What is E Ink Display Technology?

Electronic paper, or ePaper, displays offer numerous advantages over traditional LCD and LED technologies. E-paper displays are reflective and can be constructed using various technologies.

ePaper technology mimics the appearance of ink on paper, creating a low-power, paper-like display. These displays typically incorporate image memory, requiring minimal power to maintain the display and consuming power primarily during display changes. As a result, e-paper displays excel in applications with low-frequency switching requirements, such as signage and labels.

Unlike traditional displays that emit light, e-paper displays reflect light, ensuring comfortable readability even in direct sunlight. Their popularity stems from their low power consumption, high reflectivity, contrast, readability, thinness, and wide viewing angles. E-paper displays find extensive use in e-readers, real-time bus arrival displays, electronic shelf labels (ESLs), digital menu boards, traffic signs, and logistics monitoring devices.

What Exactly is E Ink Display?

Electronic paper goes by many names: e-Paper, sometimes spelled as ePaper, electronic ink, also E Ink (the company that manufactures it) , All of these names describe the same thing: a technology that mimics the appearance of normal ink on paper. Simply put, imagine you take a pen and jotted down something in a notebook. The clear, well defined lines of your text will have the same crispness and high-readability as images shown on an electronic paper display.

But why is that, and how does an electronic paper display actually display an image? And what makes it so different from all the other high-definition screens out there?
 

MILLIONS OF TINY INK CAPSULES

To answer these questions we should start at the very core of e ink technology: small capsules filled with a clear fluid containing teeny-tiny particles, each about the width of a human hair.

For e-ink display, each E Ink is made up of millions of these capsules in a thin film, with the particles inside the capsules of different colors and different electric charges. Electrodes are placed above and below the capsule film. When a positive or negative electric field is applied to an individual electrode, the color particles with the corresponding charge will move either to the top or bottom of a capsule, making the surface of the E Ink Display appear a certain color.

Capsules filled with negatively and positively charged particles color the surface of an EPD when an electric charge is applied.

In the most basic embodiment of an e-paper screen, the particles inside an e ink capsule will be either black or white. The white particles carry a positive charge and the black particles a negative one. If the electric charge applied is negative, then the negative black ink particles will be repelled to the top of the capsule and color the surface of the display black in that spot.

This is why an E Ink Display will sometimes also be called an electrophoretic display, or EPD for short: it simply means that it functions on the basis of the motion of dispersed particles in a fluid under the influence of an electric field.

The above describes the electrophoretic microcapsule technology. However, the clever you might wonder, "But I've seen electronic paper displays that are also in color." Yes, if the colors you see are not very vivid and the color saturation is not very good, then it is the result of a color filter applied on top of the electrophoretic microcapsule display. But things have not ended there. Currently, the newly released three-color, four-color, and even six-color E Ink Spectra Six displays have very vibrant colors. This brings us to the microcup technology. It is thanks to microcup technology that we can see such vivid color electronic paper displays.

The above describes the working principle of three-color electronic paper using microcup technology. The working principles of four-color and multi-color versions are similar. As you can see, colored particles move within cup-shaped liquids under the influence of an electric field. This complex structure means that the display speed of microcup technology is not as fast as electrophoretic microcapsule technology. Now you understand why the color of your e-book and e-paper display is often not as good as expected; this is because a color filter is added on top of a black-and-white e-paper screen. Such colors only exhibit good performance when there is front lighting. Although the colors of electronic paper displays using microcup technology are very vibrant, they can only be used in situations where display speed is not critically important, such as electronic shelf labels and e-paper billboards.

TWO KEY POINTS THAT MAKE A WORLD OF DIFFERENCE

The way e ink works means that it differs from other displays in two key points: it is both bistable and reflective.

WHAT’S ON THE SCREEN IS HERE TO STAY

Just like the sketch in your notebook will remain there until you erase it, the content displayed on an EPD will hold a static image, even without electricity.

The way E Ink Display works means that it differs from other displays in two key points:

An electronic paper screen reflects light from the environment so it doesn’t use its own but it can be applied and only consumes power when you change the content on the display.

This is possible because electronic paper technology is bistable, bistable is an electronic circuit which has two stable states. The tiny particles of an EPD will either be reflective or non-reflective (that is, black or white). In more advanced e-paper screens these bistable particles will also be provided in many levels of grayscale; energy is needed to put the color particles in their place, but once they are there, they stay there.

In practice this means that an EPD will be consuming power only when the content on it is changing – for example when you change the price of a product, or when the content of an e-paper parking sign changes from ‘Reserved’ to ‘Vacant’.

The rest of the time the display will simply show the image you want it to, with or without a power source and without having to constantly refresh the content shown (an LCD screen, for example, will have to refreshed about 30 times per second – that’s 30 times per second of energy consumed by every single pixel). This is what makes e ink a low-power display technology. This makes an E Ink Display ideal for battery powered devices.

NO BACKLIGHT

The second point, reflection, brings us back to the earlier point of paper and pen.

An E Ink Display shows an image by reflecting light from the environment, rather than emitting its own light, as is the case with an LCD or OLED screen. With no backlight on an e-paper screen, the strain on your eyes is kept to a minimum, since you’ll be viewing it like you would anything else in the environment – by seeing the light reflected off it.

In other words, looking at an e-paper display will be more like reading from an actual sheet of paper and less like staring at a glaring computer screen. This makes it a popular choice for e-readers, as well as any digital displays meant to be used outdoors in the bright sunlight.

In the end, E Ink is a company and electronic paper is a display technology, but both terms have become synonymous for describing one of the most energy efficient and readable display technologies available today.

E-paper Application Examples

Digital information can be displayed using e-paper in many different ways. In fact, the possibilities of electronic paper applications are virtually endless.

E-READERS

Probably the best-known application of e ink technology is the e-reader. Not only does an e ink screen reduce eye strain, it also provides an excellent reading experience even in bright sunlight. An e-reader’s battery can last for weeks thanks to the display technology’s low energy consumption.

RETAIL 

Retail is another field where electronic paper displays are rapidly gaining popularity. The most well-known example is probably the electronic shelf label, or ESL.

In this instance, each shelf or product will have its own electronic paper screen showing the current price, product information or a barcode. These electronic shelf labels can then be managed remotely and multiple prices can be changed at once with just the click of a button.

This saves time for retail employees and greatly reduces the chances of pricing errors, meaning the return of investment can be seen in a very short time period. Digital signage in general is a fast-growing field and there are several more examples of retail applications using e ink technology, such as advertising displays and smart tags. 

TRANSPORTATION

Transportation companies use electronic paper displays to show real-time arrival and departure times of buses or trains, using minimal energy to maintain high-contrast, high-resolution displays that can be read under direct sunlight. In train stations, bus stops, and even on the sides of vehicles, e-paper technology keeps passengers informed with up-to-date information.

OFFICE

E-paper displays are increasingly being adopted in office environments for digital signage, conference room scheduling displays, and personal desk signs. Their low power consumption and ability to display high-contrast text and images without glare make them suitable for various indoor settings.

INDUSTRIAL

In industrial settings, e-paper displays are used for labeling and tracking equipment, inventory, and assets. These displays can withstand harsh conditions, including exposure to dust, moisture, and extreme temperatures, making them ideal for factories, warehouses, and outdoor installations.

WEARABLES

Wearable devices such as smartwatches and fitness trackers use electronic paper displays to provide clear, easy-to-read information while conserving battery life. The high visibility of e-paper under various lighting conditions makes it a practical choice for wearable technology.

MEDICAL

In the medical field, electronic paper displays are used for patient monitoring, electronic health records, and digital drug labels. Their low power consumption and high visibility ensure critical information is accessible when needed.