快速反應液晶模式應用於反射式顯示技術之研究

Abstract

近年來，投影顯示的市場需求急驟增加，反射式單晶矽液晶(LCOS)投影顯示擁有高解析度以及輕薄短小的外型，成為投影顯示技術的主要技術之一。然而LCOS在液晶顯示元件的使用上依然存在著一些問題，例如在動態畫面下的殘影以及影像模糊，造成此現象主要原因為液晶反應速度不夠快。快速液晶應用於反射式顯示技術不只可以解決殘影以及影像模糊問題，未來搭配場色序法的光源驅動，使投影顯示出的畫面有更佳的色彩飽和度，以及提高背光源的使用效率，勢必成為未來的主流技術。 在本論文中，研究三種不同的液晶模式應用於反射式技術：扭轉向列型液晶模式、光學補償彎曲液晶模式、表面穩定鐵電式液晶模式。反射式扭轉向列型液晶模式為利用低黏滯係數液晶材料並壓低液晶盒間隙厚度使其快速反應，並尋找到扭轉角度、液晶材料Δn與反射率的最佳參數。反射式光學補償彎曲液晶模式則為利用液晶分子在彎曲態對稱的排列特性，使用混合配向液晶盒結構使光經由反射之後之路程如同光學補償彎曲液晶模式彎曲態，克服傳統OCB模式轉態時間以及驅動電壓的問題。反射式表面穩定鐵電式液晶模式使用配向層表面極性非對稱之方法，克服其水平山形袖章缺陷排列並探討反射率與液晶盒厚度關係。 此論文研究將三種液晶模式成功應用於反射式元件並且找到最佳的製程參數使其達到反應時間皆小於3 ms之快速反應，並實做表面穩定鐵電式液晶模式之LCOS元件。

Recently, the needs for liquid-crystal-on-silicon (LCOS) have been dramatically increased by the expansion of the projection display market. LCOS has the advantages of high resolution, light weight, and slim size. However, the motion blur issue, resulting from slow LC response, limits its potential for high quality display application. Fast switching LC modes were studied to solve the motion blur issue. With fast LC response less than 3 ms, the field sequential color (FSC) technique could be applied to improve the color gamut, and reduce power consumption. In this thesis, three kinds of fast switching LC modes: twisted nematic (TN), optically compensated bend (OCB) and surface stabilized ferroelectric liquid crystal (SSFLC) were studied in the reflective display technology. In reflective TN mode, low rotational viscosity LC material was utilized, and the cell gap was reduced to reduce LC response time.The parameters, such as, twisted angle, optical anisotropy, and reflectance were optimized in this research. Hybrid aligned nematic (HAN) cell was applied to solve the pre-transition time and critical operating voltage issues in the reflective OCB mode. The horizontal chevron defect issue of half-V mode FLC device was suppressed by the asymmetrical surface polarity controlled hybrid alignment technique. The reflectance of the FLC device was optimized by cell gap. The study solved the problems such as pre-transition time and alignment defect and discovered the best parameters of fabrication that it has fast response time less than 3 ms. Finally, LCOS device was fabricated in the use of SSFLC mode.