EP0445444A1 - Photographische Emulsionen - Google Patents

Photographische Emulsionen Download PDF

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Publication number
EP0445444A1
EP0445444A1 EP90302312A EP90302312A EP0445444A1 EP 0445444 A1 EP0445444 A1 EP 0445444A1 EP 90302312 A EP90302312 A EP 90302312A EP 90302312 A EP90302312 A EP 90302312A EP 0445444 A1 EP0445444 A1 EP 0445444A1
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EP
European Patent Office
Prior art keywords
silver
silver halide
emulsion
crystals
halide
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP90302312A
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English (en)
French (fr)
Inventor
Karen Nicola Harvey
Trevor James Maternaghan
David John Turner
Douglas James Edwards
Amanda Mary Jackson
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Ilford Imaging UK Ltd
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Ilford Ltd
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Publication of EP0445444A1 publication Critical patent/EP0445444A1/de
Withdrawn legal-status Critical Current

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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
    • G03C1/0051—Tabular grain 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
    • 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
    • G03C1/10—Organic substances
    • G03C1/12—Methine and polymethine dyes
    • G03C1/14—Methine and polymethine dyes with an odd number of CH groups
    • G03C1/18—Methine and polymethine dyes with an odd number of CH groups with three CH groups
    • 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
    • G03C2001/0156—Apparatus or processes for the preparation of emulsions pAg value; pBr value; pCl value; pI value
    • 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
    • G03C2001/03511—Bromide content
    • 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
    • G03C2001/03535—Core-shell grains
    • 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
    • G03C2200/00—Details
    • G03C2200/44—Details pH value

Definitions

  • This invention relates to the production of silver halide emulsions with improved sensitivity.
  • sub-developable centres are so-called sub-developable centres as they do not contribute substantially to the formation of fog when unexposed emulsions are developed. It is thought that such sub-developable centres may act as hole-trapping centres therefore increasing the speed of the emulsion without contributing directly to latent image formation.
  • sub-developable centres do not act in the same way as the sensitivity specks formed during chemical sensitisation since they do not promote the formation of latent image nuclei in the interior of the grain on exposure to light.
  • Emulsions of this type are described in British Patent Specification 1426012.
  • the sub-developable centres are formed by the action of a reducing agent during the formation of the silver halide crystals and before they have reached their final size.
  • a modification to the method of preparing such silver halide emulsions as described in BP 1426012 is described in the British patent 1445192.
  • Another method of forming sub-developable centres before the silver halide crystals have reached their full size is described in British Patent Specification 1588943.
  • a silver halide emulsion which comprises a colloid medium having dispersed therein silver halide emulsion crystals which comprise at least two layers of different silver halide composition, there being sub-developable silver centres which have been formed at the boundary between two of the layers by a reduction sensitisation step.
  • sub-developable centres small clusters of silver atoms which increase the inherent light sensitivity of the silver halide grains but which do not contribute substantially to the formation of fog when unexposed silver halide crystals are developed.
  • One test for this is the test described in BP's 1426012, 1445192 and 1588943.
  • silver halide crystals in the emulsion have been both chemically and spectrally sensitised at the surface.
  • a useful size of crystal in the emulsion is from 0.5 ⁇ to 1.5 ⁇ .
  • the population of crystals in the emulsion is monodisperse having a size coefficient of variation of 30% and preferably less than 20%.
  • the inner layer of the boundary in the silver halide crystals at which the sub-developable centres are present is silver iodobromide and the outer layer is silver bromide.
  • the amount of iodide in the silver iodobromide layer is from 2 to 35 mole % iodide.
  • both the inner and the outer layers of the silver halide crystals can comprise the same mixed halides as long as there is a marked difference in the halide ratios resulting in a abrupt change in halide composition at the boundary i.e. at least 5% difference in the proportion of a major component such as silver bromide across the boundary.
  • the clusters of sub-developable silver atoms may be formed at the silver halide layers by a reduction process.
  • an excessively long reduction treatment can lead to increased fog or formation of prelatent image specks.
  • a method of preparing a silver halide emulsion as just defined which comprises preparing in a hydrophilic colloid dispersing medium a silver halide emulsion using water-soluble silver salt solutions and water-soluble halide solutions to form silver halide. Crystals of a requisite size and having at their surface silver halide of a first composition then changing the halide/halides to form silver halide having a second composition which is laid down on the already formed silver halide crystals, then carrying out a reduction sensitisation step and continuing to add the silver and halides of the second composition until the silver halide crystals reach a final requisite size.
  • a period is allowed before resumption of addition of silver and halides.
  • the reduction sensitisation step may be carried out by adding a reducing agent to the dispersing medium, or by use of an ionising radiation or by altering the pAg and/or pH conditions to produce the silver digestion conditions as described by H W Wood J. Phot. Sci. 1 (1953) 163 in which the pAg is held relatively low from 7 to 0, preferably at 3 at a relatively high temperature of about 50 o C, the pH preferably being from 7 to 10.
  • the pAg should be less than 8 and the pH greater than 5.5. These conditions produce reduction sensitisation without any great increase in fog.
  • the reduction sensitisation step is preferably carried out after at least 1 minute of the change of halide being added to ensure that a boundary between halides of different composition has formed on the silver halide crystals.
  • the preferred reducing agents are stannous chloride and glutaraldehyde.
  • Other useful reducing agents are hydrazine and other aldehydes such as formaldehyde.
  • Sulphur containing reducing agents such as thiourea are not preferred.
  • ionising radiation to produce the sub-developable centres may be carried out as described in BP 1588943.
  • the silver halide crystals Preferably after the silver halide crystals have reached their requisite size they are then chemically sensitised using both gold and a sulphur sensitiser.
  • the silver halide crystals are then spectrally sensitised.
  • the soluble silver salt solutions and the ammonium or alkali metal halide solutions are added to the dispersing medium by the well known double-jet method of preparing silver halide emulsions.
  • the outer halide layer may be formed by an Ostwald ripening process in the presence of small crystals of different halide composition from the previously formed silver halide crystals but this is not preferred as the presence of a solvent obviates the abrupt change of halide composition.
  • the silver halide crystals of the present invention may be of any of the well known crystal habits employed in photographic silver halide emulsion. Useful habits are cubic, twinned octahedral and tabular twinned octahedral.
  • the crystals may be formed using any of the well-known techniques for forming such silver halide crystals.
  • British Patent Specification 2110831 described the formation of tabular silver halide crystals which may be twinned.
  • twinned silver halide photographic emulsions of the intermediate tetradecahedral habit may be produced by selection of the appropriate solution conditions.
  • the process of the present invention is particularly suitable for the production of twinned silver halide emulsions of the monodisperse type.
  • the outer layer of the silver halide crystals are formed by adding further silver and halide solutions by a double jetting method and at a controlled pAg.
  • the additional halide added during this stage is such that the iodide content of the final crystals is about 5 - 15 mol % which is the amount of iodide which has been found to be most beneficial, yielding high-speed emulsions for negative working photographic material.
  • the pAg can be varied during the formation of the outer halide layer to modify the habit of the final twinned emulsion crystals. For example by selection of a fixed pAg in the range 6 to 9, (100) external faces are favoured leading to cubic crystals, whereas with iodide contents greater than 5 M % and pAg values greater than 7, external octahedral faces are favoured.
  • the water-soluble salts formed or the ripening agents added during the process of the present invention may be removed by any of the well-known methods. Such methods often involve flocculating the silver halide and colloid dispersing agent, removing this flocculate from the then aqueous medium, washing it and redispersing it in water.
  • One other common method is ultrafiltration, in which the emulsion is passed over a membrane under pressure. The pore size of the membrane is such that the silver halide crystals and most of the colloid dispersing medium is retained, whilst water and solutes permeate through.
  • Most of the well-known methods allow the emulsion to be concentrated as well as washed. This is important when weak reagent solutions are employed, particularly those with concentrations below 3M.
  • the silver halide crystals are preferably chemically sensitised on the surface by any of the well known means, for example by use of sulphur or selenium compounds or salts of the noble metals such as gold, iridium rhodium, osmium, palladium or platinum.
  • Chemical sensitisation is preferably carried out in the presence of sulphur-containing ripening agents such as thioethers or thiocyanate compounds.
  • the fully grown crystals are sensitised in this manner, so that the products of chemical sensitisation are formed on the surface of the crystal so that such sensitised crystals become developable in a surface developer after exposure to light.
  • the emulsions of the present invention are preferably spectrally sensitised by the addition of spectral sensitisers for example carbocyanine and merocyanine dyes to the emulsions. Suitable dyes are described in James, The Theory of the Photographic Process. 4th Edition. McMillan. Chapter 8.
  • the emulsions may contain any of the additives commonly used in photographic emulsions for example wetting agents, such as polyalkene oxides, stabilising agents, such as tetraazaindenes, metal sequestering agents, growth or crystal habit modifying agents commonly used for silver halide such as adenine and plasticisers such as glycerol to reduce the effect of mechanical stress.
  • wetting agents such as polyalkene oxides
  • stabilising agents such as tetraazaindenes, metal sequestering agents
  • growth or crystal habit modifying agents commonly used for silver halide such as adenine
  • plasticisers such as glycerol
  • the colloid dispersing medium is gelatin or a mixture of gelatin and a water-soluble latex for example or latex vinyl acrylate-containing polymer. Most preferably if such a latex is present in the final emulsion it is added after all crystal growth has occurred.
  • a water-soluble latex for example casein, polyvinyl pyrrolidone or polyvinyl alcohol may be used alone or together with gelatin.
  • the silver halide emulsions of the present invention exhibit high speed and low granularity, thus they are of particular use in high speed camera film material.
  • the invention includes the novel silver halide emulsions, methods for preparing these emulsions and coated photographic silver halide material containing at least one such emulsion.
  • the pI of the emulsion was maintained throughout at 1.0 (monitored by the potential being maintained throughout at - 280 mV by addition of KI, measured by a silver ion electrode with standard calomel reference).
  • the median crystal size produced was 0.15 um.
  • step C One-tenth of the emulsion produced in step C was taken and 10 litres of a 5% w/v inert gel solution added with thorough agitation at 65 o C. The volume of each crystal was then increased 5-fold by monosize growth as follows; whilst the potential was maintained at -120mV at 65 o C, 4.7m solutions of silver nitrate and sodium bromide were added by double jetting. The initial flow rate was 100 cm3/min, this was progressibely increased linearly with respect to time to a final flow rate of 645 cm3/min, by which time 12720 cm3 of silver nitrate had been added.
  • the final stage of growth was to add 4.7 M silver nitrate and 4.7 M sodium bromide by double jetting.
  • the initial rate of addition was 335 cm3/min, this was linearly increased as before to 645 cm3/min until 3180 cm3 of silver nitrate had been added.
  • the overall iodide of this emulsion was 5%.
  • Emulsion 3 As for emulsion 3, except 4.7 M silver nitrate and 4.7 M sodium bromide used throughout the whole step. The SnCl2 addition was made as for Emulsion 3.
  • the overall iodide content of the emulsion 3 was 5%.
  • the overall iodide content of the emulsion 4 was 1%.
  • Figure 1 is a depiction of a silver halide crystal made according to the prior art.
  • Figure 2 is a depiction of a silver halide crystal with a halide boundary.
  • Figure 3 is a depiction of a silver halide crystal made according to the present invention.
  • Figure 4 is a depiction of a silver halide crystal having sub-developable silver centres but not at a halide boundary.
  • A represents the silver iodobromide core formed in steps A and B, that is to say the preparation of monosized silver iodide and the recrystallisation step.
  • B represents the silver bromide layer formed in step C, the growth step.
  • figure 1 which represents emulsion 1 layers A, B and C are all that are formed.
  • FIG 2 which represents emulsion 2
  • the further growth step D takes place in two stages and a silver iodobromide layer D is laid down on the silver bromide layer B. After the silver iodobromide layer D has formed the shell C of silver bromide is laid down on it.
  • FIG 3 which represents emulsion 3 the further growth step takes place in three stages.
  • a silver iodobromide layer D is laid down on the silver bromide layer B.
  • a ring of silver clusters E is formed on layer D by adding a dilute solution of stannous chloride one minute after the silver bromide layer C is starting to form on layer D.
  • This figure represents the emulsion of the present invention.
  • the further growth step takes place in two stages.
  • the formation of the shell C of silver bromide is interupted to form a ring of silver cluster E in the shell and then the remainder of shell C is formed.
  • This formation of silver clusters is carried out by adding stannous chloride to the emulsification vessel before all the silver bromide has been added in step D.
  • emulsion 1 there is no halide boundary in the shell and no ring of silver clusters.
  • emulsion 2 there is a halide boundary in the shell but no ring of silver clusters.
  • emulsion 3 which is the emulsion according to the present invention there is a halide boundary and at the halide boundary a ring of silver clusters.
  • emulsion 4 there is a ring of silver clusters in the shell but no halide boundary
  • Step E the desalination and chemical sensitisation step took place after the completion of crystal growth in step D.
  • the emulsions 1 - 4 were desalinated by ultrafiltration and redispersed with a solution of limed ossein gelatin. They were then adjusted at 40 o C to pH 6 and pAg 8.2.
  • the development time in developer A in each case was selected to give a contrast value close to a contrast value of 0.55, corresponding to a reasonable comparison for partially developed monochrome camera films.
  • the characteristic curves for more complete development, that is 10 minutes in a developer of composition B were also measured.
  • S0.1 is the foot speed in log Exposure (E) units. The higher the figure the better the result. A 0.3 log E increase in speed corresponds to a doubling of the arithmetic speed of the film coating.
  • G 1.5 is the contrast obtained. In general the higher the figure the better the result. This figure is obtained by measuring the slope of the curve between points on the photographic curve corresponding to densities of 0.1 and 1.5.
  • the reduction sensitisation step is carried out by varying the pH from the norm which is 5.
  • each of the emulsions in this Example were grown as described in Example 1 of British Patent Specification No 1596602 except that the silver iodide seed emulsion had an average size of 0.6 ⁇ m, and the addition rates of silver and bromide salt solutions during step (ii) and step (iii) were lowered to approximately 10% of those stated.
  • the emulsions had an average crystal size of 1.2 ⁇ m with a coefficient of size variation of 30% and an iodide content of 7.5 mole %.
  • the pH and pAg growth conditions were as set out below.
  • step (ii) and step (iii) were adjusted for different pAg values using the procedures described in BP 1,596,602.
  • these emulsions compared with the emulsions prepared in Example 1 comprised a silver iodobromide core obtained by the recrystallisation of the silver iodide seed crystals and a silver bromide shell formed during the further growth stage.
  • Aqueous 1.2M solutions of silver nitrate and sodium bromide were added by double jetting at 7.2 cm3 min ⁇ 1 until 36 cm3 of silver nitrate had been added.
  • the potential was maintained at -125 mV at 65 o C with stirring.
  • 1.2 M silver nitrate was added by a single jetting at 18 cm3 min ⁇ 1 until -101 mV was reached.
  • 1.2 M silver nitrate and a 1.2 M solution of 88% sodium bromide / 12% potassium iodide were added by double jetting.
  • the initial flow rate was 18 cm3 min ⁇ 1, this was linearly increased to 41cm3 min ⁇ 1 until 3312 cm3 of silver nitrate had been added.
  • the silver ion potential was maintained at -101 mV at 65 o C.
  • the emulsion was desalinated and redispersed with a solution of limed ossein gelatin. It was then re-adjusted to 65 o C, pH6 and pAg 8.
  • Step D 40% by weight of the emulsion produced in Step D was taken and 1.2 M silver nitrate was added at 15 cm3 min ⁇ 1 until a potential of -101 mV was reached with stirring.
  • 1.2 M silver nitrate and 1.2 M sodium bromide were added by double jetting at 15 cm3 min ⁇ 1 until 120 mls of silver nitrate had been added whilst maintaining the potential at -101mV at 65 o C.
  • 1.2 M silver nitrate was added at 15 cm3 min ⁇ 1 until a potential of -10 mV was reached. This is emulsion M.
  • Step D A further 40% by weight of the emulsion produced in Step D was taken and growth proceeded as above except that after 1 minute had elapsed into the double jetting stage, 20 cm3 of 0.0025 M SnCl2 was added to the precipitation vessel. This is emulsion N.
  • Samples of the emulsion M and N were then digested at 52 o C for a range of times and with a range of chemical sensitiser quantities. Optimum photographic sensitivity was found when approximately 7.11 mg sodium thiosulphate pentahydrate and 1.07 mg sodium tetrachloroaurate dihydrate per mole of silver halide were used. Then half of the emulsion samples of M and N were spectrally sensitised by addition of 0.15 g mole ⁇ 1 of a carbocyanine dye of the following formula :- Then all the emulsions M and N were stabilised using 0.41 g of 4-hydroxy-6-methyl-1,3,3,7tetraazaindene per mole of silver halide. The optimally sensitised emulsions were then coated on a triacetate base at 50 mg Ag dm ⁇ 2.
  • the development time in each case was fixed at 8 minutes.
  • the characteristic curves for a more complete development 10 minutes in a developer B as used in Example 1 were also measured.
  • FIGS. 5 and 6 are diagrammatic views of tabular Emulsions M and N as just prepared.
  • Figure 5 shows Emulsion M
  • Figure 6 shows Emulsion N.
  • the aspect ratios of both Emulsions M and N as produced were 20 : 1.
  • the silver bromide core 1 as produced in step A is surrounded by a silver iodobromide layer 2 having 12% iodide as produced in the growth step C.
  • the silver iodobromide layer 2 is surrounded by a silver bromide shell 3 as produced by the growth step E. Separating the layer 2 from the shell 3 is a halide boundary 4.
  • layer 2 and shell 3 are as in figure 5 but around the halide boundary 4 are silver halide clusters 5 forming sub-developable centres. These clusters have been formed at the boundary by the addition of Sn Cl2 after 1 minute into growth step E.
  • Step A Preparation of monosized silver iodide emulsion
  • the silver iodide seed emulsion was grown as described in Example 1 of British Patent Specification No. 1596602 except that the crystals had an average size of 0.65 ⁇ m.
  • step B 3.6 % of the emulsion produced in step B was taken, and .35 litres of a 29% w/v inert gel solution added with thorough agitation at 65°C. 0.2 cm3 of tri-n-butyl phosphate was added as an antifoam. The volume of each crystal was then increased by double jetting 1.5 m solutions of silver nitrate and sodium bromide while maintaining the potential at -33 mV at 65°C. The first 355 cm3 was added as a jetting rate of 10 cm3 minute and finally 1070 cm3 at 40 cm3/minute.
  • the emulsion was composed of AgIBr in which 15 mole % of the halide was iodide and the median crystal size was 1.0 um (based on equivalent circular diameter).
  • a further 3.6 % of the emulsion from step B was taken and growth proceeded as for Emulsion 1 with the following difference : after one minute of the first double jetting stage had elapsed, 104 cm3 of 2 g/litre glutaraldehyde bisulphite solution (made up in freshly boiled deionised water) was added dropwise.
  • the emulsions were desalinated and redispersed with a solution of lined ossein gelatin.
  • the emulsions were adjusted at 40°C to pH6 and pAg 8.2. They were then digested at 52°C for a range of times and with various quantities of chemical sensitisers. Sulphur was added as sodium thiosulphate pentahydrate at levels of 0, 7 and 13 mg per mole of silver. Gold was added as sodium tetrachloroaurate dihydrate at levels of 0, 2 and 4 mg per mole of silver. The emulsions were stabilized using 0.41 g of 4-hydroxy-6-methyl-1,3,3a,7tetrazaindene per mole of silver.
  • Each emulsion was coated on a cellulose triacetate base at a coating weight of 50 mg Ag/dm2.
  • S 0.1 is the foot speed in Log Exposure (E) units. The higher the figure the better the result.
  • a 0.3 Log E increase in S 0.1 corresponds to a doubling of the arithmetic speed of the film coating.
  • G 1.5 is the contrast obtained. In general, the higher the figure the better the result.
  • the first three lines of results compare emulsions 1,2 and 3 with no chemical sensitisation.
  • Emulsions 2 and 3 contain a halide boundary and deliberate reduction sensitisations while emulsion 1 is of identical crystal structure but with no reduction sensitisation. Hence the presence of reduction sensitisation at the sub-surface boundary gives substantially increased foot speed an contrast while fog levels remain acceptable.
  • Emulsion 1 control
  • Emulsion 3 invention
  • the etchant used was sodium thiosulphate solution.
  • Emulsion 3 after etching and latensification demonstrates the presence of sub-developable latent image centres as a result of reduction sensitisation at the compositional boundary.
  • the gold latensification method used was that described by T H James, W Vanselow and R F Quirk. Photographic Science and Engineering 5 , 219 (1961).

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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)
  • Crystallography & Structural Chemistry (AREA)
  • Silver Salt Photography Or Processing Solution Therefor (AREA)
EP90302312A 1988-09-13 1990-03-05 Photographische Emulsionen Withdrawn EP0445444A1 (de)

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GB888821433A GB8821433D0 (en) 1988-09-13 1988-09-13 Photographic emulsions

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1011016A1 (de) * 1998-12-15 2000-06-21 Agfa-Gevaert N.V. Verbesserte Silberhalogenidsensibilisierung

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0354547A (ja) * 1989-07-24 1991-03-08 Konica Corp 保存性が良好なハロゲン化銀写真感光材料
JPH0869073A (ja) * 1994-08-30 1996-03-12 Konica Corp ハロゲン化銀カラー写真感光材料

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2169360A1 (de) * 1972-01-26 1973-09-07 Agfa Gevaert Ag
DE2402130A1 (de) * 1973-01-18 1974-08-01 Eastman Kodak Co Verfahren zur herstellung einer photographischen silberhalogenidemulsion mit innenempfindlichen silberhalogenidkoernern
DE2801127A1 (de) * 1978-01-12 1979-07-19 Agfa Gevaert Ag Photographische silberhalogenidemulsionen

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GB2222694B (en) 1992-05-27

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