No Size Escapes E-Paper Technology

E-paper technology has recently captured the public’s attention with the release of Amazon’s Kindle, an eBook reader that allows users to view text and graphics on a display that mimics the surface of paper; i.e., it only relies upon ambient light for visibility. Although the technology has recently come to the forefront, it was developed by Nick Sheridon in 1970 at Xerox PARC (Palo Alto Research Center). While several applications based on the technology are already commercialized, the most widespread is the collective product group classified as eBook readers. Amazon’s Kindle is such a product.

There are several core technologies actually used by companies to manufacture electronic paper (e-paper): electrophoteric, electrochromic, electrowetting, and cholesteric liquid crystal displays (ChLCD). All the technologies have two essential elements in common-reflective displays that closely mimic ink on paper and extremely low power consumption. While the technology has numerous potential applications it is interesting to examine the potential size- just how large or for that matter, how small-the displays can be manufactured using e-paper technology.

E-Readers

Because the application uniquely suits e-paper technology, e-readers are probably its most popular application. Most of these readers are manufactured using electrophoteric technology, but other technologies have also emerged. E Ink is the most visible and successful of those companies who manufacture e-paper using electrophoteric technology. The main advantage of eBook readers is that they use reflective light, so there is no backlight display involved.  Thus the screens can be seen clearly in daylight, unlike other traditional display screens.

The other performance requirement that is universally accepted as important for paper-like displays is low power consumption.  In current e-paper technology, one way to achieve this low power consumption is to use materials platforms that are capable of holding images without electricity. As a result, the image can remain on the display screen without a power supply.

As of this writing, the product that uses the smallest e-paper surface area is arguably the 16 GB Lexar Jumpdrive Secure II Plus USB Flash drive, where Segmented Display Cells (SDC’s), an E Ink implementation, are responsible for the 10-bar capacity meter that shows the available storage space of the flash drive.

Other small devices are this wireless, bi-directional key fob by Delphi. The device provides the driver with information from his vehicle over a long range. The display, also an SDC implementation, provides readability even under direct bright sunlight; a feature that is not possible with common LCD screens. Since the display consumes minimal energy, it is ideal for a key fob whose battery is rarely, if ever, replaced. One of the advantages of segmented displays is that the symbols displayed can have curved edges, as is shown in the image.

Not all small devices use E Ink’s SDC technology. Here is a tiny MP3 player from Freestyle Audio. What differentiates it is not its small size. If you look closely, you’ll see… yes, colors! While most of what we’ve been seeing so far are gray-scaled displays, it IS POSSIBLE to have colored displays using e-paper. In this particular device, the basic physics principle of interference is used to produce the colors. The display is made up of two layers that are movable by electrostatic forces. When white light, the combination of all colors, is incident on the first layer, some wavelengths (colors) get reflected while the rest pass through. Upon reaching the second layer, some again get reflected while the rest are absorbed. The two reflected rays interfere and form the colors that are shown. The underlying principle is very similar to the reason why we see rainbow-like patterns on a thin film of oil on a flat surface.

Large E-Paper Displays

SDC’s can also be combined to produce large format displays. The Citizen Bendable Clock is such an application. Equally noteworthy as its wide surface area is the “bendability” of the clock, another important advantage of the technology.

At the EXPO 2005, in Aichi Japan, Toppan Printing exhibited a large wall-sized newspaper that made use of E Ink technology. The wall-sized newspaper was actually an application of LCD (liquid crystal display), which displayed the colored photos, and electronic paper, which was responsible for displaying the text. Perhaps future e-paper applications would be similar to this; combining various technological solutions to solve a single problem.

Similar to small devices, the applications of e-paper technology on large format displays are not limited to gray-scale presentations. One e-paper technology that has captured a lot of attention lately is the Cholesteric Liquid Crystal or (Ch-LC) Display, the technology used by the world’s first developer and provider of color reflective digital ink displays - Magink. Like E Ink, Magink displays don’t compete with ambient light, and are low on power consumption. Each display is made up of modular tiles to allow it to adapt to practically any shape or size requirement.

Ch-LC is not the only e-paper based technology that is capable of exhibiting large colorful images. Displays based on the principle of electrowetting are also capable of displaying bright colors.  To date, Liquavista, a spin off from Phillips Research, is the only company developing this technology. It has introduced its large area signage concept product called Aquarius. However, it is important to note that colored segmented displays, as well as those based on electrowetting, are only capable of limited color. The one or two colors replace black-and-white images with colors. It is not full-color that is needed to compete with traditional display technology. Work on full-color e-paper displays is being researched by several companies, who have already introduced prototypes or demonstration models. However, commercialization is still down the road for these products.

So while it is not widely known, e-paper is not just about e-readers. This very promising display technology already encompasses devices as small as flash drives and key fobs to large format displays that not only exhibit black-and-white text and symbols, but some color as well. In addition, its low power consumption makes it even more attractive for mobile devices. The milestones that electronic paper has achieved in recent years promise that it can be a viable replacement for more traditional display technologies, and even open the way to new applications for displays.