Katsuo Murakami

Development of Fluorescent Lamp with a Colour Rendering Index Ra=99

Fluorescent lamps were studied to improve colour rendering properties without the use of filters to absorb blue light.The general colour rendering index Ra could be improved effectively, when both blue-violet mercury lines and continious radiations from phosphors are controled.A new Sr-borophosphate phosphor, with a chemical formula of [2 (Sr, Eu) O·0.84 P2O5·0.16 B2O3] was discovered and its applicability in fluorescent lamp of accurate colour rendition was examined.This phosphor absobs not only UV radiations but also the visible blue radiation and emits bluegreen light, hauing lower radiant power blue-violet spectral region than the usual antimony activated Ca-halophospate phosphor.The use of this phosplor is very effective to contol the radiant powes in blue-violot spectral region, and makes it possible to produce fluorescent lamps having Ra value of as high as 99 and luminous efficacy 60 lm, /W, increased about 20%, without the use of filters.