Optical properties of electrophoretic image displays

Those variables determining the optical properties of one type of electrophoretic image display (EPID) are discussed in this paper. The working medium in the EPID with which this paper is concerned is a colloidal suspension of submicron pigment particles in a medium of matching specific gravity and contrasting color. The colloidal suspension is contained between two transparent electrodes. By changing the polarity of the applied voltage, the charged pigment particles may be moved to one or the other electrode. The effects of suspension composition, and the physical and chemical properties of the suspension components are discussed.     

Performance characteristics of nematic liquid crystal display devices

Display devices using nematic liquid crystal materials offer advantages over other display media in low-voltage low-power operation, cost of materials and fabrication methods, electrical compatibility with MOS drive circuits, and flexibility of character size and format. This paper describes liquid crystal display devices that utilize dynamic scattering to modify transmitted or reflected light. We have synthesized individual materials that have nematic temperature ranges as large as -15-115°C without super-cooling effects at low temperatures. When these materials are used in transmissive displays having liquid crystal layers 12 µm thick sandwiched between transparent electrodes, contrast ratios of 30:1 to 50:1 are realized at 10-40 V dc or ac with a current density of ∼1-10 µA/cm². Turn-on times are 10-50 ms and turn-off times are 30-100 ms, precise values being dependent on the specific material, temperature, and voltage used. The contrast ratio versus voltage exhibits a threshold so that it may be possible to matrix address liquid crystal display panels. Operating lifetime and display applications are also discussed.     

Use of barium cold cathodes for low voltage DC-gas discharge color display panels

A technique for providing barium cold cathodes in a dc-gas discharge color display panels has been developed. A 21 × 111 cell green panel, fabricated in accordance with this technique, yielded a maintenance voltage of 88 ± 8 V. This value is approximately ⅓ that for conventional nickel cathode panels, resulting in a threefold increase in luminous efficiency.     

Reflective liquid crystal television display

A new reflective television display, operating off the air, is described. The display uses the dynamic scattering mode (DSM) in nematic liquid crystals and can be viewed in high-brightness ambients. The liquid crystal cell, 6 to 12 µm thick, was addressed in real time by means of an electron beam using a wire-mosaic faceplate on a demountable cathode ray tube. Two different liquid crystal materials--anasylidene paraamino phenyl acetate (APAPA) and an RCA proprietary room temperature liquid crystal--were tested with similar results except for the difference in operating temperature (82 to 110° C and room temperature, respectively). The resolution of the 3.1-cm-square display was somewhat less than that required for commercial television (∼150 lines), limited by the mosaic structure but not the liquid crystal. Adequate resolution should be achievable in slightly larger displays. The contrast was not optimized (7.5 to 1) but several techniques are available to improve this value to 15 or 20 to 1 as has been demonstrated in static displays. The subjective evaluation of this display points out the attractiveness of reflective television panels; under suitable external illumination the panel has a wide viewing angle (±45° approximately). The current and voltage requirements to achieve the DSM in liquid crystals are such as to raise hopes that an integrated addressing approach suitable for flat television panels can be found.     

电子纸显示器技术现状与发展

CRT(阴极射线管)LCD(液晶显示)等显示器，不同程度地存在亮度、视角和携带不便、高电压等问题，只能通过研制电子纸显示器解决。CRT的平面化以及LED(液晶显示)的改进，有机电致发光二极管(OLED)、各种电泳显示器(EPID)、旋转球影像显示(Gyricon)、电致显示(FED)、隐色染料、聚合物胶体显示材料、胆甾液晶等10多种显示技术的发展，结合导电高分子薄膜晶体管(TFT)，使得电子纸显示器技术产业化逐步接近现实，EPID和Gyricon是两种比较成熟的技术。     

彩色电子纸的基础物理与操作原理

电泳式电子纸作为一种重要的反射式显示技术,已被广泛应用于电子阅读器等低功耗的显示器件中。单色电泳式电子纸从实验室走向产业化的成功催生了彩色电子纸的发展,以满足人们对反射式显示器的多样需求。然而,在成功实现彩色化之前,还有许多挑战性的问题仍待克服。为了实现电子纸的彩色化显示,本文首先介绍电泳式电子纸的基本操作原理、包括粒子带电机制,粒子表面改性等。然后,针对电子纸在驱动过程中产生的"鬼影"现象和反射率峰突现象进行了驱动波形的分析设计与优化,消除了峰突的同时仅牺牲了4%的峰值反射率。最后,我们对电子纸彩色化方案进行讨论,并首次提出将转印工艺技术与电泳式电子纸相结合,成功制备了边长为300μm的方块彩色微胶囊子像素阵列,实现了空间混色的彩色电泳式电子纸,测得其NTSC的色域在三色子像素结构下为13.7%,较于已报道的基于CF彩色电子纸的3.14%有明显提升。     

Multicolor LCD for automotive applications

Segment-type, twisted nematic liquid-crystal panels with finely striped, two-color filters within the panel are discussed. The panel has a color filter-on-indium tin oxide structure. Two types of printed filter (an offset-printed (OP) filter and a screen-printed (SP) filter) were subjected to heat treatment and evaluated. It was found that an SP filter of about 0.3 μm has less effect on the operating voltage and availability for multiplexed drive than an OP filter of about 1 μm in thickness with the same color density. The test results for panel reliability for automotive use are given. The panels can digitally display a vehicle's speed, fuel level and engine revolutions in bargraph format with good legibility using three colors     

Display-device research and development in Japan

Current work on display devices in Japan is surveyed. Work on plasma display panels includes several methods for producing gray scale on ac-driven bistable panels, a technique for moving the display on an ac-driven panel, and new types of plasma display panels. Development on several types of alphanumeric displays, including both new and older types, is summarized. Work on light-emitting diodes includes new fabrication techniques and new types of devices. The liquid-crystal work described includes addressing techniques, color modulators, and light-addressed light valves. A new cathodochromic display tube, a high-frequency oscilloscope tube, and an electroluminescent display panel are mentioned.     

An experimental fluorescent dye panel

A fluorescent europium chelate is used as the active medium of an experimental display panel. When the chelate is dissolved in an electrolytic solvent and placed between transparent conductive electrodes, 2.8 V dc will cause the ultraviolet stimulated fluorescence to be extinguished at the cathode electrode. Recovery from the quenched state occurs spontaneously when the voltage is removed or when the polarity of the potential is reversed. A cross-conductor matrix display is discussed where discrete points are quenched by applying half-voltage to the rows and columns of the matrix.     

硅基液晶（LCOS）与电光特性

文章以向列相液晶的弹性理论和Jones矩阵方法为研究基础,给出了90°MTN模式的电压-反射率实验曲线,概述了硅基液晶（LCOS）所使用的反射式显示模式的电压开态特性。对红、绿、蓝三色光,给出了90°MTN和SCTN两种模式的电压-反射率特性曲线,强调了电压开态下的色散效应。对于5V的暗态工作电压,给出了TN-ECB-1和45°MTN两种模式对比度随盒厚的变化曲线。     

Nematic liquid-crystal displays: Some properties and limitations

The objectives of this study were to determine the feasibility of utilizing nematic liquid crystals (LC) as media for aircraft displays from the point of view of their temperature range, response time, gray scale, and color control. According to this objective, the dynamic scattering and tunable birefringence mode of operation were investigated in some detail. Experiments, in agreement with derived mathematical models, led to the following conclusions : 1) The nematic temperature range can be made to fit any reasonable specification by forming multiple eutectic mixtures, provided the ingredients are compatible. 2) "Write" or "contact" times less than 2 µs have been (and less than 0.1 probably can be) realized with the help of "blocking" diodes. However, true rise times become generally longer than 1 s at temperatures below -20° C and electric fields at or below 3 V/µm. 3) The optical properties of electricallyinduced (dynamic) scattering can, in a first order approximation, be described by specifying the liquid crystal birefringence ration_{0}/n_{e}their average refractive indexbar{n}, and the applied voltage. 4) Of several possible color display approaches, electrically tunable birefringence was selected as the most promising one. The widest viewing angle, |α| ≤30°, is achieved with reflective displays and best color definition (resolution Δλ/λ≃0.2) with retardations of Γ≃3/2 in "single stage" displays, as long as the overall cell thickness fluctuationDelta d < 0.1 lambda/(n_{e}-n_{0}). In addition, nematic liquid scattering and color display features are compared to those of PLZT, an electrooptic ceramic.     

Mixed Color Sequential Technique for Reducing Color Breakup and Motion Blur Effects

This paper proposes a mixed color sequential (MCS) algorithm with high contrast enhancement technique in RGB light-emitting diode (LED) backlight display. Owing to synchronous control of liquid crystal display (LCD) and LED panels, high quality image with suppressed color breakup (CBU) and motion blur effects is achieved by our novel color sequential technique. Importantly, MCS algorithm is useful for color filter-less optical compensated bend (OCB) panel display for alleviating CBU and motion blur effects. Furthermore, high contrast image is also presented on LCD panel because of mixed red-green-blue (RGB) and cyan-magenta-yellow (CMY) backlights with optimum power consumption. In other words, MCS algorithm with high contrast enhancement technique can have the better performance compared with other field sequential color techniques. Experimental results demonstrate by an actual RGB backlight module for 32-in 1366*768 LCD panel the improvement of CBU and motion blur effects.     

DC EL materials and techniques for flat-panel TV display

The preparation and properties of direct current electroluminescent (dc EL) materials using manganese-activated ZnS powders for a flat-panel TV display are described. The firing process, the copper coating process, and the ferming process have been investigated. Suitable powder phosphors for the display panel contain 0.1-0.5 wt % manganese and 0.25-0.35 wt % copper coated on the ZnS powder surface. Although the powder-type dc EL still has low luminous efficiency, the light output can be increased to a useful level by exciting the panel with voltage pulses of high peak power. The crosstalk effect in the display panel can also be suppressed, since the brightness is very nonlinear with respect to the applied voltage. The sealing of the panel with silicone oil is effective in lengthening the life of the panel. An experimental dc EL panel with a 13-in diagonal and 50 176 picture elements has been fabricated, capable of reproducing broadcast TV images. These images have a highlight brightness of 10 fL, a contrast ratio of 20:1, a limiting resolution of about 150 TV lines in both horizontal and vertical directions, and a gray-scale capability of 16 steps.     

A liquidic matrix-addressed display

Experiments with fluid logic circuits operated in an air-dyed water mode have demonstrated the basic validity of a large area, flat panel, matrix-addressed liquidic display. Such a display is conceptually attractive, since the switching, storage, and display functions are performed by the same medium. The measurements made have demonstrated that a reflective or emissive liquidic display, matrix addressed "a line at a time," has the following advantages: a flat panel geometry, a wide viewing angle, TV or better resolution, high contrast and brightness, a gray scale and color capability, speed (for TV resolution) from dc up to 3 frames/s, a range of sizes from small up to blackboard or larger, permanent memory, and high thermal, radiation, and shock resistance. The power requirements are less than (0.015/τ) W/cm²of display area, where τ is the frame time in seconds. Most importantly, the liquidic display can be constructed in a cheap integrated form. An elemental integrated liquidic display has been built with laminated layers of photoformed ceramic and has been successfully operated. Measurements made on the deflection of a fine stream of water (a polar liquid) by a nonuniform electric field have shown that this dielectrophoretic effect forms an elegant low-voltage transducer for the liquidic display. Such a transducer can be used on the periphery of a fluidically addressed matrix. Alternatively, because of its simplicity, it is feasible to have a threshold transducer at each element and electrically matrix address the transducers.     

新型低驱动电压电子纸显示单元的研究

研制了一种基于介质上电润湿(electrowetting-on-dielectric,EWOD)的新型低驱动电压电子纸反射式显示单元器件.本文分析了器件的工作原理以及性能影响因素,并提出用优化的氮化硅与碳氟聚合物复合介质层来改善器件的驱动电压.实验证实,器件在15V低电压驱动下成功实现了"开启"、"关闭"功能,其"开启"、"关闭"响应时间小于1/30s.     

IER film and inkjet printing method for full-color transflective cholesteric LCD

A transflective cholesteric liquid crystal display (Ch-LCD) is demonstrated by using the image-enhanced reflector (IER) film on the top of the transmissive region to provide the similar paths for both transmissive and reflective light, thus, to display same image color in any ambience, improving the image quality. For full color display, the inkjet printing was applied and the patterned Ch-LC droplet was successfully deposited on the substrate. Thus, full-color Ch-LCD can be fabricated by IJP.     

The differential voltage pen for plasma panels—A light pen substitute

A new hand-held interactive pen for ac plasma panels is described. The pen uses multiple metal plates to detect positional information generated by the regular write/erase voltages in the panel. No optical detector is used. Closed-form field potential equations of a panel line outside the panel are derived. These equations enable the resolution of the pen to be optimized; they are also helpful in pointing out some avoidable troublesome secondary effects. It is shown that a multiple plated probe's resolution is seven times better than that of a single-plate probe. This new pen can achieve resolutions to within 1 cell on panel artworks as dense as 50 lines/cm. Worst case detect time is 100 ms for a one million cell panel. Difficulties and special panel requirement when applied to a panel display product are discussed.     

A comparative study of maximum-power-point trackers for photovoltaic panels using switching-frequency modulation scheme

A comparative study of the maximum power point trackers using a switching-frequency modulation scheme (SFMS) for photovoltaic panels is presented. Some commonly used dc/dc converters, which are applied for the power conversion stage of those trackers, will be examined. Method of locating the maximum power point (MPP) is based on injecting a small-signal sinusoidal perturbation into the switching frequency of the converter and comparing the ac component and the average value of the panel's terminal voltage. Apart from not requiring sophisticated computation of the panel power, this SFMS does not approximate the panel characteristics and can globally locate the MPP under wide insolation conditions. Tracking capability of the converters under investigation will be compared, using a 10-W solar panel with a controlled experimental setup. Theoretical predictions will be verified with experimental results. Operating characteristics at steady state and in large-signal change of the insolation (incident solar radiation) level will be studied.     

用于高对比度反射式显示的扭曲PDLC

开发了一种采用扭曲边界聚合物分散型液晶(TPDLC)的高亮度、高对比度反射式显示器。与普通的PDLC膜相比，TPDLC不依赖于偏振光，具有高的对比度和低的工作电压。还演示了一种利用染料掺杂TPDLC的黑白笔段式字母反射式显示器。