非對稱散射式液晶波導元件及其應用;Waveguide liquid crystal devices with asymmetrical light scattering property and their applications

Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/86044

Title:	非對稱散射式液晶波導元件及其應用;Waveguide liquid crystal devices with asymmetrical light scattering property and their applications
Authors:	王聖文;Wang, Sheng-Wen
Contributors:	光電科學與工程學系
Keywords:	液晶光電;非對稱;散射式;智慧窗戶;液晶波導;隱私保護裝置;Waveguide;liquid crystal;asymmetrical light scattering;one-way shield
Date:	2021-09-01
Issue Date:	2021-12-07 11:56:34 (UTC+8)
Publisher:	國立中央大學
Abstract:	本論文的研究主題為非對稱散射式液晶波導元件及其應用，主要探討側向光源入射以下三種元件後的非對稱散射光學特性，元件架構分別為(i)聚合物網絡液晶搭配低折射率氟化鎂(MgF2)薄膜、(ii)聚合物網絡液晶搭配膽固醇液晶聚合物以及(iii)混成扭轉型聚合物網絡液晶搭配線偏振片。論文中將說明各項元件架構的原理及性能特性，以下分別簡述之。第一部分探討側向光源入射鍍有低折射率氟化鎂(MgF2)薄膜的聚合物網絡液晶盒，利用水平配向聚合物網絡型液晶盒，並在液晶盒其中一基板蒸鍍低折射率氟化鎂(MgF2)薄膜，其中主要透過液晶波導特性以及全反射的理論，當中利用側向入射光束於上(下)基板可達成的全反射條件次數不同，以完成在散射態保有非對稱散射光學之特性。第二部分的研究是探討側向光源入射聚合物網絡液晶搭配膽固醇液晶聚合物，利用水平配向聚合物網絡型液晶盒，並在液晶盒一側架設膽固醇液晶聚合物用，藉由膽固醇液晶聚合物可反射特定波長與特定旋性之入射光特性達成於特定波段內之側向入射光有顯著的非對稱散射光學之特性，故此部分針對單一波長之入射光有較高的非對稱散射光學之特性。第三部分則探討混成扭轉型聚合物網絡液晶對不同偏振態的散射特性，由於該混成扭轉型聚合物網絡液晶上下基板的配向處理不同，兩側基板的出射光偏振程度具有相當程度上的差異，故可利用於觀測側設置一線偏振片用以提高自該液晶元件兩側觀測時的對比度差異，並實現非對稱散射光學之特性。以上三種元件架構之配置皆可達成非對稱散射式液晶波導元件，論文中亦提出於透明單向光源、具備隱私保護之液晶智慧玻璃、液晶顯示元件之液晶波導的應用，目前仍有許多性能上的挑戰需進行最佳化。 ;The main topic reported in this study is waveguide liquid crystal (LC) devices with asymmetrical light scattering property and their applications. The key points we discuss herein include the asymmetrical light scattering optical characteristics when an edge light source is coupled into the proposed three different LC devices applied with suitable electric fields, and then scattered out of the LC devices. They are (i) polymer network LC (PNLC) cell coated with a low refractive index thin film (MgF2), (ii) PNLC cell with cholesteric LC polymer (CLCP) layers, and (iii) twisted hybrid aligned PNLC (TH-PNLC) cell with a linear polarizer. We are going to explain the principle and the functional characteristics of the structures of each LC device. First of all, we discuss the properties of a homogeneous aligned PNLC (HA PNLC) cell whose one substrate is coated with a thin film having low refractive index. Such a low refractive index magnesium fluoride (MgF2) film is deposited on the top of the indium-tin-oxide film of one of the substrates of the LC cell by evaporation method. The main mechanisms adopted here are the properties of LC waveguide and total internal reflection (TIR). Based on the different times of TIR of the incident light source, occurred on the boundaries of different films, the asymmetrical output light in its scattering state can be obtained. The second part is the asymmetrical light scattering properties demonstrated by the proposed HA PNLC cell with a CLCP layer. Due to the limitation of the CLCP layer, the edge light source selected herein is a He-Ne laser with its wavelength of 632.8 nm, which is within the reflection band of the used CLCP layer. Briefly, the powers of light scattered out of the LC device from the sides with and without the CLCP layer are different, indicating that the asymmetrical light scattering property can also be realized. The last part of the research about asymmetrical light scattering property is based on the proposed TH-PNLC cell with a linear polarizer. The surface treatments of the two substrates of the TH-PNLC cell are different, one is iv homogeneous alignment, and the other one is homeotropic alignment. Moreover, the twisted and hybrid aligned PNLC structures provide light scattering with different degrees of polarization from two sides of TH-PNLC cell applied with suitable electric fields. Therefore, we can realize asymmetrical light scattering property with one polarizer stuck on the side of the TH-PNLC cell treated with a homeotropic alignment layer. Finally, the three LC devices mentioned above can be applied to various practical applications in daily life. In this thesis, the applications of the proposed waveguide LC devices, including electrically switchable one-way transparent light sources, switchable LC privacy smart windows, and LCDs with privacy protection, have also been demonstrated. However, lots of challenges, such as contrast, operation voltage, uniformity, etc., still need to be overcome
Appears in Collections:	[Graduate Institute of Optics and Photonics] Electronic Thesis & Dissertation

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