JP3832045B2 - Rare earth activated alkaline earth metal fluoride halide photostimulable phosphor or precursor thereof - Google Patents

Description

【００８２】
以上の結果より本発明の装置を用いて得られた蛍光体粒子の粒子の均一性、粒度分布の向上は明らかであり、本発明の優位性を示している。
【００８３】
実施例２
次に放射線像変換パネルの製造例を示す。
蛍光体層形成材料として、上記で得た添加ユーロピウム付活弗化臭化バリウム蛍光体（実施例１でつくった蛍光体）３５６ｇ、及び弗化ヨウ化バリウム４２７ｇをそれぞれポリウレタン樹脂（住友バイエルウレタン社製、デスモラック４１２５）１５．８ｇ、ビスフェノールＡ型エポキシ樹脂２．０ｇをメチルエチルケトン−トルエン（１：１）混合溶媒に添加し、プロペラミキサーによって分散し、粘度２５〜３０ＰＳの塗布液を調製した。この塗布液をドクターブレードを用いて下塗付きポリエチレンテレフタレートフィルム上に塗布したのち、１００℃で１５分間乾燥させて、種々の厚さの蛍光体層を形成した。
【００８４】
次に、保護膜形成材料として、フッ素系樹脂：フルオロオレフィン−ビニルエーテル共重合体（旭硝子社製ルミフロンＬＦ１００）７０ｇ、架橋剤：イソシアネート（住友バイエルウレタン社製デスモジュールＺ４３７０）２５ｇ、ビスフェノールＡ型エポキシ樹脂５ｇ、およびシリコーン樹脂微粉末（ＫＭＰ−５９０、信越化学工業社製、粒子径１〜２μｍ）１０ｇをトルエン−イソプロピルアルコール（１：１）混合溶媒に添加し、塗布液を作った。この塗布液を上記のようにして予め形成しておいた蛍光体層上にドクターブレードを用いて塗布し、次に１２０℃で３０分間熱処理して熱硬化させるとともに乾燥し、厚さ１０μｍの保護膜を設けた。以上の方法により、輝尽性蛍光体層を有する放射線像変換パネルを得た。
【００８５】
（放射線像変換パネルの評価）
感度については、放射線像変換パネルに管電圧８０ＫＶｐのＸ線を照射した後、パネルをＨｅ−Ｎｅレーザー光（６３３ｎｍ）で操作して励起し、蛍光体層から放射される輝尽発光を受光器（分光感度Ｓ−５の光電子像倍管）で受光してその強度を測定した。下記の表において感度は相対値で示されている。
【００８６】
鮮鋭度については、放射線像変換パネルに鉛製のＭＴＦチャートを通して管電圧８０ＫＶｐのＸ線を照射した後パネルＨｅ−Ｎｅレーザー光で操作して励起し、蛍光体層から放射される輝尽発光を上記と同じ受光器で受光して電気信号に変換し、これをアナログ／デジタル変換して磁気テープに記録し、磁気テープをコンピューターで分析して磁気テープに記録されているＸ線像の変調伝達関数（ＭＴＦ）を調べた。下記の表には空間周波数２サイクル／ｍｍにおけるＭＴＦ値（％）が示されている。
【００８７】
また粒状性については、放射線像変換パネルに管電圧８０ＫＶｐのＸ線を照射した後パネルをＨｅ−Ｎｅレーザー光で操作して励起し、蛍光体層から放射される輝尽発光を上記と同じ受光器で受光して電気信号に変換し、これをフィルムスキャナーによって通常の写真フィルムに記録し、得られた画像の粒状性を目視で評価した。なお下記の表において粒状性は増感紙（コニカ社製ＳＲＯ−２５０）とＸ線写真フィルム（コニカ社製ＳＲ−Ｇ）を使用した従来実用のＸ線写真撮影によって得た画像の粒状性と比較して示されている。○印は前記の増感紙とフィルムを使用したＸ線写真撮影によって得た画像と同等の粒状性を意味し、◎印はそれよりも良好な粒状性を意味する。また△印はＸ線写真撮影によって得た画像よりもやや荒い粒状性を意味し、×印はそれよりも著しく荒い粒状性を意味する。
【００８８】
【表２】

【００８９】
相対感度及び鮮鋭度は、Ａ−１を１．０とした場合の相対比較として表示した。
表２よりＡ及びＢの装置を使用したものに比較し、Ｃの装置の優位性は明らかである。又、表２よりＢｒの比率に対しＩの比率を増加したものについての優位性も明らかである。
【００９０】
上記のように、本発明に係る放射線像変換パネルは、粒子の均一性、粒度分布の向上した輝尽性蛍光体の使用により、画像品質の優れたものである。
【００９１】
【発明の効果】
本発明に係る装置を用いて得られた蛍光体粒子は粒子の均一性、粒度分布に優れており、この蛍光体粒子を用いた放射線像変換パネルは画像品質の優れたものである。
【図面の簡単な説明】
【図１】本発明に係る輝尽性蛍光体の製造装置の一実施例を示す原理図（説明図）
【符号の説明】
１；反応容器
２；液流規制中空円筒
３；反応液供給管
４；反応液供給管
５；攪拌機
６；反応液供給口
７；反応液供給口
８；撹拌シャフト（軸）[0001]
BACKGROUND OF THE INVENTION
The present invention relates to manufacturing equipment of a rare earth activated alkaline earth metal fluorohalide stimulable phosphor or a precursor thereof.
[0002]
[Prior art]
As a method for replacing the conventional radiographic method, a radiation image recording / reproducing method using a stimulable phosphor as described in, for example, JP-A No. 55-12145 is known. This method uses a radiation image conversion panel (accumulative phosphor sheet) containing a stimulable phosphor, and the radiation transmitted through the subject or emitted from the subject is stimulated by the panel. The radiation energy stored in the stimulable phosphor is absorbed by the body, and then the stimulable phosphor is excited in time series with electromagnetic waves (excitation light) such as visible light and infrared rays. It emits as fluorescence (stimulated luminescence light), photoelectrically reads this fluorescence to obtain an electrical signal, and then reproduces a radiographic image of a subject or subject as a visible image based on the obtained electrical signal. . The panel which has been read is prepared for the next photographing after the remaining image is erased. That is, the radiation image conversion panel can be used repeatedly.
[0003]
According to the above radiographic image recording / reproducing method, a radiographic image with abundant information amount can be obtained with a much smaller exposure dose than in the case of the radiographic method using a combination of conventional radiographic film and intensifying screen. There is an advantage that you can. Furthermore, the conventional radiographic method consumes a radiographic film for each radiographing, whereas in this radiographic image conversion method, the radiographic image conversion panel is used repeatedly, so that also from the viewpoint of resource protection and economic efficiency. It is advantageous.
[0004]
Stimulable phosphors are phosphors that exhibit stimulating luminescence when irradiated with excitation light after being irradiated with radiation, but in practice, wavelengths of 300 to 500 nm are obtained by excitation light having a wavelength in the range of 400 to 900 nm. Phosphors that exhibit a range of stimulated luminescence are generally utilized.
[0005]
The radiation image conversion panel used in the radiation image recording / reproducing method includes a support and a photostimulable phosphor layer provided on the surface thereof as a basic structure. However, a support is not necessarily required when the phosphor layer is self-supporting. The photostimulable phosphor layer is usually composed of a photostimulable phosphor and a binder containing and supporting the phosphor in a dispersed state. However, the photostimulable phosphor layer is known to be composed only of aggregates of photostimulable phosphors without containing a binder formed by vapor deposition or sintering.
[0006]
A radiation image conversion panel having a photostimulable phosphor layer impregnated with a polymer substance in the gaps between the photostimulable phosphor aggregates is also known. In any of these phosphor layers, the photostimulable phosphor has the property of exhibiting photostimulated luminescence when irradiated with excitation light after absorbing radiation such as X-rays. Radiation emitted from the specimen is absorbed by the stimulable phosphor layer of the radiation image conversion panel in proportion to the radiation dose, and a radiation image of the subject or subject is formed on the panel as a stored image of radiation energy. . This accumulated image can be emitted as stimulated emission light by irradiating the excitation light, and the stored image of radiation energy is imaged by photoelectrically reading this stimulated emission light and converting it into an electrical signal. It becomes possible to do.
[0007]
In addition, the surface of the photostimulable phosphor layer (the surface on the side not facing the support) is usually provided with a protective film made of a polymer film or an inorganic vapor deposition film. Protects against natural alteration or physical impact.
[0008]
The rare earth activated alkaline earth metal fluoride halide photostimulable phosphor is excellent in sensitivity and, when used as a radiation image conversion panel, provides a highly sharp radiation reconstructed image, so that it is excellent in practical use. It can be said to be a stimulable phosphor. However, as the radiation image recording / reproducing method is put to practical use, there is an increasing demand for a higher-performance photostimulable phosphor.
[0009]
[Problems to be solved by the invention]
The present invention provides a method and apparatus for producing a rare earth activated alkaline earth metal fluoride halide photostimulable phosphor or precursor thereof having a further improved particle size distribution, a photostimulable phosphor and a radiation image conversion panel. It is intended to do.
[0010]
[Means for Solving the Invention]
The problem of the present invention is as follows.
1: General formula (1)
Ba _1-x M ² xFX: yM ¹ , zLn
M ² : at least one alkaline earth metal selected from the group consisting of Mg, Ca, Sr, Zn and Cd M ¹ : at least one alkali metal selected from the group consisting of Li, Na, K, Rb and Cs X: I
Ln: Ce, Pr, Sm, Eu, Gd, Tb, Tm, Dy, Ho, Nd, Er, and Yb, at least one rare earth element x, y, and z is 0 ≦ x ≦ 0. 6, 0 ≦ y ≦ 0.05, 0 <z ≦ 0.2
In an apparatus for producing a precipitate of a rare earth activated alkaline earth metal fluoride halide photostimulable phosphor precursor represented by:
A reaction vessel containing an alkaline earth metal halide aqueous solution other than fluoride (hereinafter referred to as “first aqueous solution”), and a stirrer for stirring the alkaline earth metal halide aqueous solution in the reaction vessel; And an apparatus having a supply pipe for supplying at least a fluoride salt aqueous solution (hereinafter referred to as “second aqueous solution”) into the first aqueous solution accommodated in the reaction vessel,
The first aqueous solution contains at least an alkaline earth metal halide salt solution or fluoride salt solution other than fluoride;
The second aqueous solution contains at least a fluoride salt aqueous solution when the first aqueous solution contains an alkaline earth metal halide salt solution other than fluoride, and the first aqueous solution is a fluoride salt aqueous solution. Containing an alkaline earth metal halide aqueous solution other than fluoride,
The stirrer is an axial flow stirrer with a cylinder, and has the supply pipe on the entry side in the discharge direction with respect to the stirrer;
And the supply pipe has a second aqueous solution outlet at the lower side of the cylinder of the axial flow stirrer provided inside the reaction vessel, and the rare earth activated alkaline earth metal fluoride halide system An apparatus for producing a precipitate of a stimulable phosphor precursor.
[0015]
2. 2. The apparatus for producing a precipitate of a rare earth activated alkaline earth metal fluoride halide photostimulable phosphor precursor according to 1 above, wherein the supply pipe has a backflow prevention valve.
[0018]
The following can be mentioned as reference examples of the present invention.
(1) General formula (1)
Ba _1-x M ² xFX: yM ¹ , zLn
M ² : at least one alkaline earth metal selected from the group consisting of Mg, Ca, Sr, Zn and Cd M ¹ : at least one alkali metal selected from the group consisting of Li, Na, K, Rb and Cs X: At least one halogen selected from the group consisting of Cl, Br and I Ln: at least one rare earth selected from the group consisting of Ce, Pr, Sm, Eu, Gd, Tb, Tm, Dy, Ho, Nd, Er and Yb The elements x, y, and z are 0 ≦ x ≦ 0.6, 0 ≦ y ≦ 0.05, and 0 <z ≦ 0.2, respectively.
In the method for producing a precipitate of a rare earth activated alkaline earth metal fluoride halide photostimulable phosphor precursor represented by the above, the above-mentioned fluoride in a reaction vessel containing an aqueous alkaline earth metal halide salt other than fluoride is contained. A rare earth activated alkaline earth metal fluoride halide-based stimulant is provided, wherein at least a fluoride salt aqueous solution is supplied into the reaction vessel through a supply pipe while stirring an alkaline earth metal halide salt solution other than a fluoride. Method for producing a fluorescent phosphor precursor.
[0019]
(2) In the method for producing a precipitate of the rare earth activated alkaline earth metal fluoride halide photostimulable phosphor precursor represented by the general formula (1), in the reaction vessel containing the first aqueous solution, A rare earth-activated alkaline earth metal fluoride halide photostimulable phosphor precursor characterized in that the second aqueous solution is supplied into the reaction vessel through a supply pipe while stirring the first aqueous solution. Production method.
[0020]
(3) The first aqueous solution contains at least an alkaline earth metal halide salt solution or fluoride salt aqueous solution other than fluoride, and the second aqueous solution includes an alkaline earth metal other than fluoride. In the case of containing an aqueous solution of an alkali metal halide salt, an aqueous solution of fluoride salt is contained at least, and in the case where the first aqueous solution contains an aqueous solution of fluoride salt, an aqueous alkaline earth metal halide salt solution other than fluoride is used. The method for producing a precipitate of a rare earth activated alkaline earth metal fluoride halide stimulable phosphor precursor according to the above (2), comprising :
[0021]
(4) The rare earth activated alkaline earth according to any one of (1) to (3) , wherein X in the general formula (1) is at least one halogen selected from the group consisting of Br or I A method for producing a metal fluoride fluoride based stimulable phosphor precursor.
[0022]
(5) The rare earth activated alkaline earth according to any one of the above (1) to (4) , wherein stirring is performed with an axial flow stirrer and the supply pipe is provided on the entry side in the discharge direction with respect to the stirrer. A method for producing a precipitate of a metal halide fluoride based stimulable phosphor precursor.
[0023]
(6) The rare earth activated alkaline earth metal fluoride halide stimulable phosphor precursor according to any one of the above (1) to (5) , wherein the supply pipe has a backflow prevention valve. Precipitate production method.
[0024]
(7) Any one of (1) to (6) above, wherein the fluoride salt aqueous solution is supplied into the reaction vessel through a supply pipe communicating with an alkaline earth metal halogen salt aqueous solution other than the fluoride. A method for producing a precipitate of a rare earth activated alkaline earth metal fluoride halide photostimulable phosphor precursor.
[0025]
(8) A precipitate of a rare earth-activated alkaline earth metal fluoride halide stimulable phosphor precursor crystal obtained by the production method according to any one of (1) to (7) .
[0026]
(9) Separating precipitates of rare earth activated alkaline earth metal fluoride halide photostimulable phosphor precursor crystals obtained by the production method according to any one of (1) to (7) from an aqueous solution And a method for producing a rare earth-activated alkaline earth metal fluoride-based photostimulable phosphor, comprising firing the separated precursor crystal precipitate.
[0027]
(10) A rare earth activated alkaline earth metal fluoride photostimulable phosphor obtained by the method for producing a rare earth activated alkaline earth metal fluoride photostimulable phosphor described in (9) .
[0028]
(11) The rare earth activated alkaline earth metal fluoride halide stimulable phosphor precursor crystal precipitate represented by the general formula (1) is obtained by a liquid phase method. Rare earth activated alkaline earth metal fluoride halide photostimulable phosphor precursor crystal precipitates.
[0029]
(12) A radiation image conversion panel having a phosphor layer containing a photostimulable phosphor, comprising the rare earth activated alkaline earth metal fluoride halide photostimulable phosphor described in (11) above. Radiation image conversion panel.
[0030]
DETAILED DESCRIPTION OF THE INVENTION
Precipitation immediately after supplying a fluoride salt or a second aqueous solution by intensively studying a method for preparing a precipitate in (aqueous) of a rare earth activated alkaline earth metal fluoride halide photostimulable phosphor Therefore, it was found that it is preferable to supply the solution in the reaction vessel where the solution is most strongly stirred, that is, to add the solution to the solution, and to make the vicinity of the stirring blade as good as possible. Moreover, as for the shape of the stirrer, one that can efficiently stir the inside of the reaction tank is good, but one that causes a so-called axial flow was found to be the best.
[0031]
In the present invention, the reaction vessel contains at least an alkaline earth metal halide salt solution or fluoride salt aqueous solution other than fluoride which is a first aqueous solution, and the first aqueous solution is an alkaline earth metal halide salt other than fluoride. When the aqueous solution contains an aqueous fluoride salt solution, or when the first aqueous solution contains an aqueous fluoride salt solution, the second aqueous solution contains an alkaline earth metal halide aqueous solution other than fluoride. A precipitate of phosphor precursor is produced by supplying an aqueous solution. Hereinafter, the case where the first aqueous solution is an alkaline earth metal halide salt solution other than fluoride and the second aqueous solution contains at least a fluoride salt aqueous solution will be described as an example.
[0032]
This outline is shown in FIG. In the manufacturing apparatus of FIG. 1, four pitched paddle stirrers 5 of an upper discharge type are mounted in a reaction vessel 1 containing an alkaline earth metal halide salt solution other than fluoride. The circumference is surrounded by a cylinder 2, which makes it possible to regulate the flow and circulate efficiently. The reaction solution is supplied to the lower side of the cylinder 2, that is, the entry side of the stirrer 5 through supply tubes 3 and 4. As a result, the generated precipitate is immediately discharged out of the cylindrical part 2, and uneven growth can be prevented. The reaction solution contains at least a fluoride salt aqueous solution.
[0033]
As described above, in order to rapidly mix the alkaline earth metal halide aqueous solution other than fluoride and the aqueous fluoride salt solution to obtain fine particles, a powerful stirring device and a supply device for the aqueous solution are required. is, P887～p920 of chemical Engineering Handbook by stirring blade of a low viscosity fluid that is described in (Maruzen, published, revised 5th edition 1988), but it is to use a drive system capable of high speed rotation, in the present invention An axial flow stirrer with a cylinder is used.
[0034]
The supply pipes 3 and 4 as the supply device are preferably provided with a backflow prevention valve (check valve) for preventing the backflow of the supply liquid, and more preferably in Japanese Patent Laid-Open Nos. 59-67535 and 62-160127. The supply nozzles described can be used. Further, as described in JP-A-62-160128, it is extremely preferable to divide and supply one supply liquid into a plurality of parts in order to perform uniform and rapid mixing. It is also preferable to provide the outlets 6 and 7 for the reaction solution in the supply pipe so as to be located in an alkaline earth metal halide aqueous solution other than the fluoride inside the reaction vessel 1. Furthermore, with respect to the cylinder 2 for suppressing the flow in FIG. 1, it is also a preferable method that radial plates are arranged in the cylinder 2 above the stirrer 5 to restrict the flow in the vertical direction.
[0035]
The reaction conditions in the present invention are 10 to 100 ° C., and the concentration of the reaction solution can be arbitrarily selected. As the reagent used, various alkaline earth metal halides, rare earth halides and fluoride salts can be used.
[0036]
It is known that the photostimulable phosphor particles generally have the photostimulability depending on the particle size. JP-A-55-163500 preferably has an average particle size of 1 to 30 μm. Has been. Japanese Patent Publication No. 3-79680 discloses the relationship between the phosphor particle size and characteristic values such as sensitivity, graininess, and sharpness. However, no specific method is disclosed for the method of producing the phosphor particles with controlled sizes.
[0037]
Attempts to control the particle size and shape of these photostimulable phosphors are disclosed in Japanese Patent Application Laid-Open No. 7-233369 by a liquid phase method. Here, as a conventional method, a rare earth activated alkaline earth metal fluoride halide-based phosphor is disclosed. The production method of the exhaust phosphor is made by dry-mixing alkaline earth metal fluorides of raw material compounds, alkaline earth metal halides other than fluoride, halides of rare earth elements, ammonium fluoride together, or aqueous A method is disclosed in which a rare earth-activated alkaline earth metal fluoride halide photostimulable phosphor is precipitated in an aqueous solution, while suspended and mixed in a medium, and then fired and pulverized. However, the particle size distribution is not mentioned here, and reproducibility is not sufficient for industrial use.
[0038]
The photostimulable phosphor particles obtained by the present invention preferably have an average particle size of 1 to 30 μm, and more preferably 1 to 10 μm.
[0039]
The production of rare earth activated alkaline earth metal fluoride halide photostimulable phosphors of the general formula (1) is not a solid phase method in which the particle shape is difficult to control, but a liquid in which the particle size is easily controlled. Performed by phase method. As a representative, the case where a photostimulable phosphor is obtained by the following two liquid phase synthesis methods is shown.
[0040]
Production method 1:
BaX ₂ (BaI ₂ other than fluoride, BaBr ₂ , BaCl ₂ ) and a halide of Ln, and when x in the general formula (1) is not 0, further a halide of M ² and y is 0 If not, further contain M ¹ halide, and after dissolution, prepare an aqueous solution having a BaX ₂ (BaI ₂ , BaBr ₂ , BaCl ₂ other than fluoride) concentration of 0.5 N or more, preferably 1 N or more. The step of:
An aqueous solution of inorganic fluoride (ammonium fluoride or alkali metal fluoride) having a concentration of 1N or higher, preferably 2N or higher is maintained while maintaining the above aqueous solution at a temperature of 50 ° C or higher and lower than solubility, preferably 80 ° C or higher. Adding a rare earth activated alkaline earth metal fluoroiodide-based stimulable phosphor precursor crystal precipitate;
The addition of fluoride can be performed continuously or intermittently. By adding at a speed that does not generate new nuclei, it is possible to obtain particles with uniform particle diameters. When such an addition method is performed, the addition amount gradually increases with time, but this addition amount can be experimentally determined by trial and error.
[0041]
Separating the precursor crystal precipitate from the aqueous solution;
And it is a manufacturing method including the process of baking the separated precursor crystal precipitate (avoid sintering).
[0042]
Production method 2:
If the mother liquor contains BaX ₂ (BaI ₂ other than fluoride, BaBr ₂ , BaCl ₂ ) and a halide of Ln, and x in the general formula (1) is not 0, then further a halide of M ² and y When is not 0, further comprising a halide of M ¹ , and after dissolving them, preparing an aqueous solution having an ammonium halide concentration of 0.5 N or more, preferably 1 N or more;
An aqueous solution of an inorganic fluoride (ammonium fluoride or alkali metal fluoride) having a concentration of 1N or higher, preferably 2N or higher, while maintaining the aqueous solution at a temperature of 50 ° C. or higher and lower than solubility, preferably 80 ° C. or higher; An aqueous solution of BaX ₂ (BaI ₂ , BaBr ₂ , BaCl ₂ other than fluoride) is added continuously or intermittently while maintaining the ratio of the former fluorine and the latter Ba constant, thereby rare earth activated alkaline earth. Obtaining a precipitate of a metal-fluoride-iodide-based stimulable phosphor precursor crystal;
Similar to the production method 1, by adding at a speed at which new nuclei are not generated, a product having a uniform particle diameter can be obtained.
[0043]
Separating the precursor crystal precipitate from the aqueous solution;
And it is a manufacturing method including the process of baking the separated precursor crystal precipitate (avoid sintering).
[0044]
The addition time of the halide of Ln is not limited, and it may be in the reaction mother liquor in advance at the start of addition, or when an aqueous solution of inorganic fluoride (ammonium fluoride or alkali metal fluoride) is added, and inorganic It may be added simultaneously with or after the addition of an aqueous solution of fluoride (ammonium fluoride or alkali metal fluoride) and an aqueous solution of BaX ₂ (BaI ₂ , BaBr ₂ , BaCl ₂ other than fluoride).
[0045]
The average particle diameter in the present invention is a value obtained by randomly selecting 1000 particles from an electron micrograph of particles (crystals) and obtaining an average with a volume particle diameter in terms of a sphere.
[0046]
The particles (crystals) according to the present invention are preferably monodispersed, and the average particle size distribution (%) is preferably 20% or less, particularly preferably 15% or less.
[0047]
Details of the method for producing the photostimulable phosphor will be described below.
[0048]
(Preparation of precursor crystal precipitates, preparation of stimulable phosphors)
First, raw material compounds other than fluorine compounds are dissolved in an aqueous medium. That is, BaX ₂ (BaBr ₂ , BaI ₂ , BaCl ₂ ) and a halide of Ln, and if necessary, further a halide of M ² and further a halide of M ¹ are placed in an aqueous medium and mixed thoroughly and dissolved. Prepare an aqueous solution in which they are dissolved. However, the amount ratio between the BaX ₂ (BaBr ₂ , BaI ₂ , BaCl ₂ ) concentration and the aqueous solvent is adjusted so that the BaX ₂ (BaBr ₂ , BaI ₂ , BaCl ₂ ) concentration is 0.5 N or more. . At this time, a small amount of acid, inorganic halide (ammonium salt, K salt, Na salt, etc.), ammonia, alcohol, water-soluble polymer, water-insoluble metal oxide fine particle powder, etc. may be added as desired. . This aqueous solution (reaction mother liquor) is maintained at 50 ° C. or higher.
[0049]
Next, an aqueous solution of an inorganic fluoride (ammonium fluoride, alkali metal fluoride, etc.) is added to the aqueous solution that is maintained at 50 ° C. or higher, accommodated in the reaction vessel 1 and stirred by the stirrer 5. It injects using the pipes with a pump which are the supply pipes 3 and 4. This injection is preferably performed in a region where stirring is particularly intense. By injecting the inorganic fluoride aqueous solution into the reaction mother liquor, a rare earth activated alkaline earth metal fluoride halide phosphor precursor crystal corresponding to the general formula (1) is precipitated.
[0050]
Next, the above phosphor precursor crystals are separated from the solution by filtration, centrifugation, etc., sufficiently washed with methanol or the like, and dried. A sintering inhibitor such as alumina fine powder or silica fine powder is added to and mixed with the dried phosphor precursor crystal, and the fine powder of sintering inhibitor is uniformly attached to the crystal surface. It should be noted that the addition of the sintering inhibitor can be omitted by selecting the firing conditions.
[0051]
Next, the phosphor precursor crystals are filled in a heat-resistant container such as a quartz port, an alumina crucible, or a quartz crucible, and placed in the core of an electric furnace and fired while avoiding sintering. The range of 400-1300 degreeC is suitable for a calcination temperature, and the range of 500-1000 degreeC is preferable. The firing time varies depending on the filling amount of the phosphor raw material mixture, the firing temperature, the temperature of taking out from the furnace, and the like, but generally 0.5 to 12 hours is appropriate.
[0052]
As the firing atmosphere, a neutral atmosphere such as a nitrogen gas atmosphere or an argon gas atmosphere, a weakly reducing atmosphere such as a nitrogen gas atmosphere containing a small amount of hydrogen gas, a carbon dioxide atmosphere containing carbon monoxide, or a small amount of oxygen introduced The atmosphere is used.
[0053]
The desired rare earth activated alkaline earth metal fluoride halide photostimulable phosphor is obtained by the above-mentioned firing.
[0054]
The rare earth activated alkaline earth metal fluoride halide photostimulable phosphor represented by the general formula (1) of the present invention is BaX ₂ (BaI ₂ other than fluoride, BaBr ₂ , BaCl as described above). ₂ ) and a halide of Ln, and if x in the above general formula (1) is not 0, further contain a halide of M ² , and if y is not 0, further contain a halide of M ¹ , A step of preparing an aqueous solution having a BaX ₂ concentration of 0.5 N or higher after the dissolution thereof; maintaining an aqueous solution of inorganic fluoride and an aqueous solution of BaX ₂ while maintaining the aqueous solution at a temperature of 50 ° C. or higher. A step of obtaining a precipitate of rare earth-activated alkaline earth metal fluoride halide phosphor precursor crystals by continuously or intermittently adding while maintaining the ratio of the former fluorine and the latter Ba constant; Is the precursor crystal precipitate an aqueous solution? Step separated; and (avoiding sintering) the separated precursor crystals precipitate be utilized manufacturing method comprising the step of firing (Production Method 2) can be produced. In the present invention, X is I.
[0055]
Next, this manufacturing method will be described in detail.
[0056]
First, a raw material compound excluding BaX ₂ and a fluorine compound is dissolved in an aqueous medium. That is, BaX ₂ (BaI ₂ , BaBr ₂ , BaCl ₂ ) and a halide of Ln, and if necessary, further a halide of M ² and further a halide of M ¹ are placed in an aqueous medium and mixed thoroughly and dissolved. Prepare an aqueous solution in which they are dissolved. However, the amount ratio between BaX ₂ and water is adjusted so that the concentration of BaX ₂ falls within the range of 0.5 N or more. At this time, if desired, a small amount of acid, inorganic halide (ammonium salt, K salt, Na salt, etc.), ammonia, alcohol, water-soluble polymer, water-insoluble metal oxide fine particle powder, etc. may be added. Also good. This aqueous solution (reaction mother liquor) is maintained at 50 ° C.
[0057]
Next, an aqueous solution of inorganic fluoride (ammonium fluoride, alkali metal fluoride, etc.) and BaX ₂ are added to the aqueous solution maintained at 50 ° C., contained in the reaction vessel 1 and stirred by the stirrer 5. While adjusting the ratio of the inorganic fluoride fluoride and the latter BaX ₂ to be constant at the same time with the aqueous solution, continuously or intermittently, such as a pipe with a pump as the reaction liquid supply pipes 3 and 4 Use to inject. This injection is preferably performed in a region where stirring is particularly intense. In this way, the rare earth activated alkaline earth metal fluoride halide corresponding to the above basic composition formula (1) is obtained by proceeding the reaction in consideration of the Ba ion not being excessive during the formation of the phosphor crystal. The phosphor precursor crystals are precipitated.
[0058]
Next, the phosphor precursor crystal is separated from the solvent, dried and then baked in the same manner as in the production method 1, so that the desired rare earth activated alkaline earth metal fluoride halide-based stimulant is obtained. Fluorescent material is obtained.
[0059]
(Panel creation, phosphor layer, coating process, support, protective layer)
As the support used in the radiation image conversion panel of the present invention, various polymer materials, glass, metal and the like are used. In particular, a material that can be processed into a flexible sheet or web for handling as an information recording material is suitable. From this point, a cellulose acetate film, a polyester film, a polyethylene terephthalate film, a polyamide film, a polyimide film, a triacetate film, A plastic film such as a polycarbonate film, a metal sheet such as aluminum, iron, copper, and chromium, or a metal sheet having a coating layer of the metal oxide is preferable.
[0060]
The layer thickness of these supports varies depending on the material of the support used, but is generally 80 μm to 1000 μm, and more preferably 80 μm to 500 μm from the viewpoint of handling.
[0061]
The surface of these supports may be a smooth surface, or may be a mat surface for the purpose of improving the adhesion to the photostimulable phosphor layer.
[0062]
Further, these supports may be provided with an undercoat layer on the surface on which the photostimulable phosphor layer is provided for the purpose of improving the adhesion to the photostimulable phosphor layer.
[0063]
Examples of binders used in the stimulable phosphor layer in the present invention include proteins such as gelatin, polysaccharides such as dextran, or natural high molecular substances such as gum arabic; and polyvinyl butyral, polyvinyl acetate, Represented by synthetic polymer materials such as nitrocellulose, ethyl cellulose, vinylidene chloride / vinyl chloride copolymer, polyalkyl (meth) acrylate, vinyl chloride / vinyl acetate copolymer, polyurethane, cellulose acetate butyrate, polyvinyl alcohol, linear polyester, etc. Can be mentioned. Particularly preferred among such binders are nitrocellulose, linear polyesters, polyalkyl (meth) acrylates, mixtures of nitrocellulose and linear polyesters, mixtures of nitrocellulose and polyalkyl (meth) acrylates and It is a mixture of polyurethane and polyvinyl butyral. Note that these binders may be crosslinked by a crosslinking agent. The photostimulable phosphor layer can be formed on the undercoat layer by the following method, for example.
[0064]
First, an iodine-containing stimulable phosphor, a compound such as a phosphite for preventing yellowing, and a binder are added to a suitable solvent, and these are mixed thoroughly to add phosphor particles and A coating solution in which the compound particles are uniformly dispersed is prepared.
[0065]
As the binder used in the present invention, the film-forming binder is used. In general, the binder is used in the range of 0.01 to 1 part by weight with respect to 1 part by weight of the stimulable phosphor. However, in terms of sensitivity and sharpness of the obtained radiation image conversion panel, it is preferable that the amount of the binder is small, and the range of 0.03 to 0.2 parts by weight is more preferable in view of the ease of application.
[0066]
The mixing ratio of the binder to the stimulable phosphor in the coating solution (however, if the binder is an epoxy group-containing compound, it is equal to the ratio of the compound to the phosphor) is the intended radiation image conversion. It depends on the characteristics of the panel, the type of phosphor, the amount of epoxy group-containing compound added, and so on.
[0067]
Examples of the solvent used for the preparation of the stimulable phosphor layer coating solution include lower alcohols such as methanol, ethanol, isopropanol and n-butanol, acetone, methyl ethyl ketone, methyl isobutyl ketone, ketones such as cyclohexanone, methyl acetate, Esters of lower fatty acids and lower alcohols such as ethyl acetate and n-butyl acetate, ethers such as dioxane, ethylene glycol monoethyl ether, ethylene glycol monomethyl ether, aromatic compounds such as triol and xylol, methylene chloride, ethylene chloride, etc. Examples thereof include halogenated hydrocarbons and mixtures thereof.
[0068]
The coating solution has a dispersing agent for improving the dispersibility of the phosphor in the coating solution, and a binding force between the binder and the phosphor in the stimulable phosphor layer after formation. Various additives such as a plasticizer for improvement may be mixed. Examples of the dispersant used for such purpose include phthalic acid, stearic acid, caproic acid, lipophilic surfactant and the like. Examples of plasticizers include phosphate esters such as triphenyl phosphate, tricresyl phosphate and diphenyl phosphate; phthalate esters such as diethyl phthalate and dimethoxyethyl phthalate; ethyl phthalyl ethyl glycolate, butyl phthalyl butyl glycolate, etc. And a polyester of triethylene glycol and adipic acid, a polyester of polyethylene glycol and an aliphatic dibasic acid such as a polyester of diethylene glycol and succinic acid, and the like.
[0069]
Dispersing agents such as stearic acid, phthalic acid, caproic acid, and lipophilic surfactants for the purpose of improving the dispersibility of stimulable phosphor layer phosphor particles in the stimulable phosphor layer coating solution. May be mixed. Moreover, you may add the plasticizer with respect to a binder as needed. Examples of the plasticizer include phthalates such as diethyl phthalate and dibutyl phthalate, aliphatic dibasic esters such as diisodecyl succinate and dioctyl adipate, ethyl phthalyl ethyl glycolate, butyl phthalyl butyl glycolate And glycolic acid esters.
[0070]
The coating liquid prepared as described above is then uniformly applied to the surface of the undercoat layer to form a coating film of the coating liquid. This coating operation can be performed by using a normal coating means, for example, a doctor blade, a roll coater, a knife coater or the like.
[0071]
Next, the formed coating film is dried by gradually heating to complete the formation of the photostimulable phosphor layer on the undercoat layer. The thickness of the photostimulable phosphor layer varies depending on the characteristics of the intended radiation image conversion panel, the type of stimulable phosphor, the mixing ratio of the binder and the phosphor, and is usually 20 μm to 1000 μm. . However, this layer thickness is preferably 20 to 500 μm.
[0072]
The stimulable phosphor layer coating solution is prepared using a dispersing device such as a ball mill, a sand mill, an attritor, a three-roll mill, a high-speed impeller disperser, a Kady mill, and an ultrasonic disperser. The prepared coating solution is applied on a support using a coating solution such as a doctor blade, a roll coater, or a knife coater, and dried to form a photostimulable phosphor layer. The stimulable phosphor layer and the support may be adhered after the coating solution is applied on the protective layer and dried.
[0073]
In the foregoing, examples of stimulable phosphors such as europium-activated barium fluoride iodide have been mainly described, but europium-activated barium fluoride bromide and other stimulable phosphors represented by the general formula (1) The above may also be referred to for the manufacture of.
[0074]
【Example】
Hereinafter, the detailed contents of the present invention will be described based on examples.
[0075]
Example 1
In order to clarify the superiority of the present invention, the following apparatus was prepared.
[0076]
A A hemispherical bottom reaction tank with a capacity of 5000 ml, a four-blade inclined paddle with an upper discharge of 60 mm, supply position... Liquid level B A reaction tank with a hemispherical bottom of a capacity of 5000 ml and an upper discharge with four blades Inclined paddle, feeding position: 5 mm below the blade (5 mm below the lower end of the blade), and 15 mm in the radial direction from the center of the blade (ie, from the center of the shaft 8 to the radial direction of the blade trajectory),
C A hemispherical reaction tank with a capacity of 5000 ml, a four-blade inclined paddle with an upper discharge of 60 mm, an agitator with a cylinder with an inner diameter of 65 mm and a height of 40 mm, supply position: 5 mm below the blade (5 mm below the lower end of the blade) ) At a position of 20 mm in the radial direction from the center of the wing (that is, from the center of the axis 8 to the radial direction of the wing trajectory),
The rotation speed of the stirring blade was 600 rpm, and the following formulation 1. And prescription 2. Rare earth activated alkaline earth metal fluoride halide photostimulable phosphors were prepared.
[0077]
Formula 1. (BaFBr: Eu)
BaBr ₂ aqueous solution 2.5 mol / l 1200 ml
EuBr ₃ aqueous solution 0.2 mol / l 40 ml
1760 ml of water
To the reaction vessel to 60 ° C., NH ₄ F (5.0 mol / l)
300 ml was added in 60 minutes.
[0078]
Formula 2. (BaFBr _0.8 I _0.2 : Eu)
BaBr ₂ and BaI ₂ mixed aqueous solution (BaBr ₂ : BaI ₂ = 0.8: 0.2) 2.5 mol / l 1200 ml
EuBr ₃ aqueous solution 0.2 mol / l 40 ml
1760 ml of water
Was added to the reaction vessel to 70 ° C., and NH ₄ F (5.0 mol / l)
300 ml was added in 60 minutes.
[0079]
Formula 3. (BaFI: Eu)
BaI ₂ aqueous solution 3.5 mol / l 2500 ml
EuBr ₃ aqueous solution 0.2 mol / l 125 ml
Was added to the reaction vessel to 83 ° C., and NH ₄ F (8.0 mol / l) was added.
250 ml was added in 60 minutes.
[0080]
For the evaluation, sampling was performed after the addition of NH ₄ F, and observation was performed with a scanning electron microscope. From the electron micrograph, 1000 particles were randomly selected, and the average particle size and distribution (%) were calculated using a sphere-converted volume particle size. Here, the distribution is the standard deviation normalized by the average particle diameter and expressed in%. The results are shown in Table 1.
[0081]
[Table 1]

[0082]
From the above results, the improvement in the uniformity and particle size distribution of the phosphor particles obtained by using the apparatus of the present invention is clear, indicating the superiority of the present invention.
[0083]
Example 2
Next, an example of manufacturing a radiation image conversion panel is shown.
As the phosphor layer forming material, 356 g of the added europium-activated barium fluorobromide phosphor (phosphor prepared in Example 1) obtained above and 427 g of barium fluoroiodide were each made of polyurethane resin (Sumitomo Bayer Urethane Co., Ltd.). Manufactured by Desmolac 4125) 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 by a propeller mixer to prepare a coating solution having a viscosity of 25 to 30 PS. This coating solution was applied onto an undercoated polyethylene terephthalate film using a doctor blade and then dried at 100 ° C. for 15 minutes to form phosphor layers having various thicknesses.
[0084]
Next, as a protective film forming material, fluorine resin: fluoroolefin-vinyl ether copolymer (Lumiflon LF100, manufactured by Asahi Glass Co., Ltd.) 70 g, cross-linking agent: isocyanate (Desmodule Z4370, manufactured by Sumitomo Bayer Urethane Co., Ltd.) 25 g, bisphenol A type epoxy resin 5 g and 10 g of silicone resin fine powder (KMP-590, manufactured by Shin-Etsu Chemical Co., Ltd., particle size: 1 to 2 μm) were added to a toluene-isopropyl alcohol (1: 1) mixed solvent to prepare a coating solution. This coating solution is applied onto the phosphor layer formed in advance as described above using a doctor blade, and then heat-cured at 120 ° C. for 30 minutes to be thermally cured and dried to provide a protective layer having a thickness of 10 μm. A membrane was provided. By the above method, a radiation image conversion panel having a stimulable phosphor layer was obtained.
[0085]
(Evaluation of radiation image conversion panel)
Regarding sensitivity, after irradiating the radiation image conversion panel with X-rays with a tube voltage of 80 KVp, the panel is operated with He-Ne laser light (633 nm) to excite it, and stimulated emission emitted from the phosphor layer is received by a photoreceiver The light was received by (photoelectron image multiplier of spectral sensitivity S-5) and the intensity was measured. In the table below, sensitivity is shown as a relative value.
[0086]
For sharpness, the radiation image conversion panel is irradiated with X-rays with a tube voltage of 80 KVp through an MTF chart made of lead, and then excited by operating with the panel He-Ne laser light to emit stimulated luminescence emitted from the phosphor layer. Light is received by the same light receiver as above and converted into an electrical signal, which is converted from analog to digital and recorded on a magnetic tape. The magnetic tape is analyzed by a computer and the modulated transmission of the X-ray image recorded on the magnetic tape is performed. The function (MTF) was examined. The table below shows MTF values (%) at a spatial frequency of 2 cycles / mm .
[0087]
As for graininess, the radiation image conversion panel is irradiated with X-rays with a tube voltage of 80 KVp, and then the panel is excited by operating with He-Ne laser light. The light was received by a device and converted into an electric signal, which was recorded on a normal photographic film by a film scanner, and the graininess of the obtained image was visually evaluated. In the table below, the graininess refers to the graininess of an image obtained by conventional practical X-ray photography using an intensifying screen (Konica SRO-250) and an X-ray photographic film (Konica SR-G). Shown in comparison. The symbol “◯” means a graininess equivalent to that of an image obtained by X-ray photography using the above-described intensifying screen and film, and the symbol “◎” means a graininess better than that. Further, the Δ mark means graininess that is slightly rougher than the image obtained by X-ray photography, and the X mark means graininess that is significantly rougher than that.
[0088]
[Table 2]

[0089]
The relative sensitivity and sharpness were displayed as a relative comparison when A-1 was 1.0.
From Table 2, the superiority of the C apparatus is clear as compared with the apparatus using the A and B apparatuses. Table 2 also shows the superiority of the I ratio increased with respect to the Br ratio.
[0090]
As described above, the radiation image conversion panel according to the present invention is excellent in image quality by using a stimulable phosphor having improved particle uniformity and particle size distribution.
[0091]
【The invention's effect】
The phosphor particles obtained by using the apparatus according to the present invention are excellent in particle uniformity and particle size distribution, and a radiation image conversion panel using the phosphor particles is excellent in image quality.
[Brief description of the drawings]
FIG. 1 is a principle diagram (explanatory diagram) showing an embodiment of a stimulable phosphor manufacturing apparatus according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1; Reaction container 2; Liquid flow control hollow cylinder 3; Reaction liquid supply pipe 4; Reaction liquid supply pipe 5; Stirrer 6; Reaction liquid supply port 7; Reaction liquid supply port 8;

Claims (2)

General formula (1)
Ba _1-x M ² xFX: yM ¹ , zLn
M ² : at least one alkaline earth metal selected from the group consisting of Mg, Ca, Sr, Zn and Cd M ¹ : at least one alkali metal selected from the group consisting of Li, Na, K, Rb and Cs X: I
Ln: Ce, Pr, Sm, Eu, Gd, Tb, Tm, Dy, Ho, Nd, Er, and Yb, at least one rare earth element x, y, and z is 0 ≦ x ≦ 0. 6, 0 ≦ y ≦ 0.05, 0 <z ≦ 0.2
In an apparatus for producing a precipitate of a rare earth activated alkaline earth metal fluoride halide photostimulable phosphor precursor represented by:
A reaction vessel containing an alkaline earth metal halide aqueous solution other than fluoride (hereinafter referred to as “first aqueous solution”), and a stirrer for stirring the alkaline earth metal halide aqueous solution in the reaction vessel; And an apparatus having a supply pipe for supplying at least a fluoride salt aqueous solution (hereinafter referred to as “second aqueous solution”) into the first aqueous solution accommodated in the reaction vessel,
The first aqueous solution contains at least an alkaline earth metal halide salt solution or fluoride salt solution other than fluoride;
The second aqueous solution contains at least a fluoride salt aqueous solution when the first aqueous solution contains an alkaline earth metal halide salt solution other than fluoride, and the first aqueous solution is a fluoride salt aqueous solution. Containing an alkaline earth metal halide aqueous solution other than fluoride,
The stirrer is an axial flow stirrer with a cylinder, and has the supply pipe on the entry side in the discharge direction with respect to the stirrer;
And the supply pipe has a second aqueous solution outlet at the lower side of the cylinder of the axial flow stirrer provided inside the reaction vessel, and the rare earth activated alkaline earth metal fluoride halide system An apparatus for producing a precipitate of a stimulable phosphor precursor. 2. The apparatus for producing a precipitate of a rare earth activated alkaline earth metal fluoride halide stimulable phosphor precursor according to claim 1, wherein the supply pipe has a backflow prevention valve.

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