摘要 |
PURPOSE:To prevent any discoloration of a fluorescent lamp resulting from its prolonged lighting by coating the inner surface of a glass bulb with a fluorescent layer prepared from a mixture of a rare earth phosphor and beta type calcium pyrophosphate having a particle size similar to that of the rare earth phosphor. CONSTITUTION:First, strontium calcium chlorophosphate phosphor activated with europium, lanthanum phosphate phosphor activated with cerium and terbium and yttrium oxide phosphor activated with europium are mixed in a ratio of 2 to 4 to 4 to prepare a rear earth phosphor. Next, 100pts.wt. of the rare earth phosphor is mixed with 10-60pts.wt. of beta type calcium pyrophosphate having a particle size similar to that of the rare earth phosphor. After that, the thus prepared mixture is applied to the inner surface of a glass bulb to form a fluorescent layer, thereby making a fluorescent lamp. The use of calcium pyrophosphate with beta type crystalline structure prevents any undesirable discoloration from developing even when the lamp is lit over a long time. Besides, it is possible to achieve improved efficiency of applying the fluorescent layer. |