Surface modification of a poly(ethylene-co-vinyl acetate) layer by ion beam irradiation for the uniform alignment of liquid crystals

The post-processing of a poly(ethylene-co-vinyl acetate) (PEVA) film by ion-beam (IB) irradiation is described herein for use as a liquid crystal (LC) alignment layer. Various film curing temperatures are investigated in order to achieve a stable film prior to IB irradiation, and a uniform and homogeneous LC alignment with superior optical transparency is obtained at a curing temperature of 130 degrees C. The chemical and morphological effects of IB irradiation are further examined by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Although the surface morphology exhibits a random pattern, the IB irradiation is found to modify the chemical characteristics of the PEVA surface by simultaneously inducing van der Waals forces and strong dipole-dipole interactions with the LCs, thus leading to unidirectional LC alignment. In addition, LC cells are fabricated from the IB-irradiated PEVA films, and the LC alignment state is confirmed by polarized optical microscopy and pre-tilt angle measurements. Further, the high transparency of the deposited PEVA film compared to that of ITO-coated glass is demonstrated via transmittance measurement. In view of this superior performance, the IB-irradiated PEVA film is a promising alternative for advanced LC displays. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

Ion-beam (IB) irradiation was used to post-process poly(ethylene-co-vinyl acetate) (PEVA) films for liquid crystal (LC) alignment, resulting in stable and uniform LC alignment with superior optical transparency at a curing temperature of 130 degrees C. IB irradiation induced van der Waals forces and strong dipole-dipole interactions on the PEVA surface, leading to unidirectional LC alignment. The high transparency of IB-irradiated PEVA films compared to ITO-coated glass makes them a promising alternative for advanced LC displays.