High-performance optical films for LCDs

Abstract

Optical performance of the LCD is strongly affected by optical films such as polarizers and retardation films. The characteristics of polarizers, which determine the contrast ratio and the hue balance of the LCD, need to be improved, in particular, to meet the current requirements on high-performance LCDs. Most polarizers for LCDs are made from polyvinyl-alcohol (PVA) films and iodine compounds by the wet dyeing method. Polarizers with high polarization efficiency and transmittance can be obtained by optimizing the dyeing and stretching conditions. In transmissive LCDs, blue decolorization in black images need to be improved by controlling the chemical species of PVA-iodine complexes. The authors analyzed the dichroic ratios of chemical species by separating each absorption peak, and presented a guide for the neutralization of the hue balance of polarizers. The characteristics of reflective LCDs, on the other hand, are largely dependent on the optical design of circular polarizers and quarter-wave plates, which constitute the circular polarizers. The important design elements of reflective LCDs include wavelength dispersion and viewing angle characteristics. The authors have contributed to the improvement of the performance of reflective LCDs by enhancing the characteristics of polymer films using stretching and optical lamination technologies.