[SID] Sony Demos Organic TFT-driven Flexible E-paper

May 23, 2011
Naoki Tanaka, Tech-On!
[Click to enlarge image]
[Click to enlarge image]
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Sony Corp announced flexible electronic paper (e-paper) that is driven by organic TFTs (thin-film transistors) and can be bent to a curvature radius of at least 5mm.

The announcement was made at the 49th SID International Symposium, Seminar & Exhibition (SID 2011), the world's largest academic conference on display technologies, which took place from May 15 to 20, 2011, in Los Angeles, the US.

Sony actually bent a prototype of the new e-paper in the author's interview that followed the announcement. Researchers who saw the e-paper almost being folded let out a cheer.

The prototyped black-and-white flexible e-paper uses E Ink Corp's electrophoretic front plane laminate. The e-paper has following specifications.

Screen size: 13.3 inches
Pixel count: 1,600 x 1,200
Pixel size: 169μm x 169μm
Resolution: 150ppi
Aperture ratio: 94%
Contrast ratio: 10:1
Gradation: 16
Thickness: 120μm

Peri-Xanthenoxanthene (PXX) was used for the semiconductor layer of the organic TFT. This was also employed for Sony's OLED panel that can be wrapped around a pen and was announced in 2010 (See related article). The semiconductor layer and all the insulating layers are manufactured with a spin coating method using solution.

The highest process temperature of the organic TFT is 150°C, which is much lower than the glass-transition temperature of the flexible substrate. The organic TFT has a bottom-gate structure. Its channel length, carrier mobility and on/off ratio are 5μm, 0.5cm2/Vs and 107, respectively.