| 摘要: | 隨著科技快速的發展，從液晶電視到現在隨處可見的平板及手機，可以突顯液晶科技對於現在人類生活的重要性，此外，隨著現代社會越來越重視能源浪費的問題，故雙穩態液晶光電元件的研究便受到相當的重視。
本論文將討論多穩態散射型液晶光閥的技術，並區分為以下兩研究主題，第一個研究主題為負型向列型液晶摻雜手性分子及離子液晶並研究其光電特性，根據實驗結果，可利用外加高(低)頻率交流電場於此液晶元件上可獲得穿透(散射)態，並於外加電場關閉後，仍可維持永久的穿透態及散射態，該研究主題將探討其(1)切換機制、(2)光電特性及(3)其生成穩態的原因。且當關閉外加電場後除其穿透度可持續穩定外，該液晶光閥的散射能力與入射光的偏振方向無關，而其穿透態有良好的觀測視角，因此本論文所提出之散射型液晶光閥具有可電控、永久穩態及高對比等特性，相信於實際應用上有相當大的潛力。第二個研究主題為摻雜二色性染料之手紋態雙頻膽固醇液晶特性研究，從實驗結果可得知，利用外加電場頻率的高低可讓該液晶光閥於吸收態、散射吸收態及穿透態間作切換，於該研究主題中，將會探討其(1)各液晶態間的切換機制、(2)光電特性及(3)與White-Taylor液晶盒的差異。其主要機制為利用外加低頻電場使該液晶元件從吸收態切換至散射吸收態或穿透態後，再外加高頻電場，使其回到吸收態，並且在與White-Taylor液晶盒的比較中可得知，該液晶元件具有較低的操作電壓及較快的反應時間，因此相信該液晶元件能應用於切換擴增實境(AR)與虛擬實境(VR)且便於攜帶的裝置上。
;Due to the rapid development of technology, it is undoubtedly that the liquid crystal (LC) technology plays an important role in human life. Lots of LC displays, such as laptops, smart phones, televisions, and others, appear around our daily lives. Besides, people pay much attention to the international issue of the waste of energy, the studies of bistable LC electro-optical devices become more and more important.
The contents of the thesis include two key topics about multi-stable scattering mode LC light modulators. The first topic is the studies of electro-optical characteristics of ionic LC-doped cholesteric LCs. According to the experimental results, the stable states of transparent and scattering states of the reported LC devices can be electrically switched between each other by applying electric fields with different frequencies. Moreover, these two states are stable states after the applied external field is switched off. Considering this topic, the following three parts, including (1) the switching mechanism, (2) the electro-optical properties, and (3) the causes for obtaining bistabilities, will be discussed in detail. In addition to the permanent stabilization after the applied field is turned off, the reported LC light shutter possesses polarization-independent scattering and good viewing angle. Consequently, this study presents a scattering mode LC light shutter with the advantage of electrical switching, permanent stabilization and high contract ratio. It is definitely believed that such a LC device can be applied to fabricating practical applications of LC devices. In the second part, the studies of the fingerprint textures of dual frequency cholesteric LC doped with dichroic dye are reported. According to the experimental results, the reported light shutter can be electrically switchable between absorption, scattering-absorption and transparent types by applying electric fields with different frequencies. Here, the discussions of the following three parts of (1) the switching mechanism, (2) the electro-optical properties and (3) the comparison with White-Taylor cell, will be given. The main mechanisms of the electrically switchable LC light shutters to both scattering and absorption types by applying an electric field with low frequency, and back to absorption type by applying an electric field with high frequency are reported. Moreover, comparing with the well-known White-Taylor cell, such a reported light shutter has some advantages of the lower operating voltage and shorter response time. Hence, it is believed that the LC light shutter can be applied to be the device for switching between augmented reality (AR) and virtual reality (VR) of easy-carry devices. |
