Deformation of a pretilted nematic liquid crystal layer in an electric field

Abstract

The deformation of the optical axis of a nematic liquid crystal layer under the influence of an electric field is caused by the dielectric torque. This momentum counteracts with an elastic torque generated by interfacial forces between the surface of the electrode and the liquid crystal. By means of a variational analysis, the deformation profiles within the liquid crystal layer are calculated, assuming large interfacial energies and various angles of pretilt of the liquid crystal directors with respect to the electrodes. Both the extreme case of a homeotropic (vertical) alignment on one electrode and a homogeneous (parallel) alignment on the opposite electrode, as well as the general case of arbitrary and different alignments on both electrodes, lead to heavily pretilted liquid crystal layers, resulting in definite deformation profiles without disclinations. Liquid crystal cells prepared in this way neither show threshold voltages nor delay times when electrical fields are applied. Measured and calculated characteristics of such liquid crystal cells are presented, they show good agreement.