ing from 50 to 100 feet, measured from mean low water to the ocean floor;
At the rate of $.10 per inch diameter of pipe per foot of pipe length, plus $8.00 per foot of pipe length for any pipe laid with the patented device or using the patented process in depths of water ranging from 100 to 150 feet, measured from mean low water to the ocean floor *. [Emphasis supplied.]
We interpret the use of the disjunctive “or” to mean that the use of either the patented process (reissue patent) or the patented apparatus (’417 patent) results in the same royalty fee.
Accordingly, since we affirmed the holding that the appellant infringed the reissue patent, we need not reach the issue of whether the ’417 patent was also infringed.
III. Prejudgment Interest
The appellant further argues that the district court erroneously awarded prejudgment interest on the punitive or enhanced portion of the damages. We agree.
Contrary to appellees’ contention, citing Brian Jackson Associates, Inc. v. San Manuel Copper Corp., 305 F.Supp. 66, 163 USPQ 198 (D.Ariz.1969) and Corometrics Medical Systems, Inc. v. Berkeley Bio-Engineering, Inc., 193 USPQ 467 (N.D.Cal.1977), that the award of prejudgment interest on the punitive or enhanced portion was proper, we hold that prejudgment interest can only be applied to the primary or actual damage portion and not to the punitive or enhanced portion.
Prejudgment interest is awarded to the patent owner for the purpose of making him whole, not only for the value of the actual damage suffered but also for the loss of any possible use of the money between the time of the infringement and the date of the judgment. General Motors Corp. v. Devex Corp., — U.S. —, —, 103 S.Ct. 2058, 76 L.Ed.2d 211, 217 USPQ 1185, 1189 (1983). It is awarded to compensate for the delay in payment of the damages, and not to punish the infringer. In Trio Process Corp. v. L. Goldstein’s Sons, Inc., 638 F.2d 661 (3d Cir.1981), where the district court had doubled the damage award for willful infringement pursuant to section 284, the Third Circuit concluded that the enhanced portion was punitive in character. As such, it held that prejudgment interest could not be assessed on the enhanced portion of the damage award. The Third Circuit stated:
[I]t is clear that the rationale for awarding prejudgment interest on a remedially enhanced damage award, to the extent such a rationale exists, also implies that no prejudgment interest be awarded on a punitively enhanced portion of damages.
Id., at 663. Accord H.K. Porter Co. v. Goodyear Tire & Rubber Co., 536 F.2d 1115, 1124, 191 USPQ 486, 493 (6th Cir.1976); General Electric Co. v. Sciaky Brothers, Inc., 415 F.2d 1068, 1076, 163 USPQ 257, 263 (6th Cir.1969).
In the instant case, the enhanced portion of the damage award, $400,000, is punitive in character since it was assessed by the district court for M-K’s willful infringement of UDI’s patents. See infra. We therefore reverse the district court’s award of prejudgment interest on the enhanced or punitive portion of the damage award.
IV. Willful Infringement
Last, the appellant argues that the district court’s finding of willful infringement was erroneous. We disagree.
The district court’s finding of willful infringement is a finding of fact, and as such, the standard of review is the clearly erroneous standard. F.R.Civ.P. 52(a). The appellant, however, has failed to show that the district court’s finding was clearly erroneous. United States v. United States Gypsum Co., 333 U.S. 364, 68 S.Ct. 525, 92 L.Ed. 746 (1948). See also Kalman v. Kimberly-Clark Corp., 713 F.2d 760, 218 USPQ 781 (Fed.Cir.1983).
Where, as here, a potential infringer has actual notice of another’s patent rights, he has an affirmative duty to exercise due care to determine whether or not he is infringing. See Milgo Electronic