| 摘要 |
<p>A low-pressure discharge lamp of the invention is provided with a gas-tight discharge vessel (10) which contains an ionisable filling. Electrodes are arranged inside the discharge vessel (10), between which electrodes a discharge path extends. At least one of the electrodes has a tungsten coil (20A) which is electrically connected to current supply conductors (30A,30A') which extend to outside the discharge vessel (10). The coil (20A) has a central zone (21A) covered with an electron-emitting material (22A) and, on either side, boundary zones (23A,23A') between the central zone (21A) and respective current supply conductors (30A,30A'). The boundary zones (23A,23A') have a covering (24A,24A') of a protective material, comprising a ceramic material having a specific resistance less than 1000 mu OMEGA .cm. The lamps of the invention, while being relatively easy to manufacture, have a relatively long switching life compared with lamps without a covering of protective material. <IMAGE></p> |
