Development of Flexible Electrophoretic Electronic Paper by TOPPAN Printing
Demand for sturdy, thin and light weight display has certainly gaining in momentum, especially in the field of electronic paper, which according to Displaybank research its market growth will be some where around 6 billion dollars in 2017. With demands, come the challenge of manufacturing process, and the choice of materials in producing such display. The oxide semiconductor in recent years has attracted a lot of attention as an ideal candidate for the next generation semiconductor material due to its unique features of low process temperature, large area processability, high mobility, high stability, transparency and applicability for the printing process. Based on this, Toppan Printing has developed an electrophoretic type electronic paper by utilizing solution processed oxide semiconductor TFT (Thin Film Transistor) array at a low temperature. The oxide semiconductor layer was made by using a vacuum free solution process, while other layers were processed by using standard vacuum deposition process. In achieving thin, light weight and flexible display, Toppan’s R&D effort will be focused on flexible TFTs as well as innovative technology in fabrication process. Currently, in field of displays Toppan is collaborating with Casio Computer. The solution semiconductor material is developed by Creavis Technologies & Innovation, the strategic research and development unit of Evonik Industries AG in Germany. The front plane of this prototype is a Visplex imaging film supplied by E Ink. The size of the display is 2 inch diagonal with 80 x 60 pixel and glass as TFT substrate. The process temperature of the semiconductor has been lowered to 270 degrees, 100 degrees lower than reported value indicating that a solution TFT can be fabricated through using flexible plastic films instead of glass. Furthermore, the vacuum free process will significantly reduce the cost of equipment and process for the TFT array.
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