Inter partes review (IPR) has become a popular avenue for petitioners to challenge the validity of granted patents, as compared to challenging the patent in federal district court, based on several considerations, including the lower expected expenditures typically required to initiate and litigate an IPR, the accelerated timeline of receiving a final written decision and the technical sophistication of the Patent Trial and Appeal Board (PTAB). In an IPR, the scope of prior art available to challengers in asserting unpatentability under Sections 102 and 103 is more limited than in district court litigation and is "only on the basis of prior art consisting of patents or printed publications." 35 USC § 311(b). The recent case of Lynk Labs, Inc. v. Samsung Electronics Co., No. 2023-2346, 2025 WL 85559 (Fed. Cir. Jan. 14, 2025) provides additional insight as to the scope of prior art available for petitioners to rely on in challenging patentability.
Background and Case History
Lynk Labs owns U.S. Patent No. 10,687,400 ('400 patent), directed to lighting systems. Samsung filed a petition for IPR, asserting that the '400 patent is unpatentable on the grounds of obviousness. Samsung relied on U.S. Patent Application No. 10/417,735 ('735 application), which was filed April 16, 2003, and published as U.S. 2004/0206970 on October 21, 2004. The '735 application's filing date precedes the asserted February 24, 2004, priority date of '400 application.1 The '735 application is abandoned and no patent has issued from this application.
Lynk Labs argued that the '735 application could not serve as prior art in the underlying IPR because the '735 application did not publish and become publicly accessible until after the priority date of the application leading to grant of the '400 patent. PTAB disagreed with Lynk Labs and ultimately held the challenged claims to be unpatentable. Lynk Labs appealed the decision to the United States Court of Appeals for the Federal Circuit.
The Federal Circuit's Decision
Lynk Labs conceded to the fact that the published '735 application is a printed publication and maintained on appeal that publication of the '735 application after the priority date of the application leading to grant of the challenged '400 patent cannot render the '735 application prior art. Lynk Labs referred to the language of pre-America Invents Act (pre-AIA) Sections 102(a) and 102(b), barring an applicant from obtaining a patent if the claimed invention was "described in a printed publication ... before the invention thereof" and "described in a printed publication ... more than one year prior to the date of the application for patent in the United States," respectively. 35 USC §§102(a), (b) (pre-AIA). Because the '735 application was not published and thus not publicly accessible until after the priority date of the challenged patent, Lynk Labs argued that the '735 application cannot be prior art, and therefore PTAB could not rely on the '735 application in finding the challenged claims unpatentable.
The Federal Circuit disagreed with Lynk Labs, ultimately affirming PTAB's decision, holding that the '735 application can be utilized as prior art in an IPR.
The court relied on pre-AIA Section 102(e)(1), directed to published patent applications in which an applicant is entitled to a patent unless "an application for patent was published under [Section] 122(b), by another filed in the United States before the invention by the application for patent ... ." 35 USC § 102(e)(1) (pre-AIA). Based on the statutory language, a patent application that publishes after the priority date of a claimed invention may be used as prior art because said patent application was filed before the claimed invention. As noted by the Federal Circuit "because a published patent application is a 'printed publication,'[Section] 102(e)(1) treats this type of printed publication as prior art as of a time before it became publicly accessible—i.e., as of its filing date." Lynk Labs, 2025 WL 85559, at *3 (emphasis in original).
Lynk Labs further argued that based on pre-AIA Sections 102(a) and 102(b), a "printed publication" needs to have a temporal requirement as to the public availability of the publication for treatment as prior art. The court disagreed, noting that each of the statutory provisions dictates the critical date by which a printed publication must be publicly available to be able to be used as prior art. Pointing out the differences between the temporal requirements of Sections 102(a) and 102(b), namely prior to invention and more than one year prior to the date of a patent application, respectively, "printed publications" by themselves cannot carry a consistent temporal requirement as to public availability of the publication as this would render the various statutory provisions redundant.
Further, the Federal Circuit discussed the congressional intent behind the implementation of Section 102(e)(1), which gave published patent applications a different prior art effect than that of Sections 102(a) and 102(b) and bar patentability based on published patent applications that were filed before the priority date of the claimed invention. Allowing prior-filed but later-published applications to be available as prior art in an IPR under Section 311(b) would be consistent with congressional intent to provide "a cheaper and less time-consuming alternative to challenge patent validity" via IPRs. Id. at *7 (quoting Qualcomm Inc. v. Apple Inc., 24 F.4th 1367, 1376 (Fed. Cir. 2022)). Patents and printed publications are readily accessible, and restriction to reliance on these types of prior art references would help simplify the bases for validity challenges in an IPR. In contrast, other avenues of challenging patent validity such evidence of public sale and public use would require extensive discovery and fact-finding not appropriate for IPR.
In holding that the earlier-filed but later-published '735 application is a printed publication available as prior art under Section 311(b) in an IPR, the Federal Circuit affirmed PTAB's decision as to the unpatentability of the challenged claims of the '400 patent, which relied on application of the '735 application.
Conclusion and Practice Points
The United States patent system transitioned from maintaining complete secrecy of an applicant's patent application to rapid publication within 18 months after the earliest filing date under the American Inventors Protection Act of 1999, which became law on November 29, 2000. This established the prior art effect of prior-filed applications having an earlier priority date but whose publication may be later than the priority date of a challenged patent. Congress codified the prior art effect of these published applications under pre-AIA Section 102(e)(1). Thus, petitioners in an IPR often tailor search strategies based on filing dates, seeking those references whose filing dates, and likely their priority dates, precede the challenged patent.
The Federal Circuit's decision in Lynk Labs serves as a reminder that prior art exists under pre-AIA Section 102(e)(1) and that petitioners should seek to research, uncover and assert such references during IPR. Patent owners may demonstrate an earlier date of reduction to practice to swear behind a reference qualifying as prior art under Section 102(e)(1). See 37 CFR §1.131. Thus, petitioners, especially in close cases, should seek to advance references having a greater time gap between the priority date of the published application and that of the challenged patent to minimize the possibility of swearing behind the reference and precluding applicability as prior art.
Petitioners should also be reminded that a reference qualifying as prior art under pre-AIA Section 102(e), as well as Sections 102(f) and (g), may not be used to assert obviousness if, at the time of invention, "the claimed invention was made, owned by the same person or subject to an obligation of assignment to the same person." 35 USC § 103(c) (pre-AIA).
For More Information
If you have any questions about this Alert, please contact Patrick D. McPherson, any of the attorneys in our Inter Partes Review Group, Thomas J. Kowalski, Brandon A. Chan, Ph.D., any of the attorneys in our Intellectual Property Practice Group, or the attorney in the firm with whom you are regularly in contact.
Footnote
1. Lynk Labs maintained throughout the course of litigation that the priority date of the '400 patent was February 24, 2004. Samsung adopted this priority date during IPR. While the Federal Circuit did not resolve whether Lynk Labs was entitled to this priority date, the court also adopted this date for purposes of the case.
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