Conductive polymer dispersion, electrolytic capacitor, and method for manufacturing electrolytic capacitor

Abstract

To provide a separator and a conductive polymer for improving the ESR of an electrolytic capacitor and a method for manufacturing the separator and the conductive polymer.SOLUTION: The present invention relates to a method for manufacturing an electrolytic capacitor. There are prepared a positive electrode foil 11 and a negative electrode foil 12 having a dielectric layer, and a conductive polymer dispersion fluid including a fiber structure, a conductive polymer, and a dispersant. In the method, after the conductive polymer dispersion fluid is applied on the fiber structure, at least a part of the dispersant is removed so that a separator 13 is manufactured. After that, a positive electrode, a separator, and a negative electrode are sequentially deposited, and a capacitor element is manufactured. The dispersant contains water. The fiber structure includes at least 50% by mass of synthetic fibers. The density of the fiber structure is at least 0.2 g / cm3 and is less than 0.45 g / cm3.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a conductive polymer dispersion, an electrolytic capacitor, and a method for producing an electrolytic capacitor, and more particularly to an improvement in ESR characteristics. [Background technology]

[0002] Capacitors used in electronic devices are required to have a large capacity and a small equivalent series resistance (ESR) in the high frequency range. Electrolytic capacitors that use conductive polymers such as polypyrrole, polythiophene, polyfuran, and polyaniline as a solid electrolyte are promising capacitors with a large capacity and low ESR. In Patent Document 1, an anode foil is immersed in a dispersion of the conductive polymer to adhere the conductive polymer. In Patent Document 2, a separator is immersed in a dispersion of the conductive polymer to adhere the conductive polymer. The immersion method does not require large equipment, and the conductive polymer can be adhered in the same manner as with an electrolyte solution. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-109024 [Patent Document 2] Japanese Patent Application Laid-Open No. 2015-207573 Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, in addition to full hybrid systems, which are capable of self-propelling using only an electric motor, mild hybrid systems have been attracting attention as a form of hybrid car. Mild hybrid systems use the alternator normally installed in passenger cars as an auxiliary motor for the engine. In Europe, a power supply standard called LV148 has been established, which increases the rated voltage of installed alternators from 12V to 48V, and development is underway to commercialize mild hybrid systems.

[0005] As alternators become higher voltage, larger ripple currents flow through the electrolytic capacitors used with them. Reducing the equivalent series resistance (ESR) of the electrolytic capacitor is an effective way to suppress the heat generated by the increased ripple current. To reduce ESR, the amount of conductive polymer should be increased.

[0006] However, this method does not allow a sufficient amount of conductive polymer to be attached to the capacitor element. For example, increasing the concentration of the conductive polymer also increases the viscosity of the dispersion liquid containing the conductive polymer, making it difficult for the dispersion liquid to penetrate into the interior of the capacitor element. As a result, it is not possible to significantly increase the amount of conductive polymer attached to the capacitor element.

[0007] Furthermore, it is difficult to uniformly attach the conductive polymer to the separator. [Means for solving the problem]

[0008] In a first aspect of the first mode of the present invention, a capacitor element is produced by the steps of: preparing an anode foil, a cathode foil, and a fiber structure each having a dielectric layer; preparing a conductive polymer dispersion liquid containing a conductive polymer component and a dispersion medium; applying the conductive polymer dispersion liquid to the fiber structure and then removing at least a portion of the dispersion medium to produce a separator; and sequentially laminating the anode foil, the separator, and the cathode foil to produce a capacitor element, wherein the dispersion medium contains water, the fiber structure contains 50% by mass or more of synthetic fiber, and the density of the fiber structure is 0.2 g / cm. 3 More than 0.45g / cm 3 The present invention relates to a method for manufacturing an electrolytic capacitor, wherein the manufacturing method is less than

[0009] In the first embodiment of the present invention, a second aspect includes the steps of: preparing an anode foil, a cathode foil, and a fiber structure each having a dielectric layer; preparing a conductive polymer dispersion containing a conductive polymer component and a dispersion medium; applying the conductive polymer dispersion to the fiber structure and then removing at least a portion of the dispersion medium to prepare a separator; and sequentially laminating the anode foil, the separator, and the cathode foil to prepare a capacitor element, wherein the dispersion medium contains water, the fiber structure contains 40% by mass or more of cellulose fiber and a paper strength agent, and the density of the fiber structure is 0.2 g / cm. 3 More than 0.45g / cm 3 The present invention relates to a method for manufacturing an electrolytic capacitor, wherein the manufacturing method is less than

[0010] In the first embodiment of the present invention, a third aspect is an electrochemical cell comprising: an anode foil having a dielectric layer; a cathode foil; and a separator interposed between the anode foil and the cathode foil, the separator comprising a fiber structure and a conductive polymer component adhered to the fiber structure, the fiber structure containing 50 mass % or more of synthetic fiber, and a density of the fiber structure being 0.2 g / cm. 3 More than 0.45g / cm 3 The present invention relates to an electrolytic capacitor having a capacitance of less than 100 Ω / cm.

[0011] In the first embodiment of the present invention, a fourth aspect provides a sheet of paper comprising an anode foil having a dielectric layer, a cathode foil, and a separator interposed between the anode foil and the cathode foil, the separator comprising a fiber structure and a conductive polymer component adhered to the fiber structure, the fiber structure containing 40% by mass or more of cellulose fibers and a paper strength agent, and a density of the fiber structure being 0.2 g / cm 3 More than 0.45g / cm 3 The present invention relates to an electrolytic capacitor having a capacitance of less than 100 Ω / cm.

[0012] In a second embodiment of the present invention, a first aspect relates to a conductive polymer dispersion to be applied by a coating method to a sheet-like member constituting a capacitor element, the conductive polymer dispersion including a conductive polymer component and a dispersion medium, wherein the conductive polymer component is contained in an amount of 3 mass % or more and 15 mass % or less, and the viscosity measured at room temperature using a vibration viscometer is 100 mPa s or more.

[0013] In a second aspect of the second embodiment of the present invention, a second aspect relates to a method for manufacturing an electrolytic capacitor, comprising the steps of: preparing a sheet-like member constituting a capacitor element; preparing a first conductive polymer dispersion containing a first conductive polymer component and a first dispersion medium, wherein the content of the first conductive polymer component is 3% by mass or more and 15% by mass or less and the viscosity measured at room temperature using a vibration viscometer is 100 mPa s or more; applying the first conductive polymer dispersion to the sheet-like member by a coating method and then removing at least a portion of the first dispersion medium to form a conductive polymer layer containing the first conductive polymer component; and fabricating a capacitor element using the sheet-like member on which the conductive polymer layer has been formed.

[0014] In the second embodiment of the present invention, a third aspect provides a capacitor element including an anode foil having a dielectric layer, a cathode foil, and a separator interposed between the anode foil and the cathode foil, wherein a conductive polymer layer containing a first conductive polymer component is formed on at least one selected from the group consisting of the anode foil, the cathode foil, and the separator, and the conductive polymer layer has a mass per unit area of ​​0.04 mg / cm. 2 The above relates to the electrolytic capacitor. [Effects of the Invention]

[0015] According to the first aspect of the present invention, the occurrence of wrinkles in the separator is suppressed, and therefore a sufficient amount of conductive polymer can be uniformly attached to the separator.

[0016] According to the second aspect of the present invention, a large amount of conductive polymer can be held in the capacitor element, thereby providing an electrolytic capacitor with reduced ESR. The novel features of the present invention are set forth in the appended claims, but the present invention, both in terms of structure and content, together with other objects and features of the present invention, will be better understood from the following detailed description taken in conjunction with the drawings. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a flowchart showing an example of a manufacturing method according to a first embodiment of the present invention. [Figure 2] 1 is a flowchart showing an example of a manufacturing method according to a second embodiment of the present invention. [Figure 3] 1 is a side view schematically showing an electrolytic capacitor according to an embodiment of the present invention; [Figure 4] FIG. 2 is an exploded perspective view schematically showing a portion of the capacitor element according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0018] The increased amount of conductive polymer is realized by the first aspect characterized by the separator and / or the second aspect characterized by the conductive polymer dispersion.

[0019] A. First Aspect Cellulose is typically used as the separator for electrolytic capacitors because it is low cost and retains the electrolyte well. Cellulose contains hydroxyl groups, so it easily swells in water. As a result, wrinkles appear the moment a conductive polymer dispersed in water comes into contact with the cellulose. This makes it difficult to uniformly attach the conductive polymer to a cellulose separator. Furthermore, the swollen cellulose tends to shrink during the subsequent drying process, which can lead to new wrinkles. If the separator thickness becomes uneven due to wrinkles, the withstand voltage and inter-electrode resistance of the electrolytic capacitor may vary from location to location.

[0020] In this embodiment, water, which is easy to handle, is used as the dispersion medium for the conductive polymer component, and a fiber structure containing 50% by mass or more of synthetic fiber or cellulose fiber and a paper strength agent is used as the raw material for the separator. This suppresses the occurrence of wrinkles when the conductive polymer dispersion is brought into contact with the fiber structure. This makes it possible to obtain a separator with uniformly adhered conductive polymer components. Electrolytic capacitors fabricated using this separator have low ESR characteristics, and the uniform thickness of the formed separator suppresses variations in withstand voltage and inter-electrode resistance.

[0021] Furthermore, compared to when the polymerization reaction is carried out on the separator surface, the amount of impurities contained in the deposited conductive polymer component can be reduced. Therefore, the withstand voltage of the electrolytic capacitor using this can be increased. In addition, the method for applying the conductive polymer dispersion is not limited. For example, a coating method, a dipping method, or any other method capable of applying a wide range of conductive polymer components can be used.

[0022] In other words, in this embodiment, wrinkling of the separator during the manufacturing process is suppressed, so the method of applying the conductive polymer dispersion is not limited, and a sufficient amount of conductive polymer component can be uniformly attached to the separator. This further reduces the ESR of the electrolytic capacitor and improves its heat resistance. Therefore, the electrolytic capacitor according to this embodiment is suitable for use in products in which a large ripple current flows, as described above.

[0023] B. Second Aspect The conductive polymer dispersion according to this embodiment contains a conductive polymer component and a dispersion medium, and the conductive polymer component is contained in the conductive polymer dispersion at a concentration of 3% by mass or more and 15% by mass or less. The viscosity of this conductive polymer dispersion is 100 mPa·s or more. By applying such a high-concentration dispersion to a sheet-like member (hereinafter referred to as a "component") that constitutes a capacitor element, a larger amount of conductive polymer component than ever before can be retained in the capacitor element.

[0024] At least a portion of the conductive polymer component adheres to the surface of the component. Adhering a sufficient amount of the conductive polymer component to the surface of the component reduces the ESR of the resulting electrolytic capacitor. Furthermore, the heat resistance of the electrolytic capacitor is improved. Therefore, the electrolytic capacitor according to this embodiment is suitable for use in products in which a large ripple current flows.

[0025] Furthermore, compared to when the polymerization reaction is carried out on the surface of the component, the amount of impurities contained in the formed conductive polymer layer can be reduced, thereby increasing the withstand voltage of the electrolytic capacitor using this.

[0026] Each aspect will be described in detail. A. First Aspect [Manufacturing method of electrolytic capacitors] The electrolytic capacitor according to this embodiment can be manufactured by a method including the steps of: preparing an anode foil, a cathode foil, and a fiber structure each having a dielectric layer; preparing a conductive polymer dispersion containing a conductive polymer component and a dispersion medium; applying the conductive polymer dispersion to the fiber structure and then removing at least a portion of the dispersion medium to form a separator; and sequentially stacking the anode foil, separator, and cathode foil to form a capacitor element. The dispersion medium contains water. The fiber structure contains 50% by mass or more of synthetic fibers, or contains cellulose fibers and a paper strength agent. The density of these fiber structures is 0.2 g / cm. 3 More than 0.45g / cm 3 is less than. FIG. 1 is a flowchart showing an example of the manufacturing method according to the first embodiment. Hereinafter, an example of a method for manufacturing an electrolytic capacitor according to this embodiment will be described step by step.

[0027] (1) Step (S1) of preparing an anode foil, a cathode foil, and a fiber structure As the raw material for the anode foil and the cathode foil, for example, a metal foil containing a valve metal is prepared. A dielectric layer is formed on the surface of a metal foil to be used as an anode foil. The method for forming the dielectric layer is not particularly limited, but the metal foil can be subjected to a chemical conversion treatment. For example, the chemical conversion treatment involves immersing the metal foil in a chemical conversion solution such as an ammonium adipate solution and then heat treating it. Alternatively, the metal foil may be immersed in the chemical conversion solution and a voltage applied. A dielectric layer may be formed on the surface of a metal foil to be used as a cathode foil by the above-described method, or a conductive coating layer may be formed by sputtering or vapor deposition.

[0028] Before forming the dielectric layer and / or the coating layer, the surface of the metal foil may be roughened as needed. By roughening, a plurality of irregularities are formed on the surface of the metal foil. The roughening is preferably carried out by etching the metal foil. The etching may be carried out by, for example, direct current electrolysis or alternating current electrolysis.

[0029] (fiber structure) The fibrous structure is the raw material for the separator. The fiber structure is not particularly limited as long as it is porous, and examples of the fiber structure include woven fabrics, knitted fabrics, and nonwoven fabrics containing fibers.

[0030] To prevent wrinkles caused by the adhesion of the conductive polymer dispersion containing water as a dispersion medium, the fiber structure contains 50% by mass or more of synthetic fibers, or contains a paper strength agent in addition to cellulose fibers. By suppressing wrinkles in the fiber structure, the conductive polymer dispersion (hereinafter referred to as the first dispersion) adheres uniformly, resulting in a separator with a uniform thickness. This suppresses variations in the withstand voltage and interelectrode resistance from varying from one location to another in the electrolytic capacitor.

[0031] In a fiber structure containing 50% by mass or more of synthetic fibers (hereinafter referred to as a first fiber structure), the content of synthetic fibers may be 70% by mass or more of the fiber structure. The type of synthetic fiber is not particularly limited. In terms of strength and resistance to swelling with water, the synthetic fiber may include at least one type selected from the group consisting of nylon fiber, aramid fiber, acrylic fiber, and polyester fiber.

[0032] The first fiber structure may further contain cellulose, which has good compatibility with the first dispersion, the electrolyte solution added as needed, and the second conductive polymer dispersion solution (hereinafter referred to as the second dispersion solution) described below. Considering the retention of the electrolyte solution, the cellulose content may be 10% by mass or more of the fiber structure. The cellulose content may be less than 50% by mass, 30% by mass or less, or 20% by mass or less.

[0033] In a fiber structure containing cellulose fibers and a paper strength agent (hereinafter referred to as the second fiber structure), the type of paper strength agent is not particularly limited and may be a wet strength agent and / or a dry strength agent. These may be used alone or in combination. Examples of wet strength agents include at least one selected from the group consisting of urea-formaldehyde resin, melamine-formaldehyde resin, polyamide-polyamine epichlorohydrin, and polyvinylamine. Examples of dry strength agents include at least one selected from the group consisting of polyacrylamide, polyvinyl alcohol, starch, and carboxymethyl cellulose.

[0034] The paper strength agent may be added to the raw material of the second fibrous structure (for example, a slurry containing cellulose fibers), or may be applied to the second fibrous structure by spraying or the like.

[0035] When a paper strength agent is added, the second fibrous structure may contain cellulose in an amount of 40% by mass or more, or 70% by mass or more. The second fibrous structure may further contain synthetic fibers. The content of the synthetic fibers may be, for example, 10% by mass or more and 60% by mass or less of the second fibrous structure.

[0036] The density of each fiber structure is 0.2 g / cm 3 More than 0.45g / cm 3 Even in a fiber structure with such a low density, swelling of the fiber structure due to the aqueous dispersion medium can be suppressed by including 50% by mass or more of synthetic fibers or including a paper strength agent together with cellulose fibers. The density of the fiber structure (including the paper strength agent) is, for example, 0.25 g / cm 3 More than 0.40g / cm 3 It may be the following:

[0037] The thickness of each fiber structure is not particularly limited. The thickness of each fiber structure may be, for example, 20 μm or more and 100 μm or less, and preferably 30 μm or more and 60 μm or less. This makes it easier to prevent short circuits in the resulting electrolytic capacitor and to further improve the ESR reduction effect.

[0038] (2) Step (S2) of preparing a first dispersion A first dispersion liquid containing a first conductive polymer component (hereinafter referred to as the first polymer component) and a first dispersion medium is prepared.

[0039] (1st dispersion) The first dispersion includes a first polymer component and a first dispersion medium. The first polymer component includes a conductive polymer. Examples of the conductive polymer include polypyrrole, polythiophene, polyfuran, polyaniline, polyacetylene, polyphenylene, polyphenylene vinylene, polyacene, and polythiophene vinylene. These may be used alone or in combination of two or more types, or may be copolymers of two or more types of monomers.

[0040] In this specification, polypyrrole, polythiophene, polyfuran, polyaniline, etc. refer to polymers having polypyrrole, polythiophene, polyfuran, polyaniline, etc. as their basic skeletons, respectively. Therefore, polypyrrole, polythiophene, polyfuran, polyaniline, etc. may also include their respective derivatives. For example, polythiophene includes poly(3,4-ethylenedioxythiophene).

[0041] The first polymer component may further contain a dopant. The dopant may be a polyanion. Specific examples of polyanions include polyvinyl sulfonic acid, polystyrene sulfonic acid, polyallyl sulfonic acid, polyacrylic sulfonic acid, polymethacrylic sulfonic acid, poly(2-acrylamido-2-methylpropane sulfonic acid), polyisoprene sulfonic acid, and polyacrylic acid. These may be used alone 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.

[0042] The weight-average molecular weight of the polyanion contained in the first polymer component (hereinafter referred to as the first polyanion) is not particularly limited. The weight-average molecular weight of the first polyanion may be, for example, 1,000 or more and 200,000 or less. A first polymer component containing such a first polyanion is likely to be uniformly dispersed in the first dispersion medium and to adhere to the separator. Furthermore, the weight-average molecular weight of the first polyanion may be 1,000 or more and 70,000 or less. Even when a large amount of such a first polyanion is contained, an excessive increase in viscosity of the first dispersion is suppressed, and the amount of the first polyanion that adheres to the separator is likely to increase.

[0043] The first polymer component is dispersed in the first dispersion medium, for example, in the form of particles. The average particle size of the particles of the first polymer component is not particularly limited and can be appropriately adjusted depending on the polymerization conditions, dispersion conditions, etc. For example, the average particle size of the particles of the first polymer component may be 0.01 μm or more and 0.5 μm or less. Here, the average particle size is the median diameter in the volume particle size distribution measured using a particle size analyzer by dynamic light scattering.

[0044] The first dispersion medium contains water. The first dispersion medium may 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 account for 50% by mass or more of the first dispersion medium, 70% by mass or more, or 90% by mass or more. Examples of non-aqueous solvents used together with water include polar solvents (protic solvents and / or aprotic solvents).

[0045] Examples of protic solvents include alcohols such as methanol, ethanol, propanol, butanol, ethylene glycol (EG), propylene glycol, polyethylene glycol (PEG), diethylene glycol monobutyl ether, glycerin, 1-propanol, butanol, polyglycerin, sorbitol, mannitol, and pentaerythritol, and formaldehyde. 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.

[0046] When the first dispersion medium contains the above-mentioned alcohols (particularly polyhydric alcohols and sugar alcohols), the electrical conductivity and the separator impregnation are likely to be increased. On the other hand, polyhydric alcohols and sugar alcohols tend to swell cellulose. The fiber structure according to this embodiment is unlikely to swell even in a first dispersion medium containing such alcohols, and therefore wrinkles are suppressed.

[0047] The first dispersion can be obtained, for example, by dispersing particles of the first polymer component in a first dispersion medium, or by polymerizing a precursor monomer of the first polymer component in the first dispersion medium to produce particles of the first polymer component in the first dispersion medium.

[0048] The content of the first polymer component is not particularly limited. The first polymer component may be contained in the first dispersion in an amount of 1% by mass or more and 15% by mass or less. When the content of the first polymer component is within this range, a sufficient amount of the first polymer component can be adhered to the fiber structure. In order to increase the amount of the first polymer component that is likely to be adhered to the fiber structure, the content of the first polymer component may be 3% by mass or more.

[0049] The viscosity of the first dispersion is not particularly limited. The viscosity of the first dispersion measured at room temperature (20°C) using a vibration viscometer (for example, VM-100A manufactured by Sekonic Corporation) may be 10 mPa·s or more. The viscosity of the first dispersion measured under the above conditions may be 100 mPa·s or more and 200 mPa·s or less. A first dispersion having a viscosity in this range is particularly suitable for coating methods.

[0050] (3) Step of producing a separator (step of forming a polymer layer (S3)) After applying the first dispersion to the fiber structure, at least a portion of the first dispersion medium is removed to produce a separator comprising a first polymer component. By applying the first dispersion to the fiber structure, which is the raw material for the separator, before producing a capacitor element, a sufficient amount of the first polymer component can be adhered to the fiber structure. The first polymer component is adhered to the surface of the fibers that make up the fiber structure.

[0051] The method for applying the first dispersion is not particularly limited. The first dispersion may be impregnated into the fiber structure, or the first dispersion may be applied to the fiber structure by a coating method.

[0052] The coating method is a technique for applying a liquid substance to an object using a coater, such as a gravure coater, knife coater, comma coater, roll coater, die coater, or lip coater.

[0053] The amount of the first dispersion applied to the fiber structure is not particularly limited. For example, the amount of the first dispersion applied to the fiber structure is 0.02 mg / cm.2 The conditions may be appropriately set so that the first polymer component adheres.

[0054] The coating treatment with the first dispersion may be performed on one or both sides of the fiber structure. The coating treatment with the first dispersion may be performed multiple times on the same side of the fiber structure. This increases the amount of the first polymer component that adheres. In this case, the drying treatment may be performed after multiple consecutive coating treatments, or after each coating treatment.

[0055] From the viewpoint of mass productivity, the process for producing a separator may be performed on a long fiber structure. When coating both sides of a long fiber structure, the coating is first performed on one side, followed by drying, and then the fiber structure is wound up on a roll. Then, while the fiber structure is unwound from the roll in a reversed direction, the other side is coated again using the same or a different coater.

[0056] Since the amount of conductive polymer component is increased, the first polymer component may be attached to components other than the separator of the capacitor element. In particular, when the first polymer component is attached to the cathode foil and the separator, a sufficient amount of conductive polymer component can be retained without interfering with the self-repairing performance of the anode foil. When the first polymer component is attached to the anode foil and the separator, the adhesion between the dielectric layer formed on the surface of the anode foil and the first polymer component is improved, and the ESR is likely to be further reduced. The method for attaching the first polymer component to other components is not particularly limited, and impregnation or coating may be used.

[0057] The first dispersion medium is removed by a drying process such as heat drying or vacuum drying. The drying process is not particularly limited and may be appropriately set depending on the type of first dispersion medium, the amount of coating, etc. In this case, the drying process may be performed to an extent that does not completely remove the first dispersion medium. For example, the drying process may be performed so that the first dispersion medium contained in the first dispersion immediately after the coating process is more than 0% by mass and 10% by mass or less.

[0058] When the capacitor element is impregnated with the second dispersion and / or electrolyte in a subsequent process, if the first polymer component adheres to the separator together with the first dispersion medium, the second dispersion and / or electrolyte will be guided by the first dispersion medium and will be more likely to penetrate into the pores of the separator. This will facilitate contact between the anode foil and the cathode foil and the second dispersion and / or electrolyte, which is expected to improve the self-repairing performance of the anode foil and increase the capacitance. Furthermore, even when a long separator with the first polymer component adhered thereto is wound into a roll, cracks are less likely to occur in the first polymer component.

[0059] (4) Step (S4) of cutting the separator The long separator with the first polymer component attached thereto is cut prior to the step of fabricating the capacitor element. Other long components may also be cut, for example, in this step.

[0060] (5) Step of producing a capacitor element (S5) The anode foil and the cathode foil are laminated so that a separator is interposed between them. The laminate of the anode foil, the separator, and the cathode foil may be wound. In this case, the end of the cathode foil located in the outermost layer is fixed with a winding tape. After the cutting step, the capacitor element may be further subjected to a chemical conversion treatment (re-chemical conversion treatment) to form a dielectric layer on the cut surface of the anode foil.

[0061] (6) Step (S6) of impregnating the capacitor element with the second dispersion If necessary, the capacitor element may be impregnated with a second dispersion liquid containing a second conductive polymer component (hereinafter referred to as the second polymer component) and a second dispersion medium. The impregnation method is not particularly limited. Thereafter, a drying treatment may be performed to remove at least a portion of the second dispersion medium.

[0062] After the capacitor element is impregnated with the second dispersion, the second polymer component can be attached to the inside of the capacitor element by drying. The second polymer component is expected to further increase the capacitance and reduce the ESR. The second polymer component is mainly attached to the inside of the holes and pits in the components of the capacitor element.

[0063] (Second dispersion) The second dispersion liquid includes, for example, a second polymer component and a second dispersion medium. The second dispersion medium may be the same compound as the first dispersion medium. The second polymer component is not particularly limited and may contain the same conductive polymer and dopant as the first polymer component. The second polymer component may contain a polyanion (hereinafter referred to as the second polyanion) as a dopant. In this case, the weight-average molecular weight of the second polyanion is preferably larger than the weight-average molecular weight of the first polyanion contained in the first polymer component. This increases the electrical conductivity of the second polymer component, allowing a small amount to effectively reduce the ESR. Furthermore, the viscosity of the second dispersion is reduced, improving the impregnation into the capacitor element.

[0064] The weight average molecular weight of the second polyanion may be, for example, 1,000 or more and 200,000 or less, or 75,000 or more and 150,000 or less.

[0065] The content of the second polymer component in the second dispersion may be lower than the content of the first polymer component in the first dispersion. Specifically, the content of the second polymer component in the second dispersion is preferably 0.5% by mass or more and less than 3% by mass. The viscosity of the second dispersion measured at room temperature (20°C) using a vibration 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 vibration viscometer is preferably less than 100 mPa s.

[0066] (7) Step (S7) of impregnating the capacitor element with an electrolyte If necessary, the capacitor element may be impregnated with an electrolytic solution. The electrolytic solution may be impregnated without performing the second dispersion impregnation step, or the capacitor element may be impregnated with the second dispersion and then further impregnated with the electrolytic solution. The electrolytic solution facilitates improving the self-repairing performance of the dielectric layer. Furthermore, since the electrolytic solution essentially functions as a cathode material, it can be expected to have the effect of increasing the electrostatic capacitance. The impregnation method is not particularly limited.

[0067] (electrolyte) The electrolyte contains a solvent. Examples of solvents include sulfone compounds, lactone compounds, carbonate compounds, polyhydric alcohols, etc. 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); glycerin, etc. These may be used alone or in combination.

[0068] In particular, the solvent may contain a compound having two or more hydroxy groups. Examples of such compounds include polyhydric alcohols. The content of the compound having two or more hydroxy groups may be 50% by mass or more, 60% by mass or more, or 70% by mass or more of the total solvent.

[0069] The electrolyte may further contain an acid component. When the first polymer component or the second polymer component contains a dopant, the acid component in the electrolyte suppresses the dopant dedoping phenomenon and stabilizes the conductivity of each polymer component. Even if the dopant is dedoped from the polymer component, the acid component of the electrolyte re-dops the sites left by the dedoping, making it easier to maintain a low ESR.

[0070] The acid component in the electrolyte solution desirably does not excessively increase the viscosity of the electrolyte solution, and generates anions that easily dissociate in the electrolyte solution and move easily in the solvent. Examples of such acid 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 hydroxy group or a carboxy 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.

[0071] Examples of other acid components include carboxylic acids. The carboxylic acid preferably includes an aromatic carboxylic acid (aromatic dicarboxylic acid) 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 the conductive polymer over a long period of time, which is advantageous for extending the life of the electrolytic capacitor. The carboxylic acid may also be an aliphatic carboxylic acid such as adipic acid.

[0072] The acid component may contain a complex compound of an organic acid and an inorganic acid from the viewpoint of thermal stability. Examples of the complex compound of an organic acid and an inorganic acid include borodisalicylic acid, borodioxalic acid, and borodiglycolic acid, which have high heat resistance.

[0073] The acid component may include inorganic acids such as boric acid, phosphoric acid, phosphorous acid, hypophosphorous acid, and phosphonic acid.

[0074] In order to enhance the effect of suppressing the undoping phenomenon, the concentration of the acid component may be 5% by mass or more and 50% by mass or less, or 15% by mass or more and 35% by mass or less.

[0075] The electrolyte may contain a base component together with an acid component. The base component neutralizes at least a portion of the acid component. Therefore, corrosion of the electrode caused by the acid component can be suppressed while increasing the concentration of the acid component. From the viewpoint of effectively suppressing dedoping, it is preferable that the acid component is in excess of the base component in terms of equivalent ratio. For example, the equivalent ratio of the acid component to the base component may be 1 or more and 30 or less. The concentration of the base component contained in the electrolyte may be 0.1 mass % or more and 20 mass % or less, or 3 mass % or more and 10 mass % or less.

[0076] The base component is not particularly limited. Examples of the base component include ammonia, primary amines, secondary amines, tertiary amines, quaternary ammonium compounds, and amidinium compounds. Examples of the amines include aliphatic amines, aromatic amines, and heterocyclic amines.

[0077] The pH of the electrolytic solution 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 electrolytic solution to 4 or less, deterioration of the polymer component is further suppressed. The pH is preferably 2.0 or more.

[0078] (8) Step (S8) of sealing the capacitor element The fabricated capacitor element is housed in a bottomed case. The bottomed case can be made of a metal such as aluminum, stainless steel, copper, iron, or brass, or an alloy of these metals. The capacitor element is then sealed by horizontally drawing the area near the open end of the bottomed case and crimping the open end to a sealing member for curling. Finally, a seat plate is placed on the curled portion, completing the electrolytic capacitor. An aging process may then be performed while applying a rated voltage.

[0079] [Electrolytic capacitor] The electrolytic capacitor according to this embodiment includes an anode foil having a dielectric layer, a cathode foil, and a separator interposed between the anode foil and the cathode foil. The separator includes a fiber structure and a first polymer component attached to the fiber structure. The fiber structure contains synthetic fibers at 50% by mass or more and has a density of 0.2 g / cm. 3 More than 0.45g / cm 3 is less than.

[0080] Another electrolytic capacitor according to this embodiment includes an anode foil having a dielectric layer, a cathode foil, and a separator interposed between the anode foil and the cathode foil. The separator includes a fiber structure and a first polymer component adhered to the fiber structure. The fiber structure includes 40% by mass or more of cellulose fibers and a paper strength agent, and has a density of 0.2 g / cm. 3 More than 0.45g / cm 3 is less than. The constituent members of the capacitor element other than the separator and other constituent materials will be described below.

[0081] (first polymer component) The first polymeric component is adhered to the separator. Hereinafter, the conductive polymer component that is attached to the separator and contains the first polymer component may be referred to as a first polymer layer.

[0082] The mass of the first polymer layer per unit area of ​​the separator is not particularly limited and is set appropriately as needed. According to this embodiment, the separator has a mass of 0.02 mg / cm2 The first polymer layer can be deposited in a concentration of 0.1 mg / cm per unit area. 2 It may be the following:

[0083] The mass of the first polymer layer can be calculated from the difference in mass of the fibrous structure before and after application of the first dispersion. The mass of the first polymer layer can also be calculated by analyzing the separator using thermogravimetric analysis (TGA). For example, TGA involves measuring the thermal change and sample weight loss when the temperature of a sample is increased at a constant rate. Based on these measurements, the mass of the first polymer layer attached to the separator can be calculated.

[0084] The first polymer component adheres to the surface of the fibers that make up the separator, so that the first polymer layer can also be formed on the outer surface of the separator.

[0085] The higher the electrical conductivity of the first polymer layer, the greater the effect of reducing ESR. The electrical conductivity of the first polymer layer may be, for example, 30 S / cm or more, or 300 S / cm or more. The electrical conductivity of the first polymer layer tends to increase as the molecular weight of the conductive polymer contained therein increases. As the molecular weight of the conductive polymer increases, the viscosity of the first dispersion tends to increase. Therefore, the molecular weight of the conductive polymer should be set so that the viscosity of the first dispersion does not become excessively high.

[0086] When a first dispersion liquid having a first polymer component concentration of 3% by mass or more is used, the electrical conductivity of the first polymer layer is preferably, for example, 170 S / cm or less. This prevents the first dispersion liquid from excessively increasing in viscosity. In the above case, the electrical conductivity of the first polymer layer may be 150 S / cm or less, or may be 120 S / cm or less. The electrical conductivity of the first polymer layer is the electrical conductivity of a film obtained by applying the first dispersion liquid to a substrate and then removing the first dispersion medium. The electrical conductivity of the film is measured by a four-probe method in accordance with JIS K 7194:1994.

[0087] (Second polymer component) The capacitor element may be provided with the second polymer component described above. The second polymer component is expected to further increase the capacitance and reduce the ESR. The second polymer component is provided by, for example, impregnating the capacitor element with the second dispersion liquid. Hereinafter, a conductive polymer component other than the first polymer layer and containing the second polymer component may be referred to as a second polymer layer.

[0088] The second polymer layer may be attached to the surface of the component of the capacitor element and inside the holes and pits. The second polymer layer may be attached so as to cover a portion of the first polymer layer attached to the outer surface of the separator. Furthermore, the second polymer layer may be disposed in the gaps between the fibers that make up the separator to which the first polymer layer is attached.

[0089] The second polymer layer may have a concentration of, for example, 0.01 mg / cm in the capacitor element. 2 More than 1mg / cm 2 The adhesion amount of the second polymer layer is calculated in the same manner as for the first polymer component. When the separator is analyzed using the TGA method, the amount of the second polymer layer adhered to the separator is obtained by subtracting the adhesion amount of the first polymer layer from the calculated adhesion amount. After calculating the amount of the second polymer layer adhered to other components (e.g., anode foil and / or cathode foil) using the TGA method, the sum of this and the amount of the second polymer layer adhered to the separator is the adhesion amount of the second polymer layer on the capacitor element. The mass per unit area of ​​the second polymer layer is calculated by dividing the total adhesion amount of the second polymer layer by the total area of ​​one main surface of each component.

[0090] According to this embodiment, when the separator is viewed from the normal direction of its main surface, for example, 50% or more of the area of ​​the main surface is covered with the polymer layer. The polymer layer may include a first polymer layer and a second polymer layer. The area coverage of the polymer layer may be 60% or more, preferably 90% or more. The polymer layer may be continuous or discontinuous on the surface of the separator. A polymer layer with such a high coverage is easily formed when the first dispersion is applied by a coating method. The area coverage is calculated using a separator cut to a predetermined size used in an electrolytic capacitor. The area coverage may also be calculated by binarizing an image of the main surface of the component.

[0091] The area coverage rate of the polymer layer can be considered to be the area coverage rate of the first polymer layer. The area coverage rate of the separator surface of the second polymer layer is smaller than the area coverage rate of the first polymer layer. The area coverage rate of the second polymer layer is, for example, 90% or less, or 60% or less.

[0092] The mass (density) of the first polymer layer adhered per unit area of ​​the separator is preferably greater than the mass (density) of the second polymer layer adhered per unit area of ​​the separator. The ratio of the density of the first polymer layer to the density of the second polymer layer is determined by observing the cross section of the separator using a scanning electron microscope (SEM) or the like. The ratio of the density of the first polymer layer to the density of the second polymer layer is obtained by dividing the area of ​​the first polymer layer in contact with the separator by the area of ​​the polymer layers other than the first polymer layer. The densities of both layers are calculated by observing the same separator in the same observation field. Typically, an interface can be confirmed between the first polymer layer and the second polymer layer, making it possible to distinguish between the two layers. The adhesion amount, area coverage, density, etc. of the first polymer layer are calculated excluding the area of ​​the separator where the first polymer layer was not intentionally formed. 100 μm 2 It is desirable to set an observation field having an area of ​​at least this.

[0093] (anode foil) The anode foil is a metal foil containing at least one valve metal such as titanium, tantalum, aluminum, or niobium. 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 not particularly limited and is, for example, 15 μm or more and 300 μm or less. The thickness is the average value measured at any five points (the same applies hereinafter). The surface of the anode foil may be roughened by etching or the like.

[0094] A dielectric layer is formed on the surface of the anode foil. The dielectric layer is formed, for example, by chemically treating the anode foil. In this case, the dielectric layer may contain an oxide of a valve metal. However, the dielectric layer is not limited to this, and may be any material that functions as a dielectric. It is desirable that the dielectric layer is also formed on the end surfaces of the anode foil.

[0095] (cathode foil) The cathode foil is not particularly limited as long as it functions as a cathode. The cathode foil may be a metal foil. The type of metal is not particularly limited, and like the anode foil, it may be a valve metal or an alloy containing a valve metal. The thickness of the cathode foil is not particularly limited, and is, for example, 15 μm or more and 300 μm or less. The surface of the cathode foil may be roughened or subjected to a chemical conversion treatment, as necessary.

[0096] When the metal foil contains a valve metal, the metal foil may be provided with a conductive coating layer containing at least one metal selected from the group consisting of carbon and a metal with a lower ionization tendency than the valve metal. This facilitates improving acid resistance. When the metal foil contains aluminum, the coating layer may contain at least one metal selected from the group consisting of carbon, nickel, titanium, tantalum, and zirconium. In particular, the coating layer may contain nickel and / or titanium from the standpoints of cost and resistance.

[0097] The thickness of the coating layer is not particularly limited. The thickness of the coating layer may be, for example, 5 nm or more and 200 nm or less, or 10 nm or more and 200 nm or less. The thickness of the coating layer can be measured, for example, by X-ray photoelectron spectroscopy (XPS method). The coating layer can be formed, for example, by vapor deposition or sputtering of the above-mentioned metal on a metal foil. Alternatively, the coating layer can be formed by vapor deposition of a conductive carbon material on 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.

[0098] B. Second Aspect [Conductive polymer dispersion] The conductive polymer dispersion (hereinafter referred to as the first dispersion) contains a conductive polymer component (hereinafter referred to as the first polymer component) and a dispersion medium (hereinafter referred to as the first dispersion medium).

[0099] The first polymer component is contained in the first dispersion in an amount of 3% by mass or more and 15% by mass or less. When the content of the first polymer component is within this range, the viscosity of the first dispersion tends to be high. Therefore, a sufficient amount of the first polymer component can be applied to the component. The content of the first polymer component may be 10% by mass or less, or 8% by mass or less.

[0100] The viscosity of the first dispersion measured at room temperature (20°C) using a vibration viscometer (for example, VM-100A manufactured by Sekonic Corporation) is 100 mPa·s or more. The viscosity of the first dispersion measured under the above conditions may be 200 mPa·s or less, or may be 180 mPa·s or less. A first dispersion having a viscosity in this range is particularly suitable for coating methods.

[0101] The first polymer component includes a conductive polymer, and the conductive polymer may be the same as those exemplified in the first embodiment.

[0102] The first polymer component may further contain a dopant, and the dopants that can be used are the same as those exemplified in the first embodiment.

[0103] The first polymer component is dispersed in the first dispersion medium, for example, in the form of particles. The average particle size of the particles of the first polymer component is not particularly limited and can be appropriately adjusted depending on the polymerization conditions, dispersion conditions, etc. For example, the average particle size of the particles of the first polymer component may be 0.01 μm or more and 0.5 μm or less. Here, the average particle size is the median diameter in the volume particle size distribution measured using a particle size analyzer by dynamic light scattering.

[0104] The first dispersion medium is not particularly limited and may be water, a non-aqueous solvent, or a mixture thereof. A non-aqueous solvent is a general term for liquids other than water, and includes organic solvents and ionic liquids. Of these, the first dispersion medium may be water from the viewpoints of ease of handling and dispersibility of the conductive polymer component. Water may account for 50% by mass or more, 70% by mass or more, or 90% by mass or more of the first dispersion medium. Examples of non-aqueous solvents used together with water include polar solvents (protic solvents and / or aprotic solvents).

[0105] As the protic solvent, the same ones as those exemplified in the first embodiment can be used.

[0106] The first dispersion can be obtained, for example, by dispersing particles of the first polymer component in a first dispersion medium, or by polymerizing a precursor monomer of the first polymer component in the first dispersion medium to produce particles of the first polymer component in the first dispersion medium.

[0107] The first dispersion is suitable for applying the first polymer component to the component of the capacitor element by a coating method. The first dispersion may also be applied to the component of the capacitor element by a dipping method.

[0108] By applying the first dispersion to a component prior to fabricating a capacitor element, a sufficient amount of the first polymer component can be uniformly deposited on the component. If the component is porous or has pits on its surface, some of the first dispersion can penetrate into these pores.

[0109] After the first dispersion liquid is applied, the first dispersion liquid is dried to remove at least a portion of the first dispersion medium, whereby a conductive polymer layer containing the first polymer component (hereinafter referred to as the "first polymer layer") is formed so as to cover at least a portion of the surface of the component. In other words, at least a portion of the first polymer layer is disposed on the outermost surface of the component.

[0110] [Manufacturing method of electrolytic capacitors] The electrolytic capacitor according to this embodiment can be manufactured by a method including the steps of: preparing a sheet-like member that constitutes a capacitor element; preparing the first dispersion; applying the first conductive polymer dispersion to the sheet-like member by a coating method, and then removing at least a portion of the first dispersion medium to form a first polymer layer containing a first polymer component; and fabricating a capacitor element using the sheet-like member on which the first polymer layer has been formed. FIG. 2 is a flowchart showing an example of the manufacturing method according to the second embodiment. Hereinafter, an example of a method for manufacturing an electrolytic capacitor according to this embodiment will be described step by step.

[0111] (1) Step (S1) of preparing components Examples of sheet-like components to which the first dispersion is applied include an anode foil, a cathode foil, and a separator. The anode and cathode foils are prepared in the same manner as in the first embodiment. As a raw material for the separator, a known fiber structure may be prepared, or a fiber structure similar to that of the first embodiment may be prepared.

[0112] (2) Step (S2) of preparing a first dispersion The first dispersion containing a first polymer component and a first dispersion medium is prepared.

[0113] (3) Step of forming a polymer layer (S3) The first dispersion is applied to at least one selected from the group consisting of an anode foil, a cathode foil, and a separator by a coating method, and then at least a portion of the first dispersion medium is removed to form a first polymer layer containing a first polymer component. The coating method is as described in the first aspect. In this embodiment, the first dispersion is applied to the component using such a known coater.

[0114] It is desirable to apply the first dispersion to all of the components, since this increases the amount of the first polymer component. When an electrolyte solution is used in combination, it is desirable to apply the first dispersion to one or two of the components. This is because a sufficient amount of the first polymer component can be retained without interfering with the penetration of the electrolyte solution into the other components. In particular, when the first polymer layer is formed on the cathode foil and / or separator, a sufficient amount of the first polymer component can be retained without interfering with the self-repairing performance of the anode foil. When the first polymer layer is formed on the anode foil, the adhesion between the dielectric layer formed on the surface of the anode foil and the first polymer component is improved, making it easier to reduce the ESR.

[0115] The amount of the first dispersion applied to the component is not particularly limited. For example, the amount of the first dispersion applied to the component is 0.04 mg / cm. 2 The amount of the first dispersion to be applied may be appropriately determined so that the above-described first polymer layer is formed. 2 The amount of the first dispersion to be applied may be appropriately determined so that the above-described first polymer layer is formed. 2 The amount of the first dispersion applied may be appropriately determined so as to form the above-described first polymer layer. The amount of application is the mass per unit area of ​​all the first polymer components attached to the surface of the component and inside the holes and pits of the component.

[0116] The coating treatment with the first dispersion may be performed on one or both surfaces of at least one component selected from the group consisting of an anode foil, a cathode foil, and a separator. The coating treatment with the first dispersion may be performed multiple times on the same surface of the component, thereby increasing the amount of the first polymer layer formed. In this case, the drying treatment may be performed after multiple consecutive coating treatments, or after each coating treatment.

[0117] From the viewpoint of mass productivity, the step of forming the first polymer layer may be performed on a long component. When coating both sides of a long component, the coating is first performed on one side, followed by drying, and then the component is wound up on a roll. The component is then unwound from the roll in a reversed direction, and the other side is coated again using the same or a different coater.

[0118] When the cutting process described below is performed after the first polymer layer is formed, it is desirable to perform a coating process so that the first polymer layer is not formed on the intended cutting line of the component. This prevents the first polymer layer from being damaged or peeled off due to cutting. In particular, when the first polymer layer is formed on an anode foil, it is desirable to perform a coating process so that the first polymer layer is not formed on the intended cutting line of the anode foil. This prevents the first polymer component from adhering to the cut surface. When cutting an anode foil, there may be portions on the cut surface that do not have a dielectric layer, so the anode foil may be subjected to a chemical conversion treatment again after cutting. In this case, too, it becomes easier to form a uniform dielectric layer on the cut surface.

[0119] The first dispersion medium is removed in the same manner as in the first embodiment.

[0120] When the capacitor element is impregnated with a second conductive polymer dispersion (hereinafter referred to as the second dispersion) and / or an electrolyte in a subsequent process, if the first polymer layer contains the first dispersion medium, the second dispersion and / or the electrolyte will be guided by the first dispersion medium and will easily penetrate the surfaces of the dielectric layers of the anode foil and cathode foil, as well as the interiors of the holes and etching pits and the interiors of the separator holes. This is expected to improve the self-repairing performance of the anode foil and increase the capacitance. Furthermore, even when a long component on which the first polymer layer is formed is wound into a roll, the first polymer layer is less likely to crack.

[0121] (4) Step (S4) of cutting the components The elongated component on which the first polymer layer is formed is cut after the step of forming the first polymer layer. In this case, the first polymer layer is not disposed on the cut surface formed on the component, i.e., the end surface of the component. Other elongated components may also be cut, for example, in this step. The cutting step may be performed before the step of fabricating the capacitor element, or may be performed after the capacitor element is fabricated.

[0122] (5) Step of producing a capacitor element (S5) A capacitor element is produced in the same manner as in the first embodiment.

[0123] (6) Step (S6) of impregnating the capacitor element with the second dispersion If necessary, the capacitor element is impregnated with a second dispersion liquid containing a second polymer component and a second dispersion medium, and then dried, in the same manner as in the first embodiment.

[0124] (Second dispersion) The second dispersion liquid includes, for example, a second polymer component and a second dispersion medium. As the second dispersion liquid, the same ones as those exemplified in the first embodiment can be used.

[0125] (7) Step (S7) of impregnating the capacitor element with an electrolyte If necessary, the capacitor element is impregnated with an electrolyte solution in the same manner as in the first embodiment.

[0126] (electrolyte) The electrolytic solution contains a solvent, and the same electrolytic solutions as those exemplified in the first embodiment can be used.

[0127] (8) Step (S8) of sealing the capacitor element The produced capacitor element is housed in a bottomed case and sealed in the same manner as in the first embodiment.

[0128] Although the above description has been given taking as an example a wound electrolytic capacitor having a capacitor element including a cathode foil, the configuration of the electrolytic capacitor is not limited to this. For example, this embodiment can be applied to a stacked electrolytic capacitor having a capacitor element including an anode foil having a dielectric layer and a cathode extraction layer covering the anode foil.

[0129] The laminate-type electrolytic capacitor is manufactured, for example, as follows. After forming polymer layers on both sides of the anode foil in the same manner as above (S3), the anode foil is cut into a predetermined shape (S4). In the step (S5) of producing a capacitor element, a cathode extraction layer is formed so as to cover at least a portion of the conductive polymer layer formed on the surface of the anode foil.

[0130] The cathode extraction layer is formed by sequentially applying the carbon layer material and metal paste so as to cover the polymer layer, followed by a drying process. Then, as necessary, a step (S6) of impregnating the capacitor element with a second dispersion and / or a step (S7) of impregnating the capacitor element with an electrolyte are performed. Finally, the capacitor element is encapsulated with a resin encapsulant using a molding technique such as injection molding, insert molding, or compression molding, to obtain an electrolytic capacitor.

[0131] [Electrolytic capacitor] The electrolytic capacitor according to this embodiment includes a capacitor element including an anode foil with a dielectric layer, a cathode foil, and a separator interposed between the anode foil and the cathode foil, and a first polymer layer containing a first polymer component is formed on at least one selected from the group consisting of the anode foil, the cathode foil, and the separator. The mass of the first polymer layer per unit area is 0.04 mg / cm. 2 That's all.

[0132] Another electrolytic capacitor according to this embodiment includes a capacitor element including an anode foil with a dielectric layer and a cathode extraction layer covering the anode foil, and a first polymer layer containing a first polymer component is formed on the anode foil. The cathode extraction layer is formed so as to cover at least a portion of the first polymer layer. The mass of the first polymer layer per unit area is 0.1 mg / cm. 2 That's all. The constituent members and other constituent materials of the capacitor element will be described below.

[0133] (1st polymer layer) A first polymer layer containing a first polymer component is formed on at least one component. The first polymer layer is formed, for example, by applying the first dispersion to the component by a coating method. The first polymer layer may also be formed on the outer surface of the component.

[0134] The mass of the first polymer layer is not particularly limited and is set appropriately as needed. According to this embodiment, the mass of the first polymer layer is 0.04 mg / cm per unit area. 2 The first polymer layer can be formed as described above. In particular, the separator can be formed with a concentration of 0.04 mg / cm 2 The first polymer layer formed on the separator preferably has a density of 0.1 mg / cm per unit area. 2 For anode and cathode foils, the coating weight may be 0.1 mg / cm 2 The first polymer layer formed on the anode foil and the cathode foil has a density of 1 mg / cm per unit area. 2 It may be the following:

[0135] The mass per unit area of ​​the first polymer layer is calculated by measuring the difference in mass of the component before and after application of the first dispersion, or by thermogravimetric analysis (TGA), as in the first embodiment. TGA allows the mass of the first polymer layer attached to the component to be calculated based on the measured values.

[0136] The electrical conductivity of the first polymer layer may be, for example, 30 S / cm or more, or may be 300 S / cm or more, as in the first embodiment. When a first dispersion liquid having a first polymer component concentration of 3 mass % or more is used, the electrical conductivity of the first polymer layer is, for example, preferably 170 S / cm or less, as in the first embodiment, and may be 150 S / cm or less, or may be 120 S / cm or less.

[0137] (Second polymer layer) The capacitor element may have the second polymer layer described above disposed thereon, as in the first embodiment. The second polymer layer is expected to increase the capacitance and reduce the ESR. The second polymer layer may be present in the capacitor element at a concentration of, for example, 0.01 mg / cm. 2 More than 1mg / cm 2 Less than adhered.

[0138] The second polymer layer may be attached to the surface, holes, and pits of the component of the capacitor element, may be attached to cover the portion of the first polymer layer that is attached to the outer surface of the component, and may be disposed within the pits and holes in the component to which the first polymer layer is attached.

[0139] According to this embodiment, when the component is viewed from the normal direction of its main surface, for example, 50% or more of the area of ​​the main surface is covered with the polymer layer. The polymer layer may include a first polymer layer and a second polymer layer. The area coverage of the polymer layer may be 60% or more, preferably 90% or more. The polymer layer may be continuous or discontinuous on the surface of the component. A polymer layer with such a high coverage is easily formed when the first dispersion is applied by a coating method. The area coverage is calculated using the same method as in the first embodiment.

[0140] The coverage of the surface of the component by the second polymer layer is smaller than that by the first polymer layer, and the coverage by the second polymer layer is, for example, 90% or less, or 60% or less.

[0141] The mass per unit volume (density) of the first polymer layer is preferably greater than the mass per unit volume (density) of the second polymer layer formed on the first polymer layer. The density of the first polymer layer is calculated by the same method as in the first embodiment.

[0142] (anode foil) As the anode foil, the same foil as that exemplified in the first embodiment can be used. In the electrolytic capacitor, the end surface of the anode foil does not need to be provided with a polymer layer, but it is preferable that the end surface of the anode foil be provided with a dielectric layer.

[0143] (cathode foil) The cathode foil may be the same as that exemplified in the first embodiment.

[0144] (separator) The separator is interposed between the anode foil and the cathode foil. The separator is not particularly limited as long as it is porous, and examples of the separator include fibrous structures such as woven fabrics, knitted fabrics, and nonwoven fabrics containing fibers.

[0145] The separator material is not particularly limited. Examples of separator materials include synthetic fibers such as nylon fibers, aramid fibers, acrylic fibers, and polyester fibers, and cellulose. Among these, a cellulose fiber structure is suitable as a separator because it is low cost and has good compatibility with the first dispersion.

[0146] From the viewpoint of preventing wrinkles, the separator may be a first fibrous structure containing the synthetic fibers used in the first embodiment, or a second fibrous structure containing a paper strength agent together with cellulose fibers.

[0147] (Cathode extraction layer) The cathode extraction layer has, for example, a carbon layer formed to cover the first polymer layer and a metal paste layer formed on the surface of the carbon layer. The carbon layer contains a conductive carbon material such as graphite and a resin. The metal paste layer contains, for example, metal particles (e.g., silver) and a resin. The configuration of the cathode extraction layer is not limited to this configuration. The configuration of the cathode extraction layer may be any configuration that has a current collecting function.

[0148] (Resin sealing material) The resin encapsulant includes, for example, a thermosetting resin. Examples of thermosetting resins include epoxy resin, phenolic resin, silicone resin, melamine resin, urea resin, alkyd resin, polyurethane, polyimide, and unsaturated polyester. The exterior body material may include a filler, a curing agent, a polymerization initiator, and / or a catalyst.

[0149] FIG. 3 is a cross-sectional view of an electrolytic capacitor according to the first and second aspects of this embodiment, and FIG. 4 is a schematic view of a partially developed capacitor element of the electrolytic capacitor.

[0150] The electrolytic capacitor includes, for example, a capacitor element 10, a bottomed case 101 that houses capacitor element 10, a sealing member 102 that closes the opening of bottomed case 101, a seat plate 103 that covers sealing member 102, lead wires 104A and 104B that extend from sealing member 102 and pass through seat plate 103, and lead tabs 105A and 105B that connect the lead wires to electrodes of capacitor element 10. The vicinity of the open end of bottomed case 101 is drawn inward, and the open end is curled so as to be crimped to sealing member 102.

[0151] Capacitor element 10 is, for example, a wound body as shown in Fig. 4. The wound body includes anode foil 11 connected to lead tab 105A, cathode foil 12 connected to lead tab 105B, and separator 13. At least one of anode foil 11, cathode foil 12, and separator 13 has a first polymer layer and a second polymer layer (not shown) formed thereon.

[0152] The anode foil 11 and the cathode foil 12 are wound with a separator 13 interposed therebetween. The outermost periphery of the wound body is fixed with a stop tape 14. Note that Fig. 4 shows the wound body in a partially unfolded state before the outermost periphery is fixed.

[0153] The electrolytic capacitor may have at least one capacitor element, or may have a plurality of capacitor elements, the number of capacitor elements included in the electrolytic capacitor being determined depending on the intended use.

[0154] [Example] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples.

[0155] Example 1 An electrolytic capacitor with a rated voltage of 35V was fabricated as follows. (a) Preparation of components An aluminum foil having a thickness of 100 μm was subjected to an etching treatment to roughen the surface of the aluminum foil, and the roughened surface of the aluminum foil was subjected to a chemical conversion treatment to form a dielectric layer, thereby obtaining an anode foil. An aluminum foil having a thickness of 50 μm was subjected to an etching treatment to roughen the surface of the aluminum foil, thereby obtaining a cathode foil. A 50 μm thick nonwoven fabric was prepared as the raw material for the separator. The nonwoven fabric was composed of 50% by mass of synthetic fibers (25% by mass of polyester fibers and 25% by mass of aramid fibers) and 50% by mass of cellulose, and contained polyacrylamide as a paper strength enhancer. The density of the nonwoven fabric was 0.35 g / cm. 3 It was.

[0156] (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 ion-exchanged water. Iron (III) sulfate (oxidant) was added to the mixed solution while stirring, and a polymerization reaction was carried out. The reaction solution was then dialyzed to remove unreacted monomers and the oxidant, yielding a first dispersion A containing polyethylenedioxythiophene doped with approximately 5% by mass of PSS (dopant) (PEDOT / PSS, first polymer component). The concentration of the first polymer component in the first dispersion A was 2% by mass. The viscosity of the first dispersion A measured at room temperature (20°C) using a vibration viscometer (VM-100A, manufactured by Sekonic Corporation) was 40 mPa s.

[0157] (c) Formation of the first polymer layer (preparation of the separator) The first dispersion A was applied to both sides of the fiber structure using a gravure coater. After that, a drying process was performed to obtain a separator having a first polymer layer. The mass of the first polymer layer per unit area of ​​the separator was 0.02 mg / cm. 2 The area coverage of one main surface of the separator by the first polymer layer was 98%. The electrical conductivity of the first polymer layer was 400 S / cm.

[0158] (d) Fabrication of capacitor elements The anode foil, cathode foil and separator were each cut to a predetermined size. Anode and cathode lead tabs were connected to the anode and cathode foils, respectively, and the anode and cathode foils were wound around the lead tabs, with a separator interposed between them. Anode and cathode lead wires were connected to the ends of each lead tab protruding from the wound assembly, respectively. The resulting wound assembly was again subjected to chemical conversion, forming a dielectric layer on the end surface of the anode foil. The ends of the outer surface of the wound assembly were secured with stop tape, yielding a capacitor element.

[0159] (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 ion-exchanged water. Iron (III) sulfate (oxidant) was added to the mixed solution while stirring, and a polymerization reaction was carried out. The reaction solution was then dialyzed to remove unreacted monomers and the oxidant, yielding a second dispersion containing polyethylenedioxythiophene doped with approximately 5% by mass of PSS (dopant) (PEDOT / PSS, second polymer component). The concentration of the second polymer component in the second dispersion was 1.5% by mass. The viscosity of the second dispersion measured at room temperature (20°C) using a vibration viscometer (VM-100A, manufactured by Sekonic Corporation) was 30 mPa·s. The capacitor element was immersed in the second dispersion liquid for 5 minutes in a reduced pressure atmosphere (40 kPa), and then dried to form a second polymer layer.

[0160] (f) Electrolyte impregnation Ethylene glycol (EG) was used as a solvent. 5-sulfosalicylic acid (dibasic acid component) as a secondary sulfonic acid and triethylamine as a base component were dissolved in EG to a total concentration of 25% by mass to prepare an electrolyte solution. The equivalent ratio of 5-sulfosalicylic acid to triethylamine was 2.0. After the impregnation with the second dispersion (e), the capacitor element was immersed in the electrolyte solution for 5 minutes in a reduced pressure atmosphere (40 kPa).

[0161] (g) Encapsulation of capacitor elements The capacitor element impregnated with the electrolyte was sealed to complete the electrolytic capacitor (A1) as shown in Figure 3. After that, aging was carried out at 95°C for 90 minutes while applying the rated voltage.

[0162] <Evaluation> The electrolytic capacitor A1 was measured for capacitance and ESR after aging (measurement temperature: 20° C.) The evaluation results were shown as relative values ​​to the capacitance and ESR of the electrolytic capacitor B1 produced in Comparative Example 1.

[0163] After measuring the capacitance and ESR, the electrolytic capacitor A1 was disassembled and each component was taken out. The mass per unit area of ​​the second polymer layer in the entire capacitor element was 0.07 mg / cm. 2 The area coverage rate of one main surface of the separator with the second polymer layer was 83%.

[0164] Furthermore, the cross section of the separator was observed by SEM, and the mass per unit area of ​​the first polymer layer and the mass per unit area of ​​the second polymer layer were calculated. It was more than the mass per unit area of ​​the layer.

[0165] Example 2 An electrolytic capacitor A2 was produced and evaluated in the same manner as in Example 1, except that in the formation of the first polymer layer (c), the first dispersion A was applied to both sides of the anode foil using a gravure coater in addition to the fibrous structure. The results are shown in Table 1.

[0166] The mass per unit area of ​​the first polymer layer formed on the anode foil was 0.3 mg / cm 2 The area coverage of one main surface of the anode foil by the first polymer layer was 99%.

[0167] Example 3 Electrolytic capacitor A3 was produced and evaluated in the same manner as in Example 1, except that in the formation of the first polymer layer (c), in addition to the fiber structure, the first dispersion A was applied to both sides of the cathode foil using a gravure coater. The results are shown in Table 1. The mass per unit area of ​​the first polymer layer formed on the cathode foil was 0.3 mg / cm. 2 The area coverage of one main surface of the cathode foil by the first polymer layer was 99%.

[0168] Comparative Example 1 Except for not forming the first polymer layer (c), an electrolytic capacitor B1 was produced and evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0169] [Table 1]

[0170] Example 4 A first dispersion B was prepared in the same manner as in Example 1, except that in the preparation (b) of the first dispersion, PSS having a weight-average molecular weight of 50,000 was used. The concentration of the first polymer component in the first dispersion B was 4 mass%. The viscosity of the first dispersion B measured at room temperature (20°C) using a vibration viscometer (VM-100A, manufactured by Sekonic Corporation) was 105 mPa s.

[0171] Except for using the first dispersion liquid B, an electrolytic capacitor A4 was produced and evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0172] The mass per unit area of ​​the first polymer layer formed on the separator is 0.04 mg / cm 2 The area coverage rate of one main surface of the separator by the first polymer layer was 98%. The electrical conductivity of the first polymer layer was 150 S / cm. The area coverage rate of one main surface of the separator by the second polymer layer was 83%.

[0173] Example 5 An electrolytic capacitor A5 was produced and evaluated in the same manner as in Example 2, except for using the first dispersion B. The results are shown in Table 2.

[0174] The mass per unit area of ​​the polymer layer formed on the anode foil was 0.4 mg / cm 2 The mass per unit area of ​​the polymer layer formed on the separator is 0.04 mg / cm 2 The area coverage of one main surface of the anode foil by the first polymer component was 99%, and the area coverage of one main surface of the separator by the first polymer layer was 98%. The area coverage of one main surface of the anode foil and the separator by the second polymer component was 83%, respectively.

[0175] Example 6 An electrolytic capacitor A6 was produced and evaluated in the same manner as in Example 3, except for using the first dispersion B. The results are shown in Table 2.

[0176] The mass per unit area of ​​the first polymer layer formed on the cathode foil was 0.4 mg / cm 2 The mass per unit area of ​​the first polymer layer formed on the separator is 0.04 mg / cm 2 The area coverage of one main surface of the cathode foil by the first polymer component was 99%, and the area coverage of one main surface of the separator by the first polymer layer was 98%. The area coverage of one main surface of the cathode foil and one main surface of the separator by the second polymer layer was 83%, respectively.

[0177] Example 7 An electrolytic capacitor A7 was produced and evaluated in the same manner as in Example 4, except that in the formation of the first polymer layer (c), in addition to the fibrous structure, the first dispersion B was applied to both sides of the anode foil and the cathode foil using a gravure coater. The results are shown in Table 2.

[0178] The mass per unit area of ​​the first polymer layer formed on the anode foil and the cathode foil was 0.4 mg / cm. 2The mass per unit area of ​​the first polymer layer formed on the separator is 0.04 mg / cm 2 The area coverage by the first polymer layer on one main surface of the anode foil and cathode foil was 99% for each, and the area coverage by the first polymer layer on one main surface of the separator was 98% for each. The area coverage by the second polymer layer on one main surface of the anode foil, cathode foil, and separator was 83% for each.

[0179] [Table 2]

[0180] Example 8 The separator is made of a nonwoven fabric (density 0.35 g / cm) with a thickness of 90 μm, consisting of 50% by mass of synthetic fiber (25% by mass of polyester fiber, 25% by mass of aramid fiber) and 50% by mass of cellulose, and containing polyacrylamide as a paper strength enhancer. 3 ) was used, electrolytic capacitor A5 was fabricated in the same manner as in Example 1, and evaluated in the same manner. The results are shown in Table 3. The evaluation results are shown as relative values ​​to the capacitance and ESR of electrolytic capacitor B2 fabricated in Comparative Example 2. The area coverage of one main surface of the separator by the first polymer layer was 99%.

[0181] After measuring the capacitance and ESR, the electrolytic capacitor A5 was disassembled and each component was taken out. The mass per unit area of ​​the second polymer layer in the entire capacitor element was 0.07 mg / cm. 2 The area coverage of one main surface of the separator by the second polymer layer was 83%.

[0182] Furthermore, the cross section of the separator was observed with an SEM, and the mass per unit area of ​​the first polymer layer and the mass per unit area of ​​the second polymer layer were calculated. The mass per unit area of ​​the first polymer layer was greater than the mass per unit area of ​​the second polymer layer.

[0183] Comparative Example 2 Except for not applying the first dispersion to the fiber structure, electrolytic capacitor B2 was produced and evaluated in the same manner as in Example 8. The results are shown in Table 3.

[0184] [Table 3]

[0185] Example 9 A capacitor element and an electrolytic capacitor A9 were produced and evaluated in the same manner as in Example 1, except that in the formation of the first polymer layer (c), the first dispersion B prepared in Example 4 was applied to both sides of the anode foil instead of the fiber structure. The results are shown in Table 4.

[0186] The mass per unit area of ​​the first polymer layer is 0.4 mg / cm 2 The area coverage of one main surface of the anode foil by the first polymer layer was 99%. The electrical conductivity of the first polymer layer was 150 S / cm. The mass per unit area of ​​the second polymer layer in the entire capacitor element was 0.07 mg / cm. 2 The area coverage of one main surface of the anode foil by the second polymer layer was 83%.

[0187] Furthermore, the cross section of the anode foil was observed with an SEM, and the mass per unit area of ​​the first polymer layer and the mass per unit area of ​​the second polymer layer were calculated. The mass per unit area of ​​the first polymer layer was greater than the mass per unit area of ​​the second polymer layer.

[0188] Example 10 A capacitor element and an electrolytic capacitor A10 were produced and evaluated in the same manner as in Example 1, except that in the formation of the first polymer layer (c), the first dispersion B prepared in Example 4 was applied to both sides of the cathode foil instead of the fiber structure. The results are shown in Table 4.

[0189] The mass per unit area of ​​the first polymer layer formed on the cathode foil was 0.4 mg / cm 2The area coverage of one main surface of the cathode foil by the first polymer layer was 99%. The area coverage of one main surface of the cathode foil by the second polymer layer was 83%.

[0190] Example 11 A capacitor element and an electrolytic capacitor A11 were produced and evaluated in the same manner as in Example 1, except that in the formation of the first polymer layer (c), the first dispersion B prepared in Example 4 was applied to both sides of the anode foil and the cathode foil instead of the fiber structure. The results are shown in Table 4.

[0191] The mass per unit area of ​​the polymer layer formed on the anode foil and cathode foil was 0.4 mg / cm. 2 The area coverage of one main surface of each of the anode foil and cathode foil by the first polymer component was 99%. The area coverage of one main surface of each of the anode foil and cathode foil by the second polymer component was 83%.

[0192] [Table 4] [Industrial Applicability]

[0193] The present invention is particularly suitable for electrolytic capacitors through which a high ripple current flows. While the present invention has been described in terms of presently preferred embodiments, such disclosure is not to be interpreted as limiting. Various changes and modifications will no doubt become apparent to those skilled in the art to which the present invention pertains upon reading the above disclosure. It is therefore intended that the appended claims be interpreted to cover all changes and modifications that do not depart from the true spirit and scope of the invention. [Explanation of symbols]

[0194] 100: Electrolytic capacitor 101: Bottomed case 102: Sealing member 103: Seat board 104A, 104B: Lead wires 105A, 105B: Lead tab 10: Capacitor element 11: Anode foil 12: Cathode foil 13: Separator 14: Winding tape

Claims

1. preparing a sheet-like member that constitutes a capacitor element; preparing a first conductive polymer dispersion liquid containing a first conductive polymer component and a first dispersion medium, the first conductive polymer component content being 3% by mass or more and 15% by mass or less, and having a viscosity of 100 mPa s or more as measured at room temperature using a vibration viscometer; a step of applying the first conductive polymer dispersion to the sheet-like member by a coating method, and then removing at least a portion of the first dispersion medium to form a conductive polymer layer containing the first conductive polymer component; a step of producing a capacitor element using the sheet-like member on which the conductive polymer layer is formed; impregnating the produced capacitor element with a second conductive polymer dispersion; Equipped with the second conductive polymer dispersion liquid includes a second conductive polymer component and a second dispersion medium, a viscosity of the second conductive polymer dispersion measured at room temperature using a vibration viscometer lower than a viscosity of the first conductive polymer dispersion measured under the same conditions;

2. The content of the second conductive polymer component in the second conductive polymer dispersion is 0.5 mass% or more and less than 3 mass%, 2. The method for producing an electrolytic capacitor according to claim 1, wherein the viscosity of the second conductive polymer dispersion measured at room temperature using a vibration viscometer is less than 100 mPa·s.

3. 3. The method for manufacturing an electrolytic capacitor according to claim 1, wherein the viscosity of the first conductive polymer dispersion is 200 mPa·s or less.

4. the first conductive polymer component contains a polyanion; The method for producing an electrolytic capacitor according to any one of claims 1 to 3, wherein the weight average molecular weight of the polyanion is 1,000 or more and 70,000 or less.

5. The method for manufacturing an electrolytic capacitor according to claim 1, further comprising the step of impregnating the manufactured capacitor element with an electrolytic solution.

6. 6. The method for manufacturing an electrolytic capacitor according to claim 1, wherein in the step of forming the conductive polymer layer, a part of the first dispersion medium is removed to form the conductive polymer layer containing the first conductive polymer component and the first dispersion medium.

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