Electronic paper

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File:E-Ink Flex Tablet Display.jpg
A prototype electronic paper display, using E Ink's Electrophoretic Imaging Film

Electronic paper, also sometimes called e-paper or electronic ink, is a display technology designed to mimic the appearance of regular 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 or using processor power, while allowing the paper to be changed. One important feature needed is that the pixels be image stable, 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.

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.

File:E-ink.png

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 red, green and blue, in the same way as CRT monitors. The display is then controlled like any other electronic colour display.

Applications

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. One form or another of electronic paper is being developed by Gyricon (which was spun out of Xerox), Philips Electronics, Kent Displays (cholesteric displays), Nemoptic (bistable nematic - BiNem - technology), NTERA (electrochromic NanoChromics displays), E Ink, Prime View International, and SiPix Imaging (electrophoretic), and many others.

Commercial applications

E Ink Corporation has been working with companies like Phillips and Sony to develop commercial applications. It announced in October 2005 that it would begin shipping developer kits of 6 inch, 800x600 resolution electronic paper on November 1, 2005. On July 14 and 15th 2005 Fujitsu showcased their jointly developed electronic paper at the Tokyo International Forum. It boasts low power consumption in that it does not require electricity except during screen image changes, making electronic paper especially suited for advertisements or information bulletins in public places for which paper is currently used.

EBook readers
  • The Sony LIBRIé debuted in 2004 and was sold only in Japan. It was the first commercally available electronic device to utilize electronic paper display technology. The device featured a 6" SVGA active matrix display using E Ink'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 iLiad debuted in April of 2006. It is a portable reader capable of reading media in various electronic formats. The iLiad features an 8" XGA display using E Ink's material.
  • The STAReBOOK STK-101 e-book reader was launched in December 2006 by Taiwan-based eREAD. Marketed as the thinnest, lightest e-book on the market, it uses the same 6" SVGA EPD display as the Sony Reader.
  • eFlybook is designed for the aviation market and comes pre-loaded with maps, charts and procedural manuals. It is also capable of reading various other electronic formats. The eFlybook is a re-badged iRex iLiad.
  • Jinke Hanlin eReader V8, launched in 2006. Also uses the same 6" SVGA EPD display as the Sony Reader. Marketed as a cheaper alternative to more expensive brand eInk readers.
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. Compared with existing key fob tokens, display cards 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 from E Ink, probably similar to the Sony Reader. [1]

See also

Further reading

References

  1. ^ Crowley, J. M.; Sheridon, N. K.; Romano, L. "Dipole moments of gyricon balls" Journal of Electrostatics 2002, 55, (3-4), 247.
  2. ^ a b 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

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