Mondis Technology Ltd., et al. v. LG Electronics Inc., et al., Nos. 2023-2117, -2116 (Fed. Cir. (D.N.J.) Aug. 8, 2025). Opinion by Hughes, joined by Taranto and Clevenger.
Mondis sued LG for infringement of a patent related to controlling a specific display unit (such as a monitor) that is configured to receive video signals from an external source (such as a computer). During prosecution of the patent, a claim limitation reciting “an identification number for identifying said display unit” was amended to recite “an identification number for identifying at least a type of said display unit.”
At trial, LG challenged the asserted claims as invalid for lacking written description for the “type limitation” added during prosecution. The jury found the asserted claims not invalid and infringed. LG filed a motion for judgment as a matter of law challenging, among other things, the jury’s finding of written description support. The district court denied the motion and upheld the jury’s findings on invalidity, infringement, and willfulness, but ordered a retrial on damages. After the retrial, both LG and Mondis appealed.
The Federal Circuit held the patent claims invalid for lack of an adequate written description and thus reversed. The court agreed with LG that “no reasonable jury could find the patent’s written description conveys to a relevant artisan that the inventors possessed the type limitation.” Thus, the jury’s finding on that issue lacked substantial-evidence support.
Mondis argued that because a patent is presumed valid, it was not required to provide any evidence to prove adequate written description support. The Federal Circuit explained that while sometimes a patentee need submit no evidence, “sometimes the patent itself is clear enough that it establishes inadequacy of support in the written description for the full scope of the claimed invention unless there is contrary evidence.” Here, the applicant had amended the claim to overcome a prior art rejection, and “this amendment changed the nature of the claim’s identification number from one identifying a specific display unit to one identifying a type of display unit.”
As to the patent’s disclosure, the Federal Circuit noted that it was undisputed the patent “does not expressly disclose the type limitation.” The court explained that “it would not automatically be fatal that the type limitation was not expressly disclosed as long as substantial evidence showed that the patent disclosed identifying a type of display unit in some less express way.” On that issue, Mondis argued that testimony by its expert, admissions by LG’s expert, and the prosecution history each provided substantial-evidence support. But the Federal Circuit disagreed: “The patent and [expert] testimony established that the inventors only possessed and disclosed identifying a specific display unit,” not a type of display unit.