Comparison of the First Requirement of the Doctrine of Equivalents Between Korea and Japan

Abstract

In 2000, the Supreme Court of Korea issued the first judgment providing five requirements for applying the doctrine of equivalents to patented and allegedly infringing devices and processes. Since then, it started to interpret the first requirement of the doctrine of equivalents, namely the “identity of the problem-solving principle of the two inventions,” to mean that “the difference does not pertain to an essential part of the patented invention,” which was set forth by the Supreme Court of Japan in the Ball Spline decision. The purpose of this article is to examine whether the first requirement of the doctrine of equivalents rendered by the Supreme Court of Korea and that by the Supreme Court of Japan can be considered the same on the basis of its interpretation by the Supreme Court of Korea. To this end, the article provides a general introduction to the doctrine of equivalents in Korea and that in Japan and investigates the meanings of the key terms employed in the first requirement in Korea and that in Japan, such as “technical idea,” “problem-solving principle,” “essential part,” and “identity of the problem-solving principle.” Equating the first requirement of the doctrine of equivalents by the Supreme Court of Korea with that by the Supreme Court of Japan is theoretically inappropriate in that the Supreme Court of Korea applies the doctrine of equivalents even after verifying the interchange of an “essential part” of a patented invention. In practice, however, the Supreme Court of Korea still considers the other requirements of the doctrine of equivalents even after verifying this interchange.