E-ink on e-paper in an e-book using an e-reader. If you take the ‘e’ out of the terms they are familiar and comfortable words. But recent technology has taken books to a new dimension, away from cellulose fibres to a kind of electronic Etch-a-Sketch. E-reader sales are increasing rapidly as developing technology improves the reading experience on these book sized mobile devices. So just how does the technology in this new reading experience work?
E-readers have unique screen technology that distinguishes them from tablets such as the iPad. E-paper uses reflected light whereas LCD screens are back lit. This means LCD screens can be used in the dark and they display colours brightly. But they are difficult to see outside, especially in bright light. One advantage of E-reader screens is that they can be read in sunlight - great for enjoying a book while relaxing in the sunshine.
Other advantages of e-reader screens compared to tablets is that are that they are easier on the eyes and they use less battery power. The screen image can be viewed at an angle and is stable once it has loaded which makes it easier to read comfortably and for long periods of time. E-readers only use power when the screen image is changing. So the batteries last longer (battery time is measured in weeks not hours) and the devices can be smaller which lowers their weight.
There are two parts to e-paper technology. The nitty gritty of it all is quite technical but here is a summary of the main features. The two parts are sometimes called frontplane and backplane. The frontplane is the ink and the backplane is the electronics used to make the text patterns on the page.
The frontplane technology that e-reader screens use is commonly called E Ink. In fact this is a company name. The screen technology of the E Ink Corporation is the most widely used and best known technology – over 50 models of e-reader use E Ink.
The 'ink' used in E-Ink is made up of millions of tiny capsules. Inside the capsules are charged particles suspended in liquid. There are positively charged white particles and negatively charged black particles. When an electrical charge is applied to the capsule the corresponding particles (black or white) move to the top of the capsule. So when the black particles are at the top we see the shape of the text. Partial charges cause a mixture of black and white particles to move to the surface so shades of grey can be made.
Click here to see a diagram of the microcapsules and charged particles.
Magnified view of e-reader screen.
Image by Specious Reasons on Flickr
There are variations in ink technology. For example, QR-LPD technology uses particles suspended in air not liquid. An advantage is that the particles can move faster so the display changes more quickly.
Disadvantages of e-paper at present include a slow refresh rate and poor colour screen technology. The relatively slow movement of particles in the E Ink capsules means the current technology is unsuitable for animations or video. But the major challenge facing developers is to produce quality colour e-readers. This would tap into the market for children’s books, text books, newspapers and magazines. Existing e-paper technology, such as the use of filters, has so far produced rather dull colours as the filters reduce the amount of captured light.
If there is one thing that is constant in digital technology it is change and e-readers are no exception. Colour may be the next big thing in screen technology but the success of e-readers will also be dependent on factors such as ease of use, cost and content availability.
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