The Federal Circuit in Eidos Display, LLC v. AU Optronics Corp. (Fed. Cir. March 10, 2015) found definite claim language that had been determined indefinite by the U.S. District Court for the Eastern District of Texas and reversed the grant of summary judgment. Eidos had filed an action in district court, alleging that AU Optronics and others (“Display Manufacturers”) infringed U.S. Patent No. 5,879,958 (“the ‘958 patent”), which is directed toward a manufacturing process for an electro-optical device such as a liquid crystal display.

Claim 1 of the ‘958 patent includes a feature of “a contact hole for source wiring and gate wiring connection terminals.” Eidos argued that this disputed limitation requires separate and distinct contact holes for the source wiring connection terminals and gate wiring connection terminals, consistent with standard industry practice and the specification. Display Manufacturers countered that the plain language of the disputed limitation requires a shared contact hole for all connection terminals. During the Markman proceedings, the magistrate judge recommended that the District Court grant a motion for summary judgment of indefiniteness because “the Court is unable to arrive at a construction that would allow a person of ordinary skill in the art to determine what is claimed when the claim is read in light of the specification.”

On appeal, the Federal Circuit considered whether the claim, read in light of the specification and prosecution history, informs with reasonable certainty those skilled in the art at the time the patent was filed about the scope of the claimed invention. The Federal Circuit noted that patents are not addressed to lawyers, or even to the public generally, but rather to those skilled in the relevant art, citing Nautilus, Inc. v. Biosig Instruments, Inc. (2014). Furthermore, a claim is invalid for indefiniteness under 35 U.S.C. § 112, ¶ 2 if its language, when read in light of the specification and prosecution history, “fail[s] to inform, with reasonable certainty, those skilled in the art [at the time the patent was filed] about the scope of the invention.”

The Federal Circuit reversed the District Court’s judgment of indefiniteness because Eidos’ proposed construction for the disputed limitation reflects how a person of ordinary skill in the art at the time of the invention would have understood the limitation after reading the intrinsic record. According to the Federal Circuit, the intrinsic record here makes sufficiently clear that a person of ordinary skill in the art—someone with knowledge of LCD manufacturing—would understand the limitation at issue to call for separate, different contact holes for the source wiring connection terminals and gate wiring connection terminals, rather than one shared contact hole.  Nothing in the ‘958 patent describes deviating from the known industry practice, and the only description corresponding to the limitation at issue in the specification teaches that separate contact holes are formed for the different connection terminals.

Display Manufacturers argued that permitting separate contact holes to be covered would require rewriting the limitation, which is impermissible except in certain situations. However, the Federal Circuit noted that determining how a person of ordinary skill in the art would understand the limitation is different from rewriting the limitation.

The Federal Circuit found that the ‘958 patent teaches a person of ordinary skill in the art that “a contact hole for source wiring and gate wiring connection terminals” is formed by etching separate contact holes for the source wiring connection terminals and for the gate wiring connection terminals, as described in the specification and prosecution history. Accordingly, the Federal Circuit held that the limitation is not indefinite under 35 U.S.C. § 112, ¶ 2 and reversed the judgment of indefiniteness.

While the limitation at issue was ultimately found to be definite, Eidos Display, LLC v. AU Optronics Corp. is a reminder of the importance of avoiding ambiguity when drafting claims. Instead of the recitation of “a contact hole for source wiring and gate wiring connection terminals,” alternative claim language such as “a contact hole for source wiring connection terminals and a contact hole for gate wiring connection terminals” would have reduced the likelihood of an indefiniteness challenge. For patentees involved in litigation, this case provides support for the argument that claims should be interpreted in a way that supports validity, even if the literal language may be interpreted otherwise.