Sep 13 2007

Move Over, LCD

Prepare for paper-thin, full-color OLED displays in the not-too-distant future.

Sony has developed a paper-thin screen using organic material that is extremely flexible.

Imagine a monitor as thin as a piece of paper and nearly indestructible. Sony already has.

The electronics manufacturer recently unveiled a bendable organic light-emitting diode (OLED) video display that is sure to become a commercial flat panel display in the near future. The 2.5-inch display measures 0.3 millimeters (or 0.01 inch) thick and sports a resolution of 160 x 120 pixels with 16 million colors, a 1,000:1 contrast ratio and low power consumption.

The field known as electroluminescence, which deals with the light emission qualities of organic compounds, emerged in the early 1950s. OLEDs are solid-state devices made out of thin films of organic molecules that create light with the application of electricity. There are two types of OLEDs: passive-matrix (PM) and active-matrix (AM) displays.

Most PMOLED technology is composed of an emissive layer with a conductive layer of polymer trapped between an anode and a cathode terminal. These materials are then placed on a substrate and protected by a hermetic cover made of glass or sealed plastic. PMOLED displays are ideal for small form factors, such as cell phones.

Sony, Samsung, LG.Philips LCD and Universal Display are also developing active-matrix OLED displays. AMOLED displays provide the same performance as their PMOLED counterparts but can be manufactured in larger sizes. AMOLEDs contain a thin film transistor (TFT) array, which provides the circuitry to power and generate an image, and they consume less power because they rely on external circuitry.

Unlike TFT or plasma, both types of OLEDs can be produced with flexibility in mind, which creates a variety of new uses, such as screens woven into fabrics, portable media players and monitors, and electronic papers. OLEDs could also prove superior to existing LCD technology because they offer a wider range of colors, improved blacks (a problem with current LCD technology), better viewing angles (almost 180 degrees) and lower energy consumption.

The distinction between an active-matrix and a passive-matrix OLED display is that an AMOLED has a thin film transistor array, which provides the circuitry to form an image.

Source: www.howstuffworks.com

With OLED displays, backlighting is not required. The organic material produces its own light, so the displays require far less energy. Samsung has produced a 12-mm-thin AMOLED display with 1,600 x 1,200 resolution, 400 nits of brightness and a 1,000:1 contrast ratio.

On the Desktop

For monitors, OLED has some unique advantages over existing cathode ray tube, TFT and plasma display technology. One advantage is the relatively simple manufacturing process. There are several methods for creating OLED displays, but the most cost-effective is similar to the technology used for commercial home and office inkjet printers. Instead of spraying ink, the print head sprays organic material onto a substrate — an inexpensive means of creating large screens.

Given the advantages, it’s a wonder that we still use our old LCDs and plasma displays. But, until recently, OLED displays suffered from one crucial drawback: the short lifetime of the organic material used to create them. LCD screens have an expected life span of 50,000 hours, while OLED was about 5,000. Recent developments have improved the life span — especially for the blue colors, which were particularly problematic — to 20,000 hours.

Currently, OLED displays are fairly expensive, but this is because of the relatively small production capacity. As the technology matures and OLED displays start to ship in greater volume, prices will drop. Furthermore, because they can be created with inkjet printing technology, there is potential to produce large high-resolution TVs that cost far less than existing large LCDs and plasmas.

Sony plans to sell its first 11-inch OLED TVs this year. OLED is already in use for portable devices such as displays for MP3 players, cell phones, cameras and even small displays for electric shavers.

Iddo Genuth is the editor of the electronic magazine The Future of Things at www.thefutureofthings.com.