| 摘要 |
The object of the present invention is to provide a metal vapor discharge lamp offering a favorable performance in that it can restrain increase in metal vapor pressure inside the arc tube incident to the reduction in nitrogen gas in its outer tube, and so has smaller changes in life properties, than conventionally, when the lamp is illuminated. The present invention is a metal vapor discharge lamp including: an arc tube in which mercury, a rare gas, and at least one luminous metal are enclosed; an outer tube in which a nitrogen gas is enclosed and which covers the arc tube; and metal members which are provided in the outer tube and which include wiring for supplying power to the arc tube, where a metal material that reacts with one of nitrogen and a nitrogen compound is not adopted for any of the metal members that are exposed to a nitrogen gas atmosphere in the outer tube whose temperature exceeds 350° C. when the lamp is in a steady-state illumination. From the construction, unlike conventionally, the metal members inside the outer tube will not chemically react attributable to a nitrogen gas, thereby avoiding an excessive heating of the arc tube. Therefore, the chemical reaction attributable to a nitrogen gas under high temperature conditions will not happen, thereby effectively preventing reduction in a nitrogen gas inside the outer tube and reduction in gas pressure. The present invention is particularly effective when the metal members in the outer tube are selected from the group consisting of iron, nickel-plated iron, and an iron-nickel alloy. Furthermore, if the lamp has a structure of exposing a silica glass to the nitrogen gas atmosphere, an impurity composed of a hydrogen component included in the silica induces an unnecessary chemical reaction. Therefore, the application of the present invention to such a case produces a high degree of effectiveness. Furthermore, the arc tube has a hollow part within itself, and has thin tubes for connecting to external members. In the thin tubes, respective conductive cermets are inserted as a feeding member. Then, a glass frit is filled between each cermet and the corresponding thin tube of the arc tube, thereby sealing the arc tube. The arc tube having the stated structure, an impurity having a hydrogen component which is included in the glass frit conventionally induces an unnecessary chemical reaction. Therefore, the application of the present invention to such a case produces a high degree of effectiveness.
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