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Emerging Display Technologies

Californian high-tech company's innovation makes flexible OLED displays possible

By Conrad H. Blickenstorfer, Ph.D.

Pen Computing Magazine, March 2003 - Vitex Systems, Inc. of San Jose, CA, has developed technologies that will soon allow the production of thinner and lighter displays for mobile devices. But that is not all. Their technology will also enable flexible displays. That's because Vitex has developed a process to seal next generation "OLED" displays in flexible materials as opposed to the currently used thicker glass substrates, thus coming close to creating flexible paper. This article presents an overview of OLED displays and the Vitex technologies which will enable those thinner and eventually flexible displays.

What are OLED Displays?
OLED (Organic Light Emitting Diode) displays are one of the more interesting technological developments on the mobile computing horizon. LEDs, Light Emitting Diodes, of course, have been around for decades. The glowing red light elements were used in calculators and watches before liquid crystals became widely available and they still have many uses today. Compared to conventional LEDs which are like little lightbulbs, "organic" LED technology uses microscopic polymer materials to create incredibly small light elements that are sandwiched between an anode and a cathode layer and sit on top of a thin-film transistor. By definition, the OLED display does not need a backlight because it generates the light itself. An OLED display can therefore be much thinner than a standard LCD. In addition, it is also brighter, has a very wide viewing angle (160 degrees-plus), uses very little power, and can operate in a wide range of temperatures. Needless to say, those are all very desirable qualities for mobile displays.

Kodak did much of the basic research of small molecule OLEDs, and OLED products actually already exist. Companies such as Pioneer, Motorola, and Sanyo are using OLED displays in cellphones, audio equipment and other devices that need bright displays. Other leading electronics companies have been showing prototypes with impressively bright and vibrant OLED displays at major tradeshows. Current OLED displays are still small and the technology is still under development. Costs are still substantially higher than those of liquid crystal displays (LCDs), and current OLEDs have a lifespan of only about 10,000 hours. That's a year of uninterrupted use and not enough for applications like computer displays. Experts expect larger OLEDs to become available soon. Current forecasts predict 5-7 inch displays by 2004, 9 to 15 inch sizes by 2005, and 17-inch OLEDs by 2006. DisplaySearch, a Texas-based market projection company, predicts that global sales of OLED displays will grow from US$112 million in 2002 to US$3.1 billion in 2007. Longevity, we're told, seems primarily a problem with the blue OLEDs in the typical RGB display, and the problem is expected to be resolved shortly. As far as costs go, since OLEDs do not need a backlight and use less components, large volume production will eventually result in lower costs than those of LCDs.

Vitex's enabling technologies
I recently had a chance to talk with John McMahon, VP of Sales and Marketing at Vitex, which is a spin-off from the prestigious Battelle Institute. McMahon educated me on the state and advancement of OLED displays, and particularly the areas his company is working on--highly efficient flexible coatings to seal the very fragile OLED display layers. You see, one problem with OLED displays is that they must be extremely tightly sealed from moisture and oxygen or they quickly disintegrate and decay. That's why current OLED displays need a rigid glass substrate, moisture removers, elaborate sealing, and a metal "can" or glass lid to form a totally sealed environment. All of this adds cost, weight and thickness. Vitex's break-through contribution is a proprietary vacuum polymer coating technology that allows OLEDs to be protected without the need of glass or metal, thus not only eliminating a lot of costly components while cutting weight and thickness in half, but also making flexible displays possible.

The use of plastic in this is remarkable, explained McMahon, as water actually goes right through plastic, albeit at the slow pace of about a gram of liquid per squarefoot per day. Standard coatings reduce the amount of leakage by a factor of 100 so that your 2-Liter bottle of Coke or Pepsi wonit leak its contents. The LCDs currently in use would need sealing on the order of 1,000 times that of untreated plastic. OLEDs are far more sensitive yet and need sealing four orders of magnitude better than that required for LCDs. The challenge of providing this extreme degree of sealing seems staggering. Yet, Vitexis advanced iBarixi coating, consisting of alternating layers of polymer and ceramic thin films, can not only provide that sort extreme protection, it is also applied directly on top of the OLEDs itself as a thin film. While the Vitex process itself is ready for production, and the company has developed a manufacturing device called Guardian Tool that applies the Barix layer, there are still a few hurdles to be overcome. For example, the electronics of active matrix displays are laid down at high temperatures, thus being a problem for a plastic layer, but new low temperature polysilicon technologies will lessen that problem. Unlike the size of OLEDs themselves, the sealing process has no size limitations.

On February 25, 2003, Vitex announced a partnership with Samsung, one of the world's leading display makers. Samsung will provide funding for ongoing research and development of the Vitex processes with the goal of enabling the manufacturing of thinner and lighter displays for the mobile market.

What does it all mean?
What this all means is that weill soon be seeing a new generation of better, brighter, thinner, faster displays for the next generation of mobile devices (or perhaps the one after that). And it also means that flexible vibrant high resolution color displays may not be far away, and those will make possible entirely new devices and new uses. Imagine being able to simply roll up a display, or even fold it. Imagine sheets of paper that feel like paper but display and accept information like a computer screen. But it doesnit even stop there. Anyone who has seen the movie "Minority Report" may remember that USA Today newspaper with its moving ads and content. "Minority Report" was supposed to take place in the year 2057. With astonishing technology leaps such as the one Vitex is developing, the reality of such a flexible newspaper may be much closer than we think.

For a technical explanation of the entire process check Vitex's site. For background information on OLED technology, see Kodak's OLED page.