The meaning of the terms used in the claims is often decisive in determining whether the patent is distinct from the prior art and whether a competitor’s product is covered by the claim. The terms used are not always clear. What meaning should be given to a term if it is specifically defined in the description but not in the claim? What is the consequence of an unclearly defined term?

The claim reads “An azeotropic or nearazeotropic composition comprising from about 62.4 mole percent to about 89.4 mole percent E-HFC-1234ze and hydrogen fluoride…”. The following definition is given in the description: “E-HFC-1234ze as used herein refer to a mixture of the isomers, E-HFC-1234ze … or Z-HFC-1234ze… , wherein the predominant isomer is E-HFZ-1234ze.” There is also the explanation: “As used herein, predominant isomer is intended to mean that isomer which is present in the composition at a concentration greater than 50 mole percent.”

Citation D1 describes a process that leads to the substance HFC-1234ze. However, it is not mentioned in what proportions the isomers E-HFC-1234ze and Z-HFC-1234ze are present.

The Examining Division rejects the claim as not inventive as against D1. The Board of Appeal confirms the rejection. Because the specific meaning of the term “H-HFC-1234ze” chosen in the description is not in the claim, the claim is interpreted with the generally accepted meaning. With this general meaning, however, the claim is not inventive over citation D1.

Du Pont filed a Lawsuit against this with the Court of First Instance. The Court of First Instance initially found that it was not clear from the wording of the claim that E-HFC-1234ze was the predominant isomer of the composition. However, this feature was defined in the description and the claim was therefore to be read with this meaning. Thus, the difference between the invention and the prior art was that the division of the isomers was indicated. The Board of Appeal did not deal with this difference. The contested decision should therefore be set aside and the case reassessed.

On appeal to the Beijing IP High Court, the judgment of the court of first instance is set aside and the rejection of the claim is confirmed. The reasoning is as follows.

When interpreting the meaning of the terms of the claim, the definition given in the patent specification, i.e. the intrinsic evidence, must be taken as a starting point. This applies even if the claim does not explicitly mention this particular meaning. However, if the meaning given in the description is not clear, the claim can be read on the basis of the general and common understanding of the skilled art.

The decisive factor in the present case is how the term “E-HFC-1234ze” is interpreted in the claim. In the art, the normal and usual meaning is that a single isomer of 1,3,3,3, tetrafluoropropene is meant, in which the double bond is in the E-type position. So when the expert sees the term, he can clearly state the chemical formula and structure of the substance.

Nevertheless, the description gives a meaning, namely a mixture of E-HFC-1234ze or Z-HFC-1234ze, in which E-HFC-1234ze is the predominant part. The meaning of this definition in the description is not clear to the skilled person. DuPont argues that the word OR should be replaced by AND. However, such a meaning is inconsistent with the meaning of the term elsewhere in the description. Thus, “or” cannot be replaced by “and”.

If the meaning used in the Application is not clear to the person skilled in the art, the common and ordinary meaning in the art can be used to interpret the claim. Since the common and ordinary meaning for E-FHC-1234zz is clear, the claim is interpreted with this meaning. In the present case, this leads to the claim being rejected as not inventive over D1.

Note: It is not uncommon for the Application to give a specific definition of the terms it uses in the patent description. In this way, the scope of protection is intended to be broader or more specific as required. The judgment shows that a lack of clarity in the chosen definition can lead to serious problems, because ultimately it is not the applicant’s own definition that is assumed, but another definition that is unfavorable to the applicant.