US3853562A

US3853562A - Container for diffusion transfer films with whitening agent containing processing solution

Info

Publication number: US3853562A
Application number: US00400134A
Authority: US
Inventors: E Land; S Bloom
Original assignee: Polaroid Corp
Current assignee: Polaroid Corp
Priority date: 1973-09-24
Filing date: 1973-09-24
Publication date: 1974-12-10
Anticipated expiration: 1991-12-10

Abstract

This invention relates to photographic film units adapted for forming color transfer images viewable by reflected light and to diffusion transfer processes employing these film units wherein a non-fluorescent optical whitening reagent is provided in association with the transfer image to offset the color stain that tends to form in the image highlights during aging. The whitening reagent may be a non-fluorescent pigment or a nonfluorescent dye capable of absorbing visible light in a wavelength range complementary to the wavelength range absorbed by the color stain and is used in a concentration such that the highlights, i.e., Dmin areas of the transfer image appear substantially white initially and after aging, as observed by the eye.

Description

limited atet 1 Land et al.

[ CONTAINER FOR DIFFUSION TRANSFER FILMS WITH WHITENING AGENT CONTAINING PROCESSING SOLUTION Inventors: Edwin H. Land, Cambridge; Stanley M. Bloom, Waban, both of Mass.

Assignee: Polaroid Corporation, Cambridge,

Mass.

Filed: Sept. 24, 1973 Appl. No.1 400,134

Related U.S. Application Data Division of Ser. No. 247,048, April 24, 1974, Pat. No. 3,802,881.

U.S. Cl. 96/76 C, 96/66 R Int. Cl G03c 1/48, G03c 5/30 Field of Search 96/66 R, 76 C, 3, 29 D,

References Cited UNITED STATES PATENTS Land 96/3 cc. 10, I974 3,802,881 4/1974 Land 96/3 Primary Examiner-David Klein Assistant Examiner-Richard L. Schilling Attorney, Agent, or Firm-Sybil A. Campbell [5 7] ABSTRACT This invention relates to photographic film units adapted for forming color transfer images viewable by reflected light and to diffusion transfer processes employing these film units wherein a non-fluorescent optical whitening reagent is provided in association with V the transfer image to offset the color stain that tends to form in the image highlights during aging. The whitening reagent may be a non-fluorescent pigment or a non-fluorescent dye capable of absorbing visible light in a wavelength range complementary to the wavelength range absorbed by the color stain and is used in a concentration such that the highlights, i.e., D areas of the transfer image appear substantially white initially and after aging, as observed by the eye.

9 Claims, 7 Drawing Figures I PNEMEL, SEC 1 01974 WEEK 2 BF &

Mai

553 mwoim/ mu J 623585 @645.

PATENTE; 15 I 05973 SHEH 3%? Q CONTAINER EOR DIFFUSION TRANSFER FILMS WITI-I WHITENING AGENT CONTAINING PROCESSING SOLUTION CROSS REFERENCE TO RELATED APPLICATIONS This application is a division of application Ser. No. 247,048 filed Apr. 24, 1974, now US. Pat. No. 3,802,881.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to photography, and more particularly, it relates to diffusion transfer photographic film units adapted to provide reflection prints with improved highlights and to diffusion transfer photographic processes employing the same.

2. Description of the. Prior Art A number of photographic processes by which images may be developed and viewed within seconds or minutes after exposure have been proposed. The most useful of such processes are diffusion transfer processes, and several have been commercialized for the production of photographic images in both black-andwhite and in color. In particularly useful color diffusion transfer processes, color images are obtained by exposing a photosensitive component comprising at least one photosensitive layer, e.g., a light-sensitive silver halide layer, having a dye image-providing material associated therewith in the same or in an adjacent layer, to form a developable image; developing this exposed element with a processing composition to form an imagewise distribution of a soluble and diffusible image-providing material; and transferring this imagewise distribution, at least in part, by diffusion, to a superposed imagereceiving component comprising at least a dyeable stratum to impart to this stratum a color transfer image. The photosensitive and image-receiving components may be separate elements which are brought together during processing and thereafter either retained together as the final print or separated following image formation; or they may together comprise a unitary structure, e.g., an integral negative-positive film structure wherein the negative, i.e., photosensitive compo nent and the positive, i.e., the image-receiving component are laminated and/or otherwise physically retained together at least prior to image formation.

Of particular interest are those integral negativepositive film structures adapted for forming color transfer images viewable without separation, i.e., wherein the photosensitive component containing the dye transfer image need not be separated from the imagereceiving component for viewing purposes. Examples of such film units are those described and claimed in U.S. Pat. Nos. 3,415,644, 3,415,645, 3,415,646, 3,573,043 and 3,573,044 in the name of Edwin H. Land and in US. Pat. Nos. 3,594,164 and 3,594,165 in the name of Howard G. Rogers.

In general, in the film units described in these patents, the essential layers, namely, the photosensitive layer(s) and associated dye image-providing material and dyeable stratum are preferably contained on a transparent dimensionally stable layer or support member positioned closest to the dyeable stratum so that the resulting transfer image is viewable through this transparent layer. Most preferably, another dimensionally stable layer which may be transparent or opaque is positioned on the opposed surface of the essential layers so that these layers are sandwiched or confined between a pair of dimensionally stable layers or support members, at least one of which is transparent to permit viewing therethrough of a color transfer image obtained as a function of development of the exposed film unit in accordance with known color diffusion transfer processes. These film units optionally may contain other layers capable of performing specific desired functions and preferably also include a neutralizing layer to reduce the pH following substantial transfer of dye image-providing material to a pH at which said image-providing material is substantially non-diffusible. In a particularly preferred form such film units are employed in conjunction with a rupturable container of known description containing the requisite processing composition and adapted upon application of pressure of applying its contents to develop the exposed film unit, e.g., by applying the processing composition in a substantially uniform layer between the dyeable stratum and the photosensitive component.

Common to these composite photographic film units is the provision of a reflecting layer between the dyeable stratum and the photosensitive component in order to mask effectively the silver image or images formed as a function of development of the silver halide layer or layers and any remaining associated dye image-providing material and to provide a background for viewing the color transfer image formed in the dyeable stratum, without separation, by reflected light. This reflecting layer may comprise a preformed processing composition permeable layer of a lightreflecting agent included in the essential layers of the film unit or the light-reflecting agent may be provided after photoexposure, e.g., by including the reflecting agent in the processing composition. In addition to masking the photosensitive component and providing a background for viewing the transfer image as a color reflection print, the reflecting layer also helps to protect the photoexposed silver halide layers from postexposure fogging by light passing through the transparent support member if the photoexposed film unit is removed from the camera before image formation is complete.

US. Pat. No. 3,647,437 in the name of Edwin H. Land is concerned with improvements in the abovedescribed composite film units and diffusion transfer processes employing these unitary structuresand discloses the provision of light-absorbing materials to permit such processes to be performed outside of the camera in which photoexposure is effected and under much more intense ambient light conditions. A lightabsorbing material or reagent, preferably a dye, is provided so positioned and/or constituted as not to interfere with photoexposure but so positioned between the photoexposed silver halide layers and the transparent support during processing after photoexposure as to absorb light which otherwise might fog said photoexposed layers. After processing, the light-absorbing material is so positioned and/or constituted as not to interfere with viewing the desired image shortly after said image has been formed. In the preferred embodiments, the light-absorbing material, also sometimes referred to as an optical filter agent, is initially contained in the processing composition together with a light-reflecting agent. In a particularly useful embodiment, the lightabsorbing dye selected as the optical filter agent is highly colored at the initial pH of the processing composition but is substantially non-light-absorbing in the visible spectrum at a lower pH which is attained after substantial transfer of dye image-providing material and which is effected by an acid-reacting reagent, e.g., the neutralizing layer mentioned previously. Color changing, i.e. pH sensitive dyes, especially useful as optical filter agents in this embodiment form the subject matter of copending US. Pat. application Ser. No. 103,392 of Myron S. Simon and David P. Waller filed Jan. 4, 1971, now US. Pat. No. 3,702,245, and Ser. No. 108,260 of Stanley M. Bloom, Alan L. Borror, Pauls S. Huyffer and Paul T. MacGregor filed Jan. 21, 1971, now US. Pat. No. 3,702,244.

In the utilization of composite film structures of the aforementioned type, it has been observed that color stain tends to build up in the image highlight areas of the reflection print in time. Though fluorescent dyes are commonly used as optical brighteners in various photographic products to counteract staining in the image highlights, such dyes are subject to certain disadvantages Because they depend upon irradiation with ultraviolet light for emitting visible light, their efficiency is reduced when used in conjunction with conventional UV absorbers and their visual effectiveness differs according to the light, i.e., natural or artificial illumination used for viewing the photographic image. Also, most of the fluorescent dyes used as optical brighteners tend to decompose upon prolonged exposure to irradiation.

The present invention is concerned with enhancing the whiteness of the non-image or highlight areas of color reflection prints without the use of fluorescent materials by adding to the photographic system, a non-fluorescent optical whitening reagent, i.e., a non-fluorescent reagent which has a color complementary to that of the stain such that the combination of reagent color plus stain color reflects substantially white light. By balancing the stain color with a reagent having a complementary color, the light reflected from the D,,,,-,, areas of the reflection print, as visually perceived, appears to be white.

SUMMARY OF THE INVENTION It is, therefore, the primary object of the present in- I vention to provide diffusion transfer photographic products and processes of the foregoing description adapted to produce color reflection prints possessing a whiter background and cleaner highlights.

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

The invention accordingly comprises the processes involving the several steps and the relation and order of one or more of such steps with respect to each of the others, and the products and compositions possessing the features, properties and the relation of elements which gre exemplified in the followingdetailed disclosure, and the scope of the application of which will be indicated in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a photographic film unit embodying the invention;

FIGS. 2, 4 and 6 are diagrammatic enlarged crosssectional views of the film unit of FIG. 1, along section line 22, illustrating the association of elements during the three illustrated stages of the performance of a diffusion transfer process, for the production of a mul- .ticolor transfer image according to the invention, the thickness of the various materials being exaggerated. and wherein FIG. 2 represents an exposure stage, FIG. 4 represents a processing stage and FIG. 6 represents a product of the process; and

FIGS. 3, 5 and 7 are diagrammatic, further enlarged cross-sectional views of the film unit of FIGS. 2, 4 and 6, along section lines 3-3, 5-5 and 7-7, respectively, further illustrating, in detail, the arrangement of layers comprising the photosensitive laminate during the three illustrated stages of the transfer process.

DESCRIPTION OF THE PREFERRED EMBODIMENTS As noted above, it has been found that the problem of color stain build up observed in diffusion transfer systems where the photosensitive and image-receiving components of the film unit are retained together after development and transfer image formation may be obviated by adding to the photographic system a nonfluorescent optical whitening reagent, i.e., a reagent having a color complementary to the color of the stain in a quantity such that the color added will balance or offset the color of the stain. Stated another way, the non-fluorescent reagent employed in the present invention should be capable of absorbing visible radiation within a predetermined wavelength range complementaryto the wavelength range absorbed by the color stain and should be added in a concentration such that the light reflected from the highlights, i.e., the D areas of the transfer image both initially and upon aging appears to be substantially white, as observed by the eye. Also, it has been found that adding color to the photographic system in this manner does not cause any apparent darkening of the highlights, i.e., any darkening that is visually discernible to the viewer.

The whitening reagent employed may be any non-- fluorescent pigment or non-fluorescent dye having a color complementary to that of the stain, or it may be a substantially colorless dye precursor, such as, a temporarily shifted dye which assumes a color complementary to that of the stain when contacted with the aqueous alkaline processing composition. Though the whitening reagent may be soluble or insoluble in the aqueous alkaline processing composition, it should be nondiffusible in the processing composition or capable of being rendered substantially non-diffusible in the appropriate layer or layers of the film unit associated with the transfer image subsequent to processing. In the present invention, the whitening reagent is distributed in a substantially uniform layer, i.e., in a non-imagewise fashion, and as discussed hereinafter, the whitening reagent should be finally positioned in the reflecting layer and/or in the image-receiving component.

Suitable whitening reagents having the necessary color characteristics may be selected from arylmethane, anthraquinone, indigoid, indanthrone, methine, azomethine, quinoline, azo, phthalocyanine and any of the various other classes of pigments and dyes known in the art. If desired, a combination of pigments and/or dyes may be used for obtaining the appropriate color characteristics needed for absorbing light in the wavelength range complementary to the wavelength range absorbed by the stain.

It will be appreciated that the pigment and/or dye selected should be stable in the photographic system under the processing conditions encountered and should be stable to prolonged exposure to light. Likewise, the dye precursors if employed should be stable in their colored form.

To achieve efficient color-balancing of the stain and to prevent migration into other layers of the film unit where its presence may be undesirable, the whitening reagent should be finally positioned. in the lightreflecting layer and/or in the image-receiving component, i.e., in a layer or layers between the reflecting layer and the source of light used for viewing the color transfer image. Usually, the whitening reagent is ultimately positioned in the reflecting layer and/or in the next adjacent layer of the image-receiving component, i.e., the dyeable stratum and preferably, is contained within the light-reflecting layer.

Initially, the whitening reagent may be disposed in a layer of the film unit provided that it does not absorb actinic radiation intended to expose the photosensitive strata. For example, in unitary film structures where exposure is made through a layer adjacent the photosensitive strata, a whitening reagent in its colored form may be disposed in the image-receiving component and/or in a preformed light-reflecting layer without interfering with photoexposure. In unitary film structures where both exposure and viewing of the image is made through the transparent support layer of the image receiving component, the whitening reagent disposed in the image-receiving component and/or in a preformed reflecting layer should be substantially colorless, such as, the temporarily shifted dyes mentioned above and then rendered colored after photoexposure. Alternatively, the whitening reagent may be located outside of the photoexposure optical path by being initially disposed in the processing composition.

In the preferred embodiment of the present invention, the whitening reagent is colored intially and is introduced as a component of the processing composition. Where the processing composition is distributed between the photosensitive and image-receiving components, the reagent may be substantially nondiffusible and thus, retained substantially within the processing composition layer, or it may be diffusible and capable of being rendered substantially nondiffusible in a layer or layers of the image-receiving component, for example, by mordanting to the dyeable stratum. Where the processing composition is applied to the photosensitive strata on the surface opposite the image-receiving component, the whitening reagent should be diffusible to the light-reflecting layer and/or a layer or layers of the image-receiving component and there rendered non-diffusible.

The amount of optical whitening reagent to be added will depend primarily upon the degree of color staining together with the final location of the reagent in the film unit. For example, if the final position of the reagent is substantially within the light-reflecting layer, a larger amount of reagent will be needed than if it is finally disposed in the dyeable stratum due to the biding properties of the light-reflecting pigment. The appropriate amount of whitening reagent may be readily determined empirically for a given photographic system by measuring the minimum transfer reflection densities for red, green and blue light initially and again after prolonged standing at room temperature or after accelerated aging at elevated temperatures and then adding a pigment or dye having the requisite light absorption characteristics in an amount that will maintain the difference between the minimum densities both initially and after aging within a range such that the light reflected from the highlights appears substantially white to the viewer. Ordinarily, the whitening reagent is added in an amount sufficient to maintain the final densities, i.e., the densities after aging within about 0.08 or 0.09 density units while keeping the difference in initial densities preferably within about 0.03 or 0.04 density units.

An an illustration, in photographic systems employing composite film units of the type disclosed in aforementioned U.S. Pat. No. 3,415,644, it has been observed that the initial minimum transfer reflection den sities usually are about 0.18 or 0.19 density units for red and green light and about 0.21 density units for blue light. The densities measured after aging show a decrease in red light to about 0.16 density units and increases to about 0.23 and 0.27 density units in green and blue light, respectively. (All density measurements were referenced against magnesium carbonate as 0.00) By adding a blue pigment or dye in amounts sufficient to adjust the initial minimum density for red light to about 0.20 to 0.22 density units, the light reflected from the D,,,,-,, areas of the transfer image appears substantially white both initially and after aging.

The adjustment in the minimum transfer reflection density for red light in such film units may be achieved, for example, by including a soluble blue dye in the aqueous alkaline processing composition which is dif fusible therein but capable of being rendered substantially non-diffusible in the dyeable stratum in a substantially uniform distribution and in a concentration such that the optical reflection density of the resulting stratum does not exceed about 0.04 density units and preferably is between about 0.03 and 0.04 density units. Alternatively, the adjustment may be achieved by including an insoluble and substantially non-diffusible blue pigment in the processing composition substantially uniformly dispersed therein in a concentration such that a layer of the composition approximately 0.0025 inch thick has an optical reflection density not exceeding about 0.04 density units and preferably between about 0.03 and 0.04 density units. As discussed above, the whitening reagent may be initially included in a layer of the film unit, but preferably in the aforementioned composite film units, the whitening reagent is introduced as a component of the processing composition. Particularly useful pigments and dyes which reflect red light and which may be conveniently used to add the 0.03 to 0.04 density units to bring the initial minimum reflection density for red light up to about 0.20 to 0.22 are pigments and dyes of the phthalocyanine class.

As noted previously, various diffusion transfer systems for forming color images have heretofore been disclosed in the art. Generally speaking, such systems rely for color image formation uponthe differential in mobility or solubility of a dye image-providing material obtained as a function of development so as to provide an imagewise distribution of such material which is more diffusible and which is therefore selectively transferred, at least in part, by diffusion, to a superposed dyeable stratum to impart thereto the desired color transfer image. The differential in mobility or solubility may for example be obtained by a chemical action such as a redox reaction or a coupling reaction.

The dye image-providing materials which may be employed in such processes generally may be characterized as either (1) initially soluble or diffusible in the processing composition but are selectively rendered non-diffusible in an imagewise pattern as a function of development; or (2) initially insoluble or non-diffusible in the processing composition but which are selectively rendered diffusible in an imagewise pattern as a function of development. These materials may be complete dyes or dye intermediates, e.g., color couplers.

As examples of initially soluble or diffusible materials and their application in color diffusion transfer, mention may be made of those disclosed, for example, in US. Pat. Nos. 2,647,049; 2,661,293; 2,698,244; 2,698,798; 2,802,735; 2,774,668; and 2,983,606. As examples of initially non-diffusible materials and their use in color transfer systems, mention may be made of the materials and systems disclosed in U.S. Pat. Nos. 3,443,939; 3,443,940; 3,227,550; 3,227,551; 3,227,552; 3,227,554; 3,243,294 and 3,445,228.

In any of these systems, multicolor images are obtained by employing a film unit containing at least two selectively sensitized silver halide layers each having associated therewith a dye image-providing 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 greenand a red-sensitive silver halide layer having associated therewith, respectively, a yellow, magenta and a cyan dye image-providing material.

For purposes of clarity, the present invention will be further described in terms of the preferred embodiment of producing color transfer images utilizing initially soluble and diffusible dye-image providng materials and specifically dye developers in an integral negativepositive film unit, such as, disclosed in aforementioned U.S. Pat. No. 3,415,644 wherein at least two selectively sensitized photosensitive strata, superposed on a single support, are processed simultaneously and without separation, with a single, common image-receiving layer. A suitable arrangement of this type comprises a support carrying a red-sensitive silver halide stratum, a green-sensitive silver halide stratum and a bluesensitive silver halide stratum, said emulsions having associated therewith, respectively, for example, a cyan dye developer, a magenta dye developer and a yellow dye developer. The dye developer may be utilized in the silver halide stratum, for example, in the form of particles, or it may be employed as a layer behind the appropriate silver halide strata. Each set of silver halide strata and associated dye developer strata optionally may be separated from other sets by suitable interlayers, for example, by a layer of gelatin or polyvinyl alcohol. In certain instances, it may be desirable to incorporate a yellow filter in front of the green-sensitive emulsion and such yellow filter may be incorporated in an interlayer. However, where desirable, a yellow dye developer of the appropriate spectral characteristics and present in a state capable of functioning as a yellow filter may be employed. In such instances, a separate yellow filter may be omitted.

These film units may, and preferably, further contain pH modulating or adjusting means, e.g., a layer or layers containing a reagent for adjusting the pH following substantial transfer image formation. In those systems employing an aqueous alkaline processing composition, such film units may contain a neutralizing layer or layers, e.g., a polymeric acid layer of the type described, for example, in US. Pat. No. 3,362,819. It is also known to employ a spacer layer in conjunction with the neutralizing layer in order to time control the pH adjustment by the neutralizing layer. Spacer layers of this description are disclosed, for example, in the aforementioned US. Pat. No. 3,362,819, as well as in other patents, e.g., US. Pat. Nos. 3,455,686; 3,433,633; 3,421,893; 3,419,389; etc. The neutralizing and spacer layers are preferably contained in the image-receiving component, e.g., as layers disposed on the side of the dyeable stratum opposed from the photosensitive component. However, they may be disposed in the photosensitive component, as is described and claimed in US. Pat. No. 3,573,043. Also, modulation of the environmental pH may be effected by employing particulate acid distributed within the film unit as disclosed in US. Pat. No. 3,576,625.

A preferred unitary film structure contains, as essential layers, in sequence, a dimensionally stable alkali solution impermeable opaque layer, a layer containing a cyan dye developer, at red-sensitive silver halide emulsion layer, a layer containing a magenta dye developer, a green-sensitive silver halide emulsion layer, a layer of yellow dye developer, a blue-sensitive silver halide emulsion layer, a dyeable stratum, a spacer layer, a neutralizing layer and a dimensionally stable alkali solution impermeable transparent layer, the composite structure being employed in combination with a rupturable container retaining an aqueous alkaline processing composition including a light-reflecting agent and preferably, further including at least one optical filter agent, the container being fixedly positioned and extending along a leading edge of the composite structure so as to be capable of effecting unidirectional discharge of its contents between the dyeable stratum and the blue-sensitive silver halide emulsion layer upon application of compressive pressure.

The aforementioned dye developers, as well known in the art, are compounds which contain, in the same molecule, both the chromophoric system of a dye and also a silver halide developing function. By a silver halide developing function is meant a grouping adapted to develop exposed silver halide. A preferred silver halide development function is a hydroquinonyl group. Other suitable developing functions include ortho-dihydroxyphenyl and orthoand para-amino substituted hydroxyphenyl groups. In general, the development function includes a benzenoid developing function, that is, an aromatic developing group which forms quinonoid or quinone substances when oxidized.

The dye developers are preferably selected for their ability to provide colors that are useful in carrying out subtractive color photography, that is, the previously mentioned cyan, magenta and yellow. For example, in the above-described unitary film structure, the silver halide strata possess predominant spectral sensitivity to separate regions of the spectrum, and the dye developer associated with each of the strata possesses a spectral absorption range substantially complementary to the predominant sensitivity of its associated silver halide emulsion. In a particularly preferred embodiment, each of the silver halide strata, and its associated dye developer, is separated from the remaining strata, and

their associated dye developers by separate processing solution permeable polymeric interlayers.

Reference is now made to FIGS. 1 through 7 of the drawings wherein there is illustrated a preferred film unit of the present invention and wherein like numbers, appearing in the various figures, refer to like components.

As illustrated in the drawings, FIG. 1 sets forth a perspective view of the film unit, designated 10, and each of FIGS. 2 through 7 illustrate diagrammatic crosssectional views of film unit 10, along the stated section lines 2 2, 3-3, 55 and 7 7, during the various depicted stages in the performance of a photographic diffusion transfer process as detailed hereinafter.

Film unit 10 comprises rupturable container 11, retaining, prior to processing, aqueous processing composition 12, and photosensitive laminate 13' including, in order, dimensionally stable opaque layer 14, preferably an actinic radiation-opaque flexible sheet material; cyan dye developer layer 115; red-sensitive silver halide emusion layer 16; interlayer 17; magenta dye developer layer 18; green-sensitive silver halide emulsion layer 19; interlayer 20; yellow dye developer layer 21; bluesensitive silver halide emulsion layer 22; auxiliary layer 23, which may contain an auxiliary silver halide devel oping agent; image-receiving layer 24; spacer layer 25; neutralizing layer 26; and dimensionally stable transparent layer 27, preferably an actinic radiation transmissive flexible sheet material.

The structural integrity of laminate 13 may be maintained, at least in part, by the adhesive capacity exhibited between the various layers comprising the laminate at their opposed surfaces. However, the adhesive ca pacity exhibited at an interface intermediate imagereceiving layer 24 and the silver halide emulsion layer next adjacent thereto, for example, image-receiving layer 24 and auxiliary layer 23 as illustrated in FIGS. 2 through 7, should be less than that exhibited at the interface between the opposed surfaces of the remainder of the layers forming the laminate, in order to facilitate distribution of processing solution 12 intermediate the stated image-receiving layer 24 and the silver halide emulsion layer next adjacent thereto. The laminates structural integrity may also be enhanced or provided, in whole or in part, by providing a binding member extending around, for example, the edges of laminate 13, and maintaining the layers comprising the laminate intact, except at the interface between

layers

23 and 24 during distribution of processing composition 12 intermediate those layers. As illustrated in the figures, the binding member may comprise a pressure-sensitive tape 28 securing and/or maintaining the layers of laminate 13 together at its respective edges. Tape 28 will also act to maintain processing solution 112 intermediate image-receiving layer 24 and the silver halide emulsion layer next adjacent thereto, upon application of compressive pressure to pod 11 and distribution of its contents intermediate the stated layers. Under such circumstances, binder tape 28 will act to prevent leakage of fluid processing composition from the film units laminate during and subsequent to photographic processing.

Rupturable container 11 may be of the type shown and described in any of U.S. Pat. Nos. 2,543,181; 2,634,886; 3,653,732; 2,723,051; 3,056,492; 3,056,491; 3,152,515; and the like. In general, such containers will comprise a rectangular blank of fluidand air-impervious sheet material folded longitudinally upon itself to form two walls 29 which are sealed to one another along their longitudinal. and end margins to form a cavity in which processing composition 12 is retained. The longitudinal marginal seal 30 is made weaker than the end seals 31 so as to become unsealed in response to the hydraulic pressure generated within the fluid contents 12 of the container by the application of compressive pressure to walls 29 of the container.

As illustrated in FIGS. 1, 2 and 3, container 11 is fixedly positioned and extends transverse a leading edge of photosensitive laminate .13 whereby to effect unidirectional discharge of the containers contents 12 between image-receiving layer 24 and the stated layer next adjacent thereto, upon application of compressive force to container 11. Thus, container 11, as illustrated in FIG. 2, is fixedly positioned and extends transverse a leading edge of laminate 13 with its longitudinal marginal seal 30 directed toward the interface between image-receiving layer 24 and auxiliary layer 23. As shown in FIGS. 1, 2 and 4, container 11 is fixedly secured to laminate 13 by extension 32 of tape 28 extending over a portion of one wall 29 of the container, in combination with a separate retaining member such as illustrated retaining tape 33 extending over a portion of laminate 13s surface generally equal in area to about that covered by tape 28.

As illustrated in FIG. 6, extension flap 32 of tape 28 is preferably of such area and dimensions that upon, for example, manual separation of container 11 and tape 33, subsequent to distribution of processing composition 12, from the remainder of film unit 10, flap 32 may be folded over the edge of laminate 13, previously covered by tape 33, in order to facilitate maintenance of the laminates structural integrity, for example, during the flexations inevitable in storage and use of the processed film unit, and to provide frame, for viewing of the transfer image through the picture viewing area of transparent layer 27.

The fluid contents of the container comprise a liquid processing composition, having a pH and solvent concentration at which the dye developers are soluble and diffusible, which contains a light-reflecting agent in a quantity sufficient to mask the positive component, i.e., the silver halide emulsions and associated layers subsequent to processing and additionally contains one or more optical filter agent(s) having an absorption spectrum such that the filter agent(s) are capable of adsorbing incident actinic radiation between about 400 nm. and 700 nm. Preferably, the optical filter agent(s) comprise a pH sensitive dye or dyes, such as those disclosed and claimed in aforementioned U.S. Pat. applications Ser. Nos. 103,392 and 108,260.

As disclosed in the previously cited patents, the liquid processing composition used for effecting color diffusion transfer processes comprises at least an aqueous solution of an alkaline material, for example, diethylamine, sodium hydroxide or sodium carbonate and the like, and preferably possesses a pH in excess of 12, and most preferably includes a viscosity-increasing compound constituting a film-forming material of the type which, when the composition is spread and dried, forms a relatively firm and relatively stable film. The preferred film-forming materials disclosed comprise high molecular weight polymers such as polymeric, watersoluble ethers which are inert to an alkaline solution such as, for example, a hydroxyethyl cellulose or soa suitable mask or dium carboxymethyl cellulose. Additionally, filmforming materials or thickening agents whose ability to increase viscosity is substantially unaffected if left in solution for a long period of time are also disclosed to be capable of utilization. As stated, the film-forming material is preferably contained in the processing composition in such suitable quantities as to impart to the composition a viscosity in excess of 100 cps. at a temperature of approximately 24C. and preferably in the order of 100,000 cps. to 200,000 cps. at that temperature.

In the preferred embodiment of the present invention, the aqueous alkaline processing composition releasably retained in said rupturable container includes the above-described whitening reagent in a concentration such that, upon application of the processing composition and subsequent development and dye transfer image formation, the light reflected from the D areas of the dye transfer image visually appears substantially white both initially and after aging. As discussed above, the pigment or dye selected as the whitening reagent may be substantially non-diffusible in the aqueous alkaline processing composition so that it will remain substantially within the layer of processing composition distributed intermediate the image-receiving layer 24 and the silver halide layer next adjacent thereto. Alternatively, the whitening reagent selected may be diffusible in the aqueous alkaline processing composition provided that it is capable of being rendered substantially non-diffusible in the appropriate location in the film unit, i.e., in the layer containing the light-reflecting agent, if preformed, and/or in a layer of the imagereceiving component, preferably, a layer of the imagereceiving component next adjacent the light-reflecting layer, e.g., the dyeable stratum.

In the performance of a diffusion transfer multicolor process employing film unit 10, the unit is exposed to radiation, actinic to photosensitive laminate 13, incident on the laminates exposure surface 34, as illustrated in FIG. 2.

Subsequent to exposure, as illustrated by FIGS. 2 and 4, film unit is processed by being passed through opposed suitably gapped rolls 35 in order to apply compressive pressure to frangible container 11 and to effect rupture of longitudinal seal 30 and distribution of alkaline processing composition 12, possessing inorganic light-reflecting pigment and optical filter agent at a pH above the pKa of the filter agent and a pH at which the cyan, magenta and yellow dye developers are soluble and diffusible as a function of the point-to-point degree of exposure of red-sensitive silver halide emulsion layer 16, green-sensitive silver halide emulsion layer 19 and blue-sensitive silver halide emulsion layer 22, respectively, intermediate spacer layer 25 and auxiliary layer 23.

Alkaline processing composition 12 permeates emulsion layers 16, 19 and 22 to initiate development of the latent images contained in the respective emulsions. The cyan, magenta and yellow dye developers, or layers 15, 18 and 21, are immobilized, as a function of the development of their respective associated silver halide emulsions, preferably substantially as a result of their conversion from the reduced form to their relatively insoluble and nondiffusible oxidized form, thereby providing imagewise distributions of mobile, soluble and diffusible cyan, magenta and yellow dye developer, as a function of the point-to-point degree of their associated emulsions exposure. At least part of the imagewise distributions of mobile cyan, magenta and yellow dye developer transfers, by diffusion, to dyeable polymeric layer 24 to provide a multicolor dye transfer image to that layer which is viewable against the background provided by the reflecting pigment present in processing composition residuum 12 and cyan, magenta and yellow dye developer remaining associated with blue-sensitive emulsion layer 22, green-sensitive emulsion layer 19 and red-sensitive emulsion layer 16. Subsequent to substantial transfer image formation, a sufficient portion of the ions comprising aqueous alkaline processing composition 12 transfer, by diffusion, through permeable polymeric reception layer 24, permeable spacer layer 25 to polymeric neutralizing layer 26 whereby the environmental pH of the system decreases as a function of neutralization to a pH at which the cyan, magenta and yellow dye developers, in the reduced form, are substantially nondiffusible to thereby provide a stable multicolor dye transfer image and discharge of the pI-I-sensitive optical filter agent by reduction of the pH substantially below the pKa of such agent to thereby provide maximum reflectivity in terms of the pigment concentration present.

The alkaline processing composition, positioned intermediate the photosensitive element and the imagereceiving layer, thus permeates the emulsions to initiate development of the latent images contained therein. The respective associated dye developers are immobilized or precipitated in exposed areas as a consequence of the development of the latent images. This immobilization is apparently, at least in part, due to a change in the solubility characteristics of dye developer upon oxidation and especially as ragards its solubility in alkaline solutions. It may also be due in part to a tanning effect on the emulsion by oxidized developing agent, and in part to a localized exhaustion of alkali as a result of development. In unexposed and partially exposed areas of the emulsions, the associated 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 or element, said transfer substantially excluding oxidized dye developer. The image-receiving element 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.

Subsequent to distribution of processing composition 12, container 11 may be manually dissociated from the remainder of the film unit, as described above, to provide the product illustrated in FIG. 6.

The optical filter agent(s) selected for use in diffusion transfer processes, such as, the foregoing should exhibit at the initial pH of the processing, maximum spectral absorption of radiation at the wavelengths to which the film units photosensitive silver halide layer or layers are sensitive and preferably, should be substantially immobile or nondiffusible within the pigment dispersion, during performance of its radiation filtration function, in order to maintain and enhance the optical integrity of the dispersion as a radiation filter unit and to prevent its diffusion into and localized concentration within the image receiving layer. Commensurate with the spectral sensitivity range of the silver halide layer or layers, the dye or dyes selected as the optical filter agents should possess absorption complementary to said sensitivity range of such silver halide layers in order to provide effective protection against physical fog providing radiation during processing. Recognizing that optical filter agent absorption will derogate from image-viewing characteristics by contaminating the light-reflecting background, the selected agents should be those exhibiting major spectral absorption at the pH at which processing is effected and minimal absorption at a pH below that which obtains during transfer image formation. Accordingly, the pH-sensitive dyes selected as the optical filter agent or agents should possess a pKa below that of the processing pH and above that of the environmental pH subsequent to transfer image formation.

The selected light-reflecting agent should be one providing a background suitable for viewing the dye developer transfer image formed in the dyeable polymeric layer. In general, while substantially any reflecting agent may be employed, it is preferred that the agent selected will not interfere with the color integrity of the dye transfer image, as viewed by the observer, and will be aesthetically pleasing to the viewer without detracting from the information content of the image. Particularly desirable reflecting agents will be those providing a white background for viewing the transfer image, and specifically, those conventionally employed to provide a background for reflection photographic prints and,

especially, those agents possessing the optical properties desired for reflection of incident radiation.

Examples of reflecting agents suitable for use in the practice of the present invention include barium sulfate, zinc sulfide, titanium dioxide, barium stearate, silver flake, silicates, alumina, zirconium oxide, zirconium acetyl acetate, sodium zirconium sulfate, kaolin, mica, and the like. A particularly preferred reflecting agent comprises titanium dioxide due to its highly effective reflection properties.

In lieu of having the light-reflecting agent contained in the processing composition, the reflecting agent needed to mask the photosensitive strata and to provide the requisite background for viewing the color transfer image formed in the receiving layer may be contained initially in whole or in part as a preformed layer in the film unit. As an example of such a preformed layer, mention may be made of that disclosed in US. Pat. No. 3,615,42l and in Us. Pat. No. 3,620,724. Also, the light-reflecting agent may be generated in situ as is disclosed in US. Pat. Nos. 3,647,434 and 3,647,435.

Likewise, the optical filter agent(s) may be dispersed in any processing composition permeable layer of the composite film unit structure intermediate the photosensitive silver halide layer( s) to be protected from incident actinic radiation and the exposure surface of the film unit. When initially disposed in a layer of the film unit, they will be present at an environmental pH at which the agent or agents selected do not substantially absorb incident actinic radiation prior to photoexposure of the film unit and activation by contact with alkaline processing composition permeating such layer and thereby providing the environmental pH at which the agent or agents selected absorb incident radiation actinic to the photosensitive silver halide layer to prevent fogging during processing. In the specifically preferred film unit embodiments, however, the optical filter agents are initially disposed within the alkaline processing solution, in order to obviate the necessity of converting the filter agent from a substantially nonabsorber of actinic radiation desired to effect photoexposure of the film unit to the desired light-absorbing form during processing, by alkaline processing composition contact, subsequent to selective 'photoexposure of the film unit and to thus maximize isolation of their effects from the photosensitive silver halide crystals prior to photoexposure. In the specifically preferred film units, the light-reflecting agent also is initially disposed in the alkaline processing solution.

In general, the concentration oflight-reflecting agent or agents and optical filter agent or agents selected will be that sufficient to prevent further exposure of the film units silver halide layer or layers by actinic radiation traversing through the dimensionally stable transparent layer, subsequent to distribution of processing solution intermediate the dyeable polymeric layer and the stated layer next adjacent thereto. Accordingly, the film unit may be processed, subsequent to distribution of the composition, in the presence of such radiation, in view of the fact that the silver halide layer or layers of the laminate are appropriately protected from incident radiation, at one major surface by the distributed light-reflecting and optical filter agents and at the remaining major surface by the dimensionally stable opaque layer. Specifically, the concentration of optical filter agent is selected to provide the optical transmission density required, in combination with other layers including the light reflecting layer intermediate the silver halide layer(s) and the incident radiation, to prevent nonimagewise exposure, i.e., fogging, by incident actinic light during the performance of the photographic process. It has been found, by interposing neutral density (carbon containing) filters over a layer of titanium dioxide, that a transmission density of approximately 6.0 from said neutral density filters was effective to prevent fogging of a diffusion transfer multicolor film unit of the type described in said US. Pat. No. 3,415,644 having a transparent support layer and an Equivalent ASA Exposure Index of approximately when processed for 1 minute in 10,000 foot candles of color corrected light, a light intensity approximating the intensity of a noon summer sun. The transmission density required to protect such a film unit under the stated conditions may also be expressed in terms of the system transmission density of all the layers intermediate the silver halide layer(s) and the incident light; the system transmission density required to protect color film units of the aforementioned type and photographic speed has been found to be on the order of 7.0 to 7.2. Lesser levels of optical transmission density would, of course, provide effective protection for shorter processing times, lesser light intensities and/or films having lower exposure indices. The transmission density and the filter agent concentration necessary to provide one requisite protection from incident light may be readily determined for any photographic process by following the above described procedure or obvious modifications thereof.

It will be understood that in the performance of the present invention that the silver halide layers should be protected in all visible and non-visible regions of the spectrum to which they are sensitive. Depending upon the sensitivity of the silver halide or other photosensitive material employed, it may be desirable to use ultraviolet and/or infra-red absorbers in conjunction with the indicator dye or dyes selected as optical filter agents to provide additional protection in the nonvisible regions. Ultraviolet and infra-red absorbers are well known in the photographic art and any of the compounds conventionally used for this purpose may be employed in the present invention. Like the optical filter agents, the absorbers should provide the desired protection against post-exposure fogging during at least the initial stages of development but should not absorb radiation intended to selectively expose the photosensitive material or detract from the brilliance hues and other properties of the final image. Thus, the absorber or absorbers, as will be appropriate for the particular compounds selected, may be initially disposed in a layer of the film unit and/or the processing solution and subsequent to processing may be retained in or separated from the final product.

The film units described above including the photosensitive component comprising the photosensitive strata and associated dye image-forming material; the image-receiving component comprising the dyeable and other layers, and the processing composition including its components, such as, the alkaline material and various addenda are described in detail in aforementioned U.S. Pat. Nos. 3,415,644, 3,415,645, 3,415,646, 3,373,043, 3,573,044, 3,594,164, 3,594,165 and 3,647,437 which patents, for convenience, are specifically incorporated herein.

By way of further illustrating the practice of this invention as applied to a film unit of the type shown in the drawing, a gelatin subbed, 4 mil. opaque polyethylene tcrephthalate film base, was coated, in succession,

with the following layers to form the photosensitive component.

1. a layer of cyan dye developer dispersed in gelatin and coated at a coverage of about 100 mgs/ft. of dye and about mgsjft. of gelatin;

2. a red-sensitive gelatino silver iodobromide emulsion coated at a coverage of about 140 mgs./ft. of silver and about 70 mgs./ft. of gelatin;

3. a layer of 6030-46 copolymer of butylacrylate, diacetone acrylamide, styrene and methacrylic acid and polyacrylamide coated at a coverage of about 150 mgs./ft. of the copolymer and about 5 mgs/ft. of polyacrylamide;

4. a layer of magenta dye developer dispersed in gelatin and coated at a coverage of about 1 12 mgs./ft. of dye and about mgs./ft.- of gelatin;

5. a green-sensitive gelatino silver iodobromide emulsion coated at a coverage of about 100 mgs./ft. of silver and about 50 mgs/tt. of gelatin;

6. a layer containing the copolymer referred to above in layer 3 and polyacrylamide coated at a coverage of about 100 mgs./ft. of copolymer and about 12 mgsjft. of polyacrylamide;

7. A layer of yellow dye developer dispersed in gelatin and coated at a coverage of about 70 mgsjft. of dye and about 56 mgs./ft. of gelatin;

8. a blue-sensitive gelatino silver iodobromide emulsion layer including the auxiliary developer 4- methylphenyl hydroquinone coated at a coverage of about mgsjft. of silver, about 60 mgs./ft. of gelatin and about 30 mgs/ft. of auxiliary developer; and

9. a layer of gelatin coated at a coverage of about 50 mgs./ft. of gelatin.

The three dye developers employed were the followa cyan dye developer;

HO-CH CH 2 N-SO N N I 1 3 HOCH -CH o. o N

O O OH H a magenta dye developer; and

i Water 156.0 cc.

Potassium hydroxide (857:) 22.1 g. N-benzyl-a-picolinium bromide (50% solution in water) 6.4 g. NO

2 N-phcnethyl-a-picolinium bromide 0.8 g. C H O CH N 3 7 Sodium Carboxymethyl O cellulose (Hercules Type 7H4F providing a viscosity of 3000 cps. at l7r in water at 25C.) 4.9 Titanium dioxide 72.0 g. 0 O H ta-methyl uracil 3.36 g. 11 bis-(B-uminoethylLsullidc 0.24 g. Lithium'nitratu 0.56 g. C 2 2 Benzatriazolc 1.6 g. b-Bcnzylaminopurine 0.4 g, 6-Mcthyl-5-Bromoazabenzimidazole 0.08 g. OH

3.0 g. a yellow dye developer. HOOC so c H Then a transparent 4 mil. polyethylene terephthalate 4O film base was coated, in succession, with the following layers to form the image-receiving component.

1. as a polymeric acid layer, the partial butyl ester of polyethylene/maleic anhydride copolymer at a coverage of about 2,500 mgs./ft. i

2. a timing layer containing about a 40:1 ratio of a -3046 copolymer of butylacrylate, diacetone acrylamide, sytrene and methacrylic acid and polyacrylamide at a coverage of about 500 mgs./ft. and

3. a polymeric image-receiving layer containing a 2:1 mixture, by weight, of polyvinyl alcohol and poly-4- vinylpyridine, at a coverage of about 300 mgs./ft.

The two components thus prepared were then taped together in laminate form, at their respective edges to provide the desired integral film unit.

A rupturable container comprising an outer layer of lead foil and an inner liner or layer of polyvinyl chloride retaining an aqueous alkaline processing solution was fixedly mounted on the leading edge of each of the laminates, by pressure-sensitive tapes, interconnecting the respective container and laminates so that, upon application of compressive pressure to the container to rupture the containters marginal seal, its contents were distributed between the dyeable stratum (layer 3 of the To g. of the above processing composition was image-receiving component) and the gelatin layer added approximately 40 mgs. of copper phthalocya- (layer 9) of the photosensitive component. nine pigment as the whitening reagent, which pigment The aqueous alkaline processing composition emwas insoluble and non-diffus ble in the compos tion. ployed in the rupturable container comprised the fol- The unitary film structure was totally exposed, 1.e.,

lowing: exposed overall to incident actinic radiation and then developed by applying compressive pressure to the rupturable container in order to distribute the aqueous alkaline processing composition. Without separating the superposed photosensitive and image-receiving components, the integral densities were measured by reflectance through the transparent support layer of the image-receiving component using red, green and blue filters to give the initial minimum reflection densities. The film unit was then stored for 18 hours at a temperature of about IF., and after aging in this manner the integral densities were measured again.

A control was prepared and tested as described above except that the copper phthalocyanine pigment was omitted.

The integral optical reflection densities measured initially and after aging appear in tabular form below.

Transfer Densities Control Red Green Blue Initial 0.18 0.19 0.21 After aging 0. l 6 0.23 0.27

Example Initial 0.21 0.20 0.21 After aging 0.l9 0.24 0.27

The above Example was repeated except that the whitening reagent used was a copper phthalocyanine dye, soluble and diffusible in the processing composition, and having the formula:

Approximately 0.01 g. of this dye was added to 100 g. of the above processing composition.

The optical reflection densities measured for this example and acontrol are set out below.

Transfer Densities Control Red Green Blue Initial 0. 18 0.19 0.21 After aging 0. lo 0.23 0.27 Example Initial 0.2l 0.23 0.24 After aging 0.20 0.24 0.27

As visually observed, the reflection prints representing the control prints in the two comparisons described above appeared substantially white initially but appeared yellow after aging. However, the reflection prints prepared using the copper phthalocyanine pigment and the cooper phthalocyanine dye, respectively, appeared substantially white to the eye both initially and after aging. I

In view of the foregoing, it will be appreciated that the essence of the present invention resides in adding color in the form of a light-absorbing reagent to achieve a balance between the initial and final integral minimum reflection densities of the transfer image such that the build up of color stain in time is not visually discernible. As observed by the eye, the highlight areas of the transfer image appear substantially white both initially and after prolonged standing.

In comparison, the prior art methods employed for correcting color stain employ a light-emitting, i.e., a fluorescent reagent rather than a light-absorbing reagent. The fluorescent materials, because they are light emitters, subtract rather than add color, and depending upon their location with respect to the light source used for viewing the image, may cause undesirable lowering of the maximum densities of the transfer image.

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

What is claimed is:

l. A rupturable container for use in diffusion transfer film vunits adapted to provide color transfer images viewable by reflected light, said rupturable container releasably holding an'aqueous alkaline processing composition comprising a viscosity-increasing reagent, a light-reflecting agent and a non-fluorescent optical whitening reagent capable of absorbing visible light within a predetermined wavelength range, said whitening reagent being substantially uniformly dispersed in said composition in a concentration such that a layer of the composition approximately 0.0025 inch thick has an optical reflection density not exceeding about 0.04 density units.

2. A rupturable container releasably holding an aqueous alkaline processing composition as defined in claim I wherein said layer of composition has an optical reflection density between about 0.03 and 0.04 density units.

3. A rupturable container releasably holding an aqueous alkaline processing composition as defined in claim 1 wherein said processing composition additionally contains at least one optical filter agent.

4. A rupturable container releasably holding an aqueous alkaline processing composition as defined in claim 3 wherein said whitening reagent is insoluble and substantially non-diffusible in said processing composition.

5. A rupturable container releasably holding an aqueous alkaline processing composition as defined in claim 4 wherein said whitening reagent is a copper phthalocyanine pigment.

6. A rupturable container releasably holding an aqueous alkaline processing composition as defined in claim 3 wherein said optical whitening reagent is a soluble dye.

'7. A rupturable container releasably holding an aqueous alkaline processing composition as defined in claim 6 wherein said whitening reagent is a copper phthalocyanine dye.

8. A rupturable container releasably holding an aqueous alkaline processing composition as defined in claim 3 wherein said light-reflecting agent is titanium dioxide.

carboxymethyl cellulose.

Claims

1. A RUPTURABLE CONTAINER FOR USE IN DIFFUSION TRANSFER FILM UNITS ADAPTED TO PROVIDE COLOR TRANSFER IMAGES VIEWABLE BY REFLECTED LIGHT, SAID RUPTURABLE CONTAINER RELEASABLY HOLDING AN AQUEOUS ALKALINE PROCESSING COMPOSITION COMPRISING A VISCOSITY-INCREASING REAGENT, A LIGHT-REFLECTING AGENT AND A NONFLUORESCENT OPTICAL WHITENING REAGENT CAPABLE OF ABSORBING VISIBLE LIGHT WITHIN A PREDETERMINED WAVELENGTH RANGE, SAID WHITENING REAGENT BEING SUBSTANTIALLY UNIFORMLY DISPRESED IN SAID COMPOSITION IN A CONCENTRATION SUCH THAT A LAYER OF THE COMPOSITION APPROXIMATELY 0.0025 INCH THICK HAS AN OPTICAL REFLECTION DENSITY NOT EXCEEDING ABOUT 0.04 DENSITY UNITS.

2. A rupturable container releasably holding an aqueous alkaline processing composition as defined in claim 1 wherein said layer of composition has an optical reflection density between about 0.03 and 0.04 density units.

7. A rupturable container releasably holding an aqueous alkaline processing composition as defined in claim 6 wherein said whitening reagent is a copper phthalocyanine dye.

9. A rupturable container releasably holding an aqueous alkaline processing composition as defined in claim 3 wherein said viscosity-increasing reagent is sodium carboxymethyl cellulose.