Controlled nano structures on solution-processed inorganic/organic film for liquid crystal application

Ultraviolet (UV) nanoimprint lithography (NIL) was performed using a hybrid solution of ZnO and UV-curable polymer. The concentration of the UV-curable polymer was varied as 5, 10, and 15 wt.%, and the surface was analyzed for each film. Physical modification of the surface morphology was analyzed by atomic force microscopy, and the clearest pattern was confirmed at 15 wt.%. Through X-ray photoelectron spectroscopy analysis, it was confirmed that the difference in the concentration of the UV-curable polymer caused a difference in the atomic and bonding composition on the film surface. Through optical transmittance measurements, it was observed that all of the patterned ZnO hybrid films exhibited sufficient transmittance. To investigate liquid crystal (LC) alignment, each of these films was assembled into an antiparallel structure to fabricate LC cells. Using polarized optical microscopy and thermal stability tests, it was confirmed that the LC cells fabricated with the 15 wt.% solution showed the most stable LC alignment. Moreover, pretilt angle measurements showed that the most stable transmittance curve was obtained with the 15 wt.% LC cell. The relationship between the height of the groove pattern and alignment of the LC molecules was analyzed using Berreman’s model.