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The Big Picture: Rolltronics Display Backplane Technology Could Put a Holodeck in Your Bedroom

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By Robert X. Cringely
bob@cringely.com

Some futures take longer to arrive than others. Back in 2001, I wrote about a company called Rolltronics that was working on adapting roll-to-roll printing technology to the production of amorphous semiconductors on plastic films. Their goal was a $15 PC that could literally be printed on a press like a newspaper with different layers for battery, motherboard, graphics controller, display, keyboard, etc. Well, the company is still working toward that dream, but the more variables you try to change at once, the longer it takes and the more risk you have to accept. So on its way to the future, Rolltronics decided to make a few bucks by applying some of these ideas just to displays and the results look to be amazing. We're talking not just about displays that are cheaper to make (perhaps a third the cost of current technology), but that are flexible and paper-thin. Lower prices can lead to market acceptance, but what people really like is something that looks brand new and opens up new application possibilities, and the new Rolltronics displays promise to do that. Imagine an HDTV you take home under your arm in a cardboard shipping tube and attach to your wall with thumbtacks or carpet tape.

The most expensive part of any digital display isn't the part that we look at, but the matrix of switching transistors behind the display that turn the individual pixels on and off, called the backplane. What Rolltronics has invented isn't a new type of display, but a new type of backplane and it ought to be able to work not just with LCDs but also with plasma displays and even with electronic ink. If we ever do buy electronic paper books into which we can pour Moby Dick or Portnoy's Complaint, they may well use the Rolltronics technology called FASwitch for Flexible Array Switch.

Current displays are controlled by transistors that switch on and off, and those switches are made by melting silicon on a glass plate. This plate is what makes your LCD display rigid. Sure, you can poke your finger at the display and it will give a bit, but that the plastic-encased liquid crystal layer, not the glass backplane that lies behind, out of sight. If there is a bad pixel in your display it isn't likely the display that has failed you but the backplane where a transistor isn't working correctly. The more pixels in your display -- the higher the resolution -- the bigger the backplane has to be. Bigger backplanes mean more semiconductor real estate and more money. Bigger backplanes also mean more pixels and more chances of pixel failure so production yields are lower. Finally, bigger backplanes mean that fewer parts can be made in a single lithographic process so yields are again reduced. This explains why really big LCD and plasma displays cost so much.

But Rolltronics' FASwitch doesn't use transistors. In fact, it doesn't semiconductors at all. The backplane is made entirely from plastic and metal produced in vast quantities on a roll-to-roll press. Where traditional display backplanes cost more per unit of area the bigger the display, FASwitch displays cost LESS per unit of area the bigger they get, and this trend appears to have no practical limit, which opens up some really interesting product possibilities, below.

You could make flexible LCD displays by melting silicon on plastic, but that's a challenge since most plastics, themselves, melt at too low a temperature. Another approach is to build plastic transistors from organic polymers and plenty of people are working on that. But the folks at Rolltronics thought a simpler process involving less technical risk was in order. Their FASwitch is a tiny electro-mechanical switch made from plastic and metal that performs the function of a silicon transistor but with savings in production costs, and with less exotic materials. No materials breakthroughs were required.

A FASwitch starts with two layers of plastic, one thin and flexible, and the other thicker and rigid. The two layers are separated by an insulating epoxy spacer creating an air space. This spacer is not a layer between the two other layers, but a plastic grid that defines a large number of individual cells that correspond to the individual pixels in a display. These are the switches. They are activated electrostatically using the attraction between thin metallic films that are vacuum-deposited on the inside surfaces of both layers. A conductive metallic plate or foil is used to create electrostatic attraction to flex the thin flexible layer until it touches the thick rigid layer. This forms an electrical contact at that one point in the switch array.

Got that?

After the contacts close, the voltage on the contacts keeps them closed until power is removed. This means FASwitch backplanes can be bistable. The pixel is stable in either the ON or the OFF state, without the need for power. If FASwitch is used to drive a display, the display pixels retain their image until they are told to refresh by the controller.

Call me a geek, but I find this exciting. FASwitch backplanes can scale from a few pixels to a movie screen to the entire side of a building. Imagine outdoor advertising (a HUGE industry) that could be altered remotely over the Internet. Imagine billboards that could not just be changed at will, but that could also include video, since the FASwitches can cycle at up to 200 HZ, which is plenty fast enough for any computer gamer.

Can you say, "Holodeck?"

Or control the billboard using information based on who is driving or walking by and you have those annoying signs from the Tom Cruise movie Minority Report -- annoying but amazing.

As always, I have no financial interest in this company. I just like their stuff. If some big display manufacturer is smart and does the right thing, we'll be buying rolled-up HDTVs in about three years.

FASwitch displays open up the possibility of putting screens where we might never have done so before. Giant screen TVs will go where they have never gone before. The gadget- hungry, apartment-dwelling people of Japan, Korea, and India will never know what hit them.

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