Dicta on the Importance of Significant Digits in Patent Claims

Dicta in U.S. Philips Corporation v. Iwasaki Electric Company LTD. (Federal Circuit, November 2, 2007) recognized the importance of significant digits for ranges in claimed ranges.

According to Circuit Judge Linn:

In some scientific contexts, "1" represents a less precise quantity than "1.0," and "1" may encompass values such as 1.1 that "1.0" may not. See Viskase Corp. v. Am. Nat’l Can Co., 261 F.3d 1316, 1320–21 (Fed. Cir. 2001) (discussing distinction between "0.91 g/cm3" and "0.910 g/cm3"). In other words, "1.0" may be said to have more significant digits than "1" with no decimal point. Because "10-6" and "10-4" are simply the numbers 0.000001 and 0.0001 expressed as powers of ten, the claim language provides no basis for inferring any level of precision beyond the single digit "1." The way that power-of-ten quantities are used in the specification, discussed supra, confirms that the quantities of halogen described by the claims are not intended to be more precise. Thus, it is technically incorrect to assert, as Iwasaki does in its brief before this court, e.g., Br. for Appellee at 35, that "10-x" should be construed to mean "1.0 × 10-x." It means, simply, "1 × 10-x." "1.0 × 10-x" expresses a quantity with greater precision, reflected in the recitation of a significant digit following the decimal point. The claim construction that we affirm today is "between 1 × 10-6 and 1 × 10-4 μmol/mm3," not "between 1.0 × 10-6 and 1.0 × 10-4 μmol/mm3." We leave for another day the question of whether this claim construction is sufficient to answer the infringement questions presented by a future record. See E-Pass Techs., Inc. v. 3Com Corp., 473 F.3d 1213, 1219 (Fed. Cir. 2007)
("[A]ny articulated definition of a claim term ultimately must relate to the infringement questions that it is intended to answer.").