Abstract
Two kinds of the cold cathode fluorescent lamps (CCFLs) were operated at 5mA as a life-test with Ni plate electrodes. One kind of CCFL contained Ne-Ar-Hg (Hg CCFL) and the other contained Ne-Ar (Hg-less CCFL). The results of the operations showed that the Hg CCFL's voltage decreased with operating time continuously. On the other hand, the voltage of the Hg-less CCFL began to increase and its emitting light color changed from light violet to strong red after about 6000 hours operating time. The V-t and I-t waveforms of the Hg CCFL did not change during the life test, while those of the Hg-less CCFL at 6000 hours were different from those at 8000 hours. The wave form data seem to show that the Hg CCFL's discharge was glow mode and that the Hg-less CCFL discharge changed from glow mode to arc mode after 6000 hours operating time. The authors then observed the electrodes of both kinds of lamps at 8500 hours operating time. The shape of Hg CCFL's electrode at 8500 hours was the same as at 0 hours, but that of the Hg-less CCFL at 8500 hours was very different from at 0 hours. The tip of Hg-less CCFL's electrode at 8500 hours operating time was gouged and U-shaped. The data show that the reason for the gouging of the electrode at lamp life end, or in very low temperature operation, was the sputtering of rare gases caused by the depletion of Hg.
