Added subject matter, unclear parameters - T 1184/23 and T 1440/23
The recent decisions T 1184/23 and T 1440/23 from the Technical Board of Appeal of the European Patent Office are an important reminder for applicants in the chemical field to exercise particular caution when drafting patent applications with claims containing parametric definitions. Both cases also highlight the need to think strategically about claim amendments during prosecution. While an amendment may be acceptable to the Examining Division, it can create problems during the post-grant proceedings before the EPO.
In each decision, an added subject matter issue arose during opposition/appeal proceedings, prompting the patentee to introduce a parametric definition into claim 1 from the description. It had to be decided whether the parameter was clear. In both instances, the parameter was found to lack clarity, to the detriment of the patentee.
T 1184/23
The claims of the application as filed were directed to an aqueous transparent oil-in-water emulsion including “an octenyl succinate starch”.
Claim 1 as granted specified that the octenyl succinate starch was present “in a concentration of 0.5-600 ppm”.
During prosecution, claim 1 as amended additionally specified that the octenyl succinate starch had “a molecular weight MW-distribution of 10000-2000000 g/mol”.
The Examining Division (ED) considered the MW-distribution parameter to be unclear, on the basis that claim 1 did not specify a method for measuring the parameter. The ED also noted that the specification did not describe any method for measuring this parameter but considered that the octenyl succinate starch inevitably had the particular MW distribution.
Thus, the ED suggested deleting the parameter from claim 1, and the applicant followed suit.
An opposition was then filed; the opponent argued that claim 1 as granted extended beyond the content of the application as originally filed in that it defined the concentration of the octenyl succinate starch without mentioning the MW distribution parameter (i.e. that claim 1 contained an unallowable intermediate generalisation).
In response to the objection of added subject matter, the patentee filed an amended Main Request, in which the MW distribution feature was reintroduced into claim 1, to accompany the particular concentration of the octenyl succinate starch.
Since the parameter was absent in the granted claims, it was open to examination of clarity.
The Opposition Division found that the MW distribution feature was unclear, and this decision was upheld by the Board of Appeal.
Why was the parametric feature held to be unclear? Surely a chemist would understand what a molecular weight distribution is?!
Under EPO practice, one of the requirements of clarity in connection with defining a claimed product by parameters is that the method for measuring a parameter (or at least a reference thereto) must appear completely in the claim itself. For instance:
1. A fat composition […] wherein the fat composition has a solid fat content at 0 °C of at least 30, wherein the solid fat content is measured on unstabilised fat according to ISO 8292-1:2008
1. A lubricating composition […] wherein the lubricating composition has a kinematic viscosity at 100 °C of 0.7 to 7.0 cSt as measured according to ASTM D445-24
If the description sets out a lengthy method for determining a parameter, it might instead be possible (even preferable, particularly if the specific conditions of the method are relevant) to specify in the claim that the parameter “is determined according to the method specified in the description”.
If specifying a method is not possible at all, it is necessary to show either that:
(i) the measurement method to be employed belongs to the common general knowledge of the skilled person (e.g. because only one method exists or a specific method is commonly used, i.e. that it is within the common general knowledge which method to choose); or
(ii) all of the known methods in the field of invention for determining the particular parameter yield the same result within the appropriate limit of measurement accuracy.
Going back to the patent in suit, the opponent filed evidence (D29 and D30) showing that several methods for determining MW distributions of starches (starches in general; D29) and branched polysaccharides (D30) were available to the skilled person. None of those documents mentioned octenyl succinate starches specifically.
D29 referred to size-exclusion chromatography coupled with multi-angle light scattering (SEC-MALS), asymmetric flow field flow fractionation coupled with MALS (AF4-MALS), viscometry and sedimentation velocity or sedimentation equilibrium in the analytical ultracentrifuge.
D30 mentioned SEC-MALS, flow fractionation without stationary phase (such as AF4 mentioned in D29) or hydrodynamic chromatography (HDC). D30 also stated that SEC-MALS was “the most readily available and most developed technology for the size separation of branched polysaccharides and for obtaining their size distribution”.
The patentee argued that the skilled person would clearly select a specific method (SEC-MALS) for determining the molecular weight MW-distribution of octenyl succinate starch in the molecular weight range as defined in claim 1. The patentee also filed a document (D24) to support this position; it showed SEC-MALS experiments performed on several octenyl succinate starches, wherein their MW distribution was found to be within the claimed range.
Having considered the parties’ evidence and submissions, the Board decided that:
(a) D24 shows that SEC-MALS is merely a suitable method for determining the parameter of claim 1; it does not show that the skilled person would not consider any other suitable methods (see criterion (i) above)
(b) D29 and D30 are evidence that several possible measurement methods existed and nothing in those documents showed that it was within the common general knowledge of the skilled person to select SEC-MALS specifically (see criterion (i) above); and
(c) because the methods described in D24, D29 and D30 rely on different physical principles, they would not necessarily provide the same results within the appropriate limit of measurement accuracy (see criterion (ii) above).
Concerning point (c), the patentee argued that it would be impossible to demonstrate that criterion (ii) above was satisfied. The Board acknowledged that this might be the case, however, the Board considered that this hurdle would rather support the conclusion that a specific measurement method should have been specified in claim 1.
The claims were thus found to be unclear, and the patent was revoked. As an aside, throughout the proceedings, the patentee was prevented from pursuing the granted claims (i.e. claim 1 without the MW distribution feature). This is because the patentee filed an amended Main Request (with the MW distribution feature in claim 1) in its response to the opposition, and it never defended the granted claims as the Main Request.
T 1440/23
Claim 1 of the application as filed was directed to a hot press forming (HPF) part having “excellent powdering resistance during hot press forming”. Claim 1 as filed also contained a feature “the tau phase is prepared […] so as to allow the alloyed layer to have a thickness of 35 µm or less”.
In the European Search Opinion, the examiner considered the latter feature an unallowable result to be achieved. The applicant subsequently deleted it from the claims.
In the last office action before allowance, the ED raised an objection of lack of clarity against the feature of “excellent powdering resistance during hot press forming”. The ED considered the term to be vague and essentially interpreted it as being a result of other features of claim 1.
The applicant, again, deleted the term from the claims, and the case was swiftly allowed.
During opposition, the opponent argued that claim 1 as granted contravened the added subject matter requirements. Some of the reasons were that deleting the features that the claimed HPF part had “excellent powdering resistance during hot press forming” and that the “the tau phase is prepared […] so as to allow the alloyed layer to have a thickness of 35 µm or less” broadened claim 1 in a way that was not directly and unambiguously derivable from the application as filed.
Although the granted claims were ultimately found to add matter, the Opposition Division considered that the feature of “excellent powdering resistance during hot press forming” was an inherent consequence of the remaining features of granted claim 1, such that the deletion of this feature during prosecution was allowable. Similarly, as for the other feature (“tau phase is prepared […] thickness of 35 µm or less”), the Opposition Division noted that the way the tau phase is prepared (its composition) according to claim 1 is the decisive factor for obtaining the desired thickness, irrespective of other features.
The patent was maintained as amended based on Auxiliary Request 3 containing some further structural and product-by-process features characterizing the claimed HPF part.
The Board of Appeal was not so lenient. Concerning the deletion of the feature of “excellent powdering resistance”, the Board noted that claim 1 as amended covered HPF parts not having “excellent powdering resistance” (thus adding subject matter), unless proven to the contrary. That is, unless it could be shown that the remaining features of claim 1 compensate for the deletion.
The Board inferred from the content of the application as filed that “excellent powdering resistance during hot press forming” was disclosed as a result of several factors, including, indeed, the thickness of the alloyed layer being 35 µm or less, a factor which the Board considered to be essential to achieving “excellent resistance…”. This feature was, of course, not present in claim 1 of the Main Request before the Board.
Unlike the Opposition Division, the Board said that there was nothing in the application as filed that suggested that the remaining features of claim 1 necessarily led to the thickness of the alloyed layer to be within the particular range. Put another way, the Board considered that thicker layers could be obtained while still satisfying the remaining features of claim 1.
According to the Board, the application as filed disclosed that “by controlling the ingredients of the tau phase, it is possible to control, inter alia, the thickness of the alloyed layer to 35 µm or less. However, the application “does not disclose that no other conditions need to be met. While it is a necessary condition, nothing suggests that it is also a sufficient condition”.
Finally, looking at the examples of the application, the Board also pointed out that several process parameters could be varied when preparing the claimed HPF part, but the examples showed only little variation in the parameters.
Claim 1 of the Main Request was thus found to violate the added subject matter requirements. To try to save the patent, the patentee went straight into Auxiliary Request 21, which specified that “the alloyed layer has a thickness of 35 µm or less” (cf. the wording of claim 1 as filed).
Since the parameter was absent in the granted claims, it was open to examination of clarity.
Another clarity requirement under EPO practice in connection with parametric definitions in claims is that the skilled person should be able to easily and unambiguously verify whether they are working inside or outside the scope of the claim.
In the case at hand, there was evidence on file showing that “thickness” in the context of the invention could have different definitions – “minimum thickness”, “average thickness” or “maximum thickness”. The patent also contained comparative examples (those not according to claim 1) wherein the alloyed layer was only 1 µm and 2 µm above the upper limit of 35 µm.
Overall, the Board considered that there was ambiguity as to what “thickness” in amended claim 1 actually meant, such that the skilled person would not clearly understand this feature and its boundaries.
The patent fell because all claim requests suffered from either the added matter issue discussed above or the lack of clarity issue.
Key takeaways
T 1184/23 and T 1440/23 helpfully remind us of a few important peculiarities of EPO practice:
(a) if there is a prospect of a patent application being prosecuted before the EPO, it is important to devote time and attention during the drafting stage to ensure that any parameters are clearly and comprehensively defined, including the relevant measurement method and its conditions wherever possible. It is also necessary to consider the meaning of the parameters as they would be understood in the field of the invention - as shown by T 1440/23, even deceptively simple parameters such as “thickness” could be found to lack clarity;
(b) in both cases, the parametric definitions were not present in the granted claims. Had they been present in the claims as granted, the outcomes might have been different – the opponents would have had to attack the parameters on the ground of insufficiency of disclosure (as lack of clarity attacks would have been inadmissible), which might have been more challenging;
(c) both decisions illustrate that the stringent added subject matter requirements adopted by the EPO are not only problematic in themselves, but they can create various downstream issues during post-grant proceedings;
(d) claim amendments made during prosecution before the EPO should always be made with potential post-grant proceedings in mind. In addition, while the examiners’ suggestions regarding claim amendments may seem helpful and expedient, applicants have to be careful not to introduce vulnerabilities into claims that opponents may later exploit;
(e) relative terms (such as “stable”, “improved”, “having excellent properties”) in independent claims can cause problems before the EPO beyond mere lack of clarity.
If you would like to discuss clarity or added subject matter requirements before the EPO, or have any questions about EPO practice in general, please feel free to get in touch.
This article is for general information only and is not intended to constitute legal advice. If you would like tailored advice on a specific matter, please do not hesitate to contact me.
