PURPOSE: To provide a high pressure electric discharge lamp the sealed portions of which are prevented from undergoing dielectric breakdown so that its life characteristic is enhanced and its reliability increased and to provide a floodlight which uses the same.
CONSTITUTION: In an electric discharge lamp having electrodes 22, 23 sealed in both ends of an arc tube 20 made of quartz glass, with the end of an electrode shaft 221 sealed in each of these sealed portions 21 and a starting auxiliary electrode 28 provided outside the light emission tube and near each sealed portion, when the lamp voltage during lighting is VL (volt) and the shortest distance between the electrode shaft at each sealed portion and the surface of each sealed portion is (t)(mm), 10≤VL/t≤150 (volt/m). Since an electric field between the external auxiliary electrode and the electrode shaft at each sealed portion depends on the lamp voltage, the dielectric breakdown of each sealed portion can be prevented by proper setting of the wall thickness of each sealed portion relative to the lamp voltage, which can be achieved when the above requirements are met.
FURUYA MAMORU
TANAKA ICHIROU
