4.2.5 Functional features

In T 500/89 it could only be seen from the disclosure considered in its entirety that the prior art document did not deprive the claimed invention of novelty, because the method constituting the closest prior art differed from the claimed method in one functional characteristic. The disputed patent related to a method for the production of photographic material by the simultaneous application of several layers of fluid photographic coating materials. Although the document cited in support of the opposition listed the numerical ranges for layer thickness, viscosity, coating speed, etc. used in the method claimed, the latter was nevertheless held to be new because the cited document described the choice of these numerical ranges as leading to intermixing between two particular layers. The contested patent was to be assessed according to a different criterion because it described the application of the layers as being "substantially free from intermixing". The "intermixing" described as an objective in the citation was not merely a stated purpose not constituting one of the technical features of the method described, but a functional feature - a criterion, in effect - forming an essential element of the teaching set out in this publication.

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