Sony has unveiled a tablet barely 7mm thick that is built around an A4-sized touchscreen made of electronic paper.

The Digital Paper tablet uses the well-known E-ink display and lets people write notes on and annotate the documents it displays.

Designed for office use, Sony said that the low-power device should work for three weeks without needing to be recharged.

The wi-fi using gadget will go on sale in May and should cost $1,100 (about GH¢3,000).

The tablet is the first to be built using a new version of E-Ink's display technology developed in collaboration with Sony.

All the earlier versions of the low power display are built on glass substrates making them heavy and relatively thick. The new type of display, called Mobius, is built on plastic, making it about half the weight of one made using glass. The screen has a 1200 x 1600 resolution dot display.

The tablet displays documents in the Adobe PDF format and these can be written upon using the gadget's stylus. Documents prepared in other formats are converted to PDF before being displayed.

Despite being a touchscreen the device also retains some of the properties of paper and allows a user to rest their hand on the display while they write.

It has 4GB of internal storage that can be supplemented using micro SD memory cards.

A prototype of the Digital Paper tablet was shown off in May 2013 in demonstrations that emphasised the flexibility of its screen. However, the tablet being released in May is rigid as it has a plastic case. Publicity material provided by Sony suggests versions that retain their flexibility are in development.