JP2003203827A - Electrolytic solution for electrolytic capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrolytic capacitor having high withstand voltage and high reliability by making electrolytic capacitor contain inorganic oxide colloidal particle surface modified with organic to electrolytic solution. <P>SOLUTION: The electrolytic solution for the electrolytic capacitor is comprised of inorganic colloidal particle in the mean particle size range of 5-100 nm, surface modified with solvent, solute and organic. The electrolytic solution for the electrolytic capacitor, which is represented by particular general formula, is also a silylation agent or a silane coupling agent and is an electrolytic solution for the electrolytic capacitor, in which the inorganic colloidal particle is silica, the solvent is an organic solvent containing ethylene glycol or γ- butyrolactone mainly, and the solute is an onium compound of organic and/or inorganic acid. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an electrolytic solution for an electrolytic capacitor. More specifically, the present invention relates to an electrolytic solution for an electrolytic capacitor, which can provide an electrolytic capacitor having high withstand voltage and high reliability by containing inorganic oxide colloidal particles whose surface is modified with an organic substance.

[0002]

2. Description of the Related Art In an electrolytic capacitor, a so-called valve metal capable of forming an insulating oxide film layer such as aluminum or tantalum is used as an anode, and the surface of the insulating oxide film is made into a dielectric material by anodizing treatment or the like. The one formed as a layer is used for the anode electrode. And as an example of this, FIG.
A wound-type device structure as illustrated in Fig. 1 is generally known, in which a cathode side electrode (2) is arranged so as to face the anode side electrode (1), and a separator ( 3) is interposed to hold the electrolytic solution in this separator. This is put in an outer case (5) made of a material such as aluminum as shown in FIG. 2, and the case is inserted through a rubber packing (6) of butyl rubber, ethylene propylene rubber, silicone rubber or the like, a phenol resin laminate, polypropylene, polyphenylene. The structure is hermetically sealed using a sealing plate (7) such as sulfide.

In an aluminum electrolytic capacitor using aluminum oxide as a dielectric, the anode electrode is usually etched to increase the surface area. The electrolytic solution comes into close contact with the uneven surface of the anode side electrode and functions as a substantial cathode that transmits the electric field of the cathode side electrode. Therefore, the electrical conductivity, temperature characteristics, etc. of the electrolytic solution are the electrical characteristics of the electrolytic capacitor [impedance, dielectric loss (tan
δ), equivalent series resistance (ESR), etc.]. Further, the electrolytic solution is required to have a role (formability) of repairing deterioration and damage of the insulating oxide thin film, which affects the leakage current (LC) and life characteristics of the electrolytic capacitor. As described above, the electrolytic solution is an important component that influences the characteristics of the electrolytic capacitor.

The electric conductivity of the electrolytic solution is directly related to the energy loss and the impedance characteristics of the electrolytic capacitor, and therefore the electrolytic solution having a high electric conductivity is preferable.
On the other hand, due to the increasing demand for safety, an electrolytic capacitor with a higher withstand voltage is provided to prevent short circuit and ignition even under severe conditions where an abnormal voltage exceeding the rated voltage is applied to the electrolytic capacitor. It has been demanded. However, generally, when the electric conductivity of the electrolytic solution used increases, the withstand voltage of the electrolytic capacitor tends to decrease, which makes the development of the electrolytic capacitor difficult (Ue et al., New Capacitor, Vol. 3, 55). page,
1996). Therefore, as an attempt to obtain an electrolytic capacitor having a high withstand voltage while using an electrolytic solution having a high electrical conductivity, it has been considered to add various inorganic oxide colloidal particles to the electrolytic solution to improve the withstand voltage. There is.

For example, it has been proposed to add colloidal silica particles to an electrolytic solution to increase the withstand voltage while maintaining a high electrical conductivity of the electrolytic solution (Japanese Patent Laid-Open No. HEI-1).
No. 232713). In addition to silica, alumina (JP-A-4-145612), zirconia (JP-A-4-145613), titania (JP-A4-1).
45616), aluminosilicate (Japanese Patent Laid-Open No. 6-
283388), aluminosilicate-coated silica (JP-A-6-349684), and the like have also been proposed to be added.

[0006]

[Patent Document 1] JP-A-1-232713

[Patent Document 2] Japanese Unexamined Patent Publication No. 4-145612

[Patent Document 3] Japanese Patent Application Laid-Open No. 4-145613

[Patent Document 4] JP-A-4-145616

[Patent Document 5] Japanese Patent Laid-Open No. 6-283388

[Patent Document 6] JP-A-6-349684

[Non-Patent Document 1] Ue et al., New capacitor, 3 volumes, 5
Page 5, 1996

[0007]

However, although the electrolytic solution containing these inorganic oxide colloidal particles has a high initial withstand voltage, there is a problem that the withstand voltage is lowered during the life test and a short circuit occurs. It was Further, this phenomenon of withstanding voltage reduction was remarkable especially in the case of an electrolytic solution using polyvalent ions such as dicarboxylic acid as a solute.

[0008]

[Means for Solving the Problems] As a phenomenon common to these electrolytic solutions in which the withstand voltage decreases, gelation of the electrolyte solution and precipitation of inorganic oxides are confirmed during the life test, and the effect of improving the withstand voltage is prolonged. It was found that the added inorganic oxide colloidal particles need to maintain a stable colloidal state without causing gelation or precipitation in order to maintain the time. For the above purpose, as a result of diligent studies, it was found that the inorganic oxide colloidal particles surface-modified with an organic substance are much less likely to cause gelation or precipitation in the electrolytic solution for capacitors than conventional inorganic oxide colloidal particles. Completed the invention. That is,
The present invention relates to an electrolytic solution for an electrolytic capacitor, which is characterized by realizing an electrolytic capacitor which can maintain a high withstand voltage at high temperature for a long time by using an electrolytic solution containing inorganic oxide colloidal particles whose surface is modified with an organic substance. Is.

[0009]

By modifying the surface of the inorganic oxide colloidal particles with an organic substance, the affinity with the organic solvent is improved, the aggregation of the particles is prevented, and gelation or precipitation does not occur even when left at high temperature for a long time. Therefore, the effect of improving the withstand voltage of the inorganic oxide colloidal particles in the electrolytic capacitor can be maintained for a long time.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.
Examples of the organic substance for surface-modifying the inorganic oxide colloidal particles used in the present invention include various polymer compounds such as silylating agents, silane coupling agents, titanate coupling agents, aluminum coupling agents, alcohols, and latexes. be able to.

The silylating agent and the silane coupling agent are represented by the following general formula (1).

[Chemical 2] [Wherein, X _{1 to} X ₃ are an alkyl group, an alkenyl group, an aryl group or an aralkyl group having 1 to 20 carbon atoms, and a part of hydrogen thereof is a carboxyl group, an ester group, an amide group, a cyano group, Ketone group, formyl group, ether group, hydroxyl group, amino group, mercapto group, sulfide group,
At least one selected from the group consisting of a sulfoxide group, a hydrocarbon group (—R) optionally substituted with a sulfone group, an oxyhydrocarbon group (—OR), and a hydroxyl group (—OH), which may be different from each other. good. X ₄ has 1 to 20 carbon atoms
Is an alkoxy group or a hydroxyl group. ]

Specific examples of X _{1 to} X ₃ include a methyl group,
Alkyl groups such as ethyl group, propyl group, butyl group, decyl group and octadecyl group; alkenyl groups such as vinyl group and allyl group; aryl groups such as phenyl group and naphthyl group; aralkyl such as benzyl group and phenethyl group Hydrocarbon groups such as groups, methoxy groups, ethoxy groups, propoxy groups, butoxy groups, vinyloxy groups, phenoxy groups,
An oxyhydrocarbon group such as a benzyloxy group or a hydroxyl group can be mentioned. Furthermore, as an example of having a substituent, acryl groups such as 3-methacryloxypropyl group; 3-glycidoxypropyl group, 2- (3,4
-Epoxy groups such as epoxycyclohexyl) ethyl group; amino groups such as 3-aminopropyl group, N-phenyl-3-aminopropyl group, N- (2-aminoethyl) -3-aminopropyl group; 3- Examples thereof include mercapto groups such as mercaptopropyl group. X ₄
As specific examples of, alkoxy groups such as methoxy group, ethoxy group, propoxy group, butoxy group; hydroxyl group can be mentioned.

Among these combinations, methyltrimethoxysilane, methyltriethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, diphenyldimethoxysilane, diphenyldiethoxysilane, isobutyltrimethoxysilane. , Isobutyltriethoxysilane, decyltrimethoxysilane, decyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-glycidoxypropyl Trimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3
-Glycidoxypropylmethyldimethoxysilane, 3-
Glycidoxypropylmethyldiethoxysilane, 2-
(3,4-Epoxycyclohexyl) ethyltritrimethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltritriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-phenyl-3- Aminopropyltrimethoxysilane, N-phenyl-3-aminopropyltriethoxysilane, N- (2-aminoethyl) -3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropyltriethoxy Silane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane and the like are preferable, and among them, 3-glycidoxypropyl group having a 3-glycidoxypropyl group having a good affinity with a solvent such as ethylene glycol or γ-butyrolactone. Le trimethoxysilane, 3-glycidoxypropyl triethoxysilane, 3-glycidoxypropyl methyl dimethoxysilane, 3-glycidoxypropyl methyl diethoxy silane is particularly preferred.

Specific examples of titanate coupling agents include isopropyltriisostearoyl titanate,
Isopropyltridodecylbenzenesulfonyl titanate, isopropyl tris (dioctyl pyrophosphate) titanate, tetraisopropyl bis (dioctyl phosphite) titanate, tetraoctyl bis (ditridecyl phosphite) titanate, tetra (2,2-
Diallyloxymethyl-1-butyl) bis (ditridecyl) phosphite titanate, bis (dioctylpyrophosphate) oxyacetate titanate, isopropyl trioctanoyl titanate, isopropyl dimethacloyl isostearoyl titanate, isopropyl tri (dioctyl phosphate) titanate, isopropyl tric Milphenyl titanate, isopropyl tri (N
-Aminoethylaminoethyl) titanate and the like.

Specific examples of the aluminum-based coupling agent include aluminum ethylacetoacetate diisopropylate, aluminum tris (ethylacetoacetate), aluminum tris (acetylacetonate), aluminum bis (ethylacetoacetate) monoacetylacetonate and the like. Is mentioned. Specific examples of the alcohol include methanol, ethanol, n-propanol, iso-propanol, n-butanol, amyl alcohol, 4-methyl-2-pentanol, n-.
Heptanol, n-octanol, 2-ethylhexanol, nonanol, decanol, tridecanol, 2-
Methoxyethanol, 2-ethoxyethanol, 2-butoxyethanol, 3-methoxybutanol, 3-methyl-3-methoxybutanol, polyvinyl alcohol and the like can be mentioned.

The organic substances used for surface modification such as these silylating agents, silane coupling agents, titanate coupling agents, aluminum coupling agents, alcohols and various polymer compounds are used alone or in combination of a plurality thereof. be able to. Specific examples of the inorganic oxide colloidal particles used in the present invention include silica, alumina, titania, zirconia, antimony oxide, aluminosilicate, silica zirconia, titania zirconia, aluminosilicate-coated silica, silica-zirconia-coated silica and the like, or a mixture thereof. Can be mentioned. Among them, silica, aluminosilicate, and aluminosilicate-coated silica are particularly preferable from the viewpoint of easiness of silylation treatment, stability of colloid, and effect of improving withstand voltage.

The average particle size of the inorganic oxide colloidal particles is preferably in the range of 5 to 100 nm, more preferably 10 to 50 nm. If the particle size of the inorganic oxide colloidal particles is too small, gelation of the electrolytic solution is likely to occur, and if too large, precipitation is likely to occur, making it difficult to form a stable colloid. The inorganic oxide colloidal particles surface-modified with the silylating agent or the silane coupling agent used in the present invention can be obtained, for example, by the method described in US Pat. No. 4,027,073. The alcohol-modified inorganic oxide colloidal particles used in the present invention can be obtained, for example, by the method described in US Pat. No. 2,657,149.

The method of adding the inorganic oxide colloidal particles surface-modified with these organic substances is not particularly limited, but since they are almost insoluble in a solvent, they are generally prepared as a colloidal solution dispersed in a suitable dispersion medium. The method of adding to the electrolytic solution is preferable. Here, the dispersion medium is not particularly limited, but if ethylene glycol or the like as the above-mentioned solvent is used, there is little influence on the characteristics of the basic electrolytic solution and the diffusion into the electrolytic solution is easy. The amount of the inorganic oxide colloid particles added is preferably 0.5 to 18 of the electrolytic solution.
% By weight, particularly preferably 6 to 10% by weight. If the amount of the inorganic oxide colloid particles added is too small, the withstand voltage of the electrolytic solution will not increase sufficiently, and if it is too large, gelation or precipitation will occur easily, and a stable colloid will not be formed easily.

Since the silane coupling agent has a reactive functional group, it chemically reacts with the solvent or solute used when the inorganic oxide colloidal particles are subjected to the modification treatment or after the modification treatment. However, there is no particular problem in the present invention. For example, when 3-glycidoxypropyltrimethoxysilane is used as the silane coupling agent, the epoxy group may undergo hydrolysis or alcoholysis to open the ring, but this does not have any adverse effect.

Specific examples of the solvent used in the present invention include alcohol solvents such as ethylene glycol, glycerin and methyl cellosolve; lactone solvents such as γ-butyrolactone, γ-valerolactone and δ-valerolactone; N-
Methylformamide, N-ethylformamide, N, N
An amide solvent such as dimethylformamide, N, N-dimethylacetamide or N-methylpyrrolidinone; a carbonate solvent such as ethylene carbonate, propylene carbonate or butylene carbonate; a nitrile solvent such as 3-methoxypropionitrile or glutaronitrile;
Examples thereof include phosphate ester solvents such as trimethyl phosphate and triethyl phosphate, and mixtures thereof. Among them, ethylene glycol and γ-butyrolactone, which are organic solvents having a large dissolving power for various solutes and capable of obtaining an electrolytic solution having excellent temperature characteristics, are preferable.

Organic acid used as solute in the present invention and /
Specific examples of the organic acid component used in the onium salt of an inorganic acid include benzoic acid, toluic acid, cumic acid, t
-Aromatic monocarboxylic acids such as butylbenzoic acid, salicylic acid, and anisic acid; formic acid, acetic acid, propionic acid, 7-phenyl-7-methoxy-1-octanecarboxylic acid, 6-
Aliphatic monocarboxylic acids such as phenyl-6-methoxy-1-heptanecarboxylic acid; aromatic dicarboxylic acids such as phthalic acid, 4-methylphthalic acid, 4-nitrophthalic acid;
Maleic acid, citraconic acid, dimethyl maleic acid, 1,
Unsaturated aliphatic dicarboxylic acids such as 2-cyclohexene dicarboxylic acid; oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, tridecane Linear saturated aliphatic dicarboxylic acids such as diacids;
Dimethylmalonic acid, diethylmalonic acid, dipropylmalonic acid, 2-methylglutaric acid, 3-methylglutaric acid,
3,3-dimethylglutaric acid, 3-methyladipic acid,
2,2,4-trimethyladipic acid, 2,4,4-trimethyladipic acid, 1,6-decanedicarboxylic acid, 5,
6-decanedicarboxylic acid, 1,7-octanedicarboxylic acid, 7-methyl-7-carbomethoxy-1,9-decanedicarboxylic acid, 2,8-nonanedicarboxylic acid, 7,8,
11,12-Tetramethyl-1,18-octadecanedicarboxylic acid, 1-methyl-3-ethyl-1,7-heptanedicarboxylic acid, 1,3-dimethyl-1,7-heptanedicarboxylic acid, 5-methyl-1 , 7-Octanedicarboxylic acid, 7,12-dimethyl-1,18-octadecanedicarboxylic acid, 7-ethyl-1,16-hexadecanedicarboxylic acid, 7,8-dimethyl-1,14-tetradecanedicarboxylic acid, 1,6 -Heptanedicarboxylic acid, 6-methyl-6-carbomethoxy-1,8-nonanedicarboxylic acid, 1,8-nonanedicarboxylic acid, 8-methyl-8-carbomethoxy-1,10-undecanedicarboxylic acid, 6
-Saturated aliphatic dicarboxylic acids having a branched chain such as ethyl-1,4-tetradecanedicarboxylic acid and cyclohexanedicarboxylic acid; 7-methyl-1,7,9-decanetricarboxylic acid, 6-methyl-1,6,8- Examples thereof include tricarboxylic acids such as nonanetricarboxylic acid, 8-methyl-1,8,10-undecanetricarboxylic acid, and the like, or a mixture thereof. Specific examples of the inorganic acid component include boric acid and phosphoric acid.

Among the above-mentioned organic acid components and inorganic acid components, phthalic acid, maleic acid, benzoic acid, and adipic acid are preferable for low-voltage capacitors having a rated voltage of 100 V or less, because an electrolytic solution having a high electric conductivity can be obtained. Rated voltage 300
For high voltage capacitors of V or higher, azelaic acid, sebacic acid, 1,6-decanedicarboxylic acid, 1,7-octanedicarboxylic acid, and boric acid, which can obtain an electrolytic solution having a high withstand voltage, are preferable. Benzoic acid, adipic acid, and azelaic acid are preferable for medium-voltage capacitors having a rated voltage of more than 100 V and less than 300 V, which can provide an electrolytic solution having appropriate electric conductivity and withstand voltage.

Specific examples of onium salts include ammonium; methylammonium; dimethylammonium; tertiary ammonium such as trimethylammonium, ethyldimethylammonium, diethylmethylammonium, triethylammonium; tetramethylammonium;
Examples thereof include quaternary ammoniums such as triethylmethylammonium and tetraethylammonium, and the like or a mixture thereof.

Ammonia, which can obtain an electrolytic solution having a high withstand voltage in the combination of an ethylene glycol solvent and a dicarboxylic acid such as 1,6-decanedicarboxylic acid, is preferable for the medium- and high-voltage capacitors. For low voltage capacitors, an electrolyte with high electrical conductivity can be obtained by combining γ-butyrolactone solvent and phthalic acid.
2,3,4-Tetramethylimidazolinium, 1-ethyl-2,3-dimethylimidazolinium, tetramethylammonium, triethylmethylammonium and tetraethylammonium are preferred. The solute is preferably used in an amount of 5 to 30% by weight based on the total weight of the solvent and the solute.

Further, in the present invention, the electrolytic solution may contain water for the purpose of improving the chemical conversion property. The water content is preferably in the range of 0.01 to 30% by weight, more preferably 0.01 to 10% by weight. In addition, the electrolyte solution may further contain other additives, if necessary. Other additives include boric acid, boron compounds such as boric acid and complex compounds of polyhydric alcohols (ethylene glycol, mannitol, sorbitol, etc.); phosphoric acid, acidic phosphoric acid esters [dibutyl phosphate, phosphorus Acid bis (2-ethylhexyl)], acidic phosphonates [2-ethylhexylphosphonic acid (2-ethylhexyl) and the like] phosphorus compounds; p-nitrobenzoic acid, nitro compounds such as m-nitroacetophenone and the like. To be The electrolytic solution of the present invention can be used, for example, in a wound-type aluminum electrolytic capacitor shown in FIGS. 1 and 2, and the electrolytic solution is a separator (also referred to as a spacer) indicated by 3 in the drawings.
Is impregnated into. Kraft paper, Manila paper, etc. are generally used as the separator.

[0026]

EXAMPLES The present invention will be specifically described below based on examples, but the present invention is not limited to these examples. In Table 1 (No. 1 and No. 2), the electrolytic solution of the present invention using silica colloid particles whose surface is modified with an organic substance,
Table 2 (No. 1 and No. 2) shows the electric conductivity and the withstand voltage at 25 ° C. of the electrolytic solution using the ordinary silica colloidal particles which are not surface-modified with organic substances. In the table, the use amount and the addition amount of each component are shown in parts by weight when the total of the solvent and the solute is 100 unless otherwise specified.

As the inorganic oxide colloidal particles, silica particles having an average particle size of about 12 nm are used as they are (comparative example) or by using 3-glycidoxypropyltrimethoxysilane represented by the following general formula (2). Modified (Example,
Reference example) was used. Ethylene glycol was used as a dispersion medium for the colloid, and the colloid was added to the basic electrolytic solution (solute and solvent) to prepare an electrolytic solution having a predetermined composition.

[Chemical 3]

The withstand voltage is the voltage value at which spike or scintillation is first observed in the voltage-time rise curve when the spiral wound element shown in FIG. 1 is impregnated and a constant current is applied thereto. And The specifications of the aluminum electrolytic capacitor elements used in Examples 1 to 4 and Comparative Examples 1 to 4 have a rated voltage of 450 V and a rated capacitance of 10 μF. The specifications of the aluminum electrolytic capacitor elements used in Examples 5 to 9, Reference Examples 1 and 2, and Comparative Examples 5 to 11 are those having a rated voltage of 200 V and a rated capacitance of 68 μF. The current value applied in the withstand voltage measurement was 3 mA,
It is 10 mA. From the experimental results shown in Tables 1 and 2, it can be seen that the electrolytic solution of the present invention has an electric conductivity equivalent to that of the conventional electrolytic solution and a higher withstand voltage.

[0029]

[Table 1]

[0030]

[Table 2]

[0031]

[Table 3]

[0032]

[Table 4]

In Table 3, aluminum electrolytic capacitors having a rated voltage of 450 V and a capacitance of 10 μF were prepared by using the electrolytic solutions of Examples 1 and 2 of the present invention and conventional Comparative Examples 1 and 2.
The results obtained when a high temperature load test was performed at 1000C for 1000 hours are shown. As can be seen from the experimental results in Table 3, the electrolytic capacitor of the present invention maintained the initial value even after the high temperature load test. On the other hand, in the conventional electrolytic capacitor, many short-circuited products were generated during the high temperature load test due to the decrease in withstand voltage, and there was a problem in reliability. In Table 4, these electrolytes were sealed in vial tubes,
The number of days until gelation when heated at 115 ° C. is shown. It can be seen that the electrolytic solution of the present invention is extremely difficult to gel as compared with the conventional electrolytic solution.

[0034]

By using the electrolytic solution of the present invention, an electrolytic capacitor with lower loss and higher rated voltage can be realized,
Great industrial value.

[Brief description of drawings]

FIG. 1 is a perspective view of a wound type element of an electrolytic capacitor.

FIG. 2 is a sectional view of an electrolytic capacitor.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Masayuki Takeda             8-3-1 Chuo, Ami-cho, Inashiki-gun, Ibaraki Prefecture             Mitsubishi Chemical Corporation Tsukuba Research Center (72) Inventor Takato Ito             1 of 167-1, Higashi-Ome, Ome-shi, Tokyo             Within Nippon Chemi-Con Co., Ltd. (72) Inventor Makoto Shimizu             1 of 167-1, Higashi-Ome, Ome-shi, Tokyo             Within Nippon Chemi-Con Co., Ltd. (72) Inventor Kyoko Fukui             1 of 167-1, Higashi-Ome, Ome-shi, Tokyo             Within Nippon Chemi-Con Co., Ltd.

Claims (11)

[Claims] 1. An electrolytic solution for an electrolytic capacitor comprising inorganic oxide colloidal particles having an average particle size in the range of 5 to 100 nm, which is surface-modified with a solvent, a solute and an organic substance. 2. The electrolytic solution for an electrolytic capacitor according to claim 1, wherein the organic substance is a silylating agent or a silane coupling agent represented by the following general formula (1). [Chemical 1] [Wherein, X _{1 to} X ₃ are an alkyl group, an alkenyl group, an aryl group or an aralkyl group having 1 to 20 carbon atoms, and a part of hydrogen thereof is a carboxyl group, an ester group, an amide group, a cyano group, Ketone group, formyl group, ether group, hydroxyl group, amino group, mercapto group, sulfide group,
At least one selected from the group consisting of a sulfoxide group, a hydrocarbon group (—R) optionally substituted with a sulfone group, an oxyhydrocarbon group (—OR), and a hydroxyl group (—OH), which may be different from each other. good. X ₄ has 1 to 20 carbon atoms
Is an alkoxy group or a hydroxyl group. ] 3. The silylating agent or silane coupling agent represented by the general formula (1) is 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyl. The electrolytic solution for an electrolytic capacitor according to claim 2, which is one or more selected from dimethoxysilane and 3-glycidoxypropylmethyldiethoxysilane. 4. The electrolytic solution for an electrolytic capacitor according to claim 1, wherein the inorganic oxide colloidal particles are silica. 5. The electrolytic solution for an electrolytic capacitor according to claim 1, wherein the solvent is an organic solvent mainly containing ethylene glycol or γ-butyrolactone. 6. The electrolytic solution for an electrolytic capacitor according to claim 1, wherein the solute is an onium salt of an organic acid and / or an inorganic acid (excluding amidinium salt). 7. The organic acid is 1,6-decanedicarboxylic acid,
The electrolytic solution for an electrolytic capacitor according to claim 6, which is at least one selected from 1,7-octanedicarboxylic acid, adipic acid, benzoic acid, phthalic acid and maleic acid. 8. The electrolytic solution for an electrolytic capacitor according to claim 6, wherein the inorganic acid is boric acid. 9. The electrolytic solution for an electrolytic capacitor according to claim 6, wherein the onium salt is at least one selected from the group consisting of ammonium salts, tertiary ammonium salts and quaternary ammonium salts. 10. The solvent according to claim 1, wherein the solvent is a solvent mainly composed of ethylene glycol, the solute is an ammonium salt of an organic acid, and the inorganic oxide colloidal particles surface-modified with an organic substance are silica particles surface-treated with a silane coupling agent. Electrolytic solution for electrolytic capacitors. 11. A solvent mainly comprising γ-butyrolactone, a solute is a tertiary ammonium salt or a quaternary ammonium salt of an organic acid, and inorganic oxide colloidal particles surface-modified with an organic material are surface-treated with a silane coupling agent. The electrolytic solution for an electrolytic capacitor according to claim 1, which is silica particles.