液晶摻雜奈米碳管之介電研究

Dielectric Study of a Liquid Crystal Doped with Carbon Nanotubes

簡伯儒(Bo-Ru Jian)

指導教授 ： 李偉

中原大學/理學院/物理研究所/碩士(2010年)

https://doi.org/10.6840/cycu201000652

摘要

本論文旨在探討以多壁奈米碳管摻入液晶之離子效應—透過介電頻譜量測技術，觀察離子電荷進行傳輸行為所產生的電極極化影響；並配合電壓保持率的量測，進而探討奈米碳管添加物是否可「純化」液晶以利顯示元件之應用。
研究結果顯示，微量摻雜奈米碳管（< 0.05 wt.%）有助於吸附雜質電荷並降低離子擴散常數，達到抑制可移動離子濃度並阻礙擴散運動的效果；然而碳管的過量摻雜（> 0.05 wt.%）會使奈米碳管產生自身團聚，造成反向效果。由電壓保持率實驗結果可知，摻雜奈米碳管可有效提升電壓保持率26%；同時透過時變電壓保持率實驗之研究，我們發現奈米碳管可延長液晶盒的生命期。本論文揭示奈米碳管之添加有助於降低液晶中離子效應，故可應用於薄膜電晶體顯示元件中。

關鍵字

離子 ； 液晶 ； 奈米碳管 ； 介電

並列摘要

This thesis focuses on the ionic effect in liquid crystals doped with multiwalled carbon nanotubes (CNTs). By dielectric spectroscopy, the electrode-polarization process dictated by both the concentration and the diffusion constant of impurity ions and, thus, can be monitored, which is particularly useful for interpretation of the dopant effect on the ion transport. From the results of voltage-holding-ratio (VHR) measurements, one can investigate whether CNTs as a dopant has the potential application in display devices by “purifying” liquid crystals.
The results show that a minute amount (< 0.05 wt.%) of CNTs as a dopant not only localize impurity ions via the formation of the charge-transfer complex to reduce the measured ion concentration but also hinder ion transport to result in a smaller diffusion constant in the suspension. When the CNT concentration is larger than 0.05 wt.%, the CNTs were prone to aggregate and cause the undesired effect. The VHR results reveal that doping CNTs in a liquid-crystal cell raises the VHR by 26% and extend the life time of the cell. Our study concludes that CNTs as an additive can suppress the ionic effect, allowing its potential application in TFT–LCD devices.

並列關鍵字

liquid crystal ； carbon nanotubes ； dielectric ； ion

參考文獻

[35] 陳惠玉，《向列型液晶盒中離子傳輸之電動力學》，博士論文，中原大學物理研究所，民96年6月。

[1] N. Sasaki, “Simulation of the voltage holding ratio in liquid crystal displays with a constant charge model,” Japanese Journal of Applied Physics 37(11), 6065–6070 (1998).

[2] R. N. Thurston, J. Cheng, R. B. Meyer, and G. D. Boyd, “Physical mechanism of dc switching in a liquid-crystal bistable boundary layer display,” Journal of Applied Physics 56(2), 263−272 (1984).

[3] S. H. Perlmutter, D. Doroski, and G. Moddel, “Degradation of liquid crystal device performance due to selective adsorption of ions,” Applied Physics Letters 69(9), 1182–1184 (1996).

[4] W. Lee, C.-Y. Wang, and Y.-C. Shih, “Effects of carbon nanosolids on the electro-optical properties of a twisted nematic liquid-crystal host,” Applied Physics Letters 85(4), 513–515 (2004).