不需偏光片之軟性光電開關

Abstract

利用摻雜染料之液晶凝膠技術，我們成功地開發出不需偏光片之軟性 光電開關，此技術結合了聚合物網絡的光散射作用和染料分子的光吸 收作用。本論文中，我們討論光聚合溫度(Curing temperature)、紫 外光強度、染料濃度、聚合物單體濃度及液晶盒厚度對摻雜染料之液 晶凝膠的電光特性影響。並歸納出最佳化製作條件以達到高對比度、 快速響應、低臨界電壓的光電開關。同時，考慮光散射和光吸收效應，我們也對摻雜染料之液晶凝膠作光學特性的理論分析，由計算結果和實驗結果顯示：摻雜染料之液晶凝膠的電光特性主要由聚合物網絡(polymer network)的大小決定。此外，不需偏光片之軟性光電開關具有可撓曲和可剪裁特性，撓曲時的最小曲率半徑約21mm。此摻雜染料之液晶凝膠在光聚合溫度10oC時，可達最大反射率~55%、反射式 下的對比度~450:1、反應時間~6.4ms。此不需偏光片之軟性光電開關 未來可應用於電子紙、電子標籤、裝飾性顯示器、汽車或大樓的電控 式遮陽板等。

A polarizer-free and flexible electro-optical switch using dye-doped liquid crystal (LC) gels is demonstrated. The main mechanisms are light scattering of polymer networks and light absorption of dye molecules. In this thesis, we discussed the effects of the curing temperature, the UV intensity, the dye concentration,the monomer concentration, and the cell gap. In order to achieve an electro-optical switch with a high contrast ratio, a fast response, and a low threshold voltage, the optimal parameters of the fabrication was obtained as well based on the experimental results. In addition, the optical analysis of dye-doped LC gels was executed by combing both of the anomalous diffraction model and the absorption theory. The domain size of polymer networks is the dominant factor to the electro-optical properties of the dye-doped LC gels according to both of the experimental and calculated results. Besides, such a flexible electro-optical switch is not only bendable but also trim-able. The minimal bending curvature is 21 mm. The dye-doped LC gel shows good reflectance ~55%, good contrast ratio~450:1 in reflective mode, and fast response~6.4 ms at curing temperature 10oC. The applications of dye-doped LC gels are electronic papers, electronic tags, decorative displays, and electrically switch-able sun control film for automobiles or commercial buildings.