Solid electrolytic capacitor

Abstract

A solid electrolytic capacitor (100) according to one aspect of the present invention includes a capacitor element (170) which is provided with a first electrode layer (141), a dielectric layer (150) that is formed on the outer surface of the first electrode layer (141), a solid electrolyte layer (165a) that is formed on the outer surface of the dielectric layer (150), and a second electrode layer (160) that is formed on the outer surface of the solid electrolyte layer (165a). The solid electrolyte layer (165a) is formed of a polymer film which contains a crosslinked polymer that is obtained by crosslinking a polymer having a carbonyl group by means of a crosslinking agent that is composed of a dihydrazide compound, and a composite of polyethylene dioxythiophene and a polystyrene sulfonate.

Description

solid electrolytic capacitor

[0001] The present invention relates to a solid electrolytic capacitor. This application claims priority to Japanese Patent Application No. 2023-222782 filed on December 28, 2023, and Japanese Patent Application No. 2023-222795 filed on December 28, 2023, the contents of which are incorporated herein by reference.

[0002] Solid electrolytic capacitors are widely used in various electronic devices. Some solid electrolytic capacitors have a structure in which an anode layer made of a valve metal such as aluminum or tantalum, a dielectric layer formed on the outer surface of the anode layer, a solid electrolyte layer formed on the outer surface of the dielectric layer, and a cathode layer formed on the outer surface of the solid electrolyte layer are sequentially stacked.

[0003] Conventional solid electrolytic capacitors are described in Patent Documents 1 to 4. Patent Document 1 describes a solid electrolytic capacitor including an anode, a dielectric layer formed on the anode, a polyvinyl alcohol film formed on the dielectric layer, and a conductive polymer layer formed on the polyvinyl alcohol film.

[0004] Patent Document 2 describes a solid electrolytic capacitor including an element portion and a polymer disposed on or within the element portion. Patent Document 2 describes that the element portion includes an anode body, a dielectric layer formed on the surface of the anode body, a solid electrolyte layer covering at least a portion of the dielectric layer, and a cathode extraction layer covering at least a portion of the solid electrolyte layer. Patent Document 2 also describes that the polymer is disposed on or within the cathode extraction layer.

[0005] Furthermore, conventional solid electrolytic capacitors include those having a solid electrolyte layer formed using an aqueous dispersion of a composite of polyethylenedioxythiophene and polystyrene sulfonic acid (hereinafter, sometimes referred to as "PEDOT / PSS").

[0006] Patent Document 3 describes a process in which at least one crosslinking agent is applied to a capacitor body including at least an electrode body of an electrode material and a dielectric covering the surface of the electrode material, and a solid electrolyte including at least an electrically conductive material that completely or partially covers the dielectric surface, and then at least one solution or dispersion of a conjugated polymer is applied, and a polymer outer layer is formed by at least partially removing the solvent or dispersant. Patent Document 3 also describes that the solid electrolyte includes poly(3,4-ethylenedioxythiophene) / polystyrene sulfonic acid as a conductive polymer.

[0007] Patent Document 3 also describes that the crosslinking agent contains at least one diamine, triamine, oligoamine, or polymeric amine or a derivative thereof, at least one cation and additionally at least one amine group, or at least one polyvalent cation, and further describes that the crosslinking agent forms at least one polyvalent cation after application of a solution or dispersion.

[0008] Patent Document 4 describes a method for manufacturing a solid electrolytic capacitor including a capacitor element having a dielectric layer and a solid electrolyte layer. Patent Document 4 describes that the solid electrolyte layer is formed by sequentially performing a first step of applying a first conductive polymer solution in which conductive polymer fine particles are dispersed and drying to form a first conductive polymer layer, a second step of applying a coating solution to the first conductive polymer layer and drying, and a third step of applying a second conductive polymer solution in which conductive polymer fine particles are dispersed and drying to form a second conductive polymer layer.

[0009] Patent Document 4 also describes that pure water is added to a PEDOT / PSS solution, and the particle size of the fine particles is adjusted using a high-pressure homogenizer and a filter, thereby obtaining a first conductive polymer solution and a second conductive polymer solution. Patent Document 4 also describes that the coating solution contains at least one selected from aromatic sulfonic acids or salts thereof having a carboxyl group and a hydroxyl group, or two carboxyl groups in one molecule. Furthermore, the coating solution contains at least one selected from aromatic sulfonic acids or salts thereof having -NH２ It is disclosed that the cation of an amine compound having an amine group of a group, an —NH group, or an —N group is contained.

[0010] Japanese Patent No. 5895227 Japanese Patent Application Publication No. 2022-39775 Japanese Patent Application Publication No. 5592406 International Publication No. 2014 / 087617

[0011] Polymer films formed using aqueous dispersions of PEDOT / PSS have good electrical conductivity and heat resistance, making them suitable as materials for solid electrolyte layers. However, polymer films formed using aqueous dispersions of PEDOT / PSS have insufficient water resistance. Therefore, there is a demand for improved water resistance and durability in solid electrolytic capacitors having solid electrolyte layers made of polymer films formed using conventional aqueous dispersions of PEDOT / PSS.

[0012] One possible method for improving the water resistance of solid electrolytic capacitors is to form a cathode layer containing a metal film formed by plating. A possible method for forming the metal film that forms the cathode layer by plating is to immerse a partially manufactured laminate, which includes an anode layer, a dielectric layer, and a solid electrolyte layer, in a plating solution. The plating solution is typically an aqueous solution.

[0013] However, when manufacturing a solid electrolytic capacitor having a solid electrolyte layer made of a polymer film formed using an aqueous dispersion of PEDOT / PSS, the water resistance of the solid electrolyte layer is insufficient, making it difficult to use plating as a method for manufacturing the cathode layer. This is because if a laminate in the middle of manufacturing, in which an anode layer, a dielectric layer, and a solid electrolyte layer are formed, is immersed in a plating solution, the polymer film formed using the aqueous dispersion of PEDOT / PSS that forms the solid electrolyte layer will dissolve.

[0014] The present invention has been made in view of the above-mentioned problems, and has an object to provide a solid electrolytic capacitor having a solid electrolyte layer with good water resistance.

[0015] In order to solve the above problems, the following means are provided: A solid electrolytic capacitor according to a first aspect of the present invention includes a capacitor element including a first electrode layer, a dielectric layer formed on the outer surface of the first electrode layer, a solid electrolyte layer formed on the outer surface of the dielectric layer, and a second electrode layer formed on the outer surface of the solid electrolyte layer, wherein the solid electrolyte layer is made of a polymer film including a crosslinked polymer obtained by crosslinking a polymer having a carbonyl group with a crosslinking agent made of a dihydrazide compound, and a composite of polyethylenedioxythiophene and polystyrenesulfonic acid.

[0016] A solid electrolytic capacitor according to a second aspect of the present invention includes a capacitor element including a first electrode layer, a dielectric layer formed on the outer surface of the first electrode layer, a solid electrolyte layer formed on the outer surface of the dielectric layer, and a second electrode layer formed on the outer surface of the solid electrolyte layer, wherein the solid electrolyte layer has a polymer film containing a crosslinked polymer formed by crosslinking a composite of polyethylenedioxythiophene and polystyrenesulfonic acid with a crosslinking agent, and the crosslinking agent is a group selected from the group consisting of -NH ２ The present invention also includes salts of amine compounds containing a total of four or more of one or two types of groups selected from the group consisting of —NH— groups and —NH— groups.

[0017] A solid electrolytic capacitor according to a third aspect of the present invention includes a capacitor element including a first electrode layer, a dielectric layer formed on the outer surface of the first electrode layer, a solid electrolyte layer formed on the outer surface of the dielectric layer, and a second electrode layer formed on the outer surface of the solid electrolyte layer, wherein the solid electrolyte layer has a polymer film including a crosslinked polymer formed by crosslinking a composite of polyethylenedioxythiophene and polystyrenesulfonic acid with a crosslinking agent, and the crosslinking agent is made of a metal salt including a metal cation with a valence of two or more.

[0018] In the solid electrolytic capacitor according to the first aspect, the solid electrolyte layer included in the capacitor element is made of a polymer film containing a crosslinked polymer in which a polymer having a carbonyl group is crosslinked with a crosslinking agent made of a dihydrazide compound, and a composite of polyethylenedioxythiophene and polystyrene sulfonic acid. Therefore, the solid electrolytic capacitor according to the first aspect has good water resistance of the solid electrolyte layer and excellent water resistance. Furthermore, because the solid electrolyte layer of the solid electrolytic capacitor according to the first aspect has good water resistance, a plating method can be used to manufacture the cathode layer.

[0019] In the solid electrolytic capacitor according to the second and third aspects, the solid electrolyte layer included in the capacitor element has a polymer film containing a crosslinked polymer obtained by crosslinking a composite of polyethylenedioxythiophene and polystyrene sulfonic acid with a crosslinking agent, and the crosslinking agent is a —NH ２ The solid electrolytic capacitor according to the second and third aspects is made of a salt of an amine compound containing a total of four or more groups selected from one or two types of groups selected from the group consisting of —NH— groups and —NH— groups, or a metal salt containing a metal cation with a valence of two or more. Therefore, the solid electrolytic capacitor according to the second and third aspects has good water resistance of the solid electrolyte layer and excellent water resistance. Furthermore, because the solid electrolyte layer of the solid electrolytic capacitor according to the second and third aspects has good water resistance, a plating method can be used to manufacture the cathode layer.

[0020] FIG. 1 is a schematic cross-sectional view showing a solid electrolytic capacitor according to a first embodiment of the present invention. FIG. 2 is an enlarged cross-sectional view showing the periphery of the symbol II in FIG. 1. FIG. 3 is a schematic cross-sectional view taken along line III-III in FIG. 1. FIG. 4 is a schematic cross-sectional view showing a solid electrolytic capacitor according to a second embodiment of the present invention. FIG. 5 is a schematic cross-sectional view showing a solid electrolytic capacitor according to a third embodiment of the present invention. FIG. 6 is an enlarged cross-sectional view showing the periphery of the symbol II in FIG. 5. FIG. 7 is a schematic cross-sectional view taken along line III-III in FIG. 5. FIG. 8 is a schematic cross-sectional view showing a solid electrolytic capacitor according to a fifth embodiment of the present invention.

[0021] The present invention includes the following aspects: [1] A solid electrolytic capacitor including a capacitor element having a first electrode layer, a dielectric layer formed on the outer surface of the first electrode layer, a solid electrolyte layer formed on the outer surface of the dielectric layer, and a second electrode layer formed on the outer surface of the solid electrolyte layer, wherein the solid electrolyte layer is made of a polymer film containing a crosslinked polymer obtained by crosslinking a polymer having a carbonyl group with a crosslinking agent made of a dihydrazide compound, and a composite of polyethylenedioxythiophene and polystyrenesulfonic acid.

[0022] [2] The solid electrolytic capacitor according to [1], wherein the first electrode layer is made of aluminum foil having an average thickness of 70 μm to 220 μm, and the solid electrolyte layer has an end face thickness of 5 μm or more and a thickness of a region excluding the end faces of 25 μm or less. [3] The solid electrolytic capacitor according to [1], wherein the first electrode layer is a block-shaped material made of tantalum, and the solid electrolyte layer has vertex and edge thicknesses of 5 μm or more and a face thickness of 25 μm or less. [4] The solid electrolytic capacitor according to any one of [1] to [3], wherein the polymer having a carbonyl group has a polyvinyl alcohol skeleton.

[0023] [5] The solid electrolytic capacitor according to any one of [1] to [4], wherein the ratio of the structural units derived from the polymer having a carbonyl group to the total mass of the structural units derived from the polymer having a carbonyl group forming the crosslinked polymer and the composite is 70 mass% or less, and the ratio of the structural units derived from the crosslinking agent to the mass of the structural units derived from the polymer having a carbonyl group is 15 mass% or less. [6] The solid electrolytic capacitor according to any one of [1] to [4], wherein the ratio of the structural units derived from the polymer having a carbonyl group to the total mass of the structural units derived from the polymer having a carbonyl group forming the crosslinked polymer and the composite is 30 mass% or less, and the ratio of the structural units derived from the crosslinking agent to the mass of the structural units derived from the polymer having a carbonyl group is 10 mass% or less.

[0024] [7] The solid electrolytic capacitor according to any one of [1] to [6], wherein the second electrode layer includes a metal layer made of any metal selected from Cu, Ni, Sn, Zn, Pd, Ag, and Au.

[0025] [8] A capacitor element including: a first electrode layer; a dielectric layer formed on the outer surface of the first electrode layer; a solid electrolyte layer formed on the outer surface of the dielectric layer; and a second electrode layer formed on the outer surface of the solid electrolyte layer, wherein the solid electrolyte layer has a polymer film containing a crosslinked polymer obtained by crosslinking a composite of polyethylenedioxythiophene and polystyrenesulfonic acid with a crosslinking agent, and the crosslinking agent is -NH ２ A solid electrolytic capacitor includes a salt of an amine compound containing a total of four or more of one or two types of groups selected from the group consisting of —NH— groups and —NH— groups.

[0026] [9] A solid electrolytic capacitor including a capacitor element having: a first electrode layer; a dielectric layer formed on the outer surface of the first electrode layer; a solid electrolyte layer formed on the outer surface of the dielectric layer; and a second electrode layer formed on the outer surface of the solid electrolyte layer, wherein the solid electrolyte layer has a polymer film containing a crosslinked polymer formed by crosslinking a composite of polyethylenedioxythiophene and polystyrenesulfonic acid with a crosslinking agent, and the crosslinking agent is made of a metal salt containing a metal cation having a valence of two or more.

[0027]

[10] The solid electrolytic capacitor according to [9], wherein the cross-linking agent is calcium chloride.

[11] The solid electrolytic capacitor according to [8] or

[10] , wherein the second electrode layer includes a metal layer made of any metal selected from Cu, Ni, Sn, Zn, Pd, Ag, and Au.

[0028]

[12] The solid electrolytic capacitor according to

[11] , wherein the second electrode layer has a plating seed layer on the surface of the metal layer facing the solid electrolyte layer, and the plating seed layer contains a conductive material and a catalyst support material.

[13] The solid electrolytic capacitor according to

[12] , wherein the catalyst support material contains one or more compounds selected from polypyrrole derivatives, polythiophene derivatives, and polyfuran derivatives.

[14] The solid electrolytic capacitor according to

[12] or

[13] , wherein the conductive material is a carbon material.

[0029] The solid electrolytic capacitor of this embodiment will be described in detail below with reference to the drawings as appropriate. The drawings used in the following description may show characteristic portions enlarged for the sake of clarity. Therefore, the dimensional ratios of the components may differ from the actual ones. The materials, dimensions, etc. exemplified in the following description are merely examples, and the present invention is not limited to them. Appropriate modifications can be made within the scope of the present invention.

[0030] [First Embodiment] (Solid Electrolytic Capacitor) Fig. 1 is a schematic cross-sectional view showing a solid electrolytic capacitor according to a first embodiment of the present invention. Fig. 2 is an enlarged cross-sectional view showing an enlarged view of the area around symbol II in Fig. 1. Fig. 3 is a schematic cross-sectional view taken along line III-III shown in Fig. 1. In Figs. 1 and 3, symbol T indicates the thickness direction of capacitor element 170. In Fig. 1, symbol L indicates the length direction perpendicular to thickness direction T of capacitor element 170. In Fig. 3, symbol W indicates the width direction of capacitor element 170, which is the direction perpendicular to thickness direction T and length direction L of capacitor element 170.

[0031] 1 to 3 includes a resin mold layer 110 having a substantially rectangular parallelepiped outer shape, a plurality of capacitor elements 170 (four in FIG. 1 ) provided inside the resin mold layer 110, a first terminal 120, and a second terminal 130. The resin mold layer 110 forms the exterior of the solid electrolytic capacitor 100. The resin mold layer 110 is made of an insulating resin material containing, for example, a resin such as an epoxy resin and a filler such as silica.

[0032] The first terminal 120 is made of a conductive material such as Cu. The first terminal 120 is electrically connected to the second electrode layer 160 of each of the plurality of capacitor elements 170 and is extended to the outside of the resin mold layer 110. The portion of the first terminal 120 located outside the resin mold layer 110 is bent along the outer surface of the resin mold layer 110.

[0033] The second terminal 130 is made of a conductive material such as Cu. The second terminal 130 is electrically connected to the first electrode layer 141 of each of the plurality of capacitor elements 170 and is extended to the outside of the resin mold layer 110. The portion of the second terminal 130 located outside the resin mold layer 110 is bent along the outer surface of the resin mold layer 110.

[0034] 1 and 3, the plurality of capacitor elements 170 included in the solid electrolytic capacitor 100 are stacked in the thickness direction T. The number of capacitor elements 170 included in the solid electrolytic capacitor 100 of this embodiment is not particularly limited, and may be four as shown in FIGS. 1 and 3, one to three, or five or more.

[0035] 1 and 3, the plurality of capacitor elements 170 are electrically connected to one another by connecting conductor layers 190. Examples of connecting conductor layers 190 include a conductive adhesive containing Ag. Furthermore, as shown in FIG. 1, the ends of the first electrode layers 141 of the capacitor elements 170 adjacent to one another in the stacking direction on the side of the second terminal 130 are electrically connected to one another by resistance welding or the like.

[0036] As shown in Figures 1 and 2, each capacitor element 170 includes a first electrode layer 141, a dielectric layer 150 formed on the outer surface of the first electrode layer 141, a solid electrolyte layer 165a formed on the outer surface of the dielectric layer 150, and a second electrode layer 160 formed on the outer surface of the solid electrolyte layer 165a.

[0037] (First Electrode Layer 141) The first electrode layer 141 functions as an anode in the solid electrolytic capacitor 100. The first electrode layer 141 is made of a metal film having a finely textured surface, as shown in Fig. 2. The finely textured surface of the first electrode layer 141 increases the surface area of ​​the first electrode layer 141, thereby increasing the capacity of the solid electrolytic capacitor 100.

[0038] A film made of a valve metal such as aluminum, tantalum, niobium, titanium, hafnium, zirconium, zinc, tungsten, bismuth, or antimony can be used as the first electrode layer 141. Among the films made of the above valve metals, it is preferable to use any one selected from an aluminum film, a tantalum film, and a niobium film as the first electrode layer 141. The reason for this is that by anodizing the outer surface of the first electrode layer 141, the dielectric layer 150 can be stably formed on the outer surface of the first electrode layer 141.

[0039] When the first electrode layer 141 is an aluminum foil, it preferably has an average thickness of 70 μm to 220 μm. If the average thickness of the aluminum foil is 70 μm or more, the first electrode layer 141 has sufficient strength and the solid electrolytic capacitor 100 has sufficient capacitance. Furthermore, if the average thickness of the aluminum foil is 220 μm or less, the first electrode layer 141 can be easily electrically connected to the second terminal 130.

[0040] (Dielectric Layer 150) As shown in Fig. 2, the dielectric layer 150 is formed so as to cover the first electrode layer 141, following the irregularities on the outer surface of the first electrode layer 141. The dielectric layer 150 is made of a metal oxide film having electrical insulation properties. For example, when the first electrode layer 141 is an aluminum foil, the dielectric layer 150 is preferably made of an aluminum oxide film. The thickness of the dielectric layer 150 is usually 1 nm to 1 µm.

[0041] 2, the solid electrolyte layer 165a is formed along the outer surface of the dielectric layer 150, which is formed along the uneven shape of the outer surface of the first electrode layer 141. That is, the solid electrolyte layer 165a is formed so as to fill in the minute recesses formed in the outer surface of the first electrode layer 141 via the dielectric layer 150. The solid electrolyte layer 165a in this embodiment is made of a polymer film described below.

[0042] [Polymer Film] The polymer film forming the solid electrolyte layer 165a includes a crosslinked polymer in which a polymer having a carbonyl group is crosslinked with a crosslinking agent made of a dihydrazide compound, and a composite of polyethylenedioxythiophene and polystyrene sulfonic acid (PEDOT / PSS) represented by the following formula (1):

[0043]

[0044] (Crosslinked Polymer) The crosslinked polymer contained in the polymer film of this embodiment is obtained by crosslinking the carbonyl group of a polymer having a carbonyl group with the dihydrazide group of a dihydrazide compound, which is a crosslinking agent, through a crosslinking reaction. The crosslinked polymer has a three-dimensional network structure and has excellent water resistance, and holds the PEDOT / PSS contained in the polymer film, thereby imparting water resistance to the polymer film of this embodiment. The crosslinked polymer contained in the polymer film of this embodiment may be of only one type, or may be of two or more types.

[0045] Examples of polymers having a carbonyl group (—O—C(═O)R) that can be used to form a crosslinked polymer include water-soluble polymers having a carbonyl group, such as polyvinyl alcohol resins, polyacrylamide resins, polyethylene glycol resins, and cellulose resins.

[0046] Among these, it is preferable to use a polymer having a polyvinyl alcohol skeleton as the polymer having a carbonyl group. Crosslinked polymers in which a polymer having a polyvinyl alcohol skeleton is crosslinked with a crosslinking agent made of a dihydrazide compound have good water resistance. Therefore, polymer films containing crosslinked polymers in which a polymer having a polyvinyl alcohol skeleton is crosslinked have even better water resistance. Furthermore, an aqueous solution of a polymer having a polyvinyl alcohol skeleton can be easily mixed with an aqueous dispersion of PEDOT / PSS, allowing for efficient formation of a polymer film when produced by the production method described below. In particular, it is preferable to use a modified polyvinyl alcohol represented by the following formula (2), in which a carbonyl group is bonded to a polyvinyl alcohol skeleton. This is because it has good reactivity with a crosslinking agent made of a dihydrazide compound, making it easier to obtain a polymer film with better water resistance.

[0047] (In formula (2), n and m represent the number of repeating units, and n+m is 100 to 5000. R is a monovalent substituent.)

[0048] When a modified polyvinyl alcohol represented by formula (2) is used as the polymer having a carbonyl group (—O—C(═O)R), the average degree of polymerization represented by n+m in formula (2) can be 100 to 5,000, and preferably 300 to 3,500. When the average degree of polymerization (n+m) of the modified polyvinyl alcohol represented by formula (2) is 100 or more, a crosslinked polymer having better water resistance can be obtained, and a polymer film having better water resistance can be obtained. When the average degree of polymerization of the modified polyvinyl alcohol represented by formula (2) is 5,000 or less, it becomes easily mixed with an aqueous dispersion of PEDOT / PSS, and when a polymer film is produced by the production method described below, a polymer film can be efficiently formed.

[0049] The saponification degree [[n / (n+m)]×100] of the modified polyvinyl alcohol represented by formula (2) is preferably 95% to 99%. A saponification degree of 95% or higher improves the hydrophilicity of the modified polyvinyl alcohol represented by formula (2), allowing for the formation of an aqueous solution that is more easily mixed with an aqueous dispersion of PEDOT / PSS. Furthermore, a saponification degree of 99% or lower ensures sufficient hydrophobicity improvement due to the presence of —O—OC(═O)R groups in the modified polyvinyl alcohol represented by formula (2). As a result, a polymer film with better water resistance is more likely to be obtained.

[0050] The modified polyvinyl alcohol represented by formula (2) preferably has a carbonyl group (-O-C(=O)R), for example, in which the monovalent substituent represented by R in formula (2) is any one selected from alkyl groups having 1 to 5 carbon atoms. R in formula (2) is particularly preferably a methyl group because it is a functional group that has good reactivity with the dihydrazide compound that is the crosslinking agent. In the present embodiment, the polymer having a carbonyl group (-O-C(=O)R) used as a material for forming the crosslinked polymer may be of only one type, or may be of two or more types.

[0051] As the crosslinking agent made of a dihydrazide compound used in forming the crosslinked polymer, known dihydrazide compounds can be used, such as adipic acid dihydrazide, sebacic acid dihydrazide, isophthalic acid dihydrazide, and 7,11-octadecadiene-1,18-dicarbohydrazide. Among these, as the crosslinking agent made of a dihydrazide compound, it is preferable to use adipic acid dihydrazide represented by the following formula (3) and / or 7,11-octadecadiene-1,18-dicarbohydrazide represented by the following formula (4), because they have good reactivity with polymers having carbonyl groups. In the present embodiment, the crosslinking agent made of a dihydrazide compound used as a material for forming the crosslinked polymer may be one type or two or more types.

[0052]

[0053] In this embodiment, for example, when modified polyvinyl alcohol represented by formula (2) is used as the polymer having a carbonyl group and adipic acid dihydrazide represented by formula (3) is used as the cross-linking agent made of a dihydrazide compound, a cross-linked polymer is formed as shown below. That is, a cross-linking reaction occurs between the carbonyl group of the modified polyvinyl alcohol represented by formula (2) and the dihydrazide group of the adipic acid dihydrazide represented by formula (3), and the modified polyvinyl alcohol represented by formula (2) is cross-linked by the adipic acid dihydrazide represented by formula (3), forming a cross-linked polymer containing water and a cross-linked structure represented by the following formula (5).

[0054]

[0055] In the polymer film of this embodiment, the ratio of the structural units derived from the polymer having a carbonyl group to the total mass of the structural units derived from the polymer having a carbonyl group forming the crosslinked polymer and PEDOT / PSS is preferably 70% by mass or less, more preferably 30% by mass or less. If the ratio of the structural units derived from the polymer having a carbonyl group is 70% by mass or less, this prevents the conductivity of the polymer film from being impaired due to an excessive proportion of structural units derived from the polymer having a carbonyl group. The ratio of the structural units derived from the polymer having a carbonyl group to the total mass is preferably 5% by mass or more, more preferably 10% by mass or more, since this ensures the content of the crosslinked polymer contained in the polymer film and makes it easier to obtain a polymer film with better water resistance.

[0056] In the polymer membrane of this embodiment, the ratio of structural units derived from the polymer having a carbonyl group to the total mass is preferably 70% by mass or less, and the ratio of structural units derived from the crosslinking agent to the mass of structural units derived from the polymer having a carbonyl group is preferably 15% by mass or less. Furthermore, it is more preferable that the ratio of structural units derived from the polymer having a carbonyl group is 30% by mass or less, and the ratio of structural units derived from the crosslinking agent is 10% by mass or less. When the ratio of structural units derived from the crosslinking agent is 15% by mass or less, the conductivity of the polymer membrane can be prevented from being impaired by the presence of many structural units derived from the crosslinking agent that do not form a crosslinked structure with the structural units derived from the polymer having a carbonyl group. The ratio of structural units derived from the crosslinking agent to the mass of structural units derived from the polymer having a carbonyl group is preferably 3% by mass or more, more preferably 5% by mass or more, since this ensures the content of crosslinked polymers contained in the polymer membrane and makes it easier to obtain a polymer membrane with better water resistance.

[0057] The content of PEDOT / PSS in the polymer film of this embodiment is preferably 30% by mass or more, and more preferably 60% by mass or more. This is because a polymer film with good conductivity is obtained when the content of PEDOT / PSS is 30% by mass or more. Furthermore, the content of PEDOT / PSS in the polymer film is preferably 85% by mass or less, and more preferably 75% by mass or less. This is because a polymer film with a sufficient amount of crosslinked polymer and good water resistance is more easily obtained when the content of PEDOT / PSS is 85% by mass or less.

[0058] The polymer membrane of this embodiment contains the crosslinked polymer described above and PEDOT / PSS represented by formula (1). In addition, one or more other components may be further contained as needed depending on the intended use of the polymer membrane. Examples of such other components include known crosslinking agents other than dihydrazide compounds, known polymers without carbonyl groups, etc. As known polymers without carbonyl groups, water-soluble or water-dispersible polymers can be preferably used, and specific examples thereof include sulfonated polyester resins.

[0059] The polymer film of this embodiment includes a crosslinked polymer in which a polymer having a carbonyl group is crosslinked with a crosslinking agent made of a dihydrazide compound, and PEDOT / PSS, thereby providing the polymer film with excellent electrical conductivity, heat resistance, and water resistance.

[0060] The solid electrolyte layer 165a preferably has a sufficient thickness to fill minute recesses formed in the outer surface of the first electrode layer 141 via the dielectric layer 150, and preferably has a substantially uniform thickness. This is because the solid electrolytic capacitor 100 has a suppressed leakage current. For example, if the first electrode layer 141 is made of aluminum foil with an average thickness of 70 μm to 220 μm, the thickness of the solid electrolyte layer 165a is preferably 5 μm or more at the end faces and 25 μm or less in the region excluding the end faces. This is because the solid electrolytic capacitor 100 has a further suppressed leakage current.

[0061] Furthermore, in this embodiment, solid electrolyte layer 165a is preferably composed of two polymer films: a first polymer film disposed on the dielectric layer 150 side; and a second polymer film, which is composed of a polymer film having a different composition from the first polymer film and is disposed on the second electrode layer 160 side. The reason for this is that, for example, by making the first polymer film easy to form in minute recesses present on the outer surface of dielectric layer 150 and making the second polymer film easy to form with a sufficient thickness on the first polymer film, a more reliable solid electrolytic capacitor 100 can be obtained.

[0062] In this embodiment, when the solid electrolyte layer 165a is composed of two polymer films, it is preferable that the polymer having a carbonyl group and the cross-linking agent composed of a dihydrazide compound used as the cross-linking polymer material in the first and second polymer films are the same. This is because good adhesion between the first and second polymer films can be obtained. It is also preferable that the first polymer film does not contain any resin components other than the cross-linking polymer and PEDOT / PSS. This is because a first polymer film with better conductivity can be formed in the fine recesses present on the outer surface of the dielectric layer 150.

[0063] On the other hand, the second polymer film preferably contains, in addition to the crosslinked polymer and PEDOT / PSS, a structural unit derived from a polymer that does not have a carbonyl group, such as a sulfonated polyester resin. The reason for this is that the inclusion of a structural unit derived from a polymer that does not have a carbonyl group improves the film-formability of the second polymer film, making it easier to obtain solid electrolyte layer 165a with a small difference in thickness between the end face of first electrode layer 141, excluding the end face connected to second terminal 130 on which solid electrolyte layer 165a is not formed, and the region excluding the end face of first electrode layer 141, thereby obtaining solid electrolytic capacitor 100 with further suppressed leakage current.

[0064] 1, in capacitor element 170, solid electrolyte layer 165a is not provided on the end of the outer surface of first electrode layer 141 that is connected to second terminal 130. As shown in FIGS. 1 and 2, the region of the outer surface of first electrode layer 141 that is not provided with solid electrolyte layer 165a is covered with insulating resin layer 151. As insulating resin layer 151, for example, a layer made of insulating resin such as polyimide resin, polyamide resin, epoxy resin, or acrylic resin can be used.

[0065] (Second Electrode Layer 160) The second electrode layer 160 formed on the outer surface of the solid electrolyte layer 165a is made up of a carbon layer 161a and a metal layer 162 formed on the outer surface of the carbon layer 161a. In this embodiment, the second electrode layer 160 is described as being made up of two layers, the carbon layer 161a and the metal layer 162. However, the second electrode layer may be made up of only one layer, for example, the carbon layer 161a or the metal layer 162, or may be made up of three or more layers including a plurality of the carbon layers 161a and / or the metal layers 162.

[0066] The carbon layer 161a contains a carbon material and may contain a binder resin and / or additives as necessary. Examples of carbon materials used in the carbon layer 161a include graphite, carbon black, graphene flakes, and carbon nanotubes. Examples of binder resins that may be contained in the carbon layer 161a include known thermoplastic resins or curable resins that can be used as binder resins. Examples of additives that may be contained in the carbon layer 161a include dispersants, surfactants, antioxidants, preservatives, bases, and / or acids.

[0067] The metal layer 162 can be a metal layer made of any metal selected from Ag, Cu, Ni, Sn, Zn, Pd, and Au. Because of their good conductivity, an Ag layer or a Cu layer is preferred, and a Cu layer is particularly preferred. When the metal layer 162 is a Cu layer, the solid electrolytic capacitor 100 has good conductivity and even better water resistance. Furthermore, when the metal layer 162 is a Cu layer, the solid electrolytic capacitor 100 has even better water resistance and durability, so it is more preferred that the metal layer 162 be disposed as the outermost layer of the second electrode layer 160.

[0068] (Method of Manufacturing Solid Electrolytic Capacitor) To manufacture the solid electrolytic capacitor 100 of this embodiment, first, a plurality of capacitor elements 170 are manufactured.

[0069] First, a first electrode layer 141 made of a metal foil having a finely textured surface is prepared. The first electrode layer 141 can be formed by subjecting the surface of a metal film to a surface roughening treatment or surface enlargement treatment using a known method. Next, a dielectric layer 150 is provided on the outer surface of the first electrode layer 141. The dielectric layer 150 can be formed by oxidizing the surface portion of the first electrode layer 141. For example, when the first electrode layer 141 is an aluminum foil, the dielectric layer 150 made of an aluminum oxide film can be formed on the outer surface of the first electrode layer 141 by immersing the aluminum film in an ammonium adipate aqueous solution and anodizing it.

[0070] Next, an insulating resin layer 151 is formed on the end of the outer surface of the dielectric layer 150 that is connected to the second terminal 130 (i.e., the area where the solid electrolyte layer 165a is not formed). The insulating resin layer 151 can be formed by applying paint containing an insulating resin such as polyimide resin, polyamide resin, epoxy resin, or acrylic resin using a known method, followed by drying and curing.

[0071] (Method for manufacturing solid electrolyte layer (polymer film)) Next, a solid electrolyte layer 165a made of a polymer film containing a cross-linked polymer and PEDOT / PSS is provided on the outer surface of the dielectric layer 150 by the method described below. First, an aqueous dispersion of PEDOT / PSS, an aqueous solution of a polymer having a carbonyl group, an aqueous solution of a dihydrazide compound as a cross-linking agent, and other components that may be included as necessary are mixed and stirred to form a resin coating material.

[0072] When producing a resin coating, the order in which the aqueous dispersion of PEDOT / PSS, the aqueous solution of the polymer having a carbonyl group, and the aqueous solution of the dihydrazide compound as a cross-linking agent are mixed is not particularly limited. For example, all of the materials used in the resin coating may be mixed and stirred at the same time, or the resin coating may be produced by mixing the aqueous dispersion of PEDOT / PSS and the aqueous solution of the polymer having a carbonyl group to form a mixed liquid, and then mixing the mixed liquid with an aqueous solution of the dihydrazide compound as a cross-linking agent.

[0073] The concentrations of PEDOT / PSS in the aqueous dispersion of PEDOT / PSS used in producing the resin coating in this embodiment, the concentration of the polymer having a carbonyl group in the aqueous solution of the polymer having a carbonyl group, and the concentration of the dihydrazide compound in the aqueous solution of the dihydrazide compound are not particularly limited and can be set to concentrations that make mixing and stirring easy. The concentrations of PEDOT / PSS, the polymer having a carbonyl group, and the dihydrazide compound contained in the resin coating are set to concentrations that correspond to the proportion of PEDOT / PSS in the polymer film, the proportion of structural units derived from the polymer having a carbonyl group contained in the polymer film, and the proportion of structural units derived from the crosslinker, respectively.

[0074] The aqueous dispersion of PEDOT / PSS used in producing the resin coating can be one consisting of only PEDOT / PSS and water. The aqueous dispersion of PEDOT / PSS may contain, in addition to PEDOT / PSS and water, one or more of the other components described above. Specifically, the aqueous dispersion of PEDOT / PSS may contain PEDOT / PSS, water, and a sulfonated polyester resin, which is a polymer having no carbonyl groups.

[0075] Next, the resin paint prepared in this manner is applied to the outer surface of the dielectric layer 150, excluding the end connected to the second terminal 130 (i.e., the area where the insulating resin layer 151 is not formed), to form a coating film. The resin paint can be applied to the outer surface of the dielectric layer 150 by known methods such as immersing the area of ​​the first electrode layer 141, on whose outer surface the dielectric layer 150 and the insulating resin layer 151 are formed, where the insulating resin layer 151 is not formed, in the resin paint, dispensing, screen printing, or spray coating. A preferred method for applying the resin paint to the outer surface of the dielectric layer 150 is to immerse the area of ​​the dielectric layer 150 formed on the outer surface of the first electrode layer 141, where the solid electrolyte layer 165a is to be formed, in the resin paint. This is because the resin paint can be easily applied to the fine recesses present in the outer surface of the dielectric layer 150.

[0076] Next, the coating film formed on the outer surface of the dielectric layer 150 is dried to remove water from the coating film, which causes a reaction between the carbonyl group of the carbonyl-containing polymer and the dihydrazide group of the dihydrazide compound, which is a crosslinking agent, in the coating film to form a crosslinked polymer having a crosslinked structure, thereby forming the polymer film of this embodiment containing PEDOT / PSS and the crosslinked polymer.

[0077] As a method for removing water from the coating film, a known method such as heat treatment at a temperature of 80°C to 150°C can be used, and the method can be appropriately determined depending on the composition of the resin paint, the thickness of the coating film, etc. In this embodiment, the polymer film obtained by removing the water from the coating film may be washed. The polymer film can be washed using water, for example. By performing the above steps, a solid electrolyte layer 165a made of a polymer film is formed.

[0078] The solid electrolyte layer 165a made of the polymer membrane of this embodiment may be manufactured by applying the above-described resin coating to form a coating film and then removing the water from the coating film, either once or by repeating the above process multiple times to form a polymer membrane of a predetermined thickness. Because the polymer membrane of this embodiment has good water resistance, repeating the above process multiple times makes it easy to obtain a polymer membrane of a uniform and sufficient thickness. This is because the polymer membrane's good water resistance makes it less likely for the polymer membrane to be dissolved by the water contained in the resin coating, even if a resin coating is applied to the polymer membrane in the second or subsequent process.

[0079] On the other hand, if the water resistance of the polymer film is insufficient, for example, when a resin coating is applied to the polymer film formed in the first step in the second step, the polymer film formed in the first step will re-elute and fall off in part or in whole, resulting in an uneven or insufficient thickness of the polymer film formed in the second step.

[0080] In particular, when using a method in which the first electrode layer 141, which is made of a metal film having a dielectric layer 150 formed on its outer surface, is immersed in a resin coating to apply the resin coating, the polymer film formed on the end surface of the first electrode layer 141 is likely to fall off in the second or subsequent steps, making it difficult to form a polymer film with sufficient thickness on the end surface of the first electrode layer 141. This tends to increase the leakage current of the solid electrolytic capacitor 100. Furthermore, in order to form a polymer film with sufficient thickness on the end surface of the first electrode layer 141, the polymer film formation process must be performed many times, which makes it difficult to efficiently manufacture the solid electrolyte layer 165a. Furthermore, performing the above process many times tends to thicken the polymer film formed on the region excluding the end surface of the first electrode layer 141, which tends to increase the difference in thickness between the polymer film formed on the end surface of the first electrode layer 141 and the polymer film formed on the region excluding the end surface of the first electrode layer 141.

[0081] The polymer film of this embodiment has good water resistance. Therefore, even if the first electrode layer 141, which is a metal film having the dielectric layer 150 formed on its outer surface, is immersed in a resin coating material in the second or subsequent steps, the polymer film formed on the end surface of the first electrode layer 141 is unlikely to dissolve. Therefore, by repeating the above steps multiple times, a polymer film having a sufficient thickness can be easily formed on the end surface of the first electrode layer 141. As a result, a solid electrolytic capacitor 100 with low leakage current can be formed. Furthermore, even if the above steps are performed only a few times, a polymer film having a sufficient thickness can be formed on the end surface of the first electrode layer 141, thereby efficiently manufacturing the solid electrolyte layer 165a. Furthermore, because the polymer film formed on the end surface of the first electrode layer 141 is unlikely to dissolve, the difference in thickness between the polymer film formed on the end surface of the first electrode layer 141 and the polymer film formed in the region other than the end surface of the first electrode layer 141 is small, making it easy to form a solid electrolyte layer 165a with a uniform thickness.

[0082] Furthermore, when the solid electrolyte layer 165a in this embodiment is composed of two polymer membrane layers, a first polymer membrane disposed on the dielectric layer 150 side and a second polymer membrane disposed on the second electrode layer 160 side, it can be manufactured, for example, by the following method. First, the first polymer membrane is manufactured using the method for manufacturing the solid electrolyte layer 165a composed of a polymer membrane described above. Then, a second polymer membrane is manufactured in the same manner as the first polymer membrane on the outer surface of the dielectric layer 150 on which the first polymer membrane has been formed, using a resin paint whose components are different from the resin paint used to manufacture the first polymer membrane.

[0083] When the solid electrolyte layer 165a is composed of two polymer layers, a first polymer layer and a second polymer layer, for example, the resin paint used to manufacture the first polymer layer may be an aqueous dispersion of PEDOT / PSS consisting of only PEDOT / PSS and water, and the resin paint used to manufacture the second polymer layer may be an aqueous dispersion of PEDOT / PSS consisting of PEDOT / PSS, water, and a sulfonated polyester resin, which is a polymer without a carbonyl group.

[0084] Next, the second electrode layer 160 is provided on the outer surface of the solid electrolyte layer 165a. In the present embodiment, for example, when the second electrode layer 160 is composed of a carbon layer 161a and a metal layer 162 formed on the outer surface of the carbon layer 161a, it can be manufactured by the following method. First, a carbon paste containing a carbon material and, if necessary, a binder resin and / or additives is prepared. Then, the carbon paste is applied to the outer surface of the solid electrolyte layer 165a by a known method and dried to form the carbon layer 161a.

[0085] In this embodiment, since the solid electrolyte layer 165a is made of the above-described polymer film, the solid electrolyte layer 165a has good water resistance. Therefore, in this embodiment, when the metal layer 162 is formed using a plating method, for example, water in a plating solution can be prevented from seeping into the solid electrolyte layer 165a through the carbon layer 161a or through portions where the carbon layer 161a is not formed, preventing the solid electrolyte layer 165a from dissolving. Therefore, in this embodiment, plating can be used as a method for manufacturing the metal layer 162.

[0086] Therefore, in this embodiment, for example, when the metal layer 162 is a Cu layer, the Cu layer can be formed on the outer surface of the solid electrolyte layer 165a on which the carbon layer 161a has been formed using an electroless Cu plating method. Specifically, a seed paste containing a carbon material, polypyrrole particles, and a binder resin is prepared. The seed paste is then applied to the outer surface of the solid electrolyte layer 165a on which the carbon layer 161a has been formed by a known method, and dried to form a seed layer. The solid electrolyte layer 165a on which the carbon layer 161a and the seed layer have been formed is then immersed in a plating solution, and electroless Cu plating is performed under known conditions. This results in the formation of the metal layer 162 made of a Cu layer. The plating solution used to form the Cu layer can be a known plating solution used in electroless Cu plating, or it may be an aqueous solution.

[0087] Furthermore, when the metal layer 162 is an Ag layer, it can be manufactured, for example, by the following method. A known Ag paste containing Ag particles and a binder resin is prepared. The Ag paste is then applied by a known method to the outer surface of the solid electrolyte layer 165a on which the carbon layer 161a has been formed, and then dried and hardened. By performing the above steps, multiple capacitor elements 170 can be obtained.

[0088] Next, a plate-shaped first terminal piece that will become the first terminal 120 and a plate-shaped second terminal piece that will become the second terminal 130 are prepared and arranged in a straight line while being spaced apart from each other. Next, a plurality of capacitor elements 170 are stacked and arranged on the first terminal piece and the second terminal piece. At this time, the second electrode layer 160 of the plurality of capacitor elements 170 is placed on the first terminal piece, and the first electrode layer 141 is placed on the second terminal piece.

[0089] Then, on the second electrode layer 160 side, a conductive adhesive that will become the connecting conductor layer 190 is interposed between adjacent capacitor elements 170. Similarly, a conductive adhesive that will become the connecting conductor layer 190 is interposed between a first terminal piece and an adjacent capacitor element 170. This allows the second electrode layers 160 and the first terminal pieces of the multiple capacitor elements 170 to be electrically connected by the connecting conductor layer 190. Thereafter, one ends of the first electrode layers 141 of the multiple capacitor elements 170 are electrically connected to the second terminal piece using a method such as welding.

[0090] Next, the first terminal piece, the second terminal piece and the plurality of capacitor elements 170 are placed in a mold so that the end of the first terminal piece located opposite the second terminal piece and the end of the second terminal piece located opposite the first terminal piece are exposed, and a resin mold layer 110 is formed using an insulating resin material containing a resin such as epoxy resin and a filler such as silica.

[0091] Thereafter, the first terminal piece protruding outward from the resin mold layer 110, inside which the plurality of capacitor elements 170 are provided, is bent along the outer surface of the resin mold layer 110 to form the first terminal 120. The second terminal piece protruding outward from the resin mold layer 110 is bent along the outer surface of the resin mold layer 110 to form the second terminal 130. By performing the above steps, the solid electrolytic capacitor 100 of this embodiment is obtained.

[0092] Second Embodiment (Solid Electrolytic Capacitor) Fig. 4 is a schematic cross-sectional view showing a solid electrolytic capacitor according to a second embodiment of the present invention. Solid electrolytic capacitor 200 of this embodiment shown in Fig. 4 includes resin mold layer 11 having a substantially rectangular parallelepiped outer shape, one capacitor element provided inside resin mold layer 11, first terminal 12, and second terminal 13.

[0093] The resin mold layer 11 forms the exterior of the solid electrolytic capacitor 200, and may be the same as the resin mold layer 110 in the solid electrolytic capacitor 100 of the first embodiment.

[0094] The first terminal 12 is made of a conductive material such as Cu. The first terminal 12 is electrically connected to the second electrode layer 16 of the capacitor element by a connecting conductor layer 19 and is extended to the outside of the resin molded layer 11. The connecting conductor layer 19 may be made of, for example, a conductive adhesive containing Ag. The portion of the first terminal 12 located inside the resin molded layer 11 is bent to conform to the outer shape of the first electrode layer 14, which is a substantially rectangular block. The portion of the first terminal 12 located outside the resin molded layer 11 is bent to conform to the outer surface of the resin molded layer 11.

[0095] The second terminal 13 is made of a conductive material such as Cu. The second terminal 13 is electrically connected to the first electrode layer 14 of the capacitor element via a lead 41 and is extended to the outside of the resin mold layer 11. The portion of the second terminal 13 located outside the resin mold layer 11 is bent along the outer surface of the resin mold layer 11.

[0096] As shown in Fig. 1 , the end of the lead 41 on the first electrode layer 14 side is embedded in the first electrode layer 14. The end of the lead 41 on the first electrode layer 14 side extends from approximately the center of one of the outer surfaces of the approximately rectangular parallelepiped first electrode layer 14 toward approximately the center of the first electrode layer 14. As shown in Fig. 1 , the end of the lead 41 on the second terminal 13 side penetrates the solid electrolyte layer 60a and the second electrode layer 16 while being covered with the dielectric layer 15. The dielectric layer 15 is not formed on the surface of the end of the lead 41 on the second terminal 13 side, and the end is electrically connected to the second terminal 13 by resistance welding or the like.

[0097] The lead 41 can be made of a conductive material such as aluminum, tantalum, or niobium. The lead 41 is preferably made of the same material as the first electrode layer 14. The reason for this is that the dielectric layer 15 can be formed on the outer surface of the first electrode layer 14 and on the surfaces of the fine holes in the first electrode layer 14, and at the same time, the dielectric layer 15 can be formed on the surface of the lead 41 exposed from the first electrode layer 14, thereby enabling efficient manufacturing.

[0098] (First Electrode Layer 14) The first electrode layer 14 functions as an anode in the solid electrolytic capacitor 200. The first electrode layer 14 is a sintered body of a valve metal or a metal containing a valve metal as a main component, and is made of a porous body having a large number of fine pores (not shown) that communicate from the inside to the outside.

[0099] Examples of valve metals used as the material for the first electrode layer 14 include aluminum, tantalum, niobium, titanium, hafnium, zirconium, zinc, tungsten, bismuth, and antimony. Among the above valve metals, it is preferable to use one or more selected from aluminum, tantalum, and niobium as the material for the first electrode layer 14, and tantalum and / or niobium are more preferable. This is because the dielectric layer 15 can be stably formed by anodizing the outer surface of the first electrode layer 14 and the surfaces of the fine pores in the first electrode layer 14.

[0100] 4, the dielectric layer 15 is formed along the outer surface of the first electrode layer 14 so as to cover the first electrode layer 14. The dielectric layer 15 is also formed on the surfaces of minute holes in the first electrode layer 14. The dielectric layer 15 is also formed on the surface of the lead 41 exposed from the first electrode layer 14, excluding the end of the lead 41 on the second terminal 13 side.

[0101] The dielectric layer 15 is made of an electrically insulating metal oxide film. For example, when the first electrode layer 14 is a sintered body of tantalum, the dielectric layer 15 is preferably made of a tantalum oxide film. The thickness of the dielectric layer 15 is usually 1 nm to 1 μm.

[0102] 4, the solid electrolyte layer 60a is formed along the outer surface of the dielectric layer 15. As the solid electrolyte layer 60a in this embodiment, a polymer film similar to the polymer film that can be used for the solid electrolyte layer 165a in the solid electrolytic capacitor 100 of the first embodiment can be used.

[0103] The thickness of the solid electrolyte layer 60a in the solid electrolytic capacitor 200 of the second embodiment is preferably, for example, 5 μm or more at the vertices and sides and 25 μm or less at the faces, because this results in the solid electrolytic capacitor 200 with even greater suppression of leakage current.

[0104] (Second electrode layer 16) The second electrode layer 16 formed on the outer surface of the solid electrolyte layer 60a may be made of a carbon layer 61a and a metal layer 62 formed on the outer surface of the carbon layer 61a, similar to the second electrode layer 160 in the solid electrolytic capacitor 100 of the first embodiment.

[0105] (Method of Manufacturing Solid Electrolytic Capacitor) The solid electrolytic capacitor 200 of this embodiment can be manufactured, for example, by the method described below. First, a block-shaped first electrode layer 14 is prepared, which is a sintered body of a valve metal such as tantalum or a metal containing a valve metal as its main component. The first electrode layer 14 can be formed by molding powder containing a metal containing a valve metal as its main component into a compact by a known method, and then sintering the compact by a known method.

[0106] Next, by a known method, one end of the lead 41 is embedded from approximately the center of one of the outer surfaces of the approximately rectangular parallelepiped first electrode layer 14 toward approximately the center of the first electrode layer 14, thereby integrating the first electrode layer 14 and the lead 41. Next, a dielectric layer 15 is provided on the outer surface of the first electrode layer 14, the surfaces of the fine holes in the first electrode layer 14, and the surface of the lead 41 exposed from the first electrode layer 14. For example, if the first electrode layer 14 is a sintered body made of tantalum and the lead 41 is made of tantalum, the dielectric layer 15 made of a tantalum oxide film can be formed by anodizing treatment using ammonium acetate, sulfuric acid, phosphoric acid, or the like as a chemical conversion treatment solution (electrolyte).

[0107] Next, a solid electrolyte layer 60a made of a polymer film containing a cross-linked polymer and PEDOT / PSS is provided on the outer surface of the dielectric layer 15 by the same method as when the solid electrolyte layer 165a is provided in the solid electrolytic capacitor 100 of the first embodiment. Thereafter, a carbon layer 61a and a metal layer 62 are formed in this order on the outer surface of the solid electrolyte layer 60a by the same method as when the second electrode layer 160 is provided in the solid electrolytic capacitor 100 of the first embodiment, thereby forming the second electrode layer 16.

[0108] Next, the metal layer 62 of the second electrode layer 16 and a plate-shaped first terminal piece that will become the first terminal 12 are electrically connected by the connecting conductor layer 19. Also, the end of the lead 41 that is not embedded in the first electrode layer 14 is electrically connected to a plate-shaped second terminal piece that will become the second terminal 13. Thereafter, in the same manner as the resin mold layer 110 of the solid electrolytic capacitor 100 of the first embodiment, a resin mold layer 11 is formed from an insulating resin material that contains a resin such as an epoxy resin and a filler such as silica.

[0109] Thereafter, the first terminal piece protruding outward from the resin mold layer 11 is bent along the outer surface of the resin mold layer 11 to form the first terminal 12. Furthermore, the second terminal piece protruding outward from the resin mold layer 11 is bent along the outer surface of the resin mold layer 11 to form the second terminal 13. By performing the above steps, the solid electrolytic capacitor 200 of this embodiment is obtained.

[0110] The polymer film of this embodiment has good water resistance. Therefore, by repeatedly performing the process of applying the above-mentioned resin coating to form a coating film and then removing the water from the coating film, a polymer film with a uniform and sufficient thickness can be easily obtained. Specifically, even if a block-shaped first electrode layer made of tantalum with a dielectric layer formed on its outer surface is immersed in the resin coating and the resin coating is applied in the second or subsequent process, the polymer film formed on the vertices and edges of the first electrode layer is unlikely to dissolve. Therefore, by using a method of repeatedly performing the above process multiple times, a polymer film with sufficient thickness on the vertices and edges of the first electrode layer can be easily formed. As a result, a solid electrolytic capacitor with low leakage current can be formed.

[0111] Furthermore, even if the number of times of performing the above steps is small, a polymer film having a sufficient thickness can be formed on the vertices and sides of the first electrode layer, thereby enabling efficient production of a solid electrolyte layer. Furthermore, because the polymer film formed on the vertices and sides of the first electrode layer is less likely to dissolve, there is little difference in thickness between the polymer film formed on the vertices and sides of the first electrode layer and the polymer film formed on the surface of the first electrode layer, making it easier to form a solid electrolyte layer with a uniform thickness.

[0112] Third Embodiment (Solid Electrolytic Capacitor) Fig. 5 is a schematic cross-sectional view showing a solid electrolytic capacitor according to a third embodiment of the present invention. Fig. 6 is an enlarged cross-sectional view showing an enlarged view of the area around symbol II in Fig. 5. Fig. 7 is a schematic cross-sectional view taken along line III-III in Fig. 5. In Figs. 5 and 7, symbol T indicates the thickness direction of capacitor element 170. In Fig. 5, symbol L indicates the length direction perpendicular to thickness direction T of capacitor element 170. In Fig. 7, symbol W indicates the width direction of capacitor element 170, which is perpendicular to thickness direction T and length direction L of capacitor element 170.

[0113] 5 to 7 includes a resin mold layer 110 having a substantially rectangular parallelepiped outer shape, a plurality of capacitor elements 170 (four in FIG. 5 ) provided inside the resin mold layer 110, a first terminal 120, and a second terminal 130. The resin mold layer 110 forms the exterior of the solid electrolytic capacitor 100. The resin mold layer 110 is made of an insulating resin material containing, for example, a resin such as an epoxy resin and a filler such as silica.

[0114] The first terminal 120 is made of a conductive material such as Cu. The first terminal 120 is electrically connected to the second electrode layer 160 of each of the plurality of capacitor elements 170 and is extended to the outside of the resin mold layer 110. The portion of the first terminal 120 located outside the resin mold layer 110 is bent along the outer surface of the resin mold layer 110.

[0115] The second terminal 130 is made of a conductive material such as Cu. The second terminal 130 is electrically connected to the first electrode layer 141 of each of the plurality of capacitor elements 170 and is extended to the outside of the resin mold layer 110. The portion of the second terminal 130 located outside the resin mold layer 110 is bent along the outer surface of the resin mold layer 110.

[0116] 5 and 7, the plurality of capacitor elements 170 included in the solid electrolytic capacitor 100 are stacked in the thickness direction T. The number of capacitor elements 170 included in the solid electrolytic capacitor 100 of this embodiment is not particularly limited, and may be four as shown in FIGS. 5 and 7, one to three, or five or more.

[0117] 5 and 7 , the plurality of capacitor elements 170 are electrically connected to one another by connecting conductor layers 190. Examples of connecting conductor layers 190 include a conductive adhesive containing Ag. Furthermore, as shown in FIG. 5 , the ends of the first electrode layers 141 of the capacitor elements 170 adjacent to one another in the stacking direction on the side of the second terminal 130 are electrically connected to one another by resistance welding or the like.

[0118] As shown in Figures 5 and 6, each capacitor element 170 includes a first electrode layer 141, a dielectric layer 150 formed on the outer surface of the first electrode layer 141, a solid electrolyte layer 165b formed on the outer surface of the dielectric layer 150, and a second electrode layer 160 formed on the outer surface of the solid electrolyte layer 165b.

[0119] (First Electrode Layer 141) The first electrode layer 141 functions as an anode in the solid electrolytic capacitor 100. The first electrode layer 141 is made of a metal film having a finely textured surface, as shown in Fig. 6. The finely textured surface of the first electrode layer 141 increases the surface area of ​​the first electrode layer 141, thereby increasing the capacity of the solid electrolytic capacitor 100.

[0120] A film made of a valve metal such as aluminum, tantalum, niobium, titanium, hafnium, zirconium, zinc, tungsten, bismuth, or antimony can be used as the first electrode layer 141. Among the films made of the above valve metals, it is preferable to use any one selected from an aluminum film, a tantalum film, and a niobium film as the first electrode layer 141. The reason for this is that by anodizing the outer surface of the first electrode layer 141, the dielectric layer 150 can be stably formed on the outer surface of the first electrode layer 141.

[0121] When the first electrode layer 141 is an aluminum foil, it preferably has an average thickness of 70 μm to 220 μm. If the average thickness of the aluminum foil is 70 μm or more, the first electrode layer 141 has sufficient strength and the solid electrolytic capacitor 100 has sufficient capacitance. Furthermore, if the average thickness of the aluminum foil is 220 μm or less, the first electrode layer 141 can be easily electrically connected to the second terminal 130.

[0122] (Dielectric Layer 150) As shown in Fig. 6, the dielectric layer 150 is formed so as to cover the first electrode layer 141, following the irregularities on the outer surface of the first electrode layer 141. The dielectric layer 150 is made of a metal oxide film having electrical insulation properties. For example, when the first electrode layer 141 is an aluminum foil, the dielectric layer 150 is preferably made of an aluminum oxide film. The thickness of the dielectric layer 150 is usually 1 nm to 1 µm.

[0123] 6, the solid electrolyte layer 165b is formed along the outer surface of the dielectric layer 150, which is formed along the uneven shape of the outer surface of the first electrode layer 141. That is, the solid electrolyte layer 165b is formed so as to fill in the minute recesses formed in the outer surface of the first electrode layer 141 via the dielectric layer 150. The solid electrolyte layer 165b in this embodiment has the following polymer film.

[0124] [Polymer Film] The solid electrolyte layer 165b has a polymer film containing a crosslinked polymer in which a composite of polyethylenedioxythiophene represented by formula (1) and polystyrenesulfonic acid (PEDOT / PSS) is crosslinked by a crosslinking agent.

[0125]

[0126] The crosslinked polymer contained in the polymer film of this embodiment has a three-dimensional network structure resulting from the crosslinked structure between PEDOT / PSS and a crosslinking agent, and has excellent water resistance. The crosslinked polymer contained in the polymer film of this embodiment may be one type or two or more types.

[0127] The crosslinking agent in the polymer membrane of this embodiment is —NH ２ The salt of the amine compound includes a salt of an amine compound containing a total of four or more groups selected from one or two types of groups selected from the group consisting of an —NH— group and an —NH— group. ２ group, and —NH— group, and contains a total of four or more groups of one or two kinds selected from the group consisting of —NH ２ group, four N resulting from -NH- groups ＋ Therefore, a crosslinked structure with PEDOT / PSS can be sufficiently formed. Examples of the salt of the amine compound include hydrochlorides, phosphates, sulfonates, perchlorates, and salt-forming compounds with organic sulfonic acids such as paratoluenesulfonic acid. Hydrochlorides are preferred because they can be easily dispersed in water and have good reactivity.

[0128] Examples of such crosslinking agents include N,N'-bis(3-aminopropyl)-1,4-butanediamine tetrahydrochloride, N,N'-bis(3-aminopropyl)-1,3-propanediamine tetrahydrochloride, and N,N'-bis(2-aminoethyl)-1,3-propanediamine tetrahydrochloride, which are represented by formula (6).

[0129]

[0130] Among the above crosslinking agents, it is preferable to use N,N'-bis(3-aminopropyl)-1,4-butanediamine tetrahydrochloride represented by formula (6). N,N'-bis(3-aminopropyl)-1,4-butanediamine tetrahydrochloride represented by formula (6) is a crosslinking agent that can crosslink the -SO contained in PEDOT / PSS. ３ This is because N,N'-bis(3-aminopropyl)-1,4-butanediamine tetrahydrochloride has good reactivity with H and can form a crosslinked polymer with better water resistance. Furthermore, N,N'-bis(3-aminopropyl)-1,4-butanediamine tetrahydrochloride represented by formula (6) can be easily dispersed in water. Therefore, applying an aqueous solution of the crosslinking agent to a PEDOT / PSS film, which is easily soluble in water, is preferable because it can dissolve a portion of the PEDOT / PSS film and promote the crosslinking reaction with PEDOT / PSS. In this embodiment, the crosslinking agent used to crosslink PEDOT / PSS may be one type or two or more types.

[0131] The polymer membrane of this embodiment contains the crosslinked polymer described above, and may further contain one or more other components as needed in addition to the crosslinked polymer. Examples of other components include known resins other than PEDOT / PSS, surface tension modifiers, and the like. Examples of resins other than PEDOT / PSS include water-soluble or water-dispersible resins, specifically sulfonated polyester resins. Examples of surface tension modifiers include low-molecular-weight additives such as glycerin and ethylene glycol.

[0132] The polymer membrane of this embodiment is -NH ２ The polymer film of the present embodiment includes a crosslinked polymer in which PEDOT / PSS is crosslinked with a crosslinking agent containing a salt of an amine compound containing a total of four or more groups selected from the group consisting of —NH— groups and —NH— groups. As a result, the polymer film of the present embodiment has excellent electrical conductivity and heat resistance, as well as good water resistance.

[0133] The solid electrolyte layer 165b preferably has a sufficient thickness to fill minute recesses formed in the outer surface of the first electrode layer 141 via the dielectric layer 150, and preferably has a substantially uniform thickness. This is because the solid electrolytic capacitor 100 has a reduced leakage current. For example, if the first electrode layer 141 is made of aluminum foil with an average thickness of 70 μm to 220 μm, the thickness of the solid electrolyte layer 165b is preferably 5 μm or more at the end faces and 25 μm or less in the region excluding the end faces. This is because the solid electrolytic capacitor 100 has a reduced leakage current.

[0134] Furthermore, in this embodiment, the solid electrolyte layer 165b is preferably formed by laminating multiple layers of polymer films with different components. The reason for this is that, for example, by making the first polymer film arranged closest to the dielectric layer 150 a film that is likely to be formed in minute recesses present on the outer surface of the dielectric layer 150, and by making the second polymer film arranged on the second electrode layer 160 side of the first polymer film a film that is likely to be formed with a sufficient thickness on the first polymer film, a more reliable solid electrolytic capacitor 100 can be obtained.

[0135] For example, in the present embodiment, when the solid electrolyte layer 165b is made of two or more polymer membrane layers, the cross-linking agents used as the cross-linked polymer materials in the stacked polymer membrane layers may be different from each other, or some or all of them may be the same, and it is preferable that all of them are the same, because this improves the adhesion between the polymer membrane layers and makes it easier to obtain a solid electrolyte layer 165b with even better water resistance.

[0136] Furthermore, when the solid electrolyte layer 165b in this embodiment is composed of two or more polymer films, it may have one or more polymer films that do not contain the crosslinked polymer, in addition to the polymer film of this embodiment that contains the crosslinked polymer formed by crosslinking PEDOT / PSS with a crosslinking agent. The polymer film that does not contain the crosslinked polymer formed by crosslinking PEDOT / PSS with a crosslinking agent may contain any resin component, such as a polymer film made of uncrosslinked PEDOT / PSS or a polymer film made of self-doped PEDOT.

[0137] In this embodiment, when the solid electrolyte layer 165b is composed of two or more polymer films and includes a polymer film that does not contain a crosslinked polymer formed by crosslinking PEDOT / PSS with a crosslinking agent, the polymer film that does not contain the crosslinked polymer is preferably a first polymer film disposed closest to the dielectric layer 150. Examples of such a first polymer film include the above-mentioned polymer film made of uncrosslinked PEDOT / PSS and a polymer film made of self-doped PEDOT. When the first polymer film is a polymer film made of uncrosslinked PEDOT / PSS, it is preferable that the first polymer film does not contain any resin component other than PEDOT / PSS.

[0138] The first polymer film may contain a surface tension adjuster made of a low-molecular-weight additive such as glycerin, ethylene glycol, etc. The surface tension adjuster adjusts the surface tension of the aqueous dispersion used to form the first polymer film to a suitable range, thereby making it easier for the aqueous dispersion to fill minute recesses present on the outer surface of the dielectric layer 150.

[0139] When the first polymer film is a polymer film that does not contain a crosslinked polymer formed by crosslinking PEDOT / PSS with a crosslinking agent, the second polymer film disposed on the second electrode layer 160 side of the first polymer film has one or more layers of a polymer film that contains a crosslinked polymer formed by crosslinking PEDOT / PSS with a crosslinking agent. The second polymer film may contain a surface tension adjuster made of a low-molecular additive such as glycerin or ethylene glycol.

[0140] The polymer film containing a crosslinked polymer formed by crosslinking PEDOT / PSS with a crosslinking agent in the second polymer film preferably contains structural units derived from a polymer other than the crosslinked polymer, such as a sulfonated polyester resin. This is because the inclusion of structural units derived from a polymer other than the crosslinked polymer formed by crosslinking PEDOT / PSS improves the film-formability of the second polymer film. Specifically, this facilitates the formation of a solid electrolyte layer 165b with a small difference in thickness between the end face of the first electrode layer 141, excluding the end face connected to the second terminal 130 where the solid electrolyte layer 165b is not formed, and the region excluding the end face of the first electrode layer 141, thereby resulting in a solid electrolytic capacitor 100 with reduced leakage current.

[0141] When the second polymer film has two or more layers of polymer film, it is preferable that the polymer film arranged in contact with the first polymer film is a polymer film with good water resistance, containing a crosslinked polymer in which PEDOT / PSS is crosslinked by a crosslinking agent, and that the polymer film arranged in contact with the second electrode layer 160 is a polymer film with good film-forming properties, containing, in addition to the crosslinked polymer, structural units derived from a polymer other than the crosslinked polymer.

[0142] (Insulating Resin Layer 151) As shown in Fig. 5, in capacitor element 170, solid electrolyte layer 165b is not provided on the end of the outer surface of first electrode layer 141 that is connected to second terminal 130. As shown in Fig. 5 and Fig. 6, the region of the outer surface of first electrode layer 141 that is not provided with solid electrolyte layer 165b is covered with insulating resin layer 151. As insulating resin layer 151, for example, a layer made of insulating resin such as polyimide resin, polyamide resin, epoxy resin, or acrylic resin can be used.

[0143] (Second Electrode Layer 160) The second electrode layer 160 formed on the outer surface of the solid electrolyte layer 165b includes a conductive layer 161b and a metal layer 162 formed on the outer surface of the conductive layer 161b. In this embodiment, the second electrode layer 160 includes the metal layer 162 and the conductive layer 161b disposed between the solid electrolyte layer 165b and the metal layer 162. However, the second electrode layer may include, for example, only one layer including the conductive layer 161b or the metal layer 162, or may include three or more layers including one or more conductive layers 161b and / or one or more metal layers 162. Specifically, the conductive layer 161b preferably includes a plating seed layer disposed on the solid electrolyte layer 165b side of the metal layer 162 and a carbon layer disposed between the plating seed layer and the solid electrolyte layer 165b.

[0144] The conductive layer 161b is a layer containing a conductive material, and may contain a binder resin and / or additives as necessary in addition to the conductive material. Examples of the conductive material contained in the conductive layer 161b include carbon materials, metal materials, conductive polymers, etc., and carbon materials are preferred because they have excellent adhesion to the solid electrolyte layer 165b and a good balance between conductivity and cost. Examples of the carbon material contained in the conductive layer 161b include one or more selected from graphite, carbon black, graphene flakes, and carbon nanotubes.

[0145] Examples of the binder resin that may be contained in the conductive layer 161b include known thermoplastic resins or curable resins that can be used as binder resins, etc. Examples of the additives that may be contained in the conductive layer 161b include dispersants, surfactants, antioxidants, preservatives, bases, and / or acids, etc.

[0146] When the conductive layer 161b has a plating seed layer disposed on the solid electrolyte layer 165b side of the metal layer 162 and a carbon layer disposed between the plating seed layer and the solid electrolyte layer 165b, the carbon layer preferably comprises the above-mentioned carbon material and, if necessary, the above-mentioned binder resin and / or the above-mentioned additive. The plating seed layer preferably contains a conductive material and a catalyst support material. This is because, when the plating seed layer contains a conductive material and a catalyst support material, the metal layer 162 can be formed by a method in which a plating catalyst such as a Pd catalyst is supported on the catalyst support material in the plating seed layer and an electroless plating process is performed.

[0147] The catalyst support material contained in the plating seed layer is a compound that has the function of capturing and regenerating a plating catalyst such as a Pd catalyst. Specific examples of the catalyst support material contained in the conductive layer 161b include polymeric materials such as polypyrrole derivatives, polythiophene derivatives, and polyfuran derivatives, as well as nitrogen-containing compounds such as bipyridine and phenanthroline. Among these, from the viewpoints of stability in the plating seed layer and the function of regenerating the plating catalyst, the catalyst support material is preferably one or more compounds selected from polypyrrole derivatives, polythiophene derivatives, and polyfuran derivatives, and is particularly preferably a polypyrrole derivative.

[0148] The conductive material contained in the plating seed layer can be the carbon material described above. The plating seed layer may contain the binder resin and / or the additive described above, as needed, in addition to the conductive material and the catalyst support material.

[0149] The metal layer 162 can be a metal layer made of any metal selected from Ag, Cu, Ni, Sn, Zn, Pd, and Au. Because of their good conductivity, an Ag layer or a Cu layer is preferred, and a Cu layer is particularly preferred. When the metal layer 162 is a Cu layer, the solid electrolytic capacitor 100 has good conductivity and even better water resistance. Furthermore, when the metal layer 162 is a Cu layer, the solid electrolytic capacitor 100 has even better water resistance and durability, so it is more preferably disposed as the outermost layer of the second electrode layer 160. The metal layer 162 may be formed by a plating method using a plating catalyst captured in a catalyst support material.

[0150] (Method of Manufacturing Solid Electrolytic Capacitor) To manufacture the solid electrolytic capacitor 100 of this embodiment, first, a plurality of capacitor elements 170 are manufactured.

[0151] First, a first electrode layer 141 made of a metal foil having a finely textured surface is prepared. The first electrode layer 141 can be formed by subjecting the surface of a metal film to a surface roughening treatment or surface enlargement treatment using a known method. Next, a dielectric layer 150 is provided on the outer surface of the first electrode layer 141. The dielectric layer 150 can be formed by oxidizing the surface portion of the first electrode layer 141. For example, when the first electrode layer 141 is an aluminum foil, the dielectric layer 150 made of an aluminum oxide film can be formed on the outer surface of the first electrode layer 141 by immersing the aluminum film in an ammonium adipate aqueous solution and anodizing it.

[0152] Next, an insulating resin layer 151 is formed on the end of the outer surface of the dielectric layer 150 that is connected to the second terminal 130 (i.e., the area where the solid electrolyte layer 165b is not formed). The insulating resin layer 151 can be formed by applying paint containing an insulating resin such as polyimide resin, polyamide resin, epoxy resin, or acrylic resin using a known method, followed by drying and curing.

[0153] (Method for manufacturing solid electrolyte layer (polymer film)) Next, a solid electrolyte layer 165b having a polymer film containing a crosslinked polymer in which PEDOT / PSS represented by formula (1) is crosslinked with a crosslinking agent is provided on the outer surface of the dielectric layer 150 by the method described below.

[0154] First, an aqueous dispersion of PEDOT / PSS is prepared. The aqueous dispersion of PEDOT / PSS may be composed of only PEDOT / PSS and water. The aqueous dispersion of PEDOT / PSS may contain, in addition to PEDOT / PSS and water, one or more of the other components described above. Specifically, the aqueous dispersion of PEDOT / PSS may contain PEDOT / PSS, water, a sulfonated polyester resin, and / or a surface tension modifier.

[0155] Next, an aqueous dispersion of PEDOT / PSS is applied to the outer surface of the dielectric layer 150, excluding the end connected to the second terminal 130 (i.e., the area where the insulating resin layer 151 is not formed), to form a coating film.

[0156] As a method for applying the aqueous dispersion of PEDOT / PSS to the outer surface of the dielectric layer 150, for example, a method of immersing a region of the first electrode layer 141, on whose outer surface the dielectric layer 150 and the insulating resin layer 151 are formed, where the insulating resin layer 151 is not formed, in the aqueous dispersion of PEDOT / PSS, a dispensing method, a screen printing method, a spray coating method, or other known methods can be used. As a method for applying the aqueous dispersion of PEDOT / PSS to the outer surface of the dielectric layer 150, a method of immersing a region of the dielectric layer 150 formed on the outer surface of the first electrode layer 141, where the solid electrolyte layer 165b is to be provided, in the aqueous dispersion of PEDOT / PSS is preferably used. The reason for this is that the aqueous dispersion of PEDOT / PSS can be easily applied into minute recesses present on the outer surface of the dielectric layer 150.

[0157] Next, the coating film formed on the outer surface of the dielectric layer 150 is dried to remove water from the coating film, thereby obtaining a PEDOT / PSS film. The method for removing water from the coating film can be a known method, such as a heat treatment at a temperature of 80°C to 150°C, and can be appropriately determined depending on the concentration of PEDOT / PSS in the aqueous dispersion of PEDOT / PSS, the thickness of the coating film, etc.

[0158] In this embodiment, the PEDOT / PSS film obtained by removing water from the coating film may be washed. The PEDOT / PSS film may be washed, for example, using water. In this embodiment, the process of applying an aqueous dispersion of PEDOT / PSS to the outer surface of the dielectric layer 150, drying the resulting coating film to form a PEDOT / PSS film, and washing as necessary may be performed only once or multiple times.

[0159] Next, an aqueous solution of a cross-linking agent is applied onto the PEDOT / PSS film, whereby the PEDOT / PSS in the PEDOT / PSS film comes into contact with the cross-linking agent, and the -SO ３ H and N of the amine compound which is a crosslinking agent ＋ The cross-linking reaction is initiated.

[0160] The crosslinking agent aqueous solution preferably has a crosslinking agent content in the range of 0.01 mol% to 1 mol%, and more preferably in the range of 0.03 mol% to 1 mol%. When the crosslinking agent content is 0.01 mol% or more, the effect of forming a crosslinked structure between PEDOT / PSS and the crosslinking agent can be sufficiently achieved by applying the crosslinking agent aqueous solution onto the PEDOT / PSS film and removing the water from the crosslinking agent aqueous solution. Therefore, when the crosslinking agent content is 0.01 mol% or more, a polymer film with better water resistance is likely to be obtained. Furthermore, when the crosslinking agent content is 1 mol% or less, the impact of the remaining crosslinking agent that does not form a crosslinked structure is reduced, which is preferable.

[0161] The method of applying the aqueous solution of the crosslinking agent onto the PEDOT / PSS film can be, for example, a method of immersing the region of the dielectric layer 150 formed on the outer surface of the first electrode layer 141 where the PEDOT / PSS film is formed in the aqueous solution of the crosslinking agent, a method using various coaters, a method using various dispensers, a spray method, or any other known method. The method of applying the aqueous solution of the crosslinking agent onto the PEDOT / PSS film can be appropriately determined depending on the shape of the region of the dielectric layer 150 formed on the outer surface of the first electrode layer 141 where the PEDOT / PSS film is formed, the viscosity of the aqueous solution of the crosslinking agent, and the like.

[0162] Next, the aqueous solution of the crosslinking agent applied to the PEDOT / PSS film is dried to remove the water in the aqueous solution of the crosslinking agent, thereby removing the N-type bond between the PEDOT / PSS in the PEDOT / PSS film and the amine compound serving as the crosslinking agent. ＋ By carrying out the above steps, a solid electrolyte layer 165b is formed, which includes a polymer film of this embodiment containing a crosslinked polymer in which PEDOT / PSS is crosslinked by a crosslinking agent.

[0163] As a method for removing water from the aqueous solution of the cross-linking agent applied to the PEDOT / PSS film, a known method such as heat treatment at a temperature of 80°C to 150°C can be used, and the method can be appropriately determined depending on the shape of the area of ​​the dielectric layer 150 formed on the outer surface of the first electrode layer 141 where the PEDOT / PSS film is formed, the thickness of the coating film, etc.

[0164] In this embodiment, the crosslinking reaction is initiated by applying an aqueous solution of a crosslinking agent to the PEDOT / PSS film. This promotes the crosslinking reaction near the surface of the PEDOT / PSS film. As a result, the density of the crosslinked structures contained in the polymer film of this embodiment changes continuously or stepwise in the thickness direction, presumably increasing the closer to the surface. This results in a polymer film with particularly high water resistance at the surface, effectively achieving the effect of improving the water resistance of the polymer film due to the presence of crosslinked structures. Therefore, compared to a polymer film with a substantially uniform density of crosslinked structures produced by applying an aqueous dispersion containing PEDOT / PSS and a crosslinking agent, for example, the polymer film of this embodiment can achieve sufficient water resistance even with a smaller number of crosslinked structures. Therefore, compared to a polymer film with a substantially uniform density of crosslinked structures and equivalent water resistance, the polymer film of this embodiment can have a higher PEDOT / PSS content in the polymer film, resulting in better conductivity and heat resistance.

[0165] The polymer film forming the solid electrolyte layer 165b of this embodiment may be produced by forming the above-described PEDOT / PSS film, applying an aqueous solution of a crosslinking agent thereon, and then performing the steps of removing the water from the aqueous solution of the crosslinking agent only once, or by repeating the above steps multiple times to form a polymer film having a predetermined thickness. In this embodiment, the polymer film obtained by removing the water from the aqueous solution of the crosslinking agent may be washed. The polymer film may be washed using, for example, water.

[0166] Since the polymer film of this embodiment has good water resistance, a polymer film having a uniform and sufficient thickness can be easily obtained by repeating the above steps multiple times. This is because, if the polymer film has good water resistance, even if an aqueous dispersion of PEDOT / PSS is applied to the polymer film in the second or subsequent steps, the polymer film is unlikely to dissolve in the water contained in the aqueous dispersion of PEDOT / PSS.

[0167] On the other hand, if the water resistance of the polymer film is insufficient, for example, when an aqueous dispersion of PEDOT / PSS is applied to the polymer film formed in the first step in the second step, the polymer film formed in the first step will re-elute and some or all of the polymer film formed in the first step will fall off, resulting in an uneven or insufficient thickness of the polymer film formed in the second step.

[0168] In particular, when using a method in which the first electrode layer 141, which is a metal film having a dielectric layer 150 formed on its outer surface, is immersed in an aqueous dispersion of PEDOT / PSS and then coated with the aqueous dispersion of PEDOT / PSS, the polymer film formed on the end surface of the first electrode layer 141 is prone to falling off in the second and subsequent steps, making it difficult to form a polymer film with sufficient thickness on the end surface of the first electrode layer 141. This tends to increase the leakage current of the solid electrolytic capacitor 100. Furthermore, in order to form a polymer film with sufficient thickness on the end surface of the first electrode layer 141, the process for forming the polymer film must be repeated many times, which makes it difficult to efficiently manufacture the solid electrolyte layer 165b. Furthermore, when the process is repeated many times, the polymer film formed on the region excluding the end surface of the first electrode layer 141 tends to become thicker, which tends to increase the difference in thickness between the polymer film formed on the end surface of the first electrode layer 141 and the polymer film formed on the region excluding the end surface of the first electrode layer 141.

[0169] The polymer film of this embodiment has good water resistance. Therefore, even if the first electrode layer 141, which is a metal film having a dielectric layer 150 formed on its outer surface, is immersed in an aqueous dispersion of PEDOT / PSS and coated with the aqueous dispersion of PEDOT / PSS in the second or subsequent steps, the polymer film formed on the end surface of the first electrode layer 141 is unlikely to dissolve. Therefore, by repeating the above steps multiple times, a polymer film having a sufficient thickness can be easily formed on the end surface of the first electrode layer 141. As a result, a solid electrolytic capacitor 100 with low leakage current can be formed. Furthermore, even if the above steps are performed only a few times, a polymer film having a sufficient thickness can be formed on the end surface of the first electrode layer 141, thereby efficiently manufacturing the solid electrolyte layer 165b. Furthermore, because the polymer film formed on the end surface of the first electrode layer 141 is unlikely to dissolve, the difference in thickness between the polymer film formed on the end surface of the first electrode layer 141 and the polymer film formed in the region other than the end surface of the first electrode layer 141 is small, making it easy to form a solid electrolyte layer 165b with a uniform thickness.

[0170] Furthermore, when the solid electrolyte layer 165b of this embodiment is composed of two or more polymer films, it can be manufactured, for example, by the method described below. When the solid electrolyte layer 165b of this embodiment is composed of two or more polymer films including a crosslinked polymer formed by crosslinking PEDOT / PSS with a crosslinking agent, a first polymer film is first manufactured using the method for manufacturing the solid electrolyte layer 165b composed of a polymer film described above. Then, a second polymer film composed of one or more polymer films is manufactured on the outer surface of the dielectric layer 150 on which the first polymer film has been formed, in the same manner as the first polymer film, using an aqueous dispersion of PEDOT / PSS with different components from the aqueous dispersion of PEDOT / PSS used in manufacturing the first polymer film. When the second polymer film is composed of two or more polymer films, a polymer film is manufactured in the same manner as described above, using aqueous dispersions of PEDOT / PSS with different components, depending on the number of polymer films stacked.

[0171] When the solid electrolyte layer 165b of this embodiment is made up of two or more layers of polymer films, and has one or more layers of polymer films that do not contain the above-mentioned crosslinked polymer, along with the polymer film of this embodiment containing a crosslinked polymer in which PEDOT / PSS is crosslinked by a crosslinking agent, it can be manufactured, for example, by the method shown below.

[0172] First, a polymer film not containing the above-mentioned crosslinked polymer, such as a polymer film made of uncrosslinked PEDOT / PSS or a polymer film made of self-doped PEDOT, is formed as the first polymer film closest to the dielectric layer 150. When a polymer film made of uncrosslinked PEDOT / PSS is formed as the first polymer film, the PEDOT / PSS film may be formed in the above-mentioned method for producing a polymer film containing a crosslinked polymer. When a polymer film made of self-doped PEDOT is formed as the first polymer film, the PEDOT / PSS film may be formed in the same manner as the PEDOT / PSS film in the above-mentioned method for producing a polymer film containing a crosslinked polymer, using, for example, an aqueous dispersion containing self-doped PEDOT, water, and a surface tension modifier instead of the aqueous dispersion of PEDOT / PSS.

[0173] When the polymer film not containing the crosslinked polymer has two or more layers, the polymer film not containing the crosslinked polymer is produced on the outer surface of the dielectric layer 150 on which the first polymer film is formed in the same manner as described above using aqueous dispersions of different components according to the number of layers.

[0174] Then, on the outer surface of the dielectric layer 150 on which the polymer film not containing the crosslinked polymer is formed, one or more layers of a polymer film containing a crosslinked polymer in which PEDOT / PSS is crosslinked by a crosslinking agent are produced as a second polymer film using the method for producing the solid electrolyte layer 165b consisting of the polymer film described above.

[0175] (Method for manufacturing second electrode layer) Next, the second electrode layer 160 is provided on the outer surface of the solid electrolyte layer 165b. In the present embodiment, when the second electrode layer 160 is made of, for example, a conductive layer 161b and a metal layer 162 formed on the outer surface of the conductive layer 161b, the second electrode layer 160 can be manufactured by the method described below.

[0176] First, a conductive paste containing a carbon material and, if necessary, a binder resin and / or additives is prepared, and then the conductive paste is applied to the outer surface of the solid electrolyte layer 165b by a known method and dried to form the carbon layer of the conductive layer 161b.

[0177] Next, a seed paste containing a conductive material such as a carbon material and a catalyst support material such as a polypyrrole derivative, and which may also contain a binder resin and / or additives, is prepared, and the seed paste is applied to the carbon layer of the conductive layer 161b by a known method and dried to form a plating seed layer of the conductive layer 161b.

[0178] In this embodiment, since the solid electrolyte layer 165b has the above-described polymer film, the water resistance of the solid electrolyte layer 165b is good. Therefore, in this embodiment, when the metal layer 162 is formed using a plating method, for example, water in the plating solution can be prevented from seeping into the solid electrolyte layer 165b through the conductive layer 161b or through portions where the conductive layer 161b is not formed, preventing the solid electrolyte layer 165b from dissolving. Therefore, in this embodiment, the plating method can be used as the method for manufacturing the metal layer 162.

[0179] Therefore, in this embodiment, for example, when the metal layer 162 is a Cu layer, the Cu layer can be formed on the outer surface of the solid electrolyte layer 165b on which the conductive layer 161b is formed using an electroless Cu plating method. Specifically, for example, the solid electrolyte layer 165b on which the plating seed layer of the conductive layer 161b is formed is immersed in a pretreatment solution containing a plating catalyst such as a Pd catalyst, and then immersed in a plating solution to perform electroless Cu plating under known conditions. This forms the metal layer 162 made of a Cu layer. The plating solution used to form the Cu layer can be a known plating solution used in electroless Cu plating, or it may be an aqueous solution.

[0180] Furthermore, when the metal layer 162 is an Ag layer, it can be manufactured, for example, by the following method. First, only the carbon layer described above is formed as the conductive layer 161b. Then, a known Ag paste containing Ag particles and a binder resin is prepared. Then, the Ag paste is applied by a known method to the outer surface of the solid electrolyte layer 165b on which the conductive layer 161b made of the carbon layer is formed, and then dried and hardened. By performing the above steps, multiple capacitor elements 170 can be obtained.

[0181] Next, a plate-shaped first terminal piece that will become the first terminal 120 and a plate-shaped second terminal piece that will become the second terminal 130 are prepared and arranged in a straight line while being spaced apart from each other. Next, a plurality of capacitor elements 170 are stacked and arranged on the first terminal piece and the second terminal piece. At this time, the second electrode layer 160 of the plurality of capacitor elements 170 is placed on the first terminal piece, and the first electrode layer 141 is placed on the second terminal piece.

[0182] Then, on the second electrode layer 160 side, a conductive adhesive that will become the connecting conductor layer 190 is interposed between adjacent capacitor elements 170. Similarly, a conductive adhesive that will become the connecting conductor layer 190 is interposed between a first terminal piece and an adjacent capacitor element 170. This allows the second electrode layers 160 and the first terminal pieces of the multiple capacitor elements 170 to be electrically connected by the connecting conductor layer 190. Thereafter, one ends of the first electrode layers 141 of the multiple capacitor elements 170 are electrically connected to the second terminal piece using a method such as welding.

[0183] Next, the first terminal piece, the second terminal piece and the plurality of capacitor elements 170 are placed in a mold so that the end of the first terminal piece located opposite the second terminal piece and the end of the second terminal piece located opposite the first terminal piece are exposed, and a resin mold layer 110 is formed using an insulating resin material containing a resin such as epoxy resin and a filler such as silica.

[0184] Thereafter, the first terminal piece protruding outward from the resin mold layer 110, inside which the plurality of capacitor elements 170 are provided, is bent along the outer surface of the resin mold layer 110 to form the first terminal 120. The second terminal piece protruding outward from the resin mold layer 110 is bent along the outer surface of the resin mold layer 110 to form the second terminal 130. By performing the above steps, the solid electrolytic capacitor 100 of this embodiment is obtained.

[0185] [Fourth Embodiment] In the solid electrolytic capacitor of the fourth embodiment, similarly to the solid electrolytic capacitor of the third embodiment, the polymer film forming the solid electrolyte layer 165b contains a crosslinked polymer in which PEDOT / PSS represented by formula (1) is crosslinked by a crosslinking agent. In the solid electrolytic capacitor of the third embodiment, the crosslinking agent is -NH ２ While the solid electrolytic capacitor of the fourth embodiment has been described above with reference to an example in which the crosslinking agent contains a salt of an amine compound containing a total of four or more groups selected from one or two types of groups selected from the group consisting of ——— groups and —NH— groups, the solid electrolytic capacitor of the fourth embodiment will be described with reference to an example in which the crosslinking agent is made of a metal salt containing a metal cation with a valence of two or more. The solid electrolytic capacitor of the fourth embodiment differs from the solid electrolytic capacitor of the third embodiment only in the polymer film that forms the solid electrolyte layer 165b. Therefore, in the fourth embodiment, descriptions of the same components as in the third embodiment will be omitted.

[0186] The crosslinked polymer contained in the polymer film of this embodiment has a three-dimensional network structure resulting from the crosslinked structure between PEDOT / PSS and a crosslinking agent, and has excellent water resistance, similar to the polymer film of the third embodiment. The crosslinked polymer contained in the polymer film of this embodiment may be of only one type, or may be of two or more types.

[0187] In the fourth embodiment, the cross-linking agent in the polymer film forming the solid electrolyte layer 165b is made of a metal salt containing a metal cation with a valence of 2 or more. Examples of such a cross-linking agent include calcium chloride, magnesium chloride, and strontium chloride.

[0188] Among the above, calcium chloride is preferably used as the crosslinking agent. Calcium chloride is easily available and has a -SO ３ This is because calcium chloride has good reactivity with H and can form a crosslinked polymer with better water resistance. Furthermore, calcium chloride can be easily dispersed in water. Therefore, a method of applying an aqueous solution of the crosslinking agent onto a PEDOT / PSS film, which is easily soluble in water, can dissolve part of the PEDOT / PSS film and promote the crosslinking reaction with PEDOT / PSS, which is preferable. In the fourth embodiment, the crosslinking agent used to crosslink PEDOT / PSS may be one type or two or more types.

[0189] The polymer membrane of this embodiment contains the crosslinked polymer described above, and may further contain one or more other components as needed in addition to the crosslinked polymer. Examples of other components include known resins other than PEDOT / PSS, surface tension modifiers, and the like. Examples of resins other than PEDOT / PSS include water-soluble or water-dispersible resins, specifically sulfonated polyester resins. Examples of surface tension modifiers include low-molecular-weight additives such as glycerin and ethylene glycol.

[0190] (Method for manufacturing solid electrolyte layer (polymer membrane)) In the fourth embodiment, the polymer membrane forming the solid electrolyte layer 165b can be manufactured, for example, by the method shown below. First, an aqueous dispersion of PEDOT / PSS is prepared in the same manner as in the third embodiment. In the fourth embodiment, the aqueous dispersion of PEDOT / PSS used in manufacturing the solid electrolyte layer 165b can be the same as the aqueous dispersion of PEDOT / PSS that can be used in the third embodiment.

[0191] Next, in the same manner as in the third embodiment, the aqueous dispersion of PEDOT / PSS is applied to the outer surface of the dielectric layer 150 excluding the end connected to the second terminal 130 (i.e., the area where the insulating resin layer 151 is not formed) to form a coating film. Thereafter, in the same manner as in the third embodiment, the coating film formed on the outer surface of the dielectric layer 150 is dried to remove water from the coating film. This results in a PEDOT / PSS film.

[0192] Next, in the fourth embodiment, an aqueous solution of a cross-linking agent made of a metal salt containing a metal cation with a valence of 2 or more is applied onto the PEDOT / PSS film. This brings the PEDOT / PSS in the PEDOT / PSS film into contact with the cross-linking agent, initiating a cross-linking reaction between the PEDOT / PSS and the metal cation contained in the metal salt serving as the cross-linking agent.

[0193] The crosslinking agent aqueous solution preferably has a crosslinking agent content in the range of 0.01 mol% to 2 mol%, and more preferably in the range of 0.1 mol% to 1 mol%. When the crosslinking agent content is 0.01 mol% or more, applying the crosslinking agent aqueous solution onto the PEDOT / PSS film and removing the water in the crosslinking agent aqueous solution can provide the effect of forming a crosslinked structure between the PEDOT / PSS and the crosslinking agent. Therefore, when the crosslinking agent content is 0.01 mol% or more, a polymer film with good water resistance is likely to be obtained. Furthermore, when the crosslinking agent content is 2 mol% or less, the impact of the remaining crosslinking agent that does not form a crosslinked structure is reduced, which is preferable.

[0194] Methods for applying an aqueous solution of a cross-linking agent onto the PEDOT / PSS film include, for example, a method of immersing the area of ​​the dielectric layer 150 formed on the outer surface of the first electrode layer 141 where the PEDOT / PSS film is formed in the aqueous solution of the cross-linking agent, a method using various coaters, a method using various dispensers, a spray method, or other known methods, and can be appropriately determined depending on the shape of the area of ​​the dielectric layer 150 formed on the outer surface of the first electrode layer 141 where the PEDOT / PSS film is formed, the viscosity of the aqueous solution of the cross-linking agent, etc.

[0195] Next, the aqueous solution of the cross-linking agent applied to the PEDOT / PSS film is dried to remove the water in the aqueous solution of the cross-linking agent. This further promotes the cross-linking reaction between the PEDOT / PSS in the PEDOT / PSS film and the metal cations of the metal salt cross-linking agent. By performing the above steps, a solid electrolyte layer 165b is formed, which includes a polymer film of this embodiment containing a cross-linked polymer in which the PEDOT / PSS is cross-linked by the cross-linking agent.

[0196] As a method for removing water from the aqueous solution of the cross-linking agent applied to the PEDOT / PSS film, a known method such as heat treatment at a temperature of 80°C to 150°C can be used, and the method can be appropriately determined depending on the shape of the area of ​​the dielectric layer 150 formed on the outer surface of the first electrode layer 141 where the PEDOT / PSS film is formed, the thickness of the coating film, etc.

[0197] In this embodiment, as in the third embodiment, the crosslinking reaction is initiated by applying an aqueous solution of a crosslinking agent to the PEDOT / PSS film. This promotes the crosslinking reaction near the surface of the PEDOT / PSS film. As a result, the polymer film of this embodiment is presumed to have a continuously or stepwise change in the thickness direction of the crosslinked structures, with the density increasing the closer to the surface. This results in a polymer film with particularly high water resistance at the surface, effectively achieving the effect of improving the water resistance of the polymer film due to the presence of crosslinked structures. Therefore, compared to a polymer film with a substantially uniform density of crosslinked structures produced by applying an aqueous dispersion containing PEDOT / PSS and a crosslinking agent, for example, the polymer film of this embodiment can achieve sufficient water resistance even with a smaller number of crosslinked structures. Therefore, the polymer film of this embodiment can achieve a higher PEDOT / PSS content in the polymer film, resulting in better conductivity and heat resistance, compared to a polymer film with a substantially uniform density of crosslinked structures and equivalent water resistance.

[0198] The polymer film forming the solid electrolyte layer 165b of this embodiment may be manufactured by forming the above-described PEDOT / PSS film, applying an aqueous solution of a crosslinking agent thereon, and performing the steps of removing the water from the aqueous solution of the crosslinking agent only once, or by repeating the above steps multiple times to form a polymer film of a predetermined thickness. The polymer film of this embodiment has good water resistance. Therefore, as in the third embodiment, by forming the above-described PEDOT / PSS film, applying an aqueous solution of a crosslinking agent thereon, and performing the steps of removing the water from the aqueous solution of the crosslinking agent multiple times, a polymer film of a uniform and sufficient thickness is easily obtained.

[0199] In this embodiment, the polymer membrane obtained by removing the water from the aqueous solution of the crosslinking agent may be washed. The washing of the polymer membrane can be carried out using, for example, water.

[0200] In the solid electrolytic capacitor of this embodiment, the solid electrolyte layer 165b has the above-described polymer film, and therefore the water resistance of the solid electrolyte layer 165b is good. Therefore, in this embodiment, as in the solid electrolytic capacitor of the third embodiment, the metal layer 162 can be manufactured by plating.

[0201] Furthermore, the polymer film of this embodiment has good water resistance. Therefore, similarly to the third embodiment, by forming the above-described PEDOT / PSS film, applying an aqueous solution of a cross-linking agent thereon, and then repeatedly removing the water from the aqueous solution of the cross-linking agent, a polymer film having a uniform and sufficient thickness can be easily obtained.

[0202] In the solid electrolytic capacitor of the third embodiment, the cross-linking agent is —NH ２ In the above description, an example is given of a case in which the solid electrolytic capacitor includes a salt of an amine compound containing a total of four or more groups, one or two types of groups selected from the group consisting of an —NH— group, an —NH— group, and an —NH— group. In the solid electrolytic capacitor of the fourth embodiment, an example is given of a case in which the crosslinking agent is made of a metal salt containing a metal cation having a valence of two or more. However, when the solid electrolyte layer 165b is made of two or more polymer films, the solid electrolyte layer 165b may have a polymer film containing the above-mentioned salt of the amine compound as a crosslinking agent, and a polymer film containing the above-mentioned metal salt containing a metal cation having a valence of two or more as a crosslinking agent.

[0203] Fifth Embodiment In the solid electrolytic capacitor of the fifth embodiment, similar to the solid electrolytic capacitor of the third embodiment, the polymer film forming the solid electrolyte layer contains a crosslinked polymer in which PEDOT / PSS represented by formula (1) is crosslinked by a crosslinking agent. In the third and fourth embodiments, the first electrode layer 141 of the solid electrolytic capacitor is made of a metal film having a finely textured surface. However, in the solid electrolytic capacitor of the fifth embodiment, the first electrode layer is made of a porous body having a substantially rectangular block shape and a large number of fine pores that communicate from the inside to the outside.

[0204] 8 is a schematic cross-sectional view showing a solid electrolytic capacitor according to a fifth embodiment of the present invention. The solid electrolytic capacitor 200 shown in FIG. 8 includes a resin molded layer 11 having a substantially rectangular parallelepiped outer shape, a capacitor element provided inside the resin molded layer 11, a first terminal 12, and a second terminal 13.

[0205] The resin mold layer 11 forms the exterior of the solid electrolytic capacitor 200, and may be the same as the resin mold layer 110 in the solid electrolytic capacitor 100 of the third embodiment.

[0206] The first terminal 12 is made of a conductive material such as Cu. The first terminal 12 is electrically connected to the second electrode layer 16 of the capacitor element by a connecting conductor layer 19 and is extended to the outside of the resin molded layer 11. The connecting conductor layer 19 may be made of, for example, a conductive adhesive containing Ag. The portion of the first terminal 12 located inside the resin molded layer 11 is bent to conform to the outer shape of the first electrode layer 14, which is a substantially rectangular block. The portion of the first terminal 12 located outside the resin molded layer 11 is bent to conform to the outer surface of the resin molded layer 11.

[0207] The second terminal 13 is made of a conductive material such as Cu. The second terminal 13 is electrically connected to the first electrode layer 14 of the capacitor element via a lead 41 and is extended to the outside of the resin mold layer 11. The portion of the second terminal 13 located outside the resin mold layer 11 is bent along the outer surface of the resin mold layer 11.

[0208] As shown in Fig. 5, the end of the lead 41 on the first electrode layer 14 side is embedded in the first electrode layer 14. The end of the lead 41 on the first electrode layer 14 side extends from approximately the center of one of the outer surfaces of the approximately rectangular parallelepiped first electrode layer 14 toward approximately the center of the first electrode layer 14. As shown in Fig. 5, the end of the lead 41 on the second terminal 13 side penetrates the solid electrolyte layer 60b and the second electrode layer 16 while being covered with the dielectric layer 15. The dielectric layer 15 is not formed on the surface of the end of the lead 41 on the second terminal 13 side, and the end is electrically connected to the second terminal 13 by resistance welding or the like.

[0209] The lead 41 can be made of a conductive material such as aluminum, tantalum, or niobium. The lead 41 is preferably made of the same material as the first electrode layer 14. The reason for this is that the dielectric layer 15 can be formed on the outer surface of the first electrode layer 14 and on the surfaces of the fine holes in the first electrode layer 14, and at the same time, the dielectric layer 15 can be formed on the surface of the lead 41 exposed from the first electrode layer 14, thereby enabling efficient manufacturing.

[0210] (First Electrode Layer 14) The first electrode layer 14 functions as an anode in the solid electrolytic capacitor 200. The first electrode layer 14 is a sintered body of a valve metal or a metal containing a valve metal as a main component, and is made of a porous body having a large number of fine pores (not shown) that communicate from the inside to the outside.

[0211] Examples of valve metals used as the material for the first electrode layer 14 include aluminum, tantalum, niobium, titanium, hafnium, zirconium, zinc, tungsten, bismuth, and antimony. Among the above valve metals, it is preferable to use one or more selected from aluminum, tantalum, and niobium as the material for the first electrode layer 14, and tantalum and / or niobium are more preferable. This is because the dielectric layer 15 can be stably formed by anodizing the outer surface of the first electrode layer 14 and the surfaces of the fine pores in the first electrode layer 14.

[0212] 8, the dielectric layer 15 is formed along the outer surface of the first electrode layer 14 so as to cover the first electrode layer 14. The dielectric layer 15 is also formed on the surfaces of minute holes in the first electrode layer 14. The dielectric layer 15 is also formed on the surface of the lead 41 exposed from the first electrode layer 14, excluding the end of the lead 41 on the second terminal 13 side.

[0213] The dielectric layer 15 is made of an electrically insulating metal oxide film. For example, when the first electrode layer 14 is a sintered body of tantalum, the dielectric layer 15 is preferably made of a tantalum oxide film. The thickness of the dielectric layer 15 is usually 1 nm to 1 μm.

[0214] 8, the solid electrolyte layer 60b is formed along the outer surface of the dielectric layer 15. As the solid electrolyte layer 60b in this embodiment, a polymer film similar to the polymer film that can be used for the solid electrolyte layer 165b in the solid electrolytic capacitor 100 of the third or fourth embodiment can be used.

[0215] The thickness of the solid electrolyte layer 60b in the solid electrolytic capacitor 200 of the fifth embodiment is preferably, for example, 5 μm or more at the vertices and sides and 25 μm or less at the faces, because this results in a solid electrolytic capacitor 200 with even greater suppression of leakage current.

[0216] (Second electrode layer 16) The second electrode layer 16 formed on the outer surface of the solid electrolyte layer 60b may be made of a conductive layer 61b and a metal layer 62 formed on the outer surface of the conductive layer 61b, similar to the second electrode layer 160 in the solid electrolytic capacitor 100 of the third and fourth embodiments.

[0217] (Method of Manufacturing Solid Electrolytic Capacitor) The solid electrolytic capacitor 200 of this embodiment can be manufactured, for example, by the method described below. First, a block-shaped first electrode layer 14 is prepared, which is a sintered body of a valve metal such as tantalum or a metal containing a valve metal as its main component. The first electrode layer 14 can be formed by molding powder containing a metal containing a valve metal as its main component into a compact by a known method, and then sintering the compact by a known method.

[0218] Next, by a known method, one end of the lead 41 is embedded from approximately the center of one of the outer surfaces of the approximately rectangular parallelepiped first electrode layer 14 toward approximately the center of the first electrode layer 14, thereby integrating the first electrode layer 14 and the lead 41. Next, a dielectric layer 15 is provided on the outer surface of the first electrode layer 14, the surfaces of the fine holes in the first electrode layer 14, and the surface of the lead 41 exposed from the first electrode layer 14. For example, if the first electrode layer 14 is a sintered body made of tantalum and the lead 41 is made of tantalum, the dielectric layer 15 made of a tantalum oxide film can be formed by anodizing treatment using ammonium acetate, sulfuric acid, phosphoric acid, or the like as a chemical conversion treatment solution (electrolyte).

[0219] Next, a solid electrolyte layer 60b having a polymer film containing a crosslinked polymer formed by crosslinking PEDOT / PSS represented by formula (1) with a crosslinking agent is provided on the outer surface of the dielectric layer 15 by the same method as when providing the solid electrolyte layer 165b in the solid electrolytic capacitor 100 of the third or fourth embodiment. Thereafter, a conductive layer 61b and a metal layer 62 are formed in this order on the outer surface of the solid electrolyte layer 60b by the same method as when providing the second electrode layer 160 in the solid electrolytic capacitor 100 of the third or fourth embodiment, thereby forming the second electrode layer 16.

[0220] Next, the metal layer 62 of the second electrode layer 16 and a plate-shaped first terminal piece that will become the first terminal 12 are electrically connected by the connecting conductor layer 19. Also, the end of the lead 41 that is not embedded in the first electrode layer 14 is electrically connected to a plate-shaped second terminal piece that will become the second terminal 13. Thereafter, in the same manner as the resin mold layer 110 of the solid electrolytic capacitor 100 of the third and fourth embodiments, a resin mold layer 11 is formed from an insulating resin material that contains a resin such as an epoxy resin and a filler such as silica.

[0221] Thereafter, the first terminal piece protruding outward from the resin mold layer 11 is bent along the outer surface of the resin mold layer 11 to form the first terminal 12. Furthermore, the second terminal piece protruding outward from the resin mold layer 11 is bent along the outer surface of the resin mold layer 11 to form the second terminal 13. By performing the above steps, the solid electrolytic capacitor 200 of this embodiment is obtained.

[0222] In the solid electrolytic capacitor 200 of this embodiment, the solid electrolyte layer 165b has the above-described polymer film, and therefore the water resistance of the solid electrolyte layer 165b is good. Therefore, in this embodiment, as in the solid electrolytic capacitors of the third and fourth embodiments, the metal layer 162 can be manufactured by plating.

[0223] Furthermore, the polymer film of this embodiment has good water resistance. Therefore, similarly to the third and fourth embodiments, by forming the above-mentioned PEDOT / PSS film, applying an aqueous solution of a cross-linking agent thereon, and then repeatedly removing the water from the aqueous solution of the cross-linking agent, a polymer film having a uniform and sufficient thickness can be easily obtained.

[0224] Specifically, in the second and subsequent steps, even if a block-shaped first electrode layer made of tantalum with a dielectric layer formed on its outer surface is immersed in an aqueous dispersion of PEDOT / PSS and the aqueous dispersion of PEDOT / PSS is applied, the polymer film formed on the vertices and edges of the first electrode layer is unlikely to dissolve. Therefore, by repeating the above steps multiple times, a polymer film with sufficient thickness can be easily formed on the vertices and edges of the first electrode layer. As a result, a solid electrolytic capacitor with low leakage current can be formed.

[0225] Furthermore, even if the number of times of performing the above steps is small, a polymer film having a sufficient thickness can be formed on the vertices and sides of the first electrode layer, thereby enabling efficient production of a solid electrolyte layer. Furthermore, because the polymer film formed on the vertices and sides of the first electrode layer is less likely to dissolve, there is little difference in thickness between the polymer film formed on the vertices and sides of the first electrode layer and the polymer film formed on the surface of the first electrode layer, making it easier to form a solid electrolyte layer with a uniform thickness.

[0226] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0227] (Test Example 1-1) A 2 mass% aqueous dispersion of PEDOT / PSS represented by formula (1) was mixed with a 5 mass% aqueous solution of modified polyvinyl alcohol represented by formula (2) (n, which indicates the degree of polymerization in formula (2), was 500; R was a methyl group), to obtain a mixed solution. The aqueous dispersion of PEDOT / PSS consisted of only PEDOT / PSS and water. A 5 mass% aqueous solution of adipic acid dihydrazide represented by formula (3), which serves as a crosslinking agent, was mixed with the obtained mixed solution and stirred, to obtain a resin coating material.

[0228] The content of PEDOT / PSS and modified polyvinyl alcohol in the resin coating was 30%:70% (PEDOT / PSS:modified polyvinyl alcohol) by mass ratio of solids. The content of the crosslinker in the resin coating was 5% by mass relative to the mass of the solids of the modified polyvinyl alcohol. The resin coating thus prepared was applied to a glass plate, which was the surface on which the coating was to be formed, to form a coating film. The coating film formed on the glass plate was then dried by heat treatment at 120°C for 15 minutes to remove water from the coating film, yielding a polymer film of Test Example 1-1 with a thickness of 10 μm. The content of PEDOT / PSS in the solids of the polymer film (solids of the resin coating) is shown in Table 1.

[0229] (Test Examples 1-2 to 1-8, Comparative Test Examples 1-1 and 1-2) The types of aqueous dispersions of PEDOT / PSS, the types of aqueous solutions of modified polyvinyl alcohol (modified PVA), and the types of aqueous solutions of crosslinkers were as shown in Table 1, and the contents (mass ratio of solids) of PEDOT / PSS and modified polyvinyl alcohol contained in the resin coating material and the content (ratio relative to the mass of solids of modified polyvinyl alcohol) of crosslinker contained in the resin coating material were as shown in Table 1. The polymer films of Test Examples 1-2 to 1-8, Comparative Test Examples 1-1 and 1-2 were obtained in the same manner as Test Example 1-1. The content of PEDOT / PSS in the solids of the polymer film (in the solids of the resin coating material) is shown in Table 1.

[0230] The aqueous dispersions of PEDOT / PSS, aqueous solutions of modified polyvinyl alcohol, and aqueous solutions of crosslinking agents shown in Table 1 are as follows: [PEDOT / PSS aqueous dispersion] A: An aqueous dispersion consisting of only PEDOT / PSS represented by formula (1) and water, containing 2% by mass of PEDOT / PSS. [PEDOT / PSS aqueous dispersion] B: An aqueous dispersion consisting of PEDOT / PSS represented by formula (1), a sulfonated polyester resin which is a polymer having no carbonyl groups, and water, containing 2% by mass of PEDOT / PSS.

[0231] [Modified polyvinyl alcohol aqueous solution] a: An aqueous solution containing 5% by mass of modified polyvinyl alcohol represented by formula (2) (n, which indicates the degree of polymerization in formula (2), was 500, and R was a methyl group). [Modified polyvinyl alcohol aqueous solution] b: An aqueous solution containing 5% by mass of modified polyvinyl alcohol represented by formula (2) (n, which indicates the degree of polymerization in formula (2), was 2000, and R was a methyl group). [Crosslinking agent aqueous solution] I: An aqueous solution containing 5% by mass of adipic acid dihydrazide represented by formula (3). [Crosslinking agent aqueous solution] II: An aqueous solution containing 5% by mass of 7,11-octadecadiene-1,18-dicarbohydrazide represented by formula (4).

[0232] The water resistance of the polymer films obtained in Test Examples 1-1 to 1-8 and Comparative Test Examples 1-1 and 1-2 was evaluated by the following method. [Evaluation of Water Resistance] A glass plate on which a polymer film had been formed was immersed in stirred water at 80°C for 3 minutes and then removed. The state of the polymer film on the glass plate and the immersed water were then visually observed. Next, strength observation was performed by the following method. First, the surface of the wet polymer film on the glass plate removed from the water was scratched with a sharp-tipped metal rod to visually check for deformation. The polymer film was then air-dried, and the surface state was visually observed and evaluated according to the following criteria. The results are shown in Table 1.

[0233] (Criteria) A (excellent): No detachment of the polymer film from the glass plate was confirmed by visual observation. Furthermore, the wet polymer film was not deformed when scratched with a metal rod. B (good): No detachment of the polymer film from the glass plate was confirmed by visual observation. Furthermore, the wet polymer film was deformed when scratched with a metal rod, but returned to its original shape by air drying. C (fair): It was confirmed by visual observation that a portion of the polymer film had detached from the glass plate and that the detached polymer film was floating in the water in which it was immersed. D (poor): It was confirmed by visual observation that the entire polymer film had detached from the glass plate and that the detached polymer film was floating in the water in which it was immersed, or that the detached polymer film had dissolved in the water in which it was immersed.

[0234] The sheet resistance of the polymer films of Test Examples 1-2 to 1-8 and Comparative Test Examples 1-1 and 1-2 was measured using a low resistivity meter in accordance with JIS K 7194. The results are shown in Table 1.

[0235]

[0236] As shown in Table 1, the polymer films of Test Examples 1-1 to 1-8, which contained PEDOT / PSS and a crosslinked polymer in which modified polyvinyl alcohol (modified PVA) was crosslinked with a crosslinking agent made of a dihydrazide compound, were confirmed to have good water resistance compared to the polymer films of Comparative Test Examples 1-1 and 1-2, which did not contain a crosslinked polymer. Also, as shown in Table 1, the polymer films of Test Examples 1-1 to 1-8 had sufficiently low sheet resistance and were confirmed to be usable as solid electrolyte layers in capacitor elements.

[0237] (Example 1-1) An aluminum foil having a width of 3.5 mm and a thickness of 110 μm and having roughened surfaces on both sides was prepared. A resist layer was formed on both sides of the aluminum foil, exposing a region extending from one end of the aluminum foil to 4.5 mm in the longitudinal direction.

[0238] Next, a 3.5 mm wide, 4.5 mm long region of one end of the aluminum foil that was not covered with the resist layer was immersed in a 15% aqueous solution of ammonium adipate, and an anodization treatment was performed by applying a voltage with the aluminum foil as the positive electrode and the negative electrode immersed in the aqueous solution of ammonium adipate. This formed a dielectric layer made of an aluminum oxide film on the surface of the aluminum foil. The surface of the aluminum oxide film was then washed with water and dried.

[0239] (Formation of First Polymer Film) A 2% by mass aqueous dispersion of PEDOT / PSS represented by formula (1) was mixed with a 5% by mass aqueous solution of modified polyvinyl alcohol represented by formula (2) (n, which indicates the degree of polymerization in formula (2), was 500, and R was a methyl group) to obtain a mixed solution. The PEDOT / PSS aqueous dispersion consisted of only PEDOT / PSS and water. A 5% by mass aqueous solution of adipic acid dihydrazide represented by formula (3), which serves as a crosslinking agent, was mixed with the obtained mixed solution and stirred to obtain a resin coating material.

[0240] The content of PEDOT / PSS and modified polyvinyl alcohol in the resin coating was set to a solid mass ratio of 70%:30% (PEDOT / PSS:modified polyvinyl alcohol), and the content of the crosslinking agent in the resin coating was set to 5% by mass relative to the mass of the solid mass of the modified polyvinyl alcohol.

[0241] The resin coating was applied to the aluminum oxide coating by immersing an aluminum foil having an aluminum oxide coating formed on its surface in the resin coating thus prepared, forming a coating film. The coating film formed on the aluminum oxide coating formed on the surface of the aluminum foil was then dried by heat treatment to remove water from the coating film, yielding a polymer film. The resin coating was then applied to the aluminum oxide coating having the polymer film formed thereon, and the drying process was repeated twice in the same manner as above, to form the first polymer film of Example 1-1. The content of PEDOT / PSS in the solid content of the first polymer film (in the solid content of the resin coating) is shown in Table 2.

[0242] (Formation of second polymer film) A 2% by mass aqueous dispersion of PEDOT / PSS represented by formula (1) was mixed with a 5% by mass aqueous solution of modified polyvinyl alcohol represented by formula (2) (n, which indicates the degree of polymerization, was 500, and R was a methyl group). The PEDOT / PSS aqueous dispersion consisted of PEDOT / PSS, a sulfonated polyester resin, which is a polymer without carbonyl groups, and water. A 5% by mass aqueous solution of adipic acid dihydrazide represented by formula (3), which is a crosslinking agent, was mixed with the resulting mixture and stirred to obtain a resin coating.

[0243] The content of PEDOT / PSS and modified polyvinyl alcohol in the resin coating was 85%:15% (PEDOT / PSS:modified polyvinyl alcohol) in terms of solid mass, and the content of the crosslinking agent in the resin coating was 5% by mass relative to the mass of the solid mass of the modified polyvinyl alcohol.

[0244] The resin coating thus prepared was applied by immersion to the aluminum oxide coating on which the first polymer film had been formed, forming a coating film. The coating film formed on the aluminum oxide coating on which the first polymer film had been formed was then dried by heat treatment to remove water from the coating film, thereby forming the second polymer film of Example 1-1. The content of PEDOT / PSS in the solid content of the second polymer film (in the solid content of the resin coating) is shown in Table 2. This resulted in the solid electrolyte layer of Example 1-1, which consisted of the first polymer film and the second polymer film.

[0245] Next, a carbon paste containing a carbon material and a binder resin was applied to the outer surface of the solid electrolyte layer and dried to form a carbon layer with a thickness of 2 μm. An Ag paste containing Ag particles and a binder resin was applied to the carbon layer formed on the outer surface of the solid electrolyte layer, and then dried and cured to form a metal layer consisting of an Ag layer with a thickness of 10 μm. By performing the above steps, the capacitor element of Example 1-1 was obtained.

[0246] (Examples 1-2 to 1-7, Comparative Examples 1-1 and 1-2) The types of aqueous dispersions of PEDOT / PSS, the types of aqueous solutions of modified polyvinyl alcohol (modified PVA), and the types of aqueous solutions of crosslinkers used for the first and second polymer films are shown in Table 2. The contents of PEDOT / PSS (percentage relative to the total mass of the solids of PEDOT / PSS and the solids of modified polyvinyl alcohol) and crosslinker (percentage relative to the mass of the solids of modified polyvinyl alcohol) contained in the resin coating were as shown in Table 2. The capacitor elements of Examples 1-2 to 1-7 and Comparative Examples 1-1 and 1-2 were obtained in the same manner as in Example 1-1, except that the number of applications of the resin coating material shown in Table 2 was used to produce the first and second polymer films. The contents of PEDOT / PSS in the solids of the first and second polymer films (in the solids of the resin coating material) are shown in Table 2.

[0247] The aqueous dispersion of PEDOT / PSS, the aqueous solution of modified polyvinyl alcohol, and the aqueous solution of crosslinking agent shown in Table 2 used in Examples 1-1 to 1-7, Comparative Examples 1-1 and 1-2 were the same as those shown in Table 1.

[0248]

[0249] The capacitor elements of Examples 1-1 to 1-7 and Comparative Examples 1-1 and 1-2 obtained in this manner were evaluated for the thickness of the solid electrolyte layer at the end and face portions, the capacitance, and the leakage current by the methods described below.

[0250] [Thickness of Solid Electrolyte Layer] The cross section of the capacitor element was observed with a scanning electron microscope (SEM) at 1000x magnification. For the obtained SEM image, the thickness of the solid electrolyte layer (surface thickness) in the thickness direction of the aluminum foil (edge ​​thickness) was measured at five locations, and the maximum value was calculated. Furthermore, the thickness of the solid electrolyte layer formed at the edge of the aluminum foil in the direction perpendicular to the thickness direction of the aluminum foil (edge ​​thickness) was measured at five locations, and the average value was calculated. The results are shown in Table 3.

[0251] [Capacitance] The capacitance of the capacitor element was measured using an impedance analyzer. The results are shown in Table 3. [Leakage Current] A voltage was applied to the capacitor element for 2 minutes using a device equipped with a power supply and an ammeter, and the leakage current was measured. The results are shown in Table 3.

[0252] [Plating Possibility] Using the method described below, a metal layer consisting of a Cu layer was formed using a plating method instead of the Ag layer formed in Examples 1-1 to 1-7, Comparative Examples 1-1, and 1-2. First, similar to the capacitor elements of Examples 1-1 to 1-7, Comparative Examples 1-1, and 1-2, steps were carried out up to the formation of a carbon layer on the outer surface of the solid electrolyte layer. Next, a seed paste containing a carbon material, polypyrrole particles, and a binder resin was applied to the carbon layer formed on the outer surface of the solid electrolyte layer and dried to form a seed layer.

[0253] The entire solid electrolyte layer on which the carbon layer and seed layer were formed was then immersed in a pretreatment solution for forming Cu plating and an electroless Cu plating solution, followed by electroless Cu plating, to form a metal layer made of Cu. The Cu layer thus formed was observed and evaluated according to the following criteria. The results are shown in Table 3. B (good): No swelling, cracking, or shedding of the Cu layer occurred. D (poor): One or more of swelling, cracking, and shedding of the Cu layer occurred.

[0254]

[0255] As shown in Tables 2 and 3, the capacitor elements of Examples 1-1 to 1-7 have a solid electrolyte layer made of a polymer film containing PEDOT / PSS and a crosslinked polymer formed by crosslinking modified polyvinyl alcohol (modified PVA) with a crosslinking agent made of a dihydrazide compound. It was confirmed that the capacitor elements of Examples 1-1 to 1-7 have lower leakage current than the capacitor elements of Comparative Examples 1-1 and 1-2, which have solid electrolyte layers made of polymer films that do not contain crosslinked polymers. This is presumably because the capacitor elements of Examples 1-1 to 1-7 have thicker film thicknesses at the edges of the solid electrolyte layer than the capacitor elements of Comparative Examples 1-1 and 1-2. Furthermore, the capacitance of the capacitor elements of Examples 1-1 to 1-7 was equivalent to that of the capacitor elements of Comparative Examples 1-1 and 1-2.

[0256] Furthermore, in Examples 1-1 to 1-7, a metal layer made of a Cu layer could be formed using a plating method instead of an Ag layer. In contrast, in Comparative Examples 1-1 and 1-2, a Cu layer could not be formed using a plating method instead of an Ag layer. This is presumably because the water resistance of the polymer membrane forming the solid electrolyte layer was better in Examples 1-1 to 1-7 than in Comparative Examples 1-1 and 1-2.

[0257] [Polymer Film] (Test Examples 2-1 to 2-10) A glass plate was immersed in an aqueous dispersion containing 2% by mass of PEDOT / PSS, a surface tension modifier, and water, to form a coating film on the glass plate. The glass plate on which the coating film was formed was then heat-treated at 120°C for 15 minutes to dry the coating film and remove the water in the coating film, thereby obtaining a PEDOT / PSS film with a thickness of 10 µm.

[0258] Next, the glass plate on which the PEDOT / PSS film was formed was immersed for 3 minutes in an aqueous solution of the crosslinking agent containing the crosslinking agent shown in Table 4 in the amount shown in Table 4. Next, the aqueous solution of the crosslinking agent applied to the PEDOT / PSS film formed on the glass plate was dried by heat treatment at 80°C for 5 minutes to remove water from the aqueous solution of the crosslinking agent, and polymer films of Test Examples 2-1 to 2-10 were obtained.

[0259] Comparative Test Example 2-1 The PEDOT / PSS film formed during the production of the polymer film of Test Example 2-1 was used as the polymer of Comparative Test Example 2-1.

[0260] The crosslinking agents shown in Table 4 are as follows: [Crosslinking agent A] N,N'-bis(3-aminopropyl)-1,4-butanediamine tetrahydrochloride represented by formula (6). [Crosslinking agent B] Calcium chloride.

[0261] The water resistance of the polymer films obtained in Test Examples 2-1 to 2-10 and Comparative Test Example 2-1 was evaluated by the following method. [Evaluation of Water Resistance] A glass plate on which a polymer film had been formed was immersed in stirred water at 80°C for 3 minutes and then removed. The state of the polymer film on the glass plate and the immersed water were then visually observed. Next, strength observation was performed by the following method. First, the surface of the wet polymer film on the glass plate removed from the water was scratched with a sharp-tipped metal rod to visually check for deformation. The polymer film was then air-dried, and the surface state was visually observed and evaluated according to the following criteria. The results are shown in Table 4.

[0262] (Criteria) A (excellent): No detachment of the polymer film from the glass plate was confirmed by visual observation. Furthermore, the wet polymer film was not deformed when scratched with a metal rod. B (good): No detachment of the polymer film from the glass plate was confirmed by visual observation. Furthermore, the wet polymer film was deformed when scratched with a metal rod, but returned to its original shape after drying at 80°C for 10 minutes. C (fair): It was confirmed by visual observation that a portion of the polymer film had detached from the glass plate and that the detached polymer film was floating in the water in which it was immersed. D (poor): It was confirmed by visual observation that the entire polymer film had detached from the glass plate and that the detached polymer film was floating in the water in which it was immersed, or that the detached polymer film was dissolved in the water in which it was immersed.

[0263] The sheet resistance of the polymer films of Test Examples 2-1 to 2-10 and Comparative Test Example 2-1 was measured using a low resistivity meter in accordance with JIS K 7194. The results are shown in Table 4.

[0264]

[0265] As shown in Table 4, the polymer films of Test Examples 2-1 to 2-10, which contain crosslinked polymers in which PEDOT / PSS is crosslinked with a crosslinking agent, were confirmed to have good water resistance compared to Comparative Test Example 2-1, which is an uncrosslinked PEDOT / PSS film. Furthermore, as shown in Table 5, the polymer films of Test Examples 2-2 to 2-5 and Test Examples 2-8 to 2-9 had sufficiently low sheet resistance.

[0266] [Capacitor element] (Example 2-1) An aluminum foil having a width of 3.5 mm and a thickness of 110 μm and having roughened surfaces on both sides was prepared. A resist layer was formed on both sides of the aluminum foil, exposing a region extending from one end of the aluminum foil to 4.5 mm in the longitudinal direction.

[0267] Next, a 3.5 mm wide, 4.5 mm long region of one end of the aluminum foil that was not covered with the resist layer was immersed in a 15% aqueous solution of ammonium adipate, and an anodization treatment was performed by applying a voltage with the aluminum foil as the positive electrode and the negative electrode immersed in the aqueous solution of ammonium adipate. This formed a dielectric layer made of an aluminum oxide film on the surface of the aluminum foil. The surface of the aluminum oxide film was then washed with water and dried.

[0268] Aqueous solution A was applied to the aluminum oxide film by immersing an aluminum foil having an aluminum oxide film formed on its surface in aqueous solution A to form a coating film. The coating film formed on the aluminum oxide film formed on the surface of the aluminum foil was then dried by heat treatment to remove water from the coating film, thereby obtaining a polymer film. Thereafter, the process of applying aqueous solution A to the aluminum oxide film on which the polymer film had been formed and drying was repeated twice in the same manner as above, thereby obtaining polymer film A. Subsequently, the process of applying aqueous dispersion B to the aluminum oxide film on which polymer film A had been formed and drying was repeated three times in the same manner as above, thereby obtaining polymer film B.

[0269] Thereafter, the aluminum foil having the aluminum oxide coating on which the polymer film B was formed was immersed in the crosslinking agent A, so that the crosslinking agent A was applied to the aluminum oxide coating on which the polymer film B was formed, thereby forming a coating film. Thereafter, the coating film formed on the aluminum oxide coating on the surface of the aluminum foil was dried by heat treatment, and water in the coating film was removed, thereby crosslinking the polymer film B of Example 2-1.

[0270] Next, the crosslinked polymer membrane B was washed with water and dried by heat treatment. Thereafter, the aqueous dispersion C was applied to the crosslinked polymer membrane B in the same manner as above, and dried to obtain a polymer membrane C. Subsequently, the polymer membrane C was washed with water and dried by heat treatment. By performing the above steps, a solid electrolyte layer of Example 2-1 including the crosslinked polymer membrane B was obtained on an aluminum foil having an aluminum oxide film formed on its surface.

[0271] (Example 2-2) An aluminum foil having an aluminum oxide film formed on its surface was obtained in the same manner as in Example 2-1. The aluminum foil having an aluminum oxide film formed on its surface was immersed in aqueous solution A, and aqueous solution A was applied to the aluminum oxide film to form a coating film. Thereafter, the coating film formed on the aluminum oxide film formed on the surface of the aluminum foil was dried by heat treatment to remove water from the coating film, thereby obtaining a polymer film A. Thereafter, a step of forming a polymer film A on the aluminum oxide film on which the polymer film A had been formed was carried out again in the same manner as above.

[0272] Next, the aluminum foil having the aluminum oxide film having the polymer film A formed thereon was immersed in the aqueous dispersion B, whereby the aqueous dispersion B was applied to the aluminum oxide film having the polymer film A formed thereon to form a coating film. Thereafter, the coating film formed on the surface of the aluminum foil was dried by heat treatment to remove water from the coating film, thereby obtaining the polymer film B.

[0273] Next, the aluminum foil having an aluminum oxide film with polymer film B formed on its surface was immersed in crosslinking agent A, whereby crosslinking agent A was applied to the aluminum oxide film with polymer film B formed thereon to form a coating film. Thereafter, the coating film formed on the surface of the aluminum foil was dried by heat treatment to remove water from the coating film, thereby crosslinking the polymer film B. Subsequently, the polymer film B was washed with water and dried by heat treatment.

[0274] Thereafter, the process of forming a polymer film B on the aluminum oxide film on which the crosslinked polymer film B had been formed, applying a crosslinking agent A, drying, and washing with water was repeated twice in the same manner as described above.

[0275] Thereafter, the aluminum oxide foil having an aluminum oxide film with a crosslinked polymer film B formed on its surface was immersed in the aqueous dispersion C, whereby the aqueous dispersion C was applied onto the aluminum oxide film with the crosslinked polymer film B formed thereon to form a coating film. The coating film formed on the surface of the aluminum foil was then dried by heat treatment to remove water from the coating film, thereby obtaining a polymer film C. By performing the above steps, a solid electrolyte layer of Example 2-2 including the crosslinked polymer film B was obtained on the aluminum foil having an aluminum oxide film formed on its surface.

[0276] Example 2-3 A solid electrolyte layer of Example 2-3 including a crosslinked polymer membrane B was obtained on an aluminum foil having an aluminum oxide film formed on its surface in the same manner as in Example 2-1, except that crosslinking agent B was used instead of crosslinking agent A.

[0277] (Example 2-4) In the same manner as in Example 2-1, an aluminum foil having an aluminum oxide film formed on its surface was obtained. Thereafter, in the same manner as in Example 2-1, a step of forming a polymer film B on the aluminum oxide film having the polymer film A formed thereon was carried out.

[0278] Thereafter, the aqueous dispersion C was applied to the polymer film B in the same manner as above, and dried to obtain a polymer film C. Subsequently, the polymer film C was washed with water and dried by heat treatment.

[0279] Thereafter, the aluminum foil having the aluminum oxide coating on which the polymer film C was formed was immersed in the crosslinking agent A, thereby applying the crosslinking agent A onto the aluminum oxide coating on which the polymer film C was formed, thereby forming a coating film. Thereafter, the coating film formed on the aluminum oxide coating on the surface of the aluminum foil was dried by heat treatment to remove water from the coating film, thereby crosslinking the polymer film C.

[0280] Next, the crosslinked polymer membrane C was washed with water and dried by heat treatment. By performing the above steps, a solid electrolyte layer of Example 2-4 including the crosslinked polymer membrane C was obtained on the aluminum foil having an aluminum oxide film formed on its surface.

[0281] Example 2-5 A solid electrolyte layer of Example 2-5 including a crosslinked polymer film C was obtained on an aluminum foil having an aluminum oxide film formed on its surface in the same manner as in Example 2-4, except that crosslinking agent B was used instead of crosslinking agent A.

[0282] Comparative Example 2-1 A solid electrolyte layer of Comparative Example 2-1 including polymer membranes A to C was obtained on an aluminum foil having an aluminum oxide film formed on its surface in the same manner as in Example 2-1, except that the steps of applying crosslinking agent A onto the aluminum oxide film on which polymer membrane B had been formed and drying to crosslink polymer membrane B, and washing the crosslinked polymer membrane B with water and subjecting it to heat treatment were not performed.

[0283] The aqueous solution A, aqueous dispersion B, aqueous dispersion C, crosslinker A, and crosslinker B used in Examples 2-1 to 2-5 and Comparative Example 2-1 are as follows: "Aqueous solution A" was an aqueous solution composed of self-doped PEDOT (polyethylenedioxythiophene), a surface tension modifier, and water, containing 2% by mass of PEDOT. "Aqueous dispersion B" was an aqueous dispersion composed of PEDOT / PSS represented by formula (1), a surface tension modifier, and water, containing 2% by mass of PEDOT / PSS. "Aqueous dispersion C" was an aqueous dispersion composed of PEDOT / PSS represented by formula (1), a sulfonated polyester resin, and water, containing 2.5% by mass of PEDOT / PSS. "Crosslinker A" was N,N'-bis(3-aminopropyl)-1,4-butanediamine tetrahydrochloride represented by formula (6). "Crosslinker B" was calcium chloride.

[0284] Table 5 shows the type of crosslinking agent used in Examples 2-1 to 2-5 and Comparative Example 2-1, the content of the crosslinking agent, and the number of times the crosslinking agent was applied.

[0285]

[0286] A second electrode layer including a metal layer made of an Ag layer was formed on the outer surface of each of the solid electrolyte layers obtained in Examples 2-1 to 2-5 and Comparative Example 2-1 by the method described below. That is, a conductive paste containing a carbon material and a binder resin was applied to the outer surface of the solid electrolyte layer and dried to form a carbon layer (conductive layer) with a thickness of 2 μm. Next, an Ag paste containing Ag particles and a binder resin was applied to the carbon layer formed on the outer surface of the solid electrolyte layer, and then dried and cured to form a metal layer made of an Ag layer with a thickness of 10 μm. By performing the above steps, the capacitor elements of Examples 2-1 to 2-5 and Comparative Example 2-1 were obtained.

[0287] The capacitance and equivalent series resistance of the capacitor elements of Examples 2-1 to 2-5 and Comparative Example 2-1 obtained in this manner were measured by the methods described below.

[0288] [Capacitance] The capacitance of the capacitor element was measured at 120 Hz using an impedance analyzer. The results are shown in Table 5. [Equivalent Series Resistance] The equivalent series resistance (ESR) was measured at 100 kHz using an impedance analyzer. The results are shown in Table 5.

[0289] [Plating Possibility] Using the method described below, a second electrode layer including a metal layer made of a Cu layer was formed on the outer surface of each of the solid electrolyte layers of Examples 2-1 to 2-5 and Comparative Example 2-1, which were formed in the same manner as described above. First, similar to the capacitor elements of Examples 2-1 to 2-5 and Comparative Example 2-1, steps were carried out up to the formation of a carbon layer (conductive layer) on the outer surface of the solid electrolyte layer. Next, a seed paste containing a carbon material, polypyrrole particles, and a binder resin was applied to the carbon layer (conductive layer) formed on the outer surface of the solid electrolyte layer, and then dried to form a plating seed layer (conductive layer).

[0290] Thereafter, the entire solid electrolyte layer on which the carbon layer and the plating seed layer were formed was successively immersed in a pretreatment solution containing a Pd catalyst for forming Cu plating and an electroless Cu plating solution to perform electroless Cu plating treatment, thereby forming a metal layer consisting of a Cu layer.

[0291] The Cu layer thus formed was observed and evaluated according to the following criteria. The results are shown in Table 5. B (good): No swelling, cracking, or falling off of the Cu layer occurred. D (poor): One or more of swelling, cracking, and falling off of the Cu layer occurred.

[0292] In addition, the process up to the formation of the solid electrolyte layer was carried out in the same manner as in the capacitor elements of Example 2-1 and Comparative Example 2-1. Thereafter, without forming a carbon layer or a plating seed layer on the outer surface of the solid electrolyte layer, the entire solid electrolyte layer was sequentially immersed in a pretreatment solution containing a Pd catalyst for forming Cu plating and an electroless Cu plating solution, and electroless Cu plating was performed to form a metal layer consisting of a Cu layer. The Cu layer thus formed was observed and evaluated according to the same criteria as above. The results are shown in Table 5.

[0293] As shown in Table 5, it was confirmed that the capacitor elements of Examples 2-1 to 2-5, which have a solid electrolyte layer having a polymer film containing a crosslinked polymer crosslinked by crosslinking agent A or crosslinking agent B, have sufficient electrical characteristics as a capacitor element when they have a second electrode layer containing a metal layer made of an Ag layer. Furthermore, it was confirmed that the capacitor elements of Examples 2-1 to 2-5 can form a metal layer made of a Cu layer using a plating method by forming a conductive layer made of a carbon layer and a plating seed layer on the outer surface of the solid electrolyte layer.

[0294] In contrast, in the capacitor element of Comparative Example 2-1, which has a solid electrolyte layer made of a polymer film that does not contain a crosslinked polymer, even if a conductive layer made of a carbon layer and a plating seed layer was formed on the outer surface of the solid electrolyte layer, it was not possible to form a Cu layer using a plating method. This is presumably because the water resistance of the polymer film forming the solid electrolyte layer in Examples 2-1 to 2-5 was better than that of Comparative Example 2-1.

[0295] The solid electrolytic capacitor of this embodiment is widely used in various electronic devices.

[0296] 100, 200 solid electrolytic capacitor, 11, 110 resin mold layer, 12, 120 first terminal, 13, 130 second terminal, 14, 141 first electrode layer, 15, 150 dielectric layer, 41 lead, 151 insulating resin layer, 16, 160 second electrode layer, 61a, 161a carbon layer, 61b, 161b conductive layer, 62, 162 metal layer, 60a, 60b, 165a, 165b solid electrolyte layer, 170 capacitor element, 19, 190 connecting conductor layer.

Claims

1. A solid electrolytic capacitor comprising a first electrode layer, a dielectric layer formed on the outer surface of the first electrode layer, a solid electrolyte layer formed on the outer surface of the dielectric layer, and a second electrode layer formed on the outer surface of the solid electrolyte layer, wherein the solid electrolyte layer is composed of a polymer film containing a crosslinked polymer in which a polymer having a carbonyl group is crosslinked by a crosslinking agent composed of a dihydrazide compound and a composite of polyethylenedioxythiophene and polystyrenesulfonic acid.

2. The solid electrolytic capacitor according to claim 1, wherein the first electrode layer is made of an aluminum foil having an average thickness of 70 μm to 220 μm, and the solid electrolyte layer has a thickness of 5 μm or more at the end face and a thickness of 25 μm or less in a region excluding the end face.

3. The solid electrolytic capacitor according to claim 1, wherein the first electrode layer is a block-shaped one made of tantalum, and the solid electrolyte layer has a thickness of 5 μm or more at the vertices and edges and a thickness of 25 μm or less on the faces.

4. The solid electrolytic capacitor according to claim 1, wherein the polymer having a carbonyl group has a polyvinyl alcohol backbone.

5. The solid electrolytic capacitor according to claim 1, wherein the ratio of the structural unit derived from the polymer having a carbonyl group forming the crosslinked polymer to the total mass of the structural unit derived from the polymer having a carbonyl group and the composite is 70% by mass or less, and the ratio of the structural unit derived from the crosslinking agent to the mass of the structural unit derived from the polymer having a carbonyl group is 15% by mass or less.

6. The solid electrolytic capacitor according to claim 1, wherein the ratio of the structural unit derived from the polymer having a carbonyl group forming the crosslinked polymer to the total mass of the structural unit derived from the polymer having a carbonyl group and the composite is 30% by mass or less, and the ratio of the structural unit derived from the crosslinking agent to the mass of the structural unit derived from the polymer having a carbonyl group is 10% by mass or less.

7. The solid electrolytic capacitor according to claim 1, wherein the second electrode layer includes a metal layer made of any metal selected from Cu, Ni, Sn, Zn, Pd, Ag, and Au.

8. A capacitor element including a first electrode layer, a dielectric layer formed on an outer surface of the first electrode layer, a solid electrolyte layer formed on an outer surface of the dielectric layer, and a second electrode layer formed on an outer surface of the solid electrolyte layer, wherein the solid electrolyte layer has a polymer film including a crosslinked polymer in which a composite of polyethylene dioxythiophene and polystyrene sulfonic acid is crosslinked by a crosslinking agent, and the crosslinking agent contains a salt of an amine compound containing in total four or more of one or two kinds of groups selected from an —NH ２ group and an —NH— group, solid electrolytic capacitor.

9. A solid electrolytic capacitor comprising a first electrode layer, a dielectric layer formed on the outer surface of the first electrode layer, a solid electrolyte layer formed on the outer surface of the dielectric layer, and a second electrode layer formed on the outer surface of the solid electrolyte layer, wherein the solid electrolyte layer has a polymer film containing a crosslinked polymer in which a composite of polyethylene dioxythiophene and polystyrene sulfonic acid is crosslinked by a crosslinking agent, and the crosslinking agent is a metal salt containing a metal cation having a valence of 2 or more.

10. The solid electrolytic capacitor according to claim 9, wherein the crosslinking agent is calcium chloride.

11. The solid electrolytic capacitor according to claim 8 or claim 10, wherein the second electrode layer includes a metal layer made of any one of Cu, Ni, Sn, Zn, Pd, Ag, and Au.

12. The solid electrolytic capacitor according to claim 11, wherein the second electrode layer has a plating seed layer on the surface of the metal layer on the solid electrolyte layer side, and the plating seed layer includes a conductive material and a catalyst support material.

13. The solid electrolytic capacitor according to claim 12, wherein the catalyst support material includes any one or two or more compounds selected from polypyrrole derivatives, polythiophene derivatives, and polyfuran derivatives.

14. The solid electrolytic capacitor according to claim 12, wherein the conductive material is a carbon material.

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