Electronic paper, e-paper or electronic ink display is a display technology designed to mimic the appearance of ordinary ink on paper. Unlike a conventional flat panel display, which uses a backlight to illuminate its pixels, electronic paper reflects light like ordinary paper and is capable of holding text and images indefinitely without drawing electricity, while allowing the image to be changed later.

To build e-paper, several different technologies exist, some using plastic substrate and electronics so that the display is flexible. E-paper is considered more comfortable to read than conventional displays. This is due to the stable image, which does not need to be refreshed constantly, the wider viewing angle, and the fact that it reflects ambient light rather than emitting its own light. An e-paper display can be read in direct sunlight without the image appearing to fade. Lightweight and durable, e-paper can currently provide color display. The contrast ratio in available displays as of 2008 might be described as similar to that of newspaper, though newly-developed implementations are slightly better.[1] There is ongoing competition among manufacturers to provide full-color capability.

Applications include electronic pricing labels in retail shops, and general signage,[2] time tables at bus stations,[3] electronic billboards,[4] the mobile phone Motorola FONE F3, and e-Readers capable of displaying digital versions of books and e-paper magazines. Electronic paper should not be confused with digital paper, which is a pad to create handwritten digital documents with a digital pen.

Technology

Gyricon

Electronic paper was first developed in the 1970s by Nick Sheri don 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 [5] ). 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.[6] At the FPD 2008 exhibition, Japanese company Soken has demonstrated a wall with electronic wall-paper using this technology.[7]

[edit] Electrophoretic

Scheme of an electrophoretic display.

Scheme of an electrophoretic display using color filters.

An 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 micrometre 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 micrometres. 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 elements (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.

Examples of commercial electrophoretic displays include the high-resolution active matrix displays used in the Amazon Kindle, Barnes & Noble Nook, Sony Librie, Sony Reader, and iRex iLiad e-readers. These displays are constructed from an electrophoretic imaging film manufactured by E Ink Corporation. Also the technology has been developed by Sipix Microcup [8] and Bridgestone Quick Response Liquid Powder Display (QR-LDP).[9][10] The Motorola MOTOFONE F3 was the first mobile phone to use the technology, in an effort to help eliminate glare from direct sunlight during outdoor use.[11]

Electrophoretic displays can be manufactured using the Electronics on Plastic by Laser Release (EPLaR) process developed by Philips Research to enable existing AM-LCD manufacturing plants to create flexible plastic displays.

[edit] Development

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 a colored oil.[12] 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 micrometres 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.[6]

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 micrometres, or twice that of ordinary paper.

Appearance of pixels

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[13] of this concept requires only one layer of electrodes beneath the microcapsules.

[edit] Electrowetting

Main article: Electrowetting

Electro-wetting display (EWD) is based on controlling the shape of a confined water/oil interface by an applied voltage. With no voltage applied, the (coloured) oil forms a flat film between the water and a hydrophobic (water-repellent), insulating coating of an electrode, resulting in a coloured 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 pixel, 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 coloured 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-colour displays, leading to displays that are four times brighter than reflective LCDs and twice as bright as other emerging technologies.[14]

Instead of using red, green and blue (RGB) filters or alternating segments of the three primary colours, which effectively result in only one third of the display reflecting light in the desired colour, electro-wetting allows for a system in which one sub-pixel is able to switch two different colours independently.

This results in the availability of two thirds of the display area to reflect light in any desired colour. This is achieved by building up a pixel with a stack of two independently controllable coloured oil films plus a colour filter.

The colours used are cyan, magenta and yellow, which is a so-called subtractive system, comparable to the principle used in inkjet printing for example. Compared to LCD another factor two in brightness is gained because no polarisers are required.[15]

Examples of commercial electrophoretic displays include Liquavista [16] , ITRI [17] , PVI and ADT.[18][19]

[edit] Electrofluidic

Electrofluidic displays are a variation of an electrowetting display. Electrofluidic displays place an aqueous pigment dispersion inside a tiny reservoir. The reservoir comprises <5-10% of the viewable pixel area and therefore the pigment is substantially hidden from view.[20] Voltage is used to electromechanically pull the pigment out of the reservoir and spread it as a film directly behind the viewing substrate. As a result, the display takes on color and brightness similar to that of conventional pigments printed on paper. When voltage is removed liquid surface tension causes the pigment dispersion to rapidly recoil into the reservoir. As reported in the May 2009 Issue of Nature Photonics, the technology can potentially provide >85% white state reflectance for electronic paper.

The core technology was invented at the Novel Devices Laboratory at the University of Cincinnati. The technology is currently being commercialized by Gamma Dynamics.

[edit] Other bistable displays

See also: Bistable Kent Displays , manufacturer of cholesteric liquid crystal display (ChLCD).[21]

Nemoptic , Nematic materials[22]

TRED [23]

[edit] Other technologies

Other research efforts into e-paper have involved using organic transistors embedded into flexible substrates,[24][25] including attempts to build them into conventional paper.[26] Simple color e-paper[27] consists of a thin colored optical filter added to the monochrome technology described above. The array of pixels is divided into triads, typically consisting of the standard cyan, magenta and yellow, in the same way as CRT monitors (although using subtractive primary colors as opposed to additive primary colors). The display is then controlled like any other electronic color display.

Examples of electrochromic displays include Acreo [28] , Ajjer [29] , Aveso [30] and Ntera.[31]

[edit] Disadvantages

Electronic 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.

An e-ink screen showing the "ghost" of a previous image

Another 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.

Applications

Several companies are simultaneously developing electronic paper and ink. While the technologies used by each company provide many of the same features, each has its own distinct technological advantages. All electronic paper technologies face the following general challenges:

A method for encapsulation An ink or active material to fill the encapsulation Electronics to activate the ink

Electronic ink can be applied to both flexible and rigid materials. In the case of flexible displays, the base requires a thin, flexible material tough enough to withstand considerable wear, such as extremely thin plastic. The method of how the inks are encapsulated and then applied to the substrate is what distinguishes each company from each other. These processes are complex and are carefully guarded industry secrets. The manufacture of electronic paper promises to be less complicated and less costly than traditional LCD manufacture.

There are many approaches to electronic paper, with many companies developing technology in this area. Other technologies being applied to electronic paper include modifications of liquid crystal displays, electro chromic displays, and the electronic equivalent of an Etch A Sketch at Kyushu University. Advantages of electronic paper includes low power usage (power is only drawn when the display is updated), flexibility and better readability than most displays. Electronic ink can be printed on any surface, including walls, billboards, product labels and T-shirts. The ink's flexibility would also make it possible to develop roll able displays for electronic devices. The ideal electronic paper product is a digital book that can typeset itself and could be read as if it were made of regular paper, yet programmed to download and display the text from any book. Another possible use is in the distribution of an electronic version of a daily paper.

Commercial applications

The Motorola F3 uses an e-paper display instead of an LCD.

[edit] Education: digital schoolbooks

In January 2007, the Dutch specialist in e-Paper edupaper.nl started a pilot project in a secondary school in Maastricht, using e-Paper as digital schoolbooks to reduce costs and students' daily burden of books.

[edit] wristwatches

In December 2005 Seiko released their Spectrum SVRD001 wristwatch, which has a flexible electrophoretic display.[32]

Phosphor of Hong Kong have launched 3 series of watches using flexible electrophoretic display using eink technology.[33]

[edit] e-Books

Main article: List of e-book readers In September 2006 Sony released the PRS-500 Sony Reader e-book reader.

On October 2, 2007, Sony announced the PRS-505, an updated version of the Reader. In November 2008, Sony released the PRS-700BC which incorporated a backlight and a touchscreen.

In November 2006, the iRex iLiad was ready for the consumer market. Consumers could initially read e-Books in PDF and HTML formats, and in July 2007 support for the popular Mobipocket PRC format was added, but price was still a problem. With the introduction of the competing Cybook, prices have decreased almost 50%.

In late 2007, Amazon began producing and marketing the Amazon Kindle, an e-book with an e-paper display. In February 2009, Amazon released the Kindle 2 and in May 2009 the larger Kindle DX was announced.

[edit] Newspapers

In 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 Échos announced the official launch of an electronic version of the paper on a subscription basis. Two offers are available, combining a one year subscription and a reading device. One interesting point of the offer is the choice of a light (176g) reading device (adapted for Les Echos by Ganaxa) or the iRex iLiad. Two different processing platforms are used to deliver readable information of the daily, one based on the newly developed GPP electronic ink platform from Ganaxa, and the other one developed internally by Les Echos.

Since January 2008, the Dutch daily NRC Handelsblad is distributed for the iRex iLiad reader.

[edit] Digital Photo Frame

In the future as electronic paper displays improve and full high quality color is possible, the technology may become incorporated in digital photo frame products. Existing digital photo frames require a constant power supply and have a limited viewing angle and physical thickness that is inferior to a conventional photograph. A digital photo frame using e-paper technology would address all of these shortcomings. A well-designed digital photo frame using an electronic ink display could, in theory, run for months or years from batteries, because such a device would require electricity only to briefly boot up to connect to a USB memory stick (or other storage device) and change the display before powering off all components.

[edit] Information Board

An extension of the Digital Photo Frame concept is to display other media such as webpages or other documents. Examples include web pages such as news sites or status pages such as stocks or other information. The current days weather forecast would be a good example for installation in a domestic location such as near the front door in a hall way. Such a device could also be connected wirelessly allowing remote or automatic updates without human intervention. Such a product will have a low physical and energy footprint compared to older technology. At present (Q4 2009) no such product is available on the market despite the technology already existing to manufacture it. Unlike digital photo frames, digital information boards could run acceptably with greyscale epaper.

[edit] Displays embedded in smart cards

Flexible display cards enable financial payment cardholders to generate a one-time password to reduce online banking and transaction fraud. Electronic paper could offer a flat and thin alternative to existing key fob tokens for data security. The world’s first ISO compliant smart card with an embedded display was developed by Smartdisplayer using SiPix Imaging’s electronic paper.[34]

[edit] Status displays

Some devices, like USB flash drives, have used electronic paper to display status information, such as available storage space.[35]

[edit] Cell phones

Motorola's low-cost mobile phone, the Motorola F3, also uses an alphanumeric black/white electrophoretic display.

The Samsung Alias 2 mobile phone incorporates electronic ink from E Ink into the keypad, which allows the keypad to change character sets and orientation while in different display modes.

E-paper (sometimes called radio paper or just electronic paper) is a portable, reusable storage and display medium that looks like paper but can be repeatedly written on (refreshed) - by electronic means - thousands or millions of times. E-paper will be used for applications such as e-books, electronic newspapers, portable signs, and foldable, rollable displays. Information to be displayed is downloaded through a connection to a computer or a cell phone, or created with mechanical tools such as an electronic "pencil". There are a number of different technologies being developed: Xerox, in partnership with 3M, has created an e-paper called Gyricon that is expected to be marketed in the not-distant future and Lucent, in partnership with a company called E Ink, is working on a device (also called E Ink) that is expected to be available within the next few years. Both of these technologies enable a black (or other color) and white display; Philips is working on a type of e-paper that will be full-color, but say that the product is at least 10-15 years away.

The Gyricon version consists of a single sheet of transparent plastic, containing millions of tiny bichromal (two color) beads in oil-filled pockets. Text and images are displayed through a rotation of the beads that occurs in response to an electrical impulse: a full rotation displays as black or white, and a partial rotation displays as gray shades. Like traditional paper, Gyricon has - and needs - no lighting component.

Lucent's E Ink device uses electronic ink and combines thin, plastic, flexible transistors with polymer LEDs (light-emitting diodes) to create what are called smart pixels. The process involved - which is not dissimilar to traditional printing processes - uses silicon rubber stamps to actually print tiny (as small as those for the Pentium III processor) computer circuits onto the surface. E Ink uses electronic ink for display: a liquid plastic substance consisting of millions of tiny capsules filled with light and dark dyes that change color - charged dye particles move either up or down within the capsules - when exposed to an electric charge. According to Paul Drzaic, the director

of display technologies, prototypes of the device have been running on watch batteries. The E Ink technology has been used for retail signs.

Neither the Lucent/E Ink version nor the Gyricon version require a constant power source; the initial charge creates the display, which then remains fixed until another charge is applied to change it. Low power demand is an important consideration for a technology that is intended to - at least partially - supplant a power-independent, standalone application like paper. The challenge involved in creating viable e-paper is to develop a material that has the desirable characteristics of traditional paper in addition to its own intrinsic benefits (such as being automatically refreshable). Like traditional paper, e-paper must be lightweight, flexible, glare-free, and affordable, if it is to gain consumer approval. Developers of both the competing e-papers claim to have accomplished most of these qualities in their products. The first e-paper products will be Gyricon-based: portable, reusable pricing signs for stores that can be changed instantly through a computer link; the first Gyricon-based electronic newspaper is expected to be available within the next 3 years.

ELECTRONIC INK

HOW E-INK WORKS

With a world full of monitors and electronic displays made with liquid crystals, light-emitting diodes and gas plasma, you probably don't think of paper as being a revolutionary display technology, but the Chinese invention of paper in 105 A.D. forever changed the way the world communicates. Without it, books might still be printed on silk scrolls that only the wealthy could afford, making literacy a rare skill.

Look around you: It would be nearly impossible to live one day without coming into contact with paper in some form. This year, the world will consume an estimated 280 million tons of paper, according to the National Association of Paper Merchants in England. That is equal to 56 trillion sheets of letter-size 20-pound bond paper. (See this question of the day on paper weight.)

For nearly 2,000 years, ink on paper was the only way to display words and images, and it still beats computer displays when it comes to portability and price. Paper also doesn't require an external power supply. Yet it does have some limitations: Once you've printed words on paper, those words cannot be changed without at least leaving some marks, and it is also difficult to carry around a large number of books.

Scientists are now close to developing a revolutionary technology that could replace paper, called electronic ink! In this edition of How Stuff Will Work, you will find out about how electronic ink is made, how it will allow you to carry a whole library in one book and how it could be used for cheaper computer displays.

Next Page

Making Electronic Ink

Two companies are simultaneously developing similar electronic inks -- E Ink of Cambridge, MA, and Xerox in Palo Alto, CA. At first glance, a bottle of electronic ink looks just like regular ink, but a closer examination shows something much different. Although the two companies' products vary slightly, here are the three components of both electronic inks that give them the ability to rearrange upon command:

Millions of tiny microcapsules or cavities An ink or oily substance filling the microcapsules or cavities Pigmented chips or balls with a negative charge floating inside the

microcapsule

Electronic ink can be applied to the same materials that regular ink can be printed on. In the case of a digital book, the pages would be made out of some kind of ultra-thin plastic. The ink would cover the entire page, separated by cells that resemble the cells on graph paper. Think of these cells as pixels on your computer screen, with each cell wired to microelectronics embedded in this plastic sheet. These microelectronics would then be used to apply a positive or negative charge to the microcapsules to create the desired text or images.

Xerox and E Ink are using different techniques to develop their electronic inks. To help people understand how E Ink's technology works, the company compares the millions of microcapsules inside the ink to clear beach balls. Each of these beach balls is filled with hundreds of tiny, white ping-pong balls. And instead of air, the beach ball is filled with a blue dye. If you looked at the top of this beach ball, you would see the ping-pong balls floating in the liquid, and the beach ball would appear white. But if you looked at the bottom of the ball, it would appear blue.

Now, if you were to take thousands of these beach balls and lay them out on a field, and make the ping-pong balls move between the top and bottom of the beach balls, you could make the field change color. That's the principle behind E Ink's product.

Photos courtesy E Ink

Here you can see how E Ink's pigment chips would react to positive and negative

charges.

In reality, these microcapsules are only 100 microns wide, and roughly 100,000 microcapsules can fit into a square inch of paper. In each of those microcapsules there are hundreds of smaller pigmented chips. In prototypes, E Ink is currently working with white chips and blue ink, but it is working to develop other color inks that could lead to multicolor displays.

When an electrical charge is applied to the microcapsules, the chips will either rise to the top or be pulled to the bottom. When pushed to the top, the chips make the capsules look white; when they are pulled to the bottom, the viewer only sees the dark ink. Patterns of white and dark can then be created to form words and sentences.

Xerox is working on its own version of electronic ink, called electronic paper, which it first developed in the 1970s. However, instead of using paint chips floating in a dark liquid, it has produced microscopic balls that are black on one side and white on the other. Similar to E Ink's technology, these microscopic balls respond to an electrical charge, which rotates the ball from black to white to produce patterns on a page. To produce pages for digital books, Xerox is developing rubber sheets in which these microscopic balls will be suspended in an oily liquid.

One of the obstacles in developing a digital book out of electronic ink has been wiring the pages to create an electrical charge while still maintaining a paper-thin page. In this aspect, E Ink has taken the lead in developing digital books by signing an agreement with Lucent Technologies that would give E Ink the rights to use plastic transistors developed by Lucent. These tiny transistors can be printed onto a page to provide the adequate charge needed to switch the E Ink chips from one color to another.

Uses for Electronic Ink

The 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 Ernest Hemingway's "The Old Man and the Sea," and once you've finished that tale, you could automatically replace it by wirelessly downloading the latest "Harry Potter" book from a computer database. In May 2000, E Ink CEO Jim Iuliano predicted that electronic books could be possible by 2003 or 2004. Xerox has introduced plans 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 would 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, PDAs, pagers and digital watches. E Ink has already received financial backing from communications giant Motorola. Electronic ink displays would have several advantages over current display technology, including:

Low power usage Flexibility Readability

E Ink unveiled its first product using electronic ink -- Immedia large-area displays -- in 1999. These large signs draw only 0.1 watts of power, which means that the same power required to run a single 100-watt light bulb could power 1,000 Immedia signs. E Ink said that in electronic devices, electronic ink would use 50 to 100 times less power than liquid crystal displays because electronic ink only needs power when changing its display. For this same reason, a digital book can display the same text for weeks without any additional charge applied to it.

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. The ink's flexibility would also make it possible to develop roll-up displays for electronic devices.

Another advantage electronic ink has over traditional computer displays is its readability. It looks more like printed text, so it's a lot easier on the eyes. However, both Xerox and E Ink have to improve the resolution of their products for them to be viable in book or other small-print publications. Xerox has already made a display that has a 200 dots per inch (dpi) resolution, which is more than twice the resolution of an average LCD display. Lucent's printable transistors should allow E Ink to increase the resolution of its products to resemble the resolution of a printed book.

The developers of electronic ink don't expect people to throw all paper out or discard their computer monitors the instant these products hit the market. 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.

Electronic Paper

For a thin and bendable display, Fabric PCs will rely on a cutting-edge technology called e-paper, or electronic paper. The technology behind e-paper was pioneered in the 1970s by Nick Sheridan at the Xerox Palo Alto Research Center and has

continued to evolve since that time. Today there are several different implementations of the basic e-paper concept.

One example of e-paper technology is called E ink, made by the E ink Corporation. We'll very briefly touch here on how E Ink technology works, but to learn much more about it, read How Electronic Ink Works. Basically, this form of e-paper is created by sandwiching millions of tiny plastic wells between two sheets of flexible plastic. Each well contains both white and black particles, suspended within a clear fluid. The key to this technology is that the white and black particles have opposite charges, so when an electric voltage is applied to individual wells -- through circuitry embedded underneath -- the black and white particles can be separated to opposite sides. In this way, the face-up side of each well can be set to appear either as black or white as seen through the top layer of clear plastic. Each well functions as a separate pixel on the E ink display.

YOSHIKAZU TSUNO/AFP/Getty ImagesA Fujitsu employee displays the prototype model of an electronic paper display that is

flexible and does not blur even if it is bent or pressed by a finger.

E-paper, based on this type of design, can be curled or even folded like a sheet of laminated paper, and because of its light weight and flexibility it's also much less fragile than traditional displays. Fujitsu's Fabric PC concept designs take full advantage of these characteristics by incorporating large displays that can fold up to fit within a Fabric PC's case when it is closed. The power requirements for e-paper displays are also much lower than for traditional displays. For Fabric PC's, this will translate into longer battery life and/or smaller batteries.

Keep in mind that the Fabric PC is currently just a concept design and that even working prototypes have yet to be developed. One of the factors that Fabric PC development will depend upon is continued progress in e-paper technology. As exciting as e-paper is, it's important to stress that e-paper technology is still a work in progress, too. There are considerable technical challenges that must be overcome

before low-cost e-paper displays will be available. For example, just one of those challenges will be the ability to display a full range of colors that can also update quickly enough to accommodate video output. Bringing the cost of e-paper displays down to an affordable level will be especially important as well.

What other technologies similar to the Fabric PC concept are in store for the near future? Keep reading to find out.

E-paper on the MarketThough e-paper is still a developing technology, you've probably already seen it in products available on the market today. For example, many cell phones currently use e-paper displays, and e-paper is also present in electronic readers such as Amazon's Kindle, an electronic reading device.

E-paper Technologies Reference GuideFor almost three decades, electronic paper technologies have been evolving to combine the flexibility of digital information with the familiarity, quality, and convenience of a paper-like substrate. More than a dozen companies have announced work on active e-paper programs, and there are a number of start-ups coming to existence as well.

The production structure of electronic paper is fairly complex. E-paper is based on IP/technology developed by a handful of technology developers. In many cases this manufacturing is contracted out. In addition, E-paper generally needs some kind of backplane that is manufactured by another group of firms. It is important to note that there is an additional group of firms—consumer product firms—who design and market the product into which the e-paper display fits. For example, the e-readers marketed under the Sony brand have incorporated e-paper technology from E Ink and backplane technology from Polymer Vision.

This guide is designed to provide a background in both e-paper frontplane technologies and the current backplane technologies used to manufacture such displays. It is divided into two sections. The first will explain the various e-paper technologies that exist today and provide analysis on the pros and cons to each of them. The second section will discuss the various backplane technologies used to power the e-paper frontplanes.

FrontplanesElectrophoretic Technology

E Ink SiPix Bridgestone

Cholesteric LCD Technology

Fujitsu

Hitachi Kent Display Kodak Nemoptic ZBD Display

Electrowetting Technology

Liquivista

Electrofluidic Technology

Gamma Dynamics

Electrochromic Technology

Acreo Aveso Ntera Siemens

Interferometric Modulator Technology

Qualcomm

Photonic Crystal Technology

Opalux

REED Technology

Zikon

Bistable LCDs

Backplanes HP NEC Plastic Logic Polymer Vision Prime View International Ricoh Samsung Seiko Epson

Frontplanes for E-paper

Electrophoretic Technology

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Electrophoresis is a process, which enables separating molecules according to their size and electrical charge by applying an electric current. In an electrophoretic frontplane small, charges submicron particles are suspended in a dielectric fluid that is enclosed into a sub-pixel size cell or microcapsule. When an electric field is applied across this cell or capsule, the ink particles will move towards the electrode with the opposite charge.

With a transparent electrode the cell or capsule surface takes on the color of the ink when current is applied. The contrast is improved by using opposite colored particles. such as black and white—and charging them with opposite polarities. When current is applied, all the black particles will migrate to one side, and all the white to the other. Switch the field, and the capsule will change color. This enables switching between all black particles and all white particles on the transparent front electrode of the cell or microcapsule. This is how the high contrast ration of electrophoretic displays is created. The difference between the various electrophoretic frontplane technologies lies simply in the method of encapsulation for the charged particles and fluid medium. Some versions use a “microcup” rather than a particle.

E Ink

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The electrophoretic technology used by E Ink is the most widely known and used form of e-paper. Known as electronic ink, it is a proprietary material that is made into a film for incorporation into a paper-like display. The company states that “the principal components of electronic ink are millions of tiny microcapsules, about the diameter of a human hair. In one stage, the microcapsules contain positively charged white particles with negatively charged black particles suspended in a clear fluid. Applying a negative electric field, causes the white particles to move to the top of the microcapsule where they become visible to the user. Thus the surface area where the white particles have moved to appears white. The black particles are simultaneously moved to the bottom of the display, where they are hidden. When the process is reversed, the black particles move to the top to make that section of the display appear dark.”

The E Ink microcapsules are only 100 microns wide, which means that roughly 100,000 microcapsules can fit into a square inch of paper. Each of those microcapsules contains hundreds of smaller pigmented chips. In earlier prototypes, E Ink worked with white chips and blue ink, but later it developed other color inks for multicolored displays. Wiring the pages to create an electric charge and still maintain a paper-thin page has been a challenges in developing a digital book out of electronic ink. E Ink partnered with Lucent Technologies to enable the use of organic transistors developed by Lucent in the e-paper displays. These tiny transistors can be printed onto a page to provide the adequate charge needed to switch the E Ink chips from one color to another.

Cross-Section of Electronic-Ink Microcapsules

The display is manufactured by printing the electronic ink onto a sheet of plastic film that has been laminated to a layer of circuitry. The circuitry forms a pattern of pixels that can then be controlled by a display driver. The electronic ink, which is composed of microcapsules suspended in a liquid vehicle (carrier medium), can be screen printed onto a variety of substrates including glass, plastic, fabric and paper. The company claims that ultimately the electronic ink will be able to be printed on almost any surface to make a display.

The company also offers Vizplex imaging film. This consists of microencapsulated electronic ink coated onto an ITO-coated plastic substrate to create an ink film, which is then combined with a thin adhesive and a plastic release sheet. After converting the film into individual sheets, it is available for sale to TFT display manufacturers.

Ink-in-Motion™

Ink-In-Motion is a flashing electronic display, which utilizes the core electrophoretic technology of E Ink for integration into retail Point-of-Purchase (POP) and other signage applications. The electronic ink is processed into an imaging film, which is in turn manufactured with a customized electronics layer which provides power. A color overlay is sometimes added. Because of the low power consumption of the electronic ink technology, the product works well in a retail environment where power access is limited. As an example, a postcard display utilizing the technology can run up to six months on two AA batteries. The paper-thin displays range from simple flashing text to flashing animation. E Ink does not manufacture the product internally - it is only available from its electronics partners Neolux and Midori Mark.

Note: E Ink Corp is the name of a company in the e-paper industry. It is a common misnomer to call e-paper technologies from other companies E Ink.

SiPix

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SiPix’s microcup technology involves a microscale container which holds minute quantities of fluid and particles. The display structure, typically 150μm thin, is built upon a flexible PET plastic substrate, which may include a transparent conductor such as Indium Tin Oxide (ITO). The contents of the microcup are hermitically sealed to protect them from the environment. The microcup structure is said to enable the thinnest and most flexible electrophoretic display. The partition walls provide not only fine resolution, but also impact

resistance. Because each microcup is individually sealed, the EPD film can be cut to any shape and size.

Although the electrophoretic technology is fundamentally the same, E Ink uses a double particle in a clear fluid, while SiPix uses a single white particle in a dye. Depending on the application, it uses a honeycomb or waffle like structure, which is filled with dyes and particles. According to the company the simple structure eliminates issues with particles colliding. Since the microcups can be filled with different color dyes, it is possible to make a full-color system without external filters.

The SiPix microcup is manufactured using a high-speed roll-to-roll embossing process. Several grid shapes are available for the embossing: square or rectangular grid or a hexagonal grid.. When an electric current is applied, the charged particles migrate through the dielectric fluid. If the particles at the visible surface are white, that is the color that is seen by the viewer. Alternatively, if the alternate color particles migrate, that is the color seen. The company offers displays with alternate colors of black, red, green, blue or gold.

As of March 2009, AUO has taken a major stake in Sipix, making it the major hareholder (over 30%).

Bridgestone

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Bridgestone is also using a suspended particle technology, but instead of liquid, the particles are suspended in air. From its ongoing work in electromaterials, engineers at Bridgestone have developed an Electronic Liquid Powder (ELP), which can be made into a Quick Response Liquid Powder Display (QR-LPD), as an alternative to liquid crystal displays, first on glass, then on plastic. The ELP is a high-fluidity powder with physical properties intermediate between those of liquids and conventional, powdered solids.

According to the company, the material flows like a particulate suspension and is extremely sensitive to electricity, giving it a faster responsiveness and a broader range of viewing angles than comparable reflection-type LCDs do, as well as using less electricity. Because of the quick response, the technology can be used with a passive matrix drive, which is less expensive than an active matrix drive. It also claims that through a unique rib structure, the extremely thin displays solve the problem of image distortion when the display is bent.

In April 2009, Bridgestone debuted its ultra thin and bendable color e-paper display during a Tokyo Tradeshow. The company will be using this display for e-readers in the near future. The displays are manufactured using Bridgestone’s roll to roll manufacturing, which produces the e-paper in much the same way as a newspaper is produced. Giant rolls of plastic are imprinted with the displays, giving them a lower cost since they can be easily mass produced, and a lesser impact on the environment since they use a cold manufacturing method.

Cholesteric Liquid Crystal Display Technology

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Cholesteric materials are modified liquid crystals and extremely suited for reflective, bistable displays. A cholesteric liquid crystal is a type of liquid crystal with a helical (smooth curve like a spiral) structure.. Cholesteric liquid crystals are also known as chiral nematic liquid crystals.While solids have molecules that maintain their orientation., molecules in liquids change their orientation and move anywhere in the liquid. Some substances exist in an odd state that is similar to both liquid and solid. When they are in this state, the molecules tend to maintain their orientation, like solids, but can also move like a liquid. Liquid crystals are such materials. However, in essence they are more like a liquid and require only a little heat to move from this odd state to a liquid state.

A feature of liquid crystals is that they are affected by electric currents. Depending on the temperature and particular nature of a substance, liquid crystals can be in one of several distinct phases, including nematic phase and the cholesteric phase. LCDs use these types of crystals because they react predictably to electric current in such a way as to control light passage. The use of a cholesteric liquid crystal means that the display has a far better readability than a display using conventional nematic liquid crystals and can be made thinner, since it reflects 50 percent of certain wavelengths, removing the need for color filters and polarizing layers. This in turn means that the background color is more vivid and the contrast much better than conventional reflective-type LCDs.

Fujitsu

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Fujitsu’s color e-paper mobile display is based on reflective cholesteric liquid crystal technology. Fujitsu claims that a key advantage of its e-paper is the semi-permanent memory display system, which maintains the image without power; the absence of flicker; and the color that is three times as bright as other developed products. In July 2005, Fujitsu announced the development of the world’s first color electronic paper.

In April 2007, Fujitsu unveiled its commercialized FLEPia color e-reader, available at the time for corporate use only (as part of field marketing). In February 2009 a commercialized model was tested at a confectionary shop/restaurant in Tokyo called Fujiya (Kinshicho Termina branch). In April 2009, Fujitsu launched online consumer sales of FLEPia in Japan, in addition to its offering in 2007 for corporations in Japan.

The technology used in FLEPia is fundamentally Fujitsu proprietary technology since the display panel and device itself are developed by Fujitsu Frontech Limited and Fujitsu Laboratories Limited - however, some of the LCD technology employed in FLEPia is licensed from a third party, Kent Displays.

Hitachi

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Hitachi is working with Bridgestone towards commercial applications of information signage. In 2005, they collaborated in a field test in conjunction with East Japan Marketing & Communications, Inc., the subsidiary company of East Japan Railway Company, in the Tokyo Station underground. For the trials, Hitachi had used Bridgestone’s display modules based on Electronic Liquid Powder with a thin film transistor technology for the backplane. The displays provided updatable train schedule information right on the train platforms, in areas that had limited or no access to power. The signs were also flexible, so they could be attached to poles in the underground stations.

Hitachi has not announced any dates for future commercialization of products and frankly the activities of both Bridgestone and Hitachi in the e-paper space have received little publicity since the field trials. However, these two Japanese firms can bring huge resources to bear on marketing e-paper products of all kinds and they are also helped by Hitachi’s position as a leading consumer electronics brand.

Kent Display

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Using cholesteric LCD technology, Kent Display’s products tout a monochromatic contrast ratio as high as 25:1 with a peak reflectivity approaching 40 percent of incident light, when measured normal to the plane of the display. According to the company, Ch-LCd can be manufactured with the same cost as the super twisted nematic (STN) and is simpler to construct and the tolerance on the cell dimensions are less demanding. Ch-LCD can achieve full color operation without color filters. A unique feature of the CH-LCD technology is that not only does it reflect light, but also infrared. Thus, the display can be read with night vision goggles. One of Kent’s earlier products was used by the military.

Kodak

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Kodak aggressively pursued the research and development of electronic paper for about five years. Its work was with cholesteric liquid displays. However, about a year and a half ago, Kodak discontinued its commercialization program in the electronic paper area because it did not meet the company’s investment profile. It decided to focus its resources on OLEDs and light management films.

Nemoptic

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Nemoptic uses a technology called BiNem, which stands for Bistable Nematics. It is based on a unique patented principle called “surface anchoring breaking.” The device is constructed with a front polarizer on top, which lays on a glass sheet followed by an ITO electrode, then a standard polarizer which provides strong anchoring. The liquid crystal is in the middle. The other side is a specific weak anchoring layer, with an ITO electrode, glass sheet and a rear reflecting polarizer. BiNem has two stable states, the uniform (U) state and the twisted (T) state, which are selected by applying simple pulses. Once a state is selected, it stays there indefinitely until energy in the form of an electrical pulse is applied.

ZBD Display

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The Zenithal Bistable Display (ZBD) is said to be the first commercially available LCD that uses surface bistability. The architecture consists of a polarizer layer on the bottom, then the zenithal bistable grating, then a rubbed polymer, then a polarizer on top. The key to ZBD operation is the ability to select one state or the other using electric pulses of opposite polarity. The contoured surface is manufactured at low cost using a simple embossing

technique. ZBD Electronic Point of Purchase (EPOP) displays are monochrome passive matrix displays (102 mm or 4-inch diagonal with high brightness (39% reflectivity), high contrast (20:1) and an ultra-wide viewing angle (160º). It can hold multiples 320 x 240 pixel bitmap images in its memory at any one time. The displays have a 100-dpi resolution.

Electrowetting Technology

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Electrowetting 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. Applying voltage between the electrode and the water causes the interfacial tension to change, which causes the water to move the oil aside. The result is a partly transparent pixel; if a reflective white surface is used under the switchable element, a white pixel results. This forms the basis of the reflective display.

Displays based on electrowetting have several advantages. The switching between white and colored reflection is fast enough to display video content–supposedly pixels can switch states in around 10 milliseconds-fast enough to generate 100 new images in a second. TV-quality video only requires 25 images per second. In addition, the high reflectivity and contrast of the wetting displays make them clearer: color displays are four times as bright as LCDs and twice as bright as other e-paper technologies. Electrowetting displays reflect around 40 percent of light.

Since it is a low-power/low-voltage technology, displays can be flat and thin. Reflectivity and contrast are claimed to be better or equal to those of other reflective display types and approach those of paper. It can be used as a basis for high-brightness full-color displays. Such displays are claimed to be four times brighter than reflective LCDs and twice as bright as other emerging technologies. While it is low power, electrowetting is not bistable, so some electricity is needed for image retention. One of the advantages of electrowetting technology is that it can be integrated into existing manufacturing structures for LCD systems.

Liquivista

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Electrowetting technology was developed by Philips Research labs in 2003. Because it did not fit with Philips core technology, Philips entered into an agreement with New Venture Partners (NVP) to spin-off the technology into a new company called Liquavista. Currently, Liquavista offers two products based on electrowetting technology: ColorMatch and ColorBright. At present, Liquavista is the only firm using electrowetting technology for paper-like displays.

Electrofluidic Technology

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Images of pigment droplets and an overlay of three CMY prototypes. (Image courtesy of Nature Photonics)

Electrofluidic displays have a polymer layer with very small cavities which are filled with aqueous pigment dispersion. The underlying physics is based on electrowetting technology, but the device principles and performance are quite different. The name electrofluidic describes the mechanism which involves movement of liquids through microfluidic cavities as a result of an applied charge. Because the cavities only comprise about 5-10% of the visible area, the pixels are hidden from view. When an electromechanical voltage is applied, the pigment dispersion is pulled out of the cavities and begins to expand over the layer to encompass 90-95% of the visible area. Because the process uses pigment dispersions, it has more brightness and color saturation than currently available e-reader technologies and more closely simulates the look of traditional ink on paper. Current e-paper technologies have 40-50% reflectance. The new technology has 55%, but researchers feel an 85% reflectance of ambient light is possible (the same as that of paper). The technology also claims faster switching speeds. At present a black-and-white prototype has been demonstrated, but the inventors claim that color is not an issue. Two electronic layers would be used for color displays, which would enable a CMY subtractive approach similar to printing

ink on paper. While this would need double the power of a single plate, it would still be sufficient to be attractive to consumers. An additional advantage is the fast switching speed. By tweaking variables such as geometry, surface tension and viscosity, the speed could be maximized to a sub-millisecond. The displays can be manufactured using existing processes for producing LCDs.

Gamma Dynamics

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The electrofluidic process was developed at the Novel Devices Laboratory at the University of Cincinnati by Professor Jason Heikenfeld. Gamma Dynamics is the start-up company formed in 2009 to commercialize the technology. Sun Chemical and Polymer Vision are strategic partners along with members of the Novel Devices Laboratory from the University.

Electrochromic Technology

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Electrochromism refers to the characteristic color change of a material associated with the materials’ reduction/oxidation state. Polyaniline and polyethylenedioxythiophene (PEDOT) are examples of electrochromic materials. An EC display element consists of at least two conductors, an electrochromic material and an electrolyte combined on a carrying substrate. The optical contrast is a result of the contrast between the white paper surface and the electrochromic materials switched to its colored state. These displays arefully flexible and the printed devices are less than 100 microns thick.

One of the claimed advantages of electrochromic displays over other technologies is the high contrast, the vibrant, rich looking color image of the display against the white background. This is due to the fact that electrochromic materials absorb some light spectra and reflect others, similar to pigments used in printing. Other technologies use light scattering techniques.

Acreo

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Acreo is currently developing an in-line roll-to-roll printing process for organic electrochromic paper displays. The company is utilizing standard graphic arts equipment (a flexographic label press) and developing processes to make it possible to print displays. The substrate is conventional paper. The system has succeeded in printing thin flexographic layers with moderate conductivity, enough for certain applications. Recently, Acreo entered into an agreement with Soligie, a printed electronics manufacturer, to develop and manufacture Acreo’s printed electrochromic display technology into PaperDisplay products.

Aveso

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Aveso is also using electrochromic technology to develop displays, mainly for disposable applications. It is using its technology for smart cards to reduce fraud in financial transactions. The paper-thin (250 micron) displays are produced and scaled using traditional high-speed print technologies, mostly screen printing depending on the application. It uses reflective electrochromic technology, for blue digits on a yellow background. The company claims that process is compatible with other printed components such as batteries and antennas.

Ntera

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NanoChromic Display (NCD) technology uses nanostructured semiconducting metal oxide films with a layer of electrochromic viologen molecules to produce displays that simulate ink on paper, with a pure white background and very high contrast ratios. The use of titanium dioxide as a reflector gives the display its white, paper-like quality. The displays are manufactured in the same manner as traditional LCDs.

Siemens

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In the past two years, Siemens has done extensive research in the development of what it terms a novel electrochromic material system. The basis of the system is modified bipyridinium salts, which are dispersed in a pasty

material formulation. Using this material system, the company has developed a miniature color display using electrochromic materials. The small flexible displays use electrochromic materials holding a pattern of electrodes. A conductive plastic foil serves as the other electrode and the transparent window through which the electrochromic materials show the changing color. To date, the engineers have been using silicon switching elements to control the device. The ultimate goal is to use a printing process to manufacture the entire display, including the appropriate control electronics, from conductive and semiconducting plastics.

Interferometric Modulator Display

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An Interferometric modulator display (IMOD) uses a technology made up of subpixels which are actually miniature Fabry-Perot interferometers (etalons). An etalon, which is an optical term, reflects light at a specific wavelength and gives pure, bright colors like those in a butterfly’s wings. Moreover it consumes no power. Microelectromechanical systems (MEMS) are used to switch the display on and off.

Qualcomm

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The only provider of IMOD reflective technology powered by MEMS is QualComm MEMS Technologies, a subsidiary of Qualcomm, the wireless chip maker headquartered in San Diego. Called Mirasol technology, it is simply a MEMS display for mobile devices, which works by reflecting light so that different wavelengths interfere with each other to create color. Since it is reflective, it is viewable even in direct sunlight; the MEMS technology allows it to be bistable, thus low power.

The display has two conductive plates: one is a reflective membrane, which is suspended over a glass substrate; the other is a thin film stack atop the substrate. Air fills the gab between the two, which are separated when no power is applied. In this phase, light is reflected. The application of power pulls the plates together and the light is absorbed, resulting in a screen that appears black.

The size of the hollow space inside the cell, just a few nanometers across, can be electrically adjusted to change the color it emits. Thus the Mirasol technology is well-suited to color, because the cells can be electrically adjusted so that they reflect any wavelength of light. Moreover, those electrical adjustments can occur as quickly as a thousand times a second. Thus video speeds are much more possible than with other electronic ink technologies.

Several uses of the IMOD displays have been commercialized. These include: Acoustic Research ARWH1 Stereo Bluetooth headset device; the Showcare Monitoring system (Korea); the Hisense C108; and mp3 applications from Freestyle Audio and Skullcandy. Although not yet commercialized there are plans in the works for mobile phone by Taiwanese manufacturers Inventec and Cal-Comp; and LG claims to be developing ‘one or more’ handsets using mirasol technology.

Photonic Crystal Technology

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Another technology, which has recently entered the limelight, is based on photonic crystals, which are nanostructures arranged in a regular pattern. Changing the pattern causes a change in the color of light that the crystals reflect. Artificial opals are similar to those occurring naturally, with one exception—artificial opals can be stimulated electrically to change color. These opals can then be integrated into a layer of millions of tiny silica spheres, which are embedded into an electroactive polymer. The layer is then sandwiched between transparent electrodes. When current is applied, it causes the polymer to swell, which in turn changes the spacing of the crystals. If this movement is controlled, the crystals can be maneuvered to produce the entire light spectrum. Such layers can then be arranged into a display similar to a traditional LCD screen. The advantage of this technology is that the pixels can be individually tuned to any color, and the color is purported to be brighter and more intense.

The technology is very new, however, and commercial products are still years away. However, recently the speed at which the crystals are able to change color was improved dramatically, as were the available spectrum colors that could be achieved with the technology. The increased speed was made possible by dissolving the nanospheres into a porous polymer structure, eliminating the silica. The pores are filled with electrolyte and then the material is sandwiched between electrodes.

Nevertheless, there are still challenges to be resolved. One of the disadvantages of the photonic crystal approach is its dependence on the flow of electrolyte in response to electricity. This could mean a decrease in efficiency after repeated cycles, similar to rechargeable batteries. Furthermore, when pixels change from long wavelength colors to shorter ones the speed decreases. In addition, pixels need more color contrast. Adding nanoparticles to the polymer might improve the contrast.

Opalux

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Opalux Inc. based in Toronto, Canada, researches and develops possible market applications for its tunable photonic crystal technology, sometimes called P-Ink.It was co-founded by André Arsenault, a recent PhD graduate of the University of Toronto, to continue his doctoral research on photonic crystals with the aim of developing commercial products. At present, Opalux is the only company working on photonic crystal technology.

REED Technology

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Reverse Emulsion electrophoretic Display (REED) uses nano-droplets of a polar liquid, which are composed of a blue dye and surfactants in a measured ratio. These droplets are dispersed in a non-polar liquid. When energy is applied, the droplets reassemble in the liquid. The technology is purported to use less energy than currently available electrophoretic technologies, and have faster switching speeds, which would make video possible. Moreover, it can be produced using existing LCD manufacturing techniques.

Zikon Corp

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Headquartered in Santa Clara, CA, Zikon was established in 1996 by chemist Remy Cromer and physicist Zbig Bryning, to continue the research began by Exxon’s EPID flexible display unit. Soon after it was founded, it was granted a patent for the REED ink technology. Other patents are pending. Its goal is only to manufacture the electronic ink, not the complete display. Its initial target market is outdoor single-color displays, signage and mobile devices. No target date for commercialization is available.

Bistable LCDs

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Liquid Crystal Displays offer excellent picture quality with brilliant color and video, however, they require a brushing process on the inside of a glass sandwich to lock the twisted molecules. These twisted molecules are necessary for bistable displays, which offer low voltage advantages. Bistable LCDs use a photo-alignment process to eliminate the brushing of the glass. The process, a roll-to-roll technology, uses a new photo-alignable polymer—an azo-dye, which has an anchoring energy that can be adjusted by changing the UV exposure time. The layer is stabilized by heat polymerization after the azo-dye monomers are photo-aligned. The liquid crystal is then deposited on top.

According to researchers this arrangement is inherently low cost, likely to give much better colors than electrophoretic technology, be more robust and operate without need of a transistor active matrix backplane or ITO or alternative transparent electrodes with all their problems of cost and of cracking when bent. The display is also optically rewriteable by means of light emitting diodes (LEDs). However, currently there is no optical writing mechanism, which is small enough for the display, which is 500 nanometers thick. Commercialization is not expected for several years.

Backplanes for E-paperAs mentioned previously, there are various technologies currently being used to manufacture the backplanes to be used in e-paper displays. Although the initial offerings were thin film transistors (TFT), some of the newer introductions are rather unique technologies for backplanes. Following is a list of these manufacturers and some explanation of the technologies they are using.

HP

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Hewlett-Packard and Arizona State University have introduced a prototype of a paper-like, flexible computer display made almost entirely of plastic. The introduction is a result of several years of research and represents a milestone in industry efforts to develop a mass-market, high-resolution, flexible display.The device, created by ASU’s Flexible Display Center (FDC), was made possible by an invention by HP Labs called Sail (Self-Aligned Imprint Lithography). The SAIL technology is considered “self aligned” because the patterning information remains aligned regardless of the process-induced distortion. The key to the device is that the

new technology enables the image on the display to maintain its form despite the bending and flexing.

SAIL works by forming thin-film transistor electronics on a flexible substrate, which has been coated with all of the thin films required for the devices. Then multiple patterns required for the backplane are impressed onto different heights of the masking structure. By alternately etching the masking structure and the thin film stack, the patterns are transferred to the device layers. Current thin-film transistors are manufactured with photolithography, which requires a costly additional alignment step. Moreover, the flexible technology makes it possible to manufacture the displays using a roll-troll process, which further reduces the cost of manufacturing. The company also claims that the SAIL technology is a more sustainable, environmentally method of manufacturing displays. The new flexible substrate, called Teonex Polyethylene Naphthalate, or PEN, was developed by DuPont Teijin Films. For the e-paper frontplane, the HP-ASU display uses E Ink’s Vizplex imaging film.

NEC

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NEC LCD Technologies, headquartered in Japan, is one of the world’s leading providers of high-quality, innovative, active-matrix liquid crystal display (AM-LCDs) modules for the industrial and high-end monitor markets. It has developed multiple sizes (A3 and A4 equivalent) of electronic paper modules using the microcapsule electrophoresis system, based on E Ink technology. The screens include an NEC-developed amorphous silicon TFT active matrix that allows for a 16-step grey scale rather than just monochrome. It boasts 43% reflectivity with a contrast ratio of 10:1. The A3 e-paper module is composed of especially narrow frames, with two sides measuring just 1mm, which enables the creation of large screens that feature effective multi-tiling. The company is aiming to continue to research the technology towards implementation into the large-scale display industry.

Plastic Logic

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Plastic Logic, headquartered in the U.K., is a spin off from Cambridge University’s Cavendish Laboratory. Plastic Logic was founded to make thin film transistors, but moved into manufacturing OTFTs (organic thin film transistors) for various applications. In recent years, it has focused on backplanes for flexible displays, particularly backplanes for e-paper.

While electronic paper is typically thin and flexible, a rigid display results when it is combined with a glass-based amorphous silicon backplane. Plastic Logic developed a flexible backplane technology, thus enabling the display, and therefore the reader device to become flexible, thin, light and robust so it feels more like a sheet of paper. By extension, the whole e-paper market received a shot in the arm as a result.

The company uses solution processing and direct write inkjet printing to manufacture its OTFTs. Because what is used is an additive printing process, rather than a

subtractive masking process, both materials and processing cost is reduced compared to conventional display manufacturing.

Polymer Vision

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Polymer Vision is a spin out of Royal Philips Electronics after a first round of investment by Technology Capital, Luxembourg. After many years of development work in polymer electronics, Philips produced prototypes of ultra-thin, large-area, rollable displays. The displays combined an active-matrix, which is OTFT driven, with a reflective electronic ink front plane on a thin plastic sheet.To move the project towards commercialization, an internal venture called Polymer Vision was formed within Philips Technology Incubator Division. The Polymer Vision technology was used in the various incarnations of the Sony book readers that have appeared over the past couple of years.

Early in 2007, Polymer Vision announced its cooperation with Innos (U.K.) to establish the world’s first production facility for organic semiconductor-based rollable displays. What Polymer Vision is actually manufacturing is the active matrix backplane, which is coupled with E Ink’s electrophoretic technology to create the e-paper display. Polymer Vision has also developed a proof of concept device, called the Readius. The Readius comes with a 5” screen, which retracts into a device, which is not much bigger than a standard mobile phone. The company sees a large opportunity in the mobile market by offering consumers a large display in a small pocket size device allowing for comfortable reading anytime, any place.

In April 2009, Wired magazine reported on its Web site that Polymer Vision had missed its projected launch date of the The Readius rollable dislay and might not launch at all if the company didn’t get an infusion of cash. In July 2009, Polymer Vision went into bankruptcy and laid off its employees.

Prime View International

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Prime View International (PVI), headquartered in Taiwan, entered the e-paper business in 2005 when it acquired the e-paper display division of Philips, with all its patents and IP rights. Coupled with PMI’s technology and production capacity, the company developed MagicMirror reflective display technology to become a leading force in e-paper technology.

Prime View manufactures active matrix e-paper displays using TFT technology for the backplane based on PVI’s proprietary Magic Mirror Reflective Technology and the EPLaR process developed by Philips with an electrophoretic frontplane using E Ink’s technology. The company claims that its e-reading devices have an extensive battery life of up to 7,000 page turns per charge, equal to approximately 20-full-length books. In addition, in 2008, it added touch screen technology from F-Origin, a force-sensing touch technology supplier. (PVI has a 20% ownership in the F-Origin.) Traditional touch-screen technologies add a layer on the surface of the device, which

can diminish the reflective qualities of the display. With the addition of this touch-screen technology, the company claims it is the leading vendor for all available e-book products. Previously, PVI had introduced a flexible display, Flexi-e. The company has announced plans to begin mass production of e-paper readers in mid-2009, with color displays soon to follow. In June 2009 PVI purchased E Ink Corp for $215 million.

Ricoh

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Ricoh has developed an organic thin film transistor backplane for electronic displays using inkjet printing with 160 pixels per inch (ppi). The frontplane uses electrophoretic technology. However, the company does not expect commercialization of the technology for approximately four years.

Samsung

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In conjunction with Unidym (a majority-owned subsidiary of Arrowhead Research Corp.), Samsung Electronics has developed the world’s first carbon nanotube-based (CNT) color active matrix electrophoretic display (EPD). The e-paper display has a 14.3” format. To achieve the display, the CNT film was required to be even over large areas, compatible with different display technologies and fabrication processes and exhibit a conductivity which is comparable to ITO technology.

First developed by the Japanese, a carbon nanotube is over 10,000 times thinner than a human hair, while exhibiting unique thermal and electrical conductive capabilities. In addition, the resulting film is translucent and porous.

Seiko Epson

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Seiko Epson Corp. had developed a flexible high definition 200 ppi display, which uses the electrophoresis electronic paper developed by E Ink Corporation. The resolution of a 2-inch display extends to 320 x 240 pixels. It was developed using the company’s proprietary SUFTLA technology, which uses low-temperature polycrystalline Si thin-film transistors (TFT) in the driver to enable the dot display. (SUFTLA stands for Surface Free Technology by Laser Ablation /Annealing). Seiko Epson exhibited a prototype viewer terminal using electronic paper as a reference presentation at Embedded Technology 2007. At the time Seiko Epson announced plans to commercialize the technology in 1-2 years; however, little has been heard of the project since.

Electronic PaperIt is display that is thin and bendable like paper. It can also maintain color image contents without any power. We have developed this amazing “electronic paper“.

Contents

Characteristics

Structure

Principle

Application

Notes

Link to related sites

Characteristics

What is electronic paper?

It is a paper-like electronic display device with the following characteristics.

・With image memory function and ultra-low power consumption

・Thin and Light

・Vivid Color

・Bendable

Structure

Electronic Paper's Structure

Electronic paper displays in full color by piling 3 liquid crystal layers (blue, green, red).Drivers are attached around the liquid crystal sheets. By changing the driver positions by each liquid crystal sheet. we minimized overlaps and realized thickness close to paper.

Cross-section Diagram

In addition to the blue, red, green liquid crystal layers, you can find transparent films, transparent electrodes, electrodes, sealants, and light absorbing layer when looking at the cross-section of electronic paper.

PrincipleBecause Cholesteric Liquid Crystal is used, electronic paper has the characteristics like “thin, light, bright, and memory function”.

Cholesteric Liquid Crystal Material

Cholesteric Liquid Crystal only reflects light with certain wavelengths. When the light from sources such as the sun and light bulbs enter the liquid crystal, it displays in full color by reflecting light with the specific wavelengths of red, green, and blue.Resultant color of red/green/blue mixture is determined by additive color mixture principle. When only red is reflected, it will appear red. When red and green are reflected, it will appear yellow. When all colors are reflected, it will appear white. When none are reflected, it will appear black.

How does the display work?

By applying electric power to transparent electrodes of each liquid crystal layer, liquid crystal molecules change directions, allowing the display to switch between reflect and not reflect.

・More in Detail

(1)- Liquid crystal molecules are formed in a spiral like structure. Normally, they are lined up vertically.

(2)- By applying low voltage to the portion that the light needs to pass through, spiral shaped molecules turn horizontal. The horizontal position will be stable even after the voltage is turned off.

(3)- To the portion that the light has to be reflected, higher voltage is applied, making the spiral shaped molecules stretch. When the voltage is turned off, the molecules kickback, making the spirals vertical and stable. (Returns to the state in (1) )

Merits of cholesteric liquid crystal’s characteristics

・Ultra low power consumption and image memory function

Since cholesteric liquid crystal is stable when the spiral axis is vertical or horizontal, direction of liquid crystal molecules can be maintained semi-permanently without power. This memory characteristic allows for power consumption only when rewriting, realizing the ultra low power consumption. Since no power is applied after an image is displayed, there is no flickering, making it easy for human eyes to see.

・Thin, Light, and Bright

Thin, light, and bright display is realized since components that are in conventional LCD (polarization plate, reflectors, color filters, and backlight) are not necessary.

Applications

Electronic Paper can be used in various scenes.

Possible Applications of Electronic Paper

・Transportation (train, bus)

Use as in-car advertisement that changes contents depending on the passing area, or display information downloaded from the internet. Timetables in bus stops will be able to display real-time information such as traffic information.

・Retail (payment cards)

On credit cards, users can confirm account withdrawal dates and amount. On prepaid cards, remaining amounts can be displayed no matter how often you use it.

Rewritable media using leuco dye, widely used in prepaid cards, permits only 500-1000 times rewriting.

・Retail (price labels)

Can instantly change pricing in such cases as time services, which will make shopping more convenient for customers.

Future Plans

We are continuing efforts to realize an electronic paper that is bright like paper, and can be instantly rewritten. We are expecting an even broader range of applications

NotesSales manager Ms. A. Today she has a very important meeting with a customer, with executives in the decision-making position attending.

For such meetings, Miss A used to carry a laptop PC and printed copies of notes as preparation for unexpected questions. She carried printed copies because she can only take with her one laptop PC, and cannot request customers to prepare additional units for attendants. Ms A was different today. She only carried one bag that is light and fashionable. Why?

She was carrying electronic paper.Since electronic paper is so thin, she can carry them in her favorite bag. She only printed abstract of her presentation that she wanted to appeal.

After Ms A went through her presentations, her customer asked some unexpected questions. But, there is no need for her to panic. She can access necessary information from her PC in the office using her mobile phone. From the mobile phone, she sent and showed (via infrared interface to the electronic papers she previously distributed to the customers) the necessary information, and was able to provide appropriate answers. Suddenly, her mobile phone began to malfunction. But she does not have to panic. She can do the same with her colleague’s mobile phone. Her customer requested for the information, so she sent it from her mobile phone to the customer’s PC. The meeting finished without any problems.

Ms A was confident she could win the project. As anticipated, she received a message that the project was awarded. The customer felt confident about working with such an efficient and environmentally friendly company.

By effectively using electronic paper and conventional paper, you can minimize wasteful use of paper. You can be friendlier to the environment. As you can see, we believe that electronic paper can contribute to paperless operations in offices.