JAPAN / PATENTS / DOCTRINE OF EQUIVALENTS

A Comparative Analysis of the Japanese Supreme Court Decision

Intellectual Property Quarterly, Issue 1, 2002

C Leon Kim

(Note. For the purposes of this topic, the doctrine of equivalents is taken to mean, in the terms used by the United States Court in Fife Manufacturing Co v Stanford Engineering Co, that, if two devices do the same work in substantially the same way and accomplish substantially the same result, they are the same, even if they differ in name, form or shape. A device falling within this definition may therefore infringe a patented device, even if it does not literally match the patent claim. "The doctrine prevents parties from infringing patents with impunity by making minor changes in an invention.")

As the author makes clear in this article, there are substantial differences between the doctrine of equivalents as defined in the Spline Shaft case - the Japanese Supreme Court decision of 1998 discussed here in detail - and the doctrine applied in such other jurisdictions as the United States, the United Kingdom and Germany. The author examines the five conditions laid down by the Japanese Court for invoking the doctrine. The first condition is that the essential parts of the patented invention should be identical, while only the non-essential parts should be different but equivalent. This assumes a hierarchy among the elements of a patent claim, according to whether they are essential or not; but the author says that there is no explanation in the judgment of how an essential element may be determined. Japanese patent law has been influenced by German law; and the article refers to the important German decision in the Formstein case. It contrasts the Japanese hierarchical concept with the "all elements rule, as formulated by the United States Courts in, for example, Lemelson v United States, 1985. As to the second and third conditions laid down in the Spline Shaft case, these relate to the interchangeability of the elements; and the author criticizes them for their restrictive effects on the general test of equivalence. "Even the German Courts have not confined the equivalence test to interchangeability alone." The author also criticizes the Japanese Court's fourth condition, that the product alleged to have infringed the patent should not be identical or easily derivable from the prior art by one skilled in the art at the time of filing the plaintiff's patent application. He refers to the English case, Gillette Safety Razor Co, in which the defendant successfully argued that its safety razor was indistinguishable from the prior art or mechanically equivalent thereto; as well as to the German case, Formstein, already mentioned. On the last of the Japanese Court's five conditions, the author considers that the Japanese Court "vastly expanded the domain of prosecution history estoppel". So too did the United States Supreme Court in the Warner-Jenkinson case, but rather by way of moving from the art-based rejection to the "patentability-related" reasons and thereby making it more difficult for the patentee to argue against the application of the prosecution history estoppel. The author concludes that, given Japan's interest in international trade and the general worldwide movement to harmonise intellectual property laws and practices, further development of the doctrine of equivalents under Japanese law will be critical. [20070]