扭轉向列型液晶薄膜外加直流與交流步階電壓下的電光效應

Electro-optical effect of twist-nematic liquid crystal films applied alternating-current and direct-current step voltage

陳宏傑(Hong-Jie Chen)

指導教授 ： 莫定山

崑山科技大學/工程學院/電子工程研究所/碩士(2009年)

https://doi.org/10.6828/KSU.2009.00039

摘要

本篇論文主要在研究扭轉向列型液晶薄膜在外加直流偏壓下，其電光效應的改變，共計分成兩個部份：長時間外加直流偏壓下的電光反應，及外加交、直流步階電壓下的瞬時電光反應。
第一部份是製作兩種不同配向結構的樣品：1. 兩側均以PVA配向的對稱式樣品；2. 一側以PVA配向、一側以ITO配向的非對稱式樣品。分別施以100秒的直流偏壓，其均受到離子電荷的屏蔽效應影響，造成其電光曲線的改變，但是兩種樣品的表現並無太大的差異，表示ITO側的電荷注入效應並不顯著。
第二部份是在PVA配向的扭轉向列型液晶薄膜上外加步階電壓，觀測其瞬時的電光反應。1. 在外加5V交流電壓時，發現只在正常白、E模式下其電光曲線在下降後會有一突起的波峰產生。我們推測此現象是由於液晶在突然外加一步階高電壓時產生異常轉動所形成，經由光學模擬亦符合此種推測。2. 在外加二階段直流步階電壓時，發現其電光曲線有兩個波峰產生，第一個波峰是由於離子電荷累積所造成，經由推測導軸分佈及光學模擬，亦符合我們的假設，第二個波峰仍如前所述，是液晶異常轉動所導致。

關鍵字

扭轉向列型液晶

並列摘要

In this thesis there were two parts. The first part studied the variation of electro-optical curve of twist-nematic liquid crystal (TNLC) films applying long-time direct-current bias voltage. The change of electro-optical curve resulted from charge accumulation and built a space charge field to cancel out applying field. We expounded also the mechanism of the relations between transmittance of light and applied voltage. There were two different types of samples, symmetrical and unsymmetrical TNLC cells, manufactured by different alignment layers. But the differences of electro-optical responses between these samples were not significant.
The second part was the studies of the transient electro-optical curve of TNLC films applying alternating-current and direct-current step voltage. We applied AC voltage (AC 5V) on the films and observed only the Normally-White E-mode would produce a peak in the electro-optical curves. We surmised the origin of this peak was due to director abnormal rotation with applying high-voltage electric filed suddenly and verified our surmise by optical simulation. Once we applied two-step DC voltage on the films, we observed two peaks in the electro-optical curves. We surmised that the origin of the first peak in electro-optical curve resulted from reorienting of the LC molecules near both electrodes induced from charge accumulation, and demonstrated this surmise by calculating director tilt distribution and optical simulation. The second peak originated from the directors abnormal rotation as mentioned above.

並列關鍵字

TNLC

參考文獻

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