Alignment Effects Near Edges of Electrodes on Negative and Positive Dielectric Anisotropy Liquid Crystals Using In-Plane Switching Fields

The dynamic change in alignment behaviour of positive and negative dielectric anisotropic liquid crystal (LC) molecules upon application of in-plane switching (IPS) fields is reported herein. The observed textural behaviour exhibited dark black textures in the OFF state for both positive LC (P-LC) and negative LC (N-LC) in IPS cells. Under the applied IPS fields, textural variations were observed and resulted in the emergence of brighter states at higher voltages. The microscopic analysis revealed that more uniform and brighter textures were formed in the N-LC IPS cell than in the P-LC IPS cell. Moreover, different alignment patterns near the edges of electrodes in response to the applied IPS electric field were observed for the N-LC and P-LC IPS cells. The voltage-transmission characteristics of the P-LC and N-LC IPS cells were also found to correlate with the textural behavior. The N-LC IPS cell demonstrated more uniform switching due to the transverse response of LC molecules to the electric field, resulting in higher ON-state transmittance. On the other hand, the P-LC IPS cell displayed a non-uniform switching pattern from edges to the center, leading to lower ON-state transmittance. Additionally, the P-LC IPS cell exhibited lower threshold voltage than the N-LC IPS cell; however, the contrast ratio was similar to 3.5 times better in the N-LC IPS cell than the P-LC IPS cell. The dielectric behaviour was also analysed, and lower relaxation strength was observed for the P-LC IPS cell than the N-LC IPS cell. Thus, the findings shed light on the complex behavior of P-LC and N-LC IPS cells under varied IPS electric fields, revealing the importance of LC material and alignment in determining the electro-optical performance of IPS displays for energy efficiency.