Classifications

• • 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
  • G03C1/06—Silver halide emulsions; Preparation thereof; Physical treatment thereof; Incorporation of additives therein with non-macromolecular additives
  • G03C1/08—Sensitivity-increasing substances
• • 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
  • G03C1/46—Silver halide emulsions; Preparation thereof; Physical treatment thereof; Incorporation of additives therein having more than one photosensitive layer

Definitions

• the invention relates to silver halide photography. More specifically, the invention relates to improved spectrally sensitized silver halide emulsions and to multilayer photographic elements incorporating one or more of these emulsions.
• Kofron et al recognized that the chemically and spectrally sensitized emulsions disclosed in one or more of their various forms would be useful in color photography and in black-and-white photography (including indirect radiography). Spectral sensitizations in all portions of the visible spectrum and at longer wavelengths were addressed as well as orthochromatic and panchromatic spectral sensitizations for black-and-white imaging applications. Kofron et al employed combinations of one or more spectral sensitizing dyes along with middle chalcogen (e.g., sulfur) and/or noble metal (e.g., gold) chemical sensitizations, although still other, conventional modifying compounds, such as metal compounds, were taught to be optionally present during grain precipitation.
• middle chalcogen e.g., sulfur
• noble metal e.g., gold
• the invention is directed to an improved radiation-sensitive emulsion comprised of a dispersing medium, silver halide grains including tabular grains (a) having ⁇ 111 ⁇ major faces, (b) containing greater than 70 mole percent bromide, based on silver, (c) accounting for greater than 90 percent of total grain projected area, (d) exhibiting an average equivalent circular diameter of at least 0.7 ⁇ m, (e) exhibiting an average thickness of less than 0.07 ⁇ m, and (f) having latent image forming chemical sensitization sites on the surfaces of the tabular grains, and a spectral sensitizing dye adsorbed to the surfaces of the tabular grains, characterized in that the surface chemical sensitization sites include silver halide protrusions of a face centered cubic crystal lattice structure forming epitaxial junctions with the tabular grains and having a higher overall solubility than at least that portion of the tabular grains forming epitaxial junctions with the protrusions and a sensitivity enhancing combination of dopants are contained
• Silver chloride is a specifically preferred silver salt for epitaxial deposition onto the host ultrathin tabular grains.
• Silver chloride like silver bromide, forms a face centered cubic lattice structure, thereby facilitating epitaxial deposition.
• epitaxial deposition is preferably conducted under conditions that restrain solubilization of the halide forming the ultrathin tabular grains.
• a specifically preferred approach to silver salt epitaxy sensitization employs a combination of sulfur containing ripening agents in combination with middle chalcogen (typically sulfur) and noble metal (typically gold) chemical sensitizers.
• Contemplated sulfur containing ripening agents include thioethers, such as the thioethers illustrated by McBride U.S. Patent 3,271,157, Jones U.S. Patent 3,574,628 and Rosencrants et al U.S. Patent 3,737,313.
• Preferred sulfur containing ripening agents are thiocyanates, illustrated by Nietz et al U.S. Patent 2,222,264, Lowe et al U.S. Patent 2,448,534 and Illingsworth U.S. Patent 3,320,069.
• a preferred class of middle chalcogen sensitizers are tetrasubstituted middle chalcogen ureas of the type disclosed by Herz et al U.S. Patents 4,749,646 and 4,810,626.
• Preferred compounds include those represented by the formula: wherein X is sulfur, selenium or tellurium; each of R1, R2, R3 and R4 can independently represent an alkylene, cycloalkylene, alkarylene, aralkylene or heterocyclic arylene group or, taken together with the nitrogen atom to which they are attached, R1 and R2 or R3 and R4 complete a 5 to 7 member heterocyclic ring; and each of A1, A2, A3 and A4 can independently represent hydrogen or a radical comprising an acidic group, with the proviso that at least one A1R1 to A4R4 contains an acidic group bonded to the urea nitrogen through a carbon chain containing from 1 to 6 carbon atoms.
• X is preferably sulfur and A1R1 to A4R4 are preferably methyl or carboxymethyl, where the carboxy group can be in the acid or salt form.
• a specifically preferred tetrasubstituted thiourea sensitizer is 1,3-dicarboxymethyl-1,3-dimethylthiourea.
• Preferred concentrations of the selenium dopants are in the range of from 1 X 10 ⁇ 6 to 7 X 10 ⁇ 5 mole per silver mole, where silver represents total silver--that is, silver in the ultrathin tabular grains and in the silver halide epitaxy.
• HOMO h ighest energy electron o ccupied m olecular o rbital
• LUMO l owest energy u noccupied m olecular o rbital
• Group VIII metal ions Metal ions in Groups 8, 9 and 10 that have their frontier orbitals filled, thereby satisfying criterion (1), have also been investigated. These are Group 8 metal ions with a valence of +2, Group 9 metal ions with a valence of +3 and Group 10 metal ions with a valence of +4. It has been observed that these metal ions are incapable of forming efficient shallow electron traps when incorporated as bare metal ion dopants. This is attributed to the LUMO lying at an energy level below the lowest energy level conduction band of the silver halide crystal lattice.
• spectrochemical series can be applied to ligands of coordination complexes, it can also be applied to the metal ions.
• the following spectrochemical series of metal ions is reported in Absorption Spectra and Chemical Bonding by C. K. Jorgensen, 1962, Pergamon Press, London: Mn+ ⁇ Ni+ ⁇ Co+ ⁇ Fe+ ⁇ Cr+3 ⁇ V+3 ⁇ Co+3 ⁇ Mn+4 ⁇ Mo+3 ⁇ Rh+3 ⁇ Ru+3 ⁇ Pd+4 ⁇ Ir+3 ⁇ Pt+4
• the metal ions in boldface type satisfy frontier orbital requirement (1) above.
• the filled frontier orbital polyvalent metal ions of Group VIII are incorporated in a coordination complex containing ligands, at least one, most preferably at least 3, and optimally at least 4 of which are more electronegative than halide, with any remaining ligand or ligands being a halide ligand.
• the metal ion is itself highly electronegative, such Os+3, only a single strongly electronegative ligand, such as carbonyl, for example, is required to satisfy LUMO requirements.
• the metal ion is itself of relatively low electronegativity, such as Fe+, choosing all of the ligands to be highly electronegative may be required to satisfy LUMO requirements.
• Fe(II)(CN)6 is a specifically preferred shallow electron trapping dopant.
• coordination complexes containing 6 cyano ligands in general represent a convenient, preferred class of shallow electron trapping dopants.
• EPR signals in shallow electron traps give rise to an EPR signal very similar to that observed for photoelectrons in the conduction band energy levels of the silver halide crystal lattice.
• EPR signals from either shallow trapped electrons or conduction band electrons are referred to as electron EPR signals.
• Electron EPR signals are commonly characterized by a parameter called the g factor.
• the method for calculating the g factor of an EPR signal is given by C. P. Poole, cited above.
• the g factor of the electron EPR signal in the silver halide crystal lattice depends on the type of halide ion(s) in the vicinity of the electron. Thus, as reported by R. S. Eachus, M. T. Olm, R. Janes and M. C. R.
• test and control emulsions are each prepared for electron EPR signal measurement by first centrifuging the liquid emulsion, removing the supernatant, replacing the supernatant with an equivalent amount of warm distilled water and resuspending the emulsion. This procedure is repeated three times, and, after the final centrifuge step, the resulting powder is air dried. These procedures are performed under safe light conditions.
• Hexacoordination complexes are preferred coordination complexes for use in the practice of this invention. They contain a metal ion and six ligands that displace a silver ion and six adjacent halide ions in the crystal lattice. One or two of the coordination sites can be occupied by neutral ligands, such as carbonyl, aquo or ammine ligands, but the remainder of the ligands must be anionic to facilitate efficient incorporation of the coordination complex in the crystal lattice structure. Illustrations of specifically contemplated hexacoordination complexes for inclusion in the protrusions are provided by McDugle et al U.S. Patent 5,037,732, Marchetti et al U.S.
• an overlying emulsion layer e.g., the second emulsion layer
• the second emulsion layer is hereinafter also referred to as the optical causer layer and the first emulsion is also referred to as the optical receiver layer.
• the second emulsion layer consists almost entirely of ultrathin tabular grains.
• the optical transparency to minus blue light of grains having ECD's of less 0.2 ⁇ m is well documented in the art.
• Lippmann emulsions which have typical ECD's of from less than 0.05 ⁇ m to greater than 0.1 ⁇ m, are well known to be optically transparent.
• Grains having ECD's of 0.2 ⁇ m exhibit significant scattering of 400 nm light, but limited scattering of minus blue light.
• the resulting sensitized emulsions were coated on a cellulose acetate film support over a gray silver antihalation layer, and the emulsion layer was overcoated with a 4.3 g/m gelatin layer containing surfactant and 1.75 percent by weight, based on total weight of gelatin, of bis(vinylsulfonyl)methane hardener.
• Emulsion laydown was 0.646 g Ag/m and this layer also contained 0.323 g/m and 0.019 g/m of Couplers 1 and 2, respectively, 10.5 mg/m of 4-hydroxy-6-methyl-1,3,3a,7-tetraazaindene (Na+ salt), and 14.4 mg/m 2-(2-octadecyl)-5-sulfohydroquinone (Na+ salt), surfactant and a total of 1.08 g gelatin/m.
• Couplers 1 and 2 respectively, 10.5 mg/m of 4-hydroxy-6-methyl-1,3,3a,7-tetraazaindene (Na+ salt), and 14.4 mg/m 2-(2-octadecyl)-5-sulfohydroquinone (Na+ salt), surfactant and a total of 1.08 g gelatin/m.
• a preferred level of spectral sensitizing dye and sulfur and gold sensitizers was arrived at in the following manner: Beginning levels were selected based on prior experience with these and similar emulsions, so that observations began with near optimum sensitizations. Spectral sensitizing dye levels were varied from this condition to pick a workable optimum spectral sensitizing dye level, and sulfur and gold sensitization levels were then optimized for this dye level. The optimized sulfur (Na2S2O3 ⁇ 5H2O) and gold (KAuCl4) levels were 5 and 1.39 mg/Ag mole, respectively.
• the reactor gelatin was quickly oxidized by addition of 128 mg of OxoneTM (2KHSO5 ⁇ KHSO4 ⁇ K2SO4, purchased from Aldrich) in 20 cc H2O, and the temperature was raised to 54°C in 9 min. After the reactor and contents were held at this temperature for 9 min, 100 g of oxidized methionine lime-processed bone gelatin dissolved in 1.5 L H2O at 54°C were added to the reactor. Next the pH was raised to 5.90, and 122.5 cc of 1 M NaBr were added to the reactor.
• This emulsion was precipitated by the same procedure employed for Emulsion D, except that the flow rate ratio of AgI to AgNO3 was increased so that a uniform 12 M% iodide silver iodobromide grain composition resulted, and the flow rates of AgNO3 and NaBr during growth were decreased such that the growth time was ca. 1.93 times as long, in order to avoid renucleation during growth of this less soluble, higher iodide emulsion.
• Emulsion G profiled iodide
• This emulsion was precipitated by the same procedure employed for Emulsion D, except that after 6.75 moles of emulsion (amounting to 75 percent of total silver) had formed containing 1.5 M% I silver iodobromide grains, the ratio of AgI to AgNO3 additions was increased so that the remaining portion of the 9 mole batch was 12 M% I.
• flow rate based on rate of total Ag delivered to the reactor, was approximately 25% that employed in forming Emulsion D, (total growth time was 1.19 times as long) in order to avoid renucleation during formation of this less soluble, higher iodide composition.
• Emulsion G was determined to consist of 97 percent by number tabular grains with tabular grains accounting for greater than 99 percent of total grain projected area.
• Emulsion G contained grains dimensionally comparable to those of Emulsions D and F, containing uniformly distributed 1.5 or 4.125 M% iodide concentrations, respectively.
• Emulsion E which contained 12.0 M% iodide uniformly distributed within the grains showed a loss in mean ECD, an increase in mean grain thickness, and a reduction in the average aspect ratio of the grains.
• the epitaxially sensitized emulsion was split into smaller portions to determine optimal levels of subsequently added sensitizing components, and to test effects of level variations.
• the post-epitaxy components included additional portions of Dyes 1 and 2, 60 mg NaSCN/mole Ag, Na2S2O3.5H2O (sulfur), KAuCl4 (gold), and 11.44 mg APMT/mole Ag. After all components were added, the mixture was heated to 60°C to complete the sensitization, and after cooling to 40°C, 114.4 mg additional APMT were added.
• the resulting sensitized emulsions were coated on cellulose acetate support over a gray silver antihalation layer, and the emulsion layer was overcoated with a 4.3 g/m gelatin layer.
• Emulsion laydown was 0.646 g Ag/m and this layer also contained 0.323 g/m and 0.019 g/m of Couplers 1 and 2, respectively, 10.5 mg/m of 4-hydroxy-6-methyl-1,3,3A,7-tetraazaindene (Na+ salt), and 14.4 mg/m 2-(2-octadecyl)-5-sulfohydroquinone (Na+ salt), and a total of 1.08 g gelatin/m.
• the emulsion layer was overcoated with a 4.3 g/m gelatin layer containing surfactant and 1.75 percent by weight, based on the total weight of gelatin, of bis(vinylsulfonyl)methane hardener.
• the emulsions so coated were given 0.01" Wratten 23ATM filtered daylight balanced light exposures through a 21 step granularity step tablet (0-3 density range), and then were developed using the Kodak FlexicolorTM C41 color negative process. Speed was measured at a density of 0.30 above D min .
• Granularity readings on the same processed strips were made according to procedures described in the SPSE Handbook of Photographic Science and Engineering , edited by W. Thomas, pp. 934-939. Granularity readings at each step were divided by the contrast at the same step, and the minimum contrast normalized granularity reading was recorded. Contrast normalized granularity is reported in grain units (g.u.), in which each g.u. represents a 5% change; positive and negative changes corresponding to grainier and less grainy images, respectively (i.e., negative changes are desirable). Contrast-normalized granularities were chosen for comparison to eliminate granularity differences attributable to contrast differences.
• Emulsion H Profiled iodide, AgBr Central Region
• the first 75 percent of the silver was precipitated in the absence of iodide while the final 25 percent of the silver was precipitated in the presence of 6 M% I.
• Emulsion H was found to consist of 98 percent tabular grains, which accounted for greater than 99 percent of total grain projected area.
• Emulsion H/CR Central Region Epitaxial Sensitization
• Silver halide epitaxy amounting to 12 mole percent of silver contained in the host tabular grains was then precipitated.
• Halide and silver salt solutions were added in sequence with a two mole percent excess of the chloride salt being maintained to assure precipitation of AgCl.
• Silver and halide additions are reported below based on mole percentages of silver in the host tabular grains.
• the rate of AgNO3 addition was regulated to precipitate epitaxy at the rate of 6 mole percent per minute.
• Sensitization C-3 7.04 M % NaCl was added followed by 5.04 M % NaBr followed in turn by 1.92 M % AgI (Lippmann) followed in turn by 10.08 M % AgNO3 for a nominal composition of 12 M % AgI 0.16 Br 0.42 Cl 0.42 .
• Analytical electron microscopy (AEM) techniques were then employed to determine the actual as opposed to nominal (input) compositions of the silver halide epitaxial protrusions.
• the general procedure for AEM is described by J. I. Goldstein and D. B. Williams, "X-ray Analysis in the TEM/STEM", Scanning Electron Microscopy/1977 ; Vol. 1, IIT Research Institute, March 1977, p. 651.
• the composition of an individual epitaxial protrusion was determined by focusing an electron beam to a size small enough to irradiate only the protrusion being examined.
• the selective location of the epitaxial protrusions at the corners of the host tabular grains facilitated addressing only the epitaxial protrusions.
• the minimum AEM detection limit was a halide concentration of 0.5 M %.
• the emulsion prepared was a silver iodobromide emulsion containing 4.125 M % I, based on total silver.
• a vessel equipped with a stirrer was charged with 9.375 L of water containing 30.0 grams of phthalic anhydride-treated gelatin (10% by weight) 3.60 g NaBr, an antifoamant, and sufficient sulfuric acid to adjust pH to 2.0 at 60°C.
• phthalic anhydride-treated gelatin 10% by weight
• 3.60 g NaBr 3.60 g NaBr
• an antifoamant 3.60 g
• sulfuric acid to adjust pH to 2.0 at 60°C.
• nucleation which was accomplished by an unbalanced simultaneous 30 sec. addition of AgNO3 and halide (0.090 mole AgNO3, 0.1095 mole NaBr, and 0.0081 mole KI) solutions, during which time reactor pBr decreased due to excess NaBr that was added during nucleation, and pH remained approximately constant relative to values initially set in the reactor solution.
• the post-epitaxy components included 0.14 mg bis(2-amino-5-iodopyridinedihydroiodide) mercuric iodide, 137 mg Dye 4, 12.4 mg Dye 6, 60 mg NaSCN, 6.4 mg Sensitizer 1 (sulfur), 3 mg Sensitizer 2 (gold), and 11.4 mg APMT.
• Sensitization D-1 The sensitization, coating and evaluation procedures were the same as for Sensitization D-1, except that the halide salt solution for double jet formation of epitaxy was 92 M % Cl added as NaCl and 8 M % I added as KI.
• the emulsion prepared was a silver iodobromide emulsion containing 4.125 M % I, based on total silver.
• a central region of the grains accounting for 75 % of total silver contained 1.5 M % I while a laterally displaced region accounting for the last 25 % of total silver precipitated contained 12 M % I.
• the flow rate of AgNO3 was accelerated to approximately 8.0 times its starting value during the next 41.3 min of growth. After 4.50 moles of emulsion had formed (1.5 M % I), the ratio of flows of AgI to AgNO3 was changed such that the remaining portion of the 6 mole batch was 12 M % I. At the start of the formation of this high iodide band, the flow rate, based on rate of total Ag delivered to the reactor, was initially decreased to approximately 25% of the value at the end of the preceding segment in order to avoid renucleation during formation of this less soluble, higher iodide band, but the flow rate was doubled from start to finish of the portion of the run. When addition of AgNO3, AgI and NaBr was complete, the resulting emulsion was coagulation washed and pH and pBr were adjusted to storage values of 6 and 2.5, respectively.
• Emulsion J A 0.5 mole sample of Emulsion J was melted at 40°C, and its pBr was adjusted to ca. 4 by simultaneous addition of AgNO3 and KI solutions in a ratio such that the small amount of silver halide precipitated during this adjustment was 12 M % I.
• sensitizers This allowed variations in levels of sensitizers in order to determine optimum treatment combinations.
• the post-epitaxy components included Dye 4, Dye 6 and Dye 7, 60 mg NaSCN/mole Ag, Sensitizer 1 (sulfur), Sensitizer 2 (gold), and 8.0 mg N-methylbenzothiazolium iodide. After all components were added, the mixture was heated to 50°C for 5 min to complete the sensitization, and after cooling to 40°C, 114.35 mg additional APMT was added.
• the emulsion prepared was a silver iodobromide emulsion containing 4.125 M % I, based on total silver.
• a central region of the grains accounting for 74 % of total silver contained 1.5 M % I while a laterally displaced region accounting for the last 26 % of total silver precipitated contained 12 M % I.
• a vessel equipped with a stirrer was charged with 6 L of water containing 3.75 g lime-processed bone gelatin, 4.12 g NaBr, an antifoamant, and sufficient sulfuric acid to adjust pH to 5.41, at 39°C.
• nucleation which was accomplished by balanced simultaneous 4 sec. addition of AgNO3 and halide (98.5 and 1.5 M % NaBr and KI, respectively) solutions, both at 2.5 M, in sufficient quantity to form 0.01335 mole of silver iodobromide, pBr and pH remained approximately at the values initially set in the reactor solution.
• the methionine in the reactor gelatin was quickly oxidized by addition of 0.656 cc of a solution that was 4.74 M % NaOCl, and the temperature was raised to 54°C in 9 min. After the reactor and contents were held at this temperature for 9 min, 100 g of oxidized methionine lime-processed bone gelatin dissolved in 1.5 L H2O at 54°C, and 122.5 cc of 1 M NaBr were added to it (after which pH was ca. 5.74).
• the growth stage was begun during which 2.50 M AgNO3, 2.80 M NaBr, and a 0.0397 M suspension of AgI (Lippmann) were added in proportions to maintain a uniform iodide level of 1.5 M % in the growing silver halide crystals, and the reactor pBr at the value resulting from the cited NaBr additions prior to the start of nucleation and growth.
• This pBr was maintained until 0.825 mole of silver iodobromide had formed (constant flow rates for 40 min), at which time the excess Br ⁇ concentration was increased by addition of 105 cc of 1 M NaBr, the reactor pBr being maintained at the resulting value for the balance of the growth.
• the flow rate of AgNO3 was accelerated to approximately 10 times the starting value in this segment during the next 52.5 min of growth. After 6.69 moles of emulsion had formed (1.5 M % I), the ratio of flow of AgI to AgNO3 was changed such that the remaining portion of the 9 mole batch was 12 M % I.
• growth reactant flow rate based on rate of total Ag delivered to the reactor, was initially decreased to approximately 25% of the value at the end of the preceding segment in order to avoid renucleation during formation of this less soluble, higher iodide composition band, but it was accelerated (end flow 1.6 times that at the start of this segment) during formation of this part of the emulsion.
• AgNO3 AgI and NaBr was complete, the resulting emulsion was coagulation washed and pH and pBr were adjusted to storage values of 6 and 2.5, respectively.
• Emulsion K A 0.5 mole sample of Emulsion K was melted at 40°C and its pBr was adjusted to ca. 4 by simultaneous addition of AgNO3 and KI solutions in a ratio such that the small amount of silver halide precipitated during this adjustment was 12 M % I.
• 2 M % NaCl (based on the original amount of silver in the Emulsion F sample) was added, followed by addition of Dye 4 and Dye 6 (1173 and 106 mg/mole Ag, respectively), after which 6 mole-% epitaxy was formed as follows: A single-jet addition of 6 M % NaCl, based on the original amount of host emulsion, was made, and this was followed by a single-jet addition of 6 M % AgNO3.
• Emulsion L (no dopant)
• a silver iodobromide (2.6 M % I, uniformly distributed) emulsion was precipitated by a procedure similar to that employed by Antoniades et al for precipitation of Emulsions TE-4 to TE-11. Greater than 99 percent of total grain projected area was accounted for by tabular grains.
• the mean ECD of the grains was 2.45 ⁇ m and the mean thickness of the grains was 0.051 ⁇ m. The average aspect ratio of the grains was 48. No dopant was introduced during the precipitation of this emulsion.
• Emulsions were prepared similarly as Emulsion L, except that K4Ru(CN)6 (SET-2) was incorporated as a dopant in the ultrathin tabular grains following nucleation over an extended interval of grain growth to minimize thickening of the tabular grains. Attempts to introduce the dopant into the reaction vessel prior to nucleation resulted in thickening of the ultrathin tabular grains and, at higher dopant concentrations, formation of tabular grains which were greater than 0.07 ⁇ m in thickness. All of the emulsions, except Emulsion O, contained the same iodide content and profile as Emulsion L. Emulsion O was precipitated by introducing no iodide in the interval from 0.2 to 55 percent of silver addition and by introducing iodide at a 2.6 M % concentration for the remainder of the precipitation.
• K4Ru(CN)6 SET-2
• Table XVI The concentrations of the dopants are reported in terms of molar parts of dopant added per million molar parts of Ag (mppm).
• the Profile % refers to the interval of dopant introduction, referenced to the percent of total silver present in the reaction vessel at the start and finish of dopant introduction.
• Emulsions L through W were identically chemically and spectrally sensitized as follows: 150 mg/Ag mole NaSCN, 2.1 mmole/Ag mole of Dye 2, 20 ⁇ mole/Ag mole Sensitizer 1 and 6.7 ⁇ mole Sensitizer 2 were added to the emulsion. The emulsion was then subjected to a heat digestion at 65°C for 15 minutes, followed by that addition of 0.45 M % KI and AgNO3.
• Samples of the sensitized emulsions were then coated as follows: 0.538 g Ag/m, 2.152 g/m gelatin (half from original emulsion and half added), 0.968 g/m Coupler 1 and 1 g/Ag mole 4-hydroxy-6-methyl-1,3,3a,7-tetraazaindene (Na+ salt).
• the emulsion layer was overcoated with 1.62 g/m gelatin and 1.75 weight percent bis(vinylsulfonyl)methane, based on total gelatin in the emulsion and overcoat layers.
• Emulsion X (Se and SET in host)
• the ultrathin tabular grain emulsion contained silver iodobromide tabular grains (2.6 M % I) having an average ECD of 2.14 ⁇ m and an average thickness of 0.052 ⁇ m. The tabular grains accounted for more than 97 percent of total grain projected area.
• Epitaxial sensitization of the host ultrathin tabular grain emulsion was next undertaken by first adjusting the host emulsion to a pAg of 7.95 at 40°C, followed by the addition of 5 mmol/mole Ag of KI solution.
• Epitaxial deposition was accomplished by the following additions: 32 mmol/mole Ag of NaCl, 24 mmol/Ag mole of NaBr, 9.6 mmol/mole Ag of AgI Lippmann emulsion and 1.0 M AgNO3 solution to finalize the pAg to 7.95 at 40°C.
• the silver halide epitaxy accounted for 6 mole percent of the host emulsion.
• Finishing of the emulsion was undertaken by the addition of, for each mole of Ag, 60 mg of NaSCN, 9 ⁇ mol of the sulfur sensitizer dicarboxymethyldimethylthiourea, 2 or 3 ⁇ mol of the gold sensitizer auroustrimethyltriazolium thiolate, 5.7 mg of 1-(3-acetamidophenyl)-5-mercaptotetrazole (APMT).
• APMT 1-(3-acetamidophenyl)-5-mercaptotetrazole
• Emulsion X The preparation procedure employed for Emulsion X was repeated, except that, instead of placing the selenium dopant in the host, the same amount of the selenium dopant was introduced into the silver halide epitaxy. Grain size characteristics were similar to those of Emulsion X, except that the grains of the ultrathin tabular grain emulsion prior to epitaxial deposition had an average ECD of 2.48 ⁇ m and an average thickness of 0.050 ⁇ m.
• Emulsions X and Y were identically coated on a photographic film support and exposed for 1/100 second with a 365 nm light source.
• the coating format employed was emulsion (0.54 g Ag/m, 1.1 g/m gelatin) blended with a mixture of 0.97 g/m Coupler 1 and 1.1 g/m gelatin, 1 g/Ag mole 4-hydroxy-6-methyl-1,3,3a,7-tetraazaindene, sodium salt, surfactant, 1.6 g/m gelatin, and 1.75 percent by weight, based on the weight of total gelatin, of bis(vinylsulfonyl)methane.

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