e-Paper Technology

Electronic paper, also known as e-paper or electronic ink, ecompasses a range of display technologies which are designed to mimic the appearance of ordinary ink on paper. Unlike conventional backlit flat panel displays, electronic paper displays reflect light like ordinary paper. E-paper has been around for a while and the applications are rapidly spreading to many areas as ongoing development improves the performance of the technology.

Features

The key advantages of E-paper are:

• Low power (no power once image is loaded)
• Thin structure
• Flexible and bendable
• Rugged
• High contrast in bright ambient light

Technology

E-paper is currently present in the market mainly in e-book readers, but the technology is developing rapidly into other applications as well. E-paper is a bi-stable display technology. When a voltage is applied to a segment the fluid changes from white to black depending on the polarity of the applied voltage. Even grey scales are possible by not allowing the fluid to change fully to white or black.

The pixel state is at threshold as soon as the voltage is removed from a segment. Even colour filters have been developed for colour E-paper. The colour filter is transparent and located on top of the grey scaled segments allowing ambient light to be reflected through the colour filter. The current colour filters are using RGB filters and an added white filter enhancing the black or white colour state.

Products

1) Colour Active Matrix
The colour E-paper is the latest development and there are a few e-book readers out there with these displays now. Although impressive the colours are still muted compared to backlit TFT’s. But this will improve over time and as the colour technology develops more and more applications will benefit from these displays.

2) Monochrome Active Matrix
The more mature monochrome active matrix displays have been around for a while and most of these go into e-book readers. Improvements in response time have been achieved: older designs took just below one second to refresh a page where the latest improvements can refresh in a fraction of a second. Small dot matrix e-paper displays are now finding their way to handheld devices and watches especially areas where battery life time is critical, and readability in high ambient light is required.

3) Segmented Displays
The segmented displays are direct driven and in that way a little more simple, but the main feature of “no need for power” when the images is set, is still the key feature. These displays can be both flexible and quite large in size. An important feature for advertising and information displays in the large sizes

4) Retail Displays
One special application is the retail display where part of the display has a moving feature whereas other parts of a poster is just static printed images.

5) Touch panels
Integrated touchpanels are available in e-paper displays. Especially resistive touch panels have the advantage that they can be located behind the display, so bright ambient light won’t be reflected in the touch panel, just enhancing the display contrast. Other touch technologies like capacitive etc. that needs to be mounted in front of the display is of course also an option, but the traditional disadvantages remain for these.

If you have any projects or ideas to use e-paper technology in an application please call RDS on 01959 563345 or email info@review-displays.co.uk to discuss the possibilities.