具有高光安定性及高扭轉摻雜體之材料合成與研究

Abstract

近年來液晶顯示器被廣泛的應用在筆電、手機、電視和許多可攜式裝置中，因此液晶螢幕的可靠度、穩定性及性能都是首要被關注的目標。除了讓液晶螢幕有上述要求我們也希望液晶螢幕有更長的使用壽命及更好的品質，所以讓液晶材料擁有抗紫外光的功能就顯得相當重要。 在第二章中，我們比較自行合成抗紫外光 (UV- resistant) 參雜體 (dopant) 3HBBTfV 和市售型抗紫外光參雜體 3HBEBTf 分別混進市售型 (commercial) 液晶中，發現在照射紫外光後不論在電壓保持率 (voltage holding ratio) 和穿透度對電壓 (voltage-transmission) 等各項液晶光電特性， 3HBBTfV 的表現都比 3HBEBTf 來的優異。 在第三章中，我們比較了自行合成的一系列負介電異方向性 (negative dielectric anisotropy) 抗紫外光參雜體 4BB(FF)BVTf, 2OB(F)B(FF)BVTf 和 2OB(FF)B(FF)BVTf. 這一系列的負介電異方向性抗紫外光參雜體皆擁有液晶相。將這三支負介電異方向性抗紫外光參雜體分別混進市售型液晶中在雙折射性 (birefringence) 及介電異方向性 (dielectric anisotropy) 都有不錯的表現，此外在照射UV光後也有優異的電壓保持率。 在第四章中，我們比較了自行合成的旋光參雜體 DBN 和兩支市售型旋光參雜體S-1011及R-1011 分別混進市售型主動式液晶中，參雜旋光體 DBN的液晶在介電異方向性 (dielectric anisotropy)、電壓保持率和對比 (contrast ratio) 等各項液晶光電特性都比S-1011及R-1011突出。 在第五章中，我們合成了兩隻高螺旋扭曲力 (helical twisting power) 的旋光參雜體 Bi2F1BC8 及 Bi2BC1 和市售型旋光參雜體S-1011分別混進市售型主動式液晶中，參雜旋光體 Bi2F1BC8 的液晶在介電異方向性 (dielectric anisotropy)、電壓保持率、對比 (contrast ratio) 和應答時間 (response time)都比Bi2BC1 及 S-1011 優秀。

Recently, liquid crystal displays (LCDs) are very important and indispensable to modern life owing to their various applications, such as notebooks, monitors, mobile phones, televisions, and portable devices. To achieve the reliable request of liquid crystals (LCs) for display applications, the primary concern of stability for LC materials is as important as their performance. In order to satisfy the requirements of long operational life time and high image quality for the commercial specifications of LCDs, LC materials possessing ultraviolet (UV) resistance also play an important role to reach the long term reliability of the displays. In Chapter 2, a highly ultraviolet (UV)-resistant dopant 3HBBTfV was synthesized and mixed with a commercial LC host (A) to promote its dielectric anisotropy in LC mixture C. Their electric-optical properties were studied and compared with those of an analogous commercial LC mixture B composed of LC mixture A (as a commercial host) mixed a commercial component 3HBEBTf. The electro-optical properties of voltage holding ratio (VHR) values and voltage-transmission (V-T) curves of LC mixture C were sustained after the UV irradiation. These results showed that dopant 3HBBTfV (acting as an UV stabilizer) demonstrated a higher stability under UV exposure in contrast to commercial component 3HBEBTf. In Chapter 3, a series of novel ultraviolet (UV)-resistant dopants 4BB(FF)BVTf, 2OB(F)B(FF)BVTf, and 2OB(FF)B(FF)BVTf were designed and synthesized. All of these UV-resistant dopants possessed negative dielectric anisotropy and mesophase. Compared with LC mixture A (without any UV-resistant dopant), all of these LC mixtures B, C, and D (containing UV-resistant dopant) exhibited good UV resistance, high birefringence Δn, and excellent electro-optical properties. These results showed that UV-resistant dopants 4BB(FF)BVTf, 2OB(F)B(FF)BVTf, and 2OB(FF)B(FF)BVTf (acting as an UV stabilizer) demonstrated a higher stability under UV exposure. In Chapter 4, an excellent voltage holding ratio (VHR) chiral dopant DBN was synthesized and mixed with an active matrix LC host (AM-LC host) to promote its electric-optical properties. Their electric-optical properties (i.e., VHR, dielectric anisotropy and contrast ratio) were studied and compared with analogous commercial chiral dopant S-1011 and R-1011. The results showed that the AM-LC host mixed with chiral dopant DBN which demonstrated a higher VHR, dielectric anisotropy and better contrast ratio than commercial chiral dopant S-1011 and R-1011. In Chapter 5, two novel chiral dopants Bi2F2BC8 and Bi2BC1 has been synthesized and mixed with an active matrix LC host (AM-LC host) to study its electric-optical properties. Their electric-optical properties (i.e., VHR, dielectric anisotropy and contrast ratio) were studied and compared with analogous commercial chiral dopant S-1011. The AM-LC host mixed with chiral dopant Bi2F2BC8 which possessed a higher VHR, dielectric anisotropy and better contrast ratio than Bi2BC1 and commercial chiral dopant S-1011.