T 0428/15 30-05-2018

Reasons for the Decision

Novelty over D3

1. The finding by the opposition division that the patent as granted does not enjoy the priority dates of applications D1 and D2 with the consequence that document D3 is a prior art document pursuant to Article 54(2) EPC was not disputed by the parties. The Board has no reason to take a different view.

2. The objection of lack of novelty over D3 is only based on the specific embodiment described with Example 6 of that document which is in Japanese language. The submissions of the parties were made by reference to a computer generated English translation thereof. In the following, any indication to passages of D3 refers therefore to the computer generated translation of this document. It is undisputed that Example 6 of D3 does not explicitly disclose a composition comprising a compound having three of more mercapto groups in one molecule. It is, however, the position of the appellant that such a compound having three of more mercapto groups in one molecule is inherently formed during the preparation of component A1 used for the preparation of the composition of Example 6 of D3. It is undisputed in view of paragraph [0049] that A1 is prepared by reacting bis-(beta-epithiopropyl)sulfide and 2-amino-benzenethiol leading to the formation of 1,9-bis-(2-aminophenyl)-3,7-dimercapto 1,5,9-trithianonane according to:

FORMULA/TABLE/GRAPHIC

The appellant supports the view that at least one epithio ring of a bis-(beta-epithiopropyl)sulfide would further react with an amino group of the 1,9-bis-(2-aminophenyl)-3,7-dimercapto 1,5,9-trithianonane leading to a compound having three or more mercapto groups in the molecule. This argumentation is based on E1, i.e. the experimental results reported by the respondent in section 3.1.1 of its letter of 11 July 2013, according to which the product of the reaction also contains 2.3 wt% of an oligomer derived from bis-(beta epithiopropyl)sulfide and 1.0 wt% of bis-(beta epithiopropyl)sulfide.

2.1 The footnote of Table 1 in paragraph [0057] of the translation of D3 defines A1 to be "The preliminary reaction thing of bis-(beta-epithiopropyl)surfide and 2-MINOBENZENthiol (sic)". According to paragraph [0049] after addition, mixing and reaction of the reactants "The reaction mixture was dissolved in chloroform, the after-rinsing chloroform layer was dried, the solvent was removed and 101.81 g of 1,9-bis(2-aminophenyl)-3,7-dimercapto 1,5,9-trithianonane which is an object was obtained (95% of yield)." It is not clear from that passage whether the expression "The preliminary reaction thing" used in the translation should be understood to refer to the reaction mixture as obtained during the preliminary reaction step described in paragraph [0049] before apparently the mixture is dissolved in chloroform or to the product obtained after all theses additional steps, which also would constitute a reaction product which needs to be first prepared for the formulation described in Table 1 and accordingly could be understood to be the "preliminary reaction thing". The latter would appear to be more likely in view of paragraph [0029] which appears to define various steps to be used after synthesis of the diamine prepared by the reaction of an episulfide compound with an aromatic thiol such as "acid cleaning, base washing and rinsing". Obviously, such a rinsing step, whether or not it was preceded by other cleaning or washing steps took place in the preliminary reaction described in paragraph [0049]. Moreover the indication that 1,9-bis(2-aminophenyl)-3,7-dimercapto 1,5,9-trithianonane was characterised by 1H-NMR and obtained with a yield of 95% does not allow to conclude whether the yield is determined on the basis of the NMR spectra or on the basis of the amount of product obtained after the solvent was removed. It is also not clear whether an additional solvent was used or only chloroform, in which case removal of the solvent meant only removal of the chloroform. It is in this context referred to paragraph [0026] mentioning the use of solvents, including chloroform. Consequently, the objection that D3 anticipates the subject-matter of claim 1 is based on passages of a computer-generated translation whose quality does not allow the Board to understand with a sufficient degree of certainty what is in fact described in D3. Furthermore, the appellant did not submit a man-made translation of the relevant passages which would have clarified the issue, or provide technical explanations which would render credible that the true meaning of the vague passages concerning the use of chloroform and the apparently described rinsing step would be immaterial to the conclusion to be drawn in respect of the nature of product A1 obtained.

2.2 Furthermore, the experimental data concerning Example 6 of D3 which are referred to by the appellant are to be found in section 3.1.1. on page 4, last paragraph of the respondent's letter of 11 July 2013. This paragraph reads: "Moreover, the proprietor carried out the synthesis example 1 for the production of 1,9-bis(2-aminophenyl)-3,7-dimercapto-l,5,9-trithianonane (cf. paragraph [0049] of D3). The analysis of the reaction product revealed that the reaction product contained 96.7 wt% of 1,9-bis(2-aminophenyl)-3,7-dimercapto- 1,5,9-trithianonane, 2.3 wt% of an oligomer derived from bis-(beta-epithiopropyl)sulfide and 1.0 wt% of bis-(beta epithiopropyl)sulfide. The oligomer derived from bis-(beta epithiopropyl)sulfide was further analyzed by using a GPC-IR method to examine whether the oligomer contains any mercapto group. The GPC-IR method means that firstly the oligomer was separated by GPC (Gel Permeation Spectrography) and that secondly the separated oligomer was analyszed (sic) using IR (Infrared) Spectroscopy. The resulting IR chart did not show any absorption peak of a mercapto group. Thus, the oligomer does not contain any mercapto group". It is conspicuous that the details of the experiments carried out by the respondent are not provided. It is in particular not indicated at which point and how the amount of the various components indicated were determined, any mention of a step of dissolving the reaction product in chloroform and any possible subsequent step like the one which are apparently meant to be described in paragraph [0049] of the translation being missing. Having also regard to the content of the target product which is of 96.7 wt% in the experiment reported by the respondent, whereas the translation of D3 indicates a yield of 95% for this product, it is furthermore questionable whether the reaction product which was analysed in this experimental report can be considered to represent that described to be obtained in the translation of D3. In view of the above it cannot be ascertained whether the experiment report mentioned by the respondent represents a fair repeat of what appears to be described in paragraph [0049] of the translation of D3 for the preparation of product A1.

2.3 Furthermore, in the absence of a detailed report on the experiment carried out by the respondent, including not only an exact description of the steps employed for the synthesis, but also a description of the analytical methods used and of the data obtained, there is no apparent justification to accept on the one hand the conclusion by the respondent that the reaction product contains an oligomer derived from bis-(beta epithio-propyl)sulfide and some bis-(beta epithiopropyl)-sulfide, but on the other hand to refute that the oligomer obtained would not comprise mercapto group, which is also indicated in the report, but is disputed by the appellant. This would require more information on the experiments carried out, which however is not available. Whereas the Board agrees that the ability of the aromatic bound terminal -NH2 groups and of the mercapto groups of the 1,9-bis(2-aminophenyl)-3,7-dimercapto-1,5,9-trithianonane to react with the intermediate resulting from the opening of an epithio ring of the bis-(beta epithiopropyl)sulfide depends on their relative nucleophilicity and steric hindrance, no evidence has been submitted in support of the allegation, that in the specific situation of Example 6 of D3 these factors would result in the reaction of the aromatic bound terminal -NH2 groups, at least to the extent that compounds having 3 or 4 mercapto groups necessarily result therefrom and can be detected. Having regard to the technical meaning of a claim, the point is not whether such oligomers are theoretically present in an infinitesimal amount, as argued by the appellant, but whether that amount is technically sensible, in the sense that its presence is noticeable using conventional technics in the art. This, however, was not demonstrated by the appellant.

2.4 On that basis, the Board can only come to the conclusion that no case has been made that the subject-matter of granted claim 1 lacks novelty over the disclosure of Example 6 of D3.

Novelty over each of D4 to D6

3. The submissions of the appellant in respect of the objections that the claimed subject-matter lacks novelty over each of D4 to D6 do not go beyond showing that each of the features listed in operative claim 1 is disclosed in any of those documents. However, it is established case law that a claimed subject-matter lacks novelty only if a "clear and unmistakable teaching" of a combination of the claimed features can be found in a prior art disclosure (see Case Law of the Boards of Appeal of the EPO, 8th edition, 2016, I.C.4.2). In the absence of any pointer in those documents to the specific combination of features defined in operative claim 1, and none is apparent, as all those passages appear in separate parts of those documents, the Board has no reason to consider that claim 1 as granted lacks novelty over any of D4 to D6. This was already the position of the opposition division in the decision under appeal which was not refuted by any of the arguments of the appellant.

4. Consequently, novelty of the subject-matter of the granted patent is acknowledged.

Inventive step

Closest state of the art

5. The closest prior art for the purpose of assessing inventive step is that which corresponds to a purpose or effect similar to that of the invention and requiring the minimum of structural and functional modifications (Case Law, supra, I.D.3.1). The appellant argues inventive step of the subject-matter of claim 1 starting from either Example 6 of D3 or Example 11 of E7 as closest prior art.

5.1 The present invention relates to polymerizable compositions for producing optical materials (paragraph [0001]). The patent in suit is in particular concerned with the production of spectacle lenses, required to exhibit colorless transparency, a high refractive index and a high Abbe's number, as well as high mechanical strength (paragraphs [0002] and [0003] of the patent in suit). According to paragraph [0009], an object of the present invention was to provide a polymerizable composition for the production of optical materials which have a refractive index of around 1.60, an Abbe's number of around 40 and a high impact resistance. Both D3 and D7 are considered to represent a realistic starting point for the skilled person concerned with the goal of the present invention as mentioned in paragraph [0009] of the patent in suit, since they disclose compositions having the corresponding properties profile (D3: paragraphs [0013] and [0048] and Table 2; D7: paragraphs [0004], [0131] and [0132] and Table 1 on page 16).

5.2 As regards the structural features, the subject-matter of claim 1 solely differs from the composition disclosed in Example 6 of D3 in that it contains a compound having three or more mercapto groups in one molecule, as follows from the above assessment of novelty over D3.

5.3 Concerning the structural differences between the claimed subject-matter and the composition disclosed in Example 11 of D7, the latter comprises bis-epithiopropyl sulfide (i.e. compound (D) according to the operative claim 1) and a reactive polyisocyanate prepolymer 2 described in Example 2 of that document. It is undisputed that the reactive polyisocyanate prepolymer 2, which is obtained by reaction of a mixture of polyols and diisocyanates using a NCO/OH equivalent ratio of 2.86, comprises a mixture of NCO-terminated polyurethane prepolymer chains, some of which will comprise at least two isocyanate groups and may therefore be qualified as polyisocyanate compounds within the meaning of compound (C) of claim 1. Accordingly the reactive polyisocyanate prepolymer 2 described in Example 2 of D7 may be considered as a mixture of compounds (B) and (C) as defined in operative claim 1. The composition of Example 11 of D7 is also described to comprise DMDS, which undisputedly stands for bis(2-mercaptoethyl) sulfide, designated in paragraph [0064] of that document as 2,2'-thiodiethanethiol, i.e. a compound having two mercapto groups in one molecule. Consequently, the composition according to operative claim 1 also differs from Example 11 of E7 solely in that it contains a compound having three or more mercapto groups in one molecule.

5.4 Accordingly, both Example 6 of D3 and Example 11 of D7 are considered to represent an adequate (and equivalent) starting point for assessing inventive step, from which the claimed compositions differ solely by the presence of a compound having three or more mercapto groups in one molecule.

Problem successfully solved

6. Having regard to the disclosure of the closest prior art, the appellant and the respondent were divided as to which problem could be considered to be successfully solved by the subject-matter of claim 1 of the opposed patent. Relying on the experimental results described in E2, the respondent argued that the technical problem solved by the subject-matter of claim 1 of the main request over the closest prior art was the provision of polymerizable compositions resulting in an improved impact resistance and colorless transparency of the polymerized composition, whereas the appellant submitted that the problem solved by the claimed subject-matter was to provide an alternative to the polymerizable compositions of the prior art based on the comparative tests D12 and the argument that the comparisons offered with E2 lacked pertinence.

Experimental data E2

6.1 Having regard to E2, the respondent referred to a comparison of Comparative Examples (5) and (6) with Examples 1 and 2 (according to the invention), respectively. In addition Example 3 (in accordance with the present invention) was compared with Comparative Example (6). The compounds employed in those comparative tests (i.e. PR1, PR2, HMDI, DMDS, 3TP and 4TP) are the same as those used in the experimental part of the patent in suit, whose meaning is provided on page 13 of the specification. Flat lenses were prepared in accordance with the procedure employed in example 1 of the contested patent.

6.1.1 The three above comparisons submitted by the respondent are made with compositions containing the same proportions of compounds PR1/PR2, HMDI and D1. In addition the proportion of mercapto groups used, i.e. relative to the other compounds (PR1/PR2, HMDI and D1), was retained between the comparative examples and the examples, so that any difference in the properties obtained for the polymerized compositions cannot be attributed to the use of a different amount of mercapto groups. Finally, the compositions compared by the respondent differ only by the use of a mixture of a compound having two mercapto groups (DMDS) and a compound having three or four mercapto groups (3TP or 4TP), instead of only DMDS, the total amount of mercapto groups being the same as indicated above. Accordingly, the appellant's argument which was submitted in writing, but was not pursued during the oral proceedings, according to which there is no example according to the contested patent and a respective comparative example that differ only in the feature distinguishing the claimed composition from the closest prior art, since the comparisons submitted also differ in the relative amounts of the monomers, which does not make it possible to attribute any technical effect to the distinguishing feature, fails to convince.

6.1.2 As to the technical effects addressed in E2, it follows from the comparisons offered by the respondent, that with respect to the compositions of Comparative Examples (5) and (6) a large improvement of the impact resistance (expressed by an average falling ball impact energy value) is observed, as well as an improvement in terms of colorless transparency, which can be attributed to the use of a mixture of a compound having two mercapto groups in one molecule and a compound having three or four mercapto groups in one molecule, the refractive index and the Abbe's number staying substantially constant with values of 1.60 and 40, respectively.

6.2 The appellant also argued that the comparisons provided with E2 concerned composition comprising only one compound having two mercapto groups in one molecule, but not two of those compounds as was the case in Example 6 of D3. Accordingly, that comparison which was not made with the closest prior art would not "fulfill the requirements of the case law of the Boards of Appeal".

6.2.1 The appellant did not indicate "which requirements of the case law of the Boards of appeal" would as a matter of principle not allow the use of a comparison made with a variant of the closest prior art, which possibility has been recognized by the Boards of Appeal as early as T 35/85 (Case Law, supra, I.D.10.9). According to point 4 of the reasons for this decision the applicant or patentee may discharge his onus of proof by voluntarily submitting comparative tests with newly prepared variants of the closest state of the art making identical the features common with the invention in order to have a variant lying closer to the invention so that the advantageous effect attributable to the distinguishing features of the invention is thereby more clearly demonstrated.

6.2.2 What counts is whether the effect demonstrated in the framework of the comparative examples of E2 can be considered to take place also when starting from the composition identified as the closest prior art, namely Example 6 of D3 or Example 11 of D7. It appears credible to the Board that the use of a compound having three or more mercapto groups in one molecule in addition to the use of a compound having two mercapto groups in one molecule will lead to a different polymeric network, resulting in particular in different mechanical properties. The Board therefore considers credible that the measure of adding a compound having three or more mercapto groups in one molecule in order to bring about improved impact resistance in the context of experimental report E2 would also bring about the same effect in the context of Example 11 of D7 or of Example 6 of D3 where use is made of two compounds having two mercapto groups in one molecule. In the absence of further experimental evidence or of a technical explanation as to why colorless transparency of the polymerized composition would also be the result of using a compound having three or more mercapto groups in one molecule in the framework of Example 6 of D3 or Example 11 of D7, the Board has no reason to consider credible that this part of the problem is also effectively solved by the composition of granted claim 1.

6.2.3 Accordingly, the appellant's arguments as to the lack of suitability of E2 to demonstrate the achievement of a technical benefit over the closest prior art as far as an improvement of impact resistance is concerned cannot convince.

6.3 Moreover, the Board does not share the appellant's view that an improvement in terms of impact resistance was not shown over D3, as that document indicated values for the average falling ball impact energy of at least 12 J, whereas the values indicated in Table 2 of the patent in suit were lower. As recognized by the Case Law as early as in T 0181/82 (OJ 1984, 401; see point 4 of the Reasons for the decision), regarding only the preferred compounds from a citation as the necessary comparative composition in a comparative test implies that one concentrates on the technical progress obtained vis-à-vis the known substances considered most effective. Technical progress, however, is not a requirement for a patent under the European Patent Convention. What counts is that an effect demonstrated by means of a suitable comparative test can be regarded as an indication of inventive step. As concluded in above section 6.2.2, the Board considers credible in the light of E2 that the measure of adding a compound having three or more mercapto groups in one molecule would bring about an improved impact resistance, also in the context of Example 6 of D3. The present invention lies in the finding that the impact resistance can be improved by the use of a compound having three or more mercapto groups in one molecule, which is reflected in the wording of claim 1 as granted by the definition that the composition comprises said compound.

6.4 In that respect, the present invention resides in the use of that compound, but not in a particular amount thereof. In other words, the present invention does not reside in the finding that the selection of a particular amount of a compound is linked with an unforeseen advantage which would justify acknowledgement of an inventive step (e.g. if the use of that compound were already known in the art, but the use of a new amount thereof would provide said unforeseen advantage), but rather on the idea that the use of said compound is advantageous, which constitutes the technical contribution to the art which could in principle justify a patent monopoly. Accordingly, the appellant's objection that the problem addressed by the respondent cannot be solved over the whole scope of claim 1 on the basis that it covers infinitesimal amounts of a compound having three or more mercapto groups in one molecule fails to convince.

6.5 Moreover, the appellant's argument that a compound having three or more mercapto groups in one molecule would not lead to the improvement addressed by the respondent over the whole breadth of the claim is not supported by any evidence. In that respect the appellant submitted experimental report D12 with its statement setting out the grounds of appeal. Article 12(4) RPBA requires the Board to take into account everything presented by the parties under Article 12(1) RPBA if and to the extent that it relates to the case under appeal and meets the requirements in Article 12(2) RPBA. D12 provides the impact resistance of a cured material in accordance with claim 1 as granted, which value is compared to the value obtained in Example 11 of D7 in order to show the influence of a compound having four mercapto groups in one molecule on the impact resistance of the cured material. D12 relates therefore to the case under appeal and constitutes a response to one of the essential aspects of the reasons for the contested decision, namely that the problem solved over the closest prior art was the provision of a polymerizable composition allowing the preparation of lenses having improved impact strength. Although the data of D12 could have been submitted in the first instance, there is no indication of a lack of diligence by the patent proprietor, nor does its later filing cause unfairness to the other party. Moreover, the submission before the first instance would not have led to a more efficient processing of the case. Under the present circumstances, the Board sees no reason to make use of its discretionary power under Article 12(4) EPC to hold inadmissible D12. However, D12 does not lead to any conclusion as to the influence of a compound having three or more mercapto groups in one molecule on the impact resistance of the polymerized material, since the impact energy value obtained with the composition according to the claimed invention (prepared and tested in D12) and the impact energy value obtained with the composition of Example 11 of D7 (D7, Table 1, paragraph [0161]) are both indicated to be "> 4.95 J" without indicating any precise value for any of the two and already for this reason cannot be compared. Moreover, it was also acknowledged by the appellant that in the composition meant to represent the composition in accordance with operative claim 1 the combined amount of DMDS and PTMA (indicated to be "pentaerythritol tetrakis-3-mercapto acetate", which obviously is meant to designate pentaerythritol tetrakis-2-mercapto acetate, i.e. a compound having three or more mercapto groups in one molecule) had been slightly reduced, as well as the amount of bis-(beta-epitiopropyl)sulfide. In fact the total amount of mercapto groups in the composition was not retained as was made by the respondent with E2, but in fact is only 77 % of the amount used in Example 11 of E7, whereas the amounts of reactive polyisocyanate prepolymer 2, DETDA and MDA were kept constant and the amount of bis-(beta-epitiopropyl)sulfide was only 93% of the amount used in Example 11 of E7. This also shows that the comparison of the impact energy values provided in D12 and in Example 11 of E7 is not suitable to assess the influence of a compound having three or more mercapto groups in one molecule on the impact resistance of the polymerized material, since the compositions compared differ in more than one feature.

6.6 In view of the above mentioned evidence and arguments submitted by the parties, the Board is therefore satisfied that the technical problem effectively solved by the subject-matter of granted claim 1 over the closest prior art is the provision of polymerizable compositions resulting in an improved impact resistance of the polymerized composition.

6.7 An additional argument was also submitted by the appellant during the oral proceedings according to which that the lenses prepared in D3 were optically clear, reference being made to the wording "the polymer obtained by this example 1 was water-white" present in paragraph [0052] of the computer-made translation. It was held that the whitening of the cured articles observed for Comparative Examples (5) and (6) of E2 was the result of a lack of homogeneity and the presence of defects in the material tested, in particular the presence of tiny bubbles, which had their origin in the preparation of the samples, these inhomogeneities constituting predetermined breaking points in the flat lenses prepared. Accordingly, Comparative Examples (5) and (6) could not be considered to represent the closest prior art and the improvement of impact properties reported in E2 was not attributable to the features distinguishing the claimed compositions from the closest prior art. This was in the appellant's opinion confirmed by the fact that Comparative Examples (1) and (3) of E2 which did not result in whitening corresponded to the comparative examples having the highest impact energy.

6.8 The Board notes that the improvement of impact strength recognized by the opposition division was already based on E2. The opponent and now appellant, however, did not repeat the experiments presented with E2, in particular the comparative examples of E2, in order to show that those if conducted correctly would lead to lenses which are not whitened, but merely criticized the improper preparation of the samples tested in E2 in order to rebut the conclusions based on E2. The mere submission of these unsubstantiated allegations concerning the preparation of the samples in E2, which were submitted for the first time during the oral proceedings, so that neither the Board, nor the opposing party could assess their pertinence, is however not sufficient to raise doubts as to the validity of the conclusion concerning the technical problem effectively solved by the subject-matter of granted claim 1 over the closest prior art.

6.9 Consequently, the technical problem effectively solved by the subject-matter of granted claim 1 over the closest prior art is the provision of polymerizable compositions resulting in an improved impact resistance of the polymerized composition.

Obviousness

7. The question remains to be answered if the skilled person desiring to solve the problem identified above, would, in view of the prior art, have modified the disclosure of the closest prior art in such a way as to arrive at the subject-matter of operative claim 1. Although the closest prior art documents D3 and D7 were indicated to teach the use of a compound having three or more mercapto groups in one molecule, the appellant did not point to any knowledge of the skilled person or passage of those documents, which would suggest to use one of those compounds in order to solve the problem identified in above point 6.9. For this reason, the Board has no reason to consider that the use of a compound having three or more mercapto groups in one molecule constitutes an obvious solution to the problem underlying the patent in suit.

8. For these reasons, the Board concludes that the objection that the subject-matter of claim 1 does not involve an inventive step within the meaning of Articles 52(1) and 56 EPC fails to convince.