EP0513726A1 - Papier phototypie amélioré - Google Patents

Papier phototypie amélioré Download PDF

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Publication number
EP0513726A1
EP0513726A1 EP92107963A EP92107963A EP0513726A1 EP 0513726 A1 EP0513726 A1 EP 0513726A1 EP 92107963 A EP92107963 A EP 92107963A EP 92107963 A EP92107963 A EP 92107963A EP 0513726 A1 EP0513726 A1 EP 0513726A1
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Prior art keywords
grain
emulsion
paper according
further characterized
silver
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EP92107963A
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German (de)
English (en)
Inventor
John Calvin c/o Eastman Kodak Company Loblaw
Allen Keh-Chang c/oEastman Kodak Company Tsaur
Mamie c/oEastman Kodak Compa Kam-Ng
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Eastman Kodak Co
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Eastman Kodak Co
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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
    • G03C1/76—Photosensitive materials characterised by the base or auxiliary layers
    • G03C1/775—Photosensitive materials characterised by the base or auxiliary layers the base being of paper

Definitions

  • the invention relates to photography. More specifically, the invention relates to an improved photographic paper.
  • Figure 1 is a plot of optical density versus exposure for varied silver coverages.
  • Figure 2 is a plot of optical density versus exposure for the same emulsion with and without a contrast increasing dopant.
  • Figure 3 is a photomicrograph of a conventional tabular grain emulsion.
  • Figures 1 to 6 inclusive are characteristic curves obtained by plotting optical density as a function of exposure over an exposure range of 3.9 log E in increments of 0.15 logE, where E is exposure measured in lumen (meter-candle) seconds.
  • Phototypesetting paper is a photographic product intended to produce black, maximum density silver images on a white, minimum density background. The image is viewed by reflection from a white support.
  • Paper supports Common reference to the reflective supports as "paper" supports is a historical legacy from an earlier era in which the supports were in fact entirely paper.
  • Today white reflective plastics are commonly present to supplement or even entirely supplant paper in the reflective support.
  • Covering power is commonly defined as the maximum image density divided by developed silver per unit area, typically reported in units of g/m2 or mg/dm2.
  • FIG. 3 is a photomicrograph of an early high aspect ratio tabular grain silver bromoiodide emulsion first presented by Wilgus et al and Kofron et al to demonstrate the variety of grains that can be present in a high aspect ratio tabular grain emulsion. While it is apparent that the majority of the total grain projected area is accounted for by tabular grains, such as grain 101, nonconforming grains are also present.
  • the grain 103 illustrates a nontabular grain.
  • the grain 105 illustrates a fine grain.
  • the grain 107 illustrates a nominally tabular grain of nonconforming thickness.
  • Rods, not shown in Figure 3 also constitute a common nonconforming grain population in tabular grain silver bromide and bromoiodide emulsions.
  • a technique for quantifying grain dispersity that has been applied to both nontabular and tabular grain emulsions is to obtain a statistically significant sampling of the individual grain projected areas, calculate the corresponding ECD of each grain, determine the standard deviation of the grain ECDs, divide the standard deviation of the grain population by the mean ECD of the grains sampled and multiply by 100 to obtain the coefficient of variation (COV) of the grain population as a percentage. While very highly monodisperse (COV ⁇ 10 percent) emulsions containing regular nontabular grains can be obtained, even the most carefully controlled precipitations of tabular grain emulsions have rarely achieved a COV of less than 20 percent.
  • Item 23212 discloses the preparation of silver bromide tabular grain emulsions with COVs ranging down to 15. Research Disclosure is published by Kenneth Mason Publications, Ltd., Dudley Annex, 21a North Street, Emsworth, Hampshire P010 7DQ, England.
  • this invention is directed to a phototypesetting paper comprised of a white reflective support and an imaging layer unit coated on the support exhibiting a maximum density of at least 2.0 and a contrast in excess of 2.0 over a 0.75 log E exposure range measured from the minimum exposure required to produce a density of 0.2 above fog.
  • the imaging layer unit is comprised of a tabular grain silver halide emulsion having a grain halide content of from 0 to 5 mole percent chloride, from 0 to 15 mole percent iodide and from 80 to 100 mole percent bromide, based on total silver.
  • the phototypesetting paper is characterized in that the coefficient of variation of the tabular grain emulsion is less than 15 percent, based on the total grain population of the emulsion having an equivalent circular diameter of greater than 0.1 ⁇ m, and greater than 97 percent of the projected area of the total grain population of the emulsion having an equivalent circular diameter of greater than 0.1 ⁇ m is accounted for by tabular grains having a mean thickness of less than 0.2 ⁇ m and a tabularity of greater than 25.
  • the invention is directed to an improved phototypesetting paper.
  • the phototypesetting paper is comprised of a conventional white reflective support and an imaging layer unit coated on the support exhibiting a maximum density of at least 2.0 and a contrast in excess of 2.0 over a 0.75 log E exposure range measured from the minimum exposure required to produce a density of 0.2 above fog.
  • the phototypesetting paper employs in the imaging layer unit an emulsion containing tabular grains having a mean thickness of less than 0.2 ⁇ m and a mean tabularity of greater than 25. These emulsions, which contain thin tabular grains and exhibit high tabularities, provide the high levels of silver covering power that have rendered tabular grain emulsions particularly attractive for use in phototypesetting papers.
  • This invention improves the properties of phototypesetting papers containing thin, high tabularity tabular grain emulsions by employing tabular grain emulsions prepared by novel processes that (1) increase the proportion of the total grain population accounted for by thin tabular grains and (2) increase the monodispersity of the total grain population forming the imaging layer unit.
  • the phototypesetting paper of the invention exhibits a coefficient of variation of the tabular grain emulsion that is less than 15 percent (preferably less than 10 percent), based on the total grain population of the emulsion having an equivalent circular diameter of greater than 0.1 ⁇ m.
  • the low coefficient of variation of the total grain population having an equivalent circular diameter of greater than 0.1 ⁇ m is made possible by producing an emulsion in which the tabular grain population accounts for all or very nearly all (greater than 97 percent and optimally greater than 98 percent) of the total projected area of grains having an equivalent circular diameter of greater than 0.1 ⁇ m and by reducing the dispersity observed within the tabular grain population itself.
  • the phototypesetting papers employ in their emulsion layer units high tabularity, thin tabular grain silver halide emulsions that consist essentially of tabular grains and minimum or near minimum coefficients of variations, based on the total grain population having an equivalent circular diameter of greater than 0.1 ⁇ m.
  • the phototypesetting papers of this invention have been realized by the discovery and optimization of novel processes for the precipitation of tabular grain emulsions of reduced grain dispersities. These processes are capable of preparing emulsions suited for phototypesetting paper use having a grain halide content of from 0 to 5 mole percent chloride, from 0 to 15 (preferably 0 to 5) mole percent iodide and from 80 to 100 (preferably 90 to 100) mole percent bromide, based on total silver.
  • the grain population can consist essentially of silver bromide as the sole silver halide. Silver bromide is incorporated in the grains during both grain nucleation and growth. Silver iodide and/or silver chloride can also be present in the grains, if desired.
  • iodide is particularly beneficial to increasing emulsion speed when present in even very small amounts, such as ⁇ 0.1 mole percent, based on silver.
  • higher levels of iodide produce warmer image tones that are preferably avoided. It is therefore preferred to limit iodide to less than 5 mole percent (optimally less than 3 mole percent) based on silver.
  • Grain populations consisting essentially of tabular grains having mean thicknesses in the range of from 0.080 to 0.2 ⁇ m and mean tabularities (as defined above) of greater than 25 are well within the capabilities of the precipitation procedures set forth below. These ranges permit any mean tabular grain ECD to be selected appropriate for the photographic application. In other words, the present invention is compatible with the full range of mean ECDs of conventional tabular grain emulsions.
  • a mean ECD of about 10 ⁇ m is typically regarded as the upper limit for photographic utility.
  • the tabular grains exhibit a mean ECD of 5 ⁇ m or less. Since increased ECDs contribute to achieving higher mean aspect ratios and tabularities, it is generally preferred that mean ECDs of the tabular grains be at least about 0.4 ⁇ m.
  • Mean tabular grain aspect ratios for the tabular grains preferably range from 5 to 100 or more. This range of mean aspect ratios includes intermediate (5 to 8) and high (>8) average aspect ratio tabular grain emulsions. For the majority of photographic applications mean tabular grain aspect ratios in the range of from about 10 to 60 are preferred.
  • mean tabularities provide an even better quantitative measure of the qualities that set tabular grain populations apart from nontabular grain populations.
  • the emulsions of the invention contain exhibit tabularities of greater than 25.
  • mean tabularities of the tabular grain emulsions range up to about 500. Since tabularities are increased exponentially with decreased tabular grain mean thicknesses, extremely high tabularities can be realized ranging up to 1000 or more.
  • the emulsions contemplated for use have been made available by the discovery and optimization of improved processes for the preparation of tabular grain emulsions by (a) first forming a population of grain nuclei, (b) ripening out a portion of the grain nuclei in the presence of a ripening agent, and (c) undertaking post-ripening grain growth.
  • Minimum COV coprecipitated grain population emulsions consisting essentially of tabular grains satisfying the requirements of this invention has resulted from the discovery of specific techniques for forming the population of grain nuclei.
  • the first step is undertake formation of the silver halide grain nuclei under conditions that promote uniformity.
  • bromide ion is added to the dispersing medium.
  • halide ions in the dispersing medium consist essentially of bromide ions.
  • the balanced double jet precipitation of grain nuclei is specifically contemplated in which an aqueous silver salt solution and an aqueous bromide salt are concurrently introduced into a dispersing medium containing water and a hydrophilic colloid peptizer.
  • chloride and iodide salts can be introduced through the bromide jet or as a separate aqueous solution through a separate jet. It is preferred to limit the concentration of chloride and/or iodide to the overall levels described above or less during grain nucleation.
  • Silver nitrate is the most commonly utilized silver salt while the halide salts most commonly employed are ammonium halides and alkali metal (e.g., lithium, sodium or potassium) halides.
  • the ammonium counter ion does not function as a ripening agent since the dispersing medium is at an acid pH--i.e., less than 7.0.
  • a uniform nucleation can be achieved by introducing a Lippmann emulsion into the dispersing medium. Since the Lippmann emulsion grains typically have a mean ECD of less than 0.05 ⁇ m, a small fraction of the Lippmann grains initially introduced serve as deposition sites while all of the remaining Lippmann grains dissociate into silver and halide ions that precipitate onto grain nuclei surfaces. Techniques for using small, preformed silver halide grains as a feedstock for emulsion precipitation are illustrated by Mignot U.S. Patent 4,334,012; Saito U.S. Patent 4,301,241; and Solberg et al U.S. Patent 4,433,048.
  • the low COV emulsions contemplated for use can be prepared by producing prior to ripening a population of parallel twin plane containing grain nuclei in the presence of selected surfactants. Specifically, it has been discovered that the dispersity of the tabular grain emulsions of this invention can be reduced by introducing parallel twin planes in the grain nuclei in the presence of one or a combination of polyalkylene oxide block copolymer surfactants.
  • Polyalkylene oxide block copolymer surfactants generally and those contemplated for use in preparing the emulsions of this invention in particular are well known and have been widely used for a variety of purposes. They are generally recognized to constitute a major category of nonionic surfactants.
  • a molecule For a molecule to function as a surfactant it must contain at least one hydrophilic unit and at least one lipophilic unit linked together.
  • block copolymer surfactants A general review of block copolymer surfactants is provided by I.R. Schmolka, "A Review of Block Polymer Surfactants", J. Am. Oil Chem. Soc., Vol. 54, No. 3, 1977, pp. 110-116, and A.S. Davidsohn and B. Milwidsky, Synthetic Detergents , John Wiley & Sons, N.Y. 1987, pp. 29-40, and particularly pp. 34-36.
  • polyalkylene oxide block copolymer surfactant found to be useful in the preparation of the emulsions is comprised of two terminal lipophilic alkylene oxide block units linked by a hydrophilic alkylene oxide block unit accounting for at least 4 percent of the molecular weight of the copolymer.
  • These surfactants are hereinafter referred to category S-I surfactants.
  • the category S-I surfactants contain at least two terminal lipophilic alkylene oxide block units linked by a hydrophilic alkylene oxide block unit and can be, in a simple form, schematically represented as indicated by diagram I below: where LAO1 in each occurrence represents a terminal lipophilic alkylene oxide block unit and HAO1 represents a linking hydrophilic alkylene oxide block unit.
  • HAO1 be chosen so that the hydrophilic block unit constitutes from 4 to 96 percent of the block copolymer on a total weight basis.
  • block diagram I above is only one example of a polyalkylene oxide block copolymer having at least two terminal lipophilic block units linked by a hydrophilic block unit.
  • interposing a trivalent amine linking group in the polyalkylene oxide chain at one or both of the interfaces of the LAO1 and HAO1 block units can result in three or four terminal lipophilic groups.
  • the category S-I polyalkylene oxide block copolymer surfactants are formed by first condensing ethylene glycol and ethylene oxide to form an oligomeric or polymeric block repeating unit that serves as the hydrophilic block unit and then completing the reaction using 1,2-propylene oxide.
  • the propylene oxide adds to each end of the ethylene oxide block unit. At least six 1,2-propylene oxide repeating units are required to produce a lipophilic block repeating unit.
  • the resulting polyalkylene oxide block copolymer surfactant can be represented by formula II: where x and x' are each at least 6 and can range up to 120 or more and y is chosen so that the ethylene oxide block unit maintains the necessary balance of lipophilic and hydrophilic qualities necessary to retain surfactant activity. It is generally preferred that y be chosen so that the hydrophilic block unit constitutes from 4 to 96 percent by weight of the total block copolymer. Within the above ranges for x and x', y can range from 2 to 300 or more.
  • any category S-I surfactant block copolymer that retains the dispersion characteristics of a surfactant can be employed. It has been observed that the surfactants are fully effective either dissolved or physically dispersed in the reaction vessel. The dispersal of the polyalkylene oxide block copolymers is promoted by the vigorous stirring typically employed during the preparation of tabular grain emulsions. In general surfactants having molecular weights of less than about 16,000, preferably less than about 10,000, are contemplated for use.
  • the polyalkylene oxide block copolymer surfactants contain two terminal hydrophilic alkylene oxide block units linked by a lipophilic alkylene oxide block unit and can be, in a simple form, schematically represented as indicated by diagram III below: where HAO2 in each occurrence represents a terminal hydrophilic alkylene oxide block unit and LAO2 represents a linking lipophilic alkylene oxide block unit. It is generally preferred that LAO2 be chosen so that the lipophilic block unit constitutes from 4 to 96 percent of the block copolymer on a total weight basis.
  • block diagram III above is only one example of a category S-II polyalkylene oxide block copolymer having at least two terminal hydrophilic block units linked by a lipophilic block unit.
  • interposing a trivalent amine linking group in the polyakylene oxide chain at one or both of the interfaces of the LAO2 and HAO2 block units can result in three or four terminal hydrophilic groups.
  • the category S-II polyalkylene oxide block copolymer surfactants are formed by first condensing 1,2-propylene glycol and 1,2-propylene oxide to form an oligomeric or polymeric block repeating unit that serves as the lipophilic block unit and then completing the reaction using ethylene oxide. Ethylene oxide is added to each end of the 1,2-propylene oxide block unit. At least thirteen (13) 1,2-propylene oxide repeating units are required to produce a lipophilic block repeating unit.
  • the resulting polyalkylene oxide block copolymer surfactant can be represented by formula IV: where x is at least 13 and can range up to 490 or more and y and y' are chosen so that the ethylene oxide block units maintain the necessary balance of lipophilic and hydrophilic qualities necessary to retain surfactant activity. It is generally preferred that x be chosen so that the lipophilic block unit constitutes from 4 to 96 percent by weight of the total block copolymer; thus, within the above range for x, y and y' can range from 1 to 320 or more.
  • Any category S-II block copolymer surfactant that retains the dispersion characteristics of a surfactant can be employed. It has been observed that the surfactants are fully effective either dissolved or physically dispersed in the reaction vessel. The dispersal of the polyalkylene oxide block copolymers is promoted by the vigorous stirring typically employed during the preparation of tabular grain emulsions. In general surfactants having molecular weights of less than about 30,000, preferably less than about 20,000, are contemplated for use.
  • the polyalkylene oxide surfactants contain at least three terminal hydrophilic alkylene oxide block units linked through a lipophilic alkylene oxide block linking unit and can be, in a simple form, schematically represented as indicated by formula V below: (V) (H-HAO3) z -LOL-(HAO3-H) z' where HAO3 in each occurrence represents a terminal hydrophilic alkylene oxide block unit, LOL represents a lipophilic alkylene oxide block linking unit, z is 2 and z' is 1 or 2.
  • the polyalkylene oxide block copolymer surfactants employed can take the form shown in formula VI: (VI) (H-HAO3-LAO3) z -L-(LAO3-HAO3-H) z' where HAO3 in each occurrence represents a terminal hydrophilic alkylene oxide block unit, LAO3 in each occurrence represents a lipophilic alkylene oxide block unit, L represents a linking group, such as amine or diamine, z is 2 and z' is 1 or 2.
  • the linking group L can take any convenient form. It is generally preferred to choose a linking group that is itself lipophilic. When z + z' equal three, the linking group must be trivalent. Amines can be used as trivalent linking groups. When an amine is used to form the linking unit L, the polyalkylene oxide block copolymer surfactants employed can take the form shown in formula VII: where HAO3 and LAO3 are as previously defined; R1, R2 and R3 are independently selected hydrocarbon linking groups, preferably phenylene groups or alkylene groups containing from 1 to 10 carbon atoms; and a, b and c are independently zero or 1.
  • At least one (optimally at least two) of a, b and c be 1.
  • An amine (preferably a secondary or tertiary amine) having hydroxy functional groups for entering into an oxyalkylation reaction is a contemplated starting material for forming a polyalkylene oxide block copolymer satisfying formula VII.
  • linking group When z + z' equal four, the linking group must be tetravalent. Diamines are preferred tetravalent linking groups.
  • the polyalkylene oxide block copolymer surfactants employed can take the form shown in formula VIII:
  • HAO3 and LAO3 are as previously defined; R4, R5, R6, R7 and R8 are independently selected hydrocarbon linking groups, preferably phenylene groups or alkylene groups containing from 1 to 10 carbon atoms; and d, e, f and g are independently zero or 1. It is generally preferred that LAO3 be chosen so that the LOL lipophilic block unit accounts for from 4 to less than 96 percent, preferably from 15 to 95 percent, optimally 20 to 90 percent, of the molecular weight of the copolymer.
  • the polyalkylene oxide block copolymer surfactants employed contain at least three terminal lipophilic alkylene oxide block units linked through a hydrophilic alkylene oxide block linking unit and can be, in a simple form, schematically represented as indicated by formula IX below: (IX) (H-LAO4) z -HOL-(LAO4-H) z' where LAO4 in each occurrence represents a terminal lipophilic alkylene oxide block unit, HOL represents a hydrophilic alkylene oxide block linking unit, z is 2 and z' is 1 or 2.
  • the polyalkylene oxide block copolymer surfactants employed can take the form shown in formula X: (X) (H-LAO4-HAO4) z -L'-(HAO4-LAO4-H) z' where HAO4 in each occurrence represents a hydrophilic alkylene oxide block unit, LAO4 in each occurrence represents a terminal lipophilic alkylene oxide block unit, L' represents a linking group, such as amine or diamine, z is 2 and z' is 1 or 2.
  • the linking group L' can take any convenient form. It is generally preferred to choose a linking group that is itself hydrophilic. When z + z' equal three, the linking group must be trivalent. Amines can be used as trivalent linking groups. When an amine is used to form the linking unit L', the polyalkylene oxide block copolymer surfactants employed can take the form shown in formula XI: where HAO4 and LAO4 are as previously defined; R1, R2 and R3 are independently selected hydrocarbon linking groups, preferably phenylene groups or alkylene groups containing from 1 to 10 carbon atoms; and a, b and c are independently zero or 1.
  • At least one (optimally at least two) of a, b and c be 1.
  • An amine (preferably a secondary or tertiary amine) having hydroxy functional groups for entering into an oxyalkylation reaction is a contemplated starting material for forming a polyalkylene oxide block copolymer satisfying formula XI.
  • the linking group When z + z' equal four, the linking group must be tetravalent. Diamines are preferred tetravalent linking groups.
  • the polyalkylene oxide block copolymer surfactants employed can take the form shown in formula XII: where HAO4 and LAO4 are as previously defined; R4, R5, R6, R7 and R8 are independently selected hydrocarbon linking groups, preferably phenylene groups or alkylene groups containing from 1 to 10 carbon atoms; and d, e, f and g are independently zero or 1. It is generally preferred that LAO4 be chosen so that the HOL hydrophilic block unit accounts for from 4 to 96 percent, preferably from 5 to 85 percent, of the molecular weight of the copolymer.
  • polyalkylene oxide block copolymer surfactants of categories S-III and S-IV employ ethylene oxide repeating units to form the hydrophilic (HAO3 and HAO4) block units and 1,2-propylene oxide repeating units to form the lipophilic (LAO3 and LAO4) block units. At least three propylene oxide repeating units are required to produce a lipophilic block repeating unit.
  • each H-HAO3-LAO3- or H-LAO4-HAO4- group satisfies formula XIIIa or XIIIb, respectively: where x is at least 3 and can range up to 250 or more and y is chosen so that the ethylene oxide block unit maintains the necessary balance of lipophilic and hydrophilic qualities necessary to retain surfactant activity. This allows y to be chosen so that the hydrophilic block units together constitute from greater than 4 to 96 percent (optimally 10 to 80 percent) by weight of the total block copolymer.
  • the lipophilic alkylene oxide block linking unit which includes the 1,2-propylene oxide repeating units and the linking moieties, constitutes from 4 to 96 percent (optimally 20 to 90 percent) of the total weight of the block copolymer.
  • y can range from 1 (preferably 2) to 340 or more.
  • the overall molecular weight of the polyalkylene oxide block copolymer surfactants of categories S-III and S-IV have a molecular weight of greater than 1100, preferably at least 2,000.
  • any such block copolymer that retains the dispersion characteristics of a surfactant can be employed. It has been observed that the surfactants are fully effective either dissolved or physically dispersed in the reaction vessel. The dispersal of the polyalkylene oxide block copolymers is promoted by the vigorous stirring typically employed during the preparation of tabular grain emulsions.
  • category S-III surfactants having molecular weights of less than about 60,000, preferably less than about 40,000, are contemplated for use
  • category S-IV surfactants having molecular weight of less than 50,000, preferably less than about 30,000, are contemplated for use.
  • the propylene oxide repeating unit is only one of a family of repeating units that can be illustrated by formula XIV where R9 is a lipophilic group, such as a hydrocarbon--e.g., alkyl of from 1 to 10 carbon atoms or aryl of from 6 to 10 carbon atoms, such as phenyl or naphthyl.
  • R9 is a lipophilic group, such as a hydrocarbon--e.g., alkyl of from 1 to 10 carbon atoms or aryl of from 6 to 10 carbon atoms, such as phenyl or naphthyl.
  • the ethylene oxide repeating unit is only one of a family of repeating units that can be illustrated by formula XV: where R10 is hydrogen or a hydrophilic group, such as a hydrocarbon group of the type forming R9 above additionally having one or more polar substituents--e.g., one, two, three or more hydroxy and/or carboxy groups.
  • R10 is hydrogen or a hydrophilic group, such as a hydrocarbon group of the type forming R9 above additionally having one or more polar substituents--e.g., one, two, three or more hydroxy and/or carboxy groups.
  • each of block units contain a single alkylene oxide repeating unit selected to impart the desired hydrophilic or lipophilic quality to the block unit in which it is contained.
  • Hydrophilic-lipophilic balances (HLB's) of commercially available surfactants are generally available and can be consulted in selecting suitable surfactants.
  • surfactant weight concentrations are contemplated as low as 0.1 percent, based on the interim weight of silver--that is, the weight of silver present in the emulsion while twin planes are being introduced in the grain nuclei.
  • a preferred minimum surfactant concentration is 1 percent, based on the interim weight of silver.
  • a broad range of surfactant concentrations have been observed to be effective.
  • the preparation process is compatible with either of the two most common techniques for introducing parallel twin planes into grain nuclei.
  • the preferred and most common of these techniques is to form the grain nuclei population that will be ultimately grown into tabular grains while concurrently introducing parallel twin planes in the same precipitation step.
  • grain nucleation occurs under conditions that are conducive to twinning.
  • the second approach is to form a stable grain nuclei population and then adjust the pAg of the interim emulsion to a level conducive to twinning.
  • twin planes in the grain nuclei it is advantageous to introduce the twin planes in the grain nuclei at an early stage of precipitation. It is contemplated to obtain a grain nuclei population containing parallel twin planes using less than 2 percent of the total silver used to form the tabular grain emulsion. It is usually convenient to use at least 0.05 percent of the total silver to form the parallel twin plane containing grain nuclei population, although this can be accomplished using even less of the total silver. The longer introduction of parallel twin planes is delayed after forming a stable grain nuclei population the greater is the tendency toward increased grain dispersity.
  • the lowest attainable levels of grain dispersity in the completed emulsion are achieved by control of the dispersing medium.
  • the pAg of the dispersing medium is preferably maintained in the range of from 5.4 to 10.3 and, for achieving a COV of less than 10 percent, optimally in the range of from 7.0 to 10.0. At a pAg of greater than 10.3 a tendency toward increased tabular grain ECD and thickness dispersities is observed. Any convenient conventional technique for monitoring and regulating pAg can be employed.
  • Reductions in grain dispersities have also been observed as a function of the pH of the dispersing medium. Both the incidence of nontabular grains and the thickness dispersities of the nontabular grain population have been observed to decrease when the pH of the dispersing medium is less than 6.0 at the time parallel twin planes are being introduced into the grain nuclei.
  • the pH of the dispersing medium can be regulated in any convenient conventional manner. A strong mineral acid, such as nitric acid, can be used for this purpose.
  • Grain nucleation and growth occurs in a dispersing medium comprised of water, dissolved salts and a conventional peptizer.
  • Hydrophilic colloid peptizers such as gelatin and gelatin derivatives are specifically contemplated.
  • Peptizer concentrations of from 20 to 800 (optimally 40 to 600) grams per mole of silver introduced during the nucleation step have been observed to produce emulsions of the lowest grain dispersity levels.
  • grain nuclei containing parallel twin planes is undertaken at conventional precipitation temperatures for photographic emulsions, with temperatures in the range of from 20 to 80°C being particularly preferred and temperature of from 20 to 60°C being optimum.
  • the next step is to reduce the dispersity of the grain nuclei population by ripening.
  • the objective of ripening grain nuclei containing parallel twin planes to reduce dispersity is disclosed by both Himmelwright U.S. Patent 4,477,565 and Nottorf U.S. Patent 4,722,886.
  • Ammonia and thioethers in concentrations of from about 0.01 to 0.1 N constitute preferred ripening agent selections.
  • a silver halide solvent to induce ripening it is possible to accomplish the ripening step by adjusting pH to a high level--e.g., greater than 9.0.
  • a ripening process of this type is disclosed by Buntaine and Brady U.S. Patent 5,013,641.
  • the post nucleation ripening step is performed by adjusting the pH of the dispersing medium to greater than 9.0 by the use of a base, such as an alkali hydroxide (e.g., lithium, sodium or potassium hydroxide) followed by digestion for a short period (typically 3 to 7 minutes).
  • a base such as an alkali hydroxide (e.g., lithium, sodium or potassium hydroxide) followed by digestion for a short period (typically 3 to 7 minutes).
  • the emulsion is again returned to the acidic pH ranges conventionally chosen for silver halide precipitation (e.g. less than 6.0) by introducing a conventional acidifying agent, such as a a mineral acid (e.g., nitric acid).
  • a conventional acidifying agent such as a mineral acid (e.g., nitric acid).
  • ripening Some reduction in dispersity will occur no matter how abbreviated the period of ripening. It is preferred to continue ripening until at least about 20 percent of the total silver has been solubilized and redeposited on the remaining grain nuclei. The longer ripening is extended the fewer will be the number of surviving nuclei. This means that progressively less additional silver halide precipitation is required to produce tabular grains of an aim ECD in a subsequent growth step. Looked at another way, extending ripening decreases the size of the emulsion make in terms of total grams of silver precipitated. Optimum ripening will vary as a function of aim emulsion requirements and can be adjusted as desired.
  • the halides introduced during grain growth can be selected independently of the halide selections for nucleation.
  • the tabular grain emulsion can contain grains of either uniform or nonuniform silver halide composition.
  • the preparation procedures described above are capable of preparing emulsions capable of exhibiting a contrast of greater than 2.0 when the coating coverage is chosen to produce a maximum density of 2.0 or higher, it is recognized that the contrast of the emulsions employed can be further increased, if desired, by incorporating one or more conventional contrast increasing agents in the emulsions.
  • a Group VIII metal dopant known to enhance contrast such as rhodium, ruthenium or iridium, can be introduced during grain formation.
  • the dopant can be added to the reaction vessel prior to the start of precipitation, but is preferably added after the formation of twin planes during grain growth.
  • the metal can be added to the reaction vessel as a simple salt or as a coordination complex, such as a tetracoordination complex or, preferably, a hexacoordination complex.
  • a coordination complex such as a tetracoordination complex or, preferably, a hexacoordination complex.
  • the ligands of the complex as well as the complexed metal ion can form a part of the completed grain.
  • rhodium, ruthenium or iridium can be added in the form of simple salts of halides, preferably chloride and/or bromide.
  • ruthenium or iridium can be added in the form an ammonium or alkali metal hexahalorhodate, iridate or ruthenate, where the halides are preferably chloride or bromide.
  • Any amount of dopant up to about 1 X 10 ⁇ 5 Group VIII metal gram atom per silver mole can be employed.
  • a Group VIII metal ion concentration of at least 10 ⁇ 9 (preferably at least 10 ⁇ 8) metal gram atom per silver mole is contemplated to produce a significant further increase in contrast.
  • Group VIII metal ion concentrations to less than 10 ⁇ 6 metal gram atom per silver mole.
  • gelatino-peptizers While any conventional hydrophilic colloid peptizer can be employed, it is preferred to employ gelatino-peptizers during precipitation.
  • Gelatino-peptizers are commonly divided into so-called “regular” gelatino-peptizers and so-called “oxidized” gelatino-peptizers.
  • Regular gelatino-peptizers are those that contain naturally occurring amounts of methionine of at least 30 micromoles of methionine per gram and usually considerably higher concentrations.
  • the term oxidized gelatino-peptizer refers to gelatino-peptizers that contain less than 30 micromoles of methionine per gram.
  • a regular gelatino-peptizer is converted to an oxidized gelatino-peptizer when treated with a strong oxidizing agent, such as taught by Maskasky U.S. Patent 4,713,323 and King et al U.S. Patent 4,942,120.
  • the oxidizing agent attacks the divalent sulfur atom of the methionine moiety, converting it to a tetravalent or, preferably, hexavalent form. While methionine concentrations of less than 30 micromoles per gram have been found to provide oxidized gelatino-peptizer performance characteristics, it is preferred to reduce methionine concentrations to less than 12 micromoles per gram. Any efficient oxidation will generally reduce methionine to less than detectable levels.
  • an oxidized gelatino-peptizer When an oxidized gelatino-peptizer is employed, it is preferred to maintain a pH during twin plane formation of less than 5.2 to achieve a minimum (less than 10 percent) COV. When a regular gelatino-peptizer is employed, the pH during twin plane formation is maintained at less than 3.0 to achieve a minimum COV.
  • the category S-I surfactant is selected so that the hydrophilic block (e.g., HAO1) accounts for 4 to 96 (preferably 5 to 85 and optimally 10 to 80) percent of the total surfactant molecular weight. It is preferred that x and x' (in formula II) be at least 6 and that the minimum molecular weight of the surfactant be at least 760 and optimally at least 1000, with maximum molecular weights ranging up to 16,000, but preferably being less than 10,000.
  • the hydrophilic block e.g., HAO1
  • x and x' in formula II
  • the minimum molecular weight of the surfactant be at least 760 and optimally at least 1000, with maximum molecular weights ranging up to 16,000, but preferably being less than 10,000.
  • the category S-I surfactant is replaced by a category S-II surfactant
  • the latter is selected so that the lipophilic block (e.g., LAO2) accounts for 4 to 96 (preferably 15 to 95 and optimally 20 to 90) percent of the total surfactant molecular weight.
  • x (formula IV) be at least 13 and that the minimum molecular weight of the surfactant be at least 800 and optimally at least 1000, with maximum molecular weights ranging up to 30,000, but preferably being less than 20,000.
  • a category S-III surfactant is selected for this step, it is selected so that the lipophilic alkylene oxide block linking unit (LOL) accounts for 4 to 96 percent, preferably 15 to 95 percent, and optimally 20 to 90 percent of the total surfactant molecular weight.
  • LEL lipophilic alkylene oxide block linking unit
  • x can range from 3 to 250 and y can range from 2 to 340 and the minimum molecular weight of the surfactant is greater than 1,100 and optimally at least 2,000, with maximum molecular weights ranging up to 60,000, but preferably being less than 40,000.
  • the concentration levels of surfactant are preferably restricted as iodide levels are increased.
  • a category S-IV surfactant is selected for this step, it is selected so that the hydrophilic alkalylene oxide block linking unit (HOL) accounts for 4 to 96 percent, preferably 5 to 85 percent, and optimally 10 to 80 percent of the total surfactant molecular weight.
  • HOL hydrophilic alkalylene oxide block linking unit
  • x can range from 3 to 250 and y can range from 2 to 340 and the minimum molecular weight of surfactant is greater than 1,100 and optimally at least 2,000, with maximum molecular weights ranging up to 50,000, but preferably being less than 30,000.
  • minimum COV emulsions can be prepared with category S-I surfactants chosen so that the hydrophilic block (e.g., HAO1) accounts for 4 to 35 (optimally 10 to 30) percent of the total surfactant molecular weight.
  • the minimum molecular weight of the surfactant continues to be determined by the minimum values of x and x' (formula II) of 6. In optimized forms x and x' (formula II) are at least 7.
  • Minimum COV emulsions can be prepared with category S-II surfactants chosen so that the lipophilic block (e.g., LAO2) accounts for 40 to 96 (optimally 60 to 90) percent of the total surfactant molecular weight.
  • the minimum molecular weight of the surfactant continues to be determined by the minimum value of x (formula IV) of 13.
  • the same molecular weight ranges for both category S-I and S-II surfactants are applicable as in using regular gelatino-peptizer as described above.
  • the polyalkylene oxide block copolymer surfactant can, if desired, be removed from the emulsion after it has been fully prepared. Any convenient conventional washing procedure, such as those illustrated by Research Disclosure , Vol. 308, December 1989, Item 308,119, Section II, can be employed.
  • the polyalkylene oxide block copolymer surfactant constitutes a detectable component of the final emulsion when present in concentrations greater than 0.02 percent, based on the total weight of silver.
  • the phototypesetting papers of the invention can be constructed using conventional features, such as those set out in Research Disclosure, Item 308,119, cited above.
  • the emulsions can be washed (Section II), chemically sensitized (Section III), spectrally sensitized (Section IV, but excluding paragraphs G and L), protected by the inclusion of one or more antifoggants and sensitizers (Section VI), and hardeners (Section X).
  • the emulsion and other layers of the photographic elements can include coating aids (Section XI), plasticizers and lubricants (Section XII), antistatic layers (Section XIII), and matting agents (Section XVI).
  • Any conventional reflective support such as any reflective form of the various constructions described in Section XVII can be employed.
  • Conventional coating and drying procedures can be employed in forming the emulsion and optional additional layers, such as subbing and overcoat layers, can be employed as described in Section XV.
  • aqueous gelatin solution composed of 1 liter of water, 7 g of deionized alkali-processed gelatin, 4.5 g of potassium bromide, 1.2 ml of 1 N potassium hydroxide solution and having pBr of 1.42
  • aqueous gelatin solution composed of 1 liter of water, 7 g of deionized alkali-processed gelatin, 4.5 g of potassium bromide, 1.2 ml of 1 N potassium hydroxide solution and having pBr of 1.42
  • 25 ml of an aqueous solution of silver nitrate (containing 8.0 g of silver nitrate) and 25 ml of an aqueous solution of potassium bromide (containing 5.8 g of potassium bromide) were simultaneously added thereto over a period of 1 minute at a rate of 25 ml/min.
  • aqueous gelatin solution (composed of 1950 ml of water, 90 g of deionized alkali-processed gelatin, 15.3 ml of 1 N aqueous potassium hydroxide solution, and 3.6 g of potassium bromide) and the temperature of the mixture was raised to 75°C over a period of 10 minutes. Thereafter, ripening was performed for 50 minutes.
  • the mixture was then transferred to a 12-liter vessel, into which 200 ml of an aqueous silver nitrate solution (containing 90 g of silver nitrate) was added at a rate of 20 ml/min. Twenty-five seconds after initiating the addition of silver nitrate, 191.6 ml of an aqueous potassium bromide solution (containing 61.2 g of potassium bromide) was added thereto at a rate of 20 ml/min., the additions of both solutions being finished at the same time.
  • the resultant mixture was stirred for 2 minutes, and then 2,000 ml of an aqueous silver nitrate solution (containing 900 g of silver nitrate) and 2,000 ml of a potassium bromide solution (containing 636.9 g of potassium bromide) were simultaneously added to the aforesaid mixture at a rate of 40 ml/min for the first 20 minutes and 60 ml/min for the subsequent 20 minutes. Then, after stirring the mixture for 1 minute, the silver halide emulsion thus obtained was washed and redispersed.
  • the emulsion grains consisted essentially of silver bromide.
  • the properties of grains of this emulsion were as follows: Average Grain ECD: 1.20 ⁇ m Average Grain Thickness: 0.162 ⁇ m Average Aspect Ratio: 7.4 Average Tabularity: 45.7 Coefficient of Variation based on Total Grains: 21.3%
  • the emulsion was optimally sensitized with 70 mg/mole of sodium thiocyanate, 2.4 mg/mole of potassium tetrachloroaurate, 3.2 mg/mole of sodium thiosulfate pentahydrate, 60 mg/mole of Dye A, 3-ethyl-5-[N-(4-sulfobutyl)-4-(1H)pyridylidene]rhodanine, pyridinium salt, heat treated at 65°C for 35 min. To the finished emulsion were added 300 mg/mole of 5-methyl-s-triazole-(2-3-a)-pyrimidine-7-ol.
  • aqueous gelatin solution composed of 1 liter of water, 2.5 g of oxidized alkali-processed gelatin, 4.0
  • an aqueous silver nitrate solution containing 6.8 g of silver nitrate
  • an aqueous sodium bromide solution containing 4.4 g of sodium bromide
  • 25 ml of an aqueous silver nitrate solution containing 6.8 g of silver nitrate
  • an aqueous sodium bromide solution containing 4.4 g of sodium bromide
  • 25 ml of an aqueous silver nitrate solution containing 6.8 g of silver nitrate
  • an aqueous sodium bromide solution containing 4.4 g of sodium bromide
  • This emulsion was sensitized and finished similarly as the emulsion of Example 1.
  • the properties of grains of this emulsion are as follows: Average Grain ECD: 1.26 ⁇ m Average Grain Thickness: 0.144 ⁇ m Average Aspect Ratio of the Grains: 8.8 Average Tabularity of the Grains: 60.8 Coefficient of Variation base on Total Grains: 6.3%
  • Example 1 was repeated, except that 159 microgram of ammonium hexachlororhodate (III) was introduced over a period of 2.5 min after emulsion was transferred to the 12-liter vessel, and that 1 mole percent of potassium iodide was additionally added to the potassium bromide solution for the subsequent precipitation.
  • the emulsion thus made contained 1 mole% of iodide and 7.23 x 10 ⁇ 8 mole of ammonium hexachlororhodate (III) per silver mole.
  • an aqueous silver nitrate solution containing 1.0 g of silver nitrate
  • 7.3 ml of an aqueous sodium bromide solution containing 0.68 g of sodium bromide
  • 474.7 ml of an aqueous silver nitrate solution containing 129 g of silver nitrate
  • 473.6 ml of an aqueous halide solution containing 81 g of sodium bromide and 1.3 g of potassium iodide
  • an aqueous silver nitrate solution containing 68.9 g of silver nitrate
  • 251.1 ml of an aqueous halide solution containing 43 g of sodium bromide and 0.7 g of potassium iodide
  • the silver halide emulsion thus obtained contained 1 mole% of iodide and 7.23 x 10 ⁇ 8 mole of ammonium hexachlororhodate (III) per silver mole.
  • Example 4 was repeated, except that the amount of PLURONICTM-L63 added was increased to 5.21 wt%.
  • the silver halide emulsion thus obtained contained 1 mole% of iodide and 7.23 x 10 ⁇ 8 mole of ammonium hexachlororhodate (III) per silver mole.
  • the emulsion were sensitized and finished similarly as the emulsion of Example 1.
  • the properties of grains of this emulsion are as follows: Average Grain ECD: 1.35 ⁇ m Average Grain Thickness: 0.153 ⁇ m Average Aspect Ratio of the Grains: 8.8 Average Tabularity of the Grains: 57.7 Coefficient of Variation based on Total Grains: 7.0%
  • Example 4 was repeated, except that the amount of PLURONICTM-L63 added was increased to 6.94 wt%.
  • the silver halide emulsion thus obtained contained 1 mole% of iodide and 7.23 x 10 ⁇ 8 mole of ammonium hexachlororhodate (III) per silver mole.
  • Example 5 was repeated, except that 0.235 mg of potassium hexachloroiridate (IV) was added in place of ammonium hexachlororhodate (III).
  • the silver halide emulsion thus obtained contained 1 mole% of iodide and 4.3 x 10 ⁇ 7 mole of potassium hexachloroiridate (IV) per silver mole.
  • the emulsion of Comparative Example 1 was compared with the emulsion of Example 2 to provide a silver bromide comparison.
  • the emulsion of Comparative Example 3 was compared with the emulsion of Example 5 to provide a silver bromoiodide comparison.
  • the Example 5 emulsion was selected for comparison with the emulsion of Comparative Example 3 based on their similarities in average grain ECD, thickness and aspect ratio.
  • the emulsion comparisons are based on identical silver coverages, corresponding to silver coverages of 21.52 mg/dm2 (200 mg/ft2) on transparent film support (chosen to permit accurate measurements of maximum density) and 10.76 mg/dm2 (100 mg/ft2) on white reflective paper support.
  • the coatings were each processed in Developer A described in Table XV for 1 min at 35°C and in Fixer A described in Table XVI for 30 sec.
  • Table XV Composition of Developer A gram Water 539.0 Potassium hydroxide, 45.5% solution 178.0 Sodium metabisulfite 145.0 Sodium bromide 12.0 2-butene-dioic acid (z), homopolymer, 50 % solution 13.0 Pentetic acid, pentasodium salt, 40% solution 15.0 Sodium hydroxide, 50% solution 56.0 Benzotriazole 0.4 1-Phenyl-5-mercaptotetrazole 0.05 Boric acid 6.94 Diethylene glycol 110.0 Hydroquinone 75.0 4-Hydroxymethyl-4-methyl-1-phenyl-3-pyrazolidone 2.9 Potassium carbonate, 47% solution 120.0
  • Table XVI Composition of Fixer A gram/liter Ammonia thiosulfate 155.0 Sodium metabisulfite 190.0 Sodium acetate/acetic acid 25.0 Sodium borate, 5-hydrate 11.8 Aluminum sulfate 6.6
  • Comparative Emulsion 3 and Emulsion 5 are compared in Figure 5.
  • the superior photographic performance demonstrated by the invention emulsion, Emulsion 5, over Emulsion 3 is again clear in not only contrast but also in speed and fog. It is especially noticeable in the sharper shoulder contrast shown by Emulsion 5.
  • the results are summarized in Table XVIII.

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0596469A1 (fr) * 1992-11-04 1994-05-11 Eastman Kodak Company Procédé pour accélérer la précipitation d'une émulsion à bas coéfficient de variation
US5773207A (en) * 1996-01-09 1998-06-30 Imation Corp. Photographic emulsions

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB808228A (en) * 1956-08-16 1959-01-28 Ilford Ltd Improvements in or relating to photographic emulsions
US4797354A (en) * 1986-03-06 1989-01-10 Fuji Photo Film Co., Ltd. Silver halide emulsions comprising hexagonal monodisperse tabular silver halide grains

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB808228A (en) * 1956-08-16 1959-01-28 Ilford Ltd Improvements in or relating to photographic emulsions
US4797354A (en) * 1986-03-06 1989-01-10 Fuji Photo Film Co., Ltd. Silver halide emulsions comprising hexagonal monodisperse tabular silver halide grains

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
JOURNAL OF THE AMERICAN OIL CHEMISTS' SOCIETY. vol. 54, no. 3, 1977, CHAMPAIGN US I.R.SCHMOLKA: 'A Review of Block Copolymer Surfactants' *

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0596469A1 (fr) * 1992-11-04 1994-05-11 Eastman Kodak Company Procédé pour accélérer la précipitation d'une émulsion à bas coéfficient de variation
US5773207A (en) * 1996-01-09 1998-06-30 Imation Corp. Photographic emulsions

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