向列相液晶材料动态

夜晶是处于固态和液态之间具有一定有序性的有机物质,具有光电动态散射特性;它有多种液晶相态,例如胆田相,各种近晶相,向列相等。根据其材料性质不同,各种相态的液晶材料大都已开发用于平板显示器件中,现已开发的有各种向列相液晶、聚合物分散液晶、双（多）稳态液晶、铁电液晶和反铁电液晶显示器等,其中开发最成功的、市场占有量最大、发展最快的是向列相液晶显示器。液晶显示（LCD）模式有很多,仅向列相显示就有TN（扭曲向列相）模式、HTN（高扭曲向列相）模式、STN（超扭曲向列相）模式、TFT－AM（薄膜晶体管一有源矩阵…     

含氟三苯二炔类液晶化合物合成及其性质研究

目前,越来越多的液晶应用要求向列相液晶材料具有高双折射率性能。本文合成了5个高双折射率含氟三苯二炔类液晶化合物(Ⅳ),经过IR,1 H NMR,13 C NMR谱图鉴定,这些化合物的分子结构完全正确;通过DSC和POM对其液晶相态测试的实验结果表明该类液晶化合物具有较低的熔点和相对较宽的向列相温度范围(达到100℃左右);对其折光率测试结果表明这些液晶化合物的双折射率(Δn)值在0.47以上,改善液晶光学性能。     

低熔点高Δn值双环向列相液晶的合成研究

为了获得低熔点、折射率各向异性(Δn)大的快速响应向列相液晶材料,高Δn值的液晶混合体系中需要加入熔点在50℃以下、Δn大于0.35的双环类液晶组分,以使快速响应向列相液晶材料满足室温工作的要求。本文合成了异硫氰基含氟二苯乙炔类液晶化合物;一方面由于在分子苯环侧位引入F原子,减小分子间作用力,使化合物的熔点下降;另一方面在两个苯环间引入三键、分子末端接入异硫氰基极性基团,增加了分子的共轭性,提高了目标化合物的Δn值。获得了熔点分别为31℃和50℃、Δn为0.39和0.40,这两种低熔点化合物与目前已具有的毫秒级快速响应向列相液晶化合物混合,可使其熔点低至10℃以下。     

液晶介电常数在微波至太赫兹频段测试技术

基于液晶材料的器件成为毫米波及太赫兹波领域的重要方向之一,文中总结了毫米波太赫兹波液晶器件的研究进展,介绍了液晶移相器的基本原理及应用,分析了液晶介电常数的主要测试方法,如传输线/反射法、谐振腔法、自由空间法、时域法等,比较了不同方法的测试频率范围和优缺点,并给出了向列相液晶材料在微波毫米波及太赫兹波段的介电常数的主要测试结果。     

含氟三联苯类异硫氰酸酯类液晶合成与微波性能研究

近年来液晶在微波通信器件上的研究发展迅速,而液晶材料的介电损耗成为制约其发展的主要因素。异硫氰三联苯类化合物是一种结构稳定的低粘度、高双折射率液晶化合物,适于作为微波用液晶材料组分。本文通过偶联法合成了4种含氟三联苯异硫氰酸酯液晶化合物nPGUS(n=2～5),通过IR、~1H NMR、~(13)C NMR、~(19)F NMR确认化合物结构正确;差热分析(DSC)结果显示,它们都具有宽温向列相液晶态和相对较低的熔点,其中5PGUS的向列相温度范围达到101.8℃,熔点只有57.4℃;通过矩形谐振腔微扰法测试分析了它们在高频下的介电性能,将它们与母体液晶混合后,在18GHz时的介电常数值(Δε_r)为0.95,最大介电损耗为(tanδε_(r-max))0.007 63,相位调制系数(τ)0.265,可满足微波用向列相液晶材料性能要求。     

液晶显示基础知识（三）：液晶的粘滞与弹性性质

从物理角度介绍向列相液晶的各个粘滞系数与弹性滞数，及其最常见的测量方法。并简略介绍这些系数对于实际显示器件的影响。     

用衰减全反射法研究向列相液晶的排列性质

液晶作为一种最有前途的平板显示材料,其分子在液晶盒内的排列特性对显示器件的设计及制作无疑是极为重要的。衰减全反射法（简称ATR方法）最早应用于对金属薄膜特性的研究,后来逐渐成为研究各类介质光学性质的有力工具。最近几年,这种方法在研究液晶在液晶盒内的排列性质方面展现了强大的活力。本文介绍了衰减全反射法的基本原理、实验方法并将它应用于探测向列相液晶CP—9001 LA的排列性质。     

扭曲向列相LCoS显示模式的优化设计分析

由偏振分光棱镜、向列相液晶层、金属反射镜组成的LCoS投影微显示器件可以通过向列相液晶层的旋光效应、双折射效应而实现对入射偏振光的强度调制。为了提高光利用率,文章用Muller矩阵推导出了线偏振光经过扭曲向列相液晶层之后转变为偏振态不同的线偏振光或者圆偏振光的条件,设计了偏振转换效率为100%的常黑或常白LCoS显示模式,有效提高了光利用效率。     

对三氟甲氧基苯酚酯类液晶的合成和相变研究

设计并合成了一类新型的对三氟甲氧基苯酚酯类液晶,其相变行为通过DSC及偏光显微镜进行了观察和测试。这类液晶化合物都显示一个很宽的近晶A相和一个很窄的向列相,近晶A相的温度范围不随烷氧基端链的长度发生变化,而向列相的温度范围却随着烷氧基链的增长而缩小。四氟苯环的引入降低了化合物的热稳定性,压缩了近晶相,却有利于向列相的形成。三氟甲氧基有利于近晶相。     

基于迈克尔逊干涉液晶双折射率的测量方法设计

为了通过实验得到向列相液晶材料的双折射率,利用迈克尔逊干涉原理设计了一种新的测量方法。在迈克尔逊干涉仪中放入楔形液晶盒,通过调节入射光的偏振方向分别实现了对寻常光和非寻常光折射率的精确测定。结果表明,该测量方法将折射率测量转换为长度的测量和干涉条纹的计数,简单易行、测量精度较高,对理论研究和实际开发液晶显示器件是非常重要的,在液晶材料和液晶器件生产中具有一定的推广价值。     

Study advances use of MOVPE precursors for ZnSe blue emitters

While much attention has been focussed on the III-nitride compound semiconductors for the fabrication of short wavelength optoelectronic and electronic devices, the II–VI materials are also showing great promise. In particular, the chalcogenides, such as sulphide and selenide compounds, have a long history as display materials for efficient light emission.     

Dielectric anisotropy of new liquid-crystal mixtures and its effect on dynamic scattering

New liquid crystalline compounds with a high negative dielectric anisotropy and wide temperature range have been prepared, and their dynamic-scattering properties compared with other materials. These compounds give a slightly lower threshold voltage, followed by a rapid increase of dynamic scattering above threshold, and should provide improved performance in low-voltage display devices.     

Recent Progress in Functional Dye-Doped Liquid Crystal Devices

As a typical representative of dopants, organic functional dyes have demonstrated their significant roles in novel smart liquid crystal (LC) devices, and dye-doped LCs have also been a source of inspiration for scientists to design and fabricate stimuli-gated materials or devices for envisioned applications in a wide range of areas. In this review, the focus on dichroic dyes, fluorescent dyes, and photothermal dyes, and the recent progress of the LC devices employing these dyes as dopants are overviewed. The review highlights the developments of the novel LC devices doped with these dyes. The structures, designs, and applications of these devices are outlined. The underlying principles of dichroic dyes, fluorescent dyes, and photothermal dyes which are utilized as functional dopants in LC devices are first introduced. Subsequently, the novel developments of functional dye-doped LC devices in the application fields of smart windows, attenuators for augmented reality (AR) systems, color-changeable textiles, dichroic color filters, dual-mode circular polarizers, chirality detectors, optical limiters, switchable luminescent solar concentrators, multiple information encryption, anti-counterfeiting, photo-addressed transparent displays, circularly polarized luminescence, tunable lasers, and light-driven soft actuators are discussed. Finally, the challenge and the strategies for the future improvement of dye-doped LC devices are also discussed.     

The constructions and optical characteristics of multi-color or full-color ACTFEL display devices

II-VI compounds (such as ZnS, CaS and SrS) are useful semiconductors for electrolu-minescent display devices. Recently, much effort has been paid to the color AC thin film electroluminescent (ACTFEL) display devices. In this paper, we review the several dif-ferent kinds of constructions and materials of active layer of the color TFEL devices. The optical characteristics and chromaticity coordinates of three primary color of these color TFEL display devices will also be discussed.     

Microstructured Actuation of Liquid Crystal Polymer Networks

Smart microstructured materials enable functions such as actuation, detection, transportation, and sensing with potential applications ranging from robotics and photonics to biomedical devices. Of the many materials systems, liquid crystal polymer networks (LCN) are fascinating owing to their ability to exhibit reversible macroscopic deformation driven by a molecular order–disorder phase transition. LCN have been increasingly explored for their utility in the design and fabrication of smart actuating devices capable of complex shape changes or motions upon external stimulation of humidity, heat, light, and other stimuli, and recent studies in this field show that their actuation complexity can be enriched and actuation performance enhanced by having some sort of microstructures. Herein, the recent progress in microstructured actuation of LCN materials with substructures in scale ranging from micrometer to millimeter is reported, placing the emphasis on the main approaches to generating a microstructure in LCN, which include patterned LC director fields, patterned chain crosslinking in LCN with uniaxial orientation of mesogens, 3D/4D printing, and replica molding. The potential applications in microstructured 3D actuators and devices as well as functional LCN surfaces are also highlighted, with an outlook on important issues and future trends in smart microstructured LCN materials and actuators.     

Preparation and properties of electroluminescent phosphors for display devices

Electroluminescent phosphors for use in some electronic display devices should have brightness-voltage characteristics differing from those used in light sources, for example. The various factors of phosphor preparation and of cell construction which affect these characteristics have been studied. Special phosphor powders with unusually high or unusually low values of "discrimination ratio" (a quantity related to the change in output as the applied voltage is varied) have been developed and their performance described. It has also been shown that thin phosphor films afford extremely high values of discrimination ratio, particularly if operated on dc. The use of nonlinear materials (especially zinc oxide) as auxiliary layers to increase the discrimination ratio obtained with a given phosphor has been studied.     

应用场致相位分离和光致聚合制备的单基板液晶显示器

展示一种使用一层玻璃基板和光致聚合层的平面开关液晶盒,其制造工艺系基于电解质流动的电气力学。当散射场出现时,液晶分子聚合到强电场区,而单体扩散到弱电场区。在光聚合作用后,液晶分子则受到薄聚合层和确定液晶盒间隙聚合墙的限制。这种方法能够制造单基板大面积平板显示器件。     

蓝相液晶材料与光子学器件研究进展

蓝相液晶是一种三维手性自组装软超结构材料,具有光学各向同性,选择性反射波长,快速响应等优秀特性,无论在显示还是光子器件的应用上都具有良好的发展前景,吸引了研究人员的大量关注。近十年关于蓝相液晶显示领域的研究与工程或应用发展迅猛,于此同时催生了其在光子学这个后显示领域的研究。面对来自国际上其他先进国家的竞争与压力,中国大陆的学者们奋勇迎接,经过短短数年的发展获得了一批有显示度的成果,在国内外的优秀期刊上报道了一系列富含学术性和实用性的工作。具备高热稳定性与显著电光调制特性的新型蓝相液晶材料及其光子学器件,如衍射光栅、相位调制器、透镜、激光以及光衰减器等,相继被开发出。本文追逐这些前辈留下的脚印,从材料制备、性能到光子器件设计、应用进行了概括性的回顾,旨在通过此综述激发出蓝相液晶在非显示光子学应用领域更多的研究灵感;若能起到进一步促进该领域发展的作用,笔者将感到幸甚之至!     

平板CRT的发展趋势

ＣＲＴ器件是当前显示器件中技术最为成熟应用最为普及的主导产品,由于存在着体积大,重量重等固有的严重缺陷。ＣＲＴ器件也一直受到众多新型平板显示器件的严峻挑战,实现ＣＲＴ器件的平板化设计。一直是ＣＲＴ科研工作者不断努力和艰苦工作目标。本文简要叙述了平板ＣＲＴ的发展经历、主要类型及工作原理,并进一步探讨了平板ＣＲＴ的发展前景。     

Fluorescent Photochromic α-Cyanodiarylethene Molecular Switches: An Emerging and Promising Class of Functional Diarylethene

Fluorescent photochromic molecules that exhibit distinct light-triggered changes in their emission colors are highly desirable for the fabrication of smart soft materials and advanced photonic devices. α-Cyanodiarylethenes, that is, α-cyano-functionalized diarylethenes, as alternative “non-azo” Z/E photochromic molecular switches, are popular choices due to their unique characteristics such as their aggregation-induced emission or aggregation-induced-enhanced emission behavior in their self-assembled states, and visible changes in fluorescence colors during Z/E photoisomerization. In recent years, the development of fluorescent photochromic α-cyanodiarylethene-based compounds including α-cyanostilbenes, dicyanodistyrylbenzenes, and diaryldicyanoethenes, has mainly focused on molecular design, photochemical and photophysical behavior in solution, and smart soft matter technologies. In this review, recent significant achievements in light-responsive systems based on the Z/E photoisomerization of fluorescent photochromic α-cyanodiarylethene switches that span the range from liquid crystals to gels and finally to self-assembled nanostructures, are highlighted. The smart soft materials constructed from α-cyanodiarylethene molecular switches find use in a plethora of areas, including display, sensing, encrypting, actuating, and biomedical imaging applications, among others. The review concludes with a brief perspective on some major challenges and opportunities for the future development of light-responsive smart soft photonic materials.