Displays on a Roll
Displays built out of plastic instead of glass would be a gadget lover’s dream: they’d be rugged and lightweight, and they should be inexpensive to make on “roll-to-roll” systems similar to those used for newsprint. But to develop prototypes for flexible tablet computers and other gadgets with plastic displays, the device makers have had to develop custom equipment. That could slow the arrival of flexible displays in the market and keep their prices high.
Applied Materials is trying to solve this problem–and get an early foothold in a potentially huge market–by standardizing equipment that makes flexible displays. The company, the world’s dominant maker of equipment for manufacturing computer chips and liquid-crystal displays, is developing a process that could print flexible transistor arrays that perform just as well as those on rigid substrates. That would be required if flexible displays are to be viable.
Flexible and rugged electronics with plastic displays are likely to entice consumers. Nick Colaneri, head of the Flexible Display Center at Arizona State University, points out that devices like the iPad could be bigger, and take on new functions, if they could shed their breakable glass screens. But there’s also an appeal for manufacturers. Flexible displays could cost much less to make. They could be produced on roll-to-roll machines that operate continuously at high volumes, which is more efficient than the batch methods used to make conventional electronics.
Today, companies working on flexible display prototypes are making their own production equipment. Hewlett-Packard, for instance, has done this in its work with Phicot, a spin-out of Ames, IA-based solar company Powerfilm, to develop high-performance flexible electronic displays on plastic. “Somehow in this industry, people are going to have to have a common set of tools,” says Carl Taussig, head of the Information Surfaces Lab at HP Laboratories in Palo Alto, CA.
One challenge to making flexible displays is that they need flexible circuits. Although some flexible circuits are on the market, such as inside RFID tags, they aren’t as sophisticated and speedy as the transistor arrays that drive the pixels in a display. Making such a transistor array requires a process called chemical-vapor deposition that’s difficult to carry out on rolls of plastic or metal. Mismatches can occur between the mechanical and thermal properties of plastic and those of the active materials such as amorphous silicon. Companies including Powerfilm have tackled this challenge to create flexible cells used to gather solar energy, but making flexible display circuits is harder, partly because the circuits have multilayer, nanoscale details.
Companies have been trying to get around these difficulties by using different substrates, active materials, and patterning methods. That means this technology is far from coalescing around a standard method of production the way microprocessors have–whether made by Intel or AMD, processors are all made on silicon wafers of a standard size. For flexible displays, Applied Materials is developing a machine that performs chemical vapor deposition on a range of substrates, from films of stainless steel to the plastics being used by Hewlett-Packard and Phicot. The leader of research on the project, Neil Morrison, says the tool can produce transistor arrays that are “good enough for an e-book reader.” The company is testing the roll-to-roll machine with customers it won’t disclose, and says it expects to begin selling the equipment to manufacturers in three to five years.
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