GB726214A - Improvements relating to cathode ray tubes - Google Patents

Abstract

726,214. Colour television tubes. GENERAL ELECTRIC CO. Feb. 4, 1953 [Feb. 5, 1952], No. 3192/53. Class 39 (1). In a colour television tube in which an electron beam projected on to the back of an apertured electrode 21 at an average angle of incidence of 45 degrees, passes through the apertures 22 and is reflected by an optically transparent electrode 26 to fall on the phosphor colour pattern 23, 24, 25 carried on the front surface of the apertured electrode, the apertures and the phosphor colours between the apertures are arranged in concentric arcuate rows as shown in Fig. 5. The angle of incidence of the electron beam is constant along an individual row of apertures, and the spacing between the rows of apertures is so varied that the same difference of voltage between the two electrodes will cause the same colour to be excited for any point of the target area. The phosphors occupy an area of the order of three-quarters of the target area and the apertures occupy approximately one half of the remaining area. The apertures in the apertured electrode are formed oblique to the plane of the electrode to conform with the angle of incidence of the electron beam. The apertured electrode consists of a copperberyllium-chromium or cobalt alloy, and the apertures are formed by a photomechanical process involving etching from slightly displaced points on opposite sides of the electrode. Each colour phosphor is laid down on the apertured electrode by first printing by letterpress or lithographing a vehicle such as nitrocellulose or linseed oil along the desired lines, and then applying the phosphor in powdered form. The electrodes 21, 26, are spaced apart by glass insulating blocks 44, Fig. 1, which have conducting layers of very high resistance formed on their surfaces. Potential gradients are thus set up to reduce the possibility of arcing between the electrodes 21, 26. The electrode structure is held together by means of clamps 43. The electrode 21 is bolted to a supporting frame 41. Adjustable screws 45 on one limb of the clamps 43 press the electrode structure with interposed spacing blocks 44 against ball bearings set in the other limb of the clamps. In order to prevent vibration of the relatively thin electrode 21 thin flat strips held in blocks 61 secured to the electrode supporting frame 41 bear against the electrode 21. These strips are edge on to the electron beam. The frame 41 is provided with extensions which are bolted to conductive supports 67 bearing against and bolted to the metal body portion 11 of the envelope. Specifications 531,586, [Group II], and 713,875 are referred to.