Two Frequency Addressing of a DTN-Cell

Abstract

The authors have already reported that a DTN-cell (depolarization in a twisted nematic-cell) had several advantages to a matrix display such as a sharp threshold and wide viewing angle. But if the usual amplitude selection method is applied to a large scale matrix display using the DTN-mode, multiplex capability is limited by the cutoff frequency F_c, of a liquid crystal. Therefore, the authors investigated a two frequency addressing method, that is, simultaneous application of a constant low-frequency voltage and a variable high-frequency voltage. In this method, a liquid crystal with lower-F_c can be used. In addition, some advantages of extremely sharp threshold, high contrast and relatively fast response and recovery can be obtained by using a liquid crystal with large negative dielectric anisotropy. These advantages are useful for a large scale matrix display.