Several new e-readers, including Amazon’s Kindle and Sony’s eReader, use electronic-paper technology that is easier to read than conventional displays. But e-paper still suffers in comparison to conventional liquid crystal displays in terms of refresh speed and vividness of color. Electronics manufacturer Fujitsu says it is shipping an LCD-based electronic reader called FLEPia in Japan next month that displays vivid color, a first in the industry. It hopes the technology can compete directly with E Ink, the manufacturer of the black-and-white e-paper displays used in the Kindle and eReader, though with a pricetag of more than $1,000, FLEPia may still have a way to go.
So far, color displays have not been used in electronic books and newspapers because a typical LCD screen is hard on the eyes, and the brighter the ambient light, the brighter the screen needs to be. Moreover, the LCD backlight is a power hog, sucking energy from a battery, lasting only a couple of hours. At the same time, E Ink and others have not successfully commercialized color versions of their e-paper. Indeed, E Ink has developed prototypes for color and video e-paper, but they have yet to achieve the necessary color contrast.
Fujitsu opted to use a technology it licensed in 2005 from a company called Kent Displays. The technology, branded Reflex LCD, looks and acts significantly different from most LCDs, explains Asad Khan, vice president of technology at Kent. Like E Ink’s e-paper, it reflects ambient light instead of shining a light from within. “It’s dramatically different from traditional LCDs,” says Khan. “It’s really stripped down to its bare essentials.”
This means that the Reflex LCD display doesn’t use a power-hungry backlight, and it doesn’t have the series of optical layers that most LCDs have. Instead, liquid crystals like the ones used in computer displays are arranged between sheets of transparent conductors in such a way that light reflects off of them. To achieve color, explains Khan, Reflex LCDs use three layers of crystals; each layer reflects green, blue, or red light, and is otherwise transparent.
Layered pixel technology of the type employed by Kent differs from traditional LCDs in which red, blue, and green pixels are placed side-by-side. In such an arrangement, three pixels occupy the same amount of space as a single black or white pixel. This means that less light passes through or reflects off a color pixel than a black or white pixel, which leads to a lack of contrast and vividness. Traditional LCDs work around this problem by turning up the backlight. Khan says that Kent chose the layering approach because it allows their color displays to be as vivid as a black-and-white display without a backlight.
E Ink’s vice president of marketing, Sri Peruvemba, says that the company is also developing a color display using four subpixels: red, blue, green, and white. The E Ink displays sandwich a layer of microcapsules between layers of transparent electrodes. Back-and-white displays use microcapsules filled with white and black submicrometer flecks, which are positively and negatively charged. When a voltage is applied to the electrodes, the flecks move to opposite sides of the microcapsules, rendering words and images on a screen, where they remain static until another voltage is applied. To achieve color, engineers put a color filter on top of the existing display, but since this cuts out light, says Peruvemba, the display needs to reflect more light than those on the market now.
One major challenge for color E Ink paper, he says, is designing the electronics that control the voltage applied to the microcapsules, which require “very intricate designs, patterns that literally have to address every pixel separately,” he says.
The next major problem that all e-paper company’s face is ensuring that an e-book page can refresh fast enough to satisfy a consumer used to the speed of LCD. The new Fujitsu e-reader takes about a second to fully refresh its screen, which is about five inches by six and a half inches in size. Khan says that Kent is working closely with Fujitsu to reduce the page flip to less than a second, but this will require extra electronics that could increase power consumption or the cost of the device. Currently, Fujitsu’s reader can operate for 40 continuous hours and is already far more expensive than other e-readers.
Peruvemba says that E Ink’s forthcoming color technology refreshes at the same rate as its black-and-white technology–about a quarter of a second. In order to get even faster, he says, E Ink engineers need to work on the basic chemistry to modify the particles and the fluid within the microcapsules, as well as to develop electronics to apply the right type of voltages. The company hopes to have products based on a color display by the end of 2010.
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