利用聚合物摻雜膽固醇液晶拓寬其反射頻譜;Broadening the reflection bandwidth of cholesteric liquid crystals doped with polymers

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题名:	利用聚合物摻雜膽固醇液晶拓寬其反射頻譜;Broadening the reflection bandwidth of cholesteric liquid crystals doped with polymers
作者:	許捷翔;Hsu, Chieh-Hsiang
贡献者:	照明與顯示科技研究所
关键词:	拓寬;反射頻譜;聚合物摻雜;Broadening;reflection bandwidth;doped with polymers
日期:	2018-07-26
上传时间:	2018-08-31 14:43:56 (UTC+8)
出版者:	國立中央大學
摘要:	中文摘要本論文主要區分為兩部分的研究主題，其一為利用旋性聚合物照光聚合過程中，其所提供的螺旋力將逐漸減弱，進而使膽固醇液晶的螺距將隨之漸變，且該過程中旋性聚合物受照光聚合並形成聚合物網絡結構，該結構可穩固聚合過程漸變的螺距，進而獲得反射頻譜拓寬的結果。在此部分實驗我們發現使用適當厚度的液晶盒，右旋性聚合物單體能有效的穩固右旋性膽固醇液晶，此部分最佳拓寬後反射頻譜之波長範圍介於556 nm與813 nm之間(共約257 nm)。若以右旋性聚合物單體穩固左旋性膽固醇液，當右旋性聚合物聚合時，膽固醇液晶的螺距變化較為劇烈，導致膽固醇液晶旋性抵銷不平均，無法均勻的穩固不同旋性的螺距，故造成反射頻譜窄化的現象；本論文另一項研究重點為控溫聚合之聚合物穩固膽固醇液晶螺距，本實驗的目標是穩固部分80oC膽固醇液晶的螺距，且保有降溫至室溫時的膽固醇液晶螺距，故可利用空間上不同反射頻譜的分布拓寬該液晶合反射頻譜。此部分實驗發現，發現於厚度過大的液晶盒中，聚合完成的聚合物枝條將壓迫80oC時的膽固醇液晶螺距，使原本完整80oC時的膽固醇液晶螺距被破壞，且壓縮為更小的螺距，反射頻譜往更短波長偏移且反射率下降，但在液晶盒厚度為5 μm時，聚合物單體確實能有效穩固80oC時的膽固醇液晶螺距，但無法同時保有降溫至室溫時的膽固醇液晶螺距。;Abstract This thesis consists of two main research topics. The first part is with regard to the broadening the reflection band width of cholesteric liquid crystals (CLCs) by using the photo-polymerization of chiral polymer (LC756). The basic concept can be understood as described follows. With the illumination of UV light, the chirality of the LC mixture can be reduced due to the reduction of the amount of un-polymerized chiral polymer. Moreover, during the photo-polymerization process, the pitch length will gradually increase so that the polymerized LC756 can generate polymer network structures to stabilize the changing pitch length. It indicates that the gradient pitch, causing the broadening of the reflection spectrum, can be obtained by the polymerization process. In this part of the experiments, we found that the right-handed chiral polymer (LC756) can effectively stabilize the right-handed CLC filled into a LC cell with suitable cell gap. Experimentally, the optimized reflection band ranges between 556 and 813 nm, whose bandwidth was about 257 nm. Regarding the case of stabilization of left-handed CLCs by right-handed chiral polymer (LC756), the broadening of reflection band cannot be obtained. We infer that the CLC structure of the case of pitch increasing is much uniform than that of pitch decreasing during photo-polymerization processes. The other research topic in this thesis is the photo-polymerization process at different temperature to stabilize CLCs pitch length. Regarding the temperature dependent pitch length of CLCs, if the reflection band of CLCs at high temperature can be polymer-stabilized, the reflection band can be kept when the temperature is cooled down to room temperature. Hence, with regional photo-polymerization, the additive reflection colors in various regions can be applied to broaden the reflection band of CLCs. The cell gap, curing temperature, and material selection are the main keys to achieve such broadening reflection bands of CLCs
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