Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07D—HETEROCYCLIC COMPOUNDS
  • C07D471/00—Heterocyclic compounds containing nitrogen atoms as the only ring hetero atoms in the condensed system, at least one ring being a six-membered ring with one nitrogen atom, not provided for by groups C07D451/00 - C07D463/00
  • C07D471/12—Heterocyclic compounds containing nitrogen atoms as the only ring hetero atoms in the condensed system, at least one ring being a six-membered ring with one nitrogen atom, not provided for by groups C07D451/00 - C07D463/00 in which the condensed system contains three hetero rings
  • C07D471/14—Ortho-condensed systems
• • 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

Definitions

• This invention relates to the production of direct positive photographic materials and more particularly to photographic emulsions adapted to be processed directly to positive images.
• direct positive photographic emulsions may be made by including in a silver chloride emulsion a small proportion of a desensitising compound and fogging the emulsion by light or by chemical means. When such an emulsion is exposed and developed a positive image is directly produced.
• the emulsions have been coated on paper base and the products used for document reproduction.
• the desiderata for such emulsions for use for such purposes the following may be mentioned.
• the emulsion In the first place, it is desirable that the emulsion should have a good bleaching speed, i.e. the speed at which the fogged emulsion is reactive to the exposing light, so that in the exposed areas it affords (on development) a white background.
• a good bleaching speed i.e. the speed at which the fogged emulsion is reactive to the exposing light
• the effect of the general lighting on the exposed areas of the emulsion should not be such as to cause those areas again to become developable, i.e.
• the desensitising compound should not iself be so highly coloured that it imparts a discernible colour to the thinly coated emulsion layer.
• the material may be subjected to a first exposure by yellow light to a line image (black on a white background), thus bleaching the emulsion in the exposed areas. If the emulsion is developed at this stage United States Patent "ice 3,124,458 Patented Mar. 10, 1964 it will give a simple positive image on development, i.e. black lines on a white background.
• a direct positive photographic element which comprises a fogged gelatino silver halide emulsion of which .at least and preferably at least 99%, of the silver halide is silver chloride, which emulsion contains a desensitising compound which is a 2,2-pyridyl bis quaternary salt of the general formula:
• n is 2, 3 or 4
• X is an anion
• either or both of the pyridine nuclei may carry alkyl substituent groups.
• the said emulsion may be fogged by light or by chemical means, e.g. treatment with formaldehyde or other reducing agent.
• the preparation of allthese compounds is. described by R. F. Homer and T. E. Tomlinson, Journal of the Chemical Society, 1960, page 2498.
• Other compounds of the class are the following (with their methods of manufacture):
• the selected 2,2-dipyridyl bis quaternarysalt (which may be, for example, a bromide or other halide salt, or a sulphate, methane sulphonate or toluene-p-sulphonate salt) is preferably included in the photographic emulsion in an amount which is 0.1 to 2 g. of the compound per 100 g. of silver halide present.
• the emulsion may be prefogged by pre-exposure to light, but it is preferred to fog the emulsion chemically, for example by including formaldehyde in the emulsion and allowing the emulsion to stand at elevated temperature.
• Example I 4.4 litres of a washed photographic emulsion containing 188 g. of silver chloride and adjusted to pH 10 were treated with 12 ml. of a 4% aqueous solution of formaldehyde. The emulsion was heated at 52 C. for 35 minutes and was then neutralised by the addition of citric acid and cooled. There was then added 2 g. of 1,1-ethylene-2,2-dipyridylium dibromide dissolved in 100 ml. of ethanol. The emulsion was coated on paper base. On exposure and development the product yielded a direct positive image of high quality, of which the whites were unstained. The product after exposure and before development exhibited a relatively low forward speed.
• Example 2 The procedure of Example 1 was followed but using only 0.1 g. of the said dipyridyl compound and the emulsion was coated on film base. The resulting film was exposed by yellow light to an original consisting of black lines on a clear background. 0n development it yielded a direct positive image of high quality.
• a second portion of this film was exposed to the first original as before and then exposed by white light to a second original consisting of an arrangement of black lines on a clear background.
• the film was then developed and yielded a positive image of the first original and a superimposed negative image of the second original.
• a direct positive photographic element comprising a fogged gelatino silver chloride emulsion containing a desensitising compound selected from the class consisting of compounds of the formula:
• each R is selected from the class consisting of hydrogen and alkyl of 1 to 4 carbon atoms
• n is selected from 2, 3 and 4
• X is an anion
• the said compounds in which at least one of the pyridine nuclei carries an alkyl substituent.
• a direct positive photographic element according to claim 1 wherein the proportion of desensitising compound is O.1 to 2 g. per 100 g. of silver chloride.
• a direct positive photographic element comprising a fogged silver chloride emulsion containing, as desensitising compound, a 1,1'-ethylene-2,2'-dipyridylium salt.
• a direct positive photographic element comprising a fogged silver chloride emulsion containing, as desensitising compound, a 1,1-ethylene-2,2-dipyridylium salt in a proportion of 0.1 to 2 g. per 100 g. of silver chloride present.

Landscapes

• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Physical Or Chemical Processes And Apparatus (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
• Silver Salt Photography Or Processing Solution Therefor (AREA)
• Plural Heterocyclic Compounds (AREA)
• Non-Silver Salt Photosensitive Materials And Non-Silver Salt Photography (AREA)

Applications Claiming Priority (1)

Publications (1)

Family

ID=9862028

Family Applications (1)

Country Status (4)

Cited By (7)

Citations (2)

• 0
  • NL NL275770D patent/NL275770A/xx unknown
  • NL NL120472D patent/NL120472C/xx active
  • US US3124458D patent/US3124458A/en not_active Expired - Lifetime
• 1961
  • 1961-03-10 GB GB8928/61A patent/GB940152A/en not_active Expired
• 1962
  • 1962-03-09 DE DEJ21412A patent/DE1170779B/de active Pending

Patent Citations (2)

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