OLED phone screens mean brighter gaze ahead

Who wouldn't want a cell phone with a sharper, brighter display than the color LCDs in common use today — especially if it made the phone slimmer and doubled its battery life?

Such displays, using a technology known as Active Matrix-Organic Light-Emitting Diodes, in time could even unroll from a phone in the form of a thin, flexible sheet to display vivid images, games and videos on a screen the size of a cocktail napkin or larger.

Yet even basic AMOLED displays may not be common in handsets any time soon, say some industry analysts, because of limited manufacturing capacity. The 20-year-old technology still hasn't ramped up sufficiently, even for the relatively small displays required by handsets.

The demand is certainly there. Tech-savvy consumers crave screens using AMOLED, which in nearly all respects are superior to LCDs (Liquid Crystal Displays).

They're already appearing in TVs such as Sony's pioneering but puny 11-inch XEL-1 (selling respectably even at $2,500 retail) and LG's announced 15-inch model. Microsoft's new Zune HD incorporates an AMOLED display, as does Toyota's Lexus.

Passive-matrix OLEDs, or PMOLED, are more common but are monochrome and typically used only for simple text displays. The term "OLED," used without a prefix, usually refers to AMOLED.

OLED-display.net An LCD screen, on the left, and OLED screen on the right show the differences between the two types of displays.

OLED has found its way into a few handsets available in the United States, including Nokia's N85, Samsung's Impression (through AT&T) and newly announced Rogue (through Verizon Wireless), with many more on the market in Asia. N85 buyers on Amazon.com laud the display as "brilliant" and "bright and easily readable," though one criticized it for turning grays into browns.

OLED is a 'differentiator'
Samsung plans to use OLEDs in the Omnia 2, set for U.S. release this year, and it might announce other OLED-based handsets within the next month, said Samsung Senior VP Omar Khan.

"Right now OLED is a differentiator in our premium-tier phones, but I do imagine a time when OLED phones are the norm," Khan said.

OLEDs are attracting attention outside the electronics industry, too, in the world of lighting. A recent New York Times article described OLEDs' adoption by designers because they're long-lasting, energy-efficient, bendable and can illuminate in a wide range of colors.

"At the moment, there's no display technology on the horizon that could eclipse OLEDs," said Gartner analyst Paul O'Donovan.

OLEDs offer numerous advantages over the LCDs now used as the primary displays in many cell phones and digital music players.

OLEDs yield colors that are brighter, deeper and more natural than those from LCDs. Sony says its OLED TV can display a wider range of more colors than are prescribed as standard for U.S. television by the National Television Systems Committee.

They offer higher contrast levels than LCDs, which makes for crisper images. The stated contrast ratio for some OLEDs is 1 million to one, meaning the darkest dark is 1 million times darker than the lightest tone. In comparison, LCD contrast levels range between 1 and 5 percent of that figure, depending on the manufacturer.

OLEDs virtually eliminate the blurring and strobing that can occur on LCD screens when objects move quickly across the screen. And they have a wider viewing angle than LCDs, allowing several people to successfully see a screen from varied positions.

They also consume roughly half the power of LCDs, depending on what's being displayed. That means a phone's battery life could be doubled even without improvements in battery technology.

Light that lasts
One OLED shortcoming is that the displays wear out more quickly than LCDs. Television LCDs last 50,000 to 60,000 hours, according to manufacturers' claims, though their backlights can burn out, and as they deteriorate, the colors can change in hue.

OLEDs' phosphors — the substances that make them emit light — have shorter lives than that, with blue phosphors the shortest-lived of all. It's hard to put a number to their lifespan because it's increasing rapidly with research.

But PMOLED maker RiT Display Corp. estimates OLEDs with a lifespan of just 7,000 hours would last most cell-phone users nine years — far longer than most people own their phones, and long enough to even recycle the phone through several users.

Unlike LCDs, OLEDs can be created on flexible surfaces. Today they're usually created on glass substrates, making them rigid. But researchers are creating them on bendable plastic and on metal foil, either of which will reduce their weight and fragility.

Large, flexible, roll-out screens are three to five years away from the marketplace, said Janice Mahon, a vice president at OLED component maker Universal Display Corp. in Princeton, N.J.

Flexible-screen OLEDs "will tremendously change product designs," Mahon said. "When the necessary manufacturing capacity is in place for those, people will say, 'Why do I want a glass-based equivalent?' "

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