臺灣博碩士論文加值系統

本論文分別利用膽固醇液晶搭配四分之一波板與線偏振片、扭轉向列型液晶摻雜二色性染料以及扭轉向列型液晶摻雜二色性染料之光柵探討非對稱光學特性。
在膽固醇液晶搭配四分之一波板及線偏振片的實驗中，利用光通過線偏振片與四分之一波板產生可被平面態膽固醇液晶盒反射之旋性偏振光的特性達成非對稱光學特性。由於平面態膽固醇液晶的反射頻譜與入射角有關，因此以1D-DIMOS模擬並分析此液晶裝置之視角限制，此外，也分別討論液晶盒厚度以及外加電場於液晶盒對於此液晶裝置的影響。
在摻雜二色性染料的扭轉向列型液晶中，利用扭轉向列型液晶盒之摩擦配向方向相互垂直以及二色性染料的偏振選擇性吸收特性，達成此液晶盒對於線偏振光的非對稱吸收的特性，實驗中測量液晶盒之線偏振旋轉以及偏振選擇性吸收之特性，證實此液晶盒具有非對稱光學特性，並以MATLAB模擬實驗架設作圖與測量結果相互比對。另外，將此液晶結構應用於利用偶氮染料光配向製成的液晶光柵，藉由量測以及MATLAB模擬分析液晶光柵之線偏振旋轉特性，證實當線偏振光入射於照光面與非照光面時，因二色性染料的線偏振光選擇性吸收特性造成的非對稱繞射現象，另分析與討論此液晶盒外加電場產生繞射現象的改變。

In this thesis, we report the asymmetrical optical properties of the three liquid crystal (LC) devices, including (i) cholesteric LC coupled with a quarter-wave plate and a linear polarizer, (ii) dichroic dye-doped 90° twisted nematic LC (DDd-90° TNLC), and (iii) dye-doped TNLC gratings.
In the first part, the incident light passes through the linear polarizer and the quarter-wave plate to form a circularly polarized light which can be reflected by the planar textures of the cholesteric LC (CLC) plate, so the asymmetrical optical property can be achieved. Moreover, the reflection bandwidth and wavelength of the CLC plate is dependent on the angle of propagation direction of the incident light, so the 1D-DIMOS software was also adopted to simulate the limitation of visual angle of this LC device.
In the second part, owing to the rubbing direction of the two glass substrates are perpendicular to each other and the dichroic dyes possess the polarization selective light absorption, the DDd-90° TNLC device has the asymmetrical light absorption property. By measuring the polarization rotation and the polarization selective light absorption, the asymmetrical optical properties of the DDd-90° TNLC are completely demonstrated and analyzed, and the experimental results do agree well with the theoretical analyses. Furthermore, in the final part, we extend such an interesting structure to the dye-doped TNLC grating fabricated through the photoalignment process. According to the experimental results and the theoretical simulation about the polarization rotation properties of the dye-doped TNLC gratings, we demonstrate that the same linearly polarized light (0˚ or 90˚) incident onto the illuminated and the unilluminated surfaces presents the asymmetric diffraction property. Moreover, the diffraction efficiency based on the dichroic dye absorption and phase difference between the two kinds of LC structures of the dye-doped TNLC grating can be tuned electrically.

摘要 i
Abstract ii
誌謝 iv
目錄 v
表目錄 viii
圖目錄 ix
符號說明 xiii
第一章 緒論 1
§ 1-1 研究背景 1
§ 1-2 研究動機 1
§ 1-3 文獻回顧 2
1-3-1 液晶非對稱光學特性 2
1-3-2 向列型液晶摻雜偶氮染料之光配向研究 2
§ 1-4 論文架構 3
第二章 液晶簡介 5
§ 2-1 何謂液晶 5
§ 2-2 液晶分類 5
§ 2-3 液晶特性 9
2-3-1 液晶的光學異向性(Optical anisotropy) 9
2-3-2 液晶的介電異向性(Dielectric anisotropy, ∆ε) 13
2-3-3 液晶與溫度的關係 14
2-3-4 連續彈性體理論[15] 15
第三章 實驗相關理論 17
§ 3-1 膽固醇液晶特性 17
3-1-1膽固醇液晶之結構 17
3-1-3影響膽固醇液晶螺距之因素 21
§ 3-2 扭轉向列型液晶(Twisted nematic liquid crystal, TNLC)特性 22
3-2-1扭轉向列型液晶之結構 23
3-2-2扭轉向列型液晶之運作原理 23
§ 3-3 二色性染料(dichroic dyes) 28
§ 3-4 賓主效應(Guest-Host effect) 29
§ 3-5 線偏振度(degree of linear polarization, DoLP) 29
§ 3-6 光配向理論(Photoalignment) 30
3-6-1正力矩效應：Janossy Model[26] 30
3-6-2負力矩效應：Gibbons Model[22] 31
3-6-3光激發之同素異構化反應(Photoisomerization)[23] 32
3-6-4吸附引致液晶轉向之效應(Adsorption Effect)[24] 33
§ 3-7 光柵相關理論 34
3-7-1光柵種類 34
3-7-2 TN-grating的瓊斯矩陣運算[28][29] 35
第四章 實驗方法與過程 38
§ 4-1 材料介紹 38
§ 4-2 液晶盒製作 42
4-2-1玻璃基板準備 42
4-2-2液晶樣品配置 42
4-2-3液晶空盒製作 43
4-2-4液晶材料注入 43
§ 4-3 實驗方法與光路架設 44
4-3-1液晶空盒間隙測量 44
4-3-2液晶樣品光電特性之研究 45
4-3-3液晶樣品線偏振旋轉量測 46
4-3-4液晶樣品偏振選擇性吸收量測 47
4-3-5 液晶樣品穿透頻譜量測 48
4-3-6 偏光顯微鏡觀察液晶樣品 48
4-3-7製作TN光柵之實驗架設 48
第五章 實驗結果與討論 50
§ 5-1 膽固醇液晶之非對稱光學特性研究 50
5-1-1 膽固醇液晶搭配四分之一波板及線偏振片之非對稱光學特性 51
5-1-2 液晶盒厚度與觀測視角對膽固醇液晶非對稱光學特性的影響 57
§ 5-2扭轉向列型液晶摻雜二色性染料之非對稱光學研究 60
5-2-1 摻雜染料之扭轉向列型液晶的非對稱光學特性 60
5-2-2 摻雜染料之扭轉向列型液晶的非對稱光學特性理論分析 62
§ 5-3 摻雜二色性染料的扭轉向列型液晶光柵之非對稱光學研究 65
5-3-1 摻雜偶氮染料的扭轉向列型液晶光柵 65
5-3-2 摻雜二色性染料之扭轉向列型液晶光柵的非對稱光學特性 67
第六章 結論與未來展望 76
§ 6-1 結論 76
§ 6-2 未來展望 77
參考文獻 79

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