混合配向液晶元件的預傾角量測與計算之研究

Abstract

預傾角的量測對於顯示器的各種光電特性有很重要的影響，目前現有的預傾角量測公式，像是相位延遲極值法或者晶體旋轉法，皆是用於傾斜配向的量測方法，但對於混合配向下的預傾角量測，便無公式可將兩面混合配相的角度同時得之，因此我們希望對此種混合配向的液晶樣品，演算出一套新的公式，達到我們的目的。 在我們的公式中，是從晶體旋轉法的公式為基礎，藉由量測出的相位延遲值代入公式計算，便可得其混合預傾角，並在我們的實驗結果中相互印證。在本實驗中，我們使用POSS奈米分子摻雜於水平配向膜中，以及摩擦配向的摩擦強度控制其預傾角角度，分別與水平配向膜、垂直配向膜組成樣品，先從這兩組類型樣品中，模擬推導其公式的準確度，並對公式加以修正後，再從實際量測出的預傾角數值，確定我們公式計算出的解是正確的，最後再以實驗求得的相位延遲值的交互關係，代入其適當的公式中，驗證是否能準確求出任意混合樣品的預傾角。 最後從我們的實驗結果，確定了其公式修正後的可信度，對於量測到的相位延遲值關係不同，使用不同的公式計算，可以增加預傾角量測上的準確性，因此本篇研究中所提出的解析方法，為第一次能從量測到的相位延遲數據，同時求出混合配向的液晶盒一邊與對邊兩個不同的預傾角。

The measurement of the pretilt angle is very important for both optical and electrical properties in liquid crystal displays (LCDs). Previous methods of measurements, such as the phase-retardation-extremum method and the crystal rotation method, have been applied to liquid crystal cells whose alignment were parallelly tilted at the cell substrates. However, there was no methed for measurement of the pretilt angles of hybrid-aligned LCDs. In this thesis, a new method was proposed to provide that. We developed a theoretical model to calculate the phase retardation of the hybrid-aligned LCDs and compared with experimental results to derive its pretilt angles. In our experiments, we doped the homogeneous alignment film with the nanoparticle POSS (polyhedral oligomeric silsesquioxane) to change the pretilt angles. The hybrid-aligned sample was composed of alignment by this film and the homogeneous or vertical aligned film at the opposite side. We have used an iterative approach to derive suitable equations for the determination of accurate pretilt angle by comparing our simulated results with experimental results. In each iteration, the equations suitable for the measured phase retardation of the hybrid-aligned LC cell were modified to decrease the standard deviations of the obtained pretilt angles. We believe that, for the first time, we have developed a general approach to determine the pretilt angles of any hybrid-aligned nematic LC cells.