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

J. Polym. Sci., Part B: Polym. Phys. 2015, 53, 1123-1130 Crosslinking polymer networks are developed on the glass substrate surface in a liquid crystal cell through the polymerization process, effectively increasing the anchoring energy and governing the liquid crystal molecular reorientation. With its stronger anchoring effect, the polymer network cell shows good light transmittance and excellent vertical alignment quality. Furthermore, the alignment transformation and transmittance bounce are eliminated when the cell is operated at high voltages. Around 36% improvement in the image response is successfully achieved at a low driving voltage.

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 (∼12 V). This developed VA-IPS LC/PNs cell benefits not only the LC molecular alignment but also the electro-optical performance.