I love to read, and one of the few things I do want for Christmas is an e-book reader. But it has to be smaller - preferably much smaller - and lighter than a paperback, while being just as easy to read.
So why can’t I buy such a thing? The electronics are almost trivial, a 256Mbyte Secure Digital card is under £30, and the free books on the Project Gutenberg website could keep me going for years.
It looks like it is the lack of a suitable display that is preventing my dream from coming true.
Granted Sony has its Librié, but I am looking for something that is a bit less ridged and a bit more tactile. What I am looking for is a flexible e-book.
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| Philips' Readius |
Philips looks to be ahead of the floppy display game at the moment. Its Polymer Vision spin out showed Concept Readius in August - a true roll-up display which uses almost no power and has a clear newspaper-like reflective face.
The pocket-sized device pulls apart into a 125mm (5in.) QVGA display with four grey levels.
Polymer Vision went to E-Ink for the actual display layer which is a sheet containing fluid-filled 100µm wide capsules. In each are positively-charged white particles and negatively-charged black particles. The liquid is dark and the capsule appears white if you electrostatically push the white particles to the front and black if the black particles are pushed to the front.
The physics are such that a matrix-addressed display is impossible without thin-film transistors, and this is where Philips comes in, providing a suitable active matrix. Polymer vision has got the combined thickness of display and active matrix to 100µm. It was actually at this stage in March. “Since then we have focused on manufacturability and improving yields,” Polymer Vision’s Hans Dreassan tells Electronics Weekly. “We aim to be in volume production of the 5.1in. four greyscale monochrome display at the end of 2006.”
Although it is up to the firm’s customers, Dreassan thinks it will first find application in pocket data terminals, perhaps displaying RSS feeds with either a stand-alone radio link, Bluetooth to a phone or WiFi to a nearby computer.
Display lifetime is an issue, but should be there on the day, says Dreassan. “We need the right encapsulation and the right materials. We already have gained 15 times [more life] in the last year.”
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| Sony’s Librié |
An E-Ink display on glass is used in Sony’s Librié. This was also made by Philips, but the rights have been transferred to BVI in Taiwan, says Dreassan. Power is low enough for Sony to claim 10,000 pages can be read on one set of four AAA batteries.
Electrophoretic displays like those from E-Ink are just about as easy to read as ink on paper and, like books, can be read clearly in bright sunlight.
However, like books, they cannot be read in the dark. Backlighting is impossible as both white and black pigments are always between the backlight and the viewer. Unless there is a technological breakthrough, thin-film front lighting like that used on some PDAs is also impossible as there is not enough thickness available for a light-conductive overlay.
So night time reading will have to be by something simple like a fold-out LED, a clip-on book light, or perhaps LEDs around the periphery.
If the e-book does not have to roll up when it is not in use, there are several display technologies which are somewhat flexible and could be used in something paperback-ish.
Malvern’s ZBD has a bistable LCD technology. “We are not addressing rollable, but we have plans to introduce in future a display that can be put on plastic substrates,” says v-p of business development Manoj Thanigasalam.
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| ZBD's bistable display |
ZBD’s display needs no active matrix and, if not ink-on-paper, the display is easily as clear as any wristwatch LCD and capable of over 200dpi resolution as well as several bits of greyscale.
The limit of bendability for ZBD and many other display technologies is the ITO [indium tin oxide] used as a transparent conductor. “Varitronix has been experimenting with plastic displays and it comes down to the reliability of ITO and other connections,” says Thanigasalam. Varitronix licenses ZBD’s display technology.
According to Thanigasalam, ITO will one day be durable even when repeatedly flexed. “It will be resolved in the medium to long term,” he says, adding: “Even with paper there is only a limited number of times you can roll it.”
At this time, the firm is aiming its flexible displays at advertising and shelf-edge use in shops. The idea is that displays on plastic will be cheaper and a bit of flexibility will avoid breakage as the displays are installed.
ZBD’s is a reflective technology - so no problems reading it in sunlight. It can also be backlit and there are a few flexible backlights around that can be made in flexible thin films.
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Fujitsu's bendable bistable screen uses three
layers for colour |
One well established light source is AC electroluminescent - durable enough to be used in illuminated belts for cyclists. Something of a disadvantage here is that these need around 60V to run them so some form of inverter would be needed for night time use.
OLEDs and light-emitting polymers (PLEDs) - display technologies in themselves but a little power hungry for this hypothetical flexing e-book - could be put to backlight use as they work in extremely thin films. The brightness is there and they are far more power efficient that AC electroluminescent backlights.
The only thing missing here is an effective barrier technology to keep moisture and oxygen out of the emissive layers. “At the moment PLED displays manufactured on glass are fantastic,” says Jeremy Burrows , technical director at PLED firm CDT. “No one is into manufacture with plastic yet, but it will happen someday.”
So am I going to be disappointed this Christmas?
Sadly, if I am expecting a floppy e-book the answer is: probably. But Christmas 2006 could be a different story.
www.gutenberg.org
See also: Electronics Weekly's roundup of content related to LED Technology