Alignment Properties of Liquid Crystal Molecules under AC and DC Voltage Application Studied by Surface Plasmon Resonance and Optical Waveguide Spectroscopy

Abstract

In this study, we report the evaluation of the tilt angle of liquid crystal (LC) molecules near the surface of SiO2 alignment layers and in the whole cell when AC and/or DC voltages are applied. The LC molecule 4-cyano-4'-n-pentylbiphenyl was used. The LC cell consisted of a Au (50 nm)/SiO2 (30 nm)/LC (3 µm)/SiO2 (30 nm)/Au (100 nm) system. Surface plasmon resonance (SPR) spectroscopy and optical waveguide spectroscopy (OWS) in an attenuated total-reflection configuration were used to monitor the alignment properties of LC molecules. From the SPR/OWS angular scan properties, the profile of the tilt angle from the surface to inside the cell was obtained. Furthermore, the effect of space-charge polarization on the LC alignment properties was observed from the SPR kinetic properties. As demonstrated in this report, this technique should provide useful information for understanding the interfacial phenomena in LC displays.