A process for the formation of transfer images in colour formed by: I. image-wise exposure to electromagnetic radiation of a photographic material, which contains a silver halide emulsion layer having in effective contact with the silver halide grains, which are sensitive to said radiation, a developing agent that is resistant to diffusion in a hydrophilic colloid medium and having in effective contact with said developing agent at least one colourless reagent that is capable: 1. of diffusing in aqueous alkaline medium from said photographic material to a receptor material, 2. of forming a dyestuff by oxidative intermolecular or intramolecular coupling or coupling with a different colourless reagent being likewise capable of diffusing in the aqueous alkaline medium, and 3. of forming with the oxidation product of said developing agent a compound having a substantially smaller diffusion mobility than it has in unreacted state, Ii. contacting the exposed photographic material with an aqueous alkaline activating liquid to bring about the reducing action of the developing agent thereby forming in the exposed portions a silver image and an oxidation product of the developing agent that couples with said colourless reagent(s) to form in the exposed portions of the emulsion layer (a) compound(s) that possess(es) a substantially lower diffusion mobility than the unreacted reagents have, and Iii. transferring from the treated photographic material an amount of (the) reagent(s) that remained capable of diffusing by means of the alkaline processing liquid onto a receiving material whereon transferred reagent is intermolecularly or intramoleculary oxidatively coupled, or said different reagents are oxidatively coupled by means of an oxidising agent. Useful diffusion-resistant developing agents are of the para-phenylene diamine type. Useful colourless reagents are selected from the class of .alpha.-naphthol, phenol, reactive methylene or N,N-dialkylaniline type coupler compounds capable of oxidatively coupling with a different colourless reagent being a hydrazone compound in order to form dyes containing an azino group. The intramolecularly coupling compounds contain as a first group the reactive part of one of said coupler compounds chemically liked to a second group containing the hydrazone structure.

Current U.S. Class:	430/222 ; 430/241
Current International Class:	G03C 8/02 (20060101); G03C 8/12 (20060101); G03c 007/00 (); G03c 005/54 (); G03c 001/40 ()
Field of Search:	96/3,77,29D

Daniel; William J.

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Claims

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We claim:

1. A process for the formation of transfer images in color comprising the steps of:

a. imagewise exposing to electromagnetic radiation a photographic material, which contains a silver halide emulsion layer including the silver halide grains which are sensitive to said electromagnetic radiation and in effective contact with said grains a developing agent that is resistant to diffusion in a hydrophilic colloid medium, said layer also containing in effective contact with said developing agent a colorless reagent capable of:

1. diffusing in aqueous alkaline medium from said material to a receptor material,

2. forming a dyestuff by oxidative coupling, and

3. forming with the oxidation product of said developing agent a compound of substantially reduced diffusion mobility,

b. contacting the exposed photographic material with an aqueous alkaline activating liquid to bring about the reducing action of the developing agent thereby forming in the exposed portions a silver image and an oxidation product of the developing agent that reacts with such colorless reagent to form in the exposed portions of the emulsion layer said compound of substantially reduced diffusion mobility and

c. transferring from the treated material an amount of such colorless reagent onto a receiving material whereon such transferred reagent is subjected to oxidative coupling by means of an oxidizing agent stronger than exposed silver halide resulting in the formation of an image of said dyestuff on the receiving material,

said colorless reagent being

(A) the combination of a colorless coupler capable of forming a quinonimine or azomethine dyestuff with an oxidized p-phenylene diamine developing agent and a heterocyclic hydrazone compound corresponding to the following general formula: ##SPC56##

wherein:

R.sub.1 represents --CONH.sub.2 or a --SO.sub.2 X group in which X represents hydroxyl, an amino group, an alkyl group or an aryl group, and

z represents the necessary atoms to close a 5- or 6-membered heterocyclic nucleus or a ring system containing such nucleus, said nucleus being a nitrogen- or nitrogen and sulphur-containing heterocyclic nucleus, or

B. a composite compound capable of oxidative coupling and corresponding to the general formula:

C.sub.1 - C.sub.2

wherein:

C.sub.1 is a chemical moiety capable of forming a quinonimine or azomethine dyestuff with an oxidized p-phenylenediamine type developing agent and

C.sub.2 is a chemical moiety chemically linked to moiety C.sub.1 which contains a hydrazone group and enables the composite compound under oxidative conditions to form a dye containing an =N-N= group, said C.sub.2 moiety having the general formula: ##SPC57##

in which Z represents the necessary atoms to close a 5- or 6-membered heterocyclic nucleus or a ring system containing such nucleus, said nucleus being a nitrogen- or nitrogen and sulphur-containing heterocyclic nucleus.

2. A process according to claim 1 wherein the silver halide emulsion layer contains a non-diffusing silver halide developing agent the oxidation product of which forms a reaction product with a phenol-type or reactive methylene type coupler.

3. A process according to claim 1 wherein the contacting of the exposed photographic material with an alkaline aqueous liquid occurs in the presence of a primary developing agent that is resistant to diffusion and of an auxiliary developing agent.

4. A process according to claim 1 wherein the receiving material contains in a water-permeable image-receiving layer at least one oxidizing agent of the group comprising a non-diffusing organic peroxide, a long chain aliphatic onium salt of a peracid and a compound that splits off halogen in aqueous medium.

5. A process according to claim 4 wherein the receiving material contains as a mordanting agent for the dye formed thereon a polymer containing cationic groups.

6. A process according to claim 1 wherein the alkaline aqueous processing liquid contains at least one alkaline compound of the group comprising alkali metal carbonates, alkali metal hydroxides and aliphatic amines.

7. A process according to claim 1 for the formation of multicolor images with a photographic material containing three superposed silver halide emulsion layers, which are sensitive to blue, green and red light respectively, said process comprising the steps of:

a. exposing to a multicolor light pattern a photographic material which comprises:

1. a blue-sensitive silver halide emulsion layer containing a non-diffusing silver halide developing agent and in effective contact with said developing agent a colorless coupler and hydrazone compound that are capable of diffusing in said medium when wetted with an aqueous alkaline liquid and of forming a yellow dyestuff by oxidative coupling with each other and wherein at least one of said coupler and compound is capable of forming with the oxidation product of the developing agent a compound of substantially lower diffusion mobility than the unreacted compound,

2. a green-sensitive silver halide emulsion layer containing a non-diffusing silver halide developing agent and in effective contact with said developing agent a colorless coupler and hydrazone compound that are capable of diffusing in said medium when wetted with an alkaline aqueous liquid and of forming a magenta dyestuff by oxidative coupling with each other and wherein at least one of said coupler and compound is capable of forming with the oxidation product of the developing agent a compound of substantially lower diffusion mobility than the unreacted compound, and

3. a red-sensitive silver halide emulsion layer containing a non-diffusing silver halide developing agent and in effective contact with said developing agent a colorless coupler and hydrazone compound that are capable of diffusing in said medium when wetted with an aqueous alkaline liquid and of forming a cyan dyestuff by oxidative coupling with each other and wherein at least one of said coupler and compound is capable of forming with the oxidation products of the developing agent a compound of substantially lower diffusion mobility than the unreacted compound; wherein said hydrazone compound of each such layer is the same and corresponds to the general formula of the first hydrazone compound of claim 28,

b. contacting the exposed photographic material with an aqueous alkaline processing liquid, which starts the reducing action of such developing agent thereby forming in correspondence with the latent silver image portions of each silver halide emulsion layer a visible silver image and a developer oxidation product, which couples in its silver halide emulsion layer with at least one of said coupler and hydrazone compound to form a compound of substantially reduced diffusion mobility,

c. transferring from the treated material from step (b) residual unaffected dye-forming coupler and compound by means of the alkaline processing liquid into a receptor material wherein the coupler and hydrazone compound of each layer are oxidatively coupled together by means of an oxidant stronger than exposed silver halide resulting in the formation in the receptor material of a positive multicolor print of the multicolor light pattern.

8. A process according to claim 1 for the formation of multicolor images by imagewise transfer of a composite compound of the formula C.sub.1 -C.sub.2 as in claim 28 from a photographic material containing three superposed silver halide emulsion layers that are sensitive to blue, green and red light respectively, said process comprising the steps of:

a. exposing to a multicolor light pattern a photographic material which comprises:

1. a blue-sensitive silver halide emulsion layer containing a non-diffusing silver halide developing agent and in effective contact therewith a colorless compound of said formula C.sub.1 -C.sub.2 that is capable of diffusing in said medium with an alkaline aqueous liquid, of forming a yellow dyestuff by oxidative intramolecular or intermolecular coupling, and of forming with the oxidation product of said developing agent a compound of substantially reduced diffusion mobility,

2. a green-sensitive silver halide emulsion layer containing a non-diffusing silver halide developing agent and in effective contact therewith a colorless compound of said formula C.sub.1 -C.sub.2 that is capable of diffusing in said medium with an alkaline aqueous liquid, of forming a magenta dyestuff by oxidative intramolecular or intermolecular coupling, and of forming with the oxidation product of said developing agent a compound of substantially reduced diffusion mobility, and

3. a red-sensitive silver halide emulsion layer containing a non-diffusing silver halide developing agent and in effective contact therewith a colorless compound of said formula C.sub.1 -C.sub.2 that is capable of diffusing in said medium with an alkaline aqueous liquid, of forming a cyan dyestuff by oxidative intramolecular or intermolecular coupling, and of forming with the oxidation product of said developing agent a compound of substantially reduced diffusion mobility,

b. contacting the exposed photographic material with an aqueous alkaline liquid, which starts the reducing action of such developing agent thereby forming in correspondence with the latent silver image portions of each silver halide emulsion layer a visible silver image and a developer oxidation product, which couples in its silver halide emulsion layer with the corresponding colorless compound to form a compound of substantially reduced diffusion mobility,

c. transferring from the treated material the different residual unaffected colorless compounds with the alkaline processing liquid into a receptor material wherein the different compounds are intramolecularly or intermolecularly oxidatively coupled by means of an oxidizing agent which is stronger than exposed silver halide, resulting in the formation in the receptor material of a positive multicolor print of the multicolor light pattern.

9. A photographic process according to claim 1 wherein said developing agent is a compound the oxidation product of which forms a diffusion inhibited reaction product with an .alpha.-naphthol, phenol, reactive methylene type coupler of a N,N-dialkylaniline type coupler.

10. A photographic process according to claim 9 wherein said developing agent is an aromatic primary amino developing agent.

11. A photographic process according to claim 10 wherein the developing agent corresponds to the following general formula: ##SPC58##

wherein:

each of R.sub.1 and R.sub.2 represents an aliphatic residue, or

R.sub.1 represents the necessary methylene groups to close a 5- or 6-membered heterocyclic nucleus with the carbon atom in the 6-position of the benzene nucleus, or

R.sub.2 represents the necessary methylene groups to close a 5- or 6-membered heterocyclic nucleus with the carbon atom in the 2-position of the benzene nucleus, or

R.sub.1 and R.sub.2 together represent the necessary methylene groups to close a 5-membered nitrogen-containing nucleus, and

R.sub.3 is hydrogen, an alkyl group and an alkoxy group, provided that where R.sub.3 does not represent hydrogen, it is substituted at the 3- and/or 5-positions of said nucleus, and wherein said developing agent contains at least one alkyl group with at least 4 carbon atoms to provide resistance to diffusion in a hydrophilic colloid medium.

12. A photographic process according to claim 1 wherein said coupler which is capable of forming with the developer oxidation product a compound of substantially reduced diffusion mobility is a phenol, .alpha.-naphthol, a reactive methylene type of an N,N-dialkyl-aniline type coupler.

13. A photographic material suitable for the production of dye images by imagewise diffusion transfer of compounds soluble in an aqueous alkaline processing liquid, which material contains

a. photosensitive silver halide grains dispersed in a hydrophilic colloid layer and

b. in such layer or in water-permeable relationship to such layer a colorless reagent capable of forming a dyestuff by an oxidative coupling reaction and of diffusing in an aqueous alkaline medium from said material to a receptor material, and

c. in effective contact with said silver halide grains a developing agent which is resistant to diffusion in a hydrophilic colloid medium and which when activated in the presence of an aqueous alkaline liquid after the imagewise exposure of said layer reduces the exposed silver halide in said layer and couples in its oxidized state with said colorless reagent to form a product inhibited against diffusion from the exposed portions of the photosensitive material into the receptor material,

and wherein said colorless reagent in said photographic material is

A. the combination of a colorless color coupler capable of forming a quinonimine or azomethine dyestuff with an oxidized p-phenylene diamine developing agent and a heterocyclic hydrazone compound of the following general formula: ##SPC59##

wherein:

R.sub.1 represents a --CONH.sub.2 or --SO.sub.2 X group in which X represents hydroxyl, an amino group, an alkyl group or an aryl group, and represents the necessary atoms to close a 5- or 6-membered heterocyclic nucleus or a ring system containing such nucleus, said nucleus being a nitrogen- or nitrogen and sulphur-containing heterocyclic nucleus, or

B. a compound capable of oxidative coupling corresponding to the general formula:

C.sub.1 - C.sub.2

wherein:

C.sub.1 is a chemical moiety capable of forming a quinonimine or azomethine dyestuff with an oxidized p-phenylenediamine type developing agent, and

C.sub.2 is a chemical moiety chemically linked to moiety C.sub.1, which moiety C.sub.2 contains a hydrazone group and enables the compound under oxidative conditions to form a dye containing an =N--N= group, said C.sub.2 moiety having the general formula: ##SPC60##

in which Z represents the necessary atoms to close a 5- or 6-membered heterocyclic nucleus or a ring system containing such nucleus, said nucleus being a nitrogen- or nitrogen and sulphur-containing heterocyclic

14. A photographic material according to claim 13 wherein the colorless color coupler is a phenol, .alpha.-naphthol, or reactive methylene type of

15. A photographic material according to claim 14 wherein said colorless coupler is a phenol having the general formula: ##SPC61##

wherein:

each of R.sub.1 and R.sub.2 represents hydrogen, an alkyl group, an alkoxy group or the group --NHR in which R represents a carboxylic or sulphonic acid acyl group, with the proviso that R.sub.1 and R.sub.2 do not

16. A photographic material according to claim 14 wherein said colorless coupler is an .alpha.-naphthol having the general formula: ##SPC62##

wherein:

17. A photographic material according to claim 14 wherein said colorless coupler corresponds to one of the following general formulae:

R.sub.1 --CO--CH.sub.2 --CO--R.sub.2 (I) R.sub.1 --CO--CH.sub.2 (II)N and ##SPC63##

wherein:

R.sub.1 represents an alkyl group, an aryl group, a N-aryl-amino group or an ether group,

R.sub.2 represents an alkyl group or an aryl group,

R' represents an alkyl group or an aryl group,

R" represents an alkyl group, an aryl group, a N-aryl-amino group, a

18. A photographic material according to claim 14 wherein said colorless coupler is a N,N-dialkylaniline having the general formula: ##SPC64##

wherein:

M is hydrogen, a metal cation or cationic group,

Y is an alkylene group, and

19. A photographic material according to claim 13 wherein said developing agent has the general formula: ##SPC65##

wherein:

each of R.sub.1 and R.sub.2 represents an aliphatic residue or

R.sub.1 represents the necessary methylene groups to close a 5- or 6-membered heterocyclic nucleus with the carbon atom in the 6-position of the benzene nucleus, or

R.sub.2 represents the necessary methylene groups to close a 5- or 6-membered heterocyclic nucleus with the carbon atom in the 2-position of the benzene nucleus, or

R.sub.1 and R.sub.2 together represent the necessary methylene groups to close a 5-membered nitrogen-containing nucleus, and

R.sub.3 is hydrogen, an alkyl group and an alkoxy group, provided that when R.sub.3 does not represent hydrogen it is substituted on the 3- and/or 5-positions of said nucleus, and wherein said developing agent contains at least one alkyl group with at least 4 carbon atoms to provide the

20. A photographic material according to claim 13 wherein said moiety C.sub.1 is a group derived from an .alpha.-naphthol coupler which corresponds to the formula: ##SPC66##

21. A photographic material according to claim 13 wherein said moiety C.sub.1 is a group derived from a non-diffusion resistant reactive methylene type coupler corresponding to one of the following general formulae:

--HN--CO--CH.sub.2 --CO--R.sub.2 (I)

and

--HN--CO--CH.sub.2 --CN (II) ##SPC67## wherein:

R.sub.2 represents an alkyl group, an aryl group, an alkoxy group or an alkyl- or aryl-substituted amino group, and

R" represents an alkyl group, an aryl group, a cyano group, an alkoxy group, a carbonylalkoxy group, a N-arylamino group, a N-acylamino group,

22. A photographic material according to claim 13 wherein the silver halide grains are present in a hydrophilic colloid layer on a flexible support.

23. A photographic material according to claim 22 wherein the support is a

24. A photographic material according to claim 13 adapted for use in the formation of multicolor images by imagewise diffusion transfer of dye-forming reactants from a photographic material onto a receptor material, which photographic material comprises:

1. a blue-sensitive silver halide emulsion layer containing a non-diffusing silver halide developing agent and in effective contact therewith a colorless dye-forming reagent of the formula C.sub.1 -C.sub.2 as in claim 13 that is capable of diffusing in said medium with the aid of an alkaline aqueous liquid, of forming a yellow dyestuff by oxidative intermolecular or intramolecular coupling, and of forming with the oxidation product of said developing agent a compound of substantially reduced diffusion mobility,

2. a green-sensitive silver halide emulsion layer containing a non-diffusing silver halide developing agent and in effective contact therewith a colorless dye-forming reagent of said formula C.sub.1 -C.sub.2 that is capable of diffusing in said medium with an alkaline aqueous liquid, of forming a magenta dyestuff by oxidative intermolecular or intramolecular coupling, and of forming with the oxidation product of said developing agent a compound of substantially reduced diffusion mobility, and

3. a red-sensitive silver halide emulsion layer containing a non-diffusing silver halide developing agent and in effective contact with said developing agent a colorless dye-forming reagent of said formula C.sub.1 -C.sub.2 that is capable of diffusing in said medium with the aid of an alkaline aqueous liquid, of forming a cyan dyestuff by oxidative intermolecular or intramolecular coupling, and of forming with the oxidation product of said developing agent a compound of substantially

25. A photographic material according to claim 13 adapted for use in the formation of multicolor images by imagewise diffusion transfer of dye-forming reactants from a photographic material onto a receptor material, which photographic material comprises:

1. a blue-sensitive silver halide emulsion layer containing a non-diffusing silver halide developing agent and in effective contact therewith a non-diffusion resistant colorless coupler that is capable of forming with the developer oxidation product a compound of substantially reduced diffusion mobility and capable of forming a yellow dyestuff by oxidative coupling with a hydrazone compound of the general formula: ##SPC68##

wherein:

R.sub.1 represents a --CONH.sub.2 or --SO.sub.3 X group in which X represents hydroxyl, an amino group, an alkyl group or an aryl group, and

Z represents the necessary atoms to close a 5- or 6-membered heterocyclic nucleus or a ring system containing such nucleus, said nucleus being a nitrogen- or nitrogen and sulphur-containing heterocyclic nucleus,

2. a green-sensitive silver halide emulsion layer containing a non-diffusing silver halide developing agent in effective contact therewith a non-diffusion resistant colorless coupler that is capable of forming with the developer oxidation product a compound of substantially reduced diffusion mobility and capable of forming a magenta dyestuff by oxidative coupling with the same hydrazone compound as used in the blue-sensitive silver halide emulsion layer, and

3. a red-sensitive silver halide emulsion layer containing a non-diffusing silver halide developing agent and in effective contact therewith a non-diffusion resistant colorless coupler that is capable of forming with the developer oxidation product a compound of substantially reduced diffusion mobility and capable of forming a cyan dyestuff by oxidative coupling with the same hydrazone compound as used in the blue-sensitive silver halide emulsion layer.

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Description

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This invention relates to photographic processes for the production of colour images and to photographic materials for use in such processes.

Several techniques have been proposed for the production of monochromatic as well as multicolour pictures by image-wise diffusion transfer of compounds soluble in one of the photographic processing liquids.

Among these processes the process based on the use of so-called dye developers has become of practical importance.

In such a process described e.g. in the U.S. Pat. No. 2,983,606 of Howard G. Rogers, issued May 9, 1961, a photographic silver halide material is used containing a reagent, which is a dye possessing a developing function and which, when oxidized, provides a reaction product of lower solubility in a processing liquid than the unreacted reagent. Relying on said property of the dye developer a colour diffusion transfer process was realized, which made possible the production of positive monochromatic or multicolour prints stating from a monolayer or multilayer silver halide material containing the proper dye developer compounds.

A multilayer colour photographic material suited for use in said process has silver halide emulsion layers that are spectrally sensitive to blue, green and red light respectively and comprises three alkali-permeable colloid layers each of which is adjacent to a said emulsion layer and contains a different dye developer compound of a colour complementary to that the adjacent silver halide emulsion layer has been spectrally sensitized to. Such multilayer colour photographic material is not suited for reflex emposure since each dye developer layer acts as an absorption layer for the reflected light to which the corresponding silver halide emulsion layer is sensitive.

According to the present invention a photographic material, suitable for use in a process for the production of dye images by image-wise diffusion transfer of compounds soluble in an alkaline aqueous processing liquid, contains photosensitive silver halide grains dispersed in a hydrophilic colloid layer and contains in or in water-permeable relation to such layer at least one colourless reagent, which is capable of forming a dyestuff by an oxidative coupling reaction and of diffusing in aqueous alkaline meduim from said material to a receptor material, said photographic material also containing in effective contact with said silver halide grains a developing agent, which is resistant to diffusion in a hydrophilic colloid medium and which when activated in the presence of an alkaline aqueous liquid after the image-wise exposure of said layer reduces the exposed silver halide in said layer and which couples in oxidized state with the colourless reagent to inhibit its diffusion from the exposed portions of the photosensitive material into the receptor material.

The process for the formation of transfer colour images according to the present invention comprises the steps of:

a. image-wise exposing to electromagnetic radiation a photographic material, which contains a silver halide emulsion layer having in effective contact with the silver halide grains that are sensitive or have been sensitized to said electromagnetic radiation a developing agent that is resistant to diffusion in a hydrophilic colloid medium and having in effective contact with said developing agent at least one colourless reagent that is capable of diffusing in aqueous alkaline medium from said material to a receptor material and of forming a dyestuff by oxidative intermolecular or intramolecular coupling or coupling with another different colourless reagent being likewise capable of diffusing in aqueous alkaline medium and of forming wiht the oxidation product of said developing agent a compound having a substantially smaller diffusion mobility than it has in unreacted state,

b. contacting the exposed photographic material with an aqueous alkaline activating liquid to bring about the reducing action of the developing agent, so that in the exposed portions a silver image and an oxidation product of the developing agent form that couples with said colourless reagent(s) to form in the exposed portions of the emulsion layer (a) compound(s) that posesses(es) a substantially lower diffusion mobility than the unreacted reagents have,

c. transferring from the thus treated material an amount of the reagent molecules that remained capable of diffusing by means of the alkaline processing liquid onto a receiving material whereon transferred identical reagent molecules are intermolecularly or intramolecularly oxidatively coupled, or different reagent molecules are oxidatively coupled, the oxidative coupling proceeding with an oxidizing agent, which is stronger than exposed silver halide and resulting in the formation of a dye image on the receiving material.

According to a first embodiment of the invention the photosensitive layer has associated therewith a pair of different colourless reagents (called A and B respectively) for forming a dye by oxidative coupling and a developing agent for developing that layer and forming an oxidation product that inhibits diffusion of at least one of such reagents.

According to a second embodiment of the invention the photosensitive layer has associated therewith a colourless reagent for forming such a dyestuff by oxidative intermolecular or intramolecular coupling, and a developing agent for developing that layer so that an oxidation product forms that inhibits diffusion of said reagent.

For the operation with a photosensitive layer suitable for use in said first embodiment, the process for forming a dye image by image-wise transfer of colour-forming reactant comprises the following steps:

a. image-wise exposing a photographic material containing a silver halide emulsion layer having in effective contact with its photosensitive silver halide grains a developing agent that is resistant to diffusion in a hydrophilic colloid medium and in effective contact with said developing agent a pair of colourless reagents that are capable of diffusing in said medium with the aid of an aqueous alkaline liquid and that are capable of forming a dyestuff by oxidative coupling with each other and of which at least one of said reagents being capable of forming with the oxidation product of the said developing agent a compound with a substantially smaller diffusion mobility than said reagent has in unreacted state,

b. contacting the exposed recording material with an aqueous alkaline activating liquid to bring about the reducing action of the developing agent thereby forming in the exposed portions a silver image and a developer oxidation product that couples with at least one of said colourless reagents to form in the emulsion layer a compound that possesses a substantially lower diffusion mobility than the unreacted reagent,

c. arranging the thus treated recording material in close relationship with a receptor material to transfer thereto the residual unaffected dye-forming reagents by means of the processing liquid, and to bring about oxidative coupling of such reagents in or on said receptor material by means of an oxidizing agent, which is stronger than the exposed silver halide resulting in the formation of a dye image in the receptor material, and

d. separating the photographic material from the receptor material.

By "effective contact" is meant here that the substances that have to co-operate in the processing of the exposed recording material are provided in the recording material at the right time and in the appropriate location to operate in the desired way in the image-formation.

If there is only one said silver halide emulsion layer with associated developing agent and colour-forming reagents the process leads to the formation of a monochromatic image. However, the photographic material may comprise a plurality of light-sensitive layers sensitive in different spectral regions and different associated pairs of colour-formers as above referred to so that plural-colour image of a plural-colour original can be produced on the receptor material.

According to the first embodiment of the present invention a dye image of an individual colour can be formed on a receptor material by means of a photosensitive recording material comprising a sheetlike support and a hydrophilic colloid silver halide emulsion layer containing in effective contact with the silver halide a p-phenylene diamino type developing agent resisting diffusion and a mixture of a dye forming compound A and a dye forming compound B, which are both capable of diffusing from their hydrophilic colloid layer by means of an alkaline aqueous liquid.

Compound A as well as compound B are incorporated in the same silver halide emulsion layer or one or both of them can be incorporated in a colloid layer subjacent to the silver halide emulsion layer so that the compound(s) which has or have to be immobilized can be intercepted by the oxidized developing agent resisting diffusion.

Whereas in the production of monochromatic images no measures have to be taken to avoid unwanted coupling between separate colourless dye-forming reaction partners, such is not the case in reproduction materials by means of which multicolour images have to be manufactured. It is known that in order to produce a true multicolour print by a substractive multicolour reproduction system three dye images having the complementary colours yellow, magenta and cyan respectively have to be formed in register.

In a multicolour reproduction material that is suited for the production of multicolour prints according to the present invention the colourless dye-forming reagents are grouped in three pairs, in which the reagents of each different pair form on the receptor material by oxidatively coupling a dye of a different complementary colour, viz. a yellow, magenta and cyan dye respectively.

In practice, in the production of said multicolour prints the reaction partners of each pair of partners, which are not immobilized image-wise by reaction with the developer oxidation product, have to be the same for each pair since otherwise the oxidative coupling between image-wise transferred and overall transferred couplers proceeding along the same reaction mechanism for all the pairs would yield on the receiving material false colours resulting from the oxidative coupling of one partner of a pair with a coupler of another pair.

However, in the case both of the reaction partners of each pair are immobilized during the development it is indifferent which type of reagents is common to all of the pairs.

The photographic material incorporates in the or each light-sensitive layer a diffusion-resistant developing agent, which under the conditions of photographic processing is capable of preferentially reducing exposed silver halide to silver, i.e., of developing a latent image in an exposed silver halide emulsion.

When operating with a photosensitive layer suitable for use in said second embodiment the process for forming a dye image by image-wise transfer of colour forming reactant comprises the following steps:

a. image-wise exposing a photographic material containing a silver halide emulsion layer having in effective contact with its photosensitive silver halide grains a developing agent that is resistant to diffusion in a hydrophilic colloid medium and in effective contact with said developing agent a colourless reagent that is capable of diffusing in said medium with the aid of an aqueous alkaline liquid, of forming a dyestuff by oxidative intermolecular or intramolecular coupling, and of forming with the oxidation product of said developing agent a compound with a substantially smaller diffusion mobility than said reagent has in unreacted state,

b. contacting the exposed recording material with an aqueous alkaline activating liquid to bring about the reducing action of the developing agent, thereby forming in the exposed portions a silver image and a developer oxidation product that couples with said colourless reagent to form in the emulsion layer a compound that possesses substantially lower diffusion mobility than the unreacted reagent has,

c. arranging the thus treated recording material in close relationship with a receptor material to transfer thereto the residual unaffected dye-forming reagent be means of the alkaling liquid, and to bring about oxidative coupling of said reagent by means of an oxidising agent, which is stronger than the exposed silver halide resulting in the formation of a dye image in the receptor material, and

d. separating the photographic material from the receptor material.

By "intermolecular" oxidative coupling is meant that two separate molecules of the colourless dye-forming reagent oxidatively couple with each other to form a dye molecule.

By "intramolecular" oxidative coupling is meant that two reactive parts of the same molecule of the colourless dye-forming reagent are oxidatively coupled and form a dye molecule. Compounds for one of these types of coupling will be illustrated further on by a particular example.

The colourless colour-forming reagents for intermolecular or intramolecular coupling may be considered as consisting of two chemically linked structural parts C.sub.1 and C.sub.2 forming a compound having the general formula:

C.sub.1 - C.sub.2

wherein:

C.sub.1 in the intermolecular reaction oxidatively couples with the group C.sub.2 of a second molecule C.sub.1 -C.sub.2, and

wherein C.sub.1 in the intramolecular reaction after a rearrangement oxidatively couples with the group C.sub.2 of the molecule to which C.sub.1 itself belongs.

Having described in the preceding the principles of the invention and of some preferred embodiments and materials and having given a preliminary explanation of its utility, we now present details on preferred substances used in the present photographic process.

In a preferred embodiment of the present invention a silver halide developing agent known from silver halide colour photography is used being resistant to diffusion and capable of reacting with a phenol type or reactive methylene group type colour coupler. Such developing agent is preferably an aromatic primary amino developing agent that has been made substantially non-diffusing in a hydrophilic colloid medium and in oxidized state forms a non-diffusing coupling product with a colour-forming reagent, which is itself not resistant to diffusion and which contains one or more reactive hydrogen atoms, such reagent on diffusion into the receptor material forming with its colour-forming reaction partner a dye by oxidative coupling.

Preferably used developing compounds are of the p-phenylene diamine type and correspond to the following general formula: ##SPC1##

wherein:

each of R.sub.1 and R.sub.2 represents an aliphatic residue including a substituted aliphatic residue in which optionally one of these residues is substituted with a polar group, e.g. an acidic group providing, e.g., substantivity to a hydrophilic colloid such as gelatin and/or facilitating the homogeneous distribution of said compounds in a hydrophilic colloid medium, preferred groups being a sulphonic acid, a carboxylic acid group or an alkylsulphonylamino group, or R.sub.1 represents the necessary methylene groups including substituted methylene groups to close a 5- or 6- membered heterocyclic nucleus with the carbon atom in the 6-position of the benzene nucleus, or R.sub.2 represents the necessary methylene groups including substituted groups to close a 5- or 6- membered heterocyclic nucleus with the carbon atom in the 2-position of the benzene nucleus, or R.sub.1 and R.sub.2 together represent the necessary methylene groups including substituted methylene groups to close a 5-membered nitrogen containing nucleus,

R.sub.3 represents same or different substituents of the group comprising hydrogen or substitutents that have an influence on properties such as the developing capacity, binding force with the hydrophilic colloid or solubility in water, such as (an) alkyl group(s) e.g. (a) methyl group(s) or an alkoxy group such as methoxy or ethoxy, with the proviso that R.sub.3 in the cases that it does not represent hydrogen is limited to the 3- and/or 5- positions indicated above, and wherein said developing agent contains one or more substituents that provide the desired resistance to diffusion in a hydrophilic colloid medium e.g. at least one of said residues containing more than four carbon atoms in straight line.

The free amino group in the above p-phenylene diamine type compound may be mono-substituted with an alkyl group including a substituted alkyl group or an alkylene group ring-closed in the indicated 3- position. The free amino group may be blocked in a reversible way, e.g. by substitution with an alkyl group that is further substituted with an anionic group e.g. a sulphonic acid group, a carboxylic acid group, or a hypophosphorous acid group as described, e.g., in the United Kingdom Patent Specifications 691,815 filed Jan. 26, 1951 and 783,887 filed Aug. 30, 1954 both by Gevaert Photo-Producten N.V., and the Belgian Patent Specifications 535,687 and 535,688 both filed Feb. 14, 1955 and 557,556 filed May 16, 1957 all by Gevaert Photo-Producten N.V.

Other reversibly blocked p-phenylene diamine type developing agents in which the free amino group has reacted with an aldehyde so as to form a Schiff's base are described, e.g. in the U.S. Pat. No. 2,507,114 of David Malcolm, issued May 9, 1950, and the French Patent Specification 983,022 filed Oct. 20, 1948 by Kodak Pathe. Still other reversibly blocked p-phenylene diamine type developing agents contain a phthalimide group as described in the U.S. Pat. Nos. 2,911,410 of David W. C. Ramsay, issued Nov. 3, 1959 and 2,930,693 of Karl Otto Ganguin and David William Crichton, issued Mar. 29, 1960.

Trialkyl p-phenylenediamines and their preparation are described in the Belgian Patent Specification 532,736 filed Oct. 22, 1954 by Gevaert Photo-Producten N.V.

The preparation of other p-phenylene diamine type developers according to said general formula is known, e.g., from the United Kingdom Patent Specification 989,383 filed June 18, 1962 by Gevaert Photo-Producten N.V. and 1,191,535 filed May 24, 1967 by Gevaert-Agfa N.V. The introduction of a long aliphatic chain (containing at least four carbon atoms in straight line) can proceed according to techniques used in the production of non-diffusing colour couplers.

The preparation of preferably used non-diffusing p-phenylene diamine type developing agents is described in the German Patent Applications P 1931057.7 filed June 19, 1969 and P 2032711.1 filed July 2, 1970 both by Agfa-Gevaert AG.

Preferably used non-diffusing p-phenylene diamine type developing agents correspond to the following general formula: ##SPC2##

wherein:

R.sub.1 represents hydrogen, an alkyl group, preferably a C.sub.1 -C.sub.5 alkyl group e.g. methyl or ethyl, or an alkoxy group, preferably an alkoxy group containing at most three carbon atoms e.g. methoxy or ethoxy,

R.sub.2 represents hydrogen or an alkyl group, preferably a C.sub.1 -C.sub.5 alkyl group e.g. methyl or ethyl,

R.sub.3 represents a long chain aliphatic residue preferably a C.sub.8 -C.sub.20 alkyl group, more preferably dodecyl, heptadecyl or octadecyl,

X represents hydrogen, a sulphonic acid group, a carboxylic acid group, a hydroxyl group, or a sulphonamido group in which the amido group may be substituted with short chain alkyl e.g. methyl or ethyl, and

n represents 1 to 4.

Particularly suited non-diffusing p-phenylene diamine type developers are listed in the following table 1. ##SPC3## ##SPC4##

The non-diffusing p-phenylene diamine type developing agents also called herein primary developing agents are preferably used in combination with another reducing agent (i.e. an auxiliary developing agent) increasing the development speed. In respect thereof reference is made to pyrazolin-3-one developing compounds that may be added to the light-sensitive material and/or to the alkaline activating bath and correspond, e.g., to the following general formula: ##SPC5## formula:

wherein:

R.sub.1 represents an aryl group, including a substituted aryl group, e.g. phenyl,

R.sub.2 represents hydrogen or an acyl group such as acetyl and

each of R.sub.3, R.sub.4, R.sub.5 and R.sub.6 (the same or different) represents hydrogen, an alkyl group, including a substituted alkyl group, or an aryl group including a substituted aryl group.

Good results are obtained with the following auxiliary developing compounds corresponding to the above formula III: 1-phenyl-pyrazolidin-3-one 1-(m-tolyl)-pyrazolidin-3-one 1-phenyl-2-acetyl-3-pyrazolidin-3-one 1-phenyl-4-methyl-3-pyrazolidin-3-one 1-phenyl-5-methyl-3-pyrazolidin-3-one 1-phenyl-4,4-dimethyl-3-pyrazolidin- 3-one 1-phenyl-5,5-dimethyl-3-pyrazolidin-3-one 1,5-diphenyl-3-pyrazolidin-3-one 1-(m-tolyl)-5-phenyl-3-pyrazolidin-3-one 1-(p-tolyl)-5-phenyl-3-pyrazolidin-3-one

Pyrazolidin-3-one developing compounds can be prepared according to preparation techniques described in the United Kingdom Patent Specifications 679,677, 679,678 both filed Apr. 6, 1950 and 703,669 filed Oct. 17, 1951 all three by Ilford Ltd. and in the U.S. Pat. No. 2,772,282 of Charles F. H. Allen and John B. Byers, issued Nov. 27, 1956.

Other reducing agents activating the developing action of the p-phenylene diamine type developing agent are developing compounds used in superadditive development such as described in the United Kingdom Patent Specifications 989,383 filed June 18, 1962 by Gevaert Photo-Producten N.V., 1,191,535 filed May 24, 1967 by Gevaert-Agfa N.V., 1,003,783 filed July 10, 1961 by Gevaert Photo-Producten N.V. and 1,154,385 filed Nov. 4, 1966 by Agfa-Gevaert N.V.

More particularly good results are obtained with the following auxiliary developing agents: ##SPC6##

When used in the activating bath the auxiliary developing agents are preferably applied therein in an amount of 50 mg to 2 g per litre.

In said first embodiment preferably a non-diffusing p-phenylene diamine type developing agent is used in combination with two reagents that are capable of diffusing in an alkaline hydrophilic colloid medium and that can oxidatively couple in alkaline medium by the action of a stronger oxidizing agent than exposed silver halide to form a dye containing an azino group (=N--N=).

One of said reagents called hereinafter compound A is capable of coupling with the non-diffusing oxidation product of the p-phenylene diamine type developing agent so that the coupling product is inhibited from diffusing into a receptor material.

Compound A can, e.g., be any compound suitable to act in a dye-forming electrophilic substitution reaction of which diazo coupling is an example.

Compound A is preferably a compound of the type producing a quinone-imine or azomethine dye with an oxidizied N,N-dialkyl-p-phenylene diamine. Such compounds are sufficiently known to those skilled in the art of colour photography and are described, e.g., by Pierre Glafkides in Photographic Chemistry, Vol. II - Fountain Press London (1960), pages 596-604.

Suitable compounds A are, e.g. .alpha.-naphthol, phenol, reactive methylene type and reactive methyl couplers, i.e., diazo couplers as described, e.g., in the French Patent Specification 1,602,473 filed Dec. 26, 1968 by Gevaert-Agfa N.V. Said compounds must have a chemical structure that allows them to diffuse by means of an alkaline aqueous liguid in a hydrophilic colloid medium e.g. gelatin.

In order to improve the diffusion mobility in an alkaline hydrophilic colloid medium it is desired that the coupler molecules contain a carboxylic acid or sulphonic acid group.

Useful couplers (for use as compound A) are more particularly the phenol couplers corresponding to the following general formula: ##SPC7##

wherein:

each of R.sub.1 and R.sub.2 represents hydrogen, an alkyl group including a substituted alkyl group, an alkoxy group including a substituted alkoxy group, or the group --NHR in which R represents a carboxylic acid acyl or sulphonic acid acyl group including said groups in substituted state, e.g. an aliphatic carboxylic acid acyl group, an aromatic carboxylic acid acyl group, an heterocyclic carboxylic acid acyl group e.g. a 2 -furoyl group or a 2-thienoyl group, an aliphatic sulphonic acid acyl group, an aromatic sulphonic acid acyl group, a sulphonyl thienyl group, an aryloxy-substituted aliphatic carboxylic acid acyl group, a phenylcarbamyl aliphatic carboxylic acid acyl group or a tolyl carboxylic acid acyl group, with the proviso that R.sub.1 and R.sub.2 not represent simultaneously hydrogen and the substituents are not of such type that the diffusion of the phenol compound in an alkaline hydrophilic colloid medium is markedly hindered; a polar substituent such as a carboxylic acid or a sulphonic acid group is preferably present as a substituent to improve the mobility of the phenol couplers in said medium.

The preparation of colour couplers that are within the scope of the above general formula is described, e.g., in the U.S Pat. No. 2,772,162 of Ilmari F. Salminen and Charles R. Barr, issued Nov. 27, 1956 and 3,222,176 of Jan Jaeken, issued Dec. 7, 1965 and in the United Kingdom Patent Specification 975,773 filed Sept. 4, 1961 by Gevaert Photo-Producten N.V.

Examples of suited phenol type couplers are listed in the following Table 2. ##SPC8##

Useful couplers are further .alpha.-naphthol type couplers more particularly .alpha.-naphthol type couplers corresponding to the following general formula: ##SPC9##

wherein

R represents an alkyl group including a substituted alkyl group, an aryl group including a substituted aryl group preferably such groups that are substituted with a carboxylic acid or sulphonic acid group.

These .alpha.-naphthol type couplers are prepared, e.g., by a condensation reaction applying the phenyl ester of 1-hydroxy-2-naphthoic acid and the proper amine.

Examples of useful .alpha.-naphthol couplers are listed in the following Table 3. ##SPC10##

Suitable reactive methylene type couplers correspond to one of the following general formulae:

VI. R.sub.1 --CO--CH.sub.2 --CO--R.sub.2

VII. R.sub.1 --CO--CH.sub.2 --CN ##SPC11##

wherein:

R.sub.1 and R.sub.2 (same or different) each represents an alkyl group including a substituted alkyl group, an aryl group including a substituted aryl group, a N-arylamino group including a substituted N-arylamino group, or an ether group including a substituted ether group, e.g. an alkoxy group,

R' represents an alkyl group including a substituted alkyl group, or an aryl group including a substituted aryl group,

R" represents an alkyl group including a substituted alkyl group, an aryl group including a substituted aryl group, carbethoxy, an alkoxy group, cyano, a N-arylamino group including a substituted N-arylamino group, a N-acylamino group including a substituted N-acylamino group or an ureido group including a substituted ureido group.

Methods for the preparation of said reactive methylene type couplers can be found, e.g., in the references given by P. Glafkides in his book Photographic Chemistry, Vol. II (1960) p. 597-602 under the headings "yellow couplers" and "magenta couplers" and in the United Kingdom Patent Specifications 934,017 filed Jan. 25, 1962 by General Aniline & Film Corp., 1,062,203 filed July 6, 1964, 1,039,965 filed July 6, 1964, 1,007,847 filed Oct. 10, 1963, 1,066,334 filed Oct. 10, 1963 all four by Gevaert Photo-Producten N.V. and 1,069,533 filed July 24, 1964 by Gevaert-Agfa N.V.

Preferred reactive methylene type couplers are listed in the following Table 4. ##SPC12##

In order to illustrate the preparation of the open chain ketomethylene type couplers the preparation of the compounds 9, 10 and 11 of Table 4 is presented.

Compound 9

A mixture of 31.4 g (0.15 mole) of dimethyl-5-aminoisophthalate and 31.7 g (0.165 mole) of ethyl benzoylacetate dissolved in 165 ml of p-xylene is heated under reflux for 4 hours and the ethanol (about 9 ml) formed thereby distilled by the use of a fractionating column provided with a dephlegmator. Thereupon the reaction mixture is cooled in a mixture of finely crushed ice and sodium chloride. The crude reactive methylene coupler separates as an oily product, which becomes crystalline by stirring. The product is separated by filtration, washed with cyclohexane, and dried in a vacuum of 1 mm Hg at 50.degree.C.

Yield: 49 g or 90 percent.

Melting point: 155.degree.C.

Compound 10

A solution of 46.5 g (0.13 mole) of compound 9 of Table 4 in a mixture of 465 ml of ethanol and 30 ml of 5N aqueous sodium hydroxide is refluxed for 5 h whilst stirring. The precipitate formed being the product obtained by complete saponification is suction-filtered and removed. A mixture of 500 ml of water and 50 ml of concentrated hydrochloric acid are added slowly to the filtrate whilst stirring, whereupon the precipitate formed is separated by filtration and dried.

The crude product is purified by crystallization from acetic acid and the crystals washed with chloroform. Purification is continued by recrystallization from n-butanol.

Yield: 35 percent.

Melting point: 240.degree.C.

Compound 11

A solution of 46.5 g (0.13 mole) of compound 9 of Table 4 in a mixture of 465 ml of ethanol and 120 ml of 5N aqueous sodium hydroxide, is refluxed for 5 h whilst stirring and thereupon acidified with concentrated hydrochloric acid. The precipitate formed is suction-filtered and washed with methanol. The crude product is boiled three times in fresh n-butanol and finally washed with chloroform.

Yield: 79 percent.

Melting point: >260.degree.C.

Other suited couplers are:

N,n-dialkylanilines of the diffusing type containing as a further substituent on one of the alkyl groups, an acid substituent or a substituent containing an acid group, said acid group being present in free acid or salt form, e.g. a sulphonic acid substituent. The N,N-dialkylanilines couple with an oxidized N,N-dialkyl-p-phenylene diamine type developer to form a quino-diimine betaine type salt according to the following reaction scheme: ##SPC13##

wherein:

M is hydrogen, a metal cation or cationic group, e.g., an onium group,

Y is a bivalent organic radical, e.g., an alkylene group, and

R represents an alkyl group.

Said dialkylanilines can be prepared according to known alkylating reactions for anilines.

Useful N,N-dialkylanilines of the diffusing type are listed in the following Table 5. ##SPC14##

Reagents called hereinafter compounds B, that by oxidative coupling with the above described compounds A form a dye containing an azino (=N--N=) group are heterocyclic hydrazone compounds of the type that have diffusion mobility in an alkaline hydrophilic colloid medium. Useful heterocyclic hydrazone compounds are within the scope of the following general formula: ##SPC15##

wherein:

R.sub.1 represents a --CONH.sub.2 or --SO.sub.2 X group in which X represents hydroxyl, an amino group including a substituted amino group, an alkyl group including a substituted alkyl group, an aryl group including a substituted aryl group, and

Z represents the necessary atoms to close a 5-- or 6-- membered heterocyclic nucleus or ring system including such nucleus or ring system in substituted form.

Preferred heterocyclic hydrazone compounds correspond to the following formula: ##SPC16##

wherein:

R.sub.1 has the same meaning as described under formula X,

R.sub.2 represents hydrogen, an aliphatic group including a substituted aliphatic group, e.g. an alkyl group including a substituted alkyl group, or an aromatic group including a substituted aromatic group, e.g. an aryl group including a substituted aryl group,

L represents a methine group or nitrogen,

n is 1 or 2, and

Z.sub.1 represents the necessary atoms to close a 5- or 6-membered heterocyclic nitrogen-containing nucleus or ring system including such nucleus or ring system in substituted form, e.g. a 2nucleus, nuclues, a 2-indolinylidene nucleus or a 4-quinolinylidene nucleus.

In view of an improved diffusion mobility in an alkaline hydrophilic colloid medium said hydrazone compounds contain preferably a carboxylic acid or sulphonic acid group.

Examples of useful hydrazone couplers are given in Table 6. Table 6 ##SPC17## ##SPC18##

The preparation of said hydrazone compounds may proceed according to techniques described, e.g., in the United Kingdom Patent Specifications 975,932 filed Nov. 13, 1959, 990,628 filed Aug. 2, 1961 and 1,068,595 filed June 8, 1964 all three by Geugert Photo-Producten N.V. and the U.S. Pat. No. 3,293,032 of Jan Jaeken and Maurice Antoine de Ramaix, issued Dec. 20, 1966 and 3,525,614 of Jan Jaeken, Frans Philomena Serrien, Paul Marx and Marcel Karel Van Doorselaer, issued Aug. 25, 1970.

The synthesis of azino dyes by oxidative coupling is described in detail by Hunig et al. in the following references: Ang. Chem. 170 (1958), 215-222; Ann. 609, 143-160 (1957); Ann. 617, 203-210; Ann. 617, 216-220 (1958); Ann. 628, 46-55 (1959); Ann. 628, 69-75; Ann. 641, 104-112 (1961); Ann. 647, 77-82 (1961) and Ann. 651, 73-88 (1962).

The use of heterocyclic hydrazones in the formation of dyes containing an azino group by oxidative coupling has been described, e.g., by S. Hunig, in Angew. Chem. 74, 818-821 (1962) and Ann. 609, 160 (1957), Ann. 617, 181-202 (1958), Ann. 623, 191-203 (1959), Ann. 636, 21-31 (1960), Ann. 640, 98-110 (1961), Ann. 641, 94-103 (1961), Ann. 647, 66-76 (1961), Ann. 651, 89-101 (1962).

Developing agents that in oxidized state can couple with said hydrazone compounds and prevent these compounds from diffusing out of a hydrophilic colloid layer to a receptor material are aromatic 1,2-dihydroxy compounds that on coupling with the hydrazones form sufficiently large molecules that are immobilized in the hydrophilic colloid in which they are formed. Examples of such useful 1,2-dihydroxy compounds are listed in the following Table 7. ##SPC19##

In order to produce a coupler molecule having a sufficiently poor diffusion mobility in a hydrophilic colloid medium residues are introduced, which improve the resistance to diffusion. Suited for that purpose are organic residues that are photographically inert or at least do not give rise to fog in a silver halide emulsion layer and that consist of or comprise a straight or branched chain aliphatic group of preferably at least 8 carbon atoms. Such residues may be linked to the compound, which has to be made resistant to diffusion, either directly by a carbon-carbon link or by the intermediate of groups such as --CONH--, --SO.sub.2 NH--, --CO--, --SO.sub.2 --, --O--, --S--or --NR-- wherein R represents hydrogen or alkyl. The presence of a residue, which makes the molecule of the developing agent resistant to diffusion, does not exclude, however, the presence of one or more polar groups, which improve the compatibility with the hydrophilic colloid and facilitates the homogeneous distribution of the developing agent in the hydrophilic colloid. Suitable polar groups for that purpose are, e.g., carboxyl groups and sulphonic acid groups in free acid or salt form.

In the cases in which the molecule that has to be resistant to diffusion is large enough, e.g., for it comprises more than one aromatic or heterocyclic nucleus and no polar groups, the introduction of long chain aliphatic residues is not necessary at all or lower alkyl groups (C.sub.1 --C.sub.4) may suffice.

Apart from the hydrazones that by oxidative coupling yield azino dyes with, e.g., .alpha.-naphthol, phenol, or reactive methylene type couplers, other oxidatively dye-forming compounds can be applied that are known, e.g., from photographic integral masking techniques according to which a dye image is formed by oxidative coupling in a potassium cyanoferrate(III) bleaching bath. For such colourless compounds known from integral masking reference is made, e.g., to 4-aminopyrazolones corresponding to the following general formula: ##SPC20##

wherein:

each of R.sub.1 and R.sub.3 represents an alkyl group of at most five carbon atoms, and

R.sub.2 represents an alkyl group of at most five carbon atoms, a phenyl group including a substituted phenyl group.

The preparation of said 4-aminopyrazolones and their use in oxidative coupling for masking purposes has been described in the United Kingdom Patent Specifications 880,862 filed Dec. 31, 1956 by Gevaert Photo-Producten N.V. and the U.S. Pat. No. 3,012,884 of Maurice Antoine de Ramaix and Jan Jaeken, issued Dec. 12, 1961 and 3,013,879 of Maurice Antoine de Ramaix and Jan Jaeken, issued Dec. 19, 1961.

Other suitable oxidatively coupling dye-forming compounds are p-phenylene diamines with sterically hindered amino group and sterically hindered phenols as described, e.g., in the United Kingdom Patent Specification 1,153,561 filed Jan. 18, 1966 by Agfa-Gevaert N.V. and 975,940 filed Nov. 30, 1959 by Gevaert Photo-Producten N.V. respectively.

A multilayer photographic material suited for use according to the first embodiment of the present invention in the formation of multicolour images by image-wise diffusion transfer of dye-forming reactants from a photographic material into a receptor material comprises:

1. a blue-sensitive silver halide emulsion layer containing a non-diffusing silver halide developing agent and in effective contact with said developing agent a pair of colourless reagents that are capable of diffusing in said medium when wetted with an aqueous alkaline liquid and of forming a yellow dyestuff by oxidative coupling with each other, at least one of said reagents being capable of forming with the oxidation product of the developing agent a compound with a substantially smaller diffusion mobility than said reagent has in unreacted state,

2. a green-sensitive silver halide emulsion layer containing a non-diffusing silver halide developing agent and in effective contact with said developing agent a pair of colourless reagents, that are capable of diffusing in said medium when wetted with an aqueous alkaline liquid and of forming a magenta dyestuff by oxidative coupling with each other, at least one of said reagents being capable of forming with the oxidation product of the developing agent a compound with a substantially smaller diffusion mobility than said reagent has in unreacted state,

3. a red-sensitive silver halide emulsion layer containing a non-diffusing silver halide developing agent and in effective contact with said developing agent a pair of colourless reagents that are capable of diffusing in said medium when wetted with an alkaline aqueous liquid and of forming a cyan dyestuff by oxidative coupling with each other, at least one of said reagents being capable of forming with the oxidation product of the developing agent a compound with a substantially smaller diffusion mobility than such reagent has in unreacted state; and any said reagent, which does not form a compound with a substantially smaller diffusion mobility than such reagent has in unreacted state being a reagent, which is common to all of the pairs of reagents.

In the production of multicolour prints with such photographic material one of the reaction partners of each pair of partners has to be common to all of the pairs and those partners that are not common are to be immobilized by reaction with one or more oxidation products of a developing agent or agents. The partner that is common to all of the pairs may be applied in hydrophilic colloid layers that are adjacent to the silver halide emulsion layers. Each silver halide emulsion layer may be separated from an other silver halide emulsion layer by a suitable spacer stratum, e.g., by a layer of gelatin or polyvinyl alcohol. The spacer stratum may act as a kind of a permeable barrier layer controlling the diffusion of the dye-forming compound(s), e.g., is a layer of slowly permeable material, such as a layer of cellulose acetate-hydrogen phthalate occasionally in combination with a more water-permeable spacer layer, e.g., gelatin layer.

In the already mentioned second embodiment of the present invention for multicolour reproduction by subtractive colour photography producing yellow, magenta and cyan dyes, three different compounds C.sub.1 --C.sub.2 are used in which one group either C.sub.1 or C.sub.2 has the same structure in these three compounds or is of the same chemical type, i.e., operates along the same chemical reaction mechanism (e.g. electrophilic or nucleophilic substitution) preferably with substantially the same reaction speed.

Useful sets of colour-forming reagents C.sub.1 -C.sub.2 for three colour materials with true colour reproduction possibilities in multicolour photography contain a same structural colour-forming part and may be represented, e.g., by the following sets of chemically linked reactive molecule parts A, B, C, X, Y and Z:

A-X A-X A-Y or B-X A-Z C-X

Preferably the C.sub.1 --C.sub.2 compounds that are suitable for intermolecular or intramolecular coupling have a C.sub.1 chemical structural part capable of forming a quinonimine or azomethine dyestuff structure with an ozidized p-phenylene-diamine type developing agent, and a C.sub.2 chemical structural part containing a hydrazone group, which enables the C.sub.1 -C.sub.2 compound under oxidative conditions to form a dye containing an azino (=N--N=) group.

In particularly suited C.sub.1 -C.sub.2 compounds the part C.sub.1 is a group containing the structure of an .alpha.-naphthol coupler and corresponds to the formula: ##SPC21##

or is a group containing the structure of a reactive methylene type coupler and corresponds to one of the following general formulae:

Xiii.

--hn--co--ch.sub.2 --co--r.sub.2

--hn--co--ch.sub.2 --cn ##SPC22##

wherein:

R.sub.2 represents an alkyl group including a substituted alkyl group or an aryl group including a substituted aryl group, an alkoxy group or a substituted amino group, e.g. an alkyl or aryl substituted amino group, and

R' represents an alkyl group including a substituted alkyl group, an aryl group including a substituted aryl group, cyano, an alkoxy group, a carbonylalkoxy group, a N-arylamino group including a substituted N-arylamino group, a N-acylamino group including a substituted N-acylamino group or an ureido group including a substituted ureido group, with the proviso, however, that the substituents in said compounds are not of a type that markedly hinders the diffusion mobility of the dye-forming compounds in an alkaline hydrophilic colloid medium.

According to a preferred embodiment the part C.sub.2 in these C.sub.1 --C.sub.2 compounds corresponds to the following general formula: ##SPC23##

in which Z represents the necessary atoms to close a 5- or 6-membered heterocyclic nucleus or ring system including such nucleus or ring system in substituted form.

Particularly suitable C.sub.1 --C.sub.2 compounds contain a group C.sub.2 corresponding to the following general formula: ##SPC24##

wherein:

R.sub.2 represents hydrogen, an aliphatic group including a substituted aliphatic group or an aromatic group incuding a substituted aromatic group,

L represents methine or nitrogen,

n is 1 or 2, and

Z.sub.1 represents the necessary atoms to close a 5- or 6-membered heterocyclic nucleus or ring system, said nucleus or ring system being either or not in substituted form.

Compounds that produce a dyestuff by oxidative intramolecular coupling (except for compound 18 that couples intermolecularly) and that contain a common naphthol methylene coupler part C.sub.1 and a hydrazone part C.sub.2 are illustrated by the following examples in Table 8. below. ##SPC25##

These compounds can be prepared according to methods known to those skilled in the art. The preparation steps of the compounds 6, 14, 15, lb and 17 are given hereinafter for illustrative purposes.

Preparation of Compound 6 ##SPC26##

The intermediate compound (III)(melting point: 210.degree.C) has been prepared by a technique known for preparing .alpha.-hydroxy-.beta.-naphthoic acid anilides starting from p-fluorosulphonylaniline and the phenyl ester of .alpha.-hydroxy-.beta.-naphthoic acid.

Said intermediate compound (III) was allowed to react with hydrazine hydrate dissolved in dioxan so as to form a sulphonylhydrazine (IV) (melting point: 245.degree.C).

This sulphonylhydrazinde (IV) was used in the preparation of the compounds 1 to 6 and 8 to 13.

More particularly, in the preparation of compound 6 the sulphonylhydrazine (IV) was applied in a condensation reaction with 1-methyl- 2-phenyl-6-fluorosulphonyl-4-chloro-quinolinium methyl sulphate, the preparation of which is described in the Belgian Patent Specification 745,438 filed Feb. 4, 1970 by Gevaert-Agfa N.V.

Compound 1 is prepared from compound 6 by saponification of the fluorosulphonyl group with sodium hydroxide.

Preparation of compound 14 ##SPC27##

30.4 g of sulphonylhydrazide (II) are dissolved in 300 ml of a mixture of chloroform and dry ethanol (1:1 by volume) and allowed to react with 59 g of the quinolinium compound (I) with stirring and refluxing for 2 h. Thereupon the solvents are distilled and to the residue 300 ml of a solution of hydrochloric acid (10 percent) in ethanol are added. Refluxing is started again and maintained for 4 h. Upon cooling the obtained hydrochloride is separated and washed with acetone. The hydrochloride is dissolved in a minimum amount of pyridine and poured into a ten-fold amount of water.

First the obtained product (III) is thoroughly washed with water and then with methanol.

Yield: 52.6 g.

Melting point: about 240.degree.C. ##SPC28##

24.3 g (0.05 mole) of the amine (III) and 120 ml (0.7 mole) of the ester (IV) are heated on an oil-bath of 100.degree.C.

The reaction mixture is poured into 600 ml of p-xylene whilst stirring. The precipitate is suctionfiltered, thoroughly and successively washed with p-xylene, light petrol, methanol and acetone, and dried. The product (V) decomposes between 180.degree.-185.degree.C.

Yield: 20.5 g.

Reaction scheme C

(V) + .sub.acetone/H 0 compound 14

20 g of the sulphofluoride (V), 33 ml of sodium hydroxide (30 percent by weight in water) and 200 ml of acetone are refluxed for 30 min. with stirring.

The reaction mixture is cooled and the acetone decanted from the separated oily product, which is washed twice with acetone that is removed by decantation. The oily product is dissolved in 40 ml of water and a solid product precipitates on adding 2N hydrochloric acid. The solid is separated by suction and washed with water till complete removal of the acid. After a thorough wash with acetonitrile the compound 14 melts with decomposition at 260.degree.C.

Yield: 18 g.

Preparation of compound 16 ##SPC29##

To a solution of 9.7 g (0.02 mole) of amino compound (I) in 48.5 ml of acetic acid a solution of 4.9 g (0.03 mole) of the pyrazole compound (II) in 48.5 ml of acetic acid is added. The reaction mixture is stirred for 5 h at 20.degree.C whereupon it is poured into 1 l of water, salted out and stirred for 30 min. The obtained hydrochloride (III) is separated by suction, washed with methanol and dried.

Melting point: 210.degree.C (decomposition).

Yield: 12 g.

Preparation of Compound 17 ##SPC30##

11 g (0.0227 mole) of amino compound (I) are dissolved in a mixture of 70 ml of dimethyl-formamide and 5.5 ml of triisopropanolamine. To the obtained solution 7.35 g of the pyrazole compound (II) dissolved in 40 ml of dimethylformamide are added. The mixture is stirred for 4 h at room temperature and thereupon an additional amount of 3.67 g of the pyrazole compound is introduced. Thereafter stirring is continued for another 2 h.

The reaction mixture is then acidified with 2N hydrochloric acid and poured into 500 ml of water. The precipitate is suction-filtered and washed with water till neutral. A further thorough wash with acetonitrile and methanol yields 7 g of compound (III).

Melting point: >260.degree.C.

A particular advantage of the intramolecularly reactive compounds C.sub.1 --C.sub.2 resided in the fact that the reactive parts C.sub.1 and C.sub.2 reach the receiving material in perfect stoechiometric amounts so that practically no undesired colour fog is produced in the diffusion transfer picture and very clear whites are obtained.

Because two oxidatively colour-forming parts are united in one molecule, only one molecule of oxidized developing agent is necessary to immobilize the united parts, whereas when these parts represent separate compounds each of them is to be immobilized at the expense of two molecules of oxidized developing agent and a corresponding larger amount of silver halide.

Further, since in this second embodiment only three colour-forming reagents have to be transferred by diffusion, it is much easier to bring the composition in colour balance than in a process wherein at least four reagents are applied as is the case according to the first embodiment for multicolour reproduction.

According to the second embodiment of the present invention useful for the formation of a dye image of an individual colour on a receptor material, a photosensitive recording material is used comprising a sheetlike support and a hydrophilic colloid silver halide emulsion layer containing in effective contact with the silver halide a non-diffusing p-phenylenediamino type developing agent and said compound C.sub.1 -C.sub.2, which is capable to diffuse out of the hydrophilic colloid layer by means of an alkaline aqueous liquid.

Compound C.sub.1 -C.sub.2 is incorporated into the same silver halide emulsion layer or into a colloid layer subjacent to the silver halide emulsion layer so that the compound that has to be immobilized can be intercepted by the oxidized non-diffusing developing agent.

The silver halide of the photosensitive layer(s) used in the present invention may be of any type known in silver halide photography. For the production of a positive dye image on the image-receiving material a silver halide emulsion of the negative type is used. Preferably, silver halide emulsions are employed wherein gelatin is the carrier for the silver halide. However, the invention may be practised with any other hydrophilic colloid carrier known for the purpose of silver halide emulsion preparation.

The silver halide emulsion layer composition may contain spectral sensitizing agents.

Useful spectral sensitizing agents are in the class of the methine dyes, e.g., the cyanine dyes, hemicyanine, merocyanine, oxonol, hemi-oxonol and styryl dyes and polynucleic methine dyes such as rhodacyanine dyes and neocyanine dyes. Such sensitizing agents are described by F. M. Hamer in his book "The Cyanine Dyes and Related Compounds" (1964).

Preferably used cyanine dyes have a betaine-like structure owing to the presence on the nitrogen atom of at least one of the heterocyclic nuclei of an alkyl group carrying an anionic substituent, e.g. --SO.sub.3 .sup.-, --OSO.sub.3 .sup.-, --COO.sup.-, --SO.sub.2 N--CO--, --SO.sub.2 --N--SO.sub.2 --, --SO.sub.2 N--or ##SPC31##

group wherein each of R.sub.1 and R.sub.2 is hydrogen or a hydrocarbon radical, at least one of them being hydrogen.

Suitable spectral sensitizing dyes of that type are described, e.g. in the United Kingdom Patent Application 16,998/70 filed Apr. 9, 1970 by Agfa-Gevaert N.V. and in the published Dutch Patent Application 7004174 filed Mar. 24, 1970 by Agfa-Gevaert N.V.

Preferably used merocyanine dyes are the so-called zeromethine and dimethine merocyanine dyes containing a barbituric acid or thiobarbituric acid nucleus, e.g. as described in the U.S. Pat. No. 2,170,807 of Leslie G. S. Brooker, issued Aug. 20, 1939 and the German Democratic Republic Patent Specification 12,477 filed Sept. 20, 1954 by G. Back and J. Brunken.

The silver halide emulsion layer(s) may further contain the usual additives such as e.g., antifogging agents, chemical sensitizing agents, stabilizing agents, development accelerators, plasticizers, hardening agents and wetting agents.

The photosensitive material may contain any type of support known for silver halide photographic materials but comprises preferably a flexible support, e.g., a paper or plastic film base in sheet, web or ribbon form. For reflex exposure purposes a photographic material with a transparent or semi-transparent (at least 50 percent light transmission) support is used.

According to a preferred embodiment the imagereceiving material is a flexible plastic film or a paper sheet coated with a hydrophilic colloid layer containing an oxidizing agent that is capable of effecting the oxidative coupling of the couplers as defined above and which has a structure that makes it difficult or impossible to leave said hydrophilic colloid layer by diffusion in an aqueous alkaline liquid.

Examples of suitable oxidizing compounds are non-diffusing organic peroxides, long chain (C.sub.8 -C.sub.20) aliphatic onium salts of peracids and compounds that easily split off halogen in aqueous medium such as halogen amides and imides, examples of which are bromosuccinimide and non-diffusing chloramine T and dichloramine T type compounds.

Examples of such compounds are listed in Table 9. ##SPC32##

Useful receiving materials contain in a hydrophilic colloid layer, e.g., incorporated in gelatin an amount of 0.01-0.05 mole of dibenzoyl peroxide per sq.m.

The image-receiving element may contain agents adapted to mordant or otherwise fix the dyes, e.g. azine dyes, formed by oxidative coupling. For example the image-receiving element contains a polymer, preferably a cationic polymer that acts as a mordant for anionic dyes as described e.g. in the United Kingdom Patent Specification 1,221,195 filed Mar. 26, 1968 by Gevaert-Agfa N.V. The mordanting agent may be applied in admixture with the oxidizing agent or in a layer adjacent to the layer containing the oxidizing agent.

The aqueous alkaline activating liquid has preferably a pH between 8 and 13 and contains, e.g., from 10 to 50 g of sodium carbonate per litre. It may contain development accelerating compounds, viscosity-controlling agents, e.g. hydroxyethylcellulose, wetting agents and water-miscible organic liquids for the purpose of improving the density of the dye image on the receptor material.

The activating liquid may be applied to the photosensitive material after its exposure by any technique known in the art of applying liquids to sheet materials, e.g., by spreading, imbibition, liquid film coating practices or spraying and may be similarly applied to the image-receiving element before the latter and the photosensitive material are brought into superposed relation or contact for carrying out the diffusion transfer of oxidatively coupling compounds from the undeveloped portions.

The alkaline agent may also be applied in pods or pressure-rupturable micro-containers, e.g., microcapsules, and squeezed into contact with the receptor material.

In the preparation according to the first embodiment of the present invention of a multicolour image by selective image-wise modulated diffusion transfer of the proper pairs of oxidatively dye-forming compounds A and B, preferably multilayer photosensitive materials are used as illustrated in the accompanying FIGS. 1 and 2.

A multilayer photosensitive element according to FIG. 1 comprises a blue-sensitive silver halide emulsion layer 1 containing a non-diffusing silver halide developing agent the oxidation products of which in alkaline medium couple with an alkali-soluble coupler A.sub.1 that in its turn in the presence of a stronger oxidant than exposed silver halide oxidatively couples with an alkali-soluble reagent B and forms a yellow dye after diffusion onto a receptor material containing the stronger oxidant.

Element 2 is a hydrophilic colloid spacer layer, e.g. a gelatin layer.

Element 3 is a green-sensitive silver halide emulsion layer that is substantially insensitive to blue and red light and contains a non-diffusing silver halide developing agent the oxidation products of which in alkaline medium couple with an alkali-soluble coupler A.sub.2 that in its turn in the presence of a stronger oxidant than exposed silver halide oxidatively couples with a same alkali-soluble reagent B and forms a magenta dye after diffusion onto the receptor material containing the stronger oxidant.

Element 4 is a hydrophilic colloid spacer layer, e.g., a gelatin layer.

Element 5 is a red-sensitive silver halide emulsion layer that is substantially insensitive to blue and green light and contains a non-diffusing silver halide developing agent the oxidation products of which in alkaline medium couple with an alkali-soluble coupler A.sub.3 that in its turn in the presence of a stronger oxidant than exposed silver halide oxidatively couples with a same alkali-soluble reagent B and forms a cyan dye after diffusion onto the receptor material containing the stronger oxidant.

Element 6 is a subbing layer for a gelatino silver halide colloid layer and a support 7, which is, e.g., a film support or semi-transparent paper base.

A multilayer photosensitive element according to FIG. 2 contains a blue-sensitive silver halide emulsion layer 1 containing a non-diffusing silver halide developing agent and an alkali-soluble coupler B that in alkaline medium by means of a stronger oxidant than exposed silver halide couples to form a yellow dye with an alkalisoluble coupler A.sub.1 that is present in the hydrophilic water-permeable colloid layer 2.

The coupler A.sub.1 diffusing out of the colloid layer 2 and penetrating into the exposed emulsion layer 1 reacts therein with the non-diffusing developer oxidation products and is inhibited thereby from further migration.

Element 3 is a hydrophilic colloid spacer layer, e.g., a gelatin layer.

Element 4 is a green-sensitive silver halide emulsion layer that is substantially insensitive to blue and red light and contains a non-diffusing silver halide developing agent and a same alkali-soluble coupler B that in alkaline medium by means of a stronger oxidant than exposed silver halide couples to form a magenta dye with an alkali-soluble coupler A.sub.2 that is present in a hydrophilic water-permeable colloid layer 5.

Element 6 is a hydrophilic colloid spacer layer, e.g., a gelatin layer.

Element 7 is a red-sensitive silver halide emulsion layer that is substantially insensitive to blue and green light and contains a non-diffusing silver halide developing agent and a same alkali-soluble coupler B that in alkaline medium by means of a stronger oxidant than exposed silver halide couples to form a cyan dye with an alkali-soluble coupler A.sub.3 that is present in a hydrophilic water-permeable colloid layer 8.

Element 9 is a subbing layer, e.g., a gelatin layer and element 10 is a support, e.g., a paper support.

In the composition of the photographic recording materials as illustrated in FIG. 1 and FIG. 2 the following reaction partners A and B capable of diffusing in alkaline medium through a hydrophilic colloid mass are mentioned as examples of practice.

As common mobile reaction partner B a hydrazone compound having the following structural formula may be used: ##SPC33##

As mobile reaction partners A.sub.1 capable of forming a yellow azine dye with said common partner B the following reactive alkali-soluble methylene compounds (A'.sub.1) and (A".sub.1) may be used: ##SPC34##

The yellow azine dye formed with compound (A'.sub.1) and the hydrazone B has the following structure: ##SPC35##

As mobile reaction partners A.sub.2 capable of forming a magenta azine dye with said common partner B the following reactive alkali-soluble aromatic hydroxy couplers(A'.sub.2) and (A".sub.2) may be used. ##SPC36##

The magenta azine dye formed with compound (A'.sub.2) and the hydrazone B has the following structure: ##SPC37##

As mobile reaction partners A.sub.3 capable of forming a cyan azine dye with said common partner B the following reactive alkali-soluble sulpho-substituted N,N-dialkylanilines (A'.sub.3) and (A".sub.3) may be used: ##SPC38##

The cyan azine dye formed with compound (A'.sub.3) and the hydrazone B has the following structure: ##SPC39##

In order to improve the reactivity to couple with the oxidation products of a non-diffusing p-phenylene-diamine type developing agent a reactive --CH.sub.2 --group may be introduced in one of the alkyl groups, e.g. as exemplified in the following N,N-dialkylanilino coupler: ##SPC40##

The introduced reactive methylene group does not influence the absorption of the finally formed azine dye in the visible spectrum since the chromophoric system formed with the aid of that methylene group will only cause absorption in the non-visible short wave ultraviolet range.

A p-phenylenediamine type developing agent that is resistant to diffusion in an alkaline hydrophilic colloid medium and is particularly useful for application according to the present invention has the following formula: ##SPC41##

A multilayer photographic material suited for use according to the second embodiment of the present invention in the formation of multicolour images by imagewise diffusion transfer of intramolecularly or intermolecularly dye-forming reactants from a photographic material into a receptor material comprises preferably:

1. a blue-sensitive silver halide emulsion layer containing a non-diffusing silver halide developing agent and in effective contact therewith a colourless reagent A-X that is capable of diffusing in said medium with the aid of an alkaline aqueous liquid, of forming a yellow dyestuff by oxidative intramolecular or intermolecular coupling, and of forming with the oxidation product of the developing agent a compound with a substantially smaller diffusion mobility than it has in unreacted state,

2. a green-sensitive silver halide emulsion layer containing a non-diffusing silver halide developing agent and in effective contact therewith a colourless reagent A-Y or B-X that is capable of diffusing in said medium with the aid of an alkaline aqueous liquid, of forming a magenta dyestuff by oxidative intramolecular or intermolecular coupling and of forming with the oxidation product of the developing agent a compound with a substantially smaller diffusion mobility than it has in unreacted state,

3. a red-sensitive silver halide emulsion layer containing a non-diffusing silver halide developing agent and in effective contact with said developing agent a colourless reagent A-Z or C-X that is capable of diffusing in said medium with the aid of an alkaline aqueous liquid, of forming a cyan dyestuff by oxidative intramolecular or intermolecular coupling and of forming with the oxidation product of the developing agent a compound with a substantially smaller diffusion mobility than it has in unreacted state.

Each silver halide emulsion layer may be separated from another silver halide emulsion layer by a suitable spacer stratum, e.g., by a layer of gelatin or polyvinyl alcohol. The spacer stratum may act as a kind of a permeability controlling barrier layer, e.g., is a layer of slowly permeable material, such as a layer of cellulose acetate hydrogen phthalate occasionally in combination with a more water-permeable spacer layer, e.g., a gelatin layer.

The principles as mentioned hereinbefore and applied to said two embodiments are not only applicable in combination with differently spectrally sensitive superposed silver halide emulsion layers coated on a common support but can be used in conjunction with photographic materials embodying so-called "packet-emulsions" in which a single continuous hydrophilic colloid carrier layer contains separate minute differently spectrally sensitized silver halide emulsion portions, packed in resin envelopes forming microcapsules that are permeable for an aqueous alkaline liquid. Each silver halide emulsion portion contains the non-diffusing developing agent and also at least the reagent that has to react with an oxidation product of the developing agent. If the first embodiment is applied the reagent that does not react with the oxidation product of the developing agent may be incorporated in the continuous hydrophilic colloid phase containing the microcapsules.

Techniques for producing packet-emulsions are known to those skilled in the art and reference is made, e.g. to the United Kingdom Patent Specification 947,168 filed May 2, 1960 by Gevaert Photo-Producten N.V.

In the production of a multicolour image by image-wise diffusion transfer of oxidatively dye-forming compounds C.sub.1 -C.sub.2, preferably multilayer photosensitive materials are used of which the layer arrangement is as illustrated in the accompanying FIG. 1 and 2.

In that case the multilayer photosensitive element according to FIG. 1 comprises a blue-sensitive silver halide emulsion layer 1 containing a non-diffusing silver halide developing agent the oxidation products of which in alkaline medium couple with an alkali-soluble coupler A-X that in its turn in the presence of a stronger oxidising agent than exposed silver halide oxidatively intramolecularly or intermolecularly couples and forms a yellow dye after diffusion onto a receptor material containing the stronger oxidising agent.

Element 2 is a hydrophilic colloid spacer layer, e.g., a gelatin layer.

Element 3 is a green-sensitive silver halide emulsion layer that is substantially insensitive to blue and red light and contains a non-diffusing silver halide developing agent the oxidation products of which in alkaline medium couple with an alkali-soluble reagent A--Y or B--X that in its turn in the presence of a stronger oxidising agent than exposed silver halide oxidatively intramolecularly or intermolecularly couples and forms a magenta dye after diffusion onto the receptor material containing the stronger oxidising agent.

Element 4 is a hydrophilic colloid spacer layer, e.g., a gelatin layer.

Element 5 is a red-sensitive silver halide emulsion layer that is substantially insensitive to blue light and green light and contains a non-diffusing silver halide developing agent the oxidation products of which in alkaline medium couple with an alkali-soluble reagent A-Z or C-X, that in its turn in the presence of a stronger oxidising agent than exposed silver halide oxidatively intramolecularly or intermolecularly couples and forms a cyan dye after diffusion onto the receptor material containing the stronger oxidising agent.

Element 6 is a subbing layer for a gelatino silver halide colloid layer and a support 7, which is, e.g., a film support or semi-transparent paper base.

For use in the second embodiment a multilayer photosensitive element may contain according to FIG. 2 a blue-sensitive silver halide emulsion layer 1 containing a non-diffusing silver halide developing agent. The reagent A-X that in alkaline medium by means of a stronger oxidising agent than exposed silver halide intramolecularly or intermolecularly couples to form a yellow dye is present in the hydrophilic water-permeable colloid layer 2.

The reagent A-X diffusing out of the colloid layer 2 and penetrating into the exposed emulsion layer 1 reacts therein with the non-diffusing developer oxidation products and is inhibited thereby from further migration.

Element 3 is a hydrophilic colloid spacer layer, e.g., a gelatin layer.

Element 4 is a green-sensitive silver halide emulsion layer that is substantially insensitive to blue and red light and contains a non-diffusing silver halide developing agent. The reagent A-Y or B-X that in alkaline medium by means of a stronger oxidising agent than exposed silver halide intramolecularly or intermolecularly couples to form a magenta dye is present in a hydrophilic water-permeable colloid layer 5.

Element 6 is a hydrophilic colloid spacer layer, e.g., a gelatin layer.

Element 7 is a red-sensitive silver halide emulsion layer that is substantially insensitive to blue and green light and contains a non-diffusing silver halide developing agent. The reagent A-Z or C-X that in alkaline medium by means of a stronger oxidising agent than exposed silver halide intramolecularly or intermolecularly couples to form a cyan dye is present in a hydrophilic water-permeable colloid layer 8.

Element 9 is a subbing layer, e.g., a gelatin layer and element 10 is a support, e.g., a paper support.

In the composition of the photographic recording materials as illustrated in FIG. 1 and FIG. 2 the following reaction partners of the second embodiment are preferred.

As common part A in the general formula of the colourforming reagents A-X, A-Y and A-Z a monovalent group derived from a heterocyclic hydrazone compound of the class of the quinolin-4-one compounds is used and more preferably a group having the following structural formula: ##SPC42##

The part X in the first reagent is capable of forming a yellow azine dye by an oxidative intramolecular coupling with part A and is preferably a benzoylacetic acid anilide group, more preferably a group as represented between square brackets in the following formula: ##SPC43##

The yellow azine dye formed with such compound has the following structural formula: ##SPC44##

The part Y in the second reagent is capable of forming a magenta azine dye by an oxidative intramolecular coupling with part A and preferably is a pyrazolin-5-one group, more preferably a group as represented between square brackets in the following formula: ##SPC45##

The magenta azine dye formed with such compound has the following structural formula: ##SPC46##

The part Z in the third reagent is capable of forming a cyan dye by oxidative intramolecular coupling with part A and is preferably a .alpha.-hydroxynaphthoic acid aniline group, more preferably a group as represented between square brackets in the following formula: ##SPC47##

The cyan azine dye formed with such compound has the following structural formula: ##SPC48##

A p-phenylenediamine type developing agent that is non-diffusing in an alkaline hydrophilic colloid medium and is particularly useful for application according to the present invention has the following formula: ##SPC49##

It has to be understood that, in order to bring the final positive multicolour image produced on the receptor material in correct colour balance, reaction speed and diffusion mobility of the compounds that actively take part in the recording and dye formation can be properly adapted or controlled by their chemical structure and by the chemical and physical properties and dimensions, e.g., thickness and permeability of the separate colloid layers making part of the multilayer recording material.

The different silver halide emulsion layers need not contain the same developing agent so that by introduction of proper substituents in the developing agent molecule the coupling speed can be controlled and adjusted to the proper level for each silver halide emulsion layer.

In a multilayer silver halide recording material suited for reflex exposure of the type illustrated by FIGS. 1 and 2 no yellow filter layer is used so that the blue-sensitivity of the silver halide emulsion layers properly sensitized for green and red respectively has to be kept as low as possible. For that purpose preferably silver chloride grains are used that are sensitive only to ultraviolet and extreme violet. By excluding from the exposure light any extreme violet being of immaterial importance to the colour rendering very pure colours can be obtained in the final multicolour image.

In a multilayer silver halide recording material operating on the basis of the principles of the present invention intended for direct exposure a yellow filter layer may be used as a selectively blue-absorbing layer known from common silver halide multilayer materials for multicolour reproduction.

In the preparation of a recording material according to the present invention preferably dyestuff-forming ingredients are used that have a high diffusion mobility in alkaline medium and that are incorporated into the hydrophilic colloid medium in finely divided dispersed state. Preferably the colloid medium is slightly acidic and prevents thereby the alkali-soluble ingredients from wandering into an already coated subjacent colloid layer.

For a suitable dispersing of the ingredients mixing devices such as a colloid mill, an ultrasonic wave generator and a sand mill can be used.

The coating of the colloid layers may proceed according to any technique known to those skilled in the art of coating silver halide emulsion layers.

For suitable coating techniques reference is made, e.g., to Photographic Emulsion Chemistry by G. F. Duffin; The Focal Press, London (1966), p. 153-156.

The present invention is illustrated by the following examples. The percentages are by weight unless otherwise indicated.

Example 1

Recording material for the production of monochromatic (magenta) colour images.

A dispersion A was prepared by mixing intimately in a sand mill 5 g of the p-phenylenediamine type developing agent no. 1 of Table 1, 1.1 g of the phenol type coupler no. 1 of Table 2, and 1.6 g of the hydrazone type compound no. 1 of Table 6 in 50 ml of a 2 percent aqueous solution of a naphthalene sulphonate condensate as dispersing agent sold under the name LOMAR D by Nopco Chemical Company, Newark, N.J., U.S.A.

To the obtained dispersion was added a same volume of a 10 percent aqueous gelatin solution containing 2 percent of heptadecylbenzimidazole disodium sulphonate as wetting agent. The pH was adjusted to 5 by adding 2 ml of 1N aqueous acetic acid.

20 g of the obtained dispersion were mixed with 20 g of an aqueous gelatino silver chloride emulsion containing an amount of green-sensitized silver chloride equivalent to 62.5 g of silver nitrate pro kg, the weight ratio of silver to gelatin being 1.45. To the obtained mixture 8 ml of water and 0.5 g of chrome alum were added.

The mixture was coated onto a semi-transparent polyethylene coated paper base having a weight of 90 g/sq.m at such a coverage that an emulsion layer with an amount of silver halide corresponding with 3 g of silver nitrate per sq.m was obtained.

Receiving material

The receiving material was prepared by dispersing 25 g of dibenzoyl peroxide dissolved at 60.degree.C in 75 ml of diethyl carbonate in a composition containing 25 ml of a mixture of dibutyl phthalate/tricresyl phosphate (volume ratio of 3:8) and 250 g of a 10 percent aqueous gelatin solution containing 12.5 ml of a 20 percent aqueous solution of n-dodecylphenylsulphonic acid sodium salt as wetting agent. After effecting the dispersing in a speed-mixer the dispersion was diluted at 60.degree.C with water till a quantum of 500 g. The particle size of the dispersed phase was less than 0.5 micron.

The dispersion was coated onto an opaque paper base of 90 g/sq.m at a coverage of 8 g of dibenzoyl peroxide per sq.m.

Image-wise exposure and processing

The recording material was exposed reflectographically to an opaque original containing halftone magenta image parts. The development and image transfer proceeded in a common diffusion transfer developing apparatus by first moistening the exposed material with an aqueous alkaline activator liquid containing 50 g of sodium carbonate and 500 mg of 1-phenyl-pyrazolidin-3-one per litre. While wet it was pressed against and kept in contact with the above receiving material for 30 sec. and thereupon peeled apart therefrom. A magenta image corresponding with the magenta image parts of the original was obtained on the receiving material. In the production of the magenta dye image the above described developing agent may be replaced advantageously by the developing agents 2 to 4 of table 1, or by an aromatic 1,2-dihyroxy developing agent coupling in oxidized form with the hydrazone and having one of the following structural formulae: ##SPC50##

The hydrazone type coupler may be replaced by the hydrazone type coupler number 2 or 5 of Table 6.

The phenol type coupler may be replaced by the couplers 2 to 11 of Table 2.

Example 2

Recording material for the production of monochromatic (yellow) colour images.

A dispersion B was prepared by mixing intimately in a sand mill 5 g of the developing agent no. 1 of Table 1, 1.6 g of the reactive methylene type coupler no. 1 of Table 4 and 1.6 g of the hydrazone type compound no. 1 of Table 6 in 50 ml of water and 5.1 ml of LOMAR D (trade name).

To the obtained dispersion was added a same volume of a 10 percent aqueous gelatin solution containing 2 percent of heptadecyl benzimidazole disodium sulphonate as wetting agent.

The pH was adjusted to 4.65 with 2 ml of 1N aqueous acetic acid.

20 g of the obtained dispersion were mixed with 20 g of a blue-sensitive aqueous gelatino silver chloride emulsion of the type as described in Example 1.

The obtained light-sensitive dispersion was coated in the same way as described in Example 1 but on an opaque paper base.

The image-wise exposure was a direct exposure effected in an optical enlarger wherein a multicolour halftone transparency containing yellow image parts was used. The development and image transfer proceeded analogously as described in Example 1. A yellow image was obtained on the receiving material.

In the production of the yellow dye image the above described reactive methylene type coupler can be replaced advantageously by the couplers 2 to 7 of Table 4.

Example 3

Recording material for the production of monochromatic (cyan) colour images.

A dispersion C was prepared by mixing intimately in a sand mill 5 g of the developing agent 1 of Table 1, 1.5 g of the N,N-alkylsulphoalkylaniline compound no. 2 of Table 5 and 1.6 g of the hydrazone type compound no. 1 of Table 6 in 50 ml of water and 5 ml of LOMAR D (trade name).

To the obtained dispersion was added a same volume of a 10 percent aqueous gelatin solution containing 2 percent of heptadecylbenzimidazole disodium sulphonate as wetting agent. The pH was adjusted to 4.80 by the addition of 2 ml of 1N aqueous acetic acid solution.

20 g of the obtained dispersion were mixed with 20 g of a red-sensitive aqueous gelatino silver chloride emulsion as described in Example 1.

The obtained light-sensitive dispersion was coated in the same way on a semi-transparent paper base as described in Example 1.

The image-wise exposure and processing were carried out as described in Example 1 but using an original containing halftone cyan image parts.

In the production of the cyan dye image the above described reactive anilino type coupler can be replaced advantageously by the coupler 1, 3, 4 or 5 of Table 5 and the coupler 10 of Table 2.

The hydrazone couplers represented in Table 6 under the nos. 4,9 and 11 can be used likewise for the production of cyan dye images when applied in combination with hydroxynaphthoic acid amides and phenol couplers.

Example 4

Recording material for the production of monochromatic cyan images.

A dispersion A was prepared by mixing intimately in a sand mill 7.2 g of the p-phenylenediamine type developing agent no. 1 of Table 1 and 7.2 g of the colour-forming reagent no. 1 of Table 8 in 240 ml of a 2 percent aqueous solution of LOMAR D (trade name).

To the obtained dispersion was added a same volume of a 10 percent aqueous gelatin solution containing 2 percent of heptadecylbenzimidazole disodium sulphonate as wetting agent. The pH was adjusted to 5 with 2 ml of 1 N aqueous acetic acid.

20 g of the obtained dispersion were mixed with 20 g of an aqueous gelatino silver chloride emulsion containing an amount of red-sensitized silver chloride equivalent to 62.5 g of silver nitrate pro kg, the weight ratio of silver to gelatin being 1.45. To the obtained mixture 8 ml of water and 0.5 g of chrome alum were added.

The mixture was coated onto a semi-transparent polyethylene-coated paper base having a weight of 90 g/sq.m at such a coverage that an emulsion layer with an amount of silver halide corresponding with 1 g of silver nitrate per sq.m was obtained.

Receiving material

The receiving material was prepared by dispersing 25 g of dibenzoyl peroxide dissolved at 60.degree.C in 75 ml of diethyl carbonate in a composition containing 25 ml of a mixture of dibutyl phthalate/tricresyl phosphate (volume ratio of 3:8) and 250 g of a 10 percent aqueous gelatin solution containing 12.5 ml of 20 percent aqueous solution of n-dodecylphenylsulphonic acid sodium salt as wetting agent. After dispersing in a speed-mixer the dispersion was diluted at 60.degree.C with water till a quantum of 500 g. The particle size of the dispersed phase was less than 0.5 micron.

The dispersion was coated onto an opaque paper base of 90 g/sq.m at a coverage of 3 g of dibenzoyl peroxide per sq.m.

Image-wise exposure and processing

The recording material was exposed reflectographically to an opaque original containing halftone cyan image parts. The development and coupler transfer proceeded in a common diffusion transfer developing apparatus by first moistening the exposed material with an aqueous alkaline activator liquid containing 50 g of sodium carbonate, 10 g of potassium hydroxide and 100 mg of 1-phenylpyrazolidin-3-one per litre. While wet it was pressed against and kept in contact with the above receiving material for 60 sec. and thereupon peeled apart therefrom. A cyan image corresponding with the cyan image parts of the original was obtained on the receiving material. In the production of the cyan dye image the above described developing agent may be replaced advantageously by the developing agents 2 to 4 of Table 1, or by an aromatic 1,2-dihydroxy developing agent coupling in oxidized form with the hydrazone and having one of the following structural formulae: ##SPC51##

The colour-forming reagent may be replaced by the compounds 4 and 6 of Table 8.

Example 5

Recording material for the production of monochromatic (yellow) images.

A dispersion B was prepared by mixing intimately in a sand mill 1.2 g of the developing agent no. 1 of Table 1, 1.1 g of the colour-forming reagent no. 15 of Table 8, 50 ml of water and 5.1 ml of aqueous 40 percent solution of LOMAR D (trade name) as dispersing agent.

To the obtained dispersion was added a same volume of a 10 percent aqueous gelatin solution containing 2 percent of heptadecylbenzimidazole disodium sulphonate as wetting agent.

The pH was adjusted to 4.65 with 2 ml of 1 N aqueous acetic acid.

24 g of the obtained dispersion were mixed with 36 g of a blue-sensitive aqueous gelatino silver chloride emulsion of the type as described in Example 4.

The obtained light-sensitive dispersion was coated in the same way as described in Example 4 but on an opaque paper base.

The image-wise exposure was a direct exposure effected in an optical enlarger by the use of a multicolour halftone transparency containing yellow image parts. The development and image transfer proceeded analogously as described in Example 4. A yellow image was obtained on the receiving material.

In the production of the yellow dye image the above described colour-forming reagent can be replaced advantageously by the compounds 5, 7, 14, 16, 17 or 18 of Table 8.

Example 6

Recording material for the production of monochromatic magenta images.

A dispersion C was prepared by mixing intimately in a sand mill 0.9 g of the developing agent 1 of Table 1, 1 g of the colour forming reagent no. 8 of Table 8 together with 40 ml of water and 3 ml of a 40 percent aqueous solution of LOMAR D (trade name) as dispersing agent.

To the obtained dispersion was added a same volume of a 10 percent aqueous gelatin solution containing 2 percent of heptadecylbenzimidazole disodium sulphonate as wetting agent. The pH was adjusted to 4.80 by the addition of 2 ml of 1 N aqueous acetic acid solution.

20 g of the obtained dispersion were mixed with 20 g of a red-sensitive aqueous gelatino silver chloride emulsion as described in Example 4.

The obtained light-sensitive dispersion was coated in the same way on a semi-transparent paper base as described in Example 4.

The image-wise exposure and processing were carried out as described in Example 4 but by using an original containing halftone magenta image parts.

In the production of the magenta dye image the above described colour-forming reagent can be replaced advantageously by the compounds 2, 3, 9, 10, 11, 12 or 13 of Table 3.

In order to realize a multicolour photographic material containing a plurality of superposed silver halide emulsion layers it is advantageous to combine emulsion layers containing the separate colour-forming reagents A and B of the first embodiment with emulsion layers containing the colour-forming reagents C.sub.1 -C.sub.2 of the second embodiment of the present invention.

In the uppermost emulsion layer and optionally in the subsequent (i.e., second) emulsion layer colour-forming reagents C.sub.1 -C.sub.2 are preferably used. These reagents only require a relatively small amount of silver halide and developing agent. The separate colour-forming reaction partners A and B are used preferably in the third silver halide emulsion layer and optionally in the second emulsion layer. These reaction partners have a relatively low molecular weight and consequently a higher diffusion speed, which for the longer way they have to go to the receiving material makes an appropriate compensation.

A photographic material composed in that way offers a quick and well balanced diffusion transfer of the different oxidatively colour-forming reagents.

The following example 7 illustrates such a material and its processing.

Example 7

Preparation of the green-sensitive silver halide emulsion (dispersion A)

The following ingredients were dispersed in a sandmill so as to obtain solid particles sizing 1 .mu. on the average: ##SPC52## ##SPC53##

The obtained mixture was added to a same volume of 10 percent aqueous gelatin solution containing chrome alum as a hardener and mixed with 20 ml of the wetting agent ULTRAVON W (disodium salt of heptadecyl-benzimidazole disulphonic acid of CIBA A.G., Switzerland).

An amount of 480 g of this dispersion was mixed with 325 g of a green-sensitized silver chloride emulsion containing per kg an amount of silver chloride equivalent to 62.5 g of silver nitrate.

The pH of the mixture was adjusted to 5.3

Preparation of the blue-sensitive silver halide emulsion (dispersion B)

The following ingredients were dispersed in a sandmill so as to obtain solid particles sizing 1 .mu. on the average: ##SPC54## ##SPC55##

The obtained mixture was added to a same volume of 10 percent aqueous gelatin solution containing chrome alum as a hardener and mixed with 5 ml of ULTRAVON W (trade name).

An amount of 480 g of this dispersion was mixed with 400 g of a blue-sensitive silver chloride emulsion containing per kg an amount of silver chloride corresponding with 62.5 g of silver nitrate.

The pH of the mixture was adjusted to 5.3.

Preparation of the red-sensitive silver halide emulsion (dispersion C)

The following ingredients were dispersed in a sandmill so as to obtain solid particles sizing 1 .mu. on the average:

developing compound 1 of Table 1 24 g compound 1 of Table 8 24 g 40% aqueous solution of LOMAR D (trade 32 ml name) as dispersing agent water 800 ml

The obtained mixture was added to 800 ml of a 10 percent aqueous solution of gelatin containing chrome alum as a hardener and mixed with 16 ml of ULTRAVON W (trade name).

An amount of 320 g of this dispersion was mixed with 160 g of a red-sensitive silver chloride emulsion containing per kg an amount of silver chloride corresponding with 62.5 g of silver nitrate. Thereupon an additional amount of 160 ml of a 5 aqueous solution of gelatin was added.

The pH of the mixture was adjusted to 5.3.

Preparation of the multicolour photographic material

The dispersions A, B and C were coated on a semitransparent polyethylene coated paper base having a weight of 90 g per sq.m.

The dispersion A was coated at 180 g per sq.m. and dried. Thereupon a 2 percent aqueous gelatin solution was applied at a coverage of 200 g per sq.m.

On this intermediate gelatin coating, dispersion B was applied at a coverage of 100 g per sq.m.

As a fourth layer dispersion C was coated at a coverage of 80 g per sq.m. The multilayer composition was provided with a top-coat from a 2 percent by weight aqueous gelatin solution at a coverage of 100 g per sq.m.

Preparation of the receiving material.

To a paper base laminated with a thin polyethylene terephthalate foil for making the paper water-impermeable at the receiving side, a layer containing a polyionic polymer as mordanting agent for the oxidatively formed dyes was applied at a coverage of 100 g per sq.m from the following composition:

10% aqueous gelatin solution 600 g water 492 ml DOW ECR 34 (a copolymer of the basis of vinyl-benzyl trimethyl ammonium chloride and styrene of The Dow Chemical Company, Midland, Mich., USA) 102 g chrome alum hardener 0.1 g

To said first layer a second layer containing the oxidising agent for the oxidative coupling of the transferred colour forming agent(s) was applied starting from the following composition:

m-methyldibenzoyl peroxide dissolved at 60.degree.C in diethyl carbonate 75 ml a mixture of dibutyl phthalate/ tricresyl phosphate (volume ratio of 3:8) 25 ml 10% aqueous gelatin solution con- taining 12.5 ml of 20% aqueous so- lution of n-dodecylphenyl sulphonic acid sodium salt 250 g

After effecting the dispersing in a speed-mixer the dispersion was diluted at 60.degree.C with water so as to obtain a quantum of 500 g.

The particle size of the dispersed phase was less than 0.3 micron.

The coverage of this dispersion on the mordanting layer was 100 g per sq.m.

Image-wise exposure and processing

The photosensitive material was exposed with white light through a continuous tone multicolour transparency and developed for 20 sec at 20.degree.C by means of a solution containing the following ingredients:

sodium carbonate 50 g potassium hydroxide 10 g 1-phenyl-pyrazolidin-3-one 0.1 g water 1 l

The thus treated photosensitive material was then led between a pair of rubber rollers, the exposed side being in contact with the receiving material. After a contact time of 2 min they were separated.

On the receiving material a positive multicolour image of the original was obtained.

Example 8

This Example illustrates the use of a colour-forming compound that oxidatively couples intermolecularly:

By sand-mill mixing a dispersion was made containing the following ingredients:

colour forming compound 18 of Table 8 1.1 g developing compound 1 of Table 1 1.2 g 40% aqueous solution of LOMAR D (trade name) as a dispersing agent 2 ml 10% aqueous solution of gelatin 40 ml water 40 ml

24 g of this dispersion was added to 36 g of a bluesensitive silver chloride emulsion containing per kg an amount of silver chloride equivalent to 62.5 g of silver nitrate.

The dispersion was applied to a baryta-coated paper support at a coverage of 100 g per sq.m.

Image-wise exposure and processing were analogous to those applied in Example 1. On the receiving material a yellow positive image of an original containing yellow image markings was obtained.

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