A Novel Gray-Scale Method for Ferroelectric Liquid Crystal Displays Utilizing Ultra-Fine Particles

We have developed a novel gray-scale technique for ferroelectric liquid crystal (FLC) displays. This technique involves the addition of nanometer scale ultra-fine particles into the FLC mixture to produce micro domains, whose threshold voltages vary. Each domain has a different threshold for memory latching and is small enough to cover the full gray scale within one pixel element (less than 3 µm in diameter). Moreover, each domain maintains bistability, that is, this method doesn't inhibit passive-matrix driving. The voltage-transmittance ( V-T) curve of the cell depends on the particle-size distribution, such that if the particle-size distribution is sharp, the gradient of the V-T curve is small and vice versa. By X-ray diffraction analysis, wide tilt angle distribution of the smectic layers, which characterizes this nanometer scale particle-contained FLC, was found. The advantages of this technique are that an analog gray scale is possible and that the V-T curve can be controlled by selecting appropriate particles, which means no fundamental change in the fabrication process is required.