| 摘要 |
PURPOSE:To suppress the heat loss from pressed sealing parts, and realize enhancement of the lamp efficiency as well as stabilization of the lamp light color by providing at least one of the sealing parts with a narrow part, which has a given width and is located between a metal foil conductor and the base of an electrode. CONSTITUTION:Cuts 20 are provided on both sides of a sealing parts 4a, which is located on the lower end of a discharge space, thereby forming a narrow part 21. The narrow part 21 is located between a metal foil conductor 5a and the base of a main electrode 2a. The cuts 20 are formed along a shape 22 of the end of the discharge shape. The minimum width l of the part 21, and the inner diameter D of the part of an emission tube 1 which corresponds to the end of the electrode 2a are restricted to satisfy the relationship of l/D<=1, preferably l/D<=2/3. As a result, any heat is prevented from being conducted toward the lower side of the sealing part 4a owing to the narrow part 21. Consequently, the efficiency of a metal halide lamp can be enhanced, and the variation in the color of lamp light can be decreased. |
