Improvements in or relating to methods of controlling the spacial distribution of an evaporated film of getter material within the evacuated vessel or tube of an electron discharge device

摘要

1,086,489. Discharge apparatus. S.A.E.S. GETTERS S.p.A. Aug. 25, 1965 [Feb. 25, 1965], No. 36493/65. Heading H1D. A thin film of metal getter material is deposited within a discharge tube envelope by evaporation in the presence of a gas at a pressure sufficient to limit the mean free path of the getter metal atoms to a distance comparable with or less than the distance between the getter evaporation source and the relevant portion of the envelope whereby, in a cathoderay tube, for example, the production of an unduly thick getter layer in the centre portion of the screen may be avoided. The preferred gas is nitrogen, at a pressure between 5 x 10-2 and 1 x 10-3 torr, introduced either as such before sealing off, or as a compound which can be disassociated to yield nitrogen at a temperature below that at which the getter evaporates. The nitrogen compound, of which suitable examples are given, may be either physically separated from the getter container, or mixed with the getter material therein, or the getter container itself may be nitrogenated. In an example, a barium film is deposited in a cathode-ray tube from a getter mixture of barium/aluminium alloy and nickel, in the presence of nitrogen derived from powdered iron nitride; a baffle prevents backward deposition of the barium on the electron gun structure, and the free nitrogen is itself finally removed by the gettering action of the film.