TDK Corp developed two types of passive matrix OLED panels. One is a flexible type whose display is bendable, and the other is a see-through type. The company prototyped each panel with color and monochrome displays.
Flexible type to be rolled out at end of 2011
The flexible OLED panel is as thin as 0.3mm or less. The weights of the color-display and monochrome-display models are 1.11g and 0.96g, respectively. With the use of a resin substrate, the thickness and the weighs were reduced to about 1/6 those of existing panels using a glass substrate, TDK said.
Also, the display is not affected even if the panel is bent to a curvature radius of up to 25mm. And the company said that a panel using a resin substrate is less likely to break than a panel using a glass substrate. The flexible type is targeted at mobile devices including mobile phones.
The flexible panel has a screen size of 3.5 inches and a pixel count of 256 x 64. Though its contrast ratio, brightness and life were not disclosed, TDK said that they are almost the same as those of the company's existing panel using a glass substrate.
The structure of the panel is a bottom emission type that extracts light from the side of the resin substrate on which electrodes and light-emitting devices are formed. A vapor deposition method and a low-molecular white organic EL material are used for the formation.
The color display was realized by forming filters of red, green and blue (RGB) colors inside the panel. Organic EL devices are sealed with an inorganic film. No polarizing plate is attached to the surface of the panel.
The flexible OLED panel was prototyped at Kita Ibaraki Plant, which has production lines for OLED panels using a glass substrate. TDK plans to start volume production of the panel at the end of 2011, it said.
See-through type has transmittance of 50% or higher
The transmittance of the see-through OLED panel is 50% or higher, allowing to design devices more freely. The translucency was realized by keeping some areas inside a pixel from being occupied by, for example, organic EL devices.
Samsung Mobile Display Co Ltd has already developed an active matrix OLED panel with a transmittance of 38% or higher by using a similar technology (See related article).
"(Unlike active matrix panels), the transmittance of passive matrix panels is not lowered by driver elements (TFTs)," TDK said.
The see-through panel has a screen size of 2 inches and a pixel count of 320 x 240 (QVGA). Its resolution was enhanced by employing a driver chip developed by Dialog Semiconductor Plc of Germany. The other specifications of the panel were not disclosed.
The panel has a top-emission structure. Except for the use of a glass substrate, it is made by the same process as the flexible OLED panel, TDK said.
"If asked by device makers, we can mass-produce the panel," it said.
TDK will exhibit the newly-developed OLED panels at Ceatec Japan 2010, a trade show that will take place from Oct 5 to 9, 2010, in Japan.