| 摘要 |
In a low-pressure mercury vapour discharge lamp having a luminescent layer in which the power consumed is at least 500 W/m<2>, for satisfactory operation, the luminescent layer is so chosen as to comprise a luminescent material which has a luminous flux with 254nm excitation, which after the material has been subjected for 15 minutes to ultraviolet radiation consisting substantially of the wavelengths 185 and 254 nm, having a radiation density between 150 and 500 W/m<2> and having a ratio of 185 nm power to 254 nm power between 0.20 and 0.40, is not more than 5% lower than the initial luminous flux of the material at 254 nm excitation and measured under identical circumstances, and wherein the combination of cations in the luminescent material has an electro- negativity of not more than 1.4. Numerous examples of known luminescent material compositions, which are said to satisfy these criteria, which generally relate to maintenance of luminous flux and resistance to degrading by mercury, are given. |
