Ultraviolet blocking coating and associated coated optical element

Abstract

The UV blocking coating includes at least eight alternating layers of a first dielectric material and a second dielectric material stacked upon the surface of an optical substrate to thereby form windows, windscreens, lenses or the like. The first dielectric material has a higher index of refraction then the second dielectric material. For example, the first dielectric material can be TiO.sub.2, ZrO.sub.2 and Ta.sub.2 O.sub.5 and the second dielectric material can be MgF.sub.2 or SiO.sub.2. In addition, each layer of the second dielectric material has an optical thickness which is greater than the optical thickness of the underlying layer of the first dielectric material upon which the layer of the second dielectric material is stacked. As a result of the unique construction of the UV blocking coating, the reflectance of the UV blocking coating varies dramatically upon exposure to UV light on the one hand and to visible light on the other hand. In particular, the reflectance of the UV blocking coating as a function of wavelength defines a high reflectance region in which greater than 90% and, more typically, greater than 95% of UV light having a wavelength of 350 nm to 400 nm is reflected and a low reflectance region in which less than 5% and, more commonly, less than 2% of visible light having a wavelength of 450 nm to 700 nm is reflected.