Physicochemically constructed zinc oxide and UV-curable polymer hybrid films for liquid crystal system

Abstract

UV-nanoimprint lithography was performed with zinc oxide (ZnO) solution and a UV-curable polymer. The UV-curing time was 2, 4, or 6 min, after which the surfaces of the films were analyzed. Atomic force microscopy of the physical characteristics of the surfaces revealed that the clearest pattern was attained on the 6 min UV-cured film. Moreover, X-ray photoelectron spectroscopy analysis confirmed that varying the UV exposure time changed the composition of atoms and bonds on the surfaces of the films. Light transmittance measurements of the patterned ZnO hybrid films show that they all exhibited sufficient transmittance. To investigate the liquid crystal (LC) orientation, LC cells were fabricated with the various films into antiparallel structures. Polarized light microscopy confirmed stable LC alignment while a stable transmittance curve based on pretilt angle measurements was observed in LC cells fabricated with hybrid films exposed to UV light for more than 4 min. The relationship between the height of the groove pattern in the film and the alignment of the LC molecules was analyzed by using Berreman's model.