Rollable ePaper Displays for Mobile Devices

Manufacturers of mobile devices including mobile phones and PDAs provide numerous mobile applications which run at respectable speeds with impressive functionality. However, a major remaining restrictive element is small screen size. Many business applications would be more usable with a larger screen size than currently available.

Also driving the push for larger mobile device screen sizes is the requirement by media businesses for suitable mobile platforms for e-newspapers and e-magazines. With ad spending on newspaper Web sites growing 32% in 2005 (according to the Newspaper Association of America) publishers are emulate the music industrys penetration of the mobile media market. Print media are conscious that their lower electronic distribution costs should lower content prices and stimulate a new expansive mobile market.

Small screen size may seem like a natural restriction if mobile devices are to remain portable - until you consider rollable “e-paper” displays. Imagine being able to pull out a side panel of your mobile phone or PDA to unroll a relatively large, high resolution display allowing display of more than the usual small corner of a spreadsheet. Think how more convenient this would be for a commuter than opening up a laptop.

Another natural application example for rollable e-paper flexible displays is mobile form factor GPS devices. Maps need a large display area for a clear, usable display of topological features and any location mark-up text. Just as paper maps are rolled up for handling convenience, an e-paper map could be rolled into a compact protective casing. Recall the impressively large roll-up map used by the Mar’s surface stranded astronauts in the science fiction movie Red Planet staring Val Kilmer, Carrie-Anne Moss and Tom Sizemore?

As well as improving screen size, other onerous requirements for roll-up e-paper displays include: thinness, high flexibility, toughness, ultra-lightness, minimal power consumption, high resolution and paper-like readability even in strong sunlight – all to be delivered at an affordable price.

Manufacturers have been assulting the technical and production challenges of e-paper and have rollable display prototypes built and are launching market viable products. There are a number of e-paper manufacturers with varying technical solutions.

E Ink

E Ink have developed electronic paper displays which have high contrast for daylight viewing, ultra-low power consumption and a slim profile. As expected the screen is not emissive and requires power only to update the display.

Sonys new Sony Reader incorporates E Ink’s technology in its innovative electronic paper display. The display’s miserly power consumption allows roughly 7,500 continuous page turns between recharges. The Sony Reader can store and display documents in Adobe PDF format, RTF, text as well as JPEG photos.

To quote Sony, “The Reader’s high-resolution electronic paper display delivers a realistic print look that rivals traditional paper and results in crisp text and graphics that are easy on the eyes and readable even in bright sunlight.”

Another E Ink technology user is Motorola’s MOTOFONE handset which features a ClearVision display that utilizes E Ink’s Electrophoretic Display technology for a large, high-contrast screen that is suitable for wide angle viewing even in bright sunlight.

E-Ink also recently announced a 12-bit technology that uses filters to achieve color displays with its E-Ink product.

Polymer Vision NV

Philips Polymer Vision is expected to launch in 2007 a 5-inch, 320 x 240-pixel resolution, 1:10 contrast ratio, 100 micron thick rollable display based on E-Ink’s electrophoretic technology. The screen can roll up into a radius of 0.75 cm, has a 0.5 – 1s switching time and a refresh rate of 50Hz.

Philips is also undertaking cooperative development with SiPix of a color version of roll-up displays.

SiPix

SiPix Imaging Inc. has made progress toward commercial production of a full-color e-paper. SiPix’s Microcup Electronic Paper is flexible, high-contrast, visible over a wide (180 degrees) field-of-view yet, has ultra-low power consumption as it needs power only to change a pixel’s color. No power is required for standby mode.

The microcups are built on a 150-micron flexible plastic substrate. The substrate includes a transparent conductor that uses indium tin oxide to form domains 80 to 150 microns square, into which colored dyes can be deposited. The Microcups are then hermetically sealed and laminated onto an electrode-studded backplane that drives the display. Manufacturing uses a roll-to roll embossing process whereby a continuous sheet of PET plastic is coated, first, with transparent conductors and then with a proprietary resin. The microembosser then molds the Microcups into the resin so they can be filled with dyes, hermetically sealed and attached to the backplane.

SiPix are currently working on display applications with consumer product manufacturers including Philips and BASF.

In June SiPix and SmartDisplayer received the Display Application of the Year Award from Information Display Magazine and the Society for Information Display (SID). SiPix and SmartDisplayer created the first flexible display panel to be embedded into an ISO-compliant payment card.

Plastic Logic

UK-based Plastic Logic is expected to manufacture screens on flexible plastic sheets by 2007. Plastic Logic is manufacturing printed plastic electronic circuits for flexible displays. These circuits are constructed using solution processing and direct-write techniques and consist of transistors and other components that are produced from polymers and a variety of other materials.