Frequency-addressed liquid crystal field effect

A new nematic material in which ε∥ exhibits a dielectric loss in the audio-frequency range is reported. At 25 °C Δ ε=(ε∥−ε⊥) reverses sign at 2.5 kHz and can be as positive as 6.2 at low frequencies and as negative as −2.2 at high frequencies; the activation energy for the loss is 0.91 eV. The availability of a dielectric anisotropy of either sign depending on the frequency of the applied field allows the electrical orientation of the material with its optic axis either parallel or perpendicular to the electrodes. The possibilities for improving the voltage threshold and dynamic response of electro-optical effects by means of a two-frequency addressing scheme are demonstrated.