Should an R&D manager refer to distant technical fields? The effectiveness of new combinations with knowledge from different technical fields through the quantitative analysis of patent data related to NetZero.

This study showcases a technique to categorize NetZero-related patent applications into three technical fields according to the degree of proximity between claimed inventions and cited inventions by comparing technological classifications between the patent applications and cited applications thereof. In this technique, the author first describes the existing methods used in previous studies. The technique proposed in this article is different from those of previous studies in that it is characterized by comparing the technical fields of not only the primary classification but also the subsequent classifications. This is made possible by using two patent classifications without having a specific classification corresponding to the middle hierarchy in between, rather than using three patent classifications with different hierarchies. This technique reduces the possibility that two applications, even if they are the same in their subsequent classification, will be judged as applications in different technical fields because they are in different classes in the primary classification. Using the proposed technique, the author examined the impact on the subsequent patent application of NetZero-related patent applications filed in Japan. As a result of the analysis, the author found that approximately 33% of subject applications, whose technical field differs from the backward citations when comparing the primary classification only, match one of the subsequent classifications when comparing them in consideration of the subsequent classifications as well. The author then found that these 33% of subject applications had a greater impact on subsequent patent applications than the remaining applications.