The Korea Times reported that another Univeral Display patent was invalidated in Japan (bringing the total patents to three) - and that these patents are also being challenged in Korea (by Duksan) and in Europe. This caused UDC's stock to plummet. We knew about 2 patents back in March.
Steven Abramson, UDC's CEO responded to this in a technology investor conference. The company says that indeed Japan's court invalidated three of their patents. The basic PHOLED patent is still valid until 2018 in Japan, and this does not harm their entire portfolio. They will appeal to the Japanese high court, and in any case this only relates to products being made, used and sold in Japan - so it doesn't really pose a problem to the company.
Steven says that their patents are under challenge in several areas, and they expect it to remain so in the future, this is part of the game. In Europe there is a challenge about one patent, and there isn't a decision yet. As a reminder, previous Previous opposition in Europe regarding a flexible (non-glass) substrate patent was dismissed (and there is an appeal against UDC there). In Korea there is a challenge against their patent - but again this is not a fundamental patent.
Disclosure: the author of this post holds shares in universal display