含奈米碳管添加於配向膜之液晶盒的暫態電流特性

Properties of Transient Current in a Liquid-Crystal Cell Containing Alignment Layers Doped with Carbon Nanotubes

林代億(TAI-YI LIN)

指導教授 ： 李偉 ； 何淳雪

中原大學/理學院/應用物理研究所/碩士(2008年)

https://doi.org/10.6840/cycu200900589

摘要

本研究旨在探討添加多壁奈米碳管於配向膜之液晶顯示元件的離子電荷傳輸行為；藉由直流階梯型驅動電壓，使液晶盒內部離子在配向層堆積形成場屏蔽現象，觀察在此情況下液晶分子轉動所牽引之暫態電流，進而分析離子電荷的運動是否受配向膜中碳奈米管之添加的影響；研究中並改變液晶盒樣品厚度與溫度，記錄並比較在不同條件下的液晶盒樣品的暫態電流。
實驗結果顯示，就薄膜電晶體液晶顯示器常用的配向膜而言，當碳奈米管之添加達一定濃度時，能有效抑制離子場屏蔽現象；此外因厚度的改變液晶分子感受到的有效電場也不同，造成峰值時間與峰值電流也有所差異；而樣品溫度的增加則使液晶盒內離子運動更為明顯，造成導電電流的提升。

關鍵字

液晶盒 ； 奈米碳管

並列摘要

The purpose of this thesis is to explore the ion transport behavior in a liquid-crystal display device consisting of alignment layers doped with mutiwalled carbon nanotubes. Switching on an applied dc step voltage leads to the accumulation of positive and negative ions at both interfaces between the alignment layers and the liquid-crystal layer, which, in turn, generates the field-screening phenomenon. Observation of the transient current in the cell, induced by the reorientation of the liquid-crystal director, allows one to examine whether the movement of ion charges is dictated by the addition of carbon nanotubes into the aligning layers. Furthermore, comparisons of the transient-current behavior are made for various experimental conditions by varying the cell gap and temperature.
Experiment results indicate that, with a specific amount of the nanotube additive, the field-screen effect can be suppressed in a cell containing a typical aligning material commonly adopted in the present thin-film-transistor–liquid-crystal-display technology. Additionally, the peak current and peak time become weaker and longer, respectively, as the cell gap of the liquid-crystal device increases. Besides, the conduction current rises with increasing temperature in that the ions become more energetic at elevated temperatures.

並列關鍵字

Carbon Nanotubes

參考文獻

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

H.-Y. Chen and W. Lee, “Suppression of field screening in nematic liquid crystals by carbon nanotubes,” Applied Physics Letters 88(22), 222105 (2006).

W. Lee and H.-Y. Chen, “Observation of transient current in a nanotube-doped liquid-crystal cell induced by polarity-reversed field,” Japanese Journal of Applied 46(5A), 2962−2967 (2007).

T.-Y. Tsai, Y.-P. Huang, H.-Y. Chen, W. Lee, Y.-M. Chang, and W.-K. Chin, “Electro-optical properties of a twisted nematic− montmorillonite-clay nanocomposite,” Nanotechnology 16(8), 1053−1057 (2005).

Y.-P. Huang, H.-Y. Chen, W. Lee, T.-Y. Tasi, and W.-K. Chin, “Transient behaviour of polarity-reversed current in a liquid- crystal−montmorillonite-clay device,” Nanotechnology 16(4), 590−594 (2005).