Light-sensitive Super-sensitized Silver Halide Photographic Emulsions

Abstract

A light-sensitive silver halide photographic emulsion having a combination of two types of dyes to enable superior additivity sensitization of the emulsion, said emulsion comprising at least one compound of the general formula (I), ##SPC1## where R.sub.1 and R.sub.2 are individually an alkyl, hydroxyalkyl, carboxalkyl or sulfoalkyl group; R.sub.3 is an alkyl group; Y.sub.1 and Y.sub.2 are individually a sulfur or selenium atom; V.sub.1, V.sub.2, V.sub.3 and V.sub.4 are individually a hydrogen atom, an alkyl group, an alkoxyl group or a halogen atom, or V.sub.1 and V.sub.2 or V.sub.3 and V.sub.4 may bond to each other to form a benzene ring; X is an anion; and m is 0 or 1, and at least one compound of the general formula (II), ##SPC2## wherein R.sub.4 and R.sub.5 are individually an alkyl, hydroxyalkyl, carboxyalkyl or sulfoalkyl group or an aryl group; Z is a non-metallic atom grouping necessary to complete a heterocyclic ring, which is a benzoxazole, benzothiazole, benzoselenazole, thiazoline or pyrroline ring; and Q is a non-metallic atom grouping necessary to complete the heterocyclic ring, which is a rhodanine, 2-thiohydantoin or 2-thiooxazolidinedione ring.

Description

This invention relates to a light-sensitive silver halide photographic emulsion.

The sensitive wave length area of a silver halide photographic emulsion is ordinarily an extremely limited short wave length region of ultraviolet rays or blue light. It is well known that the use of a certain class of cyanine dye compound is markedly effective for spectral sensitization of such silver halide emulsion. It is also well known that a combination of the said dye with a certain other sensitizing dye or an organic compound is added to a silver halide emulsion, whereby a sensitivity greater than the total sum of sensitivities of the individual compounds can be imparted to the emulsion. Such effect is called super additivity sensitization, and combinations of many compounds have already been reported. In case such super additivity sensitization method is intended to be applied to a silver halide emulsion, particularly the lith-type emulsion, it is desirable that not only the increase in spectral sensitizing effect but also such requirements as mentioned below are satisfied.

1. The method should not deteriorate the characteristics of the lith-type emulsion which shows extremely high contrast.

2. The method should contribute to the improvement in quality of fine dots without degrading the sharpness of the half tone image.

3. The method should not give dye stains and fog to the photographic film after development.

Further, the method is desired to give such effects to a panchromatic lith-type emulsion, which requires a sensitivity extending to a visible wave length region, particularly a red light-sensitive region, that both the green and blue light-sensitive regions are not desensitized, and a sharp and good dot quality can be displayed by development carried out for a relatively short period of time (2 to 3 minutes).

However, most of the conventional super additivity sensitization methods are directed to usual silver iodobromide emulsions for negative, and a method applicable to high contrast lith-type silver chlorobromide emulsions is substantially nil. There is no method satisfying the aforesaid requirements as far as spectral sensitization extending particularly to the red light-sensitive region is intended.

An object of the present invention is to provide a light-sensitive silver halide photographic material which has been subjected to super additivity sensitization satisfying the aforesaid requirements.

Another object of the invention is to provide a light-sensitive silver halide photographic material which has no detrimental interactions with co-existing photographic additives, and has stable photographic properties even when the emulsion is allowed to stand or a coating of said emulsion on a support is stored over a long period of time.

As the result of extensive studies, we have found that when at least one compound of the belowmentioned general formula (I) is added to a silver halide emulsion in combination with at least one compound of the below-mentioned general formula (II), not only the spectral sensitizing effect is greatly increased but also the aforesaid requirements are satisfied.

General Formula (I): ##SPC3##

wherein R.sub.1 and R.sub.2 are individually an alkyl group or a substituted alkyl group such as hydroxyalkyl, carboxyalkyl, sulfoalkyl, etc.; R.sub.3 is an alkyl group; Y.sub.1 and Y.sub.2 are individually a sulfur or selenium atom; V.sub.1, V.sub.2, V.sub.3 and V.sub.4 are individually a hydrogen atom, an alkyl group, an alkoxyl group or a halogen atom, provided that V.sub.1 and V.sub.2 or V.sub.3 and V.sub.4 may bond to each other to form a benzene ring; X is an anion; and m is 0 or 1.

General Formula (II): ##SPC4##

wherein R.sub.4 and R.sub.5 are individually an alkyl group, a substituted alkyl group such as hydroxyalkyl, carboxalkyl, sulfoalkyl, etc., or an aryl group; Z is a non-metallic atom grouping necessary to complete the heterocyclic ring, which is a benzoxazole, benzothiazole, benzoselenazole, thiazoline or pyrroline ring; and Q is a non-metallic atom grouping necessary to complete the heterocyclic ring, which is a rhodanine, 2-thiohydantoin or 2-thiooxazolidinedione ring.

In the above formulas, the alkyl group and the alkoxy group indicate a lower alkyl group and a lower alkoxyl group both having one to two carbon atoms, and preferable as the substituted alkyl group is, for example, a .beta.-hydroxyethyl, carboxymethyl, .beta.-carboxyethyl, .beta.-sulfoethyl, .gamma.-sulfopropyl or .delta.-sulfobutyl group.

The compound of the aforesaid general formula (I) is a thia- or selena-carbocyanine dye, and the compound of the aforesaid general formula (II) is a dimethine-merocyanine dye. When these sensitizing dyes according to the present invention are used in combination with each other, there is obtained a mixed maximum sensitivity value which is different from maximum sensitivity values attained when the individual dyes are used singly, whereby optimum red and green sensitivities can be imparted to silver halide emulsions. That is, due to synergistic effect derived from specific combination of said compounds, the spectral sensitization is markedly enhanced over the red and green light region. Particularly when the combination is applied to a lith-type emulsion, which is used in a photographic material to be developed with an aldehyde-containing lith-developer (infections developer) containing hydroquinone as developing agent, there is attained such characteristic that a sharp dot image which is extremely high in contrast can be formed.

Concrete examples of the compounds represented by the aforesaid general formulas (I) and (II) are enumerated below, but compounds usable in the present invention are not limited to these.

By the way, the dye of the general formula (I) can be easily synthesized according to any of the processes disclosed in U.S. Pat. Nos. 2,450,400 and 2,213,238, and British Patent Specification No. 742,112, and the dye of the general formula (II) can be synthesized according to any of the processes disclosed in Japanese Patent Publication Nos. 18,106/71 and 18,108/71, and U.S. Pat. Nos. 2,493,748 and 2,519,001.

Examples of typical compounds of the general formula (I) are as follows: ##SPC5##

Examples of typical compounds of the general formula (II) are as follows: ##SPC6##

A light-sensitive photographic material, which has been subjected according to the present invention to super additivity sensitization by use of the combination of the above-mentioned specific compounds, has such excellent characteristics as mentioned previously and is ideal in sensitivity. Thus, the combination of said compounds can impart excellent properties not only to lith-type light-sensitive materials but also to light-sensitive photographic materials containing silver chloride or silver chlorobromide emulsions.

The sensitizing dyes according to the present invention may be added, to a silver halide emulsion, either in the form of a solution, or individual solutions, in methanol, ethanol or the like organic solvent. These sensitizing dyes may be added to a silver halide emulsion at any time during the step of preparation of the emulsion, but is preferably added after completion of second ripening of the emulsion. The amounts of the dyes to be added vary depending on the kind of silver halide emulsion. Ordinarily, however, the total amount of the dyes of the formulas (I) and (II) is within a wide range of from 1 mg. to 200 mg., and the mixing ratio of the dye of the formula (I) to the dye of the formula (II) is preferably from 1:10 to 10:1 by weight.

The silver halide emulsion used in the present invention may be any of silver chloride, silver chlorobromide, silver bromide, silver iodobromide and silver chloroiodobromide emulsions. These emulsions may have been incorporated with noble metal sensitizers, sulfur sensitizers and the like sensitizers, or with polyalkylene oxide type compounds as contrast-improving agents. Further, the sensitizing dyes according to the present invention may be used in combination with other sensitizing dyes, e.g. cyanine dyes or merocyanine dyes, and may have been incorporated with stabilizers, hardeners, coating aids and the like photographic additives which are used in general.

The above-mentioned silver halide photographic emulsion containing the compounds used in the present invention is coated according to an ordinary procedure on a suitable support such as glass, cellulose triacetate base, polyester base or paper, and then dried to obtain a light-sensitive silver halide photographic material of the present invention.

The present invention is illustrated below with reference to example, but the examples are illustrative and do, of course, not limit the scope of the invention.

EXAMPLE 1

A lith-type silver chlorobromide emulsion containing 20 mole percent of silver bromide was subjected to second ripening according to gold sensitization method, and was equally divided into several portions. To each emulsion were added, either independently or in combination, methanol solutions of the exemplified compounds shown in Table 1. This emulsion was sufficiently stabilized by stirring at about 40.degree.C. for 20 minutes, and then incorporated with a suitable amount of a polyalkylene oxide derivative as a contrast-imparting agent, and with a hardener, a stabilizer and a coating aid. Thereafter, the emulsion was coated on a film base, and then dried to obtain a panchromatic lith-type light-sensitive material.

Samples obtained in the above manner were individually exposed to light of 125 lux (2,660.degree.K) by means of Sensitometer Model KS-VII (manufactured by Konishiroku Photo Industry Co., Ltd.), using Wratten No. 25A as a red filter and Wratten No. 58 as a green filter, and then developed at 20.degree.C. for 3 minutes with a developer of the following composition: Hot water 500 ml. Formaldehyde-sodium sulfite addition product 50 g. Hydroquinone 19 g. Sodium carbonate 80 g. Boric acid 10 g. Potassium bromide 2.2 g. Water to make 1,000 ml.

The results obtained were as set forth in Table 1, in which the relative speed is a value measured by assuming as 100 the red light speed of the exemplified dye (1) and the residual color is a value of density measured by means of a color densitometer.

Table 1 __________________________________________________________________________ Sample Amount of exemplified Relative Relative Residual No. compound added green light red light color (mg/kg emulsion) speed speed __________________________________________________________________________ 1 (1) 60 mg. 30 100 0.04 2 (4) do. 10 120 0.04 3 (10) do. 60 -- 0.02 4 (14) do. 50 -- 0.03 5 (1) 30 mg. + (10) 30 mg. 70 110 0.03 6 (1) do. + (14) do. 60 105 0.03 7 (4) do. + (10) do. 80 130 0.03 8 (4) do. + (14) do. 60 120 0.03 __________________________________________________________________________

From Table 1 and from the drawings shown later, it is understood that the samples containing the combinations of the compounds according to the present invention are more excellent in photographic speeds (for green light and red light) and have been more improved in residual color than the samples containing each of the said compounds.

In the accompanying drawings,

FIG. 1 shows the spectral sensitivity curve of the silver chlorobromide emulsion;

FIG. 2 shows the spectral sensitivity curves of Sample No. 2 (dotted line) and Sample No. 3 (solid line); and

FIG. 3 shows the spectral sensitivity curve of Sample No. 7 according to the present invention in which the compounds (4) and (10) have been used in combination with each other.

EXAMPLE 2

According to the procedures of Example 1, the combinations of exemplified compounds shown in Table 2 were individually added to the same emulsion as in Example 1.

For comparison, control compounds (A) and (S) of the formulas shown below were individually added to the emulsion.

Control compound (A):

1,1'-diethyl-2,2'-cyanine iodide

Control compound (S):

3,3'-diethyl-9-methyl-4,5,4',5'-dibenzothiacarbocyanine iodide

These emulsions were individually coated on a polyester film base to prepare panchromatic lith-type light-sensitive materials, which were then treated in the same manner as in Example 1. The results obtained were as set forth in Table 2, in which the relative speed is a value measured in the same manner as in Example 1; the contrast is represented by an average gradient between the densities 0.5 and 2.0; and the evaluation of dot image is represented by a grade ranging from 1 to 5, assuming as the grade 5 the dot image which is free from fringes and is most sharp in dot. The dot image was evaluated according to a visual evaluation method in which the sample was brought into close contact with a contact screen, exposed to light, and then developed in the same manner as in Example 1, and the resulting dot image was observed by means of a microscope.

Table 2 __________________________________________________________________________ Sample Amount of exemplified Relative Relative Contrast Evaluation No. compound added green red of dot (mg/kg emulsion) light light image speed speed __________________________________________________________________________ 9 (A) 30 mg. + (S) 30 mg. 40 100 6.0 2-3 (Control) 10 (2) do. + (12) do. 70 105 14.0 4 11 (3) do. + (15) do. 60 110 13.5 5 12 (4) do. + (11) do. 75 115 12.0 5 13 (8) do. + (17) do. 70 110 11.5 4 __________________________________________________________________________

As is clear from Table 2, the samples (10) to (13) are quite excellent in every one of speed, contrast and dot property as compared with the control sample. EXAMPLE 3

A process silver chlorobromide emulsion was subjected to second ripening, and was equally divided into several portions after completion of the ripening. To each emulsion was added such combination of exemplified compounds as shown in Table 3. The emulsion was stirred at about 45.degree.C. for 20 minutes to sufficiently stabilize the emulsion, and incorporated with a suitable amount of 4-hydroxy-6-methyl-1,3,3a,7-tetrazaindene and then with a hardener and a coating aid. The thus treated emulsion was coated on a film base and then dried to prepare a sample.

Sample films prepared in the above manner were measured in photographic properties in the cases where they were stored under high temperature and humidity conditions and in the cases were they were incubated spontaneously. The results obtained were as set forth in Table 3, in which the relative speeds are values of green and red light sensitivities in the cases where the samples were developed at 20.degree.C. for 3 minutes by means of a D-11 Developer (Eastman Kodak Co.).

From Table 3, it is understood that the samples according to the present invention are more excellent in both speed and fog than the control sample (A+S), and are not deteriorated in photographic properties even when stored under high temperature and humidity conditions.

Table 3 __________________________________________________________________________ Sample Exemplified Spontaneously Incubated for Incubated for compound incubated for 3 days at 55.degree.C. 3 days at 50.degree.C. No. (mg/kg emulsion) 3 days and 80%RH Relative Relative Relative Relative Relative Relative Fog red green Fog red green Fog red green light light light light light light speed speed speed speed speed speed __________________________________________________________________________ 14 (S) 40 mg. + (A) 20 mg. 0.04 100 40 0.05 90 30 0.05 90 35 15 (3) do. + (13) do. 0.03 110 60 0.04 110 55 0.04 105 60 16 (4) do. + (10) do. 0.03 115 70 0.03 110 65 0.03 115 65 17 (5) do. + (16) do. 0.03 100 60 0.03 105 30 0.03 100 60 __________________________________________________________________________

Claims

1. A light-sensitive silver halide photographic emulsion characterized by containing in combination at least one compound of the general formula (I), ##SPC7##

wherein R.sub.1 and R.sub.2 are individually selected from the group consisting of alkyl, hydroxyalkyl, carboxyalkyl, and sulkoalkyl; R.sub.3 is an alkyl group; Y.sub.1 and Y.sub.2 are individually a sulfur or selenium atom; V.sub.1, V.sub.2, V.sub.3 and V.sub.4 are individually a hydrogen atom, an alkyl group, an alkoxyl group or a halogen atom, or V.sub.1 and V.sub.2 or V.sub.3 and V.sub.4 may bond to each other to form a benzene ring; X is an anion; and m is 0 or 1, and at least one compound of the general formula (II), ##SPC8##

wherein R.sub.4 and R.sub.5 are individually selected from the group consisting of alkyl, hydroxyalkyl, carboxyalkyl, sulfoalkyl, and aryl; Z is a non-metallic atom grouping necessary to complete a heterocyclic ring, which is a benzoxazole, benzothiazole, benzoselenazole, thiazoline or pyrroline ring; and Q is a non-metallic atom grouping necessary to complete the heterocyclic ring, which is a rhodanine, 2-thiohydantoin or

2. A light-sensitive silver halide photographic emulsion as claimed in claim 1, where the compound of the said general formula (I) is a compound selected from the group consisting of ##SPC9##

3. A light-sensitive silver halide photographic emulsion as claimed in claim 1, wherein the compound of the said general formula (II) is a compound selected from the group consisting of ##SPC10##

4. A light-sensitive silver halide photographic emulsion as claimed in claim 1, wherein the compound of the said general formula (I) and the compound of the said general formula (II) are combined at the weight ratio

5. A light-sensitive silver halide photographic emulsion as claimed in claim 1, wherein the total amounts of the compounds of the general formulas (I) and (II) is 1 mg. to 200 mg. per kilogram of the emulsion.

6. A light-sensitive silver halide photographic emulsion as claimed in claim 1, wherein the emulsion is of the lith-type.