The future of e-paper: The Kindle is only the beginning

Thin, flexible, low-power digital paper is just around the corner. Will your next book or newspaper be 'e'?

Amazon.com's Kindle has turned a long under performing category of tech gadget -- e-book readers -- into an overnight hit, and in the process has boosted interest in electronic paper display (EPD) technology. The Kindle and its rival, the Sony Reader 505, both boast e-paper displays that look unnervingly like printed pages and consume next to no power. However, today's EPDs -- and today's e-book readers -- are only the beginning.

EPD technology has been a long time coming. The idea of e-paper, a data display that looks and works like a sheet of paper, has been around for decades. In theory, such a screen could be "printed" electronically, would hold its contents without consuming power, could be viewed using reflected light (rather than the backlight required for LCD screens), and could be "erased" and "rewritten" as often as desired.

Current products like the Kindle -- a clever mix of features, including a low-power processor, inexpensive flash memory, built-in EVDO wide-area networking and, of course, an e-paper display that consumes next to no power -- have finally brought the technology into the public eye. "E-book readers have gotten the world excited about e-paper," says Barry Young, an analyst at market research firm DisplaySearch.

But although the technology behind e-paper displays has improved greatly over time, it's still just on the threshold of real success, according to Young and other observers. Displays like the Kindle's are beginning to provide the contrast and resolution of traditional ink on paper, but physical flexibility and full-color display are still around the corner.

A display technology based on electronic 'ink'

The first successful demonstration of e-paper technology was made by Nick Sheridon at Xerox's Palo Alto Research Center (PARC) in the 1970s. His technology, called Gyricon, used tiny rotating spheres of electrically charged plastic, black on one side, white on the other, suspended in bubbles of oil between transparent electrodes.

Gyricon technology never delivered the contrast and resolution that a display screen for personal electronic devices requires, but it was used for signs. (Xerox and PARC are now looking at other ways to combine paper and technology, including papers whose printed images fade away over a short period of time -- like a day.)

The current crop of EPD displays is based on electronic "ink" that the E Ink, a supplier of electronic ink technology, has been developing since 1997. E Ink's electrophoretic technology puts oppositely charged black and white pigments into tiny "microcapsules" filled with a transparent fluid. The capsules are fixed to a substrate and sandwiched between electrodes, and when a current is applied, one pigment is drawn to the positive electrode, one to the negative.

The ink is bistable -- that is, it requires electrical power only to change its state, making it very energy-efficient. Although displays based on this ink are not as high-contrast as backlit computer screens, which can make them hard to read in dim light, their reflective surface allows them to be read in daylight situations that would wash out conventional laptop displays. Most importantly, eliminating the power demands of the backlighting needed by conventional LCD displays means that e-paper displays draw negligible power.

Another advantage is that e-paper displays can now take any shape, according to Sri Peruvemba, E Ink's vice president for marketing. Until recently, they had been built on glass -- particularly the active-matrix displays used by today's e-book readers. But the technology is rapidly moving to plastic substrates that will make e-paper almost as flexible as ... paper.

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Showing up on the market

E-paper displays are already showing up in consumer applications, even though consumers may not recognize them. Jennifer Colegrove, an analyst at market researcher iSuppli, identified several product categories in addition to e-book readers, including displays for wearable and carryable products like watch dials, mobile phones, credit cards and security-system cards; instrumentation applications like the capacity meter on Lexar JumpDrive USB drives; and signage. Point-of-sale devices like electronic shelf labels can be updated remotely, Colegrove explains, or promotional signage can be updated by time of day -- breakfast specials in the morning, for example, and dinner in the evening.

EPD screens have great advantages for consumer electronics applications, says Colegrove: their very low power consumption means devices can run for days or weeks rather than hours. In active-matrix configurations, they can produce very high resolutions, and they are readable over a wide illumination range, even in sunlight.

But there are disadvantages, too. Although the displays need power only when they're redrawn, the redraw itself is much slower than an LCD screen, which makes the technology unusable for faster moving images, such as animation effects and video. Because they're reflective, EPD signage needs to be illuminated in dark areas, which makes it less attractive than electroluminescent technologies like LEDs. And even though EPD screens can be read in direct sunlight, the screen contrast is much lower than backlit LCD screens.

The resolution of EPD screens is improving rapidly. Active-matrix displays like those used on the current generation of e-book readers can work at relatively high resolutions (the Kindle screen displays 167 pixels per inch), and Seiko Epson recently showed off an A4-size (13.4-in.) display prototype with 3104 by 4128 resolution, about 385 ppi, that uses E Ink's electrophoretic ink on a Si-TFT glass substrate.

E-paper displays are currently limited to black-and-white, and they display only a limited range of gray tones (the Kindle display renders four levels of gray, iRex Technologies' iLiad reader renders 16).

These current limitations lead at least one industry observer to predict that the acceptance of e-paper displays will take a while: "E-paper is still five years from being a mainstream technology," says Len Kawell, a distinguished engineer at Microsoft. "E-paper is very slow to change state, to turn the page, almost a second -- there's that flash, that visual artifact, of the switch to black and back as the screen is cleared and redisplayed."

Kawell, who is currently working on enhancing Windows Mobile, has been interested in e-book readers for more than a decade. He bought a Kindle when they first came out and feels that the screen's contrast is too low. "While it looks like paper, it's still got a shiny, reflective screen," he says. "You get a lot of reflection from the plastic screen surface, and it's difficult to get lighting that's bright enough to read but doesn't cause a glare problem."

The slow display causes "some weird UI-ness," he continues. "Typing is difficult because the letters are slow to echo to the screen. There's a lot of work to be done yet. You're moving physical objects around and that takes physical time, not like LCD displays that change the state of electrons."

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Futures: New technologies, new economics

What kinds of technological improvements to e-paper could get consumers to adopt e-paper applications? Color is obviously one factor, and while it's not there yet, it will come, according to iSuppli's Colegrove. "There is plenty of potential for technological improvements that would increase the reflectivity of current e-paper technologies like those of E Ink and Fujitsu that use overlay filters," she says. "Further in the future, there's the possibility of color electronic ink." She predicts that color e-paper displays will be available in two or three years. E Ink's Peruvemba agreed with that time frame, and said his company will demonstrate a color display prototype at a trade show in May.

There are other technologies related to electronic ink on the horizon that promise high-quality color as well: DisplaySearch's Young cites Qualcomm's microelectromechanical system (MEMS) technology that provides saturated color, but consumes more power than e-paper.

Design and flexibility will also help determine e-paper's success, according to Young, who is particularly interested in Polymer Vision's Readius, a device that is currently available in Italy and due in the US in July or later. The Readius looks like a candy-bar-style mobile phone, but unfolds a flexible EPD screen to become an e-book reader.

The Readius screen uses organic thin-film-transistor (TFT) technology. "The Readius is the first use of organic TFT technology for an EPD screen," Young explains. According to Young, screens such as the Kindle's use an active-matrix design composed of silicon transistors. Because silicon technology is created using temperatures up to 300 degrees Centigrade -- a temperature that melts plastics -- these screens have, so far, been limited to glass. Organic TFT uses polymers rather than silicon, and so allows for more flexible materials.

Young says one company, Plastic Logic, is making large flexible displays using E Ink materials: "They can make a 10-to-12-in. display that would replace the newspaper. They have prototypes now, but we won't see product until the end of the year."

Fujitsu showed off a concept for a device based on a similar kind of large, flexible screen at the Consumer Electronics Show in January. The Fabric PC looks like a soft trifolded portfolio. Opened, it reveals a flat keyboard on one panel and a display on the other -- a display that wraps under the keyboard. Unfold the keyboard as well and the entire inner surface of the device is an EPD screen as big as a desktop display.

The Fabric PC isn't a product prototype, stresses Paul Moore, senior director of mobile product marketing at Fujitsu, but an indication of the direction the company sees the market taking. A Fujitsu subsidiary, Fujitsu Frontech, is one of the companies working on EPD technology, and it has produced sample quantities of color e-reader devices and sign panels.

While concepts like the Fabric PC get headlines, it's the smaller displays that will find a market first, said Moore. "These e-readers are pricey," he said. "But the cost factors will come down. Screens will get cheaper when incorporated into consumer devices in mass quantities. EPD displays are theoretically cheaper than LCDs -- and they're moldable, shapeable. We've just got to get over that chasm of market acceptance."

Crossing the chasm is on Peruvemba's mind as well. He expects that consumers will begin to see small e-paper displays in the short term: "We'll see more companies making little segmented displays for devices like Lexar's USB drives. If an e-book reader is a 10 in terms of complexity, they're 1's. And that's now. In three to five years, who knows?"

Overall, there is a feeling of potential about e-paper that's fueled in large part by the size of the current market for publishing on paper. If e-paper grows from its current 0.1% of that market to even just 3 per cent or 4 per cent, said Peruvemba, "you'll be looking at a $400 billion market."