Electric gas discharge lamp having two superposed luminescent layers

An electric gas discharge lamp which includes:

• means for producing ultraviolet radiation comprising a translucent envelope, at least two spaced discharge electrodes sealed in said envelope and an ionized gas disposed within said envelope, said lamp further comprising at least first and second superposed layers carried on said envelope, said first layer being a luminescent material, said second layer being farther from a discharge between said electrodes than said first layer, said second layer consisting of a mixture of luminescent material and a white material which is non-luminescent and has an absorption for ultraviolet radiation of a wavelength of more than 240 nm which is less than 20% of the absorption of this radiation by that constituent of the luminescent material which has the smallest absorption for this radiation, the ratio of the amount of white material to the amount of luminescent material within any one layer versus any other layer increasing with the distance from the discharge.