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Home Latest Articles E-Book Readers Kagoo Explains: How E Ink Works

Kagoo Explains: How E Ink Works

Updated 01 May 2020
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Resource ID 493

Welcome to ‘Kagoo Explains’ - a series of short articles explaining some of the confusing terminology used to describe technology. This week we’re looking at E Ink, the technology that powers e-book readers.

Electronic Ink - or E Ink - is a special display that mirrors the clean look of ink on paper. You have probably seen E Ink at work in e-book readers such as the Kindle or Nook, but the technology is also used for everything from smart watches to digital signage. The main benefit is that the technology requires very little power to work, as no power is needed to ‘hold’ the image on the screen - only to create it. This makes it perfect for displays that don’t need to change very often - such as books or public signs.

Benefits of E Ink

Very low power requirements.
‘Always on’ display, even without power.
Wider reading angle than digital LCD screens.
No requirement for a backlight, making E Ink displays easier to read in the dark.
Not affected by sunlight or glare.

So how does E Ink actually work? I’m glad you asked! At its most basic, an E Ink display comprises millions of very tiny microcapsules, filled with 2 different types of ink particles: white ink particles that are negatively charged, and black ink particles that are positively charged. These particles float inside the microcapsules, which in turn are suspected in a clear liquid with electrodes above and below. This is spread out under the transparent surface of the E Ink display.

Resource ID 492

Now here’s the clever bit: the electrodes can be used to apply a positive or negative electric field to specific parts of the display. When a negative charge is applied to the top electrode, the negatively charged black ink particles rise to meet it, while the positively charged white ink particles sink to the bottom. In this way individual microcapsules can be made to appear black or white, allowing the display to build up text and images.

E Ink is 'Bi-Stable', which means the particles hold their position even when the field is turned off. This is why E Ink displays have such low power consumption - the only power required is to briefly apply the electric field across the parts of the display that need to change. Some E Ink displays will ‘flash’ the entire screen when changing in order to stop the image being burnt onto the screen, but even this requires a miniscule amount of power compared to a standard LCD screen.

This is the reason why E Ink is used so much in e-book readers, and why they have such great battery life - the display only needs to be updated when you ‘turn’ the page.

Unfortunately the way E Ink works also gives it severe disadvantages. The most notable of these is a very low refresh rate - modern displays may update 60 times per second in order to smoothly display a movie or video game. E Ink technology cannot manage anywhere near that - even the most advanced E Ink displays only have a max refresh rate of 7-8 times per second. This means they can only really be used for static text or images - no movement.

The other major problem lies is that E Ink displays are generally monochromatic - the microcapsules only hold 2 colours, one of which is white to provide ‘blank’ areas on the display. Colour E Ink displays are starting to appear - commercial models may arrive in late 2020-2021 - but the progress is slow, and currently limits what E Ink can be used for. Once colour E Ink displays do become commonplace, they will be a game changer for everything from drawing tablets to watches!

So there we go - a quick 101 on Electronic Ink. If you want to see E Ink in action, check out our list of the Top E-book Readers for 2020!

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