Fluorescent lamp

Claim 1

A low-pressure mercury vapour discharge lamp having a very satisfactory colour rendition, a colour temperature of emitted white light in the range from 2300 to 3300 K. and a colour point on or near the Planckian locus, said lamp having a gas-tight radiation emitting envelope containing mercury and a rare gas, and a luminescent layer comprising: a. at least one luminescent alkaline earth metal halophosphate activated by trivalent antimony and by bivalent manganese with a colour temperature of the emitted radiation from 2900 to 5000 K.; b. at least one luminescent material activated by bivalent europium having an emission maximum in the range from 470 to 500 nm and a half-value width of the emission band of not more than 90 nm; c. a luminescent rare earth metal metaborate activated by trivalent cerium and by bivalent manganese and having a monoclinic crystal structure whose fundamental lattice is defined by the formula Ln(Mg,Zn,Cd)B 5 O 10 , in which Ln represents at least one of the elements ytrrium, lanthanum and gadolinium, and in which up to 20 mol. % of the B may be replaced by Al and/or Ga, which metaborate has a red Mn 2+ emission; and d. a luminescent aluminate activated by trivalent cerium and having a garnet crystal structure at least partly absorbing blue radiation at wavelengths below 480 nm, characterized in that the luminescent layer also comprises: e. a green luminescing material activated by bivalent manganese having an emission maximum in the range from 510 to 535 nm.