Method for manufacturing an electrolytic capacitor, and dispersion for forming a conductive polymer layer.

Abstract

The present invention provides a method for manufacturing an electrolytic capacitor that can uniformly form a conductive polymer layer on a separator placed between the anode foil and the cathode foil, while ensuring sufficient adhesion to the anode foil and the cathode foil. [Solution] The method for manufacturing an electrolytic capacitor according to the present disclosure comprises: an electrode foil preparation step of preparing an anode foil and a cathode foil having a dielectric layer; a separator preparation step of preparing a separator containing a plurality of microcapsules each containing a conductive polymer; a laminate formation step of forming a laminate by stacking the anode foil and the cathode foil via the separator after the separator preparation step; and a conductive polymer layer formation step of forming a conductive polymer layer on the separator that connects the anode foil and the cathode foil by applying external energy to the separator to break the capsule walls of the plurality of microcapsules and release the conductive polymer to the outside.

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing an electrolytic capacitor and a dispersion for forming a conductive polymer layer. [Background technology]

[0002] An electrolytic capacitor, for example, comprises a capacitor element and an electrolyte. The capacitor element typically includes an anode foil having a dielectric layer, a cathode foil positioned opposite the dielectric layer, and a separator interposed between the anode foil and the cathode foil. In such electrolytic capacitors, those containing a conductive polymer layer as the electrolyte are known. Furthermore, a method for manufacturing electrolytic capacitors using microcapsules has been known for some time.

[0003] Patent Document 1 discloses the use of microcapsules containing a curing agent on the surface or inside of a gasket used for sealing a sealed structure, such as a sealed secondary battery or electrolytic capacitor. In other words, Patent Document 1 discloses the use of microcapsules containing a curing agent as a core material.

[0004] Patent Document 2 discloses a method for manufacturing an aluminum electrolytic capacitor, in which a separator containing microcapsules with a driving electrolyte is dispersed in the separator, and the separator is interposed between the anode foil and the cathode foil and wound under pressure to form a capacitor element. In other words, Patent Document 2 discloses a method for manufacturing an electrolytic capacitor using microcapsules containing an electrolyte as the core material.

[0005] Patent Document 3 describes a method for manufacturing a capacitor in which an element is formed by winding or laminating electrode foil, metallized film, metallized paper, spacers, etc., characterized in that microcapsules containing a driving electrolyte or insulating oil are applied to the electrode foil, metallized film, metallized paper, spacers, etc., and the microcapsules are ruptured by pressurization to impregnate the capacitor element with the driving electrolyte or insulating oil contained within. In other words, Patent Document 3 discloses a method for manufacturing an electrolytic capacitor using microcapsules containing an electrolyte or insulating oil as the core material. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2009-93799 [Patent Document 2] Japanese Patent Application Publication No. 4-91417 [Patent Document 3] Japanese Patent Application Laid-open No. 61-125116 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] Incidentally, in the manufacture of electrolytic capacitors containing a conductive polymer layer as an electrolyte, after obtaining a laminate by stacking an anode foil and a cathode foil with a separator in between, a dispersion of conductive polymer or the like is sometimes impregnated into the separator in order to ensure sufficient adhesion between the anode foil and the cathode foil in this laminate and to form a conductive polymer layer. In this case, since the impregnation of the separator with the dispersion is carried out by allowing the dispersion to penetrate from the edge of the laminate, the dispersion may not be able to penetrate sufficiently into the center of the laminate. As a result, it becomes difficult to form a conductive polymer layer on the separator in the center of the laminate. Consequently, it may be difficult to form a uniform conductive polymer layer on the separator. In this case, problems such as a decrease in capacitance and an increase in equivalent series resistance (ESR) may occur in the electrolytic capacitor.

[0008] Furthermore, in the manufacture of electrolytic capacitors, a conductive polymer layer is sometimes formed uniformly on a separator or the like beforehand, and then the anode foil and cathode foil are laminated with the separator in between to obtain a laminate. In this case, sufficient adhesion may not be ensured between at least one of the anode foil and cathode foil and the conductive polymer layer in this laminate. As described above, if sufficient adhesion cannot be ensured between at least one of the anode foil and cathode foil and the conductive polymer layer, problems such as a decrease in capacitance and an increase in equivalent series resistance (ESR) may occur in the electrolytic capacitor.

[0009] While the aforementioned Patent Document 1 and others disclose techniques for improving gasket adhesion and for easily impregnating capacitor elements with electrolyte using microcapsules, sufficient research has yet to be conducted on how to uniformly form a conductive polymer layer on a separator placed between the anode foil and cathode foil, while ensuring sufficient adhesion to the anode foil and cathode foil.

[0010] This disclosure provides a method for manufacturing an electrolytic capacitor that can uniformly form a conductive polymer layer on a separator placed between the anode foil and the cathode foil, while ensuring sufficient adhesion to the anode foil and the cathode foil. This disclosure also provides a dispersion for forming a conductive polymer layer. [Means for solving the problem]

[0011] One aspect of the present invention relates to a method for manufacturing an electrolytic capacitor, comprising: an electrode foil preparation step of preparing an anode foil and a cathode foil having a dielectric layer; a separator preparation step of preparing a separator containing a plurality of microcapsules each containing a conductive polymer; a laminate formation step, after the separator preparation step, of stacking the anode foil and the cathode foil via the separator to form a laminate; and a conductive polymer layer formation step, either in or after the laminate formation step, of applying external energy to the separator to break the capsule walls of the plurality of microcapsules and release the conductive polymer to the outside, thereby forming a conductive polymer layer on the separator that connects the anode foil and the cathode foil.

[0012] Another aspect of the present invention relates to a method for manufacturing an electrolytic capacitor, comprising: an electrode foil preparation step of preparing an anode foil and a cathode foil having a dielectric layer; a separator preparation step of preparing a separator comprising a conductive polymer and a plurality of microcapsules each containing a conductive polymer treatment solution; a laminate formation step, after the separator preparation step, of stacking the anode foil and the cathode foil via the separator to form a laminate; and a conductive polymer layer formation step, either in or after the laminate formation step, of applying external energy to the separator to break the capsule walls of the plurality of microcapsules, releasing the treatment solution to the outside and impregnating the conductive polymer, thereby forming a conductive polymer layer on the separator that connects the anode foil and the cathode foil.

[0013] Another aspect of the present invention relates to a dispersion for forming a conductive polymer layer, comprising a plurality of microcapsules, each containing a conductive polymer, and a dispersion medium in which the plurality of microcapsules are dispersed.

[0014] Another aspect of the present invention relates to a dispersion for forming a conductive polymer layer, comprising a plurality of microcapsules, each containing a processing solution for a conductive polymer, and a dispersion medium in which the plurality of microcapsules are dispersed. [Effects of the Invention]

[0015] According to the present disclosure, a method for manufacturing an electrolytic capacitor capable of uniformly forming a conductive polymer layer on a separator disposed between an anode foil and a cathode foil and ensuring sufficient adhesion to the anode foil and the cathode foil can be provided. Further, according to the present disclosure, a dispersion for forming a conductive polymer layer can be provided.

Brief Description of Drawings

[0016] [Figure 1] It is a flowchart of a method for manufacturing an electrolytic capacitor according to an embodiment of the present disclosure. [Figure 2] It is a schematic cross-sectional view of an electrolytic capacitor according to an embodiment of the present disclosure. [Figure 3] It is a schematic view of a part of a capacitor element included in the electrolytic capacitor of FIG. 2 developed.

Embodiments for Carrying Out the Invention

[0017] Hereinafter, embodiments of the present disclosure will be described with examples, but the present disclosure is not limited to the examples described below. In the following description, specific numerical values and materials may be exemplified, but other numerical values, materials, etc. may be applied as long as the effects of the present disclosure can be obtained. In addition, known components may be applied to the components characteristic of the present disclosure. In this specification, when it is said "range of numerical value A to numerical value B", the range includes numerical value A and numerical value B.

[0018] In the following description, when the lower limit and the upper limit of a numerical value regarding a specific physical property or condition are exemplified, any combination of any of the exemplified lower limits and any of the exemplified upper limits can be arbitrarily combined as long as the lower limit is not greater than the upper limit. When a plurality of materials are exemplified, unless otherwise specified, one kind may be selected from them and used alone, or two or more kinds may be combined and used.

[0019] 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 permitted, provided that no technical inconsistency arises.

[0020] [Manufacturing method for electrolytic capacitors] As shown in Figure 1, the method for manufacturing an electrolytic capacitor according to the embodiment of this disclosure comprises an electrode foil preparation step (S1), a separator preparation step (S2), a laminate formation step (S3), and a conductive polymer layer formation step (S4). In the method for manufacturing an electrolytic capacitor according to the embodiment of this disclosure, an electrolytic capacitor is manufactured using a plurality of microcapsules.

[0021] In the method for manufacturing an electrolytic capacitor according to the first embodiment of this disclosure, an electrolytic capacitor is manufactured using a plurality of microcapsules containing a conductive polymer as the core material, and in the method for manufacturing an electrolytic capacitor according to the second embodiment of this disclosure, an electrolytic capacitor is manufactured using a plurality of microcapsules containing a treatment solution for a conductive polymer as the core material. In other words, the type of core material contained in the plurality of microcapsules differs between the method for manufacturing an electrolytic capacitor according to the first embodiment and the method for manufacturing an electrolytic capacitor according to the second embodiment. The methods for manufacturing electrolytic capacitors according to the first and second embodiments will be described below.

[0022] <First Embodiment> (Electrode foil preparation process S1) The electrode foil preparation step S1 of the first embodiment is a step of preparing an anode foil and a cathode foil having a dielectric layer.

[0023] Anode foil As the anode foil, a metal foil containing at least one of the valve metals such as titanium, tantalum, aluminum, and niobium can be used. The anode foil may also be a metal foil of the valve metal (for example, aluminum foil). The anode foil may contain the valve metal in the form of an alloy containing the valve metal or a compound containing the valve metal. The thickness of the anode foil is, for example, 15 μm to 300 μm. At least one main surface of the anode foil may be roughened. Preferably, both main surfaces (opposing surfaces in the thickness direction) of the anode foil are roughened. At least one main surface of the anode foil can be roughened by etching or the like.

[0024] As described above, the anode foil has a dielectric layer. The dielectric layer is formed on at least one main surface of the anode foil. The dielectric layer can be formed by chemical conversion treatment of the anode foil. In this case, the anode foil may contain an oxide of a valve metal (e.g., aluminum oxide). The dielectric layer only needs to function as a dielectric and may be formed from a dielectric other than an oxide of a valve metal.

[0025] Cathode foil The cathode foil is not particularly limited as long as it has the function of a cathode. A metal foil (e.g., aluminum foil) can be used as the cathode foil. The type of metal contained in the metal foil is not particularly limited. The metal may be a valve metal or an alloy containing a valve metal. The thickness of the cathode foil is, for example, 15 μm to 300 μm. The cathode foil may, if necessary, have at least one main surface roughened or a dielectric layer formed on it, similar to the anode foil. That is, at least one main surface of the cathode foil may be roughened or chemically treated, if necessary.

[0026] The cathode foil may include a conductive coating layer. If the metal foil includes a valve metal, the coating layer may include at least one of a conductive carbon material and a metal with a lower ionization tendency than the valve metal. This makes it easier to improve the oxidation resistance of the metal foil. If the metal foil includes aluminum, the coating layer may include at least one selected from the group consisting of conductive carbon material, nickel, titanium, tantalum, and zirconium. With an emphasis on low cost and low resistance, the coating layer may include at least one of nickel and titanium.

[0027] The thickness of the coating layer may be 5 nm or more, or 10 nm or more. The thickness of the coating layer may be 200 nm or less. The coating layer can be formed by depositing or sputtering the above-mentioned metal onto a metal foil. Alternatively, the coating layer can be formed by depositing a conductive carbon material onto a metal foil, or by applying a carbon paste containing a conductive carbon material. Examples of conductive carbon materials include graphite, hard carbon, soft carbon, and carbon black.

[0028] (Separator preparation process S2) The separator preparation step S2 of the first embodiment is a step of preparing a separator that includes a plurality of microcapsules, each containing a conductive polymer.

[0029] ≪Separator≫ A porous sheet can be used as the separator. Examples of porous sheets include woven fabrics, nonwoven fabrics, and microporous membranes. The thickness of the separator is, for example, 10 μm to 300 μm. Examples of separator materials include cellulose, polyethylene terephthalate, polybutylene terephthalate, polyphenylene sulfide, vinylon, nylon, aromatic polyamide, polyimide, polyamide-imide, polyetherimide, rayon, and glass.

[0030] Microcapsules Each of the multiple microcapsules contains a conductive polymer. Specifically, each of the multiple microcapsules has a capsule wall, and the conductive polymer is contained within the capsule wall by being enclosed within it. In other words, in the method for manufacturing an electrolytic capacitor according to the first embodiment, the core material of each of the multiple microcapsules is a conductive polymer. The conductive polymer may also be conductive polymer particles.

[0031] The capsule walls of each of the multiple microcapsules can be constructed using various known organic compounds. Examples of organic compounds include gum arabic (acacia resin), epoxy resin, phenolic resin, polyphenylene sulfide resin, polyimide resin, polyaramid resin, melamine resin, polyurea resin, and polyurethane resin.

[0032] The size of the microcapsules is, for example, between 0.02 μm and 100 μm. The size of the microcapsule refers to the diameter of the circumscribed circle of the microcapsule when viewed from above. Furthermore, microcapsules of the above size can also be used in the manufacturing method of the electrolytic capacitor according to the second embodiment described later.

[0033] Methods for encapsulating conductive polymers in microcapsules include, for example, (1) chemical methods such as interfacial polymerization and in-situ polymerization, (2) physicochemical methods such as liquid drying and coacervation, and (3) mechanical methods such as dry mixing and spray drying. In the method for manufacturing electrolytic capacitors according to the second embodiment described later, the conductive polymer processing solution can also be encapsulated in microcapsules by any of the above methods (1) to (3).

[0034] Conductive polymers are typically encapsulated in a dispersion of conductive polymer particles within a dispersion medium, with each microcapsule containing this dispersion. Therefore, each microcapsule typically contains both the conductive polymer particles and the dispersion medium. Consequently, the conductive polymer remains moist within each microcapsule due to the dispersion medium. Examples of dispersion media include water.

[0035] The separator preparation step S2 preferably includes a microcapsule introduction step in which a dispersion containing multiple microcapsules is applied to the separator. The application can be carried out by various known methods. Examples of application methods include application using a coater, application by spraying, and application by immersing the separator in the above-mentioned dispersion. Examples of application using a coater include gravure coating and die coating. In the dispersion, water can be used as the dispersion medium for dispersing the multiple microcapsules.

[0036] The separator prepared in separator preparation step S2 is subjected to laminate formation step S3. In laminate formation step S3, as described later, the anode foil and cathode foil are laminated with the separator in between to form a laminate. The lamination of the anode foil, separator and cathode foil can be carried out more smoothly if a dried separator is used. Therefore, it is preferable that the separator is dried after the dispersion described above is applied. Note that in separator preparation step S2 of the first embodiment, the microcapsule introduction step is not mandatory. The separator may be prepared by purchasing a separator containing multiple microcapsules containing a conductive polymer without performing the microcapsule introduction step.

[0037] (Laminate formation process S3) The laminate formation step S3 of the first embodiment is a step in which, after the separator preparation step S2, the anode foil and the cathode foil are laminated with a separator in between to form a laminate. In other words, the laminate formation step S3 is a step in which the anode foil, separator, and cathode foil are laminated in that order to form a laminate.

[0038] The laminate described above may be a wound body as shown in Figure 3. Specifically, it may be a wound body in which an anode foil and a cathode foil are wound with a separator in between. Therefore, the laminate may have a cylindrical shape. In the wound body shown in Figure 3, the anode foil, separator, and cathode foil are laminated in the radial direction of the wound body. When the laminate is a wound body, such a laminate may be formed by winding the anode foil, separator, and cathode foil, which are fed out from three rollers respectively, on one roller, or by overlapping the anode foil, separator, and cathode foil in one direction to obtain an overlapped body, and then winding this overlapped body on one roller. An electrolytic capacitor including such a laminate is also called a wound-type electrolytic capacitor.

[0039] The above-described laminate may be formed as a laminated body in which an anode foil, a separator, and a cathode foil are stacked in one direction. Therefore, the above-described laminate may have a flat plate shape. For example, a laminate may be formed by stacking a plurality of anode foils, a plurality of separators, and a plurality of cathode foils in one direction. An electrolytic capacitor including such a laminate is also called a multilayer electrolytic capacitor. In a typical example of such a laminate, the anode foils and cathode foils are arranged alternately in the thickness direction, and a separator is placed between the anode foils and cathode foils.

[0040] (Conductive polymer layer formation step S4) In the first embodiment, the conductive polymer layer formation step S4 is a step in which, during or after the laminate formation step S3, external energy is applied to the separator to rupture the capsule walls of each of the multiple microcapsules, releasing the conductive polymer to the outside, thereby forming a conductive polymer layer on the separator that connects the anode foil and the cathode foil. Note that if external energy is applied to the separator during the laminate formation step S3, the conductive polymer layer formation step S4 is included in the laminate formation step S3.

[0041] [External energy during the laminate formation process S3] (a) When the external energy is pressure When external energy is applied to the separator in the laminate formation process S3, in one example, this external energy is preferably the pressure generated by applying pressure to the separator in the thickness direction. Alternatively, this external energy is preferably the pressure applied to the separator when forming the laminate in the laminate formation process S3.

[0042] For example, when the laminate is a wound body as shown in Figure 3, in other words, when the laminate has a cylindrical shape, it is preferable to form the laminate such that radial pressure on the wound body is applied to the separator. For example, when forming a laminate by winding an anode foil, a separator, and a cathode foil, each unwound from three rollers, on one roller, the electrode foil (either the anode foil or the cathode foil) may be pulled in the winding direction, and the separator may be covered from the radial outside with this electrode foil. This makes it possible to obtain pressure generated by applying pressure to the separator in the thickness direction as external energy when forming a cylindrical laminate.

[0043] Furthermore, when forming a cylindrical laminate by winding a laminated body, in which the anode, separator, and cathode foil are stacked in one direction, on a single roller, the stacked body may be wound while being pulled in the winding direction. This allows pressure to be obtained as external energy by applying pressure to the separator in the thickness direction through pressure from the electrode foil (either the anode foil or the cathode foil) covering the separator from the radial outside.

[0044] Furthermore, if the laminate has a flat plate shape, the separator may be covered with an electrode foil (either an anode foil or a cathode foil) while being pressed from above in the thickness direction. This allows the pressure generated by pressurizing the separator in the thickness direction to be obtained as external energy through the upward pressure in the thickness direction applied by the electrode foil covering the separator.

[0045] (b) When the external energy is heat In other examples, when external energy is applied to the separator in the laminate formation step S3, it is preferable that this external energy is thermal energy that raises the separator to a predetermined temperature. Furthermore, it is preferable that this external energy is thermal energy applied to the separator by heating it when forming the laminate in the laminate formation step S3.

[0046] For example, when forming a laminate that is a wound body as shown in Figure 3, in other words, a cylindrical laminate, and when forming the laminate by winding an anode foil, separator, and cathode foil, each unwound from three rollers, onto one roller, the cylindrical laminate may be formed while heating at least one of the anode foil, separator, and cathode foil. This allows thermal energy to be applied to the separator as external energy when forming the cylindrical laminate. As described above, when forming a cylindrical laminate, it is preferable to heat the electrode foil (either the anode foil or the cathode foil) covering the separator from the radial outside. This suppresses the leakage of conductive polymer released from each of the multiple microcapsules due to gravity before the separator is covered by the electrode foil from the radial outside. As a result, it is possible to suppress uneven distribution of the conductive polymer on the separator. Therefore, a more uniform conductive polymer layer can be formed in the cylindrical laminate.

[0047] Furthermore, when forming a cylindrical laminate by winding a laminated body, in which the anode, separator, and cathode foil are stacked in one direction, onto a single roller, the stacked body may be preheated before winding, or it may be wound under a high-temperature atmosphere. This allows thermal energy to be added to the separator as external energy when forming the cylindrical laminate.

[0048] Furthermore, if the above-mentioned laminate has a flat plate shape, the laminate may be formed by stacking at least one of the anode foil, separator, and cathode foil in the thickness direction while heating them. This allows thermal energy to be applied to the separator as external energy when forming a laminate with a flat plate shape. As described above, when forming a laminate with a flat plate shape, it is preferable to heat the electrode foil (either the anode foil or the cathode foil) covering the separator from above in the thickness direction. This suppresses the leakage of conductive polymer released from each of the multiple microcapsules due to gravity before the separator is covered by the electrode foil from above in the thickness direction. As a result, uneven distribution of the conductive polymer in the separator can be suppressed. Therefore, a more uniform conductive polymer layer can be formed in a laminate with a cylindrical shape.

[0049] [External energy after the laminate formation process S3] (a) When the external energy is pressure When external energy is applied to the separator after the laminate formation process S3, in one example, this external energy is preferably the pressure generated by pressurizing the separator in the thickness direction. Alternatively, this external energy is preferably the pressure applied to the separator by pressurizing the entire laminate after the laminate formation process S3.

[0050] For example, if the laminate is a wound body as shown in Figure 3, in other words, if the laminate has a cylindrical shape, it is preferable to pressurize the entire cylindrical laminate so that radial pressure is applied to the separator. The cylindrical laminate may be pressed as a whole while wound on a single roller, or it may be pressed as a whole after being removed from a single roller. Note that if the entire cylindrical laminate is pressed after being removed from a single roller, the pressed laminate will have a flattened shape when viewed from the axial direction. That is, such a laminate has an elliptical cylindrical shape.

[0051] Furthermore, if the laminate has a flat plate shape, it is preferable to apply pressure to the entire laminate having a flat plate shape in the thickness direction.

[0052] (b) When the external energy is heat In other examples, when external energy is applied to the separator after the laminate formation process S3, it is preferable that this external energy is thermal energy that raises the separator to a predetermined temperature. Furthermore, it is preferable that this external energy is thermal energy applied to the separator by heating the entire laminate after the laminate formation process S3. In both the case of a cylindrical laminate as shown in Figure 3 and a laminate having a flat plate shape, the entire laminate can be heated by exposing the laminate to a high-temperature atmosphere. This allows thermal energy to be applied to the separator.

[0053] As described above, a capacitor element according to the first embodiment can be obtained by carrying out the electrode foil preparation step S1, the separator preparation step S2, the laminate formation step S3, and the conductive polymer layer formation step S4. Then, by housing this capacitor element and liquid components such as an electrolyte in a case, an electrolytic capacitor according to the first embodiment can be obtained.

[0054] In the capacitor element of the electrolytic capacitor according to the first embodiment, a conductive polymer layer connecting the anode foil and cathode foil is formed on the separator by conductive polymer released to the outside by rupturing the capsule walls of each of the multiple microcapsules. Furthermore, as described above, the conductive polymer is usually contained within each of the multiple microcapsules as a dispersion in which conductive polymer particles are dispersed in a dispersion medium. Therefore, inside each of the multiple microcapsules, the conductive polymer is in a wet state due to the dispersion medium. Since the conductive polymer layer is formed by such a wet conductive polymer, the formed conductive polymer layer can be made to adhere sufficiently to the electrode foils (anode foil and cathode foil). In addition, since the multiple microcapsules are contained in a sufficiently dispersed state in the separator, a conductive polymer layer can be formed between the anode foil and cathode foil with sufficiently suppressed bias in the distribution of conductive polymer.

[0055] <Second Embodiment> As explained above, the electrolytic capacitor manufacturing method according to the second embodiment uses a plurality of microcapsules containing a conductive polymer treatment solution as the core material to manufacture the electrolytic capacitor. The separator preparation step S2 and the conductive polymer layer formation step S4 differ between the electrolytic capacitor manufacturing method according to the first embodiment and the electrolytic capacitor manufacturing method according to the second embodiment. The separator preparation step S2 and the conductive polymer layer formation step S4 of the second embodiment will be described below. In the following, the conductive polymer treatment solution will also be simply referred to as the treatment solution.

[0056] (Separator preparation process S2) The separator preparation step S2 of the second embodiment is a step of preparing a separator that includes a conductive polymer and a plurality of microcapsules, each containing a processing liquid. Therefore, the separator preparation step S2 of the second embodiment differs from the separator preparation step S2 of the first embodiment mainly in that the conductive polymer is directly included in the separator without being encapsulated in microcapsules, and that the core material of each of the plurality of microcapsules is the processing liquid.

[0057] In the second embodiment, the separator preparation step S2 preferably includes a microcapsule introduction step in which a dispersion containing a conductive polymer and a plurality of microcapsules is applied to the separator. The application of the conductive polymer to the separator is preferably carried out using a dispersion containing the conductive polymer. That is, the separator preparation step S2 in the second embodiment more preferably includes a conductive polymer introduction step in which a first dispersion containing the conductive polymer is applied to the separator, and a microcapsule introduction step in which, after the conductive polymer introduction step, a second dispersion containing a plurality of microcapsules is applied to the separator. As the separator, a porous sheet can be used, as described in the first embodiment.

[0058] The application of the first and second dispersions to the separator can be carried out in the same manner as described in the first embodiment. The first dispersion contains a dispersion medium in which a plurality of conductive polymer particles are dispersed. The second dispersion also contains a dispersion medium in which a plurality of microcapsules are dispersed. Examples of the dispersion mediums for the first and second dispersions include water.

[0059] The separator prepared in separator preparation step S2 is used in laminate formation step S3. Therefore, in laminate formation step S3, the lamination of the anode foil, separator, and cathode foil can be carried out more smoothly if a dried separator is used. Accordingly, it is preferable that the separator be dried at least after coating with the second dispersion. Drying of the separator may also be carried out after coating with the first dispersion. Note that in separator preparation step S2 of the second embodiment, the conductive polymer introduction step is not mandatory. Separators containing conductive polymers may be purchased and prepared without performing the conductive polymer introduction step. Also, in separator preparation step S2 of the second embodiment, the microcapsule introduction step is not mandatory. Separators containing multiple microcapsules encapsulating the processing liquid may be purchased and prepared without performing the microcapsule introduction step.

[0060] ≪Processing liquid≫ The treatment solution is a liquid used to change the conductive polymer contained in the separator in a dry state to a wet state. The treatment solution contains a solvent. Examples of solvents include water and non-aqueous solvents. Examples of non-aqueous solvents include the non-aqueous solvent contained in the liquid component described later. Preferably, the treatment solution contains at least one of a sugar alcohol and a water-soluble epoxy. The sugar alcohol and water-soluble epoxy, when dissolved in the solvent, act on the conductive polymer contained in the separator, increasing the contact area between the conductive polymer layer composed of this conductive polymer and the electrode foil (anode foil and cathode foil), and the contact area between the conductive polymer layer and the separator.

[0061] The sugar alcohol is preferably at least one selected from the group consisting of xylitol and xylitol derivatives. In the following, the term xylitol compound may be used as a general term for xylitol and xylitol derivatives. Examples of xylitol derivatives include compounds in which some of the hydroxyl groups of xylitol are esterified, compounds in which some of the hydroxyl groups of xylitol are etherified, and compounds in which some of the hydroxyl groups of xylitol are anionized to form a salt. Sugar alcohols have the property of being highly soluble in non-aqueous solvents. Therefore, when the treatment solution contains a sugar alcohol, it is preferable to use a non-aqueous solvent as the solvent. Furthermore, when the sugar alcohol is a xylitol compound, it is preferable that the non-aqueous solvent contains at least one selected from the group consisting of ethylene glycol, diethylene glycol, triethylene glycol, ethylene glycol condensates with a mass-average molecular weight of 250 or less, glycerin, γ-butyrolactone, and sulfolane.

[0062] Water-soluble epoxy is an epoxy resin that has hydrophilic polar groups in its molecule. Examples of hydrophilic polar groups include ether groups, hydroxyl groups, carboxyl groups, amino groups, and sulfone groups. "Water-soluble" means that when 10 parts by mass of epoxy resin are mixed with 100 parts by mass of ion-exchanged water at room temperature (23±2℃), the resulting mixture is transparent. Specific examples of water-soluble epoxy include bisphenol A type water-soluble epoxy resin, bisphenol F type water-soluble epoxy resin, propylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin polyglycidyl ether, polyglycerin polyglycidyl ether, and sorbitol-based polyglycidyl ether. When the processing solution contains water-soluble epoxy, it is preferable to use water as the solvent.

[0063] (Conductive polymer layer formation step S4) The conductive polymer layer formation step S4 of the second embodiment is a step in which, in or after the laminate formation step S3, external energy is applied to the separator to rupture the capsule walls of each of the multiple microcapsules, releasing the processing liquid to the outside and impregnating it with a conductive polymer, thereby forming a conductive polymer layer on the separator that connects the anode foil and the cathode foil. Therefore, the conductive polymer layer formation step S4 of the second embodiment differs from the conductive polymer layer formation step S4 of the first embodiment mainly in that the target of release from the multiple microcapsules is the processing liquid.

[0064] In the conductive polymer layer formation step S4 of the second embodiment, external energy can be applied to the separator in the laminate formation step S3, or after the laminate formation step S3, in the same manner as in the conductive polymer layer formation step S4 of the first embodiment.

[0065] As described above, a capacitor element according to the second embodiment can be obtained by carrying out the electrode foil preparation step S1, the separator preparation step S2, the laminate formation step S3, and the conductive polymer layer formation step S4. Then, by housing this capacitor element and liquid components such as an electrolyte in a case, an electrolytic capacitor according to the second embodiment can be obtained.

[0066] In the capacitor element of the electrolytic capacitor according to the second embodiment, the conductive polymer contained in the separator is changed to a wet state by a processing liquid released to the outside by rupturing the walls of each of the multiple microcapsules, thereby forming a conductive polymer layer on the separator that connects the anode foil and the cathode foil. In other words, the conductive polymer layer is formed by the conductive polymer that has been changed from a dry state to a wet state. Therefore, the conductive polymer layer can be sufficiently adhered to the electrode foils (anode foil and cathode foil). Furthermore, since the multiple microcapsules are contained in a state where they are sufficiently dispersed in the separator, the uneven distribution of the wet state of the conductive polymer layer between the anode foil and the cathode foil can be sufficiently suppressed. Moreover, if each of the multiple microcapsules contains at least one of a sugar alcohol and a water-soluble epoxy, the contact area between the conductive polymer layer and the electrode foils (anode foil and cathode foil) can be increased, so the adhesion of the conductive polymer layer to the electrode foil can be further improved.

[0067] [Dispersion for forming conductive polymer layer] <First Embodiment> The conductive polymer layer-forming dispersion according to the first embodiment of this disclosure comprises a plurality of microcapsules, each containing a conductive polymer, and a dispersion medium in which the plurality of microcapsules are dispersed. The conductive polymer layer-forming dispersion according to the first embodiment can be suitably used in the method for manufacturing an electrolytic capacitor according to the first embodiment. The conductive polymer and dispersion medium can be those described above. The microcapsules containing the conductive polymer can also be manufactured in the same manner as described above.

[0068] <Second Embodiment> The conductive polymer layer-forming dispersion according to the second embodiment of this disclosure comprises a plurality of microcapsules, each containing a conductive polymer treatment solution, and a dispersion medium in which the plurality of microcapsules are dispersed. In the conductive polymer layer-forming dispersion according to the second embodiment, the treatment solution preferably contains at least one of a sugar alcohol and a water-soluble epoxy.

[0069] The dispersion for forming a conductive polymer layer according to the second embodiment may further contain a conductive polymer. In this case, the conductive polymer contained in the dispersion for forming a conductive polymer layer can further sufficiently adhere the conductive polymer layer to the electrode foil (anode foil and cathode foil). In other words, the conductive polymer can be used to form a conductive polymer layer that further sufficiently connects the surface of the anode foil and the surface of the cathode foil. The dispersion for conductive polymer according to the second embodiment can be suitably used in the method for manufacturing an electrolytic capacitor according to the second embodiment. The processing liquid, dispersion medium, and conductive polymer described above can be used. Microcapsules containing the processing liquid can also be manufactured in the same manner as described above.

[0070] [Electrolytic capacitor] An electrolytic capacitor according to an embodiment of the present disclosure comprises a capacitor element, a liquid component impregnated into the capacitor element, and a case housing the capacitor element and the liquid component. In the electrolytic capacitor according to an embodiment of the present disclosure, the capacitor element comprises an anode foil having a dielectric layer, a cathode foil disposed opposite to the dielectric layer, a separator interposed between the anode foil and the cathode foil, and a conductive polymer layer interposed between the anode foil and the cathode foil and in contact with the separator.

[0071] The electrolytic capacitor according to the embodiments of this disclosure is an electrolytic capacitor manufactured by the method for manufacturing an electrolytic capacitor according to the first embodiment or the method for manufacturing an electrolytic capacitor according to the second embodiment. In the electrolytic capacitor according to the embodiments of this disclosure, the anode foil, cathode foil, and separator are as described above. Therefore, the liquid component, case, and conductive polymer layer will be described below.

[0072] ≪Liquid components≫ The liquid component includes an electrolyte and an ionic liquid. As the electrolyte, a non-aqueous electrolyte containing a non-aqueous solvent and a solute dissolved in the non-aqueous solvent can be used. The non-aqueous solvent may be an organic solvent. For the non-aqueous solvent and solute, non-aqueous solvents and solutes used in various known electrolytic capacitors can be used. The liquid component may be a component that is liquid at room temperature (25°C), or a component that is liquid at the temperature at which the electrolytic capacitor is used.

[0073] Examples of organic solvents include glycol compounds, sulfone compounds, and lactone compounds. Examples of glycol compounds include ethylene glycol (EG), diethylene glycol (DEG), triethylene glycol (TEG), and propylene glycol (PG). Examples of sulfone compounds include sulfolane (SL), dimethyl sulfoxide (DMSO), and diethyl sulfoxide (DESO). Examples of lactone compounds include γ-butyrolactone (GBL) and γ-valerolactone (GVL).

[0074] Examples of organic solvents include carbonate compounds and monohydric or trihydric or higher alcohols. 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 monohydric or trihydric or higher alcohols include glycerin and polyglycerin. These may be used individually or in combination of two or more.

[0075] In organic solvents, if the group consisting of glycol compounds, sulfone compounds, and lactone compounds is designated as Group 1, and the group consisting of carbonate compounds and monohydric or trihydric or higher alcohols is designated as Group 2, then it is preferable that the organic solvents belonging to Group 1 make up more than 50% by mass of the organic solvent, more preferably 60% by mass or more, and more preferably 70% by mass or more. The entirety of the organic solvent may consist of organic solvents belonging to Group 1. That is, the organic solvent belonging to Group 1 may be the main solvent, and the organic solvent belonging to Group 2 may be the secondary solvent.

[0076] The liquid component preferably contains at least one organic solvent selected from the group consisting of glycol compounds, sulfone compounds, and lactone compounds. When the liquid component contains at least one of these compounds, the re-formation of the dielectric layer by the acid component contained in the liquid component can be efficiently carried out. Furthermore, the presence of a glycol compound in the liquid component allows the conductive polymer constituting the conductive polymer layer to receive protons (H) from the glycol compound. + )(Specifically, the proton (H) contained in the hydroxyl group +This allows for easy provision of the conductive polymer layer. In other words, it improves affinity with the conductive polymer layer. Furthermore, since sulfone compounds and lactone compounds are aprotic, the presence of at least one of the sulfone compound and lactone compound in the liquid component suppresses the reaction of the liquid component with the acid component described later (e.g., esterification reaction). In this case, even if the electrolytic capacitor is exposed to a high-temperature environment (e.g., an environment of 120°C or higher), the stability of the liquid component can be increased. This helps to stabilize the characteristics of the electrolytic capacitor.

[0077] From the viewpoint of donating protons to the conductive polymer, the liquid component may contain compounds other than glycol compounds. Examples of such other compounds include glycerin and polyglycerin.

[0078] The liquid component may contain water. The water content in the liquid component may be between 0.1% by mass and 6.0% by mass, between 0.2% by mass and 4.0% by mass, or between 0.5% by mass and 2.0% by mass. Including water in the liquid component within the above ranges can enhance the repairability of the dielectric layer by the liquid component. Furthermore, since sulfone compounds have excellent hydrolysis resistance, as described above, if the liquid component contains a sulfone compound, the hydrolysis resistance of the liquid component can be enhanced.

[0079] The liquid component contains an acid component (acid) and a base component (base) as solutes. The base component is also called a cationic component, and the acid component is also called an anionic component. The proportion of solute in the liquid component is preferably 70% by mass or less, and more preferably 50% by mass or less.

[0080] The acid component may be at least one selected from the group consisting of aromatic carboxylic acids, aliphatic carboxylic acids, and salts thereof. The aromatic carboxylic acids and aliphatic carboxylic acids may be polycarboxylic acids or monocarboxylic acids. Examples of aliphatic polycarboxylic acids include saturated polycarboxylic acids and unsaturated polycarboxylic acids. Examples of saturated polycarboxylic acids include oxalic acid, malonic acid, succinic acid, glutanoic acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebatic acid, 1,6-decanedicarboxylic acid, and 5,6-decanecarboxylic acid, while examples of unsaturated polycarboxylic acids include maleic acid, fumaric acid, and itaconic acid. Examples of aromatic polycarboxylic acids include phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, pyromellitic acid, and benzoic acid. Phthalic acid may also be o-phthalic acid. An example of an aromatic monocarboxylic acid is salicylic acid.

[0081] Examples of polycarboxylic acids include alicyclic polycarboxylic acids. Examples of alicyclic polycarboxylic acids include cyclohexane-1,2-dicarboxylic acid and cyclohexene-1,2-dicarboxylic acid.

[0082] Examples of monocarboxylic acids include aliphatic monocarboxylic acids and aromatic monocarboxylic acids. In this specification, aromatic monocarboxylic acids are a concept that includes oxycarboxylic acids. Examples of aliphatic monocarboxylic acids include saturated monocarboxylic acids and unsaturated monocarboxylic acids. Examples of saturated monocarboxylic acids include formic acid, acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, lauric acid, myristic acid, stearic acid, and behenic acid, while examples of unsaturated monocarboxylic acids include acrylic acid, methacrylic acid, and oleic acid. Examples of aromatic monocarboxylic acids include benzoic acid, cinnamic acid, and naphthoic acid. Examples of oxycarboxylic acids include salicylic acid, mandelic acid, and resorcinic acid.

[0083] As the aromatic carboxylic acid, it is preferable to use at least one selected from the group consisting of o-phthalic acid, salicylic acid, and benzoic acid. As the aliphatic carboxylic acid, it is preferable to use at least one selected from the group consisting of adipic acid, azelaic acid, and sebacic acid.

[0084] Inorganic acids may be used as the acid component. Examples of inorganic acids include phosphoric acid, phosphorous acid, hypophosphorous acid, alkyl phosphate esters, boric acid, borofluoric acid, tetrafluoroboric acid, hexafluorophosphoric acid, benzenesulfonic acid, and naphthalenesulfonic acid. Alternatively, a composite compound of an organic acid and an inorganic acid may be used as the acid component. Examples of such composite compounds include dicarboxylic acid derivatives such as borodiglycolic acid, borodisalic acid, and borodisalicylic acid.

[0085] The basic component may be a compound having an alkyl-substituted amidine group, such as imidazole compounds, benzimidazole compounds, and alicyclic amidine compounds (pyrimidine compounds, imidazoline compounds). Specifically, 1,8-diazabicyclo[5,4,0]undecene-7; 1,5-diazabicyclo[4,3,0]nonene-5; 1,2-dimethylimidazolinium; 1,2,4-trimethylimidazoline; 1-methyl-2-ethylimidazoline; 1,4-dimethyl-2-ethylimidazoline; 1-methyl-2-heptylimidazoline; 1-methyl-2-(3'heptyl)imidazoline; 1-methyl-2-dodecylimidazoline; 1,2-dimethyl-1,4,5,6-tetrahydropyrimidine; 1-methylimidazole; and 1-methylbenzimidazole are preferred. By using these methods, electrolytic capacitors can be made to have excellent impedance characteristics.

[0086] As the base component, a quaternary salt of a compound having an alkyl-substituted amidine group may be used. Examples of such base components include imidazole compounds, benzimidazole compounds, and alicyclic amidine compounds (pyrimidine compounds, imidazoline compounds) that have been quaternized with an alkyl or arylalkyl group having 1 to 11 carbon atoms. Specifically, 1-methyl-1,8-diazabicyclo[5,4,0]undecene-7; 1-methyl-1,5-diazabicyclo[4,3,0]nonene-5; 1,2,3-trimethylimidazolinium; 1,2,3,4-tetramethylimidazolinium; 1,2-dimethyl-3-ethylimidazolinium; 1,3,4-trimethyl-2-ethylimidazolinium; 1,3-dimethyl-2-heptylimidazolinium; 1,3-dimethyl-2-(3'heptyl)imidazolinium; 1,3-dimethyl-2-dodecylimidazolinium; 1,2,3-trimethyl-1,4,5,6-tetrahydropyrimidium; 1,3-dimethylimidazolium; 1-methyl-3-ethylimidazolium; and 1,3-dimethylbenzimidazolium are preferred. By using these methods, electrolytic capacitors can be made to have excellent impedance characteristics.

[0087] Tertiary amines may be used as the base component. Examples of tertiary amines include trialkylamines and phenyl group-containing amines. Examples of trialkylamines include trimethylamine, dimethylethylamine, methyldiethylamine, triethylamine, dimethyl-n-propylamine, dimethylisopropylamine, methylethyl-n-propylamine, methylethylisopropylamine, diethyl-n-propylamine, diethylisopropylamine, tri-n-propylamine, triisopropylamine, tri-n-butylamine, and tri-tert-butylamine. Examples of phenyl group-containing amines include dimethylphenylamine, methylethylphenylamine, and diethylphenylamine. From the viewpoint of increasing conductivity, it is preferable to use trialkylamines, and among trialkylamines, it is preferable to use at least one selected from the group consisting of trimethylamine, dimethylethylamine, methyldiethylamine, and triethylamine. As the base component, secondary amines such as dialkylamines, primary amines such as monoalkylamines, and ammonia may be used.

[0088] Heterocyclic amines may be used as the base component. Examples of heterocyclic amines include morpholines, and examples of morpholines include morpholine and morpholine derivatives. Specifically, examples include morpholine, N-alkylmorpholine, and N-hydroxyalkylmorpholine, and examples of N-alkylmorpholine include N-methylmorpholine, N-butylmorpholine, and 4-isobutylmorpholine. In addition, pyridine and imidazole can also be used as heterocyclic amines.

[0089] The liquid component may contain a salt of an acid component and a base component. The salt may be an inorganic salt or an organic salt. An organic salt is a salt in which at least one of the anion and cation contains an organic substance. Examples of organic salts include trimethylamine maleate, triethylamine borodisalicylate, ethyldimethylamine phthalate, mono-1,2,3,4-tetramethylimidazolium phthalate, and mono-1,3-dimethyl-2-ethylimidazolinium phthalate. The organic salt may be an amine salt of a long-chain dibasic carboxylic acid. Examples of amine salts of long-chain dibasic carboxylic acids include diethylamine 2-butyloctanedioate (2BA).

[0090] An ionic liquid is synonymous with a molten salt (molten salt), for example, an ionic substance that is liquid at 25°C.

[0091] Examples of cations constituting the ionic liquid include cations of nitrogen atom-containing heterocycles (imidazolium, pyrrolidinium, piperidinium, pyridinium, morpholinium, etc.), ammonium, phosphonium, sulfonium, and derivatives thereof (substituted products having substituents such as alkyl groups). The cation may be an organic cation.

[0092] Examples of anions constituting the ionic liquid include hydrogen sulfate ion (HSO4 - ), sulfate ion (SO4 2- , -SO4 - ), carboxylate anion (-COO - ), nitrate anion, sulfonate anion (-SO3 - ), and phosphonate anion (PO3 2- , -HPO3 -Examples include the above. Acids capable of generating these anions include sulfuric acid, sulfuric acid monoesters (such as methyl sulfuric acid), carboxylic acids (such as acetic acid, lactic acid, benzoic acid, and trifluoromethaneacetic acid), nitric acid, sulfonic acids (such as methanesulfonic acid, trifluoromethanesulfonic acid, and bis(trifluoromethylsulfonyl)imide anion), phosphonic acids (such as diethylphosphonic acid), and derivatives thereof (substituted products having substituents such as alkyl groups, halogenated alkyl groups, and halogen atoms). The anions may also contain a fluorine atom. Examples of fluorine atom-containing anions include the above-mentioned trifluoromethaneacetic acid, trifluoromethanesulfonic acid, bis(trifluoromethylsulfonyl)imide anion, and derivatives thereof.

[0093] Specific examples of ionic liquids include 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1-butyl-3-methylimidazolium trifluoromethanesulfonic acid, and 1-ethyl-3-methylimidazolium diethylphosphonic acid.

[0094] In the case of the electrolytic capacitor according to the first embodiment, the liquid component preferably contains at least one of a sugar alcohol and a water-soluble epoxy. This increases the contact area between the conductive polymer layer and the electrode foil (anode foil and cathode foil), thereby further improving the adhesion of the conductive polymer layer to the electrode foil.

[0095] The liquid component may contain a polymer compound. Examples of polymer compounds include polyalkylene glycol, derivatives of polyalkylene glycol, and compounds in which at least one hydroxyl group of a polyhydric alcohol is substituted with polyalkylene glycol (including derivatives). Specifically, examples include polyethylene glycol (PEG), polyethylene glycol glyceryl ether, polyethylene glycol diglyceryl ether, polyethylene glycol sorbitol ether, polypropylene glycol, polypropylene glycol diglyceryl ether, polypropylene glycol sorbitol ether, and polybutylene glycol.

[0096] Polyalkylene glycol may be a copolymer (such as a random copolymer, a block copolymer, or a random block copolymer). For example, it may be a copolymer of ethylene glycol and propylene glycol, a copolymer of ethylene glycol and butylene glycol, and a copolymer of propylene glycol and butylene glycol.

[0097] The polymer compound may be a copolymer having ethylene oxide (EO) units and propylene oxide (PO) units. The copolymer includes copolymers of EO and PO (EO-PO copolymers) and their derivatives. These may be used individually or in combination of two or more. The copolymer may be crosslinked with a crosslinking agent. Examples of the derivatives include EO-PO copolymers in which the hydroxyl groups (-OH) normally present at the ends are replaced with acrylic groups (O-CO-CH=CH2) or the like. When the entire EO-PO copolymer is considered as 1 mole, the molar ratio of EO units to PO units is preferably EO:PO = 0.9:0.1 to 0.5:0.5. That is, in the EO-PO copolymer, it is preferable that the amount of EO units is equal to or greater than the amount of PO units. This makes it possible to suppress the permeation of the EO-PO copolymer contained in the liquid component from the sealing member in an electrolytic capacitor in which the capacitor element is housed in a bottomed case and the opening of the bottomed case is sealed with a sealing member (such as sealing rubber).

[0098] The weight-average molecular weight Mw of the polymer compound may be 200 or more, 300 or more, 400 or more, or 500 or more. The weight-average molecular weight Mw of the polymer compound may be 5000 or less, 4000 or less, 3000 or less, 2000 or less, or 1000 or less. Note that the weight-average molecular weight Mw of the polymer compound is a polystyrene equivalent value measured by gel permeation chromatography (GPC).

[0099] The liquid component preferably contains an antioxidant. This prevents the acidic component in the liquid component from being oxidized and degraded by oxygen present in the case. Furthermore, if the electrolytic capacitor includes a conductive polymer layer, this prevents the conductive polymer constituting the conductive polymer layer from being oxidized and degraded by oxygen present in the case. The antioxidant may include at least one selected from the group consisting of phenolic antioxidants, amine antioxidants, phosphorus-based antioxidants, sulfur-based antioxidants, and aliphatic antioxidants. Among these, phenolic antioxidants are preferred from the viewpoint of reactivity with oxygen.

[0100] The phenolic antioxidant preferably includes at least one selected from the group consisting of monophenolic antioxidants, bisphenolic antioxidants, and polyphenolic antioxidants. Among these, polyphenolic antioxidants are preferred from the viewpoint of having many functional groups that react well with oxygen.

[0101] The monophenol antioxidants preferably include 2,6-di-tert-butyl-4-methylphenol, butylhydroxyanisole, sesamol, tocopherol, tocotrienol, and p-nitrophenol. The monophenol antioxidants may also include mono, di, or tri(α-methylbenzyl)phenol, trolox, normelatonin, and ferulic acid.

[0102] The material may also contain a bisphenol-based antioxidant, preferably an anoxomer. Furthermore, it may also contain bisphenol-based antioxidants such as 2,2'-methylenebis(4-ethyl-6-tert-butylphenol), 2,2'-methylenebis(4-methyl-6-tert-butylphenol), 4,4'-butylidenebis(3-ethyl-6-tert-butylphenol), 4,4'-thiobis(3-ethyl-6-tert-butylphenol), and the butylation reaction product of p-cresol and dicyclopentadiene.

[0103] The polyphenol antioxidants preferably include 2,5-di-tert-butylhydroquinone, 2,5-di-tert-amylhydroquinone, gallic acid, propyl gallate, chlorogenic acid, catechin, epigallocatechin, epigallocatechin gallate, rosmarinic acid, genkwanin, luteolin, carnosic acid, carnosol, ursolic acid, pyrogallol, kebradic acid, hydroxytyrosol, dopamine, caffeic acid, adrenaline, noradrenaline, catechol, bouciol, hydroquinone, and resorcinol.

[0104] Furthermore, the polyphenol antioxidants may include protocatechuic acid, rutin, gnetin C, theaflavin, luteolin, resveratrol, pinosembrin, pinobanksin, 1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, and 4,4',4”-(1-methylpropanyl-3-ylidene)tris(6-tert-butyl-m-cresol).

[0105] Amine-based antioxidants include aromatic secondary amine antioxidants, benzotriazole antioxidants, benzimidazole antioxidants, and amine-ketone antioxidants.

[0106] Aromatic secondary amine antioxidants include N-phenyl-1-naphthylamine, diphenylamine antioxidants, and phenylenediamine antioxidants. Diphenylamine antioxidants include alkylated diphenylamines such as p,p'-dioctyldiphenylamine, 4,4'-bis(α,α-dimethylbenzyl)diphenylamine, and p-(p-toluenesulfonylamide)diphenylamine. Phenylenediamine antioxidants include N,N'-di-2-naphthyl-p-phenylenediamine, N-phenyl-N'-isopyropyr-p-phenylenediamine, N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine, and N-phenyl-N'-(3-methacryloyloxy-2-hydroxypropyl)-p-phenylenediamine.

[0107] Benzotriazole antioxidants include benzotriazole, etc. Benzimidazole antioxidants include benzimidazole, 2-mercapto-benzoimidazole, 2-mercaptomethyl-benzoimidazole, and imidazole dipeptides, etc.

[0108] Amine-ketone antioxidants include 2,2,4-trimethyl-1,2-dihydroquinoline polymer, 6-ethoxy-1,2-dihydro-2,2,4-trimethylquinoline, a reaction product of diphenylamine and acetone, acetylcysteine, and melatonin.

[0109] Phosphorus-based antioxidants include phosphate ester antioxidants and phosphite ester antioxidants. Examples of esters include monoalkyl esters, dialkyl esters, and trialkyl esters. Examples of phosphite ester antioxidants include tris(nonylphenyl)phosphite.

[0110] Sulfur-based antioxidants include thioether-based antioxidants, isothiocyanates, sulfites, and pyrosulfites. Thioether-based antioxidants include phenothiazines, dibenzyl disulfide, diacetyl sulfide, and dilauryl thiodipropionate.

[0111] Aliphatic antioxidants include citric acid, L-ascorbic acid, erythorbic acid, and ethylenediaminetetraacetic acid.

[0112] The antioxidant may be used alone or in combination of two or more types. The antioxidant content in the liquid component is, for example, 0.5% by mass or more and 30% by mass or less of the total liquid component. Liquid chromatography (LC), gas chromatography-mass spectrometry (GC / MS), etc., can be used for the analysis of the antioxidant.

[0113] ≪Conductive polymer layer≫ The conductive polymer layer is formed by a conductive polymer. Preferably, the conductive polymer layer is formed by particles of the conductive polymer. Examples of conductive polymers include polypyrrole, polythiophene, polyaniline, and their derivatives. The conductive polymer may be used alone or in combination of two or more types. The conductive polymer may also be a copolymer of two or more monomers. A derivative of a conductive polymer refers to a polymer that uses a conductive polymer as its basic skeleton. For example, derivatives of polythiophene include poly(3,4-ethylenedioxythiophene).

[0114] 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, polystyrene sulfonic acid, and salts thereof. An example of a conductive polymer is poly(3,4-ethylenedioxythiophene) (PEDOT) doped with polystyrene sulfonic acid (PSS). In the electrolytic capacitor according to the first embodiment of this disclosure, the conductive polymer layer is preferably formed of particles of poly(3,4-ethylenedioxythiophene) (PEDOT) (hereinafter also referred to as PEDOT / PSS) doped with polystyrene sulfonic acid (PSS).

[0115] It is preferable that the conductive polymer layer is in contact with the anode foil, cathode foil, and separator with a sufficiently large contact area. This allows the conductive polymer layer to form a sufficient conductive path between the anode foil and cathode foil. As a result, the equivalent series resistance (ESR) of the electrolytic capacitor can be reduced, thereby improving the reliability of the electrolytic capacitor.

[0116] The conductive polymer layer is preferably formed on at least one selected from at least one main surface of the dielectric layer of the anode foil and at least one main surface of the cathode foil. The conductive polymer layer may also be formed in the voids of the separator (i.e., on the surface of the separator's constituent material surrounding the voids of the separator). This allows for the formation of a stronger conductive path between the anode foil and the cathode foil by the conductive polymer layer. The conductive polymer layer is preferably formed on at least the surface of the dielectric layer of the anode foil, more preferably on both the surface of the dielectric layer and the surface of the cathode foil, and more preferably in the voids of the separator. The conductive polymer layer is preferably formed to continuously connect the surface of the dielectric layer and the surface of the cathode foil.

[0117] ≪Case≫ The case houses the capacitor element and the liquid component. The case may be a bottomed case having a space for housing the capacitor element and the liquid component. The bottomed case can be made, for example, by processing a metal plate into a predetermined shape. The case may be a resin exterior made using a sealing resin. Various known resins can be used as the sealing resin. The sealing resin may include a thermosetting resin. Examples of thermosetting resins include epoxy resin, phenolic resin, silicone resin, melamine resin, urea resin, alkyd resin, polyurethane resin, polyimide resin, and unsaturated polyester resin. The sealing resin may contain at least one selected from the group consisting of fillers, curing agents, polymerization initiators, and catalysts.

[0118] The specific configuration of an electrolytic capacitor according to one embodiment of this disclosure will be described below with reference to Figures 2 and 3. Figure 2 is a schematic cross-sectional view showing an electrolytic capacitor 100 according to one embodiment of this disclosure, and Figure 3 is a schematic diagram showing a part of the capacitor element 10 included in the electrolytic capacitor 100 unfolded. The electrolytic capacitor 100 may be an electrolytic capacitor according to the first embodiment or an electrolytic capacitor according to the second embodiment.

[0119] The electrolytic capacitor 100 comprises a capacitor element 10, a bottomed case 101 housing the capacitor element 10, a sealing member 102 (for example, a sealing rubber) that closes the opening of the bottomed case 101, a base plate 103 that covers the sealing member 102, a base plate 103 positioned outside the bottomed case 101 so as to cover the sealing member 102 from the opening side of the bottomed case 101, a pair of lead wires 104A and 104B that are led out from the sealing member 102 and pass through the base plate 103, and a pair of lead tabs 105A and 105B that connect each of the pair of lead wires 104A and 104B to the electrodes of the capacitor element (for example, an anode foil 11 and a cathode foil 12, which will be described later). The area near the opening end of the bottomed case 101 is drawn inward, and the opening end of the bottomed case 101 is curled so as to be crimped to the sealing member 102. In the example shown in Figure 3, lead wire 104A is connected to the electrode of the capacitor element via lead tab 105A, and lead wire 104B is connected to the electrode of the capacitor element via lead tab 105B.

[0120] The sealing member 102 is formed of an elastic material containing a rubber component. Examples of rubber components that can be used include butyl rubber (IIR), nitrile rubber (NBR), ethylene propylene rubber, ethylene propylene diene rubber (EPDM), chloroprene rubber (CR), isoprene rubber (IR), Hypalon® rubber, silicone rubber, and fluororubber. The sealing member 102 may also contain fillers such as carbon black and silica.

[0121] The capacitor element 10 is configured, for example, as a wound body as shown in Figure 3. The wound body comprises an anode foil 11 connected to a lead tab 105A, a cathode foil 12 connected to a lead tab 105B, and a separator 13. The capacitor element 10 includes a conductive polymer layer (not shown). Note that the electrolytic capacitor 100 shown in Figure 1 includes the capacitor element 10 shown in Figure 3, and is therefore referred to as a wound-type electrolytic capacitor.

[0122] The anode foil 11 and cathode foil 12 are wound together with a separator 13 interposed between them to form a wound body. The outermost circumference of this wound body is then secured by a winding stopper tape 14. Figure 3 shows the state of the wound body with a portion unfolded before the outermost circumference is secured by the winding stopper tape 14.

[0123] The electrolytic capacitor according to this disclosure only needs to have at least one capacitor element, but may also have multiple capacitor elements. The number of capacitor elements in the electrolytic capacitor is determined appropriately depending on the application.

[0124] Figures 2 and 3 illustrate wound-type electrolytic capacitors, but the electrolytic capacitors according to the embodiments of this disclosure are not limited to these, and may also be chip-type electrolytic capacitors or multilayer-type electrolytic capacitors.

[0125] (Note) The following technologies are disclosed as described above. (Technology 1) An electrode foil preparation step for preparing an anode foil and a cathode foil having a dielectric layer, A separator preparation step involves preparing a separator containing multiple microcapsules, each containing a conductive polymer, and After the separator preparation step, the laminate formation step involves stacking the anode foil and the cathode foil via the separator to form a laminate, In the laminate formation step, or after the laminate formation step, an conductive polymer layer formation step is performed in which external energy is applied to the separator to break the capsule walls of each of the plurality of microcapsules and release the conductive polymer to the outside, thereby forming a conductive polymer layer on the separator that connects the anode foil and the cathode foil. Equipped with, A method for manufacturing electrolytic capacitors. (Technology 2) The separator preparation step includes a microcapsule introduction step of applying the dispersion containing the plurality of microcapsules to the separator. A method for manufacturing an electrolytic capacitor as described in Technical 1. (Technology 3) An electrode foil preparation step for preparing an anode foil and a cathode foil having a dielectric layer, A separator preparation step involves preparing a separator containing a conductive polymer and a plurality of microcapsules each containing a processing solution for the conductive polymer, After the separator preparation step, the laminate formation step involves stacking the anode foil and the cathode foil via the separator to form a laminate, In the laminate formation step, or after the laminate formation step, an conductive polymer layer formation step is performed in which external energy is applied to the separator to rupture the capsule walls of each of the plurality of microcapsules, releasing the processing liquid to the outside and impregnating it with the conductive polymer, thereby forming a conductive polymer layer on the separator that connects the anode foil and the cathode foil. Equipped with, A method for manufacturing electrolytic capacitors. (Technology 4) The separator preparation step includes a microcapsule introduction step of applying a dispersion containing the conductive polymer and the plurality of microcapsules to the separator. A method for manufacturing electrolytic capacitors as described in Technical 3. (Technology 5) The separator preparation step includes a conductive polymer introduction step in which the first dispersion containing the conductive polymer is applied to the separator, The process includes, after the conductive polymer introduction step, a microcapsule introduction step in which a second dispersion containing the plurality of microcapsules is applied to the separator, A method for manufacturing an electrolytic capacitor as described in Technology 3 or 4. (Technology 6) The processing solution comprises at least one of a sugar alcohol and a water-soluble epoxy. A method for manufacturing an electrolytic capacitor as described in any one of the techniques 3 to 5. (Technology 7) The external energy is the pressure generated by applying pressure to the separator in the thickness direction. In the laminate formation step, when forming the laminate, the pressure is applied to the separator. A method for manufacturing an electrolytic capacitor as described in any one of the techniques 1 to 6. (Technology 8) The external energy is the pressure generated by applying pressure to the separator in the thickness direction. After the laminate formation step, the entire laminate is pressurized to apply pressure to the separator. A method for manufacturing an electrolytic capacitor as described in any one of the techniques 1 to 6. (Technology 9) The external energy is thermal energy that raises the separator to a predetermined temperature. In the laminate formation step, the thermal energy is applied to the separator by heating it when forming the laminate. A method for manufacturing an electrolytic capacitor as described in any one of the techniques 1 to 6. (Technology 10) The external energy is thermal energy that raises the separator to a predetermined temperature. After the laminate formation step, the entire laminate is heated to apply the thermal energy to the separator. A method for manufacturing an electrolytic capacitor as described in any one of the techniques 1 to 6. (Technology 11) The laminate is a wound body in which the anode foil and the cathode foil are wound with the separator in between. A method for manufacturing an electrolytic capacitor as described in any one of the techniques 1 to 10. (Technology 12) Multiple microcapsules, each containing a conductive polymer, A dispersion medium in which the plurality of microcapsules are dispersed, Equipped with, Dispersion for forming conductive polymer layers. (Technology 13) Multiple microcapsules, each containing a conductive polymer treatment solution, A dispersion medium in which the plurality of microcapsules are dispersed, Equipped with, Dispersion for forming conductive polymer layers. (Technology 14) The processing solution comprises at least one of a sugar alcohol and a water-soluble epoxy. A dispersion for forming a conductive polymer layer as described in Technical 13. (Technology 15) Further containing a conductive polymer, A dispersion for forming a conductive polymer layer as described in Technical 13 or 14.

[0126] Although the present invention has been described in relation to preferred embodiments at present, such disclosure should not be interpreted restrictively. Various modifications and alterations will undoubtedly become apparent to those skilled in the art in the field to which the invention pertains by reading the above disclosure. Accordingly, the appended claims should be interpreted as encompassing all modifications and alterations without departing from the true spirit and scope of the invention. [Industrial applicability]

[0127] The method for manufacturing an electrolytic capacitor according to this disclosure can be used for manufacturing electrolytic capacitors in which it is required to form a conductive polymer layer uniformly on a separator placed between the anode foil and the cathode foil, while ensuring sufficient adhesion to the anode foil and the cathode foil. [Explanation of Symbols]

[0128] 10: Capacitor element, 11: Anode foil, 12: Cathode foil, 13: Separator, 14: Winding tape, 100: Electrolytic capacitor, 101: Bottomed case, 102: Encapsulating material, 103: Base plate, 104A, 104B: Lead wires, 105A, 105B: Lead tabs

Claims

1. An electrode foil preparation step for preparing an anode foil and a cathode foil having a dielectric layer, A separator preparation step involves preparing a separator containing multiple microcapsules, each containing a conductive polymer, and After the separator preparation step, the laminate formation step involves stacking the anode foil and the cathode foil via the separator to form a laminate, In the laminate formation step, or after the laminate formation step, an conductive polymer layer formation step is performed in which external energy is applied to the separator to break the capsule walls of each of the plurality of microcapsules and release the conductive polymer to the outside, thereby forming a conductive polymer layer on the separator that connects the anode foil and the cathode foil. Equipped with, A method for manufacturing electrolytic capacitors.

2. The separator preparation step includes a microcapsule introduction step of applying the dispersion containing the plurality of microcapsules to the separator. A method for manufacturing an electrolytic capacitor according to claim 1.

3. An electrode foil preparation step for preparing an anode foil and a cathode foil having a dielectric layer, A separator preparation step involves preparing a separator containing a conductive polymer and a plurality of microcapsules each containing a processing solution for the conductive polymer, After the separator preparation step, the laminate formation step involves stacking the anode foil and the cathode foil via the separator to form a laminate, In the laminate formation step, or after the laminate formation step, an conductive polymer layer formation step is performed in which external energy is applied to the separator to rupture the capsule walls of each of the plurality of microcapsules, releasing the processing liquid to the outside and impregnating it with the conductive polymer, thereby forming a conductive polymer layer on the separator that connects the anode foil and the cathode foil. Equipped with, A method for manufacturing electrolytic capacitors.

4. The separator preparation step includes a microcapsule introduction step of applying a dispersion containing the conductive polymer and the plurality of microcapsules to the separator. A method for manufacturing an electrolytic capacitor according to claim 3.

5. The separator preparation step includes a conductive polymer introduction step in which a first dispersion containing the conductive polymer is applied to the separator, The process includes, after the conductive polymer introduction step, a microcapsule introduction step in which a second dispersion containing the plurality of microcapsules is applied to the separator, A method for manufacturing an electrolytic capacitor according to claim 3.

6. The processing solution comprises at least one of a sugar alcohol and a water-soluble epoxy. A method for manufacturing an electrolytic capacitor according to claim 3.

7. The external energy is the pressure generated by applying pressure to the separator in the thickness direction. In the laminate formation step, when forming the laminate, the pressure is applied to the separator. A method for manufacturing an electrolytic capacitor according to any one of claims 1 to 6.

8. The external energy is the pressure generated by applying pressure to the separator in the thickness direction. After the laminate formation step, the entire laminate is pressurized to apply pressure to the separator. A method for manufacturing an electrolytic capacitor according to any one of claims 1 to 6.

9. The external energy is thermal energy that raises the separator to a predetermined temperature. In the laminate formation step, the thermal energy is applied to the separator by heating it when forming the laminate. A method for manufacturing an electrolytic capacitor according to any one of claims 1 to 6.

10. The external energy is thermal energy that raises the separator to a predetermined temperature. After the laminate formation step, the entire laminate is heated to apply the thermal energy to the separator. A method for manufacturing an electrolytic capacitor according to any one of claims 1 to 6.

11. The laminate is a wound body in which the anode foil and the cathode foil are wound with the separator in between. A method for manufacturing an electrolytic capacitor according to any one of claims 1 to 6.

12. Multiple microcapsules, each containing a conductive polymer, A dispersion medium in which the plurality of microcapsules are dispersed, Equipped with, Dispersion for forming conductive polymer layers.

13. Multiple microcapsules, each containing a conductive polymer treatment solution, A dispersion medium in which the plurality of microcapsules are dispersed, Equipped with, Dispersion for forming conductive polymer layers.

14. The processing solution comprises at least one of a sugar alcohol and a water-soluble epoxy. The dispersion for forming a conductive polymer layer according to claim 13.

15. Further containing a conductive polymer, The dispersion for forming a conductive polymer layer according to claim 13.

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