| abstract |
Novel spiropyran compounds, particularly with photochromic properties, are disclosed, as well as photochromic compositions and ophthalmic articles (e.g. lenses) containing said compounds. The photochromes have been designed so as to have a high colorability, a high sensitivity to activating radiation breaking the pyran ring, to be entirely or practically free from coloration in a non activated (non exposed) state, to have an intense coloration following activation and a high coverage of the visible spectrum in combination with at least one other photochrome, and to have high rates of coloration/decoloration. The spiropyrans are easily produced and photochemically stable, and are, e.g., of formula (i), wherein L = (a);(b). |