Conventional liquid crystal display (LCD) backlight consisting of the cold cathode fluorescence lamp (CCFL) has become more difficult to get uniform luminance as displays become larger sizes. Also it has employed mercury (Hg) causing environmental pollution as a discharge gas. The flat lamp using Xe gas instead of Hg as ultraviolet (VUV) sources is regarded as one of the solutions to solve these problems. However, Xe plasma flat lamp has demerits such as lower luminance and poor luminous efficiency of the lamp.
In this study, a coplanar type Xe plasma flat lamp with a tooth-like electrode pattern and a dielectric barrier discharge was investigated. The manufacture of electrode, dielectric and phosphor layer on the bottom glass was sequentially carried out by the screen printing method. Xe-He gas system and Xe-Ne gas system was adopted as discharge gases. The discharge characteristics of the lamp were investigated with various parameters such as gas pressure, gas composition and input pulse shapes such as applied voltage, pulse frequency and trigger pulse on-time. Also, discharge characteristics of the lamp were examined into effects of the electric dielectrics and electrode patterns.
High luminance and luminous efficiency were obtained such conditions that the Xe excitation was increased. Such conditions were obtained by the increment of Xe partial pressure and the use of helium (He) as a buffer gas. However, in these conditions, sustain voltage was increased. Low luminance of the lamp was obtained when the power consumption decreased due to the decrease of the input pulse frequency and input voltage although they lead higher luminous efficiency of the lamp. Other conditions to improve luminous efficiency were the use of the phosphor as dielectric materials and the electrode pattern obtaining larger triangular discharge shapes. Luminous uniformity was improved when the discharge generated in front of the tips had triangular shapes rather than line shapes and larger triangular shapes than small shapes.
