Measurement of Tilt Angle of Nematic Liquid Crystal Near the Surface of Rubbed Polyimide by Means of the ATR Method

An attenuated total reflection (ATR) method has been used to measure the changes of the average tilt angle of nematic liquid crystals near the surface of alignment film under the application of an electric field. The respondence of molecular alignment, in the region of about 140 nm from the liquid crystal/alignment film interface, upon the applied voltage, was obtained by this experiment. The results show that the average tilt angle near the interface increases monotonically with the applied field and tends to saturate to be 35 degrees when an adequate field is applied up to 80 volts; this saturated value is small compared with the tilt angle at the mid-plane which is 90 degrees. This behavior is well explained numerically in terms of elastic theory by assuming strong surface anchoring.