| 摘要 |
PROBLEM TO BE SOLVED: To dry a paint for a shading film in a short time without foaming the liquid constituent in the paint in relation to the manufacturing method of a light source bulb, composed by forming the shading film on the circumferential surface of a cylindrical glass tube. SOLUTION: In this manufacturing method of a light source bulb, drying of a paint P for a shading film applied to the circumferential surface 18a of a shroud tube 18 is carried out in two processes: a preliminary drying process (b) and a main drying process (c). In the preliminary drying process, the paint P is heated to 220 deg.C at a gentle temperature rate of increase, so that the liquid constituent in the paint P is evaporated. Thereby, the foaming of the liquid constituent in the paint P is prevented in advance, even if the paint P is heated at a somewhat steep temperature rise rate in the successive main drying process. In the main drying process, the paint P is heated and baked at a temperature increase rate which is steeper than that in the preliminary drying process. Thereby, the heating period as a whole is significantly reduced, as compared with the case of the conventional case where the paint P is continuously heated at a gentler temperature increase rate to an extent which does not cause foaming so as to complete the baking thereof.
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