Electrolytic capacitor

Abstract

This electrolytic capacitor comprises a capacitor element and a liquid component. The capacitor element comprises: an anode body that has a dielectric layer on the surface thereof; and an electroconductive polymer that covers at least a part of the dielectric layer. The liquid component includes an acid component and a solvent. The acid component includes a first carboxylic acid compound that has one first portion and one second portion. The first portion has a first carboxy group that contains a first carbonyl group, a second carbonyl group, and a linking group that links the first carbonyl group and the second carbonyl group to each other. The second portion includes a hetero atom that is bonded to the second carbonyl group, and a hydrocarbon group that has two or more carbon atoms and is bonded to the hetero atom.

Description

electrolytic capacitor

[0001] The present disclosure relates to electrolytic capacitors.

[0002] Electrolytic capacitors are considered promising as capacitors with small size, large capacity, and low ESR (equivalent series resistance). 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 electrolyte solution to be used in an electrolytic capacitor including an anode having a dielectric oxide film, a cathode, a separator disposed between the anode and the cathode, and a conductive polymer and an electrolyte solution held by the separator, the electrolyte solution containing a solvent containing at least one selected from the group consisting of ethylene glycol, polyethylene glycol, and derivatives thereof, and a solute containing at least one selected from the group consisting of a dicarboxylic acid having a hydroxyl group at the α-position, a polycarboxylic acid having a hydroxyl group at the α-position, and salts thereof.

[0004] Patent Document 2 proposes a solid electrolytic capacitor having a capacitor element in which an anode foil and a cathode foil are wound with a separator interposed therebetween, the capacitor element having a solid electrolyte layer, voids within the capacitor element being filled with an electrolytic solution, the electrolytic solution containing an ammonium salt of an aliphatic carboxylic acid as a solute and a polyhydric alcohol as a solvent, and the amount of the acid solute added to the solvent being 0.6 mol / kg or less.

[0005] Patent Document 3 proposes a conductive polymer hybrid aluminum electrolytic capacitor having a capacitor element in which anode electrode foil and cathode electrode foil each having an aluminum dielectric oxide film formed thereon are wound with a separator interposed therebetween, the capacitor having a conductive polymer layer formed on the dielectric oxide film and an electrolyte solution, the electrolyte solution containing a solute and a solvent, the solvent containing diethylene glycol and / or triethylene glycol, and the solute containing a salt of a long-chain dibasic carboxylic acid (dicarboxylic acid) having 12 or more carbon atoms and an amine having a boiling point of 150°C or higher.

[0006] As electrolytes for electrolytic capacitors, electrolytes containing carboxylic acids or carboxylic acid salts, as described in Patent Documents 4 to 6, are also known.

[0007] JP 2021-163877 A JP 2017-38010 A JP 2021-64768 A JP 1-103821 A JP 2004-71727 A JP 2019-102791 A

[0008] Conductive polymers, for example, can achieve high conductivity when a conjugated polymer is doped with a dopant. When the liquid component contains an acid component, it is expected that the dedoping of the dopant is suppressed, thereby maintaining the high conductivity of the conductive polymer. However, even when a liquid component containing an acid component is used, it is actually difficult to suppress the decrease in the conductivity of the conductive polymer over time when the electrolytic capacitor is used, and it may be difficult to suppress an increase in ESR.

[0009] A first aspect of the present disclosure relates to an electrolytic capacitor including a capacitor element and a liquid component, wherein the capacitor element includes an anode body having a dielectric layer on a surface thereof, and a conductive polymer covering at least a portion of the dielectric layer, wherein the liquid component includes an acid component and a solvent, wherein the acid component includes a first carboxylic acid compound each having a first site and a second site, wherein the first site has a first carboxy group including a first carbonyl group, a second carbonyl group, and a linking group linking the first carbonyl group and the second carbonyl group, and wherein the second site includes a heteroatom bonded to the second carbonyl group and a hydrocarbon group having two or more carbon atoms bonded to the heteroatom.

[0010] A second aspect of the present disclosure relates to an electrolytic capacitor including a capacitor element and a liquid component, wherein the capacitor element includes an anode body having a dielectric layer on a surface thereof, and a conductive polymer covering at least a portion of the dielectric layer, wherein the liquid component includes an acid component, a base component, and a solvent, wherein the acid component includes a first carboxylic acid compound having one first site, wherein the first site has a first carboxy group including a first carbonyl group, a second carbonyl group, and a linking group linking the first carbonyl group and the second carbonyl group, and the base component includes at least one selected from the group consisting of an amine, a quaternary ammonium compound, and an amidinium compound.

[0011] In electrolytic capacitors containing conductive polymers, the change in ESR over time can be reduced.

[0012] 1 is a schematic cross-sectional view of an electrolytic capacitor according to an embodiment of the present disclosure;

[0013] The novel features of the present invention are set forth in the appended claims, but the present invention, both in terms of structure and content, together with other objects and features of the present invention, will be better understood from the following detailed description taken in conjunction with the drawings.

[0014] When a liquid component containing an acid component is used in an electrolytic capacitor containing a conductive polymer, it is expected that the pH of the liquid component can be kept low, thereby suppressing dedoping in the conductive polymer and maintaining the high conductivity of the conductive polymer. However, in reality, even when a liquid component containing an acid component is used, the high conductivity of the conductive polymer may not be maintained. This is thought to be because the acid component has low solubility in non-aqueous solvents or reacts with the non-aqueous solvent, which does not sufficiently suppress the progress of dedoping, resulting in deterioration of the conductive polymer. As the degradation of the conductive polymer progresses with use of the electrolytic capacitor, the conductivity of the conductive polymer decreases and the ESR increases.

[0015] In electrolytic capacitors that do not contain conductive polymers but contain liquid components, the ESR of the electrolytic capacitor is significantly affected by the ionic conductivity of the liquid components and the state of electrical connections between the components of the electrolytic capacitor. In contrast, in electrolytic capacitors that contain conductive polymers but do not contain liquid components, the resistance of the conductive polymer tends to be higher than that of the cathode extraction layer or anode body that constitute the cathode body. Therefore, as mentioned above, the conductivity of the conductive polymer significantly affects the ESR. Furthermore, as mentioned above, because conductive polymers deteriorate over the use of electrolytic capacitors, stabilizing the conductive polymer is important to maintain high conductivity. When an electrolytic capacitor contains a conductive polymer and a liquid component, the liquid component significantly affects the state of the conductive polymer (including conductivity, stability, etc.). However, in electrolytic capacitors that do not contain conductive polymers but contain liquid components, there is no resistance of the conductive polymer or interaction between the conductive polymer and the liquid component. Therefore, in such electrolytic capacitors, the mechanism by which the liquid component affects the ESR of the electrolytic capacitor is completely different from that of electrolytic capacitors that contain conductive polymers and liquid components. Suppose a liquid component of an electrolytic capacitor that does not contain a conductive polymer is applied to an electrolytic capacitor that does contain a conductive polymer. However, in this case, it is unclear whether it will be effective in stabilizing the conductive polymer or suppressing the decrease in conductivity. In addition, it is unclear whether it will be effective in reducing the change in ESR over time.

[0016] 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, wherein the capacitor element includes an anode body having a dielectric layer on a surface thereof, and a conductive polymer covering at least a portion of the dielectric layer, wherein the liquid component includes an acid component and a solvent, and the acid component includes a first carboxylic acid compound having a first moiety and a second moiety, wherein the first moiety has a first carboxy group including a first carbonyl group, a second carbonyl group, and a linking group connecting the first carbonyl group and the second carbonyl group, and the second moiety includes a heteroatom bonded to the second carbonyl group and a hydrocarbon group having two or more carbon atoms bonded to the heteroatom. In the electrolytic capacitor according to the first aspect, the first carboxylic acid compound included in the liquid component may be referred to as a first carboxylic acid compound A.

[0017] (Technology 2) In the above (Technology 1), the liquid component may further contain a base component. In this case, the dissociation property of the acid component is enhanced, and higher conductivity of the conductive polymer is easily obtained.

[0018] (Technology 3) An electrolytic capacitor according to a second aspect of the present disclosure includes a capacitor element and a liquid component, wherein the capacitor element includes an anode body having a dielectric layer on its surface and a conductive polymer covering at least a portion of the dielectric layer, wherein the liquid component includes an acid component, a base component, and a solvent, wherein the acid component includes a first carboxylic acid compound having one first site, wherein the first site has a first carboxy group including a first carbonyl group, a second carbonyl group, and a linking group connecting the first carbonyl group and the second carbonyl group, and the base component includes at least one selected from the group consisting of an amine, a quaternary ammonium compound, and an amidinium compound. In the electrolytic capacitor according to the second aspect, the first carboxylic acid compound included in the liquid component may be referred to as first carboxylic acid compound B.

[0019] Hereinafter, the first carboxylic acid compound A and the first carboxylic acid compound B may be collectively referred to as the first carboxylic acid compound.

[0020] The liquid component containing the acid component including the first carboxylic acid compound can reduce the change in ESR over time (in other words, the increase over time) that occurs with use of the electrolytic capacitor. The reason why the change in ESR over time is reduced is thought to be as follows.

[0021] First, the second carbonyl group of the first carboxylic acid compound is likely to coordinate to the cationic portion of the conductive polymer due to charge imbalance, thereby stabilizing the conductive polymer. Furthermore, the ease with which the second carbonyl group coordinates to the conductive polymer also facilitates the first carboxy group's proximity to the conductive polymer, thereby stabilizing the conductive polymer. This stabilizing effect of the second carbonyl group and the first carboxy group inhibits the progression of dedoping from the conductive polymer during use of the electrolytic capacitor, thereby suppressing degradation of the conductive polymer and maintaining high conductivity. This is believed to reduce the change in ESR over time. The first carboxylic acid compound A having a second moiety advantageously has a hydrocarbon group with two or more carbon atoms bonded to the second carbonyl group via a heteroatom, thereby further improving voltage resistance. In the electrolytic capacitor according to the second aspect, combining the first carboxylic acid compound B with a more stable base component facilitates maintaining the dissociated state and thus maintaining higher repairability of the dielectric coating.

[0022] Furthermore, the first carboxylic acid compound easily forms an appropriate coating on the surface of the dielectric layer on the surface of the anode body. This coating improves the film repairability of the dielectric layer, allowing the electrolytic capacitor to maintain low leakage current even when used for a long period of time. Furthermore, the action of the first carboxylic acid compound suppresses the deterioration of the conductive polymer over time, allowing a state in which a large amount of liquid component is retained in the conductive polymer near the dielectric layer. This is also thought to enhance the film repairability of the dielectric layer. Additionally, the ease of repair of the dielectric layer also ensures high voltage resistance.

[0023] (Technology 4) In the above (Technology 2) or (Technology 3), the equivalent ratio of the base component to the first carboxylic acid compound may be 0.5 or more and 10 or less. In this case, a high degree of dissociation of the first carboxylic acid compound can be ensured. In addition, corrosion of the electrode can be suppressed and high voltage resistance can be easily ensured.

[0024] (Technology 5) In any one of the above (Technology 1) to (Technology 4), the first carboxylic acid compound may have a second moiety including a heteroatom bonded to the second carbonyl group and a hydrocarbon group bonded to the heteroatom (in the above (Technology 1), the hydrocarbon group has two or more carbon atoms). The heteroatom may be an oxygen atom or a nitrogen atom. In this case, the first moiety can be easily introduced into the first carboxylic acid compound via the oxygen atom or the nitrogen atom.

[0025] (Technology 6) In any one of the above (Technology 1), (Technology 2), and (Technology 5), the second moiety may include a residue of a hydroxy compound or a residue of an amine compound. In this case, the first moiety can be easily introduced into the first carboxylic acid compound via an oxygen atom or an amino group.

[0026] (Technology 7) In any one of the above (Technology 1), (Technology 2), (Technology 5), and (Technology 6), the second moiety may include a residue of a polyol. The polyol may be an alkylene glycol, a polyalkylene glycol, or a monoether thereof. In this case, the first moiety can be easily introduced into the first carboxylic acid compound via an oxygen atom.

[0027] (Technology 8) In any one of the above (Technology 1) to (Technology 6), the number of carbon atoms in the main chain connecting the first carbon atom of the first carbonyl group and the second carbonyl group in the linking group may be from 1 to 4. In this case, the distance between the first carboxy group and the second carbonyl group is relatively short, so that the first carboxy group is likely to take a stabilized structure when ionized, and the surroundings of the conductive polymer are likely to be kept acidic.

[0028] (Technology 9) In any one of (Technology 1) to (Technology 8) above, the linking group may include a non-aromatic cyclic divalent group or an aromatic divalent group. In this case, the solubility of the first carboxylic acid compound in a solvent and its affinity for the dielectric layer are easily adjusted. In addition, the first carboxy group is easily stabilized, and the positions of the second carbonyl group and the first carboxy group are easily fixed, which tends to lower the pH of the liquid component.

[0029] (Technology 10) In any one of the above (Technology 1) to (Technology 9), the main chain of the linking group connecting the first carbon atom of the first carbolic group and the second carbon atom of the second carbonyl group may be an aliphatic divalent group. In this case, the function of the liquid component to repair the dielectric layer can be enhanced, and the effect of reducing leakage current can be further improved.

[0030] (Technology 11) In the above (Technology 10), the aliphatic divalent group may have a first substituent, and the aliphatic divalent group may have a monovalent aliphatic hydrocarbon group having 6 or more carbon atoms as at least one of the first substituents. In this case, the effect of suppressing esterification of the first carboxy group is enhanced, making it easier to ensure higher conductivity of the conductive polymer. In addition, the voltage resistance of the electrolytic capacitor can be further improved.

[0031] (Technology 12) In the above (Technology 11), the aliphatic divalent group may have the monovalent aliphatic hydrocarbon group at the α-position of the first carbonyl group. The steric hindrance of the aliphatic hydrocarbon group further enhances the effect of suppressing esterification of the first carboxy group, thereby further suppressing fluctuations in ESR.

[0032] (Technology 13) In any one of the above (Technology 1) to (Technology 12), the acid component may further contain a second carboxylic acid compound different from the first carboxylic acid compound. In this case, the pH of the liquid component can be easily reduced, and the first carboxylic acid compound can ensure a certain level of voltage resistance, while further reducing the change in ESR over time.

[0033] (Technology 14) In any one of (Technology 1) to (Technology 13) above, the ratio of the first carboxylic acid compound to the acid component may be 20 mass% or more. In this case, the change in ESR over time can be further suppressed. In addition, higher voltage resistance can be easily ensured.

[0034] The electrolytic capacitor of the present disclosure will be described in more detail below, including the above-mentioned (Technology 1) to (Technology 14). At least one selected from the components described below can be arbitrarily combined with at least one of the above-mentioned (Technology 1) to (Technology 14) for the solid electrolytic capacitor of the present disclosure, as long as such combination is technically possible.

[0035] (Liquid Component) The liquid component contained in the electrolytic capacitor includes an acid component and a solvent. The acid component includes a first carboxylic acid compound.

[0036] (Acid Component) (First Carboxylic Acid Compound) The first carboxylic acid compound has one first moiety. The first moiety has a first carboxy group containing a first carbonyl group, a second carbonyl group, and a linking group connecting these carbonyl groups. The linking group connecting the first carbonyl group and the second carbonyl group is sometimes referred to as the first linking group. The first carboxy group and the second carbonyl group in the first moiety improve the stability of the conductive polymer, maintaining high conductivity and reducing changes in the ESR of the electrolytic capacitor over time. Furthermore, the action of the first carboxylic acid compound enhances the film repairability of the dielectric layer, suppressing increases in leakage current even after long-term use and ensuring high voltage resistance.

[0037] The presence of the first linking group creates a certain amount of space between the second carbonyl group and the first carbonyl group or the first carboxy group. This is thought to result in the first carboxylic acid compound having relatively high stability. This makes it easier for the first carboxylic acid compound to act on the conductive polymer, which is thought to be advantageous in terms of the stability and high conductivity of the conductive polymer.

[0038] In the electrolytic capacitor, the first carboxy group may be in any of the following forms: a free form, a salt form, an anion form, and a form interacting (e.g., complexing) with a conductive polymer. In this specification, the first carboxy group encompasses all of these forms.

[0039] The first carboxylic acid compound may have one second site. The second site includes a heteroatom (hereinafter sometimes referred to as the first heteroatom) and a hydrocarbon group bonded to the first heteroatom. In the second site, the first heteroatom is bonded to the second carbonyl group in the first site. The first carboxylic acid compound is easily stabilized by having the second site, and the first site facilitates stable coordination with the conductive polymer. In the second site, the hydrocarbon group bonded to the first heteroatom also includes a hydrocarbon group having a substituent (a fourth substituent, described below).

[0040] The first carboxylic acid compound includes, for example, a compound represented by the following formula (I).

[0041]

[0042] (In the formula, X １ is a primary carbonyl group, and X ２ is a secondary carbonyl group, and Y １ is a primary carboxy group, and R １ is a first linking group, and X ３ is a heteroatom (first heteroatom), and R ２ is a monovalent organic group containing a hydrocarbon group which may have a substituent (fourth substituent), and R ３ is a hydrogen atom or a substituent (the seventh substituent described below), and Z １ is the first site, and Z ２ is the second site. ３ When the number of bonds j is 2, k is 0, and when j is 3 or more, k is (j-2).

[0043] Although formula (I) exemplifies a case where the first carboxy group is in a free form, compounds of formula (I) also include cases where the first carboxy group is in a form other than the free form.

[0044] The first linking group (R in formula (I) １ ) and the second moiety (Z in formula (I) ２ The structure of each of the first carboxy group and the second carbonyl group is not particularly limited as long as it does not inhibit the action of the first carboxy group and the second carbonyl group on the conductive polymer. The first moiety may be, for example, a residue of a polycarboxylic acid or its acid anhydride. Examples of polycarboxylic acids include dicarboxylic acids, tricarboxylic acids, and tetracarboxylic acids (particularly, dicarboxylic acids). When the first moiety is a residue of a polycarboxylic acid or its acid anhydride, the second moiety is a residue of a compound (e.g., a hydroxy compound, an amine compound) that can be linked to a polycarboxylic acid or its acid anhydride. From the viewpoint of facilitating molecular design or synthesis of the first carboxylic acid compound, it is preferable that the first moiety is a residue of a polycarboxylic acid (particularly, a dicarboxylic acid) or its acid anhydride.

[0045] (First Moiety) The first moiety (e.g., Z １ ), in which the first linking group (for example, R １ ) may have a main chain and a substituent (including a side chain) bonded to the main chain, or may be composed of only the main chain (corresponding to a case where no substituent is present). Hereinafter, the substituent (including the side chain) bonded to the main chain may be referred to as the first substituent. The main chain connects the carbon atom of the first carbonyl group (first carbon atom) and the carbon atom of the second carbonyl group (second carbon atom). The main chain contains at least carbon atoms and is a linear portion, and the first carbon atom and the second carbon atom are not included in the main chain. In addition, the first substituent is not included in the main chain. Note that the main chain also includes cases where the number of carbon atoms in the main chain is one (for example, a methylene group, a methylene group having a first substituent, or a group having a methylene group and a heteroatom (second heteroatom) described below (an oxymethylene group, an oxymethylene group having a first substituent, etc.)). When there are multiple chains connecting the first carbon atom and the second carbon atom, the chain with the fewest number of atoms (carbon atoms, second heteroatoms, etc.) constituting the chain is the main chain. The first substituent may further have a substituent (second substituent).

[0046] The main chain may be a hydrocarbon chain or may contain a second heteroatom. The second heteroatom may include at least one selected from the group consisting of an oxygen atom, a sulfur atom, a nitrogen atom, and a silicon atom. The main chain may contain one or more second heteroatoms. The main chain may be linear or may form part of a ring structure. The main chain may form part of at least one ring structure selected from the group consisting of a non-aromatic ring and an aromatic ring. These rings may be hydrocarbon rings or heterocycles containing a heteroatom (third heteroatom). These rings may be bridged rings or fused rings. The third heteroatom contained in the heterocycle may be at least one selected from the group consisting of an oxygen atom, a sulfur atom, a nitrogen atom, and the like. The heterocycle may contain one third heteroatom or two or more third heteroatoms. When the third heteroatom contained in the heterocycle constitutes the main chain, the third heteroatom is the second heteroatom. Examples of the heterocycle include divalent groups corresponding to the heterocyclic groups described below for the first substituent, and the description of the heterocycle of the first substituent can be referred to.

[0047] For example, when the first linking group is a 1,1-dimethylethane-1,2-diyl group, 1,2-ethylene groups constitute the main chain, excluding the two methyl groups corresponding to the substituents. When a first carbonyl group and a second carbonyl group are bonded to the 1- and 2-positions of cyclohexane, respectively, the chain of carbon atoms at the 1st and 2nd positions of cyclohexane forms the main chain, and the number of carbon atoms in the main chain is 2. In this case, the first linking group is a cyclohexane-1,2-diyl group. When the first linking group is a 2-norbornene-5,6-diyl group, the chain of carbon atoms at the 5th and 6th positions of the norbornene ring forms the main chain, and the number of carbon atoms in the main chain is 2. When the first linking group is a 1,2-phenylene group, the chain of carbon atoms at the 1st and 2nd positions of the benzene ring forms the main chain, and the number of carbon atoms in the main chain is 2. As the main chain, an alkylene group, an alkenylene group, or the like is preferable. The main chain may be an oxyalkylene group or a polyoxyalkylene group, etc. These groups constituting the main chain may form part of a ring structure.

[0048] In the first linking group, the number of carbon atoms in the main chain may be 1 or more and 10 or less, or 1 or more and 6 or less, or 1 or more and 4 or less. In the first linking groups of at least two first moieties, the number of carbon atoms in the main chain is preferably 1 or more and 4 or less, and may be 2 or more and 4 or less. When the number of carbon atoms in the main chain is 4 or less, the distance between the first carboxy group and the second carbonyl group is relatively short, so that the first carboxy group easily forms a stabilized structure when ionized, and the surroundings of the conductive polymer are easily kept acidic. Therefore, deterioration of the conductive polymer is suppressed, and the effect of maintaining high conductivity is further enhanced.

[0049] The first linking group may include a cyclic divalent group (such as a non-aromatic cyclic divalent group or an aromatic divalent group). The cyclic divalent group may be a divalent hydrocarbon ring group or a divalent heterocyclic group. When the first linking group includes a cyclic divalent group, the solubility of the first carboxylic acid compound in a solvent and its affinity for the dielectric layer can be easily adjusted. When the first linking group includes a cyclic divalent group, the bulkiness of the ring makes it easier to stabilize the first carboxy group, and the positions of the second carbonyl group and the first carboxy group are easily fixed. As a result, the pH of the liquid component tends to be lower, making it easier to stabilize the conductive polymer. For example, the first linking group may include a non-aromatic or aromatic divalent hydrocarbon ring group (such as cyclohexane-1,2-diyl, 2-norbornene-5,6-diyl, or 1,2-phenylene) or a non-aromatic or aromatic divalent heterocyclic group. The cyclic divalent group (such as a non-aromatic cyclic divalent group or an aromatic divalent group) may further have a substituent (third substituent). The first linking group may have a structure in which a non-aromatic cyclic divalent group or an aromatic divalent group is bonded to an aliphatic divalent group. The aliphatic divalent group forms part of the main chain of the first linking group. The first linking group may have a structure in which one non-aromatic cyclic divalent group or an aromatic divalent group is bonded to one aliphatic divalent group. The first linking group may have a structure in which one non-aromatic cyclic divalent group or an aromatic divalent group is bonded to one aliphatic divalent group. The first linking group may have a structure in which one non-aromatic cyclic divalent group or an aromatic divalent group is bonded to each bond of the divalent group. The aliphatic divalent group portion may have a first substituent.

[0050] It is also preferable that the main chain of the first linking group is an aliphatic divalent group. In this case, the liquid component can enhance the ability to repair the dielectric layer, further enhancing the effect of reducing leakage current when a high voltage is applied. The aliphatic divalent group may have a first substituent.

[0051] Examples of the first substituent that the main chain of the first linking group has include a hydrocarbon group, a heterocyclic group, R ４ａ -O- group (alkoxy group, etc.), R ４ｂ -O-C(=O)- group (alkoxycarbonyl group, etc.), R ４ｃ Examples of the first substituent include a -C(=O)- group (such as an acyl group), a carboxy group, a hydroxy group, and a halogen atom (such as a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom). The first substituent is usually a monovalent group. R ４ａ , R ４ｂ and R ４ｃ Each of these groups includes a hydrocarbon group.

[0052] The hydrocarbon group as the first substituent, R ４ａ , R ４ｂ and R ４ｃEach of the hydrocarbon groups as may be saturated or unsaturated. Examples of these hydrocarbon groups include non-aromatic hydrocarbon groups (aliphatic hydrocarbon groups, alicyclic hydrocarbon groups, etc.), and aromatic hydrocarbon groups. The aliphatic hydrocarbon groups may be linear or branched. Examples of the aliphatic hydrocarbon groups include alkyl groups and unsaturated aliphatic hydrocarbon groups (alkenyl groups, dienyl groups, trienyl groups, etc.). Examples of the alkyl group include methyl groups, ethyl groups, n-propyl groups, isopropyl groups, n-butyl groups, isobutyl groups, sec-butyl groups, tert-butyl groups, pentyl groups, hexyl groups, heptyl groups, n-octyl groups, 2-ethylhexyl groups, nonyl groups, decyl groups, undecyl groups, lauryl groups (dodecyl groups), and myristyl groups. Examples of unsaturated aliphatic hydrocarbon groups include vinyl, allyl, hexenyl, 2-octenyl, 2,4,6-trimethylnonan-2-en-1-yl, decenyl, dodecenyl (including 2-dodecenyl and tetrapropenyl groups), and tetradecenyl. The number of carbon atoms in the aliphatic hydrocarbon group (monovalent aliphatic hydrocarbon group) may be 1 or more, or 6 or more. The number of carbon atoms in the aliphatic hydrocarbon group (monovalent aliphatic hydrocarbon group) may be 12 or less, 8 or less, or 5 or less. The number of carbon atoms in the aliphatic hydrocarbon group (monovalent aliphatic hydrocarbon group) may be 1 or more and 12 or less, 1 or more and 8 or less, 1 or more and 5 or less, or 6 or more and 12 or less. Examples of alicyclic hydrocarbon groups include cycloalkyl groups (such as cyclohexyl groups), cycloalkenyl groups (such as cyclohexenyl groups), cycloalkadienyl groups (such as cyclopentadienyl groups), and bridged cyclic hydrocarbon groups (such as norbornyl groups, norbornenyl groups, and dicyclopentadienyl groups). The number of carbon atoms in the alicyclic hydrocarbon group may be 5 to 16, 5 to 12, or 5 to 10. Examples of aromatic hydrocarbon groups include aryl groups (such as phenyl groups and naphthyl groups). The number of carbon atoms in the aromatic hydrocarbon group may be 6 to 14, or 6 to 10.

[0053] The heterocyclic group as the first substituent is a monovalent heterocyclic group containing a heteroatom (fourth heteroatom) as a ring constituent atom. Examples of the fourth heteroatom include at least one selected from the group consisting of an oxygen atom, a sulfur atom, and a nitrogen atom. The heterocyclic group may contain one fourth heteroatom, or may contain two or more fourth heteroatoms. The heterocyclic group may be saturated or unsaturated. The heterocyclic group may be non-aromatic or aromatic. The heterocyclic group may be, for example, 5 to 14 members, or 5 to 10 members. Examples of heterocyclic groups include oxygen-containing ring groups (such as a furanyl group or a tetrahydrofuranyl group), sulfur-containing ring groups (such as a thiophen-3-yl group), and nitrogen-containing ring groups (such as a pyrrolidinyl group, a piperidinyl group, a pyridyl group, and a morpholinyl group).

[0054] When the main chain of the first linking group is an aliphatic divalent group, this aliphatic divalent group may have a monovalent aliphatic hydrocarbon group having 6 or more carbon atoms as at least one of the first substituents. In at least two first moieties, the main chain of the first linking group may be an aliphatic divalent group, and at least one of the first substituents may have a monovalent aliphatic hydrocarbon group having 6 or more carbon atoms. In these cases, the voltage resistance of the electrolytic capacitor can be further improved. A first carboxylic acid compound in which the main chain of the first linking group is an aliphatic divalent group has a relatively low effect of lowering the pH of the liquid component, and the first carboxy group tends to be easily esterified. When at least one of the first substituents is an aliphatic hydrocarbon group having 6 or more carbon atoms, the effect of suppressing esterification is enhanced, ensuring higher conductivity of the conductive polymer. It is preferable that the first linking group has the first substituent at the α-position of the first carbonyl group. When the first linking group has an aliphatic hydrocarbon group having 6 or more carbon atoms as a first substituent at the α-position of the first carbonyl group, the steric hindrance of this group further enhances the effect of suppressing esterification of the first carboxy group, thereby maintaining the action of the first carboxylic acid compound on the conductive polymer and enhancing the effect of suppressing fluctuations in ESR.

[0055] In addition, not only in the case of an aliphatic hydrocarbon group having 6 or more carbon atoms, but also in the case of a first substituent at the α-position of the first carbonyl group that can cause steric hindrance, a high effect of suppressing fluctuations in ESR is likely to be obtained, as in the above case. For example, two first substituents may be present at the α-position of the first carbonyl group. Furthermore, a first substituent such as a tert-butyl group or a cyclic group (such as an alicyclic hydrocarbon group, an aromatic hydrocarbon group, or a heterocyclic group) may be present at the α-position of the first carbonyl group. Furthermore, an alkyl group (such as an alkyl group having 1 to 3 carbon atoms) having a cyclic group (such as an alicyclic hydrocarbon group, an aromatic hydrocarbon group, or a heterocyclic group) may be present as a first substituent at the α-position of the first carbonyl group.

[0056] The number of first substituents in the first linking group is, for example, 1 or more. The upper limit of the number of first substituents in the first linking group is not particularly limited and may be determined depending on the chain length of the main chain. The number of first substituents may be 6 or less, or may be 3 or less.

[0057] When the first substituent is a hydrocarbon group, examples of the second substituent include at least one selected from the group consisting of hydrocarbon groups other than the first substituent and groups (or atoms) other than hydrocarbon groups among the groups (or atoms) exemplified as the first substituent. When the first substituent is a heterocyclic group, examples of the second substituent include at least one selected from the group consisting of groups (or atoms) other than heterocyclic groups among the groups (or atoms) exemplified as the first substituent.

[0058] The third substituent can be selected from the substituents exemplified for the first or second substituent.

[0059] Examples of polycarboxylic acids corresponding to the first moiety include succinic acid, succinic acids having an alkyl group or an alkenyl group as a first substituent (e.g., 2,2-dimethylsuccinic acid, 2-n-butylsuccinic acid, 2-n-octylsuccinic acid, 2-n-dodecylsuccinic acid, 2-(2'-octenyl)succinic acid, 2-(2'-dodecenyl)succinic acid, etc.), polycarboxylic acids having an alicyclic hydrocarbon group as a first substituent (e.g., 2-n-cyclohexylsuccinic acid), polycarboxylic acids having an aromatic hydrocarbon group as a first substituent (e.g., 2-phenylsuccinic acid), and polycarboxylic acids in which the first linking group contains a cyclic divalent group (e.g., 1,2-cyclohexanedicarboxylic acid, 5-norbornene-2,3-dicarboxylic acid, phthalic acid, etc.). When forming the first moiety, acid anhydrides of these polycarboxylic acids may also be used. However, these are merely examples, and the polycarboxylic acid or acid anhydride corresponding to the first moiety is not limited to these.

[0060] (Second Moiety) The second moiety (e.g., Z in formula (I)) ２ ) can be, for example, a first heteroatom (e.g., in formula (I), X ３ ) and a hydrocarbon group (first hydrocarbon group) bonded to the first heteroatom. This first hydrocarbon group also includes a hydrocarbon group having a substituent (fourth substituent). The second moiety may include a first heteroatom and a monovalent organic group including the first hydrocarbon group bonded to the first heteroatom. This organic group also includes an organic group having a fourth substituent on the first hydrocarbon group and a substituent (fifth substituent) other than the fourth substituent.

[0061] The second moiety (e.g., Z in formula (I) ２ ) in which the first heteroatom (e.g., in formula (I), X ３ ) may be an oxygen atom, a nitrogen atom, a sulfur atom, or the like.

[0062] The second moiety includes a first hydrocarbon group (including a hydrocarbon group having a fourth substituent, which will be described later) bonded to the first heteroatom. The number of carbon atoms in the first hydrocarbon group may be 1 or more, or may be 2 or more. In the first carboxylic acid compound A, the number of carbon atoms in the hydrocarbon group is 2 or more.

[0063] In the first carboxylic acid compound, the second site may be a residue of a hydroxy compound, a residue of an amine compound, or a residue of a mercapto compound. When the second site is a residue of a hydroxy compound or a residue of a mercapto compound, the first heteroatom is an oxygen atom or a sulfur atom. In these cases, in formula (I), X ３ The number of bonds j is 2 and k is 0. Therefore, -X in formula (I) ３ (-R ３ ) k-group is —O— or —S—. When the second site is a residue of an amine compound, the first heteroatom is a nitrogen atom. In this case, in formula (I), X ３ The number of bonds j is 3 and k is 1. Therefore, -X in formula (I) ３ (-R ３ )k-group is -N(-R ３ )- group. X ３ is a nitrogen atom, >X ３ -R ３ The group corresponds to an amino group. An amino group includes, for example, >N—R ３ and >NH.

[0064] When the first heteroatom is an oxygen atom or a nitrogen atom, the first moiety can be easily introduced into the first carboxylic acid compound by an ester bond or an amide bond, which is preferable. In other words, the second moiety preferably contains a residue of a hydroxy compound or a residue of an amine compound.

[0065] The second site may be a residue of a polyol compound or a residue of a polyamine compound. The second site may be a residue of a polythiol compound. In these cases, the residue of one hydroxy group of the polyol compound, the residue of one amino group of the polyamine compound, or the residue of one mercapto group of the polythiol compound may be -X ３ (-R ３ The remaining hydroxy, amino, or mercapto groups correspond to the first heteroatom (e.g., X in formula (I)). ３R may be a fourth substituent carried by a hydrocarbon group bonded to the first hetero atom, or may be a fifth substituent carried by an organic group containing a hydrocarbon group bonded to the first hetero atom. ３ may be a hydrogen atom. ３ is a substituent (seventh substituent), the seventh substituent may be a hydrocarbon group (e.g., an alkyl group such as a methyl group, an ethyl group, a propyl group, an n-butyl group, a sec-butyl group, or a tert-butyl group). The number of carbon atoms in the alkyl group of the seventh substituent may be 1 or more and 10 or less, 1 or more and 6 or less, or 1 or more and 4 or less.

[0066] The organic group may be a linear group or may include a ring structure. The ring structure may constitute a part of the main chain of the organic group. The organic group may include a heteroatom (fifth heteroatom) in the main chain. The main chain may be saturated or unsaturated. The fifth heteroatom may include at least one selected from the group consisting of an oxygen atom, a nitrogen atom, and a sulfur atom. The main chain may have one fifth heteroatom or two or more fifth heteroatoms. The number of fifth heteroatoms in the main chain may be four or less. The fifth heteroatom may be different from the first heteroatom, but if it is the same as the first heteroatom, molecular design or synthesis is relatively easy. All of the two or more fifth heteroatoms may be the same as the first heteroatom.

[0067] The organic group may have a main chain and at least one of a fourth substituent and a fifth substituent bonded to the main chain. The main chain is a linear portion containing at least carbon atoms (more specifically, at least the carbon atoms contained in the first hydrocarbon group). The fourth and fifth substituents are not included in the main chain. The main chain also includes cases where the main chain has one carbon atom (e.g., a methyl group, a methyl group having a fourth substituent). The main chain containing a fifth heteroatom may include, for example, a polyoxyalkylene group or a group corresponding to a polyalkyleneamine. When the polyoxyalkylene group has a hydroxy group at its terminal, the hydroxy group corresponds to the fifth substituent. When the hydroxy group of the polyoxyalkylene group is etherified with a hydrocarbon group, the oxygen atom of the ether and the linear portion of the hydrocarbon group bonded to this oxygen atom are included in the main chain. When the group corresponding to a polyalkyleneamine has an amino group -NH at its terminal, ２ When a hydrocarbon group is bonded to the amino group, the nitrogen atom of the amino group and the linear portion (the portion with the largest number of carbon atoms) of the hydrocarbon group bonded to this nitrogen atom are included in the main chain. Furthermore, when part of the main chain has a ring structure (cyclic group), there are multiple chains that constitute the organic group. In this case, the chain with the fewest number of atoms (carbon atoms, fifth heteroatom, etc.) that constitute the chain constitutes at least part of the main chain. The ring structure may be saturated or unsaturated.

[0068] Each of the fourth and fifth substituents can be selected from the substituents exemplified as the first or second substituent, an oxo group (═O), and the like. Each of the fourth and fifth substituents may further have a substituent (sixth substituent). The sixth substituent can be selected from the substituents exemplified as the second substituent, and the like. When the second moiety contains at least one of the fourth and fifth substituents, the total number of these substituents may be 1 or more, 1 to 6, or 1 to 4.

[0069] Examples of hydroxy compounds corresponding to the second moiety include monohydroxy compounds and polyols. Examples of monohydroxy compounds include aliphatic alcohols (such as alkyl alcohols and alkenyl alcohols), alicyclic alcohols, aromatic hydroxy compounds, and alkylene oxide adducts of these hydroxy compounds. Examples of aliphatic alcohols include n-hexanol, n-octanol, n-decanol, isodecanol, 2-decenol, and 2-dodecenol. The number of carbon atoms in the aliphatic alcohol may be 1 or more and 20 or less, 6 or more and 16 or less, or 8 or more and 14 or less. Examples of alicyclic alcohols include hexanol, hexenol, and norbornan-2-ol. Alicyclic alcohols may be monocyclic or polycyclic (fused ring or bridged ring). Examples of alicyclic alcohols include alkyl alcohols having an alicyclic group (C alkyl alcohols having an alicyclic group such as cyclohexylmethanol and cyclohexylethanol). １－４ The alicyclic group portion of the alicyclic alcohol may be 5 to 12-membered, or 5 to 10-membered. Examples of aromatic hydroxy compounds include phenol, methylphenol, naphthol, etc. The number of carbon atoms in the aromatic ring of the aromatic hydroxy compound may be 6 to 14, or 6 to 10. Examples of aromatic hydroxy compounds include alkyl alcohols (C 10) having an aryl group, such as benzyl alcohol and phenethyl alcohol. ６－１４ Aryl-C １－４ Alkyl alcohols, etc.) are also included.

[0070] Examples of polyols include aliphatic polyols (such as alkane polyols and alkenediols), alicyclic polyols, aromatic polyols, and alkylene oxide adducts of these polyols, and polyalkylene glycols. Examples of alkane polyols include alkane diols (such as ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, 1,8-octanediol, 2-ethyl-1,3-hexanediol, 1,9-nonanediol, and 2-butyl-2-ethyl-1,3-propanediol), glycerin, polyglycerin (such as diglycerin, triglycerin, and tetraglycerin), trimethylolpropane, and sugars or sugar alcohols (such as mannitol, erythritol, xylitol, and pentaerythritol). The number of carbon atoms in the alkane polyol may be 1 or more and 12 or less, or 1 or more and 10 or less (or 9 or less). Within these ranges, the number of carbon atoms may be 2 or more. Examples of the alkene diol include 1,4-dihydroxybutan-2-ene. The number of carbon atoms in the alkene diol may be, for example, 2 or more and 12 or less, or 2 or more and 10 or less (or 9 or less). Examples of the polyalkylene glycol include polyethylene glycol, polypropylene glycol, and polytrimethylene glycol. Examples of the polyalkylene glycol include poly(C ２－４In the polyalkylene glycol, the number of repetitions of the oxyalkylene group (e.g., an oxyalkylene group having from 2 to 4 carbon atoms) is 2 or more, and may be 2 to 10, or may be 2 to 6. Specific examples of polyethylene glycol include diethylene glycol and triethylene glycol. Specific examples of polypropylene glycol include dipropylene glycol and tripropylene glycol. Specific examples of polytrimethylene glycol include di(trimethylene glycol) and tri(trimethylene glycol). Alicyclic polyols include polyhydroxycycloalkanes (e.g., polyhydroxycycloalkanes having from 5 to 10 carbon atoms, such as dihydroxycyclohexane and trihydroxycyclohexane), polyhydroxycycloalkenes (e.g., polyhydroxycycloalkene having from 5 to 10 carbon atoms, such as dihydroxycyclohexene), as well as poly(hydroxyalkyl)cycloalkanes (poly(hydroxy C) such as cyclohexanedimethanol). １－４ alkyl) C ５－１０ The aromatic polyols include dihydroxybenzene, biphenol, bisphenol, and the like, as well as poly(hydroxyalkyl)arenes (poly(hydroxy C) such as xylylene glycol). １－４ alkyl) C ６－１０ arenes, etc.) are also included.

[0071] Examples of alkylene oxide adducts include those in which one or more alkylene oxides (C alkylene oxides such as ethylene oxide and propylene oxide) are bonded to the hydroxy groups of the above-mentioned monohydroxy compounds or polyols. ２－４ Examples of the alkylene oxide include compounds (excluding the above-mentioned polyalkylene glycols) to which alkylene oxides such as alkylene oxides are added. The number of alkylene oxides added per hydroxy group is, for example, 6 or less, and may be 4 or less, or 3 or less. The lower limit and upper limit of the number of alkylene oxides can be combined in any manner.

[0072] In the first carboxylic acid compound, a first moiety is introduced into one hydroxy group of the polyol. The remaining hydroxy groups of the polyol may be free, etherified, esterified, salted, protected, or may interact or bond with components present in the production process or other components contained in the electrolytic capacitor. For example, the second moiety may be introduced into a polyC ２－４ Alkylene glycol mono C １－４ It may also be a residue of an alkyl ether (for example, a residue of triethylene glycol monomethyl ether, a residue of tripropylene glycol monomethyl ether, a residue of tri(trimethylene glycol) monomethyl ether, etc.).

[0073] In particular, the second moiety preferably contains a residue of a polyol. In this case, the polyol is preferably an alkylene glycol, a polyalkylene glycol, or a monoether thereof. It is also preferable that the second moiety is a residue of a monohydroxy compound (such as an aliphatic alcohol).

[0074] The amine compound corresponding to the second moiety includes monoamines and polyamines. In the amine compound, at least one amino group is an amino group having an active hydrogen (>NH, -NH ２) is preferable. Examples of monoamines include aliphatic amines (alkylamines such as methylamine, ethylamine, n-hexylamine, n-octylamine, n-decylamine, and isodecylamine; alkenylamines such as allylamine, 1-amino-2-hexene, 1-amino-2-decene, and 2-amino-2-decene), alicyclic amines (cyclohexylamine, 1-norbornylamine, and 2-cyclohexylethylamine), aromatic amines (aniline and benzylamine), and cyclic monoamines (pyrrolidine, piperidine, and morpholine). The number of carbon atoms in the aliphatic amine may be 1 to 20, 6 to 16, or 8 to 14. The alicyclic group portion of the alicyclic amine may be 5 to 12, or 5 to 10. The number of carbon atoms in the aromatic ring of the aromatic amine may be 6 to 14, or 6 to 10. Aromatic amines include alkylamines (C ６－１４ Aryl-C １－４ The cyclic monoamine may have 5 to 12 members, or 5 to 10 members.

[0075] Examples of polyamines corresponding to the second moiety include aliphatic polyamines, polyalkylene polyamines, alicyclic polyamines, aromatic polyamines, and cyclic polyamines. Examples of aliphatic polyamines include alkylenediamines (ethylenediamine, 1,4-diaminobutane, N,N'-dialkylalkylenediamines, etc.), triaminoalkanes, and tetraaminoalkanes. Examples of alkylenediamines include C ２－６ Alkylenediamines (e.g., C ２－４ Examples of N,N'-dialkyl alkylenediamines include N,N'-diC alkylene diamines such as N,N'-dialkylethylenediamine. １－６ Alkyl-C ２－６ Alkylenediamines (e.g., N,N'-diC １－４ Alkyl-C ２－４Specific examples of N,N'-dialkylalkylenediamines include N,N'-diethylethylenediamine, N,N'-diisopropylethylenediamine, and N,N'-di-t-butylethylenediamine. The number of carbon atoms in the aliphatic polyamine may be 1 or more and 10 or less, or 2 or more and 6 or less. Examples of alicyclic polyamines include polyamino C such as polyaminocycloalkanes (diaminocyclohexane, etc.), ５－１０ cycloalkanes, etc.), polyaminocycloalkenes (polyamino C such as diaminocyclohexene, etc.) ５－１０ Examples of aromatic polyamines include polyaminoarenes (polyamino C such as 1,4-phenylenediamine and triaminobenzene). ６－１０ Examples of cyclic amines include those having at least one -NH group and at least one -NH group or -NH ２ Examples of such compounds include cyclic amines (such as cytosine, guanine, and adenine) and cyclic polyamines (such as piperazine, thymine, and uracil) having an amino group as a substituent. The cyclic amine may be 5 to 12-membered or 5 to 10-membered.

[0076] The liquid component may contain, for example, as the first carboxylic acid compound, at least one compound selected from the group consisting of compounds represented by the following formula (Ia) and compounds represented by the following formula (Ib):

[0077]

[0078] (In the formula, R １ａ ~R １ｆ are each independently a hydrogen atom or a first substituent, and n1 and n2 correspond to the number of repetitions of the methylene chain which may have a first substituent. １ａ R is a cyclic divalent group (such as a non-aromatic cyclic divalent group or an aromatic divalent group) contained in the first linking group. ３ａ is Ring Z １ａ m1 is a third substituent that ring Z １ａ corresponds to the number of third substituents in R ２ , R３ , X ３ , and k are the same as in formula (I).

[0079] Formula (Ia) corresponds to the case where the main chain of the first linking group in formula (I) is an aliphatic divalent group. n1 is an integer of 0 or more, and may be an integer of 1 or more. (n1+1) and (n2+1) each correspond to the number of carbon atoms in the main chain of the first linking group. n1 and n2 may each be, for example, 1 or more and 5 or less, or 1 or more and 3 or less. When n1 is 2 or more, R bonded to each carbon atom of the main chain １ｃ At least two of may be the same, or all may be different. Similarly, when n1 is 2 or more, R １ｄ At least two of the R bonded to each carbon atom of the main chain may be the same, or all of the R bonded to each carbon atom of the main chain may be different. １ｅ (or R １ｆ At least two of the groups may be the same, or all of the groups may be different.

[0080] Preferably, the compound of formula (Ia) has at least a first substituent at the alpha position of the first carbonyl group. １ａ and R １ｂ It is preferable that at least one of the first substituents is a first substituent. It is preferable that at least one of the first substituents, which may cause steric hindrance, is present at the α-position of the first carbonyl group in addition to an aliphatic hydrocarbon group having 6 or more carbon atoms. In this case, R １ａ and R １ｂ One of R may be an aliphatic hydrocarbon group having 6 or more carbon atoms or a first substituent that may cause steric hindrance, and the other may be a hydrogen atom. １ｃ and R １ｄ may be a hydrogen atom or a first substituent, regardless of the number of n1, １ｃ and R １ｄ may each be a hydrogen atom. １ｅ and R １ｆ may be a hydrogen atom or a first substituent, regardless of the number of n2, but R １ｅ and R １ｆ may each be a hydrogen atom.

[0081] Formula (Ib) corresponds to the case where the first linking group in formula (I) contains a divalent cyclic group (such as a non-aromatic cyclic divalent group or an aromatic divalent group). n2 is an integer of 0 or more. When n2 is a ring Z, １ａ The sum of the minimum number of carbon atoms between the two bonds corresponds to the number of carbon atoms in the main chain of the first linking group. n2 may be, for example, 0 to 4, or 0 to 2. When n2 is 2 or more, the number of R bonded to each carbon atom in the main chain is １ｅ (or R １ｆ At least two of the groups may be the same, or all of the groups may be different.

[0082] In formula (Ib), m1, which corresponds to the number of third substituents, is an integer of 0 or more. １ａ The number of rings can be selected depending on the number of ring members. １ａ is a plurality of third substituents R ３ａ When the ３ａ At least two of them may be the same, or all of them may be different.

[0083] The compound represented by formula (Ib) may be, for example, a compound represented by the following formula (ib):

[0084]

[0085] (In the formula, ring Z １ｂ is a cyclic divalent group (a non-aromatic cyclic divalent group or an aromatic divalent group) contained in the first linking group. １ｅ and R １ｆ , n2, R ３ａ , m1, R ２ , R ３ , X ３ , and k is the same as above.)

[0086] In formula (ib), (n2+2) corresponds to the number of carbon atoms in the main chain of the first linking group.

[0087] In each of formula (Ia) and formula (Ib) (including formula (ib)), the second moiety R ２ -X ３ (-R ３ ) ｋFor the -, see the explanation for the second moiety above. The second moiety may be, for example, a monovalent group represented by any one of the following (iia) to (iid). In these divalent groups, * indicates a bond to the second carbonyl group. In addition to these monovalent groups, it is also preferable that the second moiety is a residue of a monohydroxy compound (such as an aliphatic alcohol) or a residue of a monoamine compound (such as an aliphatic amine).

[0088]

[0089] The second moiety represented by formula (iia) corresponds to the residue of the polyol (e.g., diol) described above. The second moieties represented by formulas (iib) to (iid) correspond to the residue of the polyamine compound described above. R ２ａ may be a chain group or a group containing a ring structure. ２ａ may have at least one of the fourth and fifth substituents described above. Formulae (iic) and (iid) are groups corresponding to the cyclic amines described above.

[0090] In formula (iia), R ２ａ may contain one or more oxygen atoms. ２ａ An example of the second moiety having the formula (iib) is a second moiety containing a residue of polyalkylene glycol (or a polyoxyalkylene group). ２ａ is one or more nitrogen atoms (or amino groups >N—R ６ ) may be included. ２ａ Examples of second moieties having R include second moieties that include a residue of a polyalkyleneamine (or a group corresponding to a polyalkyleneamine). ６ may be a hydrogen atom or a substituent (eighth substituent). The eighth substituent may be selected from the examples of the seventh substituent. ２ａ Two or more amino groups >N-R ６ When the ６ At least two of them may be the same, or all of them may be different.

[0091] R ５ａ１ , R ５ｂ１ and R５ｂ２ are each independently a hydrogen atom or a fifth substituent. ２ａ and ring Z ２ｂ corresponds to the ring structure (specifically, the nitrogen-containing ring) contained in the second moiety. ５ｃ１ and R ５ｃ２ are each independently a ring Z ２ａ and ring Z ２ｂ The substituent R ５ｃ１ p1 and the number of substituents R ５ｃ２ The upper limits of p1 and q1 are the number of rings Z ２ａ and ring Z ２ｂ The number of members may be determined according to the number of members.

[0092] The acid component may contain one type of first carboxylic acid compound or a combination of two or more types.

[0093] (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.

[0094] Examples of the second carboxylic acid compound include a carboxylic acid other than the first carboxylic acid compound, a carboxylic acid anhydride, a coordination compound of a carboxylic acid, and a carboxylic acid compound having two or more first sites (second carboxylic acid compound B). A second carboxylic acid compound other than second carboxylic acid compound B may be referred to as second carboxylic acid compound A.

[0095] Among the second carboxylic acid compounds A, examples of the carboxylic acid include aliphatic carboxylic acids and aromatic carboxylic acids. Examples of aromatic carboxylic acids include aromatic hydroxy acids (benzoic 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 coordination compounds include coordination compounds 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 this central atom. Specific examples of coordination compounds include borodisalicylic acid, borodisalic acid, borodiglycolic acid, and borodigallic acid.

[0096] The second carboxylic acid compound B includes, for example, two or more first sites and a second linking group that links the second carbonyl groups of these first sites. The second linking group may include a heteroatom (such as an oxygen atom, a nitrogen atom, or a sulfur atom) that bonds to the second carbonyl groups. This heteroatom portion corresponds to -X in formula (I) of the first carboxylic acid compound. ３ (-R ３ ) ｋ - can be expressed in the same manner as above, and the description of the first carboxylic acid compound can be referred to. The second linking group may be a residue of a polyol or a residue of a polyamine compound. In these residues, some of the hydroxy groups of the polyol or some of the amino groups of the polyamine compound may not be bonded to the first moiety. The hydroxy groups or amino groups not bonded to the first moiety may be in a free form, may form an ester bond, an ether bond, an amide bond, or the like, or may form a salt. For example, each hydroxy group or each amino group not bonded to the first moiety may be protected, may interact or bond with a component present in the production process, or may interact or bond with other components contained in the electrolytic capacitor.

[0097] For the second carboxylic acid compound B, the explanations for the first moiety and the second moiety of the first carboxylic acid compound (such as polyol, polyamine compound, and fourth to eighth substituents) can be referred to. Examples of the second carboxylic acid compound B include diesters of alkylene glycol or polyalkylene glycol with polycarboxylic acid (or its acid anhydride), and polyamides of polyamine and polycarboxylic acid (such as diamide of ethylenediamine and 2-octenylsuccinic acid, diamide of N,N'-(2'-propyl)ethylenediamine and 2-octenylsuccinic acid, and diamide of piperazine and 2-octenylsuccinic acid). Examples of the diester include esters of alkylene glycols and dicarboxylic acids or their acid anhydrides (such as diesters of ethylene glycol and succinic acid, diesters of ethylene glycol and 2-octenylsuccinic acid, diesters of ethylene glycol and 1,2-cyclohexanedicarboxylic acid, and diesters of ethylene glycol and phthalic acid), and esters of polyalkylene glycols and dicarboxylic acids or their acid anhydrides (such as diesters of triethylene glycol and 2-octenylsuccinic acid and diesters of tri(trimethylene glycol) and 2-octenylsuccinic acid). However, these are merely examples, and the second carboxylic acid compound B is not limited to these.

[0098] The acid component may contain one or more second carboxylic acid compounds. Among the second carboxylic acid compounds, aromatic carboxylic acids (phthalic acid, salicylic acid, benzoic acid, etc.) and the coordination compounds (borodisalicylic acid, borodisalic acid, borodiglycolic acid, etc.) are preferred, and phthalic acid, salicylic acid, borodisalicylic acid, etc. are particularly preferred. The acid component may contain one or more second carboxylic acid compounds A. The acid component may also contain one or more second carboxylic acid compounds B.

[0099] 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.

[0100] (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 acid, phosphinic acid, and partial esters thereof), and nitrogen-containing acids (such as nitric acid and nitrous acid).

[0101] 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.

[0102] 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.

[0103] The acid component may contain one or more of the above-mentioned other acids.

[0104] The ratio of the first carboxylic acid compound to the acid component may be 20% by mass or more, or may be 33% by mass or more. In this case, the effect of suppressing the change in ESR over time is further enhanced. In addition, higher voltage resistance is easily ensured. The ratio of the first carboxylic acid compound to the acid component is 100% by mass or less, and from the viewpoint of easily ensuring higher voltage resistance and improving the film repairability of the dielectric layer, it may be 80% by mass or less. These lower and upper limits can be combined arbitrarily.

[0105] 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 from 0 / 100 to 80 / 20, or from 20 / 80 to 67 / 33. When the mass ratio is in this range, the action of the first carboxylic acid compound is easily exerted, and the effect of reducing the change in ESR over time is enhanced while ensuring high voltage resistance.

[0106] The mass ratio of the second carboxylic acid compound B to the first carboxylic acid compound (= second carboxylic acid compound B / first carboxylic acid compound) may be 0 / 100 or more and less than 50 / 50, 0.1 / 99.9 or more and 30 / 70 or less, or 1 / 99 or more and 20 / 80 or less. When the mass ratio is in such a range, the voltage resistance can be further improved.

[0107] 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 change in 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.

[0108] The above ratios, mass ratios, and concentrations are values ​​determined based on the mass of each acid when it is in its free form.

[0109] (Oligomer Component) The liquid component may further contain an oligomer component of a second carboxylic acid compound B. When the oligomer component contains an oligomer having a carboxy group, this oligomer is included in the second carboxylic acid compound. The oligomer has, for example, a repeating structure of a first moiety and a second linking group. For example, when the second linking group is a residue of a polyol compound, the oligomer has a structure in which a polycarboxylic acid or its acid anhydride corresponding to the first moiety and a polyol compound are alternately linked by ester bonds. When the second linking group is a residue of a polyamine compound, the oligomer has a structure in which a polycarboxylic acid or its acid anhydride corresponding to the first moiety and a polyamine compound are alternately linked by amide bonds. The oligomer component may contain one type of oligomer, or may contain two or more oligomers with different structures or chain lengths.

[0110] (Base Component) The liquid component may further contain a base component. In this case, the dissociation property of the acid component such as the first carboxylic acid compound is enhanced, and acid groups such as carboxy groups can easily react with the conductive polymer. Therefore, higher conductivity of the conductive polymer can be easily obtained.

[0111] 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.

[0112] 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), etc.). 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).

[0113] 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.

[0114] 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 electrode corrosion can be suppressed. In addition, high voltage resistance can be easily ensured.

[0115] 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

[0116] 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.

[0117] 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

[0118] (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.

[0119] 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).

[0120] 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, etc.)), glycerin compounds (glycerin, polyglycerin, etc.), sugar alcohol compounds, and alkylene oxide adducts thereof (ethylene oxide adducts, polyethylene oxide adducts, etc.).

[0121] 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).

[0122] (Other) The liquid component may contain alkali metal ions (sodium ions, potassium ions, etc.). However, it is preferable that the concentration of alkali metal ions in the liquid component is low. It is also preferable that the liquid component does not contain alkali metal ions. This includes cases where the alkali metal ions in the liquid component are below the detection limit.

[0123] The concentration of alkali metal ions in the liquid component may be 100 ppm or less, or 50 ppm or less, on a mass basis.

[0124] (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).

[0125] (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.

[0126] 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.

[0127] 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).

[0128] (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.

[0129] 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.

[0130] 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.

[0131] (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.

[0132] (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).

[0133] The conjugated polymer may be used alone or in combination of two or more kinds.

[0134] 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.

[0135] In this specification, the weight average molecular weight (Mw) is a value calculated as polysaccharide as measured by gel permeation chromatography (GPC). GPC is usually performed using a polyhydroxymethacrylate gel column and an aqueous sodium nitrate solution as the mobile phase.

[0136] (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.

[0137] 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.

[0138] 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.

[0139] 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.

[0140] The Mw of the dopant is not particularly limited and is, for example, 1,000 or more and 1,000,000 or less.

[0141] 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.

[0142] (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.

[0143] 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.

[0144] 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).

[0145] 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.

[0146] (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).

[0147] 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.

[0148] (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.

[0149] 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.

[0150] 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 14) related to the solid electrolytic capacitor of the present disclosure, or may be arbitrarily combined with at least one of the above-described (Technology 1) to (Technology 14) and the components described above.

[0151] The electrolytic capacitor includes, for example, a capacitor element 10, a bottomed case 101, a sealing member 102 that closes the opening of the bottomed case 101, a seat plate 103 that covers the sealing member 102, lead wires 104A and 104B, and lead tabs 105A and 105B. The bottomed case 10 accommodates the capacitor element 10 and a liquid component (not shown). The vicinity of the open end of the bottomed case 101 is drawn inward, and the open end is curled so as to be crimped to the sealing member 102. The lead wires 104A and 104B are led out of the sealing member 102 and pass through the seat plate 103. The lead tabs 105A and 105B connect the lead wires 104A and 104B to electrodes of the capacitor element 10, respectively.

[0152] 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.

[0153] 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.

[0154] [Examples] The electrolytic capacitor according to the present disclosure will be specifically described below based on examples and comparative examples, but the electrolytic capacitor according to the present disclosure is not limited to the following examples. The components described in the following examples may be combined with the above-mentioned conceptual description, including at least one of (Technology 1) to (Technology 14).

[0155] Preparation Example 1 A first carboxylic acid compound X1 was prepared by the following procedure. 2-Octenylsuccinic anhydride (50 mmol) and ethylene glycol (250 mmol) were mixed and reacted for 15 hours at 110°C under a nitrogen atmosphere. The end point of the reaction was determined by the acid value. In this manner, an ethylene glycol solution of the first carboxylic acid compound X1 was prepared. The structure of the obtained first carboxylic acid compound X1 was confirmed by liquid chromatography mass spectrometry (LC / MS) (ion source: ESI － ) was confirmed.

[0156] Production Example 2 An ethylene glycol solution of first carboxylic acid compound X2 was produced in the same manner as in Production Example 1, except that succinic anhydride was used instead of 2-octenylsuccinic acid and the reaction was carried out for 6 hours at a reaction temperature of 100° C.

[0157] Production Example 3 An ethylene glycol solution of a first carboxylic acid compound X3 was produced in the same manner as in Production Example 1, except that 1,2-cyclohexanedicarboxylic anhydride was used instead of 2-octenylsuccinic acid and the reaction was carried out for 18 hours at a reaction temperature of 150° C.

[0158] Production Example 4 An ethylene glycol solution of a first carboxylic acid compound X4 was produced in the same manner as in Production Example 1, except that phthalic anhydride was used instead of 2-octenylsuccinic acid and the reaction was carried out for 10 hours at a reaction temperature of 150° C.

[0159] Production Example 5 Under a nitrogen atmosphere, sodium hydride (50 mmol) was added to a suspension prepared by suspending isodecanol (50 mmol) in xylene (100 g) and the mixture was stirred. 2-Octenylsuccinic anhydride (50 mmol) was added dropwise to the resulting mixture, and the mixture was allowed to react for 3 hours. After the reaction was completed, an aqueous sulfuric acid solution (5% by mass, 100 g) was added to the resulting mixture, which was then transferred to a separatory funnel and shaken thoroughly to separate into an aqueous phase and an organic phase. The aqueous phase was removed, and the organic phase was washed with pure water. The solvent was removed from the washed organic phase using an evaporator to produce first carboxylic acid compound X5.

[0160] Production Example 6: Triethylene glycol (50 mmol) was used instead of ethylene glycol (250 mmol), and sulfolane (30 g) was added as a solvent. The reaction was carried out at a reaction temperature of 170° C. for 12 hours. A sulfolane solution of first carboxylic acid compound X6 was produced in the same manner as in Production Example 1, except for the above.

[0161] Production Example 7: Tripropylene glycol (50 mmol) was used instead of ethylene glycol (250 mmol), and sulfolane (30 g) was added as a solvent. The reaction was carried out at a reaction temperature of 170° C. for 24 hours. A sulfolane solution of first carboxylic acid compound X7 was produced in the same manner as in Production Example 1, except for the above.

[0162] Production Example 8: Triethylene glycol monomethyl ether (50 mmol) was used instead of ethylene glycol (250 mmol), and sulfolane (30 g) was added as a solvent. The reaction was carried out at a reaction temperature of 170°C for 16 hours. A sulfolane solution of first carboxylic acid compound X8 was produced in the same manner as in Production Example 1, except for the above.

[0163] Examples 1 to 14 and Comparative Examples 1 to 7 Wound electrolytic capacitors (rated voltage 25 V, rated capacitance 330 μF) were fabricated and evaluated according to the following procedure.

[0164] (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.

[0165] (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.

[0166] (Preparation 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 around the lead tabs, with a separator interposed therebetween. 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. Next, the end of the outer surface of the wound body was fixed with a winding tape to prepare the wound body.

[0167] (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 poly(3,4-ethylenedioxythiophene) doped with PSS (PEDOT / PSS) as the conductive polymer. The Mw of the polymer dopant is the value measured under the conditions described above.

[0168] (Coating of the dielectric layer with a conductive polymer) The wound body was immersed in a polymer dispersion contained in a designated container in a reduced pressure atmosphere (40 kPa) for 5 minutes, and then the wound body was 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 a conductive polymer. In this manner, a capacitor element was formed. However, in Comparative Examples 8 to 10, the capacitor elements were formed without performing this process of coating the dielectric layer with a conductive polymer.

[0169] (Impregnation of Liquid Component) A mixture obtained by mixing EG, PEG (number average molecular weight Mn: 300), and SL in a volume ratio of EG:PEG:SL = 1:1:1 was used as the solvent for the liquid component. The acid component and base component shown in Table 2 (and Table 1) were dissolved in this mixture to the concentrations shown in Table 2, thereby preparing a liquid component. Table 2 also shows the equivalent ratio of the acid component to the base component. In the examples, first carboxylic acid compounds X1 to X8 produced in Production Examples 1 to 8 were used as the acid component, and in the comparative examples, second carboxylic acid components Y1 to Y5 shown in Table 1 were used. In the examples, the concentration of alkali metal ions contained in the liquid component was 40 ppm or less.

[0170] (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 allow the liquid component to be impregnated into the capacitor element.

[0171] 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.

[0172] [Evaluation] The electrolytic capacitors prepared as described above were evaluated as follows. (1) Change in Capacitance (Δcap) and Change in ESR (ΔESR) After the aging treatment, the capacitance at a frequency of 120 Hz and the ESR at a frequency of 100 kHz were measured using an LCR meter in an environment of 20°C. The average values ​​of the measured values ​​for the 20 electrolytic capacitors (initial capacitance value: c0 (F), initial ESR value: r0 (Ω)) were then calculated.

[0173] After determining c0 and r0, a high-temperature load test (accelerated test) was conducted. That is, a rated voltage was applied to the electrolytic capacitor at a temperature of 145°C for 750 hours. For the electrolytic capacitor after the accelerated test, the average capacitance value (c1 (F)) and ESR value (r1 (Ω)) after the accelerated test were determined in the same manner as for the initial capacitance value and initial ESR value.

[0174] Using the obtained c0 and c1, and r0 and r1, the initial capacity change (Δcap) and ESR change (ΔESR) were calculated according to the following formulas: Δcap=c1 / c0 ΔESR=r1 / r0

[0175] (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. The average value (e0: initial leakage current (A)) of the measured values ​​for the 20 electrolytic capacitors was calculated.

[0176] For the 20 electrolytic capacitors for which the initial leakage current e0 was measured, an accelerated test was performed at 145°C for 750 hours without applying a voltage. For the electrolytic capacitors after the accelerated test, the leakage current (A) was measured in the same manner as for the initial leakage current. The average value (e1: leakage current (A) after the accelerated test) was calculated from the measured leakage current values ​​of the 20 electrolytic capacitors. ΔLC = e1 / e0

[0177] The acid components used in the liquid components are shown in Table 1. The evaluation results of each electrolytic capacitor are shown in Table 2. In Table 2, A1 to A14 are examples, and B1 to B7 are comparative examples.

[0178]

[0179]

[0180] As shown in Table 2, a significant difference is observed, particularly in ΔESR, between the use of a liquid component containing a first carboxylic acid compound and the use of a liquid component containing another acid component (more specifically, second carboxylic acid compound A). More specifically, for samples B1 to B7, which used a liquid component containing second carboxylic acid compound A, the ΔESR was 2.89 to 1719. For samples B4 to B7, which used an aliphatic dicarboxylic acid, the ΔESR was particularly large, at 6.86 to 1719. In contrast to these results, samples A1 to A14, which used a liquid component containing a first carboxylic acid compound, had a significantly smaller ΔESR of 2.10 or less than samples B1 to B7, minimizing fluctuations in ESR during accelerated testing. The main chain of the first carboxylic acid compounds used in samples A1 to A8 and A11 to A14 can be said to be an aliphatic chain, but the ΔESR can be significantly reduced compared to samples B4 to B7, which used an aliphatic dicarboxylic acid. Furthermore, in the Examples, the leakage current after the accelerated test was kept relatively low, and a larger capacitance was obtained after the accelerated test than in the Comparative Example. Thus, the electrolytic capacitors of the Examples were able to maintain excellent capacitor performance even after the accelerated test, and had excellent reliability.

[0181] While the present invention has been described in terms of presently preferred embodiments, such disclosure is not to be interpreted as limiting. Various changes and modifications will no doubt become apparent to those skilled in the art to which the present invention pertains upon reading the above disclosure. It is therefore intended that the appended claims be interpreted to cover all changes and modifications that do not depart from the true spirit and scope of the invention.

[0182] The electrolytic capacitor of the present disclosure can be used as a hybrid electrolytic capacitor. The electrolytic capacitor can reduce the change in ESR over time. Furthermore, the electrolytic capacitor can suppress the increase in leakage current over time and ensure high voltage resistance. Therefore, the electrolytic capacitor of the present disclosure is particularly suitable for various applications requiring high reliability or long life. However, the applications of the electrolytic capacitor are not limited to these.

[0183] 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

1. An electrolytic capacitor comprising: a capacitor element; and a liquid component; the capacitor element comprises an anode body having a dielectric layer on a surface thereof; and a conductive polymer covering at least a portion of the dielectric layer; the liquid component comprises an acid component and a solvent; the acid component comprises a first carboxylic acid compound each having a first site and a second site; the first site has a first carboxy group including a first carbonyl group, a second carbonyl group, and a linking group linking the first carbonyl group and the second carbonyl group; and the second site comprises a heteroatom bonded to the second carbonyl group, and a hydrocarbon group having two or more carbons bonded to the heteroatom.

2. The electrolytic capacitor of claim 1, wherein the liquid component further comprises a base component.

3. An electrolytic capacitor comprising: a capacitor element; and a liquid component, wherein the capacitor element comprises an anode body having a dielectric layer on a surface thereof; and a conductive polymer covering at least a portion of the dielectric layer, wherein the liquid component comprises an acid component, a base component, and a solvent, wherein the acid component comprises a first carboxylic acid compound having one first site, wherein the first site has a first carboxy group including a first carbonyl group, a second carbonyl group, and a linking group linking the first carbonyl group and the second carbonyl group, and the base component comprises at least one selected from the group consisting of an amine, a quaternary ammonium compound, and an amidinium compound.

4. The electrolytic capacitor according to claim 2 or 3, wherein an equivalent ratio of the first carboxylic acid compound to the base component is 0.5 or more and 10 or less.

5. The electrolytic capacitor according to claim 1 or 2, wherein the heteroatom is an oxygen atom or a nitrogen atom.

6. The electrolytic capacitor according to claim 1 or 2, wherein the second portion includes a residue of a hydroxy compound or a residue of an amine compound.

7. The electrolytic capacitor according to claim 1 or 2, wherein the second portion comprises a residue of a polyol, and the polyol is an alkylene glycol, a polyalkylene glycol, or a monoether thereof.

8. The electrolytic capacitor according to claim 1 or 3, wherein the number of carbon atoms in the main chain connecting the first carbonyl group of the first carbonyl group and the second carbonyl group of the second carbonyl group is 1 or more and 4 or less.

9. The electrolytic capacitor according to claim 1 or 3, wherein the linking group includes a non-aromatic cyclic divalent group or an aromatic divalent group.

10. The electrolytic capacitor according to claim 1 or 3, wherein in the linking group, the main chain connecting the first carbon atom of the first carbonyl group and the second carbonyl group is an aliphatic divalent group.

11. The electrolytic capacitor according to claim 10, wherein the aliphatic divalent group has a first substituent, and at least one of the first substituents is a monovalent aliphatic hydrocarbon group having 6 or more carbon atoms.

12. The electrolytic capacitor according to claim 11, wherein the aliphatic divalent group has the monovalent aliphatic hydrocarbon group at the alpha position of the first carbonyl group.

13. The electrolytic capacitor according to claim 1 or 3, wherein the acid component further comprises a second carboxylic acid compound different from the first carboxylic acid compound.

14. The electrolytic capacitor according to claim 1 or 3, wherein the ratio of the first carboxylic acid compound to the acid component is 20 mass % or more.