Thermal curing composition, cured film and color filter

The invention provides a thermal curing composition and a cured film thereof excellent in flatness, thermal resistance, chemical resistance, adhesive property, hardness, electric reliability and transparency...etc., preferably used as a protective film of a color filter. The thermal curing composition and a cured film formed by curing the thermal curing composition are provided. The thermal curing composition is characterized by including: an epoxy compound represented by a formula (1) with n having an average value of 0.2-1.0; an epoxy compound formed by polymerizing or copolymerizing one or more polymeric unsaturated compounds wherein a glycidyl methacrylate is an essential component, with an epoxy equivalent of less than 200 g/eq and a number average molecular weight of less than 10 thousand; and a curing agent selected from a group consisting of a polycarboxylic acid, an anhydride of the polycarboxylic acid and a thermolysis ester of the polycarboxylic acid.