US2698236A

US2698236A - Photographic silver halide transfer product and process

Info

Publication number: US2698236A
Application number: US432813A
Authority: US
Inventors: Edwin H Land
Original assignee: Polaroid Corp
Current assignee: Polaroid Corp
Priority date: 1954-05-27
Filing date: 1954-05-27
Publication date: 1954-12-28
Anticipated expiration: 1971-12-28

Description

Dec. 28, 1954 LAND 2,698,236

PHOTOGRAPHIC) SILVER HALIDE TRANSFER PRODUCT AND PROCESS Filed May 27, 1954 loci \1' 5.1 Processing Agent Supporf [6 K 120 Silver Precipifoi'ing Layer FIG. I

/Prin+ Receiving Elemcnf FIG. 2

(Abrasion Rcsisiumi Coui'ing Sil vcr Prccipifaiing Layer FIG. 3

INV NTOR ma ATTORNEYS Un wd. S tes- 13mm 0.

Edwin H. Land, Cambridge, Mass, assignor to Polaroid Corporation, Cambridge, Mass., a corporation of Delaware 1 Application May 27, 1954, Serial No. 432,813

34 Claims. (Cl. 95--8) This invention relates to photographic products. and processes and more particularly to transfer processes wherein a latent image in a silver halide emulsion is developed and wherein a soluble silver complex obtained by reaction with the undeveloped silver halide of said emulsion is transferred from said emulsion and the silver thereof is precipitated in another layer to form a positive print, and to products useful as print-receiving elements in said processes.

This application is a continuation-in-part of my copending application Serial No. 164,908, filed' May 29, 1950, whlch, in turn, is a continuation-in-part of my copending application Serial No. 727,385, filed February 8, 1947, for Photographic Product and Process.

One object of the present invention is to provide a transfer process of the foregoing type and products for use in said process whereby thereare produced positive prints of good quality and stability from silver halide emulsions of high speed.

Another object of the present invention isto provide an improved product particularly useful in the foregoing transfer processes as the print-receiving element, said product comprising a novel silver precipitating layer adjacent one surface thereof, which layer serves to effect a controlled precipitation of the silver from the soluble silver complex and also acts to receive and suitably aggregate the precipitated silver to producedense positive images of excellent pictorial quality.

Another object of the present invention is to provide a print-receiving element which has a novel silver precipitating layer comprising a heavy metal sulfide for selenide as its precipitating agent andwhich also contains suitable salts for preventing diffusion or wandering-of the silver precipitating agent from its originalloeus in said layer.

Still another object of the present invention is to provide a novel print-receiving element which also includes materials for greatly improving the stability of the positive silver print formed in said element.

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

The invention accordingly comprises the several steps and relation and order of one or more of such steps with respect to each of the others, and the product possessing the features, properties and the relation of elements which are exemplified .in the following detailed disclosure, and the scope of the application-of which will be indicated inthe claims. M '1 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 l is a diagrammatic, enlarged sectional view illustrating the association of elements during one stage of the performance of a transfer process and showing asone of the elements an embodiment of the novel product of the present invention, the thicknesses of the various materials being exaggerated;

Fig. 2 is a perspective view, with parts broken away, of one form of print-receiving element upon which containers of the processing agent are so positioned as to be capable of distributing their contents between the surfaceof the print-receiving element and a photosensitive element; and

the print-receiving element of the invention.

The present invention comprehends improved processes,

, of zinc, cadmium and lead.

In general, the sulfides and selenides of the alkali metals and products of the type whereby a positive print is obtained in a single step by suitably treating a silver halide emulsion containing a latent image with a uniformly applied layer of processing liquid. Preferably, the processing liquid is in a viscous condition and .is spread in a liquid film between the photosensitive element comprising the silver halide emulsion and a print-receiving element comprising a suitable silver precipitating layer. The liquid develops the latent image in the emulsion and forms a soluble silver complex, e. g., a thiosulfate or a thiocyanate, with undeveloped silver halide. This soluble silver complex is at least in part transported in the direction'of the print-receiving element and the silver thereof is largely precipitated in the silver precipitating layer of said element to form a positive image in silver.

It has been proposed to use in the formation of the silver transfer prints by the foregoing process certain compounds and elements whose presence during the'process has a desirable effect on the amount and character of thesilver precipitated during image formation. For this purpose, such materials as, for example, the metallic sulfides and selenides, thiooxalates, and thioacetamides have been disclosed in my Letters Patent No. 2,647,056, issued July 28, 1953. Other precipitating agents have been proposed such, for example, as colloidal silver.

According to the present invention, the precipitation and aggregation of silver obtained by using the silver precipitating agents, including the above-mentioned materials, is very greatly improved by providing in the print-receiving element as a dispersing medium for said agents a layer of silica such, for example, as is formed from the hydrated colloidal silica dispersion available under the trade name Ludox or the silica aerogel avail-. able under the trade name Santocel C.

The novel silver precipitating layer including the'silica and the silver precipitating agent is preferably applied-to a suitable support, for example by being coated on the support in the form of a suspension which contains a substantially greater amount of the silica than of the precipitating agent. The support may be formed 'of materials such as paper, regenerated cellulose, polyvinyl alcohol, cellulose ethers such as methyl cellulose, ethyl cellulose, or their derivatives, such as sodium carboxymethyl cellulose and hydroxyethyl cellulose, and other natural and synthetic gums and resins which will form continuous films and which are relatively stable, meehani cally, in the presence of water and alkali.

Although the present invention comprehends, as silver precipitating agents, such materials as certain of the colloidal metals, e. g., silver, most satisfactory results: are obtained by using the relatively water-insoluble metallic sulfides and selenides. Examples of silver precipitating agents of this preferred type are the so-called heavy metal sulfides of zinc, chromium, gallium, iro'n, cadmium, cobalt, nickel, lead, antimony, bismuth, silver, cerium, arsenic, copper and rhodium and the selenides of lead, zinc, antimony and nickel. For best results, it is preferable to employ the sulfides whose solubility products in an aqueous medium at approximately 20 C;

vary between 10* and 10- and specifically the salts and alkali earth metals such as sodium, potassium, cesium,

calcium, barium, and magnesium are too soluble to give'. optimum pictorial quality, although the PIOVISlOH'Of'a" silica layer as avehicle'for such precipitating agents greatly improves'the results obtained with said agents;

The concentration of the silica in the silver precipitating" layer is preferably high enough to give a macroscopically silver precipitating agent is present in a very small amount. It has been determined that further improvements in image quality are obtained when using one or more of the heavy metal sulfides and selenides as silver precipitating: agents if the sulfide or selenide 1ons of the crystals are prevented from wandering or diffusing during prec1p1ta-. tion from their original loci in the preclpltatmg layer. In the following discussion of this and other phenomena involving the action of the sulfide and selenide salts,- reference will be made to the sulfides alone, but 1t 18 tov Patented Dec. 28,, .1954

be understood that wherever such reference is made, the same, unless otherwise stated, is generally applicable to the selenides.

To prevent the diffusion and wandering of the sulfide ions, there is preferably included in the silver precipitat inglayer or closely adjacent thereto at least one metallic salt which is substantially more soluble in the processing agent thanthe heavy metal sulfide used as the silver precipitating agent and which is irreducible in the processing agent, said more soluble salt having, as its cation, a meta whose ions form sulfides which are difiicultly soluble in the processing agent and which give up their sulfide ions to silver by displacement. Accordingly, when such sulfide ions are present, the metal ions of the more soluble salt'have the effect of immediately precipitating the sulfide. ions from solution.

The special function of this combination of a sulfide, a more soluble metallic salt and a silica will be better understood by considering the new sequence of reactions which takes place when a print-receivingelement so constituted is used in a silver halide transfer process involving a silver halide developer and a silver halide solvent, such as sodium thiosulfate. This sequence of reactions is perhaps best described in my article One-Step Photography appearing in Section A of the January, 1950 issue of the Photographic Journal (British) as follows:

First: The silver ion in the silver halide of the negative is protected by its environment in the crystalline halidefrom being reduced, but it prefers the thiosulphate ion as an associate, so the silver halide dissolves.

Second: The silver ionis now protected from reduction by the thiosulphate complex, but it prefers the sulphide ion as an associate, so that silver sulphide is formed and would be precipitated as such if it were not for the fact that the sulphide ion-in'spite of the insolubility of the crystalline compounddoes not protect the silver ion from reduction. Thus, the silver ion has been safely pried loose and transported to a new site where it becomes silver, and the transporting ions are free to carry on their cyclic efforts- Is this then the end? Actually, it is the beginning, for while we have learned how to extract the silver ions fromthe negative and to precipitate them as reduced silver rapidly, we are just beginning to consider how to build up an acceptable positive from the point of view of appearance (and of course we have not yet considered our prob,- lems of stabilizing an image resident in this complicated reagent).

What we find when we use sulphide ions to release silver ions from the thiosulphate complex is the'following gamut of problems:

(1). Sulphide ions in solution provide so many points of initiation that an enormous numberof grains start growing. betoo dense. If they remain small, the picture will be bright. yellow (you will recall that, the colour of'silver colloids depends on the particle size).

(2). There is a tendency for the grains in the shadows, opposite. the unexposed portions of the negative, where much silver is available, to grow larger than the grains in the medium tones, where the available silver concentration'is low, producing an unpleasant combination of blue shadows and yellow high lights.

(3). Some of the sulphide ions migrate into the negatlve, dropping the concentration in the positive and fogging the negative.

"Thus, having determined how to extract silver ions from the. appropriate part of the negative, and how to. reduce them to silver atoms, we are still confronted with the problem of how to build these atoms into arrays of the correct diameter for absorbing-visible light. We must also achieve adequate constancy in diameter so that highlight and shadow are the same hue.

Since the. sulphide'ions are the last factor in the chain of events leading to silver precipitation, let us consider how these might be arranged to influence the arrayof silveratoms'. Let us suppose that we can arrange the sulphide ions in clusters, allowing the diameter of the. cluster to be that of the mass of silver we seek to build. The actual mass of sulphide ions might then be very low 1ndeed-s ubject to one vital proviso, namely that as-the sulphide ons perform their cyclic function, they are retained within the diameter that we have chosenfor the cluster. If we can meet this condition, then we can cause the silver atoms to fill in the volume of the cluster to make- If these become large the whole picture will process with quite good resolving power.

our mass of silver of the required density and size. To do all this we must extend the chain of circumstances that we have been following from the negative outward.

By forming colloidal crystals of heavy metal sulphides which are not reducible generally in or soluble in the developer, and by aggregating these colloidal crystals into galaxies of our chosen diameter, we can arrange the sulphide ions as we desire them. In this new environment the sulphide ion is bound in place until the silver thiosulphate complex touches it. The silver ion-just as it once left the halide ion for the complex-now leaves the complex ion to form the sulphide. The sulphide similarly leaves the metal ion for association with the silver. Then the silver is reducedbut mark you, reduced in situ reduced at the point where we originally deposited the colloidal particle of metal sulphide. We have started well in building up our mass of silver. But the sulphide ion, now free, is not likely to encounter the metal ion to which it was bound if it escapes from the galaxy and wanders off. We are in danger of reverting to some extent to the problems that occured with the soluble sulphide. This danger can be avoided by introducing into the positive sheet at the time of manufacture a relatively high concentration of a soluble salt of the same metal that we used in the colloidal sulphide (or indeed of some other metal, providing that its sulphide is more soluble than silver sulphide and is not reducible in, or soluble in, the developer). After the viscous developer is spread, the metal salt in the positive sheet dissolves, and be cause of the relatively high concentration of these metal ions, the sulphide. that is, freed at its original site by the reduction of the silver is at once captured before it can leave that site, and reprecipitated as the sulphide of the metal. In his way, the diameter of the galaxy is maintained. in spite of the cyclic use of the sulphide ions. The silver ions are reduced to silver over the same area that wechose for the original galaxy, and the diameter of the mass of silver is such that our image is the colour we predetermined when we prepared the metal-sulphide galaxies. One remarkableaspect of pictures made in this way is, that thev silverin the positive has very high covering power.in theorder of fivetimes that of the silver in the negative. Consequently a good positive can be made from a layer of silver. halide that is many times thinner than is ordinarily required for a negative. While full thickness negatives can be used for making this new kind of positive, it is impressive to see how thin a layer of negative material suflices. The negative image, when such a thin emulsion is used, is only just visible, yet the positive derived from the same amount of silver is rich and brilliant; Thus, we see that this process provides a type of intensification. Furthermore, since only the surface of the negative'is involved, there is gain in speed, and a gain in sharpness both in exposing and printing. Indeed the. migration distance for the silver ions going from the negative sheet to the positive image can be extremely small. We have, seen that these ions come from very near the surface of the negative, and we can, if we choose, precipitate the silver in the viscous positive layer at the surface of the negative. Thus, the combination of minimized light scattering in the negative, the short migration distance-for the silver ions, and the prompt precipitation of them when they reach the positive, results in :1 Furthermore, the pictures are by all ordinary standards grainless, bccause-of the way in which the silver is deposited and aggregated. (Underlined words added or modified.) v

The silver precipitating agent is dispersed in silica which aids the formation of the aforementioned galaxies, and it is evident, from the foregoing, that the presence of the more soluble salt, which provides the cations for capturing the free sulfide ions, has the effect of maintaining this desirable aggregation of the sulfide ions during the silver precipitation. These more soluble or ioncapturing salts may be the soluble salts of any of the following metals: cadmium, cerium(ous), cobalt(ous), iron, lead, nickel, manganese, thorium and tin. Satisfactory soluble and stable salts of the above metals may be found, for example, among the following groups of salts: the acetates, the nitrates, the borates, the chlorides, the sulfates, the hydroxides, the formates, the citrates and the dithionates. The acetates and nitrates of zinc, cadmium, nickel and lead are preferred. In general, it is also preferable touse the white or lightly colored salts although for certain special purposes the more darkly colored salts can be employed.

One method of providing the print-receiving element with a silver precipitating layer containing the silver prec1p1tat1ng agent, the salts for capturing the sulfide ions and the silica is to form an aqueous dispersion of silica aerogel to which there is added a suitable quantity of one or more of the ion-capturing salts. Thereafter a substantially lesser molar quantity of a soluble sulfide, such as sodium sulfide, is added. The anions of sulfide and the cations of the ion-capturing salt combine to precipitate from the solution relatively insoluble crystals of the sulfide of the metal of the ion-capturing salt, thereby converting a portion of the latter to the sulfide. This produces a dispersion of the insoluble sulfide in the silica sol while leaving in solution the remainder of the ion-capturing salts. The concentration of the latter in the initial solution in relation to the added amount of the soluble sulfide is such as to give in the final layer a substantially greater amount of the ion-capturing salt in proportion to the sulfide.

In another method of forming the silver precipitating layer the sol of silica is first applied as a coating to the print-receiving element and is thereafter impregnated with one or more of the ion-capturing salts by immersing said coated surface of the element in a solution of said salts and permitting the same to dry. Thereafter, by dipping the sheet in a soluble sulfide a predetermined portion of the more soluble salt in the silica layer is converted to give the insoluble sulfide. Some of the ion-capturing salt is also dissolved out of the layer during the second immersion so that allowance for this loss is made in the quantity of the soluble salt which is applied in the first immersion. It may also be desirable to so form the sulfide in the silver precipitating layer that there is substantially no excess of the more soluble metallic salts in said layer and to provide the'more soluble ion-capturing salts in another layer over or under the silver precipitating layer.

- It will be readily appreciated that the performance of a photographic processing, which involves the formation of a positive print by means of a single liquid application, without recourse to baths of'liquid, is to be greatly desired where this can be accomplished to give a positive print of good pictorial quality from emulsions of high speed as can be had by following the practices described hereinabove. However, because the usual developing solution is a highly alkaline solution containing a developing agent which rapidly oxidizes in an alkaline environment, it will also be appreciated that under normal circumstances this type of liquid processing provides in the print-receiving element a material which, upon exposure to air, tends to form undesirable stains. Unless the print is subiected to a thorough Washing, this condition will normally adversely affect with time the quality of an image formed in a print-receiving layer. However, as pointed out in my Letters Patent Nos. 2,584,030, 2,635,048 and 2,644,756, it is possible to avoid this stain by including in the print-receiving layer a substance which substantially eliminates the stain-forming propensity of the developingsolution in the print-receiving layer.

.It is to be observed that the ion-capturing salts, to which reference has been made hereinabove, may also serve the function of improving the stability of the positive print provided that they possess, in addition to the aforementioned characteristics, the requisites specified in my above-mentioned Letters Patent No. 2,584,030. For example, if the ion-capturing salt is a salt of a metal which slowly forms insoluble or slightly soluble metallic hydroxides with the hydroxyl ions in the alkaline processing liquid, it will suitably control the alkalinity of the print-receiving element to substantially, if not totally,

prevent the formation of undesirable developer stains.

The stabilizing salt should not be a fogging agent and preferably should be white or lightly colored and should give hydroxides which are also white or light in color. It should not decompose in aqueous nonalkaline solutions. For this purpose, the acetates and nitrates, especially of lead, zinc, nickel and cadmium, are preferred. Of the salts hereinabove set out asbeing satisfactory for preventing the sulfide ions from wandering, all exceptthe hydroxide will function satisfactorily as stabilizing agents. In addition, the soluble salts, for example, of aluminum,

trap the wandering sulfide ions.

may be used to stabilize although they will not serve to .The use of the novel products of the present invention in the performance of a silver halide transfer process is processing agent, for example, in a manner disclosed in.

my above-mentioned Letters Patent No. 2,647,056, and the processing agent may be one of the film-forming processing agents disclosed in said patent. It may comprise, for example, a developing agent such as hydroquinone, an alkali such as sodium hydroxide, a substance, such as sodium thiosulfate, for forming a soluble silver complex with unexposed silver halide, and a high molecular. weight film-forming thickening agent such as sodium carboxymethyl cellulose. All these materials are preferably in aqueous solution. These various photographic reagents are preferably contained in solution in the processingv liquid prior to the spreading thereof as a layer 14, but they maybe in part or wholly added to the processing liquid as it is spread between

elements

10 and 12, said reagents being so located on or adjacent the surface of one or both of said elements as to be dissolved by or otherwise interacted with the liquid agent when the latter wets said surface.

The liquid processing agent may be provided for spreading as a layer 14 between

elements

10 and 12 by being contained in an elongated rupturable container 20 which, as shown in Fig. 2, has a length at least equal to the transverse dimension of the area of photosensitive element 10 to which the liquid processing agent is to be,

applied. One or more containers 20 may be attached'to one of

elements

10 and 12 and, in Fig. 2, two such containers are shown secured to the print-receiving surface of element 12, being spaced apart, lengthwise of said element, a distance equal at least to the length of a single frame of the photo-sensitive element 10.

Said elements

10 and 12 may be connected together so that they can be superposed with the container so positioned that it can release its contents in a film therebetween. The container 20 is preferably inexpensive and disposable and so constructed as to be capable of retaining the liquid processing agent or composition therein for relatively long periods of time without vapor loss or oxidation. One example of a suitable container of this type is formed from a single multilayer sheet of material comprising three laminae. The inner lamina, which provides the inner surface of the container, is formed of a material which is chemically inert to the reagents in the processing agent and which is impervious to the liquid of the agent. One class of materials suitable for this purpose, particularly where the processing agent is an alkaline solution, is the polyvinyl acetals, and of the acetals, polyvinyl butyral is a preferred species. A composition comprising to 72% by weight of polyvinyl butyral, 10% to 23% by Weight of nitrocellulose, and approximately 5% by weight of dibutyl sebacate is satisfactory as the inner lamina. The intermediate lamina is preferably impervious to the vapor of the processing agent and is formed, for example, of a metallic foil such as lead or silver foil. The outer or backing lamina is formed of a strong, deformable, relatively inexpensive sheet material such as a kraft paper. 1

The container 20 is preferably formed by taking the single sheet of three-ply material and folding the same medially at 22, and thereafter securing the end marginal portions 24 and the longitudinal portions 26 of the two,

folded faces to one another, providing a central space or cavity 28 for containing the processing liquid.

To fill the container it is possible to adhere together the opposite longitudinally extending marginal'portions 26 and one of the end marginal portions 24, the container beingd filled through the other end which is thereafter seale Photosensitive element 10 may be any of the commercially available photosensitive silver halide films, the term films being understood to include paper-backed emulsions.

I The products of the present invention are particularly useful in improving the results obtained when:

thetransfer processiiscarried out with one of the highspeed photosensitive silver halide emulsions such as the' emulsion of the relatively high-speed orthochromatic.

films, e'. g., Eastman Kodak Verichrome film, having an ASA speed rating of 0200 and an ASA exposure index rating in the daylight of 50, and the extremely high-speed panchromatic emulsions, e.g., Eastman Kodak Super X Pan having an ASA speed rating of 0400 and an ASA exposure index rating in the daylight of 100, and Ansco Triple S Pan.

Element 12 may be formed by applying to a suitable support 12a, for example, of baryta paper, a coating of a suspension or sol of the silica containing the silver precipitating agent. This so] is permitted to dry and provides layer 16. The suspension of silica may be obtained by dispersing the silica, for example, in water, and then adding the silver precipitating agent either directly or by introducing into the sol salts whose reaction product is the precipitating agent. The sol may also be applied to the sheet without the silver precipitating agent, and the sheet with the layer of silica thereon may then be dipped in a solution or mixture of the silver precipitating agent to deposit the latter in said layer.

When the foregoing liquid composition is spread or otherwise provided in a layer 14 between elements and '12, the liquid thereof permeates the photosensitive layer 10b and the developing agent acts to develop the latent image in said layer. Almost simultaneously with the development, the complex-forming substance, i. e., sodium thiosulfate, forms a soluble silver complex with the undeveloped silver halide, and the silver complex is transported by the liquid of the processing agent to layer 16 of element 12. The presence of layer 16 results in a vigorous and relatively concentrated precipitation of the silver from the silver complex to form an image of improved density and color, and having more desirable gamma and contrast characteristics than would be obtained in the absence of the silica.

Examples of processes for forming a positive image wherein a silver halide transfer takes place and examples of the novel product of the invention which is used as the print-receiving element in the performance of said processes are given below, but it is expressly understood that these examples are merely illustrative and that the invention is not limited to the materials or proportions set out therein.

Example 1 A processing agent is prepared which comprises:

' Grams Water 1860 Sodium carboxymethyl cellulose 117 Sodium sulfite 78 Sodium hydroxide 74.6 Sodium thiosulfate 14.5 Citric acid 38.5 Hydroquinone 52 The processing agent is prepared by dissolving the sodium carboxymethyl cellulose, for example the commercially available Hercules 1362 medium viscosity type, in the water in a mixer at room temperature, and the solution is mixed therein for approximately one hour. Thereafter, the sodium sulfite, sodium hydroxide, sodium thiosulfate and citric acid are added to the solution, the addition being effected in an inert atmosphere, for example of nitrogen. Upon dissolution of these materials, the hydroquinone is added and the solution is further mixed for an hour at approximately room temperature in a nonoxidizing atmosphere of nitrogen.

A print-receiving element 12 provided with a silver prccipitatingstratum 16 is prepared by having at least the baryta-coated surface portion of a strip of baryta paper immersed in a mixture comprising the following ingredients:

1% solution of sodium sulfide cc 280 Silica aerogel grams 30 Solution containing 30 g. cadmium acetate, 1 g. neutral lead acetate and 30 g. zinc nitrate dissolved 100 cc. of watere cc 92 to provide a thin coating of these materials on said surface. As'the baryta paper is removed from the bath, the excess mixture'on said surface is removed from the sheet as, 'for example, by the action of a soft buffer'roll'on said sheet as it leaves the bath.

The processing agent is spread in a layer 14 of approximately .002-003 in thickness between the coated surface of element 12 and the photosensitive silver halide emulsion 10b of a photosensitive film 10. Emulsion 10b is a relativcly high-speed orthochromatic emulsion like the emulsion of Eastman Kodak Verichrome film, and has been exposed to predetermined subject matter to form therein a latent image of said subject matter, support 10a for said emulsion being a white paper. The lamination formed by the spreading of the processing agent in a layer i4 between

elements

10 and 12 is kept intact for approximately one-half to one and one-half minutes, preferably one minute, and at the end of this time element 12 is stripped from element 10. Element 12, when so stripped, carries a positive print in silver of the subject matter of the latent image in emulsion 10b. The sodium carboxymethyl cellulose of layer 14 adheres to coating 16 of element 12 and solidifies to form a film thereon. The print obtained in this manner has good color, density and other pictorial qualities.

Other materials may be substituted for those used in the foregoing process and the proportions may be varied to an appreciable extent. For example, the film-forming material in the processing agent which imparts the desired viscosity to the latter may be any of the high molecular weight polymers which are stable to alkalis and which are soluble in aqueous alkaline solutions. For example, such other plastics as hydroxyethyl cellulose, polyvinyl alcohol and the sodium salts of polymethacrylic acid and polyacrylic acid may be used. The plastic is preferably contained in the agent in sufficient quantities to impart to the composition a viscosity in excess of 1000 centipoises ata temperature of approximately 24 C. Preferably, the viscosity of the processing agent is of the order of 1,000 to 200,000 centipoises.

Other developing agents may be used, for example one of the following: p-aminophenol hydrochloride; bromohydroquinone, chlorohydroquinone; diaminophenol hydrochloride; diaminophenol dihydrochloride; toluhydroquinone; monomethyl-p-aminophenol sulfate; a mixture consisting by weight of one-half hydroquinone and onehalf p-hydroxyphenylaminoacetic acid; and a mixture consisting by' weight of one-fourth hydroquinone and three-fourths p-hydroxyphenylaminoacetic acid.

To form the soluble silver complex, such other complexforming substances as sodium thiocyanate, ammonium thiocyanate and ammonia may be employed.

Examples of further embodiments of the novel printreceiving elements of the present invention and the processes for forming the same are given below:

Example 2 To 24 cc. of a 10% solution of lanthanum chloride there is added 4 g. of silica aerogel (Santocel C) and 6 cc. of a 1% solution of sodium sulfide, and these ingredients are thoroughly mixed in a mechanical mixer. A layer of the resulting mixture is then applied to the barytacoated surface of a sheet of baryta paper, and the sheet is permitted to stand for approximately 15 seconds. Thereafter, the excess of the liquid mixture is removed as by a soft buffer roll from the surface of the sheet.

Example 3 The process of forming the sheet described in Example 2 may be performed by substituting for the mixture therein a mixture of the following materials which gives a coating of silica containing palladium sulfide:

24 cc. of a 10% solution of palladium chloride 4 g. of silica aerogel 4 cc. of a 1% solution of sodium sulfide Example 4 The process of forming the sheet described in Example 2 may be performed by substituting for the mixture therein a mixture of the following materials which gives a coating of silica containing nickelous sulfide:

40 cc. of a 15% solution of nickelous chloride 7.5 g. of silica aerogel 20 cc. of a 1% solution of sodium sulfide Bld 8 ,28 6

96 cc. of a 20% solution of cadmium acetate 15 g. of silica aerogel '30 cc. of a 1% solution of sodium sulfide 7.5 g. of silica aerogel 30 cc. of a 1% solution of sodium sulfide Example 7 The process of forming the sheet described in Example '2 may be performed by substituting for the mixture therein a mixture of the following materials which gives a coating of silica containing magnesium sulfide:

48 cc. of a 40% solution of magnesium acetate 7.5 g. of silica aerogel 18 cc. of a 1% solution of sodium sulfide Example 8 The process of forming the sheet described in Example 2 may be performed by substituting for the mixture therein. a mixture of the following materials which gives a coating of silica containing lead selenide:

96cc. of a 40% neutral lead acetate solution 15 g. of silica aerogel 30 cc. of a 1% sodium selenide solution Example 9 To 15 grams of Ludox, a solution containing approximately 30% of hydrated colloidal silica in water, there is added 90 grams of water. Thereafter 24 cc. of a solution formed by adding 3 grams of sodium sulfide to 46 cc. of water is added to this suspension, followed by the addition of 12 cc. of a solution formed by dissolving 2.6 grams of lead acetate in 20 cc. of water.

The resulting mixture is rubbed by hand on the surface of the print-receiving support. It is preferable to wipe off any excess of the mixture from the paper after the rubbing operation.

To obtain different precipitating agents in the silver I precipitating layer that is formed according to the process of Example 9, there may be substituted for the 2.6 grams of lead acetate one of the following salts in the following quantities:

Grams Zinc acetate 1.42 Cupric acetate 1.34 Manganous acetat 1.60 Cadmium acetate 1.92

Example 10 A suspension is formed by mixing 20 grams of silica aerogel in 100 cc. of water. This sol or suspension is then rubbed onto the baryta-coated surface of a sheet of baryta paper. The sheet is then dried and dipped in a 3% water solution of sodium sulfide for thirty seconds. The excess liquid is squeegeed from the sheet as it is removed from the solution.

Example 11 A suspension is formed by mixing 20 grams of silica aerogel in 100 .cc. of water. This sol or suspension is then rubbed onto the baryta-coated surface of a sheet of baryta paper. The sheet is then dried and dlpped in a 3% water solution of sodium sulfide for thirty seconds. The excess liquid is squeegeed from the sheet as it is removed from the solution. The sheet is then again dried and dipped for ten seconds in a second solution which is a water solution of neutral lead acetate. The excess liquid is squeegeed from the surface of the sheet and the sheet is dried once more before being used.

Example 12 print-receiving elements 12 of the foregoing Examples 1 through 11, said elements may be suitably treated as follows: The surface of the element containing the silica stspension is dipped for 30 seconds in a solution consisting o 10 grams cadmium acetate 1 gram lead acetate 30 grams zinc acetate cc. of water Excess moisture is removed from the sheet as it leaves tbsI soldution, for example with a glass rod, and the sheet is me For the baryta paper of any of the foregoing examples, there may be substituted a film of plastic such, for example, as polyvinyl alcohol, hydroxyethyl cellulose, sodium carboxymethyl cellulose, regenerated cellulose or other self-supporting sheetlike materials upon which the novel silver precipitating layer'of the present invention may be deposited. t

In another form of the product of the present invention, it may be desirable to provide a coating on the silver precipitating layer 16 of a material, such as a plastic, more abrasion resistant than the silica of the precipitating layer in order to protect said layer. Thisovercoat of a plastic material may also serve as a layer which prevents the adhesion of the element 12 of the film-forming material of the layer of processing liquid 14 so that when said element 12 is stripped away from the photosensitive film 10 at the completion of the processing, the film-forming material remains attached to the photosensitive layer 101). An embodiment of a print-receiving element of this construction is shown in Fig. 3 wherein 12a is the support, 16 is the silver precipitating layer, both of which are like

layers

12a and 16 of Fig. 1, and there is applied over layer 16 a thin coating of a film-forming material 18 which may be, for example, gum arabic, cellulose acetate-hydrogen phthalate, polyvinyl alcohol, hydroxyethyl cellulose, methyl cellulose, ethyl cellulose, cellulose nitrate, sodium alginate, pectin and polymethacrylic acid. Layer 18 preferably has a thickness of the order of 1-3 microns, although if it is relatively water permeable its thickness may be appreciably greater. Layer 18 may contain one or more of the neutralizing agents which tend to improve the stability of the finished print.

To provide any of the print-receiving elements 12 of Examples 1 through 12 with a protective coating 18 of a more abrasion-resistant plastic which may also serve as a layer for minimizing the adhesion between the filmforming material of layer 14, particularly where. said material is sodium carboxymethyl cellulose, said elements 12 of each of said examples may be processed as follows:

Example 13 The processed sheet has roll coated thereon against a smooth surface such, for example, as the polished surface of a metal drum, a 5% aqueous solution of polyvinyl alcohol in a layer whose thickness is of the order of .001 inch. An equivalent amount by weight of hydroxyethyl cellulose or polymethacrylic acid may be substituted for the polyvinyl alcohol of this example.

Example 14 The processed sheet is dipped into a 2% solution of cellulose acetate, the cellulose acetate being dissolved in a mixture of methanol, ethyl acetate and methyl cellosolve, the proportions of said solvents being in the ratio of 1:3:3 by volume, respectively. The dipped baryta paper is removed from the solution in a vertical position to permit the excess liquid to drip off, a sufficient quantity of the solution remaining on the surface of the paper to provide the latter with a coating of cellulose acetate of the desired thickness.

Example 15 A 10% solution of celluloseacetate-hydrogen phthalate in acetone is roll coated on the processed sheet in a thickness of approximately .001 inch.

In a similar manner, such other materials as methyl cellulose, cellulose nitrate, sodium alginate, ethyl cellulose, gum arabic and pectin may be applied as layer 18 to the-processed sheet. It is, of course, understood that suitable solvents for the materials are employed, said solvents being preferably water for such materials as are readily water soluble, and may be toluene for ethyl cellulose anda mixture of methanol and ethyl acetate for cellulose nitrate.

'11 Although the silver precipitating layer of the present invention is constituted primarily of the silica, it may containtherein a small quantity, preferably not exceeding 10% by weight of the silica, of a film-forming substance such as gum arabic, hydroxyethyl cellulose or any Example 16 The following ingredients are mixed in the order named: Water cc 595 Gum arabic cc 3.5 Cadmium acetate grams 22.76 Silica aerogel do 36 Sodium selenide do 10 A sheet of baryta is dipped in the mixture, withdrawn, and the excess liquid squeegeed. therefrom.

Other plastics may be substituted for the gum arabic. Also, by substituting salts of other metals for the cadmium acetate different metallic selenides may be obtained in the sol.

Another class of compounds especially useful in controlling the alkalinity of the print-receiving element after the formation of the positive print therein is the organic compounds which react in alkaline solution to consume alkali, as disclosed in my above-noted Letters Patent No. 2,635,048. Preferred from this class are the esters (including lactones), the anhydrides, the alpha-halohydrins and the aldehydes which have a specific rate of alkaline hydrolysis at 25 C. greater than 80 liters per mol per minute and, from this class, the preferred species are compounds which do not volatilize too rapidly, i. e., compounds whose boiling points are in excess of 150 C.

Examples of preferred species of these compounds are: diethyl oxalate, ethyl oxamate, diethyl d-tartrate, a hydroxybenzaldehyde, dimethyl diacetyltartrate, dimethyl fumarate, dimethyl malate, dimethyl oxalate, dimethyl tartrate, polyethylene oxalate, benzoic anhydride, di-nbutyl oxalate, n-butyl oxamate, di-n-butyl tartrate, trismethyl citrate, ethyl cyanoacetate, ethyl N-B hydroxyethyl oxam'a'te, glucono delta lactone, 'glyceryl trimethyl oxalate and cellulose methyl oxalate, di-B-hydroxyethyl malonate, hydroxyethyl lactate, diethyl malate, diethyl tartrate, di-B-hydroxycthyl malate, ethyl acetoacetate, di-

butyl malate, butyl lactate, diethyl malonate, glyceryl chlorohydrin, and di-B-hydroxyethyl succinate.

The positive print is subject to severalsources of instability which stem, for example, from the oxidation of the developer in the highlights, the discoloration of some of the unexhausted chemical components in the positive prints by exposure to visible and near visible radiation,

and the partial bleaching of the silver.

It has been determined that these effects are most nearly eliminated by combining the stabilizing effects of the soluble metallic salts and the organic alkali-consuming compounds, i. e., by using at least one of each of these classes of stabilizers in the print-receiving element.

Examples of suitable print-receiving elements which embody this combination of stabilizers, together with the novel silver precipitating layer of the invention, are the following:

Example 17 The baryta-coated surface of a sheet of baryta paper is immersed in a mixture consisting of Water cc 1000 Arabol '-cc 150 Dimethyl d-tartrate grams 400 Lead acetate do 70 Cadmium, acetate do 50 Zinc acetate do 40 The sheet is then dried and there is applied over the foregoing coating a further coating consisting of:

Silica aerogel grams 300 1% aqueous solution sodium sulfide cc 2800 Cadmium acetate grams 30 Lead acetate do 1 Zinc nitrate do 30 Water ,-.-c

Example I 8 The baryta-coated surface of a sheet of baryta paper is dipped in a solution consisting of:

Ethanol cc 1000 Zinc nitrate grams 120 Ethyl oxamate do The treated surface of this sheet is then provided with a sulfide-containing coating consisting of the following:

It is to be noted from the foregoing examples that the silver precipitating agent is present in the sheet in a very small amount. Concentrations, for example, as low as 2X10" to 2 l0- gram-moles for each square foot of the surface area of the print-receiving element have proven adequate.

Although in the foregoing, submacroscopic particles of silica, preferably colloidal in size, are disclosed as preferred for the matrix of the silver precipitating layer, other materials may be usefully employed for this purpose such, for example, as those disclosed in my copending application Serial No. 727,385, including bentonite and fullers earth. In general, therefore, it is to be understood that the matrix material of the silver precipitating :layer may comprise particles of a waterinsoluble, preferably inorganic. chemically inert, adsorbent material which has a relatively low ccetficient adsorption for light as compared to silver and which gives a matrix which is substantially free of protective colloid action for silver.

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 photographic product comprising a photosensitive element including a silver halide layer, a base layer, and a rupturable containing means holding a liquid including water, said base layer having adjacent one surface thereof a dispersion of a silver precipitating agent from the class consisting of the metal sulfides and selenides which are substantially insoluble in said liquid and a dispersion of at least one metallic salt which is at least moderately soluble and'substantially irreducible in said liquid, the last-named salt having as its cation a metal which forms, with the anion of the silver precipitating agent, a salt which is substantially insoluble in said liquid and which gives up its anions to silver ions by displacement, said product'having positioned therein'photographic reagents, including a silver halide developer and a silver halide solvent, said containing means and said layers being so held together that said containing means is capable, upon rupture, of releasing at least a part of its contents to permeate superposed portions of said silver halide layer and said base layer, said liquid, upon release, rendering said silver halide developer and said silver halide solvent effective to develop a latent image in said silver halide layer and to form soluble silver complex with the undeveloped silver halide of said silver halide layer, said liquid, upon release, additionally transporting said soluble silver complex in tl1e direction of said silver precipitating agent wherein part at least of the soluble silver complex is reduced to silver to produce the positive print.

2. The product of claim 1 wherein said base layer comprises colloidal particles of silica and said silver precilpitating agent is dispersed among saidparticles of $1 ma.

3. The product of claim 1 wherein said base layer comprises a matrix of a water-insoluble, inorganic, relatively inert, adsorbent substance and said silver precipitating agent is dispersed in said matrix.

4. The product of claim 3 wherein said moderately soluble salt is from the class consisting of the nitrates and acetates of cadmium, zinc and lead.

5. A photographic product comprising a silver halide layer, a'base layer, and a rupturable container holding a liquid includingwater, said layers and said container being attached together so as to permit s'aid layers to be superposed with said container so positioned as to release its liquid for spreading in a film between said layers, the liquid in said container comprising a silver halide developer, a silver halide solvent and a thickening agent, said base layer having adjacent one surface thereof a dispersion of a silver precipitating agent from the class consisting of the metal sulfides and selenides which are substantially insoluble in said liquid and a dispersion of at least one metallic salt which is at least moderately soluble and substantially irreducible in said liquid, the last-named salt having as its cation a metal which forms, with the anion of said silver precipitating agent, a salt which is substantially insoluble in said liquid and which gives up its anions to silver ions by displacement.

6. The product of claim wherein said base layer comprises submacroscopic particles of silica and said silver precipitating agent is aggregated among said particles of silica.

7. The product of claim 5 wherein said base layer comprises a matrix of a water-insoluble, inorganic, relatively inert, adsorbent substance and said silver precipitating agent is dispersed in said matrix.

8. The product of claim 7 wherein said moderately soluble salt is from the class consisting of the nitrates and acetates of cadmium, zinc and lead.

9. A photographic product capable of forming transfer prints in conjunction with a photosensitive silver halide element, said product comprising a rupturable containing means, holding an aqueous liquid, and a sheet support upon which said containing means is mounted, said sheet support providing an image-receiving area adjacent said containing means onto which said liquid is spreadable in a thin layer directly from said containing means, said product carrying a silver halide developer and a silver halide solvent, said sheet support having, adjacent the surface mounting said containing means and at least coextensive with said image-receiving area, a dispersion of a silver precipitating agent from the class consisting of the metal sulfides and selenides which are substantially insoluble in said liquid and a dispersion of at least one metallic salt which is at least moderately soluble and substantially irreducible in said liquid, the last-named salt having as its cation a metal which forms, with the anion of the silver precipitating agent, a salt which is substantially insoluble in said liquid and which gives up its anions to silver ions by displacement, said silver halide developer, said silver halide solvent, said liquid and said salts being sufficient in amount and being so located, in relation to said image-receiving area, that the spreading of said liquid over said area disperses silver halide developer and silver halide solvent throughout said area in adequate quantity to form a transfer print of a latent image in an area of a contiguous silver halide element equivalent to said image-receiving area.

10. The product of claim 9 wherein said support comprises a matrix of submacroscopic particles of silica and said silver precipitating agent is dispersed among said particles of silica.

11. The product of claim 9 wherein said. support comprises a matrix of a water-insoluble, inorganic, relatively inert, adsorbent substance and said silver precipitating agent is dispersed in said matrix.

12. The product of claim 11 wherein said moderately soluble salt is from the class consisting of the nitrates and acetates of cadmium, zinc and lead.

13. A photographic product capable of forming transfer prints in conjunction with a photosensitive, silver halide element, said product comprising a rupturable container holding an alkaline aqueous solution of a silver halide developer, a silver halide solvent and a film-forming plastic, and a sheet support upon which said container is mounted, said sheet support providing an image-receiving area adjacent said containing means onto which said liquid solution is spreadable in a thin layer directly from said container, said sheet support having, adjacent the surface mounting said container and at least coextensive with said image-receiving area, a dispersion of a silver precipitating agent from the class consisting of the metal sulfides and selenides which are substantially insoluble in said solution and a dispersion of at least one metallic salt which is at least moderately soluble in said solution, the last-named salt having as its cation a metal which forms a substantially insoluble and relatively irreducible salt with the anion of the silver precipitating agent, said silver halide developer, said silver halide solvent, said liquid and said salts being sufiicient in amount and being so located, in relation to said image-receiving area, that the spreading of said solution over said area disperses silver halide developer and silver halide solvent throughout said area in adequate quantity to form a transfer print of a latent image in an area of a contiguous silver halide element equivalent to said image-receiving area.

14. The product of claim 13 wherein said support comprises colloidal particles of silica and said silver prlecipitating agent is dispersed among said particles of $1 ica.

15. The product of claim 13 wherein said support comprises a matrix of a water-insoluble, inorganic, relatively inert, adsorbent substance and said silver precipitating agent is dispersed in said matrix.

16. The product of claim 15 wherein said moderately soluble salt is from the class consisting of the nitrates and acetates of cadmium, zinc and lead.

17. The process of forming positive images in silver which comprises developing a latent negative image in a silver halide emulsion layer, forming an imagewise distribution of soluble silver complex with the undeveloped silver halide of said emulsion layer, transferring in solution from said emulsion layer at least part of said imagewise distribution of said soluble silver complex to an image-carrying layer so superposed adjacent said emulsion layer as to receive a depthwise diffusion of said complex from said emulsion layer without appreciably disturbing said imagewise distribution, reducing to silver the silver ions of said soluble silver complex in a stratum of said image-carrying layer which contains a dispersion of a silver precipitating agent from the class consisting of the sulfides and selenides which are substantially insoluble in said solution and at least one metallic salt which is at least moderately soluble and substantially irreducible in said solution, the last-named salt having as its cation a metal which forms, with the anion of the silver precipitating agent, a salt which is substantially insoluble in said solution and which gives up its anions to silver ions by displacement, the reduction of said silver forming an image in silver in said image-carrying layer which is a positive of the subject matter of said latent image.

18. The process of claim 17 wherein the silver precipitating agent is dispersed in a matrix comprising colloidal particles of silica and the positive silver image is formed in said matrix.

19. The process of claim 17 wherein the silver precipitating agent is dispersed among particles of a waterinsoluble, relatively inert, inorganic, adsorbent substance.

20. The process of claim 17 wherein said moderately soluble salt is from the class consisting of the nitrates and acetates of cadmium, zinc and lead.

21. A photographic product comprising a photosensitive element which includes a silver halide layer, a printreceiving element for receiving by transfer a positive print, and a rupturable containing means holding a liquid, said product having positioned therein photographic reagents including a silver halide developer and a silver halide solvent, said containing means and said elements being so held together that said containing means is capable, upon rupture, of releasing at least part of its contents to permeate superposed portions of said elements including said silver halide layer, the portion of said printreceiving element adapted to be permeated by said liquid including a mixture of salts, at least one of said salts being a silver precipitation initiator from the class consisting of metallic sulfides and selenides and at least one other of said salts being from the class consisting of the nitrates and acetates of cadmium, zinc and lead, said liquid, upon release, rendering said silver halide developer and said silver halide solvent effective to develop a latent negative image in said silver halide layer and to form soluble silver complexes with the undeveloped silver halide in said silver halide layer, said salts initiating and so controlling the precipitation of the silver from said soluble silver complex as to form a transfer image in silver adjacent the surface of the print-receiving element, said image having improved color and density characteristics.

22. A photographic product capable of forming transfer prints in conjunction with a silver halide element, said product comprising a rupturable containing means holding a liquid, and a sheet support upon which said containing means is mounted, said sheet support providing an image-receiving area adjacent said containing means onto which said liquid is spreadable in a thin layer drrectly from said containing means, said product carrying a silver halide developer and a silver halide solvent, said image-receiving area of said support including a mixture of salts, at least one of said salts being a silver precipitation initiator from the class consisting of metallic sulfides and selenides and at least one other of said salts being from the class consisting of the nitrates and acetates of cadmium, zinc and lead, said liquid and said other reagents being suflicient in amount and being rendered effective by the spreading of said liquid on the imagereceiving area to form a transfer print on said imagereceiving area of a latent image contained in an area of a silver halide element equivalent to said image-receiving area.

23. A photographic product capable of forming transfer prints in conjunction with a photosensitive silver halide element, said product comprising a rupturable containing means holding an alkaline liquid solution of a silver halide developer, a silver halide solvent and an organic filmforming colloid, and a sheet support upon which said containing means is mounted, said sheet support providing an image-receiving area adjacent said containing means onto which said liquid solution is spreadable in a thin layer directly from said containing means, said support having distributed, at least throughout said imagereceiving area, a mixture of salts, at least one of said salts being a silver precipitation initiator from the class consisting of metallic sulfides and selenides and at least one other of said salts being from the class consisting of the nitrates and acetates of cadmium, zinc and lead, said solution and said salts being sufiicient in amount so that the spreading of said liquid over said area provides reagents throughout said area in adequate quantity to form a transfer print of a latent image in an equivalent area of a silver halide element.

24. A print-receiving element for having transfer prints formed thereon by precipitating the silver of an imagewise distribution of a soluble silver complex brought into contact therewith, said element having at least one surface portion thereof permeable to an aqueous solution of a soluble silver complex, said surface portion having therein a dispersion of at least one silver precipitating agent from the class consisting of the metal sultides and selenides which are substantially water-insoluble and a dispersion of at least one metallic salt which is at least moderately soluble and substantially irreducible in an aqueous solution of a silver halide developer, the lastnamed salt being present in a substantially greater concentration than said precipitating agent and having as its cation a metal which forms, with the anion of the silver precipitating agent, a salt which is substantially insoluble in an aqueous solution and which, in said solution, gives up its anions to silver ions by displacement.

25. The print-receiving element of claim 24 wherein the said soluble salt is at least one salt from the class conill '16 sistng of the nitrates and acetates of cadmium, zinc and lea 26. The product of claim 24 wherein said element includes a sheetlike support for said surface portion and said surface portion includes a thin, macroscopically continuous, silver precipitating layer comprising particles of a water-insoluble, relatively inert, inorganic, adsorbent substance.

27. The product of claim 24 wherein said permeable surface portion comprises a macroscopically continuous stratum of submacroscopic particles of silica and said silver precipitating agent is dispersed in said stratum.

28. The product of claim 24 wherein the element includes a sheet of paper as a support for said surface portion.

29. The product of claim 24 wherein said element includes a sheet of plastic as a support for said surface portion.

30. A print-receiving element for having transfer prints formed thereon by precipitating the silver of a soluble silver complex brought into contact therewith, said element being very thin in relation to its length and breadth and having at least one surface portion thereof permeaable to a solution of a soluble silver complex, said surface portion having therein a dispersion of at least one silver precipitating agent from the class consisting of the metallic sulfides and selenides which are substantially water-insoluble and a dispersion of at least one metallic salt which is at least moderately soluble and substantially irreducible in an aqueous solution of a silver halide developer, the last-named salt being present in a substantially greater concentration than said precipitating agent and having at its cation a metal which forms with the anion of the silver precipitating agent a salt which is substantially insoluble in an aqueous solution and which in said solution gives up its anions to silver ions by displacement, said surface portion having a low optical density against which an image in silver is readily 'visible.

31. The product of claim 30 wherein said element includes a sheet of baryta paper as a support for said surface portion.

32. The product of claim 30 wherein said element includes a sheet of plastic as a support for said surface portion.

33. The product of claim 30 wherein said element includes a sheetlike support for said surface portion and said surface portion includes a thin, macroscopically continuous, silver precipitating layer comprising particles of a water-insoluble, relatively inert, inorganic, adsorbent substance.

34. The print-receiving element of claim 33 wherein the said soluble salt is at least one salt from the class consisting of the nitrates and acetates of cadmium, zinc and lead.

No references cited.

Claims

1. A PHOTOGRAPHIC PRODUCT COMPRISING A PHOTOSENSITIVE ELEMENT INCLUDING A SILVER HALIDE LAYER, A BASE LAYER, AND A REPTURABLE CONTAINING MEANS HOLDING A LIQUID INCLUDING WATER, SAID BASE LAYER HAVING ADJACENT ONE SURFACE THEREOF A DISPERSION OF A SILVER PRECIPITATING AGENT FROM THE CLASS CONSISTING OF THE METAL SULFIDES AND SELENIDES WHICH ARE SUBSTANTIALLY INSOLUBLE IN SAID LIQUID AND A DISPRESION OF AT LEAST ONE METALLIC SALT WHICH IS AT LEAST MODERATELY SOLUBLE AND SUBSTANTIALLY IRREDUCIBLE IN SAID LIQUID, THE LAST-NAMED SALT HAVING AS ITS CATION A METAL WHICH FORMS, WITH THE ANION OF THE SILVER PRECIPITATING AGENT, A SALT WHICH IS SUBSTANTIALLY INSOLUBLE IN SAID LIQUID AND WHICH GIVES IS UP ITS ANIONS TO SILVER IONS BY DISPLACEMENT SAID PRODUCT HAVING POSITIONED THEREIN PHOTOGRAPHIC REAGENTS, INCLUDING A SILVER HALIDE DEVELOPER AND A SILVER HALIDE SOLVENT, SAID CONTAINING MEANS AND SAID LAYERS BEING SO HELD TOGETHER THAT SAID CONTAINING MEANS IS CAPABLE, UPON RUPTURE, OF RELEASING AT LEAST A PART OF ITS CONTENTS TO PERMEATE SUPERPOSED POTIONS OF SAID SILVER HALIDE LAYER AND SAID BASE LAYER, SAID LIQUID, UPON RELEASE, RENDERING SAID SILVER HALIDE DEVELOPER AND SAID SILVER HALIDE SOLVENT EFFECTIVE TO DEVELOP A LATENT IMAGE IN SAID SILVER HALIDE LAYER AND TO FROM SOLUBLE SILVER COMPLEX WITH THE UNDEVELOPED SILVER HALIDE OF SAID SILVER HALIDE LAYER, SAID LIQUID, UPON RELEASE, ADDITIONALLY TRANSPORTING SAID SOLUBLE SILVER COMPLEX IN THE DIRECTION OF SAID SILVER PRECIPITATING AGENT WHEREIN PART AT LEAST OF THE SOLUBLE SILVER COMPLEX IS REDUCED TO SILVER TO PRODUCE THE POSITIVE PRINT.