What Is the Standard for Inventive Step (Non-Obviousness - Article 29(2)) in Japanese Patent Practice?

Japanese Attorney at Law - Bengoshi L.L.

• 11 min read

Beyond being novel, a patentable invention in Japan must also possess an inventive step (進歩性 - shinpo-sei), as mandated by Article 29(2) of the Japanese Patent Act. This requirement, often referred to interchangeably with non-obviousness (非容易推考性 - hi-yōi suikō-sei), dictates that a patent shall not be granted if the invention could have been easily conceived by a person of ordinary skill in the art (PSITA) in the relevant technical field, based on the prior art available before the effective filing date of the patent application.

The purpose of the inventive step requirement is fundamental: to ensure that patents are granted only for inventions that represent a genuine technical advancement and a contribution beyond what is merely a routine or obvious extension of existing knowledge. It prevents the patenting of trivial developments that would naturally emerge from the ordinary progress of technology, thereby ensuring that the patent system rewards true innovation rather than hindering it with a proliferation of patents on minor variations.

The assessment of inventive step typically follows the determination of the "gist of the invention" claimed and an assessment of its novelty. If the invention is found to be novel, its inventive step is then scrutinized.

The General Framework for Assessing Inventive Step

The core of the inventive step inquiry revolves around the hypothetical "Person of Ordinary Skill in the Art" (PSITA or 当業者 - tōgyōsha) and what they could have "easily conceived" (容易に発明をすることができた - yōi ni hatsumei o suru koto ga dekita) at the relevant time.

  1. Defining the Claimed Invention and Identifying Differences from Prior Art: The process begins by clearly defining the invention as set out in the patent claims. This invention is then compared to the closest available prior art (often referred to as the "primary reference"). Any differences between the claimed invention and this primary reference are identified.
  2. The Person of Ordinary Skill in the Art (PSITA): The assessment is made from the perspective of a PSITA in the technical field to which the invention pertains. This hypothetical person is presumed to possess the common general knowledge of that field at the time of filing and to have access to all relevant prior art.
  3. The "Easily Conceivable" Standard: The ultimate question is whether the PSITA, armed with this knowledge, could have easily arrived at the claimed invention by bridging the identified differences from the primary prior art, perhaps by considering other prior art references (secondary references) or by applying their ordinary skill.

Primary Approaches to Determining "Easy Conceivability"

Japanese patent practice, including JPO examination guidelines and court decisions, employs several established approaches to structure the inventive step analysis.

1. The Motivation Approach (動機付けのアプローチ - dōkizuke no apurōchi)

This is a primary method used when the claimed invention can be viewed as a combination of features known from different prior art documents, or as a modification of a primary reference based on teachings found in secondary references or common general knowledge.

The central inquiry is whether the PSITA would have had a motivation or suggestion to combine or modify the prior art teachings in such a way as to arrive at the claimed invention. The mere fact that elements of the invention can be found in separate prior art documents is not, by itself, sufficient to negate inventive step. There must be a reason why the PSITA would have thought to put them together.

Factors Suggesting Motivation (Affirmative Factors for Obviousness):

  • Related Technical Fields: If the primary and secondary references are from the same or closely related technical fields, it is more likely that a PSITA would consider them together.
  • Common Problem to be Solved: If the prior art references address a similar technical problem to that solved by the claimed invention, this can provide a strong motivation to combine their teachings.
  • Similar Functions or Operations: If elements in different prior art references perform similar functions or operate in analogous ways, a PSITA might be motivated to combine or interchange them.
  • Explicit or Implicit Suggestions in Prior Art: A prior art reference might itself suggest combining its teachings with other known technologies, or hint at the modification that leads to the claimed invention.

Factors Negating Motivation (Hindrances or 阻害要因 - sogai yōin):

Even if some factors suggest motivation, inventive step might still be found if there are countervailing factors, known as "hindrances":

  • Teaching Away: If a prior art reference explicitly teaches away from the combination or modification made in the claimed invention, this weighs against a finding of obviousness.
  • Inoperability or Undesirable Results: If combining the prior art teachings would lead to an inoperable result or significantly disadvantageous effects that a PSITA would seek to avoid, this can negate motivation.
  • Contrary to Established Technical Prejudices: If the claimed invention goes against a widely accepted belief or practice in the field, it is less likely to have been easily conceived.

Evolution of the Motivation Standard in Japanese Case Law:

The application of the motivation standard has evolved:

  • Early Post-IP High Court Trends: In the years following the establishment of the IP High Court in 2005, there was a period where some observers perceived a trend towards finding inventions obvious, sometimes based on relatively loose connections between prior art references (e.g., simply being in the "same technical field").
  • Shift Towards Requiring Clearer Motivation (TSM-like Considerations): Partly in response to concerns about hindsight bias, a line of IP High Court decisions, notably from panels presided over by then-Judge (later Chief Judge) Toshiaki Iimura, began to emphasize the need for more concrete evidence of a suggestion, teaching, or motivation (often analogized to the "TSM test" formerly prevalent in U.S. practice) to combine prior art.
    • The IP High Court decision of January 28, 2009 (Hanrei Jihō No. 2043, p. 117, the "Circuit Connecting Member" case or 「回路用接続部材」事件) stated that a mere inference that a PSITA might have tried to reach the invention's features is insufficient; there must be a suggestion or the like that they would have done so.
    • Similarly, in the IP High Court decision of December 25, 2008 (Hanrei Jihō No. 2046, p. 134, the "Radar" case or 「レーダ」事件), the court overturned a JPO decision finding a radar display invention obvious. The patented invention shifted the aircraft's own display position rearward as speed increased to provide a wider forward view. The cited prior art showed displaying all aircraft within range but highlighting a "warning airspace" in front, the size of which increased with speed. The court reasoned that since the prior art's objective was to identify truly critical targets within an already fully displayed area, there was no motivation to adopt an off-center display function aimed at efficiently displaying only the warning area. The differing objectives negated the motivation to combine.
  • Current Mainstream – The "Logical Reasoning Approach" (論理付けのアプローチ - ronrizuke no apurōchi): The current prevailing approach requires a well-reasoned, logical explanation (論理付け - ronrizuke) of why a PSITA would have been motivated to combine or modify the prior art to arrive at the claimed invention. The factors listed in JPO guidelines (related technical fields, common problems, similar functions, suggestions in prior art) are considered illustrative, not exhaustive. The emphasis is on constructing a plausible and evidence-based narrative of "easy conceivability," avoiding overly simplistic conclusions or rigid adherence to a strict TSM formula.
  • Preventing Hindsight in Problem Formulation: A further refinement to guard against hindsight bias is the consideration of whether the problem solved by the invention was itself obvious to identify, if it wasn't already explicitly known in the art. The IP High Court decision of January 31, 2011 (Hanrei Jihō No. 2107, p. 131, the "Ventilation Fan Filter" case or 「換気扇フィルター及びその製造方法」事件) highlighted this. The invention involved a ventilation fan filter where the metal frame and non-woven filter material were joined by a specific water-based emulsion adhesive, allowing easy separation for disposal. The JPO had found this obvious by combining a primary reference showing a filter with a secondary reference disclosing such an adhesive. The IP High Court overturned the JPO's decision, reasoning that the JPO had not established that the problem of enabling easy separation for disposal was itself a recognized or obvious problem in the art of ventilation fan filters at the time. If the problem itself isn't obvious, a PSITA wouldn't be motivated to seek solutions for it.

2. The "Design Matters, etc." Approach (設計事項等のアプローチ - sekkei jikō tō no apurōchi)

This approach is applied when the differences between the claimed invention and the closest prior art are considered to be mere routine modifications, choices, or optimizations that a PSITA would make in the ordinary course of their work, without exercising any inventive skill. If the only distinctions fall into this category, inventive step is generally denied.

Examples of such "design matters" or routine activities include:

  • Selection of an optimal material from a known class of suitable materials for a particular application.
  • Optimization or mere adjustment of a numerical range (e.g., temperature, concentration, dimension) within a known or predictable trend, without achieving any unexpected or qualitatively different effect.
  • Substitution with a well-known equivalent that performs the same function in substantially the same way to achieve the same result.
  • Minor design changes or specific applications of known techniques that involve only the exercise of ordinary engineering or design skill, without overcoming any particular technical difficulty or achieving a new technical effect.

The Role of Remarkable or Unexpected Effects (顕著な効果 - kencho na kōka)

Even if an invention, when viewed solely from a structural perspective, appears to be a prima facie obvious combination or modification of prior art, it may nevertheless be found to possess an inventive step if it produces unexpectedly advantageous or remarkable technical effects compared to what a PSITA would have predicted from the prior art.

Nature of "Remarkable Effects":

  • Qualitatively Different Effects (異質の効果 - ishitsu no kōka): The invention achieves a new type of effect or benefit that was not suggested or foreshadowed by the prior art.
  • Quantitatively Superior Effects (同質の効果であるが際だって優れた効果 - dōshitsu no kōka de aru ga kiwadatte sugureta kōka): The invention achieves a known type of effect, but to a degree that is surprisingly, significantly, or disproportionately better than what the PSITA would have reasonably expected based on the teachings of the prior art.

Foreseeability is Key: The critical aspect is that these advantageous effects must not have been reasonably foreseeable by a PSITA from the state of the art at the time of filing.

How Remarkable Effects are Considered:

There has been some theoretical debate on the precise role of such effects:

  • "Secondary Considerations" (二次的考慮説 - nijiteki kōryo setsu): This is generally considered the prevailing view in Japanese practice. Remarkable and unexpected effects serve as strong secondary evidence or objective indicia of non-obviousness. The reasoning is that if such beneficial effects were truly easy to achieve from the known art, it is likely they would have been discovered or implemented sooner by others. Their unexpected nature suggests that the path to the invention, despite any apparent structural simplicity, was not, in fact, obvious or straightforward.
  • "Independent Requirement" (独立要件説 - dokuritsu yōken setsu): Some older arguments or interpretations might have suggested that remarkable effects could almost independently confer patentability, even if the structural modification itself was very simple or prima facie obvious. However, current practice integrates the assessment of effects into the overall consideration of whether the invention as a whole, including its properties and advantages, would have been easily conceived.

The Supreme Court decision of August 27, 2019 (Saibansho Jihō No. 1730, p. 1, the "Doxepin Derivative for Ocular Diseases" case or 「アレルギー性眼疾患を処置するためのドキセピン誘導体を含有する局所的眼科用処方物」事件) underscored the importance of a thorough examination of whether the claimed invention's effects were indeed unforeseeable and significantly superior to what a PSITA would have predicted from the prior art. While not explicitly choosing between the "secondary consideration" and "independent requirement" theories, the ruling emphasized a holistic assessment.

Disclosure of Effects: For an applicant to rely on advantageous effects to support inventive step, these effects should ideally be disclosed in the patent specification as filed, or at least be reasonably inferable from the disclosure. While post-filing data demonstrating effects can sometimes be submitted and considered, its evidentiary weight may be diminished if there is no corresponding basis or suggestion of such effects in the original application.

"Obvious to Try" Scenarios: If there was a clear reason or motivation for a PSITA to try a particular combination or modification (perhaps to solve a known problem or explore a recognized path), inventive step might be denied even if the resulting invention exhibited some unexpected advantages, provided there was a reasonable expectation of some success or utility from making the attempt. This is akin to the "obvious to try" concept. The IP High Court decision of November 13, 2012 (2012 (Gyo-ke) 10004, the "Shoe Press Belt" case or 「シュープレス用ベルト」事件) involved a situation where substituting a known curing agent for safety reasons (a motivation) led to an invention that also showed unexpected improvements in crack resistance. The court, in that instance, found inventive step, emphasizing the unforeseeability of these particular performance benefits in conjunction with the safety motivation.

Specific Invention Types and Inventive Step Considerations

Certain types of inventions have specific considerations for inventive step:

1. Selection Inventions (選択発明 - sentaku hatsumei)

A selection invention involves choosing a specific member, sub-group, or sub-range from a broader, previously known genus or range disclosed in prior art.

  • For such an invention to possess an inventive step, it must typically demonstrate an unexpectedly advantageous effect that is specific to the selected species or sub-range, and which is not possessed by, or predictable from, other members of the prior art genus.
  • The mere arbitrary selection of a previously undisclosed species from a known genus, without any associated unexpected advantage, is generally considered obvious.
  • The IP High Court decision of June 14, 2017 (2016 (Gyo-ke) 10037, the "Polymerizable Compound-Containing Liquid Crystal Composition" case or 「重合性化合物含有液晶組成物等」事件) confirmed that for a selection invention, the selected sub-concept must not have been concretely disclosed in the prior art, and it must exhibit an effect that is either qualitatively different from, or quantitatively outstanding compared to, the effects suggested by the broader prior art disclosure.

2. Numerical Limitation Inventions (数値限定発明 - sūchi gentei hatsumei)

These are a specific type of selection invention where the inventive contribution lies in identifying a particular numerical range for a parameter (e.g., temperature, concentration, dimension, pH).

  • Inventive step is generally found if:
    • The claimed numerical range itself is novel (i.e., not explicitly disclosed or inherently present in the prior art).
    • Within that specific claimed range, the invention achieves a remarkable or unexpected technical effect (often demonstrating "criticality" - 臨界性 - rinkaisei) that is not observed outside this range, or which would not have been predicted by a PSITA based on the prior art.
  • Simply narrowing or optimizing a known parameter within a generally understood range to achieve a predictable improvement in a known property is usually considered to lack inventive step.

The Role of Common General Knowledge (周知技術・慣用技術)

Common general knowledge (周知技術 - shūchi gijutsu) and well-known art or conventional techniques (慣用技術 - kan'yō gijutsu) in the relevant technical field at the time of filing are always considered part of the informational background available to the PSITA. This includes:

  • Fundamental scientific principles.
  • Standard textbook knowledge.
  • Widely adopted practices and engineering norms in the field.

Common general knowledge can be used to:

  • Understand the disclosures of prior art documents.
  • Supplement the teachings of prior art (e.g., to show how a PSITA would routinely implement a general disclosure).
  • Provide a basis or motivation for combining different prior art references or for making seemingly straightforward modifications.

Avoiding Hindsight Bias (後知恵の排除 - atojie no haijo)

A persistent challenge in any inventive step assessment is to avoid hindsight bias – the tendency to view the invention as obvious once its solution is known, and to reconstruct it using the invention itself as a blueprint to select and combine pieces of prior art. Japanese courts and the JPO are acutely aware of this danger. The structured approaches to inventive step, particularly the emphasis on finding a proper motivation or logical reasoning for combining prior art references, and the consideration of whether the problem solved was itself obvious, are all designed to mitigate the influence of hindsight.

Conclusion

The standard for inventive step under Article 29(2) of the Japanese Patent Act is a crucial gatekeeper for patentability, ensuring that patents are granted for non-trivial contributions to the art. The assessment is a complex, fact-dependent inquiry centered on whether a person of ordinary skill in the relevant technical field, equipped with the knowledge of the prior art and common general knowledge, could have easily conceived of the claimed invention. Key analytical frameworks include the motivation-based approach for combinations and modifications, and the "design matters" approach for routine variations. The presence of unexpected or remarkable effects can provide strong evidence of non-obviousness, especially for selection inventions and numerical limitation inventions. Ultimately, the goal is to ensure that the Japanese patent system rewards genuine innovation that pushes the boundaries of existing technology.