05-03-2011, 12:59 PM
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ABSTRACT:
Thirty-five years in the making, electronic paper is now closer than ever to changing the way we read, write, and study — a revolution so profound that some see it as second only to the invention of the printing press in the 15th century. Made of flexible material, requiring ultra-low power consumption, cheap to manufacture, and—most important—easy and convenient to read, e-papers of the future are just around the corner, with the promise to hold libraries on a chip and replace most printed newspapers before the end of the next decade. This article will cover the history, technology, and future of what will be the second paper revolution.
INTRODUCTION
Electronic paper, e-paper or electronic ink display 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. It is capable of holding text and images indefinitely without drawing electricity, while allowing the image to be changed later.
To build e-paper, several different technologies exist, some using plastic substrate and electronics that the display is flexible. E-paper has the potential to be more comfortable to read than conventional displays. This is due to the stable image, which does not need to be refreshed constantly, the wider viewing angle, and the fact that it reflects ambient light rather than emitting its own light. An e-paper display can be read in direct sunlight without the image appearing to fade. The contrast ratio in available displays as of 2008 might be described as similar to that of newspaper, though newly-developed implementations are slightly better. There is ongoing competition among manufacturers to provide full-color capability.
I. HOW IT ALL STARTED?
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 75 and 106 micrometres across. Each sphere is a janus particle composed of negatively charged black plastic on one side and positively charged white plastic on the other (each bead is thus a dipole). 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. At the FPD 2008 exhibition, Japanese company Soken has demonstrated a wall with electronic wall-paper using this technology. Scheme of an electrophoretic display using color Filters
An electrophoretic display forms visible images by rearranging charged pigment particles using an applied electric field.
II. HOW E-PAPER WORKS
E-paper comprises two different parts: the first is electronic ink, sometimes referred to as the "frontplane"; and the second is the electronics required to generate the pattern of text and images on the e-ink page, called the "backplane".
Electrophoretic frontplane consists of millions of tiny microcapsules, each approximately 100 microns in diameter—about as wide as a human hair. Each microcapsule is filled with a clear fluid containing positively charged white particles and negatively charged black particles. When a negative electric field is applied, the white particles move to the top of In the simplest implementation of an electrophoretic display, titanium dioxide particles approximately one micrometer in diameter are dispersed in a hydrocarbon oil. A dark-colored dye is also added to the oil, along with surfactants and charging agents that cause the particles to take on an electric charge. This mixture is placed between two parallel, conductive plates separated by a gap of 10 to 100micrometres. When a voltage is applied across the two plates, the particles will migrate electrophoretically to the plate bearing the opposite charge from that on the particles. When the particles are located at the front (viewing) side of the display, it appears white, because light is scattered back to the viewer by the high-indextitania particles. When the particles are located at the rear side of the display, it appears dark, because the incident light is absorbed by the colored dye. If the rear electrode is divided into a number of small picture elements (pixels), then an image can be formed by applying the appropriate voltage to each region of the display to create a pattern of reflecting and absorbing regions.
Electrophoretic displays are considered prime examples of the electronic paper category, because of their paper-like appearance and low power consumption.the microcapsule, causing the area to appear to the viewer as a white dot, while the black particles move to the bottom of the capsule and are thus hidden from view. When a positive electric field is applied, the black particles migrate to the top and the white particles move to the bottom, generating black text or a picture.
The brightness and resolution of electrophoretic-based e-ink is better than that of bichromal-based e-ink, but both are monochromatic in nature