T 0227/92 01-07-1993

1. The appeal is admissible.

2. The only question to be considered is whether the subject-matter of the patent in suit involves an inventive step.

3. Main request

3.1. It appears to be undisputed that D1 discloses all of the features of the first part of Claim 1, because Figure 3 and the corresponding description in column 7 describe the claimed arrangement of layers, the additional radiation blocking layer shown in Figure 3 being stated to be optional. That the elements disclosed in D1 utilise a colour reaction between the analyte and a reagent is clear from a general reading of D1, a particular passage of significance being column 11, lines 45 to 55. It is also a feature of Claims 4, 22 and 33. The reagent layer is moreover porous, to the extent that it has to be permeable to the liquid sample.

3.2. The features of the characterising part of Claim 1 are (a) that the porous reagent layer is a porous matrix comprising a binder and a particulate solid and (b) that the registration layer is a porous matrix comprising a binder and a particulate solid.

3.3. As regards feature (a), Example 5 of D1 discloses an element having such a reagent layer (cellulose acetate binder plus titanium dioxide particles). This element however does not have the spreading layer 8 disclosed in Figure 3. Nor is there in the Board's view any statement in D1 which would indicate that the reagent layer in Figure 3 could be a porous matrix comprising a binder and a particulate solid so that there is no implicit disclosure of such an arrangement. Feature (a) is therefore correctly located in the characterising portion of Claim 1. The question arises, therefore, whether it is obvious for the average skilled person to form the Figure 3 element with such a reagent layer.

3.4. In the said Example 5, the role of the titanium dioxide particles is not indicated. However, in column 20, lines 64 to 68, one reads that titanium dioxide particles may be a component of a radiation blocking layer because of their pigmentary properties. The element of Example 5 does not have a radiation blocking layer, and the average skilled person could infer that the role of the titanium dioxide particles was to inhibit passage of the detecting radiation (see column 20, lines 53 to 56). Further column 21, lines 12 to 16, again with reference to radiation blocking layers, states that blushed polymers layers can also incorporate a reflective inorganic pigment to enhance reflectivity and/or spreading. In the case where only the latter property is of interest, the skilled person will recognise that particulate material other than pigment particles may be employed. The general teaching to be derived is that the presence of particulate material increases the permeability of the layer containing it, whether it be to the analyte to be tested, or the detectable species released from the reagent layer. For the average skilled person it is therefore obvious to form the reagent layer disclosed in Figure 3 as a layer containing a binder and particulate material, thereby improving its permeability to the analyte and also, if the particulate material is a pigment, inhibiting the passage of the detecting radiation. Feature (a) accordingly does not contribute to the inventivity of the subject-matter of Claim 1.

3.5. D1 does not disclose an element in which the registration layer is a porous matrix comprising a binder and a particulate solid as required by feature (b). Nevertheless, when one looks at what D1 says about the registration layer, the following emerges. In general the layers of the element, therefore also the registration layer, are permeable to the liquid under analysis (column 4, lines 63, 64). The registration layer, moreover, receives and is permeable to the diffusible product from the reagent layer (column 5, lines 52 to 55, column 6, lines 23 to 26, column 19, lines 63 to 66 inter alia). These requirements also apply to the radiation blocking layer when present (see for example column 20, lines 53 to 56) and as indicated above, the permeability of the radiation blocking layer may be enhanced by incorporating particulate material in a binder layer.

If the registration layer is insufficiently permeable to the diffusible product from the reagent layer, this will be evidenced by slow response times, which will moreover be apparent in use of the element. For the person of average skill in the art it is obvious that the permeability of the registration layer must be adapted to the molecules it has to receive and transport, and he knows (see paragraph 3.4 above) that in the case of the spreading, reagent and radiation blocking layers, this can be achieved by forming these as a binder layer incorporating particulate material. It is equally obvious that the permeability of the registration layer can be thus enhanced. In this respect, the results of the Appellant's test report submitted during the Opposition proceedings, and demonstrating a faster response, cannot be said to be surprising.

3.6. The subject-matter of Claim 1, according to the Appellant's main request therefore does not involve an inventive step.

4. Auxiliary step

4.1. Claim 1 according to the auxiliary request, differs from that according to the main request in that it identifies specific substances as the particulate material. The choice of particulate material having regard to its intended role is considered to fall within the competence of the average skilled person, so that the subject-matter of this claim also does not involve an inventive step.

5. For completeness, the Board would add that it found D3 to be of little relevance. The registration layer indeed may comprise particulate material, but here the layer is in the form of a three dimensional array of particles adhered together at their points of contact. There is no suggestion of a layer comprising particulate material in a binder. The general teaching that the registration layer should be sufficiently permeable for the intended application is self-evident.