Functional equivalence is a rationale that examiners often rely on in support of an obviousness rejection. However, as discussed in one of our previous blogs, examiners may misapply the rationale by ignoring the different function or purpose of an allegedly equivalent component disclosed in prior art. A recent decision of the Patent Trial and Appeal Board (“Board”) – Ex parte Takasu (Appeal 2021-001290) – is another illustrative case.
Appellant’s claimed invention in Takasu was a substrate of a single crystal of formula RAMO4, where, among other things, R could be Sc, A could be Al, and M could be Mg. The claimed RAMO4 substrate had an epitaxially-grown surface and a satin-finish surface, each having specific surface roughness.
Yoshii, the primary reference relied on by the Examiner, provided a sapphire substrate for epitaxial growth that could be easily polished. The Examiner found that Yoshii as evidenced by Hansen disclosed a sapphire single crystal substrate that allegedly had the claimed roughness on its front and back sides. The Examiner admitted that the sapphire substrate disclosed in Yoshii was not a RAMO4 substrate. However, the Examiner found a secondary reference, Yoshida, which disclosed ScAlMgO4 as one of the material options for a single crystalline substrate as a functional equivalent to sapphire for epitaxial growth. The Examiner thus concluded Appellant’s claimed RAMO4 substrate would have been obvious over Yoshii in view of Yoshida as evidence by Hansen.
Appellant argued that a sapphire substrate and a RAMO4 substrate were not equivalent to each other in terms of surface polishing properties.
The Board agreed with Appellant and emphasized that, as stated by the Examiner herself, Yoshida merely disclosed ScAlMgO4 as “a functional equivalent to sapphire for epitaxial growth, but … not for surface polishing properties.”
Because a sapphire substrate is not functionally equivalent to a RAMO4 substrate in terms of surface polishing properties, the Board found that the Examiner’s reliance upon Yoshida was misplaced and reversed the obviousness rejection.
Takeaway: As cautioned in MPEP § 2144.06 II, the equivalency of a proper substituting equivalent must be recognized in the prior art for the same purpose and cannot be based on applicant’s disclosure or the mere fact that the components at issue are functional or mechanical equivalents. Thus, arguments rebutting an examiner’s obviousness rejection relying on functional equivalence may be successfully advanced by carefully analyzing the function and purpose of substituted and substituting components disclosed in prior art.
Judges: J. T. Smith, B. A. Franklin, and J. R. Snay
by Yanhong Hu
Yanhong (Claire) Hu, Ph.D., is a patent attorney and partner at Element IP. She is active in patent preparation and prosecution, post-grant proceedings, and legal opinions and counseling. Her knowledge and experience in a wide variety of technical fields, combined with her legal expertise, allow her to appreciate various technologies to successfully and efficiently assist her clients.