Measurement of Polar Anchoring Coefficient for Nematic Cell with High Pretilt Angle

A method to determine the surface anchoring energy of a nematic liquid crystal is proposed. The technique implies the measurements of optical retardation of a nematic cell as a function of a strength and direction of the applied magnetic field. It enables one to get both pretilt angle α and anchoring coefficient W a in the course of the same experiment. As an example, both parameters (α=10.9° and W a =1.5×10−5 J/m2) are measured at the interface between the nematic 5CB and rubbed polyimide film.</p

Tilted Photoalignment of a Nematic Liquid Crystal Induced by a Magnetic Field

Nematic liquid crystal cells with polyvinyl cinnamate coated substrates were subjected to ultraviolet light. When this was done in the presence of an oblique magnetic field the photoalignment was found to be temporally and thermally robust, with a large pretilt angle and weak polar anchoring. Moreover, two easy axes with equal and opposite pretilt angle were obtained, such that a magnetic field could switch the director from one easy axis to the other. (C) 1998 American Institute of Physics.</p