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(11) | EP 0 321 400 A2 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Polymeric colour couplers |
| (57) A polymeric colour coupler of the formula I :-
wherein E′ and E˝ represent the end groups of the polymer chain, R₁ is methyl, hydrogen, chlorine or bromine, R₂ is a divalent organic radical, R¹¹ and R¹¹¹ are each lower alkyl groups having 1 to 6 carbon atoms, or together represent the atoms required to form a five or size-membered heterocyclic ring, R¹ is an alkylene chain or an interrupted alkylene chain, W is the residue of a colour coupler which can react with an oxidised colour developer to yield a dye and B is the residue of an ethylenically unsaturated monomer which comprises no colour coupling residue nor a water solubilising group, a is from 10 to 60% by weight of the polymer, b is from 40 to 90% by weight of the polymer and c is from 0 to 20% by weight of the polymer, at least 10% by weight of the polymer being derived from the monomer which comprises the colour coupler residue and X is an anion. |
[0001] This invention relates to new polymeric colour couplers and to a process for their production. Polymeric colour couplers are finding increasing use in photographic material instead of colour couplers which require to be incorporated in photographic layers dissolved in an oil. The presence of the oil leads to several disadvantages including rendering the layer which comprises it soft and thus liable to mechanical deformation. Furthermore photographic material in which the colour couplers are present as a polymer latex can be much thinner than material in which the colour couplers are dissolved in oil. This decrease in thickness leads to sharper images being obtained.
[0002] However it has been found to be difficult to produce latexes of polymeric colour couplers easily and economically. One reason is that owing to the high melt point of most monomeric colour couplers and their limited solubility in most of the suitable comonomers and/or inert solvents, there is a marked tendency for the couplers to crystallise out of the monomer feed during the time over which the monomer feed is introduced to the reaction vessel. This necessitates keeping the monomer solution hot to prevent crystallisation. However it is known that it is inadvisable to maintain bulk solutions of monomers at elevated temperatures for prolonged periods of time owing to the serious risk of spontaneous thermally-induced polymerisation of the monomer mixture occurring rapidly and exothermically.
[0003] Because of the difficulties in preparing polymeric colour couplers as polymer latexes some effort has been made in trying to prepare colour couplers which are water-soluble polymers. However the difficulty is to find a polymeric colour coupler which whilst being water soluble is also layer substantive when coated in photographic material.
[0004] We have found a polymeric colour coupler which is readily water soluble but which when incorporated in a gelatino silver halide emulsion layer remains substantive to this layer.
[0005] Therefore according to the present invention there is provided a polymeric colour coupler of the general formula I:-
wherein E′ and E˝ represent the end groups of the polymer chain, R₁ is methyl, hydrogen, chlorine or bromine, R₂ is a divalent organic radical, R¹¹ and R¹¹¹ are each alkyl having 1 to 6 carbon atoms, or together represent the atoms required to form a five or six-membered heterocyclic ring such as R¹ is an alkylene chain or an interupted alkylene chain, W is the residue of a colour coupler which can react with an oxidised colour developer to yield a dye and B is the residue of an ethylenically unsaturated monomer which comprises no colour coupling residue nor a water solubilising group, a is from 10 to 60% by weight of the polymer, b is from 40 to 90% by weight of the polymer and c is from 0 to 20% by weight of the polymer and X is an anion.
[0006] With reference to the E′ and E˝ end-groups, as is well-known to anyone experienced in the art, the end-groups of polymer molecules formed by free radical initiation are generally incapable of determination with any degree of certainty, however it may be expected that at least one of the end-groups may either be an initiator residue or a group formed by disproportionation or chain transfer reactions during the preparation of the polymer of the claimed structure. Initiator residues may generally include those from alkyl or aryl peroxides, azo compounds, peroxydisulphates, peresters and peroxy carbonates, and specific examples may include the following radicals:
[0007] Further examples of commonly used initiators may be found in Polymer Handbook, Second Edition, John Wiley Publishers N.Y., 1975. Editors E.H. Immergut and J. Brandrup, Chapter II.1.
[0008] End-groups formed by disproportionations reactions may be saturated or unsaturated units from M or the initiating agent. Examples of such units may be found in Principles of Polymer Chemistry, Cornell U.p., P.J. Flay, p. 111.
[0009] It is not believed that the end-groups play any significant part in the photopolymerisation process described hereinafter.
[0010] R¹ is preferably an alkylene chain having from 2 to 6 carbon atoms or is an interupted alkylene chain having from 2 to 6 carbon atoms there being an oxygen atom or an -NH- group in the chain.
[0012] Preferably R₁ is hydrogen or methyl. R₂ the divalent organic radical may be the residue of a urethane, a urea, a carbonate, an ester, an ether, a ketone or an amide. Preferably however it is a simple amido linkage -C (O) - NH -.
[0013] Preferably in the quaternary ammonium residue in the polymer colour coupler R₁ is methyl or hydrogen and R₂ is -CO-O-, R¹ is an alkylene group and R¹¹ and R¹¹¹ are each methyl groups.
[0016] Any of the monomeric colour couplers described in the prior art may be used in the polymeric colour coupler of the present invention. The colour coupler portion W of the monomer may comprise ballasting groups or leaving groups for example so that the colour coupler may act as a two equivalent coupler.
[0017] The residue of a single colour coupler may be present in the polymer or the residue of more colour couplers may be present. When the residues of a yellow, a cyan and a magenta colour coupler are present a black or blackish dye is formed on colour development.
[0018] Examples of yellow dye forming monomeric colour couplers include couplers of the general formula II:-
wherein each of R₃, R₄, R₅ and R₆ are hydrogen, halogen, alkoxy, sulphoxy or sulphonamido, R₁ and R₂ are as defined above, R₇ is hydrogen or a leaving group and L₁ and L₂ are direct linkages or -NH-.
[0019] Particularly useful linking groups R₂ are -CO-NH-
and -O-CH₂-CH₂-NHSO₂-
Preferably one of L₁ and L₂ is a direct linkage. An example of such a monomer is Monomer B which is used in the Examples which follow.
[0022] A further example of a monomer of general formula II which has a leaving group is the monomer of the formula V :-
[0024] Another class of yellow dye forming monomeric colour couplers have a pivaloyl end group rather than a benzoyl end group.
[0025] Such colour couplers have the general formulae VI:-
where R₁, R₆ and R₇ have the meanings assigned to the above.
[0027] Examples of magenta dye forming monomeric colour couplers include couplers of the general formula VIII:-
where R₁ and R₂ are as defined above, R₈ is hydrogen or a leaving group and R₁₀, R₁₁ and R₁₂ are each hydrogen, halogen or alkoxy having 1 to 6 carbon atoms.
[0028] Preferably R₁ is hydrogen or -CH₃
Preferably R₂ is -CO NH-
However other useful linking groups R₂ include
-CO NH (CH₂) -O-CO-NH
where x 2 - 6,
where in the above two formulae the phenylene group is optionally substituted.
[0030] Particularly useful monomers of formula V are those wherein at least two of R₁₀, R₁₁ and R₁₂ are chlorine atoms.
[0031] Examples of leaving groups R₇ and R₈ include the group -S- R₉ where R₉ is a long chain alkyl group having over 10 carbon atoms or is a substituted phenyl group having at least one alkyl or alkoxy group. Preferably R₉ has from 12 to 20 carbon atoms in the chain.
[0033] Examples of monomers of formula VIII are :-
and Monomer A which is used in the Examples which follow and which has the formula :-
[0035] Another type of magenta dye forming monomeric colour couplers are those of general formula XII:-
wherein R₁, R₈ and R₁₀ are as defined above and R₁₀ is alkyl, dialkyl amino, optionally substituted phenyl and optionally substituted acylamino.
[0036] Substituents in the phenyl or acylamino group include alkyl groups having from 2 to 6 carbon atoms and chlorine atoms.
[0037] These couplers may be prepared by reacting magenta colour couplers of the formula XIII :
with acryloyl or methacryloyl chloride.
[0038] Examples of cyan forming monomeric colour couplers include phenol couplers of the general formula XVI :-
and of general formula X V :
and a naphthol coupler of the general formula XVI :
where in the above three formulae R₁ is as defined above, R₁₂ is hydrogen or halogen, R₁₄ is hydrogen or a leaving group such as a halogen atom or substituted alkoxy, R₁₃ is hydrogen or alkyl having 1 to 5 carbon atoms, R₁₅ is an alkyl group having 1 to 6 carbon atoms or ac ylamino or arylamino, and R₁₇ is a linking group and y is 0 or 1, and R₁₆ is hydrogen, alkoxy having 1 to 4 carbon atoms or an amino, amido or sulphonamido group.
[0041] Examples of the linking groups R₁₇ include alkylene chains of 2 to 6 carbon atoms including interrupted alkylene chains and as mentioned above alkyl groups for example
[0042] Examples of monomers of formula XIV are
this is Monomer C which is used in the Examples which follow,
[0046] In the quaternary ammonium residue of the polymeric colour coupler of formula I,
R₁ is preferably methyl or hydrogen and R₂ is preferably - CO - O -
R¹ is preferably an alkylene group and most preferably -CH₂-CH₂- or -CH₂-CH₂-CH₂- R¹¹ and R¹¹¹ preferably are each methyl groups, X is Cl or Br or preferably is an organic anion such as para-toluene-sulphonate.
[0047] A particular useful quaternary ammonium residue is derived from dimethylaminoethyl methacrylate and has the formula :-
[0048] In order to improve the physical characteristics of the polymer of formula I it is sometimes advantageous to include up to 20% by weight of a non-coupling, non-water solubilising monomer in the coupler.
[0049] Suitable for component B comonomers include methyl acrylate, ethyl acrylate, butyl acrylate, ethyl hexyl acrylate, vinyl acetate; hydroxymethyl methacrylate, hydroxypropylmethacrylate; methacrylic acid, acrylic acid, itaconic acid, 2-carboxyethyl acrylate and the salt thereof, acrylamide, methacrylamide, N-hydroxymethyl acrylamide, styrene, N-vinyl pyrrolidone, 1-vinyl imidazole; 4-vinylpyridine, dimethylaminoethyl methacrylate, vinyl sulphonic acid and the salts thereof, acrylonitrile and vinylidene chloride.
[0050] According to another aspect of the present invention there is provided a process for the production of a polymer of formula I which comprises dissolving in a water-miscible organic solvent a monomeric colour coupler, a monomer which comprises the quaternary ammonium group and optionally another monomer in the ratio a, b and c as hereinbefore set forth, heating the solution and adding a solution of free radical polymerisation initiating agent and precipitating the polymer by addition of a water immiscible organic solvent.
[0051] The resultant polymer is water soluble. It is compatible with gelatin and when added to a silver halide emulsion yields a clear dry coating.
[0052] The polymer is layer substantive and thus when the polymer is incorporated in a gelatino silver halide emulsion and after exposure and colour development a coloured dye image is obtained in the layer in which the polymer is coated.
[0053] It is surprising that the quaternary ammonium residue when incorporated into the polymer provides water-soluble colour couplers because when various other water-soluble monomers were tried either they did not copolymerise at all with the monomeric colour couplers or they yielded a polymer which was water insoluble.
[0054] Examples of comonomers that did not copolymerise included :-
1. Vinyl sulfonic acid
2. Maleic anhydride
3. Sodium allyl sulfonate
4. acrylamido propane sulfonic acid.
[0055] Monomers that did copolymerise but did not provide water soluble colour coupler polymers included :-
1. N-vinyl pyrrolidone
2. Acrylamide
3. hydroxymethyl N-vinyl acetamide
4. tetrahydrofurfuryl methacrylate
5. N-vinyl acetamide
6. vinyl imidazole
7. vinyl imidazole-p-toluene sulfonic acid salt
[0056] According to a further feature of the present invention there is provided a method of preparing colour photographic material which comprises forming a colour coupler polymer as just described, mixing this polymer with an aqueous gelatino silver halide emulsion and coating the emulsion on a photographic base.
[0057] Such photographic material may comprise one gelatino silver halide emulsion layer comprising a colour coupler polymer of the present invention, two such silver halide emulsion layers or three such layers. In the last case the three layers will most likely be a silver halide layer in which the polymeric colour coupler yields a yellow dye, a layer in which the polymeric colour coupler yields a cyan dye and a layer in which the polymeric colour coupler yields a magenta dye.
[0058] In another embodiment the colour coupler polymer of the present invention may comprise the residue of a monomeric yellow colour coupler, the residue of a monomeric magenta colour coupler and the residue of a monomeric cyan colour coupler.
[0059] Polymeric colour couplers of this type are of particular use in monochrome camera speed silver halide material. The photographic material after imagewise exposure is developed in a colour developing bath by use of a para - phenylene diamine developing agent to yield a developed silver image and black dye image.
[0060] The material is then subjected to a bleach fix treatment which removes the developed silver image and the unexposed silver halide leaving the black dye negative image which can be used to print all types of black and white paper including variable contrast paper.
[0061] The colour former of this type can also be used to prepare monochrome paper. That is to say paper which can be processed using colour processing chemistry to yield a black dye image instead of a silver image. Paper of this type is of particular use from which to prepare proof prints.
[0062] The colour former of this type can also be used to reinforce silver halide images at such time that, as occurred some years ago, the price of silver becomes too prohibitive to use in photography when a very dense silver image is required.
[0063] The photographic material of the present invention preferably comprises gelatin as the binder in the silver halide emulsion layer.
[0064] The halide used can be any of the silver halides normally used in photography e.g. silver bromide, silver iodobromide, silver chloride, silver chlorobromide and silver iodochlorobromide. The silver halide grains may be both optically and chemically sensitised. The silver halide emulsion may contain stabilisers bactericides and any of the other additives commonly found in photographic silver halide emulsions. The gelatin may have been hardened and may contain coating aids as usual when preparing coated silver halide emulsions.
[0065] For camera speed film material the base can be any of the usual transparent bases used in photography for example subbed polyester, polycarbonate or polystyrene base, or may be a cellulose triacetate or cellulose acetate - butyrate base. If the material is to be used for proof prints the base may be any opaque base in common use for photographic print material for example baryta coated paper base or polyethylene laminated paper base.
Example 1
[0067] Para-toluene sulphonic acid (1g) was dissolved in 5cm³ of industrial alcohol. Sufficient of the monomer dimethyl aminoethyl methacrylate was added with stirring to raise the pH to 7. This required 1.3 g. This solution was placed in a 25 cc round bottom flask to which 0.5 g of a monomeric colour coupler was added. The flask was fitted with a magnetic stirrer, condenser and nitrogen inlet. The flask was immersed in an oil bath at 75°C and nitrogen was bubbled through. A solution of azobisisobutyronitrile in industrial alcohol (1.2 cm³ of a 1% solution) was added. After 2 hour a further 0.3 cm³ of the same solution was added, then left for a further two hours when a further 0.3 cm³ of the solution was added. After hours reaction time the contents of the flask were poured into 200 cm³ of ether whereupon the polymer precipitated as a solid. Yield = 2.30 g (82.1%) when the polymeric colour coupler used was yellow colour coupler Monomer B.
[0068] Yield = 1.97g (70.3%) when the monomeric colour coupler used was the magenta colour coupler Monomer A.
[0070] These solids were used to prepare colour photographic material. To 2.2 cm³ of an undyed twinned crystal iodobromide gelatino emulsion there was added 0.1 g of the solid and 7 cm₃ of water. To this emulsion there was added 0.4 cc of a 3% solution of a triazine hardener. The emulsion was then coated on clear cellulose triacetate base to provide a silver coating weight of 12 mg/dm². The coating was dried and inspected in green light to show a clear, glossy coating.
[0071] This photographic material was then exposed to a white light source for 10 seconds and processed in a colour developing solution for 3.25 minutes at 38°C.
[0074] The formula of the bleach bath used is as follows :-
| ammonium bromide | 150 g |
| ferric EDTA 1.8 M | 150 ml |
| sodium nitrate | 20 g |
| water to | 1 litre |
[0075] The material was then passed to a fixing bath at 35°C for 6½ minutes of the formula :-
| ammonium thiosulphate (80% w/v) | 190 ml |
| sodium sulphite | 19 g |
| sodium EDTA | 1.5 g |
| water to | 1 litre |
[0077] The results obtained were as follows :-
| COLOUR | λ MAX | D MAX | D MIN | |
| A | Magenta | 556 | 0.47 | 0.18 |
| B | Yellow | 452 | 0.71 | 0.46 |
[0078] These results show that the coatings yield dye images of sufficiently good quality for the polymer to be used in colour photographic material.
Example II
[0079] p-Toluene sulphonic acid (4 g) was dissolved in industrial alcohol (30 cm³). Sufficient of the monomer dimethyl-aminoethyl methacrylate was added with stirring to raise the pH to 7. This required 5.2 g. This solution was placed in a 50 cm³ flask to which were added 1 g of Monomer A (the magenta monomer), 0.5 g Monomer B (the yellow monomer) and 0.5 g of Monomer C (the cyan monomer). The flask was equipped with a condenser, nitrogen inlet, oil bath and magnetic stirrer. Nitrogen was bubbled through the solution for 10 minutes at room temperature. The flask was then heated at 70°C and maintained at that temperature.
[0080] A free radical initiator solution was prepared which comprised 0.5 g azobis(isobutyronitrile) in 50 cm³ of industrial alcohol. 4.8 cm³ of this solution was added to the flask. After 2 hours a further 1.2 cm³ of the initiator solution was added and this was repeated after a further 2 hours. After 7 hours reaction time the contents of the flask were added to ether (500 cm³) and a tacky brown solid precipitated. This solid was dissolved in industrial alcohol and reprecipitated in ether to give a free flowing white powder. Yield 7.13 g (67.3 %). The powder was found to be completely water soluble.
[0081] 0.1 g of this solid was then added to a similar emulsion as used in Example 1, and the emulsion was coated as in Example 1. A clear glossy coating was found on inspection in green light. As in Example 1 the coating was exposed to white light for 10 seconds and then was processed as set forth in Example 1.
1. A polymeric colour coupler of the general formula I :-
wherein E′ and E˝ represent the end groups of the polymer chain, R₁ is methyl, hydrogen, chlorine or bromine, R₂ is a divalent organic radical, R¹¹ and R¹¹¹ are each lower alkyl groups having 1 to 6 carbon atoms, or together represent the atoms required to form a five or size-membered heterocyclic ring, R¹ is an alkylene chain or an interrupted alkylene chain, W is the residue of a colour coupler which can react with an oxidised colour developer to yield a dye and B is the residue of an ethylenically unsaturated monomer which comprises no colour coupling residue nor a water solubilising group, a is from 10 to 60% by weight of the polymer, b is from 40 to 90% by weight of the polymer and c is from 0 to 20% by weight of the polymer, at least 10% by weight of the polymer being derived from the monomer which comprises the colour coupler residue and X is an anion.
wherein E′ and E˝ represent the end groups of the polymer chain, R₁ is methyl, hydrogen, chlorine or bromine, R₂ is a divalent organic radical, R¹¹ and R¹¹¹ are each lower alkyl groups having 1 to 6 carbon atoms, or together represent the atoms required to form a five or size-membered heterocyclic ring, R¹ is an alkylene chain or an interrupted alkylene chain, W is the residue of a colour coupler which can react with an oxidised colour developer to yield a dye and B is the residue of an ethylenically unsaturated monomer which comprises no colour coupling residue nor a water solubilising group, a is from 10 to 60% by weight of the polymer, b is from 40 to 90% by weight of the polymer and c is from 0 to 20% by weight of the polymer, at least 10% by weight of the polymer being derived from the monomer which comprises the colour coupler residue and X is an anion.
2. A polymer according to claim 1 wherein R₁ is hydrogen or methyl.
3. A polymer according to claim 1 wherein R₂ the divalent organic radical is the residue
of urethane, a urea, a carbonate, an ester, an ether, a ketone or an amide.
4. A polymer according to claim 3 wherein R₂ is the linkage - C - (O) - NH -.
5. A polymer according to claim 1 where in the quaternary ammonium residue in the
polymer colour coupler formulated in claim 1 R₁ is methyl or hydrogen and R₂ is -CO
- O -, R¹ is an alkylene group and R¹¹ and R¹¹¹ are each methyl groups.
6. A polymer according to claim 5 wherein R¹ is -CH₂ CH₂ CH₂ - or-CH₂ CH₂ CH₂ CH₂
-.
7. A polymer according to claim 5 wherein X is para-toluene sulphonate.
8. A polymer according to claim 1 wherein the quaternary ammonium residue in the polymeric
colour coupler formulated in claim 1 has the formula :-
9. A polymer according to claim 1 which comprises the residue of a yellow dye forming
monomeric colour coupler of the general formula :-
wherein each of R₃, R₄, R₅ and R₆ are hydrogen, halogen, alkoxy, sulphoxy or sulphonamido, R₁ and R₂ are as defined in claim 1, R₇ is hydrogen or a leaving group and L₁ and L₂ are direct linkages or -NH-.
wherein each of R₃, R₄, R₅ and R₆ are hydrogen, halogen, alkoxy, sulphoxy or sulphonamido, R₁ and R₂ are as defined in claim 1, R₇ is hydrogen or a leaving group and L₁ and L₂ are direct linkages or -NH-.
10. A polymer according to claim 1 which comprise the residue of a yellow dye forming
monomeric colour coupler of the general formula :-
wherein R₁ and R₂ and R₆ and R₇ are as defined in claim 9.
wherein R₁ and R₂ and R₆ and R₇ are as defined in claim 9.
11. A polymer according to claim 1 which comprises the residue of a magenta dye forming
monomeric colour coupler of the general formula :-
where R₁ and R₂ are as defined in claim 1, R₈ is hydrogen or a leaving group and R₁₀, R₁₁ and R₁₂ are each hydrogen, halogen or alkoxy.
where R₁ and R₂ are as defined in claim 1, R₈ is hydrogen or a leaving group and R₁₀, R₁₁ and R₁₂ are each hydrogen, halogen or alkoxy.
12. A polymer according to claim 1 which comprises the residue of a magenta dye forming
monomeric colour coupler of the general formula :-
wherein R₁, R₈ and R₁₀ are as defined in claim 11 and R₉ is alkyl, dialkylamino, optionally substituted aryl and optionally substituted acylamino.
wherein R₁, R₈ and R₁₀ are as defined in claim 11 and R₉ is alkyl, dialkylamino, optionally substituted aryl and optionally substituted acylamino.
13. A polymer according to claim 1 which comprises the residue of a cyan dye forming
monomeric colour coupler which is a phenol coupler of the general formula :-
or is a phenol coupler of the general formula :-
or is a naphthol coupler of the general formula
where in the above three formula R₁ and R₁₂ are as defined, R₁₄ is hydrogen or a leaving group such as a halogen atom or a substituted alkoxy group, R₁₃ is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, R₁₅ is a linking group and y is 0 or 1, and R₁₆ is an alkoxy, amino amido, or sulphonamide group.
or is a phenol coupler of the general formula :-
or is a naphthol coupler of the general formula
where in the above three formula R₁ and R₁₂ are as defined, R₁₄ is hydrogen or a leaving group such as a halogen atom or a substituted alkoxy group, R₁₃ is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, R₁₅ is a linking group and y is 0 or 1, and R₁₆ is an alkoxy, amino amido, or sulphonamide group.
14. A polymer according to claim 1 wherein the polymer comprises units derived from
simple, non-colour coupling, photographically inert comonomers.
15. A polymer according to claim 14 wherein the photographically inert comonomer is
methyl acrylate, ethyl acrylate, butyl acrylate, ethyl hexyl acrylate, vinyl acetate;
hydroxyethyl methacrylate, hydroxypropylmethacrylate; methacrylic acid, acrylic acid,
itoconic acid, 2-carboxyethyl acrylate, and the salts thereof, acrylamide, methacrylamide,
N-hydroxymethyl acrylamide, styrene, N-vinyl pyrrolidone, 1-vinyl imidazole; 4-vinylpyridine,
dimethylaminoethyl methacrylate, tetrahydrofurfuryl methacrylate; sulphoethyl methacrylate,
vinyl sulphonic acid and salts thereof, acrylonitrile and vinylidene chloride.
16. Photographic material having at least one gelatino silver halide emulsion layer
which comprises a polymeric colour coupler as claimed in claim 1.
17. A process for the production of a polymer of formula I which comprises dissolving
in a water-miscible organic solvent a monomeric colour coupler, a monomer which comprises
a quaternary ammonium group of the formula :-
wherein R₁, R₂, R¹, R¹¹ and R¹¹¹ are as defined in claim 1 and optionally another monomer in the ratio as defined in claim 1, heating the solution and adding a solution of free radical polymerisation initiating agent and precipitating the polymer by addition of a water immiscible organic sovlent.
wherein R₁, R₂, R¹, R¹¹ and R¹¹¹ are as defined in claim 1 and optionally another monomer in the ratio as defined in claim 1, heating the solution and adding a solution of free radical polymerisation initiating agent and precipitating the polymer by addition of a water immiscible organic sovlent.
18. A method of preparing colour photographic material which comprises forming a polymeric
colour coupler as claimed in claim 1, mixing this polymer with an aqueous gelatino
silver halide emulsion and coating the emulsion on a photographic base.