By Roland Piquepaille
Flexible displays based on various forms of organic LEDs (or OLEDs) will allow us to carry roll-up TVs one day. But there are still significant hurdles, according to Electronics Weekly in "Organic LEDs are on the way." One major obstacle is the life expectancy for such screens, still far below from the 10,000 hours limit considered to be the basis for a commercial distribution. But there is a bigger issue. On OLEDs displays, the different colors vanish at different rates. So you'll lose blue three times before red or green. Another very long and well-documented article on displays from Military & Aerospace Electronics, "Display technology leaps to the next generation," adds that there is still a massive $1 billion per year poured in OLED research, and that 14-inch OLED displays are already working in labs. Read more...Before looking at these articles, here is something you might one day roll out from your pocket or your purse.
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Here is an artist's rendering of a portable communication device of the future, according to Universal Display Corporation. |
Here is how starts the Electronics Weekly article.
Imagine a TV that is not just thin like a plasma screen, but thin like a birthday card. That lives in a narrow box near the ceiling and has a string you pull to unroll it.
Something from the future?
Not in the labs, but yes for your living room. There are still some significant hurdles to overcome.
The first is display lifetime. OLED materials from all manufacturers have a life which is dependent on both how hard the display is driven, and what environment the material is operating in. A life of 10,000 hours for a display is considered commercially viable.
This may not seem much - under two years continuous use - but comparing it to the 250,000 mile life expectancy of a quality car (8,300 hours at 30mph), puts this into perspective.
But as I wrote above, there is a bigger issue.
Absolute life expectance is not actually the biggest issue with OLED as, unlike LCDs which use colour filters over identical pixels, OLEDs are vulnerable to differential aging.
"The big problem for colour is red, green and blue emitters degrade at different rates," says Cobb. "Two years ago, one firm was getting through four displays a day on their stand at a show." They had to swap displays as colour-shift was obvious within hours of switch-on even though the life of its weakest OLED material was rated at 2,000 hours, explains Martin Cobb of Trident Displays.
Here is another example of this differential aging problem.
Cambridge-based display technology firm CDT is developing polymer-based OLEDs which it calls PLEDs. Blue PLEDs have the shortest life on the CDT pallet.
"Blue life has increased eight or ten fold in the last 18 months," CDT marketing manager Terry Nicklin tells Electronics Weekly. "At the May SID conference this year we showed 35,000 hours lifetime [from 100cd/m² to half brightness for blue, last month we demonstrated 70,000 hours for blue."
These figures compare with 210,000 hours for red and 200,000 for green, he says.
The Military & Aerospace Electronics article tells us another story -- but of course, military have deeper pockets than you and me.
Commercial companies are already pouring $1 billion per year into OLED research, though not necessarily for flexible displays. Companies such as Pioneer, Samsung, Philips, and Dupont are producing glass OLED displays for cell phones, says John Thomas, manager for display technology development at the General Dynamics Canada Vetronics Systems group. But those applications are just an inch or two across.
"There are 14-inch OLED displays out there, and a 12-inch from Sony, but they are just laboratory curiosities," says Thomas. "Their problems include finite lifetime and differential degradation of materials. It's not there yet; it's a new technology and is immature, but it is the one to watch."
The bottom line is the dominant position of LCDs in all display applications. CRTs are still there but shrinking fast, while OLEDs will dominate research and development for the middle future, he says.
The Army and the Navy don't think they'll see OLED applications before at least 2006.
For more information, please check the two articles linked above. They're both long, but worth reading.
Sources: Steve Bush, Electronics Weekly, November 11, 2004; Ben Ames, Military & Aerospace Electronics, October, 2004
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Famous quotes containing the words flexible, displays and/or slowly:
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