JPS5725644A - Manufacture of fluorescent lamp - Google Patents

Abstract

PURPOSE:To equalize the thickness of a double-phosphor film by coating the inner wall of a bulb with a first phosphor suspension before it is dried to form a paint film, coating the paint film with a suspension of a second phosphor having a larger specific gravity than the first phosphor before it is dried to form another paint film, and sintering these paint films simultaneously to obtain the double-phosphor film. CONSTITUTION:A suspension, which is prepared by suspending 4200K of calcium halophosphate phosphor having a smaller specific gravity in water containing a water-soluble binder, is applied on the glass side of a bulb 1, thereby a glass side phosphor paint film 2 being formed. A suspension, which is prepared by suspending 4200K of a three-component rare earth elements phosphor having a larger specific gravity in butyl acetate containing a nonwater-soluble binder, is applied on the paint film 2, thereby a discharge-side paint film 3 being formed. After that, the bulb 1 is sintered so as to make the binders to be decomposed and removed, thus a double- layer phosphor film being obtained. Since the quantity of water which is used as a solvent and contained in the film 2 is large and the water contained in the film 2 evaporates slowly, the film 2 becomes uniform. Consequently, both phosphor films coating the inner wall of the bulb 1 can be made uniform.