Abstract: The present invention provides a tungsten-halogen light bulb having an arc tube with a seal portion at one end. A filament is provided in the interior of the arc tube, and a basic gas mainly comprising at least either gaseous xenon or gaseous krypton is filled in the arc tube. When V (V) denotes a rated voltage of the tungsten-halogen light bulb, P(MPa) denotes a filling pressure of the basic gas at a room temperature, and Xe vol. % and Kr vol. % respectively denote composition ratios of the gaseous xenon and of the gaseous krypton, the following formulas (1) and (2) are satisfied simultaneously, in which ‘%’ means ‘volume %’. V≧100 (Volt)  (1) P≧0.7+{0.1×(Kr%/(Kr%+Xe%))}  (2) In these formulas, Kr %+Xe %=100(%), 0≦Kr %≦100, and 0≦Xe %≦100. Accordingly, a crack at the seal portion of the arc tube is prevented and the lifetime is improved.

Abstract: The present invention provides a tungsten-halogen light bulb having an arc tube with a seal portion at one end. A filament is provided in the interior of the arc tube, and a basic gas mainly comprising at least either gaseous xenon or gaseous krypton is filled in the arc tube. When V (V) denotes a rated voltage of the tungsten-halogen light bulb, P(MPa) denotes a filling pressure of the basic gas at a room temperature, and Xe vol. % and Kr vol. % respectively denote composition ratios of the gaseous xenon and of the gaseous krypton, the following formulas (1) and (2) are satisfied simultaneously, in which ‘%’ means ‘volume % .