Studies of binary liquid crystal alignments using photo-alignment on polymer surface and their application

• Main Authors: Ju-chin Chen, 陳儒瑾
• Other Authors: Andy Y.-G. Fuh
• Format: Others
• Language: zh-TW
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/41608592096817723345

碩士 === 國立成功大學 === 物理學系碩博士班 === 97 === This study demonstrates the feasibility of binary liquid crystal (LC) alignments based on azo dye-doped liquid crystals (ADDLCs). The fabrication process is described as follows. Firstly, a monomer film is spin-coated onto a glass substrate with a homeotropic or homogeneous alignment layer. Secondly, an unpolarized UV-light is irradiated onto the substrate through a photo-mask having a desired pattern, and then, the UV-cured polymer-pattern is retained after removing the un-polymerized monomers by a suitable solvent (Acetone 80% and alcohol 20%). Finally, binary regions having polymer film/ homeotropic (or homogeneous) alignment layer are generated. Three devices, developed using this approach, are summarized as follows. (a) Polarization-independent and electrically switchable Fresnel lens: In this part, we use a Fresnel zone plate mask to fabricate the binary regions. Orthogonally hybrid alignments between two adjacent zones are achieved. The focusing efficiency is electrically switchable. The maximum focusing efficiency of the fabricated ADDLC Fresnel lens is ~34.14%, which is much higher than that of the used Fresnel zone plate mask (~ 25.6%). (b) Liquid crystal grating: In this part, a binary LC structures are fabricated using 50 �慆 grating mask. A LC grating with homeotropic and homogeneous alignments between two adjacent zones is achieved. The results show that the first order diffraction efficiency of this grating is electrically switchable, and the maximum diffraction efficiency of the first order is about 26.98%. Additionally, the binary structures can be optically switched to another binary LC structures - homeotropic and TN structures. (c) View-angle dependent LCD: Using binary LC structures, a LC cell having hybrid and homeotropic structures is fabricated. It is placed between two cross polarizers to form a LCD, which can display two different images by changing viewing angle. Additionally, the simulated transmittance contours of this LC display at different viewing angle obtained using the software of DIMOS consist with the experimental results.