ELECTRONIC PAPER

'Electronic paper', also called 'e-paper' or 'electronic ink', is a display technology designed to mimic the appearance of ordinary ink on paper. Unlike a conventional flat panel display, which uses a backlight to illuminate its pixels, electronic paper reflects light like ordinary paper and is capable of holding text and images indefinitely without drawing electricity, while allowing the image to be changed later. Unlike traditional displays, e-paper can be crumpled or bent like traditional paper. One important feature needed is that the pixels be ''image stable'', or bistable, so that the state of each pixel can be maintained without a constant supply of power.
Electronic paper was developed in order to overcome some of the limitations of computer monitors. For example, the backlighting of monitors is hard on the human eye, whereas electronic paper reflects light just like normal paper. It is easier to read at an angle than flat screen monitors. It is lightweight, durable, and highly flexible compared to other display technologies, though it is not as flexible as paper.
Predicted future applications include e-paper books capable of storing digital versions of many books, with only one book displayed on the pages at any one time. Electronic posters and similar advertisements in shops and stores have already been demonstrated.
Electronic paper should not be confused with digital paper.

Contents

Technology

Polychrome e-paper

Inkless printing

Applications

Commercial applications

EBook readers

Newspapers

Displays embedded in smart cards

Cell phone displays

See also

Further reading

References

External links

Technology

Electronic paper was first developed in the 1970s by Nick Sheridon at Xerox's Palo Alto Research Center. The first electronic paper, called Gyricon, consisted of polyethylene spheres between 20 and 100 micrometres across. Each sphere is composed of negatively charged black plastic on one side and positively charged white plastic on the other (each bead is thus a dipole^[1]). The spheres are embedded in a transparent silicone sheet, with each sphere suspended in a bubble of oil so that they can rotate freely. The polarity of the voltage applied to each pair of electrodes then determines whether the white or black side is face-up, thus giving the pixel a white or black appearance.^[2]
In the 1990s another type of electronic paper was invented by Joseph Jacobson, who later co-founded the corporation E Ink which formed a partnership with Philips Components two years later to develop and market the technology. In 2005, Philips sold the electronic paper business as well as its related patents to Prime View International. This used tiny microcapsules filled with electrically charged white particles suspended in a colored oil.^[3] In early versions, the underlying circuitry controls whether the white particles were at the top of the capsule (so it looked white to the viewer) or at the bottom of the capsule (so the viewer saw the color of the oil). This was essentially a reintroduction of the well-known electrophoretic display technology, but the use of microcapsules allowed the display to be used on flexible plastic sheets instead of glass.
One early version of electronic paper consists of a sheet of very small transparent capsules, each about 40 micrometres across. Each capsule contains an oily solution containing black dye (the electronic ink), with numerous white titanium dioxide particles suspended within. The particles are slightly negatively charged, and each one is naturally white.²
The microcapsules are held in a layer of liquid polymer, sandwiched between two arrays of electrodes, the upper of which is made from indium tin oxide, a transparent conducting material. The two arrays are aligned so that the sheet is divided into pixels, which each pixel corresponding to a pair of electrodes situated either side of the sheet. The sheet is laminated with transparent plastic for protection, resulting in an overall thickness of 80 micrometres, or twice that of ordinary paper.

The network of electrodes is connected to display circuitry, which turns the electronic ink 'on' and 'off' at specific pixels by applying a voltage to specific pairs of electrodes. Applying a negative charge to the surface electrode repels the particles to the bottom of local capsules, forcing the black dye to the surface and giving the pixel a black appearance. Reversing the voltage has the opposite effect - the particles are forced from the surface, giving the pixel a white appearance. A more recent incarnation^[4] of this concept requires only one layer of electrodes beneath the microcapsules.
Other research efforts into e-paper have involved using organic transistors embedded into flexible substrates,^[5][6] including attempts to build them into conventional paper.^[7]

Polychrome e-paper

Simple colour e-paper^[8] consists of a thin coloured optical filter added to the monochrome technology described above. The array of pixels is divided into triads, typically consisting of the standard cyan, magenta and yellow, in the same way as CRT monitors (although using subtractive primary colors as opposed to additive primary colours), for commercial releases of e-paper in the forms of newspapers etc, it will most likely be in the 'CMYK' format, for clarity of writing. The display is then controlled like any other electronic colour display.

Inkless printing

Zero-Ink Printing is an inkless printing technology being developed by Zink Imaging, which uses a specialized paper containing dye crystals that are activated by applying heat to them.

Applications

Several companies are simultaneously developing electronic paper and ink. While the technologies used by each company provide many of the same features, each has its own distinct technological advantages. All electronic paper technologies face the following general challenges:

★ A method for encapsulation

★ An ink or active material to fill the encapsulation

★ Electronics to activate the ink
Electronic ink can be applied to both flexible and rigid materials. In the case of flexible displays, the base requires a thin, flexible material tough enough to withstand considerable wear, such as extremely thin plastic. The method of how the inks are encapsulated and then applied to the substrate is what distinguishes each company from each other. These processes are complex and are carefully guarded industry secretes. The manufacture of electronic paper promises to be less complicated and less costly than traditional LCD manufacture.
There are many approaches to electronic paper, with many companies developing technology in this area. Other technologies being applied to electronic paper include modifications of liquid crystal displays, electrochromic displays, and the electronic equivalent of an Etch A Sketch at Kyushu University. Advantages of electronic paper includes low power usage, flexibility and better readability than most displays. Electronic ink can be printed on any surface, including walls, billboards, product labels and T-shirts. The ink's flexibility would also make it possible to develop rollable displays for electronic devices. The ideal electronic paper product is a digital book that can typeset itself and could be read as if it were made of regular paper, yet programmed to download and display the text from any book. Another possible use is in the distribution of an electronic version of a daily paper

Commercial applications

EBook readers

★ The Sony LIBRIé debuted in 2004 and was sold only in Japan. It was the first commercially available electronic device to utilize electronic paper display technology. The device featured a 6" SVGA active matrix display using E Ink Corporation's electrophoretic technology.

★ The Sony Reader was announced on January 6, 2006 and launched in September 2006 as a successor to the LIBRIé for the US market. The reader uses an upgraded version of the display from the original LIBRIé.

★ iRex Technologies product iLiad debuted in April of 2006. The iLiad features an 8" XGA display using E Ink's material.

★ eFlybook is designed for the aviation market and comes pre-loaded with maps, charts and procedural manuals. The eFlybook is a re-badged iRex iLiad.

★ The STAReBOOK STK-101 e-book reader was launched in December 2006 by Taiwan-based eREAD. It uses the same 6" SVGA EPD display as the Sony Reader.

★ Jinke Hanlin eReader V8, launched in 2006. Also uses the same 6" SVGA EPD display as the Sony Reader.

Newspapers

★ In February 2006, the Flemish daily ''De Tijd'' announced plans to distribute an electronic-ink version of the paper to selected subscribers in a limited marketing study. This will be the first such application of electronic ink to newspaper publishing. The trial was conducted using a pre-release version of the iRex iLiad.

Displays embedded in smart cards

★ Flexible display cards enable financial payment cardholders to generate a one-time password to reduce online banking and transaction fraud. Electronic paper could offer a flat and thin alternative to existing key fob tokens for data security. The world’s first ISO compliant smart card with an embedded display was developed by Smartdisplayer using SiPix Imaging’s electronic paper.

Cell phone displays

★ Motorola's new candybar style mobile phone, called the Motofone, also uses a monochrome electronic paper screen

See also

★ Electronic paper display

Further reading

★ New Scientist - Electric paper (2003)

★ New Scientist - E-paper may offer video images (2003)

★ New Scientist - Paper comes alive (2003)

★ New Scientist - Most flexible electronic paper yet revealed (2004)

★ New Scientist - Roll-up digital displays move closer to market (2005)

References

1. Crowley, J. M.; Sheridon, N. K.; Romano, L. "Dipole moments of gyricon balls" Journal of Electrostatics 2002, 55, (3-4), 247.
2. New Scientist. Paper goes electric (1999)
3. Comiskey, B.; Albert, J. D.; Yoshizawa, H.; Jacobson, J. "An electrophoretic ink for all-printed reflective electronic displays" Nature 1998, 394, (6690), 253-255.
4. New Scientist. Roll the presses (2001)
5. Huitema, H. E. A.; Gelinck, G. H.; van der Putten, J. B. P. H.; Kuijk, K. E.; Hart, C. M.; Cantatore, E.; Herwig, P. T.; van Breemen, A. J. J. M.; de Leeuw, D. M. "Plastic transistors in active-matrix displays" Nature 2001, 414, (6864), 599.
6. Gelinck, G. H. et al. "Flexible active-matrix displays and shift registers based on solution-processed organic transistors" Nature Materials 2004, 3, (2), 106-110.
7. Andersson, P.; Nilsson, D.; Svensson, P. O.; Chen, M.; Malmström, A.; Remonen, T.; Kugler, T.; Berggren, M. "Active Matrix Displays Based on All-Organic Electrochemical Smart Pixels Printed on Paper" Adv Mater 2002, 14, (20), 1460-1464.
8. New Scientist. Read all about it

External links

★ Wired article on E Ink-Philips partnership, and background

★ E Ink Corp. website

★ How Electronic Ink Will Work