T 0977/98 (Ya-Ba-Cu-O superconductor/HOUSTON) 20-06-2002

Reasons for the Decision

1. Both appeals meet the requirements of Articles 106 to 109 and Rule 64 EPC and are therefore admissible.

2. Amendments

Amendments in relation to claims as granted have been made to independent claims 4 and 11 of the first and second auxiliary requests. There were no objections pursuant to Article 123(2) and (3) EPC against the amendments from the opponents, and the Board is also satisfied that the amendments comply with the requirements of Article 123(2) and (3) EPC.

3. Priority - main request and first and second auxiliary requests

3.1. The patent in suit claims four priority dates, i.e. 12. January 1987, 27 January 1987, 6 February 1987, and 26. March 1987. It is the priority date of 6 February 1987 claimed from the priority document E3 for independent claims 4 and 11 of the main request and first and second auxiliary requests, which is in dispute in the present appeal. In this connection, the opponents contended that the document E3 did not contain an enabling disclosure to realize the invention as claimed in claims 4 and 11, so that the invention as claimed was not the same as the one disclosed in the priority document E3, contrary to the requirements of Article 87(1) EPC.

Referring to the decision G 2/98, the opponents furthermore argued that claims 4 and 11 were not entitled to the priority date of document E3, since the priority document discloses neither the formula L1M2A3O6+Delta nor the numerical values of the oxygen parameter Delta as specified in claims 4 and 11.

3.2. The disclosure in the priority document E3 which is relevant to claims 4 and 11 is the Example XI. It is reproduced as Example XI in the patent in suit (cf. page 12, lines 20 to 47). Example XI describes a method of producing a Y-Ba-Cu-O sample, termed "complex" in the patent in suit (cf. item V(a) above), starting from a mixture of Y2O3, BaCO3, and CuO having the nominal composition Y1.2B0.8CuOy. After mixing the components, the oxide mixture was compressed to pellets at an applied pressure of 100 to 500 psi, followed by heating the pellets in air at 900 to 1100°C for about 15 minutes and then "rapidly quenching" the pellets to room temperature in air.

The Y-Ba-Cu-O sample produced according to the above method was shown to comprise multiple phases where at least one of the phases has a structure uncharacteristic of that of a K2NiF4 crystal and exhibited a superconducting transition between 80 and 93. K. At a temperature of 4.2 K, the sample showed a diamagnetic signal corresponding to 24% of the superconducting signal of a lead sample with similar dimensions.

3.3. According to established case law of the boards of appeal, if a method of producing a substance is disclosed, then the product resulting from the disclosed method is also disclosed, provided that the method is an enabling disclosure, i.e. a disclosure sufficiently clear and complete for it to be carried out by a skilled person. When the resulting product is in form of multiple phases, each of the phases resulting from the disclosed method are considered to be disclosed, if separation and identification of the individual phases can be carried out in a routine manner using the techniques available at the date in question.

In the present case, the Y-Ba-Cu-O sample produced by the method disclosed in Example XI contains multiple phases. The superconducting phase was not isolated but was only identified to have a crystal structure uncharacteristic of that of a K2NiF4 crystal and to have a superconducting transition between 80 and 93 K.

3.4. The arguments presented by the opponents as to why Example XI of the priority document E3 could not be considered to be an enabling disclosure were essentially as follows (cf. items XI(a) and XII(a) to (d) above): Firstly, the method of Example XI of the priority document E3 suggests a set of process parameters, in particular the short heating step and the rapid cooling (quenching) of the sample, which are so unfavorable that the skilled person following the teaching of Example XI would inevitably fail to produce an Y-Ba-Cu-O oxide superconductor having a superconducting transition above 77 K.

Secondly, claims 4 and 11 cover the case where the L-M-A-O sample consists of a superconductive phase having substantially zero electrical resistance at 77. K. The priority document E3, according to the opponents, does not provide an enabling disclosure for this case, since the method according to Example XI would at most produce a mixed phase Y-Ba-Cu-O sample, and not a single superconducting phase sample. It was not routine to separate and identify the superconducting phase in order to arrive at a sample consisting of the superconducting phase. Since the cause of the superconductivity was not known, the skilled person had no idea whether one or several phases were responsible for the superconductivity.

3.4.1. As regards the relatively short heating time of about 15. minutes and the cooling rate ("rapid quenching") employed in Example XI of the priority document E3, as accepted by the patent proprietor, these are not optimum process parameters. However, the Board accepts the patent proprietor's submission that the quenching employed in documents E6 (cf. Figures 6 to 8) and E12 (cf. page 5732, "Experimental Procedure") entailed quenching by immersing the sample directly in liquid nitrogen (cf. E9, page 954, left column, second paragraph), whereas rapid quenching employed in the priority document E3 was carried out by cooling in air. Consequently, in the Board's view, it was doubtful whether the results reported in documents E6 and E12 were applicable to the method reported in the priority document E3, and whether they conclusively show that a sample produced by quenching by cooling in air as in the priority document E3 would not contain the superconducting 123-phase.

3.4.2. Regarding the second argument that it was not routine to separate the superconducting phase from the non-superconducting phases, the Board is convinced by the patent proprietor's arguments that at the priority date of document E3, it was possible to separate and identify the superconducting phase, later known as the "123-phase", from the non-superconducting phases using standard techniques which were available at that time (cf. item X(a) above). The superconducting phase could be isolated by, for example, grinding the sample and employing the Meissner effect whereby the superconducting grains are separated from the non-superconducting grains in a magnetic field. Furthermore, the exact crystal structure of the superconducting phase could be determined using x-ray diffraction. Although these techniques may be tedious and time-consuming, they were nevertheless regarded as routine at the priority date of document E3.

3.4.3. It is furthermore documented in documents E6 and E27 that within a couple of weeks from learning about the present invention through the publication of document E7, numerous laboratories all over the world not only managed to reproduce the results of document E7, but also succeeded in isolating, identifying, and characterizing the superconducting 123-phase, although document E7 describes the fabrication process in less detail than in Example XI of the priority document E3 (cf. E6, page 545, second paragraph; E27, page 72, last paragraph to page 74, as well as the argument of the patent proprietor, items X(a) and (b) above).

Thus, taking the above facts and arguments into consideration, the Board concludes that the method of Example XI was disclosed in sufficient detail in order to enable a skilled person to produce a Y-Ba-Cu-O sample comprising a superconductive crystalline phase having a crystal structure uncharacteristic of that of a K2NiF4 crystal and having substantially zero electrical resistance at 77 K.

3.5. Claims 4 and 11 specify in addition that the superconductive crystalline phase has a formula L1M2A3O6+Delta. For the main request, the oxygen parameter Delta is set to have a numerical value of 0.1 to 1.0, whereas for the first and second auxiliary requests, the value of the oxygen parameter Delta is fixed to 1.0. It was not disputed by the patent proprietor that the priority document E3 does not explicitly disclose the formula or any numerical value of the oxygen content of the superconducting phase.

3.5.1. Regarding the main request, Opponent II argued that the feature "having a formula L1M2A3O6+Delta where Delta has a number value of 0.1 to 1.0" is not directly derivable from the priority document E3, as required following the Enlarged Board decision G 2/98, since the disclosure of a single sample cannot provide support for a whole range of the oxygen parameter Delta (cf. item XI(b) above). Furthermore, for YBa2Cu3O6+Delta, which is the superconducting phase relevant to the method of Example XI of the priority document E3, the lower limit of Delta = 0.1 is not superconducting at all, and YBa2Cu3O6+Delta fails to be superconducting at 77 K for most part of the claimed range from 0.1 to 1.0 (cf. item XI(c) above).

As to the first and second auxiliary requests, Opponent II argued that the claimed value of 1.0 for the oxygen parameter Delta is not directly derivable from the priority document E3, since carrying out the process of Example XI would not inevitably result in a superconducting phase having the oxygen parameter Delta equal to 1.0.

3.5.2. The patent proprietor responded that the 123-phase of Y-Ba-Cu-O having the general formula Y1Ba2Cu3O6+Delta is actually a mixture of a superconducting orthorhombic 123-phase corresponding to Delta = 1, and a non-superconducting tetragonal 123-phase corresponding to Delta = 0 (cf. item X(c) above). Therefore, it would have been possible for a skilled person, using known methods at the priority date E3, to separate the two 123-phases so as to produce samples having values of Delta falling within the whole range as claimed.

3.5.3. Although the Board is convinced that a skilled person following the teaching of Example XI in the priority document E3 would be able to establish the composition YBa2Cu3O6+Delta for the superconducting phase using routine techniques, the Board agrees with Opponent II that the priority document E3 does not contain any implicit disclosure of the end values 0.1 and 1.0 for the oxygen parameter Delta, since the skilled person is not taught a specific combination of process conditions which would inevitably lead to these particular values of the oxygen parameter Delta. Consequently, the priority document E3 cannot be regarded as unambiguously disclosing the same superconducting composition with Delta = 0.1 and Delta = 1.0 as the one claimed in claims 4 and 11 of the main request and first and second auxiliary requests.

3.5.4. The patent proprietor's argument that the superconducting 123-phase is a mixture of two phases having compositions with Delta = 0 and Delta = 1.0, respectively, fails to convince the Board, since, as Opponent II pointed out, it is in contradiction with the findings disclosed in documents E9 and E12 (cf. XI(d) above). Documents E9 and E12 are both published after all the priority dates of the patent in suit, and are therefore not comprised in the state of the art. However, they provide information about the material properties of Y1Ba2Cu3O6+Delta. The documents E9 and E12 report that when the oxygen parameter Delta falls below a value of about 0.4 to 0.5, an orthorhombic to tetragonal phase transition takes place and the superconductivity disappears (cf. E9, Figure 2; paragraph bridging pages 956 and 957; E12, paragraph bridging pages 5732 and 5733; as well as item XI(c) above). Above this value, Y1Ba2Cu3O6+Delta appears to be orthorhombic where the superconducting transition temperature Tc increases as Delta approaches the value of 1. These findings were not disputed by the patent proprietor.

Thus, the production and isolation of the superconducting phase having a composition with Delta equal to 1.0 is not as straightforward as the patent proprietor suggested under item X(c) above. Therefore, the Board is not convinced that the priority document E3 implicitly discloses the limits 0.1 and 1.0 for the oxygen parameter Delta, in the sense that a skilled person starting from document E3 would inevitably produce samples with varying values of Delta falling within the whole interval [0.1, 1.0] as claimed, and in particular with the endpoints 0.1 and 1.0.

Moreover, as Opponent II pointed out (cf. item XI(c) above), the lower limit of Delta = 0.1 corresponds to the tetragonal phase which is not superconducting at all. Therefore, it is highly unlikely that the superconducting phase produced according to the process in the priority document E3 had this specific composition.

3.5.5. According to G 2/98 (OJ EPO 2001, 413), priority of a previous application in respect of a claim in a European patent application is to be acknowledged only if the skilled person can derive the subject matter of the claim directly and unambiguously, using common general knowledge, from the previous application as a whole.

Since the priority document E3 does not implicitly disclose the end points 0.1, 1.0 for the oxygen parameter Delta, claims 4 and 11 according to the main request and the first and second auxiliary requests are not entitled to the priority date of E3.

4. Priority: third auxiliary request

The claims corresponding to the third auxiliary request correspond to claims 1 to 3 and 8 to 10 according to the main request. The opponents never challenged the finding in the decision under appeal that these claims are entitled to the priority date of E3, i.e. 6. February 1987. The Board is convinced that these claims are entitled to the priority date of E3.

5. Novelty and inventive step - main request, first and second auxiliary requests

Documents E7, E8, and E14 were considered most relevant by the parties in the appeal proceedings.

5.1. Document E7 is an article published on 2 March 1987 before the priority date of 26 March 1987 of the patent in suit. This document is therefore comprised in the state of the art pursuant to Article 54(2) EPC for independent claims 4 and 11 according to the main request and first and second auxiliary requests. It discloses the formation of a superconducting, mixed phase Y-Ba-Cu-O sample using powders of Y2O3, BaCO3, and CuO in the nominal composition of Y1.2Ba0.8CuO4-Delta as starting materials, which are mixed, compressed, and sintered (cf. paragraph bridging pages 908 and 909). The resulting sample comprises phases having a crystal structure uncharacteristic of that of K2NiF4 and has a superconducting transition between 80 and 93 K (cf. page 908, last paragraph to page 909, penultimate paragraph). Thus, document E7 describes the same process but in less detail than in Example XI of the priority document E3 of the patent in suit (cf. item 3.2. above).

5.2. Document E8 is a European patent application claiming a priority date of 11 March 1987. Thus, for independent claims 4 and 11 according to the main request and the first and second auxiliary requests, document E8 is an earlier European application within the meaning of Article 54(3) EPC.

Document E8 discloses various samples having compositions very close to YBa2Cu3Oy which are superconducting at 77 K (cf. column 1, line 53 to column 2, line 4; column 2, line 49 to column 3, line 17). It is furthermore taught in document E8 that the samples should be cooled slowly in oxygen in order to allow them to retain more oxygen (cf. column 2, lines 36 to 48). The corresponding disclosure is also found in the priority document E8a of 11 March 1987 (cf. page 3, line 26 to page 4, line 26).

5.3. Document E14 is a European patent application published on 13 July 1987 after the priority date of the patent in suit, and claims a priority of 10 March 1987 from the priority document E14c. Thus, for independent claims 4 and 11 according to the main request, and the first and second auxiliary requests, document E14 is an earlier European application within the meaning of Article 54(3) EPC.

Document E14 discloses the formation a Y-Ba-Cu-O sample having a superconducting phase with orthorhombic crystal symmetry which has the composition YBa2Cu3O6.9 (cf. page 4, lines 56 to 58; page 6, lines 30 to 59). The sample has zero resistance at a temperature Tc of 91.5. K (cf. Table, Example 1). The same information is found in the priority document E14c of 10 March 1987 (cf. page 8, lines 11 to 15; page 12, line 10 to page 13, line 27; Table, Example I).

5.4. Main request

5.4.1. As regards document E14, it was contended by the patent proprietor that applying the same standard of enabling disclosure as that for the priority document E3 (for the priority date of 6 February 1987) to the priority document E14c, document E14 was not entitled to the priority date of 10 March 1987, and therefore was not comprised in the state of the art pursuant to Article 54(3) EPC. In particular, it was argued that the process described in the priority document E14c, page 12, line 10 to page 13, line 27, does not specify a set of process parameters to produce a sample having a composition with the oxygen parameter Delta equal to 0.9, so that there was no enabling disclosure in the priority document E14c.

In this connection, the Board observes that there is one crucial difference between the disclosures of both the priority documents. In document E3, neither the composition with the end values Delta = 0.1 and Delta = 1.0 of the oxygen parameter, nor process conditions which inevitably produce these compositions are disclosed. In document E14c on the other hand, the composition with Delta = 0.9 is specifically disclosed, so that the skilled person knew a priori the exact composition to be produced. The optimization to this end of starting materials and the essential process conditions which are disclosed in document E14c, in the Board's view, therefore belong to the routine practice in the art.

The Board therefore concludes that the priority document E14c contains an enabling disclosure of the superconducting phase having a composition with the oxygen parameter Delta equal to 0.9. Document E14 is therefore entitled to the priority date of 10 March 1987 and thus belongs to the state of the art according to Article 54(3) EPC.

5.4.2. As mentioned above, document E14 discloses a superconducting phase a composition with the oxygen parameter Delta equal to 0.9. This value of the oxygen parameter Delta falls within the range of 0.1 to 1.0 as defined in claims 4 and 11. Therefore, the subject matters of independent claims 4 and 11 according to the main request are not new.

The main request is therefore not allowable.

5.5. First auxiliary request

5.5.1. The subject matters of independent claims 4 and 11 according to the first auxiliary request are new, since none of the cited documents E7, E8, and E14 disclose a superconducting phase having a composition with the oxygen parameter Delta equal to 1.0. Moreover, it is generally known in the art that the oxygen parameter Delta in the superconducting phase Y1Ba2Cu3O6+Delta is very sensitive to the choice of process parameters of the method of forming the superconductor, such as cooling rate and ambient oxygen content. Therefore, a skilled person carrying out the teaching of either document E7, E8 or E14 would not inevitably arrive at a sample having a superconducting phase with the oxygen parameter Delta equal to 1.

5.5.2. Since documents E8 and E14 are prior art falling under Article 54(3) EPC, they cannot be considered for inventive step. Thus, document E7 is the only remaining relevant prior art document.

5.5.3. The claimed subject matter has the advantage that the superconducting transition temperature is particularly high, and that other properties, such as critical current density, are improved over other phases having lower values of Delta. Thus, the objective problem relates to optimizing the superconductive properties of the Y-Ba-Cu-O sample, such as the transition temperature.

5.5.4. A skilled person would in the Board's opinion automatically seek to improve the properties of the mixed phase sample disclosed in document E7. As discussed under items 3.4.2 and 3.4.3 above, it appears from the parties' submissions that it was standard procedure to separate the superconducting phase from the other phases. Moreover, as evidenced from the numerous results from independent research laboratories within very short time from the publication date of document E7, it was evidently routine to change systematically the process parameters so as to maximize the transition temperature. By carrying out such routine experimentation, the skilled person would, in the Board's opinion, arrive at a sample comprising a superconducting phase having a composition with the oxygen parameter Delta equal to 1.

5.5.5. Therefore, in the Board's judgement, the subject matter of independent claim 11 according to the first auxiliary request does not involve an inventive step within the meaning of Article 56 EPC. The claims according to the first auxiliary request are therefore not allowable.

5.6. Second auxiliary request

Claim 11 according to the second auxiliary request differs from that of the first auxiliary request in that the L-M-A-O complex comprises multiple phases. Since this feature is known from document E7, the subject matter of claim 11 according to the second auxiliary request does not involve an inventive step for the same reasons as for the first auxiliary request.

5.7. Third auxiliary request

An objection of lack of novelty against the claims 1 to 3. and 8 to 10 as granted, which now form the basis of the third auxiliary request, was raised by the Opponent II in the statement of opposition having regard to document E14 on the assumption that the document belonged to the state of the art pursuant to Article 54(3) EPC. In the decision under appeal, the opposition division concluded that these claims were novel (cf. Reasons, item 5.2.4). The Opponent II filed the complete priority documents E14a to E14c with the statement of the grounds of appeal, but did not dispute the novelty of claims 1 to 3 and 8 to 10 and did not provide any arguments to substantiate such an objection. Therefore, the patentability of the claims according to the third auxiliary request was not in dispute in the appeal proceedings (cf. G 9/91, OJ EPO 1993, 408).

The description of the patent in suit needs to be adapted to the claims according to the third auxiliary request, so that the Board decides to remit the case to the opposition division for further prosecution.