Title:
PEPTIZERS FOR SILVER HALIDE EMULSIONS USEFUL IN PHOTOGRAPHY
United States Patent 3615624
Abstract:
In making photographic emulsions, silver halide is precipitated and emulsified in aqueous solution of a peptizer which is a water-soluble linear addition copolymer comprising recurring units of an amide or ester of maleic, acrylic, or methacrylic acid. The amine or alcohol condensation residue moiety of the amide or ester unit contains at least one sulfide sulfur atom connecting two alkyl carbon atoms. Presence of this sulfide sulfur atom is critical to efficient peptizing action. emulsions made with these peptizers have various uses. Specific examples describe emulsions specially suited for physical development processes, very fine grain emulsions, negative speed emulsions, etc.


Inventors:
Smith, Donald A. (Rochester, NY)
Perry, Ernest J. (Rochester, NY)
Hollister, Kenneth R. (Rochester, NY)
Application Number:
04/701084
Publication Date:
10/26/1971
Filing Date:
01/29/1968
Assignee:
Eastman Kodak Company (Rochester, NY)
Primary Class:
Other Classes:
430/629, 430/630
International Classes:
C08F8/34; C08F28/00; G03C1/053; (IPC1-7): G03C1/04
Field of Search:
96/114
View Patent Images:
Primary Examiner:
Smith, Ronald H.
Claims:
We claim

1. A process of making a photographic silver halide emulsion comprising a step of forming silver halide grains by reaction of a soluble silver salt and a soluble halide salt in an aqueous medium comprising a peptizer which is a water-soluble linear addition copolymer comprising (1) recurring units in the linear polymer chain of amides or esters of maleic, acrylic or methacrylic acids in which respective amine or alcohol condensation residues in said respective amides and esters contain an organic radical having at least one sulfide-sulfur atom linking two alkyl carbon atoms and (2) units of at least one other ethylenically unsaturated monomer.

2. A process as defined in claim 1 wherein said linear addition copolymer comprises (1) recurring units of acrylamides in which the respective amine condensation residues in said amides comprise an organic radical having at least one sulfide-sulfur atom linking two alkyl carbon atoms and (2) units of at least one another ethylenically unsaturated monomer.

3. A process as defined in claim 2 wherein said ethylenically unsaturated monomers consist essentially of acrylic acid.

4. A process as defined in claim 2 wherein said ethylenically unsaturated monomers consist essentially of acrylic acid and ethyl acrylate units.

5. A process as defined in claim 2 wherein said ethylenically unsaturated monomers consist essentially of 3-acryloyloxypropane-1-sulfonic acid, sodium salt.

6. A process as defined by claim 2 wherein said acrylamide is acryloylmethionine methyl ester.

7. A process as defined by claim 2 wherein said acrylamide is acryloylmethionine.

8. A process as defined by claim 2 wherein said acrylamide is acryloylmethionineamide.

9. A process as defined by claim 2 wherein said acrylicamide is N-(3-thiapentyl)acrylamide.

10. A process as defined by claim 2 wherein said acrylic amide is N-[2,2-bis(1-thiapropyl)ethyl]acrylamide.

11. A process as defined by claim 2 wherein said acrylamide is N-(3,6-dithiaheptyl)acrylamide.

12. A process as defined in claim 1 wherein said linear addition copolymer comprises (1) recurring units of acrylate esters in which the respective alcohol condensation residue of said esters comprise an organic radical having at least one sulfide-sulfur atom linking two alkyl carbon atoms and (2) units of at least one other ethylenically unsaturated monomer.

13. A process as defined by claim 12 wherein said acrylate ester is methylthioethyl acrylate.

14. A process according to claim 12 wherein said acrylate ester is methylthioethyl acrylate and wherein said ethylenically unsaturated monomers consist essentially of acrylic acid.

15. A process as defined by claim 12 wherein said acrylate ester is bis(2-thiabutyl)methyl acrylate.

16. A process as defined by claim 12 wherein said acrylate ester is bis(2-thiabutyl)methyl acrylate and said ethylenically unsaturated monomer consists essentially of 3-acryloyloxypropane-1-sulfonic acid, sodium salt.

17. A process as defined in claim 1 wherein said organic radical having at least one sulfide-sulfur atom is an organic radical containing one sulfide-sulfur atom linking two carbon atoms.

18. A process as defined in claim 1 wherein said linear addition copolymer comprises (1) recurring units of methacrylamides in which the respective amine condensation residues in said amides comprise an organic radical having at least one sulfide-sulfur atom linking two alkyl carbon atoms and (2) units of at least one other ethylenically unsaturated monomer.

19. A process as defined in claim 18 wherein said methacrylamide is methacryloylmethionine.

20. A process as defined in claim 18 wherein said methacrylamide is methacryloylmethionine and said ethylenically unsaturated monomer consists essentially of acrylic acid.

21. A process as defined in claim 18 wherein said methacrylamide is methacryloylpyrolylmethionine.

22. A process according to claim 18 wherein said methacrylamide is methacrylpyrolylmethionine and said ethylenically unsaturated monomer consists essentially of acrylic acid.

23. A process as defined in claim 1 wherein said linear addition copolymer comprises (1) recurring units of maleamic acids in which the respective amine condensation residues in said maleamic acid comprise an organic radical having at least one sulfide-sulfur atom linking two alkyl carbon atoms and (2) units of at least one other ethylenically unsaturated monomer.

24. A process according to claim 23 wherein said units of ethylenically unsaturated monomers consist essentially of ethylene units.

25. A process according to claim 23 wherein said ethylenically unsaturated monomers consist essentially of methyl vinyl ethers.

26. A process as defined by claim 23 wherein said maleamic acid units consist essentially of units of N-(3-methylthiopropyl)maleamic acid.

27. A process as defined by claim 23 wherein said maleamic acid units consist essentially of units of N-(2-ethylthioethyl)maleamic acid.

28. A process as defined by claim 23 wherein said maleamic acid units consist essentially of units of N-(2-methylthioethyl)maleamic acid.

29. A process as defined by claim 23 wherein said maleamic acid units consist essentially of units of N-[2-(2-carbethoxyethylthio)ethyl]maleamic acid. acid.

30. A process as defined by claim 23 wherein said maleamic acid units consist essentially of units of N-[2-(2-diethylaminoethylthio)ethyl]maleamic acid.

31. A process as defined by claim 23 wherein said maleamic acid units consist essentially of units of N-(2-propylthioethyl)maleamic acid.

32. A process as defined by claim 23 wherein said maleamic acid units consist essentially of units of N[2-N-piperidinoethylthio)ethyl]maleamic acid.

33. A process as defined by claim 23 wherein said maleamic acid units consist essentially of units of N-[2-(2-N-morpholinoethylthio)ethyl]maleamic acid.

34. A process as defined by claim 23 wherein said maleamic acid units consist essentially of units of N-(3-methylthio-1-carboxymethylpropyl)maleamic acid.

35. A process as defined in claim 1 wherein said linear addition copolymer comprises (1) recurring units of maleic acid monoesters in which the respective alcohol condensation residues of said monoesters comprise an organic radical having at least one sulfide-sulfur atom linking two alkyl carbon atoms.

36. A process as defined by claim 35 wherein said maleic acid monoester units consist of units of maleic acid mono-3-(2-diethylaminoethylthio)propyl ester.

37. A process as defined by claim 35 wherein said maleic acid monoester units are units of maleic acid mono-3-(2-diethylaminoethylthio)propyl ester and said units of ethylenically unsaturated monomers consist essentially of ethylene units.

38. A process as defined in claim 1 wherein said ethylenically unsaturated monomers are vinyl esters, vinyl esters, acrylic acids, methacrylic acids, α,β-ethylenically unsaturated sulfates, α,β-ethylenically unsaturated sulfonates or mixtures thereof.

39. A process of making a photographic silver halide emulsion comprising the step of forming silver halide grains by reaction of a water-soluble silver salt and a water-soluble halide salt in an aqueous medium comprising a peptizer which is a water-soluble linear addition copolymer comprising (1) recurring units in the linear polymer chain of amides or esters of maleic, acrylic or methacrylic acids in which the respective amine or alcohol condensation residues in said respective amides and esters contain an organic radical which contains one sulfide-sulfur atom linking two alkyl carbon atoms and (2) units of at least one other ethylenically unsaturated monomer.

40. A process according to claim 39 wherein the peptizer in said aqueous medium consists essentially of said water-soluble linear addition copolymer.

41. A product made by the process of claim 1.

Description:
This invention relates to photography and particularly to new and improved photographic silver halide emulsions and improvements in methods for making them.

In the preparation of photographic silver halide emulsions, a preliminary step is preparation of photosensitive silver halide by double decomposition reaction between a soluble silver salt, such as silver nitrate, and a soluble halide salt such as ammonium halide or an alkali metal halide, usually the potassium halides. As the insoluble silver halide is formed, it is necessary to control formation of silver halide grains by means of a peptizer which regulates grain growth and dispersion of the silver halide grains in the emulsion. Characteristics of grain growth and grain dispersion during preparation of photographic emulsions will have critical influence on the basic sensitometric and photographic properties of the emulsion such as photographic speed, contrast, graininess, and acutance. Gelatin has been the most generally used peptizer for photographic emulsions and while it remains a useful peptizer, there are certain disadvantages inherent in gelatin, for example, gelatin is subject to attack by bacteria and fungus which sometimes damage photographic emulsions. Also, since gelatins are derived from animal sources, control of uniformity of gelatin compositions used for peptizers has been a serious problem.

Among the objects of the present invention are to provide an entire new class of synthetic resin peptizers for making silver halide photographic emulsions and to provide photographic silver halide emulsions prepared with such peptizers. Some advantages obtained by these synthetic peptizers include easier and more uniform control of the peptizer composition and relative immunity from decay. Some preferred embodiments of the invention provide emulsions having properties that make them especially useful in photographic processes involving physical developement, for example, in diffusion transfer processes. The invention provides an entire new class of peptizers which provide substitutes for gelatin as peptizers and, in certain embodiments provide new and improved emulsions having photographic characteristics not previously available to emulsion makers.

The foregoing and other objects and advantages are obtained in accordance with the present invention by preparing photographic silver halide emulsions by a method which comprises a step of precipitating silver halide in an aqueous dispersion in presence of a sulfide-containing synthetic resin peptizer. The particular class of synthetic resins useful as peptizers in accordance with the present invention can be described as water-soluble linear addition copolymers of ethylenically unsaturated monomers which comprise units polymerized from monomers selected from amides and esters of maleic, acrylic, and methacrylic acids, in which the respective amine and alcohol condensation residues in said selected amides and esters comprise within their structure at least one organic group having at least one sulfide sulfur atom liking two alkyl carbon atoms. A variety of such vinyl units comprising at least one sulfide sulfur atom are described in the following paragraphs.

In the class of copolymers useful as peptizers, the monomer that contains the sulfide sulfur atom will be copolymerized with at least one other ethylenic monomer which, for example, may be selected from: α,β-ethylenically unsaturated hydrocarbons such as vinyl esters such as vinyl acetate; vinyl ethers such as methyl vinyl ether; amides such as acrylamide or methacrylamide; acrylic acids and esters such as acrylic acid, methacrylic acid, methyl methacrylate, ethyl acrylate, ethyl methacrylic, and the like; α,β-ethylenically unsaturated sulfonates such as 3-acryl-oyloxypropane-1-sulfonic acid, sodium salt, and 3-acryloyloxy-1-methylpropane-1-sulfonic acid, sodium salt; and α,β-ethylenically unsaturated sulfates such as sodium methacryloyloxyethyl sulfate.

Following are specific examples setting forth in detail several preferred embodiments and including our most preferred mode of carrying out the invention.

Example 1-- Copolymer of Acrylic acid and Acryloylmethionine methyl ester (mole ratio 3.0/1.0

A solution of 10.0 grams of acrylic acid and 10.0 grams of acryloylmethionine methyl ester in 60 milliliters dioxane is treated with 0.2 gram of azobisisobutyronitrile and kept at 60° C. under nitrogen overnight. The polymer is isolated by precipitation in ether and purified by dissolving in dioxane-methanol then precipitating in ether. Yield, 19.0 grams. Found: N= 3.2; S= 6.4. ##SPC1##

A neutral emulsion is prepared as follows. Twenty milliliters of aqueous solution containing 3.82 grams of silver nitrate is added over a period of 30 minutes to 30 milliliters of aqueous solution containing 3.275 grams of potassium bromide, 0.1 gram of potassium iodide, and 1.0 gram of the 3.0/1.0 (molar ratio) copolymer of acrylic acid and acryloylmethionine methyl ester as a peptizer. The resulting emulsion has well-dispersed silver halide grains with diameters in the range of 0.3 to 2.3 microns and shows excellent stability against clumping of grains.

An ammoniacal emulsion is prepared as follows. Twenty milliliters of an aqueous solution containing 3.82 grams silver nitrate and ammonium hydroxide just sufficient to redissolve the precipitate formed initially on addition of ammonium hydroxide to the silver nitrate solution is added with continuous stirring over a period of 85 seconds to 30 milliliters of solution containing 3.14 grams potassium bromide, 0.1 gram potassium iodide, and 1.0 gram of the acrylic acid, acryloylmethionine methyl ester copolymer as a peptizer. Stirring is continued for an additional 39-minute period. Temperature of the reaction mixture during addition and subsequent stirring is held at 45° C. The resulting emulsion consists of well-dispersed grains, mostly cube shaped with diameters in the range from 0.6 to 1.6 microns. The emulsion shows excellent stability against clumping of grains.

Example 2-- Copolymer of acrylic acid and methylthioethyl acrylate (Mole ratio 3.33/1.0 )

A solution of 8.7 grams acrylic acid and 5.3 grams methylthioethyl acrylate in 40 milliliters dioxane with 0.1 gram azobisisobutyronitrile is kept at 60° C. under nitrogen overnight. The gellike, opaque precipitate is treated with methanol to give a clear solution which is then poured into ether giving a poor precipitate with some colloidal material. After drying in vacuo the yield is 10.1 grams. Found: S= 5.8. ##SPC2##

A neutral emulsion is prepared as described in example 1, except the peptizer used in the reaction mixture is the 3.33/1.0 copolymer of acrylic acid and methylthioethyl acrylate. The resulting emulsion consists of well-dispersed octahedral grains with diameters in the range from 0.3 to 1.8 microns and possesses excellent stability against clumping of grains. An ammoniacal emulsion is prepared as in example 1 but using the acrylic acid-methylthioethyl acrylate 3.33/1.0 copolymer as the peptizer. The resulting emulsion consists of well-dispersed cubic grains with diameters in the range of 0.7 to 1.2 microns and shows excellent stability against clumping of grains.

EXAMPLE 3-- Copolymer of acrylic acid and methacryloylmethionine (Mole ratio 3.33/1.0 )

A solution of 3.85 grams acrylic acid and 3.5 grams methacryloylmethionine in 20 milliliters of dioxane is treated with 0.05 gram of azobisisobutyronitrile and kept at 60° C. under nitrogen overnight. The polymer is isolated by precipitating in ether and after drying weighs 8.0 grams. Found: N= 3.2; S= 7.0 ##SPC3##

Neutral and ammoniacal emulsions are prepared as described in example 1 substituting the 3.33/1.0 copolymer of acrylic acid and methacryloylmethionine as the peptizer. The neutral emulsion consists of well-dispersed grains with diameters in the range from 0.5 to 2.9 microns and shows excellent stability against clumping of grains. The ammoniacal emulsion has well-dispersed grains the shape of rounded cubes with diameters in the range from 0.7 to 1.2 microns. The emulsion has excellent stability against clumping of grains.

EXAMPLE 4-- Copolymer of acrylic acid and methacryloylprolylmethionine methyl ester (Mole ratio 3.33/1.0)

Acrylic acid (4.8 grams) is copolymerized by conventional procedure with the product of reaction of 3.66 grams methacryloylproline and 3.26 grams described methionine methyl ester, in the presence of triethylamine and ethyl chloroformate, which could not be obtained in crystalline form. The yield of dried polymer obtained is 9.1 grams. Found: N= 3.4; S= 3.4. ##SPC4##

A neutral emulsion is prepared by the method described in example 1 except that the peptizing copolymer contained in the aqueous medium is the 3.33/1.0 copolymer of acrylic acid and methacryloylprolylmethionine methyl ester prepared as described above. The resulting emulsion shows excellent stability against clumping of grams and consists of well-dispersed grains with diameters in the range from 0.2 to 1.3 microns.

An ammoniacal emulsion is also prepared as described in example 1 the copolymer used as a peptizer is the 3.33/1.0 copolymer of acrylic acid and methacryloylprolylmethionine methyl ester. The grains of this emulsion are mostly cube shaped and have diameters in the range from 0.25 to 1.3 microns. The emulsion shows excellent stability against clumping of grains.

EXAMPLE 5-- copolymer of acrylic acid and acryloylmethionine (Mole ratio 3.33/1.0)

A solution of 11.9 grams of acrylic acid and 10.15 grams of acryloylmethionine in 60 milliliters dioxane is treated with 0.2 gram of azobisisobutyronitrile. The mixture is heated overnight at 60° C. under nitrogen, then the resulting solution is poured into ether and the precipitated polymer is dried in vacuum. The yield is 22 grams. Calculated: N= 3.2; S= 7.3. ##SPC5##

A neutral emulsion is prepared as described in example 1 except that the peptizer in the reaction mixture is the 3.33/1.0 copolymer of acrylic acid and acryloylmethionine. The grains are well-dispersed tabular octahedral crystals including many triangle shapes with straight edges and sharp corners. Grain diameters are in the range from 0.3 to 3.5 microns. The mean grain area is 1.714 square microns. The width of the size distribution curve expressed in terms of the function known in the art as the "sigma function," corresponds to a value of sigma equal to 1.869 square microns; and the number of dislocations per emulsion grain, as determined by X-ray analysis, is 16.4. These values are distinctly different from those of an emulsion prepared by the same procedure but using gelatin as the peptizer in the reaction mixture. Characteristic parameters of such a gelatin-peptized emulsion have these values: Mean grain area = 0.808 square micron; Sigma = 0.847 micron; and Dislocations per grain = 8.5.

EXAMPLE 6-- Copolymer of acrylic acid and acryloylmethionine (Mole ratio 3.33/1.0) (By saponification)

A solution of 10.5 grams of a copolymer of acrylic acid and acryloylmethionine methyl ester (mole ratio 3.33/1.0-- prepared as in example 1 but using 11.0 grams acryloylmethionine methyl ester instead of 10.0 grams in 50 milliliters methanol is treated with 4.3 grams sodium hydroxide in 50 milliliters methanol. This causes some polymer to precipitate and this is then redissolved by addition of 50 milliliters water. The solution is submitted to vacuum evaporation, then treated with 50 milliliters of water. After keeping overnight at room temperature, the solution is poured into methanol and the precipitated polymer is dried at room temperature in vacuum. Yield, 12.2 grams. Found: N= 2.3; S= 5.4. Sodium = 16.3.

An ammoniacal emulsion is prepared by the procedure described in example 1 except that the peptizer in the reaction mixture is the 3.33/1.0 copolymer just described. The emulsion exhibits excellent stability as a photographic emulsion and consists of well-dispersed grains of rounded cube shapes with diameters in the range from 0.3 to 1.2 microns. Mean grain area is 1.355 square microns. Width of the size distribution curve corresponds to sigma equal to 0.502 square micron and the number of dislocations per grain is 13.8 A control emulsion in which gelatin is used as the peptizer has mean grain area of 1.048 square microns, sigma equal to 0.464 square micron, and dislocations per grain equal to 6.2.

EXAMPLE 7-- Copolymer of acrylic acid and acryloylmethionine (Mole ratio 5.0/1.0 )

A solution of 9.0 grams of acrylic acid and 5.1 grams acryloylmethionine in 35 milliliters dioxane is treated with 0.1 gram of azobisisobutyronitrile and kept at 60° C. under nitrogen for 2 days. The polymer is isolated by precipitation in ether and after drying in vacuo weights 13.5 grams. Found: N= 2.6; S= 4.9.

An ammoniacal emulsion is prepared by the method described in example 1 except the peptizer is the 5.0/1.0 copolymer just described. The emulsion obtained shows excellent stability against clumping of grains and contains well-dispersed silver halide grains having the shape of rounded cubes of diameters in the range from 0.5 to 1.7 microns.

EXAMPLE 8-- Copolymer of acrylic acid and acryloylmethionine (Mole ratio 1.0/1.0)

By the method described in the last previous example, 3.6 grams acrylic acid is copolymerized with 10.2 grams acryloylmethionine. Yield, 12.5 grams of copolymer. Found: N= 4.7 ; S= 10.5.

An ammoniacal emulsion is prepared by the method described in example 1 using the 1.0/1.0 acrylic acid, acryloylmethionine copolymer as the peptizer. The well-dispersed silver halide grains have the shape of rounded cubes with diameters in the range from 0.5 to 1.4 microns, and the emulsion has excellent stability against slumping of grains.

EXAMPLE 9-- Copolymer of ethyl acrylate, acrylic acid, and acryloylmethionine methyl ester (mole ratio 6.5/3.02/1.0)

A solution of 12.0 grams ethyl acrylate, 4.0 grams acrylic acid and 4.5 grams acryloylmethionine methyl ester in 50 milliliters dioxane is treated with 0.2 gram azobisisobutyronitrile and kept at 60° C. overnight. The viscous solution is diluted acryloylmethionine dioxane ad the polymer isolated by precipitation in ether. After purification by solution in dioxane and reprecipitation in ether, the dried polymer acryloylmethionine 18.5 grams. Found: N= grams) 1.5; S= 3.0.

An ammoniacal emulsion is prepared by the method described in example 1 but using the copolymer just described as the peptizer. The emulsion obtained has excellent stability against clumping of grains and contains well-dispersed octahedral silver halide grains of diameter in the range from 0.5 to 1.7 microns.

EXAMPLE 10-- Copolymer of acrylic acid and acryloylmethionine amide (Mole ratio 3.33 / 1.0) ##SPC6##

A solution of 2.4 grams of acrylic acid and 2.02 grams of acryloylmethionine amide in 12 milliliters dioxane and 6 milliliters water is treated with 0.05 gram of azobisisobutyronitrile and kept at 60° for 3 days. The solution is diluted with 30 milliliters methanol and filtered to remove a small amount of insoluble material. The polymer is isolated by precipitation in ether. After vacuum drying, it weighs 5.2 grams. Found: N= 4.1; S= 4.7.

An ammoniacal emulsion is prepared by the method described in example 1 except using the copolymer just described as the peptizer. The emulsion obtained shows excellent stability against clumping of grains and has well-dispersed silver halide grains which are mostly rounded cubes and near spherical shapes with grain diameters in the range from 0.3 to 1.2 microns.

EXAMPLE 11

Photographic emulsions prepared using the synthetic polymer peptizers described in examples 1-3, 5, and 9 above are tested and compared with a control emulsion prepared with emulsions made with gelatin peptizer to determine relative rates of solution of silver halide crystals in a photographic developer and to determine relative rates of physical development of a constant silver ion concentration supplied by a silver ion-thiosulfate complex. These measurements are made using method described by E. J. Perry in Photographic Science and Engineering, Volume, 5, page 349 (1961). The emulsions peptized by the synthetic polymers tested exhibit must faster relative rates of solution and much faster relative rates of physical development than does the gelatin peptized control emulsion. ##SPC7##

EXAMPLE 12-- Copolymer of ethyl acrylate, acrylic acid and acryloylmethionine (Mole ratio 6.0/3.0/1.0)

A solution of 15 grams ethyl acrylate, 5.4 grams acrylic acid, and 5.07 grams acryloylmethionine in 45 milliliters acetone is treated with 0.1 gram azobisisobutyronitrile and kept at 60° C. under nitrogen for 4 hours. The polymer is isolated by precipitation in ether and when dried yields 23.1 grams of product. Found: N= 1.2; S= 3.2.

An emulsion having excellent physical development properties is made and tested as follows. Under red safelight 20.5 milliliters of aqueous solution containing 2.734 grams silver nitrate and 20.5 milliliters of aqueous solution containing 2.30 grams of potassium bromide and 0.072 gram potassium iodide are added simultaneously with continuous stirring to 29.0 milliliters of aqueous solution containing 1.05 gram of the 6.0/3.0/1.0 copolymer of ethyl acrylate, acrylic acid, and acryloylmethionine which is kept at a temperature of 45° C. After complete addition of both solutions, stirring at the same temperature is continued for 6 minutes. The emulsion is then removed from a constant temperature bath and sufficient 1 N sulfuric acid is added to coagulate the emulsion grains. After chilling, the supernatant liquid is decanted and the residue is washed with distilled water. Twelve and one-half milliliters of water and sufficient Na0H to raise the pH to 7 is added with stirring and half of the resulting suspension of emulsion grains is dispersed in 20.1 milliliters (8.7 percent concentration aqueous solution of the 6.0/3.0/1.0 copolymer. Subsequently, to 9.1 grams of this emulsion are added 1 milliliter of an aqueous dispersion containing 0.375 milligram of silver proteinate nuclei ("Silver Protein Mild" made by Mallikckrodt Chemical Works), 0.7 milliliter of 3.82 percent aqueous solution of the epoxide cross-linking agent Araldite RD-2 (made by Ciba Co.), and 0.15 milliliter of 5 percent saponin solution. This emulsion is coated on cellulose acetate film base and dried. Thickness of the dried coating is 0.0003-inch. The coating obtained is then developed without any exposure to actinic light in an N-methyl-p-aminophenol-hydroquinone developer to which sodium thiocyanate has been added. A control emulsion is prepared in exactly the same manner except gelatin is used as a peptizer instead of the 6.0/3.0/1.0 copolymer. This control emulsion is coated and developed by the same steps. Comparison of development results in terms of the amount of silver development in the coating at various development times are tabulated: ---------------------------------------------------------------------------

Development Developed silver Developed silver Time mg./sq. ft. mg./sq. ft. (Seconds) Copolymer peptizer Gelatin peptizer __________________________________________________________________________ 5 16 10 54 15 88 3.3 25 152 4.7 45 9.5 85 26 125 60 __________________________________________________________________________

Development in the respective films is essentially all by physical development and the above tabulation shows that substantially faster rates of physical development result in the emulsion peptized by the synthetic sulfide-containing copolymer as compared with the gelatin-peptized emulsion.

The increased rate of physical development obtained with emulsions peptized by certain copolymers containing a sulfide-sulfur atom, as illustrated in the above example is also observed in photographic diffusion transfer processes in which silver halide complex is transferred from a silver halide emulsion layer to a receiving a layer which contains physical development nuclei. Thus, in a diffusion-transfer development process, greater quantities of silver halide will be solubilized, transferred, and developed on a receiving sheet from an emulsion peptized by the sulfide-containing peptizers than will be done from the corresponding gelatin-peptized emulsion.

EXAMPLE 13 --copolymer of ethyl acrylate, arcylic acid and acryloylmethionine (Mole ratin 5.0/2.0/1.0)

Twelve and one-half grams of ethyl acrylate, 3.6 grams acrylic acid, and 5.07 grams acryloylmethionine are copolymerized by the process described in example 12. Yield is 19.2 grams of product. Under red light, 20 milliliters of an aqueous solution containing 2.377 grams of silver nitrate and 20 milliliters of aqueous solution containing 1.871 grams potassium bromide and 0.067 gram potassium iodide are added simultaneously with continuous stirring to 30 milliliters aqueous solution containing 1.05 gram of the 5.0/2.0/1.0 copolymer of ethyl acrylate, a arcylic acid, and acryloylmethionine which is kept at 45° during addition and for a further 6-minute period of stirring,. The emulsion is coagulated by addition of approximately 25 milliliters of saturated sodium sulfate solution. After chilling, supernatant sodium sulfate solution. After chilling, supernatant liquid is decanted from the coagulated emulsion which is then washed with distilled water. Sufficient water is then added to bring the emulsion to 15 grams. The emulsion is then redispersed by stirring it into 23.9 milliliters of a heated aqueous solution containing 2.65 grams of the 5.0/2.0/1.0 copolymer described above. To 5.56 grams of this emulsion is then added 3.4 milliliters water, 0.79 milliliters of aqueous 3.82 percent solution of Araldite RD-2 and 0.15 milliliter of 5 percent saponin solution, This emulsion is coated on cellulose acetate film base and dried. Thickness of the dry coating is 0.3 mil. A diffusion transfer receiving sheet is prepared as follows. An aqueous solution (26.3 milliliters) containing 0.5 gram of the 5.0/2.0/1.0 copolymer described above, 1.25 milligrams To of silver proteinate nuclei ("Silver Protein Mild," Mallinckrodt), 0.9 milliliter of 3.82 percent solution of Araldite RD-2 and 0.2 milliliter of a 0.5 percent saponin solution is coated on a reflection print support. Thickness of the dried coating is 4×10-5 inch. For the diffusion transfer processing liquid, the following composition is used:

N-methyl-p-aminophenol 6.25 grams Hydroquinone 2.50 grams Sodium sulfite 6.25 grams Sodium thiosulfate pentahydrate 7.70 grams Potassium bromide 1.02 grams Sodium carbonate monohydrate 25.00 grams Water to make 1.00 liter

The receiving sheet is immersed for 20 seconds in this developer and then pressed for 20 seconds against the silver halide coating described above. X-ray spectrometric analysis showed the amount of silver transferred to and developed in the receiving sheet is 6.2 milligrams per square foot. A control experiment using gelatin instead of the 5.0/ 2.0/ 1.0 copolymer is run exactly as described above. In the control experiment the amount of silver transferred to and developed in the receiving sheet is only 2.2 milligrams per square foot.

Various peptizers of the invention will differ to some extent in particular effects on emulsions for which they are used; selection of a particular member from the larger group of sulfide-containing copolymers can be made to obtain particular effects. For example, negative-speed silver bromoiodide emulsions are prepared and coated by identical procedures but using as peptizers, respectively, to 3.3/1.0 copolymer of acrylic acid-acryloylmethionine methyl ester described in example 6 (before saponification and the 3.3/1.0 copolymer of acrylic acid and acryloylmethionine described in example 5. The emulsion peptized by the copolymer of acryloylmethionine methyl ester has photographic speed about four times as fast as the one peptized by the acrylolymethionine copolymer. Gamma of the former is 1.45 compared with 0.46 for the latter. Both emulsions are useful but each is significantly different from the other in its photographic properties.

The invention is not limited to making any particular type of silver halide photographic emulsion and we intend to include within the invention the use of peptizers of the invention in the silver halide precipitation and emulsifying step for making emulsions having a variety of uses, for example, we can use the peptizers of the invention for making negative-speed emulsions or for making printing-speed emulsions or for making silver bromide or chloride or bromoiodide or chlorobromide emulsions, and for making silver halide emulsions intended for various specialized uses including emulsions for color films, direct-positive films, direct-print materials, high resolution film, diffusion transfer films, printing papers, enlarging papers, etc.

A copolymer selected for use as a peptizer for a silver halide emulsion in accordance with this invention will be one that is soluble in aqueous solution at the pH of the aqueous medium to be used for precipitation of the particular emulsion. Most of the copolymers described in this specification will be soluble in aqueous solution at pH above 5 and some, for example, the copolymers containing the sulfonic acid sodium salt groups described in example 14 following, will be soluble at pH above 1.5.

To demonstrate the critical relation of the organic sulfide radical to the peptizing effect of the useful copolymers, we have prepared emulsions using copolymers containing analogous units polymerized from monomers that have another atom or group substituted for the bivalent sulfide sulfur atom. For example, instead of the sulfide copolymer in example 1, we use a copolymer of acrylic acid-acryloylmethionine sulfoxide (3.33/1.0) and the resulting emulsion is entirely unstable indicating no useful peptizing effect. Similarly, for comparison with others of the foregoing examples, control emulsions are tried, without success, using as peptizers corresponding addition copolymers of ethyl vinyl sulfone, ethyl thioacrylate, acryloylleucine methyl ester, methoxyethyl arcylate, methacryloylnorleucine, and methacryloylpropine. In all cases, these copolymers prove ineffectual as peptizers for various reasons such as complete instability or grain clumping or the like. To our minds, this demonstrates the specific criticality of the sulfide sulfur atom linking two alkyl carbon atoms, on the peptizing effect that is obtained with peptizers of the invention.

Following is an example illustrating an especially preferred embodiment in which the peptizing agent is a copolymer of an acryloyl derivative containing the critical sulfide linkage and a acrylic monomer having an appended terminal sulfonic acid group which enhances solubility of the peptizing copolymer.

EXAMPLE 14 --Copolymer of acryloylmethionine methyl ester with 3acryloyloxy-1-methylpropane-1-sulfonic acid, sodium salt (Mole ratio 1/9). Also 1/9Copolymer of N-(3 -thiapentyl)acrylamide and 3-acryloyloxy-propane1 -sulfonic acid, sodium salt

A solution of 6.94 grams of acryloylmethionine methyl ester and 66.24 grams of sodium 3-acryloyloxy-1-methylpropane-1-sulfonic acid sodium salt in 200 milliliters of redistilled dimethyl sulfoxide is purged with nitrogen, then treated with 0.37 gram of azobisisobutyronitrile. The solution is kept at60° C. overnight, then poured into acetone to precipitate the polymer. After vacuum drying at room temperature, the yield is 76.4 grams. The mole ratio of the acryloylmethionine methyl ester to 3-acryloyloxy-1-methylpropane-1sulfonic acid sodium salt in the copolymer is 1:9.

Three high-speed silver bromoiodide (94:6) negative emulsions are prepared by identical procedures except in the precipitation step for making each respective emulsion the peptizer used is: gelatin in Emulsion A; the 3.3/1.0 copolymer of acrylic acid and acryloylmethionine methyl ester (example 6 before saponification) in Emulsion B; and the 1/9 copolymer of acryloylmethionine methyl ester and 3 -acryloyloxy-1methylpropane-1-sulfonic acid sodium salt, described above, in Emulsion C.

After the silver halide grains for each emulsion have been emulsified, soluble salts are removed from the precipitation medium by conventional coagulation and redispersion, followed by redispersion in aqueous gelatin solution. Each emulsion is then digested conventionally to increase speed and after addition of conventional adjuvants and spectral sensitizing dyes, the emulsions are coated at the silver and gelatin coverages described in table I. The photographic elements so prepared are tested sensitometrically for σDH [graininess at 0.80 above base and fog, measured as described by Higgins and Stultz, J. Opt. Soc. Am., 49, 925 (Sept. 1959)], for photographic speed and for fog, using respectively: development in Kodak Developer D-76 to give γ=0.7 ; development in Kodak Developer DK-50 for 5 minutes and in DK-50 for 12 minutes and development in Kodak D-19 Developer for 6 minutes. Results tabulated in table I demonstrate that the emulsion peptized by the 1:9 copolymer of acryloylmethionine methyl ester and 3-acryloyloxy-1methylpropane-1-sulfonic acid sodium salt is able to penetrate into a region of high speed and low grandularity which is not reached, irrespective of silver coverage, development of the control emulsions peptized with gelatin and the copolymer of acryloylmethionine methyl ester and acrylic acid, Same is true for a similar emulsion (Emulsion D. table I) which is prepared and tested as above but using as peptizer a 1/9 copolymer of N-(3-thiapentyl)acrylamide and 3-acryloyloxypropane- 1 Sulfonic acid sodium salt. This copolymer is prepared by the same polymerization method described above but substituting as the monomers respectively 7.07 grams N-(3-thiapentyl)acrylamide and 86.4 grams sodium 3-acryloyloxypropane- 1-sulfonate and using 280 milliliters of redistilled dimethyl sulfoxide and 0.47 gram azobisisobutyronitrile. ##SPC8##

EXAMPLE 15 --Poly[N-(3 -thiabutyl)acrylamide-3-acryloyloxypropane-1-sulfonic acid, sodium salt] (Mole ratio 1:6) ##SPC9##

A solution of 842.4 grams (3.9 moles) of 3-acryloyl-oxpropane- 1-sulfonic acid, sodium salt in 2809 milliliters of redistilled dimethyl sulfoxide is treated with 94.25 grams (0.65 mole) of N-(3-thiabutyl)acrylamide and 4.68 grams of azobisisobutyronitrile. The system is swept with nitrogen for 15 minutes and placed in a 60° C. bath overnight. The polymer is precipitated and thoroughly washed in a large excess of acetone, and then dried under vacuum at room temperature. The product is a brittle white solid. Yield, 968.7 grams (over 100 percent theoretical).

To make the emulsion, a solution of 527 grams silver nitrate in 1190 milliliters of distilled water and a second solution containing 366 grams potassium bromide and 18.5 grams potassium iodide in 1115 milliliters distilled water are simultaneously added over a period of 4 minutes to an efficiently stirred solution maintained at 43° C. of 124 grams of 1/6 [copoly-N-(3-thibutyla)acrylamide-3-acryloyloxypropane -1 -sulfonic acid, sodium salt] dissolved in 3,940 milliliter of distilled water containing sufficient sodium hydroxide to raise the pH to 5.9. The resulting emulsion is stirred for an additional 2 minutes and a solution of 620 grams gelatin dissolved in 2,600 milliliters of distilled water is then added. The stirring is continued for an additional 10 minutes while maintaining the emulsion at 43° C. The emulsion is set by chilling, then noodled and washed to remove soluble salts. The emulsion obtained has average grain diameter of 62.7 millimicrons as determined by a light scattering method, and when examined by both photomicrography an electron micrography is found to be free from any detectable course grains or clumps. The emulsion is chemically sensitized to optimum speed; spreading and hardening agents are added and the emulsion is coated on a film support at silver and gelatin coverages respectively of 100 milligrams silver and 250 milligrams gelatin per square foot. A sample of the coating is exposed in an Eastman 1B sensitometer and then developed for 6 minutes in Kodak DK-50 developer. This is an extremely fine-grain emulsion suitable for photomicrography, direct electron recording or other photography requiring high resolution.

A control emulsion is prepared exactly as above except using gelatin as the peptizer. The control emulsion has average grain diameter about the same as the test emulsion but also contains a considerable amount of coarse grains, approximately 1.5 microns in diameter, which are detectable by photomicrography and electron micrography. The test emulsion is superior to the control because of its freedom from any detectable coarse grains or clumps,. The control emulsion would be unsuitable for any application requiring a fine-grain emulsion free from coarse grains and grain clumps.

Copolymers of Maleic Acid Esters and Amides

Additional peptizers useful in accordance with the invention can be prepared by condensing maleic anhydride copolymers with amines and alcohols containing the sulfide sulfur atom. Suitable water-dispersible anhydride-containing copolymers can be selected from those comprising maleic anhydride copolymerized with vinyl monomers such as α-olefins, vinyl ethers, vinyl esters, styrene, and the like. The sulfide-sulfur-containing copolymer is prepared by reacting the anhydride copolymer with an amine or an alcohol which contains at least one bivalent sulfur atom in a sulfide or thioether group. Reaction between the maleic anhydride moeity and an amine or alcohol is a condensation reaction, alcoholysis in the case of alcohols, aminolysis in the case of amines. The reaction product contains units derived from an amide or ester of maleic acid in which the amine or alcohol condensation residue contains the sulfide sulfur atom linking two alkyl carbon atoms in an organic sulfide radical. In preparing to make such methacrylic acid amide and ester copolymers, we first synthesize sulfur-containing amines and alcohols.

EXAMPLE 16--Preparation of 3-methylthiopropylamine

To a solution of 59.5 grams of sodium methoxide in 500 milliliters methanol at 0° C. is added 25 grams of methanethiol followed by 121 grams of 3-bromopropylamine hydrobromide. Methanol is distilled off and the residue is extracted with a total of 300 milliliters of ether which is then separated by distillation. Fractional distillation of the residue affords two principal fractions. The higher boiling fraction, 44°-54° C. at 1.1-1.7 millimeters, yields 19 grams of product having the following analysis.

Anal. Calcd. for C4 H11 SN: C--45.7; H--10.5; N--13.3; S--30.5 Found: C--45.7; H--10.4; N--12.7; S--28.7

Vapor phase chromatography analysis indicated 98 percent purity.

EXAMPLE 17--Preparation of 3-(2-diethylaminoethylthio)propanol

By the procedure described in example 16, 3-(2-diethylaminoethylthio)propanol is prepared by reaction of 85 grams diethylaminoethanethiol hydrochloride with 70 grams of 3-brom-propanol. Fifty-six grams of product (b.p. 113°-115° C.) is obtained. Vapor phase chromatography analysis indicates purity of 92 percent.

EXAMPLE 18--Preparation of 2-methylthioethylamine

2-Methylthioethylamine is prepared as follows. A solution of 25 grams of methanethiol and 1 gram of sodium methoxide in 100 milliliters methanol is cooled to 31 5° C. and 25 grams of ethyleneimine is added over a 20-minute period. Reaction temperature is then allowed to rise, the methyl mercaptan being retained in the system by a dry-ice condenser. The reaction mixture is allowed to stand overnight and then is separated by distillation. The fraction boiling at 20 -50° C./15 millimeters is collected separately. Vapor phase chromatography analysis indicates purity of 69 percent. Redistillation at atmospheric pressure yields 16.5 grams of liquid boiling at 147°-149° C. and having purity of 95 percent.

Other thiols are treated similarly with ethyleneimine to obtain various thioethylamines as tabulated in table II. ##SPC10##

Polymeric peptizers are prepared by reacting products from examples 16-18 with maleic anhydride copolymers as follows.

EXAMPLE 19

Ten grams of an ethylene-maleic anhydride addition copolymer, obtained commercially from Monsanto Chemical Co. (Monsanto DX830-11) and containing approximately 50 mole percent maleic anhydride is dissolved in 80 milliliters of dimethylformamide at room temperature. To the solution is added 10 grams of 3-methylthiopropylamine. The solution turns deep violet and the temperature rises quickly to 53° C. After standing overnight at room temperature the solution has become nearly colorless. The product, copoly[ethylene-N-(3-methylthiopropyl)-maleamic acid], is precipitated in diethyl ether followed by drying in vacuo; it weighs 19.2 grams.

Similarly, the amine products tabulated in table II are reacted, respectively, with equimolar quantities of the same ethylene-maleic anhydride copolymer to produce the corresponding maleamic acid copolymers. Yields range from 81 percent yield for the 2-(2-diethylaminoethylthio)ethylamine reaction product to near 100 percent for the 2-ethylthioethylamine and 2-methylthioethylamine reaction products.

EXAMPLE 20

To a solution of 10 grams of a methyl vinyl ethermaleic anhydride copolymer (Gantrez 119, General Aniline & Film Corp.) in 80 milliliters of dimethylformamide is added 10 grams of 3-methylthio-1-carbomethyoxypropylamine (Helv. Chim. Acta, 36, 1114 (1953)). The resulting solution is allowed to stand for two days at room temperature and the product is then isolated by precipitation in diethyl ether. The precipitate is vacuum dried to obtain near 100 percent yield of the maleic acid amide copolymer.

EXAMPLE 21

Twenty grams of 3-(2-diethylaminoethylthio (example 17) and 10 grams of an ethylene maleic anhydride copolymer (Monsanto DX830 -11) are combined and kept at 60° overnight. The resulting pasty mass is dissolved in water and the solution is poured into acetone to precipitate the product, copoly[ethylene-maleic acid mono-3-(2-diethylaminoethylthio)propyl ester]. Yield, 17.4 grams after vacuum drying.

EXAMPLE 22

A silver halide emulsion is prepared as follows. A solution of 170 grams silver nitrate in 2070 milliliters of water is added over a period of 40 minutes to a solution containing 1,580 milliliters water, 125 grams of potassium bromide, 9.96 grams potassium iodide and 24 grams of copoly(ethylene-N-ethyl-thioethyl maleamic acid, sodium salt), prepared by the process described in example 19 above using 2-ethylthioethylamine. Temperature of the emulsion which has been kept at 66° C. throughout is lowered to 30° C. The resulting emulsion is coagulated by adding sufficient sulfuric acid to lower the pH to 3.65, then the soluble salts are removed by decantation. The coagulated emulsion is redispersed in 1,500 milliliters water containing sufficient sodium hydroxide to produce a pH of 6.0. The redispersed emulsion is again coagulated by reducing the pH to 2.6 with a dilute solution of sulfuric acid. Supernatant liquid is decanted and the coagulum is redispersed at 40° C. in a sufficient amount of dilute sodium hydroxide solution to bring the total weight of the dispersion to 1,200 grams and the pH to 6.0. A solution of 200 grams gelatin in 1,560 milliliters water is then added. The emulsion is digested and then coated on a film support at a coverage of 540 milligrams per square foot of silver and 1,000 milligrams per square foot of gelatin.

A strip of this film is exposed on an Eastman 1B sensitometer and developed for 5 minutes in Kodak Developer DK-50. This is a negative-speed film suitable for a variety of photographic applications, such as for ordinary camera photography.

All of the polymers prepared in examples 19-21 are used as peptizers in making respective emulsions as in Example 22 but substituting the respective peptizers. All produce well-dispersed silver halide emulsions suitable for photography.

In the foregoing examples, we have described embodiments of the invention using copolymers that contain units polymerized from a vinyl monomer which contains within its structure at least one sulfide sulfur atom linking two alkyl carbon atoms. In still further embodiments of the invention we make silver halide emulsions using peptizers which are addition copolymers of ethylenic monomers that have more than one such sulfide linkage in a single monomer unit. For example, we can use as peptizers in precipitation of silver halide grains for photographic emulsions, copolymers of the class described in the copending U.S. Pat. application Ser. No. 701,114 now U.S. Pat. No. 3,536,677 entitled POLYTHIAALKYL ACRYLATES AND ACRYLAMIDES AND COPOLYMERS CONTAINING SAME filed by Kenneth R. Hollister on even date with the present application and incorporated herein by reference. The aforesaid Hollister application describes acrylic acid esters and amides having the formula

wherein X is selected from --0--and --NH-- and R is a polythiaalkyl group containing two sulfide sulfur atoms separated by at least one carbon atom. Specific examples of such acrylic acid esters are

N-[2,2-bis(1-thiapropyl)ethyl]acrylamide,

N-(3,6-dithiaheptyl)acrylamide,

N-(3,6-dithiaoctyl)acryamide and

Bis(2-thiabutyl)methyl acrylate.

Acrylic acid esters and amides of the foregoing description containing a polythiaalkyl radical can be copolymerized with vinyl and other ethylenic monomers to produce a copolymer useful in accordance with the present invention. For example, the above-mentioned Hollister application describes copolymers of each of the acrylates and acrylamides listed above with 3-acryloyoxypropane-1-sulfonic acid sodium salt.

EXAMPLE 23--Poly[N-(3,6dithiaoctyl)acrylamide-co-3-acryloyl-oxypropane-1-sulfonic acid, sodium salt] (Molar ratio 1:15)

A solution of 21.9 grams (0.10 mole) of N-(3,6-dithiaoctyl)acrylamide, 324.0 grams of 3-acryloyloxpropane1-sulfonic acid sodium salt, and 1.73 grams of azobisisobutyronitrile in 1,384 milliliters of redistilled dimethyl sulfoxide is swept with nitrogen for 15 minutes and placed in 60° C. bath overnight. The polymer is then precipitated and thoroughly washed in a large excess of acetone, following which it is dried under vacuum at room temperature. The product is a brittle, white solid which weights 323.4 grams (93 percent yield).

A high-speed silver bromoiodide (94:6) negative emulsion is prepared similar to the type of emulsion described by Trivelli and Smith (Phot. J., Volume 79, page 330), except that the peptizer used is poly[N-(3,6-dithiaoctyl)acrylamide-co-3-acryloyloxypropane1-sulfonic acid, sodium salt] (molar ratio 1:15), prepared as described above. The emulsion obtained is completely free from clumps and consists of octahedral silver halide crystals ranging in size from 0.35-2.0 microns (diameter). The soluble slats are then removed from the emulsion by coagulation and redispersion and the emulsion is then dispersed in gelatin. This emulsion is digested to optimum speed and, after addition of conventional emulsion adjuvants, is coated on a cellulose acetate film support at a coverage 540 milligrams of silver and 1,000 milligrams of gelatin per square foot. A sample of this film coating is exposed on an Eastman 1B sensitometer, processed for 5 minutes in Kodak DK-50 developer, fixed, washed and dried. The following sensitometric values are measured: Gamma=0.72; Fog=0.12; Relative Speed 98 as compared with speed=100 for an emulsion prepared the same except using gelatin as a peptizer.

Copolymers of the kind just described, in which each of the sulfur-containing monomer units contains two sulfide sulfur atoms, are effective as peptizers with mole ratios of the sulfur-containing monomers to the other ethylenic comonomers from about 1:1 to as low as 1:27 in some embodiments and usually, in preferred embodiments, from about 1:12 to about 1:18. By way of comparison, the copolymers described earlier in which each sulfur-containing monomer contains a single sulfide sulfur atom, the useful mole ratios will range from about 1:1 to about 1:13.5 and most of the preferred embodiments will fall in the range from about 1:3 to about 1:12, all being mole ratios of sulfur-containing units to other units in the copolymer. Notice that the polythio units can be effective to lend the peptizing effect at lower molar concentrations in the copolymer than the units containing a single sulfide atom.

The optimum concentration of the peptizing agents of this invention in the preparation medium will depend upon several factors such as the selected temperature of the precipitation medium, the selected pH of the medium, silver and halide concentrations in the medium, etc. Generally, optimum concentrations of the peptizer will be low, usually from about 0.5 percent to about 3 percent by weight, and operable concentrations can range from about 0.25 percent to about 5 percent by weight, based on total weight of the aqueous medium.

Peptizers of this invention will be effective in any of the various precipitation method employed in photographic emulsion making such as the single jet method and the double jet method which are well known and described in photographic literature as well as in other less used methods.

Silver halide emulsions prepared using the peptizers of this invention can contain other hydraulic colloids added for the purpose of a film-forming binder or other purposes. In the examples we have added gelatin but other hydrophilic colloids such as polyvinyl alcohol, synthetic soluble polymers and copolymers of acrylic acid and esters and methacrylic acid and esters and the like can be added, either alone or in mixtures with other colloids including gelatin. Emulsions prepared in accordance with this invention can be sensitized chemically with any suitable chemical sensitizers or with combinations thereof, for example, with the conventional sulfur and gold sensitizing compounds alone or in combination, or with other known chemical sensitizers for silver halide emulsions. Silver halide emulsions made in accordance with this invention can be spectrally sensitized, either by panchromatic sensitizing as for black-and-white negative emulsions or sensitized to selected wavelengths for specialty products such as color (films and the like. Emulsions can be prepared in accordance with the invention for use in X-ray recording elements, gamma-ray recording elements, electron beam recording elements, for use in various color recording films and color printing elements, for use in conventional black-and-white photography and the like. Emulsions can be prepared in accordance with the invention using various grain growth restrainers for making fine grain emulsions, using any of various procedures for grain ripening and the like. Generally, emulsions prepared in accordance with this invention can be made that will compare favorably with almost any conventional or known gelatin-peptized emulsion, and in addition, the invention will provide new emulsions having properties not available in gelatin-peptized emulsions. Generally emulsions of this invention can be prepared and finished using any of the addenda, treatments, or procedures that are used in preparing and finishing other silver halide photographic emulsions.

In the foregoing detailed description certain preferred embodiments are described to show several most preferred modes of carrying out the invention and to further illustrate the broader scope of the invention by reference to several and various embodiments.

Although the invention has been described in detail with reference to certain preferred embodiments, variations and modifications can be affected within the spirit and scope of the invention as described hereinbefore and as defined in the appended claims.