| 摘要 |
PROBLEM TO BE SOLVED: To prevent determination of a fluorescent lamp with a low luminous beam which is essentially a bad item as a good item, save waste, and reduce costs. SOLUTION: When the phosphor layer of an average adhered quantity of 2.5 mg/cm<2> or more per unit area is adhered to a glass tube inner face, light transmittance of the phosphor layer adhered to the glass tube inner face has a gradient from one end to another end of the glass tube, and a relative ratio of light transmittance in an end part with higher transmittance to light transmittance in another end part with lower transmittance is within 140%, the glass tube is determined to be a good item.
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