In a case when an accused product (or process) satisfies all
elements defined in a claim of a patent, the accused product
literally infringes the patent. As in the US and Japan, even
when an accused product does not fall within the literal scope
of the claim but is equivalent to the claimed invention, patent
infringement under the doctrine of equivalents has been
acknowledged by many precedents in Korea. As an accused product
often involves a modified element different from a patented
invention, it is important to understand the principle of the
doctrine of equivalents.
According to the decisions of the Korean courts, an accused
product that includes a modified element as compared with a
patented invention may still be recognised as infringing the
patent under the doctrine of equivalents when the following
requirements are met:
- the technical idea or principle to solve a problem is
identical between the patented invention and the accused
- the accused product with the modified element
accomplishes substantially the same function and effect as
the patented invention; and
- the modification of an element in the patented invention
to the corresponding element in the accused product is
obvious to a person skilled in the art.
Regarding requirement (i), in the past, the accused product
was considered to have the same technical idea or principle to
solve a problem as the patented invention when the modified
element of the accused product was a non-essential part of the
patented invention and the accused product thus had the
characteristic constitution of the patented invention.
In Supreme Court Case No 2012Hu1132 (July 24 2014), the
Supreme Court ruled that whether two inventions adopt the same
technical idea or principle to solve a problem should be
determined by comparing the "essence or core of the technical
idea" based on the disclosures of the specification and known
technologies as of the filing date, rather than by extracting a
part of the constitution recited in the claim.
In this case, the patented invention relates to a cutter for
dried seaweed which has cutting blades laid out in a grid
pattern. When seaweed is placed on top of the cutting blades
and pressed downward, the cut seaweed is automatically stored
in a container by sliding down an incline of a grid-patterned
box attached to the bottom of the cutting blades.
The accused product, on the other hand, has cutting blades
moving downward from above the seaweed, unlike the cutting
blades of the patented cutter fixed below the seaweed. The
seaweed cut by the cutting blades in the accused product also
automatically slides down an incline of a grid-patterned box
and then is stored in a container.
The Supreme Court decided that although the patented
invention and the accused product use different cutting blades,
the two inventions adopt the same core of the technical idea
that the incline of the grid-patterned box leads seaweed to
automatically move to a container after being cut, concluding
that the accused product falls within the scope of the patent.
This case is of significance in that the possibility of falling
under the doctrine of equivalents has been increased by
applying requirement (i) flexibly.
The doctrine of equivalents may not apply if the accused
product was already known or could have been easily conceived
from the prior art by a person skilled in the art at the time
of filing the patent, or if the accused product was
intentionally excluded from the scope of the claim during the
prosecution of the patent (see for example Supreme Court Case
No 97Hu2200 rendered on July 28 2000).
Whether a specific element was intentionally excluded from
the scope of a claim (so-called prosecution history estoppel or
file wrapper estoppel) is determined based on the prosecution
history of the patent at issue, including the examiner's office
action, the applicant's response and amendment, etc, in
addition to the patent specification (see for example Korean
Supreme Court Case No 2001Hu171 dated September 6 2002).
For example, if a broadly defined constitution is restricted
to a particular element so as to cover only a specific
embodiment of an invention in response to the examiner's
rejection for lack of an inventive step, elements other than
that specified may be considered to be excluded from the
protection scope of the claim. In contrast, when a claim
amendment is made to resolve clarity issues, whether the
deleted element(s) may be deemed to be intentionally excluded
by the applicant may be determined in consideration of special
circumstances of individual cases.
The Japanese Supreme Court recently affirmed infringement of
a process patent under the doctrine of equivalents (Chugai
Pharmaceutical Co Ltd v Takata Seiyaku Co, Ltd et al,
2017(Ju)1242, Mach 24, 2017). Also, the United Kingdom Supreme
Court provided an expanded interpretation on patent
infringement under the doctrine of equivalents in July
(Actavis UK Limited and others v Eli Lilly and
Company,  UKSC 48, July 12 2017). The Korean courts
seem to take a similar position to the current worldwide trend
of applying the doctrine of equivalents in an expanded way.
HANOL Intellectual Property & Law
6th Floor, 163, Yang Jae Cheon-Ro, Gang Nam-Gu
Seoul 06302, Republic of Korea
Tel: +82 2 942 1100
Fax: +82 2 942 2600