Abstract: A photochromic naphthopyran of formula (I) wherein R1 through R15, which may be the same or different, are independently selected from the group consisting of hydrogen, C1-C4 alkyl, C1-C4 alkoxy, halogen, C1-C4 alkylcarbonyloxy, benzoyloxy, C3-C6 cycloalkyl, phenyl, and NR16R17, wherein R16 and R17 are each C1-C4 alkyl or together with the N atom form a 5-12 membered monocyclic or polycyclic ring having, optionally, one or more further heteroatoms; R is hydrogen, alkyl or alkoxy; and >C(CnH2n=1) (CmH2m=1) is a tert-alkylene grup, wherein n and m are integers from 1 to 5.

Abstract: Polysiloxane copolymers containing both photochromic and lightstabilizing groups with enhanced UV-fatigue resistance can be used as coatings for devices with variable optical density, including lenses, glazing, textiles and the like, to provide light-sensitive darkening effects. The photochromic groups are spironaphtooxazine groups and the lightstabilizing groups are hindered amine light stabilizing (HALS) groups.