JP2002038149A - 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 (especially a fluoroiodide)-based photostimulable phosphor having a uniform particle diameter distribution with a good productivity and to provide a high-sensitivity and high-image quality radiation image conversion panel using the photostimulable phosphor. SOLUTION: This method for producing the rare earth-activated alkaline earth metal fluorohalide-based photostimulable phosphor comprises adding a solution of an inorganic fluoride to a reactional mother liquor containing barium ions and ammonium ions present therein and producing the rare earth-activated alkaline earth metal fluorohalide-based photostimulable phosphor in the method for producing the oxygen- introduced rare earth-activated alkaline earth metal fluorohalide-based photostimulable phosphor represented by the general formula (I): Ba(1-x)M2(x)FBr(y)I(1-y): aM1, bLn, cO (M1 is an alkali metal such as Li, Na, K or Rb; M2 is an alkaline earth metal such as Be, Mg or Sr; Ln is a rare earth element such as Ce, Pr, Sm or Eu; 0<=x<=0.3; 0<=y<=0.3; 0<=a<=0.05; 0<b<=0.2; and 0<=c<=0.1).

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 of the support or a self-supporting stimulable phosphor layer. Some are composed of a stimulable phosphor and a binder that supports the stimulable phosphor, and some are composed only of aggregates of the 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. Further, on the surface of the stimulable phosphor layer opposite to the side of the support, a protective film composed of a polymer film or an inorganic vapor-deposited film is usually provided.

The stimulable phosphor is usually 400 to 90.
Wavelength of 300 to 500 by the excitation light in the range of 0 nm.
Those exhibiting stimulated emission in the range of nm are generally used, and are disclosed in JP-A-55-12145 and JP-A-55-160078.
Nos. 56-74175, 56-116777, 57-23673, 57-23675, and 58-
Nos. 206678, 59-27289, 59-27
980, 59-56479, 59-56480
Rare earth element activated alkaline earth metal fluorohalide-based phosphor described in JP-A-59-75200 and JP-A-60-75200
No. 84381, No. 60-106752, No. 60-1
No. 66379, No. 60-221483, No. 60-22
No. 8592, No. 60-228593, No. 61-236
No. 79, No. 61-120882, No. 61-12088
No. 3, No. 61-120885, No. 61-235486
And divalent europium-activated alkaline earth metal fluoride halide-based phosphors described in JP-A Nos. 61-235487;
Rare earth element-activated oxyhalide phosphor described in JP-A-55-12144; Cerium-activated trivalent metal oxyhalide phosphor described in JP-A-58-69281;
Bismuth-activated alkali metal halide phosphors described in JP-A-70-48484;
No. 0-157100, divalent europium-activated alkaline earth metal halophosphate phosphors;
No. 7099, divalent europium-activated alkaline earth metal haloborate phosphor described in JP-A-60-217354; divalent europium-activated alkaline earth metal hydride halide phosphor described in JP-A-60-217354; Cerium-activated rare earth composite halide phosphor described in, for example, JP-A-61-211173 and 61-21182; Cerium-activated rare earth halophosphate phosphor described in JP-A-61-40390;
No. 78151, divalent europium-activated cerium rubidium halide phosphor described in JP-A-60-7815
The divalent europium-activated composite halide phosphor described in No. 1 is exemplified. Among them, a divalent europium-activated alkaline earth metal fluoride halide-based phosphor containing iodine, a rare earth containing iodine Although an element-activated oxyhalide phosphor and a bismuth-activated alkali metal halide phosphor containing iodine are known, a stimulable phosphor having high luminance is still required.

[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
The method of producing a stimulable phosphor from a liquid phase disclosed in, for example, Japanese Patent No. 278 is a method of adjusting the concentration of a phosphor raw material solution to obtain a particulate stimulable phosphor precursor, and has a particle size distribution. This method is effective as a method for producing a stimulable phosphor powder having uniformity. It is also known that among the rare earth-activated alkaline earth metal fluorohalide-based stimulable phosphors, those having a high iodine content are preferable from the viewpoint of reducing the radiation exposure dose. This is because iodine has a higher X-ray absorptivity than bromine.

As described above, the alkaline earth metal fluoroiodide stimulable phosphor produced in the liquid phase is advantageous in terms of brightness and granularity. Has the following problems. That is, when producing alkaline earth metal fluoroiodide stimulable phosphor precursor particles in the liquid phase,
As described in JP-A-10-88125 and JP-A-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) A method of dissolving ammonium fluoride in water and adding a barium iodide solution while stirring this 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 the alkaline earth metal fluoroiodide stimulable phosphor precursor is often about 40%. Also, in the method 2),
Requires excess barium iodide relative to inorganic fluoride and low yield. As described above, 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.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to provide a rare earth-activated alkaline earth metal fluorinated halide stimulable phosphor having a uniform particle size distribution, particularly an alkaline earth metal fluorinated iodide. It is to obtain a system stimulable phosphor with good productivity,
Further, to obtain a rare-earth activated alkaline earth metal fluorohalide stimulable phosphor having a fine particle size and uniform particle size distribution, particularly an alkaline earth metal fluoroiodide stimulable phosphor with high productivity. And high-sensitivity, high-quality radiation image conversion using the rare earth-activated alkaline earth metal fluoride halide stimulable phosphor, particularly the alkaline earth metal fluoroiodide stimulable phosphor. Is to provide a panel.

[0011]

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, a solution of an inorganic fluoride is added to a reaction mother liquor in which barium ions and ammonium ions are present, and the method is manufactured by a method for producing a rare earth activated alkaline earth metal fluoride halide stimulable phosphor. Is done.

General 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.

The concentration of ammonium ions present in the reaction mother liquor is not less than 0.2 mol / L, and the reaction mother liquor contains an alkali metal halide.
Is a preferred embodiment. The upper limit is 2.0 mo
It is preferably at most 1 / L. The above barium ion in the present invention is not less than 2.5 mol / L and not more than 5.0 mol / L.
It is preferably at most 1 / L.

Further, the rare earth activated alkaline earth metal fluorinated halide stimulable phosphor obtained by the above-mentioned production method, and the rare earth activated alkaline earth metal fluorinated halide stimulable phosphor are provided. The object of the present invention can also be achieved by a radiation image conversion panel having a phosphor layer containing:

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A typical embodiment of the method for producing a rare earth activated alkaline earth metal fluorohalide 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 Japanese Patent Application No. 8-265525 and the precursor production apparatus described in Japanese Patent Application No. 8-266718 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 not shown, but what shows to some extent may be targeted.

The production of the rare earth activated alkaline earth metal fluoroiodide 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 is 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.

(Manufacturing method) An example of a manufacturing method preferred for the present invention will be described below.

[0019] BaI comprises ₂ and Ln halide, a halide of M ₂ in the case the x in the general formula (I) is not 0, and the BaBr ₂ when y is not 0, further of M ₁ A step of adding ammonia after containing the halides and dissolving them; while maintaining the aqueous solution at a temperature of 50 ° C. or higher, preferably 80 ° C. or higher and 100 ° C. or lower, a concentration of 5 mol / L or higher, preferably 8 mol
/ L or more, more preferably 12 mol / L or more,
An aqueous solution of an inorganic fluoride (ammonium fluoride or alkali metal fluoride) having an upper limit of 15 mol / L or less is added, and a rare earth activated alkaline earth metal fluoroiodide stimulable phosphor precursor crystal is added. A step of obtaining a precipitate of the above; a step of separating the precursor crystal precipitate from the aqueous solution; and a step of firing the separated precursor crystal precipitate while avoiding sintering.

The particles (precursor crystals) according to the present invention are:
It is preferable that the average particle diameter is 1 to 10 μm and monodisperse. The average particle diameter is 1 to 5 μm and the average particle diameter distribution (%) is 20% or less. 3μ
Those having a distribution of m and an average particle size of 15% or less are preferred. Here, the monodispersity (the distribution (%) of the average particle size) refers to that represented by the following formula.

Monodispersity (%) = (Standard deviation of particle size) / (Average particle size) The average particle size in the present invention is defined by randomly selecting 200 particles from an electron micrograph of particles (crystals). The average is obtained by a sphere-equivalent volume particle diameter.

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

(Preparation of Precipitate Precipitate Crystal, 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 put in an aqueous medium, mixed well and dissolved to prepare an aqueous solution in which they are dissolved. I do. However, placing and adjusting the quantitative ratio of BaI ₂ concentration and an aqueous solvent as BaI ₂ concentration of 2 mol / L or more.
At this time, if desired, a small amount of acid, alkali, alcohol, water-soluble polymer, water-insoluble metal oxide fine particles, or the like may be added. This aqueous solution (reaction mother liquor) is at least 50 ° C. (preferably at least 80 ° C .;
(0 ° C. or less). The time to maintain is from 10 minutes to 1
20 minutes is preferred.

Next, an ammonia compound is added to the aqueous solution. There is no particular limitation on the ammonia source to be present in the aqueous solution. In the present invention, the term "reaction mother liquor" refers to a reaction solution immediately before the addition of an inorganic fluoride to form a precipitate.

Compounds serving as an ammonia source include liquid ammonia, ammonia solution, various ammonium salts (ammonium iodide, ammonium bromide, ammonium carbonate, etc.), and ammonium salts of organic acids (ammonium formate, ammonium acetate, etc.). . Of these, an aqueous ammonia solution is advantageous in terms of handling. In addition, as a preferred embodiment in which ammonia ions are present, an embodiment in which a stimulable phosphor precursor is once synthesized in a liquid phase and the liquid after solid-liquid separation is reused is also included as one preferred embodiment. The effect of the presence of ammonium ions in the reaction mother liquor is that the precursor particles do not enlarge even at lower barium ion concentrations. As described herein, there is a concentration difference between the concentration of ammonium ion and the concentration of barium ion in the reaction mother liquor, and the difference is between 0.5 mol / L and 4.5 mol / L.
Is preferred.

The concentration of ammonium ions is arbitrary, but preferably has a concentration of 0.2 mol / L or more as described above. When confirming the ammonium ion concentration, ion chromatography or the like can be used.

Next, an aqueous solution of an inorganic fluoride (ammonium fluoride, alkali metal fluoride, or the like) is added to the stirred and maintained aqueous solution at 50 ° C. or higher. There is a method of injecting 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 the injection of the inorganic fluoride aqueous solution into the reaction mother liquor, a rare earth activated alkaline earth metal fluoride halide precursor crystal corresponding to the general formula (I) is precipitated.

In the present invention, the reaction mother liquor preferably contains alkali metal ions. The particle size is also reduced by the alkali metal ions. As the alkali metal ion source, a halide thereof is preferable.
Preferred alkali metal salts include lithium iodide, sodium iodide, cesium iodide, potassium iodide, lithium bromide, sodium bromide, cesium bromide, potassium bromide and the like. Of these, sodium iodide and potassium iodide are preferred. The amount of the alkali metal ion is preferably from 0.05 mol to 5.0 mol per 1 mol of the stimulable phosphor to be produced.

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 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.

As the firing atmosphere, a neutral atmosphere such as a nitrogen gas atmosphere or an argon gas atmosphere; a weak reducing atmosphere such as a nitrogen gas atmosphere containing a small amount of hydrogen gas or a carbon dioxide atmosphere containing carbon monoxide; An oxygen introduction atmosphere is used. It is also possible to perform calcination by the method described in JP-A-2000-8034.

By the above calcination, the desired rare earth activated alkaline earth metal fluorohalide 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. In particular, in terms of handling as an information recording material, those which can be processed into a flexible sheet or web are suitable. In this regard, cellulose acetate films, polyester films, polyethylene terephthalate films, polyamide films, polyimide films, triacetate A plastic film such as a film or a polycarbonate 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 thickness of the support varies depending on the material of the support to be used and the like.
From the viewpoint of handling, preferably 10 to 500 μ
m.

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. Further, an undercoat layer may be provided on the surface on which the stimulable phosphor layer is provided for the purpose of improving the adhesion to 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 polymer substances such as gum arabic; polyvinyl butyral, polyvinyl acetate, nitrocellulose , Ethylcellulose, vinylidene chloride-vinyl chloride copolymer, polyalkyl (meth) acrylate,
Binders represented by synthetic polymer substances such as vinyl chloride-vinyl acetate copolymer, polyurethane, cellulose acetate butyrate, polyvinyl alcohol, linear polyester and the like can be mentioned.

Particularly preferred among such binders are nitrocellulose, linear polyesters, polyalkyl (meth) acrylates, mixtures of nitrocellulose and linear polyesters, nitrocellulose and polyalkyl (meth) acrylates. And a mixture of polyurethane and polyvinyl butyral. These binders may be cross-linked by a cross-linking 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, mixed well, and the phosphor particles and the compound particles are mixed in a binder solution. To prepare a coating solution in which is dispersed uniformly.

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

In general, the binder is used in an amount of 0.01 to 1 part by mass with respect to 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, as an example of a solvent for preparing a binding coating solution,
Lower alcohols such as methanol, enotal, 1-propanol, 2-propanol and 1-butanol; hydrocarbons containing chlorine atoms such as methylene chloride and ethylene chloride; ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone; methyl acetate, ethyl acetate; Esters of lower fatty acids such as butyl acetate and lower alcohols; dioxane, ethylene glycol ethyl ether,
Ethers such as ethylene glycol monomethyl ether;
Toluene; and mixtures thereof.

Examples of the solvent used for preparing the coating solution for the stimulable phosphor layer include lower alcohols such as methanol, ethanol, i-propanol and butanol; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone; Methyl acetate, ethyl acetate,
Esters of lower fatty acids and lower alcohols such as butyl acetate; ethers such as dioxane, ethylene glycol monoethyl ether and 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; ethylphthalylethyl glycolate and butylphthalylbutyl glycolate. And the like. Polyesters of polyethylene glycol and 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 general 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 performed 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 applied to a support using a coating solution 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 characteristics of the intended radiation image conversion panel, the type of the stimulable phosphor, and the mixing ratio between the binder and the stimulable phosphor. Although it differs depending on the like, it is preferably selected from the range of 10 to 1000 μm, more preferably 10 to 500 μm.

In the foregoing, examples of the stimulable phosphor such as europium-activated barium fluoroiodide have been mainly described, but europium-activated barium fluorobromide and other compounds represented by the above general formula (I) The stimulable phosphor can be produced by referring to the above description.

[0048]

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 ₂ (0.2 mol / L) were used.
(L concentration) 26.5 ml was charged into the reactor. Further, a 28% aqueous ammonia solution was added to the aqueous solution so that the ammonium ion concentration in the reaction mother liquor became 0.15 mol / L. Further, 249 g of potassium iodide was added. The reaction mother liquor in the reactor was kept at 83 ° C. while stirring. Aqueous ammonium fluoride solution (10mol / L concentration) 600ml
Was injected into the reaction mother liquor 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 ethanol 2,
Washed with 000 ml. The mass of the recovered precursor was measured and compared with the amount of BaI ₂ charged to determine the yield.

The obtained precipitate was subjected to X-ray diffraction measurement with Cu-Kα radiation using an X-ray diffractometer. Then
The average particle size of the obtained precipitate was measured.

Example 2 The same operation as in Example 1 was carried out except that the amount of ammonia added to the reaction mother liquor was adjusted so that the ammonium ion concentration in the mother liquor became 0.22 mol / L. I got 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 The same operation as in Example 1 was carried out except that the amount of ammonia added to the reaction mother liquor was adjusted so that the ammonia concentration in the mother liquor became 0.28 mol / L, and the precipitate was removed. 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 A precipitate was obtained in the same manner as in Example 1 except that ammonia and potassium iodide were 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.

Comparative Example 2 A precipitate was obtained in the same manner as in Example 1 except that ammonia was not added to the reaction mother liquor, and the amount of the ammonium fluoride aqueous solution to be injected into the reaction mother liquor was changed to 350 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 A precipitate was obtained in the same manner as in Example 1 except that ammonia was not added to the reaction mother liquor and the amount of the ammonium fluoride aqueous solution to be injected into the reaction mother liquor was changed to 450 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.

Example 4 The amount of ammonia added to the reaction mother liquor was adjusted so that the ammonia concentration in the mother liquor became 0.22 mol / L, and the amount of the ammonium fluoride solution (10 mol / L concentration) to be injected was changed. A precipitate was obtained in the same manner as in Example 1 except that the amount was 650 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 4 A precipitate was obtained in the same manner as in Example 4 except that ammonia 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 5 2,500 ml of BaI ₂ aqueous solution (3 mol / L concentration) and 26.5 ml of EuI 3 aqueous solution (0.2 mol / L concentration)
Was placed in the reactor. Further, a 28% aqueous ammonia solution was added so that the ammonia concentration in the reaction mother liquor became 0.23 mol / L. Further, 227 g of sodium iodide was added. The reaction mother liquor in the reactor was kept at 83 ° C. while stirring. 450 ml of an ammonium fluoride aqueous solution (10 mol / L concentration) was injected into the reaction mother liquor using a roller pump to generate 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 of the obtained precipitate was calculated in the same manner as in Example 1, and X-ray diffraction measurement was performed. Next, the average particle size of the precipitate was measured.

Example 6 A precipitate was obtained in the same manner as in Example 5 except that the amount of ammonia added to the reaction mother liquor was adjusted so that the ammonia concentration in the mother liquor was 0.27 mol / L. Example 1
The yield was calculated in the same manner as described above, and the precipitate was subjected to X-ray diffraction and average particle size measurement.

Example 7 A precipitate was obtained in the same manner as in Example 6 except that sodium 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.

Comparative Example 5 A precipitate was obtained in the same manner as in Example 5 except that ammonia and sodium iodide were 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.

Comparative Example 6 Ammonia fluoride aqueous solution (concentration: 10 mol / L) to be injected was changed to 260 ml without adding ammonia to the reaction mother liquor.
The same operation as in Example 5 was performed, except that the precipitate was obtained, to thereby obtain a precipitate. The yield was calculated in the same manner as in Example 1, and the precipitate was subjected to X-ray diffraction measurement and average particle size measurement.

The above results are summarized in Table 1.

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

[0065]

[Table 1]

From the comparison between Examples 1 to 4 and Comparative Examples 1 to 4,
According to the present invention, it is found that a stimulable phosphor precursor having a small particle size can be obtained with a high yield of 60%. Examples 5 and 6
From the comparison between Comparative Examples 5 and 6, it can be seen that a stimulable phosphor precursor having a small particle diameter can be obtained with a high yield even at a dilute mother liquor concentration. Further, from Example 8, a precursor having a small particle size can be obtained also in the form of a filtrate in which a precipitate is once obtained.

As described above, according to the present invention, precursor particles of europium-activated barium fluoroiodide stimulable phosphor having a small particle size can be obtained with a high yield even at a low mother liquor concentration.

(Production of stimulable phosphor) In Examples 1 to 7 and Comparative Examples 2, 3, and 6, 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. Then, 1% of ultrafine alumina powder was added, and the mixture was sufficiently stirred with a mixer to uniformly adhere the ultrafine alumina powder to the crystal surface. This is charged into a quartz core tube of a batch type rotary kiln having a core volume of 10 L,
The atmosphere was replaced by flowing a mixed gas of nitrogen / hydrogen / oxygen (93/5/2% by volume) at a flow rate of 10 L / min for 20 minutes.

After sufficiently replacing the atmosphere in the furnace core, the flow rate of the mixed gas was reduced to 2 L / min, and the furnace tube was rotated at a speed of 2 rpm while heating at a rate of 10 ° C./min.
Heated to 30 ° C. 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 temperature at 830 ° C. to replace the atmosphere. Thereafter, nitrogen / hydrogen (93 /
5% by volume) to 2 L / min.
Hold for 0 minutes. 10 ° C./mi while maintaining the flow rate of the nitrogen / hydrogen (93/5 volume%) mixed gas at 2 L / min.
After cooling to 25 ° C. at a temperature lowering rate of n, the atmosphere was returned to the atmosphere, and the produced oxygen-introduced europium-activated barium fluoroiodide 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 a 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. This coating solution was applied on a polyethylene terephthalate film with an undercoat using a doctor blade,
After drying for 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 crosslinking 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. A liquid was prepared.

This coating solution is applied using a doctor blade on the phosphor layer previously formed and placed as described above,
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) << Sensitivity >> X of a tube voltage of 80 kVp was applied to the radiation image conversion panel.
After irradiating the panel, the panel was irradiated with He-Ne laser light (63
3 nm), and the photostimulated emission emitted from the phosphor layer was received by a photodetector (photoelectron image tube with a spectral sensitivity of S-5) to measure the intensity. In Table 2, the sensitivities are shown as relative values.

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

<Granularity> After irradiating the radiation image conversion panel with X-rays having a tube voltage of 80 kVp, the panel is operated by operating with a He-Ne laser beam, 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 a normal photographic film by a film scanner, and the granularity of the obtained image was visually evaluated. The graininess is measured by using an intensifying screen (SRO-25 manufactured by Konica Corporation).
The results are shown in Table 2 in comparison with the granularity of images obtained by conventional practical X-ray photography using X-ray film (Konica Corporation: SR-G).

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

Table 2 also shows the evaluation results of each radiation image conversion panel.

[0079]

[Table 2]

The results in Table 2 show that the radiation image conversion panel having the phosphor layer containing the rare earth-activated alkaline earth metal fluoroiodide-based stimulable phosphor of the present invention shows sensitivity, sharpness, and granularity. It proves to be superior to both.

[0081]

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

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Kanae Tsuchiya 1 Sakuracho, Hino-shi, Tokyo Konica Corporation F-term (reference) 2G083 AA03 BB01 DD02 DD12 EE02 EE03 4G076 AA02 AA05 AA08 AB04 BA13 BB05 CA02 DA30 4H001 CA08 CF01 XA04 XA09 XA12 XA20 XA35 XA38 XA53 XA56 YA03 YA08 YA11 YA19 YA37 YA55 YA58 YA59 YA60 YA62 YA63 YA64 YA65 YA66 YA67 YA68 YA69 YA70

Claims (5)

[Claims] 1. A method for producing an oxygen-introduced rare earth-activated alkaline earth metal fluoride halide stimulable phosphor represented by the following general formula (I) in a liquid phase, wherein barium ions and ammonium ions are present. A method for producing a rare earth-activated alkaline earth metal fluorohalide-based stimulable phosphor, comprising adding an inorganic fluoride solution to the reaction mother liquor. 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, M
at least one alkaline earth metal selected from g, Sr and Ca; Ln is Ce, Pr, Sm, Eu, Gd, T
represents at least one rare earth element selected from b, 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, and 0 ≦ c ≦ 0.1. ] 2. The stimulable fluorescence of a rare earth activated alkaline earth metal fluoride halide according to claim 1, wherein the concentration of ammonium ions present in the reaction mother liquor is 0.2 mol / L or more. How to make the body. 3. A method for producing a rare earth activated alkaline earth metal fluoride halide stimulable phosphor according to claim 1, wherein an alkali metal halide is added to the reaction mother liquor. . 4. A stimulable phosphor of a rare earth activated alkaline earth metal fluorinated halide type obtained by the production method according to claim 1, 2 or 3. 5. A radiation image conversion panel comprising a phosphor layer containing the rare earth activated alkaline earth metal fluorohalide-based stimulable phosphor according to claim 4.