發展具雙穩態特性之雙頻Smectic-A液晶元件

Development of Bistable Dual-Frequency Smectic-A Liquid Crystal Devices

陳昇辰(Sheng-Chen Chen)

指導教授 ： 李偉

國立交通大學/光電學院/光電科技學程/碩士(2019年)

摘要

摘　　　要
本論文旨以雙頻液晶為材料並摻雜手性分子及彎曲型液晶的方式，在不同濃度下左旋與右旋手性添加劑以及彎曲型液晶混合條件下之相轉變行為與介電特性隨溫度之變化。研究內容包含雙頻棒狀液晶（HEF-951800）各別混合左旋手性添加劑（S811）及右旋手性添加劑（R811）、雙頻棒狀液晶同時混合左右旋手性添加劑、雙頻棒狀液晶混合彎曲型液晶（CB7CB），共四種組合，分別探討隨摻雜比例濃度與與觀察其相紋理轉變行為與介電特性探討。此外在針對雙頻棒狀液晶混合左旋手性添加劑、雙頻棒狀液晶同時混合左右旋手性添加劑，共兩種組合，探討雙穩態切換機制及光電量測曲線。實驗結果顯示，吾人成功在雙頻液晶的相序中誘導出層列A相，根據雙頻液晶頻率的相依介電特性，本研究所提出的雙頻層列A 可利用調控電場頻率的方式達到水平態與垂直態的直接切換。同時在電場驅動下層狀結構的重新排列後，形成雙穩態。

關鍵字

雙頻向列液晶 ； 雙穩態 ； 雙頻層列A ； 消旋混合物 ； 層列型液晶

並列摘要

ABSTRACT
The purpose of this paper is to induce smectic-A (SmA) phase in a dual-frequency liquid crystal (DFLC) by doping with chiral molecules (S811 and R811) or bent-core LC dimers (CB7CB). There are totally four kinds of investigated mixtures―DFLC + S811, DFLC + R811, DFLC + S811 + R811, and DFLC + CB7CB. We firstly discussed the phase sequence and dielectric properties of each kind of mixtures by means of temperature-dependent dielectric spectroscopy. Our results indicated that the SmA phase can successfully be induced at near room temperature as the concentration of the additive is higher than a critical value. Furthermore, the frequency-revertible dielectric feature specific for the DFLC in the SmA phase was confirmed and the crossover frequency was increased with rising temperature following the Arrhenius law. Accordingly, unique features of cells in the SmA phase, including electrical switchability and optical bistability were revealed by measuring the change of optical transmittance of the cell under crossed polarizers as a function of voltage strength. It is ensured that the cells can directly and reversibly be switched between the planar (P) and the homeotropic (H) states by modulating the frequency of applied voltages and they can stably be preserved after the voltage is removal.

並列關鍵字

Dual-Frequency nematic ； Bistability ； Dual-Frequency Smectic-A ； Racemic mixture ； Smectic

參考文獻

參考文獻

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