1992 Volume 76 Issue 10 Pages 536-542
Long-term lumen maintenance of high-load fluorescent lamps has been investigated using 3-band rare earth phosphors. The contact electric charging tendecy of a phosphor was systematically varied by depositing colloids on the phospor particle surfaces. For every phosphor system tested, the maintenance showed a maximum at a certain value in the charging tendency where the amount of mercury oxide adsorbed on the phosphor was minimum. On the other hand, the depreciation of the phosphors themselves did not depend on the charging tendency. Furthermore, the charging tendency of mercury oxide was found to lie near that for maximum maintenance. From these results, it has been concluded that the difference in charging tendency between mercury oxide and a phosphor governs mercury oxide adsorption on the phosphor; the amount of adsorbed mercury oxide becomes larger with increase in the difference causing significant fluorescent lamp depreciation.