JPH0888147A - Electolytic capacitor and electrolyte for the same - Google Patents

Abstract

PURPOSE: To make high the sparking voltage of an anodized film by inhibiting sparks, which are generated from an interface, and to stabilize the anodized film by a method wherein an electrolyte contains the quaternary ammonium of an aliphatic hydroxy acid, at least one kind of a compound selected from between an organic phosphine compound and a surface active agent and an organic solvent. CONSTITUTION: At least one kind of a compound selected from an organic phosphine compound and a surface-active agent is compounded in quaternary ammonium of an aliphatic hydroxy acid. An electrolyte is prepared by dissolving these components in an organic solvent. Thereby, an electrolyte, which can provide an anodized film which has a low specific resistance, has a high sparking voltage and is superior in withstand voltage characteristics, and a highly reliable electrolytic capacitor provided with this electrolyte can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrolytic solution for electrolytic capacitors and an electrolytic capacitor provided with this electrolytic solution.

[0002]

2. Description of the Related Art Generally, an electrolytic capacitor has a structure in which a strip-shaped aluminum foil having an oxide film formed on its surface by anodization and a counter electrode are wound with a separator paper sandwiched between them and the separator paper is impregnated with an electrolytic solution. Have. The electrolytic solution is required to have a low non-resistance so as to repair the oxide film and prevent itself from acting excessively as a resistance component. In addition, the repaired oxide film has excellent withstand voltage characteristics,
That is, it is desired to improve the spark voltage of the electrolytic solution.

By the way, as the electrolytic solution for the electrolytic capacitor, there has been known a solution obtained by dissolving a quaternary ammonium of an aliphatic oxyacid in an organic solvent as disclosed in Japanese Patent Application Laid-Open No. 2-63110. The electrolytic solution for an electrolytic capacitor containing such a quaternary ammonium of an aliphatic oxyacid has a characteristic that the specific resistance is reduced.

However, the electrolytic solution for electrolytic capacitors has a problem that the spark voltage is low, the spark voltage is unstable, and sparks are concentrated on the interface between the electrolytic solution and air. Therefore, in order to put the electrolytic solution containing the quaternary ammonium of the aliphatic oxyacid into practical use, it is necessary to increase the spark voltage and suppress the spark generated from the interface to stabilize the spark voltage. .

[0005]

DISCLOSURE OF THE INVENTION An object of the present invention is to improve the spark voltage by suppressing sparks generated from the interface, thereby stabilizing the electrolytic solution for electrolytic capacitors, and a high performance provided with this electrolytic solution. It is intended to provide a highly reliable electrolytic capacitor.

[0006]

The electrolytic solution for electrolytic capacitors according to the present invention comprises a quaternary ammonium of an aliphatic oxyacid, at least one compound selected from an organic phosphine compound and a surfactant, and an organic solvent. It is characterized by containing.

Examples of the aliphatic oxyacid include hydroxyacetic acid, lactic acid, malic acid, tartaric acid, citric acid and the like. Examples of the quaternary ammonium of this aliphatic oxyacid include tetramethylammonium, tetraerammonium, tetrapropylammonium, tetrabutylammonium, methyltriethylammonium, dimethyldiethylammonium, trimethylethylammonium, methyltripropylammonium and dimethyldipropylammonium. , Quaternary ammonium salts such as trimethylpropylammonium, dimethyldibutylammonium, trimethylbutylammonium, triethylpropylammonium, triethylbutylammonium, phenyltrimethylammonium, cyclohexyltrimethylammonium, benzyltrimethylammonium; N, N dimethylpyrrolidinium, N, N -Quaternary ammonium such as dimethylpiperidinium It can be mentioned quaternary ammonium salts such as N- ethyl-pyridinium; salt. Particularly, quaternary ammonium hydroxyacetic acid is effective because it can reduce the specific resistance of the electrolytic solution.

The quaternary ammonium of the aliphatic oxyacid can be added to the organic solvent until it is saturated and used. As the organic phosphine compound, for example, organic phosphine and its derivative can be used.
Examples of the organic phosphine include triphenylphosphine, tritolylphosphine, hydroxyphenyldiphenylphosphine, methyldiphenylphosphine, triethylphosphine, tributylphosphine, diphenylphosphine and phenylphosphine. Examples of the organic phosphine derivative include triphenylphosphine oxide, triphenylphosphine sulfide, triphenylphosphine selenide, trimethylphosphine oxide, methyldiphenylphosphine oxide, diphenylphosphine oxide, and ferlphosphine oxide.

The surfactant may be any of nonionic, cationic, anionic, amphoteric and the like as long as it is soluble in the organic solvent. However, it is preferable to avoid components such as halogen ions that impair the capacitor characteristics. Examples of such a surfactant include fluorine-based, silicone-based, and hydrocarbon-based surfactants, which have the same basic structure and are composed of a hydrophilic group portion and a hydrophobic group portion. The surfactant is classified into fluorine-based, silicone-based, etc. as described above depending on whether or not fluorine or silicone is used in the hydrophobic group portion, but any one may be used.

At least one compound selected from the organic phosphine compound and the surfactant is preferably contained in the electrolytic solution in an amount of 0.01 to 20% by weight.
If the content of the compound is less than 0.01% by weight, the compounding effect of those components cannot be sufficiently exhibited. On the other hand, if the content of the compound exceeds 20% by weight, the quaternary ammonium of the aliphatic oxyacid becomes difficult to dissolve in the organic solvent, and the resistivity of the electrolytic solution may increase. The more preferable content of the compound is 0.1 to 5% by weight.

Examples of the organic solvent include lactone solvents such as γ-butyrolactone, α-acetylbutyrolactone, β-butyrolactone, γ-valerolactone and δ-valerolactone; N-methylformamide, N, N-dimethylformamide, N -Ethylformamide, N, N-
Diethylformamide, N-methylacetamide, N,
Amide solvents such as N-dimethylacetamide, N, N-dimethylpropionamide, hexamethylphosphorylamide; ethylene carbonate, propylene carbonate,
Carbonate solvents such as butylene carbonate, dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate; nitrile solvents such as acetonitrile and propionitrile; phosphate ester solvents such as trimethyl phosphate; alcohol solvents such as ethylene glycol and methyl cellosolve; N-methyl. Pyrrolidinone, N-methyl-2-oxazolidinone, dimethyl sulfoxide, sulfolane, 1,3-dimethyl-2-imidazolidinone and the like can be mentioned, and these can be used alone or in the form of a mixture.

The electrolytic solution for electrolytic capacitors according to the present invention is permitted to contain at least one selected from phosphoric acid, organic phosphoric acid and salts thereof. These phosphoric acids and the like are preferably contained in the range of 0.01 to 10% by weight with respect to the total amount of the electrolytic solution. Further, the electrolyte solution is allowed to contain water. Water is preferably contained in the range of 0.01 to 10% by weight with respect to the total amount of the electrolytic solution.

An electrolytic capacitor according to the present invention comprises an electrolytic solution containing the above-mentioned quaternary ammonium of an aliphatic oxyacid, at least one compound selected from an organic phosphine compound and a surfactant, and an organic solvent. It is characterized by that.

In such an electrolytic capacitor, for example, a strip-shaped aluminum foil having an oxide film formed on its surface by anodic oxidation treatment and a counter electrode are wound with a separator paper sandwiched therebetween, and the separator paper is impregnated with an electrolytic solution having the above composition. It has a structured structure.

[0015]

According to the present invention, the specific resistance is reduced by dissolving the component in which the quaternary ammonium of the aliphatic oxyacid is mixed with at least one compound selected from the organic phosphine compound and the surfactant in the organic solvent. Further, the spark generated from the interface can be suppressed, and the spark voltage can be increased to, for example, 150 V or more and a stable electrolytic solution for an electrolytic capacitor can be provided.

The electrolytic solution according to the present invention has a characteristic that the specific resistance is low. A capacitor provided with this electrolytic solution has excellent high frequency characteristics. In addition, in order to miniaturize the capacitor, a method of increasing the surface area of the anode by performing fine etching on the anode is generally adopted, but the apparent resistance of the electrolyte solution increases as the fine processing of the anode progresses. Therefore, there is a limit to microfabrication.

On the other hand, since the electrolytic solution according to the present invention has a low specific resistance, the apparent resistance of the electrolytic solution is kept low even when the anode is finely etched, and as a result, the capacitor can be miniaturized.

Further, as described above, since the electrolytic solution according to the present invention has a high spark voltage and is stable, the capacitor provided with this electrolytic solution has excellent withstand voltage characteristics. further,
Since the electrolytic solution according to the present invention has excellent chemical stability, it is possible to improve reliability such as storage stability of the capacitor. Therefore, by providing the electrolytic solution having the above composition, a high performance and highly reliable electrolytic capacitor can be provided.

[0019]

EXAMPLES Examples of the present invention will be described in detail below. (Examples 1 to 6 and Comparative Examples 1 to 3) Nine kinds of electrolytic solutions for electrolytic capacitors having the compositions shown in Tables 1 and 2 below were prepared. However, γ-butyrolactone contains 3% by weight of water and 1% by weight of phosphoric acid.

The obtained Examples 1-6 and Comparative Examples 1-3
With respect to the electrolytic solution, the specific resistance, the spark voltage, and the presence or absence of spark generation at the interface were examined. The results are also shown in Tables 1 and 2. In addition, the measurement of the spark voltage is 1 as shown in FIG.
A constant current was applied up to 50 V, and an anodization voltage / current measuring instrument was used which was switched to a constant voltage after reaching 150 V. Therefore, with respect to the electrolytic solution having a spark voltage of 150 V or higher, the current change at 150 V is also shown. For the electrolytic solution having a spark voltage of less than 150, the voltage oscillation (voltage fluctuation) is also shown. For example, 125 of Comparative Example 1
˜80 indicates that the spark voltage fluctuates drastically between 125V and 80V.

[0021]

[Table 1]

[0022]

[Table 2]

As is clear from Tables 1 and 2, the electrolytic solutions of Examples 1 to 6 have low specific resistance and high spark voltage. Since the electrolytic solutions of Comparative Examples 1 to 3 have large fluctuations in the spark voltage, only the anodic oxide films having unstable withstand voltage characteristics can be obtained with these electrolytic solutions. On the other hand, as can be seen from the fact that in the electrolytic solutions of Examples 1 to 6, almost no current flows at 150 V, the withstand voltage characteristics (insulation characteristics) of the obtained anodic oxide film are high and stable.

(Embodiments 7 to 12) Six kinds of capacities 1 filled with the electrolytic solutions having the same compositions as those of the embodiments 1 to 6 and sealed.
A 00 μF aluminum electrolytic capacitor was assembled.

Each of the obtained electrolytic capacitors was replaced by 10
Prepare individual capacitors for these capacitors at 105 ° C, 500
A high temperature load test for 0 hours was performed. As a result, all the test samples exhibited stable characteristics with the fluctuation range of the changes in capacitance and dielectric loss tangent with time falling within 10% of the initial values.

[0026]

As described in detail above, according to the present invention, an electrolytic solution for an electrolytic capacitor, which can provide an anodized film having a low specific resistance, a high spark voltage and an excellent withstand voltage characteristic,
Further, it is possible to provide a highly reliable electrolytic capacitor provided with this electrolytic solution.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of measurement of anodizing voltage / current of a measuring instrument used in Examples.

Claims (2)

[Claims] 1. A quaternary ammonium salt of an aliphatic oxyacid,
An electrolytic solution for an electrolytic capacitor comprising at least one compound selected from an organic phosphine compound and a surfactant, and an organic solvent. 2. An electrolytic capacitor comprising the electrolytic solution according to claim 1.