| 摘要 |
PURPOSE:To lengthen the life of a high-pressure metal vapor discharge lamp of good lighting properties, by disposing the capillary made of alumina in a light emission tube. CONSTITUTION:An electrode 2b, a lead wire 3b and a capillary 7 are provided at the end cap 4b of a light emission tube 6 in which an additive for attaining a high color rendition and a high efficiency is sealed in a light-permeable alumina ceramic tube 1. When the light emission tube 6 is lit in a vertical position, the cap 4b has the lowest temperature in the interior of the tube 6 and the sealed additive is liquefied and stays on the cap so that the cap would be eroded due to the reaction of the liquefied additive and the cap portion in which the electrode 2b is buried would be destroyed. However, the liquefied additive is sucked up because of a capillary action based on the form of the capillary 7 made of alumina resistant to a high temperature, so that the cap 4 is not eroded, in reality. Therefore, the life of the tube 6 is lengthened.
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