US2541472A - Direct positive emulsion containing desensitizing dye - Google Patents

Direct positive emulsion containing desensitizing dye Download PDF

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Publication number
US2541472A
US2541472A US35987A US3598748A US2541472A US 2541472 A US2541472 A US 2541472A US 35987 A US35987 A US 35987A US 3598748 A US3598748 A US 3598748A US 2541472 A US2541472 A US 2541472A
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United States
Prior art keywords
emulsion
direct positive
emulsion containing
silver chloride
quinoline
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Expired - Lifetime
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US35987A
Inventor
William B Kendall
George D Hill
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Eastman Kodak Co
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Eastman Kodak Co
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Publication date
Priority to BE489729D priority Critical patent/BE489729A/xx
Application filed by Eastman Kodak Co filed Critical Eastman Kodak Co
Priority to US35987A priority patent/US2541472A/en
Priority to FR989400D priority patent/FR989400A/en
Priority to GB17049/49A priority patent/GB667206A/en
Application granted granted Critical
Publication of US2541472A publication Critical patent/US2541472A/en
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    • 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.

Description

Patented Feb. 13, 1951 DIRECT POSITIVE EMULSION CONTAINING DESENSITIZING DYE William B. Kendall and George D. Hill; Rochester, N. Y., assignors to Eastman Kodak Company, Rochester, N. Y., a corporation ofNew Jersey No Drawing. ApplicationJune 29, 1948, Serial No. 35,987
14 Claims. (CI. 95-47) This invention relates to photographic emulsions, and particularly to a direct positive photographic emulsion containing desensitizing dyes or compounds.
It is known that if a photographic silver halide emulsion which has been exposed to blue light is subsequently exposed to long-wave radiation before it is developed, some of the effect ofthe original exposure is destroyed. This is known as the Herschel effect. It is also known that desensitizing dyes may be added to the emulsion to increase reversal speed (Mees, The Theory of the Photographic Process, 1942, pages 280- 282). The experiments described in the literature in which desensitizing dyes were used, were made with silver bromide emulsions, and reversal was found to be dependent upon absorption of light by the dye adsorbed to the silver bromide rains.
In these prior processes, reversal was not complete, that is, the reversal density was not reduced to zero. For this reason, the contrastoi the image was low, and the background density high. With such processes it was impossible to obtain pure whites.
It is therefore an object of the present invention to provide a novel direct positive photographic process. 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.
These objects are accomplished according to our invention by incorporating any of certain desensitizing compounds in a silver chloride emulsion; and fogging the emulsion before imageforming exposure.
The photographic emulsion used in our process is a silver chloride emulsion containing substantially no silver bromide or silver iodide. To this emulsion we add 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.
5 The quaternary salts of the benzothiazole, quincline and indolenine compounds are also suitable. Similar compounds without the nitro group showed no appreciable enhancement of the Herschel effect.
Compounds suitable-for use according to our invention are the following:
2-(o-nitrostyryl) -3-eth ylbenzotl1iazolium iodide. Also mand p-nltrostyryl compounds /N\ N02 C2115 I 2-(o,p-dlnitrostyryl)-3-ethylbenzothiazolium iodide N l loz 2- (o,p-dinitrostyryl) -benz0tl1iaaole '2-(p-nitrostyryl)-quinoline metho-p-toluenesulfonate.
Also 6-ethoxy derivative, and oand m-nitrostyryl 4-(p-nitrostyrylhquinoline methiodide C CH=CH NO. Q
N on. I
3,3-dimethyl-2- p-iiitrostyryl) -indolenine methiodide /OCH3 chi SOB- 3 2-methyl-S-nitro-benzothiazole metho-p-toluene snlfonate 2- (p-dimethylaminostyryl) -3-etlryl-6-nitrobenzothiazolium chloride G-nitro-benzo-l,2,3-triazole. Also Lemon) and 5-chloro-clerivatives L ONC H N02 5-onitrobenzylidene-3-ethyl-rhodanine After incorporation of the nitro compound in the emulsion, 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.
Our invention will be illustrated by the following specific examples.
Eacample 1 This example illustrates fogging by light after addition. of; the reversing compound.
silveriichloride emulsion containing an equivalent of grams of silver nitrate was added 0.017 gram of 2-(p-nitrostyryl) -6-ethoxy-quinoline metho-p-toluene sulfonate. The emulsion was then coated on a non-glossy paper support and was then flashed with white light suflicient to give a density of 1.2 when developed in the following developer, diluted 1 part to 2 parts of water:
N-methyl-p-aminophenol sulfate grams 3.1 Sodium sulfite, des do 45 I-Iydroquinone do 12 Sodium carbonate, des--.- do 67.5 Potassium bromide do 1.9
Water to liter 1 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.
Seven lbs. of a silver chloride emulsion containing the equivalent of 100 g. of silver nitrate was heated to e0 C. and the pH adjusted to 7.8. Eight cc. of full strength (40%) formalin solution were added and the emulsion held for 10 minutes. At the end of the holding period the pH was adjusted to 6 0 and 0.125 g. of 2-(pnitrostyryl) -quinoline metho-p-toluene sulfonate was added. The emulsion was then coated on a support.
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.
It will be understood that the examples and modifications included herein are illustrativeonly.
We claim:
1. A direct positive photographic emulsion comprising a strongly fogged silver chloride emulsion containing a compound selected from the class consisting of benzothiazole, quinoline, indolenine;
containing a 2-(o-nitrostyryl-3-ethylbenzothia- I zolium iodide). 4. A direct positive photographic emulsionc'oin prising a'strongly fogged silver chloride emulsion containing a 2 -nitrostyryl quinoline quaternary salt.
5.A direct positive photographic emulsion comprising a strongly fogged silver chloride emulsion containing Z-(p-nitrostyryl) quinoline metho-ptoluene sulfon'ate.
6. A direct positive photographic emulsion comprising a strongly fogged silver chloride emulsioncontaining a 6-nitro-1 2,3-benzotriazole.
'7. 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.
8. The method of making 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.
9. The method of making a direct positive photographic emulsion which comprises precipitating silver chloride in gelatin, chemically strongly fogging the emulsion and adding to the fogged emulsion of 2-nitrostyrylbenzothiazole quaternary salt.
10. The method of making a direct positive photographic emulsion which comprises precipitating silver chloride in gelatin, chemically strongly fogging the emulsion and adding to the fogged emulsion Z-(o-nitrostyryl) -3-ethylbenzothiazolium iodide.
11. The method of making a direct positive photographic emulsion which comprises precipitating silver chloride in gelatin, chemically strongly fogging the emulsion and adding to the fogged emulsion a Z-nitrostyryl quinoline quaternary salt.
12. The method of making a direct positive 30 ,3 4, 93
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.
WILLIAM B. KENDALL.
GEORGE D. HILL.
REFERENCES CITED The following references are of record in the file of this patent:
UNITED STATES PATENTS Number Name Date 2,066,099 Dieterle Dec. 29, 1936 2,271,229 Peterson et a1 Jan. 27, 1942 2,324,123 Weissberger July 13, 1943 Bean Sept. 11, 1945

Claims (1)

1. A DIRECT POSITIVE PHOTOGRAPHIC EMULSION COMPRISING A STRONGLY FOGGED SILVER CHLORIDE EMULSION CONTAINING 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.
US35987A 1948-06-29 1948-06-29 Direct positive emulsion containing desensitizing dye Expired - Lifetime US2541472A (en)

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BE489729D BE489729A (en) 1948-06-29
US35987A US2541472A (en) 1948-06-29 1948-06-29 Direct positive emulsion containing desensitizing dye
FR989400D FR989400A (en) 1948-06-29 1949-06-21 New photographic emulsions and process for their preparation
GB17049/49A GB667206A (en) 1948-06-29 1949-06-28 Improvements in photographic processes and materials therefor

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Cited By (24)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2614927A (en) * 1949-06-01 1952-10-21 Eastman Kodak Co Rapid processing of photographic materials
US2774668A (en) * 1953-05-28 1956-12-18 Polaroid Corp Process and product for forming color images from complete dyes
US2947629A (en) * 1958-09-17 1960-08-02 Eastman Kodak Co Nitrosopyrimidine desensitizing compounds and photographic emulsions containing them
US2954292A (en) * 1957-10-04 1960-09-27 Ilford Ltd Photographic desensitising compounds
US2965485A (en) * 1957-08-19 1960-12-20 Ilford Ltd Photographic desensitising compounds
US3023102A (en) * 1957-09-24 1962-02-27 Gen Aniline & Film Corp Direct positive photographic emulsion
US3062651A (en) * 1959-01-21 1962-11-06 Eastman Kodak Co Unhardened, fogged emulsions and method of processing to positive images
US3189456A (en) * 1961-06-19 1965-06-15 Du Pont Radiation-sensitive emulsions and elements and their preparation
DE977335C (en) * 1953-03-16 1965-12-16 Agfa Ag Process for reducing the blue sensitivity of photographic silver halide emulsions
US3237008A (en) * 1961-01-19 1966-02-22 Eastman Kodak Co Roomlight handling radiographic element including an x-ray sensitive layer overcoated with a dye desensitized silver halide emulsion
US3250618A (en) * 1959-05-13 1966-05-10 Eastman Kodak Co Thermal resensitization of desensitized silver halide photographic emulsions
US3278307A (en) * 1961-11-21 1966-10-11 Eastman Kodak Co Photographic process for producing prints stabilized against print-out
US3284203A (en) * 1961-05-02 1966-11-08 Fuji Photo Film Co Ltd Direct positive photographic materials
US3295969A (en) * 1961-04-12 1967-01-03 Eastman Kodak Co Photographic spirit duplicating process
US3364026A (en) * 1963-02-14 1968-01-16 Eastman Kodak Co Fogged silver halide direct positive solarizing elements containing merocyanine dyes
US3367779A (en) * 1965-01-21 1968-02-06 Fuji Photo Film Co Ltd Direct positive silver halide photographic materials
US3372031A (en) * 1963-08-28 1968-03-05 Ilford Ltd Direct positive silver halide element with contiguous colloid layer containing developing agent
US3713832A (en) * 1968-07-15 1973-01-30 Fuji Photo Film Co Ltd Solarization type silver halide emulsion containing a halogenated hydroxyphthalein sensitizing dye and a desensitizing compound
US3988156A (en) * 1974-02-19 1976-10-26 Eastman Kodak Company Photographic supports and elements utilizing photobleachable o-nitroarylidene dyes
US3988154A (en) * 1974-02-19 1976-10-26 Eastman Kodak Company Photographic supports and elements utilizing photobleachable omicron-nitroarylidene dyes
US4271263A (en) * 1980-05-15 1981-06-02 Minnesota Mining And Manufacturing Company Thermally developable photosensitive compositions containing acutance agents
US4308379A (en) * 1980-05-15 1981-12-29 Minnesota Mining And Manufacturing Company Acutance agents for use in thermally developable photosensitive compositions
US4404277A (en) * 1981-08-21 1983-09-13 Minnesota Mining And Manufacturing Company Desensitizing dyes for photographic emulsions
EP0754967A1 (en) 1995-07-14 1997-01-22 Agfa-Gevaert N.V. Photographic direct positive material containing a particular stabilizer

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2865749A (en) * 1956-11-06 1958-12-23 Eastman Kodak Co Stabilized photographic emulsions

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2066099A (en) * 1928-01-31 1936-12-29 Agfa Ansco Corp Photographic emulsion
US2271229A (en) * 1939-11-10 1942-01-27 Eastman Kodak Co Fog inhibitor for photographic developers
US2324123A (en) * 1941-07-08 1943-07-13 Eastman Kodak Co Fog inhibitor for photographic developers
US2384593A (en) * 1943-08-06 1945-09-11 Eastman Kodak Co Antifoggant

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2066099A (en) * 1928-01-31 1936-12-29 Agfa Ansco Corp Photographic emulsion
US2271229A (en) * 1939-11-10 1942-01-27 Eastman Kodak Co Fog inhibitor for photographic developers
US2324123A (en) * 1941-07-08 1943-07-13 Eastman Kodak Co Fog inhibitor for photographic developers
US2384593A (en) * 1943-08-06 1945-09-11 Eastman Kodak Co Antifoggant

Cited By (24)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2614927A (en) * 1949-06-01 1952-10-21 Eastman Kodak Co Rapid processing of photographic materials
DE977335C (en) * 1953-03-16 1965-12-16 Agfa Ag Process for reducing the blue sensitivity of photographic silver halide emulsions
US2774668A (en) * 1953-05-28 1956-12-18 Polaroid Corp Process and product for forming color images from complete dyes
US2965485A (en) * 1957-08-19 1960-12-20 Ilford Ltd Photographic desensitising compounds
US3023102A (en) * 1957-09-24 1962-02-27 Gen Aniline & Film Corp Direct positive photographic emulsion
US2954292A (en) * 1957-10-04 1960-09-27 Ilford Ltd Photographic desensitising compounds
US2947629A (en) * 1958-09-17 1960-08-02 Eastman Kodak Co Nitrosopyrimidine desensitizing compounds and photographic emulsions containing them
US3062651A (en) * 1959-01-21 1962-11-06 Eastman Kodak Co Unhardened, fogged emulsions and method of processing to positive images
US3250618A (en) * 1959-05-13 1966-05-10 Eastman Kodak Co Thermal resensitization of desensitized silver halide photographic emulsions
US3237008A (en) * 1961-01-19 1966-02-22 Eastman Kodak Co Roomlight handling radiographic element including an x-ray sensitive layer overcoated with a dye desensitized silver halide emulsion
US3295969A (en) * 1961-04-12 1967-01-03 Eastman Kodak Co Photographic spirit duplicating process
US3284203A (en) * 1961-05-02 1966-11-08 Fuji Photo Film Co Ltd Direct positive photographic materials
US3189456A (en) * 1961-06-19 1965-06-15 Du Pont Radiation-sensitive emulsions and elements and their preparation
US3278307A (en) * 1961-11-21 1966-10-11 Eastman Kodak Co Photographic process for producing prints stabilized against print-out
US3364026A (en) * 1963-02-14 1968-01-16 Eastman Kodak Co Fogged silver halide direct positive solarizing elements containing merocyanine dyes
US3372031A (en) * 1963-08-28 1968-03-05 Ilford Ltd Direct positive silver halide element with contiguous colloid layer containing developing agent
US3367779A (en) * 1965-01-21 1968-02-06 Fuji Photo Film Co Ltd Direct positive silver halide photographic materials
US3713832A (en) * 1968-07-15 1973-01-30 Fuji Photo Film Co Ltd Solarization type silver halide emulsion containing a halogenated hydroxyphthalein sensitizing dye and a desensitizing compound
US3988156A (en) * 1974-02-19 1976-10-26 Eastman Kodak Company Photographic supports and elements utilizing photobleachable o-nitroarylidene dyes
US3988154A (en) * 1974-02-19 1976-10-26 Eastman Kodak Company Photographic supports and elements utilizing photobleachable omicron-nitroarylidene dyes
US4271263A (en) * 1980-05-15 1981-06-02 Minnesota Mining And Manufacturing Company Thermally developable photosensitive compositions containing acutance agents
US4308379A (en) * 1980-05-15 1981-12-29 Minnesota Mining And Manufacturing Company Acutance agents for use in thermally developable photosensitive compositions
US4404277A (en) * 1981-08-21 1983-09-13 Minnesota Mining And Manufacturing Company Desensitizing dyes for photographic emulsions
EP0754967A1 (en) 1995-07-14 1997-01-22 Agfa-Gevaert N.V. Photographic direct positive material containing a particular stabilizer

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FR989400A (en) 1951-09-07
BE489729A (en)
GB667206A (en) 1952-02-27

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