In Taiwan, is the defendant entitled to assert the 'prior art' defense as a limitation on the application of the “doctrine of equivalents” to contest the claim of infringement based on the “doctrine of equivalents”?
The Supreme Court, in its Civil Judgment rendered in July 2022 on a patent infringement case explicitly recognized the crucial role of the "prior art" defense in determining the applicability of the “doctrine of equivalents” and in turn, the infringement under the “doctrine of equivalents.” The Court further required the Intellectual Property Commercial Court (hereinafter the IPC Court), a lower court, to raise this issue with the two opposing parties and provide them with sufficient opportunities for argument and defense, in order to ensure an impartial and complete hearing of the case. As a result, in practice, Taiwanese courts have affirmed that the "prior art" defense can be used as a valid limitation on the “doctrine of equivalents” in patent infringement cases, leaving no doubt as to its admissibility.
The standard for determining "prior art” defense” in Taiwan is based on the “Patent Infringement Judgment Guidelines” issued by the Intellectual Property Office. If an allegedly infringing product reads on the claims of a patent and has all the technical features of a single prior art or can be easily combined with a single prior art in the field of technology to which the patent at issue belongs, then the “prior art” defense applies, and the “doctrine of equivalents” infringement could be precluded. The IPC Court has adopted this standard in most of its past judgments. However, most disputes involve slight differences in technical features between prior art and the allegedly infringing product. The court's focus is on whether such differences can be easily combined as a general knowledge in the field of technology existent when the application from which the patent at issue derives was filed. A recent Civil Judgment rendered by the IPC Court in 2023 involves matters regarding how to determine whether an allegedly infringing product is the same as the prior art when the prior art has additional technical features as compared with the allegedly infringing product.
The patent at issue (TW M581023) is related to a clamping mechanism used in machine tools. The clamping mechanism includes a piston seat and a clamping rod, and a protrusion extends upward from the bottom surface of the piston seat to drive the clamping rod. The plaintiff averred that the allegedly infringing product reads on most of the claims of his patent, except that it has a piston seat with a bottom surface of the same thickness but without a protrusion which is provided to drive the clamping rod. However, the piston seat of the allegedly infringing product still falls within the scope of the patent under the “doctrine of equivalents.” The defendant did not rebut regarding whether the allegedly infringing product falls within the scope of the patent at issue under the “doctrine of equivalents”, but argued that the allegedly infringing product is the same as a prior art and is subject to the application of “prior art” defense. The plaintiff then argued that the piston seat of the prior art additionally has an O-ring, which is squeezed before driving the clamping rod, indicating that the prior art includes an additional component and is not the same as the allegedly infringing product.
The IPC Court held that the technical features of the allegedly infringing product falling within the scope of the patent at issue. As to whether the piston seat, an essential element of the allegedly infringing product, reads on the claims of the patent under the “doctrine of equivalents”, the court described the piston seat as having "a bottom of the same thickness that can displace upward when the clamping rod is pushed from the top.” Regarding the plaintiff's argument that the piston seat of the prior art additionally has an additional O-ring that is different from the allegedly infringing product, the Court assumed that this O-ring does not affect the structure or function of the piston seat of the prior art compared with the allegedly infringing product that drives the clamping rod. Moreover, the allegedly infringing product falling within the scope of the patent does not include an O-ring, neither does the patented invention. Accordingly, it is not necessary to consider the connection relationship between the O-ring and other components of the prior art in determining the applicability of the “prior art” defense. The Court then held that the technical features of the allegedly infringing product falling within the scope of the patent at issue are the same as those of the single prior art, and in view of the “prior art” defense, selling of the allegedly infringing product does not constitute an infringement under the “doctrine of equivalents.”
The issue in this case is whether the prior art with additional technical features would be the same as an allegedly infringing product. The IPC Court focused on exploring whether the additional technical features of the prior art would affect the structure or function of the prior art as compared with the allegedly infringing product, and whether these additional technical features read on the claims of the patent at issue.
This case highlights the importance of accurately identifying the technical features of an allegedly infringing product and whether a prior art defense could be raised by the defendant to preclude infringement.