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

Definitions

• Direct-positive photographic elements of high speed and maximum density are prepared by incorporating in the silver halide emulsion at least one boron hydride containing from 6 to 12 boron atoms in which the skeletal framework forms a polyhedron or a fragment thereof, and which may contain heteroskeletal atoms selected from the group consisting of carbon, sulfur and nitrogen, and a gold compound.
• This invention relates to direct-positive colloid-silver halide emulsions. Most particularly it relates to such emulsions which are prefogged by a synergistic combination of chemical fogging agents.
• Direct-positive emulsions are, of course, well known and there are many different methods of producing direct positive images. For example, 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. Upon development, a direct positive image will be obtained. 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 use emulsion coated elements which have been chemically fogged with, for example, formaldehyde, hydrazine, sodium arsenite, silver ions and other fogging agents such as gold salts and sulfur compounds. Combinations of the above compounds such as hydrazine and gold salts have also been suggested.
• the prior systems have some shortcomings in terms of speed, contrast and other sensitometric characteristics.
• a sufiicient quantity of reducing agent e.g., stannous chloride
• the fogged siliver halide grains cannot be easily bleached so that excessively long exposure is required and clean backgrounds or low minimum densities cannot be obtained.
• gold compounds are used alone, difiiculties'are again experienced in obtaining sufiicieutly fogged grains and, as in the case of stannous chloride, the fogged grains are not easily bleached without impractically long exposures. It has been proposed to increase the speed of the above systems by adding certain dyes but, in many cases, this causes undesirable stain.
• 3,607,288 discloses the use of gold salts in direct positive emulsions chemically fogged with amine boranes to reduce the tendency for red light to bleach the fogged layer. Further improvements were made in shelf life or aging stability and contrast of direct positive elements by use of boron hydrides in which a skeletal framework forms a polyhedron or fragment thereof, and which may contain heteroskeletal atoms selected from the group consisting of carbon, sulfur and nitrogen. The compounds are added in quantities ranging up to 2.4X10' mole per 1.5 moles of silver under pH conditions of 3.0 to 9.0. Direct positive elements comprising such emulsions are described and claimed in assignees Bigelow, US. Patent 3,637,392, Jan. 25, 1972.
• the direct positive elements containing the borane compound have speeds ranging from 126 to 14,000.
• the boron hydride or cyclic boranes may be added in the range of 10 to 10- mole per mole of silver and the gold compound which may be a watersoluble salt or an acid such as hydrochloroauric acid may be added in the range of 1.0- to 10 mole per mole of silver nitrate.
• the gold compound which may be a watersoluble salt or an acid such as hydrochloroauric acid may be added in the range of 1.0- to 10 mole per mole of silver nitrate.
• 'Ihe synergistic combination of borane and gold compounds may be added to the emulsion at a pH9.0.
• the borane compounds may be added as a solution with a suitable solvent, i.e., Water, ethyl alcohol, benzene, acetone, dioxane, etc.
• the useful borane compounds in aqueous solutions have greater stability than the amine boranes of the above Bigelow and
• the effectiveness of some borane compounds of Bigelow, US. Pat. 3, 637,392 in fogging a silver halide emulsion is not affected by the pH of the systems and they show good fogging properties under acid as well as alkaline conditions.
• Certain borane compounds are more effective than others when used in equivalent quantities. According to this invention it is important that the borane and gold compounds be added at the beginning, during or before the end of the digestion period after the excess salts have been removed by washing.
• the pH of the system can be adjusted to 9.0 or below and preferably is adjusted to 7.0 or below.
• the fogging effect produced by the borane compound/gold ion combination is bleachable by light prior to development.
• the emulsions of the invention may also contain rhodium or iridium in an amount of 1.5 to 325 mg. of a salt of such elements per mole of silver. Suitable salts are described in ⁇ U.S. Pat. 3,445,235.
• Suitable developers are conventional, alkaline, photographic developing solutions useful for standard direct positive emulsions in the absence of the novel fogging combination. While the silver halide system used in this invention is generally a silver chlorobromide, other types, e.g., silver chloride, silver iodobromide, silver iodochloride and silver iodobromochloride, may be used with the boron hydride/gold compound combination.
• the maximum density is the highest density on the step wedge.
• the speed of a typical low speed commercial direct positive in terms of 100/E 10- is 10-3 and the conventional material has a polyhedral carboranes, representative examples of which D of about 3.5. areshown in the following list. The invention will now be illustrated in and by the following examples:
• the pH was adjusted to 5.5 using CSB 'H CI-I 0.6 M NaOH.
• the borane compound, CsB H S was added to each emulsion as shown in the table below and then a Methods of preparatwn of these compounds may be solution of hydrochloroauric acid (HAuCl was added found in The Chemistry of Boron and Its CQmPOImdS, in quantities shown in the tables and then the emulsion Meutterties, John Wiley and $0115, N'Y'! 1967; ywas digested at 130 F. for 40 minutes.
• the preselected level of pH should be maintained b1Su1fite1-6 grams during the digestion period. After digestion, the pH is Sodlum s u1fite(anhYdruS) 45-0 grams adjusted to the desired coating pH and the conventional HYQIOQHIHOHFIZ'O grams final adjuvants are incorporated with the emulsion. Coat- Sodlul?
• carbna te (anhydruS)"67-5 gTams ing aids such as saponin, sodium salts of polyether sul- POPaSSIPm brm1de j1'9 gramS fonates, long chain alkyl sulfonates and sulfates, cetyl 5O Trisodium ethylene diamine tetra acetate tr1hydratebetaine, etc., can be utilized.
• the emulsion is then coated f onto a suitable support and dried.
• the conventional coat- BenZtnaZ1e0'25 g ing processes and apparatus can be used.
• the sensitomeric characteristics of the direct positive The strip was then immersed in a conventional short elements may be determined by exposing in an intensity stop for 5-10 seconds, fixed for three minutes in a conscale sensitomer, described on page 61-6, Mees, The ventional fixer, then washed and dried.
• the emulsion was coagulated, washed and redispersed as described in Moede, U.S. 2,77 2,- 165, issued Nov. 27, 1956.
• the redispersed emulsion was added to an aqueous solution containing 6.1% gelatin and heated to 130 F. with the pH being adjusted to 5.5 with 0.6 M NaOH.
• the borane compound, (NHg B H was added as indicated in the table below followed by the ad dition of HAuCl hydrochlorauric acid as indicated.
• the emulsion was digested for minutes at 130 F.
• the temperature was reduced to 90 F. and 6 grams of poly(ethyl acrylate) as a' 32% solids solution was added along with the usual coating aids including a gelatin hardener.
• the emulsion was then coated on a photographic AgNO Upon completion of the silver halide precipitation, the composition of the emulsion was about bromide and 40% chloride.
• the pH was adjusted to 3.9, the emulsion was coagulated, washed and redispersed as described in Example I.
• the redispersed emulsion is added to an aqueous solution containing 6.1% gelatin and heated to a temperature of 130 F.
• the pH of the system was adjusted to 55:0.5 with 0.6 M NaOH.
• An aqueous solution of the cyclic borane compound CsB H S was added to portions of the emulsion as indicated in the table below together with HAuC1 as shown.
• the emulsions were digested at 130 F. for 40 minutes.
• the emulsion temperature was reduced to 90 F. and poly(ethyl acrylate) as a 32% solids solution was added along 30 with the conventional coating aids including a gelatin hardener.
• the emulsions were coated on a photographic film support and dried in a conventional manner.
• the direct positive elements may be used for reproducing continuous tone negatives, halftones, line copy, engineering drawings, etc.
• the direct positive elements of this invention may also find use in color photography.
• the photographic elements of this invention have the advantage that they provide direct positives with extremely low minimum densities and high maximum densities. They are extremely fast and require much lower quantities of the borane and gold compounds than have been necessary heretofore in the production of chemically fogged direct positive elements.
• the elements of this invention may be developed in any standard developing solution such as the continuous tone developing solution set forth in Example I above or a high contrast lithographic developer using standard techniques well known in the art. Variations in the developing solution will have much the same effect as would be obtained in developing non-reversal emulsions. No pre-exposure operations or auxiliary processing procedures are necessary or desirable in using the novel elements of this invention.
• water-permeable colloid binder for the silver halide grains as described in the above examples, other natural or synthetic water-permeable organic colloid binding agents can 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 extra-linear CH CHOH groups; hydrolyzed interpolymers of vinyl acetate and unsaturated addition poymerizable compounds such as maleic anhydride, acrylic acid and methacrylic acid ethyl esters.
• Suitable colloids of the last mentioned type are disclosed in U.S.
• the useful polyvinyl acetals include polyvinyl butyraldehyde acetal and polyvinyl sodium o-sulfobenzaldehyde acetal.
• Other useful colloid binding agents include polyvinyl butyraldehyde acetal and polyvinyl sodium o-sulfobenzaldehyde acetal.
• Other useful colloid binding agents include the poly-N- vinyllactams of Bolton, US. Patent 2,495,918, the hydrophilic copolymers of N-acrylamido alkyl betaines described in Shacklett, US. Pat. 2,833,050 and hydrophilic cellulose ethers and esters.
• the emulsions of this invention may be coated on any suitable base including paper and transparent film support.
• the cellulosic supports e.g., cellulose acetate, cellulose triacetate, cellulose mixed esters, etc.
• Polymerized vinyl compounds e.g., copolymers of vinyl acetate and vinyl chloride, polystyrene, and polymerized acrylates may also be mentioned.
• Other suitable supports are the polyethylene terephthalate/isophthalates of British specification No.
• the emulsions are generally coated on the supports in quantities to give a coating weight of about 50-75 milligrams of silver halide per square decimeter of support surface area.
• Other cyclic or polyhedral boranes than those set forth above may be used. A practical limit is imposed upon the use of certain boranes due to high toxicity and possible explosive characteristics of individual compounds.
• a direct-positive, water-permeable colloid-silver halide emulsion containing a boron hydride and a gold compound in which the has a polyhedral framework containing from 6-12 boron atoms and may contain heteroskeletal atoms selected from the groups consisting of C, S, and N, wherein, the boron hydride is present in an amount of 10" to 10- mole per mole of silver, and the gold compound is present in an amount of 10- to 10- mole per mole of silver, the combined amounts of said boron hydride and gold compound being suflicient to fog said emulsion.
• An emulsion according to claim 1 having pH 3.0-9.0.
• An emulsion according to claim 1 wherein the boron is (NH4) B1oH1 10.
• An emulsion according to claim 1 wherein the gold compound is hydrochloroauric acid.
• a photographic element comprising a support hearing a layer of an emulsion as defined in claim 1.
• a photographic element comprising a support bearing a layer of an emulsion as defined in claim 3.

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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)

Applications Claiming Priority (1)

Publications (1)

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Family Applications (1)

Country Status (7)

Cited By (2)

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• 1971
  • 1971-06-22 US US00155629A patent/US3752674A/en not_active Expired - Lifetime
• 1972
  • 1972-06-20 DE DE2229926A patent/DE2229926C3/de not_active Expired
  • 1972-06-21 FR FR7222351A patent/FR2143187B1/fr not_active Expired
  • 1972-06-21 CA CA145,342A patent/CA969413A/en not_active Expired
  • 1972-06-22 GB GB2928172A patent/GB1363600A/en not_active Expired
  • 1972-06-22 BE BE785242A patent/BE785242A/xx not_active IP Right Cessation
• 1974
  • 1974-04-05 JP JP49039383A patent/JPS581413B2/ja not_active Expired

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