T 0026/98 30-04-2002

Reasons for the Decision

1. The appeal is admissible.

Main request

2.1. Claim 1 according to the main request differs from claim 1 of the patent as maintained by the opposition division in that the conductive filler is specified as being "comprised of carbon".

2.2. As to the materials which can be used as conductive filler, the description as originally filed contains the following statements:

(a) "The conductive filler preferably comprises electrically conductive fibres, such as graphite or carbon fibres" (emphasis added) (page 6, lines 9 to 11);

(b) "The conductive filler forming the conductive network in a polymeric matrix is preferably comprised of carbon or graphite fibres" (emphasis added) (page 8, lines 26 to 28).

2.3. According to the respondent, (b) contains a general reference to carbon as preferred conductive filler and, therefore, supports the above wording of claim 1.

In the opinion of the Board, the statement (b) could also be interpreted as meaning that the filler should be comprised either of carbon fibres or of graphite fibres. However, this interpretation may constitute an unnecessary limitation to the teaching of the contested patent since it is implicit to a skilled person that carbon need not be in the form of fibres to provide a conductive network within the polymer matrix. Thus, on balance, the Board accepts the respondent's interpretation of the original disclosure and considers that claim 1 of the main request is admissible under Article 123(2) EPC.

2.4. Further minor amendments to the dependent claims and to the description are meant to remove inconsistencies with the amended claim 1 and do not give rise to any objection under Article 123(2) EPC.

2.5. As claim 1 of the main request limits the protection conferred by the patent as granted to devices comprising carbon as conductive filler, it is admissible under Article 123(3) EPC.

3. The novelty within the meaning of Article 54 EPC of claim 1 of the patent as granted or of claim 1 of the patent as maintained by the opposition division has not been disputed by the appellant. Thus, novelty is not at issue in the present case.

4.1. Both the appellant and the respondent agree that D2, which shows an electrically powered iontophoretic delivery device comprising all the features recited in the preamble of claim 1 of the contested patent, represents the closest prior art.

D2 deals, inter alia, with the problem of reducing the formation of undesirable hydronium ions at the electrode and the contamination of the drug reservoir due to the oxidation of the electrode metal. This problem is solved by selecting an electrode comprising an electrochemically active (or sacrificial) component which, when oxidised or reduced during operation of the device, produces a species which immediately reacts with ions present in the electrode or available to the electrode in order to form an insoluble salt or neutral chemical compound. In particular, the iontophoretic device according to D2 (cf. the Figure) comprises a gel or a gel matrix 18 containing the ionic drug species which is to be transdermally introduced across the skin barrier. An electrode comprising a plate 23 in contact with an optional screen 22 is located inside the drug reservoir 18.

According to a first example, the anode made of silver is oxidised and reacts with the chloride ions present in the drug. Insoluble silver chloride is formed near the surface of the silver anode while the drug cations migrate from the reservoir into the body with greater efficiency.

According to a second example, the sacrificial electrode is a cathode of electrochemically active material such as chloridized silver. In operation, the AgCl on the surface of a silver cathode is decomposed into silver metal and chloride anions which are free to migrate, along with any anionic drug, into the patient's body. A sacrificial cathode of this generic type generally comprises a metallic salt in contact with a metal cathode.

4.2. In summary, D2 teaches:

- to locate the electrode inside the drug reservoir, whereby the drug reservoir comprises a gel or a gel matrix;

- to select a suitable sacrificial electrode/drug reservoir system in order to remove unwanted (charged) species from the system and to avoid or reduce the production of H+ and thus minimise pH variation and O2 production.

4.3. As pointed out by the respondent and not contested by the appellant, the electrode used in the device according to D2 has essentially the following drawbacks:

- the tab or plate (23) of the electrode lacks the flexibility required in an iontophoretic device,

- the use of solid silver plates and/or screens is expensive considering that only the exterior surface of the silver is available for redox;

- if the electrode is used as an anode, a layer of silver halide which reduces the electrical efficiency of the iontophoresis device will build up on the metal surface;

- in case of the cathode, a higher electrical resistance is present at the outset because the surface is made of a silver halide; furthermore, the working life of the device is limited by the relatively thin layer of silver halide that can be deposited on the metal surface of the cathode;

- metal tabs, plates or screens can delaminate from the gel matrix of the drug reservoir.

4.4. The contested patent solves the above problems essentially by providing an electrode as specified in the characterising part of claim 1, i.e. an electrode which is formed by a polymer matrix containing:

- the chemical species adapted to undergo oxidation or reduction in the form of a particulate material in the amount of about 5 to 40 % vol and

- 5 to 40 % vol of conductive filler comprised of carbon and forming the conductive network through the matrix.

5.1. The appellant's arguments against the inventive step of the subject matter of claim 1 is essentially based on the assumption that the skilled person starting from document D2 and wishing to improve the electrodes shown in this document would arrive at the following conclusions in the light of cited prior art:

(a) it is advantageous to replace an active metal electrode located in the gel matrix which constitutes the drug reservoir with the same active material dispersed in particular form in a polymer matrix;

(b) the electrical efficiency of the system could be improved by using a conductive filler, such as carbon, dispersed within the matrix.

According to the appellant, (a) would be suggested by document D1 together with D8 and D10, whereas (b) would reflect the teaching of D3, D4, D5 and D7.

5.2. According to the respondent, documents D3, D4, D5, D7 and D8 referred to by the appellant should not be considered as relevant prior art in the present case because they are concerned with electrochemical generators, and the person skilled in the art of iontophoresis cannot be expected to be familiar with documents published in such a specialised electrochemical field.

6.1. Hence, a question to be considered in the present appeal relates to the appropriate definition of the skilled person.

6.2. According to T 32/81 (OJ EPO 1982, 225), if the problem prompts the person skilled in the art to seek its solution in another technical field, the specialist in that field is the person qualified to solve the problem. The assessment of whether the solution involves an inventive step must therefore be based on that specialist's knowledge and ability.

Decisions T 176/84 (OJ EPO 1986, 50) and T 195/84 (OJ EPO 1986, 121) addressed the problem of the relevant technical field, i.e. the question of the extent to which neighbouring areas beyond the specific field of the application might be taken into consideration when assessing inventive step. According to T 176/84, a skilled person would, as well as considering the state of the art in the specific technical field of the application, look for suggestions in neighbouring fields or in a broader general technical field if the same or similar problems arose and if he could be expected to be aware of such general fields. Furthermore, it is pointed out in T 195/84 that a non-specific (general) field dealing with the solution of any general technical problem which the application solved in its specific field should be added to the state of the art. Such solutions of general technical problems in non-specific (general) fields had to be viewed as forming part of the general technical knowledge which was to be attributed to those skilled persons versed in any specific technical field.

Sometimes, in particular when advanced technical fields are involved, the "skilled person" may be a group of people having different areas of expertise (cf. T 99/89 and T 222/86, supra).

6.3. Hence, as far as the definition of the skilled person is concerned, the following principles are generally applied by the boards of appeal:

- if the problem prompts the person skilled in the art to seek its solution in another technical field, then the specialist in that field is the person qualified to solve the problem;

- the person skilled in the art can be expected to look for suggestions in neighbouring fields if the same or similar problems arise in such fields;

- the skilled person may be expected to look for suggestions in a general technical field if he or she is aware of such fields;

- in advanced technical fields the competent "skilled person" could be taken to mean a team of experts from the relevant technical branches;

- solutions of general technical problems in non-specific (general) fields are considered to be part of the general technical knowledge.

6.4. In the present case, the field of electrochemical generators cannot be considered as a neighbouring field of iontophoresis. Though both fields rely on electrochemical processes, such processes have substantially different purposes and applications and, consequently, have to satisfy different requirements. For instance, as pointed out by the respondent, the electrode materials shown in D3, D4,D5, D7 or D8 are designed for use in a dry environment which is very different from the wet environment next to a patient's skin or membrane.

Furthermore, the field of electrochemical generators is a highly specialised field and cannot be considered more general then the field of iontophoresis.

6.5. Although some of the problems identified in the device according to D2 appear to be common to the field of electrochemical cells, i.e. the cost of the metal electrode, the buildup of resistance when the active electrode is sacrificed and the lack of flexibility which may be critical in some cases (see e.g. D7, column 4, lines 50 to 62), there is no reason to believe that the person skilled in the art would look for a solution to such problems in D3, D4, D5, D7 or D8 which are essentially documents relating to the generation of electricity by electrochemical means, or that such person, confronted with the problem of improving the electrode configuration of a known iontophoretic device, would seek the advice of an expert in the art of electrochemical generators when documents in the field of iontophoresis already offer some viable solution (cf. D1 and D10).

6.6. Hence, the Board considers that of all the documents referred to by the appellant only D1, D2 and D10 constitute prior art relevant to the present case.

7.1. It is known from D1 (page 16, lines 24 to 26) to use in an iontophoretic delivery device electrodes comprising "a polymeric matrix loaded with metal powder, powdered graphite or carbon fibres, or any other electrically conductive material". This teaching is confirmed by D10 which shows an iontophoretic device having electrodes made of a rubber film comprising carbon (see "EXAMPLE 2").

7.2. The application of the teaching of D1 to the iontophoresis device known from D2 would prompt the skilled person to replace the anode electrode embedded in the gel matrix with a polymer matrix loaded with an appropriate amount of silver particles. On the other hand, if applied to the cathode electrode, the teaching of D1 would result in a polymer matrix loaded with particles of silver and silver chloride. In both cases, the straightforward combination of D1 and D2 would result in a device retaining the full functionality of the device of D2 with the added advantages of a polymer electrode which could be laminated on to the drug reservoir, accounted for improved wearability on the part of the user, due to its flexibility, and allowed better utilisation of the redox material because of the more favourable surface-area-to-volume ratio of the latter.

7.3. Thus, the Board agrees with the appellant that it would be obvious to a person skilled in the art to arrive at an iontophoretic device based on the combination of D2 and D1 (cf. item 5.1 of this decision).

7.4. Moreover, it may be argued that the person skilled in the art, having applied the teaching of D1 to D2, would easily realise that a further improvement could be achieved by replacing some of the silver particles with carbon in order to decrease the cost of the electrode and/or to increase its conductivity (cf. item, 5.1 of this decision).

However, in the opinion of the Board, it would not be fair, for the purpose of assessing the inventive step, to break down an invention into two or more successive improvements of the closest prior art and to examine whether each improvement fulfils per se the requirement of Article 56 EPC. This is particularly so when, as in the present case, there is no suggestion in the closest prior art document, or in the teaching of the other relevant prior art, that a second improvement might be required or would be a necessary consequence of the first one. In fact, as pointed out above, replacing the silver electrode shown in D2 with a polymer loaded with silver particles results a priori in a viable iontophoretic device, the silver particles acting as the active chemical species and at the same time providing the electrically conductive network, and there is no reason to believe that the skilled person, starting from D2 and not from a device based on the combination of D2 and D1, would consider the addition of carbon as a conductive filler a further necessary (and obvious) measure to be taken as a consequence of the application of the teaching of D1.

8. For these reasons, the Board finds that, in the light of the known prior art, it was not obvious to a skilled person starting from D2 to arrive at an iontophoresis device falling within the terms of claim 1. Hence, the subject-matter of this claim involves an inventive step within the meaning of Article 56 EPC.

Claims 2 to 19 are directly or indirectly dependent on claim 1 and, thus, their subject-matters also involve an inventive step.

9. In summary, the Board finds that the respondent's main request is allowable and that a patent can be maintained on the basis thereof. Consequently, there is no need to consider the respondent's auxiliary request.