JP2007184307A - Electrolyte for driving electrolytic capacitor, and electrolytic capacitor using same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrolyte for driving electrolytic capacitors capable of securing high reliability in an electrolytic capacitor even if specific resistance is made low by blending water, and to provide the electrolytic capacitor. <P>SOLUTION: The electrolyte is prepared by blending carboxylic acid salt such as formic acid ammonium and adipic acid ammonium, a phosphoric acid compound, and ethylenediamineoxyphenyl acetic acid to a solvent containing water. The amount of blend of the ethylenediamineoxyphenyl acetic acid is preferably 0.1-3.0 wt.% to the entire electrolyte. Water is preferably 20.0-80.0 wt.% to the entire solution. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electrolytic solution for driving an electrolytic capacitor (hereinafter referred to as an electrolytic solution) and an electrolytic capacitor using the electrolytic solution.

Electrolytic capacitors are widely used in various electric and electronic products mainly for power supply circuits and digital circuit noise filters.
Such an electrolytic capacitor is configured by impregnating an electrolytic solution into a capacitor element, storing the capacitor element in a metal cylindrical case, sealing the opening with an elastic rubber, and then drawing the sealed portion.
Here, the capacitor element is obtained by winding an anode foil and a cathode foil through a separator, and the anode foil is generally formed by electrochemically etching a high-purity aluminum foil to increase the surface area. Then, a chemical conversion treatment is performed to form an oxide film on the surface of the etching foil. The cathode foil is obtained by etching an aluminum foil.

In recent years, with the progress of digitalization of electronic components, the demand for low loss and low impedance of electrolytic capacitors is increasing, and the electrolyte used for electrolytic capacitors is being developed for lowering the specific resistance. Yes.
Conventionally, an electrolyte solution for low pressure is prepared by dissolving an ammonium salt such as adipic acid or benzoic acid as an electrolyte in a mixed solvent in which ethylene glycol is used as a main solvent and about 10% of water is added thereto. The specific resistance of such an electrolyte is about 150 Ω · cm.

In the electrolytic capacitor, means for reducing the impedance by various methods other than the reduction of the specific resistance of the electrolytic solution has been attempted.
For example, the method of increasing the electrode area accommodated in the electrolytic capacitor and the method of reducing the density of the separator are used. Since short-circuit characteristics are reduced, these methods cannot achieve a significant reduction in impedance.

Therefore, as a method for greatly reducing the specific resistance of the electrolytic solution, a method of reducing the specific resistance of the electrolytic solution by significantly increasing the amount of water in the electrolytic solution has been proposed (for example, see Patent Documents 1 and 2). .
Japanese Patent No. 3366267 Japanese Patent No. 3366268

  However, normally, in an electrolytic capacitor using an electrolytic solution containing a large amount of water, aluminum is gradually eluted from the electrode foil to produce aluminum ions. Further, the aluminum ions react with moisture in the electrolytic solution to form aluminum hydroxide and precipitate on the foil surface. As this reaction progresses, the foil deteriorates and eventually causes a significant deterioration in the characteristics of the capacitor.

It is well known that the suppression effect of such electrode foil is recognized by the addition of phosphoric acid, but it is not sufficient. Phosphoric acid reacts with aluminum ions eluted in the electrolyte solution to form aluminum phosphate and adheres to the electrode foil, thereby suppressing the formation of aluminum hydroxide. However, phosphoric acid is consumed over time. In the end, phosphoric acid disappears from the electrolyte.
In addition, when there is too much addition amount in order to leave phosphoric acid for a long term, there exists a problem that characteristics, such as a leakage current, will deteriorate.

  In view of the above problems, an object of the present invention is to provide an electrolytic solution for driving an electrolytic capacitor that can ensure high reliability in an electrolytic capacitor even when the specific resistance is reduced by blending water. It is in.

  Another object of the present invention is to provide an electrolytic capacitor having high reliability even when the impedance is reduced by using an electrolytic solution having a low specific resistance.

  The present invention has been achieved as a result of various studies by the inventors of the present invention in order to solve the above-described problems, and focuses on the characteristics of ethylenediaminedioxyphenylacetic acid and intends to apply the characteristics to an electrolytic solution. .

  That is, in the electrolytic solution for driving an electrolytic capacitor according to the present invention, at least carboxylic acid and / or carboxylate and ethylenediaminedioxyphenylacetic acid represented by the following chemical formula are blended in a solvent containing water. Features.

  In the present invention, it is preferable that a phosphoric acid compound is further blended. As such a phosphoric acid compound, phosphoric acid, phosphorous acid, hypophosphorous acid, phosphoric acid esters or salts thereof can be used.

  In this invention, it is preferable that content of the said ethylenediaminedioxyphenylacetic acid is 0.1-3.0 wt% with respect to the whole electrolyte solution.

  In the present invention, the solvent comprises, for example, a mixed solvent of 20.0 to 80.0 wt% water and an organic solvent with respect to the entire solution.

Since ethylenediaminedioxyphenylacetic acid blended in the electrolytic solution according to the present invention has a property of trapping aluminum ions, it reacts with aluminum ions eluted from the electrode foil into the electrolytic solution, Suppresses generation.
For this reason, deterioration of the electrode foil can be suppressed over a long period of time, and the reliability of the electrolytic capacitor is high even when an electrolytic solution whose specific resistance is reduced by blending water is used.

  The electrolytic solution for driving an electrolytic capacitor according to the present invention is such that at least carboxylic acid and / or carboxylate and ethylenediaminedioxyphenylacetic acid represented by the above chemical formula are blended in a solvent containing water. Features.

  In the present invention, examples of the carboxylic acid include formic acid, acetic acid, oxalic acid, propionic acid, benzoic acid, succinic acid, glutaric acid, adipic acid, fumaric acid, maleic acid, phthalic acid, azelaic acid, and citric acid. Examples of the carboxylate include ammonium salt, sodium salt, potassium salt, and amine salt. Among these solutes, ammonium salts of formic acid and adipic acid are suitable for realizing both low specific resistance and life characteristics.

In the present invention, it is preferable that a phosphoric acid compound is further blended. As such a phosphoric acid compound, phosphoric acid, phosphorous acid, hypophosphorous acid, phosphoric acid esters or salts thereof can be used.
For example, monomethyl phosphate, dimethyl phosphate, monoethyl phosphate, diethyl phosphate, monopropyl phosphate, dipropyl phosphate, monoethylene glycol phosphate, diethylene glycol phosphate and the like can be used.

  In this invention, it is preferable that content of the said ethylenediaminedioxyphenylacetic acid is 0.1-3.0 wt% with respect to the whole electrolyte solution. When the blending amount is less than 0.1 wt%, the effect of extending the life of the electrolytic capacitor is hardly recognized, and when it exceeds 3.0 wt%, the effect on the blending amount does not appear clearly or deviates from the optimum value. May reduce the life characteristics.

Here, the said solvent consists of a mixed solvent of 20.0-80.0 wt% water and an organic solvent with respect to the whole solution, for example.
As the organic solvent, either a protonic solvent or an aprotic solvent may be used. Examples of the protonic solvent include methyl alcohol, ethyl alcohol, butyl alcohol, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, glycerin and the like, and among these, ethylene glycol is preferable. Examples of aprotic solvents include lactone compounds such as γ-butyrolactone.

Furthermore, various additives generally used as an electrolyte for driving a capacitor can be added to the electrolyte according to the present invention for the purpose of reducing leakage current, improving withstand voltage, gas absorption, and the like.
Examples of additives include sugars such as glucose, fructose, mannitol, xylose, galactose, polymer compounds such as polyvinyl alcohol, polyethylene glycol, polypropylene glycol, nitrophenol, nitrobenzoic acid, nitroacetophenone, nitroanisole, dinitrobenzoic acid, etc. Nitro compounds, silane coupling agents, and the like.

The electrolytic capacitor using the electrolytic solution constructed in this way is impregnated with electrolytic solution in the capacitor element, then housed in a metal cylindrical case, the opening is sealed with elastic rubber, and the sealed part is drawn It is constituted by doing.
Here, the capacitor element is obtained by winding an anode foil and a cathode foil through a separator, and the anode foil is generally formed by electrochemically etching a high-purity aluminum foil to increase the surface area. Then, a chemical conversion treatment is performed in a chemical conversion solution such as an aqueous ammonium borate solution or an aqueous ammonium adipate solution to form an oxide film on the etching foil surface. The cathode foil is also obtained by etching an aluminum foil.

  Since the specific resistance of the electrolytic solution according to the present invention can be reduced by mixing water, the impedance of the electrolytic capacitor can be lowered and the reliability is high.

  Examples of the present invention will be specifically described below. The following examples are for illustrating the present invention, and the present invention is not limited to the following contents.

A method for manufacturing a wound electrolytic capacitor used for the following evaluation will be described below.
High-purity aluminum foil is electrochemically etched to increase the surface area, and then subjected to chemical conversion in a chemical conversion solution such as an aqueous ammonium borate solution or an aqueous solution of ammonium adipate to form an oxide film on the etched foil surface. To obtain an anode foil. Also, a high purity aluminum foil is etched to obtain a cathode foil. Next, the anode foil and the cathode foil were wound through a separator to produce a capacitor element.
The capacitor element is impregnated with an electrolytic solution having the composition shown in Table 1, and then stored in a metal bottomed cylindrical case. Next, the opening is sealed with elastic rubber and the sealed portion is drawn. Thus, a wound electrolytic capacitor (6.3 WV-1000 μF) was produced.

  The value of specific resistance at 30 ° C. of the electrolyte used is also shown in Table 1.

  Using the electrolytic solution shown in Table 1, 10 electrolytic capacitors each having a rating of 6.3 V-1000 μF (φ10 × 12.5 mmL) were prepared, and initial characteristics were measured for capacitance and leakage current, and then at 105 ° C. A DC 6.3V load test was performed, and these characteristic values were measured again after 1000 hours, 3000 hours, and 5000 hours. The results are shown in Table 2.

  As shown in Table 2, in the conventional examples 1 to 5 in which ethylenediaminedioxyphenylacetic acid was not used, the explosion-proof valve formed in the case was activated in the 105 ° C rated application test.

  On the other hand, in Examples 1-11 of this invention which mix | blended the ethylenediamine dioxyphenyl acetic acid compound, it turns out that reliability is high compared with a prior art example. In particular, among Examples 1 to 11, Examples 1 to 3, Examples 5 to 7, and Examples 9 to 11 having a compounding amount in the range of 0.1 to 3.0 wt% have extremely good life characteristics. Show.

  However, in Example 4 in which the blending amount of ethylenediaminedioxyphenylacetic acid was less than 0.1 wt%, the explosion-proof valve was activated in 3000 hours, whereas in Example 8 in which the blending amount exceeded 3.0 wt%, 5000 hours. Thus, it can be seen that the blending amount of ethylenediaminedioxyphenylacetic acid is preferably 0.1 to 3.0 wt%.

  The amount of water as a solvent is preferably 20.0 to 80.0 wt% with respect to the entire electrolyte. If it is less than 20.0 wt%, it is unsuitable for low impedance applications, and if it exceeds 80.0 wt%, the effect of ethylenediaminedioxyphenylacetic acid cannot be sufficiently obtained.

  As described above, according to the present invention, an electrolytic capacitor having low impedance and good life characteristics can be put into practical use.

  The present invention is not limited to the above-described embodiments, and an electrolytic solution in which one or more of the various solutes exemplified above are dissolved or a general additive used in an electrolytic solution for driving an electrolytic capacitor is added. The electrolytic solution had the same effect as the above example.

Claims (6)

An electrolytic solution for driving an electrolytic capacitor, wherein a solvent containing water contains at least carboxylic acid and / or carboxylate and ethylenediaminedioxyphenylacetic acid represented by the following chemical formula.

  The electrolytic solution for driving an electrolytic capacitor according to claim 1, further comprising a phosphoric acid compound.   3. The electrolytic solution for driving an electrolytic capacitor according to claim 2, wherein the phosphoric acid compound is phosphoric acid, phosphorous acid, hypophosphorous acid, phosphoric acid ester or a salt thereof.   The electrolysis for driving an electrolytic capacitor according to any one of claims 1 to 3, wherein a blending amount of the ethylenediaminedioxyphenylacetic acid is 0.1 to 3.0 wt% with respect to the entire electrolytic solution. liquid.   5. The electrolytic capacitor according to claim 1, wherein the solvent is a mixed solvent of 20.0 to 80.0 wt% of water and an organic solvent with respect to the entire solution. Electrolytic solution for driving.   An electrolytic capacitor using the driving electrolytic solution according to claim 1.