In Wellman, Inc. v. Eastman Chemical Co., the Federal Circuit agreed that inventor testimony supported the district court’s finding that the patents at issue were invalid for failing to satisfy the “best mode” requirement. Their testimony coupled with other evidence that the patentee wanted to conceal specific embodiments as trade secrets led the court to affirm the invalidity finding.
The Patents At Issue
Wellman asserted various claims from two patents (U.S. Patent 7,129,317 and U.S. Patent 7,094,863) against Eastman. The patents stem from the same application and are directed to polyethylene terephthalate (PET) resins for use in plastic beverage containers. The resins are said to be slow-crystallizing resins that overcome probelms in the prior with resins that shrank or grew hazy when “hot-filled” with product.
The Federal Circuit identified claim 1 of the ’317 patent as representative:
1. A polyethylene terephthalate resin, comprising:
less than about 25 ppm of elemental antimony, if any;
and more than about 5 ppm of elemental phosphorus; and
wherein the polyethylene terephthalate resin has a heating crystallization exotherm peak temperature (T(CH)) of more than about 140 °C. at a heating rate of 10 °C per minute as measured by differential scanning calorimetry;
wherein the polyethylene terephthalate resin has an absorbance (A) of at least about 0.18 cm-1 at a wavelength of 1100 nm or at a wavelength of 1280 nm; and
wherein the polyethylene terephthalate resin has an L* luminosity value of more than about 70 as classified in the CIE L*a*b* color space.
The highlighted clause, also emphasized in the Federal Circuit opinion, is taught to be correlated with the “slow-crystallizing” property.
Wellman’s Commercial Product
By the time the original application was filed, Wellman had a commercial slow-crystallizing, hot-fill product on the market, known as “Ti818.” Ti818 had the following components:
Isophthalic Acid (1.4 mol %)
Diethylene Glycol (1.9 mol %)
Trimellitic Anhydride (“TMA”) (500 ppm)
Carbon-Black reheat agent (7.5 ppm)
Elemental Cobalt (30 ppm)
Titanium-based catalyst (7 ppm (Ti))
Phosphorus (5 ppm)
Potassium (25 ppm )
The patents do not disclose this specific formulation, or any other specific formulation. Instead, the patents disclose ranges of amounts of different components. However, the disclosed range for isophthalic acid (between about 1.6 and 2.4 mole %) does not encompass the amount used in Ti818. Moreover, while the patents teach a preferred concentration of 1.6 mole % for diethylene glycol, Ti818 contained 1.9 mole % diethylene glycol.
Heat-Up Rate Additives
The Wellman patents disclose optional heat-up rate (“HUR”) additives for the PET resin that improve the resin’s reheating profile during bottle blow molding. While the patents indicate a preference for copper chromite black spinel and chrome iron nickel black spinel, Ti818 included carbon black as an HUR additive. The patents refer to U.S. Patent 4,408,004 (“Pengilly”) as disclosing “satisfactory” carbon black HUR additives. Pengilly discloses a preferred average particle size for carbon black in a range of between about 15 to about 30 nm. On the other hand, Ti818 includes as carbon black HUR additive (N990) with a 290 nm particle size.
The Federal Circuit noted that two provisional applications filed early in the chain of the asserted patents “characterize carbon-based HUR additives as ‘preferabl[e]‘ and copper chromite spinels as suitable.” Only the day before the original application was filed did Wellman file a third provisional application that indicated a preference for spinel-based HURs.
The Best Mode Requirement
The Federal Circuit decision outlines the two prongs of the best mode inquiry:
- Whether, at the time of patent filing, the inventor possessed a best mode of practicing the claimed invention.
This prong is subjective, focusing on the inventor’s personal preferences as of the application’s filing date. - Whether the inventor “concealed” the preferred mode from the public.
This prong is objective, focusing on whether the patent discloses the best mode adequately to enable one of ordinary skill in the art to practice that the best mode.
If these prongs are satisfied, the court also must identify evidence of intent:
Invalidation based on a best mode violation requires that the inventor knew of and intentionally concealed a better mode than was disclosed.
The First Prong: The Inventor Testimony
The Federal Circuit noted that “[t]here is no genuine dispute that at least one inventor subjectively believed that Ti818—which contains carbon black N990—was the best resin available for hot-fill packaging at the time of filing.” The inventor testified that the 2003 Ti818 formulation was his “preferred PET recipe,” and that he believed that “there was no PET recipe better than that Ti818 recipe.”
Another inventor testified to the effect that “the specific HUR additive used in Ti818, carbon black with a 290 nm particle size, was essential.”
Although there was some evidence that the Ti818 “recipe” was evolving around the time of filing, the Federal Circuit concluded that the “evidence cannot overcome the testimony of the inventors, including Dr. Nichols’ testimony regarding his subjective belief that the 2003 recipe of Ti818 was the best.”
Thus, the Federal Circuit concluded “that Ti818 and its HUR additive carbon black N990 were considered the best mode of practicing the invention by one or more inventors at the date of filing.”
The Second Prong: The Patent Disclosure
The Federal Circuit noted two shortcomings in the Wellman patent disclosures:
With regard to the basic Ti818 formulation, the amounts of components disclosed in the patents did not encompass the amounts present in Ti818 for at least two components.
With regard to the HUR additive, the Federal Circuit agreed that “Wellman did not disclose carbon black N990 in its patent applications.” To the contrary, the court found that the patents “lead away” from N990. For example, none of the teachings related to carbon black disclosed or suggested a particle size of 290 nm.
Evidence of Intentional Concealment
On the issue of intent, the Federal Circuit found:
Wellman concealed the best mode by not disclosing the recipe for Ti818, by identifying preferred concentration ranges for certain ingredients that excluded those used in Ti818, and by identifying preferred particles sizes for the HUR additive other than that used in Ti818.
The court also found that this concealment was intentional, citing direct testimony that “Wellman chose to protect [carbon black N990] as a trade secret.”
Best Mode Vs. Trade Secret
This case illustrates the difficulties a company may face when deciding to file a patent application where it would prefer to maintain one detail of the subject matter as a trade secret. If the trade secret relates to subject matter that falls within the scope of the claims, it must be disclosed in the application if the inventor subjectively believes it to form part of the “best mode” of practicing the claimed invention. The issue may get exponentially more complicated with each additional inventor because, as illustrated here, the subjective belief of even one inventor can be relevant.
Several versions of the patent reform bills that are pending in Congress would eliminate best mode violations as a ground for invalidating a patent. For the time being, however, “best mode” remains as a another patentability requirement that is unique to U.S. patent law.
