Separator for electrolytic capacitor, electrolytic capacitor, and production methods for these

Abstract

This separator for an electrolytic capacitor comprises a fiber structure and a conductive polymer adhered to the fiber structure. The ratio G2 / G1 of the glossiness G2 of a second main surface of the separator that is on the opposite side from a first main surface of the separator to the glossiness G1 of the first main surface (where G1≤G2) is not more than 7. The glossiness G1 is not more than 2 GU. The glossiness G1 and glossiness G2 are each an 85° glossiness in accordance with JIS Z8741.

Description

Separators for electrolytic capacitors, electrolytic capacitors, and methods for manufacturing the same.

[0001] This invention relates to separators for electrolytic capacitors, electrolytic capacitors, and methods for manufacturing the same.

[0002] Patent Document 1 proposes a capacitor comprising a processed element, the processed element comprising: an anode having a dielectric on its surface and an anode conductive polymer layer on the surface of the dielectric; a cathode having a cathode conductive polymer layer; a conductive separator between the anode and the cathode; an anode lead that electrically contacts the anode; and a cathode lead that electrically contacts the cathode.

[0003] Patent Document 2 proposes a capacitor comprising "an operating element including a first dielectric, an anode including an anode conductive polymer layer on the first dielectric, a cathode, a separator between the anode conductive polymer layer and the cathode, wherein the separator includes a separator conductive polymer layer and at least one of the anode conductive polymer layer or the separator conductive polymer layer is crosslinked, and a liquid electrolyte."

[0004] Patent Document 3 proposes a capacitor comprising an operating element, the operating element comprising an anode containing a first dielectric on the anode, a cathode, a separator and a first conductive polymer provided between the first dielectric and the cathode, the first conductive polymer comprising a conductive separator that at least partially surrounds the separator, a second conductive polymer that at least partially surrounds the first conductive polymer and has higher conductivity than the second conductive polymer, an anode lead that electrically contacts the anode, and a cathode lead that electrically contacts the cathode.

[0005] Special table 2019-516241 publication Special table 2021-532576 publication Special table 2022-546020 publication

[0006] One aspect of this disclosure relates to a separator for an electrolytic capacitor, comprising a fibrous structure and a conductive polymer attached to the fibrous structure. The ratio G2 / G1 of the glossiness of a second main surface opposite to a first main surface (where G1 ≤ G2) to the glossiness G1 of the first main surface of the separator is 7 or less, and the glossiness G1 is 2 GU or less. The glossiness G1 and the glossiness G2 are 85° glossiness in accordance with JIS Z8741.

[0007] Another aspect of the present disclosure relates to an electrolytic capacitor comprising an anode foil having a dielectric layer, a cathode foil, and the separator interposed between the anode foil and the cathode foil. The anode foil and the cathode foil are wound together via the separator to form a wound body. The first main surface of the separator faces the anode foil, and the wound body is impregnated with a liquid component.

[0008] Another aspect of this disclosure relates to a method for manufacturing an electrolytic capacitor. The manufacturing method comprises the steps of: preparing a separator comprising a fiber structure and a conductive polymer attached to the fiber structure; manufacturing a capacitor element by winding an anode foil and a cathode foil through the separator; and housing the capacitor element together with a liquid component in a case. The ratio G2 / G1 of the glossiness G1 of the first main surface of the separator to the glossiness G2 of the second main surface opposite the first main surface (where G1 ≤ G2) is 7 or less, and the glossiness G1 is 2 GU or less. The glossiness G1 and the glossiness G2 are 85° glossiness in accordance with JIS Z8741. In the step of manufacturing the capacitor element, the first main surface of the separator is placed opposite the anode foil.

[0009] Another aspect of this disclosure relates to a method for manufacturing a separator for electrolytic capacitors. The manufacturing method comprises the steps of: preparing a fiber structure; preparing a conductive polymer dispersion containing a conductive polymer and a dispersion medium; and applying the conductive polymer dispersion to the fiber structure by a coating method, and then removing at least a portion of the dispersion medium to produce a separator. The ratio G2 / G1 of the gloss of the second main surface opposite the first main surface to the gloss of the first main surface of the separator (where G1 ≤ G2) is 7 or less, and the gloss of G1 is 2 GU or less. The gloss of G1 and the gloss of G2 are 85° gloss in accordance with JIS Z8741.

[0010] According to this disclosure, in an electrolytic capacitor, the repairability of the dielectric layer is improved and leakage current is suppressed.

[0011] This is a schematic cross-sectional view showing an example of an electrolytic capacitor according to one embodiment of the present disclosure. This is a perspective view showing a portion of the capacitor element of the electrolytic capacitor in Figure 1 in an unfolded state.

[0012] The challenges of conventional technology are briefly explained below.

[0013] As an electrolytic capacitor, a solid-liquid hybrid electrolytic capacitor is known, which comprises a conductive polymer and a liquid component (e.g., electrolyte). The conductive polymer contributes significantly to reducing the equivalent series resistance (ESR) of the electrolytic capacitor. The liquid component contributes to improving the repairability of the dielectric layer of the anode foil.

[0014] However, when using a separator with a conductive polymer pre-attached to it to fabricate a wound capacitor element, the repairability of the dielectric layer decreases, and the leakage current of the electrolytic capacitor tends to increase.

[0015] The embodiments of this disclosure will be described below with examples, but this disclosure is not limited to the examples described below. In the following description, specific numerical values ​​and materials may be given as examples, but other numerical values, materials, etc. may be applied as long as the effects of this disclosure are obtained. Notwithstanding, known components may be applied to components of parts that are characteristic of this disclosure. In this specification, when "the range of numerical values ​​A to numerical values ​​B" is used, that range includes numerical values ​​A and B.

[0016] In the following explanation, when examples are given of lower and upper limits for specific physical properties or conditions, any combination of either of the given lower limits and any of the given upper limits is permitted, as long as the lower limit does not exceed the upper limit. When multiple materials are given as examples, unless otherwise specified, one type may be selected and used alone, or two or more types may be used in combination.

[0017] This disclosure includes any combination of two or more claims, which may be arbitrarily selected from the claims set forth in the attached claims. In other words, any combination of two or more claims, which may be arbitrarily selected from the claims set forth in the attached claims, is possible, provided that no technical inconsistency arises.

[0018] The separator for electrolytic capacitors according to this disclosure (hereinafter also referred to as "separator (S)") comprises a fibrous structure and a conductive polymer attached to the fibrous structure. The electrolytic capacitor according to this disclosure (hereinafter also referred to as "electrolytic capacitor (C)") comprises an anode foil having a dielectric layer, a cathode foil, and a separator (S) interposed between the anode foil and the cathode foil.

[0019] In an electrolytic capacitor (C), the anode foil and cathode foil may be wound around each other via a separator (S) to form a wound capacitor element. A liquid component may be impregnated into the capacitor element. The capacitor element is housed in a case together with the liquid component. That is, the electrolytic capacitor according to this disclosure may be a wound-type solid-liquid hybrid electrolytic capacitor.

[0020] However, the form of the electrolytic capacitor is not limited to a wound-type electrolytic capacitor. For example, the electrolytic capacitor (C) may be a laminated type electrolytic capacitor comprising a laminated body formed by stacking capacitor elements, with an anode foil and a cathode foil, and a separator interposed between the anode foil and the cathode foil.

[0021] The separator (S) provided by the electrolytic capacitor (C) satisfies the following conditions (A) and (B).

[0022] Condition (A): The ratio G2 / G1 of the glossiness of the second main surface on the opposite side of the first main surface of the separator (S) to the glossiness G1 of the first main surface (where G1 ≤ G2) is 7 or less.

[0023] Condition (B): The gloss level G1 is 2 GU (Gloss Unit) or less.

[0024] However, gloss levels G1 and G2 are 85° gloss levels in accordance with JIS Z8741.

[0025] From the viewpoint of reducing the ESR of electrolytic capacitors, it is preferable to increase the adhesion between the conductive polymer and the electrode foil. However, the higher the adhesion between the conductive polymer and the electrode foil, the more restricted the flow of liquid components near the surface of the electrode foil becomes. When the flow of liquid components is restricted, the repairability of the dielectric layer decreases, and the leakage current of the electrolytic capacitor increases.

[0026] In contrast, when an electrolytic capacitor is assembled using a separator (S), the repairability of the dielectric layer is improved, and the leakage current of the electrolytic capacitor is suppressed. The reason why the repairability of the dielectric layer is improved is that, when condition (B) is met, a sufficient flow path for the liquid component (e.g., electrolyte) is secured inside the capacitor element. On the other hand, when condition (A) is met, sufficient adhesion between the conductive polymer and the electrode foil is ensured.

[0027] In order to significantly improve the repairability of a dielectric layer, the first main surface of at least one separator (S) needs to be opposed to an anode foil. In this case, a sufficient flow path for a liquid component (e.g., an electrolytic solution) is secured between the dielectric layer and the separator (S). Therefore, when a defect occurs in the dielectric layer, repair formation proceeds rapidly by the liquid component. In the case of a wound body, two separators (S) are required. In order to more significantly improve the repairability of the dielectric layer, it is preferable that the first main surfaces of both of the two separators (S) are opposed to the anode foil.

[0028] From another perspective, condition (B) means that the smoothness of the first main surface of the separator (S) is low. When such a first main surface is opposed to the anode foil, many gaps that serve as flow paths for the liquid component are secured between the separator (S) and the anode foil. As a result, the repairability of the dielectric layer is improved, and the leakage current of the electrolytic capacitor is suppressed.

[0029] On the other hand, when condition (A) is satisfied, the second main surface of the separator (S) has relatively high smoothness and easily adheres closely to a cathode foil, so the interfacial resistance between the conductive polymer contained in the separator (S) and the cathode foil is reduced. As a result, the ESR of the electrolytic capacitor is limited to a sufficiently small range.

[0030] It should be noted that there has been no report in literatures or the like that leakage current can increase by using a separator (separator (S)) including a fiber structure and a conductive polymer attached thereto, and there has also been no report that leakage current can be suppressed while ensuring low ESR by controlling the surface smoothness of the separator (S).

[0031] G1 may be 2 GU or less, but from the viewpoint of appropriately forming flow paths for the liquid component inside the capacitor element while keeping ESR as small as possible, it is preferable that 1 GU ≤ G1 ≤ 2 GU is satisfied, and it is more preferable that 1.1 GU ≤ G1 ≤ 1.8 GU is satisfied.

[0032] G2 only needs to satisfy G1 ≤ G2, but from the viewpoint of suppressing ESR as small as possible, it is preferable to satisfy 5 GU ≤ G2, and more preferable to satisfy 10 GU ≤ G2. However, from the viewpoint of allowing a liquid component to properly flow between the electrode foil and the second main surface, it is preferable to satisfy G2 ≤ 12 GU.

[0033] The ratio G2 / G1 only needs to be 7.0 or less, but from the viewpoint of sufficiently forming flow paths for the liquid component inside the capacitor element while suppressing ESR as small as possible, the ratio is preferably 4 or more, and more preferably 5 or more. However, if the ratio G2 / G1 exceeds 7.0, the adhesion between the electrode foil (particularly the cathode foil) and the separator becomes excessively high, making it difficult to sufficiently secure flow paths for the liquid component inside the capacitor element, which increases the leakage current of the electrolytic capacitor.

[0034] Glossiness G1 and G2 can be measured using a glossiness measuring device in accordance with JIS Z8741. Specifically, a light beam with a specified aperture angle is incident at a specified incident angle (85°) onto the sample surface (the first main surface and the second main surface of the separator (S)), and the light beam with the specified aperture angle reflected in the specular reflection direction is measured with a light receiver.

[0035] The separator (S) used as a sample may be a separator taken out from an electrolytic capacitor (C), or may be a separator as a raw material of the electrolytic capacitor (C) before being incorporated into the electrolytic capacitor. When a separator taken out from an electrolytic capacitor (C) is used as a sample, the capacitor element is washed with ethanol or propanol to remove the liquid component (electrolyte), then dried at 80°C to 130°C, and then the separator is taken out from the capacitor element for measurement.

[0036] The larger the amount of the conductive polymer contained in the separator, the more advantageous it is from the viewpoint of reducing the ESR of the electrolytic capacitor. The amount of the conductive polymer contained in the separator (the mass of the conductive polymer contained per unit area of the separator) is, for example, 0.05 mg / cm ２ or more is preferable, and 0.1 mg / cm ２The above is more preferable. On the other hand, from the viewpoint of sufficiently securing a flow path for the liquid component, it is preferable that the amount of the conductive polymer contained in the separator is not excessively large. The amount of the conductive polymer contained in the separator is, for example, 0.05 mg / cm ２ or more and 2 mg / cm ２ or less, may be 0.1 mg / cm ２ or more and 2 mg / cm ２ or less, may be 0.1 mg / cm ２ or more and 1.5 mg / cm ２ or less, may be 0.1 mg / cm ２ or more and 1.0 mg / cm ２ or less.

[0037] The fibrous structure is not particularly limited as long as it is a porous material composed of fibers. Examples of the fibrous structure include woven fabrics, knitted fabrics and non-woven fabrics. The fibrous structure may contain 50% by mass or more of synthetic fibers. The fibrous structure may contain a paper strength enhancer together with cellulose fibers. Wrinkles are less likely to occur in such a separator (S).

[0038] In a fibrous structure containing 50% by mass or more of synthetic fibers (hereinafter, also referred to as "first fibrous structure"), the content of synthetic fibers may be, for example, 70% by mass or more of the fibrous structure. The type of synthetic fiber is not particularly limited. From the viewpoint of strength and difficulty of swelling by water, it is preferable to use at least one selected from the group consisting of nylon fibers, aramid fibers, acrylic fibers and polyester fibers as the synthetic fiber.

[0039] The first fibrous structure may further contain cellulose. In consideration of the retention of the liquid component, the content of cellulose in the fibrous structure may be 10% by mass or more based on the fibrous structure. The content of cellulose is less than 50% by mass, may be 30% by mass or less, and may be 20% by mass or less.

[0040] In a fibrous structure containing a paper strength enhancer along with cellulose fibers (hereinafter also referred to as the "second fibrous structure"), the type of paper strength enhancer is not particularly limited and may be a wet paper strength enhancer and / or a dry paper strength enhancer. These may be used individually or in combination.

[0041] Examples of wet-strength paper enhancers include at least one selected from the group consisting of urea-formaldehyde resin, melamine-formaldehyde resin, polyamide-polyamine epichlorohydrin, and polyvinylamine.

[0042] Examples of dry paper strength enhancers include at least one selected from the group consisting of polyacrylamide, polyvinyl alcohol, starch, and carboxymethylcellulose.

[0043] The paper strength enhancer may be added to the raw material of the second fiber structure (for example, a slurry containing cellulose fibers), or it may be applied to the second fiber structure by spraying or the like.

[0044] When a paper strength enhancer is added, the second fiber structure may contain 40% by mass or more of cellulose, or 70% by mass or more. The second fiber structure may further contain synthetic fibers. The content of synthetic fibers may be, for example, 10% by mass or more and 60% by mass or less of the second fiber structure.

[0045] The density of the first and second fiber structures is, for example, 0.2 g / cm³. ３ 0.60g / cm or more ３ It is less than 0.25 g / cm³. ３ 0.40g / cm or more ３ The following is acceptable:

[0046] The thickness of each fiber structure is not particularly limited, but for example, it may be between 20 μm and 100 μm, or between 30 μm and 60 μm. This makes it easier to suppress short circuits in the resulting electrolytic capacitors and further improves the ESR reduction effect.

[0047] The thickness is measured by stacking multiple fiber structures (for example, 10 layers) and measuring at 10 arbitrary points using a push-pull micrometer. The average of the measured values ​​is then divided by the number of layers to calculate the thickness per layer.

[0048] Another fiber structure (hereinafter also referred to as the "third fiber structure") may include the first fiber and the second fiber. The first fiber and the second fiber are mixed together, and the fiber diameter D1 of the first fiber is, for example, 10 μm or more and 50 μm or less, and the fiber diameter D2 of the second fiber is, for example, 5 μm or less. Such a fiber structure can provide a separator (S) that is dense and less likely to cause internal short circuits in electrolytic capacitors even when thin.

[0049] The density of the third fibrous structure is, for example, 0.35 g / cm³. ３ 0.60g / cm or more ３ The following is the value: 0.35 g / cm³ ３ 0.45g / cm or more ３ The following is also acceptable.

[0050] The second fiber is preferably fibrillated. Fibrillation is a phenomenon in which a fiber splits and becomes smaller in the axial direction. Fibrillation of a fiber occurs when friction or pressure is applied to the fiber. Fibrillated fibers are usually highly crimped.

[0051] The third fiber structure may contain only one type of first fiber or multiple types. The fiber diameter D1 can be determined by arbitrarily selecting 20 first fibers having a fiber diameter of 10 μm or more and 50 μm or less, measuring the fiber diameter (length in the direction perpendicular to the axial direction of the fiber) of the selected first fibers, and averaging them. The fiber diameter D1 is preferably 40 μm or less, and more preferably 20 μm or more and 35 μm or less.

[0052] The third fiber structure may contain only one type of second fiber or multiple types. The fiber diameter D2 can be determined by arbitrarily selecting 20 second fibers having a fiber diameter of 5 μm or less, measuring the fiber diameter of the selected second fibers, and averaging the results. If the second fiber is fibrillated, the fiber diameter D2 should be measured by considering each fibril as a single fiber, rather than the fiber before fibrillation. The fiber diameter D2 is preferably between 1 μm and 5 μm.

[0053] The content of the second fiber in the third fiber structure relative to the total of the first and second fibers is, for example, 10% by mass or more and 50% by mass or less, and may also be 10% by mass or more and 30% by mass or less, or 30% by mass or more and 50% by mass or less. By including the second fiber in the third fiber structure at such a content, both the strength and density homogeneity of the third fiber structure are sufficiently enhanced.

[0054] The ratio of the fiber diameter D1 of the first fiber to the fiber diameter D2 of the second fiber, D1 / D2, is, for example, 3 to 15, or 3 to 10. When the first and second fibers are mixed using such a D1 / D2 ratio, there is a sufficiently large difference between the fiber diameters D1 and D2, so it is thought that pinholes in the separator (S) that may occur due to unevenness in the first fiber are more easily filled by multiple second fibers. The D1 / D2 ratio is, for example, 5 or more, or 8 or more.

[0055] The thickness of the third fiber structure is, for example, 45 μm or less, and may be between 37 μm and 43 μm. By making the third fiber structure thinner, the resistance between the anode foil and the cathode foil can be reduced. In addition, the separator (S) can increase the volume of the anode foil in the electrolytic capacitor, which is further advantageous for increasing capacitance.

[0056] Cellulose fibers include natural cellulose fibers. Examples of natural cellulose fibers include Manila hemp pulp, esparto pulp, coniferous pulp, hardwood pulp, and sisal pulp. Cellulose fibers may also be regenerated cellulose fibers or semi-synthetic cellulose fibers. Regenerated cellulose fibers include those spun using a solution of natural cellulose dissolved in a solvent (e.g., rayon). Semi-synthetic cellulose fibers include those produced by adding other materials to natural cellulose to form fibers (e.g., acetate). Cellulose fibers may be used individually or in combination of two or more types.

[0057] The synthetic fiber preferably contains at least one selected from the group consisting of aramid (aromatic polyamide), polyethylene terephthalate (PET), and vinylon (acetalized PVA). Among these, aramid is more preferred from the viewpoint of improving heat resistance and fiber strength (tensile strength). The synthetic fiber may be used alone or in combination of two or more types.

[0058] The synthetic fibers may include, in addition to those exemplified above, polybutylene terephthalate, polyphenylene sulfide, nylon, polyimide, polyamide-imide, polyetherimide, and the like. The separator may also include glass fibers. At least a portion of the separator may be carbonized.

[0059] Examples of conductive polymers to be attached to the fiber structure include polypyrrole, polythiophene, polyfuran, polyaniline, polyacetylene, polyphenylene, polyphenylene vinylene, polyacene, and polythiophene vinylene. These may be used individually, in combination of two or more, or as copolymers of two or more monomers.

[0060] In this specification, polypyrrole, polythiophene, polyfuran, and polyaniline, etc., refer to polymers that have polypyrrole, polythiophene, polyfuran, and polyaniline, respectively, as their basic skeleton. Therefore, derivatives of polypyrrole, polythiophene, polyfuran, and polyaniline, etc., may also be included. A derivative of a conductive polymer refers to a polymer that has a conductive polymer as its basic skeleton. For example, derivatives of polythiophene include poly(3,4-ethylenedioxythiophene).

[0061] The conductive polymer may contain a dopant. The dopant can be appropriately selected depending on the type of conductive polymer. Various known dopants may be used as dopants. Examples of dopants include naphthalene sulfonic acid, p-toluenesulfonic acid, and salts thereof.

[0062] The dopant may be a polyanion. Specific examples of polyanions include polyvinyl sulfonic acid, polystyrene sulfonic acid, polyallyl sulfonic acid, polyacryl sulfonic acid, polymethacrylate sulfonic acid, poly(2-acrylamido-2-methylpropanesulfonic acid), polyisoprene sulfonic acid, and polyacrylic acid. These may be used individually or in combination of two or more. Furthermore, these may be polymers of a single monomer or copolymers of two or more monomers. Among these, polyanions derived from polystyrene sulfonic acid are preferred.

[0063] The weight-average molecular weight of the polyanions contained in the conductive polymer is not particularly limited. For example, the weight-average molecular weight of the polyanions may be between 1,000 and 200,000, or between 1,000 and 70,000.

[0064] An example of a conductive polymer is poly(3,4-ethylenedioxythiophene) (PEDOT) doped with polystyrene sulfonic acid (PSS). The conductive polymer may be formed from particles of poly(3,4-ethylenedioxythiophene) (PEDOT) (hereinafter also referred to as PEDOT / PSS) doped with polystyrene sulfonic acid (PSS).

[0065] The following provides an illustrative explanation of how to manufacture the separator (S).

[0066] The separator (S) may be manufactured by a method comprising the steps of: preparing a conductive polymer dispersion containing a conductive polymer and a dispersion medium; and applying the conductive polymer dispersion to a fiber structure, and then removing at least a portion of the dispersion medium. By this method, the pre-synthesized conductive polymer adheres to the surface of the fibers constituting the fiber structure. By applying the conductive polymer dispersion to the fiber structure, which is the raw material for the separator, a sufficient amount of conductive polymer can be attached to the fiber structure.

[0067] A suitable method for applying a conductive polymer dispersion is one that allows control over the amount of conductive polymer contained in the separator. One such method is the coating method. The coating method makes it easy to control the smoothness of the first and second surfaces of the separator (S). Therefore, a separator (S) satisfying conditions (A) and (B) can be efficiently manufactured. Furthermore, by applying the conductive polymer dispersion to the fiber structure using the coating method, the amount of conductive polymer contained in the separator can be controlled, for example, to 0.05 mg / cm³. ２ 2mg / cm or more ２ It can be easily controlled to any amount within the following range.

[0068] Coating is a technique that involves applying a liquid substance to an object using a coater. Examples of known coaters include gravure coaters, knife coaters, comma coaters, roll coaters, die coaters, and lip coaters.

[0069] The conductive polymer dispersion may be applied to one or both sides of the fiber structure. The conductive polymer dispersion may be applied to both sides of the fiber structure under different conditions so that the smoothness of the first and second surfaces of the separator (S) differs. Alternatively, the conductive polymer dispersion may be applied to only one side of the fiber structure, and the smoothness of the first and second surfaces may be controlled by controlling the permeability of the conductive polymer dispersion (movement of the conductive polymer) within the fiber structure.

[0070] The conductive polymer dispersion may be applied multiple times to the same surface of the fiber structure. This increases the amount of conductive polymer adhering to the fibers. After multiple coating treatments are performed consecutively, a drying treatment may be carried out, or a drying treatment may be carried out after each coating treatment.

[0071] From the standpoint of mass production, the process for manufacturing the separator may be carried out on a long fiber structure wound into a roll. When coating both sides of such a fiber structure, the coating may be applied to one surface first, followed by a drying process, then the fiber structure may be wound into a roll, and then the fiber structure may be unwound and the coating applied to the other surface.

[0072] The dispersion medium is removed by drying treatments such as heating and drying or vacuum drying. In this case, the drying treatment may be performed to the extent that the dispersion medium is not completely removed. For example, the drying treatment may be performed so that 10% by mass or less (for example, 1% by mass or more and 10% by mass or less) of the dispersion medium remains on the separator (S) immediately after the coating treatment. This makes it easier for the liquid component to be guided into the dispersion medium and impregnate into the pores of the separator when the capacitor element is impregnated with the liquid component in a later process. As a result, the anode foil and cathode foil come into contact with the liquid component, which may improve the repairability of the dielectric layer of the anode foil.

[0073] The conductive polymer is dispersed in a dispersion medium, for example, in the form of particles. The average particle size of the conductive polymer can be adjusted as appropriate by polymerization conditions, dispersion conditions, etc. The average particle size of the conductive polymer may be, for example, 0.01 μm or more and 0.5 μm or less. The average particle size is the median diameter in the volume particle size distribution and is measured by a particle size measuring device using the dynamic light scattering method.

[0074] Conductive polymer dispersions can be obtained, for example, by dispersing conductive polymer particles in a dispersion medium, or by polymerizing conductive polymer precursor monomers in a dispersion medium to produce conductive polymer particles.

[0075] The dispersion medium preferably contains water. However, the dispersion medium may also contain a non-aqueous solvent. A non-aqueous solvent is a general term for liquids other than water, and includes organic solvents and ionic liquids. Water may constitute 50% or more by mass of the dispersion medium, 70% or more by mass, or 90% or more by mass. Examples of non-aqueous solvents used with water include polar solvents (protic solvents and / or aprotic solvents).

[0076] Examples of protic solvents include methanol, ethanol, propanol, butanol, ethylene glycol (EG), propylene glycol, polyethylene glycol (PEG), diethylene glycol monobutyl ether, glycerin, 1-propanol, butanol, polyglycerin, alcohols such as sorbitol, mannitol, and pentaerythritol, and formaldehyde.

[0077] Examples of aprotic solvents include amides such as N-methylacetamide, N,N-dimethylformamide, and N-methyl-2-pyrrolidone; esters such as methyl acetate and γ-butyrolactone (γBL); ketones such as methyl ethyl ketone; ethers such as 1,4-dioxane; sulfur-containing compounds such as dimethyl sulfoxide and sulfolane (SL); and carbonate compounds such as propylene carbonate.

[0078] When the dispersion medium contains a polyhydric alcohol or a sugar alcohol, the permeability of the conductive polymer dispersion into the fiber structure tends to increase. Although polyhydric alcohols and sugar alcohols tend to swell cellulose, the first and second fiber structures described above do not swell easily even in dispersion mediums containing such alcohols, thus suppressing the occurrence of wrinkles in the separator (S).

[0079] The content of the conductive polymer in the conductive polymer dispersion is, for example, 1% by mass or more and 15% by mass or less, and may be 3% by mass or more and 15% by mass or less.

[0080] The viscosity of the conductive polymer dispersion is, for example, between 10 mPa·s and 1000 mPa·s, and may be between 100 mPa·s and 200 mPa·s. Conductive polymer dispersions having such viscosity are particularly suitable for use in coating methods. The viscosity of the conductive polymer dispersion is measured at room temperature (20°C) using a vibrating viscometer (for example, VM-100A, manufactured by Sekonic Corporation).

[0081] The following provides an illustrative explanation of the manufacturing method for electrolytic capacitors.

[0082] An electrolytic capacitor can be manufactured by a manufacturing method comprising the steps of: preparing a separator (S); winding an anode foil and a cathode foil around the separator (S) to produce a capacitor element which is a wound body; and housing the capacitor element together with the liquid component in a case. The separator (S) may be prepared by the separator (S) manufacturing method described above.

[0083] In order to significantly improve the repairability of the dielectric layer, it is necessary to position the first main surface of the separator (S) opposite the anode foil and the second main surface of the separator (S) opposite the cathode foil during the process of manufacturing the capacitor element.

[0084] The ends of the cathode foil located in the outermost layer of the winding may be secured with winding tape. Typically, the end faces of the anode foil located at the end face of the winding immediately after construction do not have a dielectric layer. Such end faces of anode foil are formed by a cutting process. In that case, a chemical conversion treatment may be performed on the capacitor element to form a dielectric layer on the end face of the anode foil.

[0085] If necessary, the capacitor element may be impregnated with a conductive polymer dispersion. The conductive polymer dispersion contains a conductive polymer and a dispersion medium. The impregnation method is not particularly limited. Afterwards, a drying process may be performed to remove at least a portion of the dispersion medium.

[0086] By impregnating a capacitor element with a conductive polymer dispersion and then drying it, the conductive polymer can be attached to the anode and cathode foils inside the capacitor element. This is expected to increase capacitance and reduce ESR.

[0087] The conductive polymer dispersion to be impregnated into the capacitor element (hereinafter also referred to as the "second dispersion") may be selected from the conductive polymer dispersions described above that can be used in the manufacture of the separator (S) (hereinafter also referred to as the "first dispersion"). However, the content of the conductive polymer in the second dispersion to be impregnated into the capacitor element may be lower than the content of the conductive polymer in the first dispersion. Specifically, the content of the conductive polymer in the second dispersion is preferably 0.2% by mass or more and less than 3% by mass.

[0088] The viscosity of the second dispersion, measured at room temperature (20°C) using a vibrating viscometer, is preferably lower than the viscosity of the first dispersion, measured under the same conditions. The viscosity of the second dispersion, measured at room temperature (20°C) using a vibrating viscometer, is preferably less than 100 mPa·s.

[0089] If necessary, the capacitor element may be impregnated with a liquid component. The liquid component may be an electrolyte. The liquid component may be impregnated without performing the impregnation step of the second dispersion, or the capacitor element may be impregnated with the liquid component after being impregnated with the second dispersion. The liquid component significantly improves the self-healing performance of the dielectric layer. Since the electrolyte functions as a substantial cathode material, it can also be expected to increase the capacitance. The method of impregnation is not particularly limited.

[0090] The liquid component contains a solvent. Examples of solvents include sulfone compounds, lactone compounds, carbonate compounds, and polyhydric alcohols. Examples of sulfone compounds include sulfolane, dimethyl sulfoxide, and diethyl sulfoxide. Examples of lactone compounds include γ-butyrolactone and γ-valerolactone. Examples of carbonate compounds include dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), propylene carbonate (PC), and fluoroethylene carbonate (FEC). Examples of polyhydric alcohols include glycol compounds such as ethylene glycol (EG), diethylene glycol, triethylene glycol, propylene glycol, and polyethylene glycol (PEG); and glycerin. These may be used individually or in combination.

[0091] The solvent may contain compounds having two or more hydroxyl groups. Examples of such compounds include polyhydric alcohols. The content of compounds having two or more hydroxyl groups may be 50% by mass or more, 60% by mass or more, or 70% by mass or more of the total solvent.

[0092] The liquid component may further contain an acid component. When the conductive polymer contains a dopant, the acid component in the liquid component (electrolyte) suppresses the dedoping phenomenon of the dopant and stabilizes the conductivity of the conductive polymer. Therefore, the ESR can be kept low.

[0093] Examples of acidic components include aliphatic sulfonic acids having 1 to 30 carbon atoms and aromatic sulfonic acids having 6 to 30 carbon atoms. Among aliphatic sulfonic acids, monovalent saturated aliphatic sulfonic acids (e.g., hexanesulfonic acid) are preferred. Among aromatic sulfonic acids, aromatic sulfonic acids having a hydroxyl group or a carboxyl group in addition to a sulfo group are preferred, specifically oxyaromatic sulfonic acids (e.g., phenol-2-sulfonic acid) and sulfoaromatic carboxylic acids (e.g., p-sulfobenzoic acid, 3-sulfophthalic acid, 5-sulfosalicylic acid) are preferred.

[0094] Other acidic components include carboxylic acids. Preferably, the carboxylic acid includes aromatic carboxylic acids (aromatic dicarboxylic acids) having two or more carboxyl groups. Examples of aromatic carboxylic acids include phthalic acid (ortho-isomer), isophthalic acid (meta-isomer), terephthalic acid (para-isomer), maleic acid, benzoic acid, salicylic acid, trimellitic acid, and pyromellitic acid. Among these, aromatic dicarboxylic acids such as phthalic acid (ortho-isomer) and maleic acid are more preferred. The carboxyl groups of aromatic dicarboxylic acids are stable and do not easily cause side reactions. Therefore, they exhibit the effect of stabilizing conductive polymers over a long period, which is advantageous for extending the lifespan of electrolytic capacitors. Alternatively, the carboxylic acid may be an aliphatic carboxylic acid such as adipic acid. In terms of thermal stability, the acidic component may include a composite compound of organic and inorganic acids. Examples of composite compounds of organic and inorganic acids that have high heat resistance include borodisalicylic acid, borodisuoic acid, and borodiglycolic acid. The acidic component may include inorganic acids such as boric acid, phosphoric acid, phosphorous acid, hypophosphorous acid, and phosphonic acid.

[0095] In terms of enhancing the effect of suppressing the dedoping phenomenon, the concentration of the acid component may be 5% by mass or more and 50% by mass or less, and may be 15% by mass or more and 35% by mass or less.

[0096] The electrolyte may contain both an acidic and a basic component. The basic component neutralizes at least a portion of the acidic component. Therefore, it is possible to increase the concentration of the acidic component while suppressing electrode corrosion caused by the acidic component. From the viewpoint of effectively suppressing dedoping, it is preferable that the acidic component is in excess of the basic component in terms of equivalent ratio. For example, the equivalent ratio of the acidic component to the basic component may be between 1 and 30. The concentration of the basic component contained in the electrolyte may be between 0.1% by mass and 20% by mass, and between 3% by mass and 10% by mass.

[0097] The basic component is not particularly limited. Examples of basic components include ammonia, primary amines, secondary amines, tertiary amines, quaternary ammonium compounds, and amidinium compounds. Examples of amines include aliphatic amines, aromatic amines, and heterocyclic amines.

[0098] The pH of the electrolyte is preferably 4 or less, more preferably 3.8 or less, and even more preferably 3.6 or less. By setting the pH of the electrolyte to 4 or less, the degradation of the conductive polymer is further suppressed. A pH of 2.0 or higher is preferred.

[0099] The fabricated capacitor element is housed in a bottomed case along with the electrolyte. The bottomed case is made of metal. Subsequently, the capacitor element is sealed by drawing the opening near the bottomed end and crimping the opening to a sealing member. After that, an aging process may be performed while applying the rated voltage.

[0100] Figure 1 is a schematic cross-sectional view showing an example of an electrolytic capacitor (C) according to an embodiment of the present disclosure. Figure 2 is a schematic perspective view showing the configuration of a capacitor element. Figure 2 is an unfolded view of a part of the capacitor element of the electrolytic capacitor (C) of Figure 1.

[0101] The electrolytic capacitor (C) 200 comprises a capacitor element 100. The capacitor element 100 includes a wound body formed by winding an anode foil (P) 10 and a cathode foil 20 with a separator (S) 30 in between.

[0102] The capacitor element 100 includes a conductive polymer (not shown). Specifically, the conductive polymer is interposed between the anode foil 10 (dielectric layer) and the cathode foil 20, and is attached to the surface and interior of the separator (S) 30.

[0103] One end of lead tabs 50A and 50B are connected to the anode foil (P) 10 and the cathode foil 20, respectively, and the capacitor element 100 is formed by winding the lead tabs 50A and 50B. Lead wires 60A and 60B are connected to the other ends of lead tabs 50A and 50B, respectively.

[0104] A winding tape 40 is placed on the outer surface of the cathode foil 20, which is located in the outermost layer of the capacitor element 100, and the end of the cathode foil 20 is fixed by the winding tape 40.

[0105] The capacitor element 100 is housed in the closed-bottom case 211 such that the lead wires 60A and 60B are located on the opening side of the closed-bottom case 211. The material of the closed-bottom case 211 can be a metal such as aluminum, stainless steel, copper, iron, or brass, or an alloy thereof.

[0106] A sealing member 212 is placed at the opening of a bottomed case 211 in which the capacitor element 100 is housed. The opening end of the bottomed case 211 is curled so as to be crimped to the sealing member 212, and a seat plate 213 is placed on the curled portion, thereby sealing the capacitor element 100 inside the bottomed case 211.

[0107] The sealing member 212 is formed so that the lead wires 60A and 60B pass through it. The sealing member 212 can be made of an insulating material, and an elastic material is preferred. Among these, silicone rubber, fluororubber, ethylene propylene rubber, Hypalon rubber, butyl rubber, isoprene rubber, etc., which have high heat resistance are preferred.

[0108] (Note) The following technologies are disclosed based on the above description.

[0109] (Technical 1) A separator for an electrolytic capacitor comprising a fibrous structure and a conductive polymer attached to the fibrous structure, wherein the ratio G2 / G1 of the glossiness of a second main surface opposite to the first main surface to the glossiness G1 of the first main surface of the separator (where G1 ≤ G2) is 7 or less, the glossiness G1 is 2 GU or less, and the glossiness G1 and the glossiness G2 are 85° glossiness in accordance with JIS Z8741.

[0110] (Technical 2) The amount of conductive polymer contained in the separator is 0.05 mg / cm³ ２ 2mg / cm or more ２ The separator described in Technology 1 is as follows.

[0111] (Technology 3) The separator according to Technology 1 or 2, wherein the ratio G2 / G1 is 4GU or more.

[0112] (Technical 4) The separator according to any one of Technical 1 to 3, wherein the conductive polymer comprises polyethylene dioxythiophene doped with polystyrene sulfonic acid.

[0113] (Technical 5) The separator according to any one of Technical 1 to 4, wherein the fiber structure includes at least one selected from the group consisting of cellulose fibers, rayon fibers, polyethylene terephthalate fibers, and polyimide fibers.

[0114] (Technical 6) The fiber structure contains 50% by mass or more of synthetic fibers, and the density of the fiber structure is 0.2 g / cm³. ３ Above, 0.60g / cm ３ A separator described in any one of the technologies 1 to 5, which is less than [a certain value].

[0115] (Technical 7) The fiber structure contains 40% by mass or more of cellulose fibers and a paper strength enhancer, and the density of the fiber structure is 0.2 g / cm³. ３ Above, 0.60 / cm ３ A separator described in any one of the technologies 1 to 5, which is less than [a certain value].

[0116] (Technical 8) The separator according to any one of Technical 1 to 5, wherein the fiber structure includes a first fiber and a second fiber, the first fiber and the second fiber are mixed, the fiber diameter D1 of the first fiber is 10 μm or more and 50 μm or less, and the fiber diameter D2 of the second fiber is 5 μm or less.

[0117] (Technology 9) An electrolytic capacitor comprising an anode foil having a dielectric layer, a cathode foil, and a separator according to any one of Technologies 1 to 8 interposed between the anode foil and the cathode foil, wherein the anode foil and the cathode foil are wound around each other via the separator to form a wound body, the first main surface of the separator faces the anode foil, and the wound body is impregnated with a liquid component.

[0118] (Technical 10) A method for manufacturing an electrolytic capacitor, comprising the steps of: preparing a separator comprising a fiber structure and a conductive polymer attached to the fiber structure; manufacturing a capacitor element by winding an anode foil and a cathode foil through the separator; and housing the capacitor element together with a liquid component in a case, wherein the ratio G2 / G1 of the glossiness of the second main surface opposite the first main surface to the glossiness G1 of the first main surface of the separator (where G1 ≤ G2) is 7 or less, the glossiness G1 is 2 GU or less, the glossiness G1 and the glossiness G2 are 85° glossiness in accordance with JIS Z8741, and in the step of manufacturing the capacitor element, the first main surface of the separator is facing the anode foil.

[0119] (Technical 11) A method for manufacturing a separator for an electrolytic capacitor, comprising: a step of preparing a fiber structure; a step of preparing a conductive polymer dispersion containing a conductive polymer and a dispersion medium; and a step of applying the conductive polymer dispersion to the fiber structure by a coating method, and then removing at least a portion of the dispersion medium to produce a separator, wherein the ratio G2 / G1 of the glossiness of a second main surface opposite to the first main surface to the glossiness G1 of the first main surface of the separator (where G1 ≤ G2) is 7 or less, the glossiness G1 is 2 GU or less, and the glossiness G1 and the glossiness G2 are 85° glossiness in accordance with JIS Z8741.

[0120] (Technical 12) The method for manufacturing a separator according to Technical 11, wherein a gravure coater, knife coater, comma coater, roll coater, die coater, or lip coater is used as the coater in the coating method.

[0121] [Examples] The present disclosure will be described in detail below based on examples, but the present disclosure is not limited to these examples.

[0122] Examples 1-4, Comparative Examples 1-3: Electrolytic capacitors with a rated voltage of 25V, a rated capacitance of 56μF, and dimensions of 6.3mmφ × 5.8mm were fabricated in the following manner.

[0123] (a) Preparation of components: An aluminum foil with a thickness of 115 μm was etched to roughen both sides of the aluminum foil. The roughened surface of the aluminum foil was treated with a chemical conversion process to form a dielectric layer and obtain an anode foil.

[0124] A 50 μm thick aluminum foil was etched to roughen both sides of the aluminum foil, thereby obtaining a cathode foil.

[0125] A nonwoven fabric with a thickness of 50 μm was prepared as the fibrous structure. The nonwoven fabric is composed of 100% by mass of cellulose fibers (40% to 60% by mass of Manila hemp and 60% to 40% by mass of esparto fibers). The density of the nonwoven fabric is 0.35 g / cm³. ３ That was the case.

[0126] (b) Preparation of the first dispersion A mixed solution was prepared by dissolving 3,4-ethylenedioxythiophene and polystyrene sulfonic acid (PSS, weight-average molecular weight 100,000) in deionized water. Iron(III) sulfate (oxidizing agent) was added to the mixed solution while stirring, and the polymerization reaction was carried out. The reaction solution was then dialyzed to remove unreacted monomers and oxidizing agent, and a first dispersion containing polyethylenedioxythiophene (PEDOT / PSS) doped with approximately 5% by mass of PSS (dopant) was obtained.

[0127] The concentration of the conductive polymer (PEDOT / PSS) in the first dispersion was 2% by mass.

[0128] The viscosity of the first dispersion, measured at room temperature (20°C) using a vibrating viscometer (VM-100A, manufactured by Sekonic Corporation), was 40 mPa·s.

[0129] (c) Preparation of separator (S) The first dispersion was applied to both sides of the fiber structure using a gravure coater. Then, a drying process was performed to prepare a separator (S) comprising the fiber structure and the conductive polymer attached thereto. The mass of conductive polymer contained per unit area of ​​the separator was 0.1 mg / cm². ２ 0.23mg / cm or more ２ It was controlled within the following range.

[0130] Specifically, the fiber structure was placed on a resin sheet with one surface of the fiber structure facing the resin sheet, and a predetermined amount of the first dispersion was applied to the other surface of the fiber structure. By changing the application conditions of the first dispersion using a gravure coater, separators S1 to S3 having gloss levels (85° gloss level according to JIS Z8741) G1, G2 and ratio G2 / G1 as shown in Table 1 were produced.

[0131] A handheld gloss meter (PG-IIM) manufactured by Nippon Denshoku Industries, Ltd. was used for the gloss measurement. A sample of separator (S) was placed on a blank sheet of paper, and the 85° gloss was measured in both the width and length directions of the separator, and the average value (Gav1) was calculated. In addition, for each example, the 85° gloss Gav1 of three separators was measured, and the average value (Gav2) was calculated. G1 and G2 in Table 1 are the Gav2 values ​​calculated as described above.

[0132]

[0133] (d) Fabrication of Capacitor Element The anode foil, cathode foil, and a pair of separators were each cut to a predetermined size. Anode lead tabs and cathode lead tabs were connected to the anode foil and cathode foil, and the anode foil and cathode foil were wound together with the separators while winding the lead tabs. At this time, the first main surface (the side with low gloss) of the pair of separators was placed facing the anode foil or cathode foil as shown in Table 2. Anode lead wires and cathode lead wires were connected to the ends of each lead tab protruding from the wound body. The obtained wound body was subjected to chemical conversion again to form a dielectric layer on the end face of the anode foil. The outermost end of the wound body was fixed with winding tape to obtain a capacitor element.

[0134] (e) Preparation and impregnation of the second dispersion A mixed solution was prepared by dissolving 3,4-ethylenedioxythiophene and polystyrene sulfonic acid (PSS, weight-average molecular weight 100,000) in deionized water. Iron(III) sulfate (oxidizing agent) was added to the mixed solution while stirring, and the polymerization reaction was carried out. The reaction solution was then dialyzed to remove unreacted monomers and oxidizing agent, and a second dispersion containing polyethylenedioxythiophene (PEDOT / PSS) doped with approximately 5% by mass of PSS (dopant) was obtained.

[0135] The concentration of the conductive polymer (PEDOT / PSS) in the second dispersion was 1.5% by mass.

[0136] The viscosity of the second dispersion, measured using a vibrating viscometer at room temperature (20°C), was 30 mPa·s.

[0137] The capacitor elements were immersed in the second dispersion for 5 minutes in a reduced pressure atmosphere (40 kPa), and then dried to impart the conductive polymer to the capacitor elements.

[0138] (f) Ethylene glycol (EG) was prepared as the impregnation solvent for the electrolyte. The electrolyte was prepared by dissolving 5-sulfosalicylic acid and triethylamine as a base component in ethylene glycol at a total concentration of 25% by mass. The equivalent ratio of 5-sulfosalicylic acid to triethylamine was 2.0. After impregnation with the second dispersion (e), the capacitor element was immersed in the electrolyte for 5 minutes in a reduced pressure atmosphere (40 kPa).

[0139] (g) Capacitor elements were sealed by impregnating them with the sealing electrolyte to complete the electrolytic capacitors A1 to A4 of Examples 1 to 4 and the electrolytic capacitors B1 to B3 of Comparative Examples 1 to 3. Then, aging was performed at 95°C for 90 minutes while applying the rated voltage.

[0140] <Evaluation> The leakage current after aging was evaluated for each electrolytic capacitor. Specifically, for each example and comparative example, the rated voltage was applied to 10 electrolytic capacitors at 20°C, and the leakage current (LC value) after 2 minutes was measured. The average value of the 10 LC values ​​was then calculated. The results are shown in Table 2.

[0141]

[0142] Table 2 shows that when at least one first main surface of a pair of separators was facing the anode foil, leakage current was significantly suppressed.

[0143] When a separator S3 with a ratio G2 / G1 exceeding 7.0 was used, the leakage current of the electrolytic capacitor increased even though the first main surface with a glossiness G1 of 2GU or less was facing the anode foil. This is thought to be because the adhesion between the cathode foil and the separator became too high, making it impossible to secure a sufficient flow path for the liquid component inside the capacitor element.

[0144] This disclosure can be used in the manufacture of electrolytic capacitors that have high repairability of the dielectric layer and are less prone to leakage current.

[0145] 10: Anode foil, 20: Cathode foil, 30: Separator, 40: Winding stopper tape, 50A, 50B: Lead tabs, 60A, 60B: Lead wires, 100: Capacitor element, 200: Electrolytic capacitor, 211: Bottomed case, 212: Sealing material, 213: Base plate

Claims

1. A separator for an electrolytic capacitor comprising a fibrous structure and a conductive polymer attached to the fibrous structure, wherein the ratio G2 / G1 of the glossiness of a second main surface opposite to the first main surface to the glossiness G1 of the first main surface of the separator (where G1 ≤ G2) is 7 or less, the glossiness G1 is 2 GU or less, and the glossiness G1 and the glossiness G2 are 85° glossiness in accordance with JIS Z8741.

2. The amount of conductive polymer contained in the separator is 0.05 mg / cm³. ２ 2mg / cm or more ２ The separator according to claim 1, which is as follows:

3. The separator according to claim 1, wherein the ratio G2 / G1 is 4GU or more.

4. The separator according to claim 1, wherein the conductive polymer comprises polyethylene dioxythiophene doped with polystyrene sulfonic acid.

5. The separator according to claim 1, wherein the fibrous structure comprises at least one selected from the group consisting of cellulose fibers, rayon fibers, polyethylene terephthalate fibers, and polyimide fibers.

6. The fiber structure contains 50% by mass or more of synthetic fibers, and the density of the fiber structure is 0.2 g / cm³. ３ Above, 0.60g / cm ３ The separator according to claim 1, which is less than [amount missing].

7. The fibrous structure comprises 40% by mass or more of cellulose fibers and a paper strength enhancer, and the density of the fibrous structure is 0.2 g / cm³. ３ Above, 0.60g / cm ３ The separator according to claim 1, which is less than [amount missing].

8. The separator according to claim 1, wherein the fiber structure comprises a first fiber and a second fiber, the first fiber and the second fiber are mixed, the fiber diameter D1 of the first fiber is 10 μm or more and 50 μm or less, and the fiber diameter D2 of the second fiber is 5 μm or less.

9. An electrolytic capacitor comprising an anode foil having a dielectric layer, a cathode foil, and a separator according to claim 1 interposed between the anode foil and the cathode foil, wherein the anode foil and the cathode foil are wound around each other via the separator to form a wound body, the first main surface of the separator faces the anode foil, and the wound body is impregnated with a liquid component.

10. A method for manufacturing an electrolytic capacitor, comprising the steps of: preparing a separator comprising a fiber structure and a conductive polymer attached to the fiber structure; manufacturing a capacitor element by winding an anode foil and a cathode foil through the separator; and housing the capacitor element together with a liquid component in a case, wherein the ratio G2 / G1 of the glossiness of the second main surface opposite the first main surface to the glossiness G1 of the first main surface of the separator (where G1 ≤ G2) is 7 or less, the glossiness G1 is 2 GU or less, the glossiness G1 and the glossiness G2 are 85° glossiness in accordance with JIS Z8741, and in the step of manufacturing the capacitor element, the first main surface of the separator is facing the anode foil.

11. A method for manufacturing a separator for an electrolytic capacitor, comprising: a step of preparing a fiber structure; a step of preparing a conductive polymer dispersion containing a conductive polymer and a dispersion medium; and a step of applying the conductive polymer dispersion to the fiber structure by a coating method, and then removing at least a portion of the dispersion medium to produce a separator, wherein the ratio G2 / G1 of the glossiness of a second main surface opposite to the first main surface to the glossiness G1 of the first main surface of the separator (where G1 ≤ G2) is 7 or less, the glossiness G1 is 2 GU or less, and the glossiness G1 and the glossiness G2 are 85° glossiness in accordance with JIS Z8741.

12. The method for manufacturing a separator according to claim 11, wherein, in the coating method, a gravure coater, knife coater, comma coater, roll coater, die coater, or lip coater is used as the coater.

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