Patent ID: 7572391

Claim:
A method for manufacturing a fluorescent substance comprising: mixing a raw material for Eu, a raw material for Si, at least one raw material powder of alkaline earth, and at least one selected from the group consisting of raw materials for La, Gd, Cs, and K to obtain a mixture of raw materials; pre-firing the mixture for 1 to 3 hours in an air atmosphere at a temperature ranging from 500 to 700° C. to obtain a baked material; mixing the baked material and firing for 3 to 7 hours in a reducing atmosphere consisting of a mixed gas of N 2 /H 2 at a temperature ranging from 1000 to 1600° C. to obtain a first fired product; pulverizing the first fired product to obtain a pulverized first fired product; placing the pulverized first fired product into a vessel; placing the vessel housing the pulverized first fired product in a furnace; purging the furnace with nitrogen gas in vacuum; firing the pulverized first fired product for 2 to 6 hours in a reducing atmosphere consisting of N 2 /H 2 and having a hydrogen concentration of 5% to 100% at a temperature ranging from 1000 to 1600° C. to obtain a fluorescent substance consisting of an alkaline earth ortho-silicate.