Less Windows To Clean in the Future?

Glass vs. plastic
Another technical advance that should help push OLEDs into the big leagues is the eventual ability to put OLED material on plastic, creating a whole new generation of formable, flexible, even dynamic displays. In addition to the application and form-factor advantages, the ability to produce flexible displays using a roll-to-roll process is expected to bring new cost and volume advantages to display manufacturing.

"Initially, plastic will replace glass for two reasons: it is unbreakable and it is much lighter. So the benefits of going to plastic over glass will start there," said Tom Miller, vice president and general manager for DuPont Displays' passive-matrix business (Research Triangle Park, NC). "The next benefit, which is more compelling and will create new kinds of products, is the moldability of the display—with plastic, we can begin to see displays molded into kitchen appliances, auto dashboards, and other applications that are not flat. And when manufactured on a roll-to-roll basis, for the first time we can create displays of any size, even floor-to-ceiling."

In roll-to-roll manufacturing, paper, plastic, or metal foil can be coated with a material in a continuous process that drastically improves manufacturing costs and volumes when compared to batch processing. It is not a new technique, having been used in the printing industry for years, but it is a concept new to the optoelectronics and microelectronics industries. Companies such as E-Ink (Cambridge, MA) see roll-to-roll as a perfect fit for their technology. E-Ink has demonstrated an electronic ink display attached to a flexible silicon thin-film transistor backplane as part of the company's effort to develop electronic "paper" products. Here, the electronic ink is printed onto a sheet of plastic film that is laminated to a layer of circuitry. The circuitry forms a pattern of pixels that can then be controlled by a display driver. These microcapsules are suspended in a liquid medium that allows them to be printed using existing screen-printing processes.

Glowing wallpaper brightens future for lighting: Glowing wallpaper could replace lamps for lighting homes and offices, according to the government-backed Carbon Trust. The trust has given a £454,000 grant to Lomox, a Welsh start-up company, to accelerate the development of its "light emitting wallpaper". The material, which uses organic light emitting diode or OLED technology, runs on very low voltages and is twice as efficient as today's energy-saving bulbs. It could reach the market as soon as 2012, said Ken Lacey, chief executive of Lomox.

Other companies are investigating OLED technology, either for flat displays or for room lighting but have not succeeded commercially because of high costs and short operating lifetimes. Patents filed by Lomox overcame both problems, Mr Lacey said. Manufacturers would apply its light-emitting chemical on to wallpaper with low-voltage electrical connections: "It gives a very natural, sunlight-type of lighting with the full colour range." The Lomox technology might also be useful for outdoor sites, where mains power is not available. Computer and television displays are another future application.

"Lighting is a major producer of carbon emissions," said Mark Williamson, director of innovations at the Carbon Trust. "This technology has the potential to produce ultra-efficient lighting for a wide range of applications, tapping into a huge global market." The trust is looking for other technologies with good commercial prospects and significant carbon-saving potential, he said. They would be eligible to receive up to £500,000 in grant funding from its applied research scheme.



Organic light-emitting diodes - OLEDs - emit light when a current flows through them. Unlike conventional LEDs, OLEDs are made from layers of plastic and other organic (carbon-based) materials. Examples are already in mass production for displays in MP3 players and phones. Sheets of OLED material are proposed to replace light bulbs and fluorescent tubes for house and office lighting. There are several reasons why OLEDs are causing so much excitement amongst makers of gadgets and lighting products:

• The materials are deposited by industrial coating processes which are cheaper than the techniques required to make conventional LEDs.
• They are inherently thin.
• They can be made on flexible plastic substrates - which will almost certainly lead to full colour flexible displays less than 1mm thick.
• All colours, and multi-colours, are possible
• However, there are drawbacks:
• OLEDs are not yet as efficient at making light as conventional LEDs, although they are getting closer and already beat ordinary light bulbs.
• Certain materials in OLEDs are incredibly sensitive to moisture which leads to short life, particularly on plastic substrates. This is the main reasons holding back flexible OLED manufacture.
• LED technology can be divided into two: 'small molecule' championed originally by Kodak, and Cambridge Display Technology's 'polymer' type sometimes called P-OLEDs.