研究液晶盒內雜質離子之光電特性

Abstract

我們從光學量測出發，發現液晶盒內離子效應所導致的穿透率變化可分為兩種形式：Discharge effect和Charging-Up effect，不同於已經發表的相關論文，只觀察到前者而無後者。本論文用實驗首次證明了雜質離子同時存在於液晶層與配向層，因此我們將文獻中由光學量測計算液晶層離子濃度的公式再做推廣，推導出由光學量測計算配向層離子濃度的公式，使液晶盒可依自身的穿透率變化特性選擇相應的公式計算離子濃度。 本文使用的是面板廠製作的液晶盒，卻發現其穿透率對時間曲線(T-t curve)與一般實驗室自製的液晶盒有很大差異，因此我們認為液晶盒內離子的產生是由高、低解離率的雜質所造成，利用低解離率公式，我們得出液晶層與配向層雜質的解離率隨溫度變化曲線(β-T curve)，比較兩曲線可知液晶層與配向層雜質的解離率差就是造成不同溫度時有不同離子量變化幅度的原因，並由兩曲線交點得知液晶盒由Charging-Up effect轉變成Discharge effect的轉折溫度，從中也可比較液晶材料或配向材料的品質純淨度，使本文第2章的光學量測方法與公式以及第3章的高低解離率理論模型有了完美串聯與驗證。 最後為了從另一角度證實光學量測結果與高低解離率雜質所產生的離子理論，我們設計了一套電學實驗與理論模型，未來若經由實驗結果證實此電學量測理論可行，將可從電學實驗再度驗證第2、3章之結論，使高低解離率理論更加完備，並可用於量測及推導液晶層和配向層內各自的離子濃度與形成離子所需的活化能，為研究液晶盒中離子的形成機制及其所造成的光電效應，提供了一個新的方法。

We have measured the electro-optical effects of TN cells either home-made or made by a TFT-LCD panel maker. The experimental results on home-made samples showed only “Discharge effect” similar to the published results that was caused by the high-ionization-rate (HIR) impurities within the samples. However, for the first time, we have obtained experimental results on panel-maker-made samples at different temperatures that showed two different tendencies: “Discharge effect” and “Charging-Up effect”. We believe that these two different tendencies can be explained by the existences of low-ionization-rate (LIR) impurities in TN cells or alignment layers or both. For some samples, we have observed the change from Charging-Up effect at low temperature to Discharge effect at a higher temperature. We have derived equations to calculate both the ionic concentration and the ionization-rate of impurities for both tendencies. The Discharge effect was caused by more ions ionized and drifted within the LC medium than within the alignment layers under the same external applied voltage to the TN cell. The Charging-Up effect was just the opposite case. In this thesis, we also suggest new methods of measurement and analysis to obtain simultaneously the ionization rate of impurities within the LC medium and the alignment layers. This will serve as an extension of this thesis to make significant contribution on the further understanding of ionic effects within panel-maker-made LC cells consisting of LC medium and alignment layers.