JP2006511847A - High bromide content {111} tabular grain emulsion with improved dispersibility - Google Patents

Abstract

The present invention relates to tabular silver halide emulsions useful in the photographic field and in particular to methods for preparing tabular silver halide emulsions. The method of the present invention relates to a method for forming tabular grains, which is carried out in the presence of a compound having preferential adsorption on the {111} crystal face compared to the {100} crystal face. This parameter for preferential adsorption is derived from the modified Kubelka-Munk method.

Description

  The present invention relates to a method for preparing {111} tabular silver halide emulsions useful in the photographic field, particularly {111} tabular silver halide emulsions.

  {111} tabular silver halide grains having parallel twin planes (hereinafter referred to as “{111} tabular grains”) have the following photographic characteristics.

1) Since these particles have a large surface area to volume ratio (hereinafter referred to as “specific surface area”), a large amount of sensitizing dye can be adsorbed on the surface. As a result, these particles have high color sensitization sensitivity compared to their intrinsic sensitivity.
2) When an emulsion containing {111} tabular grains is coated and dried, the grain faces are arranged in parallel with the surface of the support, thereby making the coating layer thin, and thus sharpness is good.
3) If the sensitivity is the same, the amount of silver applied may be less than when using a non- {111} tabular grain emulsion and thus the sensitivity / graininess ratio is high.
4) These particles are highly resistant to natural radiation.

  Because of these many advantages, {111} tabular grains have been used in many photographic materials that have been commercially produced so far. In these photographic products, a high aspect ratio is one of the important features for fully exploiting the advantages of tabular grains. However, tabular grains having a high aspect ratio have a wide distribution of projected area diameters. This is an important drawback of existing tabular grain technology. Therefore, {111} tabular grains have the following disadvantages.

1) These particles cannot be expected to achieve a hard gradation (that is, so-called high gamma) in the characteristic curve.
2) When the population of {111} tabular grains consists of large and small grains, the optimal conditions for chemical sensitization of large grains are different from the optimal conditions for chemical sensitization of small grains, Optimal chemical sensitization cannot be realized.
3) A multilayer structure having an upper layer formed of monodispersed large particles and a lower layer formed of monodispersed small particles makes more effective use of light, and thus has a monolayer having an emulsion coating layer containing both large particles and small particles. It has higher sensitivity than the layer structure. In the case of polydisperse {111} tabular grains, this advantage of allocating different grain sizes to separate layers cannot be exploited.

  In general, {111} tabular grains are formed in three consecutive steps, that is, a nucleation step, an aging step, and a grain growth step. In the nucleation step, a polydisperse mixture of plate “nuclei” and non-plate “nuclei” is prepared. The next ripening step is designed to dissolve all non-tabular grains without reducing the total amount of tabular grains, and the final grain growth has the function of eventually increasing the size of the tabular grains to the desired size. .

  Several attempts have been made to increase the monodispersity of {111} tabular grains. One method is described, for example, in WO 90/1462, JP 53-41414, JP 50-61134, EP 1,014,175 or US Pat. No. 6,214,532. As shown, a special vessel is used for the nucleation step in addition to the ripening and growth steps. However, the use of additional tanks and addition systems is far less desirable from an economic point of view or from a process control perspective and introduces additional sources of process variation.

  Another attempt to improve monodispersity is described, for example, in US Pat. No. 5,147,771-773, US Pat. No. 5,629,142 or US Pat. No. 5,693,459. As shown, by introducing a polymer other than gelatin during nucleation. The disadvantage of using a polymer is that the average aspect ratio of {111} tabular grains is dramatically reduced and the advantages of using {111} tabular grains are reduced.

It can be concluded that increasing the average aspect ratio of {111} tabular grains results in a broader grain size distribution. The current technique requires a technique for preparing an emulsion having {111} tabular grains and having a high aspect ratio and a narrow grain size distribution.

  Several publications mention hydrolyzed gelatin. EP 0,610,796 describes the use of low molecular weight gelatin for cubic silver chloride crystals. Mol refers to the effect of enzymatically hydrolyzed gelatin on the growth of cubic silver chloride crystals in 'Photographic Gelatin', Academic Press Inc, 1972, 207-217. De Brabandere et al., 'Photographic Gelatin II', Academic Press Inc, 1976, 335-346, describe the use of small peptizers obtained by enzymatic treatment of gelatin on cubic crystals. As a result, it is concluded that the particle size distribution is worse.

Experimental data on the effect of hydrolyzed gelatin on the monodispersity of the cubic crystal population is that the cubic crystals have a completely different growth mechanism than the crystals of {111} tabular grains. It should be noted that it does not apply to its use in the process of forming shaped crystal grains. The cubic crystal is surrounded by {100} faces, while the large top and bottom surfaces of {111} tabular grains are {111} faces.
International Publication No. 90/1462 JP 53-41414 JP-A-50-61134 European Patent No. 1,014,175 US Pat. No. 6,214,532 US Pat. No. 5,147,771 US Pat. No. 5,147,772 US Pat. No. 5,147,773 US Pat. No. 5,629,142 US Pat. No. 5,693,459 European Patent No. 0,610,796 Moll, 'Photographic Gelatin', Academic Press Inc, 1972, 207-217 De Brabandere et al, 'Photographic Gelatin II', Academic Press Inc, 1976, 335-346

  One object of the present invention is to provide {111} tabular silver halide emulsions having excellent grain size distribution.

  It is a further object of the present invention to provide {111} tabular silver halide emulsions with excellent grain size distribution without introducing additional process steps.

  Another object of the present invention is to provide a silver halide emulsion having thin {111} tabular crystals having a high aspect ratio and excellent sensitivity and graininess.

  Surprisingly, it has been found that the preferential adsorption of the polymer added in the tabular grain formation process to the {111} face affects the grain size distribution. More precisely, it has been found that the object of the present invention can be achieved by adding a polymer that preferentially adsorbs to the {111} face rather than the {100} face. In addition, it has been found which polymer structures show preferential adsorption to {111} faces over such {100} faces as measured at pH = 9.

  More precisely, the object of the present invention is the presence of a water-soluble polymer compound having a preferential adsorptivity on a {111} crystal plane of -3 or less as measured at pH = 9, combining an aqueous silver salt solution and an aqueous halogen salt solution. This could be achieved by the {111} tabular silver halide emulsion preparation process, under which {111} tabular silver halide grains are formed. This value of preferential adsorption is obtained by subtracting the value for adsorption on the {111} crystal plane from the value for adsorption on the {100} crystal plane, and these values are calculated by T. Tani J. Imag. Sc 29 ( 1985) vol 29,165, and obtained in the presence of the water-soluble polymer compound by the Kubelka-Munk method. This tabular grain formation process includes a nucleation step and an aging step. Most precisely, the water-soluble polymer compound is added during the nucleation step. In one embodiment, the pH during the nucleation step is preferably 6 or higher. Preferably the pH of the nucleation step is maintained during the ripening step.

  The present invention further relates to {111} tabular silver halide emulsions produced by the method described above and having improved monodispersity. Monodispersity is represented by RDA, which is the ratio between the half width of the distribution (unit: nanometer) and the average aspect ratio.

  In yet another aspect, the present invention is a {111} slab obtained using the method according to the present invention, wherein at least 60% of the total projected grain area of the silver halide grains is at least 50% silver bromide content. Relates to a {111} tabular silver halide grain emulsion.

  The invention also relates to a photographic material comprising on a support at least one layer comprising a {111} tabular silver halide emulsion according to the invention.

  The present invention is a {111} tabular high bromide silver halide emulsion wherein at least 60% of the total projected grain area of the silver halide grains has an average aspect ratio of 6 to 40 and a thickness of 0.2 microns. Less than, emulsions that are {111} tabular silver halide grains with improved monodispersity are intended. Preferably such emulsions have a monodispersity, expressed in RDA, of less than 18, more preferably less than 16.

  The term “tabular grain” refers to a grain having two parallel grain faces that are clearly larger than any other grain face. A tabular grain emulsion is an emulsion in which tabular grains account for more than 50% of the total projected grain area.

  The aspect ratio is a value obtained by dividing the diameter of the region where the surface area of each tabular grain is maximum by the thickness of the grain. As used herein, the term “diameter” means the diameter of a circle having an area equal to the projected area of the particle, and is determined by observation with a microscope or an electron microscope. Therefore, an aspect ratio of 8 or more means that the diameter of the circle is 8 times or more the thickness of the particle.

  When the average aspect ratio is high, the polydispersity increases and the gradation of the silver halide emulsion becomes soft. In addition, pressure marks will be produced. On the other hand, if the average aspect ratio is too low, the characteristics of tabular grain emulsions excellent in sensitivity will be reduced.

An example of the aspect ratio measurement method is a replica method, in which the equivalent circular diameter (ECD) and thickness of each particle are read from a photograph of the particle taken with a transmission electron microscope. In this method, the thickness is calculated from the shadow length of the replica.

  The coefficient of variation in grain size can be expressed as a value obtained by dividing the standard deviation of the equivalent circular diameter of the projected area of all silver halide grains by the average diameter of the silver halide grains. However, in this case, since the thickness of the particle is ignored, the relationship between the aspect ratio and the variation in the particle size is not shown. Therefore, monodispersity is better represented by RDA, which is the ratio of the distribution half width (in nanometers) to the average aspect ratio.

  Tabular grains having a high aspect ratio can be formed by various methods. For example, the formation methods described in US Pat. Nos. 5,496,694 and 5,498,516 are applicable to the present invention. In addition, tabular grains having extremely high aspect ratios can be formed using the grain formation methods disclosed in US Pat. Nos. 5,494,789 and 5,503,970. When these methods are used, tabular grains having a high aspect ratio have a disadvantage of high polydispersity.

  In the method of the present invention, the monodispersity is enhanced by the addition of a polymer having preferential adsorption to the {111} face of silver halide grains. Usually, gelatin is used in the process of preparing a silver halide emulsion. In the method of the present invention, the nucleation step is preferably performed in the presence of a water-soluble polymer compound having a preferential adsorption property on the {111} plane as measured at pH = 9, and the polymer is natural gelatin or synthetic gelatin. , Selected from modified gelatin and recombinant gelatin.

  In forming monodisperse tabular grains having a high average aspect ratio, it is important to form small parallel twin nuclei in a short time. In order to form such nuclei, it is desirable to carry out nucleation in the presence of a small amount of gelatin at a low temperature for a short time.

  In the process of the present invention, special low molecular weight gelatin-like polymers are preferred. In one embodiment, the present invention comprises nucleation in the presence of a gelatinous polymer having a molecular weight of less than 50 kilodaltons, most preferably 3-25 kilodaltons.

  In the method of the present invention, in the nucleation step, the water-soluble polymer compound is added simultaneously with the silver salt and the halogen salt, instead of adding the silver salt and the halogen salt to the dispersion medium in which the polymer compound is already present. preferable. Specifically, this can be done by mixing the polymer compound with an aqueous halogen salt solution used for nucleation. This solution is mixed with an aqueous silver salt solution in a nucleation chamber inside a large container. When a special gelatin is used in the method of the present invention, preferably up to 80% of the nucleation peptizer is a special gelatin with {111} preferential adsorption as defined above, and at least the rest of the nucleation peptizer 20% consists of normal gelatin.

  When the polymer compound is a polypeptide, it preferably comprises as the carboxy terminal amino acid an amino acid selected from arginine, lysine, hydroxylysine and histidine. In this case, the nucleation step and preferably the aging step are also preferably performed at a pH of 6 or higher, more preferably higher than 7, most preferably about pH 8-11. A pH higher than 11 can be applied, but is less preferred since hydrolysis of the polypeptide may occur.

A single histidine, arginine or lysine on the N-terminal side but not the C-terminal of the polypeptide does not have the desired effect. The presence of the C-terminal carboxyl group appears to be important for preferential adsorption of the polypeptide on the {111} face of the tabular grains. However, the polypeptides of the present invention are not limited to structures having a C-terminal amino acid (such as histidine, arginine or lysine) containing a free amino group. The C-terminal side or N-terminal side of the polypeptide may also contain two amino acids close to each other, one amino acid (A) having a residue containing an amine group and the other amino acid ( B) has a residue containing a carboxyl group. These amino acids should preferably be no more than 5 amino acids, more preferably no more than 4 amino acids, still more preferably no more than 2 amino acids and most preferably no more than 1 amino acid apart. Both ends of the polypeptide can also include two or more amino acids “A” and / or “B”.
Examples of such a structure include the following.
His-Asp-gelatin, His-Gly-Asp-gelatin (C or N-terminal side),
Arg-Gly-Glu-Pro-His-Asp-gelatin,
Lys-Asp-gelatin-Glu-Arg,
His-Asp-gelatin-Glu-pro-Arg

  The nucleation step is performed in the presence of a polypeptide in which the amino acid “A” is arginine or lysine, preferably at a pH of 7 or more, more preferably at a pH of 8 or more, and even more preferably at a pH of about 8-11.

  Conveniently, the compound is present in the nucleation step in an amount of about 0.01 to 0.2 moles per mole of silver, preferably 0.05 to 0.1 moles per mole of silver.

  Preferred low molecular weight gelatin-like polymers for use in the methods of the present invention include natural gelatin or modified natural gelatin such as oxidized gelatin, phthalated gelatin, trimellitated gelatin, pyromellitic gelatin in the polypeptide chain. It can be prepared by digestion with a specific enzyme such as trypsin that cuts amino acids adjacent to lysine or arginine. Other specific enzymes may be selected from the group comprising acrosin, tryptase, lysyl, endopeptidase, benobin AB, trypsin, and peptidyl-lysine metalloendopeptidase.

  Low molecular weight gelatin-like polymers can also be synthesized by synthetic methods or as described in EP 1,014,176, US Pat. No. 5,773,249 and US Pat. No. 5,496,712 or It can also be prepared using recombinant techniques.

  The preferential adsorptivity to the {111} plane can be expressed as an adsorption parameter, which is calculated by the method described in detail in Example 1. The preferential adsorptivity of the gelatine-like compound of the present invention represented by this parameter is preferably less than −3, more preferably less than −4, and most preferably less than −6.

  When gelatin is sufficiently hydrolyzed with trypsin, a polypeptide having a molecular weight of 6.4 kilodaltons and having a carboxy terminal arginine or lysine and preferential adsorption on the {111} face of {111} tabular grains is obtained.

  It is further envisioned that additional amino acids or polyamino acids including histidine, lysine, hydroxylysine or arginine can be chemically cross-linked to the polypeptide. Methods are described in The Practice of Peptide synthesis, M. Bodansky, A. Bodansky, Springer-Verlag, Berlin 1984 and Solid Phase Peptide synthesis, J. M. Steward, J. D. Young, San Francisco, W. H. Freeman and Company, 1989.

  In this way, the additional amino acid linked to the amine of the amino acid present in the gelatine-like polypeptide can itself have two primary amines available for cross-linking of (poly) amino acids. The structure resulting in such an additional cross-linking site is called a spacer, in this case it has a functional group capable of binding to the primary amine of the gelatin-like polymer and itself has at least two free primary amines. Have. Another example of such a spacer is a dendrite.

  It has been found that the presence of free carboxyl groups is advantageous for the formation of monodisperse {111} tabular silver halide crystals. Gelatin having arginine or lysine at the amino terminal position may be chemically modified in such a way that a free carboxyl group is introduced into the amino terminal region.

  After nucleation, non-twin, single twin, and non-parallel multiple twin nuclei are dissolved by physical ripening during the ripening process step, and only parallel multiple twin nuclei are not dissolved. After this ripening step, the grains are grown by adding supplemental gelatin and then adding soluble silver salt and soluble halide. As supplementary gelatin, normal gelatin or gelatin having an amino group modified with, for example, phthalic acid, trimellitic acid or pyromellitic acid can be used.

  Another convenient way of influencing grain growth is to add silver and halide supply to the silver halide microparticles prepared separately separately or simultaneously in a separate vessel. Is to do by.

  In the grain growth step, it is also important to adjust and optimize the temperature, pH, binder content and pBr of the reaction solution, and the supply rate of silver ions and halogen ions.

  In the present invention, any of silver bromide, silver chlorobromide, silver iodobromide, silver iodochloride and silver chloroiodobromide can be used to form a silver halide emulsion. However, the use of silver iodobromide or silver chloroiodobromide is preferred. When the emulsion grains have faces containing iodide or chloride, these faces may be distributed uniformly within the grains or may be distributed non-uniformly. Other silver salts such as silver thiocyanate, silver sulfide, silver selenide, silver carbonate, silver phosphate, organic acid silver salt may exist as separate grains, or exist as components of silver halide grains. Also good.

  The bromide content in the emulsion is at least 80 mol%, preferably at least 90 mol% of the total halide content.

  A suitable iodide content in the emulsion of the present invention is 1 to 20 mol%, preferably 2 to 15 mol%, more preferably 3 to 10 mol% of the total halide content. If the iodide content is lower than 1 mol%, it is difficult to obtain the effect of enhancing the dye adsorption and the intrinsic sensitivity of the particles, which is not desirable. If the iodide content is higher than 20 mol%, it is also undesirable because it generally reduces the development rate.

  The {111} tabular silver halide crystals may be host crystals having guest crystals grown epitaxially, as described in US Pat. No. 6,337,177. The silver halide tabular grains of the present invention desirably have at least one photographically useful metal ion or complex (hereinafter referred to as “metal (complex) ion”) inside each.

The term “photographically useful metal (complex) ion” refers to a dopant added to the silver halide grains for the purpose of improving the photographic properties of the photosensitive silver halide emulsion. Metal (complex) ions added as dopants act as temporary or permanent traps of electrons or holes in the silver halide crystal, improving sensitivity and contrast, improving reciprocity characteristics, and resistance to damage by pressure Produces beneficial effects such as improvement. Suitable examples of metal ions used to dope the emulsions of the present invention include Groups 1 to 3 such as iron, ruthenium, rhodium, palladium, cadmium, rhenium, osmium, iridium, platinum, chromium, and vanadium. Transition metals and amphoteric metals such as gallium, indium, thallium and lead. When doping emulsion grains, these metal ions are used in the form of complex salts or single salts. In the case of complex ions, it is advantageous to use hexacoordinate halogeno complexes and cyano complexes having halogen ions and cyanide ions as ligands. In addition to these complexes, nitrosyl (NO), thionitrosyl (NS), carbonyl (CO), isocyanate (NCO), thiocyanate (SCN), selenocyanate (SeCN), tellurocyanate (TeCN), two atoms Organic ligands such as nitrogen (N2), azide (N3), bipyridyl, cyclopentadienyl, 1,2-dithiorenyl and imidazolyl can also be used.
Examples of other ligands that can be used in the complex as a dopant include bidentate (eg bipyridyl), tridentate (eg diethylenetriamine), tetradentate (eg triethylenetriamine) hexadentate. Multidentate ligands such as ligands (eg ethylenediaminetetraacetic acid) are included. The coordination number is preferably 6, but may be 4. Furthermore, organic ligands disclosed in US Pat. Nos. 5,457,021, 5,360,712 and 5,462,849 can also be used advantageously. In addition, it is also desirable to incorporate metal ions as oligomers, as disclosed in US Pat. No. 5,024,931.

  What is important when the metal (complex) ions are incorporated into the silver halide grains is that the metal (complex) ions are sized to be incorporated into the lattice of the silver halide grains. Furthermore, in order to dope silver halide, it is essential that a metal (complex) ion and a silver ion or a product from the halogen ion coprecipitate with the silver halide. For coprecipitation, the pKsp (the common logarithm of the reciprocal of the solubility product) of the product composed of metal (complex) ions and silver ions or halogen ions is the silver halide pKsp (silver chloride 9.8, odor It is necessary to be at the same level as silver iodide 12.3 and silver iodide 16.1). Therefore, the pKsp of the compound composed of metal (complex) ions and silver ions or halogen ions is preferably 8-20.

The amount of the above-mentioned metal (complex) ions for doping the silver halide grains is generally 10 ⁻⁹ to 10 ⁻² mol per mol of silver halide. Specifically, metal complexes that provide a temporary shallow electron trap in the sensitization step are used in the range of 10 ⁻⁶ to 10 ⁻² mole per mole of silver halide, while providing a deep electron trap in the sensitization step In the metal complex to be used, it is desirable to use in the range of 10 ⁻⁹ to 10 ⁻⁵ mol per mol of silver halide.

  The content of metal (complex) ions in the emulsion can be confirmed by atomic absorption analysis, polarization Zeeman spectroscopy analysis or ICP analysis. The ligand in the metal complex ion can be confirmed by infrared absorption (particularly FT-IR).

  Incorporation of metal (complex) ions as a dopant in the surface or internal central portion of silver halide grains, or as disclosed in US Pat. Nos. 5,132,203 and 4,997,751. It is a very shallow surface shell (so-called subsurface) that is only deep enough not to expose metal ions. In other words, the position of the dopant is selected according to the intended purpose. Two or more metal ions can also be used as dopants, which may be in the same shell or in separate shells. These compounds may be added in advance by adding the metal salt solution to the halogen aqueous solution or silver salt aqueous solution used for grain formation, or by adding the metal salt solution directly to the grain forming system. Further, silver halide emulsion fine grains doped with metal ions may be added. When the metal salt is dissolved in a suitable solvent such as water, methanol or acetone, hydrogen halide (eg HCl, HBr) thiocyanic acid or a salt thereof, or alkali halide (eg KCl, NaCl, KBr, NaBr) It is desirable to stabilize the solution by adding an aqueous solution. From the same point of view, it is also beneficial to add an acid or alkali depending on the intended purpose.

  When emulsion grains are doped with a metal ion of a cyano complex, cyan may be formed by the reaction of gelatin and the cyano complex to suppress gold sensitization. In such a case, as disclosed in JP-A-6-308653, it is desirable to use a cyano complex in combination with a compound having a function of suppressing the reaction between gelatin and the cyano complex. More specifically, it is desirable to carry out the step of doping emulsion grains with a metal ion of a cyano complex or the subsequent step in the presence of a metal ion such as zinc ion capable of forming a coordinate bond with gelatin.

  Examples of the method for preparing the above-described silver halide emulsion of the present invention and other silver halide emulsions that can be used therewith are shown below.

  The silver halide grains used in the present invention are basically obtained by a known method, for example, P. Glafkides, Chimie et Physique Photographique, Paul Montel (1967), GF Dufin, Photographic Emulsion Chemistry, The Focal Press (1966 ), VL Zelikman, et al., Making and Coating Photographic Emulsion, The Focal Press (1964). More specifically, emulsions can be prepared in various pH ranges, such as acidic, neutral or ammoniacal processes. As for the method of supplying the reactant solution, any of a single jet method, a double jet method and a combination thereof can be used. Furthermore, a so-called control double jet method in which the addition of the reactant solution is controlled so that the pAg value during the reaction is maintained at a desired value can be advantageously used. Furthermore, a method of keeping the pH value during the reaction constant may be used. During grain formation, a method of controlling the solubility of silver halide by changing the temperature, pH, or pAg value of the reaction system can be carried out, but silver halide such as thioether, thiourea, or thiocyanate can be used. A solvent can also be added. Examples of these are described in, for example, Japanese Patent Publication No. 47-11386 (the term “JP-B” used here means an examined Japanese Patent Publication) and Japanese Patent Laid-Open No. 53-144319.

  The preparation of the silver halide grains used in the present invention is generally carried out by changing a solution of a water-soluble silver salt such as silver nitrate and a solution of a water-soluble halide such as alkali halide into an aqueous solution of a water-soluble binder such as gelatin. Implement by feeding in a controlled manner. In the nucleation stage, the binder is a polymer having preferential adsorption on the {111} plane. After the formation of silver halide grains, it is desirable to carry out removal of excess water-soluble salts. Excess water-soluble salts can be removed using a noodle washing method, which gels gelatin solutions containing silver halide grains, cuts into strips, and water-soluble salts with cold water. Including washing out. Alternatively, excess water-soluble salts can be removed using an agglomeration method, in which inorganic salts containing polyvalent anions (eg sodium sulfate), anionic surfactants, anionic polymers (eg sodium polystyrene sulfonate) Alternatively, an aggregating agent such as a gelatin derivative (eg, aliphatic acylated gelatin, aromatic acylated gelatin, aromatic carbamoylated gelatin) is added to cause aggregation of the gelatin, thereby removing excess salts. Of these methods, the agglomeration method is preferable because excess salts can be removed rapidly.

  In general, it is desirable that the silver halide emulsion used in the present invention is chemically sensitized using a known sensitizing method alone or in various combinations. Chemical sensitization helps to provide high sensitivity, exposure condition stability and storage stability to the prepared silver halide grains. A chemical sensitization method which can be used advantageously is a chalcogen sensitization method using a sulfur, selenium or tellurium compound. Examples of sensitizers that can be used in the present invention include compounds that, when added to a silver halide emulsion, can release the chalcogen elements listed above to form silver chalcogenides. These sensitizers are desirably used in combination in terms of improving sensitivity and suppressing fog. In addition, it is desirable to utilize noble metal sensitization using gold, platinum, iridium or the like. In particular, gold sensitization using chloroauric acid alone or in combination with an ion capable of coordinating with gold such as thiocyanate ion is desirable because of its high sensitization effect. Further, high sensitivity can be obtained by using a combination of gold sensitization and chalcogen sensitization.

  Another sensitizing method which can be used advantageously is the so-called reduction sensitizing method, which introduces a reduced silver nucleus by using a compound having a moderate reducing power during grain formation. , Thereby increasing sensitivity. Furthermore, it is advantageous to use a reduction sensitization method in which an aromatic alkynylamine compound is added during chemical sensitization.

  When performing chemical sensitization, it is also desirable to adjust the reactivity of the system by adding various compounds that can adsorb to the silver halide grains. In order to adjust the reactivity, it is particularly desirable to use a method of adding a nitrogen-containing heterocyclic compound, a mercapto compound, or a sensitizing dye such as a cyanine dye or a merocyanine dye before chalcogen sensitization and gold sensitization. . Appropriate reaction conditions for chemical sensitization depend on the intended purpose. Specifically, the temperature is 30 ° -95 ° C, preferably 40 ° -75 ° C; the pH is 5.0-11.0, preferably 5.5-8.5, and the pAg is 6.0-10. .5, preferably 6.5 to 9.8. Chemical sensitization techniques are described, for example, in JP-A-3-110555, JP-A-5-241267, JP-A-62-253159, JP-A-5-45833, and JP-A-62-240446. In the chemical sensitization step, it is desirable to form an epitaxial protrusion on the grain surface.

The photosensitive silver halide emulsion used in the present invention is desirably subjected to so-called spectral sensitization in order to obtain sensitivity in a desired wavelength region. In particular, a color photographic material whose purpose is to reproduce a color faithful to the actual product is incorporated with a photosensitive layer having photosensitivity to each light of blue, green and red. Photosensitivity to these colors is imparted by spectrally sensitizing silver halide using a so-called spectral sensitizing dye. Such spectral sensitizing dyes include cyanine dyes, merocyanine dyes, complex cyanine dyes, complex merocyanine dyes, holopolar dyes, hemicyanine dyes, styryl dyes and hemioxonol dyes. Examples of these dyes are disclosed in US Pat. No. 4,617,257, JP-A-59-180550, JP-A-64-13546, JP-A-5-45828, JP-A-5-45834 and others. . These sensitizing dyes are used alone or in combination of two or more. The purpose of using the combination of dyes is to adjust the wavelength distribution of spectral sensitivity or to obtain a supersensitization effect. A supersensitizing combination of dyes can achieve a sensitivity that is significantly greater than the sum of the sensitivities achieved by the individual dyes. It is also desirable to utilize compounds that can exhibit a supersensitizing effect in combination with certain dyes that themselves do not spectrally sensitize silver halide emulsions or absorb light in the visible region. Such supersensitized compounds include diaminostilbene compounds. Examples thereof are disclosed in US Pat. No. 3,615,641, JP-A-63-23145 and others. These spectral sensitizing dyes and supersensitizing compounds may be added to the silver halide emulsion at any stage of emulsion preparation. Specifically, they may be added to the chemically sensitized emulsion when preparing a coating solution using the emulsion, or they may be added at the end, during or before chemical sensitization. Alternatively, the addition may be from completion of grain formation to before desalting, during grain formation or before grain formation. These addition methods may be used alone, or a combination of two or more methods may be used. In order to achieve high sensitivity, addition at a step prior to chemical sensitization is effective. Each of the spectral sensitizing dye and the supersensitizing compound can be added in an amount selected from a wide range depending on the shape and size of the emulsion grains and the properties to be imparted thereby. However, in general, the addition amount is in the range of 10 ⁻⁸ to 10 ⁻¹ mol per mol of silver halide, preferably in the range of 10 ⁻⁵ to 10 ⁻² . These compounds are dissolved in an organic solvent such as methanol or fluorinated alcohol, or dispersed in water together with a surfactant and gelatin and then added to the silver halide emulsion.

The silver halide emulsion used in the present invention may contain a wide variety of stabilizers for the purpose of fogging prevention, that is, heightening stability during storage. Suitable examples of stabilizers include nitrogen-containing heterocyclic compounds such as azaindene, triazole, tetrazole and purine, and mercapto compounds such as mercaptotetrazole, mercaptotriazole, mercaptoimidazole and mercaptothiadiazole. Details of these compounds are described in TH James, The Theory of the Photographic Process, 396-399, Macmillan (1977) and references cited therein. Of these antifoggants, mercaptoazoles having an alkyl group containing at least 4 carbon atoms and two or more aromatic groups as substituents are preferred for use in the present invention. Such an antifoggant may be added to the silver halide emulsion at any stage of emulsion formation. Specifically, they may be added during the time from the completion of chemical sensitization to the start of coating solution preparation, and may be at the end, midway or before chemical sensitization, or from the completion of particle formation to before desalting. May be during or before particle formation. These addition methods may be used alone, or a combination of two or more methods may be used. These antifoggants can be added in an amount selected from a wide range depending on the halide composition of the emulsion grains. However, in general, the addition amount is in the range of 10 ⁻⁶ to 10 ⁻¹ mol, preferably 10 ⁻⁵ to 10 ⁻² mol, per mol of silver halide.

  The aforementioned photographic additives that can be used in the present invention are described in US Pat. No. 6,337,177, columns 15-16.

  The tabular crystals may be host crystals having guest crystals grown epitaxially, as described in US Pat. No. 6,337,177.

  The {111} tabular grains of the present invention have at least two double faces per grain, and are triangular or hexagonal, and the corners may be angular or round. When the particles are hexagonal, each set of side surfaces facing each other has an outer surface parallel to each other.

  The bihedral distance in the {111} tabular grains of the present invention may be determined according to the intended purpose. For example, as disclosed in US Pat. No. 5,219,720, it can be controlled to a maximum of 0.012 μ, or as disclosed in JP-A-5-249585, It can be controlled so that the ratio of the distance between the (111) principal surfaces and the distance between the two surfaces is at least 0.015 μm.

  In the silver halide emulsion containing {111} tabular silver halide grains of the present invention, {111} tabular grains are 100 to 80%, preferably 100 to 90%, of the total grains in the emulsion based on the projected area. Particularly preferably, it accounts for 100 to 95%. When the total area of {111} tabular grains is less than 80% of the total projected area of all grains, the advantages of {111} tabular grains (improved speed / size ratio and sharpness) cannot be fully utilized. .

  In the emulsion of the present invention containing {111} tabular silver halide grains, hexagonal {111} tabular grains having a ratio of adjacent side surfaces (longest side surface / shortest side surface) in the range of 1.5 to 1, It is desirable to occupy 100 to 50%, preferably 100 to 70%, particularly preferably 100 to 80% of the total grains in the emulsion based on the projected area. Hexagonal {111} tabular grains having a ratio of adjacent side faces in the range of 1.2 to 1 are 100% to 50%, preferably 100% to 70%, especially 100% to 70% of the total grains in the emulsion, based on the projected area. Preferably it occupies 100 to 80%. Mixing with {111} tabular grains other than hexagonal grains is undesirable because it lacks grain uniformity.

  The average grain thickness of the {111} tabular crystals is 0.05 to 0.2 μm, preferably 0.05 to 0.15 μm. As used herein, the term average grain thickness refers to the arithmetic average of the thickness values of all {111} tabular grains in the emulsion. It is difficult to prepare emulsion grains having an average grain thickness of less than 0.05 microns. Emulsion grains having an average grain thickness greater than 0.2 microns are undesirable.

  A suitable average projected area diameter of the {111} tabular grains of the present invention is 0.8 to 4 μ, preferably 1 to 3.5 μ, particularly preferably 1.2 to 3 μ. As used herein, the term “average projected area diameter” refers to the arithmetic average of the projected area diameter values of all {111} tabular grains in an emulsion. An average projected area diameter of less than 0.8 microns is undesirable because it is difficult to achieve the effects of the present invention. Also, an average projected area diameter greater than 4 microns is undesirable because it degrades resistance to pressure damage.

  The projected area diameter / thickness ratio of each silver halide grain is called the aspect ratio. More specifically, the aspect ratio is a value obtained by dividing the diameter of a circle having the same area as the projected area of each silver halide grain by the thickness of the grain. As an example of a method for measuring the average aspect ratio, a replica method is known, and a transmission electron micrograph of a silver halide grain is taken, whereby a diameter of a circle having the same area as the projected area of each grain (projection) Area diameter) and the thickness of each particle. In this method, the thickness is calculated from the shadow length of the replica.

  In the emulsions of the present invention containing {111} tabular silver halide grains, {111} tabular grains having an average aspect ratio of 4 to 50 are 100% of the total silver halide grains in the emulsion based on projected area. It is desirable to occupy ~ 80%. In emulsions that are more desirable for use in the present invention, {111} tabular grains having an aspect ratio of 6 to 50 account for 100 to 80% of the total silver halide grains in the emulsion, based on projected area. Particularly advantageous for the present invention is that {111} tabular grains having an aspect ratio of 8-50 occupy 100-80% of the total silver halide grains in the emulsion, based on the projected area.

  Furthermore, the average aspect ratio suitable for all {111} tabular silver halide grains in the emulsion of the present invention is 4 to 40, preferably 6 to 40, more preferably 12 to 35. The term average aspect ratio refers to the arithmetic average of the aspect ratio values of all {111} tabular grains in the emulsion. The average grain thickness, average aspect ratio, and monodispersity can be selected from the above ranges depending on the intended purpose, but for the present invention, a monodisperse {111} plate having a thin thickness and a high aspect ratio. It is advantageous to use particle-like particles.

[Example 1A]
Measurement of {111} preferential adsorbability The surface preferentially adsorbed by the polymer compound is described in, for example, T. Tani, J. Imag. Sc, 1985, vol 29,165. It is determined by quantitative measurement using the Kubelka-Munk method.

Experimental conditions Adsorption of polymer compound on {111} plane The emulsion used is a cubic silver bromide emulsion having an average grain size of 0.70 μ and an octahedral silver bromide emulsion having an average grain size of 0.55 μ. The gelatin present in both silver bromide emulsions is gelatin that has been oxidized to weaken the interaction between the gelatin and the grain surface. 25.0 g of the emulsion was added to a vessel stirred at a temperature of 40 ° C. 150.0 ml of a 4% solution of the polymer compound was added while maintaining pH 9. Next, 1.00 ml of a dye solution containing 6.4 μmol of 3,3′-bis (4-sulfobutyl) -9-methyl-thiacarbocyanide was added 15 times at 1 minute intervals. After that, a reflectance spectrum of 400 to 700 nm was recorded using a reflection spectrometer.

In the experiment using a cubic emulsion, the reflectance of the D band at 593 nm was measured. The reflectance values at ⁵⁹³ nm of the 15 reflectance spectra were summed to obtain R ⁵⁹³ _s for the sample and R ⁵⁹³ _ref for the reference. The adsorption of the polymer compound on the {100} plane, “A ₍₁₀₀₎ ” is represented by a numerical value calculated by the following equation.
A ₍₁₀₀₎ = ((R ⁵⁹³ _s / R ⁵⁹³ _ref ) ⁻¹ ) ^* 100
If the adsorptive value on the {100} face is small, the tested polymer solution does not prevent the dye from adsorbing on the {100} face, but if the value is large, the tested polymer prevents the dye from adsorbing. I was able to.

2. Adsorption of {111} plane of polymer compound In these measurements, octahedral emulsions were used, and the reflectance of the surface dye in the J band at 620 nm was measured. The reflectance values at 620 nm of the 15 reflectance spectra were summed to obtain R ⁶²⁰ _s for the sample and R ⁶²⁰ _ref for the reference. The adsorptivity “A ₍₁₁₁₎ ” to the {111} plane was calculated by the following equation.
A ₍₁₁₁₎ = ((R ⁶²⁰ _s / R ⁶²⁰ _ref ) ⁻¹ ) ^* 40

3. Numerical value of preferential adsorption property Preferential adsorption property "S" is S = A _{100} -A _{111}
As calculated.

  The preferential adsorption properties of various gelatins measured at pH = 9 are listed in Table 1.

[Example 1B]

Measurement of Monodispersity Parameter RDA Monodispersity is expressed as RDA, which is the ratio of the distribution half-width (in nanometers) to the average aspect ratio. The distribution width is obtained by a disc type light transmission centrifugal sedimentation method using a DC 20.000 model of CPS Instruments Inc. 1 g of the crystalline emulsion is dissolved in 55 g of water and 5 g of ethanol. To this mixture is added 5 ml of 1% (by weight) surfactant solution and 0.05% (by weight) pronase solution. This mixture is incubated at 45 ° C. for 10 minutes. The injection volume is 0.05 ml. Use 20 ml of 0-8% sucrose solution and 1 ml of pure decane for the gradient. The speed applied to the disk during the measurement is 3000 rpm. A PVC latex sphere of 1.19μ was used as the reference size.

  The aspect ratio is a value obtained by dividing the diameter of the region where the surface area of each {111} tabular grain is maximum by the grain thickness. The term “diameter” as used herein is an equivalent circular diameter (ECD), which means the diameter of a circle having an area equal to the projected area of the particle, and is obtained through observation with a microscope or an electron microscope. Therefore, an aspect ratio of 8 or more means that the diameter of the circle is 8 times or more the particle thickness. Monodispersity is represented by RDA and is the ratio of the distribution half width (in nanometers) to the average aspect ratio.

Comparative Example A {111} tabular silver bromide grain emulsion was prepared as follows.
A stirred reaction vessel was charged with a solution of 1200 ml water, 1.2 g gelatin and 1.0 g potassium bromide. The pH of the solution was adjusted to 9.5 with NaOH and the temperature of the solution was kept at 40 ° C. To this solution, a 0.47 M solution of silver nitrate and a 0.82 M potassium bromide solution containing 1.2% 200 kD (kilodalton) lime-processed bone gelatin were added at the same addition rate of 50 ml / min. The addition was stopped simultaneously after 50 seconds. The temperature was raised to 70 ° C. After aging for 40 minutes, unoxidized lime-processed bone gelatin was added to increase the gelatin concentration to 22.5% by weight. Acid was added along with the gelatin to lower the pH to 5.0. Next, a total of 1.5 moles of silver nitrate was added in two growth stages. The amount of potassium bromide added between the two growth stages was pBr of 2.10 to 2.30. The rate of addition of all additions was such that no nucleation occurred during the growth phase. The particles were washed to remove salt and gelatin excess. After washing, 65 g of gelatin was added to the emulsion and the emulsion was stored at 6 ° C. The resulting emulsion contained {111} tabular grains having an average thickness of 0.141 microns and an average ECD of 1.56 microns. The full width at half maximum was 243 nm, and as a result, the coefficient of variation (RDA) was 22.1.

Comparative Example A {111} tabular silver bromide grain emulsion was prepared as in Example 2, except that a 200 kD lime-processed bone gelatin in potassium bromide solution was prepared by alkaline hydrolysis and the peptide bond was randomly cleaved. Prepared by replacing with lime-processed bone gelatin. The resulting emulsion contained {111} tabular grain grains having an average thickness of 0.134 microns and an average ECD of 1.68 microns. The full width at half maximum was 235 nm, and as a result, the coefficient of variation (RDA) was 18.8. The coefficient of variation was somewhat improved as expected from the lower molecular weight.

Comparative Example A {111} tabular silver bromide grain emulsion was prepared as in Example 2, except that 200 kD lime-processed bone gelatin in potassium bromide solution was replaced with 30 kD oxidized lime-processed bone gelatin. As a result of the oxidation, the methionine content per gram of gelatin was less than 5 micromolar. The resulting emulsion contained {111} tabular grains having an average thickness of 0.118 microns and an average ECD of 1.75 microns. The full width at half maximum was 275 nm, resulting in a coefficient of variation (RDA) of 18.5, with some further improvement in variation.

A {111} tabular silver bromide grain emulsion of the present invention was prepared as in Example 2, except that 200 kD lime-processed bone gelatin in potassium bromide solution was replaced with 6.4 kD lime-processed bone gelatin. This 6.4 kD gelatin was obtained by enzymatic hydrolysis of lime-processed bone gelatin with trypsin. Trypsin selectively cleaves Arg-X and Lys-X bonds, yielding gelatin where the C-terminal amino acid is lysine or arginine. The resulting emulsion contained {111} tabular grains having an average thickness of 0.123 microns and an average ECD of 1.81 microns. The full width at half maximum was 212 nm. As a result, the coefficient of variation (RDA) was 14.4, and a significant improvement in variation was observed.

Inventive {111} tabular silver bromide grain emulsion as in Example 2, except that 6.4 kD lime-processed bone gelatin of the present invention obtained by hydrolyzing with trypsin in a potassium bromide solution is 1. Prepared and added at a concentration of 2% by weight. In addition, 1.2 g of the 6.4 kD gelatin of the present invention was added before adding the first silver nitrate and potassium bromide to the stirred reaction vessel. The resulting emulsion contained {111} tabular grains having an average thickness of 0.120 microns and an average ECD of 1.78 microns. The full width at half maximum was 228 nm, resulting in a coefficient of variation (RDA) of 15.4, still showing significant improvement in variation, but less than adding all of the gelatin of the present invention with potassium bromide.

Inventive {111} tabular silver bromide grain emulsion as in Example 2, except that 200 kD lime-processed bone gelatin in potassium bromide solution is replaced with 6.4 kD oxidized lime-processed bone gelatin. did. This 6.4 kD gelatin was obtained by enzymatic hydrolysis of lime-processed bone gelatin with trypsin. Trypsin selectively cleaves Arg-X and Lys-X bonds, yielding gelatin where the C-terminal amino acid is lysine or arginine. As a result of the oxidation, the methionine content per gram of gelatin was less than 4 micromolar. The resulting emulsion contained {111} tabular grains having an average thickness of 0.128 microns and an average ECD of 1.68 microns. The full width at half maximum was 220 nm. As a result, the coefficient of variation (RDA) was 16.8, and a significant improvement in variation was observed. It should be noted that there is less beneficial effect on the variation of the gelatin of the present invention when applied to oxidized gelatin. Nevertheless, even oxidized gelatins of the present invention clearly improve variability.

Comparative Example A {111} tabular silver bromide grain emulsion was prepared as in Example 2, except that 200 kD lime-processed bone gelatin in potassium bromide solution was replaced with 6.6 kD lime-processed bone gelatin. This 6.6 kD gelatin was obtained by enzymatic hydrolysis of lime-processed bone gelatin with pronase. Pronase cleaves Ala-X, Gly-X, Leu-X, Ill-X, Pro-X or Val-X peptide bonds non-selectively, with only a few percent of the cleavage being lysine as the N-terminal amino acid, A gelatin is obtained which does not result in arginine or histidine. The resulting emulsion contained {111} tabular grains having an average thickness of 0.136 microns and an average ECD of 1.71 microns. The full width at half maximum is 232 nm. As a result, the coefficient of variation (RDA) is 18.5, the enzymatic hydrolysis must not be random, and it must be hydrolyzed to cleave a specific site as is done by trypsin. Was confirmed.

Invention Preparation of Gelatin A histidine group was coupled to a carboxyl group of gelatin against 30 kD lime-processed bone gelatin (Example 3). Acid-treated bone gelatin (30 kD) and 64 mmol of L-histidine methyl ester were dissolved in 400 ml of purified water. To this solution, a THF solution of 27 mmol of dicyclohexylcarbodiimide was added dropwise. After 2 hours reaction, the mixture was cooled and filtered. Thereafter, the pH of the reaction mixture was raised to remove the ester protecting group of L-histidine, and the gelatin solution was further purified by dialysis. See also The Practise of Peptide synthesis, M. Bodansky, A. Bodansky, Springer-Verlag, Berlin 1984 and Solid Phase Peptide synthesis, p143.

  A {111} tabular silver bromide grain emulsion was prepared as in Example 2, except that 200 kD lime-treated bone gelatin in potassium bromide solution was replaced with 30 kD acid-treated bone gelatin coupled with L-histidine. did. The resulting emulsion contains {111} tabular grains having an average thickness of 0.133 μm and an average ECD of 1.67 μ, with a coefficient of variation (peak width / AR (aspect ratio)) of 16.7, There was also some improvement in variability.

  Table 2 outlines the experimental results. The beneficial effect of the present invention can be clearly seen by calculating the ratio between the half width and the average aspect ratio.

  This is done because RDA depends on the aspect ratio. The higher the aspect ratio, the worse the monodispersity. The particle size determined by volume measurement of {111} tabular grains produced in Experiments 2 to 9 was 810 to 825 nm.

  From the above summary, the addition of a polymer with preferential adsorption to the (111) crystal plane significantly improves monodispersity while maintaining the desired aspect ratio of the thin {111} tabular silver halide grain emulsion. Is clearly understood.

Claims (19)

{111} tabular silver halide grains are formed by combining a silver salt aqueous solution and a halogen salt aqueous solution in the presence of a water-soluble polymer compound having a preferential adsorption property of {111} crystal plane of −3 or less, {111} A method for producing a tabular silver halide emulsion, wherein the preferential adsorption property is determined by the modified Kubelka-Munk method described in T. Tani J. Imag. Sc 29 (1985) vol 29,165. A method of subtracting the value for adsorption on the {111} crystal plane obtained by measurement at pH = 9 in the presence of the polymer compound from the value for adsorption on the {100} crystal plane.   The method of claim 1, wherein the water soluble polymer compound is present in a nucleation step.   The method of claim 1 or 2, wherein the nucleation step is performed at a pH of less than 6.   The method according to claim 1 or 2, wherein the nucleation is performed at a pH of 6 or more.   The method according to claim 1, wherein the nucleation step is performed in the presence of a compound having a preferential adsorption property to the {111} crystal plane of −6 or less.   The method according to any one of claims 1 to 5, wherein the nucleation step is performed in the presence of a compound which is one kind of peptide.   The method according to any one of claims 1 to 6, wherein the nucleation step is performed in the presence of a compound selected from natural gelatin, synthetic gelatin, modified gelatin and recombinant gelatin.   8. The method of claim 7, wherein the gelatin has an average molecular weight of less than 50 kilodaltons.   The method according to claim 7 or 8, wherein the gelatin has a molecular weight of 5 to 25 kilodaltons.   The method according to claim 1, wherein the water-soluble polymer compound is added simultaneously with the silver salt and the halogen salt in the nucleation step.   The method according to any one of claims 1 to 10, wherein the nucleation step is carried out in the presence of a compound which is a polypeptide comprising one amino acid selected from arginine, lysine, hydroxylysine and histidine as the carboxy terminal amino acid. .   The nucleation step includes one amino acid “A” having a residue containing an amine on one terminal side of the polypeptide and one amino acid “B” having a residue containing a carboxyl, And “B” are performed in the presence of a compound which is a polypeptide which is separated from each other by a maximum of 4 amino acids, preferably by a maximum of 2 amino acids, most preferably by a maximum of 1 amino acid. The method according to any one of 11.   13. The method of claim 12, wherein the nucleation step is performed at a pH of 7 or more, preferably a pH of 8 or more, more preferably about pH 8-11 in the presence of a polypeptide in which the amino acid “A” is arginine or lysine.   12. The method according to claim 11, wherein the nucleation step is performed at pH 7 or higher, preferably pH 8 or higher, more preferably about pH 8-11 in the presence of a polypeptide having arginine or lysine as the carboxy terminal amino acid.   15. In the nucleation step, the water soluble polymer compound is present in an amount of about 0.01 to 0.2 moles per mole of silver, preferably 0.05 to 0.1 moles per mole of silver. The method in any one of.   A {111} tabular silver halide grain obtained by the method of any one of claims 1 to 15, wherein at least 60% of the total projected area of the silver halide grain has a silver bromide content of at least 50%. {111} tabular silver halide emulsion.   The {111} tabular silver halide emulsion of claim 16, wherein the {111} tabular silver halide grains have an average aspect ratio of 6 to 40 and a thickness of less than 0.2μ and greater than 0.05μ.   The {111} tabular silver halide emulsion according to claim 16 or 17, wherein the monodispersity represented by RDA is less than 18, preferably less than 16. A photographic material comprising at least one layer comprising the {111} tabular silver halide emulsion according to any one of claims 16 to 18 on a support.