Title:
SYNTHETIC SILVER HALIDE EMULSION BINDER
United States Patent 3861918
Abstract:
A photosensitive silver halide emulsion wherein the emulsion binder comprises a halogenated styrene polymer.
US Patent References:
Method of polymerizing vinylidene compounds in aqueous medium in the presence of silver ion and oxalate ion
Smith - June 1949 - 2473549
Hydrophilic compositions and their preparation
Fowler - November 1956 - 2772166
Water-dispersible protein polymer compositions and silver halide emulsions containing same
Dann et al. - April 1958 - 2831767
Coupler dispersions for color photography containing protein polymers
Illingsworth et al. - September 1958 - 2852382
Flocculated gelatine emulsions containing sulphonated copolymers of styrene
Himmehmann et al. - February 1965 - 3168403
Method of polymerizing vinylidene compounds in aqueous medium in the presence of silver ion and oxalate ion
Smith - June 1949 - 2473549
Hydrophilic compositions and their preparation
Fowler - November 1956 - 2772166
Water-dispersible protein polymer compositions and silver halide emulsions containing same
Dann et al. - April 1958 - 2831767
Coupler dispersions for color photography containing protein polymers
Illingsworth et al. - September 1958 - 2852382
Flocculated gelatine emulsions containing sulphonated copolymers of styrene
Himmehmann et al. - February 1965 - 3168403
Application Number:
05/339825
Publication Date:
01/21/1975
Filing Date:
03/09/1973
View Patent Images:
Export Citation:
Assignee:
Polaroid Corporation (Cambridge, MA)
Primary Class:
Other Classes:
526/293, 430/599, 430/570, 526/251, 430/630, 430/628
International Classes:
G03C1/053; G03C1/04
Field of Search:
96/87A,87P,114
US Patent References:
Primary Examiner:
Torchin, Norman G.
Assistant Examiner:
Brammer J. P.
Attorney, Agent or Firm:
Matthews, Mart C.
Claims:
What is claimed is
1. A photosensitive silver halide emulsion wherein the emulsion binder consists essentially of a water-soluble film-forming copolymer consisting of repeating units of a first monomer of the formula: ##SPC18##
2. The product as defined in claim 1 wherein said polymer comprises 1-80 mole percent of said repeating units.
3. The product as defined in claim 1 wherein said silver halide emulsion is a silver iodobromide emulsion.
4. The product as defined in claim 1 wherein said emulsion includes at least one chemical sensitizing agent.
5. The product as defined in claim 1 wherein said emulsion includes at least one optical sensitizing agent.
6. The product as defined in claim 1 wherein said first monomer is p-fluorostyrene.
7. The product as defined in claim 1 wherein said first monomer is o-chlorostyrene.
8. The product as defined in claim 1 wherein said first monomer is p-chlorostyrene.
9. The product as defined in claim 1 wherein said first monomer is o-iodostyrene.
10. The product as defined in claim 1 wherein said first monomer is 2,3,4,5,6-pentafluorostyrene.
11. The product as defined in claim 1 wherein said first monomer is 2-(pentafluorophenyl)-1-propene.
12. In a method of preparing a photosensitive silver halide emulsion wherein a water-soluble silver salt is reacted with a water-soluble halide salt in an aqueous solution of a silver halide peptizer, the improvement which comprises:
13. The method as defined in claim 12 wherein said first monomer is p-fluorostyrene.
14. The method as defined in claim 12 wherein said first monomer is o-chlorostyrene.
15. The method as defined in claim 12 wherein said first monomer is p-chlorostyrene.
16. The method as defined in claim 12 wherein said first monomer is o-iodostyrene.
17. The product as defined in claim 12 wherein said first monomer is 2,3,4,5,6-pentafluorostyrene.
18. The product as defined in claim 12 wherein said first monomer is 2-(pentafluorophenyl)-1-propene.
19. The method as defined in claim 17 which further comprises:
20. The method as defined in claim 19 wherein said bodying polymer is polyvinyl alcohol.
21. The method as defined in claim 19 wherein said bodying polymer is gelatin.
1. A photosensitive silver halide emulsion wherein the emulsion binder consists essentially of a water-soluble film-forming copolymer consisting of repeating units of a first monomer of the formula: ##SPC18##
2. The product as defined in claim 1 wherein said polymer comprises 1-80 mole percent of said repeating units.
3. The product as defined in claim 1 wherein said silver halide emulsion is a silver iodobromide emulsion.
4. The product as defined in claim 1 wherein said emulsion includes at least one chemical sensitizing agent.
5. The product as defined in claim 1 wherein said emulsion includes at least one optical sensitizing agent.
6. The product as defined in claim 1 wherein said first monomer is p-fluorostyrene.
7. The product as defined in claim 1 wherein said first monomer is o-chlorostyrene.
8. The product as defined in claim 1 wherein said first monomer is p-chlorostyrene.
9. The product as defined in claim 1 wherein said first monomer is o-iodostyrene.
10. The product as defined in claim 1 wherein said first monomer is 2,3,4,5,6-pentafluorostyrene.
11. The product as defined in claim 1 wherein said first monomer is 2-(pentafluorophenyl)-1-propene.
12. In a method of preparing a photosensitive silver halide emulsion wherein a water-soluble silver salt is reacted with a water-soluble halide salt in an aqueous solution of a silver halide peptizer, the improvement which comprises:
13. The method as defined in claim 12 wherein said first monomer is p-fluorostyrene.
14. The method as defined in claim 12 wherein said first monomer is o-chlorostyrene.
15. The method as defined in claim 12 wherein said first monomer is p-chlorostyrene.
16. The method as defined in claim 12 wherein said first monomer is o-iodostyrene.
17. The product as defined in claim 12 wherein said first monomer is 2,3,4,5,6-pentafluorostyrene.
18. The product as defined in claim 12 wherein said first monomer is 2-(pentafluorophenyl)-1-propene.
19. The method as defined in claim 17 which further comprises:
20. The method as defined in claim 19 wherein said bodying polymer is polyvinyl alcohol.
21. The method as defined in claim 19 wherein said bodying polymer is gelatin.
Description:
BACKGROUND OF THE INVENTION
This invention relates to photography and more particularly, to novel photosensitive photographic elements, particularly novel photosensitive emulsions.
As a result of the known disadvantages of gelatin, in particular, its variable photographic properties and its fixed physical properties, for example, its diffusion characteristics; much effort has been expended in the past in order to replace gelatin with a suitable synthetic colloid binder for photographic silver halide emulsions. Many synthetic polymeric materials have heretofore been suggested as peptizers for silver halide emulsions, however, these have generally not functioned satisfactorily and frequently have not fulfilled all of the basic requirements for a photosensitive silver halide emulsion binder listed following:
1. absent (or constant) photographic activity;
2. ability to form an adsorption layer on microcrystals silver siler halide permitting stable suspensions to be obtained;
3. ability to form adsorption layers as described in (2)) above which do not prevent growth of silver halide microcrystals during physical ripening; and
4. solubility in water solution.
In addition, hithertofore, much emphasis has been placed on the ability of the synthetic polymeric material to mix with gelatin, as this property has been critical for employment in partial substitution reactions with gelatin. Consequently, many synthetic polymers of the prior art have been materials which allow for the growth of silver halide crystals only in the presence of gelatin. For example, Fowler, U.S. Pat. No. 2,772,166, describes hydrosols comprising a mixture of styrene or acrylonitrile with an alkyl ester of acrylic acid or acrylic acid itself, and including a halogenated styrene hardening component. These hydrosols are claimed to be useful for addition to photographic gelatin solutions in order to impart flexibility and other advantageous properties to the hydrophilic colloid. However, they are not described as having the properties necessary to serve as a binder for photographic silver halide emulsions in the absence of gelatin.
SUMMARY OF THE INVENTION
The present invention is directed to a photosensitive silver halide emulsion wherein the silver halide crystals are disposed in a water-soluble synthetic binder comprising a film-forming polymer having in its structure repeating units represented by the formula: ##SPC1##
Wherein R 1 is hydrogen, a lower alkyl group, i.e., 1-4 carbon alkyl group, preferably methyl or ethyl, or a halogen, i.e., chloro, bromo, or iodo; R 2 is hydrogen, a lower alkyl group, a halogen or cyano group; and at least one X is a halogen with each remaining X being hydrogen or a halogen. A preferable embodiment of the invention comprises a silver halide emulsion wherein the emulsion binder is a copolymer having 1-80 mole percent of the above-indicated repeating units and 20-99 mole percent of repeating units derived from an ethylenically unsaturated comonomer, e.g., acrylamide. The above-described polymers are herein designated for convenience as halogenated styrene polymers.
If desired, the halogenated styrene polymer may comprise only a portion of the binder, the remainder constituting gelatin or a second synthetic polymer.
DETAILED DESCRIPTION OF THE INVENTION
As indicated, the present invention is directed to photosensitive silver halide emulsions wherein photosensitive silver halide crystals are disposed in a water-soluble synthetic binder comprising a film-forming halogenated styrene polymer having in its structure repeating units represented by the formula set forth above. The term "film-forming" is intended to designate a molecular weight sufficiently high to form a film, for example, a molecular weight comparable to that of gelatin (i.e., around 15,000).
Such polymers have been found to substantially meet all the basic requirements for a gelatin substitute, as delineated above. The emulsions of the present invention are more stable against degradation than gelatin; particularly against hydrolysis in acidic or basic media of the polymeric backbone. This stability is due, in large part, to the carbon-carbon linkages in the polymeric backbone of the instant polymers, as opposed to the relatively easily hydrolyzable ester or amide linkages found in the backbone of gelatin. These polymers also show a resistance to the growth of microorganisms.
As examples of monomers represented by the formula: ##SPC2##
wherein R 1 , R 2 and X have the above-indicated definitions and which are contemplated as being suitable for providing the halogenated styrene polymers, mention may be made of the following: ##SPC3##
Preferably, the instant polymers are interpolymers or copolymers having, in addition to the repeating units defined above, any compatible repeating unit or various repeating units which are not detrimental to photographic silver halide emulsions and which allow the resultant polymer to be soluble in water. Examples of typical comonomers which may be employed in forming the polymers suitable for use in the present invention include the following ethylenically-unsaturated monomers:
11. CH 2 =CH--COOH
acrylic acid ##SPC4##
15. CH 3 CH=CH--COOH
crotonic acid
16. CH 3 CH=CH--COOH
isocrotonic acid
17. Cl--CH=CH--COOH
β-chloroacrylic acid
18. Br--CH=CH--COOH
β-bromoacrylic acid ##SPC5##
20. CH 2 =CH--COO--CH 3
methyl acrylate ##SPC6##
25. CH 2 =CH--COO--CH 2 CH 2 OH
β-hydroxyethyl acrylate
26. CH 2 =CH--COO--CH 2 CH 2 CH 2 OH
γ-hydroxypropyl acrylate ##SPC7##
28. CH 2 =CH--CO--NH 2
acrylamide ##SPC8##
35. CH 3 CH=CH--CO--NH 2
crotonamide ##SPC9##
42. CH 2 =CH--CO--NH--CH 2 OH
N-methylolacrylamide
43. CH 2 =CH--CO--NH--CH 2 CH 2 OH
N-(β-hydroxyethyl) acrylamide ##SPC10##
47. CH 2 =CH--O--CH 3
methylvinyl ether ##SPC11##
49. CH 2 =CH--O--CH 2 CH 2 Cl
β-chloroethyl vinyl ether
50. CH 2 =CH--O--CH 2 CH 2 --OCH 3
β-methoxyethyl vinyl ether ##SPC12##
58. CH 2 =CH--CHO
acrolein
59. CH 3 --CH=CH--CHO
crotonaldehyde ##SPC13##
69. CH 2 =CH--CO--NH--CH 2 --CO--NH 2
acrylamidoacetamide ##SPC14##
75. CH 2 =CH--CO--NH--CH 2 --NH--CO--CH 3
N-(acetamidomethyl)acrylamide ##SPC15##
79. HOOC--CH=CH--COOH
maleic acid
80. HOOC--CH=CH--CO--NH 2
maleic acid amide
81. HOOC--CH=CH--CO--NH--CH 2 CH 3
N-ethylmaleic acid amide
82. CH 3 --OOC--CH=CH--CO--NH--CH 3
M-methylmethylmaleate amide
83. CH 2 =CH--OOCH
vinylformate
84. CH 2 =CH--OOC--CH 3
vinyl acetate ##SPC16##
99. CH 2 =CH--CO--NH--CH 2 CH 3
N-ethylacrylamide ##SPC17##
Polymerization of the indicated monomers is achieved by conventional free radical polymerization techniques.
The following non-limiting examples illustrate the preparation of polymers within the scope of the present invention. The numerical ratio before the word copolymer in each of the following examples refers to the molar ratio of monomers in the copolymer as determined by combustion analysis.
EXAMPLE I
17.2 copolymer of acrylamide/p-fluorostyrene
7.11 g. of acrylamide, 1.22 g. of p-fluorostyrene (commercially available from PCR, Inc., Gainesville, Fla. under the designation 11280) and 0.01 g. of 2,2'-azobis-[2-methyl-propionitrile]catalyst were dissolved in 80 ml. of dimethylformamide. This solution was polymerized in a sealed tube at 65° C. for 12 hours under N 2 . The result was a white paste which was filtered and dried under vacuum at 45° C. for 12 hours.
EXAMPLE II
11:2 copolymer of acrylamide/o-chlorostyrene
The procedure of Example I was followed, except that 3.46 g. of o-chlorostyrene (commercially available from Dow Chemical Company, Midland, Mich. under the designation QX-2184) was employed as the halogenated styrene monomer.
EXAMPLE III
27:2 copolymer of acrylamide/p-chlorostyrene
The procedure of Example I was followed, except that 2.77 g. of p-chlorostyrene (commercially available from Polysciences, Inc., Warrington, Pa. was employed as the halogenated styrene monomer.
EXAMPLE IV
13:1 copolymer of acrylamide/o-iodostyrene
The procedure of Example I was followed, except that 2.30 g. of o-iodostyrene (commercially available from Polysciences, Inc., Warrington, Pa. was employed as the halogenated styrene monomer.
EXAMPLE V
15:1 copolymer of acrylamide/pentafluorostyrene
The procedure of Example I was followed, except that 1.94 g. of 2,3,4,5,6-pentafluorostyrene (commercially available from Aldrich Chemical Company, Inc., Milwaukee, Wis. under the designation 10,396-9) was employed as the halogenated styrene monomer.
EXAMPLE VI
22:1 copolymer of acrylamide/2-(pentafluorophenyl)-1-propene
The procedure of Example I was followed except that 2.08 g. of 2-(pentafluorophenyl)-1-propene (commercially available from Aldrich Chemical Company, Inc., Milwaukee, Wis., under the designation 10,338-1) was employed as the halogenated styrene monomer.
The following general procedure may be used for preparing photographic emulsions using the above-described polymers of the instant invention as the colloid binders.
A water-soluble silver salt, such as silver nitrate, may be reacted with at least one water-soluble halide, such as potassium, sodium, or ammonium bromide, preferably together with potassium, sodium or ammonium iodide, in an aqueous solution of the polymer. The emulsion of silver halide thus-formed contains water-soluble salts, as a by-product of the double decomposition reaction, in addition to any unreacted excess of the initial salts. To remove these soluble materials, the emulsion may be centrifuged and washed with distilled water to a low conductance. The emulsion may then be redispersed in distilled water. To an aliquot of this emulsion may be added a known quantity of a solution of bodying or thickening polymer, such as polyvinyl alcohol having an average molecular weight of about 100,000 (commercially available from E. I. duPont deNemours & Company, Wilmington, Del., designated Type 72-60). A surfactant, such as dioctyl ester of sodium sulfosuccinic acid, designated Aerosol OT, (commercially available from American Cyanamid Company, New York, N.Y.), may be added and the emulsion coated onto a film base of cellulose triacetate sheet having a coating of hardened gelatin.
Alternatively, the soluble salts may be removed by adding to the emulsion a solution of polyacid, such as 1:1 ethylene: maleic acid copolymer, and lowering the pH to below 5, thereby bringing about precipitation of the polyacid carrying the silver halide grains along with the precipitate. The resulting precipitate may then be washed and resuspended by redissolving the polyacid at pH 6-7.
The emulsions may be chemically sensitized with sulfur compounds such as sodium thiosulfate or thiourea, with reducing substances such as stannous chloride; with salts of noble metals such as gold, rhodium and platinum; with amines and polyamines; with quaternary ammonium compounds such as alkyl α-picolinium bromide; and with polyethylene glycols and derivatives thereof.
The emulsions of the present invention may also be optically sensitized with cyanine and merocyanine dyes. Where desired, suitable antifoggants, toners, restrainers, developers, accelerators, preservatives, coating aids, plasticizers, hardeners and/or stabilizers may be included in the composition of the emulsion.
The emulsions of this invention may be coated and processed according to conventional procedures of the art. They may be coated, for example, onto various types of rigid or flexible supports, such as glass, paper, metal, and polymeric films of both the synthetic type and those derived from naturally occurring products. As examples of specific materials which may serve as supports, mention may be made of paper, aluminum, polymethacrylic acid, methyl and ethyl esters, vinylchloride polymers, polyvinyl acetal, polyamides such as nylon, polyesters such as polymeric film derived from ethylene glycol-terephthalic acid, and cellulose derivatives such as cellulose acetate, triacetate, nitrate, propionate, butyrate, acetate propionate, and acetate butyrate. Suitable subcoats may be provided on the supports, for example a layer of gelatin, if necessary or desirable for adherence, as is well known in the art.
The polymers employed in the practice of the instant invention preferably contain from 1-80 mole percent of the above-indicated repeating units. The specific amount employed may be selected by the operator depending upon the grain particle size and habit desired.
By selecting appropriate comonomers, the instant copolymers may be made to be compatible with all water-soluble bodying polymers. Emulsions made from these novel polymers, may be bodied with any water-soluble polymers, overcoming the disadvantage encountered with gelatin which is only compatible with a very few polymers in a most limited pH range. As examples of specific materials which may serve as bodying polymers are gelatin, polyvinyl alcohol, polyacrylamide, polyalkylacrylamides, polyvinyl pyrrolidone, polymethacrylamidoacetamide, vinyl alcohol/N-vinylpyrrolidone copolymers, poly-N-ethylaziridine, poly-N-(2-hydroxyethyl) aziridine, poly-N-(2-cyanoethyl) aziridine, poly(β-hydroxyethyl acrylate), polyethylene imine and cellulose derivatives such as hydroxyethyl cellulose, hydroxypropyl cellulose and methyl cellulose. It has been found that using only a small amount of one or more of the instant polymers, large amounts of photosensitive silver halide grains may be obtained.
An emulsion made from one of these polymers of the instant invention may therefore be bodied with a water-soluble polymer such that the polymeric constitution of the resulting emulsion comprises a relatively large percentage of the bodying polymer.
By selecting appropriate comonomers, copolymers with selected diffusion characteristics may be prepared. For example, the rate of diffusion of alkali ion or a dye-developer through an emulsion comprising one of the polymers of this invention may be modified by varying the composition of the polymer.
The instant polymers containing acidic comonomers may be pH flocculated in order to remove the soluble salts formed as a byproduct of the double decomposition reaction between the water-soluble silver salt and the water-soluble halide, in addition to any unreacted excess of the initial salts. As an example, an acid copolymer may be precipitated by lowering the pH below 5 and then washed and resuspended by raising the pH to above 7.
The instant invention will be further illustrated by reference to the following non-limiting examples.
EXAMPLE VII
A solution of 4.15 g. of a dry 17:2 copolymer of acrylamide/p-fluorostyrene as prepared in Example I above, in 266 ml. of distilled water was adjusted to pH 3.0 with dilute nitric acid and maintained at a temperature of 55° C. To this solution, 88.0 g. of dry potassium bromide and 1.0 g of dry potassium iodide were added.
A solution of 55 g. of silver nitrate in 500 ml. of distilled water was prepared. From this silver nitrate solution, 100 ml. was rapidly added with continuous agitation to the polymer-halide solution and the remainder was added over a period of 22 minutes. Thereafter, the emulsion was ripened for 60 minutes at 55° C., and then rapidly cooled to below 20° C.
EXAMPLES VIII - XII
Additional emulsions were also prepared according to the procedure of Example VII employing the copolymers prepared in Examples II - VI as the emulsion binders.
EXAMPLE XIII (control)
A control emulsion employing gelatin as the emulsion binder was prepared by the following procedure:
A solution of 4.15 g. of the dry gelatin in 266 ml. of distilled water was adjusted to pH 6.3 with dilute nitric acid and maintained at a temperature of 55° C. To this solution, 44.0 g. of dry potassium bromide and 0.50 g. of dry potassium iodide were added.
A solution of 55 g. of silver nitrate in 500 ml. of distilled water was prepared. From this silver nitrate solution, 100 ml. was rapidly added with continuous agitation to the gelatin-halide solution and the remainder was added over a period of 22 minutes. Thereafter, the emulsion was ripened for 30 minutes at 55° C., and then rapidly cooled to below 20° C.
The following table summarizes the silver halide grain sizes obtained in the emulsions prepared above, all of which contained octahedral platelet crystals.
TABLE 1 ______________________________________ Approximate grain size (microns) Example Polymer range average ______________________________________ VII 17:2 acrylamide/p- 0.4-3.4 1.0 fluorostyrene VIII 11:2 acrylamide/o- -- 0.7 chlorostyrene IX 27:2 acrylamide/p- -- 0.8 chlorostyrene X 13:1 acrylamide/o- -- 1.0 iodosytrene XI 15:1 acrylamide/penta- 0.4-4.6 1.1 fluorostyrene XII 22:1 acrylamide/2-(penta- 0.4-3.6 1.4 fluorophenyl)-1-propene XIII gelatin 0.2-1.8 1.0 ______________________________________
In certain photographic applications, it may be desirable to replace part, but not all, of the gelatin in the photosensitive emulsion. In view of the characteristics of these polymers described above, and further, in view of their compatability with gelatin in substantially all proportions, it will be obvious that these polymers are ideally suited for such use.
The term photosensitive and other terms of similar import are herein employed in the generic sense to describe materials possessing physical and chemical properties which enable them to form usable images when photoexposed by radiation actinic to silver halide.
Since certain changes may be made in the above products and processes without departing from the scope of the invention herein involved, it is intended that all matter contained in the above description shall be interpreted as illustrative only and not in a limiting sense.
This invention relates to photography and more particularly, to novel photosensitive photographic elements, particularly novel photosensitive emulsions.
As a result of the known disadvantages of gelatin, in particular, its variable photographic properties and its fixed physical properties, for example, its diffusion characteristics; much effort has been expended in the past in order to replace gelatin with a suitable synthetic colloid binder for photographic silver halide emulsions. Many synthetic polymeric materials have heretofore been suggested as peptizers for silver halide emulsions, however, these have generally not functioned satisfactorily and frequently have not fulfilled all of the basic requirements for a photosensitive silver halide emulsion binder listed following:
1. absent (or constant) photographic activity;
2. ability to form an adsorption layer on microcrystals silver siler halide permitting stable suspensions to be obtained;
3. ability to form adsorption layers as described in (2)) above which do not prevent growth of silver halide microcrystals during physical ripening; and
4. solubility in water solution.
In addition, hithertofore, much emphasis has been placed on the ability of the synthetic polymeric material to mix with gelatin, as this property has been critical for employment in partial substitution reactions with gelatin. Consequently, many synthetic polymers of the prior art have been materials which allow for the growth of silver halide crystals only in the presence of gelatin. For example, Fowler, U.S. Pat. No. 2,772,166, describes hydrosols comprising a mixture of styrene or acrylonitrile with an alkyl ester of acrylic acid or acrylic acid itself, and including a halogenated styrene hardening component. These hydrosols are claimed to be useful for addition to photographic gelatin solutions in order to impart flexibility and other advantageous properties to the hydrophilic colloid. However, they are not described as having the properties necessary to serve as a binder for photographic silver halide emulsions in the absence of gelatin.
SUMMARY OF THE INVENTION
The present invention is directed to a photosensitive silver halide emulsion wherein the silver halide crystals are disposed in a water-soluble synthetic binder comprising a film-forming polymer having in its structure repeating units represented by the formula: ##SPC1##
Wherein R 1 is hydrogen, a lower alkyl group, i.e., 1-4 carbon alkyl group, preferably methyl or ethyl, or a halogen, i.e., chloro, bromo, or iodo; R 2 is hydrogen, a lower alkyl group, a halogen or cyano group; and at least one X is a halogen with each remaining X being hydrogen or a halogen. A preferable embodiment of the invention comprises a silver halide emulsion wherein the emulsion binder is a copolymer having 1-80 mole percent of the above-indicated repeating units and 20-99 mole percent of repeating units derived from an ethylenically unsaturated comonomer, e.g., acrylamide. The above-described polymers are herein designated for convenience as halogenated styrene polymers.
If desired, the halogenated styrene polymer may comprise only a portion of the binder, the remainder constituting gelatin or a second synthetic polymer.
DETAILED DESCRIPTION OF THE INVENTION
As indicated, the present invention is directed to photosensitive silver halide emulsions wherein photosensitive silver halide crystals are disposed in a water-soluble synthetic binder comprising a film-forming halogenated styrene polymer having in its structure repeating units represented by the formula set forth above. The term "film-forming" is intended to designate a molecular weight sufficiently high to form a film, for example, a molecular weight comparable to that of gelatin (i.e., around 15,000).
Such polymers have been found to substantially meet all the basic requirements for a gelatin substitute, as delineated above. The emulsions of the present invention are more stable against degradation than gelatin; particularly against hydrolysis in acidic or basic media of the polymeric backbone. This stability is due, in large part, to the carbon-carbon linkages in the polymeric backbone of the instant polymers, as opposed to the relatively easily hydrolyzable ester or amide linkages found in the backbone of gelatin. These polymers also show a resistance to the growth of microorganisms.
As examples of monomers represented by the formula: ##SPC2##
wherein R 1 , R 2 and X have the above-indicated definitions and which are contemplated as being suitable for providing the halogenated styrene polymers, mention may be made of the following: ##SPC3##
Preferably, the instant polymers are interpolymers or copolymers having, in addition to the repeating units defined above, any compatible repeating unit or various repeating units which are not detrimental to photographic silver halide emulsions and which allow the resultant polymer to be soluble in water. Examples of typical comonomers which may be employed in forming the polymers suitable for use in the present invention include the following ethylenically-unsaturated monomers:
11. CH 2 =CH--COOH
acrylic acid ##SPC4##
15. CH 3 CH=CH--COOH
crotonic acid
16. CH 3 CH=CH--COOH
isocrotonic acid
17. Cl--CH=CH--COOH
β-chloroacrylic acid
18. Br--CH=CH--COOH
β-bromoacrylic acid ##SPC5##
20. CH 2 =CH--COO--CH 3
methyl acrylate ##SPC6##
25. CH 2 =CH--COO--CH 2 CH 2 OH
β-hydroxyethyl acrylate
26. CH 2 =CH--COO--CH 2 CH 2 CH 2 OH
γ-hydroxypropyl acrylate ##SPC7##
28. CH 2 =CH--CO--NH 2
acrylamide ##SPC8##
35. CH 3 CH=CH--CO--NH 2
crotonamide ##SPC9##
42. CH 2 =CH--CO--NH--CH 2 OH
N-methylolacrylamide
43. CH 2 =CH--CO--NH--CH 2 CH 2 OH
N-(β-hydroxyethyl) acrylamide ##SPC10##
47. CH 2 =CH--O--CH 3
methylvinyl ether ##SPC11##
49. CH 2 =CH--O--CH 2 CH 2 Cl
β-chloroethyl vinyl ether
50. CH 2 =CH--O--CH 2 CH 2 --OCH 3
β-methoxyethyl vinyl ether ##SPC12##
58. CH 2 =CH--CHO
acrolein
59. CH 3 --CH=CH--CHO
crotonaldehyde ##SPC13##
69. CH 2 =CH--CO--NH--CH 2 --CO--NH 2
acrylamidoacetamide ##SPC14##
75. CH 2 =CH--CO--NH--CH 2 --NH--CO--CH 3
N-(acetamidomethyl)acrylamide ##SPC15##
79. HOOC--CH=CH--COOH
maleic acid
80. HOOC--CH=CH--CO--NH 2
maleic acid amide
81. HOOC--CH=CH--CO--NH--CH 2 CH 3
N-ethylmaleic acid amide
82. CH 3 --OOC--CH=CH--CO--NH--CH 3
M-methylmethylmaleate amide
83. CH 2 =CH--OOCH
vinylformate
84. CH 2 =CH--OOC--CH 3
vinyl acetate ##SPC16##
99. CH 2 =CH--CO--NH--CH 2 CH 3
N-ethylacrylamide ##SPC17##
Polymerization of the indicated monomers is achieved by conventional free radical polymerization techniques.
The following non-limiting examples illustrate the preparation of polymers within the scope of the present invention. The numerical ratio before the word copolymer in each of the following examples refers to the molar ratio of monomers in the copolymer as determined by combustion analysis.
EXAMPLE I
17.2 copolymer of acrylamide/p-fluorostyrene
7.11 g. of acrylamide, 1.22 g. of p-fluorostyrene (commercially available from PCR, Inc., Gainesville, Fla. under the designation 11280) and 0.01 g. of 2,2'-azobis-[2-methyl-propionitrile]catalyst were dissolved in 80 ml. of dimethylformamide. This solution was polymerized in a sealed tube at 65° C. for 12 hours under N 2 . The result was a white paste which was filtered and dried under vacuum at 45° C. for 12 hours.
EXAMPLE II
11:2 copolymer of acrylamide/o-chlorostyrene
The procedure of Example I was followed, except that 3.46 g. of o-chlorostyrene (commercially available from Dow Chemical Company, Midland, Mich. under the designation QX-2184) was employed as the halogenated styrene monomer.
EXAMPLE III
27:2 copolymer of acrylamide/p-chlorostyrene
The procedure of Example I was followed, except that 2.77 g. of p-chlorostyrene (commercially available from Polysciences, Inc., Warrington, Pa. was employed as the halogenated styrene monomer.
EXAMPLE IV
13:1 copolymer of acrylamide/o-iodostyrene
The procedure of Example I was followed, except that 2.30 g. of o-iodostyrene (commercially available from Polysciences, Inc., Warrington, Pa. was employed as the halogenated styrene monomer.
EXAMPLE V
15:1 copolymer of acrylamide/pentafluorostyrene
The procedure of Example I was followed, except that 1.94 g. of 2,3,4,5,6-pentafluorostyrene (commercially available from Aldrich Chemical Company, Inc., Milwaukee, Wis. under the designation 10,396-9) was employed as the halogenated styrene monomer.
EXAMPLE VI
22:1 copolymer of acrylamide/2-(pentafluorophenyl)-1-propene
The procedure of Example I was followed except that 2.08 g. of 2-(pentafluorophenyl)-1-propene (commercially available from Aldrich Chemical Company, Inc., Milwaukee, Wis., under the designation 10,338-1) was employed as the halogenated styrene monomer.
The following general procedure may be used for preparing photographic emulsions using the above-described polymers of the instant invention as the colloid binders.
A water-soluble silver salt, such as silver nitrate, may be reacted with at least one water-soluble halide, such as potassium, sodium, or ammonium bromide, preferably together with potassium, sodium or ammonium iodide, in an aqueous solution of the polymer. The emulsion of silver halide thus-formed contains water-soluble salts, as a by-product of the double decomposition reaction, in addition to any unreacted excess of the initial salts. To remove these soluble materials, the emulsion may be centrifuged and washed with distilled water to a low conductance. The emulsion may then be redispersed in distilled water. To an aliquot of this emulsion may be added a known quantity of a solution of bodying or thickening polymer, such as polyvinyl alcohol having an average molecular weight of about 100,000 (commercially available from E. I. duPont deNemours & Company, Wilmington, Del., designated Type 72-60). A surfactant, such as dioctyl ester of sodium sulfosuccinic acid, designated Aerosol OT, (commercially available from American Cyanamid Company, New York, N.Y.), may be added and the emulsion coated onto a film base of cellulose triacetate sheet having a coating of hardened gelatin.
Alternatively, the soluble salts may be removed by adding to the emulsion a solution of polyacid, such as 1:1 ethylene: maleic acid copolymer, and lowering the pH to below 5, thereby bringing about precipitation of the polyacid carrying the silver halide grains along with the precipitate. The resulting precipitate may then be washed and resuspended by redissolving the polyacid at pH 6-7.
The emulsions may be chemically sensitized with sulfur compounds such as sodium thiosulfate or thiourea, with reducing substances such as stannous chloride; with salts of noble metals such as gold, rhodium and platinum; with amines and polyamines; with quaternary ammonium compounds such as alkyl α-picolinium bromide; and with polyethylene glycols and derivatives thereof.
The emulsions of the present invention may also be optically sensitized with cyanine and merocyanine dyes. Where desired, suitable antifoggants, toners, restrainers, developers, accelerators, preservatives, coating aids, plasticizers, hardeners and/or stabilizers may be included in the composition of the emulsion.
The emulsions of this invention may be coated and processed according to conventional procedures of the art. They may be coated, for example, onto various types of rigid or flexible supports, such as glass, paper, metal, and polymeric films of both the synthetic type and those derived from naturally occurring products. As examples of specific materials which may serve as supports, mention may be made of paper, aluminum, polymethacrylic acid, methyl and ethyl esters, vinylchloride polymers, polyvinyl acetal, polyamides such as nylon, polyesters such as polymeric film derived from ethylene glycol-terephthalic acid, and cellulose derivatives such as cellulose acetate, triacetate, nitrate, propionate, butyrate, acetate propionate, and acetate butyrate. Suitable subcoats may be provided on the supports, for example a layer of gelatin, if necessary or desirable for adherence, as is well known in the art.
The polymers employed in the practice of the instant invention preferably contain from 1-80 mole percent of the above-indicated repeating units. The specific amount employed may be selected by the operator depending upon the grain particle size and habit desired.
By selecting appropriate comonomers, the instant copolymers may be made to be compatible with all water-soluble bodying polymers. Emulsions made from these novel polymers, may be bodied with any water-soluble polymers, overcoming the disadvantage encountered with gelatin which is only compatible with a very few polymers in a most limited pH range. As examples of specific materials which may serve as bodying polymers are gelatin, polyvinyl alcohol, polyacrylamide, polyalkylacrylamides, polyvinyl pyrrolidone, polymethacrylamidoacetamide, vinyl alcohol/N-vinylpyrrolidone copolymers, poly-N-ethylaziridine, poly-N-(2-hydroxyethyl) aziridine, poly-N-(2-cyanoethyl) aziridine, poly(β-hydroxyethyl acrylate), polyethylene imine and cellulose derivatives such as hydroxyethyl cellulose, hydroxypropyl cellulose and methyl cellulose. It has been found that using only a small amount of one or more of the instant polymers, large amounts of photosensitive silver halide grains may be obtained.
An emulsion made from one of these polymers of the instant invention may therefore be bodied with a water-soluble polymer such that the polymeric constitution of the resulting emulsion comprises a relatively large percentage of the bodying polymer.
By selecting appropriate comonomers, copolymers with selected diffusion characteristics may be prepared. For example, the rate of diffusion of alkali ion or a dye-developer through an emulsion comprising one of the polymers of this invention may be modified by varying the composition of the polymer.
The instant polymers containing acidic comonomers may be pH flocculated in order to remove the soluble salts formed as a byproduct of the double decomposition reaction between the water-soluble silver salt and the water-soluble halide, in addition to any unreacted excess of the initial salts. As an example, an acid copolymer may be precipitated by lowering the pH below 5 and then washed and resuspended by raising the pH to above 7.
The instant invention will be further illustrated by reference to the following non-limiting examples.
EXAMPLE VII
A solution of 4.15 g. of a dry 17:2 copolymer of acrylamide/p-fluorostyrene as prepared in Example I above, in 266 ml. of distilled water was adjusted to pH 3.0 with dilute nitric acid and maintained at a temperature of 55° C. To this solution, 88.0 g. of dry potassium bromide and 1.0 g of dry potassium iodide were added.
A solution of 55 g. of silver nitrate in 500 ml. of distilled water was prepared. From this silver nitrate solution, 100 ml. was rapidly added with continuous agitation to the polymer-halide solution and the remainder was added over a period of 22 minutes. Thereafter, the emulsion was ripened for 60 minutes at 55° C., and then rapidly cooled to below 20° C.
EXAMPLES VIII - XII
Additional emulsions were also prepared according to the procedure of Example VII employing the copolymers prepared in Examples II - VI as the emulsion binders.
EXAMPLE XIII (control)
A control emulsion employing gelatin as the emulsion binder was prepared by the following procedure:
A solution of 4.15 g. of the dry gelatin in 266 ml. of distilled water was adjusted to pH 6.3 with dilute nitric acid and maintained at a temperature of 55° C. To this solution, 44.0 g. of dry potassium bromide and 0.50 g. of dry potassium iodide were added.
A solution of 55 g. of silver nitrate in 500 ml. of distilled water was prepared. From this silver nitrate solution, 100 ml. was rapidly added with continuous agitation to the gelatin-halide solution and the remainder was added over a period of 22 minutes. Thereafter, the emulsion was ripened for 30 minutes at 55° C., and then rapidly cooled to below 20° C.
The following table summarizes the silver halide grain sizes obtained in the emulsions prepared above, all of which contained octahedral platelet crystals.
TABLE 1 ______________________________________ Approximate grain size (microns) Example Polymer range average ______________________________________ VII 17:2 acrylamide/p- 0.4-3.4 1.0 fluorostyrene VIII 11:2 acrylamide/o- -- 0.7 chlorostyrene IX 27:2 acrylamide/p- -- 0.8 chlorostyrene X 13:1 acrylamide/o- -- 1.0 iodosytrene XI 15:1 acrylamide/penta- 0.4-4.6 1.1 fluorostyrene XII 22:1 acrylamide/2-(penta- 0.4-3.6 1.4 fluorophenyl)-1-propene XIII gelatin 0.2-1.8 1.0 ______________________________________
In certain photographic applications, it may be desirable to replace part, but not all, of the gelatin in the photosensitive emulsion. In view of the characteristics of these polymers described above, and further, in view of their compatability with gelatin in substantially all proportions, it will be obvious that these polymers are ideally suited for such use.
The term photosensitive and other terms of similar import are herein employed in the generic sense to describe materials possessing physical and chemical properties which enable them to form usable images when photoexposed by radiation actinic to silver halide.
Since certain changes may be made in the above products and processes without departing from the scope of the invention herein involved, it is intended that all matter contained in the above description shall be interpreted as illustrative only and not in a limiting sense.