| 摘要 |
PROBLEM TO BE SOLVED: To provide a method of forming a phosphor film, capable of reducing the difference in thickness of a phosphor film in the axial direction of a glass tube, caused by dropping the phosphor dispersion liquid, for forming the phosphor film of little differences is luminance and in chromaticity, when the phosphor film is formed on the inner wall surface of the glass tube. SOLUTION: In this method of forming the phosphor film onto the inner wall surface of the glass tube by holding the glass tube 10 approximately in the vertical direction, sucking the phosphor dispersion liquid 12 from its lower end opening or allowing the dispersion liquid to flow down from its upper end opening, then supplying the drying gas from the upper end opening to dry the phosphor dispersion liquid applied on the inner wall surface of the glass tube, the upper part of the glass tube is heated from the outside, when the phosphor dispersion liquid applied on the inner wall surface of the glass tube is dried so as to form the phosphor film 17.
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