Ricoh Company Ltd developed reflective color electronic paper (e-paper) whose reflectance is 70% (with a wavelength of 550nm).
The company announced the e-paper at the 49th SID International Symposium, Seminar & Exhibition (SID 2011). In the author's interview after the announcement, it showed a movie of a prototype of the e-paper displaying a color image.
The new color e-paper was realized by an electrochromic technology to stack three electrochromic layers that reflect yellow, cyan and magenta lights, respectively. The technology can colorize a pixel without spacially dividing it, realizing bright color display. This is the first time that a color image has been displayed by using this method, Ricoh said.
The prototyped e-paper has a screen size of 3.5 inches, a 27% color gamut on NTSC standards, a resolution of 113ppi and a gradation of 64.
All of the three electrochromic layers are driven by one TFT substrate. And they are driven in four modes: initialization (white color), display of the magenta layer, display of the yellow layer and display of the cyan layer. For the TFT substrate, low-temperature polycrystalline silicon technology was used.