T 0238/98 (Superconductor/TOSHIBA) 07-05-2003

1. The appeal is admissible

2. Public availability of the Sunshine et al. pre-print

Appellant 3 contested that it could be inferred from D10, D10a and D10b and from the witness testimony that Prof. Dr Hoenig, appellant 1, and/or appellant 2 received the pre-print before the priority date, ie before 24 February 1988.

2.1. D10 is a copy of a fax which bears the following data imprinted by the fax machine of KfK: "FEB 23 '88 11.55 KFK POSTST. FAX 07247/825070" on the title page of the pre-print. Appellant 1 did not cite D10 in their notice of opposition but argued in their letter dated 2 September 1997 that the co- author B. Batlogg of this pre-print sent a copy thereof to Dr Halbritter in the "Forschungszentrum Karlsruhe" (KfK) on 12. February 1988 and signed this copy "with best regards Bertram B 2/12/1988" as shown by D10a, that Dr Halbritter then sent this pre-print to appellant 1 (to Prof. Dr H. E. Hoenig) by fax on 23 February 1988 while asking to further transmit the pre-print to interested persons, and that Prof. Dr Hoenig accordingly transmitted the pre-print among others to appellant 2. The question was raised by appellant 3 at the oral proceedings whether the date imprinted by the KfK fax machine on 23 February 1988 was the receipt date of a fax at KfK or the date at which KfK sent a fax to an addressee, ie a sender date. The witness testimony does not include any precise information in this respect. However the file contains a copy of another faxed pre-print, namely D7a which is a copy of the Maeda's pre-print sent by fax on 12 February 1988. In this case Dr Halbritter from KfK sent the pre-print on 12. February 1988 per fax to Prof. Dr Hoenig at Siemens using the same fax machine with the number 07247/825070. Identification of both the sender and the recipient is possible in view of the cover page of the fax (page 1 imprinted by the fax machine). In this case it is clear that the date imprinted by the KfK fax machine was the sender date. It cannot be completely excluded that this has not been changed between February 12, 1988 and February 23, 1988; however the board assumes in favour of appellants 1 and 2, that the date imprinted by the KfK fax machine in the case of the Sunshine et al. pre-print was also the date at which KfK sent the said pre-print.

From the page numbering imprinted by the KfK fax machine on the Sunshine et al. pre-print it can be seen that the title page of the pre-print is in fact page 7 of the fax. The fifteen pages of D10 were numbered pages 7 to 11 and 13 to 23 by the KfK fax machine. The copy D10a, which includes only the title page of the pre-print, also bears the same fax number, date, time, and page numbering (ie page 7) as the title page of D10. The copy D10b handed over by appellant 1 during the oral proceedings before the board contains the fifteen pages of the pre-print which have the same page numbering imprinted by the KfK fax machine, ie pages 7 to 11 and 13 to 23, and thus pages 1 to 6 of the fax are also missing. Although in the board's communication dated 14 May 2001 appellant 1 was asked to bring the original fax corresponding to D10a or D10 to the oral proceedings, this original document was not provided since, according to appellant 1 and to the witness Prof. Dr Hoenig, it could not be found (see minutes D40 page 4, first paragraph). The file contains no evidence from which it could be inferred to whom the fax sent by KfK on 23 February 1988 was addressed. The copies D10, D10a and D10b of the fax contain no copy of a possible cover page which might help to identify the addressee of the fax. They also contain no receipt stamp of the recipient fax machine. Although appellant 1 alleged that they received the fax, they could not provide the original fax and the copies D10, D10a or D10b do not prove beyond any reasonable doubt that they received it. This is because it cannot be excluded that Dr Halbritter sent the fax of 23 February 1988 to an addressee X other than Prof. Dr Hoenig, appellant 1 or appellant 2 and that this other addressee X then sent the incomplete copies D10 or D10b to Prof. Dr Hoenig, appellant 1 or appellant 2 per post. In this case they would not have received the information before the priority date of 24 February 1988. In these circumstances, the addressee X would himself have received the information before the priority date and would have had the possibility to gain knowledge of it before the said date; however it would still remain to prove that there existed no confidentiality agreement between Dr Halbritter and the addressee X. Such a confidentiality agreement might have existed at least up to February 26, 1988 taking into account that two US patent applications concerning the same subject-matter as the pre-print have been filed by AT&T on 12 February 1988 and 26 February 1988 (see the two priority dates and documents indicated in D1). In this context it is observed that Prof. Dr Hoenig could not exclude having received the Sunshine et al. pre-print a second time from elsewhere (see page 4 of D40, last sentence).

2.2. Appellants 1 and 2 made reference to the declaration of Prof. Dr Hoenig that he himself received the Sunshine et al. pre-print directly from Dr Halbritter. According to the witness testimony, Prof. Dr Hoenig received the pre-print directly from Dr Halbritter and was able to recognise a fax coming from Dr Halbritter by a hand-written identification on it. However Prof. Dr Hoenig could not say on which exact date he received the pre-print (see Minutes D40 page 3, 4th paragraph; page 5, 4th and 6th paragraphs; page 6, 3rd paragraph). Therefore, it cannot be excluded that Prof. Dr Hoenig received a fax containing the Sunshine et al. pre- print from Dr Halbritter on a date later than February 23, 1988. In particular it cannot be inferred from Prof. Hoenig's testimony that the faxed pre-print received by Prof. Dr Hoenig directly from Dr Halbritter was a fax bearing the date February 23, 1988. Appellant 1 has not provided the original fax received by Prof. Dr Hoenig in order to support their contested allegation that Prof. Dr Hoenig actually received the faxed Sunshine et al. pre-print on 23 February 1988 although the burden of proof lies on appellant 1 or appellant 2 in this respect. For the preceding reasons and in particular in the absence of the required evidence the board is not convinced by the appellants' allegation that Prof. Dr Hoenig received the Sunshine et al. pre-print before the priority date.

2.3. Appellants 1 and 2 further argued that Dr Halbritter was in possession of the pre-print on 23 February 1988 and that the content thereof was publicly available since Dr Halbritter represented a member of the public and was not bound by a confidentiality agreement which would restrict the transmission of the pre-print to other members of the public. The board cannot follow these arguments for the following reasons. Assuming in favour of the appellants that the date imprinted by the KfK fax machine was the sender date, ie the date at which Dr Halbritter sent the Sunshine et al. pre-print to an addressee (see point 2.1 above), then Dr Halbritter had indeed the possibility to gain knowledge of the content of the pre-print before the priority date. However, it is not clear what the circumstances of the relationship between Dr Halbritter and B. Batlogg (co-author of the pre-print) and/or the company AT&T were. It is therefore also not clear that this relationship has not been governed by an obligation of Dr Halbritter to keep the information confidential at least until a certain point in time. Appellant 3 argued at the oral proceedings that a confidentiality agreement could be derived from the fact that the company AT&T had a commercial interest in the invention and that it was in its interest not to disclose the content of the pre-print at least until the filing of the second US application on 26 February 1988. In the board's judgment it is plausible in view of the statement in D1 about the economic interest of the new materials (see column 2, lines 1 to 4) and of the priority dates of 12. February 1988 and 26 February 1988 stated in D1 that this company saw a commercial interest in the invention and was interested in filing US patent applications on the subject- matter of the pre-print. In these circumstances, it cannot be excluded that an obligation to keep the content of the pre- print confidential might have existed at least for a short period of time in February 1988 between the said co-author of the pre-print and Dr Halbritter. Although the burden of proof rested on appellants 1 and 2 as regards their allegation that there were no circumstances obliging Dr Halbritter to some kind of confidentiality, appellants 1 and 2 filed no evidence in this respect. Despite the invitation of the board to provide for the appearance of Dr Halbritter at the oral proceedings for a possible hearing as a witness who could possibly have enlightened the board as to the nature of his relationship with B. Batlogg and the firm AT&T, and in particular the circumstances of the transmission of the pre- print D10, appellants 1 and 2 deliberately chose not to present Dr Halbritter as a witness. The lack of sufficient proof resulting from the failure to do so goes to the detriment of appellants 1 and 2 who had the burden of proof. For the preceding reasons the board cannot consider on the basis of the evidence submitted that it has been proven beyond any reasonable doubt that the Sunshine et al. pre-print was made available to the public before the priority date.

Main request

3. Claim 1 of this request does not meet the requirements of Article 123(2) EPC for the following reasons. According to amended claim 1 of the main request a mixture is prepared by mixing appropriate amounts of chemical compounds of Bi, Sr, Ca, Cu, Pb and O. However, the application as filed discloses mixing appropriate amounts of Bi2O3, SrCO3, CaCO3, PbO and CuO as starting compounds to obtain the mixture to be calcined. It is not directly and unambiguously derivable from the application as filed that compounds other than the specific compounds indicated above might be used to obtain the desired superconductor having a Tc greater than 77°K. Furthermore, according to amended claim 1 a chemical composition is obtained in which the molar ratio of (Bi+Pb):Sr:Ca is 1:1:1 and the molar ratio of Pb to Bi is in the range of 5:95-85:15. Compositions having ratios of (Bi+Pb):Sr:Ca equal to 1:1:1 are indeed disclosed in the application as filed (see for example page 4a, page 6, lines 8 and 17; page 7, line 31; page 8, lines 18 and 29; page 9, line 11; claims 5 and 6) but always in combination with a specific amount of copper. It cannot be directly and unambiguously derived from the application as filed that the use of any amount of copper in combination with the molar ratio (Bi+Pb):Sr:Ca of 1:1:1 would lead to an oxide superconductor having a Tc greater than 77K. As claim 1 of the main request contravenes the provisions of Article 123(2) EPC, the main request must fail.

First and second auxiliary requests

4. The question arises whether the superconductor as defined in claim 9 of both requests, a product-by-process claim, is new with respect to the disclosure in D1. According to the established case law of the boards of appeal, claims for products defined as having been obtained by a particular process are allowable only if the product as such satisfies the requirements of patentability. In other words the product itself has to meet the requirements of novelty and inventive step. A product is not rendered novel merely by the fact that it is produced by a new process (see for example T 150/82, OJ EPO 1984, 309; T 248/85, OE EPO 1986, 261).

D1 is a document as defined in Articles 54(3) and (4) having two priority dates, namely 12 February 1988 and 26. February 1988. Only the information of D1 entitled to the priority date of 12 February 1988 forms part of the state of the art. D1 discloses superconductors manifesting a superconductivity at a temperature of at least 77K and having the nominal composition X2+y M3-y Cu2O8± Delta where X is Bi or Bi and one or more of Pb, In, Ga, Sn, Gd and Sb, M is selected from divalent ions and combinations of monovalent and trivalent ions selected such that the average valence of M is substantially equal to 2, and is typically 0 to 0.5. M is preferably selected from Ca, Sr, Ba, Mg, Cd, Na, K, Y or mixtures thereof. The superconductor has in particular the nominal composition X2.2M2.8Cu2O8+Delta where X is for example Pb and Bi, the Pb/Bi ratio being at most 0.5. An exemplary crystal having the composition Bi2.2Sr2Ca0.8Cu2O8+Delta (Delta typically 0-0.5) shows bulk superconductivity at a temperature of about 84K. D1 further teaches that substitutions of Bi with lead in the 84K phase have yielded considerable improvement in Tc, a multiphase lead substituted sample having a Tc of 107K. Powders of Bi2O3, Sr(NO3)2, Ca(NO3)2.4H2O, and CuO are used to prepare the composition of example 1. According to the general description of the process in column 8 of D1 appropriate starting materials are mixtures of metallic oxides, hydroxides, carbonates, hydrates, oxalates or other reactive precursors in the appropriate ratio to obtain the desired final composition (see column 2, lines 50 to 53; column 3, lines 13 to 19; column 7, lines 24 to 28; column 8, lines 4 to 7; example 1; claims 1 to 3). It was not disputed that this disclosure is entitled to the priority date of 12. February 1988.

The composition and the Tc of the superconductor materials disclosed in D1 fall within the broad definition indicated in claim 9 and also in claim 1 to which claim 9 makes reference. Appellant 3 argued that the product-by-process of claim 9 was novel over the disclosure in D1 since D1 used calcium nitrate and strontium nitrate as starting materials instead of calcium and strontium carbonates in the process of claim 1 and the calcination/sintering steps disclosed in D1 did not completely eliminate the nitrogen contained in the nitrates. The claimed products would thus contain a residue from the carbonates instead of a residue from the nitrates. This was disputed by appellants 1 and 2 who, from their side, argued that under the calcination and sintering conditions disclosed in D1 the nitrates would not leave any nitrogen-containing residue. In the board's judgment, in view of the calcination and sintering conditions disclosed in example 1 of D1, namely 840°C for 12 hours and then 860°C for 5 hours, it seems to be unlikely that a nitrogen-containing residue from the Ca and Sr nitrates would remain in detectable amounts in the end products. However, taking into account that the starting mixture does not contain only one nitrate but a mixture of five components including nitrates and oxides, the board cannot completely exclude that a detectable residue might remain. Only experiments using a starting mixture comprising the two said nitrates instead of the two carbonates would in fact permit to conclude whether or not there is a difference in the end products. However the appellants have provided no evidence in this respect. Taking into account that the claims as granted did not contain any product-by- process claims, the latter having been introduced during the opposition proceedings, the board considers that the burden of proof lies on appellant 3 in respect to their allegation that a residue from the nitrate would remain in the end product. The board also observes in this respect that the question whether or not a residue from the nitrate would remain in detectable amounts after the sintering step was neither discussed, nor decided by the opposition division in the decision under appeal. Therefore the latter also contains no arguments or reasons which might shift the burden of proof to appellants 1 and 2. Under these circumstances, in particular in the absence of evidence from appellant 3 to support the contested allegation, the board does not accept this allegation and thus cannot consider the subject-matter of claim 9 of the 1st and 2nd auxiliary requests to be new with respect to the disclosure of D1. This is in line with decision T 219/83 (OJ EPO 1986, 211, point 12 of the reasons) according to which, if the EPO is unable to establish the facts, it is the party whose arguments rest on these alleged facts who loses thereby.

Third auxiliary request

5. Amended claims 1 to 8 of this request meet the requirements of Article 123(2) EPC. Claim 1 is based on a combination of claims 7 and 9 as filed with features disclosed in the application as filed. The Tc of greater than 77 K and the composition ratio of Pb to Bi in the range of 5:95-85:15 in the superconductor are disclosed on page 2, lines 5 to 15, and on page 3, line 35 to page 4 line 3, of the application as filed. The molar ratio of 5:95-85-15 in the superconductor is also directly derivable from claim 12 as filed. Appellant 1's allegation that original claim 12 is not consistent with the description as filed is not convincing in view of the disclosure in the passage on page 2, lines 14 to 15, whose content is also repeated in original claim 2.

Amended claim 3 is based on the combination of original claim 13 with the calcining temperature indicated in original claim 15. The molar ratio of Pb to Bi in the range 5:95-85:15 is directly derivable from original claims 18 and 2 and from page 2, lines 11 15, of the description as filed. The features of the dependent claims 2 and 4 to 7 are disclosed in original claims 8, 14, 15, 16 and 17. Those of claim 8 find support on page 5, lines 24 to 26, of the description as filed. The scope of protection is clearly restricted by the amended claims compared to that of the granted claims.

6. Appellant 2 raised an objection of lack of clarity against claim 3 arguing that the "melting point" was not unambiguously defined taking into account that several phases with different melting points were present in the mixture. The board observes that the expression "melting point" was already stated in the granted claims and that lack of clarity pursuant to Article 84 EPC is not a ground of opposition. Thus, this expression has to be construed taking account of possible additional information in the patent in suit. The opposition division's construction indicated on page 6, third paragraph, of the decision under appeal was not contested by the parties and can also be followed by the board.

7. Appellants 1 and 2 argued that the process according to claim 1 lacked novelty over the disclosure of D1. The appellants' arguments put forward in this respect are not convincing for the following reasons. The method of preparation of the superconductor having the nominal composition Bi2.2Sr2Ca0.8Cu2O8 disclosed in example 1 of D1 is entitled to the priority date of 12 February 1988. It was not contested that the method of claim 1 differs from the method of example 1 in that the starting powder mixture contains PbO, Ca and Sr carbonates are used instead of Ca and Sr nitrates, and the ratio of Pb to Bi is in the range of 5:95-85:15. D1 further teaches that appropriate starting materials are mixtures of metallic oxides, hydroxides, carbonates, hydrates oxalates or other reactive precursors. It is also disclosed in D1 that Bi may be substituted with lead in the 84K phase yielding considerable improvement in Tc. A Pb/Bi ratio of at most 0.5 is disclosed in D1, ie a range which partially overlaps with the claimed range (see column 8, lines 1 to 7; column 7, lines 24 to 25; claim 3). This disclosure is entitled to the priority date of 12 February 1988. To arrive at the claimed process the skilled person had therefore to select from the general list of starting materials calcium carbonate and strontium carbonate, none of them being expressly mentioned in this list, to replace in the process of example 1 only the strontium nitrate and the calcium nitrate by the corresponding carbonates, to select PbO as the starting product to be added to the mixture and to choose the appropriate Pb/Bi ratio. The specific combination of starting materials as defined in claim 1 is not disclosed in D1 and confers novelty on the claimed process.

The process of claim 1 is also novel with respect to the other documents cited by the parties and published before the priority date. Claim 3 also meets the novelty requirement with respect to the cited documents. This was not in dispute so that further considerations in this respect are not necessary.

8. Turning to the issue of inventive step, D1 does not form part of the state of the art. Appellant 3 accepted at the oral proceedings that the date of publication of D7 was 20 February 1988, ie before the priority date. D7 is considered to represent the closest prior art. It discloses a method for preparing a high-Tc oxide superconductor of the Bi-Sr-Ca-Cu-O system such as the oxides BiSrCaCu2Ox having a Tc of about 105K. Appropriate amounts of powders of Bi2O3, SrCO3, CaCO3 and CuO were mixed, calcined at 800 to 870°C for 5h, thoroughly reground and then cold-pressed into pellets which were sintered in air or an oxygen atmosphere at about 870°C (see page L209, abstract, left-hand column, 4th paragraph).

8.1. Starting from D7, the technical problem underlying the patent in suit can be seen in the provision of a process leading to superconductors having a higher critical temperature Tc. It is proposed to solve this problem by the process as defined in claim 1, which differs from the process of D1 in that the starting mixture further contains PbO. In view of the examples of the patent in suit, it is credible that the addition of PbO, in particular the partial substitution of Bi with Pb results in an increase of Tc. Appellant 1 objected that the improvement was shown only for some specific compositions and had been generalised to all compositions encompassed in claim 1. Assuming that appellant 1's objection was that the problem was not solved over the whole ambit of claim 1, then the burden of proof lies on them in respect of this allegation. However, appellant 1 provided no evidence to support their allegation. In the absence of evidence to the contrary, the board considers that the technical problem has actually been solved by the claimed process.

8.2. Appellants 1 and 2' arguments that it was obvious to the skilled person to partially substitute Bi with Pb in the process of D7 in view of the teaching in D32, D31, D33 and/or D4 in order to solve the technical problem (see point VII above) are not convincing for the reasons indicated hereinafter.

8.3. D32 concerns high-Tc superconductors of the type YBa2Cu3O7 (Tc of about 90K). It deals with the question whether Y can be substituted with Pb in this system. According to D32 the motivation for studying the system Y1-xPbxBa2Cu3O7 was that lead oxide is cheaper than yttrium oxide and that a previous attempt to substitute the rare earth with Pb had led to an increase of Tc and the most significantly to a remarkable increase of the upper critical field Hc (see page 377, lines 1 to 11). However the variation of Tc with x shown on Figure 3 (page 378) reveals that the highest value for Tc is obtained when the superconductor contains no Pb (x=0). In other words the partial substitution of Y with Pb leads to a decrease of Tc in the case of the YBa2Cu3O7 superconductor. This result would lead the skilled person away from trying Pb as a substituent in the Bi-Sr-Ca-Cu-O system of D7 rather than encourage him to make such experiments.

Furthermore the detrimental effect of the partial substitution with Pb on the critical temperature is not only shown in D32 but also in D31. This document, which relates to superconducting phase transitions in the La- M-Cu-O layered perovskite system, where M=La, Ba, Sr, and Pb, discloses that the partial replacement of La by Pb in all three samples studied, ie La2-xPbxCuO4 with x=0.1, 0.2 and 0.3, resulted in a complete disappearance of the superconductivity (see page 5351, right-hand column, first complete paragraph; page 5352, table 1 and right-hand column, first complete paragraph).

In view of D31 and D32 both showing the detrimental effect of the substitution of Y or La with Pb on the critical temperature, the skilled person would have had no reason to expect that in the case of the Bi-Sr-Ca-Cu- O system according to D7 an increase of the critical temperature might be obtained by a substitution of Bi with Pb. In the absence of any reasonable expectation of success, he would not have tried such a substitution.

8.4. D33 discloses that substitutions had been performed in oxide superconductors such as Li1+xTi2-xO3 and BaPb1-xBixO3 in order to increase their critical temperature, however they remained unsuccessful (see page 120, right-hand column, lines 1 to 17 from the bottom; page 121, paragraph bridging the right-hand column and the middle column). Concerning the superconductors in the La-Ba-Cu-O or La-Sr-Cu-O systems having higher Tc of > 30K to about 40K, D33 discloses different substitutions, among others substitutions with Pb (see in particular page 124, Table 1). However it can be inferred from Table 1 that the substitution of Cu with Pb leads to a decrease of the critical temperature (compare sample Y3 with sample X24.04) and the substitution of La with Pb, and Cu with Bi also resulted in a lower Tc (compare samples L44 and L24). Therefore, substitutions with Pb in these La-Ba(Sr)-Cu-O systems having Tc of about 40K do not improve the Tc (see also page 124, the sentence bridging the left-hand and middle columns). It follows therefrom that D33 contains no additional information which would give the skilled person an incentive to partially replace Bi by Pb in the material of D7 in order to increase the Tc of the superconductors.

8.5. D4 concerns superconductors of the composition BaPb1-xBixO3. Although these superconductors have perovskite related structures, they belong to a different type of superconductors not containing any copper, having a different crystal structure and a superconductivity which arises from different crystallographic planes compared to the superconductors of D7. The combination of both Pb and Bi results in superconductivity properties, superconductivity having been observed from x=0.05-0.3. The addition of Pb to the BaBiO3 material which has a semi-conductive behaviour leads to a material having superconductive properties with a maximal critical temperature of 13K at x= 0.3, Tc then decreasing to 9K when the amount of Pb is further increased (see page 27, abstract and page 28, left-hand column, 1st paragraph). These superconductors have relatively low Tc of at most 13K compared to the much higher values of 90K in the Y-Ba- Cu-O system (D32) or 105K in the Bi-Sr-Ca-Cu-O system of D7. It cannot be inferred from this teaching that the substitution of Bi with Pb in the superconductors of the Bi-Sr-Ca-Cu-O system which, contrary to BaBiO3, already exhibit superconductivity properties) and a very high Tc of 105K might result in a further increase of the critical temperature all the more so as substitutions with Pb in YBa2Cu3O7 or in La2- xSrxCuO4 superconductors having Tc values of about 90K or about 40K respectively lead to a decrease of Tc as shown in D32 and D33. Therefore, in the absence of any reasonable expectation of success in view of the cited prior art the skilled person would not have tried substituting Bi with Pb in the superconductors of D7 in order to solve the problem stated above. The fact that chemical substitution of lead might have been well-known in many bismuth oxides as pointed out by appellant 2 cannot in any way change the preceding conclusions in the absence of further information as to which bismuth oxides are meant in D10 (see D10, hand-written page 7, first line), whether or not they exhibit superconductivity properties and what the effect of the substitution on the material properties was. The bismuth oxides meant in D10 might be those of D4.

In the board's judgement, the fact that the high-Tc superconductor of D7 was a new kind of superconductor whose substitution possibilities had not yet been explored, does not justify fully ignoring the concept of reasonable expectation of success developed in the case law. This concept is also applied in the technical field of genetic engineering where some areas have not yet been explored. For example in decision T 42/92 (OJ EPO 1997, 408, point 8.5 and ff.) where an experiment was considered to be "obvious to try" for the skilled person, it has been examined whether or not the skilled person was in a position to reasonably predict the successful conclusion of the experiment, on the basis of the existing knowledge, before starting the experiment. In the present case the skilled person was not in a position to reasonably predict that substitutions with Pb in the new superconductors of D7 would bring about an increase of Tc for the reasons given above, in particular in view of the known detrimental effect of the said substitutions in superconductors already having a relatively high Tc of for example 40K or 90K.

8.6. The considerations put forward above apply likewise to the subject-matter of claim 3. The additional documents D8, D13, and D34 were cited by appellants 1 and 2 in connection with the issue of inventive step to show that the additional melting step stated in claim 3 was known for the preparation of superconductors in the rare earth-Ba-Cu-O system (D8) and in the Y-Ba-Cu-O system (D34), or could be inferred from D13 for superconductors in the Bi-Sr-Ca-Cu-O system. They concluded that it was obvious to perform a melting step also in the case of the new Bi-Sr-Ca-Cu-O superconductors. The three cited documents indeed disclose a melting step, however they contain no information suggesting that the substitutions of any elements of the considered superconductors with Pb would increase their critical temperature. Therefore, even if the melting step were obvious to the skilled person, the subject-matter of claim 3 would still be considered to involve an inventive step for the reasons given above in connection with claim 1.

8.7. The remaining documents published before the priority date were not relied upon at the oral proceedings. These documents contain no additional information which would point towards the claimed solution as defined in claims 1 and 3.

8.8. It follows from the above that the subject-matter of independent claims 1 and 3 of the third auxiliary request meets the requirement of inventive step set out in Articles 52(1) and 56.

9. Claims 1 and 3 being allowable, the same applies to dependent claims 2 and 4 to 8, whose patentability is supported by that of claim 1.