Patterned Surface Effects on Ordering of Anisotropic Liquid Crystal Molecules

Abstract

We demonstrate an axially symmetric multi-domain liquid crystal (LC) structure regulated by patterned LC alignment layers. In our structure, a homeotropic LC alignment layer is periodically patterned on a homogeneous LC alignment layer. Before patterning, the homogeneous LC alignment layer is unidirectionally rubbed to generate pretilt in LC anchoring. The patterned homeotropic LC alignment layer is simply fabricated on the homogeneous LC alignment base layer by micromolding in capillaries (MIMIC) with a patterned elastomeric mold structure. After patterning, the patterned homeotropic LC alignment layer is notrubbed. With the MIMIC methode, we prepared two patterned substrates, where the patterned materials and the patterned structures are indentically formed, and the substrates are assembled for the rubbing direction of the homogeneous LC alignment base layer to be orthogonal to each other. Into the cavity, a nematic LC (NLC) with a negative dielectric anisotropy is filled in an isotropic phase of the NLC. Oure NLC cell has four domains in an absence of applied voltage. In the pixel areas, the NLC is vertically aligned (VA) without pretilt. At side of the pixels, the NLC is aligned with hybrid structures. Among them, thepretilt of two hybrid LC domains is determined by the rubbed homogeneous LC alignment layer of the lower substrate and the pretilt of others is determined by the rubbed homogeneous LC alignment layer of the top substrate. Therefore, the pretilt directions of two hybrid domains are orthogonal to each other. At corners, twisted nematic structures are identically formed. In this structure, the field-induced LC reorientation in thepixel area is determined by the pretilt direction of the boundary LC molecules with hybrid configuration since the LC molecules with hybrid structure respond at lower voltages than those with VA structure. Due to orthogonal boundary effects in pretilt, the textures in the pixel areas show axially symmetric multi-domain LC distribution and redistribution phenomena of LC molecules by periodically patterned surface effects are demonstrated and discussed.