US3705798A

US3705798A - Photographic color diffusion transfer unitary elements comprising an emulsion layer containing polyvinyl-hydrogen-phthalate therein

Info

Publication number: US3705798A
Application number: US78408A
Authority: US
Inventors: Peter O Kliem; Jerome L Reid
Original assignee: Polaroid Corp
Current assignee: Polaroid Corp
Priority date: 1970-10-06
Filing date: 1970-10-06
Publication date: 1972-12-12
Anticipated expiration: 1989-12-12

Abstract

PHOTOGRAPHIC PRODUCTS FOR FORMING DIFFUSION TRANSFER IMAGES, PARTICULARLY MULTICOLOR TRANSFER IMAGES, WHICH PRODUCTS CONTAIN ONE OR MORE GEL-CONTAINING LAYERS INCLUDING AN ANIONIC POLYMERIC MATERIAL.

Description

Dec. 12, 1972 P. O. KLIEM ET AL PHOTOGRAPHIC COLOR DIFFUSION-TRANSFER UNITARY ELEMENTS COMPRISING AN EMULSION LAYER CONTAINING POLYVINYL- HYDROGEN-PHTHALATE THEREIN Filed Oct. 6. 1970 2 Sheets-Sheet 1 l5; DYE DEVELOPER LAYER -/////////////7mm?M y l7- -lNTERLAYER l8-/////////////j-MAGENTA DYE DEVELOPER LAYER I R\\\\\\\\\\\N @5EE%.fiw a FIG.I

I 2l-\\\\\\\\\\\\\ 'L/YELLOW\DYE DEVELOPER LAYER -W//////////A@ 5" 23\ OVERC AQUEOUS ALKALINE PROCESSING COM POSITION Z4- 77; 777 /77/ Z IMAGE-RECEIVING LAYER I k 26 ////////////%I 'NEUTRAUZ'NG LAYER SUPPORT mvENToRs PETER (a. KLIEM on By JEROME L.RE|D

ATTORNEYS 2 Sheets-$heet 2 INVENTORS PETER 0. KLIEM and JEROME L.RE|D

0W1 W ATTORNEYS Dec. 12, 1972 P. o. KLIEM ETAL PHOTOGRAPHIC COLOR DIFFUSION-TRANSFER UNITARY ELEMENTS COMPRISING AN EMULSION LAYER CONTAINING POLYVINYL- HYDROGEN-PH'I'HALATE THEREIN Filed Oct. 6. 1970 A 5;: EQSMRE E6 5522 \NH w:

United States Patent Mass.

Filed Oct. 6, 1970, Ser. No. 78,408 Int. Cl. G03c 7/00, /54, 1/40 US. Cl. 96-3 4 Claims ABSTRACT OF THE DISCLOSURE Photographic products for forming diffusion transfer images, particularly multicolor transfer images, which products contain one or more gel-containing layers including an anionic polymeric material.

BACKGROUND OF THE INVENTION A number of photographic systems for forming images by diffusion transfer are well known in the art. Generally speaking, such systems comprise the steps of photoexposing a light-sensitive material, typically a light-sensitive silver halide layer, to form a developable image; contacting the thus exposed light-sensitive material with a photographic processing composition to develop said image and to form an imagewise distribution of mobile and d-iffusible image-forming constituents; and transferring this imagewise distribution, at least in part, by diffusion, to an image-receiving layer to impart thereto the desired transfer image. The image-receiving layer may be contained on a separate support, i.e., as a separate element, or in lieu thereof, the image-receiving layer and the photosensitive layer may be contained as a unitary product on the same support, e.g., as a laminar product including the photosensitive layer, the image-receiving layer, and any other additional layers which may be desirable or necessary in the particular photographic system employed.

Black-and white transfer images may be provided by the well known silver transfer systems wherein a lightsensitive silver halide layer, e.g., a gelatinosilver halide emulsion layer, is exposed and then developed with an aqueous alkaline processing composition including a silver halide developing agent and a silver halide solvent to form in terms of unexposed areas an imagewise distribution of a soluble silver complex which is then transferred, at least in part, by diffusion, to a silver receptive stratum where it is reduced to impart thereto a positive silver transfer image.

Color transfer images may be obtained by various systems employing color image-providing materials which may be complete dyes or dye intermediates, e.g., color couplers. The color image-providing material may be initially insoluble or nondiffusible in the particular processing composition employed or it may be initially soluble or diffusible in the processing composition. In either instance, and in accordance with the particular imageforming mechanism employed, upon contacting the exposed photosensitive layer with the appropriate processing composition, an imagewise distribution of soluble and dilfusible color image-providing material is formed and this imagewise distribution is then transferred, at least in part, by diffusion, to a superposed image-receiving layer, e.g., a dyeable stratum, to impart thereto a color transfer image. This image may be monochromatic or multicolor, depending upon the system emplo'yed, particularly whether two or more photosensitive layers and associated color image-providing material are so employed.

A particularly useful system for preparing color trans- "ice fer images is that described and claimed in US. Pat. No. 2,983,606 employing as the color image-providing material a dye developer, i.e, a dye which is also a silver halide developing agent. In such a system, an exposed silver halide layer containing a developable image is developed by contacting it with an aqueous alkaline solution containing a dye developer. The dye developer develops the exposed silver halide and is in turn oxidized to provide an oxidation product which is less mobile and diffusible than unreacted (unoxidized) dye developer. An imagewise distribution of the unoxidized dye developer is then transferred, by diffusion, to a dyeable stratum to impart thereto a positive color transfer image.

Other color image-providing materials and systems employing them to form color transfer images, are also known in the art. By wa3 of illustration, mention may be made of the materials and systems disclosed in the following US. patents: 2,647,049; 2,661,293; 2,698,244; 2,698,798; 2,802,735; 3,148,062; 3,227,550; 3,227,551; 3,227,552; 3,227,554; 3,243,294; 3,330,655; 3,347,671; 3,352,672; 3,364,022; 3,443,939; 3,443,940; 3,443,941; 3, 14,943; etc.

In any of the aforementioned systems monochromatic color transfer images may be obtained by employing a photographic product or film unit containing a single photosensitive layer which is exposed and then developed in the presence of one or, if desired, a mixture of color image-providing materials. Multicolor images may be obtained in the manner known in the art by employing a photographic product containing two or more selectively sensitized photosensitive layers each having associated therewith a color image-providing material of predetermined spectral absorption characteristics. A typical photographic product for preparing multicolor images comprises a photosensitive element comprising a blue-, a greenand a red-sensitive silver halide emulsion layer having associated therewith in the same or in a contiguous layer a yellow, a magenta and a cyan color image providing material, respectively. Thus, a typical photographic product emplo'ying dye developers may comprise a support carrying, in order, a cyan dye developer layer, a red-sensitive silver halide emulsion layer, a magenta dye developer layer, a green-sensitive silver halide emulsion layer, a yellow dye developer layer, and a blue-sensitive silver halide emulsion layer. Photographic products contemplated for use in forming multicolor transfer images may, and preferably do contain interlayers disposed between the red-sensitive silver halide emulsion layer and the magenta dye developer [or other color image-providing material] layer and/or between the green-sensitive silver halide emulsion layer and the yellow dye developer. An additional or auxiliary layer may be, and preferably is, disposed over the blue-sensitive silver halide emulsion layer.

As was mentioned previously, diffusion transfer systems of the foregoing description are well known in the art and per se comprise no part of this invention. Common to all of these systems is the use of a photographic product or film unit having one or more gel-containing layers. The gel-containing layer may be the light-sensitive layer or layers, e.g., a gelatino silver halide emulsion layer, the layer containing the color image-providing material, e.g., any of the dye developer layers previously described, and/ or the interlayers, auxiliary layer, etc.

The present invention is directed to such photographic products having a gel-containing layer, especially those photographic products adapted for forming multicolor images having a plurality of gelatin-containing layers.

SUMMARY OF THE INVENTION In accordance with the present invention, at least one gel-containing layer in these photographic products further includes an anionic polymeric material to obtain the advantages to be detailed hereinafter.

BRIEF DESCRIPTION OF DRAWING FIG. 1 is an enlarged, fragmentary, sectional view of one photographic product contemplated by this invention during processing thereof;

FIG. 2 is a partially diagrammatic, enlarged sectional view of another photographic product contemplated by this invention; and

FIG. 3 is a diagrammatic, further enlarged sectional view of the photographic product of FIG. 2 taken along section lines 33.

DESCRIPTION OF PREFERRED EMBODIMENT The preferred embodiment of this invention is directed to photographic products directed to the formation of multicolor transfer images and having a plurality of gelcontaining layers; and most particularly to such photographic products employing dye developers as the color image-providing materials.

As was mentioned previously, this invention relates to photographic products adapted for the preparation of photographic images by difiusion transfer, and more particularly to photographic products adapted for the formation of color transfer images and containing a plurality of gelatin-containing layers.

A primary object of this invention is to provide novel products and systems of the foregoing description.

Another object of this invention is to provide novel photographic products having at least one layer containing gelatin and an anionic polymeric material.

Still another object is to provide novel unitary film units including a photosensitive element and an imagereceiving element for forming multicolor transfer images, the film units being characterized as containing at least one layer comprising gelatin and an anionic polymeric material.

Other objects of the invention will in part be obvious and will in part appear hereinafter.

The invention accordingly comprises the several steps and the relation and order of one or more of such steps with respect to each of the others, and the product possessing the features, properties and the relation of elements which are exemplified in the following detailed disclosure, and the scope of the application of which will be indicated in the claims.

For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description taken in connection with the accompanying drawing.

As was mentioned previously, the present invention is directed to photographic products adapted for the formation of difiusion transfer images and having at least one and usually a plurality of gel-containing layers, the essence of the invention being including an anionic polymeric material in at least one of these gel-containing layers. Since the invention is primarily directed to photographic products for forming color transfer images and particularly multilayer products for use in preparing multicolor images, the invention will be described in greater detail by reference to such multicolor products. For a fuller understanding of the photographic products to which the present invention is directed, reference should be had to the illustrative drawings.

FIG. 1 shows one such photographic product during processing thereof to form a color transfer image. As shown in FIG. 1, the photographic product [which has been selectively exposed] comprises a support 14, carrying a layer containing a cyan dye developer; a layer 16 containing a red-sensitive gelatino silver halide emulsion; an interlayer 17; a layer 18 containing a magenta dye developer; a layer 19 comprising a green-sensitive gelatino silver halide emulsion; a second interlayer 20; a layer 21 containing a yellow dye developer; a layer 22 comprising a blue-sensitive gelatino silver halide emulsion; and a protective overcoat or auxiliary layer 23.

This photosensitive element is shown to be in processing relationship with an image-receiving element of known description comprising a support 27 carrying an acid reacting neutralizing layer 26, a spacer layer 25 and an image-receiving layer (dyeable stratum) 24. A liquid processing composition 12 is shown to be disposed between the superposed photosensitive and image-receiving elements.

The supports for the respective elementsmay be opaque or transparent, as desired, and may comprise any of the materials heretofore employed for such a purpose, e.g., paper base materials; ethylene glycol terephthalic acid; vinyl chloride polymers; polyvinyl acetate; polyamides; polymethacrylic acid methyl and ethyl esters; cellulose derivatives such as cellulose acetate, triacetate, nitrate, propionate, butyrate acetate or acetate butyrate; crosslinked polyvinyl alcohol, etc.

The respective silver halide emulsion layers may comprise gelatino mixed silver halide emulsions, e.g., silver iodobromide emulsions, selectively sensitized as noted above.

The interlayers and/or the auxiliary layer may comprise gelatin or some other suitable material. For example, each of the two interlayers may comprise the coalesced essence of a synthetic polymeric latex and a composition which provides selective permeability thereto in accordance with the invention described and claimed in the copending application of Avtges et al., Ser. No. 880,- 205 filed Nov. 26, 1969 and now abandoned.

The dye developers in each of the layers containing the same are dispersed in a suitable matrix which may, for example, be gelatin.

It will therefore be seen that each of the layers coated on support 14 to provide the photosensitive element may contain gelatin. These layers may also contain other ingredients performing specific desired functions, e.g., coating aids, stabilizers, auxiliary or accelerating developing agents, etc., as is well known in the art.

Thus, a typical photosensitive element of this descrip tion may be prepared, for example, by coating, in succession on a gelatin subbed, opaque cellulose triacetate film base, the following layers:

(1) A layer of the cyan dye developer 1,4-bis-(fi- [hydroquinonyl-u-methyl]-ethyl amino)5,8 dihydroxyanthraquinone dispersed in gelatin and coated at a coverage of about 150 mgs./ft. of dye and about 200 mgs./ft. of gelatin;

(2) A red-sensitive gelatino-silver iodobromide emulsion coated at a coverage of about 200 mgs./ft. of silver and about mgs./ft. of gelatin;

(3) A layer of gelatin coated at a coverage of about 200 mgs./ft.

(4) A layer of the magenta dye developer Z-(p-[fl-hydroquinonylethyl]-phenylazo)-4-isopropoxy 1 naphthol dispersed in gelatin and coated at a coverage of 70 mgs./ ft. of dye and about 100 mgs./ft. of gelatin;

(5) A green-sensitive gelatino-silver iodobromide emulsion coated at a coverage of about 100 mgs./ft. of silver and 60 mgs./ft. of gelatin;

(6) A layer of gelatin coated at a coverage of about mgs./ft.

(7) A layer of the yellow dye developer 4-(p- [pi-hydroquinonylethyl]-phenylazo) 3 (N-n-hexylcarboxamido)- l-phenyl 5 pyrazolone dispersed in gelatin and coated at a coverage of about 40 mgs./ft. of dye and 50 mgs./ ft. of gelatin;

(8) A blue-sensitive gelatino-silver iodobromide emulsion coated at a coverage of about 60 mgs./ft. of silver and about 50 mgs./ft. of gelatin; and

(9) A layer containing 4'-methylphenyl hydroquinone dispersed in gelatin and coated at a coverage of about 10 mgs./ft. of 4'-methylphenyl hydroquinone and about 30 mgs./ft. of gelatin.

The image-receiving element may be any of those heretofore known in the art and described, for example, in US. Pat. No. 3,362,819 issued to Edwin H. Land.

Processing composition 12 comprises at least an aqueous alkaline medium and preferably also includes a viscous film-forming reagent such as c-arboxymethyl cellulose, or hydroxyethyl cellulose, as well as specific additional reagents, and in general comprises one of the known processing compositions for use in the disclosed dye developer system.

Following processing, a multicolor image is formed on dyeab-le stratum 24 in known manner. This image may be revealed following processing by separation of the imagereceiving element containing the thus formed color image from the photosensitive element. In lieu thereof, systems are also heretofore known wherein support 27 is transparent and the respective elements are retained in superposition and the image is viewed through the transparent support. In such a system, a reflecting layer, e.g., a white pigment such as titanium dioxide, may be provided between receiving layer 24 and the photosensitive element to effectively mask the latter and to provide the requisite background for viewing the transfer image through the transparent support by reflected light. The reflecting agent may be contained in a preformed layer. However, in a particularly useful embodiment, the reflecting agent is disposed initially in processing composition 12 and the reflecting layer is formed upon spreading of this composition between the superposed elements.

Another type of photographic product to which this invention is particularly adapted is a unitary film unit of the type disclosed, for example in US. Pats. Nos. 3,415,644; 3,415,645 and 3,415,646 issued to Edwin H. Land.

Such a film unit is illustrated in FIGS. 2 and 3 as comprising a photosensitive laminate 13 including a layer 14, preferably opaque, cyan dye developer layer 15, redsensitive silver halide emulsion layer 16, interlayer 17, magenta dye developer layer 18, green-sensitive silver halide emulsion layer 19, interlayer 20, yellow dye developer layer 21, blue-sensitive silver halide emulsion layer 22, auxiliary layer 23, image-receiving layer 24, spacer layer 25, neutralizing layer 26 and transparent layer 27.

The composite may be provided with a binding member extending around, for example, the specified edges of the laminate, The binding member may comprise a pressuresensitive tape 28, as shown in the drawing. A rupturable container 11 of known type, e.g., as disclosed, for example, in US. Pats. Nos. 2,543,181; 2,634,886, etc., confining aqueous alkaline processing composition 12 is shown in FIG. 2 to be fixedly positioned and extending tranverse a leading edge of photosensitive laminate 13 whereby to effect unidirectional discharge of the containers contents 12

intermediate layers

23 and 24 upon application of compressive force to container 11. Container 11 may comprise a rectangular blank of fluidand air-impervious sheet material folded longitudinally upon itself to form two walls 29 which are sealed to one another along their longitudinal and end margins to form a cavity in which composition 12 is retained. The longitudinal marginal seal 30 is made weaker than the end seals so as to become unsealed in response to the hydraulic pressure generated within the fluid contents 12 of the container by application of compressive pressure to Walls 29 of the container, e.g., by advancing the film unit between a pair of opposed suitably gapped rolls 35. Container 11 may be fixedly secured to laminate 13 by extension 32 of tape 28 extending over one wall 29 of the container, in combination with a separate retaining member such as illustrated retaining tape 33 extending over a portion of the other wall A composite film unit of the type shown in FIGS. 2 and 3 may be prepared by first successively coating layers -23 on support 14 in the manner illustrated in connec- 6 tion with the description of the film unit of FIG. 1. Then a transparent material 27, e.g., transparent cellulose triacetate film base may be coated, in succession, with the following illustrative layers:

(1) The partial butyl ester of polyethylene/maleic anhydride copolymer prepared by refluxing, for 14 hours, 300 grams of high viscosity poly-(ethylene/maleic anhydride), 140 grams of n-butyl alcohol and 1 cc. of phosphoric acid to provide a polymeric acid layer approximately 0.75 mil. thick;

(2) A solution of hydroxypropyl cellulose in water to provide a polymeric spacer layer approximately 0.075 mil. thick;

(3) A 2:1 mixture, by Weight, of polyvinyl alcohol and poly-4-vinylpyridine, at a coverage of approximately 600 mgs./ft. to provide a polymeric image-receiving layer approximately 0.40 mil. thick; and

(4) Then baking the element at 180 F. for 30 minutes and cooling.

The two components thus prepared may then be taped together in laminate form, at their respective edges, by means of a pressure-sensitive binding tape extending around, in contact, with, and over the edges of the resultant laminate.

A rupturable container retaining an aqueous alkaline processing solution comprising:

Water cc. Potassium hydroxide grams 11.2 Hydroxyethyl cellulose (high viscosity) [commercially available from Hercules Powder Co., Wilmington, Del., under the trade name Natrasol 250] grams 3.4 N-benzyl-a-picolinium bromide do 1.5 Benzotriazole do 1.0 Titanium dioxide do 40.0

may then be fixedly mounted on the leading edge, of each of the laminates, by pressure-sensitive tapes interconnecting the respective containers and laminates, such that upon application of compressive pressure to a container its contents would be distributed, upon rupture of the containers marginal seal, between auxiliary layer 23 and image-receiving layer 24.

The photographic products, including those shown in the illustrative drawing, which have just been described were known prior to the present invention and accordingly per se comprise no part of this invention. These products have at least one and typically have a plurality of gel-containing layers.

In accordance with the present invention, a Water-soluble anionic polymeric material is included in at least one gel-containing layer, which layer may additionally contain the other materials heretofore contained in the gel layer, e.g., color image-providing material, silver halide, accelerating developer, etc. The invention is particularly directed to multilayer products containing three selectively sensitized gelatino silver halide emulsions wherein at least one and preferably all three contain an anionic polymeric material.

As examples of water-soluble anionic polymeric materials contemplated for use in the present invention, mention may be made of copolymers of methyl vinyl ether and maleic anhydride; water-soluble salts, e.g., ammonium, sodium, potassium, lithium, etc., salts of polyvinyl hydrogen phthalate (PVHP), polystyrene sulfonic acid, sulfonated vinyltoluene polymers, cellulose sulfate, etc. Particularly preferred are the water-soluble salts noted above, e.g., polyvinyl hydrogen phthalate ammonium salt, polystyrene sulfonic acid sodium salt, etc.

When employed in combination with gelatin in the aforementioned multilayer products, it has been found that it is possible to obtain greater dye transfer densities and faster diffusion rates than can be obtained with like layers containing gelatin alone. This is at least in part due to the fact that the combination permits one to use layers containing less matrix or carrier while still providing the desired physical properties such as viscosity than one could provide employing gelatin alone.

For example, the combining of gelatin and a watersoluble salt of PVHP as the colloidal carrier or matrix for the ingredients needed in the film unit provides a superadditive or synergistic effect with regard to viscosity over the viscosity obtainable with each of the ingredients alone. For instance, a 7.7% solution by weight of a limed os sein gelatin (photographic grade) possessed a viscosity of 15 cps. (read at 40 C. on a Brookfield Viscometer Model L.V.F.) and a 0.4% by weight solution of polyvinyl hydrogen phthalate ammonium salt had a viscosity of about 2.5, while the combination possessed a viscosity of 200 cps. A 13.5% solution by weight of the same gelatin possessed a viscosity of about 40 cps. measured the same way and the addition of 0.4% by weight solution of polyvinyl hydrogen phthalate ammonium salt (which, as noted above alone had a viscosity of about 2.5) provided a viscosity of about 350 cps.

This superadditive effect permits one to employ-lesser amounts of colloidal material as the matrix, for example, for the silver halide and color image-providing material and/ or to employ thinner layers of the same. This in turn provides less of a barrier to dye transfer, thus permitting one to obtain greater dye transfer (transfer images exhibiting greater dye density) with the same amount of color-providing material in the film unit and/or to obtain faster processing times to obtain color images of the desired density.

While the other illustrative anionic polymeric materials denoted above also provide similar beneficial results, it is to be noted that they do not all possess the same superadditive effect. For example, Gantrez AN-l69 (trademark of General Aniline and Film Corporation for a high molecular weight poly-(methyl vinyl ether/maleic anhydride) appears to provide a viscosity increase at low concentrations which is primarily a function of the thickener, i.e., is additive, a superadditive effect being apparent only at higher concentrations. Yet, interestingly, this same copolymer exhibits a superadditive effect with gelatino silver halide emulsions at all concentration levels.

Apart from the favorable effects on dye transfer provided by the combination of matrix ingredients of this invention, it has been found quite unexpectedly that the addition of a water-soluble salt of PVHP to a gelatino silver halide solution after ripening provides a decrease in fog level which in turn further contributes to dye transfer control and subsequent color quality of the transfer image. Moreover, the addition to the silver halide emulsion layer has further been observed to provide a slight increase (about a half a stop) in film speed. [Since the other named anionic polymeric materials have not been studied in this manner, it is not known whether they also provide these further unexpected advantages] The addition of slight amounts of anionic polymeric material to gelatino silver halide solutions, e.g., amounts which do not appreciably alter the ratio of silver to binder, has been found to prevent the tendency of the silver halide to settle, which tendency makes it extremely diflicult to coat uniform silver halide emulsion layers having a given desired amount of silver and ratio of silver to hinder.

The amount of anionic polymeric material employed in combination with gelatin in the film units of this invention will vary in accordance with the particular system, the layers employing same, and the desires of the practitioner. Accordingly, the amounts and/or ratios of gelatin to the polymeric material are not capable of precise definition. In general, they are employed in the lightsensitive silver halide layers in an amount sufficient to provide a viscosity of between about 100 and 2000 cps.

In general, the ratio of gelatin to anionic polymeric material will be on the order of about :1 to about 100:1, depending upon the particular viscosity desired.

by way of example, to a solution containing about 7.7% by weight of limed gelatin and about 12.8% by Weight of silver halide, about 0.22% by weight of PVHP ammonium salt (approximately 35:1 gel/PVHP) is needed to obtain 300 cps.; and with Gantrez AN-169, about 0.27% by weight (approximately 28:1 gel to additive) is needed to obtain the same viscosity.

The ratios and amounts employed in the other gel-containing layers of the film units may generally be on the same order.

As was stated previously, the anionic polymeric materials contemplated for use in this invention are characterized as being water-soluble and photographically nondeleterious. Accordingly, it will be understood that any such polymeric material contemplated for use in a silver halide emulsion layer should not desensitize or otherwise adversely affect the sensitivity and stability of the silver halide, at least during the contemplated shelf life period, and should further not produce any detrimental pH level in the layer. In the latter regard, the pH of a silver halide emulsion layer is typically on the order of 5-7.5 and the polymeric material should provide, or be adjusted to provide, the desired pH in the coated layer.

US. Pat. No. 2,218,255 issued to Weyerts et al. on Oct. 15, 1940, discloses the use of polyvinyl phthalate to increase the viscosity of gelatin solutions. It will be appreciated, however, that the present invention is not directed to this concept but is instead directed to the novel film units which are defined in the appended claims, which film units provide the aforementioned advantages.

Since certain changes may be made in the above products and processes without departing from the scope of the invention herein involved, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. In a photographic film unit for preparing multicolor images by diffusion transfer comprising a layer containing a cyan dye image-providing material, a red-sensitive gelatino silver halide emulsion layer, a layer containing a magenta dye image-providing material, a green-sensitive gelatino silver halide emulsion layer, a layer containing a yellow dye image-providing material, a bluesensitive gelatino silver halide emulsion layer, an image-receiving layer dyeable by said dye image-providing materials to provide said color transfer image and means for providing a layer of a white reflecting pigment between said blue-sensitive emulsion layer and said imagereceiving layer to mask said photosensitive layers and any dye image-providing materials associated therewith and to provide a background for viewing the color transfer image formed in said image-receiving layer upon development of said film unit, whereby said color transfer image is viewable as a color reflection print without separation of said image-receiving layer containing said color transfer image; the improvement wherein at least one of said gelatino silver halide emulsion layers further cOntains a water-soluble salt of polyvinyl hydrogen phthalate.

2. A photographic film unit for preparing multicolored images by diffusion transfer which comprises, in combination: a photosensitive element comprising a composite structure containing, as essential layers, in sequence, a dimensionally stable opaque layer, an alkaline solution permeable polymeric layer containing a cyan dye developer, a red-sensitive gelatino silver halide emulsion layer, an alkaline solution permeable polymeric layer containing magenta dye developer, a green-sensitive gelatino silver halide emulsion layer, an alkaline solution permeable polymeric layer containing yellow dye developer, a blue-sensitive gelatino silver halide emulsion layer, an alkaline solution permeable polymeric layer dyeable by said dye developers, an alkaline solution permeable transparent acid layer containing suificient aciditying groups to effect reduction of an aqueous alkaline processing solution from a first pH at which each of said dye developers is soluble and diffusible to a second pH at which said dye developers are substantially insoluble and nondiffusible, a dimensionally stable alkaline solution impermeable transparent layer, each of said emulsion layers further containing a water-soluble salt of polyvinyl hydrogen phthalate, the ratio by weight of said salt to gelatin in each of said emulsion layers being from about 10:1 to about 100:1, means securing at least the side edges of said opposed layers in fixed relationship, and a rupturable container retaining an aqueous alkaline processing composition having said first pH and containing dispersed therein a white pigment, fixedly positioned and extending transverse a leading edge of said photosensitive element to effect unidirectionally discharge of the containers contents between said dyeable layer and said bluesensitive gelatino silver halide emulsion layer upon compressive force to said container, said white pigment being sufiicient to provide a background for viewing said multicolor transfer image formed in said dyeable polymeric layer upon development of said film unit, whereby said transferred image is viewable as a color reflection print without separation of said dyeable polymeric layer containing said color image.

3. A film unit as defined in claim 2 wherein at least one of said dye developer layers comprises said dye developer dispersed in a matrix comprising gelatin and an anionic polymeric material.

4. A photographic process for forming multicolor images by diffusion transfer comprising the steps of exposing a photographic film unit as defined in claim 2 to form a developable image; applying compressive force to said rupturable container to effect unidirectional dis- 10 charge of the containers aqueous alkaline processing composition between said dyeable polymeric layer and said photosensitive silver halide emulsion layer next adjacent thereto; effecting thereby development of each of said silver halide emulsions; immobilizing said yellow, magenta and cyan dye, as a result of development of their respective associated silver halide emulsions; forming thereby an imagewise distribution of mobile yellow, magenta and cyan dye, as a function of the point-topoint degree of exposure of their respective associated silver halide emulsions; transferring, by diffusion, at least a portion of each of said imagewise distributions of mobile dye to said alkaline solution permeable polymeric layer dyeable by said dyes to provide thereto a multicolor dye image; transferring, by diffusion, subsequent to Substantial transfer image formation, a sufficient portion of the ions of said aqueous alkaline solution to said alkaline solution permeable polymeric acid layer to thereby reduce the alkalinity of said solution to said second pH; and maintaining said composite structure intact subsequent to processing.

References Cited UNITED STATES PATENTS 2,218,255 10/ 1940 Weyerts et a1. 96ll4 3,239,336 3/1966 Rogers et al 96-3 NORMAN G. TORCHIN, Primary Examiner A. T. SURO PICO, Assistant Examiner US. Cl. X.R.