A Brief Primer on E-Ink: What It Is and How It Works

It no longer dominates the e-reader market

E-reader amazon kindle on top of a book next to glasses

Carolyn Hebbard / Getty Images 

Electronic ink technology produces a low-power paperlike display used primarily in early e-book readers such as Amazon's Kindle.

Initial research on e-ink started at MIT's Media Lab, where the first patent was filed in 1996. The rights to the proprietary technology currently are owned by the Massachusetts-based E Ink Corporation, which was acquired by Taiwanese company Prime View International in 2009.

How E-Ink Works

E-ink technology in early e-readers works by using tiny microcapsules that are suspended in a liquid placed within a film layer. The microcapsules, which are about the same width as human hair, contain both positively charged white particles and negatively charged black particles.

Applying a negative electrical field causes the white particles to come to the surface. Conversely, applying a positive electrical field causes the black particles to come to the surface. By applying different fields at various parts of a screen, e-ink produces a text display.

E-ink displays are especially popular due to their resemblance to printed paper. Besides being considered by many as easier on the eyes than other display types, e-ink also boasts lower power consumption, particularly when compared to traditional backlit liquid crystal display (LCD) screens. These advantages, along with its early adoption by major e-reader manufacturers such as Amazon and Sony, caused e-ink to dominate the early e-book reader market.

Uses of E-Ink

In the early 2000s, e-ink was ubiquitous in the many e-readers coming to the market, including Amazon Kindle, Barnes & Noble's Nook, the Kobo eReader, Sony Reader, and others. It was praised for its clarity in bright sunlight. It is still available on some Kindle and Kobo e-readers, but other screen technologies have taken over much of the e-reader market.

E-ink technology appeared in a few early cell phones and spread to applications that included traffic signage, electronic shelf signage, and wearables.

Limitations of E-Ink

Despite its popularity, e-ink technology has its limitations. Until recently, e-ink couldn't display color. Also, unlike traditional LCD displays, typical e-ink displays don't have backlighting, which makes it a challenge to read them in dim places, and they can't display video.

To counter competition from rival displays such as reflective LCD and new screens developed by potential competitors, E Ink Corporation worked to improve its technology. It added touch-screen capabilities. The company launched its first color display in late 2010 and produced these limited-color screens through 2013.

Advanced Color ePaper

In 2016, E Ink Corporation announced Advanced Color ePaper (ACEP), which displays many thousands of colors, but the launch of the color e-paper displays was been until 2019. As it launched, this color technology is primarily targeted at the signage market, not at the e-reader market. E-ink technology, which gained recognition primarily through the e-book reader market, has expanded to wider markets in industry, architecture, labeling, and lifestyle.

ACEP is a breakthrough that brings color to low-powered e-ink displays. Each pixel contains all the pigments to make every color. It is likely that ACEP displays may enjoy a resurgence of popularity in e-readers in the future.