A study on the relationship between electrode materials and characteristic S of CCFL's negative glow plasma

Abstract

Summary form only given. CCFLs (cold cathode fluorescent lamps) generally used for the backlight of the LC-TV and the note-PC are always expected to the improvement of the electrode to make more lamp current flow for getting higher luminance. To improve the electrode to get the higher luminance, it is very important to grasp the electron emission ability of the cathode. Authors have considered that the electron emission ability determined by the nature of the material could be evaluated by the cathode fall voltage (CFV), and that CFV has the intimate relationship to the performance of negative glow's (NG's) plasma. 2 kinds of electrode materials, namely Ni and Mo, were used for this research. Though the common electrode of CCFL is hollow cathode, the electrode used here were in the shape of the plate, which had a length of 5.2 mm, a width of 1.7 mm and a thickness of 0.1 mm. This is because it is necessary to observe the NG's plasma for grasping the basic relationship between CFV and the performance of NG's plasma. The lamp diameter was 4 mm and had Ne (8 kPa) and Hg vapor. First, the relationship between a state of NG's plasma and discharge current was observed for each kind of electrode materials. The area of NG's plasma increased to whole area of the electrode as the discharge current increased. However the way to increase depended on the electrode materials. Secondly, the relationship of the CFV to the discharge current was measured. The method to measure the CFV was developed by improving the method for measuring the CFV of the fluorescent lamp. The CFV of Ni was higher than that of Mo. The ways of the change of the CFVs were similar in the following respect. That is to say, CFVs were constant until some discharge current, then increased as the discharge current increased. While, the increasing rates of CFVs were different from each other. Authors consider that the difference of gamma-coefficient causes the difference of CFV's increasing rate