Background

It is established EPO case law that a claim directed to the use of a known compound for a particular purpose (a second medical use claim) should be interpreted as including that technical effect as a functional technical feature and such a claim is novel provided the technical effect has not previously been made available to the public, even if that effect may have been inherently achieved in a known use (G 2/88 and G 6/88).

T 2387/22 concerns European patent no. 3325559 in which the granted claims related to a vacuum metallised pigment (VMP) pigment slurry comprising pigments, solvents and specific dispersing additives. Both parties appealed the decision of the Opposition Division to maintain the patent in an amended form. Whilst the Technical Board of Appeal ultimately revoked the patent, of particular note is the reasoning of the board in relation to the second non-medical use claims of auxiliary requests 9-11 in which the board addressed was whether a feature defining a relative improvement was clear. Whilst clarity objections are not permissible as a ground of opposition at the EPO, claim amendments made post-grant require that clarity is considered.

Relative improvement features in use claims

Claim 1 of each of auxiliary requests 9-11 in T 2387/22 was directed to use of a VMP pigment in a flexographic ink formulation for providing the technical effects: “fewer print defects, higher hiding and stronger colour and allowing a lower volume anilox”.

The patentee argued, citing G 2/88, that when a use claim defined technical purposes or effects, these were to be interpreted as functional features restricting the scope of protection. They further argued that it was a well-established practice of the boards to allow the definition of effects or purposes in non-medical use claims using broad and/or relative terms.

Conversely, the opponent argued that since the functional features were defined using relative terms, they did not meet the requirement of clarity under Article 84 EPC. In particular, the opponent emphasised there was no way to objectively determine whether a given use met the requirement of “providing fewer printing defects” because it was not even clear how the printing defects should be identified or measured and/or what the reference was for concluding whether the relative condition “fewer” was met.

In its decision, the Board of Appeal pointed out that the limiting functional features of a use claim are not exempt from the clarity requirement under Article 84 EPC or somehow exposed to lower standards; it acknowledged that the mere breadth of protection does not in itself imply a lack of clarity. The Board of Appeal went on to emphasise that the decisive consideration is whether the feature in question gives rise, or could plausibly give rise, to legal uncertainty when assessing whether a particular subject matter falls within or outside the scope of protection conferred by the claim. Where a claimed invention is defined by the use of a known entity to achieve a known technical effect or purpose, and the alleged technical contribution lies in a “relative improvement or enhancement of that effect or purpose”, the requirement of clarity under Article 84 EPC generally demands that the feature defining such relative improvement or enhancement be expressed in “objectively verifiable terms”, thereby ensuring legal certainty regarding the scope of protection. In these “relative-improvement” scenarios, any imprecise functional language can blur the distinction between claimed and known uses, giving rise to the very legal uncertainty that the clarity requirement is intended to prevent.

In T 2387/22, the Technical Board of Appeal found that the prior art already discloses the use of the same additive for the same, or at least very similar, technical purposes and, thus, the claimed technical effects are neither hidden nor unrecognised in the prior art. Further, the board noted that the use claim does not define distinct technical effects, but rather relative improvements in the achievement of such effects. The Technical Board of Appeal held that the subject matter of claim 1 of auxiliary requests 9-11 cannot be assessed objectively in relation to the prior art, which gives rise to legal uncertainty and, thus, the claim lacks clarity.

Key takeaways and practice points

Novelty and inventive step of a second non-medical use claim can be based on technical effects that constitute relative improvements of effects of the prior art.

“Relative improvement” features must be expressed in “objectively verifiable terms” so that the distinction between claimed uses and known uses is clear.

Vague or imprecise definitions of such “relative improvement” features can lead to legal uncertainty and, thus, clarity objections.

Case details at a glance

Jurisdiction: EPO
Decision level: Technical Board of Appeal
Parties: Sun Chemical Corporation (applicant), Schlenk Metallic Pigments GmbH and ECKART GmbH (opponents)
Citation: T 2387/22
Date: 24 June 2025
Decision: dycip.com/epo-t238722