New, Cheap Display Technology in Works

July 13, 2000 -- Imagine reading ABCNEWS.com on a paper-thin, flexible sheet of plastic at the breakfast table.

That’s one of the promises of light-emitting polymer technology, a system developed by scientists in Cambridge, England that might be the next revolution in mobile phone and computer displays.

Organic light-emitting devices such as LEPs and their cousins, small-molecule displays, are “probably one of the most exciting display technologies to come along in a number of years,” said Chris Chinnock, senior editor of Microdisplay Report, a monthly magazine focusing on small-scale display technology.

Innovation, Innovation, Innovation

Compared to current display devices, LEPs are simpler, cheaper and better, said Daniel McCaughan, president of Cambridge Display Technologies, which holds most of the patents on LEP technology. CDT is now working with licensees such as Japan’s Seiko-Epson, one of the world’s top printer makers, and electronic giant Philips, based in the Netherlands, to produce commercial LEP displays.

Currently, the majority of computer laptops use liquid crystal displays. LCDs are passive, complex, multilayered constructions with crystal molecules that redirect reflected light and pass it through a polarizing layer, which either blocks or passes through the light to a viewer’s eye.

As they emit no light of their own, LCDs require power-hungry backlights to pump light through the crystals. And if you tilt an LCD, colors shift and change because you’re looking at bent light from a different angle.

The basic technology involves molecules of plastic, called polymers, that glow when hit with electricity. An LEP screen is just two layers of polymer sandwiched between electrically charged plates and applied to a substrate, such as glass or plastic.

Unlike with liquid crystals, the polymers don’t need to be on a glass panel. And since they emit their own light, they don’t change color when tilted as LCD displays do.

“Our futurists look at the kind of longer-term future for this stuff and certainly see how you could make roll-up displays,” McCaughan said.

Recent Breakthrough

CDT has been working on the technology for years, but two recent breakthroughs have brought LEPs closer to commercial production. All colors detectable by the human eye can be constructed by a combination of red, green, and blue light. CDT developed separate monochrome displays in red, green or blue in 1996, but only figured out how to manufacture full-color displays two weeks ago.

The color screens are made by a special ink-jet printer, developed by Seiko-Epson, which can produce screens quickly and cheaply. They’ve figured out how to print small screens, like mobile phone screens — now they’re working on printers for larger and larger areas.

“We are now developing an ink-jet machine for drawing large posters, more than five meters [15 feet] without a seam. The ink jet has no limitations,” said Seiko-Epson’s Tatsuya Shimoda. The Seiko ink-jet printer can create color displays up to 200 dots per inch. Today’s standard displays are 72 dots per inch.

Ink-jet production could dramatically reduce the cost of displays, one of the most expensive single parts of a computer system. Ink cartridges are loaded with liquid versions of the red, green and blue polymers and a fourth, conductive polymer. The printer spits tiny droplets of the four polymers onto a screen backing. When slapped between electrodes, that’s a full-color display.

Not Quite There

LEPs aren’t the only OLED display technology. Kodak demonstrated a 5.5-inch display using its “small-molecule” OLED technology this May. Motorola has bought into the small-molecule camp and will be producing a cell phone with an color OLED display next year, Chinnock said.

But small-molecule OLEDs, while light and low-power, are still much more complex to manufacture than LEPs. The small-molecule versions are made of several layers of thin organic films, requiring vapor sublimation in a vacuum chamber rather than simple ink-jet printing.

LEPs aren’t quite at a commercial stage yet. CDT is perfecting its blue color, trying to extend the display life and figure out how to apply the material to plastic rather than glass substrates for a lighter, cheaper display.

“We’ve demonstrated thousands of hours. For some applications we want tens of thousands of hours,” years before brightness begins to drop on the display, McCaughan said.

LCD Crisis

Camcorders, cell phones, palmtop computers, portable televisions, flat-panel monitors — the demand for LCD screens is exploding, and there’s an industry-wide shortage as companies scramble to build new plants. The projected growth of mobile devices is fertile ground for a competitor to LCDs, said Leo Suarez, director of worldwide product marketing for IBM Mobile Systems.

“If this technology from Cambridge bears out, if and when it gets to the point where it’s available in high volumes, I think everybody in the industry would be interested in it,” he said.

McCaughan said products featuring LEP displays will be available in 2001 or 2002. But full-scale mass production is a few years down the road, Chinnock said, as the massive display-fabrication business checks out the new technology and slowly converts factories.

“It’s not going to revolutionize things next week — that’s for sure. But there is potential there, and that’s why a lot of people are excited.”