JPH09275039A - Electrolyte for electrolytic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrolyte for driving an electrolytic capacitor which maintains a higher spark generation voltage and reduces a specific resistance, to realize low loss and stable characteristic for a longer period under high temperature condition. SOLUTION: In an electrolyte for driving an electrolytic capacitor used for an electrolytic capacitor where a cathode is extracted via the electrolyte using an anode oxide film of a metal having valve function as the dielectric material, organo silica sol including silica particles in diameter of 20 to 500nm obtained by solvent replacement of silica hydro zol is added to the electrolyte using benzoic acid or its salt and/or cuminic acid or itssalt as the solvent.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an electrolytic solution for driving an electrolytic capacitor.

[0002]

2. Description of the Related Art Electrolytic capacitors are small, large-capacity, inexpensive, exhibit excellent characteristics such as smoothing of rectified output, and are one of the important constituent elements of various electric and electronic devices.
An aluminum film whose surface has been changed to an oxide film by electrolytic oxidation is used as an anode, and this oxide film is used as a dielectric, and an electrolytic solution is interposed between the aluminum film and the collector cathode.

The electrical characteristics of an electrolytic capacitor largely depend on the properties of the electrolytic solution. Maintaining the steady state of the chemical reaction that occurs between the aluminum electrode whose surface is an oxide film and the electrolytic solution, and maintaining the aluminum oxide film that is the dielectric well, are important for stabilizing performance. If the chemical steady state is disturbed by an improper method, for example, due to an excessive high voltage load, the aluminum oxide film is broken and eventually the insulation is broken.

When the voltage applied to the capacitor rises and exceeds the film forming voltage of the electrolytic solution, the anodized film is dissolved. This phenomenon is called scintillation, and the voltage at which such a phenomenon is recognized can be used as the scintillation voltage (spark voltage) to measure the withstand voltage of a capacitor. The higher the scintillation voltage, the greater the withstand voltage of the capacitor. Show. In a simple manner, it is possible to measure a state in which an unformed aluminum foil of an appropriate size is immersed in the electrolyte solution to be measured without assembling the final capacitor product.

Heretofore, as an electrolytic solution for a medium and high voltage electrolytic capacitor, a solution in which boric acid or ammonium borate is dissolved in ethylene glycol has been used. Although the boric acid-based electrolyte can increase the spark voltage, it has a large loss due to its high specific resistance.

Further, although the boric acid-based electrolytic solution can increase the spark voltage, it can increase the spark voltage, but at the same time, it raises the specific resistance, which causes a problem that the loss is worsened. Further, when a large amount of boric acid is present in ethylene glycol, an esterification reaction occurs at a high temperature such as 100 ° C. or higher to generate a large amount of water. As a result, there is a problem that the electrode foil in the capacitor is deteriorated and the internal pressure is increased, the stability of the capacitor at high temperature is lost, and the high temperature load characteristic is deteriorated.

On the other hand, it has been found that the addition of silica to the electrolytic solution has the effect of improving the withstand voltage of the electrolytic solution. Therefore, an electrolytic solution for electrolytic capacitors to which silica has been added has been proposed. JP-A-6-151250 proposes an electrolytic solution for an electrolytic capacitor in which an organosilica sol having a silica particle size of 1 to 40 nm thus obtained is added.

[0008]

However, although this electrolytic solution has a high initial breakdown voltage, there is a problem that the breakdown voltage is lowered during the life test and a short circuit occurs.

Therefore, the present invention solves the problems of the conventional electrolytic solution for electrolytic capacitors, reduces the specific resistance, realizes low loss while maintaining the high spark voltage, and is stable at high temperature and long time. An object is to provide an electrolytic solution that can exhibit the characteristics.

[0010]

The present invention relates to an electrolytic capacitor driving electrolytic solution for use in an electrolytic capacitor in which an anodized film of a valve metal is used as a dielectric and a cathode is taken out through the electrolytic solution. The salt and / or the electrolytic solution using cumic acid or its salt as a solute,
Provided is an electrolytic solution for an electrolytic capacitor, wherein an organosilica sol having a particle size of 20 to 500 nm of silica particles obtained by replacing a silica hydrosol with a solvent is added.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The electrolytic solution for an electrolytic capacitor of the present invention uses an electrolytic solution containing benzoic acid or a salt thereof and / or cumic acid or a salt thereof as a main solute as a basic electrolytic solution. In the solute of the basic electrolyte used in the present invention, the anion component is benzoic acid and / or cuminic acid, but the cation component is ammonium, and an ammonium salt of benzoic acid and / or cuminic acid may be used during compounding. However, benzoic acid and / or cumic acid may be added to adjust the pH with ammonia.

Examples of the solvent that can be used in the present invention include alcohols: monohydric alcohols (methyl alcohol, ethyl alcohol, diacetone alcohol, benzyl alcohol, amino alcohol, etc.); dihydric alcohols (ethylene glycol, diethylene glycol, etc.); Trihydric alcohol (glycerin, etc.); hexitol, etc., ethers: monoether (ethylene glycol monomethyl ether, diethylene glycol monoethyl ether, etc.); diether (ethylene glycol dimethyl ether, diethylene glycol diethyl ether, etc.), amides: formamides (N-methyl) Formamide,
N, N-dimethylformamide and the like); acetamides (N-methylacetamide, N, N-dimethylacetamide and the like); propionamides (N, N-dimethylpropionamide and the like); hexamethylphosphorylamide and the like oxazolidinones (N- Methyl-2-oxazolidinone, etc.) Lactones (γ-butyrolactone, δ-valerolactone, etc.) Nitriles (acetonitrile, acrylonitrile, etc.) Dimethyl sulfoxide, sulfolane, 1,3-dimethyl-imidazolidinone, N-methylpyrrolidone, aromatic Examples thereof include group solvents (toluene, xylene, etc.) and paraffinic solvents (normal paraffin, isoparaffin, etc.), and these solvents can be used alone or in combination.

Of these, preferred is a mixture of one or several of ethylene glycol, glycerin, and polyethylene glycol.

Benzoic acid or a salt thereof added to the above solvent is 3 to 20% by weight, preferably 5 to 15% by weight, and cumic acid or a salt thereof is 3 to 20% by weight, preferably 1%.
The range of the amount added is 0 to 15% by weight, and the range of these addition amounts was determined from the results of the solubility, the specific resistance of the electrolytic solution, and the corrosion resistance test of the electrolytic solution. In addition, the compounding ratio of benzoic acid and cuminic acid can be appropriately determined since the specific resistance and withstand voltage change substantially in proportion to the compounding ratio.

In the present invention, an organosilica sol having a silica particle size of 20 nm to 500 nm is added to an electrolytic solution containing benzoic acid or a salt thereof and / or cuminic acid or a salt thereof as a main solute. However, if the particle size of the silica particles is less than 20 nm, the silica particles aggregate, the effect of the silica particles is not exhibited, and a short circuit occurs during the life test.

Silica particles having a particle size of 20 nm to 500 nm
When an organosilica sol in the range of 10 is used, if benzoic acid or its salt and / or cuminic acid or its salt are used as the main solute, no short circuit occurs and the life characteristics are good.

In particular, when the particle size of the silica particles is 20 to 40 nm, short-circuiting does not occur, but it is considered that there is aggregation from the adsorbed state of the silica particles. On the other hand, when the particle size is larger than 40 nm and 500 nm or less, the adsorbed state is stable. Therefore, the embodiment is particularly preferable. On the other hand, when the particle size is more than 500 nm and 800 nm or less, it becomes difficult for the silica particles to enter the etch film of the ammonium oxide film, and the phenomenon that the silica particles cannot adhere to the oxide film in the etch film begins to occur, and the pressure resistance improving effect varies. When it is 800 nm or more, the effect of silica particles is not exhibited.

The method and composition for producing the organosilica sol and the silica particles used in the organosilica sol are described in JP-A-6-151250, and the addition amount of silica fine particles in the electrolyte is 1
10 to 10% by weight, preferably 3 to 8% by weight.

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. This was clarified by Auger electron spectroscopy, a surface analyzer such as an electron microscope.

[0020]

EXAMPLES The present invention will be described in more detail below with reference to Examples and Comparative Examples.

Examples 1, 2, 3, 4, 5, 6, and
Comparative Example A predetermined amount of glycerin, ammonium benzoate, ammonium cuminate shown in Table 1 was added to an ethylene glycol solvent.
Boric acid, ammonium pentaborate, and silica fine particles were dissolved to obtain driving electrolyte solutions of Examples 1 to 6 and Comparative Example.

The compositions of these electrolytic solutions and the specific resistance of each electrolytic solution measured at 25 ° C. are shown in Table 1 together with the spark voltage. Also,
Aluminum foil is used for the anode and the cathode, and the separator paper is sandwiched and overlapped and wound to form a cylindrical capacitor element, which is impregnated with the electrolytic solution of each Example and Comparative Example and stored in an outer case, The maximum voltage reached when a constant current of 5 mA / cm ² was applied to the above-mentioned capacitor element was measured using the electrolytic capacitor prepared by sealing. Rated voltage is 4
00V and 500V, rated capacity is 47μF, initial and high temperature load test (105 ℃, 1000
Table 2 and Table 3 show the average values of 10 times each.

Examples 1 to 3 have an average particle size of 30 nm, and Example 4
~ 6 used silica particles of 50 nm.

[0024]

[Table 1]

[0025]

[Table 2]

[0026]

[Table 3]

As shown in Table 1, Examples 1 to 6 realize a large reduction in specific resistance while maintaining a high spark voltage. Also, as shown in Tables 2 and 3, the initial value is low.
It achieved tan δ and maintains the initial value even after the high temperature load test.

In the above embodiment, ammonium benzoate and / or ammonium cuminate was used as the solute. However, when benzoic acid and / or cuminic acid is used as the solute, neutralization adjustment is performed with ammonia gas, so the final Is the same as that using ammonium salt of each acid.

[0029]

According to the present invention, there is provided a driving electrolytic solution for an electrolytic capacitor, which can maintain a high spark generation voltage and reduce a specific resistance, and can realize low loss and stable characteristics at high temperature and long time. To be done.

Front page continuation (72) Inventor Makoto Ue 8-3-1 Chuo, Ami-cho, Inashiki-gun, Ibaraki Mitsubishi Chemical Corporation Tsukuba Research Laboratory (72) Masayuki Takeda 8-3-1 Chuo, Ami-cho, Inashiki-gun, Ibaraki No. Mitsubishi Chemical Co., Ltd. Tsukuba Research Center

Claims (5)

[Claims] 1. An electrolytic capacitor-driving electrolytic solution for use in an electrolytic capacitor, comprising an anodic oxide film of a valve metal as a dielectric and taking out a cathode through an electrolytic solution, which comprises benzoic acid or a salt thereof and / or cuminic acid. Alternatively, an electrolytic solution for electrolytic capacitors, characterized in that an organosilica sol having a silica particle size of 20 to 500 nm obtained by solvent substitution of silica hydrosol is added to an electrolytic solution using a salt thereof as a solute. 2. The particle size of silica particles obtained by substituting the silica hydrosol of the organosilica sol added to the electrolytic solution with a solvent has a particle size of more than 40 nm and 500 nm or less. Electrolytic solution for electrolytic capacitors. 3. The amount of benzoic acid or its salt and / or cuminic acid or its salt to be dissolved is 3 to 20% by weight.
The electrolytic solution for an electrolytic capacitor according to claim 1 or 2, wherein 4. The electrolytic solution for an electrolytic capacitor according to claim 1, wherein the salt of benzoic acid is ammonium benzoate and the salt of cuminic acid is ammonium cuminate. 5. The electrolytic solution for an electrolytic capacitor according to claim 1, wherein the solvent is one or a mixture of several kinds of ethylene glycol, glycerin, and polyethylene glycol.