FORMATION OF FLUORESCENT FILM

PURPOSE:To prevent storage of viscous agent at the corner section of bulb by feeding a heated viscous agent into a heated bulb and performing spin coating and thermally drying. CONSTITUTION:In a bulb 4, the face section 4a and the neck section 4b have approximately same diameters while the funnel section 4c is acute against the face 4a. Then said bulb 4 is heated to feed a heated liquid 5 containing a photosensitive agent while directing the face 4a downward and the excessive liquid is discharged. Since the liquid 5 is heated and fluid, approximately proper quantity is left. Upon rotation of the bulb 4, the liquid 5 is collected to a corner section F but it will also flow from the corner section F to the neck 4b, thereby the liquid sump 5a will never inflate. Then the liquid 5 is dried to exhibit the viscosity, thus adhering fluorescent material powder. With such method, the liquid 5 is never cracked at the section F upon dry-up nor the effective screen of the fluorescent film is reduced because of small sump 5a.