GB2043930A - Photographic diffusion transfer products - Google Patents

Abstract

A diffusion control layer comprising a polymerisation product of a monomer capable of undergoing beta -elimination in an alkaline environment is disclosed for use in diffusion transfer processes and products, such as film units, photosensitive elements and image receiving elements. The polymerisation product comprises recurring units of the formula <IMAGE> wherein R<11> is the addition polymerisation product of an ethylenically unsaturated alkyl group of 2 to 5 carbon atoms; A, D and E are selected from hydrogen, methyl and phenyl, provided that not more than one of A, E and D may be methyl or phenyl and Y is an activating group.

Description

SPECIFICATION Photographic diffusion transfer products Various diffusion transfer systems have been disclosed in the art. Generally speaking, a transfer image is obtained by exposing a photosensitive element or negative component comprising at least one light sensitive silver halide layer to form a developable image; thereafter developing this image by applying an aqueous alkaline processing fluid; forming, as a function of this development, an imagewise distribution of soluble and diffusible image-forming material, which may be a dye, a dye intermediate or a soluble silver complex, and transferring this imagewise distribution, at least in part, by diffusion to a superposed image-receiving element or positive component including an image-receiving stratum to impart thereto a transfer image.

The dye image forming materials employed in such processes may generally be characterised as substances which are initially soluble or diffusible in the processing composition and then selectively rendered non-diffusible in an imagewise pattern as a function of development, or substances which are initially insoluble or nondiffusible in the processing composition and then selectively rendered diffusible in an imagewise pattern as a function of development. Numerous examples of both types of dye imageforming materials are recited in the patent literature. A particularly useful class of such materials are dye developers (dyes which are also silver halide developing agents) described in U.S. Patent No. 2,983,606 and many other patents.

In any of these systems, multicolor images may be obtained by employing a photosensitive element or negative component with at least two selectively sensitized silver halide layers, each having associated therewith a dye image-forming material exhibiting the desired spectral absorption characteristics. The most commonly employed elements of this type are the so called tripack structures employing a blue-, a green- and a red-sensitive silver halide layer having associated therewith, respectively, a yellow, a magenta and a cyan dye image-providing material.

The negative and positive components in such a system may be separate elements which are brought into superposition during development and therafter retained together or separated to provide the desired transfer image (e.g., as described in the aforementioned U.S. Patent No. 2,983,606), or these two components may comprise a unitary structure, such as the so called integral negativepositive film units wherein the respective components are retained together prior to exposure and following image formation. In the latter system a reflecting material such as a white pigment, e.g., titanium dioxide, is provided between the two components. This may comprise a preformed layer or one formed during development which masks the negative component and provides the desired background for viewing the image formed in the positive component as a reflection print.The respective components in such integral film units may be contained on a single dimensionally stable layer or support, or they may be confined between a pair of such supports. Of course, any support associated with the positive component should be transparent to permit viewing of the transfer image.

As examples of such integral negative-positive film units for preparing color transfer images viewable without separation, mention may be made of those described in U.S. Patents No. 3,41 5, 644; 3,415,645; 3,415,646; 3,473,925; 3,550,515; 3,573,042; 3,573,043; 3,573,044: 3,573,625; 3,578,540; 3,589,904; 3,594,164; 3,594,165; 3,607,285; 3,61 5,421; 3,615,436; 3,615,539; 3,615,540; 3,619,192; 3,619,193; 3,621,768; 3,647,437; 3,652,281; 3,652,282; 3,672,890; 3,679,409; 3,689,262; 3,690,879; and others.

With multicolor diffusion transfer products such as those described above employing two or more sets of silver halide emulsion layers, each layer having its own dye image-forming material associated therewith, premature migration of the color-providing material during processing can produce undesirable inter-image effects wherein the dye or other color providing material is controlled at least in part by the "wrong" silver halide layer, i.e., a silver halide layer other than the one which it was initially associated in the film unit.

This problem may be further illustrated by reference to a conventional tripack negative employing dye developers, wherein the negative is comprised of a support carrying a red-sensitive silver halide layer having a cyan dye developer associated therewith, a green-sensitive silver halide layer having a magenta dye developer associated therewith and a blue-sensitive silver halide layer having a yellow dye developer associated therewith. Ideally, solubilized dye developer should diffuse to its associated silver halide layer, and if not bound in that layer it diffuses further to the image receiving element. Diffusion through the silver halide layer is generally controlled by development of the silver halide layer.If the dye developer is permitted to migrate to other silver halide layers before its associated silver halide layer has been developed, the resultant transfer image will have something less than the desired Color fidelity due to dye loss and/or transfer of the wrong dye.

To illustrate further, it is possible for the magenta dye developer to back-diffuse to the red sensitive silver halide layer before development of this layer by the cyan dye developer, some of the magenta dye developer may develop silver halide in this "wrong" layer and be tied up or rendered nondiffusible. This will produce a loss of magenta dye, or so called "magenta drop off", in the transfer image. Moreover, development of the red-sensitive silver halide layer by magenta dye developer permits some of the cyan dye developer which should have instead been oxidized to diffuse to the image receiving element, thereby resulting in unwanted cyan transfer.

To obviate or minimize these inter-image#effects, layers comprised of various materials have been inserted between the emulsions and their individual supplies of dye image-forming material to prevent premature diffusion of the latter to an unassociated silver halide emulsion. Such an interlayer is permeable to the passage of processing composition so that development can take place in the emulsions on either side of the interlayer. The interlayer is impermeable for a short time to the dye image-forming material solubilized by the processing composition so that the emulsions will be substantially developed before the dye material associated with one emulsion layer can travel through the interlayer to another emulsion layer.

Control of the diffusion of color-providing substances by deferring or retarding their ability to diffuse to the image-receiving layer until after desired development has occurred is disclosed in U.S.

Patent No. 3,345,163 wherein said control is effected, e.g., by the use of a slowly hydrolyzable material as a barrier layer separating an outer emulsion and its associated color-providing substance from an inner emulsion and its associated color-providing substance.

Several other types of photosensitive element interlayer systems have been disclosed in the art.

For example, as seen in U.S. Patent No. 3,615,422 two emulsion layers may be separated by an interlayer comprised of metal-free polymeric material permeable to processing composition but impermeable to color providing substances until the polymer has become hydrated. The polymer's hydration rate is chosen so that the requisite hydration will occur subsequent to substantial development of the silver halide emulsion having the slowest development rate and prior to substantial fogging of the emulsion layer with the most rapid fogging rate. The interlayer can then retard both forward and rearward diffusion of color-providing substances or dyes. It retards rearward diffusion of dye associated with the next outer silver halide emulsion layer and forward diffusion of dye associated with the next inner silver halide emulsion layer.A variety of polymeric material found especially useful in this type of system is disclosed in U.S. Patent No. 3,421,892 which relates to the use of polyvinyl amide interlayers. These interlayers function like molecular sieves whose interstices become so enlarged by hydration of the polymer that a molecule of dye or other color-providing substance can pass through.

The interlayer material disclosed in U.S. Patent No. 3,384,483 is comprised of an alkali permeable, water insoluble polyvalent metal salt of a film forming, alkali permeable and water soluble polymer with free carboxylic acid groups. It appears that this polymeric salt, which is less permeable to dye developer in aqueous alkaline solution than the polyeric carboxylic acid used to prepare it, retards diffusion of dye developer to an unassociated emulsion layer during development via a cross-link mechanism, i.e., polyvalent metal moieties form the requisite alkali permeable, water insoluble salts by cross-linking with carboxylic acid moieties of the polymeric carboxylic acid. When this salt becomes hydrated during processing, it swells enough to permit diffusion of unoxidized dye developer through its interstices to the image receiving element.

Rather than employing an interlayer consisting essentially of only a single phase of material, an interlayer comprised of an admixture of materials may be utilized. Such a system is disclosed in U.S.

Patent No. 3,625,685, where silver halide strata are separated by interlayers containing two phases which are intimately admixed, the dye permeation-inducing component or discontinuous phase (comprised of processing composition permeable material) and a coalesced latex or continuous phase (comprised of the coalesced essence of an aqueous film-forming synthetic polymeric dispersion). In this system the dye permeation-inducing material, which may be permeable or impermeable to the processing composition and is impermeable to dye image forming material, forms a lattice structure with the coalesced latex which is permeable to processing composition. Upon contact with processing composition, the dye permeation-inducing material, which is preferably a polymer, becomes permeable to solubilized dye material, thereby making it possible for dye to pass through the interlayer.

In a preferred embodiment of the above described system, the interlayer is rendered permeable by hydration of the discontinuous phase. This phase expands when hydrated to create interstices in the interlayer's lattice structure of sufficient size to permit the passage of solubilized dye therethrough. The rate of hydration and swelling is usually chosen so as to block migration of the dye image forming material until development of all emulsion layers in the photosensitive element is substantially completed, although it can also be chosen so as to achieve layerwise development of the emulsions and diffusion of the dye image forming material.In the latter type of system, an tnter ayer between two emulsion layers would preferably prevent such dye diffusion until there had been substantial development of the outer (closer to the image-receiving element) emulsion layer.

As can be seen from the discussion above, polymers rendered permeable to the passage of solubilized dye image forming material by hydration may be used alone or in a mixture with other materials to form a barrier interlayer between two emulsions. It is believed that such an interlayer system can act as a selective barrier because of the large size of the dye (or dye precursor) molecules.

While many of the molecules of processing composition e.g., water, alkali, etc., are small enough to slip through interstices in the interlayer lattice, those of the solubilized dye imaged forming material are too large to do so in the time span contemplated for photographic processing unless these interstices are expanded by hydration of the barrier polymer.

Although such polymers have proven to be useful in delaying the diffusion of dye image-forming material, it has been found that they sometimes permit premature diffusion. This is because polymer hydration and the resultant interlayer expansion generally begin as soon as the polymer is contacted with processing composition. Thus, some dye diffusion could occur before substantial development of the silver halide emulsion protected by the interlayer. Furthermore, these polymers tend to produce rather slow interlayer expansion. Instead of switching quickly from a very impermeable condition to a highly impermeable one as would often be desired, interlayer permeability usually occurs more gradually, sometimes beginning too soon and taking too long.

U.S. Patent No. 3,362,819 discloses image-receiving elements, particularly adapted for employment in the preceding diffusion transfer processes, which comprise a support layer possessing on one surface thereof, in sequence, a polymeric acid layer, preferably an inert timing or spacer layer, and an image-receiving layer adapted to provide a visible image upon transfer to said layer of diffusible dye image-forming substance.

The acid polymer layer is disclosed to contain at least sufficient acid groups to effect a reduction in the pH of the image layer from a pH of about 12 to 14 to a pH of at least 11, and preferably to a pH of about 5 to 8 after a predetermined period.

It is, of course, necessary that the action of the polymeric acid be so controlled as not to interfere with either development of the negative or transfer of image dye formers. For this reason, the pH of the image layer is kept at a level of pH 12 to 14 until the positive dye image has been formed, after which the pH is reduced very rapidly to the desired final pH.

The inert spacer layer of the aforementioned patent, for example, an inert spacer layer comprising polyvinyl alcohol or gelatin, acts to "time" control the pH reduction by the polymeric acid layer. This timing is disclosed to be a function of the rate at which the alkali diffuses through the inert spacer layer.

The use of diffusion control layers in silver transfer processes, such as timing layers to control a neutralising layer, is known in the art; see, for example, U.S. Patent Specification 3,772,025, to which reference should be made.

This invention relates to photographic diffusion transfer products containing diffusion control layers that control the diffusion transfer of a reagent to or through a component that may be included in a diffusion transfer film unit.

A photographic diffusion transfer product according to the invention comprises a support and at least one component selected from (1) at least one photosensitive silver halide emulsion layer having associated therewith a processing composition soluble and diffusible image forming material, (2) a polymeric acid layer and (3) an image receiving layer, the product comprising also a diffusion control layer comprising polymerisation product of a monomer capable of undergoing p-eiimination in an alkaline environment, the polymerisation product comprising recurring units of the formula

wherein R" is the addition polymerisation product of an ethylenically unsaturated alkyl group of two to five carbon atoms;A, D and E are selected from hydrogen, methyl and phenyl provided that no more than one of A, E or D may be methyl or phenyl, and Y is an activating group.

One preferred product according to the invention is a photosensitive element comprising a support and at least one photosensitive silver halide emulsion having associated therewith a processing composition soluble and diffusible image forming material and including a diffusion control layer as defined. One such diffusion control layer may be present in the photosensitive element as an overcoat. It is often preferred that the photosensitive element should comprise at least two silver halide emulsion layers having associated therewith a processing composition soluble and diffusible image forming material in which event one said diffusion control layer may be present as an interlayer between the emulsion layers. A photosensitive element may include more than one of the defined diffusion control layers.Preferably the image forming material is a dye image forming material, most preferably a dye developer.

Another preferred product according to the invention is an image receiving element comprising a support, a polymeric acid layer and an alkali permeable and dyeable image receiving layer and which includes a diffusion control layer as defined. It may be present as, for instance, a timing layer between the polymeric acid and image receiving layers or as an overcoat over the image receiving layer.

Another preferred product according to the invention is a film unit comprising a photosensitive element comprising a support and at least one photosensitive silver halide emulsion layer having associated therewith a processing composition soluble and diffusible image forming material and an image receiving element and which includes a diffusion control layer as defined. This diffusion control layer may be an interlayer between the image receiving and photosensitive elements. There may be a diffusion control layer as defined in the image receiving element. There may be a diffusion control layer as defined in the photosensitive element.The image receiving element preferably comprises a support and an alkali permeable and dyeable image receiving layer and preferably is affixed to at least one edge of the photosensitive element and is superposed or capable of being superposed the photosensitive element. The film unit preferably includes an aqueous alkaline processing composition and means for discharging it within the film unit. For instance the film unit may include a rupturable container positioned to discharge its contents as a layer through the film unit.

The invention is now described in more detail partly by reference to the accompanying drawings in which Figure is a cross-sectional view of a photographic film unit including diffusion control layers of this invention; Figure 2 is a cross-sectional view of an image-receiving element including a diffusion control timing layer of this invention; Figure 3 illustrates a model arrangement for measuring the 'hold-time" of the interlayers of this invention; and Figure 4 is a graphical depiction of dye intensity as a function of time in a system including an interlayer of the present invention.

It has been found that polymerization products of monomers capable of undergoing #-elimination in an alkaline environment are useful for providing timed diffusion control in diffusion transfer photographic film units. Diffusion control layers of these-polymeriza#ion products may be formulated for use as diffusion control interlayers or overcoats in photosensitive elements, and as diffusion control, e.g., timing layers or overcoats in image-receiving elements. These polymeric materials must undergo ,B- elimination before substantial swelling occurs, #-elimination and swelling being a prerequisite to permeation by selected materials soluble in or solubilized by an aqueous alkaline processing fluid.

The p-elimination step which the polymeric materials of the diffusion control layers of this invention undergo ensures that there is a delay in permeability after contact of the diffusion control layer with the processing composition, and provides a "hold" of the alkali or soluble or solubilized material followed by a rapid "release" or opening to permit the soluble or solubilized material to pass. The polymeric materials may be thought of as "hold-release" polymers which delay diffusion therethrough of alkali or material soluble in or solubilized by processing fluid by a predetermined time, e.g., from less than five seconds to more several hundred seconds.

The diffusion control layers of this invention may-be used as interlayers between silver halide emulsion layers sensitized to different regions of the spectrum, each emulsion having an associated dye image-forming material. They may be utilized, e.g., in the manner described in aforementioned U.S.

Patent Nos. 3,61 5,422 and 3,421,892, substituting the hold-release polymers of this invention for the interlayer polymer compositions disclosed therein.

The time for ,B-elimination to occur subsequent to contact with processing composition and for subsequent hydration should be sufficient to maintain the interlayer substantially impermeable to solubilized dye image-forming material until there has been at least substantial development of the emulsions between the interlayer and the image-receiving layer but before there has been substantial fogging of the emulsion layer with the most rapid fogging rate.

The diffusion control layers of this invention may be used as timing or spacer layers employed between the alkaline processing composition introduced into the film unit and a neutralizing layer, e.g., a polymeric acid layer, to control the initiation of pH reduction by acting as a substantially impermeable barrier to the alkaline processing composition until #-elimination occurs.

The diffusion control layers of the invention can also be utilized as an overcoat layer, such as overcoat layer 19 shown in Fig. 1. The employment of such an overcoat layer can be utilized to control, for example, desired dye transfer by conversion of a substantial dye-impermeable layer to a substantially dye-permeable layer.

The introduction of double bonds into a molecule containing single bonds involves the elimination of atoms or groups from adjacent atoms. When elimination reactions involve p-substituted esters, acids, ketones, aldehydes and nitro compounds, they are called p-eliminations. According to Hendrickson, Cram and Hammond, Organic Chemistry (3rd Edition, McGraw-Hill Book Company, 1970), the electronwithdrawing groups have strong acid-strengthening effects on the a-proton which is removed by base during the reaction. This 1,2-elimination under basic conditions is very familiar as shown by Figure 14-3 from Hendrickson, Cram and Hammond which follows.

where L is a leaving group, B is a base and -NO2 a typical activating group. In general terms this might be written:

where Y is an activating group.

Substituents which activate #-elimination under basic conditions are known. The nature of the activation in p-elimination was studied by J. Crosby and C. J. M. Stirling in J. Chem. Soc. (B) 1970 page 671. It was concluded that resonance stabilisation of a carbanionic species was an important component of activation.

It has been discovered that such a p-substituted compound may be incorporated into a polymeige provide a polymer which is substantially impermeable to alkali or certain materials which are soluble in or solubilised by alkaline processing fluid until after #-elimination breaks bonds liberating groups capable of absorbing water, swelling and causing the polymer to become permeable to these soluble or solubilised materials and that such polymer may be used as a diffusion control layer, the resulting predetermined time delay preventing premature diffusion of the alkali or soluble or solubilised materials.

By controlling the mole proportion or ratio of such p-elimination moieties in the polymer, as well as the thickness of the polymeric layer, one may provide as predetermined permeability time desired for the particular diffusion transfer system.

With reference to the above general formulation for #-elimination, the leaving group, L, is the polymeric structure from which a p-substituted material is eliminated.

The ,B-elimination reaction can the be written either

where L is

and 0 0 II II R' is hydrogen or methyl and Y js selected from the group consisting of-SO2W, -C-T -S-G and -CN where W is -C8H5CH2, -CH2, -0C2H5, -C6H # -NR2-N(CH2QH5)2; T is -0C2H5 -CH3,-H, -NH2, -N R2; G is phenyl, methyl or ethyl and R is alkyl, e.g., methyl or ethyl; or

where L is

and R' and Y are as defined above.

More generally, the reaction is:

wherein R" is the addition polymerization unit of an ethylenically unsaturated alkyl group of from two to five carbon atoms, including a graft of such an ethyienically#unsaturated alkyl group onto a polymeric organic backbone, A, E and D are selected from the group consisting of hydrogen, methyl and phenyl provided that no more than one of A, E or D may be methyl or phenyl, Y is an activating group as defined above. Typical monomers which have demonstrated that they provide to their polymerization product a p-elimination activating group include 2-cyanoethyl acrylate, 2-cyanoethyl methacrylate, and 2carbethoxy-ethyl methacrylate.Other monomers which should provide the same functionality to their polymerization products include, for example, 2-p-toluenesulfonyl-ethyl acrylate and 2-methane sulfonyl-ethyl acrylate.

The reaction using the polymerization product of 2-cyanoethyl acrylate can be visualized thusly;

The diffusion control layers of the invention can comprise homopolymers or copolymers, including graft copolymers as mentioned hereinbefore. Mixtures of polymers can also be employed. Suitable copolymers for use as diffusion control layers will include, in addition to the p-eliminating component, units from comonomeric materials which provide the polymers with certain desired properties. Such materials may, for example modulate coalescence or viscosity, improve film integrity and coatability, or provide for more even fluid permeation and ion penetration. For example, butyl acrylate is useful in providing hydrophobic balance and control to the dye permeation rate. Comonomers which are nonhydrolyzable or cross-linking may be used.Acrylic acid, methacrylic acid, 2-sulfoethyl methacrylate and 2-acrylamido-2-methylpropane sulfonic acid have been found useful comonomers in assuring that all parts of the diffusion control layer allow processing composition to pass through at essentially the same time and rate so as to promote uniform #-elimination and hydration of the permeation-inducing component. Ethylene glycol dimethacrylate, a cross-linking monomer, for example, is useful in the diffusin control layer used as an interlayer to modulate dye transfer rate after the initial hold.

As shown in Figure 1 , the diffusion control layers of this invention may be employed in a photographic film unit having a photosensitive element 26 and an image-receiving element 27.

Interlayers 13 and 16 are positioned between red- and grèen-, and blue- and green-sensitive silver halide emulsions, respectively, in the photosensitive element. These interlayers and the emulsions with their associated dye image-forming material, e.g., dye developer, are preferably arranged on a support 10 in the following order from that support: cyan dye developer layer 11, red-sensitive silver halide emulsion layer 12, interlayer 13, magenta dye developer layer 14, green-sensitive silver halide emulsion 15, interlayer 16, yellow dye developer layer 17 and blue-sensitive silver halide emulsion layer 18. An overcoat layer 19 may be coated on top of the blue-sensitive silver halide emulsion layer.

The image-receiving element 27 illustrated in Figure 1 comprises in order, an image-receiving layer 21, a spacer or timing layer 22, a neutralizing layer 23 and a support layer 24. During processing the image-receiving layer is situated closest to the photosensitive element.

After the photosensitive element has been exposed, aqueous alkaline processing composition 20 is introduced between the photosensitive and image-receiving elements and permeates the emulsion layers to initiate development of the latent image carried therein and provide a medium for dye diffusion transfer to the image-receiving element. Dye image-forming materials associated with unexposed portions of the emulsion layers diffuse to the image-receiving element in known manner. As set forth in U.S. Patent No. 3,362,819, situated beneath the image-receiving layer is a neutralizing layer containing a polymeric acid to neutralize alkali in the processing composition after a predetermined period.

The timing or spacing layer, comprised of polymeric material and located between the imagereceiving and neutralizing layers is used to control the pH reduction. Diffusion control layers comprising a p-elimination polymeric material in accordance with this invention comprise, in one preferred embodiment, interlayers 13 and/or 16. Alternatively, overcoat layer 19 can comprise a diffusion control layer of a p-eliminating polymeric material. In another preferred embodiment the spacer layer 22 comprises a diffusion control layer of the invention.

The image-receiving element 27 illustrated in Figure 2 comprises in order, a support layer 28, a neutralizing layer 29, a spacer or timing layer 30, an imager-receiving layer 31 and an overcoat 32.

During processing the image-receiving element overcoat is situated closest to the photosensitive element. In one embodiment of this invention, a diffusion control layer comprising a p-elimination polymeric material in accordance with this invention comprises overcoat layer 32.

A measure of time of pH reduction can be had from a quantity which can be referred to as a "clearing time" which can be measured by use of the following system. An image-receiving element comprising in order on a support, a polymeric acid layer, a test timing layer and a mordanting layer, is spread with an alkaline processing material of high pH comprising an indicator dye which is highly colored at pH's of about 12 to 14 and colorless below about 10. A transparent cover sheet is superposed the processing material. The view through the cover sheet toward the image-receiving element is dark until the alkali has penetrated to the polymeric acid layer where the pH is reduced by alkali consumption and the indicator dye becomes colorless, the system has "cleared". A skilled operator can determine when the clearing begins and when it is complete.A "leaky" timing layer allows a trickle of alkali through from the moment of first contact and shows no precipitous change in beginning to clear nor in the final clearing. A timing layer comprising the polymers of the instant invention will hold the alkali back for a definite timed period, and then, over a very short time interval, allow sufficient alkali through to drop the pH below the transition range of the indicator dye.

Clearing time can be measured for a structure that comprises an entire image-receiving element or it can be measured for a model simplified structure that includes only the timing layer coated over the polymeric acid layer on the support. The first clearing time is referred to as "clearing through the mordant" while the second model structure clearing is referred to as "clearing through the timing layer" The diffusion control layer of this invention used as a top coat for an image-receiving element is located on top of the strata that comprise the image-receiving element.For example, in an imagereceiving element comprising in order, a support, a polymeric acid layer, a spacer layer and an alkali permeable and dyeable polymeric layer, the diffusion control layer is located next adjacent the alkali permeable and dyeable polymeric layer, furthest from the support and acts to delay permeation to the image-receiving element of the processing composition and materials solubilized by it.

The capacity of polymeric diffusion control layers of the invention to delay permeation therethrough of image-forming dye until conversion by a -elimination reaction to a relatively dyepermeable polymer can be evaluated by resort to utilization of a test structure shown in Fig. 3. In accordance with such structure dye transfer through the polymeric test material, e.g., an interlayer test material, is monitored in relation to time. The "hold-release" properties of a polymeric test material can be evaluated in simulation of the functioning of a material as, e.g. an interlayer in a photosensitive element. Such test structure and a suitable method of evaluation are set forth in detail in Examples 1 to 15 thereof.

The following examples are presented for illustrative purposes only and are not intended to be in any way limiting. Measurements were made at ambient room temperature, about 250C, unless otherwise specified.

EXAMPLES 1-10 On a transparent support, 33 in Fig. 3, a layer 34 comprising 20 mg/ft2 (215.3 mgs/m2) of a cyan dye developer

40 mg/ft2 (430.6 mgs/m2) gelatin and 1.5 mg/ft2 (16.1 mgs/m2) of succinaldehyde was coated using a conventional loop coater. Over this layer, a layer 35 containing 200 mg/ft2 (2153 mgs/m2) of the polymeric material being tested was coated.

A transparent element 38 comprising a polyester clear film base was superposed with test elements to form sandwiches and an opaque alkaline processing composition 36 comprising: Potassium hydroxide (45% aqueous solution) 22.9 g.

Lithium hydroxide 0.55 g.

Benzotriazole 1.53 g.

6-Bromo-5-methyl-4-azabenzimidazole 0.08 g.

6-methyl uracii 0.82 g.

Ethylene diamine tetraacetic acid 2.27 g.

Bis-(2-aminoethyl) sulfide 0.06 g.

Carbowax (mw 6000) 1.5 g.

Colloidalsilica 5.05 g.

6-benzylaminopurine 1.09 g.

Titanium dioxide 115.23 g.

N-phenethyl a-picolinium bromide (50% aqueous solution) 3.91 g.

N-benzyl a-picolinium bromide (50% aqueous solution) 5.09 g.

Lithium nitrate 0.27 g.

Carboxymethyl hydroxyethyl cellulose 4.82 g.

Water 100 g.

was introduced between the polymeric test material layer and the transparent element 38 at a gap of 0.0028 in (about 0.07 mm).

- The optical reflection density to red light of the processed sample, viewed through support 33 in Figure 3, as a function of time was continuously read using a MacBeth Quanta-Log densitometer equipped with a Hewlett-Packard 17505A strip-chart recorder. This density comprises contributions from the dye image-forming material in the polymeric test layer. The titanium dioxide in the processing composition makes dye image-forming material in the processing composition layer.A typical curve of density as a function of time is given in Figure 4 wherein t, is the time for dye image-forming material to solubilize, t2 is the total time the dye image-forming material is held back by the polymeric interlayer, Do is the density after the initial dissolution of the dye image-forming material, Df is the density after dye transfer through the interlayer, and the slope of the line segment between A and B is calculated as the rate of change of density.

Values for t1 t2 and slope are given below for the following hold-release polymer systems of the present invention.

1. 100 parts by weight of 2-cyanoethyl acrylate mixed with 100 parts by weight of a 95.5/4.5 copolymer of diacetone acrylamide and acrylic acid and polymerized.

2. 35 parts by weight of 2-cyanoethyl acrylate mixed with 65 parts by weight of a 95.5/4.5 copolymer of diacetone acrylamide and acrylic acid and polymerized.

3. A 47.5/56/2.5 interpolymer of diacetone acrylamide; 2-cyanoethy acrylate and acrylic acid.

4. A 63/35/2 interpolymer of diacetone acrylamide, 2-cyanoethyl acrylate and acrylic acid.

5. An 85/10/2/3 interpolymer of butylacrylate, 2-cyanoethyl acrylate, methacrylic acid and 2-acrylamido-2-methyl propane sulfonic acid.

6. An 85/10/2/3 interpolymer of butyl acrylate, 2-cyanoethyl acrylate, methacrylic acid and 2-sulfoethylmethacrylate.

7. 35 parts by weight of 2-cyanoethylacrylate mixed with 100 parts by weight of a 9.25/0.75 copolymer of 2-cyanoethylacrylamide and acrylic acid and polymerized.

8. A 63/35/2 interpolymer of diacetone acryla mide, 2-carbethoxyethyl methacryl ate and acrylic acid.

9. A 63/35/2 interpolymer of diacetone acrylamide, 2-cyanoethyl methacrylate and acrylic acid.

10. 100 parts by weight of 94/6 copolymer of diacetone acrylamide and acrylic acid mixed with 100 parts by weight of a 63/35/2 interpolymer of diacetone acrylamide, 2-cyanoethyl methacrylate and acrylic acid.

All interpolymer constituent proportions are on a weight basis

Sample t1 t, slope 1 2 26 404 2 3 22 522 3 5 15 280 4 5 15 580 5 0 11 675 6 10 16.5 737 7 0 28 250 8 0 12 200 9 7 14 870 10 1 18 525 It is apparent from the foregoing table that the present invention provides a significant hold time before solubilized dye image forming material is released, and accomplishe#s the dye release in a relatively short time span.

Hold time is longer at 450F (about 70C) and shorter at 950F (about 350C), paralleling development time. For example, sample 2 has a t2 of 21 5 secs. at 450F and a slope of 87, and has a t2 of 11 sec. at 950F and a slope of 654.

EXAMPLES 11-15 Test elements were prepared as in example 1-10. A second transplant element comprising a polyester clear film base was superposed to the test elements to form sandwiches and an opaque alkaline processing composition comprising: Potassium hydroxide (45% aqueous solution) 13.63 g.

Cesium hydroxide (50% aqueous solution) 10.65 g.

Benzotriazole 1.18 g.

5-hydroxyazabenzimidazole 0.118 g.

6-bromo-5-methyl-4-azabenzimidazole 0.059 g.

2-methylimidazole 0.42 g.

Sodium carboxymethyl cellulose 4.43 g.

Titanium dioxide 59.27 g.

N-phenethyl-a-picolinium bromide (50% aqueous solution) 4.2 g.

Water 100 g.

was introduced between the polymeric material and the uppermost transparent element at a gap of 0.0028 in. (about 0.07mm).

The time, T, needed for the dye material to permeate the polymeric material was determined by monitoring optical density of the dye through the uppermost transparent element using the densitometer designated in Examples 1-10.

Values for T in seconds are given below for the following hold-release polymer systems of the present invention: 11. 2 parts by weight of an 85/10/3/2 interpolymer of butyl acrylate, 2-cyanoethyl acrylate, 2-sulfoethyl methacrylate with 1 part by weight of a 94/6 copolymer of butyl acrylate.

12. An 85/16/2/3 interpolymer of butyl acrylate, 2-cyanoethyl acrylate, methacrylic acid and 2-acrylamido-2-methylpropane sulfonic acid.

13. An 89/6/2/3 interpolymer of butyl acrylate, 2-cyanoethyl acrylate, methacrylic acid and 2-sulfoethylmethacrylate.

14. 85 parts of an 68/10/2/5 interpolymer of butyl acrylate, 2-cyanoethyl methacrylate, 2-sulfo- ethylmethacrylate and ethyleneglycol di methacrylate polymerized around a seed of 15 parts by weight of butyl acrylate.

15. An 85/10/2/3 interpolymer of butyl acrylate, 2-cyanoethylacrylate, meth acrylic acid and 2-sulfoethylmethacrylate.

Sample T 11 70 12 30 13 12 14 10 15 120 T, while measuring the time before solubilized dye image forming material becomes available to an image receiving layer, includes the time necessary for this solubilized dye image forming material to diffuse through the alkaline processing composition and has a component related to the thickness of that alkaline processing composition layer.

The relative proportions of ingredients in the processing composition may naturally be altered where desired. For example, substitution of various preservatives, alkalies, silver halide solvents, etc. is contemplated, as well as inclusion of such components as restrainers and accelerators. The concentration of various components may also be varied over a wide range.

EXAMPLES 16-19 Image-receiving elements of the invention were prepared by coating a transparent 4 mil (0.1 mm) polyethylene terephthalate film base with the following layers to form an image-receiving component: 1. as a polymeric acid layer, the partial butyl ester of polyethylene/maleic anhydride copolymer mixed with about 10% by weight of polyvinyl butyral and coated at a coverage of about 2500 mg/ft2; (26910 mgs/m2).

2. a timing layer containing polymeric materials described in detail in the examples that follow; and 3. as a polymeric image-receiving layer a mixture of 6 parts by weight of polyvinyl alcohol, 3 parts by weight of poly-4-vinylpyridine and 1 part by weight of a graft polymer of 4-vinyl pyridinevinylbenzyltri-methyl ammonium chloride on hydroxy-ethylcellulose at a coverage of 300 mg/ft2 (3229 mgs/m2). The elements are labelled (a).

For comparison, test elements were prepared which did not have the polymeric image-receiving layer on top of the timing layers. These elements are labeled (b).

7 Timing Layer Permeation Time (sec) Coverage Example Material mg/ft2(/m2) Start Finish Control (a) I 500 (5380) 180 210 (b) l 500 (5380) 60 87 16(a) ll 250 (2690) 215 245 16(b) 11 250 (2690) 60 68 17(a) 11 500 (5380) 280 325 17(b) II 50D'(538Q) 92 105 18(a) lll 500 (5380) 33 40 18{b) lil 500 (5380) 25 29 19(a) Ill 250 (2690) 25 32 19(b) Ill 250 (2690) 15 20 where I is a 60/30/4/6 interpolymer of butyl acrylate, diacetone acrylamide, styrene and methacrylic acid blended with 9% by weight of polyvinylalcohol; II is a seed of 100 parts of a 87.5/2/0.5 interpolymer of diacetone acrylamide, acrylic acid and 2-acrylamido-2-methyl propane sulphonic acid, sodium salt around which is polymerised 49 parts of 2-cyanoethyl acrylate; and Ill is a 63/35/2 interpolymer of diacetone acrylamide, 2-cyanoethyl acrylate and acrylic acid.

100 g Water 4.02 g hydroxyethyl carboxymethyl cellulose 4.15 g 50% potassium hydroxide solution 1.12 g benzotriazole 0.50 g thymolphthalein was introduced between the polymetric test material layer and the transparent element at a gap of 0.0028 in. (about 0.07 mm). The time denoted as permeation time and measured in seconds, for the sandwich to change colour from blue to colourless is a measure of the time necessary for the processing composition to permeate the timing layer and react with the polymeric acid layer lowering the pH.

Times are recorded as "start", when the sandwich first starts to clear and "finish" when the sandwich has substantially completed clearing.

EXAMPLES 20-27 On a transparent 4 mil (0.1 mm) polyethylene terephthalate film base was coated the partial butyl ester of polyethylene/maleic anhydride copolymer mixed with about 10% by weight of polyvinyl butyral at a coverage of about 2500 mg/ft2 (26910 mgs/m2). On this layer was coated the following timing layers and image receiving layers at the coverages indicated. Permeation time was measured as detailed above.

Image Receiving Permeation Time Timing Layer Layer (sec) Coverage Coverage Example Material mg/tt2(/m# Material mg/ft2(/m2) Start Finish 20 A 2 200(21 53) 31 21 A 200(2153) D 500(5380) 54 58 22 B 200(2153) 31 23 B 200(2153) D 500(5380) 62 24 C, 600(6459) - 41 48 25 C 1000 - - 41 ~ 48 26 C 600(6459) D 500(5380) 80 92 27 C j 1000(10765) D 500(5380) 80 110 where A is a seed of an 56.7/25/5/1/2 interpolymer of butylacrylate, 2-cyanoethylacrylate, ethylene glycol dimethacrylate, acrylic acid and styrene around which is polymerized a 10/3 mixture of diacetone acrylamide and acrylic acid.The pH of A is 2.6; B-comprises the material of A with sufficient potassium hydroxide added to bring the pH to 8.0; C is a 59/40/1 interpolymer of diacetone acrylamide, 2cyanoethylacrylate and acrylic acid; and D is a graft copolymer of 4-vinyl pyridine, vinyl benzyl trimethyl ammonium chloride on polyvinyl alcohol.

Cyano-substituted acrylates have been disclosed in U.S. Serial No. 806,1 50, as silver halide grain- growing protective colloids; there-is no disclosure or suggestion of a diffusion control effect.

We describe in our copending application No. 7909408 Serial No. 2030308 (reference 679/94, corresponding to USSN 942,489) photographic diffusion transfer products that comprise a support and at least one component selected from (1) at least one photosensitive silver halide emulsion layer having associated therewith a processing composition soluble and diffusible image forming material, (2) a polymeric acid layer and (3) an image receiving layer in which the product comprises also a diffusion control layer comprising a graft copolymer comprising an organic polymeric backbone having grafted thereon recurring units from a hydrophobic monomer and recurring units from a monomer capable of undergoing #-elimination in an alkaline environment and having the formula

wherein R is an ethylenically unsaturated alkyl radical of from 2 to 5 carbon atoms, A, E and D are each selected from hydrogen, methyl and phenyl, provided that no more than one of A, E and D is methyl or phenyl, and Y is an activating group.

Claims (25)

1. A photographic diffusion transfer product comprising a support and at least one component selected from (1) at least one photosensitive silver halide emulsion layer having associated therewith a processing composition soluble and diffusible image forming material, (2) a polymeric acid layer and (3) an image receiving layer, the product comprising also a diffusion control layer comprising polymerisation product of a monomer capable of undergoing ,B-elimination in an alkaline environment, the polymerisation product comprising recurring units of the formula

wherein R" is the addition polymerisation product of an ethylenically unsaturated alkyl group of two to five carbon atoms; A, D and E are selected from hydrogen, methyl and phenyl provided that no more than one of A, E and D may be methyl or phenyl, and Y is an activating group.

2. A product according to claim 1 in which the activating group is selected from -SO2W,

and -NO2 where W is -C8H5CH3, -CH3, -0C2H5, -C6H5, -NR? - N(CH2C6H5)2; T is -OC2H5, -CH3, -H, -NH2, -NR2; G is phenyl, methyl or ethyl; and R is methyl or ethyl.

3. A product according to claim 1 in which the polymerisation product comprises poly(2-cyanoethyl acrylate).

4. A product according to claim 1 in which the polymerisation product comprises poly(2-cyanoethyl methacrylate).

5. A product according to claim 1 in which the polymerisation product comprises poly(2carbethoxy-ethyl methacrylate).

6. A product according to any preceding claim in which the polymerisation product is a product of a monomer mixture comprising also a nonhydrolysable comonomer.

7. A product according to any further preceding claim in which the polymerisation product further comprises units of a cross-linking comonomer.

8. A product according to any preceding claim in which the diffusion control layer comprises a mixture of polymers, at least one of which is a polymerisation product as defined in any of claims 1 to 7.

9. A product according to any of claims 1 to 8 in the form of an image receiving element comprising a support, a polymeric acid -layer an'd an alkali permeable and dyeable image receiving layer, and including a diffusion control layer as defined in any of claim's 1 to 8.

10. A product according to claim 9 in which the said diffusion control layer comprises a timing layer between the polymeric acid and image receiving layers.

11. A product according to claim 9 in which the said diffusion control layer comprises an overcoat over the image receiving layer.

12. A product according to any of claims 1 to 8 in the form of a photosensitive element comprising a support and at least one photosensitive silver halide emulsion having associated therewith a processing composition soluble and diffusible image forming material and including a diffusion control layer as defined in any of claims 1 to 8.

13. A product according to claim 12 in which one said diffusion control layer is present in the photosensitive element as an overcoat layer.

14. A product according to claim 12 or claim 13 in which the photosensitive element comprises at least two silver halide emulsion layers having associated therewith a processing composition soluble and diffusible image forming material.

15. A product according to claim 14 in which one said diffusion control layer is present as an interlayer between at least two silver halide emulsion layers.

16. A product according to any of claims 12 to 15 in which the image forming material is a dye image forming material.

17. A product according to any of claims 12 to 16 in which the photosensitive element comprises, in sequence, a support layer, a red sensitive silver halide layer having associated therewith a cyan dye image forming material, an interlayer, a green sensitive silver halide layer having associated therewith a magenta dye image forming material, an interlayer, and a blue sensitive silver halide layer having associated therewith a yellow image forming material, and in which each of the interlayers comprises a diffusion control layer as defined in any of claims 1 to 8.

18. A product according to claim 16 or 17 in which the or each dye image forming material is a dye developer.

19. A product according to any of claims 1 to 8 in the form of a film unit comprising a photosensitive element comprising a support and at least one photosensitive silver halide emulsion layer having associated therewith a processing composition soluble and diffusible image forming material and an image receiving element, and including a diffusion control layer as defined in any of claims 1 to 8.

20. A product according to claim 19 in which the image receiving element comprises a support and an alkali permeable and dyeable image receiving layer and is affixed to at least one edge of the photosensitive element and is superposed or capable of being superposed the photosensitive element.

21. A product according to claim 19 or 20 including an aqueous alkaline processing composition and means for discharging it within the film unit.

22. A product according to any of claims 19 to 21 including one said diffusion control layer between the image receiving layer and the adjacent photosensitive silver halide layer.

23. A product according to any of claims 19 to 21 in which the image receiving element is as defined in any of claims 9, 10 or 11.

24. A product according to any of claims 19 to 21 in which the photosensitive element is an element as defined in any of claims 12 to 18.

25. A product according to claim 1 substantially as herein described.