T 1314/10 05-05-2011

I. The Appellants (Patent Proprietors) lodged an appeal against the decision of the Opposition Division issued in writing on 31 March 2010 revoking European patent No. EP-B-0 737 513 in respect of European patent application No. 95935582.7 for lack of inventive step.

II. Two notices of opposition had been filed by Respondents I and II requesting revocation of the patent as granted in its entirety on the grounds of lack of novelty and inventive step under Article 100(a) EPC 1973. The oppositions were based inter alia on the following documents:

D1 EP-A-0 581 216

D2 EP-A-0 590 477

D6 H. Bach and H. Schroeder, "Kristallstruktur und optische Eigenschaften von dünnen organogenen Titanoxyd-Schichten auf Glasunterlagen", Thin Solid Films, 1 (1967/68), pages 255-276, Elsevier, and translation thereof in English

D7 US-A-5 165 972

D8 Y. Takahashi and Y. Matsuoka, "Dip-coating of TiO2 films using a sol derived from Ti(O-i-Pr)4-diethanolamine-H2O-i-PrOH system", Journal of Materials Science 23 (1988) page 2259-2266

D9 W. Xu et al, "Preparation an characterization of TiO2 films by a novel spray pyrolysis method", Mat. Res. Bull., Vol. 25, pages 1385-1392, 1990 and

D10 L. Meng et al, "The effect of substrate temperature on the properties of sputtered titanium oxide films", Applied Surface Science 65/66 (1993), pages 235-239.

III. The present appealed decision was based on the sole set of claims 1-6 submitted on 1 February 2005 which, according to a first appeal decision T 700/05, was found to meet the requirements of Articles 123(2), (3) and 84 EPC, independent claims 1, 5 and 6 reading as follows:

"1. A titanium dioxide photocatalyst structure comprising:

a transparent soda lime glass substrate and

a titanium dioxide film having photocatalytic activity and a linear light transmittance of at least 50% for light having a wavelength of 550 nm,

wherein the titanium dioxide film contains anatase crystals and has a thickness of 0.1 to 5mym."

5. A method for producing a titanium dioxide photocatalyst structure according to any of claims 1 to 4, comprising a producing process which includes the step of:

forming a titanium dioxide film on a transparent soda lime glass substrate by performing a pyro-sol method, a dipping method, a printing method or a CVD method.

6. Use of the titanium dioxide photocatalyst structure according to any of claims 1 to 4 for removing carbon dioxide and air pollutants to render indoor space antibacterial."

IV. The opposition division held that the claimed subject-matter was novel over the prior art D2, D6 and D10, but lacked inventive step. D2 was considered to represent the closest state of the art, because that document also related to metal-oxide thin films coated on architectural materials, such as window glass, that had excellent deodorising, anti-mould and anti-soiling properties imparted by the photocatalytic properties of the metal oxide. According to the opposition division, the skilled person would have been prompted in view of D2 to use the features defined in claim 1 as granted in order to prepare a commercial glass window with the desired transparency and photocatalytic activity. D2 indicated that titanium oxide of anatase structure was an appropriate photocatalytic material for the thin metal-oxide film and that the thickness of the film should be in the microns range if high transparency of the film was desired. The use of soda lime glass for the architectural material was obvious as D2 taught to apply the photocatalytic film on window glass. The problem of sodium diffusion into the titanium oxide, when a soda lime glass substrate was used, occurred only in the first 80 nm of the titanium oxide film as demonstrated by D6 and could therefore be ignored when a titanium oxide film having a thickness in the microns range was intended. The selection of a linear light transmittance of at least 50% for light having a wavelength of 550 nm, was arbitrary, as it neither contributed to improve the transparency over the whole visible range, nor brought about higher photocatalytic activity. This feature therefore did not contribute to an inventive step. Hence, having regard to the state of the art, the subject-matter of claim 1 was obvious to the skilled person.

V. With the statement setting out the grounds for appeal, the Appellants submitted on 30 July 2010 two sets of three claims each constituting their Main and First Auxiliary Requests, the claims of the Main Request reading as follows:

"1. A titanium dioxide photocatalyst structure comprising:

a transparent soda lime glass substrate and

a titanium dioxide film having photocatalytic activity and a linear light transmittance of at least 50% for light having a wavelength of 550 nm,

wherein, the titanium dioxide film is directly formed on the transparent soda lime glass substrate, the titanium dioxide film contains anatase crystals and has a thickness of 2.3 to 4.8 mym, or

wherein a transparent pre-coat film composed of SiO2 and having a thickness of 0.02 to 0.2 mym is disposed between the transparent soda lime glass substrate and the titanium dioxide film, the titanium dioxide film contains anatase crystals and has a thickness of 1.7 to 4.2 mym.

2. A method for producing a titanium dioxide photocatalyst structure according to claim 1, comprising a producing process which includes the step of:

forming a titanium dioxide film on the transparent soda lime glass substrate by performing a pyro-sol method, a dipping method, a printing method or a CVD method.

3. Use of the titanium dioxide photocatalyst structure according to claim 1 for removing carbon dioxide and air pollutants to render indoor space antibacterial."

The claims of the Auxiliary Request were restricted to the embodiment of the main request comprising a transparent pre-coat film composed of SiO2. According to the statement setting out the grounds for appeal, it was an object of the invention in view of D2 to provide a photocatalyst structure having improved decomposition activity. Said object had been attained by the subject-matter of claim 1. The Appellants argued that D2 did not provide any hint that structures with a titania film having a thickness lying outside of the claimed range would exhibit either inferior decomposition activity or lower light transmittance. This also was not suggested by any of documents D6, D7 or D10. Thus, an inventive step should be acknowledged. No argument in connection with the method for forming the titanium dioxide film on the transparent soda lime glass substrate was presented.

VI. In response to the statement setting out the grounds of appeal, Respondents I and II submitted that the insertion in claim 1 of the two specific ranges of thickness for the titania film, the end points of which were disclosed only in connection with specific situations shown in the examples, contravened the requirements of Article 123(2) EPC. The claims were also held to be anticipated by D1 and/or D2 and to lack inventive step starting from D2 as closest prior art. It was, in particular, pointed out that the thickness of the metal oxide layer as defined in claim 1 was not an additional distinguishing feature over document D2 and that any effect associated with it was inevitably achieved by the teaching of D2. Thus, the titania film thickness defined in the amended claims could not contribute to an inventive step. The possibility of applying the titanium dioxide film directly on the transparent substrate was taught in D2 and the use of a SiO2 pre-coat film having a thickness of 20 nm to prevent the sodium from migrating into the anatase phase was furthermore known from D6. Consequently, the subject-matter of the claims as amended lacked inventive step.

VII. A summons to attend oral proceedings before the Board was dispatched on 9 February 2011. In preparation of the oral proceedings, the Board issued a communication on 24 February 2011 in which a preliminary opinion of the Board on inventive step was expressed. As the patent in suit aimed at providing a titanium dioxide photocatalyst structure that had excellent photocatalytic activity and light transmissivity, especially for glass windows, D2 was considered, in particular in view of the embodiments described in examples 1 to 3, to represent the closest state of the art for assessing inventive step. Having regard to the results shown in figure 3 and paragraphs [0020] to [0022] of the patent in suit, it appeared that the problem solved by the claimed subject-matter over the closest prior art would be the provision of a structure having sufficient photocatalytic activity and transparency. With a view to solving this problem, the choice of a transparent soda lime glass, which was the most current architectural glass, appeared to be obvious to the skilled person, as well as the use of a titanium dioxide layer which implicitly was the preferred metal dioxide layer in document D2. D2 also taught that a transparent thin film having deodorising properties could be obtained by setting the film thickness of the metal oxide to several microns or thereabouts and its example 3 suggested that a sintering temperature between 200ºC and 400ºC provided adequate results in terms of deodorising properties for a thin film of titanium dioxide. The sintering conditions used in document D2 appeared to suggest to the skilled person that a titanium dioxide film containing anatase crystals was obtained. It also appeared in view of D8 and D9 to be known from the skilled person that the anatase phase provided higher visible light transmission. The skilled person searching for structures having sufficient photocatalytic activity and transparency, would therefore have tried film thicknesses in the range of several microns or thereabouts, thereby arriving without exercising any inventive skill to a structure falling within the ambit of claim 1 then on file. Knowing that the transparency and the photocatalytic activity depended on the amount of the anatase phase, i.e. on the thickness of the layer, the skilled person would have been able, if he so wanted, to find based on routine experimentation a range providing a suitable compromise between transparency and photocatalytic activity. Values of at least 50% for the linear light transmittance at a wavelength of 550 nm did not appear to contribute to inventive step as they seemed to be the automatic result of setting the film thickness to the values recommended in D2. Starting from the embodiments shown in figures 7 to 9 of D2, it appeared therefore that the skilled person who wanted to provide a structure having sufficient photocatalytic activity and transparency would have arrived at structures falling within the ambit of claim 1 without any inventive activity.

VIII. With their letter dated 1 April 2011, the Appellants submitted in replacements of the claims then on file two sets of claims forming the basis for their Main and Auxiliary Request I. In comparison to the claims submitted with the statement setting out the grounds of appeal, the amendments proposed consisted in restoring the original range of 0.1 to 5 mym for the thickness of the titanium dioxide film and in defining that the titanium dioxide film was obtained by a pyro-sol method. Accordingly, claim 1 of those requests read as follows:

Main Request

"1. A titanium dioxide photocatalyst structure comprising:

a transparent soda lime glass substrate and

a titanium dioxide film having photocatalytic activity and a linear light transmittance of at least 50% for light having a wavelength of 550 nm,

wherein the titanium dioxide film contains anatase crystals and has a thickness of 0.1 to 5 mym, and

wherein the titanium dioxide photocatalyst structure is obtainable by forming a titanium dioxide film on a transparent soda lime glass substrate with a pyro-sol method."

Auxiliary Request I

"1. A method for producing a titanium dioxide photocatalyst structure comprising

a transparent soda lime glass substrate and

a titanium dioxide film having photocatalytic activity and a linear light transmittance of at least 50% for light having a wavelength of 550 nm,

wherein the titanium dioxide film contains anatase crystals and has a thickness of 0.1 to 5 mym,

by forming the titanium dioxide film on a transparent soda lime glass substrate with a pyro-sol method."

IX. The Appellants held that the subject-matter of claim 1 of the Main Request was, compared to claim 1 submitted with letter dated 1 February 2005, further distinguished from the prior art in that the titanium dioxide layer was obtainable by the pyro-sol method. Contrary thereto, the titanium dioxide films according to document D2 (column 4, lines 33 to 40) were coated on the substrate by spray coating, dip coating, spin coating and sputtering. As discussed in paragraph [0084] of the opposed patent, the pyro-sol method had several advantages. In particular, high activity titanium dioxide films containing anatase crystals could be obtained in such a way as to be highly uniform and have a large area. It was also pointed out, that the formation of the films could be achieved at a temperature which was not higher than the softening temperature of glass, namely a temperature in the range of 400 to 550ºC. Working at this temperature had the further advantage that the diffusion of sodium ions from the glass substrate to the film could be retarded. It was the opinion of the Appellants that those advantages and effects could not be expected from any of the cited references because none of them referred to the pyro-sol method forming a SiO2 (sic) film containing anatase crytals (in the context SiO2 to be understood as TiO2). The subject-matter of claim 1 of the Main Request was, therefore, based on an inventive step. The same arguments also applied to Auxiliary Request I.

X. With a facsimile letter of 29 April 2011, Respondents I argued that the scope of claim 1 of the Main Request was identical to that underlying the decision under appeal and therefore that it lacked inventive step over D2. Claim 1 of Auxiliary Request I was also considered to be obvious in view of the combined teaching of D2 and D9. D9 was held to teach the production of titanium dioxide films by a pyro-sol method.

XI. During the oral proceedings before the Board, which took place on 5 May 2011, an Auxiliary Request II consisting of claim 1 of Auxiliary Request I was submitted.

XII. The arguments of Respondents I and II can be summarised as follows:

The present requests had been submitted after issuance of the summons to attend oral proceedings and were belated. They put, for the first time in these proceedings, the focus of the invention on the use of the pyro-sol method, something that had never been discussed before. Moreover, the amendments proposed were prima facie not allowable. The use of the expression "pyro-sol", which had not been clearly defined, led to a lack of clarity of the amended sets of claims. Particular reference was made to paragraph [0084] of the patent in suit that defined the pyro-sol method as a CVD method. Furthermore, it had not been shown by the Patent Proprietors that the use of the pyro-sol method for producing the titanium dioxide film implied any additional structural feature compared to claim 1 as granted. Any comparison with the structure of comparative example 3 of the patent in suit was flawed, as this structure did not correspond to those disclosed in D2 which were transparent. As this amendment provided no distinguishing structural feature over the claims as granted, it was not suitable to overcome an inventive step objection with the result that the requirements of Rule 80 EPC were not fulfilled. The new requests should therefore be rejected as inadmissible.

XIII. The Appellants' submissions concerning the admissibility of the new requests can be summarised as follows:

The present claims had been filed in reaction to the Board's communication. The amendments did not result in a combination of claims as granted, but from a restriction of the subject-matter of the granted patent to the parts relating to the use of the pyro-sol method. Claim 1 of Auxiliary Request I was based on independent claim 6 as granted, that referred to claims 1 to 5 as granted for the definition of the titanium dioxide photocatalytic structure. It merely corresponded to a restriction of an already existing independent claim, but not to the creation of a new independent claim. Rule 80 EPC was therefore not an issue. The amendments proposed could not be considered as taking the Respondents by surprise, as the pyro-sol method was described in the patent in suit as the most preferred method for producing the titanium dioxide. The pyro-sol method was used in examples 1 to 15 and was in addition amply defined in paragraph [0083] and [0084] of the patent. It was an alternative to the spraying method in which the precursor solution had undergone ultrasonic atomisation. The reference to Chemical Vapour Cracking in paragraph [0084] made it clear that CVC, but not CVD, was meant in said passage. Thus, the definition of this method did not induce any lack of clarity. The patent in suit indicated that the use of the pyro-sol method resulted in highly uniform structures, whereas in D1 and in D2 the titanium dioxide structures obtained with a titanium dioxide sol were less uniform. Particular reference was made to comparative example 3 of the patent in suit that exhibited little transparency and to the structure described in column 9, lines 31-35 of D2. Thus, the definition of the pyro-sol method as the method for producing the titania film provided a distinguishing feature over D2 on the basis of which inventive step should be analysed. Claim 6 of the patent in suit included a process using the pyro-sol method so that no further search for additional prior art was necessary. Auxiliary Request II consisting of claim 1 of Auxiliary Request I had been submitted in case Auxiliary Request I was held to be inadmissible as it also contained dependent claims. The new requests were therefore admissible.

XIV. The Appellants requested that the decision under appeal be set aside and the patent be maintained on the basis of the claims of the Main Request (claims 1 to 5) or alternatively of the claims of Auxiliary Request I (claims 1 to 4), both filed on 1 April 2011, or of the sole claim of Auxiliary Request II filed during the oral proceedings before the Board.

XV. Respondents I and II requested that the appeal be dismissed. They further requested that the Main and Auxiliary Requests I and II be rejected as inadmissible.

XVI. At the end of the oral proceedings, the decision of the Board was announced.