Science & Technology: DISPLAYS
FLATTER, BRIGHTER--AND EASY TO MAKE?
A new screen technology has the industry charged up
In a crowded room, amid the clink of champagne glasses, a woman stares at a new kind of postcard, thinks for a minute, and says "Wish you were here." On the way home that evening, she slips the card into a mailbox. A few days later and half a world away, a friend flicks a switch on the card, hears the clink of the glasses, and watches the sender and her friends jostle in front of the card. He chuckles, and forgives the cliche.
"Video postcards" won't be ready in time to commemorate that big millennium party you'replanning. But they may arrive early in the next century, thanks to a global race to perfect a powerful new kind of flat display. The screens are known as OLEDs, for organic light-emitting diodes. They'll be light and bright, ultrathin and flexible, and easier to produce than most other types of flat screens for computers and TVs. And since the diodes can also act as photodetectors, the new screens may someday be able to capture and store images as well as play them back.POSSIBILITIES. That's the concept behind video postcards. And the technology has inspired many other flights of engineering fancy. Designers at Philips Electronics--a leading player in this budding field--have sketched out newfangled laptops with screens like delicate sails that furl, so they take up less space. Marketeers at Cambridge Display Technology, an OLED startup in Cambridge, England, talk of long, thin, luminescent ceiling panels that could replace the heavy lighting fixtures on jetliner ceilings. Product designers also talk of giant video screens that consumers could one day roll like wallpaper across an entire living room wall. From "smart maps" linked to databases on the Net to glowing neon stock tickers or poetry banners stitched into T-shirts, "the possibilities are literally endless," declares Cambridge Display CEO Daniel R. Chapchal.
Like the more common light-emitting diodes that are used for dot-matrix-style message boards at airports, OLEDs rely on materials that give off light when tweaked with an electric current. But these new screens are far more versatile than the crystalline arrays that make up message boards. In OLEDs, the light-emitting materials are deposited in films and combined with a matrix of electronic circuits that switch on individual picture elements, or pixels. The first applications for such screens are unglamorous backlights for liquid-crystal displays (LCDs) in notebooks. But within two years, OLEDs will start competing with LCDs in handheld computers, cell phones, and camcorders.
For the more exotic applications, like furling notebook screens, many researchers are banking on a plastic variety of OLED--sometimes called light-emitting polymers. Here, the glowing organic materials consist of long, repetitive chains of large molecules that are suspended in solution and spun or sprayed onto a substrate. No fewer than 65 companies have jumped into the field, including Philips, Lucent Technologies, DuPont, and Dow Chemical, as well as a host of Japanese giants. "This is probably the hottest research area in the whole field of flat-panel displays," says David E. Mentley, vice-president for display-industry research at Stanford Resources Inc. in San Jose, Calif.ELEGANCE. For now, Mentley chalks off wall-size screens to hyperactive imaginations. But even without them, he says, OLED sales are likely to soar from almost nothing today to $400 million by 2004. That's small change compared with sales of LCDs, which will hit $12.4 billion this year, but OLEDs are on a steep ramp-up. "I don't think there has ever been a new display technology that went from nothing to 65 players in just three or four years," he says.
The excitement is easy to explain. Despite the efforts of display titans such as Sharp, NEC, Toshiba, and Hitachi, LCDs have never been an elegant solution to the flat-display challenge. They consist of many layers of materials and electronics, assembled in a long and costly series of manufacturing steps. More important, liquid crystals don't actually emit light. They simply shutter light passing from a fluorescent tube at the back of the screen through a complicated array of polarizers and color filters. And LCDs rarely look good viewed from the side.
Compared to all that, an OLED is elegance itself. It requires just a few layers of glowing material. And just as ink pigments come in many colors, different organic molecules emit their own light, in different colors, when excited by a voltage. So it's good-bye to filters, polarizers, or backlights. What's more, the molecules can be deposited on substrates using straightforward techniques borrowed from inkjet printing. These don't require the expensive vacuum-manufacturing gear found on LCD production lines. And the resulting screens look great from any angle.
Some of the first OLED breakthroughs came from Eastman Kodak Co. research labs. In the mid-1980s, the company patented techniques for depositing small organic molecules on a substrate. Today, Kodak maintains a team of about 40 OLED researchers. And it has licensed its technology to Pioneer Electronics, which has demonstrated a full-color, 5.2-inch display for car stereos.FAST MOVES. But the biggest breakthrough came in 1989, when Cambridge University physicist Richard H. Friend and his colleagues discovered light-emitting organic polymers. They formed Cambridge Display Technology to turn these into OLEDs, licensing the technology to Philips, Seiko Epson, and Hoechst, while doing joint-development work with DuPont. Seiko developed an inkjet production technique and quickly demonstrated 2-inch prototypes. Now, Seiko is gearing up to make OLED screens for notebooks. Says physicist Friend: "We've been able to move much faster than I ever thought possible."
OLED makers face plenty of hurdles. With dozens of manufacturers locked in fierce competition, LCD screen quality keeps improving while prices drop. OLED ventures will also have to beat a host of rival technologies. When it comes to flat, wall-hanging TVs, for example, the front-runners are plasma displays, which have drawn huge investments from the likes of Fujitsu, NEC, and Sharp.
Prices for such displays, however, run $7,000 and up. That's not at all the kind of economics Richard Friend and other OLED pioneers have in mind. "It's not fanciful," says Friend, "to think of active electronic circuits that are no more difficult to make than the glossy Sunday newspaper supplement, which you throw away on Monday." Or recycle, if plastic wins the day. The flights of fancy have only just begun.By Neil Gross in NeW YorkReturn to top