E-Paper Comes Alive

Nov. 20, 2007 — -- The new Amazon Kindle e-reader, unveiled yesterday, is the latest in a line of ever-improving black-and-white e-paper displays that don't use much power and are bright even in daylight; they more closely reproduce conventional paper and ink than do backlit displays. But bigger technology leaps are imminent. E-paper pioneer E Ink--the company whose technology underpins the Amazon gadget's display--is prototyping versions of the electronic ink that are bright enough to support filters for vivid color displays, and that have a fast-enough refresh rate to render video.

Add it all up, and it represents an emerging trifecta of color, video, and flexibility set to transform a display technology once seen as suited only for rigid black-and-white e-readers like the Kindle and the Sony Reader, and other niche applications like train-station schedule displays that don't need to change quickly. "This latest thing they've done with the video is a key milestone in the history of e-paper technology development," says Gregory Raupp, director of the Flexible Display Center at Arizona State University. "Until this point, you have been limited to static image applications."

E Ink's basic technology uses a layer of microcapsules filled with flecks of submicrometer black and white pigment chips in a clear liquid. The white chips can be positively charged, the black chips negatively charged. Above this layer is a transparent electrode; at the base is another electrode. A positive charge on the bottom electrode pushes the white chips to the surface, making the screen white. A negative charge pushes the black chips up, rendering words and images.

But the basic technology only produces a black-and-white image. So, E Ink has been refining the ingredients, the electronics, and the mechanics of that process. For example, in recent months the company has developed ultrabright inks that reflect 47 percent of ambient light--a significant improvement over the 35 to 40 percent in existing E Ink black-and-white displays. Higher reflectivity versions should go into commercial products, such as the Sony Reader, in the next year or so.