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不同初始分布向列相液晶电容特性的相场法研究
Phase field method in capacitance characteristics of nematic liquid crystals with different initial alignments
- 液晶与显示 2019年34卷第4期 页码：327-334
- 作者机构：
厦门大学 材料学院, 福建省特种先进材料重点实验室, 福建 厦门 361000
- 作者简介：
[ "王舒凯(1992-), 男, 湖北孝感人, 厦门大学材料学院研究生, 主要从事液晶物理性能的研究。E-mail: 943153819@qq.com" ]
周志东，E-mail：zdzhou@xmu.edu.cn
- 基金信息：国家自然科学基金(11572271);National Natural Science Foundation of China(11572271)
DOI：10.3788/YJYXS20193404.0327
中图分类号： O753+.2;TM532.5收稿日期：2018-10-31，
录用日期：2019-1-20，
纸质出版日期：2019-04
- 稿件说明：
移动端阅览
王舒凯, 周志东. 不同初始分布向列相液晶电容特性的相场法研究[J]. 液晶与显示, 2019,34(4):327-334.
Shu-kai WANG, Zhi-dong ZHOU. Phase field method in capacitance characteristics of nematic liquid crystals with different initial alignments[J]. Chinese journal of liquid crystals and displays, 2019, 34(4): 327-334.
王舒凯, 周志东. 不同初始分布向列相液晶电容特性的相场法研究[J]. 液晶与显示, 2019,34(4):327-334. DOI： 10.3788/YJYXS20193404.0327.
Shu-kai WANG, Zhi-dong ZHOU. Phase field method in capacitance characteristics of nematic liquid crystals with different initial alignments[J]. Chinese journal of liquid crystals and displays, 2019, 34(4): 327-334. DOI： 10.3788/YJYXS20193404.0327.
摘要
液晶盒内的液晶分子在不同的外加电场作用下重新排布，其极化指向发生改变，从而影响液晶盒整体的电学特性。本文考虑液晶材料的挠曲电效应，分析液晶盒的整体自由能表达式，包含弹性形变自由能密度、介电自由能密度和挠曲电自由能密度。基于液晶弹性理论和相场方法，构建描述液晶核指向矢分布及演化的相场方程，并运用离散方法推导出液晶盒约化电容的表达式。讨论边界强锚定的混合液晶盒（HAN）和平行液晶盒（PAN）表面电荷密度对液晶核指向矢偏转角的影响。进一步分析了挠曲电系数、表面电荷密度以及液晶盒厚度对两种不同初始指向分布液晶盒电容性能的影响。数值分析结果表明，表面电荷密度越大、挠曲电系数越小，液晶核指向矢偏角越大。在混合液晶盒中，约化电容随着表面电荷或液晶厚度的增加而增加，最终趋于饱和；而在平行液晶盒中，当表面电荷密度或液晶盒厚度达到某个临界值时，液晶核的指向矢才发生改变，液晶的约化电容才有明显的变化。随着表面电荷密度增加，液晶核指向矢发生偏转的临界厚度减小。
Abstract
Subjected to different electric fields
liquid crystal molecules would rearrange and the polarization directors would change
which could affect the capacitance characteristics of liquid crystal cells. Based on the free energy of liquid crystals due to the flexoelectric effect
the expressions of the elastic
dielectric and flexoelectric free energy density are obtained. Applying the elastic theory and the phase filed methods of liquid crystals
the phase field equations describing the distribution and switching of liquid crystal director are obtained
and the expression of the capacitance of the liquid crystal cell is derived by discrete methods. The influences of the surface charge density on the liquid crystal directors are discussed in the strong anchoring hybrid alignment nematic (HAN) and the parallel alignment nematic (PAN) liquid crystal cells. Furthermore
the effects of flexoelectricity
surface charge density and the thickness of the liquid crystal cell on the capacitance performance of two different initial alignments are analyzed in detail. The results of numerical analysis show that the larger surface charge density and the smaller flexoelectric coefficients would induce the larger angle of the director. In the HAN liquid crystal cell
the capacitance increases with increasing surface charge or liquid crystal thickness
and finally becomes saturated. In the PAN liquid crystal cell
the liquid crystal directors switch only upon the surface charge density or the thickness of the liquid crystal cell reaching a certain critical value
and the capacitance of the liquid crystal changes significantly. With increasing surface charge density
the critical thickness of the liquid crystal cell decreases.
关键词
Keywords
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