GB558241A - Improvements in or relating to cathode ray tubes - Google Patents

Abstract

558,241. Cathode-ray tubes. CINEMA-TELEVISION, Ltd. (Szegho, C. S.). Aug. 13, 1942, No. 11356. [Class 39 (i)] A cathode ray tube 1 having a glass window 5 through which can be viewed or projected an image traced on a fluorescent screen 4 by an electron beam which strikes that side of the screen facing the window, has conductive material 6 arranged in or adjacent the window and maintained at a definite potential for the purpose of preventing the window from acquiring charges which would cause undesired deflections of the electron beam. Thus the conductive material may be maintained at the same potential as an inner conducting coating 7 or collecting electrode of the tube, and must be of such a nature that it does not interfere seriously with the viewing or projection of the image. The conductive material may be in the form of a grid or mesh of metal strips or wires incorporated in the window, or arranged on the inner surface thereof ; alternatively, the interior face of the window may have a coating of a metallic fluoride of such a thickness that it reduces light reflections from the window and does not absorb a large proportion of light from the fluorescent screen. In the construction shown, a conductive grid 6 is formed by depositing on the window a continuous graphite or metallic coating, the greater part of which is subsequently removed by ruling.