Electrolytic capacitor and method for manufacturing 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, a cathode foil, a separator, a first conductive polymer layer held by the separator, and a second conductive polymer layer formed on the dielectric layer. The first conductive polymer layer contains a first conductive polymer, a polyvinyl alcohol polymer, and a boric acid compound. The second conductive polymer layer contains a second conductive polymer. The boric acid compound is at least one type of boric acid compound selected from the group consisting of boric acid and boric acid compounds. At least a portion of the polyvinyl alcohol polymer in the first conductive polymer layer is crosslinked.

Description

Technical Field

[0001] This disclosure relates to electrolytic capacitors and methods for manufacturing electrolytic capacitors. Background Technology

[0002] Electrolytic capacitors are known as windings comprising an anode foil, a separator, and a cathode foil. One example of such an electrolytic capacitor includes a conductive polymer layer disposed within the winding. The conductive polymer layer can be formed by impregnating the winding with a dispersion containing conductive polymers. Various schemes have been proposed for electrolytic capacitors comprising a conductive polymer layer.

[0003] Claim 1 of Patent Document 1 (Japanese Patent No. 6911910) describes "an electrolytic capacitor, characterized in that a solid electrolyte layer is formed in a capacitor element formed by winding an anode electrode foil and a cathode electrode foil with a separator in between, the solid electrolyte layer using particles containing conductive polymers and a dispersion of conductive polymer compounds containing sorbitol or sorbitol and polyols, and containing 60 to 92 wt% of the sorbitol or sorbitol and polyols, and the voids in the capacitor element in which the solid electrolyte layer is formed are filled with an electrolyte containing 10 wt% or more ethylene glycol in the solvent."

[0004] Claim 1 of Patent Document 2 (Japanese Patent Publication No. 2019-516241) describes "a capacitor comprising a processed element, the processed element comprising: an anode having a dielectric on its surface and an anode conductive polymer layer on the surface of the dielectric; a cathode having a cathode conductive polymer layer; a conductive membrane between the anode and the cathode; an anode lead electrically in contact with the anode; and a cathode lead electrically in contact with the cathode."

[0005] Claim 1 of Patent Document 3 (International Publication No. 2021 / 125182) describes "a hybrid electrolytic capacitor, characterized in that it comprises a cathode, an anode, and a composite electrolyte layer, wherein the cathode has a cathode substrate made of a valve metal, an oxide layer disposed on the surface of the cathode substrate and made of an oxide of the valve metal, an inorganic conductive layer disposed on the surface of the oxide layer and comprising an inorganic conductive material, and an organic conductive layer disposed on the surface of the inorganic conductive layer and comprising a conductive polymer; the anode has an anode substrate made of a valve metal, and a dielectric layer disposed on the surface of the anode substrate and made of an oxide of the valve metal constituting the anode substrate; the composite electrolyte layer has a solid electrolyte layer disposed between and in contact with the organic conductive layer of the cathode and the dielectric layer of the anode and comprising particles of conductive polymer, and an electrolyte filling the particles of conductive polymer in the solid electrolyte layer."

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent No. 6911910

[0009] Patent Document 2: Japanese Patent Publication No. 2019-516241

[0010] Patent Document 3: International Publication No. 2021 / 125182 Summary of the Invention

[0011] One aspect of this disclosure relates to an electrolytic capacitor comprising a laminate and a liquid component impregnated in the laminate. The laminate comprises an anode foil having a dielectric layer on its surface, a cathode foil, a separator, a first conductive polymer layer held in the separator, and a second conductive polymer layer formed on the dielectric layer. The first conductive polymer layer contains a first conductive polymer, a polyvinyl alcohol-based polymer, and a boric acid-based compound. The second conductive polymer layer contains a second conductive polymer. The boric acid-based compound is at least one boric acid-based compound selected from boric acid and boric acid compounds. At least a portion of the polyvinyl alcohol-based polymer in the first conductive polymer layer is crosslinked.

[0012] Another aspect of this disclosure relates to a method for manufacturing an electrolytic capacitor. The manufacturing method includes: a preparation step of preparing an anode foil having a dielectric layer on its surface; a first polymer layer forming step of forming a first conductive polymer layer comprising a first conductive polymer and a polyvinyl alcohol-based polymer within the voids of a separator; a second polymer layer forming step of forming a second conductive polymer layer on the surface of the dielectric layer; a laminate forming step of laminating the anode foil, the cathode foil, and the separator in such a manner that the separator is disposed between the anode foil and the cathode foil, thereby forming a laminate comprising the first conductive polymer layer and the second conductive polymer layer; an impregnation step of impregnating the laminate with a liquid component containing at least one boric acid-based compound selected from boric acid and boric acid compounds into the laminate; and a crosslinking step of heating the laminate impregnated with the liquid component to a temperature of 85°C or higher. In the crosslinking step, at least a portion of the polyvinyl alcohol-based polymer in the first conductive polymer layer is crosslinked by the at least one boric acid-based compound.

[0013] According to this disclosure, it is possible to obtain an electrolytic capacitor containing liquid components and a conductive polymer layer with low ESR. Attached Figure Description

[0014] Figure 1This is a side view schematically illustrating an example of an electrolytic capacitor according to an embodiment of the present disclosure.

[0015] Figure 2 This is an exploded perspective view of a capacitor element schematically illustrating an example of an embodiment of the present disclosure. Detailed Implementation

[0016] The following is a brief explanation of the problems in the existing technology.

[0017] Because dispersions containing conductive polymers have high viscosity, even when the dispersion penetrates the wound material, a sufficiently conductive polymer layer may not form inside the wound material. This inadequate formation of the conductive polymer layer can contribute to an increase in the equivalent series resistance (ESR).

[0018] The reduction of ESR in electrolytic capacitors has been a long-standing pursuit. This disclosure provides an electrolytic capacitor comprising a liquid component and a conductive polymer layer, which is capable of reducing ESR.

[0019] The following examples illustrate embodiments of the present invention, but the present invention is not limited to the examples described below. In the following description, specific numerical values ​​and materials are sometimes illustrated, but other numerical values ​​and materials can be applied as long as the invention disclosed herein can be implemented. In this specification, the phrase "numerical value A to numerical value B" includes both numerical value A and numerical value B, and can be replaced with "numerical value A or higher and numerical value B or lower." In the following description, when lower and upper limits of numerical values ​​related to specific physical properties, conditions, etc., are illustrated, any of the illustrated lower limits can be arbitrarily combined with any of the illustrated upper limits, as long as the lower limit is not higher than the upper limit.

[0020] (Manufacturing method of electrolytic capacitors)

[0021] Hereinafter, the manufacturing method of this embodiment will sometimes be referred to as "manufacturing method (M)". The manufacturing method (M) includes, in sequence, a preparation step, a polymer layer forming step (a first polymer layer forming step and a second polymer layer forming step), a laminate forming step, an impregnation step, and a crosslinking step. The order of the first polymer layer forming step and the second polymer layer forming step is arbitrary; either one can be performed first. These steps will be described later.

[0022] As described later, in manufacturing method (M), a boric acid-based compound is used to crosslink the polyvinyl alcohol-based polymer contained in the conductive polymer layer. This improves the adhesion between the anode foil and the separator, as well as between the cathode foil and the separator, thereby reducing the ESR of the electrolytic capacitor. Furthermore, the retention of the electrolyte in the conductive polymer layer is improved, thus enhancing the repairability of the dielectric layer and increasing the voltage withstand capability of the electrolytic capacitor. Moreover, during long-term use, electrolyte loss due to evaporation is suppressed, thereby extending the lifespan of the electrolytic capacitor.

[0023] (Preparation process)

[0024] The preparation process involves preparing an anode foil with a dielectric layer on its surface. The anode foil with the dielectric layer can be a commercially available product, or it can be formed by forming the dielectric layer on the surface of a metal foil (anode foil). The dielectric layer can be formed using known methods. For example, the dielectric layer can be formed by oxidizing the surface of the metal foil (anode foil).

[0025] (First polymer layer formation process)

[0026] The first polymer layer forming step is a step of forming a first conductive polymer layer comprising a first conductive polymer and a polyvinyl alcohol-based polymer within the voids of the diaphragm. The first polymer layer forming step may include: a first coating liquid application step, which applies a first coating liquid containing the first conductive polymer, the polyvinyl alcohol-based polymer, and a first liquid medium into the voids of the diaphragm; and a first liquid medium removal step, which forms the first conductive polymer layer within the voids of the diaphragm by removing at least a portion of the first liquid medium from the first coating liquid.

[0027] Polyvinyl alcohol (PVA) polymers are polymers that contain -CH₂CH(OH)- (hereinafter sometimes referred to as "vinyl alcohol units") as structural units. The proportion of vinyl alcohol units in all structural units can be 40 mol% or more, 60 mol% or more, or 80 mol% or more. Examples of structural units other than vinyl alcohol units include vinyl acetate units. The combined proportion of vinyl alcohol units and vinyl acetate units in all structural units can be 60 mol% or more, or 80 mol% or more.

[0028] Examples of polyvinyl alcohol (PVA) polymers include polyvinyl alcohol (PVA) and its derivatives. PVA polymers can be obtained by saponifying a polymer of vinyl acetate. Alternatively, PVA polymers can be obtained by saponifying a copolymer of vinyl acetate with other monomers.

[0029] The weight-average molecular weight of polyvinyl alcohol polymers can be in the range of 500 to 3500 (e.g., 1000 to 2000).

[0030] The concentration of polyvinyl alcohol-based polymer in the first coating solution can be in the range of 0.01% by mass to 3.0% by mass (e.g., 0.05% by mass to 0.5% by mass). In the first coating solution, the ratio of the mass of the polyvinyl alcohol-based polymer (Wp) to the mass of the first conductive polymer (Wc), Wp / Wc, can be 0.01 or higher, and can be in the range of 0.01 to 3.0 (e.g., 0.05 to 0.5). That is, in the first conductive polymer layer, the ratio of the mass of the polyvinyl alcohol-based polymer (Wp) to the mass of the first conductive polymer (Wc), Wp / Wc, can be 0.01 or higher, and can be in the range of 0.01 to 3.0 (e.g., 0.05 to 0.5).

[0031] (Second polymer layer formation process)

[0032] The second polymer layer forming process is a process of forming a second conductive polymer layer on the surface of the dielectric layer. The second polymer layer forming process may include: a second coating solution application process, in which a second coating solution containing a second conductive polymer and a second liquid medium is applied to the surface of the dielectric layer (the dielectric layer on the surface of the anode foil); and a second liquid medium removal process, in which at least a portion of the second liquid medium is removed from the second coating solution to form a second conductive polymer layer on the surface of the dielectric layer.

[0033] The second coating liquid may or may not contain polyvinyl alcohol-based polymers. The first conductive polymer and the second conductive polymer may be the same or different. The first liquid medium and the second liquid medium may be the same or different. The first coating liquid and the second coating liquid may be the same or different.

[0034] Conductive polymers (first conductive polymer, second conductive polymer) can be dispersed in the coating solution (first coating solution, second coating solution) in the form of particles. Examples of conductive polymers will be described later.

[0035] In the first coating solution, the ratio (Wp / Wc) of the mass of the polyvinyl alcohol-based polymer Wp to the mass of the first conductive polymer can be 0.01 or more, 0.05 or more, or 0.1 or more, or 3.0 or less, or 0.5 or less. By setting the ratio Wp / Wc to 0.01 or more, the stability of the coating solution can be maintained, and the amount of polyvinyl alcohol-based polymer crosslinked by reaction with boric acid compounds is sufficient.

[0036] The liquid medium (first liquid medium, second liquid medium) is not particularly limited, and any liquid medium capable of forming a polymer layer can be used. Examples of liquid media include water, organic solvents (e.g., alcohols), and mixtures thereof.

[0037] The liquid medium may contain water and an organic compound that does not boil at 100°C under 1 atmosphere (101325 Pa). Hereinafter, this organic compound will sometimes be referred to as "organic compound (C)". Organic compound (C) can be a single compound or a combination of multiple compounds.

[0038] The method of applying the coating liquid (first coating liquid, second coating liquid) is not limited and can be applied by known methods. For example, it can be done by using a coating machine, by spraying the coating liquid, or by impregnating the object to be coated in the coating liquid. Examples of methods using a coating machine include gravure coating and die coating. In one example of gravure coating, firstly, the coating liquid is adhered to a transfer member (gravure roller, etc.), and then excess coating liquid is removed from the transfer member. Next, by transferring the coating liquid adhered to the transfer member to a designated member (anode foil, cathode foil, or diaphragm), a layer of coating liquid of uniform thickness can be adhered to that member. In addition, the viscosity of the coating liquid can be, for example, 10 mPa·s or more (e.g., 100 mPa·s or more) and 200 mPa·s or less. In this case, it is easy to coat the anode foil, cathode foil, and diaphragm with the coating liquid, and it is easy for the coating liquid to penetrate into the diaphragm. It should be noted that the viscosity of the coating solution was determined at room temperature (20°C) using a vibratory viscometer (e.g., SEKONIC, VM-100A).

[0039] The method for removing at least a portion of the liquid medium from the coating liquid is not particularly limited and can be performed by heating, etc. When the coating liquid contains an organic compound (C), heating can be performed so that the organic compound (C) remains in the polymer layer. For example, when the coating liquid contains an organic compound (C) and water (liquid medium), by heating the coating liquid at a temperature above 100°C where the organic compound (C) does not boil or decompose, water can be removed from the coating liquid, while the organic compound (C) remains in the polymer layer. The heating temperature can be above 100°C, above 120°C, or above 140°C, or below 200°C or below 160°C. The heating temperature can be in the range of 100°C to 200°C. The heating time is not particularly limited, as long as it is sufficient to remove a portion of the liquid medium. An example heating time is in the range of 5 to 60 minutes.

[0040] By leaving the conductive polymer layers (first conductive polymer layer and second conductive polymer layer) within the organic compound (C), the shrinkage of the conductive polymer layers during the removal of the liquid medium from the coating solution can be reduced. As a result, liquid components (e.g., electrolyte) can easily penetrate into the conductive polymer layers during subsequent impregnation processes. Consequently, the dielectric layer (oxide film) formation function of the liquid components is more readily utilized, and leakage current is reduced.

[0041] In a preferred example of the manufacturing method (M), the liquid medium of the coating solution is removed such that the water content in the coating solution is 40% by mass or more (e.g., 50% by mass or more), and the mass of the organic compound (C) in the conductive polymer layer is greater than the mass of the water in the conductive polymer layer. If the water content in the coating solution is high, the electrolyte can easily penetrate into the conductive polymer layer after it is formed.

[0042] (Laminated body formation process)

[0043] The laminate formation process is a process of forming a laminate containing a first conductive polymer layer and a second conductive polymer layer by laminating an anode foil, a cathode foil and a separator in such a way that a separator is disposed between the anode foil and the cathode foil.

[0044] There is no particular limitation on the method for forming the laminate; it can be formed by known methods. The laminate can be a wound body. In this case, during the laminate forming process, the anode foil, cathode foil, and diaphragm can be wound together by placing a diaphragm between the anode foil and the cathode foil to form a wound body. In the wound body, the anode foil, cathode foil, and diaphragm are stacked in the radial direction of the wound body.

[0045] A laminate can be formed by stacking a flat anode foil, a flat cathode foil, and a flat diaphragm in one direction. For example, multiple anode foils, multiple cathode foils, and multiple diaphragms can be stacked in one direction to form a laminate. In a typical example of this laminate, the anode foils and cathode foils are arranged alternately, and the diaphragm is disposed between the anode foils and cathode foils.

[0046] (Immersion process)

[0047] The impregnation process is a process of impregnating a liquid component containing at least one boric acid compound selected from boric acid and boric acid compounds into a laminate. Hereinafter, this 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 electrolyte.

[0048] Examples of boric acid compounds include boric acid and borates. Examples of borates include ammonium salts of boric acid (ammonium borate, etc.), sodium salts of boric acid (sodium tetraborate, etc.), and potassium salts of boric acid. Boric acid compounds can be at least one selected from boric acid, ammonium salts of boric acid, sodium salts of boric acid, and potassium salts of boric acid.

[0049] The concentration of boric acid compounds in the liquid component (LC) can be in the range of 0.5% by mass to 5.0% by mass (e.g., 1.5% by mass to 3.5% by mass).

[0050] The liquid component (LC) may further contain at least one selected from ethylene glycol, diethylene glycol, triethylene glycol, ethylene glycol condensates with a molecular weight of less than 250, glycerol, γ-butyrolactone, and sulfolane. By including these compounds in the liquid component (LC), the voltage withstand capability of the capacitor can be improved. Furthermore, the loss of electrolyte due to evaporation during long-term use can be suppressed, thereby extending the lifespan of the electrolytic capacitor.

[0051] (Cross-linking process)

[0052] The crosslinking process involves heating the laminate impregnated with the liquid component (LC) to a temperature of 85°C or higher. In this crosslinking process, at least a portion of the polyvinyl alcohol (PVA) polymer in the first conductive polymer layer is crosslinked using at least one boric acid compound. Specifically, the crosslinking process involves heating the laminate impregnated with the liquid component (LC) to a temperature of 85°C or higher, thereby crosslinking the PVA polymer in the first conductive polymer layer using a boric acid compound. When the second conductive polymer layer contains PVA polymers, the PVA polymers in the second conductive polymer layer are also crosslinked using a boric acid compound. By crosslinking the PVA polymers in the conductive polymer layer, the aforementioned effects can be obtained.

[0053] The heating temperature of the laminate in the crosslinking process is above 85°C, but can be above 100°C or above 105°C. This heating temperature can be below 180°C, below 160°C, or below 135°C. The heating time of the laminate in the crosslinking process varies depending on the heating temperature and can be in the range of 30 minutes to 180 minutes (e.g., 60 minutes to 90 minutes).

[0054] Heating the laminates during the crosslinking process promotes the re-oxidation of the anode foil surface. That is, it oxidizes areas on the anode foil surface where the oxide film formation is insufficient. As a result, leakage current is reduced. Furthermore, during the crosslinking process, the anode foil can undergo further chemical transformation by applying a voltage between the anode and cathode foils. Alternatively, the re-chemical transformation of the anode foil can be performed separately from the crosslinking process.

[0055] As described above, a capacitor element can be obtained. Then, other processes can be performed as needed. For example, a process of encapsulating the capacitor element impregnated with a liquid component (LC) into an outer casing can be performed. It should be noted that a crosslinking process can also be performed after the process of encapsulating the capacitor element impregnated with the liquid component (LC) into the outer casing.

[0056] The manufacturing method (M) may include a liquid application step and a removal step sequentially after the laminate formation step and before the impregnation step. The liquid application step is the step of impregnating a liquid (hereinafter, sometimes referred to as "liquid (L)") into the laminate. The removal step is the step of removing at least a portion of the liquid (L) impregnated into the laminate. The liquid (L) may be a liquid comprising water as a main component and an organic compound (C) that does not boil at 100°C under 1 atmosphere. In this case, the removal step may be a step of removing a portion of the aforementioned liquid (L) impregnated into the laminate such that the mass of the organic compound (C) in the laminate is greater than the mass of the water in the laminate. The liquid (L) may be a liquid containing an organic solvent.

[0057] The liquid (L) used in the liquid application process can be a liquid obtained by removing the conductive polymer component from the second coating liquid used in the second polymer layer formation process. The liquid impregnation in the liquid application process can be performed using a method exemplified for the coating liquid application process of the polymer layer formation process. The removal of liquid in the removal process can be performed using a method exemplified for the liquid medium removal process of the polymer layer formation process. By performing the liquid application and removal processes, the adhesion between the first and second conductive polymer layers, as well as the adhesion between the first conductive polymer layer and the cathode foil, can be improved. It should be noted that the conductive polymer layer containing polyvinyl alcohol-based polymers crosslinked through the crosslinking process has sufficient adhesiveness; therefore, the adhesion between the first and second conductive polymer layers, as well as the adhesion between the first conductive polymer layer and the cathode foil, can be improved. Therefore, the liquid application process is not mandatory.

[0058] In an electrolytic capacitor manufactured by manufacturing method (M), the cathode foil may have an inorganic layer on its surface, and a conductive polymer layer may be bonded to the inorganic layer.

[0059] When the cathode foil is composed solely of metal foil (e.g., aluminum foil), an oxide layer forms on the surface of the metal foil, and the cathode foil also generates electrostatic capacitance. As a result, due to the combined capacitance of the anode foil and the cathode foil, the overall capacitance of the capacitor sometimes decreases. This problem can be suppressed by covering the surface of the metal foil with an inorganic layer, etc. That is, by forming an inorganic layer, only the capacitance of the anode foil can be drawn out. On the other hand, if the adhesion between the conductive polymer layer and the inorganic layer is low, the ESR becomes high. By performing the above-described liquid-applying process, the adhesion between the first conductive polymer layer and the inorganic layer can be improved.

[0060] Inorganic layers tend to repel water. Therefore, in conventional methods that form conductive polymer layers by impregnating an aqueous dispersion of conductive polymers into a laminate (capacitor element), the conductive polymers have difficulty penetrating between the inorganic layer of the cathode foil and the anode foil in the laminate. Consequently, a uniform conductive polymer layer cannot be formed on the separator disposed between the cathode and anode foils, leading to an increase in ESR. In the manufacturing method (M), a separator with a first conductive polymer layer pre-formed is used to form the laminate (capacitor element). Therefore, uneven distribution of the first conductive polymer within the separator can be suppressed.

[0061] The areal density of the conductive polymer layers (first conductive polymer layer and second conductive polymer layer) can be 0.05 mg / cm³. 2 Above, 0.1 mg / cm 2 Above, or 0.3 mg / cm 2 The above can be 1.0 mg / cm³ 2 Below, or 0.5 mg / cm 2 For example, the areal density of the conductive polymer layer can be 0.05 mg / cm³. 2 Above and 1.0 mg / cm 2 The following describes how an electrolytic capacitor with exceptionally low ESR can be obtained based on this configuration. It should be noted that areal density refers to the mass per unit area. Furthermore, when the second conductive polymer layer is formed on both sides of the anode foil, the areal density of the second conductive polymer layer refers to the areal density of one second conductive polymer layer formed on only one side of the anode foil. The areal density of the conductive polymer layer can be controlled by the concentration of the conductive polymer in the coating solution and the coating amount.

[0062] The areal density of the first conductive polymer layer can be determined by the following method. First, five samples are prepared by cutting the membrane before the formation of the first conductive polymer layer to a specified area, and the mass of these five samples is measured. Then, five samples are prepared by cutting the membrane with the first conductive polymer layer formed to the aforementioned specified area, and the mass of these samples is measured. The areal density of the first conductive polymer layer is determined by using the difference between the total mass of the five samples after the formation of the first conductive polymer layer and the total mass of the five samples before the formation of the first conductive polymer layer, and the aforementioned specified area. The areal density of the second conductive polymer layer can also be determined by the same method.

[0063] (Electrolytic capacitor)

[0064] Hereinafter, the electrolytic capacitor of this embodiment will sometimes be referred to as "electrolytic capacitor (E)". The electrolytic capacitor (E) can be manufactured using the manufacturing method (M) described above. The matters described in the manufacturing method (M) can be applied to the electrolytic capacitor (E), therefore repeated descriptions are sometimes omitted. The matters described in the electrolytic capacitor (E) can also be applied to the manufacturing method (M).

[0065] An electrolytic capacitor (E) comprises a laminate and a liquid component impregnated into the laminate. The laminate comprises an anode foil having a dielectric layer on its surface, a cathode foil, a separator, a first conductive polymer layer held in the separator, and a second conductive polymer layer formed on the dielectric layer. The first conductive polymer layer contains a first conductive polymer, a polyvinyl alcohol-based polymer, and a boric acid-based compound. The second conductive polymer layer contains a second conductive polymer. The boric acid-based compound is at least one boric acid-based compound selected from boric acid and boric acid compounds. At least a portion of the polyvinyl alcohol-based polymer in the first conductive polymer layer is cross-linked.

[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] In the first conductive polymer layer of the electrolytic capacitor (E), the ratio (Wp / Wc) of the mass Wp of the polyvinyl alcohol polymer to the mass Wc of the first conductive polymer can be within the range described above. For example, the ratio (Wp / Wc) can be 0.2 or higher.

[0068] In an electrolytic capacitor (E), the cathode foil may have an inorganic layer on its surface. In this case, the first conductive polymer layer is preferably bonded to the inorganic layer.

[0069] The liquid component (LC) of the electrolytic capacitor (E) may further contain at least one selected from ethylene glycol, diethylene glycol, triethylene glycol, ethylene glycol condensates with a molecular weight of less than 250, glycerol, γ-butyrolactone, and sulfolane.

[0070] As mentioned above, the laminate can be a wound body or a laminate other than a wound body.

[0071] The following describes examples of materials and components used in the manufacturing method (M) and the electrolytic capacitor (E). However, the materials and components used in the manufacturing method (M) and the electrolytic capacitor (E) are not limited to the examples described below.

[0072] In this specification, the term "conductive polymer component" is sometimes used. When the conductive polymer is undoped, the conductive polymer component consists of the conductive polymer itself. When the conductive polymer is doped, the conductive polymer component consists of both the conductive polymer and the dopant.

[0073] (Coating liquid (1st coating liquid, 2nd coating liquid))

[0074] The coating solutions (first coating solution, second coating solution) used in the polymer layer formation process may contain conductive polymers and water. The conductive polymers (conductive polymer components) may be contained in the coating solution in the form of particles. The coating solution may be an aqueous dispersion of the conductive polymers (conductive polymer components).

[0075] The coating solution may contain other components (e.g., organic compound (C)). Organic compound (C) may contain at least one selected from polyols, sulfolane, γ-butyrolactone, and borate esters, or may be only one of these at least one. Organic compound (C) may contain at least one selected from glycols, glycerols, sugar alcohols, sulfolane, γ-butyrolactone, and borate esters, or may be only one of these at least one.

[0076] Examples of polyols include glycols, glycerols, and sugar alcohols. Examples of glycols include ethylene glycol, diethylene glycol, triethylene glycol, polyalkylene glycols (e.g., polyethylene glycol), and polyoxyethylene-polyoxypropylene glycol (ethylene oxide-propylene oxide copolymer). Examples of glycerols include glycerol and polyglycerol. Examples of sugar alcohols include mannitol, xylitol, sorbitol, erythritol, and pentaerythritol.

[0077] Examples of conductive polymers include polypyrrole, polythiophene, polyfuran, polyaniline, polyacetylene, and their derivatives. These derivatives include polymers with polypyrrole, polythiophene, polyfuran, polyaniline, and polyacetylene as their basic backbone. For example, derivatives of polythiophene include poly(3,4-ethylenedioxythiophene). These conductive polymers can be used alone or in combination. Furthermore, conductive polymers can also be copolymers of two or more monomers. The weight-average molecular weight of conductive polymers is not particularly limited, and can, for example, range from 1,000 to 100,000. A preferred example of a conductive polymer is poly(3,4-ethylenedioxythiophene) (PEDOT).

[0078] Conductive polymers can be doped with dopants. From the viewpoint of suppressing dedoping from conductive polymers, polymeric dopants are preferred as dopants. Examples of polymeric dopants include polyvinyl sulfonic acid, polystyrene sulfonic acid, polyallyl sulfonic acid, polypropylene sulfonic acid, polymethyl methacrylate sulfonic acid, poly(2-acrylamido-2-methylpropanesulfonic acid), polyisoprene sulfonic acid, polyacrylic acid, etc. They can be used alone or in combination of two or more. At least a portion of them can be added in the form of salts. A preferred example of a dopant is polystyrene sulfonic acid (PSS).

[0079] The dopant can be polystyrene sulfonic acid, and the conductive polymer can be poly(3,4-ethylenedioxythiophene). That is, the conductive polymer component can be poly(3,4-ethylenedioxythiophene) doped with polystyrene sulfonic acid.

[0080] When using conductive polymers doped with dopants, the pH of the coating solution is preferably less than 7.0, but can also be below 6.0 or 5.0, in order to suppress dopant dedoping. The pH of the coating solution can be above 1.0 or above 2.0.

[0081] The water content in the coating solution can be 40% or more by mass, 50% or more by mass, 80% or more by mass, 90% or more by mass, or 95% or more by mass. The water content can be less than 98% by mass, less than 95% by mass, less than 90% by mass, or less than 80% by mass.

[0082] The content of organic compound (C) in the coating solution can be 1.0% by mass or more, 3.0% by mass or more, 5.0% by mass or more, or 10% by mass or more. It can be less than 30% by mass, less than 20% by mass, less than 15% by mass, or less than 10% by mass. The content of conductive polymer component in the coating solution can be 0.5% by mass or more, or 1.0% by mass or more, or less than 4.0% by mass, less than 3.0% by mass, or less than 2.0% by mass. This content can be in the range of 0.5% to 4.0% by mass or 1.0% to 4.0% by mass. Within any of these ranges, the upper limit can be set to 3.0% by mass or 2.0% by mass. From the perspective of excellent physical properties of the coating solution and its stability over time, and a good balance between the ESR of the electrolytic capacitor and cost, this content is preferably in the range of 1.0% to 3.0%. It should be noted that when the coating solution contains dopants, the mass of the dopants is included in the mass of the conductive polymer component.

[0083] There is no particular limitation on the mass of the dopant contained in the coating solution, and it can be in the range of 0.1 to 5 times (e.g., 0.5 to 3 times) the mass of the conductive polymer contained in the coating solution.

[0084] There is no particular limitation on the mass of the dopant contained in the coating solution, and it can be in the range of 0.1 to 5 times (e.g., 0.5 to 3 times) the mass of the conductive polymer contained in the coating solution.

[0085] In the coating solution, the content of water: the content of organic compound (C): the content of conductive polymer component = 40~98: 1.0~59.5: 0.5~4.0, or the content of water: the content of organic compound (C): the content of conductive polymer component = 69.5~98: 1.0~30: 0.5~4.0.

[0086] (Liquid component (LC))

[0087] Examples of liquid components (LC) used in the impregnation process include non-aqueous solvents and electrolytes. The electrolyte may be a solution containing a non-aqueous solvent and a solute dissolved in the non-aqueous solvent. It should be noted that, in this specification, the liquid component (LC) may be a component that is liquid at room temperature (25°C) or a component that is liquid at the temperature at which the electrolytic capacitor is used.

[0088] The non-aqueous solvents used in liquid components (LC) can be organic solvents, ionic liquids, or protic solvents. Examples of non-aqueous solvents include polyols such as ethylene glycol and propylene glycol, cyclic sulfones such as sulfolane (SL), lactones such as γ-butyrolactone (γBL), amides such as N-methylacetamide, N,N-dimethylformamide, and N-methyl-2-pyrrolidone, esters such as methyl acetate, carbonates such as propylene carbonate, ethers such as 1,4-dioxane, ketones such as methyl ethyl ketone, and formaldehyde.

[0089] In addition, polymeric solvents can also be used as non-aqueous solvents. Examples of polymeric solvents include polyalkylene glycols, derivatives of polyalkylene glycols, and compounds in which at least one hydroxyl group in a polyol is replaced by a polyalkylene glycol (including its derivatives). Specifically, examples of polymeric solvents include polyethylene glycol (PEG), polyethylene glycol glycerol ether, polyethylene glycol diglycerol ether, polyethylene glycol sorbitol ether, polypropylene glycol, polypropylene glycol glycerol ether, polypropylene glycol diglycerol ether, polypropylene glycol sorbitol ether, and polybutanediol. Examples of polymeric solvents also include copolymers of ethylene glycol and propylene glycol, copolymers of ethylene glycol and butanediol, and copolymers of propylene glycol and butanediol. One non-aqueous solvent can be used alone, or two or more can be used in combination.

[0090] Liquid components (LC) may contain non-aqueous solvents and base components (bases) dissolved in non-aqueous solvents. Alternatively, liquid components (LC) may also contain non-aqueous solvents and base and / or acid components (acids) dissolved in non-aqueous solvents.

[0091] As acid components, both polycarboxylic acids and monocarboxylic acids can be used. Examples of the aforementioned polycarboxylic acids include aliphatic polycarboxylic acids ([saturated polycarboxylic acids, such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, octanoic 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), and alicyclic polycarboxylic acids (such as cyclohexane-1,2-dicarboxylic acid, cyclohexene-1,2-dicarboxylic acid, etc.).

[0092] Examples of the aforementioned monocarboxylic acids include aliphatic monocarboxylic acids (1 to 30 carbon atoms) ([saturated monocarboxylic acids, such as formic acid, acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, hexanoic acid, heptanoic acid, octanoic 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, naphtholic acid), and hydroxycarboxylic acids (such as salicylic acid, mandelic acid, resorcinol acid).

[0093] Among them, maleic acid, phthalic acid, benzoic acid, pyromellitic acid, and resorcinol are heat-stable and are preferred.

[0094] Inorganic acids can be used as the acid component. Representative examples of inorganic acids include phosphoric acid, phosphorous acid, hypophosphite, alkyl phosphates, boric acid, fluoroboric acid, tetrafluoroboric acid, hexafluorophosphate, benzenesulfonic acid, and naphthalenesulfonic acid. Alternatively, complex compounds of organic and inorganic acids can also be used as the acid component. Examples of such complex compounds include borodiethylene glycol acid, borodioxalic acid, and borodisalicylic acid.

[0095] The base component can be a compound with an alkyl-substituted amidine group, such as imidazole compounds, benzimidazole compounds, alicyclic amidine compounds (pyrimidine compounds, imidazoline compounds), etc. Specifically, 1,8-diazabicyclo[5,4,0]undec-7-ene, 1,5-diazabicyclo[4,3,0]non-5-ene, 1,2-dimethylimidazolineon, 1,2,4-trimethylimidazoline, 1-methyl-2-ethylimidazoline, 1,4-dimethyl-2-ethylimidazoline, 1-methyl-2-heptylimidazoline, 1-methyl-2-(3'-heptyl)imidazoline, 1-methyl-2-dodecylimidazoline, 1,2-dimethyl-1,4,5,6-tetrahydropyrimidine, 1-methylimidazolium, and 1-methylbenzimidazole can be obtained. By using them, capacitors with excellent impedance performance can be obtained.

[0096] As a base component, quaternary salts of compounds having alkyl-substituted amidine groups can be used. Examples of such base components include imidazole compounds, benzimidazole compounds, and alicyclic amidine compounds (pyrimidine compounds, imidazole kinase compounds) that have been quaternized by alkyl or aryl alkyl groups having 1 to 11 carbon atoms. 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-ethylimidazolinium, and 1,3,4-trimethyl-2-ethylimidazolinium are preferred. Imidazoline, 1,3-dimethyl-2-heptylimidazoline, 1,3-dimethyl-2-(3'-heptyl)imidazoline, 1,3-dimethyl-2-dodecylimidazoline, 1,2,3-trimethyl-1,4,5,6-tetrahydropyrimidine, 1,3-dimethylimidazoline, 1-methyl-3-ethylimidazoline, and 1,3-dimethylbenzimidazolium. By using these, capacitors with excellent impedance properties can be obtained.

[0097] Alternatively, tertiary amines can be used as the base component. Examples of tertiary amines include trialkylamines (trimethylamine, dimethylethylamine, methyldiethylamine, triethylamine, dimethyl-n-propylamine, dimethylisopropylamine, methylethyl-n-propylamine, methylethylisopropylamine, diethyl-n-propylamine, diethylisopropylamine, tri-n-propylamine, triisopropylamine, tri-n-butylamine, tri-tert-butylamine, etc.) and phenyl-containing amines (dimethylaniline, methylethylaniline, diethylaniline, etc.). Among these, trialkylamines are preferred from the perspective of increasing conductivity, and it is more preferable that they contain at least one selected from trimethylamine, dimethylethylamine, methyldiethylamine, and triethylamine. In addition, secondary amines such as dialkylamines, primary amines such as monoalkylamines, and ammonia can also be used as the base component.

[0098] Liquid components (LC) may contain salts of both acidic and basic components. The salts can be inorganic and / or organic. Organic salts are those in which at least one of the anion and cation contains an organic compound. Examples of organic salts include trimethylamine maleate, triethylamine borosalicylate, ethyldimethylamine phthalate, mono-1,2,3,4-tetramethylimidazoline phthalate, and mono-1,3-dimethyl-2-ethylimidazoline phthalate.

[0099] To suppress dopant dedoping, the pH of the liquid component (LC) can be set to less than 7.0 or below 5.0, or to above 1.0 or above 2.0. This pH can be set to above 1.0 and less than 7.0 (e.g., in the range of 2.0 to 5.0).

[0100] The liquid component (LC) preferably contains a protic solvent. Using a protic solvent improves the adhesion of the conductive polymer layer. In addition to a protic solvent, the liquid component (LC) may also contain solvents other than protic solvents.

[0101] A protic solvent may contain at least one selected from glycols, glycerol, polyglycerol, and sugar alcohols, or it may consist of only one of these at least one compounds. A protic solvent may consist of only one compound or it may contain multiple compounds.

[0102] Organic compounds (C) and liquid components (LC) can contain the same compounds. For example, they can contain the same polyols, the same diols (ethylene glycol, etc.), and the same sugar alcohols.

[0103] (Liquid (L))

[0104] The liquid (L) may be a liquid containing the aforementioned organic compound (C) and water. In this case, it is preferable to remove water from the laminate after the liquid (L) has permeated into the laminate, while the organic compound (C) remains within the laminate. The organic compound (C) may be at least one selected from mannitol, mannitol derivatives, xylitol, and xylitol derivatives.

[0105] 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).

[0106] 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.

[0107] 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.

[0108] 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.

[0109] (Anode foil)

[0110] 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.

[0111] 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.

[0112] In electrolytic capacitors, a conductive polymer layer may not be formed on the end face of the anode foil. On the other hand, it is preferable to form a dielectric layer on the end face of the anode foil.

[0113] (Cathode foil)

[0114] The cathode foil comprises a metal foil (e.g., aluminum foil). The metal constituting the foil can be a valve metal or an alloy containing 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 greater than 15 μm and less than 300 μm. A conductive polymer layer can be formed on the surface of the cathode foil using the methods described above.

[0115] As described above, the cathode foil can have an inorganic layer on its surface. The cathode foil with the inorganic layer can be a commercially available product, or it can be formed by forming an inorganic layer on the surface of a metal foil (cathode foil). The inorganic layer can be formed by known methods. For example, the inorganic layer can be formed by vacuum evaporation or the like. Alternatively, the inorganic layer can also be formed by coating a paste containing one of carbon (especially conductive carbon materials), titanium, and nickel onto the metal foil (cathode foil) and then drying it. The amount of inorganic layer can be 50 mg / m³. 2 ~300mg / m 2 The range (e.g., 70 mg / m²) 2 ~200mg / m 2 (The scope is not specified). Examples of carbon (especially conductive carbon materials) contained in the inorganic layer include graphite, hard carbon, soft carbon, carbon black, etc. Additionally, when the inorganic layer contains titanium, it can be a layer deposited with titanium or a layer formed from titanium oxide particles. The inorganic layer can also be a carbon layer. A carbon layer is a layer containing carbon, and can be a layer with a carbon content of 50% by mass or more. In this specification, "inorganic layer" can be replaced with "carbon layer".

[0116] The cathode foil may comprise a metal foil, an inorganic layer, and a titanium-containing layer disposed between the inorganic layer and the metal foil. An example cathode foil has a laminated structure of inorganic layer / titanium-containing layer / metal foil (e.g., aluminum foil) / titanium-containing layer / inorganic layer. The titanium-containing layer may contain at least one material selected from titanium and titanium compounds. Examples of titanium compounds include titanium nitride, titanium oxide, titanium-aluminum alloys, titanium carbonate, etc. The method for forming the titanium-containing layer is not limited and can be formed by known methods. For example, the titanium-containing layer can be formed by physical vapor deposition methods such as vacuum evaporation or sputtering. The deposition amount of the titanium-containing layer can be 200 mg / m³. 2 ~500mg / m 2 The range (e.g., 250 mg / m²) 2 ~400mg / m 2 (the scope).

[0117] (Diaphragm)

[0118] The diaphragm can be made of porous sheet material. Examples of porous sheet materials include woven fabrics, nonwoven fabrics, and microporous membranes. The thickness of the diaphragm is not particularly limited and can range from 10 to 300 μm. Examples of diaphragm materials include cellulose, polyethylene terephthalate, polybutylene terephthalate, polyphenylene sulfide, vinylon, nylon, aromatic polyamides, polyimides, polyamide-imides, polyether-imides, rayon, and glass.

[0119] (outer body)

[0120] The laminate and liquid component (LC) are housed within an outer casing. The outer casing comprises a housing and / or a sealing resin. It is not limited to this; known housings and sealing resins may also be used. The sealing resin may comprise a thermosetting resin. Examples of thermosetting resins include epoxy resins, phenolic resins, silicone resins, melamine resins, urea resins, alkyd resins, polyurethanes, polyimides, unsaturated polyesters, etc. The sealing resin may contain fillers, curing agents, polymerization initiators, and / or catalysts, etc.

[0121] Hereinafter, an example of the present disclosure will be specifically described with reference to the accompanying drawings. The aforementioned constituent elements can be applied to the constituent elements of the example described below. Furthermore, the constituent elements of the example described below can be modified based on the above description. Additionally, the matters described below can be applied to the embodiments described above. Furthermore, in one example described below, constituent elements that are not essential to the electrolytic capacitor of the present disclosure can be omitted.

[0122] Figure 1 This is a schematic cross-sectional view of an electrolytic capacitor 100, illustrating an example of this embodiment. Figure 2 This is a schematic diagram obtained by unfolding a portion of the capacitor element 10 contained in the electrolytic capacitor 100.

[0123] 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.

[0124] Capacitor element 10 is, for example, as Figure 1The wound body is shown. The wound body includes an anode foil 11 connected to lead connector 105A, a cathode foil 12 connected to lead connector 105B, and a separator 13. 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.

[0125] The anode foil 11 and cathode foil 12 are wound together with a diaphragm 13 in between. The outermost periphery of the wound is fixed 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.

[0126] 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.

[0127] (Postscript)

[0128] The following technologies are disclosed through the above description.

[0129] (Technology 1)

[0130] An electrolytic capacitor comprises a laminate and a liquid component impregnated in the laminate.

[0131] The above-mentioned stacked body includes:

[0132] Anode foil with a dielectric layer on its surface;

[0133] cathode foil;

[0134] Diaphragm;

[0135] The first conductive polymer layer retained in the above-mentioned membrane; and

[0136] A second conductive polymer layer is formed on the aforementioned dielectric layer.

[0137] The aforementioned first conductive polymer layer contains a first conductive polymer, a polyvinyl alcohol-based polymer, and a boric acid-based compound.

[0138] The aforementioned second conductive polymer layer contains a second conductive polymer.

[0139] The aforementioned boric acid compounds are at least one boric acid compound selected from boric acid and boric acid compounds.

[0140] At least a portion of the polyvinyl alcohol polymer in the first conductive polymer layer is cross-linked.

[0141] (Technology 2)

[0142] According to the electrolytic capacitor described in Technique 1, in the first conductive polymer layer, the ratio (Wp / Wc) of the mass Wp of the polyvinyl alcohol polymer to the mass Wc of the first conductive polymer is 0.01 or more.

[0143] (Technology 3)

[0144] According to the electrolytic capacitor described in technique 1 or 2, the cathode foil has an inorganic layer on its surface.

[0145] The first conductive polymer layer is tightly bonded to the inorganic layer.

[0146] (Technology 4)

[0147] According to any one of the techniques 1 to 3, the electrolytic capacitor further comprises at least one selected from ethylene glycol, diethylene glycol, triethylene glycol, ethylene glycol condensates with a molecular weight of less than 250, glycerol, γ-butyrolactone, and sulfolane.

[0148] (Technology 5)

[0149] An electrolytic capacitor according to any one of techniques 1 to 4, wherein the aforementioned laminated body is a wound body.

[0150] (Technology 6)

[0151] A method for manufacturing an electrolytic capacitor, comprising:

[0152] Preparation process: Prepare an anode foil with a dielectric layer on its surface;

[0153] The first polymer layer forming process forms a first conductive polymer layer containing a first conductive polymer and a polyvinyl alcohol-based polymer within the gaps of the diaphragm.

[0154] In the second polymer layer forming process, a second conductive polymer layer is formed on the surface of the dielectric layer.

[0155] The laminate formation process involves laminating the anode foil, the cathode foil, and the diaphragm by distributing the diaphragm between the anode foil and the cathode foil, thereby forming a laminate containing the first conductive polymer layer and the second conductive polymer layer.

[0156] The impregnation process involves impregnating the laminated body with a liquid component containing at least one boric acid compound selected from boric acid and boric acid compounds; and

[0157] In the crosslinking process, the laminate impregnated with the aforementioned liquid component is heated to a temperature of 85°C or higher.

[0158] In the above crosslinking process, at least a portion of the polyvinyl alcohol polymer in the first conductive polymer layer is crosslinked by at least one boric acid compound.

[0159] (Technology 7)

[0160] According to the manufacturing method of the electrolytic capacitor described in Technology 6, in the first conductive polymer layer, the ratio (Wp / Wc) of the mass Wp of the polyvinyl alcohol polymer to the mass Wc of the first conductive polymer is 0.01 or more.

[0161] (Technology 8)

[0162] According to the manufacturing method of the electrolytic capacitor described in Technique 6 or 7, the cathode foil has an inorganic layer on its surface.

[0163] The first conductive polymer layer is tightly bonded to the inorganic layer.

[0164] (Technology 9)

[0165] According to any one of the methods for manufacturing an electrolytic capacitor described in Techniques 6 to 8, the liquid component further contains at least one selected from ethylene glycol, diethylene glycol, triethylene glycol, ethylene glycol condensates with a molecular weight of 250 or less, glycerol, γ-butyrolactone, and sulfolane.

[0166] (Technology 10)

[0167] According to any one of the technical methods 6 to 9, the manufacturing method of an electrolytic capacitor, wherein the aforementioned laminated body is a wound body.

[0168] Example

[0169] The present disclosure will now be described in more detail based on embodiments, but the disclosure is not limited to these embodiments. In this embodiment, a plurality of electrolytic capacitors are fabricated and evaluated using the following method.

[0170] (Capacitor A1)

[0171] An electrolytic capacitor (capacitor A1) is made using the following method.

[0172] (a) Preparation of constituent components

[0173] An aluminum foil (thickness: 100 μm) is etched to roughen its surface. The roughened surface is then chemically converted to form a dielectric layer. This yields an anode foil with dielectric layers on both sides. Carbon layers are then formed on both sides of an aluminum foil (thickness: 50 μm) that becomes the cathode foil. These carbon layers are formed using a vacuum evaporation method.

[0174] As a diaphragm, a nonwoven fabric (50 μm thick) is prepared. The nonwoven fabric used is a nonwoven fabric composed of polyester fiber, aramid fiber and cellulose.

[0175] (b) Formation of a conductive polymer layer

[0176] A commercially available dispersion (prepared by dispersing polyvinyl sulfonic acid (PSS)-doped polyvinyl dioxythiophene (PEDOT) particles in water was prepared. Polyvinyl alcohol and water were added to this dispersion to obtain a coating solution. The concentration of the conductive polymer component in the coating solution was set to 1.8% by mass, and the concentration of polyvinyl alcohol in the coating solution was set to 0.6% by mass.

[0177] Next, using a gravure coating machine, the coating solution is applied to one side of the anode foil (the surface of the dielectric layer). Then, a drying process is performed, forming a second conductive polymer layer on one side of the anode foil (the surface of the dielectric layer). The drying process is carried out by heating the coated anode foil at 125°C for 5 minutes. Next, the second conductive polymer layer is formed on the other side of the anode foil (the surface of the dielectric layer) using the same method. After applying the coating solution to the separator, a drying process is performed, thereby forming a first conductive polymer layer on the separator.

[0178] (c) Formation of the wound body (layered body)

[0179] The anode foil, cathode foil, and diaphragm are cut to specified sizes. Anode and cathode lead connectors are then attached to the anode and cathode foils, respectively. Next, the anode and cathode foils are wound together with the diaphragm in between. The ends of the outer surface of the wound are then secured with a winding retaining tape. Anode and cathode leads are attached to the ends of the lead connectors protruding from the wound. The resulting wound is then subjected to a chemical conversion treatment to form a dielectric layer on the end face of the anode foil. This yields a capacitor element.

[0180] (d) Infiltration of liquid components

[0181] An electrolyte (liquid component) was prepared by dissolving phthalic acid and triethylamine (base component) in ethylene glycol (solvent) at a combined concentration of 25% by mass, followed by the addition of ammonium borate. The concentration of ammonium borate in the electrolyte was set to 2.5% by mass. The capacitor element was immersed in the electrolyte for 5 minutes under reduced pressure (40 kPa). This allowed the electrolyte to permeate the capacitor element (layer).

[0182] (e) Sealing and cross-linking processes for capacitor elements

[0183] The capacitor element, impregnated with electrolyte, is sealed and assembled as follows: Figure 1The electrolytic capacitor shown is then heated at 105°C for 60 minutes while a voltage is applied between the anode and cathode foils. This process crosslinks the polyvinyl alcohol in the conductive polymer layer with ammonium borate. Furthermore, this process performs a further chemical transformation of the anode foil. Thus, an electrolytic capacitor (capacitor A1) is manufactured.

[0184] (Capacitor C1)

[0185] Except that polyvinyl alcohol is not added to the coating liquid used to form the conductive polymer layer, the electrolytic capacitor (capacitor C1) is manufactured using the same method and conditions as capacitor A1.

[0186] (Capacitor C2)

[0187] Except that ammonium borate is not added to the electrolyte, the electrolytic capacitor (capacitor C2) is manufactured using the same methods and conditions as capacitor A1.

[0188] (Capacitor C3)

[0189] Except that polyvinyl alcohol is not added to the coating liquid used to form the conductive polymer layer and ammonium borate is not added to the electrolyte, the electrolytic capacitor (capacitor C3) is manufactured using the same method and conditions as capacitor A1.

[0190] (evaluate)

[0191] For the fabricated electrolytic capacitors, the equivalent series resistance (ESR) and withstand voltage were measured. The evaluation results are shown in Table 1. A low ESR and a high withstand voltage are preferred.

[0192] [Table 1]

[0193]

[0194] Capacitor A1 is an electrolytic capacitor (E) of this disclosure manufactured by manufacturing method (M). Capacitors C1 to C3 are comparative examples. As shown in Table 1, capacitor A1 has a low ESR and a high voltage withstand capability.

[0195] Industrial availability

[0196] This disclosure can be used for electrolytic capacitors.

[0197] Explanation of reference numerals in the attached figures

[0198] 10: Capacitor Components

[0199] 11: Anode foil

[0200] 12: Cathode foil

[0201] 13: Diaphragm

[0202] 100: Electrolytic capacitor

Claims

1. An electrolytic capacitor comprising a laminate and a liquid component impregnated into said laminate, The laminate comprises: Anode foil with a dielectric layer on its surface; cathode foil; Diaphragm; The first conductive polymer layer retained in the diaphragm; and A second conductive polymer layer is formed on the dielectric layer. The first conductive polymer layer contains a first conductive polymer, a polyvinyl alcohol-based polymer, and a boric acid-based compound. The second conductive polymer layer contains a second conductive polymer. The boronic acid compound is selected from at least one boronic acid compound chosen from boronic acid and boronic acid compounds. At least a portion of the polyvinyl alcohol polymer in the first conductive polymer layer is cross-linked.

2. The electrolytic capacitor according to claim 1, wherein, In the first conductive polymer layer, the ratio of the mass Wp of the polyvinyl alcohol polymer to the mass Wc of the first conductive polymer, i.e., Wp / Wc, is 0.01 or more.

3. The electrolytic capacitor according to claim 1, wherein, The cathode foil has an inorganic layer on its surface. The first conductive polymer layer is tightly bonded to the inorganic layer.

4. The electrolytic capacitor according to claim 1, wherein, The liquid component also contains at least one selected from ethylene glycol, diethylene glycol, triethylene glycol, ethylene glycol condensates with a molecular weight of less than 250, glycerol, γ-butyrolactone, and sulfolane.

5. The electrolytic capacitor according to claim 1, wherein, The laminated body is a wound body.

6. A method for manufacturing an electrolytic capacitor, comprising: Preparation process: Prepare an anode foil with a dielectric layer on its surface; The first polymer layer forming process forms a first conductive polymer layer containing a first conductive polymer and a polyvinyl alcohol-based polymer within the gaps of the diaphragm. The second polymer layer forming process forms a second conductive polymer layer on the surface of the dielectric layer; The laminate formation process involves laminating the anode foil, the cathode foil, and the separator in such a way that the separator is disposed between the anode foil and the cathode foil, thereby forming a laminate containing the first conductive polymer layer and the second conductive polymer layer; The impregnation process involves impregnating the laminate with a liquid component containing at least one boric acid compound selected from boric acid and boric acid compounds; as well as In the crosslinking process, the laminate impregnated with the liquid component is heated to a temperature of 85°C or higher. In the crosslinking process, at least a portion of the polyvinyl alcohol polymer in the first conductive polymer layer is crosslinked by the at least one boric acid compound.

7. The method for manufacturing an electrolytic capacitor according to claim 6, wherein, In the first conductive polymer layer, the ratio of the mass Wp of the polyvinyl alcohol polymer to the mass Wc of the first conductive polymer, i.e., Wp / Wc, is 0.01 or more.

8. The method for manufacturing an electrolytic capacitor according to claim 6, wherein, The cathode foil has an inorganic layer on its surface. The first conductive polymer layer is tightly bonded to the inorganic layer.

9. The method for manufacturing an electrolytic capacitor according to claim 6, wherein, The liquid component also contains at least one selected from ethylene glycol, diethylene glycol, triethylene glycol, ethylene glycol condensates with a molecular weight of less than 250, glycerol, γ-butyrolactone, and sulfolane.

10. The method for manufacturing an electrolytic capacitor according to claim 6, wherein, The laminated body is a wound body.

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