Comparison of Patent Regimes: Japan


As innovation drives modern businesses forward, Asian countries compete to provide businesses with maximum patent protection to secure their intelligence capital

IIn the United States, third-party opinions can be submitted in the form of amicus curiae briefs, which have been actively used. By contrast, Japan had no statutory system for seeking third-party opinions in litigation until April this year, when a number of legal amendments institutionalizing the practice of amicus curiae for cases infringement of patents and utility models came into effect.

In patent infringement suits, judgments rendered on specific disputes between parties may affect many third parties. For example, technologies such as the Internet of Things and artificial intelligence have developed rapidly, and these technologies are used in multiple sectors. Court rulings on these technologies will inevitably affect many industries. Furthermore, a decision on standard essential patents has a significant impact on other countries. In such cases, the court should seek extensive third-party opinions and make a decision based on those opinions.

Hirofumi Tada
Ohno & Partners, Tokyo
Tel: +81 3 5218 2339

In the 2021 Amendment to the Patent Law, Japan implemented a new system for soliciting opinions from third parties.

Japan has experienced solicitation of third party opinions based on an agreement. In Samsung vs. Apple (2014), the Intellectual Property High Court has sought third party opinions regarding the exercise of patent rights declared fair, reasonable and non-discriminatory due to the importance of the issue and its significant impact, but this has is based on an agreement of the parties. However, obtaining consent from both parties is often not easy, and the availability of such an agreement-based approach was very limited.

The recent amendment allows the court to solicit opinions based on a request from a non-consensual party. This is a huge difference from previous practice.


Under the terms of article 105-2-11 of the amended law, the solicitation system seeks to reconcile the adversarial litigation system and the need for sufficient information for the courts. The requirements for seeking third-party advice reflect the trade-off between these two elements.


The solicitation system is available for first instance and appeal proceedings in infringement actions based on a patent right or an exclusive license right (see also Section 65(6) of the Patents Act and the Article 30 of the Utility Models Law). Cases seeking the reversal of decisions of the patent office are not covered by this amendment. In the future, the scope of cases involved could expand if regulators find this system useful.


To seek the opinion of third parties, a request must be filed by at least one party. The court alone cannot launch a solicitation without a request. This reflects the adversarial principle of the Japanese judicial system.


The court determines the need to seek opinions. In doing so, the court hears the views of the parties and takes into account various circumstances, including the difficulty of obtaining evidence for the parties and the influence of the judgment on third parties.

The subject matter of reviews includes not only legal issues and rules, but also actual business practices and business situations. This will help the court understand the circumstances surrounding the disputes and the influence of its decision.

It is also often difficult for litigants to obtain such information, which will also help them. On the other hand, it is generally not permitted to use this system to collect prior evidence. Parties are expected and required to seek and collect such evidence themselves under the Japanese system.


The court must hear the opinion of the other party. It is often expected that one party will want to solicit opinions but the other party will object as part of a litigation strategy. The court must hear the views of the other party, but the consent of the other party is not required. It is a compromise between the adversarial legal system and the court’s need for information.

In Samsung versus Apple, the court sought opinions based on the agreement of the parties. On the other hand, this amendment does not require the consent of the other party, which facilitates the solicitation of third-party opinions. This is the meaning of the amendment to the Patent Act.


The court solicits opinions from a wide range of general third parties without limitation. Therefore, anyone, including foreign natural and legal persons, can submit reviews. The Japanese court is expected to hear opinions internationally to make globally balanced decisions.


Opinions must be submitted to the court, but they do not immediately become evidence. The parties must review and choose the opinions, and then submit the chosen opinions as evidence in court. The advantages and disadvantages of such a system design have been debated during the legislative process. The court does not review all notices, but both parties are responsible for selecting and submitting notices.

It will be disappointing for a third party if their opinion is not reviewed by the court, but this is a consequence of the adversarial litigation system. Furthermore, it saves the courts from having to consider a large number of opinions. When an opinion in a foreign language is submitted for use as evidence, the party submitting the opinion must prepare the translation, similar to the submission of a document in a foreign language. This means that third parties do not bear translation costs.


The request for third party opinions will be published on the website of the Intellectual Property High Court ( In some cases, the application may be published in English. Therefore, it is recommended to consult the website if a concerned party wishes to submit a notice for a particular case.

In addition, the Japan Patent Office indicates that it is acceptable for parties to a dispute to approach and request third parties to submit opinions and provide compensation for the preparation of opinions, within the scope of legitimate judicial activities. In many cases, notices will be submitted in response to these approaches and requests. As a result, many third-party opinions will be favorable to a party. This system will be used strategically by litigants, but it should be accepted as a result of the adversarial litigation system.

Since third-party opinions are requested to assist the court in determining certain legal issues under Japanese patent law, it is recommended that you consult a lawyer or patent attorney licensed in Japan to submit an effective opinion. Their advice will help third parties prepare persuasive opinions for Japanese judges. In order for the court to reach a well-balanced decision reflecting the positions of third parties, the active use of the system is preferable.


Japanese courts have highly specialized divisions dedicated to intellectual property cases, which guarantee the quality of their decisions. A common misunderstanding is that it is difficult for a patentee to win a lawsuit in Japan. However, the situation has changed significantly recently and Japanese courts have shown a patent-friendly trend over the past five years.

In addition, the new third-party opinion solicitation system was implemented to make balanced decisions considering the impact on society. Japan’s patent litigation system is becoming more reliable and useful for global companies.

21/F Marunouchi Kitaguchi Building
1-6-5, Marunouchi, Chiyoda-ku
Tokyo – 100-0005, Japan
Tel: +81 3 5218 2331


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