T 431/07: Insufficient disclosure

In this case a proprietor filed an appeal against the decision of the Opposition Division to revoke the patent based on lack of inventive step and insufficient disclosure.

With respect to the aleged insufficient disclosure claim 5 as granted is of importance. This claim reads:

5. Universal colouring compositions according to any one of the preceding claims, characterized in that they have a viscosity of 2.0-10.0 poises at 20°C.

The specification itself did not provide any information as to how this viscosity was measured and which type of measurement equipment was used.

The subject matter of claim 5 was incorporated in claim 1 of several requests.

The proprietor (appellant) argued that the skilled person in this specific field would measure this viscosity using a so called "Stormer viscosimeter". However, the respondent filed evidence that such a viscosimeter would not provide measurement results in the absolute unit "poises" but rather in relative values.

The board then reasons (R 2.2.5) "in view of the numerous techniques and devices used in the state of the art to measure viscosity, it amounts to an undue burden for the person skilled in the art if the latter is left without any clear guidance as to how to prepare compositions which meet the required range of viscosity."

Following the established case law (e.g. T14/83, OJ EPO 1984,105) the Board concludes that the invention as claimed has not been disclosed in a manner sufficiently clear and complete within the meaning of Article 100(b) EPC.

This decision may seem straightforward, however in numerous A exams (at least in the chemistry field) candidates have had to put clear definitions in the claims of measurement methods (or other features).

From what I learned some guidance (but always judge for yourself!) may be the following:

In the exam look for sentences like "as is a generally known", or "known to the skilled person" or any similar language in the letter of the client. If you find these sentences in relation to a specific feature it is normally not necessary to put a clear definition in the claim.

On the other hand, in the absense of such language, if you find clear definitions for certain claim features you have to put these definitions in the claim and not only in the description.

Read the decision here.