Patent Publication Number: US-3879205-A

Title: Method of preparing photosensitive silver halide emulsions

Description:
United States Patent 1191 Fitzgerald et al.  
 [ METHOD OF PREPARING PHOTOSENSITIVE SILVER HALIDE EMULSIONS [75] Inventors: Maurice J. Fitzgerald, Canton:  
 Lloyd D. Taylor. Lexington. both of Mass.  
 [73] Assignee: Polaroid Corporation, Cambridge.  
 Mass.  
 [22] Filed: Aug. 23, 1973 [211 Appl. No.: 390,767  
 Related US. Application Data [63] Continuation-impart of Ser. No. 187,852. Oct. 8,  
 1971, abandoned.  
 [52] US. Cl 96/114; 96/94 [5 1] Int. Cl. G03c 1/04 1 Apr. 22, 1975 Primary E.\&#39;amt&#39;nerRonald H. Smith Attorney, Agent, or FirmPhilip G. Kiely; Mart C. Matthews [57] ABSTRACT A photosensitive silver halide emulsion wherein the emulsion binder comprises an amine-acrylamide polymer or copolymer.  
 9 Claims, No Drawings METHOD OF PREPARING PHOTOSENSITIVE SILVER HALIDE EMULSIONS CROSS-REFERENCE TO OTHER APPLICATIONS This application is a continuation-in-part of U5. application Ser. No. 187,852, filed Oct. 8, I971, now abandoned.  
 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 of silver 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.  
  A class of synthetic polymers has now been found which is not susceptible to the deficiencies of the prior art and which may replace gelatin entirely in photosensitive silver halide emulsions.  
 SUMMARY OF THE INVENTION The present invention is directed to a photosensitive silver halide emulsion wherein the silver halide crystals are disposed in a synthetic polymeric binder comprising a polymer having in its structure repeating units represented by the formula:  
 wherein R is hydrogen, lower alkyl group, e.g., 1-4 carbon alkyl group, preferably methyl or ethyl, or halogen, e.g., chloro, bromo, or iodo; R is hydrogen, lower alkyl, e.g., 1-4 carbon alkyl, halogen or cyano; R R and R each is hydrogen, lower alkyl or cycloalkyl;  
  Y is lower alkylene or cycloalkylene, e.g., 1-4 carbon atoms; and n is a positive integer greater than 1. In an alternative embodiment, the above-described polymer comprises only a portion of the binder, the remainder constituting gelatin or a second synthetic polymer.  
 DETAILED DESCRIPTION OF THE INVENTION The present invention is directed to photosensitive silver halide emulsions wherein photosensitive silver halide crystals are disposed in a synthetic polymer binder comprising a polymer having in&#39;its structure repeating units represented by the formula:  
 wherein R, is hydrogen, lower alkyl group, e.g., 1-4 carbon alkyl group, preferably methyl or ethyl, or halogen, e.g.,chloro, bromo or iodo; R is hydrogen, lower alkyl, e.g., 1-4 carbon alkyl, halogen or cyano; r;,, R, and R each is hydrogen, lower alkyl, or cycloalkyl; Y is lower alkylene or cycloalkylene, e.g., 1-6 carbon atoms; and n is a positive integer greater than 1.  
  Such polymers have been found to substantially provide all of the basic requirements for a gelatin substitute, as delineated above. The emulsions of the present invention are readily sensitized by conventional sensitizing agents and are characterized by excellent latent image stability and excellent film speed. In addition, the emulsions of the present invention are more stable against degradation, particularly hydrolysis and the growth of microorganisms than gelatin.  
  As examples of monomers represented by the formula:  
 suitable for providing the amine-acrylamide polymers, mention may be made of the following:  
 N-[3-(dimethylamin0methy1)cyclobutyllacrylamide N-(n-propyD-N-(ethylmethylaminomethyl)-,3-bromo-methacrylamide N -cyelopropyl-N -[2- (isopropylamino) prop-2-yl]acrylamidc Hz Hz C H2 C H3 N- (n-butyl) -N- (cyclopropylaminomethyl) acrylamide N -cyclobuty1-N-[fl-(cyclobutylmethylamino)ethyllmethacrylamide N -[2&#39;-(dimethylamino)cyclopropyllacrylamide The instant polymers may be homopolymers or interpolymers 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:  
 (14) CH2=CH-COOH acrylic acid C HF-C O O H methacrylic acid GH2=( 3C O OH a-chloroacrylic acid 0 H2=( J-C O 0 H a-bromoacrylic acid (18) CHaCH=CH-COOH crotonic acid CHaCH=CH-COOH isocrotonic acid (20) ClCH=CH-COOH fi-ehloroacrylic acid BrCH=CH-OOOH B-bromoacrylic acid Cl-OH=OO O OH fl-chloromethacrylic acid (23) CH2=CH-CO O-CH3 methyl acrylate (24) C Ha CHz --C O OCH2CH3 ethyl methacrylate CHz=( ]C O O-GHzCH-zCHg n-propyl-a-chlcroacrylate (26) BrCH=CHCOOCH CH isopropyl-fl-bromoacrylate CH2=(JC O O-CH2CHOHa) isobutyl methacrylatc (28) CH=CHCOOCH2CH2OH B-hydroxyethyl acrylate (29) CHz=CHCOO-CH2CH2CH2OH a-hydroxypropyl acrylate CH=-C O O-CHzCHCHs 2-hydroxy-n-propyl methacrylate (31) OII2=CHC O-NH:  
 acrylamide C lIz 3C ONHz a-chloroacrylamide 2-crotonamido-N-methylpropionamide Z-acrylamidopropionamide CH3 CH3 Z-methacrylamidopropionamide Z-(a-chloroacrylamido )-3-methylbutyramide CH =CHCONH--CH NHCOCH N-(acetamidomethyl)acrylamide N-( propionamidomethyl)methacrylamide N-( n-butyramidomethyl)a-chloroacrylamide &#39;maleic anhydride (82) HOOCCH=CHCOOH maleic acid (83) HOOCCH=CHCO-NH maleic acid amide HOOCCH=CHCONHCH CH N-ethylmaleic acid amide (85) CH OOCCH=CHCONHCH N-methyl methylmaleate amide (86) CH2=CHOOCH vinylformate (87) CHz=CH-0 O C-C H3 vinyl acetate (88) CH2=CHOH (obtained by hydrolyzing copolymerized vinyl alcohol vinyl acetate) (89) CHFC0OCCH2BI isopropenyl bromoaeetate (90 CH2=CH-OOCC{CH3) vinyl pivalate a (91) CHz=GH-NHCOOC\CHa)3 N-vinyl-tertiary butylcarbamate (92) CHz=CCH2COO-CH2CHa C 0 OH ethyl-B-carboxy-Zi-butenato CHz=CH- OJ a-vinylfuran aacryloyloxymethyl tetrahydrofuran p-hydroxystyrene nl-hydroxystyrene C H 2: C H- l OH o-hydroxystyrone CH2=CH COOH p-carboxystyrene 0 0 H m-carboxystyrene C O OH o&#39;carhoxystyreno O N-VInyI-Z-pyrrolidone C 0 OH N-acryloy1valine C O OH N-acry1oylmethionine C O-NH: N-acryloylmethionamide Polymerization of the indicated monomers is achieved by conventional free radical polymerization techniques.  
  The following non-limiting example illustrates the preparation of polymers within the scope of the present invention.  
 EXAMPLE 2:1 copolymer of acrylamide/N-[B-(dimethylamino) ethyl]acrylamide 1 7.1 g. of acrylamide and 7.1 g. of N-[B- (dimethylamino) ethyl]acrylamide were added to 200 ml. of distilled water under nitrogen. The pH was adjusted to 6.3 with nitriclacid and then 0.03 g. of potassium persulfate and 0.03 g. of sodium bisulfite were added. The polymerization was carried out at 25 C. for  
 4 hours. The thus-formed polymer was precipitated into acetone, washed, dried and redissolved for use in making an emulsion.  
  Other polymers within the scope of the present invention were prepared by similar procedures. As illustrative examples of such polymers, mention may be made of:  
 1:1 N-ethylacrylamide/N-[B (dimethylamino)ethylIacrylamide 9:1 acrylamide/N-[B-(dimethylamino)ethyl]acrylamide :1 acrylamide/N-[B-(dimethylamino)ethyllacrylamide :9: 1 acrylamide/N-B-(dimethylamino)ethyl]acrylamide/N-acryloylvaline 3:1 N-isopropylacrylamide/N-[B-(dimethylamino) ethyl acrylamide 4:1 acrylamide/N-[B-(dimethylamino)ethyl]acrylamide l .65: 1 acrylamide/N-{fi- (diethylamino)methyl]acrylamide The following general procedure may be used for preparing photographic emulsions using the 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 above-described 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. l. duPont deNemours &amp; 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 slot coated onto a base of cellulose triacetate sheet 5 mls. thick having a coating of 30 mg./sq. ft. of hardened gelatin.  
  Alternatively, the soluble salts may be removed by adding to the emulsion a solution of polyacid such as 1:1 ethylenezmaleic 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, and then to wash and resuspend the resulting precipitate 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 a-picolinium bromide; and with polyethylene glycols and derivatives thereof. The emulsions of the present invention require only 5 percent as much gold for chemical sensitization as do gelatin emulsions.  
 The polymers employed as the binders in the emulsions of the present invention may be cross-linked according to conventional procedures. As an example, polymers containing amine groups may be crosslinked with zirconium salts under alkaline conditions wherein amine-containing polymer is coated with a zirconium salt, for example, zirconium sulfate, and the pH is raised cross-linking the polymer.  
  The emulsions of the present invention may also be optically sensitized with cyanine and merocyanine dyes more easily than are gelatin emulsions. Cyanine dyes tend to aggregate less on the polymers of the instant invention than with gelatin providing less light filtering and speed loss. Where desired, suitable antifoggants, toners, restrainers, developers, accelerators, preservatives, coating aids, plasticizers, hardeners and/or stabilizers may be included in the composition of the emul sion.  
  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. These novel emulsions of the instant invention have been found to adhere to supports in a most satisfactory manner.  
  The polymers employed in the practice of the instant invention may contain from 5-100 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 watersoluble 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(B-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 watersoluble 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.  
 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 and then washed and resuspended by raising the pH to above 7.  
  The instant invention will be further illustrated by reference to the following nonlimiting examples in which the preparation of the emulsion was carried out in the following general manner.  
 Procedure A A solution of 4.15 g. of the dry polymer in 266 ml. of distilled water was adjusted to pH 6.30 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 idoide 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 an additional 396 ml. 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. Procedure B In an alternative procedure for preparing the emulsion, the pH of the polymer solution was adjusted to 3.0; the amount of dry potassium bromide used was 88.0 g. and the amount of dry potassium iodide used was 1.0 g. In addition, the emulsion was ripened for 60 minutes instead of for 30 minutes.  
  The emulsion mixture in both procedures was centrifuged and washed with water to a low conductance. The emulsion was then redispersed in distilled water. To an aliquot of this emulsion was added a known quantity of a solution of bodying or thickening polymer of polyvinyl alcohol having an average molecular weight of about 100,000 (commercially available from E. I. duPont de Nemours &amp; Company, Wilmington, Del.. designated Type 72-60). A surfactant, such as Aerosol OT, was added and the emulsion was slot coated onto a base of cellulose triacetate sheet 5 mils thick having a coating of 30 mg./sq. ft. of hardened gelatin, (Celfa, commercially available from Instar Supply Company, New York N.Y.). This film so prepared was air dried, exposed on a sensitometer. and processed with a processing solution and an image-receiving sheet from a Type 107 film assembly (Polaroid Corporation, Cambridge, Mass). The negative and image-receiving element were maintained in superposed position for 15 seconds, after which they were stripped apart. The photographic characteristics of the resulting positive print were measured on an automatic recording densitometer.  
  The following table summarizes silver halide grain sizes obtained in emulsions prepared with polymers of the present invention.  
 TABLE l-Continued Grain Size (microns) Polymer Range Average 2:1 acrylamidelN-[B-(dimethylamino )ethyl lacrylamide 0. l-l 0.5  
 lzl acrylamide/N-[B-(dimethylamino)ethyl]acrylamide 0.4-5 2 4:! acrylamide/N-[B-(dimelhylamino)ethyl]acrylamide 0.2-2 0.8  
 9:l acrylamide/N-Ifl-(dimethylamino)ethyl]acrylamide 0.3-2.5 0.8  
 3:2 N-isopropylacrylamide/N- [IS-(dimethylamino )ethyl lacrylamide 0.8-1.2 l  
 9:] N-isopropylacrylamide/N- [B-(dimethylamino)ethyllacrylamide 0.2-0.6 0.4  
 l9: 1 N-isopropylacrylamide/N- [B-(dimethylamino)ethyllacrylamide 0.8  
 1:] N-methylacrylamide/N-[B- (dimethylamino)ethyl1acrylamide 0.1-2.5 l  
 H diacetoneacrylamide/N-[B- (dimethylamino)ethyllacrylamide 0.6-1.2 l  
 4:] methacrylamidoacetamide/N-[B (dimethylamino )ethyl lacrylamide 0.3-2. 3 1.2  
 M ethylacrylamide/N-[B-(dimethylamino )ethyl1acrylamide 0. l-3 l 8: l :l acrylamide/acryloylvaline/N- [B-(dimethylamino)ethyl]acrylamide 0.3-7.0 3.0  
 9:2:9 acrylamide/methacryloylmethionine/N-[B-(dimethylamino) ethyllacrylamide 02-] 0.6  
 16:1 :l6 acrylamide/methacryloylmethionine/NI B-( dimethylamino) ethyllacrylamide 0.2-1 .5 0.7  
 1:1 acrylamidoacetamide/N-[B- (dimethylamino)ethyllacrylamide 0.2-2.2 0.9  
 99: 1 :99 acrylamide/N-acryloylmethionineamide/N-[B- (dimethylamino )ethyl lacrylamide 0.3-2. 1 l  
 10:] :9 acrylamide/N-acryloylvaline/N-[B-(dimethylamino) ethyllacrylamide 0.2-3.8 2  
 17:3 N-isopropylacrylamide/N- [B-( dimethylamino )ethyl] acrylamide 0.2-l .4 0.4  
 Poly-N-[B-(dimethylamino)ethyl] acrylamide 0.3-2 0.6  
 l l ethylacrylamide/N-[B- (dimethylamino)ethyl Iacrylamide 0. l-3 l l:2 N,N-dimethylacrylumide/N-[B- (dimethylamino)ethyllacrylamide 0.4-2.4 0.9  
 l:2 N-t-butylacrylamide/N-[B- (dimethylamino )ethyl lacrylamide 0.4-3 L3 1:3 N.N-diethylacrylamide/N-[fi- (dimethylamino)ethyl lacrylamide 0.3-3.2 1.5  
 111 acrylamidoacetamidelN-l B- (dimethylamino)ethyl lacrylamide 0.4-2 1.2  
  The following table shows densitometer readings obtained on positives prepared from emulsions within the scope of the present invention.  
 TABLE 2 Grain Growing Bodying Silver/ Polymer Silver Polymer Polymer Ratio mg/ft. &#34;max &#34;min A&#34; 2:1 acrylamide/N-[B- none 11 69.4 1.58 0.25 1.33 (dimethy1amino)ethy1] acrylamidc 2:1 acrylamide/N-[B- 7:3 vinyl 1.24 72.4 1.32 0.90 0.42 (dimethylamino)ethyl1 alcohol/N- acrylumide vinylpyrrolidine copolymcr 2:1 acrylamide/N-[B- 2:1 acrylamide/N- 0.77 138.0 1.09 0.07 1.02 (dimethylaminolethyll [B-(dimethylamino) acrylamidc ethyljacrylate 2:1 acrylamide/N-IB- polyvinyl alcohol 0.77 69.2 1.40 0.65 0.75 ldimethylaminmethyl] acrylamidc 2:1 acrylamidc/N-lfipoly-N-(Z-cyano- 0.77 74.2 0.20 0.07 0.13 (dimethylamino )ethyl] ethyl )aziridinc acrylamidc 2:1 acrylamidc/N-IB- poly-N-vinyl 0.77 39.7 1.45 1.15 0.30 (dimethylaminolethyll pyrrolidinc acrylamidc 2:1 acrylamidc/N-lfigelatin 0.79 79.4 1.88 0.56 1.32 (dimcthylamino)ethyl] acrylamidc 1:1 N-cthylacrylamide/ 7:3 vinyl alcohol/ 1.24 149.3 0.92 0.16 0.76 N-Ifi-(dimethylamino) N-vinylpyrrolidine ethyllacrylaniidc 9:1 acrylamidc/N-IB- polyvinyl alcohol 1.36 121.8 1.25 0.50 0.75 (dimethylaminolethyfl acrylamidc 5:1 acrylamidc/N-lfil none 1 144.1 1.52 0.05 1.47 (dimethylaminolethyll acrylamidc 5:1 acrylamide/N-IB- polyvinyl alcohol 0.68 134.0 1.75 0.05 1.70 (dimethylaminmethyll acrylamidc 5:1 ucrylamide/N-l [3&#39; gelatin 0.92 184.1 1.77 0.26 1.51 (dimethylamino)ethyl| acrylumide 5:1 acrylamide/N-[fi- 1:1 acrylamide/ 4.1 81.3 1.19 0.19 1.00 (dimethylamino )ethyl] N-acryloylvaline acrylamide copolymer 5:1 acrylamidc/N-[B- 1:1 acrylamide/ 1.36 64.3 1.48 0.00 1.48 (dimethylamino)cthyl]N acryloylvaline acrylamide copolymer and polyvinyl alcohol 5:1 acrylamide/Nlfi- 1:1 acrylamide/ 0.92 43.6 1.38 0.17 1.21 (dimethylamino)ethyl] N-acryloylvaline acrylamide copolymer and gelatin 10:9:1 acrylamidc/N- polyvinyl alcohol 0.68 127.6 0.92 0.18 0.74 lfi-(dimethylamino)ethyl1 acrylamide/N-acryloylvalinc 3:1 N-isopropylacrylamide/ polyvinyl alcohol 1.36 85.3 0.96 0.31 0.65 N-1B-(dimethylamino)ethyll acrylamide 4:1 acrylamide/N-[B- polyvinyl alcohol 0.91 57.2 0.92 0.20 0.72 (dimethylamino)ethyl] acrylamide 1:65:l acrylamide/N- polyvinyl alcohol 1.36 98.1 1.84 0.20 1.64  
 1B-dimethylamin0) ethyllacrylamide The emulsions of the present invention also show a significant shortening of processing time as compared with conventional silver halide emulsions. For example, an emulsion prepared with a 5 :1 acrylamide/N-[B- (dimethylamino) ethyl]acrylamide copolymer as the grain growing polymer and polyvinyl alcohol as the bodying polymer (silver polymer ratio 1.36 and silver coverage 6.43 mgs./ft. when exposed and processed with Type 107C processing composition and receiving sheet (Polaroid Corporation, Cambridge, Mass.) showed a D, of 1.31 and a D of 0.02 after 10 seconds of processing while a conventional Type 107C film unit showed 21 D of 0.36 and D, of 0.01 after 10 seconds.  
  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 work.  
  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.  
  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.  
 What is claimed is:  
  l. A method of preparing a photosensitive silver halide emulsion which comprises reacting in the absence of gelatin a water-soluble silver salt with a watersoluble halide salt in an aqueous solution containing a polymer having in its structure repeating units of the formula:  
 R and R together may be chemically joined to form a cycloalkyl group; Y is selected from the group con sisting of alkylene or cycloalkylene; and n is a positive integer greater than 1.  
 2. The method as defined in claim 1 wherein said polymer comprises a copolymer of a first monomer of the formula:  
 and a second ethylenically unsaturated monomer.  
  3. The method as defined in claim 2 wherein said first monomer is N-[B-(dimethylamino)ethyl]acrylamide.  
  4. The method as defined in claim 2 wherein said first monomer is N-(diethylaminomethyl)acrylamide.  
  5. The method as defined in claim 2 wherein said comonomer is acrylamide.  
  6. The method as defined in claim 2 wherein said comonomer is N-isopropylacrylamide.  
  7. The method as defined in claim 2 wherein said comonomer is acrylamidoacetamide.  
  8. The method as defined in claim I wherein said aqueous solution further comprises polyvinyl alcohol as a bodying polymer.  
  9. The method as defined in claim 1 wherein said aqueous solution further comprises hydroxyethyl cellulose as a bodying polymer.