Patent ID: 8436536

Claim:
A vehicle discharge lamp substantially not using mercury, comprising: a light emitting part in which a discharge space is defined and into which a discharge medium including metal halide and rare gas are sealed; and a pair of electrodes arranged in the discharge space, wherein a spherical length b, which is a length in a tube axial direction of the light emitting part, is 7.5 mm to 8.5 mm and a thickness volume V of the light emitting part is 50 mm 3 to 100 mm 3 , and wherein the following formula is satisfied: −20≦( a− 35)×5.5+( x− 13.5)×10+(1.85− t )×100+(2.5− d )×100≦20 wherein a: power [W] supplied in a stable lighting time, satisfying: 22<a≦26 x: pressure [atm] of rare gas sealed in the discharge space and ranging 10˜17 atm t: thickness [mm] of a part where a wall thickness of the light emitting part is maximum and ranging 1.3˜1.85 mm d: inner diameter [mm] of a part where the wall thickness of the light emitting part is maximum.