雙頻橫向螺旋膽固醇液晶之光電特性及其應用

Abstract

本論文針對雙頻膽固醇液晶，首先在不同液晶盒厚度與螺距之比值下，探討橫向螺旋結構（uniform lying helix structure; ULH）於不同的電壓以及頻率條件下之光學紋理圖以及白光光譜特性。其次詳述在初始態為ULH態的條件，施加特定電壓以及頻率下，所產生降低液晶盒樣本光穿透率之擾動效應並提出以頻率調變方式呈現線性灰階之技術。另外，本論文將說明雙頻膽固醇液晶之三穩態切換機制設計，即如何在液晶盒之紋理狀態於平面態（planar state）、焦錐態（focal conic state）以及ULH態間能夠以單純調變施加電壓之頻率做快速切換。最後以此切換機制提出實際應用於相關光電元件之可行性。

In this study, we firstly investigated optical textures and optical spectra of dual frequency cholesteric liquid crystals (DFCLC) with different thickness-to-pitch ratio (d/p) under the application of electric field with specific amplitudes and frequencies. Secondly, we explain the disturbance effect that lowers the transmission of light of the DFCLC cell with initial ULH state and propose a feasible technique for realizing linear gray-levels of the DFCLC by applying frequency-modulated voltage pluses. On the other hand, we establish a driving scheme to clarify the direct-two-way switching mechanism between the three-stable states (i.e., the planar state, dynamic focal conic state and ULH state) of the DFCLC. Finally, according to our proposed driving scheme, practical applications of this tristable DFCLC are suggested.