GB836881A - Improvements in or relating to cathode ray tubes - Google Patents

Abstract

836,881. Cathode-ray tubes. NATIONAL RESEARCH DEVELOPMENT CORPORATION. April 30, 1956 [May 2, 1955], No. 13256/56. Class 39(1). A " flat " cathode-ray tube suitable for use in television reception, of the type described in Specifications 794,257 and 801,841 in which an electron beam is deflected out of a plane parallel and adjacent to the flourescent screen into impingement with it, has all the deflecting, accelerating and focusing electrodes, apart from the gun electrodes, and the fluorescent screen, provided as coatings on the envelopes, the envelope consisting of two moulded glass parts 10, 11, Figs. 2, 3, joined together at 8 by sintered glass frit. The two parts are shaped and coated with conductive material such as tin oxide or paints compounded from glass frit and silver, to provide U-shaped horizontal sweep deflection electrodes 20 skirted accelerating electrodes 21, 22, first and second pairs of focusing electrodes 27, 28 and 31, 32, and vertical sweep deflection electrodes 14. A conductive base coating 13 for the fluorescent material of the screen may consist of a suspension of chromium oxide and silicic acid. Both the screen material, including the phosphor, and the deflection electrodes 14 may be transparent, or the deflection electrodes may be opaque and the screen viewed from one side only. Non-conductive material such a as chrome oxide solution, or a high-resistance leakage material such as stannic chloride may intervene between the electrode coatings. The gun 12 may be disposed within a cavity formed by the two moulded parts of the envelope and delivers the beam along the vertical edge of the screen ; the beam is bent through 90 degrees at the corner of the screen by an electrostatic mirror to pass along the lower edge of the screen. In a further embodiment, Fig. 4, the envelope has a ledge portion 55 bearing a further electrode 56 which cooperates with the lowermost of the deflection electrodes 58 to provide a strong deflecting action ; strong deflecting actions at the other electrodes 58 are obtained by the potentials of two adjacent electrodes changing at the same instant. The initial potential on electrodes 58 may be positive or negative with running negative or positive potential waves respectively.