GB682264A - Light transmissive electrically conducting optical articles suitable for use as a lens, a window or windshield, or the like - Google Patents

Abstract

A transparent article, such as a lens, window or windshield, comprises a body of glassy silicious material having a smooth continuous surface, a transparent interlayer of metal compound applied to the smooth surface and an electrically conductive, continuous metal outer film, having resistivity of not more than 150 ohms/square and of uniform thickness such that the light conductivity of the article is at least 50 per cent a heating current being passed through the metal film to prevent misting or icing of the article. The outer film is Au, Ag, Cu, Fe or Ni and the interlayer, which is 4-108 A DEG thick, is an oxide of Pb, Ag, Al, Mg, Ni, Zn, Cd, Sb, Bi, Hg, Cu, Au, Pt, Pd, Th or rare earth metals, or the sulphide, sulphate, selenide, selenate, telluride, tellurate, or fluoride of these metals. The outer film is preferably applied by thermal evaporation. The interlayer may be applied by direct thermal evaporation, e.g. in the case of the oxides of Pb, Cd, Zn, Sb, Al and the sulphides of Zn, Pb, Sb and Mg F, or in the case of Al2O3, PbO and CuO, by evaporating a metal layer and oxidizing by glow discharge in partial vacuum. Alternatively, oxidizable metal and materials (e.g. metallic sulphides) may be applied and then oxidized by heating in air at high temperatures to form the interlayer. The interlayer may also be formed by sputtering metal, e.g. Cu, Ni, Ag, Au, Pd or Pt, in a partial vacuum, thus forming an oxide coating directly. An interlayer of PbSo4 may be formed by thermally evaporating PbS and then exposing it to air to oxidize it. A protective layer of SiO2, Al2O3 or MgF may be applied to the metal film and, where SiO2 is used, a further interlayer of metallic oxide is interposed between the SiO2 and the metal film. In one example, successive coatings of Al. Au, Al were built up on glass by thermal evaporation and the Al coatings oxidized in a furnace. A further protective layer of SiO2 was applied to the Al2O3 layer and the coated glass laminated with uncoated glass to form a windshield with the metal film on the inside of the lamination. Alternatively, the windshield may be made using a gold oxide interlayer and a gold film and laminated with uncoated glass. Specifications 605,871, 605,872 and 605,873, [Group XX], are referred to.