GB1334176A - Methods of providing luminescent chalcogenides with a barrier layer - Google Patents

Abstract

1334176 Luminescent materials PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd 10 June 1971 [13 June 1970] 19906/71 Heading C4S A method of providing a luminescent chalcogenide of Zn and/or Cd with a barrier layer, comprises the steps of suspending the chalcogenide in an aqueous solution containing Zn and/or Cd ions, a lye solution, an organic thio compound which can be hydrolysed to liberate sulphide ions, and optionally a complexing agent for Zn and/or Cd, and allowing a layer of Zn and/or CdS to be homogeneously precipitated on the chalcogenide of the same or analogous structure to the chalcogenide. The chalcogenide is a sulphide and/or selenide and/or telluride and a lye solution is defined as ammonium hydroxide, an alkali metal hydroxide on a water-soluble quaternary ammonium base, e.g. tetramethylammonium hydroxide. Unactivated phosphors and Ag, Au or Cu with optionally Cl or Al as co-activator, are instanced, excited by U.V. and electrons and colour depending on Zn : Cd ratio and the activator concentration. Oscilloscope and T.V. tubes utilizing barrier layers for penetration type operation of a mixed phosphor screen are discussed. The complexing function may be fulfilled by the lye for Zn ions, for soluble zincates are formed for a lye pH of #10; and a colourless barrier layer is formed. Agents such as ammonia or ethylene-diaminetetra-acetic may be used. The thio-compound may be added after an initial suspension and heating step, and detailed examples with temperatures are given. Thio compounds may be thioacetamide and preferably thio-urea. The examples include (Zn, Cd)S; Ag, Cl; (Zn 0 . 9 - Cd 0 . 1 )S : Cu, Al; and red Y 2 O 2 S-0À05 Eu with green (Zn 0 . 6 Cd 0 . 4 )S : Ag, Cl; threshold voltages being exemplified.