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
• • 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
  • G03C1/035—Silver halide emulsions; Preparation thereof; Physical treatment thereof; Incorporation of additives therein characterised by the crystal form or composition, e.g. mixed grain
  • G03C2001/0357—Monodisperse emulsion

Definitions

• This invention relates to the field of silver halide emulsion manufacture and particularly to silver halides made by the so-called “splash-precipitation" methods. Still more particularly, this invention relates to a method for making splash-prepared silver halide emulsions with a uniform particle size distribution of the silver halide crystals.
• the silver halide crystals or grains can be prepared by two well-known methods: the single jet or “splash” method or the double jet or balanced double jet (BDJ) method.
• the splash method all of the alkali halide solution is placed in the mixing vessel together with the protective colloid (e.g., gelatin) right from the start and the silver nitrate solution is then added to this mixture.
• the silver nitrate can be added all at once, gradually over a period of time or in several, finite "splashes”.
• the halide solution and the silver nitrate solution are added simultaneously to a solution of gelatin in the mixing vessel.
• the splash precipitation process usually creates an increased number of so-called "crystal lattice defects" in which a number of ions are not positioned correctly in the silver ion - halide ion network.
• Emulsions made from these crystals can be used to make films which exhibit improved sensitometry, especially improved speed, as compared with films made from silver halide emulsions with crystals that have few or no lattice defects or disorientation.
• it is difficult to make splash-prepared emulsions with a uniform distribution of particle sizes.
• a high gradient is necessary and a wide distribution of particle sizes is not tolerable.
• This invention is directed to a process for preparing silver halide emulsions with a narrow grain size distribution, wherein silver nitrate is added by a splash method to an aqueous solution containing (a) one or more alkali halides in a protective colloid, and (b) monodisperse silver halide seed crystals.
• the process of this invention is applicable to the manufacture of any of the conventionally prepared silver halides such as silver bromide. chloride, iodide, or mixtures thereof.
• Any of the conventional colloid binder systems such as gelatin may also be used, as well as water-permeable or water-soluble polyvinyl alcohol and its derivatives, partially hydrolysed polyvinyl acetates, polyvinyl ethers, etc.
• Other useful colloid binding agents include partially hydrolysed gelatin, poly-N-vinyl lactam. etc. among others.
• Gelatin is preferred since it is well known that it is the protective colloid of choice during precipitation of the silver halides and the formation of the crystals thereof.
• the desired alkali metal halides (salts) are added to an aqueous dispersion of gelatin.
• aqueous silver nitrate is added by the splash method. This may be accomplished with two quick splashes of about 30 seconds each in duration, by one long first splash followed by a quick splash, or by a single long splash. These procedures are well known to those skilled in the art.
• some of the alkali metal halide can be added to the gelatin in the reaction vessel and the remainder added after some of the silver nitrate has been added.
• the seed crystals are made by the BDJ process following those well-known procedures. By varying those procedures it is possible to make grains of any average particle size distribution and select one to be used as desired in the ambit of this invention.
• the seed crystals can be also made of any of the conventional halides such as silver bromide, silver iodobromide, silver bromo-chloride and silver iodide, for example, Additionally, these seed crystals may be doped with other metals such as rhodium and lead, for example, as is well known.
• the emulsion is further "bulked" with colloid binder, and chemical and spectral sensitization can be accomplished as is well known.
• hardeners, wetting agents, antifoggants. stabilizers, coating aids, etc. may be added.
• the emulsion can then be coated on any of the well-known photographic substrates such as, for example, polyethylene terephthalate film, suitably subbed (subcoated) to receive the silver halide emulsion coating.
• the coated emulsion may be overcoated with a protective antiabrasion layer, such as hardened gelatin.
• These films may be used in any of the conventional ways, for example, as X-ray or graphic arts films or as direct positives. It all depends on the way the product structure is manufactured.
• Example 6 is considered to represent the best mode.
• Solution A was placed in a mixing vessel and heated to 105°F with stirring.
• Solution B was then added to A over a 30 second period (first "splash” of silver nitrate). This mixture was ripened 5 min. at 105°F and then solution C added thereto over a 30 second period (second “splash” of silver nitrate). After ripening this mixture for 8 minutes, solution D was added to stop the ripening process.
• the coagulant was then added to coagulate the gelatino-silver halide as "curds" and these curds were then washed to remove excess soluble salts by adding deionized water and decanting to remove the water and salts.
• the G solution was available to adjust the pH to 3.0.
• Example 5 For control purposes, a splash precipitation process identical to this one, but without any seeds present, was also run (Sample 5). Samples of the emulsion were then analyzed using the Particle Size Analyzer. Additionally, electron micrographs were taken of each emulsion. These results indicate that the final emulsion in each case had crystals of approximately the same volume as the control and, more importantly, that these emulsions were more uniform than the control. The control emulsion was not uniform and had a wider distribution of grain sizes.
• Example 1 To demonstrate the photographic utility of emulsions prepared according to the teachings of this invention, four more splash-prepared emulsions were prepared as described in Example 1. The seeds used in three of these emulsions were identical to those of Example 2. The addition of the silver nitrate solution to the emulsions was varied as described below:
• each emulsion was then brought to their optimum sensitivity with gold and sulfur sensitization as is well known to those skilled in the art.
• each emulsion was then coated on polyethylene terephthalate film supports suitably coated with a subbing layer and a thin anchoring substratum of gelatin.
• Each sample was overcoated with a hardened gelatin antiabrasion layer.
• Coating weights were about 47 mg AgBr/dm 2.
• Sample strips from each coating were sandwiched between two Cronex® HiPlus screens and exposed to an X-ray source operated at 60 Kvp, 100 ma at 40 inches for 40 milliseconds through a 2 ⁇ 2 aluminum step wedge. They were then processed in a standard hydroquinone/phenidone mixed developer, followed by fixing and washing in a conventional manner. Sensitometry obtained was as follows:
• Electron micrographs indicate that the control emulsion had standard splash-prepared grains with a variety of grain sizes while those of the invention were more uniform and had particle sizes close to that of the control grains. One can see that the emulsions of this invention produced better gradients in the toe region then the control.
• Example 1 Four splash-prepared emulsions were made for this example as taught in Example 1.
• the three emulsions representing this invention used seed grains identical to those of Example 2 added at 0.2 mole/mole of added AgN0 3 . Variations in the making procedures were as follows:
• the product shows equivalent speed with higher gradient.
• a direct positive emulsion was made from silver iodobromide precipitated by splash procedures in the presence of Ag(I)Br seed crystals. Three emulsions were made. One, the control, had no seeds: number two had seeds of 0.0086 ⁇ 3 present; and number three had seeds of 0.0378 ⁇ 3 . These emulsions were redispersed in gelatin, fogged with tetraazaundecane, and the usual wetting agents. antifoggants and coating aids added thereto. Each emulsion was coated on a support as previously described and strips from the coatings were exposed with an EG and G sensitometer to a tungsten flash for 10 -2 seconds. These strips were then developed in DP-2 for 90 seconds followed by fixing, washing and drying. Sensitometric results show that speed equivalent to the control with higher gradients was obtained.
• the emulsion prepared in this manner was then redispersed in gelatin, sensitized with gold and sulfur, wetting agents, antifoggants. etc. added, and coated and overcoated as previously described.
• an element was made, sensitized, and coated under the same conditions but without the addition of the seed crystals of silver halide. Samples from the coatings were exposed, developed fixed, washed and dried as previously explained with the following sensitometry:
• the film prepared from the emulsion made following the teachings of this invention had excellent gradient and top density, though somewhat lower speed than the control.
• Example 2 Following the procedures of Example 1 two additional splash-prepared emulsions were made varying the size of the seed emulsion or grains used.
• the BDJ prepared seeds were AgIBr seeds of about 0.06u 3 (ca. 2.5 % I - ) and in the second case were AgIBr seeds of about 0.039 ⁇ 3 (ca 2.5%I - ).
• the emulsions were analyzed by particle size analyzer and by electron micrograph and found to contain uniform particle sizes, indicating that one can use fairly large seed grains within the ambit of this invention.
• control normal splash mix: Experimental (seeded), made as in Example 4, Sample 1, except that 1/2 I - added to "A" solution, 1/2 I - added over 7 min. beginning with addition of 1st silver solution.

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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)
• Colloid Chemistry (AREA)

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• 1985
  • 1985-09-04 DE DE8585111158T patent/DE3582633D1/de not_active Expired - Lifetime
  • 1985-09-04 EP EP19850111158 patent/EP0174018B1/fr not_active Expired
  • 1985-09-05 JP JP19500185A patent/JPS6172229A/ja active Granted

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