PhD Thesis Presentation
Variable Liquid Crystal Pretilt Angles by Nano-Imprint Technology and Their Applications

by Mr Chung Yung LEE

 :  31 Jul 2013 (Wed)
 :  3pm
Venue  :  Room 2463, 2/F (Lifts 25-26), HKUST

Examination Committee
Prof Kun XU, MATH/HKUST (Chairman)
Prof Hoi Sing KWOK, ECE/HKUST (Thesis Supervisor)
Prof Han-Ping David SHIEH, Department of Photonics & Display Institute, National Chiao Tung University (External Examiner)
The study of inhomogeneous surfaces for liquid crystal alignment has witnessed a rapid growth in recent years. Such alignment surfaces are capable of generating any pretilt angles for liquid crystal. Several experiments showed that intermediate pretilt angles could be applied to different applications such as bistable displays and fast response time displays. This type of alignment surfaces generally comprises two kinds of domains favoring different liquid crystal orientations. The arrangement of those domains can be alternating stripped, checkerboard or even patchy patterns.
A new type of nanostructured alignment surface is proposed and demonstrated. As in previous nanostructured alignment surfaces, the new nanostructured alignment surface is capable of generating arbitrary pretilt angles for liquid crystal. The fabrication of the new nanostructured alignment surface is based on nanoimprint lithography and reactive ion etching. The domains are fixed and controllable; no randomness is involved. The uniformity and anchoring properties of this new nanostructured alignment surface have been measured to be of excellent quality. Therefore, the new nanostructured alignment surface is suitable for large area mass manufacturing. Applications that can make use of the new nanostructured alignment surface are also demonstrated.
A stereoscopic three-dimensional (3D) system using a polarization rotator is developed. The polarization rotator converts the polarizations of different eyes images in temporal multiplexing. The proposed 3D system utilizes only passive polarized glasses, which are more convenient, light weight and low cost. In addition, the polarization rotator can be applied to current 2D displays and become 3D capable display. A novel fast nematic liquid crystal mode is also proposed. The new liquid crystal mode has fast response time and high contrast; hence it is a good candidate for polarization rotator.
A new bistable splay twist liquid crystal display is proposed and demonstrated. The bistable splay twist display consists of two stable states, splay and pi-twisted states. Switching is achieved by using horizontal electric field produced by either finger electrodes or comb on plane electrodes. Optimizations of the optics and electrodes have also been performed. The display is permanent bistable and is suitable for e-paper applications.
*** ALL ARE WELCOME !! ***