Mercury-free metal halide discharge lamp, lighting device for such a lamp, and illuminating apparatus using such a lamp

摘要

Disclosed is a metal halide discharge lamp which essentially permits disusing mercury. The metal halide discharge lamp comprises a refractory and transparent hermetic vessel (1), a pair of electrodes (2) fixed to the hermetic vessel, and a discharge medium sealed in the hermetic vessel and containing a first halide, a second halide and a rare gas, the first halide being a halide of a metal which achieves a desired light emission, the second halide having a relatively high vapor pressure, being at least one halide of a metal which is unlikely to emit a visible light compared with the metal of the first halide, and acting as a buffer gas. <IMAGE>