In a case where the key issue was whether a UV absorber with a molecular weight of 699.91848, used in the defendant’s product, fell under the claim limitation of “a UV absorber with a molecular weight of 700 or more,” the IP High Court ruled as follows: (i) Regarding literal infringement, the Court interpreted the numerical limitation “700 or more” as a strict integer value without decimals, thus finding no literal infringement. (ii) Regarding Doctrine of Equivalents (“DoE”), while the Court found that the difference in molecular weight was not an essential part of the invention, it held that the applicant’s arbitrary selection of “700 or more” during the prosecution constituted an objective acknowledgment to exclude anything “less than 700” from the claims. Consequently, the Court denied Plaintiff’s DoE arguments and dismissed the Plaintiff’s claims. (IP High Court, March 4, 2025 (Case No. 2024 (Ne) 10026))
Background
This case involves a patent infringement lawsuit where the plaintiff-appellant (Nippon Shokubai Co., Ltd., the “Plaintiff”), the patent holder, sought damages, an injunction, and disposal of the defendant’s product (the “Defendant's Product”) against the defendant-appellee (Kaneka Corporation, the “Defendant”). The Plaintiff alleged that the Defendant's Product and its manufacturing method (the “Defendant’s Method”) infringed on its patent (Patent No. 4974971).
As mentioned above, one of the key issues was whether the Defendant’s Product and the Defendant’s Method fell within the technical scope of the patented invention. Especially, at issue was whether the UV absorber used in the Defendant's Product (the “Defendant's UVA”) fell within the claimed limitation of “a UV absorber with a molecular weight of 700 or more,” because the molecular weight of the Defendant's UVA was “699.91848” (Note: this value of the Defendant's UVA was not disputed by either party in the appeal stage).
The Osaka District Court, as the court of first instance, dismissed all of the Plaintiff's claims. Then, the Plaintiff appealed the decision to the IP High Court, which also found no literal or equivalent infringement.
Details of the Invention
(1) Technical Significance of the Invention
The technical significance of the invention is a thermoplastic resin composition suitable as a heat-resistant transparent material. The prior art faced challenges where molding resin compositions with a high glass transition temperature (Tg) at high temperatures often led to issues like foaming, bleed-out of the UV absorber (UVA), and problems due to UVA evaporation. The purpose of the invention is to provide a resin composition that has a high Tg and excellent heat resistance while suppressing foaming and bleed-out and reducing problems from UVA evaporation during high-temperature molding. To solve the problem, the invention provides a combination of a thermoplastic acrylic resin having a specific ring structure in its main chain with a UVA having a specific hydroxy-phenyl-triazine and a molecular weight of 700 or more.
(2) Examples
The Specification describes experimental results showing the desired effect in an Example using a UVA with a molecular weight of 958, and the absence of such effect in Comparative Examples using UVAs with molecular weights of 676 or less.
First Instance Judgment
(Osaka District Court, Feb. 26, 2024 [Case No. 2022 (Wa) 9521])
The Osaka District Court dismissed all of the Plaintiff's claims, reasoning as follows:
(1) Literal Infringement
The Court noted that the Claims and Specification list the molecular weight of the UVA as an integer, but do not clarify the calculation method or the basis for rounding to an integer (e.g., rounding the first decimal place). Therefore, it should be interpreted based on the common technical knowledge of a person skilled in the art.
The Court found that there was no established common technical knowledge that calculated molecular weights should be rounded to an integer. It also determined the molecular weight of the Defendant's UVA to be 699.91848.
Based on this, the Court concluded that this value did not meet the “molecular weight of 700 or more” requirement, and thus the Defendant’s Product and the Defendant’s Method did not satisfy such numerical limitations.
(2) Doctrine of Equivalents
Under the case law of the Supreme Court of Japan (the so-called “Ball Spline Bearing Judgment”, issued on February 24, 1998), even if there is a part in the claim that is literally different from the accused products or processes (the “products”), there is infringement under the Doctrine of Equivalents if the following five requirements are met:
The IP High Court Judgment
The IP High Court upheld the first instance judgment and dismissed the appellant's claim, but it employed different reasoning for the DoE as follows.
(1) Technical Significance of “Molecular Weight of 700 or More”
The IP High Court reasoned that “the molecular weight that has technical significance in relation to the function and effect is not a pinpoint value of 700, but rather is considered to be a number within a wide range between the Example (958) and the Comparative Example (676), and the applicant adopted the numerical limitation “700 or more” as a “rounded number.”
Based on this, it found that the numerical limitation of “700 or more” did not have a so-called critical significance (a point the Plaintiff also admitted).
(2) Finding on Literal Infringement
The Plaintiff (appellant) submitted an expert opinion and evidence to supplement common technical knowledge (JIS Handbook), arguing that “700” in “molecular weight of 700 or more” should be understood as a number rounded to the first decimal place, and thus should be interpreted as “699.5 or more.”
However, the IP High Court rejected this argument for the following reasons, stating that even if it is common practice in the art to round molecular weights to an integer, this practice does not directly apply to claim construction.
The IP High Court’s holding is as follows: “The claims define the technical scope of the patented invention (Patent Act, Art. 70(1)) and are required to function as a “public notice of rights” that guarantees predictability for third parties. Therefore, their interpretation cannot be performed without considering the unique perspective of patent law. From this viewpoint, the numerical range “(molecular weight of the UV absorber) of 700 or more” at issue here was set by the rights holder (the Plaintiff, the Applicant) to define the scope of the right, and it is nothing less than a dividing line that separates what belongs to the technical scope of the patented invention from what does not. That being the case, it is appropriate to interpret “700,” the lower limit of the said numerical range, as an integer in its true sense, having neither a truncated decimal part nor a rounded-up decimal part.”
As such, the IP High Court found that since the molecular weight of the Defendant's UVA was 699.91848, which is less than 700, it did not satisfy such numerical limitations.
(3) Equivalent Infringement
(3-1) First Requirement (Non-Essential Part)
Unlike the Osaka District Court, the IP High Court found that the First Requirement of the DoE was satisfied. It reasoned that the molecular weight of 700 lacked critical significance, there was technical significance across a wide range in relation to the function and effect, and it was not reasonable that the properties of the UV absorber would substantially differ between a molecular weight of 699.91848 and 700.
(3-2) Fifth Requirement (Special Circumstances)
The IP High Court found that since the numerical value of 700 lacked critical significance, it was a value that the appellant had arbitrarily chosen. The IP High Court noted that it would have been easy for the Plaintiff to set the lower limit to “699.5 or more” or to define the handling of decimal values, but it intentionally did not take such measures. From this, the IP High Court deemed it appropriate to find that the Plaintiff had drawn a line between “700 or more” and “less than 700” to define the technical scope and had “objectively and outwardly” acknowledged the exclusion of anything even slightly below the lower limit of “700.” As such, the IP High Court concluded this amounted to “intentional exclusion”, and thus the Fifth Requirement of the DoE was not met.
As a result, equivalent infringement was also denied.
Comments
(1) Literal Infringement
With regard to literal infringement, while there might be different views on interpreting “700” strictly as an integer, I think this is a reasonable conclusion, especially given the recent trend toward literal claim construction. As the Judgment states, if the intention was for “molecular weight 700” to mean “699.5 or more”, the applicant should have explained the calculation method for molecular weight and the handling of decimal places in the Specification before filing.
However, such an explanation alone might not always be sufficient. In this case, for example, if the Specification had mentioned the rounding of the molecular weight, it is highly likely that the Defendant’s Product would have been covered. On the other hand, for example, if an infringing product had a molecular weight of “699.4,” merely mentioning rounding in the Specification would not have been enough to cover it.
(2) DoE
In the IP High Court Judgment on DoE, unlike the first instance, the Court found that the First Requirement (Non-Essential Part) was met because the numerical limitation lacked critical significance and there was no substantial difference in the properties of the UV absorber between molecular weights of 699.91848 and 700. This means that when a numerical value itself lacks critical significance, there is room to find a technical idea or essential feature with a certain breadth, not bound by the specific range described in the claims.
The reason DoE was denied this time was the Fifth Requirement (Special Circumstances).
In this case, the IP High Court placed significant weight on the following fact: It would have been easy for the applicant to set a slightly lower value, such as “699.5,” as the lower limit before the filing, but the applicant nevertheless chose to limit it with the integer "700 or more."
(3) Takeaway
In recent years, it is said that patents are less likely to be invalidated in Japan, and it is sometimes argued that during the prosecution stage or before the filing, considering future infringement argument is more important than preparing for future (in)validity arguments.
In this case, the largest molecular weight in the Comparative Examples was 676 (the others were 659 and 315). Therefore, any number slightly larger than 676 could have been sufficient for the lower limit of the claimed numerical range. This highlights the need to thoroughly consider what scope applicants want to claim, including the relationship with the Examples and the Comparative Examples, while envisioning potential enforcement.
This case is informative not only for its perspective on infringement arguments but also for the insights it provides on matters to consider before the filing or during the prosecution. Furthermore, as the IP High Court judgment on the Fifth Requirement of the DoE relates to a part that was not excluded through prosecution history (amendments), it is considered to be practically useful.
The full text of the first instance judgment can be found here (external website, in Japanese).
The full text of this judgment (IP High Court) can be found here (external website, in Japanese).
Written by: Mr. Yuichiro Suzuki (Attorney at Law in Japan and California, Patent Attorney in Japan)