Fujitsu has made progress in its development of flexible, paper-thin displays that consume very little power.

The company unveiled its latest prototype today: a 7.8in panel that can display up to 4,096 colours. The display, which is the same size as a sheet of A5 paper, was built-in to a thin case in the form of an electronic book reader. It was on display at the Ceatec show, which opened today.

The e-book reader was rigid, but the flexibility of the displays could offer an advantage in other types of applications. Fujitsu offered the example of an electronic advertising panel that could curve around the top of a train or subway car.

The display area of the prototype shown at Ceatec was about four times as large as that of another prototype Fujitsu showed in the middle of last year.

The e-book reader was deceptively light, weighing only 180g, much less than many visitors to Fujitsu's booth expected before they took it in their hands. Its light weight comes largely from the use of a plastic substrate for the display, rather than a glass substrate such as those used for LCD (liquid crystal display) panels.

Pages could be turned with the push of a button. The screen refreshes in several sweeps, from left to right, and the time taken to redraw the image depends on its complexity and the number of colours, said Fumiyuki Hashimoto, a Fujitsu spokesman. A complex image takes around 4 seconds to refresh, while a simpler, eight-colour image can be drawn in about a second, he said.

The prototype e-book reader includes a SD memory card slot and USB-connector. Fujitsu is still developing the display and doesn't have any commercialisation plans at present.

The prototype has one other major advantage over existing panels - it doesn't require constant power to keep the image on the display. That means portable products can have a much longer battery life.