T 0001/80 (Carbonless copying paper) of 6.4.1981

Summary of Facts and Submissions

I. The European patent application No. 78100634.1 filed on 9 August 1978 and published on 7 March 1979 (publication number 0000943) was refused by decision of Examining Division 012 of the European Patent Office dated 16 November 1979. This decision is based on the original claims 1 and 2, of which claim 1 has the following wording; "Carbonless copying paper containing a solution of a dyestuff-intermediate in micro-encapsulated form characterized in that the dyestuff-intermediate is encapsulated as a solution in a hydrophobic organic solvent, and that the capsule walls consist of the polyaddition product of a diisocyanate of the formula (i) wherein R signifies a bivalent aliphatic radical, and a diamine."

II. The stated grounds for the refusal were that the subject-matter of claims 1 and 2 did not involve an inventive step in that German unexamined application (Offenlegungschrift) 2 251 381 discloses the manufacture of carbonless copying papers containing micro-encapsulated dyestuff solutions, the walls of the microcapsules consisting of a polyaddition product of a di- or triisocyanate or their addition products containing urea groups and a polyamine, in particular a diamine. In the light of this prior art the invention should only lie in the selection of the isocyanate. It was furthermore known from US patent specification 3 748 329 and German unexamined application 2 221 756 that the oxadiazinetrione diisocyanates selected by the applicant could be reacted with diamines in solution in a wide variety of solvents to form coatings of the corresponding polyaddition products. Since microcapsules also represent a kind of coating, it was to be expected that the solutions described in the two last-named patent documents would be particularly suitable for the manufacture of microcapsules in accordance with German unexamined application 2 251 381. That is to say, when a product was recommended for the manufacture of coatings, an expert would naturally expect such coatings to form coherent and impermeable films. In the selection of polyisocyanates for the micro-encapsulation of hydrophobic solutions, the most important factor in addition to choice of suitable solvents, was the formation of impervious films, for which the expert would have given preference to the trifunctional isocyanates such as the oxadiazinetrione diisocyanatesc chosen by the applicant, because of their crosslinking capability. The applicant had therefore not succeeded in demonstrating that the selection he arrived at was not obvious, either by substantiating a surprising advantage or in any other manner.

III. The appellant entered an appeal against this decision of 16 November 1979 on 21 December 1979, and submitted a Statement of Grounds on 27 February 1980. The appellant asserted - in each case supported by comparative experiments - that the oxadiazinetrione diisocyanates used in accordance with the application are not trifunctional, as alleged by the Examining Division, but difunctional, and moreover surprisingly superior to a large number of other isocyanates, including trifunctional ones, in the manufacture of carbonless copying paper by micro-encapsulation.

IV. When invited by the Technical Board of Appeal to provide further explanation and amplification of the facts asserted, the appellant responded in due time and submitted more limited claims in the following terms:

"1. Carbonless copying paper containing a solution of a dyestuff-intermediate in micro-encapsulated form, the dyestuff-intermediate being encapsulated as solution in a hydrophobic organic solvent, characterised in that the capsule walls consist of the polyaddition product of a diisocyanate of the formula I wherein R signifies an alkylene radical with 2-10 C atoms, and a diamine.

2. Use of a solution of a dyestuff-intermediate in a hydrophobic organic solvent as microcapsules containing core material, the walls of the capsules consisting of the polyaddition product of a diisocyanate of the formula I wherein R signifies an alkylene radical with 2-10 C atoms, and a diamine, for the manufacture of carbonless copying paper." The applicant requested that the decision under appeal be set aside and that the patent be granted with claims in these terms.

Reasons for the Decision

1. The appeal is in accordance with Articles 106-108 and Rule 64 EPC; it is therefore admissible.

2. There can be no formal objection to the current version of the claims, since it is adequately supported by the original documents (cf. the original two patent claims in conjunction with page 5, line 2 and last paragraph of the original documents). The revision of the preamble of claim 1 was put forward in accordance with Rule 29(1) (a) EPC, in view of the disclosure in German unexamined application 2 251 381.

3. The applicant admits that a carbonless copying paper containing a dyestuff-intermediate in micro-encapsulated form is already known (cf. the preamble of patent claim 1 in conjunction with the original description page 1, para. 2 to page 3, para. 2). The applicant considers it a disadvantage that the carbonless copying papers obtainable by the method of US patent specification 3 432 327 contain the micro-encapsulated dyestuff-intermediate dissolved in a hydrophilic solvent - such as water - since it has so far been impossible in practice to manufacture capsule films which are impermeable to water. This leads to such capsules not remaining stable during storage, and the copying papers manufactured from them rapidly losing their duplicating capacity. Copying papers as described in German unexamined application 2 311 712 had amongst other disadvantages the tendency to become stained as a result of agglomeration of the capsules.

4. According to the application, carbonless copying papers are to be produced whose microcapsules (a) are impermeable to the dyestuff-intermediate and its solvent, (b) only fracture under writing pressure, (c) do not form any agglomerates and (d) may be easily applied and immediately fixed to the surface of the paper (cf. original description page 3, lines 24-33, page 4, lines 1-6 and 11-20).

5. In German unexamined application 2 251 381 cited in the examination procedure and coming closest to the subject-matter of the application, copying papers had already been described which - like those of the application - contain the micro-encapsulated dyestuff-intermediate as a solution in an oil-like fluid (cf. page 12, para. 2 in conjunction with page 6, lines 25-34) and have capsule walls consisting of the polyaddition product of a polyisocyanate with a diamine (cf. Claims 1 and 23 in conjunction with page 12. para. 2). Such papers, which are also carbonless copying papers (cf. page 11 from line 3 to page 12, para. 1), also fulfil the requirements given above under point 4: for (a) cf. page 10 paras. 2 and 4; for (b) cf. page 5 last sentence in conjunction with page 14 penultimate sentence; for (c) cf. page 5 para. 4; and for (d) cf. page 11 para. 2 in conjunction with the examples.

6. The indisputably novel carbonless copying papers according to the application differ from these in that a more precisely presented oxadiazinetrione diisocyanate is employed as polyisocyanate. To this extent the problem could be seen as the mere preparation of another carbonless copying paper.

7. In the meantime the applicant has submitted with the Statement of Grounds for the appeal the result of a large number of comparative experiments as evidence of the inventive step of the subject of the application. There is no objection in this case to the presentation of such new evidence during the appeal proceedings. In view of the general similarity of examination procedure and appeal procedure, as presented in Articles 110 (1), (2) and 111 (1), as well as in the section on the Common Provisions (cf. in particular Articles 113 to 117) and Rules 65 and 66(1) EPC, there are no obvious grounds which could in the present case justify refusal to admit new evidence at the appeal stage.

8. As shown in comparative experiments 20-22, the applicant had defined the problem, vis-à-vis the nearest prior art as not just preparing other copying papers but improved copying papers. Experiments 20 and 21 correspond to the prior art as established by German unexamined application 2 251 381; in the latter, adducts of polyisocyanates and compounds with hydrophilic groups are described as particularly advantageous (cf. page 3, para. 3, page 10, para. 2 and page 4 in conjunction with all the examples), with the result that the trifunctional adduct employed in experiment 20 and 21 consisting of 3 mol toluylene diisocyanate (cf. also example 4 of the above-mentioned German document) or hexamethylene diisocyanate (cf. also example 1 of the above-mentioned German document) and 1 mol trimethylopropane appears well suited to a comparative experiment with respect to field of application and structure. The Examining Division also regarded a comparison with a trifunctional isocyanate as pertinent (cf. Communication dated 12.09.79).

9. The results of these comparative experiments show that a copying paper produced as described in the application (experiment 22) is superior in respect of storage stability (Column 9) to the similarly manufactured papers according to the above-mentioned German document (experiments 20 and 21) at comparable impermeability (Column 10). According to the ageing test developed by the applicant company itself in the absence of a recognised test (0, 3, 6 and 12 days' storage at 75° C and 75% relative humidity), papers in accordance with the application suffer a drop in duplicating capacity, the diffuse reflection value for the 8th copy being - at present irrefutably - constant at approx. 39% and hence above the specified value of 35%. On the other hand, copying papers manufactured in accordance with the closest prior art lose about one third of their duplicating power with similar ageing, the above-mentioned diffuse reflection value falling after 12 days' storage to 20.8%, i.e. considerably below the specified value.

10. The importance of storage stability of the microcapsules, and hence of the copying papers, had already been stressed in the original documents submitted (cf. page 3, para. 1 and lines 24-30), and the evidence for patentability in the present case was introduced in due time within the meaning of Article 114(2) EPC, since it was submitted together with the grounds of appeal.

11. In order to solve this problem the applicant proposes to encapsulate the dyestuff-intermediate as solution in a hydrophobic organic solvent and to employ as material for the capsule walls a polyaddition product of a diisocyanate particularly characterised as one having the formula with the basic structure of 2,4,6-triketo-1,3,5-oxadiazine and a diamine. It was in fact known from German unexamined application 2 251 381 that for the manufacture of copying papers using micro-encapsulated dyestuff-intermediates, including the dyestuff-intermediate in solution in an oil-like fluid, which may also be a hydrophobic organic solvent (cf. Claims 1 and 23 in conjunction with page 12, para. 2), is advantageous, and that, in principle, any polyaddition product of a polyisocyanate, such as a di- or triisocyanate, and a polyamine, e.g., a diamine, is useable for the capsule (cf. Claims 1, 5 and 12). The polyaddition products of diamines and the 1,3,5-oxadiazine-2,4,6-trione diisocyanates described in German unexamined application 2 221 756 (cf. Claims 1 and 9 in conjunction with page 18) might also be used. But from the point of view of the problem of preparing copying paper having improved storage stability, the prior art cited by the Examining Division did not give any indication for selection of the more precisely prescribed oxadiazine-trione diisocyanate according to the claim from the enormous number of possible polyisocyanates for the micro-encapsulation of dyestuff-intermediates.

12. Even if it were to be thought appropriate to regard the micro-encapsulation of dyestuff-intermediates for the purpose of manufacture of copying papers on the one hand (cf. German unexamined application 2 251 381) and the manufacture of polyurethane coatings on textile substrates, leather or artificial leather, on the other hand (cf. German unexamined application 2 221 756) as closely neighbouring fields, which does not have to be decided in the present proceedings, the last-named document does not furnish any inducement to employ the oxadiazine-trione diisocyanates for the production of improved copying papers; since this special class of compounds is merely mentioned incidentally (cf. page 17 from para. 2 to the middle of page 18 and Claim 9) and not emphasised by an example. Mere mention of a group of substances amongst numerous other groups of substances permits at best a surmise of comparable suitability and effectiveness for the purpose in hand if these groups of substances are interchanged.

13. US patent specification 3 748 329 describes only the manufacture of 2,4,6-triketo-1,3,5- oxadiazines which are substituted in the 3- and 5-position by isocyanate-group-containing radicals, and which are in some cases identical with the diisocyanates defined in the claims (Formula I). It alleges that they are suitable for the production of porous and non-porous polymers, including polyureas, by reaction with polyamines, including diamines (cf. column 1, para. 1 in conjunction with column 5, lines 25-30 and lines 51/52), which in their turn serve as coatings for wood, metal and the like, and are used in mouldings and the preparation of foams (cf. column 10 lines 60-65). Even with knowledge of this prior art the person skilled in the art could at the most expect that if he were to use these oxadiazinetrione diisocyanates to produce wall material for micro-capsules he would get only qualitatively and quantitatively similar results as in German unexamined application 2 251 381. Thus the person skilled in the art who - as in this case - had tried to improve the copying papers specified in German unexamined application 2 251 381 would, on the basis of the prior art cited, not have arrived at the solution claimed in the application. The teaching of the present application, that the employment of the oxadiazinetrione diisocaynates as claimed leads to significantly improved copying papers must - independently of whether it is expressed in the form of the product claim 1 or the use claim 2 - be regarded as surprising, and hence involving an inventive step within the meaning of Article 56 EPC.

14. Given these circumstances, the question whether the oxadiazinetrione diisocyanates used according to the application are difunctional or trifunctional under the conditions of the micro-encapsulation can be left in abeyance; since in the case of the applicant's experiments in support of the patentability of the subject-matter of the application trifunctional isocyanates were chosen for comparison as known substances for the formation of micro-capsules which, in the opinion of the Examining Division, are far superior to the difunctional isocyanates for this purpose.

15. The Board considers the appeal allowable for the foregoing reasons.

16. No application has been made for reimbursement of the appeal fee in accordance with Rule 67 EPC, and the facts of the present case would not justify such a measure.

ORDER

For these reasons, it is decided that:

1. The decision of Examining Division 012 of the European Patent Office dated 16 November 1979 is set aside.

2. The case is remitted to the first instance with the order to grant a European patent on the basis of the following documents. Description page 1 and 4-6 dated 28.1.81, received on 29.1.81, Description p. 2,3 and 7-14 dated 12.1.81, received on 13.1.81, 2 patent claims dated 28.1.81, received on 29.1.81.