Reflective supertwisted nematic liquid crystal displays

Supertwisted nematic (STN) liquid crystal displays are widely used commercially. However, there is still room for improvement. In this paper, we discuss reflective STN displays in which the rear polarizer has been removed and no retardation film is used for dispersion compensation. This new design can potentially yield higher brightness than conventional STN displays. They can also have better chromaticity. Numerical calculations and experimental data on such reflective STN liquid crystal displays with twist angles of 190-240 degrees are presented in this paper. These new displays have reasonably steep reflectance-voltage characteristics and can be multiplex-driven like ordinary transflective STN displays. An additional advantage of this new display is the absence of a viewing parallax if the reflector is placed inside the liquid crystal cell.