G1/23: Solar cell referral to shed some light on disclosure

Introduction
The Enlarged Board of Appeal, the EPO's highest judicial authority, is currently grappling with a case referred to it that tests the boundaries of what it means for a product to be publicly disclosed. The case is G1/23 (‘solar cell’) and at issue is how Article 54(2) EPC and the concept of disclosure apply to a product that is available to the public but cannot be easily reproduced. The question at the core of the referral is does the skilled person need to be able to reproduce that product, for that product to form part of the state of the art? As the date for Oral Proceedings approaches, we are here to update you on where things stand.

Background
This case started with an appeal (T 483/19) against the decision of the Opposition Division (OD). The patent in question (EP2626911) relates to a polymer material for encapsulating a solar cell, comprising a specific aluminium content. The Opponent had attacked claim 1 on the basis of a prior art document that allegedly disclosed a similar encapsulating polymer material (called “ENGAGE 8400”) fulfilling all of the requirements of claim 1 except the required aluminium content. The Opponent then argued that claim 1 lacked inventive step in combination with a second document.

However, the patent proprietor argued that although the ENGAGE 8400 polymer material was commercially available, there wasn’t enough information in the public domain to allow it to be reproduced. They argued that the skilled person would need to conduct their own research to find the right experimental conditions to make the polymer. Therefore, they argued, although the polymer was commercially available, it could not be said to have been “made available to the public” in the sense of Article 54(2) EPC and so cannot be considered for assessing novelty or inventive step. The OD agreed and upheld the patent as valid.

The Law
The appeal essentially hinges on whether the prior art polymer can indeed be said to have been made available to the public. Both parties cited the key case law on this point, the now 30-year-old G1/92:

The chemical composition of a product is state of the art when the product as such is available to the public and can be analysed and reproduced by the skilled person…. Where it is possible for the skilled person to discover the internal composition or structure of the product and to reproduce it without undue burden then both the product and its composition or internal structure become state of the art. (G1/92)

It has long been the case that a known product can be patented if it can’t be reproduced or reverse engineered without an ‘undue burden’. For mechanical inventions, this is usually straightforward. If the invention is a pair of garden pliers, it isn’t difficult to see how the invention works or to reproduce it. Instead, it is usually chemical inventions that test the limits of this case law. As the referring board pointed out, since G1/92 was decided, the Boards of Appeal have split on how to interpret G1/92 in this context.

On the one hand, it could be interpreted as meaning that the product itself is available to the public, even if its internal composition or structure are not. In this case, the prior art polymer would then be available to the skilled person as the Opponent argued. Alternatively, it may mean that if the internal composition and structure of a product are such that they can’t be readily reproduced by the skilled person, then the whole of the product has not been made available. That is the product per se, as well as its composition, is excluded from the prior art. If that is the case, then the prior art polymer could not be used for the assessment of inventive step in this case even though it is commercially available.

Therefore, what the Board of Appeal must consider in this appeal is whether the polymer, which is undoubtedly available to the public in the normal sense of the word (because it can simply be bought) might nevertheless not be considered available to the skilled person because it cannot be readily reproduced. In this case, the referring Board grappled with these questions and ultimately decided that the conflicting case law warranted a referral to the Enlarged Board of Appeal, the body responsible for ensuring uniformity in the application of the EPC. And so, we have G1/23.

Questions referred to the Enlarged Board
The Board of Appeal has referred the following questions:

• Question 1: Is a product put on the market before the date of filing of a European patent application to be excluded from the state of the art within the meaning of Article 54(2) EPC for the sole reason that its composition or internal structure could not be analysed and reproduced without undue burden by the skilled person before that date?
• Question 2: If the answer to question 1 is no, is technical information about said product which was made available to the public before the filing date (e.g. by publication of technical brochure, non-patent or patent literature) state of the art within the meaning of Article 54(2) EPC, irrespective of whether the composition or internal structure of the product could be analysed and reproduced without undue burden by the skilled person before that date?
• Question 3: If the answer to question 1 is yes or the answer to question 2 is no, which criteria are to be applied in order to determine whether or not the composition or internal structure of the product could be analysed and reproduced without undue burden within the meaning of opinion G 1/92? In particular, is it required that the composition and internal structure of the product be fully analysable and identically reproducible?

The preliminary opinion
The Enlarged Board has summoned the parties to Oral Proceedings on 12th March 2025 and has already issued its preliminary, non-binding, opinion. The Enlarged Board’s preliminary view is that the prior case G1/92 “cannot be reasonably implemented in the system of the EPC”. The Board then go on to list what they call several “unacceptable results” and “irreconcilable contradictions” that would follow from the notion that non-reproducible products should be excluded from the prior art. The Board noted that the notion that a product can be physically existing but not legally existing would lead to absurd outcomes. The Enlarged Board’s preliminary view is that the most straightforward solution is to assume that a non-reproducible product in its readily available form, is enabled by being put on the market and that the answer to Questions 1 and 2 are ‘no’ and ‘yes’ respectively and Question 3 is moot.

Our take
The decision in G1/23 could bring about a shift in what constitutes a disclosure to the public and therefore forms part of the state of the art. Patent applicants are advised to file before commercialisation and a final decision in-line with the preliminary opinion makes this advice as important as ever. Sale of a product which could not be reverse engineered or reproduced by the skilled person without undue burden has not previously excluded at least an irreproducible aspect of that product from later being protected by a patent in Europe. A decision that an irreproducible product is not excluded from forming part of the state of the art would mean that irreproducible products that have been made available to the public (e.g. by being put on sale) would no longer be patentable in Europe. The decision may also clarify whether published properties of a product, for example in the form of a technical brochure, may form part of the state of the art even if the skilled person could not or would be under undue burden to determine the underlying structure of the product and reproduce said product.

At Abel + Imray, we will be keeping you informed of what the Enlarged Board’s ultimate decision and how this might affect your patent strategy going forward. We expect we will see the final decision handed down later this year. In the meantime, we will be keeping you up to date with the latest insights as this case progresses.

We will be reporting as this case continues, so make sure to follow us on LinkedIn for the latest news and developments. For more information, please contact Chris Lindsay, Katy Pellow, or your usual Abel + Imray advisor.