JP2000164469A - Electrolytic capacitor driving electrolyte and electrolytic capacitor using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrolytic capacitor driving electrolyte with which the deterioration of cathode foil can be suppressed and an electrolytic capacitor, having a stable state for a long period at high temperature, can be obtained. SOLUTION: An electrolyte, consisting of the solute containing an organic solvent, an inorganic acid, an organic acid or the solute containing one or more kinds selected from the inorganic acid salt and the organic acid salt, and positive ion interfacial active agent as shown in the formula mentioned below (chemical 1), is formed. By forming an electrolytic capacitor using the above-mentioned electrolyte, the deterioration of cathode foil is suppressed, and the electrolytic capacitor, having stabilized characteristics at high temperature, can be accomplished. In the formula, R1 is a substituent selected from CH2-O2, C2H4-O, C2H4-O-C3H6-O, C2H4-O-C4H8-O, and R2 is a substituent selected from -H, -CH3, where n, m are arbitrary natural numbers.

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 and an electrolytic capacitor using the same.

[0002]

2. Description of the Related Art Conventionally, an electrolytic solution for driving an electrolytic capacitor (hereinafter, referred to as an electrolytic solution) used for an electrolytic capacitor usually comprises an organic compound such as .gamma.-butyrolactone or ethylene glycol as a main solvent, and can increase the discharge voltage. Used a solute made from an inorganic acid of boric acid.
In an environment exceeding 100 ° C., there is a problem that water of crystallization in boric acid evaporates as water vapor, thereby increasing the internal pressure in the package of the electrolytic capacitor and destroying it.

As means for solving this, aromatic carboxylic acids such as benzoic acid and phthalic acid, adipic acid, azelaic acid and butyloctane diacid (Japanese Patent Publication No. 60-1329)
No. 3), 5,6-decanedicarboxylic acid (JP-B-63)
It has been known to use an electrolyte containing an aliphatic carboxylic acid such as a dibasic acid having a side chain (Japanese Patent No. 2681202) or a salt thereof as a solute.

[0004] Since these organic carboxylic acids can reduce the water content of the electrolytic solution, they can suppress an increase in the internal pressure in the electrolytic capacitor due to water vapor even in an environment exceeding 100 ° C.

[0005] Polyethylene glycol (JP-B-3)
-76776), polyglycerin (JP-B-7-7)
It is also known that a spark generation voltage and a chemical conversion property can be improved by adding a surfactant such as an alkylene block polymer (Japanese Patent No. 2731241) and a surfactant such as an alkylene block polymer.

[0006]

However, in recent years, the use environment at high temperature and for a long time has been increasing with the use of high-density mounting and high ripple in the use environment of electrolytic capacitors in equipment used. In electrolytes using carboxylic acids and surfactants, although there is a slight difference depending on the type, the increase in water cannot be suppressed due to the esterification reaction with the solvent, and the increase in water can cause a high temperature environment. By exposing the electrolytic capacitor for a long time,
In particular, there has been a problem that the deterioration of the cathode foil having no chemical conversion film is promoted. The deterioration of the cathode foil accelerates gas generation and causes a problem such as a valve operation due to an excessive ripple load due to a decrease in the combined capacity of the electrolytic capacitor.

An object of the present invention is to solve such problems and to provide an electrolytic solution for driving an electrolytic capacitor having a high temperature and a long life and an electrolytic capacitor using the same.

[0008]

In order to solve the above-mentioned problems, the present invention provides an organic solvent, an inorganic acid, an organic acid or a solute of at least one of these salts, and a cationic surfactant. This is an electrolytic solution for driving an electrolytic capacitor. According to the present invention, an electrolytic capacitor having stable characteristics for a long time even at a high temperature can be provided.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The invention according to claim 1 of the present invention comprises an organic solvent, at least one solute of an inorganic acid, an organic acid or a salt thereof, and a cationic surfactant. Electrolytic solution for driving the electrolytic capacitor with a composition.The cationic surfactant is easily absorbed on the surface of the cathode foil of the capacitor element by the electric influence. Therefore, even if the electrolytic capacitor is exposed to a high temperature for a long time, it has an effect of obtaining a stable electrolytic capacitor.

A second aspect of the present invention is the invention according to the first aspect, wherein the cationic surfactant is a compound represented by the following chemical formula (2). Has the same function as the function according to the invention of (1).

[0011]

Embedded image

Here, C ₃ of the cationic surfactant is used.
Addition of H ₆ —O, C ₄ H ₈ —O alone is not desirable because it reduces the solubility in ethylene glycol. Also,
The addition of the copolymer of C ₂ H ₄ —O—C ₃ H ₆ —O and C ₂ H ₄ —O—C ₄ H ₈ —O reduces the surface tension of the driving electrolyte in the block copolymer. For this reason, there is a problem in foaming property when impregnating the capacitor element, so that it is desirable to use a random copolymer.

According to a third aspect of the present invention, there is provided an electrolytic capacitor using the electrolytic solution for driving an electrolytic capacitor according to the first or second aspect. By adopting such a configuration, the electrolytic capacitor is stable for a long time even at a high temperature. This has the effect of providing an electrolytic capacitor capable of exhibiting performance.

Hereinafter, one embodiment of the present invention will be specifically described. First, the structure of the cationic surfactant used in the present embodiment is shown in (Table 1).

[0015]

[Table 1]

As shown in (Table 1), the cationic surfactant of the present invention can have various structures because of the addition of CH ₂ -O, and the required properties include the shape and the viscosity of the liquid. Can be selected according to This has the advantage that it can be used for electrolytes in any voltage range and that the work can be simplified.

FIG. 1 shows a capacitor element used for a general electrolytic capacitor. As shown in FIG. 1, an anode foil 1 as an anode electrode made of aluminum is used.
And a cathode foil 2 also serving as a cathode electrode also made of aluminum, and wound up so as to face each other with a separator 3 interposed therebetween to constitute a capacitor element 5. An external lead wire 4 is connected to each of the anode foil 1 and the cathode foil 2 of the capacitor element 5. FIG. 2 shows a capacitor element 5 configured as described above impregnated with an electrolytic solution (not shown), sealed in a case 6 made of aluminum or the like, and sealed with a sealing member 7 such as rubber or phenol resin. This shows an electrolytic capacitor 8 configured by the above-described process.

Next, the composition and characteristics of a specific example of the present embodiment and a conventional electrolytic solution as a comparative example are shown in Table 2. At this time, the water content of the electrolytic solution was adjusted to 2%. However, in the boric acid examples and the conventional examples, the water content was adjusted to 25%.

[0019]

[Table 2]

As is clear from Table 2, since the examples of the present invention use a cationic surfactant, the conductivity is slightly lowered but the spark generation voltage can be improved. The effect of improving short-circuit property is also recognized.

Next, 20 electrolytic capacitors each using the electrolytic solution shown in (Table 2) were prepared, and the results of the life test were shown in (Table 3). The ratings of the electrolytic capacitors used here were all 200 WV and 560 μF, and the ripple load test was performed at a test temperature of 105 ° C.

[0022]

[Table 3]

As is clear from Table 3, in the conventional example, about 40% of the valves were opened after 7000 hours of the 105 ° C. ripple load test, whereas the characteristics of the electrolytic capacitor using the electrolytic solution according to the present example were stable. And no problems such as valve opening have occurred. Thus, it was found that the cationic surfactant of the present invention has a great effect on heat resistance.

Next, the same examination was carried out by using an electrolytic solution to which an organic carboxylic acid was added and to which a known surfactant shown in the conventional example was added. (Table 4) shows a comparison table between the electrolytic solution using the cationic surfactant of the present invention and the electrolytic solution using the conventional surfactant. At this time, the water content of the electrolytic solution was adjusted to 2%.

[0025]

[Table 4]

As shown in Table 4, no significant difference was observed in the electrical characteristics between the electrolytic solution of the present invention and the conventional electrolytic solution.

20 electrolytic capacitors using each of these electrolytic solutions were produced as prototypes, and the results of their life tests are shown in Tables 5 and 6. The ratings of the electrolytic capacitors used here were 400 V and 330 μF, and the test temperature was an organic carboxylic acid type (Conventional Example 3, Examples 7, 8,
9) was performed at 125 ° C., and the DC load test was performed at 95 ° C. for the boric acid system (Conventional Example 4, Examples 10, 11, and 12). In addition, organic carboxylic acids (Conventional Example 3, Example 7,
In 8 and 9), in order to make the influence of water remarkable, the electrolyte was evaluated by adding 5% water to the electrolyte.

[0028]

[Table 5]

[0029]

[Table 6]

As apparent from (Table 5) and (Table 6),
In this example, the electrical characteristics of the electrolytic solution were equivalent to those of the conventional example.However, regarding the long-term stability of the characteristics of the electrolytic capacitor at a high temperature, even though all the valves were opened in the conventional example, On the other hand, in this embodiment, it is very stable, and there is a clear difference.

To make this effect clearer,
Conventional Example 4 and Example The electrolytic capacitor after completion of the test was disassembled, and the capacity and appearance of the cathode foil were investigated. The results are shown in (Table 7).

[0032]

[Table 7]

As is clear from the results shown in Table 7, the cathode foil after the test of Conventional Example 4 had an initial capacity ratio of less than 1/2 and the surface was discolored to black. In the negative electrode foil, little change in capacity was observed, and no discoloration was found. Thereby, it was confirmed that the cationic surfactant of the present invention has a property capable of protecting the cathode foil surface even in a high-temperature environment, and therefore, it is possible to supply an electrolytic capacitor having long-term stability at high temperatures. You can do it.

Although not shown in the above embodiment, 1
Since the same cathode as in the embodiment is used in an electrolytic capacitor of 00 WV or less, the same effect can be expected in an electrolytic solution for low-pressure driving.

The natural number n of the cationic surfactant is preferably from 5 to 20 in consideration of the solubility in ethylene glycol, and the molecular weight is preferably 20,000 or less in consideration of the workability. Considering the purpose of protecting the cathode foil, the effect is remarkable for any natural number n and molecular weight, and the range is not limited.

Further, the amount of the cationic surfactant added is 0.01 wt% or more in the present invention since the adsorption to the cathode foil can occur even in a very small amount.

[0037]

As described above, according to the present invention, since the surface of the cathode foil having no chemical conversion film can be protected from moisture and a high temperature environment, it is possible to supply an electrolytic capacitor having stable characteristics and to obtain an industrial value. It is a great thing.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view showing a configuration of a capacitor element according to an embodiment of the present invention.

FIG. 2 is a half sectional front view showing the electrolytic capacitor according to the embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Anode foil 2 Cathode foil 3 Separator 4 Lead wire 5 Capacitor element 6 Case 7 Sealing member 8 Electrolytic capacitor

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Nobuhiro Takeishi 1006 Kadoma Kadoma, Osaka Pref.Matsushita Electric Industrial Co., Ltd.

Claims (3)

[Claims] 1. An electrolytic solution for driving an electrolytic capacitor comprising an organic solvent, a solute of at least one of an inorganic acid, an organic acid or a salt thereof, and a cationic surfactant. 2. The electrolytic solution for driving an electrolytic capacitor according to claim 1, wherein the cationic surfactant is represented by the following chemical formula (1). Embedded image 3. An electrolytic capacitor using the electrolytic solution for driving an electrolytic capacitor according to claim 1 or 2.