US2661293A - Process of producing a colored photographic image by means of exhaustion of developer - Google Patents

Description

. @will Dec. l, 1953 E. H. LAND E 2,661,293

RROOEss OF PROOUOING A COLORED PHOTOORAPHIO IMAGE EY MEANS OE EXRAUSTION OE DEVELOPER Filed oct. 8, 194e Developolole Phoiosensiive Moleriol ICQ) (lob |62 (IOC Developed Pholosensi'live Maierul L J Developer Solulion ,fReucfed Developer l ,H, Image Carrying Loyer W2 FIG. 4

3o (Buse 5V Image Carrying Layer FIG.

Image Carrying Layer FIG. 6

34 v Buckn La er f vPholosenslve La er F IG- 7 y V A] INVENTOR K 30 32) mail CM 5w .gm

Patented Dec. 1, 1953 PROCESS OF PRODUCING A COLORED PHOTOGRAPHIC IMAGE BY MEANS OF EXHUSTION -OF DEVELOPER Edwinl Hi. Land; Cambridge, Mass., assignorto- Polaroid. Corporation, Cambrdge', Mass., acorporatiomof- Delaware ApplicationOctober'S, 1946,' Serial'No. 702,039

8. Claims.: (CL. 954-88).

This'l invention relates to1 photographyan'd more: particularly to novel? photographicy proc--4 essesand! novell composite photogrin'zhic.- ii'lmv units for use with suchprocesses.

This application is a. continuation in4` parti of my copending. application Serial` No'. 539,550, filed. June 9;A 1944, for Photographic Product, Processand Apparatus (now abandoned and". replaced by applicationaSerial No'. 64,8370; filed-Detcember511, 19481; and WhichY issued asiPatentiNo. 2,543,181,011 February27gl951).

It:l is a principal object ofv this inventionft'o provide an improved photographic processwherein a'; visible positive image iscobtained" from a-fphotosensitive?layeri containing at latent or` de'- veloped negative'. ima-geg. by utilizing the' differ:- ential effect' created by: said photosensitive-.layer on. a substance, usable: in for-ming said visible positive image;v to control the: amount of: said substance which is:v available". for? creating:- said positive image;

Another object of the present` inventionisvto provide al photographic process wherein. a= photosensitive-layer containinga' latent or developed negative image ispermeated: with` af substance having the capability ofentering intoa-aireaction which produces a visiiile'eifect on anotherlayer; saidsubstanceis reactedewithamaterial in saidv photosens-itive layer to: selectively makev portions ofi saidsubstance-incapable' of creatingf saidivisible effect, and tbe-remainder of said substance -is usedino-create saidvisible effect on saidv other layer, said` visible-effect, due to. itsselec't-ivercrea-- tion, forming a-.positive image.-

Another object of the-presenti invention isf to. assure, in processes ofthe-above type-,. a sub.'- stantially complete reaction ofsaid substance With-.said material priori tothe crea-tion,` ofsaid visible eiiect.

Anotherobject of the invention istoprovide anovel photographic process. wherein a de'- veloper is-reacted with'. layer of photosensitive material containing` a latent negative image to causeadevelopment of said latentl negative image and the portions oi said.A developelwhich are'- not reacted by said" photosensitive material during said development reaction are'- utilized in forming-t a posit-ive: image of said.v latentv negative image in or on' anotherlayer.

Another objectof therinvention' isto': provide a posit-ive image-forming reaction'inla` processorr theabot'e type' wherein said` unreacted`l portions ci said developer are-utilized tolforma dyefcon'- stituting-afpositive-image;

Another` object of.- the invention" isto' provide 2 a positive image-forming reaction in a process' of the abovetypeA wherein said unrea'cted por-v tions of' saidv developer are utilized'toV lformal pig"- ment constitutingr a positive` image.

Another'object ofthe invention isitoimprove thecontrast off a positive` image produced-iin* a) process of thetype7 described above by prevent* ing migration of reacted'Y portions oi: saidi deir veloperfrom said photosensitive4 layer" to-` said other layer;

Other objects of theV invention willi inpart'be' obvious-y and will in part appear hereinafter.

The invention accordinglycomprisesf-the--proc"- ess comprising theseveralfsteps; andthe= relan tion'- and-orden of one ormoreof'suchf-'stepslwith respect to each of-'tlie others-which'- are exemplified in the following detaile'd'- disclosure, thescope of thev application of` which will-be' indicated"r in the' claims-.-

For afuller understanding4 of? thenatureand objects'of the-invention reference should' be had to-'the accompanying drawing wherein-z.

Figures 1i throng-hif-are* diagrammatic` representations of various steps of a preferred modiacation offthe= invention; Figure 1' showinga: photosensitivef layer' containing a*y latent.'- negative image; Fig. 2 showing the photosensitivelayer after' development; Fig; 3 showingianimagewarr-yingf layer: formedf intoaV permeable assembly with: the developed photosen'sitive layer; and Fig; e showing' the' nal' positive! image oni the image-carrying 'layer Fig. 5- isa diagrammatic cross-sectionalvievvl ofy a'. composite photographie film unit showing one-physical embodiment of the invention;

Fig: 6 isf a'rl diagrammatic cross-sectional view of all compositephotographic nlm unitf showing another physical` embodirnenti` of the invention; and? Fig; 7 is: a2 diagrammaticl cross-sectional; view'- of a'. composite photographic film un'it showing still. another physical embodiment'v ofy the" invention;

In; general: this invention relates to novel photographic processes and" products for' the pro-`v duction of." a fixed stable positive image: oi a latenter developed negative image contained in a'. photosens'itiv'e layer, the" positive iinage being formed: in or' on'a'nother layer hereinafter re'- fer-'redw to f as an image-carrying layer:

Aarealimage'of any objectiis avisiblelilreness or reproduction of that object. Photographically, an.' image mayT bei recordedF in;` a photosensitive layerby transforming: said laye1';.which isf orignally substantially homogeneousthroughout" its.

volume, to a layer such that a chemical characteristic thereof has an imagewise variation throughout the image area, the variation being a function of the brightness aspects of the original subject image. The resulting record image may be a real image, i. e., a visible image, or a latent image, i. e., an image which, While not visible per se, has the capacity upon suitable chemical treatment to produce a visible image. The term record image, when used here in its photographic sense, may be characterized as a record of the brightness aspects of any predetermined subject matter such as a person, object, or real image, the record being in the form of a layer of material of predetermined small thickness having throughout its image area an imagewise variation of a chemical characteristic of the layer, this chemical characteristic being capable of producing a visible contrast either by virtue of imparting different optical characteristics per se to said layer or by making possible the differential chemical treatment of said layer whereby differential optical characteristics are imparted to said layer.

This invention relates to the use of' such a record image in a photosensitive layer for forming another image on an image-carrying layer, said other image being reversed in the positive-negative sense With respect to said record image.

In its preferred aspect the process involves the production on an image-carrying layer of a positive image of a record negative image by permeating the layer containing said negative image with a uniform quantity of a substance in solution, selectively utilizing :the differential chemical characteristic of said layer to produce an effect on said uniformly permeated substance, said effect being a function of the imagewise variation of said chemical characteristic, transferring unaffected portions of said substance to said image-carrying layer and utilizing said unaffected portions to creat a varying visible effect which gives a positive image of said negative image.

The creation of the visible effect on the imagecarrying layer may be the result of the creation of a color.

The first step of the preferred process is to permeate a uniform quantity of a liquid composition into the photosensitive layer containing a record image comprising a latent or developed negative image. The liquid composition preferably cornprises a solution of a reactive substance. The latent or developed negative image in the photosensitive layer preferably comprises a photosensitive material having an imagewise distribution which varies as a direct function of the exposure creating said latent or developed negative image.

The amount of reactive substance permeating a unit area of the photosensitive layer is substantially uniform throughout an area thereof at least coextensive with said negative image and is preferably such that it will be substantially completely reacted by the portion of said photosensitive layer containing a highest concentration of said imagewise distributed material.

This reactive substance in the liquid composition is one having the capability of entering into a reaction with said material in said photosensitive layer and also of entering into a reaction which produces a visible effect cn said imagecarrying layer.

In the next step of the process, the reactive substance is reacted With the material in the photosensitive layer and portions of said sub- 'f stance are rendered incapable of producing a visible effect as the result of this reaction. The extent of reaction between the substance and the material in the photosensitive layer preferably varies, from point to point thereof, as a function of the point-to-point degree of exposure creating the negative image. There thus remains a distribution of unreacted substance Whose capability of creating a visible effect varies in amount from point to point.

As another step of the process, the remainder of the reactive substance, i. e., that portion thereof which did not react with the material in the photosensitive layer, is thereafter transferred to said image-carrying layer from said photosensitive layer by superimposing one of said layers on the other of said layers, the superimposing being sufficiently intimate to permit the migration of said unreacted portions of said substance Without any substantial degree of dispersion. The transferred unreacted portions of said substance are then utilized for creating a visible effect on said image-carrying layer. This Visible effect preferably comprises the creation of a color and varies from point to point in accordance With the distribution of the unreacted substance. Due to the selective visible effect, i. e., color created, there is formed a positive image of said negative image on said image-carrying layer.

Referring now to Figs. l through 4 there is shown a diagrammatic representation of the various steps of a preferred embodiment of the process of the present invention.

Referring specifically to Fig. l there is provided a layer of photosensitive material I 0, which is shown as having been exposed to a subject image to create developable portions indicated by the dots I6, these dots representing developable grains of photosensitive material. Various portions of the photosensitive layer I0 have different amounts of developable grains I6 therein, portion Illa having a maximum amount of developable grains, portion I0b having substantially no developable grains, and the portion Inc having about half of its grains developable.

In Fig. 2, the photosensitive layer I0 is shown as having been uniformly permeated with a solution of the reactive'substance. This permeation is such that there exists a predetermined quantity per unit area of the substance distributed through the photosensitive layer I0. The uniform permeation is accomplished such as by dipping the photosensitive layer in a concentrated bath of the reactive substance, the photosensitive layer being in contact With the bath only long enough to absorb a predetermined quantity of the concentrated substance I4, either 0n its surface or within the layer I0. The photosensitive layer I0 should not be left in the bath long enough to permit the transfer of reacted portions of the substance from the layer I0 to the bath. The concentration of the bath should be so high that the photosensitive layer I0 may take up and support a uniform quantity of the substance, the concentration of the substance per unit area supported by the layer I El being preferably just enough to be completely reacted by a most reactive portion of the pohotosensitive layer I0. Other methods of applying the solution of the substance to the photosensitive layer are equally feasible such as spreading a predetermined layer I4 of a viscous solution of the substance in contact With the surface of the photosensitive layer I0. The substance may also be applied by other means such as by spraying, etc.

a dye image' is formed on the image-carrying layer I2, there are a number of ways of accomplishing the dye formation, depending upon the type of developer utilized. In one method, there may be provided, for reaction with the unreacted portions of the developer, a color-former capable of coupling with these unreacted, i. e., unoxidized, portions of the developer to create a color I9. This color, due to its selective creation, varies in amount from point to point, being a minimum where there was a maximum development of the latent negative image, and being a maximum where there was a minimum development of the latent negative image. There is thus created, on the image-carrying layer I2, a positive dye image of the latent negative image in the photosensitive layer.

- In another method of forming a dye image there is utilized, to create a color, a color-former capable of coupling with oxidized, rather than unoxidized, portions of the developer. In this case, the developer is reacted with the photosensitive material containing a latent negative image to cause a development of the negative image resulting in a selective oxidation of the developer and a trapping of the oxidized developer within the developed portions of the photosensitive layer I0, it being necessary to prevent migration of the oxidized developer from the photosensitive layer IIJ. The remainder of the developer is then utilized to create a color I9 on the image-carrying llayer I2. In order to form this color, it is necessary to oxidize these unreacted portions of the developer, after the selective reaction of the developer with the latent negative image. This oxidation may be accomplished by providing an oxidizing agent on the image-carrying layer, in which case the oxidizing agent may be either a photosensitive material such as a silver halide or a nonphotosensitive oxidizing agent such as sodium perborate. It is also contemplated to oxidize the unreacted portions of the developer on the image-carrying layer by aerial oxidation which may be carried out by separating the image-carrying layer from the photosensitive layer whereby to permit the ready access of oxygen from the atmosphere to the unreacted portions of the developer. After the developer has been oxidized on the image-carrying layer it is reacted with a suitable color-former to cause a coupling and the creation of a color, the concentration and distribution of which varies from point to point substantially in inverse proportion to the amount of development in corresponding portions of the latent negative image.

In both of the above methods of dye image formation, the color-former, which is reacted with the developer to cause a coupling therebetween, is preferably located on the image-carrying layer I2 in solid form. It may, however, be coated on, or included in, the photosensitive layer I0, or it may be, in some cases, included in solution in the liquid composition. This latter modification of the invention is particularly feasible where the developer is coated on one of the layers in solid form rather than being in solution in the liquid composition.

In still another method of forming a dye image, a self-coupling developer is used. This developer may be one of the type known in the art as a direct color-forming developer, i. e., one which couples with itself when oxidized. The developer is selectively reacted with the photosensitive material containing a latent negative image, and the reacted portions are preferably trapped in the 8 photosensitive layer. Then the unreacted portions of the developer are utilized to selectively create a color I9 on the image-carrying layer I2, by oxidizing the unreacted portions of the developer.

A preferred method of permeating the photosensitive layer with a uniform quantity per unit area of a liquid composition containing the reactive substance is to release the liquid composition between the photosensitive layer and the image-carrying layer and to spread this liquid composition in a uniform thin layer between the photosensitive layer and the image-carrying layer. Such a method of uniform permeation has certain advantages and is particularly adaptableV for use with film units of the type shown in Figs. 5, 6 and 'l which show preferred examples of the physical embodiments of the present invention.

Each of these lm units may be processed by the application thereto of a single mechanical stress to cause the release and spreading of the.

liquid composition, thus making possible the processing of the film unit either within a handy camera, or as the result of ejection of the film.

unit from a hand camera.

The construction of the film unit also permits accurate spreading of the liquid composition in a uniform thin layer in a position to permeate the photosensitive layer with a uniform amount of a solution of the reactive substance.

Since the liquid composition is spread between two layers, which may be only slowly permeable to oxygen, it substantially prevents the access of oxygen to the Iliquid composition during the time it exists in a layer form within the confines of the lm unit. This arrangement prevents the aerial oxidation of the reactive substance, where such a substance is oxidizable. Separation of the image-carrying layer from the iilm unit renders the surrounding atmosphere available for effecting the aerial oxidation of oxidizable material on the image-carrying layer. This feature permits the use of reactive substances which are quite easily oxidized and prevents such oxidation until the positive image has formed, or until it is desired, to oxidize the reactive substance for the purpose of creating a positive image.

When the outer surface of the layers of the film unit are opaque to actinic light, the construction of the iilm unit permits the liquid composition, particularly where the liquid is viscous, to form a lightproof laminate of the film unit so that the film unit may be ejected from a camera into daylight immediately after the mechanical treatment. Exposure of the photosensitive layer is effected prior to the formation of said lightproof llaminate and with the photosensitive and the image-carrying layers in spread apart or separated relation with respect to each other. Since the composite laminate is opaque to actinic light, the photographic process may be carried to completion outside of the camera with no danger of destroying the latent image as the result of light reaching the photosensitive material.

Such film units should have certain features in order that they may fulfill the requirements of the process. In the first place, it is preferable that the lm units have within their confines all the materials necessary for the complete processing thereof to produce the nal positive image. In the second place, the film units should be so designed that they may inherently assure the proper sequence of reactions, or can be so used as to assure this proper sequence of reactions.

The physical embodiment of the broad invention, shown .inFigsi 5,: 6. and 7,.,generallyin- .volves..a; composite lm .unit comprising. a. photoy sensitive ,layen..aneimageecarryingi layer. and ...a :container for a liquidcomposition, ther container being -positioned lin.Y .theffilm unit for. releaseu .of its liquid .composition so asto permit thepermea- .tion of..the..liq11id..into. at .leastxthe .surfaceipon tions.v Aofnthe.,photosensitive and. image.- carrying layers. .The liquid. composition ispreferablyvi'scous v,and .preferably includes ...the ...reactive sub- .'.stance,. and at .least-.includes a...solvent .ither'emx The, film unit.. of Fig.; .preferably, comprises f a :.photosensitive .layer 30, an .imageecarrying layer 32, anda .containerglhavingtheneinLa liquid composition. and.. positioned toorelease its liquid. .betweenwthe .two .layers ..30 and .32. VFor supportingthe.. photosensitive. layer,v cthere. is provided ausualwlmbase. 36.

In another physical` Iembodiment Lof the .in-

..-vention, shown. in iFig.16,. theredsprovidedfa,

film unit of the general type:described -in con nectiQn-:with-ithediscussions oizliig. 5-,lthe.embodi ement ofeliig: 1 6. being..particularly useful .ningthose ,aprocessesxlescribed previously.A .when the reactive .carryingilayer tozcreateiaoolor.

- irReferringmow tor-:Eig 26,-. Wherealikeifnumbers correspond to likeelements.otliig-ir 5:,11thereis-.provided the usual layer., `,3[llof photosensitive material, carried by a. base'layer 36. An image.J

position Within aicohtainenl ,15 tions isolotainable in. n mercies Ways.

ivhileiti .separate 5 ...tivelyrenderedincapableof..creatine a colohby reaction, with a layer, of.. plwtosenstve materiel containingailatent negative. .image t0. cause Lthe development thereof, and the .unreed .991119115 .or.the reactivesubstance are tiliZd-.inolgri0 ...creating reactiontojorm. am Sltve. image, .an

.yimagefcarrying Jever. i In processesv Ait lis essential,tn leerrv.,the .rst reation Substantial .completionhforethesecondee I Qn r1.1-

-mences. ...The proner.sequenced the two 1 a9- ;One @obtainin described above in connection with the d is ukssion .of..-Fies.; 1 thrqughmvhere diede/ G19 leent Vof ...theA latent .negative image is ecemr lhed the letale 9f .the "6nd .greacton,i. y assembly with. .the :imegeferrying `vlever 4l 2. This way of, assuringthe proper sequence between Vhe fWQIeaCti0nsis110t as preferled .es Fliese. @YS

to Vbei/discussed hereinafter, since itis notfparticularly, adaptable foruse with a Cornpactfap paratuss ,uchh.asi a hand camera. A ,Whn :film vunitsi iofV4 Vthe type of, Eigs.. 5,. 6.v and '7 are utilized with the process .of thepreseritjiivlvention and the liquid composition f is` s'prea'd in a uniform laver within th nlm uitfwni1e ,the yariouslayers thereof are inlpermeable rel t'onship ,to eachA other, theproper sequence fof `mations. mayube assureduby ,providingH the pro'per .35, physical A, and/vor` -chemical 'rrelationship llgei'iie'en the various materials.

There ,area number of forms that this rela- 1 tionship mayltake. The rst forni, Whichvi'srp'articularly usetultvith Ithe embodiment ofQligf 5,

h en/l0 involves theprovisionof materalssuchthatthe A.'5`2 contains.'a'iiliiiallwh N ouitefreactiye withthedeveloper, the reaction ofthe developer ithl thematerial being that which creates-,a i.color'fconstitut'g 'th-positive'ii'nage."

.eretli-kez-nrlmhers Eigsrfand 6.

'.Referringf specifically to; Fig.; 7; zthere...is. pro vided a; usualephotosensitivelayered D .coated .on #the upper-surface ofk an..h image-carrying layer. L32. A container-34 i@ proyded inthe-almoneda a -fposiuonyto discharge-has iiguid' .compos-litmnzau-l 'j'ac/ent-*that surface thephotosensitive I Ylayer development of thewlatent'negative image istinherently faster thanthe Color-,creating reaction .whichiorms .the positive -ijrh'aee Anexampl lof lthis modification ,ofv the'i'nvention is one ,wherein the silver halide in the latent negative image.' is more' readiIy-i'educibIe than .the vJgnetallic jsalt `,on the image-carrying layer. Another' modication of.I lthis 4form 4ofthe invention, .useiulvv'ithr'the v ,embodiment. of Eig., 5, involves, the zprovisicm .of anv oxidizing agenten the image-.earryi'nglayer twhich oxidiz'es the'defveloper more slowlyI an the developerdevelop's. the. latent ynegative image. Another form,l of arelationshipoi materialr'or l.assuring the propersequence of reactions isthe provision ofsome means for .temporarily preventing-the color creating reaction. y Thismeansmay comprise a coating, .as shown fin Fig; 6, on the suriaceof` lthe `image-carrying layer yor hardened surface on the image-carrying layer Kwhich is adapted to retard.r penetration of the developer 5. ,pear in theVmore3detailed` ,exarnples. which illuslayer 32. For assisting.im-Spreading the liquid trate thenventipm,comprisepolyvinyl alcohol,

@composition-:11.1 e'liniferm-ihieileyle @diesem the provided a relatively impermeable er 40.

The embodiment ofFig. 7 may be utilized with -=anyfofithe- 4processesg..previouslitndescriltled; and l.1 1has-particular advantagein i.thosevprocesses wherein the reaction of the reactive-.substance the imagecarrying layermustbe sfuloj'etedtoA a definite treatment vbefore the Lu'lreactedl devel- ,.oper, on its, surfacenmayenter intoizthe-color .creation reaction.. .In onevr form .ofgthis modificavv-ithfthenegativemusmbe completed before the 75 .tion of ,.thefinvention:there iSPrOVded. .onethe image-carrying layer, a layer of unexposed photosensitive material. In this case, the unreacted developer cannot reduce this unexposed photosensitive material until it has been made developable by exposure to light. In another form, where there is used a developer which, when oxidized, couples with itself or another substance, this coupling can be prevented, if no oxidizing agent is included on or Within the image-carrying layer, or if the oxidizing agent must be treated, such as by exposure to light, before it is capable of oxidizing the unreacted portions of the developer. In this case, the developer cannot couple until the image-carrying layer has been exposed to aerial oxidation or the oxidixing agent has been activated such as by being exposed to actinic light.

Still another Way of assuring the proper sequence of reactions, as shown in Fig. 7, is to adjust the direction of permeation of the developer so that it permeates through, and is substantially completely reacted by, the photosensitive layer before reaching the image-carrying layer.

In the above discussion of the processes applicable to Figs. l through 4 and Figs. 5, 6 and 7, no

`mention is made of the preferred materials.

These materials vary in accordance with the specie processes involved and are discussed in more detail hereinafter.

In the following discussion of preferred examples of the various processes of the present invention it may be assumed that all the processes is so stated. In the following examples the numbers refer to Figs. l through 4 unless the process is particularly applicable to one of Figs. 5 through '7.

One method of creating a dye positive image from a latent negative image is to use on the image-carrying layer a material capable of coupling with unreacted portions of a reactive substance, such as a developer, to form a dye. This dye may be formed by the use of a color-former, or dye base such as a diazonium fast salt, on the image-carrying layer, which is capable of cou-,3

pling with unreacted portions of an amine orv phenol developer. Such a process is set forth in the following non-limiting example.

Example 1 The image-carrying layer I2, which may be conventional baryta coated paper, is prepared by coating with a Water solution of Naphthosol Fast Orange Salt G C and allowed to dry. Naph-i` thosol Fast Orange Salt G C is stabilized and diazotized meta chlor aniline (American Dyestuff Reported, 1939, vol. 28, No. 4, pp. 82-83). The photosensitive layer I0 comprises a relatively slow, high contrast orthochromatic silver halide emulsion, such as is employed with copying film, commonly known to the trade as contrast process ortho nlm. The photosensitive layer is exposed to actinic light and permeated with a developer by dipping for a few seconds in a solution of 1,5-i

- '69 negative is then separated from the image-carry- 12 dihydroxynaphthalene. Development of the photosensitive layer is continued for several minutes after removal from the developer bath. The developed photosensitive layer is then placed in contact with the image-carrying layer to cause the unreacted portions of the developer to migrate to the surface of the image-carrying layer where they couple with the Naphthosol Fast Orange Salt G C to form a positive dye image on the image-carrying layer. This image appears to be intensied by the aerial oxidation of the unreacted developer after the initial positive image is formed. Thus the image appears to be formed by the unreacted portions of the developer which couples, partially in its unoxidized and partially in its oxidized condition, with the color-former. Those portions of the developer oxidized as the result of the development of the latent negative image appear to be trapped within the photosensitive layer and thus cannot spoil the positive image.

In another method of forming a dye positive image from a latent negative image there is utilized a color-former capable of coupling with oxidized, rather than unoxidized, portions of the developer. Such a process where the color-former is contained in the liquid is described in the following nonlimiting example:

Example 2 The photosensitive layer` l0, which may comprise an orthochromatic emulsion of the character described in connection with Example 1, is exposed to actinic light to create therein a latent negative image. This latent negative image is developed using the following developer:

Diethylparaphenylenediamine hydro c hl o- The negative is removed from the above developing bath after approximately 5 seconds and image-carrying layer.

development is allowed to continue for a minute and a half. The developed negative is then pressed into contact with an image-carrying layer I2 containing an oxidizing agent. Such an image-carrying layer may be prepared by swabbing a sheet of paper, known in the art as imbibition paper, with a 10% solution of sodium perborate. The negative is left in contact with the image-carrying llayer for approximately four minutes to permit the sodium perborate to oxidize the unreacted portions of the developer so that they may couple with the color-former. The

ing layer to reveal the positive dye image on the The image obtained by this process is magenta and may be utilized to advantage in three-color photography.

Example 3 A cyan positive image may be obtained in Example 2 by using, as the color-former, 2,4-dichloro-l-naphthol.

Example 4 .aco-1529s 13 Lrela-tes I to a process .where z the color-.former y is i included in the developer liquid, it is equallypossible to swab a solution of one or more of the color- .g formers on the image-carrying layer. This swab- ..ing those portions of the developer unreacted by the development of the latent negative image. Other nonphotosensitive,oxidizing agents such as sodium perchlorate, ammonium dichromata'and ammonium persulfate may l.also be used.

It is also contemplated'to use a photosensitive oxidizing Yagent on or within the surface of the image-carrying layer. Such a'photosensitive ma. terial can bea silver halideand is preferably dispersed within 'the surface of the paper.

This :photosensitive material can be either exposed or vunexposed depending upon Athe desired type of process. If. exposed, it reacts with the developer sas soon as it contacts the developer.

Example The process of Example 2 is modified by eliminating the oxidizing agentfrom the image-carrying layer l2. When the image-carrying'layer has been imbibed with the developed negative for 4 or 5 minutes it is separatedtherefrom and the invisible image in unreacted developer on the rsurface of the image-carrying layer is exposed to aerial oxidation. As the developer-oxidizes it couples with the color-former to createa color and thus produces a positive image.

In the process of the type of Example 2, where a color-former couples with the oxidized developer, it isv desirable to insure the trapping, within the photosensitive layer, of all the developerthat -isoxidized `bythe development ofthe latent negative image. Such-atrapping may be improved by-including within the photosensitive layer ID a color-former` that couples With the oxidized developer to form a relatively immobile dye. Thus, as the developer is oxidized by the development of the latentA negative image, it immediately couples with the color-former in the photosensitive layer Il'andis converted into an immobile dye,` thereby kbeingtrapped Within the photosensitive layer.

This is particularly desirable Where the colorformer used to create the positive image is placed on the image-carrying layer rather thanV inthe developer solution.

AIn `still another method of form-ing a dye posi- "tive image from Aa 'latent negative image, a selfcoupling developer is used. This developer may be one of the type known in the art as a direct Vcolor-forming developer, i. e., one which'couples 'withitself to form a dye when oxidized, as set Hforth in the following nonlimiting example:

'Water `Sodiu'mearboxymethyl cellulose ;grams 4216 :154 Examplel A layer of silver halide photosensitive V film 30-36 of Fig. 5, such as orthochromatio copying film of the type described in 'Example l, is exposed to a subject image. A preferred'form of image-carrying layer 32 comprises a sheet ofimbibition paper. A suitable liquid composition contains the following .materia-1s:

cc V476 Sodium hydroxide do 17;.5 1,5-dihydroxynaphthalene d0 .19,0

With such a'liquid composition, the process lis preferably ,carried out by spreading a thin layer of the Vliquid composition between the exposed photosensitive layer 3D and the image-carrying layer 32. lThis spreading may'be accomplished `by `releasingthe liquid composition from acontainer 34 positioned between these two `layers and spreading theliquid by means such as a pair ofpressure rollers. l'The 1,5-dihydroxynaphthaiene develops 'the Vlatent negative Yimage and, where development occurs, it self-'couples toform an immobile dye. Where development does not occur, the unreacted developer migrates to the surface of the image-carrying layer. `The'imagecarrying layer 32, with 'the positive image in terms of unreacted developer on its surface, is then separated from thephotosensitive layer 30 andexpose'd te air so .as'to oxidize the unreacted developer. This oxidation causes the `developer on the image-carrying layer to self-couple,thus creating a color and forming a postiverima'ge of the subject image.

It is equally possiblejto use oxidizing agents'on the image-carrying layer of Example k6 rather than relying on aerial oxidation to oxidize't-he unreacte'd developeron the' image-carrying. layer. 'In such a case the film unit should'be of the form of Fig. 6 or 7 and theioxidizing agents may be of the Various types discussed in connection vwith Examples 2throughV 4 above.

Wherethe positive image on'the image-carryingrlayer is formed in .terms of la color created by -a pigment, as distinguished from a color create-d byV a dye, the-unreacted portions of the deve-loper may-be usedutovform this pigment by the reducingaction offthedeveloper-on alreducible salt, as set forth in the following nonlimiting example:

Emample 7 The layer ID of photosensitive material preferably comprises an orthochromatic emulsion of the copying lm type referred to in "Examplel The layer lll isexposed to actinic light to -create therein a latent negative-image. This negative image 4is-then developed by placing it in a bath containing:

l Grams Hydroquinone 425.2 Sodiumsulphite t37.8 Sodium hydroxide s 36.1 Water 900 tive paper such as arelatively fast, conventional enlargingpaper having `an emulsion lcemprismg --silverrbromide and silver chloride.

4The unire.

silver on the image-carrying layer.

` units of the type shown in Figs. 6 and 7, or in a film unit like Fig. where the image-carrying layer is sufficiently impermeable so as to delay permeation thereof by the developer. If it is desired to include a silver halide solvent in the liquid composition for the purpose of removing unreduced silver halide from the image-carrying layer of Example '7 the photosensitive material in the photosensitive layer is made of less soluble material than the silver halide in the imagecarrying layer. The unreduced silver halide may be removed from the image-receiving layer to a protective colloid lm formed between the image-carrying layer and the photosensitive layer by a plastic material such as sodium carboxymethyl cellulose carried in the liquid-processing composition or this unreduced silver halide may be transported to the base which supports the photosensitive layer.

In still another modification of the invention, a nonphotosensitive salt is added to the imagecarrying layer for the purpose of making available a material which can be reduced to a pigment by unreacted portions of the developer. This salt may be added after the invisible image in unreacted developer has been formed on the surface of the image-carrying layer. One method of practicing this feature of the invention is set forth in the following nonlimiting example:

Example 8 A copying film, of the type heretofore described, is used as the photosensitive layer i0, and a sheet of inbibition paper is used as the image- I carrying layer l2. The photosensitive layer is then exposed to a subject image and developed with a liquid composition I4 comprising a mixture of solutions A and B as follows:

Solution A:

lSodium carboxymethyl cellulose grams 20 This development is preferably accomplished by spreading the liquid composition in a uniform thin layer between the photosensitive layer 30 and the image-carrying layer 32 of Fig. 5. This spreading is preferably accomplished by releasing the liquid composition from a container 34 therefor positioned between the two layers. After several minutes the image-carrying layer 32 is separated fromY the photosensitive layer 30 and there is seen an extremely faint yellowish image, which apparently is an image in unreacted developer which has started to oxidize.

The image-carrying layer 32 is next swabbed with a dilute solution of silver nitrate and a gray positive image is developed as the result of the 16 reduction of the silver nitrate by the unreacted developer.

'Example 9 A yellow positive image can be obtained in the process of Example 8 by swabbing the imagecarrying layer 32, containing an invisible positive image in unreacted developer, with a salt such as ferric chloride, chromic trioxide or platinum chloride.

In another modification of the invention wherein unreacted portions of the developer are utilized for Creating a color in terms of a pigment, a nonphotosensitive salt is selectively reduced to colloidal particles by these unreacted portions of the developer, as set forth in the following example:

Example 10 An image-carrying layer 32 of Fig. 5 is formed of baryta paper and is prepared by swabbing with a 2% solution of chloroplatinic acid. The photosensitive layer 30 and the base layer 36 may comprise a sheet of the heretofore described copying film. With such materials the liquid composition in the container 34 preferably comprises:

Water cc 476 Sodium sulphite grams 9 Sodium hydroxide do 19.6 Sodium carboxymethyl cellulose do 42.6 Hydroquinone do 9 The film unit is processed by exposing the photosensitive layer 3) to actinic light and then passing it through a wringer. The layers are kept together for a few minutes and then separated to reveal a yellow positive image on the image-carrying layer.

Eample 11 Water cc 476 Sodium sulphite grams 9 Sodium hydroxide do 4.9 Sodium carboxymethyl cellulose do 28.4 Hydroquinone do 9 The lm unit is processed by exposing the photosensitive layer 30 to actinic light and then Y passing it through a wringer. The layers are kept together for a few minutes and then separated to reveal a yellow positive image on the imagecarrying layer.

Example 12 The contrast of the positive image obtained V by the process of Example 11 may be improved by treating the prepared image-carrying layer with (a) ammonium hydroxide or (b) ammonium hydroxide and hydrochloric acid to form colorless palladium complexes in place of the palladium chloride.

Other reducible salts, which may be nonphotosensitive or only slightly photosensitive, such as a silver salt of sodium carboxymethyl cellulose, may also be used as the reducible metallic salt on the image-carrying layer 32.

Another modification of the invention where- Y in the reaction of the developer with the negative image is inherently faster than the colorforming v'rea'ctionzis descr-ibedilinthefollowing nonlimiting example:

'Exampe 1'3 The photosensitive layer 3!) andthe base layer 36 of Fig. 5 may comprise! a:silverhal-idexphoto- Sgraphic lm such as the heretofore Ldescribed 'copying lm. :For vuse with this 'photosensitive layerS@ lthe liquid composition :in the-container The image-carrying layer f3?? is preferablyiormed of a sheet of barytafpaper which has beenswabbed with a color-former capable -o'f coupling with -unreacted4 portions voi -the-pyrocatechin. Sucha color-former may be applied bymalcing--an-alco'- xhol and water solution of -Naphthosol Fast Orange Salt -G C'. The kphotosensitive layer 30 is exposed to actinic light-and the -developeris then spread between the exposed photosensitive layer -3-0 and theimage-carrying.layer 32 by the use of pressurevrollers or `other suitable means. `rIhe pyrocatechin appears -to react first with ythe latent -negativeimage-in the-photosensitivelayer s' 30, and then the unreacted portions thereof-mi'- grate -to the image-carrying layer where they couple with the color-fermer on -thei-mage-carry- Vinglayer to give-a positive image.

In `stil-l `another anodin-cation of the `erniciocl-iment of Fig. 5 whereina `dye-positive image is obtained, a process -is -used `which yis simi-lar to that described in -Example 2; inthe-following example there is shown a lmethod of practicing this :feature of the invention with the modification-of-figf wherein the proper sequence-lof reactions is assured by using an oxidizing-agent which oxidizes the developer more slowly than the developer develops the latent-negative-imagez Example 14 Thephotose'nsitive layer 3|) 'andthe base layer 36 preferably 'comprise a sheet ofv the "copying lm of the preceding examples, and the imagecarrying layer 32 comprises 'a slie'et' of baryt'a paper Whichha's been swabb'ed With-'a 113% "'s'olu= tion oi' sodium perborat'e. A 'preferred liquid composition comprises:

H Grains Diethylp'araphenylenedialnine vh'ydio'f'hl'ovride .'75 sodium suiphite `1.5 Potassium bromide 0.6 water solution of 'sodium 'carboxymethyl cellulose 1311 A y Sodium carbonate 14562 -a-s'1owiy eimeabiepiyviiiyi 'alcohol coating is ipia'cu" 'eine fjtaiiicfsalt'to assure a proper seeii'eiicefefrracticins.

@Example '1f5 zA solution'is fprepa'red 'by adding A20 "grams of ime'rcurousinitra-te to- 200 cc. cfa "3 per -cent nitric acidfsolution. vA fs'h'eetof -baryta paper, for use as the image-carrying layer32, is placed in this solution for two miniit's'fa'nd-the excess solution is removedfrom the sheet by the use of a s'qugee. "I'heshet 4is"th'en"soaked in a 10 per cent solution "of 'sodium 'ch'l "efor'tw'o minutes, forrning'inercfdus 'chloride in Jthe surface (of the barytapaper. "The'shet 'i's then dried in air'at room temperature. KTo one ysurface of 'a s'lie't prepared as 'above "therelis laminated -a layer' 'o'f .pol'ym'yl alcohol. This 'l'aye'r '38 of polyvinyl "alcohol is 'pefeably in )the neighborhoodof OOOGVIinch'thi'ck-and is laminated to the baryta sheet by using A'a Water solution o'f .polyv'i-nyl'alc'oh'ol.` y

Forr use l:with the above d'e'so'rib'e'd 'composite sheet 'S2-3l! a `liquid composition inthe container A311l preferably comprises the "following ingredients:

For he'ne'gative photos i'tivelayer V3i---3ii'a preferred material Ia 'sheet of 'the 'previously In'ti'r'led copying The photosensitive layer 30 is' expose'to'a `subject -rn'a'ge and the film unit-is processed, as' by pa's's'in'g itV through 'a pair f 'pressure roll'r's lio-'release 'the lid'u'd compositin rfinfl the container 34 'and t'o Spread the liquid in `a unifor'rn thin lay'r between the photosensitive layer Sli-andthe polyvinyl 'alcoholcoatn'gf38'. When the 'above described 'liquid 'composition iiss'p'read 'between the exposed phot'osensi't'ive 1`ay`r'3'0 and the 'polyvinyl alcohol coating 38 l 4the 'image-carry 'gl'l'ayei 34, the developer develops the latent n gative imagein'the photosensitiv layer, 'this development being substantilly *completed be'fore'aiiy substantial peri'neatio'n of the 'polyvinyl lalcohol layer 38 takes place. Wh'e the dvelpr i'su'i'l'a'cted b'y this developnient, it permeates through the polyvinyl alcohol coating 'and 'r''due's the ""mec'uroll's chloride on the surface of the image-'carrying layer to "colloial black particles lni'ng a. v'positive im'ag' -of th'e latent negative image.

While 'the above modification -of the invention describes a preferred form" thereof,r numerous other materials and processes may be utilized. The slowly permeable layer 38 may comprise plastics other than polyvinyl alcohol, and reducible salts other than mercurous chloride may be used. The liquid composition is also susceptiblel of Wide variations without departing from the scope of the invention.

While the slowly permeable layer 38 of polyvinyl alcohol is preferably applied in the form of a sheet by laminating to the image-carrying layer, it is equally possible to cast, from an aqueous solution, a layer 3S of polyvinyl alcohol directly on the surface of the prepared image-carrying layer 32 by the use of a'doctor'blade or other coating techniques.

The slowly permeable barrier layer 38 may equally be formed of a plastic such as cellulose nitrate, as set forth in the following example:

Eample 16 In this case a sheet of baryta paper, containing mercurous chloride, is dipped in a bath containing a 2% one-half second cellulose nitrate solution in equal parts of butyl alcohol and butyl acetate. The sheet is dried, and the layer of cellulose nitrate is found to be approximately .0001 to .0002 inch thick over the mercurous chloride. Such a sheet is preferably used with a developer of the type mentioned above.

In the embodiment of the invention of Figs. 5, 6 and 7, the material which reacts with the developer on the image-carrying layer 32 may be situated on the surface thereof nearest the photosensitive layer. If such be the case with respect to Fig. '7, the photosensitive layer 30 is preferably so formed that it may be readily separated from the 'image-carrying layer 32. This separation may be assisted by including within the liquid composition a film-forming material, such as sodium carboxymethyl cellulose, which is capable of forming a strong adhesive bond between the photosensitive layer 30 and the backing layer 40. Thus when the image-carrying layer 32 is sepparated from the backing layer 40, the photosensitive layer 30 adheres to the backing layer 40. The photosensitive layer of Fig. 7 may, if desired, be carried by a suitable permeable base material such as a sheet of gelatin, in which case the base can be mounted with respect to the image-carrying layer so as to be readily separable therefrom as in the manner of conventional stripping film.

In another modification of Figs. 5, 6 and '7, the material which reacts with the unreacted portions of the developer is situated on the surface of the image-carrying layer farthest from the photosensitive layer. In this case no separation of the various layers of the lm unit is required in order to View the positive image. Visibility of the negative image, in instances where the layers of the iirm unit are to remain unseparated after positive image formation, may be prevented by the use of a suitable opaque material, for example baryta paper, for the image-carrying layer.

In still another modification of the embodiment of Figs. 5, 6 and 7 there may be one reactive material on one surface of the image-carrying layer and another reactive material on the other surface of the image-carrying layer. As an example of such an arrangement, as applied to Fig. '7, an oxidizing agent may be included on the upper surface of the image-carrying layer in a position to oxidize unreacted portions of the developer as it permeates through the composite film unit. On the lower surface of the imagecarrying layer there may be a` color-former capable of coupling with the oxidized developer. As the developer reaches the color-former on the lower surface it couples therewith to form a positive dye image.

In the physical embodiments of the invention represented by Figs. 5, 6 and '7, the container 34 preferably comprises a paper-backed metal foil coated on its inner surface with a resin, such as polyvinyl butyral, which is inert to alkalies, although it; may take numerous other forms.

The liquid composition in the container 34 preferably comprises an aqueous solution of the reactive substance. For assisting in spreading the liquid in a uniform film, the liquid preferably includes a viscosity-increasing compound constituting a film-forming material of the type which, when spread over a water-absorbent base, will form a relatively firm, dimensionally stable film. Where the aqueous solution is alkaline, the filmforming material is preferably one which :is not hydrolyzed in an alkaline solution. A preferred film-forming material is a high molecular weight polymer as, for example, a polymeric, watersoluble ether inert to an alkali solution, such as hydroxyethyl cellulose or a metal salt of carboxymethyl cellulose, e. g., sodium or aluminum carboxymethyl cellulose. Other film-forming materials or thickening agents can be used for the conversion of nonviscous solution to viscous solutions where the conditions are such that their ability to increase the viscosity of the solution is not destroyed when left in solution for a considerable length of time. The viscosity of the liquid composition is preferably in the neighborhood of 20,000 centipoises, although it may be as low as 8 centipoises. The high viscosities are preferred, since they give a more accurate control of spreading of the liquid composition.

In the various physical embodiments of the invention, the liquid composition in the container 34 preferably comprises an aqueous solution of the reactive substance. In some cases, however, it is desirable to include the reactive substance, such as a developer, in or on one of the layers of the lm unit and for the liquid composition to include only water, possibly an alkali, and possibly a film-forming material to aid in accurate spreading. In other cases, the liquid composition may, for example, comprise only an aqueous solution of the developer, and there may be included in solid form in one of the layers of the lm unit any alkali which may be required.

In still another modification of the physical embodiment of the invention the film unit may contain no liquid and may contain, in solid form, all of the various materials ordinarily carried in solution within the lm unit. Such. a modification of the invention is not as preferred as those described, since it requires the addition of a solvent to the lm unit and thus cannot be processed by the mere application of mechanical stress to the film unit. Such a modication of the invention is, however, included within the scope of the present application.

The image-carrying layer, while being preferably formed of papers such as those known in the art as baryta paper or imbibition paper, may be formed of numerous other materials such as a water-permeable plastic or a water-permeable, reversible, film-forming organic colloid capable of having high Viscosity characteristics and appreciable jelly strength, in which dye bases or salts may be suspended.

Examples of other suitable image-carrying lay- 123 than said emulsion and permeating said emulsion with liquid composition from said layer- Wise distribution While retarding contact of liquid composition with said image-receiving layer until said liquid composition has passed through the stratum of lesser permeability.

8. A process of forming positive transfer images in color as dened in claim 1 and including the step of effecting the oxidation of the unexhausted portion of said developer which is transferred to said image-receiving layer with an oxidizing agent substantially uniformly distributed throughout at least a stratum of said image-receiving layer adjacent the surface thereof to which said reagent is transferred.

EDWIN H. LAND.

References Cited in the iile of this patent UNITED STATES PATENTS Number Name Date 1,055,155 Fischer Mar. 4, 1913 1,102,028 Fischer June 30, 1914 1,900,.870 Seymour Mar. 7, 1933 1,993,576 Troland Mar. 5, 1935 2,054,261 Lierg Sept. 15, 1936 2,059,884 Mannes Nov. 3, 1936 v 2,059,887 Mannes Nov. 3, 1936 2,137,336 Gaspar Nov. 22, 1938 2,172,307 Gaspar Sept. 5, 1939 2,206,126 Schinzel July 2, i940 2,252,718 Mannes Apr. 19, 1941 2,289,714 Land July 14, 1942 2,315,966 .Knott Apr. 6, 1943 2,328,034 Sease et al Aug. 3l, 1943 2,336,327 Weissberger Dec. 7, 1943 2,342,620 Woodward Feb. 22, 1944 T24 Number Name Date 2,347,119 Michaelis Apr. 18, 1944 2,350,380 White June 6, 1944 2,352,014 Rott June 20, 1944 2,363,764 White Nov. 28, 1944 2,386,167 Murray Oct. 2, 1945 2,388,894 Yackel Nov. 13, 1945 2,397,015 Kendall Mar. 19, 1946 2,397,452 White Mar. 26, 1946 2,410,644 Fierke Nov. 5, 1946 2,500,421 Land Mar. 14, 1950 2,543,181 Land Feb. 27, 1951 FOREIGN PATENTS Number Country Date 382,975 Germany July 14, 1922 716,428 France Oct. 6, 1931 879,995 France Mar. 10, 1943 900,266 France Sept. 25, 1944 53,513 France Add July 16, 1945 53,515 France Add July 16, 1945 449,750 Great Britain June 29, 1936 451,190 Great Britain July 31, 1936 503,824 Great Britain Apr. 11, 1939 503,752 Great Britain Apr. 11, 1939 503,873 Great Britain Apr. 17, 1939 OTHER REFERENCES Stenger, Zeitschrift fur Wiss Photographie, vol. 22, 1923, pp. 195-200.

Ricketts, British Journal of Photography, vol. 61, June 5, 1914, page 446.

Clerc Photography Pitman, N. Y. 1937, pps. 231-232.

Friedman American Photography, Jan. 1939, vol. 53, pages 59-61.

Claims (1)

1. A PROCESS OF FORMING POSITIVE TRANSFER IMAGES IN COLOR WHEREIN A SINGLE APPLICATION OF LIQUID TO THE EXPOSED SILVER HALIDE EMULSION OF A PHOTOSENSITIVE ELEMENT PRODUCES THE NECESSARY SEQUENCES OF REACTIONS FOR GIVING THE FINISHED POSITIVE PRINT, SAID PROCESS COMPRISING THE STEPS OF: PERMEATING SAID SILVER HALIDE EMULSION WITH A LIQUID COMPOSITION, AND, DURING SAID PERMEATION, HAVING SAID SILVER HALIDE EMULSION SO SUPERPOSED ON AN IMAGE-RECEIVING LAYER THAT SAID LIQUID HAS ACCESS TO THE LATTER LAYER; PROVIDING WITHIN THE LAMINATION COMPRISING SAID PHOTOSENSITIVE ELEMENT AND SAID IMAGE-RECEIVING LAYER A PAIR OF REAGENTS CAPABLE OF REACTING WITH ONE ANOTHER IN THE PRESENCE OF AN OXIDIZING AGENT TO GIVE A DYE, ONE OF SAID REAGENTS BEING A COLOR FORMING SILVER HALIDE DEVELOPER AND THE OTHER A COUPLER, AND SAID REAGENTS BEING SO DISTRIBUTED THROUGHOUT SAID LAMINATION AS TO HAVE A SUBSTANTIALLY CONSTANT DEPTHWISE CONCENTRATION PER UNIT SURFACE AREA OF SAID LAMINATION AND AT LEAST ONE OF SAID REAGENTS BEING PRESENT PER EACH SAID UNIT AREA SUBSTANTIALLY ONLY IN SUCH QUANTITY AS TO CAUSE SAID REAGENT TO BE SUBSTANTIALLY COMPLETELY REACTED IN THE EMULSION IN THE EVENT OF THE FULL DEVELOPMENT OF THE SILVER HALIDE OF SAID UNIT AREA, SAID REAGENTS BEING DISSOLVABLE IN SAID COMPOSITION WHEN CONTACTED THEREBY AND WHEN DISSOLVED THEREIN BEING MOBILE IN SAID LAMINATION: DEVELOPING THE LATENT IMAGE IN THE SILVER HALIDE EMULSION BY MEANS OF SAID DEVELOPER AND CAUSING SO MUCH OF THE SAID DEVELOPER AS IS OXIDIZED BY THIS DEVELOPMENT TO BE SUBSTANTIALLY FULLY REACTED WITH THE COUPLER TO PRODUCE A DYE IMAGE IN THE EMULSION AND TO THERE EFFECT, BY REASON OF SAID REACTION, THE EXHAUSTION OF THE SAID REAGENT PRESENT IN LIMITED QUANTITY IN PROPORTION TO THE DEVELOPMENT OF SILVER PER EACH SAID UNIT AREA OF SAID LAMINATION: TRANSFERRING TO SAID IMAGE-RECEIVING LAYER IN SOLUTION IN SAID COMPOSITION AT LEAST A PART OF THE UNEXHAUSTED PORTIONS OF SAID REAGENTS; THEREAFTER, CAUSING THE TRANSFERRED UNEXHAUSTED PORTIONS OF THE SAID REAGENTS TO REACT IN THE IMAGE-RECEIVING LAYER IN THE PRESENCE OF AN OXIDIZING AGENT TO PRODUCE A DYE IMAGE IN SAID LAYER; AND, THROUGHOUT SAID PROCESS, MAINTAINING SAID IMAGE-RECEIVING LAYER FREE OF APPRECIABLE AMOUNTS OF SILVER, SILVER SALTS AND MATERIAL WHICH, DURING SAID PROCESS OR IN THE PRESENCE OF LIGHT AND AIR, WILL IMPART TO SAID IMAGE-RECEIVING LAYER A COLOR THAT WILL ADVERSELY AFFECT THE VISABILITY OF THE SAID IMAGE IN THE IMAGE-RECEIVING LAYER.

Images