Like most other countries, Japanese patent law recognizes the absolute novelty requirement. This means that even prior publication by the inventor can be detrimental to novelty. To prevent this from becoming a trap for inventors who are inexperienced with patents, there is a grace period. If a patent application is filed for the invention before the expiry of 12 months from the date of publication, the prior publication is exceptionally not prejudicial to novelty.

Prior to 2012, the Japanese Patent Act was very rigid with regard to prior publication of the invention by the inventor. Such publications could only be excluded from novelty-destroying prior art under very narrow conditions. The publication had to be either at a “world exhibition” or at a conference sponsored by the Japan Patent Office or the local Japanese government. While the so-called world’s fairs were very rare anyway and not technology-related events, the sponsored Japanese conferences were hardly ever a place for foreigners to attend. Accordingly, the statutory exception to prior art was meaningless. The fact that the time limit was only 6 months instead of 12 as in the US or Canada was not decisive under these circumstances anyway.

In 2012, the legal conditions for the grace period were greatly relaxed. Since then, any publication by the inventor that is no more than 6 months before the application date of the Patents can benefit from the grace period. It does not matter whether the first publication was made in Japan or abroad.

As of June 9, 2018, the 6-month period has now been extended to 12 months. The grace period can therefore be claimed for all inventor’s own prior publications that are no more than 12 months before the application date. The new period of one year applies to all inventions published after December 9, 2017. This results in a transitional period until December 9, 2018, during which the grace period is not yet 12 months.

However, it is still important that the prior publication is declared with a “Certificate of Proof of Disclosure” when applying for the patent.

It should be noted that the grace period is not counted from the priority date. Therefore, if a European First Filing is filed within 12 months from the date of prior publication by the inventor and then the international or Japanese Application is filed shortly before the expiry of the 12-month priority period, the Application in Japan is too late and the prior publication cannot fall under the grace period.

Note: Despite the renewals of the grace period, it is still not advisable to publish the invention first and only then apply for a patent. Using the grace period is always only an emergency measure to save what can possibly still be saved.

Left: https://www.lexology.com/library/detail.aspx?g=f4dbca58-fa39-45e4-adc0-e764c5057dab