A patent is a government-granted exclusive right that allows an inventor to prevent others from making, using, selling, or importing a patented invention for a fixed period—typically 20 years from the filing date. In exchange for this monopoly, the inventor must publicly disclose the invention in sufficient detail for others skilled in the field to reproduce it. This quid pro quo—disclosure in exchange for exclusivity—forms the philosophical backbone of every modern patent system.
The Legal Definition of a Patent
In Japan, Article 2(1) of the Patent Act (Act No. 121 of 1959) defines an “invention” as “the highly advanced creation of technical ideas utilizing natural laws.” Four key elements emerge from this definition. First, “natural laws” excludes mathematical formulas, economic principles, and mental processes as such. Second, “technical ideas” requires a reproducible technical means—not merely a discovery of something already existing in nature. Third, “creation” demands something new rather than mere identification. Fourth, “highly advanced” distinguishes patentable inventions from utility model rights (which protect more incremental innovations under the Utility Model Act).
The exclusive right itself is established by Article 68 of the Patent Act: “A patentee shall have the exclusive right to work the patented invention as a business.” The phrase “as a business” limits the monopoly to commercial activities—private, non-commercial use by individuals generally does not constitute infringement. The term “work” is defined in Article 2(3) and encompasses manufacturing, using, assigning, leasing, importing, and offering for assignment the patented product or process.
In the United States, patents are granted under 35 U.S.C. § 101, which covers “any new and useful process, machine, manufacture, or composition of matter, or any new and useful improvement thereof.” European patents are governed by the European Patent Convention (EPC), particularly Article 52, which similarly requires a “technical character” that has industrial application.
The 20-Year Term: Its Basis in International Law
The standard 20-year patent term, measured from the filing date, is mandated by Article 33 of the TRIPS Agreement (Agreement on Trade-Related Aspects of Intellectual Property Rights), which Japan ratified in 1994 as part of the WTO agreements. This global minimum standard replaced Japan’s previous 15-year term (measured from publication) and created substantial harmonization across 164 WTO member states.
For pharmaceuticals and agrochemicals, where regulatory approval processes can consume a decade or more of the patent term, Japan’s Patent Act Article 67(2) allows term extensions of up to five years to compensate for time spent in mandatory safety reviews. The United States offers a similar mechanism under 35 U.S.C. § 156 (Patent Term Extension) and § 154(b) (Patent Term Adjustment for USPTO delays). The practical consequence is that blockbuster drug patents, when combined with these extensions, can provide effective market exclusivity significantly beyond 20 years—a point of perennial controversy in healthcare policy debates.
Because prosecution (the process of obtaining a patent) typically takes one to three years after filing, the effective commercialization period is shorter than 20 years. Strategic filers therefore aim to delay prosecution where permissible to shift the effective term toward the commercial peak of a technology’s lifecycle.
The Three Substantive Requirements for Patentability
Novelty (Article 29(1) of Japan’s Patent Act; 35 U.S.C. § 102)
An invention must not have been publicly known, publicly worked, or described in a publication before the filing date—anywhere in the world. Japan’s 2012 amendment to the Patent Act eliminated geographic limitations on prior art, adopting the global novelty standard consistent with international norms.
An important exception is the “grace period” (Article 29(3)), which allows inventors who publicly disclosed their own invention to file within one year of that disclosure without losing novelty. The United States similarly provides a one-year grace period under the America Invents Act (AIA, 2011). However, many other jurisdictions—including most of Europe—provide no grace period, making early filing before any public disclosure the safest practice for international protection strategies.
Inventive Step / Non-Obviousness (Article 29(2); 35 U.S.C. § 103)
Even if novel, an invention is unpatentable if “a person with ordinary skill in the art” (POSITA) would have found it obvious to arrive at the invention from prior art. This requirement—called “inventive step” in Japan and Europe, and “non-obviousness” in the US—is the most frequently litigated patentability criterion.
Japan’s Patent Office examination guidelines evaluate whether a POSITA had motivation to combine the primary and secondary prior art references, considering factors such as technical proximity, shared problem, and common function. The US Supreme Court’s KSR International Co. v. Teleflex Inc. (550 U.S. 398, 2007) expanded the scope of what is considered obvious by allowing flexible, common-sense combinations of prior art beyond formal “teaching, suggestion, or motivation.”
Industrial Applicability (Article 29(1) preamble; 35 U.S.C. § 101)
The invention must be capable of industrial application. Japan’s Patent Office excludes certain medical methods—surgical operations, therapeutic treatments, and diagnostic methods practiced by medical professionals—from this category. Inventors seeking to protect medical innovations therefore typically protect them as physical products (drugs, devices) or manufacturing processes rather than as methods of treatment. In contrast, the US does not categorically exclude medical methods, though software and business methods face heightened scrutiny under the Alice/Mayo framework (discussed in a later article in this series).
From Filing to Registration: The Prosecution Process
Filing a patent application requires submitting, at minimum: (1) the claims (the legal definition of the invention’s scope), (2) the detailed description (specification), (3) the abstract, and (4) drawings where necessary. The claims are the most strategically critical document—they define the legal boundaries of the exclusive right and determine whether potential infringers fall within or outside the patent’s scope.
Eighteen months after the filing date (or priority date), the application is published in the official patent gazette under Japan’s Publication System (Article 64). This compulsory publication serves the disclosure function even before a patent is granted, and the applicant acquires a right to claim compensation from infringers during the period between publication and grant (Article 65).
Examination does not begin automatically. The applicant must request examination within three years of the filing date (Article 48-3); failure to do so results in the application being deemed withdrawn. Once examination begins, the JPO examiner issues an Office Action (Notice of Reasons for Refusal) if deficiencies are found. The applicant may respond with arguments (written opinion) and/or amendments to the claims. According to JPO statistics, the average pendency from examination request to first Office Action was approximately 9.5 months in FY2023.
If the examiner remains unsatisfied, the application proceeds to rejection, which the applicant may appeal to the JPO’s Board of Appeal (Trial for Appeal against Examiner’s Decision of Refusal, Article 121). Further appeal is possible to the Intellectual Property High Court and, ultimately, the Supreme Court of Japan.
What a Patent Holder Can—and Cannot—Do
A patent owner may (1) work the invention directly, (2) license the patent to third parties in exchange for royalties, (3) seek injunctive relief against infringers under Article 100, and (4) claim damages under Article 102, which provides a statutory damages calculation methodology to ease the patent holder’s evidentiary burden.
However, several doctrines constrain these rights. The doctrine of exhaustion—affirmed by Japan’s Supreme Court in the BBS case (July 1, 1997)—holds that once a patented product is legitimately sold, the patent rights over that specific item are “exhausted” and cannot be reasserted against subsequent resellers or users. Articles 69(1) exempts experimental and research use from infringement liability, though the scope of this exemption is narrower in Japan than in some other jurisdictions. Prior use rights (Article 79), discussed in detail in a later article, allow parties who were already practicing the invention before the patent application to continue doing so.
A patent also does not guarantee the right to practice the invention. A patent covering an improvement may still be blocked by a broader “blocking patent” owned by another party. This interdependency—common in technology-dense fields like smartphones, where a single device may be subject to thousands of declared patents—gives rise to cross-licensing negotiations and the broader challenge known as the “patent thicket.”
The Rationale: Disclosure in Exchange for Exclusivity
The patent system’s fundamental bargain is straightforward: society grants a temporary monopoly in exchange for the inventor’s full public disclosure of the invention. Without this incentive, inventors might choose to keep innovations as trade secrets indefinitely, depriving the public of technical knowledge. Once the patent term expires, the disclosed invention enters the public domain and can be freely exploited by anyone.
This rationale—codified in Article 1 of Japan’s Patent Act as “the promotion of the development of industry” through the “protection and utilization of inventions”—remains under ongoing scrutiny. Critics point to patent assertion entities (“patent trolls”), ever-broadening claims in software and business methods, and the tension between strong pharmaceutical patents and access to medicines in developing countries as evidence that the system’s calibration requires regular reexamination. The subsequent articles in this series examine these tensions through the lens of specific doctrine and industry practice.
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