研究垂直配向液晶盒中液晶層和配向層的離子效應

Abstract

本論文主要研究於低頻操作環境下，垂直配向液晶盒中液晶層與配向層的離子現象；同時探討在低頻操作下之單一液晶盒中，液晶層與配向層各自離子特性；並且觀察液晶層與配向層各自離子對整體液晶盒所產生的離子效應。 在實驗方面使用外差干涉儀、電感電容阻抗分析儀及半導體參數分析儀分別量測1 kHz相位差對電壓、0.1 Hz相位差對時間、1-100 kHz介電常數對頻率以及0.1 Hz電流對時間的關係數據，並將量測數據進行互相關聯運算，即可求得液晶盒中液晶層與配向層各自離子所造成的離子電壓。 在理論分析方面使用T. C. Chieu與K. H. Yang所提出離子解離和運動方程式，推導出高解離率與低解離率離子的相關方程式，並將實驗所得液晶盒中液晶層與配向層各自離子電壓的結果和推導出的理論分析公式互相作擬合，便可獲得液晶盒中液晶層與配向層各自的高解離率與低解離率離子的初始濃度、離子遷移率及相關活化能等相關物理參數，並且從擬合迴歸係數(R-square)檢定量測數據與理論分析的相關強度。而此離子解離與和運動模型，不僅適用於分析液晶盒中液晶層內部的離子行為，亦可適用於解釋配向層內部的離子行為。進一步藉由分組比對，來觀察液晶盒中液晶層與配向層各自離子對整體液晶盒所產生的影響，以選擇適當的液晶材料與配向材料應用於低頻環境。

In this thesis, we have studied the ionic phenomena of rubbed-polyimide(PI)-vertically-aligned (VA) cells whose ionic properties were originated from both liquid crystal and PI layers. In our experiments, we have used heterodyne interferometry, LCR meter and the current meter to measure the data of the phase versus voltage at 1 kHz and the phase change versus time applied by a 0.1 Hz square-wave voltage, the capacitance versus voltage from 1 k to 100 kHz, and the current versus time at 0.1 Hz, respectively, on VA cells. The ionic voltages accumulated adjacent to the PI-to-LC interfaces contributed from PI- and LC-sides were derived, respectively, from measured data. We have used ion generation and transport equations developed by T. C. Chieu and K. H. Yang for the investigation of ionic properties from measured data. The ionic parameters of high-ionization-rate (HIR) and low-ionization-rate (LIR) ions within the liquid crystal mixture and the PI layers were obtained by fitting experimental data to analytic solutions from the equations. The measured data of ionic voltage have been fitted to the analytic solutions for the derivations of ionic parameters such as ion concentrations, ionic mobility and the associated activation energies of HIR- and LIR-ions within VA liquid-crystal mixture, and PI layers, respectively. The fitting R2-value for each parameter showed good agreements between experimental results and theoretical analyses. It is a surprise to see the ion generation and transport model by Chiu and Yang can be applied to explain the ionic behaviors of PI-alignment layers of VA cells. Our results can be used to optimize the ionic properties of PI-aligned VA cells for better display qualities.