FORMATION OF FLUORESCENT FILM

PURPOSE:To prevent a phosphor layer from being formed on undesired portions in a bulb by radiating ultraviolet rays to a paint film inside a bulb face using a hood means limiting the radiation range to the desired one. CONSTITUTION:A photosensitive adhesive layer 11 is formed inside the face 10a of a bulb 10, and ultraviolet rays are radiated to it from a mercury lamp 12. A hood 13 is provided around the lamp 12, and the radiation range is limited to the required portion of the face 10a. Thereby, even if the paint film with the same quality as that of the layer 11 is formed on undesired portions such as a funnel section 10b and a neck section 10c during the process in which the layer 11 is formed, these portions are not radiated with ultraviolet rays, thus no phosphor layer is formed on these portions scattered with phosphor powder, if any. Therefore, removal of unnecessary portions is not required, and manufacturing man-hours can be reduced.