GB737861A - Improvements in and relating to electric incandescent lamps - Google Patents

Abstract

737,861. Electric incandescent lamps. DESHAW, Z. June 12, 1950 [March 11, 1949; March 16, 1949; March 11, 1949], Nos. 6673/49, 7167/49 and 14597/50. Divided out of 737,862. Class 39 (2). [Also in Group XL (a)] An electric incandescent lamp has a glass bulb coated internally with an adhering fluorescent material which is activated by the invisible energy discharge from the filament, the thickness of the coating layer and the nature and size of the particles thereof being such that not less than 95 per cent of the visible light from the filament entering the layer is emitted by the corresponding external surface of the bulb, the size of the particles being such that they will pass a 300-mesh screen. 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 nitro-cellulose with ethyl lactate as a plasticizer, and a thinner of butyl acetate and the same plasticizer. The mixture is subjected to prolonged grinding in a ball mill. Before applying the suspension to the interior of a bulb the latter 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 pour slowly out. The bulb is then allowed to stand inverted for about an hour to drain away the excess suspension and allow the remaining coating to set. The quantity of suspension retained evenly over the interior surface of a 75 mm. bulb is about 4 cubic centimetres. Compounds other than titanium dioxide, which have fluorescent properties, refractive indices preferably greater than 2.0, are capable of being reduced to a particle size of the order of 0.25 to 10 microns, and are chemically inert in the presence of the materials within the lamp bulb, may be employed as coating materials. Specification 737,862 is referred to.