Originally created 12/06/01

Big leap made in race for flexible video screen



BOSTON -- The picture is small, and it's far from crisp, but researchers claim they've taken an important step in the race to create a video screen with the thinness and flexibility of paper.

The device, described in Thursday's issue of the journal Nature, is fired by plastic transistors that are flexible, potentially inexpensive to make and work well enough to constantly refresh a screen to create moving images.

Since the 1970s, researchers have tried to find a way to combine the best qualities of paper - lightness, flexibility and a sharp contrast that makes it easy to see - with the capability of video to refresh an image.

They've dreamed of newspapers that fill themselves up with the latest stories, sports scores and movie listings, reducing the need to pulp trees for paper.

So far, researchers have been able to create high-quality active-matrix displays necessary for moving images only on glass. The silicon transistors they've used crack when overlaid on flexible material and have to be produced at temperatures so high they would melt plastic if it were used for the display.

The researchers at Royal Philips Electronics in the Netherlands used plastic to make the transistors - unlike silicon, the plastic transistors can bend and can be made at lower temperatures. That should enable development of a plastic display that could fold or crumple like paper.

The researchers claim in the article that they have crammed 4,096 of the transistors into a 2-inch display, which works well enough to create video.

For now, their device is still on glass. But they insist they've cleared the major hurdles for putting it on a flexible surface. And the circuits produce a decent picture: 64 by 64 pixels with 256 shades of gray and the contrast of black ink on paper.

Several companies, including Cambridge-based E-Ink and a Xerox spinoff called Gyricon Media Inc., are working on related technology, but they've started with static images like signs, and high-quality moving images are still years away.

"The biggest thing we've accomplished here is we integrated 4,000 transistors in one device," said Edzer Huitema, one of the Philips researchers. "There are lots of groups showing beautiful single (plastic) transistors. ... What we did is show a device with 4,000 that really functions."

It also refreshes at about 50 hertz, fast enough to stream video.

Pulling that off requires "exquisite uniformity and accuracy," said Russel Wilcox, vice president at E-Ink, which is partially owned by Philips but was not involved in the research.

"This is really impressive work," he said. "The world is moving closer to real, electronic paper."