To improve luminous brightness, by sifting phosphor powder previously, or filteredly using a paste-like composition including the phosphor powder.
Any of various kind powder, used conventionally, can be used as raw material powder to be used. Th sifting for raw material phosphor powder can be made by various kind general methods for sifting a fine particle, and sifted grading is to be 74 μm or less, preferably 50 μm or less, preferably 30 μm or less, and preferably to the utmost 20 μm or less. The filtering for a paste-like composition can be made by passing the composition through an adequate mesh screen. The operation for these in particular is effective because not only a bulky particle can be removed, or a bulky impurity can be removed; but also the grading of a using phosphor can be finely uniformed; and subsequent execution of works can be made as conventionally.
NISHIWAKI KENICHI
OKUNO HARUHIKO
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