COMPENSATION EFFECT OF POLYIMIDE THIN FILMS ON NORMALLY WHITE TWISTED NEMATIC LIQUID CRYSTAL DISPLAYS

The disadvantages of Normally White Twisted Nematic Liquid Crystal Display (NW-TN-LCD) were discussed. The reason that the negative birefringent polyimide thin films were used to compensate NW-TN-LCD to decrease off-axis leakage, improve contrast ratios and enlarge viewing angles was explained in this paper. A certain polyimide thin film was taken as an example to show compensation effect on NW-TN-LCD.

Magneto-optical effect of TEB30A liquid crystal doped with thulium oxides

The influences of an external magnetic field on the optical properties of the TEB30A nematic liquid crystal doped with thulium oxides （Gd203, Dy203, Nd203, Y203, and Sm203） are studied. It is shown that a magnetic field applied parallelly to the sample cell surface leads to the rotational orientation of mesogenes. All samples except for the sample doped with Sm203 nanoparticles undergo structural deformations. The behavior of the TEB30A/Sm203 differs from those of the TEB30A liquid crystal doped with other four nanoparticles. The presence of Sm203 nanoparticles in the TEB30A liquid crystal does not cause the structural deformation of the liquid crystal matrix. At the same time, the anchoring type of the liquid crystal molecules on the nanoparticle surface is different. The director n is parallel to the magnetic moment/~ in the TEB30A/Sm203, and inclined to the magnetic moment/~ in the TEB30A/Nd203, and perpendicular to the magnetic moment/~ in each of TEB30A/Gd203, TEB30A/Dy203, and TEB30A/Y203. Besides, the dependence of the structural deformation on the critical magnetic field for the TEB30A is obtained.

弱磁场中向列相液晶TEB30A薄膜自衍射现象研究

采用1.5mW低功率的He-Ne激光(632.8nm)正入射向列相液晶TEB30A薄膜,研究向列相液晶TEB30A薄膜在不同强度的弱磁场(0、0.464 9、0.506 2和0.518 5T)中的远场衍射特性。实验结果表明,向列相液晶TEB30A薄膜在4种不同强度的弱磁场(0,0.464 9,0.506 2和0.518 5T)中都能产生远场衍射。衍射图样会随磁场强度的增加而发生明显的变化。衍射环的数目增加,衍射环宽度变宽,衍射场向外拓展。当磁场强度为0.506 2T时,衍射环上出现了近似相互平行的干涉直条纹。当磁场强度达到0.518 5T时,干涉直条纹更加明显的趋于平行。在弱磁场的作用下,激光束在远场的散度变得明显。基于Kirchhoff-Fraunhofer衍射积分原理的理论模拟结果表明,当激光通过处在弱磁场中的向列相液晶TEB30A薄膜时,横向非线性相移会增大。随着弱磁场强度由0T增加到0.518 5T,非线性相移也由4π增加到20π。弱磁场引起样品非线性相移增大,导致其远场衍射图样发生了变化。远场衍射光强图样的变化也是透射光能量分布的改变,因此,可将弱磁场调控向列相液晶这一技术应用于磁控光开关及光限幅等领域。

聚乙二醇/纤维素纳米晶体复合液晶薄膜微观结构及湿度响应行为

【目的】探索聚乙二醇(PEG)对纤维素纳米晶体(CNC)液晶薄膜湿度响应的影响,阐明其响应机制,旨在为开发低成本、可重复使用和高灵敏度的PEG/CNC复合薄膜湿度传感器提供理论基础。【方法】将CNC与PEG共组装,制备了一种具有湿度响应性能的虹彩色手性向列相光子液晶薄膜,系统考察了PEG质量分数对液晶薄膜的微观结构、显色、力学性能及湿度响应的影响,在此基础上,研究了PEG/CNC复合液晶薄膜在不同湿度条件下的响应循环性能。【结果】对于纯CNC体系,CNC质量分数由3%增加到7%,CNC液晶薄膜的螺距减小,最大反射光波长由596.5 nm蓝移至511.0 nm;对于添加PEG的CNC体系,随着PEG质量分数的增加,PEG/CNC复合液晶薄膜的螺距由394.0 nm减小到244.0 nm,最大反射光波长由613.5 nm蓝移至350.5 nm,韧性先提升后下降,PEG质量分数为5%时为最佳,断裂能为31.9 J·m^(-2),较纯CNC薄膜提升了138%;液晶薄膜经过5次吸湿-解湿,表现出良好的湿度响应重复性,平衡波长的变化率小于0.6%。【结论】制备了一种对湿度具有敏感响应的虹彩色光子PEG/CNC复合液晶薄膜,PEG可以调控复合薄膜螺距,起到调节结构色的作用。

Molecular behaviors in thin film lubrication——Part two: Direct observation of the molecular orientation near the solid surface

Over the past twenty years, thin film lubrication(TFL) theory has been used to characterize the molecular behaviors in lubrication films thinner than 100 nm, effectively bridging the gap between elastohydrodynamic lubrication and boundary lubrication. Unfortunately, to date, the TFL molecular model proposed in 1996 has not been directly proven by experimental detection. Herein, a method based on surface-enhanced Raman spectroscopy was developed to show both the packing and orienting of liquid molecules in the TFL regime. By trapping liquid crystal molecules between a structured silver surface and a glass surface, molecular ordering states dominated by shear effect and surface effect were successfully distinguished. A nanosandwich structure consisting of an adsorbed layer, an ordered-molecule layer, and a fluid layer was demonstrated. Molecule imaging in TFL was achieved. Our results illustrate the molecular behaviors and lubrication mechanism in nanoconfined films and facilitate the lubrication design of nanoelectromechanical and microelectromechanical systems.

双膜补偿超扭曲向列相液晶显示设计软件

由于超扭曲向列相 (STN LCD)的双折射效应 ,使其在关态时出现一些颜色 ,达不到黑白显示。基于液晶连续体理论 ,用琼斯矩阵描写偏振光 ,运用邦加球表示 ,对STN盒的参数进行了优化并设计了软件 ,实现了双膜补偿下很好的黑白显示。

扭曲向列型液晶显示器的相补偿──应用各向异性薄膜增大扭曲向列液晶显示器的视角

本文简明介绍了扭曲向列型液晶显示器（ＴＮ—ＬＣＤ）的类型以及正常白型ＴＮ—ＬＣＤ的一些特征，总结几种提高对比度，增大视角，改进显示质量的相补偿方法。阐述了聚合物取向膜提高ＴＮ—ＬＣＤ对比度与视角的原理，重点说明聚酰亚胺分子由于面内取向而具备的负性双折射对ＴＮ—ＬＣＤ的相补偿作用，即：减少偏离液晶分子光轴方向上的漏光从而提高对比度，增大视角。还具体展示了我们制备的透明聚酰亚胺薄膜对一种正常白型ＴＮ—ＬＣＤ增大视角的相补偿效果。

高分子／液晶复合膜的结构与电光性质

以聚甲基丙烯酸甲酯及其改性物聚酰亚胺作为膜的基体，与向列型混合液晶ＧＲ－６３制成复合膜及其液晶盒。通过ＤＳＣ和扫描电子显微镜考察了复合膜的组分间相互作用及复合膜的相分离结构，并且研究了以该复合膜所制成的液晶盒的某些光开关性质及其相应的影响因素。

液晶及其显示器原理分析

本文简要回顾了液晶的发现过程,介绍了液晶和液晶显示器(LCD)的特性、基本原理和发展方向。