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A dotty idea

'Market disruptive' is the term used to describe the latest idea from Professor Bill Crossland's research team, because it is likely to revolutionise the way that flat screen displays, of the type most people have come across on lap-top computers, are made. Conventionally, light from fluorescent electric lamps is shone through an LCD screen which shutters the light through an array of coloured filters. About two-thirds of the light is lost in the colour filters and the LCD panels have difficulty operating at all the wavelengths in the visible light spectrum and at all the viewing angles required. By using a UV light source and then putting red, green and blue phosphor dots on the front of the screen, these disadvantages are eliminated. The UV light can pass through the LCD screen at one angle and the appropriate coloured phosphor dot then radiates out at all angles, giving a screen display with the radiant characteristics of a cathode ray tube. By using near-UV light, spatially directed, in a narrow spectral band, the job of the liquid crystals is made easier and other advantages may be obtained. This type of display is known as a photo-luminescent liquid crystal display (PLLCD).

A prototype photo-luminescent LCD producing a flat-screen display with the viewing characteristics of a cathode ray tube.

Flat screen TV

If we have an LCD which can multiplex 100 lines, then this can be improved to 500 lines using PLLCDs. That means we are talking in terms of flat screen displays for televisions, as well as high-quality computer screens,' explains Professor Crossland. 'The "right" size for a TV screen is apparently 1m x 1.5m. The PLLCD is a contender for this market because it will avoid the need for transistors at every pixel, and the phosphor screen on the front of the display should allow smaller display panels to be "tiled" to make larger ones. The magic thing is that we can use existing LCD manufacturing technology to make this new type of display.' A whole team of people and supporters has been involved in this development over the last couple of years, and patents have been filed on a number of aspects of the technology. A company, Screen Technology Ltd, has been set up to make the devices and exploit the technology through licensing.

Enquiries to Professor Bill Crossland Tel: (01223) 330264