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
  • G03C1/48592—Positive image obtained by various effects other than photohole bleaching or internal image desensitisation, e.g. Sabatier, Clayden effect
• • 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
  • G03C1/06—Silver halide emulsions; Preparation thereof; Physical treatment thereof; Incorporation of additives therein with non-macromolecular additives
  • G03C1/36—Desensitisers

Definitions

• This invention relates to photographic emulsions, and particularly to a direct positive photographic emulsion containing desensitizing dyes or compounds.
• a further object is to provide a direct positive emulsion in which high contrast images can be obtained.
• a still further object is to provide a method of producing direct positive images of low minimum density.
• the photographic emulsion used in our process is a silver chloride emulsion containing substantially no silver bromide or silver iodide.
• the desensitizing compound in amounts ranging from 0.1 gram to 2 grams ofcompound per 100 grams of silver chloride.
• the emulsion is then coated on a support and flashed with white light to fog it. It is then exposed to an image through a yellow filter-and developed in the usual way to produce a positive image.
• the reversal speed of the emulsion is approximately /400 that of ordinary contact printing paper.
• the desensitizing compounds used according to our invention are benzothiazole, quinoline, indolenine, benzotriazole, and rhodanine compounds having one or more nitro groups attached to a benzene nucleus which is either a part of the 1 heterocyclic compound or is attached to it through a doubly-bonded carbon to carbon chain.
• the emulsion is coated on the sup- 1 port, which may be of paper, glass, synthetic resin, or other suitable material.
• the emulsion is then flashed to a high density with white light.
• the fiash exposure should be of sufficient intensity to produce a high density upon development, although not necessarily the maximum density which the emulsion is capable of producing.
• a very heavy flash exposure requires a longer exposure to yellow light to remove its effect.
• the emulsion may also be fogged chemically rather than by light, and in this case the fogging may be done before or after addition of the reversing compound using non-sulfide fogging reagents.
• Addition of formaldehyde to the emulsion is a suitable way of fogging the emulsion chemically. In this case no flash exposure is needed, and the only exposure-necessary to give a positive image directly is the image-forming exposure. through the-yellow filter.
• the reversal exposure is made with minus blue light, that is, light 'of 500 to 700 m wavelength.
• a No. 12 or No. 15 filter (Wratten Light Filters, Eastman Kodak Co., 1945) may be used over the light source to produce reversing'light, or even a No. 2A filter if the blue speed of the emulsion is sufficiently, low. Maximum reversal is obtained at 520 to 540 m wavelength.
• Eacample 1 This example illustrates fogging by light after addition. of; the reversing compound.
• the prefiashed material can be exposed to an image with light modulated by a Wratten No. 15 filter.
• Example 2 This example illustrates chemical fogging before addition of the reversing compound.
• the emulsions made according to our invention produce a low minimum density and a high maximum density on reversal. They :are -es-- pecially useful for reproduction of document letters and drawings.
• a direct positive photographic emulsion comprising a strongly fogged silver chloride emulsion containing a compound selected from the class consisting of benzothiazole, quinoline, indolenine;
• a direct positive photographic emulsion comprising a strongly fogged silver chloride emulsion containing Z-(p-nitrostyryl) quinoline metho-ptoluene sulfon'ate.
• a direct positive photographic emulsion comprising a strongly fogged silver chloride emulsioncontaining a 6-nitro-1 2,3-benzotriazole.
• the method of making a direct positive photographic emulsion which comprises precipitate ing silver chloride in gelatin, adding to the emul-' sion a compound selected from the class consist-" ing of benzothiazole, quinoline, indolenine, ben-j zotriazole and rhodanine compounds and their alkyl quaternary salts having at least one nitro group attachedto a benzene nucleus and strongly fogging the emulsion in the presence of said compound.
• a direct positive photographic emulsion which comprises precipitating silver chloride in gelatin, chemically strongly fogging the emulsion and then adding to it a compound selected from the class consisting of benzothiazole, quinoline, indolenine, benzotriazole and rhodanine compounds and their alkyl quaternary salts having at least one nitro group attached to a benzene nucleus.
• photographic emulsion which comprises precipiphotographic emulsion which comprises precipitating silver chloride in gelatin, adjusting the emulsion to an alkaline condition, strongly fogging said emulsion chemically with formaldehyde, adjusting the emulsion to an acid condition and mixing with it a 2-nitrostyryl benzothiazole quaternary salt.

Landscapes

• Chemical & Material Sciences (AREA)
• Physics & Mathematics (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• General Physics & Mathematics (AREA)
• Spectroscopy & Molecular Physics (AREA)
• Non-Silver Salt Photosensitive Materials And Non-Silver Salt Photography (AREA)
• Silver Salt Photography Or Processing Solution Therefor (AREA)

Priority Applications (4)

Applications Claiming Priority (1)

Publications (1)

Family

ID=21885938

Family Applications (1)

Country Status (4)

Cited By (24)

Families Citing this family (1)

Citations (4)

• 0
  • BE BE489729D patent/BE489729A/xx unknown
• 1948
  • 1948-06-29 US US35987A patent/US2541472A/en not_active Expired - Lifetime
• 1949
  • 1949-06-21 FR FR989400D patent/FR989400A/fr not_active Expired
  • 1949-06-28 GB GB17049/49A patent/GB667206A/en not_active Expired

Patent Citations (4)

Also Published As

Similar Documents