Toppan Printing Co., Ltd. (hereafter Toppan Printing; head office: Chiyoda Ward, Tokyo; President & CEO: Naoki Adachi) has successfully driven an electrophoretic type of electronic paper by using a solution-processed oxide semiconductor TFT (Thin Film Transistor) array at a low process temperature.

The oxide semiconductor layer was processed using a vacuum-free solution process, while other layers were fabricated using a standard vacuum deposition process. The solution semiconductor material is developed by Creavis Technologies & Innovation, the strategic research and development unit of Evonik Industries AG in Germany. In collaboration with Evonik, the process temperature of the semiconductor has been suppressed at 270 degrees, which is 100 degrees lower than the reported value. This result indicates that, instead of traditional glass materials, a solution processed TFT can be fabricated using flexible plastic films, which enable flexible displays. Moreover, the vacuum-free process will dramatically decrease the equipment and process costs for the TFT array.
In order to realize thin, light-weight and flexible displays, Toppan Printing will focus on the research and development of flexible TFTs and innovations in the fabrication process. In collaboration with Casio Computer Ltd., with which Toppan Printing is currently cooperating in the field of displays, Toppan Printing will accelerate the commercialization of flexible displays.

Background
-Recently, flexible displays have attracted a lot of attention as a next generation display. Demand for none-fragile, thin and light-weight flexible displays is growing, especially in the field of electronic paper exemplified by electrophoretic type displays,
-It is estimated that with the growth of electronic book readers the market for flexible electronic paper will grow to 6 billion dollars in 2017. (Source: Displaybank)
-In contrast to a-Si or organic semiconductors, oxide semiconductors have the unique features of "low process temperature, large area processability, high mobility, high stability, transparency and applicability for the printing process". Since the first report of the a-InGaZnO TFT by Professor Hosono’s (Tokyo Institute of Technology) group in the fall of 2004, the oxide semiconductor has attracted tremendous attention as a promising candidate for a next generation semiconductor material. (Nomura et. al., Nature 432, 488 (2004))
-Toppan has been developing oxide TFTs focusing attention on the low process temperature and transparency of the oxide semiconductor.
Results of research:
December 2005: Demonstration of flexible electronic paper driven by oxide semiconductor TFT. This was the world’s first demonstration of a display driven by an oxide-based semiconductor.
December 2006: Taking advantage of transparency of the oxide semiconductor, Toppan Printing’s original display structure "Front Drive Structure" was proposed.
December 2006: Demonstration of flexible electronic paper with 400 ppi resolution. This is the world’s highest resolution flexible display.
These developments have garnered significant attention.
-The Proto-type presented in this release is fabricated using an innovative vacuum-free, low cost and low temperature process, which will dramatically reduce the equipment and process costs of the TFT.

Specifications of the prototype
Frontplane: Vizplex Imaging Film supplied by E Ink
Size of display: 2 inch diagonal (number of pixels: 80 * 60)
Substrate for TFT: Glass
Semiconductor material: transparent amorphous oxide semiconductor
Special characteristics:
Mobility of TFT fabricated on glass substrate: 0.5cm2/Vs
On/off ratio: 10^5 (comparable to conventional a-Si TFT)
Fabrication process for TFT:
Semiconductor layer: spin-coating, subsequently patterned by photolithography Other layers: conventional vacuum coating process, patterned by photolithography

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