What are negative claim limitations?
A negative claim limitation is language recited in a patent claim that speaks to the absence of a feature, as opposed to a positive claim limitation that recites the presence of a feature. Negative claim limitations may be recited with words such as “devoid,” “absence,” “without,” “(whatever)-less,” “not including,” “excluding,” “non-(whatever)” and the like.
When used properly, they can be an effective tool to distinguish your patent claims over the prior art.
Are negative claim limitations allowed?
According to MPEP § 2173.05(i), negative limitations may be claimed as long as they are clear and supported by the specification. Negative limitations must have basis in the original disclosure. The mere absence of a positive recitation is not basis for a negative limitation.
What constitutes basis in the original disclosure for an exclusion?
The MPEP does not require that the negative limitation be recited verbatim in the specification: “Note that a lack of literal basis in the specification for a negative limitation may not be sufficient to establish a prima facie case for lack of descriptive support. Ex parte Parks, 30 USPQ2d 1234, 1236 (Bd. Pat. App. & Inter. 1993).” Otherwise, applicants may be unduly burdened in having to describe every known piece of prior art so as to expressly recite what is not included in their invention.
The following are examples of sufficient basis for negative limitations:
- specification describes a reason to exclude the relevant limitation (Inphi Corp. v. Netlist, Inc.)
- specification describes alternatives (Santarus, Inc. v. Par Pharm., Inc.)
- description of prior art in the specification discusses shortcomings of certain features
- drawings that show the presence of certain features which necessitates the absence of opposite features
- specification explicitly describes the lack of a particular feature
The following are examples of insufficient basis for negative limitations:
- attempting to avoid a prior art reference by simply excluding nickel from a named group of metals claimed for a metallic protective coating without providing a patentable basis for doing so (In re Langdon)
Is there a heightened written description standard for negative limitations?
In theory, the answer is no. Negative limitations need only satisfy 35 USC § 112 requirements in the same manner as positive limitations – i.e., the standard of particularly pointing out and distinctly claiming the invention.
That being said, there has been a historical bias against the use of negative limitations. Patent examiners are humans and not machines, and those who have been around long enough to remember or have been trained with that bias may find it difficult now to accept exclusionary language. I once had a case where an examiner told me flat out that exclusionary language was unacceptable. I generally hate to recite MPEP sections, but I was compelled to mention Section 2173.05 since it clearly states that exclusionary language is allowed when properly used.