By John McHale
EWING, N.J. — Experts at Universal Display Corp. (UDC) in Ewing, N.J., won a defense contract to develop their paper-thin, bendable, full-color display for military applications.
Flexible displays may give a new dimension to digitized warfare.
Officials at the Defense Advanced Research Projects Agency (DARPA) in Arlington, Va., are asking Universal engineers to develop the flexible organic light emitting diode (OLED) flat panel display under the agency's new Flexible Display Program.
Experts believe that flexible displays offer several key advantages for military use because they are lighter, thinner, and more rugged than current, non-flexible displays, UDC officials say.
"Flexible flat panel displays offer tremendous benefits to military and commercial markets," says Steven V. Abramson, President of UDC. "By making displays flexible, manufacturers can conceivably develop products that bend, wrap around another object, or roll up when not in use. The applications for military and consumer uses are then boundless."
While the technology has the potential for all these applications, scientists are still in the early stages of development, says Janice Mahon, vice president of technology commercialization at UDC. She says UDC will develop the technology and then license it to a manufacturer, with the first glass product to be available by the end of 2001 or the beginning of 2002. The first flexible device should follow about a year later, Mahon adds.
Other potential military applications include flexible OLED displays on helmet-mounted face shields that identify enemy positions, electronic devices that attach by Velcro to one's sleeve or fold up and fit into a vest pocket to provide mission-critical field data, and pens that house roll-out displays with timely tactical data, Abramson says.
Rapidly reconfigurable camouflage also is a possibility, Mahon says. For example, many camouflage schemes could be displayed on the bottoms of airplanes to enable their pilots to blend in with blue sky, darkness and stars, clouds, fog, or terrain, she explains.
DARPA officials say their goal by 2010 is to create a lightweight, flexible, e-page display that soldiers can roll up to store and throw away when they are finished with it, Mahon says. The DARPA program manager says he would like the display eventually to cost 10 cents per square inch, she continues. However, the technology is still about an order of magnitude away from that goal, Mahon adds.
OLED technology also benefits the military by being more rugged than liquid crystal displays (LCD) and other glass displays because it is solid state technology that uses plastic, Mahon says. LCD technology literally has liquid crystals between two substrates and is subject to vibration problems as well as frozen crystals in extremely cold temperatures, she says. The OLED also will use plastic instead of glass which will enable it to have better resistance to shock, Mahon adds.
The UDC display also performs better in cold temperatures than competing displays because it is a semiconductor device, Mahon says. However at extremely high temperatures up around 200 degrees Fahrenheit, the semiconductor material will melt then cool back into a crystal instead of a solid, she explains. UDC experts are researching different materials that perform better in high temperatures, she adds.
Under the contract agreement, UDC will deliver flexible OLED displays in 1/4 VGA format — both transparent and opaque — that will demonstrate the effectiveness of flexible displays in military applications. UDC engineers will also provide DARPA with research findings relating to its development of active matrix OLEDs. DARPA is funding $500,000 and the remaining $500,000 is cost share from the participants. The DARPA contract is a $1 million, 18-month, Phase 1 Program.
How it works
The transparent, flexible organic light-emitting device uses the basic building blocks of vacuum-deposited, organic small-molecule materials that emit bright light when stimulated electrically. The thin, rugged, lightweight design has the potential to replace or augment a wide variety of existing displays, and to carve out many entirely new display applications.
UDC experts also have recently started making use of phosphorescent material as opposed to fluorescent to enable four times the power efficiency and brightness of fluorescent material, Mahon says.
In fluorescent and phosphorescent materials there are four electron combinations — three triplets and one singlet, Mahon says. However, in a fluorescent material only the singlet radiates light, with phosphorescent materials, all four radiate light, she continues. The phosphorescent material radiates more light, thereby generating less heat, creating almost 100 percent quantum efficiency, Mahon claims.
In its most common structures, known as a "single heterostructure," an organic device consists of a hole transporting layer and an electron transporting layer sandwiched between two conductive layers to form a solid-state thin-film device, Mahon says.
Typically, light emits from the bottom layer, which is transparent, while the top one, usually made of a material like aluminum, is opaque. This new technology uses a transparent top, thereby emitting light from both sides, Mahon says.
The three enabling organic device technology platforms are transparent, vertically stacked, and flexible devices. Transparent devices are possible in part because their organic materials are themselves transparent, which provides the foundation for a vertically stacked pixel architecture for high-resolution, full-color display applications.
Individual red, green, and blue transparent device elements are placed in a vertically stacked arrangement and individually contacted with a differential bias across each element, Mahon explains.
The traditional method has been to place red-green-blue organic device elements side-by-side in much the same way that CRTs and LCDs are configured for full color. It is like watching a big screen TV at a sports bar; when you are up close, the color is blurry and the human eye can see the individual red, green, and blue instead of the intended color mixture.
Yet with vertically stacked pixels, each pixel emits full color, no matter how large, Mahon says. It provides the potential for high-resolution images due to compact pixel size. This technology is equally applicable to head-mounted miniature displays, as it is wall-sized color TVs, she says.
Experts can fabricate these displays at low-cost due to the elimination of the side-by-side pixel growth, Mahon says.
UDC's Program Team includes Princeton University and the University of Southern California, as well as new, strategic partners, Battelle Memorial Institute of Columbus, Ohio, and L-3 Communications Display Systems of Alpharetta, Ga.
UDC has worked with Princeton and USC since 1994 in developing OLED technologies. Battelle experts have developed a barrier layer technology which may accelerate the fabrication of long-lived flexible displays.
For information contact Janice Mahon by phone at 609-671-0980, by email at [email protected], or on the World Wide Web at http://www.universaldisplay.com.
