New mobile screens cut battery use

A new breed of screens for mobile 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 mobile phone equipped with such a screen could continually broadcast 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 of liquids inside the screen.

Backlights are murder on batteries, Mark Gostick, CEO of Liquavista, a Philips spin-off that makes liquid-filled screens, said at a meeting in San Francisco at the Society for Information Display conference taking place last week. The backlight can consume 90 per cent of the power supplied to the display, and the display itself can consume 30 per cent or more of the phone's overall energy, he said.

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

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 normal phone LCDs in most applications, according to Qualcomm.

While the first iMod screens will show information in black, white and shades of grey, the company has already developed colour 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 colour of the lower surface of the pixel.

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

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

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