| 摘要 |
A high-pressure discharge lamp comprising a translucent airtight container having a discharge space therein, a pair of electrodes sealed in the airtight container, the electrodes having an inter-electrode distance D of 2 mm or less and facing the discharge space, and an ionizing medium sealed in the airtight container and substantially being mercury-free while it contains thulium (Tm) halide, zinc (Zn) halide and rare gas, the zinc (Zn) halide being less than 20% to 90% by mass of all metal halides sealed in the airtight container, wherein a ratio V<SUB>1</SUB>/D of a lamp voltage V<SUB>1 </SUB>(V) to the inter-electrode distance D (mm) satisfies the following formula. <?in-line-formulae description="In-line Formulae" end="lead"?>20<V<SUB>1</SUB>/D<100<?in-line-formulae description="In-line Formulae" end="tail"?>
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