HP unveils paper-thin flexible screen technology

Although similar at heart to current LCD technologies, HP's system has half a million micron-wide pillars per square millimetre of display which force the liquid crystals to stay in whatever position they adopt when pulsed with electricity. This makes the display able to retain an image after power is removed - HP showed a prototype that retained an image from two years ago despite being unplugged for the duration -- you can see this in our gallery from the event.

The pillars are imprinted in liquid transparent plastic which is then cured by ultraviolet and bonded to a flexible plastic backing. Similar techniques are used to produce other physical components of the display, which can then act as guides for inkjet deposition for the pigment filters and so on. Electrodes are formed by a combination of very thin metal wires and conductive plastics.

"There are many different techniques here, and we had to make them all work together," said Robson. "We could go to market with what we've got, there's no killer issue yet to solve. We've solved the science". However, he said that the current technology was transmissive - it needed a backlight -- and reflective displays that worked in ambient lighting had many advantages. "We're working on that, but we're not going to tell you about it yet", he said. "Commercial products are probably in the middle of the three to eight year time zone". Costs were similar to existing LCDs for small displays, he said, but HP's technology scaled up to very large displays with much lower projected increases.

Many subtleties of the display technology remain to be examined, Robson said. "By changing the geometry and spacing of the pillars we can make pixels that can be set to differing greyscale values by varying the switching pulse." As the pixels take a long time to change - updating the complete display can take several seconds - the technology is not suitable for video, but because the pixels can be printed at hundreds per square inch the display can approach paper quality. "For very large displays", he said, "you can just update the area of the display you need to change" ".

Figure 1: This image has been displayed on an unplugged screen for two years. HP says that images have an indefinite lifespan.

Figure 2: Although the display needs special pulse-shaping techniques to drive it, this should cost no more in production than current LCD driver chips.

Figure 3: The display itself looks and feels like a piece of stiff polythene. The flexibility will make it easier to produce rather than make the final display very flexible.

Figure 4: Holbein's Ambassador contemplates life in plastic – the current prototype can display 125 colours, but a full palette is promised for production.