Bromophosphonitrile lamps

Abstract

A major problem of tungsten halogen lamp technology has been the difficulty of gettering oxygen and water vapour in the finished lamp, A material, such as phosphorus, can be used to getter the oxygen providing its concentration is carefully controlled. The introduction of the getter as accurately as the halogen has been overcome by introducing both together in the form of a bromophosphonitrile, (PNBr ₂)_n. These involatile solids are introduced as a solution in a volatile, non-polar solvent. The compound is dissociated in the finished lamp by the heat of the filament and the phosphorus so produced acts as a getter and as a buffer to the reactive bromine. A 35 per cent improvement in automobile lamp life has been achieved and halogen lamp manufacture has been simplified to a point where conventional lamp machinery can be used.