US3832189A

US3832189A - Silver halide photographic supersensitized emulsions

Info

Publication number: US3832189A
Application number: US00309531A
Authority: US
Inventors: T Ikeda; A Sato; A Ogawa; K Shiba; M Hinata
Original assignee: Fuji Photo Film Co Ltd
Current assignee: Fujifilm Holdings Corp
Priority date: 1971-11-24
Filing date: 1972-11-24
Publication date: 1974-08-27
Anticipated expiration: 1991-08-27
Also published as: JPS4859828A; CA992790A; DE2257751A1; GB1408398A; FR2161053B1; JPS5514411B2; FR2161053A1

Abstract

A GREEN-SENSTIVE SILVER HALIDE PHOTOGRAPHIC EMULSION FOR COLOR PHOTOGRAPHIC MATERIALS SUPER-SENSITIZED BY A COMBINATION OF A SPECIFIC BENZIMIDAZOLO OXACARBOCYAMINE DYE AND A SPECIFIC OXACARBOCYAMINE DYE.

Description

SILVER HALIDE PHOTOGRAPHIC SUPERS ENSITIZED EMULSIONS Filed Nov. 24. 1972 ll .1. O S 55:52?

WAVELENGTH (nm) United States Patent 3,832,189 SILVER HALIDE PHOTOGRAPHIC SUPER- SENSITIZED EMULSIONS Keisuke Shiba, Masanao Hinata, Akira Sato, Akita Ogawa, and Takashi Ikeda, Kanagawa, Japan, assignors to Fuji Photo Film Co. Ltd., Kanagawa, Japan Filed Nov. 24, 1972, Ser. No. 309,531 Claims priority, application Japan, Nov. 24, 1971, 46 94,266 Int. Cl. G03c 1/14 US. Cl. 96-124 17 Claims ABSTRACT OF THE DISCLOSURE A green-sensitive silver halide photographic emulsion for color photographic materials super-sensitized by a combination of a specific benzimidazolo oxacarbocyanine dye and a specific oxacarbocyanine dye.

BACKGROUND OF THE INVENTION Field of the Invention This invention relates to a spectrally sensitized silver halide photographic emulsion and particularly to a silver halide photographic emulsion supersensitized by a combination of two kinds of sensitizing dyes. More particularly, the invention relates to a supersensitized greensensitive silver halide photographic emulsion for color photographic materials.

Description of the Prior Art Spectral sensitizing techniques or techniques of extending the sensitive wave length region of a silver halide photographic emulsion to the longer wave length side by incorporating a certain cyanine dye in a silver halide photographic emulsion are well known in manufacturing photographic light-sensitive materials.

The spectral sensitization depends upon the chemical structure of the sensitizing dye and various properties of the silver halide emulsion employed, such as the halogen composition, the crystal habit, the crystal system, the silver ion concentration, and the hydrogen ion concentration of the silver halide emulsion. The spectral sensitization is further influenced by photographic additives incorporated in the photographic emulsion, such as a stabilizer, an antifoggant, a wetting agent, a precipitant, a color coupler, etc.

In order to sensitize a definite spectral wave length region of a photographic light-sensitive material, only one kind of sensitizing dye may be used, but in many cases a combination of two or more kinds of sensitizing dyes is used. In the case of employing such a combination of sensitizing dyes, however, it frequently happens that the spectral sensitivity obtained is lower than the sensitivity obtained with the separate use of each of the sensitizing dyes. However, in certain specific cases the spectral sensitivity obtained by such a combination of sensitizing dyes is in an increased super additive manner by employing a combination of a specific sensitizing dye and one or more other specific sensitizing dyes. This phenomenon is known as supersensitization. In such a supersensitization, even if the difference of chemical structure between one sensitizing dye and the other sensitizing dye is slight, the difference in the supersensitizing action between them is frequently quite large. Accordingly, it is known that a combination of sensitizing dyes showing a supersensitizing action can hardly be predicted from the chemical structures thereof alone.

Therefore, in manufacturing photographic emulsions the sensitizing dyes to be used as a combination thereof for supersensitization must be quite carefully selected. The sensitizing dyes used in the case of applying supersensiti- "Ice zation to a silver halide photographic emulsion must also have no harmful co-action with other photographic additives and must have stable photographic properties even during the preservation of photographic light-sensitive materials which contain such dyes.

Some photographic additives, when added to a silver halide photographic emulsion, decrease the spectral sensitivity thereof, and examples of such additives are anionic compounds such as light-absorbing dyes having an anionic group, e.g., a sulfo group; gelatin precipitants having an anionic group, e.g., a sulfo group or carboxyl group; and couplers for color photographic materials. In particular, in the case of a green-sensitive silver halide photographic emulsion for color photographic light-sensitive materials, the change of spectral sensitivity when a. supersensitizing combination of dyes is present with a magenta coupler in the emulsion is important.

Sensitizing dyes are further required to leave no color stain in the photographic light-sensitive materials after development. In general, a sensitizing dye leaves color stains in the image-bearing emulsion layers and/or subsidiary layers (intermediate layers, etc.,) or on the developed and fixed support. Such a harmful influence due to remaining dyes must be corrected by photographic means used in the photo-engraving process, such as a color masking method, and such a color correction is particularly troublesome in the case of a lithographic photographic negative which must have a light grey color. This effect of the remaining dyes is also undersirable in photographic papers since in the case of black and white photographic papers a bright white color is not obtained, and in the case of color photographic papers true color reproduction becomes impossible.

Further, if a yellow or magenta color (or a yellow or magenta dye) dye remains other difliculties occur, e.g., when a part of a finished photograph is exposed to sun light the dyes at that portion are bleached by the sun light, which results in a partially bleached and partially colored image. Consequently, in the case of sensitizing photographic emulsions using sensitizing dyes, it is important to prevent the sensitizing dyes from remaining in the finished photographic paper, lithographic film, or other photographic film or plate.

Moreover, the sensitizing dyes used are also required to give a spectrally sensitive region sufiiciently stable to a safe light which is is used in processing light-sensitive materials. For color photographic light-sensitive materials, in particular color positive films or color papers, a safe light having a maximum percent transmission at about 570-620 m is generally used. Therefore, the long wave length side of the spectrally sensitive region of a greensensitive emulsion layer thus sensitized has usually been sharply cut so that the emulsion layer is stable under the safe light. If this is not done, fog is formed by the action of the safe light to cause stains on the finished photography.

SUMMARY OF THE INVENTION One object of the present invention is to provide a silver halide photographic emulsion supersensitized by a combination of sensitizing dyes which leave less residual dyes or colors in the finished photographic product.

Another object of this invention is to provide a silver halide photographic emulsion supersensitized by a combination of sensitizing dyes, the special sensitivity of which is not reduced during the storage of the silver halide emulsion thus sensitized, as well as during storage of photographic light-sensitive materials having layers of the silver halide emulsions thus sensitized, even when the silver halide emulsion or emulsion layer further contains compounds with one or more anionic group(s), such as a gelatin precipitant (as set forth in US. Pats. 3,138,461, 3,241,-

3 969, 3,366,482, 3,455,694, 3,522,053, British Pat. 1,103,- 420, German Pat. 1,238,370 etc.), an anionic activating agent (as set forth in US. Pats. 3,003,877, 3,026,202, 3,201,252, 3,415,649, etc.) or a color coupler such as a magenta coupler (refer, for example, to P. Glafkidis Photographic Chemistry, vol. II pp. 596-615).

BRIEF DESCRIPTIONOF THE DRAWING The drawing is a graph showing the spectral percent transmission curve of a safe light filter.

DETAILED EXPLANATION OF THE INVENTION The above and other objects of this invention are attained by using the combination of selected benzimidazolo.oxacarbocyanine dyes and selected oxacarbocyanine dyes. The combination of such dyes provides a valuable technical advance in the production of photographic emulsions.

Further objects of this invention will become apparent from the following descriptions of the specification.

The benzimidazolo.oxacarbocyanine dyes used in this invention are represented by the following general formula wherein A and A each represents a hydrogen atom, a halogen atom (e.g., a chlorine atom, a bromine atom, a fluorine atom, an iodine atom), a hydroxyl group, an alkoxyl group (e.g., a methoxy group, an ethoxy group), an amino group (e.g., an amino group, a methylamino group, a dimethylamino group), an acylamido group (e.g., an acetamido group), an acyloxyl group (e.g., an acetoxyl group), a carboalkoxyl group (e.g., a carboethoxy group), an alkoxycarbonylarnino group (e.g., an ethoxycarbonylamino group), a cyano group, a trifiuoromethyl group, an alkoxycarbonyl group (e.g., a methoxycarbonyl group, an ethoxycarbonyl group), an alkyl sulfonyl group (e.g., a methylsulfonyl group), a sulfamyl group, an alkylaminosulfonyl group (e.g., an ethylarninosulfonyl group, a diethylaminosulfonyl group), a morpholinosulfonyl group, a piperidinosulfonyl group, a morpholinocarbonyl group, a carbomoyl group or an alkylcarbonyl group.

A and A each represents a hydrogen atom, a lower alkyl group preferably having up to 4 carbon atoms (e.g., a methyl group, an ethyl group, an n-propyl group), a halogen atom (e.g., a chlorine atom, a bromine atom, a fluorine atom, an iodine atom), an alkoxyl group (e.g., a methoxy group, an ethoxy group), a hydroxyl group, a phenyl group (e.g., a phenyl group, a p-sulfophenyl group), a carboxyl group, an alkoxycarbonyl group (a methoxycarbonyl group, an ethoxycarbonyl group), a cyano group, a trifuoromethyl group, an amino group (e.g., an amino group, a methylamino group, a dimethylamino group), an acyl group (e.g., an acetyl group), an acyloxyl group (e.g., an acetoxyl group), an alkoxycarbonylamino group (e.g., an ethoxycarbonylamino group) or a carboalkoxyl group (e.g., a carboethoxy group).

R, R and R each represents an alkyl group which implies an unsubstituted alkyl group preferably having up to 6 carbon atoms or a substituted alkyl group as is conventionally used as an N-substituent of a sensitizing cyanine dye (e.g., a methyl group, an ethyl group, an npropyl group, a vinyl methyl group), a hydroxyalkyl group (eg, a Z-hydroxyethyl group, 4-hydroxybutyl group), an acetoxyalkyl group (e.g., a 2-acetoxyethyl group, a 3- acetoxypropyl group), an alkoxyalkyl group (e.g., a 2- methoxyetheyl group, a 4-butoxybutyl group), a carboxyalkyl group (e.g., a 2-carboxyethyl group, a 3-carboxypropyl group, a 2-(2-carboxyethoxy) ethyl group), a piii carboxy aralkyl group (e.g., carboxybenzyl group), a sulfoalkyl group (e.g., a Z-sulfoethyl group, a 3-sulfopropyl group, a 3-sulfobutyl group, a 4-sulfobutyl group, a 2- hydroxy-3-sulfopropyl group, a 2-(3-sulfopropoxy)ethyl group, a 2-acetoxy-3-sulfopropyl group, a 3-methoxy-2-(3-sulfopropoxy)propyl group, a 2-(3-sulfopropoxy)ethoxy ethyl group, a 2-hydroXy-3-(3'-sulfopropoxy)propyl group, a p-sulfophenethyl group and a p-sulfobenzyl group) or an aralkyl group (e.g., a benzyl group, a phenylethyl group).

In the above definitions, however, at least one of R and R must be alkyl group having a sulfo group or an alkyl group having a carboxyl group.

X represents an anion such as a chloride ion, a bromide ion, an iodide ion, a thiocyanate ion, a sulfate ion, a perchloride ion, a p-toluenesulfonate ion, a methylsulfate ion or an ethylsulfate ion. Finally, n represents 1 or 2, n being 1 when the dye forms an intramolecular salt (betaine-like structure).

The oxacarbocyanine dyes used in this invention are represented by the following general formula (II) II wherein B B B and B each has the same meaning as A or A in general formula (I) R represents a hydrogen atom, a lower alkyl group preferably having up to 4 carbon atoms (e.g., a methyl group, an ethyl group), or an aryl group (e.g., a phenyl group).

R and R each has the same meaning as R and R in general formula (1), X has the same meaning as X and m has the same meaning as n.

Typical examples of benzimidazolo-oxacarbocyanine dyes as are used in the present invention are shown below for purposes of illustration, but such examples should not be taken to limit the sensitizing dyes used in this invention.

Typical examples of the oxacarbocyanine dye used in this invention are shown below for purposes of illustration. However, the sensitizing dyes used in this invention v are not limited thereto.

II-S

II-ll.

HaCOOC (nnhsor (CHI) as 0 a 0 115 -CH=&CH= COO-CH; N N

l 2) a 0 a (CH2) 3S 0 11 QCCI-Is N t 0 O CH:

CH=J3CH= 113 N C1 2) asQs bnznsoanuj H 0 CH; N N

((EHz) aSOr ((EHz) 350311 The first feature of this invention is that a better supersensitization eifect is obtained using a combination of the benzimidazolo.oxacarbocyanine dye represented by general formula (I) and the oxacarbocyanine dye represented by general formula (II). A markedly high spectral sensitivity is obtained in particular when at least one of the 5-position or the 6-position of the benzimidazolo nucleus in general formula (I) is substituted with a halogen atom and the 5-position of the benzoxazole nucleus in general formula (II) is substituted with a halogen atom or an alkoxyl group.

The second feature of this invention is that when a combination of the sensitizing dyes of this invention is used, the residual color or dyes based on the sensitizing dyes in the processed photographic elements are lessened. Among conventional sensitizing dyes, sensitizing dyes where all of the nitrogen atoms of the heterocyclic ring have been substituted by lower alkyl groups, such as the comparison dyes A and B shown below, tend to leave a large amount of color stain or residual dyes in the processed photosensitive elements. In particular, when the processing time is short, the extent of color stain or residual dyes is large. On the other hand, because in the sensitizing dye represented by general formula (I) used in this invention at least one of R and R which are the substituent groups of the nitrogen atoms of the heterocyclic ring, is an alkyl group having a sulfo group or an alkyl group having a carboxy group. the amount of color stain or residual dye is extremely low. Further, the sensitizing dye of general formula (II) also gives very low color stain. Accordingly, a combination of both types of sensitizing dyes gives a silver halide photographic emulsion having a very low degree of color stain.

The third feature of this invention is that when the combination of the sensitizing dyes of this invention is used together with anionic compounds which usually degrade the spectral sensitizing action, such as a light-absorbing dye having a sulfo group in the chemical structure, a gelatin precipitant having a sulfo group, or a coupler for color photographic elements, the combination of dyes of this invention nonetheless imparts a high sensitivity to the silver halide emulsion.

It is generally believed that a sensitizing dye having a nitrogen atom in a heterocyclic ring which is substituted by an alkyl group having a sulfo group or an alkyl group having a carboxy group gives, when present together with a color coupler, a high sensitivity. However, it has been observed that the sensitizing dyes represented by general formula (I) or the sensitizing dyes represented by general formula (II) have almost no spectral sensitizing effect when these sensitizing dyes are used individually with a color coupler. Therefore, it is quite astonishing that when a combinaton of sensitizing dyes represented by the general formula (I) and general formula (II) is used with a color coupler, a high spectral sensitivity is obtained.

The fourth feature of this invention is that when a combination of the aforesaid senstizing dyes of this invention is used together with a coupler for color photographic elements in a silver halide emulsion the spectral sensitivity of the silver halide emulsion thus sensitized is not substantially reduced during storage of the silver halide emulsion or during storage of photosensitive elements containing such a silver halide emulsion.

The fifth feature of this invention is that by using sensitizing dyes selected from dyes represented by general formulae (I) and (H) a spectral sensitivity stable to a safe light as is usually employed for processing" color positive films and color photographic papers is obtained. supersensitizing combinations of certain kinds of oxacar- I bocyanine dyes and certain kinds of benzimidazolocarbocyanine dyes are known, as disclosed in Japanese Patent Publication No. 2,288/ 1968. The benzimidazolocarboxyanine dye showing the most remarkable supersensitizing effect among the dyes described in the above Japanese Patent has a benzimidazole nucleus substituted at the 5- and 6-positions thereof by a chlorine atom, and the sensitization maximum of the dye is at about 5 80 mg, although this maximum varies somewhat according to the nature of the silver halide emulsion to be employed. Also, a benzimidazolocarbocyanine dye having a benzimidazole nucleus substituted by a chlorine atom at the 5-position has a sensitization maximum at a longer wave length than 570 mu.

Accordingly, in the case of using the aforesaid benzimidazolocarbocyanine dye in which the 5- and 6-position of the benzimidazole nucleus have been substituted by a chlorine atom or in which the 5-position of the benzimidiazole nucleus has been substituted by a chlorine atom in a combination with the oxacarbocyanine dyes described in the above Japanese Patent, such a combination gives severe fog under a safe light as is used for color positive films or color photographic papers, thereby making the use of such a sensitizing combination impractical even when a small amount of the benzimidazolocarbocyanine dye is used, for instance, even when the benzimidazolocarbocyanine dye is used in an amount of A by weight of the amount of the oxacarbocyanine dye.

On the other hand, the benzimidazolo, oxacarbocyanine dye of this invention represented by. the general formula (I) in which the 5- and 6-positions have been substituted by a chlorine atom has its sensitization maximum at about 565 m at the longest, and thus a photographic emulsion containing the dyes of this invention can be safely used under a safe light, i.e., it is stable.

The dyes of general formula (I) are described in, e.g., Japanese Patent Publication No. 14,030/1969 (filed on Jan. 18, 1966), etc., and may be readily synthesized by referring to the descriptions of the above patent or may be synthesized by methods similar to the methods described in that specification.

The dyes of general formula (II) aredescribed in, e.g., iFrench Pat. 1,108,788; U.S. Pat. 2,503,776; and British Pats. 840,223 and 841,119. These sensitizing dyes may be readily synthesized by referring to the descriptions of these patents or may be synthesized by methods similar to those described in the recited patents.

The silver halide used in the photographic emulsion in this invention can be selected from among those commonly used in the photographic arts, for instance, silver chloride, silver bromide, silver iodide, silver chlorobromide, silver iodobromide, or silver chloroiodobromide.

However, the invention is quite advantageously used with a silver halide photographic emulsion containing silver chlorobromide or silver chloroiodobromide. In a silver chlorobromide emulsion, it is particularly advantageous to further add thereto a water-soluble iodide in an amount of, e.g., 0.0050.10 mole per mole of AgCl of the silver halide, or a water-soluble bromide in an amount of, e.g. 0.01-0.20 mole per mole of AgCl of the silver halide in the silver halide emulsion after forming the silver halide. Of course, a mixture of a water-soluble bromide and a water-soluble iodide may be added to the emulsion. It is effective to add the water-soluble halide(s) to the emulsion after substantial completion of chemical ripening and especially preferred to add the halide(s) after completion of chemical ripening, followed by the addition of the sensitizing dyes.

In the present invention a gelatino silver halide emulsion is ordinarily used, but other materials known to be equivalents in the art which have no harmful influence on the photosensitive silver halides, for instance, gelatin derivatives such as phthalated gelatin or malonated gelatin, albumin, agar agar, gum arabic, alginic acid, a watersoluble starch such as dextrin, a hydrophilic resin such as polyvinyl alcohol, polyvinyl pyrrolidone, polyacrylamide, or polystyrene sulphonic acid, or cellulose derivatives such as hydroxyethyl cellulose or carboxymethyl cellulose may be used instead of gelatin, or as mxitures thereof.

A supersensitizing amount of the sensitizing dyes of general formula (I) and general formula (11) may be used in various concentrations thereof, according to the nature of the silver halide emulsion, the concentration of silver halide in the emulsion and the desired effect.

The optimum concentartions of the sensitizing dyes may be determined according to known methods, e.g., by dividing a silver halide emulsion into several portions, incorporating in each portion the sensitizing dyes in different concentrations, and measuring the sensitivity of emulsion. The optimum concentrations of the supersensitizing combination of the dyes in this invention can also be easily determined according to the above method.

The sensitizing dyes may be incorporated in a silver halide emulsion by any manner well known in this art in the present invention. For example, the sensitizing dyes may be directly dispersed in a silver halide emulsion or may be incorporated therein as a solution in pyridine, methanol, ethanol, methyl Cellosolve, acetone or a mixture of such materials, or in water. The organic solvent solution of the sensitizing dyes may, if necessary, be diluted with water. The dissolution of the sensitizing dyes may be conducted using ultrasonic vibrations. Moreover, the methods described in the specifications of Japanese Pats. 8,231/ 1970, 2,389/1969, 27,555/1969, and 22,948/ 1969; German Pat. 1,947,935; and U.S. Pats. 3,485,634, 3,342,605, and 2,912,343, can also be used with success.

The sensitizing dyes may be dissolved separately in suitable solvents and the solutions may be separately added to a silver halide emulsion. Alternatively, the sensitizing dyes may be dissolved separately in the same or different solvents and the solutions may be mixed before the incorporation thereof in the silver halide emulsion. It is necessary to uniformly disperse the dyes throughout the silver halide emulsion prior to coating the emulsion containing the sensitizing dyes on a support such as a glass sheet, a cellulose derivative film, a polyvinyl resin film (such as a polystyrene film or a polyvinyl chloride film), a polyester fihn, a synthetic paper, a baryta coated paper, or a polyolefin-coated paper. The sensitizing dyes may be added to the silver halide emulsion at any time during the preparation of the emulsion, but are preferably added after the completion of the second ripening.

The supersensitizing ratio of the sensitizing dye of general formula (I) to the sensitizing dye of general formula (II) is not limited in this invention, but the preferred ratio of dye (I) to dye (II) is in the range of from about 9/1 to about 1/9 by weight, and is varied according to the desired end use. The amounts of the sensitizing dyes used may be changed according to the nature of each silver halide emulsion and the desired effect. In general, optimum sensitivity is obtained by incorporating each sensitizing dye in an amount of from about 1 10- to about 5 10- moles per gram mole of silver halide. In general, too small or too great an amount of the dye added decreases or does not increase the sensitivity of the emulsion.

The silver halide photographic emulsion of this invention may also be sensitized by any other well known procedure, i.e., by a noble metal sensitizer (see U.S. Pats. 2, 540,085, 2,597,856, 2,597,915, 2,399,083, etc) a sulfur sensitizer (see U.S. Pats. 1,574,944, 2,278,947, 2,440,206, 2,410,689, 3,189,458, 3,415,649, etc.), a reduction sensitizer (see U.S. Pats. 2,518,698, 2,419,974, etc.), or an alkyleneoxide sensitizer, or by combinations thereof. The silver halide emulson may contain, if desired, an antifoggant such as nitrobenzimidazole, or ammonium chloroplatinitc a subilizer such as 4-hydroxo-6-methyl-1,3,3a,7- tetrazaindene, a hardening agent such as formaldehyde, chromalum, 1-hydroxo-3,S-dichlorotriazine soda, glyoxal or dichloroacrolein, a Wetting agent such as saponin, or sodium alkyl benzenesulfonate, a plasticizer, a development accelerator and an air fogging preventor.

Examples of the sulfur sensitizers are allylthiocarbamide, thiourea, sodium thiosulfate and cystin.

Examples of the noble metal sensitizers are potassium chloroaurate, aurousthiosulfate and potassium chloropalladate.

Examples of the reduction sensitizers are tin chloride, phenylhydrazine and reductone.

The color couplers preferably used in this invention are described in the specifications of, e.g., U.S. Pats. 2,600,788 and 2,801,171; British Pat. 904,852; Japanese Pat. 6,031/ 1965; etc.

The following 'known couplers are exemplary of those used in this invention in combination with the sensitizing. dyes of general formulae (I) and (II):

(5) /N=G-NHC OCHzCH C15H37 Q, CCH3 N= CNH C O NHCOGH CmHaa C-CH: H S 03H 0 N: C-NH C O- Q cmooon NHCOH-CH=CHC H 3 fill-CH3 0 0 ONE cmcmcmom oGeunm) (9) sHirG) c1 m o (0 n) on 01 NHCOCHz-O- sHM NH O 0 CHICHQCHj-O s nm 12 on I NHC O-Q a nG) mo nncoon=-o-mm n 01 NHCOCH-CH=CH-Cmfiu H3O mooon @jc ONHCnHn (15) on p c omrcmcrn-Q-rmc 0111135 0 onncmcm-Q-mr c OCHa-CH-CraHss to 0H crno 0 on H33CuCH-HC ONE OCH:

ocmoonrr Halon-C ONH C O OH c ocmc ONE c 0 one ONHQ- NHCO CH-CsH1 (L-QO 51111 -cocmoonn -s 0.N

- CH2CH2CHF Q-cocmoomrO-oom nncocrwo-Q-cmm s nU ( 5O Q-cocmcomr- NHCOCHz-O C5 u( OCH; 5 11) The symbol (t) in the above formulae, where used, in-

Example 1 A series of multi-layer color photographic films were prepared as follows employing the sensitizing dyes shown in Table 1 in the green-sensitive emulsion layer: a blue sensitive gelatino silver iodobromide emulsion (I:Br ratio 1 mol percent: 99 mole percent) layer (100 g. of gelatin and 0.57 mol of Ag per kg. of emulsion) was subjected to sulfur sensitization and gold sensitization by the addition thereto of 2.0 mg of Hypo and 2.0 mg. of potassium tetrachloroaurate (III) per mole of silver halide, and then directly applied to a film support; a silver chlorobromide (Cl:Br ratio 55 mole percent: 45 mole percent) gelatin emulsion g. of gelatin and 0.57 mol of Ag per kg. of emulsion) spectrally sensitized by the following dye in the red region and further subjected to sulfur sensitization and gold sensitization in the same manner as described above was applied to the blue-sensitive emulsionlayer; Red sensitizing dye:

a silver chlorobromide emulsion as described above which was green sensitized was spcctrally sensitized by a combination of dye I-lO heretofore described in an amount of 200 mg. per mole of silver and a dye A or 9-ethyl-3,3- diethyl-S,5'-diphenyloxacarbocyanine bromide, a comparison dye outside the scope of this invention, in an amount of 100 mg. per mole of silver and sensitized by sulfur and gold in the same manner as described above in Example 1 was further applied to the silver halide emulsion layer. The green-sensitive emulsion layer further contained about 5 g./1 kg. of emulsion of the anthraquinone dye having the structure (see the specification of U.S. Pat. No. 2,865,- 752) shown below as a light absorbing dye. Two other multi-layer color photographic films were also prepared in the same manner except employing the super sensitizing combinations of this invention shown in Table 1 instead of the combination described above.

A sample of each color photographic film prepared as above was exposed through an optical wedge to green light from a tungsten source of 2854 K. through a SP-2 filter (trade name, made by Fuji Photo Film Co.) for $4 of a second by means of a sensitometer made by Fuji Photo Film Co. and then subjected to the following processings. The density of the film sample thus processed was measured to determine the green relative sensitivity and the density of contamination.

Irradiation preventing dye:

NBC SH; ONE 0 NHCHZS C Na NtiC SHqCHlk NHCHQSOaNB 1 The composition of the color developer was as follows:

G. Sodium hexametaphosphate 2.0 Sodium sulfite (anhydrous) 4.0 2-amino-5-dlethylnmine toluene monohydrochloride 3.0 Sodium carbonate monohydrate 20.0 Potassium bromide 2.0

Water to make 1 liter.

2 The compositions of the fixing solution and the bleaching solution are also conventional.

The green sensitivity was determined based on the value of log E plotted against 1.0 above fog-density of the Control.

It is seen from Table 1 that the photographic elements containing the combination of sensitizing dye I- and sensitizing dye 11-4 or sensitizing dye II-2 were superior with respect to green relative sensitivity and density of contamination as compared to the photographic element containing the control combination of sensitizing dye I- 10 and sensitizing dye A. The 9-ethyl-3,3'-diethyl-5,5'- diphenyloxacarbocyanine bromide, as compared with the dye of the present invention, is of low sensitivity and produces a high contamination density when the compound is photographically treated.

The density of contamination is the value obtained by measuring the density of the processed sample through a green filter by means of a self-recording densitometer made by Fuji Photo Film Co., Ltd..

Example 2 Samples of single layer color photographic films were prepared using the basic procedure described in Example 1 employing, however, different supersensitizing combinations as shown in Table 2. Each sample was prepared by applying to a film support a silver iodochlorobromide emulsion (100 g. of gelatin and 0.57 mol Ag/kg. of emulsion; I:Br:C1 ratio 1 mole percent:39 mole percentz60 mole percent) containing a dispersion of the pyrazolone magenta coupler (1) hereinbefore set forth in an amount of 800 g. per 1 kg. of emulsion and was subjected to a sulfur sensitization and gold sensitization as described in Example 1. The samples were compared as to extent of contamination and change in sensitivity by allowing them to stand.

In this case, one sample of each series was prepared by immediately applying the silver halide emulsion to the support, while another sample in the series was prepared by applying the silver halide emulsion to the support after allowing the emulsion to stand for 3 hours at 40 C. Each of the samples was exposed and processed as in Example 1. The results of sensitometric and stain or contamination measurements are shown in Table 2. In Table 2 the density of contamination is shown by the value obtained by measuring the density of the processed sample through a green filter by means of a self-recording densitometer made by Fuji Photo Film Co., Ltd. A and B in Table 2 are dyes outside the scope of this invention.

The results shown in Table 2 establish that the silver halide emulsion of this invention has excellent sensitivity as compared to the comparison samples, and that the silver halide emulsion showed less reducton in sensitivity 7 1 6 Example 3 Samples of single layer color photographic elements containing a coupler were prepared in the same basic manner as in Example 2 while employing different supersensitizing combinations as shown in Table 3. The samples were compared with respect to stability to a safe light.

The samples used in this example were prepared by applying a silver chlorobromide emulsion containing a dispersion of the same pyrazolone magenta coupler as was used in Example 2 in the amount which was used in Example 2, which had been subjected to sulfur sensitization and gold sensitization as described. Of each sample, one was exposed for 30 seconds to light passed through a safe light filter and then processed as in Example 1.

On the other hand, another sample was processed as in Example 1 without exposure to the safe light. The density of the sample films thus processed was then measured using a green filter by means of a self-recording densitometer made by Fuji Photo Film Co., Ltd. By comparing these exposed samples to the sample not exposed to the safe light it was found that the samples used in the tests had almost no stains or contamination.

Comparison dye C used in this example was anhydrol,1'diethyl-3,3 -disulfobutyl-5 ,5 ',6,6-tetrachlorobenzimidazolo-carbocyanine hydroxide.

The results are shown in Table 3.

TABLE 3 Green Fog density relative under sate sensitizing dye (mg. per mole of Ag) sensitivity light 0 (20) +II2(300) 89 0. 22 C (30)+II2(300) 0. 42 0. 06 132 0. 06

From the results shown in Table 3, it is clear that when comparison dye C was used in place of sensitizing dye I-l0 or I-17 in the supersensitizing combination, the silver halide emulsion was sensitized spectrally to the longer wave length side, and thus the sample film prepared using such a silver halide emulsion had an extremely low (safety) stability to a safe light.

The supersensitizing etfect obtained from the combination of the supersensitizing dyes according to the present invention will be further explained by the following examples of this invention.

Example 4 A silver chlorobromide emulsion containing 0.57 mol of Ag per kg. of the emulsion (Cl: 55 mol percent, Br: 45 mol percent) prepared in an ordinary manner was divided into several parts and each part of silver halide emulsion was sensitized by the combination of sensitizing dyes shown in Table 4.

The dyes were dissolved in a solvent therefore, such as methanol and water, and the solution added to the silver halide emulsion. The emulsion Was maintained at 40 C. for 10 minutes and then applied to a film support.

The film sample was then dried, exposed through an optical wedge and a Fuji Filter SC-52 (trade name, made by Fuji Photo Film Co., Ltd.) by means of a sensitometer made by .Fuji Photo Film Co., Ltd. and developed in a developing solution having the following composition:

G. Metol 0.31 Anhydrous sodium sulfite 39.6 Hydroquinone a 60 Anhydroussodium carbonate 18.7 Potassium bromide 0.86

Citric acid 0.68 Potassium metabisulfite 1.5

Water added to make 1 liter.

17 A sample film thus developed was fixed in an acid hardening fixing bath having the following formula, rinsed, and dried.

B solution is slowly added to the A solution with stirring. Then, water is poured into the resulting mixture to make the volume 1 liter.

The relative sensitivity and fog of each of the samples thus processed were measured and the results are shown in Table 4 together with the sensitization maximum.

The results of control samples prepared by using the same silver halide emulsion as above but containing only one of the sensitizing dyes and processed in the same Way as above are also shown in Table 4 for the sake of comparison.

As is clear from the results shown in Table 4, by using the supersensitizing combinations of this invention, remarkably higher sensitivities were obtained than in case of using the corresponding dyes individually.

Example 5 After adding the sensitizing dye or dyes shown in Tabl 5 to a silver halide emulsion as in Example 4, an aqueous solution of potassium iodide (6X 10- moles per mol of silver) was added to the emulsion. The resultant silver halide emulsion was maintained at 40 C. for 10 minutes and then applied to a film support. The sample films thus prepared were exposed and processed as in Example 4.

The relative sensitivity and fog of the samples thus processed were measured and the results are shown in Table 5 together with the sensitization maximum.

TABLE 5 Relative Sensitiza- Sample sensitizing dye (mg. sensition maxinumber permole of Ag) tivity Fog mum (m 100 0.05 About 552. 105 0.05 About 556. 135 0.05 Apout 555. 102 0.07 About 561. 100 0.05 About 552. 148 0.05 About 560. 141 0.05 Do. 129 0.08 Do. 100 0.06 About 550. 166 0.05 About 560.

From the above table, it is clear that the sensitivities obtained using the supersensitizing combinations of this inventon were remarkably higher than the cases of using the corresponding sensitizing dyes individually.

While the invention has been described in detail and with reference to specific embodiments thereof, it will be apparent to one skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope thereof.

18 What is claimed is: 1. A silver halide photographic emulsion comprising a supersensitizing amount of at least one benzimidazolo. oxacarbocyanine dye represented by general formula (I') and at least one oxacarbocyanine dye represented by general formula (II) (II) B1 0 R 0 U mat=w 1 v B1 N Iii B i l 2')m-1 wherein A and A each represents a hydrogen atom, a halogen atom, a hydroxyl group, an alkoxyl group, an amino group, an acylamido group, an acyloxyl group, an alkoxycarbonylamino group, a cyano group, a trifluoromethyl group, an alkoxycarbonyl group, an alkylsulfonyl group, a sulfamyl group, an alkylaminosulfonyl group, a morpholinosulfonyl group, a morpholinocarbonyl group, a piperidinosulfonyl group, a carbamoyl group, or an alkylcarbamoyl group; A and A each represents a hydrogen atom, a lower alkyl group, a halogen atom, an alkoxy] group, a hydroxyl group, a phenyl group, a carboxyl group, an alkoxycarbonyl group, a cyano group, a trifiuoromethyl group, an amino group, an acylamido group, an acyl group, an acyloxyl group, an al'koxycarbonyl group, or a carboalkoxyl group; B B B and B, have the same meaning as A and A R, R and R each represents an alkyl group; at least one of R and R being a sulfoalkyl group or a carboxyalkyl group; R represents a hydrogen atom, a lower alkyl group or an aryl group; R and R have the same meaning as R and R X represents an anion; m and n each represents 1 or 2; said dyes forming an intramolecular salt when m and n are 1; and X represents an anion.

Y 2. The silver halide photographic emulsion as set forth in Claim 1 wherein the halogen atom is chlorine, bromine, fluorine or iodine; the alkoxy group is methoxy or ethoxy; the amino group is an amino group, methylamino or dimethylamino; the acylamido group is an acetoamide group; the acyloxyl group isan acetoxy group; the carboalkoxy group is a carboethoxy group; the alkoxycarbonyl amino group is an ethoxycarbonyl amino group; the alkoxycarbonyl group is a methoxycarbonyl or ethoxycarbonyl group; the alkylsulfonyl group is a methylsulfonyl group; the alkylaminosulfonyl group is ethylaminosulfonyl or diethylaminosulfonyl; the lower alkyl group is methyl, ethyl or n-propyl; the phenyl group is phenyl group'or p-sulfophenyl, in each A or A or A and A and wherein the alkyl group is methyl, ethyl group, npropyl, vinylmethyl, hydroxyalkyl, acetoxyalkyl, alkoxyalkyl, alkyl having a carboxy group, alkyl having a sulfo group or aralkyl in each R, R and R or R and R 3. The silver halide photographic emulsion as set forth in Claim 2 wherein the hydroxy alkyl group is Z-hydroxyethyl or 4-hydroxbutyl; the acetoxy alkyl group is 2-acetoxyethyl or 3-acetoxypropyl; the alkoxyalkyl group is 2-methoxyethyl or 4-butoxybutyl; the alkyl group having a carboxy group is 2-carboxyethyl, 3-car-boxypropyl, 2- (2-carboxyethoxy)ethyl or p-carboxybenzyl; the alkyl group having a sulfo group is 2-sulfoethyl, 3-sulfopropyl, 3-sulfobutyl, 4sulfobutyl, 2-hydroxy-3-sulfopropyl, 2-(3- sulfopropoxy)ethyl, 2-acetoxy-3-sulfopropyl, 3-methoxy- 2-(3-sulfopropoxy)pr0pyl, 2-[2-(3-sulfopropoxy)ethoxy] ethyl, 2-hydroxy 3-(3-sulfopropoxy)propyl, sulfophen- 1 9 ethyl or p-sulfobenzyl; and the aralkyl group is benzyl or phenethyl.

4. The silver halide photographic emulsions as set forth in Claim 1 wherein there is present a binder of the emulsion comprising gelatin.

5. The silver halide photographic emulsion as set forth in Claim 1 wherein the ratio by weight of dye (I) to dye (II) is in the range of from about 9/1 to about 1/9.

6. The silver halide photographic emulsion as set forth in Claim 1 wherein the amount of the sensitizing dye added to the emulsion is in the range of from about 1 10 to about 5 X 10' moles per gram-mole halide in the emulsion.

7. The silver halide photographic emulsion as set forth in Claim 1 wherein the silver halide is silver chlorobromide or silver chloromoiodide.

8. The silver halide photographic emulsion as set forth in Claim 7 wherein the silver halide is silver chlorobromide.

9. The silver halide photographic emulsion as set forth in Claim 8 wherein said silver halide emulsion further contains an iodide in an amount of 0.005-0.l mole and/or a bromide in an amount of 0.01-0.20 mol respectively, per mole of silver chloride constituting the silver halide.

10. The silver halide photographic emulsion as set forth in Claim 1 wherein said silver halide photographic emulsion contains a color coupler.

11. The silver halide photographic emulsion as set forth in Claim 10 wherein the color coupler is a magenta coupler.

12. The silver halide photographic emulsion as set forth in Claim 1 wherein said silver halide photographic emulsion contains a light absorbing dye.

13. The silver halide photographic emulsion as set forth in Claim 1 wherein said benzimidazolo.oxacarbocyanine dye represented in general formula (I) is substituted by a halogen atom in at least one of the or 6-positions of the benzimidazole nucleus thereof.

14. The silver halide photographic emulsion as set forth in Claim 1 wherein said oxacarbocyanine dye represented by general formula (II) is substituted by a halogen atom at the 5-position of the benzoxazole nucleus thereof.

A color photographic light-sensitive element comprising a support having thereon a layer of the silver halide photographic emulsion as set forth in Claim 10.

16. The silver halide photographic emulsion containing a supersensitizing amount of the combination selected from the group of and HgCHzSOaH zCHaSOa' (2) I v N O =CH-CH=CH 5 III N (CH :SOSNa CHZGIII-"(FHCH3 S 03" and 2 5 CH-J]: C H- 15 C1 Cl N N JHflgSOzH as 03- I C H CH: CH- (11 -o1 N N lgHs JH S 0 3- and O O CzHs C H 4}: CH

Cl Cl N N (I-I?) is 0 3H (Hz) 3S 0 3' C H=C H-C H:

03 03" 93 03 and O O (llzHs =CH-C=CH Cl Cl N N dmsoH dinso- 9 a a a a -CH=C H-CH= 1 I N 0 on:

( 2) as 03' JzH and O O C2H5 =CH(E=CH N 1 1 5 AHICHQSOQH HzCHzSOa' (R2115 N 0 G1 =C H-QE-CIH- o1 l I) B CtNa JH CH fiZHCH 21 22 and References Cited UNITED STATES PATENTS 0 0,11, 0 3,397,060 8/1968 Schwan et a1. 96-124 l 5 3,580,724 5/1971 Sato et a1. 96-124 H300 3,663,210 5/1972 Sato et a1. 96-124 3 3,713,835 1/1973 Sato et a1. 96137 I (CHQMSOJH (AHMSOS' J. TRAVIS BROWN, Primary Examiner 17. The photographic emulsion of Claim 9 wherein the 10 iodide and/ or bromide are water-soluble. 9684, 100, 137