Its probably using this technology e-ink, which I became aware of in 1997, and tried to become a local distributor, but at the time there was a Japanese printing company interested in buying the original founding company out, as the technology had so many interesting applications. Eventually they were bought out, and if I am not mistaken, Phillips was involved.

Here is the original site http://www.eink.com/technology.html
Check out how the ink works, it's really a smart concept.