EP-4737611-A1 - METHOD FOR FORMING METAL OXIDE COATING

Abstract

The life of a plating solution used for forming a metal oxide coating is extended to efficiently use the plating solution. A method for forming a metal oxide coating includes: forming a metal oxide coating on a surface of a plating target with a plating solution containing a metal compound to form a coating and a boron compound as a reducing agent; and regenerating the plating solution with an adsorption filter that adsorbs boric acid.

Inventors

• YAMAMOTO, HISAMITSU
• NAKAYAMA, TOMOHARU
• KOMEDA, TAKUYA
• YOSHIDA, SHINICHIRO
• MATSUMOTO, KANJI

Assignees

• C. Uyemura & Co., Ltd.

Dates

Publication Date

20260506

Application Date

20251028

Claims (8)

1. A method for forming a metal oxide coating, the method comprising: forming a coating of a metal oxide on a surface of a plating target with a plating solution containing a metal compound to form a coating, and a boron compound as a reducing agent; and regenerating the plating solution with an adsorption filter that adsorbs boric acid.
2. The method according to claim 1, wherein the adsorption filter includes a chelating resin that selectively adsorbs boric acid.
3. The method according to claim 2, wherein the chelating resin is a resin having methylglucamine group as a chelating site.
4. The method according to any one of claims 1 to 3, wherein the forming the coating is performed by immersing the plating target in a plating tank containing the plating solution, and the regenerating is performed by causing the plating solution in the plating tank to pass through the adsorption filter to circulate the plating solution.
5. The method according to claim 4, wherein the forming the coating and the regenerating are performed simultaneously in parallel.
6. The method according to any one of claims 1 to 5, wherein the reducing agent includes dimethylaminoborane (DMAB).
7. The method according to any one of claims 1 to 6, wherein the metal is zinc.
8. A plating equipment comprising: a plating tank in which a plating solution containing a metal compound to form a coating and a boron compound as a reducing agent is placed and a plating target is immersed to form a metal oxide coating on a surface of the plating target; and a plating solution regenerator that regenerates the plating solution in the plating tank, wherein the plating solution regenerator includes an adsorption filter that adsorbs boric acid, and a pump that returns the plating solution in the plating tank to the plating tank through the adsorption filter.

Description

This application claims priority to Japanese Patent Application No. 2024-191484 filed on October 31, 2024, the disclosure of which including the specification, the drawings, and the claims is hereby incorporated by reference in its entirety. BACKGROUND The present disclosure relates to a method for forming a metal oxide coating and a plating equipment for the method. As a method for forming a metal coating on a surface of a non-conductive plating target such as a glass substrate, a method of performing electroless plating of a metal coating such as copper or gold after forming a zinc oxide coating on a surface of a plating target is known. As a method for forming a zinc oxide coating on a surface of a plating target, methods such as evaporation, spattering, and sol-gel methods are known. Among such methods, an electroless plating method has attracted attention because of easiness in forming a zinc oxide coating on a surface of a plating target. The electroless plating method of a zinc oxide coating is performed using a plating solution containing zinc nitrate and a boron-based reducing agent such as dimethylaminoborane (DMAB). This method can be performed only by immersing a plating target in the plating solution, and thus, a zinc oxide coating can be easily formed (see, for example, Japanese Patent Application Publication No. 9-278437). SUMMARY A plating solution for a zinc oxide coating, however, has the problem of a short life. In the plating solution, the boron-based reducing agent such as DMAB is rapidly decomposed and generates boron. Electroless plating of a zinc oxide coating progresses with involvement of hydroxide ions. Since boric acid in the plating solution inhibits generation of hydroxide ions and zinc hydroxide, deposition ability of the zinc oxide coating rapidly degrades even through zinc ions and the reducing agent sufficiently remain in the plating solution. This causes the necessity for frequently replacing plating solutions. Such a problem can also arise in formation of a coating of other metal oxides using a reducing agent containing boron as well as the zinc oxide coating. It is therefore an object of the present disclosure to extend the life of a plating solution for forming a coating of a metal oxide to enable efficient use of a plating solution. In an aspect of the present disclosure, a method for forming a metal oxide coating includes: forming a coating of a metal oxide on a surface of a plating target with a plating solution containing a metal compound to form a coating, and a boron compound as a reducing agent; and regenerating the plating solution with an adsorption filter that adsorbs boric acid. In the aspect of the method for forming a metal oxide coating, the plating solution is regenerated with the filter that adsorbs boric acid. Accordingly, the boric acid concentration in the plating solution can be kept low, and thus, the plating solution can be used for a long time. This can significantly enhance productivity. The method for forming a metal coating according to present disclosure can significantly extend the life of a plating solution and enables efficient coating formation. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view illustrating an example of a plating equipment for use in a method for forming a metal oxide coating according to the present disclosure. DETAILED DESCRIPTION A method for forming a metal oxide coating according to this embodiment can be performed using a plating equipment 100 as illustrated in FIG. 1. The plating equipment 100 includes a plating tank 101 in which a plating solution 104 is placed, and a circulation circuit 102 in which the plating solution 104 placed in the plating tank 101 circulates. The circulation circuit 102 includes a circulation pump 121, a first filter 122, and a second filter 123. The first filter 122 is a typical filtration filter through which foreign matter such as an aggregation in the plating solution 104 is removed. The second filter 123 is a column filled with beads of a chelating resin for selectively removing boric acid. The plating solution 104 is an electroless plating solution of a zinc oxide coating containing zinc nitrate as a metal source, and DMAB as a reducing agent. The plating target 106 such as a glass substrate is immersed in the plating solution 104 in the plating tank 101, thereby forming a zinc oxide coating on a surface of the plating target 106. In deposition of a zinc oxide coating in the plating solution 104, boric acid and electrons (e-) are generated from DMAB as a reducing agent (Equation 1). Zinc nitrate is dissociated into zinc ions and nitrate ions (Equation 2). Nitrate ions generate nitrite ions and hydroxide ions by water and electrons (Equation 3). Zinc ions are combined with hydroxide ions to form zinc hydroxide, and further, zinc hydroxide changes into zinc oxide so that a zinc oxide coating is deposited on a surface of the plating target 106 (Equations 4 and 5).CH32NHBH3+3H