Electrolytic capacitor and additive for liquid component of electrolytic capacitor

Abstract

This electrolytic capacitor includes a capacitor element and a liquid component. The capacitor element includes an anode body that is provided with a dielectric layer on the surface, and a conductive polymer that covers a part of the dielectric layer. The liquid component contains a solvent and an acid component. The acid component includes a carboxylic acid compound that has an acid anhydride group and a carboxy group.

Description

Additives for electrolytic capacitors and liquid components of electrolytic capacitors 【0001】 The present disclosure relates to electrolytic capacitors and additives for liquid components of electrolytic capacitors. 【0002】 Electrolytic capacitors are considered promising as capacitors with small size, large capacity, and low equivalent series resistance (ESR). The electrolytic capacitors include an anode body having a dielectric layer, a conductive polymer covering at least a portion of the dielectric layer, and an electrolyte. The conductive polymer includes, for example, a conjugated polymer and a dopant. The electrolyte is a liquid component such as a non-aqueous solvent or a solution in which a solute is dissolved in a non-aqueous solvent. 【0003】 Patent Document 1 proposes an electrolytic capacitor comprising a capacitor element in which an anode foil and a cathode foil, each having a dielectric oxide film formed on its surface, are wound with a separator interposed therebetween, a cylindrical metal case with a bottom that houses the capacitor element together with a driving electrolyte, and a sealing member that seals the opening of the metal case, wherein the separator has a conductive polymer that contains an acid component as a dopant attached thereto, the driving electrolyte contains a solute that contains an acid component and a base component, and a solvent, the solute contains a tertiary amine as the base component, and the solute contains the acid component in excess of the base component in terms of molar ratio. 【0004】 Patent Document 2 proposes an electrolytic capacitor including an anode body having a dielectric layer, a solid electrolyte layer in contact with the dielectric layer of the anode body, and an electrolytic solution, the electrolytic solution including a solvent and a solute, the solvent including a glycol compound, the solute including a carboxylic acid component and a base component, and the solute including 200 parts by mass or more of the carboxylic acid component per 100 parts by mass of the base component. 【0005】Patent Document 3 proposes an electrolytic capacitor comprising a capacitor element having an anode foil with a dielectric layer on its surface and a solid electrolyte layer in contact with the dielectric layer, and an electrolyte solution impregnated into the capacitor element, wherein the solid electrolyte layer contains polythiophene or a derivative thereof and a dopant made of a polyanion, and the electrolyte solution contains a first solvent made of polyalkylene glycol or a derivative thereof, and at least one of diphenylamine, naphthol, nitrophenol, catechol, resorcinol, hydroquinone, and pyrogallol. 【0006】 JP 2013-191897 A International Publication No. 2017 / 017947 JP 2016-26402 A 【0007】 A first aspect of the present disclosure relates to an electrolytic capacitor. The electrolytic capacitor includes a capacitor element and a liquid component. The capacitor element includes an anode body having a dielectric layer on its surface, and a conductive polymer covering a portion of the dielectric layer. The liquid component includes a solvent and an acid component. The acid component includes a carboxylic acid compound having an acid anhydride group and a carboxy group. 【0008】 A second aspect of the present invention relates to an additive for use in a liquid component of an electrolytic capacitor including a capacitor element containing a conductive polymer, the additive including a carboxylic acid compound having an acid anhydride group and a carboxy group. 【0009】 The fluctuation of the equivalent series resistance (ESR) over time in the electrolytic capacitor can be kept low. 【0010】 1 is a schematic cross-sectional view of an electrolytic capacitor according to an embodiment of the present disclosure; 【0011】 Electrolytic capacitors are required to have little fluctuation in ESR even after long-term use. 【0012】Phthalic acid is used as the acid component of the liquid component of electrolytic capacitors because it is easier to reduce the pH of the liquid component than aliphatic carboxylic acids. However, the carboxyl group of phthalic acid is easily deactivated by esterification, causing the pH of the liquid component to increase over time. When the pH of the liquid component is high, the conductive polymer contained in the capacitor element is more likely to be de-doped than when the pH is low, causing a gradual decrease in the conductivity of the conductive polymer and an increase in the ESR over time. Furthermore, the ESR is also likely to increase when the electrolytic capacitor is exposed to relatively high temperatures (e.g., 60°C or higher). 【0013】 In view of the above, (Technology 1) an electrolytic capacitor according to a first aspect of the present disclosure includes a capacitor element and a liquid component. The capacitor element includes an anode body having a dielectric layer on its surface, and a conductive polymer covering a portion of the dielectric layer. The liquid component includes a solvent and an acid component. The acid component includes a carboxylic acid compound having an acid anhydride group and a carboxy group. In this specification, such a carboxylic acid compound is referred to as a first carboxylic acid compound. 【0014】The first carboxylic acid compound contains a carboxyl group, which allows the liquid component to have a low pH at an early stage. Additionally, the first carboxylic acid compound contains an acid anhydride group. The presence of an acid anhydride group in the molecule facilitates the maintenance of a carboxyl group content over a long period of time. Furthermore, the maintenance of a carboxyl group content makes it difficult for esterification to proceed despite evaporation (reduction) of the liquid component. In electrolytic capacitors, acid anhydride groups are detected in qualitative analysis of the liquid component at an early stage and after a certain amount of charging and discharging (e.g., after the aging process is completed or after a predetermined voltage is applied to the capacitor for 100 hours at 125°C). On the other hand, when the concentration of acid anhydride groups in the liquid component is analyzed after repeated charging and discharging of the electrolytic capacitor for a long period of time (e.g., for 1000 hours at 125°C), a gradual decrease in the acid anhydride groups is confirmed. Based on these points, it is believed that the hydrolysis reaction in which acid anhydride groups are converted to carboxyl groups in electrolytic capacitors proceeds relatively slowly. Therefore, even if the carboxy group of the first carboxylic acid compound is esterified, two carboxy groups are generated from the acid anhydride group during repeated charge and discharge. This allows the liquid component to maintain a low pH for a long period of time. Stabilizing the pH of the liquid component over a long period of time suppresses deterioration (such as de-doping) of the conductive polymer, thereby maintaining high conductivity. Therefore, fluctuations in ESR over time can be suppressed when the electrolytic capacitor is used for a long period of time. Suppressing deterioration of the conductive polymer during long-term use of the electrolytic capacitor allows the electrolytic capacitor to maintain a relatively high capacity. The first carboxylic acid compound enhances the film repairability of the dielectric layer during long-term use of the electrolytic capacitor, thereby suppressing leakage current. Furthermore, stabilizing the pH of the liquid component by the first carboxylic acid compound maintains high conductivity of the conductive polymer and suppresses fluctuations in ESR even when the electrolytic capacitor is exposed to relatively high temperatures (e.g., temperatures of 60°C or higher and 200°C or lower). 【0015】(Technology 2) In the above (Technology 1), the carboxylic acid compound may have an aromatic ring, and each of the two bonds of the acid anhydride group may be bonded to the aromatic ring. In this case, high affinity with the conductive polymer is easily obtained, and the low pH of the liquid component can be more stably maintained. 【0016】 (Technology 3) In the above (Technology 1), the carboxylic acid compound may have two aromatic rings, and one of the two bonds of the acid anhydride group may be bonded to one of the two aromatic rings, and the other of the two bonds of the acid anhydride group may be bonded to the other of the two aromatic rings. In this case, hydrolysis of the acid anhydride group proceeds more slowly, so that the liquid component can be more stably maintained at a low pH, and fluctuations in ESR can be further suppressed. 【0017】 (Technology 4) In the above (Technology 2), the carboxy group may be bonded to the aromatic ring. In this case, the affinity of the first carboxylic acid compound with the conductive polymer is further increased, making it easier for the first carboxylic acid compound to approach the conductive polymer. As a result, a low pH is easily achieved near the conductive polymer, and higher conductivity of the conductive polymer is obtained. 【0018】 (Technology 5) In the above (Technology 3), the carboxy group may be bonded to at least one of the two aromatic rings. In this case, the affinity of the first carboxylic acid compound with the conductive polymer is further increased, making it easier for the first carboxylic acid compound to approach the conductive polymer. As a result, a low pH is easily achieved near the conductive polymer, and higher conductivity of the conductive polymer is obtained. 【0019】 (Technology 6) In the above (Technology 2) or (Technology 4), the aromatic ring may be 6-membered or more and 10-membered or less. In this case, the first carboxylic acid compound is likely to have a relatively high affinity for the conductive polymer. Therefore, the high conductivity of the conductive polymer is likely to be maintained, and fluctuations in ESR over time are likely to be further suppressed. 【0020】(Technology 7) In the above (Technology 3) or (Technology 5), each of the two aromatic rings may be 6-membered or more and 10-membered or less. In this case, the first carboxylic acid compound is likely to have a relatively high affinity for the conductive polymer. Therefore, it is easy to maintain the high conductivity of the conductive polymer and further easy to suppress fluctuations in ESR over time. 【0021】 (Technology 8) In any one of (Technology 2), (Technology 4), and (Technology 6) above, the carboxy group in the aromatic ring may be located at a meta-position or an ortho-position relative to the acid anhydride group. In this case, the acid anhydride group further inhibits the esterification of the carboxy group. Furthermore, the carboxy group facilitates the presence of the first carboxylic acid compound near the conductive polymer, and therefore the carboxy group converted from the acid anhydride group also readily resides near the conductive polymer. This facilitates maintaining a low pH near the conductive polymer, further suppressing fluctuations in ESR over time. 【0022】 (Technology 9) In any one of (Technology 3), (Technology 5), and (Technology 7) above, the carboxy group in at least one of the two aromatic rings may be located at a meta-position or an ortho-position relative to the acid anhydride group. In this case, the acid anhydride group further inhibits the esterification of the carboxy group. Furthermore, the carboxy group facilitates the presence of the first carboxylic acid compound near the conductive polymer, and therefore the carboxy group converted from the acid anhydride group also readily resides near the conductive polymer. This facilitates maintaining a low pH near the conductive polymer, further suppressing fluctuations in ESR over time. 【0023】 The meta or ortho position refers to the positional relationship between the carboxy group and the bonding position of the bond closest to the carboxy group among the two bonds of the acid anhydride group. In one molecule of the first carboxylic acid compound, the number of at least one of the carboxy groups and the acid anhydride groups may be two or more. In this case, the positional relationship between the carboxy group and the bond of the acid anhydride group that is closest to the bond of the carboxy group is the meta or ortho position. 【0024】(Technology 10) In any one of (Technology 1) to (Technology 9) above, the liquid component may further contain a base component. In this case, it is easy to maintain the dissociated state of the acid component and easy to maintain the high conductivity of the conductive polymer. 【0025】 (Technology 11) In the above (Technology 10), the equivalent ratio of the carboxylic acid compound to the base component may be 0.5 or more and 10 or less. In this case, a high degree of dissociation of the acid component is easily ensured, and corrosion of the electrode is easily suppressed. 【0026】 (Technology 12) The present disclosure also encompasses an additive (additive for a liquid component of an electrolytic capacitor) used in a liquid component of an electrolytic capacitor that includes a capacitor element containing a conductive polymer and the liquid component. This additive includes a carboxylic acid compound having an acid anhydride group and a carboxy group, i.e., a first carboxylic acid compound. By using such an additive in the liquid component of an electrolytic capacitor that includes a conductive polymer, the low pH of the liquid component can be stably maintained, and the high conductivity of the conductive polymer can be stably maintained over a long period of time. Therefore, even when the electrolytic capacitor is used for a long period of time, the fluctuation of the ESR over time can be kept low. 【0027】 The electrolytic capacitor and the liquid component additive for the electrolytic capacitor of the present disclosure will be described in more detail below, including the above (Technology 1) to (Technology 12). At least one selected from the components described below can be arbitrarily combined with at least one of the above (Technology 1) to (Technology 12) related to the electrolytic capacitor and the liquid component additive of the present disclosure, as long as such combination is technically possible. 【0028】 (Additive for Liquid Component) The additive for liquid component of the present disclosure is used in the liquid component of an electrolytic capacitor. The electrolytic capacitor in which the additive is used includes, in addition to the liquid component, a capacitor element containing a conductive polymer. 【0029】The liquid component additive includes a first carboxylic acid compound. The first carboxylic acid compound has at least one acid anhydride group and at least one carboxy group. In the case of phthalic acid, both of the two carboxy groups are easily esterified, which causes the pH of the liquid component to increase over time and reduces the conductivity of the conductive polymer. In contrast, the first carboxylic acid compound makes it difficult for the carboxy groups to be esterified due to the influence of the acid anhydride group, thereby enabling the initial ESR of the electrolytic capacitor to be kept low. Furthermore, within the electrolytic capacitor, the hydrolysis reaction of the acid anhydride group proceeds slowly, gradually generating two carboxy groups from one acid anhydride group. Therefore, even with long-term use of the electrolytic capacitor, the liquid component can be easily maintained at a low pH, the conductive polymer can maintain high conductivity, and fluctuations in ESR over time can be suppressed. Even with long-term use of the electrolytic capacitor, deterioration of the conductive polymer is suppressed, allowing the electrolytic capacitor to maintain a relatively high capacity and suppress leakage current. 【0030】 The number of carboxy groups in the first carboxylic acid compound may be 1 or more and 5 or less, or 1 or 2 or less. The number of acid anhydride groups in the first carboxylic acid compound may be 1 or more and 3 or less, or 1 or 2. The first carboxylic acid compound may have, for example, one carboxy group or two carboxy groups and one acid anhydride group. 【0031】 In the liquid component of the electrolytic capacitor, the carboxy group of the first carboxylic acid compound may be in any of the following forms: a free form, a salt form, an anion form, or a form interacting (e.g., complexing) with the conductive polymer. In this specification, the carboxy group of the first carboxylic acid compound includes all of these forms. 【0032】The first carboxylic acid compound may be aliphatic or may have a ring structure other than the acid anhydride group (such as an aliphatic hydrocarbon ring, an aromatic ring, or a heterocyclic ring). The aliphatic hydrocarbon ring may be saturated or unsaturated. The aromatic ring may be an aromatic hydrocarbon ring or an aromatic heterocyclic ring. The ring structure other than the acid anhydride group may be a monocyclic ring, a bridged ring, or a fused ring. The heterocyclic ring contains at least one heteroatom as a ring constituent atom. The heteroatom may be at least one selected from the group consisting of an oxygen atom, a sulfur atom, and a nitrogen atom. In the first carboxylic acid compound, the number of ring structures other than the acid anhydride group may be 1 to 4, or 1 to 2. For example, trimellitic anhydride has a benzene ring as a ring structure other than the acid anhydride group, and one carboxy group and one acid anhydride group bonded to the benzene ring. 【0033】 Examples of aliphatic hydrocarbon rings include cycloalkanes (cyclopentane, cyclohexane, cyclooctane, etc.), cycloalkenes (cyclohexene, etc.), cycloalkadienes (cyclopentadiene, cyclohexadiene, etc.), and bridged rings (norbornane, norbornene, adamantane, dicyclopentadiene, etc.). Examples of aromatic hydrocarbon rings include benzene, naphthalene, phenanthrene, anthracene, indene, and indane. Examples of heterocycles include aromatic heterocycles (furan, thiophene, benzofuran, etc.), and non-aromatic heterocycles (dioxane, tetrahydrofuran, etc.). 【0034】 From the viewpoint of easily obtaining a high affinity for the conductive polymer, the first carboxylic acid compound preferably has at least one aromatic ring. In this case, the two bonds of the acid anhydride group may be bonded to one aromatic ring or to each of two aromatic rings. Each aromatic ring may be 5 to 14 members. From the viewpoint of easily obtaining a higher affinity for the conductive polymer, each aromatic ring is preferably 6 to 10 members, and may be a benzene ring. From the viewpoint of easily obtaining a more stable effect by the acid anhydride group and the carboxy group, the aromatic ring may be an aromatic hydrocarbon ring. 【0035】 When two bonds of the acid anhydride group are bonded to one aromatic ring, hydrolysis of the acid anhydride group proceeds more slowly, allowing the pH of the liquid component to be maintained low for a longer period of time, thereby stabilizing the ESR of the electrolytic capacitor. In the first carboxylic acid compound, the carboxy group may be bonded to an aromatic ring to which no acid anhydride group is bonded. From the viewpoint of further suppressing fluctuations in ESR over time, at least one carboxy group may be bonded to one aromatic ring to which two bonds of the acid anhydride group are bonded. 【0036】 From the viewpoint of further suppressing the fluctuation of ESR over time, at least one of the carboxy groups in the first carboxylic acid compound may be located at the meta-position or the ortho-position relative to the acid anhydride group. More specifically, in the first carboxylic acid compound having an aromatic ring, when an acid anhydride group is bonded to the aromatic ring, at least one of the carboxy groups may be bonded to the meta-position or the ortho-position relative to the acid anhydride group bonded to the aromatic ring. 【0037】 The first carboxylic acid compound may be an acid anhydride of a polycarboxylic acid having three or more carboxy groups (acid anhydride IA), or may be an acid anhydride of a monocarboxylic acid or a polycarboxylic acid and a polycarboxylic acid (acid anhydride IB). 【0038】 Among the acid anhydrides IA, a compound having no ring structure other than the acid anhydride group may be a compound represented by the following formula (IA1): Among the acid anhydrides IA, a compound having a ring structure other than the acid anhydride group may be a compound represented by the following formula (IA2): Acid anhydride IB may be a compound represented by the following formula (IB): 【0039】 【0040】 In formula (IA1), R １ and R ２is an aliphatic group. Each of m1 and m2 is 0 or 1. Each of n1 and n2 is an integer of 1 or more. When m1 is 0, n1 is 1. When m2 is 0, n2 is 1. p1 is 0 or 1. When p1 is 0, n2 is 1. In the acid anhydride (IA1) represented by formula (IA1), the number of carboxy groups is n1 when p1 is 0, and (n1 + n2) when p1 is 1. 【0041】 In the acid anhydride (IA2) represented by formula (IA2), Z １ is a ring, and corresponds to the ring structure described above (a ring structure other than an acid anhydride group). ３ represents an aliphatic group. m3 is 0 or 1. n3 corresponds to the number of carboxy groups in the acid anhydride (IA2) and is an integer of 1 or more. 【0042】 In the acid anhydride (IB) represented by formula (IB), R ４ and R ５ Each of n4 and n5 is an aliphatic group, an aliphatic group having a ring structure, or a ring structure (cyclic group). Each of n4 and n5 is an integer of 1 or greater. p2 is 0 or 1. When p2 is 0, n5 is 1. The number of carboxy groups in acid anhydride (IB) is n4 when p2 is 0, and (n4 + n5) when p2 is 1. 【0043】 R １ , R ２ , and R ３ Examples of the aliphatic group represented by the formula (I) include a heteroatom-containing aliphatic group and an aliphatic hydrocarbon group. Examples of the heteroatom include at least one selected from the group consisting of an oxygen atom, a sulfur atom, and a nitrogen atom. From the viewpoints of relatively easy availability and easier attainment of the effects of the acid anhydride group and the carboxy group, the aliphatic group is preferably an aliphatic hydrocarbon group. Examples of the monovalent aliphatic hydrocarbon corresponding to the aliphatic hydrocarbon group include alkyl groups (C groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, and tert-butyl). １－６ Alkyl group (C １－４ alkyl groups, etc.), alkenyl groups (such as vinyl and allyl) ２－６ Alkenyl group (C２－４ An aliphatic group (such as an aliphatic hydrocarbon group) may be linear or branched. When each of m1 to m3 is 1, R １ ~R ３ The carboxy group bonded to the above corresponds to, for example, a substituent of the monovalent aliphatic hydrocarbon group. The number of carboxy groups in each of the acid anhydrides (IA1) and (IA2) is selected, for example, from the range of the number of carboxy groups in the first carboxylic acid compound. 【0044】 R １ , R ２ and R ３ Each of these may have a substituent (second substituent) other than the carboxy group (first substituent). Acid anhydrides having such a second substituent are also included in the first carboxylic acid compound. Examples of the second substituent include alkoxy groups (C groups such as methoxy, ethoxy, propoxy, and isopropoxy groups). １－６ Alkoxy group (C １－４ alkoxy groups, etc.), acyl groups (acetyl groups, etc.) ２－６ Acyl group (C ２－４ acyl groups, etc.), acyloxy groups (e.g., acetoxy groups), ２－６ Acyloxy group (C ２－４ Examples of the second substituent include an acyloxy group, an oxo group (=O), and a halogen atom (a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, etc.). Each acid anhydride may have one second substituent, or two or more second substituents. In each acid anhydride, the number of second substituents may be four or less. When each acid anhydride has two or more second substituents, at least two second substituents may be the same, or all second substituents may be different. 【0045】 In the acid anhydride (IA2), ring Z １ is selected from the examples of ring structures described above. １ is preferably an aromatic ring, more preferably an aromatic hydrocarbon ring (particularly a benzene ring). ３ ) m3-COOH group is a ring Z １ The ring Z corresponds to the substituent (third substituent) of the formula:１ is -(R ３ )m3- may have a substituent (fourth substituent) other than the COOH group and the acid anhydride group. Acid anhydrides having a fourth substituent are also included in the acid anhydride (IA2). Examples of the fourth substituent include the substituents exemplified for the second substituent, as well as hydrocarbon groups, for example, aliphatic hydrocarbon groups (alkyl groups (C １－６ alkyl group), alicyclic hydrocarbon group (cycloalkyl group such as cyclohexyl group (C ５－８ cycloalkyl groups, cycloalkenyl groups such as cyclohexenyl groups (C ５－８ cycloalkenyl groups, etc.), aromatic hydrocarbon groups (aryl groups such as phenyl groups and naphthyl groups (C ６－１０ aryl groups, etc.), aralkyl groups (C groups such as benzyl groups, phenethyl groups, etc. ６－１０ Aryl C １－４ Alkyl groups, etc.). １ The number of fourth substituents in may be 1 or more and 4 or less, may be 1 or 2, or may be 0. 【0046】 R of the acid anhydride (IB) represented by formula (IB) ４ or R ５ In relation to the above, examples of the aliphatic group include R １ ~R ３ The ring structure (cyclic group) is selected from the examples of the ring structure described above. The aliphatic group having a ring structure is selected from the examples of the ring structure described above and R １ ~R ３ Examples of the aliphatic group include a group bonded to an aliphatic group selected from the examples of R. The aliphatic group having a ring structure may be, for example, a structure (structure a) in which one ring structure is bonded to one aliphatic group, a structure (structure b) in which one ring structure is sandwiched between two aliphatic groups, or a structure (structure c) in which one aliphatic group is sandwiched between two ring structures. In these structures, the ring structure or aliphatic group bonded to the bond of the acid anhydride group is a divalent group corresponding to the exemplified ring structure or aliphatic group. The ring structure of structure b and the aliphatic group of structure c are divalent groups corresponding to the exemplified ring structure and exemplified aliphatic group, respectively. R ４ and R５ At least one of (particularly both of) may contain an aromatic ring, or may contain an aromatic hydrocarbon ring (particularly a benzene ring). 【0047】 In the acid anhydride (IB), the carboxy group is R ４ or R ５ corresponds to the substituent (fifth substituent) of R ４ and R ５ Each of R may have a substituent (sixth substituent) other than a carboxy group. Acid anhydrides having a sixth substituent are also included in the acid anhydride (IB). The sixth substituent may be selected, for example, from the substituents exemplified for the second and fourth substituents. ４ and R ５ The number of sixth substituents in each of the formulas may be 1 or more and 5 or less, 1 or more and 4 or less, 1 or 2, or 0. When the acid anhydride (IB) has two or more sixth substituents, at least two of the sixth substituents may be the same, or all of the sixth substituents may be different. 【0048】 Formulas (IA1), (IA2), and (IB) are examples of first carboxylic acid compounds having one acid anhydride group. However, the first carboxylic acid compound is not limited to these cases and may be a compound corresponding to the above formula and having two or more (e.g., two) acid anhydride groups. 【0049】 Examples of the first carboxylic acid compound include trimellitic anhydride (TMA), cyclohexane-1,2,4-tricarboxylic acid-1,2-anhydride, and an acid anhydride represented by the following formula (Ib). However, these compounds are merely examples, and the first carboxylic acid compound is not limited to these compounds. 【0050】 【0051】 In formula (Ib), n4a is an integer of 1 or more and 5 or less, and n5a is an integer of 0 or more and 5 or less. ６ and R ７are each a sixth substituent. q1 is an integer of 0 or more and 4 or less, and q2 is an integer of 0 or more and 5 or less. When the acid anhydride of formula (Ib) has two or more sixth substituents, at least two of the sixth substituents may be the same, or all of the sixth substituents may be different. 【0052】 The first carboxylic acid compound may be used alone or in combination of two or more. 【0053】 (Liquid Component) The liquid component contains a solvent and an acid component. The liquid component may further contain a base component. 【0054】 (Solvent) The solvent contained in the liquid component may be a non-aqueous solvent. Examples of the non-aqueous solvent include sulfone compounds, lactone compounds, carbonate compounds, and alcohol compounds. The liquid component may contain one type of non-aqueous solvent or a combination of two or more types. 【0055】 Among the aprotic polar solvents, sulfone compounds include cyclic sulfone compounds (such as sulfolane (SL)) and sulfoxide compounds (such as dimethyl sulfoxide and diethyl sulfoxide). Lactone compounds include γ-butyrolactone (GBL) and γ-valerolactone. Carbonate compounds include chain carbonates (such as dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate), and cyclic carbonates (such as ethylene carbonate, propylene carbonate, and fluoroethylene carbonate). 【0056】Among the non-aqueous solvents, alcohol compounds include monohydric alcohols and polyhydric alcohols. Examples of polyhydric alcohols include glycol compounds (alkylene glycols (ethylene glycol (EG), propylene glycol, etc.), polyalkylene glycols (polyethylene glycol (PEG), polypropylene glycol (PPG), polyethylene glycol-polypropylene glycol copolymers (PEG-PPG)), etc.), glycerin compounds (glycerin (GC), polyglycerin, etc.), sugar alcohol compounds, and alkylene oxide adducts thereof (ethylene oxide adducts, polyethylene oxide adducts, etc.). 【0057】 From the viewpoint of being suitable for improving the conductivity of the conductive polymer, the non-aqueous solvent preferably contains at least a glycol compound. The non-aqueous solvent may contain a glycol compound and a sulfone compound (e.g., a cyclic sulfone compound such as SL), and may additionally contain a polyalkylene glycol (e.g., PEG). 【0058】 The weight-average molecular weight (Mw) of the polyalkylene glycol may be 150 or more and 20,000 or less, or 200 or more and 20,000 or less. Within these ranges, the upper limit of the weight-average molecular weight (Mw) may be 5,000 or less, or 1,000 or less. When the weight-average molecular weight (Mw) is within such a range, not only is it easy to obtain high film repairability, but the viscosity of the liquid component is also easy to maintain relatively low, which can increase the dissociation of the acid component and the base component. 【0059】 In this specification, the weight average molecular weight (Mw) is a value calculated as polystyrene measured by gel permeation chromatography (GPC), which is typically performed using a polystyrene gel column and a water / methanol (volume ratio 8 / 2) mobile phase. 【0060】(Acid Component) The acid component includes the first carboxylic acid compound described above. For the first carboxylic acid compound, the description of the additives described above can be referred to. The liquid component may include an acid component other than the first carboxylic acid compound. Examples of such an acid component include a carboxylic acid compound other than the first carboxylic acid compound (a second carboxylic acid compound) and other acids. 【0061】 (Second Carboxylic Acid Compound) The acid component may further contain a second carboxylic acid compound different from the first carboxylic acid compound. When the acid component contains the second carboxylic acid compound, the pH of the liquid component can be further reduced. Since the decrease in the conductivity of the conductive polymer is further suppressed, it is easier to further reduce the change in ESR over time. 【0062】 Examples of the second carboxylic acid compound include carboxylic acids other than the first carboxylic acid compound, carboxylic acid anhydrides, and coordination compounds of carboxylic acids. 【0063】 Examples of the carboxylic acid include aliphatic carboxylic acids and aromatic carboxylic acids. Examples of the aromatic carboxylic acids include aromatic hydroxy acids (benzoic acid, nitrobenzoic acid, salicylic acid, etc.), aromatic polycarboxylic acids (phthalic acid, pyromellitic acid, etc.), and sulfoaromatic carboxylic acids (p-sulfobenzoic acid, 3-sulfophthalic acid, 5-sulfosalicylic acid, etc.). Examples of the carboxylic acid anhydrides include aliphatic carboxylic acid anhydrides (maleic anhydride, succinic anhydride, etc.), and aromatic carboxylic acid anhydrides (phthalic anhydride, benzoic anhydride, etc.). 【0064】 Examples of the coordination compound include a coordination compound having at least one central atom selected from the group consisting of boron, aluminum, and silicon, and an acid having a carbonyloxy bond bound to the central atom. Specific examples of the coordination compound include borodisalicylic acid, borodisalic acid, borodiglycolic acid, and borodigallic acid. 【0065】The acid component may contain one or more second carboxylic acid compounds. Among the second carboxylic acid compounds, aromatic carboxylic acids (such as phthalic acid, salicylic acid, benzoic acid, and nitrobenzoic acid) and the coordination compounds (such as borodisalicylic acid, borodisalic acid, and borodiglycolic acid) are preferred, and phthalic acid, salicylic acid, and borodisalicylic acid are particularly preferred. 【0066】 In the liquid component, the carboxy group and other acid groups (such as sulfonic acid groups, phosphoric acid groups, and phosphonic acid groups) of the second carboxylic acid compound may each be in any of the following forms: free form, salt form, anionic form, or form interacting (e.g., complexing) with the conductive polymer. The carboxy group and other acid groups of the second carboxylic acid compound each include all of these forms. 【0067】 (Other Acids) The acid component may include an acid other than the first carboxylic acid compound and the second carboxylic acid compound. Examples of such other acids include acids having a carbonyloxy bond other than carboxylic acid (such as oxocarbonic acid and Meldrum's acid) or coordination compounds thereof, phenolic compounds (such as picric acid, p-nitrophenol, pyrogallol, and catechol) or coordination compounds thereof, sulfur-containing acids (such as sulfuric acid, sulfonic acids (such as aromatic sulfonic acids), and oxyaromatic sulfonic acids (such as phenol-2-sulfonic acid)), compounds having a sulfonylimide bond, boron-containing acids (such as boric acid, halogenated boric acids (such as tetrafluoroboric acid), and partial esters thereof), phosphorus-containing acids (such as phosphoric acid, halogenated phosphoric acids (such as hexafluorophosphoric acid), phosphonic acids, phosphinic acids, and partial esters thereof (such as butyl phosphate)), and nitrogen-containing acids (such as nitric acid and nitrous acid). 【0068】Examples of compounds having a sulfonylimide bond include saccharin, 1,2-benzenedisulfonimide, cyclohexafluoropropane-1,3-bis(sulfonyl)imide, 4-methyl-N-[(4-methylphenyl)sulfonyl]benzenesulfonamide, dibenzenesulfonimide, trifluoromethanesulfonanilide, N-[(4-methylphenyl)sulfonyl]acetamide, benzenesulfonanilide, and N,N'-diphenylsulfamide. 【0069】 Examples of the coordination compound include a coordination compound having at least one central atom selected from the group consisting of boron, aluminum, and silicon, and an acid or phenol compound having a carbonyloxy bond bound to the central atom. Specific examples of the coordination compound include borodicatechol and borodipyrogallol. 【0070】 The acid component may contain one or more of the above-mentioned other acids. 【0071】 (Other) The ratio of the first carboxylic acid compound in the acid component may be 20% by mass or more, 33% by mass or more, or 50% by mass or more. In this case, fluctuations in ESR over time can be further suppressed. The ratio of the first carboxylic acid compound in the acid component is 100% by mass or less. From the viewpoint of improving the film repairability of the dielectric layer, the ratio of the first carboxylic acid compound in the acid component may be 80% by mass or less. 【0072】 The ratio of the first carboxylic acid compound in the acid component may be 20% by mass or more (or 33% by mass or more) and 100% by mass or less, 50% by mass or more and 100% by mass or less, 20% by mass or more (or 33% by mass or more) and 80% by mass or less, or 50% by mass or more and 80% by mass or less. 【0073】The mass ratio of the second carboxylic acid compound to the first carboxylic acid compound (=second carboxylic acid compound / first carboxylic acid compound) may be 0 / 100 or more and 80 / 20 or less, 20 / 80 or more and 67 / 33 or less, or 20 / 80 or more and 50 / 50 or less. When the mass ratio is within such a range, the effect of the first carboxylic acid compound is easily exerted, and fluctuation of the high ESR over time can be further suppressed. 【0074】 The concentration of the first carboxylic acid compound contained in the liquid component may be 1% by mass or more and 30% by mass or less, or 1% by mass or more and 20% by mass or less. From the viewpoint of further reducing the fluctuation of ESR over time, the concentration of the first carboxylic acid compound is preferably 1% by mass or more and 14% by mass or less, and more preferably 2% by mass or more and 12% by mass or less. 【0075】 The above ratios, mass ratios, and concentrations are values ​​determined based on the mass of each acid when it is in its free form. 【0076】 (Base Component) When the liquid component contains a base component, the dissociation property of the acid component such as the first carboxylic acid compound is enhanced, and the acid group such as a carboxy group can easily react with the conductive polymer, thereby easily obtaining higher conductivity of the conductive polymer. 【0077】 Examples of the basic component include ammonia, amines (specifically, primary amines, secondary amines, and tertiary amines), quaternary ammonium compounds, and amidinium compounds. The liquid component may contain one type of basic component or two or more types. 【0078】The amine may be any of aliphatic, aromatic, and heterocyclic. Examples of the amine include dialkylamines (diethylamine, etc.), trialkylamines (trimethylamine, ethyldimethylamine, triethylamine (TEA), tri-n-butylamine (TBA), dimethyl-n-octylamine (DMOA), etc.), alkylenediamines (ethylenediamine, etc.), aromatic amines (aniline, etc.), and heterocyclic amines (pyrrolidine, imidazole compounds (imidazole (Imd), 1,2,3,4-tetramethylimidazolinium, etc.), pyridine (Pyr), 4-dimethylaminopyridine, diazabicycloundecene (DBU), N-methylmorpholine (MMP), N-butylmorpholine, and N-isobutylmorpholine). Each of the aromatic amines and heterocyclic amines may be monocyclic or polycyclic (fused ring, bridged ring, etc.). Examples of the quaternary ammonium compound include amidine compounds (including imidazole compounds). 【0079】 The liquid component may contain the base component in a free form, a cationic form, or a salt form, and all of these forms may be referred to as the base component. 【0080】 The equivalent ratio of the first carboxylic acid compound to the base component (=first carboxylic acid compound / base component) may be 0.5 or more and 10 or less, 1.0 or more and 9.0 or less, or 1.3 or more and 8.9 or less. In this case, a high degree of dissociation of the first carboxylic acid compound can be ensured and corrosion of the electrode can be suppressed. 【0081】 The equivalent ratio of the first carboxylic acid compound to the base component is (the total number of carboxy groups per molecule of the first carboxylic acid compound) / (OH groups that can be generated per molecule of the base component) － is the ratio of the total number of moles of 【0082】The equivalent ratio of the acid component to the base component (=acid component / base component) may be 0.5 or more and 15 or less, or 1.0 or more and 10 or less. The equivalent ratio of the acid component / base component may be selected from the above-mentioned numerical range described for the equivalent ratio of the first carboxylic acid compound / base component. 【0083】 The equivalent ratio of the acid component to the base component is (the total number of acid groups per molecule of the acid component) / (OH groups that can be generated per molecule of the base component) － is the ratio of the total number of moles of 【0084】 (Capacitor Element) The capacitor element included in the electrolytic capacitor includes an anode body having a dielectric layer on its surface and a conductive polymer covering at least a portion of the dielectric layer. The conductive polymer constitutes at least a portion of the cathode body of the capacitor element. The cathode body may further include a cathode extraction layer (e.g., a cathode foil). 【0085】 (Anode Body) The anode body may contain a valve metal, an alloy containing a valve metal, or a compound containing a valve metal. These materials may be used alone or in combination of two or more. Preferred valve metals include aluminum, tantalum, niobium, and titanium. 【0086】 The anode body is preferably an anode foil. The anode body preferably has a porous portion having pores at least in the surface layer. Anode bodies other than anode foil include a porous sintered body or a porous molded body of particles containing a valve metal. 【0087】 The porous anode foil can be obtained by roughening the surface of a valve metal-containing substrate (e.g., a foil- or plate-shaped substrate). The roughening can be performed by etching (e.g., electrolytic etching or chemical etching). 【0088】 (Dielectric Layer) The dielectric layer is formed by anodizing the valve metal on the surface of the anode body. Anodization is performed, for example, by chemical conversion treatment. The dielectric layer is formed, for example, so as to cover at least a portion of the surface of the anode body. 【0089】The dielectric layer contains an oxide of the valve metal. For example, when tantalum is used as the valve metal, the dielectric layer contains Ta. ２ O ５ When aluminum is used as the valve metal, the dielectric layer contains Al ２ O ３ However, the dielectric layer is not limited to this, and may be any layer that functions as a dielectric. 【0090】 The dielectric layer is usually formed on the surface of the anode body. When the dielectric layer is formed on the surface of the porous portion of the anode body, the dielectric layer is formed along the inner wall surfaces of the pores in the porous portion and the depressions (pits) on the surface of the anode body. 【0091】 (Conductive Polymer) The conductive polymer includes, for example, a conjugated polymer and a dopant. The conductive polymer may cover at least a portion of the dielectric layer. This embodiment includes a case where the conductive polymer is in contact with at least a portion of the dielectric layer. When the capacitor element includes an anode foil and a cathode foil, the conductive polymer may be interposed between these foils. In this case, the conductive polymer may be impregnated into a separator interposed between the anode foil and the cathode foil. The conductive polymer may be in contact with at least a portion of the cathode foil in addition to at least a portion of the dielectric layer. The conductive polymer may form a layer. The conductive polymer is sometimes called a solid electrolyte. The conductive polymer forms at least a portion of the cathode body in an electrolytic capacitor. The conductive polymer may further include an additive, if necessary. 【0092】(Conjugated Polymers) Examples of conjugated polymers include known conjugated polymers used in electrolytic capacitors, such as π-conjugated polymers. Examples of conjugated polymers include polymers with a basic skeleton of polypyrrole, polythiophene, polyaniline, polyfuran, polyacetylene, polyphenylene, polyphenylene vinylene, polyacene, and polythiophene vinylene. The above polymers may contain at least one monomer unit constituting the basic skeleton. The above polymers also include homopolymers, copolymers of two or more monomers, and derivatives thereof (e.g., substituted products having substituents). For example, polythiophenes include poly(3,4-ethylenedioxythiophene) (PEDOT). 【0093】 The conjugated polymer may be used alone or in combination of two or more kinds. 【0094】 The weight average molecular weight (Mw) of the conjugated polymer is not particularly limited and is, for example, 1,000 or more and 1,000,000 or less. 【0095】 (Dopants) Examples of dopants include relatively low molecular weight anions and polymeric anions. Examples of anions include sulfate ions, nitrate ions, phosphate ions, borate ions, organic sulfonate ions, and carboxylate ions. Compounds that generate these anions are used as dopants. Examples of dopants that generate sulfonate ions include aromatic sulfonic acid compounds (such as paratoluenesulfonic acid and naphthalenesulfonic acid). The aromatic sulfonic acid compound may have at least one group selected from the group consisting of a carboxy group and a hydroxy group. 【0096】Examples of polymeric anions include polyvinyl sulfonic acid, polystyrene sulfonic acid (PSS), polyallylsulfonic acid, polyacrylic sulfonic acid, polymethacrylic sulfonic acid, poly(2-acrylamido-2-methylpropanesulfonic acid), polyisoprene sulfonic acid, polyester sulfonic acid (such as aromatic polyester sulfonic acid), phenolsulfonic acid novolac resin, and polyacrylic acid. The polymeric anion may be a polymer of a single monomer, a copolymer of two or more monomers, or a substituted product having a substituent. Among these, polyanions derived from polystyrene sulfonic acid are preferred. 【0097】 However, these dopants are merely examples and are not limited to these. One dopant may be used alone, or two or more dopants may be used in combination. 【0098】 The conductive polymer may be formed, for example, by chemically polymerizing or electrolytically polymerizing a conjugated polymer precursor on a dielectric layer in the presence of a dopant. Alternatively, a conductive polymer (e.g., a conductive polymer layer) may be formed by contacting a solution in which the conductive polymer is dissolved or a dispersion in which the conductive polymer is dispersed with a dielectric layer. The conductive polymer used in these solutions or dispersions can be obtained by polymerizing a conjugated polymer precursor in the presence of a dopant. Examples of conjugated polymer precursors include raw material monomers for conjugated polymers, and oligomers and prepolymers in which multiple molecular chains of the raw material monomers are linked together. One type of precursor may be used, or two or more types may be used in combination. 【0099】 The weight average molecular weight (Mw) of the dopant is not particularly limited and is, for example, 1,000 or more and 1,000,000 or less. 【0100】 The amount of the dopant contained in the conductive polymer is, for example, 10 parts by mass or more and 1000 parts by mass or less, and may be 20 parts by mass or more and 500 parts by mass or less, relative to 100 parts by mass of the conjugated polymer. 【0101】(Cathode Extraction Layer) The cathode extraction layer may include, for example, a first layer covering at least a portion of the conductive polymer. The cathode extraction layer may include a first layer and a second layer covering the first layer. Examples of the first layer include a layer containing conductive particles and a metal foil (cathode foil). Examples of the conductive particles include at least one selected from conductive carbon and metal powder. For example, the cathode extraction layer may include a first layer containing conductive carbon (e.g., graphite) (also referred to as a carbon layer) and a second layer containing metal powder or a metal foil. When a metal foil is used as the first layer, the cathode extraction layer may be formed of this metal foil. The cathode extraction layer can be formed by a known method depending on the layer configuration. 【0102】 The second layer containing metal powder can be formed, for example, by laminating a composition containing metal powder on the surface of the first layer. Examples of such a second layer include a metal paste layer (e.g., a silver paste layer) formed using a composition containing metal powder such as silver particles and a resin (binder resin). The resin may be a thermosetting resin such as an imide resin or an epoxy resin, or a thermoplastic resin. 【0103】 When a metal foil is used as the first layer, 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. If necessary, the surface of the metal foil may be roughened. The surface of the metal foil may be provided with a chemical conversion coating, or may be provided with a coating of a metal (dissimilar metal) or a nonmetal different from the metal constituting the metal foil. Examples of dissimilar metals and nonmetals include metals such as titanium and nonmetals such as carbon (e.g., conductive carbon). 【0104】 The coating of the dissimilar metal or non-metal (for example, conductive carbon) may be the first layer, and the metal foil may be the second layer. 【0105】(Separator) A separator may be disposed between the cathode body (e.g., cathode foil) and the anode body (e.g., anode foil). The separator is not particularly limited, and may be, for example, a nonwoven fabric containing fibers of cellulose, polyethylene terephthalate, vinylon, or polyamide (e.g., aliphatic polyamide, aromatic polyamide such as aramid). 【0106】 When the capacitor element includes a separator, the conductive polymer may be impregnated into the separator. The conductive polymer may be interposed between an anode body (e.g., an anode foil) and a cathode body (e.g., a cathode foil) and may be in contact with at least a portion of the dielectric layer and at least a portion of the cathode body. In the present disclosure, the combination of the conductive polymer with a liquid component containing a first carboxylic acid compound can maintain high conductivity of the conductive polymer, so that a decrease in ESR can be suppressed even in these embodiments. 【0107】 (Other) The electrolytic capacitor may be a wound type, and may be either a chip type or a laminated type. The electrolytic capacitor has at least one capacitor element. The electrolytic capacitor may have multiple capacitor elements. For example, the electrolytic capacitor may have a laminate of two or more capacitor elements, or may have two or more wound capacitor elements. The configuration or number of capacitor elements may be selected depending on the type or application of the electrolytic capacitor. 【0108】 In the capacitor element, one end of a cathode lead is electrically connected to the cathode extraction layer. One end of an anode lead is electrically connected to the anode body. The other end of the anode lead and the other end of the cathode lead are each drawn out from the exterior body or case. The other end of each lead exposed from the exterior body or case is used for soldering to a substrate on which the electrolytic capacitor is to be mounted, for example. Each lead may be a lead wire or a lead frame. 【0109】Fig. 1 is a cross-sectional schematic diagram of an electrolytic capacitor according to this embodiment, and Fig. 2 is a schematic diagram showing a portion of a capacitor element of the electrolytic capacitor in an exploded view. However, the electrolytic capacitor of the present disclosure is not limited to the following embodiments. Furthermore, the components of the following embodiments may be arbitrarily combined with at least one of the above-described (Technology 1) to (Technology 12) related to the electrolytic capacitor or liquid component additive of the present disclosure, or may be arbitrarily combined with at least one of the above-described (Technology 1) to (Technology 12) and the components described above. 【0110】 The electrolytic capacitor includes, for example, a capacitor element 10, a bottomed case 101 that contains capacitor element 10 and a liquid component (not shown), a sealing member 102 that closes the opening of bottomed case 101, a seat plate 103 that covers sealing member 102, lead wires 104A and 104B that extend from sealing member 102 and pass through seat plate 103, and lead tabs 105A and 105B that connect the lead wires to electrodes of capacitor element 10. The vicinity of the open end of bottomed case 101 is drawn inward, and the open end is curled so as to be crimped to sealing member 102. 【0111】 Capacitor element 10 is, for example, a wound body as shown in Fig. 2. The wound body includes anode foil 11 connected to lead tab 105A, cathode foil 12 connected to lead tab 105B, and separator 13. Anode foil 11 and cathode foil 12 are wound with separator 13 interposed therebetween. The outermost periphery of the wound body is fixed with stop tape 14. Note that Fig. 2 shows a partially unfolded state of the wound body before the outermost periphery is secured. 【0112】 In capacitor element 10, a dielectric layer (not shown) is formed on at least a portion of the surface of anode foil 11. Separator 13 and a conductive polymer (not shown) are interposed between anode foil 11 and cathode foil 12. The conductive polymer is in contact with at least a portion of the dielectric layer. The conductive polymer is also in contact with at least a portion of cathode foil 12. The conductive polymer and separator are impregnated with a liquid component. 【0113】EXAMPLES The present invention will be specifically described below based on examples and comparative examples, but the present invention is not limited to the following examples. 【0114】 Examples 1 to 10 and Comparative Examples 1 and 2 Wound electrolytic capacitors (rated voltage 35 V, rated capacitance 330 μF) were fabricated and evaluated according to the following procedure. 【0115】 (Preparation of anode body) An aluminum foil having a thickness of 100 μm was subjected to an etching treatment to roughen the surface of the aluminum foil. Then, a dielectric layer was formed on the surface of the aluminum foil by chemical conversion treatment. The chemical conversion treatment was performed by immersing the aluminum foil in an ammonium adipate solution and applying a voltage thereto. Then, the aluminum foil was cut into a size of 8 mm length x 120 mm width to prepare an anode body. 【0116】 (Preparation of 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 cut into a size of 8 mm length×120 mm width to prepare a cathode body. 【0117】 (Preparation of Wound Body) An anode lead tab and a cathode lead tab were connected to the anode body and the cathode body, and the anode body and the cathode body were wound around the lead tabs, with a separator interposed therebetween, and the ends of the outer surface of the wound body were fixed with a winding tape to prepare a wound body. An anode lead wire and a cathode lead wire were connected to the ends of each lead tab protruding from the wound body, respectively. The prepared wound body was then subjected to a chemical conversion treatment again, and a dielectric layer was formed on the cut end of the anode body. 【0118】(Preparation of Polymer Dispersion Containing Conductive Polymer) 3,4-ethylenedioxythiophene and the polymer dopant poly(4-styrenesulfonic acid) (PSS, Mw: 100,000) were dissolved in ion-exchanged water to prepare a mixed solution. While stirring the mixed solution, an oxidizing agent (iron(III) sulfate and ammonium persulfate) dissolved in ion-exchanged water was added to carry out a polymerization reaction. After the reaction, the resulting reaction solution was dialyzed to remove unreacted monomers and excess oxidizing agent, yielding a polymer dispersion containing PSS-doped poly(3,4-ethylenedioxythiophene) (PEDOT / PSS) as the conductive polymer. The weight-average molecular weight (Mw) of the polymer dopant was measured under the conditions described above. 【0119】 (Coating of the dielectric layer with a conductive polymer) The wound body was immersed in a polymer dispersion contained in a specified container in a reduced pressure atmosphere (40 kPa) for 5 minutes, and then removed from the polymer dispersion. Next, the wound body impregnated with the polymer dispersion was dried in a drying oven at 150°C for 20 minutes, and at least a portion of the dielectric layer was coated with the conductive polymer. In this way, a capacitor element was formed. 【0120】 (Preparation of Liquid Component and Impregnation into Capacitor Element) Liquid components were prepared by mixing the salts and other acid components shown in Table 1 into a solvent so that the concentrations in the liquid component were the values ​​(% by mass) shown in Table 1. As the solvent, a mixed solvent of ethylene glycol, sulfolane, and polyethylene glycol in a volume ratio of 40:30:30 was used. 【0121】 The symbols in Table 1 represent the following components. 【0122】 TMA: trimellitic anhydride TEA: triethylamine MMP: N-methylmorpholine (Assembly of electrolytic capacitor) The capacitor element was immersed in the liquid component and placed in a reduced pressure atmosphere (40 kPa) for 5 minutes to impregnate the capacitor element with the liquid component. 【0123】The capacitor element impregnated with the liquid component was placed inside a bottomed case, with the lead wires positioned on the open side of the case. A sealing member (made of an elastic material containing butyl rubber as a rubber component) formed to allow the lead wires to pass through was placed above the capacitor element. The bottomed case was then drawn near the open end, and the open end was further curled to adhere to the sealing member. In this way, the capacitor element and liquid component were sealed inside the bottomed case. An electrolytic capacitor as shown in Figure 1 was completed by placing a seat plate on the curled portion. A total of 40 electrolytic capacitors were produced for each example. The produced electrolytic capacitors were then aged at 130°C for two hours while applying the rated voltage. 【0124】 [Evaluation] The electrolytic capacitors prepared above were evaluated according to the following procedure: (1) Change in Capacitance (Δcap) and Change in ESR (ΔESR) For 20 electrolytic capacitors after the aging treatment, the capacitance at a frequency of 120 Hz and the ESR value at a frequency of 100 kHz were measured using an LCR meter in an environment of 25°C, and the average values ​​(initial capacitance value: c0 (F), initial ESR value: r0 (Ω)) were calculated. 【0125】 After measuring the initial capacitance value c0 and the initial ESR value r0, a high-temperature load test (accelerated test) was conducted. That is, a rated voltage was applied to the electrolytic capacitor for 1700 hours at a temperature of 145°C. After 1700 hours of accelerated testing, the average capacitance value (c1 (F)) and average ESR value (r1 (Ω)) of the electrolytic capacitor were determined in accordance with the initial capacitance value and initial ESR value. 【0126】 Using the obtained initial capacitance value c0, capacitance value c1 after the accelerated test, and initial ESR value r0, ESR value r1 after the accelerated test, the capacitance change (Δcap) and ESR change (ΔESR) were calculated according to the following formula. 【0127】Δcap=c1 / c0 ΔESR=r1 / r0 (2) Change in Leakage Current (ΔLC) For the remaining 20 electrolytic capacitors after the aging treatment, a 1 kΩ resistor was connected in series, and a rated voltage of 25 V was applied for 1 minute from a DC power supply, after which the leakage current was measured and the average value of the electrolytic capacitors (initial leakage current: e0 (A)) was calculated. 【0128】 The 20 electrolytic capacitors for which the initial leakage current e0 was measured were subjected to an accelerated test at 145°C for 1700 hours without applying voltage. The leakage current (A) of the electrolytic capacitors after 1700 hours of accelerated testing was measured in the same manner as for the initial leakage current, and the average value of the 20 capacitors (leakage current after 1700 hours of accelerated testing: e1 (A)) was calculated. The capacitance change (ΔLC) was calculated using the obtained initial leakage current e0 and the leakage current e1 after the accelerated testing according to the following formula: 【0129】 ΔLC=e1 / e0 The evaluation results of each electrolytic capacitor are shown in Table 1. In Table 1, A1 to A10 are examples, and B1 and B2 are comparative examples. 【0130】 【0131】 As shown in Table 1, in the Examples, after 1,700 hours of accelerated testing, a relatively high capacity was maintained while ESR fluctuations were suppressed and leakage current was significantly reduced compared to the Comparative Examples. Furthermore, since the accelerated testing was performed in a 145°C environment, it can be said that the electrolytic capacitors of the Examples also suppressed ESR fluctuations and leakage current in high-temperature environments. 【0132】 The electrolytic capacitor of the present disclosure can be used as a hybrid electrolytic capacitor. The electrolytic capacitor exhibits small fluctuations in ESR over time and is highly reliable. Therefore, it is particularly suitable for applications requiring high reliability or long life. However, the applications of the electrolytic capacitor are not limited to these. 【0133】 100: Electrolytic capacitor 101: Bottomed case 102: Sealing member 103: Seat plate 104A, 104B: Lead wire 105A, 105B: Lead tab 10: Capacitor element 11: Anode foil 12: Cathode foil 13: Separator 14: Winding tape

Claims

[Claim 1] It comprises a capacitor element and a liquid component, The capacitor element includes an anode having a dielectric layer on its surface and a conductive polymer covering a portion of the dielectric layer. The aforementioned liquid component comprises a solvent and an acid component. The acid component comprises a carboxylic acid compound having an acid anhydride group and a carboxyl group, in an electrolytic capacitor. [Claim 2] The carboxylic acid compound has an aromatic ring, The electrolytic capacitor according to claim 1, wherein each of the two bonds of the acid anhydride group is bonded to the aromatic ring. [Claim 3] The carboxylic acid compound has two aromatic rings, One of the two bonds of the acid anhydride group is bonded to one of the two aromatic rings, The electrolytic capacitor according to claim 1, wherein the other of the two bonds of the acid anhydride group is bonded to the other of the two aromatic rings. [Claim 4] The electrolytic capacitor according to claim 2, wherein the carboxyl group is bonded to the aromatic ring. [Claim 5] The electrolytic capacitor according to claim 3, wherein the carboxyl group is bonded to at least one of the two aromatic rings. [Claim 6] The electrolytic capacitor according to claim 2, wherein the number of ring members of the aromatic ring is 6 or more and 10 or less. [Claim 7] The electrolytic capacitor according to claim 3, wherein the number of ring members of each of the two aromatic rings is 6 or more and 10 or less. [Claim 8] The electrolytic capacitor according to claim 2, wherein in the aromatic ring, the carboxyl group is located at the meta or ortho position relative to the acid anhydride group. [Claim 9] The electrolytic capacitor according to claim 3, wherein in at least one of the two aromatic rings, the carboxyl group is located at the meta or ortho position relative to the acid anhydride group. [Claim 10] The electrolytic capacitor according to any one of claims 1 to 9, wherein the liquid component further comprises a basic component. [Claim 11] The electrolytic capacitor according to claim 10, wherein the equivalent ratio of the carboxylic acid compound to the base component is 0.5 or more and 10 or less. [Claim 12] An additive used in the liquid component of an electrolytic capacitor comprising a capacitor element containing a conductive polymer and a liquid component, An additive for the liquid component of electrolytic capacitors, comprising a carboxylic acid compound having an acid anhydride group and a carboxyl group.