Sony and LG.Philips, two of the world's biggest flat-panel display makers, unveiled flexible full-colour screens at a display industry show in California this week.

Sony took the wraps off its prototype and released an impressive video showing the display being bent to form a semi-circle while still displaying a moving video image. The 2.5in display has a resolution of 160 pixels by 120 pixels making it a little larger than the typical mobile phone screen with a slightly lower resolution.

The screen from LG is larger at 4in in diagonal width and has a higher resolution of 320 pixels by 240 pixels. In contrast to Sony's video, LG.Philips released only a photo that showed the display curved at a slight angle.

Typically, flat-panel displays are built onto thin sheets of glass but the Sony and LG.Philips screens are made on thin sheets of plastic and metal respectively. That allows them to be bent but also introduces a range of other problems such as keeping everything aligned and working while the panel is flexed. Indeed, the video of Sony's prototype showed several bad pixels and other problems.

Neither company has said when it thinks the displays will be ready to go on sale but early customers might be attracted to them for reasons other than their flexibility, said Paul Semenza, an analyst with iSuppli, who attended the Society for Information Display conference where they were announced.

"What tends to get forgotten is that these displays are also rugged and lightweight," he said. "Those are valuable properties."

Sony sees Oled technology as important for its future products and is putting a lot of research and development resources behind screens like that unveiled this week.

The screens are different from today's LCD and PDP (plasma display panel) screens in that Oled pixels use an organic material that emits its own light, so no backlight is needed. That means the screens consume less power and can be made thinner. Oleds also handle fast-moving images better and offer good colour reproduction.

At the Consumer Electronics Show in Las Vegas in January Sony showed off prototype televisions based on larger, non-flexible 11in and 27-inch OLED panels. Thanks to the lack of a backlight the 11in prototype was just 11mm thick but displayed a vibrant, colourful image. Sony plans to have its first Oled TVs on sale in Japan this year.

Last week in Tokyo Sony unveiled its latest Oled TV prototypes, which appeared to be close to commercialisation. The sets had an integrated digital TV tuner and could also accept a high-definition input via an HDMI (high-definition multimedia interface) connector.