JPH0130137B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a direct positive silver halide photographic material, and more particularly to a direct positive silver halide photographic material having a high maximum density and a low minimum density. Various direct positive silver halide photographic light-sensitive materials have been known, but in the case of light-sensitive materials using fog-free internal latent image type silver halide emulsions, fog treatment is performed after image exposure. After that, or while performing fogging treatment, surface development is performed to form a positive image. In this case, the method of fogging treatment can be arbitrarily selected, such as by exposing the entire surface to light, using a fogging agent, using a strong developer, or heat treatment. Regarding these various technologies, for example, US Patent No. 2592250, US Patent No. 2456953, US Patent No. 2497875,
Patent No. 2588982, British Patent No. 1151363,
Japanese Patent Publication No. 43-27405, Japanese Patent Publication No. 47-9677, No. 47-
No. 32813, No. 48-9727, No. 48-9717, Tokukosho
No. 52-34213, Japanese Patent Publication No. 50-8524, No. 50-38525
No., publications and U.S. Patent No. 3761266, U.S. Patent No.
No. 3796557, which is widely known from the descriptions in various specifications. However, in the positive image forming methods using these known techniques, for example, in terms of sufficient sensitivity, satisfactory maximum density and minimum density,
Performance sufficient for various photographic applications has not yet been achieved, and there is still much room for improvement. In other words, in order to increase the maximum density of an image, there is a method of developing under harsh conditions, but this method not only increases the minimum density and loses the sharpness of the image, but also reduces the sensitivity. There is a drawback that it is even accompanied by a decline. Additionally, the maximum density can be similarly increased by increasing the amount of silver halide emulsion coated, but this would also increase the minimum density and consume a large amount of silver resources. It cannot be said that this is a desirable technology due to the social situation. Considering its application in the field of color photography, which has become particularly popular in recent years, this is a fatal flaw in that images with low maximum density and high minimum density cannot be expected to reproduce beautiful color photographs. The development of improved technology has become an important issue. Therefore, an object of the present invention is to provide a direct positive type silver halide photographic light-sensitive material having sufficient photosensitivity, high maximum density, and low minimum density. As a result of intensive research, the present inventors have found that the above-mentioned object of the present invention is to provide a direct positive silver halide photograph having at least one layer containing a fog-free internal latent image type silver halide emulsion on a support. In the light-sensitive material, an internal latent image type silver halide emulsion having fog nuclei is contained in the same layer as the layer containing the fog-free internal latent image type silver halide emulsion or in other constituent layers. This could be achieved using a direct positive silver halide photographic material. That is, according to the direct positive-working silver halide photographic light-sensitive material of the present invention, fog-free internal latent image type silver halide emulsion is not used alone, but adjacent to it, fog is formed inside the silver halide grains. When an internal latent image type silver halide emulsion having nuclei (hereinafter simply referred to as an internal latent image type silver halide emulsion having fog nuclei) is present and used alone,
It has been discovered that an improved positive image can be obtained by activating the action of a fog-free internal latent image type silver halide emulsion that has a low ability to form a positive image. Hereinafter, the direct positive silver halide photographic material of the present invention will be explained in more detail. Regarding fog-free internal latent image type silver halide emulsions that can be effectively used in the present invention, examples include Burton's emulsion described in "Photographic Emulsions" by Wall, and U.S. Pat. No. 2,592,250. Conversion emulsion, U.S. Patent No. 3206313, Japanese Patent Publication No. 51-29012, No. 43-
29405, U.S. Patent No. 3447927, U.S. Patent No. 3317322,
Same No. 3531291, No. 3703584, No. 3761266,
Metal ion doped emulsions or internally chemically sensitized core/shell emulsions described in US Pat. No. 3,761,267, US Pat. No. 3,761,276, etc.;
Emulsions using thioethers described in US Patent Nos. 3574628, 3767413, and 3796577, US Pat.
Atomic emulsions or surface latent image emulsions containing desensitizing dyes or desensitizing dyes described in the specification of No. 15530, silver chloride and odors described in JP-A-50-8524 and JP-A-50-38525. Emulsion in which silver oxide is deposited in a layered manner, JP-A-Sho
Examples include the ammoniacal silver iodobromide emulsion described in Japanese Patent Application No. 52-156614 and the neutral silver iodobromide emulsion described in Japanese Patent Application No. 142027/1982, but are not limited to these. If it satisfies the conditions of
can be used. In other words, the maximum density when the coated test piece is exposed for an exposure time of 1 second to 1/100 seconds and developed for 3 minutes at 20°C with the internal developer described below is The emulsion has a maximum density of at least 5 times, preferably more than 10 times, when developed for 4 minutes at 20°C. Internal developer hydroquinone 15g monomethyl-p-aminophenol sulfate
15g Sodium sulfite (anhydrous) 50g Potassium bromide 10g Sodium hydroxide 25g Sodium thiosulfate (crystals) 20g Add water 1 Surface developer p-hydroxyphenylglycine 10g Sodium carbonate (crystals) 100g Add water 1st Regarding the silver halide composition of the fog-free internal latent image type silver halide emulsion used in the present invention, silver bromide is mainly used.
Particularly preferred is one in which 50 mol% or more is silver bromide. Furthermore, regarding the structure of the silver halide grains, the core/shell type silver halide, that is, in this case, chemically sensitized silver bromide is used as the core;
A structure in which this is further coated with silver bromide to form a shell is preferred. And the particle size is
Range of 0.3μm to 3.0μm, preferably 0.5μm to 3.0μm
It is preferable to have an average particle diameter of m. In addition, although the main component of the core/shell type silver bromide grains is silver bromide, the shell may contain 0 to 10 mol%, preferably 0 to 5 mol% of iodine. good. The fog-free internal latent image type silver halide emulsion used in the present invention can be chemically sensitized, if necessary. As chemical sensitization methods, for example, noble metal sensitization methods, sulfur sensitization methods, reduction sensitization methods, etc. are known, and sensitization can be carried out singly or in combination of two or more. Furthermore, the internal latent image type silver halide emulsion described above can be stabilized or prevented from fogging using a known stabilizer or antifoggant.
For this purpose, mercury compounds, triazole compounds, azaindene compounds, benzthiazolium compounds, zinc compounds, nitrogen-containing heterocyclic compounds having a mercapto group, and the like can be used. Among these additives, compounds with an azaindene ring include 4-hydroxy-6-methyl-
Examples of nitrogen-containing heterocyclic compounds having 1,3,3a,7-tetrazaindene and a mercapto group include 5-methylbenzothiazole, 5-methylbenzotriazole, 1-phenyl-5-mercaptotetrazole, 1-methyl-2 Derivatives such as -tetrazoline-5-thione are particularly preferably used. The internal latent image type silver halide emulsion described above can also be optically sensitized by using a known optical sensitizer or supersensitizer. On the other hand, in the present invention, the internal latent image type silver halide emulsion having fog nuclei used adjacent to the fog-free internal latent image type silver halide emulsion is essentially the former silver halide emulsion. Emulsions have similar properties. That is, when the coated test piece is exposed to light for an exposure time of 1 second to 1/100 second and developed for 3 minutes at 20°C with the above-mentioned internal developer, the maximum density is 20°C with the above-mentioned surface developer. , the emulsion has a maximum density of at least 5 times, preferably more than 10 times, the maximum density when developed for 4 minutes. Further, in the case of an internal latent image type silver halide emulsion having fog nuclei, the fog nuclei must be contained partially or completely inside the grains. The extent of this fogging was determined by applying the emulsion containing fog nuclei at a silver content of 3.5 to 4.5 g/m ² onto a transparent support such as a polyethylene tetophthalate film in the internal developer described above. The transmission density when developed at 20° C. for 3 minutes is at least 0.50, preferably more than 1.0. Further, the emulsion having the above-mentioned fog nuclei was prepared by exposing the above-coated test piece to light for between 1 second and 1/100 second, and then in the above-mentioned surface developer at 20°C.
The maximum density when developed for minutes is 0.40 or less, preferably 0.25 or less, and the surface is not fogged. Next, a method for producing the internal latent image type silver halide emulsion having fog nuclei used in the present invention will be described. For example, it can be produced by fogging the interior and surface of grains with a photosensitive silver halide emulsion, and then destroying the fog on the surface by treating with an oxidizing agent such as an aqueous potassium ferricyanide solution. Known methods for fogging in this case include heating and ripening the silver halide emulsion under low PAg, chemically fogging using a fogging agent, and exposing the entire surface to light. These can be used alone or in combination. Another method is to irradiate a non-fogged internal latent image type silver halide emulsion with high energy radiation such as X-rays. Still another method is known, in which silver halide having fog nuclei is first produced, and this core is then coated with non-fogging silver halide to form a shell. There is. In this case, the method for producing fogged core particles is, for example, a chemical sensitization method widely known in the art, that is,
This can be achieved by chemical sensitization to an excessive extent by using sensitization methods such as noble metal sensitization, sulfur sensitization, reduction sensitization, etc. alone or in combination. The grain size of the internal latent image type silver halide emulsion having fog nuclei produced in this way is 0.15 to 3.0μ.
The emulsion is preferably a so-called monodisperse emulsion having an average particle diameter in the range of m, preferably 0.2 to 1.0 μm, and a relatively narrow particle size distribution. In order to prepare the core/shell type grains of the internal latent image type silver halide emulsion having the fog nuclei used in the present invention, silver halide grains to be the core are first formed, and compared with the core/shell type grains. A method is adopted in which the core grains are subjected to gold sensitization treatment under an extremely high silver potential, and then the core particles are coated with silver halide that does not cause fogging. It can be preferably used to achieve the purpose. The silver halide composition of the internal latent image type silver halide emulsion having fog nuclei used in the present invention includes silver chloride, silver bromide, silver iodide, or a combination thereof. Any of these are suitable for use, but particularly preferred are silver chloride, silver bromide, silver iodobromide, and the like. The proportion of silver iodide in the silver halide composition according to the present invention as described above is 10 mol% or less, preferably 3 mol% or less. Furthermore, the average thickness of the shell forming layer in the core/shell type structure of the silver halide grains according to the present invention is 0.01 to
It is 0.3 μm, preferably 0.02 to 0.15 μm. These internal latent image type silver halide emulsions having fog nuclei are added with various known photographic additives, just as in the case of the fog-free internal latent image type silver halide emulsions described above. be able to. In the present invention, the quantitative ratio of the fog-free internal latent image type silver halide to the internal latent image type silver halide having fog nuclei is expressed as a molar ratio.
Range of 10:0.03 to 10:30, especially 10:0.5 to 10:30
A range of 10:10 is preferred. In the amount used within this range, there is no adverse effect on sensitivity. Further, the present invention is characterized by the use of a combination of a fog-free internal latent image type silver halide emulsion and an internal latent image type silver halide emulsion having fog nuclei.
The method involves replacing a portion of the former silver halide emulsion with no fog with the latter silver halide emulsion having fog nuclei, and in this case, especially when conventional silver halide emulsions are used alone, fog may occur. The effect of the present invention is that the amount of the combination of the above-mentioned two emulsions according to the present invention can be used in a smaller amount than the amount of the internal latent image type silver halide emulsion that is not used, and it significantly contributes to the reduction of silver resources. It's something you get. Furthermore, when comparing the sizes of both silver halide grains, when the internal latent image type silver halide grains having fog nuclei are smaller than the average diameter of the internal latent image type silver halide grains without fog, , an especially excellent positive image could be obtained. Furthermore, in the present invention, the internal latent image type silver halide having fog nuclei may be contained in the same emulsion layer as the internal latent image type silver halide having no fog, or may be contained in another emulsion layer adjacent thereto. In this case, an intermediate layer such as a gelatin layer may be interposed between the two emulsion layers, but the two emulsion layers may not be in direct contact with each other. Especially good results can be obtained when The layer-forming binder forming the constituent layers of the direct positive silver halide photographic material of the present invention includes:
Generally known hydrophilic binders, such as gelatin, gelatin derivatives such as acylated gelatin, guanidylated gelatin, and carbaminated gelatin, and other hydrophilic polymer compounds can be widely used. The above-mentioned photographic material can be produced by providing a photosensitive emulsion layer, a protective layer, an intermediate layer, a filter layer, a backing layer, etc. on a support as necessary. Appropriate plasticizers, wetting agents, hardeners, etc. may be added or blended into these various constituent layers depending on the purpose. Examples of hardening agents include aldehyde compounds, azine compounds, epoxy compounds, ethyleneimine compounds, vinyl sulfone compounds, and acryloyl compounds. The direct positive silver halide photographic material of the present invention prepared as described above is subjected to fogging treatment after image exposure. This fog treatment is performed either prior to surface development or at the same time as surface development, but it is usually preferable that fog treatment and surface development are performed at the same time. As mentioned above, there are many methods for the above-mentioned fogging treatment, including full-surface exposure, use of a fogging agent, use of a strong developer, high temperature treatment, and heat treatment. Among these, British Patent No. 645877 relates to the use of fogging agents.
U.S. Pat. No. 2,497,917 describes an air fog accelerator, U.S. Pat. No. 2,563,785, U.S. Pat.
No. 2685514, No. 3227552, British Patent No. 1269640
No. 1403018 Specifications, Special Publication No. 1971-17184
No., JP-A-53-3326, etc. disclose hydrazine and hydrazide compounds, U.S. Pat.
Specification No. 3615615, JP-A-47-9677, JP-A No. 52-
No. 3426, No. 52-69613, and Japanese Patent Publication No. 52-47326 disclose quaternary ammonium salt compounds, U.S. Pat.
German Patent No. 3565620 describes a carbazic acid compound, German Patent No. 2141554 and German Patent No. 2314517 describe a tin compound, U.S. Patent No. 3850638 describes a benzimidazole compound, and Japanese Patent Application No. 142026/1989 describes a carbazic acid compound. describes an amine borane compound, but it is preferable to use a hydrazine compound. These fogging agents may be added to the developer or may be added to the silver halide emulsion at an appropriate time. The surface developer used in the present invention has no or a relatively low ability to dissolve silver halide grains and contains various silver halide developing agents or reducing agents; It does not substantially contain relatively strong silver halide solubilizers (for example, water-soluble thiocyanates, thioethers, thiosulfates, ammonia, etc.), such as Kodak DK-50,
D-19, Sakura color developer CNK-4, etc., but most of the commercially available developers are included in this category. Conventional silver halide developers for the developer used in the present invention include hydroquinones, catechols, aminophenols, 3-pyrazolidones, ascorbic acid and its derivatives, reductones, and phenylenediamines or their derivatives. Contains mixtures. It is also possible to include these developers in advance in the emulsion layer and allow them to act on the silver halide during immersion in a high pH aqueous solution. The developing composition used in the present invention can further contain specific antifoggants and development inhibitors, or these compositions can be optionally incorporated into the layers of the silver halide photographic material. It is. These useful antifoggants include conventionally known heterocyclic thiones, aromatic and aliphatic mercapto compounds, and the like. After the direct positive silver halide photographic light-sensitive material of the present invention has been developed with the above-mentioned surface developer subsequent to or simultaneously with the fogging treatment, it can be fixed, washed with water, and processed in accordance with conventional processing methods. It is dried to complete the process. The constituent layers of the above-described light-sensitive material of the present invention may further contain a dye image-forming substance in combination. Examples of the dye image-forming substance include materials used in various color photography methods, and mainly so-called photographic couplers used in color development methods. These photographic couplers are used by being added in a non-diffusive form to the hydrophilic colloid layer, which is a constituent layer of photographic light-sensitive materials, and others are used by being added to color developing solutions in a diffusive form. There is, but any one is fine. These couplers can form non-diffusible dyes by performing a coupling reaction with oxidation products of color developing agents, such as p-phenylenediamine color developing agents and p-aminophenol color developing agents. Generally, it has an active methylene or active methine group in its molecule, and examples of yellow dye-forming couplers include α-acylacetanilide compounds, and magenta dye-forming couplers include 5-pyrazolone compounds. ,
Phenol compounds and naphthol compounds are known as pyrazolinobenzimidazole compounds, pyrazolotriazole compounds, or cyan dye-forming couplers. When the above dye image-forming substance is used in the present invention, it may be contained in an emulsion layer containing silver halide for forming an internal latent image having fog nuclei, or in an emulsion layer adjacent thereto. May exist. The direct positive type silver halide photographic light-sensitive material of the present invention containing a dye image-forming substance as described above can be used for color photography. In addition, the above photosensitive materials of the present invention can be used not only for general black and white purposes, but also for X-ray, printing, infrared, micro, false color,
It can be used for various purposes such as silver dye bleaching. Hereinafter, the direct positive silver halide photographic material of the present invention will be specifically explained with reference to Examples, but the embodiments of the present invention are not limited by these. Example 1 (a) Preparation of internal latent image type silver halide emulsion (A) having fog nuclei inside. An aqueous solution of 1 in which 2.2 g of potassium bromide and 20 g of gelatin were dissolved was constantly stirred at 60°C, and potassium bromide and potassium iodide were dissolved in this aqueous solution so that the concentration of halogen ions was 3.5 mol/. 150 ml of an aqueous solution and a 150 ml aqueous solution of ammoniacal silver nitrate of the same concentration were added simultaneously over 20 seconds. After stirring at 60°C for about 1 minute, 20 ml of an aqueous solution containing 10 g of silver nitrate was added, and after 10 minutes, potassium chloraurate was added per mole of silver halide.
1.56mg and ammonium thiocyanate 71.9mg
An aqueous solution dissolved in the following ratio was added and aged at 60°C for 50 minutes. In this way, silver halide grains having fog nuclei were produced. Next, 600 ml of an aqueous solution in which potassium bromide and potassium iodide were dissolved so that the halide ion concentration was 0.5 mol/l, and 500 ml of an aqueous solution of silver nitrate having the same concentration were added simultaneously. In this way, the average particle diameter is 0.40 μm.
An internal fog emulsion (A) consisting of tetradecahedral silver halide grains was obtained. (B) Preparation of internal latent image type silver halide emulsion (B) having fog nuclei inside. It was prepared in essentially the same manner as the internal fog emulsion (A) described above, but by increasing the amount of silver nitrate and halogen ions added in the final preparation step of the internal fog emulsion (A) described above, the average grain The diameter is
An internal fog emulsion (B) consisting of 0.50 μm tetradecahedral silver halide grains was obtained. The silver content of both emulsions (A) and (B) above is approximately 3.5
The specimens coated on a polyethylene terephthalate film support at a rate of g/m ² were imaged for 1/25 second and then developed for 4 minutes at 20° C. using the above-mentioned surface developer. No image appeared at all, and no fogging was observed. Furthermore, in order to investigate fog inside the silver halide grains, the above test piece was developed in the internal developer described above at 20°C for 3 minutes. As a result, a transmission density of 2.0 or more was observed for both internal fog emulsions (A) and (B). Next, a fog-free internal latent image type silver halide emulsion was prepared according to the description in Example 9 of Japanese Patent Publication No. 52-34213. Then, the surface of the silver halide grains was chemically sensitized by the method described in Example 9 of the above publication. The internal fog emulsions (A) and (B) obtained as described above were mixed into this fog-free internal latent image type silver halide emulsion in the proportions shown in Table 1 below, and then a polyethylene terephthalate film was mixed. Coated on a support. The amount of silver halide coated at this time was approximately 3.5 g/m ² in terms of silver amount for all test pieces. Each specimen was exposed for 1/25 second through an optical wedge and developed in the following fog developer at 20° C. for 6 minutes to obtain a positive image. (Fog developer) Anhydrous sodium sulfite 2.6g Trisodium phosphate _12H2O 30.0g Sodium hydroxide 2.5g 5-methylbenzotriazole 3.0g 4-hydroxymethyl-4-methyl-1-phenyl-3-pyrazolidone 1.5g Add water to make 1. The results are shown in Table 1, which shows the effect of the combination of the fog-free internal latent image type silver halide emulsion according to the present invention and the internal latent image type silver halide emulsion having fog nuclei, that is, the comparative sample. The effect of Dmax being larger and Dmin being smaller than that can be seen. In Table 1, Nos. 4 to 6 are according to the present invention.

[Table] Example 2 A fog-free internal latent image type silver halide emulsion made of silver bromide was prepared according to the description in Example 9 of Japanese Patent Publication No. 52-34213. Then, the surface of the above silver halide grains was subjected to chemical sensitization treatment by the method described in the above publication. This silver halide emulsion and the internal fog emulsion (A) prepared in Example 1 were mixed in the quantitative proportions shown in Table 2 below. On the other hand, as a magenta coupler, 1-(2,
4,6-Trichlorophenyl)-3-(2-chloro-5-octadecylsuccinimidoanilino)-
500 g of 5% gelatin aqueous solution containing sodium dodecylbenzenesulfonate and 39 g of 5-pyrazolone
An emulsified dispersion liquid was prepared by emulsifying and dispersing the mixture in ml. Next, the above emulsified dispersion was mixed at a ratio of 1.42 per mole of silver halide, and the above-mentioned fog-free internal latent image type silver halide emulsion and internal fog emulsion were mixed at fixed ratios as shown in Table 2. It was added to the mixed emulsion and mixed, and then a 5% acetone solution of tetrakis(vinylsulfonylmethyl)methane was added as a hardening agent at a rate of 70ml per mole of silver halide so that the amount of coated silver was 20mg/ ^100cm2 . was applied onto a cellulose triacetate film and dried. As a comparative sample, an emulsion prepared in exactly the same manner as above except that the internal fog emulsion was not added was used. Each sample prepared as described above was exposed to light through an optical wedge, and then developed at 20° C. for 5 minutes using the following developer. (Developer) 4-amino-3-methyl-N-ethyl-N-(β
-Methanesulfonamidoethyl)aniline sulfate 5g Sodium sulfite (anhydrous) 2g Trisodium phosphate 40g Benzimidazole 50ml 1-acetyl-2-phenylhydrazine 1g Add water 1 (Adjust to pH 12.0 with sodium hydroxide) After development, it was bleached, fixed, washed with water, and dried in the usual manner. The results of the obtained color positive images are shown in Table 2. As is clear from Table 2, the maximum density (Dmax) of the positive dye image was increased and the minimum density (Dmin) was decreased in the emulsion used in combination with the internal fogging emulsion compared to the comparative sample. and,
In particular, as shown in sample No. 4, this effect can be obtained by using a smaller amount of the combined emulsion according to the present invention than when the fog-free internal latent image type silver halide emulsion is used alone. It is clearly shown that This shows the superiority of the direct positive type silver halide photographic light-sensitive material according to the present invention.

【table】

Claims (1)

[Claims] 1. A direct positive-working silver halide photographic light-sensitive material having at least one layer containing a fog-free internal latent image type silver halide emulsion on a support, wherein said fog-free internal latent image type silver halide emulsion is provided. A direct positive silver halide emulsion comprising an internal latent image type silver halide emulsion having fog nuclei inside silver halide grains in the same layer as the emulsion-containing layer or in other constituent layers. Photographic material.