| 摘要: | 本論文主要分為三個部份，第一部份為探討向列型液晶摻雜二色性染料之特性，研究中為找出二色性染料摻雜於向列型液晶中之穿透度最大可調動態範圍，分別將不同濃度之黑色二色性染料(S428)摻雜於正型向列型液晶(E7)中，並注入於不同厚度及不同配向處理之液晶盒中，如水平配向液晶盒(Homogeneous alignment LC cell)、90°扭轉向列型液晶盒(90°-Twisted Nematic LC cell)及混成配向液晶盒(Hybrid alignment LC cell)，並根據其電壓-穿透曲線比較液晶分子排列、液晶層厚度及染料摻雜濃度間對於穿透度變化之影響，且依實驗數據與1D-DIMOS模擬結果比較，並找出該黑色二色性染料於高穿透(低吸收)及高吸收(低穿透)下之吸收係數，亦即A_∥及A_⊥，並將透過與1D-DIMOS與實驗結果所擬合而得之吸收係數與官方提供之Dichroic Ratio (DR)數值相互比較。最後取兩液晶盒正交相鄰兩基板之摩擦配向方向進行交疊，探討液晶於不同結構下之交疊方式對於穿透度可調動態範圍的影響，並與1D-DIMOS模擬結果比較。
第二部份為探討長螺距膽固醇液晶摻雜二色性染料之特性，於第一部份得知扭轉向列型液晶盒有較好之可調動態範圍，故將調整液晶於液晶盒中之旋轉角度，以手性分子(S811)及黑色二色性染料(S428)摻雜於正型向列型液晶(E7)中，透過調整手性分子濃度，將膽固醇液晶之螺距調整為長螺距，並將液晶混合物注入於兩片經水平配向所製成之液晶空盒，為探討液晶和二色性染料之旋轉角度及液晶盒厚度對於穿透度的變化，故將旋轉角度調整為180°、360°、540°及720°，並藉由所量測之電壓-穿透曲線探討旋轉角度對於穿透度的變化量，並將透過第一部份得知的二色性染料吸收係數代入1D-DIMOS中模擬，將此結果進行比較。
第三部份為探討正型向列型液晶中摻雜多種二色性染料之特性，於第一部份及Beer-Lambert定律得知，若二色性染料DR值越大，其穿透度之可調範圍越大，故此部分將更改摻雜二色性染料種類，將多種二色性染料(AB4、AZO1及AC1)摻雜於正型向列型液晶(E7)中，並將液晶混合物注入於兩片經水平配向所製成之液晶空盒，根據其電壓-穿透曲線，探討摻雜多種二色性染料之液晶層厚度對於穿透度變化之影響，且依實驗數據與1D-DIMOS模擬數據相比較，並找出該混合多種二色性染料後之有效吸收係數，包含A_∥及A_⊥，並與第一部份黑色二色性染料與第三部份多種二色性染料之DR值相互比較。最後取兩水平配向液晶盒以正交相鄰兩基板之摩擦配向方向進行交疊，探討與此情況下之交疊方式對於穿透度的變化量，並由1D-DIMOS模擬結果與實驗結果進行比較。
;The main research topics in this thesis include the following three parts. In the first part, the characteristics of dichroic dyes-doped nematic liquid crystals (DD-NLCs) and the maximum adjustable dynamic range of transmittance of DD-NLCs are discussed in detail. To achieve the absorption state, LCs with positive dielectric anisotropy (E7) doped with various concentrations of dichroic dyes (S428) are filled into LC cells with various thicknesses and/or various structures, such as homogeneous alignment (HA), twisted nematic (TN), and hybrid alignment (HB) LC cells. Based on the influences of LC arrangement, LC layer thickness, and concentration of the doped dyes on the changes of transmittance, the absorption coefficients (A_⊥ and A_∥) are determined by experimental results and 1D-DIMOS simulation results. We found that the obtained absorption coefficients are consistent with the official absorption coefficients. Finally, to enhance the performance of adjustable dynamic range of transmittance, two LC cells with the same/different structures are tandem overlapped. It should be noted that the two DD-NLC cells with the required arrangement that the LC director close to the last layer of the first DD-NLC cell should be perpendicular to that close to the first layer of the second DD-NLC cell.
The second part in this thesis is the study of the characteristics of dichroic dyes-doped cholesteric liquid crystals (DD-CLCs) with long pitch lengths. According to the results of the first part, dyes-doped TNLC cell has the largest adjustable dynamic range of transmittance. Therefore, the effect of twisted angles of dyes-doped TNLCs will be examined here. To achieve the dyes-doped TNLCs with various twisted angles, LCs (E7) mixed with dichroic dyes (S428) and chiral dopant (S811) are filled into empty LC cells, whose substrates are coated with orthogonal homogeneous alignment films with mechanical rubbing process. For the purpose of finding the influences of twisted angle onto the changes of transmittance, we adjust the concentrations of the doped chiral dopant to fabricate LC cells with twisted angles of 180°, 360°, 540° and 720°. Finally, we compare the experimental results with the 1D-DIMOS simulation results to verify the effect of twisted angles.
The third part in this thesis is the study of the characteristics of multi-dichroic dyes-doped nematic LC. As is well known, the higher the dichroic ratio of dichroic dyes, the wider the adjustable dynamic range of transmittance. Therefore, we chose the three kinds of dichroic dyes, including AB4, AZO1 and AC1, whose dichroic ratios are 12.1, 11.8, and 13.6, respectively. Next, multi-dichroic dyes (AB4, AZO1, and AC1) -doped LCs with positive dielectric anisotropy (E7) are filled into LC cells with various thicknesses, whose substrates are coated with homogeneous alignment films with mechanical rubbing process. Based on the influences of LC arrangement, LC layer thickness, and concentration of the doped dyes on the changes of transmittance, the absorption coefficients (A_⊥ and A_∥) are determined by experimental results and 1D-DIMOS simulation results. Finally, we compare the dichroic ratio of multi-dichroic dyes to that of dichroic dyes (S428). |
