JPH04290418A - Electrolyte for driving electrolytic capacitor and electrolytic capacitor using the electrolyte - Google Patents

Abstract

PURPOSE:To provide long life of highly reliable electrolyte and electrolytic capacitor by suppressing the increase of the leak current at high temperature. CONSTITUTION:In this invention, we have added as a feature sulforic salicylic acid or its salt to the electrolyte where at least benzoic acid or its salt is dissolved as a solute in the medium mainly composed of ethylene glycol. For the concentration of the benzoic acid or its salt, 3-15wt.% is suitable, and for the quantity of added sulfo salicylic acid or its salt, 0.05-0.5wt.% is suitable. Moreover, for this electrolytic capacitor, the capacitor element sealed in the case is impregnated with the electrolyte.

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

0002

[Prior Art] Generally, an electrolytic solution (hereinafter referred to as an electrolytic solution) for driving an electrolytic capacitor for medium and high voltage uses ethylene glycol as the main solvent, boric acid or an organic carboxylic acid, and aqueous ammonia or an ammonium salt of the above acid as the main solute. is used. Among the above electrolytes, boric acid-based electrolytes can increase the spark generation voltage, but they have problems such as high specific resistance and unstable high-temperature characteristics due to water produced 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 significantly at high temperatures, making them unsuitable as long-life electrolytes. That was enough.

0003

[Problem to be solved by the invention] Among organic carboxylic acid-based electrolytes, aromatic carboxylic acids such as benzoic acid are thermally stable, so they are good with little change in properties such as capacity and loss. There was a problem in that the leakage current increased significantly during the no-load test. The present invention has been made in view of the above points, and its purpose is to provide an electrolytic solution and an electrolytic capacitor that are highly reliable and have a long life by suppressing the increase in leakage current at high temperatures. It is.

0004

[Means for Solving the Problems] The present invention according to the above object is characterized in that sulfosalicylic acid or a salt thereof is added to an electrolytic solution in which at least benzoic acid or a salt thereof is dissolved as a solute in a solvent mainly composed of ethylene glycol. shall be. The concentration of benzoic acid or its salt dissolved as a solute is preferably 3 to 15 wt%, and the amount of sulfosalicylic acid or its salt added is preferably 0.05 to 0.5 wt%. Furthermore, the electrolytic capacitor according to the present invention is characterized in that a capacitor element sealed within a case is impregnated with the electrolytic solution.

[0005]

[Action] Sulfosalicylic acid is an aromatic oxyacid,
It has the property of forming a complex with aluminum. Therefore, it is thought that by adding sulfosalicylic acid or its salt to the electrolytic solution, the surface of the aluminum electrode foil is stabilized and the attack on the oxide film by moisture is suppressed.

[0006]

EXAMPLES The present invention will be explained in detail below based on examples. Tables 1 and 2 show the compositions, specific resistances, and spark generation voltages of the electrolytic solutions according to the conventional example and the examples of the present invention. Conventional example 1
and 2 are electrolytic solutions for a rated voltage of 200 V, and Examples 1 to 4 are the conventional example 1 to which sulfosalicylic acid was added. Conventional Examples 3 and 4 are electrolytic solutions for a rated voltage of 400 V, and Examples 5 and 6 are those in which sulfosalicylic 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 sulfosalicylic acid is added. In Tables 1 and 2, the block copolymer is a polyoxyethylene/polyoxypropylene block copolymer with an average molecular weight of 3000 and a weight ratio of polyoxyethylene portion (hereinafter abbreviated as PEO ratio) of 40. and a PEO ratio of 80 with an average molecular weight of 8750.
:A mixture of 2:2 was used.

[0007] Next, 200V 330μF aluminum electrolytic capacitors (not shown) were manufactured using the electrolytes of Conventional Examples 1 and 2 and Examples 1 to 4, and the results of an unloaded storage test at 105°C are shown in Table 3. Indicated. As is clear from Table 3, the leakage current after the test was suppressed to a very low value in the example according to the present invention compared to the conventional example. In addition, there were no differences from the conventional example in terms of other characteristics.

Table 4 shows conventional examples 3 and 4 and embodiments 5 and 6.
A 400 V 68 μF aluminum electrolytic capacitor was manufactured using this electrolyte, and a no-load storage test was conducted at 105° C. The results are shown below. Similar to the results in Table 3, the examples of the present invention have a great effect in suppressing the deterioration of leakage current after 1000 hours.

Table 5 shows that 450V, 330 μF capacitors were manufactured using the electrolytes of Conventional Example 5 and Example 7.
The results of a no-load storage test at 05°C are shown. As expected, the embodiment of the present invention achieved a remarkable effect in suppressing the increase in leakage current. In the present invention, as shown in Tables 1, 2, and 3, the amount of sulfosalicylic acid or its salt added in the range of 0.05 wt% to 0.5 wt% produces a very significant effect. If it is less than 0.05 wt%, the effect of suppressing leakage current deterioration is insufficient;
If it exceeds t%, the effect of suppressing leakage current deterioration will not improve much and, especially in high-voltage electrolytes, it will cause a decrease in spark generation voltage, which is not preferable.

0010

[Table 1]

[0011]

[Table 2]

0012

[Table 3]

[0013]

[Table 4]

[0014]

[Table 5]

[0015]

[Effects of the Invention] As described above, according to the present invention,
Deterioration of leakage current at high temperatures can be prevented, and a highly reliable long-life electrolytic capacitor can be provided.

Claims (3)

[Claims] 1. An electrolyte solution for driving an electrolytic capacitor, characterized in that sulfosalicylic acid or a salt thereof is added to an electrolyte solution in which at least benzoic acid or a salt thereof is dissolved as a solute in a solvent mainly composed of ethylene glycol. [Claim 2] The concentration of benzoic acid or its salt is 3 to 1.
The electrolytic solution for driving an electrolytic capacitor according to claim 1, wherein the amount of sulfosalicylic acid or its salt added is 0.05 to 0.5 wt%. 3. An electrolytic capacitor characterized in that a capacitor element sealed within a case is impregnated with the electrolytic solution according to claim 1 or 2.