US2614927A

US2614927A - Rapid processing of photographic materials

Info

Publication number: US2614927A
Application number: US96627A
Authority: US
Inventors: Broughton Geoffrey; Robert N Woodward
Original assignee: Eastman Kodak Co
Current assignee: Eastman Kodak Co
Priority date: 1949-06-01
Filing date: 1949-06-01
Publication date: 1952-10-21
Anticipated expiration: 1969-10-21
Also published as: FR1062403A; GB693632A

Description

Patented Oct. 21, 1952 UNITED;

P .RAPID PROCESSING OF PHOTOGRAPHIC' 5 MATERIALS g Geoffrey Broughton and Robert N. Woodward,

Rochester, N. Y, assignors to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey Nb Drawing. Application June 1,1949,

l Serial No.96,627 l This invention relates to "photography and particularly to the rapid processing of photo-' graphic materials.

Photographic. processing of the customary silver halide emulsions after exposure, includesthe essential steps of development',,fi xing, washing and drying. Optional, steps such as reduction,

toning,,etc., may. be included but are notessentialto the formationof a photographic image. These essential steps. consume an appreciable amount of time, andin many cases the time required for completion of each step cannot be.

shortened without lessening the quality of the finalpicture. For examplafit is well known that incomplete washing. offsilver images to remove hypo causes the images to eventuallyffade on aging. gt

.A rapid processing.method capable of pro ducing stablephotographic prints of high quality would be a desirable improyement' over the customary processing methods. It is therefore the principal object of the present invention to provide a rapid method forprocess'ing silver halide emulsions. Other objects. will; appear. from the following description of our intention. ,Ihesel objects are accomplished by the technique described below, an essential feature of.

which is the treatment of the developed image withta stabilizingagent which avoids the necessity of washing.

. According to our invention, a silver halide emulsion, preferably. a gelatino-silve'rhalide emulsion, 'containingfa developing agent is 3 exposed in the usual manner andis then devel-' oped by treatment; with an alkalinefsolution. If

7 Claims. (Cl. 95-6) the emulsion is coatedona papercr otherj'porous; support, it is desirable to wipe the-surface, of,

thecmulsion with a sponge, a rubber roll," or; other applicator wet with the alkaline solution so that the paper support is notsoaked with developing solution. Another methodpf applying the solution includes pressing the exposed layer' against a pad moistened withthe alkaline. solu: 1

tion, as willgbe described hereinafter. t p

Stabilizing agents which we may employ are compounds containing double-bonded sulfur or, an SH linkage; for example, alkali metal and ammonium thiocyanates, thioureas and thioglycollic acid as well as. alkali 'metalfand ammonium thiosulfates. These {agents are gen: erally used in lower concentration than they would be in normal fixing procedure where the emulsion is washed after fixing.

Specific'stabilizing agents which we may. use, together with the useful concentrations in aque-f,

ous solution are as follows:

. g g a T t "liericent Potassium thiocyanate a -310 Ammonium thiocyanate 5 Sodium thiosulfate i 10 p of water. SolutionsB'and C are simultaneously;

run into solution A at a uniform rate whil'e'stir- .ring the latter over a period of about 10 min utes; solution Bpreferably not being allowed to Ethylene thiourea Propylene thio urea' Thi'oglycolli'c acid (Na salt) ;ji These concentrations arevbased; on atreat ment or immersionwtime of about 30 seconds.

Lower concentrations might be used with 1 lon er application or immersion times. The upper lime it of concentration is defined :byfthe;solubilitygofl the reagent and the general tendency towards crystallization in the photographic materialwhen very high concentrations are used. v

The time of treatment will vary with the nature: of the film (that is the grain size and chemical; composition) the temperature of treatment and themanner of application of the stabilizing solution. The time necessary for the application of a given stabilizing solution may be readily judged by inspection of the emulsion layer. lLItlisnecessary that thesilver halide shall have disap-. peared fromjth'e emulsion and thegdisappearance of the halide,yvhichlindicatesv the formation of: l a stable complex withlthe stabilizing compoundmay be determined by inspection of the emulsion;

layer. 1, When the silverthalide. has Just disappeared from the emulsion, stabilization. is com-,;

plete. r a

The thiosulfatesandithioureas are jused in acid solution, the thioglycollic acid in alkaline solution, and the thiocyanates in either acid or alkaline solution. The following examplesfare illustrative:

Examplel An emulsion suitable for use in our invention is made asfollows: Solutions aremade of (A) 25 gramsof gelatin'i-nl'literwater at. 4050. (B) f gramsfjsilver nitrate in 5(l0 cc. water at 20C.

and (0]) 35 rams of sqdiumchloride in soc-cc;

run in faster than C. i Thereafter, grams of gelatin in 1500 cc. of water at 40 C. areadded.

25 grams of 3,4-dihydroxy 'diphenyl are then uissolved in 250 cc.-o f methylalcohol. This S'1u-' tion is slowly added to the aboveemulsionwith. stirring and as a result the developing agent b ecomes dispersed in.the emulsion in. minute cryssparatory. to coating an emulsionfllay'er, l formaldehyde or. other gelatin hardening agen may be added to the emulsion and the emulsion is coated on a paper supportfover .anfarealof about 500 square 'feet. The .driedproductjisj then exposed in any of I a numberiof ways {to subject; for examplalto a negative by; contact;

or projection or if thesubject is printed matter on a paper base, the exposure may be made by means of reflex printing methods or in any other tory tocoating the emulsion, formaldehyde may be added as a hardener and the emulsion is coated on a paper support over an area of about '300 square feet. The product is then exposed, developed and stabilized as described in Example 1 and the prints dried without washing. The resulting image was stable and no discolorationsof the emulsion layer appeared when the prints were incubated or exposed to ultra-violet light for moderate periods of time. i

The advantages of our process will now be apparent. One of the chief advantages lies in Grams Sodium carbonate 50 Sodium hydroxide 5 Sodium thiosulfate (crystalline) 2 Potassium bromide 816 Water to 1 liter.

Both the thiosulfate and bromide in the above formulatend to prevent fog ondevelopment of the exposed element. While the alkalinesolution can be applied with a sponge, a preferred method includes pressing the exposed layer against the surface of a pad or cloth, paper, felt, sponge rubber, or a water-permeable hydrophilic colloid layer such as gelatin, gum arabic or polyvinyl alcohol moistened with the alkaline solution. A polyvinyl alcohol pad can be prepared bycoating a paper support with an aqueous solution of polyvinyl alcohol containing a melamine-formaldehyde condensation product as a hardening agent. A typical coating composition is the following: 7

Polyvinyl alcohol ;c.. grams 237 Water cc 2300 Melamine-forma1dehydev solution cc 1% pH -Q. 4

The melamine-formaldehyde solution .in the above formulaiis prepared'by reacting 25 cc. of per cent formaldehyde at pH of 7 with six grams melamine and 100 cc. of water alt-.80 C., cooling to 40 C.,'adding 100 cc. of water and adjusting the pH to -'7. After the hardening solution has been added to the aqueous polyvinyl alcohol solution, the pH is adjusted to-e to improve hardening.

The exposed and developed but unfixed element is then'trea-ted for about 30-60 seconds with a solution of a stabilizing agent for our inventioniof which the following is-typical: i

. Grams Sodium sulfite 15 Sodium bisulfite 45 Sodium thiosulfate 150 Water to 1 liter.

As in the above development step, this stabilizationtreatmentmay be accomplished by swabbing or preferably rolling the developedelement down-onto a pad moistened with the stabilizing solution. Since, they stabilization stepconverts a1l residual silver halide to' the inactive, state,'the element need now be only dried without further treatment to provide a stable print.

' Example .2

Another faster emulsion suitable for use in our invention is made from the following solutions:

(A1 grams gelatin in 1 liter water at 40 'C.;-

(B) 100 grams silver nitrate dissolved in 500 cc. water at 20 C.; (C) 72 grams potassium bromide in 500 cc; water at 20 C. Solutions Band C are simultaneously run into solution A with stirring and afterwards a solution of 200 grams gelatin in Z'liters water at 40 C. is added. A suitable the fact that the usual developing solution containing developing agent is dispensed with. As is well known, the usual developing solutions have a very short life partly because the developing agent therein readily oxidized in the presence of air even when restrainers are incorporated in the developer; Therefore, the worker-must continually change developing solutions. Since we incorporate the developing agentinto the, emulsion layer, there is no need to use a developing agent in the alkaline treating solution although this can be done if desired. Also, with the elimination of the usual washing step, the total processing time for a print has been decreased from an hour or more to a matter'of two to three minutes, yet the images obtained are relatively stable and show little discoloration on exposure to ultraviolet light or aging under adverse conditions; for example, as long as nine days at F. and 98 per cent relative humidity. Also the prints thus stabilized are more permanent than similar prints which have been processed by normal techniques and partially washed.

The developing agents may be incorporated into emulsions of types other than shown in the above examples; for example, the v well-known direct positive type of emulsion, particularly those disclosed in the Kendall et al. U. S. Patent applicationSer. No. 35,987, filed June 29, 1948, now Patent No. 2,541,472, issued February 13, 1951, may contain the developing agent in the amounts indicated herein and'be processed in a manner similar to that described in the above examples. The result, of course, is to obtain a direct-positive stabilized image from the original copy and the print has the stability indicated above.

The concentration of developing agent in theabOVe emulsions is dependent in part onthe re sult desired but can be of the order of 350 gramsper kg. of silver nitrate, converted to'silverhalide;- used in making the emulsion, to obtain good- 1 density or about 250 grams per kg. of silver nitrate to obtain adequate density and an emulsion having optimum keeping properties.

As mentioned, our emulsions are preferably, However, we; are not limited thereto since other watergelatino-silver halide emulsions.

permeable organic colloid vehicles may-beused for dispersing the silver salt and developing: agent, e. g., polyvinyl alcohol, partially hydrolyzed polyvinyl esters and cellulose esters, etc.

The developing agents useful in emulsions processed according to our invention include-,for example, 3,4-dihydroxy diphenyl; 2,5-dihydroxy 2,3-dihydroxydiphenyl and 5.6.18 These develphate-citric acid bufier solution'of pH 5.0 prepared from a 1.5 per cent-solution of" sodium v dihydrogen phosphate and-suffi'cientcitric acid to bring the pH to 5.0. The three first-mentioned developing agents have solubilities within the range of from about .01 to 0.1 gram perhundred cc. of the buffer solution and are thus preferred. The developing agents are classified as above in terms of their solubility in a buffer solution because this approximates the solubility behavior of the preferred compounds, particularly when used in emulsion layers in our process. Other more soluble developing agents, for example, hydroquinone, pyrocatechol, and p-methylaminophenol sulfate, may be used in the emulsion layer but are less preferred partly because of their diffusion characteristics in emulsion layers which allow them to transfer to pads used in the processing operations and further because they more readily oxidize and tend to,

stain the print.

The stabilizing agents mentioned may be used as in the above examples in aqueous solution but it is preferable to make the stabilization bath acid to counteract alkali present in the developing solution. The alkali of the developing solution is not especially critical since carbonate, caustic alkali and borates all give useful results, although, as is apparent, strong alkali is preferred in the alkaline treating solution since it will increase the speed of development of emulsion layers containing weak developing agents such as the dihydroxy diphenyl compounds.

A precaution to be taken particularly if the pad method of processing is used, is to use wellhardened emulsions to prevent the emulsion from adhering to the surface of the pad. In case the emulsion has not been hardened sufficiently prior to processing, this can be done with a formaldehyde hardening bath before or after the development step or in any other suitable way.

Although the emulsion may be immersed in the alkaline and stabilizing solutions, we prefer merely to moisten the surface of the exposed emulsion with these solutions except in the case of films and plates. Thus in the case of paper supports, the support does not become wet and the drying time is greatly reduced.

It will be apparent from the foregoing description of our invention that a substantial proportion of the silver compounds remains in the emulsion after the stabilizing treatment. This differs from the customary fixing and washing in which the intent is to remove the residual silver halide from the emulsion.

It will be understood that the examples and modifications described herein are illustrative only and that our invention is to be taken as limited only by the scope of the appended claims.

We claim: l

1. A rapid process for the formation of an image in a photographic emulsion layer which comprises exposing a silver halide emulsion layer containing a developing agent selected from the group consisting of 3,4-dihydroxy diphenyl; 2,5-dihydroxy diphenyl; and 2,3-dihydroxy diphenyl, developing a silver image in said exposed layer by treatment with an alkaline solution, and immediately thereafter stabilizing said layer with a solution of a compound selected from the group consisting of alkali metal and ammonium thiccyanates and thiosulfates, thioureas and mmglycollic acid, and drying said layer without further treatment.

2. A rapid process for the formation of an image in a photographic emulsion layer which comprises exposing a silver halide emulsion layer containing a silver halide developing agent selected from the group consisting of 3,4-dihydroxy diphenyl; 2,5-dihydroxy diphenyl; and 2,3-dihydroxy diphenyl, developing a silver image in said exposed layer by treatment with an alkaline solution, and immediately thereafter stabilizing said layer with a solution of an alkali metal thiosulfate, and drying said layer without further treatment.

3. A rapid process for the formation of an image in a photographic emulsion layer which comprises exposing a silver halide emulsion layer containing a silver halide developing agent selected from the group consisting of 3,4-dihydroxy diphenyl; 2,5-dihydroxy diphenyl; and 2,3-dihydroxy diphenyl, developing a silver image in said exposed layer by treatment with an alkaline solution, and immediately thereafter stabilizing said layer with a solution of an alkali metal thiocyanate, and drying said layer without further treatment.

4. A rapid process for the formation of an image in a photographic emulsion layer which comprises exposing a silver halide emulsion layer containing a silver halide developing agent selected from the group consisting of 3,4-dihydroxy diphenyl; 2,5-dihydroxy diphenyl; and 2,3-dihydroxy diphenyl, developing a silver image in said exposed layer by treatment with an alkaline solution, and immediately thereafter stabilizing said layer with a solution of a thiourea, and drying said layer without further treatment.

5. The process of claim 1 wherein the silver halide emulsion is a direct-positive emulsion.

6. The process of claim 2 wherein the emulsion is a direct-positive emulsion.

7. A light sensitive photographic element comprising a support having thereon a direct-positive silver halide emulsion layer containing a substantially water-insoluble silver halide developing agent selected from the group consisting of 3,4-dihydroxy diphenyl; 2,5-dihydroxy diphenyl; and 2,3-dihydroxy diphenyl.

GEOFFREY BROUGHTON. ROBERT N. WOODWARD.

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

UNITED STATES PATENTS Number Name Date 742,405 Eichengrun Oct. 27, 1903 1,582,050 Johnson Apr. 27, 1926 2,005,837 Arens June 25, 1935 2,090,484 Ostromeslinsky Aug. 17, 1937 2,126,516 Szasz Aug. 9, 1938 2,214,446 Albers Sept. 10, 1940 2,397,924 Crabtree et al. Apr. 9, 1946 2,409,107 Crabtree et al. Oct. 8, 1946 2,412,674 Crabtree et al. Dec. 17, 1946 2,448,857 Brice Sept. 7, 1948 2,453,346 Russell Nov. 9, 1948 2,541,472 Kendall et al Feb. 13, 195.1

FOREIGN PATENTS Number Country Date 549,956 Great Britain Dec. 16, 1942 OTHER REFERENCES Abstract File No. 594,589, Yackel, filed May 18, 1945, published July 26, 1949 in Official Gazette, Patent Ofiice.

Claims

1. A RAPID PROCESS FOR THE FORMATION OF AN IMASGE IN A PHOTOGRAPHIC EMULSION LAYER WHICH COMPRISES EXPOSING A SILVER HALIDE EMULSION LAYER CONTAINING A DEVELOPING AGENT SELECTED FROM THE GROUP CONSISTING OF 3,4-DIHYDROXY DIPHENYL: 2.5-DIHYDROXY DIPHENYL; AND 2,3-DIHYDROXY DIPHENYL, DEVELOPING A SILVER IMAGE IN SAID EXPOSED LAYER BY TREATMENT WITH AN ALKALINE SOLUTION, AND IMMEDIATELY THEREAFTER STABILIZING SAID LAYER WITH A SOLUTION OF A COMPOUND SELECTED FROM THE GROUP CONSISTING OF ALKALI METAL AND AMMONIUM THIOCYANATES AND THIOSULFATES, THIOSULFATES, THIOUREAS AND THIOGLYCOLLIC ACID, AND DRYING SAID LAYER WITHOUT FURTHER TREATMENT.

7. A LIGHT SENSITIVE PHOTOGRAPHIC ELEMENT COMPRISING A SUPPORT HAVING THEREON A DIRECT-POSITIVE SILVER HALIDE EMULSION LAYER CONTAINING A SUBSTANTIALLY WATER-INSOLUBLE HALIDE DEVELOPING AGENT SELECTED FROM THE GROUP CONSISTING OF 3,4-DIHYDROXY DIPHENYL; 2,5-DIHYDROXY DIPHENYL; AND 2,3-DIHYDROXY DIPHENYL.