출원경과 금반언에 의한 균등의 배제 범위

The doctrine of prosecution history estoppel was established by the case law of the United States. Applying the general doctrine of estoppel barring contradictory arguments to the Patent Act, the doctrine bars patentees from making any allegations contrary to his/her own act during the prosecution of a patent application with the Patent and Trademark Office (USPTO), such as amendment claim or statement of opinion, in a subsequent patent infringement action. Supreme Court Decision 2001Hu171 Decided September 6, 2002, affirmed the doctrine by recognizing that an element “should not have been consciously excluded” to find infringement under the doctrine of equivalents. The above decision only held that whether a certain element “is consciously excluded” should be determined based on such factors as the specifications, examiner’s opinion, and the applicant’s intention as expressed in the amendment claim and the written opinion. Although the above decision did not explicitly state the scope of the exclusion under the doctrine of prosecution history estoppel, it should basically be construed as a flexible bar, given that it held that whether an element was consciously excluded should be determined by taking into account various things including the applicant’s intention. More recently, Supreme Court Decision 2014Hu638 Decided April 26, 2017, further clarified this point. It is this author’s view that the attitude of the above precedents is reasonable, given the following: (a) the purport of the doctrine of equivalents to practically protect patents even at the expense of the clarity of scope of the claims; (b) the excessive extension of the scope of equivalents can be resolved to a certain extent by means of the other four requirements of the doctrine of equivalents; and (c) Festo presumption too seems to have problems of predictability.