T 0325/95 18-11-1997

1. The appeal is admissible.

2. Compliance of the amendments brought to the description and claims with the provisions of Article 123(2) and (3) EPC

2.1. The features of present independent claims 1 and 8, including those of the luminance-balanced colour mark, were in substance already defined in independent claim 1 as originally filed, except for the statement that a contrast ratio of greater than 100 is attained. This threshold value was disclosed originally in Figure 5.

Apart from a number of corrections of merely editorial nature, the description has been adapted to the wording of the independent claims as amended and supplemented with a short summary of the relevant content of document D6, in compliance with Rule 27(1)(b) and (c) EPC.

In particular, the first paragraph of the description has been amended to make it clear that a rich-in-red light source, which was originally disclosed there as a necessary component of the invention, only represented an example of an adequate light source. This amendment is supported in particular by the second and third paragraphs on page 19 of the original description, which state that the invention can be used with a variety of light sources of which those with a high output in the red portion are only examples. Since furthermore original claim 1 did not comprise any limitation to rich-in-red light sources, which were defined only in orginal dependent claim 6, the original application documents cannot be considered to have disclosed such source as an essential feature of the invention, as was alleged by the appellant.

A few reference signs and the representation of electrodes 73 and colour patches 319 have also been corrected in Figure 8, in correspondence with the original description.

Accordingly, the amendments brought to the patent do not extend its content beyond the content of the original application documents, in compliance with the provision of Article 123(2) EPC.

2.2. As compared to independent claims 1 and 8 as granted, present claims 1 and 8 only comprise the additional features which specify that the luminance-balanced colour mask has coloured patches and a grey surround area, the coloured patches being luminance-balanced with each other and the grey surround area in order that the coloured patches and grey surround area are of substantially equal luminous transmission. These additional features restrict the scope of the claims, which do not therefore contravene the provisions of Article 123(3) EPC.

In his reasoning to the effect that the scope of the claims had been extended, the appellant considered that claim 1 as granted did not actually afford any scope of protection whatsoever, because the claim was invalid, its subject-matter lacking an inventive step.

This argumentation is thus based on the assumption that the extent of protection referred to in Article 123(3) EPC would depend not only on the actual wording of the claims, but also on their validity in view of the prior art. This assumption however is not supported by the explicit statement in Article 69 EPC that "the extent of the protection conferred by a European patent ... shall be determined by the terms of the claims"(emphasis added).

Appellant's submissions in effect also imply that claims amended in opposition proceedings shall always have a counterpart in the set of claims as granted, which is not in line with the consistent case law of the EPO either. Attention is drawn for instance to decision G 2/88 of the Enlarged Board of Appeal (OJ EPO, 1990, 093), which ruled that replacement of a granted claim to a compound or composition, the subject-matter of which had turned out to be devoid of novelty, by a claim directed to a new use of the compound or composition as was actually described in the patent but had not been claimed in the opposed patent, was admissible under Article 123(3) EPC; see points 3 to 5 of the Reasons.

The appellant admitted that the jurisprudence of the Board's of Appeal of the EPO did not support his line of argumentation; he nevertheless submitted that this jurisprudence conflicted with German practice and case law.

The appellant did not however in this respect produce convincing evidence that limitation of a granted claim by the introduction of features disclosed only in the description was actually barred by German patent law, jurisprudence or practice. The only case law referred to by the appellant, the "Formstein" decision of the Bundesgerichtshof (see OJ EPO, 1987, 551) does not actually address the admissibility of such limitation. The ruling in this decision that the scope of protection afforded by a claim cannot be extended, by an allegation of equivalency, to an embodiment which was obvious in view of the prior art (see point 5.8) can hardly be considered to mean that limitation of a granted claim by way of features disclosed only in the description is generally inadmissible.

For these reasons, the amendments brought to independent claims 1 and 8 are not considered to offend against the provisions of Article 123(3) EPC.

3. Patentability

3.1. According to the description of the present patent the invention relates to a multicolour transmissive liquid crystal display of the type in which differently colored display areas are defined by colour patches of a filter provided between a light source and the input side of the liquid crystal cell (see e.g. page 2, lines 49 to 51).

In existing multicolour transmissive liquid crystal displays of this type the underlying colour patches would still be visible in the off-state condition of the display, which resulted in an unattractive aspect. Accordingly the object of the invention is to overcome this bleed-through problem (see page 2, lines 51 to 56).

In order to solve this problem the invention as defined in present claim 1 provides a series of features directed to the construction of the liquid crystal cell, polarisers and colour mask, which together aim at causing the output panel to appear uniformly dark to an observer when the multicolour liquid crystal display device is in its off-state. The colour mask in particular has coloured patches and a grey surround area luminance-balanced with each other so that the coloured patches all have substantially equal luminous transmission.

3.2. The Opposition Division in the appealed interlocutory decision held that, apart from the specific definition of the luminance-balanced colour mask with the coloured patches and grey surround area luminance-balanced with each other, the remaining features of the liquid crystal cell light source, polariser and drive means as set out in claim 1 were obvious from document D6, considered as disclosing the nearest prior art (see points 2 and 3 of the Reasons). This opinion, which is shared also by the Board, has not been contested by the parties, and the present decision will therefore concentrate on the contribution to inventive step of the above-mentioned additionally features of the luminance-balanced colour mask only, which causes the output panel to appear uniformly dark to an observer when the multicolour liquid crystal display device is in its off-state.

Document D6, which is the sole prior art document relied upon in this respect by the appellant in the appeal procedure, does not explicitly address the technical problem of causing the output panel of multicolour liquid crystal display devices - in the sense of the present patent, i.e. devices which exhibit adjacent display areas of different colours as defined by a colour mask - to appear uniformly dark in the off-state.

Neither does document D6 even appear to be specifically dedicated to such multicolour liquid crystal display devices. As a matter of fact, the improvements proposed in this document like the limitation of the spectrum of the light source, the addition of dichroic dyes to the liquid crystal material or the use of colour filter foils to achieve a constant colour impression apply equally to liquid crystal devices for the display of characters or symbols in a single colour; see in this respect the first sentence on the fourth page which refers to the spectral transmission of "a cell for the display of red signs".

The sentence at the end of the fourth page of document D6 as referred to by the appellant is the sole passage in the document to relate to colour filters. The various colour filter foils referred to there, are said to aim at achieving an acceptable constancy of the colour impression in the reflective and in the transmissive operation of the cell. In the absence from the document of any suggestion that the cell referred to is of the multicolour type, the skilled person in the Board's jugement would most logically interpret the above explanation of the technical function of the filter foils in the sense that the filter foils should be so designed and located at "different locations in the illumination system" - e.g. behind and in front of the cell - that the brightness of the characters displayed in the on-state is substantially the same independently of the operating mode - i.e. independently of which of the two light sources referred to in the preceding paragraph of the document is activated.

This interpretation does not imply the provision of coloured patches and of a grey surround in a single colour mask, nor their mutual luminance-balancing, as was suggested by the appellant.

For these reasons the Board is not convinced that the specific structure of the colour mask with the luminance-balanced colour patches and grey surround area as set out in claim 1 can without hindsight be considered to be suggested in an obvious way by the scant reference made in document D6 to various colour filter foils.

The appellant in his argumentation established a distinction between scientific papers like document D6 and usual prior art documents such as patent publications, implying in particular that the skilled person reading a theoretical paper would be more inclined to envisage applying its general teaching to specific situations he might be aware of, than when reading the detailed description of specific embodiments as disclosed usually in a patent document. In the Board's view, however, it is the actual content of any document which matters, not the type of publication to which it belongs. In the present case, the fact that document D6 is a scientific paper cannot make up for its missing of any hint either at the technical problem solved by the invention or at the claimed solution.

The other citations no longer relied upon by the appellant in the appeal procedure do not come closer to the claimed subject-matter.

3.4. For these reasons the subject-matter of independent claim 1 is considered to involve an inventive step in the sense of Article 56 EPC.

So does the subject-matter of independent claims 8 and 9. which in substance recite the same limitations.

4. Since, taking into consideration the amendments brought to the patent, the patent and the invention to which it relates meet the requirements of the Convention, maintenance of the patent so amended can be decided under Article 102(3) EPC.