Open Innovation Effects of Patent Applications: An empirical study of inkjet technology patents

Firms apply for patents not only to obtain the right to exclude but also to prevent their rivals from obtaining patents of competing technologies. Patent applications for the latter purpose are usually called "defensive applications," which have caused the low appraisal rate of Japanese patents. However, since every patent application is published after 18 months from the application date, the defensive applications can be information sources of new technologies for firms that are not directly competing against the applicants, and the external effects of the defensive applications on different technological fields may be growing in the open innovation era. This paper examines such external effects in the field of inkjet technology using patent citation data, and confirms that even patent applications without examination requests had the effects. Moreover, this paper examines the effects of two patent policy changes on firms' patent applications: the temporary decrease in the novelty standard in the 1990s and the shortening of the examination request period since the 2000s. The regression results show that the former and the latter increased and decreased the number of patent applications, respectively.