GB737862A - Improvements in and relating to electric incandescent lamps - Google Patents

Abstract

737,862. Electric incandescent lamps. ISMAY LAMPS, Ltd. June 12, 1950 [March 11, 1949 ; March 16, 1949], Nos. 6674/49 and 7168/49. Class 39 (2). In order to produce an opalescent effect the interior surface of the glass bulb of an electric incandescent lamp is coated with an adhering layer of titanium dioxide and a binder, the thickness of the layer and the particle size of the titanium being such that not less than 95 per cent of the light entering the layer is emitted uniformly by the corresponding external surface of the bulb. Preferably, the coating layer comprises titanium dioxide of not less than 98 per cent purity and a liquid binding medium consisting of a 2 per cent solution of nitrpcellulose with ethyl lactate as a plasticizer, and a thinner of butyl acetate and the same plasticizer, this mixture being subjected to prolonged grinding in a ball mill. Before the coating is applied the interior of the bulb is washed thoroughly with a cleansing solution, then rinsed with water at 80-90‹ C., subjected to the action of steam, and finally dried by warm air. The suspension may be applied to the inside of the bulb by spraying, pouring, or other methods, e.g. an excess of the suspension is poured into a bulb and the latter is rotated about its axis while allowing the suspension to drain slowly out, after which the bulb is inverted for about an hour to drain off the excess. The bulb may be heated subsequently to a temperature of between 450‹ and 550‹ C. to evaporate the volatile contents of the suspension. The internal surface to which the covering is applied is preferably frosted internally to promote adherence of the covering thereto. Specification 737,861 is referred to.