Self aligned liquid crystals on sol-gel-processed zirconium oxide surface via nanoimprinting lithography

Abstract

In this paper, a nanopattern was effectively formed on a zirconium oxide (ZrO) film, and a uniform liquid crystal (LC) alignment layer was developed through it. One-dimensional (1D) nanopatterns from polydimethylsiloxane (PDMS) molds were transferred to ZrO films via nanoimprinting lithography (NIL). The pattern height of the PDMS mold was 30 nm, and the ZrO film was cured at 100 °C and 200 °C. The transfer of nanopatterns was analyzed by observation of surface modification through atomic force microscopy. The ZrO solution injected between the molds in a sol state by capillary force did not sufficiently solidify at 100 °C, but at 200 °C, sufficient pattern height and period were secured. Using X-ray photoelectron spectroscopy, it was confirmed that ZrO used as an alignment layer was well deposited on the substrate surface. An increase in the contact angle with pattern formation was also confirmed, indicating a decrease in surface energy and hydrophobicity of the surface. A polarized light microscope and pretilt angle were analyzed using a liquid crystal cell manufactured with an antiparallel structure, and the excellent alignment characteristics of the 200 °C cell were confirmed. The vertical alignment mode was confirmed in the voltage-transmittance curve, and a good threshold voltage was observed. Through these analysis methods, the nanopattern was successfully transferred to the ZrO film through NIL, and excellent performance as a liquid crystal alignment layer was confirmed.