GB669392A - Process for coating vitreous surfaces with powdered luminescent materials - Google Patents

Abstract

669,392. Luminescent materials. BRITISH THOMSON-HOUSTON CO., Ltd., ANDERSON, J. T., and WARD, H. F. April 29, 1949 [April 2, 1948], No. 9356/48. Class 39 (i). Process for coating a vitreous surface, e.g. a fluorescent lamp tube, with powdered luminescent material comprises coating the surface with a suspension of the material in a water solution of an organic material (other than ammonium alginate) which is capable of giving at least moderately viscous solutions and which, when heated to a decomposition temperature, leaves only a small or no residual ash, and thereafter heating the coating so formed to a temperature at which decomposition takes place. The water-soluble organic material may consist of water-soluble starch or a watersoluble cellulose such as methyl cellulose or glycoll cellulose or the water-soluble variety of " Cellophas " or a salt of alginic acid (other than ammonium alginate) such as triethanolamine alginate. A wetting agent such as that known under the Registered Trade Mark " Teepol X " which leaves no deleterious residuum after the heating to the decomposition temperature may be added to the suspension of the luminescent material. In cases where the luminescent material is readily wet by water the material may either be previously wetted with water containing the wetting agent, the material being subsequently thoroughly washed with successive lots of distilled water to remove substantially the whole of the wetting agent,'or the material may be immersed, with or without agitating, in water. The wetted powder is then added to the binder without intermediate drying. The process is applicable both to luminescent materials which are not readily soluble in water and to luminescent materials which are readily soluble in, or attacked by, water, if the process is carried out sufficiently quickly to ensure that the period of contact of the material with water is restricted.