There is provided a coating composition which can be applied to a substrate such as a plastic lens so as to form a photochromic coating layer having good photochromic properties and excellent adhesion to the substrate on the surface of the substrate.
This composition comprises, for example, as monomer components, 0.1 to 20 wt% of monomer-having a group which produces a silanol group through hydrolysis such as γ-methacryloyloxypropyltrimethoxysilane and 0.1 to 50 wt% of monomer having at least one oxycarbonyl group in a molecule. The composition can further contain a maleimide compound as a monomer component and further desirably contains an amine compound.