本論文主要探討將二色性螢光染料(2DFL-2Tp-sEOBTA)摻雜於正型向列型液晶(E7)之中，分別注入不同厚度且摩擦配向方向正交的液晶盒之中，製作成摻雜二色性螢光染料之90°扭轉向列型液晶(dichroic florescent dye-doped 90°- twisted nematic liquid crystals，簡稱DFD-90°-TNLCs)，並分析二色性螢光染料吸收450 nm藍光後所激發出的螢光特性與偏振變化。本論文主要分為兩個部分，第一部分為探討DFD-90°-TNLCs的螢光特性，研究中藉由螢光頻譜分析材料性質，並使用不同強度的激發光照射DFD-90°-TNLCs液晶盒，分析螢光染料受不同強度的藍光激發後放出的螢光變化，最後通過將兩者的實驗結果比較，證實所用的螢光染料為單光子螢光材料。第二部分為探討DFD-90°-TNLCs液晶盒在不同厚度與電場條件下的螢光偏振變化，在無外加電場時，厚度較大的DFD-90°-TNLCs液晶盒可將螢光的偏振方向完整旋轉90°，且該螢光為線偏振；厚度較薄的DFD-90°-TNLCs液晶盒因未符合Mauguin’s condition，螢光的偏振方向會與前者有相當之差異，如該出射螢光之偏振態等。此外，施加外加電場後，液晶盒由TN結構轉變為垂直排列結構，導致偏振旋轉作用消失，且螢光強度隨著外加電場的強度增加而顯著降低，此因該螢光材料具備二色性螢光特性。本論文成功證明DFD-90°-TNLCs液晶盒具備改變螢光偏振方向與偏振態之能力，未來可進一步將此類二色性螢光染料摻雜至不同的液晶結構之中，為螢光染料與液晶的結合與應用奠定基礎。;This thesis investigates the properties of incorporation of a dichroic fluorescent dye (2DFL-2Tp-sEOBTA) into a positive-type nematic liquid crystal (E7), filled into liquid crystal cells with orthogonally rubbed alignment layers with various thicknesses. The resulting structures form dichroic fluorescent dye-doped 90°-twisted nematic liquid crystals (DFD-90°-TNLCs). The optical characteristics and polarization behavior of the fluorescence emitted by the dyes upon excitation with 450 nm blue light are systematically analyzed. The content of this work can be divided into two main parts. The first part focuses on the fluorescence properties of the DFD-90°-TNLCs. Fluorescence spectra were used to evaluate the emission characteristics of the doped dyes, and the samples were exposed to blue excitation light with various intensities, followed by observations of the corresponding changes in fluorescence output. A comparison of the experimental results confirms that the dye exhibits single-photon fluorescence behavior. The second part investigates the polarization behavior of the emitted fluorescence given by DFD-90°-TNLCs having different cell thicknesses and applied electric fields. In the absence of an electric field, thicker DFD-90°-TNLC cells are able to rotate the polarization direction of the output fluorescence by 90°, resulting in linearly polarized emission. In contrast, thinner cells that do not satisfy Mauguin’s condition have different properties of the emitted fluorescence from those given by the thicker ones. Furthermore, when an external electric field is applied, the LC structure transforms from a twisted nematic to a vertical alignment state, eliminating the polarization rotation effect and significantly reducing the fluorescence intensity as the field strength increases. In summary, this study successfully demonstrates that DFD-90°-TNLC structures possess the capability to modulate both the polarization direction and polarization state of fluorescence. The results provide a foundation for future studies in which dichroic fluorescent dyes can be incorporated into other types of LC configurations, advancing the development of tunable fluorescence and LC-based optoelectronic applications.
