COATING COMPOSITION

PURPOSE:To provide a coating,composition capable of forming a 5mum or thicker, crack-free coating film on a substrate made of glass, metal, ceramic, refractory resin, or other material which coating film is excellent in all of heat resistance, hardness, adhesion to the substrate, and electrically insulating property at a high humidity. CONSTITUTION:The title composition is obtained by mixing a proper amount of an inorganic powder with a binder produced by hydrolyzing and then condensing a proper amount of an alkoxysilane represented by RnSi(OR1)4-n. The hydrolysis is conducted in a liquid medium, e.g. an organic solvent, in the presence of a colloidal silica obtained by wet-grinding a fine silica powder produced by the wet process. By applying this composition on a substrate made of glass, metal, ceramic, refractory resin, etc., and drying the coating, followed by heating preferably at 100 deg.C or higher, a thick cured film can be formed which is free from cracks and is excellent in heat resistance, hardness, adhesion to the substrate, and high-humidity electrically insulating property.