Photochromic coating composition comprising nanoscales particles and process for providing substrate coated with the same

A photochromic coating composition comprising the following components:

• (a) a silicon-containing precondensate derived from:
• (i) at least one hydrolyzable silane A containing at least one hydrolysis-stable radical R having a functional group X that is capable of undergoing at least one of a thermally induced polymerization reaction and a photochemically induced polymerization reaction, and
• (ii) optionally, at least one additional hydrolyzable compound based on elements from the group consisting of Si, Al, Ti, Zr, Ta, Nb, Sn, Zn, W, and Ge;
• (b) at least one photochromic dye selected from the group consisting of spirooxazines and naphthopyrans;
• (c) at least one stabilizer selected from the group consisting of statically hindered phenols, sterically hindered hydroquinones sterically hindered pyrocatechols, and sterically hindered aromatic amines, organic phosphites, organic phosphonates, benzophenone derivatives, substituted benzotriazoles, cinnamic acid derivatives, salicylates, 3-(5-imidazolyl)acrylic acid, and ergosterol;
• and
• (d) nanoscale particles having an average particle size of not more than 200 nm;
• where the at least one stabilizer (c) comprises from 0.1 to 5.0% by weight, based on the total weight of components (a), (b) and (c).