E-paper (e-ink) is one of the present media technologies. Only the lazy don’t write about book "readers" on its basis. E-paper has been on the market for about 5 years, but it is still considered to be a novice. Experts and analysts keep on making encouraging forecasts but things haven't got forward an inch. So what are the advantages and disadvantages of e-ink? What can we expect from e-books?
E-paper was invented as early as the 1970s but came out to the "proscenium" at the end of the 1990s. The active commercial use of this type screens have started only recently, in the past few years.
E-paper has been gaining currency as computer technology and internet has been developing. As the size of the text that one has to read on the monitor has been growing there has appeared a need for the display that wouldn’t make eyes tired. Both CRT and micro-light gas-discharge lamps of the present LCD always flicker. It adversely affects eyesight especially when one has to read a whole a few hundred-page book in a night, eyes get tired.
In e-paper, the image is formed not with the help of liquid-crystal matrix but with reflected light. And most of the energy is used for displaying of the picture. Such screens need a very small amount of energy for displaying. Thus, e-paper not only prevents eyes from getting tired but also saves energy, which enables to create long-living devices.
The first e-paper, called Hericon, was invented in the 1970s in the famous research centre Xerox PARC, where the first computer mouse, graphical interface of the OS, the modern techniques of the computer print and many other useful things were created.
Nick Sheridon introduced Hericon: a display consisting of polyethylene microspheres with negatively charged black and positively charged white halves. "Little balls" were put into a transparent silicone sheet where they could freely revolve. Depending on the polarity of the voltage with which electrodes were supplied, the spheres turned either their black or their white side – this was a picture was formed.
The technology was developed in the 1990s. Joseph Yakobson suggested filling the spheres with dyed oil and white particles of titanium dioxide. The polarity of the electric discharge defines whether they will rise to surface or the pixel will remain dyed. The size of each capsule is only 40 micrometres. While in Hericon and early electrophoretic screens "pixels" were put between two fragile glass plates, Yakobson made it possible to put capsules between plastic plates due to using polymeric material. Besides, the thickness of the display turned out to be less than of a paper sheet. Yakobson called his technique "e-ink" and registered a company of the same name in partnership with Philips which didn’t succeed much though. E-ink with all its technologies has been sold to Prime View recently. Meanwhile electrophoretic screens dominate on the market today.
But scientists don’t stand still, they are advancing. In May 2009 researchers from Cincinnati University and Sun Chemicals Company suggested using ordinary pigmental ink for e-paper. The essence of the technique is that each pixel will consist of a visible part and a mini-reservoir where there will be pigment. Under current ink will be modified into pixels and then revert.
This technology has very good prospects for coloured displays. The thing is that in traditional e-paper a complex system of filters is used for generating a coloured image, which makes this kind of display very expensive. According to the new technique one pixel can consist of several subpixels of basic colours, for instance CMYK.
Similar research is being made in the depths of Philips. Though in contrast to scientists from Cincinnati engineers of the Dutch company suggest using two reservoirs with ink mixed in certain proportions.
The main advantage of the new designs is that they will enable to make e-paper as white as possible and the image on it won’t practically differ from a printed one.
A disadvantage of all the e-paper techniques is a very long time of response. It doesn’t allow to show dynamic content and to use for interactive applictions. Besides, scaling of documents on the screen is carried out very slowly.
Another direction of the technique development is combining e-ink and cholesteric liquid crystals. Such displays have been introduced by Samsung and Pixel Qi this year. E-paper is sprung into action for generating a static picture, for example, a document. LCD-technology is for dynamic scenes.