E-Ink

E-Ink is a special kind of screen. It is mainly built into e-reader devices for books, such as the Kindle or the Tolino. Unlike a phone display, this kind of screen does not light up on its own. You only see it because light from the room falls on it and is reflected back. This is exactly how a printed book page works. That is why many people find E-Ink more pleasant on the eyes than a phone.

Why e-readers last for weeks

The biggest advantage of E-Ink is power consumption. A normal screen has to rebuild its image sixty times per second, even if nothing changes. An E-Ink screen only needs energy when the image changes. If a book page stays still, it costs zero power. That’s why an e-reader often lasts several weeks on a single battery charge, while a tablet lasts only a few hours.

Add to that readability in sunlight. A glowing screen competes with the sun outdoors and looks pale. E-Ink, on the other hand, becomes clearer the brighter it is, just like paper. That is the reason such devices work at the beach while phones are barely readable there.

A common misconception is that E-Ink is generally gentler on the eyes. What is actually proven is mainly that there is no flickering and no light shining directly into the eye. Even so, modern e-readers often have a small light at the edge so you can read in the dark. This shines onto the page, not through it.

How the color particles move

The film contains millions of tiny capsules, each smaller than the width of a hair. Inside each capsule, white and black color particles float in a clear liquid. The white and black particles carry different electrical charges. When the device applies a voltage, one type moves up and the other moves down. White particles lying on top produce a bright dot, black particles lying on top produce a dark one.

You can picture this like a very flat carpet made of snow globes. Each globe is shaken individually until the desired color ends up on top. Afterwards, the particles simply stay in place, even without power. This is exactly why an e-reader with a dead battery still keeps its image on screen.

The downside of this mechanism is sluggishness. Particles need time to migrate, and turning a page takes a fraction of a second. Videos or fast scrolling therefore work poorly. Color E-Ink displays exist by now too, but their colors look pale and muted. That’s fine for comics, but not so much for photos.

From price tags to bus stop schedules

E-Ink screens are best known from e-readers for books. But they increasingly show up in retail: many supermarkets use electronic shelf labels on their shelves. These run on a single coin-cell battery for years, because they only need power when the price changes. Digital schedules at bus stops and name plates at conference rooms also work with this technology.

In business news, the term usually comes up in connection with the company E Ink Holdings from Taiwan. It manufactures the display films and supplies almost all major e-reader vendors. When Amazon or a competitor announces a new model, it’s often about the resolution, color capability, or response time of these films.

New is the combination with AI features. Some manufacturers build e-readers with note-taking functions that convert handwritten notes into text or generate summaries. The actual computing work here usually doesn’t happen on the device itself, but on servers on the internet. E-Ink only provides the power-saving display here, not the intelligence.