JPH10197997A - Radiation image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the radiation image forming method good in silver color tone after development processing and superior in sharpness and graininess and high in image quality. SOLUTION: The radiation image is photographed by bringing a silver halide photographic sensitive material provided with silver halide emulsion layers on both sides of a support into close contact with a radiation sensitizing screen. This photographic sensitive material has the silver halide emulsion layers spectrally sensitized in the red wavelength region of 580-700nm and containing flat silver halide grains having an aspect ratio of 8-40, and light emitted from the radiation sensitizing screen passes through the emulsion layer on the screen side and this crossover light irradiates the emulsion layer on the reverse side in an intensity of 5-30%, and this radiation sensitizing screen has a light emission peak in the above red region.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a radiation image using a silver halide photographic light-sensitive material, and more particularly, to a high-quality radiation having a good silver image tone after development, and excellent sharpness and granularity. The present invention relates to an image forming method.

[0002]

2. Description of the Related Art At present, in radiographic photography, a screen / film photography system comprising a combination of a radiation-sensitive silver halide photographic material (film) and a radiographic intensifying screen is usually provided on both sides of a double-sided photosensitive material. A system with two screens is used.

[0003] Radiation films used in these screen film photographing systems are (a) about 350 to 520 n.
m, a regular type film having sensitivity in a blue region, (b) an ortho type film having sensitivity in a green region of about 500 to 600 nm, and (c) about 580 to 700.
Panchromatic type films having a sensitivity in the red region of nm are known.

Therefore, a screen having a light emission peak in a blue region for a regular type film, a screen having a light emission peak in a green region for an ortho type film, and a screen having a light emission peak in a red region for a panchromatic film. Are used in combination.

However, in any case, the silver tone after the development processing is yellowish, which makes it difficult for an observer to see and is unpleasant. Therefore, a pure black or blue-black tone is desired.

Further, the light emitted from the radiation intensifying screen passes through the silver halide emulsion layer on the screen side and is emitted to the opposite side of the silver halide emulsion layer. However, sharpness and granularity are not yet satisfactory. Therefore, there is a strong demand for a screen film having higher sharpness and granularity, and improvement has been desired.

[0007]

SUMMARY OF THE INVENTION In view of the above-mentioned problems, an object of the present invention is to provide a high-quality radiation which has a good silver image tone after development, and has excellent sharpness and granularity. An object of the present invention is to provide an image forming method.

[0008]

The above object of the present invention is achieved by the following means.

In a radiographic image forming method in which a silver halide photographic light-sensitive material having a silver halide emulsion layer provided on both sides of a support and a radiographic intensifying screen are brought into close contact with each other and photographed, the silver halide photographic light-sensitive material is 580 ~ 700n
m is spectrally sensitized to the red region and the aspect ratio is 8 to
A silver halide emulsion layer containing 40 tabular silver halide grains, and light emitted from a radiographic intensifying screen passes through the silver halide emulsion layer on the screen side and the silver halide emulsion on the opposite side. A radiation image forming method, wherein crossover light emitted to the layer is 5% or more and 30% or less, and the radiation intensifying screen is a screen having an emission peak in the red region.

A silver halide emulsion of a silver halide photographic light-sensitive material has an aspect ratio of 8 to 40 and a ratio of a length of a side having a maximum length to a length of a side having a minimum length of 1 or more and 2 or more. The radiation image forming method as described in the above item, wherein the following hexagonal silver halide grains are contained in 50% or more of the total projected area.

The radiation image forming method according to the above item, wherein the silver halide photographic material has a crossover cut layer between the support and the silver halide emulsion layer.

Hereinafter, the present invention will be described specifically.

In the tabular silver halide emulsion, the aspect ratio means the ratio of the diameter to the thickness of silver halide grains. That is, it is a value obtained by dividing the diameter of each silver halide grain by the thickness. Here, the diameter, when observing the silver halide particles with a microscope or an electron microscope,
It refers to the diameter of a circle having an area equal to the projected area of the grain. Therefore, an aspect ratio of 8 or more means that
This means that the diameter of the circle is at least eight times the thickness of the particle. The aspect ratio of the emulsion grains in the invention is from 8 to 40, preferably from 10 to 40, particularly preferably from 10 to 30.
If the aspect ratio is too high, pressure fogging or the like will occur, and if it is too low, the excellent properties of the tabular emulsion will be reduced.

As an example of a method of measuring the aspect ratio, there is a method of taking a transmission electron microscope photograph by a replica method and obtaining the equivalent circle diameter and thickness of each particle. In this case, the thickness is calculated from the length of the shadow of the replica.

The shape of the tabular grains in the present invention is preferably hexagonal. The hexagonal shape means that the shape of the main plane of the tabular grains has an adjacent side ratio (maximum side length / minimum side length) of 1 or more and 2 or less. Preferably, the adjacent side ratio is 1 or more and 1.6 or less, and more preferably, the adjacent side ratio is 1 or more and 1.2 or less. Particularly in high aspect ratio grains, triangular tabular grains increase in tabular grains. Triangular tabular grains appear when Ostwald ripening has progressed too much. For this reason, it is necessary to shorten the aging time as much as possible. For this purpose, it is necessary to make efforts to increase the ratio of tabular grains by nucleation.

The silver halide grains according to the present invention are preferably silver halide grains having a coefficient of variation in grain size of 8% to 20%, particularly preferably 8% to 17%, and more preferably 8% to 15%. % Is more preferable. The variation coefficient of the grain size means a quotient obtained by dividing the standard deviation of the equivalent circle diameter of the projected area of all the silver halide grains by the average silver halide grain diameter.

The tabular silver halide grains according to the present invention are:
It is preferably silver iodobromide or silver iodochlorobromide, and has an average silver iodide content of 0% or more and 10% (mol%).
Or less, more preferably 0% or more and 7% or less, and particularly preferably 0% or more and 3% or less.

The tabular silver halide emulsion grains according to the present invention may have at least two regions or layered structures having substantially different halogen compositions in the grains or may have a uniform composition. Those having the above layered structure are preferred. As the silver iodide content of the high silver iodide region,
It is preferable to have a portion of 6% or more and 20% or less, and 8%
More preferably, it has a portion of not less than 20%. The method for measuring the iodide ion content in the high silver iodide region in the grains can be performed by an analytical electron microscope using a transmission electron microscope.

When an electron beam used in a transmission electron microscope is incident on silver halide grains, the incident electrons cause inelastic scattering in the sample, and characteristic X-rays are generated. This characteristic X-ray is a value unique to the element and gives information on the composition of the element in the sample. It is known that when the silver iodide content increases, the intrinsic sensitivity increases when exposed to blue light, and when spectral sensitization is performed, the adsorption power of the cyanine dye increases and the coverage of the sensitizing dye increases. . In the developing process, I released during development ^- it is known that the granularity for having a development inhibiting ability is improved.

The hexagonal tabular grains according to the present invention have nucleation and
It is formed by the Ostwald ripening and growing process. Each of these steps is important in suppressing the spread of the particle size distribution, but it is impossible to narrow the spread of the size distribution generated in the previous step in the subsequent step. Care must be taken that the distribution does not spread. An important point in the nucleation process is
This is the relationship between the nucleation time for causing silver ions and bromide ions to be added to the reaction solution by the double jet method to cause precipitation, and the temperature of the reaction solution. JP-A-63-92942 describes that the temperature of the reaction solution at the time of nucleation is preferably in the range of 20 to 45 ° C. in order to improve the monodispersibility. Further, Japanese Patent Application Laid-Open No. 2-222940 states that a preferable temperature at the time of nucleation is 60 ° C. or lower.

In the present invention, by defining the time required for nucleation using a function of temperature, high aspect ratio tabular grains having high monodispersity can be obtained in any temperature range which is practically easy to use. It can be formed. When an aqueous solution of silver nitrate and an aqueous solution of potassium bromide are added to the reaction solution, silver halide precipitates immediately. The number of fine silver halide grains formed increases during the addition of silver ions and bromide ions, but does not increase in proportion to the time, but gradually increases gradually and eventually does not increase. Value. The silver halide fine particles generated by the precipitation start growing immediately after the generation. Nuclei generated earlier are easier to grow, and nuclei generated later are harder to grow.
If the size of the nucleus varies during growth during nucleation, the size variation will be further amplified by the subsequent Ostwald ripening. The spread of the size distribution of nuclei that occurs during nucleation is determined by the nucleation time and the temperature of the reaction solution. It is important to perform the nucleation at 30 ° C. for 60 seconds or less, the nucleation at 60 ° C. for 30 seconds or less, and the nucleation at 75 ° C. for 15 seconds or less. The time required until the size distribution starts to spread depends on the temperature at the time of nucleation, which reflects the dissolution of fine silver halide grains. By terminating nucleation within this time, tabular grains having a high aspect ratio can be formed without impairing the monodispersity in any temperature range that is practically easy to use.

The silver halide emulsion according to the present invention is subjected to various chemical sensitizations. For example, selenium sensitization and sensitization with a noble metal salt such as a sulfur compound or a gold salt can also be performed. Further, reduction sensitization can be performed, or sensitization can be performed by combining these methods.

580 to 70 which can be used in the present invention
For spectral sensitization to 0 nm, sensitizing dyes represented by the following general formulas (I) and (II) are preferably used.

[0024]

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In the general formula (I), R ¹ and R ⁵ may be the same or different and each represents a hydrogen atom, an alkyl group, an alkoxy group, a halogen atom or a carboxyl group. R ² and R ⁴ may be the same or different and each represents an alkyl group, and R ³ represents an alkyl group. X ¹ and X ² may be the same or different and each represents a sulfur atom or a selenium atom. Y ¹ represents a counter ion, m represents 0 or 1, and when an internal salt is formed, m = 0.

In the general formula (II), R ⁶ , R ⁷ , R ¹¹ and R ¹²
May be the same or different and each represents a hydrogen atom, an alkyl group, an alkoxy group, a halogen atom, a hydroxyl group or a carboxyl group. R ⁸ and R ¹⁰ may be the same or different and each represents an alkyl group or an aralkyl group, and R ⁹ represents an alkyl group. X ³ and X ⁴ may be the same or different and each represents a sulfur atom or a selenium atom. Y ² represents a counter ion, and n represents 0 or 1. When an internal salt is formed, n = 0.

In the formula (I), the alkyl group represented by R ¹ and R ⁵ is preferably a lower alkyl group having 1 to 5 carbon atoms, which is substituted with a hydroxyl group, a carboxyl group or a sulfo group. Is also good. As the alkoxy group represented by R ¹ and R ⁵ , a lower alkoxy group having 1 to 5 carbon atoms is preferable. Examples of the halogen atom represented by R ¹ and R ⁵ include chlorine, fluorine and iodine, and a chlorine atom is preferable. The alkyl group represented by R ² and R ⁴ is also preferably a lower alkoxy group having 1 to 5 carbon atoms, and may be substituted with a carboxyl group or a sulfo group. The alkyl group represented by R ³ is also preferably a lower alkyl group having 1 to 3 carbon atoms, and may be substituted with an aryl group or a halogen atom. Examples of the counter ion represented by Y ¹ include a halogen ion, a perchlorate ion, a thiocyanate ion, a benzenesulfonate ion,
Examples thereof include p-toluenesulfonic acid ion, methylsulfate ion and the like, wherein R ¹ or R ⁵ forms an inner salt (m
= 0).

In the general formula (II), the alkyl group, alkoxy group and halogen atom represented by R ⁶ , R ⁷ , R ¹¹ and R ¹² have been explained with respect to R ¹ and R ⁵ in the general formula (I). The same groups as each group can be mentioned. Examples of the alkyl group represented by R ⁸ and R ¹⁰ include the same groups as the alkyl groups described for R ² and R ⁴ in formula (I). R ³ and R
Examples of the aralkyl group represented by ¹⁰ include a benzyl group and a phenethyl group, and may be substituted with a carboxyl group or a sulfo group. Examples of the counter ion represented by Y ² include the same groups as those described for Y ¹ in the general formula (I), but also in the general formula (II), R ⁸ or R ¹⁰ represents an inner salt. It is preferable to form (n = 0).

Typical specific examples of the sensitizing dyes represented by formulas (I) and (II) (hereinafter referred to as sensitizing dyes of the present invention) are shown below, but are not limited thereto.

[0030]

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[0031]

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[0032]

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[0033]

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[0034]

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[0035]

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[0036]

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[0037]

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[0038]

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[0039]

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[0040]

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The spectral sensitizing dye preferably used in the present invention is contained in a silver halide emulsion layer. The timing of adding the sensitizing dye to the silver halide emulsion layer is not particularly limited, but is preferably before or during chemical sensitization.

Various hydrophilic colloids can be used as a binder in the silver halide emulsion used in the practice of the present invention. Examples of the colloid used for this purpose include gelatin, colloidal albumin, polysaccharides, cellulose derivatives, synthetic resins such as polyvinyl compounds including polyvinyl alcohol derivatives, acrylamide polymers, and other hydrophilic colloids generally used in the field of photography. . In the silver halide photographic light-sensitive material of the present invention, a water-soluble polymer can be used in the constituent layers.

In the silver halide photographic light-sensitive material according to the present invention, commonly used hardeners, thickeners, gelatin plasticizers, matting agents, latexes, coating aids and the like can be used.

Various known compounds can be added to the silver halide photographic light-sensitive material according to the present invention in order to prevent a reduction in sensitivity and generation of fog during the production process, storage or processing of the light-sensitive material.

The radiation intensifying screen used in the present invention can be produced, for example, by the following method.

The support can be appropriately selected from various materials known as supports for the radiation intensifying screen.

Examples of such materials include films of plastic substances such as cellulose acetate, polyethylene terephthalate, polyethylene naphthalate, polyamide, polyimide, polyester, triacetate, and polycarbonate; metal sheets such as aluminum foil; ordinary paper; Examples include paper, resin-coated paper, pigment paper containing a pigment such as titanium dioxide, sizing paper with polyvinyl alcohol, and the like, and ceramic plates or sheets of alumina, zirconia, magnesia, titania, and the like. When a plastic film is used as the support, a light-reflective substance such as titanium dioxide may be kneaded in the film, or a light-absorbing substance such as carbon black may be kneaded in the film. Note that an adhesiveness-imparting layer, a light-reflecting layer, a light-absorbing layer, and the like may be provided on the surface of the support of the radiation intensifying screen on which the phosphor layer is provided.
As described in Japanese Patent No. 82599, fine irregularities may be uniformly formed (the irregularities may be formed on the surface of the support on the side of the phosphor layer, the adhesion imparting layer, the light reflecting layer, and the light absorbing layer). Is provided on the surface of the substrate when it is provided.)

Next, a phosphor layer is formed on the support of the radiation intensifying screen. This phosphor layer is a layer composed of phosphor particles and a binder that supports the phosphor particles in a dispersed state.

The phosphor used in the practice of the present invention is X
Phosphors that emit in the red region of about 580-700 nm when excited by radiation such as radiation are preferred. Examples of such red-emitting phosphors include the following europium-containing phosphors. That is, a europium-activated rare earth oxysulfide-based phosphor [Y ₂ O ₂ S: Eu, Gd ₂
O ₂ S: Eu, La ₂ O ₂ S: Eu, (Y, Gd) ₂ O
₂ S: Eu, etc.], europium-activated rare earth oxide phosphor _{[Y 2 O 3: Eu, Gd} 2 O 3: Eu, Lu 2 O 3: Eu,
(Y, Gd) ₂ O ₃ : Eu etc.], europium-activated rare earth phosphate-based phosphor [YPO ₄ : Eu, GdPO ₄ : Eu, L
aPO ₄ : Eu etc.], europium-activated rare earth vanadate phosphor [YVO ₄ : Eu, GdVO ₄ : Eu, La
VO ₄ : Eu, (Y, Gd) VO ₄ : Eu, etc.].

Further, as the europium-containing phosphor, a compound represented by the following general formula A can also be used.

[(Ln _1−y Eu _y ) (VO ₄ )] _1−x (MeO ₂ ) _x ... A In the above general formula A, Ln is at least one of Y, Gd and La. , Me is at least one of Ge and Ti, and 0 <x ≦ 0.1, 0.005 ≦
y ≦ 0.2.

As the compound represented by the general formula A, A-1 Ln is Y, Me is Ge, and (y = 0.045,
x = 0.1,0.01,0.001,0.0001 or 0.00005) (5 examples) A-2 Ln is Y, Me is Ti, (y = 0.045,
x = 0.1,0.01,0.001,0.0001 or 0.00005) (5 examples) A-3 Ln is Gd or La, y = 0.045,
(MeO ₂ ) _x (GeO ₂ ) _0.0001 or (TiO ₂ )
_0.0001 (four examples) and the like can be exemplified.

The above-mentioned europium-containing phosphor is disclosed in, for example, JP-A-61-80099 and JP-B-60-1.
No. 4060 can be referred to.

Further, as a phosphor that can be used in the practice of the present invention, a compound represented by the following general formula B can be mentioned.

Bi _12-x Pr _x Ge _1-y Si _y O ₂₀ ... B However, in the general formula B, 0.01 <x <4, 0 ≦ y ≦
It is one.

Specific examples of the compound represented by the above general formula B include Bi _10.8 Pr _1.2 GeO ₂₀ Bi _10.8 Pr _1.2 GeSi _0.5 O _{20 and the} like.

The above-mentioned phosphors may be used alone or in combination of two or more. Note that, needless to say, the present invention is not limited to only the specific examples of the above-described phosphor.

The particle shape and particle size of the phosphor are optional.
The average particle size R of the phosphor particles and the standard deviation σ of the particle size distribution are 0
Phosphors satisfying <σ / R ≦ 0.5 can be preferably used.
Further, the average particle size described in JP-A-8-134443 is 0.1.
5 to 20 μm, and the ratio of the major axis to the minor axis is 1.0 to
It is also a preferable embodiment to use a phosphor composed of transparent spherical particles having a particle size of 1.5 and containing 0.001 to 5% by weight of ultrafine particles having a particle size of 0.2 μm or less.

These phosphors can be used, for example, as follows.

That is, the phosphor particles and the binder are combined with a suitable solvent (for example, a lower alcohol such as methanol, ethanol, n-propanol, or n-butanol, a chlorine atom-containing hydrocarbon such as methylene chloride or ethylene chloride, acetone, or the like). Ketones such as methyl ethyl ketone and methyl isobutyl ketone, esters such as methyl acetate, ethyl acetate and butyl acetate, dioxane, ethers such as ethylene glycol monoethyl ether and ethylene glycol monomethyl ether, and mixtures thereof) and thoroughly mixed. Thus, a coating solution in which the phosphor is uniformly dispersed in the binder solution is prepared.

Examples of the binder include proteins such as gelatin, and synthetic high molecular substances such as polyvinyl acetate, nitrocellulose, polyurethane, polyvinyl alcohol, polyalkyl (meth) acrylate, and linear polyester. Binders can be mentioned. It is preferred to use a thermoplastic elastomer as a binder. Examples of these include polystyrene, polyolefin, polyurethane, polyester, polyamide, polybutadiene, ethylene vinyl acetate, polyvinyl chloride, natural rubber, fluororubber, polyisoprene, chlorinated polyethylene, styrene-butadiene rubber, and silicone rubber. Can be. The softening point or melting point of the thermoplastic elastomer is preferably from 30 to 150C. The component ratio between these thermoplastic elastomers and other binders is 10 to 10.
It is preferably 100% by weight, particularly preferably 100% by weight of the thermoplastic elastomer.

Further preferred binders include —SO _{3
M, -OSO 3 M, COOM,} -PO (OM) 2 and -O
PO (OM) ₂ (where M is a hydrogen atom, or Li,
Resins containing at least one hydrophilic polar group selected from the group consisting of alkali metals such as K and Na). As the resin, polyurethane, polyester, polyvinyl chloride, polyamide, polyvinyl butyral, various synthetic rubber resins and the like can be used. 1 g of the resin
The amount of the hydrophilic group contained therein is preferably from 0.3 to 80 mg.

The mixing ratio between the binder and the phosphor in the coating solution is usually (1: 1) to (1: 100) (weight ratio), and further (1: 8) to (1:40) (weight ratio). (Weight ratio).

Various additives such as a dispersant for improving the dispersibility of the phosphor and a plasticizer for improving the bonding force between the phosphor and the binder after forming the coating film are added to the coating solution. It may be.

Examples of dispersants include phthalic acid, stearic acid, caproic acid, lipophilic surfactants and the like. Examples of the plasticizer include phosphate esters such as triphenyl phosphate and tricresyl phosphate; phthalate esters such as diethyl phthalate and dimethoxyethyl phthalate; ethyl phthalyl ethyl glycolate; and butyl phthalyl butyl glycolate. And polyesters of ethylene glycols such as polyesters of triethylene glycol and adipic acid, polyesters of diethylene glycol and succinic acid, and polyesters of aliphatic dibasic acids.

This coating solution is uniformly applied to the surface of the support to form a coating film of the coating solution, and then the coating film of the coating solution is dried to complete the formation of the phosphor layer on the support. Alternatively, a coating solution may be applied to a temporary support, dried, and then peeled off from the temporary support to form a phosphor sheet, which may be adhered to another support. The temporary support may be arbitrarily bonded from the above-mentioned support material. The temporary support can be arbitrarily selected from the above materials for the support. In addition, a release agent may be applied to the surface of the temporary support in advance so that the phosphor sheet can be easily peeled off from the temporary support. As a method for applying the phosphor layer coating solution, a doctor blade, a roll coater, a knife coater, or the like, which is a usual coating means, can be used. The thickness of the phosphor layer is generally 50 to 50.
0 μm.

Pressurization and compression can be performed to increase the filling rate of the phosphor. Examples of the compression apparatus include a calender roll and a hot press.

Further, a transparent protective film for physically and chemically coating and protecting the phosphor layer may be provided on the surface of the phosphor layer opposite to the side in contact with the support. Examples of the material used for the transparent protective film include cellulose acetate, polymethyl methacrylate, polyethylene terephthalate, and polyethylene. The thickness of the transparent protective film is usually about 3 to 20 μm.

In the present invention, a crossover light-cutting layer is provided between the photosensitive silver halide emulsion layer of the radiation-sensitive silver halide photographic material and the support. The crossover cut ratio is a ratio of crossover light emitted to a rear photosensitive layer of the silver halide photographic material to light emitted from a radiation intensifying screen disposed in front of the silver halide photographic material. means.

It is preferable that the crossover cut ratio is set to be 10 to 30%. To increase the crossover cut ratio, a dye layer can be provided.

The dye has a maximum absorption wavelength of 580 to 700 nm.
Is preferable, and the coating amount is 1 to 100 mg / m ^2.
Is fine. It is also desired that the dye does not remain after development. Therefore, the structure of the dye itself after processing is preferably 20% by weight or less, more preferably 5% by weight or less, before the development processing. The polyvalent metal ion content in the dye layer is preferably 3000 ppm or more.

In the method for developing a silver halide photographic light-sensitive material according to the present invention, the steps from development to drying are completed within 45 seconds when the processing is performed by an automatic processor including development, fixing, washing and drying steps. Let it. That is, the time from when the tip of the photosensitive material starts to be immersed in the developing solution to the time when the tip exits the drying zone through the processing step (so-called DryT)
o Dry) is within 45 seconds, more preferably 15 seconds to 45 seconds. The conveying speed of the automatic developing machine is preferably 2500 to 10000 mm / min. The automatic developing machine can be dried using infrared rays, especially far infrared rays.

The support used in the silver halide photographic light-sensitive material of the present invention includes a polyethylene terephthalate film. The surface of the support may be provided with an undercoat layer or subjected to corona discharge, ultraviolet irradiation, or the like in order to improve the adhesiveness of the coating layer.

The photographic processing of the light-sensitive material of the present invention can be performed, for example, by the methods described in Research Disclosure (RD) 17643, XX to XX.
XXI. XX to X of 29 to 30 pages or (RD) 308119
XI. Processing with a processing solution as described on pages 1011 to 1012 may be performed. This process may be a black and white photographic process for forming a silver image. Processing temperature is usually 18
Processed in the range of 50 ° C to 50 ° C.

As developers in black-and-white photographic processing, dihydroxybenzenes (for example, hydroquinone), 3-pyrazolidones (for example, 1-phenyl-3-pyrazolidone),
Aminophenols (for example, N-methyl-P-aminophenol) and the like can be used alone or in combination. In the developer, for example, known preservatives, alkali agents, pH buffering agents, antifoggants, hardeners, development accelerators,
Surfactants, defoamers, colorants, water softeners, dissolution aids,
A viscosity imparting agent or the like may be used as needed.

The fixing solution contains a fixing agent such as thiosulfate and thiocyanate, and may further contain a water-soluble aluminum salt such as aluminum sulfate or potassium alum as a hardening agent. In addition, it may contain a preservative, a pH adjuster, a water softener and the like.

[0077]

The present invention will be described below in more detail with reference to examples.

Example 1 (Production of radiographic intensifying screen S) Particles of trivalent eurobium-activated gadolinium oxysulfide phosphor (Gd ₂ O ₂ S: Eu ³⁺ ) and linear polyester resin Byron # 500 (Toyobo Co., Ltd.) Methyl ethyl ketone to the mixture
Further, a dispersion liquid containing phosphor particles in a dispersed state was prepared by adding nitrocellulose having a nitrification degree of 11.5%.

Next, tricresyl phosphate, n-
Butanol and methyl ethyl ketone were added. Thereafter, the mixture is sufficiently stirred and mixed using a propeller mixer, so that the phosphor particles are uniformly dispersed, and the mixing ratio of the binder and the phosphor is 1: 1.
20 (weight ratio) and viscosity 25-35PS (25 ° C)
Was prepared.

Next, a white pigment-kneaded polyethylene terephthalate film (support,
(Thickness: 250 μm) was uniformly applied using a doctor blade. After the coating, the support on which the coating film was formed was put into a drier, and the temperature inside the drier was set to 25 ° C.
From 100 ° C. to 100 ° C. for drying. Thus, a phosphor layer having a thickness of about 180 μm was formed on the support.

A transparent film of polyethylene terephthalate (thickness: 12 μm, to which a polyester-based adhesive has been applied) is placed on the phosphor layer with the adhesive layer side facing down, and adhered to the transparent protective film. Was formed to produce a radiographic intensifying screen S composed of a support, a phosphor layer and a transparent protective film.

(Preparation of Particles) Emulsion A In a reaction vessel having a volume of 4 liters, an average molecular weight of 15
An aqueous solution containing 1200 000 gelatin (1200 ml of water, 7 g of gelatin, 4.5 g of KBr) was added.
1.9M A by double jet method with stirring
A gNO ₃ aqueous solution and a 1.9 M KBr aqueous solution were simultaneously added at a rate of 25 ml / min for 70 seconds each to obtain nuclei of tabular grains. 350 ml of this emulsion was used as a seed crystal, and 650 ml of an inert gelatin aqueous solution (20 g of gelatin, KBr
Was added containing) a 1.2g, aged for 40 minutes the temperature was raised to 75 ° C., it was added a AgNO ₃ aqueous solution (containing AgNO ₃ 1.7 g) over a period of 1 minute 30 seconds, then NH ₄ NO ₃
6.2 ml of (50% by weight) aqueous solution and 6.2 ml of NH ₃ (25% by weight) were added, and the mixture was further aged for 40 minutes. Next, the emulsion was adjusted to pH 7 with HNO ₃ (3N), 1 g of KBr was added, and 405 ml of a 1.9 MAg NO ₃ aqueous solution and K were added.
An aqueous Br solution was added while maintaining the pAg at 8.3. At the beginning of the addition, the mixture is added at 2.6 ml / min and the ratio between the initial speed and the final speed is 1
The addition was performed while accelerating the flow rate so as to be 0 times.

After lowering the temperature to 55 ° C., 0.6M AgN
O ₃ aqueous solution 40ml and 0.6M KBr aqueous solution 40ml
Was added over 10 minutes. Add KBr and add pA
g was adjusted to 8.9, and 157 ml of a 1.9 M AgNO ₃ aqueous solution and 157 ml of a 1.9 M KBr aqueous solution were added to 26 g.
Emulsion A was obtained by adding over a period of minutes.

The method for preparing Emulsion A was based on the examples in JP-A-2-838.

In the obtained emulsion A, the ratio of hexagonal tabular grains having an aspect ratio of more than 8 to the projected area was 0%. The coefficient of variation of the particle size was 10%. The average particle size was 0.75 μm in sphere equivalent diameter.

Table 1 shows the obtained emulsion A.

Emulsion B Emulsion B was prepared in the same manner as in the preparation method of Emulsion A,
After the temperature was raised, the aqueous AgNO ₃ solution added in Emulsion A and NH ₄
Only aging for 80 minutes was performed without adding an aqueous solution of NO _{3 and an} aqueous solution of NH ₃ . Emulsion B was obtained by performing the following steps after grain growth in the same manner as for emulsion A.

In the obtained emulsion B, the ratio of hexagonal tabular grains having an aspect ratio of more than 8 to the projected area was 70%, but the variation coefficient of the grain size was 29%.

Table 1 shows the obtained emulsion B.

Emulsion C Emulsion C formed grains in the same manner as Emulsion B, but iodine ions were introduced into the added halogen solution.

Nucleation was carried out in the same manner as in Emulsion A.
After the temperature was raised to 5 ° C., ripening was carried out for 80 minutes in the same manner as in Emulsion B without adding a silver halide solvent.

Next, the emulsion was adjusted to pH 7.0 with HNO ₃ ,
After adding 1 g of Br, 1.9 M AgNO ₃ aqueous solution 40
5 ml, 1.9 M KBr and KI (98/2 by molar ratio)
The aqueous solution was added while maintaining the pAg at 8.3.

After lowering the temperature to 55 ° C., 0.6M AgN
40 ml of an O ₃ aqueous solution and 40 ml of a 0.6 M KI aqueous solution were added over 10 minutes to form a high iodine region.

After adjusting the pAg to 8.9 by adding KBr, 157 ml of a 1.9M AgNO ₃ aqueous solution and 1.9K were added.
Emulsion C was obtained by adding 157 ml of an aqueous Br solution over 26 minutes.

In the emulsion C, the ratio of the hexagonal tabular grains having an aspect ratio of more than 8 to the projected area was 26%, and the variation coefficient of the grain size was 34%.

Emulsion D A 1.9 MAgNO ₃ aqueous solution and 1.9 M KB were added to the aqueous solution in the same reaction vessel as Emulsion A by the double jet method.
The aqueous solutions were simultaneously added at 25 ml / min for 35 seconds. 350 ml of this emulsion was used as a seed crystal, and 650 ml of inert gelatin (containing 20 g of gelatin and 1.2 g of KBr) was added thereto. The temperature was raised to 75 ° C. and ripening was performed for 80 minutes.
Next, the emulsion was adjusted to pH 7.0 with HNO ₃ , 1 g of KBr was added, and 405 ml of a 1.9 M AgNO ₃ aqueous solution and a 1.9 M KBr and KI (98/2 by molar ratio) aqueous solution were maintained at pAg of 8.3. Was added. After lowering the temperature to 55 ° C., 40 ml of 0.6M AgNO ₃ aqueous solution and 0.6 ml
40 ml of MKI aqueous solution was added over 10 minutes. K
1.9 MAg after adjusting pAg to 8.9 by adding Br.
NO ₃ aqueous solution 157 ml and 1.9 M KBr aqueous solution 15
Emulsion D was obtained by adding 7 ml over 26 minutes.

In the emulsion D, the ratio of the hexagonal tabular grains having an aspect ratio of more than 8 to the projected area was 54%, and the variation coefficient of the grain size was 19%.

Emulsion E Emulsion E was prepared in the same manner as in Emulsion D, except that the nucleation time was 25 minutes.
The preparation was performed in the same manner except that the time was changed to seconds.

Table 1 shows the obtained emulsions C, D and E.

(Chemical sensitization) The obtained emulsions A to E were subjected to the following chemical sensitization at 60 ° C, pH 6.20 and pAg 8.4. First, spectral sensitizing dyes as shown in Table 1 were added. Subsequently, 3.0 × 10
^-3 moles of potassium thiocyanate, 4 × 10 ^-6 to 8 × 10
^-6 moles of potassium chloroaurate, 1 × 10 ^-5 to 2 × 10 ^-5 moles of sodium thiosulfate and selenium compound-1 were added, and the conditions were adjusted so that optimum chemical sensitization could be performed for each emulsion. did.

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(Preparation of Emulsion Coating Layer) The following chemicals were added to the chemically sensitized emulsions A to E per mole of silver halide to prepare a coating solution.

2,6-bis (hydroxyamino) -4-diethylamino-1,3,5-triazine 72 mg trimethylolpropane 9 g dextran (average molecular weight 39,000) 18.5 g potassium polystyrene sulfonate (average molecular weight 60 1.8 g Compound E-1 3.4 mg Compound E-2 4.8 g Snowtex C (Nissan Chemical Co., Ltd.) 29.1 g Gelatin Adjusted so that the total amount applied to one side is 1.6 g / m ^2. did.

Rubber agent (1,2-bis (vinylsulfonylacetamido) ethane) The swelling ratio was adjusted to 230%.

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(Preparation of Coating Solution for Surface Protective Layer) Coating for the surface protective layer was prepared such that each component had the following coating amount (g / m ² ).

Gelatin 0.800 Sodium polyacrylate (average molecular weight 400,000) 0.023 Compound (P-1) 0.013 Compound (P-2) 0.045 Compound (P-3) 0.0065 Compound (P -4) 0.003 Compound (P-5) 0.001 Compound (P-6) 0.0012 Polymethyl methacrylate (average particle diameter 3.7 μm) 0.087 Proxel 0.0005 (adjusted to pH 7.4 with NaOH) )

[0108]

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(Preparation of Dye Dispersion K for Undercoat Layer) The following dyes were ball-milled by the method described in JP-A-63-197943.

[0110]

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434 ml of water and Triton X20
0 (manufactured by Union Carbide Co., Ltd.) in a 6.7% aqueous solution 7
91 ml were placed in a 2 liter ball mill. Dye 2
0 g was added to this solution. Zirconium oxide (Zr
O) beads (400 ml, 2 mm diameter) were added and the contents were ground for 4 days. After that, 12.5% gelatin 160
g was added. After decontamination, the ZrO beads were removed by filtration. Observation of the resulting dye dispersion revealed that the particle size of the crushed dye was 0.37 μm. Furthermore, dye particles having a size of 0.9 μm or more were removed by centrifugation. Thus, a dye dispersion K was obtained.

(Preparation of Support) Biaxially stretched thickness 18
A 3 μm polyethylene terephthalate film is subjected to corona discharge, and a first undercoating liquid having the following composition is applied by a wire bar coater so as to have a coating amount of 5.1 ml / m ² and dried at 175 ° C. for 1 minute. did. Next, a first undercoat layer was similarly provided on the opposite surface. The used polyethylene terephthalate contains 0.04 of the dye having the following structure.
What contained wt% was used.

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Composition: Butadiene-styrene copolymer latex solution 79 ml (solid content 40% butadiene / styrene polymerization ratio = 31/69) Emulsifier / dispersant Sodium dihexylsuccinate-1-sulfonate 0.4 wt. % Containing 2,4-dichloro-6-hydroxy-s-triazine sodium salt 4% solution 20.5 ml distilled water 900.5 ml A second undercoat layer having the following composition was formed on the first undercoat layer on both sides described above. One side by side so that the coating amount is the amount described below, 150 on both sides by a wire bar coater method
Coated and dried at ℃.

Gelatin 160 mg / m ² Dye dispersion K The amount of the crossover cut shown in Table 1 was added.

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(Preparation of photosensitive material) The above emulsion layer and surface protective layer were coated on both sides of the support prepared as described above by a simultaneous extrusion method. The amount of silver applied per side was 1.75.
g / m ² . Thus, the sample No. No. 1 to No. 1
1 was obtained.

The compositions of the developing solution and the fixing solution used in the present invention are shown below.

Developer Composition Part-A (for finishing 12 liters) Potassium hydroxide 450 g Potassium sulfite (50% solution) 2280 g Diethylenetriaminepentaacetic acid 120 g Sodium bicarbonate 132 g Boric acid 40 g 5-Methylbenzotriazole 1.4 g 1-phenyl -5-mercaptotetrazole 0.25 g 4-hydroxymethyl-4-methyl-1-phenylpyrazolidone 102 g hydroquinone 390 g diethylene glycol 550 g Add water to make 6000 ml Part-B (for finishing 12 liters) Glacial acetic acid 70 g 5-nitro Indazole 0.6 g Glutaraldehyde (50% solution) 8.0 g N-acetyl-DL-penicillamine 1.2 g Starter Glacial acetic acid 120 g HO (CH ₂ ) ₂ S (CH ₂ ) ₂ S (C) H ₂ ) ₂ OH 1 g Potassium bromide 225 g CH ₃ N (C ₃ H ₆ NHCONHC ₂ HSC ₂ H ₅ ) ₂ 1.0 g Add pure water to make up to 1.0 liter Fixer formulation Part-A (18.3) For liter finishing) ammonium thiosulfate (70 wt / vol%) 4500 g sodium sulfite 450 g sodium acetate 450 g boric acid 110 g tartaric acid 60 g sodium citrate 10 g gluconic acid 70 g 1- (N, N-dimethylamino) -ethyl-5-mercaptotetrazole 18 g ice 330 g of acetic acid 62 g of aluminum sulfate Finish to 7200 ml with pure water Developing solution is prepared by adding Part-A, Par to about 5 liters of water.
t-B was added at the same time, and water was added while stirring and dissolving.
Finished to 2 liters and adjusted pH to 10.53. This is used as a development replenisher.

To 1 liter of the replenisher, 20 ml / liter of the above starter was added to adjust the pH to 10.3.
Adjust to 0 and use as working solution.

The fixer was prepared by adding Part 5 to about 5 liters of water.
-A was added, water was added while stirring and dissolving to make up to 18.3 liters, and the pH was adjusted to 4.6 using sulfuric acid and NH4OH.
Was adjusted. This is used as a fixing replenisher.

For development, an automatic developing machine SRX-503 (manufactured by Konica Corporation) was modified and Dry to D was performed in the following steps.
ry (all processing steps) were processed in a 25 second mode. However,
Each sample was subjected to a running treatment from a new solution so that the activity of the treatment solution was in an equilibrium state. The replenishment amounts of the developing solution and the fixing solution during the running process were 100 ml / m ² respectively.

Processing Step Step Processing Temperature (° C.) Processing Time (Second) Development + Cover 35 7.8 Fixation + Cover 33 5.4 Rinse + Cover 18 4.3 (Rinse Water 7 L / min.) Squeeze 40 3 ..1 Dry 50 4.4 Total-25.0 Sample No. The following photographic characteristics were evaluated for 1 to 11.

(Evaluation of Sharpness and Graininess) For the assembly of the radiation intensifying screen and the photosensitive material to be evaluated, a chest phantom manufactured by Kyoto Kagaku was used with an X-ray source of 120 kVp (equipped with a 3 mm-thick aluminum equivalent filter). , Distance 14
A phantom was placed at a position of 0 cm, then an anti-scatter grid having a grid ratio of 8: 1, and then an assembly of a photosensitive material and a radiographic intensifying screen were taken. The development was performed under the above conditions. In each photograph, the highest density part of the lung field was adjusted to a density of 1.8 ± 0.05 by changing the X-ray exposure amount by changing the exposure time. The finished photograph was visually observed, and the sharpness, granularity, and silver tone were evaluated according to the following evaluation criteria. The results are shown in Table 1.

Evaluation criteria for sharpness A: very sharp B: good but slightly blurred C: blur is noticeable and there is some difficulty in image interpretation D: difficulty in reading due to blur Grade evaluation criteria A: almost inconspicuous B: slightly Conspicuous C: Slightly obstructive interpretation D: Very conspicuously obstructive interpretation Silver tone evaluation criteria A: Pure black B: Slightly yellowish C: Yellowish, slightly annoying at diagnosis No D: Strong yellowness, giving discomfort at the time of diagnosis

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[Table 1]

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From the results shown in Table 1, it can be seen that all of the samples using the silver halide photographic light-sensitive material of the present invention are excellent in silver tone, sharpness and graininess.

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According to the present invention, it is possible to provide a high-quality radiation image forming method which has a good silver image color tone after the development processing, and is excellent in sharpness and granularity.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI G03C 1/825 G03C 1/825 G21K 4/00 G21K 4/00 A

Claims (3)

[Claims] 1. A method for forming a radiation image in which a silver halide photographic light-sensitive material having a silver halide emulsion layer provided on both sides of a support and a radiation intensifying screen in close contact with each other is used. But 580-700n
m is spectrally sensitized to the red region and the aspect ratio is 8 to
A silver halide emulsion layer containing 40 tabular silver halide grains, and light emitted from a radiographic intensifying screen passes through the silver halide emulsion layer on the screen side and the silver halide emulsion on the opposite side. A radiation image forming method, wherein crossover light emitted to the layer is 5% or more and 30% or less, and the radiation intensifying screen is a screen having an emission peak in the red region. 2. A silver halide emulsion of a silver halide photographic light-sensitive material having an aspect ratio of 8 to 40 and a ratio of the length of the side having the maximum length to the length of the side having the minimum length of 1 2. The radiation image forming method according to claim 1, wherein said hexagonal silver halide grains of not less than 2 are contained in an amount of 50% or more of the total projected area. 3. The method according to claim 1, wherein the silver halide photographic material has a crossover cut layer between the support and the silver halide emulsion layer.