Most popular e-readers available today tend to be based around a 6-inch screen. Though you can read technical manuals, textbooks (with graphics and tables), comic strips or electronic magazines on these devices, the roughly paperback-sized display does tend to feel just a little cramped. The Kno double-screened digital textbook offered hope of bigger display real estate a few years back, but dedicated hardware was abandoned in favor of a multi-device app. Together with E Ink Holdings, Sony has developed a new flexible electronic paper display technology called Mobius, that will make its debut in a new 13.3-inch Reader prototype at EDIX 2013 in Tokyo between May 15 and 17.

The "flexible" part of the recently-detailed Mobius e-paper display technology doesn't necessarily relate to its ability to bend, but rather to its lightweight, shatterproof or rugged characteristics. It's based around a thin film transistor technology that's formed on a plastic substrate rather than glass. This results in significant weight savings over equivalent glass-based products, meaning that Sony can increase the display size without making a reader that's just too heavy to handle.

The prototype is reported to tip the scales at a student-backpack-friendly 358 g (12.6 oz), which is not too bad at all for a device with dimensions of 233 x 310 x 6.8 mm (9.1 x 12.2 x 0.26 in).

The e-reader has a 13.3-inch, 1200 x 1600 dot resolution screen – that's roughly the size of an A4 sheet of paper – with a 16-level gray scale, and is topped by an electromagnetic induction touch panel for page swipes and menu options. Rather than having to type notes on a virtual keyboard, though, students will also be able to write in the margin using a pen stylus.

There's 802.11b/g/n Wi-Fi, 4 GB of included storage (with microSD card expansion), and a Li-ion battery that offers about three weeks of usage between charges (with the wireless technology switched off). At the moment, the prototype appears to be limited to PDF file support only, but that will likely change prior to release.

Sony has announced that it will now field trial the new Reader in collaboration with three universities ahead of commercial availability later this year for an, as yet, undisclosed price.

Sources: Sony Japan, E Ink via Engadget