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Organic LEDs gear up for portables push

Posted: 29 May 2002 ?? ?Print Version ?Bookmark and Share

Keywords:OLED? LCD? Society for Information Display?

That OLEDs have displaced LCDs as the young Turk of flat-panel displays could be seen by the show floor activity and in the papers presented at the Society for Information Display 2002 conference this past week. Prices need to come down, and certain technical challenges must be overcome, before they can compete seriously with active-matrix LCDs?today's flat panel of choice. However, industry watchers say that it won't be long before OLEDs make their way into handheld electronic products.

"It is the next big thing in displays," said David Mentley, vice president of market research firm Stanford Resources Inc. "The displays just look great, and a complete manufacturing infrastructure is now developing."

Mentley cited "more than 50 companies putting serious money into developing organic light-emitting diodes," including some with deep pockets. Philips and DuPont, for example, have demonstrated their first products and are set up to deliver full OLED-based system solutions. "We can expect products soon in handheld applications," Mentley said.

The OLED's attractive features include operation at low voltages (5V to 20V); thin, lightweight monolithic structures; and full-color graphics. Because this is an emissive technology, OLEDs yield a wide viewing angle and high contrast. Unlike voltage-controlled LCDs, OLEDs are current-controlled and do not throttle, but generate and modulate light when and where it is needed.

Still, vendors face a number of technical hurdles if they are to bring down prices?which now surpass those of passive-matrix LCDs?and move OLEDs into the volume market. These include lifetime differential aging, temperature sensitivity, color purity and manufacturing yield.

"All current OLEDs compete with passive-matrix LCDs for now and are higher priced," said Mentley. "And while active-matrix OLEDs will be phased in by most current LCD manufacturers, AM-OLEDs cannot seriously compete until beyond 2007."

In fact, most big LCD manufacturers have research teams investigating OLEDs, just in case. But the debate continues as to the timing and extent of the technology's inroads into AM-LCD territory.

"We've had other contending technologies, such as field-emissive devices and plasma displays, that went after the LCD space, but none showed the characteristics that OLEDs bring to the party," said Stewart Hough, vice president of business development for Cambridge Display Technology, in a SID panel. "It took 15 years for LCDs to take over the CRT as the display technology for computers; it will take much less [time] for OLEDs to make an incursion into applications currently served by AM-LCDs."

Shaving by OLED

Studies have shown that users prefer emissive-display technologies, especially for such small-form-factor applications as cellular phones, handheld games and PDAs?the applications and form factors OLEDs now serve. Philips even demonstrated an electric shaver that uses an OLED to display timing and shaving effectiveness. When turned off, the display becomes a mirror. The shaver will be available in the United States next month, Philips said.

Making larger displays for notebook computers might prove problematic, however, said Jun Sook, an executive at Samsung Electronics Co. Ltd. "There are fundamental issues that need to be addressed before we relegate AM-LCDs to the 'dinosaur of displays' status," he said.

Among large-OLED demos that have been making the rounds of conferences like SID in the last year or so is a 17-inch-diagonal full-color display from Toshiba and a 13-inch panel from Sony Electronics. The 17-incher is considered the biggest OLED panel ever manufactured, but its price is "around $2 million with delivery," a Toshiba Corp. booth handler at SID confessed.

The Sony panel is an 800x600-pixel OLED in the SVGA format that was produced as a low-temperature polysilicon thin-film-transistor AM display. Its light output is said to be greater than 300cd/m?. Pixel pitch is 0.35-by-0.33mm, and the 264-by-198mm panel itself is a thin 1.4mm.

The OLED's touted brightness and "live" colors were on show at the Eastman Kodak booth, in a Gameboy terminal with an enticing OLED display. Observers said that once kids get a look at an OLED game they will never go back to an LCD model.

One clear challenge to OLED proliferation is volume manufacturing. "We need to apply roll-to-roll manufacturing lines to OLED production to reduce costs," said Roger Stewart of Alien Technology, whose Fluidic Self-Assembly (FSA) technology makes it possible to place large numbers of small components across a panel surface, tile style. In an SID paper, Alien described its manufacturing setup for OLEDs in the company's Pleasanton facility.

The authors detailed a new polymer-LED display architecture that is said to be suitable for AM OLEDs. The driver ICs, called NanoBlocks, are uniformly embedded within the display backplane using the FSA process. Each NanoBlock IC drives the nearest eight pixels with 16-level gray-scale capability. Successful integration of the NanoBlock/FSA process with the light-emitting polymers needed for AM-OLEDs is expected to yield high-performance, emissive, flexible-plastic displays.

Market analyst Display Search pegs the worldwide OLED market at roughly $100 million this year, rising to $2.8 billion by 2007?assuming the supporting infrastructure is established, including current-operated driver circuits. Both DuPont and Philips are among those working on such drivers.

DuPont Displays has announced the first in a series of OLED driver ICs developed with Clare Inc. The companies collaborated on the design and production of the Mxed 301 integrated driver controller, with full support for gray-scale and video applications. Designed for single-color, passive-matrix polymer-based OLED displays, it features a 128-column current-sourcing anode driver, 80 common-cathode row drivers and 4-bit gray scale. Samples are due by year's end.

At SID, DuPont showed both passive, single-color displays (a 128x64-pixel, 2.1-inch unit and a 160x160-pixel, 2.7-inch OLED) and active-matrix, full-color ones. The AM demonstrations included a 4-inch QVGA display inside a Pocket PC PDA.

"Our aim is to provide OLEDs, period, whether as passive-matrix or active-matrix devices, on glass or plastic?with flexible plastic as the ultimate goal," said Dalen E. Keys, chief technology officer at DuPont Displays. While Keys doesn't see OLEDs entering notebooks for the next five years, he said that OLEDs in the sub-8.3-inch form factor will be feasible with next-generation materials.

Philips, too, says it is ready to provide OLED drivers. "As the No. 1 provider of driver ICs for both CRTs and LCDs, I see no problem in retooling to bring out drivers for OLED displays, when appropriate," said Jan H. Pape, general manager at the company's BL Large Display Solutions.

Might be the year

Not all of the 40th annual SID conference was devoted to OLEDs. Also drawing attention were electroluminescent technology from iFire Technology, LCD-based head-mounted eyewear from MicroOptical and paperlike AM microencapsulated electrophoretic displays from E-Ink. National Semiconductor Corp. introduced a single-chip column-driver IC for LCD-based notebooks and Amulet Technologies unwrapped a combo LCD controller/GUI engine that eliminates the need for complex code to draw each pixel on an LCD.

Still, OLEDs pretty much stole the show. Said Omid Milani, director of NEC's display business unit, "2002 may be a watershed year for them."

? Nicolas Mokhoff

EE Times





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