POWDER HAVING MULTILAYER FILM ON ITS SURFACE AND PROCESS FOR PREPARING THE SAME

摘要

The refractive index of a metal oxide film on the surface of a powder is enhanced to give a high-reflectance, vividly colored powder, and the number of the layers constituting the metal oxide film is reduced to give a powder having a small particle diameter. The powder comprises a base powder and a multilayer film that has at least a metal oxide film formed by the hydrolysis of a metal alkoxide and that has been heat-treated. The process for preparing the above powder comprises the steps of: dispersing a base powder in a metal alkoxide solution; hydrolyzing the metal alkoxide to prepare a metal oxide, thereby forming a metal oxide film on the surface of the base powder; repeating the above steps a plurality of times to form a multilayer film; conducting heat treatment at least in the final step; and regulating a combination of the substances constituting the multilayer film and the film thickness to change the interference color of the multilayer film, thereby imparting a vivid color to the powder.