JP2008112877A - Manufacturing method of electrode foil for electrolytic capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of electrode foil for electrolytic capacitor, with which capacitance of anodic oxidation coating can be increased by improving preprocessing solution. <P>SOLUTION: In the manufacturing method of electrode foil for electrolytic capacitor, with which etched aluminum foil is anodized, aluminum foil is immersed in hydrogen peroxide solution whose concentration is 0.1 to 5.0 weight% as a pre-processing of anodic oxidation. A temperature of hydrogen peroxide solution is 70°C or above. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing an electrode foil for an electrolytic capacitor.

  When manufacturing the electrode foil for electrolytic capacitors, an anodized film is formed on the foil surface by performing anodization (chemical conversion) on the etched aluminum foil in a chemical conversion solution. Further, as a chemical conversion solution for producing an electrode foil for an electrolytic capacitor, generally, an aqueous solution of boric acid or a salt thereof, phosphoric acid or a salt thereof, adipic acid or a salt thereof is used (for example, non-patent). Reference 1).

  In recent years, there is a high demand for miniaturization of electrolytic capacitors in electrode foils for electrolytic capacitors. Therefore, a method for producing an anodic oxide film having a larger capacitance is required.

For this reason, when manufacturing an electrode foil for an electrolytic capacitor etched into a tunnel shape, an aluminum foil is immersed in high-temperature pure water as a pretreatment to form a hydrated film, and then an anode in a chemical conversion solution. It is oxidized.
By generating the above hydrated film, the crystallinity of the anodized film is enhanced, and an electrode foil having a large electrostatic capacity can be obtained (for example, see Non-Patent Document 1).

Isaya Nagata, “Cathode Aluminum Electrolytic Capacitor”, Nihon Denki Kogyo Kogyo Co., Ltd., February 24, 1997, 2nd edition, 1st printing, P262-331

  As described above, in order to increase the capacitance of electrolytic capacitor electrode foils, a method of anodizing after immersing in high-temperature pure water to form a hydrated film is used. Therefore, further increase in capacitance is required.

  Therefore, an object of the present invention is to provide a method for producing an electrode foil for an electrolytic capacitor that can increase the capacitance of an anodized film by improving a pretreatment liquid.

  In order to solve the above problems, the present invention provides a method for producing an electrode foil for an electrolytic capacitor in which an etched aluminum foil is anodized, and the aluminum foil is immersed in hydrogen peroxide water as a pretreatment for the anodization. This is a method for producing an electrode foil for an electrolytic capacitor.

  Moreover, the solution used for said pre-treatment is a hydrogen peroxide solution having a hydrogen peroxide concentration of 0.1 to 5.0% by weight.

  Furthermore, the temperature of the hydrogen peroxide solution is 70 ° C. or more.

  In the present invention, it is considered that the crystallinity of the oxide film generated by anodic oxidation is improved by improving the quality of the hydrated film generated by the pretreatment, and the capacitance is higher than that of the conventional method. Electrode capacitor electrode foils can be manufactured.

In this case, the hydrogen peroxide solution preferably has a hydrogen peroxide concentration of 0.1% by weight or more.
The concentration of industrially produced hydrogen peroxide is 30 to 50% by weight, but since it can be mixed with water at an arbitrary ratio, it is diluted with pure water to be 0.1% by weight or more. Thus, hydrogen peroxide water can be easily used as the pretreatment liquid.
Further, when the concentration of hydrogen peroxide is 6.0% by weight or more, it corresponds to a deleterious substance and the hydrogen peroxide water is easily decomposed.

In the present invention, since the hydrogen peroxide solution is used for the pretreatment for chemical conversion, the pretreatment liquid itself has chemical oxidizability.
Therefore, a hydrated film having a composition closer to boehmite can be obtained than a hydrated film formed by immersing in pure water, so that the crystallinity of γ-alumina, which is an oxide film generated by anodic oxidation, is considered to be higher. Thus, an electrode foil for an electrolytic capacitor having a high capacitance can be produced.
Therefore, it is possible to reduce the size and cost of the electrolytic capacitor.

  In the present invention, when manufacturing an anode foil used for an electrolytic capacitor, an aluminum foil etched in a tunnel shape is anodized in a chemical conversion solution. In performing such anodization, as a pretreatment, it is immersed in a hydrogen peroxide solution having a concentration of 0.1 to 5.0% by weight and a temperature of 70 ° C. or higher.

  Hereinafter, based on an Example, this invention is demonstrated more concretely. In this example, the etched aluminum foil is anodized after being immersed in a high temperature hydrogen peroxide solution under the conditions shown in Table 1.

[Examples 1 and 5 to 8] Concentration comparison of pretreatment liquid (hydrogen peroxide solution) In this example, an aluminum foil for medium pressure etched in a tunnel shape was prepared, and the concentration of 0.1, After forming the hydrated film on the surface by immersing the above-mentioned etching foil in hydrogen peroxide water of 0.5, 1.0, 3.0, 5.0% by weight and a temperature of 90 ° C. for 3 minutes, a chemical conversion solution Anodization was performed using 10.0 wt% boric acid aqueous solution.
At this time, anodic oxidation was performed under a constant current condition in which the current density was kept constant at 20 mA / cm ² , and the anodic oxidation was performed while maintaining the constant voltage state for 30 minutes after reaching the constant voltage of 250V.

  Next, heat treatment for 5 minutes in an atmosphere at a temperature of 500 ° C. and voltage application for 5 minutes in the chemical conversion solution were repeated twice to complete the anodic oxidation.

[Examples 2 to 5] Temperature comparison of pretreatment liquid (hydrogen peroxide solution) In this example, the same aluminum foil as in Example 1 was prepared, and a hydrogen peroxide solution having a concentration of 0.5% by weight was used as the pretreatment liquid. The temperature was set at 60, 70, 80, and 90 ° C., and the above-mentioned etching foil was immersed for 3 minutes to form a hydrated film on the surface, and then the same anodic oxidation as in Example 1 was performed.

(Conventional examples 1 and 2)
Anodization was performed in the same manner as in Example 1 except that the etching foil was immersed in pure water at 80 ° C. and 90 ° C. as a pretreatment liquid.

[Evaluation results]
Table 1 shows the capacitance and the rate of change in capacitance of the electrode foil for electrolytic capacitors produced as described above. The capacitance change rate is expressed as a ratio (%) to Conventional Example 1.

[Comparison of pretreatment liquids: Comparison between Example (hydrogen peroxide solution) and conventional example (water)]
As is apparent from Table 1, in Examples 1 and 3 to 8 using hydrogen peroxide water as the pretreatment liquid, it can be seen that the capacitance is increased as compared with Conventional Examples 1 and 2.

[Concentration comparison of pretreatment liquid (hydrogen peroxide solution) (Examples 1 and 5 to 8)]
The above effect is obtained when the hydrogen peroxide concentration is 0.1% by weight or more, and if it is less than 0.1% by weight, sufficient effect cannot be obtained. However, if the concentration of hydrogen peroxide is 6.0% by weight or more, it corresponds to a deleterious substance, and the hydrogen peroxide solution is likely to be decomposed and difficult to handle. preferable.
As mentioned above, it is preferable that the density | concentration of hydrogen peroxide is 0.1 to 5.0 weight%.

[Temperature comparison of pretreatment liquid (hydrogen peroxide solution) (Examples 2 to 5)]
Comparing the temperature of the hydrogen peroxide solution, the higher the temperature at 70 to 90 ° C., the higher the capacitance value. A temperature of 60 ° C. is not preferable because the effect of improving the capacitance value by the hydrogen peroxide solution is small (Example 2).

  In addition, this invention is not limited to the said Example, It can also be used as a pre-processing of a well-known anodizing process.

Claims (3)

In the method of manufacturing an electrode foil for an electrolytic capacitor that anodizes an etched aluminum foil,
A method for producing an electrode foil for an electrolytic capacitor, wherein the aluminum foil is immersed in a hydrogen peroxide solution as a pretreatment for the anodization.   2. The method for producing an electrode foil for an electrolytic capacitor according to claim 1, wherein the solution used for the pretreatment is a hydrogen peroxide solution having a hydrogen peroxide concentration of 0.1 to 5.0% by weight. .   The method for producing an electrode foil for an electrolytic capacitor according to claim 1 or 2, wherein the temperature of the hydrogen peroxide solution is 70 ° C or higher.