US3460942A

US3460942A - Color diffusion transfer process utilizing ultraviolet light absorbers

Info

Publication number: US3460942A
Application number: US744595*A
Authority: US
Inventors: Howard G Rogers
Original assignee: Polaroid Corp
Current assignee: Polaroid Corp
Priority date: 1959-01-14
Filing date: 1968-05-31
Publication date: 1969-08-12
Anticipated expiration: 1986-08-12
Also published as: DE1135756B; GB890861A; FR1247014A; DE1555673A1

Description

Aug. 12, 1969 H. 5. ROGERS 3,

COLOR. DIFFUSION TRANSFER PROCESS UTILIZING ULTRAVIOLET LIGHT ABSORBERS Original Filed Jan. 14, 1959 2 SUPPORT {LAYER CONTAINING |4 A COLOR-PROVIDING SUBSTANCE l PHOTOSENS TIvE ELEME'NOT 16 PHOTOSENS'TNE LAYER PROCESSING soLUTIoN 20 T LAYER CONTAINING AN I. I 033K033:(3101 1 331 I XQIK X'I K :331 31g 32 ULTRAVIOLET LIGHT ABSORBER IMAGE-RECEIVING ELEMENT 3O DYEABLE IMAGE- 34 RECEIVING STRATUM 36 SUPPORT STRATUM INVENTOR.

ATTORNEYS United States Patent Office 3,460,942 Patented Aug. 12, 1969 3,460,942 COLOR DIFFUSION TRANSFER PROCESS UTILIZ- ING ULTRAVIOLET LIGHT ABSORBERS Howard G. Rogers, Weston, Mass, assignor to Polaroid Corporation, Cambridge, Mass :1 corporation of Delaware Continuation of application Ser. No. 354,963, Mar. 26, 1964, which is a continuation-in-part of application Ser. No. 786,766, Jan. 14, 1959. This application May 31, 1968, Ser. No. 744,595 The portion of the term of the patent subsequent to Dec. 18, 1979, has been disclaimed Int. Cl. G03c 5/54, 7/00, 1/40 US. CI. 9629 4 Claims ABSTRACT OF THE DISCLOSURE The present invention is concerned with the protection of dye images formed by color diffusion transfer processes by effecting transfer to an image-receiving layer through an alkali-permeable polymeric layer containing a nonditfusible ultraviolet light absorber.

This application is a continuation of application Ser. No. 354,963 filed Mar. 26, 1964, now abandoned, which in turn is a continuation of application Ser. No. 786,766 filed Ian. 14, 1959, now abandoned.

The present invention relates to color photography and more particularly to novel photographic processes.

One object of this invention is to provide novel photographic processes which produce color transfer images which have enhanced resistance to sunlight.

Other objects of the 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 which are exemplified in the following detailed disclosure, and the scope of the application of which will be indicated in the claims.

For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description taken in connection with the accompanying drawing wherein FIGURE 1 is a diagrammatic enlarged sectional view illustrating the association of elements during one stage of a preferred process of this invention, the thickness of the various materials being exaggerated.

The present invention is particularly related to color diffusion transfer processes. In such processes a photosensitive element including a silver halide emulsion layer is exposed and developed. Concurrent with and under the control of this development, an imagewise distribution of mobile organic color-providing substances is formed. At least a portion of these color-providing substances is transferred to a superposed image-receiving stratum to form a colored image thereon. As examples of such processes, mention may be made of the processes disclosed and claimed in US. Patent No. 2,983,606, issued May 9, 1961 to Howard G. Rogers, wherein dye developers (i.e., compounds which contain in the same molecule both the chromophoric system of a dye and also a silver halide developing function) are the color-providing substances; the processes claimed and disclosed in US. Patent No. 2,647,049, issued July 28, 1953 to Edwin H. Land, wherein color developers are employed to develop the latent image and color couplers are the color-providing substances; and the processes disclosed in US. Patent No. 2,774,668, issued Dec. 18, 1956 to Howard G. Rogers, wherein complete, prefromed dyes are used as the colorproviding substances. By the term organic color-providing substances, as used herein, is meant dyes, including dye developers, and dye intermediates, e.g., color couplers.

In an especially useful mode of carrying out color diffusion transfer processes such as described above, the color-providing substances are disposed in a separate alkali-permeable layer in the photosensitive element. The separate alkali-permeable layer may be placed either in front of or behind the photosensitive emulsion with which it is associated; however, in a preferred embodiment it is placed behind, i.e., on the side of the emulsion which is most distant from the photographed subject when the emulsion is exposed, and preferably also adapted to be most distant from the image-receiving element when in superposed relationship therewith. In carrying out the processes, the photosensitive element is exposed and wetted with an aqueous alkaline processing solution, for example, by immersing, coating, spraying, flowing, etc., in the dark, and the photosensitive element is superposed, prior to, during or after Wetting, on an image-receiving element. In a preferred embodiment the aqueous alkaline processing solution contains a viscosity-increasing compound and is applied to the photosensitive element in a substantially uniform layer as the photosensitive element is brought into superposed position with the image-receiving element. The alkaline aqueous processing solution permeates the photosensitive emulsion and alkalipermeable layers and solubilizes the color-providing substances to provide a substantially uniform distribution of the color-providing substances therein. An imagewise distribution of mobile color-providing substances is formed in undeveloped areas as a function of development. At least a portion of the mobile color-providing substances is transferred to and imbibed on the dyeable stratum of the image-receiving element to form the transfer image. The image is viewed by stripping the image-receiving element from the photosensitive element.

Sometimes in the processes generally described above, the color-fastness of the transfer image, upon continued exposure to sunlight, leaves something to be desired.

The present invention is concerned with providing means for protecting such dye images through the use of ultraviolet light absorbers, without requiring subsequent coating operations.

In a preferred mode of carrying out this invention, it has been found that, prior to processing, an ultraviolet light absorber may be incorporated in a layer over the dyeable stratum of an image-receiving element and, during processing, that a substantial portion of the transferred color-providing substances may be caused to permeate through such a layer to the underlying dyeable stratum to form a color image which is protected from the deleterious effects of sunlight by the ultraviolet light absorber in the overlying layer.

Referring now to FIG. 1, there is shown the association of elements during one stage of a preferred method of carrying out the present invention. In FIG. 1 there is provided a photosensitive element 10, an image-receiving element 30, and a layer of processing composition 20.

The photosensitive element 10 comprises a support 12, which in turn has been coated with a layer 14 containing a color-providing substance, and a photosensitive layer 16, e.g., a silver halide emulsion layer. The image-receiving element 30 comprises a base layer 36, a dyeable imagereceiving stratum 34 and a layer 32 containing an ultraviolet light absorber. In a preferred modification, the processing composition 20 comprises an aqueous alkaline solution and preferably contains a viscosity-increasing material such as sodium carboxymethyl cellulose, hydroxyethyl cellulose, etc. As examples of alkaline materials which may be present in the processing composition, mention may be made of sodium hydroxide, sodium carbomate, and diethylamine. In some cases it may also contain color-providing substances, developing agents, and conventional photographic reagents such as accelerators, restrainers, etc. For example, as disclosed in the aforementioned U.S. Patent No. 2,983,606, the color-providing substance (in this case the dye developer) may be present initially in the processing composition in lieu of being present in a layer in the photosensitive element, as illustrated herein in the drawing.

According to the present invention, a photosensitive element is exposed and wetted in the dark with the processing solution 20 and the photosensitive element 10 is superposed, prior to, during, or after said wetting, on the image-receiving element 30, as shown in FIG. 1. The processing solution permeates the photosensitive element 10 and an imagewise distribution of mobile color-providing substances is formed as a function of development. At least a portion of the mobile color-providing substances is transferred to the image-receiving element 30. The transferred color-providing substances permeate through layer 32 so that a substantial portion of them are deposited on the dyeable image-receiving stratum 34 where they are protected from the deleterious effects of sunlight by layer 32. Imbibition periods of approximately one minute have been found to give good results; however, this contact period may be varied, where necessary, to compensate for variation in temperature or other conditions. After completion of the imbibition period, the transfer image may be viewed by stripping the image-receiving element from the photosensitive element 10.

In order that a substantial portion of the color-providing substances may be permeated through the layers containing the ultraviolet light absorbers, it is required that the polymers which are used as the carriers for such layers be permeable to the processing solution which is employed. As mentioned previously, such solutions are preferably of an aqueous alkaline nature; however, in certain instances they may contain water-miscible organic solvents such as ethanol, methanol, tetrahydrofuran, etc. When the term alkali-permeable is used to describe the polymers which are used as the carriers for the ultraviolet light absorber, it should be understood that said term refers to polymers which are permeated by aqueous alkaline solutions. It should be further understood that the aqueous alkaline solutions may contain water-miscible organic solvents such as mentioned above.

It is further desirable for good permeation that the polymers have a low aflinity for the particular color-providing substances employed and at least that they have a lower aflinity for the color-providing substances than the polymers which are used for the dyeable stratum of the image-receiving element. The preferred polymers are those which are substantially nondyeable by the colorproviding substances. As will be understood, the afiinity of the polymers will vary depending upon the color-providing substances employed. Suitable polymers, having low aflinity for the color-providing substances, may be readily selected by simple dyeability tests which are well known to the art, e.g., a film of the polymers is dipped in a bath of the color-providing substance, washed, and observed for retained dye. When dye developers are empolyed as the color-providing substances, mixtures of cellulose acetate hydrogen phthalate and cellulose acetate have been found to be particularly useful as carriers. As examples of other polymers contemplated to be useful as carriers for the ultraviolet light absorbers, mention may be made of polyvinyl, sulfoand carboxy-substituted benzals of polyvinyl alcohol, copolymers of N,N- diethylacrylamide and acrylic acid, copolymers of N,N- diethylacrylamide and acrylamide, and copolymers of dimethylarninoethyl-methacrylate and methacrylic acid. It should be understood that mixtures of polymers may be used to provide layers having the desired properties.

The permeation of the color-providing substances through the outer ultraviolet light absorber layers may be further facilitated by incorporating mordants for the color-providing substances in the underlying dyeable image-receiving stratum so that such stratum will be preferentially dyed. A further means of facilitating premation comprises incorporating precipitating agents for the color-providing substances in the dyeable stratum. When the color-providing substances are dye developers, oxidizing agents such as benzoquinones may be used to bring about precipitation.

When hydrophilic, alkali-permeable polymers are used as carriers for the ultraviolet light absorbers, small amounts of hydrophobic polymers, e.g., cellulose acetate, cellulose nitrate, may be added to such layers to reduce their water sensitivity. In certain instances, depending upon the color-providing substances employed, such hydrophobic polymers may be further used to reduce the dyeability of such layers. The amount added usually may be varied to suita particular needs. Generally, about three parts of the hydrophobic polymer to about eight parts of the hydrophilic polymer have been found to be particularly useful.

Ultraviolet light absorbers for use in this invention may be selected from the many compounds of this nature which are commercially available. The amount of ultraviolet light absorber used will vary with many factors such as the efficiency of the ultraviolet light absorber itself, the original color-fast-ness of the color-providing substances, the amount of sunlight the transfer image will be exposed to during its life expectancy, etc. Generally, about one part of the ultraviolet light absorber to about five parts of the carrier have been found effective in enhancing the color-fast'ness of the images.

As an example of a class of ultraviolet light absorbers which have been found to be especially useful in the processes and products of this invention, mention may be made of the thiazolidine ultraviolet light absorbers disclosed in U.S. Patent No. 2,808,330, and particularly those having substituents rendering them substantially nonditfusible. Such ultraviolet light absorbers may be represented by the formula:

wherein R represents a hydrogen atom, an alkyl or an aryl group, R is an aryl group and Q is a divalent nonmetallic atom (e.g., oxygen, sulfur) or radical (e.g., imino). As an example of an ultraviolet light absorber within this class and which is insoluble in aqueous alkaline solutions, mention may be made of 5-benzilidene-3- hexadecyl-Z-phenylimino-4-thiazolidone.

As examples of other useful ultraviolet light absorbers, mention may be made of those described and claimed in the copending applications of Norman W. Schuler, Ser. No. 301,958 filed Aug. 14, 1963, now U.S. Patent 3,330,- 656 and 319,693 filed Oct. 29, 1963, now U.S. Patent 3,183,219, and in the copending application of Howard C. Haas, Ser. No. 319,653 filed Oct. 29, 1963, now U.S. Patent 3,330,680. The polymeric ultraviolet light absorbers described and claimed in these applications may be employed alone or with a polymeric carrier such as heretofore described.

The ultraviolet light absorbers employed may be soluble or insoluble in the photographic processing solutions. Ultraviolet light absorbers which are insoluble in such solutions are especially useful in that they are not dissolved during the permeation step and remain over the dyeable stratum of the image-receiving element. It should be understood that when such insoluble ultraviolet light absorbers are used, they are disposed in polymeric layers which are permeated but not solubilized by the processing solutions. When ultraviolet light absorbers which are soluble in the photographic processing solutions are used, at

least a portion of the ultraviolet light absorber is dissolved by the processing solution during processing and deposited on the dyeable stratum of the image-receiving element along with the color-providing substances. Since the ultraviolet light absorbers are dissolved during processing, the polymeric layer, in which they are disposed, may or may not be soluble in the processing solution. In order that the soluble ultraviolet light absorber will be preferentially deposited on the dyeable stratum, it is desirable, when selecting ultraviolet light absorbers, to select those which have an afiinity for the particular dyeable stratum which is to be used. It is further desirable in selecting soluble ultraviolet light absorbers to select those which have a lower rate of mobility than the color-providing substances so that they will tend to be deposited over the color-providing substances on the dyeable stratum.

The image-receiving elements, over which the ultraviolet light absorber layers are coated, generally comprise a sheet of dyeable material, e.g., baryta. In a preferred embodiment, such elements comprise a support which in turn has been coated with an image-receiving stratum of a dyeable material. As examples of dyeable materials which have been found useful for the image-receiving stratum, mention may be made of gelatin, a mixture of polyvinyl alcohol and polyvinyl pyrrolidone, a mixture of polyvinyl alcohol or gelatin and poly-4-vinylpyridine, copolyrners of vinyl alcohol and vinyl pyrrolidone, and nylons such as N-methoxymethyl polyhexamethylene adipamide.

The ultraviolet light absorber layers may be applied to the image-receiving elements from suitable coating solutions, using coating techniques well known to the art. The concentrations of the coating solutions can usually be varied to suit particular needs. Generally, coating solutions comprising 2 to 5% solids have been found to be particularly useful. The preferred solvents for use in the coating solutions are those which are solvents for both the ultraviolet light absorber and the polymeric carrier. By using such solvents, the ultraviolet light absorber is molecularly dispersed in the resulting layer and thus provides the most effective coverage.

The products and processes of this invention are especially useful when dye developers are the color-providing substances. Dye developers, as noted above, 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 radical which is capable of developing an exposed silver halide image. In a preferred embodiment, the silver halide developing function in such compounds is provided by the presence of a benzenoid developing radical therein, e.g., a hydroquinonyl radical. Ex amples of representative dye developers are given in the previously mentioned U.S. Patent No. 2,983,606.

In color diffusion transfer processes employing dye developers, the dye developer, as mentioned previously for color-providing substances in general, is preferably but not necessarily placed in a separate alkali-permeable layer behind the photosensitive layer. Upon processing, the aqueous alkaline processing solution permeates to the separate alkali-permeable layer and solubilizes the dye developer therefrom. As the process proceeds, the exposed silver halide in the photosensitive element is developed and, as a result of this development, the dye developer in the exposed areas is oxidized and substantially immobilized. At least a portion of the unreacted dye developer is imbibed on a superposed image-receiving layer to create thereon the positive dye image. In such processes the immobilization of the dye developers in the exposed areas is apparently due, at least in part, to a change in the solubility characteristics of the dye developer upon oxidation. It may also be due in part to a tanning effect on the emulsion by the oxidized developer and in part to localized exhaustion of alkali due to development.

The following nonlimiting example illustrates the preparation of an image-receiving element within the scope of this invention.

Example An image-receiving element was prepared by successively coating a cellulose acetate-coated baryta paper with the following coating solutions:

(1) An ethanol solution comprising 4% of N-methoxymethyl polyhexamethylene adipamide, and

(2) A tetrahydrofuran-methanol solution (1 to l, by volume) comprising 2.0% cellulose acetate hydrogen phthalate, 0.75% cellulose acetate and 0.5% of S-benzilidene-3-hexadecyl-2-phenylimino-4-thiazolidone.

A photosensitive element for use with the above imagereceiving element may be prepared, for example, by successively coating a gelatin-subcoated cellulose acetate support with a solution comprising a methanol-tetrahydrofuran solution (1 to 1, by volume) comprising 3% 0f 2-[p-(2',5'-dihydroxyphenethyl)-phenylazo] 4 n-propoxy-l-naphthol and 2% of a sodium sulfobenzal of p lyvinyl alcohol, followed, after drying, by a silver iodobromide emulsion coating.

The above photosensitive emulsion may be processed, after exposure, by spreading a processing solution such, for example, as an aqueous solution comprising:

Percent Sodium carboxymethyl cellulose 5.0 Sodium hydroxide 3.0 l-phenyl-3-pyrazolidone 1.2 -nitrobenzimidazole 0.12 2,5-bis-ethyleneiminohydroquinone 0.9

between said photosensitive element and the image-receiving element as said elements are brought into superposed relationship. After an imbibition period of approximately one minute, the image-receiving element is separated and contains a dense magenta positive dye image of the photographed subject.

The effectiveness of the image-receiving elements of this invention was tested by exposing such elements, after transfer, to a bank of sun lamps along with a control, prepared as above, in absence of the ultraviolet light absorber layer. After an exposure of seventy-two hours, the transfer images, prepared by using the image-receiving elements of this invention, were substantially more stable than the control images.

Although the use of the image-receiving element was demonstrated above, using a dye developer, it is to be understood that this was for purposes of illustration only and that other color-providing substances may be used. It should be further understood that the image-receiving elements of this invention are equally useful in multicolor diffusion transfer processes. As examples of photosensitive elements useful in such processes, mention may be made of the elements disclosed in the previously mentioned U.S. Patents Nos. 2,647,049 and 2,983,606, as Well as those disclosed in the copending application of Edwin H. Land and Howard G. Rogers, Ser. No. 565,135, filed Feb. 13, 1956.

The image-receiving elements of this invention are especially useful in composite roll film units intended for use in a Polaroid Land Camera, sold by Polaroid Corporation, Cambridge 39, Mass, or a similar camera structiire such, for example, as the camera forming the subject matter of U.S. Patent No. 2,435,717, issued to Edwin H. Land on Feb. 10, 1948. In general, such composite roll film units comprise a photosensitive roll, a roll of image-receiving material and a plurality of pods containing an aqueous alkaline processing solution. The rolls and pods are so associated with each other that, upon processing, the photosensitive element may be superposed on the image-receiving element and the pods may be ruptured to spread the aqueous alkaline processing solution between the superposed elements. The nature and construction of the pods used in such units are well 7 known to the art. See, for example, U.S. Patents Nos. 2, 543,181 and 2,634,886, issued to Edwin H. Land.

It has also been found that, in lieu of being present initially in a layer overlying the image-receiving stratum, the ultraviolet light absorber may be suppiled to the processing composition and deposited along with the colorproviding substances on the image-receiving stratum. The ultraviolet light absorber may be initially placed in the processing solution itself or it may be placed in the photosensitive element and solubilized therefrom during processing. The ultraviolet light absorbers used in this mode of the invention should be soluble in the aqueous alkaline processing solutions and should be inert in any reactions to which the color-providing substances may be subjected, e.g., color coupling. When the ultraviolet light absorber is initially placed in the processing solution, best results are obtained when measures are taken to prevent the ultraviolet light absorbers from being prematurely deposited on the image-receiving stratum. On such measure is to use as the image-receiving stratum a material which has a slower rate of permeation by the processing solution than the materials used in the photosensitive elements.

When the ultraviolet light absorbers are initially disposed in the photosensitive elements, they may be incorporated in various positions throughout such elements. In a preferred embodiment, the ultraviolet light absorber is incorporated in a separate alkali-permeable layer along with the color-providing substances. Upon processing, the ultraviolet light absorber is solubilized by the processing solution and transferred along with the imagewise distribution of color-providing substances to the image-receiving layer. The preferred ultraviolet light absorbers for use in this embodiment have rates of mobility in the processing solution such that they will not be transferred before the color-providing substances.

In another useful embodiment, the ultraviolet light absorber is disposed in a separate alkali-permeable layer apart from the color-providing substance in the photosensitive element. The layer bearing the ultraviolet light absorber is preferably placed behind the layer containing the color-providing substances so that during processing the ultraviolet light absorber will be dissolved after the color-providing substances and tend to be deposited over them on the image-receiving stratum. In a further embodiment, the separate alkali-permeable layer containing the ultraviolet light absorber may be applied over the photosensitive emulsion. This embodiment is especially useful when an ultraviolet light absorber is used which has a lower rate of mobility than the color-providing substance. This embodiment is particularly advantageous in that the ultraviolet light absorber layer can perform other useful functions in addition to protecting the transferred colorproviding substance. One such function would be to act as a haze filter and antiabrasion coat for the photosensitive emulsion. Another such function would be to decrease the etfect of ultraviolet light on blue-sensitive emulsions when such emulsions have excessive ultraviolet sensitivity. It would be further useful in multicolor, multilayer photosensitive elements and especially in those wherein a yellow filter is placed behind a bluesensitive emulsion and it is desirable to cut down the amount of ultraviolet light transmitted to the red and green layers. In a still further embodiment, an ultraviolet light absorber may be placed in the photosensitve emulsion stratum. Since in some cases ultraviolet light absorbers may tend to desensitize the photosensitive material, suitable precautions should be taken in selecting the ultraviolet light absorber to be so used.

In still another embodiment, a transparent image-receiving element is employed and an ultraviolet light absorber is disposed in the supporting stratum of said element. Upon processing, the color-providing substances are transferred to the dyeable stratum of the image-receiving element and an opaque background, preferably white, is provided behind the dyeable stratum so that the transfer image is viewed through the support by reflection. The opaque background behind the dyeable stratum may be provided by various methods. As an example of one such method, mention may be made of a thin, permeable layer, e.g., containing a white pigment such as titanium dioxide, located over the dyeable stratum and through which the color-providing substances difiuse to the dyeable stratum. Use also may be made of the processes disclosed in U.S. Patent No. 2,647,056, wherein an opacifier is incorporated in the viscous processing solution and the processing solution is adapted so as to preferentially adhere to the image-receiving stratum. Another mode of providing an opaque background comprises incorporating a material in the processing solution and another material on the surface of the image-receiving stratum which, when reacted with the former material, produces an opaque product. An example of this method may be found in U.S. Patent No. 2,607,685, wherein sodium carbonate is used in the processing solution and zinc hydroxide is incorporated in the image-receiving stratum. It should be understood that the opacifiers or opacifying reagents may be incorporated in separate processing solutions which are distinct from those used to process the photographic image. When it is desirable to use such separate solutions, film units which contain a plurality of rupturable reagent containers, such as those disclosed in the above-mentioned U.S. Patent No. 2,607,685, may be employed. In a further mode of providing an opaque background, the image-receiving element may be superposed on and adhered to an opaque sheet after processing.

The images produced in the above embodiment will appear reversed when viewed through the support. In most instances this reversal will not be objectional but, if it is desirable to remedy it, one may use a camera which contains an odd number of mirrors in the focal path between the lens and the photosensitive element. Examples of such cameras may be found in U.S. Patent No. 2,834,269.

In cases where the ultraviolet light absorbers exhibit color changes in an alkaline medium, provisions may be made to provide that the image-receiving element, after processing, will have a suitable pH to render such ultraviolet light absorber substantially colorless. One such provision would be to use a volatile alkaline material in the processing composition so that after processing it would volatilize from the image-receiving element and reduce the pH of said element. As examples of volatile alkaline materials, mention may be made of diethylamine, ethylamine, ethanolamines, etc. Another useful provision which may be used would be to incorporate an acid into the image-receiving element which would neutralize any alkaline material which may be deposited thereon during processing. As examples of suitable acids, mention may be made of citric acid, oxalic acid, etc. A particularly useful method of controlling the pH of the imagereceiving element is the use of a polymeric acid layer, as disclosed and claimed in the copending application of Edwin H. Land, Ser. No. 234,864, filed Nov. 1, 1962, and now U.S. Patent 3,362,819.

A particularly useful class of ultraviolet light absorbers are those which are phototropic, i.e., ultraviolet light absorbers which are substantially colorless when not absorbing ultraviolet radiation and which are activated when strongly irradiated by ultraviolet radiation. Although such phototropic ultraviolet light absorbers may become colored when activated by strong ultraviolet radiation, they revert to the colorless form when such radiation is removed.

The concept of applying the ultraviolet light absorber to the processing composition in lieu of having it initially in a layer over the dyeable image-receiving stratum, e.g., layer 32 overlying layer 34 of the drawing, is described and claimed in copending application Ser. No. 247,866

9 filed Dec. 28, 1962, now U.S. Patent 3,249,435 which in turn is a continuation-in-part of application Ser. No. 786,766 filed Jan. 14, 1959, now abandoned.

Since certain changes may be made in the above processes 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:

1. In a process of forming a photographic image in color wherein an exposed silver halide emulsion is developed in the presence of at least one dye developer to provide an imagewise distribution of mobile dye developer, said dye developer being a compound which is both a dye and a silver halide developing agent, and said imagewise distribution of mobile dye developer is transferred to a superposed image-receiving stratum to produce a transfer image thereon, the improvement wherein said transfer is effected to an image-receiving element having an ultraviolet light absorber in an alkali-permeable polymeric stratum over the dyeable image-receiving stratum and transferring a substantial portion of the said mobile dye developer through said polymeric stratum to said dyeable image-receiving stratum, said polymeric stratum having less afiinity for the said dye developer than the imagereceiving stratum, said polymeric stratum comprising an alkali-insoluble polymer and said ultraviolet light absorber being nondifiusible.

2. In a process of forming a color transfer image by diffusion transfer, wherein a photosensitive element comprising an exposed silver halide emulsion is developed by an aqueous alkaline solution in the presence of a dye developer, said dye developer being a compound which is both a silver halide developing agent and a dye, and an imagewise distribution of diffusible, unoxidized dye developer is formed in undeveloped areas of said exposed silver halide emulsion as a function of development, and at least a portion of said imagewise distribution of dye developer is transferred by diffusion to an image-receiving element including an image-receiving layer to provide said color transfer image, and said image-receiving element is separated from its superposed relationship with said silver halide emulsion, the improvement wherein said image-receiving element includes an alkali-permeable polymeric stratum containing an alkali-insoluble ultraviolet light a-bsorber positioned over said image-receiving layer, said polymeric stratum having a substantially lower affinity for said unoxidized dye developer than does said image-receiving layer whereby said unoxidized dye developer transfers through said polymeric stratum to said image-receiving layer, and said alkali-permeable polymeric stratum remains adhered to said image-receiving layer when said image-receiving element is separated from said photosensitive element.

3. A process as defined in claim 2 wherein said ultraviolet light absorber comprises a nondiffusible thiazolidine ultraviolet light absorber.

4. A process as defined in claim 2 wherein said nondiffusible ultraviolet light absorber comprises a polymeric ultraviolet light absorber in an alkali-permeable polymeric carrier.

References Cited UNITED STATES PATENTS 2,808,330 10/1957 Sawdey 9684 2,882,150 4/1959 Van Allen et al. 96--84 2,888,346 5/1959 Tulagin et al. 9684 3,069,262 12/1962 Haas 96-29 I. TRAVIS BROWN, Primary Examiner U.S. Cl. X.R. 96-3, 77, 84