Emerging Technology: Thinner and Flexible Panels on the Horizon
May 27, 2008 12:55 PM,
By John DeWitt
Recent technology developments continue the pursuit of key design and performance goals for digital signage and other display applications: more vivid pictures, thinner form factors, lower power consumption, and flexible screens. MIT’s Technology Review has reported this spring on two encouraging developments in display-related technologies. Researchers are hoping to harness the latest advances in nanotechnology and organic semiconductors to finally commercialize field-emission displays, after years of promising yet challenging development efforts. And low-cost techniques for producing organic semiconductors could lead to a variety of applications using rollup or foldable displays.
Field-emission displays
Manufacturers and researchers for more than a decade have pursued the development and commercialization of field-emission displays, for example. Field-emission displays offer several distinct advantages—including lower power consumption than plasma and LCDs with the sharper, brighter picture of a CRT in a very thin package. “They work on a similar principle as CRTs, but are only a few millimeters thick,” writes Prachi Patel-Predd in a May 6 article. “Instead of using a single electron gun, they use millions of tiny electron emitters to shoot electrons at red, green and blue phosphors coated on a screen.”
Unfortunately, efforts to commercialize field-emission displays have faced a number of economic and technical challenges, often centered around the electron emitters. David Barns, a DisplaySearch analyst, says that it can be hard to create and maintain the vacuum that separates the electron emitters and the phosphor-coated glass. A decade ago, Sony and Motorola both tried using micrometer-sized metal tips as emitters, but found (among other challenges) that high voltages at the tips can degrade the emitters.
Nanotechnology has sparked more promising approaches to emitter designs, however. Over the past few years, both Samsung and Motorola have developed field-emission displays using carbon nanotubes as emitters. Sony spinoff company Field Emission Technologies is employing metal nanotips. And in a recent development, Kyekyoon Kim and Hyungsoo Choi, researchers at the University of Illinois-Urbana Champaign are using a new manufacturing method to grow upright copper nanowires—between 70 nanometers and 250 nanometers thick—on silicon, glass, metal, and plastic surfaces. The small size reduces the voltages required to power emitters.
Nanotech-based field-emission displays are expected to appear on the market as soon as 2009.
Organic semiconductors
Researchers at the National Institute of Standards and Technology (NIST) are working to build “the ‘evolutionary link’ between the microelectronics of today built from semiconductor compounds and future generations of devices made largely from complex organic molecules,” according to the NIST website. An NIST team, led by David Gundlach, has demonstrated that “a single layer of organic molecules can be assembled on the same sort of substrate used in conventional microchips.”
These developments have significant implications for displays and other devices, Patel-Predd notes in a March 5 Technology Review article.
“Current flat-panel displays,” he explains, “are rigid because they use amorphous silicon to make the transistors that control the pixels. Organic electronic circuits could pave the way for roll-up displays: foldable electronic readers, large screens that can be rolled up and tucked into cell phones, and smart bandages that monitor wounds and sense the need for drugs.”
New techniques eliminate the costly stage of patterning semiconductors over a large area, using lithographic or inkjet techniques, because the organic semiconductor molecules are coaxed to self-assemble around chemically pretreated electrodes to form field-effect transistors. Eventually this could pave the way towards large-scale manufacturing of organic electronic circuits for flexible displays and other applications.
