Patent ID: 7443092

Claim:
A fluorescent lamp comprising: a multi-ringed bulb including: a plurality of ring bulbs in which a plurality of straight tube portions, each having an outside diameter of from 12 to 20 mm, are connected to each other through bent portions on a same plane, said ring bulbs being placed concentrically on the same plane; electrodes provided hermetically at respective ends of outermost and innermost bulbs of the plurality of ring bulbs; and a connection portion connecting other adjacent ends of the outermost and innermost bulbs to each other so that the outermost and innermost bulbs communicate with each other to thereby form a single discharge path; a phosphor layer formed on inner surfaces of at least the straight tube portions of the multi-ringed bulb; and a discharge medium with which the multi-ringed bulb is filled, wherein each of the straight tube portions has a length “l ” of from 150 to 500 mm, and a radius of curvature “r ” of the bent portion satisfies an expression of 0.03 ≦r/l ≦0.3.