US3804629A - Process for the production of a stain-resistant photographic silver halide emulsion - Google Patents

Process for the production of a stain-resistant photographic silver halide emulsion Download PDF

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US3804629A
US3804629A US00286291A US28629172A US3804629A US 3804629 A US3804629 A US 3804629A US 00286291 A US00286291 A US 00286291A US 28629172 A US28629172 A US 28629172A US 3804629 A US3804629 A US 3804629A
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emulsion
silver
silver halide
chloride
halide emulsion
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US00286291A
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H Hammerstein
H Reuss
E Moisar
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Agfa Gevaert AG
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    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03C—PHOTOSENSITIVE MATERIALS FOR PHOTOGRAPHIC PURPOSES; PHOTOGRAPHIC PROCESSES, e.g. CINE, X-RAY, COLOUR, STEREO-PHOTOGRAPHIC PROCESSES; AUXILIARY PROCESSES IN PHOTOGRAPHY
    • G03C1/00—Photosensitive materials
    • G03C1/005—Silver halide emulsions; Preparation thereof; Physical treatment thereof; Incorporation of additives therein
    • G03C1/015—Apparatus or processes for the preparation of emulsions
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03C—PHOTOSENSITIVE MATERIALS FOR PHOTOGRAPHIC PURPOSES; PHOTOGRAPHIC PROCESSES, e.g. CINE, X-RAY, COLOUR, STEREO-PHOTOGRAPHIC PROCESSES; AUXILIARY PROCESSES IN PHOTOGRAPHY
    • G03C1/00—Photosensitive materials
    • G03C1/005—Silver halide emulsions; Preparation thereof; Physical treatment thereof; Incorporation of additives therein
    • G03C1/035—Silver halide emulsions; Preparation thereof; Physical treatment thereof; Incorporation of additives therein characterised by the crystal form or composition, e.g. mixed grain

Definitions

  • Photographically active dust such as abrasion dust from metal contaminates the light-sensitive silver halide emulsion layer in spite of all precautions.
  • the metal particles or their compounds or other photographically active substances dissolve in the photographic layers, auxiliary layers or supports with varying degrees of rapidity.
  • the dissolved products diffuse in the layers and are liable to cause considerable harm to the photographic properties, e.g. by exerting a sensitizing or desensitizing effect.
  • the well-known black or white patchiness is then found in the light-sensitive photographic materials after they have been processed in photographic baths in the usual manner.
  • a similar harmful effect may also be caused by impurities e.g. in the raw material used for the production of the paper support.
  • impurities e.g. in the raw material used for the production of the paper support.
  • black or white patchiness is found in the material after development, especially if the material is stored under conditions of elevated temperature and moisture.
  • a process for the production of a photographic silver halide emulsion comprising the steps of precipitation of the silver halide in the presence of a protective colloid, physical ripening, washing of the ripened emulsion to remove the soluble salts and chemical ripening has now been found in which a gelatin emulsion containing essentially only silver chloride is added to the physically ripened and washed emulsion before it is chemically ripened, or the silver chloride which is to be added is produced in the physically ripened and washed silver halide emulsion by precipitation by the addition of alkali metal chloride and silver nitrate solutions.
  • the method according to the invention results in the formation of silver chloride hillocks on the silver halide grains of the original emulsion. These hillocks surprisingly produce excellent resistance to the formation of stains by particles of dirt. These silver chloride hillocks on the particles of the original silver halide emulsions, which is preferably a silver bromide emulsion, are clearly visible under an electron microscope.
  • the concentration of silver chloride produced in the original silver halide emulsion either by the addition of a silver chloride emulsion or by precipitation may vary within wide limits.
  • the optimum quantity can be determined by tests well known in the art. Quantities of from 2 to 10 mol of silver chloride, based on the total quantity of silver halide in the physically ripened and washed emulsion have generally been found to effect sufficient stabilization for practical purposes.
  • the silver halides used for the emulsion which is to be stabilized may be silver chloride, silver bromide or mixtures of these if derived with a silver iodide content of up to 10
  • the silver halides are dispersed in the usual hydrophilic binders, e.g. in proteins, preferably gelatin, carboxyrnethyl-cellulose, polyvinyl alcohol, polyvinyl pyrrolidone or alginic acid and its derivatives such as salts, esters or amides.
  • the emulsions may be chemically ripened in the usual manner and treated with the usual additives.
  • the emulsion may be optically sensitized with cyanines rhodacyanines or merocyanines, e.g. as described in The Cyanine Dyes and related Compounds by F. M. HAMER, published by Intersci-' ence Publishers (1964). i
  • the emulsions may be chemically sensitized in the usual manner, e.g. with reducing agents such as tin(ll) salts, polyamines such as diethyltriamine or sulfur compounds as described in U.S. Pat. specification No. 1,574,944. Salts of noble metals such as ruthenium, rhodium, palladium, iridium, platinum or gold may also be added as chemical sensitizers, as described in the publication by R. KOSLOWSKY in Z. Wiss. Phot. 46, 65 72 (1951).
  • the emulsions may also contain polyalkylene oxides as chemical sensitizers and in particular polyethylene oxides and derivatives thereof.
  • the emulsions may be stabilized against spontaneous fogging by the addition of the usual stabilizers such as organic mercury compounds or mercury salts, e.g. mercury triazole compounds, simple mercury salts or mercury double salts.
  • stabilizers are in particular azaindenes, e.g. tetraor pentaazaindenes and particularly those which are hydr 'oxyl substituted or amino substituted, as described in the publication by BIRR in Z. Wiss. Phot. 47, 2 58 (1952).
  • Heterocyclic mercapto compounds such as l-phenyl-S-mercaptotetrazole, quaternary benzothiazole derivatives and benzotriazoles may also be used.
  • the emulsion is hardened in the usual manner, e.g. with aldehydes such as formaldehyde, dialdehydes or halo substituted aldehydes which contain a carboxyl group, e.g. mucochloric acid or mucobromic acid, or diketones or sulfonic acid esters such as methanesulfonic acid esters.
  • aldehydes such as formaldehyde, dialdehydes or halo substituted aldehydes which contain a carboxyl group, e.g. mucochloric acid or mucobromic acid, or diketones or sulfonic acid esters such as methanesulfonic acid esters.
  • the emulsions prepared in accordance with the invention may be used for various photographic materials. They are particularly suitable for silver halide emulsion layers used for photographic copying materials mounted on a paper support but they may also be used for X-ray films, unsensitized emulsions, orthochromatically or panchromatically sensitized emulsions or emulsions which are sensitive to the infra-red region of the spectrum.
  • the emulsions may be used in materials for the silver saltdiffusion process, in color photographic materials and also in photographic materials for the silver dye bleaching process.
  • EXAMPLE 1 A silver bromide emulsion containing 14 mols of silver chloride and 1 mol of silver iodide is prepared in the usual manner by precipitation in the presence of gelatin.
  • the emulsion is flocculated after physical ripening and the soluble salts resulting from precipitation are removed by washing with water.
  • the silver halide is then melted at pH 5.5 with the addition of gelatin and water.
  • the emulsion then contains 55 g of silver halide per kg and 220 g of gelatin per kg. It is then ripened to the required sensitivity at 53 C.
  • optical sensitizer 10 ml of a 0.1 aqueous solution of optical sensitizer of the following formula:
  • the emulsion is applied to a baryta-coated paper support to which a layer of gelatin containing iron dust has been applied to test the effectiveness of the process according to the invention.
  • the emulsion is uniformly exposed and developed in a developer of the following composition:
  • the sample obtained after processing is uniformly black. It has numerous white patches which can be attributed to the harmful effect of the iron dust.
  • an emulsion is prepared by the same method except that, after washing and before chemical ripening, 20 ml of a aqueous sodium chloride solution and 83 ml ofa 5 aqueous silver nitrate solution are added. When precipitation takes place, hillocks of silver chloride are formed on the grains of the original emulsion. The quantity of silver chloride produced by precipitation is 8.3 mols of silver chloride based on the amount of silver halide in the original emulsion. The emulsion is then chemically ripened and processed as described above.
  • the developed and fixed sample is practically free from stains.
  • practically no white stains are formed even if the sample has been stored in an air conditioning cupboard at C and 40 atmospheric humidity for 2 days before processing.
  • the formation of stains is increased under these conditions.
  • EXAMPLE 2 A silver bromide emulsion containing 4.8 mols of silver chloride and 1.5 mols of silver iodide is prepared in the usual manner by precipitation in the presence of gelatin as protective colloid.
  • the emulsion It is physically ripened and the emulsion is flocculated and the soluble salts are removed by washing.
  • the silver halide is then redispersed by the addition of gelatin and water at pH 5.5.
  • the emulsion then contains 55 g of silver halide and 160 g of gelatin per kg.
  • the emulsion is then divided into two portions. 4 ml of a 10 sodium chloride solution and 17 ml of a 5 aqueous silver nitrate solution are added to one portion.
  • the quantity of silver chloride produced, which forms hillocks on the grains of the original silver bromide emulsion, is 1.7 mols based on the amount of original emulsion.
  • Example 1 The material is processed in the same way as de scribed in Example 1.
  • EXAMPLE 3 The procedure is the same as that described in Example l, but instead of adding sodium chloride solution and silver nitrate solution to the physically ripened and washed emulsion, a previously prepared silver chloride gelatin emulsion is added.
  • Example 1 The subsequent treatment is the same as described in Example 1. Examination of the sample shows equally good results to those obtained in Example I.
  • Equally effective stabilization and prevention of the formation of white stains is achieved if instead of the 6 times the equimolar quantity of chloride ions is present when the silver chloride emulsion is added or the silver chloride is formed by precipitation.

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Silver Salt Photography Or Processing Solution Therefor (AREA)

Abstract

The stability of silver halide emulsion layers against the deleterious effect of dust in particular metal dust is improved by adding to the physically ripened and washed emulsion before chemical ripening a silver chloride emulsion or by precipitating silver chloride on to the physically ripened and washed silver halide emulsion.

Description

United States Patent [191 Hammerstein et al.
[ Apr. 16, 1974 PROCESS FOR THE PRODUCTION OF A STAIN-RESISTANT PHOTOGRAPHIC SILVER HALIDE EMULSION Inventors: Hanns Hammerstein, Hamburg;
Helmut Reuss, Leverkusen; Erik Moisar, Cologne, all of Germany Assignee: Agfa-Gevaert Aktiengesellschaft,
Leverkusen, Germany Filed: Sept. 5, 1972 Appl. No.: 286,291
Foreign Application Priority Data Sept. 3, 1971 Germany 2144127 US. Cl. 96/94 R, 96/110 Int. Cl G03c 1/02, G036 l/72 Field of Search 96/1 10, 94
References Cited UNITED STATES PATENTS 3,600,180 8/1971 Judd et al. 96/94 R Primary Examiner-Norman G. Torchin Assistant ExaminerAlfonso T, Suro Pico Attorney, Agent, or Firm-Connolly and Hutz [57] ABSTRACT 3 Claims, No Drawings PROCESS FOR THE PRODUCTION OF A STAIN-RESISTANT PHOTOGRAPHIC SILVER HALIDE EMULSION The invention relates to a method for decreasing the formation of small stains caused by the presence of heavy metals and/or their compounds or other contaminating substances in photographic silver halide emulsions, auxiliary layers and supports for photographic silver halide emulsions.
It is known that cleanliness is extremely important in the manufacture of light-sensitive photographic materials. Photographically active dust such as abrasion dust from metal contaminates the light-sensitive silver halide emulsion layer in spite of all precautions. The metal particles or their compounds or other photographically active substances dissolve in the photographic layers, auxiliary layers or supports with varying degrees of rapidity. The dissolved products diffuse in the layers and are liable to cause considerable harm to the photographic properties, e.g. by exerting a sensitizing or desensitizing effect. The well-known black or white patchiness is then found in the light-sensitive photographic materials after they have been processed in photographic baths in the usual manner.
A similar harmful effect may also be caused by impurities e.g. in the raw material used for the production of the paper support. In that case, black or white patchiness is found in the material after development, especially if the material is stored under conditions of elevated temperature and moisture.
Various additives have been described for preventing this effect. These additives areincorporated either in the emulsion or in adjacent layers. Most of these substances, however, produce only a slight effect whilst others become sufficiently effective only at high concentrations at which they often give rise to other harmful side effects.
It is an object of this invention to modify the process for producing the photographic silver halide emulsion so that patchiness due to the presence of dust and heavy metal particles will not occur.
A process for the production of a photographic silver halide emulsion comprising the steps of precipitation of the silver halide in the presence of a protective colloid, physical ripening, washing of the ripened emulsion to remove the soluble salts and chemical ripening has now been found in which a gelatin emulsion containing essentially only silver chloride is added to the physically ripened and washed emulsion before it is chemically ripened, or the silver chloride which is to be added is produced in the physically ripened and washed silver halide emulsion by precipitation by the addition of alkali metal chloride and silver nitrate solutions.
The method according to the invention results in the formation of silver chloride hillocks on the silver halide grains of the original emulsion. These hillocks surprisingly produce excellent resistance to the formation of stains by particles of dirt. These silver chloride hillocks on the particles of the original silver halide emulsions, which is preferably a silver bromide emulsion, are clearly visible under an electron microscope.
The concentration of silver chloride produced in the original silver halide emulsion either by the addition of a silver chloride emulsion or by precipitation may vary within wide limits. The optimum quantity can be determined by tests well known in the art. Quantities of from 2 to 10 mol of silver chloride, based on the total quantity of silver halide in the physically ripened and washed emulsion have generally been found to effect sufficient stabilization for practical purposes.
It is preferable to use an excess of chloride ions for producing the silver chloride hillocks. This excess should preferably be from 1.2 to 2 times to required equimolar quantity of chloride ions. The production of silver halide emulsions modified in accordance with the invention is otherwise carried out by the usual process which comprises the following steps:
1. Precipitation of the silver halides in the presence of a protective colloid and physical ripening;
2. Removal of the excess water-soluble salts formed in the process of precipitation by washing the ripened emulsion; and
3. Chemical ripening of the washed emulsion to provide the desired photographic properties, in particular the desired sensitivity.
The silver halides used for the emulsion which is to be stabilized may be silver chloride, silver bromide or mixtures of these if derived with a silver iodide content of up to 10 The silver halides are dispersed in the usual hydrophilic binders, e.g. in proteins, preferably gelatin, carboxyrnethyl-cellulose, polyvinyl alcohol, polyvinyl pyrrolidone or alginic acid and its derivatives such as salts, esters or amides.
After the treatment with silver chloride in accordance with the invention, the emulsions may be chemically ripened in the usual manner and treated with the usual additives. The emulsion may be optically sensitized with cyanines rhodacyanines or merocyanines, e.g. as described in The Cyanine Dyes and related Compounds by F. M. HAMER, published by Intersci-' ence Publishers (1964). i
The emulsions may be chemically sensitized in the usual manner, e.g. with reducing agents such as tin(ll) salts, polyamines such as diethyltriamine or sulfur compounds as described in U.S. Pat. specification No. 1,574,944. Salts of noble metals such as ruthenium, rhodium, palladium, iridium, platinum or gold may also be added as chemical sensitizers, as described in the publication by R. KOSLOWSKY in Z. Wiss. Phot. 46, 65 72 (1951). The emulsions may also contain polyalkylene oxides as chemical sensitizers and in particular polyethylene oxides and derivatives thereof.
The emulsions may be stabilized against spontaneous fogging by the addition of the usual stabilizers such as organic mercury compounds or mercury salts, e.g. mercury triazole compounds, simple mercury salts or mercury double salts. Other useful stabilizers are in particular azaindenes, e.g. tetraor pentaazaindenes and particularly those which are hydr 'oxyl substituted or amino substituted, as described in the publication by BIRR in Z. Wiss. Phot. 47, 2 58 (1952). Heterocyclic mercapto compounds such as l-phenyl-S-mercaptotetrazole, quaternary benzothiazole derivatives and benzotriazoles may also be used.
The emulsion is hardened in the usual manner, e.g. with aldehydes such as formaldehyde, dialdehydes or halo substituted aldehydes which contain a carboxyl group, e.g. mucochloric acid or mucobromic acid, or diketones or sulfonic acid esters such as methanesulfonic acid esters.
The emulsions prepared in accordance with the invention may be used for various photographic materials. They are particularly suitable for silver halide emulsion layers used for photographic copying materials mounted on a paper support but they may also be used for X-ray films, unsensitized emulsions, orthochromatically or panchromatically sensitized emulsions or emulsions which are sensitive to the infra-red region of the spectrum. The emulsions may be used in materials for the silver saltdiffusion process, in color photographic materials and also in photographic materials for the silver dye bleaching process.
EXAMPLE 1 A silver bromide emulsion containing 14 mols of silver chloride and 1 mol of silver iodide is prepared in the usual manner by precipitation in the presence of gelatin.
The emulsion is flocculated after physical ripening and the soluble salts resulting from precipitation are removed by washing with water. The silver halide is then melted at pH 5.5 with the addition of gelatin and water. The emulsion then contains 55 g of silver halide per kg and 220 g of gelatin per kg. It is then ripened to the required sensitivity at 53 C.
In addition, the following additives are introduced into the casting solution:
10 ml of a 0.1 aqueous solution of optical sensitizer of the following formula:
10 ml of a l aqueous solution of a 2-mercapto-4- keto-3,4-dihydro-pyrimidine of the following formula as stabilizer:
20 ml ofa 5 aqueous solution of saponin and 0.75 ml of a 30 aqueous solution of formaldehyde.
The emulsion is applied to a baryta-coated paper support to which a layer of gelatin containing iron dust has been applied to test the effectiveness of the process according to the invention.
The emulsion is uniformly exposed and developed in a developer of the following composition:
p-methylaminophenol Na,SO, sicc. l hydroquinone soda sicc. 2
per litre of water The sample obtained after processing is uniformly black. It has numerous white patches which can be attributed to the harmful effect of the iron dust.
In another test, an emulsion is prepared by the same method except that, after washing and before chemical ripening, 20 ml of a aqueous sodium chloride solution and 83 ml ofa 5 aqueous silver nitrate solution are added. When precipitation takes place, hillocks of silver chloride are formed on the grains of the original emulsion. The quantity of silver chloride produced by precipitation is 8.3 mols of silver chloride based on the amount of silver halide in the original emulsion. The emulsion is then chemically ripened and processed as described above.
The developed and fixed sample is practically free from stains. In the case of the emulsion prepared according to the invention, practically no white stains are formed even if the sample has been stored in an air conditioning cupboard at C and 40 atmospheric humidity for 2 days before processing. In the comparison emulsion the formation of stains is increased under these conditions.
EXAMPLE 2 A silver bromide emulsion containing 4.8 mols of silver chloride and 1.5 mols of silver iodide is prepared in the usual manner by precipitation in the presence of gelatin as protective colloid.
It is physically ripened and the emulsion is flocculated and the soluble salts are removed by washing. The silver halide is then redispersed by the addition of gelatin and water at pH 5.5. The emulsion then contains 55 g of silver halide and 160 g of gelatin per kg.
The emulsion is then divided into two portions. 4 ml of a 10 sodium chloride solution and 17 ml of a 5 aqueous silver nitrate solution are added to one portion. The quantity of silver chloride produced, which forms hillocks on the grains of the original silver bromide emulsion, is 1.7 mols based on the amount of original emulsion.
Both portions are then chemically sensitized to the required sensitivity under the same conditions at 49 C. Saponin and formaldehyde are then added as in Example l and in addition 5.3 ml of a l methanolic solution of l-phenyl-5-mcrcaptotetrazole as stabilizer.
The material is processed in the same way as de scribed in Example 1.
Examination of the resulting sample shows that the formation of white stains has again been practically completely suppressed by the process according to the invention while the comparison sample has numerous white stains.
EXAMPLE 3 The procedure is the same as that described in Example l, but instead of adding sodium chloride solution and silver nitrate solution to the physically ripened and washed emulsion, a previously prepared silver chloride gelatin emulsion is added.
The subsequent treatment is the same as described in Example 1. Examination of the sample shows equally good results to those obtained in Example I.
Equally effective stabilization and prevention of the formation of white stains is achieved if instead of the 6 times the equimolar quantity of chloride ions is present when the silver chloride emulsion is added or the silver chloride is formed by precipitation.
3. The process of claim 1, wherein the amount of Si]- ver chloride introduced by the addition of silver chloride or by precipitation in the washed emulsion is from 2 to 10 mols based on the silver halide of the original silver halide emulsion.

Claims (2)

  1. 2. The process of claim 1, wherein from 1.2 to 2 times the equimolar quantity of chloride ions is present when the silver chloride emulsion is added or the silver chloride is formed by precipitation.
  2. 3. The process of claim 1, wherein the amount of silver chloride introduced by the addition of silver chloride or by precipitation in the washed emulsion is from 2 to 10 mols %, based on the silver halide of the original silver halide emulsion.
US00286291A 1971-09-03 1972-09-05 Process for the production of a stain-resistant photographic silver halide emulsion Expired - Lifetime US3804629A (en)

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GB (1) GB1377407A (en)

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS511116A (en) * 1974-06-21 1976-01-07 Mitsubishi Paper Mills Ltd HAROGEN KAGINSHASHINNYUZAINO SEIZOHO
US4094684A (en) * 1977-02-18 1978-06-13 Eastman Kodak Company Photographic emulsions and elements containing agel crystals forming epitaxial junctions with AgI crystals
US4142900A (en) * 1977-02-18 1979-03-06 Eastman Kodak Company Converted-halide photographic emulsions and elements having composite silver halide crystals
US4435501A (en) 1981-11-12 1984-03-06 Eastman Kodak Company Controlled site epitaxial sensitization
US4463087A (en) * 1982-12-20 1984-07-31 Eastman Kodak Company Controlled site epitaxial sensitization of limited iodide silver halide emulsions
US4643966A (en) * 1985-09-03 1987-02-17 Eastman Kodak Company Emulsions and photographic elements containing ruffled silver halide grains
EP0215612A2 (en) 1985-09-03 1987-03-25 EASTMAN KODAK COMPANY (a New Jersey corporation) Silver halide photographic emulsions with novel grain faces (5)
EP0793139A1 (en) * 1996-02-21 1997-09-03 Imation Corp. Photographic materials with improved image tone

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3064900D1 (en) * 1979-06-01 1983-10-27 Konishiroku Photo Ind Photographic silver halide emulsion comprising epitaxial composite silver halide crystals, silver iodobromide emulsion and process for preparing the same

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3600180A (en) * 1968-11-04 1971-08-17 Eastman Kodak Co Method of making a blend of fogged,direct positive silver halide emulsions of different grain sizes

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1214083B (en) * 1964-08-14 1966-04-07 Agfa Gevaert Ag Photographic light-sensitive material comprising at least one silver salt emulsion light-sensitive layer

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3600180A (en) * 1968-11-04 1971-08-17 Eastman Kodak Co Method of making a blend of fogged,direct positive silver halide emulsions of different grain sizes

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS511116A (en) * 1974-06-21 1976-01-07 Mitsubishi Paper Mills Ltd HAROGEN KAGINSHASHINNYUZAINO SEIZOHO
JPS5725825B2 (en) * 1974-06-21 1982-06-01
US4094684A (en) * 1977-02-18 1978-06-13 Eastman Kodak Company Photographic emulsions and elements containing agel crystals forming epitaxial junctions with AgI crystals
US4142900A (en) * 1977-02-18 1979-03-06 Eastman Kodak Company Converted-halide photographic emulsions and elements having composite silver halide crystals
US4435501A (en) 1981-11-12 1984-03-06 Eastman Kodak Company Controlled site epitaxial sensitization
US4463087A (en) * 1982-12-20 1984-07-31 Eastman Kodak Company Controlled site epitaxial sensitization of limited iodide silver halide emulsions
US4643966A (en) * 1985-09-03 1987-02-17 Eastman Kodak Company Emulsions and photographic elements containing ruffled silver halide grains
EP0215612A2 (en) 1985-09-03 1987-03-25 EASTMAN KODAK COMPANY (a New Jersey corporation) Silver halide photographic emulsions with novel grain faces (5)
EP0793139A1 (en) * 1996-02-21 1997-09-03 Imation Corp. Photographic materials with improved image tone
US5851751A (en) * 1996-02-21 1998-12-22 Imation Corp. Photographic materials with improved image tone

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FR2151106A1 (en) 1973-04-13
GB1377407A (en) 1974-12-18
DE2144127B2 (en) 1979-10-31
DE2144127A1 (en) 1973-03-08
BE787868A (en) 1973-02-23
FR2151106B3 (en) 1975-10-03
DE2144127C3 (en) 1983-12-15

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