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  • York Faulkner

A Brief Overview of Japanese Patent Law

Updated: Mar 21, 2021



Patent Term & Statute of Limitations. Article 67 of the Patent Act establishes a twenty (20) year patent term, beginning from the date that the patent application was filed. After allowance of the patent application, patent rights are effective upon registration of the patent grant and payment of the prescribed maintenance fees. See Article 66 of the Patent Act. Article 724 of Japan’s Civil Code imposes an absolute twenty (20) year limitation on the right to demand compensation for infringement. However, the law accelerates the limitations period upon discovery of the infringement and extinguishes the right to demand compensation “if it is not exercised by the victim . . . within three years from the time when he/she comes to know of the damages and the identity of the perpetrator.”


Standing to Bring Suit. Article 100(1) of the Patent Act provides that “[a] patentee or exclusive licensee may demand a person who infringes or is likely to infringe the patent right or exclusive license to stop or prevent such infringement.” However, exclusive licensees and patentees who receive patent rights by assignment must satisfy the registration requirement under Article 98 of the Patent Act, which requires the registration of the patent assignment or exclusive license with the Japanese Patent Office in order “to take effect” under the law. In addition, Article 467 of Japan’s Civil Code requires actual notice of an assignment to be sent to an obligor before an obligation can be enforced against the obligor. Accordingly, only properly registered patentees and exclusive licensees who give notice of their rights have standing to sue.


Literal Infringement & Claim Construction. As in the United States, the infringement inquiry conducted by Japanese courts involves two steps: (1) interpretation of the patent claim elements and (2) comparison of the claim elements with the accused product or process.


Article 70 of the Patent Act directs the courts’ construction of the patent claims or “technical scope of the patented invention” as follows:


(1) The technical scope of a patented invention shall be determined based upon the statements in the scope of claims attached to the application.


(2) In the case of the preceding paragraph, the meaning of each term used in the scope of claims shall be interpreted in consideration of the statements in the description and drawings attached to the application.


(3) In the case of the preceding two paragraphs, statements in the abstract attached to the application shall not be taken into consideration.


Although Japanese courts will apply the ordinary meaning of claim terms in the absence of other evidence, Article 70 of the Patent Act focuses the claim construction exercise on the language of the claims and statements in the patent specification. As under U.S. law, this feature of the Japanese Patent Act provides patentees with considerable latitude in acting as their own lexicographers in defining the scope, meaning, and usage of claim terms. In the past, when interpreting claims, the Japanese courts had emphasized the patent specification and exemplified embodiments of the invention to the extent of importing limitations from the specification and exemplified embodiments into the claims themselves. That tendency has substantially subsided, and the courts now look to the recited embodiments as merely exemplary and seem reluctant to unnecessarily import limitations into the patent claims.


Although Article 70 directs the courts to look to the patent drawings, specifications, and claim language to interpret the claim terms, the courts, in practice, have extended their claim construction inquiry to statements made by the patentee during prosecution, including claim amendments, arguments in support of patentability, and characterizations of the prior art. As a consequence, patentees are often estopped from asserting constructions of the patent claims that conflict with positions that they took during prosecution.


The Japanese Patent Act provides a unique procedural option to the courts during claim construction, especially in grappling with technically difficult claim constructions. Article 71 of the Patent Act permits the courts to request an advisory opinion from the Japanese Patent Office “on the technical scope of a patented invention.” Upon receipt of such a request, the Act directs the Commissioner of the Patent Office to “designate three trial examiners to make an advisory opinion on the requested matter.”


After construing the “technical scope of the patented invention” by assessing the meaning of the patent claim elements, the court then compares the patent claims with the evidence presented about the accused product or process. A finding of literal infringement requires that each claim element be manifest in the accused product or process. If one or more elements of the patent claims are not found in the accused product or process, then the patent claims are not literally infringed.


Infringement by Equivalence. The Japanese Patent Act does not address infringement by equivalence, i.e., the notion that a product that lacks a certain patent claim element and does not literally infringe the claim may yet be held to infringe because it has a feature that is equivalent in function to the claim element. Nevertheless, the Japanese Supreme Court established the “doctrine of equivalence” as a matter of jurisprudence in its 1998 decision in Tsubakimoto Seiko Co. Ltd. v. THK K.K., 1994 H-6(o) 1083 (Sup. Ct., Feb. 24, 1998). The Supreme Court identified five requirements for applying the doctrine of equivalents:


1. The “equivalent” claim element at issue must not be an essential aspect of the invention;


2. Utilizing the “equivalent” feature, the accused product or process accomplishes the same object, function, and effect as the invention;


3. Replacing the claim element with the “equivalent” feature would have been a readily conceivable substitution at the time of infringement by one of ordinary skill in the art;


4. Utilizing the “equivalent” feature, the accused product or process was neither the same as the prior art nor an obvious extension of the prior art at the time of the patent application; and


5. There are no special circumstances arising from the prosecution of the patent application, such as argument or limiting claim amendments made by the patentee, that manifest the intended exclusion of the equivalent from the scope of the claim.


These factors impose a significant burden on patentees in asserting infringement by equivalence. The first factor, or “essence of the invention test,” has perhaps presented the most significant challenge to the courts and practitioners. This test necessarily invokes qualitative judgments in ranking patent claim elements as either “essential” or “non-essential.” One of the earliest and most influential attempts at interpreting the test is district court opinion that an “essential part of the patented invention” is one that “gives rise to the meritorious effects peculiar to the patented invention or, in other words, if substituted with other means would result in a different technical concept, as a whole, from the patented invention.” Judgment rendered on Sept. 17, 1998 , Osaka District Court, Hei 8 (wa) 8927, Hanji No. 1664, page 122.


At its core, the fundamental notion of the test is that if the essence of the invention would be lost by substituting the alleged “equivalent” feature, then the doctrine of equivalents is not available to prove infringement. As a practical matter, the purpose of the Supreme Court’s first factor appears to merge with the second factor, which requires that, even utilizing the “equivalent” feature, the accused product or process accomplishes the same object, function, and effect as the invention.


The third factor addresses the underlying policy of the doctrine of equivalents, namely, preventing one from appropriating the benefits of an invention by making trivial and readily apparent changes to a product or process that avoid the literal scope of the claims without changing the properties or function of the product or process. In practice, this test is similar to the known interchangeability test under U.S. law.


The fourth factor addresses the fear that the doctrine of equivalents might be applied in ways that would expand the scope of patent claims to encompass the prior art. The test ensures that the public may freely practice the prior art, and, as a result of the doctrine of equivalents, the patentee will not be awarded a patent scope that would not have been granted by the JPO.


The fifth factor imposes a similar significant restriction on the doctrine of equivalents by precluding its application to potential embodiments of the invention that were given up by the patentee during prosecution of the application. Patentees most often give up claim scope either by way of limiting amendments to the patent claims or by statement or argument about what the claimed invention is or is not. The fifth factor is akin to the body of case law in the United States on the issue of prosecution history estoppel.


Direct & Indirect Infringement. Japanese law imposes liability for both direct and indirect infringement. As in the United States, “direct” infringement entails an act of infringement that involves all elements (or their equivalents) of the claimed invention. In contrast, “indirect” infringement involves less than all of the elements of the claimed invention but nonetheless entails conduct that induces or contributes to the infringement of all claimed elements (or their equivalents) by someone.


Direct infringement under Japanese law is thought of as the infringement of the patentee’s exclusive right, which Article 68 of the Patent Act defines as, “the exclusive right to work the patented invention as a business. . . .” This notion of “working” the patented invention often causes unnecessary consternation among foreigners studying Japanese patent law. That confusion is a consequence of translation. The Japanese word “実施” (“jisshi”) in the Patent Act is most commonly translated as “work” but another acceptable and useful translation of the word is “implement.” Thus, the meaning suggested to the reader of the native Japanese statute encompasses the idea of a patentee’s “exclusive right to implement the patented invention.”


Additionally, the qualifying phrase “as a business” foretells that the patentee’s “exclusive” right is not absolute. Indeed, the Patent Act recognizes, for example, certain non-infringing experimental and medical uses of patented inventions and exemptions for goods and equipment merely in transit through Japan. See, e.g., Article 69 of the Patent Act.


Although the phrase “as a business” is not defined in the act, the term “working the patented invention” is defined, and Article 2(3) of the Patent Act provides an extensive list of conduct that, if not otherwise authorized, directly infringes the patentee’s exclusive right:


(i) in the case of an invention of a product (including a computer program, etc., the same shall apply hereinafter), producing, using, assigning, etc. (assigning and leasing and, in the case where the product is a computer program, etc., including providing through an electric telecommunication line, the same shall apply hereinafter), exporting or importing, or offering for assignment, etc. (including displaying for the purpose of assignment, etc., the same shall apply hereinafter) thereof;


(ii) in the case of an invention of a process, the use thereof; and


(iii) in the case of an invention of a process for producing a product, in addition to the action as provided in the preceding item, acts of using, assigning, etc., exporting or importing, or offering for assignment, etc. the product produced by the process.


Indirect infringement under Japanese law can be divided into two broad categories. The first category under Article 101(i) and (iv) includes the manufacture, sale, or importation of products which have no practical use or application other than for infringement. It is a defense to this type of infringement to show that accused products have other real, non-theoretical, practical uses. The relevant code provisions are stated below:


(i) where a patent has been granted for an invention of a product, acts of producing, assigning, etc., importing or offering for assignment, etc. any product to be used exclusively for the producing of the said product as a business;


(iv) where a patent has been granted for an invention of a process, acts of producing, assigning, etc., importing or offering for assignment, etc. any product to be used exclusively for the use of the said process as a business;


The second category of indirect infringement under Article 101(ii) and (v) extends to situations in which, although the accused product may be susceptible to multiple uses, the accused product is indispensable to the infringement and the accused infringer acts knowing of the patented invention and that the accused product is used for the practice of the invention. The relevant code provisions are reproduced below:


(ii) where a patent has been granted for an invention of a product, acts of producing, assigning, etc., importing or offering for assignment, etc. any product (excluding those widely distributed within Japan) to be used for the producing of the said product and indispensable for the resolution of the problem by the said invention as a business, knowing that the said invention is a patented invention and the said product is used for the working of the invention;


(v) where a patent has been granted for an invention of a process, acts of producing, assigning, etc., importing or offering for assignment, etc. any product (excluding those widely distributed within Japan) to be used for the use of the said process and indispensable for the resolution of the problem by the said invention, knowing that the said invention is a patented invention and the said product is used for the working of the invention as a business;


In this second category of indirect infringement, the accused infringer may escape liability by proving that that the accused product is “widely distributed within Japan,” which is the corollary to the “staple article . . . of commerce suitable for substantial noninfringing use” exception to infringement under 35 U.S.C. § 271(c) under U.S. law.


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