| 摘要 |
PROBLEM TO BE SOLVED: To provide a new phosphate-treated silicate fluorescent substance which exhibits an improved lumen maintenance factor in comparison with an untreated fluorescent substance, when used in a fluorescent lamp. SOLUTION: In one aspect of the invention, the phosphate-containing protective surface layer is formed by treating a fluorescent substance in an aqueous phosphate solution, filtering the treated fluorescent substance and then annealing the treated fluorescent substance. Especially, the BaSi2O5:Pb fluorescent substance (treated in this mode) exhibits an improved maintenance factor in a fluorescent lamp, and a characteristic X-ray diffraction figure which proves the presence of the phosphate-containing protection surface layer.
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