非強錨定扭轉型液晶盒的電光特性研究

Abstract

液晶盒的邊界錨定能強弱會影響液晶分子的方向分佈，造成其電光效應的差異。我們製作了不同表面處理與摻雜手徵性分子的一系列光配向扭轉型液晶盒。使用不同的光配向材料可以得到錨定能具明顯差異的液晶盒。利用液晶連續體彈性形變理論與Rapini-Papoular表面自由能密度表示式，經由液晶盒的厚度與液晶分子的實際扭轉角度之測量結果，我們獲得了液晶盒的扭轉角錨定能。再配合預傾角與傾角錨定能的量測進行液晶盒電光效應的數值模擬。由實驗與模擬曲線的比較分析得到錨定能的強弱對液晶盒電光特性的影響，並進而探討R-P表面自由能密度表示式的適用性。

The anchoring properties of liquid crystal devices significantly influences the orientational distribution of liquid crystal molecules, and therefore results in different electro-optical properties. In this thesis, we prepared several twisted liquid crystal cells with different anchoring strengths by using photo-alignment technique. Based on the continuum mechanic model of liquid crystal medium and the Rapini-Papoular form of surface free energy density, we were able to accurately determine the azimuthal anchoring strengths with the measured cell thickness and actual twist angles. We further calculated the electro-optical properties of these liquid crystal cells based on the measured values of pretilt angle and polar anchoring strength. Our approach leads to a clear demonstration of the influence of anchoring strength on the EO properties of twisted LC devices. Our results indicate the simple R-P form of surface free energy is not appropriate for the LC devices with medium to weak anchoring strengths.