InfoSync World has an article about Philips E Ink technology.
E Ink, Philips show paper-like display
Philips and E Ink have unveiled a new paper-like display prorotype at the Society for Information Display (SID) show, boasting higher resolution than anything seen before.
[…]
The display features a resolution at 160 pixels per inch (ppi), which is significantly higher than anything demonstrated previously. Enabled by continued improvement in E Ink’s electronic ink display material and Philips’ custom designed thin-film-transistor (TFT) backplane and driver electronics, the new displays are a result of the collaboration between the two companies that have been ongoing since early in 2001.
A picture of the device is also shown.
It took me some days to dig this up (since I had disabled the search in my blog), but Viewsonic are already selling a 200 ppi display:
http://www.extremetech.com/article2/0,3973,525370,00.asp