The invention relates to a low-pressure gas-
discharge lamp which, with its light in the red spectral region, influences the biological
circadian rhythm by controlling
melatonin secretion. The tubular glass
discharge vessel, which can also be in the shape of a double
helix, is filled with a
noble gas or noble-gas mixture and mercury. Electrodes for the supply of energy are arranged at both ends of the
discharge vessel. The discharge vessel is multicoated on the inside by
phosphor layers applied one after the other. The first
phosphor layer located on the glass surface consists of
phosphor which is excited both by
ultraviolet mercury
radiation between 180 nm and 400 nm and also by the blue
radiation between 400 nm and 490 nm emitted by the mercury discharge, and by the
visible radiation emitted by the second or further phosphor
layers between 400 nm and 550 nm, where visible light having emission maxima in the region between 500 nm and 650 nm is generated. In combination with light sources for
melatonin suppression, the low-pressure gas-discharge lamp is, with its warm light, particularly suitable for stimulation of the quasi-
circadian rhythm in an individual in the absence of external conditions, such as
sunlight. Owing to its good colour
reproduction and
high energy efficiency, it meets all necessary requirements of a
light source for illumination tasks and is thus also suitable for general lighting.