Researchers at HP Labs are testing a flexible, full-color display that saves power by reflecting ambient light instead of using a backlight. The prototype display's pixels are controlled by fast-switching silicon transistors printed on top of plastic. If the technology can be commercialized, the display will compete with liquid crystal screens as well as other low-power color flexible displays in the works.

Reflective color: This prototype display uses stacks of red, blue, and green dyes and electrically controlled mirrors to produce color images without the need for a backlight.
HP Labs

"Our goal is to make a display with the color saturation of newsprint that can be manufactured for about $10 per square foot," says Carl Taussig, director of the Information Surfaces Lab at HP's Palo Alto, CA, research center. At this price, reflective color displays could replace paper for applications such as signs and billboards, Taussig says, although he estimates that this will take a year or two at least.

HP is collaborating with Phicot, a subsidiary of Ames, IA-based Powerfilm, which prints high-performance transistors on plastic. HP plans to target both the e-reader and tablet PC markets.

The e-reader screen market is dominated by E-Ink, a company based in Cambridge, MA, that makes black-and-white reflective displays incorporating tiny microcapsules. E-Ink's screens have the look of paper, do not need a backlight, and do not require any power once the pixels have switched between black and white. But it is also too slow to show video and, as yet, is only available in black and white.

In contrast, Apple's iPad uses a more conventional liquid crystal display. This means it produces vibrant color, but it is also expensive, power-hungry, and vulnerable to glare. The display is also relatively fragile because it's built on top of glass. Many manufacturers believe there is still a market for low-power reflective displays.

Flexible display manufacturers are watching how consumers respond to the iPad. But they're also working to develop robust reflective displays built on plastic that use less battery life without giving up the functionality of LCDs.

"Color will make all the difference," says Nick Colaneri, director of the Flexible Display Center at Arizona State University, which partners with most of the major display manufacturers on technology development. Without color, reflective displays will be limited to niche markets, he says. Using plastic transistor arrays, which promise better durability, will also be key, he says, although major manufacturing challenges remain.

"The first company to get one of these out will have a strong position, but at the end of the day it comes down to cost," Colaneri says. "There are several radically different approaches to manufacturing, and it's too early to say what the costs will be."