Japanese case law has established the following five requirements for finding patent infringement under the doctrine of equivalents (see Ball Spline Bearing Case, Supreme Court decision of February 24, 1998, and Maxacalcitol Case, Supreme Court decision of March 24, 2017).
(1) An element of a patented invention that is different from the alleged infringer’s product is not an essential element of the patented invention (non-essential element).
(2) The purpose, functions, and effect of the patented invention can be achieved by substituting the deviating feature with the defendant’s product (possibility of substitution and identity of functions and effect).
(3) It was readily conceivable at the time of manufacture of the defendant’s product to replace the deviating feature with the feature of the defendant’s product (readily substitutable).
(4) The defendant’s product was not identical to the generally known prior art or not readily conceivable on the basis of the generally known prior art at the time the patented invention was filed.
(5) There are no special circumstances such as that the defendant’s product was intentionally excluded from the claim in the prosecution of the patented invention.
It was common for Japanese courts to refuse to apply the fifth requirement based on a doctrine called “file wrapper estoppel” and to deny infringement under the doctrine of equivalents with respect to a constitutive element added by amendment in the course of the proceedings in response to a rejection notice for lack of novelty or inventive step.
Meanwhile, the Tokyo District Court issued two judgments holding that the fifth requirement was satisfied and recognizing infringement under the doctrine of equivalents with respect to a constitutive feature added by an amendment in response to a rejection notice for lack of inventive step. These cases are analyzed below in comparison with developments in the United States, Germany, and the United Kingdom.
Tokyo District Court, 2017 (Wa) 18184, Osteotomy Spreader Case
The court recognized a infringement under the doctrine of equivalents by satisfying the fifth requirement as follows: “The written statement does not contain any statement indicating that the plaintiff was aware of the issue of whether the interventional part is designed as part of the swing element or as an element separate from the swing element. Therefore, it cannot be concluded from the statement in the written opinion that the plaintiff intentionally excluded the configuration of the engagement part separate from the swing member from the scope of the claim at the time of adding the component E by the amendment filed together with the written opinion.”
Tokyo District Court, 2016(Wa) 25436, Method of producing L-glutamic acid case
The court confirmed the existence of infringement under the doctrine of equivalents by satisfying the fifth requirement as follows: “It was not readily possible for the applicant to specify a specific configuration using a mutated yggB gene from Corynebacterium callunae that would solve the problem to be solved by invention 2 and to recite it in the claims in a form that would satisfy the support requirement and other description requirements at the time the application for invention 2 was filed. Therefore, no special circumstances can be found.”
It is particularly noteworthy that the time at which it could be determined whether the configuration was foreseeable was when the application was filed. Although the reason for this is not explained in the text of the ruling, it would be too strict for an applicant to make this determination by reference to the time of amendment. In other words, assuming that it was readily possible for the applicant to indicate the configuration in the claims in a form that satisfied the support requirement and other description requirements at the time of amendment, the amendment is only possible within the scope of the original description at the time of filing.
The question of whether the equivalent was foreseeable at the time of filing is consistent with the U.S. Supreme Court’s May 2002 decision in Festo. The Court, while acknowledging that a “flexible bar” approach was being applied, identified the following three possible reasons for rebutting the “prosecution history estoppel”: (i) the equivalent was not foreseeable at the time of filing; (ii) the rationale underlying the amendment is only tangentially related to the equivalent; or (iii) there is some other reason indicating that the patentee could not reasonably be expected to describe the equivalent in the specification. (However, the Court of Appeals for the Federal Circuit has subsequently issued many decisions determining such foreseeability with respect to the timing of the amendment; in particular, many subsequent CAFC decisions have provided a basis for the criterion that “such foreseeability with respect to the timing of the amendment” is different from the decision in the Festo case cited above.)
(Yasuyuki Aichi, “Prosecution history estoppel and the doctrine of equivalent material at the time of filing date, and the doctrine of equivalents” Japan Industrial Property Law Academy Journal (2015))
This prevailing approach to recognizing infringement under the doctrine of equivalents for components added in response to an Office Action for lack of inventive step, subject to the application of the “flexible barrier” approach, was also upheld by the UK and German Supreme Courts in the Eli Lilly cases, which were litigated in the courts of several countries immediately preceding the two Japanese court cases mentioned above. The authors expected that the Japanese courts would follow this approach, and indeed they did.
The Eli Lilly cases in the U.S., U.K., and Germany: all courts affirmed infringement under the doctrine of equivalents with respect to a narrowed claim under Amendment.
● UK Supreme Court decision  UKSC48 (v. Actavis), the first UK Supreme Court decision to affirm infringement under the doctrine of equivalents
⇒The court held that the amendment in question, which narrowed the claims in the European patent application process, was made for the sole purpose of satisfying the requirements for amendment, i.e., to avoid rejection on the basis of new subject matter that constituted an impermissible intermediate generalization.
● Federal Court of Justice  X ZR 29/15 (v. Actavis).
The court held that infringement under the doctrine of equivalents must be denied if the amendment was made to limit the subject matter over the prior art; however, such infringement is not precluded if the amendment was necessary to satisfy formality requirements (e.g., requirement of new subject matter or clarity requirement) because such an amendment was not based on a voluntary decision of the patentee.
● U.S. CAFC [2019.8.9] (Eli Lilly and Company v. Hospira, Inc.)
⇒An applicant who amended the claim to narrow its scope in order to resolve substantial issues of patentability during prosecution is barred by prosecution history estoppel. An applicant who has made such an amendment is presumed to have waived any equivalents that might exist between the original claim and the amended claim. The patentee can rebut this presumption by showing that the amendment has no more than a tangential relationship with the equivalent in question.
Finally, I would like to introduce the March 24, 2017, Japanese Supreme Court decision, the Maxacalcitol case, which is an important court case discussing the fifth requirement of the doctrine of equivalents. It should be noted that this decision refers to a disclosure-dedication doctrine, not the file wrapper estoppel mentioned above. Broadly speaking, the disclosure-dedication doctrine is a rule that precludes a patentee from invoking the doctrine of equivalents because the patentee is deemed to have dedicated to the public any subject matter that is disclosed but not claimed in the specification.
The Supreme Court held as follows: “If an applicant omitted the configuration of the defendant’s product from his claim at the time of filing the application, even if it was readily conceivable, and if the applicant can be presumed to be unaware of the configuration of the defendant’s product, the doctrine of equivalents applies, and if the applicant can be presumed to have expressed an intent to omit the configuration from the claim even though he recognized that the configuration may objectively and visibly substitute for the configuration recited in the claim, a special circumstance may be found, such as B., that the defendant’s product was intentionally excluded from the claim in the course of prosecuting the patented invention.”
That being said, there are few, if any cases in Japan, including the Maxacalcitol case, where the court applied the disclosure-dedication doctrine to refuse to apply the fifth requirement of the doctrine of equivalents. This is a general theory inferred by the Supreme Court’s decision, but there may be some risk for alleged infringers to rely on it.
NAKAMURA & PARTNER
Attorney at Law