This study presents an empirical analysis of how mandatory prior art disclosure by patent applicants affects patent examination in Japan's patent system.
The Prior Art Literature Disclosure System, introduced in 2002, was a institutional reform that mandated patent applicants to disclose relevant prior art literature. This institutional reform significantly improved the quality of literature disclosed by applicants, with particularly pronounced effects observed for high-value inventions. The increase in high-quality disclosed literature resulted in accelerated patent registration processes, appropriate narrowing of claim scope at filing, and reduced amendments during examination.
Detailed analysis of examination impacts revealed that high-quality disclosed literature improved patent examiners' comprehensiveness in prior art citation, consequently shortening the time to patent registration. While the institutional reform simultaneously increased disclosed literature not directly utilized in examination, any registration delay effects from this were offset by the acceleration effects from high-quality disclosure.
The impact on post-reform patent disputes represents a significant finding, with confirmed reductions in both invalidation trials and appeals against rejection decisions. This indicates that high-quality disclosure by applicants enhanced patent stability and examination accuracy. Although a substitutive relationship exists between applicant-cited and examiner-cited literature, the total volume of prior art literature used by examiners increased after the reform, demonstrating that applicant disclosure does not simply substitute for examiner search efforts but rather strengthens the overall prior art base used in patent examination.
The research, conducted by Ryo Kadowaki of Hitotsubashi University, RIETI Faculty Fellow Sadao Nagaoka, and Takahiro Maeda of Ambience Corporation, leveraged this natural experiment to identify causal relationships, empirically demonstrating that applicant disclosure complements examiner search activities and contributes to strengthening the overall prior art base in patent examination.