JPH10265774A - Rare earth-activating alkaline earth metal fluorohalide system accelerated phosphorescent substance and radioactive ray image transforming panel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the subject phosphorescent substance having excellent sensitivity, erasability and image characteristic expressed by an instantaneous emission and afterglow value by making a content of rare earth elements contained in the surface region smaller than the central region. SOLUTION: This accelerated phosphorescent substance is composed of rare earth-activating alkaline earth metal fluorohalide system and an amount of A (at least one kind of rare earth element selected from the group of Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu) contained in the surface region of the substance is made smaller than a content of A in a composition of a central region of the substance. Preferably, the composition of the central region is expressed by BaFX:xA X is Cl, Br or T; (x) is 0<(x)<=0.5}.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rare-earth activated alkaline earth metal fluorohalide-based stimulable phosphor and a radiation image conversion panel using the stimulable phosphor.

[0002]

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

According to the above-described radiographic image recording / reproducing method, a radiation having a much smaller amount of exposure and a richer amount of information than a conventional radiographic method using a combination of a radiographic film and an intensifying screen. There is an advantage that an image can be obtained. Furthermore, the conventional radiographic method consumes radiographic film for each photographing operation, whereas the radiographic image conversion method uses a radiographic image conversion panel repeatedly, so that resource conservation and economic efficiency are also reduced. It is advantageous.

A stimulable phosphor is a phosphor that emits stimulable light when irradiated with radiation and then with excitation light. However, in practice, the stimulable phosphor has a wavelength of 400 to 900 nm due to the excitation light. Phosphors that exhibit stimulated emission in the 500 nm wavelength range are commonly used.

The radiation image conversion panel used in the radiation image recording / reproducing method has, as a basic structure, a support and a phosphor layer (stimulable phosphor layer) provided on the surface of the support. However, when the phosphor layer is self-supporting, a support is not necessarily required. The stimulable phosphor layer usually comprises a stimulable phosphor and a binder containing and supporting the stimulable phosphor in a dispersed state. However, as the stimulable phosphor layer, a layer composed of only an aggregate of the stimulable phosphor without a binder formed by a vapor deposition method or a sintering method is known.

There is also known a radiation image conversion panel having a stimulable phosphor layer impregnated with a polymer substance in a gap between stimulable phosphor aggregates. In any of these phosphor layers, the stimulable phosphor has a property of exhibiting stimulable emission when irradiated with excitation light after absorbing radiation such as X-rays. Radiation 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 the subject is formed on the panel as an accumulated image of radiation energy. . This accumulated image can be emitted as stimulated emission light by irradiating the excitation light, and the accumulated image of radiation energy is imaged by photoelectrically reading the stimulated emission light and converting it into an electric signal. It is possible to do.

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

An example of a stimulable phosphor conventionally used for a radiation image conversion panel is disclosed in JP-A-55-1214.
No. 5 (Ba _1-X , M ²⁺ _X ) F
X: yA (where M ²⁺ is at least one of Mg, Ca, Sr, Zn and Cd, X is at least one of Cl, Br and I, A is Eu, Tb, Ce,
At least one of Tm, Dy, Pr, Ho, Nd, Yb, and Er, and x is 0 ≦ x ≦ 0.6, y
Is 0 ≦ y ≦ 0.2). There is a rare earth element activated alkaline earth metal fluorinated halide phosphor represented by a composition formula:

In the above conventional example, no attention was paid to the content of the rare earth metal, particularly Eu, in the composition of the surface of the stimulable phosphor and the composition of the center of the stimulable phosphor. .

However, when the composition of the surface of the stimulable phosphor and the content of the rare earth metal in the composition at the center of the stimulable phosphor are the same, the level of lattice defects on the surface of the stimulable phosphor is large, and particularly, The present inventors have found that when a halide phosphor is used, the instantaneous light emission upon X-ray irradiation on the surface of the stimulable phosphor increases, and the instantaneous emission afterglow value increases.

The instantaneous emission afterglow value is added to the read signal as a nozzle component when reading a radiation image accumulated from the stimulable phosphor in the radiation image conversion panel after X-ray irradiation, and the S / N The value drops.

Furthermore, when the instantaneous emission afterglow value is large, high-sensitivity imaging cannot be performed on the panel, and the X-ray source is susceptible to X-ray dose unevenness, and the instantaneous emission afterglow unevenness increases. Occur.

[0013]

SUMMARY OF THE INVENTION The present invention aims to solve the above-mentioned problems, and has particularly excellent sensitivity, erasability and image characteristics represented by instantaneous emission afterglow value (S / N value). An object of the present invention is to provide a rare earth activated alkaline earth metal fluoride halide stimulable phosphor and a radiation image conversion panel.

[0014]

Means for Solving the Problems The above problems are: A stimulable phosphor comprising a rare earth-activated alkaline earth metal fluorinated halide, wherein the content of A contained in the composition of the surface region of the stimulable phosphor is the stimulable phosphor. Is smaller than the content of A contained in the composition of the central region (where A is Sc, Y, La, Ce, Pr, Nd,
Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, T
At least one rare earth element selected from the group consisting of m, Yb, and Lu. ) Is a rare earth activated alkaline earth metal fluorohalide-based stimulable phosphor.

2. The stimulable phosphor represented by the above 1, wherein the composition of the center of the stimulable phosphor is represented by the following general formula (1):
A rare earth-activated alkaline earth metal fluorohalide-based stimulable phosphor characterized by being a compound represented by the formula:

General formula (1) BaFX: xA (X is at least one kind of halogen composed of Cl, Br, I, and A is Sc, Y, La, Ce, Pr, Nd, P
m, Sm, Eu, Gd, Tb, Dy, Ho, Er, T
At least one rare earth element selected from the group consisting of m, Yb, and Lu, and x is a numerical value in the range of 0 <x ≦ 0.5. ) 3. 2. The phosphor according to 2, wherein X is Cl,
A rare earth-activated alkaline earth metal fluorinated halide-based stimulable phosphor comprising at least one halogen selected from Br and I.

4. 2. The phosphor according to 2, wherein A is Eu. 3. A rare earth activated alkaline earth metal fluoride halide stimulable phosphor. 3.

5. 2. The phosphor according to the item 2, wherein at least one of the following M ¹ , M ² , and M ³ is contained as an impurity: a rare earth activated alkaline earth metal fluoride halide stimulable phosphor. body.

M ¹ : At least one kind of alkaline earth metal selected from Ca, Mg and Sr, and is contained at 5.0 × 10 ^{−6 to} 0.1 wt% with respect to the stimulable phosphor.

M ² : SiO ₂ , TiO ₂ , Al ₂ O ₃ ,
At least one selected from InF ₃ and Ga ₂ O ₃ , wherein the stimulable phosphor is 5.0 × 10 ⁻⁶ to 5.0 × 10 ⁻⁶ .
0.1 wt% is contained.

M ³ : At least one kind of alkali metal selected from Na, K and Rb, contained in an amount of 1.0 × 10 ^{−5 to} 0.1 wt% with respect to the stimulable phosphor.

6. A stimulable phosphor represented in the 5, and the content for the M ^1, M ² and total phosphor of M ³ phosphor central region, M ¹ of the phosphor surface ^area, M ² and M ³ Characterized in that the content of the total phosphor with respect to the phosphor is different.

7. A stimulable phosphor represented by the 6, for M ^1, M ² and M M ¹ content to the total phosphors is in the center of the ^3, M ² and total phosphor of M ³ of the surface area A rare earth activated alkaline earth metal fluorohalide-based stimulable phosphor characterized by having a content greater than the content.

8. A rare earth activated alkaline earth metal fluoride halide stimulable phosphor, wherein A is contained in the composition of the surface of the stimulable phosphor, and A is contained in a central region of the stimulable phosphor. (However, A is Sc, Y, La, Ce, P
r, Nd, Pm, Sm, Eu, Gd, Tb, Dy, H
At least one rare earth element selected from the group consisting of o, Er, Tm, Yb, and Lu. ), And M ¹ , M ² ,
At least one rare earth activated alkaline earth, characterized in that it contains as an impurity a metal fluoride halide stimulable phosphor of M ^3.

9. A stimulable phosphor represented by the 8, and content for the M ^1, M ² and total phosphor of M ³ phosphor central region, M ¹ of the phosphor surface ^area, M ² and M ³ Characterized in that the content of the total phosphor with respect to the phosphor is different.

10. 9. The stimulable phosphor shown in 9 above, wherein the content of the total phosphor of M ¹ , M ² and M ^{3 in} the surface region is based on the total phosphor of M ¹ , M ² and M ^{3 in} the center. A rare earth activated alkaline earth metal fluorohalide-based stimulable phosphor characterized by having a content greater than the content.

11. The stimulable phosphor shown in the above 8, 9 or 10, wherein the composition of the center of the stimulable phosphor is a compound represented by the general formula (1). Earth metal fluorinated halide stimulable phosphor.

12. 11. The stimulable phosphor described in 11 above, wherein said X contains at least one halogen selected from Cl and Br, and I, and a rare earth activated alkaline earth metal halogen fluoride. Compound-based stimulable phosphor.

13. 12. The stimulable phosphor described in 11 above, wherein A is Eu. The stimulable phosphor of a rare earth activated alkaline earth metal fluoride halide.

14. A radiation image conversion panel having a phosphor layer containing a stimulable phosphor, comprising the rare earth-activated alkaline earth metal fluoride halide stimulable phosphor according to any one of claims 1 to 13. Characteristic radiation image conversion panel.

Is solved by each of

(Definition of phosphor surface and center in the present invention) In setting the position of the surface and the center, the center of the phosphor is defined. The center of the phosphor is defined as a point at which a point perpendicular to l and w is orthogonal to the longest diameter (l) of the phosphor particles and a diameter (w) perpendicular to l. The phosphor center region refers to a portion having a radius of 0.2 μm or less from the center of the phosphor. The phosphor surface region is a portion of the phosphor excluding the phosphor central region.

(Definition of Impurities) 1. Impurities are substances other than the essential elements and compounds as the phosphor host crystal and activator ions.

For example, in the case of a BaFX: Eu phosphor, trace elements (Sr, Ca, Mg) contained even when the raw material is of high purity
Elements and compounds that are difficult to separate in the purification of raw materials, such as homologous elements of the constituent elements of the phosphor host crystal such as elements and compounds, and elements and compounds added for purposes other than improving the luminous efficiency of the stimulable phosphor are referred to as impurities in the present invention. I do.

2. Influence by the presence of impurities The presence state of impurities in the phosphor affects activator ions that emit light.

Specifically, it affects the potential energy of the activator ion. Normally, activator ions enter the excited state from the ground state with external energy, lose heat and vibrational energy, reach a stable luminescence level in the excited state, and then emit light when returning to the ground state. On the other hand, if an impurity is present, the stable emission level is reduced and the luminous efficiency is reduced. The range of energy is widened, and the emission spectrum is also broadened.

3. Presence of impurities The elements (Ba, Ba) constituting the phosphor BaFX: xA of the present invention
F, halogen rare earth elements other than F (Eu, Gd, Ce)
Was purified and sufficiently purified, and the effect of impurities was investigated by adding new impurities.

Since sufficient purification is not possible on an industrial scale, when dissolved as in the present invention, impurities are present in the mother liquor as in the case of adding the impurities.

Elements not described in the present invention are below the detection limit in ICP analysis.

Although the impurities of the present invention are present in the host crystal, they do not take a repeating structure like the host crystal, but rather hinder the repeating structure of the host crystal. In many cases, the repetitive structure is randomly entered in the host crystal.

In addition, depending on the element, instead of the activator ions, the activator ions enter the host crystal and do not allow the activator ions in the host crystal to enter the host crystal, or the distance between the activator ion and the nearest ion of the host crystal is randomly determined. In some cases, light emission may be hindered.

4. ICP Analysis by ICP is based on the reference book "ICP fluorescence analysis".
Perform as described in Kyoritsu Publishing Co., Ltd. “Haraguchi etc.” (Production of phosphors having different compositions in the central region / surface region of phosphor) When phosphors having different compositions in the central region / surface region of the phosphor are prepared in the liquid phase, the concentration of the mother liquor is set as high as possible. After the phosphor precursor is generated in the liquid, it is necessary to perform ripening sufficiently. The higher the concentration of the mother liquor, the better, and the longer the ripening, the better. Phosphors produced with low ripening and low concentration are likely to have the same composition at the surface and center of the phosphor even when produced in the liquid phase, not having sufficient stimulable luminescence and having large instantaneous luminescence. Become. The composition of the obtained phosphor particles may change gradually from the center to the surface.

[0043]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. The production of the rare earth-activated alkaline earth metal fluorohalide-based stimulable phosphor of the present invention is performed not by a solid phase method in which control of particle shape is difficult but by a liquid phase method in which particle size control is easy. Is preferred. In particular, it is preferable to obtain a stimulable phosphor by the following two liquid phase synthesis methods. The production of a rare earth activated earth metal fluoroiodide-based stimulable phosphor will be described below as a representative.

That is, the center composition of the phosphor is BaFI: xA (1A) The surface composition of the phosphor is BaFX: xA (2A) M ¹ : at least one alkaline earth metal selected from Ca, Mg, and Sr 5.0 × 10 ⁻⁶ ≦ M ¹ (wt%) ≦ 0.1, preferably 5.0 × 10 ⁻⁶ ≦ M ¹ (wt%) ≦
1.0 × 10 ^{−2, more} preferably 5.0 × 10 ⁻⁶ ≦ M ¹ (wt%) ≦
5.0 × 10 ⁻⁴ M ² : SiO ₂ , TiO ₂ , Al ₂ O ₃ , InF ₃ , G
at least one selected from a ₂ O ₃ and Fe ₂ O ₃ 5.0 × 10 ⁻⁷ ≦ M ² (wt%) ≦ 0.1, preferably 5.0 × 10 ⁻⁷ ≦ M ² (wt%) ≦
1.0 × 10 ⁻³ M ³ : at least one selected from Na, K and Rb 1.0 × 10 ⁻⁵ ≦ M ³ (wt%) ≦ 0.1, preferably 1.0 × 10 ⁻⁵ ≦ M ³ (Wt%) ≦
1.0 × 10 ⁻² A (A is Sc, Y, La, Ce, Pr, Nd, Pm, S
m, Eu, Gd, Tb, Dy, Ho, Er, Tm, Y
b, at least one rare earth element selected from the group of Lu. Production of a rare earth activated earth metal fluorinated iodide-based stimulable phosphor which is at least one rare earth element selected from the group consisting of:

M ¹ , M ² and M ³ are contained in the above-mentioned wt% with respect to the stimulable phosphor. That is, M ¹ ,
The content of ^{M 1,} M 2, ^{M 3} is a as above for the stimulable phosphor M ^{2, M 3} is contained.

[0046] Production Method 1: BaI comprises ₂ and A halide of a further halide of ^{M 1} if a is not zero, and comprises a further alkoxide compound of ^{M 2} if y is not 0, z There comprises a halide of M ^3, if not zero, is BaI ₂ concentration after they have dissolved 2N
A step of preparing an aqueous solution of preferably 2.7 N or more,
While maintaining the above aqueous solution at a temperature of 50 ° C. or more, preferably 80 ° C. or more, an aqueous solution of an inorganic fluoride (an ammonium fluoride or a fluoride of an alkali metal) having a concentration of 5N or more, preferably 8N or more is added to the aqueous solution to prepare a rare earth element. A step of obtaining a precipitate of an activated alkaline earth metal fluoroiodide-based stimulable phosphor precursor crystal, a step of separating the precursor crystal precipitate from an aqueous solution, and firing the separated precursor crystal precipitate. This is a manufacturing method including a step of firing while avoiding sintering.

[0047] The halides of M ¹ in the case Preparation 2 mother liquor is not a is 0 comprises a halide of ammonium halide and A, and an alkoxide compound of M ² if y is not 0, z
Is not 0, further contains a halide of M ³ , and after dissolving them, adjusting the aqueous solution having an ammonium halide concentration of 3 N or more, preferably 4 N or more. While maintaining the above temperature, an aqueous solution of an inorganic fluoride (ammonium fluoride or alkali metal fluoride) having a concentration of 5 N or more, preferably 8 N or more, and an aqueous solution of BaI ₂ are combined with the former fluorine and the latter Ba. Obtaining a precipitate of rare earth activated alkaline earth metal fluoroiodide-based stimulable phosphor precursor crystals by continuous or intermittent addition while maintaining the ratio of
A production method comprising a step of separating the above-mentioned precursor crystal precipitate from an aqueous solution, and a step of firing the separated precursor crystal precipitate while avoiding sintering.

Regardless of the timing of addition of the halide of A, it may be present in the reaction mother liquor or the like in advance at the start of addition, or at the time of addition of an aqueous solution of inorganic fluoride (ammonium fluoride or alkali metal fluoride). Aqueous solution of inorganic fluoride (ammonium fluoride or alkali metal fluoride) and Ba
Simultaneously or it may be added during a later addition of an aqueous solution of I _2.

Hereinafter, the method for producing the stimulable phosphor will be described in detail. (Preparation of Precipitate Crystal Precipitate, Preparation of Stimulable Phosphor) First, a raw material compound other than a fluorine compound is dissolved using an aqueous medium. That is, the halides of BaI ₂ and A, and if necessary, the halide of M ¹ and the alkoxide compound of M ² and further the halide of M ³ were sufficiently mixed and dissolved in an aqueous medium, and these were dissolved. Prepare the aqueous solution. However, the ratio of the BaI ₂ concentration to the aqueous solvent is adjusted so that the BaI ₂ concentration is 2N or more. At this time, if desired, a small amount of acid, ammonia,
Alcohol, a water-soluble polymer, a water-insoluble metal oxide fine particle powder, or the like may be added. This aqueous solution (reaction mother liquor) is maintained at a constant temperature.

Next, an aqueous solution of an inorganic fluoride (ammonium fluoride, fluoride of an alkali metal, etc.) is injected into the aqueous solution maintained at a constant temperature and stirred by using a pipe with a pump or the like. This injection is preferably carried out in the region where the stirring is particularly violent. By the injection of the inorganic fluoride aqueous solution into the reaction mother liquor, a rare earth activated alkaline earth metal fluorinated halide precursor crystal corresponding to the general formula (1A) is precipitated.

Next, the above phosphor precursor crystals are filtered,
The solution is separated from the solution by centrifugation, washed thoroughly 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 to uniformly adhere the sintering inhibitor fine powder to the crystal surface. The addition of the sintering inhibitor can be omitted by selecting the firing conditions.

Next, the crystal of the phosphor precursor is filled in a heat-resistant container such as a quartz port, an alumina crucible, or a quartz crucible, placed in an electric furnace, and baked while avoiding sintering. The firing temperature is suitably in the range of 400C to 1300C, and preferably in the range of 500C to 1000C. 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.
5 to 12 hours are appropriate.

The firing atmosphere may be 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 the like. A trace oxygen introduction atmosphere is used.

By the above calcination, the desired rare earth-activated alkaline earth metal fluoroiodide (halide) -based stimulable phosphor is obtained.

The rare earth-activated alkaline earth metal fluoroiodide (halide) -based stimulable phosphor represented by the general formula (2) of the present invention is, as described above, an ammonium halide (N).
H ₄ Br or _NH 4 Cl or _NH 4 I) and and a halide of Ln, and a in formula (2) is 0
A halide of M ¹ if not, and an alkoxide compound of M ² if y is not 0, further comprising a halide of M ^3, aqueous ammonium halide concentration is above 3N after they have dissolved While maintaining the aqueous solution at a constant temperature, the aqueous solution of inorganic fluoride and the aqueous solution of BaI ₂ are continuously or intermittently added thereto while maintaining the ratio of the former fluorine and the latter Ba constant. A step of obtaining a precipitate of a rare earth activated alkaline earth metal fluorinated iodide-based phosphor precursor crystal by separating the precursor crystal precipitate from an aqueous solution; and sintering the separated precursor crystal precipitate. It can also be manufactured using a manufacturing method (manufacturing method 2) including a step of firing while avoiding.

Next, this manufacturing method will be described in detail. First, a raw material compound except for BaI ₂ and a fluorine compound using an aqueous medium, and an ammonium halide (NH ₄ B
r or NH ₄ Cl or NH ₄ I) is dissolved.

That is, an ammonium halide and a halide of A, and if necessary, a halide of M ¹ , an alkoxide compound of M ² if necessary, and a halide of M ³ are further placed in an aqueous medium, and thoroughly mixed. Dissolve to prepare an aqueous solution in which they are dissolved. However, the amount ratio between ammonium halide and water is adjusted so that the concentration of ammonium halide falls within the range of 3N or more. At this time, if desired, a small amount of acid, ammonium,
Alcohol, water-soluble polymer, water-insoluble metal oxide fine particle powder, and the like may be added. This aqueous solution (reaction mother liquor) is maintained at a constant temperature.

Next, is maintained at this constant temperature, the aqueous solution being stirred, inorganic fluoride with an aqueous solution and an aqueous solution of BaI ₂ of (ammonium fluoride, alkali metal fluoride, etc.) at the same time, the inorganic fluoride The injection is carried out continuously or intermittently using a pipe with a pump or the like while adjusting the ratio of fluorine to the latter BaI ₂ to be constant. This injection is preferably carried out in the region where the stirring is particularly violent. Thus, B during phosphor crystal formation
By proceeding the reaction while taking care not to make the a ion excessive, the inside of the phosphor corresponds to the general formula (1) and the outside (surface) of the phosphor corresponds to the general formula (2). Active alkaline earth metal fluoroiodide (halide) -based phosphor precursor crystals precipitate.

Next, the phosphor precursor crystal is separated from the solvent, dried and calcined in the same manner as in the production method 1 to obtain the desired rare earth activated alkaline earth metal fluoride iodide. A stimulable phosphor is obtained.

The average particle size of the rare earth activated alkaline earth metal fluorohalide stimulable phosphor in the present invention is 0.8.
To 15 μm, more preferably 1 to 8 μm. The average particle diameter is obtained by randomly selecting 200 particles from an electron micrograph of the particles (crystals) and calculating the average by a sphere-equivalent volume particle diameter.

The particles (crystals) according to the present invention are preferably monodisperse, and the average particle size distribution (%) is preferably 20% or less, particularly preferably 15% or less.

(Preparation of Panel, Phosphor Layer, Coating Step, 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. Especially in handling as information recording material,
Those that can be processed into a flexible sheet or web are preferable. In this regard, plastic films such as cellulose acetate film, polyester film, polyethylene terephthalate film, polyamide film, polyimide film, triacetate film, and polycarbonate film, aluminum ,iron,
A metal sheet such as copper or chromium or a metal sheet having a coating layer of the metal oxide is preferable.

The thickness of the support varies depending on the material of the support to be used and the like.
0 μm, and more preferably 80 μm to 500 μm from the viewpoint of handling.

The surface of the support may be a smooth surface or a mat surface for the purpose of improving the adhesion to the stimulable phosphor layer.

Further, in these supports, an undercoat layer may be provided on the surface on which the stimulable phosphor layer is provided for the purpose of improving the adhesion to the stimulable phosphor layer.

Examples of the binder used in the stimulable phosphor layer in the present invention include proteins such as gelatin, polysaccharides such as dextran, and natural high molecular substances such as gum arabic; and polyvinyl butyral, Vinyl acetate, nitrocellulose, ethylcellulose,
A binder represented by a synthetic polymer such as 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 polyester, polyalkyl (meth) acrylate, a mixture of nitrocellulose and linear polyester, nitrocellulose and polyalkyl (meth) acrylate. And a mixture of polyurethane and polyvinyl butyral. In addition, these binders may be cross-linked by a cross-linking agent. The stimulable phosphor layer can be formed on the undercoat layer by the following method, for example.

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

Examples of the binder used in the present invention include proteins such as gelatin, polysaccharides such as dextran or gum arabic, polyvinyl butyral,
Polyvinyl acetate, nitrocellulose, ethyl cellulose, vinyl chloride / vinyl chloride copolymer, polymethyl methacrylate, vinyl chloride / vinyl acetate copolymer, polyurethane, cellulose acetate butyrate,
A film-forming binder usually used for a layer structure such as polyvinyl alcohol is used. Generally, the binder is used in an amount of 0.01 to 1 part by weight based on 1 part by weight of the stimulable phosphor. However, from the viewpoint of the sensitivity and sharpness of the obtained radiation image conversion panel, it is preferable that the amount of the binder is small, and the range of 0.03 to 0.2 part by weight is more preferable in consideration of the ease of application.

The mixing ratio between the binder and the stimulable phosphor in the coating solution (however, when the entire binder is an epoxy group-containing compound, the mixing ratio is equal to the ratio between the compound and the phosphor)
The characteristics of the target radiation image conversion panel, the type of phosphor,
Depends on the amount of epoxy group-containing compound added, etc.
In general, examples of the solvent for preparing the binding coating solution include: lower alcohols such as methanol, enotal, 1-propanol, 2-propanol and n-butanol; hydrocarbons containing chlorine atoms such as methylene chloride and ethylene chloride; acetone, methyl ethyl ketone Ketones such as methyl isobutyl ketone; esters of lower fatty acids such as methyl acetate, ethyl acetate and butyl acetate with lower alcohols; dioxane, ethylene glycol ethyl ether,
Ethers such as ethylene glycol monomethyl ether; toluene; and mixtures thereof.

Examples of the solvent used for preparing the coating solution for the stimulable phosphor layer include lower alcohols such as methanol, ethanol, isopropanol and n-butanol, acetone, methyl ethyl ketone, methyl isobutyl ketone, and the like.
Ketones such as cyclohexanone, esters of lower fatty acids such as methyl acetate, ethyl acetate and n-butyl acetate with lower alcohols, dioxane, ethers such as ethylene glycol monoethyl ether and ethylene glycol monomethyl ether, aromatic compounds such as triols and xylol And halogenated hydrocarbons such as methylene chloride and ethylene chloride, and mixtures thereof.

The coating solution contains a dispersant for improving the dispersibility of the phosphor in the coating solution, and the dispersant between the binder and the phosphor in the stimulable phosphor layer after formation. Various additives such as a plasticizer for improving the bonding strength may be mixed. Examples of dispersants used for such purposes include phthalic acid, stearic acid, caproic acid, and lipophilic surfactants. Examples of the plasticizer include phosphoric esters such as triphenyl phosphate, tricresyl phosphate and diphenyl phosphate; phthalic esters such as diethyl phthalate and dimethoxyethyl phthalate; ethylphthalylethyl glycolate and butylphthalylbutyl glycolate; Glycolic acid esters of
And polyester of polyethylene glycol and aliphatic dibasic acid, such as polyester of triethylene glycol and adipic acid, polyester of diethylene glycol and succinic acid, etc. can be mentioned.

For the purpose of improving the dispersibility of the stimulable phosphor layer phosphor particles in the stimulable phosphor layer coating solution, stearic acid, phthalic acid, caproic acid, lipophilic surfactants, etc. May be mixed. If necessary, a plasticizer for the binder may be added. Examples of the plasticizer include phthalic acid esters such as diethyl phthalate and dibutyl phthalate; diisodecyl succinate and aliphatic dibasic acid esters such as dioctyl adipate; ethyl phthalyl ethyl glycolate; butyl phthalyl butyl glycolate And the like.

The coating solution prepared as described above is then uniformly applied to the surface of the undercoat layer to form a coating of the coating solution. This coating operation can be performed by using ordinary coating means, for example, a doctor blade, a roll coater, a knife coater, or the like.

Next, the formed coating film is dried by gradually heating to complete the formation of the stimulable phosphor layer on the undercoat layer. The thickness of the stimulable phosphor layer depends on the characteristics of the target radiation image conversion panel, the type of the stimulable phosphor, the mixing ratio of the binder and the phosphor, and the like.
μm to 1 mm. However, this layer thickness is 50 to 5
It is preferably set to 00 μm.

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

The thickness of the stimulable phosphor layer of the radiation image conversion panel of the present invention depends on the characteristics of the intended radiation image conversion panel.
Although it depends on the type of the stimulable phosphor, the mixing ratio of the binder and the stimulable phosphor, etc., it is preferably selected from the range of 10 μm to 1000 μm, more preferably from the range of 10 μm to 500 μm. .

[0078]

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

Example 1 In order to synthesize a stimulable phosphor precursor of europium-activated barium fluoroiodide, an aqueous solution of BaI ₂ (3.5N) 2 was used.
500 ml and 125 ml of EuI ₃ aqueous solution (0.04N)
Was placed in the reactor. Further, when the Sr concentration is 100
ppm, Na so that SrI ₂ ,
NaI was added.

While stirring the reaction mother liquor in this reactor, 8
The temperature was kept at 3 ° C. Ammonium fluoride aqueous solution (8N) 25
0 ml was injected into the reaction mother liquor using a roller pump,
A precipitate formed. After completion of the injection, the precipitate was aged by keeping the temperature and stirring for 12 hours. Next, the precipitate was separated by filtration, washed with methanol, and dried under vacuum to obtain europium-activated barium fluoroiodide crystals.

In order to prevent a change in particle shape due to sintering during firing and a change in particle size distribution due to fusion between particles, 1% by weight of ultrafine alumina powder is added, and the crystal surface is sufficiently stirred with a mixer. Alumina ultrafine particles were uniformly adhered to the substrate. This was filled in a quartz boat and calcined at 850 ° C. for 2 hours in a hydrogen gas atmosphere using a tube furnace to obtain europium-activated barium fluoroiodide phosphor particles. Next, particles having an average particle diameter of 7 μm were obtained by classifying the phosphor particles.

As a phosphor-forming material, 342 g of the europium-activated barium fluoroiodide phosphor obtained above and 18 g of a polyester resin (Toyobo Byron 200) were added to a mixed solvent of methyl ethyl ketone and toluene (1: 1), and the mixture was mixed with a propeller mixer. It was dispersed to prepare a coating solution having a viscosity of 25 to 30 PS.

The coating solution was applied onto a polyethylene terephthalate film with an undercoat using a doctor blade, and then dried at 100 ° C. for 15 minutes to form a phosphor layer.

Next, 70 g of a fluororesin: fluoroolefin-vinyl ether copolymer (Lumiflon LF100 manufactured by Asahi Glass Co., Ltd.) and 25 g of a cross-linking agent: isocyanate (Nippon Polyurethane c-3041) were used as a protective film forming material in toluene-isopropyl alcohol (1). 1) The mixture was added to a mixed solvent to prepare a coating solution.

This coating solution is applied onto the phosphor layer previously formed as described above using a doctor blade, and then heat-treated at 120 ° C. for 30 minutes to be thermally cured and dried. A 10 μm protective film was provided. By the above method, a radiation image conversion panel having a stimulable phosphor layer was obtained.

Example 2 A radiation image conversion panel was produced in the same manner as in Example 1 except that dimethoxydimethylsilane was added to the reaction mother liquor to obtain a stimulable phosphor precursor crystal.

Example 3 In order to synthesize a stimulable phosphor precursor of europium-activated barium fluorobromide, an aqueous solution of BaBr ₂ (2.35 N) was used.
2125 ml and EuBr ₃ aqueous solution (0.04N) 125
ml was placed in the reactor. Furthermore, the Ca concentration in the reaction mother liquor was 8
0 ppm, Na concentration is 1000 ppm, K concentration is 20 ppm
CaBr ₂ , NaBr,
KBr was added.

While stirring the reaction mother liquor in this reactor, 8
The temperature was kept at 3 ° C. A stimulable phosphor precursor was prepared in the same manner as in Example 1 except that the reaction mother liquor in Example 1 was changed to the above reaction mother liquor, and a radiation image conversion panel was manufactured in the same manner as in Example 1.

Comparative Example 1 In order to synthesize a europium-activated barium fluoroiodide phosphor, BaI ₂ .2H ₂ O powder (427.2 g) and B
aF ₂ powder (175.4 g) and EuI ₃ powder 1.6 g
Was sufficiently mixed in a mortar and heated and melted at 1000 ° C. for 4 hours in a hydrogen gas atmosphere using a tube-type electric furnace to obtain a europium-activated barium fluoroiodide phosphor.

The obtained phosphor was pulverized and classified, and the average particle size was 7
A μm phosphor was obtained. A radiation image conversion panel was obtained in the same manner as in Example 1 using the above phosphor.

Comparative Example 2 In order to synthesize a europium-activated barium fluorobromide phosphor, BaBr ₂ .2H ₂ O powder (333.2 g) and B
aF ₂ powder (175.4 g) and EuI ₃ powder 1.6 g
Was thoroughly mixed in a mortar and heated and melted at 1100 ° C. for 4 hours in a hydrogen gas atmosphere using a tube-type electric furnace to obtain a europium-activated barium fluorobromide phosphor.

The obtained phosphor was pulverized and classified, and the average particle size was 7
A phosphor image conversion panel was manufactured in the same manner as in Example 3 using a phosphor having a thickness of μm.

Comparative Example 3 In order to synthesize a europium-activated barium fluorobromide phosphor, 2625 ml of an aqueous solution of BaBr ₂ (1.14 N) and 125 ml of an aqueous solution of EuBr ₃ (0.04 N) were placed in a reactor. 83 ° C. while stirring the reaction mother liquor in this reactor
Was kept warm. Ammonium fluoride aqueous solution (8N) 250m
1 was injected into the reaction mother liquor using a roller pump to form a precipitate. After completion of the injection, the precipitate was matured by keeping the temperature and stirring for 2 hours. Next, the precipitate was separated by filtration, washed with methanol, and dried under vacuum to obtain europium-activated barium fluorobromide crystals.

A radiation image conversion panel was manufactured in the same manner as in Example 3 using the obtained crystals.

The phosphor composition of the above example was as follows.

[0096] Example 1 Internal BaFI: xEu external _{(Ba 1-a, Sr a} ) FI: zNa · xEu x = 0.002, a = 0.0001, z = 0.001

[0097] Example 2 Internal BaFI: xEu external _{(Ba 1-a, Sr a} ) FI · ySiO 2: zN
a.xEux = 0.002, a = 0.0001, z = 0.001,
y = 0.01

Example 3 Internal BaFBr: xEu External (Ba _{1 -a} , Ca _a ) FBr: yNa · y′K
XEux x = 0.002, a = 0.0002, y = 0.000
1, y '= 0.0001

The method for detecting the phosphor composition of the embodiment is as follows. The phosphor sample is decomposed from the surface of the aqua regia and filtered and separated when the phosphor particles have a radius of 0.2 μm or less. The filtrate is analyzed by ICP as the phosphor surface composition. Undissolved phosphor particles are taken out after washing with alcohol, dissolved in aqua regia, and analyzed by ICP to obtain the phosphor internal composition value.

ICP is inductively coupled plasma emission spectroscopy. The ICP used for the phosphor analysis is ICP.
P-MS is a combination of ICP and mass spectrometer. The instrument used for measurement is Seiko Denshi Kogyo ICP-
MS. In the measurement, a calibration curve is prepared from a reference reagent (a solution of a known amount of a target element) for each element to be measured, and the measurement is performed for each of the elements to be measured from a solution of decomposed phosphor. In addition, about the measurement principle of ICP, etc., the ICP emission spectrometry by Kyoritsu Shuppansha, Keiichiro Fuwa, etc. can be referred.

(Evaluation Results of Radiation Image Conversion Panel) Evaluations were performed using the radiation image conversion panels obtained in Examples 1 to 3 and Comparative Examples 1 to 3. Evaluation items ・ Sensitivity (S) / Instantaneous emission afterglow (N) ・ Plate sensitivity characteristics after one month at 60 ° C and 90% RH ・ Plate erasing characteristics after one month at 60 ° C and 90% RH

(Evaluation method of radiation image conversion panel) Intensity evaluation After irradiating the radiation image conversion panel with X-rays having a tube voltage of 80 KVp, the panel was irradiated with a 200 mW semiconductor laser (780 n
m), which are excited by scanning and stimulated emission emitted from the phosphor layer is received by a photodetector (a photomultiplier tube R130 manufactured by Hamamatsu Photonics KK).
The light was received in 5) and the intensity was measured.

The value S measured immediately after the production of the radiation image conversion panel was set to 100%, and the measured value was 60 ° C. and 90%
The value obtained by leaving the sample in a room set at RH for one month and performing the same sensitivity measurement was defined as S ′, and the value of S ′ / S × 100 was defined as the sensitivity change rate. If there is no change in sensitivity, it is 100%, and the greater the change in sensitivity, the lower the sensitivity. When the signal value S obtained at the time of the sensitivity measurement is obtained through a Log amplifier, the signal value S is converted into a linear value and evaluated.

Erasing Evaluation After irradiating the radiation image conversion panel with X-rays having a tube voltage of 80 KVp, the panel was irradiated with a 200 mW semiconductor laser (780 n
m), which are excited by scanning and stimulated emission emitted from the phosphor layer is received by a photodetector (a photomultiplier tube R130 manufactured by Hamamatsu Photonics KK).
The light was received in 5) and the intensity S was measured.

After the intensity was measured, the radiation image conversion panel was uniformly irradiated for 10 seconds using a 700 W three halogen lamp, and the remaining X-ray image was scanned with a semiconductor laser in the same manner as described above without irradiating X-rays. And stimulated emission intensity S '
Was measured. S '/ S was used as the remaining amount of erasure. Evaluation of sensitivity S / instant light afterglow N After irradiating the radiation image conversion panel with X-rays having a tube voltage of 80 KVp, the panel was irradiated with a 200 mW semiconductor laser (780 n).
m), which are excited by scanning and stimulated emission emitted from the phosphor layer is received by a photodetector (a photomultiplier tube R130 manufactured by Hamamatsu Photonics KK).
The value obtained by measuring the intensity of the light received in step 5) was designated as S, and N / S was indicated with N as the intensity read by a light receiver without scanning with a laser after X-ray irradiation. Table 1 shows the results.

[0106]

[Table 1]

Example 4 In order to confirm the profile of the above-mentioned grains, it is sufficient to analyze the halogen composition on the outside and inside of the grains and also on the Eu. However, the second portion is provided only near the surface of the grains. There is a problem in the analysis accuracy. The following experiment was conducted to clarify the effectiveness of the present invention.

The device used was of the B type. BaI
₂ (3.5 mol / l, 2500 ml), EuI
₃ (0.2 mol / l, 125 ml) was added to the reaction vessel, the temperature was raised to 85 ° C., and NH ₄ F 8.0 mol / l, 175 m
l, simultaneously with EuI ₃ 0.2 mol / l, 125 ml
After the addition in 2 minutes, 150 ml of a 4.0 mol / l aqueous solution having a ratio of NH ₄ Br: NH ₄ F = 1: 1 was added in 18 minutes.

The analysis method uses the water-soluble property of BaFI, suspends the taken out particles in water at 40 ° C., filters, observes with an electron microscope, calculates the average particle size, and calculates the particle size of the first part. Conditions were examined by trial and error. Halogen was examined using X-ray fluorescence, and Eu was analyzed using ICP-MASS.
It investigated using. The results are shown below.

[0110]

[Table 2]

Incidentally, the ratio of halogen is shown as a relative value when I is 1 in the first portion and Br is 1 in the second portion.

Example 5 The same as Example 2 except that Ca was used instead of Sr and gadolinium iodide was used instead of europium iodide.

Example 6 The same as Example 2 except that Mg was used instead of Sr and cerium iodide was used instead of europium iodide.

Example 7 The same as Example 1 except that the temperature / ripening time step was shortened.

Example 8 The same as Example 7 except that the temperature ripening time step was made shorter than in Example 7.

[0116]

[Table 3]

[0117]

[Table 4]

However, the unit of A, M ¹ , M ² and M ³ is “wt% based on the phosphor”. "-" Indicates IC
P indicates below the detection limit.

As is clear from the above embodiment, the present invention evaluates the sensitivity S and the instantaneous emission afterglow value (N) (S / N
Value), the intensity change rate, and the image characteristics represented by the erasing characteristics are all excellent.

[0120]

According to the present invention, a rare earth activated alkaline earth metal fluoride halide stimulant excellent in both sensitivity, erasability and image characteristics represented by instantaneous emission afterglow value (S / N value). And a radiation image conversion panel.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hideaki Wakamatsu 1 Sakuracho, Hino-shi, Tokyo Konica Corporation

Claims (14)

[Claims] 1. A stimulable phosphor comprising a rare earth-activated alkaline earth metal fluorinated halide, wherein the content of A contained in the composition of the surface region of the stimulable phosphor is: Less than the content of A contained in the composition of the central region of the stimulable phosphor (where A is Sc, Y, La, Ce, P
r, Nd, Pm, Sm, Eu, Gd, Tb, Dy, H
At least one rare earth element selected from the group consisting of o, Er, Tm, Yb, and Lu. ) Is a rare earth activated alkaline earth metal fluorohalide-based stimulable phosphor. 2. The stimulable phosphor according to claim 1, wherein the center composition of said stimulable phosphor is represented by the following general formula (1):
A rare earth-activated alkaline earth metal fluorohalide-based stimulable phosphor characterized by being a compound represented by the formula: General formula (1) BaFX: xA (X is at least one halogen composed of Cl, Br, I, and A is Sc, Y, La, Ce, Pr, Nd, P
m, Sm, Eu, Gd, Tb, Dy, Ho, Er, T
At least one rare earth element selected from the group consisting of m, Yb, and Lu, and x is a numerical value in the range of 0 <x ≦ 0.5. ) 3. The rare earth-activated alkaline earth metal according to claim 2, wherein said X includes at least one halogen selected from Cl and Br and I. Fluoride halide stimulable phosphor. 4. The phosphor according to claim 2, wherein A is Eu. 4. The phosphor according to claim 2, wherein A is Eu. 5. The phosphor according to claim 2, wherein at least one of the following M ¹ , M ² , and M ³ is contained as an impurity. Compound-based stimulable phosphor. M ¹ : At least one kind of alkaline earth metal selected from Ca, Mg, and Sr, and is contained at 5.0 × 10 ^{−6 to} 0.1 wt% with respect to the stimulable phosphor. M ² : SiO ₂ , TiO ₂ , Al ₂ O ₃ , InF ₃ , G
and at least one selected from a ₂ O _3, are contained 5.0 × ¹⁰ -6 ~0.1wt% with respect to the stimulable phosphor. M ³ : at least one kind of alkali metal selected from Na, K, and Rb, wherein the alkali metal is 1.0% with respect to the stimulable phosphor.
× 10 ^{-5 to} 0.1 wt%. 6. The stimulable phosphor according to claim 5, wherein the content of M ¹ , M ² and M ³ in the phosphor central region with respect to the total phosphor, and M ^{1 in the} phosphor surface region. , M ^2, and a rare earth activated alkaline earth, characterized in that the content is different to the total phosphors of M ³ metal fluoride halide stimulable phosphor. 7. The stimulable phosphor according to claim 6, wherein the total content of M ¹ , M ² and M ^{3 in} the surface region with respect to the total phosphor is M ¹ , M ² and M ^3. A rare earth-activated alkaline earth metal fluorohalide-based stimulable phosphor, wherein the content is greater than the total content of the phosphor to the phosphor. 8. A stimulable phosphor of a rare earth-activated alkaline earth metal fluoride halide type, wherein A is contained in the composition of the surface of the stimulable phosphor, and a central region of the stimulable phosphor is provided. Contains A (where A is Sc, Y, La, Ce, Pr, N
d, Pm, Sm, Eu, Gd, Tb, Dy, Ho, E
At least one rare earth element selected from the group consisting of r, Tm, Yb, and Lu. ) And a rare-earth-activated alkaline earth metal fluorohalide-based stimulable phosphor comprising at least one of M ¹ , M ² , and M ³ as an impurity M. 9. The stimulable phosphor according to claim 8, wherein the content of M ¹ , M ² and M ³ in the phosphor central region relative to the total phosphor and the M ^{1 in the} phosphor surface region. , M ^2, and a rare earth activated alkaline earth, characterized in that the content is different to the total phosphors of M ³ metal fluoride halide stimulable phosphor. 10. The stimulable phosphor according to claim 9, wherein the total content of M ¹ , M ² and M ^{3 in} the surface region relative to the phosphor is M ¹ , M ² and M ^{3 at the} center. A rare earth-activated alkaline earth metal fluorohalide-based stimulable phosphor, wherein the content is greater than the total content of the phosphor to the phosphor. 11. The stimulable phosphor according to claim 8, 9 or 10, wherein the center composition of the stimulable phosphor is a compound represented by the general formula (1). Rare earth activated alkaline earth metal fluoride halide stimulable phosphor. 12. The stimulable phosphor according to claim 11, wherein X is at least one selected from Cl and Br.
A rare earth activated alkaline earth metal fluorohalide-based stimulable phosphor comprising a kind of halogen and I. 13. The stimulable phosphor according to claim 11, wherein A is Eu. 13. The stimulable phosphor according to claim 11, wherein A is Eu. 14. A radiation image conversion panel having a phosphor layer containing a stimulable phosphor, wherein the rare earth-activated alkaline earth metal fluorinated halide stimulable phosphor according to any one of claims 1 to 13. A radiation image conversion panel comprising a body.