A fast‐switching OCB‐mode LCD for high‐quality display applications

Abstract— Optically compensated bend (OCB) mode is a promising technology, due to its wide range of viewing angles without gray‐scale inversion or color shift, fast response, high contrast ratio, and wide temperature range. This paper summarizes the fundamental characteristics of OCB mode and discusses the development of field‐sequential‐color displays and 3‐D displays for future high‐quality display applications.     

A field‐sequential‐color display with a local‐primary‐desaturation backlight scheme

Abstract— Field‐sequential‐color technology eliminates the need for color filters in liquid‐crystal displays (LCDs) and results in significant power savings and higher resolution. But the LCD suffers from color breakup, which degrades image quality and limits practical applications. By controlling the backlight temporally and spatially, a so‐called local‐primary‐desaturation (LPD) backlight scheme was developed and implemented in a 180‐Hz optically compensated bend (OCB) mode LCD equipped with a backlight consisting of a matrix of light‐emitting diodes (LEDs). It restores image quality by suppressing color breakup and saves power because it has no color filter and uses local dimming. A perceptual experiment was implemented for verification, and the results showed that a field‐sequential‐color display with a local‐primary‐desaturation backlight reduced the color breakup from very annoying to not annoying and even invisible.     

Analysis of electro‐optical properties of polymer‐stabilized OCB and the application to TFT‐LCDs

Abstract— A 9‐in. full‐color polymer‐stabilized OCB TFT‐LCD with stable bend alignment in the absence of an electric field was developed. The condition of the polymer stabilization, the characteristics of UV‐curable monomers, and their influence on the configurations of the polymer network in the cell were studied. Possible models of the configuration were proposed and their relationship to the electro‐optical properties was analyzed using a novel simulation method considering the distribution of anchoring effects from both alignment surfaces and the polymer network. It was suggested that a good performance such as high contrast ratio and fast response could be expected in the polymer network originating from newly developed monomers composed of multifunctional LC acrylates due to a relatively weak‐anchoring effect and presumably its localization near the alignment surfaces. By using the newly developed monomers under the optimized polymer‐stabilizing process, a high contrast ratio of 250:1 and fast response nearly equal to that of a conventional OCB cell were achieved.     

Relationship between mode‐boundary from surface color to fluorescent appearance and preferred gamut on wide‐gamut displays

Abstract— Color‐gamut design is a major concern in wide‐gamut displays. To determine a preferred gamut for displaying object color in natural scenes on a wide‐gamut display, subjective evaluations were conducted to investigate the preferred color and acceptable limit. Then, simple synthesized images were used to determine the mode boundary between surface color and fluorescent color appearance. It was found that (1) observers perceived the colors with high saturation and high lightness as fluorescent colors and (2) the fluorescent appearance decreased preference. The color‐mode index (CMI) was defined as an evaluation index of the color‐appearance mode so that the boundary between surface color and fluorescent color appearance was defined as CMI 100. Additionally, it was found that the CMI 100 loci could be interpreted as an optimal color loci. Then, it was clarified that the mode boundary and the preferred gamut were closely related and that the acceptable limit for L* was 1.1 times L* for CMI 100.     

Single‐cell‐gap transflective liquid‐crystal display using double‐ and single‐mode approaches

Abstract— In this paper, many popular methods to study transflective liquid‐crystal‐displays (LCDs) have been discussed, and several new transflective LCD configurations with a single‐cell gap have been proposed. The traditional double‐cell‐gap method gives the best match of the transmittance/reflectance voltage curve (TVC/RVC) and also the widest viewing angle, but also brings the highest fabrication complexity. The single‐cell‐gap transflective LCD is much easier to fabricate and also shows a good match of TVC/RVC. A new methodology has been shown to find optimal configurations for single‐cell‐gap transflective LCDs. New configurations using multimode in a single pixel include twisted nematic (TN) optically compensated bend (OCB), TN electrically controlled birefringence (ECB), and TN low‐twisted nematic (LTN). TN and hybrid‐aligned nematic (HAN) modes have been investigated for single‐mode transflective LCDs. The results exhibit high contrast ratio, a good match of TVC/RVC, as well as wide viewing angle.     

A photon‐mode full‐color rewritable image using photochromic compounds

Abstract— A photon‐mode full‐color rewritable image has been demonstrated. Three types of photochromic fulgides having yellow, magenta, and cyan color were used as rewritable dyes. Photochromic fulgides were mixed and coated on a white polyethylene terephthalate film. Upon irradiation with three (red, green, and blue) visible light beams, a wide hue extent, a high white reflectance of over 80%, and a high contrast ratio of over 45:1 were attained. A full‐color image retains its colors for over 1 hour under standard‐office‐brightness conditions (700 lx). The photochemical coloration‐decoloration cycles could be repeated over 100 times without substantial losses.     

Sequential‐color LCD based on OCB with an LED backlight

We have fabricated a 13.3‐in. XGA (1024 × 768) TFT sequential‐color liquid‐crystal display using optically compensated birefringency (OCB), illuminated by an LED backlight. We fabricated the sequential‐color display feasible process technology, and examined the performance and potential of a field‐sequential‐color scheme. The display was connected to a laptop computer and examined for flicker.     

High‐pixel‐rate grating‐light‐valve laser projector

Abstract— A high‐pixel‐rate, high‐contrast (30,000:1) wide‐color‐gamut grating‐light‐valve laser projector is reported. A new optical engine enabling high‐frame‐rate (240 Hz) scan projection is employed. Panoramic wide‐angle‐scan projection with a 64:9 aspect ratio was also developed. Speckle noise is eliminated using a simple but highly efficient technique. The optical throughput efficiency of the grating‐light‐valve laser projector is reviewed.     

Patterned liquid‐crystal laser film for multi‐dimensional multi‐color emissive film technology

Abstract— A two‐dimensional array consisting of dye‐doped reflection‐mode holographic‐polymer‐dispersed liquid crystal (H‐PDLC) lasers with alternating pitch lengths is presented. These post structures each reflect at a narrow bandwidth of light. The addition of laser dye to the H‐PDLC system allows for the generation of laser emission at the edge of the reflection band, or photonic band gap. In patterning these H‐PDLC post structures, a narrow‐linewidth patterned emissive color film is realized. The potential of such films and their implication in the display industry is discussed. In creating a three‐color array, an active emissive color film could replace the backlight and color filter components within the display. Such a patterned system would possess a wide color gamut, through spatial color synthesis, formed by narrow‐linewidth lasing structures with well‐defined wavelengths of emission.     

Electro‐optic properties of an intrinsic half‐V‐mode FLCD and its application to field‐sequential full‐color LCDs using a poly‐Si TFT matrix array

Abstract— An intrinsic half‐V‐mode ferroelectric liquid‐crystal display (FLCD) exhibiting a high contrast ratio (300:1), owing to defect‐free gray‐scale capability, with a high response speed (τ ? 400 μsec) and good switchability with TFTs, has been developed. Furthermore, this FLCD features high‐temperature reliability owing to the use of a special hybrid alignment technique. We successfully fabricated an active‐matrix poly‐Si TFT field‐sequential full‐color (FS FC) LCD with XGA specifications and a 0.9‐in. diagonal using a half‐V‐mode FLCD and an RGB light‐emitting‐diode (LED) array microdisplay. It is shown that the fabricated active‐matrix FS FCLCD exhibits good moving‐image performance with high full‐color display capability.     

Development of 100‐in. TFT‐LCDs for HDTV and public‐information‐display applications

Abstract— LCDs have achieved a full‐high‐definition resolution of 1920 × 1080 (16:9), 600‐nit brightness, 3000:1 dynamic contrast ratio, 92% color gamut, 178° viewing angle, and 5‐msec response time at all gray levels and are targeted for HDTV and public‐information‐display applications. Some unique technologies, such as Cu bus line, advanced wide view polarizer, and wide‐color‐gamut lamp, were applied. A new stitching‐free technology was developed to overcome the size limitation of the photomask in both the TFT and color‐filter processes. The size of the panel (100 in.), based on the wide format (16:9), is determined by the maximum efficiency of the world's first seventh‐generation line (glass size, 1950 × 2250 mm) in LG.Philips LCD's (LPL) Paju display cluster. The issues facing 100‐in. TFT‐LCDs will be discussed.     

High‐efficiency optical system for ultra‐short‐throw‐distance projector based on multi‐laser light source

Abstract— A novel laser‐light‐source projector having the three outstanding features of high brightness, ultra‐short throw distance, and high color reproduction has been developed.These features have recently come to be required in the high‐end projector market. The technologies for the laser‐light‐source projectors fully utilize the advantages of lasers, such as high luminance, small étendue, and high color purity. By integrating a triple‐rod illumination system with a multi‐laser light source and an ultra‐wide‐angle projection system, the developed high‐efficiency optical system has achieved a brightness of 7000 lm and a throw ratio of 0.28 with an image size of 100–150 in. Another new technology, laser color processing (LCP), has offered vivid color reproduction which has a color gamut that is up to 180% wider than the BT.709 standard without appearing unnaturally colored. Furthermore, a speckle suppression effect produced by the multi‐laser light source has been demonstrated. In this paper, an overview of these newly developed technologies that are used in the novel laser‐light‐source projector is presented, and solutions to the issues of speckle noise and safety are presented.     

Novel WV film for wide‐viewing‐angle TN‐mode LCDs

Abstract— A new optical compensation film refered to as WV‐EA film for TN‐mode TFT‐LCDs has been developed, resulting in higher contrast ratio, wider‐viewing‐angle characteristics, and improved color shift than their predecessors, especially in the horizontal direction. These features of the new WV film were achieved as a result of haze reduction and optimizing the optical characteristics of the polymerized discotic material layer and TAC film. These features are suitable for large‐sized and wide‐aspect‐ratio LCD monitors and TVs.     

A new solution for splay‐to‐bend transition in OCB mode with a twisted area

Abstract— Quick, stable transition from splay‐to‐bend alignment in optically compensated bend (OCB) mode is crucial for practical use. This has been achieved by surface treating part of a pixel with a chiral dopant to induce a twist alignment while controlling the twist direction. The effectiveness of this new method was confirmed in a prototype TFT‐LCD panel.     

Heuristic approach to selecting a color appearance model for hue‐preserved wide‐color gamut mapping

With the advent of wide‐gamut system colorimetry for ultra‐high definition television, the development of a gamut mapping algorithm for wide to standard gamuts is greatly needed. Most gamut mapping techniques have been developed to retain the perceived hues of the source as predicted by a color appearance model. However, some color appearance models erroneously predict the saturated colors, generating a serious hue discontinuity in wide‐color gamut mapping onto the Rec. 709 gamut boundary. This paper presents a heuristic approach to determining whether a color appearance model may create such artifacts when used in hue‐preserved gamut mapping algorithms.     

Color‐conversion method for a multi‐primary display to reduce power consumption and conversion time

Abstract— A color‐conversion method for a light‐emitting multi‐primary‐color display is proposed. While amulti‐primary‐color display uses four or more primary colors to reproduce a wide color gamut, multiple sets of primary‐color signals are needed to reproduce one color. Therefore, linear programming, which results in low power consumption, was adopted to uniquely determine the set of primary‐color signals. Although a highly accurate color conversion was achieved by using linear programming with low power consumption, it requires a very long time to convert colors of high‐resolution images. Therefore, by categorizing the color conversion of linear programming as a classification problem, colors are converted by using the decision‐tree method, which is a classification method. As a result, color conversion with high accuracy, low power consumption, and short conversion time was achieved.     

Super‐large‐sized TFT‐LCD (55 in.) for HDTV application

Abstract— We have developed the world's largest TFT‐LCD, which has a 55‐in.‐diagonal size. This LCD features a 1920 × 1080 (16:9) resolution for full‐HDTV images, 500‐nit luminance, 72% color gamut, and 12‐msec response time at all gray levels. The size of the panel (55 in.) was determined by the maximum efficiency of our fifth‐generation line (glass size: 1100 × 1250 mm). To overcome the limitation of size in photolithography equipment, a new stitcking‐free technology was applied in both the TFT and color‐filter side. And the super‐IPS mode was used as a wide‐viewing‐angle technology because it is suitable in the fabrication of large panels. In this paper, we present issues on both the fabrication and characteristics of the 55‐in. TFT‐LCD.     

Transmissive electrowetting‐based displays for portable multimedia devices

Abstract— Electrowetting‐based displays have been successfully demonstrated in reflective mode, showing video capability and high optical performance. However, because this technology is based on a high‐efficiency optical switch operating between a light‐absorbing state and a light‐transmitting state, the technology lends itself naturally to a transmissive mode enabling a complete range of applications. This paper describes the first active‐matrix full‐color transmissive electrowetting displays including its main technical and system aspects. Two architectures have been demonstrated: one uses color filters, the other field‐sequential‐color illumination. The paper also introduces alternative concepts for more efficient color transmissive electrowetting displays with multiple absorbing layers.     

A continuous‐viewing‐angle‐controllable liquid‐crystal display using a blue‐phase liquid crystal

Abstract— A continuous‐viewing‐angle‐controllable liquid‐crystal display (LCD) using a blue‐phase liquid crystal is proposed. To realize both wide‐viewing‐angle (WVA) mode and narrow‐viewing‐angle (NVA) mode with a single liquid‐crystal panel, each pixel is divided into a main pixel and a subpixel. The main pixel is for displaying images in both modes. The subpixel is for displaying images in WVA mode and controlling the viewing angle in NVA mode. The device exhibits a good viewing‐angle‐controlling characteristic and high transmittance.     

LED‐backlight feedback control system with integrated amorphous‐silicon color sensor on an LCD panel

Abstract— Thin‐film‐transistor liquid‐crystal displays (TFT‐LCDs) have the largest market share of all digital flat‐panel displays. An LCD backlighting system employing a three‐color red‐green‐blue light‐emitting diode (RGB‐LED) array is very attractive, considering its wide color gamut, tunable white point, high dimming ratio, long lifetime, and environmental compatibility. But the high‐intensity LED has problems with thermal stability and degradation of brightness over time. Color and white luminance levels are not stable over a wide range of temperature due to inherent long‐term aging characteristics. In order to minimize color point and brightness differences over time, optical feedback control is the key technology for any LED‐backlight system. In this paper, the feasibility of an optical color‐sensing feedback system for an LED backlight by integrating the amorphous‐silicon (a‐Si) color sensor onto the LCD panel will be presented. To minimize the photoconductivity degradation of a‐Si, a new laser exposure treatment has been applied. The integrated color‐sensor optical‐feedback‐controlled LED‐backlight system minimized the color variation to less than 0.008 Δu'v' (CIE1976) compared to 0.025 for an open‐loop system over the temperature range of 42–76°C.