JPS61264336A - Direct positive type silver halide photographic sensitive material - Google Patents

Abstract

PURPOSE:To obtain the titled material having sufficiently a large max. concn. and sufficiently a small min. concn. and an excellent storage stability and a high sensitivity by forming at least a part of a shell coated a core of a silver halide particle having an internal latent image type under an acidic condition. CONSTITUTION:The silver halide particle is composed of the core and the shell, and at least the part of the shell is formed under the acidic condition having <=5 pH value, preferably, <=4 pH value. At least one of the steps of forming the shell composed of the silver halide on the core composed of the silver halide emulsion particle which is chemically sensitized, or is dopped with a metal ion, is performed under the acidic condition. The conditioning agent for controlling a pH value to the acidic condition is comprised various kinds of acids. The preferable acid is contained for example, an inorg. acid such as hydrochloric acid, and an org. acid such as acetic acid.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a direct positive silver halide photographic light-sensitive material, and more specifically, after image exposure, fogging treatment (for example, full-surface exposure or removal of a fogging agent) is performed. The present invention relates to a photographic light-sensitive material having an internal latent image type silver halide emulsion layer from which a positive image can be directly obtained by surface development processing in the presence of the present invention.

[Prior Art] Conventionally known methods for obtaining direct positive images are mainly divided into two types. One type is to use a silver halide emulsion that has fog nuclei in advance, and to destroy the fog nuclei or latent image in exposed areas using solarization blindness or the Burschel effect.
A positive image is obtained after development. The other type uses an internal latent image type silver halide emulsion that has not been fogged in advance, performs fogging treatment (development nucleation treatment) after image exposure, and then performs surface development, or performs fogging treatment after image exposure. A positive image can be obtained by performing surface development while performing (development nucleation treatment).

The above fogging process (development nucleation process) may be performed by exposing the entire surface to light, chemically using a fogging agent, or using a strong developer, and further heat treatment. etc. may also be used.

Of the above two methods for forming a positive image, the latter type of method generally has higher sensitivity than the former type of method, and is suitable for applications requiring high sensitivity.

In this technical field, various techniques are known so far, such as U.S. Pat. No. 2,592,250, U.S. Pat.
, No. 588.982, No. 3,761,288, No. 3.
The methods described in No. 781.27θ, No. 3.798,577 and British Patent No. 1,151.3E13 are known.

[Problems to be Solved by the Invention] Although it is possible to produce photographic materials that form positive images by using these known techniques, it is more difficult to apply these photographic materials to various photographic fields. Further improvement in photographic properties is desired.

For example, U.S. Pat. Nos. 3,781,287 and 3,20
Higher sensitivity can be obtained by chemically sensitizing the interior of silver halide grains or by using a core/shell type emulsion doped with polyvalent metal ions, as disclosed in No. 8.313. However, this type of emulsion has the disadvantage of low image density. Also, US Patent 3,7Ei
1, No. 278 discloses that the surface of the silver halide grains is subjected to a certain degree of chemical ripening treatment in order to improve the above-mentioned drawback of low image density, but the minimum density of the image is high. The stability of silver halogenide emulsions during long-term storage is extremely poor, and the stability of production is also poor, which is disadvantageous.

On the other hand, the silver chloride emulsion mainly composed of silver chloride disclosed in JP-A No. 47-32820 has a relatively high maximum density of a positive image, but the minimum density is not sufficiently small. , resulting in an unclear image.

Therefore, in order to put a direct positive light-sensitive material suitable for the latter method into practical use, it is necessary to develop an internal latent image type silver halide emulsion that has a sufficiently high maximum density, a sufficiently low minimum density, and has excellent storage stability. It is hoped that it will appear.

By using a unique internal latent image type silver halide emulsion, the present invention provides a highly sensitive silver halide photographic material with a sufficiently large maximum density and a sufficiently small minimum density, as well as excellent storage stability. The technical challenge is to provide

[Means for Solving the Problems] The present inventor has made extensive studies to solve the above problems, and as a result, has arrived at the present invention.

That is, the direct positive silver halide photographic light-sensitive material according to the present invention has at least one silver halide emulsion layer containing internal latent image type silver halide grains whose grain surfaces are not fogged in advance, and after image exposure. In a photographic light-sensitive material in which a positive image can be obtained directly by surface development after being subjected to a fogging treatment and/or while being subjected to a fogging treatment, the internal latent image type silver halide grains are chemically sensitized. Alternatively, it comprises a core doped with metal ions and a shell covering the core, and at least a part of the seal is formed under acidic conditions.

The present invention will be explained in detail below.

In the present invention, silver halide emulsion grains consist of a core and a shell, of which at least a portion of the shell is formed under acidic conditions. In addition, when the shell is composed of two or more shells, it is sufficient that at least one of the shells satisfies the conditions of the present invention.

In the present invention, acidic conditions mean that at least a part of the step of forming a shell made of silver halide in an emulsion containing silver halide emulsion grains made of a core doped with a pH value of 5 or more is acidic. carried out under conditions.

Various acids can be used as adjusting agents for adjusting pH under acidic conditions. Examples of preferred acids include inorganic acids such as hydrochloric acid, sulfuric acid, and nitric acid, and organic acids such as acetic acid, oxalic acid, and tartaric acid.

In the present invention, at least a part of the shell is formed under acidic conditions, but acidic conditions are preferable at the initial stage of shell formation, and acidic conditions at the initial stage are preferred when forming a shell containing silver chloride. It is particularly preferred that the pH at the time of shell formation is constant or may be changed as the shell is formed; this change may be in the direction of increasing pH value or in the direction of decreasing pH value. There may be one, or it may be random.

In the present invention, in order to control the pH during shell formation to a certain value, the pH in the reaction layer is measured or detected, and acid is automatically or manually applied to adjust the pH based on the detected value. or a base for neutralization can be introduced.

The core of the silver halide grains of the present invention preferably mainly consists of silver bromide and may further contain silver chloride and/or silver iodobromide. For example, it may be cubic, octahedral, dodecahedral, or a mixture thereof, or it may be spherical, tabular, or irregularly shaped particles. Although the average particle size and particle size distribution of silver halide grains can be varied widely depending on the desired photographic performance, it is more preferable for the particle size distribution to have a narrow distribution. Preferably, it is substantially monodisperse.

Here, silver halide grains with a monodisperse core are defined as silver halide grains constituting the core in which the total weight of silver halide within a grain size range of ±20% around the average grain size 〒 is halogenated. This refers to silver that accounts for 60% or more by weight, preferably 70% or more, and particularly preferably 80% or more.

In this specification, the average particle size f means the particle size ri at which the product nLXrx of the frequency ni of particles having the particle size ri and rl is the maximum (3 significant figures, the smallest digit is 5 to 40
people).

In the case of spherical silver halide grains, the grain size here means the diameter thereof, or in the case of grains having a shape other than spherical, the diameter when its projected image is converted into a circular image of the same area.

The particle size can be obtained, for example, by magnifying the particles 10,000 to 50,000 times with an electron microscope and projecting the particles, and actually measuring the particle diameter or the area at the time of projection on the print (the number of particles measured is nil). Suppose there are more than 1,000 types of discrimination.)

In this specification, the term average particle size shall be used in the meaning defined above.

The method for producing the above-mentioned monodisperse core emulsion is, for example,
g-36890, JP-A-54-48520, JP-A-54
The double jet method disclosed in Japanese Patent Application No.-65521 and the like can be used. In addition, a premix method described in JP-A-54-158220 and the like may also be used.

The cores of the silver halide grains in the present invention are chemically sensitized or doped with metal ions.

Many methods are known for chemical sensitization. That is,
These sensitization methods include sulfur sensitization, gold sensitization, reduction sensitization, noble metal sensitization, and a combination of these sensitization methods. As the sulfur sensitizer, thiosulfates, thioureas, thiazoles, rhodanines, and other compounds can be used. Such methods are described, for example, in U.S. Pat. No. 1,574,944;
No. 623.489, No. 2,4108813, No. 3,8
No. 58,955, etc.

The core of the silver halide grains used in the present invention is, for example, US Pat.
No. 2,842,381, etc.,
Sensitization can be carried out with a water-soluble gold compound or with a reduction sensitizer. For such methods, see, for example, US Pat. No. 2,487,850.

Reference can be made to the descriptions in No. 2,518,898, No. 2,983,810, etc.

Furthermore, noble metal sensitization can also be carried out using noble metal compounds such as platinum, iridium, palladium, and the like. Such methods are described, for example, in U.S. Pat.
, 080 and British Patent No. 818,081.

The core of the silver halide grains in the present invention can be doped with metal ions. To dope the core with metal ions, the metal ions can be added as water-soluble salts, for example, during any process of forming the core particle. Preferred specific examples of metal ions include iridium,
There are metal ions such as lead, antimony, bismuth, gold, osmium, and rhodium. These metal ions are preferably used in a concentration of 1×10 −8 to 1×10 moles per mole of silver.

The shell of the silver halide grains of the present invention preferably contains silver chloride in an amount of 2 mol % or more, more preferably 5 mol % or more, and may also contain silver bromide or silver iodide.

It is more preferable that the shell of the silver halide grain in the present invention covers 50% or more of the surface area of the core, which is chemically sensitized or doped with metal ions. Particularly preferred is complete coverage.

As a method for forming the shell, the double jet method or premix method described above can be used. It is also possible to form the core emulsion by mixing fine grains of silver halide and performing Ostwald ripening.

It is preferable that the silver halide grains of the present invention are not chemically sensitized on the surface of the grains, or are sensitized only to a small extent.

When chemically sensitizing the surface of the silver halide grains of the present invention,
This can be carried out in the same manner as the chemical sensitization of the core particles.

The silver halide grains in the present invention preferably have a narrow grain distribution and are substantially monodisperse even after shell formation, that is, the silver halide grains as a whole are preferably substantially monodisperse. .

Monodisperse silver halide grains herein refer to those in which the weight of silver halide contained within a grain size range of ±20% around the average grain size f is 80% or more of the total weight of silver halide,
Preferably it is 70% or more, particularly preferably 80% or more.

The ratio of silver halide between the core and the shell of the present invention can be arbitrarily determined, but it is preferable that the ratio of the shell is 10% to 88% based on the total silver halide of the silver halide grains.

The composition ratio of the silver halide grains of the present invention is necessarily determined by the silver halide composition of the core, the silver halide composition of the shell, and the ratio of the core to the shell. is preferably 5% to 80%.

The meaning that the grain surface is not fogged in advance means that the emulsion used in the present invention is coated on a transparent film support in a layer of 35 gAg/c, and the test piece is coated with the following surface developer without being exposed to light. It means that the density obtained when developing at 20° C. for 10 minutes at A is not more than 0.8, preferably not more than 0.4.

Surface developer A Metol 2.5g Ascorbic acid 10g NaBOz ・4Hz 0 35gKBr
Add 1 g of water 1 sentence Furthermore, the silver halide emulsion according to the present invention can be prepared using internal developer B having the following formulation after exposing the test piece prepared as described above.
It gives sufficient density when developed with.

Internal developer B Metol 2g Sodium sulfite (anhydrous) 90g Hydroquinone 8g Soda carbonate (-hydrate) 52.5gKB r
5gKI
To be more specific, a portion of the test specimen was exposed to a light intensity scale for a defined period of time up to about 1 second, and then treated with internal developer B for 20 minutes. When developed for 10 minutes at 20° C., it is at least 5 times, preferably at least 10 This shows the maximum concentration of 2 times.

The silver halide emulsion according to the present invention can be optically sensitized with a commonly used sensitizing dye, and is used for supersensitization of internal latent image type silver halide emulsions, negative type silver halide emulsions, etc. Combinations of sensitizing dyes are also useful in the silver halide emulsions of this invention. For information on sensitizing dyes, see Research Disc.
osure) No. 15162 and No. 17843
You can refer to the issue.

The photographic light-sensitive material of the present invention is image exposed (photographed) by a conventional method.
After that, a positive image can be easily obtained directly by surface development. That is, the main step of directly creating a positive image is to remove fogging nuclei by chemical or photochemical action after exposing the photographic light-sensitive material of the present invention, which has an internal latent image type silver halide emulsion layer that has not been fogged in advance, to one image. The process consists of performing surface development after and/or while performing a fogging process. Here, the fogging treatment can be carried out using a compound that provides full exposure or generates fogging nuclei, that is, a fogging agent.

In the present invention, the entire surface exposure is carried out by immersing or moistening the image-exposed photosensitive material in a developer or other aqueous solution, and then exposing the entire surface uniformly to light.

The light source used here may be any light within the wavelength range to which the photographic light-sensitive material is sensitive; high-intensity light such as flash light may be applied for a short period of time, or weak light may be applied for a long period of time. Further, the total exposure time can be varied over a wide range depending on the photographic material, development processing conditions, type of light source used, etc. so as to ultimately obtain the best positive image.

A wide variety of compounds can be used as the fogging agent used in the present invention, and it is sufficient that the fogging agent is present during the development process. (preferably in the silver oxide emulsion layer) or in the developing solution or processing solution prior to development processing.The amount used can be varied over a wide range depending on the purpose. When added to a silver emulsion layer, the amount is 1 to 1500 layers per mole of silver halide, preferably 10 to 10
00mg. When added to a processing solution such as a developer, the preferred amount is 0.01 to 5 g/l, particularly preferably 0.05 to Ig/l.

Fogging agents used in the present invention include, for example, U.S. Pat.
563,785, hydrazines described in 2.588.982, or U.S. Pat. No. 3,227,5
Hydrazide or hydrazone compounds described in US Pat. No. 52; US Pat. No. 3,615,815, US Pat.
No. 9, No. 3,719,494, No. 3,734,738
No. 4 and heterocycle No. 4 described in No. 3,751,901
Further examples include compounds having an adsorption group on the silver halide surface, such as acylhydrazinophenylthioureas described in US Pat. No. 03G, 925.

Moreover, these fogging agents can also be used in combination.

For example, Research Disclosure (ResearchD)
No. 15182 describes the use of a non-adsorption type fogging agent in combination with an adsorption type fogging agent, and this combination technique is also effective in the present invention.

As the fogging agent used in the present invention, either an adsorption type or a non-adsorption type can be used, and they can also be used in combination.

Specific examples of useful fogging agents include hydrazine hydrochloride,
Phenylhydrazine hydrochloride, 4-methylphenylhydrazine hydrochloride, 1-formyl-2-(4-methylphenyl)hydrazine, 1-acetyl-2-phenylhydrazine, 1-acetyl-2-(4-acetamidophenyl)hydrazine, 1-methylsulfonyl-2-phenylhydrazine, 1-benzoyl-2-7enylhydrazine, 1
- Hydrazine compounds such as methylsulfonyl-2-(3-phenylsulfonamidophenyl)hydrazine and formaldehyde phenylhydrazine; 3-(2-formylethyl)-2-methylbenzothiazolium bromide, 3-(2-formylethyl) )-2-propylbenzothiazolium bromide, 3-(2-acetylethyl)-2-benzylbenzoselenazolium bromide, 3
-(2-acetylethyl)-2-benzyl-5-phenyl-benzoxacilium bromide, 2-methyl-3
-[3-(phenylhydrazino)propyl]benzothiazolium bromide, 2-methyl-3-(3-CP-)
Benzothiazolium bromide, 2-methyl-3-[3=(p-sulfophenylhydrazino)propyl]benzothiazolium bromide, 2-methyl-3-[3-(p-sulfo) phenylhydrazino)pentyl 1benzothiazolium iodide, 1,
2-dihydro-3-methyl-4-phenylpyrido [2,
1-bl benzothiazolium bromide, 1,2-dihydro-3-methyl-4-phenylpyrido [2,1-bl
-5-phenylbenzoxacilium bromide, 4.
4'-Ethylenebis(1,2-dihydro-3-methylpyrido[2,1-bl benzothiazolium bromide)
, 1,2-dihydro-3-mef) Lr-4-phenylpyrido[2,1-bl N-substituted quaternary cycloammonium salts such as benzoselenazolium bromide; 5-[1-
ethylnaf) (1,2-b)thiazolin-2-ylideneethylidene]-1-(2-phenylcarbazoyl)methyl-3-(4-sulfamoylphenyl)-2-thiohydantoin, 5-(3- Ethyl-2-penzothiazolinylidene)-3-(4-(2-formylhydrazino)phenyl]rhodanine, 1-[4-(2-]t-lumylhydrazino)phenylco3-phenylthiourea, 1.3
-bis(4-(2-formylhydrazino)phenylcothiourea) and the like.

After image exposure, the photographic light-sensitive material having a silver halide emulsion layer according to the present invention is subjected to full-surface exposure or surface development treatment in the presence of a fogging agent to directly form a positive image. This surface development processing method means processing with a developer substantially free of silver halide solvent.

Developers that can be used in the surface developer used for developing the photographic light-sensitive material according to the present invention include common silver halide developers, such as polyhydroxybenzenes such as hydroquinone, aminophenols, and 3-pyrazolidones. , ascorbic acid and its derivatives, reductones, phenylenediamines, etc., or mixtures thereof. Specifically, hydroquinone, aminophenol, N
-71 thylaminophenol, 1-phenyl-3-pyrazolidone, l-phenyl-4,4-dimethyl-3-pyrazolidone, l-phenyl-4-methyl-4-hydroxymethyl-3-pyrazolidone, ascorbic acid, N, ethyl-p-phenylenediamine, diethylamino-0
-Toluidine, 4-amino-3-methyl-N-ethyl-
N-(β-methanesulfonamidoethyl)aniline,
Examples include 4-amino-3-methyltoethyl (β-hydroxyethyl)aniline. These developers can also be included in the emulsion in advance and allowed to act on the silver halide during immersion in a high pH aqueous solution.

The developer used in the present invention can further contain specific antifoggants and development inhibitors, or these developer additives can be optionally incorporated into the constituent layers of the photographic material. be.

Depending on the purpose, various photographic additives such as wetting agents, film property improvers, and coating aids may be added to the silver halide emulsion according to the present invention. Examples of wetting agents include dihydroxyalkanes, and examples of film property improvers include copolymers of alkyl acrylates or alkyl methacrylates and acrylic acid or methacrylic acid, styrene-maleic acid co-I1, styrene maleic anhydride, etc. Water-dispersible particulate polymeric substances obtained by emulsion polymerization such as acid half-alkyl ester copolymers are suitable, and coating aids include, for example, saponin, polyethylene glycol lauryl ether, and the like. Other photographic additives include gelatin plasticizers, surfactants,
UV absorbers, pH adjusters, antioxidants, antistatic agents,
Thickeners, graininess improvers, dyes, mordants, brighteners.

A development speed regulator, matting agent, etc. may also be used.

The silver halide emulsion prepared as described above is coated on a support via a subbing layer, anti-halation layer, filter layer, etc. as necessary, and is then coated on a support to form the internal latent image type silver halide photographic photosensitive material of the present invention. Get the materials.

It is useful to apply the photographic light-sensitive material according to the present invention for color purposes; in this case, cyan,
Preferably, magenta and yellow dye image-forming couplers are included, and any commonly used couplers can be used.

In addition, it is useful to use ultraviolet absorbers such as thiazolidone, benzotriazole, acrylonitrile, and benzophenone compounds to prevent browning of dye images caused by short-wavelength actinic rays.
It is advantageous to use 0, 326, 327, and 328 (all manufactured by Ciba Geigy) alone or in combination.

Examples of the support for the photographic light-sensitive material according to the present invention include polyethylene terephthalate film, polycarbonate film, polystyrene film, polypropylene film, cellulose acetate film, glass, baryta paper, polyethylene laminate paper, etc., which have been subjected to undercoating as necessary. It will be done.

In addition to gelatin, suitable gelatin derivatives can be used as protective colloids or binders in the silver halide emulsion layer according to the present invention, depending on the purpose. Suitable gelatin derivatives include, for example, acylated gelatin, guanidylated gelatin, carbamylated gelatin, cyanoethanolated gelatin, and esterified gelatin.

In addition, in the present invention, other hydrophilic binders can be included depending on the purpose, and colloidal albumin, agar, gum arabic, dextran, alginic acid, and acetyl can be hydrolyzed to a content of 19 to 20%. cellulose derivatives such as cellulose acetate, polyacrylamide, imidized polyacrylamide, casein, vinyl alcohol polymers containing urethane carboxylic acid groups or cyanoacetyl groups such as vinyl alcohol-vinylaminoacetate copolymers, polyvinyl alcohol, polyvinylpyrrolidone, hydrated These include decomposed polyvinyl acetate, polymers obtained by polymerizing proteins or saturated acylated proteins with monomers having vinyl groups, polyvinylpyridine, polyvinylamine, polyaminoethyl methacrylate, polyethyleneamine, etc., and include emulsion layers or intermediate layers, protective layers, It can be added to the constituent layers of photographic light-sensitive materials such as the filter layer and backing layer depending on the purpose, and the above-mentioned wood-philic binder can also contain a suitable plasticizer, lubricant, etc. depending on the purpose. .

Further, the constituent layers of the photographic light-sensitive material according to the present invention can be hardened with any suitable hardening agent. These hardeners include chromium salts, zirconiums, aldehydes such as formaldehyde and mucohalogen acids, halotriazine, polyepoxy compounds, ethyleneimine,
Examples include vinyl sulfone hardeners, acryloyl hardeners, and the like.

Further, the photographic light-sensitive material according to the present invention has, on a support, at least one photosensitive emulsion layer containing the internal latent image type l-silver halide grains according to the present invention, as well as a filter layer, an intermediate layer, and a protective layer. It is possible to provide a large number of different photographic constituent layers, such as layers, subbing layers, backing layers, antihalation layers, etc.

When the photographic light-sensitive material of the present invention is used for full color use, at least a red-sensitive silver halide emulsion layer, a green-sensitive silver halide emulsion layer, and a blue-sensitive silver halide emulsion layer are coated on the support. will be established. In this case, it is sufficient that at least one photosensitive silver halide emulsion layer contains the internal latent image type silver halide grains according to the present invention, but all the photosensitive silver halide emulsion layers according to the present invention It is preferable that each photosensitive silver halide emulsion layer contains internal latent image type l\\ silver halide grains according to In this case, it is sufficient that at least the same color-sensitive layers having different IR sensitivities contain the internal latent image type silver halide grains according to the present invention, but all the emulsion layers may be It is preferable that it contains the internal latent image type/\silver halide grains of the present invention.

The photographic light-sensitive material according to the present invention is suitable for general black and white use, for X-ray use,
For color, for false color, for printing, for infrared, for micro,
It can be effectively applied to various uses such as silver dye bleaching, and can also be applied to colloid transfer method, silver salt diffusion transfer method, Rogers U.S. Pat.
No. 7 and No. 2,983,130 [No. 1.

U.S. Pat. No. 3,253,915 to Weyertz et al., U.S. Pat. No. 3,227.550 to Whitemore et al., U.S. Pat. U.S. Patent 3 of Rand et al.
, No. 415,844, No. 3,415,845 and No. 3
The present invention can be applied to a color image transfer method and a color diffusion transfer method as described in No. 415,848.

[Effects of the Invention] By using the internal latent image type silver halide emulsion unique to the present invention, a highly sensitive silver halide photograph with sufficiently high maximum density and sufficiently low minimum density and excellent storage stability can be obtained. A photosensitive material can be obtained.

[Examples] The present invention will be illustrated below with reference to Examples, but the embodiments of the present invention are not limited thereto.

Example 1 A monodisperse core/shell emulsion was prepared as follows.

A cubic silver bromide emulsion with an average grain size of 0.8 gra was prepared by simultaneously adding equimolar amounts of silver nitrate aqueous solution and potassium bromide aqueous solution over 40 minutes using a controlled double jet method while controlling the temperature of an aqueous solution containing gelatin at 50°C. Obtained. To the core emulsion thus obtained were added 2.0 mg of sodium lithiosulfate per mole of silver and 1.5 g of potassium chloroaurate per mole of silver, and chemical ripening was carried out at 60°C for 60 minutes. This emulsion is called Emulsion A.

Next, the obtained emulsion was divided into four parts to obtain four types of emulsions, emulsions A-1 to A-4 as shown below.

Emulsion A-1: A silver nitrate aqueous solution and a potassium bromide aqueous solution were simultaneously added to the chemically sensitized core emulsion A to obtain a cubic core/shell type emulsion with an average grain size t and op ■. However, by adding ammonia at this time, the pH becomes 8.
, 0, the shell was formed. The obtained emulsion had a narrow particle size distribution and was a monodisperse emulsion.

Emulsion A-2 = A shell was precipitated in the chemically sensitized core emulsion A in the same manner as A-1, and the average grain size was 1, OJLra
A cubic core/shell type emulsion was obtained. However, at this time, ammonia was not added and the shell was formed under the conditions of pH 5.8. The resulting emulsion was a monodisperse emulsion.

Emulsion A-3=A shell was precipitated on the chemically sensitized core emulsion A in the same manner as in A-1 to obtain a cubic core/shell type emulsion with an average grain size of 1 Opm. However, at this time, nitric acid was added instead of ammonia, and a shell was formed under conditions of pH 4 and 5. The resulting emulsion was a monodisperse emulsion.

Emulsion A-4=A shell was precipitated on the chemically sensitized core emulsion A in the same manner as in A-3 to obtain a cubic core/shell type emulsion with an average grain size of 1.0 l. However, at this time pH3
, 0, the shell was formed.

The resulting emulsion was a monodisperse emulsion.

In the above emulsions A-1 to A-4, 1.0 mg of sodium 1,000 sulfate per mole of silver and 1.0 mg of potassium chloroaurate per mole of silver were added.
．． 5 mg was added, and chemical sensitization was performed at 60° C. for 30 minutes.

After adding a commonly used spreading agent and hardening agent to each emulsion obtained,
A sample was obtained by coating on a cellulose triacetate support and drying so that the coated silver amount was 35 g/100 cm''.

These samples were subjected to the following treatments. That is, each sample was stored for 3 days at a temperature of 20°C and a relative humidity of 55% (condition-1).
) and stored at a temperature of 50°C and a relative humidity of 80% for 3 days (condition-2).The obtained sample was exposed to light through an optical wedge for sensitometry using a photosensitive needle (hereinafter referred to as wedge exposure), and then Developed at 20°C for 4 minutes using a developer with the following formula:
Next, washing with water, fixing, washing with water, and drying were carried out in a conventional manner.

Phenidone 0.4g Sodium sulfite (anhydrous) 75g Hydroquinone 10g Soda carbonate (
- water salt) 40 g Potassium bromide 4 g 5-methylbenzotriazole 105 g 1-acetyl-2-phenylhydrazine (fogging agent) 0.1 g Water was added (adjusted to pH 12.5 with sodium hydroxide). Table 1 shows the results of measuring the maximum and minimum densities of the images.

As is clear from Table 1, the emulsion of the present invention has a large maximum density, a small minimum density, and has significantly improved storage stability.

Example 2 A monodisperse core/shell emulsion was prepared as follows.

While controlling the temperature of an aqueous solution containing gelatin at 50°C, equimolar amounts of a silver nitrate aqueous solution and a potassium bromide aqueous solution were simultaneously added over a period of 40 minutes using a controlled double jet method to produce tetradecahedral bromide with an average particle size of 0.8 l. A silver emulsion was obtained. 2.0+sg of sodium thiosulfate per mole of silver was added to the core emulsion thus obtained, and chemical ripening was performed at 80° C. for 80 minutes. This emulsion is called emulsion B.

Next, the obtained emulsion was divided into three parts to obtain three types of emulsions, emulsions B-1 to B-3 as shown below.

Emulsion B-1 = A silver nitrate aqueous solution and a potassium bromide aqueous solution were added simultaneously to the chemically sensitized core emulsion B to obtain an average grain size of 1. A tetradecahedral core/shell type emulsion of Opm was obtained.

However, by adding sulfuric acid at this time, the pH becomes 2.0.
A shell was formed under these conditions. The obtained emulsion had a narrow particle size distribution and was a monodisperse emulsion.

Emulsion B-2=A shell was precipitated on the chemically sensitized core emulsion B in the same manner as B-1 (pH-2.0), and the average grain size was 1. A dodecahedral core/shell type emulsion of OJL+* was obtained. However, at this time, instead of potassium bromide aqueous solution, potassium bromide and sodium chloride (molar ratio KBr/NaC)
l2 = 9515) was added. The resulting emulsion was a monodisperse emulsion.

Emulsion B-3: A shell was precipitated in the chemically sensitized core emulsion B in the same manner as B-2 (pH -2.0) to form a tetradecahedral core/shell type emulsion with an average grain size of 1.94 m. Obtained. However, at this time, the molar ratio of potassium bromide and sodium chloride was 55/45, which was the pH condition. The resulting emulsion was a monodisperse emulsion.

Parts of the four emulsions B-1-B-3 and Emulsion A-2 of Example 1 were taken, and 1.0 mg of sodium thiosulfate per mole of silver was added to each emulsion. 58
Chemical ripening was performed at ℃ for 30 minutes.

Emulsions B-1-B-3 obtained above and Emulsion A-2 of Example 1 were divided into eight types of emulsions: emulsions whose surfaces were not chemically sensitized and emulsions whose surfaces were chemically sensitized.
The following sensitizing dyes were added respectively.

2Hs In addition, the magenta coupler 1-(2,4,8-)lichlorophenyl)-3-(2-chloro-5-octadecylsuccinimidoanilino)-5~pyrazolone was added to a mixed solvent of dibutyl phthalate and ethyl acetate. An emulsion was prepared by dissolving and dispersing the gelatin in an aqueous gelatin solution.

Next, these emulsified dispersions were added to and mixed with the above emulsion, and a hardening agent was added so that the amount of coated silver was 2011 g/1.
A sample was obtained by coating the sample on a cellulose triacetate support and drying it so as to give 00crn'.

These samples were wedge exposed through a yellow filter and developed for 3 minutes at 30° C. in a developer of the following formulation.

4-Amino-3-methyl-N-ethyl-N-(β-methanesulfonamidoethyl) aniline sulfur salt g Sodium sulfite (anhydrous) 2 g Sodium carbonate (-hydrate) 15 g Potassium bromide 1 g Add benzyl alcohol 11 (The pH was adjusted to 10.2 with potassium hydroxide.) However, the entire surface was uniformly exposed to white light of 1 lux for 1 minute from 30 seconds after the start of development. Then, it was washed with water, bleached, washed with water, and dried in a conventional manner.

Table 2 shows the results of measuring magenta positive images for each sample obtained. However, the sensitivity is (minimum concentration among maximum concentration)
It is expressed as a relative value of the reciprocal of the exposure amount that gives a density of XI/2.

As is clear from the results in Table 2, it can be seen that the emulsion of the present invention has a high maximum density and high sensitivity even when surface chemical sensitization is performed or not.

Example 3 A monodisperse core emulsion was prepared in the same manner as Emulsion A in Example 2. However, 5 minutes after starting the addition of silver nitrate aqueous solution and potassium bromide aqueous solution, 0.02 m/mole of silver was added.
g of potassium was added with hexachloride resort. The obtained emulsion is referred to as Emulsion C.

Next, a silver nitrate aqueous solution and a potassium bromide aqueous solution were simultaneously added to the obtained emulsion C to obtain a cubic core/shell emulsion with an average grain size of 1 Ogm. At this time, add sulfuric acid to adjust the pH.
The shell was formed using 3.0. The obtained emulsion is emulsion C.
-1.

Emulsion C-1 was coated on a support according to Example 2 to obtain a sample. Table 3 shows the measurement results for the positive image obtained by wedge exposure and development.

Table 3 As is clear from Table 3, the emulsion of the present invention doped with metal ions also provides good positive images.

Example 4 Sample No. in Example 2. In 9 and 10, the sensitizing dye was replaced with the following, and the coupler was replaced with the cyan coupler 2,4-dichloro-3-methyl-8-(α-(
A sample was prepared with the only difference being that 2.4-tert-aminophenoxy)butyramidophenol was used, and after wedge exposure, the surface was developed in the same manner.

The maximum and minimum densities and sensitivities of the obtained cyan positive images were similar to the results in Table 2.

Danjin color east C2Hs

Claims (1)

[Claims] It has at least one silver halide emulsion layer containing internal latent image type silver halide grains whose grain surfaces are not fogged in advance, and after image exposure, after fogging treatment, and/or
Alternatively, in a photographic light-sensitive material in which a positive image can be obtained directly by surface development while being subjected to a fogging process, the internal latent image type silver halide grains are chemically sensitized or doped with metal ions as a core. 1. A direct positive silver halide photographic light-sensitive material comprising: and a shell covering the core, at least a part of the shell being formed under acidic conditions.