Within patent law, there are two primary mechanisms that attempt to afford the appropriate balance between patent owners and subsequent inventors. First are the disclosure doctrines: a patent applicant cannot claim more than what she has actually disclosed in the patent application. A claim that is overly broad because it lacks adequate support in the patent specification is invalid. There is a clear link between the extent of the patent disclosure and the permissible scope of the claims contained therein. The second constraint on a patentee’s ability to obtain claim scope is the prior art. A claimed invention must be both novel and non-obvious to be patent eligible. If a patent claim runs into the prior art because it is anticipated or obvious, then the patent applicant will have to narrow the scope of the claim to avoid the prior art. Generally, issues of the sufficiency of the disclosure and validity vis-à-vis the prior art are considered in isolation. However, every litigated patent is also a potential piece of prior art. Because it is the disclosure of the patent that controls its impact as a piece of prior art, and not the particular claims in the patent, there is a relationship between patent disclosure and the prior art doctrines. A patent is good for what it teaches as a piece of prior art, not for what it claims. In this regard, the Federal Circuit’s approach to disclosure law, and the written description requirement in particular, creates the potential for a “patent free” zone, which I have dubbed the “written description gap.” As further elaborated below, the Federal Circuit has held that, if a patent discloses a variant of the invention that would render the particular claim obvious, such disclosure nevertheless is insufficient to satisfy the written description requirement. That particular applicant would be unable to claim that version of the invention. But what happens once the original patent is now used as prior art against a subsequent applicant? If the later patent claims the obvious variant, then the subsequent applicant also is unable to obtain patent coverage. No one will be able to obtain patent protection for that particular variant, and it effectively falls into the public domain. This Essay elaborates the operation of this gap and assesses whether it is normatively good or bad as a matter of patent policy. I ultimately conclude that, by creating an incentive to enhance patent disclosures, the gap is good, notwithstanding that some potentially important variants could fall into the public domain.

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