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
  • 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
• • 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
  • G03C1/04—Silver halide emulsions; Preparation thereof; Physical treatment thereof; Incorporation of additives therein with macromolecular additives; with layer-forming substances
  • G03C1/043—Polyalkylene oxides; Polyalkylene sulfides; Polyalkylene selenides; Polyalkylene tellurides

Definitions

• a photographic chemical adjuvant is incorporated into a hydrophilic colloid composition by dispersing a solution of the chemical adjuvant in the hydrophilic colloid composition in the presence of a high-boiling substantially water-insoluble aliphatic alcohol or ethoxylated derivative thereof which corresponds to the formula:
• R is hydrogen or when n is 1 may be alkyl
• each of R and R stands for a straight-chain or branchedchain alkyl group or together represent the atoms necessary to complete an aliphatic ring structure, R and R together comprising at least 5 carbon atoms.
• the colloid composition can be a light-sensitive silver halide emulsion or a non-light sensitive water-permeable colloid composition.
• the high boiling alcohols or ethoxylated derivatives thereof have the particular advantage of reducing the viscosity of the colloid compositions and maintaining the viscosity at a stable level.
• the present invention is concerned with the use of high-boiling substantially water-insoluble aliphatic alcohols or ethox'ylated derivatives thereof in dispersing chemical adjuvants into hydrophilic colloids employed in the formation of photosensitive and even non-photosensitive layers of photographic silver halide elements.
• adjuvants In the manufacture of a photographic material numerous adjuvants should be brought into operative association in one or more of the hydrophilic colloid layers of the said material.
• adjuvants include amongst others color couplers, competing couplers, mask-forming compounds, dyes e.g. filter dyes, antihalation dyes and sensitizing dyes, stabilizers, U.V. -absorbers, optical brightening agents, etc.
• color coupler any compound which in silver halide photography couples with an oxidized aromatic primary amino color developing agent to form a dye image.
• mask-forming compound is meant a compound which oxidatively couples with a color coupler in an oxidizing bleaching bath as for example described in British Pats. Nos. 880,862 and 975,932 to form a colored mask image.
• ballast groups eg a long straight-chain or branched-chain aliphatic group such as an alkyl or alkylene group comprising from 5 to 20 carbon atoms.
• the presence of this ballast group imparts to the molecule a hydrophobic character and therefore, these non-dilfusible color couplers and maskformers are generally also provided with one or more salt-forming groups eg carboxy groups and preferably sulpho groups, so that these compounds can be dissolved in the photographic emulsions in the form of their soluble alkali salts.
• Couplers may be used which are waterinsoluble and contain no salt-forming groups.
• the couplers are dissolved in water-immiscible, oily type solvents or crystalloids such as tricresyl phosphate and di-n-butyl phthalate and the resulting solution added to an aqueous phase containing a dispersing agent such as gelatin or a higher fatty alcohol sulphate.
• the mixture is then passed through a homogenizing apparatus wherein is formed a dispersion of the oily coupler solution in the aqueous medium.
• the dissolution of the coupler in the oily solvent is facilitated by the use of an auxiliary low-boiling water-immiscible solvent which is subsequently removed by evaporation.
• the above dispersion of coupler is then mixed with a gelatino silver halide emulsion and coated in the usual manner to produce a system in which particles of coupler, surrounded by an oily membrane, are distributed throughout the gel matrix.
• a new dispersion technique has now been found for incorporating chemical adjuvants into photographic hydrophilic colloid coating compositions for forming waterpermeable colloid layers of a photo-sensitive silver halide element, which new technique does not show the disadvantages of the above dispersion technique.
• this new method may be employed with particular advantage to introduce non-diffusing color couplers 3 and mask-formers into photographic photosensitive emul sions it can also be used to introduce into photo-sensitive emulsions other photographic emulsion auxiliary compounds such as competing couplers, which are used in color photography as described in British Pat. 861,138, light-screening dyes, sensitizing dyes, stabilizers, etc. Moreover, the method of the present invention can also be employed in the preparation of uniform dispersions of photographic compounds in unsensitized photographic colloid compositions.
• it may be used in the production of water-permeable intermediate layers in which it is desired uniformly to disperse a light-absorbing filter or antihalation dye, competing couplers and other photographic active substances such as UV-absorbers, optical brightening agents, etc.
• the method of the invention may be particularly employed for the incorporation of substantially water-insoluble compounds say compounds of which not more than 3% by weight dissolves in water at room temperature
• a photographic chemical adjuvant is uniformly distributed throughout a hydrophilic colloid coating composition for forming one of the layers of a photographic silver halide element by dispersing a solution of the said chemical adjuvant in the said photographic hydrophilic colloid coating composition, or, first dispersing the said solution in water or in an aqueous solution of a water-soluble colloid for example gelatin and then mixing the dispersion thus formed with the said hydrophilic colloid coating composition, wherein the said dispersing occurs in the presence of a high-boiling substantially water-insoluble aliphatic alcohol or ethoxylated derivative thereof corresponding to the formula:
• n stands for or 1
• n stands for 0 to 30, preferably 0 to 12,
• each of R and R stands for a straight-chain or branchedchain alkyl group or together stand for the atoms necessary to close an alicyclic ring structure, R and R together comprising at least 5 C-atoms.
• the resulting coating composition comprises the said colloid having homogeneously distributed therein droplets comprising the chemical adjuvant and the high-boiling alcohol.
• the high-boiling alcohol is readily penetrated by the photographic developing solution and other processing baths. Photographic color images are produced with high maximum density and excellent sharpness.
• the high-boiling substantially water-insoluble aliphatic alcohol or ethoxylated derivative thereof has a favourable effect on the viscosityof gelatin coating compositions in that the viscosity can be maintained at a stable level.
• many chemical adjuvants when incorporated in photosensitive or non-photosensitive hydrophilic colloid compositions cause changes in the viscosity of these compositions when added thereof.
• the viscosity increases with time so that uniform coating thicknesses cannot be realized.
• color couplers comprising a carboxyl group. These color couplers cannot be dispersed according to known dispersion techniques into hydrophilic colloid compositions and when dissolved therein from alkaline solutions they require high pH-values in order to prevent flocculation.
• a photographic element according to the invention comprises a water-permeable layer having a Water-soluble colloid binder, such as a photo-sensitive gelatino silver halide emulsion layer or a non-photo-sensitive gelatin layer, in which are dispersed droplets comprising a chemical adjuvant and a high-boiling alcohol as defined above.
• a Water-soluble colloid binder such as a photo-sensitive gelatino silver halide emulsion layer or a non-photo-sensitive gelatin layer, in which are dispersed droplets comprising a chemical adjuvant and a high-boiling alcohol as defined above.
• alcohols corresponding to the above formula are the widely known branched-chainprimary oxoalcohols having at least 8 C-atoms such as isooctyl alcohol, isodecyl alcohol, isotridecyl alcohol, isohexadecyl alcohol and isooctadecyl alcohol.
• Isooctyl alcohol is a commercial material prepared from'c -olefins by means of the oxo-synthesis, (of. H. Rompp, Chemie Lexikon- Francksche Verlag-Stuttgart, West Germany), and is a mixture of primary branched-chain C -alcohols.
• Isodecyl alcohol is a commercial material prepared from C -olefins (tripropylene) by means of the oxo-reaction and is a mixture ofprimary branched-chain C -alcohols.
• Isotridecyl alcohol is a commercial material prepared from C olefins (triisobutylene, tetrapropylene or di(2-methyl-lpentene) by means of the oXo-reaction and is a mixture of primary branched-chain C -alcohols.
• Isohexadecyl alcohol and isooctadecyl alcohol are commercial materials prepared by aldol-condensation of C or C -aldehydes formed by oxo-synthesis; isohexadecyl alcohol is a mixture of branched-chain O -alcohols mainly consisting of alcohols as represented by the formula:
• branched-chain alcohols are hydroabietyl alcohol which is an alicyclic alcohol having the formula:
• alcohols suitable for use in accordance with the present invention are those having recurring oxyethylene units which can be prepared from the above examples of alcohols by ethoxylation.
• the high-boiling alcohols of use in accordance with the present invention are substantially colourless, from light-viscous to heavy viscous liquids at ordinary temperatures. They are inert toward light-sensitive silver halide emulsions and are stable toward light, heat and humidity in addition to being inert to the various processing baths which may be encountered such as developers, oxidized developers, bleach baths, fixing baths, etc. and to the photographic compounds that may be associated with them in the photographic material.
• the chemical adjuvants may be dissolved in the high-boiling alcohol whereupon the solution is dispersed directly in the photographic hydrophilic colloid coating composition or--particularly when it is intended to distribute photographic silver halide emulsion auxiliary compounds in a silver halide emulsion ready for coating-first dispersed in water or gelatin solution or in any aqueous colloid which is miscible with the said coating composition, the resulting dispersion then being stored to create stocks of concentrated dispersions from which, Whenever required, parts can be taken for addition to hydrophilic colloid coating compositions such as a gelatino silver halide emuls on.
• the dispersion of the above solution into the aqueous phase may be assisted by the use of high-speed stirrers, homogenizers, colloid mills, ultrasonic wave generators or the like and the dispersions may be stabilized by the addition of emulsifying or dispersing agents.
• the dispersion may also be formed by dispersing into an aqueous phase i.e. into water, into a gelatin solution or other aqueous colloid or into the hydrophilic colloid coating composition a solution of chemical adjuvant and the high-boiling alcohol in one or more auxiliary organic solvents, which may be low-boiling substantially waterinsoluble organic solvents or appreciably water-soluble organic solvents or a mixture of both, and subsequently removing the said auxiliary solvent from the aqueous phase. It is also possible to add auxiliary solvent(s) to the aqueous phase before dispersing therein the solution comprising chemical adjuvant, high-boiling alcohol and auxiliary solvent(s).
• Low-boiling substantially water-immiscible solvents suitable for use together with the high-boiling alcohol preferably have a solubility in Water of at most 25% by weight at room temperature, say 20 C. They preferably have a boiling point of at last 130 C. and a sufficiently high vapor pressure so that they can be removed from the dispersions made by evaporation, if necessary, by applying a vacuum of 500 to mm. Hg at a temperature of 25 to 80 C.
• Suitable substantially water-insoluble solvents that may be used in the method of the present invention are: methylene chloride, methyl formate, ethyl formate, n-butyl formate, methyl acetate, ethyl acetate, npropyl acetate, isopropyl acetate, butyl acetate, methyl propionate, ethyl propionate, carbon tetrachloride, sym.- tetrachloroethane, 1,1,2 trichloroethane, 1,2 dichloropropane, chloroform, n-butyl alcohol, diethyl ketone,
• this solvent is preferably removed during and/ or after dispersing the solution into the water, the aqueous colloid or the hydrophilic colloid coating composition. Removal of the said solvent occurs by evaporation, if necessary by applying a reduced pressure, say from 500 mm. to 10 mm. Hg, and/or moderate heating.
• the water-soluble organic solvents can be removed from the dispersion in the aqueous colloid or from the hydrophilic colloid coating composition-unless this is deemed unnecessary because they have no disadvantageous effect on the physical or photographic properties of the photographic element when left in the dispersion by washing the chilled and thereby gelled colloid composition.
• a low-boiling substan tially water-insoluble solvent they are removed together With the said low-boiling solvent by evaporation unless they have too high a vapor pressure, in which case they can be removed, if necessary, as indicated above.
• aqueous phase which may be water or an aqueous colloid or a hydrophilic colloid coating composition for forming a layer of a photographic light-sensitive silver halide element
• an emulsifying or dispersing agent it is desirable to use an emulsifying or dispersing agent.
• the dispersing or emulsifying agent is generally added to the aqueous phase into which the solution of chemical adjuvant in high-boiling alcohol and auxiliary solvent(s), if employed, is dispersed it is also possible to add said dispersing or emulsifying agent already at the step of dissolving the said chemical adjuvant in the high-boiling alcohol and the auxiliary solvent, if employed.
• wetting agents are: the sodium salt of N-methyloleyl tauride, sodium stearate, Z-heptadecenylbenzimidazole 5-sulphonic acid sodium salt, sodium sulphonates of higher aliphatic alcohols e.g. 2-methoxyhexanol sodium sulphonate, sodium diisooctyl-sulphosuccinate, sodium dodecyl sulphate, and tetradecyl benzene sulphonic acid sodium salt.
• n, R R and R have the same significance as shown, and
• X is alkylene, aralkylene or arylene, or the group Y-A4O M wherein Y is oxygen or sulphur and A stands for alkylene, substituted alkylene, e.g. alkylene substituted by hydroxyl, or aralkylene, M being hydrogen, an alkali metal atom such as lithium, sodium and potassium, ammonium or organic ammonium, e.g. diethanol ammonium, triethanol ammonium and morpholinium.
• ionic surface active compounds corresponding to the foregoing general formula can be found e.g. in copending applicants Nos. 27,049/ 70, 27,050/70, 27,080/70 and 27,081/70.
• the preferred embodiment of the present invention for incorporating photographic chemical adjuvants into photographic hydrophilic colloid coating compositions comprises the steps of dissolving the said adjuvant in the said high-boiling alcohol and a low-boiling substantially waterinsoluble organic solvent e.g. ethyl acetate dispersing the solution formed in the presence of an emulsifying or dispersing agent into water or an aqueous colloid, removing substantially all of the low-boiling substantially waterinsoluble organic solvent by evaporation and admixing the resulting dispersion of liquid particles of chemical adjuvant and high-boiling alcohol in water or the aqueous colloid with the hydrophilic colloid coating composition e.g. a photo-sensitive silver halide emulsion.
• a photo-sensitive silver halide emulsion e.g. a photo-sensitive silver halide emulsion.
• the amount of high-boiling alcohol used in the method according to the present invention is dependent on the solubility of the particular chemical adjuvant therein and on the optional use of the low-boiling substantially waterinsoluble organic solvent or the appreciably water-soluble organic solvent or the mixture of both. This amount can vary within very Wide limits but is preferably restricted to a minimum, taking care that the dispersed particles of compound and alcohol in the photographic hydrophilic colloid coating composition for forming a layer of a photographic photosensitive silver halide material are liquid under the conditions of coating and processing the said material.
• the ratio of chemical compound to high boiling alcohol is generally comprised between 1:10 and 1:1
• the amount of said alcohol can be reduced to one part or less than one part per part of chemical compound by the use of an auxiliary solvent, preferably a low-boiling waterimmiscible solvent.
• the chemical adjuvant is preferably dissolved in a solvent mixture of such composition that the ratio of chemical adjuvant to high-boiling alcohol will be one part of chemical adjuvant to one part or less than one part of the said high-boiling alcohol, for instance a ratio of chemical adjuvant to high-boiling alcohol comprised between 1:1 and 1.
• the water or aqueous colloid such as aqueous gelatin into which the solution comprising chemical adjuvant and alcohol can be dispersed prior to admixture with the hydrophilic colloid coating composition preferably comprises a minimum of water in order to obtain dispersions as concentrated as possible which is particularly advantageous for storing purposes.
• the amount of stored dispersion to be added to the hydrophilic colloid coating composition for forming a layer of a photographic photo-sensitive silver halide element is such that the chemical adjuvant is present in the resulting layer in the concentration desired. This amount is naturally dependent on the concentration of the said adjuvant in the said dispersion.
• the amount of dispersing agent or emulsifying agent used in making the dispersions in the aqueous phase of photographic compounds according to the method of the present invention may vary within very wide limit; it is generally comprised between 2 and 30% by Weight relative to the weight of adjuvant to be dispersed.
• hydrophilic colloid media Although in applying the method according to the present invention for incorporating chemical adjuvants in hydrophilic colloid media, the use of gelatin as hydrophilic colloid is favoured, other water-soluble colloidal materials or mixtures of them can be used too e.g. colloidal albumin, zein, casein, a cellulose derivative such as carboxymethyl cellulose, a synthetic hydrophilic colloid such as polyvinyl alcohol, poly-N-vinyl pyrrolidone, etc.
• colloidal albumin colloidal albumin
• zein zein
• casein a cellulose derivative
• a synthetic hydrophilic colloid such as polyvinyl alcohol, poly-N-vinyl pyrrolidone, etc.
• the solution formed was admixed by means of a highspeed stirrer with 58 g. of a warm (55 C.) 10% aqueous solution of gelatin. After having homogenized the mixture for 2 minutes, 40 ml. of water heated to 55 C. were added and then the mixture was homogenized again for 2 minutes. The ethyl acetate was removed by evaporation at 55 C. and a reduced pressure of 200 mm. Hg whereupon water was added to the gelatin composition to make ml.
• a homogeneous dispersion was obtained which after having been stored for 24 hours at 5 C. did not at all show a crystallization tendency.
• the gelatin composition formed could be admixed by gentle stirring with a gelatino silver halide emulsion ready for coating.
• EXAMPLE 2 1.5 g. of the color coupler of Example 1 was dissolved in a mixture of 4.5 ml. of ethylacetate and 1.5 ml. of isooctadecyl alcohol. The solution was dispersed by means of a high-speed stirrer into 58 g. of a warm (55 C.) 10% aqueous solution of gelatin to which 3 m1. of a 10% aqueous solution of sodium isooctadecyloxypropyl sulphonate having the formula:
• the mixture was dispersed for 2 minutes whereupon 40 ml. of water heated to 55 C. were added and homogenizin g was continued for 2 minutes.
• the very stable homogeneous dispersion of particles of the alcohol containing color coupler could then be admixed with a gelatino silver halide emulsion coating.
• QQCONIL-C HQa-n were dissolved in a mixture of 15 ml. of ethyl acetate and 0.65 ml. of isohexadecyl alcohol (commercially available e.g. from Esso Belgium N.V;, Antwerp; Belgium).
• the solution obtained was dispersed by means of an ultrasonic wave generator into 50 g. of a aqueous solution of gelatin which had been heated to 55 C. and to which 10 ml. of a 5% aqueous solution of sodium isohexadecyl sulphate had been added.
• the mixture was dispersed for 5 minutes whereupon 30 ml. of water heated to 55 C. were added and homogenizing was continued for 5 minutes.
• Stable and very fine dispersions in gelatin of the above color coupler could also be obtained by using potassium isohexadecyl sulphate or sodium isohexadecyloxy propyl sulphate as surfactant. 7
• EXAMPLE 4 5 g. of the color coupler of Example 3 .were dissolved in a mixture of 30 ml. of ethyl acetate and 5 ml. of isohexadecyl alcohol. The solution was dispersed by means of a high speed stirrer in 37.5 ml. of Water to which 12.5 ml. of a 5% aqueous solution of sodiumisohexadecyl sulphate had been added. The mixture was homogenized for 3 minutes whereupon the ethyl acetate was removed as described in Example 1 and water was added to make 80 ml.
• the mixture was homogenized for 5 minutes whereupon 20 ml. of water were added and homogenizing was continued for 5 minutes. After removal of the ethyl acetate as described in Example 1 water was added to make 50 ml.
• the dispersion obtained could then be admixed by gentle stirring with a gelatino silver halide emulsion.
• soiN m aa were dissolved in a mixture of 3 ml. of ethyl acetate and 0.7 ml. of isohexadecyl alcohol.
• the solution was dispersed by means of a high speed stirrer into 15 g. of a 10% aqueous solution of gelatin heated to 55 -C., to which 3 ml. of a 5% aqueous solution of sodium isooctadecyloxypropyl sulphonate had been added.
• the dispersion was then further treated as described in Example 5 and the final dispersion obtained was admixed with a gelatino silver halide emulsion.
• ethyl acetate was dissolved in a mixture of 15 ml. of ethyl acetate and 0.5 g. of hydroabietyl alcohol (commercially available e.g. from Hercules Powder Company Inc., Wilmington, Del., U.S.A.).
• the solution was dispersed in 50 g. of a 10% aqueous solution of gelatin heated to 55 C. and comprising 5 ml. of a 10% aqueous solution of sodium Z-n-butyl-n-octyloxypropyl sulphonate. After having dispersed the mixture for 5 minutes, 30 m1. of water heated to 55 C. were added and then homogenizing was continued for 5 minutes.
• the ethyl acetate was removed by evaporation as described in Example 1 whereupon hot waterwas added to make ml.
• the dispersion obtained could then be admixed by gentle stirring with an aqueous gelatin coating composition for forming an intermediate layer between the redsensitized and green-sensitized emulsion layers of a negative photographic multilayer color material.
• This multilayer material comprises in order on a support a redsensitized silver halide emulsion layer comprising a color coupler for cyan, intermediate layer comprising a colorless coupling compound, a green-sensitized silver halide emulsion layer comprising a color coupler for magenta, a yellow filter layer comprising colloidal silver and a spectrally unsensitized blue-sensitive silver halide emulsion layer comprising a color coupler for yellow.
• Example 7 was repeated with the difference that now 0.5 g. of isooctadecyl alcohol was used instead of 0.5 g. of hydroabietyl alcohol and that the surfactant was replaced by ml. of a aqueous solution of sodium isooctadecyloxypropyl sulphonate.
• the solution formed was dispersed into g. of a 10% aqueous solution of gelatin which was heated to C.-
• the dispersion formed could then be admixed by gentle stirring with a conventional gelatino silver halide emulsion ready for coating.
• This example illustrates the favorable effect of the highboiling alcohol on thhe viscosity of the hydrophilic colloid 3g. of1 the color coupler of Example 1 were dissolved in 18 ml. of ethyl acetate. and 1.5 g. of isobctadecyl alcohol. The solution was dispersed in 96 g. of 10% aqueous gelatin in the presence of 4.5 ,ml. of 10% aqueous sodium dodecylbenzene sulphonate. [Iheethyl acetate was removed by evaporation as described in Example 1 whereupon 8 ml.
• the solution formed as well as 8 ml. of 10% aqueous sodium 2-heptadecenyl benzimidazole-5-sulphonatev and 0.7 ml. of 10%ethano1ic mucochloric acid were added to 96 g. of 10% aqueous gelatin. Water was added to make 225 ml. and the pH was adjustedrto pH 6 by means of N succinic acid.
• n 0 to 30
• each of R and R stands for a straight-chain or branchedchain alkyl group or together stand for the atoms necessary to close an alicyclic ring structure, R and R together comprising at least 5 C-atoms.
• Method according to claim 4 which comprises removing the said organic solvent simultaneously with or subsequently to dispersing the said solution comprising the said chemical adjuvant and the said alcohol or ethoxylated alcohol into the hydrophilic colloid coating composition, water or aqueous solution of a water-soluble colloid.
• R R R n and m have the same significance as in claim 1, and Z stands for the group SO M, -OSO M,
• M stands for hydrogen, an alkali metal atom, ammonium or organic ammonium
• X is alkylene, aralkylene or arylene
• Y is oxygen or sulphur
• A stands for an alkylene, or aralkylene group.
• hydrophilic colloid coating composition is a photosensitive gelatino silver halide emulsion.

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

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Cited By (12)

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• 1970
  • 1970-08-13 GB GB3911670A patent/GB1346426A/en not_active Expired
• 1971
  • 1971-06-04 US US00150214A patent/US3788857A/en not_active Expired - Lifetime
  • 1971-07-09 FR FR7125561A patent/FR2101616A5/fr not_active Expired
  • 1971-07-09 BE BE769751A patent/BE769751A/nl unknown
  • 1971-07-21 DE DE19712136492 patent/DE2136492A1/de active Pending

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