T 0340/13 11-06-2015

Reasons for the Decision

1. The appeal is admissible.

2. Main Request: Article 123(2) EPC and Article 84 EPC 1973

2.1 Claim 1 of the main request includes the feature: "the DBR forming part of the face of only the window which is not being used to exit useful light". The Board, however, finds no disclosure in the application as filed of the DBR forming part of the window (or the face of the window); the DBR and the window are disclosed as two separate features. In this respect, therefore, the subject-matter of claim 1 does not meet the requirements of Article 123(2) EPC.

Moreover, a DBR is a three-dimensional object having a volume, and hence the Board does not see how it could ever be reasonably described as forming part of a face, i.e. a two dimensional surface. The clarity requirements of Article 84 EPC 1973 are therefore not met.

Objections essentially corresponding to those mentioned above formed part of the Board's provisional opinion set out in the communication under Article 15(1) RPBA. During the oral proceedings the appellant offered no comments in this regard, and the Board sees no reason to change its position.

The main request cannot therefore be allowed, as claim 1 does not meet the requirements of Article 123(2) EPC and Article 84 EPC 1973.

3. 1st Auxiliary Request: Novelty

3.1 Claim 1 of the 1st auxiliary request defines a transparent substrate "forming an outermost layer on one side of the light emitting diode". If the substrate is identified with "GaP-Substrat 1" in document D4, then the claimed feature is not disclosed.

On the other hand, if the element 1 and the layers collectively labelled 10 in Fig. 2 of document D4 could reasonably be regarded as forming a composite substrate on which LED 20 is formed, then the cited feature would have to be considered as being disclosed.

In semiconductor technology the term "substrate" often refers to a structure comprising a single layer, but is also routinely used to refer to a structure having multiple layers, and it can well be imagined that cases may arise in which it is unclear whether one or more layers should properly be regarded as being part of the substrate or part of a device deposited on the substrate, or where such a distinction is essentially arbitrary.

The Board is satisfied that the device of document D4 does not represent such a case. The invention of document D4 relates to a bicolour light emitting semiconductor device in which a key idea is to deposit two active devices (first and second LEDs 10 and 20, having different wavelengths) on the same substrate. According to the normal terminology used in the field, the layers of the LED 10 do not form part of a composite substrate on which the LED 20 is formed, but form a separate active device, itself deposited on substrate 1.

It is therefore not disclosed in document D4 that the substrate 1 forms an outermost layer on one side of the light emitting diode, and hence the subject-matter of claim 1 of the 1st auxiliary request is new within the meaning of Articles 52(1) EPC and 54 EPC 1973.

4. 1st Auxiliary Request: Inventive step

4.1 Document D5 was identified in the contested decision as the closest prior art. For the reasons set out in the communication under Article 15(1) RPBA, and further explained to the appellant during oral proceedings, the Board does not regard this document as a suitable starting point for the discussion of inventive step, and document D4 also is not considered suitable. The closest prior art is in fact seen as the second working example of document D1 (Figs. 3(a) to 5, and paragraphs [0030] to [0041]).

As best seen in Fig. 3(a), this example discloses a light emitting diode comprising a transparent substrate 1, a light emitting region 3, a window 5 and a Distributed Bragg Reflector (DBR) 9 that reflects light in a range of wavelengths arriving at a range of incident angles (true of any DBR).

Hence, claim 1 of the 1st auxiliary request differs in that:

- "light generated by the light emitting diode exits through the transparent substrate, the transparent substrate forming an outermost layer on one side of the light emitting diode"; and

- "the DBR being formed directly on the window, such that the DBR is positioned on another side of the light emitting diode that is opposite to the one side from which the light exits the light emitting diode."

4.2 In other words, Fig. 3(a) of document D1 discloses an arrangement essentially according to Fig. 1 of the present application, whereas what is presently claimed is the arrangement of Fig. 2 (hereinafter referred to as the "inverted" arrangement). Compared to an LED having no reflector, both of these arrangements can be seen as solving the problem alluded to in the description of the present application (see page 1, lines 19-22) of reducing light loss.

4.3 However, the application does not disclose any specific advantage of the arrangement of Fig. 2 over that of Fig. 1, and gives no indication that these two arrangements represent anything other than alternative possibilities for solving the above problem. Since the Board does not see any clear advantage offered by the claimed inverted arrangement in comparison with the non-inverted arrangement of the closest prior art, the problem is regarded as providing an alternative arrangement for reducing light loss in an LED.

4.4 Fig. 1 of document D5 discloses such an alternative arrangement, namely to use the light transmitted through a transparent (sapphire) substrate, and to locate the reflecting layer on the window side to provide light recycling and prevent loss. This would immediately suggest to the skilled person that a solution to the posed problem could be found in relocating the reflective layer of document D1 to the position proposed in Fig. 1 of document D5.

The layer 6a in document D5 is made of a highly reflective metal (paragraph [0009]), this being necessary as it serves a dual function as both a reflecting layer and a (conductive) current diffusion layer. In the arrangements of document D1 the reflecting films have no such dual function and no specific conductive properties are required; hence either a metallic film or a dielectric film may be used. The skilled person would therefore understand that an inverted arrangement could be implemented for the devices of document D1 by an appropriate relocation either of the metallic mirror 8 of Fig. 1 or of the DBR 9 of Fig. 3(a) depending on requirements, the second option leading directly to the distinguishing features noted above.

4.5 The Board does not believe that the skilled person would be deterred by any concomitant adaptations required in switching to an inverted design, for example in terms of electrode placement or device mounting; it would be well within the capacity of a person skilled in LED design to effect such modifications.

In view of these considerations, the Board concludes that it would be obvious for the skilled person to arrive at the claimed subject-matter on the basis of documents D1 and D5.

4.6 The appellant's counter-arguments are not found persuasive. The initial steps of the appellant's approach amount to the following:

a) noting that document D5 identifies a problem in the prior art (represented by Fig. 2) of insufficient light output due to the low optical transmission displayed by layer 6, which is made of an unspecified electrically conducting material;

b) arguing that the equivalent layer in document D1 is the GaN contact layer 5, and asserting that this layer would also display a low optical transmission, resulting in a correspondingly poor light output; and

c) concluding that the objective problem is to further increase the amount of light exiting the structure.

Firstly, this argument is based on pure speculation, in that no evidence has been adduced that GaN would have the same or similar transmission properties as those of the (unspecified) electrically conducting material of document D5.

Secondly, and more fundamentally, it represents an impermissible attempt to confect a problem based purely on the contents of prior art documents, without any reference to the subject-matter claimed.

Within the context of the problem-solution approach it is well-established that the objective problem is formulated on the basis of the technical effect achieved by the features distinguishing the claim from the closest prior art. Moreover, the objective problem should be plausibly solved by the invention over the whole breadth of the claim.

In the present case, the claimed subject-matter is distinguished from the closest prior art by the feature referred to above as the inverted arrangement, and hence, to accept the problem formulated by the appellant (i.e. increasing the amount of light exiting the structure), it would need to be plausible that an LED with an inverted arrangement would invariably produce a greater light output than an otherwise identical LED having a non-inverted arrangement.

There is not so much as a hint in the description of the present application that this is the case, nor can the Board see any reason to believe it to be so. The appellant's arguments are therefore considered to be based on a wrong application of the problem-solution approach which leads to an incorrect formulation of the objective problem. Consequently they do not persuade the Board.

4.7 The Board judges that claim 1 of the 1st auxiliary request does not involve an inventive step within the meaning of Articles 52(1) EPC and 56 EPC 1973. The 1st auxiliary request therefore cannot be allowed.