T 0323/13 05-03-2015

Reasons for the Decision

1. The appeal is admissible.

2. Admissibility of documents

2.1 Documents D8b and D36 to D52 were filed in the course of the present appeal proceedings.

2.2 D8b and D36 to D48 were submitted by the appellants at the earliest possible time during the appeal proceedings, namely with their respective statements of grounds of appeal. The documents do not create any fresh case but support the appellants' attacks based on the grounds of Article 100(c) EPC (D36 and D37) and lack of inventive step (D8b and D38 to D48). The board therefore decided to admit these documents into the proceedings.

2.3 D49 to D50 were filed by the respondent in response to the statements of grounds of appeal, i.e. equally at the earliest possible time during the appeal proceedings. D49 and D50 represent a continuation of the respondent's defence against the appellant's attacks on novelty (D49) and inventive step (D50) and therefore do not create any fresh case in the present appeal proceedings. D51 merely illustrates the structure of the respondent's claim requests and was not objected to by the appellants. Therefore, the board decided to admit D49 to D51 into the proceedings.

2.4 D52 was filed by appellant III with its letter of 5 February 2015. The respondent did not object to the admittance of this document and the board does not see any reasons for not admitting it. Accordingly, the board decided to also admit D52 into the proceedings.

Main request

3. Admittance into the proceedings

The main request differs from the first auxiliary request held allowable by the opposition division in that the back-reference in claim 7 to any one of the preceding claims 1 to 6 was amended to a back-reference to claims 1 to 5 and in that the erroneous double denomination of "2-phenxylbenzoxazole" was removed. These amendments constitute a reaction to objections raised by the board during the oral proceedings and, in the absence of any objection from the appellants' side, the board admitted the main request into the proceedings.

4. Amendments - Article 123(2) EPC

The amendment of the back-reference in claim 7 merely excludes the back-reference to claim 6, which was erroneous since the compounds referred to in claim 7 all form five-membered rings while claim 6 requires the rings to consist of six atoms.

The deletion of "2-phenxylbenzoxazole" was necessary since this compound was cited twice in claim 7.

These amendments thus do not add any subject-matter to claim 7 and therefore meet the requirements of Article 123(2) EPC.

5. Amendments - Article 100(c) EPC

5.1 Claim 1 contains the feature "An organic light emitting device comprising an anode, a cathode and an emissive layer, wherein the emissive layer is located between the anode and the cathode,...". According to appellants I and III, this feature is not based on the application as filed.

5.1.1 The board does not concur with this view, but considers claim 1 as filed to provide a basis for this feature. This claim discloses "An organic light emitting device comprising an emitter layer ...". Hence, claim 1 as filed provides a basis for OLEDs comprising an emitter layer. The board acknowledges that claim 1 as filed does not disclose the presence of an anode and a cathode in the OLED in an explicit manner. However, the board in this respect agrees with the respondent that it belonged to the skilled person's common general knowledge at the priority date of the patent that every OLED contained an anode and a cathode with the emissive layer being located therebetween. This is in fact supported by the application as filed. More specifically, the application as filed uses the terms "organic light emitting diode" and "organic light emitting device" synonymously and, as not disputed by the appellants, diodes contain by definition an anode and cathode. Reference is made in this respect to the title on page 1 ("ORGANIC LEDS", LED standing for light emitting diode), page 4, line 8 ("organic light emitting diodes") and page 1, line 15 as filed ("Organic light emitting devices").

5.1.2 Appellants I and III argued in this respect that D36 and D37 proved that OLEDs not having an anode or cathode existed, and that hence the disclosure of an OLED in claim 1 of the application as filed did not imply the presence of an anode and a cathode.

The board does not agree. Firstly, D36 and D37 are from 2013 and 2004, respectively, and thus cannot prove that at the priority date of the patent (1999) the skilled person would have considered OLEDs to not necessarily contain an anode and a cathode. Secondly, the devices disclosed in these documents are denoted electroluminescence devices ("FIPEL device" in D36 and "EL device" in D37) rather than OLEDs. In fact, D36 even contrasts the FIPEL device described in this document to a standard organic-light emitting diode (OLED) (first and second paragraph of the introduction). So, these documents disclose EL devices without anode and cathode, rather than OLEDs without anode or cathode.

5.1.3 The appellants argued that OLEDs containing an anode, a cathode and only one emitter layer, which are covered by claim 1 of the main request, were not based on the application as filed. However, as set out above (point 5.1.1), in the same way as claim 1 of the main request, claim 1 as filed refers to OLEDs comprising an emitter layer, which covers the presence of only one emitter layer. The appellants' argument is therefore not accepted.

5.1.4 Former appellant II had argued in the written proceedings that the application as filed only disclosed organic layers separating the anode and cathode which, in its view was different from a layer between the anode and cathode as required by claim 1 of the main request. However, the board is not able to see any difference between layers separating or being between an anode and cathode, and in the absence of any further arguments from appellants I and III, does not find this argument convincing.

5.1.5 Therefore, the feature "An organic light emitting device comprising an anode, a cathode and an emissive layer, wherein the emissive layer is located between the anode and the cathode,..." is based on the application as filed.

5.2 Claim 1 requires the ligand L in complex L2MX to be a monoanionic bidentate ligand. According to appellants I and III, this definition of L is not based on the application as filed.

The board does not concur with this view either and considers page 12, lines 11 to 15 of the application as filed as an appropriate basis for the definition of L in claim 1. In this passage, the following is disclosed:

"The invention is further directed to organometallic complexes of metal species M with a bidentate monoanionic ligand in which M is coordinated with an sp**(2) hybridized carbon and a heteroatom at the ligand. The complex may be of the form L3M (wherein each ligand L is the same), LL'L''M (wherein each ligand species L, L', L'' is distinct), or L2MX wherein X is a monoanionic bidentate ligand."

The first sentence of this passage requires the complex to have a bidentate monoanionic ligand in which M is coordinated with an sp**(2) hybridized carbon and a heteroatom at the ligand. The next sentence gives examples of such complexes, the first one being complexes of the formula L3M. The only ligand present in this complex is ligand L. Consequently, based on the definition in the first sentence, L must be a bidentate monoanionic ligand coordinated to M with an sp**(2) hybridized carbon and a heteroatom. The same ligand L is present in the further example given in this sentence, namely in complex L2MX. Hence also in this complex, which is the one of claim 1, L must be a bidentate monoanionic ligand coordinated to M with an sp**(2) hybridized carbon and a heteroatom. This definition of L is identical to the definition of L in claim 1, which is thus based on the application as filed.

5.3 Claim 1 as filed contains the feature "wherein the emitting layer provides an emission which has a maximum at a particular wavelength". This feature has been deleted in claim 1 of the main request. Appellant III argued during the written proceedings that by way of this deletion, claim 1 extended over the content of the application as filed.

However, since claim 1 requires the OLED to comprise an emissive layer, it is inherent to the organic light emitting device of claim 1 that it has an emission with a maximum at a certain wavelength. Therefore, the deletion referred to by appellant III does not violate the requirements of Article 100(c) EPC.

5.4 Each of claims 5 to 10 are dependent on more than one of the corresponding previous claims. According to appellants I and III, the combination of features created by several of these claim dependencies is not based on the application as filed.

The appellants in particular argued that claim 8, in so far as it is dependent on claim 7, was not based on the application as filed. Claim 8 defines ligand X by a list of five compounds and claim 7 defines ligand L by a list of nine compounds. These ligands are disclosed on page 17, lines 24 to 25 (ligands X) and page 17, lines 20 to 23 (ligands L) of the application as filed. From the ligands X disclosed in the application as filed, all the ligands have been chosen in claim 1, and from ligands L, nine of the eleven have been chosen.

The definitions for ligands X and L are disclosed in the above-mentioned passages of the application as filed in general terms. The skilled person reading the application as filed would therefore clearly and unambiguously derive therefrom that these definitions apply to all embodiments disclosed in the application as filed, and that hence the disclosure of the ligands X also applies to and thus can be combined with that of the ligands L. The fact that only nine of the eleven ligands L disclosed in the application as filed have been chosen does not change this conclusion since such a selection does not represent a singling out of specific embodiments. Consequently, claim 8 as dependent on claim 7 is based on the application as filed.

The same applies to all other claim dependencies attacked by the appellants, i.e. the features of the attacked claims are disclosed in the application as filed in a general way, which features the skilled reader would combine with other embodiments of the invention. Nor does such a combination of features lead to the singling out of particular embodiments.

5.5 For the above reasons, the ground under Article 100(c) EPC does not prejudice the maintenance of the patent in the form of the main request.

6. Amendments - Article 123(3) EPC

6.1 Former appellant II argued in the written proceedings that claim 11 violated the requirements of Article 123(3) EPC. To arrive at claim 11 from claims 18 and 19 of the patent as granted the term "display device" has been amended to read "device". Hence the word "display" has been deleted and according to the appellant, this broadens the scope of protection conferred by the patent.

6.2 However, the broadest claim of the patent as granted is claim 1 and this refers to an organic light emitting device without any restriction to a display device or any other type of device. Therefore, the fact that the device of claim 11 is no longer restricted to a display device does not extend the scope of protection conferred by the granted patent. Consequently, the requirements of Article 123(3) EPC are not violated.

7. Sufficiency

7.1 The complex referred to in claim 1 is defined in structural terms in that it contains one metal M, two ligands L and one ligand X (formula L2MX) and in that (a) the two ligands L are monoanionic bidentate ligands each coordinated to the metal M through an sp**(2) hybridized carbon and a heteroatom and (b) ligand X is a monoanionic bidentate ligand that is not equivalent to ligand L. At the same time, the complex is functionally defined as being phosphorescent.

Appellants I to III argued that not all complexes having a structure as required by claim 1 were phosphorescent. Therefore, the skilled person had to find phosphorescent complexes by trial an error. This amounted to an undue burden such that the invention defined in claim 1 was insufficiently disclosed.

7.1.1 As set out in T 544/12 (point 4.2), a definition of a group of compounds in a claim by both structural and functional features is generally acceptable under Article 83 EPC as long as the skilled person is able to identify, without undue burden, those compounds out of the host of compounds defined by the structural feature(s) in the claim which also fulfil the claimed functional requirement(s). Sufficiency of disclosure may for instance be acknowledged if all embodiments defined by the structural feature(s) of the claim also meet the claimed functional requirement(s). If this is not the case, sufficiency may still be acknowledged if the common general knowledge at the priority date of the patent, or the patent itself, provides the skilled person with sufficient guidance on how to select those compounds out of the host of compounds defined by the structural feature(s) of the claim that also meet the claimed functional requirement(s).

7.1.2 In the present case, it has been shown by the appellants in D35 that Irppy2acac, which falls under the structural definition of claim 1, has no phosphorescent emission at all. Furthermore, in its letter of 5 February 2015, appellant III cited eight iridium complexes falling under the structural definition of claim 1 that had either a very weak or no emission at all. These facts were not put into question by the respondent. There can thus be no doubt that not all complexes falling under the structural definition given in claim 1 are phosphorescent.

7.1.3 The crucial question therefore is whether the patent or the common general knowledge provides the skilled person with sufficient guidance to select those complexes falling under the structural definition of claim 1 that are phosphorescent.

7.1.4 This question has to be answered in the affirmative. Firstly, the patent contains numerous examples of complexes which are phosphorescent (page 11, line 4 to page 13, line 40 and figures 8, 10, 12, 14, 17, 19, 21, 22, 25, 26, 27, 29, 31 33, 35 and 36). Secondly, apart from these specific complexes, the patent provides guidance how to select ligands L and X within the structural definition of claim 1 in order to obtain complexes that are phosphorescent. Firstly, the patent teaches in paragraph [0090] to use ligands L that have a high fluorescent quantum efficiency, since thereby it is possible to use the strong spin orbit coupling of the Ir metal to efficiently intersystem cross in and out of the triplet states of the ligands. Secondly the skilled person is taught by paragraph [0099] to use ligands X that have higher triplet levels than the L2Ir framework since otherwise the energy from the triplet levels of the L ligands is transferred to the triplet levels of the X ligands such that emission comes from the X rather than from the L ligands. Thirdly, the skilled person is taught by paragraph [0100] not to use hexafluoro-acac and diphenyl-acac as ligand X.

Consequently, unlike the case in T 544/12, the patent in the present case provides a number of specific examples and a general teaching how to obtain complexes falling under the structural definition of claim 1 that are phosphorescent. This teaching would also enable the skilled person to avoid the failures reported by the appellants. More specifically, nearly all complexes cited in appellant III's letter of 5 February 2015 contain the X ligand acac and a pyrazol structure in ligand L. Acac has a lower triplet level than the pyrazol group, which is to be avoided according to the teaching of the patent (paragraph [0099]). Furthermore, the patent (paragraph [0100]) explicitly teaches the skilled person not to use complexes with hexafluoro-acac ligands as tested in D35 and furthermore also teaches one how to transform the failure in D35 into success, namely by choosing ligands X with a higher triplet level.

Consequently, at the very least for iridium complexes, no undue burden is needed to select those that are phosphorescent.

7.1.5 Appellants I and III argued that the invention as defined in claim 1 was not sufficiently disclosed for platinum complexes. In order to arrive at octahedral complexes L2PtX as covered by claim 1, the platinum would have to be in the oxidation state III. No such complexes would exist.

However, the patent explicitly mentions in paragraph [0070] the octahedral complex PtL3, which, according to the general synthesis method given in the patent, would be the starting material for L2PtX complexes. No proof was provided by the appellants that the reference in the patent to PtL3 was wrong. In the light of this reference in paragraph [0070] of the patent to PtL3, the appellants' objection amounts to a mere allegation which cannot succeed.

As regards this paragraph [0070] of the patent, the appellants argued that it was stated in this passage that complexes PtL3 could not be sublimed. It was thus not possible in their view to manufacture OLEDs containing PtL3 or L2PtX complexes. However, all that is stated in paragraph [0070] is that compounds of the formula PTL3 cannot be sublimed without decomposition. This only implies that OLEDs on the basis of these platinum complexes cannot be prepared by sublimation of the complex. However, as set out by the respondent during the oral proceedings, and as not disputed by the appellants, it is also possible to incorporate platinum as a solution into the host and apply this dopant-host system in the form of a solution rather than by sublimation. Consequently, the statement in paragraph [0070] of the patent does not imply that it is not possible to manufacture OLEDs containing complexes of platinum.

Appellants I and III finally argued that the skilled person would not be able on the basis of the opposed patent to identify platinum complexes that were phosphorescent. However, as explained by the respondent during the oral proceedings and as not disputed by the appellants, the teaching given in the patent to identify ligands L and X that lead to phosphorescent complexes is applicable irrespective of the type of metal present in the complex. Consequently, the skilled person is enabled by this teaching in the patent to prepare phosphorescent platinum complexes.

Hence, also for complexes different from iridium complexes, and in particular for platinum complexes, no undue burden is required to identify those that are phosphorescent.

7.2 Appellants I and III argued that claim 1 did not specify the structure of the OLED. The skilled person had therefore to find out by way of trial and error which OLED structures gave phosphorescent emission.

The board does not agree with this argument. Firstly, the patent teaches the skilled person how to select appropriate OLED structures. More specifically, the general structure of OLEDs is described in paragraphs [0021] to [0031]. Suitable host materials are described in paragraphs [0082] to [0083]. The type of layers present in the OLED and specific examples thereof are disclosed in paragraphs [0084] to [0089]. Secondly, OLEDs were known for several years before the priority date of the opposed patent and hence the patent does not represent the first invention about an OLED. Basics of OLED structures thus formed part of the skilled person's common general knowledge at the priority date. Consequently, taking the patent and its common general knowledge into account, the skilled person would have been able to select without undue burden appropriate OLED structures that led to phosphorescence.

7.3 Appellants I and III additionally argued that it was not sufficiently defined in the patent to what extent the complex according to claim 1 had to emit phosphorescent light in order to qualify as being phosphorescent.

This argument is not persuasive. It is true that claim 1 does not define the extent of phosphorescence. However this only means that it covers phosphorescent complexes irrespective of whether their emission is weak or strong, which is an issue of broadness rather than clarity. Furthermore, even if the extent of phosphorescence is unclear in claim 1, this as such would not lead to any insufficiency of disclosure (T 593/09, catchword and point 4.1.4)

7.4 According to the appellants, phosphorescence is dependent on numerous conditions such as temperature, environment and the concentration of the complex.

The appellants have not however provided any proof for this assertion. They have in particular not shown that the alleged lack of clarity is present to such an extent that the feature "phosphorescent" is deprived of any real meaning such that it does not function as a selection criterion for the identification of suitable complexes. Therefore, this argument of the appellants, if anything, is also only concerned with lack of clarity.

7.5 Appellant I additionally argued in the written proceedings that there was no guidance in the patent on how complexes having a six-membered ring comprising the metal, an sp**(2) hybridised carbon atom and a heteroatom could be synthesized. There is however no evidence that it is not possible to synthesise these complexes or that the synthesis route that is described in the patent in general terms (reaction scheme in paragraph [0044]) is not applicable for ligands L forming a six-membered ring. In the absence of any such proof, the appellant's assertion cannot be accepted.

7.6 Former appellant II argued in the written proceedings that in so far as ligand L was coumarin, as e.g. required by claim 7, it could not act as a monoanionic bidentate ligand coordinating through an sp**(2) hybridised carbon and a heteroatom. No further details or evidence were however provided. In view of this, also this objection is without substance.

7.7 Appellants I and III finally argued that the complex in figure 12 of the patent showed an emission with a lifetime of less than 1 µs, which according to paragraph [0072] of the patent implied that the emission was not a phosphorescent emission.

The board does not agree. In paragraph [0072], it is stated that in most cases the tested iridium complexes had emissions with lifetimes of 1 to 3 µs and that such a lifetime was indicative of phosphorescence. This statement does not however allow the reverse conclusion to be drawn that an emission with a lifetime of less than 1 µs automatically is a non-phosphorescent emission.

7.8 For the above reasons, the ground under Article 100(b) EPC does not prejudice the maintenance of the patent in the form of the main request.

8. Novelty

8.1 Novelty was only attacked in view of D5.

8.2 The priority dates of D5 are 30 June and 10 August 2000, which both are after the priority date of the opposed patent (1 December 1999). D5 thus is only prior art if the priority of the claims of the main request is not valid.

The priority document of the opposed patent is identical to the application as filed. For the same reasons as given above under Article 100(c) EPC, the subject-matter of the claims of the main request is therefore clearly and unambiguously derivable from the priority document. Consequently, the priority of the claims of the main request is valid. D5 thus does not form part of the prior art and thus cannot be used to attack novelty of the claimed subject-matter.

9. Inventive step

9.1 The invention underlying the opposed patent is directed to OLEDs with phosphorescent emitters (paragraphs [0008] to [0010]).

9.2 In the same way as the opposed patent, D2 refers to phosphorescent OLEDs (second paragraph of the left-hand column on page 4). Therefore, in line with the arguments of all parties, D2 can be considered to represent the closest prior art.

D2 describes the performance of an OLED containing, as a luminescent layer, the organometallic iridium compound Irppy3 doped into a CBP (4,4'-N,N'-dicarbazole-biphenyl) host (abstract and penultimate paragraph of page 4). This layer is located between a cathode and an anode (first paragraph of the left-hand column on page 5). As acknowledged by all parties, the organometallic compound of claim 1 differs from that of D2 in that only two rather than all three ligands of the metal are the same, i.e. in that it has a formula L2MX rather than L3M.

9.3 The respondent argued that the objective technical problem solved in view of D2 was to expand the range of emission colours of OLEDs and to allow fine tuning of these colours. This issue is addressed in the opposed patent in paragraph [0013] and section "V.B.4 Color Tuning".

9.4 As a solution to this problem, the patent proposes the organic light emitting device of claim 1, which is characterised in that it contains an emissive layer, which comprises the phosphorescent organometallic compound L2MX rather than the L3M complex of D2.

9.5 It has be be examined whether the above problem (point 9.3) has been credibly solved.

9.5.1 D50 shows the emission colour of (i) Irppy3 and Ir(ppy)2acac, (ii) IrBQ3 and IrBQ2acac and (iii) Irthpy3 and Irthpy2acac. It follows from D50 that by replacing one of the three identical ligands in any of Irppy3, IrBQ3 and Irthpy3 by acac, a shift in emission colour occurs. Furthermore, it can be seen in figure 37 of the opposed patent that the variation of X in L2IrX (X = pico, acac and sd) leads to a shift of the emission spectra.

9.5.2 Appellants I and III argued that a colour shift was not obtained for all complexes covered by claim 1. Firstly, the patent states in paragraph [0097] that the emission spectra of some IrL3 and L2IrX complexes were "very similar" and that in some cases there was "no significant shift in emission" between IrBQ3 and Irthpy3 on the one hand and their respective IrL2acac derivatives on the other hand. Secondly, according to paragraph [0097], Irppy3 and Irppy2acac both gave a strong green emission with the same lambdamax of 510nm.

However, the fact that emission stays "very similar" and "no significant shift" occurs does not necessarily imply that there is no change in emission colour at all. Furthermore, the fact that the emission maximum for both complexes Irppy3 and Irppy2acac is observed at the same wavelength does not necessarily mean that the colours are identical. More specifically, what matters for the emission colour is not only the wavelength of the maximum lambdamax but also the shape of the emission curve, and the latter is not disclosed in paragraph [0097].

In fact, it is deducible from D50 that there is a change in colour if, in any of Irppy3, IrBQ3 and Irthpy3, one ligand is exchanged by an acac ligand. So, the appellants' interpretation of paragraph [0097] of the patent contradicts the experimental findings in D50.

9.5.3 Appellants I and III furthermore argued that D1 proved that the replacement of one of the 1-phenylisochinoline ligands in Ir(1-phenylisochinoline)3 by acac did not change the emission colour (bottom of page 2 and figure 1). However, the board concurs with the respondent's view expressed during the oral proceedings that the two emission spectra in figure 1 of D1 are not identical. It thus cannot be deduced from this figure that no colour shift occurs.

9.5.4 Appellants I and III argued that the results in D50 did not support inventive step since the effect demonstrated in D50, namely a colour shift in terms of CIE coordinates, was not derivable from the patent. This is however not correct. More specifically, the question whether the substitution by different ligands affects emission colour is discussed in detail in paragraph [0013] and section "V.B.4 Color Tuning" of the patent and CIE coordinates are a commonly used means to characterise emission colour.

9.5.5 Appellants I and III argued that no experimental details such as the type of host or the measurement temperature were given in D50 and that the types of complexes (meridional or facial) were not given. Possibly at other temperatures, hosts or types of complexes, no colour shift would have occurred.

These arguments are however pure speculation which, without any substantiation, cannot be accepted.

9.5.6 Appellants I and III finally argued that it could not be excluded that the complex L2MX transferred its energy to another emitter in the host, and that therefore the phosphorescence observed in the OLED as claimed could also come from this other emitter. Therefore any colour shift in the phosphorescence of the complex L2MX did not necessarily result in a colour shift of the phosphorescence emitted by the OLED.

However, claim 1 requires the emissive layer to comprise the phosphorescent complex. The only meaningful construction of the claim is therefore that the emission of the OLED results from the phosphorescence of this complex rather than any other emitter not mentioned in the claim. A shift in the phosphorescence of this complex thus will result in a shift of the emission of the claimed OLED.

9.5.7 Consequently, the problem of expanding the range of emission colours of OLEDs and of fine tuning these colours has been credibly solved over D2. This problem thus represents the objective technical problem.

9.6 It remains to be examined whether the claimed solution is obvious.

9.6.1 D2 does not address the problem of expanding the range of emission colours of OLEDs. Furthermore, D2 does not contain any motivation to replace one of the three identical ppy ligands of Irppy3 by a different ligand, let alone suggest that thereby the range of emission colours of OLEDs could be expanded.

Appellants I and III argued in this respect that the claimed solution was obvious over D2 since this document stated in the last paragraph of the left-hand column on page 6 that new phosphorescent compounds deserved intensive investigation. The skilled person would therefore have looked for complexes different from Irppy3. He would furthermore have known that exchanging one of the three identical ligands in the Irppy3 complex of D2 would have resulted in a colour shift. Therefore, the skilled person not only could but also would have arrived at the claimed solution.

The board does not concur with this view. Firstly, even if the skilled person would have envisaged modifying the Irppy3 complex of D2, he could have done so in various ways, e.g., by changing the metal present in the complex or by exchanging all three identical ligands by three different ligands. Secondly, as explained by the respondent during the oral proceedings, the claimed solution is based on the finding that meridional isomers of L3Ir complexes show a marked red shift compared to their facial forms. This had motivated the inventors of the patent to test L2MX complexes instead of L3M complexes since L2MX complexes exist only in the form of meridional isomers and thus were expected to lead to a colour shift compared to the L3M complex present as meridional and facial isomer (paragraph [0077] of the patent). The appellant's argument that the skilled person reading D2 would have modified one of the three ligands to obtain a colour shift is therefore based on hindsight.

Consequently, the claimed solution is not obvious in view of D2 alone.

9.6.2 Appellants I and III furthermore argued that the subject-matter of claim 1 was obvious in view of D2 in combination with D3.

D3 is a scientific abstract about a phosphorescent complex. Even if one assumes in the appellants' favour that this complex has a structure as defined in claim 1, D3 does still not suggest that this complex can be incorporated into the emitting layer of an OLED, let alone that thereby the range of emission colours of an OLED could be expanded. Therefore, the skilled person starting from D2 and reading D3 would not have replaced the complex of D2 by that of D3 in order to solve the objective technical problem.

9.6.3 Appellants I and III furthermore argued that the subject-matter of claim 1 was obvious in view of D2 in combination with D7.

D7 is a scientific article disclosing the synthesis of iridium complexes having a formula as required by claim 1 (complexes 16 to 21 on page 192). Even if one assumes in the appellants' favour that the skilled person reading D7 would consider these complexes to be phosphorescent, the subject-matter of claim 1 is not obvious in view of D2 and D7. Firstly, D7 is in a technical field completely unrelated to that of OLEDs, namely that of biological marker molecules. The skilled person starting from D2 and being confronted with the objective technical problem would thus not even have considered D7. Secondly, even if the skilled person had looked into D7, he would not have found any motivation therein to use the complex disclosed in this document instead of that disclosed in D2 in order to expand the emission range of OLEDs.

9.6.4 Appellants I and III additionally argued that the subject-matter of claim 1 was obvious in view of D2 in combination with D8/D8b.

D8/D8b is a PhD thesis that discloses the synthesis of the complex Irmppy2pic, which has a formula according to claim 1. Upon UV irradiation in dichloromethane, a bright green glow is observed (second sentence on page 286). Even if one assumes in the appellants' favour that this implies phosphorescence, the subject-matter of claim 1 is not obvious in view of D2 and D8. Firstly, D8 is in an entirely different technical field than OLEDs, namely that of photochemistry (see reference to photo-reducing agents in the right-hand column on page 276 and to the redox potential of the excited state in the last sentence of the right-hand column on page 286 of D8b). The skilled person would therefore not even have considered D8/D8b when starting from D2 and trying to solve the objective technical problem. Furthermore even if the skilled person had considered this document, he would not have found therein any indication that by replacing the complex of D2 by that of D8/D8b, he would have solved the problem of expanding the emission range of OLEDs.

9.6.5 The appellants finally argued in the written proceedings that the subject-matter of claim 1 lacked an inventive step in view of closest prior art document D2 in combination with any of D6, D14, D15, D16, D18, D25, D27, D29, D30, D31 and D32.

However, in the same way as D3, D7 and D8, none of these documents suggests that by replacing one of the three identical ligands in the complex of D2, the problem of expanding the range of emission colours of OLEDs could be solved.

9.6.6 Consequently, the subject-matter of claim 1 and by the same token of all remaining claims is inventive in view of D2, taken alone as well as in combination with any of the further cited documents.

9.7 D4 as the closest prior art

9.7.1 Apart from D2, the appellants also used D4 as the closest prior art. It was a matter of dispute between the parties whether this document constituted prior art under Article 54(2) EPC.

9.7.2 On the left-hand corner of the first page, D4 contains the following information:

"Pure Appl. Chem. Vol. 71, No. 11, pp. 2095-2106, 1999. Printed in Great Britain © 1999 IUPAC".

This seems to indicate that D4 has been published within the priority year of the opposed patent (1999). However, Ms Meyers, associate director of the International Union of Pure and Applied Chemistry, stated in her letter D49 that "the November 1999 issue (Vol. 71, No. 11) was printed on July 5, 2000" and that there was no release online before printing. The issue referred to in this letter is the one containing D4. D4 was thus published on 5 July 2000, i.e. after the priority date of the opposed patent. Consequently, D4 is not prior art under Article 54(2) EPC and thus not relevant to inventive step.

The title on the first page of D4 contains a reference to a footnote reading "Lecture presented at the 4th International Symposium on Functional Dyes - Science and Technology of Functional Pi-Electron Systems, Osaka, Japan, 31 May - 4 June 1999, pp 2009-2160." The date mentioned in the footnote is before the priority date of the opposed patent. Appellant III argued during the written proceedings that the written disclosure of D4 was identical to the presentation given orally during the mentioned international symposium. However no proof was provided for this allegation. In fact, since D4 cites a document from the year 2000 (reference 11), which is after the date of this international symposium, it must rather be assumed that the content of D4 is not identical to that presented orally at the symposium.

9.7.3 Irrespective of this, taking D4 as the closest prior art does not alter the finding on inventive step. In the same way as D2, it is directed to phosphorescent OLEDs and discloses Irppy3. Hence, the same distinguishing feature is present and the same objective technical problem applies as with regard to D2.

9.7.4 Therefore, the appellant's inventive step attack starting from D4 as the closest prior art must fail.

9.8 The ground under Article 100(a) thus does not prejudice the maintenance of the patent in the form of the main request.