US2698237A

US2698237A - Photographic silver halide transfer product and process

Info

Publication number: US2698237A
Application number: US449995A
Authority: US
Inventors: Edwin H Land
Original assignee: Polaroid Corp
Current assignee: Polaroid Corp
Priority date: 1954-08-16
Filing date: 1954-08-16
Publication date: 1954-12-28
Anticipated expiration: 1971-12-28

Description

Dec. 28, 1954 E. H. LAND I l 2,698,237

PHoToGRAPHIc SILVER HALIDE TRANSFER PRODUCT AND PRocEss Filed Aug. is, 1954 Supporlj (Pholosenslvc Silver Halde Emulsion Processing |4 Agnf l\\( l2 Supporl j I6 j (l2n Silver Precipilul'ng Layer FIG. I

/Prinl Receiving Elemn+ FIG. 2

Abrasion Resislanl Cooling L\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\lQ Silver Precpihxlng Layer" FIG. 3

ATTORNEYS United States Patent@ 4PHOTOGRAPHIC"SENER1HALIDE TRANSFER PRODUCTv ANDl PROCESS vEdwin H. Land, Cambridge, Mass., assigner tollolaroid Corporation, CambridgepMass., a corporation of Delaware rApplication August 16, Y'1954,' Serial No'. 449,995

31 Claims. (Cl: 95;@

Thisl'linvention relatesit'o photographic products and "processes landprofe-particularly to Atransfer processes l,wherein -a latent image in a silver halldeV emulsion is developed and wherein a'vsoluble-Ysilver` complex obtained;byreaction with the'undeveloped silver halide of said emulsion is transferred from` said emulsion and theesilver thereof is precipitated in anotherwlayer to `for-ma positive print, and `tofproducts useful as printreceiving elements in said processes.

This application is `a=contii'iuationin-part ofpmy. copending application Serial 'Non 164,908, led May 29, 1950, for vPhotographic SilverHalide Transfer Product and Process, now abandoned, which, in. turn, is a continuation-in-part of my copendingapplication Serial No. 727,385, ledFebruary 8, 1947 for Photographic Prodf uct and Process.l

One objectV of the present invention is to provide a transfer process of the foregoing type and products for i use' in -said process wherebyvthere are produced positive prints of good quality andy stability from silver'halide emulsions of high speed.

Another object `of the present invention is to provide an improved 'product particularly useful in the` foregoing i transfer processes as the print-receiving element, sa1d product comprising a novel silver precipitatinglayer adjacent one surface thereof,which layer serves to` eifect a'controlled precipitation of the silver from'the soluble y silver complex and alsoacts to receive and suitably precipitating agent is suitably'supported;

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

Other.objects'oftheinvention will in part be obvious and lwill in part appear hereinafter'.

` The invention accordingly comprises the kseveral steps and relation and orderof one or more of such steps with respectfto each of theothers, and theproductpossessing the' features, properties and the relation of elements which are lexemplified in the following-detailed disclo- 'sure'p'andthe 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 drawings wherein:

Figure 1 is a diagrammatic enlarged sectional View illus'trating the' association of 'elements'during one v'stage 'ofthe performance of a transfer process and showing as ione of the elements an embodiment ofthe novelproduct`ofthe present invention, the thicknesses of. the various materials being'exaggerated;

- Fig-2 is a perspective view, ywith parts broken away,

v, of one' form of print-receiving element upon which containers of the processingagent are so positioned as to be'capableof 'distributing their contentssbetween the surface of the print-receiving. element and a photosensi- .tive Aelement; and

y Fig. 3 is a viewflsimiiai te Figa of another form of the print-:receiving element of the invention. The present invention comprehends improved processes rand products ofthe .type whereby a positive print is ob- 2,698,237 Patentedy Dec. 28, 1954 ICE tained in a single step nby suitably treating .afsilver halide emulsion containing a latent. limage with. a uniformly applied layer of processingliqud. l Preferablygtheprocessing liquid is in a viscous condition and is spread in a liquid iilm between the,.photosensitiveelementcomprising the silver halidev emulsion and a print-receiving element comprising a suitablesilver precipitating layer. The liquid develops thelatent image in theernulsion and forms a soluble silver complex, e. g.,.athiosulfate or a thiocyanate, with undevelolgaedsilver,halidejv This soluble silver complex is at leastvin rpart Ttransported. inthe direction of the.print-receiving.element andthe silver thereof is largely-precipitated,inthesilver precipitating layer of said element to form a positive image in silver.

It has been proposed to use in-,theformationof the silver transfer prints by the foregoingnprocess certain compounds and elements` whose` presence during, the process has Va desirable-effect onsthetamountand character of the silver precipitatedduring imageformation. For this purpose,1such materials asnforexample, the metallic suldes and selenides,` rthioo'xalates, and .thioacetamides have been-disclosed inmy .U.'S. PatentNo. 2,647,056, issued July 28, .1953.' for.` One-Step Photographic Transfer Process..H Other .precipitating 4agents have beenproposed such, forexample, kas colloidal-silver.

VAccording to Athe present inventionpthe precipitation and aggregation of silver ,obtained byusing.silverf,pre cipitating agents, includingl the above-mentioned fnaterials, is very ygreatly .improved'and kexpedited by' providing in the print-receiving elementas la dispersingtmedium or matrix for said agents a layer formed primarily of particles of silica. Ther particles are Vsmall enough so that when laid down as a thin layer they present acontinuous surface tothe naked eyeM rather than a skeletal or porous structure'. To', this end the particles aresubmacroscopic in size, i. e., small enough to beindistinguishable as discrete or separate particles bythe' naked eye. Preferably they are so small as `to yapproach `or be of colloidal size but are nevertheless discrete particles rather than integral parts of asingle continuous coalesced mass. Thus, the matrix of thejpresent invention is formed of definite particles which are'essentiallylsilica and which are sufliciently smallv to be indistinguishable as vparticles by the naked eye'- when formed, into a layer andwhose minimum average 'size iswof'colloidaly rather than of molecular proportions.'4 The essentially ipure forms of silica such as the silica laero'gel available' under the trade vname "Santoc'el C2 or the solid contentof the hydrated silica dispersione available under the trade 'names Ludox and Syton give best results. However, it is possible to use highly pulverized-formsof the -les'sl pure silic'as such, for example, as those/obtained frornnatural sources, provided,` however,l thatl these materials fhave a high silica :content of approximately 70% orgreater by weight and the'particles thereof are submacroscopic in size.v Exampleslofsuch materials arethe silicas derived from diatornites variouslykn'own as diatomaceous earth. kieselgnhr'andV infusorial earth. Also useful, when pulverized to particles small enough in size,'is powdered glass. However, the` preferred materials aresilicas whose solid con tent comprises'of the orderof 97% ormore of SiOz.

`The ynovel silver precipitating layer including the' silica and the silver precipitating agent lis preferably applied to a suitable'support, forfexamplesby beingcoated on .thesupport ingthe form of a suspension which contains a substantiallyngreaterwamountpfl'the silica thanof the `precipitating' agent." The supportfmay'be `formed'fof a non-siliceous` material Vsucll'tasi'paper,"regenerated cellulose; polyvinylalcohol,'cellulose ethers such as methyl cellulose, "rethyl;cellulose, or their.derivatives, such as sodium carboxymethylg cellulose and: hydroxyethyl cellulose,'and other natural and-'synthetic gums and resins whi'ch willfform continuouslms`and which are rela- `tively'fstable, mechanically, inrthepresence of water and lalkaliL-- These supportingsheets 1 are opaquewhen a relection print is desired `andtransparent.when a transparency is desired.

4Suitable assilverprecipitatingagents,arethe metallic `sulfides and selenides, these Hterms. being understood to include' the selenosulidesthe polyr'sultides',N and thei-poly- Vselen'ides.' ,Preferredin' .this I. groupware. kthe vso-called heavy metal sulfides, e. g., of zinc, chromium, gallium, iron, cadmium, cobalt, nickel, lead, antimony, bismuth, silver, cerium, arsenic, copper; and the heavy metal selenides, e. g., of lead, zinc, antimony and nickel. For best results it is preferred to employ the sulfides whose solubility products in an aqueous medium at approximately C. vary between 10-23 and 1030 and specifically the salts of zinc, cadmium and lead. Also suitable as precipitating agents are heavy metals such as silver, gold, platinum, palladium and mercury, and in this category the noble metals are preferred and are preferably provided in the matrix as colloidal particles. Also useful as silver precipitating agents are the salts of these heavy metals, preferably the simple inorganic and readily reducible salts such as silver nitrate, gold chloride and gold nitrate. In some instances, the metals are introduced into the matrix as salts and then reduced in situ prior to the use of the reception material in the silver transfer process to give a layer whose silver precipitating agent is the colloidal metal. Where the salts are relatively lightor heat-sensitive, this reduction may be accomplished simply by exposing the silver precipitating layer to diffuse light or to heat. Still other satisfactory silver precipitating agents are certain of the thio compounds, e. g., dithiooxamate and its lead and zinc complexes, potassium dithiooxalate and the lead and nickel complexes thereof and thioacetamide. The silver precipitating agents as noted above are provided in a highly dispersed condition, preferably as colloidal particles.

In general, the sulfides and selenides of the alkali metals and alkali earth metals such as sodium, potassium, cesium, calcium, barium and magnesium are too soluble to give optimum pictorial quality, although the provision of a silica layer as a vehicle 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 continuous discrete stratum thereof on the surface of the print-receiving element when applied thereto and the 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 ions of the crystals are prevented from wandering or diffusing during precipitation from their original loci in the precipitating 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 it is to 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 precipitating layer or closely adjacent thereto at least one metallic salt which is substantially more soluble in the processing agent than the 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 metal whose ions form sulfides which are difficultly soluble in the processing agent and which give up their sulfide ions to silver by displacement. Accordingly, when such sulfied ions are present, the metal ions of the more soluble salt have the effect of immediately precipitating the sulfied 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-receiving element 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:

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

Second: The silver ion is 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 .f0.1` 'Che fact that the sulphide ionin spite of the insolubility of the crystalline compound-does 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 from the 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 problems of stabilizing an image resident in this complicated reagent).

What we nd 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 number of grains start growing. If these become large the whole picture will be too 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 negative, 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 high light 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 corisider how these might be arranged to inuence the array of silver atoms. 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 indeed-subject to one vital proviso, namely that as the sulphide ions perform their cyclic function, they are retained within the diameter that we have chosen for 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 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 complexnow leaves the complex ion to form the sulphide. The sulphide similarly leaves the metal ion for association with the silver. Then the silver is reduced-but 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 occurred with the soluble sulphide. This danger can be avoided by intro ducing 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 because 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 this way, the diameter of the Mft-9,698,237

f galaxyf-isf-maintainedyinspitewof the-cyclic use of the sulphide-ions'f.- vThe-silver ions-1am reduced-to-silver over metal-sulphide galaxies.

One remarkable aspect of picturesmade in this way fis that the-silver'inthef positive has-,very high covering V-power-in'the-order-of tive -times thatfrof the silver in l `the negative.*Consequently a good Apositive-canbe made from a layerof silverhalidethatis many times thinner f.

of positive, it is impressive to see how thin -a `layer of negative material suflicest-The negative image, when i such4 a ,thin emulsion is' used, is only just visibleyet the positive derived'from thesamefa'mou'ntf of'silver'is rich "."Land brilliant. t L" type'of intensification: Furthermore, v*since onlythe sur- 1 Thus, we see that this process provides a .L .face of the'negative" isf-involved, there is gainin speed,

`Indeed the migration" distance for ,the silver ions going from'thenegativesheet -to-thepositive imagecanbe extremelysmall'; vWe have seen'that'these ions'co'me from very nearthe'surfaceof the-negative, and 'we c'an,1if we f vchoose,-.prec'ipitate*thefsilver in `the viscouspositive layer r aids theformation-fof'the-aforementionedgalaxies, and

" the dithionates.

f miumynickeland-lead are preferred.

- .'fatl the surfaceof-the-Lnegative,-Thus,the combination of minimizedv light'scatteri'ng vinthe-negative, the short mi- .s'gration' distance for theV silver ions, and rthe-prompt pre- -cipitationA of-th'em :when they `"rea'ch'tthepositive,- results f in ka processi Withfquite'goodmesolving' power. -Further- Y. more, the-pictures are` by all-ordinary standards ygrainless,

Vthe-same area that-We-chcsetor the-original. galaxy, and the, rdiameter .ofN the fmassof silveris such thatfounimage A isfthe'colour@we-predetermined when we prepared the .l

- than lis` ordinarily-*required for aqnegative. V-`While full thickness-negatives can be usedffonmaking this new kind .form the 'sulde inthesilverpreeipitatingflayer thatthere isy substantially noexcess of `the more solubleelmetallic saltsffm saidlayer and toprovide the more-soluble ionrfeap'turingsalts in another-layer over or Iunder the.. silver precipitatinglayer.

lt will be :readily appreciated that the performance of a photographicprocessing, which involves the-formation zor" aflpositive print by means-of a single liquid applicaltion;.withoutrecourse-to baths'of liquid, is toibe greatly desired-Where this can be accomplished to give -a positive print of good pictorial quality from emulsionsof high speed-as caribe had by following the practicesdescribed E:l'iereinabove:4 `However, because theusual developing solution is `a highlyl alkaline solution containing a develcoping; agent-which-zrapidly oxidizes in an alkaline envronment;y 1t will `also-be appreciated that 4'undernormal we'fcircumstance's this type fof-'liquid processingv provides in -the print-receivingelement a material which, upon exposure to air, tends to-formundesirable stains. ,-Unless the print is snbiected'- toa thorough washing, this condition will normally adverselyr alectwith time the` quality "of an image vformed in' aprint-receiving layen.y .How-

I' ever,O afs pointed out in my U. S.- Patents ,No1 2,584,030,

issueddanuary 29 1952, No; 2,635,048, issued April 14, y1953, and No.'2,64-4,756, issuedl July ,7, Y1953,.it;is possible to avoid this stain by includingin the print-receiv- 'because ofthe way in wliiclrthe silver isideposited and aggregated?v- (Underlined words added or modiiied.)

- The silver"precipitatingr agent is'dispersed in silica which it is evident, from theforeg'oing, thatthe presence of the' more soluble salt, whichprovides thecations for -1 e' capturing.' they fr'eesuldeiions, has the-effect of -malntainingthis desirable'aggregationf-of thesulfide ions durzing i-the-"silver'l precipitationn-These more soluble or ron- A capturing salts may be the soluble salts of any of the following metals: cadmium, cerium(ous),f cobaldgus),

atlsiro'nf'lead,nickel,"manganese,` thorium and tin.` factoryfsoluble 'a1d"stable" salts 'of the' above metals may be found, for'example,among the"following.groups of salts: the"aceta't`es,the nitrates, the borates,`the chlorides, theisulfates, thev hydroxides, theformates, 'the fcitrates and Theac'etates and nitratesof zinc, cadalso preferable'to use the :white orlightly colored salts I although for "certain specialfpurposes the more darkly colored salts can be employed.

Y i -One method of` providing the print-'receiving' element f j with a'jsilver 'precipitating-layer Icoiitairllngithe'silver prel 'clipitatingagenn the salts fo'rscapturmgl the 'sulfide ions In general, it is ing layera substance Which- `substantially ,eliminates the stain-formingpropensltyof the developing solution in the y y rint-receivin yla er. 30A D g Y lIt-istto 'bev observed that the fion-capturing-salts, to

" -which'freference has been madefhereinabove',umay also "serveth'e function of improving-the stability of the positive4 yprin'r` provided that they possess, in addition to the f Vaforementioned characteristics, the requisitesspeeied in my `above-mentionediU. S. 'Patent No.A 2,584,030. For

i example,- ifY the ion-capturing salt is a-salt of-a rnetal'which slowly forms insolublefor slightly soluble metallic hydroxides' with the hydroxyl ions/in the alkaline processing liquid, it Vwill suitably control the alkalinity of the print- -receiving element .to substantially, if not totally, prevent i they formation ofundesirable developerr stains.

The-stabilizing saltshould noty be a fogging agent and l preferably should be White or lightly colored and should tions.

give hydroxides which are 'also whiteA or light in color.

llt'-shrmld-not decompose Vin aqueous non-alkaline solu- For this purpose, the acetates and-nitrates,1 especially--of^lead, zinc; nickel and cadmium, are preferred.

Of the salts hereinabove set out as being satisfactory for preventing-the sulfide ions from wandering, allexcept the hydroxide will 'function satisfactorily as stabilizing-agents.

Inl addition,-the soluble salts, -for example, of=alurninum` maybe-medio stabilize although they will not'serve to 2 trap ythe wandering sulfide ions.

Theuse of the novel products ofthepresent invention in theiperformance of a silver-halide transfer process is illustrateddiagrammaticallyin Fig. l, wherein 10 repandthe silica-is to form-an aqueous d ispersion of silica aerogelto which there'is 'addeda-'smtable quantity of v one or'more'of theiori-capturing saltsra'lihereafter a substantially less'erlmolar `quantity of' a Asoluble sulfide,

such assodium sulde, is'added.'l The-'anions 'of sulde r andlthe cations'offthetioncapturing"salt combinefto precipitate from "the solution relatively insoluble crystals of the's'ulfide'lof the *metal of -theion-capturing salt, thereby'eonverting `a portion" ofk the latter`to`the'lsullide'. This produces "afdispersion of the-insoluble suldeinfthe silica solt while'leaving in solution th'e remainder of the loncapturing saltsx" The' concentrationi of theflatter 1n the v ini-tiall solutionu in relation to the added amountcf the soluble sulde is such asto give lin the final layer' a sub- A 4:st'antially greater-amount of the'ion-eapturing `salt 1n pro- 'portion to thesulde. n U

ln another" method of forming Vthesilverpreclpltatmg vlayerfthesol'of `silicavisiirs't applied as acoatingy to the print-'receiving element and7 isl thereafter impregnated with one'ormore'of the ion-capturingg s alts1by'immersing said coated-surface of the element 1n a-solut1on of said' salts and permitting the same to dryl-v Thereafter,

l' by dippihg'thefsheet in `asoluble sulfide va predetermined i portion' vofy the fmoresoluble salblin-the silica layer is 'fconvertedto give-the insoluble sulde. ySome-ofthe ion- *'jcapturing saltV is alsodissolved out' of the layer-'during the Y"second immersion so that allowance for this loss is i rnadein ftheduantity of theV soluble salt'which'isapplied in the firstimmersione-HR. may also befdesirableto 'so -resents aphotosensitiveelement comprising-a support 10a and= a A-photosensitive, silver halide emulsion layer 10b, lift-representsa layer of relatively viscousprocessing agent, and -12 -is one-embodiment of the-novel printreceiving element of the invention upon which a transfer print-is obtained-fby the-process. As shown, the printreceiving element 12 comprises a suitableA support 12a and al silver precipitating layer 16.

- lLiquid layer 14 may be obtained byspreading the processing-agent,V for example, in a manner disclosed in my above-mentioned-U S. Patent No. 2,647,056, and the t processing agent may be oneofthe lm-formingprocessn they may be in partfor wholly added to thejprocessing 0U' liquid as it is spread betweenelementst-l@ and -12, said 4reagents beingso located on or kadjacent the surface of onefor both of'- said elements asto be dissolvedY by or H otherwise interacted with the-*liquidy agent When-the latter "wets said-surface. 1

lTheliquidproeessing-agent may be providedforspreading 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 elcment 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 photosensitive 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 60% to 72% by weight of polyvinyl butyral, 10% to 23% by weight of nitrocellulose, and approximately 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.

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 being filled through the other end which is thereafter sealed.

Photosensitive element may be any of the cornmercially available photosensitive silver halide films, the term films being understood to include paper-backed emulsions. The products of the present invention are particularly useful in improving the results obtained when the transfer process is carried 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 XX 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 sol 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

10 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 f 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.

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 sullite, 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 precipitating stratum 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. cadium acetate, l g. neutral lead acetate and 30 g. zinc nitrate dissolved in 100 cc. of water 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 0n said sheet as it leaves the bath.

The processing agent is spread in a layer 14 of approximately .C02-.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 relatively high-speed orthoehromatic 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 laminations formed by the spreading of the processing agent in a layer 14 between

elements

10 and 12 is kept intact for approximtaely 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 sufiicient quantities to .impart to the composition a viscosity in excess of 1,000 centipoises at a ftemperaturez'of approximatelyiteff 24 C.v Preferably,V the viscosityof lthe processingfagene-V is ofthe orderof 1,000 to 200,000'centipoisesr'f 2 Otherdeveloping agents rfi-.ty be used, vfor example one el:

of the following: p-aminophenolhydrochloride; bromohydroquinone; i ehlorohydroquinone; vdiami-nophenol; hy# drochloride; diaminophenol dihydrochlorid'e;toluliydri quinone; monomethyl-paininophenol sulfatej' afl mixture consisting 'oy Weight of one-half hydroquinonefand one-H half p-'hydroxyphenylaminoacetic-y acid;` 'land =a=iimixturef S10- consisting by weight of onefourth-hydroquinone vand .1 :if

three-.fourths p-hydroxyphenylaminoacetic acid.V i t To form. the soluble silver complex,such otherlcom-x-w plex-forming substances asl sodiumithiocyanate,i-ammow nium thiocyanate and ammonia `may be. employedel l Examples of further iembedirnentsofi the' novelpririt-Fv receiving elements of the present invention 'and theprocfiw' esses for forming the same are given below:`

ExampleZ 20 Example 3- The process of forming thesheet described' in Example.`

therein a mixture of the following materials which gives a coating of silica containing palladlum sulde:...

Example 5 The process of forming thesheet-described in Example 2 maybe performed by substitutingfor the mixturey therein a mixture of the followingm aterials which gives a coating of silica containing cadmlum sulfide:

96 cc. of a 20% solution of cadmium acetate:v i g. .of silica aerogel 30 cc. of a l% solution of sodiumsulide"` Example. 6 The process of forming theV sheet 'described in Example 2 may be performed by substitutingformthe mixture therein a mixture of the following materials which gives a coating of silica containing'zinc sulfide::-"`

cc. of a 37.5% solution of zinc nitrate 7.5 g. of silica aerogel v v cc..of a 1% solution of sodium sulfide Example -7 The process of` forming thesheet describedin Example 2 may be performed by substituting "for-'themixture therein a Vmixture ofthe following .materials-which givesfi` a coating of silica 'containing magnesiumtsulde'zi:

48 cc. 'of a 40% solutionof magnesium acetate.. 7.5 g. of silica aerogely 18 cc. of a 1% solution of sodiurn'suliideV Example 8 The process of forming the sheet'described inEimniple` Cfr 2 mayibeperformed by"substitutng`-for thejmixture"'-` therein a mixture of the following'materials which 'givesi a coating `of silica containing lead selenide:

96 cc. cfa 40%-neutral lead acetatesolution 15 g. .of/silica aerogel 30 cc..of..a 1%i sodiumselenide` solution ma 85 aerogel in 100 cc. of water.

A a film 10 at; the completion ofthe processingi-the film forming VnmaterialLremains attached to the. photosensitive 'Y 10 Example 9T To lSSgramsOfLudox, asolutio'n.,eor1tainingapproxi: mately.,30% 'ofhydrated colloidal sili ca..in` water\,.there is added .9.0 .gramsof water....Thereafter 24 cc.4 of 4a solut tion formed by adding 3.grams of sodium sulfide Ato 46icc. of water 4is added: 'no .this suspension,.followedby'. the is...

additionoflZ ccfofa solutionformed .bydissolving 2.6; grams'of lead acetate-in 20 cc`.`of Water. .1

,The resulting mixture isrubbedfby hand onthe-.surface s of the print-receiving support. Itis preferable t'o..wipe off any, excess of the mixture fronithe. paper .afterthe rubbingopera'tion'.

To obtain different precipitating. agentsin ,the silver. precipitating layerthat is formed accordingI to .theprocess of Example. 9, there maybe substituted forithe 2.6: grams.-... of lead acetate one of the following salts in the fllowing quantities:

Gramsw Zinc facetate 1.42 Cupricjfacetate S 1.34 l'.Manganous acetate' 1.60

Cadmiumacetate 1.92

Example 1.0i

A suspension is formed by mixing 420 grams of silica This sol or suspension is then rubbed: ionto-` the baryta-coated i surface of af 'sheet of baryta'paper; xThe sheetis then dried and dippedy ina 3% waterisolutionl of sodium sulfide forthirty seconds. The excess liquid .issqueegeed from the-sheetfas -it is re- -1 movedx-fromf the solution.- L 2 may be performed by substituting for the mixture Example. :1 1

-A suspension'isftforrned'by `mixingf20 grams"of-silicalit I aerogel inf cc.'\of=water..1lThis s`o1-or suspensionfis' then rubbed onto the baryta-coated surfaceff'of VAa-shee`t=0f- A baryta paper. The sheet is :thendried and dipped in a 3% Water solution of sodium sulfide for thirty seconds. The excesslliquidis sq'ueegeedr-froinftheY sheetas kvitis `rey movedzifrom the solution. '*The sheety is `then again driedll and dipped for ten seconds in =a second solution'which fis c a 5%1 water solution of neutral lead-acetate. "The 'excess liquidzissqueegeedfrom the surface'of -the sheethand the' sheet yistdried onceftmorebefore being` used.

ExcessV moisture is removed from the sheet as it leaves theN ).3 olut1on,'for example with a glass rod, .and.the..sheetlis..

ried.

For the baryta paper of any of the foregoing examples;

, there may be substituted a filmof plastic such, for exampleiexas polyvinyl-alcohol,v hydroxyethylv 'cellulosef' i sodium carboxymethyl cellulose, regenerated cellulose or f other .self-supporting sheetlike materials upon which the.....\.: novel vg'silverprecipitatinglayer of theV present invention may berdeposited.

In anotherform of theproduct of the present invention,

.it mayz'be desirable to provide acoating onthe silvergw..k

precipitatinglayer '1'6" of 'a material, such as a plastic, more abrasionLresistantzthan the silicaof the precipitating layer in order to protectisaid layer. Thisovercoat' of ai plastic materialtmay also serve as a layer whichprevents'" the adhesionto. the element 1-2wof the film-forming'rnaL i l' terial Iof lthe-llayertof processing'liquid 14 'so fthatwhenf said element 12 is stripped away from the photosensitive 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 l2 with a protective coating 18 of a more abrasion-resistant plastic which may also serve as a layer for minimizing the adhesion between the film-forming 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 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 I4 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 olf, a sullicicut 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 cellulose acetate-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 and a mixture of methanol and ethyl acetate for cellulose nitrate.

Although the silver precipitating layer of the present invention is constituted primarily of the silica, it may contain therein 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 of the other materials heretofore mentioned as being suitable for the abrasion-resistant coating 18 on layer 16. The addition of this small quantity of plastic facilitates application of the layer 16 onto the support therefor. An example of one way of forming a layer 16 containing a small quantity of film-forming material is the following:

Example 16 The following ingredients are mixed in the order named:

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 vrltetate different metallic selenides may be obtained in e so 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 U. S. Patent No. 2,635,048. Preferred from this class are the esters (including lactones), the anhydrides, the alphaahalohydrins and the aldehydes which have a specific rate of alkaline hydrolysis at C. greater than 80 liters per mol per minute and, from this class, the preferred species are compounds which do not volatilze too rapidly, i. e., cornpounds 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 oxamate, glucono delta lactone, glyceryl trimethyl oxalate and cellulose methyl oxalate, di-B-hydroxyethyl malonate, hydroxyethyl lactate, diethyl malate, diethyl tartrate, di-B-hydroxyethyl malate, ethyl acetoacetate, dibutyl malate, butyl lactate, diethyl malonate, glyceryl chlorohydrin, and di-B-hydroxyethyl succinate.

The positive print is subject to several sources of instability which stem, for example, from the oxidation Y 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 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:

Silica aerogel grams-- 300 1% aqueous solution sodium sulde cc-- 2800 Cadmium acetate grams..- 30 Lead acetate do l Zinc nitrate do 30 Water cc-- 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*6 to 2 l0"5 gram-moles for each square foot of the surface area of the print-receiving element have proven adequate.

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 material which includes a silver halide layer, a base layer having adjacent one surface thereof a silver precipitating stratum, said stratum comprising a silver precipitating agent dispersediamong colloidal:particles-.ofv silica, and a rupturable containing means holding a1 liquid,-

said product having positioned thereiniphotographic reagents, including a sliver haiide developer and asilver halide-51 solvent, said containing means and said layers .Y

being so held together that saidcontaining means is capable, upon rupture, of releasingat least a :part ofy receive a depthwise diffusion of said solution fromlsaid its contents tol permeate superposedy portions'iof said y silverighalide layer and said base layer, saidiliquid, upon withthe undeveloped silver halide of said silver halide layer, said liquid, upon release, additionally transport ing said soluble silver complex infthe direction of said silver precipitating agent wherein part at leastof the 1 soluble silvencomplex is reduced to silvei.to produce the positive print. v

2. A photographic product comprising a silver halide layer, abase layer and -a rupturable container holding 'a liquid, said layers and said container being attached together so as to permit said 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 lbase layer having adjacent one surface thereof a stratum includinga silverprecipitating agent dispersed among colloidalA particles of silica.

3. A photographic product capable of forming transfer printsl in conjunction with a photosensitive'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 directly from said containing means, saidproduct carrying a silver halide developer and a silver halide solvent, said sheet support having,- adjacent the surface mounting said containingv means and at least coextensive with said image-receiving arb a silver precipitating stratum Acomprising a silver precipitating agent dispersed among colloidal particles of silica, said silver halide developer, said silver halide solvent and said liquid being suiicient in amount and being so located, in relation to said image-receiving l area that the spreading of said liquid over said-area disperses silver halide developer and silver halidesolvent throughout said area in adequate quantity to form a transfer print of a latent image in an area of a contiguous silverfhalide element equivalent to said image-receiving area. 'Y

4. A ph-otographic product capable of forming transfer printsin `conjunction with a photosens'itive silver-"halide element-, said product comprising a rupturable containing means, holding an alkaline liquid solution of aA silver halide developer, a silver halide solvent and a film-forming plastic, and a sheet support upon which said'containing means is mounted, said sheet support providing an image-receiving area adjacent said containing means lori-to whichl said liquid solution is spreadable in a thin layer directly from said containing means, said support having a silver precipitating stratum at least coextensive in area with said image-receiving area, said silver precipitating stratum comprising a silver precipitating agent dispersed among colloidal particles of silica, said solution and the silver precipitating agent in said stratum being suliicient jf in amountso that the spreading of said liquid over said image-receiving area provides afdispersion of silver halide developer-and silver halide solvent in adequate quantity to form a transfer print of a latent image in an area of Aa contiguous `silver halide element equivalent to said image-receiving area.

5. The process of forming Vpositive images in silver which comprises developing a latent negative image in a silver halide emulsion layer with a solution comprising a silver halide developer and a silver halide solvent to form an--imagewise distribution of soluble silver complex in said emulsion layer, transferring from said emulsion layer by-limbibition at least part of said imagewise dis-V tribution of said soluble silver complex toran image-carryf ing layer comprising a support and an image receiving stratum so superposed adjacent said emulsionlayer as to emulsion layeiwithout appreciably disturbing. the image- Wise `distribution of the silver complex in. said solution, said stratum comprising a distinct and separately applied coating of colloidal silica on said support and including/ff a silver precipitating agent dispersed in said coating,fandl reducing to silver the silver lions of said solublesilver com# l plex in said stratum to forni an image in silver`amongA colloidal particles of saidsilica which is a positiveof the subject matter of said latent image.

6. A print-receiving element for having transfery prints I Y formed thereon by precipitating the silver -of an image-V wise distribution of a soluble silver complex brought intocontact therewith, said element comprising a support and a silver precipitating layer, at least one surface portion off. v

said element, including said layer, being permeable to an aqueous solution of a soluble silver complex, said layer comprising a silver precipitating agent linely dispersed' among colloidal particles of silica, said support for the silver precipitating layer comprising a sheet 'of' baryta paper, said silver precipitating agent being at least'one substance from the class consisting of heavy metals, metal suliides and selenides, and organic thio compounds.

7. A print-receiving element for having transfer-prints formed thereon by precipitating the silverof an-image-f wise distribution of a soluble silver complex brought-into f contact therewith, said element comprising a support and a silver precipitating layer, at least one surface portion of said element, including said layer, being permeable yto an aqueous solution of a solubleisilver complex, said layer being a distinct and separately applied coating on said support and comprising a silver dispersed among colloidal particles of silica, said silver precipitating agent being at least one substance from the class consisting of heavy metals, metal -suliides and selenides, and organic thio compounds and being present in a concentration of the order of 2 10*5 gram-moles for each square fo-ot of the surface area of said layer.

.8. A photographic product comprising a photosensitive material which includes a silver halide layer, a basel layer having adjacent one surface thereof a silver precipitating stratum, said stratum comprising a matrix of subrnacroscopic discrete particles of silica and a silver precipitating agent dispersed in said matrix, and a ruptur-l able containing means holding a liquid, said product-havv ing positioned therein photographic reagents, including'a lsilver halide developer and a silver halide solvent, said containing means and said layers being so held together v that s aid containing means is capable, upon rupture, of'

releasing `at. least a part of its con-tents to 'permeate superL posed portions of said silver halide layer and saidl base i layer, said liquid, upon release, rendering said silverhalide developer and said silver halide solvent effective todevelop 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 re-- lease, additionally transporting said soluble silver come" plex in the direction of said silver precipitating agen-t wherein part at least of the soluble silver complex is reduced to silver to produce the positive print.

9. A photographic product comprising a silver halide layer, a base layer and a rupturable container holding a liquid, said layers and said container vbeing attached together so as to permit said 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 i halide solvent and a thickening agent, said base layer com# prising a non-siliceous support and having adjacent one surface thereof a stratum including a silver precipitating agent dispersed among submacroscopic particles ofV silica which on lthe average are not smaller than colloidalin size.

10. A photographic product capable of forming transfer prints in conjunction with a ph-otosensitive 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 y thin layer directly from said containing means, said produ' uct carrying a *silver halidedeveloper and a'silverfh-aldef solvent, said sheet support having, adjacent the surface l' precipitating agent finely mounting said containing means and at least coextensive with said image-receiving area, a silver prec1p1tating stratum comprising a matrix of submacroscopic discrete particles of silica and a silver precipitating agent dispersed in said matrix, said silver halide developer, said silver halide solvent and said liquid being sucient in amount and being so located, in relation to said imagereceiving area, that the spreading of said liquid over said area disperses silver halide developer and silver halide solvent throughout said area in adequate quantity t-o form a transfer print of a latent image in an area of a contlguous silver halide element equivalent to said image-receiving area.

11. 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 a film-forming plastic, and a sheet support upon which said containing means is mounted, said sheet support providing an imagereceiving area 4adjacent said containing means onto which said liquid solution is spreadable in a thin layer directly from said containing means, said support having a silver precipitating stratum at least coextensive in area with said image-receiving area coated on a non-siliceous sheet, said silver precipitating stratum comprising a silver precipitating agent dispersed among submacroscopic particles of silica which on the average are not smaller than colloidal in size, said solution and the silver precipitating agent in said stratum being sullcient in amount so that the spreading of said liquid over said image-receiving area provides a dispersion of silver halide developer and silver halide solvent 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.

l2. The process of forming positive images in silver which comprises developing a latent negative image in a silver halide layer, reacting a silver halide solvent wi-th part at least of the undeveloped silver halide of said layer to form `an imagewise distribution of soluble silver complex in said layer, transferring in solution at least part of said imagewise distribution of said soluble silver complex to an image-receiving material comprising a support and a distinct and separately applied coating of submacroscopic, discrete particles of silica on said support and so located in relation to said silver halide layer as to receive the solution of said complex without appreciably disturb- Ving its imagewise distribution, said coating having -a silver precipitating agent dispersed among said silica particles, and reducing to silver the silver ions of said soluble silver complex at said image-receiving material to form an image yin silver.

13. The process of claim 12 wherein said support is a flexible sheet support.

14. The process of claim 13 wherein said sheet support `is paper.

15. The process of claim 13 wherein said sheet support is a sheet of transparent plastic.

16. The process of claim 12 wherein said silver precipitating agent is from the class consisting of heavy metals, metal sulfides and selenides, and organic thio compounds.

17. The process of forming positive images in silver which comprises developing a latent negative image in a silver halide emulsion layer with a solution comprising a silver halide developer and a silver halide solvent to form an im-agewise distribution of soluble silver complex in said emulsion layer, transferring from said emulsion layer by imbibition at least part of said imagewise dis- F tribution of said soluble silver complex to an image-carrying element comprising a support and a distinct and separately applied coating of submacroscopic particles of silica a-t least colloidal in size and so superposed adjacent said emulsion layer as to receive a depthwise diffusion of said solution from said emulsion layer without appreciably disturbing the imagewise distribution of the silver complex in said solution, said coating having a silver precipitating agent dispersed among said particles of silica, and reducing to silver the silver ions of said soluble silver complex in said coating to form an image in silver among said particles of silica.

18. The process of claim 17 wherein said particles of silic-a form a macroscopically continuous matrix for said (iii precipitating agent and said matrix is a coating on a flexible sheet support.

19. The process of claim 18 wherein said sheet support is a sheet of paper.

20. The process of claim 18 wherein the sheet support is a sheet of transparent plastic.

21. The process of claim 17 wherein said silver precipitating agent is from the class consisting of heavy metals, metal suliides and selenides, and organic thio compounds.

22. The process of claim 17 wherein said silver precipitating agent is a colloidal heavy metal.

23. The process of claim 17 wherein said silver precipitating agent is a colloidal noble metal.

24. The process of claim 17 wherein said silver precipitating agen-t is at least one compound from the class consisting of the heavy metal suldes and selenides.

25. The process of claim 17 wherein said silver precipitating agent is an organic thio compound.

26. 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 comprising a support and a substantially nonphot-osensitive silver precipitating layer provided as a discrete macroscopically continuous, distinct and separately applied coating on one surface of said support, one surface portion of said element including said layer being permeable to an aqueous solution of a soluble silver complex, said layer having a major proportion by weight of submacroscopic particles of silica on the average at least colloidal in `size and having finely dispersed therethrough a minor proportion by weight of particles of a silver precipitating agent for aiding the reduction and precipitation of metallic silver from silver complex ions in the presence of a reducing agent, said silver precipitating agent being from the class consisting of heavy metals, metal suldes and selenides, and organic thio compounds.

27. 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 comprising a support and a substantially non-photosensitive silver precipitating layer provided as a discrete macroscopically continuous, distinct and separately applied coating on one surface of said support, one surface portion of said element including said layer being permeable to an aqueous solution of a soluble silver complex, said layer having a major proportion by weight of colloidal particles of substantially pure silica and having finely dispersed therethrough la substantially lesser amount by weight of particles of a silver precipitating agent for aiding the reduction and precipitation of metallic silver from silver complex ions in the presence of a reducing agent, said silver precipitating agent being from the class consisting of heavy metals, metal suliides and selenides, and organic thio compounds.

28. 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 comprising a non-siliceous support and a substantially non-photosensitive vsilver precipitating layer provided as a discrete macroscopically continuous, distinct and separately applied coating on one surface of said support, one surface portion of said element including said layer being permeable to an aqueous solution of a soluble silver complex, said layer having a major proportion by weight of submacroscopic particles of silica aerogel and having finely dispersed therethrough a substantially lesser amount by weight of particles of a silver precipirating agent for aiding the reduction and precipitation of metallic silver from silver complex ions in the presence of a reducing agent, said silver precipitating agent being from the class consisting of heavy metals, metal suldes and selenides, and organic thio compounds.

29. The product of claim 26 wherein said silver precipitating agent is a colloidal heavy metal.

30. The product of claim 26 wherein the silver precipitating agent is a compound from the class consisting of the heavy metal sulfides and selenides.

31. The product of claim 26 wherein said silver precipitating agent is an organic thio compound.

(References on following page) References Cited in the le of this patent UNITED STATES PATENTS Number Number Name Date 2,296,636 Hanahan Sept. 22, 1942 5 59365 2,352,014 Rott June 20, 1944 2,626,867 Webster Jan. 27, 1953 18 FOREIGN PATENTS Country Date Great Britain Oct. 15, 1931 France Mar. 23, 1942 Netherlands May 16, 1947 OTHER REFERENCES Burmistrov, Phofographic Journal, vol. 60, August 10 1936, pp. 452-459.

Claims

1. A PHOTOGRAPHIC PRODUCT COMPRISING A PHOTOSENSITIVE MATERIAL WHICH INCLUDES A SILVER HALIDE LAYER, A BASE LAYER, HAVING ADJACENT ONE SURFACE THEREOF A SILVER PRECIPITATING STRATUM, SAID STRATUM COMPRISING A SILVER PRECIPITATING AGENT DISPERSED AMOUNG COLLOIDAL PARTICLES OF SILICA, AND A REPTURABLE CONTAINING MEANS HOLDING A LIQUID, SAID PRODUCT HAVING POSITIONED THREIN 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 SUPERPOSES 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 LATEN 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.