| 摘要 |
PROBLEM TO BE SOLVED: To provide a long-life discharge lamp with excellent initial ultraviolet ray strength and with little degradation of ultraviolet ray strength during lighting. SOLUTION: With the discharge lamp with an arc tube made of a transparent quartz tube having an electrode at both sides inside which rare gas and mercury are sealed in, and on the inside face of which a protection film of aluminum oxide is arranged, the protection film of aluminum oxide consists of fine powder of article diameter of 0.1 micron or less, and deposit volume per unit area on the inside face the arc tube is to be 20 to 100 (μg/cm2).
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