JP2001329262A - Method for producing phosphor precursor crystal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a novel method for producing a phosphor precursor crystal whereby the control width of particle size and particle shape is widened and their controllability can be improved. SOLUTION: In this method for producing a phosphor precursor crystal, a reaction mother liquor and an additional liquor are reacted in the presence of a water-soluble organic monomer and/or a water-soluble organic polymer containing at least one kind of group selected from among carboxyl, hydroxyl, amino, nitro, sulfone, phosphone, fluoro, chloro, and iodo groups. An embodiment wherein the water-soluble monomer and water-soluble polymer contain carboxyl groups is preferable.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phosphor for a radiation image conversion panel and a method for producing a precursor crystal of a phosphor for a radiographic intensifying screen used for X-ray photography or the like.

[0002]

2. Description of the Related Art A phosphor precursor crystal is an intermediate product of a phosphor, and a phosphor is obtained by firing the phosphor precursor crystal at a predetermined temperature. The phosphor is used as a material for a radiation image conversion panel (storage phosphor sheet). The radiation image conversion panel can be used as an alternative to the conventional radiography, for example, as described in JP-A-55-12145. It is used for a radiation image recording / reproducing method as described above. In this method, radiation transmitted through a subject or emitted from a subject is absorbed by a stimulable phosphor of a radiation image conversion panel, and then the stimulable phosphor is irradiated with electromagnetic waves such as visible light and infrared light (excitation light). Light) to excite the radiation energy accumulated in the stimulable phosphor as fluorescence (stimulated luminescence),
This fluorescence is read photoelectrically to obtain an electric signal, and then 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 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. Furthermore, in the conventional radiographic method, radiographic film is consumed for each photographing,
In this radiation image conversion method, since the radiation image conversion panel can be used repeatedly, it is advantageous in terms of resource conservation and economic efficiency.

[0004] As the radiation image recording / reproducing method has been put to practical use, there is an increasing demand for further improving the performance of the stimulable phosphor. In order to achieve high performance, it is extremely important to control the particle shape of the phosphor particles. For that purpose, it is necessary to obtain the phosphor precursor crystals by a liquid phase reaction and by a uniform reaction. It is. For example, JP-A-7-2
No. 33369 and JP-A-10-147778 disclose a method for producing a tetrahedral rare earth activated alkaline earth metal fluorinated halide-based stimulable phosphor in which the particle shape and the particle aspect ratio are controlled by a liquid phase reaction. It is shown.
In the conventional liquid phase synthesis, particle size and particle shape were controlled by the ion concentration of the reaction solution and the rate of addition of the reaction solution. This method is suitable for controlling the particle size and particle shape because the ion concentration of the reaction solution becomes dominant, but there is a certain limit to such control, and the particle size and particle size exceeding the control range are limited. The shape cannot be obtained, and it is desired to further increase the control width and controllability of the particle size and the particle shape.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional problems and achieve the following objects. That is, an object of the present invention is to provide a novel method for producing a phosphor precursor crystal that can increase the control range of the particle size and the particle shape and improve the controllability thereof.

[0006]

According to the present invention, as a result of intensive studies, in the liquid phase reaction of phosphor precursor crystals, a water-soluble organic monomer or a water-soluble organic polymer having a specific group is added to a reaction solution. By adding, the crystal growth of the phosphor precursor crystal can be suppressed, and only the growth of a specific crystal plane can be controlled. As a result, particles in a range that was difficult to achieve conventionally can be easily synthesized, The present inventors have found that the control range of the size and the particle shape can be expanded, and have completed the present invention.

The means for solving the above-mentioned problems are as follows. That is, <1> carboxyl group, hydroxyl group, amino group,
Presence of at least one of a water-soluble organic monomer and a water-soluble organic polymer containing at least one group selected from the group consisting of a nitro group, a sulfone group, a phosphone group, a fluoro group, a chloro group, a bromo group and an iodo group. The following is a method for producing a phosphor precursor crystal, which comprises reacting a reaction mother liquor with an additive solution. <2> The method for producing a phosphor precursor crystal according to <1>, wherein the water-soluble organic monomer and the water-soluble organic polymer include a carboxyl group. <3> The method for producing a phosphor precursor crystal according to <2>, wherein the water-soluble organic monomer is acrylic acid. <4> When the total amount of the water-soluble organic monomer and water-soluble organic polymer is N, where N is the amount of the precipitate of the phosphor precursor crystal finally obtained, the amount is 1 × 10 ⁻⁶ N to 1x
10 is a method for producing a phosphor precursor crystals according ⁰ N a is the items <1> or <3>. <5> The reaction mother liquor contains an aqueous solution of an alkaline earth metal halide other than fluoride and / or an aqueous solution of ammonium halide other than fluoride, and the additive liquid contains an aqueous solution of a fluoride salt. 4> The method for producing a phosphor precursor crystal according to any one of the above items. <6> The method for producing a phosphor precursor crystal according to <5>, wherein a main component of the phosphor precursor crystal is represented by the following basic composition formula (I). ^{_{(Ba 1-a, M II}} a) FX ··· (I) [ where, M ^II represents at least one alkaline earth metal selected from the group consisting of Sr and Ca, X is Cl, B
represents at least one halogen selected from the group consisting of r and I, and a represents a numerical value in the range of 0 ≦ a <1. ]

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. The method for producing a phosphor precursor crystal of the present invention includes a carboxyl group, a hydroxyl group, an amino group, a nitro group, a sulfone group, a phosphone group, a fluoro group, a chloro group, a bromo group and at least one selected from the group consisting of iodine groups. The reaction mother liquor and the addition liquid are reacted in the presence of at least one of a water-soluble organic monomer and a water-soluble organic polymer containing one type of group (hereinafter, referred to as “specific group”). The water-soluble organic monomer and the water-soluble organic polymer containing the specific group function as a crystal habit controlling agent that causes a difference in the growth rate of the crystal plane. This is thought to be because the water-soluble organic monomer or water-soluble organic polymer containing the specific group is adsorbed on a plane parallel to the C axis of the crystal, thereby suppressing the growth of particles in that direction. Can be Therefore, the function is clearly different from gelatin or the like used for preventing aggregation of particles.

When the reaction mother liquor and the additive solution are reacted under the condition that the water-soluble organic monomer containing the specific group and the water-soluble organic polymer are not present at all, for example, if columnar particles are obtained, For example, by the presence of at least one of the water-soluble organic monomer containing the specific group and the water-soluble organic polymer, particles having a larger particle aspect ratio than the particles but having a smaller particle size (median diameter) are synthesized. can do. This is, as mentioned above,
This is because, by controlling only the growth of a specific crystal plane, it is possible to easily control the particle shape and particle size that have been difficult to achieve until now. Here, the particle aspect ratio refers to a value of long side ÷ short side.

At least one of the water-soluble organic monomer containing the specific group and the water-soluble organic polymer may be put in the reaction mother liquor or may be added together with the addition liquid. If present during the reaction with
You may add using any method.

In the method for producing a phosphor precursor crystal according to the present invention, the specific group may be a carboxyl group.
It is preferable from the viewpoint of adsorptivity to the crystal surface. Specific examples of the water-soluble organic monomer containing the specific group include acrylic acid and methacrylic acid. Among them, acrylic acid is particularly preferable in view of the effect of suppressing the growth of a specific crystal plane. Further, specific examples of the water-soluble organic polymer containing the specific group include polyacrylic acid and polymethacrylic acid. Among them, polyacrylic acid is preferred in terms of the effect of suppressing the growth of a specific crystal plane. Is particularly preferred. These may be used alone or in combination of two or more.

[0012] The total amount of the water-soluble organic monomer containing the specific group and the water-soluble organic polymer is as follows, where N is the amount of the precipitate of the phosphor precursor crystal finally obtained.
Preferably, it is 1 × 10 ⁻⁶ N to 1 × 10 ⁰ N.
More preferably, it is from × 10 ⁻⁴ N to 1 × 10 ⁻³ N.
If the total amount is less than 1 × 10 ⁻⁶ N, the growth inhibitory effect may not be sufficient, while the total amount may be 1 × 10 ⁻⁶ N.
^If it exceeds ⁰ N, normal crystal growth may be inhibited.

In the method for producing a phosphor precursor crystal according to the present invention, if at least one of the water-soluble organic monomer containing the specific group and the water-soluble organic polymer is present, the reaction mother liquor and the additive liquid are added. Although the composition of is not particularly limited, the reaction mother liquor contains an aqueous solution of an alkaline earth metal halide other than fluoride and / or an aqueous solution of ammonium halide other than fluoride, and the additive solution is a fluoride. It is preferable to include an aqueous salt solution.

In particular, the method for producing a phosphor precursor crystal of the present invention is suitably used for producing a phosphor precursor crystal whose main component is represented by the following basic composition formula (I). ^{_{(Ba 1-a, M II}} a) FX ··· (I) [ where, M ^II represents at least one alkaline earth metal selected from the group consisting of Sr and Ca, X is Cl, B
represents at least one halogen selected from the group consisting of r and I, and a represents a numerical value in the range of 0 ≦ a <1. ]

A in the above basic composition formula (I) is preferably 0.5 or less. In addition, the above basic composition formula (I)
Does not indicate that the composition is stoichiometrically F: X = 1: 1, but a compound having a PbFCl type crystal structure represented by (Ba _1-a , M ^II _a ) FX Is shown. In general, a state in which many F ⁺ (X ⁻ ) centers, which are vacancies of X ⁻ ions, are generated in the BaFX crystal is preferable from the viewpoint of increasing the photostimulation efficiency with respect to light of 600 to 700 nm. At this time, F is often slightly more than X.

When the intended phosphor precursor crystal is a precursor crystal of a rare earth activated alkaline earth metal fluorohalide phosphor represented by the following basic composition formula (II):
Although not shown in the basic composition formula (I), the phosphor precursor crystal contains a rare earth component as an activator. ^{_{(Ba 1-a, M II}} a) FX: zLn ··· (II) wherein, M ^II, X, and a are respectively synonymous with basic composition formula (I), Ln is, Ce, Pr, Sm, Eu, T
represents at least one rare earth element selected from the group consisting of b, Dy, Ho, Nd, Er, Tm, and Yb, and z represents a numerical value in the range of 0 <z <0.2.

Although omitted in the basic composition formula (I), the following additives may be added as necessary. bA, wN ^I , xN ^II , yN ^III where N ^I represents at least one alkali metal compound selected from the group consisting of Li, Na, K, Rb and Cs, and N ^II is Mg and Be. at least one rare earth metal compound selected from the group consisting of the N ^III is, Al, Ga, in, Tl , Sc,
It represents at least one trivalent metal compound selected from the group consisting of Y, La, Gd and Lu. As these metal compounds, it is preferable to use halides as described in JP-A-59-75200, but it is not limited thereto.

A represents a metal oxide such as Al ₂ O ₃ , SiO ₂ or ZrO ₂ . In order to prevent sintering between BaFX particles preferably has low reactivity with ^{_{(Ba 1-a, M II}} a) FX ultra fine average particle size below 0.1μm of primary particles, especially Al ₂ O ₃ is preferred. Note that b, w, x
And y are the charged addition amounts when the number of moles of (Ba _1-a , M ^II _a ) FX is 1, and 0 ≦ b ≦ 0.5, 0 ≦ w ≦
2. Numerical values in the ranges of 0 ≦ x ≦ 0.3 and 0 ≦ y ≦ 0.3 are respectively shown. These figures do not represent the element ratios contained in the final composition for additives that are reduced by baking or subsequent washing. Some of the compounds remain as added in the final composition, while others react with BaFX or are taken up.

In addition, as required, Japanese Patent Application Laid-Open No. 55-121
No. 45, Zn and Cd compounds;
TiO which is a metal oxide described in No. 0078_Two, Be
O, MgO, CaO, SrO, BaO, ZnO, Y
_TwoO_Three, La_TwoO_Three, In_TwoO_Three, GeO _Two, SnO_Two, Nb_Two
O_Five, Ta_TwoO_Five, ThO_TwoJP-A-56-116777
And Zr and Sc compounds described in JP-A-57-23673.
Compound B described in JP-A-57-23675
As and Si compounds described in JP-A-59-27980.
Tetrafluoroborate compound described in JP-A-59-472.
No. 89 hexafluorosilicic acid, hexafluoro
Monovalent of titanic acid and hexafluorozirconic acid
Hexafluoro compound comprising divalent salt
V, Cr, Mn, Fe, C described in No. 59-56480
o, and a transition metal compound such as Ni
Good. However, the object of the present invention includes the above-mentioned additives.
Not limited to phosphor precursor crystals
Considered as an earth metal fluorohalide-based phosphor precursor crystal
Anything that basically contains the composition
You may.

The phosphor precursor crystal represented by the basic composition formula (I) usually has an aspect ratio in the range of 1.0 to 5.0. When the phosphor precursor crystal obtained by the production method of the present invention has a particle aspect ratio of 1.0 to 2.0, the median diameter (Dm) of the particle size is 1 to 10 μm.
(More preferably, 3 to 7 μm) and σ / Dm is 50% when the standard deviation of the particle size distribution is σ.
It is preferably in the range below (more preferably 40% or less). On the other hand, the particle aspect ratio is 2.0 to 5.0.
, The median diameter (Dm) of the particle size is 1 to 2
Σ / D in the range of 0 μm (more preferably 3 to 10 μm) and the standard deviation of the particle size distribution is σ.
m is preferably in the range of 50% or less (more preferably, 40% or less). In addition, as the shape of the particles, there are a rectangular parallelepiped type, a regular hexahedral type, a regular octahedral type, an intermediate polyhedral type thereof, a tetrahedral type, etc., and a tetrahedral type is preferable, but the particle aspect ratio, particle size and particle size distribution If it satisfies, it is not necessarily limited to the tetrahedral type.

The alkaline earth metal fluorohalide-based phosphor precursor crystal represented by the basic composition formula (I) is:
Production method (A) described in JP-A-7-233369
And (B), and further produced by the following production method (C).

(A) BaX ₂ ; when a in the formula (I) is not 0, a halide, nitrate, nitrite or acetate of M ^II ; a water-soluble organic monomer containing the specific group And at least one of a water-soluble organic polymer; and a BaX ₂ concentration after dissolving them, wherein X is Cl or Br.
A mother liquor preparation step of preparing a reaction mother liquor of not more than 5.0 mol / l, when X is I, not more than 5.0 mol / l, and finally obtaining the reaction mother liquor while maintaining the reaction mother liquor at a temperature of 20 to 100 ° C. 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. To adjust the aqueous solution of the inorganic fluoride salt (additive solution)
And a separation step of separating the precipitate of the phosphor precursor crystal from the aqueous solution. This is a method for producing a phosphor precursor crystal.

(B) NH ₄ X; when a in the basic composition formula (I) is not 0, a halide, nitrate, nitrite or acetate of M ^II ; a water-soluble organic compound containing the specific group A reaction mother liquor is prepared which is an aqueous solution containing at least one of a monomer and a water-soluble organic polymer, and has an NH ₄ X concentration of 2.0 mol / L or more and 4.5 mol / L or less after dissolution. A mother liquor preparing step, and maintaining the reaction mother liquor at a temperature of 20 to 100 ° C., where the amount of the precipitate of the phosphor precursor crystal finally obtained is N, the phosphor produced during the addition and the amount of the precipitate of the precursor crystals by adjusting the addition rate so that the range of 0.001 N / min 10 N / min, an aqueous solution of an inorganic fluoride salt and an aqueous solution of BaX ₂ (additive solution), an inorganic fluoride Ratio of fluoride of fluoride salt to BaX ₂ And a separation step of separating the precipitates of the phosphor precursor crystals from the aqueous solution. This is a method for producing an earth metal fluorohalide-based phosphor precursor crystal.

(C) BaX ₂ ; BaCO ₃ ; when a in the formula (I) is not 0, a halide, nitrate, nitrite or acetate of M ^II ; A water-soluble suspension containing at least one of an organic monomer and a water-soluble organic polymer, wherein the concentration of BaX ₂ after dissolving them is such that X is Cl or Br.
And a mother liquor preparation step of preparing a reaction mother liquor of not more than 2.5 mol / l 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 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. Adjusting the rate of addition so that an aqueous solution (addition liquid) of hydrofluoric acid is added to form a precipitate of the phosphor precursor crystals; and a precipitation step of the phosphor precursor crystals. And a separating step of separating the substance from the aqueous solution.

In the production methods (A), (B) and (C), at least one of the water-soluble organic monomer and the water-soluble organic polymer containing the specific group is added to the reaction mother liquor. However, it is not limited to this,
For example, it may be added together with the additive liquid.

In the present invention, the term "aqueous solution" refers to a solution obtained by dissolving a "solute" in an "aqueous medium". Also,
The term “aqueous medium” is a concept that includes not only water, but also a liquid having a high affinity for water (eg, alcohol or the like) singly or in combination, 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, “solute” refers to the type of aqueous solution (raw material solution, reaction mother liquor,
And an aqueous solution for addition.

In the production methods (A) and (B), barium fluoride powder may be used instead of the inorganic fluoride salt aqueous solution. In order to control the particle shape, particle aspect ratio, particle size, and particle size distribution of the phosphor precursor crystals in a wide range, a synthesis method combining the ion concentration of the reaction mother liquor and the addition rate of the additive solution can also be used. . Furthermore, a synthesis method in which an additive such as an activator or an alkali metal compound is added simultaneously with an aqueous solution of an inorganic fluoride salt in order to improve the emission characteristics of the phosphor finally obtained by firing the phosphor precursor crystal. May be used.

The manufacturing methods (A) and (B) will be described separately for each step. [Production method (A)] i) Mother liquor preparation step First, a raw material compound other than a fluorine compound is dissolved using an aqueous medium to prepare a reaction mother liquor. That is, BaX ₂ and / or at least one of a water-soluble organic monomer and a water-soluble organic polymer containing the specific group, and if necessary, L
n water-soluble compound, M ^II halide, nitrate, nitrite or acetate are placed in an aqueous medium, mixed well and dissolved to prepare an aqueous solution (reaction mother liquor) in which these components are dissolved. At this time, X is the BaX ₂ concentration in the case of Cl or Br 2.5 mole / liter or less, if X is I so BaX ₂ concentration of 5.0 mol / liter or less, BaX ₂ and aqueous solvent Is adjusted in advance. L
Examples of the water-soluble compound of n include halides (chlorides, bromides, etc.), nitrates, acetates, and the like of the rare earth elements. If desired, a small amount of acid, ammonia, water-insoluble metal oxide fine particles, or the like may be added to the reaction mother liquor. The obtained reaction mother liquor is maintained at 20 to 100 ° C, preferably 40 to 80 ° C, and stirred.

Ii) Precipitation Forming Step While maintaining the reaction mother liquor at a temperature of 20 to 100 ° C.,
To this is added an aqueous solution of an inorganic fluoride salt using a known metering pump, for example, a precision cylinder pump, a precision gear pump, a tube pump, a diaphragm pump, or the like.
Among these, preferably added using a precision cylinder pump, to grow the crystal nuclei of the phosphor precursor crystal,
A precipitate of the phosphor precursor crystal is obtained. As the inorganic fluoride salt, ammonium fluoride, alkali metal fluoride,
Alkaline earth metal fluorides, transition metal fluorides, hydrofluoric acid, and the like, among which ammonium fluoride and alkali metal fluorides are preferred in terms of solubility, luminescence characteristics, and pH change during the reaction. .

When the amount of the precipitate of the phosphor precursor crystals finally obtained in the addition of the aqueous solution of the inorganic fluoride salt is defined as 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. If the addition speed is higher than the above, it may not be possible to take sufficient time for uniform mixing.On the other hand, if the addition speed is lower than the above, the residence time in the reaction cell may be too long to cause crystal growth in the cell. There is. In order to precisely adjust the rate of addition, it is preferable to add with a precision cylinder pump. Further, this addition is usually performed at a constant addition rate, but the addition rate is continuously or intermittently n-order function (n = 1, 2, 3), exponential function, differential function with respect to the addition time. May be changed. This addition is preferably carried out in the region where the stirring is particularly vigorous.

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.

[Production Method (B)] i) Mother Liquid Preparation Step First, a raw material compound other than a fluorine compound is dissolved in an aqueous medium to prepare a reaction mother liquor. That is, at least one of NH ₄ X, a water-soluble organic monomer containing the specific group and a water-soluble organic polymer, and if necessary, L
n water-soluble compound, M ^II halide, nitrate, nitrite or acetate are placed in an aqueous medium, mixed well and dissolved to prepare an aqueous solution (reaction mother liquor) in which these components are dissolved. At this time, the NH ₄ X and the aqueous solvent are mixed so that the NH ₄ X concentration becomes 2.0 mol / L or more and 4.5 mol / L or less, preferably 3.0 mol / L or more and 4.5 mol / L or less. Adjust the volume ratio of. Examples of the water-soluble compound of Ln include halides (chlorides, bromides, and the like) of the rare earth elements, nitrates, acetates, and the like. If desired, a small amount of acid, ammonia, water-insoluble metal oxide fine particles, or the like may be added to the reaction mother liquor. The obtained reaction mother liquor is maintained at 20 to 100 ° C, preferably 40 to 80 ° C, and stirred.

Ii) Precipitation Forming Step While maintaining the reaction mother liquor at a temperature of 20 to 100 ° C.,
An aqueous solution of an inorganic fluoride salt and an aqueous solution of BaX ₂ are simultaneously added thereto, so that the molar ratio of fluorine of the inorganic fluoride salt to BaX ₂ is kept constant, a known metering pump, for example, a precision cylinder pump, Add using a precision gear pump, tube pump, diaphragm pump, etc. Of these, the addition is preferably performed using a precision cylinder pump to grow the crystal nuclei of the phosphor precursor crystals and obtain a precipitate of the phosphor precursor crystals. The inorganic fluoride salt used here is the same as in the production method (A).

When adding an aqueous solution of an inorganic fluoride salt and an aqueous solution of BaX ₂ , and the amount of the precipitate of the phosphor precursor crystal finally obtained is defined as N, the phosphor precursor crystal formed during the addition is formed. Of the precipitate of 0.001 N / min to 10 N /
Min (more preferably 0.01 N / min to 1.0 N / min).
It is preferable to add the aqueous solution of the inorganic fluoride salt and the aqueous solution of BaX ₂ by adjusting the addition rate so as to be within (minute range). If the addition speed is higher than the above, it may not be possible to take sufficient time for uniform mixing.On the other hand, if the addition speed is lower than the above, the residence time in the reaction cell may be too long to cause crystal growth in the cell. There is. In order to precisely adjust the rate of addition, it is preferable to add with a precision cylinder pump. Further, this addition is usually carried out at a constant addition rate, but the addition rate is continuously n-order function (n = 1, 2, 3), exponential function, differential function,
It may change intermittently. This addition is preferably carried out in the region where the stirring is particularly vigorous.

Iii) Separation Step The precipitate of the phosphor precursor crystal obtained as described above is subjected to a separation step of separating from the aqueous solution to obtain the desired alkaline earth metal fluoride halide-based phosphor precursor crystal. can get. Details of the separation step are the same as those in the manufacturing method (A).

The alkaline earth metal fluorohalide-based phosphor precursor crystals obtained by the above-mentioned production methods (A), (B) and (C) are phosphor raw materials containing the phosphor precursor crystals. Through a raw material mixing step of obtaining a phosphor raw material mixture, a firing step of firing the phosphor raw material mixture, and, if necessary, other steps of washing, drying, sieving, drying, and the like. Thus, a rare earth activated alkaline earth metal fluorohalide-based phosphor can be obtained. The phosphor is suitably used as a phosphor material for forming a phosphor layer of a radiation image conversion panel. Hereinafter, the raw material mixing step, the firing step, and the like will be described.

(Raw Material Mixing Step) The phosphor raw material used in the raw material mixing step is not particularly limited as long as it contains the phosphor precursor crystal obtained by the method for producing a phosphor precursor crystal of the present invention. The phosphor raw material obtained by any of the above methods may be contained. As the phosphor material,
The following phosphor raw materials (1) to (6) can be exemplified. (1) BaFCl, BaFBr or B to which a rare earth element is added, which is obtained by the method for producing a phosphor precursor crystal of the present invention.
aFI. When used as a phosphor raw material, alkaline earth metals other than Ba and alkali metals may not be contained at this time. (2) BaF ₂ , BaCl ₂ , BaBr ₂ , BaI ₂ , Ba
At least one barium halide selected from the group consisting of FCl, BaFBr and BaFI. (3) MgF ₂ , MgCl ₂ , MgBr ₂ , MgI ₂ , Ca
F ₂ , CaCl ₂ , CaBr ₂ , CaI ₂ , SrF ₂ , Sr
At least one alkaline earth metal halide selected from the group consisting of Cl ₂ , SrBr ₂ and SrI ₂ . (4) LiF, LiCl, LiBr, LiI, NaF,
NaCl, NaBr, NaI, KF, KCl, KBr,
KI, RbF, RbCl, RbBr, RbI, CsF,
At least one alkali metal halide selected from the group consisting of CsCl, CsBr and CsI. (5) At least one metal oxide selected from the group consisting of Al ₂ O ₃ , SiO ₂ and ZrO ₂ . (6) Rare earth element compounds such as halides, oxides, nitrates and sulfates (Ce, Pr, Nd, Pm, Sm, Eu,
At least one compound selected from the group consisting of Gd, Tb, Dy, Ho, Er, Tm, and Yb). If desired, further ammonium halide (NH
₄ X ', wherein X' represents F, Cl, Br, or I. ) May be used as the flux.

The phosphor raw material mixture is prepared by arbitrarily selecting a desired raw material from each of the phosphor raw materials (1) to (6), and selecting a composition ratio corresponding to the basic composition formula (I). The phosphor raw material mixture is prepared by weighing and mixing stoichiometrically as much as possible. The method for preparing the phosphor raw material mixture can be appropriately selected from known mixing methods, and for example, by the following methods (i) to (iv):
A phosphor raw material mixture may be prepared. (I) A method in which the phosphor raw materials (1) to (6) are weighed and simply mixed. (Ii) The phosphor raw materials (1) to (5) are weighed and mixed, and the mixture is heated at a temperature of 100 ° C. or higher for several hours, and then the phosphor material (6) is mixed with the obtained heat-treated product. Preparation method. (Iii) A method in which the phosphor raw materials (1) to (6) are weighed and mixed, and the mixture is heated at a temperature of 100 ° C. or higher for several hours to prepare the mixture. (Iv) The phosphor raw materials (1) to (5) are mixed in the form of a suspension, and the suspension is heated, preferably 50 to 2 times.
A preparation method in which the phosphor material (6) is mixed with the obtained dried substance after drying under reduced pressure, vacuum drying, spray drying, or the like at 00 ° C. As a modification of the preparation method (iv), a preparation method (iv-2) in which the phosphor materials (1) to (6) are mixed in a suspension state and the suspension is dried,
Alternatively, in the case of preparing by performing firing twice or more, the phosphor raw materials (1) to (3) are mixed in a suspension state, and the phosphor raw materials (4) to (5) are mixed after the primary firing. After the addition, the suspension is heated, preferably at 50-200 ° C.
Drying under reduced pressure, vacuum drying, spray drying, etc.
A preparation method (iv-3) of mixing the phosphor material (6) with the obtained dried product, and the like can also be suitably mentioned.

Further, in mixing the phosphor raw materials, a preparation method (v) utilizing a means capable of imparting a shearing force, and a means capable of controlling various conditions such as addition of each phosphor raw material and timing of mixing were employed. It can also be prepared by the preparation method (vi). The mixing apparatus used for the mixing in the preparation methods (v) and (vi) can be appropriately selected from known mixing apparatuses, and includes, for example, various mixers, a V-type blender, a ball mill, a rod mill, and a jet. mill,
An automatic mortar and the like can be mentioned.

In the production of the phosphor represented by the basic composition formula (II), the following various additives may be added for the purpose of further improving the stimulating light emission amount, the erasing performance and the like. An element other than the elements included in the basic composition formula (II),
For example, a non-metallic element represented by B, O, S, As, A
amphoteric elements represented by l, Ge, Sn, V, Be, M
Examples include metal elements represented by n, Fe, Ni, Co, Cu, and Ag, as well as a tetrafluoroborate compound and a hexafluoro compound. When the above-mentioned additive component is added, the additive component is added and mixed when the phosphor raw materials are weighed and mixed or before firing.

(Firing Step) Before the firing step of the phosphor raw material mixture, a preliminary firing step may be performed. The pre-baking step is a step of pre-baking the phosphor raw material mixture in a temperature range of 200 to 900 ° C. and lower than the firing temperature in the baking step for 0.1 to 10 hours. The sintering in the general sintering step is responsible for all the functions of imparting photostimulated luminescence properties to the obtained phosphor, such as synthesis of phosphor crystals (mixed crystal) at high temperature and diffusion of activator into the crystals. On the other hand, one of the objects of the preliminary firing is to synthesize the phosphor crystals (mixed crystal) at a temperature lower than the temperature at the time of the firing. By performing the role of the preliminary firing in this way, the role of the main firing in the subsequent firing step is reduced, and the emission characteristics of the obtained phosphor can be more freely controlled.

Also, since the pre-baking does not have the function of imparting the photostimulated luminescent property to the phosphor, it does not require strict atmosphere control unlike the main baking, and therefore, the pre-baking is performed in a firing furnace such as an atmosphere furnace. Since it is not necessary to perform the process, the process can be performed in a furnace having a simple structure. Since various components contained in the phosphor raw material mixture to be scattered are scattered in advance by the calcination, the sintering hardly scatters in the subsequent sintering, and the sintering furnace is hardly polluted in the sintering. Suppression of the contamination of the firing furnace, which requires strict atmosphere management, leads to stabilization of the emission characteristics of the obtained phosphor and reduction of the load of maintenance work. From the viewpoint of stain prevention,
The raw material to be fired in the temporary firing is not necessarily a phosphor raw material mixture, and the individual raw materials before mixing may be temporarily fired individually, and the temporarily fired raw materials may be mixed and finally fired. The preliminary firing is performed as described above. The phosphor material mixture after pre-baking does not need to be crushed or the like, but it is preferable to easily loosen it in a mortar or the like in view of the phosphor particle size and the uniformity of the phosphor material.

The rare earth activated alkaline earth metal fluoride halide-based phosphor is fired by the following firing method. That is, a step of filling the phosphor raw material mixture mixed in the raw material mixing step or pre-fired in the pre-firing step into a heat-resistant container such as a quartz boat or a quartz crucible, and the phosphor raw material mixture filled in the heat-resistant container. , Put it in the core of the electric furnace,
At a temperature of 500 to 1000 ° C. for 0.5 to 12 hours, a neutral atmosphere such as a nitrogen gas atmosphere, an argon gas atmosphere, a nitrogen gas atmosphere containing a small amount of hydrogen gas, a carbon dioxide atmosphere containing carbon monoxide, and the like. Baking in a weak reducing atmosphere, a reduced pressure atmosphere, or a trace oxygen introduction atmosphere. In the above-described firing method, a trace amount oxygen introducing method, a firing step incorporating a slow cooling step, a cooling step in which the atmosphere is controlled, and the like may be combined for the purpose of improving the emission characteristics of the obtained phosphor. Through the above steps, the desired rare earth activated alkaline earth metal fluorohalide-based phosphor can be obtained.

(Other Steps) In the phosphor fired in the firing step, post-treatment is preferably performed since the phosphor particles may cause slight sintering or agglomeration. Dissolve sintering and aggregation of phosphor particles,
The loosening process is performed for the purpose of increasing the yield of the phosphor. Furthermore, when the phosphor particles are strongly sintered and grow large by firing, and used for the phosphor layer of the radiation image conversion panel, the image quality of the panel is remarkably high. A sieving step is performed for the purpose of removing phosphor particles having a large particle size that reduces the particle size. Finally, a general drying step is performed to obtain the desired rare earth activated alkaline earth metal fluorohalide-based phosphor.

[0045]

EXAMPLES Examples of the present invention will be described below, but the present invention is not limited to these examples. Example 1 In order to synthesize a phosphor precursor of europium-activated barium fluorobromide, an aqueous solution of BaBr ₂ (2.5
Mole / liter) 1200 ml, EuBr ₃ aqueous solution (0.2 mole / liter) 37.5 ml, acrylic acid 0.1 as a water-soluble organic monomer having the specific group
Reaction mother liquor (BaB) consisting of 1 g and 1762.5 ml of water
(r ₂ concentration: 1.0 mol / l) was placed in a reaction vessel having a volume of 4 liters. The reaction mother liquor in the reaction
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.

150 ml of an aqueous solution of ammonium fluoride (10 mol / l) and 150 ml of water are mixed, and 300 ml of the mixed solution is introduced into the reaction mother liquor kept warm under the above-mentioned stirring at 5 ml / min by using a precision cylinder pump. At a rate of addition to produce a precipitate. Next, the precipitate was separated by suction filtration and washed with 2 liters of methanol.
Next, the washed precipitate was taken out and vacuum-dried at 120 ° C. for 4 hours to obtain about 330 g of a europium-activated barium fluorobromide phosphor precursor crystal.

Example 2 Europium-activated fluorofluoroiodide
To synthesize a phosphor precursor of lium, BaI _TwoWater soluble
1975 ml of liquid (4.5 mol / l), EuI_Threewater
25 ml of solution (0.2 mol / l)
Acrylic acid as a water-soluble organic monomer having a group of
0.07 g of the reaction mother liquor (BaI_TwoThe concentration is 4.5m
Per liter) into a 4 liter reaction vessel.
Was. The reaction mother liquor in the reaction vessel is kept at 60 ° C.
45m in diameter with a mixing chamber with a volume of about 100ml
m using a screw-type stirring blade of 500 m
And react to generate upward flow from the mixing chamber.
The mother liquor was stirred.

100 ml of an aqueous solution of ammonium fluoride (10 mol / l) and 200 ml of water are mixed, and 300 ml of this mixed solution is introduced into the reaction mother liquor, which is kept under stirring, at a rate of 5 ml / min using a precision cylinder pump. At a rate of addition to produce a precipitate. Next, the precipitate was separated by suction filtration and washed with 2 liters of methanol.
Next, the washed precipitate was taken out and vacuum-dried at 120 ° C. for 4 hours to obtain about 260 g of a europium-activated barium fluoroiodide phosphor precursor crystal.

Example 3 In order to synthesize a phosphor precursor of europium-activated barium fluorobromide, 1780 ml of an aqueous NH ₄ Br solution (4.5 mol / l), EuBr
( ₃ ) 25 ml of an aqueous solution (0.2 mol / l), 0.07 g of acrylic acid as a water-soluble organic monomer having the specific group, and 195 ml of water as a reaction mother liquor (NH
₍₄ Br concentration of 4.0 mol / l) was placed in a 4 liter reaction vessel. The reaction mother liquor in this reaction vessel
Keeping the temperature at 0 ° C., using a screw-type stirring blade with a diameter of 45 mm provided with a mixing chamber having a volume of about 100 ml around the periphery,
This was rotated at 500 rpm to stir the reaction mother liquor so as to generate an upward flow from the mixing chamber.

NH ₄ F aqueous solution (10 mol / l) 1
00 ml and BaBr ₂ aqueous solution (2.5 mol / l)
400 ml of the NH ₄ F aqueous solution was added to the reaction mother liquor kept under stirring with a separate precision cylinder pump so that the molar ratio between NH ₄ F and BaBr ₂ was constant at a constant rate of 10 ml. The aqueous solution of BaBr ₂ was added at a constant rate of 40 ml / min at a constant rate of / min to produce a precipitate. Next, the precipitate was separated by suction filtration and washed with 2 liters of methanol. Next, the washed precipitate was taken out and vacuum-dried at 120 ° C. for 4 hours to obtain about 220 g of a europium-activated barium fluorobromide phosphor precursor crystal.

Comparative Example 1 Europium-activated barium fluorobromide was prepared in the same manner as in Example 1 except that acrylic acid, which was a water-soluble organic monomer having the specific group, was added. About 330 phosphor precursor crystals
g was obtained.

Comparative Example 2 Europium-activated barium fluoroiodide was prepared in the same manner as in Example 2 except that acrylic acid, which was a water-soluble organic monomer having the above-mentioned specific group, was added. About 260 phosphor precursor crystals
g was obtained.

Comparative Example 3 Europium-activated barium fluorobromide was prepared in the same manner as in Example 3 except that acrylic acid, which was a water-soluble organic monomer having the above-mentioned specific group, was added. About 220 phosphor precursor crystals
g was obtained.

The phosphor precursor crystals obtained in Examples 1 to 3 and Comparative Examples 1 to 3 were evaluated as follows. <Particle size distribution> The particle size distribution was measured in a volume standard mode using a laser diffraction type particle size distribution measuring device (LA-500, manufactured by Horiba, Ltd.), and evaluated by a distribution table. Ethanol was used as the dispersion medium. As the particle size, a value of a median diameter (Dm) was used. The results are shown in Table 1 below.

<Particle shape / particle aspect ratio> Scanning electron microscope (JSM-5400LV, manufactured by JEOL Ltd.)
Was used to evaluate the particle shape by observing the obtained photograph. The particle aspect ratio is obtained by measuring the aspect ratio of 200 points of the particles of the photograph obtained by the above-described apparatus to obtain an average value,
It was calculated from the average value. The results are shown in Table 1 below.

[0056]

[Table 1]

From the results shown in Table 1, the phosphor precursor crystals obtained in Example 1 were columnar particles having a high aspect ratio, while the phosphor precursor crystals obtained in Comparative Example 1 had an aspect ratio of The particles became tetrahedral particles close to 1, and particles far apart were generated. Compared with the phosphor precursor crystal obtained in Comparative Example 3, which is an effective method for synthesizing columnar particles, the particle aspect ratio is almost the same, but the particle size is significantly smaller. Further, the phosphor precursor crystals obtained in Example 2 were significantly smaller than the particle size of the phosphor precursor crystals obtained in Comparative Example 2. Example 3
In the phosphor precursor crystal obtained in the above, the particle aspect ratio was significantly larger than that of the phosphor precursor crystal obtained in Comparative Example 3. By adding acrylic acid to the solution, it became possible to easily change the particle size and particle shape without depending on the change in the ionic concentration of the solution.

[0058]

According to the present invention, it is possible to provide a novel method for producing a phosphor precursor crystal, in which the control range of the particle size and the particle shape can be expanded and the controllability thereof can be improved. .

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G21K 4/00 G21K 4/00 B

Claims (6)

[Claims] 1. A water-soluble compound containing at least one group selected from the group consisting of a carboxyl group, a hydroxyl group, an amino group, a nitro group, a sulfone group, a phosphon group, a fluoro group, a chloro group, a bromo group and an iodo group. And reacting the reaction mother liquor with the additional solution in the presence of at least one of the organic monomer and the water-soluble organic polymer. 2. The method according to claim 1, wherein the water-soluble organic monomer and the water-soluble organic polymer include a carboxyl group. 3. The method for producing a phosphor precursor crystal according to claim 2, wherein the water-soluble organic monomer is acrylic acid. 4. The total addition amount of the water-soluble organic monomer and water-soluble organic polymer is 1 × 10 ⁻⁶ , where N is the amount of the precipitate of the phosphor precursor crystal finally obtained. N
Method for producing a phosphor precursor crystals according to claim 1 which is ~1 × 10 ⁰ N 3 of. 5. The method according to claim 1, wherein the reaction mother liquor includes an aqueous solution of an alkaline earth metal halide other than fluoride and / or an aqueous solution of ammonium halide other than fluoride, and the additive liquid includes an aqueous solution of fluoride salt. 5. The method for producing a phosphor precursor crystal according to any one of 4. 6. The method for producing a phosphor precursor crystal according to claim 5, wherein a main component of the phosphor precursor crystal is represented by the following basic composition formula (I). ^{_{(Ba 1-a, M II}} a) FX ··· (I) [ where, M ^II represents at least one alkaline earth metal selected from the group consisting of Sr and Ca, X is Cl, B
represents at least one halogen selected from the group consisting of r and I, and a represents a numerical value in the range of 0 ≦ a <1. ]