HIGH-VOLTAGE DISCHARGE LAMP, HEAD LAMP FOR AUTOMOBILE AND ARC TUBE FOR THE HIGH-VOLTAGE DISCHARGE LAMP

摘要

A high−voltage discharge lamp (1A) includes an arc tube (2A) made of semitransparent ceramic, having a pair of openings (2a), a light emitting portion (2b) and an internal space (6) filled with an ionization light emitting substance and a starter gas; a pair of discharging electrodes (5) housed in the internal space (6); and an electrode holding member (4) to which the discharging electrodes (5) is attached and which is fixed in the opening (2a). In the light emitting portion (2b), the arc tube (2A) is provided with thick portions (2g) and a thin portion (2c). The transverse section of the thin portion (2c) has a sectional area of 35 % to 80 % of that of the thick portions (2g). The light emitting portion (2b) has a brightness center (9) located at the thin portion (2c).