| 摘要 |
PURPOSE:To reduce cracks and improve lamp characteristics by forming an electrode axis fixed to and supported by a closing member with conductive ceramics having a coefficient of thermal expansion between those of the closing member and a sintered emitter. CONSTITUTION:A luminous tube formed by sealing the open end of a cominous tube bulb 1 made of translucent ceramics with a closing member 2 of which at least a part of a member supporting an electrode 4 is made up of conductive ceramics is provided. The electrode 4 is formed by fixing a sintered emitter 6 consisting of a high melting point metal and an electron radioactive material to an electrode axis 5 made of conductive ceramics, and the conductive ceramics used in the electrode axis 5 is structured to have a thermal expansion coefficient between those of the sintered emitter 6 and the closing member 2. Thus, possibilities of causing cracks on an electrode fixing part of the closing member and a sintered emitter fixing part of the electrode axis are substantially reduced, preventing lamp start-up defects and premature deterioration of other characteristics.
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