MEDIA frenzy over the launch of last week overlooked the fact that, like its predecessors and competitors, it remains resolutely monochrome. Not for long, though. A full-colour version of electronic paper, which forms the display of these devices, is to be demonstrated later this month.
of Cambridge, Massachusetts, says it will be demonstrating a colour version of its e-paper at the Society for Information Display conference in San Antonio, Texas, on 31 May, and that products based on its colour e-paper will be on the market by the end of 2010.
The aim is to have a reflective display that uses very little power and is as easy on the eye as the printed word. Like E Ink鈥檚 monochrome e-paper, used in Sony and Amazon readers, the colour version will be based on technology called an electrophoretic display.
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In black-and-white e-paper, each pixel is made up of around 60 plastic microcapsules that contain a negatively charged black powder and a positively charged white powder. To make a pixel black, electrodes underneath the display apply a negative charge to push the black powder to the top. To reproduce shades of grey, some electrodes are positive and others negative, so some microcapsules are white while others in the same pixel are black. Once a page is set, this arrangement uses no power- critical for reading book-length content.
In the new colour display, each pixel will be split into four subpixels showing red, green, blue and white in their 鈥渙n鈥� states. That means squeezing four times as many transistors beneath each pixel to control the electrodes, which has been a challenge too far- until now. 鈥淭he transistor resolution is now getting fine enough,鈥� says Sri Peruvemba of E Ink. But the proof will be in the quality of image they demonstrate in Texas.
鈥淪queezing four times as many transistors beneath each pixel has been a challenge 鈥� until now鈥�
E-paper is not the only game in town, however. in Japan makes the LCD-based Flepia e-reader, which has a colour screen 20 centimetres on the diagonal. It uses a thin sandwich of red, green and blue layers made from a novel liquid crystal material that, like e-paper, only draws power when changing a page.
Early next year, Plastic Logic of Cambridge, UK, plans to launch A4 e-book readers with flexible transistors- which will make e-reader screens more robust and will also allow the gadgets to begin mimicking the bendiness of paper.
