A TECHNIQUE originally used to cut headlight glare in cars鈥� rear-view mirrors has been adapted to create a new 鈥渆lectronic paper鈥� display for MP3 players and mobile phones. Called a NanoChromic display, or NCD, it was shown operating on a converted iPod by Dublin-based company Ntera at the DEMO@15 technology show in Scottsdale, Arizona, last week.
Unlike LCDs, electronic paper displays can be viewed from almost any angle and in a wide range of lighting conditions, much like paper itself. Another key characteristic is that they require very little, if any, power to maintain an unchanging image.
At the heart of an NCD is a layer of a so-called 鈥渆lectrochromic鈥� material, which is normally transparent but turns blue when a negative charge is applied. It requires no moving parts. This makes NCDs unique among electronic paper technologies, says Dan Wood of Ntera.
Advertisement
Electrochromic material has been used in the past to darken rear-view mirrors in cars. In Ntera鈥檚 new display, an array of transparent electrodes made of metal oxide semiconductor, mounted on a transparent film, allows it to produce images with a resolution of around 0.25 millimetres, or 100 dots per inch. Adding an opaque white layer of titanium dioxide behind the electrochromic layer creates a white backdrop to the monochromatic images that makes them more readable. The company is also planning eventually to develop a colour display.
鈥淯nlike LCDs, electronic paper can be viewed from almost any angle and in a wide range of lighting conditions鈥�
Adrian Geisow, head of display research at Hewlett-Packard Labs in Bristol, UK, says there should be room for a variety of different types of display. 鈥淗istorically there has never been a universal display. They all have trade-offs,鈥� he says. He expects that different technologies will lend themselves to different applications.
Displays that require no power to maintain the image might be best suited for poster-like advertising banners. Others might be more suited to mobile devices or for shelf-edge displays that show prices in supermarkets, where power consumption is less important than the ability to change prices quickly throughout the store. So far, none of the companies making electronic paper has been able to achieve good high-resolution colour images.
Although Ntera鈥檚 NCDs have no moving parts, the displays are unable to switch pixels on and off fast enough to be used in TVs or in streaming video on a computer monitor. This is because electrochromic displays can take some time to build up charge, says Geisow.
Ntera hopes that its display will give it the edge in applications that require high definition. It has designed the electrodes to have an uneven surface, to maximise the number of electrochromic molecules that make contact with it. This creates a denser, better-defined image and also allows the pixels to be switched on and off faster.
