Tunable Liquid Crystal Alignment and Driving Mode on Lanthanum Aluminum Zirconium Zinc-Oxide Thin Film Achieved by Convenient Brush-Coating Method

Abstract

Tunable liquid crystal (LC) alignment with twisted nematic (TN) and vertical alignment (VA) driving modes is achieved by a convenient brush-coating method. The brush-coating process combines film deposition and alignment treatment processes, and lanthanum aluminum zirconium zinc oxide (LaAlZrZnO) is used for the LC alignment layer. X-ray photoelectron spectroscopy results confirm LaAlZrZnO film formation with fine optical transparency. Atomic force microscopy and line profile data indicate nano/micro surface structure with dense or directional morphologies induced by shear stresses according to film curing temperature. Low-temperature-cured films exhibit hydrophobic properties with low surface energy, whereas high-temperature-cured films show hydrophilicity with high surface energy. The geometric constraints and chemical affinities of the films induce homeotropic and homogeneous LC alignments on the surface according to the film curing temperature, respectively. The LC alignment state is verified by polarized optical microscopy and pretilt angle analysis. The brush-coated LaAlZrZnO film demonstrates high thermal budget for advanced LC systems. The VA-mode and TN-mode LC cells based on the LaAlZrZnO film enable high electro-optical performances and low power consumption. Therefore, the brush-coating method is expected to be adoptable for next-generation LC device applications.