Toshiba Corporation today announced that it has developed the world’s first prototype of a full-color polymer organic light emitting display (OLED), a 2.85-inch display supporting 260,000 colors in Q-CIF format and a 64-level (6-bit) gray scale. The breakthrough display was achieved by development of technology for forming a light-emitting polymer film on a low temperature polysilicon thin film transistor (TFT) array. The company expect to commercialize OLED in April 2002.
An OLED displays data via an organic light-emitting diode in the pixels formed on a TFT array. The display itself emits light and has no need of the backlight required by LCDs, opening the way to thinner, lighter display panels that consume less power. OLEDs also offer the faster response time required for motion pictures and support a wider viewing angle.
Toshiba developed its prototype display by combining a breakthrough in the OLED manufacturing process with technologies it developed in pioneering low-temperature polysilicon TFT LCDs.
All OLEDs commercialized to date are mono-color or area-color, and use small molecules in the light-emitting organic film rather than polymers. They require vacuum-evaporation technology in the production process, which is unsuitable for the fabrication of large-sized, high-resolution displays on a large mother glass substrate, as required in the TFT production process. Toshiba has overcome these limitations with the development of new ink-jet printing and solvent-material technologies for depositing a polymer film. Both advances can be applied to the achievement of high resolution displays and efficient mass production without any need for a vacuum environment.
Like LCDs, OLEDs fall into two broad categories, passive-matrix and active-matrix displays. A large-sized, full color OLED requires an active matrix driver in respect of panel lifetime, power consumption and picture quality. The high level of carrier mobility required for driving OLED in the active matrix TFTs can be realized only by polysilicon, not by amorphous silicon. Toshiba established such technology in the process of becoming the world’s first manufacturer of low temperature polysilicon TFT LCDs, and has transferred it to the OLED.
Toshiba expects to start production of OLEDs in fiscal 2002. Production will initially target cellular phones and small- and medium-sized PDAs, and then medium- and large-sized displays, including high-end portable PCs that requires higher resolution and a gradation surpassing a 64-gray scale.
Toshiba’s OLED will be exhibited at the Society for Information Display (SID) 2001 at San Jose, California, from June 5 to 7, 2001.