JPS5482869A - Making of coating film for bulb - Google Patents

Abstract

PURPOSE: To raise the adhesive powder of fluorescent substance, by electrostatically painting the powder on the inside surface of a glass bulb for a fluorescent mercury lamp and thereafter projecting steam to the powder while controlling the temperature of the glass bulb.

CONSTITUTION: The glass bulb 1 is heated over 180°C in a heating furnace 3. A sprayer 5 is inserted into the bulb 1 to project the powder of fluorescent substance to make a coating film 16 of the fluorescent substance on the inside surface of the bulb 1. In this case, grounded anode of an electrostatic power source 2 is connected to the bulb 1, and the cathode of the power source is connected to discharge electrodes 9a, 9b located at the open end of a projecting tube 6 of the sprayer 5 to make a potential difference between the discharge electrodes. The powder of the fluorescent substance is projected from the projecting tube 6 and charged by corona discharge between the electrodes 9a, 9b so that the powder is electrostatically coated on the inside surface of the bulb connected to the anode. Then, the bulb 1 is cooled below 70°C by air supplied from nozzles 11 of an air supply pipe 10. A steam introducing pipe 13 is inserted into the bulb instead of the sprayer 5 to project steam from projecting holes 15 of a projecting head 14. The steam is impregnated in the fluorescent substance layer 16, thereby raising the adhesive power of the layer to the bulb.

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