Not 100%, but it is not mentioned anywhere in their literature, and the one I saw in the store did not really have 170 degree+ viewing angles that are indicative of IPS panels. It would explain the poor black levels though.
EDIT: Hmm, according to hdguru, all of LG's 2012 line of Smart 1080p 2D LCDs use IPS displays except the 65" versions. Although it lists out several models, and the LS4500 is not among them. Only seems to specify smart TVs and not dumb ones like this one, so it would cover the LS5600 line, but not necessarily the LS4500.http://hdguru.com/ces-2012-lgs-hdtv-line/7018/
If you want to check, you can look closely at the screen with a magnifying glass. If the pixels are chevron shaped ">" then it has an IPS panel.Edited by Munkee Boy - 12/5/12 at 8:31am