| 摘要 |
PROBLEM TO BE SOLVED: To provide a lamp having a long durably life by providing a plug body having an outermost layer, consisting of a weldable material on at least one end of a discharge tube, connecting a lead wire to the outermost layer through a weld part, and fixing the innermost layer to the end part of the discharge tube without glass wax. SOLUTION: A plug body 11 is formed of four axially laminated circular rings 11a-11d, and the inner most part is turned on a discharge side. The circular ring 11a of the innermost part consists of a cermet containing a small quantity of pure aluminum oxide or a metal and partially fitted to the end part 6a of a discharge tube and sintered directly, that is, without glass wax. The second ring 11b contains 10-25 vol.% of a metal, and the third ring 11c consists of a cermet containing 25-40 vol.% of a metal. The fourth ring 11d contains at least 50 vol.% of a metal and is capable of being welded, and its outer surface is connected to a lead-in wire 9 by laser welding. The metal contained in each circular ring is preferably molybdenum. |
