Light-sensitive silver halide color photographic material

Abstract

 There is disclosed a light-sensitive silver halide color photographic material comprising a support and at least one light-sensitive silver halide emulsion layer applied thereon and containing a photographic coupler which reacts with an oxidized form of a color developing agent to form a dye, characterized in that the silver halide included in said light-sensitive silver halide emulsion layer is composed of a silver halide substantially free from iodine, and grains of said silver halide are distributed therein in a monodisperse state and are contained therein in a proportion of 5 x 10" grains/m² or more, and said photographic coupler is contained in said light-sensitive silver halide emulsion layer so that the amount of said photographic coupler may be 3.5 x 10^-15 gram equivalent or less per grain of said silver halide.

Description

[0001] This invention relates to a light-sensitive silver halide color photographic material in which the utilization of a photographic coupler is improved in order to enable the formation of a high dye image.

[0002] The dye image on the light-sensitive silver halide color photographic material is generally formed by a coupling reaction of a photographic coupler with an oxidized form of a color developing agent produced in reducing, to a silver image, a silver halide latent image which has been formed by exposing the light-sensitive material. With regard to the aforesaid photographic coupler (hereinafter referred to simply as a coupler), there are known the so-called four-equivalent coupler which requires four atoms of silver to form one molecule of a dye and the so-called two-equivalent coupler which requires only two atoms of silver.

[0003] In the light-sensitive color photographic material, there should exist coupler molecules corresponding to dye molecules, which is required to provide its maximum density, per unit area of the silver halide emulsion and silver halide molecules corresponding to a numerical value obtained by multiplying the amount of the coupler by the equivalent number of the coupler. As described in, for example, T. H. James, "Theory of Photographic Process", Chap. 12, Sec. II, Macmillan Co., Ltd. (1977), however, the above-mentioned oxidized form of a color developing agent is involved in a variety of reactions with other additives, in addition to the reaction with the coupler. Therefore, all of the oxidized form of a color developing agent is not utilized to form a color developing dye. For this reason, it is generally necessary that the concentration of the coupler is adjusted to obtain a maximum density of the dye from a certain amount of the silver halide and that the equivalent concentration of the coupler relative to the silver halide is set in accordance with its usage. In the case of a color photographic paper, for example, the amount of the used coupler with respect to the silver halide is generally set to 50 to 70% by equivalent.

[0004] Under such conditions, a percentage of a portion to be exhausted for the formation of the dye image with respect to the total amount of the oxidized form of the color developing agent which is produced in color developing (hereinafter referred to as a coloring efficiency) and a percentage of a portion to be exhausted for the formation of the dye image with respect to the total amount of the used coupler (hereinafter referred to as a coupler utilization efficiency) are merely 45 to 65% and 50 to 95%, respectively.

[0005] Particularly, in cases where 2-pyrazoline-5-one type magenta coupler among the couplers is employed, the coloring efficiency and the coupler utilization efficiency thereof are as low as 40 to 50% and 50 to 60%, respectively.

[0006] An object of this invention is thus to provide a light-sensitive silver halide color photographic material having an improved and enhanced coloring efficiency and coupler utilization efficiency.

[0007] As a result of repeated researches by the inventors of this invention, it have been found that the aforesaid object can be achieved by a light-sensitive silver halide color photographic material comprising a support and at least one light-sensitive silver halide emulsion layer applied thereon and containing a photographic coupler which reacts with an oxidized form of a color developing agent to form a dye, in which the silver halide included in the light-sensitive silver halide emulsion layer is composed of a silver halide substantially free from iodine, and grains of the silver halide are distributed therein in a monodisperse state satisfying the following formula (I) and are included therein in a proportion of 5 x 10¹¹ grains/m² or more, preferably 1.0 x 10¹² or more, and the photographic coupler is included in the light-sensitive silver halide emulsion layer so that the amount of the photographic coupler may be 3.5 x 10-¹⁵ gram equivalent or less per grain of said silver halide:

wherein



wherein ri is the grain diameter of the i-th grains, and ni is the number of the i-th grains.

[0008] Effects of the light-sensitive silver halide color photographic material according to this invention can be obtained by enhancing the supply-source density of an oxidized form of a color developing agent relative to the coupler and by distributing, in a monodisperse state, the silver halide grains in the light-sensitive silver halide emulsion layer to uniformize the concentration of the oxidized form of the color developing agent.

[0009] This invention will be further described in detail as follows:

In the light-sensitive silver halide color photographic material according to this invention, a silver halide substantially free from iodine is employed as the silver halide grains included in the light-sensitive silver halide emulsion layer (hereinafter referred to simply as a silver halide emulsion layer). Therefore, the silver halide which is referred to in this invention means a silver halide including neither, for example, silver iodobromide nor silver chloroiodobromide which are however useful in other photographic arts. In this invention, effective is the silver halide emulsion layer where the grains of the silver halide free from iodine are distributed in a monodisperse state satisfying formula (I) described above and where the silver halide grains are included in the emulsion layer in a proportion of 5 x 10¹¹ grains/m² or more.

[0010] It can be supposed that the effects of this invention may be achieved even by using a multi-disperse emulsion having a wide grain diameter distribution, but when such a multi-disperse silver halide emulsion including 5 x 10¹¹ silver halide grains/m² or more and a coupler are practically employed, the effects of this invention cannot be accomplished even under the same addition conditions as in this invention.

[0011] Reasons for this fact, though not necessarily definite, may be presumed as follows: Being different'in induction period before the start of the development or in a developing speed after the start of the development from each other of the respective silver halide grains, even when exposure is given thereto in an amount necessary for the acquisition of a maximum density, and many silver halide grains being present which do not contribute to the formation of a dye image even under exposure. In consequence, the more uniform the size of the used silver halide grains, the more greater the effect of this invention become, and it is preferred that the grains of the silver halide have such a diameter destribution as defined particularly by formula (I) below:

The silver halide grains according to this invention are those where a numerical value obtained by dividing their standard deviation S by their average grain diameter r is 0.15 or less;

More preferably, the S/r value is not more than 0.10.

[0012] The average grain diameter here referred to means an average diameter of the silver halide grains if they are spherical. When the grains are cubic or in a shape other than the sphere, their projected image is converted into a circular image having the same area, and an average diameter of the circular image is taken as the average grain diameter. When the diameter of an individual silver halide grain is represented with r_i and the number of the grains is represented with ni, the average grain diameter r can be defined by the following formula:

The measurement of the aforesaid grain diameter can be carried out, for the above purpose, by any of various processes which are usable in the art. Typical processes are described in Love-land, "Analytical Method of Grain Diameter" A.S.T.M. Symposium on Light Microscopy, p. 94 - 122 (1955) and Miece and James, "Theory of Photographic Process", Edit. III, Macmillan Co., Ltd., Chap. 2 (1966). The grain diameter may be measured by use of a projected area or a diametrical approximate value of the grain. When the grains are substantially uniform in shape, the grain diameter distribution can be represented fairly accurately by the diameter or projected area thereof.

[0013] The grain diameter distribution may be determined according to the manner which is described in Tribery and Smith, "Experiential Relation between Sensitometry Distribution and Grain Diameter Distribution", The Photographic Journal, Vol. LXXIX, p. 330 - 338 (1949).

[0014] The silver halide grains used in the light-sensitive silver halide color photographic material according to this invention may be of the so-called twinned crystal having an irregular shape such as sphere or plate, or may have a regular shape such as cube, octahedron or tetra- decahedron. Further, it is also possible to employ a mixture of such irregular and regular grains.

[0015] The light-sensitive silver halide color photographic material according to this invention comprises a coupler in an amount of 3.5 x 10^-15 gram equivalent or less, preferably in an amount of 2.0 x 10^-15 gram equivalent per grain of the silver halide used in this invention. The gram equivalent just mentioned of the coupler is here represented with 1/2 mole in connection with a two-equivalent coupler and with 1/4 mole in connection with a four-equivalent coupler.

[0016] The total amount of the coupler in the silver halide emulsion layer, which has a color sensitivity to each wave-length region, of the light-sensitive color photographic material according to this invention may be the amount which can provide a maximum density required for a dye image.

[0017] The amount of the coupler varies depending upon the usage of the light-sensitive color material in which the silver halide emulsion layer is incorporated, therefore any particular limitation is not made on the amount, but it is needless and wasteful to add the coupler in a stoichiometric amount or more. However, in order to heighten the coloring efficiency of the coupler, the amount of the coupler is preferably near to the stoichiometric amount. For example, it is preferred that a two-equivalent coupler is used in an amount of 0.25 to 0.5 mole and a four-equivalent coupler in an amount of 0.125 to 0.25 mole.

[0018] The silver halide emulsion layer used in this invention means a unit emulsion layer having a sensitivity to a light of a specific wavelength and having an ability to form a specific dye image as described above, but the unit layer may compose plural emulsion layers. In such a layer constitution, the number of the silver halide grains in each layer of the plural layers constituting the unit layer, and the total concentration of the coupler therein should satisfy the aforesaid requirements of this invention. As the silver halide emulsion which is comprised in the silver halide emulsion layer according to this invention, an emulsion of silver chloride, silver chlorobromide, silver bromide or the like is preferably employed which is excellent in developability, but, for example, a silver iodobromide emulsion is difficult to obtain the effects of this invention.

[0019] The silver halide grains for the silver halide emulsion used in this invention may be prepared by means of any of the acid process, the neutral process and the ammonia process. Further, a method is also acceptable in which seed grains are prepared in the acid process and are caused to grow up to a desired size in the ammonia process by which a growth rate is accelerated. For the growth of the silver halide grains, it is preferred that pH and pAg of the material in a reactor are controlled and the respective amounts of silver ions and halide ions are simultaneously added thereto in succession corresponding to the growth rate of the silver halide grains, as described in Japanese Provisional Patent Publication No. 48521/1979.

[0020] The silver halide in this invention may be chemically sensitized with an active gelation; a sulphur sensitizer such as allylthiocarbamide, thiourea or cystine; a selenium sensitizer; a reduction sensitizer such as tin (II) salt, thiourea dioxide or polyamine; a noble metal sensitizer such as a gold sensitizer, for example, potassium aurithiocyanate, potassium chloroaurate, 2- aurothio-3-methylbenzothiazolium chloride;_' or a sensitizer of a water-soluble salt of ruthenium, palladium, platinum rhodium or iridium or the like, for example, ammonium chloropalladate, potassium chloroplatinate or sodium chloropalladate (some of these serve as sensitizers or fog restrainers, depending on the amount). These sensitizers may be used alone or in combination thereof (for example, a combination of the gold sensitizer and the sulfur sensitizer, or a combination of the gold sensitizer and selenium sensitizer).

[0021] As mentioned above, the silver halide emulsion layer used in this invention comprises the unit layer having the sensitivity to a light in a specific wavelength region, but the light-sensitive silver halide color photographic material according to this invention may comprise three of the above-mentioned unit layers which are independently sensitive to different wavelength regions.

[0022] These light-sensitive layers may have separately a light sensitivity to wavelength regions of, for example, 400 to 500 nm, 500 to 600 nm and 600 to 700 nm, respectively, and the layers are called a blue-sensitive emulsion layer, a green-sensitive emulsion layer and a red-sensitive emulsion layer, respectively.

[0023] In this invention, an optical sensitization of each silver halide emulsion layer to a desired wavelength region can be accomplished by use of an optical sensitizer, for example, a cyanine dye such as zeromethine dye, monomethine dye, dimethine dye or trimethine dye, or a merocyanine dye in single or in combination thereof (for example, a super- color-sensitization).

[0024] In the thus optically sensitized silver halide emulsion layer according to this invention, there may be included a compound which reacts with an oxidized form of a color developing agent to form a dye, i.e. a coupler.

[0025] In this invention, a yellow coupler, a magenta coupler and a cyan coupler which are heretofore known may be adopted as the aforesaid coupler. Examples of the preferred couplers include a-acylacetanilide yellow coupler, 5-pyrazolone magenta coupler, pyrazolinobenzoimidazole magenta coupler, pyrazolotriazole magenta coupler, indazolone magenta coupler, phenol cyan coupler and naphthol cyan coupler. As the coupler to be used, any type of a two-equivalent coupler, a four-equivalent coupler or a polymeric coupler is acceptable. If the selected coupler is soluble in an alkali, it may be used in the form of an alkaline solution, and if it is soluble in an oil, it is preferred that the same is dissolved and dispersed in a high boiling solvent, and is added to the silver halide emulsion, in accordance with the procedure described in U._S. Patents Nos. 2,322,027, 2,801,170, 2,801,171, 2,272,191 and 2,304,940. In this case, it is also possible to additionally add any other coupler, a hydroquinone derivative, an ultraviolet ray absorber, a discoloration preventing agent or the like, if desired. A mixture of two or more couplers may also be employed.

[0026] Examples of the aforesaid high boiling solvents include di-n-butyl phthalate, tri-cresyl phosphate, dioctyl phthalate and n-nonyl phenol, and as the low boiling solvents there are known, for example, methyl acetate, butyl propionate, cyclohexanol and diethylene glycol monoacetate. These solvents may be used alone or in a combination thereof. The coupler which is thus dissolved in the solvent may be mixed with an aqueous solution containing a hydrophilic binder such as gelatin and an anionic surface active agent such as alkylbenzenesulfonate or alkylnaphthalenesulfonate and/or a nonionic surface active agent such as sorbitan monolaurate. The resultant mixture may be then emulsified in a colloid mill, a supersonic dispersing unit or the like, and may be added to the silver halide emulsion.

[0027] Further, the aforementioned coupler may be dispersed in the photosensitive material in accordance with a latex dispersing method. This latex dispersing method and its effects are described in Japanese Provisional Patent Publications Nos. 74538/1974, 59943/1976 and 32552/1979, and "Research Disclosure", No. 14850, p. 77 - 79 (August, 1976).

[0028] Examples of suitable latexes include homopolymers, copolymers and terpolymers of monomers such as styrene, ethyl acrylate, n-butyl acrylate, n-butyl methacrylate, 2-acetoacetoxyethyl methacrylate, 2-(methacryloyloxy)-ethyltrimethylammonium sulfate, sodium 3-(methacryloyloxy)-propane-l-sulfonate, N-isopropylacrylamide, N-[2-(2-methyl-4-oxopentyl)]acrylamide and 2-acrylamido-2-methylpropane sulfonate.

[0029] In the light-sensitive silver halide color photographic material according to this invention, a combination of the silver halide emulsion layer and the coupler may be set so that the color sensitivity of the emulsion layer and the color of the coloring dye formed with the aid of the coupler which is added to the emulsion layer may lie in the relation of a complementary color, as in the case of the ordinary light-sensitive silver halide color photographic material. Further, the layer and the coupler may take a false color system such as a combination of the magenta coupler and the blue-sensitive emulsion layer, the yellow coupler and the green-sensitive emulsion layer, or the cyan coupler and the red-sensitive emulsion layer. Constitutions of other layers regarding the light-sensitive color photographic material according to this invention or emulsion layers for the constitutions are described in Research Disclosure, _Vol. 176, No. 17643; Vol. 184, No. 18431; Vol. 187, No. 18716 and elsewhere.

[0030] For the purpose of preventing the dye from discoloration due to active rays having a short wavelength, it is advantageous to use ultraviolet ray absorbers such as thiazolidone, benzotriazole and benzophenone compounds together with the coupler in this invention. Particularly, an alone or an additional employment of Tinuvin (available from Ciba-Geigy AG) is effective.

[0031] The hydroquinone derivatives used together with the coupler also include their precursors. Examples of the discoloration preventing agents used together with the coupler include chroman, coumaran and spirochroman compounds and the like.

[0032] The light-sensitive color photographic material according to this invention can form a color image thereon by means of an ordinary color development process after exposure. The basic processes in the negative-positive method include the color development, bleaching and fixing processes. These basic processes can be conducted differently in an independent manner or simultaneously in one step by the use of a processing solution having these functions, instead of two or more treating steps. As examples of the one-step methods, there are a combined color processing method of using a processing solution containing a color developing agent, a ferric salt as a bleaching constituent and a thiosulfate as a fixing constituent, and a combined bleach-fix method of using a processing solution containing an iron (III) complex of ethylenediaminetetraacetic acid as a bleaching constituent and a thiosulfate as a fixing constituent.

[0033] No restriction is particularly put on the processing method of the light-sensitive color photographic material according to this invention, and any method is applicable in this invention. As typical examples of the methods, there are a method comprising color development, bleach-fix, if necessary, washing and stabilization; a method comprising color development, bleaching, fixing, if necessary, washing and stabilization; a method comprising pre-hardening, neutralization, color development, stopping and fixing, washing, bleaching, fixing, washing, post- hardening and washing; a method comprising color development, washing, subsidiary color development, stopping, bleaching, fixing, washing and stabilization; a method comprising halogenation bleaching of the developed silver generated by color development, color development again to increase the amount of a formed dye.

[0034] The color developing agent used to treat the light-sensitive color material according to this invention is an aqueous alkaline solution including the developing agent and at pH 8 or more, preferably at pH 9 to 12. An aromatic primary amine developing agent eligible as the above developing agent means a compound having a primary amino group on the aromatic ring and further having an ability to develop the exposed silver halide, or a precursor for forming such a compound.

[0035] As the aforementioned developing agents, p-phenylenediamines are typical, and preferred examples of them include 4-amino-N,N-diethylaniline, 3-methyl-4-amino-N,N-diethylaniline, 4-amino-N-ethyl-N-S-hydroxyethylaniline, 3-methyl-4-amino-N-ethyl-N-S-hydroxyethylaniline, 3-methyl-4-amino-N-ethyl-N-β-methanesulfonamidoethylaniline, 3-methyl-4-amino-N-ethyl-N-β-methoxyethyl-4-amino-N,N-diethylaniline, 3-methoxy-4-amino-N-ethyl-N-β-hydroxyethylaniline, 3-methoxy-4-amino-N-ethyl-N-β-methoxyethyl- aniline, 3-acetamido-4-amino-N,N-diethylaniline, 4-amino-N,N-dimethylaniline, N-ethyl-N-β-[β-(β-methoxyethoxy)-ethoxy]ethyl-3-methyl-4-aminoaniline, N-ethyl-N-β-(β-methoxyethoxy)ethyl-3-methyl-4-aminoaniline, and their salts such as sulfate, hydrochloride, sulfite, p-toluenesulfonate and the like.

[0036] In Japanese Provisional Patent Publications Nos.64932/1973, 131526/1975, 95849/1976 and Bent et al., "Journal of the American Chemical Society", Vol. 73, p. 3100 - 3125 (1951), typical examples of the developing agents are also enumerated.

[0037] The amount of the aromatic primary amino compound to be used depends on a desired activity level of the developing solution, but in order to elevate the activity, the amount of the compound should be increased. It is generally used in an amount ranging from 0.0002 mole/liter to 0.7 mole/ liter. Further, the compounds may be used in a combination of several kinds thereof in accordance with a use.

[0038] The combinations of the compounds are optionally made in compliance with their uses, but there are, for example, a combination of 3-methyl-4-amino-N,N-diethylaniline and 3-methyl-4-amino-N-ethyl-N-β-methansulfonamidoethylaniline, and a combination of 3-methyl-4-amino-N-ethyl-N-β-methansulfonamidoethylaniline and 3-methyl-4-amino-N-ethyl-N-β-hydroxyethylaniline.

[0039] The color developing solution used in this invention may further contain optionally a variety of components which are usually added thereto, for example, an alkali agent such as sodium hydroxide or sodium carbonate, an alkali metal sulfite, an alkali metal bisulfite, an alkali metal thiocyanate, an alkali metal halide, benzyl alcohol, a water softening agent, a thickening agent and a development accelerator.

[0040] As additives to be added to the color developing solution, in addition to the just mentioned substances, there are compounds for a quick processing solution, for example, bromides such as potassium bromide and ammonium bromide, alkali iodide, nitrobenzoimidazole, mercaptobenzoimidazole, 5-methylbenzotriazole and 1-phenyl-5-mercaptotetrazole, stain preventing agents, sludge preventing agents, preservatives, interlayer effect accelerators, chelating agents and the like.

[0041] As bleaching agents in the bleaching solutions or in the bleach-fix baths, there are known substances in which metal ions of iron, cobalt, copper and the like are coordinated with organic acids of aminopolycarboxylic acid, oxalic acid, citric acid and the like. Typical examples of the aminopolycarboxylic acids mentioned above include:

Ethylenediaminetetraacetic acid,

diethylenetriaminepentaacetic acid, propylenediaminetetraacetic acid,

nitrilotriacetic acid,

iminodiacetic acid,

ethyletherdiaminetetraacetic acid, ethylenediaminetetrapropionic acid,

disodium ethylenediaminetetraacetate,

pentasodium diethylenetriaminepentaacetate, and sodium nitrilotriacetate.

[0042] The bleaching solution may contain a variety of additives together with the aforesaid bleaching agent. When the bleach-fix bath is employed in the bleaching process, there may be applied a solution containing, besides the bleaching agent, a silver halide fixing agent of a thiosulfate, a thiocyanate, a thiourea or the like. Further, the bleach-fix bath may contain a halide such as potassium bromide. Furthermore, as in the case of the aforementioned bleaching solution, there may be contained, in the bleach-fix bath, a variety of additives, for example, a pH buffering agent, a brightening agent, an anti-foaming agent, a surface active agent, a preservative, a chelating agent, a stabilizer, an organic solvent and the like.

[0043] The silver halide fixing agents used in this invention are compounds, as used in a usual fixing treatment, for forming water-soluble silver salts through the reaction with silver halides, which compounds include, for example, sodium thiosulfate, ammonium thiosulfate, potassium thiocyanate, sodium thiocyanate, thioureas and thioethers. The fixing solution comprising the aforementioned component may be incorporated with a variety of additives, as required, for example, a pH buffering agent such as boric acid, sodium hydroxide, sodium bicarbonate, acetic acid, sodium acetate or the like, in a single or a combined form of two or more kinds thereof.

[0044] In addition to the aforesaid additives, the fixing solution may contain, for example, a brightening agent, an anti-foaming agent, a surface active agent, a preservative, a chelating agent, a stabilizer, an organic solvent and the like, and if desired, a conventional fixing accelerator may be further added thereto at will.

[0045] This invention will be described with reference to the following examples. It is to be understood, however, that these examples only typify this invention and are not to be regarded as limiting in any way.

EXAMPLE 1

[0046] Monodisperse emulsions 1, 3 and 5 containing cubic silver halide grains which were set forth in Table 1 were prepared according to a control double process while pAg was maintained at 5.0. To each emulsion were added 50 mg of a sensitizing dye (compound A defined below) and 10 mg of a stabilizer (compound B defined below) per mole of silver, and then were further added 5 mg of sodium thiosulfate and 40 mg of potassium thiocyanate per mole of silver, and the resultant mixture was ripened at 50°C for 100 minutes to prepare a green-sensitive silver chlorobromide emulsion. Next, separately from the above, 2.5 g of a magenta coupler (compound C defined below) was dissolved in a mixed solution of 2.5 mℓ of dibutyl phthalate and 7.5 mi of ethyl acetate under heating conditions at 60°C, and the resultant solution was added to 70 mi of an aqueous solution at 40°C which contains 3.5 g of gelatin and 0.25 g of sodium dodecylbenzenesulfonate, and the mixture was then vigorously stirred and dispersed by means of a homogenizer to prepare an emulsified dispersion of the coupler.

[0047] The thus obtained emulsified dispersion of the coupler was added to the already prepared green-sensitive silver chlorobromide emulsion, and 10 mℓ of a 3% methanol solution of 1,3,5-triacryloyl-hexahydro-S-triazine was then added thereto as a hardening agent. The resultant mixture had its last pH adjusted to 6.2, and was applied to polyester bases in such a way that the amounts of the silver, the gelatin and the magenta coupler were 0.3 g/m², 1.7 g/m² and 0.41 g/m² (80% of the stoichiometric amount), respectively, in order to obtain samples 1, 3 and 5.

Sensitizing dye (compound A)

Stabilizer (compound B)

Magenta coupler (compound C)

[0048] Further, a mixture previously prepared by mixing an aqueous gelatin solution with an excessive halide was introduced into a reactor maintained at 60°C in a gravity-drop manner to obtain poly-disperse emulsions 2, 4 and 6 which were set forth in Table 1 below. Similarly to the above, there were added, to the obtained respective emulsions, the sensitizing dye, the stabilizer, the sodium thiosulfate and the potassium thiocyanate, followed by ripening to prepare the green-sensitive silver chlorobromide emulsion.

[0049] The same emulsified dispersion of the coupler and hardening agent solution as mentioned above were mixed with each of emulsions 2, 4 and 6 above, and the resultant mixture had its last pH adjusted to 6.2 and was applied to polyester bases in such a way that the amounts of the silver, the gelatin and the magenta coupler were 0.3 g/m², 1.7 g/m² and 0.41 g/m² (80% of the stoichiometric amount), respectively, in order to prepare samples 2, 4 and 6.

Each sample above was exposed to a green light through an optical wedge and was subjected to the following treatments, and measurements were successively carried out.

[0050] [Measurement of silver amount]

[0051] [Measurement of color density]

[Stop solution]

[0052] 2% aqueous acetic acid solution

[Fixing solution]

[0053] 

[0054] The pH value was adjusted to 6.0 with acetic acid.

[Bleach-fix bath]

[0055] 

TABLE 2 below exhibits the amount of the developed silver and the density of the magenta dye image at a maximum density portion on each sample above.

As TABLE 2 indicates, samples 1, 3 and 5 according to this invention are higher in the density of the dyes which were formed from the developed silver per unit area and are also higher in the coloring efficiency, as compared with samples 2, 4 and 6 not according to this invention which satisfies the requirements of this invention except that they are not monodisperse emulsions. Further, it will also be understood from the table that the coupler utilization efficiency is enhanced, in addition to the increase in the amount of the developed silver obtained from the same amount of the silver halide.

EXAMPLE 2

[0056] The same procedure as in Example 1 was repeated to prepare silver iodobromide emulsions 7 and 8 having components and properties exhibited in TABLE 3 below.

In this example, emulsions 7 and 8 just described and emulsions 3 and 4 prepared in Example 1 were employed. Instead of the sensitizing dye, a yellow coupler (compound D defined below) was added to each of the four emulsions, and application was carried out in all the same manner as in Example 1 so that amounts of the silver, the gelatin and the yellow coupler may be 0.3 g/m², 1.7 g/m² and 0.885 g/m² (80% of stoichiometric amount), respectively, in order to prepare samples 7, 8, 9 and 10.

[0057] Each sample above was exposed to a blue light through an optical wedge and was subjected to the same treatments as in Example 1, and the amount of the developed silver and the density of the yellow dye image at a maximum density portion on each sample were measured. Results obtained are set forth in TABLE 4 below.

Yellow coupler (compound D)

[0058] 



TABLE 4 above indicates that sample 9 according to this invention where the yellow coupler was incorporated into the blue-sensitive silver halide emulsion layer can produce a great amount of the coloring dye per unit amount of the developed silver. On the contrary, in the case of sample 7 which satisfies the requirements of this invention except that the silver iodobromide emulsion is used, the increase in the coloring efficiency is not so noticeable, and the developing speed is also lagging, as compared with sample 9 according to this invention, it is therefore definite that sample 7 is poor in the coupler utilization efficiency. Further, as for samples 8 and 10 unconcerned with this invention which satisfy no requirements of this invention, the coupler utilization efficiency is lower, as seen from the results in TABLE 4.

EXAMPLE 3

[0059] The same procedure as in Example 1 was repeated to prepare cubic silver chlorobromide emulsions (70% of Br and 30% of Cl) which were different in average grain diameter, as exhibited in TABLE 5 below. Afterward, samples 11 to 15 were prepared following the manner of Example 1, except that a sensitizing dye (compound E defined below) and a cyan coupler (compound F defined below) were added to each emulsion, and in such a way that the application amount of the gelatin was 1.7 g/m², and the application amounts of the silver and the cyan coupler were set as shown in TABLE 6 below.

[0060] Each sample thus prepared was exposed to a red light through an optical wedge and was then subjected to the same treatments as in Example 1. The amount of the developed silver and the density of the cyan dye image at a maximum density which were obtained on each sample are set forth in TABLE 6 below.

Sensitizing dye (compound E)

[0061] 

Cyan coupler (compound F)

[0062] 

[0063] As exhibited in TABLE 6, sample 11 according to this invention which contains a red-sensitive silver halide emulsion is more excellent in the coloring efficiency and the coupler utilization efficiency, as compared with samples 12 and 13, unconcerned with this invention, in which the number of the silver halide grains is small, and samples 14 and 15, unconcerned with this invention, in which the equivalent number of the coupler per grain of silver halide is great.

Claims

1. A light-sensitive silver halide color photographic material comprising a support and at least one light-sensitive silver halide emulsion layer applied thereon and containing a photographic coupler which reacts with an oxidized form of a color developing agent to form a dye, characterized in that the silver halide included in said light-sensitive silver halide emulsion layer is composed of a silver halide substantially free from iodine, and grains of said silver halide are distributed therein in a monodisperse state satisfying the following formula (I):

wherein



wherein r_i is the grain diameter of the i-th grains, and n_i is the number of the i-th grains. and are contained therein in a proportion of 5 x 10¹¹ grains/m² or more, and said photographic coupler is contained in said light-sensitive silver halide emulsion layer so that the amount of said photographic coupler may be 3.5 x 10-¹⁵ gram equivalent or less per grain of said silver halide.

2. A light-sensitive silver halide color photographic material according to Claim 1, wherein said silver halide substantially free from iodine is selected from silver bromide, silver chloride and silver chlorobromide.

3. A light-sensitive silver halide color photographic material according to Claim 1, wherein the S/r value is not more than 0.1.

4. A light-sensitive silver halide color photographic material according to Claim 1, wherein said silver halide are contained in a proportion of 1.0 x 10¹² grains/m² or more.

5. A light-sensitive silver halide color photographic material according to Claim 1, wherein the amount of said photographic coupler is in the range of 0.25 to 0.5 mole per one mole of the silver halide when the coupler is a two-equivalent coupler, and the amount of said photographic coupler is in the range of 0.125 to 0.25 mole per one mole of the silver halide when the coupler is a four-equivalent coupler.

6. A light-sensitive silver halide color photographic material according to Claim 1, wherein the amount of said photographic coupler is 2.0 x 10-¹⁵ gram equivalent or less.

7. A light-sensitive silver halide color photographic material according to Claim 1, wherein said coupler is contained in said light-sensitive silver halide emulsion layer so that the amount of said coupler may stoichiometrically be 100% or less of said silver halide.