Curable resin composition, a protective film and method of forming

Required transparency, heat resistance, surface hardness, fulfills adhesion, excellent load bearing even under heating, sublimates during firing is small, also to flatten the level difference of the color filter formed on a base substrate curable resin composition capable of forming an excellent optical device protective film performance, the protective film formed from the composition, and to provide a method of forming the protective film. (A) The ratio of polystyrene-reduced weight average molecular weight measured by and gel permeation chromatography has two or more epoxy groups (Mw) and number average molecular weight in terms of polystyrene (Mn) (Mw / Mn) is 1.7 or less in a polymer and (B) (a) a curable resin composition containing different cationically polymerizable compound is a component.