Electrolytic capacitor

Abstract

To provide an electrolytic capacitor excellent in heat resistance.SOLUTION: The electrolytic capacitor includes capacitor element 10 and a liquid component. The capacitor element includes an anode body 21 having a dielectric layer on its surface, and a conductive polymer component covering a part of the dielectric layer. The liquid component includes a first solvent selected from the group consisting of polyols and derivatives thereof, a base component, and an acid component. The first solvent is at least one selected from the group consisting of polyols and derivatives thereof. The base component includes a first base whose conjugate acid has an acid dissociation constant of 5 or more and 10 or less and that has no boiling point or has a boiling point of 100 °C or more.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to electrolytic capacitors that include conductive polymer components. [Background technology]

[0002] Electrolytic capacitors are considered promising as small, high-capacity capacitors with low equivalent series resistance (ESR). These capacitors are made up of an anode body with a dielectric layer, a conductive polymer covering at least a portion of the dielectric layer, and an electrolyte. The electrolyte is made up of 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 using a solvent, an acid, and a base with a base dissociation degree of 10 or more in an electrolyte solution for an electrolytic capacitor.

[0004] Patent Document 2 proposes an electrolyte for an electrolytic capacitor to be impregnated into the gaps in the solid electrolyte layer of a capacitor element, which is a salt of a cation of a basic compound and an anion of an acidic compound, in which the pKa of the conjugate acid of the basic compound is 14.0 or less and the boiling point of the basic compound is 90°C or more. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-224646 [Patent Document 2] Japanese Patent Application Laid-Open No. 2016-15365 Summary of the Invention [Problem to be solved by the invention]

[0006] Depending on the application, electrolytic capacitors may be used in high-temperature environments. In recent years, there has been a demand for increasing the allowable ripple current of electrolytic capacitors. As the ripple current increases, the heat generated by the electrolytic capacitor increases, and the temperature of the electrolytic capacitor tends to rise. Therefore, there is a demand for further improvement in the heat resistance of electrolytic capacitors. [Means for solving the problem]

[0007] A first aspect of the present disclosure includes a capacitor element and a liquid component, the capacitor element includes an anode body having a dielectric layer on a surface thereof, and a conductive polymer component covering a portion of the dielectric layer; the liquid component includes a first solvent, a base component, and an acid component; the first solvent is at least one selected from the group consisting of polyols and derivatives thereof; The electrolytic capacitor relates to a base component, wherein the base component contains a first base whose conjugate acid has an acid dissociation constant of 5 or more and 10 or less, and which has no boiling point or a boiling point of 100°C or higher. [Effects of the Invention]

[0008] An electrolytic capacitor with excellent heat resistance can be provided. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a cross-sectional schematic view of an electrolytic capacitor according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is a schematic diagram for explaining the configuration of the capacitor element of FIG. DETAILED DESCRIPTION OF THE INVENTION

[0010] Depending on the application, electrolytic capacitors containing conductive polymer components may be used in high-temperature environments. Furthermore, heat generated by ripple current can cause the temperature of the electrolytic capacitor to rise. For this reason, electrolytic capacitors are required to have high heat resistance. When an electrolytic capacitor is exposed to high temperatures, the dopants contained in the conductive polymer components are prone to dedoping. When dedoping occurs, the conductivity of the conductive polymer components decreases and the ESR increases.

[0011] Impregnating the capacitor element of an electrolytic capacitor with a liquid component containing an acid and a base can improve the film repairability of the dielectric layer to some extent, while the acid component can help to suppress dedoping to some extent. However, in high-temperature environments, the liquid component tends to volatilize, making it difficult to ensure sufficient film repairability. Furthermore, the conductive polymer component is more susceptible to oxidative degradation due to its increased contact with air. Furthermore, in high-temperature environments, the concentration of the acid component in the liquid component tends to decrease due to decomposition, etc., which can lead to dedoping of the dopant contained in the conductive polymer component. Oxidative degradation of the conductive polymer or dedoping of the dopant increases the ESR. Using a base component with a high boiling point can somewhat reduce the volatilization of the liquid component, even in high-temperature environments. However, if the acid dissociation constant (pKa) of the conjugate acid of the base component is high, it will more readily react with the dopant contained in the conductive polymer component, accelerating dopant dedoping. On the other hand, if the pKa of the conjugate acid of the base component is small, dedoping can be reduced to some extent, but the dissociation degree of the acid component contained in the liquid component tends to be low, which tends to accelerate the deterioration of film repairability. The deterioration of film repairability increases leakage current. Thus, particularly in high-temperature environments, it is difficult to achieve both a high effect of suppressing oxidative degradation and dedoping of the conductive polymer component and excellent film repairability.

[0012] The electrolytic capacitor according to the above aspect of the present disclosure uses a liquid component including at least one first solvent selected from the group consisting of polyols and their derivatives; a base component including a first base whose conjugate acid has a pKa of 5 to 10 and either no boiling point or a boiling point of 100°C or higher; and an acid component. Therefore, even when the electrolytic capacitor is exposed to high temperatures, the volatilization of the liquid component is reduced, thereby suppressing oxidative degradation of the conductive polymer component and suppressing dedoping from the conductive polymer component. Furthermore, high film repairability of the dielectric layer is ensured, thereby suppressing thermal degradation of the electrolytic capacitor. Therefore, while suppressing an increase in ESR, an increase in leakage current can be suppressed. Thus, according to the present disclosure, even when the electrolytic capacitor is exposed to high temperatures, degradation of the electrolytic capacitor's performance is suppressed. Therefore, according to the present disclosure, an electrolytic capacitor with excellent heat resistance can be obtained. Thus, particularly in high-temperature environments, controlling the pKa of the base component is important to achieve both high suppression of oxidative degradation and dedoping of the conductive polymer component and excellent film repairability.

[0013] In this specification, the acid dissociation constant (pKa) refers to the acid dissociation constant in water at a temperature of 25°C. The pKa of the conjugate acid of a base is the pKa of the cation of the base. When the conjugate acid of a base or an acid exhibits multiple pKa values, the highest pKa (i.e., pKa1) is meant.

[0014] The electrolytic capacitor will be described in more detail below.

[0015] [Electrolytic capacitor] The electrolytic capacitor includes a capacitor element and a liquid component.

[0016] (liquid component) (solvent) (First solvent) The first solvent contained in the liquid component is at least one selected from the group consisting of polyols and their derivatives. From the viewpoint of ensuring higher film repairability, the polyol derivative preferably has a hydroxy group, more preferably two or more hydroxy groups. From the same viewpoint, it is preferable to use a first component having two or more hydroxy groups. Furthermore, using a first component having three or more or four or more hydroxy groups makes it easier for the conductive polymer to be oriented, thereby increasing conductivity.

[0017] The first solvent has high polarity, so it can easily dissolve basic and acidic components, and also exhibits a high dielectric constant, ensuring high ionic conductivity. The first solvent may be a protic solvent. The first solvent may itself not dissociate in the liquid component. The first solvent preferably does not contain heteroatoms other than oxygen atoms (such as sulfur atoms, boron atoms, phosphorus atoms, and nitrogen atoms) and carbonyl groups.

[0018] The first solvent may include a polyhydroxyalkane component, a polyalkylene glycol component, a glycerin component, and a sugar alcohol component.

[0019] The polyhydroxyalkane component may be, for example, a component other than glycerin or sugar alcohol. The polyhydroxyalkane component may be a di- or trihydroxyalkane component. Examples of such polyhydroxyalkane components include alkylene glycol components and trimethylolpropane. Examples of alkylene glycol components include C 2-10 Alkylene glycols include C 2-6 Alkylene glycols, especially C 2-4 Alkylene glycols (ethylene glycol, propylene glycol, etc.) are preferred.

[0020] In this specification, C x-y means that the number of carbon atoms is x or more and y or less. For example, C 2-10The alkylene glycol means an alkylene glycol having 2 to 10 carbon atoms.

[0021] Among these, alkylene glycol components, polyalkylene glycol components, glycerin components, and sugar alcohol components are preferred. The use of such a first solvent can suppress the evaporation of liquid components when the electrolytic capacitor is exposed to high temperatures, making it easier to ensure higher film repairability. From the perspective of making it easier to achieve higher film repairability, polyalkylene glycol components, glycerin components, and sugar alcohol components are more preferred. The sugar alcohol component includes sugar alcohols with four or more hydroxy groups and derivatives of such sugar alcohols.

[0022] It is preferable to use at least a polyalkylene glycol component as the first solvent, and more preferable to use at least a polyalkylene glycol component having a weight-average molecular weight of 150 or more. The first solvent may be a combination of a polyalkylene glycol component (solvent 1A) and a first solvent other than solvent 1A (solvent 1B). Specific examples of solvent 1B include at least one selected from the group consisting of polyhydroxyalkane components (alkylene glycol components, trimethylolpropane, etc.), glycerin components, and sugar alcohol components. When a polyalkylene glycol component having a weight-average molecular weight of 150 or more is used as the first solvent, the alkylene glycol component of solvent 1B may be, for example, a polyalkylene glycol component having a weight-average molecular weight of less than 150 (diethylene glycol, triethylene glycol, and dipropylene glycol). The first solvent may contain one type of solvent 1B or a combination of two or more types.

[0023] Combining solvent 1B with solvent 1A increases the effect of suppressing the evaporation of the liquid components, thereby preventing the conductive polymer from coming into contact with air and suppressing oxidative degradation of the conductive polymer. This helps to keep the increase in ESR low even when the electrolytic capacitor is exposed to high temperatures.

[0024] Furthermore, the use of at least one of a glycerin component and a sugar alcohol component tends to increase the viscosity of the liquid component. When these components are used, combining them with a polyalkylene glycol component can maintain a relatively low viscosity of the liquid component. This makes it easier to ensure high dissociation of the acid component and the base component, and therefore makes it easier to ensure high film repairability of the dielectric layer.

[0025] The ratio of solvent 1A in the first solvent is, for example, preferably 90% by mass or more, and may be 95% by mass or more, or 99% by mass or more. The ratio of solvent 1A is 100% by mass or less. The first solvent may be composed of solvent 1A alone.

[0026] Among the first solvents, the polyalkylene glycol component may be one having a repeating alkylene oxide structure. Examples of alkylene oxides include C 2-4 Alkylene oxides include C 2-3 The polyalkylene glycol component may be an alkylene oxide. Specific examples of alkylene oxides include ethylene oxide, propylene oxide, trimethylene oxide, and butylene oxide. The polyalkylene glycol component may contain one type of alkylene oxide unit, or may contain two or more types of alkylene oxide units. The polyalkylene glycol component containing two or more types of alkylene oxide units may be, for example, a polyalkylene glycol component containing an ethylene oxide unit and a C 3-4 The polyalkylene glycol component containing two or more types of alkylene oxide units may be used to enhance the effect of reducing the viscosity of the liquid component.

[0027] Examples of polyalkylene glycol components include polyalkylene glycols, copolymers containing two or more alkylene oxide units, and polyalkylene oxide adducts of polyhydric alcohols. Examples of polyhydric alcohols include glycerin, trimethylolpropane, and sugar alcohols. Examples of sugar alcohols include sugar alcohols having four or more hydroxy groups (monosaccharide alcohols, disaccharide alcohols, etc.). Examples of sugar alcohols include sorbitol, mannitol, erythritol, pentaerythritol, threitol, arabinitol, ribitol, xylitol, galactitol, rhamnitol, isomaltose, maltitol, lactitol, palatinose, and reduced forms thereof (e.g., reduced palatinose). In the polyalkylene oxide adduct, two or more polyalkylene oxide chains may be the same polyalkylene oxide chain, or all of the polyalkylene oxide chains may be different.

[0028] The liquid component may contain one type of polyalkylene glycol component, or may contain two or more types of polyalkylene glycol components.

[0029] The weight-average molecular weight (Mw) of the polyalkylene glycol component (or solvent 1A) is, for example, 150 or more, preferably 200 or more. In particular, for polyalkylene glycol, from the viewpoint of ensuring higher film repairability, Mw is preferably 150 or more, more preferably 200 or more. Furthermore, a polyalkylene glycol component having an Mw of 150 or more (preferably 200 or more) may be combined with a polyalkylene glycol component having an Mw of less than 150 (or less than 200). The Mw is, for example, 20,000 or less, or may be 10,000 or less, 5,000 or less, or 2,000 or less, or 1,000 or less. When Mw is within this range, the effect of suppressing volatilization of the liquid component can be enhanced. Furthermore, since the viscosity of the liquid component can be easily maintained relatively low, the dissociation of the acid component and the base component can be enhanced, the effect of suppressing dedoping can be enhanced, and high conductivity can be easily ensured. These lower and upper limits can be combined arbitrarily.

[0030] In this specification, the weight-average molecular weight (Mw) is a value calculated as polystyrene measured by gel permeation chromatography (GPC), which is usually performed using a polystyrene gel column and water / methanol (volume ratio 8 / 2) as the mobile phase.

[0031] The content of solvent 1A in the liquid component is, for example, 30% by mass or more, preferably 50% by mass or more, or 60% by mass or more. In this case, the effect of reducing volatilization of the liquid component is enhanced, and higher film repair properties are likely to be obtained. Even when combined with solvent 1B, the viscosity of the liquid component can be kept low. The content of solvent 1A in the liquid component is, for example, 95% by mass or less, preferably 90% by mass or less, and may be 85% by mass or less, 80% by mass or less, 75% by mass or less, or 70% by mass or less. In this case, thermal degradation of the electrolytic capacitor can be more effectively suppressed even when the electrolytic capacitor is used in a high-temperature environment. These lower and upper limits can be combined as desired.

[0032] Examples of the glycerin component include glycerin, glycerin derivatives, polyglycerin, polyglycerin derivatives, etc. The liquid component may contain one type of glycerin component, or may contain two or more types of glycerin components.

[0033] Polyglycerol contains a repeating structure of glycerol units. The number of repeating glycerol units contained in polyglycerol is, for example, from 2 to 20, or may be from 2 to 12 or from 2 to less than 12, or from 2 to 10 or from 2 to 6. Diglycerol, triglycerol, etc. are also preferred as polyglycerol.

[0034] Examples of derivatives of glycerin or polyglycerin include esters in which at least some of the hydroxy groups of glycerin or polyglycerin are esterified, and alkylene oxide adducts of glycerin or polyglycerin. Examples of esters include organic acid esters (such as acetate esters). More specifically, examples of alkylene oxide adducts include adducts in which one molecule of alkylene oxide is added to at least some of the hydroxy groups. Examples of alkylene oxides include C 2-4 Alkylene oxides include C 2-3 Alkylene oxide or ethylene oxide is preferred. When the alkylene oxide adduct contains a plurality of alkylene oxide units, at least two of the alkylene oxide units may be of the same type, or all of the alkylene oxide units may be of different types.

[0035] The number of hydroxy groups in the derivative is not particularly limited. The derivative may have no hydroxy groups. The number of hydroxy groups in the derivative may be, for example, 0 to 10, 0 to 8, 1 to 8, or 2 to 8.

[0036] From the viewpoint of facilitating the orientation of the conductive polymer, it is preferable to use a glycerin component having hydroxy groups on at least two adjacent carbon atoms. As a derivative, an alkylene oxide adduct is preferable. These glycerin components not only easily swell the conductive polymer but also easily orient it. Therefore, the film repair effect of the dielectric layer is enhanced and the ESR can be reduced.

[0037] The Mw of the glycerin component is not particularly limited, but may be 100 or more or 150 or more. When the Mw of the glycerin component is 100 or more (or 150 or more), the effect of suppressing the volatilization of the liquid component when the electrolytic capacitor is exposed to high temperatures is enhanced, and the film repairability can be further improved. The Mw of the glycerin component may be, for example, 2000 or less, or 1500 or less. When the Mw is within this range, the viscosity of the liquid component can be suppressed from increasing, and the dissociation properties of the acid component and the base component can be further improved. These lower and upper limits can be combined arbitrarily.

[0038] The liquid component may contain one type of glycerin component, or may contain two or more types of glycerin components.

[0039] Among the sugar alcohol components, examples of the sugar alcohol include those sugar alcohols described for the polyalkylene glycol component. The number of hydroxy groups in the sugar alcohol may be, for example, 10 or less, or 8 or less. Examples of sugar alcohols include tetritols (erythritol, pentaerythritol, threitol, etc.), pentitols (arabinitol, ribitol, xylitol, etc.), hexitols (mannitol, sorbitol, etc.), heptitols, and octitols.

[0040] As the sugar alcohol, tetritol, pentitol, mannitol, sorbitol, heptitol, and octitol are preferred, and mannitol, sorbitol, erythritol, and pentaerythritol are more preferred. These sugar alcohols not only easily swell the conductive polymer but also easily orient the conductive polymer. Therefore, the film repair effect of the dielectric layer can be enhanced and the ESR can be reduced.

[0041] The number of hydroxy groups in a sugar alcohol derivative is not particularly limited. The derivative may have no hydroxy groups or may have more hydroxy groups than the corresponding sugar alcohol. The number of hydroxy groups in the derivative may be, for example, 0 to 10, 0 to 8, 1 to 8, or 2 to 8. Examples of the derivative include esters in which at least some of the hydroxy groups in the sugar alcohol are esterified, and alkylene oxide adducts of sugar alcohols. Examples of esters include organic acid esters (acetylated sugar alcohols, etc.). More specifically, examples of alkylene oxide adducts include adducts in which one molecule of alkylene oxide is added to at least some of the hydroxy groups. Examples of alkylene oxides include C 2-4 Alkylene oxides include C 2-3 Alkylene oxide or ethylene oxide is preferred. Specific examples of alkylene oxide include those described for the polyalkylene glycol component. When the alkylene oxide adduct contains multiple alkylene oxide units, at least two of the alkylene oxide units may be the same type, or all of the alkylene oxide units may be different types.

[0042] The liquid component may contain one type of sugar alcohol component, or may contain two or more types of sugar alcohol components.

[0043] From the viewpoint of facilitating the orientation of the conductive polymer, it is preferable to use a sugar alcohol component having hydroxy groups on at least two adjacent carbon atoms.

[0044] Among the sugar alcohol components, sugar alcohol derivatives are preferred. As the sugar alcohol derivative, alkylene oxide adducts are preferred. These sugar alcohol components not only easily swell the conductive polymer but also easily orient the conductive polymer. Therefore, the film repair effect of the dielectric layer is enhanced and the ESR can be reduced.

[0045] The content of the first solvent in the liquid component is, for example, 5% by mass or more, and may be 10% by mass or more, 25% by mass or more, 30% by mass or more, 50% by mass or more, 75% by mass or more, or 77% by mass or more. In this case, the dissociation of the acid component and the base component can be further enhanced, and the film repairability when the electrolytic capacitor is exposed to high temperatures can be further improved. The content of the first solvent in the liquid component may be, for example, 99.9% by mass or less, 99.7% by mass or less, 95% by mass or less, 90% by mass or less, less than 90% by mass, 80% by mass or less, 75% by mass or less, 70% by mass or less, or 50% by mass or less. In this case, the contents of the acid component and the base component can be relatively increased, thereby further enhancing the effect of suppressing undoping. These lower and upper limits can be combined arbitrarily. The content of the first solvent in the liquid component may be, for example, 50% by mass to 99.9% by mass, 75% by mass to 99.9% by mass, or 77% by mass to 99.7% by mass. Within these ranges, from the viewpoint of further suppressing the initial ESR and ESR fluctuation, the content of the first solvent is preferably 85% by mass to 99.9% by mass, and more preferably 90% by mass to 99.7% by mass. Furthermore, from the viewpoint of further suppressing the initial leakage current and leakage current fluctuation, the content of the first solvent is preferably 75% by mass to 95% by mass, and more preferably 77% by mass to 90% by mass.

[0046] (Non-aqueous solvent (second solvent)) The liquid component may contain a non-aqueous solvent other than the first solvent (hereinafter, sometimes referred to as the second solvent). Examples of the second solvent include a sulfone compound, a lactone compound, and a carbonate compound. The second solvent may be an aprotic solvent.

[0047] Examples of sulfone compounds include sulfolane, dimethyl sulfoxide, and diethyl sulfoxide. Examples of lactone compounds include γ-butyrolactone and γ-valerolactone. Examples of carbonate compounds include dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, ethylene carbonate, propylene carbonate, and fluoroethylene carbonate.

[0048] The liquid component may contain one or more of these second solvents.

[0049] From the viewpoint of ensuring higher film repairability of the dielectric layer when the electrolytic capacitor is exposed to high temperatures, the content of such a second solvent in the liquid component is preferably 10% by mass or less, more preferably 5% by mass or less or 1% by mass or less.

[0050] (solute) The liquid component contains an acid component and a base component. The acid component and the base component act as solutes. When the liquid component contains an acid component, the dedoping phenomenon of the dopant can be suppressed, and the conductivity of the conductive polymer component can be stabilized. Furthermore, even if the dopant is dedoped from the conductive polymer component, the acid component is redoped at the site of the dedoping, making it easier to maintain a low ESR. The acid component and the base component are different from the solvent. It is preferable that the dissociability of the acid component and the base component in the liquid component is higher than the dissociability of the solvent.

[0051] Furthermore, since the liquid component contains a base component, the base component neutralizes at least a portion of the acid component, thereby increasing the concentration of the acid component and suppressing corrosion of the electrodes caused by the acid component.

[0052] The liquid component may contain the acid component and the base component in a free state or in the form of a salt.

[0053] (acid component) Examples of acid components include carboxylic acids, acids containing heteroatoms other than oxygen atoms, acidic coordination compounds, oxocarbonic acids, Meldrum's acid, and picric acid. Examples of heteroatoms include at least one selected from the group consisting of sulfur, boron, phosphorus, and nitrogen atoms. The above-mentioned heteroatom-containing acids may contain oxygen atoms in addition to heteroatoms other than oxygen atoms. Examples of the above-mentioned heteroatom-containing acids include sulfur-containing acids (such as sulfuric acid, sulfonic acid, and saccharin), 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). Examples of sulfonic acids include aliphatic sulfonic acids having 1 to 30 carbon atoms and aromatic sulfonic acids having 6 to 30 carbon atoms.

[0054] The liquid component may contain one or more types of acid components.

[0055] Of the acid components, carboxylic acids, coordination compounds, saccharin, oxocarbonic acids, Meldrum's acid, picric acid, and the like are preferred.

[0056] Examples of carboxylic acids include aliphatic carboxylic acids and aromatic carboxylic acids. Among these, aromatic carboxylic acids are preferred due to their high stability. Polycarboxylic acids having two or more hydroxy groups are also preferred. Specifically, phthalic acid, pyromellitic acid, and the like can be used as aromatic carboxylic acids. Among these, phthalic acid is preferred.

[0057] Among the acid components, coordination compounds include, for example, those containing at least one central atom selected from the group consisting of boron, aluminum, and silicon, and an organic molecule having multiple coordination atoms bonded to the central atom. In other words, the organic molecule has multiple coordination atoms bonded to the central atom. Here, the multiple coordination atoms are, for example, at least one selected from the group consisting of oxygen atoms and nitrogen atoms. Hereinafter, an organic molecule having multiple coordination atoms bonded to a central atom will also be referred to as a "coordination organic molecule."

[0058] The coordinating atom is at least one selected from the group consisting of an oxygen atom and a nitrogen atom.

[0059] When the coordinating atom is an oxygen atom, the coordinating atom may be bonded to a carbonyl group or to a carbon atom that does not have an oxo group (=O). The coordination compound may contain both a coordinating atom bonded to a carbonyl group and a coordinating atom bonded to a carbon atom that does not have an oxo group. When the coordinating atom is an oxygen atom, the oxygen atom is an oxygen atom that does not form a carboxy group or a carboxy anion.

[0060] More specifically, the oxygen atom as a coordinating atom may be an alcoholic or phenolic hydroxyl group or alkoxy oxygen, an oxy group, or an oxy group of a carboxy group. Among these, it is preferable that at least one of an alcoholic or phenolic alkoxy oxygen and an oxy group of a carboxy group is bonded to the central atom because the bond with the central atom is stable.

[0061] On the other hand, when the coordinating atom is a nitrogen atom, the nitrogen atom is a nitrogen atom that forms an amino group, an amide group, an imide group, an imide anion, or the like.

[0062] The coordination organic molecule is not particularly limited, but may form a complex anion together with the central atom. In this case, the coordination organic molecule may be, for example, an organic group in which a proton bonded to the coordination atom is deprotonated.

[0063] Coordination organic molecules preferably contain electron-withdrawing substituents. Such substituents tend to stabilize the electrons of the coordinating atoms of the organic molecules, making it difficult for the hydrolysis products to corrode the capacitor electrodes. Examples of electron-withdrawing substituents include nitro groups, carboxy groups, ester groups, halogen atoms (fluorine atoms, chlorine atoms, etc.), acyl groups, tosyl groups, keto groups, cyano groups, and methylsulfonyl groups.

[0064] On the other hand, organic molecules may contain electron-donating substituents. Such substituents facilitate electron flow into the vacant orbital on the central atom, stabilizing the molecule, contributing to the stability of the liquid component, particularly when water is added or in a high-humidity environment. Examples of electron-donating substituents include amino groups, alkyl groups, aryl groups (e.g., phenyl groups), and alkoxy groups.

[0065] Examples of the coordination organic molecules include hydroxy acids and polycarboxylic acids (dicarboxylic acids, etc.). Hydroxy acids include aliphatic hydroxy acids (glycolic acid, lactic acid, tartronic acid, α-, β-, or γ-hydroxybutyric acid, malic acid, citric acid, etc.) and aromatic hydroxy acids (salicylic acid, hydroxybenzoic acid, mandelic acid, benzilic acid, gallic acid, etc.). Polycarboxylic acids include aliphatic polycarboxylic acids (oxalic acid, malonic acid, succinic acid, adipic acid, maleic acid, etc.) and aromatic polycarboxylic acids (phthalic acid, etc.).

[0066] The coordinating organic molecule may be, for example, a polyol having an aromatic ring and a group containing at least a primary hydroxy group and a secondary hydroxy group. The primary hydroxy group may be bonded to the aromatic ring. The group containing the secondary hydroxy group may be bonded to the ortho position relative to the primary hydroxy group of the aromatic ring. The group containing the secondary hydroxy group may be a secondary hydroxy group or an alkyl group having a secondary hydroxy group. Examples of alkyl groups having a secondary hydroxy group include alkyl groups having 1 to 4 carbon atoms and having a secondary hydroxy group. Examples of alkyl groups having a secondary hydroxy group include a methylol group, an ethylol group, a propylol group, or a butyrol group. A methylol group is preferred from the viewpoint of the stability of the complex anion.

[0067] More preferred examples include coordination organic molecules represented by the following general formula (1), (2), (3), (4), (5) or (6).

[0068] [ka]

[0069] [ka]

[0070] [R 1 , R 2 , R 3 , R 4 , R 5 and R 6 each independently represents a hydrogen atom, a halogen atom, a hydroxy group, an alkoxy group having 1 to 10 carbon atoms, a carboxy group, a group having 2 to 10 carbon atoms and an ester bond, a saturated aliphatic hydrocarbon group having 1 to 24 carbon atoms which may have a substituent, an unsaturated aliphatic hydrocarbon group having 2 to 24 carbon atoms which may have a substituent, or an aromatic hydrocarbon group having 6 to 14 carbon atoms which may have a substituent.

[0071] Examples of the halogen atom include a fluorine atom, a chlorine atom, and a bromine atom.

[0072] Examples of the alkoxy group having 1 to 10 carbon atoms include a methoxy group, an ethoxy group, an n- or iso-propoxy group, an n-, sec-, iso- or tert-butoxy group, an n-pentoxy group, an n-hexoxy group, an octoxy group, a decoxy group, and a phenoxy group.

[0073] Examples of the group having 2 to 10 carbon atoms and an ester bond include an alkoxycarbonyl group having 2 to 10 carbon atoms. Examples of the alkoxycarbonyl group include groups in which the hydrogen atom of a carboxy group is substituted with a methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, octyl group, or nonyl group.

[0074] Examples of the saturated aliphatic hydrocarbon group having 1 to 24 carbon atoms which may have a substituent include an alkyl group having 1 to 24 carbon atoms and a cycloalkyl group having 3 to 24 carbon atoms. Examples of alkyl groups include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, 2-methylbutyl, 3-methylbutyl, 2-ethylpropyl, n-hexyl, 1-methylpentyl, 2-methylpentyl, 3-methylpentyl, 4-methylpentyl, 1-ethylbutyl, 2-ethylbutyl, 1-propylpropyl, 2-propylpropyl, 1-isopropylpropyl, 2-isopropylpropyl, n-heptyl, 1-methylhexyl, 2-methylhexyl, 3-methylhexyl, 4-methylhexyl, 5-methylhexyl, 1-ethylpentyl, 2-ethylpentyl, 3-ethylpentyl, 2,2-dimethylpropyl, and 1-propylbutyl. , 2-propylbutyl group, 1-isopropylbutyl group, 2-isopropylbutyl group, n-octyl group, 1-methylheptyl group, 2-methylheptyl group, 3-methylheptyl group, 4-methylheptyl group, 5-methylheptyl group, 6-methylheptyl group, 1-ethylhexyl group, 2-ethylhexyl group, 3-ethylhexyl group, 4-ethylhexyl group, 1-propylpentyl group, 2-propylpentyl group, 1-isopropylpentyl group, 2-isopropylpentyl group, 3-propylpentyl group, 3-isopropylpentyl group, 1-butylbutyl group, 2-butylbutyl group, 1-isobutylbutyl group, 2-isobutylbutyl group, 1-tert-butylbutyl group, 2-tert-butylbutyl group, 1,1,3,3-tetramethylbutyl group, nonyl group, and decyl group. The number of carbon atoms in the alkyl group may be 1 to 20, 1 to 16, or 1 to 12, etc. Examples of the cycloalkyl group include a cyclopentyl group, a cyclohexyl group, a cyclopentyl group, and a cyclooctyl group. The number of carbon atoms in the cycloalkyl group may be 5 to 10 or 5 to 8.

[0075] Examples of the unsaturated aliphatic hydrocarbon group having 2 to 24 carbon atoms, which may have a substituent, include an alkenyl group. Examples of the alkenyl group include a vinyl group, a propenyl group, a butenyl group, a pentenyl group, a hexenyl group, an octenyl group, a decenyl group, and an isopropenyl group. The number of carbon atoms in the unsaturated aliphatic hydrocarbon group may be 2 to 18.

[0076] Examples of the substituent that the saturated aliphatic hydrocarbon group having 1 to 24 carbon atoms or the unsaturated aliphatic hydrocarbon group having 2 to 24 carbon atoms may have include a hydroxy group, an alkoxy group (e.g., an alkoxy group having 1 to 4 carbon atoms), a carboxy group, a nitro group, a halogen atom, a cyano group, and an amino group.

[0077] Examples of the aromatic hydrocarbon group having 6 to 14 carbon atoms, which may have a substituent, include an aryl group and an arylalkyl group (or an aralkyl group). Examples of the aryl group include a phenyl group, a tolyl group, a xylyl group, and a naphthyl group. The aryl group may have an aromatic hydrocarbon ring having 6 to 10 carbon atoms. Examples of the arylalkyl group include an alkyl group having 1 to 4 carbon atoms and an aryl group having 6 to 10 carbon atoms. Examples of the arylalkyl group include a benzyl group and a phenethyl group. Examples of the substituent include an alkyl group (such as an alkyl group having 1 to 6 carbon atoms), a hydroxy group, an alkoxy group (such as an alkoxy group having 1 to 4 carbon atoms), a carboxy group, a nitro group, a halogen atom, a cyano group, and an amino group.

[0078] More specifically, examples of polyols having a secondary hydroxy group bonded to an aromatic ring include catechol, pyrogallol, gallic acid, gallic acid esters (such as alkyl gallates (esters with alkyls having 1 to 4 carbon atoms)), hexahydroxybenzene, 1,2-dihydroxynaphthalene, 2,3-dihydroxynaphthalene, 4,4'-(2,3-dimethyltetramethylene)dipyrocatechol, and 2,3,4,4'-tetrahydroxydiphenylmethane. The aromatic rings of these polyols may have a substituent bonded thereto.

[0079] Typical examples of polyols having an alkyl group (such as a methylol group) having a primary hydroxy group and a secondary hydroxy group include salicylic alcohol, 2,5-dihydroxybenzyl alcohol, 2,6-bis(hydroxymethyl)-p-cresol, etc. The aromatic rings of these polyols may have a substituent bonded thereto.

[0080] Examples of the substituent that the aromatic ring of the polyol may have include R 1 ~R 6 Examples of the groups or atoms include those described for (excluding hydrogen atoms).

[0081] At least one coordinating organic molecule selected from the group consisting of, for example, hydroxy acids, polycarboxylic acids, and polyols is coordinated to the central atom. The number of coordinating organic molecules coordinated to one central atom may be one or two or more. From the viewpoint of the stability of the complex anion, coordinating organic molecules may be selected such that two or more (e.g., two or three) coordinating organic molecules are coordinated to two central atoms.

[0082] When the central atom is boron or aluminum, for example, a tetracoordinated complex anion can be formed. Typical examples include complex anions in which two molecules of a coordinating organic molecule (e.g., hydroxy acid, dicarboxylic acid, diol) are coordinated to a boron atom or an aluminum atom. Examples of such complex anions include, but are not limited to, borodisalicylic acid, borodisalic acid, borodiglycolic acid, borodicatechol, borodipyrogallol, borodigallic acid, and borodigallic acid alkyl ester. Examples of the alkyl of the borodigallic acid alkyl ester include, for example, C 1-6 Alkyl (e.g., methyl, ethyl, n-propyl, isobutyl, n-butyl), preferably C 1-4In addition, when the central atom is silicon, for example, a penta- or hexa-coordinated complex anion can be formed. A typical example is a complex anion in which three diol molecules are coordinated to the silicon atom as the coordinating organic molecule.

[0083] The central atom and the coordinated organic molecule (or complex anion) bonded thereto exhibit acidity, and can therefore contribute to controlling the pH of the liquid component within the range described below.

[0084] The concentration of the complex anion contained in the liquid component may be, for example, greater than 0.1% by mass or 1.0% by mass or more. The inclusion of such a complex anion significantly enhances the stability of the liquid component at high temperatures, significantly improving the heat resistance of the electrolytic capacitor. However, from the viewpoint of maintaining a suitable viscosity of the liquid component, the content of the complex anion contained in the liquid component may be, for example, 30% by mass or less, or 20% by mass or less.

[0085] Here, the concentration of complex anions is defined as the maximum amount of complex anions that can be formed by a central atom contained in the liquid component and an organic molecule having multiple coordinating atoms with the above structure. Here, the maximum amount is calculated assuming that all central atoms and organic molecules form complex ions, regardless of whether or not they actually form complex anions. However, if the equivalent weight of the central atom and the equivalent weight of the organic molecule are different, the maximum amount can be calculated using the smaller equivalent weight.

[0086] The quantitative and qualitative analysis of the complex anion can be carried out, for example, by the following method.

[0087] <Qualitative analysis> First, 30 mL of the liquid component is weighed into a glass container with a sealed lid, and the infrared absorption spectrum (IR) of the liquid component in the container is measured using a specified measuring device (IRSprit [Shimadzu Corporation]). Next, the container containing the liquid component is sealed and kept in a high-temperature environment for a certain period of time. After that, the liquid component in the container is allowed to cool, and the IR is measured again. The stability of the complex anion can be evaluated from the change in the stretching vibration spectrum of the bond between the central atom and the coordinating atoms. The smaller the spectral change, the higher the stability of the complex anion.

[0088] <Quantitative analysis> First, 30 mL of the liquid component is weighed into a glass container with a sealed lid. The nuclear magnetic resonance (NMR) spectrum of the liquid component in the container is measured using a specified measuring device (AVANCEIII HD [BRUKER]), and the initial complex anion generation ratio (G0) is determined from the peak intensity. Next, the container containing the liquid component is sealed and kept in a high-temperature environment for a certain period of time. After that, the liquid component in the container is allowed to cool, and NMR is measured again to determine the generation ratio (G1) of the complex anion to unreacted organic molecules. The decomposition rate of the complex anion can be calculated using the following formula, and the stability of the complex anion can be evaluated. A smaller decomposition rate indicates a higher stability of the complex anion.

[0089] Complex anion generation ratio G1 (%) = (complex anion peak intensity) / (complex anion peak intensity + unreacted organic molecule peak intensity) × 100 Complex anion decomposition rate (%) = initial complex anion generation ratio G0 (%) - complex anion generation ratio G1 (%)

[0090] Among the acid components, the above-mentioned coordination compounds, as well as saccharin, oxocarbonic acid, Meldrum's acid, and picric acid, are less likely to undergo dehydration condensation reactions with the hydroxyl groups of the first solvent, unlike carboxylic acids. This further enhances the effect of suppressing the evaporation of liquid components, thereby achieving a higher suppression effect on dedoping. Furthermore, because the above-mentioned coordination compounds have a relatively low pKa, high dissociation properties of the acid and base components can be ensured even when combined with a base component whose conjugate acid has a relatively low pKa. Therefore, using the above-mentioned coordination compounds is advantageous from the perspective of ensuring higher film repairability and conductivity.

[0091] It is also preferable to use at least one selected from the group consisting of saccharin, oxocarbonic acid, Meldrum's acid, and picric acid. Examples of oxocarbonic acids include deltaic acid, squaric acid, croconic acid, rhodizonic acid, and heptagonic acid. Unlike carboxylic acids, these acid components do not release carbon dioxide gas even when electrolytic capacitors are exposed to high temperatures. Electrolytic capacitors are generally soldered to substrates through a reflow process that exposes them to high temperatures. If a large amount of gas is generated during the reflow process, the airtightness and reliability of the electrolytic capacitor are reduced. Therefore, using such acid components can prevent the reduction in airtightness and reliability during the reflow process.

[0092] From the viewpoint of easily ensuring higher dissociation properties of the acid component, the pKa of the acid component is preferably 7 or less, and more preferably 6 or less or 5 or less. From the viewpoint of reducing corrosion of the electrode, the pKa of the acid component is preferably 1 or more, and more preferably 2 or more. These upper and lower limit values ​​can be combined arbitrarily.

[0093] The acid component may include an acid having a pKa of 1 or more and 6 or less (e.g., 1 or more and 5 or less, 2 or more and 6 or less, or 2 or more and 5 or less). When such an acid component is used, it is easy to ensure higher film repairability even when a base component with relatively low dissociation property is used.

[0094] (base component) (first base) The base component includes a first base whose conjugate acid has a pKa of 5 or more and 10 or less, and which has no boiling point or a boiling point of 100° C. or more. By including the first base in the liquid component, volatilization of the liquid component is suppressed even when the electrolytic capacitor is exposed to high temperatures, and it is possible to achieve both a high de-doping suppression effect by the acid component and high film repairability.

[0095] The pKa of the conjugate acid of the first base may be 5 or more and 10 or less, such as 5 or more and 8 or less, 6 or more and 8 or less, 6 or more and 10 or less, 7 or more and 10 or less, or more than 8 but less than 10. If the pKa of the conjugate acid exceeds 10, the effect of the acid component in inhibiting dedoping is reduced. Furthermore, electrode corrosion is more likely to occur. If the pKa of the conjugate acid is less than 5, the dissociation of the acid component and the base component is significantly reduced, resulting in significant volatilization of the liquid component, reduced film repairability, and reduced conductivity. Furthermore, the base component may contain, as the first base, a conjugate acid having a pKa of 5 or more and 8 or less (e.g., 6 or more and 8 or less), or a conjugate acid having a pKa of 6 or more and 10 or less (e.g., 7 or more and 10 or less, or more than 8 but less than 10).

[0096] When using a first base whose conjugate acid has a pKa of 5 or more and 8 or less, it is preferable to use at least a coordination compound as the acid component. When using a first base whose conjugate acid has a pKa of 5 or more and 8 or less, it is also preferable to use an acid whose pKa is at least 2 or more and 5 or less as the acid component. When using a carboxylic acid (such as an aromatic carboxylic acid) as the acid component, it is preferable to use at least a first base whose conjugate acid has a pKa of more than 8 and 10 or less. In such a combination, a higher undoping suppression effect can be ensured, and the dissociation of the acid component and the base component is enhanced, making it easier to ensure higher film repairability.

[0097] The boiling point of the first base may be 100°C or higher. From the viewpoint of suppressing volatilization of the liquid component and easily achieving higher film repairability, the boiling point of the first component is preferably 130°C or higher, more preferably 150°C or higher. The first base may not have a boiling point. The thermal decomposition temperature of a first base that does not have a boiling point may be within the temperature range described above as the boiling point.

[0098] From the viewpoints of suppressing precipitation of the first base in the liquid component and easily maintaining the viscosity of the liquid component low, the first base is preferably liquid at room temperature (a temperature of 20°C or higher and 35°C or lower), and the melting point of the first base is more preferably 30°C or lower.

[0099] Examples of the first base include amine compounds and ammonium compounds. The amine compound may be any of primary amines, secondary amines, and tertiary amines. Using at least one of secondary amines and tertiary amines is advantageous because it can suppress electrode corrosion while ensuring high dissociation of the acid component and a high dedoping suppression effect of the acid component. Examples of ammonium compounds include quaternary ammonium compounds corresponding to tertiary amines. Such quaternary ammonium compounds have an additional organic group (such as an alkyl group or an aryl group) on the nitrogen atom of the tertiary amine. The base component may contain one type of first base or two or more types of first bases.

[0100] The amine compound may be any of aliphatic amines, alicyclic amines (e.g., cycloalkylamines such as cyclohexylamine, amantadine), aromatic amines, and heterocyclic amines. These amines are sometimes referred to as primary amine compounds. Primary amine compounds do not contain a polyalkylene oxide chain (or a polyoxyalkylene chain). Among these, aliphatic amines and heterocyclic amines are preferred from the viewpoint of easily controlling the boiling point and the pKa of the conjugate acid within the above-mentioned ranges. The amine compound also includes secondary amine compounds containing a polyalkylene oxide chain. Examples of such secondary amine compounds include polyalkylene oxide adducts in which a polyalkylene oxide is added to a primary amine compound or ammonia. In an amine compound, the pKa of the conjugate acid and the boiling point of the base component can be adjusted by selecting at least one of the number of carbon atoms in the organic group bonded to the nitrogen atom of the amine, the structure of the organic group, the functional group possessed by the organic group, the number of repeating alkylene oxides in the polyalkylene oxide chain, and the number of groups having a polyalkylene oxide chain.

[0101] Examples of aliphatic amines include C 4-20 Examples include trialkylamines having at least one alkyl group, tertiary alkanolamines, and polyalkylenepolyamines.

[0102] The above trialkylamines are C 4-20 Alkyl group (preferably C 4-10 In addition to alkyl groups, C 1-4 It may have an alkyl group. 4-20 The number n1 of alkyl groups is 1 to 3, and C 1-4 The number n2 of alkyl groups is 0 to 2, and n1 + n2 = 3. Of the three alkyl groups in the trialkylamine, at least two may be the same or all may be different. Specific examples of such trialkylamines include tributylamine, triisobutylamine, dimethylhexylamine, and diethylhexylamine.

[0103] The tertiary alkanolamine may have at least one hydroxyalkyl group, and may have a hydrocarbon group in addition to the hydroxyalkyl group. The number of hydroxyalkyl groups in the alkanolamine, n3, is 1 to 3, and the number of hydrocarbon groups, n4, is 0 to 2, so that n3+n4=3. The hydroxyalkyl group may be a hydroxy group such as hydroxy C 1-10 Alkyl groups are preferred, and hydroxy C 1-6 Alkyl or hydroxy C 1-4 The hydrocarbon group may be an alicyclic or aromatic hydrocarbon group, but an aliphatic hydrocarbon group is preferred, and among these, an alkyl group is more preferred. Examples of the alkyl group include C 1-22 Alkyl groups include C 1-20 may be an alkyl group, 1-10 may be an alkyl group, 1-6 Alkyl group or C 1-4 The alkyl group may be a C 8-22 Alkyl group, C 10-22 Alkyl group, or C 14-22 It may be an alkyl group. Specific examples of tertiary alkanolamines include dimethylethanolamine, diethylethanolamine, triethanolamine, stearyldiethanolamine, octadecyldiethanolamine, and behenyldiethanolamine.

[0104] Examples of polyalkylene polyamines include poly(C 2-4The number of alkylene units in the polyalkylene polyamine is, for example, 2 or more and 10 or less, and may be 2 or more and 6 or less. Specific examples of polyalkylene polyamines include ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, spermidine, and spermine. Polyalkylene polyamines also include those having a substituent such as an alkyl group or a hydroxyalkyl group on a nitrogen atom. The alkyl moiety of the alkyl group or hydroxyalkyl group may be C 1-20 Alkyl groups include C 1-10 may be alkyl, C 1-6 Alkyl or C 1-4 It may also be alkyl.

[0105] From the viewpoint of further enhancing the effect of reducing changes in ESR and leakage current, it is also preferable that the first base contains at least a heterocyclic amine. Examples of heterocyclic amines include 4- to 20-membered or 4- to 10-membered heterocyclic amines. The heterocycle may be a bridged heterocycle. The heterocyclic amine may have one or more nitrogen atoms constituting the heterocycle. The heterocycle may have one or more heteroatoms other than nitrogen atoms (oxygen atoms, sulfur atoms, etc.) as ring constituent atoms. The heterocycle may be saturated or unsaturated. The heterocyclic amine may be a secondary amine or a tertiary amine. In particular, it is preferable to use at least a heterocyclic amine that is a tertiary amine. Heterocyclic amines also include those having one or more substituents (e.g., hydroxyl group, amino group or substituted amino group, alkyl group, alkoxy group, hydroxyalkyl group, etc.) on the heterocycle. Specific examples of heterocyclic amines include pyrrolidine, piperidine, piperazine, morpholine, N-alkylmorpholines (such as N-methylmorpholine and N-butylmorpholine), N-hydroxyalkylmorpholines, pyridine, hydroxyalkylpyridines (such as hydroxyethylpyridine), pyridazine, pyrimidine, pyrazine, and 4-dimethylaminopyridine. Among heterocyclic amines, tertiary amines are preferred, and unsaturated tertiary amines are more preferred, from the viewpoint of easily adjusting the boiling point and the pKa of the conjugate acid to a suitable range. Furthermore, heterocyclic amines that do not have a free amino group are preferred, from the viewpoint of easily suppressing electrode corrosion while maintaining a high dedoping suppression effect of the acid component. Among heterocyclic amines, pyridine, N-alkylmorpholines, and N-hydroxyalkylmorpholines are more preferred. The number of carbon atoms in the alkyl group or the alkyl moiety of the hydroxyalkyl group on the nitrogen atom of morpholine may be 1 to 20 or 1 to 10. The alkyl portion may be methyl or ethyl, but from the viewpoint of easily adjusting the boiling point and the pKa of the conjugate acid to a suitable range, C 3-20 Alkyl is preferred, C 4-20 Alkyl or C 4-10Alternatively, the alkyl group may be an alkyl group (butyl, etc.). From the viewpoint of easily adjusting the degree of dissociation of the primary amine compound within an appropriate range, the number of carbon atoms in the alkyl group or the alkyl moiety of the hydroxyalkyl group on the nitrogen atom of the morpholine is preferably 1 to 4. In particular, in N-alkylmorpholine, it is preferable that the number of carbon atoms in such an alkyl group is within this range.

[0106] Examples of the polyalkylene oxide chain in the secondary amine compound include poly C 2-4 alkylene oxide chains, polyC 2-3 The alkylene oxide chain (particularly, a polyethylene oxide chain) may be used. In one polyalkylene oxide chain, the number of repeating alkylene oxides may be, for example, 2 or more or 4 or more. In one organic group, the number of repeating alkylene oxides may be 100 or less, 50 or less, or 30 or less. These lower and upper limits can be combined arbitrarily. The types of alkylene oxide units contained in the secondary amine compound may all be the same, or two or more types of alkylene oxide units may be contained.

[0107] Among secondary amine compounds, alkylene oxide adducts of alkanolamines are preferred. The alkanolamine portion is a primary, secondary, or tertiary alkanolamine having 1 to 3 hydroxyalkyl groups. Examples of tertiary alkanolamines include those listed above. Examples of primary or secondary alkanolamines include mono- or di-C 1-10 Alkanolamines include mono- or di-C 1-6 It may be an alkanolamine, mono or di C 1-4 The primary or secondary alkanolamine may be an alkanolamine. Specific examples of primary or secondary alkanolamine include ethanolamine, diethanolamine, propanolamine, and dipropanolamine.

[0108] In the secondary amine compound, the alkylene oxide unit may be attached to the nitrogen atom of the primary amine compound or ammonia, and when the primary amine compound is an alkanolamine, the alkylene oxide unit may be attached to the hydroxy moiety of the hydroxyalkyl group bonded to the nitrogen atom of the amine. When the alkylene oxide unit is attached to the hydroxy moiety of the hydroxyalkyl group, the repeat number of the alkylene oxide is counted, for convenience, including the oxyalkylene group portion corresponding to the hydroxyalkyl group (i.e., counting the entire polyalkylene oxide chain bonded to the nitrogen atom).

[0109] The base component only needs to contain at least the first base, and may contain a second base other than the first base. A higher ratio of the first base in the base component is preferable so that the effect of the first base is fully exerted. The ratio of the first base in the base component is, for example, 90% by mass or more, or may be 95% by mass or more, or may be 99% by mass or more. The ratio of the first base in the base component is 100% by mass or less. The base component may be composed of only the first base.

[0110] (second base) Examples of the second base include a base that satisfies (a) the pKa of the conjugate acid is greater than 10 or less than 5, or (b) the boiling point is less than 100°C, or both (a) and (b).

[0111] Examples of the second base 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 second base, or two or more types.

[0112] The amine may be aliphatic, alicyclic, aromatic, or heterocyclic. Examples of the amine include mono-, di-, or tri-C 1-4Examples of the quaternary ammonium compound include alkylamines (methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, N,N-diisopropylethylamine, etc.), aniline, phenethylamine, toluidine, etc. Examples of the quaternary ammonium compound include amidine compounds (including imidazole compounds). Examples of the imidazole compound include imidazole, 1,2,3,4-tetramethylimidazole, 1,3-dimethyl-2-ethylimidazole, etc.

[0113] (others) The molar ratio of the acid component to the base component (=acid component / base component) is, for example, 0.1 or more, and may be 0.2 or more, 0.5 or more or 0.8 or more, 1 or more or 1.01 or more, 1.02 or more or 1.05 or more, or even 1.1 or more. When a carboxylic acid is used as the acid component, it is preferable to use the acid component in excess of the base component in order to ensure a higher undoping suppression effect. In this case, the molar ratio is preferably 1.01 or more or 1.02 or more, and may be 1.05 or more or 1.1 or more. The molar ratio of the acid component to the base component is, for example, 50 or less, may be 30 or less, or may be 10 or less. These lower and upper limits can be combined arbitrarily.

[0114] The total concentration of the acid component and the base component in the liquid component may be, for example, 0.1% by mass or more, 0.3% by mass or more, 0.5% by mass or more, 5% by mass or more, or 10% by mass or more. When the solute concentration is within this range, by combining it with the first solvent, the acid component and the base component can be dissociated with high dissociation in the liquid component, ensuring higher film repairability of the dielectric layer. The total concentration of the acid component and the base component may be 25% by mass or less, 23% by mass or less, 15% by mass or less, 12% by mass or less, or 10% by mass or less. When the solute concentration is within this range, the effect of suppressing dopant dedoping can be further enhanced. These lower and upper limits can be arbitrarily combined. The total concentration of the acid component and the base component in the liquid component may be, for example, 0.1% by mass or more to 25% by mass or less, or 0.3% by mass or more to 23% by mass or less. Within these ranges, from the viewpoint of further suppressing the initial ESR and ESR fluctuation, the total concentration of the acid component and the base component is preferably from 0.1 to 12% by mass, more preferably from 0.3 to 10% by mass. Also, from the viewpoint of further suppressing the initial leakage current and leakage current fluctuation, the total concentration of the acid component and the base component is preferably from 5 to 25% by mass, more preferably from 10 to 23% by mass.

[0115] The pH of the liquid component is preferably 6 or less, more preferably 4 or less, and may be 3.8 or less, or 3.6 or less. By setting the pH of the electrolyte solution within this range, deterioration of the conductive polymer component is easily suppressed. The pH is preferably 1.0 or more.

[0116] (Capacitor element) The capacitor element includes at least an anode body having a dielectric layer on its surface, and a conductive polymer component covering a portion of the dielectric layer.

[0117] (anode body) The anode body can contain a valve metal, an alloy containing a valve metal, a compound containing a valve metal, or the like. These materials can be used alone or in combination of two or more. Examples of preferred valve metals include aluminum, tantalum, niobium, and titanium. Anode bodies with porous surfaces can be obtained by roughening the surface of a substrate (such as a foil-shaped or plate-shaped substrate) containing a valve metal, for example, by etching. The anode body can also be a compact of particles containing a valve metal, or a sintered body thereof. The sintered body has a porous structure.

[0118] (dielectric layer) The dielectric layer is formed by anodizing the valve metal on the surface of the anode body using a chemical conversion treatment or the like. The dielectric layer may be formed so as to cover at least a portion of the anode body. The dielectric layer is usually formed on the surface of the anode body. Since the dielectric layer is formed on the porous surface of the anode body, it is formed along the inner wall surfaces of holes and depressions (pits) on the surface of the anode body.

[0119] The dielectric layer contains an oxide of a valve metal. For example, when tantalum is used as the valve metal, the dielectric layer contains Ta2O5, and when aluminum is used as the valve metal, the dielectric layer contains Al2O3. However, the dielectric layer is not limited to this, and may be any material that functions as a dielectric. When the surface of the anode body is porous, the dielectric layer is formed along the surface of the anode body (including the inner wall surfaces of the pores).

[0120] (Conductive polymer component) The conductive polymer component includes, for example, a conductive polymer and a dopant. The conductive polymer component is attached so as to cover a portion of the dielectric layer. The conductive polymer component attached to the surface of the dielectric layer may constitute a conductive polymer layer. The conductive polymer layer is sometimes called a solid electrolyte layer. The conductive polymer component constitutes at least a portion of the cathode body in the electrolytic capacitor. The conductive polymer component may further contain an additive, if necessary.

[0121] Examples of conductive polymers include π-conjugated polymers. Examples of conductive polymers include polypyrrole, polythiophene, polyfuran, polyaniline, polyacetylene, polyphenylene, polyphenylene vinylene, polyacene, and polythiophene vinylene. These may be used alone or in combination of two or more types, or may be copolymers of two or more types of monomers.

[0122] In this specification, polypyrrole, polythiophene, polyfuran, polyaniline, etc. refer to polymers having polypyrrole, polythiophene, polyfuran, polyaniline, etc. as their basic skeletons, respectively. Therefore, polypyrrole, polythiophene, polyfuran, polyaniline, etc. may also include their respective derivatives. For example, polythiophene includes poly(3,4-ethylenedioxythiophene).

[0123] The dopant may be a polyanion. Specific examples of polyanions include polyvinyl sulfonic acid, polystyrene sulfonic acid, polyallyl sulfonic acid, polyacrylic sulfonic acid, polymethacrylic sulfonic acid, poly(2-acrylamido-2-methylpropane sulfonic acid), polyisoprene sulfonic acid, and polyacrylic acid. These may be used alone or in combination of two or more. Furthermore, these may be polymers of a single monomer or copolymers of two or more monomers. Among these, polyanions derived from polystyrene sulfonic acid are preferred.

[0124] The conductive polymer layer can be formed, for example, by chemical polymerization and / or electrolytic polymerization of raw material monomers on the dielectric layer. Alternatively, the conductive polymer layer can be formed by contacting the dielectric layer with a solution in which the conductive polymer is dissolved or a dispersion in which the conductive polymer is dispersed. The conductive polymer layer may be formed so as to cover at least a portion of the dielectric layer.

[0125] As with the anode body, a metal foil may also be used for the cathode body. 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.

[0126] (separator) When a metal foil is used for the cathode body, a separator may be disposed between the metal foil and the anode body. 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).

[0127] (others) The electrolytic capacitor may be of a wound type, chip type, or laminate type. The configuration of the capacitor element may be selected depending on the type of electrolytic capacitor.

[0128] The electrolytic capacitor may have at least one capacitor element, or may have a plurality of capacitor elements, the number of capacitor elements included in the electrolytic capacitor being determined depending on the intended use.

[0129] The electrolytic capacitor of the present disclosure will be described in more detail below based on embodiments, but the electrolytic capacitor of the present disclosure is not limited to the following embodiments.

[0130] FIG. 1 is a cross-sectional view of the electrolytic capacitor according to this embodiment, and FIG. 2 is a schematic view of a partially developed capacitor element of the electrolytic capacitor.

[0131] 1 includes a capacitor element 10, a bottomed case 11 that houses capacitor element 10, a sealing member 12 that closes the opening of bottomed case 11, a seat plate 13 that covers sealing member 12, lead wires 14A and 14B that extend from sealing member 12 and pass through seat plate 13, lead tabs 15A and 15B that connect the lead wires to electrodes of capacitor element 10, and a liquid component (not shown). The open end of bottomed case 11 is curled so as to be crimped to sealing member 12.

[0132] Capacitor element 10 is made from a wound body as shown in FIG. 2. The wound body is a semi-finished product of capacitor element 10, in which a conductive polymer is not disposed between anode body 21 and cathode body 22, each having a dielectric layer on its surface. The wound body is formed by winding anode body 21 connected to lead tab 15A and cathode body 22 connected to lead tab 15B, with separator 23 interposed between them. The outermost periphery of the wound body is fixed with stop tape 24. Note that FIG. 2 shows a state in which the wound body is partially unfolded before the outermost periphery is fixed.

[0133] Anode body 21 comprises a metal foil with a roughened surface, and a dielectric layer is formed on the roughened surface. A conductive polymer is attached to at least a portion of the surface of the dielectric layer to form capacitor element 10. Capacitor element 10 is housed in an exterior case together with a liquid component (not shown).

[0134] An example of a method for manufacturing an electrolytic capacitor will now be described. (i) A step of preparing an anode body 21 and a cathode body 22 having a dielectric layer A metal foil made of a valve metal is used as the raw material for anode body 21 and cathode body 22. In the case of anode body 21, the surface of the metal foil is roughened by etching or the like, and a plurality of projections and depressions are formed on the surface of the metal foil. Next, a dielectric layer is formed on the roughened surface of the metal foil by chemical conversion or the like. The surface of cathode body 22 may also be roughened as needed.

[0135] (ii) Preparation of the wound body Anode body 21 and cathode body 22 are wound with separator 23 interposed therebetween to produce a wound body. Separator 23 may be a nonwoven fabric containing synthetic cellulose or the like as a main component. Stop tape 24 is placed on the outer surface of cathode body 22, which is located in the outermost layer of the wound body, to fix the end of cathode body 22. If necessary, the wound body is further subjected to a chemical conversion treatment.

[0136] (iii) Step of forming capacitor element 10 For example, a liquid polymer dispersion is impregnated into the dielectric layer to form a conductive polymer film that covers at least a portion of the dielectric layer. This results in a capacitor element 10 in which a conductive polymer is disposed between the anode body 21 and the cathode body 22. The step of applying the polymer dispersion to the surface of the dielectric layer may be repeated two or more times. Thereafter, the capacitor element 10 can be impregnated with a liquid component. This results in an electrolytic capacitor comprising a conductive polymer and a liquid component.

[0137] (iv) Sealing the capacitor element Capacitor element 10 is housed in bottomed case 11 together with the liquid component so that lead wires 14A and 14B are located on the opening side of bottomed case 11. Next, the opening of bottomed case 11 is sealed with sealing member 12 through which each lead wire passes, and the open end is crimped to sealing member 12 and curled, and seat plate 13 is placed on the curled portion, completing the electrolytic capacitor as shown in Figure 1.

[0138] In the above embodiment, a wound-type electrolytic capacitor has been described, but the scope of application of the present invention is not limited to the above, and the present invention can also be applied to other electrolytic capacitors, such as chip-type electrolytic capacitors that use a metal sintered body as an anode body, and stacked-type electrolytic capacitors that use a metal plate as an anode body.

[0139] [Example] The present invention will be specifically described below based on examples and comparative examples, but the present invention is not limited to the following examples.

[0140] <<Fabrication of electrolytic capacitors A1 to A35 and B1 to B5>> A wound electrolytic capacitor (diameter 10 mm×L (length) 10 mm) with a rated voltage of 25 V and a rated capacitance of 330 μF was fabricated. A specific method for fabricating the electrolytic capacitor will be described below.

[0141] (Preparation of the anode body) An aluminum foil with a thickness of 100 μm was subjected to an etching treatment to roughen the surface of the aluminum foil. A dielectric layer was then 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 of 45 V. The aluminum foil was then cut to prepare anode bodies.

[0142] (Preparation of the cathode body) An aluminum foil having a thickness of 50 μm was subjected to an etching treatment to roughen the surface of the aluminum foil, and then the aluminum foil was cut to prepare a cathode body.

[0143] (Production of wound body) An anode lead tab and a cathode lead tab were connected to the anode body and the cathode body, and the anode body and the cathode body were wound around the lead tabs, with a separator interposed therebetween. 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 wound body was again subjected to a chemical conversion treatment, and a dielectric layer was formed on the cut end of the anode body. Next, the ends of the outer surface of the wound body were fixed with a stop tape to produce the wound body.

[0144] (Preparation of polymer dispersion) A mixed solution was prepared by dissolving 3,4-ethylenedioxythiophene and the polymer dopant polystyrene sulfonic acid (PSS, weight-average molecular weight 100,000) in ion-exchanged water. Iron (III) sulfate (oxidant) dissolved in ion-exchanged water was added to the mixed solution while stirring, and a polymerization reaction was carried out. After the reaction, the resulting reaction solution was dialyzed to remove unreacted monomer and excess oxidant, yielding a polymer dispersion containing approximately 5% by mass of PSS-doped polyethylenedioxythiophene (PEDOT / PSS).

[0145] (Formation of conductive polymer layer) 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 removed from the polymer dispersion. The wound body impregnated with the polymer dispersion was then dried in a drying oven at 150°C for 20 minutes to form a conductive polymer layer that covered at least a portion of the dielectric layer. In this way, a capacitor element was formed.

[0146] (Preparation of liquid components) The solvents shown in the table were prepared. If necessary, the solvent mixture was heated to 95°C under stirring. The acid and base components shown in the table were added to the prepared solvent and mixed so that the concentrations in the liquid components were as shown in the table. In this way, the liquid components were prepared.

[0147] (assembly of electrolytic capacitors) The wound body with the conductive polymer layer formed thereon was immersed in the liquid component for 5 minutes in a reduced pressure atmosphere (40 kPa). This resulted in a capacitor element impregnated with the liquid component. The resulting capacitor element was sealed to complete the electrolytic capacitor shown in Figure 1. Subsequently, the element was subjected to an aging treatment at 130°C for 2 hours while applying the rated voltage.

[0148] [Evaluation: ESR and leakage current measurements] The ESR (initial ESR (Z0)) of the electrolytic capacitor was measured at a frequency of 100 kHz using a four-terminal LCR meter in an environment of 20°C. In addition, the rated voltage was applied to the electrolytic capacitor in an environment of 20°C, and the leakage current (initial leakage current L0) was measured after 2 minutes had passed.

[0149] The electrolytic capacitors were then held at 145°C for 2000 hours with the rated voltage applied. The ESR (Z1) and leakage current (L1) of the electrolytic capacitors held at 145°C were measured at 20°C using the same procedures as for the initial ESR and leakage current. The increase in ESR (ΔESR) was calculated by calculating the ratio (Z1 / Z0) of the ESR (Z1) of the electrolytic capacitors held at 145°C to the initial value (Z0). The change in leakage current was calculated by calculating the ratio (L1 / L0) of the leakage current (L1) of the electrolytic capacitors held at 145°C to the initial value (L0).

[0150] The evaluation results are shown in Tables 1 to 4 below. In the tables, A1 to A35 are working examples, and B1 to B5 are comparative examples. In the tables, the ESR and leakage current after being held at 145°C are shown as ESR and leakage current after being held at high temperature.

[0151] [Table 1A]

[0152] [Table 1B]

[0153] [Table 2A]

[0154] [Table 2B]

[0155] [Table 3A]

[0156] [Table 3B]

[0157] [Table 4A]

[0158] [Table 4B]

[0159] 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. [Industrial Applicability]

[0160] The electrolytic capacitor of the present disclosure can be used as a hybrid electrolytic capacitor. The electrolytic capacitor is particularly suitable for applications requiring high heat resistance. However, the applications of the electrolytic capacitor are not limited to these. [Explanation of symbols]

[0161] 10: Capacitor element 11: Bottomed case 12: Sealing member 13: Seat board 14A, 14B: Lead wire 15A, 15B: Lead tab 21: Anode body 22: Cathode body 23: Separator 24: Winding tape

Claims

[Claim 1] a capacitor element and a liquid component, the capacitor element includes an anode body having a dielectric layer on a surface thereof, and a conductive polymer component covering a portion of the dielectric layer; the liquid component includes a first solvent, a base component, and an acid component; the first solvent is at least one selected from the group consisting of polyols and derivatives thereof; The base component includes a first base whose conjugate acid has an acid dissociation constant of 5 or more and 10 or less, and which has no boiling point or a boiling point of 100°C or more.

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