US Patent 7180649 - Electrochromatic nanoparticle displays

http://www.freepatentsonline.com/7180649.pdf

E Ink is a company that is working on producing flexible electronic paper which can provide the attributes of electronic displays to media having a paper-like consistency. This patent uses electrochromatic (i.e. color controllable) nanoparticles for such displays. Claim 1 reads:

1. A display comprising: first and second electrodes spaced from one another, at least one of the first and second electrodes comprising a layer of an electrically conductive metal or metal oxide, and a semiconductor layer; and a plurality of electrochromic nanoparticles disposed between the first and second electrodes, each of the nanoparticles having an electron-rich state and an electron-depleted state, the two states differing in at least one optical characteristic, such that injection of charge from at least one of the first and second electrodes will cause at least some of the nanoparticles to switch between their electron-rich and electron-depleted states.