Performance characteristics of nematic liquid crystal display devices

Abstract

Display devices using nematic liquid crystal materials offer advantages over other display media in low-voltage low-power operation, cost of materials and fabrication methods, electrical compatibility with MOS drive circuits, and flexibility of character size and format. This paper describes liquid crystal display devices that utilize dynamic scattering to modify transmitted or reflected light. We have synthesized individual materials that have nematic temperature ranges as large as -15-115°C without super-cooling effects at low temperatures. When these materials are used in transmissive displays having liquid crystal layers 12 µm thick sandwiched between transparent electrodes, contrast ratios of 30:1 to 50:1 are realized at 10-40 V dc or ac with a current density of ∼1-10 µA/cm 2 . Turn-on times are 10-50 ms and turn-off times are 30-100 ms, precise values being dependent on the specific material, temperature, and voltage used. The contrast ratio versus voltage exhibits a threshold so that it may be possible to matrix address liquid crystal display panels. Operating lifetime and display applications are also discussed.