In this examination appeal Claim 1 of the main request before the Board read:
An electroluminescent device comprising:
- a first charge-carrier injecting layer for injecting positive charge carriers and a second charge-carrier injecting layer for injecting negative charge carriers, at least one of the charge-carrier injecting layers being patterned so as to comprise spaced-apart charge-injecting regions;
- an organic light-emitting layer located between the first and second charge-carrier injecting layers; and
- an unpatterned conductive polymer layer located between the organic light-emitting layer and the patterned charge-carrier injecting layer, the resistance of the conductive polymer layer being sufficiently low to allow charge carriers to flow through it from the charge-injecting regions to generate light in the organic light-emitting layer and the sheet resistance of the conductive polymer layer being greater than 106 Ohms/square so as to resist lateral spreading of charge carriers beyond the charge-injecting regions.
Claim 1 of the first auxiliary request had an additional disclaimer:
…excluding electroluminescent devices wherein the unpatterned conductive polymer layer comprises polyaniline emeraldine salt.
The Board found these requests unallowable:
Main request
Novelty, inventive step
[2.1] Since document D3 is pre-published prior art in accordance with A 54(2) EPC 1973, as opposed to document D2 which is considered as comprised in the state of the art in accordance with A 54(3) EPC and Article 54(4) EPC 1973, it is considered expedient to consider document D3 first.
Novelty
[2.2] Document D3 relates to an organic electroluminescence device, which can be easily fabricated and used as a large area light emitting device for various displays. The device comprises a light emitting layer and a charge transport layer disposed between a pair of electrodes, the charge transport layer comprising a conducting polymer […].
In particular, document D3 discloses, in the terms of claim 1, an electroluminescent device comprising:
a first charge-carrier injecting layer for injecting positive charge carriers and a second charge-carrier injecting layer for injecting negative charge carriers (2, 4);
an organic light-emitting layer (3) located between the first and second charge-carrier injecting layers; and
an unpatterned conductive polymer layer (5) located between the organic light-emitting layer and charge-carrier injecting layer (2).
Moreover, according to D3, when the light emitted is to be taken out from the conducting polymer side of the EL device, the electrical conductivity of the conductive polymer is preferably 0.1 S/cm or less […].
The thickness of the conductive polymer layer is for instance 100 Å. In fact, as can be seen from the specific examples in table 1, the best results are obtained with a conductive polymer layer of polyaniline with a thickness of 100 Å (example 11) […].
The sheet resistance of a conductive polymer layer having a thickness t of 100 Å and an electrical conductivity σ of 0.1 S/cm or less, using
Rs = 1/ σ t
is 107 Ohm/square or more.
Accordingly, the conductive polymer layer according to example 11 has a “sheet resistance [...] being greater than 106 Ohms/square” as per claim 1.
The appellant argued that D3 provided no direct and unambiguous disclosure of a conductive polymer layer having a sheet resistance of greater than 106 Ohms/square. It was clear that there was no explicit disclosure of this sheet resistance in D3. Following the EPO Guidelines for Examination Part G, Chapter VI, section 6, “an objection of lack of novelty of this kind should be raised by the examiner only where there can be no reasonable doubt as to the practical effect of the prior teaching”. However, there was reasonable doubt as to the practical effect of the disclosure of D3. In order to provide a novelty-destroying disclosure the skilled person would have needed to have combined one particular value of the layer thickness with a particular value for electrical conductivity of the layer from separate passages of the disclosure and in a further step combine these parameters using the above equation to arrive at a value for the sheet resistance.
For an implicit disclosure to be novelty destroying the skilled person had to inevitably arrive at a result falling within the terms of the claim. Even if the skilled person had considered combining the disclosed range of conductivity with a value for layer thickness in order to arrive at a value for sheet resistance the skilled person would not have inevitably arrived at a value of greater than 106 Ohms/square. For example, instead of taking the value of 100 Å as proposed by the Board the skilled person could equally have taken a value of 1 μm, leading to a sheet resistance of 105 Ohms/square for a conductivity of 0.1 S/cm, or 10 μm, leading to a sheet resistance of 104 Ohms/square, outside of the claimed range. Reference was also made to decisions T 793/93 and T 204/00 as cited in the Case Law, 6th edition, 2010, page 560.
The board, however, cannot agree with the above arguments. According to document D3, the electrical conductivity of the conductive polymer layer is 0.1 S/cm or less […].
In particular, it is disclosed in D3 that
“it is known that the conducting polymer of the general formula (2) has an increased electrical conductivity when doped with impurities such as sulfuric acid, iodine, iron (II) chloride, etc. It is also known that, in the state in which the electrical conductivity is increased as described above, absorbance in a visible wavelength region is also increased and optical transmittance is greatly reduced to lose transparency. Therefore, the doping is not preferably carried out when a light emitted is to be taken out from the conducting polymer side of the EL device. Since the absorption spectrum correlates with the electrical conductivity, the electrical conductivity is preferably 0.1 S/cm or less”.
Conductivity values outside the range of 0.1 S/cm or less are in fact not disclosed in D3 and only this range is claimed in D3.
As to the thickness of the conductive polymer layer, document D3 discloses, with respect to the embodiment of figure 2 of relevance in the present case,
“for example, 50 angstroms to 10 micrometers and preferably 100 angstroms to 1 micrometer to increase a current density so as to increase a light emitting efficiency” […].
Moreover, as pointed out above, a number of specific examples are provided […] in which example 11 with a layer thickness of 100 Å is indicated to provide the best results in terms of the uniformity of the emitted light.
Accordingly, a conductive polymer layer having a thickness of 100 Å and a conductivity of 0.1 S/cm or less is an embodiment of document D3.
It is noted that, contrary to what the appellant’s arguments would appear to suggest, in D3 no selection from two or more lists of a certain length has to be made in order to arrive at the specific combination of thickness and conductivity, leading to the sheet resistance value claimed (i.e. a selection according to the “two-lists principle”). In fact, for a thickness of e.g. 100 Å as discussed above, the entire range of disclosed conductivities of 0.1 S/cm or less results in a sheet resistance falling within the claimed range. Accordingly, for the conductivity there is no selection from a list. Even for the thickness of the layer, it is doubtful whether a selection from a list in the sense of the above two-lists principle is present, as in D3 the specific thickness of 100 Å is highlighted as producing a device with the best light-emitting properties (table 1, caption).
Neither can it be held that in a further step the skilled person would have to “combine” these parameters using an equation to arrive at a value for the sheet resistance. What is required in the present case in order to arrive at the claimed value for the sheet resistance, is the mere conversion, using a standard equation, of the physical quantities (electrical conductivity and thickness) used in D3 to define the physical properties of the conductive polymer layer into the physical quantity (sheet resistance) used in claim 1 of the present application.
Furthermore, it is noted that both the “practical effect of the prior teaching”, as mentioned in the Guidelines for Examination in the EPO, and in the decisions T 793/93 and T 204/00 referred to by the appellant, relate to the case where it cannot be determined with certainty that the outcome of a prior art teaching, for instance a manufacturing process, leads to e.g. a particular parameter value falling within the terms of the claim, as not all conditions are specified. This has, however, no bearing on the present case, as no uncertainty exists as to what might or might not be the result of carrying out the prior art teaching. In fact, the thicknesses and conductivities of the conductive polymer layer are unambiguously specified in D3, and with that the resulting sheet resistance of the layer.
Moreover, the appellant’s argument that other thickness disclosed in D3, in combination with a conductivity of 0.1 S/cm, would provide sheet resistances falling outside the claimed range is of no relevance, as for lack of novelty it is not a prerequisite that all embodiments of the prior art fall within the claimed subject-matter.
In document D3, however, neither of the first and second charge-carrier injecting layers (2, 4) is “patterned so as to comprise spaced-apart charge-injecting regions” as defined in claim 1.
Accordingly, the subject-matter of claim 1 of the main request is new over document D3 (A 54(1) EPC 1973).
Inventive step
[2.3] As discussed above, the subject-matter of claim 1 differs from document D3 in that at least one of the charge-carrier injecting layers is patterned so as to comprise spaced-apart charge-injecting regions.
The effect of hereof is that the electroluminescent device can produce a patterned image.
In view of the above, the objective problem to be solved relative to D3 is to make the organic electroluminescent device of D3 suitable for displaying a patterned image.
However, as also acknowledged by the appellant, patterning is common in organic electroluminescent devices. Moreover, it would be obvious to a person skilled in the art working in the field at issue of electroluminescent devices, to pattern at least one of the charge-carrier injecting layers so that it comprises spaced-apart charge-injecting regions providing the desired patterned image.
The appellant argued that document D3 did not provide a patterned charge-carrier injecting layer and was not concerned with resisting lateral spreading of charge carriers beyond charge-carrier injecting regions and blurring of the display image. Thus, the skilled person would not have been motivated to consider the sheet resistance of the polymer layer, and would therefore not be taught to combine the parameters of conductivity and layer thickness in the manner suggested by the board. In fact, document D3 was concerned with the uniformity of the display [...]. Accordingly, it was not a suitable starting point for an assessment of inventive step.
It is however noted that also with a patterned charge-carrier injecting layer, applying the teaching of document D3 regarding the conductive polymer layer, i.e. providing a layer of 100 Å with a conductivity of 0.1 S/cm or less, results in a conductive polymer layer with a sheet resistance within the claimed range and which, consequentially, adequately resists lateral spreading of charge carriers beyond charge-carrier injecting regions and prevents blurring of the display image. Moreover, it is noted that the uniformity of the light emission of the organic electroluminescence display device, the light emitting efficiency and luminance addressed in D3 are equally important properties for a display device providing a patterned image. Since in D3 the conductive polymer layer, in particular its conductivity and thickness, is selected so as to optimise these properties, it would be obvious to the skilled person to use the same conductive polymer layer for a display device providing a patterned image.
The subject-matter of claim 1 according to the main request, thus, lacks an inventive step in the sense of A 56 EPC 1973.
Accordingly, the appellant’s main request is not allowable.
First auxiliary request
[3] Claim 1 according to the first auxiliary request includes with respect to claim 1 of the main request the following addition:
“excluding electroluminescent devices wherein the unpatterned conductive polymer layer comprises polyaniline emeraldine salt”.
The above addition to claim 1 is an undisclosed disclaimer intended to confer novelty over D2, which is considered as comprised in the state of the art under A 54(3) EPC and A 54(4) EPC 1973.
However, according to G 1/03 [order 2.3]
“a disclaimer which is or becomes relevant for the assessment of inventive step [...] adds subject-matter contrary to A 123(2)”.
Since in the present case the subject-matter of claim 1, disregarding the disclaimer, lacks an inventive step for the reasons given above for the main request, the disclaimer becomes relevant for the assessment of inventive step of the subject-matter of claim 1 according to the first auxiliary request and thus, in accordance with G 1/03 above, adds subject-matter contrary to A 123(2).
Accordingly, the appellant’s first auxiliary request is not allowable.
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