透過頻率電控膽固醇液晶摻雜液晶二聚體形成之均勻橫向螺旋結構及其光學特性之研究

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姓名	陳稼橙(Jia-Cheng Chen) 查詢紙本館藏	畢業系所	光電科學與工程學系
論文名稱	透過頻率電控膽固醇液晶摻雜液晶二聚體形成之均勻橫向螺旋結構及其光學特性之研究 (Studies of uniform lying helix structures formed by frequency-controlled cholesteric liquid crystals doped with liquid crystal dimers and their optical properties)
檔案	[Endnote RIS 格式] [Bibtex 格式] [相關文章] [文章引用] [完整記錄] [館藏目錄] 至系統瀏覽論文 (2029-7-23以後開放)
摘要(中)	本論文探討了透過頻率電壓調控由摻雜液晶二聚體之膽固醇液晶所形成之均勻橫向螺旋(Uniform Lying Helix, ULH)結構的光學特性，主要目的是分析並優化這些結構在反射式電子紙顯示器中的應用，以提高顯示對比度和性能。本論文研究內容分為兩部分，第一部分探討未摻雜及摻雜液晶二聚體(CB7CB)的膽固醇液晶在不同厚度液晶盒中的特性變化，在未摻雜CB7CB的膽固醇液晶於不同厚度液晶盒的特性影響研究發現，隨著液晶盒厚度從3.22 μm增加至5.25 μm，整體穿透率降低，其電光特性也發生顯著改變，進而影響顯示效果；而摻雜CB7CB的膽固醇液晶在三種不同反射光波段(RGB)中的表現，透過適當的電壓和頻率控制，可誘導形成穿透率約為53%的焦錐態及穿透率約為82%的ULH結構，此結構在增加前向散射(Forward scattering，最佳提升約29%)方面表現出顯著的優勢，摻雜CB7CB的液晶在不同螺距下(399 nm、335 nm及267 nm)的整體穿透率和結構特性存在些微差異。第二部分則深入探討摻雜液晶二聚體對膽固醇液晶的光電特性影響，首先分析摻雜液晶二聚體後的膽固醇液晶對反應時間的影響，並對施加直流電場或低頻交流電場的反應時間進行量測。結果顯示摻雜CB7CB對比未摻雜CB7CB能有效縮短反應時間約8秒，且在適當頻率及電場下，螺距越小對反應時間縮短越顯著，最短反應時間約為一秒內。另亦透過實驗發現CB7CB對灰階顯示的效果也有些微提升，若在適當的d/p值(d/p = 12，其中d為液晶盒厚度，p為螺距)及電壓與頻率下，穿透率表現最為線性(電壓-穿透率曲線接近斜直線)，且最高穿透率(82%)與最低穿透率(53%)差異最大，灰階調控效果較佳。本論文另釐清透過摻雜離子材料(SDS)是否亦能增強動態散射效果並降低反應時間，以及摻雜不同液晶二聚體(CB11CB)觀察其對膽固醇液晶的影響。由實驗結果顯示上述方法皆無法使膽固醇液晶形成ULH結構。
摘要(英)	This thesis reports on the optical properties of uniform lying helix (ULH) structures generated by the application of electric fields with different frequencies and by doping liquid crystal (LC) dimers into cholesteric LCs (CLCs), the structure is used to enhance forward scattering (light scattering towards the photodetector) and reduce backward scattering (light scattering towards the observer), thereby enhancing display contrast. The thesis is divided into two parts, with the primary objective of analyzing and optimizing the CLC structures for applications in electronic papers of reflective mode displays to enhance contrast and performance. In the first part of the experiment, the properties of undoped and CB7CB-doped CLCs filled into LC cells with different cell gaps were studied. First, the overall transmittance decreases with the increase of cell gap, such as from 3.22 μm to 5.25 μm. The influences of the LC cell gap on the electro-optical properties of CLCs without doped LC dimers significantly affect display performance. Additionally, the performance of CB7CB-doped CLCs with three different reflective light spectra (RGB) was analyzed in detail. With appropriate voltage and frequency control, focal conic (FC) structures with a transmittance of approximately 53% and ULH structures with a transmittance of approximately 82% can be achieved. These structures demonstrated significant advantages in enhancing forward scattering (the best improvement of roughly 29%) from the CLC structures. The differences in overall transmittance and structural properties were also examined using CB7CB-doped CLC with different helical pitches, such as 399 nm,335 nm, and 267 nm). The second part of the experiment delved into the impacts of doping LC dimers on the optoelectrical properties of CLCs. First, the effect of doping LC dimers on the response time of CLCs was analyzed. The response times of LCs applied with electric fields with direct current or low-frequency alternating current were measured. The experimental results indicated that doping CB7CB effectively shortens the response time by approximately 8 seconds compared to the undoped CB7C. Moreover, at suitable frequencies and electric fields, a smaller pitch length significantly enhanced the reduction in response time, with the shortest response time being approximately within one second. Additionally, experimental findings revealed a slight enhancement in grayscale display effectiveness with CB7CB. Optimal grayscale modulation was observed under suitable d/p ratios (d/p = 12, d represents the LC cell gap, and p represents the pitch), applied voltages, and frequency conditions. The transmittance shows the highest linearity, with the greatest difference between the highest transmittance (82%) and the lowest transmittance (53%), resulting in better grayscale control (voltage-transmittance curve is close to a oblique straight line). Furthermore, the study also explored whether doping ion materials (SDS) could enhance dynamic scattering and reduce response time. The impact of another LC dimer, CB11CB, doped into CLCs was also examined. Unfortunately, the experimental results showed that the ULH structures cannot be generated using these methods.
關鍵字(中)	★ 均勻橫向螺旋結構 ★ 液晶二聚體 ★ 膽固醇液晶 ★ 頻率電控	關鍵字(英)	★ Uniform lying helix ★ Liquid crystal dimers ★ Cholesteric liquid crystals ★ Frequency-controlled
論文目次	摘要 I Abstract III 誌謝 V 目錄 VI 圖目錄 IX 表目錄 XXI 符號說明 XXII 第一章緒論 1 §1-1前言 1 §1-2研究動機 1 §1-3文獻回顧 2 §1-4論文架構 4 第二章液晶簡介 6 §2-1 液晶起源 6 §2-2 液晶分類 7 §2-2-1棒狀液晶 8 §2-3 液晶的光電特性 13 §2-3-1光學異向性(Optical Anisotropy) 14 §2-3-2介電異向性(Dielectric Anisotropy)[10] 18 §2-3-3連續彈性體理論(Elastic continuum theory) 19 §2-3-4溫度對向列型液晶的影響 20 第三章實驗相關理論 22 §3-1 反射式電子紙顯示器 22 §3-1-1電泳式顯示器(Electrophoretic Display, EPD) 22 §3-1-2電濕潤式顯示器(Electrowetting display, EWD) 23 §3-1-3膽固醇液晶顯示器(Cholesteric liquid crystal display, CLCs) 24 §3-2 膽固醇液晶結構 26 §3-3 液晶二聚體(Liquid Crystal Dimer) 29 §3-3-1彎電效應(Flexoelectric effect) [23] 30 §3-3-2介電效應(Dielectric effect) 31 §3-3-3彈性係數(Elastic constant) 32 §3-3-4電流體效應(Electrohydrodynamic effect，EHD)[32] 33 §3-4 膽固醇液晶雙穩態之灰階顯示 33 第四章實驗方法與流程 35 §4-1材料介紹 35 §4-1-1向列型液晶 5CB 35 §4-1-2手性分子 R5011 35 §4-1-3 離子材料 SDS 36 §4-1-4液晶二聚體 CB7CB 36 §4-1-5液晶二聚體 CB11CB 37 §4-1-6水平配向膜 PVA 37 §4-2液晶空盒製備 37 §4-2-1玻璃基板裁切與清洗 38 §4-2-2玻璃基板之水平表面配向 38 §4-2-3液晶空盒製作 39 §4-2-4液晶材料注入液晶盒 39 §4-3實驗架設 40 §4-3-1 液晶盒厚度量測 40 §4-3-2 穿透率-電壓-頻率曲線量測架設 41 §4-3-3 反應時間(Response Time) 43 §4-3-4 樣品觀測 44 第五章實驗結果與討論 46 §5-1 電控均勻橫向螺旋結構於摻雜液晶二聚體之膽固醇液晶 46 §5-1-1 未摻雜CB7CB之膽固醇液晶於不同厚度液晶盒之特性影響 47 §5-1-2 利用不同電壓與頻率分析摻雜CB7CB之不同螺距膽固醇液晶分子於RGB反射光波段對應之穿透率 53 §5-1-3 利用外加電場分析摻雜CB7CB之不同螺距的膽固醇液晶分子於RGB反射光波段對應之穿透率與結構特性 56 §5-2 電控摻雜液晶二聚體之膽固醇液晶之材料光電特性與影響 74 §5-2-1 摻雜液晶二聚體之膽固醇液晶對反應時間之探討 74 §5-2-2 摻雜液晶二聚體之膽固醇液晶對灰階顯示之影響 81 §5-2-3 摻雜液晶二聚體之膽固醇液晶於摻雜離子材料以分析膽固醇液晶之影響 84 §5-2-4 摻雜不同液晶二聚體(CB11CB)對於生成結構之影響 87 第六章結論與未來展望 92 §6-1結論 92 §6-1-1 電控均勻橫向螺旋結構於添加液晶二聚體之膽固醇液晶 92 §6-1-2 電控添加液晶二聚體之膽固醇液晶之材料光電特性與影響 94 §6-2未來展望 95 參考文獻 97
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指導教授	鄭恪亭孫文信(Ko-Ting Cheng)	審核日期	2024-7-31
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