Blog Post

Federal Court Invalidates Patents for Ambiguity

In its recent decision in Tekna Plasma Systems Inc. v. AP&C Advanced Powders & Coatings Inc., 2024 FC 871, the Federal Court (the “Court”) determined that both patents at issue—Canadian Patent No. 3,003,502 and Canadian Patent No. 3,051,236—are invalid and not infringed.

This is an extraordinary case where the Court invalidated the patents on the basis of ambiguity—a rare occurrence and a good reminder that it can happen. This rarity was even noted by Justice McHaffie, who stated:

I therefore find that despite the Court’s general disinclination to find a patent claim ambiguous, all of the claims of the ’502 Patent and most of the claims of the ’236 Patent are invalid for ambiguity.

Patent claims communicate the monopoly that the patentee is claiming to the public. The claims provide notice of the boundaries of the invention and, in doing so, the area that is prohibited. Accordingly, the Patent Act requires the claims of a patent to define “distinctly and in explicit terms” the subject matter of the invention for which an exclusive privilege or property is claimed. 

While the claims of a patent must define its subject matter “distinctly and in explicit terms,” they do not need to be “perfect or a model of lucidity.” The claims are addressed to the person skilled in the art who aims to understand and give them a fair meaning. The Court has repeatedly found that a lack of clarity or potential competing constructions of claims is not fatal if they can be fairly understood by the person skilled in the art. For this reason, it is rare for the Court to find invalidity solely on the basis of ambiguity.

The patents at issue in this case relate to the production of reactive metal powders, which are particularly useful in 3D printing. Both parties are manufacturers of metal powders. The claims of the patents include the essential element of the formation of a “depletion layer” or a system configured to control the formation of a depletion layer. The meaning of the term “depletion layer” and the ability to determine whether a powder particle has a depletion layer were fundamental to the disputes in this action. The term “depletion layer is not generally used in the field of powder manufacturing—it is not a term of art. Accordingly, the meaning of “depletion layer” had to be determined from the patent. The Court found that it was impossible for the skilled person to determine whether or not a powder particle has a depletion layer within the meaning of the claims.

This case serves a reminder that (1) ambiguity remains an effective ground for challenging the validity of a patent; and (2) any essential elements of claims that are not terms of art should be clearly defined during prosecution.