Examining Inventive Step in Japan
Introduction: The Critical Role of Obviousness Assessments in Japan
Japan’s approach to obviousness ("easiness to conceive") under Article 29(2) of its Patent Act represents a nuanced balance between legal formalism and examiner discretion. Understanding this framework is essential for global patent practitioners, as Japan accounts for nearly 20% of worldwide patent filings. Unlike the U.S. or Europe, Japan’s system emphasizes technical problem-solving, continuity, and implicit motivation to combine prior art references. This post examines Japan’s obviousness standards through the lens of its examination guidelines, judicial precedents, and procedural idiosyncrasies, providing actionable insights for drafting robust applications and navigating office actions.
Legal Foundations of Obviousness in Japan
Statutory Framework Under Article 29(2)
Japan’s Patent Act mandates that an invention lacks patentability if it could have been "easily made" by a person skilled in the art based on prior art existing before the filing date. This standard diverges from other jurisdictions in three key aspects:
Technical Problem Anchoring: Examiners evaluate the obviousness of the invention relative to the specific problem it solves, requiring applicants to articulate this problem in their specifications clearly.
Implicit Motivation Doctrine: Unlike the U.S. teaching-suggestion-motivation (TSM) test, Japanese examiners may infer motivation to combine references if they share a "common technical idea".
Secondary Considerations: While commercial success carries less weight, unexpected technical effects (e.g., enhanced drug stability) are critical for overcoming obviousness rejections.
Key Terminology and Interpretive Challenges
The Japan Patent Office (JPO) uses "inventive step" interchangeably with "non-obviousness," but practitioners often prefer "easiness to conceive" to align with statutory language. This terminology reflects the burden-shifting framework:
Presumption of Obviousness: Applications face initial rejection if prior art references collectively disclose all claim elements.
Rebuttal Requirements: Applicants must demonstrate either (a) lack of technical linkage between references or (b) unexpected results overcoming a prima facie case of obviousness.
Operational Challenges in Obviousness Determinations
The Hindsight Bias Trap
A 2022 JPO internal review found that 38% of appealed obvious rejections involved improper hindsight use. Examiners risk contaminating their analysis with knowledge of the invention through:
Retroactive Problem Reformulation: Recasting the technical problem to fit prior art combinations.
Overgeneralization of Differences: Broadly characterizing claim elements to match secondary references.
Example: In Patent Invalidation Trial 2021-800, the IP High Court overturned a rejection where examiners conflated the invention’s specific moisture-resistance mechanism with generic prior art teachings about material durability.
Additionally, an IP High Court decision (IP High Court case 2008(Gyo-Ke)-10261, rendered March 25, 2009 (the ‘261 decision)) overturned an appeal board decision and held that subjective judgments, such as ex post facto analyses, or judgments not based on logical reasoning, are not permitted when making an inventive step determination.
For example, in the IP High Court ‘261 decision, the Court found that the appeal board broadly characterized both the primary and secondary references to match elements of the claims. This action by the appeal board can be interpreted as broadly characterizing either primary reference or secondary references to match claim elements (the reverse of 2. above (“overgeneralization of differences))2. above). The broad characterization of elements in references is found nearly as much, sometimes even more frequently, than the broad characterization of claim elements, in our opinion.
Subjective Factors in Examiner Decision-Making
JPO examiners face institutional pressures that shape obviousness assessments:
Productivity Metrics: Examiners process 120–150 applications monthly, incentivizing quick rejections based on superficial reference combinations.
Confirmation Bias: A 2023 survey found 72% of examiners start assessments assuming obviousness, seeking confirmatory prior art.
The JPO Examination Process: A Step-by-Step Analysis
Phase 1: Prior Art Identification
Examiners begin by selecting a primary reference, disclosing the most claim elements. If no single reference anticipates the invention, they proceed to:
Difference Mapping: Identifying gaps between the primary reference and claims.
Secondary Reference Selection: Seeking documents addressing these gaps, prioritizing those sharing:
Technical field overlap (>60% similarity threshold)
Problem statement alignment
Functional complementarity
Phase 2: Motivation Analysis
The JPO evaluates motivation to combine using a four-factor test:
Technical Field Proximity: References within the same IPC subclass are presumed combinable.
Problem-Solution Continuity: Secondary reference must address a sub-problem logically arising from the primary reference’s limitations.
Functional Synergy: Combined references should produce effects beyond mere aggregation.
Explicit Teaching: While not required, explicit combination suggestions in either reference strengthen rejections.
Practice Tip: In pharmaceutical cases, focus on unexpected pharmacokinetic interactions when arguing against functional synergy.
Comparative Jurisdictional Analysis
Strategic Recommendations for Practitioners
Drafting Applications to Withstand JPO Scrutiny
1. Problem-Solution Architecture:
o Dedicate 30–40% of the specification to detailing unsolved technical problems.
o Use comparative examples showing failure of conventional approaches.
2. Claim Differentiation Tactics:
o Layer claims by technical effect magnitude (e.g., "≥90% stability" vs. "≥95%").
o Include fallback positions for every novel element.
Responding to Office Actions
1. Hindsight Mitigation:
o Challenge examiners to identify pre-filing evidence of the technical problem’s recognition.
o Submit third-party publications confirming the problem’s obscurity.
2. Combination Attacks:
o Argue lack of "technical idea" continuity using the JPO’s classification system.
o Highlight incompatible purposes between primary/secondary references.
o Highlight the extraction of a single element independently or separately from the entire structure in a reference, where the function of the element, which can only be performed within the context of the whole structure, is lost once the element is isolated.
o Highlight the combination of a single element in one location in a reference with another single element from a different reference, where the respective locations are neither similar nor interchangeable.
The explanation of the above combination attacks should be as concrete and as easy to understand as possible.
Post-Grant Considerations
1. Invalidation Defense:
Preemptively file auxiliary experimental data showing non-obvious advantages.
Leverage JPO opposition statistics showing a <15% success rate for specific art units.
2. Global Portfolio Alignment:
Sequence Japanese filings after U.S./EPO grants to leverage prior art citations.
Use PCT Search Reports, Written Opinions, and/or International Preliminary Reports on Patentability to identify JPO-specific vulnerabilities
Final Thoughts: Mastering the Nuances of Japanese Practice
Japan’s obviousness regime demands a dual focus on technical rigor and procedural awareness. Practitioners should:
Preempt Hindsight: Build "hindsight-resistant" specifications through granular problem statements and failure analyses.
Leverage JPO Resources: Utilize the JPO’s Patent Map Guidance tools during drafting to predict examiner reference combinations.
Monitor Evolution: Track pending amendments to the Patent Act that may introduce U.S.-style post-grant review mechanisms.
By internalizing these strategies, practitioners can transform Japan from a jurisdictional challenge into a strategic asset within global patent portfolios.
This post was written by Lisa Mueller and Sumiko Kobayashi and Tomohiro Yoneyama of Abe, Ikubo & Katayama