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 t he changes of the average tilt angle of nematic liquid crystals near t he surface of alignment film under the application of an electric fiel d. 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 av erage tilt angle near the interface increases monotonically with the a pplied field and tends to saturate to be 35 degrees when an adequate f ield 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 behavi or is well explained numerically in terms of elastic theory by assumin g strong surface anchoring.