Application of the Doctrine of Equivalents

Under the current practice, after an allegedly infringing article or method is found to be non-infringing literally, a determination will generally be made to determine whether there is infringement under the doctrine of equivalents. 

The Taiwan Intellectual Property Office (TIPO) published the Important Notes on Patent Infringement Assessment in 2004, which outlined several important principles that guide the determination based on the doctrine of equivalents. According to said Notes, if any one of the technical features of a claim is found to be completely absent in the object under analysis after construction, the doctrine of equivalents will not be applicable.

In DuPont Taiwan v. ThinFlex Corporation, a patent infringement lawsuit filed in January 2005 and involving a patent relating to a polyimide laminate, a major issue in dispute is whether the doctrine of equivalents is applicable. The essential feature of the invention in issue is an aprotic solvent comprising 1 to 30 weight % of acetone as recited in claim 1. The District Court and the High Court both found that the doctrine of equivalents was not applicable on grounds that the polar aprotic solvent in the defendant’s product does not contain acetone and mainly has 1-Methy-2-Pyrrolidinone (NMP). The Supreme Court issued a decision in March 2010 to remand the case to the Intellectual Property Court for reconsideration, which was established in 2008 to handle IP-related civil actions, among others. The Supreme Court did not make any determinative indication as to the disputed issue, and merely instructed the IP Court to investigate and consider the issues raised by DuPont Taiwan: whether NMP and acetone have equivalent expressions; whether the allegedly infringing product and the invention in issue are substantially the same in function, way, and result; and expert testimony as to whether use of NMP alone and NMP containing 2% acetone can achieve the same effect in terms of viscosity and solubility. 

Since the allegedly infringing product does not contain acetone and since it is stated in the specification that the intended object of the invention in issue cannot be achieved when acetone is less than 1%, not to mention that the polar aprotic solvent system used in the embodiments of the invention in issue is a combination of acetone and NMP, the applicability of the doctrine of equivalents in this case should be questionable. Accordingly, the Supreme Court’s decision might raise issues regarding the applicability of the doctrine of equivalents among patent practitioners.

The IP Court’s decision is eagerly awaited and is expected to have an impact on the application of the doctrine of equivalents.

The above contents are intended as general discussion of the subject matter only and shall not be deemed as legal advice to any particular case or issue.