T 0254/86 (Yellow dyes) 05-11-1987

Reasons for the Decision

1. The appeal complies with Articles 106 to 108 and Rule 64 EPC and is, therefore, admissible.

2.No formal objection can be raised against the further amendments of the claims. In effect, the main claim is now restricted to preferred compounds (1) to (4) which were originally numbered (13), (18), (19) and (23), all specifically disclosed in the patent. The other claims have also been appropriately restricted in a manner which is supported by the original disclosure and both the claims and the amended text therefore comply with Article 123(2) and (3) EPC.

3.The subject-matter of the patent relates to four compounds which represent yellow dyes. Compounds of similar structure and colour were also disclosed in the closest state of the art which is document (10). In the view of the Board, the technical problem in respect of this disclosure was how to achieve a substantial improvement of colour value whilst maintaining the fastness properties generally substantially at the same level or in certain instances at least at an acceptable level. The solution of this problem comprises the four claimed dyes showing some modifications on the chromophoric part. In particular, the substituents in the closest compound "C" were supplemented with a further sulpho-group on the naphthalene radical whilst one of the original sulpho-groups was shifted to an adjacent position. In addition, the methyl substituent on the phenyl group was either replaced by an acylamino or an ureido group, or supplemented with a methoxy group in the opposition position on the ring.

4.The disclosure in the specification suggests that the compounds in the case have about the same colour fastness (i.e. 3-4) in the presence of hypochloride as compound "C" of the prior art (cf. also original Example 1 disclosing the same compound "C" with test results) and somewhat marginally improved fastness in respect of perspiration and sunlight, particularly at the higher concentration level (3%). This was apparent from the data in the specification and from the evidence presented on behalf of the patentee (31.1.86). It was also suggested there that the colour values, i.e. tinctorial value, for the compounds of the invention were about doubled when compared to compound "C".

5.The Respondent challenged these results by submitting evidence suggesting that the reduction of fastness to hypochlorite was significant, in particular under the more stringent conditions of prolonged treatment. The same would apply to light sensitivity (Table II received on 12.5.87). Even if the tests and inferences from the Respondent were conclusive beyond any doubt or uncertainty, the outcome could not be interpreted as a failure on the part of the patentee to solve the stated technical problem. Any losses in fastness properties are small and are particularly insignificant when it comes to fastness in relation to perspiration and sunlight. Such consequences cannot render the substantial improvement in colour value irrelevant or insignificant. The combination of all these properties must be taken into consideration when assessing the overall value of the improvement. In addition, some of the aspects may become more or less relevant depending on the circumstances of use.

6.It is, therefore, the view of the Board that an invention which relies on a surprising substantial improvement of a particular property need not also show advantages with regard to other properties relevant to its use provided the latter are maintained at a reasonable level so that the improvement is not completely offset by disadvantages in other respects to an unacceptable degree or in a manner which contradicts the disclosure of the invention fundamentally (following T 57/84, "Tolylfluanid", 12.8.86, to be reported and T 155/85, "Passivation of Catalyst", 28.7.87, to be reported).

7. In the present situation the prolonged exposure to light or more severe conditions of hypochlorite bleaching could well be included in test systems, which are designed to evaluate and compare the properties of material under standardised conditions if the need arises. This should not mean, however, that certain results or the best results are obligatory, or are economically optimal, in respect of certain dyed materials. The overall result could still be very advantageous in some special situations, where repeated exposure to hypochlorite laundering was unlikely, e.g. in the case of fine curtain materials or neckties. In other words, some properties, other than the advantageous colour value, may become irrelevant to certain types of merchandise which are only used in particular circumstances. The invention need not, therefore, possess all the desired properties in all circumstances for any kind of user, in comparison with the closest state of the art. In view of the fact that the dyes claimed in the patent-in- suit demonstrate a very reasonable maintenance of fastness properties especially under less stringent conditions, whilst showing a substantial improvement of the colour value, the solution of the stated problem appears to have been achieved by making the claimed compounds available. Since none of the documents cited in these proceedings disclose these compounds, they are also novel. This is not contested by the Respondent.

8. As to the question of the inventive step, it is apparent that the structural differences between the claimed compounds and the closest state of the art, i.e. compounds "C" and "D" of (10) are minor. Thus, it would have been reasonable to expect that any such modification should, at the best, maintain the level already achieved in (10) unless there was a good reason to the contrary. The comparative success of the doubly reactive variants described in the same document (10) through the introduction of the second reactive group (vinyl-sulphonyl) was, nevertheless, confined to "the degree of fixation" in the cited art (page 584). There was no such improvement in light fastness (pages 584 and 586, Table 2). The fixation already reached 90% which is difficult to surpass and it was not envisaged that circumstances other than reactivity, which also influence the colour value, i.e. affinity, diffusion speed etc., could or would make a striking difference in the fixation rate. Increased solubility through the additional sulpho-group could have been expected to reduce the reactive affinity of the dye to the material, and improved substantivity might well reduce the diffusion power (14).

9. Notwithstanding the complex character of the various mechanisms contributing to the increased colour value, it is most relevant that this is achieved in proportion with the concentration of the bath. This is not only apparent from the evidence from the patentee but also from the submissions of the Respondent who uses lower, occasionally much lower, concentration of the dye in the solution to achieve the same colour strength as that employed for the compound from the state of the art (cf. submissions on 7.5.87). Inevitably, much less material of the invention was exposed to extreme conditions as in the case in comparison but specific fastness was then better than what could be expected in such circumstances.

10. The modification of the substitution was not in itself implying an expectation of an improvement in colour value. Although carboxamide groups were associated with an increase of substantivity according to (14), i.e. affinity to fibres, this appears to have been rather linked with the problem of colour and shift of wavelength to longer wavelengths (cf. page 343). In any case, the reference relied on carboxamide of J-acids which are not relevant to the present case where the same substituent is only linked to a nitrogen atom and not to a carbon atom, if at all.

11. The reliance on document (15), in order to predict the properties of the compounds at hand, is also unconvincing. This reference mentions the chromophoric groups of both (10) and the present patent side by side including acetylamino and ureido substituents but without any reactive groups. It is remarked that the "main considerations are colour strength and certain fastness properties". There is no information as to the relative level of these properties or that one should expect improvements one way or another when switching from one of the two kinds of chromophores to the other.

12. If the skilled person would have considered this presentation of alternative chromophores to modify the closest state of the art (10), he would have also been aware that on his way towards the compounds of the invention he should have passed through the compound described in Japanese patent publication No. 2634/1964 presented in the present specification (page 4, lines 45- 50), which represents the same chromophore carrying the ureido substitution, and also the first reactive group and the whole anilino group suitable for carrying the second reactive group in (10). The numerous disappointing properties of this "nearly there" intermediary structure are listed in the present patent (page 5, lines 18-21), and were never challenged in opposition. The suggested disadvantages include high temperature dying, lack of exhaustion dying ability, inability to produce the desired colour density and poor stability. The skilled person would have been discouraged from embarking on the route from (15) to modify (10) in view of such warnings very close to the desired goal.

13. The further argument on the basis of (13) about expectations for increased fixing rate on the basis of mesomerism mentioned in document (13) cannot be accepted either. Any equilibrium between alternative structures might deepen the colour according to the citation. There was not even a suggestion here that this might be correlated with substantivity, as it was mentioned in respect of carboxamides in (14). In addition, the colour deepening effect was demonstrated with different chromophores, not azo-dyes, carrying different substituents. In any case, no real improvement of the colour value through the fixing rate could be reasonably expected since this was already at a 90% level in document (10). There was no hint in any document that other characteristics which influence the colour value would be beneficially affected by the modifications with substituents which the claimed compounds display.

14. In summary, it can be stated that the combination of the problem solving effects could not be envisaged on the basis of the state of the art. The structural elements now responsible for achieving this were also associated with unimpressive properties pointing away from their use. There was no one-way-street situation for the skilled person in the direction of the invention on any grounds, which must therefore be recognised as representing an unexpected problem solving effect, and as such inventive.

15. The alternative submission of the Appellant that the closest, and therefore most relevant prior art to assess the inventive step, is a kind of dye which is commercially successful with only one reactive group, must be rejected. The fact that the cited closest state of the art is not commercially exploited could be due to various unknown and irrelevant circumstances, and cannot therefore cast shadow on its information content as a disclosure available to the skilled person, let alone lead to the exclusion of the same from consideration. On the contrary, any non-obviousness vis-à-vis such art, if not closest to the invention, would be irrelevant and inconclusive to validity without the assessment of the inventive step in respect of the objectively closest state, i.e. the most promising springboard towards the invention which was, available to the skilled person (cf. T 164/83, "Antihistamines" OJ EPO 1987, 149).