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
  • G03C1/485—Direct positive emulsions
  • G03C1/48515—Direct positive emulsions prefogged
  • G03C1/48523—Direct positive emulsions prefogged characterised by the desensitiser
  • G03C1/4853—Direct positive emulsions prefogged characterised by the desensitiser 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
  • G03C1/485—Direct positive emulsions
  • G03C1/48515—Direct positive emulsions prefogged

Definitions

• This invention relates to direct positive colloid silver halide photographic emulsions. More particularly it relates to such emulsions which are prefogged by a chemical fogging agent.
• Direct positive emulsions are, of course, well known and there are many different methods of producing direct positive elements.
• a silver halide emulsion may be given a short overall exposure of high intensity radiation and then given a longer imagewise exposure of lower intensity.
• Another method is to expose imagewise and develop and bleach out developed silver and then flash expose and redevelop.
• a still further method is to chemically fog the silver halide grains with, for example, formaldehyde, hydrazine, sodium arsenite, silver ions and other nonsulfide fogging agents instead of using a solarizing exposure. Upon lmagewise exposure and development of such chemically fogged elements, a positive image is obtained.
• This invention provides a process for preparing a direct positive photographic silver halide emulsion which may contain minor amounts of silver chloride, which comprises:
• the pH of the emulsion is adjusted to between 5.0 and 7.0 with a suitable adjuvant, e.g., citric acid or sodium hydroxide and the usual coating aids, e.g., gelatin, hardeners, surfactants, etc., are added and the emulsion is coated on a support and dried in a conventional manner.
• a suitable adjuvant e.g., citric acid or sodium hydroxide
• the usual coating aids e.g., gelatin, hardeners, surfactants, etc.
• Part (a) has neither iodide nor optical sensitizing dye added thereto.
• Part (b) shows the effect of adding an iodide salt at the beginning of digestion but no optical sensitizing dye at the end of digestion.
• Part (c) shows the effect of adding only the dye at the end of digestion and
• Part (d) shows the synergistic effect of adding the iodide salt at the beginning of digestion and an optical sensitizing dye at the end of digestion.
• the sensitometric characteristics of the direct positive emulsion may be determined by processing test strips of the coated layer in the following manner.
• a test strip of the following examples is fixed out in a conventional photographic fixer to provide a means of establishing the minimum density (D Test strips are exposed in an intensity scale sensitometer (described on page 616, Mees, The Theory of the Photographic Process. MacMillen Company, New York, 1942) using a [2 step wedge and Log E of 5.71. The exposed strips are developed for 1 /2 minutes at 68 F. in a developer having the composition:
• the minimum density (D equals the lowest density above that of the fixed out strip mentioned above.
• the maximum density is the highest density above D,,,,-,,.
• the speed is expressed in terms of /EXO.
• the speed of a typical commercial direct positive in terms of 100/EX10 is 10.3 and said material has a D,,,,-,, of 0.01 and a D of 4.5.
• emulsion-coated elements prepared according to this invention good duplicates can be made by contact-printing, using either carbon arc lamps or tungsten photofloods as a light source.
• the elements may be used for reproducing continuous tone negatives, half-tones, line copy, engineering drawings, etc.
• the direct positive elements of this invention may also find use in color photography.
• Optical sensitizing dyes other than those disclosed below may be used, either acid or nonacid and the art is replete with useful dyes.
• gelatin is the colloid carrier most used in the photographic manufacturing art
• other carriers for the silver halide crystals may be used.
• other natural and synthetic water permeable colloid binding agents may be used.
• Such agents include water-permeable or water-soluble polyvinyl alcohol and its derivatives, e.g., partially hydrolyzed polyvinyl acetates, polyvinyl ethers, and acetals containing a large number of CH CHOH groups; hydrolyzed interpolymers of vinyl acetate and unsaturated addition polymerizable compounds such as maleic anhydride, acrylic and methacrylic acid esters and styrene.
• Suitable colloids of the last-mentioned type are disclosed in U.S. Pat. Nos.
• the useful polyvinyl acetals include polyvinyl butyraldehyde acetal and polyvinyl sodium o-sulfobenzaldehyde acetal.
• Other useful colloid bind ing agents include the poly N-vinyl-lactams of Bolton, U.S. Pat. No. 2,495,918, the hydrophilic copolymers of N- acrylamido alkyl betaines described in Shacklett, U.S. Pat. No. 2,833,050 and hydrophilic cellulose ethers and esters.
• the emulsions made bygthe process of this invention may be coated on any suitable base including paper and transparent film supports.
• the cellulose supports e.g., cellulose acetate, cellulose triacetate, cellulose mixed esters, etc.
• Polymerized vinyl compounds e.g., copolymerized vinyl acetate and vinyl chloride, polystyrene, and polymerized acrylates may also be mentioned.
• the film formed from the polyesters made according to the teachings of Alles, U.S. Pat. No. 2,779,684 and patents referred to in the specification of that patent.
• Other suitable supports are the polyethylene terephthalate/isophthalates of British Pat. No. 766,290 and Canadian Pat. No.
• terephthalic acid and dimethyl terephthalate those obtainable by condensing terephthalic acid and dimethyl terephthalate with propylene glycol, diethylene glycol, tetramethylene glycol or cyclohexane -l,4-dimethanol (hexahydro-p-xylene alcohol).
• the films of Bauer, et al., U.S. Pat. No. 3,059,543 may also be used.
• the above polyester films are particularly suitable because of their dimensional stability.
• the emulsions are generally coated on the supports in quantities to give a coating weight of about 50-75 mg. of silver halide per square decimeter of support surface area.
• the resulting emulsion was coagulated, washed and redispersed in the manner disclosed in Moede, U.S. Pat. No. 2,772,165, issued Nov. 27, 1956.
• the temperature of the redispersed emulsion was raised to 130 F. and there was then added 87 g. of gelatin, and the pH adjusted to 6.0 with sodium hydroxide. There was then added 2.70 mg. of morpholine borane.
• the emulsion was divided into 4 parts and labeled (a), (b), (c) and (d). Part (a) was digested at 130 F. for 40 minutes.
• a gelatin hardener was added and the emulsion was coated on a photographic film support and dried in a conventional manner.
• Part (b) was treated as above except that 6.67 millimoles of potassium iodide per mole of silver halide was added at the start of digestion.
• Part (c) was treated as 1(a) except that at the end of digestion there was added 33.34 milligrams of the optical sensitizing dye 4( l,3,4-trimethylindolidi nyl) ethylidene-(3-methyl-l-p-sulfophenyl)-5-pyrazolone of the formula:
• Part ((1) was treated as in Part (21) except that at the beginning of digestion there was added 6.67 millimoles of potassium iodide and at the end of digestion there was added 33.34 mg. of the sensitizing dye disclosed above in 1(c).
• the sensitometric results are shown in the following table as processed in the manner described above.
• Example I was repeated using 1(a) and 1(b) emulsions as controls which are designated ll(a) and ll(b). To Part "(0), there was added 66.67 mg. per mole of silver halide of the optical sensitizing dye having the formula:
• Part ll(d) was treated as described in 1(a) except that the amount of potassium iodide disclosed in I(b) was added before digestion and the amount of optical sensitizing dye shown above was added after digestion.
• the sensitometric results are shown in the following table when processed as described above.
• Example 1 EXAMPLE in Example 1 wasrepeated using 1(a) and 1(b) as controls but designated as lll(a) and [ll(b). To Part Ill(c), there was added just after digestion 66.67 mg. per mole of silver halide of the optical sensitizing dye having the formula:
• Part lIl(d) was treated as described in 1(a) except that the amount of potassium iodide disclosed in 1(b) was added just before digestion and the amount of optical sensitizing dye shown above was added just after digestion.
• the sensitometric results are shown in he following table when processed as described above.
• Example 1 was repeated except that in place of 2.70 mg. of morpholine borane there were added 133.34 mg. of
• Example ll was repeated using 1(a) and l(b) as controls which are designated Vll(a) and Vll(b).
• the emulsion was divided into 8 portions and the (c), (d), (e), (f), (g), and (h) portions containing the addition of 66.67 mg. of the optical sensitizing dye as described in Example ll also contained varying amounts of potassium iodide as shown in the following table.
• Example 11 was repeated except that in place of 2.7 mg. of morpholine borane there was added 2.70 mg. of tertiary butyl amine borane per mole of silver halide.
• the emulsion was divided into 4 parts and designated (a), (b), (c), and (d).
• Sample Vlll(a) contained neither iodide nor optical sensitizing dye.
• Sample Vlll(b) contained 13.34 millimoles of potassium iodide per mole of silver halide added just prior to digestion and Sample Vlll(c) was the same as (a) only with the addition just after digestion of 66.67 mg. of the optical sensitizing dye of Example 11 per mole of silver halide.
• Sample Vlll(d) was the same as (a) except that 13.34 millimoles of potassium iodide was added just before digestion and 66.67 mg. was added just after digestion.
• the sensitometric results are shown in the following table when processed as described in Example 1.
• the process of this invention provides direct positive elements having extremely high speeds as compared to commercial direct positive material of the prior art as described, above.
• the direct positive elements prepared by the process described here also have high maximum densities and very low minimum densities.
• the elements may be developed in standard developing solutions using standard techniques. Variations in the developing solution will have much the same effect as it would in developing nonreversal emulsions. No preexposure operations or auxiliary processing procedures are necessary or desirable using elements made by the process of this invention. It is unnecessary to use desensitizing compounds as is commonly done in the direct positive art.
• amine boranes as chemical fogging agents are far superior to formaldehyde, the principle fogging agent of the prior art, because the borane compounds do not have any hardening effect on the gelatin layer.
• any of the amine boranes listed in Bigelow & Burt US. Pat. No. 3,161,564, Jan. 2, 1968, can be used.
• Preferred alkyl amine boranes have the formula:
• R is an alkyl radical of 1-20 carbon atoms, and R and R are each taken from the group consisting of H and alkyl of 1-20 carbon atoms.
• a process for preparing a direct positive photographic silver halide emulsion whichcomprises a. adding approximately 5-15 millimoles of a water-soluble inorganic iodide. per mole of silver halide to a redispersion in an aqueous medium of a precipitated, ripened and washed water-permeable colloid silver chlorobromide or bromide emulsion, and adjusting the pH to approximately 5-9 and digesting the emulsion at 110 to 150 F. for about 15-60 minutes, there being added during the adjusting or digesting of the emulsion per mole of silver halide 0.00033 to 12.0 g. of an amine borane as a'fogging agent; characterized in that. after the digesting step is essentially complete, there is added per mole of silver halide approximately 10-100 mg. of an optical sensitizing dye.
• sensitizing dye is 4(1,3,3-trimethylindolidinyl) ethylidene-( 3-methyll -psulfophenyl)-5-pyrazolone.
• sensitizing dye is 2(3-ethyl thiazolylidene) ethylidene-3 carboxymethyl- 5-rhodanine.
• sensitizing dye is 4(p-dimethylbenzal) 3-methyl-l-p-sulfophenyl-5- pyrazolone.
• sensitizing dye is 3,3(2-carboxyethyl)-5,6,5,6 tetramethyl benzoxazole carbocyanine.
• amine borane is an alkyl amine borane of the formula 1?: Rr-IIVBH Ra 40 wherein R, is an alkyl radical of l-20 carbon atoms, and R,
• R are each taken from the group consisting of H and alkyl of l-ZQcarbon atoms.

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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)
• Non-Silver Salt Photosensitive Materials And Non-Silver Salt Photography (AREA)

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Citations (8)

• 0
  • BE BE757384D patent/BE757384A/xx unknown
• 1969
  • 1969-10-13 US US865976A patent/US3647455A/en not_active Expired - Lifetime
• 1970
  • 1970-10-10 DE DE2049797A patent/DE2049797C3/de not_active Expired
  • 1970-10-12 FR FR7036752A patent/FR2065337A5/fr not_active Expired
  • 1970-10-12 GB GB48430/70A patent/GB1282084A/en not_active Expired

Patent Citations (8)

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