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Printed Electronics World
Posted on January 29, 2010 by  & 

The new generation of liquid crystal displays

A new generation of flat panel displays is being developed which may ultimately supersede Liquid Crystal Displays (LCDs). The first stable liquid crystals were invented at the University of Hull's chemistry department in 1971.
Industry giants such as Sony, LG and Kodak amongst others are currently developing OLED screens that are just millimetres thick and have a far sharper picture than plasma or LCD screens. Unlike existing screens which need a backlight, OLED pixels radiate light, making them far more energy efficient.
Although the first OLED TVs are already being manufactured, they are on sale in low volume and their price tag is still comparatively high. There are also some technical issues with these new materials especially in their production and manufacturing on a large scale.
There are several approaches to producing OLED materials - each has their individual benefits and drawbacks.
The materials, being developed by Polar OLED, a spin-out company from University of Hull, may be far more cost effective to manufacture and are different in make-up from the OLEDs currently being developed elsewhere.
Sony and Kodak are using a small molecule approach which is difficult to scale-up and can only be deposited on glass surfaces. Others are using ink jet printing methods to produce small size displays, but resolution becomes an issue in larger sizes.
Polar OLED use an altogether different approach. They use liquid crystal based polymer networks. Liquid crystals are the 'fourth state of matter' and were originally developed at the University of Hull, the home of Polar OLED. By using these materials, they are able to print or cast using solvents, the light emitting or charge transport layer. By then exposing this to UV or other suitable radiation, the Polar OLED material is cross-linked forming an insoluble layer. By using lithographic techniques, sub-micron resolution patterning is possible. By forming the insoluble layer, additional layers can then be added using different colour materials or patterns as required.
Fully RGB devices have already been demonstrated. This technology allows for high quality displays on both plastic or glass substrates as in the p-OLED approach but without the high cost of manufacture associated with the sm-OLED system.
Professor Steve Kelly founder of Polar OLED and head of the Organophotonics Research group at University of Hull, worked with Professor George Gray who pioneered the original liquid crystal research. He says: "I remember how rewarding it was to work with liquid crystals in the 1970s; to see how our work led to a new era in TV manufacturing - from the bulky cathode ray tube to the streamlined liquid crystal displays - was quite spectacular. What we are experiencing with OLED technology is just as much of a seismic shift and to be a part of this cutting-edge optoelectronic research is immensely exciting."
The company is working alongside the University of Hull and IP Group plc to develop and commercialise the patented materials.
Reference: University of Hull and Polar OLED
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