Demonstrations of the latest in electronic paper technology indicate that it may finally be ready to "roll up" and "plug in" to the electronic office.
E-paper comprises organic electronics that use conductive materials containing tiny balls of ink. These balls, which respond to electric charges, act like pixels on a computer display. They change in response to the charges in a process known as electrophoresis and electrochromism. The Xerox Palo Alto Research Center originated e-paper technology (known then as Gyricon). But a number of companies, such as E-Ink Corp., have joined the fray (Fig. 1).
E-paper has seen steady improvements in contrast ratios, resolutions, and brightness levels, and reversibility has become a standard feature. While full-color paper has yet to be realized, research continues. Perhaps the biggest boost in e-ink and epaper technologies can be linked to progress in developing suitable substrates on which to deposit the inks or display elements (see "Progress On The Flexible Substrate Front," p. 53).
AT YOUR NEAREST BOOKSTORE
Products in the e-paper market are finally emerging. Take, for instance, the Sony Reader ebook, which will debut later this year in Borders bookstores, as well as in more than 30 Sony Style stores around the U.S. Based on a display from E-Ink, the handheld unit can store hundreds of books in its 64 Mbytes of internal flash memory. It measures 6.9 by 4.9 by 0.5 in. and weighs 8.8 oz (Fig. 2). The unit features a 6-in. SVGA (800 by 600 pixels) display and four gray-scale levels. Also, it accepts PDF, MP3, and BBeB formats, and it's powered by a rechargeable lithium-ion battery/ac adapter or a USB cable (for recharging only).
The ER 0100 iliad from iRex Technologies offers an 8.1-in. diagonal display unit, 16 levels of gray, and 1024 by 768 pixels of resolution (Fig. 3). It contains up to 64 Mbytes of RAM (224 Mbytes of flash memory), measures 155 by 217 by 16 mm (screen size is 122 by 163 mm), and weighs 390 g. Based on the Intel 400-MHz X-Scale processor, it supports TXT, PDF, XHTML, and MP3 formats. Additional formats will be announced in the future.
Tainjin Jinke Electronics Inc. launched its V8-model Hanlin eBook series in China in January. Using e-ink from E-Ink Corp., the V8 runs on the Wolf operating system for the Chinese language. The V2, debuting in the U.S. this month, will run on the Linux operating system. It will come in four different models, with a choice of 7.5-, 6.4-, and 4.3-in. display diagonals and resolutions of 840 by 640, 640 by 480, or 240 by 160 pixels, as well as storage capacities of 64 Mbytes up to 1 Gbyte. Applications for e-paper are expanding beyond e-books. Market forecasters foresee even larger applications in magnetic cards and signage areas. According to iSuppli Corp., the largest application for flexible displays in 2013 will be magnetic cards—financial payment cards, club cards at stores, and gift cards. The next biggest application will be electronic shelf labels in retail outlets and stores, as well as point-of-sale locations (Fig. 4).
E-Ink's AM-100 EPD electronic paper display Linux development kit includes a 170-dot/in., 6-in. diagonal SVGA (800 by 600 pixels) module that supports four shades of gray. Meanwhile, e-paper vendor SiPix is putting e-ink on secure digital cards made by a company in Taiwan. The cards are used to track and display remaining capacity.
Siemens Corp. is developing inexpensive, paper-thin e-displays to replace conventional labels on disposable-package products commonly found in supermarkets, such as cereal boxes and milk cartons. The company believes it will take another couple of years for these products to be market-ready.
More public showings of products based on e-paper, eink, and flexible displays have taken place than actual products appearing on the market. One of the more dramatic demonstrations involved Japanese printing company Toppan Printing Co. Ltd. Last year, it exhibited a wallsized electronic newspaper at Expo 2005 in Aichi, Japan.
Yomiuri Shimbun issued the newspaper in cooperation with Toppan. It displayed the news twice daily in morning and evening editions. Measuring 2.2 m high and 2.6 m wide, it's the world's largest newspaper display. It consists of 272 individual electronic paper tiles, each of which is made up of a combination of an e-ink frontplane laminated onto a pc board with 4-mm2 pixel electrodes.
Last September, Philips' subsidiary Polymer Vision NV demonstrated its Readius e-reader at a consumer electronics exhibition in Berlin, Germany, and at this year's Consumer Electronics Show in Las Vegas. The 100-mm thick display features a 5-in. diagonal, QVGA resolution (320 by 240 pixels), and a 10:1 contrast ratio.
It can be rolled up with a radius of curvature of less than 7.5 mm. Additionally, it displays four gray levels. The company doesn't intend to commercialize the display, though, leaving that up to future customers. Polymer Vision NV says that the goal of the exhibition was to demonstrate the viability of a roll-up display.
Citizen Watch Co. and Citizen T.I.C. Co. developed a large four-digit digital clock that uses electronic paper. A prototype displayed at Japan's Eco-Products 2005 exhibition last December comprised 23- by 36-cm E-Ink displays for each of the four digits.
Ntera and Seiko Epson Corp. have successfully produced working prototypes of electronic paper featuring the world's highest-resolution naturally reflective electronic displays. The displays use Ntera's visual DNA brand electrochromic display technology. The prototypes feature 200- and 400-dot/in. (QVGA) resolution. They were produced using Epson's solution processable inkjet methods.
Ntera's electrochromic technology reflects any ambient light, including bright sunlight, so that images are always visible. By eliminating backlights, the company claims its ink-on-paper appearance comes at a fraction of the power consumption of existing electronic displays.
STRONG DEVELOPMENTS AFOOT
Many leading companies are committed to the development of e-ink, e-paper, and flexible displays. In fact, a number of joint development efforts are under way, such as those with Polymer Vision.
While the company has strategic partnerships with Dupont, E-Ink, and SiPix, as well as a close working relationship with Philips, Polymer Vision is looking for even more partnerships. Some of these companies may build products around their technologies, while others will license out their technology.
E-Ink and Ambient Devices joined forces to create a simple household device that reliably forecasts the local weather. Their Weather Wizard uses E-Ink's ink to continuously display fiveday weather forecasts, broadcast in real time, over Ambient's nationwide wireless network (Fig. 5).
Device makers such as Ixys already have driver ICs for e-ink displays on the market. Ixys introduced the industry's first standard product driver for e-paper displays based on E-Ink's e-ink technology. Also, Hitachi Ltd. and Bridgestone Corp. recently reached an agreement to mutually cultivate the market for e-paper displays with an eye toward commercialization.
Researchers at the California Institute of technology in Pasadena and the University of California in Los Angeles designed a single-dye compound that can display the three primary colors of red, green, or blue, depending on the applied voltage. The compound is a bistable catenane, a molecule that consists of two interlocking rings. It can be used as a single pixel that can be turned on to any of the three primary colors. Further development is needed to make the material feasible, though.
A full-color flexible display is the ultimate goal for Universal Display Corp. It's using an active-matrix organic light-emitting diode (OLED) display, fabricated on a flexible metal foil substrate, based on Universal's proprietary technology.
The company already has installed a novel full-color OLED deposition system. The system, made by Japan's Tokki Corp., is sold through Hitachi High Technologies Corp. It's designed to deposit a variety of organic and metallic films using vacuum sublimation and evaporative techniques with high-resolution patterning capabilities. With this design, the system can handle transparent, opaque, rigid, and flexible plastic, glass, and metal foil substrates.
ADDRESSING FUTURE NEEDS WITH NEW MATERIALS
Use of nano-structured materials for later generations of flexible displays is under investigation. "In today's display industry, indium tin oxide is almost exclusively used as a transparent conductor," says Robert Murphy, a researcher at the Center for Advanced Photonics and Electronics (CAPE) at the University of Cambridge in the U.K.
"However, this material has three serious drawbacks for next-generation displays," he notes. "Its cost has risen by over an order of magnitude in the past five years. It is not compatible with the need for flexible displays. And, it is difficult to recycle."
Murphy's observations are part of a report on a research project issued by Advanced Nanotech while collaborating with CAPE. Together with CAPE, the company is developing a carbon nanotube flexible display that's environmentally friendly and more efficient to manufacture than present materials.
Researchers at the University of Tokyo are using organic semiconductor devices to make a rollable display in Braille. The display consists of plastic actuators driven by organic pentacene thin-film transistor (TFT) devices on top of a 20- m thin polyimide plastic substrate.
Voltages are fed to conductive polymer actuators, moving them upward and pushing attached hemispheres on the underside of the rubber-like surface. This lets the display form bumps in the shape of Braille letters. Up to 24 letters can be formed on a 4- by 4- by 0.1-cm display. The display dissipates less than 1 mW.
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Advance Nanotech Inc.