Engineers Try to Solve Ultrathin TVs
From The Wall Street Journal - Tuesday May 17, 2011
By EVAN RAMSTAD
SEOULóRo Jae-song, a materials science professor here, has spent the past eight years researching a display technology called OLED, which is now used for some high-end cellphone screens.
Mr. Ro does contract research for South Korea's two big electronics makers, Samsung Electronics Co. and LG Electronics Co., on a difficult problem: How to build OLED screens big enough for large televisions.
It's one of the hot topics among display researchers and manufacturers who are meeting in Los Angeles for the annual conference of the Society for Information Display, or SID. More academic gabfest than trade show, engineers will trot out their latest ideas for displays as small as sheet-like films that roll up in a pen to as large as roadside billboards.
Some companies are working on better screens for tablet computers. Samsung and a U.S. firm called Nouvoyance discussed Monday a higher-resolution tablet screen. There's also a race to build touch technology of touchscreens into the screen itself.
"At the moment, touch is outside of the display," says Jang Jin, professor at the Advanced Display Research Center at Kyung Hee University in Seoul and former chairman of SID. "What we call 'inside touch' would save money for all of these devices that are becoming so popular."
Other firms are pushing energy-saving ideas. 3M Corp. researchers, for instance, will show a new power-saving design for desktop computer monitors, drawing their juice from the PC they're attached to rather than requiring a separate plug-in.
But for the TV makers that pull in biggest share of the industry's money, the focus is on OLED as a potential successor to LCD, or liquid crystal display, as the main technology for flat-screen TVs.
OLED, which stands for organic light emitting diode, has brightness and energy efficiency advantages over LCD. Today, however, only a handful of OLED TVs are available. Most are small and cost thousands of dollars.
So far, researchers haven't figured out a way to deposit the organic material over the large surface of a TV-sized screen with the speed required to build millions of units. "That is the most critical issue for OLED TV mass production," Mr. Ro said.
In the 1990s, display industry researchers were grappling with a similar problem in LCDs. At that time, the only way to evenly disperse liquid crystal was to let it seep in vapor form between two sealed pieces of glass, a time-consuming process.
At the 2001 SID meeting, International Business Machines Corp. researchers unveiled a dispersal method for liquid crystal that became known as "one drop fill." The idea revolutionized LCD production and, coupled with advances in the size of glass, made possible cost-efficient production of large-sized LCD-TVs.
The search for a similar advance to produce bigger OLED screens faces a major technical constraint. While only one coating of liquid crystal is needed in an LCD, an OLED screen actually takes three organic materials, one each for red, green and blue, the colors from which all other colors are formed on video displays.
The difficulty lies in aligning the OLED material so that colors are accurate across a large area. Just like liquid crystal was back in the 1990s, OLED material today is deposited in vapor form in a vacuum across a substrate and masks are used to align the three layers of material.
That technique works fine on screens the size of cellphones, but the masks tend to sag unevenly when pulled across larger surfaces. The result is that the OLED material is distributed imprecisely, creating mashed up colors or dead spots on a screen. "Everybody is working on this, all the big names," Mr. Ro says.
His company, called EnSilTec Co., worked with a Samsung affiliate on another OLED challenge involving the substrate. But the work is competitive and, late last week, the two companies were discussing how much they'd reveal during their scheduled presentation at the conference.
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