Episode 23

Supreme Court rulings on the doctrine of equivalents include the Ball Spline case (Supreme Court ruling of February 24, 1998) and the Maxacalcitol case (Supreme Court ruling of March 24, 2017).
The doctrine of equivalents presented in the Ball Spline case typically assumes relief for patent holders when a new material with the same effect appears after filing, and the judgment of ease of substitution is also based on the time of infringement. In contrast, the Maxacalcitol case was a case in which the question of whether or not there was an infringement of equivalents occurred when a material with the same effect that already existed at the time of filing was used (Reference: Bessatsu Patent November 2021 issue, "Revisiting the Doctrine of Equivalents (Further Consideration of the Fifth Requirement of Equivalents)," by Ryoichi Mimura (https://jpaa-patent.info/patent/viewPdf/3830)).
In the original trial in the Maxacalcitol case (Intellectual Property High Court Grand Bench Judgment of March 25, 2016), the court ruled in determining the first requirement of equivalents (non-essential portions) that "given that the substantial value of a patented invention is determined according to the degree of contribution made by it in comparison with the prior art in its technical field, the essential portions of a patented invention should be determined from the claims and description of the specification, particularly a comparison with the prior art described in the specification; and, (i) if the degree of contribution made by the patented invention is evaluated as being greater than that of the prior art, then a portion of the claims will be recognized as a higher conceptualization, and (ii) if the degree of contribution made by the patented invention is evaluated as not being that great compared to the prior art, then it will be recognized almost the same as the description in the claims.
" Based on this premise, in determining the fifth requirement of equivalents (special circumstances), the court ruled that "when it is objectively and externally recognized that at the time of filing the application, another configuration outside the scope of the patent claim was recognized as a substitute for a different part of the configuration described in the claims, the fact that the applicant did not describe that other configuration in the claims can be said to be a 'special circumstance' under the fifth requirement."
The Supreme Court ruling in the Maxacalcitol case confirmed the above-mentioned ruling of the lower court. The Maxacalcitol case stipulated a set of methods for determining the first requirement of equivalents (non-essential parts) and the fifth requirement (special circumstances) so that infringement of equivalents could be applied even in cases where a material with the same effect that already existed at the time of filing was used.
The doctrine of equivalents was created in the Ball Spline case and fostered in the Maxacalcitol case.
Since the Maxacalcitol case, patent infringement litigation has entered a new stage, and literal infringement and infringement of equivalents have come to be examined together in patent infringement proceedings. In cases where the plaintiff does not claim infringement of equivalents, the courts have the practice of encouraging the plaintiff to claim infringement of equivalents. However, even if the court encourages the plaintiff to claim infringement of equivalents, it does not necessarily intend to recognize infringement of equivalents. This is to prevent the first instance court from pointing out the lack of fairness in its proceedings in the appeal court.