Patent ID: 8106589

Claim:
A direct-current high-voltage discharge bulb for a vehicle lamp, comprising: a ceramic arc tube body having a discharge emission chamber at a middle portion in a longitudinal direction thereof; a light-emitting substance which is sealed inside the discharge emission chamber together with a starting rare gas; and an anode and a cathode which are disposed so as to face each other inside the discharge emission chamber, wherein an inside diameter of the ceramic arc tube body where the discharge emission chamber is defined is made to gradually decrease from a side of the anode to a side of the cathode; wherein the inside diameter gradually decreases from a distal end of the anode to a distal end of the cathode; wherein a first distance between an outer circumference of the anode at the distal end of the anode and a tube wall of the arc tube body is larger than a second distance between an outer circumference of the cathode at the distal end of the cathode and the tube wall of the arc tube body; wherein a volume of the cathode is smaller than a volume of the anode.