JPH02271347A - Direct positive silver halide photosensitive material - Google Patents

Abstract

PURPOSE:To lower the minimum density of a photosensitive material and to enhance the contrast of a toe part by sensitizing the core of each silver halide grain by gold.sulfur and fogging its surface of a shell. CONSTITUTION:This photosensitive material uses core/shell type silver halide grains, and each core is chemically ripened in the presence of a gold compound, such as a chloroauric acid, and thiosulfate, such as sodium thiosulfate, to form core grains in a monodispersion, and each core is coated with a silver halide shell and the surface of each shell is fogged in advance.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a pre-fogged direct positive silver halide photosensitive material. This invention relates to a direct positive silver halide photosensitive material that has been photo- or chemically fogged in advance.

[Prior art]

Direct positive silver halide photographic materials are often used primarily in the printing industry for the "one turn" process in the photolithography process.

In this "returning" process, the original original image is reproduced from a positive image to a positive image or from a negative image to a negative image, but the important point in this process is to faithfully reproduce the fine lines and halftone dot images of the original image. required.

The photographic properties of the direct positive silver halide emulsion used to meet these requirements are that the tone is high (particularly high contrast in the toe area), the maximum density (Dmax) is high, and the minimum density (Dm
i n) is required to be low.

More recently, light sources rich in ultraviolet light, such as xenon,
Direct positive silver halide photosensitive materials for bright rooms that are exposed using metal halides, mercury lamps, or ultra-high pressure mercury lamps and handled under fluorescent lamps that block ultraviolet rays are increasingly being used.

This photosensitive material has the advantage of being extremely easy to work with because it can be handled in a bright room compared to conventional photosensitive materials that are handled in a dark room. Such sensitive materials for use in bright rooms are required to have good safelight properties under fluorescent lamps that block ultraviolet rays.

Furthermore, photosensitive materials for bright room use are exposed to ultraviolet rays with higher energy intensity than conventional visible light sources for exposure, but when exposed with such light sources, in addition to reversed images, high exposure areas It is well known that a re-inverted negative image is formed. This re-inversion negative image increases the Dmfn, which greatly impairs the quality of the photosensitive material.

The occurrence of such a reversal negative image is unique to direct positive reversal emulsions and varies depending on the type of silver halide, manufacturing conditions, etc., but as mentioned above, it significantly deteriorates the quality of the photosensitive material. Therefore, there is a strong desire to develop an effective method to suppress re-inversion.

Generally, emulsions used in direct positive silver halide photosensitive materials can be broadly divided into two types. One is a type of emulsion consisting of silver halide grains with an electron-trapping compound that is said to trap electrons inside the grains, and whose surfaces are fogged in advance. Invert.

The other type of emulsion is one in which the electron-trapping compound is not formed inside the silver halogenide grains, but the grain surfaces are fogged, and the inversion occurs only when an organic desensitizer is added.

This patent belongs to the former type.

The former emulsion is disclosed in US Patent No. 3. 367, 778
, 3,632,340, etc.

In this patent, a core emulsion is made in advance, and the core emulsion is
The shell is coated by chemical sensitization treatment such as sulfur sensitization, gold sensitization, reduction sensitization, and treatment with metals belonging to Group 8 of the periodic table (rhodium, palladium, iridium, osmium, platinum, ruthenium, etc.) A method is described in which the surface of the shell is then fogged to directly produce a positive reversal emulsion.

Further, when a metal belonging to Group 8 of the periodic table is used as an electron trapping compound, a method of adding the metal at the time of silver halide precipitation when preparing an emulsion is also a known technique.

However, the reversal emulsions produced by these methods do not always produce a good reversal image, especially when exposed to ultraviolet light, and the reversal image may be soft in tone, have a high Dmin, or
At present, it is difficult to obtain sufficient quality required in the plate-making process, as re-inverted negative images appear conspicuously.

(Objective of the Invention) The object of the present invention is to provide a silver halide photosensitive material for direct positive use, which does not cause re-inversion in the high exposure range, has a low Dmin, and has high contrast in the toe area, especially a silver halide photosensitive material for direct positive use in a bright room. The purpose of the present invention is to provide photosensitive materials.

(Structure of the Invention) The object of the present invention is to provide a silver halide grain comprising a core/shell type silver halide grain, the core being chemically ripened in the presence of a gold compound and a thiosulfate, and a silver halide shell covering the core. This was achieved using a silver halide photosensitive material for direct positive use, which is characterized in that its surface is pre-fogged.

In addition, in the chemical ripening of the core using a gold compound and thiosulfate in the present invention, it is important to generate photosensitive nuclei in the core.
There is no need to generate fog nuclei in the core by excessive chemical aging.

The gold compounds used in the present invention are monovalent and trivalent water-soluble gold salts, such as chloroauric acid, gold thiocyanate, sodium chloroaurate, potassium aurate, potassium chloroaurate,
Examples include potassium bromoaurate, potassium iodoaurate, potassium gold cyanide, potassium gold thiocyanide, sodium gold thiomaylate, and gold thioglucose.

Examples of the thiosulfate used in the present invention include ammonium thiosulfate, sodium thiosulfate, potassium thiosulfate, and the like.

Core/shell type silver halide grains are produced by mixing a fine-grain emulsion with a core emulsion that has been chemically ripened in the presence of a gold compound and thiosulfate, and then coating the core grains with a silver halide shell through physical ripening. A silver halide shell is formed on top of the core grains by the so-called controlled double jet method, in which a silver nitrate solution and a halide compound are simultaneously added to the chemically aged monodisperse core emulsion while keeping the silver ion concentration constant. Although there are methods of coating the material, the latter method is particularly preferred for application of the present invention.

The halogen compositions of the core and shell may be the same or different. Further, the molar ratio of the amount of silver halide in the core to the amount of silver halide in the shell is 1:1 or more, preferably 1:2 to 1.
:10 gives good results.

Although the halogen composition of the core and shell is not particularly limited, silver chlorobromide and silver bromide are preferable to silver chloride in terms of the reversal characteristics of the reversal emulsion, particularly Dm f n. For silver chlorobromide, the amount of silver chloride is preferably 10 mol % or less.

The size of the core/shell type silver halide grains used in the present invention is 0.05 to 1 micron, but 0.05 to 1 micron is used as a bright room direct positive silver halide photosensitive material.
A thickness of 2 microns or less is desirable.

If the size is larger than that, the safe light property will deteriorate and the tone will become soft.

The core/shell type silver halide grains may be regular crystals such as cubes or octahedrons, or irregular crystals such as spherical or plate shapes, but the grain size distribution is preferably monodisperse.

The conditions for chemical ripening of the core particles using a gold compound and thiosulfate according to the present invention will be described below, and may be appropriately selected depending on the desired photographic properties.

Aging temperature is 40-70℃, pH is 4-10, preferably 5.
~7. The time is 30 minutes to 120 minutes, and the amount of gold compound used is the amount of silver halide in the core emulsion (converted to the amount of silver nitrate).
It is preferably 0.002 to 0.25 mmol per kg, preferably 0.025 to 0.1 mmol.

The amount of thiosulfate is 0.2 to 2 mmol, preferably 0.4 to 1.2 mmol, per 1 kg of silver halide (converted to silver nitrate) in the core emulsion.

The fogging on the shell surface of silver halide grains carried out in the present invention is described in U.S. Pat.
632,340, 3.501°305, JP-A-1973-
Fogging can be carried out using a known method such as using a reducing agent alone or a reducing agent and a gold compound, or using light, as described in No. 68133.

The fogging conditions may be varied depending on the desired photographic properties, but generally the pH is 6 to 10 and the temperature is 40 to 80°C.
, pAg ranges from 4 to 9.

Reducing agents include aldehydes such as formalin, hydrazine, triethylenetetramine, thiourea dioxide,
Stannous chloride, amine borane, etc. are used.

The amount of the reducing agent used is 0.1 to 100 mmol, preferably 10 mmol or less, per 1 kg of silver halide (in terms of silver nitrate).

The gold compound used is the same as that used for chemical sensitization of the core described above.

The amount used is 1k of silver halide (converted to silver nitrate)
0.002 to 0.3 mmol per g, preferably 0.0
5 to 0.15 mmol.

Gelatin is most preferred as a protective colloid and binder for silver halide grains used in the practice of the present invention, but polymeric compounds other than gelatin (for example, polyvinyl alcohol, polyvinylpyrrolidone, polyacrylamide, polyacrylic acid , polyvinylimidazole, polyethylene glycol, maleic anhydride, polystyrene sulfonic acid, polyvinylpyridine, cellulose derivatives such as methylcellulose, hydroxymethylcellulose, carboxymethylcellulose, copolymers of these monomers, etc.) to replace part or all of the gelatin. I can do it.

The gelatin used is alkali-treated gelatin, acid-treated gelatin (
Isoionic point 5-9), enzyme-treated gelatin, low calcium content gelatin (content fi 100 ppm or less),
High jelly strength gelatin (PAGI method jelly strength 270 or higher), gelatin derivatives (for example, chemically modified gelatin such as phthalated gelatin and carbamylated gelatin), etc. are used.

Also, to improve dimensional stability as part of the binder,
Polymer latex can be used. Examples of the polymer latex include polyacrylic acid types such as polyvinyl acetate, polymethyl acrylate, ethyl, and butyl, polymethacrylic acid types such as polymethyl methacrylate, ethyl, and butyl, polystyrene types, polybutadiene types, and the like. There are copolymers of monomers, etc. Although the particle size and physical properties of the polymer latex, such as glass transition point, are not particularly limited, it is desirable that the particle size is 1 μm or less and the glass transition point is 50° C. or less.

Dyes with absorption wavelengths between 400 nm and 700 nm can be used in the practice of this invention.

These dyes can be added to emulsion layers, protective layers, interlayers, subbing layers, and backing layers. In particular, in direct positive silver halide light-sensitive materials for bright room use, in order to improve safelight properties in bright room conditions, it is necessary to reduce or cut the photosensitivity of silver halide in the visible light region, and to maximize absorption. 400
It is desirable to use a dye having a wavelength of 550 nm to 550 nm, which is eluted during the development of the photosensitive material or whose color is erased by an alkali, reducing agent, etc. in the processing solution. Examples of these dyes include oxonol dyes, azo dyes, benzylidene dyes, merocyanine dyes, styryl dyes, and quinoline dyes. 59-154439, 58-176635
, 58-215643, 52-20822, 49
-5616 shows a dye with absorption maximum between 400 and 700 nm. In the direct positive silver halide light-sensitive material of the present invention, particularly for bright room use, it is desirable to contain these dyes, and the amount of the dye used is 0.000. It can be used in a range of 0.02 to 0.3 g, preferably 0.05 to 0.2 g.

Spectral sensitizers and organic desensitizers can be used in the practice of this invention.

Spectral sensitizing dyes include known dyes such as dimethine dyes, trimethine cyanine dyes, halogen-substituted hydroxyphthalein dyes, phenazine dyes, benzothiazole, cyanine dyes containing a benzoselenazole nucleus, cyanine dyes containing a naphthoxazole nucleus, and trimethine dyes. Phenylmethane dyes, cyanine dyes containing indolenine nuclei, cyanine dyes containing thiazole nuclei, etc. can be used.

Organic desensitizers may be used, although reversal is possible even if they are not used in the practice of the present invention.

As organic desensitizers, those having a positive sum of oxidation potential and reduction potential are effective as desensitizers. Particularly known desensitizers include pinacriptol yellow, pinacriptol green, phenosafranine, 5-nitrobenzotriazole, etc.
Organic desensitizers described in et al. can also be used.

Known additives can be added to the direct positive silver halide photosensitive material used in the present invention.

Stabilizers include mercapto compounds, benzotriazole compounds, oxazole compounds, etc. Hardeners are not particularly limited, but include aldehyde compounds, 2-hydroxy-4,
6-dichloro-1,3,5-triazine, N-methylol compound, vinyl sulfone compound, etc. Coating aids include saponin, alkylene oxide type, glycidol type nonionic surfactant, carboxylic acid, sulfonic acid, phosphoric acid. , anionic surfactants containing acidic groups such as sulfate ester groups and phosphate ester groups, amphoteric surfactants such as amino acids and aminosulfonic acids, and polyalkylene oxide compounds.

Supports used in the practice of the present invention include, for example, glass,
Film bases such as cellulose acetate, polyethylene terephthalate, baryta paper, resin coated paper, aluminum foil, concrete, etc. can be used.

The direct positive silver halide photosensitive material of the present invention may also contain a brightening agent, an ultraviolet absorber, a matting agent, an antistatic agent, etc., if necessary.

The direct positive silver halide photosensitive material of the present invention can be processed under various conditions, and the processing is not particularly limited, such as high-temperature rapid automatic processor processing at 30 to 50°C for 20 to 60 seconds, manual image processing, etc. .

As the developer, it is possible to use either a developer used for silver halide photographic light-sensitive materials or a lithium developer.

〔Example〕

1. Preparation of core/shell emulsions Comparative (A-G) and inventive emulsions (H-J)
) was prepared.

Emulsion A (for comparison) A 2N potassium bromide aqueous solution containing 200 mg of rhodium chloride per 1 kg of silver nitrate and a silver nitrate aqueous solution of the same concentration were mixed at 50°C for 30 minutes using a controlled double jet method to prepare a core emulsion. After that, 1 part of a 2N potassium bromide aqueous solution and a silver nitrate aqueous solution containing no rhodium chloride were added.
A core/shell emulsion was prepared by mixing for 00 minutes.

This emulsion was demineralized and washed with water by the flocculation method, then inert gelatin was added and redissolved at 40°C. The ratio of silver nitrate to gelatin was 2:1. The shapes of the core particles and the particles after being coated with the shell were both cubic, with average particle diameters of 93 mμ and 152 mμ, respectively.

Emulsion B (for comparison) Instead of rhodium chloride in Emulsion A, potassium hexachloroiridate (III) was added at 127 μg per 1 kg of silver nitrate.
Emulsion A was prepared in exactly the same manner as Emulsion A.

Emulsion C (for comparison) Emulsion C was also prepared in the same manner as A, and ammonium hexachloroiridate (IV) was added to silver nitrate ib at a concentration of 127
■ was used.

Emulsion D (for comparison) Emulsion D was also prepared in the same manner as A, and hexachloroplatinum (
IV) 100 mg of sodium acid was used per 1 kg of silver nitrate.

Emulsion E (for comparison) A 2N potassium bromide aqueous solution and a silver nitrate aqueous solution of the same concentration were mixed at 50°C for 30 minutes using a controlled double jet method, and this core emulsion was prepared by adding 70 mg of sodium thiosulfate to 1 kg of silver nitrate. After chemical ripening at 50° C. for 120 minutes, a 2N potassium bromide aqueous solution and a silver nitrate aqueous solution were mixed for 100 minutes to prepare a core/shell emulsion in which the core was chemically sensitized. Desalting, washing with water, and redissolving were carried out in the same manner as in Emulsion A.

The shape and size of the particles after coating with the core particles and shell were not different from those of Emulsion A.

Emulsion F (for comparison) A 2N potassium bromide aqueous solution and a silver nitrate aqueous solution of the same concentration were mixed at 50°C for 30 minutes using the controlled double jet method, and this core emulsion was mixed with 50 μg of thiourea dioxide per 1 kg of silver nitrate. After addition and chemical ripening at 50° C. for 40 minutes, a 2N potassium bromide aqueous solution and a silver nitrate aqueous solution were mixed for 100 minutes to prepare a core/shell emulsion in which the core was chemically sensitized.

Desalting, washing with water, and redissolving were carried out in the same manner as in Emulsion A. The grain size is the same as emulsion A.

Emulsion G (for comparison) When chemically ripening the core of Emulsion F, in addition to thiourea dioxide, 7μ of chloroauric acid was added to 1 kg of silver nitrate, and the mixture was heated at the same temperature.
It matured over time. The following was prepared in exactly the same manner as Emulsion F.

Emulsion H (invention) A 2N potassium bromide aqueous solution and a silver nitrate aqueous solution of the same concentration were mixed at 50°C for 30 minutes using a controlled double jet method, and this core emulsion was mixed with 70 μm of sodium thiosulfate and chloride per 1 kg of silver nitrate. Add 7μ of gold acid and heat at 50°C for 12
After chemically ripening for 0 minutes, a 2N potassium bromide aqueous solution and a silver nitrate aqueous solution were mixed for 100 minutes to prepare a core/shell emulsion in which the core had been chemically ripened.

Desalting, washing with water, and redissolving were carried out in the same manner as in Emulsion A.

Emulsion I (Invention) In Emulsion I, sodium thiosulfate and chloroauric acid were added in amounts of 70 and 15, respectively, per 1 kg of silver nitrate during chemical ripening of the core, and ripened at the same temperature and time.

Emulsion J (invention) A 2N potassium bromide aqueous solution containing 5 mol% sodium chloride and a silver nitrate aqueous solution of the same concentration were mixed at 50°C for 10 minutes using a controlled double jet method, and this core emulsion was mixed with 1 kg of silver nitrate. To the mixture, 70@g of sodium thiosulfate and 7 μg of silver chloride/auric acid were added, and after chemical aging at 50°C for 80 minutes, the same 2N potassium bromide aqueous solution and silver nitrate aqueous solution as the core were mixed for 120 minutes. A core/shell emulsion in which the core was chemically sensitized was prepared. Desalting, washing with water, and redissolving were carried out in the same manner as in Emulsion A.

The shape and size of the particles were both cubic, and the average particle diameter was 120 mμ after being coated with a shell of 65 mμ.

2. Preparation of emulsion provided with fog nuclei.

Emulsions (A-J') were given fog nuclei under the same conditions.

To the redissolved emulsion, 150 μg of thiourea dioxide and 2 μg of chloroauric acid were added to 1 kg of silver nitrate, the pH was adjusted to 6, and after heating at 60°C for 60 minutes, the temperature was lowered to below 40°C. Ta.

An appropriate amount of 2-hydroxy-4゜6-dichloro-1,3,5) riazine as a hardening agent and sodium lauryl sulfonate as a surfactant were added to this emulsion, and a polyethylene terephthalate film base with a thickness of 100μ was added. The amount of silver nitrate was 5 g per 1 d. The protective layer was coated with a coating solution containing 1 g of gelatin per 1 d of gelatin and a yellow dye having the following structural formula (100 cm/d).

The polyethylene terephthalate film base used had been coated with a backing layer containing a yellow dye having the following structural formula (100 square meters per dye).

Yellow dye CI (3-C-C===CH C-C-CH3 N C=0 0Na-CN Maximum absorption wavelength 20 nm The coated emulsion was heated at 50°C for 4 days, then exposed, developed,
Fixed and washed with water.

Exposure was performed using a light wedge for sensitometry and a bright room printer (Dainippon Screen P627 printer) for 4 and 32 counts, and then developed with Geracol (manufactured by Mitsubishi Paper Mills Co., Ltd.) at 20°C for 90 seconds and fixed. , washed with water and dried. (Note: The number of counts is the exposure amount; 32 counts is an exposure amount that is four times the amount of 4 counts.) The transmission density of the sample was measured using a Macbeth transmission densitometer (model RD917) to obtain photographic characteristics.

The results are shown in Table 1 below.

(The following is a blank space) [Effects of the Invention] As shown in Table 1, emulsions H, I, and J of the present invention have a low Dmin without occurrence of re-inversion at a high exposure dose (32 counts). It also has a high gamma and has extremely good photographic properties compared to other comparative emulsions A-G.

Claims (1)

[Claims] It consists of core/shell type silver halide grains, the core is chemically ripened in the presence of a gold compound and thiosulfate, and the surface of the silver halide shell covering the core is fogged in advance. Characteristic direct positive silver halide photosensitive material.