by Dennis Crouch
E.I. DuPont de Nemours & Co. v. Unifrax I LLC (Fed. Cir. 2019)
In 2014, DuPont sued Unifrax for infringing its patented flame-barrier that is both lightweight and thin. U.S. Patent 8,607,926 (“Composite Flame Barrier Laminate for a Thermal and Acoustic Insulation Blanket”). The jury sided with DuPont — finding the asserted claims infringed and not proven invalid. Over a dissent from Judge O’Malley, the Federal Circuit has affirmed — finding that substantial evidence supports the verdict. (Majority authored by Judge Reyna and joined by Judge Hughes).
When 90% counts as 100%: A key issue on appeal was the meaning of the claim term “100%.” DuPont’s claims required an “inorganic refractory layer” made of “platelets in an amount of 100% by weight.” That particular limitation was added during prosecution to get around a prior art reference that taught a platelet concentration of less than 100%.
The accused product layer approximates 100% platelets, but has some small amount of residual dispersant that didn’t fully evaporate. Prior to trial, the district court sided with DuPont on claim construction and ruled that “100%” be interpreted as allowing for “some residual dispersant.” This substantially foreclosed Unifrax’s non-infringement argument that it had hoped to take to the jury.
On appeal, the Federal Circuit affirmed — finding a more-relaxed construction of 100% was correct because of how the mathematical construct was used in the patent document itself. The key phrase from the specification is as follows:
The refractory layer comprises platelets. Preferably at least 85% of the layer comprises platelets, more preferably at least 90% and most preferably at least 95%. In some embodiments, platelets comprise 100% of the layer. The refractory layer may comprise some residual dispersant arising from incomplete drying of the platelet dispersion during manufacture.
According to the court, the final sentence of this paragraph — allowing for residual dispersant in the layer — applies to all of the embodiments, including the 100% layer. Thus, when the patent says “100%” platelets, it really meant almost-all platelets with potentially a bit of dispersant. According to the majority the defendant is wrong that “‘100%’ means one hundred percent.”
Writing in dissent, Judge O’Malley argued that the majority’s construction “ignores the plain meaning of ‘100%’ and introduces more ambiguity than it resolves.”
There is no ambiguity in this language. The “platelets” must be present in the refractory layer “in an amount of 100% by weight.” The “100% by weight” language, coupled with the requirement that the platelets exist in an “inorganic refractory layer,” clearly contemplates that the platelets—i.e., inorganic material—constitute the entirety of the refractory layer. That leaves no room for other organic additives. There is perhaps no clearer or simpler way the patentee could have conveyed such a requirement.
The claim language is actually quite mess in the same clause it indicates that the refractory layer comprises “platelets in an amount of 100% by weight” but may also have a moisture content of up to 10% by weight. 110% by weight concentration is not ordinarily allowed in physics. However, we do sometimes talk about “110% effort” and Cecil Quillin has reported a USPTO’s patent grant rate as greater than 100% (by comparing original filings to all patents issued in the resulting family).
I pulled up the prosecution history and found that the 100% and 10% elements were added at the same time in the same amendment with the statement that the claim now “requires a refractory layer containing 100% platelets (and also requires . . . a defined residual moisture content).” In my mind, this works strongly in the patentee’s favor — that the 100% allows for residual moisture. Still, it is unfortunate that the ultimate holding is a rejection of the defendant’s argument that “‘100%’ means one hundred percent.”
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Product on sale before the patent filing. A unique aspect of this lawsuit is that the accused products were already on sale before DuPont filed its patent application.
Unifrax’s product was on-sale by May 2011; DuPont filed its application in December 2011. To be clear, DuPont’s patent does claim priority to prior applications, but only as a continuation-in-part. The prior applications apparently do not sufficiently disclose the invention at-issue here.
For DuPont, the fact that its patent was filed prior to the AIA saved its bacon. On appeal, the Federal Circuit agreed that DuPont had presented substantial evidence to antedate Unifrax’s prior use/sale.
The critical point of law focused on proof of the prior invention. The courts have long been suspicious of inventor’s self-serving testimony regarding prior inventorship. Here, the duPont provided inventor testimony along with substantial documentation of the prior invention timing. However, the company did not provide o corroborating evidence as to one particular limitation in the claims — a requirement that the refractive layer have a “dry areal weight of 15 to 50 gsm.”
On appeal, the Federal Circuit sided with duPont — reflecting on the requirement for corroboration.
[O]ur case law does not require that evidence have a source independent of the inventors on every aspect of conception and reduction to practice. . . Here, the law requires only that the corroborative evidence, including circumstantial evidence, support the credibility of the inventors’ story.
The reason for corroboration is a concern that inventors will commit perjury. Thus, the role of corroboration is help ensure inventor credibility.