E-Paper Technology 20

1. INTRODUCTION

Today's electronic displays have ever more evolved to be more lightweight, efficient and clear. Yet the importance of the paper has not diminished. We still prefer it to others for a variety of reasons including its readability, high contrast, convenient handling, minimum power requirement cost and strain less reading it offers. At the same time, an electronic display offers us a paperless environment and relieves us from carrying loads of paper for referring to information when required.Electronic ink is a pioneering invention that combines all the desired features of a modern electronic display and the sheer convenience and physical versatility of sheet of paper. E-paper or electronic paper is sometimes called radio paper or smart paper. Paper would be perfect except for one obvious thing: printed words can't change. The effort is to create a dynamic high-resolution electronic display that's thin and flexible enough to become the next generation of paper.The technology has been identified and developed is well under way. Within five years, it is envisioned electronic books that can display volumes of information as easily as flipping a page and permanent newspapers that update themselves daily via wireless broadcast. They deliver the readability of paper under virtually any condition, without backlighting. And electronic ink displays are persistent without power, drawing current only when they change, which means batteries can be smaller and last longer.

1.1 HistoryElectronic paper was first developed in the 1970s by Nick Sheridon at Xeroxs Palo Alto Research center. The first electronic paper, called Gyricon, consisted of tiny, statically charged balls that were black on one side and white on the other. The "text" of the paper was altered by the presence of an electric field, which turned the balls up or down.

In the 1990s another type of electronic paper was invented by Joseph Jacobson, who later co- founded the corporation E Ink which formed a partnership with Philips Components two years later to develop and market the technology

2. TECHNOLOGY USED2.1 GyriconElectronic paper was first developed in the 1970s by Nick Sheridon at Xerox's Palo Alto Research Center. The first electronic paper, called Gyricon, consisted of polyethylene spheres between 75 and 106 micrometers across. Each sphere is a Janus particle composed of negatively charged black plastic on one side and positively charged white plastic on the other(each bead is thus a dipole). The spheres are embedded in a transparent silicone sheet, with each sphere suspended in a bubble of oil so that they can rotate freely. The polarity of the voltage applied to each pair of electrodes then determines whether the white or black side is face-up, thus giving the pixel a white or black appearance. At the FPD 2008 exhibition, Japanese company Soken has demonstrated a wall with electronic wall-paper using this technology

2.2 ElectrophoreticAn electrophoretic display forms visible images by rearranging charged pigment particles using an applied electric field.

In the simplest implementation of an electrophoretic display, titanium dioxide particles approximately one micrometer in diameter are dispersed in a hydrocarbon oil. A dark-colored dye is also added to the oil, along with surfactants and charging agents that cause the particles to take on an electric charge. This mixture is placed between two parallel, conductive plates separated by a gap of 10 to 100 micrometers. When a voltage is applied across the two plates, the particles will migrate electrophoretically to the plate bearing the opposite charge from that on the particles. When the particles are located at the front (viewing) side of the display, it appears white, because light is scattered back to the viewer by the high- index titanium particles. When the particles are located at the rear side of the display, it appears dark, because the incident light is absorbed by the colored dye. If the rear electrode is divided into a number of small picture lements (pixels), then an image can be formed by applying the appropriate voltage to each region of the display to create a pattern of reflecting and absorbing regions.

Electrophoretic displays are considered prime examples of the electronic paper category, because of their paper- like appearance and low power consumption. Electrophoretic displays can be manufactured using the Electronics on Plastic by Laser Release (EPLaR) process developed by Philips Research to enable existing AM-LCD (Active matrix liquid crystal display) manufacturing plants to create flexible plastic displays.

2.2.1. Electronics on Plastic by Laser Release (EPLaR) :Electronics on Plastic by Laser Release (EPLaR) is a method for manufacturing flexible electrophoretic display using conventional AM-LCD manufacturing equipment avoiding the need to build new factories. The technology can also be used to manufacture flexible OLED (Organic LED) displays using standard OLED fabrication facilities. The technology was developed by Philips Research and uses standard display glass as used in TFT-LCD processing plants. It is coated with a layer of polyimide using a standard spin-coating procedure used in the production of AM-LCD displays. This polymide coating can now have a regular TFT matrix formed on top of it in a standard TFT processing plant to form the plastic display, which can then be removed using a laser to finish the display and the glass reused thus lowering the total cost of manufacture.2.2.2 Development in Electrophoretic Display:In the 1990s another type of electronic paper was invented by Joseph Jacobson, who later co- founded the E Ink Corporation which formed a partnership with Philips Components two years later to develop and market the technology. In 2005, Philips sold the electronic paper business as well as its related patents to Prime View International. This used tiny microcapsules filled with electrically charged white particles suspended in colored oil. In early versions, the underlying circuitry controlled whether the white particles were at the top of the capsule (so it looked white to the viewer) or at the bottom of the capsule (so the viewer saw the color of the oil). This was essentially a reintroduction of the well-known electrophoretic display technology, but the use of microcapsules allowed the display to be used on flexible plastic sheets instead of glass.

One early version of electronic paper consists of a sheet of very small transparent capsules, each about 40 micrometers across. Each capsule contains an oily solution containing black dye (the electronic ink), with numerous white titanium dioxide particles suspended within. The particles are slightly negatively charged, and each one is naturally white.

The microcapsules are held in a layer of liquid polymer, sandwiched between two arrays of electrodes, the upper of which is made transparent. The two arrays are aligned so that the sheet is divided into pixels, which each pixel corresponding to a pair of electrodes situated either side of the sheet. The sheet is laminated with transparent plastic for protection, resulting in an overall thickness of 80 micrometers, or twice that of ordinary paper. The network of electrodes is connected to display circuitry, which turns the electronic ink 'on' and 'off' at specific pixels by applying a voltage to specific pairs of electrodes. Applying a negative charge to the surface electrode repels the particles to the bottom of local capsules, forcing the black dye to the surface and giving the pixel a black appearance. Reversing the voltage has the opposite effect - the particles are forced from the surface, giving the pixel a white appearance. A more recent incarnation of this concept requires only one layer of electrodes beneath the microcapsules.2.3 Electro wettingElectro-wetting display (EWD) is based on controlling the shape of a confined water/oil interface by an applied voltage. With no voltage applied, the (colored) oil forms a flat film between the water and a hydrophobic (water-repellent), insulating coating of an electrode, resulting in a colored pixel.When a voltage is applied between the electrode and the water, the interfacial tension between the water and the coating changes. As a result the stacked state is no longer stable, causing the water to move the oil aside.

This results in a partly transparent pixel, or, in case a reflective white surface is used under the switchable element, a white pixel. Because of the small size of the p ixel, the user only experiences the average reflection, which means that a high-brightness, high-contrast switchable element is obtained, which forms the basis of the reflective display. Displays based on electro-wetting have several attractive features. The switching between white and colored reflection is fast enough to display video content.

It is a low-power and low-voltage technology, and displays based on the effect can be made flat and thin. The reflectivity and contrast are better or equal to those of other reflective display types and are approaching those of paper. In addition, the technology offers a unique path toward high-brightness full-color displays, leading to displays that are four times brighter than reflective LCDs and twice as bright as other emerging technologies.

Instead of using red, green and blue (RGB) filters or alternating segments of the three primary colors, which effectively result in only one third of the display reflecting light in the desired color, electro-wetting allows for a system in which one sub-pixel is able to switch two different colors independently. This results in the availability of two thirds of the display area to reflect light in any desired color. This is achieved by building up a pixel with a stack of two independently controllable colored oil films plus a color filter.2.4 ElectrofluidicElectrofluidic displays are a variation of an electrowetting display. Electrofluidic displays place an aqueous pigment dispersion inside a tiny reservoir. The reservoir comprises 85% white state reflectance for electronic paper.

3. KEY BENEFITSE-Paper has numerous benefits. The reader does not need to get used to a new format - reading an E-Paper equals reading a printed newspaper. However, E-Paper guarantees independency regarding room and time. E-Paper can be read everywhere in the world, at every hour, and since digital editions can also be received on PDAs and smart phones, mobility is almost limitless. Additionally, E-Paper saves resources. On the one hand, paper and space are saved - because E-Paper does not pile up anywhere - on the other hand, valuable time is saved. Since the complete pages are displayed on the PC monitor, one instantly gets an overview over all headlines and thus gets to the relevant articles a lot faster Unlike conventional LCD's and other kinds of reflective displays, an electronic ink display is exceptionally bright and is ready viewable under both bright and dim lighting conditions. To be more assertive we could compare electronic ink display with the latest liquid crystal displays.

Table 3.1: Comparison of E- ink & LCD

3.1 Paper-like ReadabilityPaper is easily readable over wide variations in lighting conditions and viewing angle. E Ink's electronic ink technology approaches printed paper in performance by incorporating the same coloring pigments often used to make paper white and ink black. When reading text, both reflectance and contrast are important factors in determining the readability of a display. In fact, the contrast of E Ink is nearly twice that of printed newspaper. As can be seen from its high reflectance and contrast the E Ink display is much more readable than LCD. The bright paper-white background of electronic ink eliminates the need for a backlight is most conditions.

3.2 Ultra-Low Power ConsumptionElectronic ink displays offer greatly reduced power consumption. Lower power consumption translates to longer battery life, and perhaps more importantly, the ability to use smaller batteries in electronic ink devices- reducing device weight and cost. The reason for the reduced power consumption offered by electronic ink displays is two- fold: (1) they are completely reflective requiring no backlight and (2) they are inherently bi-stable for extended periods of time. Once an image is written on an electronic ink display, it will be retained without additional power input until the next image is written. Hence the power consumption of an electronic ink display will ultimately depend upon the frequency at which the displayed image is changed. However, in both cases, a reduction in power consumption by several orders of magnitude can be achieved by using electronic ink with its bi-stable imaging.3.3 Thin, Light Form FactorAn electronic ink display module is thinner, lighter weight, and more robust than conventional LCD's. These benefits are especially important in smart handheld applications where portability is paramount. First generation, electronic ink displays will be but by laminating electronic ink to a conventional glass TFT substrate In addition, no polarizes are required for electronic ink displays. The resulting electronic ink display cell is also about half that of a typical LCD cell. Elimination of the glass top sheet means that displays made with an electronic ink display module should be inherently more robust.3.4 The Ultimate Mobile Display SolutionPaper-like viewing characteristics and appearance, combined with ultra- low power consumption and thin light form factors, make E ink's electronic ink display material the ideal technology solution for information intensive, handheld devices such as PDAs, mobile phones and electronic readers; or any applications requiring a high degree of display legibility.3.5 TwistableElectronic Paper is made using soft plastic containing small particles and fluid. As there is no hard material, Electronic Paper is highly flexible and it is able to be twisted or bended into different curvatures. The Electronic Paper can be applied to different shapes of products, without being limited to being bonded to flat display panels. The end product becomes more imaginative in shape and style.3.6 Simple Manufacturing Process

The manufacturing process is carried out using a roll- to-roll method, similar to printing paper, by injecting dielectric fluid and charged particles into the layer of capsules, and then sealing the top layer. The production is performed continuously at high speed. The Electronic Paper can be produced in a large form and then cut into any desired size and shape for different application requirements.

4. HIGHLIGHTS OF ELECTRONIC INK

Electronic ink moves information display to a new dynamic level, with dramatic benefits over traditional media.

Superior Look - Because it's made from the same basic materials as regular ink and paper, electronic ink retains the superior viewing characteristics of paper, including high contrast, wide viewing angle, and bright paper-white background.

Versatile - Electronic ink can be printed on almost any surface, from plastic to metal to paper. And it can be coated over large areas cheaply.

Low Power - Electronic ink is a real power miser. It displays an image even when the power is turned off and it's even legible in low light reducing the need for a backlight. This can significantly extend battery life for portable devices.

Scalable - E Ink's electronic ink process is highly scalable, which makes it competitive against today's older technologies.

5. ADVANTAGES & DISADVANTAGES5.1 Advantages5.1.1 ReadableE-Paper is easily readable even in direct sunlight because E-Paper displays reflect light like ordinary paper.An E-paper display has the appearance of ordinary ink on paper, for it reflects light like ordinary paper. Unlike conventional LCD displays, which emit lights, the E-paper display is highly readable, not only indoors but also in direct sunlight, and the image on it is clear and modest,without flickering, and the viewing angle is near 180. Therefore, its very suitable for reading.5.1.2 RuggedE-Paper displays are rugged... meaning they are flexible, lightweight, durable and reliable. Compared to LCD displays, the E-paper displays have obvious advantage in thickness and eight, and due to the polymer film based structure, it'sflexible in shape and size. What's more, E-paper is durable and reliable. The flexibility feature of E-paper enables its various applications, even for some extreme requirements that other types of display technology cannot meet.5.1.3 GreenIf we could replace all paper newspapers with eNewspapers tomorrow, it would save 95 million trees which could remove 98 million tons of greenhouse gas each year. The E-paper display is energy efficient due to two advantages it has. Firstly, it doesn't use a back light which consume most power, but rather, it mimics the picture by reflecting ambient light. Secondly, it's bi-stable, which means no power is needed to hold a static picture. This makes the E-paper display consume much less power than conventional displays, such as LCD displays. We know that less power consumption means longer lasting battery life. Therefore, E-paper displays are highly suitable for the products which are limited to the size or require extreme battery condition.

5.2. Disadvantages5.2.1 Very low refresh rateElectronic paper technologies have a very low refresh rate comparing with other low power display technologies, such as LCD. This prevents producers from implementing sophisticated interactive applications (using fast moving menus, mouse pointers or scrolling) like those which are possible on handheld computers. An example of this limitation is that a document cannot be smoothly zoomed without either extreme blurring during the transition or a very slow zoom.

5.2.3 Ghost imagesAnother limitation is that an imprint of an image may be visible after refreshing parts of the screen. Those imprints are known as "ghost images", and the effect is known as "ghosting". This effect is reminiscent of screen burn- in but, unlike it, is solved after the screen is refreshed several times. Turning every pixel white, then black, then white, helps normalize the contrast of the pixels. This is why several devices with this technology "flash" the entire screen white and black when loading a new image, in order to prevent ghosting from happening.

6. APPLICATIONSElectronic Paper behaves similarly to conventional paper, allowing high readability under low or high light conditions, and being thin and lightweight and fully pliable. In addition, Electronic Paper has the advantage of allowing the content to be changed easily at any time via the electronic Paper driver IC. Electronic Paper will provide a viable substitute to paper in certain areas. Some examples of Electronic Paper applications are described below.

6.1 Electronic Shelf LabelIn a large department store or supermarket, there are many price tag labels on the shelves indicating product price. Whenever there is a change of price information, it is very tedious to change the price tags individually. By replacing the paper price tag with Electronic Paper, the price information can be easily updated once the Electronic Paper price tags are connected via a wireless network.

The Electronic Paper price tag requires no battery power to maintain display and prices can be updated using the energy from the RF wave to change the image content.

6.2 Electronic Watch and Clock

Watch and clock designs can become more imaginative using Electronic Paper.

For example, a watch using Electronic Paper will allow time and image to be displayed on the wrist strap of the watch.

6.3 e-Books

In 2004 Sony released Libri EBR-1000EP in Japan, the first e-book reader with an Electronic paper display. In November 2006, the iRex iLiad was ready for the consumer market. In November 2009 Barnes and Noble launched the Barnes & Noble Nook, based on the Android operating system. In late 2007, Amazon began producing and marketing the Amazon Kindle, an e-book reader with an e-paper display.

6.4 Smart Card DisplayToday, many credit cards contain a smart card to store information such as accumulated credit and money expenses etc. Since Electronic Paper has the advantage of lower power consumption and is as flexible as the card, it offers a good solution to displaying this type of information on the card.

6.5 NewspapersIn February 2006, the Flemish daily De Tijd distributed an electronic version of the paper to select subscribers in a limited marketing study, using a pre-release version of the iRex iLiad. This was the first recorded application of electronic ink to newspaper publishing. In September 2007, the French daily Les chos announced the official launch of an electronic version of the paper on a subscription basis. Since January 2008, the Dutch daily NRC Handelsblad is distributed for the iRex iLiad reader.

6.6 Other ProductsE- Ink unveiled its first product using electronic ink- immediate large-area displays- in 1999. These large signs draw only 0.1 watts of power, which means that the same power required running a single 100-watt light bulb, could power 1,000 immediate signs. E Ink said that in electronic devices, electronic ink would use 50 to 100 t imes power than liquid crystal displays because electronic ink only needs power when changing its display. Electronic ink can be printed on any surface, including walls, billboards, product labels and T-shirts. Homeowners could soon be able to instantly change their digital wallpaper by sending a signal to the electronic ink painted on their walls.

7. THE FUTURE SCENARIOThe Holy Grail of electronic ink technology is a digital book that can typeset itself and that readers could leaf through just as if it were made of regular paper. Such a book could be programmed to display the text from a literary work and once you've finished that tale, you could automatically replace it by wirelessly downloading the latest book from a computer database. Xerox had introduced plants to insert a memory device into the spine of the book, which would allow users to alternate between up to 10 books stored on the device.

Just as electronic ink could radically change the way we read books, it could change the way you receive your daily newspaper. It could very well bring an end to newspaper delivery, as we know it. Instead of delivery people tossing the paper from their bike or out their car window, a new high- tech breed of paper deliverers who simply press a button on their computer that would simultaneously update thousands of electronic newspapers each morning. Sure, it would look and feel like your old paper, but you wouldn't have to worry about the newsprint getting smudged on your fingers, and it would also eliminate the piles of old newspapers that need recycling. Prior to developing digital books and newspapers E-Ink will be developing a marketable electronic display screen for cell phones, PDA's, pagers and digital watches.

8. CONCLUSIONElectronic ink is not intended to diminish or do away with traditional displays. Instead electronic ink will initially co-exist with traditional paper and other display technologies. In the long run, electronic ink may have a multibillion-dollar impact on the publishing industry. Ultimately electronic ink will permit almost any surface to become a display, bringing information out of the confines of traditional devices and into the world around us.

9. BIBLIOGRAPHY[1] http://en.wikipedia.org/wiki/Electronic_paper.[2] Comiskey, B.; Albert, J. D.; Yoshizawa, H.; Jacobson, J. "An electrophoretic ink for allprinted reflective electronic displays" Nature 1998, 394, (6690), 253-255.

Bsc. Information TechnologyMGMs Dr. G. Y. Pathrikar College of CS & IT