Effect of crosslinking polymer networks on the molecular reorientation and electro-optical performance of in-plane switching vertically aligned liquid crystal devices

The effects of crosslinking polymer networks (PNs) on the molecular reorientation and electro-optical properties of vertically aligned (VA) liquid crystal (LC) devices are investigated by applying an in-plane switching (IPS) electric field. Through the polymerization process, crosslinking PNs are developed on the substrate surface, effectively increasing the anchoring energy and governing the LC molecular reorientation. With its stronger anchoring effect, the PNs cell shows good light transmittance and excellent vertical alignment quality, as compared to the pure LC cell. Furthermore, the alignment transformation and transmittance bounce resulting from the transient process of LC molecular reorientation are eliminated when the cell is operated at high voltages. The rising-time (t(r)) and falling-time (t(f)) responses of the PNs cell are significantly improved, and around 36% improvement in the optical switching response is obtained. In addition, the dynamic gray-level t(r) and t(f) responses of the PNs cell are enhanced by around 55% and 42%, respectively, at a low driving voltage (approximate to 12 V). This developed VA-IPS LC/PNs cell benefits not only the LC molecular alignment but also the electro-optical performance. (c) 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015, 53, 1123-1130