Liquid crystal alignment effect and electro-optical characteristics of rubbing-atmospheric plasma coprocessing in ZnO alignment film according to concentration

We describe liquid crystal (LC) alignment in varying solution-derived zinc oxide (ZnO) concentrations after treatment with atmospheric plasma. In order to implement a high-performance display, uniform alignment of an LC alignment layer is one of essential process factors. The atmospheric plasma and inorganic alignment layer introduce new high-efficiency manufacturing process and the possibility of application in various fields. After irradiating the rubbing alignment method and atmospheric plasma, we analyzed the surface modification, LC alignment, and electro-optical characteristics as the ZnO concentration of the alignment increased from 0.1 to 0.3 mol/L. Surface energy calculations are used to confirm that the dispersive energy decreases, while the polar energy increases, as the ZnO layer concentration is increased. Furthermore, we show that the ZnO surface causes the pretilt angle to increase and increases the dipole moment between LC molecules. Voltage-transmittance characteristic are used to confirm the driving voltage of the sample. The sample with a ZnO concentration of 0.2 mol/L showed an improvement of more than 66% in driving voltage compared to other conditions. All samples had a rapid response time (<20 ms). In this study, the optimal process conditions for manufacturing ZnO alignment films were determined using rubbing-atmospheric pressure plasma coprocessing. Graphical Abstract Graphical Abstract shows the LC cell manufacturing process using rubbing-atmospheric plasma coprocessing of the ZnO alignment layer fabricated at a concentration of 0.1–0.3 mol/L through the sol–gel method. The LC cell is made of an AP LC cell in which liquid crystals are arranged in the opposite direction and a TN LC cell in which liquid crystal molecules are twisted at 90 o . In this study, we confirmed the liquid crystal alignment effect using atmospheric plasma in the alignment film produced at a concentration of 0.1–0.3 mol/L.