JP2002038143A - Method for producing rare earth-activated alkaline earth metal fluorohalide-based photostimulable phosphor, rare earth-activated alkaline earth metal fluorohalide-based photostimulable phosphor and radiation image conversion panel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a finely particulate rare earth-activated alkaline earth metal fluorohalide-based photostimulable phosphor having a uniform particle diameter distribution with a high productivity and to provide a high-sensitivity and high-image quality radiation image conversion panel using the rare earth- activated alkaline earth metal fluorohalide-based photostimulable phosphor. SOLUTION: This method for producing the rare earth-activated alkaline earth metal fluorohalide-based photostimulable phosphor is characterized by removing a solvent from a solution at >=3.3 mol/L barium concentration in a reactional mother liquor and thereby obtaining a photostimulable phosphor precursor in the method for producing the oxygen-introduced rare earth-activated alkaline earth metal fluorohalide-based photostimulable phosphor represented by general formula (I): Ba(1-x)M2(x)FBr(y)I(1-y): aM1, bLn, cO in the liquid phase.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a rare earth activated alkaline earth metal fluoroiodide-based stimulable phosphor, a method for producing the stimulable phosphor, and a radiation image using the stimulable phosphor. Regarding the conversion panel.

[0002]

2. Description of the Related Art A radiation image recording / reproducing method using a stimulable phosphor described in JP-A-55-12145 or the like is known as an effective diagnostic means which can replace the conventional radiographic method. This method utilizes a radiation image conversion panel (also referred to as a stimulable phosphor sheet) containing a stimulable phosphor, and transmits radiation transmitted through a subject or emitted from a subject to a stimulable phosphor. And stimulates the stimulable phosphor in a time series with electromagnetic waves such as visible light and ultraviolet rays (referred to as excitation light), and radiates the stored radiation energy as fluorescence (referred to as stimulating light). Then, the fluorescence is read photoelectrically to obtain an electric signal, and a radiation image of the subject or the subject is reproduced as a visible image based on the obtained electric signal. After the reading of the conversion panel, the remaining image is erased and used for the next photographing.

According to this method, compared to a radiographic method using a combination of a radiographic film and an intensifying screen,
There is an advantage that a radiographic image with a large amount of information can be obtained with a much smaller exposure dose. Further, in the radiographic method, the film is consumed for each photographing, whereas the radiographic image conversion panel is used repeatedly, which is advantageous in terms of resource conservation and economic efficiency.

A radiation image conversion panel comprises only a support and a stimulable phosphor layer provided on the surface thereof or a self-supporting stimulable phosphor layer, and the stimulable phosphor layer is usually a stimulable phosphor layer. Some are composed of a stimulable phosphor and a binder for dispersing and supporting the stimulable phosphor, and others are composed only of aggregates of stimulable phosphor formed by a vapor deposition method or a sintering method. In addition, there is also known one in which a polymer substance is impregnated in the gaps of the aggregate. Furthermore, on the surface of the stimulable phosphor layer opposite to the support side,
Usually, a protective film composed of a polymer film or an inorganic vapor-deposited film is provided.

As the stimulable phosphor, usually 400 to 9
With excitation light in the range of 00 nm, wavelengths of 300-5
Those exhibiting stimulated emission in the range of 00 nm are generally used, and are disclosed in JP-A-55-12145 and JP-A-55-1600.
No. 78, No. 56-74175, No. 56-116777
No. 57-23673, No. 57-23675, No. 58-206678, No. 59-27289, No. 59
-27980, 59-56479, 59-56
No. 480, etc .; rare earth element-activated alkaline earth metal fluorohalide-based phosphors;
No. 60-84381, No. 60-106752, No. 6
No. 0-166379, No. 60-221483, No. 60
-228592, 60-228593, 61-
No. 23679, No. 61-120882, No. 61-12
No. 0883, No. 61-120885, No. 61-235
Nos. 486, 61-235487, etc .; divalent europium-activated alkaline earth metal fluorohalide-based phosphors; rare earth element-activated oxyhalide phosphors described in JP-A-55-12144; Cerium-activated trivalent metal oxyhalide phosphor described in JP-A-58-69281; Bismuth-activated alkali metal halide phosphor described in JP-A-60-70484;
No. 60-157100, divalent europium-activated alkaline earth metal halophosphate phosphors;
JP-A-60-217, divalent europium-activated alkaline earth metal haloborate phosphor described in JP-A-157099;
No. 354, divalent europium-activated alkaline earth metal hydride halide phosphors;
No. 3, No. 61-21182, etc .; cerium-activated rare earth composite halide phosphors;
Cerium-activated rare earth halophosphate phosphor described in JP-A-60-78151; divalent europium-activated cerium rubidium halide phosphor described in JP-A-60-78151;
No. 78151, such as divalent europium-activated composite halide phosphors described in No. 78151, among which divalent europium-activated alkaline earth metal fluoride halide phosphors containing iodine and rare earth elements containing iodine Activated oxyhalide phosphors and bismuth-activated alkali metal halide phosphors containing iodine are known, but still,
There is a demand for a high-luminance stimulable phosphor.

[0006] Further, as the use of a radiation image conversion method using a stimulable phosphor has progressed, it has been required to further improve the image quality of the obtained radiation image, for example, the sharpness and the graininess. Came.

The method for producing a stimulable phosphor described above is a method called a solid phase method or a sintering method, which requires pulverization after firing, and controls the particle shape which affects sensitivity and image performance. It has the problem of being difficult. Among the means for improving the image quality of a radiation image, it is effective to make the stimulable phosphor finer and to make the particle size of the stimulable phosphor finer, that is, to narrow the particle size distribution.

[0008] JP-A-7-233369, 9-291
No. 278 discloses a method for producing a stimulable phosphor from a liquid phase, which is a method of adjusting the concentration of a phosphor raw material solution to obtain a particulate stimulable phosphor precursor. This is effective as a method for producing a stimulable phosphor powder having a uniform distribution. From the viewpoint of reducing the radiation exposure, it is known that among the rare earth-activated alkaline earth metal fluorohalide-based stimulable phosphors, those having a high iodine content are preferable. This is because iodine has a higher X-ray absorptivity than bromine.

The alkaline earth metal fluoroiodide-based stimulable phosphor produced in the liquid phase as described above is advantageous in terms of brightness and granularity, but obtains a precursor crystal in the liquid phase. You have the following problems. That is, JP-A-10-88125
No. 9-291278, 1) Barium iodide is dissolved in water or an organic solvent, and an inorganic fluoride solution is added while stirring the solution. 2) Ammonium fluoride is added. A method of dissolving in water and adding a barium iodide solution while stirring the solution is effective. However, in the method 1), an excess of barium iodide needs to be present in the solution. Therefore, the stoichiometric ratio between the charged barium iodide and the barium fluoroiodide obtained after the solid-liquid separation is 0. It is often a small value of about 4. In other words, for the barium iodide
The yield of alkaline earth metal fluoroiodide stimulable phosphor is 4
It is often about 0%.

The method 2) also requires an excess of barium iodide with respect to the inorganic fluoride, resulting in a low yield. Thus, the liquid phase synthesis of barium fluoroiodide has a problem that the yield is low and the productivity is poor. If the concentration of barium iodide in the mother liquor is lowered to increase the yield, the particles will be enlarged, which is not preferable in terms of image quality.

An attempt to increase the yield of a rare earth activated alkaline earth metal fluorinated stimulable phosphor, particularly an alkaline earth metal fluorinated iodide stimulable phosphor, is disclosed in Japanese Unexamined Patent Publication No.
No. 1-29324, the concentration of the reaction mother liquor and the fluorine source were added, and the mixture was concentrated to obtain the basic composition formula BaFI: xLn
(Ln: at least one rare earth element selected from Ce, Pr, Sm, Eu, Gd, Tb, Tm, and Yb, and x represents a numerical value of 0 <x ≦ 0.1). A method for obtaining a barium fluoroiodide crystal is disclosed.

However, as a result of the present inventors' additional tests,
Although BaFI prismatic crystals were formed as described, it was found that the productivity was extremely low due to concentration by spontaneous evaporation, which was not industrially practical. Further, it was found that the obtained square crystals also had a large particle size and a wide particle size distribution, so that the image characteristics were poor and they could not be put to practical use.

[0013]

An object of the present invention is to obtain a rare earth activated alkaline earth metal fluorinated halide stimulable phosphor having a uniform particle size distribution with high productivity. It is an object of the present invention to obtain a rare earth activated alkaline earth metal fluorohalide-based stimulable phosphor having a fine particle size and uniform particle size distribution with high productivity. An object of the present invention is to provide a high-sensitivity, high-quality radiation image conversion panel using a stimulable phosphor.

[0014]

SUMMARY OF THE INVENTION The object of the present invention is to produce an oxygen-introduced rare earth activated alkaline earth metal fluoride halide stimulable phosphor represented by the following general formula (I) in the liquid phase. In the method, the barium concentration in the reaction mother liquor is 3.3 m.
This is achieved by a method for producing a rare earth-activated alkaline earth metal fluorohalide-based stimulable phosphor, in which a stimulable phosphor precursor is obtained by removing a solvent from a solution of ol / L or more.

[0015] Formula _{(I) Ba (1-x} ) M 2 (x) FBr (y) I (1-y): aM 1, bLn, c
In the formula, M ₁ is at least one alkali metal selected from Li, Na, K, Rb and Cs, and M ₂ is Be, Mg,
At least one alkaline earth metal selected from Sr and Ca, Ln is Ce, Pr, Sm, Eu, Gd, Tb,
Represents at least one rare earth element selected from Tm, Dy, Ho, Nd, Er and Yb, and x, y, a, b and c represent 0 ≦ x ≦ 0.3 and 0 ≦ y ≦ 0.3, respectively. , 0 ≦
a ≦ 0.05, 0 <b ≦ 0.2, and 0 ≦ c ≦ 0.1.

It is preferable that the mass after the removal of the solvent is 0.97 or less with respect to the mass before the removal. The method of removing the reaction solvent is, in addition to natural drying, a method in which the reaction solution is heated for removal, and it is preferable to use a means for removing another solvent in combination with the method. For this purpose, it is preferable to pass through a process of keeping the inside of the reaction vessel under reduced pressure, and / or a method of passing dry gas and / or forming a wet wall of the solution during the operation of removing the solvent.
The reaction mother liquor is preliminarily containing 0.1 to 4 alkali metal halides.
It is preferable that it is contained at a concentration of mol / L.

A rare earth-activated alkaline earth metal fluorohalide-based stimulable phosphor obtained by the above method,
A radiation image conversion panel having a phosphor layer containing the rare earth-activated alkaline earth metal fluorohalide-based stimulable phosphor also achieves the object of the present invention.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION A typical embodiment of the method for producing a rare earth activated alkaline earth metal fluorohalide-based stimulable phosphor of the present invention will be described in detail below.

For the production of the stimulable phosphor precursor by the liquid phase method, the precursor production method described in JP-A-10-140148 and the precursor production apparatus described in JP-A-10-147778 are preferably used. it can. Here, the stimulable phosphor precursor refers to a state in which the substance of the general formula (I) has not passed through a high temperature of 400 ° C. or higher, and the stimulable phosphor precursor has a stimulable luminescent property or an instantaneous luminescent property. Is hardly shown. In the present invention, in the method for synthesizing the precursor of the stimulable phosphor represented by the general formula (I) in a liquid phase, it is preferable that the liquid phase contains at least a barium component and an inorganic fluoride. It is preferable to start the removal immediately after at least the barium component and the inorganic fluoride component are present in the liquid phase. The order of adding the barium component and the inorganic fluoride to the reaction mother liquor is not particularly limited, but the addition of the inorganic fluoride is preferably the last. Further, there is no limitation on the order in which the raw materials of the other components constituting the stimulable phosphor represented by the general formula (I) are added, and they may be added in the liquid phase or may be added during firing.

In the present invention, it is preferable to obtain a precursor by the following liquid phase synthesis method. The production of the rare earth-activated alkaline earth metal fluoroiodide-based stimulable phosphor represented by the general formula (I) is not a solid phase method in which control of the particle shape is difficult, but the particle size can be easily controlled. It is preferable to carry out by a liquid phase method.
In particular, it is preferable to obtain a stimulable phosphor by the following liquid phase synthesis method.

[0021] includes (Process) BaI ₂ and Ln halide, wherein when x in the general formula (I) is not 0, further halide of M _2, if y is not 0 BaBr ₂
And, if a is not 0, contains the halides of M ₁ and after their dissolution, the barium concentration is 3.3 mol
/ L or higher, preferably 3.5 mol / L or higher, and preferably 5.0 mol / L or lower as an upper limit; while maintaining the solution at a temperature of 50 ° C or higher, preferably 100 ° C or higher, In addition to this, a concentration of 5 mol / L or more,
Preferably 8 mol / L or more, more preferably 12 mol / L
A solution of an inorganic fluoride (ammonium fluoride or a fluoride of an alkali metal) of not less than 1 / L and preferably not more than 15 mol / L as an upper limit is added, and the rare earth activated alkaline earth metal fluorinated iodide is stimulated. A step of obtaining a precipitate of phosphor precursor crystals; a step of removing a solvent from the reaction solution while adding the inorganic fluoride or after the addition is completed; a step of separating the precursor crystal precipitates from the reaction solution; And baking the separated precursor crystal precipitate while avoiding sintering.

The particles (precursor crystals) according to the present invention are:
Those having an average particle diameter of 1 to 10 μm and monodispersity are preferable, those having an average particle diameter of 1 to 5 μm, and a distribution (%) of the average particle diameter of 20% or less are more preferable, and in particular, having an average particle diameter of 1 ~
Those having a size of 3 μm and an average particle size distribution of 15% or less are preferred.

In the present invention, the average particle diameter is obtained by randomly selecting 200 particles from an electron micrograph of particles (crystals) and calculating the average in terms of sphere-equivalent volume particle diameter.

The details of the method for producing the stimulable phosphor will be described below.

(Preparation of Precipitate Crystal Precipitate, Preparation of Stimulable Phosphor) First, a raw material compound other than a fluorine compound is dissolved in an aqueous medium. That is, a halide of BaI ₂ and Ln, and if necessary, a halide of M ₂ , and further a halide of M ₁ are placed in an aqueous medium, thoroughly mixed and dissolved to prepare an aqueous solution in which they are dissolved. I do. However, the BaI ₂ concentration was 3.3 mol /
The ratio of the BaI ₂ concentration to the aqueous solvent is adjusted so as to be at least L, preferably at least 3.5 mol / L.
At this time, if the barium concentration is low, a precursor having a desired composition cannot be obtained, or even if obtained, the particles are enlarged. Therefore,
It is necessary to appropriately select the barium concentration, and as a result of studies by the present inventors, it has been found that fine precursor particles can be formed at 3.3 mol / L or more. At this time, a small amount of acid, ammonia, alcohol, a water-soluble polymer, a water-insoluble metal oxide fine particle powder or the like may be added as required. It is also a preferred embodiment to add an appropriate amount of a lower alcohol (methanol, ethanol, etc.) as long as the solubility of BaI ₂ is not significantly reduced. This aqueous solution (reaction mother liquor) is maintained at 50 ° C., preferably at 80 ° C. or higher, and preferably at 100 ° C. or lower as an upper limit.

Next, while maintaining the temperature at 50 ° C. or higher, an aqueous solution of inorganic fluoride is added and reacted, the temperature of the reaction solution during the reaction is maintained at 50 ° C. or higher, and more preferably at 80 ° C. or higher. Is preferred. For the addition, an aqueous solution of an inorganic fluoride (ammonium fluoride, alkali metal fluoride, or the like) is injected into the stirred aqueous solution using a pipe with a pump or the like. This injection is preferably carried out in the region where the stirring is particularly violent. By injecting the aqueous solution of inorganic fluoride into the reaction mother liquor, the above-mentioned general formula (I)
Rare earth activated alkaline earth metal fluorohalide-based phosphor precursor crystals corresponding to the above are precipitated.

Next, the solvent is removed from the reaction solution. To remove the solvent from the reaction mother liquor of the present invention means, in addition to the process of evaporating the solvent by natural drying, removing the solvent by artificially applying a process of removing the solvent at a rate exceeding the evaporation rate by natural drying. Refers to The timing of removing the solvent is not particularly limited, but it is preferably performed immediately after the start of the addition of the inorganic fluoride solution until the precipitate (precursor) is separated. Here, “immediately after the start of the addition” means both during the addition and at the end of the addition.

The removal of the solvent may be performed once or in a plurality of times, or may be performed continuously. For example, 1) after the addition of the inorganic fluoride solution is completed, the solvent is removed, and the reaction mother liquor is allowed to stand.
After the second solvent removal, the reaction mother liquor is allowed to stand, the second solvent removal is performed, and the reaction mother liquor is left again. 3) After the addition of the inorganic fluoride solution, continuous until the precipitate is separated. , Etc. may be performed.

It is preferable to remove the solvent after the completion of the addition of the inorganic fluoride solution, and it is more preferable to start the removal immediately after the completion of the addition of the organic solution.

Here, the solvent according to the present invention has the same definition as that recognized by those skilled in the art, and is a component used for dissolving a solute. For example, in the present invention, the solute basically corresponds to at least a raw material, an intermediate, a catalyst, and the like used for obtaining the stimulable phosphor represented by the general formula (I). The solvent removal step of the present invention not only removes a single solvent, but also when a plurality of types of solvents are contained in the mother liquor,
All of them are targets for solvent removal, but the targets for removal are not limited.

The amount of solvent removed is preferably 3% or more by mass ratio before and after removal. Below this, the crystal may not have a desirable composition. Therefore, the removal amount is preferably 3% or more, more preferably 5% or more. In addition, even if it is removed too much, there may be a problem in handling, such as an excessive increase in the viscosity of the reaction solution. Therefore, the removal amount of the solvent is preferably 50% or less, more preferably 30% or less, and even more preferably 20% or less in terms of mass ratio before and after the removal. Here, “after removing the solvent” refers to after finishing all the solvent removing steps.

The time required for removing the solvent not only greatly affects the productivity, but also the shape and particle size distribution of the particles are affected by the method for removing the solvent. Therefore, it is necessary to appropriately select a removing method. 2.0 kg of solvent removal per unit area
/ M is preferably carried out at ² · hr or more 20.0 kg / m ² · hr or less speed, even 3.0 Kg / m ² · hr or more 10.0 kg / m ² · hr or less speed is more preferable. Here, the unit area refers to the area of the reaction mother liquor in contact with the atmosphere. Generally, when removing the solvent,
The method of heating the solution and evaporating the solvent is selected. This method is also useful in the present invention. By removing the solvent, a precursor having an intended composition can be obtained. Here, "heating the solution" means to maintain or raise the temperature of the reaction mother liquor in the solvent removing step even during the solvent removing step. It is preferable to heat the reaction mother liquor so as to keep it at 50 ° C. or higher and 80 ° C. or higher.

Further, in order to increase the productivity and maintain the particle shape appropriately, it is preferable to use another solvent removing method in combination. The method for removing the solvent used in combination is not particularly limited. In the present invention, it is preferable to select the following removal method from the viewpoint of productivity.

1. Ventilation of dry gas The reaction vessel is made to be a closed type, provided with holes through which at least two or more gases can pass, and the dry gas is ventilated therefrom. The type of gas can be arbitrarily selected. In terms of safety,
Air and nitrogen are preferred. The solvent is entrained and removed from the gas depending on the saturated water vapor amount of the gas to be passed. In addition to the method of ventilating the void portion of the reaction vessel, a method of ejecting gas as bubbles into the liquid phase and absorbing the solvent into the bubbles is also effective.

2. Depressurization As is well known, reducing the pressure reduces the vapor pressure of the solvent. The solvent can be efficiently removed by the vapor pressure drop. The degree of reduced pressure can be appropriately selected depending on the type of the solvent. 86,450 Pa when the solvent is water
The following is preferred.

3. The solvent can be removed efficiently by enlarging the liquid film evaporation area. As in the present invention, when heating and stirring using a reaction vessel having a fixed volume to carry out the reaction, the heating method is a method of immersing the heating means in a liquid or attaching the heating means to the outside of the vessel. Is common. According to this method, the heat transfer area is limited to a portion where the liquid and the heating means come into contact, and the heat transfer area decreases with the removal of the solvent, and thus the time required for the solvent removal becomes longer. In order to prevent this, it is effective to use a pump or a stirrer to spray the solution on the wall surface of the reaction vessel to increase the heat transfer area.

Thus, the liquid is sprayed on the wall surface of the reaction vessel,
The method of forming a liquid film is known as "wet wall".
As a method of forming a wet wall, in addition to a method using a pump,
Examples thereof include a method using a stirrer described in JP-A-6-335627 and JP-A-11-235522.

These methods may be used alone or in combination. A combination of a method of forming a liquid film and a method of reducing the pressure in the container, a combination of a method of forming a liquid film and a method of aerating a dry gas, and the like are effective. The former is particularly preferred, and the method described in JP-A-6-335627 is preferably used.

Next, the above phosphor precursor crystals are filtered,
Separate from the solution by centrifugation or the like, sufficiently wash with methanol or the like, and dry. In this dried phosphor precursor crystal,
A sintering inhibitor such as alumina fine powder and silica fine powder is added and mixed to uniformly adhere the sintering inhibitor fine powder to the crystal surface. Note that the addition of the sintering inhibitor can be omitted by selecting the firing conditions.

Next, the crystal of the phosphor precursor is filled in a heat-resistant container such as a quartz port, an alumina crucible, or a quartz crucible, and placed in a furnace of an electric furnace to perform sintering while avoiding sintering. The firing temperature is suitably in the range of 400 to 1,300 ° C, and preferably in the range of 500 to 1,000 ° C. The firing time varies depending on the filling amount of the phosphor raw material mixture, the firing temperature, the temperature of taking out from the furnace, and the like.
12 hours is appropriate.

The firing atmosphere may be a neutral atmosphere such as a nitrogen gas atmosphere, an argon gas atmosphere, a weakly reducing atmosphere such as a nitrogen gas atmosphere containing a small amount of hydrogen gas, a carbon dioxide atmosphere containing carbon monoxide, or the like. A trace oxygen introduction atmosphere is used. As the firing method, a method described in JP-A-2000-8034 is preferably used.

By the above calcination, the desired rare earth-activated alkaline earth metal fluorohalide-based stimulable phosphor is obtained.

(Preparation of Radiation Image Conversion Panel) As the support used in the radiation image conversion panel of the present invention, various polymer materials, glass, metal and the like are used. Particularly, in terms of handling as an information recording material, a material that can be processed into a flexible sheet or web is preferable. In this regard, plastics such as cellulose acetate, polyester, polyethylene terephthalate, polyamide, polyimide, triacetate, and polycarbonate film are preferable. Film; a metal sheet of aluminum, iron, copper, chromium, or the like, or a metal sheet having a coating layer of the metal oxide is preferable.

The layer thickness of the support varies depending on the material of the support to be used and the like.
From the viewpoint of handling, more preferably 10 to 50
0 μm.

The surface of the support may be a smooth surface or a mat surface for the purpose of improving the adhesion to the stimulable phosphor layer. Furthermore, an undercoat layer may be provided on the surface on which the stimulable phosphor layer is provided, for the purpose of improving the adhesiveness with the stimulable phosphor layer.

Examples of the binder used in the stimulable phosphor layer include proteins such as gelatin, polysaccharides such as dextran, and natural high molecular substances such as gum arabic; polyvinyl butyral, polyvinyl acetate, nitrocellulose , Ethylcellulose, vinylidene chloride-vinyl chloride copolymer, polyalkyl (meth) acrylate,
Examples of the binder include synthetic polymer substances such as vinyl chloride / vinyl acetate copolymer, polyurethane, cellulose acetate butyrate, polyvinyl alcohol, and linear polyester. Particularly preferred among these are nitrocellulose, linear polyester, polyalkyl (meth) acrylate, a mixture of nitrocellulose and linear polyester, a mixture of nitrocellulose and polyalkyl (meth) acrylate, and polyurethane and polyvinyl butyral. Is a mixture with In addition, these binders may be crosslinked with a crosslinking agent.

The stimulable phosphor layer can be formed on the undercoat layer by the following method, for example.

First, an iodine-containing stimulable phosphor, a compound such as a phosphite for preventing yellowing, and a binder are added to an appropriate solvent, and these are mixed well and the phosphor is added to the binder solution. A coating solution in which particles and particles of the compound are uniformly dispersed is prepared.

Examples of the binder used in the present invention include proteins such as gelatin, polysaccharides or gum arabic such as dextran, polyvinyl butyral, polyvinyl acetate, nitrocellulose, ethyl cellulose, and the like.
A film-forming binder usually used for the layer constitution such as vinyldene chloride / vinyl chloride copolymer, polymethyl methacrylate, vinyl chloride / vinyl acetate copolymer, polyurethane, cellulose acetate butyrate, polyvinyl alcohol, etc. is used. .

In general, the binder is used in an amount of 0.01 to 1 part by mass per 1 part by mass of the stimulable phosphor. However, from the viewpoint of the sensitivity and sharpness of the obtained radiation image conversion panel, it is preferable that the amount of the binder is small, and the range of 0.03 to 0.2 part by mass is more preferable in consideration of the ease of application.

Mixing ratio of the binder and the stimulable phosphor in the coating solution (however, when the entire binder is an epoxy group-containing compound, it is equal to the ratio of the compound to the phosphor)
The target varies depending on the characteristics of the radiation image conversion panel, the type of phosphor, the amount of the epoxy group-containing compound added, etc., but, in general, examples of solvents for preparing a binding coating solution include methanol, enotal, 1-propanol, Lower alcohols such as 2-propanol and butanol; hydrocarbons containing chlorine atoms such as methylene chloride and ethylene chloride; ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone; lower fatty acids such as methyl acetate, ethyl acetate and butyl acetate and lower alcohols; Esters of dioxane, ethylene glycol ethyl ether, ethylene glycol monomethyl ether and the like; toluene; and mixtures thereof.

Examples of solvents used for preparing the coating solution for the stimulable phosphor layer include lower alcohols such as methanol, ethanol, 1-propanol and butanol; acetone,
Ketones such as methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone; esters of lower fatty acids such as methyl acetate, ethyl acetate and butyl acetate with lower alcohols;
Dioxane, ethylene glycol monoethyl ether,
Ethers such as ethylene glycol monomethyl ether;
Aromatic compounds such as triol and xylol; halogenated hydrocarbons such as methylene chloride and ethylene chloride, and mixtures thereof.

The coating solution contains a dispersant for improving the dispersibility of the phosphor in the coating solution, and a binding force between the binder and the phosphor in the stimulable phosphor layer after formation. Various additives such as a plasticizer for improving the viscosity may be mixed. Examples of dispersants used for such purposes include phthalic acid, stearic acid, caproic acid, and lipophilic surfactants. Examples of the plasticizer include phosphoric esters such as triphenyl phosphate, tricresyl phosphate and diphenyl phosphate; phthalic esters such as diethyl phthalate and dimethoxyethyl phthalate; ethyl phthalyl ethyl glycolate and butyl phthalyl butyl glycolate And polyesters of aliphatic dibasic acid such as polyesters of triethylene glycol and adipic acid, polyesters of diethylene glycol and succinic acid, and the like.

The coating solution prepared as described above is uniformly applied to the surface of the undercoat layer to form a coating film of the coating solution. This coating operation can be performed using a usual coating means, for example, a doctor blade, a roll coater, a knife coater or the like. Next, the formed coating film is dried by gradually heating to complete the formation of the stimulable phosphor layer on the undercoat layer.

The preparation of the coating solution for the stimulable phosphor layer is carried out using a dispersing device such as a ball mill, a sand mill, an attritor, a three-roll mill, a high-speed impeller disperser, a Kady mill, and an ultrasonic disperser. The prepared coating solution is coated on a support using a coating device such as a doctor blade, a roll coater, or a knife coater, and dried to form a stimulable phosphor layer. After coating and drying the coating solution on the protective layer, the stimulable phosphor layer and the support may be bonded.

The thickness of the stimulable phosphor layer of the radiation image conversion panel depends on the desired properties of the radiation image conversion panel, the type of stimulable phosphor, and the mixing ratio between the binder and the stimulable phosphor. Although it depends on the like, it is preferably selected from the range of 10 to 1,000 μm, more preferably from the range of 10 to 500 μm.

While the examples of the stimulable phosphor such as europium-activated barium fluoroiodide have been mainly described above, europium-activated barium fluorobromide and other compounds represented by the above general formula (I) can be used. The stimulable phosphor can also be produced with reference to the above.

[0058]

The present invention will now be illustrated by way of examples.

Example 1 In order to synthesize a stimulable phosphor precursor of europium-activated barium fluoroiodide, BaI was placed in a pressure-resistant container having two holes.
2500 ml of ₂ aqueous solution (4 mol / L concentration) and 26.5 ml of EuI ₃ aqueous solution (0.2 mol / L concentration) were added.
Further, 992 g of potassium iodide was added to the aqueous solution.

While stirring the reaction mother liquor in this reactor, 8
The temperature was kept at 3 ° C. Ammonium fluoride aqueous solution (10mol
/ L concentration) was injected into the reaction mother liquor using a roller pump to produce a precipitate. After completion of the injection, dry air was blown at a rate of 10 L / min for 20 minutes. The mass ratio of the solution before and after aeration was 0.94. The reaction vessel was sealed and stirred at that temperature for 90 minutes. After stirring for 90 minutes, the mixture was filtered and washed with 2,000 ml of ethanol.

The yield was determined by measuring the mass of the recovered precursor and comparing it with the theoretical yield determined from the amount of Ba charged. The obtained precipitate was subjected to X-ray diffraction measurement (Cu-
Kα radiation). Next, the average particle size of the precipitate was also measured.

Example 2 After the addition of ammonium fluoride was completed, the pressure inside the reaction vessel was set to 74,480 Pa using a circulating aspirator, and the solvent was concentrated under reduced pressure. Concentration was performed for 15 minutes. The mass ratio of the reaction solution before and after concentration was 0.92.

Except for this, the same operation as in the first embodiment is performed.
A precipitate was obtained. The yield was calculated in the same manner as in Example 1, and the precipitate was subjected to X-ray diffraction and average particle size measurement.

Example 3 After the addition of ammonium fluoride was completed, the reaction solution was sprayed on the wall surface of the reaction vessel using a pump to evaporate the solvent while forming a liquid film. This operation was performed for 15 minutes. The mass ratio of the reaction solution before and after concentration was 0.94.

Otherwise, the same operation as in Example 1 was performed,
A precipitate was obtained. The yield was calculated in the same manner as in Example 1, and the precipitate was subjected to X-ray diffraction and average particle size measurement.

Comparative Example 1 In order to synthesize a stimulable phosphor precursor of europium-activated barium fluoroiodide, 2,500 ml of an aqueous BaI ₂ solution (4 mol / L concentration) and an aqueous solution of EuI ₃ (0.2 mol / L) were used.
(L concentration) 26.5 ml was charged into the reactor. Further, 332 g of potassium iodide was added to the aqueous solution. The reaction mother liquor was kept at 83 ° C. while stirring. 250 ml of an ammonium fluoride aqueous solution (10 mol / L concentration) was injected into the reaction mother liquor by using a roller pump to form a precipitate. After completion of the injection, the mixture was stirred at the same temperature for 90 minutes. After stirring for 90 minutes, the mixture was filtered and washed with 2,000 ml of ethanol. The yield was calculated in the same manner as in Example 1, and the precipitate was subjected to X-ray diffraction and average particle size measurement.

Comparative Example 2 The amount of the aqueous ammonium fluoride solution to be injected into the reaction mother liquor was 60
A precipitate was obtained in the same manner as in Comparative Example 1 except that the amount was 0 ml. The yield was calculated in the same manner as in Example 1, and the precipitate was subjected to X-ray diffraction and average particle size measurement.

Comparative Example 3 The amount of the aqueous ammonium fluoride solution injected into the reaction mother liquor was 60
0 ml, and after injecting ammonium fluoride solution, 15
Over time, the solution was concentrated by spontaneous evaporation. The mass ratio of the reaction solution before and after concentration was 0.89.

A precipitate was obtained in the same manner as in Comparative Example 1 except for this. The yield was calculated in the same manner as in Example 1, and the precipitate was subjected to X-ray diffraction and average particle size measurement.

Example 4 A precipitate was obtained in the same manner as in Example 1 except that the amount of potassium iodide added to the reaction mother liquor was changed to 500 g. The yield was calculated in the same manner as in Example 1, and the precipitate was subjected to X-ray diffraction and average particle size measurement.

Example 5 A precipitate was obtained in the same manner as in Example 1 except that potassium iodide was not added to the reaction mother liquor. The yield was calculated in the same manner as in Example 1, and the precipitate was subjected to X-ray diffraction and average particle size measurement.

Example 6 After adding ammonium fluoride, the pressure in the reaction vessel was increased to 7
The reaction liquid was sprayed on the wall surface of the reaction vessel using a pump at 4,480 Pa, and the solvent was removed while forming a liquid film. This operation was performed for 7 minutes. The mass ratio of the reaction solution before and after concentration was 0.93.

Otherwise, the same operation as in the first embodiment is performed.
A precipitate was obtained. The yield was calculated in the same manner as in Example 1, and the precipitate was subjected to X-ray diffraction and average particle size measurement.

The results are summarized in Table 1.

From the results of X-ray diffraction, a peak at 2θ = 29.4 ° was identified as BaF _{2 as a by-} product.

[0076]

[Table 1]

As is clear from Table 1, by removing the solvent from the reaction solution, a europium-activated barium fluoroiodide stimulable phosphor precursor is obtained in high yield while preventing the particles from becoming large. be able to. The effect of preventing particle enlargement is remarkable due to the presence of potassium ions.

Example 7 Cesium iodide was added to a reaction mother liquor, and the amount of aqueous ammonium fluoride solution added to the reaction mother liquor was adjusted to 700 ml.
A precipitate was obtained in the same manner as in Example 2, except that the solvent was removed under a reduced pressure of 280 Pa for 30 minutes. The mass ratio of the reaction solution before and after the removal of the solvent was 0.90. The yield was calculated in the same manner as in Example 1, and the precipitate was subjected to X-ray diffraction and average particle size measurement.

Example 8 Cesium iodide was added to the reaction mother liquor, and the amount of the aqueous ammonium fluoride solution added to the reaction mother liquor was adjusted to 800 ml.
A precipitate was obtained in the same manner as in Example 2, except that the solvent was removed at a reduced pressure of 280 Pa for 35 minutes. The mass ratio of the reaction solution before and after the removal of the solvent was 0.88. The yield was calculated in the same manner as in Example 1, and the precipitate was subjected to X-ray diffraction and average particle size measurement.

Comparative Example 4 Cesium iodide was added to a reaction mother liquor, and the concentration of the reaction mother liquor was adjusted to 4
A precipitate was obtained in the same manner as in Example 2, except that the mol / L was changed to 3.2 mol / L, and the amount of the ammonium fluoride solution to be added was changed to 480 ml. The mass ratio before and after the removal of the solvent was 0.98. The yield was calculated in the same manner as in Example 1, and the precipitate was subjected to X-ray diffraction and average particle size measurement.

Comparative Example 5 The concentration of the reaction mother liquor was changed from 4 mol / L to 3.2 mol / L, and the amount of the ammonium fluoride solution to be added was 200 ml.
A precipitate was obtained in the same manner as in Comparative Example 1 except that the precipitate was changed. The yield was calculated in the same manner as in Example 1, and the precipitate was subjected to X-ray diffraction and average particle size measurement.

Table 2 shows the results of Examples 7 and 8 and Comparative Examples 4 and 5.
It is summarized and shown.

[0083]

[Table 2]

As is clear from Table 2, according to the production method of the present invention, a fine stimulable phosphor precursor can be obtained in high yield.

(Production of Stimulable Phosphor) Examples 1 to 8
For Comparative Examples 1 and 3 to 5, 1% by mass of ultrafine alumina powder was added in order to prevent a change in particle shape due to heat sintering and a change in particle size distribution due to fusion between particles, and a mixer was sufficient. By stirring, ultrafine alumina powder was uniformly attached to the crystal surface. This was filled into a quartz core tube of a batch type rotary kiln having a core volume of 10 L, and a mixed gas of nitrogen / hydrogen / oxygen (93/5/2% by volume) was passed at a flow rate of 10 L / min for 20 minutes. The atmosphere was replaced. After sufficiently replacing the atmosphere inside the furnace core,
The flow rate of the mixed gas was reduced to 2 L / min, and the reactor was heated to 830 ° C. at a rate of 10 ° C./min while rotating the furnace tube at a speed of 2 rpm. After the sample temperature reached 830 ° C., a nitrogen / hydrogen (93/5% by volume) mixed gas was passed at a flow rate of 10 L / min for 20 minutes while maintaining the sample temperature at 830 ° C. to replace the atmosphere. Thereafter, the flow rate of the mixed gas of nitrogen / hydrogen (93/5% by volume) was increased to 2 L / m.
in and held for 90 minutes. Nitrogen / hydrogen (93/5
(Volume%), the mixture was cooled to 25 ° C. at a rate of 10 ° C./min while maintaining the flow rate of the mixed gas at 2 L / min, the atmosphere was returned to the atmosphere, and the resulting oxygen-introduced europium-activated barium fluoroiodide The phosphor was taken out.

Next, an example of manufacturing a radiation image conversion panel will be described.

As the phosphor layer forming material, 427 g of the europium-activated barium fluoroiodide phosphor obtained above, 15.8 g of polyurethane resin (Desmolac 4125, manufactured by Sumitomo Bayer Urethane Co., Ltd.), and bisphenol A type epoxy resin 0 g of methyl ethyl ketone, toluene (1: 1)
Add to the mixed solvent, disperse by propeller mixer,
A coating solution having a viscosity of 25 to 30 PS was prepared. After applying this coating solution on a polyethylene terephthalate (PET) film with an undercoat using a doctor blade,
After drying at 0 ° C. for 15 minutes, a phosphor layer was formed.

Next, as a protective film forming material, 70 g of a fluorine-based resin (fluoroolefin-vinyl ether copolymer, Lumiflon LF100 manufactured by Asahi Glass Co., Ltd.) and 25 g of a cross-linking agent (isocyanate, Desmodur Z4370 manufactured by Sumitomo Bayer Urethane Co., Ltd.) , Bisphenol A type epoxy resin, 5 g, and silicone resin fine powder (KMP-590, manufactured by Shin-Etsu Chemical Co., Ltd .: KMP-590, particle size: 1-2 μm) are added to a mixed solvent of toluene and i-propyl alcohol (1: 1) and coated. I made a liquid.

This coating solution is applied onto the phosphor layer formed in advance as described above using a doctor blade.
Next, it was heat-treated at 120 ° C. for 30 minutes, thermally cured, and dried to provide a protective film having a thickness of 10 μm. Thus, a radiation image conversion panel having a stimulable phosphor layer was obtained.

(Evaluation of Radiation Image Conversion Panel) Each radiation image conversion panel was evaluated as follows.

<< Sensitivity >> A tube voltage of 8 is applied to the radiation image conversion panel.
After irradiating with 0 kVp X-rays, the panel is excited by operating with a He-Ne laser beam (633 nm), and the photostimulable emission emitted from the phosphor layer is received by a photodetector (photoelectron image tube having a spectral sensitivity of S-5). ) And the intensity was measured. In Table 3, the sensitivity is shown as a relative value.

<Sharpness> After irradiating the radiation image conversion panel with X-rays having a tube voltage of 80 kVp through a lead MTF chart, the panel is operated with a He-Ne laser beam to be excited and emitted from the phosphor layer. The stimulated emission is received by the same light receiver as in the sensitivity measurement, converted into an electrical signal, converted from analog to digital, recorded on a magnetic tape, analyzed by a computer, and recorded on a magnetic tape. The modulation transfer function (MTF) of the existing X-ray image was examined. Table 3 shows the MTF value (%) at a spatial frequency of 2 cycles / mm.

<< Granularity >> After irradiating the radiation image conversion panel with X-rays at a tube voltage of 80 kVp, the panel is operated by He-Ne laser light to be excited, and the stimulated emission emitted from the phosphor layer is as described above. The light was received by the same light receiver and converted into an electric signal, which was recorded on an ordinary photographic film by a film scanner, and the granularity of the obtained image was visually evaluated in three steps.

In Table 3, the graininess was determined by conventional X-ray photography using an intensifying screen (Konica: SRO-250) and an X-ray film (Konica: SR-G). The results are shown in comparison with the graininess of the image obtained.

The symbol ○ means graininess equivalent to that of an image obtained by X-ray photography using the intensifying screen and the film, and the symbol ◎ means better graininess. or,
The symbol “Δ” means graininess slightly coarser than the image obtained by radiography, and the symbol “×” means graininess significantly coarser than that.

Table 3 also shows the evaluation results of each radiation image conversion panel.

[0097]

[Table 3]

The radiation image conversion panel according to the present invention is excellent in sensitivity, sharpness, and granularity.

[0099]

According to the present invention, a rare earth activated alkaline earth metal fluoroiodide stimulable phosphor required for a radiation image conversion panel having excellent brightness, sharpness and granularity can be produced with high productivity. Can be obtained at

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Kanae Tsuchiya 1 Sakuracho, Hino-shi, Tokyo Konica Corporation F-term (reference) 2G083 AA03 BB01 DD02 EE02 EE03 4H001 CA04 CA08 CF01 XA04 XA09 XA12 XA20 XA35 XA38 XA53 XA56 YA03 YA11 YA19 YA37 YA55 YA58 YA59 YA60 YA62 YA63 YA64 YA65 YA66 YA67 YA68 YA69 YA70

Claims (9)

[Claims] 1. A method for producing an oxygen-introduced rare earth-activated alkaline earth metal fluorohalide-based stimulable phosphor represented by the following general formula (I) in a liquid phase, wherein a barium concentration in a reaction mother liquor is 3: A method for producing a rare earth-activated alkaline earth metal fluorohalide-based stimulable phosphor, comprising obtaining a stimulable phosphor precursor by removing a solvent from a solution having a concentration of 3 mol / L or more. General formula _{(I) Ba (1-x} ) M 2 (x) FBr (y) I (1-y): aM 1, bLn, c
O wherein M ₁ is at least one alkali metal selected from Li, Na, K, Rb and Cs; M ₂ is Be,
At least one alkaline earth metal selected from Mg, Sr and Ca; Ln is Ce, Pr, Sm, Eu, Gd,
Represents at least one rare earth element selected from Tb, Tm, Dy, Ho, Nd, Er and Yb, and represents x, y, a,
b and c are respectively 0 ≦ x ≦ 0.3, 0 ≦ y ≦ 0.
3, 0 ≦ a ≦ 0.05, 0 <b ≦ 0.2, 0 ≦ c ≦ 0.
It is one. ] 2. The rare earth-activated alkaline earth metal fluoride halide photostimulability according to claim 1, wherein the mass of the reaction solution is (after solvent removal / before solvent removal) ≦ 0.97. A method for producing a phosphor. 3. A rare earth activated alkaline earth metal halogen fluoride according to claim 1, wherein the reaction solution is heated to remove the reaction solvent, and a means for removing another solvent is used in combination. Method for producing a stimulable phosphor. 4. A rare earth-activated alkaline earth metal fluorinated halide stimulant according to claim 1, 2 or 3, wherein a step of keeping the inside of the reaction vessel under reduced pressure is performed to remove the reaction solvent. Method for producing luminescent phosphor. 5. A rare earth-activated alkaline earth metal fluorohalide-based stimulable fluorescent light according to claim 1, wherein the method of removing the solvent is a method of passing dry gas. How to make the body. 6. The rare earth-activated alkaline earth metal fluorohalide-based stimulable phosphor according to claim 1, wherein the solution forms a wetting wall during the operation of removing the solvent. Production method. 7. The rare earth-activated alkaline earth metal fluoride halide stimulant according to claim 1, wherein an alkali metal halide is previously added to the reaction mother liquor. Method for producing luminescent phosphor. 8. A rare earth-activated alkaline earth metal fluorohalide-based stimulable phosphor obtained by the production method according to claim 1. 9. A radiation image conversion panel comprising a phosphor layer containing the rare earth activated alkaline earth metal fluorohalide-based stimulable phosphor according to claim 8.