Flexible Displays Come into Their Own at Display Week 2009
For the first time, the Society for Information Display has designated official sessions for flexible-display papers at Display Week. This year, there are seven sessions devoted exclusively to flexible-display technology: Flexible Display Components, Flexible-Display Manufacturing (a joint session with manufacturing), Flexible Active-Matrix Backplanes, Organic TFTs, e-Paper, Emerging Active-Matrix Technologies (a joint session with Active-Matrix Devices), and Flexible AMOLEDs.
by Jenny Donelan
INTEREST IN FLEXIBLE DISPLAYS has been steadily growing within the industry; while on the outside, end users are becoming intrigued as well. So, as the research papers in this area proliferate, flexible-display products are also being developed that have the potential to exercise considerable consumer appeal. Among these, for example, are flexible e-books, cell-phone skins that can be programmed to change colors, and flexible OLED displays – all topics that will be presented at Display Week 2009.
"It is a relatively hot area," says Flexible Displays Subcommittee Chair David Morton from the Army Research Laboratory. Even in a sluggish economy, he notes, "We did a little better this year than last in terms of paper submissions." For this reason, and because the technology has developed a momentum of its own, flexible displays will have their own dedicated sessions at Display Week 2009 for the first time. "There have always been papers that address flexible displays" says Morton, "but some would go to electronic paper and some would go to OLEDs." If you wanted to follow flexible displays you had to be a well-prepared session hopper.
Now, however, that SID has created an official destination for flexible-display papers, it will be much easier to follow the technology. This year, there are seven sessions devoted to flexible displays: Flexible Display Components, Flexible Display Manufacturing (a joint session with manufacturing), Flexible Active-Matrix Backplanes, Organic TFTs, e-Paper, Emerging Active-Matrix Technologies (a joint session with Active-Matrix Devices), and Flexible AMOLEDs. There is also a keynote address from Plastic Logic on flexible e-books – a paper originally scheduled for the above manufacturing session, notes Morton.
A flexible OLED display developed by Universal Display Corp. and LG Display represents just one of the technologies currently under development for potential military and commercial applications. Image courtesy of UDC.
One of the standout topics this year is the commercialization of flexible e-books, which will be covered in the joint session with manufacturing. Now that the Kindle and other e-readers have stirred public interest, the potential for flexible media seems greater than ever. Papers on this topic are "Flexible e-Books" by Ian French from Prime View International and "Rollable Displays: From Concept to Manufacturing" by Edzer Huitema from Polymer Vision, Ltd. "The key here is that these companies are working on flexible e-books and at some level claim to have products available in the coming year," says Morton. "So, one thrust of this session will be lightweight, rugged, flexible e-books for newspapers." Another will be the advent of this technology into other types of light-weight, rugged, zero-power displays.
Advances in flexible OLED displays will be another area of focus at this year's symposium. Chief among these advances is the ability to put devices on plastic rather than steel or other metals. "The question then is how long will they last?" says Morton, noting that encapsulation is therefore also an important topic, but one that not many papers addressed this year. One of those flexible OLED papers to watch for is from Dong Un Jin of Samsung SDI Corp. titled "World's Largest (6.5 in.) Flexible Full-Color Top-Emission AMOLED Display on Plastic Film and Its Bending Properties." Another related presentation of interest will be "Active-Matrix PHOLED Displays on Temporary Bonded Polyethylene Naphthalate Substrates with 180°C a-Si:H TFTs" by Douglas Loy from the Flexible Display Center at Arizona State University.
An additional highlight, which does not have high-resolution aspects but is bound to appeal to consumers – especially teenagers – are programmable cell-phone skins that can change color, which will be covered in "Flexible Electronic Skin Displays" by Erica Montbach from Kent Displays. "This is not necessarily a highlight in terms of content, but they well sell a lot of them," say Morton.
The aforementioned flexible OLED paper from Samsung discusses how AMOLEDs are uniquely suited to flexible displays and describes the fabrication of a (relatively) large, full-color flexible display based on this technology.
Critical elements of a-Si technology on plastic for AMOLED applications is the subject of "Amorphous-Si TFTs with 100-Year Lifetimes in a Clear Plastic Compatible Process for AMOLEDs" by James C. Sturm from Princeton University.
Semiconducting nanofibers help achieve excellent charge properties in low-cost large-area flexible organic thin-film transistors, as described in "Organic TFTs Based on Semiconducting Nanofibers Embedded in Insulating Polymer" by Kilwon Cho from the Pohang University of Science and Technology.
"A Reliable Flexible OLED Display with an OTFT Backplane Manufactured Using a Scalable Process" will be presented by Mao Katsuhara from Sony Corp. The paper describes how the Sony team developed a full-color top-emission AMOLED display using a scalable, lift-off, and shadow-mask-free process.
Trends in Flexible Displays
Now that flexible displays have a category of their own at Display Week, what's next on the horizon? Advances in flexible OLED displays will definitely be an area to continue watching, according to Morton. He also notes that he has been seeing some worthwhile student papers and that interesting work is in fact coming out of academia in general. "When you look at flexible displays, there are still so many areas to work on, such as barrier films, organic TFTs … even the mechanical stuff, the ability [of the material] to survive the actual flexing." Flexible displays, in other words, offer more uncharted territory than, say, LCDs, which have been around longer. "There are still going to be advancements made in LCDs, but it is a lot harder to find something unique to do your Ph.D. on," he says. •
An Hitachi mobile phone features a flexible display from E Ink on its cover. Image courtesy of E Ink.