Patent ID: 6873109

Claim:
A metal halide discharge lamp which essentially permits disusing mercury, comprising: (a) a refractory and light-transmitting hermetic vessel; (b) a pair of electrodes fixed to said hermetic vessel; (c) a discharge medium sealed in the hermetic vessel and containing a first halide and a second halide, (i) said first halide being a halide of at least one metal which emits a visible light and being a halide of at least one metal selected from the group consisting of sodium, scandium and a rare earth metal, and (ii) said second halide having a vapor pressure less than 5 atmospheres during lighting so as to act as a buffer gas to maintain a lamp voltage and being a halide of at least one metal which emits a visible light less than that emitted by the metal of the first halide; and (d) an outer tube housing said hermetic vessel.