GB480356A - Improvements in or relating to electric discharge lamps comprising material adapted to be excited to luminescence by an electric discharge - Google Patents

Abstract

480,356. Luminescent materials. GENERAL ELECTRIC CO., Ltd., McKEAG, A. H., and RANDALL, J. T. July 23, 1936, Nos. 20445/36, 34284/36, 5694/37, and 12704/37. [Class 98 (i)] Means for producing light comprises in combination a source of radiation which in operation emits the mercury spectrum and luminescent material exposed to the radiation wherein the material is activated zinc-beryllium silicate with or without other luminescent materials. The preferred composition of material is ZnO.BeO.Si02 activated with manganese, the colour of the emitted light varying with the proportion of the activator. The material may be prepared by mixing powdered beryllium oxide, zinc oxide, and silica with water to a stiff paste and adding sufficient MnCl2 to give À5 per cent Mn in the final product. The mixture is then heated in a silica boat to 1250‹ C. for 3 to 4 hours, ground, and sieved to the desired particle size. With a higher proportion of manganese a lower temperature is used, e.g. with 1À5 per cent Mn, a temperature of 1150‹ C. The material may be used with high or low pressure mercury vapour lamps. For example, a cold electrode tube with a mercury-argon filling gives a white light when the material is distributed on the inner surface of the envelope, a current density of 5-50mA /cm<2> being used. To increase the proportion of red light in the emission cadmium silicate activated with manganese may be included in the mixture. Specifications 431,409, [Group XL], and 478,302 are referred to.