We propose a reflective dual-mode liquid crystal display (RD-LCD) which has advantages of long memory retention time and high contrast ratio. The proposed device adopts ideal bistable characteristics, a cell thickness over pitch (d/p) of 0.25. It can realize long memory retention time, thereby reducing power consumption. In addition, an optical configuration for the RD-LCD makes low light leakages at dark state and shows good dispersion characteristics in both dark and bright states over the entire visible ranges. We experimentally confirmed retention time over 6 months in memory mode and memory and dynamic contrast ratios of 47:1 and 43:1 under ambient light, respectively. As a result, the proposed RD-LCD demonstrates convincingly that it is a candidate for green display.

In this study, we have proposed a dual-mode liquid crystal display (D-LCD) that can display both the memory and dynamic modes in one cell. The two stable states of the memory mode use splay and -π-twist states. The operation of the dynamic mode is realized by the transition behavior between the two stable states of its memory mode. For a green display, we have also proposed a reflective D-LCD with an optically compensated structure. We found that both the memory and dynamic modes have contrast ratios (CRs) of 30:1 by a good wavelength dispersion of dark state.