# 2017/10/03

Q&A regarding Patent Litigation in Japan – liability, provisional rights, approach potential infringer, etc.

1. Under Japanese patent law is there a notice requirement for liability for patent infringement?  By that I mean is an unauthorized user of a patented invention liable for infringement even if he or she did not know about the existence of the patent?

Under the Japanese patent law, an infringer of a patent is basically liable for infringement without receiving any notice from a patentee after the patent is registered even if the infringer did not know the existence of the patent. However, with respect to the infringement during the period between the registration of the patent and the issuance of the patent, the patentee has a burden of proof showing that the infringer knew the existence of the patent (for example, by showing the fact of sending the infringer a notification of the existence of the patent) in order to claim compensation for damages caused by the infringement during the period.

 

2. If there is no notice requirement for patent infringement liability, is there a Japanese statute of limitations for patent infringement?  For example, while not likely to be relevant today because the patent issued less than a year ago, can a patentee only recover damages for infringement that took place no more than a certain period of time prior to filing a lawsuit?  If so, what is that period of time? 

A patentee can only recover damages for infringement that took place no more than three years prior to claiming infringement or filing a lawsuit.

 

3. Under US law a patentee also has so-called “provisional rights” relating to the time from publication of the patent application up to the issue date of the patent.  Does Japanese patent law recognizes such provisional rights?  If so, what would be the relevant start date for those rights in this case, the publication date of the underlying PCT application in English or the publication date of Japanese patent application?

Under the Japanese patent law, an applicant also has so-called “provisional rights” relating to the time from publication (i.e., laying open) of the patent application in Japanese language up to the registration of the patent, under a certain condition. That is, in order for the patentee to get compensation for infringement during that period, it is required that the infringer knew the existence of the patent application and that both the claim of the patent application and that of the patent cover the subject matter of the infringement. In other words, there must be evidence that the infringer was aware of a claim of a patent application that a deed of the infringer infringed, and that the deed of the infringer would still infringe a patented claim. In practice, in order to establish such evidence, the applicant of the patent application sends a warning letter to the infringer when the applicant has found out such infringement. When an applicant of a patent application has sent a warning letter stating the publication number of the relevant patent application after the laying open of the patent application, the applicant may claim compensation against the potential infringer. The amount of the compensation is prescribed to be equivalent to the royalty of a license that would have been charged for the period from the date of the warning to the registration of the patent. When the warning has not been given, the applicant has a burden of proof showing that the potential infringer knew the existence of the patent application. The applicant can exercise the right to demand compensation within three years from the registration of the patent if the applicant knew the working of the claimed invention or the person who worked the invention, prior to the registration of the patent.

 

4. Please educate us about the legal implications of the various ways in which a patentee might approach a potential infringer/licensee. For example, under US law if the patentee is too aggressive in approaching the potential infringer/licensee, then the potential infringer/licensee can take the initiative in filing a lawsuit, which gives some strategic advantages to the potential infringer/licensee at the expense of the patentee.

In Japan, it is a common practice for a patentee to approach a potential infringer by sending a warning letter. The warning letter may say that, if after issuance of the patent, (1) the patentee requires the potential infringer to stop working the invention immediately and inform the patentee how many products it sold/manufactured, or (2) the patentee is prepared to grant a license if the potential infringer is interested in obtaining such license, and (3) the patentee requests the potential infringer to reply within a certain period of time (e.g. two weeks). Further, if the patentee has confidence in believing the existence of infringement, the patentee add that he is prepared to take a legal action if he does not receive sincere reply in response. Then, usually, the patentee gets into negotiation with the potential infringer. The potential infringer may say that (1) the accused deed would not infringe the patent and accordingly there is no need to show the number of the products sold/manufactured, (2) it would like to obtain a license under a reasonable condition, or (3) it would need some time for confirming the infringement, meaning that it would need a time to conduct a search for any prior art that would invalidate the patent or to get a professional opinion on infringement.