Analysis of thermo-physical and optical properties of a diffuser using PET/PC/PBT copolymer in LCD backlight units

The effect of water absorption and thermo-physical properties on the warpage of a diffusing plate fabricated with poly(ethylene terephtalate)/polycarbonate/polybutylene terephtalate copolymer in a direct-lit backlight unit (BLU) of a liquid crystal display (LCD) has been investigated. The warpage of the new diffusing polymer was significantly reduced relative to that of a conventional PMMA diffusing plate. To improve the diffusivity of a diffuser, a new manufacturing technology, a stripe coating method, was suggested. By using this method, scattering characteristics of the new diffusing material was measured and compared to that of the diffuser which was not treated with stripe coating. Spatial profiles of the luminance are displayed for a BLU having cold cathode fluorescent lamps (CCFLs) array and a flat fluorescent lamp (FFL). As with the superior thermo-physical property that alleviates the warpage, the diffuser plate partially coated with diffusing agents is expected to achieve better uniformity and/or slimmer BLU.