TUBULAR BULB PROVIDED WITH DIFFUSING FILM

PURPOSE:To provide a tubular bulb in which illuminance irregularity is not generated in an irradiated surface by forming a diffusing film out of a cloudy film comprising metal oxide/nirtide througu a CVD method, and forming the film thickness and the film structure uniform. CONSTITUTION:A semi-fabricated product with quartz surface a glass bulb 1 cleaned is put into a CVD reaction chamber, the inside of the reaction chamber is made vacuum, and the bulb 1 is heated until its surface reaches a specified temperature. Next, gas generated by the use of tetraisopropoxy titanium and oxygen gas are introduced into the reaction chamber simultaneously at a specified flow rate. A gas introducing time is regulated in accordance with required cloudiness of the film. After that, nitrogen gas is introduced into the reaction chamber, and the sewi-fabricated product is taken out. Respective surfaces of a head top part 11, a sealing part 12, and a boundary range 13 between them are thus coated with a drffusing film of the desired cloudiness having the uniform film thickness and the film structure in addition to the external surface of a straight tube part 10.