SURFACE AZIMUTHAL ANCHORING ENERGY BETWEEN THE GRATING SURFACE AND NEMATIC LIQUID CRYSTAL LAYER STUDIED BY USING A GEOMETRIC MODEL

A simple geometric model is proposed for estimating the azimuthal anchoring energy between the sinusoidal relief grating surface and nematic liquid crystal layer of a liquid crystal display (LCD) device as a function of the grating height and grating pitch. The model parameters are determined experimentally, and the model is then used to predict the surface azimuthal anchoring energy for gratings with various pitches and heights. It is shown that a good agreement exists between the predicted results for the surface azimuthal anchoring energy and the experimental data. Moreover, a good agreement is also observed between the estimated results and those obtained from Berreman's expression and finite element method (FEM) simulations, respectively. Overall, the experimental and numerical results show that for the nematic liquid crystal considered in the present study (4-n-pentyl-4'-cyanobiphenyl (5CB)), the surface azimuthal anchoring energy increases with an increasing grating height or a reducing grating pitch.