Electrolytic capacitor and method for manufacturing electrolytic capacitor

Abstract

An electrolytic capacitor according to the present invention comprises a capacitor element and a liquid component impregnated in the capacitor element. The capacitor element includes: an anode foil provided with a dielectric layer; a cathode foil; a wound body obtained by winding a separator interposed between the anode foil and the cathode foil; a first electroconductive polymer layer formed on the separator; and a winding stop tape for fixing a winding end portion of the wound body. The coating amount of the first electroconductive polymer layer on the separator is 0.04 mg / cm2 or more. A lactone compound is present in the liquid component in a proportion of 40 mass% or less.

Description

Electrolytic capacitor and method for manufacturing an electrolytic capacitor

[0001] This disclosure relates to an electrolytic capacitor and a method for manufacturing an electrolytic capacitor.

[0002] Patent Document 1 discloses a wound-type energy storage device having an electrolyte and an energy storage element formed by winding a separator coated with a conductive polymer together with an anode and a cathode. The end of the energy storage element is fixed with winding tape.

[0003] Patent Document 2 discloses a wound-type electrolytic capacitor that uses an adhesive tape made of a polyphenylene sulfide substrate for winding the capacitor element.

[0004] International Publication No. 2015 / 033566 JP 2-277215 Publication

[0005] A first aspect of this disclosure relates to an electrolytic capacitor comprising a capacitor element and a liquid component impregnated in the capacitor element. The capacitor element includes an anode foil having a dielectric layer, a cathode foil, a winding body in which a separator interposed between the anode foil and the cathode foil is wound, a first conductive polymer layer formed on the separator, and a winding stopper tape for fixing the winding end of the winding body. The coating amount of the first conductive polymer layer on the separator is 0.04 mg / cm². ２ That concludes the procedure. The proportion of the lactone compound in the liquid component is 40% by mass or less.

[0006] A second aspect of this disclosure relates to a method for manufacturing an electrolytic capacitor. The manufacturing method comprises, in this order, a preparation step of preparing an anode foil, a cathode foil, and a separator, each having a dielectric layer; a first conductive polymer layer formation step of applying a first processing solution containing a first conductive polymer component to the separator to form a first conductive polymer layer; a winding body formation step of sequentially stacking the anode foil, the separator with the first conductive polymer layer formed on it, and the cathode foil and winding them to form a winding body; a capacitor element formation step of fixing the winding end of the winding body with a winding stopper tape to form a capacitor element; and a liquid component impregnation step of impregnating the voids of the capacitor element with a liquid component. The coating amount of the first conductive polymer layer on the separator is 0.04 mg / cm². ２ That concludes the procedure. The proportion of the lactone compound in the liquid component is 40% by mass or less.

[0007] According to this disclosure, an electrolytic capacitor can be obtained in which the increase in ESR due to an increase in the inter-electrode distance between the anode foil and the cathode foil is suppressed.

[0008] This is a schematic side view showing an electrolytic capacitor according to an embodiment of the present disclosure. This is a schematic exploded perspective view showing a capacitor element according to an embodiment of the present disclosure.

[0009] In a wound electrolytic capacitor, such as the energy storage device described in Patent Document 1, where a capacitor element is formed by winding a separator with a conductive polymer layer pre-formed between the anode foil and the cathode foil, the adhesive strength between the anode foil and the cathode foil may be weaker compared to a wound electrolytic capacitor in which the conductive polymer layer is formed on the separator after winding with the separator interposed between the anode foil and the cathode foil. In such cases, exposure to high temperatures during the reflow process or other processes can cause loosening of the wound capacitor element, increasing the inter-electrode distance between the anode foil and the cathode foil constituting the laminate, and consequently increasing the equivalent series resistance (ESR).

[0010] The following describes embodiments of the present invention with examples, but the present invention is not limited to the examples described below. In the following description, specific numerical values ​​and materials may be given as examples, but other numerical values ​​and other materials may be applied as long as the invention relating to this disclosure can be carried out. In this specification, the description "numerical value A to numerical value B" includes numerical value A and numerical value B, and can be read as "numerical value A or greater and numerical value B or less". In the following description, when lower and upper limits of numerical values ​​relating to specific physical properties or conditions are given as examples, either of the given lower limits and either of the given upper limits can be arbitrarily combined as long as the lower limit does not exceed the upper limit.

[0011] [Electrolytic Capacitor] The electrolytic capacitor of this embodiment comprises a capacitor element and a liquid component. The capacitor element comprises an anode foil having a dielectric layer, a cathode foil, a separator, a first conductive polymer layer formed on the separator, and a winding stop tape. The separator is interposed between the anode foil and the cathode foil. The first conductive polymer layer is interposed between the anode foil and the cathode foil and is in contact with the separator. The winding stop tape fixes the end of the winding of the winding body in which the anode foil and cathode foil are wound with the separator in between.

[0012] The coating amount of the first conductive polymer layer is 0.04 mg / cm², from the viewpoint of forming a sufficient conductive path. ２ Preferably, the concentration is 0.07 mg / cm³. ２ It is even more preferable that the concentration be greater than or equal to 0.1 mg / cm³. ２ The above is particularly preferable. On the other hand, if the amount of coating in the first conductive polymer layer is too large, the thickness of the separator increases, which necessitates reducing the number of turns in the winding to keep it within a certain size, leading to a decrease in capacitance. Therefore, from the viewpoint of suppressing the decrease in capacitance, 2.0 mg / cm is preferred. ２ Preferably, the following is the case: 1.0 mg / cm³ ２ The following is even more preferable:

[0013] In this specification, the coating amount refers to the mass per unit area. Therefore, the coating amount of the first conductive polymer layer in the separator refers to the mass of the first conductive polymer layer per unit area of ​​the separator.

[0014] The proportion of the lactone compound in the liquid component is preferably 40% by mass or less, and more preferably 30% by mass or less. Furthermore, from the viewpoint of suppressing the deterioration of properties at low temperatures, the proportion of the lactone compound in the liquid component may be greater than 0% by mass, or 10% by mass or more. Note that the liquid component does not have to contain the lactone compound.

[0015] Lactone compounds containing cyclic esters are lipophilic and polar, allowing them to easily penetrate the polymer components of the adhesive in the re-wrapping tape and potentially reduce the intermolecular cohesive forces of these polymers. Furthermore, applying heat can reduce the viscosity of the lactone compounds and the adhesive, promoting the penetration of the lactone compounds and potentially further increasing the release properties of the re-wrapping tape.

[0016] However, satisfying the above conditions prevents the lactone compounds contained in the liquid component from causing the adhesive of the winding tape to dissolve. As a result, loosening of the winding is suppressed, and the increase in ESR due to an increase in the inter-electrode distance between the anode foil and cathode foil can be suppressed. Furthermore, even when the temperature of the electrolytic capacitor rises during the reflow process performed to solder the electrolytic capacitor onto the substrate, the increase in ESR can be suppressed.

[0017] An electrolytic capacitor may further comprise a case housing the capacitor element and liquid component, and a sealing body that closes the opening of the case. Preferably, the ratio of the total volume of the capacitor element and liquid component to the internal volume of the case excluding the sealing body is 50% by volume or more. Furthermore, from the viewpoint of suppressing the occurrence of mounting defects caused by swelling of the sealing body and case due to heat during substrate mounting, it is preferable that it be 90% by volume or less.

[0018] In the capacitor element of the present embodiment, a second conductive polymer layer may be formed on the surface of the dielectric layer facing the separator. A conductive path is formed by the second conductive polymer layer between the dielectric layer and the separator, reducing the ESR of the electrolytic capacitor, and improving the adhesion between the first conductive polymer layer formed on the separator and the second conductive polymer layer, thereby increasing the adhesion between the anode foil (dielectric layer) and the separator and suppressing loosening of the wound body.

[0019] In the capacitor element of the present embodiment, a third conductive polymer layer may be formed on the surface of the cathode foil facing the separator. A conductive path is formed by the third conductive polymer layer between the cathode foil and the separator, reducing the ESR of the electrolytic capacitor, and improving the adhesion between the first conductive polymer layer formed on the separator and the third conductive polymer layer, thereby increasing the adhesion between the cathode foil and the separator and suppressing loosening of the wound body.

[0020] The coating amount of the second conductive polymer is preferably 0.05 mg / cm ２ or more, and more preferably 0.1 mg / cm ２ or more. When the first conductive polymer layer is formed on both sides of the anode foil, the above coating amount is the total mass of the layers formed on both sides of the anode foil.

[0021] The coating amount of the third conductive polymer is preferably 0.05 mg / cm ２ or more, and more preferably 0.1 mg / cm ２ or more. When the first conductive polymer layer is formed on both sides of the cathode foil, the above coating amount is the total mass of the layers formed on both sides of the cathode foil.

[0022] The amount of coating can be determined by the following method. First, five samples are prepared by cutting out a predetermined area from the component (anodic foil, cathode foil, or separator) before the conductive polymer layer is formed, and the mass of these five samples is measured. Next, five samples are prepared by cutting out the component (anodic foil, cathode foil, or separator) with the conductive polymer layer formed on it, from the same predetermined area as above, and the mass of these samples is measured. The difference between the total mass of the five samples after the conductive polymer layer formation and the total mass of the five samples before the conductive polymer layer formation is divided by the total predetermined area of ​​the five samples to determine the mass of the conductive polymer layer per unit area (amount of coating).

[0023] The first conductive polymer layer, the second conductive polymer layer, and the third conductive polymer layer each contain a corresponding conductive polymer component and at least one selected from the group consisting of sugar alcohol, polyvinyl alcohol, and water-soluble epoxy resin. By including at least one selected from the group consisting of sugar alcohol, polyvinyl alcohol, and water-soluble epoxy resin in these conductive polymer layers, the adhesion between the conductive polymer layers formed on each member is improved, and a strong conductive path can be formed between the anode foil and the cathode foil by the conductive polymer layer.

[0024] The conductive polymer component may include a conductive polymer, or it may consist solely of a conductive polymer. Alternatively, the conductive polymer component may include a conductive polymer and a dopant. The same conductive polymer component may be used for the first conductive polymer layer, the second conductive polymer layer, and the third conductive polymer layer, or different conductive polymer components may be used for each. Furthermore, the same conductive polymer component may be used for two of the first, second, and third conductive polymer layers, and a different conductive polymer component may be used for the remaining one.

[0025] 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 the basic skeleton. For example, derivatives of polythiophene include poly(3,4-ethylenedioxythiophene). These conductive polymers may be used individually or in combination of multiple types. Furthermore, the conductive polymer may be a copolymer of two or more monomers. The weight-average molecular weight of the conductive polymer is not particularly limited and may be in the range of, for example, 1,000 to 100,000. A preferred example of a conductive polymer is poly(3,4-ethylenedioxythiophene) (PEDOT).

[0026] In a conductive polymer, a dopant may be doped into the conductive polymer. The dopant may be a negatively charged anion, and the conductive polymer may be a positively charged cation. The ionized dopant and the conductive polymer can interact by Coulomb forces. The doped conductive polymer may be dispersed in the first treatment solution in particulate form.

[0027] (Liquid component) The liquid component comprises a solvent and a solute. The solvent may contain at least one selected from the group consisting of ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, glycerin, polyethylene glycol, polyglycerin, polypropylene glycol, polyalkylene glycol, ethylene oxide-propylene oxide copolymer, and lactone compounds.

[0028] Examples of lactone compounds include γ-butyrolactone and γ-valerolactone.

[0029] The solute may include at least one selected from the group consisting of acids, bases, and electrolyte salts.

[0030] Polycarboxylic acids and monocarboxylic acids can be used as the acid component. Examples of the above polycarboxylic acids include aliphatic polycarboxylic acids, saturated polycarboxylic acids (e.g., 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 (e.g., maleic acid, fumaric acid, itaconic acid), aromatic polycarboxylic acids (e.g., phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, pyromellitic acid), and alicyclic polycarboxylic acids (e.g., cyclohexane-1,2-dicarboxylic acid, cyclohexene-1,2-dicarboxylic acid, etc.).

[0031] Examples of the monocarboxylic acids mentioned above include aliphatic monocarboxylic acids (1 to 30 carbon atoms), saturated monocarboxylic acids (e.g., formic acid, acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, lauric acid, myristic acid, stearic acid, behenic acid), unsaturated monocarboxylic acids (e.g., acrylic acid, methacrylic acid, oleic acid), aromatic monocarboxylic acids (e.g., benzoic acid, cinnamic acid, naphthoic acid), and oxycarboxylic acids (e.g., salicylic acid, mandelic acid, resorcinic acid).

[0032] Among these, maleic acid, phthalic acid, benzoic acid, pyromellitic acid, and resorcinic acid are thermally stable and are therefore preferred.

[0033] Inorganic acids may be used as the acid component. Typical examples of inorganic acids include phosphoric acid, phosphorous acid, hypophosphorous acid, alkyl phosphate esters, boric acid, borofluoric acid, tetrafluoroboric acid, hexafluorophosphoric acid, benzenesulfonic acid, and naphthalenesulfonic acid. In addition, composite compounds of organic and inorganic acids may be used as the acid component. Examples of such composite compounds include borodiglycolic acid, borodioxalic acid, and borodisalicylic acid.

[0034] The basic component may be a compound having an alkyl-substituted amidine group, for example, an imidazole compound, a benzimidazole compound, or an alicyclic amidine compound (pyrimidine compound, imidazoline compound). Specifically, 1,8-diazabicyclo[5,4,0]undecene-7, 1,5-diazabicyclo[4,3,0]nonene-5, 1,2-dimethylimidazolinium, 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-methylimidazole, and 1-methylbenzimidazole are preferred. By using these, a capacitor with excellent impedance performance can be obtained.

[0035] As the base component, a quaternary salt of a compound having an alkyl-substituted amidine group may be used. Examples of such base components include imidazole compounds, benzimidazole compounds, and alicyclic amidine compounds (pyrimidine compounds, imidazoline compounds) that have been quaternized with an alkyl or arylalkyl group having 1 to 11 carbon atoms. Specifically, 1-methyl-1,8-diazabicyclo[5,4,0]undecene-7, 1-methyl-1,5-diazabicyclo[4,3,0]nonene-5, 1,2,3-trimethylimidazolinium, 1,2,3,4-tetramethylimidazolinium, 1,2-dimethyl-3-ethylimidazolinium, 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-tetrahydropyrimidium, 1,3-dimethylimidazolium, 1-methyl-3-ethylimidazolium, and 1,3-dimethylbenzimidazolium are preferred. By using these, a capacitor with excellent impedance performance can be obtained.

[0036] A tertiary amine may 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.), phenyl group-containing amines (dimethylphenylamine, methylethylphenylamine, diethylphenylamine, etc.). Among them, trialkylamines are preferred in terms of high conductivity, and it is more preferable to contain at least one selected from the group consisting of trimethylamine, dimethylethylamine, methyldiethylamine, and triethylamine. Further, as the base component, secondary amines such as dialkylamines, primary amines such as monoalkylamines, and ammonia may be used.

[0037] The electrolyte salt may be an inorganic salt and / or an organic salt. An organic salt is 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-tetramethylimidazolinium phthalate, mono-1,3-dimethyl-2-ethylimidazolinium phthalate, etc. may be used.

[0038] To suppress the dedoping of the dopant, the pH of the liquid component may be less than 7.0 or 5.0 or less, and may also be 1.0 or more, or 2.0 or more. The pH may be 1.0 or more and less than 7.0 (for example, in the range of 2.0 to 5.0).

[0039] The liquid component may further contain a tacky component including at least one selected from the group consisting of sugar alcohols, polyvinyl alcohol, and water-soluble epoxy resins.

[0040] Examples of sugar alcohols include mannitol, sorbitol, xylitol, pentaerythritol, trimethylolpropane, and their derivatives.

[0041] Examples of water-soluble epoxy resins include biphenyl-type epoxy resins, bisphenol A-type epoxy resins, bisphenol F-type epoxy resins, bisphenol AD-type epoxy resins, naphthalene-type epoxy resins, glycidylamine-type epoxy resins, phenol novolac-type epoxy resins, phenolphthalein-type epoxy resins, polyglycol-modified epoxy resins, polyolefin-modified bisphenol A-type epoxy resins, alicyclic epoxy resins, dicyclopentadiene-type epoxy resins, and polyether-type epoxy resins.

[0042] The mass content (mass ratio) of each component in a liquid can be measured using various analytical methods, such as gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS).

[0043] Next, examples of components of the electrolytic capacitor relating to this disclosure will be further described. However, the components of the electrolytic capacitor are not limited to the following examples.

[0044] (Anode Foil) The anode foil is a metal foil containing at least one valve metal such as titanium, tantalum, aluminum, and niobium. The anode foil may also be a metal foil of the valve metal (e.g., aluminum foil). The anode foil may contain the valve metal in the form of an alloy containing the valve metal or a compound containing the valve metal. The thickness of the anode foil 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.

[0045] A dielectric layer is formed on the surface of the anode foil. The dielectric layer may be formed by chemical conversion treatment of the anode foil. In this case, the dielectric layer may contain an oxide of the valve metal (e.g., aluminum oxide). The dielectric layer may be formed of any dielectric material other than an oxide of the valve metal, as long as it functions as a dielectric.

[0046] In electrolytic capacitors, a conductive polymer layer does not necessarily have to be formed on the end face of the anode foil. On the other hand, it is desirable that a dielectric layer be formed on the end face of the anode foil.

[0047] (Cathode Foil) The cathode foil is not particularly limited as long as it has the function of a cathode. Examples of cathode foil include metal foil (e.g., aluminum foil). The type of metal is not particularly limited and may be a valve metal or an alloy containing a valve metal. The thickness of the cathode foil may be 15 μm or more and 300 μm or less. The surface of the cathode foil may be roughened or chemically treated as needed.

[0048] The cathode foil may include a conductive coating layer. If the metal foil includes a valve metal, the coating layer may include carbon and at least one metal having a lower ionization tendency than the valve metal. This makes it easier to improve the acid resistance of the metal foil. If the metal foil includes aluminum, the coating layer may include at least one selected from the group consisting of carbon, nickel, titanium, tantalum, and zirconium. In particular, the coating layer may include at least one of nickel and titanium due to its low cost and resistance.

[0049] The thickness of the coating layer may be 5 nm or more, 10 nm or more, or 200 nm or less. The coating layer may be formed by depositing or sputtering the above-mentioned metal onto a metal foil. Alternatively, the coating layer may be formed by depositing a conductive carbon material onto a metal foil or by applying a carbon paste containing a conductive carbon material. Examples of conductive carbon materials include graphite, hard carbon, soft carbon, and carbon black.

[0050] (Separator) A porous sheet can be used as the separator. Examples of porous sheets include woven fabrics, nonwoven fabrics, and microporous membranes. The thickness of the separator is not particularly limited and may be in the range of 10 μm to 300 μm. Examples of separator materials include cellulose, polyethylene terephthalate, polybutylene terephthalate, polyphenylene sulfide, vinylon, nylon, aromatic polyamide, polyimide, polyamideimide, polyetherimide, rayon, and glass.

[0051] (Wrapping tape) The wrapping tape comprises a base material and an adhesive. Examples of base material materials include polyethylene terephthalate (PET), polypropylene (PP), polyphenylene sulfide (PPS), polyimide (PI), polyetherimide (PEI), and plant fibers.

[0052] It is preferable that the re-wrapping tape contains highly heat-resistant polyphenylene sulfide (PPS) so that the re-wrapping tape can be used without melting even when the capacitor elements are exposed to high temperatures during reflow processing.

[0053] The base material of the winding tape may be a resin film of the above material, or it may be formed from resin fibers.

[0054] Furthermore, when the base material is made of a resin film, it is preferable that it be a stretched film (for example, a uniaxially oriented film or a biaxially oriented film) from the viewpoint of improving heat resistance.

[0055] The thickness of the substrate is not particularly limited, but for example, it may be 5 to 100 μm, or 9 to 50 μm.

[0056] The surface of the substrate may be subjected to appropriate surface treatment. Examples of surface treatments include corona treatment to improve adhesion with the adhesive, and release treatment performed on the surface of the substrate that does not come into contact with the adhesive layer.

[0057] The adhesive of the re-wrapping tape may contain at least one selected from the group consisting of acrylic resin, silicone resin, or epoxy resin.

[0058] Examples of acrylic resins include polymethyl methacrylate, polybutyl acrylate, ethylhexyl acrylate, methyl acrylate, hydroxyl acrylate, and 2-ethylhexyl methacrylate.

[0059] Examples of silicone resins include polydimethylsiloxane, silicone elastomers, and liquid silicone rubber.

[0060] Examples of epoxy resins include bisphenol A type epoxy resin, bisphenol F type epoxy resin, and aliphatic epoxy resin.

[0061] (Case) The case is a container for housing the capacitor element, and its structure and function are as follows:

[0062] The case has a cylindrical shape and an opening at one end. The cylindrical shape contains a space for housing a capacitor element. The opening functions as an entry point for housing the capacitor element and electrolyte inside the case, and the case is sealed by attaching a sealing body after the capacitor element and electrolyte are housed inside. The case may be made of metal, and aluminum may be used for weight reduction.

[0063] In the following, an example of an electrolytic capacitor relating to this disclosure will be specifically described with reference to the drawings. The components of the example described below can be the components described above. Furthermore, the components of the example described below can be modified based on the above description. In addition, the matters described below may be applied to the above embodiments. Furthermore, in the example described below, components that are not essential to the electrolytic capacitor of this disclosure may be omitted.

[0064] Figure 1 is a schematic cross-sectional view showing an example of an electrolytic capacitor 100 according to this embodiment. Figure 2 is a schematic diagram showing a portion of the capacitor element 10 included in the electrolytic capacitor 100 unfolded.

[0065] The electrolytic capacitor 100 comprises a capacitor element 10, a bottomed case 101 housing the capacitor element 10, a sealing body 102 closing the opening of the bottomed case 101, a base plate 103 covering the sealing body 102, lead wires 104A and 104B extending from the sealing body 102 and passing through the base plate 103, and lead tabs 105A and 105B connecting the lead wires to the electrodes of the capacitor element 10. The area near the opening end of the bottomed case 101 is tapered inward, and the opening end is curled so as to be crimped to the sealing body 102.

[0066] The capacitor element 10 in this embodiment includes a wound body as shown in Figure 2. The wound body comprises an anode foil 11 connected to a lead tab 105A, a cathode foil 12 connected to a lead tab 105B, and a separator 13. A first conductive polymer layer (not shown) is formed on the separator 13.

[0067] The anode foil 11 and cathode foil 12 are wound around each other via a separator 13. The outermost edge of the winding is secured with a winding stopper tape 14. Figure 2 shows the state in which a portion of the winding is unfolded before securing the outermost edge.

[0068] An electrolytic capacitor only needs to have at least one capacitor element, but it may also have multiple capacitor elements. The number of capacitor elements included in an electrolytic capacitor should be determined according to its application.

[0069] The electrolytic capacitors relating to this disclosure can be manufactured by the manufacturing method described below. However, electrolytic capacitors may also be manufactured by methods other than those described below.

[0070] [Method for Manufacturing an Electrolytic Capacitor] The method for manufacturing an electrolytic capacitor according to this embodiment comprises, in this order, a preparation step, a first conductive polymer formation step, a winding body formation step, a capacitor element formation step, and a liquid component impregnation step. In the preparation step, an anode foil, a cathode foil, and a separator, each having a dielectric layer, are prepared. In the first conductive polymer formation step, a first processing solution containing a first conductive polymer component is applied to the separator to form a first conductive polymer layer. In the winding body formation step, the anode foil, the separator with the first conductive polymer layer formed on it, and the cathode foil are sequentially laminated and wound to form a winding body. In the capacitor element formation step, the winding end of the winding body is fixed with winding tape to form a capacitor element. In the liquid component impregnation step, the voids of the capacitor element are impregnated with a liquid component. Here, the coating amount of the first conductive polymer layer on the separator is 0.04 mg / cm². ２ The above conditions are met, and the proportion of lactone compounds in the liquid component is 40% by mass or less.

[0071] <Preparation Process> The process of preparing the anode foil, cathode foil, and separator having a dielectric layer is not particularly limited.

[0072] Anode foils having a dielectric layer on their surface may be commercially available, or they may be formed by creating a dielectric layer on the surface of the anode foil. When forming a dielectric layer on the surface of the anode foil, the surface may be etched beforehand. Etching creates fine irregularities on the surface of the anode foil. These irregularities significantly increase the surface area, making it possible to store more charge in the same volume. In addition, the increased contact area with the conductive polymer layer or liquid component reduces resistance in the conductive path.

[0073] The cathode foil, like the anode foil, may be etched or chemically treated as needed.

[0074] The anode foil, cathode foil, and separator may be cut to a predetermined width from a sheet or roll. Maintaining consistent dimensions for the electrode foils and separator reduces variations in the capacitance of the capacitor elements, stabilizes the electrical characteristics, and thus ensures uniform product quality.

[0075] The materials of the anode foil, cathode foil, and separator are not particularly limited. The materials described above may be used as the anode foil, cathode foil, and separator.

[0076] <First Conductive Polymer Layer Formation Step> In the step of applying the first treatment solution containing the first conductive polymer component to the separator, there are no limitations on the method of applying the first treatment solution, and it may be applied by known methods. For example, it may be applied using a coater, sprayed, or the object to be coated may be immersed in the first treatment solution. Examples of methods using a coater include gravure coating and die coating. In the gravure coating method, the first treatment solution is applied to a transfer member such as a gravure roll, excess first treatment solution is removed from the transfer member, and then the first treatment solution attached to the transfer member is transferred to the separator, thereby allowing a layer of the first treatment solution of uniform thickness to be applied to the separator. Note that methods of applying the first treatment solution to the separator include impregnating the separator with the first treatment solution. The first treatment solution applied to the separator penetrates into the interior of the separator, and the conductive polymer component can be applied to the entire thickness of the separator.

[0077] The viscosity of the first treatment solution may be, for example, 10 mPa·s or more (or 100 mPa·s or more) and 200 mPa·s or less. In this case, the first treatment solution is easy to apply to and impregnate the separator. The viscosity of the first treatment solution is determined at room temperature (20°C) using a vibrating viscometer (for example, VM-100A, manufactured by Sekonic Corporation).

[0078] The first processing solution comprises a conductive polymer component and a liquid medium, and may also contain an adhesive component as described later. The liquid medium preferably contains water. The liquid medium may also contain an organic compound that does not boil at 100°C at 1 atmosphere (hereinafter also referred to as "organic compound (C)"). The first processing solution may contain other components as needed. As organic compound (C), an organic compound that is easily soluble in water is preferably used. The liquid medium may contain one type of organic compound (C) or multiple types. Organic compound (C) can be read as "at least one type of organic compound".

[0079] Examples of organic compound (C) include polyhydric alcohols (excluding sugar alcohols), sulfolanes, γ-butyrolactones, and boric acid esters. Organic compound (C) may include at least one selected from the group consisting of polyhydric alcohols, sulfolanes, γ-butyrolactones, and boric acid esters, or it may be at least one such at least one.

[0080] Examples of polyhydric alcohols include glycols and glycerin compounds. Examples of glycols include ethylene glycol, diethylene glycol, triethylene glycol, polyalkylene glycol (e.g., polyethylene glycol), and polyoxyethylene polyoxypropylene glycol (ethylene oxide-propylene oxide copolymer). Examples of glycerin compounds include glycerin and polyglycerin.

[0081] In this specification, unless otherwise specified, boiling point means boiling point at 1 atmosphere. Examples of organic compound (C) include organic compounds with boiling points higher than 100°C. If organic compound (C) has a boiling point, it may be 110°C or higher, 150°C or higher, or 200°C or higher, and may be 400°C or lower, 300°C or lower, 250°C or lower, or 200°C or lower. The boiling point may be in the range of 110°C to 400°C (for example, in the range of 150°C to 350°C).

[0082] In a preferred example of the manufacturing method, it is preferable that the water content in the first treatment solution is 40% by mass or more (for example, 50% by mass or more), so that after the first conductive polymer layer is formed, the second treatment solution containing an adhesive component or a liquid component (for example, an electrolyte) can easily penetrate into the conductive component layer. When an organic compound (C) is used, the content of the organic compound (C) in the first treatment solution may be 0% by mass or more and 10% by mass or less.

[0083] Water boils and evaporates at approximately 100°C at 1 atmosphere. On the other hand, organic compound (C) is a compound that does not boil at 100°C at 1 atmosphere. Therefore, by heating the first treatment solution at a temperature above 100°C that does not cause organic compound (C) to boil or decompose, water can be removed from the first treatment solution while the organic compound (C) remains. As a result, organic compound (C) remains in the formed first conductive polymer layer. In this case, solutions containing adhesive components or liquid components (e.g., electrolyte) can then easily penetrate the first conductive polymer layer.

[0084] <Second Conductive Polymer Layer Formation Step> In the step of applying a second treatment solution containing a second conductive polymer component to the dielectric layer of the anode foil, there are no limitations on the method of applying the second treatment solution, and it may be applied using the same method as in the first conductive polymer layer formation step. The second treatment solution may be the same as the first treatment solution. Alternatively, it may contain a different liquid medium or conductive polymer component than the first treatment solution.

[0085] <Third Conductive Polymer Layer Formation Step> In the step of applying the third treatment solution containing the third conductive polymer component to the cathode, there are no limitations on the method of applying the third treatment solution, and it may be applied using the same method as in the first conductive polymer layer formation step. The third treatment solution may be the same as the first treatment solution. It may also contain a different liquid medium or conductive polymer component than the first treatment solution.

[0086] <Winding Formation Process> The winding formation process is a process of winding a material formed by sequentially laminating an anode foil, a separator with a first conductive polymer layer formed on it, and a cathode foil. If a second conductive polymer layer is formed on the surface of the dielectric layer of the anode foil, the winding formation process may also be a process of winding a material formed by laminating the anode foil, cathode foil, and separator so that a separator is placed between the anode foil and the cathode foil and the first conductive polymer layer and the second conductive polymer layer face each other. Alternatively, if a third conductive polymer layer is formed on the surface of the cathode foil, the process may also be a process of winding a material formed by laminating the anode foil, cathode foil, and separator so that the first conductive polymer layer and the third conductive polymer layer face each other. In the winding material, the anode foil, cathode foil, and separator are laminated in the radial direction of the winding material.

[0087] <Capacitor Element Formation Process> The capacitor element formation process involves fixing the winding end of the capacitor element with winding tape to form the capacitor element.

[0088] The width of the reinforcing tape is preferably 40% or more of the width of the edge of the winding end, and more preferably 100% or more. The width of the reinforcing tape may also be equal to the width of the edge of the winding end. When this condition is satisfied, the reinforcing tape has a sufficient contact surface with the winding body, improving the anti-slip effect, making it less likely for the tape to come off and preventing the capacitor element from loosening. Through this process, a capacitor element is formed in which the winding end of the winding body is fixed with reinforcing tape.

[0089] <Adhesive component impregnation process> After the capacitor element formation process and before the liquid component impregnation process, an adhesive component impregnation process may be performed in which the capacitor element is impregnated with a second processing liquid containing an adhesive component.

[0090] In the adhesive component impregnation process, the capacitor element is impregnated with a second processing solution containing an adhesive component. This allows the conductive polymer layer to contain the adhesive component.

[0091] The adhesive component can be at least one selected from the group consisting of sugar alcohols, polyvinyl alcohols, and water-soluble epoxy resins. Examples of sugar alcohols include mannitol, sorbitol, erythritol, and pentaerythritol. Examples of water-soluble epoxy resins include biphenyl-type epoxy resins, bisphenol A-type epoxy resins, bisphenol F-type epoxy resins, bisphenol AD-type epoxy resins, naphthalene-type epoxy resins, glycidylamine-type epoxy resins, phenol novolac-type epoxy resins, phenolphthalein-type epoxy resins, polyglycol-modified epoxy resins, polyolefin-modified bisphenol A-type epoxy resins, alicyclic epoxy resins, dicyclopentadiene-type epoxy resins, and polyether-type epoxy resins.

[0092] The solvent of the second treatment solution preferably contains at least water. 80% by mass or more, and more preferably 90% by mass or more (preferably 100%), of the solvent in the second treatment solution may be water. The solvent in the second treatment solution may also contain an organic solvent. Ethylene glycol, sulfolane, and γ-butyrolactone can be used as organic solvents. The mass percentage of the adhesive component in the second treatment solution is preferably 15% by mass to 60% by mass, and may be 10% by mass to 75% by mass.

[0093] Preferably, the majority of the adhesive component is a sugar alcohol. Preferably, 80% by mass or more (more preferably 90% by mass or more) of the adhesive component contained in the second treatment liquid is sugar and / or sugar alcohol.

[0094] The solvent of the second treatment solution may contain the organic compound (C) described above. If necessary, the second treatment solution may also contain other components.

[0095] The total content of adhesive components and organic compounds (C) in the second treatment solution may 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. The content may be 59.5% by mass or less, 45% by mass or less, 30% by mass or less, 25% by mass or less, 20% by mass or less, 15% by mass or less, or 10% by mass or less. The content may be in the range of 1 to 59.5% by mass, 3 to 59.5% by mass, or 5 to 59.5% by mass. In any of these ranges, the upper limit may be replaced with 45% by mass, 30% by mass, 25% by mass, 20% by mass, 15% by mass, or 10% by mass.

[0096] There are no limitations on the method of impregnating the capacitor element with the second processing solution. For example, the capacitor element may be impregnated with an adhesive component by immersing at least a portion of it in the second processing solution. The steps of immersing at least a portion of the capacitor element in the second processing solution and removing at least a portion of the solvent may be performed multiple times (for example, two or more times or three or more times). When immersing at least a portion of the capacitor element in the second processing solution, the second processing solution may be heated to 40°C to 90°C. The step of removing at least a portion of the solvent may be performed, for example, by heating the capacitor element to 100°C or higher. The drying time may be, for example, five minutes or more.

[0097] In the manufacturing method described above, when a second conductive polymer layer is formed on the surface of the dielectric layer, and a third conductive polymer layer is further formed on the surface of the cathode foil, the first conductive polymer layer formed on the separator, the second conductive polymer layer formed on the surface of the dielectric layer, and the third conductive polymer layer formed on the surface of the cathode foil can connect to form a single conductive polymer layer. According to the manufacturing method described above, a mixed region can be formed at the boundary between the first conductive polymer layer and the second conductive polymer layer, where a part of the first conductive component layer and a part of the second conductive component layer are mixed. Also, a mixed region can be formed at the boundary between the first conductive polymer layer and the third conductive polymer layer, where a part of the first conductive component layer and a part of the third conductive component layer are mixed. In other words, the first conductive polymer layer, the second conductive polymer layer, and the third conductive polymer layer can adhere to each other. Therefore, a strong conductive path is formed between the anode foil and the cathode foil by the electrolyte (conductive polymer layer), reducing the ESR of the electrolytic capacitor and greatly improving the adhesion between the anode foil and the cathode foil.

[0098] <Liquid component impregnation process> The liquid component impregnation process is a process of impregnating the voids of the capacitor element with a liquid component. There are no limitations on the method of impregnating the voids within the capacitor element with a liquid component. For example, the capacitor element may be impregnated with a liquid component by immersing at least a part of the capacitor element in the liquid component.

[0099] The liquid component includes a solvent and a solute. The solvent and solute are the materials described above.

[0100] Furthermore, the liquid component may contain the same adhesive component as in the adhesive component impregnation step.

[0101] <Sealing Process> In the sealing process, the capacitor element is inserted through the opening of the case. After housing the capacitor element in the case, a liquid component may be injected to impregnate the capacitor element with the liquid component.

[0102] Next, a sealing element is placed in the opening of the case, and the opening is sealed by crimping the area around it. At this time, the lead wires of the capacitor element are pulled out of the case through through holes formed in the sealing element. This forms an electrolytic capacitor.

[0103] <Aging Process> The aging process is a process in which voltage is applied to an electrolytic capacitor and current is passed through it at a high temperature in order to improve the performance and reliability of the electrolytic capacitor. In this process, the electrolytic capacitor is first placed in an aging device and a predetermined voltage is applied for a predetermined time. By passing current through it at a high temperature, the formation and repair of the dielectric layer inside the electrolytic capacitor is promoted and the insulating properties of the dielectric layer are stabilized.

[0104] In this way, electrolytic capacitors are manufactured. The manufacturing method may include steps other than those described above, as needed.

[0105] [Note] The above description of embodiments discloses the following technologies.

[0106] (Technical 1) An electrolytic capacitor comprising a capacitor element and a liquid component impregnated in the capacitor element, wherein the capacitor element comprises a winding body formed by winding an anode foil having a dielectric layer, a cathode foil, and a separator interposed between the anode foil and the cathode foil, a first conductive polymer layer formed on the separator, and a winding stopper tape for fixing the winding end of the winding body, wherein the coating amount of the first conductive polymer layer on the separator is 0.04 mg / cm² ２ The electrolytic capacitor wherein the proportion of the lactone compound in the liquid component is 40% by mass or less.

[0107] (Technology 2) In Technology 1 described above, the capacitor element further includes a second conductive polymer layer formed on the surface of the dielectric layer facing the separator, wherein the coating amount of the second conductive polymer layer is 0.05 mg / cm². ２ That's all for electrolytic capacitors.

[0108] (Technology 3) In Technology 1 or Technology 2 described above, the capacitor element further includes a third conductive polymer layer formed on the surface of the cathode foil facing the separator, wherein the coating amount of the third conductive polymer layer is 0.05 mg / cm². ２ That's all for electrolytic capacitors.

[0109] (Technology 4) An electrolytic capacitor in which, in any one of the above technologies 1 to 3, the first conductive polymer layer comprises at least one selected from the group consisting of sugar alcohol, polyvinyl alcohol, and water-soluble epoxy.

[0110] (Technology 5) An electrolytic capacitor in any one of the above technologies 1 to 4, wherein the winding tape contains polyphenylene sulfide.

[0111] (Technology 6) An electrolytic capacitor in which the adhesive of the winding stopper tape comprises at least one selected from the group consisting of acrylic resin, silicone resin, or epoxy resin.

[0112] (Technology 7) An electrolytic capacitor in which, in any one of the above technologies 1 to 6, the liquid component further comprises at least one selected from the group consisting of ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, glycerin, polyethylene glycol, polyglycerin, polypropylene glycol, polyalkylene glycol, and ethylene oxide-propylene oxide copolymer.

[0113] (Technology 8) An electrolytic capacitor comprising, in any one of the above technologies 1 to 7, a case for housing the capacitor element and the liquid component, and a sealing body for closing the opening of the case, wherein the ratio of the total volume of the capacitor element and the liquid component to the internal volume of the case excluding the sealing body is 90 volume% or less.

[0114] (Technical 9) The process comprises, in this order: a preparation step of preparing an anode foil, a cathode foil, and a separator having a dielectric layer; a first polymer layer formation step of applying a first processing solution containing a first conductive polymer component to the separator to form a first conductive polymer layer; a winding body formation step of sequentially laminating the anode foil, the separator on which the first conductive polymer layer is formed, and the cathode foil and winding them together to form a winding body; a capacitor element formation step of fixing the winding end of the winding body with a winding stopper tape to form a capacitor element; and a liquid component impregnation step of impregnating the voids of the capacitor element with a liquid component, wherein the coating amount of the first conductive polymer layer is 0.04 mg / cm². ２ The method for manufacturing an electrolytic capacitor, wherein the proportion of the lactone compound in the liquid component is 40% by mass or less.

[0115] (Technical 10) A method for manufacturing an electrolytic capacitor, comprising, in the above-mentioned Technical 9, an adhesive component impregnation step in which the capacitor element is impregnated with a second processing liquid containing an adhesive component after the capacitor element formation step and before the liquid component impregnation step.

[0116] (Technical 11) A method for manufacturing an electrolytic capacitor, wherein the liquid component in the above-mentioned Technical 9 includes an adhesive component.

[0117] (Technical 12) A method for manufacturing an electrolytic capacitor, wherein the adhesive component comprises at least one selected from the group consisting of sugar alcohol, polyvinyl alcohol, and water-soluble epoxy resin, in the above-mentioned Technical 10 or Technical 11.

[0118] [Examples] The present disclosure will be described in more detail below based on examples, but the present disclosure is not limited to these examples. In these examples, multiple electrolytic capacitors were fabricated and evaluated using the following method.

[0119] 《Example 1》 In this example, a wound electrolytic capacitor (Φ (diameter) 6.3 mm × L (length) 5.8 mm) with a rated voltage of 35 V and a rated capacitance of 47 μF was manufactured. The specific manufacturing method of the electrolytic capacitor is described below.

[0120] (a) Preparation of components An aluminum foil (thickness 115 μm) was etched to roughen the surface of the aluminum foil. The roughened surface of the aluminum foil was treated with a chemical conversion process to form a dielectric layer. In this way, an anode foil with dielectric layers formed on both sides was obtained.

[0121] An aluminum foil (50 μm thick) was etched to roughen its surface, thereby obtaining a cathode foil.

[0122] A nonwoven fabric (50 μm thick) was prepared as a separator. The nonwoven fabric was composed of 100% cellulose by mass, and its density was 0.35 g / cm³. ３ That was the case.

[0123] (b) Preparation of the first treatment solution A dispersion (commercially available) in which polystyrene sulfonic acid (PSS) doped polyethylene dioxythiophene (PEDOT) particles are dispersed in water was prepared as the first treatment solution.

[0124] (c) Formation of conductive polymer layer The first treatment solution was applied to the separator using a gravure coater. Then, a drying treatment was performed to form the first conductive polymer layer on the separator. The drying treatment was performed by heating the anode foil coated with the first treatment solution at 135°C for 5 minutes.

[0125] A second conductive polymer layer was formed on the dielectric layer of the anode foil using the same method as the method used to form the first conductive polymer layer on the separator. Furthermore, a third conductive polymer layer was formed on the surface of the cathode foil using the same method as the method used to form the first conductive polymer layer on the separator.

[0126] (d) Fabrication of the capacitor element The anode foil, cathode foil, and separator were each cut to a predetermined size. Anode lead tabs and cathode lead tabs were connected to the anode foil and cathode foil. Next, the anode foil and cathode foil were wound together via the separator to form a winding body. Anode lead wires and cathode lead wires were connected to the ends of each lead tab protruding from the winding body.

[0127] (e) Fabrication of capacitor elements The ends of the outer surface of the wound body were fixed with winding tape to obtain capacitor elements. The obtained capacitor elements were subjected to chemical conversion treatment again to form a dielectric layer on the end face of the anode foil.

[0128] (f) Impregnation of liquid components: Ethylene glycol (EG), sulfolane (SL), ethylene oxide-propylene oxide copolymer (EOPO), and γ-butyrolactone (GBL) were used as solvents for the liquid components. Phthalic acid (ortho form) was used as the acid component of the solute as an organic carboxylic acid compound. Triethylamine (tertiary amine compound) was used as the basic component of the solute as an amine compound. Liquid components were prepared using the above solvents and solutes.

[0129] The proportion of each component to the total mass of EG, SL, and EOPO contained in the solvent was kept constant. The proportion of GBL was as shown in Table 1. The solute content relative to the total liquid component was 29% by mass. The molar ratio of the acid component to the base component (acid component / base component) was 2.6. At least a portion of the acid component (phthalic acid) was added as a salt (triethylamine phthalate) with the base component (triethylamine).

[0130] The capacitor element was immersed in the liquid component for 5 minutes in a reduced pressure atmosphere (40 kPa). This impregnated the capacitor element with the liquid component.

[0131] (g) The electrolytic capacitor was completed by sealing the capacitor element impregnated with the sealing liquid component of the capacitor element. Specifically, the capacitor element was placed in a bottomed case so that the lead wires were located on the opening side of the bottomed case, and a sealing body (an elastic material containing butyl rubber as the rubber component) formed to allow the lead wires to pass through was placed above the capacitor element to seal the capacitor element inside the bottomed case. Then, the bottomed case was drawn near the opening end, the opening end was curled, and a base plate was placed on the curled portion to complete the electrolytic capacitor as shown in Figure 1. After that, an aging treatment was performed at 105°C for 90 minutes while applying a voltage of 44V.

[0132] 《Comparative Examples 1-4, Examples 2-5》 Electrolytic capacitors (Comparative Examples 1-4, Examples 2-5) were prepared in the same manner as in Example 1, except that the concentration of GBL in the liquid component was changed.

[0133] Example 6: An electrolytic capacitor (Example 6) was fabricated in the same manner as in Example 1, except that the amount of coating on the anode foil, cathode foil, and separator was reduced.

[0134] Example 7: An electrolytic capacitor (Example 7) was fabricated in the same manner as in Example 1, except that the amount of coating on the anode foil and cathode foil was increased.

[0135] [Evaluation] (Measurement of coating amount) Five samples were prepared by cutting out predetermined areas from the components (anodic foil, cathode foil, and separator) before the conductive component layer was formed, and the coating amount per unit area was determined using the method described above.

[0136] (ESR Measurement) The initial ESR was measured for the electrolytic capacitors after the aging process described above. The measurement temperature was 20°C. Next, the electrolytic capacitors were subjected to reflow (RF) processing by heating them at 200°C to 255°C for 70 seconds, and the ESR after reflow processing was measured. The measurement temperature was 20°C. The initial ESR and the ESR after reflow processing were averaged from measurements taken for five electrolytic capacitors.

[0137] From these initial ESR and post-reflow ESR values, the ESR change rate was calculated using the following formula (1): ESR change rate = (Post-reflow ESR - Initial ESR) ÷ Initial ESR (1) Table 1 shows the evaluation results of the ESR change rate. In Table 1, the ESR change rate for Example 1 is set to 1.0, and for Comparative Examples 1 to 4 and Examples 2 to 7, the values ​​are shown as relative values ​​to the ESR change rate of Example 1.

[0138] (Measurement of element diameter) For the electrolytic capacitors of Examples 1 to 7 and Comparative Examples 1 to 2, the diameter of the capacitor element (α1 and α2 in Figure 1) was measured using an optical microscope to determine the initial element diameter α1. Then, the electrolytic capacitor was subjected to reflow (RF) processing by heating it at 200°C to 255°C for 70 seconds, and the element diameter α2 after reflow processing was measured. The element diameter α1 and the element diameter α2 after reflow processing were averaged from measurements taken for five electrolytic capacitors. The element diameter change rate of the capacitor element was then calculated using the following formula (2): Element diameter change rate = (α2 - α1) ÷ α1 (2) Table 1 shows the evaluation results of the element diameter change rate. In Table 1, the element diameter change rate for Example 1 is set to 1.0, and for Comparative Examples 1 to 4 and Examples 2 to 7, the values ​​are shown as relative values ​​to the element diameter change rate of Example 1.

[0139]

[0140] From the results of Examples 1-5 and Comparative Examples 1-4 in Table 1, it can be seen that the rate of change in ESR can be suppressed by reducing the proportion of lactone compounds in the liquid component to 40% by mass or less.

[0141] Furthermore, from the results of Examples 1, 6, and 7 shown in Table 1, it was confirmed that the rate of change in ESR of the electrolytic capacitor decreased as the amount of conductive polymer coating on the anode foil, cathode foil, and separator increased. It is thought that as the amount of conductive polymer coating increased, the amount of adhesive component contained in the conductive polymer layer also increased, thereby improving the adhesive strength between the anode foil, cathode foil, and separator components. It is thought that this improvement in adhesive strength suppressed the increase in the inter-electrode distance between the anode foil and cathode foil after reflow processing, and thus suppressed the rise in ESR.

[0142] The above results are thought to be influenced by the manufacturing process and the concentration of lactone compounds in the finished electrolytic capacitors.

[0143] This disclosure can be used for electrolytic capacitors in automotive, industrial, and consumer electronics.

[0144] 10: Capacitor element 11: Anode foil 12: Cathode foil 13: Separator 14: Winding tape 100: Electrolytic capacitor 101: Bottomed case 102: Sealing body 103: Base plate 104A, 104B: Lead wires 105A, 105B: Lead tabs

Claims

1. An electrolytic capacitor comprising a capacitor element and a liquid component impregnated into the capacitor element, wherein the capacitor element comprises: an anode foil having a dielectric layer; a cathode foil; a separator interposed between the anode foil and the cathode foil; a wound body formed by winding these; a first conductive polymer layer formed on the separator; and a winding stopper tape for fixing the winding end of the wound body, wherein the coating amount of the first conductive polymer layer on the separator is 0.04 mg / cm² ２ The above is true, and the proportion of the lactone compound in the liquid component is 40% by mass or less, wherein the electrolytic capacitor.

2. The capacitor element further includes a second conductive polymer layer formed on the surface of the dielectric layer facing the separator, wherein the coating amount of the second conductive polymer layer is 0.05 mg / cm². ２ The electrolytic capacitor described in claim 1 is as described above.

3. The cathode foil further comprises a third conductive polymer layer formed on the surface facing the separator, wherein the coating amount of the third conductive polymer layer is 0.05 mg / cm². ２ The electrolytic capacitor according to claim 1 or 2.

4. The electrolytic capacitor according to claim 1 or 2, wherein the first conductive polymer layer comprises at least one selected from the group consisting of sugar alcohol, polyvinyl alcohol, and water-soluble epoxy.

5. The electrolytic capacitor according to claim 1 or 2, wherein the winding tape comprises polyphenylene sulfide.

6. The electrolytic capacitor according to claim 5, wherein the adhesive of the winding tape comprises at least one selected from the group consisting of acrylic resin, silicone resin, or epoxy resin.

7. The electrolytic capacitor according to claim 1 or 2, wherein the liquid component further comprises at least one selected from the group consisting of ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, glycerin, polyglycerin, polypropylene glycol, polyalkylene glycol, and ethylene oxide-propylene oxide copolymer.

8. The electrolytic capacitor according to claim 1 or 2, further comprising a case for housing the capacitor element and the liquid component, and a sealing body for closing the opening of the case, wherein the ratio of the total volume of the capacitor element and the liquid component to the internal volume of the case excluding the sealing body is 90 volume% or less.

9. The process comprises, in this order: a preparation step of preparing an anode foil, a cathode foil, and a separator having a dielectric layer; a first conductive polymer layer formation step of applying a first processing solution containing a first conductive polymer component to the separator to form a first conductive polymer layer; a winding body formation step of sequentially laminating the anode foil, the separator with the first conductive polymer layer formed on it, and the cathode foil and winding them together to form a winding body; a capacitor element formation step of fixing the winding end of the winding body with a winding stopper tape to form a capacitor element; and a liquid component impregnation step of impregnating the voids of the capacitor element with a liquid component, wherein the coating amount of the first conductive polymer layer on the separator is 0.04 mg / cm². ２ The method for manufacturing an electrolytic capacitor, wherein the proportion of the lactone compound in the liquid component is 40% by mass or less.

10. A method for manufacturing an electrolytic capacitor according to claim 9, comprising an adhesive component impregnation step of impregnating the capacitor element with a second processing liquid containing an adhesive component, after the capacitor element formation step and before the liquid component impregnation step.

11. The method for manufacturing an electrolytic capacitor according to claim 9, wherein the liquid component includes an adhesive component.

12. The method for manufacturing an electrolytic capacitor according to claim 10 or claim 11, wherein the adhesive component comprises at least one selected from the group consisting of sugar alcohol, polyvinyl alcohol, and water-soluble epoxy resin.

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