Patent ID: 7098596
Filing Date: 2006-08-29
Classification: H01J,H05B

Abstract:
1. A mercury-free arc tube for a discharge lamp unit comprising: a spheroidal closed glass bulb; a pinch seal on each end of the closed glass bulb; and opposing electrodes disposed in the glass bulb, the glass bulb being filled with a primary light-emitting metal halide and a starting rare gas, a pressure of the starting rare gas being 8 to 20 atm, wherein an inner diameter of the glass bulb at a middle part between the opposing electrodes is 1.5 to 2.7 mm, a distance between the opposing electrodes is 1.0 to 4.0 mm, a length of each of the electrodes extending into the glass bulb is 0.3 to 1.8 mm, and a stable discharge is produced with a power of 15 to 30 W, wherein a ratio of an inner diameter D wherein a ratio of a tube current I (unit: A) supplied to the arc tube to the outer diameter d (unit: mm) of the electrodes sticking out inside the glass bulb (I/d) is 1.0 to 4.0 (A/mm).