US2596756A

US2596756A - Photomechanical copy method

Info

Publication number: US2596756A
Application number: US783914A
Authority: US
Inventors: Henry C Yutzy; Edward C Yackel
Original assignee: Eastman Kodak Co
Current assignee: Eastman Kodak Co
Priority date: 1947-11-04
Filing date: 1947-11-04
Publication date: 1952-05-13
Anticipated expiration: 1969-05-13
Also published as: US2763553A; GB725667A; DE927307C; GB655273A; DE874704C; FR1092963A; GB726543A; BE517064A; US2592368A; BE517066A; FR980399A; US2675313A; FR980401A; BE485609A; FR1089934A; GB655274A; BE485611A

Description

y 1952 H. c. YUTZY ETAL 2,596,756

/ PHOTOMECHANICAL COPY METHOD Filed Nov.v 4, 1947 F/LM 0R PAPER SUPPORT J0 FIG. 1 k EXPOSED & TANNING 51 7 27%?23 DEVELOPED P/GMENTED l1 16 EMULSION LAYER 16 12 .sILvER IMAGE IN TANNED aqua/p a 14 TEANsFERkEo STRATUM or uNExP05Eo P/GMENTED FIG 2 13 UNTANNED EMULSION PAPER .suPPokf 15 SULF/DED 0/? ExmsEp AND DEVELOPED 0R P/GMENTED 13 EMULSION STRATUM PAPER SUPPORT 15 I 4 ABJORBED EMULSION p vEIaPED BY HEAT AESORBED H0276' ROLLER ULSION BEING EXPOSED Q WANSFER ROLLER 19 RECEIVING SHEET Q ExPos/Na 13 LIGHT 6 .7 uIvTANNEa EMULSION BEING ABSORBED IN RECEIVING .sI-IEEr TAN/VED NEGATIVE -HZIZILmEQZmICQEAM 1E QNTANNED 1 23 W ENRY C YUT URF CE I .5 -4 A RES/PU EDWARD c. YACKEJL UN774NNED EMULSION- INVENTORS.

ATTORNEYS l atentecl May 13, 1952 [Taos -rn ras Parse NT.-

oar-lacs? PHOTOMECHANICALI COPYLlvIETHODQ Henry .C. .Yut'zy andEdward' C'iYackel, Rochester,

N. .Y., assignor's to Eastman. Kodak Company,"

RochestenNi Y.,fla "corporation of New'Jersey Application November 4, 1947; Serial No.':783,914

moiaims. (01:95:51-

Thisziiriventionrrelates to-photographyand more particularly to." a photomechanical copy: method fonnse: in :the. reproductionof: printed :n'ia-tter;

There naretira '2 number of: f well-known: photographic methods :of reproducing designs; such as printed matterionpaper: or other supports; For instanceybytheso-calledtrefiex copy method an emulsion layerrlis exposed through :its: support and thevprinted matter :is. reproduced as :a nege ative;-2 Or 'oneiima-y print a negative "and-a :positive' therefromeby conventional methods. In the photomechanicaliarti a :common practice is to expose a suitable photographic element such: as a'tissue andto transfer theiexpcsed elementto a meta1..plate after which the unexposed emulsionis :washed ofi the .plate orstheiwashing. off may' occurI bef-ore transfer of the-resist to the plate. Similarlmin the Pinatype Jprocessafter forming-' a hardened image, colored :matter; :is printed from *the' unhardened area of I the element but the' colloid vehicle :is 'not transferred fromthat area 'tothe printing surface. Arliinitedamount 'of endeavor which apparently. has not been successful has been 1 directed to 'a 'proc ess wherein after exposing a-dichromated al bum-en element; the unexposed and'Unhardened portion of 1 the element is transferred :to a2 sec on-d' 'support." We have discovered a simple photographic method not" apparentfrom-the prior art-- te'achin'gs; includingdifie'rentially hardening silver salt emulsion layers and transferring 1 unhardened'strata 'cf such layers to a su-pport to obtain'useful images: The -advantag es= of our process are at once apparent particularly "when considering "-the rela-tive--advantages of dichromated albumen and silversaltemulsion' layers. Bothm'aterials have reached-a high state of development-"and the latter exce1-bcause--of the wide range: of: speed," contrast, density; etc; ob-'- tainable therefrom: These 'advantages,--'as well as others; :as will be- "apparent; accrue tous-by use ofsilversalt-"emulsions in our-process; A further advantage-of ourproces's lies in the-fact that we are able to 'makeicleairtrans'fers of a stratum ot; and not just the r'wholerof an unh'ardened'tphotographiclimage and thus manyprints are phtairiabld by oun 'rocess. In" addition, by utilizing silver salt emulsions we obtain'sensitive products whichpossess decidedly better keeping,properties,-and materials through which'in-v creases in speed may be effected by means ofide velopmentrather than exposure alone. We are -not=aware that. silver salt. emulsion. layers ..with their attendant ladvantages have previously been thus-processed to producedirect positive images.

According t0=therbroadest aspect-of our. invene tion a silversaltemulsion'layer such-as gelatin:- silver halide,- containing pigments or. other: materials if so desired, (is exposed to a suitable .sube jec-tgjsuch. as line or half-tonetsubjects.-(twotone subjects)- excludingcontinuous tonewsubjects, .developed in the: presence'of .a tanning type of .developerfollowing which theelement is. squeegeed-into contact witha secondsupport whereby after drawing joff the -developed element a stratum "of the image of the original-subject will have been transferred to the second -.supp0rt.'

One objectof our invention isto provideasiznpie photographic process of :1eproducinga-subj act such as -printed-matter by transfer of strata of substantially. unhardened emulsion to :a support. Another: object :is-to provide the materials and photographict-and-mechanical-processes and' variations of the same-toxwhich our. invention is'sus- -ceptible.- Other objects will-become apparent from 'the following descriptionof, our invention.

Our -:invention may be' better understood. by reference to the accompanying 5 drawing wherein Fig. 1 shows. in cross-sectional view the .ap pearance? of a-silver halide emulsion-bearing support-afterexposure :to'a subject and'developmentrin: thefipresence of :a tanning developer.

Fig.:2 showswin; enlargedacrossesectionzzl. yiew the appearance :of the-transferred :unhardened emulsion. image-stratum imprinting relation to the element-of 1..

Fig. 13.1- shows-fin enlarged.nrossesectional.view@ a modification of .Qouit invention" after; .the transferred imagesstratunrrofz Fig; :2 ;has::been';further treated to'increase'its opticalzdensity. 1'

Fig. 4 is a diagrammatic sectionalfiieW oftypital-apparatus; materials andzmethodssused in our m'ventiom Our invention-will iiow be describedin greater detail witli referenceto th' accompanyirig' drawingsr In therpreferr'ed embodimentof our invention we" take-a substantially =unha-rdened light-sensitive; -preferab1y pigmented; gelatino silver halide emuisionia ertn a paper or othersupport and-expose it from the-emulsion side}- -for--* ex am'plei with the-emulsion surface-contact with the 'front of a sheet carryin -printed'- matter. After this'thexposed layer is "developed in "thepresence of a tanning developing:- agent which mayhave been incorporated into the emulsion layer, of the type-and :in themanner disclosed in the copending Yackel U. S; patent a plication "Serial Number" 783,912; filed-"concurrently,

nowPate'nt Nor-2,592,368 ;%=dat'ed April"- 8. 19525111 agents have a solubility of from about .01 to .2"

gram per 100 cc. of buffer solution. Developing agents falling within the above classification are, for example, 3,4-dihydroxy diphenyl, 2,5-dihydroxy diphenyl, 5,6,7,8-tetrahydronaphthohydroquinone, and 2,3-dihydroxy diphenyl. The mentioned diphenyl compounds are preferred because they possess the combination of the common properties, high rate of development, high tanning efiiciency, and solubility in the preferred range. Here. and in the appended claims, where the tanning developing agents are mentioned as incorporated in the emulsion, the desired compounds are, for example, those mentioned and having the mentioned characteristics. Otherwise, where tanning developing agents as hydroquinone and pyrocatechol, in absence of sulfite, are used, they are less desirable but useful results may be obtained. Compounds like 2-hydroxy- 5-amino diphenyl or 3,4-diamino diphenyl are not especially useful because of their poor stability or failure to tan. It is, therefore, apparent that after exposure to a subject the difierential hardening of the exposed emulsion can take place in the presence of a tanning developing agent and that this includes whether or not the agent is in the emulsion before exposure.

Thus, if there is no developing agent in the emulsion, after exposure we may treat with a solution of tanning developing agent and then a solution of alkali. This process is less preferred because of the tendency for a developing agent like hydroquinone to transfer and give rise to stain. Similarly, we can pretreat the exposed sensitive material with a tanning developing agent and place it in contact with the receiving support with a layer of alkali solution between, at which time development starts and when it is finished the sheets are separated leaving a stratum of the direct positive image on the receiving support. Pigments of the type useful in the emulsion layer are metallic silver, carbon black, dyes or pigments such as Monastral Fast Blue BWD (copper phthalocyanine dye) or other insoluble pigments.

The colloid binder for the emulsion layer is preferably gelatin although other materials such as polyvinyl alcohol, hydrolyzed cellulose esters, and resins which have the property of being hardened withtanning developers locally in the region of the exposed image may be used.

After exposure and development in the presence of a tanning developing agent the processed photographic element would appear substantially as shown in Fig. l of the drawings, wherein enlarged cross-sectional view layer I0 is a film, paper or other support to which is affixed the exposed and tanning developed silver halide emulsion layer H containing the silver and tanned gelatin image [2.

We next place the moist element of Fig. 1 into printing relation to, and the layer II in contact with an absorbent support of a sheet of paper or other material such as wood, cloth, etc., and by of heat, the unexposed and unhardened portion 56 of layer H is caused to adhere to the sheet of paper. Following this the element is stripped off the sheet leaving the transferred unhardened image stratum on the sheet as shown in Fig. 2 wherein layer !3 is the paper sheet which has received the untanned pigmented images [4. By rewetting the balance of image It on support [0 with the alkaline solution, (water wetting is less preferred), additional transfers may be made. Whether or not pigment has been incorporated into emulsion layer H of Fig. 1 prior to exposure, we may next further increase the optical density of images M by treatment of the silver halide therein with a sulfide such as sodium or zinc sulfide, alkaline thiourea, metal salts and the like, according to well-known toning methods or we may further expose image I 4 and treat with a reducing agent or develop in alkaline solution which may contain the developing agent in case no developing agent was present originally in the emulsion layer. Since appreciable amounts of silver salt, developer and alkali will transfer with image M, the density may be increased quickly by exposing and heating the print. The transferred image now appears as shown in Fig. 3 wherein layer i3 represents the receiving support carrying the darkened images I5. After exposure of image [4, a coupler-developer solution may be used in the manner conventional to present day color photography methods to transform image l4 into a dye image. Similarly, the components of coupler-development may be incorporated together with or instead of pigment into the emulsion layer, or only the coupler may be in the emulsion layer, and darkening of the image is effected by use of a developing agent, the oxidation product of which combines with the coupler. If the color developer is added to the emulsion layer it should be of such character that it does not compete with the tanning developer, e. g., the developing rate should be less. It is also apparent that the color developer or coupler used or both should be relatively nondiffusing in the alkaline bath used for development, in order that they remain in the colloid layer to participate in the transfer process.

The various materials used as above for increasing the optical density of image i4, previous to the transfer operation may have been coated onto the receiving surface i3. Thus, when image 14 contacts a sulfided or thiourea-treated surface the silver halide reacts therewith. Alkali required to promote development of a developercontaining emulsion may be coated on support [3 prior to the transfer. When the exposed element contacts the surface in the presence of moisture tanning development occurs and the tanned emulsion may be stripped from support l3 leaving untanned image. In addition development may be commenced by treating the exposed element with ammonia solution or fuming the element with ammonia. Stripping of the tanned images from the paper may be facilitated by a surface coating on the paper, for example, citric acid, and tendency toward staining of the prints on ageing can be minimized by pretreating the receiving paper with sulfite, bisulfite or ascorbic acid.

The colloid of the transferred image may be hardened by treatment with alum, chromium salts, etc., if desired.

Our invention is further illustrated by consideration of Fig. 4 of the drawings wherein is shown diagrammatically in cross-sectional view the method of producing prints by our process.

. Qfrom the surfacefby squeegee.

tres .5715 The pa-per 'bas'e Ni -carrying the 'tanned' negative nd untan-n'e'd remulsion area l i 'see Figel) is'shown'as' supported by the 1evel-'siirface "-20. *In order to make a print from im'ages 16" there- ".ceiving sheet l3is rolled down by roller 19 ontdarkened image *(see Fig;3)." It' -isapparent fthatif desired, the flreceiving' sheet can-be aflixed ""to surface20 iand the processed element rolled iddwn'onto the sheet' in a similarfmanner. -'-=F'ur- "'ther, images H5 can be difierent-subject-imagesas 1 would be'present on a rollioi exposed film wh'ich is to be processed gin a continuous 'processing apparatus.

The following specific examplesfare given? as illustrative of means of carrying out'ouriinventio'n butare'to be'consi'dered as in'noway limiting If the scope of our application aSL'dGfiIIGd 'in' the "appendedclaims.

. :Examplei A TA'nemulsion' suitable for use in"ourprocessican' .be' made by preparing solutions "of (P0125 grams 'ofgelatin in 1' liter ofwater at40C.,"(B) 100 ;grarns silver nitrate in 500' ccwater"at"'20 C. and

(C)' l35 grams of sodium chloride in 500 ccfiof ,wa,ter.,Solutions B and Oare'simultaneously run 1.}intosolutionA at ajuniform rate while stirring lithe latter over a period of about IOiminutes; solujt'ioxi 3 preferably not being allowed, to runj'in faster; than 'C. "Thereafter;150 grams of gelatin in 1500. cc..'of water at 40C. are added. ThefpH of the emulsion may thenfbe adjusted'to 5.0. If

Ythe emulsion is to contain a developing'agentit added, for example, as iollowsf'25 grams of 3,4-dihydroXy diphenyl are dissolved,in"250"cc.'iof

. methylalc'ohol. Y This solution is slowly added to l the above emulsion with stirring and as a result the developingagent'becomes dispersed in..the emulsion in minute .crystals. .'.Preparatory to -.coating .an emulsion layer 2 cc. of. 10% .formalde-.

Hhyde' maybe added andthis composition is-c'oated' :onasupport as papercontaining.notagenttending -;to. further. harden the, emulsion After; drying,

Ltheproductis.readyflforuse. I If the. emulsion is --peraturebdryness of-the'squeegeed surface gelatin -softness,-"etc.)- duplicate "images maybe inade by "rewettir'ig the negative with thedev'eloper solution 4 for a few seconds;-'againsqueegeeing and tra-nsit' is Uri-desirable. t0. incorporate the .deVlODer the emulsion; the exposed" sheet may be placed in a I1 hydr'oquinone solutioniiKadueous) fjfor about 1 minute .prior to development.-

the .sofdium carbonate solution. jlUnder. suchlc'onditions it maybe -nece'ssary,.'dependinguporith develop- ,7 a t} d,, .t rnodifyl' th'e' .developingbath slightly -to.-obtain{ optimum result, .i'roeexampie, when hydroquinoneisused as a developing'agent,

.a small amount, of sodiumIsu1phite".l(apprdxi- .mately 0.2 to 0.3%); .a-dded to the s'cidiumca'rbonate gives more desirable results.

While in the preferred embodiment-ofrourinvention We use a pigment in the emulsion layer to make the stratum of transferred image more 'visiblewe may instead, if so desired, addtothe emulsion layer at least one of the well known coupling components of diazo compounds. After exposure, coupling occurs under influence of=alka1i in the subsequently applied developing solution. This dye then is transferred with-theun'tanned image. aspreviously described.

If one diazo' component is""in"-*thei emulsion layer, the other may "becarried by the sheet receiving the'transferred untanned 'image and by .virtue of .alkalipresent, couplingwill "takepla'ce to form a dye image which wilbrerhain in-the transferred area.

' When it is desired to make-anappreciable'num, her of reproductions from the element "of 'Fig; 1, wecan make several "good prints 'ofgelatinfiand pigment asishown in Fig; 2 following which "the negative image left'o'n" supportlil is treated-with a reducing agent such as sodium sulfite','and this is'squeegeed into contact with a support carrying a layer of dyebleachable with sulfite, such'as Malachite Green'Dye. A direct'positive image of the'original subjectiindyethus=resu1ts. Also We may roll 'a suitable" ink or pigment into the matrix, remaining afterthe soft emulsion-has been removed from the element of Figt'l-and transfer it in aimanner similar to. that usedwhen 1 transferring. the unharden'ed' emulsion.

to contain .no l'developingiagent, I it is coatedae.

above butthe developing agentisiomitted.

Example 2 The-methodof using an emulsion madeas above and contai ing a developing agent is ,as

"The emulsion" layer" we .use' in "our process-can Q be. of the well-known. variety of sensitive silver salt compositions, such "as silver halidedispe'rs'ed in a colloid vehicle such as gelatin or aresinias I polyvinyl alcohol or polyacrylamide, capable'of beingv differentially tanned as above" mentioned.

' The concentration of"developingflagent'inthe .Qfollows: I'hephGfi ial hic emulsion is expose '60' emulsion. is dependent in part upohthefresult desired but can be of the order'of BSQ'grams of -}by.-contactor projection, face to face. with the -subject. Q'The exposed sheet isfplaced in a- 3% NazCO3 bath for about '15 seconds. during which Eti-mealnegatiVe image is developed in. tanned .gelatin. The excess alkaline solution is removed A1 sheet'of bond paper isr'o'lled into' contact with the photographic copy andimmediately removed. .On removal a .portion. .of. the unhardened emulsionv will 'have 7 ..been' transferred to the bond paper. If itis' mashed. to light of exposing intensity, it will de- -.velop toapo's'itivef image. This. development is I..acceleratedbyheat. 'Since. only apart of 'the untanned emulsion is used during the first'-trans "Ter lthe amount" controlled by pressure, tem- .tanning developing agent per kg. of silvernitrate, converted ,to silver halide, "used in "making"the emulsion, .toj obtainfgood "density." or about *2'50 grams per kg. 'ofsilver'nitrateto obtain adequate density and anemulsion'having ,optimumkeepsolution. per pound for." a sample agedmhree to "sixdn'dfiths. By Substantially lInhafdEnd" as used here, and in the appended claims, it is to be understood that this means a hardness of the order obtained with gelatin treated with formaldehyde under the conditions above. Emulsion layers appreciably harder will not transfer satisfactorily. Similarly, if after development of the tanned image it is found that the layer is too hard, and to accommodate variations in hardness and tanning encountered, we can use variations of temperature or pressure when making a transfer. To this end we ordinarily apply pressure or temperature or both whenrolling the developed emulsion down onto the receiving support. With an emulsion which transfers slowly with heat or pressure applied, we can, without use of increased heat or pressure during transfer, make the transfer by treatment of the developed emulsion with solutions having a softening effect upon the colloid vehicle. With a gelatin emulsion the treating solution can contain, for example in addition to alkali, the following compounds in the amounts indicated based on weight of an alkaline developing solution:

Per cent Formamide 2-20 Ethylene chlorohydrin 5-20 Urea 2-20 Sodium nitrate 5-20 Glycerol -20 One feature and advantage of our process which is important, lies in the fact that the images prepared as above are non-smudging in contrast to ordinary printed images.

Our process is adaptable to making prints by mean-s of stencils. We merely coat the emulsion layer on a porous support as cloth, silk or highly porous paper and, after exposure and tannin development, transfer the unhardened image away from the support in one or more transfers as strata until the support becomes pervious to a printing ink in the unhardened area. Prints are then made from the resulting stencil in the usual manner using a low viscosity ink with the result that a large number of positive prints can be made.

In the preferred embodiment of our invention we transfer, at any one time, only a thin stratum of the unhardened and unexposed area of the emulsion to the absorbtive receiving support. However, if we so desire, we can transfer substantially all of the Luihardened gelatin; in one operation. This may be efiected by selection or preparation of an emulsion layer of suitable softness or thickness or both, by selection of a suitable temperature or application of suitable pressure during transfer, or a combination of these factors.

It is apparent that our process provides a quick means of making stable negatives; after transfer of the sensitive unexposed emulsion from the positive regions there remains a negative which contains little or no chemicals likely to deteriorate the image on keeping. In the usual processes of photography, unexposed silver halide must be fixed-out and the negative washed by wellknown methods to insure preservation.

The advantges of our process are now appar ent. We employ in the simplest modification, only an exposure step, a development step and a transfer step, or development and transfer may be combined. No subsequent or intermediary washing steps are required in contrast to most photographic processes. Further, our proces is a direct-positive process.

By the term "pigment" as used herein and in terials of nature such that they impart optical density to the copy.

The invention having been described, we would have it understoodthat the disclosure herein is by way of example, and included in the invention are all modifications and equivalents falling within the scope of the appended claims.

What we claim is:

1. A method of photographic reproduction which comprises forming by exposure to a twotone subject and development in a light-sensitive substantially unhardened organic colloidsilver halide emulsion layer, a hardened colloid image and leaving substantially unhardened colloid in the remaining area of said layer, said unhardened layer being not harder than a gelatin layer containing 0.7 gram of formaldehyde per pound of gelatin freshly coated, removing excess Water from the surface of said emulsion layer, pressing a sheet having an absorbent surface against said emulsion layer while said 'emulsion is moist and its surface free of greasy material, to cause only said unhardened colloid portion of said layer to adhere to said sheet, and separating said sheet and said emulsion layer to transfer only a stratum of the unhardened colloid portion of said layer to said sheet.

2. A method of photographic reproduction which comprises forming by exposure to a twotone subject and development in a light-sensitive substantially unhardened organic colloidsilver halide emulsion layer, in the presence of a tanning developing agent, a hardened colloid image and leaving substantially unhardened colloid in the remaining area of said layer, said unhardened layer being not harder than a gelatin layer containing 0.7 gram of formaldehyde per pound of gelatin freshly coated, removing excess water from the surface of said smulsion layer, pressing a sheet having an absorbent surface against said emulsion layer While said emulsion is moist and its surface free of greasy material, to cause only said unhardened colloid portion of said layer to adhere to said sheet, and separating said sheet and said emulsion layer to transfer only a stratum of the unhardened colloid portion of said layer to said sheet.

3. A method of photographic reproduction which comprises forming by exposure to a twotone subject and development in a light-sensitive substantially unhardened organic colloidsilver halide emulsion layer containing a tanning developing agent, a hardened colloid'image and leaving substantially unhardened colloid in the remaining area of said layer, said unhardened layer being not harder than a gelatin layer containing 0.7 gram of formaldehyde per pound of gelatin freshly coated, removing excess water from the surface of said emulsion layer, pressing a sheet having an absorbent surface against said emulsion layer while said emulsion is moist and its surface free of greasy material, to cause only said unhardened colloid portion of said layer to adhere to said sheet, and separating said sheet and said emulsion layer to transfer only a stratum of the unhardened colloid portion of said layer to said sheet.

4. A method of photographic reproduction which comprises forming by exposure to a twotone subject and development in a light-sensitive substantially unhardened organic colloidsilver halide emulsion layer containing a tanning developing agent of the class consisting of 3.4-

tumof-the unhardened colloidportion ofi said layerto .said sheet.

5. A method of photographic reproduction which comprises forming by exposure .to a two- -tone subject and development in alight-sensitive substantially unhardened organic colloidsilver halide emulsion layer containing a tanning developing agent havinga solubility ina phosphate-citrio acid buffer of pH 5.0, of from .005 to 1.0 gram per 100 cc. of said buffer, a hardened colloid image and leaving substantially unhardened colloid in the remaining area of said layer, said unhardened layer being not harder than a gelatin layer containing 0.7 gram of formaldehyde. per pound of gelatin freshly coated, re-

moving excess water from the surface of. said emulsion layer, pressing a sheet having an absorbent surface against said emulsion layer while said emulsion is moist andits surface, free of greasy material, to cause only said unhardened colloid portion of said layer to adhere to said sheet, and separating said sheet and said emulsion layer to transfer only a stratum of the unhardened colloid portion of said layer to.,said sheet.

6. A method of photographic reproduction which comp-rises forming by exposure to a two,- tone subject and development in a light-sensi tive substantially unhardened organic. colloidsilver halide emulsion layer containing a tanning developing agent having a solubility in a phosphate-citric acid buffer solution of pH 5.0, of from .005 to 1.0 gram per 100 cc. of said buffer and said emulsion containing finely divided pigment particles, a hardened colloid image and leaving substantially unhardened colloid in the remaining area of. said layer, said unhardened layer being not harder than a gelatin layer containing 0.7 gram of formaldehyde per pound of gelatin freshly coated, removing excess water from the surface of said emulsion layer, pressing a sheet-having an absorbent surface againstsaid emulsion layer while said emulsion is moist and its surface free of greasy material, to cause only said unhardened colloid portion of said layer to adhere, to said sheet, and separating saidsheet and said emulsion layerto transfer only a stratum of the unhardened colloid portion of said layer to said sheet.

7. A method of photographic reproduction which comp-rises forming by exposure to a twotone subject and development in a light-sensitive substantially unhardened organic colloidsilver halide emulsion layer containing a' tanning developing agent having' a solubility in. a phosphate-citric acid buffer solution of pH 5.0, of from .005 to 1.0 gram per 100 cc. of said buffer and said emulsion containing finely divided pigment particles, a hardened colloid image and leaving substantially unhardened colloid in the remaining area of said layer, said unhardened layer being not harder than a gelatin layer containing 0.7 gram of formaldehyde per pound of gelatin. freshly coated, removing excess water from the surface of said emulsion layer, pressing a sheet having an absorbent surface against said emulsion layer while said emulsion is moist and its surface free of greasy material,to causeonly said unhardened" colloid portion of said layer to adhere to said sheet, and separating said sheet and said emulsion layer to transfer onlya stratum of the unhardened colloid portion of said layer to said sheet and treating said transferred stratum :so' as to increase its opticaldensity.

' 8. .A method of photographic reproduction which; comp-rises forming by exposure to a= -twotone subject and developmentin a light sensitive substantially unhardened organic colloidsilver halide emulsion layer containing a tanning developing .agenthaving' a'solubility in a phos phate-fcitrida-cid buffer solutionof pH"5-.0,"-of from .005to 1.0; gram per '100- cc-.-of saidbilifer and containing finely divided pigment-particles, a hardened colloid image andleaving substantially unhardened colloid-in the remainingarea of said layer, said unhardened layer being not harder than a gelatinlayer containing 0.7; gram .of formaldehyde per pound of gelatin freshly coated, removing excess water from the surface of said emulsion layer, pressing a sheet having an absorbent surface against said emulsion layer while said emulsion is moistand its surface free of greasy material, to cause only said unhardened colloid portion of said layer to adhere to saidsheet; and separating said sheetv and said emulsion layer to transfer only a stratum of the unhardened colloid portion of said layer'to said sheet; said absorbent sheet carrying an agent which reacts with .said transferred straturn' to o m a ar imae 9. .A nethod of photographic reproduction which comprisesforming byexposure to a twotone jsubject and development in alight-sensitive substantially unhardened gelatino-silver halide emulsionlayerin the presence of a tanning developing agent, a" hardened colloid image and leaving substantially unhardened colloid in the remaining area of said layer, said unhardened layer being not harder than a, gelatin layer containing 0.7 gram of formaldehyde per, pound of g'elatin freshly coated, removing excess water from'the surface of said emulsioniayer, pressing a sheet having an absorbent surface against said emulsion; layer while said emulsion is moist and its surfacefree of greasy material, to cause only said unhardened colloid portion of said layer to adhere to said'sheet, and separating said sheet and said emulsion layer to transfer only a stratum of the unhardened colloid portion of said layer'to said sheet.

10. A method of photographic reproduction which com'prisesforming by exposure to a twotone subject and development in Y a light-sensitive substantially unhardened gelatinoesilver halide emulsionlayer containing a tanning. developing agent having a solubility' in a phosphate-citric acid buffer ofpH 5.0,:offil0m ;005 to.1.0 gramper cc. of said buffer, a hardened colloid image and'leaving substantially unhardened'colloid' in the remaining area of said layer, said unhardened layer being not harder thana gelatin layer containing 0.7 gram of formaldehyde per pound of gelatin freshly coated, removing excess water from the surface of said emulsion layer, pressing a sheet having an absorbent surface against said emulsion layer while said emulsion is moist and its surface free of greasy material, to cause only said unhardened colloid which comprises forming by exposure to a twotone subject and development in a light-sensitive substantially unhardened gelatino-silver halide emulsion layer containing a tanning developing agent having a solubility in a phosphate-citric acid bufier of pH 5.0, of from .005 to 1.0 gram per 100 cc. of said buffer, a hardened colloid image and leaving substantially unhardened colloid in the remaining area of said layer, said unhardened layer being not harder than a gelatin layer containing 0.7 gram of formaldehyde per pound of gelatin freshly coated, removing excess water from the surface of said emulsion layer, pressing a sheet having an absorbent surface against said emulsion layer while said emulsion is moist and its surface free of greasy material, to cause only said unhardened colloid portion of said layer to adhere to said sheet, and separating said sheet and said emulsion layer to transfer only a stratum of the unhardened colloid portion of said layer to said sheet, and moistening the residue of said emulsion layer and transferring another stratum of said unhardened colloid portion to an absorbent sheet.

12. A method of photographic reproduction which comprises forming by exposure to a twotone subject and development in a light-sensitive substantially unhardened organic colloidsilver halide emulsion layer coated on a porous support, in the presence of a tanning developing agent, a hardened colloid image and leaving substantially unhardened colloid inthe remaining area of said layer, said unhardened layer being not harder than a gelatin layer containing 0.7 gram of formaldehyde per pound of gelatin freshly coated, removing excess water from the surface of said emulsion layer, pressing a sheet having an absorbent surface against said emulsion layer while said emulsion is moist and its surface free of greasy material, to cause only said unhardened colloid portion of said layer to adhere to said sheet, and separating said sheet and said emulsion layer to transfer only a stratum of the unhardened colloid portion of said layer to said sheet.

13. A method of photographic reproduction which comprises forming by exposure to a twotone subject and development in a light-sensitive substantially unhardened organic colloidsilver halide emulsion layer coated on a porous support, in the presence of a tanning developing agent, a hardened colloid image and leaving substantially unhardened colloid in the remaining area of said layer, said unhardened layer being not harder than a gelatin layer containing 0.7 gram of formaldehyde per pound of gelatin freshly coated, removing excess water from the surface of said emulsion layer, pressing a sheet having an absorbent surface against said emulsion layer while said emulsion is moist and its surface free of greasy material, and stripping off a stencil having porous areas corresponding to the unhardened colloid portions of said emulsion layer.

14. A method of photographic reproduction which comprises developing a hardened gelatin image in a substantially unhardened gelatinosilver halide emulsion layer containing a tanning developing agent, and leaving substantially unhardened gelatin in the remaining area of said layer, said unhardened layer being not harder than a gelatin layer containing 0.7 gram of formaldehyde per pound of gelatin freshly coated, removing excess water from the surface of said emulsion layer, pressing a sheet having an absorbent surface against said emulsion layer, while said emulsion is moist and its surface free of greasy material, to cause only said unhardened gelatin to adhere to said sheet, separating said sheet and emulsion .layer to transfer only a stratum of the unhardened gelatin of said layer to said sheet, and thereafter exposing and heating the transferred stratum'in the presence of moisture to increase its optical density.

15. A method of photographic reproduction which comprises exposing to a two-tone subject a substantially unhardened gelatino-silver halide emulsion layer containing a gelatin tanning silver halide devolping agent, said emulsion layer being not harder than a gelatin layer containing 0.7 gram of formaldehyde per pound of gelatin freshly coated, developing the exposed emulsion layer with an alkaline solution to obtain a hardened gelatin and silver, image in the region of exposure and substantially unhardened gelatin and silver halide in the unexposed region of the emulsion layer, pressing a sheet having an absorbent surface against said emulsion layer while said emulsion layer is moist to cause only said unexposed regions to adhere to said sheet and separating said sheet and emulsion layer to transfer only a stratum of the unexposed region to the sheet, said exposed emulsion layer having been treated subsequent to exposure and prior to transfer of said stratum, to increase the optical density of the unexposed portions of the emulsion layer.

HENRY C. YUTZY. EDWARD C. YACKEL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date Re. 20,694 Miller Apr. 12, 1938 116,720 Laemmel July 4, 1871 663,539 Giesecke Dec. 11, 1900 1,118,479 Dodge Nov. 24, 1914 1,567,333 Scharschawsky Dec. 29, 1925 1,709,569 Gorsky Apr. 16, 1929 1,793,070 Eldridge Feb. 17, 1931 1,812,981 Gorsky July 7, 1931 1,944,123 Fleishmann et a1. Jan. 16, 1934 2,367,939 Gregory Jan. 23, 1945 FOREIGN PATENTS Number Country Date 168,578 Great Britain June 1, 1922 231,413 Great Britain Apr. 30, 1925 324,330 Great Britain Jan. 13, 1930 581,479 Great Britain Oct. 14, 1946

Claims

1. A METHOD OF PHOTOGRAPHIC REPRODUCTION WHICH COMPRISES FORMING BY EXPOSURE TO A TWOTONE SUBJECT AND DEVELOPMENT IN A LIGHT-SENSITIVE SUBSTANTIALLY UNHARDENED ORGANIC COLLOIDSILVER HALIDE EMULSION LAYER, A HARDENED COLLOID IMAGE AND LEAVING SUBSTANTIALLY UNHARDENED COLLOID IN THE REMAINING AREA OF SAID LAYER, SAID UNHARDENED LAYER BEING NOT HARDER THAN A GELATIN LAYER CONTAINING 0.7 GRAM OF FORMALDEHYDE PER POUND OF GELATIN FRESHLY COATED, REMOVING EXCESS WATER FROM THE SURFACE OF SAID EMULSION LAYER, PRESSING A SHEET HAVING AN ABSORBENT SURFACE AGAINST SAID EMULSION LAYER WHILE SAID EMULSION IS MOIST AND ITS SURFACE FREE OF GREASY MATERIAL, TO CAUSE ONLY SAID UNHARDENED COLLOID PORTION OF SAID LAYER TO ADHERE TO SAID SHEET, AND SEPARATING SAID SHEET AND SAID EMULSION LAYER TO TRANSFER ONLY A STRATUM OF THE UNHARDENED COLLOID PORTION OF SAID LAYER TO SAID SHEET.