electrolytic capacitor

Abstract

To provide an electrolytic capacitor capable of sufficiently maintaining an electrostatic capacitance and an ESR.SOLUTION: An electrolytic capacitor comprises a capacitance element, and an electrolyte liquid. The capacitance element comprises: a positive electrode body having a chemical coating; and a solid electrolyte contacted with the chemical coating. The electrolyte liquid contains a solvent, a polymer component, and a solute. The solvent contains at least one selected from the group consisting of a lactone compound, a glycol compound, and a sulfone compound. A concentration of the polymer component in the electrolyte liquid is 15 mass% or less. The solute contains at least one of benzene-dicarboxylic acid and its derivative as a first acid component, and at least one of an amin and an amidine as a basic component. The concentration of the solute in the electrolyte liquid is 15 mass% or more and 40 mass% or less. A ratio V / Vw of a formation voltage V applied to the positive electrode body for forming the chemical coating and a rating voltage Vw of the electrolytic capacitor is 1.7 or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an electrolytic capacitor comprising a solid electrolyte and an electrolytic solution. [Background technology]

[0002] Hybrid electrolytic capacitors, which contain a solid electrolyte and an electrolytic solution, are considered promising as small-sized, large-capacity capacitors with low ESR (equivalent series resistance). For example, Patent Document 1 discloses a hybrid electrolytic capacitor in which an oxide film (chemical conversion film) is formed on the surface of an anode body. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2011 / 099261 Brochure Summary of the Invention [Problem to be solved by the invention]

[0004] However, with conventional hybrid electrolytic capacitors, when the ratio of the formation voltage to the rated voltage was lowered, it was not possible to maintain sufficient capacitance and equivalent series resistance (ESR). [Means for solving the problem]

[0005] In view of the above, a first aspect of the present invention provides a method for manufacturing a semiconductor device comprising: An electrolytic capacitor comprising a capacitor element and an electrolyte, the capacitor element includes an anode body having a chemical conversion coating and a solid electrolyte in contact with the chemical conversion coating; The electrolyte solution includes a solvent, a polymer component, and a solute, the solvent contains at least one selected from the group consisting of a lactone compound, a glycol compound, and a sulfone compound; The concentration of the polymer component in the electrolyte solution is 15% by mass or less, the solute includes, as a first acid component, at least one of benzenedicarboxylic acid and its derivatives, and as a base component, at least one of amines and amidines; The concentration of the solute in the electrolytic solution is 15% by mass or more and 40% by mass or less, The electrolytic capacitor has a ratio of a chemical conversion voltage V applied to the anode body to form the chemical conversion coating to a rated voltage Vw of the electrolytic capacitor: V / Vw, which is 1.7 or less.

[0006] This specification discloses the following techniques. (Technology 1) An electrolytic capacitor comprising a capacitor element and an electrolyte, the capacitor element includes an anode body having a chemical conversion coating and a solid electrolyte in contact with the chemical conversion coating; The electrolyte solution includes a solvent and a solute, the solvent contains at least one selected from the group consisting of lactone compounds, glycol compounds, and sulfone compounds; the solute includes, as a first acid component, at least one of benzenedicarboxylic acid and its derivatives, and as a base component, at least one of amines and amidines; The concentration of the solute in the electrolytic solution is 15% by mass or more and 40% by mass or less, an electrolytic capacitor, wherein the ratio of a chemical conversion voltage V applied to the anode body to form the chemical conversion coating to a rated voltage Vw of the electrolytic capacitor: V / Vw is 1.7 or less; (Technology 2) 2. The electrolytic capacitor according to claim 1, wherein the benzenedicarboxylic acid is o-phthalic acid. (Technology 3) An electrolytic capacitor comprising a capacitor element and an electrolyte, the capacitor element includes an anode body having a chemical conversion coating and a solid electrolyte in contact with the chemical conversion coating; The electrolyte solution includes a solvent and a solute, the solvent contains at least one selected from the group consisting of lactone compounds, glycol compounds, and sulfone compounds; the solute includes, as a first acid component, at least one of a composite compound of an organic acid and an inorganic acid and a derivative thereof, and as a base component, at least one of an amine and an amidine; The concentration of the solute in the electrolytic solution is 10% by mass or more and 40% by mass or less, an electrolytic capacitor, wherein the ratio of a chemical conversion voltage V applied to the anode body to form the chemical conversion coating to a rated voltage Vw of the electrolytic capacitor: V / Vw is 1.7 or less; (Technology 4) 4. The electrolytic capacitor according to any one of techniques 1 to 3, wherein the pH of the electrolytic solution is 4.5 or less. (Technology 5) The electrolyte solution further contains a polymer component, 5. The electrolytic capacitor according to any one of techniques 1 to 4, wherein the concentration of the polymer component in the electrolytic solution is 1% by mass or more and 15% by mass or less. (Technology 6) 6. The electrolytic capacitor according to any one of techniques 1 to 5, wherein the rated voltage Vw is 100 volts or less. (Technology 7) 7. The electrolytic capacitor according to any one of techniques 1 to 6, wherein the concentration of the base component in the electrolytic solution is 3.5 mass % or more. (Technology 8) the solute further comprises a second acid component other than the first acid component; 8. The electrolytic capacitor according to any one of techniques 1 to 7, wherein the concentration of the second acid component in the electrolytic solution is 3 mass % or more. (Technology 9) 9. The electrolytic capacitor according to any one of techniques 1 to 8, wherein the lactone compound is γ-butyrolactone. (Technology 10) 10. The electrolytic capacitor according to any one of techniques 1 to 9, wherein the glycol compound is ethylene glycol. (Technology 11) 11. The electrolytic capacitor according to any one of techniques 1 to 10, wherein the sulfone compound is sulfolane. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a hybrid electrolytic capacitor that can sufficiently maintain capacitance and equivalent series resistance (ESR). [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a cross-sectional view of an electrolytic capacitor according to an embodiment of the present invention; [Figure 2] 2 is a schematic diagram for explaining the configuration of a capacitor element according to the same embodiment. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0009] [First embodiment] The electrolytic capacitor according to this embodiment includes a capacitor element and an electrolytic solution. The capacitor element includes an anode body having a chemical conversion coating, and a solid electrolyte in contact with the chemical conversion coating.

[0010] In hybrid electrolytic capacitors, the solid electrolyte and the chemical conversion film are in contact with each other. Therefore, to reduce leakage current, the formation voltage V has traditionally been set at a high value, about twice the rated voltage Vw of the electrolytic capacitor, to form a sufficiently thick chemical conversion film. This has made it difficult to increase the capacitance of hybrid electrolytic capacitors or to miniaturize them by reducing the ratio of the rated voltage Vw to the formation voltage V (V / Vw).

[0011] As a result of extensive research, the inventors discovered that by using an electrolyte with a specific composition, it is possible to maintain the capacitance and ESR of a hybrid electrolytic capacitor even when the ratio (V / Vw) of the rated voltage Vw to the formation voltage V is reduced.

[0012] First, a specific solute is used, and its content is set within a specific range. Specifically, a solute containing at least one of benzenedicarboxylic acid and its derivatives as a first acid component and at least one of amine and amidine as a base component is used. The concentration of the solute in the electrolyte, i.e., the total concentration of the acid component including the first acid component and the base component, is set to 15% by mass or more and less than 40% by mass.

[0013] Second, a specific solvent is used, specifically, at least one solvent selected from the group consisting of γ-butyrolactone, ethylene glycol, and sulfolane.

[0014] By using an electrolyte with the above composition, the first acid component contained in the solute can easily reach defects in the anode body. This improves the self-repairing performance of the chemical conversion coating, allowing the capacitance and ESR to be maintained. This allows the ratio of the chemical conversion voltage V to the rated voltage Vw (V / Vw) to be 1.7 or less.

[0015] When the electrolyte solution contains a polymer component, the concentration of the polymer component is set to 1% by mass or more and 15% by mass or less. This makes it difficult for the migration of the first acid component to be hindered even when the electrolyte solution contains a polymer component, thereby achieving the above-mentioned effects.

[0016] The chemical conversion coating is not limited to a coating formed by a method (hereinafter referred to as the first method) in which a predetermined chemical conversion voltage is applied to an anode body while the anode body is immersed in an acidic aqueous solution (hereinafter referred to as the chemical conversion solution). For example, the chemical conversion coating may be formed by heat treating the anode body while the anode body is immersed in the chemical conversion solution (hereinafter referred to as the second method). When a chemical conversion coating is formed by the first method, a chemical conversion coating having a thickness T corresponding to the chemical conversion voltage is formed. In other words, the chemical conversion voltage can be determined from the thickness T of the chemical conversion coating. Even when a chemical conversion coating is formed by the second method, the chemical conversion voltage required to form the chemical conversion coating by the first method can be determined from the thickness T. In other words, the chemical conversion voltage V includes the voltage applied to the anode body to form a chemical conversion coating with the thickness T and the voltage required to form a chemical conversion coating with the thickness T.

[0017] The rated voltage Vw is the upper limit voltage specified as a rating, and is the maximum value of the voltage that can be applied between the electrodes of the electrolytic capacitor. [Electrolyte] The electrolyte includes a solvent and a solute.

[0018] The pH of the electrolyte solution is preferably 4.5 or less. By setting the pH of the electrolyte solution to 4.5 or less, the undoping phenomenon of the solid electrolyte is easily suppressed. Therefore, the ESR can be maintained. The pH of the electrolyte solution is more preferably 4 or less, and particularly preferably 3.8 or less. In addition, the pH of the electrolyte solution is preferably 2 or more.

[0019] The electrolytic solution preferably has a conductivity of 0.01 mS / cm or more and 3 mS / cm or less, which facilitates further improvement of the self-repairing performance when the ratio of the formation voltage V to the rated voltage Vw (V / Vw) is set to 1.7 or less. (solvent) The solvent preferably contains at least one solvent (hereinafter referred to as the main solvent) selected from the group consisting of γ-butyrolactone (γBL), ethylene glycol (EG), and sulfolane (SL). The main solvent may be a glycol compound other than EG, a sulfone compound other than SL, or a lactone compound other than γBL. Examples of glycol compounds other than EG that can be used include diethylene glycol, triethylene glycol, and propylene glycol. Examples of sulfone compounds other than SL that can be used include dimethyl sulfoxide and diethyl sulfoxide. Examples of lactone compounds other than γBL that can be used include γ-valerolactone. The proportion of the main solvent (e.g., the total of γBL, EG, and SL) contained in the solvent is preferably 50% by mass or more, more preferably 60% by mass or more, and even more preferably 70% by mass or more.

[0020] The solvent may contain a carbonate compound, a monohydric or trihydric or higher alcohol, or the like, as a solvent other than the main solvent (hereinafter referred to as a secondary solvent). Examples of the carbonate compound that can be used include dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), propylene carbonate (PC), and fluoroethylene carbonate (FEC). Examples of the alcohol that can be used include glycerin and polyglycerin. These may be used alone or in combination. (solute) The solute concentration is 15% by mass or more and 40% by mass or less, more preferably 20% by mass or more and 40% by mass or less, and particularly preferably 20% by mass or more and 35% by mass or less.

[0021] The concentration of the solute is the sum of the concentrations of the acid component and the base component. The acid component includes a first acid component and a second acid component other than the first acid component. The base component includes an amine and / or amidine (hereinafter referred to as the first base component) and a second base component other than the first base component.

[0022] The solute contains at least one of benzenedicarboxylic acid and its derivatives as the first acid component. The benzenedicarboxylic acid may be o-phthalic acid, m-phthalic acid, or p-phthalic acid. Examples of derivatives of benzenedicarboxylic acid include 3-sulfophthalic acid, 3,5-disulfophthalic acid, 4-sulfoisophthalic acid, 2-sulfoterephthalic acid, and 2-methyl-5-sulfoterephthalic acid, each of which has a sulfo group. Of these, o-phthalic acid is preferred.

[0023] The concentration of the first acid component contained in the electrolytic solution is preferably 5% by mass or more, more preferably 15% by mass or more, in view of ease of dissociation, and is preferably 35% by mass or less, more preferably 30% by mass or less.

[0024] The acid component may include a second acid component other than the first acid component.

[0025] Examples of organic acids used as the second acid component include polycarboxylic acids, monocarboxylic acids, and polyhydric phenols.

[0026] Examples of polycarboxylic acids include aliphatic polycarboxylic acids (saturated polycarboxylic acids such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, 1,6-decanedicarboxylic acid, and 5,6-decanedicarboxylic acid, and unsaturated polycarboxylic acids such as maleic acid, fumaric acid, and itanoic acid), aromatic polycarboxylic acids (such as trimellitic acid and pyromellitic acid), and alicyclic polycarboxylic acids (such as cyclohexane-1,2-dicarboxylic acid and cyclohexene-1,2-dicarboxylic acid).

[0027] Examples of monocarboxylic acids include aliphatic monocarboxylic acids (having 1 to 30 carbon atoms): ([saturated monocarboxylic acids such as 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, and behenic acid], and [unsaturated monocarboxylic acids such as acrylic acid, methacrylic acid, and oleic acid]), aromatic monocarboxylic acids (such as benzoic acid, cinnamic acid, and naphthoic acid), and oxycarboxylic acids (such as salicylic acid, mandelic acid, and resorcylic acid). Of these, maleic acid, benzoic acid, pyromellitic acid, and resorcylic acid are preferred because of their high electrical conductivity and thermal stability.

[0028] Examples of polyhydric phenols include catechol, resorcinol, hydroquinone, pyrogallol, and phloroglucin.

[0029] Inorganic acids used as the second acid component include carbon compounds, hydrogen compounds, boron compounds, sulfur compounds, nitrogen compounds, and phosphorus compounds. Representative examples of inorganic acids include phosphoric acid, phosphorous acid, hypophosphorous acid, alkyl phosphate esters, boric acid, fluoroboric acid, tetrafluoroboric acid, hexafluorophosphoric acid, benzenesulfonic acid, and naphthalenesulfonic acid.

[0030] The second acid component may be a composite compound of an organic acid and an inorganic acid, such as borodiglycolic acid, borodisoxalic acid, or borodisalicylic acid.

[0031] Among these, the second acid component is preferably at least one selected from the group consisting of aromatic polycarboxylic acids, polyhydric phenols and oxycarboxylic acids, in terms of further improving the self-repairing performance.

[0032] The concentration of the second acid component is preferably 3% by mass or more, more preferably 5% by mass or more, and is preferably 25% by mass or less, more preferably 15% by mass or less.

[0033] The solute includes at least one of an amine and an amidine as the first basic component.

[0034] The amine may be a primary amine, a secondary amine, or a tertiary amine. Each amine may be an aliphatic amine, an aromatic amine, or a heterocyclic amine. Among these, tertiary amines are preferred because they have an enhanced effect of stabilizing ESR over the long term.

[0035] 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-t-butylamine, etc.), and phenyl group-containing amines (dimethylphenylamine, methylethylphenylamine, diethylphenylamine, etc.). Among these, trialkylamines such as trimethylamine, dimethylethylamine, methyldiethylamine, and triethylamine are preferred because of their high electrical conductivity.

[0036] As the amidine, a compound having an alkyl-substituted amidine group is preferred in terms of high electrical conductivity. Examples of the compound having an alkyl-substituted amidine group include imidazole compounds, benzimidazole compounds, and alicyclic amidine compounds (pyrimidine compounds, imidazoline compounds). 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-ethyl-imidazoline, 1,4-dimethyl-2-ethylimidazoline, 1-methyl-2-heptylimidazoline, 1-methyl-2-(3'heptyl)imidazoline, 1-methyl-2-dodecylimidazoline, 1,2-dimethyl-1,4,5,6-tetrahydropyrimidine, 1-methylimidazole, 1-methylbenzimidazole, 1-methyl-1,8-diazabicyclo[5,4,0]undecene-7, 1-methyl- Examples include 1,5-diazabicyclo[4,3,0]nonene-5, 1,2,3-trimethylimidazolinium, 1,2,3,4-tetramethylimidazolinium, 1,2-dimethyl-3-ethyl-imidazolinium, 1,3,4-trimethyl-2-ethylimidazolinium, 1,3-dimethyl-2-heptylimidazolinium, 1,3-dimethyl-2-(3'heptyl)imidazolinium, 1,3-dimethyl-2-dodecylimidazolinium, 1,2,3-trimethyl-1,4,5,6-tetrahydropyrimidium, 1,3-dimethylimidazolium, 1-methyl-3-ethylimidazolium, and 1,3-dimethylbenzimidazolium.

[0037] The concentration of the first base component contained in the electrolytic solution is preferably 3.5% by mass or more, more preferably 5% by mass or more, and is preferably 20% by mass or less, more preferably 10% by mass or less.

[0038] When the electrolyte contains an amine, the concentration thereof is preferably 3.5% by mass or more, more preferably 5% by mass or more, and is preferably 20% by mass or less, more preferably 10% by mass or less.

[0039] When amidine is contained in the electrolyte solution, its concentration is preferably 3.5% by mass or more, more preferably 5% by mass or more, and is preferably 20% by mass or less, more preferably 10% by mass or less.

[0040] The base component may contain a second base component other than the first base component.

[0041] Examples of the second base component include ammonia and quaternary ammonium compounds. The concentration of the second base component is preferably 0.1% by mass or more, more preferably 3% by mass or more. The concentration of the second base component is preferably 20% by mass or less, more preferably 10% by mass or less.

[0042] From the viewpoint of effectively suppressing dedoping of the dopant contained in the conductive polymer, the acid component is preferably in excess of the base component in terms of equivalent ratio. For example, the equivalent ratio of the acid component to the base component is desirably 1 to 30. (polymer component) The electrolyte may contain a polymer component to suppress evaporation of the electrolyte and improve the withstand voltage.

[0043] The polymer component is not particularly limited. Examples of the polymer component include polyalkylene glycol, polyalkylene glycol derivatives, and compounds in which at least one hydroxyl group of a polyhydric alcohol is substituted with polyalkylene glycol (including derivatives). Specific examples include polyethylene glycol, polyethylene glycol glyceryl ether, polyethylene glycol diglyceryl ether, polyethylene glycol sorbitol ether, polypropylene glycol, polypropylene glycol glyceryl ether, polypropylene glycol diglyceryl ether, polypropylene glycol sorbitol ether, and polybutylene glycol. These may be used alone or in combination of two or more.

[0044] The polyalkylene glycol may be a copolymer (random copolymer, block copolymer, random block copolymer, etc.), such as a copolymer of ethylene glycol and propylene glycol, a copolymer of ethylene glycol and butylene glycol, or a copolymer of propylene glycol and butylene glycol.

[0045] The weight average molecular weight of the polymer component is preferably at least 200. From the viewpoint of solubility in a solvent, the weight average molecular weight of the polymer component is preferably at most 20,000, more preferably at most 5000.

[0046] The concentration of the polymer component in the electrolyte is preferably 1% by mass or more and 15% by mass or less. If the concentration of the polymer component is within this range, evaporation of the electrolyte is suppressed and the migration of the first acid component is not hindered. This improves the self-repairing performance of the chemical conversion coating. The concentration of the polymer component in the electrolyte is more preferably 1% by mass or more and 10% by mass or less. (solid electrolyte) The solid electrolyte includes, for example, a manganese compound and a conductive polymer. Examples of the conductive polymer include polypyrrole, polythiophene, polyaniline, and derivatives thereof. The solid electrolyte includes a dopant. More specifically, the solid electrolyte may include poly(3,4-ethylenedioxythiophene) (PEDOT) as the conductive polymer and polystyrene sulfonic acid (PSS) as the dopant.

[0047] The solid electrolyte may be formed by applying a solution containing a monomer and a dopant to the chemical conversion coating and then chemically or electrolytically polymerizing the solution in situ. However, it is preferable to form the solid electrolyte by applying a conductive polymer to the chemical conversion coating, as this is expected to provide excellent voltage resistance. That is, the solid electrolyte is preferably formed by impregnating the chemical conversion coating with a polymer dispersion containing a liquid component, a conductive polymer dispersed in the liquid component, and a dopant, and then volatilizing the liquid component.

[0048] The concentration of the conductive polymer contained in the polymer dispersion is preferably 0.5 to 10% by mass. The conductive polymer preferably has an average particle size D50 of, for example, 0.01 to 0.5 μm. Here, the average particle size D50 is the median diameter in the volume particle size distribution determined by a particle size distribution analyzer using the dynamic light scattering method. (Formation voltage V and rated voltage Vw) The ratio V / Vw of the chemical conversion voltage V applied to the anode body to form a chemical conversion coating having a thickness T to the rated voltage Vw of the electrolytic capacitor is 1.7 or less. V / Vw may be 1.6 or less. From the viewpoint of suppressing an increase in leakage current, V / Vw is preferably 1.4 or more, and more preferably 1.5 or more.

[0049] The formation voltage V is not particularly limited and may be set appropriately depending on the rated voltage Vw so that V / Vw is 1.7 or less. The thickness T of the chemical conversion coating increases in proportion to the formation voltage V. For example, when the formation voltage V is 17 volts, the thickness T of the chemical conversion coating is 24 nm. When the formation voltage V is 170 volts, the thickness T of the chemical conversion coating is 238 nm. In other words, when the thickness T of the chemical conversion coating is 238 nm, the formation voltage V applied to or required for the anode body is 170 volts.

[0050] The rated voltage Vw is not particularly limited, but the effects of the present invention are particularly pronounced when the rated voltage Vw is 100 V or less (i.e., when the thickness T of the chemical conversion coating is 238 nm or less). In particular, the effects of the present invention are even more pronounced when the rated voltage Vw is 70 V or less, at which point the chemical conversion coating becomes even thinner.

[0051] The present invention will be described in more detail below based on embodiments, but the present invention is not limited to the following embodiments.

[0052] FIG. 1 is a cross-sectional view of the electrolytic capacitor according to this embodiment, and FIG. 2 is a schematic view of a partially developed capacitor element of the electrolytic capacitor.

[0053] The electrolytic capacitor includes, for example, a capacitor element 10, a bottomed case 11 that houses the capacitor element 10, a sealing member 12 that closes the opening of the bottomed case 11, a seat plate 13 that covers the sealing member 12, lead wires 14A and 14B that extend from the sealing member 12 and pass through the seat plate 13, lead tabs 15A and 15B that connect the lead wires to the electrodes of the capacitor element 10, and an electrolyte (not shown). The vicinity of the open end of the bottomed case 11 is drawn inward, and the open end is curled so as to be crimped to the sealing member 12.

[0054] Capacitor element 10 is produced from a wound body as shown in Fig. 2. The wound body includes anode body 21 connected to lead tab 15A, cathode body 22 connected to lead tab 15B, and separator 23. The wound body is a semi-finished product in which no solid electrolyte is formed between anode body 21 and cathode body 22.

[0055] Anode body 21 and cathode body 22 are wound with separator 23 interposed therebetween. The outermost periphery of the wound body is fixed with stop tape 24. Note that Fig. 2 shows a partially unfolded state of the wound body before the outermost periphery is fixed.

[0056] Anode body 21 comprises a metal foil whose surface has been roughened to have projections and recesses, and a chemical conversion coating is formed on the metal foil having projections and recesses. A solid electrolyte is attached to at least a portion of the surface of the chemical conversion coating. The solid electrolyte may cover at least a portion of the surface of cathode body 22 and / or the surface of separator 23. Capacitor element 10 on which the solid electrolyte has been formed is housed in bottomed case 11 together with an electrolytic solution. <Manufacturing method of electrolytic capacitors> Hereinafter, an example of a method for manufacturing an electrolytic capacitor according to this embodiment will be described step by step. (i) A step of preparing an anode body 21 having a chemical conversion coating First, a metal foil is prepared as the raw material for the anode body 21. The type of metal is not particularly limited, but it is preferable to use a valve metal such as aluminum, tantalum, or niobium, or an alloy containing a valve metal, because this facilitates the formation of a chemical conversion coating.

[0057] Next, the surface of the metal foil is roughened. By roughening, a plurality of projections and depressions are formed on the surface of the metal foil. The roughening is preferably carried out by etching the metal foil. The etching may be carried out by, for example, direct current electrolysis or alternating current electrolysis.

[0058] Next, a chemical conversion coating having a thickness T is formed on the surface of the roughened metal foil. The formation method is not particularly limited, but the coating can be formed by subjecting the metal foil to a chemical conversion treatment. In the chemical conversion treatment, for example, the metal foil is immersed in a chemical conversion solution such as an ammonium adipate solution and then heat-treated. Alternatively, the metal foil may be immersed in the chemical conversion solution and a voltage may be applied.

[0059] Typically, from the viewpoint of mass production, a large-sized foil (metal foil) of a valve metal or the like is subjected to a surface roughening treatment and a chemical conversion treatment. In this case, the treated foil is cut to a desired size to prepare anode body 21. (ii) Step of preparing cathode body 22 As with anode body 21, metal foil can be used for cathode body 22. There are no particular limitations on the type of metal, but it is preferable to use a valve metal such as aluminum, tantalum, or niobium, or an alloy containing a valve metal. If necessary, the surface of cathode body 22 may be roughened.

[0060] Furthermore, a layer containing titanium or carbon may be formed on the surface of the cathode body 22 . (iii) Preparation of the wound body Next, a wound body as shown in FIG. 2 is produced using anode body 21, cathode body 22, and separator 23. The end of cathode body 22 located in the outermost layer is fixed with stop tape 24. If anode body 21 is prepared by cutting a large metal foil, the wound body may be further subjected to a chemical conversion treatment in order to provide a chemical conversion coating on the cut surface of anode body 21. As separator 23, for example, a nonwoven fabric containing as a main component cellulose, polyethylene terephthalate, vinylon, aramid fiber, or the like can be used. (iv) Step of forming capacitor element 10 Next, a solid electrolyte is applied to the surface of the chemical conversion coating contained in the wound body, producing the capacitor element 10. If the solid electrolyte contains a conductive polymer, a polymerization solution may be used to synthesize the conductive polymer in situ by chemical polymerization or electrolytic polymerization, and then the conductive polymer may be applied to the chemical conversion coating. The polymerization solution is a solution containing a monomer or oligomer, a dopant, etc. In the case of chemical polymerization, an oxidizing agent is added to the polymerization solution. Alternatively, a pre-synthesized conductive polymer may be applied to the chemical conversion coating. Examples of the monomer or oligomer include pyrrole, aniline, thiophene, and derivatives thereof.

[0061] A polymer dispersion is preferably used as the pre-synthesized conductive polymer. The polymer dispersion includes a liquid component, a conductive polymer dispersed in the liquid component, and a dopant. A simple and preferred method for applying the polymer dispersion to the surface of the chemical conversion coating is, for example, to impregnate a rolled body with the polymer dispersion and dry it. The polymer dispersion preferably includes PEDOT as the conductive polymer and PSS as the dopant.

[0062] The step of applying the polymer dispersion to the surface of the chemical conversion coating and the step of drying the wound body may be repeated two or more times, thereby increasing the coverage of the solid electrolyte with respect to the chemical conversion coating. (v) A step of impregnating the capacitor element 10 with an electrolyte Next, the electrolyte is impregnated into capacitor element 10. The method for impregnating capacitor element 10 with the electrolyte is not particularly limited. (vi) Sealing the capacitor element Next, capacitor element 10 is housed in bottomed case 11. Bottomed case 11 can be made of a metal such as aluminum, stainless steel, copper, iron, or brass, or an alloy of these. Thereafter, a horizontal drawing process is performed near the open end of bottomed case 11, and the open end is crimped to sealing member 12 to form a curl. Then, seat plate 13 is placed on the curled portion, completing the electrolytic capacitor as shown in FIG. 1. Thereafter, an aging process may be performed while applying a rated voltage.

[0063] In the above embodiment, a wound-type electrolytic capacitor has been described, but the scope of application of the present invention is not limited to the above, and the present invention can also be applied to other electrolytic capacitors, such as chip-type electrolytic capacitors that use a metal sintered body as an anode body, and stacked-type electrolytic capacitors that use a metal plate as an anode body. [Second embodiment] An electrolytic capacitor according to a second embodiment of the present invention will be described. The electrolytic capacitor according to the second embodiment has the same configuration as the first embodiment, except that the first acid component contains at least one of a composite compound of an organic acid and an inorganic acid and its derivatives, and therefore, overlapping content will not be described.

[0064] In this embodiment, the complex compound as the first acid component preferably contains one or more selected from the group consisting of borodisalicylic acid, borodiglycolic acid, and borodisalic acid.

[0065] The concentration of the solute contained in the electrolyte, i.e., the total concentration of the acid component including the first acid component and the base component, is set to 10% by mass or more and less than 40% by mass. The solute concentration is more preferably 15% by mass or more and 35% by mass or less, and particularly preferably 20% by mass or more and 35% by mass or less. When a composite compound is used as the first acid component, its degree of dissociation in the electrolyte is high, so even if the solute concentration is 10% by mass or more, the first acid component can easily reach the vicinity of defects in the anode body, as in the first embodiment, and the self-repair performance of the chemical conversion coating can be improved. Furthermore, because the composite compound has excellent heat resistance, the electrolyte containing the composite compound easily maintains pH, suppressing undoping from the conductive polymer and thereby maintaining the ESR. [Example] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples. Example 1 A wound electrolytic capacitor (Φ10 mm x L (length) 10 mm) with a rated voltage Vw of 25 volts and a rated capacitance of 33 μF was fabricated in the following manner. (Preparation of the anode body) An aluminum foil with a thickness of 100 μm was etched to roughen the surface. The roughened aluminum foil surface was then chemically treated to form a chemical conversion coating. The chemical conversion treatment was performed by immersing the aluminum foil in an ammonium adipate solution and applying a voltage of 40 volts to the aluminum foil. The aluminum foil was then cut into a 6 mm × 120 mm anode body. The V / Vw ratio was set to 1.6. The thickness T of the chemical conversion coating was 55 nm. (Preparation of the cathode body) An aluminum foil having a thickness of 50 μm was subjected to an etching treatment to roughen the surface of the aluminum foil, and then the aluminum foil was cut into a size of 6 mm×120 mm to prepare a cathode body. (Production of wound body) An anode lead tab and a cathode lead tab were connected to the anode body and the cathode body, respectively, and the anode body and the cathode body were wound with the lead tabs interposed between them. An anode lead wire and a cathode lead wire were connected to the ends of the lead tabs protruding from the wound body, respectively. The resulting wound body was again subjected to chemical conversion, and a chemical conversion coating was formed on the cut ends of the anode body. The ends of the outer surface of the wound body were fixed with stop tape. (Preparation of polymer dispersion) A mixed solution was prepared by dissolving 3,4-ethylenedioxythiophene and polystyrene sulfonic acid (PSS, weight-average molecular weight 100,000) in ion-exchanged water. Iron (III) sulfate (oxidant) was added to the mixed solution while stirring, and a polymerization reaction was carried out. The reaction solution was then dialyzed to remove unreacted monomers and the oxidant, yielding a polymer dispersion containing approximately 5% by mass of PSS-doped polyethylenedioxythiophene (PEDOT / PSS). (Formation of solid electrolyte) The wound body was immersed in the polymer dispersion in a reduced pressure atmosphere (40 kPa) for 5 minutes, and then removed from the polymer dispersion. The wound body impregnated with the polymer dispersion was then dried in a drying oven at 150°C for 20 minutes to form a solid electrolyte that covered at least a portion of the chemical conversion coating. (Electrolyte impregnation) γ-Butyrolactone (γBL) and sulfolane were prepared as solvents. o-Phthalic acid as the first acid component and triethylamine as the first base component were dissolved in this solvent at a total concentration of 19% by mass and an equivalent ratio (initial equivalent ratio) of 1. PEG (weight-average molecular weight 300) was dissolved in the resulting solution at a concentration of 10% by mass. Finally, 12% by mass of o-phthalic acid and 3% by mass of pyrogallol were added to adjust the pH of the electrolyte to 3.5 to prepare an electrolyte solution. A capacitor element was immersed in the electrolyte solution for 5 minutes in a reduced pressure atmosphere (40 kPa). The concentrations of each component are expressed as a percentage of the mass of the resulting electrolyte solution taken as 100%. The acid component concentration was 28.2% by mass, and the base component concentration was 5.8% by mass. (Sealing of capacitor elements) The capacitor element impregnated with the electrolyte was sealed to complete the electrolytic capacitor (A1) as shown in Figure 1. Thereafter, aging was carried out at 95°C for 90 minutes while applying the rated voltage Vw. <Evaluation> The capacitance and ESR of capacitor A1 were measured after aging and after 2500 hours. The value after 2500 hours was divided by the value after aging to calculate the rate of change. The results are shown in Table 1. Examples 2 to 5 Electrolytic capacitors A2 to A5 were produced and evaluated in the same manner as in Example 1, except that the concentration of PEG was changed as shown in Table 1. The results are shown in Table 1. Comparative Example 1 Electrolytic capacitor B1 was fabricated and evaluated in the same manner as in Example 1, except that the initial equivalent ratio of the first acid component to the first base component was kept the same, the initial solute concentration was 10 mass%, the concentration of additional o-phthalic acid was 4 mass%, and pyrogallol was not added (total solute concentration was 14 mass%). The results are shown in Table 1. The concentration of the acid component was 10.9 mass%, and the concentration of the base component was 3.1 mass%. Comparative Example 2 Except for setting the formation voltage V to 45 volts and V / Vw to 1.8, electrolytic capacitor B2 was fabricated and evaluated in the same manner as in Comparative Example 1. The results are shown in Table 1.

[0066] [Table 1]

[0067] Example 6 An electrolytic capacitor A6 was produced and evaluated in the same manner as in Example 1, except that 4% by mass of pyromellitic acid and 5% by mass of pyrogallol were added instead of the additional o-phthalic acid (12% by mass) and the concentration of PEG was changed to 15% by mass. The results are shown in Table 2. Example 7 Electrolytic capacitor A7 was fabricated and evaluated in the same manner as in Example 1, except that the initial equivalent ratio of the first acid component to the first base component was kept the same, the initial solute concentration was 12 mass%, and 3 mass% of pyromellitic acid was added instead of pyrogallol. The results are shown in Table 2. Example 8 Electrolytic capacitor A8 was fabricated and evaluated in the same manner as in Example 1, except that the initial equivalent ratio of the first acid component to the first base component was kept the same, the initial solute concentration was 10 mass%, and pyrogallol was not added. The results are shown in Table 2. Example 9 Except for changing the concentration of the added o-phthalic acid to 6 mass %, electrolytic capacitor A9 was produced and evaluated in the same manner as in Example 1. The results are shown in Table 2. Example 10 An electrolytic capacitor A10 was fabricated and evaluated in the same manner as in Example 1, except that the initial equivalent ratio of the first acid component to the first base component was kept the same, the initial solute concentration was 25% by mass, the concentration of the added o-phthalic acid was 10% by mass, and the concentration of pyrogallol was 5% by mass. The results are shown in Table 2.

[0068] [Table 2]

[0069] Example 11 An electrolytic capacitor A11 was fabricated and evaluated in the same manner as in Example 1, except that the formation voltage V was set to 35 volts, V / Vw was set to 1.4, and pyrogallol was not added. The results are shown in Table 3. Comparative Example 3 Except for setting the formation voltage V to 35 volts and V / Vw to 1.4, electrolytic capacitor B3 was fabricated and evaluated in the same manner as in Comparative Example 1. The results are shown in Table 3.

[0070] [Table 3]

[0071] Example 12 Electrolytic capacitor A12 was fabricated and evaluated in the same manner as in Example 1, except that the amidine 1,2,3,4-tetramethylimidazolinium was used instead of triethylamine as the first base component, and the initial equivalent ratio of the first acid component to the first base component was kept the same, and the initial solute concentration was set to 14 mass%. The results are shown in Table 4. The concentration of the acid component was 22.2 mass%, and the concentration of the base component was 6.8 mass%. Example 13 Except for not adding PEG, electrolytic capacitor A13 was produced and evaluated in the same manner as in Example 12. The results are shown in Table 4.

[0072] [Table 4] [Industrial Applicability]

[0073] The present invention can be applied to a hybrid electrolytic capacitor having a solid electrolyte and an electrolytic solution. [Explanation of symbols]

[0074] 10: Capacitor element, 11: Bottomed case, 12: Sealing member, 13: Seat plate, 14A, 14B: Lead wires, 15A, 15B: Lead tabs, 21: Anode body, 22: Cathode body, 23: Separator, 24: Winding tape

Claims

1. An electrolytic capacitor comprising a capacitor element and an electrolyte, the capacitor element includes an anode body having a chemical conversion coating and a solid electrolyte in contact with the chemical conversion coating; The electrolyte solution includes a solvent, a polymer component, and a solute, the solvent contains at least one selected from the group consisting of lactone compounds, glycol compounds, and sulfone compounds; The concentration of the polymer component in the electrolyte solution is 1% by mass or more and 10% by mass or less, the solute includes, as a first acid component, at least one of benzenedicarboxylic acid and its derivatives, and as a base component, at least one of amines and amidines; The concentration of the solute in the electrolytic solution is 20% by mass or more and 40% by mass or less, The concentration of the first acid component in the electrolytic solution is 15% by mass or more, The pH of the electrolyte is 4.0 or less, an electrolytic capacitor, wherein the ratio of a chemical conversion voltage V applied to the anode body to form the chemical conversion coating to a rated voltage Vw of the electrolytic capacitor: V / Vw is 1.5 or more and 1.7 or less.

2. 2. The electrolytic capacitor according to claim 1, wherein the polymer component comprises at least one selected from the group consisting of polyethylene glycol, polyethylene glycol glyceryl ether, polyethylene glycol diglyceryl ether, polyethylene glycol sorbitol ether, polypropylene glycol, polypropylene glycol glyceryl ether, polypropylene glycol diglyceryl ether, polypropylene glycol sorbitol ether, and polybutylene glycol.

3. 3. The electrolytic capacitor according to claim 1, wherein the pH of the electrolytic solution is 3.7 or less.

4. 4. The electrolytic capacitor according to claim 1, wherein the rated voltage Vw is 100 volts or less.

5. 5. The electrolytic capacitor according to claim 1, wherein the concentration of the base component in the electrolytic solution is 3.5% by mass or more.

6. The solute further includes a second acid component other than the first acid component, 6. The electrolytic capacitor according to claim 1, wherein the concentration of the second acid component in the electrolytic solution is 3% by mass or more.

7. 7. The electrolytic capacitor according to claim 6, wherein the second acid component comprises at least one selected from the group consisting of polycarboxylic acids, monocarboxylic acids, and polyhydric phenols.

8. 8. The electrolytic capacitor according to claim 1, wherein the lactone compound is γ-butyrolactone.

9. 9. The electrolytic capacitor according to claim 1, wherein the glycol compound is ethylene glycol.

10. The electrolytic capacitor according to any one of claims 1 to 9, wherein the sulfone compound is sulfolane.

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