JPH0512436B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a method of manufacturing an electrode for an electrolytic capacitor having a large capacitance. [Problems to be solved by conventional techniques and inventions] Since the advent of transistors and ICs (integrated circuits), electrical and electronic devices have been miniaturized. For this reason, electrolytic capacitors used in electrical equipment and the like are also being made smaller. In order to miniaturize electrolytic capacitors, it is necessary to particularly increase the surface area of the anode and increase the capacitance per unit area. Conventionally, in electrolytic capacitors using aluminum foil, in order to increase the surface area of the anode, etching is performed by acid corrosion to create irregularities on the surface. Regarding this etching process,
Various studies have been conducted. The inventors of the present invention had also conducted various studies to expand the surface area of aluminum foil, but at that time, they believed that the condition of the surface of the material, aluminum foil, was more important than the etching technology. .
That is, rolling oil generally adheres to the surface of aluminum foil in the form of a film, and for this reason, it is thought that even if etching treatment is performed, sufficient etching cannot be performed. As a result of various studies based on this point of view, the inventors of the present invention have found that by treating aluminum foil with a specific surface treatment agent, the surface area can be further expanded than in the past with the same etching process. I discovered that. [Means and actions for solving the problems] That is, the present invention provides a method for solving the problems by using a method that uses sodium hydroxide, lithium hydroxide, potassium hydroxide, sodium carbonate, sodium bicarbonate, tribasic sodium phosphate, and dibasic sodium phosphate. Manufacture of an electrode for an electrolytic capacitor characterized by treating the surface of an aluminum foil with a surface treatment agent consisting of a selected alkali metal compound, an anionic surfactant, and an organic reducing agent, and then performing an etching treatment. It is about the method. The surface treatment agent used in the present invention is composed of an alkali metal compound, an anionic surfactant, and an organic reducing agent. As the alkali metal compound, sodium hydroxide, lithium hydroxide, potassium hydroxide, soda carbonate, sodium bicarbonate, potassium silicate, tribasic sodium phosphate, and dibasic sodium phosphate are used alone or in combination. Among these, sodium hydroxide is particularly preferred for use in the present invention. Examples of anionic surfactants include fatty acids, alkylbenzene sulfonates, alkyl sulfonates, α-olefin sulfonates, dialkyl sulfosuccinates, α-sulfonated fatty acid salts, alkylnaphthalene sulfonates, N-methyl-N −
Oleyl taurine, alkyl phosphate, alkyl sulfate, polyoxyethylene alkyl ether phosphate, polyoxyethylene alkyl phenyl ether phosphate, polyoxyethylene alkyl phenyl ether sulfate, naphthalene sulfonate formaldehyde condensate, Various materials such as polyoxyethylene alkyl ether sulfate are used.
Among these, sodium alkylnaphthalene sulfonate can be particularly preferably used in the present invention. Any organic reducing agent can be used as long as it prevents oxidation of the surface of the aluminum foil, but specific examples include monoethanolamine, ethylenediamine, hydrazine,
Formaldehyde, acetaldehyde, L-ascorbic acid, etc. are used. Among these, amine compounds, particularly monoethanolamine, can be suitably used in the present invention. The blending ratio of anionic surfactant and organic reducing agent to alkali metal compound is not critically determined, but 50 parts of anionic surfactant to 100 parts (by weight, same below) of alkali metal compound.
~100 parts and 20 to 450 parts of the organic reducing agent are good. When the amount of anionic surfactant becomes less than 50 parts,
There is a tendency that the surface of the aluminum foil cannot be uniformly treated, and if the amount exceeds 500 parts, the effect tends to reach its limit. If the amount of the organic reducing agent is less than 20 parts, the ability to prevent oxidation on the aluminum foil surface tends to be weakened, although it depends on the reducing power of the reducing agent, and even if the amount is more than 450 parts, the ability to prevent oxidation will decrease. It tends to become saturated. The surface treatment agent used in the present invention is dissolved in about 2 to 20 parts of water before use. The surface of the aluminum foil is treated using this surface treatment agent. Then, an electrode for an electrolytic capacitor is obtained by etching the aluminum foil treated with a surface treatment agent by a conventionally known method. The reason why the electrostatic capacitance of the electrolytic capacitor electrode obtained in this way increases, that is, the reason why the etching ratio of the aluminum foil increases is not clear, but the surface treatment agent used in the present invention It is assumed that this is not only to remove rolling oil, but also to remove harmful inorganic substances such as silicon and calcium from the surface of the aluminum foil during the etching process. [Example] Aluminum foil with a thickness of 0.100 mm and a purity of 99.99% was surface treated with various blending ratios of sodium aquatic acid (component A), sodium alkylnaphthalene sulfonate (component B), and monoethanolamine (component C). (Examples 1-6). Then, it is annealed at high temperature in an inert gas atmosphere and
Electrolytic etching was carried out for 500 seconds by passing a direct current at a current density of 16 A/dm ² in a 5% aqueous hydrochloric acid solution at .degree. Subsequently, a chemical conversion treatment was performed in a boric acid solution at a voltage of 375 V to create an aluminum foil anode electrode. In addition, a surface treatment agent (Example 7) consisting of potassium hydroxide (component A), sodium alkyl sulfonate (component B), and ethylenediamine (component C), lithium hydroxide (component A), and sodium alkyl phosphate (component B) ) and acetaldehyde (component C) (Example 8), Example 1
An aluminum foil anode electrode was prepared by processing in the same manner as in steps 6 to 6. Furthermore, for comparison, a commercially available surface treatment agent (Comparative Example 1, Almeco 36 10% aqueous solution, manufactured by Henkel Hakusuisha) was used.
Using this, aluminum foil anode electrodes were prepared in the same manner as in Examples 1 to 6. The capacitance of these electrodes was measured. The results are shown in the table. Note that the capacitance was measured by the AC bridge method (frequency 120 Hz).

【table】

〔Effect of the invention〕

Since the electrolytic capacitor electrode obtained by the method according to the present invention was treated with a certain surface treatment agent,
By simply performing the same etching process as in the conventional case, the etching magnification of the aluminum foil is improved compared to the conventional case, and as a result, the electrostatic capacitance is increased.

Claims (1)

[Scope of Claims] 1. An alkali metal compound selected from the group consisting of sodium hydroxide, lithium hydroxide, potassium hydroxide, soda carbonate, sodium bicarbonate, tribasic sodium phosphate, and dibasic sodium phosphate, and an anionic interface. A method for manufacturing an electrode for an electrolytic capacitor, comprising treating the surface of an aluminum foil with a surface treatment agent comprising an activator and an organic reducing agent, and then performing an etching treatment. 2. The method for producing an electrode for an electrolytic capacitor according to claim 1, wherein the alkali metal compound is sodium hydroxide. 3 Claim 1 or 2 in which the anionic surfactant is sodium alkylnaphthalene sulfonate
A method for manufacturing an electrode for an electrolytic capacitor as described in . 4. The method for producing an electrode for an electrolytic capacitor according to claim 1, 2 or 3, wherein the organic reducing agent is monoethanolamine.