Flexoelectricity in the Hybrid Aligned Nematic Cell

Abstract

The reorientation process of an HAN cell submitted to electric fields is studied both theoretically and experimentally. To isolate the flexoelectric effect from the dielectric one, the experiments are made under d.c. and a.c. excitations. Preliminary results on 6 μm thick MBBA have been reported. In this paper we investigate the influence of the thickness in the range between 3 and 15 μm for MBBA. The theoretical model includes into the free energy the flexoelectric term in the hypothesis that the true inner electric field is due to the effective conduction anisotropy. In such a way we derive simultaneously from the experiments the surface anchoring energy and the sum of the flexoelectric coefficients; the found values are in good agreement with those derived by other groups with different techniques.