Abstract: The method of the invention comprises: a) forming a hydrophilic polyurethane prepolymer with isocyanate end groups, by the polyaddition reaction of at least one polyol and at least one diisocyanate in the presence of at least one internal emulsifying agent; b) mixing the polyurethane prepolymer with a photochromic agent; c) adding water or a mixture of water and solvent, under agitation, to the mixture of the polyurethane prepolymer and the photochromic agent, to form an emulsion; and d) adding at least one chain extension agent to the emulsion and performing a chain extension reaction to give the final photochromic polyurethane latex. Application to the production of ophthalmic articles having photochromic properties.

Abstract: Described are photochromic polyurethane coatings that meet commercially acceptable “cosmetic” standards for optical coatings. Also described are articles having such coatings. The coatings exhibit a Fischer microhardness of from 50 to 150 Newtons per mm and improved photochromic properties, i.e., the formation of darker activated colors and faster rates of photochromic activation and fade when irradiated with ultraviolet light.