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New cell phone screens battery-friendly

Mobile phone screen technology in development can keep displays running all day, thanks to the sun and water. Photos: 3D screens

SAN FRANCISCO--A new breed of screens for cell phones, now in development, is getting back to nature.

Qualcomm and others are promoting new screen technology for handhelds and mobile devices that can stay on all day without sapping battery life, thanks to the sun or liquids. As a result, a cell phone equipped with such a screen could stock quotes, news stories or show a music video to go along with a built-in MP3 player. Currently, phone screens stay dark--mostly by necessity.

The difference is that the new screens don't need to be backlit, as do current screens. Instead, they are primarily illuminated by light from the sun or the movement by liquids inside the screen.

Backlights are murder on batteries, Mark Gostick, CEO of Liquavista, a Royal Philips Electronics spinoff that makes liquid-filled screens, said at a meeting here at the conference taking place this week. The backlight can consume 90 percent of the power supplied to the display, and the display itself can consume 30 percent or more of the phone's overall energy, he said.

"The display is the largest drain on the power of the phone," added Paul Jacobs, CEO of Qualcomm, which is trying to market the iMod screen to cell phone manufacturers.

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The iMod screen is essentially a complex mirror. The phone creates images, which then become visible when sunlight or ambient artificial light strikes the screen. Electronics embedded in the iMod screen ensure even lighting and other effects.

In low-light conditions, an integrated light will illuminate the screen. Still, the screen consumes far less energy than regular phone LCDs (liquid crystal displays) in most applications, according to Qualcomm.

While the first iMod screens will show information in black, white and shades of gray, the company has already developed color displays that are capable of showing video, Jacobs said.

"You can have an always-on display," Jacobs said. "You get the full frame rate." Qualcomm obtained the technology when it bought Iridigm in 2004.

Liquavista screens, meanwhile, rely on electrowetting. Each pixel contains water and a droplet of dyed oil. When an electric charge is applied to the outside surface of the pixel, it becomes hydrophilic. The water is attracted to the surface, forcing the oil to the side and making the pixel take on the color of the lower surface of the pixel.

When the charge is reversed and the surface becomes hydrophobic, the pixel takes on the color of the dyed oil.

The first Liquavista screens will appear in watches that can be color-tinted to match outfits. The screens will subsequently appear in phones and provide a full spectrum of colors.

"There is no intrinsic barrier to size. In five years, you could see this in notebooks," Gostick said.

What will it take to become popular? Both companies have completed the basic technology for their products. The hurdle now lies in convincing hardware makers that the screens can be made cheaply and efficiently in large quantities.

"The mobile phone guys want tens of millions of these things," Gostick said. "Right now, the only game in town is LCD."

Other companies, such at Toppoly, continue to promote organic light-emitting diodes, or OLEDS, which are made up of materials that light up when electronic charges are applied. MP3 makers and some phone makers have already begun to adopt OLEDs.