2025 Week 45
This week we report on two recent and important UPC Court of Appeal decisions. Each considers claim interpretation and the relevance of expert and experimental evidence to UPC proceedings.
Seoul Viosys v. Expert Klein – first instance recap
A year ago (see UPC Weekly 2024 w42), we commented on the first instance decision in Seoul Viosys v. Expert Klein, in which the patent fell into a black hole of invalidity, trapped between added matter and a restriction on amending the claim to extend the scope of protection.
The patent is EP 3223320 B1, granted from a divisional application of EP 2757598 A2. The original parent application was actually filed in the Korean language (published as WO 2013/039344 A2) but the divisional application itself was filed in English.
Original claim 1 of the parent application started with these features:
- A light emitting diode comprising:
a first conductive type semiconductor layer;
a plurality of mesas separated from each other on the first conductive type semiconductor layer and each comprising an active layer and a second conductive type semiconductor layer;
reflective electrodes each disposed on the corresponding mesa area and in ohmic contact with the second conductive type semiconductor layer; and ...
Claim 1 of the patent (EP 3223320 B1) as granted included these amendments:
- A light emitting diode, comprising:
a first conductivity type semiconductor layer (110) formed on a substrate (100);
a mesa disposed on the first conductivity type semiconductor layer (110), the mesa comprising an active layer (120) and a second conductivity type semiconductor layer (130);
a reflective electrode (140) disposed on the mesa and configured to be in ohmic-contact with the second conductivity type semiconductor layer (130); ...
As you can see, claim 1 of the granted patent uses the singular for the mesa and the reflective electrode.
The UPC Local Division (LD) reached a view that claim 1 as granted required that there is only a single mesa and only a single reflective electrode. That is, they considered that granted claim 1 excludes embodiments with plural mesas and plural reflective electrodes.
The LD decided that the patent included added matter, due to this change. This specific objection was raised for the first time at the oral hearing, by the LD. The patent was revoked.
Seoul Viosys v. Expert Klein – what happened in the appeal?
In the CoA decision Seoul Viosys v. Expert Klein (5 November 2025), the CoA interpreted the claim differently to the LD. Reassuringly, they noted that claim 1 uses the open wording “comprising” and so the claim should not be interpreted as requiring “only one” mesa, but “at least one” mesa. Given that most of the patent description concerns embodiments with multiple mesas, and based on the apparent plain meaning of the granted English language claim, overturning the LD’s claim interpretation on this point seems right.
With the claim interpreted as covering “at least one mesa”, the CoA decided that there was still added matter compared with the parent application, because all the relevant disclosure in the parent application had multiple mesas and multiple reflective electrodes. The CoA expressly stated that it was fine for the objection to have been raised by the LD for the first time at the oral hearing.
The patentee had two main lines of argument against the substance of the objection. The first was that the skilled person would consider that the LD’s understanding of the relevant embodiments was technically wrong. The CoA criticised this – if the patentee needed to land this argument, it would be necessary to provide expert evidence to substantiate it.
The second line of argument was that the original Korean language PCT application has not been translated correctly on entry of the parent application into the European regional phase. They therefore sought to file a corrected version, in which the relevant passages were more precisely translated, and in a way that supported the patentee’s position on added matter. While the CoA acknowledged that this may work, the firm assumption is that the translation filed at the EPO is correct and the burden of proof is on the patentee to show that this original translation was incorrect, again using expert evidence of the subtleties of the Korean language.
Although an amendment to the claim to require multiple mesas would presumably have saved the patent, the patentee did not propose this amendment. This was because the alleged infringement had only one mesa.
Although the reasoning is slightly different, the CoA reached the same ultimate conclusion as the LD and the appeal was dismissed. So the patent is still revoked.
Otec v. Steros – first instance
The Hamburg Local Division awarded a preliminary injunction (PI) to Steros in the first instance decision in June 2025, based on EP 4249647 B1.
The patent defines a composition for use in electropolishing. There were some key questions around claim interpretation and so the first part of claim 1 is reproduced below.
- Electrolytic medium comprising:
- a set of solid electrolyte particles, comprising solid particles that retain a conductive solution, the set presenting an electrical conductivity greater than 10 µS/cm, and
- a non-conductive fluid immiscible in the conductive solution, immiscible being understood as not forming a single phase in any proportion from 0 to 100°C, the non-conductive fluid when being at rest at room temperature not significantly conducting electrical current
the electrolytic medium being suitable for an electropolishing process comprising … [various steps for electropolishing].
Everything turned on the interpretation and properties of the “non-conductive fluid”. In some of the embodiments and in the alleged infringement, the electrolytic medium was made by adding the solid electrolyte particles to an emulsion. The emulsion has droplets (micelles) of a first liquid suspended in a continuous phase of a second liquid.
Although the claim defines the electrical conductivity of the conductive solution, neither the claim nor the patent defines the conductivity threshold for a non-conductive liquid. The LD decided that, in the absence of other guidance, it was reasonable to take the 10 µS/cm value in the claim and use this as the upper threshold.
Steros submitted experimental evidence on the alleged infringement. They had separated the different phases of the emulsion and showed that the conductivity of the oil phase was 0.291 µS/cm. The LD was satisfied that the patent was likely valid and infringed.
Otec v. Steros – what happened in the appeal?
The CoA decision in Otec v. Steros (7 November 2025) agreed with the LD interpretation of the claim about the degree of allowable conductivity of the non-conductive fluid. This was on the basis that there was nothing else in the patent to explain the limit of “non-conductive”.
However, the CoA disagreed with the LD on how this should be measured. In the case of an emulsion that separates into different phase layers at rest, the LD considered that it would be appropriate to measure the conductivity of one of the layers. But the CoA noted that the description allowed the “non-conductive fluid” to be an emulsion, rather than for the non-conductive fluid to be one phase of the emulsion. Therefore it would be correct to measure the electrical conductivity of the overall emulsion. Doing this with the alleged infringement showed a conductivity above 400 µS/cm.
Steros filed further experimental evidence in the course of the appeal. The purpose of this was to try to show that one of the example embodiments in the patent would also use an emulsion having a conductivity higher than 10 µS/cm. The usual approach of the UPC is to try to interpret the claims so that the described embodiments of the invention fall inside the scope of the claims. And so the argument was that the claims should be given an interpretation that covered both this example and the alleged infringement.
The CoA was critical of the experimental evidence. In their view, the way Steros had run the experiments was not representative of how the skilled person would have tried to implement the example to be consistent with the claimed invention. More generally, the CoA remarked (and placed in the sole headnote to the decision) that experimental data that is not disclosed in the patent should not be used to interpret the claims. This seems stark. For different cases, it seems possible that experimental evidence (or expert evidence) could be helpful to show what the skilled person would have understood from the content of the patent.
The outcome was that the appeal was allowed on the basis that there was likely no infringement of the patent, and so the PI was lifted.
