| abstract |
(57) [Summary] [Purpose] The objective is to obtain a high-performance, long-life metal halide lamp with a simple process. [Structure] A columnar arc tube 1 having a pair of electrodes 2 and 3 at both ends and which does not require bulb molding is filled with mercury, a rare gas for starting and a metal halide. 10 Is a heat insulating film for increasing the temperature of the lower part. The inner diameter R of this arc tube is 9.0 (mm) ≤ R ≤ 12.0 (mm), the internal volume V Is 0.80 (cc) ≦ V ≦ 1.30 (cc). This makes it possible to manufacture an arc tube for a metal halide lamp by a simple process, and to achieve high performance and a long life. |