DISPLAYS & UIS
Display technology - ePaper displays stepping into a new colour dimension
Dirk Troelenberg, Corporate Product Sales Manager Displays bei Rutronik, and Zhen LIU, Business Development Manager bei Holitech Europe GmbH
D
ynamic labelling is easy, energy efficient, and cost-effective with ePaper displays. However, a full colour display has been limited, until now. N colour technology is now changing all that and opening up completely new application areas for these displays. ePaper displays are vastly different from other technologies, such as LCD, TFT, and (O) LED. They have their advantages, but also their limitations. Due to their operating principle, ePaper displays offer viewers a contrast ratio like that of paper, as well as excellent, flicker- free readability from any viewing angle (180°),
even in direct sunlight. Furthermore, power consumption is extremely low compared to other technologies, as the displays only need power when the displayed content is refreshed. This means the display remains totally visible, even when the current and voltage are zero. Depending on the actual size of a display, only a few microwatts of power are required to refresh the content. Therefore, ePaper displays are ideal for battery-powered and wearable (IoT) applications. Current applications include supermarket shelf labels and price tags featuring product information. The evolution of ePaper from monochrome to colour display is giving this technology a completely new boost.
New application areas thanks to full- colour display
N colour ePaper displays from Holitech are based on all-in-one IC technology and can provide a colour image with seven basic colours even without the use of a colour filter. The displays comprise microcapsules. Each of these capsules contains four colour particles,
32 MARCH 2024 | ELECTRONICS FOR ENGINEERS
which are magenta, yellow, cyan, and white, and these are dissolved in a transparent liquid. The colour pigments are charged differently, so yellow, cyan, and white are negative, and magenta is positive. By applying a specific voltage, each microcapsule displays a corresponding combination of the colour particles and thus a specific hue.
The individual pixels are controlled by means of matrix displays. If different voltages are applied, the corresponding colour capsules move to the surface, where they become visible to the viewers. Combining the seven basic colours, red, green, blue, cyan, magenta, yellow, and white, enables the display of
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