Case Comment

Mobil Oil Corporation et al v.
Hercules Canada Inc.

citation(s): (1995), 63 C.P.R. (3d) 473 (F.C.A. per Marceau J.A.)

copyright 1997-2007 Donald M. Cameron




The Decision

At p. 482

"In the course of construing the patent and determining what the claims and specifications meant, the learned trial judge drew some clear conclusions. In his understanding, the phrase "said polypropylene layer and copolymer layer containing no slip agent which adversely affects the adhesion of the sustrate to a metallized coating" found in claim 12 of patent 1,223,228 meant that the film could contain some amount of slip agent in either layer, so long as that amount of slip agent does not adversely affect the adhesion of the substrate to the metallized coating. It was his view that in 1980, the relevant date for construing the patent, a person skilled in the art, when reading the phrase, would appreciate that the exact amount permissible could be determined through well understood experimental techniques, such as the use of the Suter test for measuring bond strength as described in the patent."

At p. 483-484

"The trial judge held that the phrase "said layer" in claim 15 was "avoidably ambiguous, at least from the point of view of the experts who gave evidence at the trial". He wrote (at p. 21 of the reasons): "Given the diverse opinions of the experts with respect to this phrase and the insufficiency of the disclosure to illuminate the meaning, the patent, the judge, as mentioned above, had come to the conclusion that the phrase necessarily referred to the copolymer bonding layer, as that was "the only reasonable interpretation possible when the claim is read as a whole". And he was, in my view, quite right in that respect. I reproduce again the sentence in which the contentious phrase appears:

coextruding a homopolymer polypropylene layer which is from about 80% ot 100% isotactic and has a melt index of from about 2 to about 10 grams/10 minutes with an ethylene propylene copolymer layer on at least one side of said polypropylene layer, said copolymer containing from about 2% to 4% by weight of ethylene and from about 96% ot about 98% by weight of propylene, said layer containing either no slip agent or no slip agent which adversely affects the adhesion of the substrate to a metallized coating;

The phrase "said layer" immediately follows a description of the copolymer layer. Looking at the structure of the sentence, "said layer" must refer to the copolymer layer. Furthermore, claim 15 teaches that the slip agent must not adversely affect bonding of the metal to the substrate. Given that the metal is applied to the copolymer layer, it is only logical that this is the meaning of "said layer".

I simply do not see how a phrase which can be interpreted using grammatical rules and common sense can be found to be ambiguous. The trial judge relied on the fact that the experts appeared to adopt different ways of reading the text and, as a result, provided conflicting interpretations of the phrase. So, the learned trial judge permitted the conflict among the experts to outweigh his own interpretations and, moverover, a common sense interpretation. With respect, I think that was an error. Ther expertise of the witnesses had nothing to do with grammatical and linguistic difficulties and no doubt common sense was not their exclusive prerogative. In any event, a recalled above, it is a well settled principle that, while a judge may seek the assistance of experts in construing a patent, he should never forget that he is the final interpreter of the language.

Consequently, the finding that claim 15 is invalid because of the ambiguity of the phrase "said layer" is, in my respectful opinion, completely untenable."

At pp. 484-485

"At page 16 of his reasons, the trial judge set out the defendant's submissions as regards sufficiency. The disclosure is not sufficent to support claims which would allow for some amount of slip agent to be present in the film, because it does not teach the reader where the slip agent may be present or how the substrate containing slip agent is to be manufactured nor does is set out clearly the amount of slip agent which could be used successfully in the film to achieve the promised of the patent, an amount which can only be determined after a great deal of experimentation and testing. Having thus set out the defendant's submission, the trial judge proceeded to respond to it:

"[...] In his fourth edition of The Canadian Law and Practice Relating to Letters Patent for Inventions (Toronto: Carswell, 1969), Harold Fox discusses, at page 171, the necessity for experiments. Although the patentee must not present problems in his specification, that does not relieve the skilled person in the art from having to make certain experiments in order to arrive at a sucessful result based on a patent specification. What cannot be required is that the skilled person exercise any inventive faculty in arriving at that result."

At p. 485-486

"Once it is established that the specifications did not have to go further as to the acceptable amount and location of the slip agent contemplated, since a person skilled in the art could be expected to go through the testing and experimentation required to make the determination, what exactly can be seen as missing? The mere statement of the judge does not help. It is true that the experts, in their testimonies, have mentioned that it was not obvious nor easy to determine how to put the slip agent into the film and test its effect because it migrates from one layer to the other depending upon the time and temperature. But is that not a difficulty which simply necessitates proper experimentaiton and testing? A person skilled in the art did not have to be taught of this phenomenon of migration or, at least, could not fail to become aware of it in the course of his experiments. There is no assertion from anyone that, to realize the promise of the patent with the presence of a slip agent, some form of inventiveness was required of a person skilled in the art.'


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