Lynk Labs v. Samsung: published patent applications as prior art in IPR proceedings

On January 14, 2025, the US Court of Appeals for the Federal Circuit (CAFC) issued a precedential ruling in Lynk Labs, Inc. v. Samsung Electronics Co., Ltd. concerning the earliest date a cited patent application publication (PUB) can be relied on as prior art in an inter parties review (IPR) proceeding. That date is the date the application underlying the PUB was filed (the effective filing date), not the PUB’s publication date. 

Patent examiners have historically assessed prior-art issues under 35 USC § 102(a) and (b). Under these two statutory provisions, prior art has historically constituted any printed publication before the invention by the patent applicant or if the claimed invention was “described in a printed publication… more than one year prior to the date of the application for patent.” Printed publications have historically included books, journal articles, dissertations, and granted patents, all of which constitute published documents. 

Prior to 2000, US patent applications themselves were not published. Since November 29, 2000, patent applications have been published, subject to certain exceptions, after 18 months of maintaining the application in confidence under 35 USC § 122(b).  

In 2002, the Patent Statute was amended to state that “[a] person shall be entitled to a patent unless (e) the invention was described in: (1) “an application for patent, published under § 122(b) filed by another filed in the United States before the invention by the applicant for patent… (2) a patent granted on an application for patent by another filed in the United States before the invention by the applicant for patent…”  35 USC § 102(e)(1) and (2). Thus, today two types of patent publications may serve as prior art: 1) a patent application publication; and 2) an issued patent publication. 

Patent claims may be subject to invalidation attempts during the patent’s lifetime either through the Patent Trial and Appeal Board (PTAB)-administered proceedings or during a patent infringement lawsuit.

Samsung initiated its PTAB-administered IPR against Lynx Labs to try and invalidate several of Lynx Lab’s patent claims based on a patent application publication (the Martin PUB), published on October 21, 2004, or after Lynx Labs’ application’s effective filing date of February 25, 2004. 

Section 311(b) of the Patent Act permits IPR unpatentability challenges “on the basis of prior art consisting of patents or printed publications.” Lynx Labs argued that the Martin PUB could not be “backdated” to its effective filing date of April 21, 2003 (18 months earlier) because the application only became publicly accessible on October 21, 2004, when the application was published. That is, Lynx Labs attempted to equate the Martin PUB to, e.g., a journal article under § 102a wherein the prior art date is the date the journal article is published.

The CAFC disagreed with this approach and emphasized that “‘printed publications include,’ within its literal scope challenges, based upon a published patent application.” The Martin PUB was thus prior art as of its underlying application’s filing date of April 21, 2003, 10 months prior to Lynx Labs’ application’s effective filing date of February 25, 2004). 

Furthermore, “§ 102(e)(1) [itself]states that a published patent application is deemed prior art as of its filing date.” Slip opinion at 10. The Martin PUB was thus accepted as valid prior art subsequently resulting in the invalidation of several of Lynx Labs’ patent claims. Slip opinion at

Take home points

Even the most thorough prior art searches will have black holes because potentially problematic prior art may not have yet been published under § 122(b) at the time a patent search is conducted. Also, patent applications may not be examined for well over a year after submission. Accordingly, a patent examiner may find patent application publications that have been published since the filing of the patent application. Ideally, patent applications are filed when prior art search results are still ripe. If not, another prior art search should be conducted to find any new patent application publications.

The patent applicant should always verify that any patent publication prior art cited by the examiner is applicable by conducting an effective date comparison. This same consideration applies when a patent owner is faced with the prospect of claims invalidation due to “discovered” prior art. Determining the applicability of any cited prior art begins with an assessment of its effective filing date (publication date in the case of non-patent document prior art) versus the patent application’s or issued patent’s effective filing date.  

Once a patent is issued, patent owners may wish to proactively thwart a potential attempt at claims invalidation by availing themselves of a reissue or re-examination proceeding before the USPTO under certain circumstances. Each of these procedures has its nuances and requirements and should be handled by experienced counsel. A positive outcome may well help cement patent claims from validation challenges.

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