| 摘要 |
PURPOSE:To determine the quantity of coated phosphor most economically and to reduce the cost by forming a double layered phosphor layer and assigning the transmittance of rectilinearly propagating light of each phosphor layer in prescribed values. CONSTITUTION:A fluorescent lamp is provided with a laminated double phosphor layer to be luminous being excited by radiation through discharging. A more expensive phosphor based on weight is used for the discharge side and a cheaper phosphor is used for the glass side. T1+2, the transmittance of rectilinearly propagating light corresponding to the combined two phosphor layers, and T1, the transmittance of rectilinearly propagating light corresponding to only glass side phosphor layer, are defined to satisfy relations, 25<=T1+2<=40, and T1+2+2<=T1<=11T1+2/ 10+15/2. |
