| 摘要 |
PURPOSE:To improve the luminous efficiency and the color rendering performance of a metal halide lamp by using a first layer consisting of a heat-absorbing member and a second layer consisting of a heat-reflecting member to form a heat-insulating film and restricting an area coated with the first heat-protecting film to within a specified range. CONSTITUTION:The outer surface of one end of an emission tube 1 is coated with a first heat-insulating film 11 consisting of a heat-absorbing member and a second heat-insulating film 12 consisting of a heat-reflecting member in that order so that the temperature of the coldest point is maintained high. For instance, in an emission tube 36, a first heat-insulating film 37 consisting of aqua duck and a second heat-insulating film 38 consisting of zirconium oxide are respectively formed on almost the same areas which are comprised of a press seal area 28, a part of an electrode-encircling area 29 extending along a border line 39 between the encircling area 29 and the press seal area 28, and an area extending from the center of the above part of the electrode-encircling area 29 to almost the pointed end of an electrode coil 35 along an electrode 3. Owing to the above constitution, no rapid changes in optical color occur and variation in the optical color decreases. |
