METAL-HALIDE LAMP, METAL-HALIDE LAMP LIGHTING DEVICE AND AUTOMOTIVE HEAD LIGHT APPARATUS

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PROBLEM TO BE SOLVED : To provide a metal-halide lamp of which rising of flux of light is quickened, its lighting device and automotive head light apparatus. SOLUTION : The lamp includes a discharge container and a discharge medium to turn on with electric power of not more that 100 W without using mercury. In the discharge container, when a distance between electrode ends is L (mm), a distance between an intersection point of a first imaginary straight line connecting between discharge starting points of the electrodes and a second imaginary straight line extending from an inner surface of a central upper portion in a discharge space perpendicularly to the first imaginary straight line and the inner surface of the central upper portion in the discharge space is Dc/2 (mm), the maximum thickness of an airtight container at the position of 80% of the distance between the electrodes toward the center is t (mm), 0.25 ≤Dc/L≤0.96 and 0.16 ≤t/L≤1.10 are satisfied; and when a distance between each of inner surfaces at both ends of the discharge space and an inflection point of the inner surface shape is p1 (mm) and the projecting length of the electrode is p2 (mm), 0.6 ≤p2/p1 ≤1.7 is satisfied. The discharge medium contains first halide from among a plurality of halides including at least Na, Sc or rare earth metal, second halide from among metal halides hardly emitting light to visible region and noble gas. COPYRIGHT : (C)2006, JPO&NCIPI