ELECTRONIC-INK DISPLAY:
A revolutionary combination of ink and paper.
Ms Priyanka Ingale & Ms Aanchal Agrawal

ABSTRACT This paper surveys a system that allows tiny, electrically-charged microcapsules to render text and images on a page. To put it literally it’s a display designed to mimic appearance of regular ink on paper. Conventional flat panel displays use a backlight to illuminate its pixels, while electronic paper reflects light like ordinary paper and is capable of holding text and images indefinitely without drawing electricity or using processor power. It can display different colors when exposed to electric field. It is made through a two step process that involves creating two-toned charged particles, the resulting nanoparticle shells are suspended in a solvent encapsulated in a transparent polymeric shell, when required the ink can be applied to a surface. It is lightweight, durable and highly flexible compared to other displays. Electronic paper combines the advantageous viewing characteristics of conventional paper with the ability to electronically manipulate the information displayed on paper.

INDEX TERMS:
1. Historical background.
2. Construction. 2.1 Manufacturing Polymer ink. 2.2 Thin film electrode.
3. Advantages.
4. Disadvantages.
5. Application areas.
6. Conclusion.
7. References.

1. HISTORICAL BACKGROUND The prototype of e-ink was developed in the late 1970s, at Xerox PARC, Palo Alto, CA. It used millions of tiny magnets that had oppositely colored sides (black and white) embedded on a thin, soft, rubber surface. When an electric charge was introduced the magnets flipped making either a black or white mark, appear to be viewed. After a decade, scientist Sheridon embedded plastic beads in a flexible transparent film. As thick as human hair, each bead was two-toned (black and white) with an opposing electrical charge on each half. On applying electric field to the transparent surface, beads could be rotated to lock either white or black dot onto the viewing plane thus creating, an ink that twists itself into the right place. But this version of e-paper was as rigid as a board.

[pic] Fig 1. Magnified image of e-ink display.

In 1995, Joe Jacobson, a researcher at MIT, conceived a variation of the PARC idea using reversible particles. Instead of pigment-carrying beads, he used transparent polymer microcapsules containing a blue liquid dye and white particles. Eventually, he created electronic ink, w. Jacobson called this "electrophoretic ink," or e-ink.

2. CONSTRUCTION. The display on our monitors are crafted using pixels, likewise here the polymeric cells render images. Each cell is wired to microelectronics embedded in ultra thin plastic sheets. This microelectronics would then be used to apply a positive or negative charge to the microcapsules to create the desired text or images. Although various companies have stepped into this stream to launch their own e-ink products, their platforms vary slightly. Below are the three basic components of electronic inks that give them the ability to rearrange upon command: • Millions of tiny microcapsules or cavities • An ink or oily substance filling the microcapsules • Charged pigmented chips (single colored or sometimes two-toned) floating inside the microcapsule.

[pic]
Fig 2. Encapsulated pigments subjected to charges.

The microcapsules are only 100 microns wide and roughly 100000’s of them fit into a square inch of paper. In each of those microcapsules there are hundreds of smaller pigmented chips. A variety of raw materials are used in the production of electronic ink. These include polymers, reaction agents, solvents, and colorants. Polymers are high molecular weight materials which are made up of chemically bonded monomers. These materials are useful because they liquefy when heated, solidify when cooled and maintain stable dipoles which are long lasting.
2.1 MANUFACTURING POLYMER INK. Making of electronic ink involves a two discrete step fashion. Firstly, the two contrasting inks are given opposite charges, and then the ink encapsulated in conductive micro spheres and applied to the desired surface. Initially two contrasting liquid polymers in atomized state, are loaded into separate containers which have attached nozzles. These nozzles are kept at opposite potentials. The filling is kept heated to maintain a liquid state. Pressure is then used to force the inks through the nozzles causing them to break into tiny particles and also acquire the opposing charges. The containers are situated next to each other so when the ink exits the nozzles they come in contact. As they have opposite charges, they are attracted to each other and thus forming larger and neutral particles. Now, the materials are allowed to cool causing them to solidify. This results in a small two-toned solid particles having oppositely charged sides. The particles are then run past a heating element which reduces surface tension and creates a more perfect sphere. The particles are then run through a set of electrodes separating out the imperfectly charged. As they pass the electrodes, the imperfect particles are attracted to the corresponding electrode and then removed. The rest of the particles are transferred to the encapsulating area.
[pic]
Fig 3. Microscopic view of two-toned pigments. The particles are moved into a tank which contains a liquid solution of monomer in silicone oil. The particles are mixed thoroughly so they are evenly dispersed. This solution is combined with an aqueous phase which creates an emulsion. An emulsion is a semi-stable mixture of oil and water. The electronic ink particles remain in the silicone oil which is surround by water. A cross-linking agent is added to the solution which causes the monomer to react with itself. This produces tiny spheres which contain some silicone oil and the electronic ink particles. The ink particles can then be separated from the aqueous phase for various applications. This can be done by evaporation with subsequent solvent washing. After the reactions are complete, the electronic ink articles are stored in a liquid solvent until they can be applied. Depending on the final product, this application process can involve spreading the liquid ink on specialized paper, fabric, or other kinds of fibers.
2.2 THE THIN FILM ELECTRODE. The front plane of e-ink contains small, sub-micron, ink particles that are given electric charges and then suspended in a dielectric fluid medium that is encapsulated into a sub-pixel size cell or microcapsule. The display foil is basically composed of a matrix of picture elements (pixels). Thousands or millions of such pixels together generate an image on the display film. The flipping of pigments take place as we switch the charges rendered on its surface. These charges however, need to be driven by a special kind of emissive transistors printed n flexible sheets instead of glass substrate using a commercial printing technique. These transistors are called as TFT (thin film transistors), they act as switches to individually turn pixels on or off (+ve or –ve charge in this case). A switching speed of 100 Hz has been achieved and each pixel is driven by their own individual TFT’s. Thus, the name "active-matrix TFT."
[pic]
Fig 4. e-ink is crammed between a layer of such foils

Older displays did not have this 'switch', just a matrix of connections, and are known as passive matrix displays. They have the disadvantage of requiring a complete screen refresh just in order to change a single pixel, which makes them far too slow for most modern applications. The usual way of fabricating the transistors used to construct the backplane switches is to deposit a thin layer of silicon onto a glass substrate and then use conventional semiconductor manufacturing techniques to create the transistors and associated circuitry. organic electronic materials that are soluble, and can thus be used to fabricate the electronics at room temperature thereby allowing the circuitry to be mounted upon a flexible plastic substrate. Another advantage of organic semiconductors is that the circuitry can be created using conventional screen printing and ink jet technologies.

3. ADVANTAGES.
1. Appearance: Bright, high contrast, full viewing angle, sunlight viewable.
2.Ultra low power consumption: Power consumed only while editing display and not while maintaining an image.
3.Form: Thin, light weight, shatterproof, flexible.
4. Gives the experience of reading from paper yet updatable as required.
5. As it is a reflective technology no front or back lighting required.
6. Viewable under a wide range of lighting conditions including direct sunlight.
7. Bi-stable display.
8. They can be produced at low cost and in high volume.
9. Handwritten notes and diagrams can be taken down in case of touch screens.
10. Do not distort when touched and flexed.

4. DISADVANTAGES
1. It has low switching speed, as the required display is not obtained unless all the pigments are flipped.
2. Present thickness is more like cardboard than paper. Hence the bending angle is limited to 2cm.
3. It uses monochrome.
4. Display resolution limited by bead (pigment) size.
5. Precludes the use of thin flexible plastics if the conventional method of depositing silicon is used, as it is carried out at high temperatures that may melt the foil.
6. Display only in gray scales.

5. APPLICATION 1. Used as display panels at trade shows or even dynamic signs at supermarkets. 2. E-books made of e-ink can be used for high-resolution display of hundreds of pages of information. 3. To make a product stand out with their bright, bold look and unlimited viewing angle. E.g: Cell phone displays or PDA’s. 4. In e-paper which are readable as well as rewritable. 5. In e-watches. 6. Most importantly e-newspapers. 7. Memory indication in USB’s. 8. With a wireless link such message boards or posters can be remotely changed and updated. 9. Display screens for computers or television sets.

[pic](a) e-newspapers. (b) Billboards. (c) Rewrittable display. (d) e-watches.

[pic] [pic] (e) USB with e-ink display. (f) Display for PC’s.

6. CONCLUSION

Thus we conclude that e-ink display is a system that allows tiny, electrically-charged microcapsules to render text and images on a page. It requires incredibly little electricity to operate, because it emits no light and uses energy only when the page is refreshed. This new, lightweight, flexible display material has most certainly overcome the limitations of computer displays as wel as traditional paper, combining only their positive aspects.

7. REFERENCES

1.e-books: Wireless Optical Communication Systems, by Hranilovic Polymers for Electronic Components, by Keith Cousins

2.Links: http://www.plasticlogic.com/news-detail.php?id=167 http://spicygadget.com/2006/11/20/review-sony-reader/ http://searchmobilecomputing.techtarget.com/sDefinition/0,,sid40_gci535045,00.html http://wiki.mobileread.com/wiki/E-book_Reader_Matrix http://en.wikipedia.org/wiki/Electronic_paper http://www.media.mit.edu/micromedia/elecpaper.html http://en.wikipedia.org/wiki/Electronic_paper http://www.eink.com/technology/howitworks.html http://electronics.howstuffworks.com/e-ink1.html http://www.madehow.com/Volume-6/Electronic-Ink.html