【Patent】Legal Constraints on Disclaimer-Type Post-Grant Amendments: Practical Implications of the 2025 Min Zhuan Shang Zi No. 7 Civil Judgment
I. Introduction and Case Background
In the underlying dispute, the Appellant alleged that the “TR-646 Hollow Rotary Hydraulic Cylinder” manufactured and sold by the Appellee infringed its Utility Model Patent No. M510203 (hereinafter, the “patent at issue”). The parties did not contest that the accused product fell within the literal scope of the asserted claims. Nevertheless, the Intellectual Property and Commercial Court (IPCC) held the patent at issue lacked an inventive step and was therefore invalid. As a result, the infringement claim necessarily failed, and judgment was entered in favor of the Appellee.
Notably, the dispositive issue in this case did not arise from claim construction or infringement analysis. Rather, it centered on the patentee’s unsuccessful attempt to preserve the patent’s validity through a post-grant amendment incorporating a disclaimer. The judgement underscores the narrow and exceptional nature of disclaimer practice under Taiwan patent system.
II. Doctrinal Framework Governing Disclaimer-Type Amendments
1. Definition and Statutory Constraints
According to the Patent Examination Guidelines[1], a “disclaimer” (or “negative recitation”) refers to a claim amendment (including a post-grant amendment) whereby a patentee employs exclusionary language, such as “excluding” or “but not including,” to remove specific technical features previously encompassed by the claim. While such amendments may narrow claim scope, they are subject to particularly stringent limitations during amendment proceedings.
Based on Paragraph 2 of Article 67 of the Patent Act, a post-grant amendment is prohibited from extending beyond the scope of content disclosed in the specification, claim(s), or drawing(s) as originally filed. Any amendment that introduces “new matter” is impermissible, as noncompliance with the “original disclosure” principle undermines public reliance on the predictability and legal certainty of the patent’s metes and bounds.
2. Exceptional Circumstances Allowing Disclaimers
Notwithstanding the foregoing restrictions, patent practice recognizes that disclaimers may be tolerated in narrowly circumscribed circumstances. These circumstances are generally limited to two scenarios:
- To Overcome Novelty Issues:
When a claim is partially anticipated by a single prior art reference, resulting in a lack of novelty (or deemed loss of novelty), the overlapping portion may be carved out, provided that:
(1) the disclaimer is strictly confined to the content disclosed in said prior art; and
(2) the remaining scope is clear and definitively identifiable.
(2) the remaining scope is clear and definitively identifiable.
- To Remedy Noncompliance with the First-to-File Principle:
Disclaimers may be allowed to address conflicts arising from the first-to-file principle, particularly to avoid double patenting. In such situations, claim scope may be narrowed to eliminate overlap with earlier-filed patent applications.
Outside these exceptional circumstances, courts adopt a highly restrictive stance toward disclaimer-type post-grant amendments.
3. Inadmissibility of the Disclaimer in this Case
In the present case, the Appellant sought to amend claim 1 by adding the recitation ‘but not including 1.357 to 1.7” to overcome the challenge posed by the Appellee’s Exhibit 3. However, the IPCC ruled the post-grant amendment inadmissible for the following three reasons:
- Fundamental Distinction between Inventive Step and Novelty:
The IPCC emphasized that the exception for disclaimers is primarily intended to cure novelty defects. Because the Appellee’s Exhibit 3 was cited as an inventiveness challenge rather than a novelty-destroying reference, the legal foundation for invoking a disclaimer was absent.
- Lack of Correspondence Between the Disclaimer and the Prior Art:
The Appellee’s Exhibit 3 disclosed only a single numerical value “1.357,” not the broader range of “1.357 to 1.7.” By excluding an expanded numerical interval not directly taught by the prior art, the Appellant introduced a new technical boundary unsupported by the original disclosure. Such an amendment constituted impermissible new matter.
- Failure to Meet the “Direct and Unambiguous Derivability” Standard:
The IPCC reaffirmed that any post-grant amendment must be directly and unambiguously derivable from the originally filed specification or drawings, as understood by a person having ordinary skill in the art. Because the original specification did not disclose the value “1.357,” nor articulate the technical significance of the proposed numerical range, the amendment failed this standard and risked prejudicing the public interest.
III. The Evidentiary Weight of “Advantageous Effects”
To bolster its inventive step argument, the Appellant asserted that the patent at issue facilitated “continuous feeding” via a central bore of optimized diameter. The IPCC found this argument groundless based on the following:
- Incomplete Disclosure:
The specification only described effects like reduced volume, cost savings, and extended service life, without any mention of “continuous feeding.”
- Lack of Reasonable Derivation:
The IPCC held that a person having ordinary skill in the art could not reasonably derive a definitive technical correlation between the “oil seal ratio” and “feeding convenience” from the existing disclosure. Absent a demonstrable causal link in the original disclosure, such asserted advantages could not compensate for the lack of an inventive step.
IV. Implications for Patent Prosecution and Litigation
1. Importance of Explicit Disclosure of Technical Effects
Under the Patent Act, protection is afforded to a technical solution rather than to a mere physical configuration. Where an invention yields specific technical or competitive effects, such effects should be expressly disclosed in the specification at the time of filing. Absent an explicit disclosure, the patentee may bear a heightened evidentiary burden in subsequent invalidation or infringement proceedings to establish that advantages manifested in a commercial product properly support the existence of an inventive step.
2. Strategic Drafting of Numerical Ranges
The case further illustrates the dual nature of numerical ranges as both a drafting tool and a potential vulnerability. Applicants are advised to conduct comprehensive prior art searches and to employ layered, alternative, or stepped numerical ranges where appropriate. Such drafting techniques can mitigate the risk that later amendments will be deemed to introduce new matter.
3. Legal Instability of Utility Model Patents
The case further reveals the inherent instability of utility model patents arising from the absence of substantive examination. For technologies of significant commercial or strategic value, utility models should be regarded as interim measures rather than as stable exclusionary rights. Once confronted with a credible combination of prior art, patentees face severe limitations in curing validity defects through post-grant amendments. Accordingly, applicants should prioritize invention patents for core technologies or promptly obtain a Technical Evaluation Report[2] following grant of a utility model patent to assess and enhance enforceability.
