JP7391815B2 - Electrolytic capacitor - Google Patents

Description

The present invention relates to electrolytic capacitors.

As an electrolytic capacitor, an electrolytic capacitor is known which includes a capacitor element having an anode having a dielectric oxide film, a cathode, a separator disposed between the anode and the cathode, and an exterior body in which the capacitor element is housed. (See Patent Document 1). Patent Document 1 describes an electrolytic capacitor in which a conductive polymer and a liquid agent are present between an anode and a cathode.

[Problems to be solved by the invention] of Patent Document 1 include that air is trapped in the main body case (exterior body) of an electrolytic capacitor during sealing, and that air is trapped between the main body case and the sealing body and between lead terminals. Oxidizing substances such as air can enter the main body case over time from between the sealing body and the electrolytic capacitor.Therefore, if an electrolytic capacitor is used for a long period of time, the conductive polymer will oxidize and the ESR of the electrolytic capacitor will increase. It is stated that what happened. To solve this problem, in the electrolytic capacitor of Patent Document 1, an insulating sheet holding an oxidation inhibitor is disposed between the top surface of the main body case and the capacitor element. The oxidation inhibitor held in the insulating sheet traps oxidizing substances in the main body case or chemically changes them into compounds with low oxidizing properties, thereby suppressing oxidation of the conductive polymer. In addition, the liquid in the main body case (the liquid that is impregnated into the capacitor element) may also contain oxidizing substances, but the oxidizing inhibitor held in the insulating sheet captures the oxidizing substances in the liquid or It has been described that oxidation of conductive polymers can be suppressed by chemically changing the conductive polymer to a compound with a low carbon content (see [0036], [0037], etc. of Patent Document 1).

Japanese Patent Application Publication No. 2020-4800

In the electrolytic capacitor described above, the insulating sheet holding the oxidation inhibitor is present on the top surface side (upper surface side) of the main body case (exterior body). When the capacitor is first used, the liquid is present throughout the main body case and is in contact with the insulating sheet on the top side. However, as time passes, the liquid agent evaporates and the liquid agent disappears from within the capacitor body. The liquid disappears from the top side (top side) of the capacitor body, and as time passes, the liquid no longer comes into contact with the insulating sheet on the top side. If the liquid agent no longer comes into contact with the insulating sheet, the effect of suppressing the oxidation of the liquid agent by the insulating sheet cannot be obtained.
Therefore, in the above-mentioned configuration, although the insulating sheet has the effect of suppressing oxidation of the liquid agent in the initial period of use of the capacitor, it is predicted that this effect will not be obtained in the long term.

Further, although the bottom side of the main body case is sealed with a sealing body, oxidizing substances such as air enter from between the sealing body and the main body case over time. The oxidizing substances that entered the main case from the bottom side come into contact with the liquid agent inside the main case before the insulating sheet on the top side. Therefore, the liquid agent is always in an atmosphere in which oxidizing substances are taken in or in contact with oxidizing substances.

Conventionally, electrolytic capacitors are known that utilize a liquid containing polyalkylene glycol as a liquid contained in a capacitor body (exterior body). By using a solution containing polyalkylene glycol, the repair performance of the dielectric oxide film on the anode is improved, so it can be expected to have the effect of reducing leakage current. In addition, parts of the anode that could not be covered with the conductive polymer layer (etching pits, etc.) are covered with the above solution, resulting in higher capacity and withstand voltage than when only the conductive polymer layer is formed. You can expect effects such as improvement in

However, polyalkylene glycol is known to decompose and/or become low molecular weight due to thermal oxidative degradation (S. Han et al, Polymer, 1997, Vol. 38, p. 317-323). Due to thermal oxidative deterioration of the polyalkylene glycol, unintended evaporation of the polyalkylene glycol occurs, and the liquid agent disappears from the capacitor body (exterior body) in a shorter time than originally expected.

As described above, the electrolytic capacitor described in Patent Document 1 has a problem in that the effect of suppressing oxidation of the liquid agent by the insulating sheet cannot be obtained over a long period of time.
Furthermore, on the bottom side of the capacitor body, the liquid agent is always in an atmosphere that takes in oxidizing substances or an atmosphere that is in contact with oxidizing substances. When a liquid agent containing polyalkylene glycol is used in this atmosphere, thermal oxidative deterioration of the polyalkylene glycol progresses, thereby increasing the transpiration rate of the polyalkylene glycol. As a result, the liquid agent containing polyalkylene glycol disappears from the capacitor body more quickly than expected.

Furthermore, thermal oxidative degradation of polyalkylene glycol is an autoxidation reaction, which occurs repeatedly in a radical chain mechanism. Therefore, once thermal oxidative deterioration of polyalkylene glycol occurs, evaporation of the polyalkylene glycol does not stop. Further, the oxidizing substance generated by the radical chain mechanism oxidizes the conductive polymer.

These problems become factors that cause deterioration of capacitor characteristics. Therefore, it is desired to effectively suppress thermal oxidative deterioration of polyalkylene glycol. Furthermore, it is desirable to suppress deterioration of capacitor characteristics over a long period of time by retaining a liquid agent containing polyalkylene glycol within the capacitor body for a long period of time.

An object of the present invention is to suppress deterioration of capacitor characteristics over a long period of time in an electrolytic capacitor in which a liquid agent is housed together with a capacitor element having a conductive polymer layer in the exterior body of the electrolytic capacitor.

The electrolytic capacitor of the present invention includes an anode having a dielectric oxide film, a cathode, a separator disposed between the anode and the cathode, and a conductive polymer layer formed on the dielectric oxide film. A solid electrolytic capacitor comprising: a capacitor element having a capacitor element; and an exterior body in which the capacitor element is housed; , an antioxidant, the antioxidant includes a phenolic antioxidant, and the phenolic antioxidant is a compound having two or more phenol structures. Here, "a compound having two or more phenol structures" is a compound having two or more phenol structures in one molecule.

From the findings of the present inventors, the inclusion of the antioxidant in a liquid containing at least one of polyalkylene glycol, polyglycerin, and their derivatives (hereinafter referred to as polyalkylene glycol, etc.), It was found that transpiration was suppressed. It has also been found that a liquid containing polyalkylene glycol or the like can be retained for a long period of time in the exterior body of an electrolytic capacitor. Thereby, deterioration of the characteristics of the electrolytic capacitor can be suppressed over a long period of time.

The phenolic antioxidant may be a compound having a phenol structure of 2 or more and 4 or less.

The antioxidant may include a sulfur-based antioxidant in addition to the phenolic antioxidant. A sulfur-based antioxidant is a compound having a sulfur atom.

The sulfur-based antioxidant is selected from mercaptothiazole and its derivatives, mercaptobenzothiazole and its derivatives, mercaptobenzimidazole and its derivatives, mercaptothiazoline and its derivatives, and 3,3'-thiodipropionic acid diester. It is preferable that it is at least one type.

The "compound having two or more phenol structures" contained in the phenolic antioxidant may contain a sulfur atom. In other words, the phenolic antioxidant may contain a compound having two or more phenol structures and a sulfur atom in one molecule. An antioxidant containing a compound having two or more phenol structures and a sulfur atom is both a phenolic antioxidant and a sulfur-based antioxidant.

The above-mentioned "compound having two or more phenol structures and a sulfur atom" may have a thioether bond or a thiol bond.

In the above-mentioned "compound having two or more phenol structures and a sulfur atom", the phenol structure may be bonded to the sulfur atom.

In the above-mentioned "compound having two or more phenol structures and a sulfur atom", the phenol structure may be bonded to the sulfur atom via a hydrocarbon group.

According to the present invention, in an electrolytic capacitor that contains a liquid containing polyalkylene glycol or the like together with a capacitor element having a conductive polymer layer on the exterior of the electrolytic capacitor, deterioration in capacitor characteristics can be suppressed over a long period of time.

FIG. 1 is a front cutaway view of essential parts of an electrolytic capacitor according to an embodiment of the present invention. FIG. 2 is an exploded perspective view of the capacitor element shown in FIG. 1. FIG.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

As shown in FIG. 1, the electrolytic capacitor 1 includes an exterior case 2, an exterior body 4 having a sealing body 3 that seals an opening of the exterior case 2, and a capacitor element 5 housed in the exterior body 4. . The exterior body 4 houses a capacitor element 5 and a liquid (not shown).

As shown in FIG. 2, the capacitor element 5 is formed by winding an anode 11 and a cathode 12 into a cylindrical shape with a separator 13 in between, and is secured by a tape 14 attached to the outer peripheral surface.

Lead tabs (not shown) are connected to the anode 11 and the cathode 12, respectively. Anode 11 is connected to lead terminal 21 via a lead tab. The cathode 12 is connected to a lead terminal 22 via a lead tab. As shown in FIG. 1, the lead terminal 21 and the lead terminal 22 are drawn out through holes 31 and 32 formed in the sealing body 3, respectively.

The anode 11 is a valve metal having a dielectric oxide film formed on its surface. Examples of the valve metal include at least one selected from the group consisting of aluminum, tantalum, niobium, and titanium. The dielectric oxide film is formed, for example, by roughening the surface of a valve metal foil by etching and then performing a chemical conversion treatment.

A conductive polymer layer having electrical conductivity is formed on the dielectric oxide film of the anode 11 . The conductive polymer is not particularly limited. For example, polythiophene, polypyrrole, polyaniline, or a derivative thereof is used as the conductive polymer, and polyethylenedioxythiophene (PEDOT) is generally used. As the dopant, p-toluenesulfonic acid, polystyrenesulfonic acid (PSS), etc. are generally used. Moreover, the method of forming the conductive polymer layer is not particularly limited. The method for forming a conductive polymer layer includes, for example, immersing or impregnating it in a polymer dispersion in which a conductive polymer is dispersed in a solvent or in a conductive polymer solution in which a conductive polymer is dissolved in a solvent, and then soaking in a solvent. A method of forming by removing the dielectric film, and a method of forming the film by chemical polymerization or electrolytic polymerization on the dielectric oxide film are used.

The cathode 12 is formed using a valve metal. As the cathode 12, for example, a valve metal foil whose surface is roughened by etching, or a foil whose surface is roughened and then subjected to a chemical conversion treatment is used. As the cathode 12, a plain foil that is not subjected to etching treatment may be used. Further, as the cathode 12, a material selected from the group consisting of titanium, nickel, titanium carbide, nickel carbide, titanium nitride, nickel nitride, titanium carbonitride, and nickel carbonitride is applied to the surface of the roughened foil or plain foil. A coating foil may be used on which a thin metal film containing at least one metal is formed. Further, as the cathode 12, a coated foil in which a carbon thin film is formed on the surface of a roughened foil or a plain foil may be used.

The material of the separator 13 is not particularly limited. As the separator 13, for example, one mainly made of cellulose may be used.

The capacitor element 5 and a liquid (not shown) are accommodated in the exterior body 4 shown in FIG. 1. This liquid contains at least one member selected from the group consisting of polyalkylene glycol, polyglycerin, and derivatives thereof, and an antioxidant. Hereinafter, this liquid may be referred to as a "liquid containing polyalkylene glycol."

The liquid containing polyalkylene glycol exists as a layer covering the conductive polymer layer. The liquid containing polyalkylene glycol may be present as a layer covering the separator 13. The separator 13 may be impregnated with a liquid containing polyalkylene glycol.

Polyalkylene glycol is obtained by addition polymerizing alkylene oxide to alcohol. Moreover, as the polyalkylene glycol, one obtained by copolymerizing or polymerizing a polyhydric alcohol may be used. Furthermore, as the polyalkylene glycol, a polyhydric alcohol may be copolymerized or polymerized, and a polyhydric alcohol may be polymerized. The polyhydric alcohol here has two or more hydroxy groups, and each of the two or more hydroxy groups is bonded to a different carbon. Examples of copolymerized or polymerized polyhydric alcohols include copolymerized or polymerized dihydric alcohols, copolymerized or polymerized trihydric alcohols, and copolymerized dihydric alcohols and trihydric alcohols. It will be done.
The polyalkylene glycol may be one obtained by addition polymerizing two or more alkylene oxides to an alcohol. Hydrogen in the alkylene oxide may be substituted with a substituent such as a hydroxy group. As the polyalkylene glycol, a copolymer of two or more polyhydric alcohols may be used. As the polyalkylene glycol, one obtained by polymerizing one type of polyhydric alcohol may be used. As the polyalkylene glycol, a copolymerization of two or more polyhydric alcohols or a polymerization of one or more polyhydric alcohols may be used. .
The number of carbon atoms in the alkylene group of the polyalkylene glycol is not particularly limited. The polyalkylene glycol may contain one or more oxyalkylenes. The hydrogen of this oxyalkylene group may be substituted with a substituent such as a hydroxy group. The polyalkylene glycol may contain an alkylene group. The hydrogen of this alkylene group may be substituted with a substituent such as a hydroxy group.
The number average molecular weight of the polyalkylene glycol may be 300 or more, preferably 400 to 4,000. Polyalkylene glycols are not limited to specific compounds.

A polyalkylene glycol derivative is, for example, a polyalkylene glycol in which one or both of the two terminal hydroxyl groups are etherified, esterified, halogenated, aminated, or carbonylated. A polyalkylene glycol derivative is, for example, a compound having a functional group such as an amino group or a carboxyl group at one or both of the two terminals of the polyalkylene glycol.

Examples of polyalkylene glycol and/or derivatives of polyalkylene glycol include polyethylene glycol, polypropylene glycol, polybutylene glycol, polytetramethylene ether glycol, copolymers of ethylene glycol and propylene glycol, glycerin or polyglycerin and ethylene glycol. copolymers of glycerin or polyglycerin and propylene glycol, and derivatives thereof.

Polyglycerin is a polymerized glycol. The number of carbon atoms in polyglycerin is not particularly limited. The number average molecular weight of polyglycerin is preferably 400 to 4,000. Polyglycerols are not limited to specific compounds.

The polyglycerin derivative is, for example, one in which one or both of the three terminal hydroxyl groups of polyglycerin are etherified, esterified, halogenated, aminated, or carbonylated. A polyglycerin derivative is, for example, a compound having a functional group such as an amino group or a carboxyl group at one or both of the two terminals of polyglycerin.

The liquid containing polyalkylene glycol may contain one or more polyalkylene glycols and/or polyglycerin. The polyalkylene glycol-containing liquid may contain one or more polyalkylene glycol derivatives and/or polyglycerin derivatives. The liquid containing polyalkylene glycol may contain one or more types of polyalkylene glycol and/or polyglycerin, and one or more types of polyalkylene glycol derivative and/or polyglycerin derivative. good. The liquid containing polyalkylene glycol may contain a solvent other than polyalkylene glycol, polyglycerin, a polyalkylene glycol derivative, and a polyglycerin derivative.

The content of at least one selected from the group consisting of polyalkylene glycol, polyglycerin, and derivatives thereof is not particularly limited. "The content of at least one selected from the group consisting of polyalkylene glycol, polyglycerin, and their derivatives" refers to the content of polyalkylene glycol, polyglycerin, and their derivatives based on 100 wt% of the solvent of the liquid containing polyalkylene glycol. The total content (total content) of at least one selected from the group consisting of derivatives of The content of polyalkylene glycol, polyglycerin, and their derivatives may be, for example, 40 wt% or more.

The following antioxidants are included in the solution containing polyalkylene glycol.

(1) Antioxidants include phenolic antioxidants. A phenolic antioxidant is a compound having two or more phenol structures. In other words, a phenolic antioxidant is a compound having two or more phenol structures in one molecule.

In the present invention, the phenol structure is a structure in which one or more hydrogen atoms of a benzene ring are substituted with a hydroxy group. The number of hydroxy groups contained in the phenol structure is one or more. The number of hydroxy groups contained in the phenol structure is not particularly limited as long as it is one or more. As long as at least one hydrogen atom among the hydrogen atoms possessed by the benzene ring is substituted with a hydroxy group, even if the other hydrogen atoms are substituted with a hydroxy group or with a substituent other than the hydroxy group, This is the phenol structure of the present invention. As long as at least one hydrogen atom among the hydrogen atoms possessed by the benzene ring is substituted with a hydroxy group, the phenol structure of the present invention can be obtained even if other hydrogen atoms are not substituted, that is, even if they remain as hydrogen atoms. It is.

As long as two or more phenol structures exist in a compound having two or more phenol structures in one molecule, the number of phenol structures is not limited. The compound having two or more phenol structures in one molecule may be, for example, a compound having two or more and four or less phenol structures in one molecule. Examples of compounds having 2 or more and 4 or less phenol structures in one molecule include bisphenol, trisphenol, and tetrakisphenol. The phenolic antioxidant may include, for example, at least one selected from the group consisting of bisphenol, trisphenol, and tetrakisphenol.

A compound having two or more phenol structures in one molecule may have one or more phenol structures in one molecule.
The phenolic antioxidant may contain one or more of the above compounds.

(2) The antioxidant may include a sulfur-based antioxidant in addition to the phenolic antioxidant mentioned in (1) above. A sulfur-based antioxidant is a compound having a sulfur atom. The number of sulfur atoms contained in the compound having sulfur atoms is not particularly limited. The sulfur-based antioxidant may contain one or more types of "compounds having a sulfur atom".

The compound having a sulfur atom contained in the sulfur-based antioxidant is not particularly limited. A compound having a sulfur atom may have, for example, a thioether bond and/or a thiol bond. The compound having a sulfur atom is selected, for example, from mercaptothiazole and its derivatives, mercaptobenzothiazole and its derivatives, mercaptobenzimidazole and its derivatives, 3,3'-thiodipropionic acid diester, and mercaptothiazoline and its derivatives. It may be at least one type. Examples of derivatives of mercaptothiazole include those in which the hydrogen group contained in mercaptothiazole is substituted with an alkyl group. Similar to the above-mentioned example of the mercaptothiazole derivative, examples of derivatives of other compounds include those in which the hydrogen group contained in the compound is substituted with an alkyl group. Examples of the 3,3'-thiodipropionic acid diester include 3,3'-thiodipropionic acid in which the hydroxy group is substituted with a hydrocarbon group. Hydrogen in this hydrocarbon group may be substituted with another substituent. Examples of 3,3'-thiodipropionic acid diesters include those in which the hydroxy group of 3,3'-thiodipropionic acid is substituted with an alkyl group, an aryl group, a vinyl group, an allyl group, or the like. As the 3,3'-thiodipropionate diester, for example, didodecyl 3,3'-thiodipropionate may be used.

(3) The compound having two or more phenol structures contained in the phenolic antioxidant may further contain a sulfur atom. In other words, the phenolic antioxidant may include "a compound having two or more phenol structures and a sulfur atom in one molecule." An antioxidant containing "a compound having two or more phenol structures and a sulfur atom in one molecule" is both a phenolic antioxidant and a sulfur-based antioxidant.

In "a compound having two or more phenol structures and a sulfur atom in one molecule", the number of phenol structures is not limited as long as it is two or more. In "a compound having two or more phenol structures and a sulfur atom in one molecule", the number of phenol structures may be, for example, 2 or more and 4 or less. The phenol structure is the same as the phenol structure (1) described above.

In the "compound having two or more phenol structures and sulfur atoms in one molecule", the number of sulfur atoms is not limited as long as it is one or more.

In "a compound having two or more phenol structures and a sulfur atom in one molecule", at least one phenol structure may be bonded to a sulfur atom. For example, one phenol structure may be bonded to one sulfur atom. Two phenol structures may be bonded to one sulfur atom. The phenol structure does not need to be bonded to the sulfur atom. A phenol structure may be bonded to the sulfur atom via a hydrocarbon group. Hydrogen of this hydrocarbon group may be substituted with a substituent, for example.

"A compound having two or more phenol structures and a sulfur atom in one molecule" may have a thioether structure or a thiol structure. "A compound having two or more phenol structures and a sulfur atom in one molecule" may have both a thioether structure and a thiol structure.

"A compound having two or more phenol structures and a sulfur atom in one molecule" may have a thioether structure in which one phenol structure is bonded to one sulfur atom. "A compound having two or more phenol structures and a sulfur atom in one molecule" may have a thioether structure in which two phenol structures are bonded to one sulfur atom. "A compound having two or more phenol structures and a sulfur atom in one molecule" includes a thioether structure in which one or two phenol structures are bonded to one sulfur atom via a hydrocarbon group. good. "A compound having two or more phenol structures and a sulfur atom in one molecule" refers to a thioether structure in which one or two phenol structures are bonded to one sulfur atom via a heteroatom other than a hydrocarbon group. May have.

"A compound having two or more phenol structures and a sulfur atom in one molecule" may have a thiol structure in which one phenol structure and one hydrogen atom are bonded to one sulfur atom. "A compound having two or more phenol structures and a sulfur atom in one molecule" may have a thiol structure in which a phenol structure is bonded to one sulfur atom via a hydrocarbon group. "A compound having two or more phenol structures and sulfur atoms in one molecule" may have a thiol structure in which a phenol structure is bonded to one sulfur atom via a heteroatom other than a hydrocarbon group. .

The antioxidant may contain one or more types of "compounds having two or more phenol structures and sulfur atoms in one molecule."

The above (1) to (3) may be arbitrarily combined. For example, the antioxidant may satisfy the above (1). The antioxidant may satisfy the above (2). The antioxidant may satisfy the above (3). The antioxidant may satisfy all of the above (1) to (3). For example, "a compound having two or more phenol structures and a sulfur atom in one molecule" and a sulfur-based antioxidant may be used. "A compound having two or more phenol structures and a sulfur atom in one molecule", a sulfur-based antioxidant, and "a compound having two or more phenol structures in one molecule" may be used. The content of antioxidant is not particularly limited. Moreover, the liquid containing polyalkylene glycol may contain antioxidants other than the above-mentioned phenolic antioxidants and sulfur-based antioxidants. Moreover, the liquid containing polyalkylene glycol may contain additives other than antioxidants.

The electrolytic capacitor 1 described above is manufactured, for example, by the following method.
Lead tabs for external extraction electrodes are connected to the anode 11 and cathode 12 cut to a predetermined width. By winding the anode 11 and the cathode 12 to which the lead tabs are connected with a separator 13 in between, a main body portion that will become the capacitor element 5 is produced. The anode 11 is a valve metal on which a dielectric oxide film is formed.

Next, the main body is subjected to a chemical conversion treatment in order to repair the cut portion of the main body or the dielectric oxide film that was lost during the fabrication of the main body. The chemical conversion treatment is performed by applying a voltage to the main body in a chemical conversion solution. Examples of the chemical conversion liquid used in the chemical conversion treatment include an aqueous solution containing at least one of adipic acid and an adipate salt.

Subsequently, in order to form a conductive polymer layer, the main body portion is immersed in a liquid containing a conductive polymer and then dried.
As the liquid containing the conductive polymer, for example, a polymer dispersion containing PEDOT/PSS may be used. A polymer dispersion containing PEDOT/PSS is one in which a composite consisting of poly(3,4-ethylenedioxythiophene) (PEDOT) and polystyrene sulfonic acid (PSS) is dispersed in water. When using a polymer dispersion containing PEDOT/PSS, the main body is immersed in the polymer dispersion containing PEDOT/PSS at least once, and then the solvent is removed by drying. As a result, a conductive polymer layer (PEDOT/PSS layer) is formed on the dielectric oxide film.
Thereby, capacitor element 5 is obtained.
Although the case where the main body is immersed in the polymer dispersion is exemplified above, the main body may be impregnated with the polymer dispersion.

Next, the capacitor element 5 is immersed in a liquid containing at least one member selected from the group consisting of polyalkylene glycol, polyglycerin, and derivatives thereof and the above-mentioned antioxidant. At this time, the main body portion may be immersed in the liquid, or the main body portion may be impregnated with the liquid. Thereafter, the capacitor element 5 is dried (moisture due to moisture absorption etc. is removed).

The dried capacitor element 5 is housed in a metal case. Thereby, electrolytic capacitor 1 is obtained.

The following findings were obtained from the research conducted by the present inventors.
By using a liquid containing at least one selected from the group consisting of polyalkylene glycol, polyglycerin, and their derivatives, the self-healing performance of the dielectric oxide film can be assisted, the capacitance can be increased, and the durability can be improved. Effects such as improved voltage can be obtained. However, it is known that polyalkylene glycol, polyglycerin, and their derivatives decompose and/or become low molecular weight due to thermal oxidative deterioration, and evaporate. A liquid containing at least one selected from the group consisting of polyalkylene glycol, polyglycerin, and derivatives thereof tends to run out of the capacitor quickly.
However, if the above-mentioned antioxidant is contained in a liquid containing at least one selected from the group consisting of polyalkylene glycol, polyglycerin, and their derivatives, polyalkylene glycol, polyglycerin, and their derivatives It was found that transpiration can be suppressed. Furthermore, it has been found that it is possible to prevent the liquid containing at least one selected from the group consisting of polyalkylene glycol, polyglycerin, and derivatives thereof from disappearing from the capacitor at an early stage. Thereby, deterioration of capacitor characteristics can be suppressed over a long period of time.

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples.

[Experiment 1]
500 mg of a solution prepared under the following conditions was heated at 180° C. for 24 hours in the air. In the atmosphere, the components, humidity, temperature, etc. are not artificially controlled.

(Comparative example a)
A solution containing 90 wt% polyethylene glycol (PEG400) and 10 wt% ethanol (EtOH) was prepared. "PEG400" is polyethylene glycol with a number average molecular weight of 400. No antioxidants were added to this solution.

(Comparative example b)
Add 71.9 mg (0.033 mmol/g) of 2,4-di-tert-butyl-4-methylphenol as an antioxidant to 10 g of a solution containing 90 wt% of polyethylene glycol (PEG400) and 10 wt% of ethanol (EtOH). Added.

(Comparative example c)
Stearyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate was added as an antioxidant to 10 g of a solution containing 90 wt% of polyethylene glycol (PEG400) and 10 wt% of propylene glycol monomethyl ether (PGME). 177.3 mg (0.033 mmol/g) was added.

(Comparative example d)
36.0 mg (0.033 mmol/g) of catechol was added as an antioxidant to 10 g of a solution containing 90 wt% of polyethylene glycol (PEG400) and 10 wt% of ethanol (EtOH).

(Comparative example e)
36.0 mg (0.033 mmol/g) of resorcinol was added as an antioxidant to 10 g of a solution containing 90 wt% of polyethylene glycol (PEG400) and 10 wt% of ethanol (EtOH).

(Comparative example f)
36.0 mg (0.033 mmol/g) of hydroquinone was added as an antioxidant to 10 g of a solution containing 90 wt% of polyethylene glycol (PEG400) and 10 wt% of ethanol (EtOH).

(Comparative example g)
41.2 mg (0.033 mmol/g) of phloroglucinol was added as an antioxidant to 10 g of a solution containing 90 wt% of polyethylene glycol (PEG400) and 10 wt% of ethanol (EtOH).

(Comparative example h)
41.2 mg (0.033 mmol/g) of pyrogallol was added as an antioxidant to 10 g of a solution containing 90 wt% of polyethylene glycol (PEG400) and 10 wt% of ethanol (EtOH).

(Comparative example i)
55.5 mg (0.033 mmol/g) of gallic acid was added as an antioxidant to 10 g of a solution containing 90 wt% of polyethylene glycol (PEG400) and 10 wt% of ethanol (EtOH).

(Example j)
To 10 g of a solution containing 90 wt% of polyethylene glycol (PEG400) and 10 wt% of ethanol (EtOH), 124.9 mg (0. 033 mmol/g) was added.

(Example k)
To 10 g of a solution containing 90 wt% of polyethylene glycol (PEG400) and 10 wt% of ethanol (EtOH), 111.2 mg (0. 033 mmol/g) was added.

(Example 1)
To 10 g of a solution containing 90 wt% polyethylene glycol (PEG400) and 10 wt% ethanol (EtOH), 120.3 mg (0. 033 mmol/g) was added.

(Example m)
To 10 g of a solution containing 90 wt% of polyethylene glycol (PEG400) and 10 wt% of ethanol (EtOH), 128.2 mg (0.033 mmol/g) of 2,2'-methylenebis(6-cyclohexyl-p-cresol) was added as an antioxidant. ) was added.

(Example n)
To 10 g of a solution containing 90 wt% polyethylene glycol (PEG400) and 10 wt% ethanol (EtOH), 113.8 mg (0 .033 mmol/g) was added.

(Example o)
2,4,6-tris(3',5'-di-tert-butyl-4') was added as an antioxidant to 10 g of a solution containing 90 wt% of polyethylene glycol (PEG400) and 10 wt% of propylene glycol monomethyl ether (PGME). 253.1 mg (0.033 mmol/g) of -hydroxybenzyl)mesitylene was added.

(Example p)
Pentaerythritol tetrakis [3-(3,5-di-tert-butyl-4-hydroxyphenyl)] was added as an antioxidant to 10 g of a solution containing 90 wt% of polyethylene glycol (PEG400) and 10 wt% of propylene glycol monomethyl ether (PGME). 384.5 mg (0.033 mmol/g) of [propionate] was added.

(Example q)
Add 117.1 mg (0.033 mmol) of 4,4'-thiobis(6-tert-butyl-m-cresol) as an antioxidant to 10 g of a solution containing 90 wt% of polyethylene glycol (PEG400) and 10 wt% of ethanol (EtOH). /g) added.

(Example r)
Add 117.1 mg (0.033 mmol) of 4,4'-thiobis(6-tert-butyl-o-cresol) as an antioxidant to 10 g of a solution containing 90 wt% of polyethylene glycol (PEG400) and 10 wt% of ethanol (EtOH). /g) added.

(Example s)
To 10 g of a solution containing 90 wt% polyethylene glycol (PEG400) and 10 wt% ethanol (EtOH), 153.7 mg (0. 033 mmol/g) was added.

(Example t)
2,2'-thiodiethylenebis[3-(3,5-di-tert-butyl-4-hydroxy) was added as an antioxidant to 10 g of a solution containing 90 wt% polyethylene glycol (PEG400) and 10 wt% ethanol (EtOH). 209.9 mg (0.033 mmol/g) of phenyl)propionic acid was added.

(Example u)
To 10 g of a solution containing 90 wt% polyethylene glycol (PEG400) and 10 wt% ethanol (EtOH), 111.2 mg (0. 033 mmol/g) and 49.0 mg (0.033 mmol/g) of 2-mercaptobenzimidazole were added.

(Example v)
To 10 g of a solution containing 90 wt% of polyethylene glycol (PEG400) and 10 wt% of ethanol (EtOH), 111.2 mg (0. 033 mmol/g) and 38.9 mg (0.033 mmol/g) of 2-mercaptothiazoline were added.

(Example w)
To 10 g of a solution containing 90 wt% of polyethylene glycol (PEG400) and 10 wt% of ethanol (EtOH), 111.2 mg (0. 033 mmol/g) and 54.6 mg (0.033 mmol/g) of 2-mercaptobenzothiazole were added.

(Example x)
Add 111.2 mg of 2,2'-methylenebis-(6-tert-butyl-m-cresol) as an antioxidant to 10 g of a solution containing 90 wt% of polyethylene glycol (PEG400) and 10 wt% of propylene glycol monomethyl ether (PGME). (0.033 mmol/g) and 168.1 mg (0.033 mmol/g) of didodecyl 3,3'-thiodipropionate were added.

Table 1A, Table 1B, Table 1C, and Table 1D show the solution preparation conditions and experimental results of Experiment 1.

From Table 1, the following was found.
The weight reduction rate of Comparative Example a to which no antioxidant was added was 99%. When no antioxidant was added, almost all of the liquid containing polyethylene glycol evaporated.
In Comparative Examples b to f, an antioxidant was added to polyethylene glycol, but the weight loss rate was large. In Comparative Examples b to f, a large amount of polyethylene glycol was also evaporated.

On the other hand, the weight loss rates of the solutions of Comparative Examples g to i and Examples j to x were less than 25%. In Comparative Examples g to i and Examples j to x, the evaporation of the liquid containing polyethylene glycol was suppressed by 70% or more compared to Comparative Example a in which no antioxidant was added.

From the above, when a compound having a phenol structure (1) is used as an oxidizing agent, when trihydroxybenzene with a large number of hydroxyl groups is used (Comparative Examples g to i), evaporation of a solution containing polyethylene glycol is suppressed. I understand. Furthermore, it was found that when bisphenol, trisphenol, tetrakisphenol, etc. having two or more phenol structures were used as an antioxidant (Examples j to x), evaporation of a solution containing polyethylene glycol was suppressed. Furthermore, it was found that when a compound having two or more phenol structures and a sulfur atom was used as an antioxidant (Examples q to t), evaporation of a solution containing polyethylene glycol was suppressed. It was also found that when a phenolic antioxidant and a sulfur-based antioxidant were used as antioxidants (Examples u to x), evaporation of a solution containing polyethylene glycol was suppressed.

[Experiment 2]
A simulated capacitor was fabricated using the following method. The obtained capacitor was heated in the atmosphere at 180° C. for 24 hours.

[Comparative example 1]
An aluminum lead tab for an external lead electrode was connected to the anode foil and cathode foil that were cut to a predetermined width. The anode aluminum foil has a dielectric oxide film formed by roughening the surface of the aluminum foil, which is a valve metal, by performing an etching process and then performing a chemical conversion treatment. The cathode foil is carbon-deposited aluminum foil. A main body serving as a capacitor element was prepared by winding anode aluminum foil and cathode aluminum foil with an electrolytic paper (separator) mainly made of cellulose interposed therebetween.

Chemical conversion treatment was performed to repair the dielectric oxide film that was damaged at the cut end of the anode foil and the attachment part of the lead tab. The chemical conversion treatment was performed by applying a voltage close to the chemical conversion voltage value of the dielectric oxide film while the capacitor element was immersed in the chemical conversion solution. As the chemical conversion liquid, an ammonium adipate aqueous solution having an ammonium adipate concentration of 2 wt % was used.

Next, the main body was immersed in an aqueous dispersion (polymer dispersion) containing 2.0 wt% PEDOT/PSS for 30 minutes in a reduced pressure environment of 90 kPa, and then in a constant temperature bath at 160°C for 30 minutes. Dry. By repeating this impregnation and drying twice, a conductive polymer layer was formed. Thereby, a capacitor element was obtained.

After the capacitor element was housed in an aluminum exterior case, the periphery of the opening of the exterior case was curled. A solid electrolytic capacitor was manufactured by applying a rated voltage of 20 WV to the capacitor element housed in the outer case in a constant temperature bath set at 150° C. and performing an aging treatment. The solid electrolytic capacitor created in this experiment has a rated voltage of 20 WV, a rated capacitance of 150 μF, and a product size of φ8×7 L (mm).
Note that in this experiment, the heating temperature of the capacitor was 180°C. At temperatures exceeding 150° C., the sealing rubber that closes the case opening has insufficient heat resistance, so there is a risk that the case opening cannot be stably sealed with the sealing rubber. Therefore, in this experiment, the case opening was not sealed with sealing rubber.

[Comparative example 2]
After forming the conductive polymer layer, the capacitor element was impregnated with the solution of Comparative Example a of Experiment 1, and then dried. A capacitor was manufactured in the same manner as Comparative Example 1 except for the above.

[Comparative example 3]
After forming the conductive polymer layer, the capacitor element was impregnated with the solution of Comparative Example b of Experiment 1. Thereafter, the capacitor element was dried. A capacitor was manufactured in the same manner as Comparative Example 1 except for the above.

[Comparative example 4]
After forming the conductive polymer layer, the capacitor element was impregnated with the solution of Comparative Example c of Experiment 1. Thereafter, the capacitor element was dried. A capacitor was manufactured in the same manner as Comparative Example 1 except for the above.

[Comparative example 5]
After forming the conductive polymer layer, the capacitor element was impregnated with the solution of Comparative Example d of Experiment 1. Thereafter, the capacitor element was dried. A capacitor was manufactured in the same manner as Comparative Example 1 except for the above.

[Comparative example 6]
After forming the conductive polymer layer, the capacitor element was impregnated with the solution of Comparative Example e of Experiment 1. Thereafter, the capacitor element was dried. A capacitor was manufactured in the same manner as Comparative Example 1 except for the above.

[Comparative example 7]
After forming the conductive polymer layer, the capacitor element was impregnated with the solution of Comparative Example f of Experiment 1. Thereafter, the capacitor element was dried. A capacitor was manufactured in the same manner as Comparative Example 1 except for the above.

[Comparative example 8]
After forming the conductive polymer layer, the capacitor element was impregnated with the solution of Comparative Example g of Experiment 1. Thereafter, the capacitor element was dried. A capacitor was manufactured in the same manner as Comparative Example 1 except for the above.

[Comparative Example 9]
After forming the conductive polymer layer, the capacitor element was impregnated with the solution of Comparative Example h of Experiment 1. Thereafter, the capacitor element was dried. A capacitor was manufactured in the same manner as Comparative Example 1 except for the above.

[Comparative Example 10]
After forming the conductive polymer layer, the capacitor element was impregnated with the solution of Comparative Example i of Experiment 1. Thereafter, the capacitor element was dried. A capacitor was manufactured in the same manner as Comparative Example 1 except for the above.

[Example 1]
After forming the conductive polymer layer, the capacitor element was impregnated with the solution of Example j of Experiment 1. Thereafter, the capacitor element was dried. A capacitor was manufactured in the same manner as Comparative Example 1 except for the above.

[Example 2]
After forming the conductive polymer layer, the capacitor element was impregnated with the solution of Example K of Experiment 1. Thereafter, the capacitor element was dried. A capacitor was manufactured in the same manner as Comparative Example 1 except for the above.

[Example 3]
After forming the conductive polymer layer, the capacitor element was impregnated with the solution of Example 1 of Experiment 1. Thereafter, the capacitor element was dried. A capacitor was manufactured in the same manner as Comparative Example 1 except for the above.

[Example 4]
After forming the conductive polymer layer, the capacitor element was impregnated with the solution of Example m of Experiment 1. Thereafter, the capacitor element was dried. A capacitor was manufactured in the same manner as Comparative Example 1 except for the above.

[Example 5]
After forming the conductive polymer layer, the capacitor element was impregnated with the solution of Example n of Experiment 1. Thereafter, the capacitor element was dried. A capacitor was manufactured in the same manner as Comparative Example 1 except for the above.

[Example 6]
After forming the conductive polymer layer, the capacitor element was impregnated with the solution of Example 0 of Experiment 1. Thereafter, the capacitor element was dried. A capacitor was manufactured in the same manner as Comparative Example 1 except for the above.

[Example 7]
After forming the conductive polymer layer, the capacitor element was impregnated with the solution of Example p of Experiment 1. Thereafter, the capacitor element was dried. A capacitor was manufactured in the same manner as Comparative Example 1 except for the above.

[Example 8]
After forming the conductive polymer layer, the capacitor element was impregnated with the solution of Example q of Experiment 1. Thereafter, the capacitor element was dried. A capacitor was manufactured in the same manner as Comparative Example 1 except for the above.

[Example 9]
After forming the conductive polymer layer, the capacitor element was impregnated with the solution of Example r of Experiment 1. Thereafter, the capacitor element was dried. A capacitor was manufactured in the same manner as Comparative Example 1 except for the above.

[Example 10]
After forming the conductive polymer layer, the capacitor element was impregnated with the solution of Example s of Experiment 1. Thereafter, the capacitor element was dried. A capacitor was manufactured in the same manner as Comparative Example 1 except for the above.

[Example 11]
After forming the conductive polymer layer, the capacitor element was impregnated with the solution of Example t of Experiment 1. Thereafter, the capacitor element was dried. A capacitor was manufactured in the same manner as Comparative Example 1 except for the above.

[Example 12]
After forming the conductive polymer layer, the capacitor element was impregnated with the solution of Example u of Experiment 1. Thereafter, the capacitor element was dried. A capacitor was manufactured in the same manner as Comparative Example 1 except for the above.

[Example 13]
After forming the conductive polymer layer, the capacitor element was impregnated with the solution of Example v of Experiment 1. Thereafter, the capacitor element was dried. A capacitor was manufactured in the same manner as Comparative Example 1 except for the above.

[Example 14]
After forming the conductive polymer layer, the capacitor element was impregnated with the solution of Example w of Experiment 1. Thereafter, the capacitor element was dried. A capacitor was manufactured in the same manner as Comparative Example 1 except for the above.

[Example 15]
After forming the conductive polymer layer, the capacitor element was impregnated with the solution of Example x of Experiment 1. Thereafter, the capacitor element was dried. A capacitor was manufactured in the same manner as Comparative Example 1 except for the above.

[Example 16]
After forming the conductive polymer layer, the capacitor element was impregnated with a solution containing the same antioxidant as in Example R of Experiment 1. Thereafter, the capacitor element was dried. This solution contains 90 wt% polyethylene glycol (PEG300) and 10 wt% ethanol (EtOH). "PEG300" is polyethylene glycol with a number average molecular weight of 300. A capacitor was manufactured in the same manner as Comparative Example 1 except for the above.

[Example 17]
After forming the conductive polymer layer, the capacitor element was impregnated with a solution containing the same antioxidant as in Example R of Experiment 1. Thereafter, the capacitor element was dried. This solution contains 40 wt% polyethylene glycol (PEG400), 50 wt% ethylene glycol (EG), and 10 wt% ethanol (EtOH). A capacitor was manufactured in the same manner as Comparative Example 1 except for the above.

Tables 2A and 2B show conditions for manufacturing the capacitor of Example 2.

(evaluation)
As initial characteristics, the capacitance (Cap.), tangent of loss angle (tan δ), and equivalent series resistance (ESR) of each capacitor were measured in an environment of 20°C. Thereafter, each capacitor was heated in the atmosphere at 180° C. for 24 hours, and then the capacitance (Cap.), tangent of loss angle (tan δ), equivalent series resistance (ESR), and weight loss of the capacitor were measured. These were defined as the characteristics after the accelerated test. The rate of change with respect to the initial characteristics was calculated for the capacitance (Cap.), tangent of loss angle (tan δ), and equivalent series resistance (ESR) after the accelerated test. The evaluation results are shown in Table 3A and Table 3B.

After the accelerated test, the rate of change in capacitance (Cap.) of Comparative Example 1 was large, the rate of change in tangent of loss angle (tan δ) was large, and the rate of change in equivalent series resistance (ESR) was large. After the accelerated test, the characteristics of the capacitor of Comparative Example 1 were significantly degraded. In Comparative Example 1, the amount of weight loss was small because the liquid containing polyalkylene glycol was not contained in the exterior body.

In Comparative Examples 2 to 10 and Examples 1 to 15, a liquid containing a high concentration of polyethylene glycol was contained in the outer package.
In Comparative Examples 2 to 9, the rate of change in capacitance (Cap.) was large, the rate of change in tangent of loss angle (tan δ) was large, and the rate of change in equivalent series resistance (ESR) was large. The rate of change in capacitance (Cap.) in Comparative Example 10 was large. That is, the characteristics of the capacitors of Comparative Examples 2 to 10 were significantly degraded. Furthermore, the amount of weight loss in Comparative Examples 2 to 10 was large. Since the polyethylene glycol-containing liquid of Comparative Example 2 did not contain an antioxidant, it is thought that a large amount of polyethylene glycol evaporated. The polyethylene glycol-containing liquids of Comparative Examples 3 to 10 contain antioxidants, but the antioxidants (monohydroxybenzene, dihydroxybenzene, trihydroxybenzene) of Comparative Examples 3 to 10 affect the evaporation of polyethylene glycol and the characteristics of the capacitor. It turned out that the decline could not be suppressed.

The rate of change in capacitance (Cap.) of Examples 1 to 17 is as small as 15% or less, and the rate of change in tangent of loss angle (tan δ) as small as 20% or less (-20% to 20%), and The rate of change in equivalent series resistance (ESR) was small, less than 70%. Further, the amount of weight change in Examples 1 to 17 was suppressed to 30 mg or less. In Examples 1 to 17, compared to Examples j to x of Experiment 1, the amount of liquid containing polyethylene glycol used was smaller, and under the heating condition of heating at 180 ° C. for 24 hours, Examples j to x of Experiment 1 It evaporates more easily. However, in Examples 1 to 17, as in Examples j to x of Experiment 1, the amount of weight change of the liquid containing polyethylene glycol was small.
From the above results, it can be seen that the decrease in the weight change of the liquid containing polyethylene glycol was suppressed, thereby suppressing the decrease in capacitor characteristics such as capacitance.
Furthermore, in Examples 1 to 17, good results were obtained despite the use of solutions containing a high concentration of polyethylene glycol, which easily evaporates.
From this, it was found that the antioxidants used in Examples 1 to 17 (bisphenol, trisphenol, tetrakisphenol, etc. having two or more phenol structures) caused evaporation of the liquid containing polyethylene glycol and a long-term deterioration of the capacitor properties. It was found that it was possible to suppress

In Examples 8 to 11, a compound having two or more phenol structures and a sulfur atom (a hybrid type having the functions of both a phenolic antioxidant and a sulfur antioxidant) was used as the antioxidant. . Good results were also obtained with this antioxidant.
In Examples 12 to 15, both a phenolic antioxidant and a sulfur antioxidant were used (non-hybrid type). Good results were also obtained in this case.
From the above, it was found that even when a phenolic antioxidant and a sulfur-based antioxidant are combined, evaporation of a solution containing polyethylene glycol and deterioration of capacitor characteristics over a long period of time can be suppressed. In addition, even when using a compound (hybrid type) that has the functions of both a phenolic antioxidant and a sulfur-based antioxidant, two types of antioxidants are used: a phenolic antioxidant and a sulfur-based antioxidant. (non-hybrid type), it was found that good effects can be obtained even when

In Example 16, the same antioxidant as in Example 9 (Example r of Experiment 1) was used, but PEG300 (polyethylene glycol with a number average molecular weight of 300) was used as the polyethylene glycol. The polyethylene glycol (PEG300) used in Example 16 evaporates more easily than the polyethylene glycol (PEG400 (polyethylene glycol having a number average molecular weight of 400)) used in Example 9. Nevertheless, the amount of weight change in Example 16 was small. Furthermore, the rate of change in capacitance (Cap.), the rate of change in tangent of loss angle (tan δ), and the rate of change in equivalent series resistance (ESR) in Example 16 were small.
From this, it was found that even when polyethylene glycol (PEG300), which evaporates more easily, is used, the antioxidant can suppress the evaporation of the liquid containing polyethylene glycol and the deterioration of the capacitor's characteristics over a long period of time.

In Example 17, the same antioxidant as in Example 9 (Example r of Experiment 1) was used, but the proportion of polyethylene glycol (40 wt%) was lower than in Example 9. The solution of Example 17 contains 50 wt% of ethylene glycol, which has a lower boiling point than polyethylene glycol (PEG400), so under heating conditions of 180°C, the solution of Example 17 evaporates more than the solution of Example 9. Cheap. However, the amount of weight change in Example 17 was small. Further, the rate of change in capacitance (Cap.), the rate of change in tangent of loss angle (tan δ), and the rate of change in equivalent series resistance (ESR) in Example 17 were small.
From this, it was found that even when using a solution that easily evaporates with a small proportion of polyethylene glycol, it is possible to suppress the evaporation of the liquid containing polyethylene glycol and the long-term deterioration of the characteristics of the capacitor.

According to the above experiments 1 and 2, the transpiration of polyethylene glycol and/or its derivatives was reduced by containing a phenolic antioxidant containing a compound having two or more phenol structures in a liquid containing polyethylene glycol and/or its derivatives. It turns out that things can be suppressed. It has also been found that it is possible to prevent the liquid containing polyethylene glycol and/or its derivative from disappearing from the capacitor at an early stage. It has been found that this allows the deterioration of capacitor characteristics to be suppressed over a long period of time.

Furthermore, it has been found that the above effects can also be obtained when a sulfur antioxidant is used together with the phenolic antioxidant. Also, when using an antioxidant that has the functions of both a phenolic antioxidant and a sulfur antioxidant, specifically, a compound that has two or more phenol structures and sulfur in one molecule, It was found that the above effects can be obtained.
It has also been found that the above effects can be enhanced when these antioxidants are used.

In addition, from the above experiments 1 and 2, when (1) a phenolic antioxidant containing a compound having two or more phenol structures is used as an antioxidant, (2) the above phenolic antioxidant and sulfur oxidation It has been found that the above effects can be obtained when an inhibitor is used and (3) when a compound having two or more phenol structures and sulfur in one molecule is used. From this, it is considered that the above effects can be obtained even when the above (2) and (3) are combined. A case in which the above (2) and (3) are combined is (4) a case in which a compound having two or more phenol structures and sulfur in one molecule and a sulfur antioxidant is used, and (5) a case in which a sulfur antioxidant is used. This is a case where a compound having two or more phenol structures and sulfur in one molecule, a sulfur antioxidant, and a compound having two or more phenol structures are used.

The antioxidant of the present invention is not limited to the compounds used in the above experiments.
For example, in the above experiments, bisphenol having two phenol structures, trisphenol having three phenol structures, or tetrakisphenol having four phenol structures was used as the phenolic antioxidant (Examples 1 to 17). . However, compounds having five or more phenolic structures may also be used. Even when a compound having five or more phenol structures is used, the same effects as above can be obtained.

Furthermore, in the above experiments, compounds having two phenol structures and a thioether structure were used as compounds having two or more phenol structures and sulfur (Examples 8 to 11, 16, and 17). However, the antioxidant of the present invention is not limited to this antioxidant. For example, a compound having three or more phenol structures and sulfur may be used as an antioxidant. Furthermore, a compound having two or more phenol structures and thiol structures may be used as the antioxidant. Even when these compounds are used, effects similar to those described above can be obtained.

Furthermore, in the above experiment, in Examples 12 to 15 in which a phenolic antioxidant and a sulfur-based antioxidant were used, bisphenol having two phenol structures was used as the phenolic antioxidant. However, the phenolic antioxidant used together with the sulfur-based antioxidant may be a compound having three or more phenol structures. Further, the phenolic antioxidant added together with the sulfur-based antioxidant may be a bisphenol other than 2,2'-methylenebis-(6-tert-butyl-m-cresol). In addition to these, compounds having two or more phenol structures and sulfur in one molecule may be used. Further, a compound having two or more phenol structures and sulfur in one molecule may be used together with the sulfur-based antioxidant. Even when these compounds are used, effects similar to those described above can be obtained.

In the above experiment, 2-mercaptobenzimidazole, 2-mercaptothiazoline, 2-mercaptobenzothiazole, or didodecyl 3,3'-thiodipropionate was used as the sulfur-based antioxidant added together with the phenolic antioxidant. was used (Examples 12 to 15). However, the sulfur-based antioxidant added together with the phenolic antioxidant is not limited to the above compounds. For example, derivatives of the above compounds may be used. Furthermore, 3,3'-thiodipropionate diesters other than didodecyl 3,3'-thiodipropionate may be used. Also, mercaptothiazole and/or its derivatives may be used. Even when these compounds are used, effects similar to those described above can be obtained.

Furthermore, in the above experiment, a case was explained in which polyethylene glycol was used as the polyalkylene glycol. However, the same effects as above can be obtained also when other polyalkylene glycols are used. Further, the same effects as above can be obtained also when a derivative of polyalkylene glycol is used. Further, even when one or more types of polyalkylene glycol and/or one or more types of polyalkylene glycol derivatives are used, the same effects as described above can be obtained. Furthermore, the same effects as above can be obtained when polyglycerin and/or one or more derivatives of polyglycerin are used. Furthermore, the same effects as above can be obtained when at least one selected from the group consisting of one or more polyalkylene glycols, polyglycerin, and derivatives thereof.

Although the embodiments of the present invention have been described above based on examples, it should be understood that the specific configuration is not limited to these embodiments. The scope of the present invention is indicated by the claims rather than the above description, and includes all changes within the meaning and scope equivalent to the claims.

For example, in the above experiment, a solid electrolytic capacitor with a rated voltage of 20 WV, a rated capacitance of 150 μF, and a product size of φ8 x 7 L (mm) was produced, but the rated voltage, rated capacitance, and product size of the solid electrolytic capacitor of the present invention is not limited to the above.

1 Electrolytic capacitor 2 Exterior case 3 Sealing body 4 Exterior body 5 Capacitor element 11 Anode 12 Cathode 21, 22 Lead terminal

Claims (8)

A capacitor element having an anode having a dielectric oxide film, a cathode, a separator disposed between the anode and the cathode, and a conductive polymer layer formed on the dielectric oxide film, and the capacitor. An electrolytic capacitor comprising an exterior body in which an element is housed,
A liquid containing at least one of polyalkylene glycol, polyglycerin, and derivatives thereof and an antioxidant is housed in the exterior body together with the capacitor element,
The antioxidant includes a phenolic antioxidant,
An electrolytic capacitor, wherein the phenolic antioxidant is a compound having two or more phenol structures. The electrolytic capacitor according to claim 1, wherein the phenolic antioxidant is a compound having a phenol structure of 2 or more and 4 or less. 3. The electrolytic capacitor according to claim 1, wherein the antioxidant includes a sulfur-based antioxidant. The sulfur-based antioxidant is selected from mercaptothiazole and its derivatives, mercaptobenzothiazole and its derivatives, mercaptobenzimidazole and its derivatives, mercaptothiazoline and its derivatives, and 3,3'-thiodipropionic acid diester. The electrolytic capacitor according to claim 3, characterized in that the electrolytic capacitor is at least one type. 5. The electrolytic capacitor according to claim 1, wherein the compound having two or more phenol structures contains a sulfur atom. 6. The electrolytic capacitor according to claim 5, wherein the compound having two or more phenol structures has a thioether bond or a thiol bond. 7. The electrolytic capacitor according to claim 5, wherein in the compound having two or more phenol structures, the phenol structure is bonded to a sulfur atom. 7. The electrolytic capacitor according to claim 5, wherein in the compound having two or more phenol structures, the phenol structure is bonded to a sulfur atom via a hydrocarbon group.

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