Originally posted on sciy.org by Ron Anastasia on Fri 05 Oct 2007 04:23 PM PDT
Bright Future Ahead for Organic TVs
By Larry Greenemeier
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Image: Courtesy of Sony |
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ORGANIC VISION: Sony's new XEL-1 television may have only an 11-inch screen, but it uses organic light-emitting diode (OLED) technology that promises advanced levels of contrast and brightness, a broad spectrum of color reproduction and a rapid video response rate. |
At a time when the screen size of television sets is growing so fast that it appears headed to eclipse that of movie theater screens, the latest breakthrough in display technology has come in the form of an ultraslim 11-inch (28-centimeter) screen that is a mere 0.12 inch (three millimeters) thick at its thinnest point.
The innovation in Sony's new XEL-1 television is its use of organic light-emitting diode (OLED) technology that promises advanced levels of contrast and brightness, a broad spectrum of color reproduction and a rapid video response rate. OLED technology is also touted for its environmental friendliness.
Sony plans to introduce the XEL-1 television in December exclusively to the Japanese market at a cost of 200,000 yen (around $1,700) per unit. The company has not announced plans to offer an OLED TV in North America, although it is considering marketing it outside of Japan, a Sony spokesman says. He adds that Sony is "actively working on larger OLED screen sizes."
Whereas a liquid-crystal display (LCD) removes light from a backplane to create its picture, an OLED emits light, which creates "a rather substantial amount of efficiency," says Stephen Forrest, a University of Michigan at Ann Arbor vice president for research and a professor of electrical engineering and computer science. Since OLED pixels only consume energy when they're in use, they can consume up to 40 percent less energy than LCDs. "LCD screens also have polarizers (applied to the LCD glass plate)," he says, "that make viewing very angle dependent. OLEDs don't have all of the viewing angle deficiencies."
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| Image: Courtesy of Sony | |
| TRIM TV: Seen here in profile, the XEL-1 is 3 mm at its thinnest point. |
"The displays that Sony is making are really quite beautiful," says Mark Thompson, chairman of the University of Southern California's chemistry department, who has studied the use of organic molecules to create an organic LED. "It's a shame they're only 11 inches."
There are several obstacles to making larger OLED displays. The most glaring: in an OLED TV, there is a transistor backplane that controls the brightness of each pixel. "You need millions and millions of these transistors—with very few failures—to make this work," Thompson says. In order for an OLED to be more energy efficient and produce a clearer picture than an LCD screen, there needs to be a way to deposit red, green and blue pixels where each transistor is positioned. This challenge grows exponentially as the screen size grows.
Sony has demonstrated a 27-inch OLED prototype display, but the screen actually consists of four individual displays arranged to produce a single image, Thompson says. This sets up an additional hurdle, because the colors are difficult to match from one display to the next.
To make OLED a practical technology that's used more broadly, Sony will also have to find ways to ensure that the color quality of the screen can last long enough to justify the price. Sony said the XEL-1 has a viewing life of 30,000 hours, which allows a user to watch eight hours of television each day for 10 years. "When you put light through organic material, it tends to degrade rapidly over time," Forrest says. "We have to have long-lifetime displays, otherwise people won't buy them."
Sony's research into the use of organic materials began in 1994 and a decade later led to the mass production of small-size, color OLED panels in mobile devices. The company last month began mass producing the organic panel used in the XEL-1, which Sony says is the first stage of its OLED TV business. Sony rival Samsung demonstrated a 40-inch OLED TV in 2005 but has not moved the technology into production. Fremont, Calif.–based iriver America uses OLED technology in the displays of its Clix digital audio players, and Nokia offers OLED displays in some of its cell phones.
"Sony's approach is to develop a reliable production line for making moderate-size displays," Thompson says. "What Sony is doing is very smart, because they're saying, 'Let's just start manufacturing.'"If OLED technology takes off, LCD's days are numbered. "LCD is having a real problem with advances in video, because it can't keep up with the millisecond video response rates as well as CRT (cathode-ray tube) and plasma screens can," Thompson says.
OLED technology will have an impact well beyond video screens as the U.S. Department of Energy encourages replacing old incandescent bulbs with more efficient and environmentally friendly alternatives. Fluorescent bulbs have proved to be an efficient option, but they contain hazardous chemicals such as mercury that are not easy to dispose of when they run out of juice.
Forrest is researching the use of electroluminescent light sources such as OLEDs to replace incandescent and fluorescent lighting sources. It is a formidable challenge, given that more than 125 years of manufacturing experience has enabled companies to sell incandescent bulbs for less than a dollar. Fluorescent lighting is coming down in price and uses only a quarter the energy of incandescent bulbs, "but you can't just throw them away when you're done with them," he says. "They need to be recycled."
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