| 摘要: | 本論文的研究分為三個部份，第一部份為探討電控及光控摻雜二色性染料之吸收型液晶光閥，以負型向列型液晶(HNG30400-200)摻雜二色性染料(S428)並注入基板經摩擦配向處理與否的垂直配向膜(Vertical alignment polyimide)備製下之液晶空盒，並比較二者之切換機制、操作電壓及反應時間等。切換機制及操作電壓方面，藉由量測二者的電壓-穿透率曲線以確立二者之穿透率及吸收態並求出吸收係數α_⊥及α_∥。本論文提出一種基於Beer-Lambert定律的模型以計算基板未經摩擦配向處理的液晶盒於施加電場為5 Vrms@1 KHz之穿透率，將此模型結合其偏振選擇性吸收特性曲線以確立其液晶排列；反應時間方面，藉由量測二者之穿透率-時間曲線以確立其上升及下降時間。最後於基板經摩擦配向處理的液晶盒與光敏電阻串聯，以光控方式調整施加於液晶盒之電場以控制其灰階。
第二部份為探討電控摻雜離子材料之散射型液晶光閥，以負型向列型液晶(HNG30400-200)摻雜離子材料(SDS′)並注入基板經垂直配向膜(DMOAP)備製下之液晶空盒，並比較施加直流電場及不同頻率之交流電場之切換機制及操作電壓，於施加交流電場(1 KHz)下分析動態結構及反應時間等特性。切換機制及操作電壓方面，藉由量測施加不同頻率的電壓-穿透率曲線以確立施加直流電場及交流電場(1 KHz)之穿透及散射態；動態結構方面，本論文提出一種結合Carr-Helfrich及第一部份的模型以計算亮暗線位置與分布，藉由量測偏振選擇性散射特性曲線及加上檢偏片與否之穿透式偏光顯微鏡下之觀測圖以分析其動態結構；反應時間方面，藉由量測穿透率-時間曲線以確立其上升及下降時間。
第三部份為探討電控摻雜二色性染料及離子材料之吸收/散射型液晶光閥，以負型向列型液晶(HNG30400-200)摻雜二色性染料(S428)及離子材料(SDS′)並注入基板經垂直配向膜(DMOAP)備製下之液晶空盒，並比較施加直流電場或不同頻率交流電場之切換機制及操作電壓，於施加交流電場(1 KHz)下分析該動態結構及反應時間等特性。切換機制及操作電壓方面，藉由量測施加不同頻率的電壓-穿透率曲線以確立施加直流電場及交流電場(1 KHz)之穿透及散射態；動態結構方面，以第二部份的模型計算亮暗線位置與分布，藉由量測偏振選擇性吸收特性曲線及加上檢偏片與否之穿透式偏光顯微鏡下之觀測圖以分析其動態結構；反應時間方面，藉由量測穿透率-時間曲線以確立其上升及下降時間。;The topics in this thesis include the following two sections. In the first section, electrically and optically controllable absorption-mode liquid crystal (LC) light shutters are discussed in detail. To achieve the absorption state, dichroic dyes (S428)-doped LCs with negative dielectric anisotropy (HNG30400-200) are filled into the empty LC cell, whose substrates are coated with vertical alignment films with mechanical rubbing process or not, to demonstrate the “Rubbed vertical alignment dye-doped nematic LCs (RVA-DdNLC)” and “Vertical alignment dye-doped nematic LCs (VA-DdNLC)” light shutters. The comparisons of the switching mechanism, driving voltages, and response times of the two LC light shutters are also discussed. In the aspect of the switching mechanism and driving voltage, the transparent and absorption states of the two LC light shutters, as well as the absorption coefficients α_⊥ and α_∥ are determined by examining the transmittance versus applied voltage curves. The model of calculating the transmittance of VA-DdNLC applied with 5 Vrms@1 KHz square wave based on the Beer-Lambert law is proposed in this thesis. The alignments of LCs and dichroic dyes of VA-DdNLC are determined by connecting the model and the curve of polarization-selective absorption. In the aspect of the response time, the rise and decay times of the two LC light shutters are determined by the measurements of these transmittance versus time curves. Eventually, the proposed RVA-DdNLC light shutter is connected with the light dependent resistor (LDR) in series to control its grayscales optically.
The second section in this thesis is the study of electrically controllable scattering-mode LC light shutters. To achieve the scattering state, the same LCs in the first section doped with few ionic materials (SDS′) are filled into the empty LC cell, whose substrates are coated with vertical alignment films, to demonstrate the “Vertical alignment of ion-doped nematic LCs (VA-IdNLC)” light shutters. The comparisons of the switching mechanism and driving voltage of DC or AC square waves with different frequencies, as well as the dynamic structures and response times by applying a voltage of 1 KHz square wave onto the VA-IdNLC are discussed. In the aspect of the switching mechanism and driving voltage, the transparent and scattering states are determined by examining the transmittance versus applied voltage (DC and 1 KHz square waves) curves. Regarding the dynamic structures, the model for calculating the position (distribution) of the bright and dark stripes of VA-IdNLC applied with 31.5 Vrms@1 KHz square wave based on the combination of the Carr-Helfrich and the model in the first section is proposed. The alignment of LCs of VA-IdNLC is speculatively clarified by connecting the model, patterns observed under a polarized optical microscope with an analyzer or not, and the curves of polarization-selective scattering. In the aspect of the response time, the rise and decay times of VA-IdNLC are determined by the measurements of its transmittance versus time curves.
The third section in this thesis is the study of electrically controllable absorption-/scattering-mode LC light shutters. To achieve the absorption-/scattering state, the same LCs in the first two sections doped with dichroic dyes (S428) and few ionic materials (SDS′) are filled into the empty LC cell, whose substrates are coated with vertical alignment films, to demonstrate the “Vertical alignment of ion and dye-doped nematic LCs (VA-IDdNLC)” light shutters. The comparisons of the switching mechanism and driving voltage of DC or AC square waves with different frequencies, as well as the dynamic structures and response times by applying a voltage of 1 KHz square wave onto the VA-IDdNLC are discussed. In the aspect of the switching mechanism and driving voltage, the transparent and absorption-/scattering state are determined by examining the transmittance versus applied voltage (DC and 1 KHz square waves) curves. Regarding the dynamic structures, the model for calculating the position (distribution) of the bright and dark stripes of VA-IdNLC applied with 27.5 Vrms@1 KHz square wave based on the second section is proposed. The alignment of LCs and dichroic dyes of VA-IdNLC is speculatively clarified by connecting the model, patterns observed under a polarized optical microscope with an analyzer or not, and the curves of polarization-selective absorption-/scattering. In the aspect of the response time, the rise and decay times of VA-IDdNLC are determined by the measurements of its transmittance versus time curves. |
