Electrolytic capacitor, method for manufacturing electrolytic capacitor, and sheet for electrolytic capacitor

Abstract

The electrolytic capacitor includes a laminate and a liquid component impregnated into the laminate. The laminate includes an anode foil having a dielectric layer on the surface thereof, a cathode foil, and a sheet disposed between the anode foil and the cathode foil. The sheet includes a separator and a first conductive polymer layer formed in a gap of the separator. The resistivity of the sheet in the thickness direction is 300 k [Omega] cm or less. The air permeability resistance of the sheet as measured by an air permeability tester is from 0.40 kPa.s / m to 0.60 kPa.s / m (inclusive).

Description

TECHNICAL FIELD

[0001] The present disclosure relates to an electrolytic capacitor, a method for manufacturing an electrolytic capacitor, and a sheet for electrolytic capacitor. BACKGROUND

[0002] As an electrolytic capacitor, an electrolytic capacitor including a wound body of an anode foil, a separator, and a cathode foil is known. One example of such an electrolytic capacitor includes a conductive polymer layer disposed in the wound body. The conductive polymer layer can be formed by impregnating a dispersion liquid containing a conductive polymer into the wound body. Various proposals have been made regarding electrolytic capacitors including a conductive polymer layer.

[0003] In claim 1 of Patent Literature 1 (Japanese Patent Application Laid-Open No. 2019-516241), “a capacitor including a processed element, the processed element including: an anode including a dielectric on a surface and an anode conductive polymer layer on a surface of the dielectric; a cathode including a cathode conductive polymer layer; a conductive separator between the anode and the cathode; an anode lead in electrical contact with the anode; and a cathode lead in electrical contact with the cathode” is described.

[0004] In claim 1 of Patent Literature 2 (International Publication No. 2021 / 125182), “a hybrid electrolytic capacitor characterized by including a cathode having a cathode base body composed of a valve metal, an oxide layer composed of an oxide of the valve metal provided on a surface of the cathode base body, an inorganic conductive layer containing an inorganic conductive material provided on a surface of the oxide layer, and an organic conductive layer containing a conductive polymer provided on a surface of the inorganic conductive layer, an anode having an anode base body composed of a valve metal, and a dielectric layer composed of an oxide of the valve metal constituting the anode base body provided on a surface of the anode base body, and a composite electrolyte layer having a solid electrolyte layer containing particles of a conductive polymer provided between and in contact with the organic conductive layer of the cathode and the dielectric layer of the anode, and an electrolyte filled between the particles of the conductive polymer in the solid electrolyte layer” is described.

[0005] In claim 1 of Patent Literature 3 (Japanese Patent Application Laid-Open No. 2018-110233), “a solid electrolytic capacitor characterized by including: a capacitor element in which an anode foil and a cathode foil are opposed with a separator interposed therebetween, a solid electrolyte layer composed of a conductive polymer and formed in the capacitor element, and an electrolyte containing a sugar alcohol derivative of four or more and filled in a void portion in the capacitor element in which the solid electrolyte layer is formed” is described.

[0006] PRIOR ART DOCUMENTS

[0007] Patent Literature

[0008] Patent Literature 1: Japanese Patent Application Laid-Open No. 2019-516241

[0009] Patent Literature 2: International Publication No. 2021 / 125182

[0010] Patent Literature 3: Japanese Patent Application Laid-Open No. 2018-110233 SUMMARY

[0011] One aspect of the present disclosure relates to an electrolytic capacitor including a laminate and a liquid component impregnated into the laminate. The laminate includes an anode foil having a dielectric layer on a surface thereof, a cathode foil, and a sheet disposed between the anode foil and the cathode foil. The sheet includes a separator and a first electrically conductive polymer layer formed in a void of the separator. The sheet has a specific resistance in a thickness direction of 300 kΩ·cm or less. The sheet has a gas permeation resistance of 0.40 kPa·s / m or more and 0.60 kPa·s / m or less as measured by a gas permeability tester.

[0012] Another aspect of the present disclosure relates to a sheet for an electrolytic capacitor, in which the electrolytic capacitor includes a capacitor element and a liquid component impregnated into the capacitor element. The sheet includes a separator and an electrically conductive polymer layer formed in a void of the separator. The sheet has a specific resistance in a thickness direction of 300 kΩ·cm or less. The sheet has a gas permeation resistance of 0.40 kPa·s / m or more and 0.60 kPa·s / m or less as measured by a gas permeability tester.

[0013] Another aspect of the present disclosure relates to a method of manufacturing an electrolytic capacitor. The method includes a preparation step of preparing an anode foil having a dielectric layer on a surface thereof, a sheet formation step of forming a sheet including a separator and a first electrically conductive polymer layer formed in a void of the separator, a laminate formation step of forming a laminate by laminating the anode foil, a cathode foil, and the sheet in a manner that the sheet is disposed between the anode foil and the cathode foil, and an impregnation step of impregnating a liquid component into the laminate. The sheet formation step includes a first coating liquid application step of applying a first coating liquid containing a first electrically conductive polymer and a first liquid medium into the void of the separator, and a first liquid medium removal step of forming the sheet by removing at least a portion of the first liquid medium from the first coating liquid. The sheet has a specific resistance in a thickness direction of 300 kΩ·cm or less. The sheet has a gas permeation resistance of 0.40 kPa·s / m or more and 0.60 kPa·s / m or less as measured by a gas permeability tester.

[0014] According to the present disclosure, an electrolytic capacitor including a liquid component and a conductive polymer layer and having a low ESR can be obtained. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 is a side view schematically showing one example of an electrolytic capacitor of an embodiment of the present disclosure.

[0016] Figure 2 is an exploded perspective view schematically showing one example of a capacitor element of an embodiment of the present disclosure. DETAILED DESCRIPTION

[0017] Hereinafter, problems in the related art will be briefly explained.

[0018] Since the viscosity of the dispersion liquid containing the conductive polymer is high, even if the dispersion liquid is impregnated into the wound body, a sufficient conductive polymer layer can not be formed inside the wound body. Insufficient formation of the conductive polymer layer can be a cause of an increase in equivalent series resistance (ESR).

[0019] Reduction in ESR of electrolytic capacitors has been sought. The present disclosure provides an electrolytic capacitor including a liquid component and a conductive polymer layer and having a low ESR.

[0020] Hereinafter, an embodiment of the present disclosure will be explained by way of example, but the present disclosure is not limited to the example explained below. In the following explanation, specific numerical values, materials, and the like are sometimes exemplified, but other numerical values, other materials can also be applied as long as the invention of the present disclosure can be implemented. In this specification, a description such as "numerical value A to numerical value B" includes numerical value A and numerical value B, and can be replaced with "numerical value A or more and numerical value B or less". In the following explanation, in a case where a lower limit and an upper limit of a numerical value related to a specific property, condition, or the like are exemplified, as long as the lower limit is not more than the upper limit, any one of the exemplified lower limits and any one of the exemplified upper limits can be arbitrarily combined.

[0021] (METHOD FOR MANUFACTURING ELECTROLYTIC CAPACITOR)

[0022] Hereinafter, the manufacturing method of the present embodiment will be referred to as "manufacturing method (M)". The manufacturing method (M) of the electrolytic capacitor includes a preparation step, a sheet formation step, a laminate formation step, and an impregnation step. The sheet formation step, the laminate formation step, and the impregnation step are performed in this order. The preparation step is performed before the laminate formation step. The respective steps will be described later.

[0023] As described later, in the manufacturing method (M), a sheet having a resistivity and a gas permeation resistance in a prescribed range is used. Therefore, an electrolytic capacitor having a low ESR and a low leakage current can be obtained.

[0024] (PREPARATION STEP)

[0025] The preparation step is a step of preparing the anode foil having the dielectric layer on the surface. The anode foil having the dielectric layer on the surface can be used as a commercially available product, or can be formed by forming a dielectric layer on the surface of a metal foil (anode foil). The dielectric layer can be formed by a publicly known method. For example, the dielectric layer can be formed by oxidizing the surface of the metal foil (anode foil).

[0026] (Sheet forming step)

[0027] The sheet forming step is a step of forming a sheet containing the separator and the first electrically conductive polymer layer formed in the void of the separator. Hereinafter, the sheet formed by the sheet forming step is sometimes referred to as "sheet (S)". The sheet forming step includes a first coating liquid application step of applying a first coating liquid containing a first electrically conductive polymer and a first liquid medium to the void of the separator, and a first liquid medium removal step of forming the sheet (S) by removing at least a part of the first liquid medium from the first coating liquid.

[0028] The first electrically conductive polymer can be dispersed in the first coating liquid in the state of a particle. Examples of the electrically conductive polymer are described later.

[0029] The first liquid medium is not particularly limited, and a liquid medium capable of being used for forming a polymer layer can be used. Examples of the first liquid medium include water, an organic solvent (for example, an alcohol), and a mixed solvent thereof, and the like.

[0030] The first liquid medium can contain water and an organic compound that does not boil at 100°C under 1 atmosphere (101325 Pa). Hereinafter, the organic compound is sometimes referred to as "organic compound (C)". The organic compound (C) can be one compound, or can be composed of a plurality of compounds.

[0031] The method of imparting the first coating liquid is not limited, and can be imparted by a publicly known method. For example, it can be a method using a coater, or the first coating liquid can be sprayed, or the object to be imparted can be immersed in the first coating liquid. Examples of the method using a coater include a gravure coater method, a die coater method, and the like. In one example of the gravure coater method, first, the coating liquid is attached to a transfer member such as a gravure roll, and then, excess coating liquid is removed from the transfer member. Next, by transferring the coating liquid attached to the transfer member to a prescribed member (anode foil, cathode foil, or separator), a layer of the coating liquid of uniform thickness can be attached to the member. In addition, the viscosity of the coating liquid can be, for example, 10 mPa-s or more (for example, 100 mPa-s or more) and 200 mPa-s or less. In this case, the coating liquid is easily applied to the anode foil, cathode foil, or separator, and the coating liquid is easily impregnated into the separator. Note that the viscosity of the coating liquid is measured at room temperature (20°C) using a vibration-type viscometer (for example, VM-100A manufactured by SEKONIC Corporation).

[0032] The method of removing at least a portion of the first liquid medium from the first coating liquid is not particularly limited, and can be performed by heating or the like. In the case where the first coating liquid contains the organic compound (C), heating can be performed so that the organic compound (C) remains in the first electrically conductive polymer layer. For example, in the case where the first coating liquid contains the organic compound (C) and water (liquid medium), by heating the coating liquid at a temperature at which the organic compound (C) does not boil and decompose and 100°C or higher, it is possible to remove the water from the first coating liquid, while leaving the organic compound (C) in the polymer layer. The heating temperature can be 100°C or higher, 120°C or higher, or 140°C or higher, and can be 200°C or lower or 160°C or lower. The heating temperature can be in the range of 100°C to 200°C. The heating time is not particularly limited, and can be a time that is appropriate to remove a portion of the first liquid medium. One example of the heating time is in the range of 5 to 60 minutes.

[0033] By leaving the organic compound (C) in the first electrically conductive polymer layer, it is possible to reduce shrinkage of the electrically conductive polymer layer when the first liquid medium is removed from the first coating liquid. As a result, in a subsequent impregnation process, the liquid component (for example, electrolyte solution) easily penetrates into the first electrically conductive polymer layer. As a result, the function of forming a dielectric layer (oxidation film) possessed by the liquid component is easily sufficiently exerted, and the leakage current is reduced.

[0034] In a preferred example of the production method (M), the first liquid medium of the applied first coating liquid is removed in a manner such that the content rate of water in the first coating liquid is 40% by mass or more (for example, 50% by mass or more) and the mass of the organic compound (C) in the first conductive polymer layer is greater than the mass of water in the first conductive polymer layer. If the content rate of water in the first coating liquid is high, the electrolytic solution easily infiltrates the first conductive polymer layer after the first conductive polymer layer is formed.

[0035] The sheet (S) has a thickness direction resistivity (hereinafter, sometimes referred to as "resistivity Re") of 300 kΩ·cm or less. By setting the resistivity Re to 300 kΩ·cm or less, the ESR of the electrolytic capacitor can be reduced. The resistivity Re can be 200 kΩ·cm or less. The resistivity Re can be 100 kΩ·cm or more, or 150 kΩ·cm or more.

[0036] The resistivity Re can vary depending on the concentration of the first conductive polymer in the first coating liquid, the amount of the first coating liquid that is given into the voids of the separator, and the like. By increasing the amount of the first conductive polymer that is disposed in the voids of the separator, the resistivity Re can be reduced.

[0037] The resistivity Re can be measured by the following method. First, two aluminum plates (size: 2 cm x 3 cm, area Ss: 6 cm 2 ) are used to hold the sheet (S) that is cut to a predetermined size (2.5 cm x 3.5 cm). In addition, two glass plates are used to hold the aluminum plates that hold the sheet (S) from the outside, and a clamp is used to press the two glass plates, thereby causing the two aluminum plates to be in close contact with the sheet (S). Then, the resistance Rs between the two aluminum plates is measured. In addition, the average thickness Ta of the sheet (S) is measured. Then, the resistivity Re is calculated from the area Ss, the measured resistance Rs, and the average thickness Ta. Note that the average thickness Ta of the sheet (S) is measured by the method described later.

[0038] The sheet (S) has a gas permeation resistance (hereinafter, sometimes referred to as "gas permeation resistance Rg") of 0.40 kPa·s / m or more, which can be 0.45 kPa·s / m or more, or 0.49 kPa·s / m or more. The gas permeation resistance Rg can be 0.60 kPa·s / m or less, which can be 0.58 kPa·s / m or less, or 0.49 kPa·s / m or less. The smaller the gas permeation resistance Rg, the easier it is for gas to permeate the sheet (S). The gas permeation resistance Rg can be measured by the method described in the examples.

[0039] By setting the air permeation resistance Rg to 0.40 kPa-s / m or more, the sheet (S) can have a higher resistivity, and the ESR of the electrolytic capacitor can be reduced. By setting the air permeation resistance Rg to 0.60 kPa-s / m or less, the amount of the liquid component (LC) to be held in the sheet (S) can be increased, and the repair function of the dielectric layer by the liquid component (LC) can be improved. As a result, the leakage current of the electrolytic capacitor can be reduced.

[0040] The air permeation resistance Rg can vary depending on the concentration of the first conductive high polymer in the first coating liquid, the amount of the first coating liquid to be applied to the voids of the separator, and the like. By reducing the amount of the first conductive high polymer to be disposed in the voids of the separator, the air permeation resistance Rg can be reduced.

[0041] In the sheet formation process, the ratio of the volume Vd of the first coating liquid impregnated into the separator to the volume Vs of the voids of the separator (Vd / Vs) can be 0.95 or more. By setting the ratio Vd / Vs to 0.95 or more, the conductive high polymer layer can be formed uniformly in the voids of the separator. The ratio Vd / Vs can be 1.0 or less.

[0042] The volume Vs of the voids of the separator is obtained by multiplying the value obtained by subtracting the nominal density of the separator from the density of the material of the separator (separator material density - nominal density) by the volume of the separator (area of the separator x average thickness of the separator). In addition, the volume Vd of the first coating liquid impregnated into the separator can be obtained by dividing the mass of the first coating liquid impregnated into the separator by the specific gravity of the first coating liquid (volume Vd = (mass of the first coating liquid) / (density of the first coating liquid)). Note that the average thickness of the separator can be measured by the same method as the method of measuring the average thickness Ta of the sheet described later.

[0043] The areal density of the first conductive high polymer layer can be 0.05 mg / cm 2 0.1 mg / cm 2 0.3 mg / cm 2 1.0 mg / cm 2 0.5 mg / cm 2 0.1 mg / cm 2 1.0 mg / cm 2 According to this configuration, an electrolytic capacitor having an especially low ESR can be obtained. Note that the areal density refers to the mass per unit area. The areal density of the first conductive high polymer layer can be controlled by the concentration of the first conductive high polymer in the first coating liquid and the coating amount of the first coating liquid.

[0044] The area density of the first conductive polymer layer can be calculated by the following method. First, five samples are prepared by cutting the separator before formation of the first conductive polymer layer to a predetermined area, and the mass of the five samples is measured. In addition, five samples are prepared by cutting the separator on which the first conductive polymer layer is formed to the predetermined area, and the mass of the sample is measured. The area density of the first conductive polymer layer is calculated from the difference between the sum of the masses of the five samples after formation of the first conductive polymer layer and the sum of the masses of the five samples before formation of the first conductive polymer layer, and the predetermined area. Note that the area density of the second conductive polymer layer described later can also be calculated by the same method.

[0045] The average thickness (hereinafter, sometimes referred to as "average thickness Ta") of the sheet (S) can be 20 μm or more, or 40 μm or more, and can be 70 μm or less, or 60 μm or less. By setting the average thickness Ta to 20 μm or more and 70 μm or less, the gap between the electrodes can be ensured, and the penetration of the electrolyte into the gap between the electrodes can be promoted.

[0046] The average thickness Ta of the sheet (S) can be measured by the following method. First, the film thickness is measured at any 10 points of the sheet (S) by a film thickness measuring device (micrometer or the like). Then, the average thickness Ta is obtained by performing an arithmetic average of the 10 measured values.

[0047] (Laminate formation step)

[0048] The laminate formation step is a step of forming a laminate by laminating the anode foil, the cathode foil, and the sheet (S) in a manner that the sheet (S) is disposed between the anode foil and the cathode foil.

[0049] The method of forming the laminate is not particularly limited, and the laminate can be formed by a publicly known method. The laminate can be a wound body. In this case, in the laminate formation step, the anode foil, the cathode foil, and the sheet (S) can be wound in a manner that the sheet (S) is disposed between the anode foil and the cathode foil, thereby forming the wound body. In the wound body, the anode foil, the cathode foil, and the sheet (S) are laminated in the radial direction of the wound body.

[0050] The laminate can be formed by laminating a flat anode foil, a flat cathode foil, and a flat sheet (S) in one direction. For example, a plurality of anode foils, a plurality of cathode foils, and a plurality of sheets (S) can be laminated in one direction to form the laminate. In a typical example of the laminate, the anode foils and the cathode foils are alternately disposed, and the sheet (S) is disposed between the anode foils and the cathode foils.

[0051] (Infiltration step)

[0052] The impregnation step is a step of impregnating the liquid component into the laminate. Hereinafter, the liquid component is sometimes referred to as "liquid component (LC)". The method of impregnating the liquid component (LC) into the laminate is not limited. For example, the liquid component (LC) can be impregnated into the laminate by immersing at least a portion of the laminate in the liquid component (LC). The liquid component (LC) can be an electrolytic solution.

[0053] As described above, the capacitor element can be obtained. Then, other steps can be performed as necessary. For example, a step of sealing the capacitor element impregnated with the liquid component (LC) into an exterior body can be performed.

[0054] (Polymer layer forming step)

[0055] The production method (M) can further include, before the laminate forming step, a polymer layer forming step of forming a second conductive polymer layer on the surface of the dielectric layer. The polymer layer forming step includes a second coating liquid application step of applying a second coating liquid containing a second conductive polymer and a second liquid medium to the surface of the dielectric layer (the dielectric layer on the surface of the anode foil), and a second liquid medium removing step of forming the second conductive polymer layer by removing at least a portion of the second liquid medium from the second coating liquid.

[0056] The first conductive polymer and the second conductive polymer can be the same or different. The first liquid medium and the second liquid medium can be the same or different. The first coating liquid and the second coating liquid can be the same or different. The surface density of the second conductive polymer layer can be within the range exemplified for the surface density of the first conductive polymer layer.

[0057] The method of applying the second coating liquid to the surface of the dielectric layer is not particularly limited, and the method exemplified in the first coating liquid application step can be applied. The method of removing at least a portion of the second liquid medium from the second coating liquid is not particularly limited, and the method exemplified in the first liquid medium removing step can be applied.

[0058] The production method (M) can include, in order after the laminate forming step and before the impregnation step, a liquid application step and a removing step. The liquid application step is a step of impregnating a liquid (hereinafter, sometimes referred to as "liquid (L)") into the laminate. The removing step is a step of removing at least a portion of the liquid (L) impregnated into the laminate. The liquid (L) can be a liquid containing water as a main component and an organic compound (C) that does not boil at 100°C under 1 atmosphere. In this case, the removing step can be a step of removing a portion of the liquid (L) impregnated into the laminate so that the mass of the organic compound (C) in the laminate is greater than the mass of the water in the laminate.

[0059] The liquid (L) used in the liquid application process can use a liquid obtained by removing the first electrically conductive polymer component from the first coating liquid used in the sheet formation process. The impregnation of the liquid (L) of the liquid application process can be performed by the method exemplified for the first coating liquid application process of the sheet formation process. The removal of the liquid (L) in the removal process can be performed by the method exemplified for the first liquid medium removal process of the sheet formation process. By performing the liquid application process and the removal process, the adhesion of the first electrically conductive polymer layer to the second electrically conductive polymer layer and the adhesion of the first electrically conductive polymer layer to the cathode foil can be improved.

[0060] In the electrolytic capacitor manufactured by the manufacturing method (M), the cathode foil can have an inorganic layer on the surface, and the first electrically conductive polymer layer can be in adhesion with the inorganic layer.

[0061] In the case where the cathode foil is composed only of a metal foil (e.g., an aluminum foil), an oxide layer is formed on the surface of the metal foil, and the cathode foil also generates an electrostatic capacitance. As a result, due to the combined capacity of the electrostatic capacitance of the anode foil and the electrostatic capacitance of the cathode foil, there is a problem that the electrostatic capacitance of the entire capacitor decreases at times. By covering the surface of the metal foil with an inorganic layer or the like, it is possible to suppress the occurrence of such a problem. That is, by forming an inorganic layer, it is possible to extract only the capacity of the anode foil. On the other hand, if the adhesion of the electrically conductive polymer layer to the inorganic layer is low, the ESR becomes high. By performing the above-described liquid application process, it is possible to improve the adhesion of the first electrically conductive polymer layer to the inorganic layer.

[0062] The inorganic layer easily repels water, and therefore, in the conventional method in which the electrically conductive polymer layer is formed by impregnating a water dispersion liquid of an electrically conductive polymer into the laminate (capacitor element), the electrically conductive polymer has difficulty in entering between the inorganic layer of the cathode foil and the anode foil in the laminate, and therefore, it is not possible to uniformly form the electrically conductive polymer layer on the separator disposed between the cathode foil and the anode foil, leading to an increase in ESR. In the manufacturing method (M), the laminate (capacitor element) is formed using a separator on which the first electrically conductive polymer layer is formed in advance. Therefore, it is possible to suppress uneven distribution of the first electrically conductive polymer within the separator.

[0063] (Electrolytic Capacitor)

[0064] Hereinafter, the electrolytic capacitor of the present embodiment will be sometimes referred to as "electrolytic capacitor (E)". The electrolytic capacitor (E) can be manufactured by the above-described manufacturing method (M). Matters described with respect to the manufacturing method (M) can be applied to the electrolytic capacitor (E), and therefore, repeated descriptions will be sometimes omitted. Matters described with respect to the electrolytic capacitor (E) can also be applied to the manufacturing method (M).

[0065] An electrolytic capacitor (E) includes a laminate and a liquid component impregnated into the laminate. The laminate includes an anode foil having a dielectric layer on a surface thereof, a cathode foil, and a sheet (sheet (S)) disposed between the anode foil and the cathode foil. The sheet includes a separator and a first electrically conductive polymer layer formed in a void of the separator. A resistivity Re in a thickness direction of the sheet (S) is 300 kΩ·cm or less. A gas permeation resistance Rg of the sheet measured by a gas permeability tester is 0.40 kPa·s / m or more and 0.60 kPa·s / m or less.

[0066] According to the electrolytic capacitor (E), the effects described in the manufacturing method (M) can be obtained. For example, according to the configuration of the electrolytic capacitor (E), the ESR can be reduced.

[0067] The surface density of the first electrically conductive polymer layer of the electrolytic capacitor (E) can be 0.1 mg / cm 2 and 1.0 mg / cm 2 or more.

[0068] The average thickness Ta of the sheet (S) of the electrolytic capacitor (E) can be 20 μm or more and 70 μm or less.

[0069] The electrolytic capacitor (E) can further include a second electrically conductive polymer layer formed on the dielectric layer of the surface of the anode foil.

[0070] In the electrolytic capacitor (E), the cathode foil can have an inorganic layer on a surface thereof, and the first electrically conductive polymer layer can be adhesively bonded to the inorganic layer.

[0071] As described above, the laminate can be a wound body, or can be a laminate other than the wound body.

[0072] (Sheet for electrolytic capacitor)

[0073] The sheet of the present embodiment is the sheet (S) described above. The sheet (S) can be formed by the sheet forming process described above. In the description of the manufacturing method (M), matters described in the sheet forming process and the sheet (S) can be applied to the sheet (S), and thus the repeated description is sometimes omitted. The sheet (S) is disposed in a position where the separator is disposed in the electrolytic capacitor, and can be used instead of the separator.

[0074] The sheet (S) is a sheet used in an electrolytic capacitor including a capacitor element and a liquid component impregnated into the capacitor element. The sheet (S) includes a separator and an electrically conductive polymer layer (first electrically conductive polymer layer) formed in a void of the separator. A resistivity Re in a thickness direction of the sheet (S) is 300 kΩ·cm or less. A gas permeation resistance Rg of the sheet (S) measured by a gas permeability tester is 0.40 kPa·s / m or more and 0.60 kPa·s / m or less.

[0075] As described above, the areal density of the electrically conductive polymer layer (first electrically conductive polymer layer) formed in the voids of the sheet (S) can be 0.1 mg / cm 2 0.1 mg / cm and 1.0 mg / cm 2 0.1 mg / cm and 1.0 mg / cm

[0076] As described above, the average thickness of the sheet (S) can be 20 μm or more and 70 μm or less.

[0077] Hereinafter, examples of the manufacturing method (M) and the materials and constituent elements used in the electrolytic capacitor (E) will be described. However, the manufacturing method (M) and the materials and constituent elements used in the electrolytic capacitor (E) are not limited to the examples described below.

[0078] In the present specification, the term "electrically conductive polymer component" is sometimes used. In the case where no dopant is doped in the electrically conductive polymer, the electrically conductive polymer component is composed of the electrically conductive polymer. In the case where a dopant is doped in the electrically conductive polymer, the electrically conductive polymer component is composed of the electrically conductive polymer and the dopant.

[0079] (Coating liquid (first coating liquid, second coating liquid))

[0080] The coating liquid (first coating liquid, second coating liquid) used in the polymer layer forming step can contain an electrically conductive polymer and water. The electrically conductive polymer (electrically conductive polymer component) can be contained in the coating liquid in the state of a particle. The coating liquid can be an aqueous dispersion of the electrically conductive polymer (electrically conductive polymer component).

[0081] The coating liquid can include other components (for example, an organic compound (C)). The organic compound (C) can include, or can be, at least one selected from the group consisting of a polyol, a sulfolane, a gamma-butyrolactone, and a borate ester. The organic compound (C) can include, or can be, at least one selected from the group consisting of a glycol, a glycerol, a sugar alcohol, a sulfolane, a gamma-butyrolactone, and a borate ester.

[0082] Examples of the polyol include glycols, glycerols, and sugar alcohols. Examples of the glycol include ethylene glycol, diethylene glycol, triethylene glycol, polyalkylene glycol (for example, polyethylene glycol), polyoxyethylene polyoxypropylene glycol (ethylene oxide-propylene oxide copolymer), and the like. Examples of the glycerol include glycerol, polyglycerol, and the like. Examples of the sugar alcohol include mannitol, xylitol, sorbitol, erythritol, pentaerythritol, and the like.

[0083] Examples of the electrically conductive polymer include polypyrrole, polythiophene, polyfuran, polyaniline, polyacetylene, and derivatives thereof. The derivatives include polymers having polypyrrole, polythiophene, polyfuran, polyaniline, and polyacetylene as a basic skeleton. For example, derivatives of polythiophene include poly(3,4-ethylenedioxythiophene) and the like. These electrically conductive polymers can be used alone or in combination of a plurality of kinds. In addition, the electrically conductive polymer can be a copolymer of two or more kinds of monomers. The weight average molecular weight of the electrically conductive polymer is not particularly limited, and for example, can be in the range of 1000 to 100000. A preferred example of the electrically conductive polymer is poly(3,4-ethylenedioxythiophene) (PEDOT).

[0084] The electrically conductive polymer can be doped with a dopant. From the viewpoint of suppressing dedoping from the electrically conductive polymer, as the dopant, a high molecular dopant is preferably used. Examples of the high molecular dopant include polyvinylsulfonic acid, polystyrene sulfonic acid, polyallylsulfonic acid, polypropylsulfonic acid, polymethacrylsulfonic acid, poly(2-acrylamido-2-methylpropanesulfonic acid), polyisoprenesulfonic acid, polyacrylic acid, and the like. These can be used alone or in combination of two or more kinds. At least a part of them can be added in the form of a salt. A preferred example of the dopant is polystyrene sulfonic acid (PSS).

[0085] The dopant can be polystyrene sulfonic acid, and the electrically conductive polymer can be poly(3,4-ethylenedioxythiophene). That is, the electrically conductive polymer component can be poly(3,4-ethylenedioxythiophene) doped with polystyrene sulfonic acid.

[0086] In the case of using the electrically conductive polymer doped with the dopant, in order to suppress dedoping of the dopant, the pH of the coating liquid is preferably less than 7.0, and can be 6.0 or less or 5.0 or less. The pH of the coating liquid can be 1.0 or more or 2.0 or more.

[0087] The content ratio of water in the coating liquid can be 40% by mass or more, 50% by mass or more, 80% by mass or more, 90% by mass or more, or 95% by mass or more. The content ratio can be 98% by mass or less, 95% by mass or less, 90% by mass or less, or 80% by mass or less.

[0088] The content of the organic compound (C) in the coating liquid can be 1.0 mass% or more, 3.0 mass% or more, 5.0 mass% or more, or 10 mass% or more. It can be 30 mass% or less, 20 mass% or less, 15 mass% or less, or 10 mass% or less. The content of the electrically conductive polymer component in the coating liquid can be 0.5 mass% or more, or 1.0 mass% or more, and can be 4.0 mass% or less, 3.0 mass% or less, or 2.0 mass% or less. The content can be in the range of 0.5 to 4.0 mass%, or in the range of 1.0 to 4.0 mass%. In any of these ranges, the upper limit can be 3.0 mass% or 2.0 mass%. From the aspects of the physical properties of the coating liquid and the excellent stability thereof over time, and the aspect of the good balance between the ESR of the electrolytic capacitor and the cost, the content is preferably in the range of 1.0 to 3.0%. Note that, in the case where the coating liquid contains a dopant, the mass of the dopant is included in the mass of the electrically conductive polymer component.

[0089] The mass of the dopant contained in the coating liquid is not particularly limited, and can be in the range of 0.1 to 5 times, for example, in the range of 0.5 to 3 times, the mass of the electrically conductive polymer contained in the coating liquid.

[0090] In the coating liquid, the content of water : the content of the organic compound (C) : the content of the electrically conductive polymer component can be 40 to 98 : 1.0 to 59.5 : 0.5 to 4.0, or the content of water : the content of the organic compound (C) : the content of the electrically conductive polymer component can be 69.5 to 98 : 1.0 to 30 : 0.5 to 4.0.

[0091] (Liquid component (LC))

[0092] Examples of the liquid component (LC) used in the impregnation step include nonaqueous solvents and electrolytic solutions. The electrolytic solution can use an electrolytic solution containing a nonaqueous solvent and a solute dissolved in the nonaqueous solvent. Note that, in the present specification, the liquid component (LC) can be a component that is in a liquid state at room temperature (25°C), or a component that is in a liquid state at the temperature at which the electrolytic capacitor is used.

[0093] The nonaqueous solvent used in the liquid component (LC) can be an organic solvent, an ionic liquid, or a protic solvent. Examples of the nonaqueous solvent include polyhydric alcohols such as ethylene glycol and propylene glycol, cyclic sulfones such as sulfolane (SL), lactones such as gamma-butyrolactone (γBL), amides such as N-methylacetamide, N,N-dimethylformamide, and N-methyl-2-pyrrolidone, esters such as methyl acetate, carbonate compounds such as propylene carbonate, ethers such as 1,4-dioxane, ketones such as methyl ethyl ketone, and formaldehyde.

[0094] In addition, as the non-aqueous solvent, a high molecular solvent can also be used. Examples of the high molecular solvent include polyalkylene glycol, a derivative of polyalkylene glycol, a compound in which at least one of the hydroxyl groups in a polyhydric alcohol is replaced with polyalkylene glycol (including a derivative), and the like. Specifically, examples of the high molecular solvent include polyethylene glycol (PEG), polyethylene glycol glyceryl ether, polyethylene glycol diglyceryl ether, polyethylene glycol sorbitol ether, polypropylene glycol, polypropylene glycol glyceryl ether, polypropylene glycol diglyceryl ether, polypropylene glycol sorbitol ether, polybutylene glycol, and the like. Examples of the high molecular solvent also include a copolymer of ethylene glycol-propylene glycol, a copolymer of ethylene glycol-butylene glycol, a copolymer of propylene glycol-butylene glycol, and the like. The non-aqueous solvent can be used alone or in combination of two or more.

[0095] The liquid component (LC) can contain a non-aqueous solvent and a base component (base) dissolved in the non-aqueous solvent. In addition, the liquid component (LC) can also contain a non-aqueous solvent and a base component and / or an acid component (acid) dissolved in the non-aqueous solvent.

[0096] As the acid component, a polycarboxylic acid and a monocarboxylic acid can be used. As examples of the polycarboxylic acid, aliphatic polycarboxylic acids ([saturated polycarboxylic acids such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, 1,6-decanedicarboxylic acid, 5,6-decanedicarboxylic acid], [unsaturated polycarboxylic acids such as maleic acid, fumaric acid, itaconic acid]), aromatic polycarboxylic acids (such as phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, pyromellitic acid), alicyclic polycarboxylic acids (such as cyclohexane-1,2-dicarboxylic acid, cyclohexene-1,2-dicarboxylic acid, and the like) can be given.

[0097] As examples of the monocarboxylic acid, aliphatic monocarboxylic acids (carbon number 1 to 30) ([saturated monocarboxylic acids such as formic acid, acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, caproic acid, heptanoic acid, caprylic acid, nonanoic acid, lauric acid, myristic acid, stearic acid, behenic acid], [unsaturated monocarboxylic acids such as acrylic acid, methacrylic acid, oleic acid]), aromatic monocarboxylic acids (such as benzoic acid, cinnamic acid, naphthoic acid), hydroxycarboxylic acids (such as salicylic acid, mandelic acid, resorcylic acid) can be given.

[0098] Among them, maleic acid, phthalic acid, benzoic acid, pyromellitic acid, and resorcylic acid are thermally stable, and are preferably used.

[0099] As the acid component, an inorganic acid can be used. As examples of the representative inorganic acid, phosphoric acid, phosphorous acid, hypophosphorous acid, alkyl phosphates, boric acid, fluoroboric acid, tetrafluoroboric acid, hexafluorophosphoric acid, benzene sulfonic acid, naphthalene sulfonic acid, and the like can be given. In addition, a complex compound of an organic acid and an inorganic acid can also be used as the acid component. As examples of such a complex compound, boro-diglycolic acid, boro-dioxalic acid, boro-diphenylacetic acid, and the like can be given.

[0100] The base component can be a compound having an alkyl-substituted amidine group, and for example, can be an imidazole compound, a benzimidazole compound, an alicyclic amidine compound (a pyrimidine compound, an imidazoline compound), and the like. Specifically, 1,8-diazabicyclo[5,4,0]undec-7-ene, 1,5-diazabicyclo[4,3,0]non-5-ene, 1,2-dimethylimidazolinium, 1,2,4-trimethylimidazoline, 1-methyl-2-ethyl-imidazoline, 1,4-dimethyl-2-ethylimidazoline, 1-methyl-2-heptylimidazoline, 1-methyl-2-(3'-heptyl)imidazoline, 1-methyl-2-dodecylimidazoline, 1,2-dimethyl-1,4,5,6-tetrahydropyrimidine, 1-methylimidazole, 1-methylbenzimidazole are preferable. By using them, a capacitor having excellent resistance properties can be obtained.

[0101] As the base component, a quaternary salt of a compound having an alkyl-substituted amidine group can be used. As examples of such a base component, an imidazole compound, a benzimidazole compound, an alicyclic amidine compound (a pyrimidine compound, an imidazoline compound) which have been quaternized with an alkyl group having a carbon number of 1 to 11 or an arylalkyl group can be given. Specifically, 1-methyl-1,8-diazabicyclo[5,4,0]undec-7-ene, 1-methyl-1,5-diazabicyclo[4,3,0]non-5-ene, 1,2,3-trimethylimidazolinium, 1,2,3,4-tetramethylimidazolinium, 1,2-dimethyl-3-ethyl-imidazolinium, 1,3,4-trimethyl-2-ethylimidazolinium, 1,3-dimethyl-2-heptylimidazolinium, 1,3-dimethyl-2-(3'-heptyl)imidazolinium, 1,3-dimethyl-2-dodecylimidazolinium, 1,2,3-trimethyl-1,4,5,6-tetrahydropyrimidinium, 1,3-dimethylimidazolium, 1-methyl-3-ethylimidazolium, 1,3-dimethylbenzimidazolium are preferable. By using them, a capacitor having excellent resistance properties can be obtained.

[0102] In addition, a tertiary amine can be used as the base component. As examples of the tertiary amine, mention can be made of trialkylamines (trimethylamine, dimethylethylamine, methyldiethylamine, triethylamine, dimethyl-n-propylamine, dimethyl-i-propylamine, methylethyl-n-propylamine, methylethyl-i-propylamine, diethyl-n-propylamine, diethyl-i-propylamine, tri-n-propylamine, tri-i-propylamine, tri-n-butylamine, tri-t-butylamine, and the like), and amines containing a phenyl group (dimethylphenylamine, methylethylphenylamine, diethylphenylamine, and the like). Among these, from the viewpoint of increasing the electrical conductivity, trialkylamines are preferred, and at least one selected from the group consisting of trimethylamine, dimethylethylamine, methyldiethylamine, and triethylamine is more preferred. In addition, a secondary amine such as a dialkylamine, a primary amine such as a monoalkylamine, and ammonia can also be used as the base component.

[0103] The liquid component (LC) can contain a salt of the acid component and the base component. The salt can be an inorganic salt and / or an organic salt. The organic salt refers to a salt in which at least one of the anion and the cation contains an organic substance. As the organic salt, for example, trimethylamine maleate, triethylamine borodisalicylate, ethyldimethylamine phthalate, mono-1,2,3,4-tetramethylimidazolium phthalate, mono-1,3-dimethyl-2-ethylimidazolium phthalate, and the like can be used.

[0104] In order to suppress de-doping of the dopant, the pH of the liquid component (LC) can be set to less than 7.0 or 5.0 or lower, and can be set to 1.0 or higher or 2.0 or higher. The pH can be set to 1.0 or higher and less than 7.0 (for example, in the range of 2.0 to 5.0).

[0105] The liquid component (LC) preferably contains a protic solvent. By using a protic solvent, the electrically conductive polymer layer can be particularly swelled. In addition to the protic solvent, the liquid component (LC) can contain a solvent other than the protic solvent.

[0106] The protic solvent can contain and can be at least one selected from the group consisting of a glycol, glycerol, a polyglycerol, and a sugar alcohol. The protic solvent can be composed of only one compound, or can contain a plurality of compounds.

[0107] The organic compound (C) and the liquid component (LC) can contain the same compound. For example, they can contain the same polyol, the same glycol (ethylene glycol or the like), or the same sugar alcohol.

[0108] (Liquid (L))

[0109] The liquid (L) can be a liquid containing the above-described organic compound (C) and water. In this case, it is preferable to remove the water from the laminate after impregnating the liquid (L) into the laminate, under conditions in which the organic compound (C) remains in the laminate. The organic compound (C) can be at least one selected from the group consisting of mannitol, a mannitol derivative, xylitol, and a xylitol derivative.

[0110] The liquid (L) may contain at least one selected from sugars, sugar alcohols, epoxy resins, and polyvinyl alcohol (hereinafter, sometimes referred to as "substance X"). By containing substance X in the liquid (L), the adhesion between the conductive polymer layer and the cathode foil can be improved. The content of substance X in the liquid (L) may be in the range of 10% by mass to 70% by mass (e.g., 30% by mass to 50% by mass).

[0111] The sugar alcohol may include at least one selected from mannitol, mannitol derivatives, xylitol, and xylitol derivatives, or may be only one of these at least one. Substance X may be at least one selected from mannitol, mannitol derivatives, xylitol, and xylitol derivatives. Mannitol, mannitol derivatives, xylitol, and xylitol derivatives have the effect of acting as an adhesive to tightly bond the conductive polymer layer to the cathode foil. Examples of mannitol derivatives include compounds in which a portion of the hydroxyl group of mannitol is esterified, compounds in which a portion of the hydroxyl group of mannitol is etherified, and compounds in which a portion of the hydroxyl group of mannitol is anionized to form a salt. Examples of xylitol derivatives include compounds in which a portion of the hydroxyl group of xylitol is esterified, compounds in which a portion of the hydroxyl group of xylitol is etherified, and compounds in which a portion of the hydroxyl group of xylitol is anionized to form a salt.

[0112] The organic solvent contained in the liquid (L) may contain at least one selected from ethylene glycol, diethylene glycol, triethylene glycol, and polyethylene glycol, or it may contain only that one. By containing these substances in the liquid (L), the conductivity of the conductive polymer layer can be improved.

[0113] A preferred example of a liquid (L) is a liquid containing xylitol in at least one organic solvent selected from triethylene glycol and polyethylene glycol.

[0114] (Anode foil)

[0115] Examples of anode foils include metal foils containing at least one valve metal such as titanium, tantalum, aluminum, and niobium, or metal foils containing a valve metal (e.g., aluminum foil). The anode foil may contain the valve metal in the form of an alloy or a compound containing the valve metal. The thickness of the anode foil may be 15 μm or more and 300 μm or less. The surface of the anode foil may be roughened by etching or the like.

[0116] A dielectric layer is formed on the surface of the anode foil. This dielectric layer can be formed by chemically converting the anode foil. In this case, the dielectric layer may contain an oxide of the valve metal (e.g., aluminum oxide). It should be noted that the dielectric layer can function as a dielectric, or it can be formed from a dielectric material other than an oxide of the valve metal.

[0117] In the electrolytic capacitor, the conductive polymer layer can not be formed on the end surface of the anode foil. On the other hand, it is preferable that the dielectric layer is formed on the end surface of the anode foil.

[0118] (cathode foil)

[0119] The cathode foil includes a metal foil (e.g., an aluminum foil). The metal constituting the metal foil can be a valve metal or an alloy including a valve metal. The surface of the metal foil can be roughened by etching or the like. The thickness of the cathode foil can be 15 μm or more and 300 μm or less. The conductive polymer layer can be formed on the surface of the cathode foil by the above-described method.

[0120] As described above, the cathode foil can have an inorganic layer on the surface. The cathode foil having the inorganic layer on the surface can be used as a commercially available product, or can be formed by forming the inorganic layer on the surface of the metal foil (cathode foil). The inorganic layer can be formed by a publicly known method. For example, the inorganic layer can be formed by a vacuum evaporation method or the like. Alternatively, the inorganic layer can be formed by applying a paste containing one selected from the group consisting of carbon (particularly, a conductive carbon material), titanium, and nickel on the metal foil (cathode foil) and then drying the paste. The attachment amount of the inorganic layer can be in the range of 50 mg / m 2 ~ 300 mg / m 2 (e.g., in the range of 70 mg / m 2 ~ 200 mg / m 2 ). Examples of the carbon (particularly, a conductive carbon material) contained in the inorganic layer include graphite, hard carbon, soft carbon, carbon black, and the like. In the case where the inorganic layer contains titanium, the layer can be a layer in which titanium is evaporated, or a layer formed of particles of titanium oxide. The inorganic layer can be a carbon layer. The carbon layer is a layer containing carbon, and can be a layer in which the content of carbon is 50% by mass or more. In the present specification, "inorganic layer" can be replaced with "carbon layer".

[0121] The cathode foil can include a metal foil, an inorganic layer, and a layer containing titanium disposed between the inorganic layer and the metal foil. One example of the cathode foil has a layered structure of an inorganic layer / a layer containing titanium / a metal foil (e.g., an aluminum foil) / a layer containing titanium / an inorganic layer. The layer containing titanium can contain at least one selected from the group consisting of titanium and a titanium compound. Examples of the titanium compound include titanium nitride, titanium oxide, a titanium-aluminum alloy, titanium carbonate, and the like. The method of forming the layer containing titanium is not limited, and the layer can be formed by a publicly known method. For example, the layer containing titanium can be formed by a vacuum evaporation method, a physical evaporation method such as a sputtering method, or the like. The attachment amount of the layer containing titanium can be in the range of 200 mg / m 2 ~ 500 mg / m 2 (e.g., in the range of 250 mg / m 2 ~ 400 mg / m 2 ).

[0122] (separating membrane)

[0123] The separator can use a porous sheet formed using an insulating material. Examples of the porous sheet include woven fabric, nonwoven fabric, and a microporous membrane. The thickness of the separator is not particularly limited and can be in the range of 10 to 300 μm. Examples of the material of the separator include cellulose, polyethylene terephthalate, polybutylene terephthalate, polyphenylene sulfide, vinylon, nylon, aramid, polyimide, polyamide-imide, polyetherimide, rayon, glass, and the like.

[0124] The air permeation resistance of the separator monomer (a separator in which the first conductive polymer layer is not formed) measured using an air permeability tester can be 0.25 kPa s / m or more, or 0.30 kPa s / m or more, and can be 0.40 kPa s / m or less, or 0.35 kPa s / m or less.

[0125] (Outer Container)

[0126] The laminate and the liquid component (LC) are housed in the outer container. The outer container includes a case and / or a sealing resin. It is not limited thereto, and a known case and sealing resin can be used. The sealing resin can include a thermosetting resin. Examples of the thermosetting resin include an epoxy resin, a phenol resin, a silicone resin, a melamine resin, a urea resin, an alkyd resin, a polyurethane, a polyimide, an unsaturated polyester, and the like. The sealing resin can include a filler, a curing agent, a polymerization initiator, and / or a catalyst, and the like.

[0127] Hereinafter, one example of the present disclosure will be specifically described with reference to the drawings. The above-described constitutional elements can be applied to the constitutional elements of one example of the following description. In addition, the constitutional elements of one example of the following description can be changed based on the above-described description. In addition, the matters described below can be applied to the above-described embodiments. In addition, in one example of the following description, the constitutional elements that are not essential for the electrolytic capacitor of the present disclosure can be omitted.

[0128] Figure 1 is a schematic cross-sectional view of the electrolytic capacitor 100 of one example of the present embodiment. Figure 2 is a schematic view of a portion of the capacitor element 10 contained in the electrolytic capacitor 100, which is obtained by unfolding the capacitor element 10.

[0129] The electrolytic capacitor 100 includes a capacitor element 10, a bottom housing 101 for housing the capacitor element 10, a sealing member 102 that blocks the opening of the bottom housing 101, a base plate 103 covering the sealing member 102, leads 104A and 104B extending from the sealing member 102 and through the base plate 103, and lead connectors 105A and 105B connecting the leads to the electrodes of the capacitor element 10. The bottom housing 101 is drawn inward near the opening end, and the opening end is rolled in a manner that tightens it against the sealing member 102.

[0130] Capacitor element 10 is, for example, as Figure 1 The wound body is shown. The wound body includes an anode foil 11 connected to a lead connector 105A, a cathode foil 12 connected to a lead connector 105B, and a sheet 13. The sheet 13 includes a separator and a first conductive polymer layer formed within the gaps of the separator. The capacitor element 10 (wound body) includes a conductive polymer layer (not shown). The conductive polymer layer may contain an organic compound (C). The electrolytic capacitor 100 includes a liquid component (LC) (e.g., electrolyte) impregnated into the capacitor element 10.

[0131] The anode foil 11 and cathode foil 12 are wound together with a sheet 13 in between. The outermost periphery of the wound is secured by a winding fixing tape 14. It should be noted that... Figure 2 This indicates the unfolded state of a portion of the fixed winding before its outermost circumference.

[0132] An electrolytic capacitor may have at least one capacitor element or multiple capacitor elements. The number of capacitor elements in an electrolytic capacitor is determined by its intended use.

[0133] (Postscript)

[0134] The following technologies are disclosed through the above description.

[0135] (Technology 1)

[0136] An electrolytic capacitor comprises a laminate and a liquid component impregnated in the laminate.

[0137] The aforementioned laminate includes an anode foil having a dielectric layer on its surface, a cathode foil, and a sheet disposed between the anode foil and the cathode foil.

[0138] The aforementioned sheet includes a diaphragm and a first conductive polymer layer formed within the pores of the diaphragm.

[0139] The resistivity of the above-mentioned sheet material in the thickness direction is below 300 kΩ·cm.

[0140] The air permeation resistance of the sheet measured by an air permeation tester is 0.40 kPa-s / m or more and 0.60 kPa-s / m or less.

[0141] (Technology 2)

[0142] The electrolytic capacitor according to Technology 1, wherein the surface density of the first conductive polymer layer is 0.1 mg / cm 2 or more and 1.0 mg / cm 2 or less.

[0143] (Technology 3)

[0144] The electrolytic capacitor according to Technology 1 or 2, wherein the average thickness of the sheet is 20 μm or more and 70 μm or less.

[0145] (Technology 4)

[0146] The electrolytic capacitor according to any one of Technologies 1 to 3, further comprising a second conductive polymer layer formed on the dielectric layer.

[0147] (Technology 5)

[0148] The electrolytic capacitor according to any one of Technologies 1 to 4, wherein the cathode foil has an inorganic layer on the surface,

[0149] The first conductive polymer layer is tightly adhered to the inorganic layer.

[0150] (Technology 6)

[0151] The electrolytic capacitor according to any one of Technologies 1 to 5, wherein the laminate is a wound body.

[0152] (Technology 7)

[0153] A sheet for an electrolytic capacitor, wherein the electrolytic capacitor includes a capacitor element and a liquid component impregnated into the capacitor element,

[0154] The sheet for an electrolytic capacitor includes a separator and a conductive polymer layer formed in a void of the separator,

[0155] The sheet has a thickness-direction resistivity of 300 kΩ-cm or less,

[0156] The sheet has an air permeation resistance of 0.40 kPa-s / m or more and 0.60 kPa-s / m or less, measured by an air permeation tester.

[0157] (Technology 8)

[0158] The sheet for an electrolytic capacitor according to the above-mentioned technique 7, wherein the surface density of the conductive polymer layer is 0.1 mg / cm 2 0.1 mg / cm and 1.0 mg / cm 2 0.1 mg / cm and 1.0 mg / cm

[0159] (Technique 9)

[0160] The sheet for an electrolytic capacitor according to the above-mentioned technique 7 or 8, wherein the average thickness of the sheet is 20 μm or more and 70 μm or less.

[0161] (Technique 10)

[0162] A method for manufacturing an electrolytic capacitor, comprising:

[0163] a preparation step of preparing an anode foil having a dielectric layer on a surface thereof;

[0164] a sheet formation step of forming a sheet including a separator and a first conductive polymer layer formed in a void of the separator;

[0165] a laminate formation step of forming a laminate by laminating the anode foil, a cathode foil, and the sheet in a manner that the sheet is disposed between the anode foil and the cathode foil; and

[0166] an impregnation step of impregnating a liquid component into the laminate,

[0167] the sheet formation step includes:

[0168] a first coating liquid application step of applying a first coating liquid containing a first conductive polymer and a first liquid medium into the void of the separator; and

[0169] a first liquid medium removal step of forming the sheet by removing at least a portion of the first liquid medium from the first coating liquid,

[0170] a specific resistance in a thickness direction of the sheet is 300 kΩ·cm or less,

[0171] an air permeation resistance of the sheet measured by an air permeability tester is 0.40 kPa·s / m or more and 0.60 kPa·s / m or less.

[0172] (Technique 11)

[0173] The method for manufacturing an electrolytic capacitor according to the above-mentioned technique 10, wherein, in the sheet formation step, a ratio (Vd / Vs) of a volume Vd of the first coating liquid impregnated into the separator with respect to a volume Vs of the void of the separator is 0.95 or more.

[0174] (Technique 12)

[0175] The manufacturing method of the electrolytic capacitor according to any one of techniques 10 to 12, wherein the surface density of the first conductive polymer layer is 0.1 mg / cm 2 0.1 mg / cm and 1.0 mg / cm 2 or more.

[0176] (Technique 13)

[0177] The manufacturing method of the electrolytic capacitor according to any one of techniques 10 to 12, wherein the average thickness of the sheet is 20 μm or more and 70 μm or less.

[0178] (Technique 14)

[0179] The manufacturing method of the electrolytic capacitor according to any one of techniques 10 to 13, wherein the manufacturing method further includes a polymer layer forming step of forming a second conductive polymer layer on the surface of the dielectric layer before the stack forming step,

[0180] The polymer layer forming step includes:

[0181] a second coating liquid application step of applying a second coating liquid containing a second conductive polymer and a second liquid medium to the surface of the dielectric layer; and

[0182] a second liquid medium removing step of forming the second conductive polymer layer by removing at least a part of the second liquid medium from the second coating liquid.

[0183] (Technique 15)

[0184] The manufacturing method of the electrolytic capacitor according to any one of techniques 10 to 14, wherein the cathode foil has an inorganic layer on the surface,

[0185] the first conductive polymer layer is tightly adhered to the inorganic layer.

[0186] (Technique 16)

[0187] The manufacturing method of the electrolytic capacitor according to any one of techniques 10 to 15, wherein the stack is a wound body.

[0188] Example

[0189] Hereinafter, the present disclosure will be described in more detail based on an example, but the present disclosure is not limited to the example. In the example, a plurality of electrolytic capacitors were produced by the following method and evaluated.

[0190] (Capacitor Al)

[0191] An electrolytic capacitor (Capacitor Al) was produced by the following method.

[0192] (a) Preparation of constituent members

[0193] An aluminum foil (thickness: 100 μm) was subjected to an etching treatment to roughen the surface of the aluminum foil. The surface of the roughened aluminum foil was subjected to a chemical conversion treatment to form a dielectric layer. Thus, an anode foil having a dielectric layer formed on both surfaces was obtained. A carbon layer was formed on both surfaces of an aluminum foil (thickness: 50 μm) to be a cathode foil. The carbon layer was formed by a vacuum evaporation method.

[0194] As a separator, a nonwoven fabric (thickness: 50 μm) was prepared. The nonwoven fabric was a nonwoven fabric composed of polyester fibers, aramid fibers, and cellulose.

[0195] (b) Formation of a conductive polymer layer

[0196] As a coating liquid, a dispersion liquid (commercially available product) in which particles of polyethylene dioxythiophene (PEDOT) doped with polystyrene sulfonic acid (PSS) were dispersed in water was prepared. The concentration of the conductive polymer component in the coating liquid was 2.0 wt.%.

[0197] Next, the coating liquid was applied to one surface (the surface of the dielectric layer) of the anode foil using a gravure coater. Then, a drying treatment was performed to form a second conductive polymer layer on one surface (the surface of the dielectric layer) of the anode foil. The drying treatment was performed by heating the anode foil on which the coating liquid was applied at 125°C for 5 minutes. Next, a second conductive polymer layer was also formed on the other surface (the surface of the dielectric layer) of the anode foil by the same method.

[0198] Next, the above coating liquid was applied to the separator and then subjected to a drying treatment to form a first conductive polymer layer in the voids of the separator. Thus, a sheet a1 including the separator and the first conductive polymer layer was formed.

[0199] (c) Formation of a wound body (laminate)

[0200] The anode foil, the cathode foil, and the sheet a1 were cut into predetermined sizes, respectively. An anode lead tab and a cathode lead tab were attached to the anode foil and the cathode foil, respectively. Next, the anode foil and the cathode foil were wound with the sheet a1 interposed therebetween. At this time, the end portions of the outer surfaces of the wound body were fixed with a winding fixing tape. An anode lead and a cathode lead were attached to the end portions of the respective lead tabs protruding from the wound body. The obtained wound body was again subjected to a chemical conversion treatment to form a dielectric layer on the end surface of the anode foil. Thus, a capacitor element was obtained.

[0201] (d) Impregnation of liquid components

[0202] An electrolytic solution (liquid component) was prepared by dissolving phthalic acid, triethylamine (alkali component) in ethylene glycol (solvent) at a concentration of 25 mass% in total. The capacitor element was immersed in the electrolytic solution for 5 minutes in a reduced pressure atmosphere (40 kPa). Thus, the electrolytic solution was impregnated into the capacitor element (laminate).

[0203] (e) Sealing of the capacitor element

[0204] The capacitor element impregnated with the electrolytic solution was sealed to produce an electrolytic capacitor as shown in Figure 1 . Then, aging was performed at 95°C for 90 minutes while applying a voltage. Thus, an electrolytic capacitor (capacitor Al) was produced.

[0205] (capacitors A2 to A3 and C1 to C2)

[0206] The sheets a2 to a3 and cl to c2 were produced by the same conditions and methods as in the production of the sheet al of the capacitor Al except that the coating amount of the coating solution on the separator was changed. The coating amount of the coating solution was changed by adjusting the settings of the gravure coater. By increasing the coating amount of the coating solution, the amount of the first conductive polymer filled into the voids of the separator increased, and the air permeation resistance of the sheet became larger. The electrolytic capacitors (capacitors A2 to A3 and C1 to C2) were produced by the same methods and conditions as in the production of the capacitor Al except that these sheets were used instead of the sheet al.

[0207] (determination of the air permeation resistance of the sheet)

[0208] The sheets al to a3 and cl to c2 produced were measured for the air permeation resistance by using an air permeability tester. Specifically, the measurement was performed by the following method. First, the sheet was cut into a 5 cm square to produce a sample. The sample was set to the opening portion (opening area: 2π cm 2 ) of the air permeability tester. Next, air was made to permeate the sample at a permeation rate of 4 cm 3 / cm 2 ·s (4 cm 2 per 1 cm 3 per second). Then, the pressure loss at that time was measured. The air permeation resistance was calculated from the measured pressure loss. The air permeability tester used was an air permeation resistance tester (KES-F8) by KATO TECH Co., Ltd.

[0209] (evaluation of the capacitor)

[0210] The equivalent series resistance (ESR) and the leakage current were measured for the produced capacitors. The evaluation results are shown in Table 1. It is preferable that the ESR and the leakage current be low.

[0211] [table 1]

[0212]

[0213] Capacitors Al to A3 are electrolytic capacitors (E) of the present disclosure manufactured by the manufacturing method (M). Capacitors Cl to C2 are comparative capacitors. Sheets al to a3 are sheets (S) of the present disclosure. Sheets cl to c2 are comparative sheets.

[0214] As shown in Table 1, the ESR and the leakage current of the capacitors Al to A3 are low. It is considered that this is because the air permeation resistance of the sheets al to a3 is low. On the other hand, the ESR of the capacitor Cl is high. It is considered that the ESR of the capacitor Cl becomes high because the air permeation resistance of the sheet cl is low and the amount of the conductive high molecular layer formed on the sheet cl is too small. The air permeation resistance of the sheet c2 is high and the leakage current of the capacitor C2 is high. It is considered that the amount of the electrolyte solution permeated and held in the sheet c2 decreases because the amount of the conductive high molecular layer formed on the sheet c2 is too large, as a result of which the function of repairing the dielectric layer decreases and the leakage current of the capacitor C2 becomes high.

[0215] Industrial applicability

[0216] The present disclosure can be used for electrolytic capacitors.

[0217] Explanation of reference numerals

[0218] 10: Capacitor element

[0219] 11: Anode foil

[0220] 12: Cathode foil

[0221] 13: Sheet

[0222] 100: Electrolytic capacitor

Claims

1. An electrolytic capacitor comprising a laminate and a liquid component impregnated into the laminate, the laminate comprising an anode foil having a dielectric layer on a surface thereof, a cathode foil, and a sheet disposed between the anode foil and the cathode foil, the sheet comprising a separator and a first electrically conductive polymer layer formed in a void of the separator, a resistivity in a thickness direction of the sheet is 300 kΩ-cm or less, a gas permeation resistance of the sheet measured by a gas permeability tester is 0.40 kPa-s / m or more and 0.60 kPa-s / m or less.

2. The electrolytic capacitor of claim 1, wherein, The areal density of the first electrically conductive polymer layer is 0.1 mg / cm 2 The areal density of the first electrically conductive polymer layer is 0.1 mg / cm 2 The areal density of the first electrically conductive polymer layer is 0.1 mg / cm 3. The electrolytic capacitor of claim 1, wherein, an average thickness of the sheet is 20 μm or more and 70 μm or less.

4. The electrolytic capacitor according to claim 1, further comprising a second electrically conductive polymer layer formed on the dielectric layer.

5. The electrolytic capacitor of claim 1, wherein, the cathode foil has an inorganic layer on a surface thereof, the first electrically conductive polymer layer is in close contact with the inorganic layer.

6. The electrolytic capacitor of claim 1, wherein, the laminate is a wound body.

7. A sheet material for electrolytic capacitors, wherein, the electrolytic capacitor comprises a capacitor element and a liquid component impregnated into the capacitor element, the sheet for the electrolytic capacitor comprises a separator and an electrically conductive polymer layer formed in a void of the separator, a resistivity in a thickness direction of the sheet is 300 kΩ-cm or less, a gas permeation resistance of the sheet measured by a gas permeability tester is 0.40 kPa-s / m or more and 0.60 kPa-s / m or less.

8. The sheet for electrolytic capacitors according to claim 7, wherein The surface density of the conductive polymer layer is 0.1 mg / cm 2 The surface density of the conductive polymer layer is 0.1 mg / cm 2 The surface density of the conductive polymer layer is 0.1 mg / cm 9. The sheet for electrolytic capacitors according to claim 7, wherein an average thickness of the sheet is 20 μm or more and 70 μm or less.

10. A method for manufacturing an electrolytic capacitor, comprising: a preparation step of preparing an anode foil having a dielectric layer on a surface thereof; a sheet forming step of forming a sheet comprising a separator and a first electrically conductive polymer layer formed in a void of the separator; a laminate forming step of forming a laminate by laminating the anode foil, a cathode foil, and the sheet in a manner that the sheet is disposed between the anode foil and the cathode foil; and an impregnation step of impregnating a liquid component into the laminate, the sheet forming step comprises: a first coating liquid imparting step of imparting a first coating liquid containing a first electrically conductive polymer and a first liquid medium into the void of the separator; and a first liquid medium removing step of forming the sheet by removing at least a part of the first liquid medium from the first coating liquid, a resistivity in a thickness direction of the sheet is 300 kΩ-cm or less, a gas permeation resistance of the sheet measured by a gas permeability tester is 0.40 kPa-s / m or more and 0.60 kPa-s / m or less. in the sheet forming step, a ratio of a volume Vd of the first coating liquid impregnated into the separator to a volume Vs of the void of the separator, i.e., Vd / Vs, is 0.95 or more. an average thickness of the sheet is 20 μm or more and 70 μm or less.

11. The method of manufacturing an electrolytic capacitor according to claim 10, wherein, the method further comprises, before the laminate forming step, a polymer layer forming step of forming a second electrically conductive polymer layer on a surface of the dielectric layer, 12. The method of manufacturing an electrolytic capacitor as claimed in claim 10, wherein, The areal density of the first electrically conductive polymer layer is 0.1 mg / cm 2 above and 1.0 mg / cm 2 below.

13. The method of manufacturing an electrolytic capacitor as claimed in claim 10, wherein, the polymer layer forming step comprises:

14. The method of manufacturing an electrolytic capacitor of claim 10, wherein, a second coating liquid imparting step of imparting a second coating liquid containing a second electrically conductive polymer and a second liquid medium to the surface of the dielectric layer; and ​ ​ The second liquid medium removing step forms the second electroconductive polymer layer by removing at least a part of the second liquid medium from the second coating liquid.

15. The method of manufacturing an electrolytic capacitor of claim 10, wherein, The cathode foil has an inorganic layer on a surface, The first electroconductive polymer layer is tightly adhered to the inorganic layer.

16. The method of manufacturing an electrolytic capacitor of claim 10, wherein, The laminate is a roll body.

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