Mercury-free metal halide-lamp

摘要

A lamp voltage corresponding to a lamp comprising mercury is obtained by comprising at least a rare gas, a trivalent of indium halide and a thallium iodide in an arc tube 1, and thereby a long life can be accomplished. In addition, when an enclosed amount of the trivalent of indium halide is approximately 90.0mg/cc or less per unit internal volume of the arc tube and the rare gas is xenon gas with an enclosed pressure of 2.5MPa or less, the luminous flux and the light colour most appropriate for a light source for motor vehicle headlights are obtained. Furthermore, when the thallium iodide is enclosed, the lamp voltage can be made even higher and the luminous flux can be increased. <IMAGE>