Patent ID: 9310541
Filing Date: 2016-04-12
CPC Classification: G02B

Claim Text:
1. A layered photochromic composition for providing protection from impinging solar light that includes ultraviolet light, said composition comprising first and second layers of photochromic material, the first layer receiving said solar light and the second layer receiving light from the first layer, said first layer having an outer surface receiving said solar light and an inner surface facing said second layer, said first layer containing a first photochromic material that is reversibly activated by impinging ultraviolet light having wavelengths within a first activation spectral band, and said second layer having a first surface facing the inner surface of said first layer and a second surface facing away from said first layer, said second layer containing a second photochromic material that is reversibly activated by ultraviolet light received from said first layer and having wavelengths within a second activation spectral band that is non-overlapping or only partially overlapping with said first activation spectral band, said second photochromic material being more susceptible to fatigue from exposure to ultraviolet light than said first photochromic material, wherein the absorption of ultraviolet light by said first layer reduces the amount of ultraviolet light that reaches said second layer.