???
A is the owner of a patent for a novel process for manufacturing high-strength plastic adhesives, which was filed in 2020 and granted in 2022. The process and several variants of the adhesive are described in the patent. In 2025, A notices that a competitor, B, is using a similar process to manufacture adhesives and distribute them to customers. At first glance, it seems likely that B is infringing the patent. The patent covers not only the manufacturing process, but also the adhesive itself in the form of a substance claim describing its chemical structure.
When confronted with the patent, B discovers the prior art: adhesives with this composition were already known before the filing date. The process, on the other hand, which was described in detail in the application, is claimed independently and is not anticipated by the known prior art.
For a patent to be infringed, all the features of a patent claim must be fulfilled. At the same time, this patent claim must also be legally valid, i.e., there must be no grounds for invalidity. A patent can only be enforced to the extent that it is legally valid, i.e., valid and patentable. If it turns out that a patent claim is not legally valid—for example, because it is not new—this has two consequences: First, the patent must be amended and limited in nullity proceedings so that it only retains the scope of protection that is compatible with the prior art and complies with the law. Second, the patent holder can no longer take action against objects that fall within the part that has been removed by this limitation.
The practical significance of this connection is clearly illustrated by the adhesive patent. The substance claim to the adhesive itself is not legally valid because a composition covered by the claim was already known before the filing date and is therefore part of the prior art. This claim is therefore invalid because it is not new.
However, this does not mean that the patent is worthless as a whole. The process claim, which describes a specific manufacturing process, remains unaffected, provided that this process itself is new and inventive. If this exact process is carried out, a specific composition is created which, although it partially overlaps with the known adhesive, is only accessible in this form through the protected process. However, the patent holder must prove that the process has been used.
Now let us consider cases in which a limitation of the patent may be advantageous for the owner. Such a limitation can help to maintain the patent within a narrower scope and at the same time drive a competing product out of the market. This is particularly possible if the alleged infringer uses a specific, more detailed technical design that is included in the patent specification. In such a case, the patent holder can limit the claim to this narrower technical design and thus adjust the scope of protection of the patent so that it remains enforceable.
However, this requires that the narrower technical design itself meets the criteria for patentability – it must be new and inventive. If this is not the case, even the limitation cannot secure the validity of the patent. A successful limitation therefore requires that the features included in the narrower claim represent a genuine difference from the prior art.
Suppose the infringer uses the same manufacturing process as described in the patent, but this process is difficult to prove in practice. It is therefore hardly possible to prove directly that he is actually imitating the process step by step.
However, the patent specification also contains a more detailed description of the composition of the resulting adhesive. This specific composition is not known in the prior art and is therefore protectable. The patent holder therefore has the option of limiting the originally broader patent claim to this particular composition.
This reduces the patent to a narrower but legally valid core. The decisive advantage is that the infringer's adhesive has exactly this composition. His product therefore falls under the limited claim, which remains valid. In this way, the patent holder can continue to take successful action against the infringer despite the problem of proving the process.
From the perspective of a potential infringer, examining a patent is particularly challenging if the subject matter of the infringement falls under the patent but the independent patent claim is invalid. It is not sufficient to simply invalidate the broadest independent patent claim. Even if this claim is not legally valid, this does not automatically mean that the entire patent is harmless. This is because a patent usually consists of several dependent or even subordinate claims that are formulated as fallback positions.
For the infringer, this means that they must analyze not only the main claim, but all claims in detail. Added to this is the difficulty that they often cannot know in advance how the patent office or a court will limit the claims in the event of a dispute. Even a feature that initially appears to be insignificant could make a decisive difference in a limited version of the claim and ultimately lead to one's own product infringing the claim.
The risk therefore lies in the fact that the patent does not exist in a single form, but can potentially continue to exist in several variants. Therefore, an infringer must always keep an eye on the entire patent and consider all possible fallback positions in order to make an informed assessment of the risk of infringement.
Suppose that four different adhesive compositions and different manufacturing processes are described in the patent specification. The independent patent claim initially claims, in general terms, an adhesive composition with certain components. However, this claim is not legally valid because one of the compositions is already known from the prior art.
This does not mean that the potential infringer can breathe a sigh of relief. Even if claim 1 is vulnerable, the patent owner can attempt to fall back on one of the specifically described compositions and limit their patent accordingly. Each of these four compositions therefore represents a possible fallback position for the infringer.
This means that the potential infringer must examine each individual composition described to determine whether it is new and patentable in relation to the prior art – and whether his own product falls under it. Otherwise, there is a risk that the patent holder will enforce precisely this composition as a limited claim in the event of a dispute.
This shows that not only the granted claim, but the entire disclosure in the patent specification is potentially relevant and must be examined.
Special Case: Pre-Published infringing object
A special case concerns situations in which the allegedly infringing subject matter was already publicly known before the filing date. Such subject matter is therefore part of the prior art. If it falls completely under the patent claim, the claim lacks novelty and is invalid. If the claim is limited, two scenarios may arise: Either the subject matter no longer falls under the new claim – in which case a valid patent remains, but the subject matter does not infringe it. Or the subject matter continues to fall under it – in which case the new claim is also invalid. If, on the other hand, the previously published subject matter falls outside the scope of the patent claim, the claim remains valid, even if the subject matter may be freely used. It follows that an object that was already publicly known before the application was filed cannot be removed from the market by a patent granted later.
If the alleged infringing object—in this case, the adhesive—is already part of the prior art, the situation is clear: if the adhesive falls within the wording of the patent claim, then this claim lacks novelty. It is therefore invalid and cannot constitute an infringement. If the patent is limited by additional features, for example in a dependent claim that specifies a particular composition, the problem remains: if the known adhesive also falls under this narrower claim, it is also invalid. Any patent claim that is covered by the previously published adhesive is not legally valid. If, on the other hand, the adhesive falls outside the scope of a patent claim, that claim may still be valid, but it is not infringed by the adhesive. This means that the adhesive may be freely manufactured and distributed despite the existing patent. This makes it clear that a previously published object can no longer be monopolized by a patent granted at a later date.
The extension of the scope of protection of a patent after it has been granted is legally inadmissible. The purpose of this principle is to ensure that the general public can trust that the patent does not extend beyond the scope specified in the granted version. If the owner were allowed to subsequently delete features or generalize the claim, the scope of protection could be retroactively extended and third parties would suddenly find themselves in a prohibited area that did not exist at the time of grant. This public confidence in the defined limits of the patent is a central tenet of patent law. Therefore, once a patent has been granted, the scope of protection may not be extended, but may at most be restricted.
In the application process, the patent was restricted to specific adhesives with a certain feature, while the originally intended manufacturing process was no longer claimed. Thus, the scope of protection now only covers these specific adhesives (with the feature) .
If a third party uses a different adhesive that does not fall under this limited version, there is no infringement – even if they use the process originally described.
A subsequent amendment to the patent to include other adhesives is not permitted, even if these adhesives were already described in the application. Nor can the process be reincorporated into the claims at a later date. Both would constitute an extension of the scope of protection, which is no longer possible after the patent has been granted. The scope of protection therefore remains permanently limited to the adhesives restricted during the application process.
Summary
???
???
???
???
???
???
???
???
