Electronic Display is an output device that presents information in visual. Today the market is flooded with tons of display devices mainly based on LED & LCD Display Technologies. Starting from a humble seven segment display, to television display, computer display and smart phone display, all are based on different variations of underlying technology which is either LED or LCD. Recently while working on a project on RGB LED matrix display system with Raspberry Pi, several years’ old memory came afresh when I had first used Amazon Kindle and had realized that the display technology it uses was neither LCD nor LED. It was an Electronic Paper Display!

Electronic Paper Display technology may not be as popular as LED or LCD display technology but it is quite fascinating and promises numerous advantages when it comes to applications in some of the niche areas like e-book readers, status displays in USB drive for example, label display in retail shops, displays embedded in smart cards and even low cost mobile phones. The most popular commercial product in which electronic paper display is seen to be used is e-book reader.

What is electronic paper display and why it is used in above said applications is discussed in this article.

Electronic Paper Display is a technology that mimics the appearance of ordinary ink on paper. Electronic ink is a fusion of chemistry, physics & electronics and uses the same pigment as used in printing industry today. Electronic ink in electronic paper display is made up of millions of tiny microcapsules, about the diameter of a human hair. Each microcapsule contains positively charged white particles and negatively charged black particles suspended in a clear fluid. When a positive or negative electric field is applied, corresponding particles move to the top of the microcapsule where they become visible to the viewer. This makes the surface appear white or black at that spot. The charge to microcapsules may also be bifurcated resulting in half white, half black surface thus increasing the resolution.

Electronic paper display is bistable in nature which means that the display will retain its content even if all the power sources are removed from it, power is only needed when something is changing on the display like for example in e-book reader power will be consumed when a reader is turning to a new page. This is remarkable feature which leads to very low power consumption. Second most remarkable feature is that the display is reflective in nature which means it does not have any back light. Ambient light is reflected from the surface of the display back to the eyes of the user, just like reading from the normal paper. This means that reading from the electronic paper display will not cause any eye fatigue when reading for long times thus improve readability and it also promises very long battery life. These are the reasons why it finds applications in above said areas.

Electronic paper display being flexible in nature can be manufactured on flexible plastic substrate and can be used in making flexible displays. It supports variety of touch solutions like resistive, capacitive, IR etc.

Today there are many electronic paper displays available in market in different sizes and can be used in students’ projects etc. They can be explored for the use in projects as an alternate to LED & LCD Display.

There is however one downside to electronic paper display, it has a very low refresh rate when compared to other display technologies and hence cannot be used in interactive applications.

By – Sagar Juneja, Research Associate, Chitkara University

References
https://en.wikipedia.org/wiki/Electronic_paper
http://www.eink.com/technology.html