| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide a light radiation device that is able to radiate light of 300-400-nm wavelength for a long time, by preventing entry of metal halide into a sealing part, thereby providing a metal halide lamp having a long life.SOLUTION: A light radiation device comprises a metal halide lamp of a long arc type and a reflection mirror arranged on the rear of the metal halide lamp, and radiates ultraviolet rays of 300-400-nm wavelength. In the metal halide lamp, the arc tube made of quarts glass contains iron as a luminescent material. The end part of the arc tube has a holding cylinder supporting the shaft part of an electrode. A molybdenum foil is buried in the sealing part. If the length of the holding cylinder is L(mm), and the current of the lamp is I(A), L/I (mm/A) is equal to or greater than 0.17. A specific metal formed from at least one of the following: tin, bismuth, gallium, lead and zinc, is sealed in the arc tube.</p> |
