Applications Of Liquid Crystal Alignment Based On The Development Of Dynamic Photo-patterning

Liquid crystals (LCs) are organic compound matter in a low-dimensional ordered state that has properties between those of conventional liquid and those of solid crystal, and have unique liquidity and optical properties (such as birefringence). The birefringence arises from the anisotropic orientation of LCs’ molecules which are arranged in the external conditions such as electric field, stress and thermal irradiation. So, it is critical to realize the alignment of LCs’molecules for the fundamental research of LCs’properties and related devices. LCs have played an important role in display and photonics, et al.Liquid crystal alignment technology has a long development history and can be classified as rubbing and non-contact alignment by its various types of processes. Rubbing process is simple and cost effective, so it has a high market acceptance in large scale industrial production. But rubbing has inherent defects such as static friction, dust accumulation and large groove diameter, et al., which lead to low yield LCs devices. In recent years, lots of non-contact processes such as oblique vapor deposition of silicon oxide, ion beam alignment and photo-alignment have been came up to solve these problems. Among them, photo-alignment has received widespread concern for the reasons that it has a high accuracy, is easy to realize local polarization control and solves the problem of a narrow perspective of LCD.This work mainly includes two parts:Develop and improve a DMD-based dynamic photo-patterning micro-lithography system with imaging optics theory and optical design principles. In this part, we design projection lens with a double telocentric structure with Code V software to eliminate heterogeneous effects of DMD, system optical aberration and diffraction, and develop a multi-purpose platform with Labview software to enhance mechanical resolution. This system has a lot of advantages such as easier control, higher efficiency, low distortion and needless masks compared to conventional contact lithography and scanning lithography.Apply this system to conventional micro lithography, liquid crystal alignments and local polarization control for light wave front. In this part, arbitrary patterns are designed with Adobe illustrator and Auto CAD, and generated by the DMD. And then these patterns are focused on photo-alignment layer (SD1) which is located on the focusing plane, to further guide the LC molecules orientations. We realized complex1D/2D patterns such as grating, bar codes and hexagonal lattice with the experimental resolution up to5micrometers. Transformation of different bar codes is achieved based on the excellent alignment rewritable properties of SD1. And subarea control of random gray scale is realized with pseudo-random codes. Besides, all the LC devices above possess switching and tuning effects. The dynamic photo-patterning lithography technique has a wide use in information display and identification, tunable photonic devices, etc.