宽波反射胆甾相液晶材料研究进展

Research Progress of Cholesteric Liquid Crystals with Broad Reflection Band

具有宽波反射特性的胆甾相液晶材料因其特殊的光学性能及其在反射型显示器件、光增亮膜、智能节能玻璃以及激光防护、军事红外隐身等各个领域的广阔应用前景而备受关注。近年来,通过国内外众多科研工作者的努力,多种行之有效的拓宽反射谱带的方法已被提出。概况而言,需在胆甾相材料体系中构筑螺距非均匀分布(包括螺距梯度分布或螺距随机分布)以实现反射波谱的拓宽。根据其拓宽机理可分为层叠法、光诱导分子扩散法、热扩散法、外场刺激手性材料浓度变化或螺旋扭曲力变化法、胆甾相与扭曲晶界相两相共存法。通过对各个材料体系的研究,胆甾相的反射波宽得到了显著的拓宽,为胆甾相液晶材料的实际应用奠定了基础。而开发新材料体系、进一步优化器件性能和制备工艺是今后研究发展的重要方向。

Cholesteric liquid crystal(ChLC)materials with broad reflection band are witnessing a significant surge in in￣terest due to their unique optical properties and potential applications in areas such as reflective polarizer￣free displays,light enhancement films,smart switchable windows,laser protection or IR￣stealth.In the decades,extensive investigations have been made on broadening the reflection bandwidth.And several effective methods and processing techniques have been devel￣oped.In summary,a variation of pitch(whether a pitch gradient or a random distribution in the volume of materials)is inte￣gral to obtain a ChLC with a broad reflection band.According to the broadening mechanisms,they are classified to be stac￣king method,light induced molecular diffusion method,thermal diffusion method,method of external stimuli￣induced varia￣tion in concentration or helical twisting power of chiral compounds,and fabrication of a architecture that combined Ch and twist grain boundary phase nanostructures.Based on these studies,the reflection bandwidth of ChLC has been greatly broad￣ened in each material system,which makes it possible to practical applications.And there are still much works to be done in the future in making innovations in ChLC materials with excel￣lent optical performance,improving performances of functional devices and developing preparation technologies or procedures for industrial production.