FLUORESCENT LAMP

PROBLEM TO BE SOLVED : To provide a mercury vapor discharge fluorescent lamp (10) having a phosphor layer (16) containing yttria system red color emitting rare earth phosphor. SOLUTION : The phosphor layer (16) is formed by coating water phosphor slurry on the inner surface of a glass envelope (12) of a lamp, and then by baking in a glass annealing furnace so as to evaporate or decompose the non-phosphor component in the slurry and by letting remain the final phosphor layer. The phosphor slurry contains preferably a deionization thickner such as polyethylene oxide, but does not contain any of calcium carbonate or cabonates. The phosphor layer (16) contains an yttrium system red color emitting rare earth phosphor.