17 September 2008--Plastic electronics is no longer a technology of the future.
Today in Dresden, Germany, Plastic Logic opened its commercial-scale plastic electronics factory. The company is using the plant to produce its much-touted e-reader, which it demonstrated last week in San Diego and plans to roll out by early 2009. It's rival Polymer Vision started production at its plant in Southampton, England, at the end of 2007 and plans to have its readers on sale by the end of the year.
Plastic Logic's factory ”is a fully automated production facility that can support about one million pieces of these readers,” says Konrad Herre, vice president of manufacturing at Plastic Logic. Currently, Plastic Logic's manufacturing process takes one to two weeks to produce displays. But it plans to reduce that manufacturing time to just a day or two. In a press release, Plastic Logic, claimed its plant was the first commercial facility to begin production, but Polymer Vision says its plant has been running for at least nine months.
Plastic Logic's as-yet-unnamed e-reader is 22 centimeters by 28 cm and just 7 millimeters thick. It is aimed at the business professional and has the ability to download, store, and transfer documents. It consists of a front plane that uses the E Ink electronic-paper technology found in other e-readers like the Kindle, and a back plane to control the electronic paper, which consists of an array of transistors built on plastic.
Polymer Vision's Readius is a pocket-size e-reader with a 5-inch (diagonal) rollable display. It also uses E-ink's electronic paper technology.
E-readers and other portable displays are usually built on glass. But Edzer Huitema, chief technology officer of Polymer Vision thinks plastic electronics will do particularly well in the mobile-device markets. ”There's a large reason to go into plastic displays: to reduce the weight,” he says. Plastic electronics are also flexible, more durable than glass, and may eventually be less expensive.
Making electronics on plastic has proven difficult. Typically, silicon electronics are made at temperatures ranging from 150 to 300 C, which would melt most plastics. To get around these high temperatures, Plastic Logic and Polymer Vision are using polymer organic semiconductors, which can be processed at room temperature. However, in terms of performance, silicon transistors built on glass still have the edge. ”It will take quite some time before organic electronics will be a competitor for performance,” Huitema adds.
The heat of processing is not plastic's only problem. Cooling, water, and the chemicals used cause the plastic to morph, swell, and wilt. So in Plastic Logic's process the plastic substrate is first glued to a glass sheet so that it keeps its shape.
There are a number of different techniques for building organic transistors on plastic. Polymer Vision uses a photolithography process, a way of etching a circuit pattern using light and light-sensitive chemicals, which is essentially how silicon chips are made. In contrast, Plastic Logic is using a type of inkjet printing. Its printing machine fires tiny droplets of semiconductor, conductor, or insulator onto the plastic substrate to form circuits.
Inkjet printing has both potential advantages and potential disadvantages, says Huitema. It could reduce materials cost and could allow for circuit design changes to be accommodated more quickly. But inkjet printing is more error prone than other techniques--the tiny globules sometimes spread out when they are dropped on the plastic and fuse together.
Plastic Logic has developed a proprietary printing technology and would not disclose the full details of it, but Herre says it combines inkjet printing with photolithography and spray coating, among other techniques. Plastic Logic has also filed patents on a procedure to make transistors with reduced current leakage, by using laser patterning to cut away bits of excess semiconductor material surrounding the pixel electrodes.