TFT- LCD용 휘도성능을 향상시키는 나노 와이어 그리드 편광필름에 관한 연구

Abstract

FPD (Flat panel displays) encompass a growing number of technologies enabling video displays that are much lighter and thinner than traditional television and video displays that use cathode ray tubes, and are usually less than 100 mm (4 inches) thick. FPD include TFT-LCD (Thin film transistor liquid crystal displays), PDP (Plasma display panels) and OLED (Organic light emitting diode) displays. TFT-LCD is a liquid crystal displays (LCD) which uses thin-film transistor (TFT) technology to improve image quality. Because TFT-LCD cannot emit light by itself, the source, BLU (Back light Unit) is an indispensible part for TFT-LCD to display images. TFT-LCD consists of LCD panel on the top, circuit unit on the side and BLU on the bottom. The recent development issues of BLU-dependent TFT-LCD have been power consumption minimization, slimmerization and size maximization. As a result of this trend, LED is adopted as BLU instead of CCFL to increase brightness and to reduce thickness. In liquid crystal displays, the light efficiency is below 10% due to the loss of light in the path from a light source to an LCD panel and presence of absorptive polarizers. This low efficiency results in low brightness and high power consumption. One way to circumvent this situation is to use a reflective polarizer between backlight units and LCD panels. The use of multi-layer optical films with controlled refractive index anisotropy and thickness of alternating polymer layers is now the industry standard for this purpose. Since a nano-wire grid polarizer has been known as a reflective polarizer, an idea was proposed that it can be used for the enhancement of the brightness of LCD. The use of reflective polarizing film is increasing as edge type LED TV and 3D TV markets are growing. The reflective polarizing film market is growing significantly to keep up with green design trend such as low power consumption and LED adoption despite of the high price of the film. Although LED efficiency and the penetration ratio of the panel expect to be improved on the second half of 2010, the reflective polarizing film is still hard to remove form BLU. BLU makers are demanding representatives of DBEF to lower the manufacturing cost. Therefore, it’s urgent to develop an independent domestic manufacturing technology of the reflective polarizing film to solve this supply system. This study has been carried out to fabrication of the nano-wire grid polarizer(NWGP) and investigated the brightness enhancement of LCD through polarization recycling by placing a NWGP between an LCD panel and a backlight unit. NWGPs with a pitch of 200nm were fabricated using laser interference lithography and aluminium sputtering and wet etching. And The NWGP fabrication process was using by the UV imprinting and was applied to plastic PET film. The results were a transmission of light (Tp) 46.7%, reflectance (Rs) 40.1% and a contrast ratio of above 16 for the visible light range. In this case, the brightness of an LCD with NWGPs was 1.21 times higher than that without NWGPs due to polarization recycling.