The race is on to come up with the world's thinnest cell phone screen. On Tuesday, both Japan's Sharp and Taiwan's AU Optronics (AUO) said they had developed prototype displays that are less than a millimeter thick.

The Sharp LCD measures 2.2 inches across the diagonal and is just 0.68 millimeter thick, making it the thinnest cell phone screen in the world, the company said Tuesday. Coming in just behind in the AUO screen, which is a 1.9-inch model that's just 0.69 millimeter thick.

The screens used in most of today's phones are on average between 1.5 millimeters and 2.5 millimeters thick, so the new Sharp screen is significantly thinner, said Miyuki Nakayama, a spokeswoman for Sharp in Tokyo.

Sharp is coy about just how it managed to reduce the thickness but said innovations lay in two major areas: improvements in production technology that enable the use of thinner glass sheet and a reduction in the thickness of the backlight that sits behind the screen.

Thinner cell phone screens are good news for consumers because they allow phone makers to either produce slimmer phones or to pack more technology into the same-size space. Some recent models of cell phone have been getting larger in part because of the addition of new features such as digital TV tuners and smartcards.

However, there's no word from Sharp on when the screen might start appearing in cell phones. The company is currently in talks with cell phone makers and hasn't decided when it will start production, said Nakayama.

The svelte screens will be unveiled at FPD Expo, which runs from Wednesday to Friday in Yokohama, Japan.