Article 52(1) of the European Patent Convention states that European patents shall be granted for inventions which are new, involve an inventive step, and are susceptible of industrial application. The first of these requirements, novelty, is met if the invention does not form part of the state of the art, that is the invention has not already been disclosed (Article 54(1)). On the face of it therefore, if the invention as claimed is not the same as any prior disclosure i.e. it is different, then it is novel.

Unfortunately, it is not always that simple.

European patent application publication number EP1898450 concerns epitaxial silicon wafers and methods of making them. Epitaxial silicon wafers are thin layers of silicon of controlled and defined orientation which are grown on a supporting layer or base layer of silicon. Such wafers are useful in semiconductor technology. In the invention, the angular profile of the silicon layer onto which the epitaxial layer was grown was carefully controlled and was defined by reference to an inclination angle azimuth which is an angle in the horizontal plane measured from a given reference point, and which defines the point from which the angle of inclination, or vertical angle, was measured.

The main claim was directed to an epitaxial silicon wafer comprising a silicon wafer and an epitaxial layer wherein the main surface of the silicon wafer had an inclination angle azimuth in the range of more than 0 degrees and less than 20 degrees. The prior art disclosed a silicon wafer having an epitaxial layer where the inclination angle azimuth was 0 degrees.

At first sight, the claimed silicon wafer was different from, and therefore novel with respect to, the silicon wafer of the prior art as the range of the inclination angle azimuth of the claimed silicon wafer is not the same as and could not encompass 0 degrees by virtue of the wording “more than”.

However, the Technical Board of Appeal, “the Board” assessing the question of novelty, referred to decision T 0594/01 which related to the preparation of ethylene glycols. In this case, the main claim included the feature that “the process is performed with less than 0.1% wt. of carbon dioxide in the reaction mixture.” The prior art disclosed a similar process in which the level of carbon dioxide in the reaction mixture was equal to 0.1% wt. Again, at first sight, the main claim would be novel as “less than 0.1% wt.” is not the same as nor does it encompass “equal to 0.1% wt.”

In T 0594/01 in point 4.5.1 of the Reasons for the Decision (“the Reasons”), it was noted that it is common general knowledge that every experimental measurement in quantitative analytical chemistry as well as any result of any physical measurement cannot be dissociated from the margin of uncertainty attached to that measurement. On this basis, the Board in T 0594/01 found that the feature “less than 0.1% wt.” was insufficient to distinguish the claim from the prior art as the value 0.1% wt. itself fell within the margin of experimental error and therefore within the claimed range. Accordingly, the main claim was not novel.

Using similar reasoning, the Board in T 0386/17 at point 2.8 of the Reasons found that the feature of an angle of more than 0 degrees does not confer novelty over a disclosure of an angle of 0 degrees as this feature encompasses values closer to 0 degrees than the margin of error to which the measurement of such angles would be subject and therefore such angles would, in practice, be indistinguishable from 0 degrees.

The decisions of T 0386/17 and T 0594/01 provide a salutary reminder that, for inventions defined by the measurement of parameters, the requirement that a claimed invention be novel is not met merely by those parameters being arithmetically different from those of the prior art. The assessment of novelty must be made with reference to the skilled person and the common general knowledge with respect to the precision of the techniques used in the determination of the values of those parameters, and those values must differ from those of the prior art by more than the associated margins of error.