Analysis of weak-anchoring effect in nematic liquid crystals

Abstract

A generalized Rapini-Papoular-type anchoring energy formula [J. Phys. (Paris) Colloq. 30, C4-54 (1969)] with two coupling constants is established through a second-order spherical-harmonic expansion. Using this formula, we analyze the threshold and saturation properties of twisted nematic devices with unidirectional planar anchorage, assuming that the azimuthal and polar anchoring strengths are both finite and distinct from each other. We also discuss the voltage-controlled-twist effect [G. P. Bryan-Brown et al, Nature (London) 392, 365 (1998)]. It is shown that the predicted behavior is consistent with the experimental observations.