When (and whether) contradictory claim language invalidates a patent
“Indefinite” patent language can invalidate a patent, leaving it unenforceable and creating a cascade of negative consequences for a company or individual relying on its protections. The U.S. Court of Appeals for the Federal Circuit, the court that hears all patent-related appeals, has shed some light on how contradictory language can affect the indefiniteness analysis.
Claim limitations power patent challenge
Maxell Ltd. owns a patent for a rechargeable lithium-ion battery. The patent requires at least two lithium-containing transition metal oxides, represented by formulas that include a transition metal element dubbed “M1.” Two claim limitations in the patent — one broad and one narrow — state requirements for M1.
Maxell sued Amperex Technology Limited for infringement of the patent after Amperex challenged the patent’s validity. The trial court held that the claim language defining M1 was indefinite on the ground that the two limitations contradicted each other.
Contradiction in terms
A patent will be found invalid for indefiniteness if it doesn’t conclude with at least one claim that particularly points out and distinctly claims the invention. The patent must inform, with reasonable certainty, those skilled in the relevant art about the scope of the patented invention.
The trial court took issue with the following phrase that combined the two limitations in question: “M1 represents at least one transition metal element selected from Co [cobalt], Ni [nickel] and Mn [manganese], … wherein the content of Co in the transition metal M1 of the formulae (1) and (2) is from 30% by mole to 100% by mole.”
The court reasoned that the phrase was indefinite because the first limitation didn’t require the presence of cobalt (nickel or manganese would suffice, too), but the second limitation did require cobalt. For an element to be both optional and required, it said, was a “contradiction on its face.”
Two things are possible
Maxell turned to the Federal Circuit for relief. The appellate court didn’t disagree with the trial court that a contradiction in a claim can produce indefiniteness, leading to the invalidation of a patent. But Maxell prevailed nonetheless, as the Federal Circuit found no such contradiction. The two claims’ limitations, it said, weren’t contradictory because it was “perfectly possible” for a transition metal element to satisfy both.
And it made no difference that the two requirements were placed in separate limitations, rather than both appearing in the first limitation (requiring that the metal element contain cobalt, nickel or manganese). This placement, the court said, didn’t alter the logical point that it’s possible to meet both requirements. After all, an individual trying to understand the scope of an invention should know not only that any particular claim language must be read in the context of the full claim, but also that all limitations must be considered when determining the scope.
While the appellate court implied that a “more artful” way of stating the two requirements in the same claim existed, it found a readily discernible explanation for the placement: The second requirement was added during patent prosecution to avoid an earlier reference that primarily used nickel as a transition metal. Moreover, the fact that there were other ways of drafting the claim didn’t render the claim language contradictory or indefinite.
Words matter
Ultimately, the appellate court’s ruling was good news for Maxell. But other patentees and would-be patentees shouldn’t overlook the underlying lesson: Contradictory claim language can invalidate a patent, so careful crafting is essential.
Maxell, Ltd. v. Amperex Technology Ltd., No. 23-1194 (Fed. Cir. March 6, 2024).
From the August/September 2024 Cantor Colburn IP Newsletter © 2024
