is 76.5 to 92.5% by mass of 100% by mass of the solid electrolyte layer. However, from the viewpoint of reducing ESR, it is preferably 78.0 to 92.5% by mass, more preferably 80.0 to 92.5% by mass, even more preferably 80.0 to 92.0% by mass, and particularly preferably 82.0 to 90.0% by mass of 100% by mass of the solid electrolyte layer.

[0022] There are no particular restrictions on the method for manufacturing the solid electrolyte layer; for example, the method for manufacturing a solid electrolytic capacitor described later can be used. According to the method for manufacturing a solid electrolytic capacitor described later, a solid electrolyte layer can be formed (manufactured) by attaching a conductive polymer-containing dispersion, described later, to the surface of the dielectric film described above, and drying the conductive polymer-containing dispersion. The conductive polymer-containing dispersion and each component contained in the conductive polymer-containing dispersion and also contained in the solid electrolyte layer manufactured using the conductive polymer-containing dispersion will be described in detail below.

[0023] (Conductive Polymer-Containing Dispersion) The conductive polymer-containing dispersion used to form the solid electrolyte layer is not particularly limited as long as it contains a conjugated conductive polymer, a polyanion, and an electrical conductivity improver. It may or may not contain, as needed, a dispersion medium, other polymers other than the conjugated conductive polymer and polyanion, alkaline compounds, and other additives, as described later. The conjugated conductive polymer and the polyanion contained in the conductive polymer-containing dispersion and also contained in the solid electrolyte layer produced using the conductive polymer-containing dispersion are not particularly limited, but from the viewpoint of stability, it is preferable that they form a composite. Hereinafter, the composite containing the conjugated conductive polymer and the polyanion may simply be referred to as "composite particles." The composite particles are not particularly limited, but from the viewpoint of reducing the equivalent series resistance (ESR) of the solid electrolytic capacitor and the dispersibility of the composite particles, they may or may not contain, as needed, other polymers other than the conjugated conductive polymer and polyanion, as described later. When the composite particles contain other polymers, there are no particular restrictions on the structure of the composite particles, but from the viewpoint of stability, it is preferable that the polyanions coordinate to the other polymers and cover part or all of the surface of the other polymers.

[0024] There are no particular restrictions on the content of composite particles, but it is preferably 0.1 to 20.0% by mass, more preferably 0.5 to 15.0% by mass, and particularly preferably 1.0 to 10.0% by mass, per 100% by mass of the conductive polymer-containing dispersion. If the content is above the lower limit of the above range, the equivalent series resistance (ESR) of the solid electrolytic capacitor tends to decrease. If the content is below the upper limit of the above range, the conductive polymer-containing dispersion tends to have a viscosity that is easy to handle, and the composite particles tend to disperse easily.

[0025] There are no particular restrictions on the content of the composite particles, but it is preferably 5 to 20% by mass, more preferably 5 to 15% by mass, and most preferably 10 to 15% by mass, of 100% by mass of the solid electrolyte layer. Within the above range, the equivalent series resistance (ESR) of the solid electrolytic capacitor tends to decrease.

[0026] -Conjugated Conductive Polymers- Conjugated conductive polymers are contained in composite particles and conductive polymer-containing dispersions, and are also contained in solid electrolyte layers produced using conductive polymer-containing dispersions. The above-mentioned conjugated conductive polymers are not particularly limited as long as they are organic polymer compounds having a π-conjugated system in their main chain. They may be homopolymers of monomers that become the constituent units of the conjugated conductive polymers described later, or copolymers obtained by copolymerizing two or more monomers that become the constituent units of the conjugated conductive polymers. The above-mentioned conjugated conductive polymers may be used alone or in combination of two or more.

[0027] There are no particular restrictions on the content of the conjugated conductive polymer, but from the viewpoint of conductivity of the composite particles and stability in the conductive polymer-containing dispersion, it is preferably 5 to 70% by mass, more preferably 10 to 60% by mass, and particularly preferably 15 to 50% by mass, based on 100% by mass of the composite particles.

[0028] There are no particular restrictions on the content of the conjugated conductive polymer, but it is preferably 0.1 to 50% by mass, more preferably 0.1 to 20% by mass, and most preferably 0.1 to 10% by mass, based on 100% by mass of the solid electrolyte layer. Within this range, the compound is more easily stabilized.

[0029] There are no particular restrictions on the conjugated conductive polymer, and examples include polypyrroles, polythiophenes, polyisothianaphthenes, polyacetylenes, polyphenylenes, polyphenylenevinylenes, polyanilines, polyacenes, polythiophenevinylenes, and copolymers thereof. These may be used individually or in combination of two or more. Among these, polypyrroles, polythiophenes, and polyanilines are preferred from the viewpoint of ease of handling and availability, with polythiophenes being more preferred. Furthermore, there are no particular restrictions on the conjugated conductive polymer, but from the viewpoint of high conductivity, it may have substituents such as alkyl groups, carboxyl groups, sulfo groups, alkoxy groups, hydroxyl groups, and cyano groups.

[0030] The polypyrroles are not particularly limited. For example, 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) and the like can be mentioned. These may be used alone or in combination of two or more.

[0031] There are no particular restrictions on polythiophenes, for example, 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-hexyloxythiophene), poly(3-heptyloxythiophene), poly(3-octyloxythiophene), poly(3-decyloxythiophene), poly(3-dodecyloxythiophene), poly(3-octadecyloxythiophene), poly Poly(3,4-dihydroxythiophene), poly(3,4-dimethoxythiophene), poly(3,4-diethoxythiophene), poly(3,4-dipropoxythiophene), poly(3,4-dibutoxythiophene), poly(3,4-dihexyloxythiophene), poly(3,4-diheptyloxythiophene), poly(3,4-dioctyloxythiophene), poly(3,4-didecyloxythiophene), poly(3,4-didodecyloxythiophene), poly(3,4-ethylenedioxythiophene) Examples include 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), and poly(3,4-ethyleneoxythiathiophene). These may be used individually or in combination of two or more.

[0032] There are no particular restrictions on the polyanilines. For example, polyaniline, poly(2-methylaniline), poly(3-isobutylaniline), poly(2-anilinesulfonic acid), poly(3-anilinesulfonic acid), etc. may be mentioned. These may be used alone or in combination of two or more.

[0033] Among the above, as the conjugated conductive polymer, from the viewpoint of high conductivity, polypyrrole, polythiophene, poly(N-methylpyrrole), poly(3-methylthiophene), poly(3-methoxythiophene), poly(3,4-ethylenedioxythiophene) are preferable, and from the viewpoint of excellent heat resistance, poly(3,4-ethylenedioxythiophene) is more preferable.

[0034] There are no particular restrictions on the monomer for obtaining the conjugated conductive polymer, that is, the monomer that becomes the constituent unit of the conjugated conductive polymer. However, from the viewpoint of the stability of the compound, it preferably contains one or more compounds selected from the group consisting of pyrroles, anilines, and thiophenes. The compound may or may not have a substituent X. There are no particular restrictions on the substituent X. For example, an alkyl group having 1 to 18 carbon atoms, an aryl group having 6 to 10 carbon atoms, a heteroaryl group having 5 to 10 carbon atoms, an alkoxy group having 1 to 18 carbon atoms, an alkylthio group having 1 to 18 carbon atoms, a carboxy group, a hydroxyl group, a halogen atom, a cyano group, etc. may be mentioned. The substituent X may be used alone or in combination of two or more. Further, two or more of these substituents X may be bonded to each other by condensation or the like to form a ring. Furthermore, these alkyl groups, aryl groups, heteroaryl groups, alkoxy groups, and alkylthio groups have no particular restrictions. For example, they may or may not have a further substituent Y such as a carboxy group, a hydroxyl group, a halogen atom, a cyano group, etc. The substituent Y may be used alone or in combination of two or more.

[0035] There are no particular restrictions on the monomers that form the constituent units of the conjugated conductive polymer, and examples include pyrroles such as pyrrole, N-methylpyrrole, 3-methylpyrrole, 3-ethylpyrrole, 3-n-propylpyrrole, 3-butylpyrrole, 3-octylpyrrole, 3-decylpyrrole, 3-dodecylpyrrole, 3,4-dimethylpyrrole, 3,4-dibutylpyrrole, 3-carboxylpyrrole, 3-methyl-4-carboxylpyrrole, 3-methyl-4-carboxyethylpyrrole, 3-methyl-4-carboxybutylpyrrole, 3-hydroxypyrrole, 3-methoxypyrrole, 3-ethoxypyrrole, 3-butoxypyrrole, 3-hexyloxypyrrole, 3-methyl-4-hexyloxypyrrole, and 3-methyl-4-hexyloxypyrrole;Thiophene, 3-methylthiophene, 3-ethylthiophene, 3-propylthiophene, 3-butylthiophene, 3-hexylthiophene, 3-heptylthiophene, 3-octylthiophene, 3-decylthiophene, 3-dodecylthiophene, 3-octadecylthiophene, 3-bromothiophene, 3-chlorothiophene, 3-iodothiophene, 3-cyanothiophene, 3-phenylthiophene, 3,4-dimethylthiophene, 3,4-dibutylthiophene, 3-hydroxythiophene, 3-methoxythiophene, 3-ethoxythiophene, 3-butoxythiophene, 3-hexyloxythiophene, 3-heptyloxythiophene, 3-octyloxythiophene, 3-decyloxythiophene, 3-dodecyloxythiophene, 3-octadecyloxythiophene, 3,4-dihydroxythiophene, 3,4-dimethoxythiophene, 3,4-diethoxythiophene Thiophenes such as cythiophene, 3,4-dipropoxythiophene, 3,4-dibutoxythiophene, 3,4-dihexyloxythiophene, 3,4-diheptyloxythiophene, 3,4-dioctyloxythiophene, 3,4-didecyloxythiophene, 3,4-didodecyloxythiophene, 3,4-ethylenedioxythiophene, 3,4-propylenedioxythiophene, 3,4-butylenedioxythiophene, 3-methyl-4-methoxythiophene, 3-methyl-4-ethoxythiophene, 3-carboxythiophene, 3-methyl-4-carboxythiophene, 3-methyl-4-carboxyethylthiophene, 3-methyl-4-carboxybutylthiophene, and 3,4-ethyleneoxythiathiophene; anilines such as aniline, 2-methylaniline, 3-isobutylaniline, 2-anilinesulfonic acid, and 3-anilinesulfonic acid; and so on. These may be used individually or in combination of two or more. Among these, 3,4-ethylenedioxythiophene is more preferred, and 3,4-ethylenedioxythiophene is particularly preferred.

[0036] As monomers that form the constituent units of the conjugated conductive polymer, from the viewpoint of obtaining a conjugated conductive polymer with high conductivity, it is preferable to include a thiophene compound represented by the following formula (1) (hereinafter sometimes simply referred to as "the compound represented by formula (1)"). The compound represented by formula (1) may be used alone or in combination of two or more types.

[0037]

[0038] In formula (1), R １ and R ２ Each is 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 １ and R ２ The two atoms are bonded together to form an alicyclic ring having 3 to 10 carbon atoms which may be substituted, an aromatic ring having 6 to 10 carbon atoms which may be substituted, an oxygen-containing heterocyclic ring having 2 to 10 carbon atoms which may be substituted, an oxygen-containing heterocyclic ring having 2 to 10 carbon atoms which may be substituted, or an oxygen-containing heterocyclic ring having 2 to 10 carbon atoms which may be substituted.

[0039] The substituents that may be replaced are not particularly limited, and examples thereof include a carboxy group, a hydroxy group, a halogen atom, a cyano group, and the like. The oxygen atom-containing heterocyclic ring is not particularly limited, but the number of oxygen atoms constituting the ring is preferably 1 to 3. Examples thereof include an oxirane ring, an oxetane ring, a furan ring, a hydrofuran ring, a pyran ring, a pyrone ring, a dioxane ring, a trioxane ring, and the like. These may be used alone or in combination of two or more. The sulfur atom-containing heterocyclic ring is not particularly limited, but the number of sulfur atoms constituting the ring is preferably 1 to 3. Examples thereof include a thiirane ring, a thietane ring, a thiophene ring, a thiane ring, a thiopyran ring, a thiopyrylium ring, a benzothiopyran ring, a dithiane ring, a dithiolane ring, a trithiane ring, and the like. These may be used alone or in combination of two or more. The sulfur atom and oxygen atom-containing heterocyclic ring is not particularly limited, but the total number of sulfur atoms and oxygen atoms constituting the ring is preferably 1 to 3. Examples thereof include an oxathiolane ring, an oxathiane ring, and the like.

[0040] The content of the compound represented by the formula (1) is not particularly limited, but from the viewpoints of the uniformity of the conjugated conductive polymer and good conductivity, etc., in 100% by mass of the monomer that is a constituent unit of the conjugated conductive polymer, it is preferably 90 to 100% by mass, more preferably 95 to 100% by mass, and particularly preferably 100% by mass.

[0041] The compound represented by the formula (1) is not particularly limited, but preferably includes a compound represented by the following formula (2), and more preferably includes 3,4-ethylenedioxythiophene.

[0042]

[0043] In the formula (2), R ３ and R ４ are each independently a hydrogen atom, an optionally substituted alkyl group having 1 to 4 carbon atoms, or an optionally substituted oxygen atom-containing heterocyclic ring having 2 to 6 carbon atoms formed by bonding R ３ and R ４ to each other.

[0044] R ３ and R４ There are no particular restrictions, however R ３ and R ４ It is preferable that the oxygen atom-containing heterocycle has 2 to 6 carbon atoms and may be substituted, formed by the bonding of these atoms to each other. There are no particular restrictions on the oxygen atom-containing heterocycle, but it is preferable that the number of oxygen atoms constituting the ring is 1 to 3, for example, a dioxane ring, a trioxane ring, etc. Among these, a dioxane ring is preferred. Furthermore, there are no particular restrictions on the substituents that the oxygen atom-containing heterocycle has, but it is preferable that they be unsubstituted. The substituents to be substituted here are the same as substituent Y described above, for example, a carboxyl group, a hydroxyl group, a halogen atom, a cyano group, etc.

[0045] -Polyanions- Polyanions are contained in the composite particles and the conductive polymer-containing dispersion, and are also contained in the solid electrolyte layer produced using the conductive polymer-containing dispersion. The above polyanions are polymers having two or more anionic groups and function as dopants for conjugated conductive polymers. Furthermore, when the composite particles contain other polymers, the polyanions are thought to coordinate to the outside of the domains of the other polymers and act as protective colloids. The above polyanions may be used individually or in combination of two or more types.

[0046] The polyanion content (including, if other polymers are included, those coordinated to the outside of the domains of the other polymers; the same applies hereinafter) is not particularly limited, but from the viewpoint of the conductivity of the composite particles and stability in a conductive polymer-containing dispersion, it is preferably 30 to 95% by mass, more preferably 40 to 90% by mass, and particularly preferably 50 to 85% by mass, of 100% by mass of the composite particles.

[0047] There are no particular restrictions on the polyanion content, but it is preferably 0.1 to 90% by mass, more preferably 0.1 to 80% by mass, and most preferably 0.1 to 50% by mass, of 100% by mass of the solid electrolyte layer.

[0048] There are no particular restrictions on the polyanion content in the solid electrolyte layer, but it is preferably 45 to 1900 parts by mass, more preferably 70 to 900 parts by mass, and even more preferably 100 to 500 parts by mass, per 100 parts by mass of the conjugated conductive polymer.

[0049] Examples of anionic groups include groups made of sulfonic acid or its salts, groups made of phosphoric acid or its salts, monosubstituted phosphate ester groups, groups made of carboxylic acid or its salts, and monosubstituted sulfuric acid ester groups. These may be used individually or in combination of two or more. Among these, strongly acidic groups are preferred, groups made of sulfonic acid or its salts and groups made of phosphoric acid or its salts are more preferred, and groups made of sulfonic acid or its salts are particularly preferred. In other words, as a polyanion, a polymer having two or more groups made of sulfonic acid or its salts is preferred. There are no particular restrictions on the salts, and examples include salts of sodium, potassium, magnesium, calcium, ammonium, etc.

[0050] The anionic group may be bonded to the main chain or to the side chain of the polymer constituting the polyanion. When the anionic group is bonded to the side chain, there are no particular restrictions, but from the viewpoint of obtaining a high doping effect for conjugated conductive polymers, it is preferable that the anionic group is bonded to the end of the side chain. The anionic group may be directly bonded to the main chain, or it may be bonded via other structures. It is preferable that the anionic group is bonded via a benzene ring, and in this case, it is more preferable that the anionic group is bonded to the para position relative to the main chain.

[0051] The polyanion may or may not have substituents other than the anionic group. The substituents other than the anionic group may be bonded to the main chain or side chain of the polymer constituting the polyanion. When substituents other than the anionic group are bonded to the side chain, there are no particular restrictions, but from the viewpoint of exhibiting the properties of the substituent, it is preferable that the substituent is bonded to the end of the side chain. Examples of substituents other than the anionic group include alkyl groups, hydroxyl groups, alkoxy groups, cyano groups, phenyl groups, hydroxyphenyl groups, ester groups, alkenyl groups, imide groups, amide groups, amino groups, oxycarbonyl groups, carbonyl groups, halogen atoms, etc. These may be used individually or in combination of two or more. Among these, alkyl groups, hydroxyl groups, cyano groups, hydroxyphenyl groups, and oxycarbonyl groups are preferred, and alkyl groups, hydroxyl groups, and cyano groups are more preferred.

[0052] There are no particular restrictions on the main chain structure of the polymer constituting the polyanion; examples include polyalkylene, polyimide, polyamide, and polyester. Among these, polyalkylene is preferred from the viewpoint of ease of synthesis and availability.

[0053] The polyalkylene in the main chain structure is a polymer containing constituent units derived from ethylenically unsaturated monomers, and the main chain structure may or may not contain carbon-carbon double bonds. There are no particular restrictions on the polyalkylene, and examples include polyethylene, polypropylene, polybutene, polypentene, polyhexene, polyvinyl alcohol, polyvinylphenol, poly(3,3,3-trifluoropropylene), polyacrylonitrile, polyacrylate, polymethacrylate, polystyrene, polybutadiene, and polyisoprene. These may be used individually or in combination of two or more.

[0054] There are no particular restrictions on the weight-average molecular weight of the polyanion, but from the viewpoint of solubility in the dispersion medium and doping effect on the conjugated conductive polymer, it is preferably 1,000 to 1,000,000, more preferably 5,000 to 500,000, and particularly preferably 50,000 to 300,000. The weight-average molecular weight of the polyanion can be determined by the measurement method described in the examples.

[0055] There are no particular restrictions on the polyanion, but from the viewpoint of improving the dispersibility of monomers that form the constituent units of conjugated conductive polymers in the dispersion medium, as described above, it is preferable to have a group consisting of sulfonic acid or a salt thereof as the anionic group. A group consisting of sulfonic acid, i.e., a sulfo group (-SO ２ There are no particular restrictions on the polyanion having an OH group. Examples include polyvinyl sulfonic acid, polystyrene sulfonic acid, polyallyl sulfonic acid, ethyl sulfonic polyacrylate, butyl sulfonic polyacrylate, poly(2-acrylamido-2-methylpropanesulfonic acid), polyisoprene sulfonic acid, and copolymers thereof. These may be used individually or in combination of two or more. Among these, polystyrene sulfonic acid, polyisoprene sulfonic acid, ethyl sulfonic polyacrylate, and butyl sulfonic polyacrylate are preferred, with polystyrene sulfonic acid being more preferred, from the viewpoint of stability in conductive polymer-containing dispersions and the effect of reducing the ESR of solid electrolytic capacitors manufactured using conductive polymer-containing dispersions. Furthermore, from the viewpoint of water solubility, those in which the sulfo group is replaced with a sulfonic acid base are preferred, for example, sodium polystyrene sulfonate is suitably used. There are no particular restrictions on the method for producing the above polyanion. For example, it can be produced by a known production method described in Japanese Patent Publication No. 2005-76016, or a commercially available product can be used.

[0056] - Electrical Conductivity Enhancers - Electrical conductivity enhancers are contained in conductive polymer-containing dispersions and also in solid electrolyte layers manufactured using conductive polymer-containing dispersions. There are no particular restrictions on the electrical conductivity enhancers, and examples include aromatics such as acetophenone, benzyl alcohol, cresol, nitrobenzene, and tetrahydronaphthalene; amides such as formamide; ethers such as diethylene glycol monobutyl ether; esters such as butyl carbitol acetate; lactones such as γ-valerolactone; and polyalcohols such as triethanolamine, triethylene glycol, diethylene glycol, polyethylene glycol 400, glycerin, diglycerin, and ethylene glycol. These may be used individually or in combination of two or more. Among these, polyalcohols are preferred from the viewpoint of reducing ESR, and triethylene glycol, diethylene glycol, polyethylene glycol 400, glycerin, diglycerin, and ethylene glycol are more preferred.

[0057] The electrical conductivity improver may contain an organic solvent that does not have an oxygen atom in one molecule, or an organic solvent that has one or more oxygen atoms in one molecule, or an organic solvent that has two or more oxygen atoms in one molecule (hereinafter simply referred to as "organic solvent L"). Ｏ２ It may also be called "organic solvent L"), and may contain three or more oxygen atoms in one molecule (hereinafter simply referred to as "organic solvent L"). Ｏ３ It may also be called ). The organic solvents with different numbers of oxygen atoms in one molecule may be used individually or in combination of two or more. Also, the organic solvents with the same number of oxygen atoms in one molecule may be used individually or in combination of two or more. Among these, from the viewpoint that a solvent effect occurs with the conjugated conductive polymer due to the oxygen atoms in the molecule, thereby improving the conductivity of the conjugated conductive polymer, it is preferable that the electrical conductivity improver contains an organic solvent having two or more oxygen atoms in one molecule, or an organic solvent having three or more oxygen atoms in one molecule.

[0058] Organic solvent L Ｏ２There are no particular restrictions on the organic solvent L, but examples include diethylene glycol monobutyl ether, butyl carbitol acetate, γ-valerolactone, triethanolamine, triethylene glycol, diethylene glycol, polyethylene glycol 400, glycerin, diglycerin, ethylene glycol, etc. These may be used individually or in combination of two or more. Ｏ３ There are no particular restrictions on the choice of materials, but examples include diethylene glycol monobutyl ether, butyl carbitol acetate, triethanolamine, triethylene glycol, diethylene glycol, polyethylene glycol 400, glycerin, and diglycerin. These may be used individually or in combination of two or more.

[0059] There are no particular restrictions on the electrical conductivity improver, but it is preferable to include an organic solvent with a boiling point of 200°C or higher, from the viewpoint of suppressing evaporation during drying and facilitating the formation of conductive pathways in the conjugated conductive polymer. The organic solvents with different boiling points may be used individually or in combination of two or more. Furthermore, the electrical conductivity improver may be an organic solvent that does not contain an oxygen atom in one molecule, an organic solvent that contains one or more oxygen atoms in one molecule, or an organic solvent L. Ｏ２ , and organic solvent L Ｏ３ including at least one of the following 、 If the boiling point of the organic solvent is 200°C or higher, then the electrical conductivity improver can be said to contain an organic solvent with a boiling point of 200°C or higher. That is, the organic solvent with a boiling point of 200°C or higher may be an organic solvent with a boiling point of 200°C or higher that does not contain oxygen atoms in a single molecule, or an organic solvent with a boiling point of 200°C or higher that contains one or more oxygen atoms in a single molecule, and so on, as long as the organic solvent L has a boiling point of 200°C or higher. Ｏ２ It may also be an organic solvent L with a boiling point of 200°C or higher. Ｏ３ This may also be the case. Among these, from the viewpoint of low ESR, an organic solvent L with a boiling point of 200°C or higher is preferred. Ｏ２ , an organic solvent L with a boiling point of 200°C or higher Ｏ３ That is the case.

[0060] There are no particular restrictions on the content of the electrical conductivity improver in the solid electrolytic capacitor, but from the viewpoint of improving the conductivity of the solid electrolytic capacitor and suppressing the increase in viscosity of the conductive polymer-containing dispersion, it is preferably 20 to 2000 parts by mass, more preferably 120 to 1800 parts by mass, and even more preferably 200 to 1600 parts by mass per 100 parts by mass of composite particles.

[0061] There are no particular restrictions on the content of the conductivity enhancer, but it is preferably 0.5 to 50.0% by mass, more preferably 3.0 to 45.0% by mass, and most preferably 5.0 to 40.0% by mass, per 100% by mass of the conductive polymer-containing dispersion. Within this range, it is easier to achieve both the stability of the dispersion and the electrical conductivity of the solid electrolyte layer.

[0062] -Dispersion Medium- The conductive polymer-containing dispersion may contain a dispersion medium as needed. There are no particular restrictions on the dispersion medium, but it is preferable to use one that can maintain the conductive polymer-containing dispersion more efficiently and with high dispersion stability. Furthermore, it is preferable that the dispersion medium can dissolve or disperse the conductivity improver, more preferably one that can dissolve it, and particularly preferable one that can dissolve all of the conductivity improver contained in the conductive polymer-containing dispersion.

[0063] There are no particular restrictions on the dispersion medium, and examples include water; amides such as N-vinylpyrrolidone, hexamethylphosphortriamide, N-vinylformamide, and N-vinylacetamide; phenols such as cresol, phenol, and xylenol; polyhydric alcohols such as dipropylene glycol, 1,3-butylene glycol, 1,4-butylene glycol, diglycerin, isoprene glycol, butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,9-nonanediol, and neopentyl glycol; carbonate compounds such as ethylene carbonate and propylene carbonate; ethers such as dioxane, diethyl ether, propylene glycol dialkyl ether, polyethylene glycol dialkyl ether, and polypropylene glycol dialkyl ether; heterocyclic compounds such as 3-methyl-2-oxazolidinone; and nitriles such as acetonitrile, glutalodinitrile, methoxyacetonitrile, propionitrile, and benzonitrile. These may be used individually or in combination of two or more. Among these, water is preferred from the viewpoint of dispersion stability and ease of manufacture of the conductive polymer-containing dispersion. There are no particular restrictions on the amount of water, but from the viewpoint of stability of the conductive polymer-containing dispersion, it is preferably 1 to 100% by mass, more preferably 50 to 100% by mass, and particularly preferably 100% by mass (water only) of the dispersion medium.

[0064] There are no particular restrictions on the content of the dispersion medium, but from the viewpoint of imparting appropriate viscosity and dispersion stability to the conductive polymer-containing dispersion, it is preferably 30 to 98% by mass, more preferably 45 to 97% by mass, and particularly preferably 60 to 94% by mass, of 100% by mass of the conductive polymer-containing dispersion.

[0065] -Other Polymers- The composite particles, the conductive polymer-containing dispersion, and the solid electrolyte layer produced from the conductive polymer-containing dispersion may contain other polymers as needed. In this case, from the viewpoint of dispersibility in the conductive polymer-containing dispersion, it is preferable that the other polymers have polyanions coordinated to their surface, and it is preferable that the polyanions cover part or all of the surface of the other polymers. Other polymers having polyanions on their surface function as seed particles in the production of composite particles. The other polymers in this embodiment are not conjugated conductive polymers. That is, the other polymers are polymers that are not classified as conjugated conductive polymers. The other polymers in this embodiment are not polyanions. That is, the other polymers are polymers that are not classified as polyanions.

[0066] There are no particular restrictions on the content of other polymers, but from the viewpoint of the dispersion stability of the conductive polymer dispersion and the effect of reducing the ESR of solid electrolytic capacitors manufactured using the conductive polymer dispersion, it is preferably 0 to 50% by mass, more preferably 0 to 40% by mass, and particularly preferably 0 to 25% by mass, of 100% by mass of composite particles.

[0067] There are no particular restrictions on the content of other polymers, but it is preferably 0.1 to 60% by mass, more preferably 0.1 to 55% by mass, and most preferably 0.1 to 50% by mass, based on 100% by mass of the solid electrolyte layer.

[0068] Other polymers are not particularly limited, but polymers containing structural units derived from ethylenically unsaturated monomers are preferred, and homopolymers or copolymers consisting of structural units derived from ethylenically unsaturated monomers are more preferred. Furthermore, other polymers are not particularly limited, but nonionic polymers are more preferred. The other polymers may include either homopolymers or copolymers, or both. These may be used individually or in combination of two or more. The other polymers may also have a crosslinked structure.

[0069] Other ethylenically unsaturated monomers from which the constituent units of polymers are derived are not particularly limited and include, for example, (meth)acrylates having linear, branched, or cyclic alkyl groups; 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 alkanate; monoolefins such as ethylene, propylene, butylene, and isobutylene; conjugated diolefins such as butadiene, isoprene, and chloroprene; α,β-unsaturated mono or dicarboxylic acids such as (meth)acrylic acid, crotonic acid, itaconic acid, maleic acid, and fumaric acid; vinyl cyanide compounds such as acrylonitrile; and carbonyl group-containing vinyl compounds such as acrolein and diacetone acrylamide. These may be used individually or in combination of two or more.

[0070] Other polymers may have crosslinking structures that are not particularly limited. For example, structures derived from compounds having multiple independent ethylenically unsaturated bonds can be mentioned. Here, multiple independent ethylenically unsaturated bonds mean multiple ethylenically unsaturated bonds that do not form conjugated dienes with each other. The crosslinking structure is not particularly limited. For example, it may be formed by a polymer having a first reactive functional group and a crosslinking agent having multiple second reactive functional groups that react with the first reactive functional group, or it may be formed by intramolecular or intermolecular reactions of polymers having both the first and second reactive functional groups. By making other polymers copolymers having a crosslinking structure (hereinafter sometimes simply referred to as "crosslinked copolymers"), the water resistance, moisture resistance, and heat resistance of solid electrolytes using them tend to improve.

[0071] When no crosslinking agent is used, the content of structural units forming the crosslinked structure in the other polymer is preferably 50% by mass or less, more preferably 30% by mass or less, and even more preferably 15% by mass or less, based on 100% by mass of the other polymer. When a crosslinking agent is used, the total content of structural units forming the crosslinked structure in the other polymer and structural units derived from the crosslinking agent is preferably 50% by mass or less, more preferably 30% by mass or less, and even more preferably 15% by mass or less, based on 100% by mass of the other polymer.

[0072] There are no particular restrictions on the monomers that form the crosslinking structure in other polymers. Examples include epoxy group-containing α,β-ethylenically unsaturated compounds such as glycidyl (meth)acrylate; hydrolyzable alkoxysilyl group-containing α,β-ethylenically unsaturated compounds such as vinyltriethoxysilane and γ-methacryloxypropyltrimethoxysilane; and polyfunctional vinyl compounds such as ethylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, allyl (meth)acrylate, divinylbenzene, and diallyl phthalate. These may be used individually or in combination of two or more. Furthermore, a monomer that forms a crosslinking structure, such as a carbonyl group-containing α,β-ethylenically unsaturated compound (containing a ketone group), may be combined with a polyhydrazine compound (especially one having two or more hydrazide groups, such as oxalic acid dihydrazide, succinic acid dihydrazide, adipic acid dihydrazide, and polyacrylate hydrazide) to crosslink other polymers.

[0073] There are no particular restrictions on the other polymers, but it is preferable that they be obtained in a dispersed state in a dispersion medium (hereinafter sometimes simply referred to as "other polymer-containing dispersion"), and more preferably in an emulsion state (hereinafter sometimes simply referred to as "other polymer emulsion").

[0074] The 50% volume cumulative particle size (d) of the other polymers in the dispersion containing other polymers ５０There are no particular restrictions on the 50% volume cumulative particle size (d) above, but from the viewpoint of dispersibility and suppression of sedimentation of other polymer-containing dispersions, it is preferably 0.01 to 10 μm, more preferably 0.05 to 1 μm, even more preferably 0.1 to 0.8 μm, and particularly preferably 0.3 to 0.6 μm. ５０ ) is obtained by the method described in the examples below.

[0075] Other polymers can be produced by radical polymerization reactions in atmospheric pressure or pressure-resistant reactors, and the production method may be batch, semi-continuous, or continuous.

[0076] The other polymers preferably have polyanions on their surface and are preferably produced by emulsion polymerization, in which a raw material solution containing an ethylenically unsaturated monomer is continuously or intermittently added to a polyanion-containing solution. Emulsification polymerization efficiently yields composite particles in which the polyanion coordinates to the other polymer, and the polyanion domain is formed outside the domain of the other polymer. In such composite particles, the polyanion is thought to act as a protective colloid. Such polyanions contribute to the dispersion stability of the other polymer-containing dispersion. The polyanions contained in the other polymer-containing dispersion and the polyanions contained in the conductive polymer-containing dispersion may be the same or different (for example, with different cations bonded).

[0077] There are no particular restrictions on the content of the ethylenically unsaturated monomer used in the production of other polymers, but from the viewpoint of suppressing thickening and ensuring stability of the dispersion containing other polymers, it is preferably 10 to 100 parts by mass, more preferably 20 to 90 parts by mass, and particularly preferably 30 to 80 parts by mass, per 100 parts by mass of polyanion.

[0078] There are no particular restrictions on the type of dispersion medium included in the other polymer-containing dispersion, but an aqueous medium is preferred, and water or a mixed solvent of water and a water-soluble solvent is more preferred. There are no particular restrictions on the content of the aqueous medium in the mixed solvent, but from the viewpoint of the dispersion stability of particles during the polymerization reaction, it is preferably 30% by mass or less in 100% by mass of the mixed solvent. There are no particular restrictions on the water-soluble solvents mentioned above, and examples include alcohols such as methanol, ethanol, and isopropanol; ketones such as acetone; glycols such as ethylene glycol and propylene glycol; ethers such as ethylene glycol monomethyl ether and ethylene glycol monobutyl ether; and so on. These may be used individually or in combination of two or more.

[0079] There are no particular restrictions on the content of the dispersion medium in the other polymer-containing dispersion, but from the viewpoint of the dispersion stability of the other polymer-containing dispersion, it is preferably 30 to 99% by mass, more preferably 50 to 95% by mass, and even more preferably 70 to 90% by mass, of 100% by mass of the other polymer-containing dispersion.

[0080] There are no particular restrictions on other polymer-containing dispersions, but from the viewpoint of obtaining good dispersion stability, in addition to other polymers and polyanions that contribute to the stability of other polymer-containing dispersions, emulsifiers, aliphatic amines, water-soluble polymers, etc. may be included as needed. These may be used individually or in combination of two or more. The type and content of emulsifiers and aliphatic amines are appropriately adjusted according to the type of ethylenically unsaturated monomer, the polyanion content, and the composition. The type and content of water-soluble polymers are appropriately adjusted within a range that does not impair the properties of the conductive polymer-containing dispersion in this embodiment.

[0081] There are no particular restrictions on the emulsifier, and examples include anionic surfactants such as alkyl sulfate salts, 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. These may be used individually or in combination of two or more.

[0082] There are no particular restrictions on the aliphatic amines, and examples 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. These may be used individually or in combination of two or more.

[0083] There are no particular restrictions on the water-soluble polymers used; examples include polyvinyl alcohol, methylcellulose, carboxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, and polyvinylpyrrolidone. These may be used individually or in combination of two or more.

[0084] As described above, other polymers can be produced by radical polymerization reactions. There are no particular restrictions on the polymerization initiators used in the radical polymerization reactions, and examples include inorganic peroxides such as hydrogen peroxide, persulfate, ammonium persulfate, potassium persulfate, and sodium persulfate; organic peroxides such as benzoyl peroxide and tert-butyl hydroperoxide; and azo compounds such as 2,2'-azobisisobutyronitrile and 4,4'-azobis(4-cyanovaleric acid). These may be used individually or in combination of two or more. In addition, the polymerization initiators may be combined with sodium sulfoxylate formaldehyde, ascorbic acid, sulfites, tartaric acid or its salts, iron(II) sulfate, etc., to carry out redox polymerization. Furthermore, chain transfer agents such as alcohols and mercaptans may be used as needed. There are no particular restrictions on the reaction temperature in the radical polymerization reaction, but it is preferably 10 to 100°C, more preferably 30 to 90°C. There are no particular restrictions on the reaction time in radical polymerization reactions; it is adjusted as appropriate depending on the amount of raw materials, the type of polymerization initiator, and the reaction temperature.

[0085] There are no particular restrictions on the reaction products obtained by the radical polymerization reaction, but it is preferable to desalt them from the viewpoint of quality stability of the dispersion containing other polymers. There are no particular restrictions on the desalting method, and examples include dialysis, centrifugal washing, and ion exchange using ion exchange resin.

[0086] - Alkaline Compounds - The conductive polymer-containing dispersion and the solid electrolyte layer produced from the conductive polymer-containing dispersion may contain alkaline compounds as needed, from the viewpoint of adjusting the pH and suppressing corrosion of metals and other materials in contact with them.

[0087] When the conductive polymer-containing dispersion contains an alkaline compound, there are no particular restrictions on the pH of the raw material solution (1) described later. However, from the viewpoint of suppressing corrosion of metals and other materials that come into contact with the conductive polymer-containing dispersion, and from the viewpoint of suppressing dedoping of polyanion composite particles, the pH is preferably 3.0 to 8.0, more preferably 4.0 to 7.5, and particularly preferably 4.5 to 7.0. The pH of the conductive polymer-containing dispersion can be determined by the measurement method described in the examples.

[0088] There are no particular restrictions on the content of the alkaline compound, but it is preferably 0.00 to 15.00% by mass, more preferably 0.05 to 10.00% by mass, and most preferably 0.10 to 5.00% by mass, per 100% by mass of the conductive polymer-containing dispersion.

[0089] There are no particular restrictions on the content of the alkaline compound, but it is preferably 0 to 5.0% by mass, more preferably 0 to 4.0% by mass, even more preferably 0 to 3.5% by mass, and most preferably 0 to 2.0% by mass, based on 100% by mass of the solid electrolyte layer.

[0090] There are no particular restrictions on the alkaline compound; organic or inorganic alkaline compounds can be used. The alkaline compound may be used alone or in combination of two or more.

[0091] There are no particular restrictions on the organic alkaline compounds used; examples include aromatic amines, aliphatic amines, heterocyclic amines, and alkali metal alkoxides. These can be used individually or in combination of two or more.

[0092] There are no particular restrictions on the aromatic amines, and examples include nitrogen-containing heteroaryl compounds such as pyridines, imidazoles, pyrimidines, pyrazines, and triazines. These may be used individually or in combination of two or more. Among these, pyridines, imidazoles, and pyrimidines are preferred from the viewpoint of solubility and other factors.

[0093] There are no particular restrictions on the aliphatic amines, and examples include ethylamine, n-octylamine, diethylamine, diisobutylamine, methylethylamine, trimethylamine, triethylamine, allylamine, 2-ethylaminoethanol, 2,2'-iminodiethanol, and N-ethylethylenediamine. There are no particular restrictions on the heterocyclic amines, and examples include azetidines, pyrrolidines, piperidines, piperazines, morpholines, and thiomorpholines. These may be used individually or in combination of two or more. Among these, morpholines are preferred from the viewpoint of versatility.

[0094] There are no particular restrictions on the morpholines used; for example, morpholine, 4-methylmorpholine, 4-ethylmorpholine, 4-n-propylmorpholine, 4-isopropylmorpholine, 4-n-butylmorpholine, 4-isobutylmorpholine, 4-pentylmorpholine, 4-hexylmorpholine, (R)-3-methylmorpholine, (S)-3-methylmorpholine, cis-2,6-dimethylmorpholine, 4-(1-cyclohexenyl)morpholine, 1-morpholino-1-cyclopentene, 4-phenylmorpholine, 4-(p-tolyl)morpholine, 4-(2-aminoethyl)morpholine, 4-(3-aminopropyl)morpholine, 2-morpholinoaniline, 4-morpholino Examples include aniline, 4-(2-morpholinoethoxy)aniline, 4-(4-pyridyl)morpholine, 4-aminomorpholine, 4-(2-hydroxypropyl)morpholine, 4-(2-hydroxyethyl)morpholine, 4-(3-hydroxypropyl)morpholine, 2-hydroxy-3-morpholinopropanesulfonic acid, 2-morpholinoethanesulfonic acid, 3-morpholinopropanesulfonic acid, 4-acetylmorpholine, 4-acetoacetylmorpholine, 4-acryloylmorpholine, 4-allylmorpholine, phenylmorpholine, 3-(morpholino)propionate ethyl, 4-formylmorpholine, 4-(4-formylphenyl)morpholine, and salts thereof. These may be used individually or in combination of two or more. Among these, morpholine, 4-ethylmorpholine, 4-n-butylmorpholine, 4-isobutylmorpholine, 4-phenylmorpholine, 4-(2-hydroxypropyl)morpholine, 4-(2-hydroxyethyl)morpholine, and 4-(3-hydroxypropyl)morpholine are preferred from the viewpoint of availability and ease of handling, morpholine, 4-ethylmorpholine, and 4-(2-hydroxyethyl)morpholine are more preferred, and morpholine is particularly preferred.

[0095] There are no particular restrictions on the alkali metal alkoxide; for example, sodium alkoxides such as sodium methoxide and sodium ethoxide; potassium alkoxides; calcium alkoxides; etc. These may be used individually or in combination of two or more.

[0096] There are no particular restrictions on the inorganic alkaline compound; examples include ammonia, sodium hydroxide, potassium hydroxide, calcium hydroxide, and ammonia. These may be used individually or in combination of two or more.

[0097] -Other Additives- The conductive polymer-containing dispersion and the solid electrolyte layer produced from the conductive polymer-containing dispersion may contain other additives besides the components described above, as necessary, from the viewpoint of imparting physical properties suitable for solid electrolytic capacitors. The type and content of other additives are not particularly limited, as long as they do not significantly adversely affect the effects of this embodiment or the viscosity of the conductive polymer-containing dispersion. Examples of other additives are not particularly limited and include water-soluble polymer compounds, water-dispersible compounds, surfactants, defoamers, coupling agents, antioxidants, etc. These may be used individually or in combination of two or more.

[0098] Water-soluble polymer compounds and water-dispersible compounds can adjust the viscosity of conductive polymer-containing dispersions and improve their coating performance. When a conductive polymer-containing dispersion contains at least one of a water-soluble polymer compound and a water-dispersible compound, 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 particularly preferably 3 to 30 parts by mass, per 1 part by mass of composite particles in the conductive polymer-containing dispersion. In this specification, "water-dispersible compound" means a compound in which a portion of the low hydrophilicity is replaced with a highly hydrophilic functional group, or a compound having a highly hydrophilic functional group is adsorbed around a low hydrophilic compound (for example, an emulsion), and which disperses in water without settling.

[0099] There are no particular restrictions on the water-soluble polymer compound, and examples include polyoxyalkylenes, water-soluble polyurethanes, water-soluble polyesters, water-soluble polyamides, water-soluble polyimides, water-soluble polyacrylics, water-soluble polyacrylamides, polyvinyl alcohol, and polyacrylic acid. These may be used individually or in combination of two or more. Among these, polyoxyalkylenes are preferred. The above-mentioned polyoxyalkylenes are not particularly limited, and examples include oligoethylene glycol, triethylene glycol monochlorohydrin, diethylene glycol monochlorohydrin, oligoethylene glycol monochlorohydrin, triethylene glycol monobromehydrin, diethylene glycol monobromehydrin, oligoethylene glycol monobromehydrin, polyethylene glycol, glycidyl ethers, polyethylene glycol glycidyl ethers, polyethylene oxide, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, dipropylene glycol, tripropylene glycol, polypropylene glycol, polypropylene dioxide, polyoxyethylene alkyl ether, polyoxyethylene glycerin fatty acid ester, and polyoxyethylene fatty acid amide. These may be used individually or in combination of two or more.

[0100] There are no particular limitations on the water-dispersible compound, and examples include polyester, polyurethane, acrylic resin, silicone resin, and modified versions thereof with the introduction of functional groups. Also, block copolymers or graft copolymers of acrylic resin with polyester or polyurethane are examples. These may be used individually or in combination of two or more.

[0101] There are no particular restrictions on the surfactants used, and examples 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, aminocarboxylates, and imidazolium betaine; and nonionic surfactants such as polyoxyethylene alkyl ethers, polyoxyethylene glycerin fatty acid esters, ethylene glycol fatty acid esters, and polyoxyethylene fatty acid amides. These may be used individually or in combination of two or more.

[0102] There are no particular restrictions on the defoaming agent; examples include silicone resin, polydimethylsiloxane, and silicone oil. These may be used individually or in combination of two or more.

[0103] There are no particular restrictions on the antioxidants used; examples include phenolic antioxidants, amine antioxidants, phosphorus antioxidants, sulfur antioxidants, and vitamins. These may be used individually or in combination of two or more.

[0104] (Method for producing a conductive polymer-containing dispersion) There are no particular restrictions on the method for producing a conductive polymer-containing dispersion. For example, it can be produced by polymerizing monomers that form the constituent units of a conjugated conductive polymer and polyanions in a raw material solution (1) containing these monomers and polyanions, and then adding an electrical conductivity improver. If necessary, alkaline compounds and other additives may be added after polymerization of the monomers, before or after the addition of the electrical conductivity improver. The raw material solution (1) may contain other polymers. These other polymers may form complexes with polyanions. These complexes may form a structure in which polyanions are coordinated to the outside of the domains of the other polymers. The other polymers may also be added to the raw material solution (1) using the other polymer-containing dispersion described above. The polyanions used in the production of the conductive polymer-containing dispersion, i.e., the polyanions that may be contained in the raw material solution (1), other polymer-containing dispersion, etc., may be the same as the polyanions contained in the conductive polymer-containing dispersion, or they may be different (for example, with different cations bonded).

[0105] The amount of electrical conductivity improver added to 100 parts by mass of raw material liquid (1) can be adjusted as appropriate depending on the type of electrical conductivity improver, and there are no particular restrictions, but it is preferably 20 to 55 parts by mass, more preferably 25 to 50 parts by mass.

[0106] There are no particular restrictions on the raw material liquid (1), but from the viewpoint of suppressing uneven progress of the polymerization reaction, it is preferable that monomers that form the constituent units of the conjugated conductive polymer are dissolved, emulsified, or dispersed in it. There are no particular restrictions on the method of preparing the raw material liquid (1), and examples include stirring with a stirrer such as a homomixer or homogenizer; ultrasonic irradiation; etc. These may be used individually or in combination of two or more.

[0107] In the preparation of the raw material solution (1), even if a mixture containing polyanions and other polymers is used, such as in a dispersion containing other polymers, additional polyanions may be added from the viewpoint of suppressing particle aggregation in the raw material solution (1). That is, the raw material solution (1) may contain a complex in which polyanions are coordinated to the outside of the domains of other polymers, and the additionally added polyanions. The additionally added polyanions may have the same structure as the polyanions forming the complex, or they may have a different structure. There are no particular restrictions on the content of the additionally added polyanions, but it is preferably 99% by mass or less, more preferably 10 to 90% by mass, even more preferably 30 to 80% by mass, and particularly preferably 40 to 70% by mass, of the total 100% by mass of polyanions in the raw material solution (1).

[0108] There are no particular restrictions on the polyanion content in the raw material liquid (1), but from the viewpoint of dispersion stability of the conductive polymer-containing dispersion, the effect of reducing the equivalent series resistance (ESR) of the solid electrolytic capacitor manufactured using the conductive polymer-containing dispersion, and the effect of increasing capacitance, the amount of anionic groups is preferably 0.25 to 30 moles, more preferably 0.5 to 25 moles, and even more preferably 0.8 to 20 moles per mole of monomers that form the constituent units of the conjugated conductive polymer.

[0109] There are no particular restrictions on the dispersion medium in the raw material liquid (1), and examples include water; amides such as N-vinylpyrrolidone, hexamethylphosphoramide, N-vinylformamide, and N-vinylacetamide; phenols such as cresol, phenol, and xylenol; polyhydric alcohols such as dipropylene glycol, 1,3-butylene glycol, 1,4-butylene glycol, diglycerin, isoprene glycol, butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,9-nonanediol, and neopentyl glycol; carbonates such as ethylene carbonate and propylene carbonate; ethers such as dioxane, diethyl ether, propylene glycol dialkyl ether, polyethylene glycol dialkyl ether, and polypropylene glycol dialkyl ether; heterocyclic compounds such as 3-methyl-2-oxazolidinone; and nitriles such as acetonitrile, glutalodinitrile, methoxyacetonitrile, propionitrile, and benzonitrile. These may be used individually or in combination of two or more. There are no particular restrictions on the dispersion medium in the raw material liquid (1), but it is preferable that it contains water. If water is included, there are no particular restrictions on the amount of water, but it is preferably 1% by mass or more, more preferably 50% by mass or more, and most preferably 100% by mass, of 100% by mass of the dispersion medium in the raw material liquid (1). Furthermore, there are no particular restrictions on the dispersion medium in the raw material liquid (1), but from the viewpoint of ease of manufacturing the conductive polymer-containing dispersion, it is preferable that it is the same as the dispersion medium that can be contained in the conductive polymer-containing dispersion.

[0110] There are no particular restrictions on the content of the dispersion medium in the raw material liquid (1), but from the viewpoint of appropriate viscosity and reactivity during the polymerization reaction, it is preferably 1 to 99.9% by mass, more preferably 10 to 99% by mass, and particularly preferably 30 to 99% by mass, of 100% by mass of the raw material liquid (1).

[0111] There are no particular restrictions on the polymerization reaction for synthesizing conjugated conductive polymers, but it is preferable to carry it out in the presence of an oxidizing agent. The oxidizing agent is not particularly limited and examples include peroxodisulfates such as peroxodisulfate, ammonium peroxodisulfate, sodium peroxodisulfate, and potassium peroxodisulfate; metal halogen compounds such as boron trifluoride; transition metal compounds such as iron(III) chloride, iron(III) sulfate, and copper(II) chloride; metal oxides such as silver oxide and cesium oxide; peroxides such as hydrogen peroxide and ozone; organic peroxides such as benzoyl peroxide; and oxygen. These may be used individually or in combination of two or more. Among these, peroxodisulfate, peroxodisulfates, and transition metal compounds are preferred, and peroxodisulfates and transition metal compounds are more preferred. There are no particular restrictions on the content of the above-mentioned oxidizing agent, but from the viewpoint of appropriately promoting the polymerization reaction, it is preferably 50 to 1500 parts by mass, more preferably 70 to 1000 parts by mass, and most preferably 100 to 500 parts by mass, per 100 parts by mass of monomers that form the constituent units of the conjugated conductive polymer.

[0112] There are no particular restrictions on the reaction temperature for the polymerization reaction to synthesize the conjugated conductive polymer, but from the viewpoint of achieving an appropriate reaction rate and suppressing an increase in the viscosity of the reaction solution, it is preferably 5 to 80°C, more preferably 10 to 60°C, and most preferably 15 to 40°C. Furthermore, the reaction temperature may be appropriately changed as the reaction progresses.

[0113] There are no particular restrictions on the polymerization reaction for synthesizing conjugated conductive polymers, but it is preferable to carry out the reaction while stirring from the viewpoint of suppressing the aggregation of particles in the reaction solution. There are no particular restrictions on the stirring method, and examples include circulating and stirring the reaction solution using a high-shear mixer or the like.

[0114] <Electrolyte> A solid electrolytic capacitor may contain an electrolyte impregnated into the solid electrolyte layer, if necessary. There are no particular restrictions on the electrolyte, and known electrolytes for electrolytic capacitors can be used, such as polar organic solvents. The polar organic solvent may or may not contain salts.

[0115] The polar organic solvent of the electrolyte may be a protic solvent or an aprotic solvent. These may be used individually or in combination of two or more.

[0116] There are no particular restrictions on the protic solvent, and examples include monohydric alcohols such as ethanol, propanol, butanol, pentanol, hexanol, cyclobutanol, cyclopentanol, cyclohexanol, and benzyl alcohol; polyhydric alcohols such as ethylene glycol, diethylene glycol, propylene glycol, glycerin, methyl cellosolve, ethyl cellosolve, methoxypropylene glycol, dimethoxypropanol, polyethylene glycol, and polyoxyethylene glycerin; and oxyalcohol compounds. These may be used individually or in combination of two or more.

[0117] There are no particular restrictions on the aprotic solvent, and examples include sulfones such as dimethyl sulfone, ethyl methyl sulfone, diethyl sulfone, sulfolane, 3-methylsulfolane, and 2,4-dimethylsulfolane; amides such as N-methylformamide, N,N-dimethylformamide, N-ethylformamide, N,N-diethylformamide, N-methylacetamide, N,N-dimethylacetamide, N-ethylacetamide, N,N-diethylacetamide, and hexamethylphosphoric amide; lactones and cyclic amides such as γ-butyrolactone, γ-valerolactone, δ-valerolactone, N-methyl-2-pyrrolidone, ethylene carbonate, propylene carbonate, butylene carbonate, and isobutylene carbonate; nitriles such as acetonitrile, 3-methoxypropionitrile, and glutaronitrile; and oxides such as dimethyl sulfoxide. These may be used individually or in combination of two or more.

[0118] There are no particular restrictions on the salts that can be contained in polar organic solvents. Examples include ammonium salts; quaternary ammonium salts such as tetramethylammonium salt, triethylmethylammonium salt, and tetraethylammonium salt; amidinium salts such as ethyldimethylimidazolinium salt and tetramethylimidazolinium salt; primary amine salts such as methylamine salt, ethylamine salt, and propylamine salt; secondary amine salts such as dimethylamine salt, diethylamine salt, ethylmethylamine salt, and dibutylamine salt; tertiary amine salts such as trimethylamine salt, triethylamine salt, tributylamine salt, ethyldimethylamine salt, and ethyldiisopropylamine salt; sodium salts; potassium salts, etc. These may be used individually or in combination of two or more.

[0119] There are no particular restrictions on the acids that make up the salt. Examples include carboxylic acids such as oxalic acid, succinic acid, glutaric acid, pimelic acid, suberic acid, sebacic acid, phthalic acid, isophthalic acid, terephthalic acid, maleic acid, adipic acid, benzoic acid, toluic acid, enanthic acid, malonic acid, 1,6-decanedicarboxylic acid, 1,7-octanedicarboxylic acid, azelaic acid, resorcinic acid, phloroglucic acid, gallic acid, gentisic acid, protocatechuic acid, pyrocatechuic acid, trimellitic acid, and pyromellitic acid; sulfonic acids; and other organic acids. Other examples include boric acid, phosphoric acid, phosphorous acid, hypophosphorous acid, carbonic acid, and silicic acid. Other examples include boron complexes such as borosalicylic acid, borosaloic acid, borosiglycolic acid, borosimalonic acid, borosuccinic acid, borosiadipic acid, borosizelaic acid, borosibenzoic acid, borosimalic acid, borosilactic acid, borosimalic acid, borosilactic acid, borosicic acid, borosiphthalic acid, borosi(2-hydroxy)isobutyric acid, borosirsorcinic acid, borosilimethylsalicylic acid, borosinaphthoic acid, borosimandelic acid, and borosi(3-hydroxy)propionic acid. These may be used individually or in combination of two or more.

[0120] The electrolyte may or may not contain additives as needed. There are no particular restrictions on the additives, and examples include: complex compounds of boric acid with polysaccharides such as mannitol and sorbitol; complex compounds of boric acid with polyhydric alcohols; boric acid esters; nitro compounds such as o-nitrobenzoic acid, m-nitrobenzoic acid, p-nitrobenzoic acid, o-nitrophenol, m-nitrophenol, p-nitrophenol, and p-nitrobenzyl alcohol; phosphate esters; and so on. These may be used individually or in combination of two or more.

[0121] [Method for Manufacturing a Solid Electrolytic Capacitor] The method for manufacturing a solid electrolytic capacitor according to this embodiment is a method for manufacturing a solid electrolytic capacitor comprising an anode, a dielectric film provided on the surface of the anode, and a solid electrolyte layer in contact with the dielectric film, comprising: attaching a conductive polymer-containing dispersion to the surface of the dielectric film, and drying the conductive polymer-containing dispersion to form a solid electrolyte layer containing a conjugated conductive polymer, a polyanion, and an electrical conductivity improver, wherein the content of the electrical conductivity improver is 76.5 to 92.5% by mass of 100% by mass of the solid electrolyte layer. By this manufacturing method, a solid electrolytic capacitor with excellent equivalent series resistance (ESR) in the high-frequency range can be obtained.

[0122] There are no particular limitations on the method for attaching the conductive polymer-containing dispersion to the surface of the dielectric film; for example, known methods such as coating, spraying, and immersion can be used. These may be used individually or in combination of two or more methods. Among these, immersion is preferred from the viewpoint of evenly and uniformly penetrating and attaching the conductive polymer-containing dispersion to the surface of the dielectric film. Furthermore, if the anode equipped with the dielectric film is a porous anode, immersion may be performed under reduced pressure from the viewpoint of sufficiently penetrating the conductive polymer-containing dispersion into fine details such as the pores of the porous anode.

[0123] When a conductive polymer-containing dispersion is applied to the surface of a dielectric film by immersion, the immersion time of the dielectric film (anode equipped with a dielectric film) is adjusted appropriately according to the type and viscosity of the dispersion medium of the conductive polymer-containing dispersion, and there are no particular restrictions, but it is preferable to immerse it for about 10 seconds to 10 minutes.

[0124] A solid electrolyte layer is formed by drying the conductive polymer-containing dispersion, that is, by removing the dispersion medium and a portion of the conductivity enhancer in the conductive polymer-containing dispersion. As described above, the conductive polymer-containing dispersion contains a conjugated conductive polymer, polyanions, and a conductivity enhancer, so a solid electrolyte layer containing a conjugated conductive polymer, polyanions, and a conductivity enhancer can be formed.

[0125] There are no particular restrictions on the method for drying the conductive polymer-containing dispersion, but from the viewpoint of efficiently drying (removing) a portion of the dispersion medium and the electrical conductivity improver, it is preferable to dry it by heat treatment. The heating temperature for the heat treatment is set appropriately considering the boiling point and volatility of the dispersion medium, the oxidative degradation of the polymer and the element, etc., and is not particularly limited, but is preferably 25°C to 250°C, more preferably 60 to 200°C, even more preferably 100°C to 180°C, and particularly preferably 120 to 150°C. The heating time for the heat treatment is set appropriately considering the boiling point and volatility of the dispersion medium, the oxidative degradation of the polymer and the element, etc., and is not particularly limited, but is preferably 10 to 200 minutes, more preferably 20 to 120 minutes, and particularly preferably 30 to 60 minutes. There are no particular restrictions on the heating device used for the heat treatment, and examples include hot plates, ovens, hot air dryers, etc. These may be used individually or in combination of two or more. Furthermore, drying may be performed under reduced pressure from the viewpoint of improving drying efficiency.

[0126] The embodiment will be described in more detail below with reference to examples and comparative examples, but this embodiment is not limited to the following examples.

[0127] [Measurement Method] The measurement methods for various physical properties in the examples and comparative examples are as follows.

[0128] <Weight-average molecular weight (Mw)> The weight-average molecular weight (Mw) was measured by gel permeation chromatography under the following conditions and determined as the molecular weight equivalent to standard polystyrene. <Measurement conditions> Measuring instrument: "Shodex GPC 101", manufactured by Showa Denko K.K. Column used: "OHpak SB-806M HQ", manufactured by Showa Denko K.K. Column temperature: 40°C Eluten: Water Elution rate: 1 mL / min Standard sample: Polystyrene

[0129] <50% volume cumulative particle diameter (d ５０ ) > 50% volume cumulative particle diameter (d ５０ The particle size distribution was measured using a particle size distribution analyzer (Microtrac UPA model, manufactured by Nikkiso Co., Ltd.).

[0130] <pH> The pH of each solution was measured using a pH meter ("HM-30G", manufactured by Toa DKK Co., Ltd.; 25°C).

[0131] <Solid Content Concentration (Mass %)> The solid content concentration of each liquid was determined by measuring the amount of solids in approximately 10 g of each liquid and calculating the solid content (mass %) in 100 mass% of each liquid. The amount of solids was determined by weighing approximately 10 g of the conductive polymer-containing dispersion liquid (hereinafter sometimes simply referred to as "precursor dispersion liquid") before adding the conductivity improver, and measuring the evaporation residue after heating for 30 minutes at a temperature 10°C higher than the boiling point of the dispersion medium with the highest boiling point in the precursor dispersion liquid using an infrared moisture meter ("FD-720", manufactured by Kett Scientific Research Institute Co., Ltd.). For example, if the dispersion medium is water, the heating conditions are 110°C for 30 minutes. The above solid content is the evaporation residue based on composite particles, alkaline compounds, and other additives.

[0132] <Content of Conductivity Enhancer in Solid Electrolyte Layer (Mass %)> The mass (A) of a solid electrolytic capacitor element equipped with an anode having a dielectric film was measured, and the mass (B) after a conductive polymer-containing dispersion was attached to the surface of the dielectric film was measured. The amount of conductive polymer-containing dispersion attached (C) was calculated from (B) - (A). Using the solid content concentration in the conductive polymer-containing dispersion, the mass of solids contained in the solid electrolyte layer after drying (D) was calculated from the amount attached (C). Next, the mass (E) of the solid electrolytic capacitor after drying was measured, and the mass of the conductivity enhancer contained in the solid electrolyte layer (F) was calculated from (E) - (A) - (D) (where (E) - (A) represents the mass of the solid electrolyte layer). The content (mass %) of the conductivity enhancer in 100 mass% of the solid electrolyte layer was calculated from (F) / ((E) - (A)) × 100.

[0133] <Content (mass%) of conjugated conductive polymer, polyanion, conductivity enhancer, alkaline compound, and other additives in the solid electrolyte layer> The content (mass%) of each component (conjugated conductive polymer, polyanion, conductivity enhancer, alkaline compound, and other additives) in 100% by mass of the solid electrolyte layer was calculated using the mass (D) of the solid content, the mass of the solid electrolyte layer ((E) - (A)), and the mass ratio of each component used when the conductive polymer-containing dispersion was manufactured.

[0134] <Equivalent Series Resistance (ESR) (mΩ)> The equivalent series resistance (ESR) (mΩ) of the manufactured solid electrolytic capacitors was measured using a precision LCR meter ("E4980A", manufactured by Agilent Technologies, Inc.) under conditions of 100 kHz.

[0135] [Preparation of Conductive Polymer-Containing Dispersion] (Preparation Example 1) 86 g of styrene, 49 g of 2-ethylhexyl acrylate, 15 g of divinylbenzene, and 500 g of a 22% by mass aqueous solution of sodium polystyrene sulfonate (polyanion, "Polinas PS-5", manufactured by Tosoh Finechem Co., Ltd., weight-average molecular weight (Mw): approximately 120,000; the same applies hereafter) (110 g of sodium polystyrene sulfonate) were stirred and mixed to prepare raw material solution (a). In addition, 1000 g of a 22% by mass aqueous solution of sodium polystyrene sulfonate (220 g of sodium polystyrene sulfonate) was heated to 80°C while stirring, and 2 g of potassium persulfate was added to prepare raw material solution (b). Raw material solution (a) was added dropwise to raw material solution (b) over 2 hours, and then 40 g of a 2.5% by mass aqueous solution of potassium persulfate was added dropwise over 2.5 hours, reacted at 80°C for 2 hours, and then cooled to 25°C. To the solution after the above reaction, 1500 mL of cation exchange resin ("Amberlite IR120B-H", manufactured by Organo Corporation; hereinafter the same) and 1500 mL of anion exchange resin ("Amberlite IRA410-OH", manufactured by Organo Corporation; hereinafter the same) were added, and after stirring for 12 hours, the ion exchange resin was filtered off. Pure water was added to obtain a dispersion containing other polymers (other polymer emulsion) with polyanions coordinated on the surface (other polymer d ５０ : 0.46 μm, solid content concentration: 15.0% by mass).

[0136] In a 1 L polyethylene container, 34.0 g of the above-mentioned other polymer emulsion, 31.5 g of a 12% by mass aqueous solution of sodium polystyrene sulfonate (3.78 g of sodium polystyrene sulfonate), and 223.2 g of pure water were stirred and mixed at 32°C. To this, 2.80 g of 3,4-ethylenedioxythiophene was added, and the mixture was emulsified and mixed for 30 minutes using a homomixer ("Robomix", manufactured by Primix Corporation, 4000 rpm; the same applies hereafter) to prepare monomer solution (A) (total sodium polystyrene sulfonate content: 1.9 moles of sodium sulfonate groups per mole of 3,4-ethylenedioxythiophene).

[0137] 291.5 g of the above monomer solution (A) was placed in a stainless steel container connected to a high-sheer mixer ("Milder MDN303V", manufactured by Taiheiyo Kiko Co., Ltd., 5000 rpm, 32°C) and a circulation pump. The mixture was stirred while circulating it with the stirring blades and the high-sheer mixer, and 5.89 g of sodium peroxodisulfate and 6.88 g of a 1% by mass aqueous solution of iron(III) sulfate hexahydrate were added. The polymerization reaction was carried out for 24 hours to prepare a composite particle-containing solution (solid content (composite particle) concentration: 5.80% by mass, total content of sodium polystyrene sulfonate: 261 parts by mass per 100 parts by mass of conjugated conductive polymer). The above composite particle-containing solution was diluted to 1500 mL with pure water (solid content (composite particle) concentration: 4.73% by mass), and then subjected to dispersion treatment for 45 minutes using a high-pressure homogenizer ("TwinPanda 600", manufactured by Niro Soavi; 400 bar (40 MPa); the same applies hereafter). Furthermore, 1500 mL of the composite particle-containing solution diluted with pure water (solid content (composite particle) concentration: 3.99% by mass) was subjected to dispersion treatment for 135 minutes using a high-pressure homogenizer. 125.6 mL of cation exchange resin and 109.9 mL of anion exchange resin were added to this composite particle-containing solution, and the mixture was stirred for 3 hours to desalt it. The ion exchange resin was then filtered off (pH: 1.9, solid content (composite particle) concentration: 1.65% by mass). To 1000 g of the desalted liquid containing the composite particles described above, 7.5 g of morpholine (an alkaline compound) and 22.5 g of pure water were added to prepare the raw material liquid (1) (solid content (composite particles) concentration: 1.6% by mass, pH: 4.7).

[0138] [Manufacturing of Solid Electrolytic Capacitors] (Example 1) To 100 parts by mass of the raw material liquid (1) obtained in Manufacturing Example 1, 30 parts by mass of triethylene glycol was added and stirred at 25°C to prepare a conductive polymer-containing dispersion. A porous anode (material of the porous anode having a dielectric oxide film on its surface, aluminum) of a solid electrolytic capacitor element (withstand voltage 35V, design capacitance 150μF) was impregnated in the conductive polymer-containing dispersion for 5 minutes, and then dried in a hot air dryer ("ST-110", manufactured by ESPEC Corporation; the same applies hereafter) at 120°C for 30 minutes to manufacture a solid electrolytic capacitor 1 in which a solid electrolyte layer was formed on the surface of the dielectric oxide film of the porous anode. Table 1 shows the drying conditions of the solid electrolytic capacitor 1, the content (mass%) of each component in 100% by mass of the calculated solid electrolyte layer, and the equivalent series resistance (ESR) measured using the solid electrolytic capacitor 1.

[0139] (Examples 2-7, Comparative Examples 1-8) In Example 1, instead of 30 parts by mass of triethylene glycol, the electrical conductivity improvers shown in Table 1 and parts by mass thereof were used. Also, in Example 1, instead of drying at 120°C for 30 minutes, drying was performed at the heating temperature and heating time shown in Table 1. Solid electrolytic capacitors 2-15 were obtained in the same manner as in Example 1, except as described above. Table 1 shows the drying conditions for solid electrolytic capacitors 2-15, the content (by mass) of each component in 100% by mass of the calculated solid electrolyte layer, and the equivalent series resistance (ESR) measured using solid electrolytic capacitors 2-15.

[0140] In Table 1, "n.d." means that it was not detected.

[0141] As can be seen from the results shown in Table 1, Examples 1 to 7 of this embodiment (solid electrolytic capacitors in which the content of the electrical conductivity improver is 76.5 to 92.5% by mass of 100% by mass of the solid electrolyte layer) were found to have superior (lower) equivalent series resistance (ESR) in the high-frequency range (100 kHz) compared to Comparative Examples 1 to 8 of this embodiment (solid electrolytic capacitors in which the content of the electrical conductivity improver is not 76.5 to 92.5% by mass of 100% by mass of the solid electrolyte layer). Although the detailed mechanism of the above results is unknown, it is presumed that the predetermined amount of electrical conductivity improver present in the solid electrolyte layer inhibits the aggregation of the conjugated conductive polymer in the solid electrolyte layer, making it easier for the conjugated conductive polymer to form conductive paths.

Claims

1. A solid electrolytic capacitor comprising an anode, a dielectric film provided on the surface of the anode, and a solid electrolyte layer in contact with the dielectric film, wherein the solid electrolyte layer contains a conjugated conductive polymer, a polyanion, and an electrical conductivity improver, and the content of the electrical conductivity improver is 76.5 to 92.5% by mass of 100% by mass of the solid electrolyte layer.

2. The solid electrolytic capacitor according to claim 1, wherein the electrical conductivity improving agent comprises an organic solvent having two or more oxygen atoms in one molecule.

3. The solid electrolytic capacitor according to claim 1, wherein the electrical conductivity improving agent comprises an organic solvent having three or more oxygen atoms in one molecule.

4. The solid electrolytic capacitor according to any one of claims 1 to 3, wherein the electrical conductivity improving agent comprises an organic solvent having a boiling point of 200°C or higher.

5. A method for manufacturing a solid electrolytic capacitor according to any one of claims 1 to 3, comprising an anode, a dielectric film provided on the surface of the anode, and a solid electrolyte layer in contact with the dielectric film, the method comprising: attaching a conductive polymer-containing dispersion to the surface of the dielectric film; and drying the conductive polymer-containing dispersion to form a solid electrolyte layer containing a conjugated conductive polymer, a polyanion, and an electrical conductivity improver, wherein the content of the electrical conductivity improver is 76.5 to 92.5% by mass of 100% by mass of the solid electrolyte layer.

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