| 摘要 |
PROBLEM TO BE SOLVED: To provide a metal halide lamp of high efficiency exhibiting little reduction in an initial luminous flux maintenance factor, and allowing lighting by using a ballast for a mercury lamp. SOLUTION: The metal halide lamp includes: an outer tube OT provided with a translucent ceramic air-tight container 1, a pair of electrodes 2, and a discharge medium; an arc tube IT; and a start-up means ST. The metal halide contains NaX, CeX<SB>3</SB>, Cex<SB>2</SB>, and TlX, satisfies 10≤NaX/CeX<SB>3</SB>≤31, 0.02≤CaX<SB>2</SB>/(NaX+CeX<SB>3</SB>)≤1.1, and 0.03≤TlX/(NaX+CeX<SB>3</SB>)≤0.20 respectively in molar composition ratios, and a ratio Le/Dm satisfies 1≤Le/Dm≤4, in the arc tube, where Dm represents the maximum inside diameter of the translucent ceramic air-tight container, and where Le represents a distance between the pair of electrodes 2. COPYRIGHT: (C)2011,JPO&INPIT
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