PURPOSE: A fluorescent substance that is prepared by adding a specific amount of an alkali metal to a fluorescent substance of rare earth orthophosphate activated with cerium and terbium, thus showing remarkaly increased luminous efficiency and reduced deterioration at the baking stage in the production of fluorescent tubes.
CONSTITUTION: A novel fluorescent substance that emits green light with ultraviolet rays is obtained by adding an alkali metal such as lithium or sodium to a fluorescent substance of rare earth orthophosphate activated with cerium and terbium by 6×10-1W1×10-3 atom per mole of the fluorescent substance.
EFFECT: Even when lithium is used as the alkali metal, the line spectrum characterized by lithium is not observed with in the above concentration range.
USE: The resultant composition is suitably used for fluorescent lamps of high efficiency and color redering properties, e.g., fluorescent lamps for lighting using three primary colors.
ASADA MASAO
SUGANO SATOSHI
NISHIMURA TOSHIO
KIMURA YOSHIO
