配向膜對液晶盒內離子電荷效應之影響

Abstract

TFT-LCD是目前最熱門的液晶顯示器，但薄膜電晶體卻在閘極(Gate)與汲極(Drain)間存在雜散電容，使得輸入液晶層的驅動電壓會有無可避免的直流成份，液晶層中的雜質電荷就會因為直流偏壓的誘因產生運動，造成顯示元件出現閃爍或影像殘留的缺陷。本文主要探討在直流偏壓下配向膜厚度對液晶盒中電容-時間曲線(C-t curve)的影響，以及在交流訊號下液晶盒兩側不同厚度的配向膜對穿透率-時間曲線(T-t curve)的影響。在實驗中我們發現配向膜越厚會造成越強的離子捕捉效應；此外，若液晶盒兩側的配向膜厚度不一樣，即使是在交流訊號的驅動下依然會有離子電荷運動的效應；我們用這些實驗數據推論一個合理的模型說明離子電荷的運動機制，進而更以模擬來印證模型的正確性，且藉由改變各參數探討其對電容-時間曲線的影響。

The purpose of this thesis is to discuss the capacitance -time characteristics of a liquid crystal cell in dc bias by charging different alignment layer and the transmittance - time characteristics of a liquid crystal cell in ac bias with different thickness of alignment layer in each side. From the experimental results, we know that the alignment layer is thicker, the ionic trapping effect is stronger. Besides, when the alignment layer thickness is different in each sides of a liquid crystal cell, it also has ionic moving effect even the driving signal is ac bias. According to these results, we proposed a reasonable model to explain the ionic moving mechanism, and simulated the C-t and T-t characteristics which are with good accordance to our measuring results. We also discussed the influence of parameters to C-t and T-t characteristics by charging them in this simulation.