ZT: Battle over e-book display alternatives heats up

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Until a recently, the biggest worry for E Ink, maker of the Vizplex technology used in Amazon's Kindle and a host of other e-book readers, was the many e-paper competitors looking to loosen its grip on the market. Then Steve Jobs announced Apple's iPad tablet, which uses a standard LCD display that sacrifices e-paper's readability and zero-power modes but offers higher refresh rates and full color. Will consumers sacrifice "green" e-paper on the altar of fast color, relegating the nascent technology category to a niche? For the analysts who track the display market, the question is a page turner, and they're of a mixed mind on the likely conclusion. E-paper displays can replace virtually any printed page with a nonvolatile image that is changed electronically. Beyond e-paper versions of books and periodicals, developers envision applications for blueprints, maps, shelf labels, signage, smart cards and even "skins" that cover your iPhone with changing patterns. For green paper replacement, the e-paper display must retain its image without any energy being expended (called zero-power or bistable mode). That capability and the lack of a backlight requirement are how e-book readers maintain their long battery lifetimes—which are sometimes measured in page turns, since energy is expended only when the displayed image changes. (LCDs, by contrast, run down a battery in a few hours, regardless of what is being displayed.) The e-paper category today is dominated by e-books using E Ink's Vizplex display, which looks remarkably like a clean, white sheet of paper printed with black ink. "Vizplex is widely used today for its best-of-breed whiteness and because it is already being mass produced," said Gartner analyst Amy Tang, who tracks the e-paper market. Most other bistable display technologies bounce ambient light off a highly reflective surface, making text look like it is written on a mirror. The paperlike appearance of E Ink's Vizplex is the result of bouncing ambient light off the same white and black pigments that are used in traditional inks; in the Vizplex, the pigments fill the charged microcapsules that form the display pixels

E Ink's monochrome display (no color yet) commands at least a 20 percent price premium over other e-paper solutions. It handles page refreshes fast enough for menus, windows and simple animations, but it cannot display live video. About two dozen independent development efforts worldwide are working to address the Vizplex's shortcomings. But E Ink itself makes no apologies for its success. Unique benefits
"All these competing technologies have something unique to offer," said E Ink marketing vice president Sri Peruvemba. "But in e-publishing applications, a great digital reading experience is key. Fast color is better suited for gaming than for reading." Though Peruvemba has a point, there is concern that tablets like the iPad could topple the fortunes of the whole e-paper ecosystem. Display vendors, chip makers and OEMs have been holding their breath since Jobs' announcement, waiting to see how consumers react in March when Apple starts delivering

"E Ink does provide great readability over reading text on an LCD," said Tang. "But consumers who planned to buy an e-book reader will be comparing the iPad's multiple functions and multimedia content to decide if they are worthy enough to exchange for the readability of an e-paper display. Heavy book readers will stay with the readability of e-paper, but that market alone is comparatively smaller." "If the iPad really gives 10 hours of battery life, as [Apple] claims, then that will change the equation away from E Ink," said Richard Doherty, principal analyst at Envisioneering. "All the disadvantages of electrophoretic displays—that they aren't color and can't show motion video—are solved by going with active-matrix LCDs."


"I think LCD tablets like the iPad and dedicated e-readers will coexist," said Paul O'Donovan, who follows the LCD market for Gartner. "My personal opinion is that the LCD tablet market might never really take off and that e-readers will evolve to eventually include color with video and animation capabilities. "We'll just have to wait and see how this market plays out within the next 18 months." Tight competition
The stakes are high for the e-paper competitors vying to break E Ink's virtual monopoly on the market. Research firm iSuppli predicts that the market for zero- and ultralow-power e-paper displays will top $516 million by 2012. With shipments slated to pass the 10 million-unit mark this year, vendors are scrambling to line up mass-production capabilities to rival E Ink's, but at a lower cost to OEMs, while they simultaneously claim to be adding color and video capabilities. "E Ink is the favorite son today for the low-power market. But when worldwide volumes hit the 10 million-unit mark sometime later this year, investors are going to start seeing that all sorts of other possibilities begin to make sense," said Envisioneering's Doherty. "A year from now, E Ink is going to have a lot of competition; 2010 is going to be the year of shakeouts." LCD manufacturer Primeview International bought E Ink last year and has licensed its process to Chi Mei Optoelectronics and LG Display Co. Ltd. The deals bring E Ink plenty of capacity to meet demand in expanding consumer markets. Matching E Ink's production capability, but without announced design wins, is SiPix, which was purchased last year by LCD panel manufacturing giant AU Optronics Corp. "SiPix/AUO is an electrophoretic alternative to E Ink," said Gartner's Tang. "I foresee that SiPix will stimulate E Ink to enlarge their scale of production even further by strategically partnering with other LCD fabs, and as a result supply will become more stable and prices will go down."

E Ink's patented electrophoretic display sandwiches its microcapsules of oppositely charged black and white pigments in a fluid between two polymers. When a voltage is applied at a pixel location, its polarity attracts either the black or the white pigment to the backplane. Grayscales are represented by mixing some white microcapsules with some black ones. After power is removed, the page remains displayed because the microcapsules are bistable and will hold their position indefinitely. Proprietary process
SiPix uses the same technique but adds a proprietary roll-to-roll embossing process that impresses microcups into a polymer, then fills them with the transparent liquid containing the charged pigment. The microcups can be filled with pigments of any color, although the company is reportedly still perfecting color pigments that do not fade. Later this year, SiPix expects to begin delivery of a variety of display sizes, from two inches (for shelf signs) up to 20 inches diagonally (for public information displays), including both 6-inch and 9-inch versions with built-in touch panels for e-books. "SiPix is using a similar technology to E Ink, but they are able to build much larger displays," said Vinita Jakhanwal, principal analyst at iSuppli. "And there will be other options regarding electrophoretic suppliers in 2010."

Qualcomm's Mirasol MEMS display uses the phase difference between light reflected off a membrane and a thin-film stack to reinforce colors selectively

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Bridgestone has developed an approach that is similar to electrophoretic displays but uses a grid and a charged dry pigment called electronic liquid powder (ELP). The ELP is lightweight and reacts up to 1,000 times more quickly than pigments suspended in a liquid—so fast that Bridgestone is reportedly working to reduce wear and tear on the backplane from the impact of the fast-moving pigments at video frame rates. The company has demonstrated both monochrome and color displays.

Bridgestone's technology "could answer the slow-refresh concerns with electrophoretic displays," said iSuppli's Jakhanwal. "I think they currently have a 0.2ms refresh rate, compared with 200ms for E Ink."

Also headed for commercial mass production this year is a MEMS display that its developer, Qualcomm MEMS Technologies, has branded Mirasol. "If I was to predict the most likely display technology to replace E Ink, it would probably be Qualcomm's Mirasol," said O'Donovan. "My reasoning is that Mirasol is a reflective technology that uses very low power but, more importantly, offers video capabilities. I think that will be a critical advantage for future e-books supplemented by video content—graphical diagrams that come to life, or video or some kind of moving content. This could be a killer application in the educational e-textbook market."

QMT thus far has gained design wins for small, cell-phone-sized displays only, but it has shown a 6-inch prototype that could be used to build an e-book reader. The company recently built a dedicated manufacturing facility in Longtan's Science Park in collaboration with industrial giant Cheng Uei Precision Industry Co. Ltd.

Mirasol uses an optically resonant cavity housing a Fabry-Perot interferometer, consisting of a thin-film stack and a deformable reflective membrane. Normal ambient light reflects off both the thin-film stack at the top of the cavity and the reflective membrane at the bottom. Phases are controlled to reinforce specific colors selectively, thereby yielding light amplification without any filters or polarizers to cut down on the reflected light. That eliminates the need for a backlight. The display can be sidelit for reading in the dark.

Electrophoretic replacements
For now, however, "we are only going to see Mirasol-style displays for pocket- and pen-sized displays—and I mean literally on the side of a pen," predicted Envisioneering's Doherty. "You need very bright ambient light, and even so the colors offered by Mirasol are too washed out except for applications like highlighting text. Advertisers are definitely not going to want their ads displayed on a Mirasol."

Besides Mirasol, "to my mind, there are only two other likely [electrophoretic] replacements on the horizon," said O'Donovan. One is Liquavista's electrowetting technique, he said, and the other is "of the LCD derivatives, such as Pixel Qi's transflective screen."

Electrowetting displays work by modification of surface tension in a simple optical switch that electrically contracts droplets in a colored-oil film. Without a voltage, the colored oil forms a continuous film and a solid color is visible. When a voltage is applied to the display pixel, the oil is displaced into a droplet in the corner, and the pixel becomes transparent. While the display is not bistable, it can be updated as infrequently as every few seconds, making its image retention ultralow-power.

"Liquavista's main advantage is that its display looks very good," said Jakhanwal.

Liquavista has collaborated with Texas Instruments to support its electrowetting displays with a development system for TI's OMAP-based e-book development platform, which also works with E Ink's display.

Dialog Semiconductor, Epson, Freescale and Marvell also supply support chips for E Ink's display.

- R. Colin Johnson
EE Times

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