Low temperature nanocomposite alignment films for optically compensated bend liquid crystal displays

Low temperature processes have been highly desired for the development of flexible displays. However, traditional polyimide alignment films require high-temperature hard baking for at least 1 h to complete the cyclization polymerization. It is thus difficult to design liquid crystal displays with flexible substrates. In this paper,we proposed to use ultraviolet-curable liquid crystal polymer (LCP) in conjunctionwith polyhedral oligomeric silsequioxane (POSS) nano-particles (2-5 nm) to develop a low temperature alignment technology with wide range of liquid crystal pre-tilt angles. The photo-polymerization process was relatively fast, and the polymer rubbing particle issues could be avoided. The results showed that, if 0.05 wt.% POSS nano-particle was added in the 28-nm LCP nanocomposite film, the pretilt angle would be 42° for the optically compensated bendmode liquid crystal displays. The cell gapwas about 4 μm. The POSS nano-particles provided a homeotropic alignment force,while the LCP gave homogeneous alignment force in the horizontal direction. The force balance would result wide range pretilt angles, according to the nanocomposite compositions. The low temperature alignment technology will help the advancements in fast-response and flexible displays.