T 2472/22 (Electrode Base Material/TORAY) 08-11-2024

1. Admission/consideration of document E30

1.1 The respondent requests that experimental evidence E30, which aims at reproducing Example 3 of E1, not be admitted since it should already have been filed before the opposition division (Article 12(6) RPBA).

This was even more the case since Example 3 of E1 had not even been mentioned in the notice of opposition.

1.2 However, for the reasons set out below E30 is considered.

In response to the opposition division's preliminary opinion, which acknowledged that E1 discloses Feature 4 and Feature 4.1, the now respondent, two months before the oral proceedings, submitted new, different feature mapping, according to which the left side of the left peak and the right side of the right peak of Figure 2c of E1 could not be construed as parts of the "carbon sheet" of claim 1.

Compared with the preliminary opinion, the opposition division changed its view in the decision under appeal and accepted the new feature mapping (see item II.6.4).

In contrast to the qualitative Figure 2c of E1, the reproduction of Example 3 of E1 in E30 allows a quantitative assessment of the fluorine intensity profile through the carbon sheet.

Under these circumstances, E30 merely further develops the novelty objection against the subject-matter of claim 1 over E1 and is a fair reaction to the feature mapping used in the impugned decision.

In this specific context, it is of no relevance that Example 3 of E1 had not been mentioned in the notice of opposition.

As E30 was moreover submitted at the beginning of the appeal proceedings it is admitted (Article 12(4) RPBA).

2. Main request: novelty over E1

For the reasons set out below, neither Example 3 of E1 nor its general disclosure anticipates the subject-matter of claim 1 (Article 54 EPC).

2.1 Example 3 of E1 with due consideration of E30

2.1.1 E1 discloses in Figures 2a to 2c a gas diffusion electrode substrate comprising a porous carbon sheet, which comprises a carbon fibre and a binding material (see for example paragraphs [0001], [0006], [0015] and [0020]). The binding material includes a fluorine-based polymer (paragraph [0015] "erstes Fluor kohlen wasserstoff polymer").

Contrary to the respondent's view, the "carbon sheet" of claim 1 not only extends between reference numerals "10" and "11" of Figures 2a to 2c of E1 but also encompasses the hatched regions above and below in Figure 2b.

Because of the presence of protruding carbon fibres, the surface of the carbon sheet of E1 is not as even as shown in schematic Figures 2a to 2c, but has a certain roughness. Consequently, the carbon sheet does not end precisely at 10 and 11 but extends into the regions left of "10" and right of "11" in Figure 2c.

This is in line with the decreasing fluorine intensities in these regions. Because of the protruding fibres, the density of fibres in these outer regions is lower than in the centre of the carbon sheet and decreases towards the outside. As explained in paragraph [0040] of E1, polymer and solvent initially contained in the centre of the carbon sheet move towards the outer surfaces upon heating. The solvent evaporates and the fluorine-comprising polymer remains attached to the carbon fibres in the outer regions. As the appellant submitted during the oral proceedings, this was shown in Figure 1 of E10. As there are fewer fibres to which fluorine can attach in the outer regions of the carbon sheet, fluorine intensity progressively decreases towards the outside, to the left to "10" and to the right to "11", in Figure 2c of E1.

In this regard it is noted that a fluorine intensity distribution measured in an uncompressed, fibrous carbon sheet cannot be plotted directly (i.e. without conversion of the scale) as a function of the measured thickness because thickness is measured while the carbon sheet is being compressed (as explained in paragraph [0027] of the patent in suit, for example).

If, by contrast, a portion of the fluorine polymer really left the carbon sheet of E1 upon heating and was deposited on the outer surface of the carbon sheet (as argued by the respondent and as apparently suggested by Figures 2a and 2b of E1), fluorine intensity in these polymer bulks in the outer regions in Figure 2c would be higher than in the central portion, not lower. Moreover, in view of the low polymer concentration in the solution in Example 3, i.e. 3% PTFE, deposition outside on the surface of the carbon sheet is not credible, and the respondent has failed to provide experimental evidence for such manifestly impossible behaviour.

The fact that the peak at "10" in Figure 2c is higher than that at "11" is a consequence of the asymmetric process of E1, with heating only being provided from above (Figure 2a). This results in increased evaporation on the upper side of the carbon sheet (i.e. on the left side in Figure 2c) (see also E1: paragraph [0040], lines 14 to 21).

While the fluorine intensity profile of Figure 2c of E1 does not allow a quantitative evaluation (just like Figure 2 of the patent in suit), it allows the conclusion:

- that there has to be a surface having a 50% average fluorine intensity in the region left of "10"

- that there has to be a surface having a 50% average fluorine intensity in the region right of "11"

- that it is possible to define, from the left to the right in Figure 2c, a section with layers X, Z and Y having a decreasing average fluorine intensity in the order X > Y > Z.

Thus a layer X containing the peak at "10", a layer Y containing the peak at "11" and a layer Z in-between can be defined.

2.1.2 These findings are confirmed by E30, in which Example 3 of E1 is reproduced and in which a fluorine intensity profile resembling that of Figure 2c of E1 is obtained (see Figure 2 of E30).

The respondent argued that E30 was not a reliable reproduction of Example 3 of E1. According to expert declaration E32, infrared heating used in Example 3 of E1 and convection heating used in E30 were not comparable. The influence of the heating was confirmed by paragraph [0046] of E1. Moreover, in E30 only one sample was used, i.e. sample 9 ("Probe 9: LV22/11-7"), while paragraph [0109] of the patent in suit (and hence claim 1) required 50 samples.

However, these assertions are not convincing. Paragraph [0046] of E1 indicates that it is the heating rate (and thus the energy input) which is important, not the type of heating. Paragraph [0032] of E1 even mentions convection and infrared heating as alternatives.

With regard to the number of samples, the use of a single sample in E30 is perhaps not as reliable as the use of 50 samples. However, the respondent has provided no quantifiable distribution of the fluorine intensity to counter these findings.

2.1.3 On the other hand, the microporous layer of Example 3 of E1 is applied to the surface Y side of the carbon sheet, not to its surface X side as required by Feature 5 of claim 1.

In Example 3 of E1, while infrared heating is applied from above, a paste comprising a PTFE dispersion is applied to the bottom side. According to paragraph [0058]

- the paper is placed onto a scaffold ("Das Papier wird aus der L sung entnommen und auf ein Gestell aus rostfreiem Stahl gelegt"),

- infrared heating is applied from above ("Eine Infrarotw rme wird ber dem eingeweichten Kohlefaserpapier von einer Infrarot fl chen heizeinrichtung [...] aufgebracht" [...]), and

- a paste comprising a PTFE dispersion is applied to the opposite side, i.e. the bottom side towards the scaffold ("[...] wird eine Paste, die [...] PTFE-Dispersion [...] enth lt, auf die R ckseite (d.h. die w hrend des Trocknens gegen das Gestell gehaltene Seite) des Kohlefaserpapiers [...] stangen beschichtet)".

The appellant did not contest this, but argued that an integral layer of the carbon sheet of Example 3 of E1 could be construed as the microporous layer of Feature 5. The pores of carbon fibre Toray TGP-H060 were in the micrometre range (see scales in the figures on page 1 of E24 and at the top of Figure 1 of E30).

This is not convincing. E8, which illustrates the common general knowledge of the skilled person in the field of diffusion media, confirms that such a microporous layer has much smaller pores, i.e. pores having diameters between 100 nm and 500 nm (page 9, right-hand column, first paragraph).

Consequently, a layer of the carbon sheet of E1 closest to layer X cannot be construed as the microporous layer of Feature 5 of claim 1 of the patent in suit.

Consequently, Feature 5 is a distinguishing feature over Example 3 of E1.

2.2 General disclosure of E1

The appellant also argued that the general disclosure of E1 anticipated the subject-matter of claim 1.

This is not convincing either. Paragraph [0006] of E1 discloses a microporous layer on a desired side of the carbon sheet ("eine gew nschte Seite"). Although there are only two possible sides of the carbon sheet, this does not necessarily anticipate Feature 5 of claim 1 (see T 651/91, catchword). In addition, an example constitutes a specific embodiment that cannot be combined with other information of the description (T 210/05, Reasons 2.3).

Moreover, the general part of E1 does not disclose in a direct and unambiguous manner the claimed order of fluorine intensities in layers X, Y and Z (Feature 4.1). A merely probable disclosure, e.g. due to heating from only one side, is not sufficient. An explicit disclosure of the combination of features as claimed is not present in the general part of E1.

3. Main request: inventive step over E1

For the reasons set out below, Example 3 of E1 in combination with E2/E2a renders the subject-matter of claim 1 obvious (Article 56 EPC).

3.1 The invention relates to a gas diffusion electrode substrate.

3.2 E1 also deals with a gas diffusion electrode substrate and also aims at improving the water management (paragraphs [0001] and [0006]).

Since E1 relates to the same technical field as the invention and since in particular Example 3 has numerous features in common with the subject-matter of claim 1, as set out above, this example is a suitable starting point for assessing inventive step.

3.3 According to the patent in suit, the problem to be solved is to provide a gas diffusion electrode substrate having high electrical conductivity for extracting generated electric current in addition to excellent gas diffusivity and water removal performance (paragraph [0022]).

3.4 It is proposed that this problem be solved by the gas diffusion electrode substrate of claim 1 being characterised by a microporous layer on the surface X side of the carbon sheet.

3.5 The respondent submitted comparative data E17 to prove the benefits of the invention.

In contrast to inventive Example 2 of the patent in suit, comparative example 3 of E17 has the microporous layer on the surface Y side of the carbon sheet. This results in an undesirable decrease in output voltage from 0.43 V (last line of Table 1 of the patent) to 0.29 V (last line of Table 3 of E17). Consequently, a microporous layer on the surface X side would result in improved output voltage and thus in improved anti-flooding characteristics.

3.6 However, even if it were accepted that the problem posed has been successfully solved, inventive step cannot be acknowledged.

E2/E2a also relates to a gas diffusion electrode substrate (paragraph [0001]). Paragraph [0080] teaches that by arranging the microporous layer on the surface X side, i.e. the side having a higher fluorine intensity, the "cell performance of a fuel cell is more improved" and "drying of the electrolyte membrane is more inhibited by the back-diffusion of generated water".

In view of this incentive, the proposed solution is clearly taught in E2/E2a and the subject-matter of claim 1 does not involve an inventive step (Article 56 EPC).

The respondent argued that the arrangement of the microporous layer on the surface Y side in Example 3 of E1 was "teaching away".

This is not persuasive. Since paragraph [0006] of E1 indicates that the microporous layer is applied to a desired side ("auf eine gew nschte Seite") and as E1 discloses no reason why the microporous layer should not be applied to the surface X side of the carbon sheet, there is no "teaching away".

3.7 Therefore the requirements of Article 56 EPC are not met and the main request is not allowable.

4. Remittal to the opposition division

The appellant requested that the case not be remitted.

In accordance with Article 11 RPBA, a case shall not be remitted to the department of first instance unless there are special reasons.

In the case at hand, document E30, in which Example 3 of E1 was reproduced, was filed only during appeal proceedings and is admitted (see point 1. above). As explained in points 2.1 and 3., consideration of E30 is decisive for the negative assessment of inventive step, thereby leading to a change in the case compared with the impugned decision.

In addition, the auxiliary requests are not dealt with in the decision under appeal.

These are special reasons within the meaning of Article 11 RPBA, and in this context it is appropriate to remit the case to the opposition division.