Layered photochromic composition and device

摘要

An optical power-limiting passive (self-adaptive) device and method for limiting optical power transmission in lenses and windows, using layers of different photochromic compositions that exploit the full solar ultraviolet (UV) and short visible light spectrum. While a typical single photochromic material is activated by a UV band of wavelengths, e.g. 340 to 380 nm, adding a layer of photochromic material that is activated by an additional band of wavelengths, e.g., 380 to 420 nm, allows the efficient use of a wider band of solar UV and short visible light, e.g., 340 to 420 nm, thus enhancing the photochromic response to solar light.

主权项

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.