三維紅外光譜法探討液晶分子傾角

Three-dimensional infrared spectrometer study the tilt angle of liquid crystal molecules

鄭哲宇(Tse-Yu Cheng)

指導教授 ： 游信和

國立虎尾科技大學/電機資訊學院/光電與材料科技研究所/碩士(2009年)

摘要

近年來，液晶顯示器已成為廣泛使用的平面顯示器之一，其中ㄧ些關鍵參數，如液晶盒間距、預傾角，明顯地影響其光學特性。而又以量測液晶實際傾角至為關鍵。本論文主要目的在於提供一種三維紅外光譜量測裝置，直接量測向列型液晶在外加電場作用下的傾斜角度變化。我們發現，在液晶分子(E7)中5CB的氮鍵(碳氮伸縮振動C≡N)與電場有明顯的相依性，在三維紅外光譜分析中，除可直接量測未加電場時的液晶傾角，亦即預傾角外，還根據三軸紅外光譜發現，配向方向的紅外光譜吸收值在電場作用下明顯降低，而厚度方向的紅外光譜吸收值明顯提高，證明外加電場會使C≡N鍵從原來的液晶盒配向方向順著電場作用旋轉到液晶盒厚度方向。這與使用相位差量測法而得到的液晶分子傾斜角具有相同的變化趨勢。

關鍵字

向列型液晶 ； 三維紅外光譜 ； 預傾角

並列摘要

In recent years, liquid crystal displays (LCDs) have becoming one of the most widely used flat panel displays. Some critical parameters of the LCD, such as cell gap and molecule pretilt angle, are significantly affecting their optical properties. Therefore, it’s most important key point for measuring the tilt angle of LCDs. In this study, we provided a simple method, three-dimensional Fourier transform infrared spectroscopy (3-D FTIR), to measure the tilt angle of the liquid crystal molecules in a nematic liquid crystal (E7) cell as power applied. From the infrared spectra analysis, we found that the nitrile band for 5CB of NLC molecules array was strongly affected by external voltage. Moreover, the pretilt angles of the LC cells can be predicted by 3-D FTIR without voltage supplied. Infrared absorption in the LC cell thickness direction was enhanced but the peak in the rubbing direction was reduced after applied voltage rising. Furthermore, the tilt angles of the liquid crystal cell under different voltages possess same tendency for both Heterodyne Interferometric method and 3-D FTIR method predictions.

並列關鍵字

nematic liquid crystal ； 3D-FTIR ； pretilt angle

參考文獻

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