7.5.2 Doctrine of equivalents
There are no Japanese statutes that refer to finding patent infringement under the doctrine of equivalents. However, case law has introduced the concept of equivalence into Japanese patent law.
7.5.2.1 Five requirements of the Ball Spline Bearing Case
In the Ball Spline Bearing Case,194 the Supreme Court stated that a patent can be found to have been infringed not only by a product or process that falls within the literal scope of a patent claim but also under the doctrine of equivalents. The Supreme Court set out five requirements for finding patent infringement under the doctrine of equivalents:
- 1. The claim elements that are lacking in an allegedly infringing product or process are not essential parts of the patented invention.
- 2. The purpose of the patented invention can be achieved, and the same function and effect can be obtained, if the lacking claim elements are replaced with corresponding parts in the allegedly infringing product or process.
- 3. It would have been easy for a person having ordinary skill in the art to conceive of the idea of replacing the lacking claim elements with the corresponding parts in the allegedly infringing product or process at the time of the act of infringement.
- 4. The allegedly infringing product or process was neither identical to nor easily conceived from prior art at the time the application for the patent was filed.
- 5. No special circumstances preclude the doctrine of equivalents, such as where the allegedly infringing product or process was intentionally excluded from the scope of the claim during patent prosecution before the JPO.
The Supreme Court explained the grounds for finding patent infringement under the doctrine of equivalents in relation to these five requirements as follows:
It is extremely difficult to foresee all the types of infringements which may occur in the future and to formulate the scope of the patent claim in the specifications, and it will greatly reduce the incentive for invention in society in general if persons are able to easily avoid becoming subject to grants of injunctive relief and other exercises of rights by the patent holder by merely replacing part of the claim elements with the substance or technology which came to be known after the patent application. This would not only be contrary to the purposes of Patent Act – to the promotion of the development of industry through the protection and encouragement of invention – but would also be contrary to the principle of social justice and the idea of fairness.
Taking this into account, the substantive value of the patented invention extends to the technology which a third party can easily conceive as substantially equivalent to the construction as indicated in the scope of the patent claim in the specification, and third parties should be expected to foresee this.
On the other hand, technologies which were already in the public domain, or which a person having an average knowledge in the area of the technology used in this invention could easily have conceived at the time of the patent application, since no one could in any case have obtained a patent therefor (Patent Act, Article 29), cannot be found to fall within the technical scope of the patented invention.
Furthermore, if a patent holder has acknowledged that technology is not within the technical scope of the patent claim, or their behaviour has indicated this to be the case, for example, by intentionally excluding the technology from the scope of the patent claim during patent prosecution, the patent holder is not entitled to claim otherwise afterwards, since this is against the doctrine of estoppel.
7.5.2.2 Burden of proof
According to decisions of the lower courts that have followed the Ball Spline Bearing Case and the Grand Panel of the IP High Court in the Maxacalcitol Case (see below):
- A patentee bears the burden of proof regarding Requirements 1–3 as prescribed in the Ball Spline Bearing Case to establish patent infringement under the doctrine of equivalents.
- An alleged infringer bears the burden of proof in relation to Requirements 4–5 for denying patent infringement under the doctrine of equivalents.195
7.5.2.3 Requirement 1: nonessential part
The criteria used to determine whether claim elements are essential have been the subject of case law. In the Maxacalcitol Case, the Grand Panel of the IP High Court opined as follows:
The substantial value of an invention which the Patent Act intends to protect exists in the disclosure to society of a means with a specific structure for solving a technical problem that could not have been solved by prior art, which is based on a unique technical idea that is not seen in prior art. Therefore, the essential part of a patented invention should be understood as the characteristic part which constitutes a unique technical idea that is not seen in prior art in the statements in the scope of claims of the patented invention. The aforementioned essential part should be found by first understanding the problem to be solved and the means for solving the problem of the patented invention […] and its effects […] based on the statements in the scope of claims and the specification and then determining the characteristic part that constitutes a unique technical idea that is not seen in prior art in the statements in the scope of claims of the patented invention.
The above opinion aligns with the majority of lower court decisions that have followed the Ball Spline Bearing Case.196 However, this formula was not enough to resolve the issue in the Maxacalcitol Case, where the enforced patent claim required that the starting material and intermediate for producing maxacalcitol were cis-form vitamin D structures, while those used in the allegedly infringing process had trans-form vitamin D structures that were geometric isomers. That is, even after finding that the claim element was a part of the patented invention, there remained the question as to whether the cis-form was essential or not. As to this question, the Grand Panel of the IP High Court found that the cis-form was not essential, on the following grounds:
That is, taking into account that the substantial value of a patented invention is defined depending on the degree of contribution in comparison with prior art in the relevant technical field, the essential part of a patented invention should be found, based on the statements in the scope of the claim and the specification and, in particular, through comparison with prior art stated in the specification, to be in accordance with the following principle: (i) If the degree of contribution of the patented invention is considered to be large in comparison to the prior art, an essential part of the patented invention is found to be a superior concept in relation to part of the statements in the scope of claims.[…] (ii) If the degree of the contribution of the patented invention is evaluated as not much more than prior art, an essential part of the patented invention is found to be the same as literally stated in the scope of claims.
However, if the statement of the problem in the specification, which is described as one that prior art could not solve, is objectively insufficient in light of prior art as of the filing date […] prior art that is not stated in the specification should also be taken into consideration for the purpose of finding a characteristic part which constitutes a unique technical idea of the patented invention that is not seen in prior art. In such cases, the essential part of the patented invention is found to be closer to the statements in the scope of claims compared to cases where it is found only based on the statements in the scope of claims and the specification, and the scope of application of the doctrine of equivalents is considered to be narrower.
In addition, in determining the fulfillment of the first requirement, that is, whether an element which is different from the allegedly infringing product, etc., is a non-essential part, it is not appropriate to first divide the claim elements stated in the scope of claims into essential parts and non-essential parts, and then consider that the doctrine of equivalents is not applicable to all of the claim elements that fall under essential parts, but it is necessary to first determine whether the allegedly infringing product, etc., commonly has the essential part of the patented invention as mentioned above, and then consider a difference not to be an essential part if the subject product, etc., is recognized as having said essential part. Even if the allegedly infringing product, etc., has a difference which is not the characteristic part that constitutes a unique technical idea that was not seen in prior art, this fact does not become a reason for denying the fulfillment of the first requirement.197
7.5.2.4 Requirement 2: possibility of replacement
The second requirement of the doctrine of equivalents is often referred to as the “possibility of replacement.” It is not always clear how or whether the function and effect of the allegedly infringing product or process can be judged to be the “same” as those of the patented invention when only allegedly trivial or immaterial differences exist. The courts have not provided any clear guidance on this issue.198
7.5.2.5 Requirement 3: ease of replacement
Regarding the third requirement, such judgment needs to be made in light of the level of technology at the time of the act of infringement. Therefore, for example, if an alleged infringer’s manufacturing and distribution of an allegedly infringing product continue despite pending court proceedings, a judgment should be made based on the level of technology at the time of the closing of the oral hearings.
7.5.2.6 Requirement 4: difficulty of conception
As stated above, an alleged infringer bears the burden of proof when arguing its defense under the fourth requirement. The alleged infringer’s argument under this requirement may overlap, to some extent, with a defense based on patent invalidity due to a lack of novelty or inventive step. Under this requirement, the alleged infringer needs to establish that the allegedly infringing product or process was neither identical to nor easily conceived from the prior art while also establishing patent invalidity, which requires that the patented invention was identical to or easily conceived from the prior art.
7.5.2.7 Requirement 5: no special circumstances
The fifth requirement is that there are no special circumstances that might preclude the application of the doctrine of equivalents. A typical “special circumstance” which the Supreme Court referred to in the Ball Spline Bearing Case is where the allegedly infringing product or process was intentionally excluded from the scope of the claim during patent prosecution before the JPO. This is similar to prosecution history estoppel, which can be raised by an alleged infringer as a defense against literal infringement.
In the Maxacalcitol Case, the alleged infringer argued that there was a special circumstance preventing patent infringement from being found based on the doctrine of equivalents. The applicant had not crafted the patent claim so that it included the process where the starting material and intermediate for producing maxacalcitol had trans-form vitamin D structures, even though ordinary persons having ordinary skill in the art could have easily conceived using such a material at the time of patent filing. The Supreme Court accepted the appeal of the alleged infringer on this issue but ultimately rejected the argument:
- (1) […] even in a situation where the scope of patent claims written by the patent applicant do not mention the structure for allegedly infringing products or processes different in part from the structure stated in the scope of claims while the applicant was able to easily conceive the structure for such allegedly infringing products or processes at the time of filing the application, the mere fact of such omission in the scope of the patent claims does not constitute a special circumstance such as where the allegedly infringing products or processes were intentionally excluded from the scope of patent claims in the course of filling the patent application.
(2) […] in cases where the applicant has failed to describe the structure of allegedly infringing products or processes that are different from corresponding elements of the structure stated in the patent claims, the existence of special circumstances, such as the intentional exclusion of allegedly infringing products or processes from the scope of patent claims in the course of filing an application for a patent, should be found if the applicant is objectively and visibly determined to have indicated their intention of omitting statements concerning allegedly infringing products or processes in the scope of the patent claims while recognizing that the structure for the allegedly infringing products or processes could substitute for the structure stated in the scope of the patent claims.
In light of the facts explained in the above, nothing contained in the application for the patent indicates objectively and visibly the applicant’s intention of omitting to mention the structure for the applicant’s process in the scope of claims while recognizing that the structure adopted by the applicant, which was different in part from the structure stated in the scope of claims, could substitute for said structure.199
7.5.2.8 Other relevant cases
In an early equivalence case delivered shortly after the judgment in the Ball Spline Bearing Case and prior to the establishment of the IP High Court, the Osaka High Court found indirect infringement under Article 101 of the Patent Act with respect to a product that was used exclusively for the exploitation of the allegedly infringing process. The court decided that the process for which the product was exclusively used was equivalent to the process that fell within the literal scope of the patented claim.200 In another, more recent case, a patentee’s right to seek compensation for the unauthorized use of a patented invention – after the publication of an unexamined application but prior to registration of the patent right under Article 65 of the Patent Act – was found to extend to the unauthorized use of products or processes equivalent to those falling within the literal scope of the patented claim.201