LCD BACKLIGHTING SYSTEM WITH HIGH LUMINANCE AND GOOD UNIFORMITY

초록

The edge-lighting type backlight units that are generally used as a light source of LCD displays employ dot-pattern to obtain luminance uniformity on the top surface of the light guide. However, this method has low luminous efficiency and high power consumption. Recently, to improve these disadvantages of conventional backlight units, highly scattering optical transmission (HSOT) polymer plate as a light guide has been introduced1,2). In this paper, we analyzed multiple ray tracing in the HSOT polymer plate by means of the Monte carlo simulation. Light transmission behavior in the light guide was simulated by a 3-dimensional ray tracing program considering scattering angle given by the Mie theory and mean free path. As results, it was revealed that the luminance uniformity keeps constant within some range of the distance from the lamp, but decreases abruptly over that range. This leads us to employ additionally dot or prism patterns to obtain backlight units with high luminance and good uniformity. Therefore, we calculated the light transmission behavior for the light guide with polymer in PMMA and dot-patterns on the bottom plate which is expected to be applicable to a bright and uniform backlight unit for a large size LCD panel of more than 12 inch. Under the optimized conditions for the diameter of the polymer, the size of the dot-pattern, a mean free path and so on, in this new structure, we were able to improve greatly the luminous uniformity of the backlighting systems as shown in Fig.1(b).