US3741767A - Photographic emulsions containing alkali metal ferricyanides - Google Patents

Photographic emulsions containing alkali metal ferricyanides Download PDF

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Publication number
US3741767A
US3741767A US00155611A US3741767DA US3741767A US 3741767 A US3741767 A US 3741767A US 00155611 A US00155611 A US 00155611A US 3741767D A US3741767D A US 3741767DA US 3741767 A US3741767 A US 3741767A
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United States
Prior art keywords
emulsion
alkali metal
sensitivity
ferricyanide
added
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Expired - Lifetime
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US00155611A
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English (en)
Inventor
J Baylis
A Bond
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Ilford Imaging UK Ltd
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Ilford Ltd
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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

Definitions

  • the silver halide is precipitated in the presence of a medium which comprises a protective colloid, usually gelatin, this is called the emulsification step. Then the silver halide crystals are caused to increase in size by maintaining the medium at a raised temperature, there being present in the medium a silver halide solvent, for example an alkali metal halide. During this stage in the emulsion making process which is usually called the physical ripening stage and hereinafter is so referred, the smaller silver halide crystals increase in size. When the crystals of the silver halide have achieved an optimum crystal size for the type of emulsion being prepared the emulsion is flocculated.
  • a medium which comprises a protective colloid usually gelatin
  • This flocculate may be washed to remove soluble by-products if required.
  • the flocculate is thereafter dispersed in an aqueous medium and a digestion or chemical sensitisation stage is carried out wherein the emulsion is digested at an elevated temperature in the presence of chemical sensitisers, often sulphur compounds.
  • this stage is referred to as the chemical ripening stage but in order to differentiate it from the physical ripening stage referred to above, this stage is hereinafter referred to as the digestion stage.
  • the silver halide grains in silver halide emulsions have internal sensitivity centres and surface sensitivity centres.
  • the internal sensitivity centres are formed during the physical ripening stage of the emulsion making process and the external sensitivity centres are formed during the chemical digestion stage of the emulsion making process.
  • Photographic emulsions can be prepared which have a very large number of internal sensitivity centres and they are said to have a high internal sensitivity and a low surface sensitivity.
  • photographic emulsions have a relatively high surface sensitivity and a low internal sensitivity while -a third type of emulsion may be formed wherein the ratio between the internal sensitivity and the surface sensitivity is such that its surface sensitivity is not substantially greater than its internal sensitivity.
  • a gelatino silver halide emulsion which comprises the steps of emulsification, physical ripening, flocculation and digestion, there is provided the step of adding to the emulsion at a stage in the emulsion making, prior to flocculation, an alkali metal ferricyanide.
  • the alkali metal ferricyanide is added to the emulsion after emulsification step.
  • the preferred alkali metal ferricyanide is potassium ferricyanide. Most preferably the alkali metal ferricyanide is added to the emulsion as an aqueous solution.
  • the step of adding the alkali metal ferricyanide to the emulsion has the elfect of reducing the number of internal sensitivity centres which are formed during the physical ripening stage.
  • the process of the present invention leads to emulsions having reduced internal sensitivity and in some cases yields emulsions having improved properties in regard to speed and/or contrast.
  • the ratio of internal sensitivity to external sensitivity is normally very low, it is very difficult to show any improvement because the reduction in the internal sensitivity of the emulsion is of little practical importance.
  • a process for the production of a silver halide photographic emulsion which has a high surface sensitivity relative to internal sensitivity by a process of which comprises the steps of emulsification, physical ripening flocculation and digestion, which comprises modifying the aforesaid method of production of a silver halide photographic emulsion whigh when so manufactured will have a surface sensitivity not substantially greater than its internal sensitivity, by adding to the emulsion, at a stage prior to flocculation, an alkali metal ferricyanide.
  • the alkali metal ferricyanide is potassium ferricyanide and the alkali metal ferricyanide is added to the emulsion as an aqueous solution.
  • the preferred amount of alkali metal ferricyanide to be added to the emulsion prior to the flocculation thereof is from 0.01 to 1.0 g. per 1.50 moles of silver present in the emulsion and most preferably 0.2 to 0.5 g. It has been found that when alkali metal ferricyanide is added to a photographic emulsion prior to the flocculation thereof, the chemical digestion stage usually has to be extended to reach the optimum sensitivity for the emulsion. When much more than 1.0 g. of alkali metal ferricyanide per 1.50 moles of silver is added, the length of time of the chemical digestion stage has to be extended to an unacceptable level. I
  • EXAMPLE 1 In order to show the difference between the internal sensitivity of an emulsion made by the process of the present invention and an emulsion wherein the step of adding an alkali ferricyanide has been omitted, a photographic emulsion was prepared as follows:
  • a solution of silver nitrate was added to an aqueous solution of gelatin, potassium bromide, sodium chloride and hydrochloric acid to give a precipitate of 1.5 moles of silver chloro-bromide consisting of 74% bromide.
  • a solution of the double salt of sodium chloride-rhodium trichloride was added.
  • the gelatin concentration was 1.6% the pH was 3.9 and the chloride ion concentration was 0.5 N.
  • the emulsion was physically ripened for 20 minutes at 54 C. The emulsion was then flocculated and redispersed in extra gelatin.
  • Sulphur sensitiser in the form of sodium thiosulphate was added and the emulsion was digested for a time chosen to give optimum speed and contrast.
  • the emulsion was stabilized with l-phenyl-lH-tetrazole-S-thiol and 4- hydroxy-6-methyl-2-methylthio-l,3,3a,7 tetraazaindene.
  • the emulsion was optically sensitised and coated on a photographic quality paper base at a silver coating weight of 1.5 gms. per square metre.
  • a similar emulsion was prepared to which 0.25 g. of potassium ferricyanide were added as an aqueous solution to a portion of the emulsion which comprises 1.5 moles of silver.
  • the ferricyanide solution was added during the physical ripening stage of the emulsion making.
  • the two emulsions so made were coated onto strips and exposed in an intensity scale sensitometer to a tungsten light source for seconds.
  • the surface image which is a measure of the surface sensitivity of the grains of the silver halide in the two strips was determined by developing sample strips of the two emulsions in a developer consisting of 30 parts of glycin, 44 parts of anhydrous sodium carbonate and water to 1000 parts by volume.
  • the internal image which is a measure of the internal sensitivity of the grains of the two samples of emulsion was determined by bleaching the surface image by immersing the strips for two minutes at 20 C. in a 0.1% solution of potassium ferricyanide. The strips were washed for five minutes and then developed for three minutes at 20 C. in a general purpose photographic developer of the following formula G.
  • a gelatin silver chlorbromide emulsion was prepared by simultaneously adding a silver nitrate solution and a mixed solution of ammonium chloride and ammonium bromide to a solution of 35 gms. of gelatin and mls. of 3 N silver nitrate in 580 mls. of distilled water. The solutions were added at equal rates over a period of 2 minutes to give a precipitate of silver halides containing 1.5 moles of silver and consisting of 67% silver bromide. Throughout the precipitation a constant concentration of 0.1 N silver nitrate was maintained.
  • the emulsion obtained was then flocculated and re-dispersed in gelatin.
  • Sulphur, sensitiser in the form of sodium thiosulphate was added and the emulsion chemical digested for a time chosen to give optimum speed and contrast.
  • the emulsion was stabilised with a tetraazaindene stabiliser, optically sensitised and then coated on a photographic quality paper base at a silver coating Weight of 2 gms. per sq. metre.
  • a control emulsion without the addition of potassium ferricyanide was also prepared.
  • the same emulsions were also coated with hydroquinone in the emulsion and then processed in an Ilford Limiter Ilfo-printer machine type 1501 using a caustic soda based activator solution consisting of 80 gms. of sodium hydroxide, 20 gms. of sodium sulphite and water to 1 litre, and an ammonium thiocyanate based image stabiliser solution consisting of gms. of ammonium thiocyanate, 60 gms. of glacial acetic acid, 60 gms. of sodium acetate and water to 1 litre.
  • This type of development develops, for all practical purposes, the surface image only.
  • the invention includes photographic silver halide emulsions when prepared by any one of the processes of the present invention and photographic material comprising such emulsions.
  • step 1 which comprises adding to the emulsion at a stage in the emulsion making, prior to flocculation, an alkali metal ferricyanide in an amount ranging 0.01 to 1.0 gram per 1.5 gram equivalents of silver present in the emulsion.
  • a process as claimed in claim 1 which comprises adding the alkali metal ferricyanide to the emulsion after the emulsification step.
  • a process as claimed in claim 2 which comprises adding the alkali metal ferricyanide to the emulsion after the emulsification step, the alkali metal ferricyanide being present during substantially the whole physical ripening stage.
  • a process as claimed in claim 1 which comprises adding potassium ferricyanide to the emulsion.
  • a process as claimed in claim 2 which comprises adding potassium ferricyanide to the emulsion.
  • a process as claimed in claim 1 which comprises adding the ferricyanide in the form of an aqueous solution.
  • a process as claimed in claim 2 which comprises adding the ferricyanide in the form of an aqueous solution.

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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)
  • Silver Salt Photography Or Processing Solution Therefor (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
US00155611A 1970-06-26 1971-06-22 Photographic emulsions containing alkali metal ferricyanides Expired - Lifetime US3741767A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB3116670 1970-06-26

Publications (1)

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US3741767A true US3741767A (en) 1973-06-26

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ID=10319020

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US00155611A Expired - Lifetime US3741767A (en) 1970-06-26 1971-06-22 Photographic emulsions containing alkali metal ferricyanides

Country Status (9)

Country Link
US (1) US3741767A (ja)
JP (1) JPS5331365B1 (ja)
BE (1) BE769053A (ja)
CA (1) CA965289A (ja)
CH (1) CH547507A (ja)
DE (1) DE2131455C3 (ja)
ES (1) ES392612A1 (ja)
FR (1) FR2099906A5 (ja)
GB (1) GB1287978A (ja)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3890154A (en) * 1969-12-24 1975-06-17 Fuji Photo Film Co Ltd Light-sensitive silver halide photographic materials

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0814682B2 (ja) * 1988-01-18 1996-02-14 富士写真フイルム株式会社 ハロゲン化銀感光材料

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3684985A (en) * 1971-08-30 1972-08-15 Amerace Esna Corp Convertible timing device

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3890154A (en) * 1969-12-24 1975-06-17 Fuji Photo Film Co Ltd Light-sensitive silver halide photographic materials

Also Published As

Publication number Publication date
DE2131455A1 (de) 1972-01-13
ES392612A1 (es) 1975-10-16
CA965289A (en) 1975-04-01
GB1287978A (ja) 1972-09-06
DE2131455B2 (de) 1979-09-20
BE769053A (fr) 1971-12-27
CH547507A (de) 1974-03-29
DE2131455C3 (de) 1980-06-04
JPS5331365B1 (ja) 1978-09-02
FR2099906A5 (ja) 1972-03-17

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