GB615812A - Improvements in and relating to cathode ray luminescent screens - Google Patents

Abstract

615,812. Luminescent screens for cathode-ray tubes. BRITISH THOMSON-HOUSTON CO., Ltd. (General Electric Co.). Aug. 9, 1946, No. 23706. [Class 39 (i)] A luminescent screen for a cathode-ray apparatus producing a contrasting trace for moving objects in range finding and direction finding equipment comprises a first luminescent layer emitting light or ultra-violet radiation under electron bombardment, an intermediate electron impervious layer and a second layer consisting of a mixture of two luminescent materials giving lights of contrasting colours in response to the light or ultraviolet radiation, and of different responses and rates of decay. The screen (Fig. 2) carried on the glass wall 62 of a C.R. tube has a first layer 31 comprising a material, e.g. silver activated zinc sulphide, which emits ultra-violet and bluish light under cathode-ray excitation, an electron absorbing layer 32, e.g. of an alkaline. silicate of which a number of layers may be sprayed on, and a layer 30 consisting of a mixture of two phosphors, e.g. red fluorescing copper activated zinc cadmium sulphide (CdS 25-40 per cent) which has a quick pick-up and decay and green fluorescing copper-activated zinc sulphide which has a slow pick-up and decay. Alternatives for the latter are yellow fluorescing copper-activated zinc cadmium sulphide (12 per cent CdS) or blue fluorescing bismuth-activated strontium sulphide. Specification 598,545 is referred to.