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
  • G03C1/06—Silver halide emulsions; Preparation thereof; Physical treatment thereof; Incorporation of additives therein with non-macromolecular additives
  • G03C1/08—Sensitivity-increasing substances
  • G03C1/09—Noble metals or mercury; Salts or compounds thereof; Sulfur, selenium or tellurium, or compounds thereof, e.g. for chemical sensitising
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03C—PHOTOSENSITIVE MATERIALS FOR PHOTOGRAPHIC PURPOSES; PHOTOGRAPHIC PROCESSES, e.g. CINE, X-RAY, COLOUR, STEREO-PHOTOGRAPHIC PROCESSES; AUXILIARY PROCESSES IN PHOTOGRAPHY
  • G03C1/00—Photosensitive materials
  • G03C1/005—Silver halide emulsions; Preparation thereof; Physical treatment thereof; Incorporation of additives therein
  • G03C1/06—Silver halide emulsions; Preparation thereof; Physical treatment thereof; Incorporation of additives therein with non-macromolecular additives
  • G03C1/08—Sensitivity-increasing substances
  • G03C1/09—Noble metals or mercury; Salts or compounds thereof; Sulfur, selenium or tellurium, or compounds thereof, e.g. for chemical sensitising
  • G03C2001/093—Iridium
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03C—PHOTOSENSITIVE MATERIALS FOR PHOTOGRAPHIC PURPOSES; PHOTOGRAPHIC PROCESSES, e.g. CINE, X-RAY, COLOUR, STEREO-PHOTOGRAPHIC PROCESSES; AUXILIARY PROCESSES IN PHOTOGRAPHY
  • G03C1/00—Photosensitive materials
  • G03C1/005—Silver halide emulsions; Preparation thereof; Physical treatment thereof; Incorporation of additives therein
  • G03C1/06—Silver halide emulsions; Preparation thereof; Physical treatment thereof; Incorporation of additives therein with non-macromolecular additives
  • G03C1/08—Sensitivity-increasing substances
  • G03C1/09—Noble metals or mercury; Salts or compounds thereof; Sulfur, selenium or tellurium, or compounds thereof, e.g. for chemical sensitising
  • G03C2001/094—Rhodium

Definitions

• the present invention relates to a photosensitive silver halide emulsion and a photosensitive material containing said emulsion. More specifically the present invention is related to a silver halide emulsion with enhanced image contrast.
• a silver halide material used for industrial applications needs a very high flexibility in its practical properties for use, like for instance the light temperature range for exposure, the range of development times in which an optimal image quality can be realized, etc..
• One of the means increasingly used in the art is the introduction of a deep electron trap in the silver halide crystal which can be arranged by doping with certain metal ligand complexes. Such an electron trap is called deep if it easily holds a captured electron.
• the LUMO lowest unoccupied molecular orbital
• the incorporated molecular entity (related complex) should be situated at least 0.5 eV below the conduction band while the trapping lifetime should be longer than 0.2 s (R.S.Eachus, M.T.Olm in "Cryst.Latt.Def.and Amorph.Mat.”, 1989(18), 297-313).
• the LUMO of the related complex thus has the ability to trap an electron from the conduction band (D.F.Shriver, P.W.Atkins, C.H.Langford in “Inorganic Chemistry”- Oxford Univ.Press (1990), Oxford-Melbourne-Tokyo).
• a general property of a d eep e lectron t rapping a gent (here further called 'DETA') is that it always creates loss in sensitivity which is inherent in this created lattice defect.
• the DETA lowers the efficiency of the latent image formation process at the surface of the crystal by capturing a photo electron. Because the amount of these molecules is equally distributed over the solid silver halide the larger and intrinsically most sensitive emulsion grains will contain the most DETA-molecules (compared with the smaller less sensitive emulsion grains). These intrinsically most sensitive emulsion grains are therefore desensitized to a larger extent than the smaller and intrinsically less sensitive grains.
• RhCl 6 3- -complex in aqueous solutions which is especially active in a matrix rich in silver chlorobromide as has been demonstrated in EP-A 0 557 616 and in JP-A 6,035,093 and which is cheaper than the other complexes.
• disadvantages related therewith are the formation of a chloro-aqua complex which is less active as a DETA, the activity decrease in a bromide or bromoiodide matrix and the impracticability in a silver chloride matrix.
• DETA which can be effectively used in a photosensitive silver halide emulsion containing chloride, bromide, iodide or a mixture of at least two of these halides. More in particular its use in pure silver chloride or silver bromide microcrystals is envisaged.
• a still further object of the present invention is to provide a DETA as a dopant for photosensitive silver halide emulsions which can easily be prepared with relative low costs.
• a photosensitive image-forming element comprising on a support at least one photosensitive layer containing silver halide crystals which are internally doped with a transition metal complex (more preferably a metal halide chalcogenic cyanate complex, further called a 'MHCC'-complex) forming a deep and permanent electron trap, wherein said transition metal complex satisfies the following general formula (1): MX 6-n (H 2 O) n1 (L) n2 m- wherein:
• the precipitation of a photosensitive silver halide emulsion is conducted in an aqueous dispersing medium including, at least during grain growth, a peptizer wherein silver ions and halide ions are brought together.
• Grain structure and properties can be selected by control of several parameters like precipitation temperature, pH and relative proportion of the silver and halide ions in the dispersing medium.
• the precipitation is commonly conducted on the halide side of the equivalence point which is defined as "the point at which the silver and halide ion activity is equal".
• the silver halide emulsions of the current invention are prepared in the presence of compounds which can be occluded in the crystal structure.
• a compound also called dopant
• the dopant can be distinguished from the metal-complex introduced in the emulsion as an additive by EPR-or ENDOR-techniques.
• the EPR-technique and sample preparation has been described in US-A 5,457,021 by Olm et al and by H.Vercammen, T.Ceulemans, D.Schoenmakers, P.Moens and D.Vandenbroucke in Proc.
• dopants are modifying the crystal structure and are further influencing the properties of the crystal.
• a lot of parameters like sensitivity, gradation, pressure sensitivity, high or low intensity reciprocity failure (LIRF), stability, dye desensitization, and several other sensitometric aspects of a photosensitive silver halide emulsion can be modified by selection of the dopant, including its concentration, its valency and its location in the crystal in case of incorporation of the single metal ion.
• the dopant including its concentration, its valency and its location in the crystal in case of incorporation of the single metal ion.
• coordination complexes or even oligomeric coordination complexes are used the different ligands bound at the central metal ion can be occluded in the crystal lattice too and can in this way influence the photographic properties of the silver halide material as well (see Research Disclosure No.
• the dopant utilized in accordance with the present invention is a transition metal complex which can be defined by the general formula (1) as described hereinbefore and which is applied as a deep electron trapping agent or DETA.
• the complex satisfying formula (1) contains at least one chalcogenic cyanate complex and differs from the other known chalcogenic cyanate complexes in different ways.
• M represents a metal selected from the group consisting of the elements Rh, Ir and Os. It is important to know that with respect to the present invention the element Rhodium (Rh) is most preferred.
• X further represents one or a mixture of at least two of the halogen atom(s) selected from the group consisting of F, Cl, Br and I. (It is desirable for the purpose of the present invention to provide one or a mixture of at least two of the halogen atom(s) selected from the group consisting of F, C1, Br and I.)( ??? ) Most preferred for use in the present invention is the element chlorine (Cl).
• the ligand L in formula (1) is a chalcogenic cyanate group represented by YCN or NCY wherein Y represents a chalcogene atom selected from the group consisting of S, Se and Te.
• Y represents a chalcogene atom selected from the group consisting of S, Se and Te.
• n equals an integer having a value from 1 up to less than 6, while m equals a value of 1, 2 or 3.
• Rh can be replaced by the element Iridium (Ir) or Osmium (Os), wherein the negative charge of the transition metal complex depends on the charge of the metal ion (as e.g. +3 or +4 in case of Ir; +4 in case of Os).
• the complexes of the present invention satisfying formula (1) and which are used as deep electron trapping agents (DETA), can be prepared in different ways as described for instance for the CNS- or SCN-ligand complexes in 'Gmelins Handbuch der Anorganische chemie' (Verlag chemie, Germany), Vol.64(1955), p.70,71 and in US 3,507,928 (Rh-complexes), in GB 1,418,391 (Rh-and Ir-complexes), in Horns U.,Preetz W.,Z.Anorg.Alg.
• DETA deep electron trapping agents
• RhCl 6 3(-) -complex with a SCN - or a NCS - -ligand.
• the said mixture of complexes is the result of an exchange between the Cl- and the SCN-ligand which forms a more strongly bond with the metal atom(s) of the mixture of complexes and which is therefore also more stable.
• the amount of dopant which can effectively be incorporated in the emulsion grains in order to get the desired effect as described in the present invention should be situated in the range between 10 -10 and 10 -2 mole per mole of silver halide, preferably in the range between 10 -9 and 10 -4 mole per mole of silver halide and even more preferrably between 10 -8 and 5.10 -6 mole per mole of silver halide.
• the complex(es) or dopant(s) according to formula (1) is(are) preferably concentrated in the inner portion of the silver halide crystals, wherein said inner portion is defined as the portion which does not contain more than 90 mole % of the silver present in each crystal, more preferably less than 50 mole % and even more preferably less than 25 mole % of the silver present in each crystal.
• Introducing the dopants according to the general formula (1) in the photosensitive silver halide crystals of the present invention leads to an image-forming element with improved sensitometric characteristics with respect to gradation and sensitivity.
• Dopants which are used for the present invention according to the formula (1) are essentially those which act as a deep and permanent electron trap in the silver halide crystal and which satisfy (as already taught hereinbefore) two conditions:
• the doping procedure itself can normally be performed at any stage during the grain growth phase of the emulsion preparation where the reactants are added to the reaction vessel in the form of solutions of silver and halide salts or in the form of preformed silver halide nuclei or fine grains which easily dissolve in the precipitation medium. It is important to know that the dopants can also be added in an indirect way by addition of a dispersion containing very fine soluble silver halide grains or nuclei already comprising the dopant. Individual reactants for the formation of silver halide can be added through surface or subsurface delivery tubes by hydrostatic pressure or by an automatic delivery system for maintaining control of pH and/or pAg in the reaction vessel and of the rate of the reactant solutions introduced therein.
• the reactant solutions or dispersions can be added at a constant rate or a constantly increasing or fluctuating rate in combination with stepwise delivery procedures as desired. More details about possible ways of making a silver halide emulsion which can be principally used in practizising this invention are summarized in Research Disclosure No. 38957 (1996), p. 591-639, section I-C. Special attention should be paid to the way in which the dopants are introduced during the grain growth process. Therefore the solution containing the dopants is preferentially introduced making use of a third jet, in a zone in the reactor wherein the compounds are rapidly incorporated in the growing microcrystals.
• the advantage of the use of such a third jet is that a solvent can be used for the given dopant which is most suitable for the stability of that compound. Further the temperature of the dopant solution can be adjusted in order to maximize the stability too. The most stable conditions for the dopant solution are preferably tested by UV-VIS absorption.
• the third jet itself can be adjusted automatically or manually.
• the dopant can be added at a constant rate or at any rate profile as has e.g. been described in JP-A 03163438, wherein the dopant is occluded in two different concentrations in the silver halide grains of a direct positive emulsion, thereby having the highest dopant concentration closest to the grain centre.
• the said JP-Application describes a method to get a silver halide emulsion with improved gradation without paying attention to the sensitivity level, which, contrary thereto, is also one of the targets of the present invention.
• the photographic emulsions prepared in this way for use in the imager-forming element of the present invention contain silver halide crystals comprising chloride, bromide or iodide alone or combination thereof.
• Other silver salts which can be incorporated in a limited amount in the silver halide lattice are silver phosphate, silver thiocyanate, silver citrate and some other silver salts.
• the chloride and bromide salts can be combined in all ratios in order to form a silver chlorobromide salt.
• Iodide ions however can be coprecipitated with chloride and/or bromide ions in order to form a iodohalide with an iodide amount which depends on the saturation limit of iodide in the lattice with the given halide composition: this means up to a maximum amount of about 40 mole percent in silver iodobromide and up to at most 13 molevig in silver iodochloride both based on silver.
• the activity of the complex(es) or dopant(s) satisfying formula (1) is almost not influenced by the halide composition of the silver halide crystals used.
• the composition of the silver halide in the crystal volume can change in a continuous or in a discontinuous way.
• Emulsions containing crystals composed of various sections with different halide compositions are used for several differing photographic applications.
• Such a structure with a difference in halide composition between the center and the rest of the crystal known as so-called “core-shell"-emulsion) or with more than two crystal parts differing in halide composition (called a "band"-emulsion) may occur.
• the changes in halide composition can be realized by direct precipitation or in an indirect way by conversion wherein fine silver halide grains of a certain predetermined halide composition are dissolved in the presence of the so-called host grains forming a "shell" or "band” on the given grain.
• the crystals formed by the methods described above have a morphology which can be tabular or non-tabular like cubic, octahedral, etc..
• the aspect ratio (ratio of equivalent circular diameter to thickness) of the grains can vary from low ( ⁇ 2) over “medium” or “intermediate” (from 2 up to 8) to "high” (> 8) where especially in the case of the ultrathin tabular crystals (from 0.05 up to 0.15 ⁇ m) high aspect ratios can be realized.
• the major faces of the tabular grains may have a (111) or a (100)-habitus, the structure of which is (respectively) stable or has to be stabilized (for instance by a "crystal habit modifying agent").
• crystal habit modifying agent In the class of non-tabular grains there are a lot of possible crystal habits which can be divided in the more regular shaped crystals or in crystals with a mixed crystal habit.
• the emulsions can include silver halide grains of any conventional shape or size. Specifically the emulsions can include coarse, medium or fine silver halide grains.
• the silver halide emulsions can be either monodisperse or polydisperse after precipitation.
• dopants which are deep electron traps as described by formula (1) can be added to the silver halide emulsion. These are optionally introduced, essentially because of their specific influence on the photographic characteristics.
• Different classes of dopants are known: dopants resulting in a non-permanent trapping behaviour or a shallow electron trap or SET (such as IrCl 6 3- or Ru(CN) 6 2- , described in Research Disclosure No 36736 (1994), p. 657, or a recombination or hole trapping center. These dopants are essentially all those not obeying the conditions for creating a deep electron trap. Many examples of this category have already been described in the patent literature but cover different silver halide systems like e.g.
• the silver halide emulsions of the present invention which are prepared in one of the ways described hereinbefore contain crystals which have a spherical equivalent diameter (SED) which is situated between 0.01 ⁇ m and 1.5 ⁇ m, more preferably between 0.01 ⁇ m and 1.0 ⁇ m and even more preferably between 0.01 ⁇ m and 0.9 ⁇ m.
• SED spherical equivalent diameter
• the emulsions can be surface-sensitive emulsions which form latent images primarily at the surface of the silver halide grains or they can be emulsions forming their latent-image primarily in the interior of the silver halide grain. Further the emulsions can be negative-working emulsions such as surface sensitive emulsions or unfogged internal latent image-forming emulsions. However direct-positive emulsions of the unfogged, latent image-forming type which are positive-working by development in the presence of a nucleating agent, and even pre-fogged direct-positive emulsions can be used in the present invention.
• the silver halide emulsions can be surface-sensitized by chemical sensitization which can be done in many different ways, in presence of a chalcogen as sulfur, selenium or tellurium, in presence of a noble metal as e.g. gold or in combination with a chalcogen and noble metal. Sometimes it can be necessary to add a sulphur sensitizer in the form of a dispersion of solid particles as has been described in EP-A 0 752 614. Reduction sensitization is another method of sensitizing a photosensitive silver halide emulsion which if desired can be combined with the chalcogen/noble metal-sensitization.
• Reduction sensitization should especially be mentioned with respect to the present invention as a way of introducing hole traps in the silver halide crystals for use in the image-forming elements according to the present invention in order to optimize the efficiency of latent image formation.
• Reduction sensitization can be performed by decreasing pAg of the emulsion or by adding thereto reducing agents as e.g. tin compounds (see GB-Patent 789,823), amines, hydrazinederivatives, formamidine-sulphinic acids, silane compounds, ascorbic acid, reductic acid and the like. Care should however be taken in order to avoid generation of fog in an uncontrollable way. It is clear that the incorporation of hole traps in silver halide can also be realized by incorporating special dopants like for instance Cu (+) , Ni (2+) , etc..
• the silver halide emulsions used in the image-forming elements according to the present invention are spectrally sensitized with dyes from different classes which include polymethine dyes comprising cyanines, merocyanines, tri-, tetra- and polynuclear cyanines and merocyanines, oxonols, hemioxonols, styryls, merostyryls and so on. Sometimes more than one spectral sensitizer may be used in the case that a larger part of the spectrum should be covered.
• desensitizers should be used, as for instance in pre-fogged direct-positive or in daylight handling materials, various chemical compounds are proposed for practical use. Principally all these compounds which are used as desensitizers in silver halide materials and which are for instance summarized in EP-A 0 477 436 can be used in combination with the elements of the present invention.
• the photographic elements comprising the said silver halide emulsions may include various compounds which should play a role of interest in the material itself or afterwards as e.g. in the processing, finishing or warehousing the photographic material.
• These products can be stabilizers and anti-foggants (see RD No. 38957(1996), section VII), hardeners (RD No.38957(1996), section IIB), brighteners (RD No.38957(1996), section VI), light absorbers and scattering materials (RD No.38957(1996), section VIII), coating aids (RD No.38957(1996), section IXA), antistatic agents (RD No.38957(1996) section IXC), matting agents (same RD No. 38957(1996), section IXD) and development modifiers (same RD, section XVIII).
• the silver halide material can also contain different types of couplers, which can be incorpated as described in the same RD, section X.
• the photographic elements can be coated on a variety of supports as described in RD No. 38957(1996), section XV, and the references cited therein.
• the photographic elements may be exposed to actinic radiation, especially in the visible, near-ultraviolet and near-infrared region of the spectrum, in order to form a latent image (see RD No. 38957(1996) section XVI).
• the latent-image formed can be processed in many different ways in order to form a visible image (same RD, section XIX). So photothermographic materials are not excluded either.
• Processing to form a visible dye image for colour materials means contacting the element with a colour developing agent in order to reduce developable silver halide and to oxidize the colour developing agent which in turn normally reacts with the coupler to form a dye (RD. No. 38957(1996), section XX).
• Example 1 Application of dopants to a silver chloride emulsion.
• - Solution A1 gelatin 75 g demineralized water 1500 ml - Solution A2 AgNO 3 750 g demineralized water 1500 ml - Solution A3 : NaCl 171.8 g demineralized water 1500 ml - Solution A4 KSCN 194.2g demineralized water in order to make 1l.
• Solution Dot 1 was allowed to stand 24 hours before precipitation.
• - Solution Dot 2 KSCN 194.2g Na 3 [RhCl 6 ].
• Solution Dot 2 was allowed to stand 24-48 hours before precipitation.
• the pH of the solutions A1 and A3 was brought to 2.80 using therefore a sulphuric acid solution.
• the solutions A2 and A3 were kept at room temperature, while solution A1 was heated to 50° Celsius.
• the pAg was set at 7.05 using a NaCl solution.
• Solution A2 was added to solution Al at a constant rate during 3 minutes, while solution A3 was added at a rate in order to keep the pAg constant at a value of 7.05.
• the addition rate for solution A2 was slightly raised during 3 minutes while the addition rate of solution A3 was varied in order to raise the pAg over a pAg interval of 0.5 in 3 minutes.
• Solution A2 was further added during 60 minutes at an constantly accelerating rate of 6 ml/min to 25 ml/min, while solution A3 was added at a rate in order to keep the pAg constant at 7.5.
• the thus prepared silver chloride emulsion has a monodisperse grain size distribution, having a grain size of 0.41 ⁇ m and amitual variation coefficient of about 15 % in grain size.
• Emulsion (2) was prepared in the same way, except that 1.31 ml of the solution Dotl, containing a Rhodium complex, was added in the first part of the precipitation phase to solution Al at a constant rate using a third jet.
• the position of the dopant in the emulsion grains was situated after the addition of 5 % and before the addition of 20 % of the total amount of silver used.
• Emulsion (3) was prepared in the same way, except that 1.31 ml of the solution Dot 2, containing a Rhodium complex, was added to solution A1 at constant rate using a third jet.
• the position of the dopant in the emulsion grains was also situated here after the addition of 5 % and before the addition of 20 % of the total amount of silver used.
• Emulsion (4) was prepared in the same way, except that 1.31 ml of the solution A4, containing KSCN without the Rhodium salt, was added to solution Al at constant rate using a third jet.
• the position of the salt added in the preparation step of the grains for this emulsion was also situated after the addition of 5 % and before the addition of 20 % of the total amount of silver used.
• the silver chloride emulsions were subsequently ripened at a pAg and pH equal to 7.7 and 4.6 respectively with 3.2 10 -5 mole of sodium toluenesulphonate per mole of silver, a gold trichloride solution containing 3.36 10 -6 mole per mole of silver and 5.1* 10 -6 mole of a dimethylcarbamoylsulfide compound per mole of silver at 50° Celsius for 120-150 minutes.
• the pH was adjusted to 5.20.
• the emulsions were coated on a substrated PET base at 4 g gelatine/m 2 and 4 g of AgNO 3 /m 2 .
• the emulsions were image-wise exposed through a step-wedge originally using a 10 -3 sec Xenon flash.
• the exposed photographic materials were developed in a surface developer at room temperature for 5 minutes and fixed for 5 minutes in a commercial fixer G333C (Trademark of AGFA) which was 1/3 diluted with demineralized water.
• the fog levels for the materials were about 0.03 for the unripened emulsions and about 0.07 for the sensitized emulsions.
• the contrast G was measured around this point ( between 25% and 75% of the maximum density).
• Sensitometric results Unripened emulsion Ripened emulsion Speed S Contrast G Speed S Contrast G Comparative (1) 100 100 100 100 100 100 100 Comparative (2) 79 104 74 98 Inventive (3). 15 199 6 159 Comparative (4) 162 110 26 53
• Example 2 Application to a silver chlorobromoiodide emulsion.
• - Solution B1 NaCl 9.2 g gelatin 70 g demineralized water 1540 ml - Solution B2: AgNO 3 500 g demineralized water 1000 ml - Solution B3: NaCl 109.4 g KBr 125.8 g H 2 SO 4 8.23 g demineralized water up to a total volume of 850 ml.
• the pH of the solution B3 is set at 2.30, using a sulphuric acid solution, in order to form a more stabilized environment for the dopant solution Dot 2 and solution Dot 3. These are administered to solution B3 just prior to precipitation.
• the solutions B2 and B3 are kept at 30 degrees Celsius, while solutions B1 and B4 are heated up to 35° Celsius.
• Solution B2 was started by addition to solution B1 through a funnel in 3 minutes 30 seconds, 10 seconds later followed by solution B3 running simultaneously in B1 together with B2 for 3 minutes. The temperature was elevated to 42 degrees in 3 minutes and 20 seconds. 4 minutes and 45 seconds after the start of solution B2, solution B4 was added in 1 minute at 42° C.
• the thus prepared mixed silver chlorobromoiodide emulsion has a monodisperse grain size distribution, having a grain size of 0.275 ⁇ m and amitual variation coefficient of about 18-20 % in grain size.
• This emulsion satisfying the present invention was prepared in the same way, except for not adding solution Dot 3 to B3 but adding instead 1.07 ml of the solution Dot 4, containing another Rhodiumcomplex, which was manually added to solution B1 after 1 minute of the start of the precipitation in a 1 minute time interval (the total precipitation time was 3 minutes 30 seconds).
• the position of the dopant in the emulsion grains was not exactly known.
• Dopant solution Dot 4 was added as soon as possible after nucleation in order to incorporate the dopant as deep in the core as possible.
• the silver chlorobromide emulsions were subsequently ripened at a pAg and pH equal to 7.1 and 5.3 respectively with sodium toluenethiosulphonate (8.1 10 -5 mole/mole Ag), [potassium iodide (1.8 10 -3 mol/mol Ag), a gold trichloride solution ( 2 10 -4 mole/mole Ag), sodium thiosulphate (2.1 10 -5 mole/mole Ag) and sodium sulphite (6.7 10 -5 mole/mole Ag) at 50° Celsius for 180 minutes.
• These emulsions were spectrally sensitized with a red spectral sensitizer, the formula of which is given hereinbefore. The pH was adjusted to 6.
• the emulsions were coated on a substrated PET base at 2 g gelatine/m 2 and 6 g AgNO 3 /m 2 .
• a layer containing gelatin (1 g/m 2 ), a di-vinyl sulphonyl hardener and surfactants was coated on top of the emulsion layer.
• the emulsions were exposed through a continuous wedge to a He-Ne Laser at 670 nm for 10 -7 - 10 -8 sec.
• the exposed photographic materials were developed in a G101C commercial developer (trademarked by AGFA) using a Rapiline 26 machine (trademarked by AGFA) at 35 degrees for 30 seconds and fixed at 35° for 30 seconds in a G333c fixer (trademarked by AGFA).
• the fog levels for the materials are around 0.03 for both emulsions.
• the contrast G is measured in the shoulder (between 75 % and 90 % of maximum density). All the values are relative to the values of comparative (1) which is each time taken as 100 %.
• a decrease of 50 % means a sensitivity loss of a factor 2 while a decrease in gradation G is always proportional. Sensitometric results.
• Example 3 Application to a tabular silver bromide emulsion.
• the pH of the solution C1 was adjusted at a value of 1.8 with a sulphuric acid solution and pBr adjusted at 2.39 with Kbr.
• the solutions C2, C3 and C4 were kept at room temperature while solutions C1 and C5 were heated to 45° Celsius. 7.35 ml of solution C2 and 12 ml of solution C3 were added to solution C1 in 9 seconds. After 2 minutes the temperature was elevated to 70 degrees in 25 minutes followed by the addition of solution C5 and adjusting of the pH at 6 with NaOH. After waiting for 6 minutes the following steps are subsequently carried out:
• Emulsion (2) was prepared in the same way, except that 1 ml of solution Dot 5, containing a Rhodium complex, was added to solution C1 at a constant rate using a third jet.
• the position of the dopant in the emulsion grains was expressed as amitual amount of the crystal volume at the moment where the addition of the third jet was started and as amitual amount of the crystal volume at the moment where the addition of the third jet was stopped. In this particular case it was situated between 20 and 25 %.
• Emulsion (3) was prepared in the same way, except that 1 ml of the solution Dot 6, containing a Rhodium complex, was added to solution C1 at a constant rate using a third jet.
• the position of the dopant in the emulsion grains was expressed as thetempo amount of the crystal volume at the moment where the addition of the third jet was started and thetempoual amount of the crystal volume at the moment where the addition of the third jet was stopped. In this inventive emulsion it was situated between 20 and 25 % too.
• Emulsion (4) was prepared in the same way as in the inventive emulsion, except that 1 ml of the solution C7, containing only the KSCN salt, was added to solution C1 at a constant rate using a third jet.
• the position of the salt in the emulsion grains was expressed as thetempoual amount of the crystal volume at the moment where the addition of the third jet was started and thetempoual amount of the crystal volume at the moment where the addition of the third jet was stopped. Also in this emulsion the KSCN salt was also situated between 20 and 25 %.
• the tabular bromoiodide emulsions were ripened at a pAg and pH equal to 7.38 and 5.5 respectively with 8.9*10 -3 mole per mole of silver of anhydro 5,5'-dichloro-3,3'-bis(n-sulphobutyl)-9-ethyl-oxacarbocyanine hydroxide as a spectral sensitizer, 1.4*10 -3 mole of a potassium thiocyanate solution per mole of silver, 3.24*10 -7 mole of a toluene sodium thiosulphonate solution per mole of silver, 1.5*10 -5 mole of a sodium thiosulphate solution per mole of silver, 1.35*10 -6 mole of a gold trichloride solution per mole of silver and 1.3 *10 -4 mole of a mercaptotetrazole compound per mole of silver, at 55 °C for 200 minutes.
• the emulsions were coated on a substrated PET base at 1.7 g gelatine/m2 and 5 g AgNO3/m2.
• the emulsions were image-wise exposed through a step-wedge originally using a 10 -3 sec Xenon flash.
• the exposed photographic materials were developed in a surface developer at room temperature for 5 minutes and fixed for 5 minutes in a commercial fixer G333C (Trademark of AGFA) which was 1/3 diluted with demineralized water.
• the fog levels for the materials were situated at about 0.07 for the ripened emulsions.
• the speed S measured was the logaritm of the energy of the illumination needed in order to obtain an optical density equal to 1 above fog level.
• the contrast G is measured around this point. All the values which are summarized in Table 4 are relative to the values of comparative emulsion (1) which is taken 100 % each time. For the sensitivity S a decrease of 50 % means a sensitivity loss with a factor of 2 while a decrease in gradation G is always proportional.

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• 1999
  • 1999-01-11 EP EP99200087A patent/EP0933671B1/de not_active Expired - Lifetime

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