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Publication numberUS2541472 A
Publication typeGrant
Publication dateFeb 13, 1951
Filing dateJun 29, 1948
Priority dateJun 29, 1948
Publication numberUS 2541472 A, US 2541472A, US-A-2541472, US2541472 A, US2541472A
InventorsHill George D, Kendall William B
Original AssigneeEastman Kodak Co
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Direct positive emulsion containing desensitizing dye
US 2541472 A
Abstract  available in
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Claims  available in
Description  (OCR text may contain errors)

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

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US2066099 *Jul 16, 1932Dec 29, 1936Agfa Ansco CorpPhotographic emulsion
US2271229 *Nov 10, 1939Jan 27, 1942Eastman Kodak CoFog inhibitor for photographic developers
US2324123 *Jul 8, 1941Jul 13, 1943Eastman Kodak CoFog inhibitor for photographic developers
US2384593 *Aug 6, 1943Sep 11, 1945Eastman Kodak CoAntifoggant
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US2614927 *Jun 1, 1949Oct 21, 1952Eastman Kodak CoRapid processing of photographic materials
US2774668 *May 28, 1953Dec 18, 1956Polaroid CorpProcess and product for forming color images from complete dyes
US2947629 *Sep 17, 1958Aug 2, 1960Eastman Kodak CoNitrosopyrimidine desensitizing compounds and photographic emulsions containing them
US2954292 *Sep 29, 1958Sep 27, 1960Ilford LtdPhotographic desensitising compounds
US2965485 *Sep 10, 1958Dec 20, 1960Ilford LtdPhotographic desensitising compounds
US3023102 *Sep 24, 1957Feb 27, 1962Gen Aniline & Film CorpDirect positive photographic emulsion
US3062651 *Jan 21, 1959Nov 6, 1962Eastman Kodak CoUnhardened, fogged emulsions and method of processing to positive images
US3189456 *Jun 19, 1961Jun 15, 1965Du PontRadiation-sensitive emulsions and elements and their preparation
US3237008 *Jan 19, 1961Feb 22, 1966Eastman Kodak CoRoomlight handling radiographic element including an x-ray sensitive layer overcoated with a dye desensitized silver halide emulsion
US3250618 *Aug 8, 1962May 10, 1966Eastman Kodak CoThermal resensitization of desensitized silver halide photographic emulsions
US3278307 *Nov 21, 1961Oct 11, 1966Eastman Kodak CoPhotographic process for producing prints stabilized against print-out
US3284203 *Mar 8, 1965Nov 8, 1966Fuji Photo Film Co LtdDirect positive photographic materials
US3295969 *Apr 12, 1961Jan 3, 1967Eastman Kodak CoPhotographic spirit duplicating process
US3364026 *Feb 14, 1963Jan 16, 1968Eastman Kodak CoFogged silver halide direct positive solarizing elements containing merocyanine dyes
US3367779 *Jan 21, 1965Feb 6, 1968Fuji Photo Film Co LtdDirect positive silver halide photographic materials
US3372031 *Jul 30, 1964Mar 5, 1968Ilford LtdDirect positive silver halide element with contiguous colloid layer containing developing agent
US3713832 *Jul 15, 1969Jan 30, 1973Fuji Photo Film Co LtdSolarization type silver halide emulsion containing a halogenated hydroxyphthalein sensitizing dye and a desensitizing compound
US3988154 *Feb 3, 1975Oct 26, 1976Eastman Kodak CompanyPhotographic supports and elements utilizing photobleachable omicron-nitroarylidene dyes
US3988156 *Feb 3, 1975Oct 26, 1976Eastman Kodak CompanyPhotographic supports and elements utilizing photobleachable o-nitroarylidene dyes
US4271263 *May 15, 1980Jun 2, 1981Minnesota Mining And Manufacturing CompanyThermally developable photosensitive compositions containing acutance agents
US4308379 *Nov 24, 1980Dec 29, 1981Minnesota Mining And Manufacturing CompanyAcutance agents for use in thermally developable photosensitive compositions
US4404277 *Aug 21, 1981Sep 13, 1983Minnesota Mining And Manufacturing CompanyDesensitizing dyes for photographic emulsions
DE977335C *Mar 17, 1953Dec 16, 1965Agfa AgVerfahren zur Verminderung der Blauempfindlichkeit von photographischen Halogensilberemulsionen
EP0754967A1Jul 14, 1995Jan 22, 1997AGFA-GEVAERT naamloze vennootschapPhotographic direct positive material containing a particular stabilizer
Classifications
U.S. Classification430/597
International ClassificationG03C1/36, G03C1/485
Cooperative ClassificationG03C1/36, G03C1/48592
European ClassificationG03C1/485V, G03C1/36