Prosecution history estoppel in Japanese patent law (in German)

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Dr. Klaus Hinkelmann, in Mitteilungen der deutschen Patentanwälte (Communication of the German Patent Attorneys), pages 10-14, 2024.

The patent claims are decisive for determining the subject matter of an invention in patent infringement proceedings, although the description and drawings of the patent application can be used if the terms are unclear. Under the doctrine of equivalence applied in Japan, the courts are to apply five criteria when determining equivalent infringement. The fifth criterion is that there are no "special circumstances" under which a court should deny equivalent infringement on equitable grounds. The accused product must not have been intentionally removed from the technical scope of the patent claim by the applicant during the patent grant procedure. The application of the doctrine of equivalence may be precluded in particular by declarations and/or claim amendments on the part of the applicant during the grant procedure, but also by a failure to claim similar embodiments which cannot be explained by special circumstances. This article deals with the interpretation of the scope of protection of patents in patent infringement proceedings with regard to the fifth criterion, with a particular focus on the application of prosecution history estoppel.