基于FFS架构实现宽窄视角切换

基于公共场合隐私保护的需求,宽窄视角可切换的液晶显示技术有着迫切的市场需求。现有宽窄视角切换技术不但增加了显示装置的厚度与成本,而且降低了原本宽视角模式下的显示效果。本文研究了一种基于负性液晶FFS模式的宽窄视角切换技术,它通过在彩色滤光片一侧形成高预倾角配向(40°～60°),在同侧第三电极施加弱电场时,液晶分子离轴方向具有较大相位延迟,形成大视角观看时的暗态漏光与对比度下降,实现窄视角显示模式。而同侧第三电极施加强垂直电场时,大的预倾角液晶分子因负介电各项异性使得倾角降低,可减少暗态漏光和提升对比度,实现宽视角显示模式。验证结果表明:宽视角模式时,其上下左右视角均可达到85°以上;而窄视角模式时,左右视角仅为40°,且具有较好的对称性。本技术结构简单,驱动灵活,在防窥显示领域具有很好的应用前景。     

Theoretical and experimental study of nematic liquid crystaldisplay cells using the in-plane-switching mode

In this paper a two-dimensional (2-D) dynamic model, based on a tensor formulation and solved numerically by combining finite elements and finite differences, is proposed and used for analyzing nematic liquid crystal (LC) test cells with interdigital electrodes. We compare theoretical and experimental results concerning the switching behavior, response mechanism, and viewing angle characteristics of nematic LC pixel structures which use the in-plane-switching (IPS) mode. The good agreement observed between theory and experiment in terms of electro-optical properties validates our modeling and demonstrates its potential for design optimization. We show that the proposed LC test cells, using the in-plane-switching mode, ensure switching-ON and -OFF response times of 22 and 28 ms, respectively, and excellent viewing angle characteristics     

一种宽视角和快速响应的连续视角可控液晶显示

在垂面排列液晶显示模式中,液晶分子垂直取向,具有暗态良好、高对比度的特点,但是其视角特性不佳。采用MVA和PVA技术等多畴结构可以使VA模式的视角情况得到改善,但MVA模式中凸起结构引起的液晶分子初始预倾状态会导致暗态漏光,从而降低显示的对比度。而PVA模式中的狭缝结构虽然不会影响对比度,但其响应速度比较慢。文中提出一种新型垂面排列液晶显示器结构,其像素电极四周刻蚀有弧形狭缝,公共电极中心刻蚀有孔洞。施加电压时液晶分子向中心倾倒,形成中心对称的多畴结构,实现了对比度均匀的宽视角,且这一结构在保证高透过率的同时还可以实现快速响应。另外,通过在公共电极上施加偏置电压,该结构还可实现视角的连续可控。     

High transmittance in-plane switching liquid crystal displays

We have developed a high-transmittance in-plane switching (HT-IPS) liquid crystal display (LCD) using special electrode design on the same substrate. The featured electrode configuration generates substantial horizontal electric fields between the electrode groups, and fringe fields with rich horizontal components within the regions of electrode groups. The former is similar to the IPS mode and the latter is similar to the fringe-field switching (FFS) mode. The HT-IPS mode exhibits a high transmittance (> 90 % of twisted nematic (TN) mode), as well as wide viewing angle for cells using both positive and negative dielectric anisotropy LC materials. In addition, we also compare the electro-optical performance of the HT-IPS with IPS and FFS cells under the same conditions.     

高透过率共面转换液晶显示器

我们开发了一种在同一个基板上使用特殊电极设计的高透过率共面转换(HT-IPS)液晶显示器。这种特殊的电极构造在电极组之间产生实际的水平电场,在电极组区域内的边缘电场具有较高水平场成份。上半部分类似于IPS模式,而下半部分类似于边缘场转换(FFS)模式。HT-IPS模式显示出了很高的透过率[大于扭曲向列相(TN)模式的90%],同时,无论使用正性或负性各向异性的液晶材料,液晶盒都具有宽视角。此外,我们对比了相同条件下HT-IPS与IPS、FFS盒的光电特性。     

单玻璃基板与各向异性聚合物膜的IPS-LCD的应用

介绍了一种使用单片玻璃基板和各向异性聚合物膜的轻型、共面转换液晶显示(IPS-LCD)技术。液晶分子由伸长的聚合物膜内的颗粒排列。各向异性聚合物膜的取向性能与聚酰亚胺(PI)摩擦层相当。良好的液晶取向性能使新器件的对比度(514:1)、驱动电压和响应时间都能够与双玻璃基板LCD相比拟。这种各向异性膜也能作为拓宽视角的相位补偿膜来使用。该技术特别引人注目之处在于制作单基板显示器,同时它也具有实现双层宾主显示和IPS-LCD柔性显示的潜在应用。     

IPS-LCD using a glass substrate and an anisotropic polymer film

A lightweight in-plane-switching liquid crystal display (IPS-LCD) using a single glass substrate and an anisotropic polymeric film is demonstrated. The liquid crystal molecules are aligned by the elongated polymer grain of the film. The alignment capability of the anisotropic film is comparable to a buffed polyimide layer. Compared to the LCD using two glass substrates, our new device exhibits a comparable contrast ratio (/spl sim/514:1), driving voltage, and response time because of good LC alignment. Such an anisotropic film can also function as a phase compensation film for widening the viewing angle. This technology is particularly attractive for making single-substrate displays and also has potential for a double-layered guest-host display and a flexible display using IPS LCDs.     

Modeling of Blue Phase Liquid Crystal Displays

We propose a numerical model based on Kerr effect for simulating the electro-optics of polymer-stabilized blue phase liquid crystal displays (BP-LCDs). Parameters affecting the electro-optics of BP-LCDs in in-plane-switching (IPS) structures, such as wavelength, temperature, electrode dimension, and cell gap are investigated. In addition, viewing angle and color shift of IPS BP-LCDs are studied.      

一种新型单偏振片反射式液晶显示器的设计

提出一种新型单偏振片反射式液晶显示器的设计方案。采用共面转换模式并在液晶和反射板之间加入四分之一光延迟膜。通过使用参数空间表示法优化选择器件参数,获得了高反射率、低色散和宽视角的常白、常黑反射式显示模式。     

Wide-View and Broadband Circular Polarizers for Transflective Liquid Crystal Displays

A simple wide-view and broadband circular polarizer comprising of a linear polarizer and two uniaxial films is proposed to enhance the viewing angle of transflective liquid crystal displays (LCDs). For the transmissive mode, over the entire 90deg viewing cone, the normalized light leakage from two stacked circular polarizers is suppressed to below 1.5times10^-2, and contrast ratio over 10:1 is obtained using a normally black vertically aligned transflective LCD. At the same time, this configuration warrants a broadband operation and reasonably good viewing angle (10:1 contrast ratio is over 40 at all directions) for the reflective mode. The physical mechanisms for achieving broadband operation and wide viewing angle are discussed.     

VA和IPS液晶盒固有对比度与温度的关系

我们测量了介于“理想”正交偏光片组之间的VA和JPS液晶盒在不同温度下的固有漏光。在温度低于向列相到液态的转变（清亮点）温度时,测量到的VA液晶盒固有漏光与温度变化无关,相反,JPS液晶盒无论是o光模式还是e光模式结构中固有漏光都随温度的增加而增加。我们推导出基于向列相液晶指向矢涨落引起光散射的理论公式,以解释我们的实验结果。     

共面转换型42英寸液晶电视的发展

我们通过使用超级共面转换(SuperIn-Plane-Switching)模式和过驱动(Over-Driving)电路技术,开发出具有宽视角和快速响应的42英寸(1280×768,159)大尺寸液晶电视(LCD-TV)。通过使用膜超级共面转换技术获得了在任意方向的宽视角,通过优化液晶材料和液晶盒的设计,获得了更快的响应时间(12ms)。     

一种采用内部线栅偏振片的半透半反射式液晶显示器

为了同时获得具有高透射率和反射率的液晶显示器,提出了一种采用内部线栅式偏振片(wiregridpolarizer,WGP)的单倍盒间距的半透半反式液晶显示器方法。在反射模式中,液晶盒内嵌的WGP作为依赖于偏振的外界光的反射器;在透射模式中,不需要消色差的四分之一波片。基于液晶盒的初始取向,该器件可用于正常显黑模式(垂直取向)和正常显白模式(扭曲向列相取向)。本文研究了这两种器件结构详细的电光特性,如电压依赖光效率特性和视角特性。     

Wide-View MVA-LCDs With an Achromatic Dark State

A multi-domain vertical alignment liquid crystal display (MVA LCD) using a negative C-plate and a biaxial film is proposed to obtain an achromatic dark state. In comparison to conventional approach which uses a negative C-plate and a positive A-plate, the maximum light leakage over entire viewing cone is reduced by ~ 6X at lambda = 450 nm and ~ 4X at lambda = 650 nm. The achromatic dark state is essential for improving the contrast ratio, viewing angle and color saturation of MVA LCDs.     

Bending angle effects on the multi-domain in-plane-switching liquid crystal displays

The electro-optic properties of a multi-domain in-plane switching liquid crystal display (IPS LCD) are investigated through a three-dimensional (3-D) simulator, which combines the finite element and finite difference methods for fast solutions. The bending angle between the chevron-shaped electrodes makes an important contribution to the operating voltage and response time, and suppresses the color shift. Using optimized uniaxial compensation films, the viewing cone of the multi-domain IPS LCD is widened to /spl plusmn/80/spl deg/ at 100:1 contrast ratio. These properties are especially desirable for LCD TV and computer monitor applications.     

Recent Trends on Patterned Vertical Alignment (PVA) and Fringe-Field Switching (FFS) Liquid Crystal Displays for Liquid Crystal Television Applications

This paper reviews the recent trends on super-patterned vertical alignment (S-PVA) and fringe-field switching (FFS) technologies for liquid crystal display (LCD)-television (TV) applications. For PVA mode, Samsung originally announced S-PVA technology in 2004 to enhance off-axis viewing quality of conventional PVA mode. S-PVA is a new technology which enables screen quality advantages over super-in plane switching (S-IPS) and multi-domain VA (MVA), including high transmittance, >2300:1 contrast ratio, and wide viewing angle with no off-axis image inversion. This paper explores and updates Samsung's latest developments toward its goal of ultimate LCD-TV performance. For FFS mode, the technology appeared in 1998 by HYDIS and now it has been commercialized in all kinds of display applications, implying its technical importance. This paper reviews recent developments and performance of LCD-TV using the FFS mode based on published papers and our knowledge.     

A transflective liquid crystal display using an internal wire grid polarizer

To obtain high transmittance and reflectance simultaneously, a single cell gap transflective liquid crystal (LC) display using internal wire grid polarizer (WGP) is proposed. For the reflective mode, the imbedded WGP serves as a polarization-dependent reflector for the ambient light. For the transmissive mode, no achromatic quarter-wave film is needed. This device can be used as a normally black mode (using vertical alignment) and a normally white mode (using twist-nematic alignment), based on the initial LC cell alignment. Detailed electro-optic performance, such as voltage-dependent light efficiency and viewing angle of these two device configurations, is investigated.     

基于菱形电极结构的高对比度平面内扭转模式蓝相液晶显示器件设计

以往研究发现平面内扭转(In-Plane Switching,IPS)模式蓝相液晶显示器件的图像显示对比度明显低于理论预期。本文对导致这一问题的物理原理进行理论分析和实验验证,据此提出改进的菱形电极结构设计以解决这一问题。实验证明,调整走向后的IPS电极结构能使蓝相液晶显示器件的暗态漏光减小2/3,使其显示对比度提升至10 000∶1以上。基于这一实验发现,本文提出了全新的菱形电极结构设计,以求获得高对比度显示效果。除此以外,采用Techwiz仿真分析改进后的菱形IPS电极蓝相液晶显示器件的电光特性,发现其伽玛偏移和灰度反转可分别减小3/4和2/3,并且其驱动电压和透过率与传统IPS模式蓝相液晶显示器件相仿。可见,基于改进的菱形IPS电极结构的蓝相液晶显示器件相较传统蓝相液晶显示器件具备更好的显示性能和市场竞争力。     

Possibility of stereoscopic displays by using a viewing angledependence of twisted nematic liquid crystal cells

Stereoscopic displays that use the viewing angle dependence of twisted nematic (TN) liquid crystal cells to direct light to either the left or right eye have been investigated. From a calculation that combined Frank's elastic theory and Berreman's 4×4 matrix method, it is observed that a luminance ratio defined as the luminance of viewing direction divided by that from the opposite direction largely depends on a pretilt angle of liquid crystal material and the cell thickness. The maximum luminance ratio is obtained at the cell thickness of the second-minimum. From experimental results, clear transmittance inversion between left and right directions observed. The experimental results of the viewing angle dependence are in good agreement with calculation results. The luminance ratios were 4.7 in the cell with polyimide alignment layer (the pretilt angle 4.5°) and 17 in the cell with alignment layer of SiO oblique evaporation (the pretilt angle=40°)     

窄视角蓝相液晶显示器

基于克尔效应的聚合物稳定蓝相液晶显示器被设计出窄视角显示模式,用于公共场所下私人信息的保护。通过使用几个简单的单轴膜,聚合物稳定蓝相液晶显示器就可以呈现出极佳的窄视角效果,即,对比度大于10°的可视区在20°极角范围内。此外,该显示器的驱动电压为14 V,最大透过率为71%,不仅满足了当前主流非晶硅薄膜晶体管的驱动需求,还进一步提高了背光源的光利用率。本文提出的窄视角蓝相液晶显示器与传统的窄视角模式相比较而言,没有复杂的电极结构以及繁琐的补偿方案,较3M公司的保护膜而言,具有生产成本低的优势,这些优势使其具备了在工业上生产的条件。在信息时代,窄视角液晶显示器将在防止私人信息的泄露上扮演越来越重要的作用。