GB407521A - Improvements in or relating to mosaic electrode structures for use in cathode ray apparatus for television and similar purposes and to methods of manufacture of the same - Google Patents

Abstract

407,521. Cathode - ray tubes &c. MARCONI'S WIRELESS TELEGRAPH CO., Ltd., Marconi House, Strand, London.- (Assignees of Essig, S. F. ; 334, Milne Street, Philadelphia, U.S.A.) Feb. 24, 1933, No. 5700. Convention date, Feb. 24, 1932. [Class 39 (i).] Mosaic electrodes comprising individual insulated particles of electrically-conductive material supported in spaced relation on a base and suitable for use as the photo-electric screen of a cathoderay tube in a television transmitter are made by applying a layer of metal or metal compound to the base and heating so that the metal layer applied or produced breaks up into globules. Silver oxide or carbonate may be applied as a layer to a mica sheet 10, Fig. 4, by spraying, flowing, printing or dusting, for example, by allowing a fog of fine particles to settle on to the sheet. The sheet is heated to 800‹ C. for 15 seconds in a furnace to form a layer of silver which runs into minute spaced globules 24, the process of applying oxide and heating being repeated if necessary until sufficient globules are formed. The sheet is then inserted into the cathode-ray tube and the globules 24 are oxidized as at 26, Fig. 7, by ionizing a filling of oxygen at .1 mm. pressure by a high-frequency field. Caesium 28 is then deposited on the globules from a capsule containing caesium. To insulate the globules and to bring them to their maximum photo-electric sensitivity, the caesium between the globules and the excess of caesium on the globules is removed by heating, the tube being connected to a pump and the sheet being baked first at 200-225‹ C. until the globules are near their maximum sensitivity and then at 100-150‹ C. for a longer period. During this heating, the electron gun is heated by a high-frequency field to prevent the condensation of caesium thereon. In a television transmitter, the globules charge up according to the brightness of the image at the corresponding point and are discharged by the cathode ray. Instead of applying initially a layer of metal compound to the sheet 10, a metal layer may be applied by spraying, by evaporating or sputtering in a vacuum or chemically as from a solution obtained by mixing an ammonial silver oxide solution and a reducing solution containing sucrose. The Specification as open to inspection under Sect. 91 comprises also the use of a sheet of aluminium coated with aluminium oxide as the base. This subject-matter does not appear in the Specification as accepted.