液晶电控双折射特性研究
摘要
液晶学是一门综合性的边缘学科，它涉及物理、化学、生物等多门基础学科，作为一种新材料，液晶越来越广泛的得到应用。作为一种凝聚态物质，液晶的特性与结构介于固态晶体与各向同性液体之间，是有序性的液体。从宏观物理性质看，它既具有液体的流动性、粘滞性，又具有晶体的各向异性，能如晶体一样发生双折射、布拉格反射、衍射及旋光效应，也能在外场作用下产生热光、电光或磁光效应。现在，液晶技术已被广泛应用于各个技术领域，在电子显示装置、光通信、光信息处理、化工的公害测定、高分子反应的定向聚合、航空机械及冶金产品的无损探伤和微波测定、医学上的皮癌检查、体温测量等，都显示出巨大的优越性。
在液晶的众多特性中，液晶的电控双折射特性是最重要的一个。当对液晶施加电场时，液晶分子的排列方向发生变化，从而引起液晶光轴的转动，最终导致了液晶双折射率的变化，这就是液晶的电控双折射特性。利用此性质可将液晶用于液晶显示、光通信、光信息处理等方面。液晶的电控双折射特性之所以应用广泛，主要是因为它有以下几个独特的优点：(1)可应用光谱范围特别宽。许多液晶在紫外、可见光和红外都具有较大的双折射率和良好的透射性(除了在液晶电子或分子振动吸收带附近)。(2)调谐电压低。通常，较小的电压(0-3伏)就足以产生较大的双折射率的变化(0.2)，具体的电压值由所用液晶材料决定。(3)双折射率连续可调。在很小的电压范围内就可以实现双折射率的连续变化。(4)输出光束不会发生偏离。(4)温度对液晶双折射率的影响可通过电压的变化得到补偿。(5)损耗低、重复率高、稳定性好。(6)用液晶制作各种器件制作简单且成本较低。因此，对液晶的电控双折射特性进行深入研究是非常必要的。但目前国内在这一方面的研究主要侧重于应
摘要 第 二 歹
用，对这一持性的专门研究较少，而且普遍存在一个缺点，
就是不考虑液晶的吸收效应对液晶电控双折射特性的影响。
本论文就是在考虑液晶吸收效应的前提下，研究了液晶的电
控双折射特性。＠
论文共分四章。第一章绪论筒要介绍了液晶电控双折射
特性的研究现状及意义。由于液晶电控双折射效应广泛的应
用性，已经引起越来越多的物理学家的兴趣c目前，国内外，
尤其是在国外，有不少学者从事这方面的研究。国内在这一
颌域的研究主要侧重于应周方面，而且研究液晶的电控双折
射荧性时没有考虑液晶分子的吸收效应。
第二章介绍了液晶的基础知识，并对向列相液晶作了重
点说明。向列相液晶是白长径比很大的棒状分子组成，分子
质。。没有长程有序性。具有类似于普通流体的流动性，分子
不排列成层，它能上下、左右、前后滑动，只在分子长轴方
向上保持相互平行或近于平行。分子问短程相互作用微弱。
属 Van der waa 5］力。向列相液晶最大的特点是在磁场、．
电场、表面力和机械力的影响下，分子排列一律倾向子同一
方向。这种分子长轴彼此互相平行的自发取向过程使液晶产
生高度的双折射性。本文就是以向列相液晶BL．009为例对
液晶的电控双折射特性进行研究的。
第三章介绍了各种材料的双折射性质，对一般晶体材
料、电光材料、压光材料的双折射均作了介绍，特别是对液
晶的电控双析射特性作了详细说明。对子一般晶体的双折射
以方解石为倒作了说明．而电光材料，当对它施加电场时，
他的双折射产生变化。对于缺少对称中心的晶体。当相对于
晶体的对称轴的一定方向施加电场时，所产生的电光效应是
线形的，即双折射的改变与电场的大小成正比。在另一类情．
况中，双折射的变化与外施场的平方成正比，这时所产生的
电先效应是二次的。压先效应类似子电光效应，但是为使材
摘要 第3 页
料的双析射产生变化用的是压力而不是电场。当一些各向同
性的材料在与光束成直角的方向上受应力时，它们就转变为
单勃材料，而且产生与应力成正比的相位延迟。对于液晶，
．当对液晶盒加上外部电压时，由于液晶介电常数和电导率的
各向异性，使液晶分子受到一种使分子轴取向改变的作用
力．在液晶的弹性界限内，这种电场所引起的转矩，使分子
轴旋转，最后受到弹性还原力的平衡．因此在这种状态时，
液晶盒的光学性质应与加电场前不同，双折射率也会改变．
这就是液晶的电控双析射效应，它是液晶电光效应的一科．
至今所知道的液晶的电光效应主要有以下几种：畴的形成、
动态散射、光轴的转动（电控双析射效应）、先轴的变形、
扭曲结构的再排列、宾主相互作用、记忆效应、N－1相变、
螺距的增减、螺旋轴的转动．
第四章对液晶电控双折射的实验研究作了详细阐述．在
Liquid crystal optics is a synthetic and marginal subject. It relates to physics, chemistry, biology, and other based subjects. As a new material, it has been applied more and more widely. As a condensation product, its characters are between the isotropic solid crystal and the anisotropic liquid. It is ordered fluid. As the macroscopical characters are concerned, it have the flowing power and viscidity like liquid, and the anisotropy like crystal.lt has birefringence, Bragg reflection, diffraction and optical rotation like crystal. Furthermore, it has thermal light effect, electrical light effect or magneto optical effect in outside field. Now, liquid crystal technology has been used in many fields widely, as electrical display device, optic communications, optical information processing, the public nuisance of chemical industry, the oriented polymer of macromolecular reaction, the nondestructive evaluation and microwave determination of aviational machine and metallurgic product, checking skin cancer in medicine, body temperature measurement, etc. It has showed the great superiority. In many characters of liquid crystals, the voltage-dependent birefringence is the most important character. When let it in the electric field, the oritation of liquid crystal molecule will change. It induced the optic axis to change. At last, the birefringence will change. This is the Voltage-dependent birefringence of liquid crystal.It
is applied in liquid crystals display, light communication, light information processing, etc. The Voltage-dependent birefringence of liquid crystal is widely used because of many merits. (l)Its applicable spectral range is extraordinarily broad. Many nematic LCs show very large birefringence and good transparency in both near-UV, visible, and IR regions (except in the vicinities of some resonant electronic and molecular vibrational absorption bands). (2)The required voltage is very small. Usually, a large birefringence change (0.2) can be achieved by a relatively small voltage(a few volts, depending on the LC used).Its wavelength taxability is determined by the controlled birefringence of the liquid crystal used. (3)Continuous variable birefringence. The Continuous variable birefringence can be achieved by a relatively small voltage.(4)No deviation in the outgoing beams takes place.(5)Applied voltage can compensate the temperature effect on the filter' s perfermance. (6)The low lost, high recurrence rate, and good stability. (7)The device fabrication is simple and cost is low. So, studying deeply in the LC voltage-dependent birefringence is very necessary. But in china, the study of this character is mostly the application. The special study is short. Furthermore, one shortage, that we don' t often think of the absorption, is prevalent. This paper studied the voltage-depended birefringence of liquid crystal, thinking of the absorption of LC.
The theme includes four sections. The function and general situation in present of LC voltage-dependent birefringence was introduced in the first chapter. Because of the wide application, more and more scientists have been interested in studying LC voltage-dependent birefringence. Now, in china, many scientists are studying it, especially abroad. In china, they mainly studied in the application, and they did not think of the absorption of LC molecules.
The basic knowledge of LC is introduced in the second chapter, especially the nematic liquid crystal. The nematic liquid crystal molecule is rodlike with big slenderness ratio. The barycenter of molecule is not long-range order. It has fluidity like liquid. The molecules do not tirer up. They can slide up and down, left and right, forward and backward. They only hold parallel or nearly parallel in the long axis orientation of the molecules. The interactivity of the molecules is weak. It belongs to Vander waals attractive force. The biggest character of nematic liquid crystal is that the orientation of the molecules leans to the same direction when LC is affected by magnetic field, electric field,
在液晶的众多特性中，液晶的电控双折射特性是最重要的一个。当对液晶施加电场时，液晶分子的排列方向发生变化，从而引起液晶光轴的转动，最终导致了液晶双折射率的变化，这就是液晶的电控双折射特性。利用此性质可将液晶用于液晶显示、光通信、光信息处理等方面。液晶的电控双折射特性之所以应用广泛，主要是因为它有以下几个独特的优点：(1)可应用光谱范围特别宽。许多液晶在紫外、可见光和红外都具有较大的双折射率和良好的透射性(除了在液晶电子或分子振动吸收带附近)。(2)调谐电压低。通常，较小的电压(0-3伏)就足以产生较大的双折射率的变化(0.2)，具体的电压值由所用液晶材料决定。(3)双折射率连续可调。在很小的电压范围内就可以实现双折射率的连续变化。(4)输出光束不会发生偏离。(4)温度对液晶双折射率的影响可通过电压的变化得到补偿。(5)损耗低、重复率高、稳定性好。(6)用液晶制作各种器件制作简单且成本较低。因此，对液晶的电控双折射特性进行深入研究是非常必要的。但目前国内在这一方面的研究主要侧重于应
摘要 第 二 歹
用，对这一持性的专门研究较少，而且普遍存在一个缺点，
就是不考虑液晶的吸收效应对液晶电控双折射特性的影响。
本论文就是在考虑液晶吸收效应的前提下，研究了液晶的电
控双折射特性。＠
论文共分四章。第一章绪论筒要介绍了液晶电控双折射
特性的研究现状及意义。由于液晶电控双折射效应广泛的应
用性，已经引起越来越多的物理学家的兴趣c目前，国内外，
尤其是在国外，有不少学者从事这方面的研究。国内在这一
颌域的研究主要侧重于应周方面，而且研究液晶的电控双折
射荧性时没有考虑液晶分子的吸收效应。
第二章介绍了液晶的基础知识，并对向列相液晶作了重
点说明。向列相液晶是白长径比很大的棒状分子组成，分子
质。。没有长程有序性。具有类似于普通流体的流动性，分子
不排列成层，它能上下、左右、前后滑动，只在分子长轴方
向上保持相互平行或近于平行。分子问短程相互作用微弱。
属 Van der waa 5］力。向列相液晶最大的特点是在磁场、．
电场、表面力和机械力的影响下，分子排列一律倾向子同一
方向。这种分子长轴彼此互相平行的自发取向过程使液晶产
生高度的双折射性。本文就是以向列相液晶BL．009为例对
液晶的电控双折射特性进行研究的。
第三章介绍了各种材料的双折射性质，对一般晶体材
料、电光材料、压光材料的双折射均作了介绍，特别是对液
晶的电控双析射特性作了详细说明。对子一般晶体的双折射
以方解石为倒作了说明．而电光材料，当对它施加电场时，
他的双折射产生变化。对于缺少对称中心的晶体。当相对于
晶体的对称轴的一定方向施加电场时，所产生的电光效应是
线形的，即双折射的改变与电场的大小成正比。在另一类情．
况中，双折射的变化与外施场的平方成正比，这时所产生的
电先效应是二次的。压先效应类似子电光效应，但是为使材
摘要 第3 页
料的双析射产生变化用的是压力而不是电场。当一些各向同
性的材料在与光束成直角的方向上受应力时，它们就转变为
单勃材料，而且产生与应力成正比的相位延迟。对于液晶，
．当对液晶盒加上外部电压时，由于液晶介电常数和电导率的
各向异性，使液晶分子受到一种使分子轴取向改变的作用
力．在液晶的弹性界限内，这种电场所引起的转矩，使分子
轴旋转，最后受到弹性还原力的平衡．因此在这种状态时，
液晶盒的光学性质应与加电场前不同，双折射率也会改变．
这就是液晶的电控双析射效应，它是液晶电光效应的一科．
至今所知道的液晶的电光效应主要有以下几种：畴的形成、
动态散射、光轴的转动（电控双析射效应）、先轴的变形、
扭曲结构的再排列、宾主相互作用、记忆效应、N－1相变、
螺距的增减、螺旋轴的转动．
第四章对液晶电控双折射的实验研究作了详细阐述．在
Liquid crystal optics is a synthetic and marginal subject. It relates to physics, chemistry, biology, and other based subjects. As a new material, it has been applied more and more widely. As a condensation product, its characters are between the isotropic solid crystal and the anisotropic liquid. It is ordered fluid. As the macroscopical characters are concerned, it have the flowing power and viscidity like liquid, and the anisotropy like crystal.lt has birefringence, Bragg reflection, diffraction and optical rotation like crystal. Furthermore, it has thermal light effect, electrical light effect or magneto optical effect in outside field. Now, liquid crystal technology has been used in many fields widely, as electrical display device, optic communications, optical information processing, the public nuisance of chemical industry, the oriented polymer of macromolecular reaction, the nondestructive evaluation and microwave determination of aviational machine and metallurgic product, checking skin cancer in medicine, body temperature measurement, etc. It has showed the great superiority. In many characters of liquid crystals, the voltage-dependent birefringence is the most important character. When let it in the electric field, the oritation of liquid crystal molecule will change. It induced the optic axis to change. At last, the birefringence will change. This is the Voltage-dependent birefringence of liquid crystal.It
is applied in liquid crystals display, light communication, light information processing, etc. The Voltage-dependent birefringence of liquid crystal is widely used because of many merits. (l)Its applicable spectral range is extraordinarily broad. Many nematic LCs show very large birefringence and good transparency in both near-UV, visible, and IR regions (except in the vicinities of some resonant electronic and molecular vibrational absorption bands). (2)The required voltage is very small. Usually, a large birefringence change (0.2) can be achieved by a relatively small voltage(a few volts, depending on the LC used).Its wavelength taxability is determined by the controlled birefringence of the liquid crystal used. (3)Continuous variable birefringence. The Continuous variable birefringence can be achieved by a relatively small voltage.(4)No deviation in the outgoing beams takes place.(5)Applied voltage can compensate the temperature effect on the filter' s perfermance. (6)The low lost, high recurrence rate, and good stability. (7)The device fabrication is simple and cost is low. So, studying deeply in the LC voltage-dependent birefringence is very necessary. But in china, the study of this character is mostly the application. The special study is short. Furthermore, one shortage, that we don' t often think of the absorption, is prevalent. This paper studied the voltage-depended birefringence of liquid crystal, thinking of the absorption of LC.
The theme includes four sections. The function and general situation in present of LC voltage-dependent birefringence was introduced in the first chapter. Because of the wide application, more and more scientists have been interested in studying LC voltage-dependent birefringence. Now, in china, many scientists are studying it, especially abroad. In china, they mainly studied in the application, and they did not think of the absorption of LC molecules.
The basic knowledge of LC is introduced in the second chapter, especially the nematic liquid crystal. The nematic liquid crystal molecule is rodlike with big slenderness ratio. The barycenter of molecule is not long-range order. It has fluidity like liquid. The molecules do not tirer up. They can slide up and down, left and right, forward and backward. They only hold parallel or nearly parallel in the long axis orientation of the molecules. The interactivity of the molecules is weak. It belongs to Vander waals attractive force. The biggest character of nematic liquid crystal is that the orientation of the molecules leans to the same direction when LC is affected by magnetic field, electric field,
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