T 0593/96 18-11-1996

Reasons for the Decision

1. The appeal is admissible.

2. In the grounds for the decision refusing the application, the examining division referred to the reasons given in three communication (see paragraph II above). It is clear from the content of these communication (see paragraphs III, V and VII above) that the reasons for the refusal were lack of inventive step of the subject-matter of claim 22 then under consideration and undue breadth of this claim. The remaining claims, apart from those appendant to claim 22, were stated to be acceptable (see paragraph V above). However the Enlarged Board of Appeal has decided in the case G10/93 (OJ EPO 1995, 172) that in an appeal from a decision of an examining division in which a European patent application has been refused, the board of appeal has the power to examine whether the application or the invention to which it relates meets the requirements of the EPC and that this is true for requirements which the examining division regarded as having been met. If there is reason to believe that such a requirement has not been met, the board shall include this ground in the proceedings.

In the present case, the Board sees no reason to doubt the examining division's finding that the said remaining claims were acceptable, and will therefore confine it considerations, in respect of the main request, to claim 23 and claims referring back thereto.

3. As compared with the corresponding claim 27 originally filed, claim 23 has been reformulated in the two-part form, the first part containing the features of known liquid developers disclosed for example in US-A-3 841 893. It also includes the additional wording that the charge director compound should be present in an amount sufficient to charge the tones particles to a level suitable for a liquid tones process. This would seem to be a self-evident requirement and in any case is implicit in the description, for example on page 2, lines 3 to 15. The original claim 27 merely required that the total amount of the charge director compound is associated essentially only with the toner particles. In the characterising portion of claim 23, this has been amplified to make it clear that this occurs at concentrations suitable for use in a liquid toner. The basis is to be found in the description, page 10, line 30 to page 13, line 6 and examples 16 and 17. The characterising portion also includes an indication of how this feature is identified, based on page 12, lines 26 to 30 and examples 16 and 17. The requirement of Article 123(2) EPC is therefore satisfied. The claim is also clear in that by a simple procedure (centrifugation followed by IR spectroscopy analysis of the supernatant)it can be established whether or not a liquid developer falls within the scope of claim 23. To this extent the requirement of Article 84 EPC is satisfied. As regards the objection of undue breadth raised by the examining division, this is more conveniently dealt with after the evaluation of novelty and inventive step.

4. In its international preliminary examination report, the examining division expressed the opinion that the claim on which claim 23 was based lacked novelty as well as inventive step over the disclosure in US-A-3 841 893. It noted that it was not mentioned in this document that the total amount of the charge director compound was associated with the toner particles, but that this was certainly the case when small amounts of charge director compounds are used. This position was maintained in the communications dated 16 June 1993 and 31 August 1994, but the result of consultation dated 25 January did not mention lack of novelty.

The Board, in agreement with the appellant, is of the opinion that US-A-3 841 893 does not disclose a liquid developer in which at concentrations suitable for use in a liquid toner, essentially the entire amount of the charge director is associated essentially only with the toner particles in the manner required by claim 23. The charge directors (called charge control agents in US-A-3 841 893)are indeed soluble in the carrier liquid (see claim 1) and are present in the liquid developer in any suitable amount (column 4, line 19 et seq). By this is meant however that there should be enough of the charge director so that the charge control effect is adequate but not so much that the volume resistivity of the developer is lowered excessively. The Board accepts the argumentation of the appellant, reflected in the paragraph on lines 12 to 23 of page 30 of the description, that for known charge directors, at concentrations suitable for use in liquid toners, there is a balance between the amount of the charge director associated with the toner particles and the amount dissolved in the carrier liquid. While it may be, though this is not certain, that, as argued by the examining division, at low concentrations the charge directors disclosed in US-A-3 841 893 may be associated entirely with the toner particles, at such concentrations the liquid developer will not be suitable for use in a liquid tones process. In this respect the Board can agree with the appellant that the amount of charge director stated to be suitable in US-A-3 841 893, that is 0.5 to 2.0 per cent by volume of the developer, is much greater than that of the application in suit, namely 2.5 to 600 ppm by volume of the developer. The subject-matter of claim 23 is therefore novel over US-A-3 841 893.

The subject-matter of claim 23 is also not obvious over the disclosure in US-A-3 841 893. As previously indicated, the Board sees no reason to doubt the appellant's contention that in all prior art liquid developers, at useful concentrations part of the charge director remains dissolved in the carrier liquid and there is not even the suggestion that a liquid developer having the features claimed in claim 23 would be an obvious desideratum. One advantage of the claimed developer is that because the charge director is associated entirely with the toner, the two will be depleted in use at the same proportionate rate and can therefore be replenished from a single source of toner combined with the appropriate amount of charge director. This is clearly a simplification as compared with prior art processes where toner and charge director are depleted at different rates so that more control is required for replenishing. Moreover less charge director is required since substantially none is lost to the carrier liquid.

5. The Board can agree with the appellant that the examining division's objection to claim 23 as being of undue breadth should be considered as an objection under Article 84 EPC rather than Article 83 EPC, because at least examples 16 and 17 describe how to carry out the invention claimed.

The liquid developers particularly described comprise the organosilicon compounds defined in claim 1 as features (c) (i) and (c) (ii). The applicant discovered that at least some of these liquid developers had the property that at concentrations suitable for use in liquid toner processes, the total amount of the charge director was associated only with the toner particles. Claim 23 is a generalisation from this to embrace all liquid toner wherein the charge director compound behaves thus.

The examining division in effect took the view that this generalisation went beyond what was warranted by the applicant's contribution to the art. On the other hand, the appellant considers that the generalisation is justified because of the pioneering character of the invention. It is true that, as stated in the Guidelines for Examination in the EPO, C-III 6.2, an invention which opens up a whole new field is entitled to more generality in the claims than one which is concerned with advances in a known technology. Now in the Board's view it would be something of an exaggeration to say that the present invention had opened up a whole new field. Nevertheless each case should be judged on its merits, and the present application discloses for the first time liquid developers wherein at useful concentrations the total amount of charge director is associated essentially only with the tones particles. Accordingly in the absence of any relevant prior art, the Board finds that the invention claimed in claim 23 lies closer to one opening up a new field than to one concerned with advances in a known technology and therefore that claim 23 is not unduly broad.

6. The question of lack of unity of invention between claim 23 (or any claim corresponding thereto)and claim 1 was raised during the PCT Chapter II proceedings and again during the examination proceedings (communication dated 31 August 1994). In the first place it should be noted that the International Search Report was drawn up in respect of all claims. This is not in itself an indication that the requirement of Article 82 EPC is necessarily complied with but in such a situation the Board would have some reservations about raising or maintaining an objection on the ground of lack of unity. In any case, in the Board's opinion there is sufficient overlap in the subject-matter of claims 1 and 23 that unity of invention can be recognised. Claim 1 includes within its scope liquid developers which, at least at certain charge director concentrations, fall within the scope of claim 23. Further, although the particular advantage of the liquid developer according to claim 23 is the simplicity of replenishment as set out above (end of paragraph 4), this clearly contributes to achieving the object of the invention as claimed in claim 1, namely improved time stability and therefore copy quality (see page 4, lines 10 to 15 and the examples)because the constitution of the liquid developer remains substantially constant with time.

7. In view of the foregoing, it is not necessary for the Board to consider the auxiliary request.

8. It is not apparent from the file that the description has been examined for conformity with the requirements of the EPC. In any case it will require to be adapted to the amended claims. The case is therefore remitted to the examining division for completion of the examination in these respects in accordance with Article 111 (1) EPC.