This is an appeal of the patent proprietor against the revocation of the opposed patent.
I found the case interesting because it shows how difficult it is to draft allowable product claims for composite objects parts of which undergo changes during the production step but can only be well characterised before undergoing these changes. The patent drafter chose to draft a product claim, but, as will become clear in the discussion by the Board, there is a product-by-process feature hidden in the claim.
Claim 1 of the main request before the Board read (in English translation):
Membrane-electrode assembly for polymer electrolyte fuel cells having a working temperature of up to 250°C, comprising two flat gas diffusion electrodes, a polymer membrane comprising at least one basic polymer, wherein the polymer membrane is sandwiched between said electrodes, and a dopant, wherein the gas diffusion electrodes are loaded with the dopant so that the dopant content in the gas diffusion electrodes amounts to 60% to 120% of the weight of the basic polymer in the polymer membrane, in order to form a dopant reservoir for the polymer membrane, wherein the polymer membrane is fixedly connected to the gas diffusion electrodes in a proton conducting manner via the dopant after the action of pressure and temperature and has a conductivity of at least 0.1 S/m at a temperature of no less than 25° C in the doped state.
In what follows, the Board discusses the novelty of this claim:
*** Translation of the German original ***
[2.1] The [opponent] was of the opinion that [claim 1] was not novel over the documents D1/D4, D5, and D6.
[2.1.1] D1 […] and D4 (which has the same author and the disclosure of which is identical to the disclosure of D1 for the present purpose) disclose methods for producing a membrane-electrode assembly (MEA) having a polymer membrane made of polybenzimidazole (PBI), a basic polymer, and phosphoric acid as dopant, wherein an acid doped polymer membrane is hot pressed (150°C, 2.2∙104 kPa, 10 minutes) with gas diffusion electrodes that are also acid doped. One may assume that the doped membrane of the MEA known from D1 has a conductivity of at least 0.1 S/m, and this has not been contested by the [patent proprietor].
D1 does not disclose the amount of phosphoric acid, relative to the weight of the basic polymer in the polymer membrane, that was used for impregnating the gas diffusion electrodes. The statements below the table on page 61 appear to refer to another impregnating method and cannot be applied to the conditions of production method 3 disclosed in D1 without further ado.
Interpretation of claim 1 as granted
[2.1.2] Before novelty can be assessed, it is necessary to appropriately interpret claim 1.
The [patent proprietor] submitted that the claimed amount of dopant in the gas diffusion electrodes (i.e. the loading of the electrodes) had to be understood as the amount of dopant before the subsequent action of pressure and temperature […]. The parties agreed on that matter and the Board adopts this point of view.
Moreover, the [patent proprietor] argued that product claim 1 of the impugned patent was directed to a MEA the polymer membrane was not, or at least insignificantly, doped and which, as a consequence, did not have any proton conductivity yet. The dopants still were in the gas diffusion electrodes, in an amount of 60% to 120% of the weight of the basic polymer in the polymer membrane, forming a dopant reservoir. Thus claim 1 was exclusively directed to a primary product (Vorprodukt) for a MEA in the state preceding the impact of pressure and temperature. This claimed primary product could then, by the action of pressure and temperature (i.e. by hot pressing), be transformed into a MEA suitable for use in a fuel cell, wherein the polymer membrane was proton conducting manner via the dopant, fixedly connected to the gas diffusion electrodes, and has a conductivity of at least 0.1 S/m at a temperature of no less than 25° C in the doped state. However, the Board cannot adopt this view, for the following reasons:
First of all, the indication of the conductivity of the polymer membrane in the doped states of at least 0.1 S/m in the claim manifestly indicates that the polymer membrane already has to be in the conductive, doped state, i.e. the state resulting from hot pressing, and that the dopant already has to have migrated from the reservoir formed by the gas diffusion electrodes to the membrane. This view is in line with the further claim feature according to which “the polymer membrane is … proton conducting via the dopant”.
Secondly, the claim defines a MEA the polymer membrane of which is “fixedly connected to the gas diffusion electrodes … via the dopant”. Such a connection can only be obtained by hot pressing.
Therefore, the Board is of the opinion that the present product claim is to be interpreted such that it concerns a MEA after hot pressing, i.e. ready for use. The same holds true for the ready-for-use fuel cell, but the amount of dopant given in the claim corresponds to the amount that has to be used before the action of pressure and temperature and which has to be provided in the gas diffusion electrodes acting as a dopant reservoir.
[2.1.3] It was not contested that after the electrodes have been hot pressed with the polymer membrane it was unknown how much dopant was still in the gas diffusion electrodes and how much of it had migrated to the polymer membrane during the hot pressing (cf. paragraphs [0013] and [0023] of the impugned patent). The latter also depends on whether the polymer membrane has been pre-doped, which is not excluded in the claim. Under these circumstances, the claim feature according to which “the gas diffusion electrodes are loaded with … [a] dopant content … amount[ing] to 60% to 120% of the weight of the basic polymer in the polymer membrane” does not delimit [the claim] with respect to the prior art because it does not define the amount of dopant present in the gas diffusion electrodes of the claimed end product.
[2.1.4] As all the other claim features are known from D1, the Board is of the opinion that the novelty of the product claim depends on whether it is plausible that the amount of dopant used in the gas diffusion electrodes according to the invention can confer concrete properties to the final product (MEA) that distinguish it over the MEA produced according to D1. However, the [patent proprietor] has not submitted any such concrete product properties, and the Board cannot spot any in the description. The advantages of the invention asserted by the [patent proprietor] manifestly refer to the production method and not, or not necessarily, to the final product (i.e. the MEA). Therefore, they cannot serve as evidence for a difference over the prior art.
A good contact between the polymer membrane and the electrodes, which has been asserted as being one of the advantages [of the invention], is also obtained [in a MEA] according to D1 because it is a prerequisite for the functioning of the MEA.
[2.1.5] Therefore, the Board comes to the overall conclusion that the subject-matter of claim 1 is not novel over D1 (A 54). As a consequence, the main request is not allowable […].
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