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
  • G03C1/04—Silver halide emulsions; Preparation thereof; Physical treatment thereof; Incorporation of additives therein with macromolecular additives; with layer-forming substances
  • G03C1/047—Proteins, e.g. gelatine derivatives; Hydrolysis or extraction products of proteins

Definitions

• This invention relates to a method for prep-aring washed silver-halide photographic emulsions in which the silver halide is preparedin a solution of gelatin, mixed with gelatin derivative, acidcoagulated, washed, and then re-dispersed.
• gelatin has been principally depended upon as the carrier for the silver halide and as the peptizing agent employedin its preparation.
• the emulsion maker has in the past been limited in the scope of his operations bythe physical properties peculiar to gelatin.
• our invention involves the mixing of gelatin derivatives into dispersions of silver halide in gelatin in sufficient amount to impart coagulating properties to the entire mass.
• the gelatin derivatives which are employed in accordance with our-invention may bepreparedlfrom gelatin by adjusting: a solution or suspension of gelatin to a pH value of 8 to 11 or more with a suitable base, such as sodium hydroxide or ammonium hydroxide and then adding a reagent which will react therewith, ordinarily at a temperature of 25-60 C.
• a suitable base such as sodium hydroxide or ammonium hydroxide
• the reaction between the reagent and the gelatin usually takes 5-20minutes after which the gelatin derivative may be employed either in the solution in which it is formedor in solid condition.
• gelatin derivatives which have been found to be especially useful in the process in accordance with our invention are those of the aromatic sulfonyl chlorides, the carboxylic acid chlorides, the carboxylic' acid anhydrides, especially of the dicarboxylic type, the aryl isocyanates, and the IA-diketones.
• the following" compounds have been found to be useful for preparing gelatin derivatives suitable for use in our invention:
• our invention comprises the formation of the silver-halide grains in an aqueous solution of gelatin whereby good dispersion is obtained followed by the addition to this solution of a gelatin derivative in sufficient proportion to impart coagulating properties to the
• the amount of gelatinderivative which must be added to insure satisfactory coagulation is determined by two features: (1) the concentration of normal gelatin which ..is present and (2) the concentration of salt which is
• the ratio of gelatin derivative to normal gelatin should be of the order of 4 to 1. If large quantities of salt are present, the ratio of the gelatin derivative to the gelatin may be as little as 2 to 1 for good emulsion coagulation properties.
• the silver-halide dispersion is prepared in normal gelatin in accordance with the usual procedure.
• the silver-halide formation and such ripening as is desired is carried out.
• gelatin derivative in an amount which will give the mass the property of being acid coagulable.
• This may be a proportion of gelatin derivative of 2 to l derivative to gelatin, 4 to l, or, if desired, an even larger proportion of gelatin derivative may be added, although as a practical matter, proportions of less than to l are most satisfactory.
• the gelatin derivative is thoroughly stirred into the silver-halide dispersion whereupon acid is added to reduce the pH to less than 4.5, the amount of salt present determining the lower limit of the pH range. If the nitrate resulting as a by-product from the preparation of the silver halide is present, the pH may be reduced to 3 and coagulation will be obtained in this case, the salt being on the order of approximately 0.2 normal. If for some reason higher concentrations of salt are present, a still greater range of pH may be employed for the coagulation. Upon reducing the pH tothe coagulation range, the gelatin derivative coagulates and carries down the gelatin and silver halide therewith.
• the phenomenon which occurs is characterized by an enveloping of the silver-halide grains by the coagulated gelatin derivative so that a rainy mass is obtained. This mass may then be subjected to repeated washings, thereby removing substantially all of the water-soluble salts from the coagulum.
• the coagulum may be employed directly without any further washing than the removal of the mother liquor from the precipitated material.
• extended washing is not necessary.
• the coagulum- may be rinsed by treatment with cool water, preferably with a pH adjusted to the isoelectric point of the gelatin derivative.
• the number of rinses necessary to reduce the salt content of the coagulum to the desired point is usually within the range of l to 4 changes of water.
• the coagulum may be dissolved in water at an elevated pH, such as by using wat r taining a small proportion of sodium or ammonium hydroxide to bring the pH of the mass up to 6 or more.
• the temperature of the mass is raised to approximately 40 0., and the Whole is stirred for a few minutes to effect re-dispersion of the coagulum.
• the gelatin derivative may be coagulated by the addition of an appropriate acid solution to reduce the pH to the coagulation point of the derivative.
• the coagulum will settle and is separated from the mother liquor in the same manner as in the first coagulation step.
• the coagulation and re-dispersion operation may be repeated as often as necessary but for normal purposes one cycle of washing is suflicient.
• the coagulum which has been washed by either of the two general methods outlined above may then be re-dispersed to form photographic emulsions suitable for the subsequent finishing and coating operations by treating with the required quantity of water, normal gelatin or gelatin derivative and base to raise the pH of the Whole to 5 or 6 or even greater.
• the mixture of coagulum, water, gelatin or gelatin derivative and any other materials which have been added is then stirred at approximately 40 C. for the time required. to effect complete re-dispersal of the coagulum.
• the time required is normally of the order of ten to twenty minutes but may vary depending upon the chemical nature of the particular gelatin derivative used.
• the emulsion thus prepared behaves similarly to emulsions prepared using a similar emulsification and ripening technique in which noodle washing is employed.
• the emulsions prepared in accordance with our invention respond readily to the standard methods of chemical sensitization or after ripening, and optical sensitization. They may be coated by the techniques usual in coating photographic emulsions.
• the use of gelatin derivatives for obtaining washed emulsions presents considerable advantage over other techniques described in the literature for the washing of emulsions. It has been well known for years that gelatin silver-halide emulsions could be coagulated by the addition of suflicient quantities of suitable organic solvents of which methanol, ethanol, or acetone may serve as an example.
• the dispersion was stirred for five minutes-at 40 C., after which approximately 20cc. of 5-N sulfuric acid were added to reduce the pH to 3.0. After standing at this pH for several minutes a coagulum of silver halide and gelatin settles out. The mother liquor was decanted 01f and the coagulum was redispersed in one liter of distilled water by stirring vigorously for five minutes at 40 C. There was then. added to the emulsion approximately 15 cc. of 3 N am- A 400 cc. portion of this emulsion was melted at 40 C. andB N ammonium hydroxide wasadded until the mixture was approximately neutral.
• Example 2 To the second portion of the silver-halid dispersion prepared as described .in
• Example 1 there was added 75 g. of the phenyl isocyanate derivative of gelatin, thereby imparting to the dispersion the .property of being acid coagulable.
• gelatin derivative used here was preparedin the same mannerjas that of Example 1 except that phenylisocyanatewas employed instead of benzene sulfonyl chloride as the reagent.
• the coagulation, decantation, washing, and finishing of the emulsion followed the same procedure as .in Example 1.
• photographic proper A small amount of potassium bromide was added r according to the procedure well known in the art,
• The' derivative employed was'prepared' by adding 10.5 g. of m-carboxy' benzene sulfonyl chloride in' 50 cc. of dry acetone to a solution of 100 810i gelatin in 900 cc. of water at 40 over aperiod "of two hours; The pH' of the gelatin solution was adjusted to 10.0 and maintained there by the use of 10% sodium hydroxide throughout the reaction. The pH was then adjusted to 7.0 with dilute sulfuric acid. The gelatin solution was se by chilling, sliced, washed and dried.
• the emulsion obtained by the procedure described was washed by successive coagulations as described in Example 1, was brought to its final xvolume,land was finished and coated onto glass plates for sensitometrio tests. A photographic emulsion having good properties was obtained.
• Example 5 The procedure described in Example 1 was followed except that in place of the benzene sulfonyl chloride derivative of gelatin 50g. ofp-tolylisocyanate derivative of gelatin was mixed with the silver-halide dispersion and after reduction of the pH to produce a 'coagulum, the mother liquor was decanted therefrom and the coagulum was redispersed in distilled water at 40 C. Recoagulation was obtained. byrai'sing 'the pH to 4.1 with 3 N ammonium hydroxide. The mother liquor wasdecanted off and after redispersing the coagulum in '75 g. of gelatin and sufficient water to adjust the weight to 1.36 kg. the emulsion was finished in the same manner as in Example 1. A portion of the finished emulsion was coated on glass plates and sensitometric tests showed that it had good'photographic properties.
• Example 6 The procedure of Example 1 was followed except thatthe derivative obtained by reacting maleic anhydride with gelatin was employed to impart acid coagulability to the silverhalide dispersion.
• the derivative employed was prepared by dissolving 50 g. of gelatin in 400 cc. of distilled water and adjusting the pH to 10 with sodium hydroxide. The mass was then,
• Example 9 The procedurefollowed here was the same as that used in Example 7 except that v the coagulum-produced by acidifying the mixture of silver-halide dispersion and benzoyl chloride derivative of gelatin was washed twice in" cold water before final dispersion in the gelatin solution. The ammonia coagulation described in Examples '7 and'l was omitted. The final emulsion was finished by heat treatment and coated on I glass plates as described in Example 7. Sensitometric tests showed that the emulsion had satisfactory photographic properties.
• Example 10 A silver-halide dispersion in gelatin was prepared as described in the first This dispersion was halved and to this half portion'was added 50 g. of abenzoyl chloride derivative of'gelatin as described in Example 7. To the resulting mixture 20: cc. of aqueous sulfuric acid was'added to reduce the pHtoB. A' coagulum of silver halide andgelatin formed and-was allowed to settle. The mother liquor was decanted from the coagulum, and the latter was redispersed in'one liter 'of distilled water at 40 C. and a pH of 6.5
• Example 11 The procedure of the precedingexample was followed except that the. benzoyl chlorid derivative of gelatin was prepared from a glue stock instead of from high viscosity gelatin. The procedure of coagulating, washing, and decanting, final adjustment of composition, and finishing described in the examples above gave an emulsion having good sensitometric properties.
• Example 12 The procedure described in Example! was followed except that the second half of the silver-halid dispersion prepared as described in Example 10 was employed with the exception that '75 'g. of the benzoyl chloride derivative of glue (or unrefined gelatin) was employed to impart acid. coagulating properties. to
• the silver-halidedispersion wascoagulated, decanted and washed in cold water.
• the coagulum was then dispersed in 75 g. of gelatin solution as the vehicle therefor and ad.- justed to a total weight of 1.36 kg.
• This mixture was stirred for twentyminutes at 40 C. and1was then cooled to C. and chilled.
• a test portion of 400 cc. was melted at C. giving heat treatment for approximately forty minutes at C. and was coated on glass plates. The platecoatings were exposed and werefound to givegood sensitometric results.
• Example 13 The following solutions I were prepared: solution A, 200 cc: of aqueous solution containing 50 silver nitrate by weight; solution B, having a total volume of 200 cc. and containing 190 cc. of an aqueous solution containing 40% potassium bromide by weight and 9% cc. of a solution containing 25% potassium iodide by a weight, .65 g. of a polyvinyl.v alcohol solution containing 203% polyvinyl alcohol and 205 cc. of water stirred at 93 C. for fifteenminutes to assure complete solution of the. polyvinyl alcohol.
• gelatin the aromatic isocyanate derivatives of gelatin and the 1,4 diketone derivatives of gelatin, the carboxylic acid anhydride derivahalide by adjusting to said pH whereby silver halide-polyvinyl alcohol-gelatin derivative grains areformed and. subsequently separating those grains. from the liquid portion of the mass.
• a method of preparing washed silver halide dispersions the steps which comprise mixing a water-soluble silver salt and a water-soluble halide salt in an aqueous solution of a peptizing colloid, mixing therewith at least 2 parts of a carboxylic acid anhydride derivative of gelatin per part of the peptizing colloid, thereby rendering the silver halide dispersion coagulable at a pH Within therange of pH 3-4.5, coagulating the silver halide dispersion by adjusting to said pH whereby silver halide-peptizer-gelatin derivative 'grains are formed and subsequently separating the thus-formedgrains from the liquid portion of the mass.
• a method of preparing washed silver halide dispersions the steps which comprise mixing a water-soluble silver salt and a water-soluble halide salt in an aqueous solution of gelatin as the peptizing colloid, mixing therewith at least 2 parts of a carboxylic acid anhydride dcrivative of gelatin per part of the peptizing colloid, thereby rendering the silver halide dispersion'coagulable at a pH'within the range ofpI-I 3-4.5, coagulating the silver halide dispersion by adjustingto said pH whereby silver halidegelatin-gelatin derivative grains are'formed and subsequently separating the thus-formed grains from the liquid portion of the mass.
• a method of preparing Washed silver halide dispersions the steps which comprise mixing together a water-soluble silver salt and awatersoluble'halide salt in an aqueous solution of a peptizing colloid, mixing therewith at" least 2 parts of th benzene sulfonyl chloride derivative of gelatin'per part 'of the peptizing colloid; thereby rendering the silver halide dispersion 'coagulable at a pH within the rangeo'f pH-3-'4;5; coagulating the silver halide dispersion by adjusting to said pH whereby silver'lialide-peptizergelatin derivative grains are formed and subsequently separating those grains from the liquid portion of the mass.
• a method-of preparing washed silverhalide dispersions the steps which comprise mixing together a water-soluble silver salt "and a water-soluble halide salt in an aqueous solution of a p eptizing colloid, mixing therewith at least 2 parts of the phenyl i'socyanate derivative of gelatin per part of the peptizing 'colloidy-"thereby rendering the silverhalide'dispersion coagulable at a pH within the range of pH 3-4.5, coagulating the silver halide dispersion by adjusting to said pH whereby silver halide peptizer-gelatin derivative grains are "formed and; subsequently separating" those grains fromthe liquid portion of the mass.
• a method of preparing a washed'silver halide photosensitive emulsion which comprises mixinga water-soluble silver salt and a watersoluble halide salt in an" aqueous solution of a peptizing "colloid, mixing therewith 'at least 2 partsof the phthalic anhydride derivative of gelatin per part of the peptizing colloid, thereby renderingthe silver halide dispersion coagulable at a pH within the range of pH 3-4.5, coagulatingthe'silve'r halide dispersion by adjusting to said pH whereb'y silver halide-peptiZer-gelatin derivative grains are formed, separating those grains from the liquid portion of the mass and subsequent by mixing those grains with gelatin and water as a protective colloid for the silver halide whereby a photosensitive emulsion is formed, b q
• a method of preparing washed silver halide dispersions the steps which comprise mixing a water-soluble silver salt and a watersoluble halide salt in an aqueous solution of a peptizing colloid, mixing therewith approximate- 1y 4 parts of a gelatin derivative per part of the pepti zing colloid, thereby rendering the silver halide'jdiSpersion coagulable at a pH within the range'of pI-I 3-4.5,which gelatin derivative is selected from the group consisting of the aromatic sulfonyl chloride derivatives of gelatin, the carboxylic acid chloride derivatives of gelatin, thecarboxylic acid anhydride derivatives of gelatin, the aromatic isocyanate derivatives of gelatin and the 1,4 diketone derivatives of gelatin, coagulating the dispersion of silver halide by adjusting to said pH whereby silver halidepeptizer-gelatin derivative grains are formed and subsequently separating those grains from the liquid portion of the mass.

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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)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
• Colloid Chemistry (AREA)
• Non-Silver Salt Photosensitive Materials And Non-Silver Salt Photography (AREA)
• Compositions Of Macromolecular Compounds (AREA)

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Citations (4)

• 0
  • BE BE484325D patent/BE484325A/xx unknown
• 1947
  • 1947-08-13 US US768476A patent/US2614929A/en not_active Expired - Lifetime
  • 1947-08-13 US US768475A patent/US2614928A/en not_active Expired - Lifetime
• 1948
  • 1948-03-09 GB GB7274/48A patent/GB649546A/en not_active Expired
  • 1948-03-09 GB GB7273/48A patent/GB649545A/en not_active Expired
  • 1948-08-11 FR FR980386D patent/FR980386A/fr not_active Expired

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