JP2000096047A - Gadolinium-activated yttrium tantalate fluorescent substance, radioactive ray-sensitized screen, united body of radioactive ray-sensitized screen with halogenated silver photosensitive material, and formation of image by radioactive ray - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject fluorescent substance represented by a specific composition formula, having extremely improved radioactive ray-afterglow characteristics, and high sensitivity, hardly causing afterimage halation, excellent in diagnostic characteristics, and rapid and low supplement-treating suitability, and useful for achieving image-forming system by radioactive rays, or the like. SOLUTION: This fluorescent substance is produced by burning a mixture of fluorescent raw materials under 0.3-4.0, preferably 0.5-4.0 kg/cm2 gauge pressure at 1,100-1,300 deg.C for 8-12 hr, and represented by the formula [(x) is 0<(x)<=0.1]. Preferably, the intensity of the radioactive ray-afterglow of the obtained gadolinium-activated yttrium tantalate fluorescent substance is <=50%, preferably <=30% of the intensity of the radioactive afterglow of a fluorescent substance produced by burning under an atmospheric pressure. The radioactive ray image is preferably formed by constituting a radioactive ray-sensitized screen of the fluorescent substance, combining the radioactive ray-sensitized screen with a photosensitive material containing an emulsion containing >=50 mol% tabular particles of a high silver chloride having the (100) face as a principal plane, and utilizing 300-350 nm luminescence.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gadolinium-activated yttrium tantalate phosphor which emits light in the ultraviolet region. The present invention also relates to a radiographic intensifying screen using the phosphor, an assembly of the radiographic intensifying screen and a silver halide photographic material, and a radiographic image forming method using the phosphor.

[0002]

2. Description of the Related Art A radiographic method (radiation image forming system) using a combination of a radiation intensifying screen containing a phosphor and a silver halide photographic light-sensitive material has been well known. In this method, a radiation intensifying screen is arranged on one or both sides of a silver halide photographic material, and radiation such as X-rays transmitted through a subject or emitted from a subject is absorbed by a phosphor of the intensifying screen. To emit light in the visible region, and sensitize the photographic light-sensitive material with the emitted light together with the radiation to form a latent image on the light-sensitive material. Then, the light-sensitive material is developed and fixed, and the radiation image is formed on the light-sensitive material. Are visualized. Conventionally, as the phosphor, a phosphor that absorbs radiation and emits light in the visible region, such as calcium tungstate or a rare earth activated alkaline earth metal fluoride halide phosphor, has been used.

[0003] The radiation intensifying screen has, as a basic structure, a support and a phosphor layer provided on the surface thereof. However, when the phosphor layer is self-supporting, a support is not necessarily required. The phosphor layer is usually formed of a phosphor and a binder containing and supporting the phosphor in a dispersed state. The silver halide photographic material basically comprises a support and at least one silver halide emulsion layer provided on one or both surfaces thereof. Usually, a silver halide emulsion layer is provided on both sides of the support, and a crossover cut layer containing a dye or the like is provided between both layers in order to reduce crossover light generated between both layers.

In recent years, it has been proposed to use a radiation intensifying screen containing a phosphor which emits light in an ultraviolet region having a wavelength of about 400 nm in this radiation image forming system.
For example, in U.S. Pat. No. 4,225,653,
An X-ray intensifying screen using a yttrium tantalate phosphor (YTaO ₄ ) or a phosphor obtained by adding Gd, Nb, and Tb to the phosphor is described. JP-A-8-286293 describes an image forming system using a combination of a radiation intensifying screen having an emission peak in an ultraviolet region and a photographic light-sensitive material containing tabular silver chloride particles. YTaO ₄ to which Gd is added as an example of a phosphor used for an intensifying screen
A phosphor is described. YTa to which this Gd is added
Conventionally, the production of O ₄ phosphor has been carried out by mixing the phosphor raw materials and then baking the mixture at atmospheric pressure for a long time.

According to the image forming system utilizing the light emission of the intensifying screen in the ultraviolet region (ie, exposure to the photographic material), the photosensitive material is subjected to spectral sensitization in the visible region (ie, visible). Since there is no need to add dyes or dyes for crossover cut, there is no contamination of the processing solution due to elution of the dyes and dyes during processing, and contamination of the automatic developing machine is reduced. Maintenance is greatly simplified. Further, since there is no problem such as coloring (residual color) of the photosensitive material due to the remaining of the pigment or dye in the photosensitive material,
It can be carried out advantageously with rapid and low developer replenishment.

[0006]

SUMMARY OF THE INVENTION As described above, the present inventor has argued that an image forming system utilizing light emission (exposure) in the ultraviolet region has various advantages, and that the inherent absorption of a silver chloride photographic emulsion is improved. Notices that it is high on the short wavelength side even in the ultraviolet region, and is gadolinium-activated yttrium tantalate (YT
aO ₄ : Gd) Research was continued on phosphors. This YT
Since the aO ₄ : Gd phosphor has an emission peak at about 314 nm, it becomes possible to expose a photographic material using the intrinsic absorption of silver chloride. As a result, it is possible to reduce or eliminate the use of the spectral sensitizing dye conventionally added to the photosensitive material, and it is possible to reduce the contamination of the developing solution.
In addition, since the substantial sensitivity of the photosensitive material can be increased, the diagnostic performance can be improved while reducing the exposure dose during X-ray imaging. Furthermore, since the crossover light of this light emission is mostly absorbed by the support of the photosensitive material, there is almost no need to provide a crossover cut layer,
Since the solid disperse dye, the crossover cut dye and the like are not eluted, the contamination of the developing solution can be further reduced.

Further, tabular grains having a high silver chloride content are known to be suitable for rapid and low replenishment processing. However, they have found that they are particularly suitable for rapid low replenishment processing.

In consideration of the above points, YTaO ₄ : Gd
An image forming system using a radiographic intensifying screen using a phosphor and a photographic material containing a tabular grain emulsion of high silver chloride has excellent suitability for rapid and low replenishment processing and is extremely useful from the viewpoint of environmental pollution and the like. I understand.

[0009] Even in an image forming system by ultraviolet exposure having many advantages as described above, the sensitivity of the system and the image quality (sharpness and granularity) of an obtained image, that is, the sensitivity of an intensifying screen and a photographic light-sensitive material, and the like. It is required that the quality of a radiation image to be obtained be improved as much as possible. Therefore, it is desired that the YTaO ₄ : Gd phosphor be further improved in its light emission characteristics and afterglow characteristics. In particular, if the afterglow is large when irradiating the phosphor with X-rays or the like, when the intensifying screen is repeatedly used, an unused film is exposed to the afterglow from the screen. However, there is a problem that accuracy of medical diagnosis and the like is reduced.

Accordingly, an object of the present invention is to provide a gadolinium-activated yttrium tantalate phosphor having improved afterglow characteristics against radiation such as X-rays. Another object of the present invention is to provide a radiation intensifying screen which emits light in the ultraviolet region of 300 to 350 nm and does not cause afterimage fog. Further, the present invention provides
To provide a combination of a radiographic intensifying screen and a silver halide photographic light-sensitive material, which are excellent in diagnostic performance without any residual image fogging, excellent in rapid low replenishment development processing suitability, and have improved environmental problems, and a radiographic image forming method. Also its purpose.

[0011]

SUMMARY OF THE INVENTION According to the present invention, a mixture of phosphor raw materials is prepared at a gauge pressure of 0.3 to 4.0 kg / cm ² and a temperature of 1100 to 1300 ° C. for 8 to 1 kg.
A gadolinium-activated yttrium tantalate phosphor represented by the following composition formula (1), which is produced by firing for 2 hours. Composition formula (I): YTaO ₄ : xGd (I) [where x is a numerical value in the range of 0 <x ≦ 0.1]. ]

The present invention also provides a phosphor represented by the above composition formula (1), wherein the radiation afterglow intensity of the phosphor produced by firing under atmospheric pressure is Gadolinium-activated yttrium tantalate phosphor which is 50% or less of the above. Here, the radiation afterglow intensity is
A value obtained by normalizing the luminous intensity of the phosphor at the time when 20 seconds have passed after irradiating the phosphor with the instantaneous luminous intensity,
The radiation includes various kinds of radiation such as X-rays, electron beams, α-rays, β-rays, and γ-rays.

Further, the present invention provides a radiographic intensifying screen containing the above-described gadolinium-activated yttrium tantalate phosphor, a radiographic intensifying screen containing the above-mentioned gadolinium-activated yttrium tantalate phosphor, and (10)
There is also a combination with a silver halide photographic light-sensitive material containing an emulsion containing 50 mol% or more of high silver chloride tabular grains having a 0) plane as a main plane.

Further, the present invention contains a radiographic intensifying screen containing the above-described gadolinium-activated yttrium tantalate phosphor and 50 mol% or more of high silver chloride tabular grains having a (100) plane as a main plane. There is also a radiation image forming method using a silver halide photographic light-sensitive material containing an emulsion in combination and utilizing light emission in the ultraviolet region having a wavelength of 300 to 350 nm.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, a method for producing a gadolinium-activated yttrium tantalate phosphor of the present invention will be described in detail.

Tantalum oxide, yttrium oxide and gadolinium oxide are prepared as phosphor raw materials, and lithium fluoride or lithium chloride is added as a flux to these compounds, and these compounds are sufficiently mixed with mechanical stirring. At this time, for the purpose of improving the emission intensity, aluminum oxide may be added in the range of 0.01 to 10 mol%, preferably in the range of 0.1 to 5 mol% with respect to the phosphor raw material. The obtained mixture is filled in a heat-resistant container such as a quartz boat, an alumina crucible, a quartz crucible, and placed in a furnace core of an electric furnace for firing.

At the time of this firing, the pressure inside the electric furnace, which is a characteristic requirement of the present invention, is set to 0.3 to 4.0 k
Set high pressure (ie, gauge pressure) in the range of g / cm ² . The gauge pressure is preferably 0.5 to 4.0 kg / cm ² from the viewpoint of improving the afterglow characteristics against radiation such as X-rays.
Range.

At this time, in order to improve the emission intensity, the inside of the furnace is temporarily changed to a substantially vacuum state (for example, 0.0 mm) instead of air.
After the pressure is reduced to 1 Torr or less, a mixed gas of oxygen and nitrogen may be introduced to carry out firing at a high oxygen partial pressure. Mixing ratio of oxygen / nitrogen in mixed gas (volume ratio)
Is generally in the range of 0.28 to 0.8, preferably in the range of 0.28 to 0.46. Firing temperature is 1100
To 1300 ° C. is appropriate, and particularly preferred is 1 to 300 ° C.
It is around 200 ° C. The baking time varies depending on the filling amount of the mixture, the gauge pressure, the baking temperature, the temperature at which the mixture is taken out of the furnace, and the like, but is generally suitable for 8 to 12 hours, particularly preferably 9 to 11 hours.

After firing, the temperature in the furnace is lowered to room temperature, the pressure is reduced to atmospheric pressure, and the fired product is taken out of the furnace.
The obtained fired product is washed with water and then dried to obtain a gadolinium-activated yttrium tantalate phosphor represented by the following composition formula (I). YTaO ₄ : xGd (I) [where x is a numerical value in the range of 0 <x ≦ 0.1]. ]

As described above, by firing the phosphor raw material mixture at a pressure higher than the atmospheric pressure, the afterglow intensity when the obtained phosphor is irradiated with radiation such as X-rays can be significantly reduced. it can. FIG. 1 is a graph showing the relationship between the pressure (gauge pressure) in the furnace during firing and the X-ray afterglow intensity of the phosphor. Note that the relative X-ray afterglow intensity on the vertical axis is
This is a value obtained by normalizing the emission intensity at 20 seconds after irradiating the phosphor with X-rays by the instantaneous emission intensity. The X-ray afterglow intensity of the phosphor obtained by firing under atmospheric pressure (gauge pressure 0) To 100
Expressed as

As is clear from FIG. 1, when the gauge pressure in the furnace is in the range of 0.3 to 4.0 kg / cm ² ,
The X-ray afterglow intensity of the obtained phosphor is 50% or less of the X-ray afterglow intensity of the phosphor fired under atmospheric pressure. In particular, when the gauge pressure in the furnace was in the range of 0.5 to 4.0 kg / cm ² , the X-ray afterglow intensity of the obtained phosphor was lower than that of the phosphor fired under atmospheric pressure. It is 30% or less of the afterglow intensity. Therefore, the phosphor of the present invention has a radiation afterglow intensity of 50% or less of the radiation afterglow intensity of the phosphor produced by firing under atmospheric pressure. Preferably, it shows a value of 30% or less.

In the radiation intensifying screen of the present invention, the phosphor layer contains the above gadolinium-activated yttrium tantalate phosphor. The phosphor layer may further contain other phosphors and / or additives such as colorants.

The phosphor layer of the radiation intensifying screen of the present invention can be formed on a support by the following known method. First, phosphor particles and a binder are added to a solvent and mixed well to prepare a coating solution in which phosphor particles are uniformly dispersed in a binder solution. 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. In general, the mixing ratio between the binder and the phosphor is from 1: 1 to 1: 1. 1: 1
00 (weight ratio), and particularly preferably from 1: 8 to 1:40 (weight ratio). This coating solution is then uniformly applied to the surface of the support to form a coating film. This coating operation can be performed by using a normal coating means, for example, a doctor blade, a roll coater, a knife coater or the like.

The support can be arbitrarily selected from materials known as supports for conventional radiographic intensifying screens. In a known radiographic intensifying screen, the side on which the phosphor layer is provided in order to strengthen the bond between the support and the phosphor layer or to improve the sensitivity or image quality (sharpness, granularity) as the intensifying screen. A polymer material such as gelatin is applied to the surface of the support to provide an adhesion-imparting layer, or a light-reflective layer made of a light-reflective material such as titanium dioxide, aluminum or lead carbonate, or a light-absorbing material such as carbon black It is known to provide a light absorbing layer made of a substance. The support used in the present invention can also be provided with these various layers. Alternatively, a light-reflective substance or a light-absorbing substance may be contained in the support itself, or fine irregularities may be provided on the surface of the support. These configurations can be arbitrarily selected according to the purpose, use, and the like of a desired radiographic intensifying screen.

After forming the phosphor-containing coating film on the support as described above, the coating film is dried to complete the formation of the phosphor layer on the support. The thickness of the phosphor layer varies depending on the characteristics of the intended radiographic intensifying screen, the type of the phosphor, the mixing ratio of the binder and the phosphor, and the like.
m to 1 mm. This layer thickness is especially 50-500μ
m is preferable. Note that the phosphor layer does not necessarily need to be formed by directly applying a coating liquid on the support as described above. For example, the coating liquid is separately coated on a sheet such as a glass plate, a metal plate, or a plastic sheet. After the phosphor layer is formed by drying, the phosphor layer may be joined to the support by pressing the phosphor layer on a support or using an adhesive.

It is preferable to provide a protective film on the phosphor layer in order to protect the phosphor layer from chemical deterioration or physical impact. The protective film is formed by applying a solution prepared by dissolving a transparent organic polymer substance such as a cellulose derivative, polymethyl methacrylate, or a fluororesin in an appropriate solvent onto the phosphor layer, or An organic polymer film such as polyethylene terephthalate or a protective film forming sheet such as a transparent glass plate is separately formed and provided on the surface of the phosphor layer with an appropriate adhesive, or an inorganic compound is fluorinated by vapor deposition or the like. Those formed on the body layer are used. The surface of the protective film may be embossed, or a light scattering substance such as titanium oxide, a slip agent such as a polysiloxane skeleton-containing oligomer, or a conductivity imparting agent such as zinc oxide may be applied to the protective film. You may make it contain.

According to the above-mentioned method, the radiation-enhancing method of the present invention, in which a phosphor layer comprising the above-mentioned gadolinium-activated yttrium tantalate phosphor and a binder containing and supporting the phosphor in a dispersed state, is provided on a support. A feeling screen can be manufactured.

Next, a silver halide photographic light-sensitive material which is preferably used as an assembly with the above-described radiation intensifying screen will be described.

The silver halide emulsion preferably used in the silver halide photographic light-sensitive material of the present invention contains at least a dispersion medium and silver halide grains, and the silver halide grains have a (100) plane as a major plane. Of high silver chloride tabular grains of at least 50 mol%. Here, high silver chloride means silver chloride alone or silver chloride containing a small amount of other silver halide such as silver bromide (for example, 1 mol% or less based on silver). The major plane refers to the largest outer surface of the tabular grains. That is, the silver halide used in the silver halide photographic light-sensitive material of the present invention has a Cl ^- content of from 50 to 10.
It is in the range of 0 mol%. Further, the silver halide grains other than silver chloride are preferably tabular grains having an aspect ratio (diameter / thickness) of 2 or more in 50 to 100% of the total projected area. The aspect ratio is a value obtained by dividing a projected area of a silver halide grain by an equivalent sphere diameter by a thickness, and is generally used in the art as an index of tabularity of the silver halide grain. Here, the diameter means the diameter of a circle having an area equal to the projected area of the tabular grains, and the thickness is 2
Means the distance between two principal planes. The grains having an aspect ratio of 2 or more include tabular grains having a (100) main plane and tabular grains having a (111) plane. The thickness of the tabular grains is preferably 0.35 μm or less, more preferably in the range of 0.05 to 0.3 μm, and particularly preferably in the range of 0.05 to 0.25 μm. The aspect ratio is 2 or more, preferably in the range of 2 to 25, more preferably in the range of 5 to 20.

The nucleation of an emulsion having the (100) plane as the main plane is described in JP-A-5-204073 and JP-A-51-40773.
Nos. 88017 and 63-24238, and the like, and in the present invention, any of the nucleation methods described therein can be used. In particular, a method of performing crystal ripening by physical ripening (an operation in which fine particles are dissolved and substrate particles grow) in the presence of silver halide fine particles is preferably used. In the case of the fine grain emulsion addition method, 0.
001-0.15 μm range, preferably 0.001-0.15 μm
A method is used in which an AgX fine grain emulsion having a diameter in the range of 0.1 μm is added, and tabular grains are grown by Ostwald ripening. The halogen composition of the fine particles is AgCl, Ag
BrCl, AgBr, AgBrI and mixed crystals of two or more thereof. For other details of the nucleation method, the description in JP-A-6-59360 can be referred to. The total amount of fine grains added is 20% of the amount of silver halide.
Or more, and preferably 50-98%
Range. The fine particles have a Cl ^- content of 50 to 100.
A mole% range is preferred. As a dispersion medium at the time of nucleation, ripening and growth, a conventionally known dispersion medium for an AgX emulsion can be used, and particularly, a methionine content of 0 to 50.
Gelatin in the range of μmol / g can be preferably used. The pH at the time of growth by adding fine particles needs to be 2.0 or more, and preferably in the range of 4.0 to 8.0. Also, pCl needs to be 1.0 or more, but preferably 1.6 or more. Here, pCl is a relational amount with respect to the activity [Cl ⁻ ] of Cl ions in the solution.
pCl = -log [Cl ^-] is defined. The monodispersibility of silver halide emulsions is described in JP-A-59-74548.
It is preferably 30% or less, more preferably 5% or less, based on the coefficient of variation defined by the method described in Japanese Patent Publication No.
２５25%.

It is not always necessary to sensitize a silver halide emulsion with a spectral sensitizer, but when performing spectral sensitization, a spectral sensitizer having an absorption maximum in the range of 300 to 350 nm (hereinafter referred to as UV sensitizer). Sensitizers). The addition amount is 1. mol per mol of silver halide.
It is preferably in the range of 0 × 10 ^{−5 to} 1.0 × 10 ⁻² mol, and particularly preferably 1.0 × 10 ^{−4 to} 3.0 × 10 mol.
^-3 mole range. It is particularly preferred to add this UV sensitizer before the end of chemical sensitization of the emulsion. UV sensitizers are described in, for example, WO 93/09468, U.S. Pat. Nos. 5,169,748 and 5,275,928. Hereinafter, specific examples of the UV sensitizer preferably used in the present invention will be described.

[0032]

Embedded image

[0033]

Embedded image

Chemical sensitization methods include a gold sensitization method using a so-called gold compound, a sensitization method using a metal such as iridium and platinum, a sulfur sensitization method using a sulfur-containing compound, a reduction sensitization method using a polyamine or the like, a selenium compound. And various known methods such as a sensitization method using a tellurium compound and a sensitization method using a tellurium compound can be used in combination.

The formation of tabular grains having a (100) plane having a high silver chloride content as a main plane (hereinafter sometimes simply referred to as (100)) is described in JP-A-4-139439 and JP-A-4-1439.
A mixture of an aqueous halogen solution and an aqueous silver nitrate solution immediately before using an apparatus such as a multiple coaxial nozzle described in JP-A-39440, JP-A-4-134441 and US Pat. No. 5,104,786. Is preferably added to the reaction vessel.

Further detailed technical information on the silver halide emulsion used in the silver halide photographic light-sensitive material of the present invention is described in the above-mentioned JP-A-8-286293.

The silver halide photographic material has at least one silver halide-containing emulsion layer (photographic emulsion layer) on at least one surface of the support. It is preferred to provide an emulsion layer on both sides of the support to enhance the sensitivity of the photographic light-sensitive material. The amount of silver in the light-sensitive material, preferably per side in the range of 0.5 to 5 g / m ^2, more preferably in the range of 1~3.4g / m ^2. From the viewpoint of rapid processing suitability, it is preferred that the amount does not exceed 5 g / m ² (per side).

Further, a dye layer (crossover cut layer) for absorbing ultraviolet crossover light may be provided between the support and the emulsion layer, if necessary, in order to enhance the sharpness of the image. Alternatively, a surface protective layer may be provided on the emulsion layer.

The material of the support used in the silver halide photographic light-sensitive material of the present invention, the dispersing medium for the emulsion layer, the dye, and the additives are not particularly limited.
The materials, dyes and various additives described in JP-A No. 9 can be used. Further, the methods described in the above-mentioned publications can also be used for the method for producing a silver halide emulsion, the method for chemical sensitization, the method for forming a support and each layer, and the like.

Next, the radiation image forming method of the present invention using the above-described radiation intensifying screen and silver halide photographic light-sensitive material will be described.

First, a radiographic intensifying screen is placed in close contact with at least one side (subject or subject side) of a photographic light-sensitive material. Preferably, intensifying screens are respectively adhered to both sides of a light-sensitive material having an emulsion layer provided on both sides of a support. Next, the subject is irradiated with radiation such as X-rays, and radiation transmitted through the subject or radiation such as β-rays directly emitted from the subject is made to enter the intensifying screen. The gadolinium-activated yttrium tantalate phosphor in the intensifying screen is excited by this radiation to 300 to
The emission at an emission wavelength in the ultraviolet region of 350 nm is shown (peak wavelength: about 314 nm, see FIG. 2). The silver halide photographic emulsion of the light-sensitive material is also exposed to radiation, but most of the light is exposed to the emitted light in the ultraviolet region, and silver halide containing high silver chloride (100) tabular grains in the emulsion layer is It becomes blackened silver to form a latent image. The photosensitive material on which the latent image is formed is then subjected to processing such as development, fixing, washing with water, and drying by using an automatic development processing device or the like, so that a radiation image of the subject or the subject can be visualized.

As a developing solution, an ascorbic acid developing solution is preferable. Ascorbic acid and its derivatives include compounds represented by the general formula (I) described in JP-A-5-165161 and compound examples I-1. ~ I-
8, II-9 to II-12 can be preferably used.
Further, ascorbic acids, enediol type, enaminol type, enediamine type, thiol enol type and enamine-thiol type are generally known as compounds,
Examples of these compounds are described in U.S. Pat. No. 2,688,549 and JP-A-62-237443. Ascorbic acids can also be used in the form of alkali metal salts such as lithium, sodium and potassium salts. These ascorbic acids are used in an amount of 1 to 100 g, preferably 5 to 8 g, per liter (L) of the developer.
Use in the range of 0 g.

It is preferable to use 1-phenyl-3-pyrazolidone or p-aminophenol as a developing agent together with the above ascorbic acids. The developing agent is usually used in the range of 0.001 to 1.2 mol / L.

Examples of the alkaline agent used for setting the pH include pH adjusters such as sodium hydroxide, potassium hydroxide, sodium carbonate and potassium carbonate. Examples of the sulfite preservative used in the developer include sodium sulfite, potassium sulfite, and sodium bisulfite. The sulfite is used in an amount of 0.01 mol / L or more, preferably 0.02 mol / L or more, and the upper limit is 2.5 mol / L.
It is preferable that

Examples of the method for preparing a developer include the methods described in JP-A-61-177132 and JP-A-3-1346.
Nos. 66 and 3-67258 can be used. For the replenishment of the developing solution, see JP-A-5-21.
The method described in JP-A-6180 can be used. The replenishment rate of the treatment liquid is preferably in the range of 0.1 to 10 mL / quarter or less, more preferably in the range of 0.1 to 5 mL / quarter or less.

Preferred embodiments of the processing method used in the radiation image forming method of the present invention will be described below. (1) A processing method in which the developer is a one-part concentrated developer. (2) Total processing time (Dry to Dry) is 20 to 1
Processing method that is in the range of 00 seconds. (3) A processing method in which the heating means of the roller portion provided in the preceding stage of the drying section of the automatic developing apparatus and in contact with the photosensitive material is at 70 ° C. or higher. (4) A processing method in which a chemical mixer is incorporated in the automatic developing apparatus, and the automatic developing apparatus has a mechanism in which a developer and a fixing solution cartridge are used simultaneously.

(5) A processing method in which the opening ratio of the developing tank of the automatic developing apparatus is 0.04 cm ^-1 or less. (6) A processing method in which the concentrated developing solution and the concentrated fixing solution are made up of one part, and each concentrated solution and water are diluted in each tank into a working solution and supplied as a replenisher (just before mixing and dilution method). (7) A processing method in which the containers for the concentrated developing solution and the concentrated fixing solution are integrated packaging materials. (8) A processing method using an automatic developing apparatus provided with a rinsing tank and a rinsing roller (crossover roller) between the developing tank and the fixing tank and between the fixing tank and the washing tank.

(9) A processing method using an automatic development processing apparatus provided with a stock tank for water in which various water rust preventive agents (antibacterial agents) are supplied to a washing tank and a rinsing tank. (10) A processing method using an automatic developing apparatus in which a solenoid valve is installed at a drain port of a washing tank. (11) A processing method wherein 70 mol% or more of all cations in the developer are potassium ions. (12) A processing method in which the developer is a powder. (13) A processing method in which the developing solution and the fixing solution are of a working liquid type. (14) A processing method in which the washing tank of the automatic development processing apparatus has a multi-chamber tank and a multi-stage countercurrent washing system.

[0049]

EXAMPLES Example 1 Production of Gadolinium-Activated Yttrium Tantalate Phosphor Ta ₂ O ₅ (25 g), Y ₂ O ₃ (12.26 g), Gd ₂ O ₃ (0.82 g), and flux L
iCl (12.5 g) was stirred and mixed using a mixer for 1 hour. After placing the obtained mixture in a crucible and placing it in an electric furnace, the inside of the furnace was evacuated to a vacuum of 0.01 Torr.
Then, a mixed gas of oxygen and nitrogen (oxygen / nitrogen (volume ratio) = 0.34) compressed to a high pressure was sealed, and the gauge pressure was set to 0.5 kg / cm ² . Then, while controlling so that the inside of the furnace is maintained at this gauge pressure, 1200 ° C.
For 10 hours. After firing, the temperature in the electric furnace was lowered to room temperature, the pressure was reduced to atmospheric pressure, the obtained fired product was taken out, washed with water and dried, and the gadolinium-activated yttrium tantalate (YTaO ₄ : 0.04G
d) A phosphor was obtained.

Further, the gauge pressure in the electric furnace is set to 0 to 4.0.
Various gadolinium-activated yttrium tantalate phosphors were obtained by performing the same operation as described above while changing the amount in the range of kg / cm ² .

[Evaluation of Characteristics of Phosphor] Afterglow characteristics of various gadolinium-activated yttrium tantalate phosphors obtained in Example 1 were evaluated by the following method. Each phosphor 50mg
Was filled in a sample holder, and this was irradiated with molybdenum X-rays (80 kVp, 200 mA) for 0.1 second to excite it, and the time dependence of the emission intensity at the emission peak wavelength (about 314 nm) was measured. Then, X-ray irradiation is performed for 20
The X-ray afterglow intensity was determined by normalizing the emission intensity after the second with the instantaneous emission intensity, and expressed as a relative value with the X-ray afterglow intensity when the gauge pressure was 0 (= atmospheric pressure) as 100. Also,
The instantaneous emission spectrum when the phosphor was excited by X-rays was also measured. The results obtained are shown in FIGS.

FIG. 1 is a graph showing the relationship between the gauge pressure and the relative X-ray afterglow intensity during firing of the YTaO ₄ : 0.04 Gd phosphor. FIG. 2 is a graph showing the instantaneous emission spectrum of the YTaO ₄ : 0.04 Gd phosphor.

As is apparent from FIG. 1, YTaO ₄ : 0.
The 04Gd phosphor has a gauge pressure during firing of 0.3 to 4.0 k.
In the case of g / cm ^2, the X-ray afterglow intensity was reduced by 50% or more compared with the conventional phosphor obtained by firing under atmospheric pressure (gauge pressure 0). In particular, the gauge pressure is 0.5-4.
When it was within the range of 0 kg / cm ² , the X-ray afterglow intensity decreased by 70% or more. Also, as is clear from FIG.
YTaO of the present invention _4: 0.04Gd phosphor 300-330
It emits light in the ultraviolet region of nm, and its peak wavelength is about 31 nm.
4 nm.

Example 2 Radiation intensifying screen YTa obtained in Example 1 was used as a material for forming a phosphor layer.
O ₄ : 0.04 Gd phosphor (calcined at a gauge pressure of 0.5 kg / cm ² , 200 g), polyurethane resin (manufactured by Dainippon Ink and Chemicals, Pandex T-5265)
H) (8 g) and an epoxy resin (Epicoat 1001 manufactured by Yuka Shell Epoxy Co., Ltd.) (2 g) were added to methyl ethyl ketone, dispersed with a propeller mixer, and had a viscosity of 25.
A coating solution of ℃ 30 PS (25 ° C.) was prepared. This coating solution was applied on a polyethylene terephthalate temporary support to which a silicone release agent had been applied.
Dried for minutes. Next, the dried coating film was peeled off from the temporary support to obtain a phosphor sheet having a thickness of 300 μm. Next, this phosphor sheet is overlaid on a polyethylene terephthalate film with an undercoat (thickness: 300 μm), and heat-pressed using a heating roll at 60 to 70 ° C. to form a phosphor on a support via an undercoat layer. Layer (thickness: 200 μm)
Was formed.

A transparent polyethylene terephthalate film (thickness: 10 μm, provided with a polyester-based adhesive layer on one side) is laminated on the above-mentioned phosphor layer with the adhesive layer on the lower side. The protective film was formed by thermocompression bonding using a heating roll at 100 ° C. Thus,
A radiographic intensifying screen of the present invention comprising a support, a phosphor layer and a protective film was produced.

Example 3 Silver halide photographic light-sensitive material and radiation image forming system Emulsion A: Preparation of {100} high silver chloride tabular grain emulsion 1582 mL of aqueous gelatin solution in a reaction vessel [Gelatin-1]
(Deionized alkali-treated bone gelatin having a methionine content of about 40 μmol / g) 19.5 g, an aqueous solution containing 7.8 mL of 1N HNO ₃ solution; pH 4.3), and NaC
Solution 1-1 (containing 10 g of NaCl in 100 mL of water) 1
3 mL, keeping the temperature at 40 ° C., keep the Ag-1 solution (20 g of AgNO _{3 in} 100 mL of water) and X-1
A liquid (containing 7.05 g of NaCl in 100 mL of water) was added at a rate of 62.4 mL / min. After stirring for 3 minutes, the Ag-2 solution (containing 2 g of AgNO _{3 in} 100 mL of water) and the X-2 solution (containing 1.4 g of KBr in 100 mL of water) at 80.6 mL / min.
The mixture was simultaneously mixed in 2 mL portions. After stirring this mixture for 3 minutes, the Ag-1 solution and the X-1 solution were added at 62.4 mL / min.
6.8 mL of the mixture was added simultaneously. After stirring for 2 minutes,
203 mL of gelatin aqueous solution (13 g of gelatin-1, N
1.3 g of aCl, 1 N Na to adjust pH to 6.5
(Aqueous solution containing OH) was added to adjust the pCl to 1.75, the temperature was raised to 63 ° C., and then 6 × 10 ⁻⁴ mol of hydrogen peroxide was added to 1 g of gelatin, and pCl was added to 1.75 g.
70 and aged for 3 minutes. Thereafter, the AgCl fine grain emulsion (E-1, average grain diameter 0.1 μm) was added to AgC fine grain emulsion.
1 at a rate of 2.68 × 10 ^-2 mol / min.
Minutes. After completion of the addition, the mixture was aged for 40 minutes, and then the following sedimentation agent was added. Add an aqueous solution of alkali-treated gelatin and adjust the pH at 60 ° C.
Adjusted to 6.0. A TEM image (transmission electron micrograph image) of a replica of the obtained particles was observed. The resulting grains were high silver chloride {100} tabular grains containing 0.44 mol% of AgBr based on silver.

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The shape characteristics of the particles were as follows. (Total projected area of {100} tabular grains having an aspect ratio of 2 or more and 30 or less / sum of projected areas of all silver halide grains) × 1
00 = a1 = 95% (average aspect ratio (average diameter / average thickness) of {100} tabular grains having an aspect ratio of 2 or more and 30 or less) = a2 =
15.5 (Average projected area diameter of {100} tabular grains having an aspect ratio of 2 to 30) = a3 = 1.40 μm (principal edge length ratio of {100} tabular grains having an aspect ratio of 2 to 30) = A4 = 0.90 (average thickness of {100} tabular grains having an aspect ratio of 2 to 30) = a5 = 0.09 μm (average thickness of {100} tabular grains having an aspect ratio of 2 to 30) Coefficient of variation (standard deviation of thickness / average thickness))
= A6 = 0.11 (the projected area sum / aspect ratio of two dislocation lines extending from the corner of the {100} tabular grain having an aspect ratio of 2 or more and 30 or less that can be observed with a transmission electron microscope) (Projected area sum of {100} tabular grains of 2 or more and 30 or less) × 100 = a7 = 87% (average angle of angle formed by two dislocation lines) = a8 = 56 ° Further, a direct TEM image of the tabular grains is taken. Observed at
In the emulsion after coating, the above dislocation lines could be observed in grains having a projected area of 57%.

Emulsion B: Preparation of {111} silver bromide tabular grain emulsion 6.0 g of potassium bromide and 7.0 g of low molecular weight gelatin having a weight average molecular weight of 15,000 were added to 1 liter of water in a container. Thereafter, into a container kept at 55 ° C., 37 ml of an aqueous silver nitrate solution (4.00 g of silver nitrate) and 38 mL of an aqueous solution containing 5.9 g of potassium bromide were added by a double jet method over 37 seconds while stirring. Next, after adding 18.6 g of gelatin, the temperature was raised to 70 ° C.
L (9.80 g of silver nitrate) was added over 22 minutes. Here, 7 mL of a 25% aqueous ammonia solution was added, and after physical aging for 10 minutes at the same temperature, 6.5 mL of a 100% aqueous acetic acid solution was added. Subsequently, 153 g of silver nitrate
Aqueous solution 435 mL of potassium bromide and aqueous solution 573 g of potassium bromide 6
While maintaining the pAg at 8.5 mL with the addition of 77 mL, the silver nitrate aqueous solution was added by the controlled double jet method over 35 minutes until the total amount of the silver nitrate aqueous solution was added. Then, 15 mL of a 2N potassium thiocyanate solution was added. After physical aging at the same temperature for 5 minutes, the temperature was lowered to 35 ° C. a1 = 95
%, A2 = 12.0, a3 = 1.20 μm, a5 = 0.
Monodispersed pure silver bromide {111} tabular grains having a diameter of 10 μm and a variation coefficient of projected area diameter of 15.5% were obtained. Thereafter, soluble salts were removed by a sedimentation method. The temperature was raised again to 40 ° C., and 30 g of deionized and alkali-treated gelatin, 2.35 g of phenoxyethanol and 0.8 g of sodium polystyrenesulfonate as a thickener were added, and adjusted to pH 5.90 and pAg 8.00 with sodium hydroxide and silver nitrate solution. did.

Emulsion C: Preparation of {100} high silver bromide tabular grain emulsion A gelatin aqueous solution [1.2 liters of H ₂ O,
Contains 25g of gelatin, 0.11g of NaCl, HNO ₃
Put adjusted] to pH3.9 in a liquid, stirring Solution Ag-1 maintained at 40 ℃ (AgNO ₃ 10g / l) 8.0
mL was added in 2 seconds. After 5 minutes, X-1 solution (KBr1
40g / liter) and Ag-2 liquid (AgNO ₃ 200g)
/ Liter) at 50 mL / min for 1 minute and almost simultaneously. However, the start of the addition of the X-1 solution was performed one second before the start of the addition of the Ag-2 solution. After completion of addition 1
Minutes later, a NaOH solution was added to adjust the pH to 5.5. Further, an aqueous polyvinyl alcohol solution [5 g of polyvinyl alcohol having an average degree of polymerization of vinyl acetate of 500 and an average saponification rate to alcohol of 98%, and 50 mL of H ₂ O] and an aqueous solution of a polyvinyl imidazole copolymer (represented by the following formula) Polyvinyl imidazole copolymer; weight average molecular weight 1.5 × 10 ⁵ , x: y: z: w = 60: 7: 13: 3
0 and 10 mL of H ₂ O).
The silver potential was set to 50 mV and the temperature was raised to 75 ° C. After the temperature was raised, the silver potential was readjusted to 50 mV. After aging for 30 minutes, Ag-3 solution (AgNO ₃ 100 g / l)
And liquid X-2 (KBr 71 g / liter) while maintaining the silver potential at 50 mV, and adding Ag-3 liquid at an initial speed of 5 mL /
For 30 minutes at a linear flow rate acceleration of 0.05 mL / min. After 3 minutes, a sedimentation agent was added, the temperature was lowered to 30 ° C, and the pH was lowered.
4.0 and the emulsion was allowed to settle. Wash the sedimented emulsion with water, 3
The temperature was raised to 8 ° C. and then a gelatin solution was added to redisperse the emulsion. Observation of a TEM image of a replica of the obtained emulsion grains revealed the following. 92% of the total projected area of all AgX has a {100} principal plane, and the projected outline shape is a shape in which one or two of the four corners (corners) of a rectangular parallelogram are missing. The average chipping rate was about 10% of the edge length. The edge face with no corner was a {110} face. Average diameter is 1.4μ
m, the average aspect ratio was 10.0, and the coefficient of variation of the diameter distribution (standard deviation of diameter / average diameter) was 0.21.

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Chemical sensitization The particles A to C prepared as described above were stirred at 56 ° C.
Sensitization was performed while maintaining the temperature. First, the following thiosulfonic acid compound was added in an amount of 1 × 10 ⁻⁴ per mol of silver halide.
AgBr with an average particle diameter of 0.10 μm
Fine grains were added in an amount of 1.0 mol% with respect to the total silver amount, and after 5 minutes, a 1% by weight KI solution was added at a concentration of 1.times.
0 ^-3 mol was added, 1 × thiourea dioxide after a further 3 minutes
10 ^-6 mol / mol Ag was added, and held for 22 minutes to perform reduction sensitization. Next, 4-hydroxy-6-methyl-1,3,3a, 7-tetraazaindene was added to 3 × 10 6
^-4 mol / mol Ag and the sensitizing dye (2-1, 2-2,
2-3) was added, respectively. Then, calcium chloride was added at 1 × 10 ^-2 mol / mol Ag. Further, 1 × 10 ⁻⁵ mol / mol Ag of chloroauric acid and 3.0 × 10 ⁻³ mol / mol Ag of potassium thiocyanate are added, and then sodium thiosulfate (6 × 10 ⁻⁶ mol / mol) is added. Ag)
And the following selenium compound (4 × 10 ⁻⁶ mol / mol Ag) were added. After a further 3 minutes, chloroauric acid (0.5 g / mol A)
g) was added. After 40 minutes, the following water-soluble mercapto compound was added, and the mixture was cooled to 35 ° C. Thus, the preparation of the emulsion (chemical ripening) was completed.

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(Preparation of Emulsion Layer Coating Solution) The following chemicals were added to 1 mol of silver halide to the above chemically sensitized emulsion to prepare an emulsion layer coating solution. -Gelatin (including gelatin in the emulsion) 50.0 g-Dextran (average molecular weight 39,000) 10.0 g-Sodium polyacrylate (average molecular weight 400,000) 5.1 g-Sodium polystyrene sulfonate (average molecular weight 600,000) 1.2 g-78 mg of potassium iodide-Hardener 1,2-bis (vinylsulfonylacetamido) ethane Adjusted amount of addition so that the swelling ratio becomes a value of 90%-Compound A-1 42.1 mg-Compound A-2 10.3 g Compound A-3 0.11 g Compound A-4 8.5 mg Compound A-5 0.43 g Compound A-6 0.04 g Compound A-7 70 g

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Dye emulsion a (as solid content of dye) 0.50 g

(Preparation of Dye Emulsion a)
0 g, 2,2.8 g of 2,4-diamylphenol, 62.8 g of dicyclohexyl phthalate and 33 of ethyl acetate
3 g were melted at 60 ° C. Next, 65 mL of a 5% by weight aqueous solution of sodium dodecylbenzenesulfonate, 94 g of gelatin and 581 mL of water were added and emulsified and dispersed at 60 ° C. for 30 minutes with a dissolver. Then, 2 g of methyl p-hydroxybenzoate and 6 liters of water were added, and
The temperature was lowered to ° C. Further, using an ultrafiltration lab module (ACP1050, manufactured by Asahi Kasei Corporation), the total amount was 2 kg.
And concentrated to 1 g of methyl p-hydroxybenzoate
Was added to obtain a dye emulsion a.

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Dye emulsion m (as dye solids) pH was adjusted to 6.1 with 30 mg NaOH.

(Preparation of Dye Emulsion m)
After weighing 0 g and dissolving in a solvent consisting of 10 mL of tricresyl phosphate and 20 mL of ethyl acetate, the dye emulsion m was emulsified and dispersed in 100 mL of a 15% by weight aqueous gelatin solution containing 750 mg of the following anionic surfactant. Was prepared.

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(Preparation of Dye Layer Coating Solution) A dye layer coating solution was prepared so that each component had the following coating amount.・ Gelatin 0.25 g / m ²・ Compound A-8 1.4 mg / m ²

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• Sodium polystyrene sulfonate (average molecular weight: 600,000) 5.9 mg / m ² • Dye dispersion i (as dye solids) 20 mg / m ²

(Preparation of Dye Dispersion i) The following Dye-3 was handled as a wet cake without drying, and weighed to a dry solid content of 6.3 g. Next, the following Dispersing Aid V was treated as a 25% by weight aqueous solution, and was added so that the dry solid content was 30% by weight based on the solid content of the dye. Water was added to make a total amount of 63.3 g, and mixed well to form a slurry. 1 zirconia beads with an average diameter of 0.5 mm
Prepare 00 mL, put it in a vessel together with the slurry, disperse it for 6 hours using a disperser (1 / 16G sand grinder mill, manufactured by Imex Co., Ltd.), and add water so that the dye concentration becomes 8% by weight. A dye dispersion was obtained. The obtained dispersion is mixed so that the solid content of the dye is 5% by weight and the gelatin for photographic use is equal to the solid content of the dye, and the following additive D as a preservative is distilled so as to be 2000 ppm with respect to the gelatin. Water was added for refrigeration and stored in a jelly form.
Thus, a jelly-like dye dispersion i was obtained as a non-elutable solid fine particle dispersion dye having a light absorption maximum at 915 nm. The average particle diameter of the solid fine particles of the dye dispersion i was 0.4 μm.

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(Preparation of Surface Protective Layer Coating Solution) A surface protective layer coating solution was prepared so that each component had the following coating amount.・ Gelatin 0.780 g / m ²・ Sodium polyacrylate (average molecular weight: 400,000) 0.025 g / m ²・ Sodium polystyrene sulfonate (average molecular weight: 600,000) 0.0012 g / m ²・ Matte agent-1 shown below (Average particle size: 3.7 μm) 0.072 g / m ² · Matting agent-2 below (average particle size: 0.7 μm) 0.010 g / m ²

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[0079] - Compound ^{A-9 0.018 g / m 2} · Compound ^{A-10 0.037 g / m 2} · Compound A-11 0.0068g / m ² · Compound A-12 0.0032g / m ² · Compound A-13 0.0012 g / m ² · Compound A-14 0.0022 g / m ² · Compound A-15 0.030 g / m ² · Proxel (manufactured by ICI) 0.0010 g / m ² NaOH and pH 6.0. Adjusted to 8.

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(Preparation of Support) (1) Formation of First Undercoat Layer Corona was coated on a biaxially stretched polyethylene terephthalate film having a thickness of 175 μm (containing dye-1 at 0.04% by weight). Discharging was performed, and a first undercoating liquid having the following composition was applied by a wire converter so as to have a coating amount of 4.9 mL / m ^2, and dried at 185 ° C. for 1 minute. Next, the first undercoat layer was similarly provided on the opposite surface. First undercoat liquid-Butadiene-styrene copolymer latex solution (solid content 40%, butadiene / styrene weight ratio = 31/69) 158 mL-2,4-dichloro-6-hydroxy-s-triazine sodium salt 4% by weight Solution 41mL ・ Distilled water 801mL (Compound A shown below as emulsifying dispersant in latex solution)
-16 based on the latex solids content)

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(2) Formation of a second undercoat layer A second undercoat liquid comprising the following components was applied to the surface of the first undercoat layer on both sides of the above-mentioned wire bar so that the application amount was as follows. It was applied by a coder method and dried at 155 ° C. Second undercoat liquid: gelatin 100 mg / m ² · compound A-17 1.8 g / m ² · compound A-18 0.27 g / m ² · matting agent (polymethyl methacrylate having an average particle size of 2.5 µm) 5 g / m ²

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(Production of a photographic light-sensitive material) The above-mentioned coating solutions for the dye layer, emulsion layer and surface protective layer were combined and coated on both sides of the support prepared as described above by a coextrusion method, dried and photographed. A photosensitive material was obtained. The coated silver amount per one side was 1.4 g / m ² , and the total coated gelatin amount per one side was 1.8 g / m ² .

(Measurement of Swelling Ratio) First, the photographic light-sensitive material to be measured was allowed to stand at 40 ° C. and 60% RH for 7 days. Next, this photosensitive material was immersed in distilled water at 21 ° C. for 3 minutes, and this state was frozen and fixed with liquid nitrogen. This photosensitive material was cut by a microtome so as to be perpendicular to the surface of the photosensitive material, and then freeze-dried at -90 ° C. The swelled film thickness Tw was determined by observing the treated product under a scanning electron microscope. On the other hand, the film thickness Td in a dry state was also determined by cross-sectional observation using a scanning electron microscope. Tw obtained in this way
The swelling ratio (unit%) was defined as a value obtained by dividing the difference between Td and Td by Td and multiplying by 100. {(Tw−Td) / Td} × 100 = Swelling rate (%) In the manufactured photographic material, Td = 3.5 μm, Tw =
6.65 μm, and the swelling ratio was 90% from the above equation.

(Preparation of Developing Solution) A developing solution containing sodium erythorbate of the following formulation as a developing agent was prepared. Diethylenetriaminepentaacetic acid 8.0 g Sodium sulfite 20.0 g Sodium carbonate monohydrate 52.0 g Potassium carbonate 55.0 g Sodium erythorbate 60.0 g 4-Hydroxymethyl-4-methyl-1-phenyl-3-pyrazolidone 13.2 g 3,3'-diphenyl-3,3'-dithiopropionic acid 1.44 g diethylene glycol 50.0 g

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Water was added to make up to 2 liters, and NaOH was added to p.
It was adjusted to H10.1.

(Preparation of developer replenisher) The above developer was used as it was as a developer replenisher.

(Preparation of a developing mother liquor) Two liters of the above developing solution was taken, and a starter solution having the following composition was added in an amount of 55 mL per liter of the developing solution, and a developing solution having a pH of 9.5 was used as a developing mother liquor. Starter liquid Potassium bromide 11.1 g Acetic acid 10.8 g Water was added to make up to 55 mL.

(Preparation of concentrated fixing solution) A concentrated fixing solution having the following formulation was prepared. Water 0.5 l Ethylenediaminetetraacetic acid dihydrate 0.05 g sodium thiosulfate 200 g sodium bisulfite 98.0 g sodium hydroxide 2.9 g The pH was adjusted to 5.2 with NaOH, and water was added to make 1 liter.

(Preparation of Fixing Replenisher) The concentrated fixing solution was diluted by a factor of two with a first washing water waste solution and used as a fixing replenisher.

(Preparation of Fixing Mother Solution) 2 L of the above concentrated fixing solution was diluted with water to make 4 L. pH was 5.4.

(Preparation of Replenisher for Washing Water) A replenisher for washing water having the following formulation was prepared. Glutaraldehyde 0.3 g Diethylenetriamine-pentaacetic acid 0.5 g Diluted with distilled water and adjusted to pH 4.5 with NaOH to obtain 1 liter of a finished solution.

(Processing of photographic light-sensitive material) An automatic developing machine (CEPROS-S, manufactured by Fuji Photo Film Co., Ltd.) was remodeled.
The washing tank was used as two-stage countercurrent washing, and the second washing tank was supplemented with washing water. The opening ratio of the developing tank and the fixing tank was improved to 0.02. Each of the washing tanks had a capacity of 6 liters. The drying was performed by a heat roller method (roller surface temperature: 85 ° C.). Using the developing mother liquor, the fixing mother liquor and the washing water replenisher, the developing replenisher, the fixing replenisher and the washing water replenisher were all 65 mL / m ^{2 of the} photosensitive material.
Treated with replenishment.

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[Table 1]

[Evaluation of photographic performance] The radiation intensifying screen obtained in Example 2 was adhered to both sides of the photographic light-sensitive material obtained in Example 3, and X-ray exposure was performed. Thereafter, processing was performed by an automatic developing machine as described above, and an image was formed. As a result, it was confirmed that a good X-ray image was formed on the photosensitive material.

[0099]

According to the present invention, the raw material mixture is calcined at a pressure higher than the atmospheric pressure in the production process of the gadolinium-activated yttrium tantalate phosphor, so that the radiation afterglow intensity is reduced under the conventional atmospheric pressure. The phosphor can be reduced to 50% or less of the phosphor obtained by firing, so that the afterglow characteristics can be significantly improved. Thereby, when this phosphor is used for the radiation intensifying screen, 300 to 350 n
m, which emits light in the ultraviolet region, has high sensitivity, and does not cause afterimage fog even when used repeatedly. Further, by using this radiation intensifying screen in combination with a photographic light-sensitive material containing a tabular grain emulsion of high silver chloride having a (100) plane as a main plane, excellent diagnostic performance without residual image fogging and rapid reduction in speed are obtained. A radiation image forming system having excellent suitability for replenishment processing and reduced environmental pollution and the like can be achieved.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between gauge pressure and relative X-ray afterglow intensity during firing of a YTaO ₄ : 0.04 Gd phosphor.

FIG. 2 is a graph showing an emission spectrum of the YTaO ₄ : 0.04 Gd phosphor of the present invention by X-ray excitation.

Claims (7)

[Claims] 1. A mixture of a phosphor raw material and a gauge pressure of 0.
A range of 3 to 4.0 kg / cm ² and a temperature of 1100
Composition formula (I): YTaO ₄ : xGd (I) produced by baking for 8 to 12 hours in the range of 〜1300 ° C., where x is a numerical value in the range of 0 <x ≦ 0.1. is there. ] A gadolinium-activated yttrium tantalate phosphor represented by the formula: 2. A gauge pressure of 0.5 to 4.0 kg / cm ^2.
2. The gadolinium-activated yttrium tantalate phosphor according to claim 1, wherein 3. Composition formula (I): YTaO ₄ : xGd (I) [where x is a numerical value in the range of 0 <x ≦ 0.1]. And a gadolinium-activated yttrium tantalate phosphor having a radiation afterglow intensity of 50% or less of the radiation afterglow intensity of the phosphor produced by firing under atmospheric pressure. . 4. The gadolinium-activated yttrium tantalate phosphor according to claim 3, wherein the radiation afterglow intensity is 30% or less of the radiation afterglow intensity of the phosphor produced by firing at atmospheric pressure. 5. A radiographic intensifying screen comprising the gadolinium-activated yttrium tantalate phosphor according to claim 1. Description: 6. A radiographic intensifying screen comprising the gadolinium-activated yttrium tantalate phosphor according to claim 1, and tabular grains of high silver chloride having a (100) plane as a main plane. With a silver halide photographic light-sensitive material containing an emulsion containing at least 50 mol% of 7. A radiographic intensifying screen containing the gadolinium-activated yttrium tantalate phosphor according to claim 1, and tabular grains of high silver chloride having a (100) plane as a main plane. Is used in combination with a silver halide photographic light-sensitive material containing an emulsion containing 50 mol% or more of
A radiation image forming method using light emission in the ultraviolet region having a wavelength of 300 to 350 nm.