Title:
MULTICOLOR DYE DEVELOPER SYSTEMS
United States Patent 3617272


Abstract:
Photographic elements wherein at least two adjacent image-forming units (each comprising silver halide and dye developer) are separated by an alkali-permeable, water-insoluble stratum of a polyvalent metal salt and a film-forming, alkali-permeable, water-soluble polymer having free carboxylic acid groups, are processed in the presence of a material that is a chelating agent for the polyvalent metal, the chelating function of said material being destroyed imagewise in just exposed areas as a function of development.



Inventors:
STEWART PAUL H
Application Number:
04/797283
Publication Date:
11/02/1971
Filing Date:
02/06/1969
Assignee:
EASTMAN KODAK CO.
Primary Class:
Other Classes:
430/215, 430/218, 430/505
International Classes:
G03C8/36; G03C8/16; (IPC1-7): G03C5/54; G03C1/40
Field of Search:
96/29D,3,76,77
View Patent Images:
US Patent References:
3477849MULTI-COLOR DYE DEVELOPER SYSTEMS1969-11-11Becker
3345163Photographic diffusion transfer color processes1967-10-03Land et al.
3262781Photographic products1966-07-26Ryan et al.
3196015Diffusion transfer process1965-07-20Ryan



Other References:

Martell, A. E. and Calvin, M., Chemistry of the Metal Chelate Compounds, Third Printing (1956); Prentice-Hall, Englewood Cliffs, N. J., Pages 134-138 and 556..
Primary Examiner:
Torchin, Norman G.
Assistant Examiner:
Suropico, Alfonso T.
Claims:
I claim

1. In a photographic element comprising a support having coated thereon at least two dye image-forming units with an alkali-permeable, water-insoluble salt stratum positioned between at least two of said dye image-forming units, said dye image-forming units comprising a silver halide emulsion layer and a dye developer contiguous to silver halide of said emulsion, and said salt stratum comprising an alkali-permeable, water-insoluble salt of a polyvalent metal and a film-forming, alkali-permeable, water-soluble polymer having free carboxylic acid groups, said salt stratum being less permeable to dye developers comprising said dye image-forming units in aqueous alkaline solution than said water-soluble polymer used to prepare said salt stratum, the improvement which comprises having coated on the salt stratum side of the photographic element a material that is a chelating agent for said polyvalent metal, the chelating function of said material being destroyed imagewise in just exposed area as a function of development.

2. A photographic element as defined by claim 1 wherein said material is an auxiliary developer.

3. In a photographic element comprising a support having coated thereon at least two dye image-forming units with an alkali-permeable, water-insoluble salt stratum positioned between at least two of said dye image-forming units, said dye image-forming units comprising a silver halide emulsion layer and a dye developer contiguous to silver halide of said emulsion, and said salt stratum comprising an alkali-permeable, water-insoluble salt of an alkaline earth metal and a film-forming, alkali-permeable, water-soluble polymer having free carboxylic acid groups, said salt stratum being less permeable to dye developers comprising said dye image-forming units in aqueous alkaline solution than said water-soluble polymer used to prepare said salt stratum, the improvement which comprises having coated on the salt stratum side of the photographic element a catechol which develops silver halide and is a chelating agent for said polyvalent metal.

4. A photographic element as defined by claim 3 wherein the salt stratum is calcium alginate.

5. A photographic element as defined by claim 3 wherein the catechol has the formula: ##SPC4##

6. A photographic element as defined by claim 4 wherein the catechol is 4-phenylcatechol.

7. A photographic element comprising superposed on a photographic support three dye image-forming units in layers capable of recording red, green and blue light respectively, the dye image-forming unit recording blue light being furthest from the support and the dye image-forming unit recording red light being most proximate to the support, and an alkali-permeable, water-insoluble stratum of calcium alginate positioned between each of the said image-forming units, said dye image-forming units comprising a gelatino-silver halide emulsion layer and an underlying contiguous layer containing a dye developer substantially complementary in color to the color of light recorded in the contiguous silver halide emulsion layer, and a catechol which develops silver halide and is a chelating agent for calcium ions being positioned between said support and said stratum of calcium alginate, said catechol being present in an amount sufficient to increase the permeability of said stratum in just the unexposed areas.

8. A photographic element comprising superposed on a photographic support three dye image-forming units in layers capable of recording red, green and blue light respectively, the dye image-forming unit recording blue light being furthest from the support and the dye image-forming unit recording red light being most proximate to the support, and an alkali-permeable, water-insoluble stratum of calcium alginate positioned between the said image-forming units recording red and green light, said dye image-forming units comprising a gelatino-silver halide emulsion layer and an underlying contiguous layer containing a dye developer substantially complementary in color to the color of light recorded in the contiguous silver halide emulsion layer, and a catechol which develops silver halide and is a chelating agent for calcium ions being positioned between said support and said stratum of calcium alginate, said catechol being present in an amount sufficient to increase the permeability of said stratum in just the unexposed areas.

9. In the processing of an imagewise exposed photographic element comprising a support having coated thereon at least two dye image-forming units with an alkali-permeable, water-insoluble salt stratum positioned between at least two of said dye image-forming units, said dye image-forming units comprising a silver halide emulsion layer and a dye developer contiguous to silver halide of said emulsion, and said salt stratum comprising an alkali-permeable, water-insoluble salt of a polyvalent metal and a film-forming alkali-permeable, water-soluble polymer having free carboxylic aid groups, said salt stratum being less permeable to dye developers comprising said dye image-forming units in aqueous alkaline solution than said water-soluble polymer used to prepare said salt stratum, which comprises treating the photographic element with an alkaline processing liquid, developing latent images in the regions of exposure of the silver halide emulsion layers and thereby immobilizing dye developers in said regions of exposure, dye developers in undeveloped regions diffusing imagewise in register to a reception layer for dye developer images, the improvement which comprises carrying out said treating of the photographic element in the presence of a material that is a chelating agent for said polyvalent metal, the chelating function of said material being destroyed imagewise in just exposed areas as a function of development.

10. The process as defined in claim 9 wherein said material is an auxiliary developer coated in a layer on the salt stratum side of the photographic element.

11. In the processing of an imagewise exposed photographic element comprising a support having coated thereon at least two dye image-forming units with an alkali-permeable, water-insoluble salt stratum positioned between at least two of said dye image-forming units, said dye image-forming units comprising a silver halide emulsion layer and a dye developer contiguous to silver halide of said emulsion, and said salt stratum comprising an alkali-permeable, water-insoluble salt of an alkaline earth metal and a film-forming alkali-permeable, water-soluble polymer having free carboxylic acid groups, said salt stratum being less permeable to dye developers comprising said dye image-forming units in aqueous alkaline solution than said water-soluble polymer used to prepare said salt stratum, which comprises treating the photographic element with an alkaline processing liquid, developing latent images in the regions of exposure of the silver halide emulsion layers and thereby immobilizing dye developers in said regions of exposure, dye developers in undeveloped regions diffusing imagewise in register to a reception layer for dye developer images, the improvement which comprises carrying out said treating of the photographic element in the presence of a catechol which develops silver halide and is a chelating agent for said polyvalent metal.

12. The process as defined in claim 11 wherein the catechol is coated in a layer on the salt stratum side of the photographic element.

13. The process as defined in claim 11 wherein the catechol is present in the alkaline processing liquid.

14. The process as defined in claim 11 wherein the salt stratum is calcium alginate.

15. The process as defined in claim 11 wherein the catechol has the formula: ##SPC5##

16. The process as defined in claim 11 wherein the catechol is 4-phenylcatechol.

Description:
The present invention relates to the art of photography, and more particularly, to multicolor dye diffusion transfer systems utilizing dye developers.

Compounds which contain in the same molecule both the chromophoric system of a dye and a photographic silver halide developing moiety have been described in the photographic art as useful compounds in photographic elements for preparing color images by diffusion transfer processes. Such compounds are commonly called "dye developers". Photographic elements containing such dye developers generally comprise a plurality of photosensitive silver halide emulsions wherein each of the emulsions is selectively sensitized to a different region of the spectrum. A dye developer is positioned contiguous to the silver halide in each of such emulsions, the dye developer more generally being substantially complimentary in color to the color of light recorded in the contiguous silver halide. Such a photoelement is processed with an alkaline composition. The latent image is developed in the negative image areas with the dye developers, this development immobilizing the dye developers in such negative image areas. The dye developers in the unexposed areas diffuse to the surface imagewise and are transferred to a reception layer or receiving sheet to form a positive multicolor image. Such color diffusion transfer processes are disclosed in U.S. Pats. Nos. 2,983,606, 3,253,915, British Pat. 804,971, and French Pat. 1,313,767, as well as elsewhere in the literature.

Ideally, each dye developer should develop only contiguous silver halide, to wit, the cyan dye developer should develop only the red-sensitive silver halide emulsion layer, the magenta dye developer should develop only the green-sensitive silver halide emulsion layer, and the yellow dye developer should develop only the blue-sensitive silver halide emulsion layer in a conventional three-color system. However, in practice, each dye developer has been found to develop to an undesirable extent each silver halide emulsion layer. The result of this effect is to produce color contamination and desaturation of colors in the transfer prints, red in particular being a color of relatively poor quality. Conventional interlayers or barrier layers between each of the color-forming units of such materials as gelatin have been utilized, such layers, however, only being effective to a limited degree in improving the interimage characteristics in multicolor dye developer diffusion transfer systems.

Becker U.S. Pat. No. 3,384,483, issued Mar. 25, 1968, describes photographic elements useful in preparing multicolor dye developer diffusion transfer images containing certain alkali-permeable, water-insoluble salt strata or barrier layers between the silver halide emulsion layers that can be utilized to reduce color contamination of the transferred images. However, such barrier layers tend to prevent some of the soluble image-forming dye developer in underlying layers, particularly cyan dye developer, from diffusing to the receiving sheet for the multicolor dye developer images, thus resulting in lowered Dmax in the transferred image for the undercoated dye developer.

An improvement was found in photographic elements having barrier layers of the type described in Becker U.S. Pat. No. 3,384,483. The improvement, which is described by Becker in Belgian Pat. 708,491 issued Jan. 31, 1968, features the use of an organic sequestering agent for the polyvalent metal of the barrier. The sequestering agents described therein substantially uniformly increase the permeability of the barrier to underlying dye developer. This results in improved color saturation, although color contamination is increased.

It would be highly desirable to provide an improvement in dye developer systems utilizing a salt stratum of the type described in Becker U.S. Pat. No. 3,384,483 whereby the salt stratum could be rendered more permeable to dye developers in just the unexposed areas. Such an improvement would result in good diffusion of dye developers from unexposed areas, while effectively inhibiting undesired diffusion of dye developers from exposed areas.

It is an object of this invention to provide novel photographic elements useful for preparing multicolor dye developer diffusion transfer images having high color saturation as well as low color contamination.

It is another object of this invention to provide novel photographic elements particularly useful for preparing multicolor dye developer diffusion transfer images having high red saturation as well as low red contamination.

It is still another object of this invention to provide a new method for preparing multicolor dye developer diffusion transfer images having high color saturation as well as low color contamination utilizing photographic elements containing alkali-permeable, water-insoluble strata of a polyvalent metal and a polymeric carboxylic acid positioned between at least two of the dye image-forming units of such elements.

These and other objects of the invention are accomplished with photographic elements comprising a support having coated thereon (1 ) at least two dye image-forming units composed of a light-sensitive silver halide emulsion and a dye developer contiguous to silver halide of the emulsion, and (2) an alkali-permeable and water-insoluble stratum or barrier layer of a polyvalent metal salt of a film-forming, alkali-permeable, water-soluble polymeric carboxylic acid positioned between at least two of the dye image-forming units, such stratum being less permeable to dye developers in aqueous alkaline solution than the polymeric carboxylic acid used to prepare the salt stratum. Such photographic elements are described in Becker U.S. Pat. No. 3,384,483, issued Mar. 25, 1968. In accordance with the present invention, the processing of such photographic elements is carried out in the presence of a material that is chelating or sequestering agent for the polyvalent metal moiety of the salt stratum, the chelating function of said material being destroyed imagewise in just exposed areas as a function of development. The material thus increases permeability of the barrier layer in just the unexposed areas.

The chelating materials employed in this invention can be initially present in the light-sensitive photographic element, in the processing composition or in the dye developer image receiving element.

Materials which are capable of chelating the polyvalent metal moiety of the salt stratum, and which are auxiliary developer for the dye-developer systems, are highly useful in the practice of this invention. In exposed areas the auxiliary developer is oxidized to a form which does not change the permeability of the barrier layer. In unexposed areas, such auxiliary developers chelate the polyvalent metal of the salt stratum, thereby increasing permeability in unexposed areas.

Catechols are typical useful auxiliary developers which are chelating agents. The catechol chelates the polyvalent ions of the barrier strata in the unexposed areas, rendering the barrier permeable to underlying dye-developer after such dye-developer has developed exposed silver halide contiguous thereto. In exposed areas, the catechol is an auxiliary developer, as shown in my copending U.S. Pat. application Ser. No. 676,603, filed Oct. 19, 1967, and now abandoned. This invention results in color prints having high color saturation and low color contamination.

Any catechol can be used in the practice of this invention which chelates the polyvalent metal moiety of the salt stratum barrier layer and which is a silver halide developing agent. The catechols are preferably colorless and soluble in the alkaline processing solution. The word "catechol" is used generically herein to include 1,2-dihydroxybenzenes, which can contain additional hydroxyl groups, such as a 1,2,3-trihydroxybenzene, a 1,2,4-trihydroxybenzene or a 1,2,3,4,5tetrahydroxybenzene. Suitable catechols include those having the structural formula: ##SPC1##

wherein: R1 , R2 , R3 and R4 can be hydrogen, an alkyl radical, preferably of about 1 to 8 carbon atoms (e.g., methyl, ethyl, propyl, butyl, amyl, hexyl, heptyl, octyl, etc.,), an aryl radical (e.g., phenyl, tolyl, naphthyl, etc.), hydroxyl, aryloxy such as phenoxy, halogen such as chlorine or bromine, carboxy or R2 and R3 or R3 and R4 , when taken together with the carbon atoms to which they are attached, represent the atoms to complete a cycloalkyl group containing from 4 to 6 carbon atoms (e.g., cyclohexyl, cyclopentyl, etc.) which can contain an endomethylene group (e.g., methanocyclohexyl, methanocyclopentyl, etc.). Salts and esters of these catechols can also be used.

A preferred class of catechols having the aforesaid structural formula are those in which R1 , R2 , R3 and R4 are either hydrogen or an alkyl radical of from 1 to 8 carbon atoms.

Examples of suitable catechols include:

catechol

4-methylcatechol

4-isopropylcatechol

3 -isopropylcatechol

4tert-butylcatechol

4phenylcatechol

3,6-dimethylcatechol

1,2dihydroxy-5,8-methano-5,6,7,8-tetrahydronaphthalene

hexoylcatechol

1,2,3-trihydroxybenzene

3-phenylcatechol

4-octylcatechol

4l octylcatechol

1,2,4-trihydroxybenzene

p-chlorocatechol

4,5-dibromocatechol

1,2,4,5-tetrahydroxybenzene

caffeic acid

4-phenoxycatechol

The amount of chelating material utilized in the invention can be widely varied, the amount varying with such variables as the number and type of barrier layers of polyvalent metal-poly carboxylic acid salt in the photographic element, the amount of polyvalent ion present in the system, the particular chelating material, the processing time, the particular positioning of the material in the system, the use of other auxiliary developers and related variables. Sufficient chelating material should be used to increase permeability in just unexposed areas. When catechol is employed, typical useful concentration ranges are about 1 to 150 mg. of catechol per square foot when utilized in the light-sensitive element, about 50 to 200 mg. of catechol per square foot when utilized in the dye developer image receiving sheet or layer, and about 0.1 to 5 percent by weight of the alkaline processing composition when utilized therein. Good results are obtained when a catechol is the only chelating or sequestering agent present during processing.

The chelating material can be coated in combination with other constituents in the present photographic elements and image receiving sheets, or it can be coated in separate layers. The chelating material can be coated in an organic hydrophilic colloid as an aqueous coating melt. Likewise, the chelating material can be dissolved in a high-boiling (e.g., greater than 175° C.) solvent and dispersed in finely divided droplets in a hydrophilic colloid and the resulting dispersion coated.

The salt strata or barrier layers utilized in the subject dye developer diffusion transfer system can be prepared with a variety of polyvalent metal salts and polymeric carboxylic acids. The subject salt strata can be formed on the element by coating a solution, on a water-permeable substrate, containing the polyvalent metal in water-soluble form on a polymeric carboxylic acid layer previously coated on the element to form a thin layer of a water-insoluble salt. The polyvalent metal in water-soluble form can be coated directly on silver halide emulsion layers if the vehicle for the silver halide is a polymeric carboxylic acid that forms a water-insoluble salt with the polyvalent metal moiety. Interlayers of water-permeable materials can be utilized on either side of the subject water-insoluble salt strata. Such salt strata are preferably utilized between the magenta and cyan dye image-forming units to particularly improve red purity and saturation of the transferred dye developer images. Similarly, the subject salt strata can be utilized between the yellow and the magenta dye image-forming units as well as between both the magenta and the cyan dye image-forming units to improve color purity and saturation of the transfer dye developer images.

A wide variety of film-forming, alkali-permeable, water-soluble polymeric compositions containing free carboxylic acid groups, and including water-soluble salts thereof, can be utilized to form the subject salt strata with polyvalent metal moieties. Typically, such polymers contain about 5 percent to 60 percent by weight of polymer of free carboxylic acid groups (i.e., available for reaction with the subject polyvalent metal moieties in aqueous alkaline solutions) or the equivalent weight of water-soluble salts thereof. Typical of such suitable acid polymers include:

1. natural occurring carboxylic acid group-containing polymers and derivatives thereof including such proteins as gelatin, casein and the like,

2. natural occurring high molecular weight carboxylic acid group-containing polysaccharides and derivatives thereof such as alginic acid, pectic acid, tragacanthic acid, carboxymethyl cellulose, and the like, and

3. synthetic linear polymers containing carboxylic acid groups such as addition vinyl polymers and condensation polymers wherein the monomeric repeating units are connected with such groups as

and the like, illustrative of such synthetic polymers are disclosed in U.S. Pat. No. 2,565,418, U.S. Pat. No. 3,062,674, U.S. Pat. No. 3,007,901 and British Pat. No. 886,882 and include succinoylated polyvinyl alcohol, maleic acid-styrene polymers, alkylacrylate-acrylic acid polymers, formaldehyde-salicylic acid polymers, acidic polyesters, acid polyamides and the like.

Polyvalent metal moieties are utilized to form the present salts as such moieties can be used to cross-link carboxylic acid moieties of the polymeric carboxylic acid to form the present strata which have the proper degree of alkali permeability and water-insolubility to serve as barrier layers to prevent color contamination and interdevelopment between dye image-forming units. A wide variety of polyvalent metal moieties can be utilized in preparing the subject salt strata. Suitable polyvalent metals with which suitable salt strata of the invention can be prepared include alkaline earth metals, such as calcium, barium and strontium, and the like polyvalent metals that form alkali-permeable, water-insoluble salts with the above-described polymeric materials containing carboxylic acid groups.

The amount of polymeric salt utilized in the subject salt strata can be widely varied, the amount varying with the effect desired and the nature of the polyvalent metal and the polymeric carboxylic acid. More generally, the amount or coverage of the polyvalent metal-polymeric carboxylic acid salt stratum utilized is that which is substantially equivalent in permeability to dye developers in aqueous alkaline solution to the calcium alginate formed when a stratum consisting essentially of sodium alginate is reacted with calcium chloride coated thereover at a coverage of about 5 to 100 mg. per square foot.

Typical alkali-permeable water-insoluble salts comprising the barrier layers of the light-sensitive photographic elements used in the invention include:

strontium gelatinate,

barium gelatinate,

calcium pectinate,

calcium alginate,

calcium-succinoylated polyvinyl alcohol,

calcium-polyacrylic acid,

barium alginate,

magnesium alginate,

strontium alginate,

calcium-condensation of formaldehyde and salicylic acid, and the like, and including mixtures thereof.

Dye developers are well known in the photographic art. Such compounds function both as a silver halide developing agent and as a dye in photographic diffusion transfer systems. Dye developers are characterized as being relatively nondiffusible in colloid layers such as the hydrophilic organic colloids used in photographic emulsions at neutral pH, but diffusible in the photographic elements in the presence of alkaline processing solutions. Generally, such dye developers are substantially insoluble in water, which property usually necessitates the use of organic solvents to incorporate the dye developers into the organic colloid layers of the photoelements. The dye developers are particularly characterized as containing both a chromophoric or dye moiety and at least one moiety having a silver halide developing agent function. Particularly useful dye developers are those wherein the chromophoric moiety is an azo or anthraquinone dye moiety and the silver halide developing moiety is a benzenoid moiety such as a hydroquinonyl moiety.

Representative dye developers of use in the dispersions of the invention have the general formula M-N=N-D in which M is an aromatic or heterocyclic ring or ring system such as a benzene, napthalate, tetralin, anthracene, anthraquinone, pyrazole, quinoline, etc., ring which can be substittuted with such groups as hydroxyl, amine, keto, nitro, alkoxy, aryloxy, acyl, alkylamido, alkylaryl, carboxamido, sulfonamide, carboxyl or sulfo groups. D represents a silver halide developing agent moiety imparting the developing agent function to the dye developer such as a hydroquinonyl group which can be substituted with amino, alkylamino, alkyl, hydroxyl, alkoxyl or halogen groups.

Typical useful dye developers are described in columns 9-13 of U.S. Pat. No 3,146,102, as well as elsewhere in the patent literature, including: Australian 220,279 ; German 1,036,640 ; British 804,971 and 804,973-5; Belgian 554,935; French 1,168,292; and Canadian 557,021 and 579,038.

In the photographic elements of the invention, the dye developers are preferably incorporated in hydrophilic organic colloidal vehicles or carriers comprising the layers of the photographic element dissolved in high-boiling or crystalloidal solvents and dispersed in finely divided droplets. In preparing such dispersions of dye developers, high-boiling or substantially water-immiscible organic liquids having boiling points above about 175° C. are utilized. The high-boiling solvent can be used alone in dissolving the dye developer and in forming the dispersion or it can be mixed with a low-boiling organic solvent e.g., boiling at least 25° C. below the boiling point of the higher boiling solvent), or a water-soluble organic solvent, as an auxiliary solvent to facilitate solution of the dye developer. A preferred range of proportions of high-boiling solvent to auxiliary is 1/0 to 1 /10 on a weight basis. Such auxiliary solvents can be readily removed from the high-boiling solvent, for example, by air-drying a chilled, noodled dispersion or by continuous water washing. Several of such high-boiling solvents and auxiliary solvents utilized for incorporating dye developers are described in French Pat. No. 1,313,765. The dye developers can also be incorporated into vehicles soluble in organic solvents which are also solvents for the dye developer. Likewise, other incorporating techniques for the dye developer such as ball-milling can be utilized.

The photographic elements of the invention desirably contain auxiliary developing agents, in addition to catechols, such as colorless substantially water-insoluble hydroquinone derivatives, e.g., those disclosed in French Pat. No. 1,313,086. Such auxiliary developing agents can be incorporated in the silver halide emulsion layers, in overcoat layers, in inter-layers or in other layers of the element.

The silver halide emulsions utilized in preparing the photographic elements of the invention are more generally the conventional negative-type developing-out emulsions, positive transfer images resulting from such emulsions. However, reversal emulsions such as solarized emulsions and emulsions that form latent images predominantly internal to the silver halide grains as described in U.S. Pat. No. 2,592,250, can also be used, negative transfer images resulting from such emulsions. Typical suitable silver halides include silver chloride, silver bromide, silver bromoiodide, silver chloroiodide, silver chlorobromoiodide, etc. Useful sensitizers are those in Kennard Ser. No. 337,792, filed Jan. 15, 1964. Mixtures of more than one of such silver halides can also be utilized. In preparing such silver halide emulsions, a wide variety of hydrophilic organic colloids can be utilized as the vehicle or carrier. I prefer to utilize gelatin as the hydrophilic colloid or carrier material although such material as polyvinyl alcohol and its water-soluble derivatives and copolymers, water-soluble copolymers such as polyacrylamide, imidized polyacrylamide, etc., or polymerized vinyl compounds such as those disclosed in U.S. Pat. Nos. 3,142,568, 3,193,386, 3,062,674 and 3,220,844, and including the water-insoluble polymers of alkyl acrylates and methacrylates, acrylic acid, sulfoalkyl acrylates or methacrylates and the like.

In the present photographic elements, the dye developers are disposed integral with the element and contiguous to silver halide of each of the light-sensitive silver halide emulsion layers. Such dye developers can be incorporated directly in the light-sensitive silver halide emulsion layers or in separate layers contiguous to the layers containing the silver halide. The present photographic elements contain at least two dye image-forming units, each unit comprising a light-sensitive silver halide emulsion and a dye developer contiguous to silver halide in the unit. Each dye image-forming unit is preferably spectrally sensitized to record light that is substantially complementary to the color of the dye developer in the unit.

The various layers utilized in preparing the present photographic elements can be coated on a wide variety of transparent and opaque photographic supports. Typical supports include cellulose nitrate film, cellulose acetate film, polyvinyl acetal film, polystyrene film, polyethylene terephthalate film, polyethylene film, polypropylene film, paper, polyethylene-coated paper, glass.

A wide variety of receiving sheets can be utilized to receive the dye developer images from the present light-sensitive photographic elements. The sequestering agents used in the invention can be positioned in any of the layers of the receiving sheet. Typical reception layers for dye developer receiving sheets which are, or include, mordants for dye developers, are such material as linear polyamides, proteins such as gelatin, polyvinyl pyrrolidones, poly-4-vinyl pyridine, polyvinyl alcohol, polyvinyl salicylal, partially hydrolyzed polyvinyl acetate, methyl cellulose, regenerated cellulose, carboxymethyl cellulose and hydroxyethyl cellulose, or mixtures of such. These reception layers can be coated on a suitable support of the type described above for the light-sensitive elements of the invention and including transparent as well as opaque supports. Also, receiving sheets that release acidic material such as that derived from an acidic polymer or other acidic compound at a controlled rate are as described in U.S. Pat. No. 2,584,030 are particularly useful. Such acidic materials are typically positioned in layers on the receiving sheet below the dye developer reception layer, there suitably being a spacer layer between the acid layer and the mordanting layer to control the release of acidic material. Such acidic materials serve to neutralize residual portions of the alkaline activator on the receiving sheet. A wide variety of nondiffusible cationic or basic dye-mordanting compounds can be used in liquid permeable reception layers including amines such as polymeric amines, quaternary ammonium compounds, quaternary phosphonium compounds and tertiary sulfonium compounds. Such mordants are nondiffusible in the alkaline processing composition and contain at least one hydrophobic ballast group.

To facilitate a clean stripping away of the receiving sheet from the negative element after the transfer of the dye developer images to the receiving sheet, the receiving sheet can be prepared by superficially hardening with a nondiffusing hardener and a surfactant. For example, a dye developer image receiving layer on a receiving sheet containing poly-4-vinyl pyridine mordant in polyvinyl alcohol can be efficaciously treated with an oxyguar gum hardener solution containing a surfactant such as soidum cetyl sulfate or sodium N-methyl-N-oleoyl taurate.

Light-sensitive elements containing integral reception layers for dye developer images can also be utilized. Such integral reception layers can be coated beneath the emulsion and dye developer layers near the support. A stripping layer coated over the integral reception layer can be used to facilitate the removal of the overcoated layers after the diffusion of the dye developer images to the reception layer.

The processing compositions or activators used to initiate development of the exposed light-sensitive elements of the invention are strongly alkaline. Such processing compositions generally have a pH of at least about 12 or contain a least 0.01 N hydroxyl ion. Alkali metal hydroxides, such as sodium hydroxide, and potassium hydroxide, are advantageously used in the composition for imparting such high alkalinity. However, volatile amines such as diethyl amine can also be used, such amines having the advantage of being volatilized from the prints to leave no residue of alkali. Such processing compositions are generally aqueous liquids or solutions, and when utilized in rupturable pods for in-camera processing, generally contain thickening agents such as hydroxyethyl cellulose, particularly as described in U.S. Pat. No. 3,266,894, or carboxymethyl cellulose. Onium compounds such as are disclosed in U.S. Pat. No. 3,146,102 are preferably utilized in the alkaline processing composition. The described sequestering agents can also be utilized in the alkaline processing compositions used in the processes of the invention.

Camera apparatus of the type useful for exposing and processing the sensitive elements of the invention have been described, for example, in U.S. Pat. No. 2,435,717. The processing of the subject photographic elements can also be effected outside of camera apparatus by imbibing either the receiving element or the negative element or both in the alkaline processing composition, and thereafter sandwiching together the two elements to allow the dye developer images to diffuse to the receiving element.

In accordance with usual practice, the positioning of the dye image-forming units of the photographic elements of the invention can be varied. In three-color systems, it is preferred to utilize the cyan dye image-forming unit most proximate to the support, the yellow dye-forming unit furthest from the support, the yellow dye image-forming units. It is also preferred to utilize the dye developers in the respective dye image-forming units in a separate underlying layer contiguous to the silver halide emulsion layer. Likewise, it is preferred to utilize in each dye image-forming unit a dye developer that is substantially complementary in color to the color of light recorded by the silver halide in the unit.

The following examples are included for a further understanding of the invention:

EXAMPLE 1

A photographic element, element 1,

prepared by coating successively the following layers on a subbed cellulose acetate film support:

Layer No.

1. Cyan Dye Developer Layer

A coating of the cyan dye developer, 5,8-dihydroxy-1,4-bis[β-hydroquinonyl-α-methyl)ethylamino]-anth raquinone, dissolved in N-n-butylacetanilide, dispersed in gelatin and coated on the support.

2. Red-sensitive Emulsion Layer

A coating of a developing-out negative gelatino-silver bromoiodide emulsion sensitized to red light coated at a coverage of about 180 mg. of silver per square foot.

3. Gelatin Layer

A gelatin layer is coated over the red-sensitive emulsion layer.

4. Sodium Alginate Layer

A coating of sodium alginate at a coverage of about 30 mg. per square foot is applied over the gelatin layer.

5. Magenta Dye Developer Layer

A coating of the magenta dye developer, 4-isopropoxy-2-[p-(β-hydroquinonylethyl)-phenylazo]-1-naphthol, dissolved in N-n-butylacetanilide, dispersed in gelatin and containing about 2 mg. 4' -methylphenyl-hydroquinone and about 15 mg. of calcium chloride per square foot is coated over layer 4. the calcium chloride reacts with the sodium alginate in layer 4 to form a calcium alginate salt barrier layer between the two layers.

6. Green-Sensitive Emulsion Layer

A coating of a developing-out negative gelatino-silver bromoiodide emulsion sensitized to green light is then coated at a coverage of about 110 mg. of silver per square foot.

7. Interlayer

A gelatin layer is coated containing about 5 mg. per square foot 4' -methylphenylhydro quinone.

8. Sodium Alginate Layer

Sodium alginate is coated at about 15 mg. per square foot.

9. Yellow Dye Developer Layer

A coating of the yellow dye developer, 1-phenyl-3-N-n-hexylcarboxamide-4-[p-(2', 5' -dihydroxyphenethyl)-phenylazo]-5-pyrazolone, dissolved in ditetrahydrofurfuryl adipate, dispersed in gelatin and containing about 2 mg. of 4' -methylphenylhdeydroquinone and about 10 mg. of calcium chloride per square foot. The calcium chloride reacts with the sodium alginate in the adjacent layer to form a calcium alginate salt barrier between the two layers.

10. Blue-Sensitive Emulsion Layer

A developing-out negative gelatino-silver bromoiodide emulsion that is inherently sensitive to blue light is coated at a coverage of about 70 mg. of silver per square foot, the emulsion also containing about 25 mg. 4' -methylphenyl-hydroquinone per square foot.

11. Overcoat Layer

A gelatin layer is coated over layer 10.

The photographic element described above is the control. Another element, element 2, is prepared exactly the same as element 1, the control, except, except that element 2 also contains 20 mg. per square foot 4-phenylcatechol in layer no. 3. Another element, element 3, is exactly the same as element 1, the control, except that element 3 also contains 30 mg. per square foot 4-phenylcatechol in layer no. 7. The photographic elements obtained are each exposed through a 0.3 density increment color step wedge in an intensity scale sensitometer one-fiftieth inches to a 500 watt positive lamp using a blue colored filter that absorbs some red light to convert the tungsten exposure to daylight color balance, and processed with a processing solution disposed in a processing pod and having a composition like that described by Land in example 7 of U.S. Pat. No. 3,362,821 issued Jan. 9, 1968. The exposed film is processed at a gap of 0.004 inch (corresponding to the thickness of the activator layer) for a period of 60 seconds in contact with a color receiving sheet. The receiving sheet is a cellulose acetate butyrate subbed paper support carrying in the following order:

1) a polymeric acid layer for pH control,

2) a polyvinyl alcohol spacer layer

3) a mordant layer comprising poly-4-vinyl pyridine and polyvinyl alcohol, and

4) a polyvinyl alcohol protective layer.

The reflection densities of the graduated scales of the transferred dye images on the receiving sheets are determined. Table A below shows the neutral scale maximum density for the red (cyan dye developer), green (magenta dye developer and blue (yellow dye developer). Magenta drop-off is a measure of the amount of density of the magenta dye developer image resulting from the magenta developer developing in the red-sensitive emulsion layer. It is determined by substracting the magenta density in the red scale from the magenta Dmax. The magenta density in the red scale is measured at a point 0.8 log E greater exposure than the log E value of a 0.6 density in the neutral scale. Yellow drop-off is a measure of the amount of desaturation of the yellow dye developer image resulting from the yellow dye developer developing in the green sensitive emulsion layer. It is determined by subtracting the yellow density in the green scale from yellow Dmax. Yellow density in the green scale is measured at a point 0.8 log E slower than the log E value of a 0.6 density in the neutral scale. Table A shows the increased cyan dye developer image saturation, without undesirable increases in magenta and yellow drop-off, due to the use of a catechol in accordance with the invention. ##SPC2##

It will be observed that the use of catechol results in high red Dmax, without sacrificing color purity (as indicated by the small increases in magenta and yellow drop-off). Similar results are obtained with 4-phenylcatechol in element 2 is replaced with 20 mg. of catechol; 3-isopropylcatechol; 4-tertbutylcatechol; p-chlorocatechol or 4-phenoxycatechol. Essentially the same results are obtained as with element 3 when the calcium alginate barrier layers are replaced with a zirconium gelatinate layer; a chromium alginate layer; a calcium pectinate layer or a lead-carboxymethy cellulose layer.

EXAMPLE 2

A photographic element, element 4, is prepared exactly the same as element 1 of example 1, with the following exceptions:

No 4' -methylphenylhydroquinone in layer 5;

Layer 7contains 140 mg. of gelatin and 10 mg. of 4' -methylphenylhydroquinone per square foot;

Layer 8 (sodium alginate) is omitted;

Layer 9 contains no calcium chloride or 4' -methylphenyl-hydroquinone;

Layer 10 contains 12 mg. of 4' -methylphenylhydroquinone. Element 4 is a control. Element 5 is prepared in the same manner except that layer 1 also contains 20 mg. of 4-phenylcatechol per square foot. The elements are exposed and processed exactly the same as in example 1. The results are shown in table B. --------------------------------------------------------------------------- TABLE B

Element 4-Phenyl- Neutral Scale Dmax. Magenta No. catechol Red Green Blue Drop-Off __________________________________________________________________________ 4 None 1.28 2.02 1.47 1.13 5 20 mg. in 1.49 1.98 1.44 0.17 Layer 1 __________________________________________________________________________

As will be observed in the above table, increased cyan dye developer saturation is obtained without undue loss in purity when the catechol incorporated in the dye developer layer itself, rather than in an interlayer.

EXAMPLE 3

A photographic element is prepared having the same composition as element 4 of example 2 (no catechol being incorporated in the element). Three samples of the freshly coated film are placed on a vacuum plate in a horizontal position and treated with an acetonitrile solution. Element 1 serves as control and the acetonitrile solution contains no catechol. Element 2 and 3 are treated with an acetonitrile solution which contains, respectively, sufficient 4-phenyl-catechol to provide coverages of 0.32 and 0.64 millimoles of 4-phenylcatechol per square foot. The treated negatives are then exposed and processed exactly as described in example 1. the results are shown in table C below. ##SPC3## *

As shown by the above date, the 4-phenylcatechol treated negatives give prints with decidedly more red density than the control. Similar results are obtained when the 4-phenylcatechol is contained in the receiving sheet rather than in an activator solution.

The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention as described hereinabove and as defined in the appended claims.