高分子穩定配向液晶顯示器之光電特性研究

Electro-Optical Characteristics of Liquid Crystal Display Stabilized by Aligned Polymer

陳智全(Chih-Chuan Chen)

指導教授 ： 陳殿榮 ； 吳俊傑

國立臺北科技大學/機電學院/光電工程系所/碩士(2006年)

摘要

本研究利用高分子穩定液晶分子排列製作液晶顯示元件，並探討其光電特性。首先探討利用高分子聚合物製作的光學補償彎曲模式（Optically Compensated Bend Mode；簡稱OCB Mode）液晶顯示元件。將微量的高分子單體與液晶混合物，在適當的組成濃度及固化電壓下，照射紫外光(365nm)用以形成高分子穩定的彎曲式液晶，藉此改善外加電壓下擴散模式轉換到彎曲模式的暖機時間問題。經由響應時間、透光率對電壓及透光率對視角之相依曲線的測量，評估其光電顯示特性，並利用DIMOS軟體模擬預傾角來驗證其特性。
其次也將微量的特殊高分子(由兩種高分子單體所組成)，混入向列型液晶材料，混合後照射到UV光區域會形成高預傾角的配向，藉此形成OCB轉態之成核(Nucleation)區域，樣品製作時，以外加光罩照射UV光形成two-domain的結構，其中ㄧ個區域形成垂直配向結構提供OCB mode轉態功用，在低電壓驅動時，明顯達到warm-up time的縮短。
此外，也嘗試製作高分子穩定的扭轉向列型模式，應用在半穿反液晶顯示器(Transflective Liquid Crystal Display；TRLCD)。根據光散射原理，入射光打在光學非均勻介質時會有散射現象出現，若打到光學均勻介質中，則會穿透而呈現出透明的狀態。本文研究的半穿反液晶顯示器，穿透部分是以調變相位延遲來改變亮暗態，而反射部分則以控制散射量來改變亮暗態，達到半穿反顯示的效果。

關鍵字

光學補償彎曲模式 ； 高分子穩定配向 ； 暖機時間 ； 半穿反液晶顯示器

並列摘要

In this thesis, polymer stabilized liquid crystals are used to develop various liquid crystal devices for flat panel display applications. Firstly, a mixture of nematic liquid crystal and monomer is employed to prepare OCB mode LC cells. High voltage Vuv is applied on the cells as being irradiated by UV light (wavelength 365 nm) in order to produce high pretilt angle for the LC cells. With appropriate polymer concentration and under appropriate curing voltage, polymer-aligned OCB liquid crystal is formed in the sample cells. In the curing process, temperature is set at 30°C and 55°C, respectively. The response time, T-V curves and viewing angle dependence of the sample cells are measured to evaluate their potential in the display application. Simulation on the T-V characteristics of the OCB mode with different pretilt angle is also shown.
Secondly, a geometric structure is proposed that can provide a uniform splay-to-bend transition by forming a vertical domain structure at the edge of an OCB cell. The bend transition spreads from the edge of the vertical state to the bulk region with an initial splay state after a voltage is applied to the cells. It is found that an OCB cell with the vertical domain structure is efficient for obtaining a fast and reliable bend transition in comparison with a conventional OCB cell. Use of the vertical domain structure to display panels can achieve a uniform bend pixel distribution and a fast bend transition.
Thirdly, we propose a novel design of a single-cell-gap transflective LCD. A polymer-dispersed liquid crystal confined in a 90° twisted cell is demonstrated. A control of light transmittance can be also achieved by both direct and reverse mode PDLCs. The operation principle is based on the modulation of light scattering properties of liquid crystal domains dispersed in a polymer matrix by means of a suitable electric field. The transmissive and reflective pixels have similar voltage-light intensity dependence. The polymer stabilization technique can be easily implemented in manufacturing.

並列關鍵字

OCB Mode ； Polymer Stabilized ； Warm-up time ； Transflective LCD

參考文獻

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