To develop a heat-curable resin composition with a low refractivity, capable of giving a cured product which is excellent in heat resistance, adhesion, hardness, solvent resistance, and transparency, and having excellent coating properties suitably used as a clear coating agent, etc., for an optical good, such as a liquid crystal display panel and a color filter protecting film.

A copolymer having a specific structure is obtained by copolymerizing a fluorine-containing monofunctional (meth)acrylate compound, a monofunctional (meth)acrylate compound having one hydroxy in its structure, and a silicon-containing monofunctional (meth)acrylate compound. The resin composition contains the copolymer, a melamine-based compound, and a diluent.