JAPAN Law and Practice Contributed by: Yoshiyuki Inaba, Hiroshi Nemoto, Makoto Okada and Atsushi Sato, TMI Associates
3.5 Defences Against Infringement If a patent right is exercised abusively, it can lead to certain defences for the accused party. For example, if a patent holder who has declared their commitment to FRAND (fair, reasonable, and non-discriminatory) terms later seeks an injunction against a party that intends to be licensed under those terms or demands dam- ages exceeding what would normally be con- sidered a fair licensing fee, the defendant may invoke the defence of abuse of rights. If the defendant has practised a patented inven- tion or prepared for such practice at the time of the patent application filing, the defendant can claim “prior use” as a defence. If the patentee, when filing an application, makes assertions that exclude the technology that is to be included in the technical scope of a patented invention (based on the common meaning of the term being used), it is typical for the technical scope of the patented invention to be construed in a limited manner as a result. Where the products in question were assigned from a patentee or person with legitimate rights, no patent infringement will be admitted, as the patent right will have been exhausted. In addition, the defendant may claim that their use of the patented invention was experimental and, therefore, beyond the scope of the patent right. Even though the Patent Act provides for three types of non-exclusive licences to be granted by the JPO Commissioner (eg, compulsory licenc- es), as of the end of 2024, no such compulsory licence has ever actually been granted in Japan (see 2.2 Third-Party Remedies to Remove the Effects of Intellectual Property ).
The fact that the defendant’s infringing con- duct was an exercise of their patent right can- not be used as a defence against the patentee’s infringement claim. As to the statute of limitations, the patentee can- not claim damages for an infringement if more than three years have passed since the date on which the patentee became aware of an infringe- ment and the identity of the infringer who caused the damage. There is an overall limit of 20 years from the act of infringement. 3.6 Role of Experts Experts involved in patent litigation are mainly judicial research officials and expert advisers. Judicial research officials are full-time court employees who conduct examinations on tech- nical matters necessary for judicial decisions and report to a judge. Judicial research officials are primarily appointed from the pool of JPO employees or patent lawyers. Expert advisers are part-time employees appointed by the courts who get involved in proceedings to arrange issues and evidence, to examine evidence, and to enter into a settle- ment in the court proceedings. Expert advisers are usually involved in proceedings to arrange issues and evidence (preparatory proceedings, etc) and make oral explanations on technical matters. In patent litigation, in order to have a proper understanding of technical issues, expert advisers are often involved and conduct techni- cal explanation sessions in preparatory proceed- ings. It is common for an expert in the technical field to which a patented invention belongs (usu- ally a university professor or patent lawyer) to be appointed as an expert adviser.
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