Polymer-stabilized ferroelectric liquid crystal devices with grayscale memory

A novel grayscale-memory ferroelectric liquid crystal device with polymer dispersion has been studied. The ferroelectric liquid crystal molecules are stabilized by a low-concentration doped polymer, which induces an enormous number of small liquid crystal domains with different threshold voltages for bistable switching. The polydomain has a spatial grayscale effect due to domain distribution. In forming the polymer-dispersion system with phase separation under ultraviolet light irradiation, a solution of liquid crystal and prepolymer was heated at the chiral nematic phase, and the directors of liquid crystal and prepolymer molecules were oriented parallel to the rubbing direction of alignment layers on substrates. A unique microscopic striped texture extending parallel to the rubbing direction was observed at a room temperature, and could be used to form the small domains. The 2-μm-thick device, fabricated by addition of 4 wt% polymer and strong ultraviolet irradiation of 40 mW/cm², exhibited excellent grayscale memory according to applied voltage pulses of a few V. It has much potential for use in high-resolution matrix panel displays.