Low-Frequency Dielectric Relaxations in Nematics and Dual-Frequency Addressing of Field Effects

Abstract

Novel low threshold nematic mixtures are presented exhibiting very low dielectric crossover frequencies f_c ≃ 1 kHz at 20°C and unusually large, low- as well as high-frequency dielectric anisotropies ΔEL > 4 and ΔEH < 4 respectively. ΔEL and ΔEH are shown to be independently adjustable. The frequency and temperature dependence of the dielectric constants as well as the optical, elastic and viscous material constants are measured. Approximations are derived which quantitatively describe the influence of the LC material properties on the static electro-optical performance of dual-frequency addressed twisted nematic displays. It is shown that the number of multiplexable lines of dual-frequency addressed TN-LCDs comprising the new materials can be increased by more than a factor of 30 compared with conventional addressing. Moreover, very short turn-off times are reported.