| 摘要 |
PROBLEM TO BE SOLVED: To provide a high pressure discharge lamp, an illumination optical device and an image display having a long service life by optimizing a mercury sealing quantity and a halogen gas concentration, and restraining the generation of residual gas in a luminous tube of unwanted gas in operation. SOLUTION: A conductor comprising an electrode 4, a metal foil 5 and an external lead 6 is sealed in a sealing part 3 so that the electrode 4 is positioned in a light-emitting part 2. The electrode 4 is provided with an electrode coil 4a made of tungsten, in which the content of potassium oxide K2 O is not more than 5 ppm, at the tip of an electrode rode 4b made of tungsten in which the content of potassium oxide K2 O is not more than n5 ppm. The metal foil 5 has into one end connected to rear end of the electrode rod 4b. An external lead 6 has its one end connected to the other end of the metal foil 5. A distance between electrodes is 1.5 mm. In a light-emitting part 2, 28.5 mg(about 0.16 mg/mm<3> ) of mercury is sealed, and also 1.0×10<-4> mol/mm<3> Br is sealed therein a halogen gas.
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