21 Application of the Doctrines Limiting the Doctrine ofEquivalents and Claim Drafting Concerning U.S. Patents－Foreseeability and Importance of Claim Limitations in
Limiting the Range of Equivalents－
Short-term Overseas Research Fellow: Taijiro Takase（*）
In the modern United States, the doctrine of equivalents has been applied for the purpose of preventing
infringers from copying patented inventions by making a minor variation of the invention. The application of
the doctrine had been expanding since the Graver Tank Supreme Court decision until such trends turned
around to limit the application of the doctrine in the wake of the Warner-Jenkinson Supreme Court decision.
This is due to the application of doctrines limiting application of the doctrine of equivalents, and the strict
application of the All Elements Rule has much to do with it. Behind that there is difficulty in finding acompromise between the protective function of claims, which has been expanded by the doctrine of equivalents,
and the definitional and public-notice functions, which claim language is required to fulfill, due to theirconflicting relationship. In this research, the author studied the role of claim limitations in limiting applicationof the doctrine of equivalents and the recent way of thinking about their importance, focusing on the latest CAFC
decisions. The author also discussed claim drafting that is adapted to the current situation, as well as
examining the movement to introduce foreseeability by a person skilled in the art into doctrines limiting
application of the doctrine of equivalents.

Ⅰ Introduction
The doctrine of equivalents functions as aneffective means of protecting inventions against
patent infringing embodiments that cannot becovered by literal infringement. On the other hand,the excessive application of the doctrine may force
competitors to conduct commercial activities under
the constant concern that they might be infringing
patented inventions, which are unclear. This hinders
sound technological and market competition, which
is an ongoing problem with the application of thedoctrine of equivalents.
The U.S. Supreme Court’s 1950 decision in theGraver Tank(*1) case laid the foundation of aformula for applying the doctrine of equivalents inthe modern era. However, the loss of the
public-notice and definitional functions of claims
was of concern since the doctrine of equivalents
had been applied to claims “as a whole.”
Subsequently, in the Warner-Jenkinson Supreme
Court decision(*2) in 1997, the court adopted theguideline for application of the doctrine ofequivalents on an element-by-element basis, which
was presented by the Pennwalt en banc decision.(*3)
Thereby, the current system was established. This
report studied mainly decisions rendered and
（*）
(*1)
(*2)
(*3)

discussions held by the United States Court ofAppeals for the Federal Circuit (CAFC) to know
the present situation of application of the doctrineof equivalents placing emphasis on limitations.
Moreover, this report introduces the determinationof infringement of a functional claim and theprinciples of claim construction that have recently
been reexamined by practitioners and scholars in
the United States, for the purpose of considering a
guideline for claim drafting and the future directionof the doctrine of equivalents. Then, this reportmakes some comparisons between the ideas ofprotection by patent and public interest behindthese U.S. decisions and requirements forapplication in Japan, and considers the similarities
and differences between them.

Ⅱ Recent Decisions Relating to theDoctrine of Equivalents andClaim Construction Principles
1Application of the doctrine of equivalents
placing emphasis on limitations(1) Where application of the doctrine ofequivalents is precluded
The application of the All Elements Rule toCurrently Intellectual Property Division, The Furukawa Electric. Co., Ltd.
339 U.S. 605, 70 S.Ct. 854 (1950).
520 U.S. 17, 117 S.Ct. 1040 (1997).
833 F.2d 931, 4 USPQ2d 1737 (Fed.Cir. 1987).

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the doctrine of equivalents presented in the
Warner-Jenkinson Supreme Court decision was
handed down in subsequent court decisions,
including the Sage Products decision(*4) in 1997.
When a limitation is deemed to have clearly
limited a relevant invention, the doctrine ofequivalents will not be applied to it on the groundthat a meaningful limitation of a claim will be
vitiated if the doctrine is applied. This doctrine iscalled a “claim vitiation doctrine,”(*5) of which oneof the purposes is to prevent the unfair act ofattempting to expand rights under the doctrine ofequivalents during litigation after undergoing
examination with narrow claims. This doctrine isapplicable in two cases. One is a case relating to asimple structural invention, such as Sage andFreedman. In such cases, the doctrine ofequivalents is not applicable because these cases
are considered to not involve unforeseeability due
to change in technology, and the inventor thus
must bear the cost of its failure to claim a subject
matter.
In Freedman,(*6) a structure of stowable seatsthat are usable in public transportation vehicles
was deemed to be a “relatively simple” structural
invention because the relevant patent claim
included a clear limitation. Consequently, thedoctrine of equivalents was not applied to othertypes of four bar mechanisms, which, except forthe slider crank, constitute the principal part ofthe invention.
On the other hand, inventions with a morethan-simple structure are excluded fromapplication of the doctrine of equivalents due toapplication of the “specific exclusion” principle(*7)
not only when the claim language includes a clear
limitation but also intrinsic evidence is deemed tohave excluded a specific subject matter. The
reason for exclusion is that a finding ofequivalence to a specifically excluded subject
matter would vitiate the limitation. Although
extrinsic evidence and frequency of appearances
in description in the specification are also taken
into consideration, the meaning of a limitation isbasically determined to be clear when argument
for patentability or content of the specification isconsistent. In Gaus, (*8) application of thedoctrine of equivalents was denied on the
grounds that the claim language was clear andthat the patentee avoided prior art and clarified
the invention in intrinsic evidence. In Asyst
Tech(*9) (claim1) also, a limitation was construed
not to include the invention excluded by intrinsic
evidence.
It is not only when a claim limitation is clear
and when limitation of the scope of an invention
has been clearly specified during the prosecutionthat the meaning of language is defined byintrinsic evidence and analysis is conducted onwhether application of the doctrine of equivalents
vitiates a limitation. In V-Formation,(*10) the
parties concerned discussed whether rivets
qualify as “releasable fasteners” used to attach awheeled plate. However, the scope of releasable
fasteners cannot be defined by claim language
alone. In this case, the scope of “releasable” thatone skilled in the art recognizes was determined
not to include rivets, based on the prior art
disclosed in intrinsic evidence (Information
Disclosure Statement; IDS). On the ground of alack of literal correspondence, the court
concluded that if the accused product was foundto meet the limitation under the doctrine ofequivalents, the limitation would be ignored.
In Gaus, the court stated that a disclaimer isdeemed to disclaim particular subject matterirrespective of whether it is express or implied,
so it may be undeniable the possibility to be taken
as a disclaimer even if a subject matter is not
expressly disclaimed.
With regard to the application of the doctrineof equivalents that is considered to “ignore alimitation,” discussion on claim 6 in Ethicon(*11) in
1998 -relating to a patent for medical stapler- is
informative. The court implied that it would notdeny application of the doctrine of equivalents if
the lockout mechanism were located near thelongitudinal slots as stipulated in the claim.
However, the court determined the accused
device, which has the lockout mechanism
opposite the stapler, to be substantially different
from the claimed device even though it has notbeen “specifically excluded.”(*4) 126 F.3d 1420, 44 USPQ2d 1103 (Fed.Cir. 1997).
(*5) 420 F.3d 1350, 1362, 76 USPQ2d 1001 (Fed.Cir. 2005).
(*6) 420 F.3d 1350.
(*7) 402 F.3d 1188, 1195, 74 USPQ2d 1272 (Fed.Cir. 2005).
(*8) 363 F.3d 1284, 70 USPQ2d 1380 (Fed.Cir. 2004).
(*9) 402 F.3d 1188, 74 USPQ2d 1272 (Fed.Cir. 2005).
(*10) 401 F.3d 1307, 74 USPQ2d 1042 (Fed.Cir. 2005).
(*11) 149 F.3d 1309, 47 USPQ2d 1272 (Fed.Cir. 1998).

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(2) Where the doctrine of equivalents is
applicable
As mentioned below, application of thedoctrine of equivalents will not be precluded if a
claim limitation and the allegedly infringing
product have a certain relationship. On the other
hand, cases where the doctrine is broadly applied“as a whole” are consolidated into cases involving
after-arising equivalents and pioneer inventions.
This point is mentioned later.
(a) Subtle difference in degree
In Ethicon, the court determined thatequivalence between claim 24 and the accused
device under the doctrine of equivalents could not
be denied because there was merely a “subtle
difference in degree” between them in terms oftiming of releasing the lockout mechanism toprevent glitches of the pusher bar (as short as a
few thousandths of a second).
In addition, in Riles,(*12) the accused method
was not found to literally meet the “metal-tometal bearing contact” limitation because there
was a layer of wooden timbers on the surface
where the leveling porch and the piling come incontact. However, it was found to meet thelimitation under the doctrine of equivalents on
the ground that the difference is “insubstantial.”
Inserting about a 20 cm layer of wood timbers
into a several dozen-meter structural member is
included within the scope of “subtle difference indegree,” as mentioned in Wright Medical(*13) andEthicon.
(b) Combination of limitations and separationof a limitation
Two examples of application of the doctrineof equivalents studied at this time are based on
the “combination of limitations and separation ofa limitation.” In Eagle,(*14) regarding a sealing
structure attached to the collet of a signal filter,the court determined that the “front cap” and“rear body” limitations were not lost due tocombination of the “front cap” and “rear body” ofthe collet assembly, but that the “self-seals at theinterface between the collet assembly and thefilter housing” limitation was essential.
Riles relates to a patent of process of installing
offshore platforms. The court determined that theclaimed “stabbing connection (an end-to-end
joining of two metal tubes by the insertion of an

extension attached to the end of one of the tubes
into the end of the other)” limitation is not literally
met by the corresponding part of the accused
platform, which consists of multiple components (a“guide sleeve” that guides the piling to the end of
the leveling porch and a “leveling porch” that
contacts the piling at the end; without either an“extension” or insertion into the end of the tube),
but it is met under the doctrine of equivalents.
That is, by assuming that extension and the end ofpiling, which is inserted to guide sleeve, areequivalent, and based on the description in thespecification that the piling side may be inserted
into the other side contrary to the structure of theembodiment, the court found that substantially thesame function as that performed by the claimed“stabbing connection” limitation was performed by
the two elements of the accused process (in thisreport, “separation of a claim” refers to cases
where one limitation of a claim corresponds tomultiple components of the allegedly infringing
product).
In short, even if the form of the patented
invention and that of the accused product are not
the same, for example, in the case where two
claim limitations are simply combined into one in
the accused product, like in Eagle, or where acomponent corresponding to one claim limitationis separated in the accused product, like in Riles,
the difference would be regarded as insubstantial
if substantially the same function, action andeffect are achieved.
This idea is similar to the idea of separationof a limitation of claim 24 in Ethicon. In this case,it was determined that two components of theaccused device may function as one claim
limitation unless the “movable by” limitation isvitiated.
That is, discussion on substantial identity interms of separation of a limitation does not seemto require strong structural identity unless theessential technical idea in the limitation is lost.
Therefore, if the applicant could successfully set
a limitation in the nature of the technical idea
(dominant conception) in the claim language, as inthese cases, the structural rigidness will be
alleviated and the doctrine of equivalents may be
applied based on separation of a limitation.
(c) Reciprocal change
If a reciprocal relationship exists between(*12) 298 F.3d 1302, 63 USPQ2d 1819 (Fed.Cir. 2002).
(*13) 122 F.3d 1440, 43 USPQ2d 1837 (Fed.Cir. 1997).
(*14) 305 F.3d 1303, 64 USPQ2d 1481 (Fed.Cir. 2002).

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claim limitations and the relationship issubstantially maintained, the doctrine ofequivalents will be applied. In Corning Glass(*15)
in 1989, an optical fiber that increases therefractive index through addition of a dopant tothe core was claimed. In the accused fibers, therefractive index was decreased through additionof a dopant to the cladding. In this case, the court
found equivalence under the doctrine ofequivalents, placing importance to the refractive
index differential between the core and cladding.
Unlike this case, the doctrine of equivalents is notapplicable to a rearrangement of three or more
limitations.
(A) Amendment and discussion
In Eagle, the court examined application of
the prosecution history estoppel to a combinationof the two limitations of the patent claim. Afterthe patentee’s consistent argument during theprosecution, the examiner added an amendment
and the patent was registered. On the contrary,
the alleged infringer argued that application of thedoctrine of equivalents was precluded not under
the amendment-based estoppel but under the“argument-based estoppel.” An argument-based
estoppel requires a “clear and unmistakablesurrender of subject matter,” and for the reasonof lack of such surrender, a combination of two
limitations was found to be equivalent to the“front cap” and “rear insert body” limitations
under the doctrine of equivalents. Also in Riles,
the court admitted application of the doctrine ofequivalents on the ground that the argument on
the “metal-to-metal bearing contact” limitation
made by the patentee during the prosecution does
not clearly surrender the disputed subject matter.
On the other hand, when the patentee has
made an amendment, it has to prove any one of
the three conditions for rebuttal presented in
Festo, based on the presumption that any
amendment relates to patentability.(*16) In addition,
grounds for rebuttal have to be those which havebeen shown in intrinsic evidence, except for the
first ground relating to foreseeability.(*17) It seems
that there have not been sufficient judicial
precedents with respect to the guideline formeeting conditions for rebuttal based onforeseeability as of present. Taking these points
into account, applicants should, as a matter ofcourse, avoid making unnecessary amendments
when possible and make minimum necessary
assertions wherever possible.
2

Claims including equivalents in theirlanguage – Functional claims

In the present situation where a clear
limitation of a claim is used to limit theapplication of the doctrine of equivalents,
functional claims by which technical ideas can be
expressed in functional language may work
effectively. However, functional claims involvethe concept of “equivalent structure,” so there isthe concern that such claims are restrictively
construed depending on the content disclosed in
the specification. To prevent this, it is necessary
to pay attention to giving the embodiment room
to expand while taking into consideration the ideathat the range of equivalent structures maychange depending on the importance of structuralfeatures in the function.(*18)
In regard to relationships between the rangeof equivalent structures and the importance ofstructural features that characterize functional
elements, it has been pointed out that IMS
Tech(*19) and Kemco(*20) are conflicting.(*21) In IMS
Tech, the court stated that the range of equivalent
structures should be determined not based on
structural similarities but in the context of theinvention, and that the range might be broadened
depending on the importance of the structuralfeatures of functional elements. On the other
hand, in Kemco, the court stated that the range ofequivalent structures would be determinedmerely based on a comparison of structures. In
light of this, a recent trend is considered below,
through examination of Asyst Tech and Utah
Medical.(*22)
In Asyst Tech relating to a system ofcontrolling semiconductor wafers, the court heldthat the entire function of “sensing the presence(*15) 868 F.2d 1251, 9 USPQ2d 1962 (Fed.Cir 1989).
(*16) 122 S.Ct. 1831, 62 USPQ2d 1705 (2002).
(*17) 344 F.3d 1359, 1369, 1370, 68 USPQ2d 1321 (Fed.Cir. 2003).
(*18) Intellectual Property Management, vol. 48, no. 5 (1998): 663.
(*19) 206 F.3d 1422, 54 USPQ2d 1129 (Fed.Cir.2000).
(*20) 208 F.3d 1352, 54 USPQ2d 1308 (Fed.Cir.2000).
(*21) 16 Berkeley Tech. L.J. 71, 2001; 3 N.C. J.L. & Tech. 101, Fall 2001.
(*22) 350 F.3d 1376, 69 USPQ2d 1136 (Fed.Cir. 2003).

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of a container” was functionally identical to thestructure of “sensing means” disclosed in theembodiment, without being bound by the specificstructure of embodiment. This is because
structural features are not very important, as thesensing means only performs function of sensing
the presence of a container and that is not
functionally complex. The determination in thiscase is similar to determination in IMS Tech, inwhich the court held that the range of equivalent
structures might be broadened.
On the other hand, Utah Medical relates to ameans of stiffening the cable of the pressuretransducer. In this case, as with in Chiuminatta,(*23)
functional elements of functional claims arelargely characterized by the structure. Therefore,
the equivalent structures of “stiffener means”
shall be those like a steel stylet permanently
encased in the cable means, which is disclosed in
the embodiment. However, based on thedescription that the stiffener means is apermanent component of the overall cable means,the court applied determination in IMS Tech to
the effect that a structural limitation is notstrongly required.(*24) Thereby, “stiffener means”
was construed to include the plastic casing of thecable means. In this manner, this case shows thepossibility that the range of equivalent structures
may be broadened without being constrained
owning to support by the specification’s
description. Chiuminatta relates to a rotary saw
for cutting concrete before being completely
hardened. The two small wheels of the accused
device were found not to be substantially thesame as the skid plate of the claimed embodimenton the basis that they are different in terms ofimpact on a concrete surface as a “means forsupporting the surface of the concrete.” However,in this case, the court stated that the patent
disclosed the wheels but never suggested thatthe wheels could be replaced by the skid plate.
Therefore, if the patent suggested it, the result
might have been the same as in Utah Medical.
That is, when using a functional claim, it isimportant to consider the characteristics of thesubject matter and to describe the specification ina manner that prevents the range of equivalent
structures from being restrictively construed. If
only one embodiment has been disclosed and thespecification contains no description that opens
up options, the specification can only cover
structures that are almost identical to thedisclosed structure. In cases not involving
after-arising equivalents, if an accused structure
was found not to be an equivalent of the claimed
structure in literal analysis, it will be precluded
from application of the doctrine of equivalents forthe same reason. In this case, there is no point inusing functional claims, because the scope that iscovered is almost the same as the literal scope of
the patent in cases where it was claimed byordinary structural limitations.
3This principle is the one that has been in
existence from a long time ago as in Autogiro.(*25)
This study cover the principle in this reportbecause U.S. scholars and practitioners have beenreviewing it recently, as in Phillips.(*26) Below is
an outline of precedents relating to application of
the principle.
Where the principle is applicable(A) Different
claimshave
different
scopes.(*27)(B) Limitations stated in dependent claims
are not to be read into independent claim
from which they depend.(*28)(C) If different embodiments and functions
are disclosed in a dependent claim, an
independent claim is considered to include
them (the same applies in the case of
relationships
betweenindependent(*29)
claims).
Where the principle is not applicable(D) If a difference is only in style and not incontent, the principle is not applicable.(*30)(E) This principle cannot enlarge the scopeof claims determined by the content
disclosed in the specification as well asarguments during the prosecution.(*31)(F) If the difference between two different
claims is not merely superfluous, the(*23) 145 F.3d 1303, 46 U.S.P.Q.2d 1752 (Fed.Cir. 1998).
(*24) 350 F.3d at 1382-84.
(*25) 384 F.2d 391, 155 USPQ 697 (Ct.Cl. 1967).
(*26) 415 F.3d 1303, 75 USPQ2d 1321 (Fed.Cir. 2005).
(*27) 384 F.2d 391, 404, 413-414 (Ct.Cl. 1967).
(*28) 403 F.3d 1364, 1370 (Fed.Cir. 2005).
(*29) 415 F.3d 1303, 1324-27 (Fed.Cir. 2005).
(*30) 384 F.2d at 407 (Ct.Cl. 1967).
(*31) 831 F.2d 1017, 1023-24 (1987).

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principle will not be applicable.(*32)(G) If a presumption of “equivalent
structure” based on functional language iscontrary to this principle, the presumption
based on functional language will be given
priority (a presumption under §112, ¶6 isstronger than a presumption under claim
differentiation).(*33)
Among the above (A) to (C), presumption
works most strongly in the case of (B).(*34) In
short, the most basic way of using this principle is(B) above, in which the applicant stipulates alimitation, which is not desired to be read into anindependent claim, as a dependent claim. In
addition, the principle can be understood as therelationship between two random claims sinceeach claim is construed in the manner that its
corresponding embodiments and functions aredifferent from those corresponding to otherclaims.(*35)
However, since claim differentiation is firmly
based on relative relationships between two
claims, a claim can be determined only after adifference between that claim and the other claim
is primarily determined (for example, in (F)).
Moreover, this presumption is not at all strong
and it does not allow construction beyond thescope that is considered appropriate, based onother grounds. In such a case, several claims may
indicate the same scope.(*36)
Where an independent claim is a functional
claim, a structural claim as one form of functional
language seems unnecessary because of
relationships with an equivalent structure of afunctional claim as indicated in (G). In otherwords, where an equivalent structure of afunctional limitation is restrictively construed
into an embodiment, claim differentiation
presumption cannot expand the scope of thefunctional limitation since presumption based onfunctional language is stronger, and therefore, thestructural claim will not have any meaning. In thiscase, it is more important to broaden equivalent
structures of the functional claim.
Compared with the doctrine of equivalentsthat leaves uncertainties in claim language, thisprinciple appears to conform to the current trendemphasizing the public-notice function of claim
language since it does not go beyond the literal
scope. In other words, while the doctrine ofequivalents protects what could have been
undetermined at the time of filing due to theiruncertainties, the role of the claim differentiation
principle is contrasting to the doctrine ofequivalents in that it is designed to appropriately
construe what have been disclosed.

Ⅲ

Comparison with Requirements
for Application of the Doctrineof Equivalents in Japan

This chapter considers similarities anddifferences between Japan and the United States
based on the CAFC decisions and the trend
discussed in studies on cases after the Supreme
Court presented the guideline for application of
the doctrine of equivalents in Japan.(*37)
1First and second requirements

There is the view that the first requirement
for application of the doctrine of equivalents inJapan, i.e., the “essential part,” refers to the“scope to which the technical idea of the patented
invention extends” or the “identity of theprinciple of the solution.”(*38) There are two ideas
regarding determination of equivalence: (1)dividing an invention into the essential part andthe non-essential part and finding equivalence
only in terms of the non-essential part; (2)equivalence should be found if differences fromthe essential part is insubstantial.(*39) The second(*32) 73 F.3d 1573, 1580-81 (Fed.Cir. 1996).
(*33) 424 F.3d 1293, 1304 (Fed.Cir. 2005).
(*34) 413 F.3d at 1368-69 (Fed.Cir.2005)(*35) 403 F.3d at 1370 (Fed.Cir.2005).
(*36) 413 F.3d at 1369 (Fed.Cir.2005).
(*37) Supreme Court decision on February 24, 1998, Minshu, vol. 52, no. 1: 113 (Jokoku appeal instance for Ball Spline
Bearing case; Case No.: Heisei 6 (O) 1083).
(*38) Ryoichi Mimura, Jurist, no. 1134 (1998): 117; Toshiaki Makino, “Tokkyohatsumei no honshitsuteki bubun ni tsuite”(Concerning the essential part of a patented invention) (contained in Ryuichi Murabayashi and Etsuji Kotani, ed.,Tokkyosaiban ni okeru kintōron: nichibeiō sankyoku no taihi (Doctrine of equivalents in patent court: comparison
among Japan, the United States and Europe)) (Research Institute of Economy, Trade and Industry, 2003), 219;
Intellectual Property Management, vol. 51, no. 8 (2001): 1246.
(*39) Ryuichi Shitara, “Bōrusupurainjiken saikōsaihanketsu no kintōron to kongo no shomondai” (Doctrine of equivalents in
the Ball Spline Supreme Court decision and expected problems) (contained in Ryuichi Murabayashi and Etsuji Kotani,ed., cited above), 450; Seiji Ohno, Intellectual Property Management, vol. 54, no. 9 (2004): 1348-49.
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requirement, “interchangeability,” largely overlaps
the first requirement, therefore, some question
the significance of its existence.(*40) These
requirements are hard to distinguish, and arethought to function in a mutually complementarymanner while being similar in large part.
Also in the United States, the triple identity
test is not recognized as sufficient for assessing
the substantial identity of patent claims and theaccused product, and it is believed that thesubstantial
identityshouldbeexamined
flexibly.(*41) Multiple standards for determinationand flexible determination are used in combination
both in Japan and in the United States, and there isa similarity between the two countries despite thedifference in the perspective of determination by
tests.
The scope of “insubstantial difference” issimilarly understood in the two countries.
Specifically, it is understood as “subtle difference
in design” in Japan while as “subtle difference indegree” in the United Sates in the abovementioned Ethicon case. However, there is thedifference between these countries in the pointthat discussion is held in consideration of theimportance of limitations in Japan (*42) while it isheld based on the premise that “all limitations arematerial” due to introduction of the All Elements
Rule.
However, the substantial difference between
the two countries is not as significant as it
appears. Firstly, application of the All Elements
Rule serves as the premise of the way of
invention (i.e. the identity of the principle of the
problem solution),(*43) and there are exceptions toapplication of the “specific exclusion” principle,
such as “combination of limitations andseparation of a limitation” and “reciprocalchange.” Therefore, the essential part can becovered by them with some margin of error.
In addition, the “specific exclusion” principle
covers both the case where specific exclusionindicates the essential part of the invention, likein Dolly,(*44) and the case where it is considered to
be an intentional exclusion under the fifth
requirement.
2

Third and fifth requirements

The third requirement “interchangeability”
corresponds to “known interchangeability” in the
United States. The fact that both countries adopt
the time of infringement as the timing ofdetermination shows that they share the basic
idea that “after-arising equivalents” should beprotected.(*45) The most disputed point regarding
this requirement is the technical level of a person
skilled in the art, which is adopted in determining
whether an interchange could have been “easily
arrived.” In Japan there are two opinions that therequired technical level is (i) the same as that for
inventive step(*46) and is (ii) slightly lower thanthat for inventive step.(*47)
As for the United States, in Tanabe
Seiyaku,(*48) the court acknowledged avoidance of
application of the doctrine of equivalents bydesign-arounds since the accused product, which
the patentee argued was equivalent to theclaimed invention, had required further
improvement and the alleged infringer had foundconditions for that improvement through its
independent development.
Prior failures are cited in the secondary
consideration as the standard for determining
non-obviousness.(*49) The standard level of aperson skilled in the art in determining known
interchangeability is thought to be the same as(*40) On the other hand, there are opinions as in Seiji Ohno cited above (page 1349) and in Intellectual Property
Management, vol. 51, no. 8 (page 1248).
(*41) 520 U.S. at 39-40 (1997).
(*42) Ryuichi Shitara, cited above, 450; Seiji Ohno, Intellectual Property Management, vol. 51, no. 8: 1349.
(*43) 833 F.2d at 1577.
(*44) 16 F.3d 394, 29 USPQ2d 1767 (Fed.Cir. 1994).
(*45) Supreme Court decision cited above “Jokoku appeal instance for Ball Spline Bearing case”; 520 U.S. at 37 (1997).
(*46) Ryuichi Shitara, cited above, 453-454; Toshiko Takenaka, “Tanin no seihintō ga meisaisho no tokkyoseikyū no hani
ni kisaisareta kōsei to kintōnamono toshite tokkyohatsumei no gijutsutekihani ni zokusuru to kaisubeki bāi” (Casewhere another party’s product, etc. should be considered to belong to the technical scope of a patented invention as
an equivalent of a structure described in the scope of claims in the specification) (contained in Ryuichi Murabayashi
and Etsuji Kotani, ed., cited above), 485.
(*47) Nobuhiro Nakayama, Kōgyōshoyūkenhō jō: tokkyohō dai2han (Industrial property law (1): patent law (2nd ed.)),398; Etsuji Kotani, “Kintōron no dōkō” (Trend of the doctrine of equivalents) (contained in Ryuichi Murabayashi
and Etsuji Kotani, ed., cited above), 621.
(*48) 109 F.3d 726, 41 USPQ2d 1976 (Fed.Cir. 1997).
(*49) For example, Martin J. Adelman, Randall R.Rader, John R. Thomas & Halord C. Wegner, Cases and Materials on
Patent Law 369 (Thomson West 2d ed. 2003) (1998).

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that in determining non-obviousness.
The fifth requirement “intentional exclusion”
is represented by the prosecution history
estoppel. In Japan, amendment in response to arefusal under Section 36 of the Patent Law is also
seen as “act understood as such in appearance” incomparison with another amendment relating topatentability, and such amendment is subject tothe estoppel.(*50) This is similar to the fact that in
the United States, any amendment is considered
to be subject to the presumption that it “relates
to patentability.” However, there is a difference
on the point that, in the United States, the meansof rebutting presumption were presented in the
Festo decision in 2002.(*51)
Moreover, the systems of these countries aredifferent on the point that the United States
adopts the disclosure-dedication rule that waspresented by the Johnson & Johnston en bancdecision in 2002.(*52)Ⅳ
1Subject matter protected under
the doctrine of equivalents
Subject matter to be protected

In the United States, it is believed thatafter-arising equivalents should be primarily
protected. After-arising equivalents refer to what
could not have been known by a person skilled in
the art at the time of filing, and have become
outside the scope of claim language at the time of
infringement due to subsequent technologicaladvances. One of the related precedents is
Hughes,(*53) in which the court found that theembodiment of the infringing product createdthrough advancement of computer technology
after filing could have not been covered by claim
language. In addition, Judge Rader stated, as an
example, that regarding a claim using the terms“anode” and “cathode” before 1948, a lack of literalcorrespondence should be covered by the doctrineof equivalents if these terms are replaced with theterms “emitters” and “collectors” of transistor
technology after 1949.(*54)
It is also believed in Japan that the doctrineof equivalents should be applied to after-arisingequivalents.
With regard to pioneer inventions, thedoctrine of equivalents is also applicable to themin the United States, as mentioned above.(*55) On
the other hand, the broad scope of claims can beachieved due to the pioneering nature of theinventions, and there is neither a legal definitionof pioneer inventions nor a test for determining
them.(*56) Therefore, pioneering inventions appear
to be ambiguous and it is hard to paint a precise
picture of them. This is also the same in Japan.(*57)
2

Unprotected subject matter

There is also the discussion on limiting
application of the doctrine of equivalents based onforeseeability, and the patentee’s obligation andresponsibility in patent drafting is used as ameans thereof.
(1) What is foreseeable
In the United States (CAFC), Judge Rader
has been strongly advocating the limitation of
application of the doctrine of equivalents to what
is foreseeable by a person skilled in the art.(*58) In
the United States, the concept of foreseeability is
now applied in relation to the prosecution history
estoppel. If it becomes applicable in relation to
the entire doctrine of equivalents, after-arisingequivalents may become the only things to which
the doctrine of equivalents is applicable. On theother hand, there are some opinions that
foreseeability should be employed in limiting
application of the doctrine of equivalents in Japan.
In the United States, there is a Supreme
Court opinion that claim drafters “may be
expected to draft claims encompassing readily
known equivalents.”(*59) There is also the CAFC
en banc opinion that “When one of ordinary skill
in the relevant art would foresee coverage of an(*50) Intellectual Property Management, vol. 51, no. 9: 1404-1405.
(*51) 535 US 722, 740-741, 122 S.Ct.1831 (2002).
(*52) 285 F.3d at 1054-1055 (Fed.Cir. 2002).
(*53) 140 F.3d 1470, 46 USPQ2d 1285 (Fed.Cir. 1998).
(*54) 234 F.3d at 619 (Fed.Cir. 2000).
(*55) 822 F.2d 1528, 1532, 3 USPQ2d 1321 (Fed.Cir. 1987).
(*56) 181 F.3d 1291, 1301, 50 USPQ2d 1900 (Fed.Cir. 1999).
(*57) Shuhei Shiotsuki, “Chitekizaisanhō to gendaishakai (Makino Toshiaki hanji taikankinen ronbunshū)” (Intellectual
property law and modern society (collected papers commemorating the retirement of Judge Toshiaki Makino)): 105.
(*58) 344 F.3d at 1377 (Fed.Cir. 2003).
(*59) 535 US at 740 (2002).

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invention, a patent drafter has an obligation toclaim (all of) those foreseeable limits.” (*60) In
Japan as well, there is the opinion that “the prior
art exerting the same effect, which exists at thetime of filing, must be examined in relation tonegative requirements.”(*61) The two countries
are considered to be of one accord in terms of the
anticipated orientation.
However, Judge Lourie’s dissenting opinion(*62)
will require consideration if foreseeability isapplied in relation to the entire doctrine ofequivalents, though the opinion will have nothing
to do with filing and obtaining of rights as long as
foreseeability is applied only in relation to theprosecution history estoppel because it is appliedon the patentee’s side. His opinion is: “There is
the possibility that the alleged infringer will
restrain filing of an application for a similar
invention for the purpose of avoiding infringement
by using foreseeability, and this is contrary to thebasic philosophy of the patent system(encouraging filing and disclosure).”With respect to the standard level of aperson skilled in the art, no clear answer has
been indicated in Japan or the United States. In
the United States, the standard level is considered
to be the level of a “skilled claim drafter,”(*63) “oneof ordinary skill,”(*64) or “any accessible priorart.”(*65) On the other hand, in Japan, there is theopinion that “if an ordinary person writes together
by necessity when he sees … not protected if hedoes not write,” and the opinion taking an
ordinary drafter as the standard(*66) (if a drafter
did not write a dominant conception or a derived
claim that an ordinary attorney would write, thedominant conception or derived claim will not beprotected under the doctrine of equivalents).
If the standard level of a person skilled in
the art for foreseeability is the same as the levelfor non-obviousness, there will be the concernthat contradiction will arise with known
interchangeability, as pointed out by Judge
Newman and Judge Lourie.(*67) In this case,application of the doctrine of equivalents to a
subject matter other than after-arising equivalents
will be denied. This type of discussion may
influence patent drafting as well as the range ofequivalents -other than after-arising equivalentsin the case where foreseeability is introduced tolimit application of the doctrine of equivalents,
depending on how the foreseeability standard-designed to rebut the prosecution history
estoppel- will be treated in the future.
At any rate, if foreseeability is introduced
into application of the doctrine of equivalents,
there will be three standards to be considered:inventive
step(non-obviousness),easyinterchangeability (known interchangeability) andforeseeability. It is considered difficult todistinguish these three standards in practice if allof them are adopted.(*68) Discussion is anticipated
for the future on whether evidence forforeseeability should be expanded to include the“entire prior art,” including the question ofwhether the doctrine of equivalents will be kept
applicable to subject matter other than afterarising equivalents as a matter of fact.
In this manner, while the way of setting
standards for distinguishing infringement andnoninfringment under the doctrine of equivalents
has been increasing its complexity, there is theidea of making adjustments by injunction of
infringing products and compensation fordamages since these are solutions in patent
infringement suits. It seems a realistic solution toallow flexibility in the amount of damages,
depending on the quality of infringement, even if
an infringement was found.(*69)(*70)(*60) 285 F.3d at 1057 (Fed.Cir. 2002).
(*61) Ryoichi Mimura, cited above: 115; Toshiaki Makino, cited above, 209.
(*62) 285 F.3d at 1063 (Fed.Cir. 2002).
(*63) 126 F.3d at 1425 (Fed.Cir. 1997).
(*64) 285 F.3d at 1057 (Fed.Cir. 2002).
(*65) 344 F.3d at 1377 (Fed.Cir. 2003).
(*66) Toshiaki Makino and Takashi Honma, ed., “Zasankai: tokkyokureimu kaishaku no ronten wo megutte” (Round-table
talk: over points of issue concerning patent claim construction): 83; Seiji Ohno, cited above, Intellectual Property
Management, vol. 51, no. 8: 1351(*67) 285 F.3d at 1063 (Fed.Cir. 2002); 344 F.3d at 1383 (Fed.Cir. 2003).
(*68) Ryuichi Shitara, cited above, 453-454; Toshiko Takenaka, cited above, 485.
(*69) Shoji Matsui, “Nichibei ryōkoku saikōsai ni yoru, kintōyōningenhanketsuhaki no hanketsu ga, nichibei no kotonaru
tokkyoseido no naka de motsu igi” (Meaning of the Japan and U.S. Supreme Court decisions, which reversed theoriginal decision admitting application of the doctrine of equivalents, in the different patent systems of bothcountries) (contained in Ryuichi Murabayashi and Etsuji Kotani, ed., cited above), 244-245.
(*70) Nobuhiro Nakayama, “Kintōron” (Doctrine of equivalents) (contained in Ryuichi Murabayashi and Etsuji Kotani,ed., cited above), 641-642.

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(2) What the inventor failed to claim
In terms of the inventor’s fault, the“Underarm absorption pad case” is introduced as
an example in Japan.(*71) This case relates to theinventor’s fault in claim drafting. Specifically, theinventor contrarily drafted a claim with thephrase “of a small curvature,” though he shouldhave described it with the phrase “of a small
curvature radius. Since this error in thedescription was not unambiguously clear, thecourt allowed construing it only literally and did
not allow covering what the inventor failed todescribe under the doctrine of equivalents. The
idea that a contrary meaning cannot be covered
under the doctrine of equivalents is considered tobe similar to the idea of “specific exclusion.” The
way of thinking about an inventor’s error indescription in this case is similar to that in Fuji
Photo Film,(*72) though this subject is not related
to the doctrine of equivalents. If the applicant
failed to correct errors in drafting during theprosecution, he must bear responsibility for that
failure, and it is also very difficult to cover thematter that he failed to describe under thedoctrine of equivalents both in Japan and theUnited States.
This case involves the error in description of
the disputed claim limitation, specifically,
describing the term “taking lens” without theword “means.” The court rejected the patentee’s
argument that the “taking lens” should beconstrued by adding the word “means.” Thereason for this rejection was that exclusion of theword would not cause inconsistency between
claims and embodiments. The court also rejected
the patentee’s argument that the “means”
language in dependent claim 3 can beincorporated into claim 1 from which it depends
on the basis that the problem of inconsistency canalso be resolved by omitting the word “means”
from claim 3. The court also did not accept theargument that an inadvertent omission should becorrected. As grounds for this, the court statedthat if the applicant kept silence on theexaminer’s statement about claim scope, there
will arise the inference that description was not
inadvertent(*73) and that the court had no way ofknowing whether this amendment was acceptedsince the applicant did not take any opportunity tomake appropriate amendment.(*74)

Ⅴ Conclusion
The subject matter of protection under thedoctrine of equivalents in Japan is similar to thatin the United States from a broad perspective.
The principal role of the doctrine of equivalents
seems to be being consolidated into cases
involving subsequent change in the state of theart. In fact, the doctrine of equivalents has beenrarely applied to cases not involving subsequentchange in the state of the art. In the United States,
the public-notice function under the doctrine ofequivalents has been enhanced through combined
employment of the All Elements Rule and theprosecution history estoppel. This is in line with
the Supreme Court’s intention.
It seems that the role of claim differentiation
has been reviewed recently. It also appears that asharing of roles has been being established, inwhich the applicant discloses all equivalents thatare foreseeable at the time of filing, cases not
involving after-arising technology are covered byclaim differentiation, and unforeseeable infringing
embodiments that subsequently arise are dealt
with through the doctrine of equivalents.
There are actually movements to further
limit application of the doctrine of equivalents byforeseeability. Depending on the degree oflimitation by foreseeability, there is the possibility
that after-arising technology will become the only
subject matter of application of the doctrine ofequivalents. The level of a person skilled in theart will be clarified in association with ways toapply foreseeability in relation to the prosecution
history estoppel. Future movement is to bewatched.

(*71) Based on the explanation in (1) Osaka High Court, Heisei 8 (Wa) 5784 (Underarm absorption pad case) and (2)First Subcommittee of the Second Patent Committee, “Kintō 5 yōken ni kansuru ronten no bunseki to ryūiten
(sono 2)” (Analysis of the argument for five requirements for equivalence and the points to be noted (2), Intellectual
Property Management, vol. 51, no. 9: 1406.
(*72) 386 F.3d 1095, 72 USPQ2d 1769 (Fed.Cir. 2004).
(*73) 350 F.3d 1365, 1373-74 (Fed.Cir.2003).
(*74) 126 F.3d 1420, 1425 (Fed.Cir.1997).

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