Electrolytic capacitor and its manufacturing method

Abstract

To provide an electrolytic capacitor with a reduced equivalent series resistance (ESR), and a method for manufacturing the electrolytic capacitor.SOLUTION: A method for manufacturing an electrolytic capacitor includes the steps of: preparing a positive electrode foil 11, a negative electrode foil 12, and a first conductive polymer diffusion liquid including a first conductive polymer component and a first dispersant; a step of applying the first conductive polymer diffusion liquid on a surface of the electrode foils by a coating technique, removing at least a part of the first dispersant, and forming a first conductive polymer layer including the first conductive polymer compound; and a step of manufacturing a capacitor element by using the electrode foils with the first conductive polymer layer formed.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to an electrolytic capacitor and a manufacturing method thereof, 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 solid electrolytes 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. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-109024 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 heat generation that accompanies an increase in ripple current. Increasing the amount of conductive polymer reduces ESR. However, this method does not allow a sufficient amount of conductive polymer to adhere to the capacitor element. [Means for solving the problem]

[0006] A first aspect of the present invention relates to a method for manufacturing an electrolytic capacitor, the method comprising the steps of: preparing an electrode foil; preparing a first conductive polymer dispersion containing a first conductive polymer component and a first dispersion medium; applying the first conductive polymer dispersion to a 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 fabricating a capacitor element using the electrode foil on which the first conductive polymer layer has been formed.

[0007] A second aspect of the present invention relates to an electrolytic capacitor comprising a capacitor element having an electrode foil, wherein a conductive polymer layer is formed on the electrode foil, and 90% or more of the area of ​​one main surface of the electrode foil is covered with the conductive polymer layer, and the conductive polymer layer comprises a first conductive polymer layer containing a first conductive polymer component, and a second conductive polymer layer covering a portion of the first conductive polymer layer and containing a second conductive polymer component. [Effects of the Invention]

[0008] According to 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]

[0009] [Figure 1] 1 is a flowchart illustrating an example of a manufacturing method according to an embodiment of the present invention. [Figure 2] 1 is a cross-sectional view schematically illustrating an example of an electrolytic capacitor according to an embodiment of the present invention. [Figure 3] FIG. 1 is an exploded perspective view schematically showing a portion of a capacitor element according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] In this embodiment, in order to adhere a large amount of conductive polymer, a dispersion containing the conductive polymer is applied to the electrode foil by a coating method. This allows a sufficient amount of conductive polymer component to adhere to at least a portion of the surface of the electrode foil. By adhering a sufficient amount of conductive polymer component to the surface of the electrode foil, the ESR of the resulting electrolytic capacitor is reduced. Furthermore, the heat resistance of the electrolytic capacitor is also improved. Therefore, the electrolytic capacitor according to this embodiment is suitable for use in products that carry a large ripple current.

[0011] Furthermore, compared to when the polymerization reaction is carried out on the surface of the electrode foil, 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.

[0012] The electrode foil may be an anode foil, a cathode foil, or both an anode foil and a cathode foil. The anode foil has a dielectric layer on its surface. When a 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 more likely to adhere to each other, further reducing the ESR. When a conductive polymer component is disposed on the surface of the cathode foil, the self-repairing performance of the anode foil is less likely to be hindered.

[0013] [Manufacturing method of electrolytic capacitors] The electrolytic capacitor according to this embodiment can be manufactured by a method including the steps of: preparing an electrode foil; preparing a first conductive polymer dispersion containing a first conductive polymer component and a first dispersion medium; 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 fabricating a capacitor element using the electrode foil on which the first conductive polymer layer has been formed. FIG. 1 is a flowchart showing an example of a manufacturing method according to this embodiment. Hereinafter, an example of a method for manufacturing an electrolytic capacitor according to this embodiment will be described step by step.

[0014] (1) Step of preparing electrode foil (S1) (1-1) Preparation of anode foil When the anode foil is to be coated with the first conductive polymer dispersion, the anode foil is prepared. As a raw material for the anode foil, for example, a metal foil containing a valve metal is used. An anode foil is prepared by forming a dielectric layer on the surface of a metal foil. The method for forming the dielectric layer is not particularly limited, but it can be formed by subjecting the metal foil 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.

[0015] Before forming the dielectric layer, the surface of the metal foil may be roughened as needed. By roughening, a plurality of projections and depressions 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.

[0016] In addition, a cathode foil and a separator are prepared as necessary as components of the capacitor element. The raw material of the cathode foil is, for example, a metal foil containing a valve metal. A dielectric layer may be formed on the surface of the metal foil used as the cathode foil by the above-mentioned method, or a conductive coating layer may be formed by sputtering or vapor deposition. Before forming the dielectric layer and the coating layer, the surface of the metal foil may be roughened as necessary. The raw material of the separator is, for example, a fibrous structure.

[0017] (1-2) Preparation of cathode foil When the first conductive polymer dispersion is coated on a cathode foil, a cathode foil is prepared. The cathode foil is as described above. In addition, the anode foil and, if necessary, the separator are prepared as components of the capacitor element.

[0018] (2) Step (S2) of preparing a first conductive polymer dispersion A first conductive polymer dispersion (hereinafter referred to as the first dispersion) containing a first conductive polymer component (hereinafter referred to as the first polymer component) and a first dispersion medium is prepared.

[0019] (1st dispersion) The first dispersion includes a first polymer component and a first dispersion medium. 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, the viscosity of the first dispersion is likely to be in a range suitable for coating methods. This makes it easier to uniformly adhere a sufficient amount of the first polymer component 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.

[0020] 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.

[0021] 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.

[0022] 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).

[0023] 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.

[0024] 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 electrode foil. 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 liquid is suppressed, and the amount of the first polyanion that adheres to the electrode foil is likely to increase.

[0025] 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.

[0026] 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).

[0027] 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.

[0028] 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.

[0029] (3) Step (S3) of forming a first conductive polymer layer After applying a first dispersion to 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. By applying the first dispersion to the electrode foil before fabricating a capacitor element, a sufficient amount of the first polymer component can be adhered to the electrode foil. At least a portion of the first polymer component adheres to the surface of the electrode foil. A portion of the first dispersion can also penetrate into the interior of the etching pits in the electrode foil. A portion of the first dispersion can also penetrate into the surface and pores of the dielectric layer of the anode foil.

[0030] The coating method is a technique for applying a liquid substance to an object using a coater. Examples of coaters include known devices such as a gravure coater, a knife coater, a comma coater, a roll coater, a die coater, and a lip coater. In this embodiment, the first dispersion is applied to the surface of the electrode foil using these known devices.

[0031] The amount of the first dispersion applied to the electrode foil is not particularly limited. For example, 2 The conditions may be appropriately set so that the first polymer component adheres.

[0032] The coating process with the first dispersion may be performed on one or both sides of the electrode foil. The coating process with the first dispersion may be performed multiple times on the same side of the electrode foil. This allows the thickness of the formed polymer layer to be increased. In this case, the drying process may be performed after multiple consecutive coating processes, or after each coating process.

[0033] From the viewpoint of mass production, the step of forming the first polymer layer may be performed on a long electrode foil. When coating both sides of a long electrode foil, the coating is first performed on one side, followed by drying, and then the electrode foil is wound up on a roll. The electrode foil is then unwound from the roll in a reversed direction, and the other side is coated again using the same or a different coater.

[0034] 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 planned cutting line of the electrode foil. This prevents the first polymer layer from being damaged or peeled off by cutting and prevents the first polymer component from adhering to the cut surface. In the case of an anode foil, this makes it easier to form a uniform dielectric layer on the cut surface even when the anode foil is subjected to another chemical conversion treatment after cutting.

[0035] In order to increase the amount of the conductive polymer component, the first polymer component may be attached to a component other than the electrode foil of the capacitor element. The method for attaching the first polymer component to the other component is not particularly limited, and the coating method as described above or impregnation may be used. An example of a component other than the electrode foil of the capacitor element is a separator.

[0036] The first dispersion medium is removed by a drying process such as heat drying or vacuum drying. The drying conditions are not particularly limited and may be set appropriately depending on the type of first dispersion medium, the amount of coating, and the like. In this case, the drying process may be performed to an extent that the first dispersion medium is not completely removed. 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.

[0037] 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 be more likely to penetrate into the etching pits of the electrode foil and even into the holes in the dielectric layer of the anode foil. This is expected to increase the capacitance. Furthermore, the self-repairing performance of the anode foil can be improved. Additionally, even when a long electrode foil on which the first polymer layer is formed is wound into a roll, cracks are less likely to occur in the first polymer layer.

[0038] (4) Electrode foil cutting process (S4) The long electrode foil 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 electrode foil, i.e., the end surface of the electrode foil. Other long components may also be cut, for example, in this step. The cutting step may be performed before the step of producing the capacitor element, or may be performed after the capacitor element is produced.

[0039] (5) Preparation of capacitor element (S5) The anode foil and the cathode foil are laminated so that a first polymer layer (and further a separator) is interposed between them. The laminate of the anode foil and the cathode foil may be wound. In this case, the end of the cathode foil located at the outermost layer is fixed with a winding tape. If the cutting step is performed, 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.

[0040] (6) Step (S6) of impregnating the capacitor element with a second conductive polymer 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.

[0041] 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.

[0042] (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.

[0043] 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.

[0044] 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 may be 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 an oscillating 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 an oscillating viscometer is preferably less than 100 mPa s.

[0045] (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.

[0046] (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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] The acid component may contain a composite compound of an organic acid and an inorganic acid from the viewpoint of thermal stability. Examples of the composite compound of an organic acid and an inorganic acid include borodisalicylic acid, borodioxalic acid, and borodiglycolic acid, which have high heat resistance.

[0052] The acid component may include inorganic acids such as boric acid, phosphoric acid, phosphorous acid, hypophosphorous acid, and phosphonic acid.

[0053] 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.

[0054] The electrolyte may contain a base component in addition to an acid component. The base component neutralizes at least a portion of the acid component. Therefore, it is possible to suppress corrosion of the electrode by the acid component 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.

[0055] 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.

[0056] 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.

[0057] (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.

[0058] Although the above description has been given taking as an example an electrolytic capacitor including a capacitor element in which an anode foil and a cathode foil are laminated and wound, the configuration of the electrolytic capacitor is not limited to this. When the object to be coated with the first conductive polymer dispersion is an anode foil, this embodiment can be applied to, for example, a laminated electrolytic capacitor including a capacitor element including an anode foil with a dielectric layer and a cathode extraction layer covering the anode foil.

[0059] The multilayer electrolytic capacitor is manufactured, for example, as follows. In the same manner as above, first polymer layers are formed on both sides of the anode foil (S3), and the anode foil is then 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 first polymer layer formed on the surface of the anode foil.

[0060] 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.

[0061] [Electrolytic capacitor] The electrolytic capacitor according to this embodiment includes a capacitor element having an electrode foil. A conductive polymer layer is formed on the electrode foil. The electrode foil on which the conductive polymer layer is formed (hereinafter sometimes referred to as a coated electrode foil) may be an anode foil, a cathode foil, or both an anode foil and a cathode foil. The anode foil has a dielectric layer on its surface. 90% or more 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 containing a first conductive polymer component, and a second conductive polymer layer covering a portion of the first conductive polymer layer and containing a second conductive polymer component. This reduces the ESR.

[0062] 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. A conductive polymer layer is formed on the anode foil. The cathode extraction layer is formed so as to cover at least a portion of the conductive polymer layer. 90% or more 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 containing a first conductive polymer component, and a second conductive polymer layer covering a portion of the first conductive polymer layer and containing a second conductive polymer component.

[0063] When the coated electrode foil is viewed from the normal direction of its main surface, 90% or more of the area of ​​the main surface is covered with the conductive polymer layer. The conductive polymer layer includes the first polymer layer and the second conductive polymer layer (hereinafter referred to as the second polymer layer). The area coverage by the conductive polymer layer is preferably 95% or more. 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 to a predetermined size used in an electrolytic capacitor. The area coverage may be calculated by binarizing an image of the main surface of the coated electrode foil.

[0064] The area coverage rate of the conductive polymer layer can be considered to be the area coverage rate of the first polymer layer. This is because the area coverage rate of the second polymer layer relative to the surface of the coated electrode foil 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, and may be 60% or less.

[0065] The constituent members and other constituent materials of the capacitor element will be described below. (1st polymer layer) The first polymer component adheres to the inner walls of the etching pits in the coated electrode foil and may also adhere to the exterior of the etching pits. In other words, the first polymer layer is formed so as to cover 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 interposed between the coated electrode foil and a separator, or between the coated electrode foil and another electrode foil. The first polymer layer does not have to be formed on the end surface of the coated electrode foil.

[0066] The mass of the first polymer layer per unit area of ​​the coated electrode foil is not particularly limited and is set appropriately as needed. According to this embodiment, the coated electrode foil has a mass of 0.1 mg / cm per unit area. 2 The mass of the first polymer layer can be 1 mg / cm. 2 This makes it easier to prevent a decrease in the withstand voltage of the resulting electrolytic capacitor.

[0067] The mass of the first polymer layer can be calculated from the difference in mass of the electrode foil before and after application of the first dispersion. The mass of the first polymer layer can also be calculated by analyzing the coated electrode foil using thermogravimetric analysis (TGA). For example, TGA measures the thermal change and sample 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 coated electrode foil can be calculated.

[0068] 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.

[0069] 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.

[0070] (Second polymer layer) The capacitor element is provided with the second polymer layer described above. The second polymer layer is expected to further increase the capacitance and reduce the ESR. The second polymer layer is provided, for example, by impregnating the capacitor element with the second dispersion liquid.

[0071] The second polymer component can be attached to the inside of holes or pits in the constituent members of the capacitor element, and also attached 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.

[0072] 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 layer. When analyzing a coated electrode foil using TGA, the amount of the second polymer layer adhered to the coated electrode foil can be 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., other electrode foils and / or separators) using TGA, the sum of this amount and the amount of the second polymer layer adhered to the coated electrode foil is the adhesion amount of the second polymer layer on the capacitor element. The mass of the second polymer layer adhered per unit area of ​​the capacitor element can be obtained by dividing the total adhesion amount of the second polymer layer by the total area of ​​one main surface of each component.

[0073] 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 density of the first polymer layer to the density of the second polymer layer is determined by observing the cross section of the coated electrode foil 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 calculated by dividing the area of ​​the first polymer layer in contact with the electrode foil by the area of ​​the polymer layers other than the first polymer layer. The densities of both layers are calculated by observing the same coated electrode foil in the same observation field. Usually, an interface between the first polymer layer and the second polymer layer can be confirmed, making it possible to distinguish between the two layers. The deposition amount, area coverage, density, etc. of the first polymer layer are calculated excluding the area of ​​the coated electrode foil 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.

[0074] (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.

[0075] 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.

[0076] (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.

[0077] 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.

[0078] 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.

[0079] (separator) When multiple electrode foils are stacked, a separator may be interposed between the electrodes together with the first polymer layer. If a first polymer layer of sufficient thickness is disposed between the electrodes, the separator may be omitted.

[0080] 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.

[0081] 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.

[0082] On the other hand, cellulose has hydroxyl groups and therefore easily swells in water. Therefore, when the first dispersion comes into contact with a separator made of cellulose, wrinkles are likely to occur. To prevent wrinkles, the separator may contain synthetic fibers and may contain a paper strength agent together with the cellulose fibers. By suppressing wrinkles in the separator, the thickness of the separator becomes uniform. Therefore, in an electrolytic capacitor, variations in withstand voltage and interelectrode resistance depending on the location are suppressed.

[0083] In the fiber structure containing synthetic fibers (hereinafter referred to as the first fiber structure), the content of the synthetic fibers may be 50% by mass or more, or 70% by mass or more, of the fiber structure. The type of synthetic fiber is not particularly limited.

[0084] The first fiber structure may further contain cellulose, which has good compatibility with the first dispersion and, optionally, the second dispersion and the electrolyte. The cellulose content may be 10% by mass or more of the fiber structure, taking into account the electrolyte retention. The cellulose content may be less than 50% by mass, 30% by mass or less, or 20% by mass or less.

[0085] 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.

[0086] 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.

[0087] 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.

[0088] The density of each fiber structure is not particularly limited. Even in the case of a fiber structure with a low density, swelling of the fiber structure due to the first dispersion liquid 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 can be, for example, 0.2 g / cm. 3 More than 0.45g / cm 3 may be less than 0.25 g / cm 3 More than 0.40g / cm 3 It may be the following:

[0089] 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.

[0090] (Cathode extraction layer) The cathode extraction layer includes, for example, a carbon layer formed to cover 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 (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.

[0091] (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.

[0092] FIG. 2 is a cross-sectional view that schematically shows an example of an electrolytic capacitor (wound electrolytic capacitor) according to this embodiment, and FIG. 3 is a perspective view in which a portion of a capacitor element of the electrolytic capacitor is developed.

[0093] 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.

[0094] Capacitor element 10 is, for example, a wound body as shown in Fig. 3. 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 and cathode foil 12 has a first polymer layer and a second polymer layer (not shown) formed thereon.

[0095] 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. 3 shows the wound body in a partially unfolded state before the outermost periphery is fixed.

[0096] 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.

[0097] [Example] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples.

[0098] 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.

[0099] (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 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 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.

[0100] (c) Formation of the first polymer layer The first dispersion was applied to both sides of the anode foil using a gravure coater. After that, 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 one main surface of the anode foil by the first polymer layer was 99%. The electrical conductivity of the first polymer layer was 400 S / cm.

[0101] (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.

[0102] (e) Preparation of a second dispersion and formation of a second polymer layer 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.

[0103] (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).

[0104] (g) Encapsulation of capacitor elements The capacitor element impregnated with the electrolyte was sealed to complete the electrolytic capacitor (A1) as shown in Figure 2. After that, aging was carried out at 95°C for 90 minutes while applying the rated voltage.

[0105] <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.

[0106] 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 of one main surface of the anode foil by the second polymer layer was 83%.

[0107] Example 2 Electrolytic capacitor A2 was fabricated and evaluated in the same manner as in Example 1, except that in the formation of the first polymer layer (c), the first dispersion was applied to both sides of the anode foil and 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 anode foil and the cathode foil was 0.3 mg / cm. 2 The coverage of one main surface of each of the anode foil and cathode foil with the first polymer component was 99%.

[0108] Example 3 Electrolytic capacitor A3 was fabricated and evaluated in the same manner as in Example 1, except that 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 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 separator is 0.02 mg / cm 2 The area coverage rate of one main surface of the anode foil with the first polymer layer was 99%, and the area coverage rate of one main surface of the separator with the first polymer layer was 98%.

[0109] Example 4 A first dispersion was prepared in the same manner as in Example 1, except that PSS with 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.

[0110] Except for using the first dispersion liquid, electrolytic capacitor A4 was produced and evaluated in the same manner as in Example 1. 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 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.

[0111] 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.

[0112] [Table 1]

[0113] Example 5 Electrolytic capacitor A5 was fabricated and evaluated in the same manner as in Example 1, except that in the step (c) of forming the first polymer layer, the first dispersion was applied to both sides of a cathode foil using a gravure coater instead of an anode foil. 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 coverage of one main surface of the cathode foil by the polymer layer was 99%.

[0114] Example 6 Electrolytic capacitor A6 was fabricated and evaluated in the same manner as in Example 1, except that in the formation of the first polymer layer (c), instead of using an anode foil, a gravure coater was used to apply the first dispersion to both sides of the cathode foil and the separator. 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 separator is 0.02 mg / cm 2 The area coverage rate of one main surface of the cathode foil with the first polymer layer was 99%, and the area coverage rate of one main surface of the separator with the first polymer layer was 98%.

[0115] Example 7 An electrolytic capacitor A7 was produced and evaluated in the same manner as in Example 5, except that the first dispersion prepared in Example 4 was used. 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%.

[0116] [Table 2] [Industrial Applicability]

[0117] The present invention is particularly suitable for electrolytic capacitors through which a high ripple current flows.

[0118] 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]

[0119] 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. providing a wide anode foil material having a first dielectric layer thereon; 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 to the surface of the anode foil material 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; cutting the anode foil material on which the first conductive polymer layer is formed to produce a narrow anode foil having a cut end surface; forming a second dielectric layer on the cut end surface of the anode foil; and producing a capacitor element using the anode foil including the first dielectric layer, the first conductive polymer layer, and the second dielectric layer, the first conductive polymer dispersion is applied to the surface of the anode foil material in such a manner that the first conductive polymer layer is not formed on a line along which the anode foil material is to be cut.

2. providing an anode foil material having a first dielectric layer on a surface thereof; 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 to the surface of the anode foil material 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; cutting the anode foil material on which the first conductive polymer layer has been formed to form a cut surface; forming a second dielectric layer on the cut surface of the anode foil material; and producing a capacitor element using the anode foil material including the first dielectric layer, the first conductive polymer layer, and the second dielectric layer, the first conductive polymer dispersion is applied to the surface of the anode foil material in such a way that the first conductive polymer layer is not formed in a location on the anode foil material where the cut surface is to be formed.

3. the first conductive polymer component is contained in the first conductive polymer dispersion in an amount of 1% by mass or more and 15% by mass or less, 3. The method for producing an electrolytic capacitor according to claim 1, wherein the viscosity of the first conductive polymer dispersion measured at room temperature using a vibration viscometer is 10 mPa·s or more.

4. impregnating the produced capacitor element with a second conductive polymer dispersion containing a second conductive polymer component and a second dispersion medium; removing at least a portion of the second dispersion medium to form a second conductive polymer layer containing the second conductive polymer component, 4. The method for manufacturing an electrolytic capacitor according to claim 1, wherein a viscosity of the second conductive polymer dispersion measured at room temperature using a vibration viscometer is lower than a viscosity of the first conductive polymer dispersion measured under the same conditions.

5. 5. The method for manufacturing an electrolytic capacitor according to claim 4, wherein a mass concentration of the second conductive polymer component contained in the second conductive polymer dispersion is lower than a mass concentration of the first conductive polymer component contained in the first conductive polymer dispersion.

6. 4. The method for manufacturing an electrolytic capacitor according to claim 1, further comprising the step of impregnating the capacitor element having the first conductive polymer layer formed thereon with an electrolytic solution.

7. 6. The method for manufacturing an electrolytic capacitor according to claim 4, further comprising the step of impregnating the capacitor element having the first conductive polymer layer and the second conductive polymer layer formed thereon with an electrolytic solution.

8. A method for manufacturing an electrolytic capacitor described in any one of claims 1 to 7, wherein the first conductive polymer component includes polythiophene or a derivative of polythiophene.

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