Practice Notes Doctrine of equivalents: recent developments
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Introduction / Supreme Court guidelines / Comment
A patented invention is infringed when another invention (hereinafter the ‘accused invention’) comprises all elements of the patented invention and the relationship between the elements of the accused invention are the same as those in the patented claim (all elements rule).
The all elements rule applies not only to literal infringement but also to equivalent infringement. Equivalent infringement is acknowledged when a specific modified element is evaluated as having equivalence to the corresponding element in the patented claim.
According to the doctrine of equivalents, even when the accused invention includes a modified element in contrast with the elements in the patented claim, if they are practically equivalent, the accused invention infringes the patented invention.
The Supreme Court has set the following guidelines for applying the doctrine of equivalents (Case 2017HU424, 31 January 2019):
- the accused invention and the patented invention must adopt the same problem-solving principle;
- the accused invention must exhibit substantially the same working effects as those of the patented invention (modifiability);
- a person with ordinary knowledge in the technical field to which the invention pertains (a person skilled in the art) must be able to obviously make such a modification (obvious modifiability);
- the accused invention should not represent art which was known at the time of filing the application of the claimed invention or art which could easily be conceived by a person skilled in the art from publicly known art (free-to-work technology defence); and
- the changed element of the accused invention should not represent that which was intentionally omitted from the claims of the claimed invention during the prosecution of the application of the claimed invention (file wrapper estoppel).
In order to meet the infringement requirements based on the doctrine of equivalents, all of the above factors must be satisfied. If one of the negative conditions applies – namely, either the fourth or fifth factor, there is no infringement.
The Supreme Court has specifically addressed the first factor as follows:
When determining whether the accused invention and the patented invention adopt the same problem-solving principle, there should be substantial examination as to what the core of the technical idea forming the basis of the unique problem-solving principle of the patented invention is, in comparison with the prior art, taking into consideration the disclosures in the detailed description of the specification and known technologies at the time of filing of the patented invention. In particular, how broadly or narrowly to interpret the problem-solving principle of the patented invention should be determined according to the extent of the contribution made by the patented invention to the advancement of technology, in consideration of the prior art.
According to this ruling, if the core of the technical idea was not already disclosed at the time of filing the patented invention, it must be determined whether the broadly interpreted problem-solving principle is implemented in the accused invention. If so, the first factor will be considered satisfied. Even if there are additional differences in the elements that are not directly related to the problem-solving principle, the first factor will still be considered satisfied.
If this factor is satisfied in this way, the second factor will also be considered satisfied as long as the modified element has no significant difference in the working effects compared with those of the patented invention.
In contrast, if the core of the technical idea was already disclosed at the time of filing the patented invention, since the problem-solving principle cannot be said to be unique to the patented invention, it must be determined whether the modified element has the same working effects in terms of individual functions or roles (Case 2018DA267252, 31 January 2019). Thus, in most cases, the second factor would be considered unsatisfied.
In accordance with these court rulings it is now possible for patents to be protected according to the real value of the invention, which is appraised in consideration of prior art. The problem is that judgments may vary with respect to what constitutes the core of the technical idea forming the basis of the unique problem-solving principle of the patented invention. As such, there is arguably increased uncertainty about the possibility for equivalent infringement.
Wirtten by Young-min KIM