IP Law Daily, PATENT—Fed. Cir.: Rejections affirmed as to patentability of microporous polymer film, (Feb 19, 2026)

By Kevin M. Finson, J.D.

Claims relating to the production of films used in certain types of batteries were anticipated or obvious because the inventor’s own earlier patent publications disclosed an identical method.

An inventor of microporous polymer film used in batteries failed to show any error in the PTAB’s rejection of two of his patent applications, the U.S. Court of Appeals for the Federal Circuit has held. The claims were anticipated or obvious over several pieces of prior art, including notably the inventor’s own patent publications which disclosed an identical method ((In Re: Kwangjin Song, No. 25-1653 (Fed. Cir. Feb. 18, 2026)) and In Re: Kwangjin Song, No. 25-1705 (Fed. Cir. Feb. 18, 2026)).

Kwangjin Song was the listed inventor of U.S. Patent Applications Nos. 15/707,151 (the ’151 application) and 18/199,940 (the ’940 application) both of which related to porous films used in separating the positive and negative electrodes in certain batteries. The examiners had rejected numerous claims of each application on anticipation and obviousness grounds, and the rejections were affirmed by the Patent Trial and Appeal Board (PTAB). Song appealed. The Federal Circuit issued two separate per curiam decisions.

The ’151 application. Song’s primary argument as to the ’151 application was that the board erred in finding that claim 48 was anticipated by U.S. Patent Publication No. 2012/0145468 (Pekala). The Pekala reference was directed to a microporous polymer film for us in an energy storage device. The court found that the board’s findings as to the teachings of Pekala were supported by substantial evidence in the form of expert testimony. The court also noted that Song seemed to incorrectly believe that the fact his claims were broader than those of the prior art reference overcame anticipation, while the law was that a claim is anticipated if it reads on even a single embodiment in the prior art.

The ’940 application. As to the other application, Song argued that the board erred by finding that the claims were anticipated by or obvious over his own prior patent publications; specifically, that the board did not read the preamble language that the film was for use as a separator is as limiting. The prior art references contained no such limitation, so if the requirement for use as a separator was limiting, the claims would not be anticipated. The court found that the board had properly determined that the claim in question recited a structurally complete device without the preamble, so the preamble was not limiting. The court further found no error in the board’s determination that the prior art references and the application disclosed identical methods.

The court affirmed the rejections as to both applications.

The Case is No. 25-1653 and No. 25-1705.

Judge: Per Curiam.

Attorneys: Kwangjin Song (Liso Plastics LLC) for Kwangjin Song. Mary L. Kelly, U.S. Patent and Trademark Office, for John A. Squires.

Cases: Patent FedCirNews USPTO