US 3617282 A
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United States Patent  Inventors Charleton C. Bard;
Arthur D. Kuh; Richard J. Malloy, all of Rochester, N.Y.
 Appl. No. 38,492 A  Filed May 18, 1970  Patented Nov. 2, 197 1  Assignee Eastman Kodak Company Rochester, N.Y.
Continuation-impart of application SertNo. 803,941, Mar. 3, 1969, now abandoned.
 NUCLEATING AGENTS FOR PHOTOGRAPHIC '51 int. ci eases/5r;  Field of Search 96/22, 59
 References Cited UNITED STATES PATENTS 1,552,791 9/1935 Capstaff 96/59 Primary Examiner-Norman G. Torchin Assistant Examiner-Alfonso T. SuroPico Attorneys-Walter O. Hodsdon and Wendell l-l. McDowell ABSTRACT: Chelated stannous ion silver halide nucleating agents are used in photographic reversal processes. The nucleating agents are useful in reversal developer solutions or in prebaths employed prior to reversal development. The nucleating agents are especially useful for processing multilayer color products where the emulsion layers contain color couplers or for selective reversal processing of multilayer color products where the couplers are present in the color developing solutions.
NUCLEATING AGENTS FOR PHOTOGRAPHIC REVERSAL PROCESSES This application is a continuation-in-part of U.S. Pat. application Ser. No. 803,941 filed Mar. 3, 1969, and now abandoned. This invention relates to an improved method of photographic processing, and more particularly, to the reversal processing of photographic silver halide emulsions.
It is known that in the processing of photographic silver halide emulsions of color films, the exposed emulsions can be subjected to a first(negative) developer which is a conventional black-and-white developer, followed by reversal reexposure and subsequent color development. Certain nucleating agents have been used in a solution applied following the first development step or in the second developer solution in place of the reversal reexposure step, but several disadvantages which limit their utility. For example, the most successful nucleating agents have been the boron compounds such as alkali metal borohydrides or borane, phosphine, arsine and stilbene compounds described in U.S. Pat. Nos. 2,984,567 and 3,246,987. The amine boranes have been especially useful as nucleating agents. However, these nucleating agents are not as stable as is desired. For example, the boranes tend to decompos'e when used in an acid stop solution for nucleation prior to the second development step. This requires the borohydrides and boranes to be packaged in alkaline solution such as a developer solution where they are still subject to decomposition by serial oxidation.
We have discovered that when stannous salt reducing agents for silver halide are chelated and the resultant chelated stannous ions used as nucleating agents in the photographic reversal process, the disadvantages of other nucleating agents are substantially avoided. In particular, when chelated stannous ion is used in the reversal color process, unexpectedly significant improvement in structure of the color image is obtainable. More particularly, the chelated stannous salts have good stability in both acid and alkaline solutions and, therefore, can be packaged for use in acid or alkaline prebaths prior to the second development step, or can be packaged in the second alkaline developer composition.
The literature, such as British Pat. No. 500,796 and U.S. Pat. No. 295,013, vaguely suggests, but does not clearly show, how stannous salts, such as stannous chloride, can be successfully used in reversal processes for nucleation of the silver halide not developed in the first development step. Our investigations show that an acid stannous chloride solution, only at fairly high concentrations, will nucleate silver halide and render it developable by a subsequent alkaline silver halide developer solution. However, the stannous salt gradually undergoes aerial oxidation in the acid solution and the resulting stannic oxide deposits on the emulsions as dirt which, particularly in color processes, seriously reduces the quality of the color reproduction. Also, we have found that nonchelated stannous salt cannot be incorporated in alkaline developer solutions for nucleation and development of silver halide emulsion layers because an insoluble precipitate at once forms and no nucleation occurs. On the other hand, when the chelated stannous salts are used as nucleating agents according to our invention, no insoluble product is formed in either acid or alkaline nucleating solutions and the dirt problem is avoided. ln addition, a substantial improvement in photographicimage structure, such as definition is obtainable.
In preparing the chelated stannous salt nucleating agents for use in photographic reversal processes a polydentate ligand, such as Nitrilo-N,N,N trimethylenephosphonic acid is dissolved in water and stannous salt, such as-stannous chloride, then added. At least stoichiometric proportions, and preferably an excess of about percent of the ligand, are used to .prevent the formation of insoluble stannic compounds in the solution through aerial oxidation or in the subsequent development solution where the chelated stannous ion is oxidized. Sufficient acid, preferably organic acid such as acetic acid, is added to give a strongly acid solution of pH of about 2 to 7 and to provide buffering capacity. Useful buffering cnpuclty in obtained when the chelated stannous salt solution such contains about 0.1 to 5 molar concentration of the acid. The resulting acid solution containing chelated stannous ion can then be employed as a stop bath following the negative development step to nucleate the unexposed silver halide. Thereafter, treatment of the nucleated silver halide image with alkaline developer solution produces the reversal positive image in black and white or color depending on the photographic system under consideration.
When the chelated stannous ion nucleating agents are employed in an alkaline developer composition, a solution of stoichiometric proportions, preferably about l0 percent excess ligand, is prepared and the stannous salt then added. This solution is then added to the developer solution. Alternatively, these proportions of the ligand and stannous salt in solid form are dissolved in that order in the alkaline developer solution. Otherwise, the formation of insoluble tin salt in the solution can be expected.
Water-soluble stannous salts useful in preparing the chelated stannous ion nucleating agents include, e.g. stannous halides such as stannous chloride, bromide and fluoride, and stannous acetate, stannous sulfate, stannous tartrate, etc.
A preferred class of heavy metal chelating agents useful for preparing the chelated stannous ion nucleating agents includes organo phosphorous chelating agents. A useful class of chelating agents includes the aminopolymethylenephosphonic acid chelating agents and their watersoluble salts. These phosphonic acids have the general formula RN(CH PO M,), wherein M represents a hydrogen atom or a cation which imparts water solubility, such as alkali'metal atom (e.g. sodium, potassium, etc., ammonium, Pyridinium, triethanol'ammonium, triethyl ammonium, etc., and R represents an alkyl group, such as methyl, ethyl, propyl, isopropyl, butyl, etc. (e.g. an alkyl group containing from one to four carbon atoms), an aryl group, such as phenyl, omand p-tolyl, oand p-carboxyl-phenyl (and water soluble salts thereof, such as sodium, potassium, etc.), an aralkyl group, such as benzyl-fi-phenethyl, o-acetamidobenzyl, etc. -(.e.;g. an aralkyl group containing from seven to nine carbon atoms), an alicyclic group,-such as cyclohexyl, cyclopentyl, etc. (e.g. an alicyclic group containing from five to six carbon atoms), .ora heterocyclic radical, such as a heterocyclylalkyl group (e.g. pyrrolidylmethyl, pyrrolidylbutyl, benzothiazolymethyl, tetrahydroquinolylmethyl, etc.). The R group can be further substituted (especially where R represents an alkylgroup) with a radical, such as hydroxyl, --PO;M,, --CH,PO M,, or
N(CH,PO where M has the values given above,
chlorine, alkoxyl('e.g. methoxyl, ethoxyl, etc.), etc.
Representative useful compounds having this general formula are the followin g:
.Ethylenediamine-N,N,N',N-tetramethylenephosphonic acid Nitrilo-N,N,N-trimethylenephosphonic acid l,2-cyclohexanediamine-N ,N,N ,N -tetramethylenephosphonic acid o-carboxyanilino-N,N-dimethylenephosphonic acid Propylamino-N,N-dimethylenephosphonic acid Propylamino-N,N-dimethylenephosphonic acid 4-(N-pyrrolidino)butylamine-N,N- bis(methylenephosphonic acid) l,3-diaminopropanol-N,N,N' ,N tetramethylenephosphonic acid l,3-propanediam-ine-N,N,N',N'-tetramethylenephosphonic acid 1,6-hexanediamine-N,N,N',N'-tetramethylenephosphonic acid o-acetamidobenzylamino-N,N-dimethylenephosphonic acid o-toluidine-'N,N-.dimethylenephosphonic acid 2-pyridylamino-N',N'-dimethylenephosphonic acid A second class of organo phosphorous chelating agents have the following general formula RR,C(PO,M,), wherein R represents hydrogen, alkyl, aryl or aralkyl as described above, or PO -,M,; R, represents hydrogen, hydroxyl, alkyl as above or PO M and M represents the values given above.
Representative compounds having this formula are:
l-hydroxyethylidene-l l-diphosphonic acid ethylidene- 1 l l -triphosphonic acid l-hydroxypropylidene-l ,1 -diphosphonic acid l-hydroxy-2-phenylethylidenel l -diphosphonic acid It can be expected that the chelated stannous salts will differ in their ability to nucleate silver halide and, therefore, render it developable. lt is usually desirable to test each chelated stannous salt in the photographic process under consideration to determine which give optimum results.
In the reversal processing of multilayer, multicolor photo graphic elements, the first developer forms a negative blackand-white image. Photographic elements of the multilayer, multicolor type which do not contain color-forming couplers in the silver halide emulsion layers then are given a selective reversal reexposure of one silver halide emulsion layer at a time followed by color development of the reversal exposed layer with a color developer containing a color-forming coupler which reacts with the oxidized p-phenylenediamine type developer to form the appropriate dye image corresponding to the positive silver image formed. After selective reversal reexposure and color development of one layer, a second layer is selectively reversal reexposed and color developed, then the third layer is selectively reversal reexposed and color developed. The silver images and remaining silver halide are then removed by bleaching and fixing to leave the three dye images. The chelated stannous ion nucleating agents of our invention are used to advantage to eliminate the reversal reexposure required for the last color developed layer. For this purpose, the nucleating agents are either used in a nucleating bath with which the film is contacted after the second layer is color developed and before the third layer is color developed, or alternatively, the nucleating agent is incorporated in the color developer used to develop the third layer.
Particularly useful color products for reversal processing according to the method of our invention comprise a conventional support, such as cellulose esters, paper, glass, polyester film, polyvinyl acetal film, polycarbonate film, etc., having coated thereon at least two silver halide layers which have been sensitized to particular regions of the spectrum. These emulsions have incorporated therein the color-forming components or couplers, which combine with the oxidation products of the photographic color developers, to produce the desired color images. For example, a typical color film, useful in practicing our invention comprises a support having coated thereon a red-sensitized photographic silver halide emulsion having incorporated therein a coupler for the cyan image (e.g. a phenolic coupler), a green-sensitized photographic silver halide emulsion having incorporated therein a coupler for the magenta image (e.g. pyrazolone coupler), and a blue-sensitized photographic silver halide emulsion containing a coupler for the yellow image (e.g. a coupler containing an openchain ketomethylene group). The photographic element can also contain conventional interlayers and filter layers, such as a yellow filter layer beneath the blue-sensitized emulsion to prevent exposure by blue light to either the redor green-sensitized emulsion. Photographic color films of the abovedescribed type can be reversal processed by a technique requiring fewer steps than the selective reversal processing of the multilayer color films mentioned above. According to our invention, for the processing of the emulsions having coupler compounds incorporated therein, it is only necessary to treat the exposed color film with the usual black-and-white developer for producing a negative silver image, followed by treatment with the aqueous chelated stannous ion nucleating solutions and followed by conventional color developer or, alternatively, followed by treatment with the color developer to which has been added one of the chelated stannous ion nucleating agents. In the practice of the present invention, any
of the conventional couplers as described in the prior art can be used. Couplers which are particularly useful in color developers for selective reversal processes illustrated in example 4 below, include Couplers 1-64 listed in columns 3-5of Spath U.S. Pat. No. 2,956,876, issued Oct. 18, l960. Couplers 65-77 described in the same patent in column 5 are useful in the photographic silver halide emulsion layers of reversal processes such as shown in example 2 below. Other couplers suitable for use in the emulsions include those described in Spence and Carroll U.S. Pat. No. 2,640,776, issued June 2, 1953, Weissberger et al. U.S. Pat. No. 2,407,2 l0, issued Sept. 3, 1946 and Weissberger et al. U.S. Pat. No. 2,474,294, issued June 28, 1949. Other couplers which can be used in the emulsions include the acylamino-substituted couplers, as disclosed in Salminen and Weissberger U.S. Pat. No. 2,423,730, issued July 8, 1947.
The above organo phosphorous stannous ion chelates have unexpected advantages as compared with the aminopolycarboxylic acid stannous ion chelates, such as ethylenediamine tetraacetic acid stannous ion chelate. That is, the organo phosphorous chelates can be used over a wider range of concentrations. The significance of this range of concentrations is that these chelates can be used at higher concentrations with the result that the nucleating solutions have considerably better stability under aerial oxidation because a larger excess can be tolerated without causing undue development of silver halide. At these higher concentrations the polyaminocarboxylic acid chelates tend to develop some of the silver halide rather than just nucleating it. Thus while these polyaminocarboxylic acid chelates can be used in the range of concentration of about 2 to 2,500 mgs. of stannous ion (calculated as tin) per liter, the organo phosphonic acid nucleating agents can be used in a range of about 2 to 7,000 mgs. per liter depending on the photographic element in use. A further advantage resides in the fact that since larger amounts of the or gano phosphorous chelates can be used in making up the nucleating solutions more accurate solutions can be prepared which results in more uniform processing of the photographic elements.
Example I -Black-and-White Reversal Process Using Chelated Stannous lon An ordinary gelatin-silver bromoiodide emulsion layer is exposed to a subject and developed for 3 minutes in the following composition:
N-methyl-p-aminophenol sulfate 2.0 g. Sodium sulfite, anhydrous 90.0 g. Hydroquinone 8.0 g.
Sodium carbonate monohydrate 52.5 g. Potassium bromide 50 g. Water to make I liter The developed film is then rinsed thoroughly with water and bleached for 2 minutes in a composition having the following formula:
Potassium bichrornate 9.4 g Sulfuric acid I20 cc Water to make I liter The bleached emulsion layer is then rinsed thoroughly with water and redeveloped for 3 minutes at 68 F. in the following solution:
N-methyl-p-aminophenolsulfate 0.6 Sodium sulfite, anhydrous 50.0 g. Hydroquinone 20.0 g Potassium bromide 8.0 g. Sodium thiocyunate 6.0 g. Sodium hydroxide 20.0 g.
Stannous chloride solution 20.0 cc. Water to make 1 liter *25 g. of (l-hydroxyethylidene-l.l-diphosphonic acid). 5.0 g. of SnCl=- 2H1O to one liter water.
The emulsion is then fixed out in the usual hypo fixing bath to obtain a high density black-and-white silver image in the emulsion layer.
The above process can also be carried out following the bleach step, by nucleating the unexposed silver halide with an acid solution of the chelated stannous salt such as the Nucleating Solution" shown in example 2 below followed by development of the nucleated silver halide with the above developer solution not containing the chelated stannous compound.
Example 2 -Reversal Color Process Using ChelatedStannous Ion An incorporated coupler multilayer color film is provided comprising red, green and blue sensitive gelatin-silver halide emulsion layers on a support, a yellow filter being coated between the blue and green sensitive emulsion layers. The emulsion layers contain reactive methylene and phenolic coupler compounds reactive with p-phenylenediamine developing agents to form dyes of color complementary to the sensitivity of the respective layers. The film in sheet or roll form is exposed to a colored subject and processed in a roller transport system such as shown in 11.8. Pat. No. 3,025,779 having staggered driven rollers which advance the film through a series of tanks and a drying chamber as follows:
Prehardener- 150 seconds, 95 F.
Dimcthoxytetrahydrofuran 4.3 g p-Toluenesulfinic acid, sodium salt 0.5 g Sodium bisulfate 8.0 5 Potassium bromide 231 g Sodium acetate, anhydrous 92.0 g Sodium sulfate, anhydrous 91.0 g Formalin, 37% 29.2 g. Water to make 1 liter Sodium hydroxide or sulfuric as required to give pl'14-7.
Neutralizer-75 seconds, 97 F.
Sodium hydroxide 6.32 g. Acetic acid, glacial 10.5 g. Sodium bromide 2.0 g. Hydroxylamine sulfate 18.0 g. Sodium sulfate, anhydrous 50.0 g. Boric anhydride 0.68 g. Water to make 1 liter First Developer- 150 seconds, 100 F.
Quadrofos 2.00 g. Sodium sulfite, des. 47.00 g. Phenidone 0.35 g. Hydroquinone 5.50 g. Sodium carbonate, monohydrate 32.00 g. Sodium bicarbonate 1.00 g. Boric anhydride 0.85 g. Sodium thiocyanate 1.38 g. Sodium bromide 1.30 g. Potassium iodide 0.013 g. Water to make 1 liter First Stop75 seconds, 100 F.
Alternately, in preparing the formula above, instead of adding the above 30 cc. solution of preformedchelated stannous ion, 15 gram of l-hydroxyethylidene-l ,l-diphosphonic acid can be added followed by 3.0 gram SnC1 21-1 0 and then add water to 1 liter.
Second Stop-75 seconds, 1 10 F.
Sodium bisulfate 10.0 g. Sodium acetate, anhydrous 13.0 g. Sodium thiosulfate, anhydrous 31.86 g. Water to make 1 liter Wash-75 seconds, F.
Bleach-J5 seconds, 1 10 F.
Fix-75 seconds, 1 10 F.
Ammonium thiosulfate, 58% 163.0 cc. Sodium bisulfate, anhydrous l 1.0 g. Boric acid 8.0 g, Acetic acid, glacial 19.0 cc. Sodium hydroxide 8.0 g. Zirconium sulfate tetrahydrate 5.0 g. Water to make 1 liter Adjust to pH 4.0
Wash-75 seconds, 90 F. Dry-150 seconds, F.
As a result of processing the color film in this manner, the chelated stannous ion in the color developer nucleates the unexposed silver halide in the emulsion layers and this silver halide is then developed by the color developing agent which then couples with the couplers in the respective emulsion layers to form dye images at the sites of development.
In the above process, the chelated stannous ion can be omitted from the color developer formula and the following solution used in place of the First Stop:"
Nucleatin Solution Sodium acetate, anhydrous 3.58 g. .Organo phosphorous chelating agent 1.5 g.
Acetic acid, glacial 28.85 g.
Water to make 1 liter Same chelating agent as the color developer above or Nitrilo-N,N N- trimethylenephosphonic acid.
The unexposed silver halide is thus nucleated and is developed by the subsequent color developer.
An advantageous and unexpected result of using the chelated stannous ion in the above color processes is noted as additional quantities of film are processed through the solutions. That is, according to the mechanism of the process mentioned above, during the color development reaction the chelated stannous ion present in the color developer solution, or any which is introduced by the acid prebath before color development, is oxidized to chelated stannic ion which does not precipitate from the developer solution. Stannous salt (nonchelated) cannot be used in the color developer solution instead of chelated stannous ion because the solution immediately becomes dirty and useless and the dirt is not removable from the emulsion surface. Similarly, if nonchelated stannous salt is used in the acid prebath instead of chelated stannous ion, dirt gradually builds up in the prebath and deposits on the emulsion surface from which it is not removable. Also, any nonchelated tin salt carried over from the prebath by the emulsion layers is immediately precipitated as dirt in the subsequent alkaline developer solution.
Example 3-Comparison of Reversal Processes Using Chelated Stannous Salt and Borane Nucleating Agents The process of example 2 is carried out except replacing the chelated stannous salt in the color developer by .073 g. of tert. butylamineborane. A useful subtractively colored positive reproduction of the subject is obtained. However, when the image structure is compared with that obtained in example 2 using the chelated stannous ion for nucleation, it is found that the example 2 process using chelated stannous ion produces dye images wherein the red colors contain less cyan contamination, i.e. the red colors are much brighter. Also, the example 2 process yields blue colors having less yellow contamination, i.e. the blue colors are brighter. In addition, the cyan colors are more saturated and there is a significant improvement in definition in images obtained in the example 2 process.
Example 4 -Selective Reversal Color Process Using Chelated Stannous Ion A conventional multilayer color film is provided having superimposed on a transparent support in order red, green and blue light-sensitive gelatin-silver halide emulsion layers free of color-forming couplers. A yellow filter layer is positioned between the blue and green sensitive emulsion layers. After exposure to a colored subject, the film is developed in the usual MQ black-and-white developer solution, washed, reexposed through the base to red light and developed with a conventional color developer solution containing a phenolic cou pler for the cyan dye image. After washing, the film is reexposed to blue light from the emulsion side and developed as usual in a color developer containing a reactive methylene type coupler which forms the yellow dye image. After washing, the film is treated at 83 F. for one minute and 13 seconds in the following magenta reversal bath:
Water 700.0 cc. Quadrofos 4.0 g. Sodium hydroxide 3.0 g. Stannous chloride solution 60.0 cc. Water to make 1 liter *25 grams Nitrilo-N,N,N-trimethylenephosphofic acid and 5.0 grams SnClz Hz to 1 liter of water,
This results in nucleation of the unexposed silver halide in the Water Sulfuric acid, (cone.)
Trisodium phosphatelZl-Ifl 40.0 g. Sodium sulfite (desiccated) 5.0 g. Sodium thiocyanate 1.0 g. Z-Amino-S-diethylaminotoluene 2.60 g. hydrochloride Citrazinic acid 0.70 g. Ethylenediamine 3.0 g. Polyethylene glycol 0.25 g. Sodium sulfate (anhydrous) 50.0 g. Sodium hydroxide 0.32 g. 2,4,6-(trichlorophcnyl)-3-p- 1.60 g. nitroanilino-2-pyrazoline-5-one Hexylene glycol 5.0 ml. Sodium bromide 0.5 g. Potassium iodide (0.1%) 7.5 ml. Water to make I liter The film is then washed, bleached with ferricyanide solution for rehalogenating the silver as usual followed by washing and fixing with hypo solution. The dye images obtained in the film have a good density and contrast. There is no evidence of dirt in the solutions or on the film even after a considerable amount of film has passed through the solutions.
If desired, the above process can be carried out in the manner of example 2 by omitting the above magenta reversal bath and incorporating the following solution into the above magenta color developer composition: 20 cc. of a solution containing 25 grams of Nitrilo-N,N,N-
.trimethylenephosphonic acid and 5.0 grams SnCl '2H 0 made to 1 liter with water. Thus, the undeveloped silver in the green sensitive layer is both nucleated and color developed by the developer solution.
In general, the amount of chelated stannous ion nucleating agent used in the color reversal process as illustrated in the above examples is such that the undeveloped silver halide is nucleated fully or to the required extent under the processing conditions of time and temperature. The amount of silver halide initially present in the emulsion layer or layers will, to some extent, determine the solution concentration of stannous ion; but generally the amount of silver halide left after the first development step of the reversal process determines the stannous ion concentration under the conditions of operation, and is that amount of stannous ion sufficient to nucleate the available silver halide. Thus, if too much nucleating agent is used, some silver halide is reduced leaving an insufficient amount of nucleated silver halide for use in the subsequent color development step. In a black-and-white reversal process coneentration of the nucleating agent is not as critical. Accordingly, when the nucleating agents are used in an acid prebath before color development at about -l25 F. for about 30-90 seconds as shown in example 2, for average emulsion layers about 2 to 7,000 mgs. per liter of stannous ion, calculated as tin, is useful, e.g. about 3.8 mg. to 13.3 g. SnCl '2BY20 is useful in making a liter of the chelated stannous ion solution. Thus, at the higher concentrations, nucleation of silver halide takes place but some silver halide in an outer emulsion layer may be reduced with concomitant loss in dye density in that layer.
When chelated stannous ion is used in a color developer in processes such as shown in examples 2 and 4 with average emulsion layers, about 2to 7,000 mgs. per liter as tin is also useful at about 80 F.- F. when processing for the time necessary to complete development. In black-and-white processes illustrated in example 1, also about 2 to 7,000 mgs. stannous ion as tin per liter of the developer solution is useful and about 2 to 7,000 mgs. stannous ion as tin per liter when the chelate is employed in an acid prebath before the blackand-white development step. Accordingly, it will be understood that the optimum concentrations of the chelated stannous ion in the solutions is best determined by experiment with the particular single or multilayer photographic elements in use under the conditions of operation. As discussed above, an excess of the ligand component of the chelate should be present, e.g., about 10 percent excess.
The chelated stannous ion nucleating agents in accordance with the formula given above are used as nucleating agents as disclosed in examples 1 and 2 especially either in an acid prebath or color developer for development of incorporated coupler color products, or in an acid prebath or color developer solution in selective reversal color processes such as described in example 4.
Color development, as described in the above examples, can be carried out using any of the well-known color-forming developing agents which are capable of coupling with the color-forming components or couplers. Particularly useful color-forming developing agents are the p-phenylenediamines and substituted derivatives thereof. Typical of such colorforming developing agents are the sulfonamide-substituted pphenylenediamines disclosed in Weissberger US. Pat. No. 2,548,574, issued Apr. 10, 1951, the substituted p-phen ylenediamines disclosed in Weissberger et a1. U.S. Pat. Nos. 2,552,240; 2,552,241 and 2,552,242, issued May 8, 1951, and the substituted p-phenylenediamines disclosed in Weissberger et al. US. Pat. No. 2,566,271, issued Aug. 28, 1951. Other phenylenediamine color-forming developing agents can be employed to like advantage in the process of our invention.
The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.
1. In a photographic reversal process wherein a silver halide emulsion layer is exposed to an image, the emulsion layer is developed in the regions of exposure with a first silver halide developing solution, a reversal positive image is obtained by nucleating the unexposed silver halide of the emulsion layer by contacting the layer with a chemical nucleating agent to render it developable with a second silver halide developing solution and developing the resulting nucleated silver halide, the improvement for obtaining better photographic reproduction and definition comprising nucleating the unexposed silver halide by contacting it with an aqueous solution of organo phosphorous chelated stannous ion silver halide nucleating agent.
2. In a photographic reversal color process wherein a photographic element containing at least two silver halide emulsion layers differentially sensitized to different spectral regions is exposed to a colored image, images are developed in the emulsion layers in the regions of exposure using a first silver halide developing solution, and reversal positive colored images are obtained by nucleating the unexposed silver halide of the emulsion layers by contacting the layers with a chemical nucleating agent to render at least one of them developable with a second silver halide color developing solution, and developing the resulting nucleated silver halide to form the positive colored images, the improvement for obtaining better color reproduction and definition comprising nucleating the unexposed silver halide by contacting it with an aqueous solution of organo phosphorous chelated stannous ion silver halide nucleating agent.
3. In a photographic reversal color process wherein a photographic element containing at least two silver halide emulsion layers differentially sensitized to different spectral regions and color forming coupler compounds is exposed to a colored image, images are developed in the emulsion layers in the regions of exposure using a first silver halide developing solution, and reversal positive colored images are obtained by nucleating the unexposed silver halide of the emulsion layers by contacting the layers with a chemical nucleating agent to render them developable with a second silver halide color developin solution, and developing the resulting nucleated silver hall e to form the positive colored images, t e Improvement for obtaining better color reproduction and definition comprising nucleating the unexposed silver halide by contacting it with an aqueous solution of organo phosphorous chelated stannous ion silver halide nucleating agent.
4. The process of claim 3 wherein the unexposed silver halide is nucleated by treatment with an acid solution of the chelated stannous ion prior to treatment of the emulsion layers with the color developing solution.
5. The process of claim 3 wherein chelated stannous ion is present in a developing solution containing color developing agent to nucleate the unexposed silver halide and render it developable by the color developing agent.
6. In a photographic reversal color process wherein a photographic element containing at least two silver halide emulsion layers differentially sensitized to different spectral regions and free of color-forming coupler compounds is exposed to a colored image, silver images are developed in the emulsion layers in the regions of exposure using a first silver halide developing solution, reversal positive colored images are obtained by consecutive reversal reexposure of the emulsion layers except for the last one and developing the reexposed layers separately with color developing solutions containing color-forming coupler compounds, and the unexposed silver halide of said one emulsion layer is then nucleated by contacting it with a chemical nucleating agent followed by developing the resultant nucleated silver halide with a color developing solution containing a color-forming coupler compound, the improvement for obtaining better color reproduction and definition comprising using organo phosphorous chelated stannous ion as the chemical nucleating agent.
7. The process of claim 6 wherein the chelated stannous ion is present in the color developing solution used for development of the nucleated silver halide.
8. The process of claim 3 wherein the photographic element contains three superimposed silver halide emulsion layers sensitive respectively to the red, green and blue regions of the spectrum and each emulsion layer contains a coupler compound for formation of a dye image in the layer of a color complementary to the sensitivity of emulsion layer, and the nucleation of the silver halide is effected by the use of an organo phosphorous stannous ion silver halide nucleating agent present in the color developing solution.
9. An aqueous solution for the nucleating of photographic silver halide emulsion layers containing organo phosphorous chelated stannous ion silver halide nucleating agent and sufficient organic acid to give a pH of about 2 to 7 and provide buffering capacity.
10. A solution for nucleating and developing photographic silver halide emulsion layers comprising alkali, a silver halide developing agent and organo phosphorous chelated stannous ion silver halide nucleating agent.
11. The developing solution of claim 10 wherein the developing agent is a primary aromatic amino silver halide developing agent.
12. The developing solution of claim 11 further containing a coupler compound reactive with the oxidation product of the developing agent to form a dye.