GB570200A - Improvements in or relating to methods of coating surfaces by evaporation - Google Patents

Abstract

570,200. Coating surfaces with quartz. CINEMA-TELEVISION, Ltd., and SOMMER, A. Dec. 23, 1941, No. 16553. [Class 56] [Also in. Groups II, XV and XL] Surfaces within an evacuated envelope, particularly a photoelectric cell or other electron discharge tube, are coated by evaporating a substance, e.g. quartz, from a source through apertures in a foraminated member on to a supporting member to form a layer, the foraminated member being so disposed as to cause the formation of a layer of more uniform thickness than if the member was not interposed between the source and the supporting member. The source is usually unsymmetrically disposed with regard to the supporting member. A pellet 2 of the coating material is supported on a helix 3 connected to leads which extend to the exterior of the envelope 1 and screened from the portion of the latter forming the window by a shield 4, e.g. in the form of a cylindrical or hemispherical cup. A foraminated member 6 comprising a mesh or grid of wire or fibre is so disposed that when the coating material is evaporated from the pellet 2 by passing a current through the helix 3, only a portion of the evaporated material reaches the envelope nearest the helix, while in a position most remote from the pellet all the coating material leaving the pellet reaches the envelope. The grid or mesh may be provided with spacing or apertures and/or wire diameter of graded size.