T 1297/20 04-11-2022

1. The appeal is admissible.

2. Main request - Inventive step

2.1 Closest prior art

As held by the examining division in its decision, the closest prior art is constituted by the three primary-color organic light emitting display of document D1.

This was not contested by the appellant and the board agrees that document D1 represents the closest prior art.

2.2 Difference

The examining division held that the four-primary-color organic light emitting display defined in claim 1 of the main request differed from the device disclosed in document D1 in that:

(1) in the display panel a plurality of fourth-color pixels are disposed,

(2) the digital-to-analog converter is to generate fourth-color data voltages and to apply the fourth-color data voltage to the fourth-color pixels,

(3) the maximum grayscale voltages for the fourth-color data voltages are adjusted to be different on the single gamma graph defined as the input grayscale versus output voltage,

(4) the data modulator is configured to bypass first-color digital video data as the modulated first-color video data, and then to bypass second-color digital video data as second-color video data if the second-color digital video data does not exceed the second-color maximum grayscale value or to replace second-color digital video data by the second-color maximum grayscale value if second-color digital video data exceeds the second-color maximum grayscale value, and to bypass third-color digital video data as third color video data if the third-color digital video data does not exceed the third-color maximum grayscale value or to replace third-color digital video data by the third-color maximum grayscale value if third color digital video data exceeds the third-color maximum grayscale value, and to bypass fourth-color digital video data as fourth-color video data if the fourth-color digital video data does not exceed the fourth-color maximum grayscale value or to replace fourth-color digital video data by the fourth-color maximum grayscale value if fourth-color digital video data exceeds the fourth-color maximum grayscale value.

This was not contested by the appellant and the board agrees that document D1 fails to disclose at least differences (1) to (4).

The board notes that the appellant generally referred to the features of difference (4), i.e. in particular the limitation of data values above a respective maximum grayscale value to the maximum value, as "clipping". This expression will also be used in the following.

2.3 Two separate problems

Based on the above listed differences, the examining division identified two separate problems to be solved. The features listed under (1) to (3) were directed at increasing the luminous efficiency and thus reducing the power consumption of a three-primary-colour OLED.

The features listed under (4) solved the problem of simplifying the structure of the data modulator.

2.4 Solution of the first problem

The examining division argued that the person skilled in the art would combine the teachings of D1 with their general knowledge, as exemplified by any of documents D2 or D3, to solve the first problem.

This was not contested by the appellant and the board agrees with the examining division's conclusion.

2.5 Solution of the second problem

2.5.1 The examining division argued that, in order to solve the second problem, the skilled person would have combined the teaching of D1 with the teaching of D6 (or its family members) and arrived at a display device with in particular the technical features of differentiating feature (4). The examining division argued with reference to the Guidelines for Examination (see Guidelines for Examination, November 2019, Part G, VII 10.1) that the implementation of the technical features (4) in the device of document D1 was the result of a foreseeable disadvantageous modification, which the skilled person could clearly predict and correctly assess and which was not accompanied by an unexpected technical advantage.

2.5.2 The appellant contested this conclusion and argued that the skilled person, starting from document D1 as closest prior art, would not consult document D6. In addition, even if the skilled person were to combine the documents D1 and D6, the skilled person would not arrive in an obvious way at the subject-matter according to claim 1.

2.5.3 The board is not convinced by the examining division's line of argument but follows the appellant's reasoning for the following reasons.

D1, like the present application, deals with the problem of differing luminous efficiencies of primary colour pixels in multi-colour displays. According to D1, this problem is solved by converting the input N-bit digital video data into M-bit digital video data, wherein M is larger than N. This conversion is performed by mapping the value of the respective input N-bit digital video data for the R, G, and B pixels with a predetermined M-bit value through corresponding look-up tables (see paragraphs [0047] to [0051] and Table 1). As the conversion via a look-up table as disclosed in D1 avoids the need for "clipping" of the input data, D1 does not contain a hint towards replacing the look-up table approach by "clipping" the input data.

The board acknowledges that document D6 explicitly mentions "clipping" (see paragraphs [0032] and [0033] and Figure 2A and 2B). However, D6 does not disclose "clipping" as a solution for simplifying the data modulator but as an unwanted side effect that occurs when display code values are boosted in order to compensate for a reduction in light source illumination (see e.g. paragraph [0032], last sentence). D6 therefore presents "clipping" as an effect which occurs inadvertently and which should in fact be avoided, but not as a technical means to achieve a certain purpose, in particular not to simplify the structure of the data modulator of D1, which already solves the problem of differing luminous efficiencies by employing a look-up table and an individual conversion of input values for each colour.

The board is therefore of the opinion that the skilled person does not receive a hint, neither from document D1 nor from document D6, that the data modulator of D1 could be simplified by realising a "clipping" of the digital video data as claimed.

2.5.4 Further documents

In the context of document D6 the examining division also referred to "more than ten different patent families from the same applicant published over a period of more than five years". With respect to the "clipping", the disclosure of these documents does not go beyond the disclosure of document D6. In addition, none of the other documents cited by the examining division discloses the differentiating features (4).

2.5.5 In conclusion, the subject-matter of claim 1 involves an inventive step over document D1 as closest prior art (Article 56 EPC).

2.5.6 Main request - Independent claim 9

Claim 9 is directed to the corresponding method for driving the four-primary-color organic light

emitting display of claim 1. Therefore, the subject-matter of claim 9 of the main request involves an inventive step over document D1 as closest prior art on file (Article 56 EPC).

2.5.7 Main request - Dependent claims

The same conclusion applies to dependent claims 2 to 8 and 10 to 11 of the main request by virtue of the reference in these claims to claims 1 and 9, respectively.

2.6 The board concludes that the main request is allowable.