E-paper Technologies Reference Guide
For almost three decades, electronic paper technologies have been evolving to combine the flexibility of digital information with the familiarity, quality, and convenience of a paper-like substrate. More than a dozen companies have announced work on active e-paper programs, and there are a number of start-ups coming to existence as well.
The production structure of electronic paper is fairly complex. E-paper is based on IP/technology developed by a handful of technology developers. In many cases this manufacturing is contracted out. In addition, E-paper generally needs some kind of backplane that is manufactured by another group of firms. It is important to note that there is an additional group of firms—consumer product firms—who design and market the product into which the e-paper display fits. For example, the e-readers marketed under the Sony brand have incorporated e-paper technology from E Ink and backplane technology from Polymer Vision.
This guide is designed to provide a background in both e-paper frontplane technologies and the current backplane technologies used to manufacture such displays. It is divided into two sections. The first will explain the various e-paper technologies that exist today and provide analysis on the pros and cons to each of them. The second section will discuss the various backplane technologies used to power the e-paper frontplanes.
Frontplanes for E-paper
Electrophoresis is a process, which enables separating molecules according to their size and electrical charge by applying an electric current. In an electrophoretic frontplane small, charges submicron particles are suspended in a dielectric fluid that is enclosed into a sub-pixel size cell or microcapsule. When an electric field is applied across this cell or capsule, the ink particles will move towards the electrode with the opposite charge.
With a transparent electrode the cell or capsule surface takes on the color of the ink when current is applied. The contrast is improved by using opposite colored particles. such as black and white—and charging them with opposite polarities. When current is applied, all the black particles will migrate to one side, and all the white to the other. Switch the field, and the capsule will change color. This enables switching between all black particles and all white particles on the transparent front electrode of the cell or microcapsule. This is how the high contrast ration of electrophoretic displays is created. The difference between the various electrophoretic frontplane technologies lies simply in the method of encapsulation for the charged particles and fluid medium. Some versions use a “microcup” rather than a particle.
The electrophoretic technology used by E Ink is the most widely known and used form of e-paper. Known as electronic ink, it is a proprietary material that is made into a film for incorporation into a paper-like display. The company states that “the principal components of electronic ink are millions of tiny microcapsules, about the diameter of a human hair. In one stage, the microcapsules contain positively charged white particles with negatively charged black particles suspended in a clear fluid. Applying a negative electric field, causes the white particles to move to the top of the microcapsule where they become visible to the user. Thus the surface area where the white particles have moved to appears white. The black particles are simultaneously moved to the bottom of the display, where they are hidden. When the process is reversed, the black particles move to the top to make that section of the display appear dark.”
The E Ink microcapsules are only 100 microns wide, which means that roughly 100,000 microcapsules can fit into a square inch of paper. Each of those microcapsules contains hundreds of smaller pigmented chips. In earlier prototypes, E Ink worked with white chips and blue ink, but later it developed other color inks for multicolored displays. Wiring the pages to create an electric charge and still maintain a paper-thin page has been a challenges in developing a digital book out of electronic ink. E Ink partnered with Lucent Technologies to enable the use of organic transistors developed by Lucent in the e-paper displays. These tiny transistors can be printed onto a page to provide the adequate charge needed to switch the E Ink chips from one color to another.
Cross-Section of Electronic-Ink Microcapsules
The display is manufactured by printing the electronic ink onto a sheet of plastic film that has been laminated to a layer of circuitry. The circuitry forms a pattern of pixels that can then be controlled by a display driver. The electronic ink, which is composed of microcapsules suspended in a liquid vehicle (carrier medium), can be screen printed onto a variety of substrates including glass, plastic, fabric and paper. The company claims that ultimately the electronic ink will be able to be printed on almost any surface to make a display.
The company also offers Vizplex imaging film. This consists of microencapsulated electronic ink coated onto an ITO-coated plastic substrate to create an ink film, which is then combined with a thin adhesive and a plastic release sheet. After converting the film into individual sheets, it is available for sale to TFT display manufacturers.
Ink-In-Motion is a flashing electronic display, which utilizes the core electrophoretic technology of E Ink for integration into retail Point-of-Purchase (POP) and other signage applications. The electronic ink is processed into an imaging film, which is in turn manufactured with a customized electronics layer which provides power. A color overlay is sometimes added. Because of the low power consumption of the electronic ink technology, the product works well in a retail environment where power access is limited. As an example, a postcard display utilizing the technology can run up to six months on two AA batteries. The paper-thin displays range from simple flashing text to flashing animation. E Ink does not manufacture the product internally - it is only available from its electronics partners Neolux and Midori Mark.
Note: E Ink Corp is the name of a company in the e-paper industry. It is a common misnomer to call e-paper technologies from other companies E Ink.
SiPix’s microcup technology involves a microscale container which holds minute quantities of fluid and particles. The display structure, typically 150μm thin, is built upon a flexible PET plastic substrate, which may include a transparent conductor such as Indium Tin Oxide (ITO). The contents of the microcup are hermitically sealed to protect them from the environment. The microcup structure is said to enable the thinnest and most flexible electrophoretic display. The partition walls provide not only fine resolution, but also impact resistance. Because each microcup is individually sealed, the EPD film can be cut to any shape and size.
Although the electrophoretic technology is fundamentally the same, E Ink uses a double particle in a clear fluid, while SiPix uses a single white particle in a dye. Depending on the application, it uses a honeycomb or waffle like structure, which is filled with dyes and particles. According to the company the simple structure eliminates issues with particles colliding. Since the microcups can be filled with different color dyes, it is possible to make a full-color system without external filters.
The SiPix microcup is manufactured using a high-speed roll-to-roll embossing process. Several grid shapes are available for the embossing: square or rectangular grid or a hexagonal grid.. When an electric current is applied, the charged particles migrate through the dielectric fluid. If the particles at the visible surface are white, that is the color that is seen by the viewer. Alternatively, if the alternate color particles migrate, that is the color seen. The company offers displays with alternate colors of black, red, green, blue or gold.
As of March 2009, AUO has taken a major stake in Sipix, making it the major hareholder (over 30%).
Bridgestone is also using a suspended particle technology, but instead of liquid, the particles are suspended in air. From its ongoing work in electromaterials, engineers at Bridgestone have developed an Electronic Liquid Powder (ELP), which can be made into a Quick Response Liquid Powder Display (QR-LPD), as an alternative to liquid crystal displays, first on glass, then on plastic. The ELP is a high-fluidity powder with physical properties intermediate between those of liquids and conventional, powdered solids.
According to the company, the material flows like a particulate suspension and is extremely sensitive to electricity, giving it a faster responsiveness and a broader range of viewing angles than comparable reflection-type LCDs do, as well as using less electricity. Because of the quick response, the technology can be used with a passive matrix drive, which is less expensive than an active matrix drive. It also claims that through a unique rib structure, the extremely thin displays solve the problem of image distortion when the display is bent.
In April 2009, Bridgestone debuted its ultra thin and bendable color e-paper display during a Tokyo Tradeshow. The company will be using this display for e-readers in the near future. The displays are manufactured using Bridgestone’s roll to roll manufacturing, which produces the e-paper in much the same way as a newspaper is produced. Giant rolls of plastic are imprinted with the displays, giving them a lower cost since they can be easily mass produced, and a lesser impact on the environment since they use a cold manufacturing method.
Cholesteric Liquid Crystal Display Technology
Cholesteric materials are modified liquid crystals and extremely suited for reflective, bistable displays. A cholesteric liquid crystal is a type of liquid crystal with a helical (smooth curve like a spiral) structure.. Cholesteric liquid crystals are also known as chiral nematic liquid crystals.While solids have molecules that maintain their orientation., molecules in liquids change their orientation and move anywhere in the liquid. Some substances exist in an odd state that is similar to both liquid and solid. When they are in this state, the molecules tend to maintain their orientation, like solids, but can also move like a liquid. Liquid crystals are such materials. However, in essence they are more like a liquid and require only a little heat to move from this odd state to a liquid state.
A feature of liquid crystals is that they are affected by electric currents. Depending on the temperature and particular nature of a substance, liquid crystals can be in one of several distinct phases, including nematic phase and the cholesteric phase. LCDs use these types of crystals because they react predictably to electric current in such a way as to control light passage. The use of a cholesteric liquid crystal means that the display has a far better readability than a display using conventional nematic liquid crystals and can be made thinner, since it reflects 50 percent of certain wavelengths, removing the need for color filters and polarizing layers. This in turn means that the background color is more vivid and the contrast much better than conventional reflective-type LCDs.
Fujitsu’s color e-paper mobile display is based on reflective cholesteric liquid crystal technology. Fujitsu claims that a key advantage of its e-paper is the semi-permanent memory display system, which maintains the image without power; the absence of flicker; and the color that is three times as bright as other developed products. In July 2005, Fujitsu announced the development of the world’s first color electronic paper.
In April 2007, Fujitsu unveiled its commercialized FLEPia color e-reader, available at the time for corporate use only (as part of field marketing). In February 2009 a commercialized model was tested at a confectionary shop/restaurant in Tokyo called Fujiya (Kinshicho Termina branch). In April 2009, Fujitsu launched online consumer sales of FLEPia in Japan, in addition to its offering in 2007 for corporations in Japan.
The technology used in FLEPia is fundamentally Fujitsu proprietary technology since the display panel and device itself are developed by Fujitsu Frontech Limited and Fujitsu Laboratories Limited - however, some of the LCD technology employed in FLEPia is licensed from a third party, Kent Displays.
Hitachi is working with Bridgestone towards commercial applications of information signage. In 2005, they collaborated in a field test in conjunction with East Japan Marketing & Communications, Inc., the subsidiary company of East Japan Railway Company, in the Tokyo Station underground. For the trials, Hitachi had used Bridgestone’s display modules based on Electronic Liquid Powder with a thin film transistor technology for the backplane. The displays provided updatable train schedule information right on the train platforms, in areas that had limited or no access to power. The signs were also flexible, so they could be attached to poles in the underground stations.
Hitachi has not announced any dates for future commercialization of products and frankly the activities of both Bridgestone and Hitachi in the e-paper space have received little publicity since the field trials. However, these two Japanese firms can bring huge resources to bear on marketing e-paper products of all kinds and they are also helped by Hitachi’s position as a leading consumer electronics brand.
Using cholesteric LCD technology, Kent Display’s products tout a monochromatic contrast ratio as high as 25:1 with a peak reflectivity approaching 40 percent of incident light, when measured normal to the plane of the display. According to the company, Ch-LCd can be manufactured with the same cost as the super twisted nematic (STN) and is simpler to construct and the tolerance on the cell dimensions are less demanding. Ch-LCD can achieve full color operation without color filters. A unique feature of the CH-LCD technology is that not only does it reflect light, but also infrared. Thus, the display can be read with night vision goggles. One of Kent’s earlier products was used by the military.
Kodak aggressively pursued the research and development of electronic paper for about five years. Its work was with cholesteric liquid displays. However, about a year and a half ago, Kodak discontinued its commercialization program in the electronic paper area because it did not meet the company’s investment profile. It decided to focus its resources on OLEDs and light management films.
Nemoptic uses a technology called BiNem, which stands for Bistable Nematics. It is based on a unique patented principle called “surface anchoring breaking.” The device is constructed with a front polarizer on top, which lays on a glass sheet followed by an ITO electrode, then a standard polarizer which provides strong anchoring. The liquid crystal is in the middle. The other side is a specific weak anchoring layer, with an ITO electrode, glass sheet and a rear reflecting polarizer. BiNem has two stable states, the uniform (U) state and the twisted (T) state, which are selected by applying simple pulses. Once a state is selected, it stays there indefinitely until energy in the form of an electrical pulse is applied.
The Zenithal Bistable Display (ZBD) is said to be the first commercially available LCD that uses surface bistability. The architecture consists of a polarizer layer on the bottom, then the zenithal bistable grating, then a rubbed polymer, then a polarizer on top. The key to ZBD operation is the ability to select one state or the other using electric pulses of opposite polarity. The contoured surface is manufactured at low cost using a simple embossing technique. ZBD Electronic Point of Purchase (EPOP) displays are monochrome passive matrix displays (102 mm or 4-inch diagonal with high brightness (39% reflectivity), high contrast (20:1) and an ultra-wide viewing angle (160º). It can hold multiples 320 x 240 pixel bitmap images in its memory at any one time. The displays have a 100-dpi resolution.
Electrowetting is based on controlling the shape of a confined water/oil interface by an applied voltage. With no voltage applied, the (colored) oil forms a flat film between the water and a hydrophobic (water-repellent), insulating coating of an electrode, resulting in a colored pixel. Applying voltage between the electrode and the water causes the interfacial tension to change, which causes the water to move the oil aside. The result is a partly transparent pixel; if a reflective white surface is used under the switchable element, a white pixel results. This forms the basis of the reflective display.
Displays based on electrowetting have several advantages. The switching between white and colored reflection is fast enough to display video content–supposedly pixels can switch states in around 10 milliseconds-fast enough to generate 100 new images in a second. TV-quality video only requires 25 images per second. In addition, the high reflectivity and contrast of the wetting displays make them clearer: color displays are four times as bright as LCDs and twice as bright as other e-paper technologies. Electrowetting displays reflect around 40 percent of light.
Since it is a low-power/low-voltage technology, displays can be flat and thin. Reflectivity and contrast are claimed to be better or equal to those of other reflective display types and approach those of paper. It can be used as a basis for high-brightness full-color displays. Such displays are claimed to be four times brighter than reflective LCDs and twice as bright as other emerging technologies. While it is low power, electrowetting is not bistable, so some electricity is needed for image retention. One of the advantages of electrowetting technology is that it can be integrated into existing manufacturing structures for LCD systems.
Electrowetting technology was developed by Philips Research labs in 2003. Because it did not fit with Philips core technology, Philips entered into an agreement with New Venture Partners (NVP) to spin-off the technology into a new company called Liquavista. Currently, Liquavista offers two products based on electrowetting technology: ColorMatch and ColorBright. At present, Liquavista is the only firm using electrowetting technology for paper-like displays.
Electrofluidic displays have a polymer layer with very small cavities which are filled with aqueous pigment dispersion. The underlying physics is based on electrowetting technology, but the device principles and performance are quite different. The name electrofluidic describes the mechanism which involves movement of liquids through microfluidic cavities as a result of an applied charge. Because the cavities only comprise about 5-10% of the visible area, the pixels are hidden from view. When an electromechanical voltage is applied, the pigment dispersion is pulled out of the cavities and begins to expand over the layer to encompass 90-95% of the visible area. Because the process uses pigment dispersions, it has more brightness and color saturation than currently available e-reader technologies and more closely simulates the look of traditional ink on paper. Current e-paper technologies have 40-50% reflectance. The new technology has 55%, but researchers feel an 85% reflectance of ambient light is possible (the same as that of paper). The technology also claims faster switching speeds. At present a black-and-white prototype has been demonstrated, but the inventors claim that color is not an issue. Two electronic layers would be used for color displays, which would enable a CMY subtractive approach similar to printing ink on paper. While this would need double the power of a single plate, it would still be sufficient to be attractive to consumers. An additional advantage is the fast switching speed. By tweaking variables such as geometry, surface tension and viscosity, the speed could be maximized to a sub-millisecond. The displays can be manufactured using existing processes for producing LCDs.
The electrofluidic process was developed at the Novel Devices Laboratory at the University of Cincinnati by Professor Jason Heikenfeld. Gamma Dynamics is the start-up company formed in 2009 to commercialize the technology. Sun Chemical and Polymer Vision are strategic partners along with members of the Novel Devices Laboratory from the University.
Electrochromism refers to the characteristic color change of a material associated with the materials’ reduction/oxidation state. Polyaniline and polyethylenedioxythiophene (PEDOT) are examples of electrochromic materials. An EC display element consists of at least two conductors, an electrochromic material and an electrolyte combined on a carrying substrate. The optical contrast is a result of the contrast between the white paper surface and the electrochromic materials switched to its colored state. These displays are
fully flexible and the printed devices are less than 100 microns thick.
One of the claimed advantages of electrochromic displays over other technologies is the high contrast, the vibrant, rich looking color image of the display against the white background. This is due to the fact that electrochromic materials absorb some light spectra and reflect others, similar to pigments used in printing. Other technologies use light scattering techniques.
Acreo is currently developing an in-line roll-to-roll printing process for organic electrochromic paper displays. The company is utilizing standard graphic arts equipment (a flexographic label press) and developing processes to make it possible to print displays. The substrate is conventional paper. The system has succeeded in printing thin flexographic layers with moderate conductivity, enough for certain applications. Recently, Acreo entered into an agreement with Soligie, a printed electronics manufacturer, to develop and manufacture Acreo’s printed electrochromic display technology into PaperDisplay products.
Aveso is also using electrochromic technology to develop displays, mainly for disposable applications. It is using its technology for smart cards to reduce fraud in financial transactions. The paper-thin (250 micron) displays are produced and scaled using traditional high-speed print technologies, mostly screen printing depending on the application. It uses reflective electrochromic technology, for blue digits on a yellow background. The company claims that process is compatible with other printed components such as batteries and antennas.
NanoChromic Display (NCD) technology uses nanostructured semiconducting metal oxide films with a layer of electrochromic viologen molecules to produce displays that simulate ink on paper, with a pure white background and very high contrast ratios. The use of titanium dioxide as a reflector gives the display its white, paper-like quality. The displays are manufactured in the same manner as traditional LCDs.
In the past two years, Siemens has done extensive research in the development of what it terms a novel electrochromic material system. The basis of the system is modified bipyridinium salts, which are dispersed in a pasty material formulation. Using this material system, the company has developed a miniature color display using electrochromic materials. The small flexible displays use electrochromic materials holding a pattern of electrodes. A conductive plastic foil serves as the other electrode and the transparent window through which the electrochromic materials show the changing color. To date, the engineers have been using silicon switching elements to control the device. The ultimate goal is to use a printing process to manufacture the entire display, including the appropriate control electronics, from conductive and semiconducting plastics.
Interferometric Modulator Display
An Interferometric modulator display (IMOD) uses a technology made up of subpixels which are actually miniature Fabry-Perot interferometers (etalons). An etalon, which is an optical term, reflects light at a specific wavelength and gives pure, bright colors like those in a butterfly’s wings. Moreover it consumes no power. Microelectromechanical systems (MEMS) are used to switch the display on and off.
The only provider of IMOD reflective technology powered by MEMS is QualComm MEMS Technologies, a subsidiary of Qualcomm, the wireless chip maker headquartered in San Diego. Called Mirasol technology, it is simply a MEMS display for mobile devices, which works by reflecting light so that different wavelengths interfere with each other to create color. Since it is reflective, it is viewable even in direct sunlight; the MEMS technology allows it to be bistable, thus low power.
The display has two conductive plates: one is a reflective membrane, which is suspended over a glass substrate; the other is a thin film stack atop the substrate. Air fills the gab between the two, which are separated when no power is applied. In this phase, light is reflected. The application of power pulls the plates together and the light is absorbed, resulting in a screen that appears black.
The size of the hollow space inside the cell, just a few nanometers across, can be electrically adjusted to change the color it emits. Thus the Mirasol technology is well-suited to color, because the cells can be electrically adjusted so that they reflect any wavelength of light. Moreover, those electrical adjustments can occur as quickly as a thousand times a second. Thus video speeds are much more possible than with other electronic ink technologies.
Several uses of the IMOD displays have been commercialized. These include: Acoustic Research ARWH1 Stereo Bluetooth headset device; the Showcare Monitoring system (Korea); the Hisense C108; and mp3 applications from Freestyle Audio and Skullcandy. Although not yet commercialized there are plans in the works for mobile phone by Taiwanese manufacturers Inventec and Cal-Comp; and LG claims to be developing ‘one or more’ handsets using mirasol technology.
Photonic Crystal Technology
Another technology, which has recently entered the limelight, is based on photonic crystals, which are nanostructures arranged in a regular pattern. Changing the pattern causes a change in the color of light that the crystals reflect. Artificial opals are similar to those occurring naturally, with one exception—artificial opals can be stimulated electrically to change color. These opals can then be integrated into a layer of millions of tiny silica spheres, which are embedded into an electroactive polymer. The layer is then sandwiched between transparent electrodes. When current is applied, it causes the polymer to swell, which in turn changes the spacing of the crystals. If this movement is controlled, the crystals can be maneuvered to produce the entire light spectrum. Such layers can then be arranged into a display similar to a traditional LCD screen. The advantage of this technology is that the pixels can be individually tuned to any color, and the color is purported to be brighter and more intense.
The technology is very new, however, and commercial products are still years away. However, recently the speed at which the crystals are able to change color was improved dramatically, as were the available spectrum colors that could be achieved with the technology. The increased speed was made possible by dissolving the nanospheres into a porous polymer structure, eliminating the silica. The pores are filled with electrolyte and then the material is sandwiched between electrodes.
Nevertheless, there are still challenges to be resolved. One of the disadvantages of the photonic crystal approach is its dependence on the flow of electrolyte in response to electricity. This could mean a decrease in efficiency after repeated cycles, similar to rechargeable batteries. Furthermore, when pixels change from long wavelength colors to shorter ones the speed decreases. In addition, pixels need more color contrast. Adding nanoparticles to the polymer might improve the contrast.
Opalux Inc. based in Toronto, Canada, researches and develops possible market applications for its tunable photonic crystal technology, sometimes called P-Ink.
It was co-founded by André Arsenault, a recent PhD graduate of the University of Toronto, to continue his doctoral research on photonic crystals with the aim of developing commercial products. At present, Opalux is the only company working on photonic crystal technology.
Reverse Emulsion electrophoretic Display (REED) uses nano-droplets of a polar liquid, which are composed of a blue dye and surfactants in a measured ratio. These droplets are dispersed in a non-polar liquid. When energy is applied, the droplets reassemble in the liquid. The technology is purported to use less energy than currently available electrophoretic technologies, and have faster switching speeds, which would make video possible. Moreover, it can be produced using existing LCD manufacturing techniques.
Headquartered in Santa Clara, CA, Zikon was established in 1996 by chemist Remy Cromer and physicist Zbig Bryning, to continue the research began by Exxon’s EPID flexible display unit. Soon after it was founded, it was granted a patent for the REED ink technology. Other patents are pending. Its goal is only to manufacture the electronic ink, not the complete display. Its initial target market is outdoor single-color displays, signage and mobile devices. No target date for commercialization is available.
Liquid Crystal Displays offer excellent picture quality with brilliant color and video, however, they require a brushing process on the inside of a glass sandwich to lock the twisted molecules. These twisted molecules are necessary for bistable displays, which offer low voltage advantages. Bistable LCDs use a photo-alignment process to eliminate the brushing of the glass. The process, a roll-to-roll technology, uses a new photo-alignable polymer—an azo-dye, which has an anchoring energy that can be adjusted by changing the UV exposure time. The layer is stabilized by heat polymerization after the azo-dye monomers are photo-aligned. The liquid crystal is then deposited on top.
According to researchers this arrangement is inherently low cost, likely to give much better colors than electrophoretic technology, be more robust and operate without need of a transistor active matrix backplane or ITO or alternative transparent electrodes with all their problems of cost and of cracking when bent. The display is also optically rewriteable by means of light emitting diodes (LEDs). However, currently there is no optical writing mechanism, which is small enough for the display, which is 500 nanometers thick. Commercialization is not expected for several years.
Backplanes for E-paper
As mentioned previously, there are various technologies currently being used to manufacture the backplanes to be used in e-paper displays. Although the initial offerings were thin film transistors (TFT), some of the newer introductions are rather unique technologies for backplanes. Following is a list of these manufacturers and some explanation of the technologies they are using.
Hewlett-Packard and Arizona State University have introduced a prototype of a paper-like, flexible computer display made almost entirely of plastic. The introduction is a result of several years of research and represents a milestone in industry efforts to develop a mass-market, high-resolution, flexible display.
The device, created by ASU’s Flexible Display Center (FDC), was made possible by an invention by HP Labs called Sail (Self-Aligned Imprint Lithography). The SAIL technology is considered “self aligned” because the patterning information remains aligned regardless of the process-induced distortion. The key to the device is that the new technology enables the image on the display to maintain its form despite the bending and flexing.
SAIL works by forming thin-film transistor electronics on a flexible substrate, which has been coated with all of the thin films required for the devices. Then multiple patterns required for the backplane are impressed onto different heights of the masking structure. By alternately etching the masking structure and the thin film stack, the patterns are transferred to the device layers. Current thin-film transistors are manufactured with photolithography, which requires a costly additional alignment step. Moreover, the flexible technology makes it possible to manufacture the displays using a roll-troll process, which further reduces the cost of manufacturing. The company also claims that the SAIL technology is a more sustainable, environmentally method of manufacturing displays. The new flexible substrate, called Teonex Polyethylene Naphthalate, or PEN, was developed by DuPont Teijin Films. For the e-paper frontplane, the HP-ASU display uses E Ink’s Vizplex imaging film.
NEC LCD Technologies, headquartered in Japan, is one of the world’s leading providers of high-quality, innovative, active-matrix liquid crystal display (AM-LCDs) modules for the industrial and high-end monitor markets. It has developed multiple sizes (A3 and A4 equivalent) of electronic paper modules using the microcapsule electrophoresis system, based on E Ink technology. The screens include an NEC-developed amorphous silicon TFT active matrix that allows for a 16-step grey scale rather than just monochrome. It boasts 43% reflectivity with a contrast ratio of 10:1. The A3 e-paper module is composed of especially narrow frames, with two sides measuring just 1mm, which enables the creation of large screens that feature effective multi-tiling. The company is aiming to continue to research the technology towards implementation into the large-scale display industry.
Plastic Logic, headquartered in the U.K., is a spin off from Cambridge University’s Cavendish Laboratory. Plastic Logic was founded to make thin film transistors, but moved into manufacturing OTFTs (organic thin film transistors) for various applications. In recent years, it has focused on backplanes for flexible displays, particularly backplanes for e-paper.
While electronic paper is typically thin and flexible, a rigid display results when it is combined with a glass-based amorphous silicon backplane. Plastic Logic developed a flexible backplane technology, thus enabling the display, and therefore the reader device to become flexible, thin, light and robust so it feels more like a sheet of paper. By extension, the whole e-paper market received a shot in the arm as a result.
The company uses solution processing and direct write inkjet printing to manufacture its OTFTs. Because what is used is an additive printing process, rather than a subtractive masking process, both materials and processing cost is reduced compared to conventional display manufacturing.
Polymer Vision is a spin out of Royal Philips Electronics after a first round of investment by Technology Capital, Luxembourg. After many years of development work in polymer electronics, Philips produced prototypes of ultra-thin, large-area, rollable displays. The displays combined an active-matrix, which is OTFT driven, with a reflective electronic ink front plane on a thin plastic sheet.
To move the project towards commercialization, an internal venture called Polymer Vision was formed within Philips Technology Incubator Division. The Polymer Vision technology was used in the various incarnations of the Sony book readers that have appeared over the past couple of years.
Early in 2007, Polymer Vision announced its cooperation with Innos (U.K.) to establish the world’s first production facility for organic semiconductor-based rollable displays. What Polymer Vision is actually manufacturing is the active matrix backplane, which is coupled with E Ink’s electrophoretic technology to create the e-paper display. Polymer Vision has also developed a proof of concept device, called the Readius. The Readius comes with a 5” screen, which retracts into a device, which is not much bigger than a standard mobile phone. The company sees a large opportunity in the mobile market by offering consumers a large display in a small pocket size device allowing for comfortable reading anytime, any place.
In April 2009, Wired magazine reported on its Web site that Polymer Vision had missed its projected launch date of the The Readius rollable dislay and might not launch at all if the company didn’t get an infusion of cash. In July 2009, Polymer Vision went into bankruptcy and laid off its employees.
Prime View International (PVI), headquartered in Taiwan, entered the e-paper business in 2005 when it acquired the e-paper display division of Philips, with all its patents and IP rights. Coupled with PMI’s technology and production capacity, the company developed MagicMirror reflective display technology to become a leading force in e-paper technology.
Prime View manufactures active matrix e-paper displays using TFT technology for the backplane based on PVI’s proprietary Magic Mirror Reflective Technology and the EPLaR process developed by Philips with an electrophoretic frontplane using E Ink’s technology. The company claims that its e-reading devices have an extensive battery life of up to 7,000 page turns per charge, equal to approximately 20-full-length books. In addition, in 2008, it added touch screen technology from F-Origin, a force-sensing touch technology supplier. (PVI has a 20% ownership in the F-Origin.) Traditional touch-screen technologies add a layer on the surface of the device, which can diminish the reflective qualities of the display. With the addition of this touch-screen technology, the company claims it is the leading vendor for all available e-book products. Previously, PVI had introduced a flexible display, Flexi-e. The company has announced plans to begin mass production of e-paper readers in mid-2009, with color displays soon to follow. In June 2009 PVI purchased E Ink Corp for $215 million.
Ricoh has developed an organic thin film transistor backplane for electronic displays using inkjet printing with 160 pixels per inch (ppi). The frontplane uses electrophoretic technology. However, the company does not expect commercialization of the technology for approximately four years.
In conjunction with Unidym (a majority-owned subsidiary of Arrowhead Research Corp.), Samsung Electronics has developed the world’s first carbon nanotube-based (CNT) color active matrix electrophoretic display (EPD). The e-paper display has a 14.3” format. To achieve the display, the CNT film was required to be even over large areas, compatible with different display technologies and fabrication processes and exhibit a conductivity which is comparable to ITO technology.
First developed by the Japanese, a carbon nanotube is over 10,000 times thinner than a human hair, while exhibiting unique thermal and electrical conductive capabilities. In addition, the resulting film is translucent and porous.
Seiko Epson Corp. had developed a flexible high definition 200 ppi display, which uses the electrophoresis electronic paper developed by E Ink Corporation. The resolution of a 2-inch display extends to 320 x 240 pixels. It was developed using the company’s proprietary SUFTLA technology, which uses low-temperature polycrystalline Si thin-film transistors (TFT) in the driver to enable the dot display. (SUFTLA stands for Surface Free Technology by Laser Ablation /Annealing). Seiko Epson exhibited a prototype viewer terminal using electronic paper as a reference presentation at Embedded Technology 2007. At the time Seiko Epson announced plans to commercialize the technology in 1-2 years; however, little has been heard of the project since.
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