What Constitutes Indirect Patent Infringement Under Japanese Law, and How Can It Be Proven?

Japanese patent law, like that of many other industrialized nations, recognizes that the effective enforcement of patent rights requires more than just addressing direct acts of infringement. Often, the most commercially significant or easiest party to pursue is not the end-user directly infringing the patent, but rather a supplier or manufacturer whose activities are preparatory or contributory to that direct infringement. To address this, Article 101 of the Japanese Patent Act provides for indirect patent infringement (間接侵害 - kansetsu shingai), deeming certain contributory acts themselves to be infringements of the patent right.

This doctrine is crucial for patentees as it can provide a basis for obtaining injunctive relief and damages against entities that facilitate infringement, even if they do not themselves perform every element of the claimed invention. Understanding the nuances of indirect infringement is therefore vital for businesses operating in or with Japan.

The Foundation: Existence of (Potential) Direct "Working"

Indirect infringement under Article 101 is fundamentally linked to a direct "working" (実施 - jisshi) of the patented invention by an entity, typically a third party (e.g., a customer of the alleged indirect infringer). This direct working must occur, or be imminently likely to occur, within Japan. The direct working itself can be a literal infringement of the patent claims or an infringement under the Doctrine of Equivalents.

A critical question arises: must this underlying direct working by the third party be a culpable or actionable infringement for indirect infringement to be established? Or is it sufficient that the third party's act formally corresponds to the definition of "working" the invention, even if that third party has a valid defense to a direct infringement claim (such as experimental use or private use)?

Japanese law and practice have evolved a nuanced approach to this, often referred to as the "Scope of Limiting Provisions Theory" (制限規定等射程説 - seigen kitei tō shatei setsu). Instead of a blanket "dependent" (requiring culpable direct infringement) or "independent" (formal correspondence is enough) rule, this theory examines the purpose and scope of the specific legal provision that renders the direct user's act non-infringing. The key is whether the policy underlying that defense for the direct user should also extend to protect the alleged indirect infringer.

• Private/Household Use (Art. 68, Patent Act): If a direct user's working is non-infringing because it's for personal or household use, a commercial supplier of a product exclusively for such working may still be liable for indirect infringement. The policy of exempting private use (minimal economic impact on the patentee, privacy concerns) generally does not extend to shielding commercial entities that systematically enable or induce widespread private working of the invention. This effectively leads to an "independent theory" outcome in this context.
• Experimental or Research Use (Art. 69(1), Patent Act): If the direct user's working is exempt because it's for experimental or research purposes, the supplier of a product exclusively for such experimentation is also generally not liable for indirect infringement. The strong public policy of promoting research and development would be undermined if researchers could not obtain necessary tools and materials. This leads to a "dependent theory" outcome.
• Other Defenses for Direct User: Similar "dependent theory" outcomes are typically seen where the direct user has a defense based on an employer's statutory license for an employee invention (Art. 35(1)), a prior user right (Art. 79), or patent exhaustion. The rationale is that denying suppliers the ability to provide necessary parts or products to these legitimate users would effectively nullify the direct user's defense.

It's also important to note that the concept of "production" (生産 - seisan) by the direct user (relevant for indirect infringement related to product patents) is interpreted broadly. It can include not just manufacturing from scratch but also acts like assembling supplied components into a finished patented product or installing software to make a device operate as the patented invention. For example, courts have found "production" by a user when they installed software onto a computer, thereby creating the patented information processing device (Tokyo District Court, February 1, 2005, Hanrei Jihō No. 1886, p. 21, the "Ichitaro" case), or when a user attached a replacement hammer to a patented crushing machine (Osaka District Court, April 24, 1989, Mutaishū Vol. 21, No. 1, p. 279, the "Hammer for Crushing Machine" case). However, merely supplying two separate components that a user might combine, without the supplier's act leading to the creation of the specifically claimed combination at the user's end, might not trigger indirect infringement if the user's act itself isn't "production" of the claimed product.

Categories of Indirect Infringement under Article 101

Article 101 defines several distinct acts that are "deemed to be an infringement." These are categorized based on whether the patent is for a product or a process, and further subdivided by the nature of the supplied article and the supplier's intent. All acts must be performed "in the course of trade" (業として - gyō to shite).

A. For Inventions of a Product (Art. 101, items 1 and 2)

These items deal with the supply of articles used for the production of a patented product.

1. Item 1: The "Only-Use" or Dedicated Component Type (「にのみ」型 - ni nomi gata)

This provision targets the supply of articles that are exclusively (にのみ - ni nomi) used for the production of the patented product. The prohibited acts are producing, assigning, leasing, importing, or offering for assignment or lease such dedicated articles.

• Meaning of "Exclusively": This is a key interpretive point. Does the mere theoretical possibility of some other obscure use negate exclusivity? The prevailing judicial approach focuses on whether there are any actual, commercially significant, or practically viable alternative uses for the article at the relevant time. If all realistic uses lead to the production of the patented product, the "only-use" requirement is likely met. The relevant time for assessing other uses is generally the time of the infringing act for damages, and the conclusion of oral arguments for injunctive relief.
• The "Someday Will Use" (itsuka wa tsukau) Criterion: An interesting line of cases, exemplified by the Osaka District Court decision of October 24, 2000 (Hanrei Times No. 1081, p. 241, the "Bread Maker" case or 「製パン器」事件), explored situations where a product had both infringing and non-infringing modes of use. The court suggested that if it's unrealistic for a typical user to only use the non-infringing mode indefinitely, and they would inevitably use the infringing mode, the "only-use" requirement could be satisfied. This reasoning has been subject to criticism, particularly after the 2002 Patent Act amendments introduced the "multi-functional" type of indirect infringement (discussed next), which provides a more tailored framework for such dual-use articles. Nevertheless, some later decisions have still referenced this criterion.
• "Idle" Components in Non-Infringing Uses: If a supplied article can be used with a non-patented main product, but a specific feature of the article (which is key to the patented invention when used with a patented main product) remains unused or "idle" in that non-infringing combination, courts have found that the "only-use" requirement is not met for the article as a whole. The article itself has a viable non-infringing use, even if one of its features is dormant in that use (e.g., Tokyo District Court, February 25, 1981, Mutaishū Vol. 13, No. 1, p. 139, the "Single-Lens Reflex Camera" case or 「一眼レフレックスカメラ」事件).

2. Item 2: The Multi-Functional / Essential Element Type (多機能型 / 不可欠型 - takinō gata / fukaketsu gata)

This provision, introduced by the 2002 amendments, addresses situations where the supplied article is not exclusively for the patented product but is still a key contributor to the infringement. It prohibits producing, assigning, etc., an article (that is not a staple commercial article or commodity widely distributed in Japan - 汎用品 han'yōhin) to be used for the production of the patented product, where that article is indispensable for the resolution of the problem by the said patented invention (不可欠要件 - fukaketsu yōken), and the supplier knows that the invention is patented and that the article is to be used for working the invention.

Key elements here are:

• Knowledge (主観的要件 - shukanteki yōken): The supplier must know of the patent and know that their article will be used to work that patented invention. This knowledge requirement is often satisfied once the patentee sends a warning letter or files an infringement suit. The relevant time for assessing knowledge is the time of the act for past damages and the close of oral arguments for future injunctions (IP High Court Grand Panel, September 30, 2005, Hanrei Jihō No. 1904, p. 47, the "Ichitaro" case).
• "Not Widely Distributed in Japan" (Staple Commercial Article Exception / 非汎用品要件 - hi-han'yōhin yōken): This exempts common, general-purpose articles (e.g., generic screws, raw materials) from this type of indirect infringement, even if they are technically "indispensable." The interpretation of "widely distributed" or "staple commercial article" is not based merely on sales volume. If an article, even if made of common materials, is specifically configured or includes features particularly adapted for the patented invention, it may be deemed not to be a "staple commercial article" for the purposes of this provision.
• "Indispensable for the Resolution of the Problem" (不可欠要件 - fukaketsu yōken): This is a heavily litigated and complex element.
  • Initial legislative intent suggested it might be similar to the "essential part" concept in the Doctrine of Equivalents. However, simply being an "essential" known component is not enough.
  • "Characteristic Technical Means" Theory (特徴的技術手段説 - tokuchōteki gijutsu shudansetsu): Many court decisions have interpreted this to mean that the supplied article must embody or constitute the characteristic technical means newly disclosed by the patented invention for solving the problem addressed by the prior art. If the article is merely a known component, even if essential for the patented combination, it might not meet this "indispensable" criterion in this heightened sense. (See, e.g., Tokyo District Court, April 23, 2004, Hanrei Jihō No. 1892, p. 89, the "Clip for Printed Circuit Board Jig" case or 「プリント基板用治具に用いるクリップ」事件).
  • "Injunctive Appropriateness" Theory (差止適格性説 - sashitome tekikakusei setsu): An alternative (though less consistently adopted) perspective, notably discussed in the Ichitaro Grand Panel case, suggests that "indispensable" might mean a simpler "but-for" causality. The primary filter for multi-functional items would then be the "non-staple article" requirement, interpreted to ask whether an injunction against the article could be tailored to stop its infringing use without unduly suppressing its legitimate non-infringing uses (e.g., if the infringing feature can be easily removed or disabled).
    The "Characteristic Technical Means" theory appears to be the more dominant approach in recent practice for defining "indispensable."

B. For Inventions of a Process (Art. 101, items 4 and 5)

These provisions mirror items 1 and 2 but apply to the supply of articles used for the working of a patented process.

• Item 4: Prohibits producing, assigning, etc., an article to be used exclusively for the working of the patented process.
• Item 5: Prohibits producing, assigning, etc., an article (not a staple commercial article) to be used for the working of the patented process and indispensable for the resolution of the problem by that invention, with the requisite knowledge.

The interpretive challenges concerning "exclusively," "indispensable," "knowledge," and "staple commercial article" are analogous to those for product patents.

Special Scenarios and Advanced Considerations

Several specific factual scenarios further illustrate the complexities of indirect infringement.

1. Goods Transforming into the Patented Invention at the User's End

What happens if a product sold by the defendant is not infringing at the point of sale but, through normal handling, passage of time, or a simple user action, inevitably becomes the patented invention?

• Substantially Complete Production: If the transformation is rapid and occurs within the typical distribution or initial use period, courts might deem the "production" of the patented invention to be substantially complete at the point of sale by the defendant, leading to direct infringement liability for the seller. The Tokyo District Court decision of November 4, 1999 (Hanrei Jihō No. 1706, p. 119, the "Mold Killer" case or 「カビキラー」事件), found direct infringement where a household cleaning agent composition changed to meet claim limitations within 28-30 days, a period considered typical for distribution and initial use.
• User Completes Production: Alternatively, if the user performs a final step (e.g., dissolving a supplied agrochemical in water, thereby creating the claimed composition), the user might be seen as performing the "production." The supplier could then be liable for indirect infringement for providing the article used in that production.
• Period of Non-Infringing Use: If the supplied product has a significant period of legitimate, non-infringing use before it transforms or wears into an infringing state, establishing indirect infringement (especially of the "only-use" type) becomes more difficult. The "multi-functional/essential element" type might be more relevant, but the analysis will be fact-intensive (e.g., the IP High Court decision of July 18, 2003, 2002 (Ne) 4193, the "Doctor Blade" case or 「ドクターブレード」事件, where a blade only infringed after wear over time).

2. Working by Multiple Entities (Divided Infringement)

This situation often arises with method patents where different entities perform different steps of the claimed method. If no single entity performs all the claimed steps, there may be no single direct infringer. This poses a challenge for indirect infringement, which typically presumes a direct "working" by someone.

Japanese courts have developed theories to address this:

• "Joint Working" or "Concerted Action" Theory (共同遂行理論 - kyōdō suikō riron): If multiple parties act in concert, with a common plan or control, to collectively perform all steps of the invention, they may be held jointly liable for direct infringement. (See Osaka District Court, May 4, 1961, Kaminshū Vol. 12, No. 5, p. 937, the "Foamed Polystyrene" case or 「発泡性ポリスチロール」事件).
• "Tool" or "Instrumentality" Theory (道具理論 - dōgu riron): If one entity (Y) performs some steps and provides an intermediate product to another entity (Z) for completion of the remaining steps, and the intermediate has no substantial non-infringing use other than for Z to complete the patented process, Y might be deemed to have used Z as a "tool" or instrumentality to perform the entire process. Y could thus be held liable for direct infringement. (See Tokyo District Court, September 20, 2001, Hanrei Jihō No. 1764, p. 112, the "Electrodeposited Image Forming Method" case or 「電着画像の形成方法」事件).

The underlying goal is to prevent easy circumvention of patent rights by merely splitting the infringing acts among different parties acting with a degree of coordination or where one party effectively controls or directs the entire infringing outcome.

3. "Indirect Indirect Infringement" (間接の間接侵害 - kansetsu no kansetsu shingai)

The IP High Court Grand Panel in the "Ichitaro" software case (September 30, 2005) seemed to reject the concept of "indirect indirect infringement" in the context of method patents. The specific facts involved a computer program. The program itself could be an article whose supply leads to indirect infringement of a product patent (claiming a computer system including that program). However, if the patent was for a method performed by that computer system, the court suggested that the computer system itself would be the article whose supply leads to indirect infringement of the method patent (under Art. 101, item 5). Supplying the program (a component of that computer system) was seen as one step further removed – supplying a component of an article that is itself used to work the method. The court appeared unwilling to extend indirect infringement liability to this "component of a component" for a method patent.

This aspect of the Ichitaro decision has drawn academic criticism for lacking a clear statutory basis and for potentially creating arbitrary distinctions depending on how claims are drafted. Some commentators argue that the ruling might be limited to its specific facts, particularly involving intangible software as the "component of a component".

Remedies and Relation to Other Provisions

Since Article 101 deems the specified acts to be infringements, the patentee can seek the same remedies as for direct infringement, primarily:

• Injunctions (差止請求 - sashitome seikyū) under Article 100 of the Patent Act, to stop the infringing acts.
• Damages (損害賠償請求 - songai baishō seikyū) under Article 102 of the Patent Act (based on general tort principles of Civil Code Article 709).

Furthermore, when seeking an injunction against a direct infringer, Article 100(2) allows the patentee to request the disposal of articles that constituted the act of infringement, products made by the infringing act, or facilities used exclusively for the infringing act. If such a disposal request targets components, the principles underpinning indirect infringement (especially the "only-use" or "indispensable" nature and lack of other significant uses) would likely inform whether disposal of such components is appropriate, to avoid overreach.

Conclusion

Indirect infringement under Article 101 of the Japanese Patent Act is a vital tool for patentees, extending protection beyond acts of direct working to encompass preparatory and contributory activities that are commercially significant. The law distinguishes between "only-use" (dedicated) articles and "multi-functional but indispensable" articles, with specific knowledge requirements for the latter. The interpretation of these provisions, particularly terms like "exclusively," "indispensable," and the interplay with defenses available to direct users, has been shaped by extensive case law. Scenarios involving goods that transform post-sale or infringements divided among multiple entities further add to the complexity. Successfully proving or defending against a claim of indirect infringement requires a meticulous analysis of the statutory language, the relevant precedents, and the specific factual circumstances surrounding the accused acts and the nature of the supplied articles.