Case Study: Prior User Defence In Patent Law And The Possibility Of Improving The Invention

In cases involving patent disputes, the party that has used, in business dealings, a product that infringes the patent will usually try to prove that the infringement did not occur as not all the features of an independent claim have been implemented. Another standard defence strategy is an attempt to eliminate the patent by invalidating it before the Patent Office of the Republic of Poland.

In certain situations, two entities may independently develop the same solution to a technical problem at similar times, with one deciding to protect it by obtaining a patent, and the other using it only for commercial purposes. Therefore, in the case of the latter entity, it may happen that it has acquired the so-called prior user right, which protects the entity against patent infringement claims, as it constitutes patent limitation.

The authors encountered such a situation when they invoked the prior use defence in patent infringement proceedings. What made this case unique was that the product alleged to infringe the patent was different from the one produced by the defendant as a prior user when the invention was filed by the plaintiff. Therefore, the main axis of the dispute was the question whether the right tomodify or improve the invention was covered by the prior user right.

Prior user right in patent law

A prior user right is provided for in Article 71(1) of the Industrial Property Law, which sets forth that a person who, on the date according to which the priority for the grant of a patent is determined, exploited the invention in good faith in the territory of the Republic of Poland, may continue to exploit it free of charge withintheir enterprise, to the extent to which they have used the invention thus far.

If it is established that the defendant has demonstrated the grounds for acquiring the prior user right and the plaintiff has not challenged the presumption of the defendant's good faith, the court should dismiss the case.

For effective invocation of the prior user right, several conditions must be met cumulatively, i.e., such use:

• must relate to an invention covered by a patent granted to another entity (as interpreted also through the prism of the patent description and drawings, and taking into account equivalent features). If the solution used before the date according to which the priority was determined did not include all the necessary features of the patent claim, the prior user right will not be acquired.
• must occur before the date according to which the priority of the patent is determined, which includes not only use, but also the preparation for use, e.g. of production equipment;
• must be in good faith, i.e. the user must be subjectively convinced that they do not violate another entity's rights;
• must be limited to the scope of prior use, in other words, it must correspond to the scope in which the invention was used on the date according to which the priority for granting a patent was determined. This is particularly the case if the scale of production after the date according to which thepriority was determined exceeds the production capacity on that date. In such a case, the prior user defence will not be effective with respect to the production exceeding this scale;
• this defence will also not be effective if the use relates to a different solution.

Prior user defence and the possibility of improving the invention

In the dispute mentioned at the outset, the key element was the changes made to theproducts – multi-layer (six- or seven-layer) roofing films, which had been used before the date according to which the priority was determined, as opposed to the product which was the subject of an action for infringement of a patent (a five-layer film). In other words, the defendant simplified the construction of their products, by reducing the number of layers, while retaining all their properties and functional features. In such a case, it was reasonably asked whether the modifications introduced by the prior user to the product would still allow the invention to be used within the scope of this right.

Although the admissibility of modifying the invention by a prior user has not yet been addressed in judicial decisions in Poland, it has been noted in the doctrine.

Dr. Marta Sznajder assumes that the user should have the right to use such variants of the invention that are obvious to a person skilled in the art, which stems from the need to provide the user with the opportunity to naturally develop and improve the inventionin line with technological progress.

According to German jurisprudence regarding the institution of prior user, the invention may be modified to a limited extent. In its judgement of 14 May 2019 in case X ZR 95/18, the German Federal Court of Justice (Der Bundesgerichtshof), adopted a position that an invention used could be modified, provided that such modification did not extend the scope of its use. This may be a case where the improvement provides an additional advantage that the product in the original embodiment did not offer, such as an additional feature included in a dependent claim or disclosed elsewhere in the patent specification.

This was also the situation considered by the National Court in Düsseldorf ( Landgericht), which, inits judgement of 3 March 2020 in case Az. 4a O 111/18 refused to take into account prior user arguments, stating that the product, in its current form, exceeded the scope of prior user rights due to the addition of further advantages disclosed in dependent claims and the patent specification.

However, if a patent claim mentions two fully equivalent alternatives for a given feature, and the prior user originally only used one of these alternatives before using the other, this will not exceed the permitted scope. The same applies if a patent description discloses a deviation from the solution included in the prior user's product which, from the point of view of a person skilled in the art, is an obvious modification.

The same court issued a similar ruling of 30 June 2022 in case Az 4b O 51/21 concerning a portable hydraulic unit. In this ruling, it was assumed that the general term "rescue tools" in the claims did not warrant a restrictive interpretation and included not only cutting equipment (as in the case of the product for which the user right was acquired), but also spreaders, combined equipment and rescue cylinders (as in the case of the disputed product).

Therefore, the decisive factor in determining whether a modification to an earlier form of use of the invention is covered by the prior user right is whether the modification provides an additional technical advantage or whether it constitutes a fully equivalent alternative or an obvious modification from the point of view of a person skilled in the art. The mere fact that a given "new" feature has been mentioned in a patent document (e.g. in a dependent claim) does not justify the refusal of protection to be granted on the basis of the prior user right, if it was possible to add this feature also without disclosing it in the patent description due to its obviousness in the light of the available knowledge. However, if this feature has been inspired solely by the teaching of the patent, it should be assumed that the scope of protection resulting from the prior userright has been exceeded.

In the case of the dispute in question, the differences between the products before the date according to which the priority was determined and the disputed product included:

• the use of one layer of material as a separation layer, instead oftwo such adhesive-bonded material layers in the earlier products and, accordingly, a reduction in the weight of the entire separation layer;
• the elimination of one membrane layer and one material separation layer from the inside ofthe film, reducing the number of layers in the product from seven tofive;
• the use of different weights of the outermost and inner material layers, applied to protect the layers 'inside', so that the outermost layer was heavier than the inner layer.

In this situation, for invoking the prior user defence, the functional wording of the patent claims, which allowed for various methods of implementation, and the fact that the prior user's product, on the date according to which the priority was determined, fulfilled not only the features of the independent claim, but also those of dependent ones, was not without significance. The changes to the product, which simplified its structure and fundamentally 'reduced' the number of layers to a form consistent solely with the independent claim, suggested that such a scope of modification could be acceptable, as it did not extend the scope of infringement, and the technical function was maintained. In other words, the features of the basic variant according to the patent must be implemented each time in the case for the preferred variant according to any of dependent claims.

Importantly, the five-layer structure of the film itself was known in the state of the art at that time. Multi-layered structures could be derived from published patent documents. Therefore, it was also possible to consider these modifications through the prism of knowledge available to a person skilled in the art, regardless of the disclosure made in the patent.

On the other hand, the different weights of the inner and outer layers were a solution typically used in other products manufactured by the prior user, and were also rooted in the known state of the art.

Summary

Whether a given modification falls within the scope of prior use by a prior user, i.e. whether it is acceptable, should be examined in two stages:

• Firstly, it should be established whether the feature that constitutes the modification has been disclosed in the patent document.
• Secondly, it should be established whether this feature could have been introduced without the knowledge of the disclosure, despite the disclosure being made in the document, as the feature was obvious to a person skilled in the art fromthe publicly available knowledge.

The permissible scope of use of the invention and the effectiveness of the prior user defence invoked in the proceedings will only be determined by a positive answer to the latter question.

The content of this article is intended to provide a general guide to the subject matter. Specialist advice should be sought about your specific circumstances.