Electrolytic capacitor and method for manufacturing the same

Abstract

A method for manufacturing an electrolytic capacitor comprises: a step of preparing an electrode foil; a step of preparing a first conductive polymer dispersion liquid containing a first conductive polymer component and a first dispersion medium; a step of applying the first conductive polymer dispersion liquid to the surface of the electrode foil by a coating method, and then removing at least a portion of the first dispersion medium to form a first conductive polymer layer containing the first conductive polymer component; and a step of manufacturing a capacitor element using the electrode foil formed with the first conductive polymer layer.

Description

[0001] This application is a divisional application of an application with a filing date of January 29, 2020, application number 202080011873.6, and invention name “Electrolytic capacitor and method for manufacturing the same”. Technical Field

[0002] The present invention relates to an electrolytic capacitor and a method for manufacturing the same, and more particularly to improvement of ESR characteristics. Background Art

[0003] Capacitors used in electronic devices are required to have large capacitance and low equivalent series resistance (ESR) in high-frequency regions. As capacitors with large capacitance and low ESR, electrolytic capacitors using conductive polymers such as polypyrrole, polythiophene, polyfuran, and polyaniline as solid electrolytes are promising. In Patent Document 1, an anode foil is immersed in a dispersion of a conductive polymer to adhere the conductive polymer.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2011-109024 Summary of the invention

[0007] Problems to be solved by the invention

[0008] In recent years, as one of the forms of hybrid vehicles, in addition to systems that can run by themselves using only electric motors (full hybrid systems), systems called mild hybrid systems have also attracted attention. In mild hybrid systems, the AC generator usually installed in passenger cars is used as an auxiliary motor for the engine. In Europe, the LV148 power supply standard was established to increase the rated voltage of the AC generator installed from 12V to 48V, and development was carried out towards the practical application of mild hybrid systems.

[0009] If the AC generator is increased in voltage, a larger ripple current flows through the electrolytic capacitor used with the AC generator. In order to suppress the heat generated by the increase in ripple current, it is effective to reduce the equivalent series resistance (ESR) of the electrolytic capacitor. In order to reduce the ESR, it is sufficient to increase the amount of conductive polymer. However, in the above method, it is impossible to attach a sufficient amount of conductive polymer to the capacitor element.

[0010] Means for solving problems

[0011] A first aspect of the present invention relates to a method for manufacturing an electrolytic capacitor, comprising: a step of preparing an electrode foil; a step of preparing a first conductive polymer dispersion containing a first conductive polymer component and a first dispersion medium; a step of applying the first conductive polymer dispersion to the surface of the electrode foil by a coating method, and then removing at least a portion of the first dispersion medium to form a first conductive polymer layer containing the first conductive polymer component; and a step of making a capacitor element using the electrode foil formed with the first conductive polymer layer.

[0012] A second aspect of the present invention relates to an electrolytic capacitor comprising a capacitor element, the capacitor element comprising an electrode foil, a conductive polymer layer formed on the electrode foil, more than 90% of the area of ​​a main surface of the electrode foil is covered by the conductive polymer layer, and the conductive polymer layer comprises: a first conductive polymer layer comprising a first conductive polymer component, and a second conductive polymer layer covering a portion of the first conductive polymer layer and comprising a second conductive polymer component.

[0013] Effects of the Invention

[0014] According to the present invention, a capacitor element can hold a large amount of conductive polymer, thereby providing an electrolytic capacitor with reduced ESR.

[0015] The novel features of the present invention are described in the appended claims, but both the structure and content of the present invention, together with other objects and features of the present invention, will be better understood from the following detailed description with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a flowchart showing an example of a manufacturing method according to an embodiment of the present invention.

[0017] Figure 2 It is a cross-sectional view schematically showing an example of an electrolytic capacitor according to an embodiment of the present invention.

[0018] Figure 3 It is a developed perspective view schematically showing a part of the capacitor element according to the embodiment of the present invention. DETAILED DESCRIPTION

[0019] In this embodiment, in order to attach a large amount of conductive polymer, a dispersion containing conductive polymer is applied to the electrode foil by a coating method. Thus, a sufficient amount of conductive polymer components are attached in a manner that covers at least a portion of the surface of the electrode foil. By attaching a sufficient amount of conductive polymer components to the surface of the electrode foil, the ESR of the resulting electrolytic capacitor is reduced. In addition, the heat resistance of the electrolytic capacitor is also improved. Therefore, the electrolytic capacitor of this embodiment is suitable for products that circulate large ripple currents.

[0020] Furthermore, compared with the case where the polymerization reaction is carried out on the surface of the electrode foil, the amount of impurities contained in the formed layer containing the conductive polymer can be reduced, so that the withstand voltage of the electrolytic capacitor using the same can be improved.

[0021] The electrode foil may be an anode foil, a cathode foil, or both. The anode foil has a dielectric layer on its surface. When the conductive polymer component is disposed on the surface of the anode foil, the conductive polymer and the dielectric layer formed on the surface of the anode foil are easily adhered, and the ESR is further reduced. When the conductive polymer component is disposed on the surface of the cathode foil, it is not easy to hinder the self-repairing performance of the anode foil.

[0022] [Method for manufacturing electrolytic capacitor]

[0023] The electrolytic capacitor of the present embodiment can be manufactured by a method comprising the following steps: a step of preparing an electrode foil; a step of preparing a first conductive polymer dispersion containing a first conductive polymer component and a first dispersion medium; a step of applying the first conductive polymer dispersion to the surface of the electrode foil by a coating method, and then removing at least a portion of the first dispersion medium to form a first conductive polymer layer containing the first conductive polymer component; and a step of using the electrode foil formed with the first conductive polymer layer to make a capacitor element.

[0024] Figure 1 This is a flowchart showing an example of the manufacturing method of this embodiment.

[0025] Hereinafter, an example of a method for manufacturing an electrolytic capacitor according to the present embodiment will be described step by step.

[0026] (1) Step of Preparing Electrode Foil (S1)

[0027] (1-1) Preparation of anode foil

[0028] When applying the first conductive polymer dispersion liquid on the anode foil, the anode foil is prepared.

[0029] As a raw material of the anode foil, for example, a metal foil containing a valve action metal can be used.

[0030] A dielectric layer is formed on the surface of the metal foil to prepare the anode foil. The method for forming the dielectric layer is not particularly limited, and the dielectric layer can be formed by subjecting the metal foil to a chemical conversion treatment. In the chemical conversion treatment, for example, the metal foil is immersed in a chemical conversion solution such as an ammonium adipate solution and subjected to a heat treatment. Alternatively, the metal foil may be immersed in a chemical conversion solution and a voltage may be applied.

[0031] Before forming the dielectric layer, the surface of the metal foil may be roughened as needed. By roughening, a plurality of concave and convex portions are formed on the surface of the metal foil. The roughening is preferably performed by etching the metal foil. The etching process may be performed, for example, by direct current electrolysis or alternating current electrolysis.

[0032] In addition, as a component of the capacitor element, a cathode foil and a separator are prepared as needed. The raw material of the cathode foil is, for example, a metal foil containing a valve metal. On the surface of the metal foil used as the cathode foil, a dielectric layer can be formed by the above method, and a conductive coating layer can also be formed by sputtering or evaporation. Before forming the dielectric layer and the coating layer, the surface of the metal foil can be roughened as needed. The raw material of the separator is, for example, a fiber structure.

[0033] (1-2) Preparation of cathode foil

[0034] When the cathode foil is coated with the first conductive polymer dispersion, the cathode foil is prepared. The cathode foil is as described above. In addition, as a component of the capacitor element, the anode foil and the separator as required are prepared.

[0035] (2) Step of Preparing a First Conductive Polymer Dispersion Liquid (S2)

[0036] A first conductive polymer dispersion (hereinafter referred to as a first dispersion) containing a first conductive polymer component (hereinafter referred to as a first polymer component) and a first dispersion medium is prepared.

[0037] (First Dispersion Liquid)

[0038] The first dispersion liquid contains a first polymer component and a first dispersion medium.

[0039] The content of the first polymer component is not particularly limited. The first polymer component may be contained in the first dispersion at a content of 1% by mass or more and 15% by mass or less. If the content of the first polymer component is within this range, the viscosity of the first dispersion is easily within a range suitable for the coating method. Therefore, it is easy to make a sufficient amount of the first polymer component uniformly adhere to the surface of the electrode foil. The content of the first polymer component may be 10% by mass or less, 5% by mass or less, or 3% by mass or less.

[0040] 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 (e.g., VM-100A manufactured by SEKONIC Co., Ltd.) may be 10 mPa·s or more. In addition, the viscosity of the first dispersion measured under the above conditions may be 100 mPa·s or more, or 200 mPa·s or less. The first dispersion having a viscosity in such a range is particularly suitable for a coating method.

[0041] The first polymer component comprises a conductive polymer. As the conductive polymer, polypyrrole, polythiophene, polyfuran, polyaniline, polyacetylene, polyphenylene, polyphenylene vinylene, polyacene, polythiophene acetylene, etc. can be mentioned. They can be used alone, two or more can be used in combination, and can also be a copolymer of two or more monomers.

[0042] It should be noted that, in this specification, polypyrrole, polythiophene, polyfuran, polyaniline, etc. refer to polymers with polypyrrole, polythiophene, polyfuran, polyaniline, etc. as basic skeletons, respectively. Therefore, polypyrrole, polythiophene, polyfuran, polyaniline, etc. may also include their respective derivatives. For example, polythiophene includes poly(3,4-ethylenedioxythiophene) and the like.

[0043] The first polymer component may further include a dopant. The dopant may be a polyanion. Specific examples of polyanions include polyvinyl sulfonic acid, polystyrene sulfonic acid, polyallyl sulfonic acid, polyacrylic acid sulfonic acid, polymethacrylic acid sulfonic acid, poly(2-acrylamide-2-methylpropane sulfonic acid), polyisoprene sulfonic acid, polyacrylic acid, etc. They may be used alone or in combination of two or more. In addition, they may be a polymer of a single monomer or a copolymer of two or more monomers. Among them, polyanions derived from polystyrene sulfonic acid are preferred.

[0044] The weight average molecular weight of the polyanion (hereinafter referred to as the first polyanion) contained in the first polymer component is not particularly limited. The weight average molecular weight of the first polyanion can be, for example, more than 1000 and less than 200000. The first polymer component containing such a first polyanion is easily dispersed in the first dispersion medium in a homogeneous manner and easily adheres to the electrode foil. In addition, the weight average molecular weight of the first polyanion can be more than 1000 and less than 70000. Even in the case of containing a large amount of such a first polyanion, the excessive viscosity increase of the first dispersion is suppressed, and the amount attached to the electrode foil is easily increased.

[0045] The first polymer component is dispersed in the first dispersion medium in the form of particles, for example. The average particle size of the particles of the first polymer component is not particularly limited and can be appropriately adjusted by polymerization conditions, dispersion conditions, etc. For example, the average particle size of the particles of the first polymer component can be 0.01 μm or more and 0.5 μm or less. Here, the average particle size is the median particle size in the volume particle size distribution measured by a particle size measuring device based on a dynamic light scattering method.

[0046] The first dispersion medium is not particularly limited and may be water, a non-aqueous solvent, or a mixture thereof. Non-aqueous solvent refers to a general term for liquids other than water, including organic solvents and ionic liquids. Among them, from the viewpoint of operability and dispersibility of the conductive polymer component, the first dispersion medium may be water. Water may account for more than 50% by mass of the first dispersion medium, may account for more than 70% by mass, and may account for more than 90% by mass. As non-aqueous solvents used together with water, polar solvents (protic solvents and / or non-protonic solvents) may be mentioned.

[0047] Examples of the protic solvent include alcohols such as methanol, ethanol, propanol, butanol, ethylene glycol (EG), propylene glycol, polyethylene glycol (PEG), diethylene glycol monobutyl ether, glycerol, 1-propanol, butanol, polyglycerol, sorbitol, mannitol, pentaerythritol, and formaldehyde. Examples of the aprotic solvent 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.

[0048] 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 a first dispersion medium to generate particles of the first polymer component in the first dispersion medium.

[0049] (3) Step of forming a first conductive polymer layer (S3)

[0050] After applying the first dispersion liquid on the surface of the electrode foil by a coating method, at least a portion of the first dispersion medium is removed to form a first conductive polymer layer (hereinafter referred to as the first polymer layer) containing a first polymer component. Before making a capacitor element, by applying the first dispersion liquid to the electrode foil, a sufficient amount of the first polymer component can be attached to the electrode foil. At least a portion of the first polymer component is attached to the surface of the electrode foil. A portion of the first dispersion liquid can also penetrate into the interior of the etching pit of the electrode foil. A portion of the first dispersion liquid can also penetrate into the surface and holes of the dielectric layer of the anode foil.

[0051] The coating method is a technique of applying a liquid substance to an object using a coater. As the coater, for example, known devices such as a gravure coater, a blade coater, a comma coater, a roll coater, a die coater, and a lip coater can be cited. In the present embodiment, the first dispersion is applied to the surface of the electrode foil using these known devices.

[0052] The amount of the first dispersion liquid applied to the electrode foil is not particularly limited. For example, it can be appropriately set to 0.1 mg / cm 2 The above-mentioned first polymer component may be attached to the electrode foil.

[0053] The coating treatment using the first dispersion can be performed on one side or both sides of the electrode foil. The coating treatment using the first dispersion can be performed multiple times on the same side of the electrode foil. Thus, the thickness of the formed polymer layer can be increased. In this case, the drying treatment can be performed after the coating treatment is performed multiple times in succession, or the drying treatment can be performed each time the coating treatment is performed.

[0054] From the perspective of mass production, the step of forming the first polymer layer can be performed on a long strip of electrode foil. When coating both sides of the long strip of electrode foil, firstly one side is coated, and after drying, the electrode foil is wound on a roll. Then, while the electrode foil is rolled out from the roll in a reverse manner, the other side is coated again using the same or different coating machine.

[0055] In the case of performing the cutting process described later after forming the first polymer layer, it is preferred to perform the coating process in a manner that the first polymer layer is not formed on the predetermined cutting line of the electrode foil. In this way, it is possible to suppress the first polymer layer from being damaged or peeled off due to cutting, and it is possible to avoid the first polymer component from adhering to the cut surface. In the case of the anode foil, even if the chemical conversion process is performed again after cutting, it is easy to form a dielectric layer uniformly on the cut surface.

[0056] From the aspect that the amount of the conductive polymer component increases, the first polymer component may be attached to a component other than the electrode foil of the capacitor element. The method of attaching the first polymer component to other components is not particularly limited, and the coating method may be used as described above, or impregnation may be used. As a component other than the electrode foil of the capacitor element, a spacer may be cited.

[0057] The first dispersion medium is removed by, for example, a drying treatment such as heating drying or reduced pressure drying. The drying conditions are not particularly limited and can be appropriately set according to the type of the first dispersion medium, the coating amount, etc. In this case, the drying treatment can be performed to an extent that the first dispersion medium is not completely removed. For example, the drying treatment can be performed in a manner such that the first dispersion medium contained in the first dispersion liquid immediately after the coating treatment is more than 0% by mass and less than 10% by mass.

[0058] In the subsequent process, when the second conductive polymer dispersion (hereinafter referred to as the second dispersion) and / or the electrolyte is impregnated into the capacitor element, if the first polymer layer contains the first dispersion medium, the second dispersion and / or the electrolyte is induced by the first dispersion medium, and it becomes easy to infiltrate into the inside of the etching pit of the electrode foil, and then into the inside of the hole of the dielectric layer of the anode foil. As a result, an increase in electrostatic capacitance can be expected. In addition, an improvement in the self-healing performance of the anode foil can be expected. In addition, when the long strip of electrode foil formed with the first polymer layer is wound into a roll, it is not easy to produce cracks in the first polymer layer.

[0059] (4) Electrode foil cutting step (S4)

[0060] The long strip of electrode foil formed with the first polymer layer is cut after the step of forming the first polymer layer. In this case, the first polymer layer is not arranged on the cut surface formed on the electrode foil, that is, the end surface of the electrode foil. Other long strip components may also be cut in this step. The cutting step may be performed before the step of making the capacitor element, or after the step of making the capacitor element.

[0061] (5) Fabrication of capacitor elements (S5)

[0062] The anode foil and the cathode foil are stacked in a manner that the first polymer layer (and thus the spacer) is interposed between the anode foil and the cathode foil. The stack of the anode foil and the cathode foil can be wound. In this case, the end of the cathode foil located at the outermost layer is fixed with a stop tape. In the case of the cutting process, in order to form a dielectric layer on the cut surface of the anode foil, the capacitor element can be further subjected to a chemical conversion treatment (re-chemical conversion treatment).

[0063] (6) Step of impregnating the capacitor element with the second conductive polymer dispersion (S6)

[0064] 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. Then, a drying treatment may be performed to remove at least a portion of the second dispersion medium.

[0065] After the second dispersion is impregnated into the capacitor element, it is dried, so that the second polymer component can be attached to the inside of the capacitor element. Through the second polymer component, it can be expected that the electrostatic capacitance will be further increased and the ESR will be reduced. The second polymer component is mainly attached to the inside of the holes and pits of the components of the capacitor element.

[0066] (Second Dispersion Liquid)

[0067] The second dispersion liquid contains, for example, a second polymer component and a second dispersion medium.

[0068] Examples of the second dispersion medium include the same compounds as those for the first dispersion medium.

[0069] The second polymer component is not particularly limited and may include the same conductive polymer and dopant as the first polymer component. The second polymer component may include 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 greater than the weight average molecular weight of the first polyanion contained in the first polymer component. Thus, the conductivity of the second polymer component becomes high, so the ESR can be effectively reduced with a smaller amount of the second polymer component. In addition, the viscosity of the second dispersion is also reduced, so the impregnation into the capacitor element is improved.

[0070] The weight average molecular weight of the second polyanion may be, for example, 1,000 to 200,000, or 75,000 to 150,000.

[0071] In the second dispersion, the content of the second polymer component may be less than the content of the first polymer component in the first dispersion. Specifically, the content of the second polymer component in the second dispersion may be 0.5 mass % or more and less than 3 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.

[0072] (7) Step of impregnating capacitor element with electrolyte solution (S7)

[0073] As required, the electrolyte can be impregnated into the capacitor element. The electrolyte can be impregnated into the capacitor element without performing the impregnation process of the second dispersion, or after the second dispersion is impregnated into the capacitor element, the electrolyte can be further impregnated into the capacitor element. The electrolyte can easily improve the self-repairing performance of the dielectric layer. In addition, the electrolyte functions as a substantial cathode material, so the effect of increasing the electrostatic capacitance can be expected. The method of impregnation is not particularly limited.

[0074] (Electrolyte)

[0075] The electrolyte contains a solvent.

[0076] As solvents, sulfone compounds, lactone compounds, carbonate compounds, polyols, etc. can be mentioned. As sulfone compounds, cyclopentane, dimethyl sulfoxide and diethyl sulfoxide can be mentioned. As lactone compounds, γ-butyrolactone, γ-valerolactone, etc. can be mentioned. As carbonate compounds, dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), propylene carbonate (PC) and fluoroethylene carbonate (FEC) can be mentioned. As polyols, glycol compounds such as ethylene glycol (EG), diethylene glycol, triethylene glycol, propylene glycol and polyethylene glycol (PEG); glycerol, etc. can be mentioned. They can be used alone or in combination.

[0077] The solvent may contain a compound having two or more hydroxyl groups. Examples of such compounds include polyols. The content of the compound having two or more hydroxyl groups may be 50% by mass or more of the total solvent, 60% by mass or more, or 70% by mass or more.

[0078] The electrolyte may further include an acid component. When the first polymer component or the second polymer component includes a dopant, the acid component in the electrolyte suppresses the dedoping phenomenon of the dopant and stabilizes the conductivity of each polymer component. In addition, even when the dopant is dedoped from the polymer component, the acid component of the electrolyte is re-doped to the dedoped site, so that the ESR is easily maintained low.

[0079] The acid component in the electrolyte preferably does not excessively increase the viscosity of the electrolyte, is easily dissociated in the electrolyte, and generates anions that are easily mobile in the solvent. As such an acid component, for example, aliphatic sulfonic acids having 1 to 30 carbon atoms and aromatic sulfonic acids having 6 to 30 carbon atoms can be cited. Among aliphatic sulfonic acids, monovalent saturated aliphatic sulfonic acids (such as hexylsulfonic acid) are preferred. Among aromatic sulfonic acids, aromatic sulfonic acids having a hydroxyl group or a carboxyl group in addition to a sulfonic group are preferred, and specifically, oxyaromatic sulfonic acids (such as phenol-2-sulfonic acid) and sulfoaromatic carboxylic acids (such as p-sulfobenzoic acid, 3-sulfophthalic acid, and 5-sulfosalicylic acid) are preferred.

[0080] As other acid components, carboxylic acids can be mentioned. Carboxylic acids preferably include aromatic carboxylic acids (aromatic dicarboxylic acids) having more than two carboxyl groups. As aromatic carboxylic acids, for example, phthalic acid (ortho-body), isophthalic acid (meta-body), terephthalic acid (para-body), maleic acid, benzoic acid, salicylic acid, trimellitic acid, and pyromellitic acid can be mentioned. Among them, aromatic dicarboxylic acids such as phthalic acid (ortho-body) and maleic acid are more preferred. The carboxyl group of aromatic dicarboxylic acids is stable and is not easy to react with side reactions. Therefore, the effect of stabilizing the conductive polymer for a long time is shown, which is conducive to the long life of the electrolytic capacitor. In addition, the carboxylic acid can be an aliphatic carboxylic acid such as adipic acid.

[0081] From the viewpoint of thermal stability, the acid component may contain a composite compound of an organic acid and an inorganic acid. Examples of the composite compound of an organic acid and an inorganic acid include borodisalicylic acid, borodiacetic acid, borodiaglycolic acid, etc., which have high heat resistance.

[0082] The acid component may include an inorganic acid such as boric acid, phosphoric acid, phosphorous acid, hypophosphorous acid, and phosphonic acid.

[0083] From the viewpoint of improving the effect of suppressing the dedoping phenomenon, the concentration of the acid component may be 5% by mass or more and 50% by mass or less, or 15% by mass or more and 35% by mass or less.

[0084] The electrolyte may contain an acid component and an alkali component at the same time. At least a portion of the acid component is neutralized by the alkali component. Therefore, the concentration of the acid component can be increased, and the corrosion of the electrode caused by the acid component can be suppressed. From the viewpoint of effectively suppressing dedoping, the acid component is preferably excessive in terms of equivalent ratio compared to the alkali component. For example, the equivalent ratio of the acid component to the alkali component can be more than 1 and less than 30. The concentration of the alkali component contained in the electrolyte can be more than 0.1 mass % and less than 20 mass %, or can be more than 3 mass % and less than 10 mass %.

[0085] The base component is not particularly limited. Examples of the base component include ammonia, primary amines, secondary amines, tertiary amines, quaternary ammonium compounds, and amidine compounds. Examples of the amines include aliphatic amines, aromatic amines, and heterocyclic amines.

[0086] The pH of the electrolyte is preferably 4 or less, more preferably 3.8 or less, and even more preferably 3.6 or less. By setting the pH of the electrolyte to 4 or less, the degradation of the polymer component is further suppressed. The pH is preferably 2.0 or more.

[0087] (8) Step of sealing capacitor element (S8)

[0088] The produced capacitor element is stored in a bottom shell. As the material of the bottom shell, metals such as aluminum, stainless steel, copper, iron, brass, or their alloys can be used. Then, by performing a transverse drawing process near the open end of the bottom shell, the open end is riveted to the sealing member and curled, thereby sealing the capacitor element. Finally, a seat plate is arranged on the curled part to complete the electrolytic capacitor. Then, the aging process can be performed while applying the rated voltage.

[0089] In the above, an electrolytic capacitor having a capacitor element formed by stacking and winding an anode foil and a cathode foil is described as an example, but the structure of the electrolytic capacitor is not limited to this. In the case where the coating object of the first conductive polymer dispersion is the anode foil, this embodiment can be applied to a stacked electrolytic capacitor having a capacitor element, the capacitor element including an anode foil having a dielectric layer and a cathode lead layer covering the anode foil.

[0090] A multilayer electrolytic capacitor is manufactured, for example, as follows.

[0091] After forming the first polymer layer 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 of manufacturing the capacitor element (S5), a cathode lead layer is formed in a manner covering at least a portion of the first polymer layer formed on the surface of the anode foil.

[0092] The cathode lead layer is formed by sequentially coating the material of the carbon layer and the metal paste in a manner covering the polymer layer and drying. Then, as required, a step (S6) of impregnating the capacitor element with the second dispersion and / or a step (S7) of impregnating the capacitor element with the electrolyte are performed. Finally, the capacitor element is sealed with a resin sealing material using a molding technique such as injection molding, insert molding, and compression molding, thereby obtaining an electrolytic capacitor.

[0093] [Electrolytic capacitors]

[0094] The electrolytic capacitor of the present embodiment includes a capacitor element, and the capacitor element includes an electrode foil. A conductive polymer layer is formed on the electrode foil. The electrode foil forming the conductive polymer layer (hereinafter, sometimes referred to as a coated electrode foil) can be an anode foil, a cathode foil, or both. The anode foil has a dielectric layer on its surface. More than 90% of the area of ​​one main surface of the coated electrode foil is covered with the conductive polymer layer. The conductive polymer layer includes: a first conductive polymer layer including a first conductive polymer component, and a second conductive polymer layer covering a portion of the first conductive polymer layer and including a second conductive polymer component. As a result, the ESR is reduced.

[0095] Another electrolytic capacitor of the present embodiment includes a capacitor element, which includes: an anode foil including a dielectric layer and a cathode lead layer covering the anode foil. A conductive polymer layer is formed on the anode foil. The cathode lead layer is formed in a manner covering at least a portion of the conductive polymer layer. More than 90% of the area of ​​one main surface of the anode foil is covered by the conductive polymer layer. The conductive polymer layer includes: a first conductive polymer layer including a first conductive polymer component, and a second conductive polymer layer covering a portion of the first conductive polymer layer and including a second conductive polymer component.

[0096] When the coated electrode foil is observed from the normal direction of the main surface of the coated electrode foil, more than 90% of the area of ​​the main surface is covered by the conductive polymer layer. The conductive polymer layer includes the above-mentioned first polymer layer and the above-mentioned second conductive polymer layer (hereinafter referred to as the second polymer layer). The area coverage brought by the conductive polymer layer is preferably more than 95%. The conductive polymer layer may be continuous or discontinuous on the surface of the coated electrode foil. The area coverage is calculated using the coated electrode foil cut into a specified size used in electrolytic capacitors. The area coverage can be calculated by binarizing the image obtained by photographing the main surface of the coated electrode foil.

[0097] It should be noted that the area coverage rate brought by the conductive polymer layer can be regarded as the area coverage rate brought by the first polymer layer. This is because the area coverage rate of the second polymer layer on the surface of the coated electrode foil is less than the area coverage rate brought by the first polymer layer. The above-mentioned area coverage rate of the second polymer layer is, for example, less than 90%, and can be less than 60%.

[0098] Hereinafter, constituent members and other constituent materials of the capacitor element will be described.

[0099] (First polymer layer)

[0100] The first polymer component is attached to the inner wall of the etching pit of the coated electrode foil, and may also be attached to the outside of the etching pit. That is, the first polymer layer is formed in a manner that covers at least a portion of the surface of the coated electrode foil. The first polymer layer is easily formed when the first dispersion is applied by a coating method. At least a portion of the first polymer layer is between the coated electrode foil and the spacer, or between the coated electrode foil and other electrode foils. The first polymer layer may not be formed on the end face of the coated electrode foil.

[0101] The mass of the first polymer layer per unit area of ​​the electrode foil is not particularly limited and can be appropriately set as needed. According to the present embodiment, the mass per unit area of ​​0.1 mg / cm 2 The first polymer layer is attached to the coated electrode foil. The mass of the first polymer layer can be 1 mg / cm2 As a result, it is easy to suppress a decrease in the withstand voltage of the obtained electrolytic capacitor.

[0102] The mass of the first polymer layer can be calculated based on the difference in mass of the electrode foil before and after the first dispersion is applied. In addition, the mass of the first polymer layer is calculated by analyzing the coated electrode foil using a thermogravimetric analysis method (TGA method). In the TGA method, for example, the thermal change when the temperature of the sample is increased at a certain speed and the amount of reduction of the sample are measured. Based on the measured value, the mass of the first polymer layer attached to the coated electrode foil can be calculated.

[0103] The higher the conductivity of the first polymer layer, the more the ESR reduction effect can be obtained. The conductivity of the first polymer layer can be, for example, 30S / cm or more, or 300S / cm or more. The greater the molecular weight of the conductive polymer contained, the easier it is for the conductivity of the first polymer layer to become higher. If the molecular weight of the conductive polymer increases, the viscosity of the first dispersion liquid tends to increase. Therefore, it is sufficient to set the molecular weight of the conductive polymer in such a way that the viscosity of the first dispersion liquid does not increase excessively.

[0104] When using a first dispersion liquid having a concentration of 3% by mass or more of the first polymer component, the conductivity of the first polymer layer is preferably set to 170 S / cm or less, for example. Thus, excessive viscosity increase of the first dispersion liquid is suppressed. In the above case, the conductivity of the first polymer layer can be 150 S / cm or less, or 120 S / cm or less. The conductivity of the first polymer layer is the conductivity of the film obtained by applying the first dispersion liquid to a substrate and removing the first dispersion medium. The conductivity of the film is measured by a 4-probe method according to JIS K 7194:1994.

[0105] (Second polymer layer)

[0106] The second polymer layer is disposed in the capacitor element. The second polymer layer can further increase the electrostatic capacitance and further reduce the ESR. The second polymer layer is disposed, for example, by impregnating the capacitor element with the second dispersion.

[0107] The second polymer component may adhere to the inside of the holes or pits of the capacitor element constituent member. In addition, the second polymer component adheres to the surface of the coated electrode foil so as to cover a portion of the first polymer layer formed on the surface of the coated electrode foil.

[0108] For example, 0.01 mg / cm 2 Above and less than 1mg / cm 2The second polymer layer. The attachment amount of the second polymer layer is calculated by the same method as the first polymer layer. In the case of using the TGA method to analyze the coated electrode foil, the amount of the second polymer layer attached to the coated electrode foil is obtained by subtracting the attachment amount of the first polymer layer from the calculated attachment amount. After the amount of the second polymer layer attached to other constituent members (for example, other electrode foils and / or spacers) is calculated using the TGA method, the sum of the amount of the second polymer layer attached to the coated electrode foil is the attachment amount of the second polymer layer to the capacitor element. By dividing the total attachment amount of the second polymer layer by the total value of the area of ​​one main surface of each constituent member, the mass of the second polymer layer attached per unit area of ​​the capacitor element can be calculated.

[0109] The mass (density) of the first polymer layer attached per unit area of ​​the coated electrode foil is preferably greater than the mass (density) of the second polymer layer attached per unit area of ​​the coated electrode foil. The ratio of the above-mentioned density of the first polymer layer to the above-mentioned density of the second polymer layer can be obtained by observing the cross-section of the coated electrode foil using a scanning electron microscope (SEM) or the like. The ratio of the above-mentioned density of the first polymer layer to the above-mentioned density of the second polymer layer is calculated by dividing the area of ​​the first polymer layer in contact with the electrode foil by the area of ​​the polymer layer other than the first polymer layer. The density of the two layers is calculated by observing the same coated electrode foil with the same observation field of view. Usually, an interface can be confirmed between the first polymer layer and the second polymer layer, so the two layers can be distinguished. The adhesion amount, area coverage and density of the first polymer layer are calculated by excluding the area in the coated electrode foil where the first polymer layer is intentionally not formed. It is preferably set to have 100μm 2 Observation field of view of the area above.

[0110] (Anode Foil)

[0111] The anode foil is a metal foil containing at least one valve metal such as titanium, tantalum, aluminum and 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, for example, it is 15 μm or more and 300 μm or less. The thickness is the average value of any five points (the same below). The surface of the anode foil can be roughened by etching or the like.

[0112] A dielectric layer is formed on the surface of the anode foil. The dielectric layer is formed, for example, by chemically converting the anode foil. In this case, the dielectric layer may include an oxide of a valve metal. It should be noted that the dielectric layer is not limited thereto, as long as it is a layer that functions as a dielectric. The dielectric layer is preferably also formed on the end face of the anode foil.

[0113] (Cathode Foil)

[0114] The cathode foil is not particularly limited as long as it has the function of a cathode. The cathode foil may be a metal foil. The type of metal is not particularly limited, and similarly to 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 may be, for example, 15 μm or more and 300 μm or less. The surface of the cathode foil may be roughened as needed, or may be subjected to a chemical conversion treatment.

[0115] When the metal foil includes a valve metal, the metal foil may have a conductive coating layer, and the conductive coating layer includes at least one selected from carbon and a metal having a lower ionization tendency than the valve metal. Thus, acid resistance is easily improved. When the metal foil includes aluminum, the coating layer may include at least one selected from carbon, nickel, titanium, tantalum and zirconium. Among them, the coating layer may include nickel and / or titanium in consideration of cost and resistance.

[0116] The thickness of the coating layer is not particularly limited. The thickness of the coating layer can be, for example, more than 5 nm and less than 200 nm, or more than 10 nm and less than 200 nm. 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 evaporating the above-mentioned metal, sputtering, etc. onto a metal foil. Alternatively, the coating layer can be formed by evaporating a conductive carbon material onto a metal foil, or by coating a carbon paste containing a conductive carbon material onto a metal foil. As conductive carbon materials, graphite, hard carbon, soft carbon, carbon black, etc. can be cited.

[0117] (Spacer)

[0118] When a plurality of electrode foils are stacked, a spacer may be interposed between the electrodes together with the first polymer layer. When a first polymer layer having a sufficient thickness is arranged between the electrodes, the spacer may be omitted.

[0119] The separator is not particularly limited as long as it is porous. Examples of the separator include fiber structures such as woven fabrics, knitted fabrics, and nonwoven fabrics containing fibers. The thickness of the separator is not particularly limited, and is, for example, 10 to 300 μm.

[0120] The material of the spacer is not particularly limited. Examples of the material of the spacer include synthetic fibers such as nylon fibers, aramid fibers, acrylic fibers, and polyester fibers, and cellulose. Among them, a fiber structure made of cellulose is suitable as a spacer because it is low-cost and has good compatibility with the first dispersion.

[0121] On the other hand, since cellulose has hydroxyl groups, it is easy to swell with water. Therefore, if the first dispersion comes into contact with the cellulose spacer, wrinkles are easily generated. From the viewpoint of preventing wrinkles, the spacer may contain synthetic fibers, or may contain cellulose fibers and a paper strength enhancer at the same time. By suppressing the wrinkles of the spacer, the thickness of the spacer becomes uniform. Therefore, in the electrolytic capacitor, the withstand voltage and inter-electrode resistance can be suppressed from deviating due to the location.

[0122] In the fiber structure including synthetic fibers (hereinafter referred to as the first fiber structure), the content of the synthetic fibers may be 50% by mass or more of the fiber structure, or 70% by mass or more. The type of synthetic fibers is not particularly limited.

[0123] The first fiber structure may further contain cellulose from the aspect of good compatibility with the first dispersion liquid, and further with the second dispersion liquid and electrolyte added as needed. If the retention of the electrolyte is taken into consideration, the content of cellulose may be 10% by mass or more of the fiber structure. The content of cellulose may be less than 50% by mass, or less than 30% by mass, or less than 20% by mass.

[0124] In the fiber structure containing both cellulose fibers and a paper strength enhancer (hereinafter referred to as the second fiber structure), the type of the paper strength enhancer is not particularly limited, and may be a wet paper strength enhancer and / or a dry paper strength enhancer. They may be used alone or in combination. As the wet paper strength enhancer, for example, at least one selected from urea formaldehyde resin, melamine formaldehyde resin, polyamide polyamine epichlorohydrin and polyvinylamine may be cited. As the dry paper strength enhancer, for example, at least one selected from polyacrylamide, polyvinyl alcohol, starch and carboxymethyl cellulose may be cited.

[0125] The paper strength enhancer may be added to the raw material of the second fiber structure (for example, slurry containing cellulose fibers), or may be applied to the second fiber structure by spraying or the like.

[0126] When a paper strength enhancer is added, the second fiber structure may contain 40% or more cellulose, or 70% or more cellulose. The second fiber structure may further contain synthetic fibers. The content of the synthetic fibers may be, for example, 10% or more and 60% or less of the second fiber structure.

[0127] The density of each fiber structure is not particularly limited. Even for a fiber structure with a low density, swelling of the fiber structure caused by the first dispersion can be suppressed by including 50% by mass or more of synthetic fibers, or by including cellulose fibers and a paper strength enhancer at the same time. The density of the fiber structure can be, for example, 0.2 g / cm 3 Above and less than 0.45g / cm3 , can also be 0.25g / cm 3 Above and 0.40g / cm 3 the following.

[0128] The thickness of each fiber structure is not particularly limited. The thickness of each fiber structure can be, for example, 20 μm or more and 100 μm or less, preferably 30 μm or more and 60 μm or less. This makes it easy to suppress short circuits in the resulting electrolytic capacitors, and the effect of reducing ESR is easy to further improve.

[0129] (Cathode extraction layer)

[0130] The cathode lead layer includes, for example, a carbon layer formed in a manner covering the polymer layer and a metal paste layer formed on the surface of the carbon layer. The carbon layer includes a conductive carbon material such as graphite and a resin. The metal paste layer includes, for example, metal particles (such as silver) and a resin. It should be noted that the composition of the cathode lead layer is not limited to this composition. The composition of the cathode lead layer can be any composition as long as it has a current collection function.

[0131] (resin sealing material)

[0132] The resin sealing material includes, for example, a thermosetting resin. Examples of the thermosetting resin include epoxy resins, phenolic resins, silicone resins, melamine resins, urea resins, alkyd resins, polyurethanes, polyimides, and unsaturated polyesters. The outer body material may include a filler, a curing agent, a polymerization initiator, and / or a catalyst.

[0133] Figure 2 is a cross-sectional view schematically showing an example of an electrolytic capacitor (a wound electrolytic capacitor) according to the present embodiment. Figure 3 This is a perspective view of a portion of a capacitor element of the electrolytic capacitor that is unfolded.

[0134] The electrolytic capacitor includes, for example, a capacitor element 10, a bottomed case 101 accommodating the capacitor element 10, a sealing member 102 blocking an opening of the bottomed case 101, a seat plate 103 covering the sealing member 102, leads 104A and 104B extending from the sealing member 102 and penetrating the seat plate 103, and lead tabs 105A and 105B connecting the leads to electrodes of the capacitor element 10. The vicinity of the opening end of the bottomed case 101 is drawn inward, and the opening end is curled in a manner riveted to the sealing member 102.

[0135] The capacitor element 10 is, for example, Figure 3The wound body includes: anode foil 11 connected to lead tab 105A, cathode foil 12 connected to lead tab 105B, and separator 13. A first polymer layer (not shown) is formed on at least one of anode foil 11 and cathode foil 12, and a second polymer layer is further formed.

[0136] The anode foil 11 and the cathode foil 12 are wound with the separator 13 interposed therebetween. The outermost periphery of the wound body is fixed by the anti-winding tape 14. Figure 3 The partially unfolded state is shown before the outermost circumference of the wound body is fixed.

[0137] The electrolytic capacitor only needs to include at least one capacitor element, and may include a plurality of capacitor elements. The number of capacitor elements included in the electrolytic capacitor may be determined according to the intended use.

[0138] [Example]

[0139] Hereinafter, the present invention will be described in more detail based on Examples, but the present invention is not limited to the Examples.

[0140] 《Example 1》

[0141] Follow the steps below to make an electrolytic capacitor with a rated voltage of 35V.

[0142] (a) Preparation of components

[0143] An aluminum foil having a thickness of 100 μm was subjected to etching treatment to roughen the surface of the aluminum foil, and a dielectric layer was formed on the roughened surface of the aluminum foil by chemical conversion treatment to obtain an anode foil.

[0144] An aluminum foil having a thickness of 50 μm was subjected to etching treatment to roughen the surface of the aluminum foil, thereby obtaining a cathode foil.

[0145] A nonwoven fabric with a thickness of 50 μm was prepared as a raw material for the spacer. 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 .

[0146] (b) Preparation of the first dispersion

[0147] 3,4-ethylenedioxythiophene and polystyrene sulfonic acid (PSS, weight average molecular weight 100,000) were dissolved in ion exchange water to prepare a mixed solution. Iron (III) sulfate (oxidant) was added while stirring the mixed solution to perform a polymerization reaction. The reaction solution was then dialyzed to remove unreacted monomers and the oxidant, thereby obtaining a first dispersion containing polyethylenedioxythiophene (PEDOT / PSS, the first polymer component) doped with about 5% by mass of PSS (dopant).

[0148] The concentration of the first polymer component in the first dispersion was 2% by mass. The viscosity of the first dispersion measured at room temperature (20° C.) using a vibration viscometer (VM-100A manufactured by SEKONIC CORPORATION) was 40 mPa·s.

[0149] (c) Formation of the First Polymer Layer

[0150] The first dispersion was applied to both sides of the anode foil using a gravure coater. Then, a drying process was performed to form a first polymer layer on both sides of the anode foil. 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 the first polymer layer on one main surface of the anode foil was 99%. The electrical conductivity of the first polymer layer was 400 S / cm.

[0151] (d) Fabrication of capacitor elements

[0152] The anode foil, cathode foil and separator are cut into predetermined sizes.

[0153] The anode lead connector and the cathode lead connector are connected to the anode foil and the cathode foil, and the anode foil and the cathode foil are wound through the spacer while the lead connector is wound in. The anode lead and the cathode lead are respectively connected to the ends of each lead connector protruding from the winding body. The obtained winding body is chemically converted again to form a dielectric layer on the end face of the anode foil. The end of the outer surface of the winding body is fixed with a stop tape to obtain a capacitor element.

[0154] (e) Preparation of Second Dispersion Liquid and Formation of Second Polymer Layer

[0155] 3,4-ethylenedioxythiophene and polystyrene sulfonic acid (PSS, weight average molecular weight 100,000) were dissolved in ion exchange water to prepare a mixed solution. Iron (III) sulfate (oxidant) was added while stirring the mixed solution to carry out a polymerization reaction. Then, the reaction solution was dialyzed to remove unreacted monomers and oxidant, and a second dispersion containing polyethylenedioxythiophene (PEDOT / PSS, second polymer component) doped with about 5% by mass of PSS (dopant) was obtained.

[0156] 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.

[0157] The capacitor element was immersed in the second dispersion liquid in a reduced pressure atmosphere (40 kPa) for 5 minutes and then dried to form a second polymer layer.

[0158] (f) Impregnation of electrolyte

[0159] Ethylene glycol (EG) was prepared as a solvent. 5-sulfosalicylic acid (divalent acid component) as the second sulfonic acid and triethylamine as the base component were dissolved in EG at a total concentration of 25 mass %, thereby preparing an electrolyte solution. The equivalent ratio of 5-sulfosalicylic acid to triethylamine was 2.0.

[0160] After the impregnation with the second dispersion (e), the capacitor element was immersed in the electrolyte solution in a reduced pressure atmosphere (40 kPa) for 5 minutes.

[0161] (g) Sealing of capacitor elements

[0162] The capacitor element impregnated with electrolyte is sealed and completed. Figure 2 Then, the electrolytic capacitor (A1) was aged at 95°C for 90 minutes while applying the rated voltage.

[0163] <Evaluation>

[0164] The electrolytic capacitor A1 was measured for capacitance and ESR after aging (measurement temperature: 20° C.). The evaluation results are shown as relative values ​​of capacitance and ESR to those of the electrolytic capacitor B1 produced in Comparative Example 1.

[0165] After measuring the electrostatic capacitance and ESR, the electrolytic capacitor A1 was disassembled and the components were 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 anode foil by the second polymer layer was 83%.

[0166] 《Example 2》

[0167] In the formation of the first polymer layer (c), the first dispersion was coated on both sides of the anode foil and the cathode foil using a gravure coater. The same operation as in Example 1 was performed to produce an electrolytic capacitor A2, and the evaluation was performed in the same manner. The results are shown in Table 1. The mass per unit area of ​​the first polymer layer formed on the anode foil and the cathode foil was 0.3 mg / cm 2The area coverage of the first polymer component on one main surface of the anode foil and the cathode foil was 99% respectively.

[0168] 《Example 3》

[0169] In the formation of the first polymer layer (c), the first dispersion was applied to both sides of the anode foil and the separator using a gravure coater. The same operation as in Example 1 was performed to produce an electrolytic capacitor A3, and the evaluation was performed in the same manner. The results are shown in Table 1. The mass per unit area of ​​the first polymer layer formed on the anode foil was 0.3 mg / cm 2 The mass per unit area of ​​the first polymer layer formed on the spacer is 0.02 mg / cm 2 The area coverage of one main surface of the anode foil by the first polymer layer was 99%, and the area coverage of one main surface of the separator by the first polymer layer was 98%.

[0170] 《Example 4》

[0171] A first dispersion was prepared in the same manner as in Example 1 except that PSS having a weight average molecular weight of 50,000 was used. The concentration of the first polymer component in the first dispersion was 4% by mass. The viscosity of the first dispersion measured at room temperature (20° C.) using a vibration viscometer (VM-100A manufactured by SEKONIC CORPORATION) was 105 mPa·s.

[0172] Electrolytic capacitor A4 was produced in the same manner as in Example 1 except that the first dispersion was used, and the evaluation was performed in the same manner. The results are shown in Table 1. The mass per unit area of ​​the first polymer layer formed on the anode foil was 0.4 mg / cm 2 The area coverage of the first polymer layer on one main surface of the anode foil was 99%. The electrical conductivity of the first polymer layer was 150 S / cm.

[0173] Comparative Example 1

[0174] The electrolytic capacitor B1 was produced in the same manner as in Example 1 except that the formation of the first polymer layer (c) was not performed, and was evaluated in the same manner.

[0175] [Table 1]

[0176] Electrolytic capacitors Electrostatic Capacitance ESR A1 1.01 0.94 A2 1.02 0.92 A3 1.01 0.94 A4 1.01 0.93 B1 1 1

[0177] 《Example 5》

[0178] In the formation of the first polymer layer (c), the first dispersion was applied to both sides of the cathode foil using a gravure coater instead of the anode foil. The same operation as in Example 1 was performed to produce an electrolytic capacitor A5, and the evaluation was performed in the same manner. The results are shown in Table 2. The mass per unit area of ​​the first polymer layer attached to the cathode foil was 0.3 mg / cm 2 The area coverage of one main surface of the cathode foil by the polymer layer was 99%.

[0179] Example 6

[0180] In the formation of the first polymer layer (c), the first dispersion was applied to both sides of the cathode foil and the separator using a gravure coater instead of the anode foil. The same operation as in Example 1 was performed to produce an electrolytic capacitor A6, and the evaluation was performed in the same manner. The results are shown in Table 2. The mass per unit area of ​​the first polymer layer formed on the cathode foil was 0.3 mg / cm 2 The mass per unit area of ​​the first polymer layer formed on the spacer is 0.02 mg / cm 2 The area coverage of one main surface of the cathode foil by the first polymer layer was 99%, and the area coverage of one main surface of the separator by the first polymer layer was 98%.

[0181] 《Example 7》

[0182] Electrolytic capacitor A7 was produced in the same manner as in Example 5 except that the first dispersion prepared in Example 4 was used, and the evaluation was performed in the same manner. The results are shown in Table 2. The mass per unit area of ​​the first polymer layer formed on the cathode foil was 0.4 mg / cm 2 The area coverage of one main surface of the cathode foil by the first polymer layer was 99%.

[0183] [Table 2]

[0184] Electrolytic capacitors Electrostatic Capacitance ESR A5 1.02 0.93 A2 1.02 0.92 A6 1.02 0.93 A7 1.03 0.92 B1 1 1

[0185] Industrial Applicability

[0186] The present invention is particularly suitable for electrolytic capacitors that flow high ripple currents.

[0187] The preferred embodiments of the present invention are described, but such disclosure should not be interpreted in a limiting manner. By reading the above disclosure, various modifications and changes are undoubtedly obvious to those skilled in the art in the technical field to which the present invention belongs. Therefore, the attached claims should be interpreted as including all modifications and changes without departing from the true spirit and scope of the present invention.

[0188] Description of Reference Numerals

[0189] 100: Electrolytic capacitor

[0190] 101: Shell with bottom

[0191] 102: Sealing member

[0192] 103: Seat plate

[0193] 104A, 104B: Lead wire

[0194] 105A, 105B: Lead connector

[0195] 10: Capacitor components

[0196] 11: Anode foil

[0197] 12: Cathode foil

[0198] 13: Spacer

[0199] 14: Stop tape

Claims

1. A method for manufacturing an electrolytic capacitor, comprising: A step of preparing an anode foil having a dielectric layer; a step of preparing a first conductive polymer dispersion liquid including a first conductive polymer component and a first dispersion medium; A step of coating the first conductive polymer dispersion on the surface of the anode foil by a coating method, and then removing at least a portion of the first dispersion medium to form a first conductive polymer layer containing the first conductive polymer component; a step of manufacturing a capacitor element using the anode foil having the first conductive polymer layer formed thereon; as well as a step of impregnating the produced capacitor element with a second conductive polymer dispersion; The second conductive polymer dispersion liquid comprises a second conductive polymer component and a second dispersion medium. The content of the second conductive polymer component is smaller than the content of the first conductive polymer component in the first conductive polymer dispersion.

2. The method for manufacturing an electrolytic capacitor according to claim 1, in, The first conductive polymer dispersion contains 1 mass % or more and 15 mass % or less of the first conductive polymer component, The viscosity of the first conductive polymer dispersion liquid measured at room temperature using a vibration viscometer is 10 mPa·s or more.

3. The method for manufacturing an electrolytic capacitor according to claim 1, in, The first conductive polymer component comprises a first polyanion, The weight average molecular weight of the first polyanion is 1,000 or more and 70,000 or less. 4 . 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.

5. The method for manufacturing an electrolytic capacitor according to claim 4, in, The electrolyte solution contains a solvent and an acid component.

6. The method for manufacturing an electrolytic capacitor according to claim 4, in, The electrolyte solution includes a solvent having two or more hydroxyl groups.

7. The method for manufacturing an electrolytic capacitor according to claim 1, in, The viscosity of the second conductive polymer dispersion liquid measured at room temperature using a vibration viscometer is lower than the viscosity of the first conductive polymer dispersion liquid measured under the same conditions.

8. The method for manufacturing an electrolytic capacitor according to claim 1, in, In the step of forming the first conductive polymer layer, a portion of the first dispersion medium is removed to form the first conductive polymer layer including the first conductive polymer component and the first dispersion medium.

9. The method for manufacturing an electrolytic capacitor according to any one of claims 1 to 8, in, The anode foil is a long strip. After the step of forming the first conductive polymer layer, a step of cutting the anode foil is provided.

10. The method for manufacturing an electrolytic capacitor according to claim 9, in, After the step of cutting the anode foil, a step of forming a dielectric layer on the cut surface is provided.

11. An electrolytic capacitor obtained by the method for producing an electrolytic capacitor according to claim 1, comprising a capacitor element in which an anode foil having a dielectric layer and a cathode foil are stacked. A conductive polymer layer is formed on the anode foil. At least 90% of the area of ​​one main surface of the anode foil is covered with the conductive polymer layer. The conductive polymer layer includes a first conductive polymer layer including a first conductive polymer component and a second conductive polymer layer covering a portion of the first conductive polymer layer and including a second conductive polymer component.

12. The electrolytic capacitor according to claim 11, in, The first conductive polymer component comprises a first polyanion, The second conductive polymer component comprises a second polyanion, The weight average molecular weight of the second polyanion is greater than the weight average molecular weight of the first polyanion.

13. The electrolytic capacitor according to claim 11 or 12, in, The mass per unit area of ​​the first conductive polymer layer is 0.1 mg / cm 2 above.

14. The electrolytic capacitor according to claim 11 or 12, in, The electrical conductivity of the first conductive polymer layer is 170 S / cm or less.

15. The electrolytic capacitor according to claim 11 or 12, in, The first conductive polymer layer is not formed on the end surface of the anode foil.

16. The electrolytic capacitor according to claim 11 or 12, in, A dielectric layer is formed on the end surface of the anode foil.

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