| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an extra-high pressure mercury lamp preventing extreme temperature rising of quartz glass constituting a sealing tube part to prevent bending of an electrode shaft part, thereby increasing the service life. Ž<P>SOLUTION: In the extra-high pressure mercury lamp in which 0.15 mg/mm<SP>3</SP>or more of mercury is filled in an arc tube made of quartz glass and having an arc tube part and a sealing tube part which is coupled to the arc tube part and a pair of electrodes are disposed in opposition by embedding and holding base end parts of shafts thereof in the sealing tube part, in the pair of electrodes, the electrode operating as a negative electrode includes a head part disposed on its leading end side and having a diameter larger than the shaft part and a cylinder part which is coupled to a rear end of the head part, and the cylinder part axially extends to surround the electrode shaft part and an inner peripheral surface thereof is formed apart from the electrode shaft part. Ž<P>COPYRIGHT: (C)2010,JPO&INPIT Ž
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