高双折射液晶化合物的研究进展

Research progress of high birefringence liquid crystal compounds

近年来,液晶器件的响应速度得到了很大的改善,响应时间已经从25ms减少到3ms甚至更短。虽然这种改善与液晶层厚度的变薄有关,但主要原因应该归因于新型液晶材料的发展和使用。色序液晶显示能产生更高质量的图像,但前提是必须有能快速工作的液晶材料。液晶材料的旋转黏度系数、双折射和液晶层的厚度是影响液晶器件响应时间的3个主要因素。本文以液晶双折射这一因素为主线,从液晶化合物结构的角度介绍了影响液晶双折射数值的若干因素,包括中心环结构、中心基团上的桥键、极性基团和侧位-F对液晶双折射的影响等,延长分子的π电子共轭长度能有效提高液晶的双折射。本文列举了国内外已合成的高双折射向列相液晶的分子结构及双折射值,最后对高双折射液晶的研究进行了展望。

In recent years,the response speed of LCDs has been greatly improved.The response time has been reduced from 25 ms to 3ms or less.Although this improvement related to reducing thickness of the liquid crystal layer,the main reason was attributed to the studying and using of novel liquid crystal mixtures.Sequential color LCDs can produce higher quality images,but prerequisite is to have fast response liquid crystal materials.The three main factors which influence the response time of the LCDs are the rotational viscosity coefficient of the liquid crystal,the birefringence and thickness of the liquid crystal layer.This paper focuses on the birefringence of liquid crystal and describes several factors which influence the birefringence from the molecular structure of the liquid crystal compounds,including the central ring structure,the bridging groups on the center,the polar group and the＂-F＂on the lateral.Extending the length of π-electron conjugation of molecules can improve the birefringence of liquid crystal.This paper lists the molecular structures and birefringence of several nematic liquid crystal compounds with high birefringence which has been synthesized.Finally,the research of high birefringence liquid crystal is prospected.