Patent ID: 6292302
Filing Date: 2001-09-18
Classification: B60R,C03C,G02B

Abstract:
A heat-treatable dichroic mirror, comprising:a) a transparent substrate having a glass transition temperature in the range of 650-800.degree. C.;b) a sputtered silicon nitride base film carried on said substrate and contiguous thereto;c) a plurality of sputtered films carried on said substrate and forming at least two pairs of contiguous films, the films of each pair having disparate refractive indices differing by at least about 0.2 so as to provide between them a reflective interface, the films including a first film that is a member of a said contiguous film pair and comprising an oxide of a metal, a second film positioned further from the substrate than the first film and that is a member of a said contiguous film pair, the second film comprising an oxidizable metal or semi-metal, and a protective overcoat of a thickness and composition sufficient to substantially prevent permeation of oxygen therethrough when heat treated at said glass transition temperature, said mirror, after said heat treatment, exhibiting a transmittance of at least 24% in the wavelength range of 550-650 nm, a reflectance of at least 45%.