Japanese Firms Announce Top-emission Flexible OLED Display

May 22, 2013
Tetsuo Nozawa, Nikkei Electronics
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Semiconductor Energy Laboratory (SEL) Co Ltd, Sharp Corp and Advanced Film Device (AFD) Inc announced that they have prototyped a 3.4-inch flexible OLED display panel and explained its manufacturing method at SID 2013 (lecture number: 18.2).

Also, they demonstrated the panel in the interview after the lecture.

The three companies developed a 3.4-inch vertically-long flexible OLED display panel whose display area measures 42.12 x 74.88mm. It has a pixel count of 540 x 960 x RGB (red green and blue), resolution of 326ppi, thickness of 70μm and weight of 2g. The minimum curvature radius of the panel's peripheral area can be 4mm.

At SID 2012, SEL, Sharp and AFD announced a bottom-emission OLED display panel formed on a stainless-steel foil (See related article). This time, they prototyped a top-emission panel that has the same screen size and pixel count and is equipped with a plastic substrate by using a transcription technology.

The manufacturing procedure of the top-emission panel is as follows. First, a metal "separating layer" is formed on a glass substrate. And sealing, TFT and OLED layers are formed on it. Likewise, a color filter is formed on a glass substrate and separating layer by using a sealing layer.

Next, the OLED layer and color filter layer are attached to each other by using an adhesive. After that, the glass substrate and separating layer on the side of the color filter are removed, and, then, those on the side of the OLED layer are detached. Flexible substrates are attached in place of them. As a result, it becomes a flexible OLED panel whose TFT, OLED and color filter layers are sandwiched by two sealing layers.

The TFT used in this process is an InGaZnO (CAAC-IGZO) TFT that has the CAAC (c-axis aligned crystal) structure and was developed by SEL.