Liquid component for electrolytic capacitor, electrolytic capacitor, and method for manufacturing electrolytic capacitor

Abstract

The liquid component used in electrolytic capacitors containing conductive polymers includes a non-aqueous solvent and a dicarboxylic acid compound. This dicarboxylic acid compound comprises component (A): an aromatic dicarboxylic acid, and component (B): a monoester formed by esterification of one carboxyl group of the aromatic dicarboxylic acid with an aliphatic group having a hydroxyl group.

Description

Technical Field

[0001] This disclosure relates to liquid components for electrolytic capacitors, electrolytic capacitors, and methods for manufacturing the same. Background Technology

[0002] Electrolytic capacitors, which are small, high-capacity capacitors with low ESR (equivalent series resistance), are considered promising. They consist of an anode foil with a dielectric layer, a cathode foil, and a conductive polymer and electrolyte between the anode and cathode foils. As the electrolyte, liquid components such as solutions that dissolve the solute in non-aqueous solvents or non-aqueous solvents can be used.

[0003] Patent Document 1 discloses an electrolytic capacitor comprising: a capacitor element having an anode having a dielectric layer formed on its surface; a solid electrolyte layer disposed on the dielectric layer and comprising a conductive polymer and a polymer dopant; and an electrolyte impregnated into the capacitor element and comprising a polyol and a borate ester.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: International Publication No. 2017 / 073062 Summary of the Invention

[0007] The first aspect of this disclosure relates to a liquid component for electrolytic capacitors. The liquid component for electrolytic capacitors is a liquid component used in electrolytic capacitors containing conductive polymers. The liquid component comprises a non-aqueous solvent and a dicarboxylic acid compound. The dicarboxylic acid compound comprises:

[0008] Ingredient (A): Aromatic dicarboxylic acid; and

[0009] Component (B): A monoester formed by esterification of one carboxyl group of an aromatic dicarboxylic acid with an aliphatic group having a hydroxyl group.

[0010] The second aspect of this disclosure relates to an electrolytic capacitor. The electrolytic capacitor comprises the aforementioned liquid component and a capacitor element. The capacitor element comprises: an anode foil having a dielectric layer; a cathode foil disposed opposite to the dielectric layer; and a conductive polymer disposed between the anode foil and the cathode foil.

[0011] A third aspect of this disclosure relates to a method for manufacturing an electrolytic capacitor. The method includes: a step of fabricating a capacitor element comprising an anode foil having a dielectric layer, a cathode foil, and a conductive polymer between the anode foil and the cathode foil; a step of housing the capacitor element and the liquid component together in a housing and sealing them; and a step of heating the sealant obtained in the sealing step at a temperature of 130°C or higher for at least 10 minutes.

[0012] This disclosure provides electrolytic capacitors with high reliability and liquid components used in electrolytic capacitors. Attached Figure Description

[0013] Figure 1 This is a cross-sectional schematic diagram of an electrolytic capacitor according to one embodiment of the present disclosure.

[0014] Figure 2 It is Figure 1 A schematic diagram of a portion of the capacitor element of an electrolytic capacitor. Detailed Implementation

[0015] The liquid components used in electrolytic capacitors containing conductive polymers may include, for example, acidic components or non-aqueous solvents. For instance, when only component (A): an aromatic dicarboxylic acid, is used as the acid, the low pH of the liquid component initially ensures high conductivity of the conductive polymer. However, sometimes a non-aqueous solvent with hydroxyl groups reacts with component (A) (esterification), reducing the amount of component (A) as the acid. Such reactions tend to occur at high temperatures. For example, esterification reactions sometimes occur due to self-heating caused by the ripple current generated during the use of the electrolytic capacitor. Additionally, esterification reactions sometimes occur by using the electrolytic capacitor at high temperatures (e.g., temperatures above 140°C (temperatures between 140°C and 160°C, etc.)). As component (A) decreases, the pH of the liquid component rises, leading to a decrease in conductivity of the conductive polymer due to dedoping, and an increase in the equivalent series resistance (ESR). Furthermore, the reaction of the non-aqueous solvent with hydroxyl groups with component (A) (esterification) generates water, increasing the water content in the liquid component. If the amount of water inside an electrolytic capacitor increases, the expansion of the electrolytic capacitor may become significant when it is exposed to high temperatures (e.g., temperatures above 200°C (temperatures between 200°C and 300°C)).

[0016] In view of the above, (Technology 1) the liquid component of the first aspect of this disclosure is used in an electrolytic capacitor comprising a conductive polymer. The liquid component comprises a non-aqueous solvent and a dicarboxylic acid compound. The dicarboxylic acid compound comprises a monoester formed by esterification of a dicarboxylic acid and one carboxyl group of the dicarboxylic acid with an aliphatic group having a hydroxyl group.

[0017] In the liquid component of aspect 1, for example, the dicarboxylic acid compound described above comprises component (A): an aromatic dicarboxylic acid, and component (B): a monoester formed by esterification of one carboxyl group of the aromatic dicarboxylic acid with an aliphatic group having a hydroxyl group.

[0018] In this disclosure, by using dicarboxylic acid and monoester (more specifically, component (A) and component (B)) in combination as described above, high reliability of the electrolytic capacitor can be ensured. This will be explained in more detail below. If the liquid component of this disclosure is used, the reduction of component (A) in the liquid component can be suppressed. This is because even if a reaction occurs between a non-aqueous solvent with hydroxyl groups and component (A) (esterification reaction), a hydrolysis reaction occurs simultaneously between water in the liquid component and component (B), generating component (A). Furthermore, self-heating sometimes occurs due to ripple current during the use of the electrolytic capacitor, or the electrolytic capacitor is used in a high-temperature environment. Even in the presence of such thermal effects, in this disclosure, because the liquid component contains a certain concentration of component (A), a low pH of the liquid component can be maintained. Therefore, the deterioration of the conductive polymer (deterioration caused by dedoping, etc.) is suppressed, and high conductivity is maintained. As a result, the rise in ESR can be suppressed. Furthermore, the water generated by the reaction of a non-aqueous solvent with hydroxyl groups with component (A) (esterification reaction) is used in the hydrolysis reaction with component (B), thus suppressing the increase in the amount of water in the liquid component. Therefore, it is also possible to suppress the expansion of electrolytic capacitors when exposed to high temperatures (e.g., temperatures above 200°C and below 300°C) during reflux processing and the like.

[0019] (Technology 2) Based on (Technology 1) above, the aromatic dicarboxylic acid of component (A) can be the same as or different from the aromatic dicarboxylic acid of component (B). When the aromatic dicarboxylic acids of the two components are the same, the equilibrium reaction between component (A) and component (B) is less likely to shift, and it is easier to obtain stable pH and reduced moisture content, which is therefore advantageous.

[0020] (Technology 3) Based on (Technology 1) or (Technology 2) above, the aromatic dicarboxylic acid of component (A) and the aromatic dicarboxylic acid of component (B) can both be phthalic acid. When the aromatic dicarboxylic acid of both components is phthalic acid, the equilibrium reaction between component (A) and component (B) is less likely to shift, and it is easier to obtain stable pH and reduced moisture content, which is therefore advantageous.

[0021] (Technology 4) Based on any of (Technology 1) to (Technology 3) above, the non-aqueous solvent may contain at least an aliphatic diol. In this case, water is readily generated through esterification with component (A). In this disclosure, even in such a case, water can be utilized by hydrolysis reaction using component (B). Therefore, the increase in the amount of water in the liquid component can be suppressed. Therefore, the high conductivity of the conductive polymer can be maintained, and the expansion of the electrolytic capacitor when exposed to high temperatures can be suppressed.

[0022] (Technology 5) Based on (Technology 4) above, the aliphatic diol may include alkylene diols selected from those having 2 or more and 6 or fewer carbon atoms, and poly(C) diols with a repeating number of 15 or fewer alkylene groups. 2-4 At least one of alkylene glycols. In the case of these aliphatic glycols, water is readily generated through esterification with component (A). In this disclosure, even in such cases, water is utilized through a hydrolysis reaction by using component (B). Therefore, the increase in the amount of water in the liquid component can be suppressed. Therefore, the high conductivity of the conductive polymer can be maintained, and the expansion of the electrolytic capacitor when exposed to high temperatures can be suppressed.

[0023] (Technology 6) Based on any one of (Technology 1) to (Technology 5) above, the molar ratio (B / A) of the component (B) to the component (A) can be 0.05 or more and 0.5 or less. When the molar ratio B / A is in such a range, the increase in ESR can be suppressed, and the expansion of the electrolytic capacitor exposed to high temperatures can be suppressed. Furthermore, since the excessive reduction in the amount of water caused by the hydrolysis reaction between the water in the liquid component and component (B) is suppressed, the film repairability of the dielectric layer can be maintained, and the increase in leakage current can be suppressed.

[0024] (Technology 7) Based on any one of (Technology 1) to (Technology 5) above, the dicarboxylic acid compound may further include component (C): a diester formed by esterification of two carboxyl groups of an aromatic dicarboxylic acid with an aliphatic group having a hydroxyl group. Since component (B) and component (C) undergo a hydrolysis reaction to generate component (A), the high conductivity of the conductive polymer can be maintained, and the increase in ESR can be further suppressed. In addition, through the above-mentioned hydrolysis reaction, the water content is further reduced, thereby further reducing the expansion of the electrolytic capacitor when exposed to high temperatures (e.g., temperatures above 200°C and below 300°C).

[0025] (Technology 8) Based on the above (Technology 7), the molar ratio of the above component (C) to the above component (A) (C / A) can be 0.01 or more and 0.10 or less. When the molar ratio C / A is within such a range, an increase in ESR can be suppressed, and the expansion of the electrolytic capacitor when exposed to high temperatures can be suppressed. In addition, an excessive decrease in the amount of moisture due to the hydrolysis reaction of the moisture in the liquid component and component (B) is suppressed. Therefore, the film restorability of the dielectric layer can be maintained, and an increase in leakage current can be suppressed.

[0026] The above molar ratio B / A and molar ratio C / A are values of the liquid component collected from the initial electrolytic capacitor.

[0027] In this specification, the initial electrolytic capacitor refers to an electrolytic capacitor after aging or pre-charge / discharge (Japanese: 慣らし充放電), or an unused electrolytic capacitor if it is a commercially available product.

[0028] (Technology 9) Based on any one of the above (Technology 1) to (Technology 8), the above aliphatic group having a hydroxyl group can be a hydroxyalkyl group, or -R(-O-R) m -OH (where R is an alkylene group, and m represents the number of repetitions of the oxyalkylene group and is an integer of 1 or more). In this case, through the hydrolysis reaction of component (B) or component (C), alkylene glycol or polyalkylene glycol is generated together with component (A). The film restorability of the dielectric layer of these diols is high, and the effect of suppressing leakage current is improved.

[0029] (Technology 10) Based on the above (Technology 9), it can be that the number of carbon atoms of the above hydroxyalkyl group is 2 or more and 6 or less, and in the above -R(-O-R) m -OH group, R is an alkylene group having 2 or more and 4 or less carbon atoms, and m is an integer of 1 or more and 14 or less. In this case, a higher film restoration effect of the dielectric layer can be obtained, and leakage current can be further suppressed.

[0030] (Technology 11) Based on any one of the above (Technology 1) to (Technology 10), the liquid component can further contain an alkali component. The molar ratio of the above alkali component to the above dicarboxylic acid compound (alkali component / dicarboxylic acid compound) can be 1 or less. In this case, the dissociation degree of the dicarboxylic acid compound can be increased, and the film restorability of the dielectric layer can be improved.

[0031] (Technology 12) Based on the above (Technology 11), the pKa of the conjugate acid of the above alkali component can be 10 or less. In this case, it is easier to maintain the high dissociation degree of the dicarboxylic acid compound and the high conductivity of the conductive polymer.

[0032] 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 the base component refers to the pKa of the cation of the base component. In cases where the conjugate acid of the base component exhibits multiple pKa values, the lowest pKa (i.e., pKa1) is used.

[0033] (Technology 13) The electrolytic capacitor of this disclosure comprises the liquid component and capacitor element described in any one of (Technology 1) to (Technology 12) above. The capacitor element may include: an anode foil having a dielectric layer, a cathode foil disposed opposite to the dielectric layer, and a conductive polymer disposed between the anode foil and the cathode foil. Since the electrolytic capacitor contains the liquid component, it is possible to suppress the rise of ESR and suppress the expansion of the electrolytic capacitor when exposed to high temperatures.

[0034] (Technology 14) This disclosure also includes a method for manufacturing an electrolytic capacitor. The method for manufacturing an electrolytic capacitor may include:

[0035] The process of manufacturing a capacitor element, wherein the capacitor element comprises an anode foil having a dielectric layer, a cathode foil, and a conductive polymer between the anode foil and the cathode foil;

[0036] The process of housing and sealing the capacitor element together with the liquid component described in any one of (Technology 1) to (Technology 13) in a housing; and

[0037] The process involves heating the sealant obtained in the above-described sealing process at a temperature of 130°C or higher for at least 10 minutes. Through this heating process, the hydrolysis reaction of component (B) or component (C) becomes easier to proceed, the water content is reduced, and the expansion of the electrolytic capacitor when exposed to high temperatures (e.g., temperatures above 200°C and below 300°C) can be further suppressed.

[0038] The liquid composition, electrolytic capacitor, and manufacturing method thereof of the present disclosure will be described in more detail below, including (Technique 1) to (Technique 14) above. At least one of the constituent elements selected below can be arbitrarily combined with at least one of (Technique 1) to (Technique 14) of the liquid composition, electrolytic capacitor, or manufacturing method thereof of the present disclosure, as long as they can be technically combined.

[0039] [Liquid component]

[0040] The liquid component contains a solvent and an acid. The liquid component may further contain a base. The liquid component may contain other components as needed. More specifically, the liquid component of this disclosure contains a non-aqueous solvent and a dicarboxylic acid compound.

[0041] (Non-aqueous solvent)

[0042] Examples of non-aqueous solvents include protic solvents and aprotic solvents. Examples of non-aqueous solvents include organic solvents containing hydroxyl groups, sulfone compounds, lactone compounds, carbonate compounds, and ether compounds. A liquid component may contain one non-aqueous solvent or a combination of two or more non-aqueous solvents.

[0043] In organic solvents containing hydroxyl groups, the hydroxyl groups can be alcoholic hydroxyl groups. Using organic solvents containing alcoholic hydroxyl groups can improve the film repairability of the dielectric layer. Preferably, the non-aqueous solvent contains aliphatic diols (first solvent).

[0044] (First solvent)

[0045] Examples of aliphatic diols include alkylene glycols and polyalkylene glycols. Preferably, the liquid component comprises at least one selected from alkylene glycols having 2 or more but less than 6 carbon atoms and polyalkylene glycols having 15 or fewer repeating alkylene groups.

[0046] Alkylene glycols can have 2 or more but less than 6 carbon atoms, or 2 or more but less than 4 carbon atoms. The alkylene group of an alkylene glycol can be linear or branched. Specific examples of alkylene glycols include ethylene glycol (EG), propylene glycol, trimethylene glycol, tetramethylene glycol, and 1,6-hexanediol.

[0047] Polyalkylene glycols, for example, are made from HO-R (-O-R). m -OH represents alkylene. Here, R is alkylene, and m represents the repetition number of the oxyalkylene group. The oxyalkylene group in the polyalkylene glycol as a whole also includes the -O-R- part of the HO-R- group, represented by (m+1). (m+1) can be less than 15, less than 12, or less than 10. (m+1) is 2 or more.

[0048] From the perspective of easily obtaining higher coating repair performance of the dielectric layer, poly(C) is preferred among polyalkylene glycols. 2-4 Alkylene glycols, more preferably poly(C) 2-3 Alkylene glycols. Specific examples of polyalkylene glycols include polyethylene glycol, polypropylene glycol, and polyethylene oxide-polypropylene oxide copolymers. Polyethylene glycol includes diethylene glycol (DEG), triethylene glycol, and other polyethylene glycols with the number of repeating alkylene groups (m+1) within the range described above.

[0049] (Second solvent)

[0050] Organic solvents containing hydroxyl groups that are not aqueous solvents (second solvent) other than the first solvent include monohydric alcohols and polyhydric alcohols other than aliphatic diols. Examples of monohydric alcohols include aliphatic alcohols (such as hexanol, octanol, lauryl alcohol, etc.). 6-18Alkyl alcohols, etc.), aralkyl alcohols (benzyl alcohol, phenylethanol, etc.). Examples of polyols include glycerol compounds (glycerol (SGC), polyglycerol, etc.), sugar alcohol compounds, or their alkyl oxide adducts (ethylene oxide adducts, polyethylene oxide adducts, etc.).

[0051] Examples of sulfone compounds include cyclic sulfone compounds (such as sulfolane (SL)) and sulfoxide compounds (such as dimethyl sulfoxide and diethyl sulfoxide). Examples of lactone compounds include γ-butyrolactone (GBL) and γ-valerolactone. Examples of carbonate compounds include chain carbonates (such as dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate) and cyclic carbonates (such as ethylene carbonate, propylene carbonate, and fluoroethylene carbonate). Examples of ether compounds include the aforementioned aliphatic diols, monohydric alcohols, and alkyl ethers of the aforementioned polyols. In ether compounds, some or all of the hydroxyl groups may be etherified.

[0052] (other)

[0053] From the perspective of ensuring higher film repairability, the proportion of aliphatic diols in the total non-aqueous solvent can be, for example, 30% by mass or more, or 50% by mass or more. The proportion of aliphatic diols in the total non-aqueous solvent is less than 100% by mass.

[0054] (Dicarboxylic acid compounds)

[0055] A dicarboxylic acid compound comprises component (A) and component (B). A dicarboxylic acid compound may further comprise component (C). In addition, a dicarboxylic acid compound may comprise dicarboxylic acid compounds other than components (A) to (C) (component (D)).

[0056] (ingredient (A))

[0057] Component (A) is an aromatic dicarboxylic acid. Component (A) is represented, for example, by the following formula (A).

[0058] HOOC-X-COOH (A)

[0059] X is an aromatic divalent group. The aromatic divalent group represented by X also includes aromatic divalent groups with substituents (first substituents). Examples of first substituents include halogen atoms.

[0060] Examples of aromatic divalent groups represented by X include arylene groups (phenylene, tolyne, naphthylene, etc.) and diarylene groups (e.g., divalent groups corresponding to biphenyl, diphenylalkanes (diphenylmethane, 2,2-diphenylpropane, etc.), diphenyl ethers, or diphenyl sulfides, etc.). The number of carbon atoms in an aromatic divalent group can be 6 or more and 20 or less, or 6 or more and 14 or less.

[0061] Specific examples of component (A) are phthalic acid (ortho-form), isophthalic acid (meta-form), terephthalic acid (para-form), 2,3-naphthalenedicarboxylic acid, 2,4-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, and biphenyl dicarboxylic acid. However, component (A) is not limited to these specific examples.

[0062] A liquid component may contain one component (A) or a combination of two or more components (A).

[0063] (Component (B))

[0064] Component (B) is a monoester with a structure formed by esterifying one carboxyl group of an aromatic dicarboxylic acid containing component (A) with an aliphatic group having a hydroxyl group. By combining component (A) and component (B), high reliability of the electrolytic capacitor can be ensured. In addition, the expansion of the electrolytic capacitor when exposed to high temperatures (e.g., temperatures above 200°C and below 300°C) can be suppressed.

[0065] Regarding the aromatic dicarboxylic acid corresponding to component (B), please refer to the description of the aromatic dicarboxylic acid for component (A). The aromatic dicarboxylic acid of component (A) and the aromatic dicarboxylic acid corresponding to component (B) may be the same or different. Both the aromatic dicarboxylic acid of component (A) and the aromatic dicarboxylic acid of component (B) may be phthalic acid.

[0066] Component (B) can also be described as a monoester formed by esterification of one carboxyl group of an aromatic dicarboxylic acid with one hydroxyl group of an aliphatic diol. Therefore, the aliphatic group having a hydroxyl group corresponds to the portion of the aliphatic diol excluding the hydroxyl group. For information on aliphatic diols, please refer to the description of aliphatic diols (first solvent) as described as non-aqueous solvents.

[0067] Examples of aliphatic groups containing hydroxyl groups include hydroxyalkyl groups and -R (-O-R). m -OH, etc. Here, R is an alkylene group, and m represents the number of repetitions of the alkylene group. m is an integer greater than or equal to 1.

[0068] Hydroxyalkyl corresponds to the alkylene glycols mentioned above. The number of carbon atoms in a hydroxyalkyl group can be 2 or more and 6 or less, or 2 or more and 4 or less. The alkyl portion of a hydroxyalkyl group can be straight-chain or branched. Specific examples of hydroxyalkyl groups are hydroxyethyl, 2-hydroxy-1-methyl-ethyl, 3-hydroxy-n-propyl, 4-hydroxy-n-butyl, and 6-hydroxy-n-hexyl.

[0069] -R (-O-R) mThe -OH group corresponds to polyalkylene glycols. The alkylene group represented by R can be alkylene, propylene, or other alkylene groups with 2 or more but less than 4 carbon atoms (alkylene groups with 2 or 3 carbon atoms). The number of repetitions m of the oxyalkylene group can be a range determined from the range of (m+1) above. For example, m can be an integer greater than 1 and less than 14. In -R (-O-R) m In the -OH group, at least two of the plurality of alkylene Rs can be the same (e.g., all the same) or all different.

[0070] Component (B) may include, for example, a compound represented by the following formula (B).

[0071] HOOC-X-COO-R 2 (B)

[0072] Regarding X, please refer to the explanation of equation (A). R 2 -R 2a -OH group or the above-mentioned -R-(O-R) group m -OH group. -R 2a The -OH group corresponds to the hydroxyalkyl group mentioned above.

[0073] Specific examples of component (B) are hydroxyethyl phthalate and hydroxyethyl 2,3-naphthalenedicarboxylate. As component (B), hydroxyl C corresponding to these hydroxyethyl esters can be cited. 3-6 Alkyl esters (e.g., hydroxyl C) 3-4 Alkyl esters and the hydroxyethyl moiety of these hydroxyethyl esters are replaced with -R (-O-R). m Esters formed with -OH groups, etc. However, component (B) is not limited to these specific examples.

[0074] A liquid component may contain one component (B) or a combination of two or more components (B).

[0075] The molar ratio (B / A) of component (B) to component (A) can be 0.01 or more, 0.02 or more, or 0.05 or more. When the molar ratio B / A is in this range, the increase in ESR after high-temperature holding and the expansion of the electrolytic capacitor when exposed to high temperatures can be further suppressed. The molar ratio B / A can be 1.00 or less, or 0.70 or less. When the molar ratio B / A is in this range, excessive reduction in water content caused by the hydrolysis reaction of water in the liquid component with component (B) is suppressed. Therefore, the film repairability of the dielectric layer can be maintained, and the increase in leakage current can be suppressed. From the viewpoint of maintaining higher film repairability of the dielectric layer and further suppressing the increase in leakage current, the molar ratio B / A is preferably 0.50 or less.

[0076] The molar ratio B / A can be greater than or equal to 0.01 and less than 1.00 (or less than 0.70), greater than or equal to 0.02 and less than 1.00 (or less than 0.70), greater than or equal to 0.05 and less than 1.00 (or less than 0.70), greater than or equal to 0.01 and less than 0.50, greater than or equal to 0.02 and less than 0.50, or greater than or equal to 0.05 and less than 0.50.

[0077] (Component (C))

[0078] Component (C) is a diester with the structure formed by esterification of two carboxyl groups of an aromatic dicarboxylic acid having component (A) with an aliphatic group having a hydroxyl group. By combining component (A) with components (B) and (C), it is possible to further suppress the increase in ESR after high-temperature holding and the expansion of electrolytic capacitors when exposed to high temperatures.

[0079] Regarding the aromatic dicarboxylic acid corresponding to component (C), please refer to the description of the aromatic dicarboxylic acid for component (A). The aromatic dicarboxylic acid of component (A) and the aromatic dicarboxylic acid corresponding to component (C) may be the same or different. The aromatic dicarboxylic acid corresponding to component (B) and the aromatic dicarboxylic acid corresponding to component (C) may be the same or different. The aromatic dicarboxylic acid of component (A), the aromatic dicarboxylic acid corresponding to component (B), and the aromatic dicarboxylic acid corresponding to component (C) may all be the same. The aromatic dicarboxylic acid of each of components (A) to (C) may all be phthalic acid.

[0080] Component (C) can also be described as a diester formed by esterifying the two carboxyl groups of an aromatic dicarboxylic acid with one hydroxyl group of an aliphatic diol. Therefore, the aliphatic group with the hydroxyl group corresponds to the portion of the aliphatic diol excluding the hydroxyl group. For information on aliphatic diols, please refer to the description of aliphatic diols (first solvent) as described as non-aqueous solvents.

[0081] As for the aliphatic group containing hydroxyl groups, please refer to the description for component (B).

[0082] Component (C) may include, for example, a compound represented by the following formula (C).

[0083] R 2 -OOC-X-COO-R 2 (C)

[0084] Regarding X, please refer to the explanation of equation (A). R 2 Please refer to the explanation in formula (B). R 2 -R 2a -OH group or the above-mentioned -R-(O-R) group m -OH group. -R 2aThe -OH group corresponds to the hydroxyalkyl group mentioned above. In formula (C), the R group contained in the two ester moieties... 2 They can be the same or different.

[0085] Specific examples of component (C) are di(hydroxyethyl) phthalate and di(hydroxyethyl) 2,3-naphthalenedicarboxylate. As component (C), di(hydroxyC) esters corresponding to these di(hydroxyethyl) esters can be cited. 3-6 Alkyl esters (e.g., di(hydroxyC) esters) 3-4 Alkyl esters and the hydroxyethyl moiety of these di(hydroxyethyl) esters are replaced with -R (-O-R). m Diesters formed from -OH groups, etc. However, component (C) is not limited to these specific examples.

[0086] Liquid components may contain one component (C) or a combination of two or more components (C).

[0087] The molar ratio (C / A) of component (C) to component (A) can be 0.001 or more and 0.150 or less, or 0.01 or more and 0.10 or less (or 0.010 or more and 0.100 or less). When the molar ratio C / A is within this range, the increase in ESR can be suppressed, and the expansion of the electrolytic capacitor exposed to high temperatures can be suppressed. Furthermore, excessive reduction in moisture content caused by the hydrolysis reaction of water in the liquid component with component (B) is suppressed. Therefore, the film repairability of the dielectric layer can be maintained, and the increase in leakage current can be suppressed.

[0088] (other)

[0089] Examples of components (D) include aliphatic and alicyclic dicarboxylic acids, and their esters (monoesters, diesters). Esters can have structures like components (B) or (D) where the carboxyl group of a dicarboxylic acid is esterified by an aliphatic group containing a hydroxyl group. Liquid components may contain one component (D) or a combination of two or more components (D).

[0090] In liquid components, the carboxyl group of a dicarboxylic acid compound can be in any of the following forms: free, salt, anionic, or formed through interaction with conductive polymers (such as complexation). The carboxyl group of a dicarboxylic acid compound encompasses all of these forms.

[0091] In this specification, the dicarboxylic acid compound comprises component (A), component (B), component (C), and component (D). The total amount of components (A) to (C) in the whole dicarboxylic acid compound can be 50% by mass or more, 75% by mass or more, or 90% by mass or more. The total amount of components (A) to (C) in the whole dicarboxylic acid compound can be 100% by mass or less. The dicarboxylic acid compound may also consist solely of components (A) to (C) (or components (A) and (B)). When the total amount of components (A) to (C) is within such a range, it is easier to obtain higher reliability of the electrolytic capacitor. In addition, it is possible to further suppress the expansion of the electrolytic capacitor when exposed to high temperatures (e.g., temperatures above 200°C and below 300°C). The above proportions are values ​​calculated based on the mass when the carboxyl group is in a free form.

[0092] (Acidic component)

[0093] The acid component contained in the liquid component includes components (A) and (B) that have carboxyl groups. Component (D) also contains components with carboxyl groups. The acid component also includes carboxylic acid compounds (other carboxylic acid compounds) and other acids, in addition to components (A), (B), and (D). The liquid component may contain at least one selected from other carboxylic acid compounds and other acids.

[0094] Other carboxylic acid compounds include carboxylic acids other than components (A), (B), and (D), as well as coordination compounds of carboxylic acids.

[0095] Examples of other carboxylic acids include aliphatic carboxylic acids and aromatic carboxylic acids. Examples of aliphatic carboxylic acids include aliphatic monocarboxylic acids, aliphatic polycarboxylic acids, and aliphatic hydroxycarboxylic acids. Examples of aromatic carboxylic acids include aromatic hydroxy acids (benzoic acid, nitrobenzoic acid, salicylic acid, etc.), aromatic polycarboxylic acids other than component (A) (trimethicone, pyromellitic acid, etc.), and sulfonated aromatic carboxylic acids (p-sulfonated benzoic acid, 3-sulfophthalic acid, 5-sulfosalicylic acid, etc.).

[0096] Examples of coordination compounds include those formed by the bonding of at least one central atom selected from boron, aluminum, and silicon to an acid having a carbonyl group bonded to that central atom. Specific examples of coordination compounds include borosilicate acid, borodioxalic acid, borodiglycolic acid, and borodigalic acid.

[0097] Other acids include, for example, acids other than carboxylic acids with carbonyl groups (oxocarbonic acid, Michaelis-Baumann acid, etc.) or their coordination compounds, phenolic compounds (picric acid, p-nitrophenol, pyrogallol, catechol, etc.) or their coordination compounds, sulfur-containing acids (sulfuric acid, sulfonic acid (aromatic sulfonic acid, etc.), oxyaromatic sulfonic acid (phenol-2-sulfonic acid, etc.) etc.), compounds with sulfonylimide groups, boron-containing acids (boric acid, haloboric acid (tetrafluoroboric acid, etc.), or their esters, etc.), phosphorus-containing acids (phosphoric acid, halophosphoric acid (hexafluorophosphoric acid, etc.), phosphonic acid, hypophosphonic acid, or their esters (butylphosphoric acid, etc.) etc.), and nitrogen-containing acids (nitric acid, nitrous acid, etc.).

[0098] In the liquid component, the carboxyl group and other acid groups (sulfonic acid group, phosphoric acid group, phosphonic acid group, etc.) of the acid component can be in any of the following forms: free form, salt form, anionic form, and form after interaction with conductive polymers (compounding, etc.). The carboxyl group and other acid groups of the acid component include all their forms.

[0099] The proportion of dicarboxylic acid compounds (components (A) to (D)) in the total acid composition can be 50% by mass or more, 75% by mass or more, or 90% by mass or more. The proportion of dicarboxylic acid compounds (components (A) to (D)) in the total acid composition is 100% by mass or less. The acid composition may also consist solely of dicarboxylic acid compounds. By maintaining the proportion of dicarboxylic acid compounds within such a range, electrode corrosion is suppressed, and the high efficiency derived from components (A) to (C) is easily obtained. The above proportions are values ​​of the liquid composition collected from the initial electrolytic capacitor.

[0100] The concentration of the acid component in the liquid can be greater than 1% by mass and less than 30% by mass, or greater than 1% by mass and less than 20% by mass. This concentration is the value of the liquid component collected from the initial electrolytic capacitor.

[0101] The concentration of component (A) in the liquid composition can be 1% by mass or more and 20% by mass or 5% by mass or more and 15% by mass. This concentration is the value of the liquid composition collected from the initial electrolytic capacitor.

[0102] The above ratios and concentrations are calculated based on the mass of acid groups such as carboxyl groups in their free form.

[0103] (Alkaline component)

[0104] When the liquid component contains an alkaline component, the dissociation of acidic components such as dicarboxylic acid compounds increases, making it easier for acidic groups such as carboxyl groups to interact with conductive polymers. Therefore, it is easier to obtain polymers with higher conductivity.

[0105] Examples of base components include ammonia, amines (specifically, primary, secondary, and tertiary amines), quaternary ammonium compounds, and amidine compounds. Liquid components may contain one or more base components.

[0106] Amines can be aliphatic, aromatic, or heterocyclic. Examples of amines include dialkylamines (diethylamine, etc.), trialkylamines (trimethylamine, dimethylethylamine, triethylamine (TEA), tri-n-butylamine (TBA), dimethyl-n-octylamine (DMOA, etc.), alkylene diamines (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.)). Aromatic amines and heterocyclic amines can each be monocyclic or polycyclic (fused ring, bridged ring, etc.). Examples of quaternary ammonium compounds include amidine compounds (including imidazole compounds).

[0107] The base component may include heterocyclic amines. Examples of heterocyclic amines include those with 4 or more but less than 20 or more but less than 10 members. A 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, sulfur, etc.) as constituent atoms of the ring. The heterocycle may be saturated or unsaturated. A heterocyclic amine may be a secondary or tertiary amine. Furthermore, heterocyclic amines also include those having one or more substituents (e.g., hydroxyl, amino, or substituted amino, alkyl, alkoxy, hydroxyalkyl, etc.) on the heterocycle. Specific examples of heterocyclic amines include pyrrolidine, piperidine, piperazine, morpholine, N-alkylmorpholine, N-hydroxyalkylmorpholine, pyridine, pyridazine, pyrimidine, pyrazine, 4-dimethylaminopyridine, etc. Among heterocyclic amines, tertiary amines are preferred from the viewpoint of easily adjusting the pKa of the conjugate acid to a suitable range, and unsaturated tertiary amines are more preferred. Furthermore, from the viewpoint of maintaining the high dedoping suppression effect brought about by the acid component and easily suppressing electrode corrosion, heterocyclic amines are preferably compounds without free amino groups. Among heterocyclic amines, pyridine, N-alkylmorpholine, N-hydroxyalkylmorpholine, etc., are more preferred. The alkyl or hydroxyalkyl moiety on the nitrogen atom of the morpholine can be C10. 1-20 Alkyl group. The alkyl group can be straight-chain or branched. From the viewpoint of easily adjusting the pKa of the conjugate acid to a suitable range, the alkyl group is preferably C1. 3-20 Alkyl groups (propyl, isopropyl, n-butyl, isobutyl, etc.) can also be C24. 4-20 Alkyl or C 4-10Alkyl groups. From the viewpoint of easily ensuring high initial capacity and low ESR, as well as easily obtaining high voltage resistance, N-alkylmorpholines and N-hydroxyalkylmorpholines (especially N-alkylmorpholines) are preferred. Examples of N-alkylmorpholines include N-methylmorpholine, N-isopropylmorpholine, N-butylmorpholine, and N-isobutylmorpholine.

[0108] The base component can include a base with a pKa of 10 or less for the conjugate acid (the first base). The pKa of the conjugate acid of the first base can be 3.5 or more and 10.0 or less, or 3.5 or more and 7.5 or less. Within this range of pKa, it is easier to maintain the dissociation state of the acid component and to inhibit the esterification of component (A), thus making it easier to maintain the high conductivity of the conductive polymer.

[0109] Liquid components can contain alkaline components in free form, in the form of cations, or in the form of salts. Sometimes, the term "alkaline component" includes all of these forms.

[0110] The molar ratio of the alkali component to the dicarboxylic acid compound (alkali component / dicarboxylic acid compound) can be less than 1, more than 0.1 and less than 1.0, more than 0.2 and less than 0.9, or more than 0.3 and less than 0.8. In this case, a high degree of dissociation of the dicarboxylic acid compound can be ensured, making it easier to ensure higher conductivity of the conductive polymer. In addition, electrode corrosion can be suppressed.

[0111] The equivalent ratio of acid to base (= acid / base) can be 0.5 or more and 15 or less, 1.0 or more and 10 or less, or 1.0 or more and 9.0 or less.

[0112] The equivalence ratio of acid to base is (the total number of acid groups per molecule of acid) / (the number of OH groups that can be generated per molecule of base). - The ratio of the total number of moles.

[0113] Electrolytic capacitors

[0114] The electrolytic capacitor disclosed herein comprises the aforementioned liquid components and capacitor elements.

[0115] (Capacitor element)

[0116] A capacitor element comprises an anode having a dielectric layer and a solid electrolyte in contact with the dielectric layer. The solid electrolyte comprises a conductive polymer. The solid electrolyte (or conductive polymer) constitutes at least a portion of the cathode of the capacitor element. The cathode may further comprise a cathode lead-out layer (cathode foil, etc.). The solid electrolyte (or conductive polymer) may be disposed between the anode (anode foil, etc.) and the cathode foil. For example, a capacitor element may have an anode foil having a dielectric layer, a cathode foil disposed opposite to the dielectric layer, and a solid electrolyte (or conductive polymer) disposed between the anode foil and the cathode foil.

[0117] (Anode)

[0118] The anode body may contain a valve-acting metal, an alloy containing a valve-acting metal, or a compound containing a valve-acting metal. These materials may be used alone or in combination of two or more. For example, aluminum, tantalum, niobium, and titanium are preferred valve-acting metals.

[0119] As the anode body, an anode foil is suitable. The anode body preferably has a porous portion with fine pores at least in the surface layer.

[0120] Anode foils with porous structures are obtained, for example, by roughening the surface of a substrate (such as a foil or plate-shaped substrate) containing a valve-acting metal. Roughening can be performed by etching (e.g., electrolytic etching or chemical etching).

[0121] (Dielectric layer)

[0122] The dielectric layer is formed, for example, in a manner that covers at least a portion of the surface of the anode body.

[0123] The dielectric layer may contain, for example, an oxide of the valve-acting metal. For instance, when tantalum is used as the valve-acting metal, the dielectric layer contains Ta₂O₅; when aluminum is used as the valve-acting metal, the dielectric layer contains Al₂O₃. It should be noted that the dielectric layer is not limited to these examples; any dielectric layer that functions as a dielectric is acceptable.

[0124] The dielectric layer is typically 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, it is formed along the pores of the porous portion and the inner wall of the depressions (pits) on the surface of the anode body.

[0125] (Solid electrolyte)

[0126] The conductive polymer constituting the solid electrolyte may include, for example, a conjugated polymer and a dopant. The solid electrolyte (or conductive polymer) may cover at least a portion of the dielectric layer. This includes cases where the solid electrolyte (or conductive polymer) is in contact with at least a portion of the dielectric layer. In the case where the capacitor element comprises an anode foil and a cathode foil, the solid electrolyte (or conductive polymer) may be positioned between these foils. In addition to contacting at least a portion of the dielectric layer, the solid electrolyte (or conductive polymer) may also contact at least a portion of the cathode foil. The solid electrolyte (or conductive polymer) may also form a layer. The solid electrolyte may further contain additives based on the conductive polymer, as needed.

[0127] In the case where the capacitor element includes a separator, the separator is located between the anode foil and the cathode foil. In this case, a solid electrolyte (or conductive polymer) can permeate into the separator. The solid electrolyte (or conductive polymer) can be located between the anode body (anode foil, etc.) and the cathode body (cathode foil, etc.), and in contact with at least a portion of the dielectric layer and at least a portion of the cathode body.

[0128] (Conjugated polymers)

[0129] Examples of conjugated polymers include those known to be used in electrolytic capacitors, such as π-conjugated polymers. Examples of conjugated polymers include those with a basic backbone of polypyrrole, polythiophene, polyaniline, polyfuran, polyacetylene, polyphenylene, polyphenylene vinylidene, polyphenylene oxide, and polythiophene vinylidene. These polymers may contain at least one monomer unit constituting the basic backbone. These polymers also include homopolymers, copolymers of two or more monomers, and their derivatives (substitutes with substituents, etc.). For example, polythiophene also includes poly(3,4-ethylenedioxythiophene) (PEDOT).

[0130] Conjugated polymers can be used alone or in combination of two or more.

[0131] There are no particular restrictions on the weight-average molecular weight (Mw) of conjugated polymers, for example, it can be above 1,000 and below 1,000,000.

[0132] It should be noted that the weight-average molecular weight (Mw) in this specification is a converted value of polystyrene determined by gel permeation chromatography (GPC). It should also be noted that GPC is typically performed using a polystyrene gel column and a water / methanol (8 / 2, v / v) mobile phase.

[0133] (Dopant)

[0134] Examples of dopants include relatively small molecular weight anions and high molecular weight 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 p-toluenesulfonic acid and naphthalenesulfonic acid). Aromatic sulfonic acid compounds may, for example, have at least one group selected from carboxyl and hydroxyl groups.

[0135] Examples of polymeric anions include polyvinyl sulfonic acid, polystyrene sulfonic acid (PSS), polyallyl sulfonic acid, polypropylene sulfonic acid, polymethpropylene sulfonic acid, poly(2-acrylamido-2-methylpropanesulfonic acid), polyisoprene sulfonic acid, polyester sulfonic acid (aromatic polyester sulfonic acid, etc.), phenol sulfonic acid phenolic resin, and polyacrylic acid. Polymeric anions can be polymers of a single monomer, copolymers of two or more monomers, or substituted products with substituents. Among these, polyanions derived from polystyrene sulfonic acid are preferred.

[0136] However, these dopants are merely examples and are not limited to. A single dopant can be used alone, or two or more dopants can be used in combination.

[0137] Conductive polymers can be formed, for example, by at least one of chemical polymerization and electrolytic polymerization of a conjugated polymer precursor on a dielectric layer in the presence of a dopant. Alternatively, a conductive polymer (e.g., a layer of solid electrolyte) can be formed by contacting a solution containing a dissolved conductive polymer or a dispersion containing a dispersed conductive polymer 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 of conjugated polymers, oligomers formed by linking multiple molecular chains of raw material monomers, and prepolymers. One precursor can be used, or two or more can be used in combination.

[0138] There are no particular restrictions on the Mw of the dopant, for example, it can be above 1,000 and below 1,000,000.

[0139] The amount of dopant contained in a conductive polymer is, for example, more than 10 parts by mass and less than 1000 parts by mass, or more than 20 parts by mass and less than 500 parts by mass, relative to 100 parts by mass of the conjugated polymer.

[0140] (Cathode lead-out layer)

[0141] The cathode lead-out layer may, for example, have a first layer covering at least a portion of the solid electrolyte. The cathode lead-out layer may also have a first layer and a second layer covering the first layer. Examples of the first layer include a layer containing conductive particles, a metal foil (cathode foil), etc. Examples of conductive particles include at least one selected from conductive carbon and metal powder. For example, the cathode lead-out layer may be composed of a layer containing conductive carbon (graphite, etc.) as the first layer (also called a carbon layer) and a layer containing metal powder or a metal foil as the second layer. When a metal foil is used as the first layer, the cathode lead-out layer may also be composed of that metal foil. The cathode lead-out layer can be formed using known methods depending on the layer configuration.

[0142] The second layer, containing metal powder, can be formed, for example, by laminating a composition containing metal powder onto the surface of the first layer. Examples of such a second layer include a metal paste layer (silver paste layer, etc.) formed using a composition containing metal powder such as silver particles and a resin (binder resin). As the resin, thermosetting resins such as imide resins and epoxy resins, or thermoplastic resins, can be used.

[0143] When using metal foil as the first layer, the type of metal is not particularly limited, but valve-acting metals such as aluminum, tantalum, and niobium, or alloys containing valve-acting metals, are preferred. The surface of the metal foil can be roughened as needed. A dielectric layer can be formed on the surface of the metal foil, or a film of a different metal (dissimilar metal) or non-metal can be formed. Examples of dissimilar metals and non-metals include metals such as titanium and non-metals such as carbon (conductive carbon, etc.).

[0144] Alternatively, the film of the aforementioned dissimilar metal or non-metal (e.g., conductive carbon) can be used as the first layer, and the aforementioned metal foil can be used as the second layer.

[0145] (Diaphragm)

[0146] A diaphragm can be disposed between the cathode body (cathode foil, etc.) and the anode body (anode foil, etc.). There are no particular limitations on the diaphragm; for example, a nonwoven fabric containing fibers can be used. As the material constituting the fibers, nonwoven fabrics containing fibers of cellulose, polyethylene terephthalate, vinylon, polyamide (e.g., aliphatic polyamide, aromatic polyamide, etc.) can be used.

[0147] (other)

[0148] Electrolytic capacitors can be wound, chip-type, or multilayer. An electrolytic capacitor has at least one capacitor element. An electrolytic capacitor can also have multiple capacitor elements. For example, an electrolytic capacitor can have a multilayer structure with two or more capacitor elements, or it can have two or more wound capacitor elements. The composition or number of capacitor elements is selected according to the type or application of the electrolytic capacitor.

[0149] In a capacitor element, the cathode lead layer is electrically connected to one end of the cathode lead. The anode body is electrically connected to one end of the anode lead. The other ends of the anode lead and the cathode lead are respectively led out from the outer casing or housing. The other ends of each lead exposed from the outer casing or housing are used for soldering connections to the substrate on which the electrolytic capacitor is to be mounted. Each lead can be a wire or a lead frame.

[0150] [Manufacturing method of electrolytic capacitors]

[0151] Electrolytic capacitors are manufactured, for example, by a manufacturing method that includes the steps of housing the capacitor element together with the liquid component in a casing and sealing it. The manufacturing method may further include a step of fabricating the capacitor element. The manufacturing method may further include a step of preparing the liquid component. The steps of fabricating the capacitor element and preparing the liquid component may be performed separately before the sealing step described above.

[0152] Capacitor elements can be manufactured according to the specifications for their components. Liquid components are prepared by dissolving dicarboxylic acid compounds, acidic components, alkaline components, etc., in a solvent (non-aqueous solvent).

[0153] In the sealing process, after the capacitor element and the liquid components are placed together in the housing, the opening of the housing is sealed using a sealing member or the like, thereby obtaining the product.

[0154] The manufacturing method disclosed herein may further include a step of heating the sealant obtained in the sealing process described above. In the heating step, the sealant may be sealed at a temperature of 130°C or higher. The heating temperature may be 130°C or higher and 150°C or lower. The heating time may be 10 minutes or more, or 10 minutes or more and 60 minutes or less. In such a heating step, the hydrolysis reaction of component (B) or component (C) readily occurs. Therefore, even if moisture is generated within the electrolytic capacitor due to the reaction (esterification reaction) between a non-aqueous solvent containing hydroxyl groups and component (A), the moisture content can be reduced through the hydrolysis reaction. Therefore, the expansion of the electrolytic capacitor when exposed to high temperatures (e.g., temperatures of 200°C or higher and 300°C or lower) can be further suppressed.

[0155] Figure 1 This is a cross-sectional schematic diagram of the electrolytic capacitor according to this embodiment. Figure 2 This is a schematic diagram showing a portion of the capacitor element of the electrolytic capacitor unfolded. However, the electrolytic capacitor of this disclosure is not limited to the following embodiments. Furthermore, the constituent elements of the following embodiments can be arbitrarily combined with at least one of the liquid components, electrolytic capacitors, or manufacturing methods thereof described above (Technique 1) to (Technique 14), or arbitrarily combined with at least one of the above (Technique 1) to (Technique 14) and the constituent elements described above.

[0156] An electrolytic capacitor, for example, includes a capacitor element 10, a bottom housing 101 housing the capacitor element 10 and a liquid component (not shown), a sealing member 102 blocking the opening of the bottom housing 101, a base plate 103 covering the sealing member 102, wires 104A and 104B extending from the sealing member 102 and passing through the base plate 103, and lead connectors 105A and 105B connecting the wires to the electrodes of the capacitor element 10. The bottom housing 101 is drawn inward near the opening end, and the opening end is curled in a manner that tightens it against the sealing member 102.

[0157] Capacitor element 10 is, for example, as Figure 2 The wound body shown has an anode foil 11 connected to lead connector 105A, a cathode foil 12 connected to lead connector 105B, and a diaphragm 13. The anode foil 11 and cathode foil 12 are wound together with the diaphragm 13 in between. The outermost periphery of the wound body is fixed by a winding fixing tape 14. It should be noted that... Figure 2 This indicates the state where a portion of the coiled body, before its outermost circumference, has been unwound.

[0158] In capacitor element 10, a dielectric layer (not shown) is formed on at least a portion of the surface of anode foil 11. A separator 13 and a solid electrolyte (conductive polymer, etc., not shown) are separated between anode foil 11 and cathode foil 12. The solid electrolyte is in contact with at least a portion of the dielectric layer. Additionally, the solid electrolyte is in contact with at least a portion of cathode foil 12. Furthermore, a liquid component is impregnated in both the solid electrolyte and the separator.

[0159] [Example]

[0160] The present invention will now be described in detail based on embodiments and comparative examples, but the present invention is not limited to the following embodiments.

[0161] Examples 1-10 and Comparative Examples 1-2

[0162] Fabricate and evaluate a wound electrolytic capacitor (10 mm in diameter and 10 mm in length) with a rated voltage of 25 V and a rated capacitance of 560 μF, following the steps below.

[0163] (Preparation of anode foil)

[0164] A 120 μm thick aluminum foil was etched to roughen its surface. Then, a dielectric layer was formed on the surface of the aluminum foil through a chemical conversion treatment. This chemical conversion treatment was performed by immersing the aluminum foil in an ammonium adipate solution and applying a voltage. The aluminum foil was then cut to dimensions of 6 mm x 200 mm to prepare the anode foil.

[0165] (Preparation of cathode foil)

[0166] A 50μm thick aluminum foil is etched to roughen its surface. The foil is then cut to a size of 6mm x 220mm to prepare the cathode foil.

[0167] (Making of the wound body)

[0168] The anode and cathode lead connectors are connected to the anode and cathode foils, respectively, and the anode and cathode foils are wound around the lead connectors while being wound through a diaphragm. The ends of the outer surface of the wound body are then secured with a winding fixing tape to create the wound body. Anode and cathode wires are connected to the ends of each lead connector. The wound body is then subjected to another chemical conversion treatment to form a dielectric layer at the cut-off end of the anode body.

[0169] (Preparation of polymer dispersions containing conductive polymers)

[0170] A mixed solution was prepared by dissolving 3,4-ethylenedioxythiophene and poly(4-styrenesulfonic acid) (PSS, Mw 100,000) as a polymeric dopant in ion-exchanged water. While stirring the mixed solution, oxidants (ferric sulfate (III) and ammonium persulfate) dissolved in ion-exchanged water were added to carry out a polymerization reaction. After the reaction, the resulting reaction solution was dialyzed to remove unreacted monomers and excess oxidant, yielding a polymeric dispersion containing PSS-doped poly(3,4-ethylenedioxythiophene) (PEDOT / PSS) as a conductive polymer. It should be noted that the Mw of the polymeric dopant was measured under the above conditions.

[0171] (Coating of a dielectric layer using conductive polymers)

[0172] Under reduced pressure (40 kPa), the wound body is immersed in a polymer dispersion contained in a specified container for 5 minutes, and then the wound body is lifted out of the polymer dispersion. Next, the wound body impregnated with the polymer dispersion is dried in a drying oven at 150°C for 20 minutes, so that the conductive polymer adheres to cover at least a portion of the dielectric layer. This forms a capacitor element. In the capacitor element, the separator and the conductive polymer are separated between the anode foil and the cathode foil.

[0173] (Preparation of liquid components)

[0174] A liquid composition was prepared by dissolving components (A) and the salt of morpholine, as well as components (A) to (C), shown in Table 1, in a mixed solvent of ethylene glycol, polyethylene glycol (Mw300), and sulfolane. Regarding the mass ratio of ethylene glycol (EG), polyethylene glycol (PEG), and sulfolane (SL) in the solvent, with all solvents set to 100, EG:PEG:SL = 30:20:50. The proportions of each component were adjusted so that the salt concentration in the liquid composition was 13% by mass and the overall concentration of components (A) to (C) was approximately 10% by mass. The pH of the prepared liquid composition was approximately 4.0 ± 0.5. It should be noted that in Comparative Example 2, a borate ester was used instead of components (A) to (C). This borate ester was a condensation product of a mixture of triethylene glycol monomethyl ether and diethylene glycol with boric acid.

[0175] (Assembly of electrolytic capacitors)

[0176] The capacitor element is immersed in a liquid component and placed under a reduced pressure atmosphere (40 kPa) for 5 minutes to allow the liquid component to penetrate the capacitor element.

[0177] A capacitor element impregnated with a liquid component is housed within a bottomed housing with its leads positioned on the open side of the housing. A sealing member (an elastic material containing butyl rubber as the rubber component), formed with the leads passing through it, is positioned above the capacitor element. Then, a deep drawing process is performed near the open end of the bottomed housing, and the open end is further curled to seal it tightly against the sealing member. This seals the capacitor element and the liquid component within the bottomed housing. A base plate is then placed on the curled portion to complete the process. Figure 1 The electrolytic capacitors shown are examples of this. A total of 40 electrolytic capacitors were manufactured in each example. The manufactured electrolytic capacitors were subjected to a heat treatment at 135°C for 60 minutes, and then heated at 105°C for 60 minutes while applying a voltage of 31.3V, thereby undergoing an aging treatment.

[0178] (evaluate)

[0179] (a) Reliability

[0180] The initial leakage current X0 (LC) and initial equivalent series resistance Y0 (ESR) of the electrolytic capacitor after aging treatment were measured.

[0181] Next, to evaluate reliability, the electrolytic capacitors with the rated voltage (25V) applied were kept at 145°C for 1000 hours to confirm the changes in leakage current (ΔLC) and ESR (ΔESR).

[0182] ΔLC is expressed as the ratio (X / X0) of LC(X) after holding at 145°C to the initial value (X0). It should be noted that, regarding leakage current, a voltage of 25V is applied between the anode and cathode of the electrolytic capacitor, and the leakage current is measured after 120 seconds at room temperature.

[0183] ΔESR is expressed as the ratio (Y / Y0) of the ESR (Y) after holding at 145°C to the initial value (Y0). It should be noted that the ESR is the value of the electrolytic capacitor measured at a frequency of 100kHz using an LCR meter at room temperature.

[0184] (b) Determination of the expansion of electrolytic capacitors

[0185] For 10 aged electrolytic capacitors, the maximum distance α1 from the bottom surface of the casing to the upper surface of the sealing member was measured using a micrometer. Then, the electrolytic capacitors were heated to 200°C for 5 minutes, and the maximum distance α2 from the bottom surface of the heated casing to the upper surface of the sealing member was measured. For each capacitor, the expansion amount was calculated by subtracting α1 from α2, and the average value (mm) of the 10 capacitors was obtained. The capacitors were then evaluated according to the following criteria.

[0186] A: The expansion amount is less than 0.17mm.

[0187] B: Expansion amount exceeds 0.17mm but is less than 0.25mm.

[0188] C: Expansion amount exceeds 0.25mm but is less than 0.30mm.

[0189] D: Expansion exceeds 0.30mm.

[0190] The evaluation results are shown in Table 1. Table 1 also includes the molar ratios of component (B) to component (A) (B / A) and component (C) to component (A) (C / A). In Table 1, E1 to E10 represent examples, and C1 to C2 represent comparative examples.

[0191] [Table 1]

[0192]

[0193] As shown in Table 1, in Comparative Example C2, which used a liquid component containing borate esters, the leakage current after the reliability test was more than seven times the initial value. Furthermore, in Comparative Example C1, which used only component (A) as the acid component, the ΔESR after the reliability test was a large value. In contrast, in Examples E1 to E10, which used liquid components containing both components (A) and (B), the ΔLC after the reliability test was significantly reduced compared to the comparative examples, and the ΔESR was lower. Additionally, in Examples E1 to E10, the expansion of the electrolytic capacitor exposed to high temperature (200°C) was also reduced compared to Comparative Example C1. In Examples E8 to E10, which used liquid components containing components (A) to (C), the ΔESR after the reliability test was further reduced compared to Example E3, which contained both components (A) and (B), and the expansion of the electrolytic capacitor exposed to high temperature (200°C) was also further reduced.

[0194] Industrial availability

[0195] The liquid composition disclosed herein is useful for electrolytic capacitors (e.g., hybrid capacitors) that incorporate capacitor elements containing conductive polymers. However, the applications of electrolytic capacitors are not limited to these.

[0196] Explanation of reference numerals in the attached figures

[0197] 100: Electrolytic capacitor

[0198] 101: Bottom shell

[0199] 102: Sealing component

[0200] 103: Seat board

[0201] 104A, 104B: Conductors

[0202] 105A, 105B: Lead wire connectors

[0203] 10: Capacitor Components

[0204] 11: Anode foil

[0205] 12: Cathode foil

[0206] 13: Diaphragm

[0207] 14: Winding and fixing tape

Claims

1. A liquid component for electrolytic capacitors, comprising a conductive polymer used in electrolytic capacitors. The liquid component contains a non-aqueous solvent and a dicarboxylic acid compound. The dicarboxylic acid compound comprises: Ingredient (A): Aromatic dicarboxylic acid; and Component (B): A monoester formed by esterification of one carboxyl group of an aromatic dicarboxylic acid with an aliphatic group having a hydroxyl group.

2. The liquid component for electrolytic capacitors according to claim 1, wherein, The aromatic dicarboxylic acid in component (A) is the same as the aromatic dicarboxylic acid in component (B).

3. The liquid component for electrolytic capacitors according to claim 1 or 2, wherein, Both the aromatic dicarboxylic acid of component (A) and the aromatic dicarboxylic acid of component (B) are phthalic acid.

4. The liquid component for electrolytic capacitors according to claim 1 or 2, wherein, The non-aqueous solvent contains at least an aliphatic diol.

5. The liquid component for electrolytic capacitors according to claim 4, wherein, The aliphatic diol comprises alkylene diols selected from those having 2 or more but less than 6 carbon atoms and poly(C) diols with a repeating number of 15 or less alkylene groups. 2-4 At least one of alkylene glycols.

6. The liquid component for electrolytic capacitors according to claim 1 or 2, wherein, The molar ratio of component (B) to component (A), i.e., B / A, is 0.05 or more and 0.5 or less.

7. The liquid component for electrolytic capacitors according to claim 1, wherein, The dicarboxylic acid compound further comprises: Component (C): A diester formed by esterification of two carboxyl groups of an aromatic dicarboxylic acid with an aliphatic group having a hydroxyl group.

8. The liquid component for electrolytic capacitors according to claim 7, wherein, The molar ratio of component (C) to component (A), i.e., C / A, is 0.01 or more and 0.10 or less.

9. The liquid component for an electrolytic capacitor according to claim 1 or 7, wherein, The aliphatic group containing a hydroxyl group is a hydroxyalkyl group or -R (-O-R). m -OH, where R is an alkylene group and m represents the number of repetitions of the alkylene group, which is an integer greater than or equal to 1.

10. The liquid component for an electrolytic capacitor according to claim 9, wherein, The hydroxyalkyl group has 2 or more but less than 6 carbon atoms. The -R (-O-R) m In the -OH group, R is an alkylene group with 2 or more but less than 4 carbon atoms, and m is an integer with 1 or more but less than 14.

11. The liquid component for an electrolytic capacitor according to claim 1 or 7, further comprising an alkaline component. The molar ratio of the alkali component to the dicarboxylic acid compound, i.e., the ratio of alkali component to dicarboxylic acid compound, is less than 1.

12. The liquid component for an electrolytic capacitor according to claim 11, wherein, The pKa of the conjugate acid of the base component is less than 10.

13. An electrolytic capacitor comprising the liquid component and capacitor element as described in claim 1 or 7. The capacitor element comprises: Anode foil with a dielectric layer; A cathode foil arranged opposite to the dielectric layer; and A conductive polymer located between the anode foil and the cathode foil.

14. A method for manufacturing an electrolytic capacitor, comprising: The process of manufacturing a capacitor element, wherein the capacitor element comprises an anode foil having a dielectric layer, a cathode foil, and a conductive polymer between the anode foil and the cathode foil; The process of housing and sealing the capacitor element together with the liquid component as described in claim 1 or 7 in a housing; and The process of heating the sealant obtained in the sealing process at a temperature of 130°C or higher for 10 minutes or more.

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