Erasable E-Paper Saves Trees, Cuts Costs

R. Colin Johnson

• Electronic paper that runs through thermal printers but can be electrically erased and rewritten aims to make tree paper obsolete. The paper makes use of flexible plastic that retains printed text without batteries or moving parts.
  With all the movement to green technology, the day was bound to come when ordinary sheets of paper were replaced with electronic versions that run through printers but can be erased electrically and rewritten over and over. Made of a durable plastic, e-paper uses a similar technology to reflective e-readers, but in a more flexible form factor that does not require a battery and which can be instantly erased.
  "Most printed pages in the office will be discarded in only a few days or weeks after being printed," said Janglin Chen, vice president and general director of ITRI’s Display Technology Center. "Our e-paper, on the other hand, can be erased and re-printed hundreds of times with no ink or toner or tree products being consumed, making it both efficient and green."
  
  Shown here in an ornamental scroll, ITRI's e-paper, which can be produced in normal cut sheet formats too, indefinitely retains images printed on it thermally. 
  The new e-paper from the Industrial Technology Research Institute (ITRI, Taiwan) will cost about 50 cents for a letter-size sheet when it become available in 2012, but will replace a half-ream of ordinary paper by being electrically erased and rewritten up to 260 times. In fact, the green factor landed ITRI the 2011 R&D Award earlier this year. Users can also write on the paper to make notes or other annotations using water-based marker pens, which can later be washed off before reusing the e-paper.
  ITRI predicts that its e-paper will first be used in a variety of business applications--since it requires that currently available printers retool their thermal print heads. For advertising banners, corporate visitor ID badges, mass transit passes, parking lot tickets, museum passes and other similar applications there will be special printers available early in 2012, with upgraded consumer-grade printers appearing later in the year.
  For the future, ITRI is experimenting uploading chapters of digital books into blank-page e-paper booklets which can then be erased and reloaded with different chapter after you read the first one. Since the e-paper can be produced in any size, future versions are also planned for wall banners, electronic bulletin boards and other large-scale applications.
  ITRI's e-paper works by virtue of a flexible cholesteric liquid-crystal core (similar to that of reflective e-reader displays) sandwiched between an opaque silver-coated backing and a transparent indium tin oxide (ITO) front layer. Resolutions as high as 300 dots per inch retain crisp printed images indefinitely after a thermal printer head write them, with no toner, no ink and no paper consumed during the process. Cholesteric liquid crystals are reflective and can be manufactured for printing in red, green and blue colors (albeit in monochrome today, although full color versions are under development at ITRI).
  The e-paper can be fabricated on cheap roll-to-roll manufacturing lines, can be bent down to a one centimeter radius without damage, is just 160 microns thick, and is set-up so that all its components parts--from the polymer substrate to the liquid crystals, ITO and silver-backing films--can all be recovered from spent sheets and reused in the manufacture of new ones.