CA1040916A - Photographic products - Google Patents

Abstract

ABSTRACT OF TECHNICAL DISCLOSURE
Diffusion transfer processes are disclosed which may be performed in ambient light after removal of the film from a camera. Further exposure during such processing is prevented by the presence of a light-absorbing material or optical filter agent. The optical filter agent is initially present in a binder-free,, substantially colorless layer of at least one optical filter agent in a non-crystalline, solid form, preferably coated over the photosensitive element.

Description

lQ4~)916 This application is concerned with photography and more particularly with diffusion transfer processes performed outside of a camera in ambient light.
U. S. Patent No. 3,647,437 issued March 7, 1972 to Edwin H. Land discloses and claims photographic processes wherein a photosensitive element is developed in ambient light but further exposure during processing is prevented by a light- -absorbing material or optical filter agent which i8 retained in the processed film. In the preferred embodiments, the light-absorbing material is a pH-sensitive dye which is colored above a particular pH and colorless below said pH. The pH-sensitive dye is preferably included in the processing composi-tion, but disclosure is made, e.g., in Fig. 6 of said patent, of the possibility of initially positioning the pH-sensitive ~ 15 dye in a layer over the photosensitive element provided said .t dye is colorless during exposure. While the use of an optical 3 filter agent in a colorless form in the photosensitive film has certain advantages, there has been an undesirably long period between application of an alkaline processing composition .~ , .
and conversion of the optical filter agent or precursor from a colorless to colored state. Some of this delay is believed to ~ be due to the time required for permeating the polymer or ^~ binder in which the optical filter agent or precursor is disposed.;~
The present invention is directed to providing techniques and -film structures by which optical filter agents may be incor-porated in photographic elements in a colorles~ state and be quickly rendered light-absorbing.
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~4'~916 The invention seeks to provide photographic products, particularly photosensitive elements, adapted for processing in ambient light, and con-taining a colorless precursor of a colored optical filter agent in a binder-free stratum.
The invention also seeks to provide photosensitive elements includ-ing a substantially colorless, binder-free stratum of a pH-sensitive dye in a non-crystalline form.
According to the present invention there is provided a photographic product comprising a support, at least one silver halide emulsion layer and a binder-free layer of at least one pH-sensitive dye in a colorless, non-crystalline, solid form, said dye being capable of absorbing visible light when contacted with an alkaline material.
According to the present invention there is further provided a photographic product comprising a first support; a red-sensitive silver halide emulsion; a green-sensitive silver halide emulsion; and a blue-sensitive silver halide emulsion; said silver halide emulsions having associated there-with, respectively~ a cyan dye developer, a magenta dye developer and a yellow dye developer; an image-receiving layer for receiving image dyes transferred thereto by diffusion as a unction of exposure and development of said silver -halide emulsion layers; a second support which is transparent and through which said image-receiving layer may be viewed; a rupturable container releas-ably holding alkaline processing composition adapted, upon distribution be-, tween predetermined layers of said film to develop said silver halide emulsions and to effect the formation of a transfer image in dye in said image-receiving layer, said processing composition also being adapted to provide a permanent laminate including said developer silver halide emulsions and said image-receiving layer; and means providing a light-reflecting layer between said -~
image-receiving layer and said silver halide emulsions effective to provide a white background for viewing said transfer image and for masking said developed 30 ~ilYer halide emulsions; said product including a binder-free, substantially , ~ - 2 -s c 1~4~9~6 colorless layer of at least one pH-sensitive dye in a colorless, non-crystalline, solid form positioned between said silver halide emulsion layers and said light-reflecting layer, said pH-sensitive dye being adapted to be-come colored when contacted by said alkaline processing composition.
For a fuller understanding of the nature of the invention, refer-ence should be had to the following detailed description of the invention taken in conjunction with the accompanying drawing wherein:
The Figure 1 is a diagrammatic enlarged schematic illustration of a diffusion transfer film unit embodying a preferred embodiment of the present invention.
This invention is particularly concerned with diffusion transfer processes wherein the layer containing the diffusion transfer image, i.e., the image-receiving layer, is not separated from the developed photosensitive , layers after processing but both components are retained together as part ~ of a permanent laminate. Film units particularly adapted to .~ '.

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provide such diffusion transfer images have frequently been referred to as ~integral negative-positive" film units. The resulting image may be referred to as an "integral negative-positive" film units. The resulting image may be referred to as an "integral negative-positive reflection print" and a8 80 used is intended to refer to a reflection print wherein the developed photosensitive layers have not been separated from the image layer, i.e., the layer containing the transfer image. A light-reflecting layer between the developed photosensitive layer (8) and the image layer provides a white background for the transfer image and masks the developed photo-sensitive layer(s). These layers are part of a permanent laminate which usually includes dimensionally stable outer or support layers, the transfer image being viewable through one of said sup?orts.
The present invention is applicable to a wide variety of diffusion transfer processes, particularly color diffusion transfer processes, and the arrangement and order ~ -of the individual layers of the film used in such processes may vary in many ways as is known in the art.
A number of diffusion transfer photographic processes have been proposed wherein the resulting photograph comprises the developed silver halide emulsions retained with dye-image carrying layer as part of a permanent laminate. The image- ~;
carrying layer is separated from the developed silver halide ;~
emulsions in said laminate by a light-reflecting layer,~ ~ ~
preferably a layer containing titanium dioxide. Illustrative --of patents describing such products and processes are U. S.
Patent No. 2,983,606 issued Marah 9, 1961 to Howard G. Rogers, ~ -U. S. Patents No. 3,415,644, 3,415,645 and 3,415,646 issued .~ ' -,~ , .~ .
..... . .. . . . . .... . .. ... ... .. . . ..

~4~916 Dece~riber 10, 1968 to Edwin H. Land, U. S. Patent~ No.
3,594,164 and 3,594,165 issued July 20, 1971 to Howard G.
Rogers, and U. S. Patent No. 3,647, 347 issued March 7, 1972 to Edwin H. Land.
Referring more specifically to the aforementioned U. S. Patent No. 3,647,347, said patent discloses photographic products and processes employing dye developers wherein a photosensitive element and an image-receiving layer are maintained in fixed relationship prior to photoexposure and this fixed relationship i9 maintained after processing and image formation to provide a laminate including the processed silver halide emulsions and the image-receiving layer. Photo-exposure is made through a transparent (support) element and application of a proce3sing composition provides a layer of lS light-reflecting material to provide a white background for viewing the image and to mask t~e developed silver halide -emulsions. ~he desired color transfer image is viewed through said transparent support against said white background. For convenience, the more specific description of the present invention will be by use of dye developer diffusion transfer color processes and of integral negative-positive film units of the type contemplated in the above-mentioned U. S. patents.
As noted above, U. S. Patent 3,647,347 discloses the t use of optical filter agents, preferably pH-sensitive dyes, to prevent undesired exposure of a photosensitive element during processing in a lighted area. In accordance with the present invention, a binder-free essentially continuous stratum of one or more optical filter agents in a non-crystalline state i~ provided as part of the photographic film unit. The stratum of optical filter agent is substantially colorless, i.e., ~ ' ., ., .
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1~14~91~
it does not absorb light by which the photosensitive material is exposable, during photoexposure, but the optical filter agent(s) i~ rendered colored and absorbing of said light extremely rapidly by application of a processing composition.
In the preferred embodiments, the optical filter agent is a pH-sensitive dye which is present in said stratum in a colorless form and which i8 rendered colored by contact with an alkaline processing fluid.
The stratum of optical filter agent is provided by precipitating from solution one or more optical filter agents on the appropriate layer of the film, the precipitated optical filter agent(s) being deposited in a solid, non-crystalline, amorphous or glass-like state. The resulting stratum is pref-erably optically clear and colorless so that photoexposure may be effected through it. The stratum of optical filter agent is free of any polymer or other binder. As a result, the precipitated optical filter agent i8 rendered colored as soon as it is wetted by the processing composition. The time period between application of the processing composition and the generation in situ of a light-absorbing stratum is reduced to a virtual minimum.
Suitable pH-sensitive dyes include phthalein dyes and particularly dye-q disclosed in the previously cited U. S.
Patent No. 3,647,347, and in U. S. Patent No. 3,702,244 issued -~ 25 November 7, 1972 to Stanley M. Bloom, Alan L. Borror, Paul S.
.~ . .
l Huyffer and Paul T. MacGregor, and U. S. Patent No. 3,702,245 --isQued November 7, 1972 to Myron S. Simon and David P. Waller. -~
j The ability of a given pH-sensitive or othex dye to form a non-1 crystalline, amorphous binder-free layer, alone or in combina-~, 1 30 tion with one more other pH-sensitive or other dyes may be ç: . . . - .

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1C~4I~9~6 readily determined by routine testing. The coating solution used to apply the dye(s) should have as high a solid content as possible to facilitate coating operations. The u~e of organic solvent(s) is preferred as this reduces or eliminates penetration of the dissolved dye(s) into the layer, usually a water-soluble polymer such as gelatin, on which the pH-sen~itive dye solution is coated.
The quantity of the light-absorbing material required to provide protection of the photosensitive material will vary with the process being performed and the conditions (light level) under which it i9 expected that the process will be performed, and may be readily determined by routine tests.
The presence of a light-reflecting layer between the source of light and the light-absorbing material will materially reduce the required quantity of light-absorbing material, and will also reduce the amount of heat generated within the film unit by absorption of incident light during processing. Genera guides for determining suitable concentration~ of light-absorbing materials may be found in the previously mentioned Z0 U. S. Patent No. 3,647,437. -¦ Image dye-providing materials which may be employed generally may be characterized as either (1) initially soluble or diffusible in the proces-sing composition but are selectively rendered non-diffu~ible ~ 25 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 or provide a diffusible product in an imagewise pattern as a function of development. These materials may be complete dyes or dye intermediates, e.g., color couplers. The requisite differential in mobility or solubility may, for example, be obtained by a chemical action such as a redox reaction or a coupling reaction.
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 U. S. Patents Nos. 2,774,668; 2,968,554; 2,983,606; 2,087,817;
3,185,567; 3,230,082; 3,345,163; and 3,443,943. As examples of initially non-diffusible material9 and their use in color transfer systems, mention may be ma~e of the materials and ` 15 systems disclosed in U. S. Patents No~. 3,185,567; 3,443,939;
i~ 3,443,940; 3,227,550; and 3,227,552. Both types of image- -dye providing substances and film units useful therewith also i are discussed in the aforementioned U.S. Patent No. 3,647,437 '~ to which reference may-be made.
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 there-with an image dye-providing material exhibiting desired spectral absorption characteristics. The most commonly employed elements of this type are the so-called tripack structures employing blue-, a green- and a red-sensitive 1 silver halide layers having associated therewith, respectively, a yellow, a magenta and a cyan image dye-providing material, as di~closed in U. S. Patent No. 3,345,163 issued October 3, 1967 to Edwin H. Land and Howard G. Rogers.
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lQ45~916 A particularly useful system for forming color images by diffusion transfer i8 that described in U. S. Patent No.
; 2,983,606, employing dye developer~ (dyes which are also ~ilver halide developing agents) as the image dye-providing materials. In such systems, a photosensitive element comprising at least one silver halide layer having a dye developer associated therewith (in the same or in an adjacent layer) i~ developed by applying an aqueous alkaline proce~sing composition. Development of exposed silver halide results in oxidation of the dye developer to provide an oxidation product which is appreciably less diffusible than the unreacted dye developer, thereby provid-ing an ;magewise distribution of diffusi~le dye developer in tenms of unexposed areas of the silver halide layer, which imagewise distribution is then transferred, at least in part, ~ by diffusion, to a dyeable Qtratum to impart~thereto a i positive dye transfer image. Multicolor images may be obtain-ed with a photosensitive element having two or more selective-ly sènsitized silver halide layers and associated dye devel-oper~, a tripack structure of the type described above in various patents including the aforementioned U. S. Patents No~. 2,983,606 and 3,345,163 being especially suitable for accurate color recordation of original subject matter.
In such color diffusion transfer systems, color transfer images are obtained by exposing a photo~ensitive St ~lement, sometimes referred to as a "negative componentn, comprising at least a light-senSitive layer, e.g., a gelatino silver halide emulsion layer, having an image dye-providing ~aterial associated therewith in the same or in an ad;acent layer, to form a developable image; develop~ng this exposed i, " ' .

104~916 element with a proceqsing composltion to form an imagewise distribution of a diffusible image dye-providing material;
and transferring this imagewise di~tribution, at least in ~ -part, by diffusion, to a superposed image-receiving layer, sometimes referred to as a ~positive component~, comprising at least a dyeable stratum to provide a color transfer image.
The negative and positivQ components initially may be carried on separate supports which are brought ~ogether during processing and thereafter retained together as the final $ntegral negative-positive reflection print, or they may initially comprise a unitary structure, e.g., integral negative-positive film units wherein the negative and po~itive com-ponents are part of ~ photosensitive ~aminate or they may other-wise be physically retained together in superpo~ed relation-ship prior to, during and after image formation. (Procedures for forming Juch film units wherein the positive and negative component~ are temporarily laminated together prior to ex-po~ure are described, for example,in U. S. Patent No.
3,652,281 to Albert J. Bachelder and Frederick J. Binda and in U. S. Patent No. 3,652,282 to Edwin H. ~and, both is~ued ' March 28, 1972.) In either instance, the po~tive component not removed from the negativa component for ~iewing purpo~es.
The preferred film unit~ comprise a plurality of essential l~yer~ including a negative component comprising at least one ~- 25 light-sensit~ve silver halide and as~ociated dye image-I providing material and a positive component compri~ing a dye-} abla ~tratum. These components may be laminated together or otharwisa secured together in phy~ical juxtaposition.
Film unit~ intended to provide multicolor imagés comprise two or more selectively sensitized . _ g_ .-' .. . .
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~4~916 silver halide layers each having a~sociated therewith n appropriate image dye-providing material providing an image dye having spectral absorption characteristics substantially com-plementary to the light by which the associated silver halide is exposed. The most commonly employed negative components for forming multicolor images are of the trlpack structure and contain blue-, green- and red-sensitive silver halide layers each having associated therewith in the same or in a contiguou~ layer a yellow, a magenta and a cyan image dye-providing material respectively. Interlàyers or spacer layers may, if desired, be provided between the respective silver halide layers and associated image dye-providing materials or between other layers. In addition to the afore-mentioned essential layers, such film units further include means for providing a reflecting layer between the dyeable stratum and the negative component in order to mask effec-tively the silver image or images formed as a function of development of the silver halide layer or layers and al~o tQ mask image dye-providing material which i~ not transferred, thereby providing a background, preferably white, for viewing the color image formed in the dyeable stratum, without .~ .
separation, by reflected light. This reflecting layer may ~; comprise ~ preformed layer of a reflecting agent included in the film unit or the reflecting agent may be provided after photoexposure, e.g., by including the reflecting agent in the processing composition. The dye transfer image i3 then ~ . , .
viewable through a dimensionally stable protective layer or ~upport. Most preferably another dimensionally ~table layer or ~upport, which may be transparent or opa~ue, is positioned on the opposed surface of the essential layers 90 that the --1 0-- .- .
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lV4'~916 aforementioned es~ential layer~ are between ~ pair of di-mensionally stable layer~ or support members, one of which is transparent to permit viewing therethrough of the color transfer image. A rupturable container of known de~cription contains the requisite processing composltion and is adap~ed upon application of pre~3ure to relea~e it~
contents or development of the expo~ed film unit, e.g., by distri~uting the proce~sing composition in a substantially uniform layer between a pair of predeterminèd layers. In film units of the type illustrated in the Figure, a processing composition containing a white pigment may be di~tributed ~ -between the dyeable stratum and the negative component to provide the light-reflecting layer. --In lieu of having the light-reflecting pigment in the processing compo~ition, the light-reflecting pigment used to mask the photo~ensitive strata and to provide the requisite background for viewing the color transfer image formed in the receiving layer may be pre~ent initially in whole or in part as a preformed layer in the film unit. As an example -of ~uch a preformed layer, mention may be made of that dis-clo~ed in U. S. Patent No. 3,615,421 issued October 26, 1971 ~ and in U. S. Patent No. 3,620,724 issued November 16, 1971, ; bo~h in the name of Eawin H. Land. ~he reflectlng agent may be generated in situ as i~ disclosed in U. S. Patents No.
`~ 25 3,647,434 and 3,647,435, both i~sued March 7, 1972 to Edwin H. Land.
~he dye developers ~or other image dye-providing sub~tance~) are preferably selected for their ability to provide color~ that are useful in carrying out subtractive "

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1~14~916 color photography, that i~, the prevtously ~entioned cyan, magenta and yellow. They may be incorporated in the respective silver halide emulsion or, in the preferred em-bodiment, in a separate layer behind the respective silver halide emulsion. Thus a dye developer may, for ~xample, be in a coating or layer behind the respective silver halide emulsion and such a layer of dye developer may be applied by use of a coating solution containing the respective dye developer distributed, in a concentration calculated to give the desired coverage of dye developer per unit area, in a film-forming natural, or synthethic, polymer, for example, gelatin,polyvinyl alcohol, and the like, adapted to be permeated by the processing composition.
~ye developers, as noted above, are compounds which contain the chromophoric ~ystem of a dye and also a silver halide developing function. By ~a sllver halide developing function~ i~ meant a groupinq adapted to develop exposed ~ilver hallde. A preferred silver hàlide development function ~ is a hydroquinonyl group. Other suitàble developing functions i~ 20 include ortho-dihydroxyphenyl and ortho-and para-amino sub-~tituted hydroxyphenyl groups. In general, the development -function includes a benzenoid developing function, that is, an aromatic devèloping group which forms quinonoid or quinone substance~ when oxidized.
The image-roceiving layer may comprise one of the ~-~
materials known in the art, such as polyvinyl alcohol, gelatin, etc. It may contain agents adapted to mordant or 1 otherwise fix the transferred image dye~). Preferred ¦ material~ comprise polyvinyl alcohol or gelatin containing ~ 30 a dyo mord~nt suah a~ poly-4-vinylpyridine, as disc:osed in .
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104~916 U. S. Patent No. 3,148,061, i~sued September 8, 1964 to Howard C. Haas. If the color of the transferred image dye(s) i8 affected by changes in pH, the pH of the image layer may be ad~usted to provide a pH affording the desired color.
In the various color diffwion tran3fer systems which have previou~ly been described and which employ an aqueous alkaline proce~sing fluid, it i8 well known to employ an acid-react~ng reagent in a layer of the film unit to lower ... ... .
; the environmental pH following substantial dye transfer in order to increase the image stability and/or to ad~ust the pH from the first pH at which the image dye~ are dif-fusible to a second (lower) p~ at which they are not. For example, the previously mentioned U. S. Patent No. 3,415,644 discloses systems wherein the desired pH reduction may be effected by providing a polymer~c acid layer ad~acent the dyeable stratum. These polymeric acids may be polymers which contain acid groups, e.g., carboxylic acid and sulfonic acid groups, ~hieh are eap~ble of forming salt~ with alkali metals or with organie bases; or potentially acid-yielding .; . ~. . . -.:
groups sueh as anhydrides or lactones. Preferably the acid polymer eontains free carboxyl groups. Alternatively, the acid-reacting reagent may be in a layer adjacent the ~ilver halide most distant from the image-receiving layer, as dis-i~ closed in U. S. Patent No. 3,573,043 issued March 30, 1971 to ~dw$n H. ~and. Another system for providing an acid-. ~. .
reacting reagent is disclosed in U. S. Patent No. 3,576,625 i~8ued April 27, 1971 to Edwin H. Land. ~ -An inert interlayer or spae0r layer may be ana i9 -pre~erably dispo~ed b~tween the polymeric acid layer and the dye~blQ ~tratum in order to control or "time" the pH

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~t~4~J916 reduction so that it i8 not premature and interfere with the development process. Suitable spacer or ~timing~ layer~
for this purpose are described with particularity in U. S.
Patents ~o~. 3,362,819; 3,419,389J 3,421,893; 3,455,686; and 3,575,701.
While the acid layer and associated spacer layer are preferably contained in the positive component employed in systems wherein the dyeable stratum and ph~tosensitive strata are contained on separate supports, e.g., between the support for the receiving element and the dyeable stratum;
or associated with the dyeable stratum in those integral film unit~, e.g., on the side of the dyeable stratum oppo~ed from the negative components, if desired they may be alternatively or additionally associated with the photosensitive strata, as is disclosed, for example, in U. S. Patents Nos.
3, 362, 821 and 3, 573, 043. In film units such as those described in the aforementioned U. S. Patents Nos. 3,594,164 and 3,594,165, they also may be contained on the spreader sheet employed to facilitate application of the processing fluid.
As is now well known and illustrated, for example, in the previously cited patents, the liquid processing composition referred to for effecting multicolor diffusion transfer procQsses comprises at lea~t an agueous solution of an aIkaline material, for example sodium hydroxid~, potassium r 25 hydroxide, and the like, and preferably possessing 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 rela~ively firm and relatively stable fi~m. The - -pr ferred fllm-forming materials disclosed compri~e high , .
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1¢~4~9~6 molecular weight polymers such as polymeric, water-qol~ble ethers which are inert to an alkaline solution such as, for example, a hydroxyethyl celluloqe or sodium carboxy-methyl cellulose. Other film-forming materials or thickening agents whose ~bility to increase viscosity is substantially unaffectea if left in solution for a long period of time are also known to be capable of utilization.
As stated, the film-forming materlal is preferably contained in the processing compo~ition in such ~uitable quantities as to imp~rt to the composition a visc08ity in excess of lOOcps.
at a temperature of approximately 24 C. and preferably in the order of 100,000 Cp8. to 200,000 cp at that temperature.
The Figure illustrate~ a preferred embodiment of this invention wherein an opa~ue film support 10 carries, in order, a layer 12 of a cyan dye developer, a layer 14 of a red-~ensitive ~ilver halide emulsion, an interlayer 16, a J~ layer 18 of a magenta dye developer, a layer 20 of a green-sen~itive silver halide emulsion, an interlayer 22, a layer 24 of a yellow dye developer, and a layer 26 of a blue-~en~
tive silvex halide emulsion. Over the latter layer there i8 provided an essentially colorless, binder-free layer or stratum of at least one optical filter agent in a solid, j non-crystalline or amorphous form. A second support 32 (transparent) carries a polymeric acid layer 34, a spacer or timing layer 36, and an image-receiving layer 38. Follow-ing photoexposure through the transparent support 32 and the layers carried thereon, the container 30 i8 ruptured and ~;~
~. the processing composition contained therein is distributed .~ .. - ' .:
between the opposing surfaces of layers 28 and 38. Contact by the alkaline processing composition is effective to cause -X
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1~4~916 the pH-sensitive dye to become colored. The processing composi-tion in the container 30 includes a light-reflecting material, e.g., titanium dioxide, and a light-reflecting layer is thereby provided between layers 28 and 38. After a suitable period, the polymeric acid layer 34 is permeated by alkali and the pH
is reduced~to a predetermined level~ Tn the preferred embodiment, the final pH is one below the pKa of the pH-sensi-tive dyets), thereby discharging their color. The final multicolor transfer image in the image-receiving layer 38 is viewed through the transparent support 32 against a white background provided by the titanium dioxide. Suitable binder tape, not shown, may be provided to secure the various layers in fixed relationship prior to, during and after photoexposure and processing. Such film units may be ejected out of a camera into ambient light.
In the most preferred embodiments, the optical ~ -filter agent contains a long chain substituent or "ballast"
group effective to prevent substantial diffusion of the optical filter agent during processing. Where the optical filter agent contains a ballast group of sufficient ~ize to prevent wandering, `~
or it is mordanted, e.g., by the gelatin of the silver halide layer, the optical filter agent will remain in place behind the light-reflecting layer. Under these circumstances, the light-reflecting layer will be substantially white throughout the process, thereby providing a desirable aesthetic advantage.
~, A further advantage of utilizing a ballast group is that such a substituent may help to prevent crystallization and thereby promote the deposition of the optical filter agent as an amorphous solid. The use of mixtures of optical filter agents may also promote deposition of an amorphous coprecipitate :

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~ ~ 4f~ 9 1 6 even though the individual optical filter agents may not crystallize as an amorphous solid.
The following example is given for purposes of illustration only.

Example An image-receiving element and a multicolor dye developer photosensitive element similar to that described in Example 2 of United States Patent No. 3,801,318 issued April 2, 1974 to Edwin H. Land, Stanley M. Bloom and Howard G, Rogers. The photosensitive element was coated, over the -outermost gelatin layer thereof, with a 1:1 by volume solu- ;
tion of acetone and tetrahydrofuran containing 0.38% by weight of -HOOC H H S2 16H33-n (, ` ~ '~"'' W ' ~
and 1.68% by weight of ' .
OH OH

COOH HOOC
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104~9~6 to provide an essentially continuous and colorless solid, amorphous, non-crystalline stratum of said pH-sensitive dyes at a coverage of about 20 mg./ft.2. Following photoexposure, a layer approximately 0.0026" thick of a processing like that in said Example 2 (except that no pH-sen~itive dyes were included) was distributed between the image-receiving layer and the pH-sensitive dye stratum and the resulting laminate brought into room light. The appearance of the multicolor transfer image in the image-receiving layer wa~ continously observed through the tranqparent support carrying the image-receiving layer. The titanium dioxide layer provided by distribution of the processing composition was found to remain uncolored by the pH-sensitive dyes throughout proces~sing, confirming that said dyes remained behind the titanium lS dioxide layer. When this example was repeated using a control portion of the same photosensitive element which did not have the overcoat of the pH-sensitive dyes, some fogging of the silver halide (i.e., reduction in transfer image density) was observed under the same light levels. This control confirmed the fact that the pH-sensitive dyes had become colored in the test and had been effective to protect the photosensitive e}ement from further exposure at the light level of the room.
It will be understood that dye transfer image which are neutral or black-and-white instead of multicolor may be obtained by use of a mixture of dyes of the appropriate colors, the transfer of which may be controlled by a single layer of ---silver halide, in accordance with known techniques. It is also to be understood that "direct positive" silver halide q emulsions may also be used, depending upon the particular dye .f ~ .

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~4`'~916 image-providing substances employed and whether a positive or negative color transfer image is desired.
It will be understood that a quantity of an optical filter agent dissolved in the processing composition may be used in combination with the binder-free stratum of optical filter agent. In such embodiments, the light-reflecting layer providing by a white pigment dispersed in the processing composition will initially be colored, but the color thereof will be less i~tense than if the total required optical filter agent were provided in the processing composition.
The provision of a short dark time, e.g., five to fifteen seconds, following application of the processing composition will permit development to be completed un er higher light levels than otherwise would be permitted by small concentrations of optical filter agents.
The present invention makes possible the use of optical filter agents which are not sufficiently stable to alkali to be initially positioned in a processing composition ,~! stored for a long period prior to use. In addition, the retention of the optical filter agent behind the light-reflecting layer, makes it feasible to utilize optical filter agents I which remain colored at the final pH or optical filter agents which become colorless at a lower pKa, e.g., a pH of about 10, ~ than would be desirable for aesthetic reasons if-they were < 25 present in, and imparted color longer to, the light-reflecting . layer.
Since certa~n 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 ~ 30 contained in the above description shall be interpreted as - illu~trative and not in a limiting sense. ---19- -.
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Claims (30)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A photographic product comprising a support, at least one silver halide emulsion layer and a binder-free layer of at least one pH-sensitive dye in a colorless, non-crystalline, solid form, said dye being capable of absorbing visible light when contacted with an alkaline material.

2. A photographic product as defined in claim 1 wherein said silver halide emulsion layer has associated therewith a dye image-providing sub-stance.

3. A photographic product as defined in claim 2 comprising a support carrying a red-sensitive silver halide emulsion layer, a green-sensitive silver halide emulsion layer, and a blue-sensitive silver halide emulsion layer, said red-sensitive silver halide emulsion having associated therewith a cyan image dye-providing substance, said green-sensitive silver halide emulsion having associated therewith a magenta image dye-providing substance, and said blue-sensitive silver halide emulsion having associated therewith a yellow image dye-providing substance, each said image dye-providing sub-stance being selected from the group consisting of image dyes and image dye intermediates, the outermost said silver halide emulsion layer carried by said support carrying a binder-free, colorless layer of at least one pH-sensitive dye in a colorless non-crystalline solid form, said pH-sensitive dye being colored at an alkaline pH.

4. A photographic product as defined in claim 3 wherein said image dye-providing substances are, respectively, a cyan dye developer, a magenta dye developer and a yellow dye developer.

5. A photographic product as defined in claim 2 including an image-receiving layer; means providing a light-reflecting layer between said image-receiving layer and said silver halide emulsion(s) to mask said silver halide emulsion(s) after development thereof and to provide a white back-ground for viewing a transfer image in said image-receiving layer; a trans-parent support through which said transfer image in said image-receiving layer may be viewed; a rupturable container providing an alkaline processing composition for developing said silver halide emulsion(s) after photo-exposure and for forming said transfer image in said image-receiving layer;
said layer of pH-sensitive dye being positioned between said silver halide emulsion layer(s) and said light-reflecting layer.

6. A photographic product as defined in claim 5 wherein each said image-providing substance is an image-dye providing substance selected from the group consisting of image dyes and image dye intermediates.

7. A photographic product as defined in claim 5 wherein each said image dye-providing substance is a dye.

8. A photographic product as defined in claim 7 wherein each said dye is a dye developer.

9. A photographic product as defined in claim 6 wherein each said image dye-providing substance is an intermediate for an image dye.

10. A photographic product as defined in claim 5 wherein said silver halide emulsion(s) are adapted to be exposed through said transparent support.

11. A photographic product as defined in claim 5 wherein said pH-sensitive dye is a phthalein dye.

12. A photographic product as defined in claim 5 wherein a mixture of at least two pH-sensitive dyes is present in said binder-free optical filter agent precursor layer.

13. A photographic product as defined in claim 5 wherein said means providing a light-reflecting layer comprise a white pigment dispersed in said processing composition, and said processing composition is contained in a rupturable container positioned to distribute said processing com-position containing said pigment between said image-receiving layer and said silver halide emulsion(s).

14. A photographic product as defined in claim 13 wherein said binder-free optical filter agent precursor layer is coated over the outermost silver halide emulsion layer.

15. A photographic product comprising a first support; a red-sensitive silver halide emulsion; a green-sensitive silver halide emulsion; and a blue-sensitive silver halide emulsion; said silver halide emulsions having associated therewith, respectively, a cyan dye developer, a magenta dye developer and a yellow dye developer; an image-receiving layer for receiving image dyes transferred thereto by diffusion as a function of exposure and development of said silver halide emulsion layers; a second support which is transparent and through which said image-receiving layer may be viewed;
a rupturable container releasably holding alkaline processing composition adapted, upon distribution between predetermined layers of said film to develop said silver halide emulsions and to effect the formation of a trans-fer image in dye in said image-receiving layer, said processing composition also being adapted to provide a permanent laminate including said developer silver halide emulsions and said image-receiving layer; and means providing a light-reflecting layer between said image-receiving layer and said silver halide emulsions effective to provide a white background for viewing said transfer image and for masking said developed silver halide emulsions; said product including a binder-free, substantially colorless layer of at least one pH-sensitive dye in a colorless, non-crystalline, solid form positioned between said silver halide emulsion layers and said light-reflecting layer, said pH-sensitive dye being adapted to become colored when contacted by said alkaline processing composition.

16. A photographic product as defined in claim 15 wherein said means for providing a light-reflecting layer comprises a preformed layer of a white pigment.

17. A photographic product as defined in claim 15 wherein said means for providing a light-reflecting layer comprises a white pigment dispersed in said processing composition.

18. A photographic product as defined in claim 15 wherein said first support is opaque.

19. A photographic product as defined in claim 15 wherein said trans-parent support is a polyester.

20. A photographic product as defined in claim 19 wherein said poly-ester is polyethylene terephthalate.

21. A photographic product as defined in claim 20 wherein said opaque support is polyethylene terephthalate.

22. A photographic product as defined in claim 15 wherein said trans-parent support and said image-receiving layer comprise a separate element adapted to be brought into superposed relationship with said silver halide emulsions.

23. A photographic product as defined in claim 15 wherein said layers are held in fixed relationship between said supports prior to and during exposure.

24. A photographic product as defined in claim 23 wherein said fixed relationship is provided by a binder tape along at least two parallel sides of said product.

25. A photographic product as defined in claim is wherein the blue-sensitive silver halide emulsion layer is between said image-receiving layer and said other silver halide emulsion layers.

26. A photographic product as defined in claim 15 wherein the blue-sensitive silver halide emulsion layer is between said first support and said other silver halide emulsion layers, and said first support is transparent.

27. A photographic product as defined in claim 15 including means to reduce the pH of a layer of said processing composition from a first pH
to a second pH.

28. A photographic product as defined in claim 27 wherein said means to reduce the pH comprises a layer of an acid-reacting reagent positioned between said transparent support and said image-receiving layer.

29. A photographic product as defined in claim 28 wherein said acid-reacting reagent is a polymer.

30. A photographic product as defined in claim 15 wherein said process-ing composition includes an additional optical filter agent which is colored at the pH of said processing composition, said optical filter agent being adapted to be rendered colorless by reducing said pH.