Segmented displays
The electrochrome effect can be exploited to realize displays for advertising boards, for portable devices, or for tag labels, to cite but a few examples. Electrochromic displays based on organic electrochromic polymers can be screen-printed on a plastic substrate, which makes them very thin and flexible. They can work in reflectance, meaning that the displays reflect ambient light instead of using a back light. This operation mode allows ultra-low power consumption.
A short-duration voltage pulse (typically 100 ms) is applied by the display driver to these segments that must be turned on. Then, the display keeps its information without power supply, while the contrast fades out over a few hours. If the information must be preserved, a small refresh pulse (typically 25 ms) must be applied every other 15 minutes. The information can be updated at any moment by turning several segments entirely on or off, the energy per square centimeter of segment for that being about 0.6 mJ/cm2.
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The opposite figure is a computer rendering of a four-segment electrochromic device produced by Ynvisible Interactive Inc [1], partner of the project. The device represents an exclamation mark that can be used to signal a warning. Thanks to the presence of four electrochromic segments, four levels of warning can be indicated by switching on 1, 2, 3 or 4 segments. In the drawing, 2 segments are colored, signaling a warning of level two. |