JPH1010685A - Radiation image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radiation image forming method of a silver halide photographic sensitive material having high sensitivity and high contrast and improved graininess and sharpness of images even at the time of ultra-rapid processing of <=35 seconds. SOLUTION: The thickness of the phosphor layer for the back side of sensitizing screens is 150 to 250μm, the thickness of the phosphor layer for the front side is >=30 to <=90% of the thickness of the phosphor layer for the back side in the radiation image forming method for executing photographing with the two radiation sensitizing screens. The gamma value when such silver halide photographic sensitive material is processed dry to dry for >=15 to <=35 seconds is >=3.3 to <=4.0. The silver halide photographic sensitive material of <=1.1g in the water absorption amt. just before drying per sheet of 10×12 inch size in the processing stage of the silver halide photographic sensitive material is used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiation image forming method capable of obtaining an improved image.

[0002]

2. Description of the Related Art In recent years, rapid processing of silver halide photographic light-sensitive materials has progressed rapidly, and is particularly remarkable in the medical industry. For example, in addition to 90 seconds processing and 45 seconds processing which have conventionally been mainstream, a new 30 seconds processing has been performed. Is spreading. This is to address the rapid diagnosis in emergency medicine.

[0003] On the other hand, the user side is required to have higher contrast and sharpness in head angiography, bone imaging of phalanges such as phalanges, as well as rapid processing. That is the fact.

Conventionally, many techniques have been proposed for rapid processing of silver halide photographic materials.
Regarding a radiographic image forming method that obtains high sensitivity, high contrast, and high sharpness even in the case of rapid processing in a short time of 30 seconds or less, disclosure of appropriate technology and information suggesting it are as follows. not enough.

Therefore, even in ultra-rapid processing, there has been a strong demand for a radiation image forming method which has high sensitivity, high contrast, improved granularity and sharpness of an image, and improved diagnostic performance.

[0006]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a high sensitivity and a high sensitivity even in a short time of 35 seconds or less.
An object of the present invention is to provide a method for forming a radiation image of a silver halide photographic light-sensitive material having high contrast and improved image graininess and sharpness.

[0007]

The object of the present invention has been attained by the following.

(1) In a radiographic image forming method, a silver halide photographic material having a silver halide emulsion layer on both sides of a support is photographed by sandwiching it between two radiographic intensifying screens. The thickness of the phosphor layer for the back side of the screen is 150 to 250 μm, and the thickness of the phosphor layer for the front side is 30% or more of the thickness of the phosphor layer for the back side.
0% or less, and the silver halide photographic material is
A gamma value when processed in y to Dry for 20 seconds or more and 35 seconds or less is 3.2 or more and 4.0 or less.

(2) In the processing step of a silver halide photographic light-sensitive material, the amount of water absorbed immediately before drying is 1.1 g per one cut into four pieces.
The radiation image forming method according to (1), wherein the following silver halide photographic material is used.

Hereinafter, the present invention will be described in detail.

When the radiation intensifying screen used in the present invention with the silver halide photographic light-sensitive material interposed therebetween is divided into a front side and a back side when viewed from the X-ray irradiation direction, both of them have a phosphor content. And the thickness of the layers are different. That is, the thickness of the phosphor layer for the back side is 150 to 250 μm, and more preferably 170 to 240 μm. or,
The thickness of the phosphor layer for the front side is 90% or less of the thickness of the phosphor layer for the back side, and specifically 80 to 225 μm.
m, preferably 95 to 130 μm. The thickness of the phosphor layer in the present invention refers to the thickness of only the layer containing the phosphor.

The radiation intensifying screen of the present invention is preferably filled with a phosphor in a gradient particle size structure. In particular, it is preferable to apply phosphor particles having a large particle diameter to the surface protective layer side and phosphor particles having a small particle diameter to the support side, and the phosphor particles having a small particle diameter are 0.5 to 3.5 μm. 4.5-3 particle size
A range of 0 μm is preferred.

The intensifying screen used in the present invention is characterized in that the thickness of the phosphor layer is different between the front side and the back side, which means that the filling rate of the phosphor particles is changed between the front side and the back side. do not do.

The X-ray absorption of the intensifying screen according to the present invention is such that the X-ray absorptance per 30 μm of the phosphor layer is 30 μm.
% Is preferable. The specific sensitivity on the front side of the intensifying screen of the present invention is 60 to 90 with respect to the back side.
%.

The filling factor of the phosphor is not particularly limited, but in the case of the present invention, the phosphor layer for the back side is preferably 50 to 80, and the phosphor layer for the front side is preferably 50 to 80.
Preferably it is 80.

The amount of X-ray absorption can be determined as follows. That is, X-rays generated from a tungsten target operated at 80 kVp from an X-ray generator equivalent to 2.2 mm of aluminum and passed through a 3 mm-thick aluminum plate having a purity of 99% or more are supplied by three-phase power supply. 200c from the tungsten anode in the target tube
to the radiation intensifying screen fixed at position m,
Next, 50c from the phosphor layer of the radiographic intensifying screen.
The position after m was measured using an ionizing dosimeter to determine the amount of X-ray absorption. As a reference, the X-ray dose at the above measurement position measured without passing through the intensifying screen was used.

The filling rate of the phosphor can be determined from the porosity of the phosphor layer formed on the support by the following equation (1).

[0018]

(Equation 1)

Where V is the total volume of the phosphor layer Vair; the air volume in the phosphor A; the total weight of the phosphor layer px; the density of the phosphor py; the density of the binder pair; the density of the air a; Weight b; weight of the binder Further, in the formula (1), since pair is almost 0, the formula (1) can be approximately expressed by the following formula (2).

[0020]

(Equation 2)

However, the definitions of V, Vair, px, py, a and b are the same as in the equation (1).

In the present invention, the porosity of the phosphor layer was determined by equation (2). The filling rate of the phosphor is given by the following equation (3).
Can be obtained by

[0023]

(Equation 3)

However, the definitions of V, px, py, a and b are the same as in the equation (1). Preferred phosphors used in the radiation intensifying screen according to the present invention include the following.

Tungstate phosphors (CaWO ₄ ,
MgWO ₄ , CaWO ₄ : Pb, etc.), terbium-activated rare earth oxysulfide-based phosphor [Y ₂ O ₂ S: Tb, Gd ₂ O ₂ S:
Tb, La ₂ O ₂ S: Tb, (Y, Gd) ₂ O ₂ S: Tb,
Tm etc.), terbium-activated rare earth phosphate-based phosphor (YP
O ₄ : Tb, GdPO ₄ : Tb, LaPO ₄ : Tb, etc.),
Terbium-activated rare earth oxyhalide phosphor La
OBr: Tb, LaOBr: Tb. Tm, LaOCl:
Tb, LaOCl: Tb. TmGdOBr: Tb, Gd
OCr: Tb, etc.), thulium-activated rare earth oxyhalide phosphor (LaOBr: Tm, LaOCl: Tm)
Etc.), barium sulfate-based phosphor [BaSO ₄ : Pb, Ba
SO ₄ : Eu ²⁺ , (Ba.Sr) SO ₄ : Eu ²⁺ etc.], 2
Eurobium-activated alkaline earth metal phosphate-based phosphor [Ba ₃ (PO ₄ ) ₂ : Eu ²⁺ , (Ba, Sr) ₃ , (PO
₄ ) ₂ : Eu ² etc.] divalent eurobium-activated alkaline earth metal fluorohalide-based phosphor [BaFCl: E
u ²⁺ , BaFBr: Eu ²⁺ , BaFCl: Eu ²⁺ .T
b, BaFBr: Eu ²⁺ . Tb, BaF ₂ .BaCl ₂ .
XBaSO ₄ . KCl: Eu ²⁺ , (Ba.Mg) F ₂ . B
aCl2. KCl: Eu ²⁺ etc.], iodide-based phosphor (CS
I: Na, CSI: Tl, NaI. KI: Tl, etc.) sulfide-based phosphor [ZnS: Ag, (Zn.Cd) S: Ag,
(Zn.Cd) S: Cu, (Zn.Cd) S: Cu. A
l etc.], a hafnium phosphate-based phosphor (HfP ₂ O ₇ : Cu
Etc.) However, the phosphor used in the present invention is not limited to these, and any phosphor that emits light in the visible or near-ultraviolet region upon irradiation with radiation can be used.

Preferred binders used in the radiation intensifying screen according to the present invention include thermoplastic elastomers. Specifically, it is selected from the group consisting of polystyrene, polyolefin, polyurethane, polyester, polyamide, polybutadiene, ethylene vinyl acetate, polyvinyl chloride, natural rubber, fluorine rubber, polyisoprene, chlorinated polyethylene, styrene-butadiene rubber and silicone rubber. At least one thermoplastic elastomer is included.

The method of manufacturing the intensifying screen includes a step of forming a phosphor sheet comprising a binder and a phosphor, placing the phosphor sheet on a support, and at a temperature equal to or higher than the softening temperature or melting point of the binder. It is preferable to manufacture the phosphor sheet in a step of bonding the phosphor sheet to a support while compressing the phosphor sheet. The phosphor sheet serving as the phosphor layer of the radiation intensifying screen of the above, a coating solution prepared by uniformly dispersing the phosphor in a binder solution is applied on a temporary support for forming the phosphor sheet, and dried, It can be manufactured by peeling off from the temporary support. That is, first, a binder and phosphor particles are added to an appropriate organic solvent, and the mixture is stirred and mixed to prepare a coating solution in which the phosphor is uniformly dispersed in the binder.

As the binder, the softening temperature or melting point is 3
A thermoplastic elastomer at 0 to 150 ° C. is used alone or together with another binder. Since the thermoplastic elastomer has elasticity at room temperature and becomes fluid when overheated, it is possible to prevent the phosphor from being damaged by the pressure at the time of compression. Examples of the thermoplastic elastomer include polystyrene, polyolefin, polyurethane, polyester, polyamide, polybutadiene, ethylene vinyl acetate, polyvinyl chloride, natural rubber, fluorine rubber, polyisoprene, chlorinated polyethylene, styrene-butadiene rubber, and silicon rubber. At least one type of thermoplastic elastomer selected from the group is exemplified. The mixing ratio of the thermoplastic resin in the binder is 10% by weight or more and 100% by weight or more.
The binder may be made up of as much thermoplastic elastomer as possible, in particular 100% by weight.

Examples of the solvent for preparing the coating solution include lower alcohols such as methanol, ethanol, n-propanol and n-butanol, hydrocarbons containing chlorine atoms such as methylene chloride and ethylene chloride, acetone, methyl ethyl ketone and methyl isobutyl ketone. Ketones, esters of lower fatty acids with lower alcohols such as methyl acetate, ethyl acetate and butyl acetate, ethers such as dioxane, ethylene glycol monoethyl ester and ethylene glycol monomethyl ester, and mixtures thereof.

The mixing ratio between the binder and the phosphor in the coating solution varies depending on the characteristics of the intended radiographic intensifying screen, the type of the phosphor, and the like. Generally, the mixing ratio between the binder and the phosphor is from 1: 1 to 1: 1. It is selected from the range of 1: 100 (weight ratio), and particularly preferably selected from the range of 1: 8 to 1:40 (weight ratio).

In the coating solution, a dispersant for improving the dispersibility of the phosphor in the coating solution, or a binding agent between the binder and the phosphor in the phosphor layer after the formation is improved. Various additives such as a plasticizer may be mixed.

Examples of dispersants include phthalic acid, stearic acid, caproic acid, lipophilic surfactants and the like.

Examples of the plasticizer include triphenyl phosphate,
Phosphoric acid esters such as tricresyl phosphate and diphenyl phosphate, phthalic acid esters such as diethyl phthalate and dimethoxyethyl phthalate, glycolic acid esters such as ethyl phthalyl ethyl glycolate and butyl phthalbutyl butylate, and triethylene glycol and adipic acid Examples thereof include polyesters, polyesters of polyethylene glycol and aliphatic dibasic acids such as polyesters of diethylene glycol and succinic acid, and the like.

The coating solution containing the phosphor and the binder prepared as described above is uniformly applied to the surface of the temporary support for sheet formation to form a coating film of the coating solution.

As the application means, for example, a doctor blade, a roll coater, a knife coater or the like can be used.

As the temporary support, for example, those made of various materials such as glass, wool, cotton, paper, and metal can be used. What can be processed into is preferred. From this point, for example, cellulose acetate film, polyester film, polyethylene terephthalate film, polyamide film, polyimide film, triacetate film, plastic film such as polycarbonate film, aluminum sheet, metal sheet such as aluminum alloy foil, general paper and, for example, photographic base paper Base paper for printing such as paper, coated paper or art paper, baryta paper, resin coated paper, Belgian patent 7
Particularly preferred are processed papers such as paper sized with polysaccharide as described in JP-A-84,615, pigment paper containing a pigment such as titanium dioxide, and paper sized with polyvinyl alcohol.

A coating solution for forming a phosphor layer is applied on a temporary support, dried, and then separated from the temporary support to form a phosphor sheet to be a phosphor layer of a radiographic intensifying screen. Therefore, it is preferable that a release agent is applied to the surface of the temporary support in advance so that the formed phosphor sheet is easily peeled from the temporary support.

The following is a description. A sheet for setting the phosphor formed as described above is prepared. This support can be arbitrarily selected from the materials listed for the temporary support.

Known radiographic intensifying screens include an undercoat layer for imparting adhesiveness by coating a polymer material such as gelatin on the surface of the support in order to strengthen the bond between the support and the phosphor layer. In order to improve the image quality (sharpness, granularity), a light reflecting layer made of a light reflecting material such as titanium dioxide or a light absorbing layer made of a light absorbing material such as carbon black may be provided.

The support used in the present invention can also be provided with these various layers, and the configuration thereof can be arbitrarily selected according to the desired purpose and application of the radiographic intensifying screen.

The phosphor sheet thus obtained is placed on a support, and the phosphor sheet is adhered to the support while being compressed at a temperature not lower than the softening temperature or the melting point of the binder.

As described above, by utilizing the method of pressing the phosphor sheet on the support without previously fixing the sheet, the sheet can be spread thinly, and not only can the phosphor be prevented from being damaged, but also the sheet can be spread. As compared with the case where the pressure is fixed and pressurized, a high phosphor filling rate can be obtained even at the same pressure.

Examples of a compression apparatus used for the compression processing include generally known apparatuses such as a calender roll and a hot press. For example, the compression treatment using a calender roll is performed by placing the phosphor sheet obtained on a support and passing the phosphor sheet at a constant speed between rollers heated to a temperature higher than the softening temperature or melting point of the binder. However, the compression device used in the present invention is not limited to these devices, and may be any device capable of compressing the sheet while heating it. The compression pressure is 50kg
/ Cm ² or more.

Usually, in the radiographic intensifying screen, a transparent protective film for physically and chemically protecting the phosphor layer is provided on the surface of the phosphor layer opposite to the side in contact with the support described above. . It is preferable that such a transparent protective film (hereinafter simply referred to as a protective film) is also provided for the radiation intensifying screen of the present invention. The thickness of the protective film is generally 0.1 to
It is in the range of 20 μm.

The protective film is made of, for example, a cellulose derivative such as cellulose acetate or nitrocellulose, or a synthetic polymer such as polymethyl methacrylate, polyethylene terephthalate, polyvinyl butyral, polyvinyl formal, polycarbonate, polyvinyl acetate, or vinyl chloride / vinyl acetate copolymer. It can be formed by a method in which a solution prepared by dissolving in a suitable solvent is applied to the surface of the phosphor layer.

Alternatively, a plastic sheet made of polyethylene terephthalate, polyethylene naphthalate, polyethylene, polyvinylidene chloride, polyamide, or the like, or a sheet for forming a protective film such as a transparent glass plate is separately prepared and is appropriately bonded to the surface of the phosphor layer. It can be formed by a method such as bonding using an agent.

The protective film used in the radiation intensifying screen of the present invention is particularly preferably a film formed by a coating film containing a fluorinated resin soluble in an organic solvent. Fluorine-based resin is an olefin containing fluorine (fluoroolefin)
Or a copolymer containing an olefin containing fluorine as a copolymer component. The film formed by the coating film of the fluorine-based resin may be cross-linked. The advantage of a protective film made of a fluorine-based resin is that dirt such as a plasticizer that comes out of a film or the like when coming into contact with another material or an X-ray film hardly penetrates into the protective film, so that the dirt can be easily removed by wiping or the like. There is.

When a fluorine-based resin soluble in an organic solvent is used as the material for forming the protective film, the resin was prepared by dissolving the resin in an appropriate solvent. That is, the protective film is formed by uniformly applying a coating liquid for a protective film forming material containing a fluorine-based resin soluble in an organic solvent to the surface of the phosphor layer using a doctor blade or the like, followed by drying. The formation of this protective film may be performed simultaneously with the formation of the phosphor by simultaneous multilayer coating.

The fluorine-based resin may be a polymer of a fluorine-containing olefin (fluoroolefin) or a copolymer containing a fluorine-containing olefin as a copolymer component, such as polytetrafluoroethylene, polychlorotrifluoroethylene, or polyfluorene. Examples include ethylene fluoride, polyvinyl fluoride, polyvinylidene fluoride, tetrafluoroethylene-hexafluoropropylene copolymer, and fluoroolefin-vinyl ether copolymer.

The fluorine-based resin is generally insoluble in an organic solvent, but a copolymer containing a fluoroolefin as a copolymer component becomes soluble in an organic solvent by a structural unit other than the fluoroolefin to be copolymerized. A protective layer can be easily formed by applying a solution prepared by dissolving in a suitable solvent on the phosphor layer and drying. Examples of such a copolymer include a fluoroolefin-vinyl ether copolymer. Also, polytetrafluoroethylene and its modified products are soluble in a suitable fluorine-based organic solvent such as a perfluoro solvent, and thus are protected by coating in the same manner as the copolymer containing the above-mentioned fluoroolefin as a copolymer component. A film can be formed.

The protective film may contain a resin other than the fluorine-based resin, and may contain a crosslinking agent, a hardener, a yellowing inhibitor and the like. However, in order to sufficiently achieve the above object, the content of the fluorine-based resin in the protective film must be 30% by weight.
It is preferably at least 50% by weight, more preferably at least 70% by weight.

Examples of the resin other than the fluorine-based resin contained in the protective film include polyurethane resin, polyacryl resin, cellulose derivative, polymethyl methacrylate, polyester, epoxy resin and the like.

The protective film of the radiation intensifying screen of the present invention may be formed from a coating film containing either or both of a polysiloxane skeleton-containing oligomer and a perfluoroalkyl group-containing oligomer. The polysiloxane skeleton-containing oligomer has, for example, a dimethylpolysiloxane skeleton, and preferably has at least one functional group, for example, a hydroxyl group, and preferably has a molecular weight of 500 to 100,000. In particular, the molecular weight is preferably in the range of 1,000 to 100,000, more preferably 3,000 to 1,000.
It is in the range of 0. The oligomer containing a perfluoroalkyl group, for example, a tetrafluoroethylene group, preferably has at least one functional group, for example, a hydroxyl group in the molecule, and has a molecular weight of 500 to 100.
000 is preferable. Especially the molecular weight is 10
It is preferably in the range of 100 to 100,000, and more preferably in the range of 100 to 100,000.

If an oligomer containing a functional group is used, a crosslinking reaction occurs between the oligomer and the resin for forming the protective layer when the protective film is formed, and the oligomer is incorporated into the molecular structure of the resin for forming the film. An oligomer having a functional group, because the oligomer is not removed from the protective film even by an operation such as long-term repeated use of the radiation intensifying screen or cleaning of the protective film surface, and the effect of adding the oligomer is effective for a long time. Is advantageous. The oligomer is contained in the protective film in an amount of 0.01 to
Preferably, it is contained in an amount of 10% by weight, especially 0.1%.
Preferably, it is contained in an amount of 1 to 2% by weight.

The protective film may contain perfluoroolefin resin powder or silicon resin powder. As the perfluoroolefin resin powder or the silicon resin powder, those having an average particle size in the range of 0.1 to 10 μm are preferable, and particularly preferably the average particle size is 0.3 to 5 μm.
m. These perfluoroolefin resin powder or silicon resin powder is preferably contained in the protective film in an amount of 0.5 to 30% by weight, more preferably 2 to 20% by weight, based on the weight of the protective film. Is preferred, most preferably in an amount of 5 to 15% by weight.

The protective film of the radiation intensifying screen is preferably a transparent synthetic resin layer having a thickness of 5 μm or less, formed on the phosphor layer. By using such a thin protective layer, the distance from the phosphor of the radiographic intensifying screen to the silver halide emulsion is shortened, which contributes to improvement in the sharpness of the obtained X-ray image.

The silver halide emulsion used in the silver halide photographic light-sensitive material of the present invention is preferably silver bromide, silver iodobromide, silver chlorobromide, or silver chloroiodobromide. The silver halide grains may be normal crystal grains or tabular grains, but preferably tabular grains having an aspect ratio of 3 or more are used. The average value of the aspect ratio (referred to as average aspect ratio), which is a ratio of (particle diameter / thickness), is preferably 3 or more, more preferably 3 to 30, and still more preferably 3 to 30. -20, particularly preferably 4-15.

The silver iodobromide or silver chloroiodobromide grains in the present invention have an average silver iodide content of 0 mol% to 1.0 mol%, more preferably 0.1 mol% to 0 mol%. It may be 0.8 mol%. The average silver chloride content of the silver chloroiodobromide grains in the present invention is preferably from 0 mol% to 20 mol%, and more preferably from 0 mol% to 12 mol%.

The silver halide particles of the silver halide photographic light-sensitive material of the present invention have a volume average particle size of 0.5 μm, preferably 0.45 μm, and more preferably 0.4 μm or less.

The method for calculating the volume average particle size is described in JP-A-7-31.
No. 9093.

The silver halide grains of the silver halide photographic light-sensitive material of the present invention are preferably monodisperse. A particularly preferred highly monodispersed emulsion is that the width of distribution defined by (standard deviation of particle size) / (average particle size) × 100 = (width of distribution) (%) is preferably 30% or less. , More preferably 25% or less, and still more preferably 20% or less.

The silver halide emulsion layer of the silver halide photographic light-sensitive material of the present invention has a coated silver amount of 2.0 g / m 2 per side.
The effect of the present invention is preferably at most ² and more preferably at most 1.5 g / m ² .

In the silver halide photographic light-sensitive material of the present invention, the amount of water absorbed immediately before drying in the developing step is preferably 1.1 g / quarter, preferably 0.9 g or less, more preferably 0.8 g or less. That is, the effect of the present invention is favorably exhibited. As a means for this, for example, the gelatin coating amount is set to 3.1 g / m ² or less, preferably 2.8 g / m ² or less. Further, a 1.5% NaOH aqueous solution (30%
(C) is 10 minutes or more.

In the silver halide photographic light-sensitive material of the present invention, gelatin is most preferable as a hydrophilic binder, but a substance other than gelatin may be further added and used. Preferred hydrophilic colloids include, for example, dextran. It can be used in a range of 0.05 to 1.5 g / m ² per one side. Dextran has a molecular weight of 1000
It is most preferable to use those having a molecular weight of up to 200,000 in the emulsion layer.

The non-light-sensitive layers other than the emulsion layer of the silver halide photographic light-sensitive material of the present invention, for example, a protective layer, a dye layer, an intermediate layer, and the like, contain an organic compound having a mercapto group to provide photographic performance. Can be improved. Preferred mercapto compounds include mercaptotetrazoles.

The silver halide photographic light-sensitive material of the present invention may be subjected to various chemical sensitizations, for example, sulfur sensitization, noble metal sensitization, selenium or tellurium sensitization, and the like.
Preferable chemical sensitizers include a sulfur compound and a selenium compound.
The range may be from 1 to 0.4 mol.

In the emulsion used in the silver halide photographic light-sensitive material of the present invention, various photographic additives can be used before and after physical ripening or chemical ripening.

Compounds used in such a step include, for example, Research Disclosure (RD) N
o. No. 17643, ibid. No. 18716 and (RD); 308119 (December 1989) can be used. The types and locations of the compounds described in these three (RD) are described below.

[0069]

[Table 1]

A suitable support for use in the silver halide photographic light-sensitive material of the present invention is, for example, a polyethylene terephthalate film or the like. On the surface of such a support, an undercoat layer may be provided in order to improve the adhesion of the coating layer. , Corona discharge, ultraviolet irradiation, or the like.

In the processing method of the present invention, JP-A-4-15641 and JP-A-4-168 are used as developing agents.
No. 41, dihydroxybenzene, for example, hydroquinone, para-aminophenols, for example, p-aminophenol, N-methyl-p-aminophenol,
Examples of 3-pyrazolidones such as 2,4-diaminophenol include 1-phenyl-3-pyrazolidones,
1-phenyl-3-pyrazolidone, 1-phenyl-4-
Methyl-4-hydroxymethyl-3-pyrazolidone,
It is preferable to use 5,5-dimethyl-1-phenyl-3-pyrazolidone or the like, or to use them in combination. Further, in the image forming method of the present invention, ascorbic acid or erythorbic acid and salts thereof may be used as a developing agent.

In the developing solution, sulfites,
For example, it may contain potassium sulfite, sodium sulfite, reductones, such as piperidinohexose reductone, etc., which are preferably 0.2-1 mol / l, more preferably 0.3-0.6 mol / l. It is better to use liters. Also, addition of a large amount of ascorbic acids leads to processing stability.

As the alkaline agent, sodium hydroxide,
PH adjusters such as potassium hydroxide, sodium carbonate, potassium carbonate, sodium tertiary phosphate and potassium tertiary phosphate are included. Further, borate described in JP-A-61-28708,
A buffer such as saccharose, acetoxime, 5-sulfosalicylic acid, phosphate, carbonate described in JP-A-60-93439 may be used. The content of these chemicals can be adjusted so that the pH of the developer is 9.0 to 13, preferably 10 to 12.
Choose 5 Examples of the dissolution aid include polyethylene glycols and esters thereof, and examples of the sensitizer include quaternary ammonium salts, and other development accelerators.
A surfactant or the like can be contained.

In the processing method of the present invention, the development processing temperature is preferably 25 ° C. to 50 ° C., and more preferably 3 ° C.
0 ° C to 40 ° C. Processing time is Dry to Dry
And 35 seconds or less.

A preferable distribution of the processing time is, for example, insertion + developing + crossing = 4 seconds to 13 seconds Fixing + crossing = 2 seconds to 7 seconds Washing + crossing = 2 seconds to 6 seconds Squeeze + drying = 4 seconds to 11 seconds In the present invention, more preferable Dry to Dry time is 15 seconds to 3 seconds.
5 seconds. Note that Dry to Dr
The term y means the time from when the leading end of the film is inserted into the automatic processor until it comes out through the drying zone.

[0076]

Next, the present invention will be described with reference to examples. The following examples do not limit the invention.

Example 1 <Preparation of X-ray films 2 to 6> (Preparation of seed emulsion-1) Seed emulsion-1 was prepared by the following method.

[A ₁ ] Ossein gelatin 24.2 g Distilled water 9657 ml Polypropyleneoxy-polyethyleneoxy-disuccinate sodium salt (10% aqueous methanol) 6.78 ml Potassium bromide 10.8 g 10% nitric acid 114 ml [B ₁ ] 2.5N AgNO ₃ aqueous solution 2825 ml [C ₁ ] Potassium bromide 841 g Finished to 2825 ml with water [D ₁ ] 1.75 N KBr aqueous solution The following silver potential control amount: 42 ° C, JP-B-58-58288, 58-5828
Using a mixing stirrer described in No. 9, 464.3 ml of each of the solution B ₁ and the solution C ₁ was added to the solution A ₁ by a simultaneous mixing method over 1.5 minutes to form nuclei.

After stopping the addition of the solution B ₁ and the solution C ₁ ,
Over a period of 40 minutes of time to raise the temperature of the solution A ₁ to 50 ° C., after adjusting the pH to 5.0 with 3% KOH, respectively solution B ₁ and solution C ₁ by the simultaneous mixing method again, 55 0.4 ml /
Min was added at a flow rate of 42 minutes. From this 42 ° C to 50
The silver potential (measured with a silver ion selective electrode using a saturated silver-silver chloride electrode as a reference electrode) during the temperature rise to 0 ° C. and re-mixing with the solutions B ₁ and C ₁ was +8 mV and +16 mV respectively using the solution D _1. It controlled so that it might become.

After completion of the addition, the pH was adjusted to 6 with 3% KOH, and immediately, desalting and washing were performed. In this seed emulsion 1, 90% or more of the total projected area of the silver halide grains was composed of hexagonal tabular grains having a maximum adjacent side ratio of 1.0 to 2.0, and the volume average grain size was 0.2 μm.

(Preparation of Tabular Silver Bromide Emulsion) A tabular pure silver bromide emulsion was prepared using the above seed emulsion-1 and the following three kinds of solutions.

[A ₂ ] Ossein gelatin 34.03 g Polypropylene oxy-polyethylene oxy-disuccinate sodium salt (10% aqueous solution of methanol) 2.25 ml Seed emulsion 1 1.218 mol equivalent Equivalent to 3669 ml with water [B ₂ ] Potassium bromide 1747 g Finished to 3669 ml with water [C ₂ ] Silver nitrate 2493 g Finished to 4193 ml with water While maintaining solution A ₂ at 50 ° C. in a reaction vessel, vigorously stirring, and then adding the total amount of solution B ₂ and solution C ₂ to 60 Over a period of minutes, the mixture was added by the simultaneous mixing method. During this time, the pH was kept at 9.0 with the KOH solution, and the pAg was kept at 8.6 throughout. Here, the addition rates of the solution B ₂ and the solution C ₂ were changed functionally with respect to time so as to match the critical growth rate. That is, they were added at an appropriate addition rate so that no small particles were generated except for the seed particles that were growing, and that they did not become multicomponent due to Ostwald ripening.

After completion of the addition, the emulsion was cooled to 40 ° C., and 1800 ml of an aqueous solution of 13.8% (by weight) of a modified gelatin modified with a phenylcarbamoyl group (substitution rate: 90%) was added as an aggregating polymer. Stir for 3 minutes. Thereafter, a 56% (by weight) aqueous solution of acetic acid is added to adjust the pH of the emulsion.
Was adjusted to 4.6 and stirred for 3 minutes, allowed to stand for 20 minutes, and the supernatant was drained by decantation.
1.25 l was added, and after stirring and standing, the supernatant was drained.

Subsequently, an aqueous gelatin solution and sodium carbonate 1
A 0% (by weight) aqueous solution was added to adjust the pH to 5.80, and the mixture was stirred at 50 ° C. for 30 minutes and redispersed. After redispersion, the pH was adjusted to 5.80 and the pAg to 8.06 at 40 ° C.

When the obtained silver halide emulsion was observed with an electron microscope, it was found to be tabular silver halide grains having a volume average particle size of 0.35 μm, an average aspect ratio of 7.0 and a coefficient of variation of 20%. The amount of gelatin at the end of physical ripening was 15.9 g per mol of silver halide.

After the emulsion prepared above was heated to 55 ° C., anhydro-5,5'-dichloro-9- was used as a spectral sensitizing color.
Ethyl-3,3'-di- (3-sulfopropyl) -oxacarbocyanine hydroxide (D-1) and anhydro-5,5-di- (butoxycarbonyl) -1,1-diethyl-3,3 A dispersion (described below) with '-di- (3-sulfobutyl) -benzimidazolocarbocyanine hydroxide (D-2) was added in an amount of 40 per mole of silver halide.
0 mg was added for spectral sensitization.

Next, 4-hydroxy-6-methyl-1,
3,3a, 7-tetrazaindeneazaindene (TA
I) was added in an appropriate amount. After 10 minutes, silver halide 1
3.5 mg of chloroauric acid, 10 mg of sodium thiosulfate and an appropriate amount of a thiocyanate compound were added per mol. After another 50 minutes, an appropriate amount of triphenylphosphine selenide was added as a selenium compound, and after another 40 minutes (TA
5 minutes after adding I), 13 g of trimethylolpropane,
After adding 30 g of gelatin, the mixture was rapidly cooled, and the emulsion was gelled to complete the chemical sensitization.

<Dispersion of spectral sensitizing dye> 9.87 g of D1 and 0.13 g of D2 of the above spectral sensitizing dye were taken, and 490 g of water previously adjusted to 27 ° C. was added thereto. Dissolver) at 30-120 rpm at 3,500 rpm
The dispersion of the spectral sensitizing dye was obtained by stirring for minutes. The average particle size of the disperse dye was 0.7 μm.

<Preparation of X-Ray Film 2> The emulsion thus sensitized was heated and redissolved, and the following additives were added to obtain an emulsion coating solution. At the same time, a coating solution for the protective layer was prepared. The amount of silver applied per side was 1.4 g /
^Two slide hopper type coaters were used to simultaneously coat both sides of the support and dried to obtain a sample, so that the amount of gelatin attached at 3.1 m / m ² was 3.1 g / m ² .

The support had a thickness of 175 μm and a concentration of 0.1 μm.
Dilution 17 was carried out so that the concentration of a copolymer composed of three monomers of 50 wt% of glycidyl methacrylate, 10 wt% of methyl methacrylate, and 40 wt% of butyl methacrylate was 10 wt% on both sides of a polyethylene terephthalate film base for radiography which was colored blue. The following filter dye and gelatin were dispersed in the aqueous copolymer dispersion thus obtained and applied as a subbing liquid. The coating weight at this time was 15 mg / m ^{2 for the} dye and 0.15 for the gelatin.
mg / m ² .

[0091]

Embedded image

The additives added to the emulsion are as follows.
The amount of addition is shown in an amount per mole of silver halide.

1,1-Dimethylol-1-bromo-1-nitromethane 70 mg Polyvinylpyrrolidone (molecular weight 10,000) 1.0 g Styrene-maleic anhydride copolymer 2.5 g Nitrophenyl-triphenylphosphonium chloride 50 mg C ₄ H ₉ OCH ₂ CH (OH) CH ₂ N (CH ₂ COOH) ₂ 1.0 g 1-phenyl-5-mercaptotetrazole 8.5 mg Dextran (molecular weight 40,000) 4 g

[0094]

Embedded image

Protective Layer Solution Next, the following was prepared as a protective layer coating solution. The following addition amounts are shown per 1 liter of the coating solution.

Lime-treated inert gelatin 68 g Acid-treated gelatin 2.0 g Sodium-i-amyl-n-decylsulfosuccinate 1.0 g Polymethyl methacrylate (a matting agent having an area average particle size of 3.5 μm) 1.1 g Silicon dioxide particles (Mat agent having an area average particle diameter of 1.2 μm) 0.5 g 1-phenyl-5-mercaptotetrazole 37 mg (CH ₂ ＣＨCHSO ₂ CH ₂ ) ₂ (hardener) 500 mg C ₄ F ₉ SO ₃ K 2.0 mg _{C 12 H 25 CONH (CH 2} CH 2 O) 5 H 2.0g

[0097]

Embedded image

<Preparation of X-ray film 3> Film 3 was prepared in the same manner as film 2 except that the amount of gelatin added to film ² was reduced to 2.5 g / m ² .

<Preparation of X-ray film 4> A film 4 was prepared in the same manner as the film 2 except that the amount of gelatin added to the film ² was reduced to 1.7 g / m ² .

<Preparation of X-ray film 5> An X-ray film 5 was prepared in the same manner as the X-ray film 4 except that the chemical sensitization of the silver halide emulsion was changed as follows.

(Chemical Sensitization of Emulsion) After the emulsion was heated to 60 ° C., the dispersion of the spectral sensitizing dye was added as a dispersion of solid fine particles at a concentration of 0.7 mmol per mol of silver halide. A mixed aqueous solution of potassium thiocyanate, chloroauric acid and sodium thiosulfate and an appropriate amount of triphenylphosphine selenide were added, and the mixture was aged for a total of 2 hours.

At the end of ripening, an appropriate amount of 4-hydroxy-6-methyl-1,3,3a, 7-tetrazaindene (TAI) was added as a stabilizer.

<Preparation of X-ray film 6> Same as X-ray film 5 except that the silver chloride content was changed to 80 mol% by changing the ratio of sodium chloride to potassium bromide during physical ripening of the silver halide emulsion. Thus, an X-ray film 6 was produced.

<Production of Radiation Intensifying Screens 1 to 4> (Screen 1) Phosphor Gd ₂ O ₂ S: Tb (average particle size: 1.8 μm) 200 g Binder Polyurethane thermoplastic elastomer, Demolac TPKL-5-26 25 <solid content 40%> (manufactured by Sumitomo Bayer Urethane Co., Ltd.) 20 g Nitrocellulose (digestibility 11.5%) 2 g was added to a methyl ethyl ketone solvent and dispersed with a propeller mixer to obtain a phosphor having a viscosity of 25 PS (25 ° C.). A coating solution for forming a layer was prepared.

(Binder / Phosphor ratio = 1/22) Separately, 90 g of a soft acrylic resin solid content and 50 g of nitrocellulose were added to methyl ethyl ketone as a coating liquid for forming an undercoat layer, and dispersed and mixed to obtain a viscosity of 3 to 3. 6PS (25
C).

250 μm thickness kneaded with titanium dioxide
Of polyethylene terephthalate (support) is placed horizontally on a glass plate, and the above-mentioned coating solution for forming an undercoat layer is uniformly applied on the support using a doctor blade, and then gradually raised from 25 ° C to 100 ° C. The coating film was dried by drying to form an undercoat layer on the support. (Thickness of coating film: 15 μm) The above coating solution for forming a phosphor layer was dried so as to have a thickness of the phosphor layer shown in Table 2, and then compressed. Compression was performed using a calender roll at a thickness of 300 kgW / cm ² and a temperature of 80 ° C. After this compression,
A transparent protective film having a thickness of 3 μm was formed by the method described in Example 1 of No. 75097.

The radiation intensifying screen 1 comprising the support, the undercoat layer, the phosphor layer and the transparent protective layer as described above
Was manufactured.

(Screen 2) A screen 2 was obtained in the same manner as the screen 1 except that the thickness of the phosphor layer of the screen 1 was changed as shown in Table 2 for the front side and for the back side. (Screens 3 and 4) Screens were made in the same manner as Screen 1 except that the front and back phosphor layers were equally divided into upper and lower layers, and the particle size and thickness were changed as shown in Table 2. 3, 4 were obtained.

Table 2 shows the breakdown of the four types of screens obtained. The sensitivity in the table refers to the X-ray dose required to obtain a density of minimum density + 1.0 for each screen, and the sensitivity was calculated from the reciprocal of the required dose. When the sensitivity of the obtained screen number 1 was set to 100, it was represented by the specific sensitivity of another screen number.

[0110]

[Table 2]

It can be seen that the screen of the present invention has a higher sensitivity than the comparison.

The development was carried out by an automatic developing machine using a developing solution and a fixing solution of the following formulation.

Developer Formulation Part-A (for finishing 12 liters) Potassium hydroxide 450 g Potassium sulfite (50% solution) 2280 g Diethylenetetraamine pentaacetic acid 120 g Sodium bicarbonate 132 g 5-methylbenzotriazole 1.2 g 1-phenyl- 5-mercaptotetrazole 0.2 g 1,4-dihydroxybenzene 340 g Add water to make up to 5000 ml Part-B (for finishing 12 liters) Glacial acetic acid 170 g Triethylene glycol 185 g 1-Phenyl-3-pyrazolidone 22 g 5-Nitroindazole 0 .4g Starter liquid formulation (for 1 liter finishing) Glacial acetic acid 120g Potassium bromide 225g Add water to make up to 1000ml Fixing solution formulation Part-A (for 18 liter finishing) Ann thiosulfate Monium (70 wt / vol%) 6000 g Sodium sulfite 110 g Sodium acetate trihydrate 450 g Sodium citrate 50 g Gluconic acid 70 g 1- (N, N-dimethylamino) -ethyl-5-mercaptotetrazole U 18 g Part-B (18 liters) Finish) Aluminum sulfate 800g Preparation of developer Solution of developer is prepared by adding Part-A, Pa
rt-B was added at the same time, and water was added while stirring and dissolving.
After finishing to 1 liter, the pH was adjusted to 10.40 with glacial acetic acid to obtain a developer.

20 ml of a starter solution was added per liter of the developing solution, and the pH was adjusted to 10.40 to obtain a working solution.

Preparation of Fixing Solution Fixing solution was prepared by adding Part-A, Par
t-B was added at the same time, and water was added while stirring and dissolving to give 18
Liters, p with sulfuric acid and sodium hydroxide
H was adjusted to 4.4, and this was used as a fixing solution working solution and a fixing solution replenisher.

The processing time is 3 to Dry to Dry.
At 0 seconds, the distribution of the processing steps is as shown below.

Process Processing temperature Processing time Supplementary charge (° C) (seconds) Insertion-0.8 Development + transfer 35 9.7 (15 ml / quarter 1 sheet) Fixation + transfer 33 5.5 (15 ml / Washing + migratory 18 4.8 (1 liter / min) Squeeze 55 3.8 Drying 70 5.4 Total 30.0 (How to determine relative sensitivity and water absorption) Medical X-ray Radiation intensifying screen SRO-250 using a cassette for photography
(Konica Corporation) front side and back side combination, X-ray photography by distance method, automatic developing machine SRX-
Both 502 (Developer XD-SR, Fixer XF-SR) were treated with Konica Corporation for 45 seconds.

The relative sensitivity was SR-H (Em No. 254).
9, Expiration date 1998-2 X-ray film (manufactured by Konica Co., Ltd.).

The water absorption was improved by modifying the above processor, increasing the line speed by about 1.5 times, and increasing the line speed by 30% by Dryto Dry.
Seconds. Thereafter, the drying rack was removed, the drying air was turned off, the heater was turned off, and the X-ray film was processed until the wetness of the squeeze rack reached equilibrium. Then, the X-ray film samples 2 to 4 according to the present invention were processed, Immediately after coming out of the squeeze (Wet), the weight was measured, and the temperature was 23 ° C and RH50.
%, And the value obtained by subtracting the weight after Dry (quartz (30.5 × 25.4 cm) W / sheet)
et-Dry) was taken as the water absorption. Table 3 shows the obtained results.

[0120]

[Table 3]

As is clear from Table 3, the silver halide photographic materials (X-ray film Nos. 2 to 6) according to the present invention have a small water absorption.

Example 2 The following evaluation was performed by combining the X-ray film produced in Example 1 and the radiographic intensifying screen used in Example 1 as shown in Table 4 below.

However, the line speed of the automatic developing machine was doubled, and the development processing was carried out by adjusting the processing to Dry to Dry for 15 seconds.

<Evaluation of Relative Sensitivity> The relative sensitivity was determined in the same manner as in Example 1, and the sample No. The sensitivity of one film is 10
It is shown as a relative value when 0 is set.

<Evaluation of γ (gamma)> Fog of sample +
It was determined from the slope of a straight line connecting the density of 0.25 and the density of fog +2.0.

<Evaluation of graininess (visual observation)> A: Almost no graininess B: Slightly noticeable C: Remarkably noticeable, slightly impaired image interpretation D: Very noticeable, impaired image interpretation <Evaluation of sharpness ( Visual)> A: very sharp B: slightly blurred C: blurred D: difficult to read due to blurred Table 4 shows the results.

[0127]

[Table 4]

As is clear from Table 4, the combination according to the present invention was remarkably excellent in the graininess and sharpness of the image as compared with the conventional product. Further, the sensitivity and the contrast (γ) were not inferior to the comparison.

[0129]

As has been demonstrated in the examples, according to the present invention, an image forming method for a silver halide photographic light-sensitive material for X-rays having excellent image granularity and sharpness, and having high sensitivity and high contrast is obtained. I was able to do it.

Claims (2)

[Claims] 1. A method for forming a radiographic image in which a silver halide photographic material having a silver halide emulsion layer on both sides of a support is photographed by sandwiching the material between two radiographic intensifying screens. The thickness of the phosphor layer for the back side is 150 to 250 μm, and the thickness of the phosphor layer for the front side is 30% or more and 90% or more of the thickness of the phosphor layer for the back side.
Wherein the silver halide photographic light-sensitive material is Dry
A method for forming a radiation image, wherein the gamma value when processed in toDry for 15 seconds or more and 35 seconds or less is 3.2 or more and 4.0 or less. 2. A silver halide photographic light-sensitive material having a water absorption immediately before drying of 1.1 g or less per sheet in a processing step of the silver halide photographic light-sensitive material. The method for forming a radiation image as described in the above.