| 摘要 |
PROBLEM TO BE SOLVED: To provide a long-life metal halide lamp by restraining occurrence of devitrification. SOLUTION: With the metal halide lamp, a diffusion layer 8 of the thickness of 1.0 to 5.0μm containing at least one kind selected from Y2O3, CeCO2, TiO2, Ho2O3, Sc2O3, HfO2, is formed on the inner face of a light-emitting tube 1a made of quartz glass. The diffusion layer 8 plays a role of restraining reaction of the quartz glass with a sealed substance.
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