JP2000192031A - Rare-earth-activated alkaline earth metal fluoride halide stimulable phosphor, its production, and radiation image transformation panel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rare-earth-activated alkaline earth metal fluoride halide which, when utilized in a radiation image recording reproduction method, exhibits a very high sharpness, can give a high image quality, and has high sensitivity and extinction, a process for producing the same, and a radiation- image transformation panel. SOLUTION: This phosphor is represented by the formula: Ba1-xMIIxFX:yMI, zLn [wherein MII is an alkaline earth metal; MI is an alkali metal; Ln is a rare earth element; 0<=x<=0.5; 0<=y<=0.05; and 0<z<=0.2] and satisfies: Dm=1-10 μm (wherein Dm is the median diameter of the particles sizes; σ/Dm<=50% (wherein σ is the deviation in the particle size distribution; and aspect ratio of particles = 1.0-2.0. It is desirable that each particle has the form of a tetradecahedron.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a rare earth-activated alkaline earth metal fluorohalide-based stimulable phosphor, particularly 14
The present invention relates to a face-type rare earth activated alkaline earth metal fluorohalide-based stimulable phosphor, a method for producing the phosphor, and a radiation image conversion panel.

[0002]

2. Description of the Related Art As an alternative to the conventional radiographic method, there is known a radiation image recording / reproducing method using a stimulable phosphor as described in, for example, JP-A-55-12145. This method uses a radiation image conversion panel (a stimulable phosphor sheet) containing a stimulable phosphor, and transmits radiation transmitted through a subject or emitted from a subject to the stimulable phosphor of the panel. By absorbing the stimulable phosphor with electromagnetic waves (excitation light) such as visible light and infrared light in a time series manner, the radiation energy stored in the stimulable phosphor is absorbed by the body. The fluorescent light is emitted (stimulated emission light), the fluorescent light is read photoelectrically to obtain an electric signal, and a radiation image of a subject or a subject is reproduced as a visible image based on the obtained electric signal. . After the reading of the panel is completed, after the remaining image is deleted, the panel is prepared for the next photographing. That is, the radiation image conversion panel can be used repeatedly.

According to the above-described radiographic image recording / reproducing method, a radiographic image having a much smaller amount of exposure and a richer amount of information than a radiographic method using a combination of a conventional radiographic film and an intensifying screen. There is an advantage that can be obtained. Further, in the conventional radiographic method, a radiographic film is consumed for each photographing, whereas in the radiographic image conversion method, the radiographic image conversion panel can be used repeatedly, thereby conserving resources and saving economy. It is also advantageous in terms of efficiency.

[0004] A stimulable phosphor is a phosphor that emits stimulable light when irradiated with excitation light after being irradiated with radiation. However, in practice, the stimulable phosphor has a wavelength within a range of 400 to 900 nm due to excitation light having a wavelength of 400 to 900 nm. Is generally used. Examples of stimulable phosphors conventionally used in radiation image conversion panels include rare earth-activated alkaline earth metal fluorinated halide-based phosphors. The radiation image conversion panel used in the radiation image recording / reproducing method has, as a basic structure, a support and a stimulable phosphor layer provided on the surface of the support. However, when the stimulable phosphor layer is self-supporting, a support is not necessarily required. The stimulable phosphor layer usually comprises a stimulable phosphor and a binder containing and supporting the stimulable phosphor in a dispersed state. However, there is also known a stimulable phosphor layer which does not include a binder formed by a vapor deposition method or a sintering method and is composed of only an aggregate of the stimulable phosphor. Further, there is known a radiation image conversion panel having a stimulable phosphor layer in which a polymer substance is impregnated in a gap between stimulable phosphor aggregates. In any of these stimulable phosphor layers, the stimulable phosphor has a property of exhibiting stimulable emission when irradiated with excitation light after absorbing radiation such as X-rays. Radiation transmitted through the subject or emitted from the subject is absorbed in the stimulable phosphor layer of the radiation image conversion panel by an amount of energy proportional to the radiation dose, and the panel displays the radiation image of the subject or the subject. It is formed as an image of accumulated radiation energy. This accumulated image can be emitted as stimulated emission light by irradiating the excitation light, and the accumulated image of radiation energy is imaged by photoelectrically reading the stimulated emission light and converting it into an electric signal. It is possible to do.

The surface of the stimulable phosphor layer (the surface not facing the support) is usually provided with a protective film such as a polymer film or an inorganic vapor-deposited film. The phosphor layer is protected from chemical alteration or physical impact.

The rare earth activated alkaline earth metal fluorohalide-based stimulable phosphor has excellent sensitivity and, when used as a radiation image conversion panel, produces a radiation-reproduced image with high sharpness. It can be called an excellent stimulable phosphor. However, as the radiation image recording / reproducing method has been put to practical use, there has been an increasing demand for further improving the performance of the stimulable phosphor. Then, when the particle shapes of the rare earth activated alkaline earth metal fluorohalide-based stimulable phosphors used so far were examined, they were found to be composed of plate-like particles. Conventionally known methods for producing a rare earth activated alkaline earth metal fluorohalide-based stimulable phosphor include a starting compound alkaline earth metal fluoride, an alkaline earth metal halide other than fluoride, and a rare earth element. A halide, ammonium fluoride, etc. are mixed together in a dry system or suspended in an aqueous medium and mixed, and then, if necessary, a sintering inhibitor is added, followed by calcination and pulverization. Process. Therefore, in the conventional production method, the pulverization step after firing is substantially essential, and the particles of the rare earth activated alkaline earth metal fluoride halide stimulable phosphor thus obtained are mostly contained. Were plate-like particles (hereinafter sometimes simply referred to as “plate-like phosphor”).

However, in the stimulable phosphor layer obtained by mixing such a plate-shaped phosphor with a binder resin solution, coating the mixture on a support, and drying, the plate-shaped phosphor is seen in FIG. As a result, the plate-like phosphor surface and the support plane tend to be arranged in parallel. When a radiation image is stored in a radiation image conversion panel having a stimulable phosphor layer on which a plate-like phosphor is arranged as described above, and the excitation light is irradiated, the excitation light and the generated stimulable luminescence are generated in a lateral direction ( This tends to spread in a direction parallel to the plane of the support (see the horizontal arrow in FIG. 1), which causes a problem that the sharpness of the obtained reconstructed radiation image is easily reduced.

In order to suppress the decrease in the sharpness of a radiation reproduced image in the radiation image recording / reproducing method as described above, a substantially cubic stimulable phosphor disclosed in JP-A-62-86086 is used. It is conceivable to use particles.
However, the method for producing the substantially cubic stimulable phosphor particles disclosed in the above publication does not have sufficient reproducibility for industrial use.

Further, Japanese Patent Application Laid-Open No. 7-233369,
Japanese Patent Application No. 6-315573 and Japanese Patent Application Laid-Open No. 10-19.
No. 5431 discloses a method for producing a tetrahedral rare earth activated alkaline earth metal fluorinated halide-based stimulable phosphor (hereinafter sometimes simply referred to as “phosphor”) in which the particle shape and the particle aspect ratio are controlled. It is shown. Radiation image conversion panel having a stimulable phosphor layer on which a tetradecahedral rare earth activated alkaline earth metal fluorinated halide stimulable phosphor (hereinafter sometimes simply referred to as “tetrahedral phosphor”) is disposed. Then, as shown in FIG. 2, in the stimulable phosphor layer, 1
Since the tetrahedral phosphor has an arrangement with less directivity, undesired spread of the excitation light and the stimulated emission light in the lateral direction is reduced, and the sharpness of the obtained radiation reproduction image is improved.
Although the emission characteristics, particularly sharpness, of the phosphor obtained by the manufacturing method disclosed in the above publication are extremely high, further improvement in sensitivity and erasing characteristics when used in a radiation image recording / reproducing method has been desired. .

[0010]

According to the present invention, when used in a radiation image recording / reproducing method, extremely high sharpness is obtained and high image quality is obtained, and other light emitting characteristics, particularly sensitivity and erasing characteristics, are not improved. An object of the present invention is to provide a high rare earth activated alkaline earth metal fluorinated halide-based stimulable phosphor, a production method excellent in suitability for producing the phosphor, and a radiation image conversion panel using the phosphor. .

[0011]

Means for Solving the Problems In the above-mentioned documents relating to the phosphor, there is no mention of the particle size and particle size distribution of the phosphor. On the other hand, in order to improve image quality when a phosphor is used in a radiation image conversion panel, it is not enough to control only the particle shape and particle aspect ratio of the phosphor to be used. It is desired to control. The present invention has been achieved by finding that the particle size and the particle size distribution are factors that greatly affect image quality when a phosphor is used in a radiation image conversion panel, and by narrowing down the appropriate range. .

Simultaneous control of particle shape, particle aspect ratio, particle size and particle size distribution is performed by BaX
₂ (X is Cl, at least one halogen selected from the group consisting of Br and I), but will be implemented in the precipitation reaction of the phosphor precursor crystals to an aqueous solution of the reaction mother liquor, the BaX ₂ concentration in that case Only by controlling, the control range is narrow, and it is difficult to simultaneously satisfy the conditions of each of the above particles. Therefore, by controlling a combination of the rate of addition of the reaction solution with BaX ₂ concentration in the reaction mother liquid consists of inorganic fluoride aqueous solution, it found that can satisfy the condition of each particle at the same time, leading to the present invention.

That is, the present invention provides: <1> Basic composition formula (I): Ba _{1 -x} M ^II _x FX: y M ^I , zLn (I) [where M ^II is a group consisting of Sr and Ca It represents more least one alkaline earth metal selected, M ^I is Li,
X represents at least one alkali metal selected from the group consisting of Na, K, Rb and Cs, and X represents Cl, Br and I
Ln represents Ce, Pr, Sm, Eu, Gd, Tb, Tm
And at least one rare earth element selected from the group consisting of Yb and Xb, x, y and z are 0 ≦ x ≦ 0.5, 0 ≦
Numerical values in each range of y ≦ 0.05 and 0 <z ≦ 0.2 are shown. And the median diameter (Dm) of the particle size is 1 to 10 μm, and σ / Dm when the standard deviation of the particle size distribution is σ is in the range of 50% or less. A rare earth activated alkaline earth metal fluorinated halide stimulable phosphor, wherein the ratio is in the range of 1.0 to 2.0.

<2> The rare earth-activated alkaline earth metal fluoride halide stimulable phosphor according to <1>, wherein the particle shape is a tetradecahedral type.

<3> Ln in the basic composition formula (I)
Is Ce or Eu. <1> or <2>, wherein the rare earth activated alkaline earth metal fluoride halide stimulable phosphor is used.

<4> Any one of <1> to <3>
The method for producing a rare earth-activated alkaline earth metal fluoride halide stimulable phosphor according to the above item, wherein BaX ₂ ; a water-soluble compound of Ln; and wherein x in the basic composition formula (I) is not 0, An aqueous solution containing a halide, nitrate, nitrite or acetate of M ^II ; and when y in the basic composition formula (I) is not 0, further a halide, nitrate, nitrite or acetate of M ^I ; The concentration of BaX ₂ after dissolution is 2.5 when X is Cl or Br.
A mother liquor preparation step of preparing a reaction mother liquor of not more than 5.0 mol / l, and when X is I, not more than 5.0 mol / l; Assuming that the amount of the precipitate of the phosphor precursor crystal is N, the addition rate is such that the amount of the precipitate of the phosphor precursor crystal generated during the addition is in the range of 0.001 N / min to 10 N / min. A precipitate generating step of adding an aqueous solution of an inorganic fluoride salt to generate a precipitate of the phosphor precursor crystal, and a separation step of separating the precipitate of the phosphor precursor crystal from the aqueous solution, A sintering step of firing the separated precipitate of the phosphor precursor crystal while avoiding sintering, a method for producing a rare earth-activated alkaline earth metal fluoride halide stimulable phosphor. It is.

<5> The rare earth-activated alkaline earth metal fluoride halide stimulable phosphor according to <4>, wherein the inorganic fluoride salt is ammonium fluoride or an alkali metal fluoride. It is a manufacturing method of.

<6> A rare earth activated alkaline earth metal fluoride halide system as described in <4> or <5>, wherein a precision cylinder pump is used for the addition of the inorganic fluoride aqueous solution in the precipitation forming step. This is a method for producing a stimulable phosphor.

<7> Any one of <4> to <6>, wherein the rate of addition of the aqueous solution of inorganic fluoride in the precipitation forming step is adjusted to 0.01 N / min to 1.0 N / min. 3. The method for producing a rare earth activated alkaline earth metal fluorohalide-based stimulable phosphor described in 1. above.

<8> The rate of addition of the inorganic fluoride aqueous solution in the step of forming a precipitate varies at a constant rate or continuously or intermittently with respect to the addition time. <4>
> The method for producing a rare earth-activated alkaline earth metal fluorohalide-based stimulable phosphor according to any one of <1> to <7>.

<9> A radiation image conversion panel having a stimulable phosphor layer containing a stimulable phosphor, wherein the stimulable phosphor is any one of <1> to <3>. A radiation image conversion panel characterized by being an activated alkaline earth metal fluoride halide stimulable phosphor.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. Rare earth activated alkaline earth metal fluoride halide stimulable phosphor First, the rare earth activated alkaline earth metal fluoride halide stimulable phosphor of the present invention will be described.

The rare earth activated alkaline earth metal fluoride halide stimulable phosphor of the present invention has a basic composition formula (I): Ba _{1 -x} M ^II _x FX: y M ^I , zLn (I) Wherein M ^II represents at least one kind of alkaline earth metal selected from the group consisting of Sr and Ca, M ^I represents Li,
X represents at least one alkali metal selected from the group consisting of Na, K, Rb and Cs, and X represents Cl, Br and I
Ln represents Ce, Pr, Sm, Eu, Gd, Tb, Tm
And at least one rare earth element selected from the group consisting of Yb and Xb, x, y and z are 0 ≦ x ≦ 0.5, 0 ≦
Numerical values in each range of y ≦ 0.05 and 0 <z ≦ 0.2 are shown. ].

Ln in the above basic composition formula (I) is
Particularly, it is preferably Ce or Eu. The rare earth activated alkaline earth metal fluoride halide stimulable phosphor represented by the basic composition formula (I) usually has an aspect ratio in the range of 1.0 to 5.0. The rare earth activated alkaline earth metal fluoride halide stimulable phosphor of the present invention has a particle aspect ratio in the range of 1.0 to 2.0 (more preferably, 1.0 to 1.5) and a particle size of 1.0 to 1.5. The median diameter (Dm) is 1 to 10 μm (more preferably, 2 to 7 μm).
μm) and σ / Dm is 50% or less when the standard deviation of the particle size distribution is σ (more preferably,
(40% or less). Further, as the shape of the particles, there are a rectangular parallelepiped type, a regular hexahedron type, a regular octahedral type, an intermediate polyhedral type thereof, a tetrahedral type, and the like, and a tetrahedral type is preferable, but the particle aspect ratio, particle size and particle size distribution are preferable. If the condition is satisfied, the effects of the present invention can be achieved without being necessarily limited to the tetrahedral type.

The median diameter (Dm) of the particle size is from 1 to 1.
The reason why the thickness is preferably set to 0 μm will be described below using experimental data. The particle shape is tetrahedral, the particle aspect ratio is in the range of 1.02 to 1.09, and σ / Dm is 3
The value of the median diameter (Dm) of the particle size was adjusted to 0.75 to 12.3 while adjusting the particle size to be in the range of 4.0 to 39.0%.
A rare earth activated alkaline earth metal fluorohalide-based stimulable phosphor shaken in a range of 2 μm was produced. The sensitivity and erasure value of the rare earth-activated alkaline earth metal fluoride halide stimulable phosphor were evaluated by the following methods. The results are shown in Table 1 below.

Sensitivity: 80 kV, 100 m for each rare earth activated alkaline earth metal fluorohalide-based stimulable phosphor
After irradiating X-rays of R, a He-Ne laser beam
Irradiation was performed at 2.4 J / m ² , and the amount of stimulated emission from the rare earth activated alkaline earth metal fluorinated halide stimulable phosphor was determined to calculate the sensitivity level value.

Erased value: 80 kV, 100 m for rare earth activated alkaline earth metal fluorohalide-based stimulable phosphor
After irradiating X-rays of R, a He-Ne laser beam
Irradiation at 2.4 J / m ² , the amount of stimulated emission from the rare earth-activated alkaline earth metal fluorohalide-based stimulable phosphor is determined as an initial emission amount (initial value), and then the rare earth The activated alkaline earth metal fluorohalide-based stimulable phosphor is irradiated with a white fluorescent lamp under the condition of 400,000 lx · s, and then irradiated with a He-Ne laser beam at 12.4 J / m ² , and the rare earth is irradiated. The emission level of stimulated emission from the activated alkaline earth metal fluorohalide-based stimulable phosphor was determined to obtain an erasing level value. The value obtained by normalizing the erase level value with the initial value was used as the erase value.

[0028]

[Table 1]

FIGS. 3 and 4 are graphs showing the relationship between the median diameter (Dm) of the particle size and the sensitivity or erasure value based on the results shown in Table 1 above. As is clear from the graphs of FIGS. 3 and 4, when the median diameter (Dm) of the particle size of the rare earth activated alkaline earth metal fluorohalide stimulable phosphor is reduced, the sensitivity is particularly deteriorated. However, it can be seen that the erasure value deteriorates as the value increases.

Judging from the above results, from the viewpoint of emission characteristics (balance between sensitivity and erasure), the median diameter (Dm) of the particle size of the rare earth activated alkaline earth metal fluorohalide stimulable phosphor is as follows: The range is preferably from 1 to 10 μm, more preferably from 2 to 7 μm.

The rare earth activated alkaline earth metal fluoride halide stimulable phosphor of the present invention can be advantageously used as a stimulable phosphor material for forming a phosphor layer of a radiation image conversion panel. it can.

Manufacturing Method The rare earth activated alkaline earth metal fluorohalide-based stimulable phosphor of the present invention is manufactured by the following manufacturing method. BaX ₂ ; a water-soluble compound of Ln; when x in the basic composition formula (I) is not 0, further halide, nitrate, nitrite or acetate of M ^II ; when y in the basic composition formula (I) is not 0 Furthermore halide of M ^I in, nitrate, nitrite or acetate; an aqueous solution containing, and are BaX ₂ concentration after they have dissolved, X
Is 2.5 mol / liter or less when is Cl or Br,
When X is I, a mother liquor preparation step of preparing a reaction mother liquor having a concentration of 5.0 mol / liter or less;
While maintaining the temperature at 0 ° C., the amount of the precipitate of the phosphor precursor crystal finally obtained is defined as N, and the amount of the precipitate of the phosphor precursor crystal generated during the addition is 0.001N. / Min to 10 N / min by adjusting the rate of addition,
A precipitate forming step of adding an aqueous solution of an inorganic fluoride salt to generate a precipitate of a phosphor precursor crystal; a separating step of separating the precipitate of the phosphor precursor crystal from an aqueous solution; And baking a precipitate of the precursor crystal while avoiding sintering.

In the present invention, the term "aqueous solution" refers to
"Solute" refers to a substance dissolved by "aqueous medium". The term “aqueous medium” is a concept that includes not only water, but also a liquid having a high affinity for water (for example, alcohol or the like) alone or a mixture of a plurality of them, or a mixture of these and water. Of these, water is most preferred. Therefore, the term “aqueous solution” in the present invention is a concept including all the solutions prepared by the “aqueous medium” of the present invention, and it is most preferable to use water as the “aqueous medium”. On the other hand, the “solute” is appropriately selected depending on the type of the aqueous solution (raw material solution, reaction mother liquor, aqueous solution for addition, etc.). The manufacturing method will be described for each process.

I) Preparation of mother liquor First, a raw material compound other than the fluorine compound is dissolved in an aqueous medium to prepare a reaction mother liquor. That is, BaX ₂
And water-soluble compounds of Ln, and halides of M ^II optionally, nitrate, nitrite or acetate, halide M ^I if necessary, nitrate, nitrite or acetate, in an aqueous medium The components are sufficiently mixed and dissolved to prepare an aqueous solution (reaction mother liquor) in which these components are dissolved. At this time, when X is Cl or Br, Ba
X ₂ is adjusted so that the concentration of X ₂ is 2.5 mol / liter or less.
When I is I, the quantitative ratio between BaX ₂ and the aqueous solvent is adjusted so that the BaX ₂ concentration becomes 5.0 mol / liter or less. Examples of the water-soluble compound of Ln include halides of the rare earth elements (specifically, chlorides, bromides, etc.), nitrates, acetates and the like. The reaction mother liquor contains a small amount of acid, ammonia, a water-soluble polymer,
Water-insoluble metal oxide fine particles may be added.

Ii) Precipitate formation step The reaction mother liquor obtained above is maintained at 20 to 100 ° C, preferably 40 to 80 ° C, and stirred. An aqueous solution of an inorganic fluoride salt is added thereto to obtain a precipitate of phosphor precursor crystals. As inorganic fluoride salts, ammonium fluoride,
Alkali metal fluorides, alkaline earth metal fluorides, hydrofluoric acid, etc., among which ammonium fluoride and alkali metal fluorides are preferred in view of solubility, luminescence characteristics, and pH change during the reaction. .

When the amount of the precipitate of the phosphor precursor crystals finally obtained upon adding the aqueous solution of the inorganic fluoride salt is set to N, the amount of the precipitate of the phosphor precursor crystals formed during the addition Is adjusted within a range of 0.001 N / min to 10 N / min (more preferably, a range of 0.01 N / min to 1.0 N / min), and an aqueous solution of an inorganic fluoride salt is added. Is preferred.

The reason why the addition rate of the aqueous solution of the inorganic fluoride salt is preferably within the above range will be described below with reference to experimental data. As a reaction mother liquor, 1.0 mol /
Liter, 1.5 mol / l, 2.0 mol / l, 2.5 mol / l concentration of four levels of BaBr ₂
Aqueous solution of NH ₄ F (5 mol / l 300 ml) as an aqueous solution of an inorganic fluoride salt to be further added.
Using an inorganic fluoride salt aqueous solution at a rate of 0.3 m
1 / min, 3 ml / min, 30 ml / min, 300 ml
Was actually added under 5 conditions of 3000 ml / min to obtain a precipitate of a phosphor precursor crystal. (Details of this experiment are the same as those of Example 1 except for the rate of addition of the inorganic fluoride salt aqueous solution. 1 (concentration of aqueous solution of BaBr ₂ : 1.0 mol / l) to the same as in Example 4 (concentration of aqueous solution of BaBr ₂ : 2.5 mol / l).

The obtained precipitate of the phosphor precursor crystal is subjected to a separation step and a firing step described later (specifically, Example 1 described later).
Is the same as ) To produce a rare earth activated alkaline earth metal fluorohalide-based stimulable phosphor. The measured values of the median diameter (Dm) of the particle size of the rare earth activated alkaline earth metal fluoride halide stimulable phosphor thus produced are as shown in Table 2 below.

[0039]

[Table 2]

FIG. 5 is a graph showing the relationship between the concentration of BaBr ₂ in the reaction mother liquor, the rate of addition of the inorganic fluoride salt aqueous solution, and the median diameter (Dm) of the particle size, based on the results in Table 2 above. It is. The graph of FIG. 5 shows the lower limit 1 μm of the median diameter (Dm) of the target particle size specified in the present invention.
m, the upper limit of which is 10 μm, and the lower limit of 0.1 μm, which is the production limit concentration of the precipitate of the phosphor precursor crystal in the aqueous solution of BaBr ₂ .
The range surrounded by 5 mol / l and the upper limit of 2.5 mol / l as the saturated concentration of the aqueous solution of BaBr ₂ is shown as the usable range.

From the graph of FIG. 5, it can be seen that when the addition rate of the aqueous solution of the inorganic fluoride salt is from 3 ml / min to 3000 ml / min, most of the range of the usable range in the graph is stably contained. .

Judging from the above results, since the amount of the aqueous solution of the inorganic fluoride salt is 300 ml as described above, the amount of the aqueous solution is eventually 0.1 ml.
It is found that the range of 001 N / min to 10 N / min is preferable, and the range is more preferably 0.01 N / min to 1.0 N / min.

In order to precisely adjust the addition rate, it is preferable to add by a precision pump (for example, a precision cylinder pump, a precision gear pump, a tube pump, a diaphragm pump). Further, the addition is usually performed at a constant addition rate, but the addition rate is n with respect to the addition time.
It may be continuously or intermittently changed as a quadratic function (n = 1, 2, 3), an exponential function, or a differential function (see FIG. 6). This addition is preferably carried out in the region where the stirring is particularly vigorous. By adding the aqueous solution of the inorganic fluoride salt to the reaction mother liquor, the phosphor precursor crystal of the rare earth activated alkaline earth metal fluoride halide stimulable phosphor represented by the basic composition formula (I) is precipitated. I do. In the present invention, in addition to the particle shape, the object is to simultaneously control the particle aspect ratio, the particle size, and the particle size distribution. And BaX ₂ concentration of the reaction mother liquor.

Iii) Separation Step The precipitate of the phosphor precursor crystal obtained as described above is separated from the aqueous solution by separation means such as suction filtration, pressure filtration, and centrifugation. The separated precipitate of the phosphor precursor crystal is sufficiently washed with a lower alcohol such as methanol and dried.

Iv) Firing Step The separated precipitate of the phosphor precursor crystal is fired while avoiding sintering. As a method of avoiding sintering, for example, a sintering inhibitor consisting of a metal oxide fine powder such as alumina, silica, zirconia, titania, and magnesia is added to the phosphor precursor crystal and mixed, and the sintering is performed on the crystal surface. A method of baking the fine powder of the anti-sizing agent to uniformly adhere it is exemplified. The addition of the sintering inhibitor can be omitted by appropriately adjusting the firing conditions.

As a specific firing method, if necessary, the phosphor precursor crystals having the fine powder of the sintering inhibitor attached to the surface thereof are placed in a heat-resistant container such as a quartz boat, an alumina boat, a quartz crucible, or an alumina crucible. Filling and placing in a furnace core such as an electric furnace. Firing temperature 400 ~ 13
The range of 00 ° C is preferable, and the range of 500 to 1000 ° C is more preferable. Firing time varies depending on the filling amount of the phosphor precursor crystal, the firing temperature and the unloading temperature,
Generally, 0.5 to 12 hours is appropriate. The firing atmosphere may be a neutral atmosphere such as a nitrogen gas atmosphere, an argon gas atmosphere, a weak reducing atmosphere such as a nitrogen gas atmosphere containing a small amount of hydrogen gas, a carbon dioxide atmosphere containing carbon monoxide, or a trace oxygen introducing atmosphere. Used.
By the above calcination, the desired rare earth activated alkaline earth metal fluorohalide-based stimulable phosphor is obtained.

Method for Manufacturing Radiation Image Conversion Panel Next, a method for manufacturing a radiation image conversion panel using the rare earth activated alkaline earth metal fluoride halide stimulable phosphor of the present invention will be described.

The rare earth activated alkaline earth metal fluorohalide-based stimulable phosphor of the present invention (hereinafter sometimes simply referred to as "stimulable phosphor") is a stimulable phosphor of a radiation image conversion panel. Included in the layer. Usually, it comprises a stimulable phosphor and a binder containing and supporting the stimulable phosphor in a dispersed state. The stimulable phosphor layer may further contain another stimulable phosphor and / or an additive such as a colorant.

A method for manufacturing a radiation image conversion panel will be described by taking, as an example, a case where the stimulable phosphor layer comprises a stimulable phosphor and a binder containing and supporting the stimulable phosphor in a dispersed state.

The stimulable phosphor layer can be formed on a support by the following known method. First, a stimulable phosphor and a binder are added to a solvent and mixed well to prepare a coating solution in which the stimulable phosphor is uniformly dispersed in a binder solution. The mixing ratio between the binder and the stimulable phosphor in the coating solution varies depending on the intended characteristics of the radiation image conversion panel, the type of the stimulable phosphor, and the like. Is selected from the range of 1: 1 to 1: 100, especially 1: 8 to 1:40.
It is preferable to select from the range. Next, the coating solution containing the stimulable phosphor and the binder prepared as described above is uniformly applied to the surface of the support to form a coating film. This coating operation is performed by a normal coating means, for example,
It can be performed by using a doctor blade, a roll coater, a knife coater or the like.

The support can be arbitrarily selected from those conventionally known as materials for supports of radiation image conversion panels. In known radiation image conversion panels, photostimulation is used to enhance the bond between the support and the photostimulable phosphor layer or to improve the sensitivity or image quality (sharpness, granularity) of the radiation image conversion panel. A polymer material such as gelatin is applied to the surface of the support on which the conductive phosphor layer is provided to provide an adhesion-imparting layer, or a light-reflective layer made of a light-reflective material such as titanium dioxide, or carbon black. It is known to provide a light absorbing layer made of a light absorbing substance. The support used in the present invention can also be provided with these various layers, and the configuration thereof can be arbitrarily selected depending on the desired purpose and application of the radiation image storage panel. Further, as described in JP-A-58-200200, the surface of the support on the side of the stimulable phosphor layer (the stimulable phosphor When an adhesiveness-imparting layer, a light-reflecting layer, a light-absorbing layer, or the like is provided on the surface on the layer side, it means the surface), and fine irregularities may be formed.

After forming a coating on the support as described above, the coating is dried to form a stimulable phosphor layer on the support. The thickness of the stimulable phosphor layer varies depending on the intended properties of the radiation image storage panel, the type of the stimulable phosphor, the mixing ratio of the binder to the stimulable phosphor, and the like.
0 μm to 1 mm. The layer thickness is 50 to 500 μm
It is preferred that The stimulable phosphor layer does not necessarily need to be formed by directly applying the coating solution on the support as described above. For example, the stimulable phosphor layer may be separately applied on a sheet such as a glass plate, a metal plate, or a plastic sheet. After forming the phosphor layer by applying and drying the liquid, this is pressed onto the support, or even if the support and the stimulable phosphor layer are joined by using an adhesive or the like. Good.

As described above, a protective film is usually provided on the stimulable phosphor layer. The protective film is formed by applying a solution prepared by dissolving a transparent organic polymer substance such as a cellulose derivative or polymethyl methacrylate in an appropriate solvent onto the stimulable phosphor layer. An organic polymer film such as polyethylene terephthalate or a protective film forming sheet such as a transparent glass plate is separately formed and provided on the surface of the stimulable phosphor layer with an appropriate adhesive, or an inorganic compound. Those formed on the stimulable phosphor layer by vapor deposition or the like are used. Also, formed by a coating film of a fluorine-based resin soluble in an organic solvent,
It may be a protective film in which perfluoroolefin resin powder or silicone resin powder is dispersed and contained.

For the purpose of improving the sharpness of the obtained image, at least one of the above layers constituting the radiation image conversion panel absorbs excitation light and does not absorb stimulated emission light. Coloring agent, or an independent colored intermediate layer may be provided.
-23400).

By the above method, a stimulable phosphor comprising the rare earth-activated alkaline earth metal fluorinated halide-based stimulable phosphor of the present invention and a binder containing and supporting the fluorinated phosphor of the present invention in a dispersed state. A radiation image conversion panel provided with a luminescent phosphor layer can be manufactured.

[0056]

The present invention will be specifically described below with reference to examples. In Examples and Comparative Examples, “aqueous solution”
Means a general aqueous solution using only water as a medium, regardless of the concept in the present invention.

Example 1 In order to synthesize a stimulable phosphor precursor of europium-activated barium fluorobromide, BaB was used.
r ₂ aqueous solution (2.5 mol / l) 1200 ml, E
uBr ₃ aqueous solution (0.2 mol / L) 37.5 m
l and 1762.5 ml of water (B)
aBr ₂ concentration: 1.0 mol / l) was placed in a 4 liter reactor. The reaction mother liquor in this reactor is
C., and a 45-mm diameter screw-type stirring blade provided with a mixing chamber having a volume of about 100 ml around the periphery was rotated at 500 rpm to stir the reaction mother liquor so as to generate an upward flow from the mixing chamber. did.

An aqueous solution of ammonium fluoride (NH ₄ F) (1
(0 mol / l) 150 ml of water and 150 ml of water are mixed, and 300 ml of the mixed solution is added to the mixing chamber in the reaction mother liquor kept warm under the above stirring, using a precision cylinder pump, at an addition rate of 3 ml / min. And a precipitate was formed. After completion of the addition, the mixture was kept warm and stirred for 2 hours to ripen the precipitate.

Next, the precipitate was separated by filtration and 2 liters of methanol was added.
And washed with water. Then, the washed precipitate is taken out, and 12
Vacuum-dried at 0 ° C for 4 hours for europium-activated fluorobromination
About 330 g of barium crystals were obtained. Europiu obtained
Activated barium fluorobromide crystals by sintering during firing
Changes in particle size due to changes in particle shape and fusion between particles
1% by weight of ultra-fine alumina powder
And mix well with a mixer.
Was uniformly adhered. Take 100g of this
Into a quartz boat and use a tube furnace to
Bake at 850 ° C for 2 hours
Active fluorinated barium bromide stimulable phosphor particles (BaFBr:
0.005Eu ²⁺) Got.

Example 2 In order to synthesize a stimulable phosphor precursor of europium-activated barium fluorobromide, BaB was used.
r ₂ aqueous solution (2.5 mol / l) 1800 ml, E
uBr ₃ aqueous solution (0.2 mol / L) 37.5 m
l, and 1162.5 ml of water (B)
ABR ₂ concentration: 1.5 mol / liter) were placed in a reactor 4 liter volume. The reaction mother liquor in this reactor is
C., and a 45-mm diameter screw-type stirring blade provided with a mixing chamber having a volume of about 100 ml around the periphery was rotated at 500 rpm to stir the reaction mother liquor so as to generate an upward flow from the mixing chamber. did.

NH ₄ F aqueous solution (10 mol / l) 1
50 ml and 150 ml of water are mixed, and this mixed solution 300
ml was added to the mixing chamber in the reaction mother liquor kept warm under the above stirring at an addition rate of 3 ml / min using a precision cylinder pump to form a precipitate. After completion of the addition, the mixture was kept warm and stirred for 2 hours to ripen the precipitate.

Next, the precipitate was separated by filtration and washed with 2 liters of methanol. Then, the washed precipitate is taken out, and 12
Vacuum drying was performed at 0 ° C. for 4 hours to obtain about 330 g of europium-activated barium fluorobromide crystals. The obtained europium-activated barium fluorobromide crystal was fired in the same manner as in Example 1 to obtain europium-activated barium fluorobromide stimulable phosphor particles (BaFBr: 0.005Eu ²⁺ ).

Example 3 In order to synthesize a stimulable phosphor precursor of europium-activated barium fluorobromide, BaB was used.
r ₂ aqueous solution (2.5 mol / l) 2400 ml, E
uBr ₃ aqueous solution (0.2 mol / L) 37.5 m
and a reaction mother liquor (BaB
(r ₂ concentration: 2.0 mol / l) was placed in a 4 liter reactor. The reaction mother liquor in this reactor was kept at 60 ° C., and a screw-type stirring blade having a diameter of 45 mm provided with a mixing chamber having a volume of about 100 ml was used to rotate it at 500 rpm. The reaction mother liquor was stirred to generate.

NH ₄ F aqueous solution (10 mol / l) 1
50 ml and 150 ml of water are mixed, and this mixed solution 300
ml was added to the mixing chamber in the reaction mother liquor kept warm under the above stirring at an addition rate of 3 ml / min using a precision cylinder pump to form a precipitate. After completion of the addition, the mixture was kept warm and stirred for 2 hours to ripen the precipitate.

Next, the precipitate was separated by filtration and washed with 2 liters of methanol. Then, the washed precipitate is taken out, and 12
Vacuum drying was performed at 0 ° C. for 4 hours to obtain about 330 g of europium-activated barium fluorobromide crystals. The obtained europium-activated barium fluorobromide crystal was fired in the same manner as in Example 1 to obtain europium-activated barium fluorobromide stimulable phosphor particles (BaFBr: 0.005Eu ²⁺ ).

Example 4 In order to synthesize a stimulable phosphor precursor of europium-activated barium fluorobromide, BaB was used.
3000 ml of aqueous r ₂ solution (2.5 mol / l) and aqueous EuBr ₃ solution (0.2 mol / l)
5 ml of the reaction mother liquor (BaBr ₂ concentration: 2.5 mol / l) was placed in a 4 liter reactor. The reaction mother liquor in this reactor was kept at 60 ° C., and a screw-type stirring blade having a diameter of 45 mm provided with a mixing chamber having a volume of about 100 ml was used to rotate it at 500 rpm. The reaction mother liquor was stirred to generate.

NH ₄ F aqueous solution (10 mol / l) 1
50 ml and 150 ml of water are mixed, and this mixed solution 300
ml was added to the mixing chamber in the reaction mother liquor kept warm under the above stirring at an addition rate of 3 ml / min using a precision cylinder pump to form a precipitate. After completion of the addition, the mixture was kept warm and stirred for 2 hours to ripen the precipitate.

Next, the precipitate was separated by filtration and washed with 2 liters of methanol. Then, the washed precipitate is taken out, and 12
Vacuum drying was performed at 0 ° C. for 4 hours to obtain about 330 g of europium-activated barium fluorobromide crystals. The obtained europium-activated barium fluorobromide crystal was fired in the same manner as in Example 1 to obtain europium-activated barium fluorobromide stimulable phosphor particles (BaFBr: 0.005Eu ²⁺ ).

Comparative Example NH ₄ B was used to synthesize a stimulable phosphor precursor of europium-activated barium fluorobromide.
r aqueous solution (4.5 mol / l) 220 ml, EuB
r ₃ aqueous solution (0.2 mol / liter) 25 ml, BaB
Reaction mother liquor (NH ₄ Br concentration: 480 ml of an aqueous r ₂ solution (2.5 mol / l) and 1295 ml of water:
0.5 mol / liter, BaBr ₂ concentration: 0.6 mol /
Liters) into a 4 liter volume reactor. The reaction mother liquor in this reactor was kept at 60 ° C., and a 45 mm-diameter Skrewuk type stirring blade provided with a mixing chamber having a volume of about 100 ml around the circumference was rotated at 500 rpm to flow upward from the mixing chamber. The reaction mother liquor was stirred to generate.

NH ₄ F aqueous solution (10 mol / l) 1
00 ml and 400 ml of an aqueous solution of BaBr ₂ (2.5 mol / l) were separately prepared. Into the mixing chamber in the reaction mother liquor, which was kept warm under the stirring, the NH ₄ F aqueous solution was added at a rate of 2 ml / min using separate precision cylinder pumps so that the ratio between NH ₄ F and BaBr ₂ became constant. , An aqueous solution of BaBr ₂ was simultaneously added at an addition rate of 8 ml / min to form a precipitate. After completion of the addition, the mixture was kept warm and stirred for 2 hours to ripen the precipitate.

Next, the precipitate was separated by filtration and washed with 2 liters of methanol. Then, the washed precipitate is taken out, and 12
After vacuum drying at 0 ° C. for 4 hours, about 220 g of europium-activated barium fluorobromide crystals were obtained. The obtained europium-activated barium fluorobromide crystal was fired in the same manner as in Example 1 to obtain europium-activated barium fluorobromide stimulable phosphor particles (BaFBr: 0.005Eu ²⁺ ).

[Measurement of Shape of Phosphor Particles] With respect to the shape of each phosphor particle obtained in Examples 1 to 4 and Comparative Example, a light diffraction type particle size distribution measuring device (manufactured by Horiba, Ltd.) LA-500) and a scanning electron microscope (JSM-5400LV, manufactured by JEOL Ltd.), and the following measurements were performed. The results are summarized in Table 3 below.

Median diameter of particle size: The value measured by a light diffraction type particle size distribution measuring device was used as it is. Particle size distribution: Calculated from a distribution table (FIG. 7) measured by a light diffraction type particle size distribution measuring device. Particle shape: It was determined by observing a photograph obtained with a scanning electron microscope. Particle aspect ratio: Calculated by measuring and averaging the aspect ratio of 200 particles in a photograph obtained by a scanning electron microscope.

[Production of radiation image conversion panel] As the material for forming the stimulable phosphor layer, each phosphor (BaFBr: 0.005Eu ²⁺ ) obtained in the above Examples 1 to 4 and Comparative Example was used.
356 g, 15.8 g of polyurethane resin (Desmolac 4125, manufactured by Sumitomo Bayer Urethane Co., Ltd.) and 2.0 g of bisphenol A type epoxy resin were added to a mixed solvent of methyl ethyl ketone-toluene (1: 1), and dispersed using a propeller mixer. Then, a coating solution having a viscosity of 25 to 30 PS was prepared. This coating solution was applied on a support of a polyethylene terephthalate film (250 μm thick) on which an undercoat layer (acrylic resin; Criscoat P1018GS, manufactured by Dainippon Ink and Chemicals, Inc., thickness: 20 μm) was formed using a doctor blade. And dried at 100 ° C. for 15 minutes to form a stimulable phosphor layer having a thickness of 150 to 300 μm.

Next, as a protective layer forming material, a fluororesin: fluoroolefin-vinyl ether copolymer (Lumiflon LF-100 manufactured by Asahi Glass Co., Ltd.) 70 g, a cross-linking agent: isocyanate (Sumitomo Bayer Urethane Co., Ltd.)
Desmodur Z4370) 25 g, bisphenol A
5 g of epoxy resin and silicone resin powder (KMP-590, manufactured by Shin-Etsu Chemical Co., Ltd., particle diameter 1-2 μm)
m) 10 g was added to a toluene-isopropyl alcohol (1: 1) mixed solvent to prepare a coating solution. This coating solution is applied to the stimulable phosphor layer side on the support on which the stimulable phosphor layer has been formed, using a doctor blade.
A heat treatment was performed at 20 ° C. for 30 minutes, followed by thermal curing and drying, to provide a protective layer having a thickness of 10 μm. According to the method described above, radiation image conversion panels having stimulable phosphor layers of various thicknesses including the phosphors obtained in Examples 1 to 4 and Comparative Example were obtained.

[Evaluation Method of Radiation Image Conversion Panel] Each of the obtained radiation image conversion panels was evaluated by the following method.
Each evaluation of sensitivity, sharpness, and granularity was performed. The evaluation results are shown in Table 3 below. Sensitivity: After irradiating each radiation image conversion panel with X-rays having a tube voltage of 80 kV, a He-Ne laser beam (wavelength: 63
(2.8 nm), and the stimulated emission intensity emitted from the stimulable phosphor layer was measured, and evaluated as a relative value when the result of Example 1 was set to 100. The result of the sensitivity indicates that the larger the value, the better the sensitivity.

Sharpness: Each radiation image conversion panel is irradiated with X-rays having a tube voltage of 80 kV through a CTF chart, and then scanned with a He-Ne laser beam (wavelength: 632.8 nm) to obtain an image of the CTF chart. Was. The contrast transfer function (CTF) was measured from the obtained image, and the sharpness was evaluated by the CTF value at a spatial frequency of 2 cycles / mm.

Granularity: Each radiation image conversion panel was uniformly irradiated with X-rays at a tube voltage of 80 kV, and then scanned with a He-Ne laser beam to obtain uniform exposure images. The granularity of the obtained image signal was measured as an RMS value, and evaluated as a relative value when the result of Example 1 was set to 100. The results of the graininess indicate that the smaller the value, the better the graininess.

[0079]

[Table 3]

The phosphors of Examples 1 to 4 are monodisperse as shown in FIG. 7, and have a σ / Dm of 50% as shown in Table 3.
On the other hand, the phosphor of the comparative example has σ / Dm of 5
It can be seen that the particle size distribution exceeds 0% and tends to spread. Further, the image quality of the radiation image conversion panels including the phosphors of Examples 1 to 4 was good in sensitivity, sharpness, and granularity balance as shown in Table 3, while the particle size distribution as in Comparative Example was good. The image quality of the panel using a wide phosphor showed a tendency to deteriorate.

[0081]

According to the present invention, the particle shape, particle aspect ratio, particle size (median diameter) of the rare earth activated alkaline earth metal fluorohalide-based stimulable phosphor contained in the radiation image conversion panel, By controlling the particle size distribution, the image quality (especially sharpness and structural noise) of the radiation image conversion panel can be improved. In addition, by combining the conditions for synthesizing the phosphor precursor in an aqueous solution, synthesis under a wider range of concentration conditions than in the prior art is possible, and the controllability of particle size and particle size distribution and the synthesis efficiency are further improved.

[Brief description of the drawings]

FIG. 1 shows the arrangement of a conventional plate-like rare earth activated alkaline earth metal fluorinated halide-based stimulable phosphor in a stimulable phosphor layer of a radiation image conversion panel, and the arrangement in the stimulable phosphor layer. It is a figure which shows the direction of light conduction typically.

FIG. 2 shows a diagram of 1 in a phosphor layer of a radiation image conversion panel.
It is a figure which shows typically the arrangement | sequence of the tetrahedral-type rare earth activated alkaline earth metal fluorohalide stimulable phosphor, and the direction of the photoconduction in the phosphor layer.

FIG. 3 is a graph showing a relationship between a median diameter (Dm) of particle size and sensitivity.

FIG. 4 is a graph showing the relationship between the median diameter (Dm) of the particle size and the erasure value.

FIG. 5 shows the concentration of BaBr ₂ in the reaction mother liquor, the rate of addition of an aqueous solution of an inorganic fluoride salt, and the median diameter (D
7 is a graph showing the relationship with m).

FIG. 6 is a diagram showing an example of an addition pattern in a precipitate generation step in the present invention.

FIG. 7 is a diagram showing the particle size distribution of the rare earth activated alkaline earth metal fluorinated halide stimulable phosphors obtained in Examples and Comparative Examples.

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) G21K 4/00 G21K 4/00 MF term (reference) 2G083 AA03 BB01 DD02 DD11 DD12 DD14 DD15 EE01 EE02 EE03 4G076 AA04 AA05 AA18 AC02 BA15 BA39 BD02 CA08 CA26 CA29 CA40 DA30 4H001 CA04 CF01 XA09 XA17 XA20 XA35 XA38 XA53 XA56 YA03 YA11 YA19 YA37 YA55 YA58 YA59 YA62 YA63 YA64 YA65 YA69 YA70

Claims (9)

[Claims] 1. A basic composition formula (I): Ba _{1 -x} M ^II _x FX: y M ^I , zLn (I) [where M ^II is at least one kind selected from the group consisting of Sr and Ca. represents an alkaline earth metal, M ^I is Li,
X represents at least one alkali metal selected from the group consisting of Na, K, Rb and Cs, and X represents Cl, Br and I
Ln represents Ce, Pr, Sm, Eu, Gd, Tb, Tm
And at least one rare earth element selected from the group consisting of Yb and Xb, x, y and z are 0 ≦ x ≦ 0.5, 0 ≦
Numerical values in each range of y ≦ 0.05 and 0 <z ≦ 0.2 are shown. And the median diameter (Dm) of the particle size is 1 to 10 μm, and the standard deviation of the particle size distribution is σ / Dm
Is in the range of 50% or less, and the particle aspect ratio is in the range of 1.0 to 2.0. A rare earth activated alkaline earth metal fluoride halide stimulable phosphor. 2. The stimulable phosphor of the rare earth activated alkaline earth metal fluoride halide type according to claim 1, wherein the particle shape is a tetrahedral type. 3. Ln in the basic composition formula (I) is Ce
3. The stimulable phosphor of rare earth activated alkaline earth metal fluoride halide system according to claim 1, wherein the phosphor is Eu. 4. A method for producing a rare earth activated alkaline earth metal fluorinated halide stimulable phosphor according to claim 1, wherein BaX ₂ ; a water-soluble compound of Ln; X of the composition formula (I)
When is not 0, further halides, nitrates, nitrites or acetates of M ^II ; when y of the basic composition formula (I) is not 0, further halides, nitrates of M ^I ;
An aqueous solution containing nitrite or acetate; and
A mother liquor preparation step for preparing a reaction mother liquor having a BaX ₂ concentration of 2.5 mol / l or less when X is Cl or Br and 5.0 mol / l or less when X is I While maintaining the reaction mother liquor at a temperature of 20 to 100 ° C., when the amount of the precipitate of the phosphor precursor crystal finally obtained is N, the phosphor precursor crystal generated during the addition is The precipitation rate is adjusted so that the amount of the precipitate is in the range of 0.001 N / min to 10 N / min, and an aqueous solution of an inorganic fluoride salt is added to produce a precipitate of a phosphor precursor crystal. A generating step, a separating step of separating the precipitate of the phosphor precursor crystal from the aqueous solution, and a firing step of firing the separated precipitate of the phosphor precursor crystal while avoiding sintering. Characterized rare earth activated alkaline earth metal halo fluoride Method of manufacturing the emission product stimulable phosphor. 5. The stimulable phosphor according to claim 4, wherein the inorganic fluoride salt is ammonium fluoride or an alkali metal fluoride. Production method. 6. The rare earth-activated alkaline earth metal fluoride halide stimulant according to claim 4, wherein a precision cylinder pump is used for adding the inorganic fluoride aqueous solution in the precipitation forming step. A method for producing a phosphor. 7. The method according to claim 4, wherein the rate of addition of the inorganic fluoride aqueous solution in the precipitation forming step is adjusted to 0.01 N / min to 1.0 N / min. A method for producing a rare earth activated alkaline earth metal fluoride halide stimulable phosphor. 8. The method according to claim 4, wherein the rate of addition of the aqueous solution of inorganic fluoride in the step of forming a precipitate changes at a constant rate or continuously or intermittently with respect to the time of addition. 5. The method for producing a rare earth-activated alkaline earth metal fluorohalide-based stimulable phosphor according to item 1. 9. A radiation image conversion panel having a stimulable phosphor layer containing a stimulable phosphor, wherein the stimulable phosphor is a rare earth-activated alkaline earth according to any one of claims 1 to 3. A radiation image conversion panel, which is a fluorinated metal-based stimulable phosphor.