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Publication numberUS3457078 A
Publication typeGrant
Publication dateJul 22, 1969
Filing dateMar 2, 1965
Priority dateMar 11, 1964
Also published asDE1447577B1
Publication numberUS 3457078 A, US 3457078A, US-A-3457078, US3457078 A, US3457078A
InventorsOskar Riester
Original AssigneeAgfa Ag
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Supersensitized silver halide emulsions
US 3457078 A
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Description  (OCR text may contain errors)

July 22, 1969 o. RIESTER 3,457,078

SUPERSENSITIZED SILVER HALIDE EMULSIONS Filed March 2, 1965 FIG. 1 2

10 5b Ibo 'rs'om 1o 50 :60 750mg INVENTOR.

OSKAR R/ESTER Y [M M QM A r IORNE Y5 United States Patent 3,457,078 SUPERSENSITIZED SILVER HALIDE EMULSIONS Oskar Riester, Leverkusen, Germany, assignor to Agfa Aktiengesellschaft, Leverkusen, Germany, a corporation of Germany Filed Mar. 2, 1965, Ser. No. 436,460 Claims priority, application Germany, Mar. 11, 1964, A 45,450 Int. 'Cl. G03c 1/28 U.S. Cl. 96104 8 Claims ABSTRACT OF THE DISCLOSURE Silver halide emulsions spectrally sensitized with symmetrical or unsymmetrical pentamethine cyanines and their higher vinylene homologues such as heptaor nonamethine cyanines, are supersensitized by further adding relatively large amounts of a mercapto-substituted heterocycle such as an oxazine, oxazole, thiazole, thiodiazole, imidazole or tetrazole, the sensitizing compound further containing an electronegative substituent such as halogen, trifluoromethyl, SO R where R is lower alkyl or aryl, sulfonamide, sulfonic acid, carboxyl, phenyl or a fused benzene ring. Small amounts of the supersensitizer lower sensitivity.

This invention relates to silver halide emulsions which are sensitized by symmetrical and unsymmetrical pentamethine cyanines and their higher vinylene homologues which are simultaneously supersensitized and stabilized by addition of heterocyclic mercapto compounds.

It is known that the sensitivity of silver halide emulsions can be increased by several methods including optical and chemical sensitization. The present invention is concerned primarily with the former type of sensitization. Optical sensitization of silver halide emulsions results in an increase of the optical range of sensitivity and speed. The action of sensitizing dyes is usually influenced by another compound adsorbed to the surface of the silver halide grains. Generally, the result is diminished sensitizing, but certain materials produce a considerable increase in the sensitization, and this is called supersensitization.

While an increase in speed of sensitivity and speed of photographic emulsions is advantageous, the utility of highly sensitive emulsions, in particular of chemically sensitized emulsions is sometimes limited by the fact that certain sensitizers cause marked increases in the fog level of the emulsion. In order to reduce the fog formation it is common practice to add stabilizers or antifoggants to the emulsions. While it may be possible in some instances to control the fog level, many stabilizers in particular heterocyclic mercapto compounds reduce rather severely the speed levels and the supersensitization of the silver halide emulsions. Frequently also the 'y-values of the emulsions are deleteriously affected. It is therefore necessary to employ the smallest possible stabilizingamount, but in which the unfavourable secondary effects are just tolerable. These considerations apply both to the unsensitized photographic layers and also, to a particularly high degree, the sensitized photographic layers, since the sensitizers are displaced by the stabilizers from the surface of the silver halide grains and thus become ineffective.

It is accordingly an object of the invention to provide optically sensitized silver halide emulsions. Another object is to provide silver halide emulsions which contain optical sensitizers showing supersensitization effects. Still another object of the invention is to provide silver halide emulsions which are optically supersensitized and additionally contain stabilizers in order to prevent fog formaice tion and to stabilize the supersensitization effect. Other objects will become apparent from a consideration of the following description and examples.

I now have found that emulsions which are spectrally sensitized with pentamethine, heptamethine and nonamethine cyanines are simultaneously supersensitized and stabilized by addition of a relatively high amount of heterocyclic mercapto compounds which contain one or more electronegative substituents.

The optical sensitizers used according to the invention comprise symmetrical and unsymmetrical pentamethine cyanines and their higher vinylene homologues such as heptaor nonamethine cyanines. These sensitizing dyes are known and described, for example, by F. M. Hamer in Quarterly Reviews 4 (1950), pages 335-339 or by Gotze and Socher in Beihefte zur Angewandte Chemie," 40 (1940), pages 9-13 or in the handbook The Cyanine Dyes and Related Compounds, by F. M. Hamer, published by Interscience Publishers 1964.

Preferred are compounds the methine chain of which is linked to 5- or 6-membered nitrogen-containing heterocyclic rings of the following groups: thiazole, benzthiazole, naphthothiazole, oxazole, benzoxazole, naphthoxazole, naphthoxazine, selenazole, benzselenazole, naphthoselenazole, imidazole, benzimidazole, indoline, pyrrolidine, tetrazole, thiodiazole or quinoline.

The heterocyclic rings may be substituted with radicals including alkyl, preferably lower alkyl groups up to 5 carbon atoms, aryl, preferably phenyl, alkoxy, with preferably up to 5 carbon atoms. The methine chain can also be substituted, for example, with alkyl, particularly lower alkyl up to 6 carbon atoms, such as methyl and ethyl, aryl, preferably phenyl, cycloalkyl such as cyclohexyl or heterocyclic compounds, such as imidazole and thiazole, which can also be substituted with the substituents mentioned hereinbefore.

As known in the art, higher polymethine dyes can under ordinary conditions only be added in relatively small quantities to the silver halide emulsion. Moreover, penta-, heptaor nonamethine cyanines are of limited utility since they do not provide stable sensitization effects. Consequently, it is the more surprising that the otherwise desensitizing heterocyclic mercapto compounds produce in this case a stable supersensitization of considerable degree. It is particularly remarkable that the supersensitizing effect is maintained in the presence of other photographic additives, for example, color couplers. Generally it is known that a supersensitization effect with pentamethine cyanines can also be produced by certain additives such as compounds of the optical brightener type. In these cases, however, the supersensitization is cancelled out in the presence of other ingredients such as color couplers.

It is further known that polymethine dyes with a relatively long methine chain can be easily supersensitized by simple rinsing with water or by treatment with solutions of ammonia, amines or silver salts. This increase in sensitivity is, however, not stable, so that a material treated in this way must be processed in a few weeks or even days. Contrary thereto, the combination with the heterocyclic mercapto compounds according to the present invention provides a stable supersensitization with a concomitant reduction in fogging.

The silver halide emulsions of the invention are also stable with respect to fogging under the conditions of high temperature and humidity occurring for example in tropical climates.

The concentration of the polymethine sensitizing dyes in the emulsion can vary from about 1 to about 30 mg. per liter emulsion. The suitable and most economical concentration for any given emulsion will be apparent to 3 one skilled in the art upon making the tests customary applied in the art of emulsion making.

To prepare gelatine silver halide emulsions sensitized with the polymethine dyes the following procedure is satisfactory:

A quantity of the sensitizing dye is dissolved in a suitable solvent and a volume of this solution is added to about 1 liter of the silver halide gelatine emulsion. With most of the ordinary emulsions 3 to 20 mg. of the sensitizing dye suffice to produce the maximum sensitization.

As stabilizers and supersensitizers are suitable mercapto substituted heterocyclic compounds. Suitable heterocyclic rings are for instance the following: oxazine, oxazole, thiazole, thiodiazole, imidazole or tetrazole. The heterocyclic mercapto compounds must further contain electronegative substituents, such as halogens, preferably chlorine or bromine, trifluoromethyl, sulphonic groupings of the formula SO -R, R representing alkyl, preferably with up to carbon atoms, or aryl, preferably phenyl, sulfonamide radicals which can be substituted by alkyl groups, preferably lower alkyl groups having up to 5 carbon atoms, or aryl groups, preferably phenyl, sulfonic acid, carboxyl groups, phenyl radicals or fused benzene rings.

Particularly utility is exhibited by heterocyclic mercapto compounds which are watersoluble and which are substituted by watersolubilizing groups, such as sulfonic acid, carboxyl or sulfonamide groups in addition to the mercapto group. Especially suitable compounds are the following heterocyclic compounds: oxazine, oxazole, thiazole, thiodiazole, imidazole and tetrazole.

Suitable substances includes the following:

Sodium-Z-mercapto-naphtho-1',8:4,6-oxazine-3- sulfonate Sodium-Z-mercapto-naphtho-3,2:4,5-oxazole-7'- sulfonate Sodium-2-mercapto-4,5-benzobenzoxazole-6- sulfonate Sodium-2-mercapto-5-chlorobenzoxazole-7- sulfonate 2-mercapto-benzoxazole-5-carboxylic acid Z-mercapto-S-(p-chlorophenylamino sulfone)-benzthiazole 2-mercapto-4- (p-carboxy-phenyl -thiadiazo1- ethione- 5 2-mercapto-1-dodecy1 benzimidazole-S-sulfonic acid 2-m'ercapto-l-methyl benzimidazole-S-ethyl sulfone 2-mercapto-l-pheny1 tetrazole Z-mercapto-S-phenyl benzoxazole The effect of the heterocyclic mercapto compounds are illustrated by the attached FIGURES 1 and 2. In those graphs the axis of ordinates represents the sensitivity or speed of the emulsions in steps of the wedge image plotted against the quantity of the heterocyclic mercapto compound in mg. per liter of emulsion as axis of abscisses.

-As already known from silver halide emulsions customarily employed in addition of the usual amounts of a stabilizer such as heterocyclic mercapto compounds cause a considerable decrease of sensitivity. By further addition of the heterocyclic mercapto compound the sensitivity of the emulsion is increased after having passed through a minimum. The curve shown in the accompanying figures illustrated the most unexpected discovery that certain heterocyclic mercapto compounds which at usual concentrations act only as stabilizers and which first reduce the speed of the emulsion act at higher concentrations as supersensitizers. Another unexpected and desirable advantage is the effect that this supersensitization is stable against further additives and at high temperature and humidity.

The concentration of the heterocyclic mercapto compound in the emulsion can vary widely, i.e., from about 30 mg. to about 500 mg. per liter of flowable emulsion. The specific concentration will depend very much on the type of light-sensitive emulsion and the effects desired. Generally the concentration of the heterocyclic mercapto compound is several times the concentration customarily employed if the compounds are used as antifoggants. Preferred are concentrations of 2-l0 times the usual concentrations. With most ordinary silver halide emulsions 250 mg. of heterocyclic mercapto compounds per liter of emulsion suffice to produce the stabilized supersensitization. With highly sensitive emulsions to which customarily no or only some mgs. of stabilizers of the heterocyclic mercapto compound type can be added, somewhat lower concentrations between 30-100 mgs. of the supersensitizer may be sufficient to obtain supersensitization. Preferred are concentrations of between 60-200 mgs. of the heterocyclic mercapto compound.

The optical range of the sensitivity of the supersensitized emulsions is approximately the same the optical sensitivity of the original emulsion. The supersensitization results in an increase of speed.

As light-sensitive silver compounds can be used silver halide, silver bromide, or silver chlorobromides, which may contain a small amount up to 10 mol percent of silver iodide. The silver halide emulsions can be prepared with any hydrophilic colloids. Known to be satisfactory for dispersing silver halides, are for example natural materials, such as gelatine, albumine, alginic acid or derivatives thereof, such as salts particularly of alkali metals, amides or esters and hydrophilic synthetic resins such as polyvinyl alcohol, polyvinyl pyrrolidone, cellulose esters or cellulose ethers, such as carboxymethyl cellulose.

The emulsions stabilized in accordance with the present invention can be chemically sensitized by any of the accepted procedures. The emulsions can be treated with salts of the noble metals such as ruthenium, rhodium, palladium, iridium and platinum. Suitable compounds are well known in the art. The emulsions can also be sensitized with gold salts as described by R. Koslowsky, Z. wiss. Phot. 46, pages 65-72 (1951).

The emulsions can also be chemically sensitized with reducing agents such as stannous salts, polyamines, sulfur compounds, such as described in the US. Patent 1,574,944, polyethylene oxides and the like.

The emulsions may contain another known stabilizer such as mercury compounds, triazoles and azaindenes, such as disclosed by Birr in Z. wiss. Phot. vol. 47 (1952), pages 2-28.

The emulsions may be hardened by any suitable hardener, such as formaldehyde, halogen substituted aliphatic acids such as mucobromic acid.

EXAMPLE 1 10 mg. of bis-(3 ethyl benzthiazole)-pentamethine cyanine perchlorate are dissolved in the ratio 112000 in methanol and added to 1 liter of a gelatino-silver chlorobromide emulsion of medium sensitivity.

After adding a wetting agent such as 30 ml. of a. 7.5 percent aqueous solution of saponin per liter emulsion and hardening agent such as 15 ml. of a 10 percent aqueous formaldehyde solution, 10 g. of a cyan coupler are also added, for example sodium-l-hydroxy-Z-(carboxylic stearyl amide)-naphthalene 4 sulfonate as a 5 percent aqueous solution.

A layer of this emulsion applied to paper shows in the spectrograph an optical sensitization in the deep red with a .maximum at approximately 695 m,u. The material is exposed through a stepped wedge. with a factor of per step in a common sensitometer behind an Agfa 45 red filter which transmits only red light above approximately 610 m and, after development in a color forming developer, this wedge shows 16 steps.

On addition of increasing quantities of sodium-Z-mercapto-naphtho-1,2:4,6 oxazine 3' sulfonate used as stabilizing supersensitizer to several portions of the above emulsion and identical processing the sensitivity initially decreases at 30 mg. per liter of emulsion to 13 steps. The optimum sensitivity of 24 steps is reached with a further increase in quantity to about 120 mg. per liter. The dependence of the number of /=steps on the added quantity of stabilizer in mg. of stabilizer per liter of emulsion is shown in FIGURE 1.

EXAMPLE 2 6 mg. of bis-(3 ethyl benzselenazole)-pentamethine cyanine perchlorate are added in methanolic solution to 1 liter of a gelatine-silver chlorobromide emulsion, such as that used for the production of photographic copy papers. Wetting and hardening agents and g. of the cyan color coupler as described in Example 1 are also added. The above emulsion is then coated onto a paper support and dried. A spectral sensitization is obtained with a maximum at about 717 me.

On addition of sodium 2 mercapto 5 chlorobenzoxazole-7-sulfonate as antifoggant to portions of the emulsion and identical processing, the spectral sensitivity is initially reduced down to a minimum at about mg. per liter of emulsion. On further addition of the stabilizers an optimum is reached at 180' to 200 mg.

The control emulsion which does not contain the stabilizer yields upon exposure through a stepped wedge in a sensitometer as described in Example 1 and after the customary colorphotographic processing a colored wedge with 10 steps. The sample containing the optimum concentration of the stabilizer yields upon identical processing a colored wedge with 20 steps, corresponding to an increase by about 9 times. The dependence of the number of reproduced wedge steps on the added quantity of stabilizer is illustrated in FIGURE 2.

EXAMPLE 3 2 mg. of bis-(3 ethyl benzthiazole) heptamethine cyanine iodide are added to 1 kg. of a silver chlorobromide emulsion of medium sensitivity and the aforementioned additives are also added. The above emulsion is then coated onto a paper support and dried. The resulting light-sensitive layer has a spectral sensitivity with a sensitisation maximum at 810 m The unstabilized emulsion yields after usual exposure through a stepped wedge in a sensitometer and processing with a color-forming developer a wedge image with 7 ste s.

an adding increasing quantities of sodium-Z-mercapto- 5-chlorobenzoxazole-7- sulfonate to the above emulsion and identical processing, the sensitivity initially decreases at 50 mg. per kg. to 3 steps. The sensitivity then rises sharply and reaches the optimum value at about 150 mg. with 16.5 steps. Thus approximately 9 times the sensitivity is obtained in this way.

EXAMPLE 4 An emulsion sensitized with the dye described in Example 1 and provided with the said additives and containing 1 (4' phenoxy 3' sulfonic acid-phenyl)-3 heptadecyl-S-pyrazolone as red color coupler is brought to about 6 times the sensitivity by adding 120 mg. of sodium 2 mercapto-naphtho 1'-8:4,6 oxazine-3- sulfonate.

A similar efiect is obtained if l-hydroxy 2 naphthoic acid-2'-(methyl octadecyl amino) 5' sulfonic acid anilide is used as cyan color coupler. An emulsion sensitized in the same way is increased in sensitivity by about 4 times using 200 mg. of 2 mercapto-benzoxazole-S-carboxylic acid.

EXAMPLE 5 26 mg. of bis-(3-ethyl benzthiazole) 9,11 (2',2-dimethylcyclotrimethylene 1,3) pentamethine cyanine 6 iodide and the said additives are added to 1 kg. of a silver chlorobromide emulsion. The sensitization maximum is at about 693 my and, on addition of sodium-2- mercapto 5 chlorobenzoxazole 7 sulfonate, the sensitization is reduced to less than half at 50-60 mg. per kg. The sensitization increases to twice the original height at an addition of 100420 mg. of the above stabilizer per kg. of emulsion.

EXAMPLE 6 A highly sensitive silver bromide gelatine emulsion containing about 4 mol percent of silver iodide is sensitized with a methanolic solution of 3 mg. of bis-(3-ethyl- S-methyl benzthiazole)-pentamethine cyanide bromide.

The above emulsion is coated onto a transparent support of cellulose acetate and dried.

The resulting light-sensitive material is sensitive to red light with a maximum in the infrared region at about 709 III/L.

After exposure behind a red separation wedge, a sensitivity of 9 /2 steps is obtained. .If 30 mg. per kg. of one of the following stabilizing supersensitizers are added, the following sensitivities are obtained.

Additive: v Steps Without 9.5 2-mercapto-5-chlorobenzoxazole 7 sulfonic acid 12 2-mercapto-4,5-benzobenzoxazole 6 sulfonic acid 12 2mercapto-naphtho-l,8:4,6-oxazine 3 sulfonic acid 13 l-dodecyl-Z-mercapto-benzimidazole 5-sulfonic acid 13.5

EXAMPLE 7 A supported silver chlorobromide gelatine emulsion layer containing the additives described in Example 1 and 3 mg. of bis-(3-ethyl-benzthiazole)-l0-[meso] phenyl pentamethine perchlorate per kg. emulsion shows a sensitization in the deep red with a maximum at about 700 mu.

After exposure in a sensitometer behind a red separation wedge and usual processing a wedge image with 16 steps is obtained. After adding 200 mg. of Z-mercapto-S- chlorobenzoxazole-7-sulfonic acid per kg. of emulsion, the sensitivity rises to 23 steps, that is to say, to 5 times the original value.

EXAMPLE 8 A supported silver chlorobromide gelatine emulsion layer containing the additives of Example 1 and 20 mg. of bis-(1-methyl-3-ethy1 benzimidazole) 10 (2'-[1'- methyl-3'-ethyl-benzimidazolium]-pentamethine) cyanine diodide per kg. emulsion shows a broad spectral sensitivity with a maximum at 560 m After exposure in a sensitometer behind a yellow separation wedge and usual processing a wedge image showing 6 steps is produced. On addition of 200 mg. of 2-mercapto-5-chlorobenzoxazole-7-sulfonate, this speed is increased to 24 steps, i.e. by about 60 times.

EXAMPLE 9 A supported silver chlorobromide gelatine emulsion layer containing 12 mg. of bis-(3-propionic acid benzthiazole)-pentamethine cyanine iodide per kg. of emulsion and containing the additives described in Example 1 shows a sensitization with a maximum at 704 III/1., and a sensitivity of 8 X i-steps behind a red separation wedge and usual processing. On adding 200 mg. of sodium-2-mercapto-naphtho- 3',2:4,S-oxazole-7'-sulfonate, the speed is increased to 20 steps, i.e. by about 16 times.

7 EXAMPLE 10 A supported silver chlorobromide gelatine emulsion layer of medium sensitivity intended for photographic papers, containing 12 mg. of bis-(3-omega-sulfo-propylbenzthiazole)-pentamethine cyanine shows a sensitization with a maximum at 708 mp. and a sensitivity of 15 steps when it is exposed in a sensitometer behind a red separation wedge and processed according to common practice. On adding 200 mg. of sodium 2 mercapto-naphtho- 1',8:4,6-oxazine-3'-sulfonate to a portion of the above emulsion and identical processing, the sensitivity increases to 19 steps, i.e. by about 2 /2 times.

EXAMPLE 11 A supported silver chlorobromide gelatine emulsion layer containing a cyan color coupler, wetting agents and hardening agents as described in Example 1 and 10 mg. of 3-ethyl benzoxazole-3-ethyl-benzthiazole pentamethine cyanine iodide shows a sensitization maximum at 667 mg.

The unstabilized emulsion yields after usual exposure in a sensitometer behind a stepped wedge and processing with a color-forming developer, for instance of the primary aromatic amine type, a wedge image with 17 /2 steps. On adding 200 mg. of sodium-Z-mercapto-7-chlorobenzoxazole-S-sulfonate to another portion of the emulsion which is otherwise identical and with identical processing a wedge image with 23 steps is produced, that is to say, an increase in speed by about 4 times.

EXAMPLE 12 An emulsion sensitized as in Example 1 and provided with the other additives is brought to a sensitivity 4 times higher on addition of 180 mg. of 1-methyl-2-mercapto-5- ethylsulfone benzimidazole. Approximately the same increase is achieved on adding 100 mg. of 2-mercapto-5- phenyl benzoxazole or 45 mg. of 1-phenyl-2-mercapto tetrazole or 60 mg. of 1-methyl-2-mercapto-S-trifluoromethyl benzimidazole.

EXAMPLE 13 6 mg. of bis(3-ethyl-6-methoxybenzthiazole)-pentamethine cyanine ethyl sulfate are added with the previously described additives to 1 kg. of a silver chlorobromide emulsion. The above emulsion is then coated onto a paper support and dried. The sensitivity of the emulsion is increased by 2 /2 times by addition of 90 mg. of 2-mercapto- -(p-chlorophenylaminosulfone)-benzthiazo1e.

EXAMPLE 14 A supported silver chloride gelatine emulsion layer of medium sensitivity, containing the usual wetting agents and hardening agents as described in Example 1 and also containing 3 mg. of bis-(3-ethyl-5,6-benzobenzthiazole)- pentamethine cyanine bromide is exposed behind a stepped wedge in an ordinary sensitometer. The resulting image obtained upon usual processing shows a red sensitivity of 14 steps. An otherwise identical emulsion which however additionally contains 120 mg. of 2-mercapto-5-(p-chlorophenyl aminosulfone)-benzthiazole shows after identical processing an increased sensitivity of 22 /2 steps, i.e. by about 7 times.

EXAMPLE 15 A supported silver chlorobromide gelatine emulsion layer which contains 6 g. of bis-(3-ethyl benzthiazole)- pentamethine perchlorate and 10 g. of sodium-l-hydroxy- Z-(carboxy stearyl-amido)-napthalene-4-sulfonate per kg. emulsion is exposed behind a stepped wedge in an ordinary sensitometer. The resulting image obtained upon usual processing shows a sensitivity of 16 steps behind a red filter.

An otherwise identical emulsion which however additionally contains 250 mg. of 2-mercapto-thiodiazole thione-(S)-4-(phenyl-4-carboxylic acid), shows after identical processing an increased sensitivity of about double its original value, and simultaneously the color fogging is strongly reduced.

Heterocyclic mercapto compounds which can be used in accordance with the invention are described, for example, in the handbook Photographic Chemistry by P. Glafkides vol. 1, pages 374-380, published by Fountain Press, London 195 8.

I claim:

1. A light-sensitive silver halide emulsion optically sensitized by a sensitizing amount of a pentamethine cyanine or heptamethine cyanine dye containing a thiazole, selenazole, imidazole, or oxazole ring, the emulsion also containing a supersensitizing amount of a mercapto-substituted oxazine, oxazole, thiazole, thiodiazole, imidazole, or tetrazole, the mercapto-substituted compound further containing at least one electronegative substituent of the group consisting of halogen, trifiuoromethyl, sulfo, SO R where R is lower alkyl or aryl, sulfonamide, earboxyl, phenyl and a fused benzene ring.

2. The combination of claim 1 in which the mercaptosubstituted material has a Z-mercaptooxazole or thiazole structure.

3. The combination of claim 1 wherein the dye ring is substituted by alkyl containing up to 5 carbon atoms, phenyl or alkoxy having up to 5 carbon atoms.

4. The combination of claim 1 wherein the electronegative substituent is a water solubilizing sulfo, carboxyl or sulfonamide group.

5. The combination of claim 1 wherein the dye is present in an amount from about 3 to 20 mg. per liter emulsion and the heterocyclic mercapto compound is present in an amount between 60 and 200 mg. per liter emulsion.

6. The combination of claim 1 in which the emulsion contains to 250 mg. of the heterocyclic mercapto compound per liter.

7. The combination of claim 1 in which the optical sensitizing dye is a pentamethine cyanine dye.

8. The combination of claim 1 in which the optical sensitizing dye is a heptamethine cyanine dye.

References Cited UNITED STATES PATENTS 2,177,635 10/ 1939 Carroll etal 96-107 2,546,642 3/1951 Koerber et a1. 96104 2,734,900 2/ 1956 Haseltine 96106 3,266,897 8/ 1966 Kennard et al 96-109 3,305,362 2/1967 Riester et a1 96109 2,824,001 2/ 1958 Allen et a1. 96106 1. TRAVIS BROWN, Primary Examiner US. Cl. X.R. 96107, 109

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Referenced by
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US3753719 *Mar 19, 1971Aug 21, 1973Konishiroku Photo IndLight-sensitive color photographic material
US4030927 *Jan 14, 1976Jun 21, 1977Fuji Photo Film Co., Ltd.Supersensitizing combinations of halogen substituted benzotriazoles and cyanine dyes
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US5994051 *Jul 17, 1998Nov 30, 1999Eastman Kodak CompanySilver halide light sensitive emulsion layer having enhanced photographic sensitivity
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US6306570Mar 27, 2000Oct 23, 2001Eastman Kodak CompanySilver halide light sensitive emulsion layer having enhanced photographic sensitivity
US6514682Jun 20, 2001Feb 4, 2003Eastman Kodak CompanySurface treating with formate to sensitize
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Classifications
U.S. Classification430/576, 430/611, 430/584
International ClassificationG03C1/20, G03C1/28
Cooperative ClassificationG03C1/28, G03C1/20
European ClassificationG03C1/20, G03C1/28