Effect of 2+2 dynamic drive scheme on electro-optical characteristics in cholesteric liquid crystal displays

We have developed and extended the basic idea of 2+2 dynamic driving scheme (DDS) for a VGA (640×480) panel and optimized it to show the ON–OFF switching characteristic. The temperature dependence of selection time of 2+2 DDS is similar with that of 3+2 DDS. The position dependence upon pre and post selection is serious and not suitable for driving the panel. We found that two steps of a propagation period provide the most stable homeotropic state and ON–OFF switching system. With this new driving scheme the potential gray scale for Ch-LCD in a 640×480 pixels matrix was examined. The gray scale can be obtained at a relatively higher voltage. We obtain 32 gray numbers and above 20 potential grays with 40 V of Vpeak and 1.2 ms/line of scan driving time in the VGA panel. Our 2+2 DDS may be useful for foldable display applications, such as for electronic paper.