GB782983A - Improvements in or relating to the formation of evaporated layers - Google Patents

Abstract

782,983. Coating by vapour deposition. ELECTRIC & MUSICAL INDUSTRIES, Ltd. July 25, 1955 [July 27, 1954], No. 21831/54. Class 82(2) [Also in Group XL(a)] A layer of uniform thickness is formed on a surface by evaporating material to form the layer from a point source disposed at a distance from said surface and from a ring source disposed closer to said surface than the point source, the point source being on the axis of the ring source. As shown, an electron discharge device comprising an envelope 1 and glass window 2 is first provided with a transparent conducting layer 3, by spraying the window when hot with a stannous or stannic chloride solution, and then with a spongy layer 4 of the photoconductive antimony trisulphide by evaporation from (a) a point source 8 which may be a Ta boat containing the antimony trisulphide or a filament containing a bead of the material and (b) the ring source 7 formed by evaporating on to the surface of the ion trap mesh 5 a ring of antimony trisulphide. The deposition is performed in argon at a pressure of about 1 mm. Preferably the deposition from the point source is interrupted after half the quantity of antimony trisulphide therein has been deposited in order that the mesh 5 may be cleared by heating so as to sinter the deposit thereon but so as not to cause evaporation from the mesh or ring source. The remaining antimony trisulphide is then evaporated from the point source and finally the antimony trisulphide is evaporated from the ring source and mesh by e.g. eddy current heating the anode 6. During deposition from the point source, the window 2 may be maintained at a temperature of 50‹C. and during the evaporation from the ring source and mesh, the window may be kept cool by immersing it in iced water.