US2552229A - Fog inhibitors for photographic emulsions - Google Patents

Fog inhibitors for photographic emulsions Download PDF

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Publication number
US2552229A
US2552229A US91426A US9142649A US2552229A US 2552229 A US2552229 A US 2552229A US 91426 A US91426 A US 91426A US 9142649 A US9142649 A US 9142649A US 2552229 A US2552229 A US 2552229A
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fog
silver halide
photographic
emulsions
compounds
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US91426A
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Robert E Stauffer
William F Smith
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Eastman Kodak Co
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Eastman Kodak Co
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Priority to US91426A priority Critical patent/US2552229A/en
Priority to GB19403/49A priority patent/GB665515A/en
Priority to FR1000478D priority patent/FR1000478A/en
Priority to BE492744D priority patent/BE492744A/xx
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    • A—HUMAN NECESSITIES
    • A01—AGRICULTURE; FORESTRY; ANIMAL HUSBANDRY; HUNTING; TRAPPING; FISHING
    • A01B—SOIL WORKING IN AGRICULTURE OR FORESTRY; PARTS, DETAILS, OR ACCESSORIES OF AGRICULTURAL MACHINES OR IMPLEMENTS, IN GENERAL
    • A01B13/00—Ploughs or like machines for special purposes ; Ditch diggers, trench ploughs, forestry ploughs, ploughs for land or marsh reclamation
    • A01B13/08—Ploughs or like machines for special purposes ; Ditch diggers, trench ploughs, forestry ploughs, ploughs for land or marsh reclamation for working subsoil
    • A—HUMAN NECESSITIES
    • A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
    • A23B—PRESERVING, e.g. BY CANNING, MEAT, FISH, EGGS, FRUIT, VEGETABLES, EDIBLE SEEDS; CHEMICAL RIPENING OF FRUIT OR VEGETABLES; THE PRESERVED, RIPENED, OR CANNED PRODUCTS
    • A23B7/00—Preservation or chemical ripening of fruit or vegetables
    • A23B7/14—Preserving or ripening with chemicals not covered by groups A23B7/08 or A23B7/10
    • A23B7/144—Preserving or ripening with chemicals not covered by groups A23B7/08 or A23B7/10 in the form of gases, e.g. fumigation; Compositions or apparatus therefor
    • A23B7/152—Preserving or ripening with chemicals not covered by groups A23B7/08 or A23B7/10 in the form of gases, e.g. fumigation; Compositions or apparatus therefor in a controlled atmosphere comprising other gases in addition to CO2, N2, O2 or H2O ; Elimination of such other gases
    • 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
    • G03C1/06—Silver halide emulsions; Preparation thereof; Physical treatment thereof; Incorporation of additives therein with non-macromolecular additives
    • G03C1/08—Sensitivity-increasing substances
    • G03C1/09—Noble metals or mercury; Salts or compounds thereof; Sulfur, selenium or tellurium, or compounds thereof, e.g. for chemical sensitising

Definitions

  • This invention relates to fog-inhibiting agents and stabilizers for photographic emulsions and to photographic emulsions containing them.
  • Photographic fog is of two types: local and general. Local fog is formed by exposure of the film or plate at undesired points as by a light leak in the camera.
  • General fog is formed in a number of ways. It may be caused by the conditions under which the film or plate is stored such as conditions of high temperature or humidity or unusually long time of storage. The nature of the emulsion may also produce general fog as well as the conditions of development of the emulsion as by development for protracted periods of time or at temperatures above normal. We are primarily concerned with the fog and sensitivity changes in films or plates which have been stored under adverse conditions of temperature and humidity.
  • General fog and loss of sensitivity of the emulsion are especially likely to occur when the sensitive material is stored under conditions other than ideal, that is, under conditions of high temperature and humidity as in tropical 1 regions.
  • a further object is to provide antifoggin agents which stabilize the initial sensi- I Diethylenediammine palladous chloride,
  • the useful compounds include the complexes in which the group bound to the palladium atom is either ethylene, ammonia or an organic base, e. g., methyl, ethyl, propyl or iso-propylamines, heterocyclic tertiary nitrogen compounds as quinoline and pyridine; benzylamine or ethylene diamine.
  • the anion of the complex may, for example, be either halide, sulfate, carbonate or nitrate.
  • the object of our invention is to maintain the sensitivity and fog of silver halide emulsions at or close to initial optimum values under keeping conditions of high temperature and humidity.
  • the fog inhibitors which we propose to use are added to the emulsion during the process of manufacture to avoid loss of sensitivity and to inhibit the growth of fog with passage of time under non-ideal conditions of storage.
  • a solution of the compounds of the invention when added in suitable concentration before coating to unsensitized or optically sensitized photographic emulsions does not appreciably affect the sensitometric values for sensitivity and fog when measurements are made soon after coating.
  • sensitometric measurements are made at appreciable intervals of time under tropical or dry conditions of storage at elevated temperatures, however, these compounds do stabilize photographic speed and maintain fog at a low level.
  • the preparation of silver halide emulsions involves three separate operations (1) the emulsification and digestion or ripening of the silver halide, (2) the freeing of the emulsion from excess soluble salts usually by washing, (3) the second digestion or after-ripening to obtain in 3 creased sensitivity.
  • the most useful concentration 5 Grams range of fog inhibitor is from .26 to 3.9 gm, of Monomethyl paraminophenol sulfate 2.5 fog inhibitor per kilogram of silver nitrate used Sodium sulfite (desiccated) in making the particular silver halide emulsion Hydroquinone 2,5 and converted to silver halide.
  • the quantity Sodium metaborate 10 u e will of course vary for example depending 10 Potassium bromide 0.5 on the silver halide or mixture of halides used Water to one liter.
  • the anti-foggant and stabilizing action was determined by incubation of the emulsions under simulated tropical conditions and also by incubation at low relative humidity at F. for various lengths of time from 12 days to one month. The results of these tests are tabulated here and are compared with the initial speed, gamma and fog of the emulsions with and without the antifoggant and stabilizing compound.
  • the palladous halide complexes of ammonia, the heterocyclic tertiary nitrogen compounds and ethylene are the most efiective compounds for stabilizing both speed and log of emulsions and of these three preferred groups of complexes, the ammonia complexes appear to be most efiective, the heterocyclic tertiary nitrogen complexes next, and the ethylene complexes least effective since the latter tend to inhibit fog less.
  • diamrninepalladous chloride is prepared by the addition of concentrated aqueous ammonia to an aqueous palladous chloride solution until the precipitate first formed just dissolves. The solution is then evaporated to dryness, extracted with water and heated slightly to remove excess ammonia. After cooling and acidifying with excess concentrated hydrochloric acid, the product is allowed to crystallize. The resultant yellow crystalline powder is then washed with a limited quantity of water and dried at 100 C.
  • the iodo compound prepared as above is less soluble in water but nevertheless gives satisfactory results as an antifoggant at concentrations of the order shown in the above table.
  • the other palladium compounds of the invention are prepared and used in an analogous manner.
  • the fog inhibiting agents which we have described may be used in various kinds of photographic emulsions. In addition to being useful in ordinary non-sensitized emulsions they may also be used in orthochromatic, panchromatic and X-ray emulsions. If used with sensitizing dyes, they may be added to the emulsion before or after the dyes are added.
  • Various silver salts may be used as the sensitive salt such as silver bromide, silver iodide, silver chloride and miX- tures of these.
  • the dispersing agents may be gelatin or other colloid such as collodion, albumen, cellulose organic derivatives or synthetic resins.
  • a photographic silver halide emulsion containing an acido-palladium complex as a stabilizing agent 1.
  • a light-sensitive photographic element comprising a silver halide emulsion layer and an organic colloid layer contiguous to said emulsion layer, at least one of said layers containing an acido-diammine-palladium complex as a stabilizing agent for said emulsion layer.

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  • Chemical & Material Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Physics & Mathematics (AREA)
  • Polymers & Plastics (AREA)
  • Zoology (AREA)
  • Food Science & Technology (AREA)
  • Wood Science & Technology (AREA)
  • General Chemical & Material Sciences (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Materials Engineering (AREA)
  • General Physics & Mathematics (AREA)
  • Mechanical Engineering (AREA)
  • Soil Sciences (AREA)
  • Environmental Sciences (AREA)
  • Pyridine Compounds (AREA)
  • Silver Salt Photography Or Processing Solution Therefor (AREA)

Description

Patented May 8, 1951 FOG INHIBITORS FOR PHOTOGRAPHIC EMULSIONS Robert E. Stauficr and William F. Smith, Rochester, N. Y., assignors to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey No Drawing. Application May 4, 1949, Serial No. 91,426
11 Claims.
This invention relates to fog-inhibiting agents and stabilizers for photographic emulsions and to photographic emulsions containing them.
It is known that photographic emulsions, particularly ultra-sensitive emulsions or those containing optical sensitizers exhibit a tendency to form a deposit of silver in the emulsion. This deposit extends more or less uniformly over the entire emulsion and is known as fog. Photographic fog is of two types: local and general. Local fog is formed by exposure of the film or plate at undesired points as by a light leak in the camera. General fog is formed in a number of ways. It may be caused by the conditions under which the film or plate is stored such as conditions of high temperature or humidity or unusually long time of storage. The nature of the emulsion may also produce general fog as well as the conditions of development of the emulsion as by development for protracted periods of time or at temperatures above normal. We are primarily concerned with the fog and sensitivity changes in films or plates which have been stored under adverse conditions of temperature and humidity.
General fog and loss of sensitivity of the emulsion are especially likely to occur when the sensitive material is stored under conditions other than ideal, that is, under conditions of high temperature and humidity as in tropical 1 regions.
It is an object of the invention to provide novel anti-fogging or fog-inhibiting compounds for emulsions. A further object is to provide antifoggin agents which stabilize the initial sensi- I Diethylenediammine palladous chloride,
Pd (-H NC H.,l lH C1; Ethyldimnminepalladous chloride, Pd (CgH5NH2)2C1g Dipyridiniumpalladous chloride, Pd(C H N) Cl Diainminepalladous chloride, Pd(NIl Cl Diquinolimumpalladous chloride, Pd CgH7N)2C1g 2 Benzyldiamminepalladous chloride, Pd CQHDN :Cl Diethylenepalladous chloride, Pd (C2H4)2C12 Diamminepalladous bromide, Pd (NH;;)' Br- Diamminepalladous iodide, Pd (NH3)2'I2 Diamminepalladous sulfate, Pd(NH:;)2SO Diamminepalladous carbonate, Pd(N'H )2CO Diamminepalladous nitrate, Pd(Nl-1 (NO These compounds are described in the Textbook of Inorganic Chemistry by M. M. J. Sutherland, published by Charles Griffin and Company, Ltd., London, vol. 10, pp. 193-243 (1928), and may be called acido-palladium compounds or complexes in which the basic compounds, or ethylene, exists in the cation strongly bonded to the palladium atom and the anion of the complex is a monovalent or di-valent anion of an acid. As is apparent the useful compounds include the complexes in which the group bound to the palladium atom is either ethylene, ammonia or an organic base, e. g., methyl, ethyl, propyl or iso-propylamines, heterocyclic tertiary nitrogen compounds as quinoline and pyridine; benzylamine or ethylene diamine. The anion of the complex may, for example, be either halide, sulfate, carbonate or nitrate.
The object of our invention is to maintain the sensitivity and fog of silver halide emulsions at or close to initial optimum values under keeping conditions of high temperature and humidity. The fog inhibitors which we propose to use are added to the emulsion during the process of manufacture to avoid loss of sensitivity and to inhibit the growth of fog with passage of time under non-ideal conditions of storage.
A solution of the compounds of the invention when added in suitable concentration before coating to unsensitized or optically sensitized photographic emulsions does not appreciably affect the sensitometric values for sensitivity and fog when measurements are made soon after coating. When sensitometric measurements are made at appreciable intervals of time under tropical or dry conditions of storage at elevated temperatures, however, these compounds do stabilize photographic speed and maintain fog at a low level.
The preparation of silver halide emulsions involves three separate operations (1) the emulsification and digestion or ripening of the silver halide, (2) the freeing of the emulsion from excess soluble salts usually by washing, (3) the second digestion or after-ripening to obtain in 3 creased sensitivity. (Mees, The Theory of the Photographic Process, 1942.) We prefer to add the fog-inhibiting agents after the final digestion or after-ripening although they may be added used a high-speed silver bromoiodide emulsion exposed on an Eastman type IB sensitometer and developed for five minutes in a developer of the following composition:
before digestion. The most useful concentration 5 Grams range of fog inhibitor is from .26 to 3.9 gm, of Monomethyl paraminophenol sulfate 2.5 fog inhibitor per kilogram of silver nitrate used Sodium sulfite (desiccated) in making the particular silver halide emulsion Hydroquinone 2,5 and converted to silver halide. The quantity Sodium metaborate 10 u e will of course vary for example depending 10 Potassium bromide 0.5 on the silver halide or mixture of halides used Water to one liter.
Conditioned to R. H.
Gms. of compound Sample per Kg.AgN 03 Original 18 da. 120 F.
No. (converted to AgX) incmulsion gg Gamma Fog Gamma Fog Control None 105 .98 .03 49 .82 .21 PIKNHQMBI: 0. 50 108 .95 08 84 .87 07 Pd(NH5)2Brz 1. 00 98 .98 .02 90 .05 07 Pd(NHs)1'Bra. 1.50 94 .08 .02 02 .93 .00 ramnmn. 0.50 90 .05 .03 .94 .08 Pd(NH5)zI2 1. 00 92 .99 .04 82 .98 .05 'Pd(NH.-,)1Iz. 1.50 94 1.07 .02 .98 .00 Control None 115 .97 .04 76 .83 .10 Pd(NHa)zClz 0. 50 110 97 02 94 .90 08 Pd(NHa)2C1z.. 1.00 105 1.01 .02 88 .89' .07 Pd(NH3)2C12. 1. 50 100 .07 02 88 89 09 Conditioned to 60% R. H. Conditioned to 70%,R. H.
3 Original 18 (33.120 F. Original 0 15. 120 F.
1 1 ll 11 11 Speed Gamma. Fog spod Gamma Fog sped Gamma Fog Sped Gamma Fog 100 1.02 .02 39 .77 High Fog 110 1. 00 .02 70 .87 73 .90 .00 08 1.02- .02 08 .88 05 .85 .09 100 1.08 .01 88 .93 63 .87 .10 1.08 .02 01 .91 55 .92 .09 1.09 .02 .90 92 1.12 .02 00 .89 05 .08 .07 .05 .02 37 .75 24 .80 .88 110 .98 .02 05 .87 53 .84 .15 100 .09 .02 82 .86 53. .80 .10 98 .99 .02 88 .86 59 .87 .12
Original 4 Wk. Tropical Sample Gms. of compound per KgJlgNOa (converted o. to AgX) 1n emulsion loli 10 speed Gamma Fog Speed Gamma Fog Control None 1,180 1. 24 .00 780 1.07 .22 10 None 980 1. 20 .07 400 1. 30 22 Pd(CzH NHi)2C15 1.5 1,100 1.20 .00 940 1.14 .08 rdwinimqolz 1.0 1,080 1.24 .07 1,080 1.23 .11
PdwnnoHzNHmGn 1.0 1,120 1.17 .05 1,200 1.18 .10 Control None 1,850 1. 39 .21 1,120 0. 90 .85 do None 2, 200 1. 28 22 1, 400 1. 00 .30 PMC2110401; 0. 25 1,850 1.40 .10 1,750 0.91 .28 Pd(HzNC'.-H4NH2)1CL 0.25 2,000 1.23 .20 1, 320 0. 95 .38
and upon the specific complex salt used as a stabilizer and fog inhibitor.
The anti-foggant and stabilizing action was determined by incubation of the emulsions under simulated tropical conditions and also by incubation at low relative humidity at F. for various lengths of time from 12 days to one month. The results of these tests are tabulated here and are compared with the initial speed, gamma and fog of the emulsions with and without the antifoggant and stabilizing compound. The tests from which the following tabulation was made It will be apparent from the above data that, considering all of the stabilizing compounds of our invention, the palladous halide complexes of ammonia, the heterocyclic tertiary nitrogen compounds and ethylene are the most efiective compounds for stabilizing both speed and log of emulsions and of these three preferred groups of complexes, the ammonia complexes appear to be most efiective, the heterocyclic tertiary nitrogen complexes next, and the ethylene complexes least effective since the latter tend to inhibit fog less.
One of the advantages of our invention is the fact that the compounds are readily prepared with high purity. The compounds are prepared by the methods shown in the Textbook of Inorganic Chemistry by M. M. J. Sutherland, published by Charles Griifin and Company, Ltd, London, vol. 10, pages 193 to 243 (1928). For example, diamrninepalladous chloride is prepared by the addition of concentrated aqueous ammonia to an aqueous palladous chloride solution until the precipitate first formed just dissolves. The solution is then evaporated to dryness, extracted with water and heated slightly to remove excess ammonia. After cooling and acidifying with excess concentrated hydrochloric acid, the product is allowed to crystallize. The resultant yellow crystalline powder is then washed with a limited quantity of water and dried at 100 C.
The iodo compound prepared as above is less soluble in water but nevertheless gives satisfactory results as an antifoggant at concentrations of the order shown in the above table. The other palladium compounds of the invention are prepared and used in an analogous manner.
The fog inhibiting agents which we have described may be used in various kinds of photographic emulsions. In addition to being useful in ordinary non-sensitized emulsions they may also be used in orthochromatic, panchromatic and X-ray emulsions. If used with sensitizing dyes, they may be added to the emulsion before or after the dyes are added. Various silver salts may be used as the sensitive salt such as silver bromide, silver iodide, silver chloride and miX- tures of these. The dispersing agents may be gelatin or other colloid such as collodion, albumen, cellulose organic derivatives or synthetic resins.
We also contemplate as a part of our invention those cases where it is desirable to coat the antifoggant in a colloid layer such as gelatin on either or both sides of or also in a silver halide emulsion layer, so that the antifoggant is contiguous to the silver halide emulsion. In these cases we use the same or a slightly greater ratio of rare metal salt to silver halide as when the salt is in the emulsion layer.
It will be understood that we contemplate as included within our invention all modifications and equivalents falling within the scope of the appended claims.
We claim:
1. A photographic silver halide emulsion containing an acido-palladium complex as a stabilizing agent.
2. A photographic silver halide emulsion containing as a stabilizing agent a dipyridiniumpalladous halide.
3. A photographic silver halide emulsion containing as a stabilizing agent, dipyridiniumpalladous chloride.
1. A photographic silver halide emulsion containing as a stabilizing agent, an acido-diammine-palladium complex.
5. A photographic silver halide emulsion containing as a stabilizing agent, a diamminepalladous halide.
6. A photographic silver halide emulsion containing as a stabilizing agent, diamminepalladous chloride.
7. A photographic silver halide emulsion containing as a stabilizing agent, a diethylenepalladous halide.
8. A photographic silver halide emulsion containing as a stabilizing agent, diethylenepalladous chloride.
9. A light-sensitive photographic element comprising a silver halide emulsion layer and an organic colloid layer contiguous to said emulsion layer, at least one of said layers containing an acido-diammine-palladium complex as a stabilizing agent for said emulsion layer.
10. A photographic silver halide emulsion containing as a stabilizing agent an acido-palladium complex containing in the cation a palladium atom and a basic nitrogen atom.
11. A photographic silver halide emulsion containing as a stabilizing agent an acido-palladium complex containing in the cation a palladium atom and a basic nitrogen atom of a heterocyclic ring compound.
ROBERT E. STAUFFER. WILLIAM F. SMITH.
REFERENCES CITED The following references are of record in the file of this patent:
UNITED STATES PATENTS Number Name Date 2,448,060 Smith et al Aug. 31, 1948 2,448,857 Brice Sept. 7, 1948

Claims (1)

1. A PHOTOGRAPHIC SILVER HALIDE EMULS ON CONTAINING AN ACIDO-PALLADIUM COMPLEX AS A STABILIZING AGENT.
US91426A 1949-05-04 1949-05-04 Fog inhibitors for photographic emulsions Expired - Lifetime US2552229A (en)

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US91426A US2552229A (en) 1949-05-04 1949-05-04 Fog inhibitors for photographic emulsions
GB19403/49A GB665515A (en) 1949-05-04 1949-07-22 Improvements in sensitive photographic materials
FR1000478D FR1000478A (en) 1949-05-04 1949-11-30 New photographic emulsions
BE492744D BE492744A (en) 1949-05-04 1949-12-15

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Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2717833A (en) * 1952-05-12 1955-09-13 Sperry Rand Corp Direct positive emulsions
US3036916A (en) * 1958-06-16 1962-05-29 Du Pont Polymerizable elements
US4102312A (en) * 1975-10-30 1978-07-25 Toyota Jidosha Kogyo Kabushiki Kaisha Thermally developable light-sensitive materials
US4163669A (en) * 1977-04-27 1979-08-07 Mitsubishi Paper Mills, Ltd. Multilayer silver halide color photographic material
US5021336A (en) * 1987-04-11 1991-06-04 Agfa Gevaert Aktiengesellschaft Color photographic material
EP0722115A1 (en) * 1994-12-16 1996-07-17 Eastman Kodak Company Photographic element and coating composition
US5650265A (en) * 1995-12-22 1997-07-22 Eastman Kodak Company Silver halide light-sensitive element
US5811226A (en) * 1996-03-14 1998-09-22 Eastman Kodak Company Method of processing a silver halide photographic element which reduces fog

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4981781A (en) * 1989-08-28 1991-01-01 Eastman Kodak Company Photographic emulsions containing internally modified silver halide grains

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2448060A (en) * 1945-08-30 1948-08-31 Eastman Kodak Co Photographic emulsions sensitized with salts of metals of group viii of the periodicarrangement of the elements
US2448857A (en) * 1945-10-25 1948-09-07 Eastman Kodak Co Stabilization of photographic emulsions

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2448060A (en) * 1945-08-30 1948-08-31 Eastman Kodak Co Photographic emulsions sensitized with salts of metals of group viii of the periodicarrangement of the elements
US2448857A (en) * 1945-10-25 1948-09-07 Eastman Kodak Co Stabilization of photographic emulsions

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2717833A (en) * 1952-05-12 1955-09-13 Sperry Rand Corp Direct positive emulsions
US3036916A (en) * 1958-06-16 1962-05-29 Du Pont Polymerizable elements
US4102312A (en) * 1975-10-30 1978-07-25 Toyota Jidosha Kogyo Kabushiki Kaisha Thermally developable light-sensitive materials
US4163669A (en) * 1977-04-27 1979-08-07 Mitsubishi Paper Mills, Ltd. Multilayer silver halide color photographic material
US5021336A (en) * 1987-04-11 1991-06-04 Agfa Gevaert Aktiengesellschaft Color photographic material
EP0722115A1 (en) * 1994-12-16 1996-07-17 Eastman Kodak Company Photographic element and coating composition
US5614360A (en) * 1994-12-16 1997-03-25 Eastman Kodak Company Photographic element and coating composition
US5650265A (en) * 1995-12-22 1997-07-22 Eastman Kodak Company Silver halide light-sensitive element
US5811226A (en) * 1996-03-14 1998-09-22 Eastman Kodak Company Method of processing a silver halide photographic element which reduces fog
US5935771A (en) * 1996-03-14 1999-08-10 Eastman Kodak Company Method of processing a silver halide photographic element which reduces fog

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FR1000478A (en) 1952-02-12
GB665515A (en) 1952-01-23

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