PURPOSE: To render fog resistance to a substrate by converting the surface of an inorg. coating film into a hydrophilic surface.
CONSTITUTION: When an inorg. coating film is subjected to defogging treatment, a terminal of a compd. forming a hydrophilic polymer infiltrated into fine gaps in the structure of the film is exposed to the surface of the film and the angle of contact of the surface with water is regulated to ≤50°. The coating film is formed by a known coating method such as vacuum deposition or ion sputtering at a temp. below the m.p. of an evaporating material, perferably at ≤200°C. The inorg. coating film is an optically transparent homogenous film having a microporous structure enabling the diffusion of a monomer for polymn. The inorg. coating film subjected to defogging treatment is useful for a substrate unfit for vacuum deposition at a high temp., especially for a plastic lens with an inorg. antireflection film.