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

Definitions

• the present invention concerns a silver halide photographic emulsion with improved sensitivity.
• silver halide emulsions that is to say emulsions whose coefficient of variation, defined as the relationship 100 x (sigma/v), where sigma is the volume standard deviation and v the mean volume of the population of the grains, is greater than 35% and preferably greater than 25%.
• Silver halide emulsions comprising at least two halides are also known, one of which is present in a higher concentration in at least one region or phase of the grain.
• silver bromoiodide emulsions of advantageous sensitivity can be obtained, when the iodide is localised in precise phases of the grains, as is the case for example with so-called "core/shell" emulsions. It is also desirable to use monodisperse emulsions when it is wished to modify the form of the sensitometric curve and especially the contrast, including by mixing two or more monodisperse emulsions.
• silver bromoiodide emulsions with localised iodide are more difficult to prepare than emulsions where the iodide is distributed throughout the grain.
• the object of the present invention is a monodisperse silver bromoiodide emulsion, chemically sensitized to an optimum extent, but without its stability in storage being affected.
• the photographic emulsion according to the invention is a monodisperse silver bromoiodide emulsion where the iodide is uniformly distributed in the grains (uniform intra-grain distribution), chemically sensitized with sulphur and gold, to the same level as a polydisperse silver bromoiodide emulsion, with the same speed/granularity compromise.
• the addition of the gold and sulphur sensitisers is effected at a temperature between 30 and 60°C and advantageously between 40 and 50°C.
• Gold sensitisers are well known. These are notably the gold salts with a degree of oxidation of +1 or +3, described in US patents 2,399,083, 2,597,915 or 2,597,856. Suitable compounds are for example potassium chloroaurite, potassium chloroaurate, ammonium aurithiocyanate, potassium iodoaurate, potassium aurithiocyanate, auric triochloride, N-methyl-2-aurobenzosulphobenzothiazolium chloride, and bis (1,4,5-trimethyl-1,2,4-triazolium-3-thiolate)-Au(I)-tetrafluoroborate.
• Preferred gold sensitizers are the gold (I) compounds disclosed in USP 5,049,485. These compounds include those represented by the formula : AuL2+X ⁇ or AuL(L1)+X ⁇ wherein L is a mesoionic compound X is an anion and L1 is Lewis acid donor.
• Sulphur sensitisers are also known. These are principally alkali metal thiosulphates, thiourea or thiourea derivatives, thioethers, etc. Useful compounds as well as the afore mentioned gold sensitizers are described in Research Disclosure, September 1994, publication 36544, Section IV, "Chemical Sensitisation”. These gold and sulphur sensitisers are used in quantities which are well known and reported in the literature. For example, the gold compound is used in a proportion of 10 ⁇ 6 moles to 10 ⁇ 1 moles per mole of silver and the sulphur compound in a proportion of 10 ⁇ 5 moles to 10 ⁇ 1 moles per mole of silver.
• the thiocyanate used in step (b) of the process defined above is preferably a thiocyanate of an alkali metal, sodium or potassium.
• the optimum quantity of thiocyanate depends on the composition of the emulsion and the desired characteristics, but is in general between 0.1 and 1.5 g/mole of silver and preferably between 0.2 and 1.0 g/mole of silver.
• the temperature stage is observed for a conventional period, usually lying between 5 and 60 minutes and advantageously between 10 and 30 minutes.
• a modifying compound is added which is able to reduce fogging without reducing sensitivity.
• the invention therefore comprises the embodiment which consists of using such modifying agents.
• These agents are azaindenes, azapyrimidines, benzothiazolium salts and compounds with one or more heterocycles. Examples of these compounds are cited in US patents 2,131,038, 3,411,914, 3,554,754, 3,565,631 and 3,901,714, in Canadian patent 778,723 and in Photographic Emulsion Chemistry by Duffin, Focal Press (1966) New York, pages 138-143, or in Research Disclosure, September 1994, publication No 36544, section VII.
• phenylmercaptotetrazole antifogging agents Any of the mercaptoheterocyclic nitrogen compounds, as described herein, will act as antifoggants in the practice of this invention. However, particularly good results are obtained with the mercaptotetrazoles, especially the 5-mercaptotetrazoles.
• 5-mercaptotetrazoles which can be employed include those having the structure : where R is a hydrocarbon (aliphatic or aromatic) radical containing up to 20 carbon atoms. The hydrocarbon radicals comprising R can be substituted or unsubstituted.
• Suitable substituents include, for example, alkoxy, phenoxy, halogen, cyano, nitro, amino, amido, carbamoyl, sulfamoyl, sulfonamido, sulfo, sulfonyl, carboxy, carboxylate, ureido and carbonyl phenyl groups.
• an -SH group as shown in formula A-I, an -SM group can be substituted, where M represents a monovalent metal cation.
• Various other conventional substances may be added to the emulsion, during or after precipitation.
• solvents for silver halides maturation agents, such as in particular thioethers as described in US patents 3,062,646 or 3,271,157, dyes for spectral sensitisation, dopants, or other modifying agents.
• dyes for spectral sensitisation dyes for spectral sensitisation, dopants, or other modifying agents.
• These compounds may be adsorbed on the surface of the grains, or at certain predetermined places on this surface, or buried in the grains.
• the additives may be introduced initially into the precipitation reactor, or added separately with one of the halides then introduced into the reactor, in accordance with normal techniques.
• dopants such as compounds of noble metals in group VIII, may be present during the precipitation.
• the silver salts and halides may be introduced into the reactor by means of feed pipes arriving just below the surface of the contents of the reactor, whilst controlling the flow rate, pH and pAg. Suitable techniques are described in US patents 3,821,002 and 3,031,304, and by Claes et al in Photographisches Korrespondenz, Vol 102, No 10, page 162, 1967. Agitation arrangements can be provided to accelerate the homogenisation of the reagents in the reactor, as described in Research Disclosure, Vol 166, paragraph 16662, February 1978, or in US patents 2,996,287, 3,342,605, 3,415,650, 3,785,777, 4,147,551 and 4,171,224.
• a dispersion medium is first introduced into the reactor, this normally consisting of a mixture of water and a vehicle which is a binder and/or a peptiser.
• This vehicle is usually a hydrophilic colloid, notably a proteinic one, such as gelatin, for example bone gelatin (treated with an alkali), pigskin gelatin (treated with an acid), modified gelatin, for example acetylated gelatin, phthalylated gelatin, etc, optionally associated with hydrophobic substances.
• the vehicle may also comprise synthetic substances, for example acrylamide polymers, cellulose derivatives, polyvinyl alcohol, etc. These substances do not necessarily have to be present at the time of precipitation. They may be added at the time of coating.
• the emulsion is preferably washed in order to eliminate the soluble salts therefrom. This may be achieved by decantation, filtration, solidification, coagulation, centrifugation or flocculation, as described for example in US patents 2,316,845, 3,396,027, 2,618,556, 2,614,928, 2,565,418, 3,241,969, 2,489,341, 2,996,287, 3,498,454.
• the emulsions can be dried and kept before use, as described in Research Disclosure, Vol 101, paragraph 10152, September 1972.
• the emulsion may contain yet other substances such as light-absorbent agents, surfactants, tanning agents, etc. These agents may also be incorporated in auxiliary layers. Information concerning these agents are given in Research Disclosure, September 1994, sections VIII and IX.
• the emulsion according to the invention can be spectrally sensitized by the addition of one or more sentising dyes.
• the sentising dye can be added at different stages in the preparation of the emulsion.
• the most usual operating methods consisting of adding it just before the sensitisation or chemical maturation, during this maturation or afterwards.
• the usual sensitising dyes are well known; these are for example cyanines or merocyanines described with their bibliographic references in Research Disclosure, December 1989, publication No 308119, Section IV, "Spectral Sensitisation and Desensitisation".
• An emulsion of silver bromoiodide was prepared, containing 3% molar silver iodide, by the double jet technique.
• an initial growth step was effected by introducing, by the accelerated double jet method, the following reagents: AgNO3 (2 M/l) NaBr (1.94 M/l) KI (0.06 M/l) duration 27.2 minutes pAg 9.3 temperature 60°C
• a second growth step was effected with the following parameters and the following reagents, introduced by double jet method at constant flow rates: AgNO3 (2M/l) NaBr 1.94 M/l) KI (0.06 M/l) 36.7 minutes pAg 9.3 temperature 60°C
• a 20 minute stage is effected at 70°C.
• the emulsion was then hold at 70°C for 20 minutes.
• the emulsion samples were coated at 8.07 x 100 mg of Ag, 32.3 x 100 mg gelatin and 10.5 x 100 mg of coupler per m.
• the coatings were exposed 1/100 sec at a tungsten source of 5500°K through a Wratten filter No 9, plus a color conversion filter DL5A.
• the ESD is 1.085 ⁇ m for sample A, and 0.66 ⁇ m for sample B.
• the COV (by volume) is 6.1% for A and 9.6% for B.
• the two samples were developed for 3 minutes 15 seconds in an AUTOPAN machine using the Kodak C41 process for colour negative development.
• the coupler had the formula:
• Example 1 The operating method of Example 1 was repeated, except that the sensitisation was effected as follows (quantities in mg/mole of silver) and the holding stage is 20 minutes at 60°C.
• the anti-fogging modifier had the formula:
• the gold compound is bis(1,4,5-trimethyl-1,2,4-triazolium-3-thiolate) Au(I) tetrafluororborate.
• the emulsion was coated, exposed and developed as in Example 1.
• a polydisperse silver bromoiodide emulsion with 12% molar iodide was prepared, sensitized with sulphur and gold with thiocyanate digestion and spectrally sensitized by means of the mixture of dyes I and III.
• This emulsion had an equivalent diameter, of 0.84 ⁇ m and was coated at 8.07 x 100 mg of silver, 32.3 x 100 mg of gelatin and 10.5 x 100 mg of coupler per m.
• the sensitising dyes had the formulas:
• Example 1 The product is exposed and developed as in Example 1.
• Table 1 The results obtained, appearing in Table 1, show that the monodisperse emulsions according to the invention give sensitometric results comparable to those of the reference emulsion of Example 3.
• the coupler has the formula:

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• Physics & Mathematics (AREA)
• Chemical & Material Sciences (AREA)
• Spectroscopy & Molecular Physics (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• General Physics & Mathematics (AREA)
• Silver Salt Photography Or Processing Solution Therefor (AREA)
• Non-Silver Salt Photosensitive Materials And Non-Silver Salt Photography (AREA)

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Citations (34)

• 1994
  • 1994-10-26 FR FR9413053A patent/FR2722009A1/fr active Granted
• 1995
  • 1995-06-28 EP EP95420173A patent/EP0691569A1/en not_active Withdrawn
  • 1995-07-03 JP JP7167393A patent/JPH0843977A/ja active Pending

Patent Citations (34)

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