All appeals are dismissed.

The costs of appeal are assessed against the defendant.

The grounds of appeal are examined (to the extent of supplement in case of supplemental appellate briefs not timely filed).

1. If a patent becomes null and void, the patent shall be deemed never to have existed except in the case of Article 133(1)4 of the Patent Act (Article 133(3) of the Patent Act). However, if a patent becomes null and void after the conclusion of the patent license agreement, whether the patent becomes void after the conclusion of the patent license agreement should be determined separately from the effects of the patent.

If a patent license agreement is concluded, a patentee can not file a claim against the licensee for damages or prohibition of patent infringement against the licensee’s working of the patented invention, and the working of a third party’s patented invention is prohibited according to the exclusive and exclusive effects of the patent before the patent becomes void.

In light of this point, if it is not impossible to practice a patented invention which is the subject of a patent license agreement, it cannot be deemed that the patent license agreement, which is concluded as an object of the patent invalidation, was in a state of original impossibility from the time when the contract was concluded, notwithstanding the retroactive effect of the invalidation of the patent. However, if the invalidation of the patent becomes final and conclusive, the license agreement of the patented invention should be deemed

(see, e.g., Supreme Court Decision 2012Da42666, 42673, Nov. 13, 2014). Therefore, even if a patent becomes null and void after the conclusion of a patent license agreement, the patent license agreement was in a state of original impossibility of performance.

Unless a patent license agreement itself has separate grounds for invalidation, a patentee may, in principle, claim a royalty for the period during which the patent license agreement exists effectively.

2. The lower court recognizes the following facts:

The plaintiff and the defendant shall make oral statements to the defendant on or before June 2011.