JPS5482870A - Making of coating film of fluorescent substance for bulb - Google Patents

Abstract

PURPOSE: To make a coating film of fluorescent substance at a low heating cost, by coating powder of the fluorescent substance on the inside surface of a glass bulb for a fluorescent mercury lamp by an electrostatic painting method and binding the powder with steam and baking the powder at a relatively low temperature.

CONSTITUTION: The glass bulb 1 is heated at a temperature of 150 to 200°C in a heating furnace 8 so that the bulb 1 is made electroconductive. A sprayer 3 is inserted into the bulb 1. The powder of the fluorescent substance is projected from a projecting pipe 4 so that the powder is coated on the inside surface of the bulb 1. In this case, the grounded anode of an electrostatic power source 2 is connected to the bulb 1 and the cathode of the power source 2 is connected to a discharge plate 7 and a wind regulator 6 of the syprayer 3 through an electroconductive rod 5. The grains of the fluorescent substance are charged by corona discharge from the discharge plate 7 so that the grains are electrostatically coated on the inside surface of the bulb 1. Thereafter, a steam projeting nozzle is inserted into the bulb 1 to project steam to raise the binding force and adhering force of the powder of the fluorescent substance. Then, the bulb 1 is heated at a temperature of 200 to 400°C in a baking furnace 11 so that the steam is evaporated and the fluorescent substance layer 10 is dried and baked. Since the bulb 1 is heated at relatively low temperatures, the heating cost is low.

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