Perfluorinated Stripping Agents for Diffusion Transfer Assemblages

This invention relates to photography, and more particularly to black-and-white and color diffusion transfer photography wherein certain perfluorinated stripping agents are employed to enable an image-receiving layer to be separated from the rest of the assemblage after processing. Transparencies or prints which are less bulky can thereby be obtained from integral assemblies.

Various formats for color, integral transfer elements are described in the prior art, such as U.S. Pat. Nos. 3,415,644; 3,415,645; 3,415,646; 3,647,437; 3,635,707; 3,756,815, and Canadian Pat. Nos. 928,559 and 674,082. In these formats, the image-receiving layer containing the photographic image for viewing remains permanently attached and integral with the image generating and ancillary layers present in the structure when a transparent support is employed on the viewing side of the assemblage. The image is formed by dyes, produced in the image generating units, diffusing through the layers of the structure to the dye image-receiving layer. After exposure of the assemblage, an alkaline processing composition permeates the various layers to initiate development of the exposed photosensitive silver halide emulsion layers. The emulsion layers are developed in proportion to the extent of the respective exposures, and the image dyes which are formed or released in the respective image generating layers begin to diffuse throughout the structure. At least a portion of the imagewise distribution of diffusible dyes diffuse to the dye image-receiving layer to form an image of the original subject. The user does not have to time this process.

A problem with the integral assemblages described above is that the silver halide and other imaging layers, the spent pod which originally contained processing fluid, and the trap which retains excess processing fluid remain with the print after processing. The resulting prints are bulky and are somewhat difficult to stock or store in albums.

Peel-apart formats for color diffusion transfer assemblages have previously been described, for example, in U.S. Pat. Nos. 2,983,606, 3,362,819 and 3,362,821. In these formats, the image-receiving element must be separated from the photosensitive element after a certain amount of time has elapsed, usually about one minute. This requires the customer to time the process which may be a disadvantage if a clock is not available. Also, the portion of the assemblage to be discarded is wet with caustic processing fluid, and care must be taken with its handling.

It would be desirable to provide a diffusion transfer assemblage in which a print can be obtained without the spent imaging layers, pod and trap, as in the peel-apart format described above, but with the elimination of the necessity for timing the process and the handling of wet discarded materials, as in the integral format described above. Such a print would comprise the support, dye image-receiving layer and reflecting layers only, and would more closely resemble conventional prints in appearance and handling. These advantages are provided by our invention.

Stripping layers have been previously employed in diffsion transfer photography as shown, for example, in U.S. Pat. Nos. 3,220,835, 3,730,718 and 3,820,999. The materials described in these patents for the stripping layer include gum arabic, sodium alginate, pectin, cellulose acetate hydrogen phthalate, polyvinyl alcohol, hydroxyethyl cellulose, polymethacrylic acid, plasticized methyl cellulose, ethyl cellulose, methyl methacrylate and butyl methacrylate. As will be shown by comparative tests hereinafter, many of these materials have unacceptable swell in alkali which causes a loss in sharpness of the transferred images. Others of these materials do not provide a clean separation of the two elements, with unwanted portions of the emulsion layers adhering to the dye image-receiving layer.

The materials employed in the stripping layer of our invention have previously been used in photographic elements. In U.S. Pat. No. 4,267,265, these materials are disclosed as being useful on the outermost layer of a photographic element to provide anti-adhesion and anti-static properties. In U.S. Pat. No. 3,779,768, these materials are described for use in a vesicular film. Neither of these patents, however, discloses the use of these materials in diffusion transfer elements to provide the advantage as described herein.

U.S. Pat. No. 4,229,524 describes the use of copolymers having a fluorinated alkyl group containing acrylic or methacrylic acid ester monomers. These materials are used to prevent static electricity and are not disclosed for use in diffusion transfer photography.

U.S. Pat. No. 3,806,346 discloses the use in diffusion transfer elements of a reagent to suppress triboluminescence when delamination of a receiving element from a photosensitive element is effected by spreading a processing composition therebetween. The only reagent material disclosed is the ammonium salt perfluorooctanoic acid. We are employing different compounds in our elements for a different purpose.

Research Disclosure, Vol. 176, December 1978, Item 17622 discloses image transfer formats and concepts for removal of expended processing materials from image transfer units after processing. No specific materials are disclosed in this reference, however.

A photographic assemblage according to our invention comprises:

(a) a photosensitive element comprising a support having thereon at least one photosensitive silver halide emulsion layer; and

(b) an image-receiving layer, and wherein the assemblage contains a stripping agent comprising a straight chain alkyl or polyethylene oxide perfluoroalkylated ester or perfluoroalkylated ether in such a concentration that the image-receiving layer may be separated, after processing, from the rest of the assemblage, and that the separated image-receiving layer will have substantially none of the emulsion layer adhered thereto.

In forming a black-and-white image, the exposed photosensitive element is developed. In the unexposed areas, a silver halide complexing agent dissolves the silver halide and transfers it to the image-receiving layer. Silver precipitating nuclei in the image-receiving layer then cause the transferred silver halide complex to be reduced to silver, thereby forming an image pattern corresponding to the original. Details of the process are well known to those skilled in the art as shown, for example, by U.S. Pat. Nos. 3,220,835 and 3,820,999 discussed above, the disclosures of which are hereby incorporated by reference.

In a preferred embodiment of our invention, the silver halide emulsion layer has associated therewith a dye image-providing material.

In another preferred embodiment of our invention, the stripping layer has the following formula: ##STR3## wherein

R.sup.1 is an alkyl or substituted alkyl group having from 1 to about 6 carbon atoms such as methyl, ethyl, butyl, isopropyl, 2-hydroxyethyl, or 2-ethoxyethyl; or an aryl or substituted aryl group having from about 6 to about 10 carbon atoms such as phenyl, p-tolyl or p-methoxyphenyl; ##STR4##

R.sup.3 is H or R.sup.1 ;

n is an integer of from about 4 to about 20; and

x and y each independently represents an integer of from 2 to about 50, and

z represents an integer of from 1 to about 50.

In another preferred embodiment, R.sup.1 is ethyl, R.sup.2 is ##STR5## n is 8 and x' is about 25 to about 50. In another preferred embodiment, R.sup.1 is ethyl, R.sup.2 is ##STR6## n is 8 and y' is about 25 to about 50. In yet another preferred embodiment, R.sup.1 is ethyl, R.sup.2 is --CH.sub.2 --O--CH.sub.2 --CH.sub.2 --O).sub.z H, n is 8 and z' is about 1 to about 30.

The stripping agent employed in our invention may be employed in any amount which is effective for the intended purpose, i.e., clean separation between the image-receiving layer and the rest of the assemblage with substantially none of the emulsion layer or layers adhering to the image-receiving layer. In general, good results have been obtained at a concentration of from about 5 to about 500 mg/m.sup.2 of element. The particular amount to be employed will vary, of course, depending on the particular stripping agent employed and the particular diffusion transfer element selected.

Our invention can be used in diffusion transfer assemblages where a reflection print is obtained without the bulkiness of silver halide and other layers, the spent pod and trap. In other words, our invention combines the handling and storage characteristics of conventional photographs with the convenience and benefits of instant photography. In addition, transparency elements can also be obtained with our invention which requires a transparent support and the removal of residual image dye, silver halide and opacifying layers. By removing the silver halide and dye image-providing material layers from the assemblage, there is also provided the option of recovery of these expensive materials from the discarded portion of the assemblage, if it is economically feasible to do so.

There are many requirements for a stripping layer in a diffusion transfer assemblage. The layer must be easily coatable and dye passing through it on the way to the mordant must not be hindered. The assemblage must maintain physical integrity during storage, during the high pH processing and during the time after the pH is lowered by the process control layers. After the imaging procedure and before the intended separation time, physical integrity of the assemblage must be maintained throughout normal handling and flexing, and spontaneous separation must not occur. The layers must also function to provide an easy and clean separation at some point in time after image transfer has taken place.

Image transfer assemblages usually use masks or other fluid restricting devices and thus have "dry" areas and areas wet by processing fluid adjoining each other. Stripping is usually initiated at an edge in a dry area to avoid contact with highly alkaline processing fluid. This requires a weak dry bond to have a point to initiate stripping. Stripping must then be continuous and without fracturing as the separating action passes between the wet/dry interface.

If the sytem is employed to obtain a transparency element with high magnification projection, there is an additional requirement for maintaining sharpness. To accomplish this, the diffusion path must be as short as possible. This necessitates the use of a stripping layer which is nonswelling and which is as thin as possible.

The above requirements of a stripping layer are met by the compounds described herein. Our stripping layer provides "controlled adhesion". It strips cleanly, fails adhesively, and does not materially alter the surface properties at the stripping interface. By contrast, most conventional water-swellable polymeric stripping layers fail cohesively, leaving uneven areas of polymer "skin" on each surface.

Our stripping layer also provides a weak dry adhesion, unlike other known stripping layers which have strong dry adhesion. A strong dry adhesion would make it difficult to initiate separation and have clean separation into and through a "wet" area.

Our stripping layer can also be coated at less than one-third the quantity required for a cellulose stripping layer. This provides a significant improvement in image sharpness.

The preferred location for our stripping layer is adjacent to the mordant or image-receiving layer. It could also be located in the mordant layer or other positions in the assemblage, such as between pigmented gelatin vehicle layers, if desired.

The stripping agents described herein can also be mixed with other materials, such as cellulose materials, e.g., Natrosol.RTM.G., if so desired.

Specific stripping agents useful in our invention include the following: ##STR7##

This material is supplied commercially as Fluorad.RTM.FC-431 (3M Company). It is useful at 80 to 250 mg/m.sup.2 of the commercial material coatable from a water/ethanol mixture. ##STR8##

This material is supplied commercially as Fluorad.RTM.FC-432 (3M Company). It is useful at a minimum of 250 mg/m.sup.2 of the commercial material coatable from a 0.5 solution in 2-butanone. ##STR9##

This material is supplied commercially as Fluorad.RTM.FC-170 (3M Company). It is useful at a minimum of 250 mg/m.sup.2 of the commercial material coatable from methanol.

A process for producing a photographic image in color according to our invention comprises:

(I) exposing a photosensitive element comprising a support having thereon at least one photosensitive silver halide emulsion layer having associated therewith a dye image-providing material;

(II) treating the element with an alkaline processing composition in the presence of a silver halide developing agent to effect development of each exposed silver halide emulsion layer, whereby:

(a) an imagewise distribution of the dye image-providing material is formed as a function of the development of the silver halide emulsion layer; and

(b) at least a portion of the imagewise distribution of the dye image-providing material diffuses to a dye image-receiving layer; and

(III) separating the dye image-receiving layer from the rest of the photosensitive element by means of a stripping agent as described above, in such a concentration that the separated dye image-receiving layer will have substantially none of the emulsion layer adhered thereto.

The photographic element of the above-described process can be treated with an R.sup.2 is effect or initiate development in any manner. A preferred method for applying processing composition is by use of a rupturable container or pod which contains the composition.

In a preferred embodiment of our invention the photographic assemblage comprises:

(a) a photosensitive element comprising a support having thereon at least one silver halide emulsion layer having associated therewith a dye image-providing material;

(b) a transparent cover sheet located over the layer outermost from the support of the photosensitive element;

(c) a dye image-receiving layer located either in the photosensitive element or on the transparent cover sheet; and

(d) an alkaline processing composition and means containing same for discharge between the photosensitive element and the transparent cover sheet; and wherein the assemblage contains a stripping agent as described above.

In a preferred embodiment of the invention, the means containing the alkaline processing composition is a rupturable container or pod which is adapted to be positioned during processing of the film unit so that a compressive force applied to the container by pressure-applying members, such as would be found in a camera designed for in-camera processing, will effect a discharge of the container's contents within the film unit. In general, the processing composition employed in this invention contains the developing agent for development, although the composition could also just be an alkaline solution where the developer is incorporated in the photographic element or cover sheet, in which case the alkaline solution serves to activate the incorporated developer.

The dye image-providing material useful in this invention is either positive- or negative-working, and is either initially mobile or immobile in the photographic element during processing with an alkaline composition. Examples of initially mobile, positive-working dye image-providing materials useful in this invention are described in U.S. Pat. Nos. 2,983,606; 3,536,739; 3,705,184; 3,482,972; 2,756,142; 3,880,658 and 3,854,985. Examples of negative-working dye image-providing materials useful in this invention include conventional couplers which react with oxidized aromatic primary amino color developing agents to produce or release a dye such as those described, for example, in U.S. Pat. No. 3,227,550 and Canadian Pat. No. 602,607. In a preferred embodiment of this invention, the dye image-providing material is a ballasted, redox dye-releasing (RDR) compound. Such compounds are well known to those skilled in the art and are, generally speaking, compounds which will react with oxidized or unoxidized developing agent or electron transfer agent to release a dye. Such nondiffusible RDR's include negative-working compounds, as described in U.S. Pat. Nos. 3,728,113 of Becker et al; 3,725,062 of Anderson and Lum; 3,698,897 of Gompf and Lum; 3,628,952 of Puschel et al; 3,443,939 and 3,443,940 of Bloom et al; 4,053,312 of Fleckenstein; 4,076,529 of Fleckenstein et al; 4,055,428 of Koyama et al; 4,149,892 of Deguchi et al; 4,198,235 and 4,179,291 of Vetter et al; Research Disclosure 15157, November, 1976 and Research Disclosure 15654, April, 1977.

Such nondiffusible RDR's also include positive-working compounds, as described in U.S. Pat. Nos. 3,980,479; 4,139,379; 4,139,389; 4,199,354, 4,232,107, 4,199,355 and German Pat. No. 2,854,946, the disclosures of which are hereby incorporated by reference.

In a preferred embodiment of the invention, RDR's such as those in the Fleckenstein et al patent referred to above are employed. Such compounds are ballasted sulfonamido compounds which are alkalicleavable upon oxidation to release a diffusible dye from the nucleus and have the formula: ##STR10## wherein:

(a) Col is a dye or dye precursor moiety;

(b) Ballast is an organic ballasting radical of such molecular size and configuration (e.g., simple organic groups or polymeric groups) as to render the compound nondiffusible in the photosensitive element during development in an alkaline processing composition;

(c) G is OR.sup.4 or NHR.sup.5 wherein R.sup.4 is hydrogen or a hydrolyzable moiety and R.sup.5 is hydrogen or a substituted or unsubstituted alkyl group of 1 to 22 carbon atoms, such as methyl, ethyl, hydroxyethyl, propyl, butyl, secondary butyl, tertiary butyl, cyclopropyl, 4-chlorobutyl, cyclobutyl, 4-nitroamyl, hexyl, cyclohexyl, octyl, decyl, octadecyl, docosyl, benzyl or phenethyl (when R.sup.5 is an alkyl group of greater than 6 carbon atoms, it can serve as a partial or sole Ballast group);

(d) Y represents the atoms necessary to complete a benzene nucleus, a naphthalene nucleus or a 5- to 7-membered heterocyclic ring such as pyrazolone or pyrimidine; and

(e) m is a positive integer or 1 to 2 and is 2 when G is OR.sup.4 or when R.sup.5 is a hydrogen or an alkyl group of less than 8 carbon atoms.

For further details concerning the above-described sulfonamido compounds and specific examples of same, reference is made to the above-mentioned Fleckenstein et al U.S. Pat. No. 4,076,529.

In another preferred embodiment of the invention, positive-working, nondiffusible RDR's of the type disclosed in U.S. Pat. Nos. 4,139,379 and 4,139,389 are employed. In this embodiment, an immobile compound is employed which as incorporated in a photographic element is incapable of releasing a diffusible dye. However, during photographic processing under alkaline conditions, the compound is capable of accepting at least one electron (i.e., being reduced) and thereafter releases a diffusible dye. These immobile compounds are ballasted electron accepting nucleophilic displacement compounds.

A format for integral negative-receiver photographic elements in which the present invention is useful is disclosed in Canadian Pat. No. 928,559. In this embodiment, the support for the photographic element is transparent and is coated with the image-receiving layer, a substantially opaque, light-reflective layer and the photosensitive layer or layers described above. A rupturable container, containing an alkaline processing composition including a developing agent and an opacifier, is positioned between the top layer and a transparent cover sheet which has thereon, in sequence, a neutralizing layer, and a timing layer. The film unit is placed in a camera, exposed through the transparent cover sheet and then passed through a pair of pressure-applying members in the camera as it is being removed therefrom. The pressure-applying members rupture the container and spread processing composition and opacifier over the negative portion of the film unit to render it light-insensitive. The processing composition develops each silver halide layer and dye images, formed as a result of development, diffuse to the image-receiving layer to provide a positive, right-reading image which is viewed through the transparent support on the opaque reflecting layer background. For further details concerning the format of this particular integral film unit, reference is made to the above-mentioned Canadian Pat. No. 928,559.

Still other useful integral formats in which this invention can be employed are described in U.S. Pat. Nos. 3,415,644; 3,415,645; 3,415,646; 3,647,437 and 3,635,707. In most of these formats, a photo-sensitive silver halide emulsion is coated on an opaque support and a dye image-receiving layer is located on a separate transparent support superposed over the layer outermost from the opaque support. In addition, this transparent support also contains a neutralizing layer and a timing layer underneath the dye image-receiving layer.

In another embodiment of the invention, the neutralizing layer and timing layer are located underneath the photosensitive layer or layers. In that embodiment, the photosensitive element would comprise a support having thereon, in sequence, a neutralizing layer, a timing layer and at least one photosensitive silver halide emulsion layer having associated therewith a dye image-providing material. The dye image-receiving layer would be provided on transparent cover sheet with the processing composition being applied therebetween.

The film unit or assemblage of the present invention is used to produce positive images in single or multicolors. In a three-color system, each silver halide emulsion layer of the film assembly will have associated therewith a dye image-providing material which possesses a predominant spectral absorption within the region of the visible spectrum to which said silver halide emulsion is sensitive, i.e., the blue-sensitive silver halide emulsion layer will have a yellow dye image-providing material associated therewith, the green-sensitive silver halide emulsion layer will have a magenta dye image-providing material associated therewith and the red-sensitive silver halide emulsion layer will have a cyan dye image-providing material associated therewith. The dye image-providing material associated with each silver halide emulsion layer is contained either in the silver halide emulsion layer itself or in a layer contiguous to the silver halide emulsion layer, i.e., the dye image-providing material can be coated in a separate layer underneath the silver halide emulsion layer with respect to the exposure direction.

The concentration of the dye image-providing material that is employed in the present invention can be varied over a wide range, depending upon the particular compound employed and the results desired. For example, the dye image-providing material coated in a layer at a concentration of 0.1 to 3 g/m.sup.2 has been found to be useful. The dye image-providing material is usually dispersed in a hydrophilic film forming natural material or synthetic polymer, such as gelatin, polyvinyl alcohol, etc, which is adapted to be permeated by aqueous alkaline processing composition.

A variety of silver halide developing agents are useful in this invention. Specific examples of developers or electron transfer agents (ETA's) useful in this invention include hydroquinone compounds, catechol compounds, and 3-pyrazolidinone compounds as disclosed in column 16 of U.S. Pat. No. 4,358,527, issued Nov. 9, 1982. A combination of different ETA's, such as those disclosed in U.S. Pat. No. 3,039,869, can also be employed. These ETA's are employed in the liquid processing composition or contained, at least in part, in any layers or layers of the photographic element or film assemblage to be activated by the alkaline processing composition, such as in the silver halide emulsion layers, the dye image-providing material layers, interlayers, image-receiving layer, etc.

In this invention, in which dye image-providing materials can be used which produce diffusible dye images as a function of development, either conventional negative-working or direct-positive silver halide emulsions can be employed. If the silver halide emulsion employed is a direct-positive silver halide emulsion, such as an internal image emulsion designed for use in the internal image reversal process, or a fogged, direct-positive emulsion such as a solarizing emulsion, which is developable in unexposed areas, a positive image can be obtained on the dye image-receiving layer by using ballasted dye image-providing materials. After exposure of the film assemblage or unit, the alkaline processing composition permeates the various layers to initiate development of the exposed photosensitive silver halide emulsion layers. The developing agent present in the film unit develops each of the silver halide emulsion layers in the unexposed areas (since the silver halide emulsions are direct-positive ones), thus causing the developing agent to become oxidized imagewise corresponding to the unexposed areas of the direct-positive silver halide emulsion layers. The oxidized developing agent then cross-oxidizes the dye image-providing material compounds and the oxidized form of the compounds then undergoes a base-initiated reaction to release the dyes imagewise as a function of the imagewise exposure of each of the silver halide emulsion layers. At least a portion of the imagewise distributions of diffusible dyes diffuse to the image-receiving layer to form a positive image of the original subject. After being contacted by the alkaline processing composition, a neutralizing layer in the film unit or image-receiving unit lowers the pH of the film unit or image receiver to stabilize the image.

Internal image silver halide emulsions useful in this invention are described more fully in the November, 1976 edition of Research Disclosure, pages 76 through 79, the disclosure of which is hereby incorporated by reference.

The various silver halide emulsion layers of a color film assembly employed in this invention are disposed in the usual order, i.e., the blue-sensitive silver halide emulsion layer first with respect to the exposure side, followed by the green-sensitive and red-sensitive silver halide emulsion layers. If desired, a yellow dye layer or a yellow colloidal silver layer can be present between the blue-sensitive and green-sensitive silver halide emulsion layers for absorbing or filtering blue radiation that is transmitted through the blue-sensitive layer. If desired, the selectively sensitized silver halide emulsion layers can be disposed in a different order, e.g., the blue-sensitive layer first with respect to the exposure side, followed by the red-sensitive and green-sensitive layers.

The rupturable container employed in certain embodiments of this invention is disclosed in U.S. Pat. Nos. 2,543,181; 2,643,886; 2,653,732; 2,723,051; 3,056,492; 3,056,491 and 3,152,515. In general, such containers comprise a rectangular sheet of fluid- and air-impervious material folded longitudinally upon itself to form two walls which are sealed to one another along their longitudinal and end margins to form a cavity in which processing solution is contained.

Generally speaking, except where noted otherwise, the silver halide emulsion layers employed in the invention comprise photosensitive silver halide dispersed in gelatin and are about 0.6 to 6 microns in thickness; the dye image-providing materials are dispersed in an aqueous alkaline solution-permeable polymeric binder, such as gelatin, as a separate layer about 0.2 to 7 microns in thickness; and the alkaline solution-permeable polymeric interlayers, e.g., gelatin, are about 0.2 to 5 microns in thickness. Of course, these thicknesses are approximate only and can be modified according to the product desired.

Scavengers for oxidized developing agent can be employed in various interlayers of the photographic elements of the invention. Suitable materials are disclosed on page 83 of the November 1976 edition of Research Disclosure, the disclosure of which is hereby incorporated by reference.

Any material is useful as the dye image-receiving layer in this invention, as long as the desired function of mordanting or otherwise fixing the dye images is obtained. The particular material chosen will, of course, depend upon the dye to be mordanted. Suitable materials are disclosed on pages 80 through 82 of the November 1976 edition of Research Disclosure, the disclosure of which is hereby incorporated by reference.

Use of a neutralizing material in the film units employed in this invention will usually increase the stability of the transferred image. Generally, the neutralizing material will effect a reduction in the pH of the image layer from about 13 or 14 to at least 11 and preferably 5 to 8 within a short time after imbibition. Suitable materials and their functioning are disclosed on pages 22 and 23 of the July 1974 edition of Research Disclosure, and pages 35 through 37 of the July 1975 edition of Research Disclosure, the disclosures of which are hereby incorporated by reference.

A timing or inert spacer layer can be employed in the practice of this invention over the neutralizing layer which "times" or controls the pH reduction as a function of the rate at which alkali diffuses through the inert spacer layer. Examples of such timing layers and their functioning are disclosed in the Research Disclosure articles mentioned in the paragraph above concerning neutralizing layers.

The alkaline processing composition employed in this invention is the conventional aqueous solution of an alkaline material, e.g, alkali metal hydroxides or carbonates such as sodium hydroxide, sodium carbonate or an amine such as diethylamine, preferably possessing a pH in excess of 11, and preferably containing a developing agent as described previously. Suitable materials and addenda frequently added to such compositions are disclosed on pages 79 and 80 of the November, 1976 edition of Research Disclosure, the disclosure of which is hereby incorporated by reference.

The alkaline solution permeable, substantially opaque, light-reflective layer employed in certain embodiments of photographic film units used in this invention is described more fully in the November, 1976 edition of Research Disclosure, page 82, the disclosure of which is hereby incorporated by reference.

The supports for the photographic elements used in this invention can be any material, as long as it does not deleteriously affect the photographic properties of the film unit and is dimensionally stable. Typical flexible sheet materials are described on page 85 of the November, 1976 edition of Research Disclosure, the disclosure of which is hereby incorporated by reference.

While the invention has been described with reference to layers of silver halide emulsions and dye image-providing materials, dotwise coating, such as would be obtained using a gravure printing technique, could also be employed. In this technique, small dots of blue-, green- and red-sensitive emulsions have associated therewith, respectively, dots of yellow, magenta and cyan color-providing substances. After development, the transferred dyes would tend to fuse together into a continuous tone. In an alternative embodiment, the emulsions sensitive to each of the three primary regions of the spectrum can be disposed as a single segmented layer, e.g., as by the use of microvessels, as described in Whitmore U.S. patent application Ser. No. 194,714, filed Sept. 8, 1980, now abandoned.

The silver halide emulsions useful in this invention, both negative-working and direct-positive ones, are well known to those skilled in the art and are described in Research Disclosure, Volume 176, December, 1978, Item 17643, pages 22 and 23, "Emulsion preparation and types"; they are usually chemically and spectrally sensitized as described on page 23, "Chemical sensitization", and "Spectral sensitization and desensitization", of the above article; they are optionally protected against the production of fog and stabilized against loss of sensitivity during keeping by employing the materials described on pages 24 and 25, "Antifoggants and stabilizers", of the above article; they usually contain hardeners and coating aids as described on page 26, "Hardeners", and pages 26 and 27, "Coating aids", of the above article; they and other layers in the photographic elements used in this invention usually contain plasticizers, vehicles and filter dyes described on page 27, "Plasticizers and lubricants"; page 26, "Vehicles and vehicle extenders"; and pages 25 and 26, "Absorbing and scattering materials", of the above article; they and other layers in the photographic elements used in this invention can contain addenda which are incorporated by using the procedures described on page 27, "Methods of addition", of the above article; and they are usually coated and dried by using the various techniques described on pages 27 and 28, "Coating and drying procedures", of the above article, the disclosures of which are hereby incorporated by reference.

The term "nondiffusing" used herein has the meaning commonly applied to the term in photography and denotes materials that for all practical purposes do not migrate or wander through organic colloid layers, such as gelatin, in the photographic elements of the invention in an alkaline medium and preferably when processed in a medium having a pH of 11 or greater. The same meaning is to be attached to the term "immobile". The term "diffusible" as applied to the materials of this invention has the converse meaning and denotes materials having the property of diffusing effectively through the colloid layers of the photographic elements in an alkaline medium. "Mobile" has the same meaning as "diffusible".

The term "associated therewith" as used herein is intended to mean that the materials can be in either the same or different layers, so long as the materials are accessible to one another.

The following examples are provided to further illustrate the invention.

A cover sheet was prepared by coating the following layers, in the order recited, on a poly(ethylene terephthalate) film support:

(1) an acid layer comprising poly(n-butyl acrylate-co-acrylic acid), (30:70 weight ratio equivalent to 140 meq. acid/m.sup.2);

(2) a layer comprising gelatin (3.8 g/m.sup.2) and bis(vinylsulfonyl)methane (0.038 g/m.sup.2); and

(3) a timing layer comprising 5.4 g/m.sup.2 of a 1:1 physical mixture by weight of poly(acrylonitrile-co-vinylidene chloride-co-acrylic acid latex) (weight ratio of 14/80/6) and a carboxy ester lactone formed by cyclization of a vinyl acetate-maleic anhydride copolymer in the presence of 1-butanol to produce a partial butyl ester, ratio of acid:ester of 15:85.

An integral imaging-receiver (IIR) element was prepared by coating the following layers in the order recited on a transparent poly(ethylene terephthalate) film support. Quantities are parenthetically given in grams per square meter, unless otherwise stated.

(1) Image-receiving layer of poly(styrene-co-N-benzyl-N,N-dimethyl-N-vinylbenzylammonium chloride-co-divinylbenzene (molar ratio 49/49/2) (2.2) and gelatin (2.3);

(2) Stripping layer (as shown in Table 1 below);

(3) Negative silver halide emulsion (0.97) and cyan RDR A (see Example 2) (0.97);

(4) Gelatin layer (7.0) and

(5) Phthalated gelatin layer (1.1).

The emulsion was a 0.6.mu. diameter monodisperse cubic silver chloride emulsion.

A pod containing the following composition was prepared:

These components were used as follows:

The IIR element was laminated to the cover sheet spreading the pod contents at room temperature using a pair of 100 .mu.m gap undercut rollers. After 12 minutes, the laminated units was separated by hand-peeling apart. The extent of area of emulsion removed was evaluated visually to determine the effectiveness of "wet-stripping". Ideally all the emulsion should be retained on the cover sheet plus imaging layer part of the unit (layers 5 to 3) and not with the mordant receiver layer 1. Thus "100% emulsion stripping" represents very effective separation, "0% emulsion stripping" means the stripping layer did not strip and layer 3 with the upper gelatin layers was retained with the receiver. It is not easy to ascertain nor is it critical to know how the stripping layer 2 partitioned. In some instances the emulsion layer 3 fractured during the wet stripping operation and was retained. In this case, an estimate of the area separating was made and proportionately higher values indicate better stripping and less retention of layer 3 on the mordant receiver layer 1.

Dry stripping of the IIR was also compared. To avoid the tendency of the layer to peel variably depending upon the way the separation was started, a "tape test" was used. A small area (approximately 1/2".times.2") of a transparent tape (such as 3M Highland.RTM. 6200 Permanent Mending Tape) was pressed to the top gelatin overcoat of the IIR leaving enough area free to serve as a handle for pulling the tape. Ideally, a clean separation occurred at the stripping layer. These results were more subjective to evaluate and thus have been classified as poor, fair and good. The latter indicates clean separation at the stripping layer.

The results of the wet and dry stripping test were as follows:

Under these test conditions, only FC-431 gave good stripping at both coverages. At the higher coating level, FC-432 and FC-170 were also useful. The other materials were not satisfactory, failing either for wet or dry stripping.

In separate tests the following materials were also examined with this format as stripping layers and found to be unsatisfactory:

This example shows the improved sharpness that is obtainable with the Fluorad.RTM. FC-431 stripping layer compared to a state of the art cellulosic stripping layer.

An integral imaging-receiver (IIR) element was prepared by coating the following layers in the order recited on a transparent poly(ethylene terephthalate) film support. Quantities are parenthetically given in grams per square meter, unless otherwise stated.

(1) image-receiving layer of poly(styrene-co-N-benzyl-N,N-dimethyl-N-vinylbenzylammonium chloride-co-divinylbenzene (molar ratio 49/49/2) (3.2) and gelatin (3.2);

(2) stripping layer of FC-431 (0.16);

(3) gelatin layer (0.54);

(4) opaque layer of carbon black (1.2) and gelatin (1.3);

(5) cyan dye-providing layer of gelatin (1.0) and cyan RDR A (1.0);

(6) red-sensitive, direct-positive silver bromide emulsion (0.77 silver), gelatin (0.81), Nucleating Agent (4.0 mg/Ag mole) and 2-(2-octadecyl)-5-sulfohydroquinone potassium salt (16,000 mg/Ag mole);

(7) interlayer of gelatin (0.54) and 2,5-di-sec-dodecylhydroquinone (0.54);

(8) magenta dye-providing layer of magenta RDR B (1.1) (dispersed in diethyllauramide) and gelatin (1.3);

(9) green-sensitive, direct-positive silver bromide emulsion (0.80 silver), gelatin (0.91), Nucleating Agent (4.5 mg/Ag mole) and 2-(2-octadecyl)-5-sulfohydroquinone potassium salt (16,000 mg/Ag mole);

(10) interlayer of gelatin (0.54) and 2,5-di-sec-do-decylhydroquinone (0.54);

(11) yellow dye-providing layer of yellow RDR C (1.6) dispersed in di-n-butyl phthalate and gelatin (1.7);

(12) blue-sensitive, direct-positive silver bromide emulsion (0.82 silver), gelatin (0.91), Nucleating Agent (4.8 mg/Ag mole) and 2-(2-octadecyl)-5-sulfohydroquinone potassium salt (16,000 mg/Ag mole);

(13) layer of gelatin (1.1); and

(14) overcoat layer of poly(n-butyl methacrylate-co-hydrochloride-co-1-vinylimidazole (50:30:20) (0.86).

The direct-positive emulsions are approximately 0.8.mu. monodispersed, octahedral, internal image silver bromide emulsions, as described in U.S. Pat. No. 3,923,513.

A comparison coating was made identical to that above except that Layer 2 was composed of Natrosol.RTM. hydroxyethylcellulose (0.13) and Methocel.RTM. methyl cellulose (0.065). ##STR13##

A sample of the IIR was exposed in a sensitometer through a "sine-wave" MTF chart to yield a neutral at a visual density of approximately 1.0. The exposed sample was then processed at 21.degree. C. by rupturing a pod containing the viscous processing composition described below between the IIR and the cover sheet described above in Example 1, by using a pair of juxtaposed rollers to provide a processing gap of about 65 .mu.m.

The processing composition was as follows:

52.2 g potassium hydroxide

10 g 4-methyl-4-hydroxymethyl-1-p-tolyl-3-pyrazolidinone

8 g 1,4-cyclohexanedimethanol

10 g 5-methylbenzotriazole

57 g carboxymethylcellulose

10 g 11-aminoundecanoic acid water to 1 liter

After a period of ten minutes, the receiver was separated and the sensitometry of the resulting MTF chart was read using a microdensitometer. The relative sharpness was evaluated by calculating visual CMT acutance values. (This technique is discussed in an article entitled: "An Improved Objective Method for Rating Picture Sharpness: CMT Acutance", by R. G. Gendron, Journal of the SMPTE, 82, 1009-12 (Dec., 1973).) Two separate tests were run. The following results were obtained:

The results indicated that the Fluorad.RTM. FC-431 stripping layer gave a much sharper image than the control material.

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