JPH0354810A - Electrolytic capacitor - Google Patents

Abstract

PURPOSE:To avoid hydration reaction of an Al electrode foil even if a large content of water is mixed for the purpose of reducing specific resistivity by a method wherein a capacitor element is impregnated with electrolyte obtained by dissolving at least one among boric acid, organic acid and their salts and crown ether in main solvent, i.e., ethylene glycol. CONSTITUTION:As crown ether captures protons in electrolyte with which a capacitor element is impregnated and shows the property of cation surface active agent, it is adsorbed by the surface of a cathode foil, and thereby hydration reaction of the cathode foil and generation of hydrogen gas are avoided. One of three types of crown ether, i.e., 15-crown-5 expressed by the formula (1), dicyclohexyl-18-crown-6 expressed by the formula (2) and benzo-18-crown-6 expressed by the formula (3) is employed. With this constitution, even if a large content of water is contained in an electrolytic capacitor, degradation of the reliability can be suppressed.

Description

[Detailed description of the invention] Industrial applications The present invention relates to electrolytic capacitors.

Conventional technology Conventionally, the electrolytic solution impregnated into a 7-luminium electrolytic capacitor element has often been an electrolytic solution prepared by dissolving one or more of boric acid and organic acids or their salts in a solvent mainly composed of ethylene glycol. A large amount of water is added to reduce the specific resistance.

Problems to be Solved by the Invention In recent years, as the impedance of 7luminium electrolytic capacitors has become lower, smaller, and more reliable, electrolytic solutions that have low resistivity and are stable over a wide temperature range have been required. ing.

In an electrolytic solution in which one or more of boric acid and an organic acid or its salt is dissolved in a solvent mainly composed of ethylene glycol, conventional electrolytic solutions with an increased water content in order to lower the resistivity are used. However, increasing the water blending ratio significantly reduces reliability under high temperature atmospheres.
There were problems such as the formation of an aluminum hydroxide film due to hydration of the cathode foil and abnormal appearance due to the generation of hydrogen gas.

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventor created an electrolytic solution in which ethylene glycol is used as the main solvent and at least one of boric acid, an organic acid or a salt thereof, and crown ether are dissolved. This is an electrolytic capacitor characterized by impregnating the capacitor element.

Function The electrolytic solution according to the present invention prevents the hydration reaction of the aluminum electrode foil even when a large amount of water is mixed in with the electrolytic solution due to its low specific resistance, and significantly improves reliability in a high-temperature atmosphere.

In other words, crown ether has properties as a cationic surfactant by taking in protons in the electrolyte impregnated into the capacitor element, so it adsorbs to the surface of the cathode foil, causing a permanent reaction of the cathode foil and generating hydrogen gas. This is to prevent

Example Examples of the present invention will be described below.

Table 1 shows comparative examples regarding the structure and specific resistance of electrolytes used in electrolytic capacitors of the present invention and conventional electrolytic capacitors.

Electrolyte sample symbols A, B, and C in Table 1 are conventional examples, D1E,
F%G, l-1, IJ, K%L, M, N are examples of the present invention.

The crown ether in the above example has the following structural formula:
Three types were used: 5-crown-5, dicyclohexyl-18-crown-6, and dibenzo-18-crown-6.

In addition, Structural formula of oxygen “0” "CH2" are combined.

Dicyclohemosyl-18-crown 6 Dibenzo-18 Crown-6 Table 1 As is clear from Table 1, the electrolytic solution according to the present invention (sample symbols D, E%F, G, H, I, J%K , L%M, N), compared to conventional electrolytic solutions (sample symbols A, B, C), significantly suppress the decrease in withstand voltage even when a large amount of water is added to lower the specific resistance.

Table 2 shows the rating 2 prototypes made using the electrolytes shown in Table 1.
00,3301. The results of a high temperature load test at 105°C for 2000 hours on LF aluminum electrolytic capacitors are shown.

As is clear from Table 2, electrolytic capacitors using the electrolytic solution of the present invention (sample symbols D, E, F, G, H, I, J%K1L, M, N) are different from conventional electrolytic capacitors. In comparison, the decrease in reliability caused by blending a large amount of water has been significantly improved.

In addition to the above crown ether, 12-crown-4
, 18-crown-6, etc., which have a different number of cyclic ethylene oxides, or those containing a 7-alkyl group, a cyclohexyl group, etc. in the crown ether molecule also exhibit similar effects.

Effects of the Invention As is clear from the above results, an electrolytic method characterized in that a capacitor element is impregnated with an electrolytic solution in which ethylene glycol is used as a main solvent, and one or more of boric acid, an organic acid or its salt, and a crown ether are dissolved. The capacitor prevents the hydration reaction of the aluminum electrode foil even in the presence of a large amount of water as a result of lowering the specific resistance, exhibits excellent characteristics over a wide temperature range, and has great industrial and practical value.

Claims (1)

[Claims] An electrolytic capacitor characterized in that a capacitor element is impregnated with an electrolytic solution containing ethylene glycol as a main solvent and dissolving at least one of boric acid, an organic acid or its salt, and crown ether.