| 摘要 |
An arc tube (6) of discharge lamp comprises a main tube body (11) of translucent ceramic sealed with a terminal plate (13) at both ends thereof. The main tube body (11) comprises integrally a large diameter portion (11A), a tapered portion (11B) which is disposed at both sides of the large diameter portion (11A) and has a smaller diameter toward the forward end thereof, and a small diameter portion (11C) which is connected to the forward end of the tapered portion (11B). In this arrangement, the discharge lamp can be produced more easily than the conventional structure having a narrow portion integrally formed at both ends of a ceramic tube body, making it possible to drastically reduce cost. Further, since a low temperature zone can be only with difficulty formed inside the arc tube during discharge, the luminous efficiency can be raised.
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