Improved Nucleation and Transition by Plasma Treatments for Fast Response Optically-Compensated-Bend Displays

The optically-compensated-bend mode pi-cell displays exhibit fast-response time and wide-viewing angle characteristics. However, it requires a transition of the liquid crystal molecule from an initial splay state to the bend state configuration before providing the quick operation. A high voltage and a long warm-up time are needed to transform to the bend state. In this paper, the polyimide alignment films have been modified to reduce the splay-to-bend transition time by plasma beam treatments. The proposed method was demonstrated to be highly effective in improving the overall transition time. The number of splay-to-bend nucleation sites in the assembled liquid crystal cells could be increased dramatically by up to 20 times at the initial stage, and the improvement in the cell warm-up time was achieved at 45-71% reduction at 5.5 V. The plasma processing parameters were optimized at the plasma power of 700 W, the plasma distance of 25 mm, and the plasma scan speed of 600 mm/s. In addition, we maintained the excellent optical properties and response time characteristics for the optically-compensated-bend mode liquid crystal displays.