Toshiba develops 11.7-inch flexible organic EL panel

Toshiba has developed a 11.7-inch flexible organic EL panel and published a related paper (Serial No.: 74.2L) at the “SID 2012” held in Boston, USA. At the developer's meeting, in addition to the image of the panel work demonstration, Toshiba also displayed a driving element (TFT) formed on the film.

The product developed this time with a pixel size of 960×540 and a resolution of 94 ppi. It is driven by an oxide semiconductor amorphous IGZO TFT. A combination of a white organic EL material and an RGB tricolor color filter (CF) is used for color display. The structure of the organic EL element is a bottom emission type that extracts light from the TFT substrate. The aperture ratio of the panel is 42%.

The manufacturing process is as follows: After a polyimide (PI) having a thickness of about 10 μm is coated on a glass substrate, an amorphous IGZO TFT is formed by vacuum film formation and photolithography; then, a color filter and a white filter are formed on the TFT array. Organic EL; Finally, peel off the glass substrate to make a flexible panel. Toshiba said that "the production and large screen can be realized most easily."

The amorphous IGZO TFT is a bottom gate type in which an etching stopper is provided on the top of the semiconductor layer. In order to improve the reliability, after the formation of the etching stopper and the source and drain electrodes, an annealing treatment of 300° C. or less is added. The carrier mobility was 17.3 cm2/Vs, the threshold voltage was 0.86 V, and the subthreshold swing was 0.21 V/dec.

Toshiba also introduced an intuitive user interface (UI) that combines the development of the product with a sensor and operates with a curved display section. As a result, the flexible panel not only has light weight and bendable characteristics, but also “can provide new added value” (the company). The demo shows the actual scene of zooming in or zooming out of the map application by slightly bending the panel.