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For the past couple of years electronics companies researching OLED, or Organic Light Emitting Diode, displays have been making technology promises that are almost as bright as the displays themselves, but commercial products have been lacking.

The first commercial OLED began shipping in March. However, both it and the latest batch of prototypes suggest that the power-reduction promises made about the technology may have been optimistic, at least for the first generation of products.

Differences on Display

OLEDs are a fundamentally different technology to LCDs. They are made by sandwiching a layer of organic material between two electric connectors. When a charge is applied to one connector it flows through the organic material, causing it to glow.

This means that, unlike an LCD, no backlight is needed and so the entire display panel can be made thinner, lighter, and will require less power than an equivalent LCD. At least, that's what was promised. Current prototypes, on display Wednesday in Tokyo at the Electronic Display Expo, consume around the same power as an LCD and in some cases more.

A prototype 2.1-inch panel from Seiko Epson consumes around 150 mW (milli Watts) when displaying a moving image. A thin film transistor LCD of a similar size consumes just over 150 mW with its backlight switched on, making the OLED power saving negligible.

"The technology is still young," said Tsutomu Takenouchi of Seiko Epson's OLED technology division. "We hope to improve the power saving with future generations."

Prototype versions of 2.2-inch and 3.5-inch panels were also displayed by Toshiba Matsushita Display Technology. Commercial production is scheduled to begin sometime in 2004, said Jun Hanari of the company's research and development center. On power consumption, he said that in some cases, such as a still screen of black text on a white background, it could be as much as double that of a modern LCD.

Added Benefits

However, to write off OLED technology just because it doesn't live up to promises about power consumption would be to ignore its other features, and to dismiss a market that DisplaySearch estimates will reach $3 billion in 2007.

In addition to being physically smaller, the prototype displays on show in Tokyo on Wednesday were brighter, showed more vibrant colors, and were much better at displaying moving images than similar LCDs.

One of the biggest hurdles to commercialization for many companies is the length of time the display can be used before its organic structure breaks down, said David Hsieh, an analyst at DisplaySearch in Taiwan. The problem is that the organic layer slowly succumbs to a chemical reaction that eventually renders it useless, he said.

"The stability of the organic materials is not easy to control," said Hsieh, "but if the layers can be well controlled, OLED stability is will be achievable and then commercialization will follow."

For applications such as cellular telephones and camcorders, the industry is aiming for a lifetime of over 10,000 hours. Most of the prototypes developed so far, Hsieh estimates, have a lifetime of between 6,000 and 8,000 hours.

Product Plans

Eastman Kodak and Sanyo Electric were showing a new 2.16-inch OLED developed by their SK Display joint venture. Sanyo said the display has a lifetime of 5,000 hours measured at full white light, which is its most power consuming state, and will last in average use for between two and five years when used in a digital still camera.

The display is the first commercial, full-color, active-matrix OLED to be produced and has found its first home inside Kodak's just-launched EasyShare LS633 digital still camera.

The display has a resolution of 521 pixels by 218 pixels, luminance of 120 candela per square meter and is less than .07 inches thick. Sanyo also was showing a prototype 2.2-inch OLED. It is targeted at cell phones and so has a lower resolution of 176 pixels by 220 pixels but is also full color.

It is these qualities in small displays that led DisplaySearch to predict that five markets--mobile phones, mobile phone sub-displays, PDAs, digital cameras, and camcorders--will lead the OLED market over the next few years.

Bigger Picture

It's not just in small-size displays that work is taking place. Because of their bright and high-contrast images and suitability for moving images, some companies are looking at using the technology in future flat-screen televisions. For larger displays there is more work to be done, said Hsieh.

"I think 10,000 hours is easy to achieve but once you get up to above 15,000 hours, the organic layer will have lifetime issues," he said. While a lifetime of 15,000 hours and above is not essential for portable electronics, it is a requirement for displays that will be used as televisions or computer displays.

The Sanyo booth featured a prototype 15-inch OLED, the largest on display at the Tokyo show, and Taiwan's Chi Mei Optoelectronics recently announced development of a larger screen.

Chi Mei, IBM, and their International Display Technology joint venture have worked together to develop a 20-inch OLED, said Katy Chang, of Chi Mei's investor relations department. The display has a resolution of 1,280 pixels by 768 pixels (WXGA resolution) and a brightness of 300 candela per square meter.

The display is not just larger but will also be cheaper to mass produce, the company said. It uses amorphous silicon transistors, which are cheaper to fabricate over a large area than the polycrystalline silicon transistors used in many current OLEDs. The 20 inch display will be officially unveiled at The Society for Information Display (SID) 2003 conference in the U.S. in May, said Chang.

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