Ushio Denki Kabushiki Kaisha

Hidetoshi Ichinose

Akihiko Sugitani

Tetsu Takemura

Toshiyuki Okamoto

Keisuke Ohkubo

A method for producing a fused silica envelope for use in a discharge lamp in which the inner surface of a fused silica tube is coated with a formulation containing titanium alcoholate and the coating treated by the steps including baking at a temperature of at least 1720.degree. C. to cause TiO.sub.2 to diffuse into the tube. The method results in a Ti concentration in a range of 1 .mu.m-10 .mu.m from the inner surface of the wall of the envelope is 0.5%-7% in terms of TiO.sub.2 and the product of the overall average Ti concentration and the thickness of the wall of the envelope ranges from 3.7% .mu.m to 42% .mu.m. During the baking step, the tube is shaped to include a bulb-like portion by inflating the silica tube.

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Fujisawa, Japan

Hidetoshi Ichinose