STRONG DEVELOPMENTS AFOOT
Many leading companies are committed to the development of e-ink, e-paper, and flexible displays. In fact, a number of joint development efforts are under way, such as those with Polymer Vision.
While the company has strategic partnerships with Dupont, E-Ink, and SiPix, as well as a close working relationship with Philips, Polymer Vision is looking for even more partnerships. Some of these companies may build products around their technologies, while others will license out their technology.
E-Ink and Ambient Devices joined forces to create a simple household device that reliably forecasts the local weather. Their Weather Wizard uses E-Ink's ink to continuously display fiveday weather forecasts, broadcast in real time, over Ambient's nationwide wireless network (Fig. 5).
Device makers such as Ixys already have driver ICs for e-ink displays on the market. Ixys introduced the industry's first standard product driver for e-paper displays based on E-Ink's e-ink technology. Also, Hitachi Ltd. and Bridgestone Corp. recently reached an agreement to mutually cultivate the market for e-paper displays with an eye toward commercialization.
Researchers at the California Institute of technology in Pasadena and the University of California in Los Angeles designed a single-dye compound that can display the three primary colors of red, green, or blue, depending on the applied voltage. The compound is a bistable catenane, a molecule that consists of two interlocking rings. It can be used as a single pixel that can be turned on to any of the three primary colors. Further development is needed to make the material feasible, though.
A full-color flexible display is the ultimate goal for Universal Display Corp. It's using an active-matrix organic light-emitting diode (OLED) display, fabricated on a flexible metal foil substrate, based on Universal's proprietary technology.
The company already has installed a novel full-color OLED deposition system. The system, made by Japan's Tokki Corp., is sold through Hitachi High Technologies Corp. It's designed to deposit a variety of organic and metallic films using vacuum sublimation and evaporative techniques with high-resolution patterning capabilities. With this design, the system can handle transparent, opaque, rigid, and flexible plastic, glass, and metal foil substrates.
ADDRESSING FUTURE NEEDS WITH NEW MATERIALS
Use of nano-structured materials for later generations of flexible displays is under investigation. "In today's display industry, indium tin oxide is almost exclusively used as a transparent conductor," says Robert Murphy, a researcher at the Center for Advanced Photonics and Electronics (CAPE) at the University of Cambridge in the U.K.
"However, this material has three serious drawbacks for next-generation displays," he notes. "Its cost has risen by over an order of magnitude in the past five years. It is not compatible with the need for flexible displays. And, it is difficult to recycle."
Murphy's observations are part of a report on a research project issued by Advanced Nanotech while collaborating with CAPE. Together with CAPE, the company is developing a carbon nanotube flexible display that's environmentally friendly and more efficient to manufacture than present materials.
Researchers at the University of Tokyo are using organic semiconductor devices to make a rollable display in Braille. The display consists of plastic actuators driven by organic pentacene thin-film transistor (TFT) devices on top of a 20- m thin polyimide plastic substrate.
Voltages are fed to conductive polymer actuators, moving them upward and pushing attached hemispheres on the underside of the rubber-like surface. This lets the display form bumps in the shape of Braille letters. Up to 24 letters can be formed on a 4- by 4- by 0.1-cm display. The display dissipates less than 1 mW.