GB1176955A - Improvements in or relating to Low Pressure Mercury Vapour Fluorescent Electric Discharge Lamps and their Manufacture - Google Patents

Abstract

1,176,955. Luminescent materials. GENERAL ELECTRIC & ENGLISH ELECTRIC COMPANIES Ltd. 17 July, 1968 [17 July, 1967], No. 32690/67. Heading C4S. [Also in Division H1] In a L.P.M.V. fluorescent discharge lamp containing a rare starting gas at a pressure of a few mm. Hg, and designed in normal operation to develop a minimum wall temperature exceeding 55‹ C., the coating on the internal surface of the envelope includes dispersed in association with the fluorescent material, one or more of the metals Cu, Ag, Au, Zn, Al, Tl, Sn, Pb, Bi, Fe, Co, Ni, in the form of a finely divided powder and in a total amount exceeding 0À3 gram atom per gram atom of the total mercury contained in the envelope. The metal forms an amalgam during processing or initial operation of the lamp to reduce the mercury vapour pressure in operation. The high wall temperature may result either from a power loading exceeding 0À4 watt per sq. inch of the internal surface of the envelope or from operation in conditions of high ambient temperature e.g. in an enclosed fitting. The powder may be uniformly dispersed in the fluorescent material or as a separate layer between the fluorescent material and the envelope. The preferred metals are Sn and Pb which do not oxidize during baking, in particle sizes of 10-50 Á. The coating operation is as described in Specification 1,176,954. A lamp is described having a filling of mercury and argon at a pressure of 2À5 mm. Hg and a coating of a halophosphate phosphor containing Sn powder in an amount of 1À69 gram atoms of Sn per gram atom of Hg. A higher power lamp has a filling of mercury and a mixture of 80% neon and 20% argon at a pressure of 2 mm. Hg and a coating of halophosphate phosphor containing 0À54 gram atom of powdered Sn per gram atom of Hg.