Classifications

• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03C—PHOTOSENSITIVE MATERIALS FOR PHOTOGRAPHIC PURPOSES; PHOTOGRAPHIC PROCESSES, e.g. CINE, X-RAY, COLOUR, STEREO-PHOTOGRAPHIC PROCESSES; AUXILIARY PROCESSES IN PHOTOGRAPHY
  • G03C1/00—Photosensitive materials
  • G03C1/005—Silver halide emulsions; Preparation thereof; Physical treatment thereof; Incorporation of additives therein
  • G03C1/0051—Tabular grain emulsions
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03C—PHOTOSENSITIVE MATERIALS FOR PHOTOGRAPHIC PURPOSES; PHOTOGRAPHIC PROCESSES, e.g. CINE, X-RAY, COLOUR, STEREO-PHOTOGRAPHIC PROCESSES; AUXILIARY PROCESSES IN PHOTOGRAPHY
  • G03C1/00—Photosensitive materials
  • G03C1/005—Silver halide emulsions; Preparation thereof; Physical treatment thereof; Incorporation of additives therein
  • G03C1/015—Apparatus or processes for the preparation of emulsions
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03C—PHOTOSENSITIVE MATERIALS FOR PHOTOGRAPHIC PURPOSES; PHOTOGRAPHIC PROCESSES, e.g. CINE, X-RAY, COLOUR, STEREO-PHOTOGRAPHIC PROCESSES; AUXILIARY PROCESSES IN PHOTOGRAPHY
  • G03C1/00—Photosensitive materials
  • G03C1/005—Silver halide emulsions; Preparation thereof; Physical treatment thereof; Incorporation of additives therein
  • G03C1/015—Apparatus or processes for the preparation of emulsions
  • G03C2001/0157—Ultrafiltration

Definitions

• the present invention relates to a method for the preparation in a cost-effective way of a photographic silver (iodo)bromide emulsion with tabular grains showing an intermediate aspect ratio and a low coefficient of variation of their grain size distribution.
• Tabular grains are known in the photographic art for quite some time. As early as 1961 Berry et al described the preparation and growth of tabular silver bromoiodide grains in Photographic Science and Engineering, Vol 5, No 6. A discussion of tabular grains appeared in Duffin, Photographic Emulsion Chemistry, Focal Press, 1966, p. 66-72. Early patent literature includes Bogg US Patent 4,063,951, Lewis US Patent 4,067,739 and Maternaghan US Patents 4,150,994; 4,184,877 and 4,184,878. However the tabular grains described herein cannot be regarded as showing a high diameter to thickness ratio, commonly termed aspect ratio. In a number of US Patent Applications filed in 1981 and issued in 1984 tabular grains with high aspect ratio and their advantages in photographic applications are described.
• So Wilgus US Patent 4,434,226 discloses tabular silver bromoiodide grains having a thickness less than 0.2 ⁇ m, a diameter of at least 0.6 ⁇ m and an average aspect ratio greater than 8:1 and accounting for at least 50 percent of the total projected area of all the emulsion grains.
• Kofron US Patent 4,439,520 discloses similar grains which are spectrally sensitized.
• Abbott US Patent 4,425,425 describes radiographic materials containing tabular grains with an aspect ratio of at least 8:1 and Abbott US Patent 4,425,426 discloses similar grains with an aspect ratio between 5:1 and 8:1.
• a survey on high aspect ratio silver halide emulsions appeared in Research Disclosure, Volume 225, Jan 1983, Item 22534.
• Monodisperse emulsions on the other hand show the advantages of high gradation, good sharpness and excellent reproducibility. Because of the photographic benefits of on one hand monodisperse emulsions and on the other hand tabular grain emulsions, it was obvious that emulsion technologist tried and still try to combine the advantages of both classes.
• Mignot US 4,386,156 describes a method for the preparation of tabular grains with a variance of less than 30 % by transforming cubic seed crystals into tabular grains.
• Saitou DE 3 707 135 discloses hexagonal tabular grains with a low coefficient of variation by taking certain defined measures in the precipition and physical ripening stages.
• Nottorf US 4,722,866 discloses a preparation method for tabular grains with narrow size distribution by a rather complex precipitation process comprising at least five distinct stages.
• Zola EP 0 362 699 describes silver bromoiodide grains with an average aspect ratio greater than 12 characterized in that the quotient of the average aspect ratio of the tabular grains divided by the coefficient of variation of the total grain population is greater than 0.7. In this way the monodispersity is correlated with the aspect ratio because of the greater difficulty of preparing monodisperse tabular grains with very high aspect ratios.
• An essential feature of the preparation method consists in a nucleation stage characterized by a very high flow rate and concentrated solutions. Still other methods are disclosed in US 4,977,0774 and EP 0 391 560.
• European Patent Application filed on 20 Febr. 1992 under Application No. 92200498, a method is described for preparing an emulsion containing a monodispers tabular grain fraction by using an aminoazaindene as crystal growth modifier. However this method can give rise to development problems.
• emulsion preparation in general, not restricted to tabular grains, is an economic one.
• kettle yield In order to manufacture emulsions in a cost-effective way the so-called kettle yield should be maximized, meaning a minimal end volume of the precipitation mixture for a maximal amount of precipitated silver halide.
• Mignot US 4,334,012 discloses an elegant way of concentrating the reaction mixture volume in the kettle by applying the well-known emulsion washing technique known as ultrafiltration in a continuous way during the precipitation steps.
• the teachings of Mignot do not include specific examples on tabular grain or monodispers emulsion preparation.
• the objects of the present invention are realized by providing a method for the preparation of a photographic silver (iodo)bromide emulsion containing tabular grains wherein at least 70 % of the total projected area of all grains is occupied by said tabular grains, and wherein said tabular grain fraction exhibit :
• the precipitation includes a nucleation step and at least one growth step alternated by at least one physical ripening step.
• the dispersion medium is characterized by a gelatin concentration between 0.01 and 1 percent, a temperature preferably not exceeding 45 °C and a pAg corresponding to an electrochemical potential preferably varying between -3 and -90 mV measured with a silver electrode versus a standard calomel electrode. Additional gelatin can be added at a later stage of the emulsion preparation, e.g. before growth, after precipitation before chemical sensitization, or before coating in order to establish optimal coating conditions and/or to establish the required thickness of the coated emulsion layer.
• the relative volume of the dispersion medium may not be excessive in order to allow an end amount of at least 2 moles silver halide precipitated per liter end volume of the reaction mixture.
• the total silver halide preferably 0.5 % to 5.0 % is precipitated during the nucleation step while the rest of the silver and halide salts is added during one or more consecutive double jet growth steps.
• the nucleation stage is characterized by very high flow rates leading to high local supersaturation, a temperature maintained at a value preferably not exceeding 45 °C, and a pAg between -3 and -90 mV, preferably between -33 and -75 mV.
• the physical ripening step between the nucleation stage and the first growth step is characterized by an increase in the gelatin concentration to at most 3 % ; the temperature is risen to preferably at least 70 °C and the pAg is maintained in the same range as in the nucleation stage. In this way parallel twins are selectively grown out.
• an increasing flow rate of silver and halide solutions is preferably established, e.g. a linearly increasing flow rate.
• the flow rate at the end is about 3 to 5 times greater then at the start of the growth step.
• the flow rate can vary according to a quadratic equation as disclosed in DE 2107118, or to another exponential equation.
• several consecutive growth steps are established with consecutively increasing increments of the linaerly increasing fow rates. In this way a quadratic or exponential increment of the flow rate can be simulated.
• These flow rates can be monitored by e.g. magnetic valves.
• the pAg is maintained at a constant value corresponding to a silver potential between -3 and -60 mV.
• the pH is preferably established at a value between 4.0 and 9.0. Due to the concentrating effect of the continuous ultrafiltration the gelatin concentration is kept preferably between 1 % and 2 %. Under the described precipitation conditions no additional twin crystals are formed anymore but the anisotropic growth of existing crystals with parallel twin planes is promoted.
• An essential feature of the present invention is the application of ultrafiltration during the precipitation steps in such a way that, when applied, the permeate flux of the aqeous salt solution which is pouring through the ultrafiltration membrane, is at any moment equal to or greater than the sum of the flow rates of the silver ion and halide ion solutions.
• This ultrafiltration or membrane flux is a function of the total operative surface of the membrane and the trans-membrane pressure.
• the ultrafiltration flux is constant and equal or slightly greater than the sum of the maximal flow rates of the silver and halide ion solutions.
• the ultrafiltration procedure is applied in a continuous way during the precipitation steps, but, if necessary, it can be interrupted for short periods.
• the ultrafiltration module is conceived in such a way that the total volume of the ultrafiltration module and of its connecting means, is lower than 1/3 of the total precipitation volume. Moreover the circulation flux through the ultrafiltration module preferably is high enough, as to achieve a delay time in the module of any liquid volume unit of lower than 60 seconds and, most preferably lower than 30 seconds. Even delay times as low as 10 seconds can be achieved. It was stated experimentally that this factor was important in order to achieve good monodispersity of the tabular grains.
• a preferred ultrafiltration module for the practice of this invention is a ROMICON HF2-20-PM10, provided with a MASTERFLEX pump.
• a constant flux of about 50 ml/min is applied.
• a flux of about 200 ml/min can be established if needed.
• the kettle volume can be readjusted, e.g. kept constant, by the application of an extra jet of water.
• the emulsions containing tabular grains prepared according to the method of the present invention can be used in various types of photographic elements. However because of their (iodo)bromide composition they are preferably used in those applications for which high sensitivity is required.
• Preferred embodiments include black-and-white or colour negative recording materials for still photography or for cinematographic application, black-and-white or colour reversal materials, graphic arts camera sensitive films.
• their incorporation in radiographic recording materials constitutes the most preferred embodiment, thanks to the neutral hue of the developed tabular grains as was explained above.
• the iodide content of the tabular grains prepared according to the invention is limited to about 15 %, and for the preferred application in a radiographic material, is preferably comprised between 1 % and 5 %.
• the photographic element containing one or more emulsions prepared in accordance with the present invention can be composed of one single emulsion layer, as is the case for many applications, or it can be built up by two or even more emulsion layers.
• two identical emulsion layers can be applied on both sides of the support.
• the material contains blue, green and red sensitive layers each of which can be single or multiple.
• the photographic material can contain several non-light sensitive layers, e.g. a protective layer, one or more backing layers, one or more subbing layers, and one or more intermediate layers e.g. filter layers.
• the emulsions containing tabular silver (iodo)bromide grains prepared in accordance with the present invention can be chemically sensitized as described e.g. in "Chimie et Physique Photographique” by P. Glafkides, in “Photographic Emulsion Chemistry” by G.F. Duffin, in “Making and Coating Photographic Emulsion” by V.L. Zelikman et al, and in "Die Grundlagen der Photographischen Sawe mit Silberhalogeniden” edited by H. Frieser and published by Akademische Verlagsgesellschaft (1968).
• chemical sensitization can be carried out by effecting the ripening in the presence of small amounts of compounds containing sulphur e.g.
• emulsions can be sensitized also by means of gold-sulphur ripeners or by means of reductors e.g. tin compounds as described in GB 789,823, amines, hydrazine derivatives, formamidine-sulphinic acids, and silane compounds.
• reductors e.g. tin compounds as described in GB 789,823, amines, hydrazine derivatives, formamidine-sulphinic acids, and silane compounds.
• the tabular silver (iodo)bromide emulsions under consideration can be spectrally sensitized with methine dyes such as those described by F.M. Hamer in "The Cyanine Dyes and Related Compounds", 1964, John Wiley & Sons.
• Dyes that can be used for the purpose of spectral sensitization include cyanine dyes, merocyanine dyes, complex cyanine dyes, complex merocyanine dyes, hemicyanine dyes, styryl dyes and hemioxonol dyes.
• Particularly valuable dyes are those belonging to the cyanine dyes, merocyanine dyes and complex merocyanine dyes.
• the emulsion layer(s) in accordance with the present invention or the non-light-sensitive layers may comprise compounds preventing the formation of fog or stabilizing the photographic characteristics during the production or storage of the photographic elements or during the photographic treatment thereof.
• Many known compounds can be added as fog-inhibiting agent or stabilizer to the silver halide emulsion. Suitable examples are e.g.
• heterocyclic nitrogen-containing compounds such as benzothiazolium salts, nitroimidazoles, nitrobenzimidazoles, chlorobenzimidazoles, bromobenzimidazoles, mercaptothiazoles, mercaptobenzothiazoles, mercaptobenzimidazoles, mercaptothiadiazoles, aminotriazoles, benzotriazoles (preferably 5-methyl-benzotriazole), nitrobenzotriazoles, mercaptotetrazoles, in particular 1-phenyl-5-mercapto-tetrazole, mercaptopyrimidines, mercaptotriazines, benzothiazoline-2-thione, oxazoline-thione, triazaindenes, tetrazaindenes and pentazaindenes, especially those described by Birr in Z.
• benzothiazolium salts such as benzothiazolium salts, nitroimidazoles, nitrobenzimidazoles, chlor
• colour negative or colour reversal photographic material the usual ingredients specific for colour materials can be present e.g. colour couplers, couplers bearing a releasable photographic useful group and scavengers for oxidized developer.
• These typical ingredients for colour materials can be soluble or added in dispersed form, e.g. with the aid of so-called oilformers or they can be added in polymeric latex form.
• the gelatin binder of the photographic elements can be hardened with appropriate hardening agents such as those of the epoxide type, those of the ethylenimine type, those of the vinylsulfone type e.g. 1,3-vinylsulphonyl-2-propanol, chromium salts e.g. chromium acetate and chromium alum, aldehydes e.g. formaldehyde, glyoxal, and glutaraldehyde, N-methylol compounds e.g. dimethylolurea and methyloldimethylhydantoin, dioxan derivatives e.g.
• appropriate hardening agents such as those of the epoxide type, those of the ethylenimine type, those of the vinylsulfone type e.g. 1,3-vinylsulphonyl-2-propanol, chromium salts e.g. chromium acetate and
• 2,3-dihydroxy-dioxan active vinyl compounds e.g. 1,3,5-triacryloyl-hexahydro-s-triazine, active halogen compounds e.g. 2,4-dichloro-6-hydroxy-s-triazine, and mucohalogenic acids e.g. mucochloric acid and mucophenoxychloric acid.
• active vinyl compounds e.g. 1,3,5-triacryloyl-hexahydro-s-triazine
• active halogen compounds e.g. 2,4-dichloro-6-hydroxy-s-triazine
• mucohalogenic acids e.g. mucochloric acid and mucophenoxychloric acid.
• the binder can also be hardened with fast-reacting hardeners such as carbamoylpyridinium salts as disclosed in US 4,063,952 and with the onium compounds as disclosed in EP 0 408 143.
• the photographic element used in connection with the present invention may further comprise various kinds of surface-active agents in the photographic emulsion layer or in at least one other hydrophilic colloid layer.
• Suitable surface-active agents include non-ionic agents such as saponins, alkylene oxides e.g.
• Such surface-active agents can be used for various purposes e.g. as coating aids, as compounds preventing electric charges, as compounds improving slidability, as compounds facilitating dispersive emulsification and as compounds preventing or reducing adhesion.
• Preferred surface-active coating agents are compounds containing perfluorinated alkyl groups.
• the photographic material can contain several non light sensitive layers, e.g. an anti-stress top layer, one or more backing layers, and one or more intermediate layers eventually containing filter-or antihalation dyes that absorb scattering light and thus promote the image sharpness.
• Suitable light-absorbing dyes are described in e.g. US 4,092,168, US 4,311,787, DE 2,453,217, and GB 7 907 440.
• One or more backing layers can be provided at the non-light sensitive side of the support.
• These layers which can serve as anti-curl layer can contain e.g. matting agents like silica particles, lubricants, antistatic agents, light absorbing dyes, opacifying agents, e.g. titanium oxide and the usual ingredients like hardeners and wetting agents.
• the support of the photographic material may be opaque or transparent, e.g. a paper support or resin support.
• a paper support preference is given to one coated at one or both sides with an Alpha-olefin polymer, e.g. a polyethylene layer which optionally contains an anti-halation dye or pigment.
• an organic resin support e.g. cellulose nitrate film, cellulose acetate film, polyvinylacetal) film, polystyrene film, polyethylene terephthalate film, polycarbonate film, polyvinylchloride film or poly-Alpha-olefin films such as polyethylene or polypropylene film.
• the thickness of such organic resin film is preferably comprised between 0.07 and 0.35 mm.
• These organic resin supports are preferably coated with a subbing layer which can contain water insoluble particles such as silica or titanium dioxide.
• the photographic material containing tabular grains prepared according to the present invention can be image-wise exposed by any convenient radiation source in accordance with its specific application.
• processing conditions and composition of processing solutions are dependent from the specific type of photographic material in which the tabular grains containing emulsions prepared according to the present invention are applied.
• an automatically operating processing apparatus is used provided with a system for automatic regeneration of the processing solutions.
• a nucleation step was performed by introducing solution A and solution B simultaneously in dispersion medium C both at a flow rate of 25 ml/min during 28 seconds. After a physical ripening time of 15 minutes during which the temperature was risen to 70 °C, 48 g of phtaloylated gelatin, dissolved in 432 ml of water, was added and the mixture was stirred for an additional 5 minutes. Then a first growth step was performed by introducing simultaneously during 564 seconds solution (A) at a flow rate of 5 ml/min and solution B in such a way that a constant silver potential of -33 mV is maintained.
• a second growth step was performed by introducing by a double jet during 3763 seconds solution A starting at a flow rate of 5 ml/min and linearly increasing the flow rate to an end value of 25 ml/min, and solution B at an increasing flow rate as to maintain a constant silver potential value of -33 mV.
• the precipitation scheme was identical to emulsion 1 with the exception that during the two growth steps the silver potential was maintained at -3 mV instead of -33 mV.
• a nucleation step was performed by introducing solution A and solution B simultaneously in dispersion medium C both at a flow rate of 46.8 ml/min during 28 seconds. After a physical ripening time of 20 minutes during which the temperature was risen to 70 °C, 47.5 g of phtaloylated gelatin, dissolved in 475 ml of water, was added and the mixture was stirred for an additional 10 minutes. Then a first growth step was performed by introducing simultaneously during 174 seconds solution (A) at a flow rate of 7.5 ml/min and solution B in such a way that a constant silver potential of -33 mV is maintained.
• a second growth step was performed by introducing by a double jet during 3763 seconds solution A starting at a flow rate of 5 ml/min and linearly increasing the flow rate to an end value of 25 ml/min, and solution B at an increasing flow rate as to maintain a constant silver potential value of -33 mV.
• the precipitation scheme was identical to emulsion 4 with the exception that during the two growth steps the silver potential was maintained at -3 mV instead of -33 mV.
• the end volume was likewise about 1 l.
• a second growth step was performed by introducing simultaneously during 440 seconds solution A starting at a flow rate of 25 ml/min and linearly increasing the flow rate to an end value of 56 ml/min, and solution B at an increasing flow rate as to maintain a constant silver potential value of -33 mV.
• a third growth step was performed by introducing simultaneously during 445 seconds solution A starting at a flow rate of 56 ml/min and linearly increasing the flow rate to an end value of 100 ml/min, and solution B at an increasing flow rate as to maintain a constant silver potential value of -33 mV.
• the chacteristics of the control emulsions 1 to 3, and of the invention emulsions 4 to 7 are represented in table 1 : TABLE 1 emulsion UF ds v ds dEM th AR v dEM em. 1 - 0.64 0.42 1.42 0.12 13 0.32 inv. em. 4 + 0.59 0.38 1.36 0.19 6.7 0.26 inv. em. 6 + 0.60 0.31 1.25 0.19 6.5 0.18 contr. em. 2 - 0.57 0.46 1.33 0.13 10 0.15 inv. em. 5 + 0.59 0.38 1.36 0.23 4.8 0.15 inv. em. 7 + 0.33 0.31 0.75 0.23 3.3 0.17 contr.
• ds average sphere-equivalent diameter in micron of the entire grain population, the sphere-equivalent diameter being defined as the diameter of a hypothetical spherical grain with the same volume as the actual non-spherical grain
• v ds coefficient of variation or variance of the sphere-equivalent diameter distribution of the entire grain population, defined as the standard deviation of said sphere-equivalent diameter distribution divided by the average sphere-equivalent diameter
• dEM average electron microscopic diameter in micron of the tabular grain fraction, the electron microscopic diameter being defined as the diameter of a circle having an area equal to the projected area of the actual tabular grain as viewed on an electron photomicrograph
• th average thickness of the tabular grain fraction as deduced from electron photomicrography
• AR average aspect ratio of the tabular grain fraction, defined as the average electron microscopic diameter of the tabular grain fraction divided by the average thickness of
• the invention emulsion shows the better fog for a comparable sensitivity.

Landscapes

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

Priority Applications (3)

Applications Claiming Priority (1)

Publications (2)

Family

ID=8210767

Family Applications (1)

Country Status (3)

Cited By (3)

Families Citing this family (1)

Citations (4)

• 1992
  • 1992-07-10 EP EP19920202114 patent/EP0577886B1/fr not_active Expired - Lifetime
  • 1992-07-10 DE DE1992616083 patent/DE69216083T2/de not_active Expired - Fee Related
• 1993
  • 1993-06-30 JP JP18906493A patent/JP3225134B2/ja not_active Expired - Fee Related

Patent Citations (4)

Also Published As

Similar Documents

Legal Events