Novel concept for full‐color electronic paper

Abstract— Despite a steep increase in commercial devices comprising paper‐like displays, a much desired feature is still missing: bright full‐color electronic paper. A new reflective‐display technology has been developed to solve this issue. For the first time, the principles behind this in‐plane electrophoretic technology will be presented, which enables the realization of full‐color reflective displays with a higher brightness than presently available e‐paper technologies, without compromising paper‐like properties such as viewing angle and ultra‐low power consumption. An additional major advantage (e.g., for future low‐cost manufacturing) is that, besides direct‐drive and active‐matrix configurations, a passive‐matrix option with analog gray levels has been successfully developed.     

Bright e‐skin technology and applications: Simplified gray‐scale e‐paper

Abstract— Bright‐color electronic‐paper technology based on in‐plane electrophoresis is very suitable for application in non‐emissive digital surfaces, such as electronic skins, eco‐skins, and electronic wallpaper for atmosphere creation. Aimed at these applications, simplified electrode geometries, aperiodic cell geometries, and a novel concept for built‐in gray levels have been developed.     

Transfer printing for fabrication of flexible RGB color e‐paper

Electrophoretic display (EPD) has been a prevailing paper‐like display technology for years, owing to its advantages of flexibility, low‐power consumption, and good sunlight readability. However, it is regrettable that the black/white EPD still dominates the majority of the market while a commercially sold full‐color EPD is still unavailable. In this paper, we proposed a facile yet feasible method to fabricate a color EPD by a tape‐assisted transfer method, which is the first demonstration using transfer method to achieve color micro‐encapsulated EPD.     

Ambient‐light‐adaptive image quality enhancement for full‐color e‐paper displays using a saturation‐based tone‐mapping method

Full‐color e‐paper displays that have a small color gamut encounter image tone distortions and contour artifacts in high‐saturation regions. To solve these issues, in this paper, we comprehensively measure the colorimetric responses of input image signals and demonstrate that the perceptual colorfulness in terms of chroma abnormally declines when the input saturation is beyond a certain value. Accordingly, saturation‐based tone‐mapping curves are developed to map the abnormal high saturation to the range that the display is able to normally render. By testing several test charts and natural images, the recoveries of the original image tones and the removals of the contour artifacts are experimentally verified. More important, by discussing how to conduct a database of tone‐mapping curves for different ambient lights and utilize the database for an unknown ambient light, the proposed method is proven to be completely ambient light adaptive.     

Predicting the viewing direction performance of e‐paper displays with front light under ambient lighting conditions

The inherent advantages of reflective e‐paper displays (EPD) – wide viewing direction range and excellent readability even under bright sunlight – can be extended into low‐light conditions by the addition of an integrated lighting unit (ILU) such as a front light. A methodology for predicting the viewing direction dependence of ambient contrast and color from display measurements and illumination models is here applied to reflective EPD where the ILU is switched on. The predictions can be used to optimize task lighting. The ILU improves the indoor performance of EPD without compromising their superior daylight performance.     

Color displays and flexible displays using quick‐response liquid‐powder technology for electronic paper

Abstract— Color displays and flexible displays that use electronic liquid powder have been developed. Novel types of color displays using either a colored powder or a color filter are discussed. We have also developed a flexible display with low‐cost substrate films with a high‐throughput roll‐to‐roll manufacturing method. These technologies enable a QR‐LPD to be widely used as an electronic‐paper display.     

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.     

A Flexible electronic‐paper display with an ultra‐thin and flexible LSI driver using quick‐response liquid‐powder technology

Abstract— A thin and flexible LSI driver with a thickness of less than 35 μm for a passive‐matrix‐driven Quick‐Response Liquid‐Powder Display (QR‐LPD?) was successfully mounted onto the flexible printed circuit (FPC) and the back substrates of a flexible QR‐LPD?. Amounted LSI driver on a plastic substrate shows no significant degradation in the driving performances and maintains physical flexibility without any connection failures. This technology can realize a fully flexible electronic paper in combination with a plastic‐substrate QR‐LPD? fabricated by a roll‐to‐roll process.     

A scalable manufacturing process for flexible active‐matrix e‐paper displays

Abstract— A scalable manufacturing process for fabricating active‐matrix backplanes on low‐cost flexible substrates, a key enabler for electronic‐paper displays, is presented. This process is based on solution processing, ink‐jet printing, and laser patterning. A multilayer architecture is employed to enable high aperture ratio and array performance. These backplanes were combined with E Ink electrophoretic media to create high‐performance displays that have high contrast, are bistable, and can be flexed repeatedly to a radius of curvature of 5 mm.     

The color properties of a reflective CMYK module using polymer‐dispersed liquid crystal (PDLC)

A reflective CMYK (cyan, magenta, yellow, and black) module using polymer‐dispersed liquid crystal (PDLC) is investigated for multi‐color reflective display. Combined with the electro‐optical properties and visible spectral reflectivity of PDLC films, the color properties of the reflective CMYK module were evaluated in terms of the Uniform Color Space‐CIE 1976 L*a*b*. It is found that the blue light reflectivity of the PDLC films is lower than green light and red light reflectivity. With the increase of the voltage applied on PDLC, the color lightness of the CMYK module generally decreases, while the color saturation increases. When the voltage changed from 0 to 70 V with a 5‐V change amplitude, modules C, M, Y, and K severally exhibit at least five, six, three, and seven colors.     

Color‐breakup evaluation of spatio‐temporal color displays with two‐ and three‐color fields

Abstract— Spatio‐temporal color displays have higher transmission and resolution than conventional LCDs, but suffer from color breakup. In this paper, a 120‐Hz display with two‐color filters and two‐color fields is described and the amount of color breakup is compared with that of a 180‐Hz full‐color‐sequential display with no color filters and three‐color fields. The results indicate that color breakup in a color‐filterless display is annoying, whereas it is just visible in displays with two‐color filters even though the refresh rate is much lower.     

Microcup® displays: Electronic paper by roll‐to‐roll manufacturing processes

Abstract— Rolls of flexible displays or electronic paper have recently been prepared by a high‐speed roll‐to‐roll manufacturing process based on SiPix's novel Microcup® and top‐sealing technologies. Both Microcup® electrophoretic displays (EPDs) and LCDs have been demonstrated. The display rolls are format flexible and may be cut into desirable size and shape for a variety of applications. High‐performance flexible passive‐matrix Microcup® EPDs having a wide range of threshold voltages have also been demonstrated.     

Surface treatment,reflectance, and age effects on electronic‐paper reading performance

Abstract— This study is intended to explore the legibility and visual fatigue of different age users under various surface treatments and reflectance of electronic paper. Through the method of character‐search task, the results indicated that compared with single types of treatment [anti‐reflection (AR) 0.8%, anti‐glare, 43% haze), the compound treatment of anti‐reflection and anti‐glare (ARC) exhibited the same legibility, and it showed superior properties to effectively reduce visual fatigue. Hence, it is suggested that electronic‐paper manufacturers should choose the compound surface treatment for better visual performance. On the other hand, the findings also validated that enhancing the reflectance of electronic paper to the same level as regular paper (about 80%) is worthy to be practically implemented. Based on the results of this study, electronic‐paper manufacturers can take useful information to fulfill ergonomic requirements on product design.     

Super‐reflective color LCD with PDLC technology

Abstract— A novel reflective color LCD without polarizers has been developed using a PDLC film and a retro‐reflector. Bright color images including moving images are achievable with ambient light. This novel LCD will enable the new application area of electronic paper.     

Active matrix monolithic micro‐LED full‐color micro‐display

An active matrix monolithic micro‐LED full‐color micro‐display with a pixel density of 317 ppi is demonstrated. Starting from large‐scale and low‐cost GaN‐on‐Si epilayers, monolithic 64 × 36 blue micro‐LED arrays are fabricated and further transformed to full‐color micro‐displays by applying a photo‐patternable color conversion layer. This full‐color fabrication scheme shows feasible manufacturability, suggesting a potential for volume production of micro‐LED full‐color micro‐display.     

Review of operating principle and performance of polarizer‐free reflective liquid‐crystal displays

Abstract— In this paper the operational principle and performance of guest‐host, liquid‐crystal/polymer‐composite scattering, and cholesteric liquid‐crystal reflective displays are reviewed. These displays do not use polarizers and have the advantage of providing high reflectance and compatibility with flexible plastic substrates.     

Color reproduction with a various number of sub‐pixels

Monochrome reflective‐type displays are widely used for portable reading applications such as electric papers because this type does not need a back light unit and can be used outdoors for a long time. Color reflective‐type displays without back light units are desired to expand the market further. The current color reproduction is based on three sub‐pixel red, green and blue (RGB) methods, and when used in reflective type, its luminance is reduced to a third of that of monochrome type. Adding a white sub‐pixel to the current method can improve the luminance, making the sub‐pixel number four. However, in the case of a high resolution display with a four‐sub‐pixel method, the pixel structure is complex, and the luminance improvement may be limited. Instead of increasing the sub‐pixel number, two sub‐pixel methods are investigated. These methods can improve luminance with limited color gamut. The performances are compared with those of other methods quantitatively.     

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.     

Controling color of liquid‐crystal displays

Abstract— Two newly derived characterization models for a liquid‐crystal (LC) display have been tested for five LC‐based displays. Data measured from a series of test colors indicated that all LC‐based displays showed similar characteristics, including an S‐shaped tone curve and poor channel chromaticity constancy. Because they include a hyperbolic function in their definition, the models do not have analytical inverses, and so iterative mathematical techniques are applied. It was shown that a new characterization model based on a hyperbolic function fits the tone curve very accurately with only four coefficients per channel for any type of LCD. In addition, it was also shown that the first derivative of the function provides a means of accurate correction of the chromaticity variation.     

Seventeen‐inch laser backlight in‐plane switching liquid crystal display with 8K, 120‐Hz driving,and BT.2020 color gamut

We have developed a 17‐inch laser backlight in‐plane switching liquid crystal display satisfying the main BT.2020 specifications, which are 8K, 120‐Hz driving, and a BT.2020 wide color gamut. The color gamut of the developed in‐plane switching liquid crystal display covers 98% of the BT.2020 wide color gamut, thanks to a laser backlight and appropriate color filters. The liquid crystal response time of 5 ms, which is sufficient for 120‐Hz driving, is achieved by adapting a faster in‐plane switching liquid crystal display, namely, the short‐range lurch control in‐plane switching liquid crystal display.