扭轉向列型液晶盒非對稱光學響應之探討

Study on Asymmetric Optical Response of Twist Nematic Liquid Crystal Cell

苟孝第(Hsiao-Ti Kou)

指導教授 ： 吳俊傑 ； 陳殿榮

國立臺北科技大學/電資學院/光電工程系研究所/碩士(2010年)

摘要

目前液晶顯示器已經被廣泛的使用在各種電子產品上，但是液晶盒因離子效應所產生的問題，像是電壓保持率、畫面閃爍、影像殘留等缺陷，也一直影響到影像顯示的品質，所以目前一直被廣為討論與研究。 本論文從兩部分來研究液晶盒的離子效應。第一部分探討正、負電壓保持率中不對稱的光電響應。我們藉由模型解釋、公式推導和模擬軟體的分析得知，造成此不對稱光電響應的原因是由於液晶盒中存在本質電場，而此本質電場的方向與外在電場的極性方向和大小無關，但是對於顯示器的影像品質還是會有很大的影響；第二部分則是從照光方面研究離子效應，架構分為照射背光模組(冷陰極射線管,CCFL)和紫外光源兩方面。我們經由觀察照光時間與對應偏光圖的關係，發現照光會使液晶盒內部離子效應更為明顯，並使照光區域與遮光區域的光學特性有所不同。本論文將藉由探討離子效應和照光後的光電特性來解釋顯示器缺陷產生的原因。

關鍵字

離子 ； 電壓保持率 ； 本質電場 ； 背光模組 ； 紫外光

並列摘要

Nowadays, liquid crystal display (LCD) has been widely used in many kinds of electronic products. But some defects such as voltage holding ration (VHR), flicker, and image-sticking effect are usually produced in LCD that reduces the display performance. These defects have extensively been discussed and researched upon the ionic effect.
In this study, the asymmetric electro-optical properties of twist nematic LCD are investigated based on the ionic effect. First, a model of intrinsic electric field and formulas are proposed to discuss the asymmetric VHR in TN-LCD. We confirm that the asymmetric VHR is caused due to the existence of intrinsic electric field in the LCD. The direction of intrinsic electric field is independent of the polarity of external applied voltage. On the other hand, we discuss the ionic effect in the LCD with a backlight irradiating to the cell. Two kinds of light source, Cold Cathode Fluorescent Lamp (CCFL), and ultraviolet light are used in this study. While irradiating backlight to the LCD for a long time, some optical responses of LCD are changed. We observe these changes by controlling the irradiating time of backlight. According to the observation of microscopic textures, the changes of optical response of LCD as a function of irradiating time of backlight is suggested to relate to the ionic effect. The relation between the ionic effect and optical response of LCD is clarified, so as to explain the formation of defects in LCD.

並列關鍵字

ion ； voltage holding ratio ； intrinsic electric field ； back light module ； ultraviolet

參考文獻

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