The Future of E-paper

The Kindle is only the beginning.

This version of this article originally appeared in Computerworld's print edition.

Amazon.com Inc.'s Kindle has turned a long underperforming category of tech gadget -- e-book readers -- into an overnight hit and in the process has boosted interest in electronic-paper display (EPD) technology. Both the Kindle and its rival, the Sony Reader 505, display images of pages that look uncannily like printed pages and consume next to no power.

"E-book readers have gotten the world excited about e-paper," says Barry Young, an analyst at market research firm DisplaySearch. But a few key characteristics are still around the corner.

Current EPD displays are based on electronic "ink" that E Ink Corp. 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 current is applied, one pigment is drawn to the positive electrode, the other to the negative.

The ink is bi-stable -- that is, it requires electrical power only to change its state, making it very energy efficient. The reflective surface of the displays makes them readable in daylight that would wash out conventional laptop displays. Most important, EPDs use only a fraction of the power that conventional LCD displays require.

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

The resolution of EPD screens is improving rapidly. Active-matrix displays like those used on the current generation of e-book readers can offer relatively high resolutions (the Kindle screen displays 167 pixels per inch, or ppi), and Seiko Epson Corp. recently showed off a 13.4-in. display prototype with 3104 x 4128 resolution, about 385 ppi, that uses E Ink's electrophoretic ink on a silicon thin-film transistor glass substrate.

EPDs are already showing up in other consumer products, including watch dials, cell phones, credit cards and security cards. They're also found in instrumentation applications, like the capacity meter on Lexar JumpDrive USB drives, and in signage, says Jennifer Colegrove, an analyst at market researcher iSuppli Corp.

But there are disadvantages. Redrawing an image on an EDP takes longer than it does on an LCD screen, which makes the technology unusable for animation. Because EPDs are reflective, signage needs to be illuminated in dark areas. And screen contrast is much lower than it is with backlit LCD screens.

Moreover, e-paper displays currently are limited to black and white and a range of gray tones. (The Kindle display renders four levels of gray; iRex Technologies BV's iLiad reader, 16.)

These constraints may delay acceptance of the medium. "E-paper is still five years from being a mainstream technology," says Len Kawell, a distinguished engineer at Microsoft Corp.

Still, overall, there is a feeling of potential about e-paper that's fueled largely by the size of the current market for publishing on real paper. If e-paper grows from its current 0.1% of that market to even 3% or 4%, says E Ink's Peruvemba, "you'll be looking at a $9 billion to $12 billion market."

DeJean is a freelance writer who began writing about computers after Cobol but before C++.

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Copyright © 2008 IDG Communications, Inc.

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