JP3334192B2 - Electrolyte for electrolytic capacitors - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of an electrolytic solution for an electrolytic capacitor, and more particularly, to increasing a spark voltage while suppressing an increase in specific resistance of an electrolytic capacitor by adding a specific additive. The present invention relates to an improvement in an electrolytic solution for an electrolytic capacitor.

[0002]

2. Description of the Related Art Electrolytic capacitors are small, large-capacity, inexpensive and have excellent characteristics such as smoothing of rectified output.
It is one of the important components of electronic equipment. Generally, an aluminum film whose surface has been changed to an oxide film by electrolytic oxidation is used as the anode, and this oxide film is used as a dielectric to interpose an electrolyte between the collector and the collector. Produced. During use, the oxide film is constantly regenerated, so that the oxide film is stable.

[0003] Since an electrolytic capacitor is used while performing a chemical reaction, its characteristics greatly depend on the properties of an electrolytic solution. It is important to maintain the steady state of the chemical reaction between the aluminum electrode with the oxide film on the surface and the electrolytic solution and the aluminum oxide film as the dielectric to stabilize the performance. If the chemical steady state is disturbed by, for example, an excessively high voltage load or the like by mistake in the method, the aluminum oxide film is destroyed, and eventually the insulation is broken.

A phenomenon in which a change in the physical properties of a dielectric due to a high voltage load due to an increase in the load voltage of a capacitor and a temporal change in the dielectric constant results in a fluctuation in the electrochemical state is called scintillation. The perceived voltage can be used as a measure of the withstand voltage of the capacitor as a scintillation voltage (spark voltage). A higher scintillation voltage indicates that the withstand voltage of the capacitor is higher. Conveniently, without assembling the final capacitor product,
The measurement can be performed in a state where an unformed aluminum foil of an appropriate size is immersed in the electrolytic solution to be measured.

In a conventional general electrolytic solution for electrolytic capacitors, an acid such as boric acid or a salt thereof is added as a main solute to the electrolytic solution in order to obtain high withstand voltage. Also,
Various attempts have been made other than these. For example, sulfamic acid (Japanese Patent Application Laid-Open No. 49-82963), suberic acid (Japanese Patent Application Laid-Open No. 49-133860), dodecyl phosphate (Japanese Patent Application Laid-Open No. 49-73659), alkylphosphoric acid (Japanese Patent Application Laid-Open No. 153154), addition of diphosphorous acid (Japanese Patent Application Laid-Open No. 57-141913), boric acid-mannite type (Japanese Patent Application Laid-Open No. 57-60829), boric acid-mannite-polyvinyl alcohol type. (Japanese Patent Laid-Open No. 5
However, it has not always been possible to sufficiently improve the withstand voltage while maintaining high conductivity by using these methods.

On the other hand, a compact capacitor in which colloidal silica is dispersed in an electrolytic solution to reduce the capillary action and improve the eigenvalue has been proposed in the specification of Eastern German Patent DD212351. On the other hand, in recent years, it has been found that the addition of silica has an effect of improving the pressure resistance of an electrolytic solution (JP-A-4-12512, JP-A-4-12512).
No. 518512 and JP-A-4-139712).

[0007]

However, even if an attempt is made to add silica to the electrolytic solution according to the descriptions in these publications, the dispersion of the silica is unstable, the effect varies greatly depending on the silica particles used, and However, even if the initial withstand voltage is improved, there is a problem that the leakage current is high and the compatibility with the anodic oxide film is poor. An object of the present invention is to provide an electrolytic solution for driving an electrolytic capacitor that solves these problems and that can increase the spark voltage while suppressing an increase in the specific resistance of the electrolytic capacitor.

[0008]

That is, the present invention relates to a method for driving an electrolytic capacitor in which an electrolyte is dissolved in an organic polar solvent used for an electrolytic capacitor which takes out a cathode through an electrolytic solution using an anodic oxide film of a valve metal as a dielectric. An electrolyte,
The present invention provides an electrolytic solution for an electrolytic capacitor, wherein an organosilica sol having a particle diameter of 1 to 40 nm of silica particles obtained by solvent replacement of a silica hydrosol in the electrolytic solution composition is added. .

In the present invention, the electrolytic solution for the electrolytic concentrator to which the organosilica sol is added is obtained by dissolving an organic acid or an inorganic acid or a salt thereof in an organic polar solvent.
The electrolytic solution may be one to which various auxiliary solutes such as conventionally used phosphoric acid derivatives and nitrobenzene derivatives have been added. If necessary, a small amount of water may be added to these electrolytic solutions.

Specific examples of the solvent which can be used alone or in combination with the organic polar solvent of the electrolytic solution include the following solvents: Protic polar solvents ethanol, propanol, butanol, pentanol, hexanol, cyclohexane. Monohydric alcohols such as butanol, cyclopentanol, cyclohexanol, benzyl alcohol, and tetrahydrofurfuryl alcohol; ethylene glycol, propylene glycol, glycerin, methoxyethanol, ethoxyethanol,
Polyhydric alcohols and alcohol ethers such as methoxypropylene glycol and dimethoxypropanol.

Aprotic polar solvents N-methylformamide, N, N-dimethylformamide, N-ethylformamide, N, N-diethylformamide, N-methylacetamide, N, N-dimethylacetamide, N-ethylacetamide, N-ethylacetamide Amide solvents such as, N-diethylacetamide, N-methyl-2-pyrrolidone, and hexamethylphosphoric amide;
-Lactone / carbonate solvents such as butyrolactone, ethylene carbonate, propylene carbonate, butylene carbonate, isobutylene carbonate; nitrile solvents such as acetonitrile and methoxypropionitrile; phosphate solvents such as trimethyl phosphate;
Sulfur-containing solvents such as dimethylsulfoxide, sulfolane, 3-methylsulfolane, and ethylene sulfite.

[0012] can be exemplified an electrolyte such as: Specific examples of the sole to the electrolyte of the electrolytic solution or in combination electrolyte may be used Quality: organic acids formic acid, acetic acid, propionic acid, aliphatic monocarboxylic acids such as enanthic acid Aliphatic dicarboxylic acids such as malonic acid, succinic acid, glutaric acid, adipic acid, methylmalonic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, decanedicarboxylic acid, maleic acid, citraconic acid, and itaconic acid; Aromatic carboxylic acids such as acids, phthalic acid, salicylic acid, toluic acid, and pyromellitic acid.

Inorganic acids Inorganic acids such as boric acid, phosphoric acid, silicic acid, HBF ₄ , HPF _{6 and the} like. Ammonium ammonium (NH ₄ ^+); methylammonium, ethylammonium, and mono-alkyl ammonium, such as propyl ammonium; dimethylammonium, diethylammonium, ethyl methyl ammonium, and dialkyl ammonium such as dibutyl ammonium; trimethylammonium, triethylammonium, and tributylammonium Quaternary ammoniums such as tetramethylammonium, triethylmethylammonium, tributylmethylammonium, tetraethylammonium, and N, N-dimethylpyrrolidinium; and other phosphoniums, sulfoniums, and arsoniums. .

The electrolyte of the present invention has a particle diameter of 1 to 40 nm, preferably 7 to 40 nm, in the above electrolyte composition.
30 nm of an organosilica sol is added. The silica concentration in the organosilica sol is usually
The content is preferably 1 to 50% by weight, but 40% by weight to prevent gelation.
It is more preferable that the content be not more than% by weight. The method for producing silica fine particles is roughly classified into a method in which sodium silicate (water glass) is dealkalized with a hydrogen-type cation exchange resin, and the obtained silicic acid solution is polymerized in an alkaline atmosphere (ion exchange method). A method in which water glass is neutralized with an acid to form a gel, and then the salt is washed away with water, and the gel obtained is peptized by an autoclave (pulverization method); a silica obtained by hydrolyzing ethyl silicate with an acid; There are a wet method such as a method of heating and aging an acid solution (sol-gel method) and a dry method such as a method of hydrolyzing chlorosilane or the like at a high temperature in an oxyhydrogen flame (combustion method). Silica sol is
The silica hydrosol produced by the wet method is obtained by replacing the aqueous solvent with an organic solvent.

As the solvent for the organosilica sol, the organic solvent used for the above-mentioned electrolytic solution is used.
Polyhydric alcohols, especially ethylene glycol, are preferred.
The solvent replacement is performed, for example, by adding ethylene glycol to a silica hydrosol produced by an ion exchange method and distilling off water. It is preferable that the water content in the organosilica sol be small, and it is generally preferable that the content be 5% by weight or less, though it depends on the amount of the silica fine particles added to the electrolytic solution.

The silica fine particles produced by the wet method are usually supplied as a colloidal sol stabilized with a cation such as Na ⁺ or a silica powder obtained therefrom. Silica powder is not preferred because the particles are easily associated with each other, and the silica fine particles produced by the dry method have few hydroxyl groups on the particle surface, and an effective organosilica sol for improving withstand voltage cannot be obtained. . Silica hydrosols produced by the wet method include, for example, ion exchange hydrosol; "Snowtex" (trade name) manufactured by Nissan Chemical Industries, sol-gel hydrosol; "Quatron Colloid" PL series (trade name) manufactured by Tonen Chemical Co., Ltd. Are commercially available. Among these, an ion-exchange silica hydrosol is preferable. In particular, an Al-type silica hydrosol in which the surface of silica fine particles is partially substituted with Al atoms and the Al content in silica is 0.2 to 1% by weight is used. The leakage current of the electrolytic capacitor obtained by using the added electrolytic solution is excellently reduced most preferably.

The ion exchange silica hydrosol is usually
It is commercially available as a sol containing 20 to 50% by weight of silica fine particles. Depending on the method of stabilization, Na type, NH ₄
Type, H type and Al type. An example of the pH of a silica hydrosol containing 20% by weight of silica fine particles having a particle size of 10 to 20 nm and the contents (% by weight) of Na and Al in silica is as follows. pH Na (% by weight) Al (% by weight) Na type 9.5 to 10.0 0.8 0.1 NH ₄ type 9.0 to 10.0 0.1 0.01 H type 2 to 4 0.1 0.1 Al type 8.5-9.0 0.5 0.4

The amount of the organosilica sol to be added to the electrolytic solution is such that the fine silica particles are contained in the electrolytic solution in an amount of 1 to 10% by weight, preferably 3 to 8% by weight.

[0019]

The electrolytic solution of the present invention has a function of promoting the growth of the oxide film by adsorbing several layers of the added silica fine particles of the organosilica sol on the anodic oxide film. The present inventors have clarified this with a surface analyzer such as Auger electron spectroscopy and an electron microscope.

[0020]

EXAMPLES The present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not limited to the following examples. Experimental Example 1 Triethylmethylammonium benzoate 2
5% by weight of γ-butyrolactone solution is mixed with ethylene glycol obtained by using various silica fine particles as a solvent.
0% by weight of organosilica sol and water are added, and 18.69% by weight of triethylmethylammonium benzoate, γ
-Butyrolactone 59.81% by weight, ethylene glycol 14.95% by weight, silica 5.61% by weight, water 0.9
An electrolytic solution consisting of 4% by weight was prepared. Further, as a reference example, a silica-free electrolytic solution having the same component ratio except for silica was prepared. The conductivity of these electrolytes (mS /
cm) and withstand voltage (V) are shown in Table 1.

The conductivity was adjusted at 110 ° C.
, And then cooled and measured at 25 ° C.
The withstand voltage is determined by preparing an electrolytic capacitor using these electrolytes, applying a constant current of 5 mA at 110 ° C., and examining the voltage-time rise curve. Alternatively, the voltage (V) at which scintillation was observed was defined as the withstand voltage. The specifications of the electrolytic capacitor prepared for use in the withstand voltage test are as follows. An anode foil formed at 240 V is wound together with a separator and a cathode foil, and the electrolytic solution is impregnated into a capacitor element having a lead wire drawn out from the wound end surface (at 40 ° C.). Then, the device was housed in a metal case, the opening was closed with sealing rubber, and the end of the outer case was tightly wound to form an electrolytic capacitor. The rated voltage of this electrolytic capacitor is 160 WV, the capacitance 2
2 μF.

The organosilica sol is prepared by adding ethylene glycol to a silica hydrosol and distilling off water to make the water content 1% by weight or less. For a silica powder, adding the ethylene glycol to ethylene glycol. And stirred with a homogenizer to obtain 30% by weight of each organosilica sol.

[0023]

[Table 1]

Experimental Example 2 18.52% by weight of triethylammonium benzoate, 59.26% by weight of γ-butyrolactone, 14.81% by weight of ethylene glycol, 5.56% by weight of silica, 0.93% by weight of dibutyl phosphate, 0.9% by weight of water.
An electrolytic solution consisting of 92% by weight was prepared, and its electric conductivity and withstand voltage were measured. The results are shown in Table 2.

[0025]

[Table 2]

Experimental Example 3 Using the electrolytic solutions of Examples 7 to 9, 10 electrolytic capacitors of 10φ × 20 L, 100 wV, 56 μF were prepared.
The characteristic values after the 0-hour high-temperature load test were measured. Table 3 shows the results.

[0027]

[Table 3]

[0028]

According to the present invention, it is possible to provide an electrolytic solution for an electrolytic capacitor which has a high withstand voltage while suppressing an increase in the specific resistance of the electrolytic capacitor and has a low leakage current.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Tatsuki Tsuji 1-167, Higashi-Ome, Ome-shi, Tokyo Japan Nippon Chemi-Con Corporation Inspector Hiroshi Ebata (56) References JP-A-4-313210 (JP, A) JP-A-58-145614 (JP, A) JP-A-63-123807 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01G 9/02

Claims (6)

(57) [Claims] 1. An electrolytic solution for driving an electrolytic capacitor in which an electrolyte is dissolved in an organic polar solvent used for an electrolytic capacitor which uses a valve metal anodized film as a dielectric and takes out a cathode through the electrolytic solution. The particle size of the silica particles obtained by solvent replacement of the silica hydrosol in the composition is 1 to 40 n
m, wherein an organosilica sol of m is added. 2. The silica particles having a particle size of 7 to 30 nm.
The electrolytic solution according to claim 1, wherein It 3. A silica hydrosol, ion exchange method, is obtained by the peptization method or sol-gel method,
The electrolytic solution according to claim 1 or 2 , wherein: 4. The addition amount of the organosilica sol electrolytic solution according to any one of claims 1 to 3 silica fine particles is characterized in that an amount in the range of 1 to 10 wt% in the electrolyte. Solvent wherein organosilica sol is characterized in that the ethylene glycol according to claim 1 to 4 Noise
An electrolytic solution according to any of the preceding claims. 6. A silica fine particles of organo silica sol, that is intended to include Al atomic 0.2-1 wt%
The electrolytic solution according to any one of claims 1 to 5, characterized in that: