| 摘要 |
PROBLEM TO BE SOLVED: To prolong a long life by reducing changes with respect to lapse of time while improving initial characteristics of lamp characteristics such as color characteristic and efficiency, in the case of a metal halide lamp in which at least dysprosium iodide and cesium iodide are enclosed. SOLUTION: Dysprosium iodide and cesium iodide, such that a mol ratio of dysprosium iodide vs. cesium iodide of 2:3, are enclosed with 3.5 mg in a luminous tube 1 in which electrodes 11 are sealed at its both ends, while 0.5 mg of thallium iodide, 10 mg of mercury, and 6.7×10<3> pascal of argon gas are sealed therein, an infrared reflection film 13 which reflects 60% of infrared rays in 800 to 900 nm range, having 852 nm and 894 nm as center wavelength is provided on an outer surface of the luminous tube. The luminous tube 1 is disposed in a lamp outer tube 2, thus constituting a metal halide lamp.
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