Unlike most conventional screens, which emit light (i.e. are backlit), e-paper displays typically reflect ambient light. E-paper technology is based on the principle of electrophoresis and uses electronic ink in the form of charged particles in microcapsules. The capsules, which are around 40 micrometres in size, contain white and black pigments with different charges. Electrical voltage is used to move the black and white pigments to the surface of the display or into the background. The pigments on top are then visible to the viewer.
It is possible to display up to 16 shades of grey. For this purpose, the electrical voltage is controlled in such a way that only a certain proportion of the pigments of each colour reach the surface. Coloured representations are made possible either by colour filters or by additional coloured pigments in the capsules.
A key feature of the technology is that once an image has been generated, it remains visible without any power supply; power is only required for changes to the image content. Compared to other display technologies, however, a lot of time is needed to change the image, which is why e-paper displays are particularly suitable for static images and text.
