Priority, added matter and an intervening publication

Priority is not a reward for filing any earlier application; under Article 87(1) EPC it covers only the same invention. The priority document must disclose the subject-matter of the claim in a manner that is clear and complete enough for it to be carried out. Claim 1 as filed requires topcoat C. The provisional does not mention C at all, and the June 2022 lab report is not the priority document. Therefore claim 1 as filed is not entitled to priority and has the EP filing date of 2 March 2023 as its effective date. The proposed claim without C is different. Layers A and B with porosity 40-60% are expressly described in the provisional, so that subject-matter is the same invention as the priority disclosure. If the amendment is allowable under Article 123(2) EPC, the proposed claim has the priority date of 3 March 2022. The key check is whether the application as filed provides a basis for deleting C. If the description presents C as essential to every embodiment, deletion is likely to be added matter; if A+B+porosity is disclosed as a separate embodiment or in a general list, deletion is more defensible. The amendment also broadens claim 1, so the basis must be unambiguous.

(a) Claim 1 as filed is not entitled to priority, so its effective date is 2 March 2023. Beta's article was published on 1 February 2023 and is therefore prior art under Article 54(2) EPC for claim 1. However, the article discloses A+B and porosity 45-55% but no topcoat C. Claim 1 requires C, so the article does not disclose all features and does not destroy novelty. It can still be used for inventive step, for example by arguing that adding C to the known membrane was obvious. (b) The proposed claim without C is entitled to priority only if the deletion of C is allowable under Article 123(2) EPC and the priority document discloses A+B+porosity. If priority is valid, the effective date is 3 March 2022 and Beta's article of 1 February 2023 is after that date, so it is not prior art at all. If priority is not valid, for example because the amendment is not allowable or because the priority document is found not to disclose the claimed subject-matter, the effective date is 2 March 2023. Beta's article then discloses A+B and porosity 45-55%, which falls within 40-60%, so it anticipates the proposed claim. The priority analysis therefore controls the novelty result.

Alpha should not simply keep claim 1 and argue that Beta is irrelevant. Claim 1 as filed has lost priority, so Beta is prior art for inventive step, even though it does not anticipate because it lacks C. The better strategy is to run two requests. The main request can keep C and argue inventive step over Beta, relying on the technical effect of the UV-cured topcoat if the application as filed provides data or a credible effect. The first auxiliary request should be the claim without C, which recovers the priority date and removes Beta as prior art. Before filing that auxiliary request, Alpha must identify the exact basis in the application as filed: a paragraph, example or embodiment that discloses A+B+porosity without C. If C is described as essential, the auxiliary request should not be filed because it will fail under Article 123(2) EPC. Alpha should also verify the priority document and file a priority translation if required. Procedurally, amendments should be filed before the Rule 71(3) communication; after that, amendment requires the examiner's discretion. Alpha should present the auxiliary request conditionally and explain why the deletion is a permissible selection from the original disclosure. It should also consider filing third-party observations only if it has useful material, not as a substitute for a proper amendment strategy.