本論文藉由在向列型液晶裡摻雜偶氮手性材料Q1-3c-S，完成一個全光控可重複切換亮暗態的液晶顯示元件，且該顯示元件不需外加電壓即可顯示寫入之資訊。此元件以布拉格反射在紅外光波段的平面結構做為亮態，而散射態的焦錐結構做為暗態，並可藉由紫光的照射時間控制其穿透度，即此元件具有灰階顯示的能力。而該顯示元件利用光切換亮暗態的原理如下，實驗中所使用之摻雜偶氮手性材料的膽固醇液晶螺距在照射兩種不同波長的光後可被增長或縮短，如此即可藉由拉長螺距使膽固醇液晶的焦錐結構的自由能升高而轉變成平面結構。另外，利用偶氮手性材料經光引致同分異構化的分子運動擾動對平面結構的擾亂，可達成從平面結構到焦錐結構的切換。
實驗中亦發現當紫光的照射時間過長時，將會導致偶氮手性材料的cis態分子數量過多，因而降低膽固醇液晶的秩序參數，使得做為亮態的平面結構的穿透度下降，但在停止照射紫光後，樣品會因cis態分子的自發性轉換為trans態分子(dark-relaxation)的過程而逐漸回升到原來的穿透度。再者，實驗中發現藉由在此液晶顯示元件的其中一面玻璃基板上作微弱的水平配向處理，可達到延長灰階顯示的穩定時間的目的。最後本論文亦完成一個可重複寫入並抹除資訊的全光控膽固醇液晶顯示元件。

In this study, we report an all optically switchable display device based on azo chiral(Q1-3c-S)-doped nematic liquid crystal. The bright and dark states of the display device are at planar texture and focal conic texture, respectively, and can be repeatedly switched between each other. Notably, the bright state is achieved using the Bragg reflection of the planar textures is selected in infrared region. Moreover, the grayscales can also be achieved by illuminating the cell with purple light for different irradiation duration. The mechanism for switching the device between bright and dark states is described as follows. Briefly, the pitch length of the used material can be elongated and shortened by illuminating with purple and green light, respectively. When the pitch length is elongated, the free energy focal conic texture will be enhanced and the focal conic texture will be switched to planar texture. Moreover, the switching of textures from planar to focal conic can be obtained optically resulting from the disturbance of photo-isomerized azo molecules.
It is also found that if the irradiation duration with purple light is too long, resulting in too much cis-isomers of the azo chiral material, the order parameter of the cholesteric liquid crystal is reduced so that the transmittance of the planar texture decreases. Yet, after blocking off the purple light from the sample, the transmission will recovers to the initial value. The cause can be understood since the cis-isomers will transfer to trans-isomers naturally, that is dark relaxation. About the demonstration of grayscales, the surface of treatment with weak anchoring (planar alignment) onto only one substrate of the LC device can be adopted to improve the stability of grayscales. Finally, we also demonstrate an all optically switchable display device that is optically addressable, erasable and rewritable.

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