SURFACE-TREATED PRECOATED METAL SHEET, PROCESS FOR PRODUCING SAME, AND SURFACE-TREATING SOLUTION

摘要

Disclosed is a surface-treated precoated metal sheet of which resistance against contamination with a photocatalyst and a self-cleaning function can be retained for a long period. Also disclosed are a method and a surface-treating solution for producing the surface-treated precoated metal sheet properly. The surface-treated precoated metal sheet is characterized by comprising a precoated metal sheet comprising an under metal sheet and an organic resin coating layer provided on the surface of the under metal sheet and a coating film having at least two layers, having a photocatalytic activity and formed on the precoated metal sheet, wherein the coating film having at least two layers comprises an inorganic-organic composite resin composed of a condensed product of an alkoxysilane selected from a group consisting of an alkoxysilane having an organic group selected from a group consisting of an alkyl group having 1 to 12 carbon atoms, an aryl group, a carboxyl group, a hydroxy group and a combination of two or more of these groups, an alkoxysilane having an epoxy group, an alkoxysilane having an amino group, a tetraalkoxysilane and a combination of two or more of the alkoxysilanes and contains a substance having a photocatalytic activity in such an amount that the content of the substance is highest in the outermost layer of the coating film and is gradually decreased toward an inner layer of the coating film.