JP3169625B2 - Electrolytic solution for driving electrolytic capacitor and electrolytic capacitor using the same - Google Patents

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 driving an electrolytic capacitor which suppresses an increase in leakage current in a high-temperature no-load test, and an electrolytic capacitor using the same.

[0002]

2. Description of the Related Art In general, an electrolyte for driving an electrolytic capacitor for medium and high pressures (hereinafter referred to as an electrolyte) is mainly composed of ethylene glycol as a main solvent and boric acid or an organic carboxylic acid and ammonia water or an ammonium salt of the acid as a main solute. Is used. Among the above electrolytes, a boric acid-based electrolyte can increase the spark generation voltage, but has a problem that the specific resistance is high and the high-temperature characteristics are unstable due to water generated by esterification. . On the other hand, aliphatic dicarboxylic acids such as adipic acid, azelaic acid and decanedicarboxylic acid are widely used as organic carboxylic acid-based electrolytes, but their characteristics change greatly at high temperatures, making them unsuitable as long-life electrolytes. Was enough.

[0003]

Among the organic carboxylic acid-based electrolytes, aromatic carboxylic acids such as benzoic acid are thermally stable, so that their characteristics such as capacity and loss are small and good. There is a problem that the leakage current in the no-load test increases significantly. The present invention has been made in view of the above points, and an object of the present invention is to provide a highly reliable long-life electrolytic solution and electrolytic capacitor that suppresses an increase in leakage current at high temperatures. is there.

[0004]

According to the present invention for the above object, a solvent mainly composed of ethylene glycol is mixed with a main solute.
And salicylic acid or a salt thereof is added to an electrolytic solution in which benzoic acid or a salt thereof is dissolved. The concentration of benzoic acid or a salt thereof dissolved as a solute is 3 to 15 w
t, and the added amount of salicylic acid or a salt thereof is 0.0%.
5 to 3 wt% is desirable. The electrolytic capacitor according to the present invention is characterized in that a capacitor element hermetically sealed in a case is impregnated with the electrolytic solution.

[0005]

Salicylic acid is an aromatic oxyacid and has the property of forming a complex with aluminum. Therefore, it is considered that the addition of salicylic acid or a salt thereof to the electrolyte stabilizes the surface of the aluminum electrode foil and suppresses the attack of the oxide film by moisture.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail based on embodiments. Tables 1 and 2 show the compositions, specific resistances, and spark generation voltages of the electrolyte solutions according to the conventional example and the example of the present invention. Conventional example 1
And 2 are electrolytes for a rated voltage of 200 V, and Examples 1 to 4 are obtained by adding salicylic acid to Conventional Example 1.
Conventional Examples 3 and 4 are electrolytes for a rated voltage of 400 V, and Examples 5 and 6 are those in which salicylic acid is added. Conventional example 5 is an electrolytic solution for a rated voltage of 450 V, and example 7 is an electrolytic solution to which salicylic acid is added. In Tables 1 and 2, the block copolymers are polyoxyethylene and polyoxypropylene block copolymers having an average molecular weight of 3000 and a weight ratio of polyoxyethylene portions (hereinafter abbreviated as PEO ratio) of 40. And a mixture having a mean molecular weight of 8750 and a PEO ratio of 80 at a ratio of 8: 2.

Next, a 200 V 330 μF aluminum electrolytic capacitor (not shown) was manufactured using the electrolytes of Conventional Examples 1 and 2 and Examples 1 to 4, and the results of a no-load test at 105 ° C. are shown in Table 3. Indicated. As is clear from Table 3, the leakage current after the test is suppressed to a very low value in the example according to the present invention as compared with the conventional example. Other characteristics were not different from the conventional example.

Table 4 shows Conventional Examples 3 and 4 and Examples 5 and 6.
A 400 V 68 μF aluminum electrolytic capacitor was prepared using the above electrolyte solution, and the result of a no-load test at 105 ° C. was shown. As in the case of the results in Table 3, the embodiment of the present invention has a great effect in suppressing an increase in leakage current after 1000 hours.

[0009] Table 5 shows the results of producing an aluminum electrolytic capacitor of 450 V 330 µF using the electrolytic solutions of Conventional Example 5 and Example 7 and performing a no-load test at 105 ° C. Again, the embodiment of the present invention has a remarkable effect in suppressing an increase in leakage current. In the present invention, as shown in Tables 1, 2 and 3, the amount of salicylic acid or a salt thereof has a very remarkable effect in the range of 0.05 wt% to 3 wt%. If the content is less than 0.05 wt%, the effect of suppressing the deterioration of the leakage current is insufficient. If the content exceeds 3 wt%, the effect of suppressing the deterioration of the leakage current is not so much improved. Is not preferred because it causes a decrease in

[0010]

[Table 1]

[0011]

[Table 2]

[0012]

[Table 3]

[0013]

[Table 4]

[0014]

[Table 5]

[0015]

As described above, according to the present invention, it is possible to prevent the deterioration of the leakage current at a high temperature and to provide a highly reliable long-life electrolytic capacitor.

Claims (3)

(57) [Claims] 1. An electrolytic solution for driving an electrolytic capacitor, wherein salicylic acid or a salt thereof is added to an electrolytic solution in which benzoic acid or a salt thereof is dissolved as a main solute in a solvent mainly composed of ethylene glycol. 2. The concentration of benzoic acid or a salt thereof is 3-15.
wt%, and the amount of salicylic acid or a salt thereof added is 0.1%.
2. The electrolytic solution for driving an electrolytic capacitor according to claim 1, wherein the amount is from 0.5 to 3% by weight. 3. An electrolytic capacitor, characterized in that a capacitor element hermetically sealed in a case is impregnated with the electrolytic solution according to claim 1 or 2.