ROHM & Haas Company & Anor v Collag Ltd & Anor

A patent cannot ordinarily be construed by reference to another patent or later patent application. The meaning of technical language must be determined from the patent specification, read in its proper context, with appropriate expert evidence and in accordance with Patents Act 1977, section 125 and the Protocol on Interpretation. A later document showing how a party used the same word cannot establish the meaning of that word in the earlier patent. Fresh evidence is immaterial to an appeal where it depends on such inadmissible comparative material and cannot materially affect the construction issue.

The applicants appealed a preliminary infringement decision concerning a patent for producing water-dispersible propanil granules. Neuberger J had held that two materials used in the respondents’ process were not surfactants within claim 1 and had declared that the process did not infringe.

Before the appeal was heard, the applicants sought leave to introduce a further expert report referring to a patent application published after the patent in suit. They relied on the later application’s use of the expression surfactant and on technical evidence concerning random copolymers. The central issue was whether that later application could assist in construing surfactant in the earlier patent.

1. Application refused. The applicants were ordered to pay the respondents’ costs, assessed at £9,200.
2. The proposed evidence depended principally on the proposition that the respondents’ later patent application described certain non-amphiphilic copolymers as surfactants, and that this usage should determine the meaning of surfactant in the earlier patent. That proposition was inadmissible and irrelevant to construction of the patent in suit.
3. The court applied the principle illustrated by Glaverbel SA v British Coal Corporation [1995] RPC 255: a patent cannot be construed with the aid of another document, including a later patent or evidence of subsequent transactions. The court also followed the similar approach in Minnesota Mining & Manufacturing Co v Plastus Kreativ AB [1997] RPC 737, where dictionaries and other documents could not determine the meaning of technical language in a patent.
4. Technical evidence may properly instruct the court about possible meanings of a technical term. However, construction is then governed by the specification, the context in which the term is used, section 125 of the Patents Act 1977, and the Protocol on Interpretation. The use of surfactant in a patent application drafted nine years later could not assist that exercise.
5. The fact that the proposed technical evidence might establish that random copolymers were not amphiphilic did not alter the conclusion. Its relevance depended on the inadmissible comparison between the later application and the patent in suit. The evidence therefore could not materially affect the appeal.

• Chancery Division: Neuberger J decided on 28 July 2000 that process B did not infringe the patent and granted declarations concerning the meaning of surfactant.
• Court of Appeal (Civil Division): The application to introduce fresh evidence was refused. The appeal itself was to be heard later.