本研究主要內容為藉由改良液晶光閥(Liquid crystal light shutter)之材料組成，改善現今高耗能之傳統液晶光閥，形成節能液晶光閥，並探討其光電性質。研究分為兩大實驗系統。首先，利用摻混低濃度之強誘電性奈米粉體-鈦酸鋇(Ferroelectric nanoparticles-Barium titanate, NPs-BaTiO3)，降低液晶光閥之驅動電壓，進而改善了傳統液晶光閥之電耗能；更進一步，利用膽固醇液晶/紫外光硬化單體的最適化條件，研發出雙穩態液晶光閥，成功解決傳統液晶光閥之高耗能缺點。
本研究第一部分之內容聚焦於藉由摻混NPs-BaTiO3改善強誘電性液晶(Ferroelectric liquid crystal, FLC)與向列型液晶(Nematic liquid crystal, NLC)兩種液晶材料，及其各自衍生之液晶光閥之光電性質。經適當濕式研磨而得之NPs-BaTiO3均勻分散至強誘電性液晶及向列型液晶中，填充入平行配向之液晶試片中，前者形成表面穩定強誘電性液晶光閥(Surface stabilized ferroelectric liquid crystal light shutter, SSFLC light shutter)，後者形成電控雙折射模式模式(Electrically controlled birefringence mode, ECB mode)，並進一步加入紫外光硬化預聚物，填充入未經配向處理之液晶試片，形成強誘電性奈米粉體、液晶、高分子三成分之高分子分散液晶光閥(Polymer dispersed liquid crystal light shutter, PDLC light shutter)。藉由於液晶中導入具有強大偶極矩之NPs-BaTiO3, 增進液晶之物理性質[液晶相表現、介電性質、自發極化值]及液晶光閥之光電表現[電壓-穿透度特性、反應時間]。另外就PDLC光閥而言, 相分離過程中部分的NPs-BaTiO3包覆於高分子基材中，進而改變高分子基材之折射率，降低偏軸霧效應。
本研究第二部分之內容聚焦於修改兩種傳統高分子穩定膽固醇液晶光閥(Polymer stabilized cholesteric texture light shutter, PSCT light shutter)。針對反向模式PSCT光閥，我們探討不同紫外光照射強度及紫外光硬化壓克力單體濃度，對Reverse mode PSCT之網狀高分子，因施加垂直試片基板方向之高電壓脈衝後，所產生的扭曲現象之影響。利用較高之紫外光照射強度及較低單體濃度，所形成適當的網狀高分子型態，發生扭曲後可穩定散射態焦錐扇紋理，而經回溫處理後可回復至透明態平面紋理，構成電場-熱能可切換雙穩態反向模式高分子穩定膽固醇液晶紋理光閥(Electro-thermal switchable bistable reverse mode PSCT light shutter, reverse mode ETSB-PSCT light shutter)，其具有散射態-透明態之灰階效果及無需電場施加即可維持散射態與透明態兩個光學狀態，成為具節能且隔熱優點之智慧窗。針對正向模式PSCT光閥，我們藉由提高紫外光硬化壓克力單體濃度，增加傳統正向模式PSCT 之遲滯現象，製成電場-熱能可切換雙穩態正向模式PSCT光閥(Electro-thermal switchable bistable normal mode PSCT light shutter, normal mode ETSB-PSCT light shutter)，我們亦製備不同旋光濃度之normal mode ETSB-PSCT光閥，隨著旋光濃度增加, 此雙穩態光閥之透明態與散射態之對比度上升，且轉變至散射態之回溫處理所需溫度較低，成功節省切換時所需之熱能。最後，有鑑於ETSB-PSCT之研究成果，我們發現液晶與單體之濃度於特定組成比例下所製成的normal mode ETSB-PSCT光閥，於不同的電壓驅動下，在零電場時擁有多個穩定之光學狀態，成功開發出更具節能優點及應用性之電場可切換多穩態正向模式高分子穩定膽固醇液晶紋理光閥(Electrically switchable multistable normal mode polymer stabilized cholesteric texture light shutter, normal mode ESM-PSCT)。

In this study, we aim to increase the efficiency of conventionally energy intensive liquid crystal (LC) light shutters by integrating material composition and investigating the electro-optical properties. The study was divided into two experimental systems. First, low concentrations ferroelectric nanoparticles-Barium titanate (NPs-BaTiO3) was doped in order to reduce the driving voltage of a conventional LC light shutter, hence improving its power consumption. Secondly, the optimal production conditions of the LC/monomer were adopted to achieve bistable without applying an electric field. These two effects should allow for a more efficient LC light shutter.
The first part of this study focuses on the improvement of ferroelectric liquid crystals (FLC) and nematic liquid crystals (NLC), by doping with NPs-BaTiO3, and the electro-optical properties of the derived LC light shutters, respectively. The ferroelectric nanoparticles were well dispersed in the FLC and NLC using appropriate wet grindings. By filling into the homogeneous cells, the former became a surface stabilized ferroelectric liquid crystal (SSFLC) light shutter and the latter formed an electrically controlled birefringence (ECB) mode. Subsequently, the addition of a UV-curable prepolymer to fill the untreated substrate of the cell resulted in the polymer dispersed liquid crystal (PDLC) light shutter consisting of NLC, NPs-BaTiO3 and polymer. We introduced NPs-BaTiO3 with a large permanent electric dipole moment into the LC in order to enhance the physical properties and the electro-optical performance. Moreover, in the case of the PDLC light shutter, the part of the NPs-BaTiO3 coated by the polymer can modify the refractive index of the polymer during phase separation; this can be harnessed to increase the viewing angles of the on-field state and reduce the off-axis haze effect.

The second part of this study focuses on the modification of the two conventional polymer stabilized cholesteric texture (PSCT) light shutters. For the reverse mode PSCT light shutter, we studied the effects of different UV curing intensities and monomer concentrations on the distortion of the polymer network of reverse mode PSCT after the application of a high voltage pulse perpendicular to the cell substrate. With the use of a higher UV curing intensity and a lower monomer concentration, we created an optimized polymer network that could stabilize the scattering focal conic texture after distortion, and revert to the transparent planar texture via the annealing treatment, thereby giving rise to an electro-thermal switchable bistable reverse mode PSCT light shutter (Reverse mode ETSB-PSCT light shutter). This exhibited excellent gray scale performance, and the ability to maintain the transparent and scattering states without the need of an applied electric field, and thereby holds tremendous promise for use in energy efficient and thermally insulating switchable windows. For the normal mode light shutter, we utilized higher concentrations of monomers to enhance hysteresis of conventional normal mode PSCT, fabricating an ETSB-PSCT light shutter. We have also fabricated normal mode ETSB-PSCT light shutters with various chiral dopant concentrations and the effects of the chiral dopant concentrations on the morphology of polymer network and electro-optical performance were studied. As the chiral dopant concentrations increased, electro-optical experiments indicated that the contrast ratio of the transparent and scattering states of the ETSB-PSCT increased and the required annealing temperature for reverting to the scattering FC state decreased. This indicates a successful reducing in the required heat during energy conversion. Finally, considering these research results of normal mode ETSB-PSCT light shutter, we found that the prepared PSCT under a specific LC/monomer ratio and different driving voltage possess multistable optical states with no applied electric field. This can be considered to be the successful development of an energy efficient electrically switchable multistable normal mode polymer stabilized cholesteric texture light shutter (Normal mode ESM-PSCT light shutter).

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