Patent ID: 8471474

Claim:
A mercury-free vehicle discharge bulb comprising: an arc tube comprising a light-emitting tube portion, pinch sealed portions between which the light-emitting tube portion is disposed, and a pair of electrodes provided in the pinch-sealed portions such that distal end portions of the pair of electrodes protrude into a discharge space of the light-emitting tube portion in an opposed manner; a glass shroud extending in a front-rear direction to cylindrically surround the arc tube, the glass shroud comprising a front end portion and a rear end portion that are welded to the arc tube; a metal band surrounding and holding the rear end portion of the glass shroud; and an insulating plug supporting the glass shroud in a fixed manner via the metal band, wherein a ratio S 1 /S 2 of a first area S 1 to a second area S 2 is 1 to 3, wherein the first area S 1 is a surface area of an outer surface of the glass shroud in a region from a circumference of the glass shroud at a position of a center of the discharge space to a front end edge of the metal band, and wherein the second area S 2 is a surface area of a surface of the metal band that touches the glass shroud.