Product-by-Process Claims in Japan: How Are They Interpreted and What Is a 'True PBP Claim'?

Product-by-process (PBP) claims are a unique feature in patent law, defining a product not by its structural characteristics but by the method of its manufacture. These claims are particularly prevalent and often necessary in fields like chemistry and biotechnology, where the intricate structure of a novel substance might be unknown, exceedingly complex to define, or where the manufacturing process itself imparts unique, non-structurally definable properties to the end product. For instance, a PBP claim might read: "Compound X, obtained by reacting substance A with substance B under conditions Y and Z," or it might appear as a component within a broader claim, such as "A pharmaceutical composition comprising copolymer P, wherein said copolymer P is obtained by the steps of..."

While PBP claims offer a practical way to claim inventions in such scenarios, their interpretation for determining patent infringement has been a complex and debated issue in many jurisdictions, including Japan. The core question revolves around whether the claim covers only products made by the recited process or any product that is identical to the one produced by the process, regardless of its actual manufacturing method. A landmark decision by the Grand Panel of Japan's Intellectual Property High Court (IPHC) has provided significant clarification on this front.

The Nature and Utility of Product-by-Process Claims

The necessity for PBP claims often arises when conventional means of defining a product—by its chemical structure, physical parameters, or other inherent characteristics—are insufficient or impractical at the time of filing the patent application. This could be because the exact structure is yet to be elucidated, or an attempt to define it structurally would be overly complex and might not accurately capture the invention.

Historically, Japanese patent law, under a previous version of Article 36(5)(ii) of the Patent Act, generally required patent claims for products to recite the indispensable structural features of the invention. However, with the evolution of technology and the increasing complexity of inventions, especially in areas like polymers and biological materials, the law has adapted. Current Japanese patent law no longer mandates that a product invention be defined solely by its concrete structure, allowing for greater flexibility in claim drafting and leading to a wider acceptance of PBP claims.

The Interpretive Dilemma: Process-Limited vs. Product-Identity

The unique wording of PBP claims—defining a product through its process of creation—gives rise to two primary, and often conflicting, theories of claim interpretation when assessing infringement:

1. The Process-Limited Theory (Seihō Gentei Setsu): This theory posits that the scope of a PBP claim is restricted to products manufactured using the specific process recited in the claim. If an accused product, though structurally identical to the product that would be made by the claimed process, was actually produced by a different method, it would not infringe. The rationale often cited is that all limitations in a claim, including process steps in a PBP claim, must be given meaning and effect, as per the general principles of claim construction (rooted in Article 70(1) of the Patent Act, which states the technical scope of a patented invention shall be determined based on the statements in the claims).
2. The Product-Identity Theory (Mono Dōitsusei Setsu or Product Per Se Theory): Conversely, this theory argues that since a PBP claim is ultimately directed to a product, its scope should cover any product that is identical to the product resulting from the claimed process, irrespective of the actual method used to produce it. The process language, in this view, serves primarily to identify and define the novel product itself, especially when direct structural definition is difficult.

This interpretive divergence historically created uncertainty for both patentees, who were unsure of the true scope of their protection, and for third parties, who faced ambiguity when trying to assess freedom to operate or design around existing PBP claims.

The Japanese Approach: The IPHC Grand Panel Decision (Pravastatin Sodium Case)

Seeking to resolve this uncertainty and establish a consistent framework, the Grand Panel of the Intellectual Property High Court of Japan delivered a pivotal judgment on January 27, 2012, in a case concerning pravastatin sodium. This decision has since become the leading authority on the interpretation of PBP claims in Japan.

The IPHC's approach is nuanced, establishing a general rule but allowing for a significant exception:

General Rule: Process-Limited Interpretation for "Nominal PBP Claims"

The Grand Panel held that, as a general principle, the technical scope of a product-by-process claim should be determined based on the literal wording of the claim. This means that the manufacturing process recited in the claim is generally considered a limiting feature. The Court emphasized that treating PBP claims differently from other types of claims without a compelling reason could undermine the public's reliance on the clear language of patent claims and thereby harm legal stability. Therefore, for what can be termed "nominal PBP claims" (or "pseudo PBP claims" – termed fuseishin PBP kurēmu in some commentaries), where the product could have been defined by its structure or characteristics at the time of filing, the process acts as a genuine limitation on the claimed product.

The Exception: Product-Identity Interpretation for "True PBP Claims"

The IPHC carved out a critical exception for what it designated as "true PBP claims" (shinsei PBP kurēmu).

• Defining a "True PBP Claim": A PBP claim qualifies as a "true PBP claim" if, at the time the patent application was filed, "circumstances existed that made it impossible or difficult to directly specify the product by its structure or characteristics." These circumstances might include the product having an unknown or highly complex structure, limitations in analytical technology at the time of filing that prevented precise structural elucidation, or situations where the process uniquely defines the product's novel and non-obvious properties which cannot otherwise be captured.
• Interpretation of "True PBP Claims": If a PBP claim is determined to be a "true PBP claim" due to such circumstances, the manufacturing process recited in the claim is viewed as having been included for the essential purpose of identifying and defining the novel product itself. In these exceptional cases, the technical scope of the patented invention is not limited to products made exclusively by the recited process. Instead, it extends to cover any product that is identical to the product defined by the claim, regardless of the method by which that identical product was manufactured. Essentially, the product-identity theory applies to "true PBP claims."

Burden of Proof for "True PBP Claim" Status

A crucial aspect of the IPHC's decision concerns the burden of proof. The Court clarified that the party asserting that a PBP claim should be interpreted broadly under the product-identity theory (i.e., that it is a "true PBP claim") bears the burden of proving the existence of the aforementioned exceptional circumstances—that it was indeed impossible or difficult to define the product by its structure or characteristics at the time of filing. This party is typically the patentee.

If the patentee fails to discharge this burden of proof, the claim will not be treated as a "true PBP claim." Consequently, it will be interpreted according to the general rule: the recited process will be considered a limitation, and the claim's scope will be restricted to products made by that specific process.

The distinction can be summarized as follows:

Implications of the IPHC Grand Panel Decision

The IPHC's 2012 decision has brought a greater degree of clarity and a structured analytical framework to the interpretation of PBP claims in Japan.

• For Patentees:
  • Drafting Strategy: When drafting patent applications, applicants should carefully assess whether a product can indeed be adequately defined by its structure or properties. If a PBP claim format is chosen out of necessity, it is crucial to gather and preserve evidence demonstrating why direct structural or characteristic-based definition was impossible or difficult at the time of filing. This evidence will be vital if the patentee later needs to argue for a broader, product-identity interpretation during enforcement.
  • Litigation: If a patentee wishes to assert a PBP claim against a product made by a different process, they must be prepared to prove to the court that their claim qualifies as a "true PBP claim" by demonstrating the requisite impossibility or difficulty at the filing date.
• For Third Parties:
  • Freedom-to-Operate Analysis: When assessing potential infringement risks related to a PBP claim, third parties should analyze whether the claim is likely to be considered "true" or "nominal." If the product described in the PBP claim could have been defined by its structure or properties at the time the application was filed, it is more likely that the claim will be interpreted in a process-limited manner. This might offer greater scope for designing around the patent by using an alternative manufacturing process that still yields an identical or similar product.
  • Invalidity Challenges: Third parties might also challenge the validity of a PBP claim if the patentee attempts to assert a broad product-identity scope without sufficient justification for the "true PBP claim" status, or if the product, however defined, lacks novelty or inventive step.

Conclusion

The Japanese approach to interpreting product-by-process claims, as crystallized by the Intellectual Property High Court's Grand Panel decision in the Pravastatin Sodium case, strikes a balance. It generally upholds the principle that claim language, including process limitations, should be respected to ensure legal certainty for the public (process-limited view for "nominal PBP claims"). However, it also recognizes the practical necessities of certain technological fields by allowing for a broader, product-identity interpretation for "true PBP claims," where defining a product by its structure or properties was genuinely impossible or difficult at the time of filing. The key determinant is the existence of these specific circumstances, and the burden of proving them lies with the patentee seeking the broader interpretation. This framework provides a clearer, albeit still fact-intensive, pathway for analyzing the scope of these uniquely drafted patent claims in Japan.