| 摘要 |
PROBLEM TO BE SOLVED: To provide a structure for preventing depletion of an emitter in early stage due to excessive evaporation from the cathode tip, while ensuring smooth emitter supply thereto, and smooth lighting even at the time of initial lighting, in a discharge lamp where an emitter other than thorium is added to the negative electrode in a luminous tube.SOLUTION: The body 31 in a negative electrode 3 is composed a high melting point metal material not containing thorium, the tip 32 is composed of a high melting point metal material containing an emitter (excepting thorium), a rhenium-tungsten alloy portion is formed on the apical surface thereof, and in a sealed space 33 formed in the body and/or the tip, a sintered compact 34 containing an emitter (excepting thorium) at a higher concentration than that contained in the tip is embedded. |
