US2624674A - Photographic emulsion sensitized with gold compounds and sulfur sensitizers - Google Patents

Photographic emulsion sensitized with gold compounds and sulfur sensitizers Download PDF

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Publication number
US2624674A
US2624674A US680514A US68051446A US2624674A US 2624674 A US2624674 A US 2624674A US 680514 A US680514 A US 680514A US 68051446 A US68051446 A US 68051446A US 2624674 A US2624674 A US 2624674A
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Prior art keywords
emulsion
silver halide
percent
polyvinyl
weight
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US680514A
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Inventor
Raife G Tarkington
Wesley G Lowe
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Eastman Kodak Co
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Eastman Kodak Co
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Priority to FR959922D priority Critical patent/FR959922A/fr
Priority to BE474236D priority patent/BE474236A/xx
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Priority to US680514A priority patent/US2624674A/en
Priority to GB26450/46A priority patent/GB631243A/en
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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
    • G03C1/06—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 sensitized photographic emulsions and to a process for preparing the same.
  • Photographic silver halide emulsions prepared in non-gelatin vehicles (or carrier) are, in general, sensitized with sulfur compounds (1, e. sulfur sensitizers) with more difflculty than the corresponding silver halide emulsions prepared in gelatin.
  • non-gelatin silver halide emulsions can be sensitized by adding to the emulsions one or more soluble gold compounds (i. e. one or more gold compounds which provide gold ions in aqueous media) and one or more sulfur sensitizers.
  • the speed increases caused by the combination of gold compound and sulfur sensitizer in the non-gelatin emulsions are at least equal to, and in some cases very much greater than, the speed increases which can be obtained employing a combination of gold compound and sulfur sensitizer in a gelatino-silver-halide emulsion.
  • our invention we incorporate in a non-gelatin photographic silver halide emulsion, at any stage of its preparation, at least one soluble gold compound and at least one sulfur sensitizer.
  • Our invention is directed primarily to non-gelatin developing-out silver halide emulsions in which the silver halide is predominately silver bromide, i. e. silver halide emulsions in which the silver halide is Wholly silver bromide and silver bromide emulsions containing smaller amounts of silver chloride or silver iodide or both.
  • non-gelatin silver halide emulsions advantageously employed in practicing our invention are silver halide emulsions prepared using as the vehicle or carrier polyvinyl alcohol (polyvinyl alcohol is herein intended to include all water-soluble hydrolyzed polyvinyl esters containing an ester group content equivalent to from to by weight of polyvinyl ester); silver halide emulsions prepared using as the vehicle or carrier hydrolyzed polyvinyl acetate containing an acetate group content equivalent to from 59 to 71% by weight of polyvinyl acetate; silver halide emulsions prepared using as the vehicle or carrier polyvinyl acetals containing a large proportion of polyvinyl alcohol hydroxyl groups, e.
  • polyvinyl alcohol is herein intended to include all water-soluble hydrolyzed polyvinyl esters containing an ester group content equivalent to from to by weight of polyvinyl ester
  • Any polyvinyl compound especially those containing only carbon, hydrogen and oxygen atoms, or those containing carbon, hydrogen, oxygen and amino nitrogen atoms or ammonium nitrogen atoms, which is soluble in a mixture of ethyl alcohol and water (containing from 0 to 50% by volume of ethyl alcohol) to the extent of 10 g. per g. of solvent can be employed as the vehicle or carrier in preparing our non-gelatin silver halide emulsions.
  • any other resinous or colloidal material soluble in an ethyl alcohol-water mixture or in water can be employed in preparing our nongelatin silver halide emulsions, e. g.
  • colloidal materials which can be employed as vehicles or carriers in preparing our non-gelatin emulsions are hydrolyzed cellulose carboxylic esters, such as hydrolyzed cellulose acetate or hydrolyzed cellulose acetate propionate, containing from 19 to 33% by weight of acyl groups, for example.
  • Any cellulose compound especially those containing only carbon, hydrogen and oxygen atoms, or those containing only carbon, hydrogen, oxygen and amino nitrogen atoms or ammonium nitrogen atoms, which is soluble in a mixture of ethyl alcohol and water (containing from 0 to 50% by volume of ethyl alcohol) to the extent of 10 g, per 100 g. of solvent can be employed as the vehicle or carrier in preparing our non-gelatin silver halide emulsions.
  • the silver halide emulsions can be prepared using gelling agents, such as phenols, e. g. orcinol, gallic acid, 2,4-dihydroxybenzoic acid, 4-chlororesorcinol, anaphthol, phloroglucinol, 2,7 -dihydroxynaphthalene, etc.
  • the non-gelatin silver halide emulsions can be prepared using silver halide dispersing agents, 6. g.
  • starch acetate starch acetate, gum arabic, a copolymer of maleic anhydride and vinyl acetate, low viscosity methyl cellulose, water-soluble amino carbohydrate dispersing agents (e. g. diethanolamine cellulose acetate or any other of these agents described in United States Patent 2,360,238, dated October 10, 1944) amino resin dispersing agents (e. g.
  • the speeds obtained with the combination of gold salt and sulfur sensitizer are sometimes as great as ten times the speeds that can be obtained with sulfur sensitizers alone.
  • the speeds are more of the order of 3 to 4 times the speeds obtained with the sulfur sensitizers alone.
  • Typical soluble gold compounds which we employ in practicing our invention are gold halides, such as auric chloride, or complex goldhalides,
  • potassium auric chloride KAU.C14
  • KAU.C14 potassium auric chloride
  • auric sulfate sodium auric chloride, potassium or sodium auric bromide, potassium or sodium auric iodide
  • complex goldsalts such as alkali metal aurous thiosulfates, alkali metal aurous sulfites, a complex salt formed by the interaction of thiourea and auric chloride, complex salts, such as gold thiosinamine complexes, etc.
  • gold compounds can be used.
  • the gold compound is advantageously employed in a concentration equal to from about 0.0005 to about 0.025% by moles of the silver halide present. Optimum results are obtained ordinarily at concentrations between about 0.001 and 0.02% by moles of the silver halide present.
  • the gold compounds can be added to the emulsions at any stage of their preparation.
  • the gold compounds are advantageously incorporated in the emulsions in the form of their solutions in a suitable solvent such as water, methyl or ethyl alcohol.
  • Metal or ammonium thiocyanates e. g. sodium, potassium, ammonium, cadmium, calcium, etc. thiocyanates can also be employed.
  • One or more sulfur sensitizers can be employed, and one or more thiocyanates selected from the group consisting of metal and ammonium thiocyanates can be employed in conjunction with a sulfur sensitizer other than a thiocyanate containing a cation selected from the group consisting of metal and ammonium cations.
  • the sulfur sensitizers are advantageously incorporated in the emulsions 4 in the form of their solutions in a suitable solvent, such as water, methyl or ethyl alcohol.
  • the sulfur sensitizers can be incorporated in the emulsions at any stage of the preparation of the emulsion, i. e. during precipitation of the silver halides, during washing of the emulsions or during digestion or heat treating of the emulsions.
  • the amount can vary widely.
  • an amount of thiocyanate equal to from about 2 to about 15 per cent by moles of the silver halide in the emulsion is employed. If the thiocyanate or other sulfur sensitizer is not added until later in the preparation, e. g.
  • an amount equal to from about 0.1 to about 2.5 per cent by moles of the silver halide present in the emulsion in the case of metal and ammonium thiocyanates, and an amout equal to from about 0.006 to about 0.06 er cent by moles of the silver halide in the case of other sulfur sensitizers.
  • the digestion can be carried out at from to 150 F. for example. The lower the temperature of digestion, the longer it will require to arrive at optimum speed. Ordinarily at F., digestion for from 1 to 2 hours produces optimum speed.
  • the pH of the emulsion is advantageously adjusted to th acid side of neutrality, e. g. between 5 and 6.5 for aqueous systems. Maintenance of the emulsion on the acid side of neutrality is also advantageous during coating.
  • Example 1 Polyvinyl alcohol emulsion 200 g. of silver nitrate .l ⁇ Watcr to 400 cc. volume ,JTempu-awm Blli5723 g. (ill potassium bronldc uni g. 0 p0 assium iodi e 'lcm .i-raiurc 80 l".
  • One-half of the melted emulsion was coated on a cellulose acetate film base in the usual manner. Upon exposure and development for 6 minutes at 70 F. in Eastman Kodak Companys D-16 developer, the coated emulsion showed a speed (IO/i) of 0.20, and a gamma of 1.5.
  • Example 2 Hydrolyzed cellulose acetate propionate silver bromiodide emulsion was prepared as follows:
  • Example 3 F 8 g. of urea and 2 cc. of con- 40 g. silver nitrate Water to cc. volume A Then add sulficient concentrated ammo- Temperature 80 F.
  • Example 4 An emulsion was prepared as in Example 2. Instead of dividing the emulsion into halves and adding sodium thiocyanate and gold compound as in Example 2, portions of the emulsion were treated as follows:
  • Example 5 An emulsion was prepared as in Example 2. Instead of dividing the emulsion into halves and adding sodium thiocyanate and gold compound as in Example 2, portions of the emulsion were treated as follows:
  • non-gelatin silver halide emulsions do not respond to sensitization with sulfur sensitizers readily, and heretofore, it has been desirable to use silver halide dispersing agents such as water-soluble amino carbohydrate dispersing agents or water-soluble amino resin dispersing agents in order to arrive at sulfur sensitized non-gelatin silver halide emulsions having speeds paralleling those of gelatino-silverhalide emulsions.
  • silver halide dispersing agents such as water-soluble amino carbohydrate dispersing agents or water-soluble amino resin dispersing agents
  • non-gelatin silver halide emulsions of greatly enhanced sensitivity can be obtained without the use of the aforesaid dispersing agents, although our invention contemplates non-gelatin silver halide emulsions, sensitized as described herein, containing the aforesaid dispersing agents.
  • the thiocyanates which we have found are most advantageously employed in practicing our invention are the alkali metal thiocyanates, e. g. sodium or potassium thiocyanate, the alkaline earth metal thiocyanates, e. g. calcium thiocyanate, and the ammonium .thiocyanates, e. g. NHrSCN.
  • alkali metal thiocyanates e. g. sodium or potassium thiocyanate
  • the alkaline earth metal thiocyanates e. g. calcium thiocyanate
  • ammonium .thiocyanates e. g. NHrSCN.
  • thiocyanates containing cations which cations are known to have, in themselves, a deleterious effect on silver halide emulsions should be avoided. Otherwise the beneficial effects attained by our invention would be partiallynullified by thedeleterious action ofthe cation.
  • sensitizing dyes of all types can be employed to spectrally (optically) sensitize our new emulsions, e. g. erythrosin, Congo red, any of the sensitizing cyanine dyes (monomethine, trimethine, pentamethine, heptamethine, etc.,), any of the sensitizing merocyanine dyes (see United States Patent 2,078,233, dated April 27, 1937, for example), any of the sensitzing hemicyanine dyes (see United States Patent 2,166,736, dated'July 18, 1939, for example), any of the sensitizing hemioxonol dyes (see United States Patent 2,216,441, dated October 1, 1940, and United States Patent 2,165,339, dated July 11, 1939, for example), etc.
  • Photographic elements comprising our new emulsions can be made up in the usual manner by coating the flowable emulsions onto a support of a suitable material, such as glass, photographic paper, cellulose derivative or resinfilm, etc. to desired thickness, and then setting the coated emulsion.
  • a suitable material such as glass, photographic paper, cellulose derivative or resinfilm, etc.
  • Our new emulsions can contain hardening agents, setting agents, stabilizing agents, supersensitizing combinations of sensitizing dyes or a supersensitizing combination of one or more sensitizing dyes and another substance.
  • a photographic silver halide emulsion in which the silver halide is predominantly silver bromide and in which the carrier for the silver halide is polyvinyl alcohol, sensitized with a soluble gold compound and a thlocyanate selected from the group consisting of alkali metal and ammonium thiocyanates, the concentration of the gold compound in the emulsion being equal to from about 0.0005 to about 0.025 per cent by mols of the silver halide present in the emulsion, and the concentration of the thiocyanate being equal to from about 0.1 to about 2.5 percent by mols of the silver halide present in the emulsion.
  • a photographic silver halide emulsion in which the silver halide is predominantly silver bromide and in which the carrier for the silver halide is a hydrolyzed cellulose carboxylic ester in which the acyl groups contain from 2 to 3 carbon atoms, said cellulose ester containing from 19 to 33 percent by weight of said acyl groups, sensitized with a soluble gold compound and a thiocyanate selected from the group consisting of alkali metal and ammonium thiocyanates, the concentration of the gold compound in the emulsion being equal to from about 0.0005 to about 0.025 percent by mols of the silver halide present in the emulsion, and the concentration of the thiocyanate being equal to from about 0.1 to
  • a photographic silver halide emulsion in Which the silver halide is predominantly silver bromide and in which the carrier for the silver halide is a hydrolyzed cellulose acetate propionate containing from 19 to 33 percent by weight of acyl groups, sensitized with a soluble gold compound and a thiocyanate selected from the group consisting of alkali metal and ammonium thiocyanates, the concentration of the gold compound in the emulsion being equal to from about 0.0005 to about 0.025 percent by mols of the silver halide present in the emulsion, and the concentration of the thiocyanate being equal to from about 0.1 to about 2.5 percent by mols of the silver halide present in the emulsion.
  • a photographic silver halide emulsion in which the silver halide is predominantly silver bromide and in which the carrier for the silver halide is a hydrolyzed polyvinyl acetate containing an acetate group content equivalent to from 59 to 71 percent by weight of polyvinyl acetate, sensitized with a soluble gold compound and a thiocyanate selected from the group consisting of alkali metal and ammonium thiocyanates, the concentration of the gold compound in the emulsion being equal to from about 0.0005 to about 0.025 percent by mols of the silver halide present in the emulsion, and the concentration of the sulfur sensitizer being equal to from about 0.1 to about 2.5 percent by mols of the silver halide present in the emulsion.
  • a photographic silver halide emulsion in which the silver halide is predominantly silver bromide and in which the carrier for the silver halide is a polyvinyl acetaldehyde acetal containing polyvinyl acetaldehyde acetal groups equivalent to at least 50 percent by weight of polyvinyl acetaldehyde acetal and polyvinyl alcohol hydroxyl groups equivalent to at least percent by weight of polyvinyl alcohol, sensitized with a soluble gold compound and a thiocyanate selected from the group consisting of alkali metal and ammonium thiocyanates, the concentration of the gold compound in the emulsion being equal to from 0.0005 to about 0.025 per cent by mols of the silver halide present in the emulsion, and the concentration of the sulfur sensitizer being equal to from about 0.1 to about 2.5 percent by mols of the silver halide present in the emulsion.
  • a photographic silver halide emulsion in which the silver halide is predominantly silver bromide and in which the carrier for the silver halide is a polyvinyl propionaldehyde acetal containing polyvinyl alcohol hydroxyl groups equivalent to from 45 to 60 percent by weight of polyvinyl alcohol, sensitized with a soluble gold compound and a thiocyanate selected from the group consisting of alkali metal and ammonium thiocyanates, the concentration of the gold compound in the emulsion being equal to from about 0.0005 to about 0.025 percent by mols of the silver halide present in the emulsion, and the concentration of the sulfur sensitizer being equal to from about 0.1 to about 2.5 percent by mols of the silver halide present in the emulsion.
  • the carrier for the silver halide is a colloidal material selected from the group consisting of polyvinyl alcohol, hydrolyzed polyvinyl acetate containing an acetate group content equivalent to from 59 to 71 percent by weight of polyvinyl acetate, polyvinyl acetaldehyde acetals containing polyvinyl acetaldehyde acetal groups equivalent to at least 50 percent by weight of polyvinyl acetaldehyde acetal and polyvinyl alcohol hydroxyl groups equivalent to at least 15.
  • the step which comprises digesting the emulsion in the presence of a soluble gold compound and a sulfur sensitizer, the concentration of the gold compound in the emulsion being equal to from about 0.0005 to about 0.025 percent by mols of the silver halide present in the emulsion, and the concentration of the sulfur sensitizer being equal to from about 0.006 to about 2.5 percent by mols of the silver halide present in the emulsion.
  • the step which comprises digesting the emulsion on the acid side of neutrality in the presence of a soluble gold compound and a thiocyanate selected from the group consisting of alkali metal and ammonium thiocyanates, the concentration of the gold compound in the emulsion being equal to from about 0.0005 to about 0.025 percent by mols of the silver halide present in the emulsion, and the concentration of the thiocyanate being equal to from about 0.1 to about 2.5 percent by mols of the silver halide present in the emulsion.
  • the step which comprises digesting the emulsion on the acid side of neutrality in the presence of a soluble gold compound and a thiocyanate selected from the group consisting of alkali metal and ammonium thiocyanates, the concentration of the gold compound in the emulsion being equal to from about 0.0005 to about 0.025 percent by mols of the silver halide present in the emulsion, and the concentration of the thiocyanate being equal to from about 0.1 to about 2.5 percent by mols of the silver halide present in the emulsion.
  • the step which comprises digesting the emulsion on the acid side of neutrality in the presence of a soluble gold compound and a thiocyanate selected from the group consisting of alkali metal and ammonium thiocyanates, the concentration of the gold compound in the emulsion being equal to from about 0.0005 to about 0.025 percent by mols of the silver halide present in the emulsion, and the concentration of the thiocyanate being equal to from about 0.1 to about 2.5 percent by mols of the silver halide present in the emulsion.
  • the step which comprises digesting the emulsion on the acid side of neutrality in the presence of a soluble gold compound and a thiocyanate selected from the group consisting of alkali metal and ammonium thiocyanates, the concentration of the gold compound in the emulsion being equal to from about 0.0005 to about 0.025 per cent by mols of the silver halide present in the emulsion, and the concentration of the thiocyanate being equal to from about 0.1 to about 2.5 percent by mols of the silver halide present in the emulsion.
  • the step which comprises digesting the emulsion on the acid side of neutrality in the presence of a soluble gold compound and a thiocyanate selected from the group consisting of alkali metal and ammonium thiocyanates, the concentration of the gold compound in 12 the emulsion being equal to from about 0.0005 to about 0.025 percent by mols of the silver halide present in the emulsion, and the concentration of the thiocyanate being equal to from about 0.1 to about 2.5 percent by mols of
  • the step which comprises digesting the emulsion on the acid side of neutrality in the presence of a soluble gold compound and a thiocyanate selected from the group consisting of alkali metal and ammonium thiocyanates, the concentration of the gold compound in the emulsion being equal to from about 0.0005 to about 0.025 percent by mols of the silver halide present in the emulsion, and the concentration of the thiocyanate being equal to from about 0.1 to about 2.5 percent by mols of the silver halide present in the emulsion.

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  • Physics & Mathematics (AREA)
  • Chemical & Material Sciences (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • General Physics & Mathematics (AREA)
  • Colloid Chemistry (AREA)
  • Silver Salt Photography Or Processing Solution Therefor (AREA)
  • Non-Silver Salt Photosensitive Materials And Non-Silver Salt Photography (AREA)
US680514A 1946-06-29 1946-06-29 Photographic emulsion sensitized with gold compounds and sulfur sensitizers Expired - Lifetime US2624674A (en)

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FR959922D FR959922A (en, 2012) 1946-06-29
BE474236D BE474236A (en, 2012) 1946-06-29
US680514A US2624674A (en) 1946-06-29 1946-06-29 Photographic emulsion sensitized with gold compounds and sulfur sensitizers
GB26450/46A GB631243A (en) 1946-06-29 1946-09-03 Improvements in sensitive photographic emulsions

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Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3113026A (en) * 1959-01-19 1963-12-03 Gen Aniline & Film Corp Polyvinyl alcohol photographic silver halide emulsions
US3128185A (en) * 1960-01-25 1964-04-07 Eastman Kodak Co Antifoggants for formaldehydehardened photographic layers
US3128184A (en) * 1960-01-25 1964-04-07 Eastman Kodak Co Antifoggants for gold sensitized emulsions in the presence of reduction sensitizers
US3312550A (en) * 1959-04-10 1967-04-04 Eastman Kodak Co Processing photographic elements containing developing agent
US3632343A (en) * 1969-07-29 1972-01-04 Eastman Kodak Co Photographic emulsions and processes
US3977880A (en) * 1973-10-18 1976-08-31 Fuji Photo Film Co., Ltd. Direct-positive emulsion containing silver halide grains internally doped with metal ions, surface ripened with gold and sulfur compound and fogged by light exposure

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2743182A (en) * 1952-11-08 1956-04-24 Eastman Kodak Co Chemical sensitization of photographic emulsions

Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB190106609A (en) * 1901-03-29 1901-12-14 Maurice Berges Improvements in or relating to the Manufacture of Photographic Printing Papers and the like.
US836461A (en) * 1905-10-17 1906-11-20 Carl Sofus Poulsen Self-toning photographic paper.
US1574944A (en) * 1924-06-06 1926-03-02 Eastman Kodak Co Photographic light-sensitive material and process of making the same
US1995444A (en) * 1931-09-03 1935-03-26 Ilford Ltd Photographic printing emulsion
US2001951A (en) * 1933-03-22 1935-05-21 Ilford Ltd Photographic printing emulsion and its production
US2110491A (en) * 1936-04-16 1938-03-08 Eastman Kodak Co Photographic emulsions
GB498049A (en) * 1937-06-18 1939-01-03 Ig Farbenindustrie Ag Improvements in phosphate glass
DE692828C (de) * 1936-01-15 1940-06-27 Versuchsanstalt Fuer Luftfahrt Verfahren zur Herstellung hoechstempfindlicher photographischer Emulsionen
US2399083A (en) * 1942-02-13 1946-04-23 Ilford Ltd Photographic materials

Patent Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB190106609A (en) * 1901-03-29 1901-12-14 Maurice Berges Improvements in or relating to the Manufacture of Photographic Printing Papers and the like.
US836461A (en) * 1905-10-17 1906-11-20 Carl Sofus Poulsen Self-toning photographic paper.
US1574944A (en) * 1924-06-06 1926-03-02 Eastman Kodak Co Photographic light-sensitive material and process of making the same
US1995444A (en) * 1931-09-03 1935-03-26 Ilford Ltd Photographic printing emulsion
US2001951A (en) * 1933-03-22 1935-05-21 Ilford Ltd Photographic printing emulsion and its production
DE692828C (de) * 1936-01-15 1940-06-27 Versuchsanstalt Fuer Luftfahrt Verfahren zur Herstellung hoechstempfindlicher photographischer Emulsionen
US2110491A (en) * 1936-04-16 1938-03-08 Eastman Kodak Co Photographic emulsions
GB498049A (en) * 1937-06-18 1939-01-03 Ig Farbenindustrie Ag Improvements in phosphate glass
US2399083A (en) * 1942-02-13 1946-04-23 Ilford Ltd Photographic materials

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3113026A (en) * 1959-01-19 1963-12-03 Gen Aniline & Film Corp Polyvinyl alcohol photographic silver halide emulsions
US3312550A (en) * 1959-04-10 1967-04-04 Eastman Kodak Co Processing photographic elements containing developing agent
US3128185A (en) * 1960-01-25 1964-04-07 Eastman Kodak Co Antifoggants for formaldehydehardened photographic layers
US3128184A (en) * 1960-01-25 1964-04-07 Eastman Kodak Co Antifoggants for gold sensitized emulsions in the presence of reduction sensitizers
US3632343A (en) * 1969-07-29 1972-01-04 Eastman Kodak Co Photographic emulsions and processes
US3977880A (en) * 1973-10-18 1976-08-31 Fuji Photo Film Co., Ltd. Direct-positive emulsion containing silver halide grains internally doped with metal ions, surface ripened with gold and sulfur compound and fogged by light exposure

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FR959922A (en, 2012) 1950-04-07
BE474236A (en, 2012)
GB631243A (en) 1949-10-31

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