PURPOSE: To obtain the title composition free from unevenness of reflecting color when reflection preventing film is formed on rigid coating film formed by applying to plastic glass lens by dispersing diamond fine granules into a coating liquid containing a coating film-forming ingredient.

CONSTITUTION: The aimed composition obtained by dispersing diamond fine granules (preferably having 10-100nm granule size) into a coating liquid containing a coating film-forming ingredient (preferably organosilicon compound or hydrolysate thereof) and further as necessary adding a curing catalyst (preferably aluminum chelate compound) thereto. The coating film has excellent scratch resistance, surface hardness, abrasion resistance, flexibility, transparency, heat resistance and antistatic properties, large degree of surface reflection and good adhesion with reflection preventing film, metallized film, etc., and slippery characteristics of coating film surface.