Osaka District Court, 1998 (Wa) 7191 [Ink Tube for a Writing Instrument] *A case in which adding another substance to an otherwise infringing accused product resulted in noninfringement!!
Updated: 6 hours ago
Article information
Article type: Case note
Category: Patents
Topics: —
First published on this website: 2026-11-01
Display and classification checked: November 2, 2026
Originally published on Ameblo: 2024-09-08 (Japan time). Full English translation.
Osaka District Court, 1998 (Wa) 7191 [Ink Tube for a Writing Instrument] *A case in which adding another substance to an otherwise infringing accused product resulted in noninfringement!!
*Without a gelling agent the limitation was satisfied, but adding a gelling agent resulted in non-satisfaction.
In light of the invention's purpose (a backflow-preventing agent), gelled polybutene was found to be a different substance from polybutene before gelation.
⇒ “The backflow-preventing agent is polybutene” not satisfied
Cf. Tokyo District Court, 2005 (Wa) 14346
(Excerpts from the court's reasoning)
…Although the polybutene in the backflow-preventing agent of the accused product is gelled by a gelling agent, it continues to exist as polybutene within the gelling agent's three-dimensional network. There is therefore some room to view it as having the configuration of the device at issue, “the backflow-preventing agent consists of polybutene.” …
Polybutene gelled by a gelling agent is found normally to exhibit high viscosity, while, as ink flows out during writing, the shear rate of the backflow-preventing agent increases, lowering its apparent viscosity so that it follows the ink. …
From the standpoint of its use as a backflow-preventing agent, it is inappropriate to divide polybutene gelled by a gelling agent into “addition of the gelling agent (or the network structure of the gelling agent)” and “polybutene,” and treat the former as a merely additional configuration. Pure polybutene and polybutene gelled by a gelling agent should be considered different substances. Accordingly, the accused product, whose backflow-preventing agent consists of polybutene gelled by a gelling agent, must be said not to have the configuration of the device at issue, “the backflow-preventing agent consists of polybutene.”
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November 2, 2026: Added article information, classification, topics, language navigation, related articles where the same case was confirmed, consultation guidance, and SEO. The original text and first-published date were preserved.
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