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
  • G03C1/015—Apparatus or processes for the preparation of emulsions

Definitions

• the formed silver halide dispersion is ripened which means that the dispersion is kept for a certain time at a certain temperature in order to obtain the desired grain size and grain distribution.
• the dispersion is first jellified by cooling.
• the formed gel is noodled or finely divided in another way and the salts present are extracted from the noodles with water at low temperature by dialysis.
• the washed emulsion is melted by heating whereupon gelatin and other ingredients such as chemical sensitizers are added. Thereupon the emulsion is chemically ripened.
• optical sensitizers, color couplers, hardeners, anti-fogging agents, wetting agents, matting agents, etc. can be added.
• This process has the great disadvantage of needing considerable time for setting, noodling and washing. Moreover, this process has to be carried out in the presence of a relative large amount of binding agent which cannot be decreased at will.
• a concentration of at least 4% of binding agent is necessary.
• a relatively large amount of light-sensitive silver halide per unit of area is necessary.
• Such emulsions can be concentrated by evaporating the water present whereby, however, the ratio of binding agent to light-sensitive salt remains unchanged.
• more concentrated emulsion is only obtained together with an increased viscosity which hinders the coating of the emulsion so that, rather than concentrating the emulsion too much, it is usually preferable to apply several emulsion layers one upon another in order to obtain the desired amount of silver salt per unit of area.
• the gelation and the noodling of the above mentioned photographic emulsion can be avoided by coagulating this emulsion either by adding a large amount of a water miscible organic solvent wherein the binding agent does not dissolve or by salting out the binding agent by the adding of salts such as lead, titanium, thorium, zirconium, ammonium, barium, calcium, sodium and zinc salts.
• salts such as lead, titanium, thorium, zirconium, ammonium, barium, calcium, sodium and zinc salts.
• gelatin content of the dispersion is not higher than 2% and the weight ratio of gelatin to silver nitrate (calculated on an equivalent weight basis to the silver halide) varies between A and 7 and (2)
• the gelatin silver halide coprecipitate is hardened before the washing step by treating it with a concentrated aqueous solution of ammonium sulfate.
• the emulsions prepared in such circumstances are not decreased in sensitivity.
• a part of the ammonium sulfate can be formed in situ, in the preparation of an ammoniacal emulsion during the coprecipitating of the gelatin and the silver halide, by adding, together with the concentrated solution of ammonium sulfate, sulfuric acid while the pH of the medium may not fall below pH 7.
• the sulfuric acid is preferably added as a mixture with the concentrated ammonium sulfate.
• the concentration of the ammonium sulfate varies preferably between 5 and 20% at the end of the precipitation. In the hardening stage the concentration of the ammonium sulfate amounts preferably to between 7 and 40%.
• Distilled water, demineralized water and tap water preferably with a French degree of hardness not higher than 45 can be used as wash water.
• the draining off of the supernatant liquid after cot2 precipitation of the gelatin and the silver halide is preferably carried out until the precipitate remaining amounts to about to /s part of the original volume.
• the process according to the invention has, in comparison with the process of the U.S. patent specification 2,618,556, the advantage of avoiding a decrease of sensitivity of the ammoniacal emulsions by precipitating with acids below a pH of 7.
• the amount of gelatin used for the preparation according to the present invention of photographic lightsensitive silver halide emulsions can vary between 2 and g. per 100 g. of silver nitrate and depends on the size of the silver halide grains while the gelatin concentration of the silver halide dispersion before precipitating preferably does not exceed 3% by weight of the water present. A gelatin concentration from 0.5 to 2% is to be preferred.
• the formed precipitate consists of flocculent particles of gelatin containing silver halide crystals dispersed therein, so that the several crystals stay separated from each other.
• the hardened gelatin particles of the precipitate are in a finely divided form so that they can be easily and rapidly washed with water, preferably at low temperature (:10" C.). After washing the precipitate is easily dispersed in water by heating and thereupon the desired amount of binding agent is added.
• the final amount of binding agent which is added to the light-sensitive salts can be chosen at pleasure so that emulsions can be obtained with a high amount of light-sensitive silver salt without increasing the content of gelatin and that a large amount of silver salts can be coated with less viscous emulsions onto relatively smaller surfaces.
• These emulsions with easily adjustable concentrations are especially suited for special coating techniques such as air-knife coating and extrusion.
• the desired grain distribution of the silver halide is obtained.
• the light-sensitivity of the silver halide crystals can be increased by chemical sensitization.
• the chemical sensitizers are mostly added after wash ing the emulsion. They may also be added during the precipitation of the silver halide or during the Ostwald ripening for instance when an active gelatin is used as dispersing agent for the silver halide.
• the emulsion can be ripened with active gelatin or sulfur compounds can be added to the silver halide emulsion such as allyl isothiocyanate, allyl thiourea, sodium thiosulfate or potassium selenocyanide.
• sulfur compounds can be added to the silver halide emulsion such as allyl isothiocyanate, allyl thiourea, sodium thiosulfate or potassium selenocyanide.
• the emulsions can also be sensitized with reducing agents such as tin salts or imino-aminomethane sulfinic acid compounds (German patent specification 1,020,864, filed April 28, 1956).
• reducing agents such as tin salts or imino-aminomethane sulfinic acid compounds (German patent specification 1,020,864, filed April 28, 1956).
• the highi-sensitive negative emulsions prepared according to the invention can especially be sensitized with gold (I) thiocyanate and sodium thiosulfate as described in French patent application 893,935, filed April 10, 1962.
• ingredients may be added such as optical sensitizing dyestuifs, stabilizers, fog inhibiting agents, color couplers, hardening agents, wetting agents and matting agents.
• Example 1 300 parts of silver nitrate are dissolved in 2900 parts of distilled water and then at 40 C., while vigorously stirring, added in 2 min. to a solution of 250 parts of potassium bromide, 45 parts of gelatin and 5 parts of potassium iodide in 1200 parts of water.
• the mixture is washed for another four to five times; each time with 4000 parts of water and the supernatant solution is each time decanted till a volume of 1200 parts is left. After the last washing and decanting stages 600 parts of distilled water and 250 parts of gelatin are added.
• the mixture is stirred at 45 C. for 1 hr. and the emulsion is diluted with distilled water up to 3000 parts. Finally, the emulsion is chemically ripened at The emulsion is coated onto a cellulose ester support. A fog-free photographic material is obtained.
• Example 2 250 parts of silver nitrate are dissolved in a mixture of 200 parts of concentrated ammonium hydroxide and 220 parts of water. This solution is then at once added to a solution of 570 parts of potassium'bromide, 10 parts of potassium iodide and 28 parts of gelatin in 2300 parts of water. Immediately thereafter a solution of 250 parts of silver nitrate in 220 parts of water and 200 parts of ammonium hydroxide are added in 5 min. The temperature of these solutions amounts to 52 C. The physical ripening takes place in 35 min. at 55 C. Then, while vigorously stirring 1300 parts of a 50% aqueous solution of ammonium sulfate is added.
• a precipitate of silver bromide and gelatin is formed which is allowed to settle for min.
• the supernatant mother-lye is decanted till a volume of 500 parts is left in the reaction flask.
• 500 parts of a 50% aqueous solu tion of ammonium sulfate are added.
• the mixture is stirred for another 20 min. and then four times washed with 300 parts of water followed each time by decanting till a volume of 500 parts is left in the vessel.
• the thus obtained emulsion is coated onto a cellulose triacetate support.
• a contrasty photographic material is obtained.
• Example 3 100 parts of silver nitrate dissolved in 85 parts of water and 82 parts of concentrated ammonium hydroxide are added in 1 min. to a solution of 130 parts of potassium bromide, 5 parts of potassium iodide and 20 parts of gelatin in 880 parts of distilled water. The temperature of the solutions amounts to 50 C. After about 5 min. a solution of 150 parts of potassium bromide in 300 parts of water are added and then a solution of 150 parts of silver nitrate in 130 parts of distilled water and 125 parts of concentrated ammonium hydroxide are added in 4 min. The pH of the emulsion amounts at this moment to about 10. The emulsion is allowed to digest at 55 C. for 30 min.
• Washing is repeated for 4 to 6 times till the conductivity of the water is reached.
• a process for the manufacture of high sensitive neutral and ammoniacal silver halide emulsions comprising: (1) Preparing a silver halide dispersion by reacting a water-soluble halide with silver nitrate in a medium selected from the group consisting of neutral and ammoniacal aqueous media, said medium containing gelatin in an amount not in excess of about 2% and within the range of 2-25% of said silver nitrate, (2) Introducing into said dispersion a concentrated solution of ammonium sulfate in an amount sufiicient to co-precipitate said gelatin and silver halide but not suificient to decrease the pH of said medium below about pH 7,
• step (3) The process of claim 1 wherein said ammonium sulfate is introduced into said dispersion in step (2) in an amount sufficient to give a concentration of said ammonium sulfate of about 5-20%.
• step (4) 4. The process of claim 1 wherein said additional ammonium sulfate is admixed in step (4) in an amount sutficient to give a concentration thereof of about 740%.

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• 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)
• Compositions Of Macromolecular Compounds (AREA)
• Non-Silver Salt Photosensitive Materials And Non-Silver Salt Photography (AREA)

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Cited By (6)

Citations (5)

Family Cites Families (2)

• 0
  • BE BE603491D patent/BE603491A/xx unknown
• 1961
  • 1961-08-01 DE DEG32843A patent/DE1148867B/de active Pending
• 1962
  • 1962-05-07 US US192988A patent/US3153593A/en not_active Expired - Lifetime
  • 1962-05-08 GB GB17712/62A patent/GB1008694A/en not_active Expired

Patent Citations (5)

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