Classifications

• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03C—PHOTOSENSITIVE MATERIALS FOR PHOTOGRAPHIC PURPOSES; PHOTOGRAPHIC PROCESSES, e.g. CINE, X-RAY, COLOUR, STEREO-PHOTOGRAPHIC PROCESSES; AUXILIARY PROCESSES IN PHOTOGRAPHY
  • G03C8/00—Diffusion transfer processes or agents therefor; Photosensitive materials for such processes
  • G03C8/42—Structural details
  • G03C8/52—Bases or auxiliary layers; Substances therefor
  • G03C8/54—Timing layers

Definitions

• the present invention relates to photographic products adapted for employment in forming photographic diffusion transfer images.
• the present invention is directed toward photographic diffusion transfer film units including diffusion control layers comprised of certain polymers hydrolyzable in the presence of alkali.
• DE-A 29 10 271 discloses graft polymers used in diffusion control layers of photographic diffusion transfer products.
• the copolymers have repeating units of the formula wherein R" is the addition polymer of an ethylenically unsaturated group having 2 to 5 carbon atoms;
• A, D, and E are hydrogen, methyl and phenyl, wherein not more than one A, E or D may be methyl or phenyl;
• Y is an activatinq qroup, such as wherein W is ⁇ C 6 H 5 CH 3 , -CH 3 , -OC 2 H 5 , ⁇ C 6 H 5 , -NR 2 , ⁇ N(CH 2 C 6 H 5 ) 2 ;
• T is -OC 2 H 5 , -CH 3 , -H, -NH 2 , -NR 2 ;
• G is phenyl, methyl or ethyl; and R is methyl or ethyl.
• copolymers are capable of ⁇ -elimination under the alkaline conditions of an alkaline photographic processing composition and are converted from a condition of impermeability to alkali to a condition of substantial permeability thereto.
• GB-A-20 30 308 discloses photographic diffusion transfer products containing a diffusion control layer comprising a ⁇ -eliminating graft copolymer.
• the graft copolymer has grafted on units from a hydrophobic monomer and units from a monomer capable of ⁇ -elimination in an alkaline environment and havinq the formula wherein R is an ethylenically unsaturated radical, A, E and D are selected from H, methyl and phenyl, not more than one being methyl or phenyl and Y is an activating group e.g. ⁇ SO 2 W, ⁇ CO ⁇ T, ⁇ SO ⁇ G, ⁇ CW or -N0 2 , where W is -C 6 H 4 CH 3 , -CH 3 , -OC 2 H 5 , ⁇ C 6 H 5 , -NR 2 , -N(CH 2 C 6 H 5 ) 2 ; T is -OC 2 H 5 , -CH 3 , H, NH 2
• polymers which comprise recurring units capable of undergoing hydrolysis in an alkaline environment to convert a layer comprising one or more of said polymers from a condition of impermeability to alkali or materials soluble in or solubilized by an aqueous alkaline processing composition to a condition of substantial permeability thereto.
• Layers comprising these hydrolyzable polymers can be used as diffusion control interlayers or overcoats in diffusion transfer film units or a timing layers in such film units for the predetermined control of diffusion transfer therein.
• a photographic product comprising: a support layer; at least one photosensitive silver halide layer; an alkaline processing composition permeable image-receiving layer; and at least one diffusion control layer; said photographic product providing, as a function of development, an imagewise distribution of image-providing material diffusible to said image-receiving layer; said diffusion control layer including a polymer adapted to conversion from a condition of impermeability to alkali or materials soluble in or solubilized by an alkaline processing composition to a condition of substantial permeability thereto; such product is characterized in that said diffusion control layer includes a polymer hydrolyzable under the alkaline conditions of an alkaline photographic processing composition to said condition of substantial permeability, the hydrolyzable polymer comprising repeating units having the formula wherein R is hydrogen, halogen or lower alkyl; A and D are each independently hydrogen, alkyl, alkoxy, aryl, alkaryl or aralkyl; and Z represents a
• R S is alkyl, aryl, alkaryl or aralkyl.
• R When R is halogen or lower alkyl, it may be chloro or methyl, respectively;
• the diffusion control layers of the photographic products hereof function by forming an impermeable "barrier" layer which prevents passage or diffusion therethrough of either alkali or materials soluble in or solubilized by an aqueous alkaline processing composition for a predetermined length of time during processing of the film unit and then converting over a relatively short time period to a condition of substantial permeability to these materials as a result of the polymers hereof undergoing said predetermined hydrolysis.
• the diffusion control layers are, thus, "hold-release” layers in that materials intended to be subject to diffusion control by the layer (such as diffusible image-forming dyes) are “held” in place for a predetermined period of time and then are "released” in substantial quantity over a relatively short time period, i.e., allowed to rapidly diffuse through the layer.
• the hydrolyzable polymers hereof are capable of converting a layer comprising one or more of the polymers from a condition of impermeability to alkali or materials soluble in or solubilized by an aqueous alkaline processing composition to a condition of substantial permeability thereto by undergoing a hydrolysis reaction in an alkaline environment.
• the polymers can be variously used in diffusion control layers of photographic diffusion transfer film units.
• the diffusion control layer can, for example, be an overcoat or interlayer in a photosensitive element or negative component of a diffusion transfer film unit or can be a timing layer or overcoat in an image-receiving element or positive component of a diffusion transfer film unit.
• the desirable "hold-release" behavior of the diffusion control layers hereof may be contrasted with the diffusion control properties of diffusion control layers which are not capable of undergoing a precipitous change in permeability but rather are initially permeable to some degree, and thus allow a slow leakage of material from the start of processing, and gradually become more permeable during the processing interval.
• repeating units of formula (I) are derived from monomeric compounds containing a pendant moiety characteristics of esters and that the esters contain a substituent moiety, Z.
• the repeating units of formula (1) are hereinafter referred to simply as "hydrolyzable units".
• the nature of the Z group of the hydrolyzable units can vary depending upon the predetermined and desired diffusion control characteristics of a layer containing the polymer hereof, on the nature of any comonomeric units as may be present in the polymer, or the nature of other polymeric materials as may be present in admixture with the polymer hereof in a diffusion control layer.
• the Z group will be a moiety which activates or assists in the degradation of the polymers by alkaline hydrolysis of the pendent ester group or will be a moiety which itself is hydrolyzed with accompanying formation of a residual carboxylic anion, as described hereinafter.
• R 2 may e.g. be methyl or ethyl, phenyl, tolyl or benzyl; or wherein Y represents the radical where R 5 , R 6 , R' and W are defined as above, W may e.g. be a methyl sulfonyl group.
• Z is a cyano group, it will be appreciated that this group, owing to possible by-product formation of hydrogen cyanide, will not be preferred.
• Preferred Z groups herein are electron-with-drawing groups having the formula wherein Y is alkyl (e.g., methyl) or alkoky (e.g., methoxy or ethoxy). Accordingly, preferred polymers herein are polymers including repeating units of Formula (II) or (III) as follows, where R is hydrogen or lower alkyl and R 2 is alkyl:
• each of A and D is hydrogen, although in the case of repeating units of type represented by Formula II, it will be preferred that each of A and D be methyl.
• the Z group in the above-illustrated acetonyl acrylate polymer (i.e., the group) is believed to activate the hydrolysis of the pendant ester group thereof with the accompanying degradation and formation of the anionic acrylate species.
• the hydrolytic degradation occurs after a predetermined "hold" time such that an increase in permeability of a layer containing the polymer is observed.
• hydrolytic degradation can occur as the result of hydrolysis of the Z group itself and accompanying formation of a carboxylic anionic species.
• carboxylic anionic species can activate or assist further hydrolysis with formation of an acrylate anion, as is illustrated by the following reaction scheme:
• polymers useful herein include those containing the hydrolyzable repeating units of the following formulas:
• the polymers used in this invention can be copolymers comprising the substituted-ester hydrolyzable units and a variety of comonomeric units incorporated into the polymer to impart thereto predetermined properties.
• the "hold time" i.e., the time interval during which a diffusion control layer remains impermeable during processing, can be affected by the relative hydrophilicity of the layer resulting from incorporation of a given comonomer or mixture of comonomers into the hydrolyzable polymer.
• the more hydrophobic the polymer the slower will be the rate of permeation of alkali into a diffusion control layer to initiate the hydrolysis reaction, i.e., the longer the hold time.
• diffusion control interlayers in a film unit be initially substantially permeable to alkali, water, and various other components of the processing composition while substantially impermeable to the image-providing materials of the film unit up to a predetermined point in the development process.
• Such selective permeability can be achieved in the present invention by inclusion of appropriate comonomeric units, generally of a relatively hydrophilic nature, into the hydrolyzable polymers hereof or, more particularly, by "balancing" the hydrophobic and hydrophilic moieties to achieve the desired permeability.
• suitable comonomers for use in the present invention include acrylic acid; methacrylic acid; 2-acrylamido-2-methylpropane sulfonic acid; N-methyl acrylamide; methacrylamide; ethyl acrylate; butyl acrylate; methyl methacrylate; N-methyl methacrylamide; N-ethyl acrylamide; N-methylolacrylamide; N,N-dimethyl acrylamide; N,N-dimethyl methacrylamide; N-(n-propyl) acrylamide; N-isopropyl acrylamide; N-( ⁇ -hydroxy ethyl) acrylamide, N-(D-dimethylaminoethyl)acrylamide; N-(t-butyl) acrylamide; N-[ ⁇ 3-(dimethylamino)ethyl]methacrylamide; 2-[2'-(acrylamido) ethoxy]ethanol; N-(3'-methoxy propyl)-acrylamide
• hydrolytic degradation which the hydrolyzable polymers of the diffusion control layer used in this invention undergo ensures that those materials intended to be subject to diffusion control by the diffusion control layer are "held” in place for a predetermined period of time and then "released” over a relatively short time period, the polymer layer undergoing a relatively rapid increase in hydrophilicity and water swellability and, thus, permeability as a result of the hydrolysis reaction.
• the predetermined hold time may be adjusted as appropriate for a given photographic process by means such as controlling the mole ratio or proportion of hydrolyzable units in the polymer; altering the thickness of the diffusion control layer; incorporating appropriate comonomeric units into the polymer to impart thereto a desired hydrophobic/ hydrophilic balance or degree of coalescence; utilizing different electron-withdrawing groups Z to affect the rate of hydrolysis; or utilizing other materials, particularly polymeric materials, in the diffusion control layer to modulate the permeation therethrough of alkali or aqueous alkaline processing composition, thereby altering the time necessary for substantial hydrolysis to occur.
• This latter means of adjusting the hold time of the layer may include, for example, utilization of a matrix polymer material having a predetermined permeability to alkali or aqueous alkaline processing composition as determined, for example, by the hydrophobic/hydrophilic balance or degree of coalescence thereof.
• a matrix polymer material having a predetermined permeability to alkali or aqueous alkaline processing composition as determined, for example, by the hydrophobic/hydrophilic balance or degree of coalescence thereof.
• increased permeability to alkali or aqueous alkaline processing composition and, thus, a shorter hold time may be obtained by increasing the hydrophilicity of the matrix polymer or decreasing the degree of coalescence.
• matrix polymers may also be used to modulate the permeability of the layers to alkali or materials soluble in or solubilized by an aqueous alkaline processing composition and thus affect the functionality of the layers within a film unit.
• relatively hydrophobic matrix polymers or matrix polymers having a relatively high degree of coalescence may help to render diffusion control layers hereof substantially impermeable to alkali until hydrolysis occurs, thus providing functionality to such layers as alkali neutralization timing layers or overcoat layers in image-receiving elements or other elements of diffusion transfer film units.
• relatively hydrophilic matrix polymers or matrix polymers having a relatively low degree of coalescence may help to render diffusion control layers hereof initially permeable to alkali while remaining impermeable to materials soluble in or solubilized by an aqueous alkaline processing composition, e.g., image dye-providing materials, until hydrolysis occurs, thus providing functionality to such layers as interlayers or overcoat layers in photosensitive elements negative components or other elements of diffusion transfer film units.
• Utilization of matrix polymers can thus provide an alternative or complementary means to the above- mentioned use of suitable comonomers in the hydrolyzable copolymers hereof as a method of modulating the hold time or functionality of the diffusion control layers used in this invention. It will be understood, however, that the hydrolysis of the hydrolyzable units is necessary to achieve the relatively rapid change in permeability of the layer.
• Matrix/hydrolyzable unit polymer systems adapted to utilization in a diffusion control layer can be prepared by physical mixing of the respective polymers, or by preparation of the matrix polymer in the presence of the hydrolyzable polymer.
• a polymer containing hydrolyzable units can be formed in the presence of a preformed matrix polymer.
• Polymers which may be used as matrix polymers will generally be copolymers which comprise comonomeric units such as acrylic acid; methacrylic acid; methylmethacrylate; 2-acrylamido-2-methylpropane sulfonic acid; acrylamide; methacrylamide; N,N-dimethylacrylamide; ethylacrylate; butylacrylate; diacetone acrylamide; acrylamido acetamide; and methacrylamido acetamide.
• the comonomeric units, as well as the ratios thereof, should be chosen on the basis of the physical characteristics desired in the matrix polymer and in the diffusion control layer in which it is to be utilized. For example, a more hydrophilic and thus a generally more permeable matrix material can be had by increasing the respective ratio of hydrophilic comonomers, such as acrylic acid or methacrylic acid, within the matrix polymer.
• a particularly preferred matrix/hydrolyzable unit polymer system is a matrix system comprising about 80 to 90 parts by weight of a 50.5/44/5/0.5 part-by-weight matrix copolymer of diacetone acrylate/butyl acrylate/acrylic acid/2-acrylamido-2-methylpropane sulfonic acid; and the balance to 100 parts, i.e., 10 to 20 parts, of a 75/25 part-by-weight copolymer of carbomethoxymethyl acrylate/diacetone acrylamide.
• the hydrolyzable polymers hereof can be utilized in a number of diffusion transfer products and processes based upon imagewise transfer of a diffusible image-providing material, e.g., a diffusible dye, dye intermediate, or soluble silver complex.
• the diffusion transfer products of the present invention in the form of film units comprise as essential layers, a support layer; at least one photosensitive silver halide emulsion layer providing or having associated therewith a diffusion transfer process image-providing material (a soluble silver complex or an image-providing material other than a soluble silver complex, such as an image-dye providing material); an alkaline processing composition permeable image-receiving layer; and at least one diffusion control layer comprising the hydrolyzable polymers.
• the silver halide emulsion is developed with an aqueous alkaline processing composition and, as a function of development, an imagewise distribution of diffusible image-providing material is formed which is transferred, at least in part, to the superposed image-receiving layer.
• the diffusion control layers of such film units may be used to control diffusion of alkali or of the image-providing material in accordance with the disclosures contained herein.
• Products within the present invention in the form of film units include those wherein the silver halide emulsion layers and the image-receiving layer are initially contained in separate elements.
• Such film units may thus comprise: (a) a photosensitive element comprising a support layer which is preferably opaque and a negative component comprising at least one photosensitive silver halide emulsion layer providing or having associated therewith a diffusion transfer process image-providing material; (b) an image-receiving element comprising a support layer which may be opaque or transparent as appropriate for a given process and a positive component comprising .an image-receiving layer; and (c) a diffusion control layer comprising the polymers used in this invention in at least one of said photosensitive element or image-receiving element.
• the respective elements may be brought into superposition subsequent or prior to exposure. Subsequent to exposure, an aqueous alkaline processing composition is distributed between the superposed elements to initiate development.
• the image-receiving element provides an opaque reflective background
• the image formed may be viewed as a reflection print upon separation of the elements.
• the resultant image may be viewed as a transparency upon separation of the elements.
• the photosensitive element and/or processing composition contains a light reflecting layer, e.g., a white pigment such as titanium dioxide
• the image may be viewed as a reflection print against the background provided by the light-reflecting layer, without separation of the elements.
• the photosensitive element may also comprise a neutralization layer, e.g., an acid polymer layer, and a timing layer positioned between the support layer and the negative component with the neutralization layer positioned adjacent the support.
• the environment pH of the film unit may be lowered.
• the timing layer functions to prevent premature pH reduction by slowing diffusion of the alkali toward the neutralization layer.
• the diffusion control layers used in this invention can also be used in diffusion transfer film units wherein the photosensitive layers and image-receiving layer are in a single element, i.e. integral negative-positive film units wherein the negative and positive components are contained in a photosensitive laminate or otherwise retained together in a superposed relationship at least prior to exposure.
• the diffusion control layers herein can be used in integral film units of the type described in US-A-3,415,644, which film units are particularly adapted for formation of color images.
• Film units of this type include, for example, those comprising: (a) a photosensitive laminate comprising a composite structure containing, in sequence, an opaque support layer, preferably an actinic radiation-opaque flexible sheet material, a negative component comprising at least one photosensitive silver halide emulsion layer providing or having associated therewith an image dye-providing material, a positive component comprising an image-receiving layer dyeable by the image dye-providing material, and a transparent support layer, preferably an actinic radiation transmissive flexible sheet material, the photosensitive laminate also comprising a diffusion control layer comprising the polymers of the present invention; (b) means retaining an aqueous alkaline processing composition integrated with the film unit so that the processing composition can be distributed between the negative and positive components.
• a light-reflecting pigment is preferably provided by the processing composition such that the distribution of the processing composition between the negative and positive components provides a light-reflecting layer against which a dye image formed in the image-receiving layer can be viewed without separation of the components.
• the diffusion control layers of this invention can also be used in integral negative-positive film units of the type described in U.S.-A-3,594,165.
• Film units of this type include, for example, those comprising: (a) a photosensitive laminate comprising, in sequence, a transparent support layer, preferably an actinic radiation transmissive flexible sheet material, a positive component comprising an image-receiving layer, a processing composition permeable, light-reflecting layer against which a dye image formed in the image-receiving layer can be viewed, and a negative component comprising at least one photosensitive silver halide emulsion layer providing or having associated therewith an image dye-providing material; (b) a transparent sheet superposed substantially coextensive the surface of photosensitive laminate opposite the transparent layer; (c) means retaining an aqueous alkaline processing composition, which includes an opacifying agent, integrated with the film unit such that the processing composition can be distributed between the photosensitive laminate and the transparent sheet; and (d) a diffusion control
• the essential photosensitive and image-receiving layers and a diffusion control layer hereof can be provided on a single support layer and the film unit can be processed, for example, by imbibing the photoexposed film unit in a photographic processing composition.
• Multicolor images may be prepared in the products of the present invention in the form of film units which comprise at least two selectively sensitized silver halide emulsion layers, each associated with an image dye-providing material which provides an image dye possessing spectral absorption characteristics substantially complementary to the predominant sensitivity range of its associated emulsion.
• the most commonly employed negative components for forming multicolor images are of the tripack structure and contain blue, green, and red sensitive silver halide layers each having associated therewith in the same or a contiguous layer a yellow, a magenta, and a cyan image dye-providing material respectively.
• each of the silver halide emulsion layers, and its associated image dye-providing material be spaced from the remaining emulsion layers, and their associated image dye-providing materials, by separate alkaline solution permeable interlayers, such as those provided by the instant invention.
• each dye developer is associated with a separate silver halide emulsion layer and is, most preferably, substantially soluble in the reduced form only at the first pH provided by the processing composition, possessing subsequent to photoexposure or processing a spectral absorption range substantially complementary to the predominant sensitivity range of its associated emulsion.
• the processing composition is applied and permeates the emulsion layers to initiate development of the latent image contained therein.
• the dye developer is immobilized or precipitated in exposed areas as a consequence of the development of the latent image.
• unexposed and partially exposed areas of the emulsion the dye developer is unreacted and diffusible and thus provides an imagewise distribution of unoxidized dye developer dissolved in the liquid processing composition, as a function of the point-to-point degree of exposure of the silver halide emulsion. At least part of this imagewise distribution of unoxidized dye developer is transferred, by imbibition, to a superposed image-receiving layer, said transfer substantially excluding oxidized dye developer.
• the image-receiving layer receives a depthwise diffusion, from the developed emulsion, of unoxidized dye developer without appreciably disturbing the imagewise distribution thereof to provide the reversed or positive color image of the developed image.
• the image-receiving layer may contain agents adapted to mordant or otherwise fix the diffused, unoxidized dye developer.
• the environmental pH of the film unit be adjusted downward to a second pH at which the residual dye developers remaining within the negative structure are precipitated or otherwise rendered non-diffusible in either their reduced or oxidized state.
• the pH adjustment is generally accomplished by means of an acid neutralization layer, preferably a polymeric acid layer, as detailed hereinbelow.
• FIG. 1 sets forth a perspective view of an integral film unit of the type described in referenced U.S.-A-3,415,644, shown with the processing composition 26 distributed between the negative and positive components.
• Film unit 10 comprises photosensitive laminate 11 including in order, opaque support layer 12; cyan dye developer layer 13; red-sensitive silver halide emulsion layer 14; interlayer 15; magenta dye developer layer 16; green-sensitive silver halide emulsion layer 17; interlayer 18; yellow dye developer layer 19; blue-sensitive silver halide emulsion layer 20; overcoat layer 21; image-receiving layer 22; spacer layer 23; neutralizing layer 24; and transparent support layer 25.
• processing composition 26 Following photoexposure through transparent support layer 25, processing composition 26, initially retained in a rupturable container (not shown) is distributed between overcoat layer 21 and image-receiving layer 22to initiate development of the silver halide emulsion layers. It is preferred that processing composition 26 contains an opacifying agent of the type described for example, in U.S.-A-3,647,437, such that the layer of processing composition 26 is able to prevent further exposure of the photosensitive layers of the film unit during the processing of the film unit outside of the camera. As a consequence of development, an imagewise distribution of diffusible dye developer is formed which is transferred, at least, in part to image-receiving layer 22.
• the layer provided by processing composition 26 preferably comprises a light-reflecting pigment, such as titanium dioxide, against which the color image formed in image-receiving layer 22 can be viewed. Subsequent to substantial transfer image formation, a sufficient portion of the alkali provided by processing composition 26 permeates image-receiving layer 22 and spacer layer 23, to gain access to neutralizing layer 24 whereupon neutralization of the alkali occurs to lower the pH of the system to a level at which the dye developers are insoluble and non-diffusible, to provide thereby a stable color transfer image.
• a light-reflecting pigment such as titanium dioxide
• spacer layer 23 and neutralizing layer 24 may be disposed intermediate support layer 12 and cyan dye developer layer 13, with neutralizing layer 24 positioned adjacent to support layer 12.
• the alkali provided by processing composition 26 permeates layers 13 through 21 and spacer layer 23 to gain access to neutralizing layer 24 whereupon neutralizing of the alkali is effected as described hereinabove.
• magenta dye-developer of layer 16 If it is possible for the magenta dye-developer of layer 16 to back-diffuse to red-sensitive silver halide emulsion layer 14 before substantial development of this layer and resultant substantial formation of an imagewise distribution of the cyan dye developer in layer 13, some of the magenta dye developer may become oxidized and rendered non-diffusible as a function of red exposure and development of the red-sensitive emulsion layer. Thus, there is produced a loss in magenta dye density in the transfer image. Moreover, that portion of cyan dye developer which should have been oxidized in preference to the magenta dye developer remains in the reduced form and may diffuse to image-receiving layer 22 with resultant cyan dye contamination of the transfer image. Thus, accurate color reproduction of a photographed object is hindered by such inter-image effects.
• diffusion control layers hereof may be employed as interlayers positioned between the respective silver halide layers, and their associated dye developers, such as interlayers 15 and 18 in FIG. 1.
• the hydrolysis step undergone by the hydrolyzable polymer(s) within these layers ensures a delay in permeability of these layers during initial processing of the film unit and thus "holds” the dye developer and substantially prevents diffusion to unassociated silver halide layers at least until after substantial development of these layers and formation of the intended imagewise distributions of the dye developers.
• the "release" of the diffusible dye developers should occur prior to substantial fogging of the emulsion layer with the most rapid fogging rate.
• the "hold-release" behavior of the interlayers used in this invention provides advantages over those interlayers which allow a slow leaking of dye developer at the start of the processing interval in that the dye developers are better confined to their associated emulsion layer during the critical initial development interval and then released rapidly and in substantial quantity so as to allow rapid and essentially simultaneous transfer of the color image-forming materials.
• interlayers comprising the polymers hereof may be used to provide increased capacity for accurate color reproduction over a range of temperatures.
• the lowering of the temperature at which processing occurs slows both the rate of development and the rate of dye diffusion. If the respective rates are slowed disproportionately, i.e., if the decrease in the development rate is proportionately greater than the decrease in the rate of diffusion, color reproduction may be adversely affected by diffusion of the dye away from its associated emulsion layer prior to substantial development of that layer.
• interlayers comprising the polymers hereof which have been found to provide markedly longer "hold” times at lower temperatures, e.g., 7°C relative to the "hold” time observed at higher temperatures, e.g., 24°C.
• the interlayers may be utilized to hold the dye developer in association with the silver halide emulsion for longer time periods at lower temperatures to accommodate the system to slower development rates at these temperatures while allowing for a proportionately faster "release" as the temperature and development rate increase.
• overcoat layers of photosensitive elements or negative component overcoat layers such as overcoat layer 21 in FIG. 1.
• overcoat layers can be used, for example, to prevent premature migration of the dye developer most proximate to the distributed processing composition or to provide a means by which the various color image-forming materials may be made available essentially simultaneously to the mordant sites within the image-receiving layer.
• the processing compositions employed in diffusion transfer processes of the type contemplated herein usually are highly alkaline, having a pH in excess of 12 and frequently in excess of 14 or higher.
• the highly alkaline environment facilitates the conduct of dye diffusion to provide satisfactory diffusion rates and image dye densities.
• the environment pH of the film unit be lowered to at least 11 or lower subsequent to substantial transfer image formation to achieve improved stability to the dye image.
• U.S.-A-3,415,644 discloses that in integral film units wherein the negative and positive components remain in a superposed contiguous relationship subsequent to substantial transfer image formation, an in-process adjustment of the environmental pH of the film unit from a pH at which transfer processing is operative to a pH at which dye transfer is inoperative subsequent to substantial transfer image formation is highly desirable in order to achieve a more stable dye transfer image in terms of the chemical and light stability of the image dye molecules and in terms of preventing post-processing transfer of residual image dye-providing materials within the negative structure to the image-receiving layer.
• reduction in the environmental pH of the film unit is preferably achieved by conduct of a neutralization reaction between the alkali provided by the processing composition and a layer comprising immobilized acid reactive sites, i.e., a neutralization layer.
• Preferred neutralization layers are those comprising a polymeric acid such as cellulose acetate hydrogen phtalate; polyvinyl hydrogen phtalate; polyacrylic acid; polystyrene sulfonic acid; and partial esters of polyethylene/maleic anhydride copolymers.
• Premature pH reduction as evidenced, for example, by a decrease in image dye density, can be prevented by interposing, between a neutralization layer and a layer of processing composition, a spacer or timing layer which slows diffusion of the alkali toward the neutralization layer.
• diffusion control layers of this invention may be used as such timing layers, forming an alkali impermeable barrier for a predetermined time interval and then converting to a relatively alkali permeable condition upon occurrence of hydrolysis to allow the alkali access to the neutralization layer in a rapid and quantitavely substantial fashion.
• timing layers comprising the hydrolyzable polymers hereof can be used in image-receiving elements of the type disclosed in U.S.-A-3,362,819 or as a component part of the positive component of integral negative-positive film units of the type disclosed in previously referenced U.S.-A-3,415,644 and 3,594,165.
• the timing and neutralization layers may be associated with the negative component as is disclosed, for example, in U.S.-A-3,362,821 and 3,573,043.
• these layers may also be carried by a transparent sheet employed to facilitate application of a processing composition.
• Image-receiving element 27 comprises in order a support layer 28, a neutralizing layer 29, a spacer of timing layer 30 comprising a hydrolyzable polymer used in the present invention, and an image-receiving layer 31.
• the processing composition penetrates image-receiving layer 31 to provide a sufficient pH for image formation therein and is then subsequently neutralized by penetrating through timing layer 30 upon hydrolysis of the diffusion control polymer contained therein to gain access to neutralizing layer 29.
• the permeability of the diffusion control layers used in this invention to alkali may be controlled in a predetermined manner by the use of comonomeric units which provide to the polymer a suitable hydrophilic/hydrophobic balance and/or a suitable degree of coalescence or by the use of a matrix material providing the required hydrophilicity or coalescence.
• increased hydrophobicity and coalescence will render the diffusion control layer relatively less permeable to alkali and to the processing composition prior to the hydrolysis reaction.
• an overcoat layer comprising the polymers hereof may be provided to the image-receiving element or positive component of the film unit contiguous the image-receiving layer and opposite the neutralization layer.
• Overcoat layers of this type in this position within the film unit may function to control diffusion of alkali or materials soluble in or solubilized by an aqueous alkaline processing composition.
• the permeation characteristics of the polymers hereof utilized in timing layers can be evaluated by measuring the time necessary for downward adjustment of the environmental pH to a predetermined lower level as evidenced by color transition of an indicator dye, preferably initially contained in the processing composition, from a colored form at the initially high processing composition pH to a colorless form at said predetermined lower pH level. Evaluations of this type may be carried out utilizing a test structure comprising in order a support, a polymeric acid layer, a test timing layer, and an image-receiving layer.
• a transparent cover sheet is superposed coextensive the test structure contiguous to the image-receiving layer and an alkaline processing composition (comprising an indicator dye which is highly colored at a pH of 12 or higher and colorless below a predetermined lower pH level of about 9 or 10) is spread between the cover sheet and the image-receiving layer.
• the indicator dye remains colored, and may be viewed as such through the transparent cover sheet, until the alkali penetrates through the test timing layer to gain access to the polymeric acid whereupon neutralization of a substantial portion of the alkali present occurs to lower the pH to a level at which the indicator dye is colorless.
• the measurement of the time necessary for substantial "clearing" of the indicator is generally referred to as the "clearing time".
• Test structures comprising timing layers which allow a slow initial leakage of alkali and gradually become more permeable show no precipitous change in color but rather a gradual clearing while structures comprising the timing layers described herein will show a precipitous change in color after an initial delay evidencing the rapid change in alkali permeability undergone by the timing layer upon hydrolysis.
• the capacity of diffusion control layers comprising polymers hereof to delay permeation therethrough of dye image-providing materials until conversion by hydrolysis to a relatively dye-permeable condition can be evaluated by utilization of the test structure shown in FIG. 3.
• transfer of the image dye-providing material through the test diffusion control layer is monitored in relation to time.
• the "hold-release" properties of the hydrolyzable polymer test material can be evaluated in simulation of the functioning of the material, e.g., as an interlayer in a photosensitive element.
• Such test structure and a suitable method of evaluation are set forth in detail in Example 6.
• the polymers used in the present invention can be prepared by polymerization in known manner of a polymerizable monomeric ester of the formula (IV) wherein R, A, D and Z have the meanings aforedescribed.
• the monomeric esters of formula (IV) can, for example, be suitably prepared by reaction of an acrylic acid halide (e.g., chloride) of the formula (V): (wherein R as the aforedescribed meaning and Hal represents halide) with an alcohol having the formula (VI) (wherein each of A, D and Z has the aforedescribed meaning).
• the monomeric ester can be prepared by reaction of the acrylic acid with a halogen- substituted ester in accordance with the following representative reaction scheme which illustrates the preparation of carbomethoxymethyl acrylate:
• the monomers prepared by any of the above methods may be polymerized according to different polymerization techniques such as bulk, solution, suspension, or emulsion polymerization.
• the polymerization may be conducted in the presence of the suitable polymers, i.e., a polymeric matrix material, to prepare a matrix system which may be used as a diffusion control layer.
• the polymerization can be initiated chemically, e.g., by suitable free radical or redox initiators or by other means such as heat or incident radiation.
• suitable free radical or redox initiators or by other means such as heat or incident radiation.
• chemical initiators mention may be made of azobisisobutyronitrile, potassium persulfate, sodium bisulfite, benzoyl peroxide, diacetyl peroxide, hydrogen peroxide, and diazo- aminobenzene.
• the chosen means of initiation should be substantially incapable of degrading or otherwise adversely reacting with either the reactants or products of the reaction.
• the amount of catalyst used and the reaction temperature may be varied to suit particular needs.
• the polymerization should proceed satisfactorily by carrying out the reaction at a temperature between 25°C and 100°C and using less than 5% by weight of initiator, based on the starting weight of the polymerizable monomer or monomers.
• the ice bath was replaced by a water bath to control the mildly exothermic reaction between 22­27°C for 28 hrs.
• the mixture was vacuum filtered, and the filter cake was washed with methylene chloride (2 x 100 ml) and pressed dry with a rubber dam.
• the crude, dark amber oil (524-532 g) was distilled at reduced pressure through a standard Claisen head, giving, after an initial forerun (30-35 g), the hydroxyacetone acrylate as a colorless liquid (307-320 g, 60 ⁇ 64% yield, b.p. 52-5°C/1.5-0.9 mm).
• a mixture of 128 g of deionized water and 0.20 g of emulsifier (dioctyl sodium sulfosuccinate, available as Aerosol OT-75 from American Cyanamid Company) was heated to 80°C under a nitrogen atmosphere.
• emulsifier dioctyl sodium sulfosuccinate, available as Aerosol OT-75 from American Cyanamid Company
• a first portion five parts by weight of the total
• a monomeric mixture consisting of 25 grams hydroxyacetone acrylate prepared as described in EXAMPLE 1, 36.2 g methyl methacrylate, 1.25 g methacrylic acid and 0.12 g of Aerosol°OT-100 emulsifier.
• 0.25 g of ammonium peroxydisulfate was introduced into the resulting mixture.
• the hydrolyzable polymer prepared in the manner described in Example 2 was evaluated using a test structure, 32 in FIG. 3, comprising a transparent support 33; a layer 34 comprising about 215 mg/m 2 of a cyan dye developer of the formula about 430 mg/m 2 gelatin, and about 16 mg/m 2 of succindialdehyde; and a layer 35 containing about 2150 mg/m 2 of the polymeric material. Layers 34 and 35 were coated sequentially on support 33 using a conventional loop coater.
• a transparent sheet 37 comprising a polyester clear film base wsa superposed with test structure 32 and an opaque alkaline processing composition 36 comprising: was introduced between polymeric test material layer 35 and transparent sheet 37 at a gap of 0.071 mm.
• the optical reflection density to red light of the sample was monitored through transparent support 33 as function of time by use of a MacBeth Ouanta-LogO densitometer equipped with a strip-chart recorder.
• the density measured as a function of time was that of the cyan dye developer in the original dye-containing layer 34 and the cyan dye developer in polymer test layer 35.
• Dye developer which had diffused through test layer 35 into the processing composition was masked by the titanium dioxide contained therein and, thus, did not contribute to the red absorption. In this manner, the diffusion of dye developer through the test layer and into the processing composition could be monitored.
• FIG. 4 is shown a curve of red absorption density as a function of time where t, is the time for the cyan dye developer to become wetted by the processing composition, t 2 is the total time the cyan dye developer is held back by the polymer interlayer, Do is the absorption density after dissolution of the dye developer, and D f is the final absorption density of the residual dye developer remaining in layers 34 and 35 after completion of dye diffusion.
• the slope of the line segment between A and B is calculated and serves as an indication of the rapidity with which the test layer undergoes a change in dye permeability.
• the polymeric material prepared as described in EXAMPLE 2 herein was blended with a matrix copolymer and was coated and evaluated as a diffusion control test layer 35 in the above-described test structure. Values for t, and t, (in seconds) and slope were determined.
• the polymeric material of EXAMPLE 2 is referred to in Table 1 as Component X.
• the blend was comprised of 30 parts Component X and 70 parts of Component Y (a copolymer of diacetone acrylamide/butylacrylate/acrylic acid/2-acrylamido-2-methylpropane sulfonic acid, 50.5/44/5/0.5 parts by weight, respectively). Results are reported in Table 1 as follows:
• the organic solution (about 3.5 to 3.75 liters) was then dried (magnesium sulfate) and evaporated in vacuo (water apirator) at ⁇ 30°C to provide a very pale-yellow product.
• the product was purified by addition of 1 g of 2,6-di-tert-butyl-p-cresol as a free radical inhibitor and vacuum distilling through a distillation column. The purified product exhibited a boiling point of 50°C (1.2 mm) to 56°C (1.9 mm).
• matrix/hydrolysable unit polymer system comprising 80 parts of 50.5/44/4/0.5 copolymer of diacetone acrylamide/butyl acrylate/acrylic acid/2-acrylamido-2-methylpropane sulfonic acid; and 20 parts 75/25 copolymer of carbomethoxymethyl acrylate/diacetone acrylamide.
• the latex was slowly heated over a two-hour period to 80°C with continued stirring and nitrogen flow.
• a solution of polymerization initiator (prepared by dissolving 2.66 g of ammonium persulfate in 167 ml of deionized water that had been nitrogen purged for at least ten minutes) was placed into a dropping funnel and was added to the reaction flask at maximum rate. After one minute the subsurface nitrogen purge was changed to a blanket and the flow was increased to five ml/min. At 1.5 minutes after the addition of the initiator solution, the addition of a solution of monomers was commenced, at a feed rate of 8.15 ml/minute. The addition was effected uniformly over a period of 1.5 hours.
• the monomer feed solution (which had been prepared by stirring together 183.3 g of diacetone acrylamide, 550 g of carbomethoxymethyl acrylate prepared as described in EXAMPLE 4, and 0.62 g of Aerosol OT-100 emulsifier and filtering the mixture) contained the respective polymerizable monomers thereof at a ratio of 25/75 by weight.
• the reaction vessel contents were heated for 90 minutes at a temperature of 80°C.
• the polymerization product was cooled to room temperature and filtered through cheese cloth.
• the solids content of the polymeric product was about 31.3% by weight.
• a solution of monomer feed was prepared by: mixing in a beaker 509.4 g diacetone acrylamide, 389.4 grams butyl acrylate, 3.0 g acrylic acid, 198 g ethyl acrylate, 198 grams carbomethoxymethyl acrylate and 3.2 g Aerosol O OT-75; placing the mixture in a 35°C water bath; stirring the contents to facilitate dissolution, while maintaining the temperature below 25°C; and filtering the resulting solution.
• a solution of initiator was prepared by mixing 40 ml of water and 7.3 g ammonium persulfate and the initiator solution was set aside.
• a first portion of the monomer feed solution (65 g; 5% of the solution) was charged to the reaction vessel without opening the vessel to the atmosphere.
• the nitrogen inlet tube was adjusted above the liquid surface to provide a nitrogen blanket and flow was reduced to 80 ml/minute.
• the initiator solution was then charged to the reaction vessel without opening the vessel to the atmosphere.
• the remaining portion (95%) of the monomer feed solution was introduced uniformly over a four-hour period.
• the batch was heated for one hour at 80°C, was cooled to ambient temperature and filtered through cheese-cloth to provide a polymeric latex.
• a photographic diffusion transfer film unit was prepared in the following manner.
• a 0.18 mm. subbed polyethylene terephthalate transparent support (containing a minor amount of carbon black for protection against light piping and halation effects) was coated successively with the following layers:
• the photographic film unit was photoexposed (four meter-candle-seconds) to a test target, or step wedge, from the direction of the transparent support.
• the film unit was then processed in a darkroom in a bath of alkaline photographic processing composition by introducing the photoexposed film unit into a light-tight chamber containing a photographic processing composition (at room temperature, 22°C) having the following composition:
• the film unit was removed from the bath through a pair of rollers (to remove excess fluid) and into the darkness of the darkroom where the film unit remained for an additional 1.5 minutes. The film unit was then brought into ambient light. A photographic image was viewed as a reflection image against light-reflecting layer 13 described hereinbefore.

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• 1984
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