Earlier this week Sony unveiled a new digital paper prototype device with a couple of key differences over what we’re used to seeing in e-readers. The first is its size. Rather than the typical 6-inch displays such as the Kindle uses, Sony has gone with a 13.3-inch 1200 x 1600 A4 panel. The other key difference is the fact you can use a stylus to scribble notes on your e-books.All we had for the announcement a few days ago was a picture of the device, but Sony has now decided to show off what its digital paper notepad can do at a trade show. You can see it in action in the video below:What’s clear immediately is how light the notepad is in the hand. As you can see, most people are easily holding it in one hand. That’s due to the fact it doesn’t use glass for the display, just plastic. In fact, the display is the new E Ink Mobius panel, which has been created with the help of Sony who brought their mass production experience into the mix.Writing on the notepad looks like it could be a pleasant experience despite the clear delay before characters appear. The resolution of the screen also helps to keep the text looking very crisp and allows you a lot of space to write without having to constantly move to a new sheet of digital paper.Sony is carrying out a test release of the device at three universities in Japan soon, but has also promised a commercial release before the end of 2013. All that’s missing now is a price point. I’m really hoping Sony can come in lower than tablets, otherwise this digital notepad is going to be a hard sell.