GB501102A - Improvements in or relating to electric gas discharge lamps - Google Patents

Abstract

501,102. Discharge lamps; illuminant enclosures. NAAMLOOZE VENNOOTSCHAP PHILIPS' GLOEILAMPENFABRIEKEN. April 9, 1938, No. 10941. Convention date, April 12, 1937. Drawings to Specification. [Class 39 (i)] [Also in Group XI] The rays from a gas- or vapour-filled discharge tube excite two successively arranged luminescent layers, of which one at least is a glass layer, the layer nearer to the discharge responding to radiation of shorter wave-length than that to which the more distant layer responds. Greater efficiency is obtained than in a mixture of the materials, as absorption of short-wave radiation by the layer excited by the longer wave-length is avoided. The envelope of a low-pressure mercury-vapour lamp may be of uranium glass coated internally with green-fluorescent zinc silicate. The lamp may be surrounded by a fluorescent glass envelope with the other layer on it or on the lamp envelope. Both layers may be luminescent glass ; copper and uranium glasses may form the internal and external layers respectively of a duplex glass envelope. Specification 473,587 is referred to. The Specification as open to inspection under Sect. 91 includes cases in which neither layer is of glass. In one form the envelope of a lowpressure mercury - vapour lamp is coated internally with blue-fluoreseent zinc sulphide responsive to 3600A radiation, on which is superimposed a layer of red-fluorescent zinccadmium silicate responsive to 2537 A radiation, phosphoric acid being used as a binder. Alternatively the layers may be applied to the exterior of the envelope or on either side of it. This subject-matter does not appear in the Specification as accepted.