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
  • G03C1/76—Photosensitive materials characterised by the base or auxiliary layers
  • G03C1/825—Photosensitive materials characterised by the base or auxiliary layers characterised by antireflection means or visible-light filtering means, e.g. antihalation
  • G03C1/83—Organic dyestuffs therefor
  • G03C1/832—Methine or polymethine dyes
• • 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
• • 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
  • G03C1/74—Applying photosensitive compositions to the base; Drying processes therefor
  • G03C2001/7448—Dispersion
• • 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
  • G03C7/00—Multicolour photographic processes or agents therefor; Regeneration of such processing agents; Photosensitive materials for multicolour processes
  • G03C7/30—Colour processes using colour-coupling substances; Materials therefor; Preparing or processing such materials
  • G03C7/388—Processes for the incorporation in the emulsion of substances liberating photographically active agents or colour-coupling substances; Solvents therefor

Definitions

• the present invention relates to methods of preparing dispersions of photographically useful compounds ready-for-use in coating solutions of hydrophilic layers of photographic materials, said compounds having ionisable acid sites on their molecules.
• Photographically active ingredients for use in one or more hydrophilic layers of silver halide photographic materials are well-known.
• Particularly well-known ingredients are dyes which can be used as filter dyes, accutance dyes or antihalation dyes, stabilisers, coloured or uncoloured couplers, colour coupler precursors, developing agents, development activators and deactivators, hardeners, sensitisers or desensitisers.
• Normally storage dispersions of the said solid particle dispersions are formed in aqueous gelatinous medium by means of ball milling, sand milling, roller milling and other techniques. Said techniques have no economical interest as long as milling times from 6 to 24 hours and even up to 72 hours are not exceptionnal.
• the mechanical load therein is very hard as temperature increases may lead to a partial destruction of the dyes.
• milling techniques are leading to blocking of the mechanical process as the viscosity is increasing dramatically.
• a long preparation time makes a preparation "directly ready-for-incorporation in coating solutions" impossible.
• the dispersions should be stored and desintegration of the dispersing colloid and/or agglomeration of the particles may occur.
• Microprecipitation technique have e.g.
• the said dispersing aid is a stabiliser, a dispersant, a surfactant, a polymeric colloid or a mixture of them.
• Dispersions of dyes and other photographically useful compounds having ionisable acid sites on their molecules prepared according to the microprecipitation technique, especially when starting from a concentrated slurry in aqueous medium, are usually containing big agglomerated particles and the microprecipitation is carried out at a high concentration. As a consequence such dispersions are not suitable as ingredients for coating solutions of hydrophilic layers in photographic materials comprising photographically useful compounds having ionisable acid sites on their molecules.
• a method for preparing a concentrated dispersion of a photographically useful compound ready-for-use in coating solutions of hydrophilic colloid layers of a silver halide photographic material, wherein said compound has at least one ionisable acid site on its molecule, the said method comprising the steps of
• the term "dispersion of photographically active or photographically useful compound(s) or ingredient(s)” for use in one or more hydrophilic layers of silver halide photographic materials is related with filter dyes, accutance dyes or antihalation dyes, stabilisers, coloured or uncoloured (colourless) couplers, colour coupler precursors, developing agents, development activators or deactivators, hardeners, sensitisers or desensitisers.
• the term "dispersion of at least one dye” has to be interpreted, if more than one dye is present in the said dispersion, as resulting from a mixture of "microprecipitated dispersions", microprecipitated separately, or as resulting from a mixture of at least one "co-microprecipitated dispersion", wherein both mixtures are milled during and/or after the microprecipitation step, according to the method of this invention.
• dispersions are prepared of merostyryl dyes, oxonol dyes, developing agents, activating agents or deactivating agents... etc., without however being limited thereto.
• microprecipitate is obtained by the method of acidifying an aqueous alkaline solution of photographically useful compounds having ionisable acid sites on their molecules, that are deprotonised in alkaline medium and, as a consequence, that are solubilised.
• an input of energy resulting in thoroughly mixing the alkaline solution of photographically useful compounds and the acidic solution at the moment that the alkaline solution is brought into contact with the acidic solution.
• said mixing is provided by "low shear mixing", “high shear mixing” or "axial-flow impeller mixing”.
• high shear mixers are “Ultra Turrax” (Janke & Kunkel) and “Misch Sirene” (Kotthoff).
• axial-flow impellers are e.g. a Rushton turbine, an anchor impeller, a blade or paddle impeller, described in Chem. Eng. Sc., Vol. 47 (1992), p. 1401-1410.
• the impellers are therein driven by a variable speed motor (Zeromax, Model K, Zeromax Inc., Toronto). Effects of impellers are e.g. described in Chem. Eng. Progress, February 1994, p. 45-48.
• Ultrasonic transducers are the "Branson Liquid Processor” and the “Branson Sonifier 250", a schematic view of which is described on p. 83 and 88 respectively in the Engineer's Thesis “Ultrasound Dispersing", Univerity of Leuven, Belgium, 1987/1988 from B. Horsten.
• an ultrasound apparatus is optionally combined with at least one part of the apparatus in which the microprecipitate is formed or collected after precipitation.
• Combinations of different sources can be applied.
• the said energy can also be made variable by changing the parameters, changing the input energy in one apparatus, whether or not combined with another one, as e.g. by changing the stirring rate of a stirrer, by changing the dimensions of the mixing vessel (diameters, heights, distances, ...), flow rates etc... So in Perry's Chem. Eng. Handbook p. 19-22, a description is given of a suitable apparatus as e.g. the "Kenics static mixer” (Chemineer, Inc.) and the “Sulzer static mixer” (Koch Engineering Co., Inc.).
• the microprecipitation step making part of the method used in this invention may be carried out in a small "nucleation" vessel, wherein small amounts of acid solutions are continuously injected at a controlled rate into the alkaline solution of a solubilised photographically useful compound which is flowing at a predetermined rate throughout the said "nucleation vessel” to a larger vessel, collecting the microprecipitated compound(s).
• suitable ingredients like e.g.
• a dispersing agent a solvent, a binder or a combination thereof, may be present which should be avoided in the nucleation stage or which should be present there in much lower concentrations than before the milling step, especially when the microprecipitated dispersion should be stored for some time before being coated on a film support or substrate.
• an ultrasound treatment step can be applied in the "nucleation vessel", in the mains connecting the said "nucleation vessel” and a “collecting vessel” or in the "collecting vessel”.
• the dispersion can be formed batch-wise in one vessel by microprecipitation.
• This discontinous process can be interrupted at whatever a stage of the microprecipitation step in order to change e.g. mixers, in order to start an ultrasound treatment for a well-defined time period, etc..
• An ultrasound treatment step during and/or after the microprecipitation step is highly preferred in many cases.
• Combinations of energy input are thus possible in order to get a predictable average size and size distribution for the particles of the dispersion of photographically useful compounds.
• Aqueous solutions of photographically useful compounds used in the method according to this invention are made alkaline with a base as e.g. sodium hydroxide or potassium hydroxide.
• a base e.g. sodium hydroxide or potassium hydroxide.
• organic acids as acetic acid, propionic acid and the like are used or diluted inorganic acids as hydrochloric acid, sulphuric acid or phosphorous acid.
• the said microprecipitation step is performed in the presence of at least one dispersing agent, at least one hydrophilic colloid or a mixture thereof.
• the said microprecipitation step is performed in the absence of a dispersing aid, such as a dispersing agent and/or a hydrophilic colloid
• a dispersing aid such as a dispersing agent and/or a hydrophilic colloid
• Suitable hydrophilic colloids therefore are e.g. gelatin, colloidal silica sol, and synthetic, semi-synthetic, or other natural polymers.
• Synthetic substitutes for gelatin are e.g. polyvinyl alcohol, poly-N-vinyl pyrrolidone, polyvinyl imidazole, polyvinyl pyrazole, polyacrylamide, polyacrylic acid, and derivatives thereof, in particular copolymers.
• Natural substitutes for gelatin are e.g. other proteins such as zein, albumin and casein, cellulose, saccharides, starch, and alginates.
• semi-synthetic substitutes for gelatin are modified natural products as e.g.
• gelatin derivatives obtained by conversion of gelatin with alkylating or acylating agents or by grafting of polymerisable monomers on gelatin, and cellulose derivatives such as hydroxyalkyl cellulose, carboxymethyl cellulose, phthaloyl cellulose, and cellulose sulphates.
• the said hydrophilic colloid should dispose of an acceptably high number of functional groups, which by reaction with an appropriate hardening agent can provide a sufficiently resistant layer after coating.
• functional groups are especially amino groups, but also carboxylic groups, hydroxy groups, and active methylene groups.
• Solvents can also be used as e.g. methyl alcohol, ethyl alcohol, isopropyl alcohol, tetrahydrofuran, dimethylformamide, dioxane, N-methyl-pyrrolidone, acetonitrile, ethylene glycol, ethyl acetate, tetrahydrofuran etc., the proviso that the solution comprises a solution of a surfactant in water containing a polymer, ionisable by base.
• Suitable dispersing agents used in the microprecipitation step of the dispersion preparation method according to this invention are an ionisable polymer and/or an amphoteric and/or a surface active agent.
• Surface-active agents having a hydrophobic moiety e.g. a long-chain aliphatic group or an aliphatic-aromatic group and a hydrophilic moiety e.g. an anionic or cationic group, an amphoteric group or a non-ionic group as ethylene oxide groups are suitable.
• These surface anionic agents comprising an acid group such as a carboxy, sulpho, phospho, sulphuric or phosphoric ester group; ampholytic agents such as aminoacids, aminoalkyl sulphonic acids, aminoalkyl sulphates or phosphates, alkyl betaines, amine-N-oxides; cationic agents such as alkylamine salts, aliphatic, aromatic, or heterocyclic quaternary ammonium salts, aliphatic or heterocyclic ring-containing phosphonium or sulphonium salts.
• the said agents especially have the function of facilitating the dispersive emulsification of ingredients in silicic acid during the preparation procedure.
• These surface-active compounds may e.g.
• the dispersing agents are preferably present in amounts from 0,1 to 20 % by weight versus the amount of the dye.
• microprecipitation step making part of the method used in this invention is carried out in a milling vessel, small amounts of acid solutions are continuously injected at a controlled rate into the alkaline solution which is flowing at a predetermined rate throughout the said vessel to a collector, collecting the simultaneously microprecipitated and milled photographically useful compound(s).
• suitable ingredients like e.g. a dispersing agent, a solvent, a hydrophilic colloid or a combination thereof, may be present which, for whatever a reason are avoided in the "microprecipitation and milling step" or are present therein in much lower concentrations.
• an ultrasound treatment step is recommended, to be performed during and/or after the said microprecipitating step and/or milling step, especially when lower amounts of hydrophilic colloid are used e.g. for reasons of viscosity. It is e.g. possible to have an ultrasound treatment step in the collector after the said "microprecipation and milling step, during and/or after microprecipitation".
• the milling step is performed during and/or after the microprecipitation process by the well-known mechanical milling techniques such as e.g. ball milling, roller milling, pearl milling, basket milling or microfluidizing, the said step being performed in the corresponding "milling apparatus" as in the so-called “ball-mill”, “sand-mill”, “pearl-mill”, “basket-mill” or “roller-mill” apparatus, the said apparatus however not being limited thereto.
• the photographically useful compounds are therein, apart or together, preferentially microprecipitated and milled, during and/or after microprecipitation in the presence of gelatin.
• the presence of hydrophilic colloids differing from gelatin is thereby not excluded. Suitable hydrophilic colloids are the same as given hereinbefore.
• Preparation methods according to this invention of (a) dispersion(s) of photographically useful compounds are leading to particle sizes of the dispersion(s) smaller than 500 nm.
• To reach a particle size of not more than 500 nm by only applying an acidifying step of alkaline solutions (coating solutions or separate solutions containing at least one photographically useful group) microprecipitation in well-defined pH-conditions is required. Therefor a pH-stat apparatus can be used to controll these conditions, but the rate at which the acidic solutions are added is important too. Both conditions are not only determining the ultimate particle size of the microprecipitated particles, but are also determining the photographic activity as in the case of e.g.
• dye particles wherein they are determining the absorption over a specific wavelenght region e.g. from 370 to 700 nm, depending on their chemical structure.
• a milling step during and/or after microprecipitation is thus required in order to further make the size of the particles decrease.
• amounts which are generally used in hydrophilic layers of photographic materials are from 10 to 500 mg/m 2 and, more preferably, from 100 to 300 mg/m 2 .
• preferred absorption densities in well-defined wavelength region of e.g. 370 to 700 nm are at least 0.3, and, more preferably, at least 0.6. It is evident that more finely dispersed dye particles require a lower coating amount of the said dyes in order to reach the preferred absorption densities.
• finer alkali soluble dye particles are decolored more quickly and are more easily removed from the silver halide photographic material. It is clear that this is in favour of rapid processing applications of the photographic materials in which e.g. dye dispersions, prepared according to the method of this invention, are coated.
• a desalting step after the microprecipitating step is recommended especially to reduce coating failures due to the presence of said salts.
• the presence thereof can lead to e.g. sticking phenomena.
• Said desalting step is preferably performed by means of e.g. dialysis, ultrafiltration etc., without however being limited thereto.
• suitable concentrations are from 0.5 to 15 % by weight, more preferably from 1 to 10 % and still more preferably from 2 to 10 %.
• Application of the desalting techniques mentioned above is recommended in order to enhance said concentrations.
• the said dispersions may comprise more than one dye, whether or not resulting from mixing separate dispersions or co-precipitation and milling, to be incorporated in at least one hydrophilic layer of a silver halide photographic material.
• at least one oxonol dye is present in the dispersion prepared according to the method of this invention.
• at least one oxonol dye corresponding to the formula (I), given hereinafter, is present and at least one merostyryl dye corresponding to the formula (II) may be present.
• Said oxonol dye(s) has (have) been described e.g. in US-P's 4,092,168 and 4,288,534.
• Preferred merostryl dyes which are optionally present, are represented by the general formula (II) given hereinafter wherein n represents 0 or 1; each of p and q independently represents 0, 1 or 2; Q represents the atoms necessary to form an acidic nucleus; each of R 1 and R 2 independently represents hydrogen, (substituted or unsubstituted) alkyl, (substituted or unsubstituted) aryl, COOR 3 , NHCOR 4 or NHSO 2 R 5 with R 3 representing hydrogen or (substituted or unsubstituted) alkyl, each of R 4 and R 5 independently representing (substituted or unsubstituted) alkyl, or (substituted or unsubstituted) aryl, X represents OR 6 , SR 6 or NR 7 R 8 , wherein R 6 represents H, (substituted or unsubstituted) alkyl, (substituted or unsubstit
• the acidic nucleus is preferably a pyrazolone, barbituric acid, thiobarbituric acid, rhodanine, hydantoine, oxazolidindione, thio-oxazolidindione or an isoxazolinone.
• the necessary atoms represented by L 1 -L 3 are mono- or trimethine.
• Dyes according to the general formula (II) have been described in e.g. EP-A's 0 586 748; 0 587 230; US-P 5,344,749 and in EP-A 0 656 401.
• a merostyryl dye particularly in "microprecipitated-milled" form
• the dispersion(s) of e.g. dyes prepared according to the method of this invention are incorporated in at least one hydrophilic colloid layer of a silver halide photographic material wherein the absorption spectrum is in the region from 370 to 700 nm.
• the amount per sq.m. of the oxonol dye(s) is preferably about 0.1 g, i.a. from 0.09 to 0.11 g.
• At least one merostyryl dye can thus be necessary in the dispersion, wherein the amount per sq.m. of the merostyryl dye(s), corresponding to the formula (II) is from 0.1 to 0.3 g.
• the ratio by weight, of the said at least one merostyryl dye corresponding to the formula (II) and the said at least one oxonol dye corresponding to the formula (I) preferably is from 3:1 to 1:1 in said at least one hydrophilic colloid layer of the silver halide photographic material.
• Suitable hydrophilic layers wherein, photographically useful compounds as e.g. dye dispersions, prepared according to the method of this invention are used, are non-light-sensitive as well as light-senstive layers as in the case of dyes e.g., an antihalation undercoat layer, coated, between the support and the silver halide emulsion layer, situated more close to the support; one or more silver halide emulsion layers; one or more interlayers between the silver halide emulsion layers in a multilayer arrangement; in a filter layer between the emulsion layer farthest from the support and a protective layer or in a protective layer which may further be composed of one or more layers. Any combination is possible, depending on the specific requirements for each material.
• Suitable silver halide photographic materials coated from layers wherein dispersions of photographically useful compounds prepared according to the method of this invention can be used are radiographic materials having a multilayer arrangement e.g. as described in EP-Application No. 95201822, filed July 4, 1995, coated on one or both sides of a support; materials for micrography, duplicating materials, materials for use in graphic applications, colour materials etc.
• dye dispersions are incorporated into non-light sensitive hydrophilic colloid layers of a radiographic material, the said layers being provided at both sides of the support with a silver halide emulsion layer and an antistress layer as a protective antistress layer coated thereover.
• the radiographic material preferably has on both sides of the film support silver halide emulsion coatings that are split into two distinctive emulsion layers having silver halide crystals of different average grain size one of which is a high speed emulsion layer and the other is a low speed emulsion layer; the high speed emulsion layer being situated at a larger distance from the support than the low speed emulsion layer.
• the layer arrangement may also be opposite to the previously cited sequence in order to get a higher contrast. Moreover even without using a separate anti-crossover layer this layer arrangement reduces cross-over, especially in the critical low density area.
• said layers containing the dispersions, particularly dye dispersions prepared according to the method of this invention the said cross-over reduction is improved without leaving a colour stain upon processing, especially upon rapid processing in less than 60 seconds, preferably in 45, 38 or 30 seconds as reference processing times of materials with high-throughput.
• one or more backing layers may be present, one or more of which may comprise dispersions of at least one photographically useful group, prepared according to the method of this invention.
• the coating pH has a value of 6.5 or less, preferably from 5.5 to 6.5.
• the dye dispersions prepared by the method of this invention are incorporated in optical photoconductive layers, coated from non-aqueous coating solutions.
• Suitable supports used for the materials described hereinbefore can be found in the said RD 36544 and in e.g. EP-A 0 619 514. Especially preferred supports are polyethylene terephthalate and polyethylene naphthalate.
• aqueous stock solution of about 5.2% by weight of dye I-1 was prepared by sprinkling 30 g of the fully protonated dye in about 450 g of distilled water while stirring with an axial-flow impeller. About 99 ml of an aqueous 2 N solution of NaOH were added at a rate of about 9 ml per minute in order to give a final pH of about 9. The solution was filtered to remove undissolved contaminants and could be stored for about 24 hours without chemical degradation of the dye I-1.
• Microprecipitation was carried out by pouring 54 ml of an aqueous 6 N solution of sulphuric acid in the stock solution. While pouring in the aqueous acid the stock solution was stirred with a high shear mixer to create a very effective mixing of the two solutions. After this microprecipitation-step the suspension was heated up to 40°C while stirring with an axial-flow impellor and about 65 ml of an aqueous 2 N solution of NaOH were added to give a final pH value of about 5.2.
• This suspension was mixed with a solution of 20% by weight of gelatin in water and was subsequently milled in a bead mill to form a stable dispersion, As a milling material zirconium oxide pearls sizing 0.6 to 0.8 ⁇ m were used therein.
• a comparative dispersion was prepared in the same way as above except for the milling step: no milling in a bead mill was performed after mixing the suspension of the dye I-1 with a solution of 20% by weight of gelatin in water in order to obtain a stable dispersion.
• a comparative dispersion was produced by bead milling the fully protonated dye I-1.
• Water 38 ml
• About 5 g of fully protonated dye I-1 were added under stirring with a high shear mixer.
• This suspension was consecutively milled in a bead mill.
• the milling time of this comparative dispersion was taken four times longer than the milling time in the example with the microprecipitated protonated dye I-1.
• the obtained suspension was consecutively admixed with a solution of gelatin, 20 % by weight, to obtain a more stable dispersion.
• Table 1 Dispersion Mean Particle Size (in ⁇ m) Number of particles per ml > 5 ⁇ m microprecipitated and milled 0.420 37 000 compar. ex. 1 0.437 2 640 697 compar. ex. 2 0.645 141 000
• An aqueous stock solution of about 15% by weight of dye II-1 was prepared by the steps of adding 50 ml distilled water and 60 ml of an aqueous solution of 2 N NaOH to about 20 g of fully protonated dye II-1. The solution was stirred with an axial-flow impeller while heating up to about 45°C. The final pH was about 12.0. The solution was filtered to remove some undissolved product. Microprecipitation was carried out by pouring 25 ml of a sulphuric acid solution 6 N in the stock solution. While pouring in the aqueous acid, the stock solution was heavily stirred with a high shear mixer to create a very effective mixing of the stock solution with the aqueous acid.
• a comparative dispersion was produced by bead milling fully protonated dye II-1.
• a mixture of 57 ml of water and about 100 ml of a solution (1 % by weight) of a solution of dispersing agent "Aerosol OT" (trademarked product from American Cyanamid) was prepared.
• an amount of about 20 g of fully protonated dye II-1 was added while stirring with a high shear mixer.
• This suspension was subsequently milled in a bead mill.
• the milling time of this comparative dispersion took eight times longer in comparison with the milling time in the example with the microprecipitated protonated dye II-1.
• the suspension obtained was subsequently admixed with a solution (7,2 % by weight) of gelatin to obtain a more stable dispersion.
• aqueous stock solution of about 4% by weight of dye III-1 was prepared by sprinkling 40 g of the fully protonated dye III-1 in about 824 g of distilled water while stirring with an axial-flow impeller. About 176 ml of an aqueous 2 N solution of NaOH were added at a rate of about 15 ml per minute in order to reach a final pH value of about 7.5. The solution was filtered to remove undissolved residu and could be stored for about 10 days without chemical degradation of the dye III-1.
• An aqueous stock solution of about 6.4 % by weight of dye IV-1 was prepared by sprinkling 80 g of the fully protonated dye IV-1 in about 930 g of distilled water while stirring with an axial-flow impellor. About 230 ml of an aqueous 2 N solution NaOH were added at a rate of about 15 ml per minute to give a final pH value of about 9.1. The solution was filtered to remove undissolved residu. The aqueous stock solutions of dye IV-1 and of dye III-1 were poured together in volume ratio of 1.25 : 1.00 and mixed for a while.
• the microprecipitation was carried out by pouring 114 ml of an aqueous 6 N solution of sulphuric acid in the mixture of the stock solutions. During the pouring step the stock solution mixture was stirred with a high shear mixer to create a very effective mixing of the solutions. After this micro-co-precipitation-step the suspension was heated up to 43°C while stirring with a high shear mixer and about 40 ml of an aqueous 2N solution of NaOH was added to give a final pH of about 5.1. This suspension was mixed with a solution of 24 % by weight of gelatin in water and subsequently milled in a bead mill. A stable dispersion was obtained.
• a comparative dispersion was produced in the same way as described above without the step of milling in a bead mill. A stable dispersion was also obtained.
• Example 3 It is common knowledge that dispersions of filter dyes with a smaller particle size do result in a much higher yield of the dye. The same conclusions as set forth hereinbefore in Example 2 can be drawn from Example 3.
• An aqueous stock solution of about 12% by weight of dye I-1 was prepared by adding 5 l of ethanol and about 25 l of distilled water to an amount of 5 kg of the fully protonated dye I-1 whereupon, while stirring, 6.4 l of an aqueous solution of NaOH 2 N were added at a rate of about 3 l per minute to give a final pH value of about 10.3. The solution was filtered to remove the undissolved residu and could be stored at least for about 60 minutes without chemical degradation of the dye V-1.
• Microprecipitation was carried out in a bead mill by pumping in the mill the solution of the dye V-1 at a rate of 490 ml per minute, further simultaneously pumping into the milling apparatus from an adjacent site in the vicinity of the solution of the dye V-1 an aqueous solution of sulphuric acid solution 6 N at a rate of 60 ml per minute. Meanwhile the bead mill was stirred at normal operating speed. As a milling material zirconium oxide pearls sizing 0.6 to 0.8 ⁇ m were used therein. After the "microprecipitation-milling" process an amount of a 12.8 % by weight of a gelatin solution was added in order to solidify the obtained dispersion.
• An aqueous stock solution was prepared of about 11 % by weight of dye V-1 by adding 330 ml of distilled water to an amount of 50 g of fully protonated dye V-1 whereupon while stirring about 72 ml of 2 N aqueous NaOH were added at a rate of about 15 ml per minute in order to give a final pH of about 10.8.
• the solution was filtered to remove some undissolved residu.
• the solution was heated to 45° C and an amount of 510 ml of an aqueous solution of gelatin (9.7 % by weight) was admixed to the solution by an axial-flow impeller.
• Microprecipitation was carried out in a bead mill under normal operating conditions while circulating the mixture of the solution of the dye V-1 and the gelatin solution at a speed of 2.5 l per minute by pumping in the mill 22.5 ml of an aqueous H 2 SO 4 solution 6 N at a rate of about 60 ml per minute.
• zirconium oxide pearls sizing 0.6 to 0.8 ⁇ m were used therein. After a while the suspension was collected and cooled in order to obtain a solidified dispersion.
• a comparative dispersion was produced by making the same mixture of the solution of the dye V-1 and of the aqueous solution of gelatin as in Example 4.2.. Microprecipitation was carried out by pouring about 22.5 ml of an aqueous solution of sulphuric acid 6 N in the mixture mentioned before. While pouring the aqueous acidic solution the mixture was stirred with a shear mixer to create a very effective mixing of the solutions. After this microprecipitation-step the suspension was subsequently milled in a bead mill in the same operating conditions as set forth in Example 4.2.. No microprecipitation was thus performed in the milling device. After cooling a solidified dispersion was obtained.
• microprecipitation performed in a milling device yields even smaller average mean particle diameters if compared with microprecipitation, followed in a subsequent step by milling of the separately microprecipitated dispersion.
• microprecipitation performed in a milling device yields even a smaller number of agglomerated particles as is clear from Table 4. Moreover the number of agglomerates obtained strongly depends on the chemical structure of the photographically useful compounds, as is the case for the dye V-1 used in this example.
• An aqueous stock solution of about 11% by weight of dye V-1 was prepared by adding 333 ml of distilled water to an amount of 50 ml of fully protonated dye V-1 whereupon, while stirring, about 67 ml of an aqueous solution of NaOH 2 N were added at a rate of about 15 ml per minute to give a final pH value of about 10.1.
• the solution was filtered to remove the undissolved residu and could be stored at least for about 60 minutes without chemical degradation of the dye V-1.
• Said microprecipitation was carried out by pouring about 22.5 ml 6 N aqueous sulphuric acid in the mixture mentioned before. While pouring in the aqueous acid the mixture was stirred with a shear mixer to create a very effective mixing of the solutions. After this microprecipitation-step the suspension was heated up to about 43°C while stirring with an axial-flow impeller and about 50 ml of a 9.7 % by weight gelatin solution was admixed to obtain a solidified dispersion.
• Example 5 The results are presented in Table 5.
• the volume ratio refers to the the reference volume, set equal to 1.0 for Example 5.1 before microprecipitation.
• the volumes obtained for the other Examples before and after microprecipitation are referred thereto.
• Table 5 Dispersion Mean Particle Size (in ⁇ m) Volume ratio before after microprecipitation Example 5.1 0.352 1.00 1.05
• Example 5.3 0.345 1.15 1.20 It can be seen from Table 5 that it is possible to obtain a dispersion with about the same particle size and, consequently, the same photographic properties.
• An aqueous stock solution of 15 % by weight of dye II-1 was prepared by adding 50 ml of distilled water and 60 ml of an aqueous solution of NaOH 2 N to about 20 g of fully protonated dye II-1. The solution was stirred with an axial-flow impeller while heating to about 47°C. The final pH was about 12.0. The solution was filtered to remove some undissolved product. Microprecipitation was carried out by pouring 25 ml of an aqueous solution of sulphuric acid 6 N in the stock solution. While pouring the aqueous acid solution, the stock solution was stirred with an axial-flow impeller to create a very effective mixing of the stock solution with the aqueous acid solution.
• Example 6.2 A comparative dispersion was produced in the same way as described above in Example 6.1. with the only difference that use was made of a high shear mixer during the microprecipitation.
• Example 6.1 A comparative dispersion was produced in the same way as described above in Example 6.1. with the difference that use was made of an ultrasonic device to create a micromixing flow during the microprecipitation.

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Silver Salt Photography Or Processing Solution Therefor (AREA)
• Emulsifying, Dispersing, Foam-Producing Or Wetting Agents (AREA)
• Colloid Chemistry (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=8220526

Family Applications (1)

Country Status (2)

Cited By (4)

Citations (5)

Family Cites Families (5)

• 1996
  • 1996-07-19 JP JP8208865A patent/JP2835711B2/ja not_active Expired - Fee Related
  • 1996-07-19 EP EP96202056A patent/EP0756201A1/fr not_active Withdrawn

Patent Citations (5)

Also Published As

Similar Documents

Legal Events