JP2007045937A - Halogenated compound photostimulable phosphor, method for production thereof and radiographic image transformation panel using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a halogenated compound photostimulable phosphor having uniformed particle size distribution, particularly producing the photostimulable phosphor of oxygen-introduced, rare earth-activated alkaline earth metal fluoro-halide, and provide high sensitivity and high image quality radiographic image transformation plate. <P>SOLUTION: The method for production of the halogenated compound photostimulable phosphor comprises the step where at least two or more kinds of inorganic solutions are added to a halogenated compound ionic solution and the precursor crystals of the halogenated compound photostimulable phosphor is precipitated from the mixed inorganic solution and the step where the solvent is removed from the precursor crystals to obtain the precursor crystals. The precursor crystals are calcined in a calcination furnace satisfying specific requirement to produce the halogenated compound photostimulable phosphor. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a halide-based stimulable phosphor, in particular, an oxygen-introduced rare earth-activated alkaline earth metal fluorohalide stimulable phosphor, a method for producing the stimulable phosphor, and a radiation image conversion panel using the same. It is about.

  A radiation image recording / reproducing method using a photostimulable phosphor is known as one of image forming methods that can replace conventional radiography (see Patent Document 1). This method uses a radiation image conversion panel (also referred to as a storage phosphor sheet) containing a stimulable phosphor, and the radiation transmitted through the subject or emitted from the subject is stimulated by the fluorescence. It is absorbed into the body, and the stimulable phosphor is excited in time series with electromagnetic waves (referred to as excitation light) such as visible light and ultraviolet light, and the accumulated radiation energy is fluorescent (referred to as stimulated emission light). The fluorescence is photoelectrically read to obtain an electrical signal, and a radiographic image of the subject or subject is reproduced as a visible image based on the obtained electrical signal. The conversion panel after reading is subjected to erasure of the remaining image and used for the next photographing.

  According to this method, there is an advantage that a radiographic image having a large amount of information can be obtained with a much smaller exposure dose than radiography using a combination of a radiographic film and an intensifying screen. In contrast, the radiographic method consumes a film every time it is taken, whereas the radiographic image conversion panel is used repeatedly, which is advantageous in terms of resource protection and economic efficiency.

  The radiation image conversion panel comprises only a support and a photostimulable phosphor layer provided on the surface thereof, or a self-supporting photostimulable phosphor layer, and the photostimulable phosphor layer is usually a stimulable phosphor. And those composed only of aggregates of stimulable phosphors formed by vapor deposition or sintering. Also known is a polymer material impregnated in the gaps between the aggregates. Further, a protective film made of a polymer film or an inorganic vapor deposition film is usually provided on the surface of the photostimulable phosphor layer opposite to the support side.

  As the photostimulable phosphor, those that exhibit photostimulated luminescence in the wavelength range of 300 to 500 nm by excitation light in the range of 400 to 900 nm are generally used. 55-160078, 56-74175, 56-116777, 57-23673, 57-23675, 58-206678, 59-27289, 59-27980, 59 Rare earth element activated alkaline earth metal fluorohalide phosphors described in JP-A-56479, 59-56480, etc .; JP-A-59-75200, JP-A-60-84381, JP-A-60-106752, 60-166379, 60-222143, 60-228592, 60-228593, 61-23679, 61- Divalent europium-activated alkaline earth metal fluorohalide phosphors described in No. 20882, No. 61-12083, No. 61-12085, No. 61-235486, No. 61-235487; Rare earth element activated oxyhalide phosphors described in JP-A-55-12144; cerium-activated trivalent metal oxyhalide phosphors described in JP-A-58-69281; disclosed in JP-A-60-70484 Bismuth-activated alkali metal halide phosphors; divalent europium-activated alkaline earth metal halophosphate phosphors described in JP-A-60-14183, JP-A-60-157100, etc .; JP-A-60-157099 Divalent europium activated alkaline earth metal haloborate phosphor described in JP-A-60-217354 A divalent europium-activated alkaline earth metal hydride phosphor described in JP-A-61-21173, JP-A-62-11822, and the like; A cerium-activated rare earth halophosphate phosphor described in JP-40390; a divalent europium-activated cerium-rubidium phosphor described in JP-A-60-78151; described in JP-A-60-78151 Divalent europium-activated composite halide phosphors such as divalent europium-activated alkaline earth metal fluorohalide phosphors containing iodine, rare earth element-activated oxyhalide phosphors containing iodine And iodine-containing bismuth-activated alkali metal halide phosphors are known, A high-luminance photostimulable phosphor is required.

  Further, as the use of a radiation image conversion method using a stimulable phosphor progresses, improvement in the image quality of the obtained radiation image, for example, improvement in sharpness and graininess, has been further demanded. Among the means for improving the image quality of the radiation image, it is effective to make the stimulable phosphor finer and to equalize the particle diameter of the microstimulated phosphor, that is, to narrow the particle size distribution.

  The various photostimulable phosphors described above can be manufactured by a method called a solid phase method or a sintering method. However, in this method, pulverization after firing is essential, and there is a problem that it is difficult to control the particle shape that affects sensitivity and image performance.

  On the other hand, the method for producing a photostimulable phosphor from a liquid phase disclosed in JP-A-7-233369, JP-A-9-291278, etc. adjusts the concentration of the phosphor raw material solution to form a particulate stimulant. This is a method for obtaining a phosphor precursor crystal (hereinafter also referred to as “stimulable phosphor precursor”), and is effective as a method for producing a stimulable phosphor powder having a uniform particle size distribution. Further, from the viewpoint of reducing radiation exposure, it is known that a rare earth activated alkaline earth metal fluorohalide stimulable phosphor having a high iodine content is preferable. This is because iodine has a higher X-ray absorption rate than bromine (see, for example, Patent Documents 2, 3, and 4).

  However, alkaline earth metal fluorohalide photostimulable phosphors produced in the liquid phase are advantageous in terms of luminance and granularity, but the following problems occur when obtaining precursor crystals in the liquid phase: have. When producing alkaline earth metal fluoroiodide-based stimulable phosphor particles in the liquid phase, as described in JP-A-10-88125 and 9-291278, 1) barium iodide is water or organic Dissolve in the solvent and add the inorganic fluoride solution while stirring the solution. 2) A method in which ammonium fluoride is dissolved in water and a solution of barium iodide is added while stirring this solution is effective. However, in the method 1), an excess of barium iodide needs to be present in the solution. Therefore, the stoichiometric ratio of the charged barium iodide and the barium fluoroiodide obtained after solid-liquid separation is 0. Often a small value of around 4. That is, the yield of the alkaline earth metal fluoroiodide stimulable phosphor is often about 40% with respect to the charged barium iodide. The method 2) also requires an excess of barium iodide with respect to the inorganic fluoride, and the yield is low. Thus, the liquid phase synthesis of barium fluoroiodide has the problem of low yield and poor productivity. Lowering the barium iodide concentration in the mother liquor to increase the yield leads to particle enlargement. Particle enlargement is not preferable in terms of image quality characteristics.

  As an attempt to increase the yield of rare earth-activated alkaline earth metal fluorohalide stimulable phosphors, particularly alkaline earth fluoroiodide-based stimulable phosphors, JP-A-11-29324 discloses a reaction mother liquor. The basic composition formula BaFI: xLn (Ln: at least one rare earth element selected from the group consisting of Ce, Pr, Sm, Eu, Gd, Tb, Tm, and Yb) is obtained by concentrating after adding a concentration and a fluorine source. A method for obtaining filled rare earth-containing angular barium fluoroiodide crystals is disclosed. As a result of the further examination by the present inventors, although BaFI square crystals were produced as described, it was found that productivity was remarkably low due to the use of concentration by natural evaporation, and this was not practical from an industrial viewpoint. Further, it was found that the obtained rectangular crystals have a large particle size and a wide particle size distribution, so that the image characteristics, particularly the structural mottle, are poor and cannot be put to practical use.

Japanese Patent Application Laid-Open No. 2002-38143 describes a method of obtaining a highly productive precursor by concentrating from a state in which the mother liquor concentration is increased. However, since a large amount of BaF _{2 as an} intermediate exists at the start of concentration, it is not preferable in terms of image characteristics of the obtained phosphor.
Japanese Patent Laid-Open No. 55-12145 JP 2003-268369 A JP 7-233369 A JP 2003-268365 A

  In view of the above problems, an object of the present invention is to provide a halide-based stimulable phosphor having a uniform particle size distribution, particularly an oxygen-introduced rare earth-activated alkaline earth metal fluorohalide stimulable phosphor with high productivity and high yield. Another object of the present invention is to provide a production method that can be obtained at a high rate, and to provide a high-sensitivity high-quality radiation image conversion plate using a photostimulable phosphor produced using the production method.

  The above-described problems of the present invention can be solved by the following configuration.

(1)
In the method for producing a halide-based stimulable phosphor, a step of precipitating a halide-based stimulable phosphor precursor crystal from a mixed solution prepared by adding at least two inorganic solutions to a halide ion solution And a step of removing the solvent from the mixed solution tank for precipitating the crystals to obtain a halide-based stimulable phosphor precursor crystal and firing in a firing furnace satisfying the following requirements 1) to 4): And a method for producing a halide-based stimulable phosphor.
Requirements:
1) The firing furnace has a furnace core tube having a structure in which a quartz glass cylinder having a smaller diameter is connected to both ends of a quartz glass cylinder, and a stimulable phosphor is provided in a large diameter portion at the center of the furnace core tube. The precursor can be charged, and the inside of the core tube can be heated to 600 to 900 ° C. while rotating the core tube.
2) The reactor core tube can replace the atmosphere gas inside the reactor core tube, and at least three kinds of atmosphere gases, that is, an atmosphere gas containing at least hydrogen, an atmosphere gas containing at least oxygen, and a nitrogen gas are supplied at respective flow rates. It has a function that can be controlled and introduced into the core tube and discharged.
3) The member of the furnace core tube that occupies 80% or more of the total surface area of the surface portion in contact with the atmospheric gas is quartz glass or a metal covered with a fluororesin.
4) The firing furnace has a heat source disposed outside the core tube, and when the core tube is cooled, the heat source can be moved to a position away from the core tube.

(2)
In the method for producing a halide-based stimulable phosphor, it takes a longer time to remove the solvent than the step of adding the inorganic solution, and the halide-based stimulable phosphor precursor crystal is obtained from the mixed solution. The method for producing a halide-based photostimulable phosphor according to (1) above, wherein the solvent is removed simultaneously with the precipitation.

(3)
The halide photostimulable phosphor according to (1) or (2) above, wherein the halide photostimulable phosphor is a rare earth activated alkaline earth metal fluorobromide stimulable phosphor Manufacturing method.

(4)
(1) to (3), wherein the halide-based stimulable phosphor is an oxygen-introduced rare earth-activated alkaline earth metal fluorobromide stimulable phosphor represented by the following general formula (EFS1): The method for producing a halide-based stimulable phosphor according to any one of the above.
General formula (EFS1)
Ba _1-x M ² _x FX _1-y Br _y : aM ¹ , bLn, cO
[Wherein, M ¹ : at least one alkali metal selected from the group consisting of Li, Na, K, Rb and Cs, at least one halogen element selected from X: Cl or I, M ² : Be, Mg, Sr And at least one alkaline earth metal selected from the group consisting of Ca, at least one selected from the group consisting of Ln: Ce, Pr, Sm, Eu, Gd, Tb, Tm, Dy, Ho, Nd, Er, and Yb The rare earth elements x, y, a, b and c are 0 ≦ x ≦ 0.3, 0 ≦ y ≦ 1.0, 0 ≦ a ≦ 0.05, 0 <b ≦ 0.2, 0 <c, respectively. Represents ≦ 0.1. ]
(5)
A halide-based stimulable phosphor produced by the method for producing a halide-based stimulable phosphor according to any one of (1) to (4).

(6)
A radiation image conversion panel comprising a halide-based stimulable phosphor produced by the method for producing a halide-based stimulable phosphor according to any one of (1) to (4).

  By the constitution of the present invention, a halide-based stimulable phosphor having a uniform particle size distribution, particularly an oxygen-introduced rare earth-activated alkaline earth metal fluorohalide stimulable phosphor can be obtained with high productivity and high yield. In addition, it is possible to provide a high-sensitivity and high-quality radiation image conversion plate using a stimulable phosphor manufactured using the method.

  Hereinafter, the present invention and components will be described.

(Halide-based stimulable phosphor)
The halide-based stimulable phosphor according to the present invention is obtained by a novel production method. That is, in the method for producing a halide-based stimulable phosphor, the stimulable phosphor is produced by a stimulable phosphor producing apparatus that satisfies the above-mentioned specific requirements. In the production method described in detail later, a step of precipitating a halide-based stimulable phosphor precursor crystal from a mixed solution prepared by adding at least two inorganic solutions to a halide ion solution; It was obtained by passing through the process of removing a solvent from the mixed solution tank which precipitates a crystal, It is characterized by the above-mentioned.

  Here, the photostimulable phosphor precursor crystal according to the present invention is a crystal precipitated from a mixed solution in the above-described production method, and has not undergone a baking treatment at a high temperature of 600 ° C. or higher. Say. The photostimulable phosphor precursor crystal shows almost no photostimulable luminescence or instantaneous luminescence.

  The composition of the elements constituting the halide photostimulable phosphor as a precursor of the halide photostimulable phosphor of the present invention is variously changed according to the purpose of use, the wavelength of the excitation light, the intensity, etc. And is not limited to a specific composition. However, a halide-based stimulable phosphor represented by the following basic composition formula (I) is theoretically preferable.

Basic composition formula (I): Ba _1-x M ² _x X ¹ X ² _1-y X ³ _y : aM ¹ , bLn
[However, M ¹ : at least one alkali metal selected from the group consisting of Li, Na, K, Rb and Cs, M ² : at least one alkaline earth metal selected from the group consisting of Be, Mg, Sr and Ca , X ¹ , X ² , X ³ : at least one halogen element selected from the group consisting of F, Cl, Br, and I, Ln: Ce, Pr, Sm, Eu, Gd, Tb, Tm, Dy, Ho, Represents at least one rare earth element selected from the group consisting of Nd, Er and Yb, wherein x, y, a and b are 0 ≦ x ≦ 0.5, 0 ≦ y ≦ 1.0 and 0 ≦ a ≦, respectively. The numerical value of the range represented by 0.05 and 0 <b <= 0.2 is represented. ]
Further, among the stimulable phosphors represented by the basic composition formula (I), rare earth activated alkaline earth metal fluorohalide-based stimulable phosphors theoretically represented by the following basic composition formula (II): Is preferred.

Basic composition formula (II): Ba _1-x M ² _x FX _1-y I _y : aM ¹ , bLn
[However, M ¹ : at least one alkali metal selected from the group consisting of Li, Na, K, Rb and Cs, M ² : at least one alkaline earth metal selected from the group consisting of Be, Mg, Sr and Ca , X: at least one halogen element selected from Cl or Br, 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 X, y, a, and b are represented by 0 ≦ x ≦ 0.5, 0 ≦ y ≦ 1.0, 0 ≦ a ≦ 0.05, and 0 <b ≦ 0.2, respectively. Represents a range number. ]
The photostimulable phosphor represented by the basic composition formula (I) or (II) may contain various additive components as described below for the purpose of further improving the photostimulated luminescence amount, the erasing characteristics and the like. Good. For example, nonmetallic elements typified by B, O, and S, amphoteric elements typified by Al, Ge, and Sn, and metallic elements typified by Mg, Fe, Ni, Cu, and Ag are included. The amount of these additive components is preferably 1000 ppm or less with respect to the photostimulable phosphor represented by the basic composition formula (I).

  In particular, a stimulable phosphor obtained by introducing oxygen into the stimulable phosphor represented by the above basic composition formula (I) or (II), which is theoretically represented by the following basic composition formula (III). An oxygen-introduced rare earth-activated alkaline earth metal fluorohalide photostimulable phosphor.

Basic composition formula (III): Ba _1-x M ² _x FX _1-y Br _y : aM ¹ , bLn, cO
[However, M ¹ : at least one alkali metal selected from the group consisting of Li, Na, K, Rb and Cs, M ² : at least one alkaline earth metal selected from the group consisting of Be, Mg, Sr and Ca , X: at least one halogen element selected from Cl or Br, 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 X, y, a, and b represent elements, respectively, 0 ≦ x ≦ 0.5, 0 ≦ y ≦ 1.0, 0 ≦ a ≦ 0.05, 0 <b ≦ 0.2, 0 <c <A numerical value in a range represented by 0.1 is represented. ]
In the present invention, the most preferable halide photostimulable phosphor is an oxygen-introduced rare earth-activated alkaline earth metal fluorobromide photostimulable phosphor theoretically represented by the following general formula (EFS1).

General formula (EFS1): Ba _1-x M ² _x FX _1-y Br _y : aM ¹ , bLn, cO
[Wherein, M ¹ : at least one alkali metal selected from the group consisting of Li, Na, K, Rb and Cs, at least one halogen element selected from X: Cl or I, M ² : Be, Mg, Sr And at least one alkaline earth metal selected from the group consisting of Ca, at least one selected from the group consisting of Ln: Ce, Pr, Sm, Eu, Gd, Tb, Tm, Dy, Ho, Nd, Er, and Yb The rare earth elements x, y, a, b and c are 0 ≦ x ≦ 0.3, 0 ≦ y ≦ 1.0, 0 ≦ a ≦ 0.05, 0 <b ≦ 0.2, 0 <c, respectively. Represents ≦ 0.1. ]
The stimulable phosphors represented by the basic composition formulas (I) to (III) usually have an aspect ratio in the range of 1.0 to 5.0. The stimulable phosphor of the present invention has a particle size median diameter (Dm) in the range of 1 to 10 μm (more preferably 2 to 7 μm) when the particle aspect ratio is 1.0 to 2.0. Further, it is preferable that σ / Dm when the standard deviation of the particle size distribution is σ is in the range of 50% or less (more preferably 40% or less). On the other hand, when the particle aspect ratio is 2.0 to 5.0, the median diameter (Dm) of the particle size is in the range of 1 to 20 μm (more preferably 2 to 15 μm) and the standard deviation of the particle size distribution. When σ is σ, σ / Dm is preferably in the range of 50% or less (more preferably 40% or less). The shape of the particle includes a rectangular parallelepiped type, a regular hexahedron type, a regular octahedron type, an intermediate polyhedron type, a tetrahedron type, and the like, as long as the particle aspect ratio, the particle size, and the particle size distribution are satisfied. The effects of the present invention can be achieved. In the basic composition formulas (I) to (III), Ln is preferably Ce or Eu from the viewpoint of improving the light emission characteristics (sensitivity, erasing characteristics, response, etc.).

Preferable specific examples of the rare earth activated alkaline earth metal fluorohalide-based stimulable phosphor as the precursor crystal include, for example, BaFI: 0.005 Eu, BaFI: 0.001 Eu, Ba _0.97 Sr _0.03 FI: 0.0. 0001K, 0.013Eu, BaFI: 0.0002K, 0.005Eu, Ba _0.998 Ca _0.002 FI: 0.005Eu, BaFI: 0.005Ce, Ba _0.99 Ca _0.01 FI: 0.0002K, 0.005Eu, BaFI: 0. Examples include, but are not limited to, 0001Ce and 0.0001Tb.

(Preparation method of precursor crystal and photostimulable phosphor)
As described in detail below, the halide-based stimulable phosphor according to the present invention is manufactured by a stimulable phosphor manufacturing apparatus that satisfies specific requirements, and further includes at least a halide ion solution. A step of depositing a halide-based stimulable phosphor precursor crystal from a mixed solution prepared by adding two or more inorganic solutions, and a step of removing the solvent from the mixed solution tank for depositing the crystal Is obtained. In addition, about the stimulable phosphor precursor manufacture by the liquid phase method concerning this invention, the precursor manufacturing method described in Unexamined-Japanese-Patent No. 10-140148 and the precursor described in Unexamined-Japanese-Patent No. 10-147778 Manufacturing equipment and the like can be taken into consideration.

  Below, the detail of the manufacturing method of the photostimulable phosphor which concerns on this invention is demonstrated.

First, raw material compounds other than the fluorine compound are dissolved in an aqueous medium. That is, a halide of BaBr ₂ and Ln (Ce, Pr, Sm, Eu, Gd, Tb, Tm, Dy, Ho, Nd, Er, and Yb), and if necessary, a halide. Further, M ² halide, and further M ¹ halide are placed in an aqueous medium, mixed well and dissolved to prepare an aqueous solution in which they are dissolved. However, the quantitative ratio between the BaBr ₂ concentration and the aqueous solvent is adjusted so that the BaBr ₂ concentration is 0.5 mol / L or more, preferably 1.5 mol / L or more. At this time, if the barium concentration is low, a precursor having a desired composition cannot be obtained, or even if obtained, the particles are enlarged. Therefore, it is necessary to appropriately select the barium concentration, and as a result of the study by the present inventors, it has been found that fine precursor particles can be formed at 0.5 mol / L or more. At this time, if desired, a small amount of acid, ammonia, alcohol, water-soluble polymer, water-insoluble metal oxide fine particle powder or the like may be added. It is also a preferred embodiment that an appropriate amount of lower alcohol (methanol, ethanol) is added within a range in which the solubility of BaBr ₂ is not significantly reduced. This aqueous solution (reaction mother liquor) is maintained at 60 ° C.

  Next, an aqueous solution of an inorganic fluoride (ammonium fluoride, alkali metal fluoride, etc.) is poured into the aqueous solution maintained at 60 ° C. and stirred. This injection is preferably carried out in the region where the stirring is particularly intense. By injecting this inorganic fluoride aqueous solution into the reaction mother liquor, an oxygen-introduced rare earth-activated alkaline earth metal fluorobromide-based phosphor precursor crystal corresponding to the general formula (1) is precipitated.

  In the present invention, the solvent is removed from the reaction solution when the inorganic fluoride aqueous solution is added. The timing for removing the solvent is not particularly limited as long as it is being added. The ratio (removal ratio) of the total mass after removal of the solvent to the mass before removal (the sum of the mass of the reaction mother liquor and the mass of the added aqueous solution) is preferably 0.97 or less. Below this, the crystal may not become BaFBr in some cases. Therefore, the removal ratio is preferably 0.97 or less, and more preferably 0.95 or less. Moreover, even if it removes too much, inconvenience may arise in terms of handling, such as an excessive increase in the viscosity of the reaction solution. Therefore, the solvent removal ratio is preferably up to 0.5. The time required for removing the solvent not only greatly affects the productivity, but also the shape and particle size distribution of the particles are affected by the method of removing the solvent, so the removal method needs to be appropriately selected.

  Generally, when removing the solvent, a method of heating the solution and evaporating the solvent is selected. This method is also useful in the present invention. By removing the solvent, a precursor having the intended composition can be obtained. Furthermore, in order to increase productivity and to keep the particle shape appropriately, it is preferable to use other solvent removal methods in combination. The method for removing the solvent used in combination is not particularly limited. It is also possible to select a method using a separation membrane such as a reverse osmosis membrane. In the present invention, it is preferable to select the following removal method from the viewpoint of productivity.

1. The reaction vessel for ventilating the dry gas is sealed, and at least two holes through which the gas can pass are provided, and the dry gas is vented there. The kind of gas can be selected arbitrarily. Air and nitrogen are preferable from the viewpoint of safety. Depending on the amount of saturated water vapor in the gas to be vented, the solvent is entrained in the gas and removed. In addition to the method of venting the void portion of the reaction vessel, a method of jetting gas as bubbles in the liquid phase and absorbing the solvent in the bubbles is also effective.

2. Depressurization As is well known, the depressurization reduces the vapor pressure of the solvent. The solvent can be efficiently removed by the vapor pressure drop. The degree of reduced pressure can be appropriately selected depending on the type of solvent. When the solvent is water, 86 kPa or less is preferable.

3. Liquid film The solvent can be removed efficiently by increasing the evaporation area. As in the present invention, when a reaction is carried out by heating and stirring using a constant volume reaction vessel, the heating method is a method of immersing the heating means in a liquid or mounting the heating means outside the container. Is common. According to this method, the heat transfer area is limited to a portion where the liquid and the heating means are in contact with each other, and the heat transfer area decreases with the removal of the solvent, and thus the time required for the solvent removal increases. In order to prevent this, a method of increasing the heat transfer area by spraying on the wall surface of the reaction vessel using a pump or a stirrer is effective. Such a method of spraying a liquid on the reaction vessel wall surface to form a liquid film is known as a “wetting wall”. Examples of the method for forming the wet wall include a method using a stirrer described in JP-A-6-335627 and JP-A-11-235522, in addition to a method using a pump.

  These methods may be used not only alone but also in combination. A combination of a method of forming a liquid film and a method of reducing the pressure in the container, a combination of a method of forming a liquid film and a method of ventilating dry gas, and the like are effective. The former is particularly preferable, and the methods described in JP-A-6-335627 and Japanese Patent Application No. 2002-35202 are preferably used.

  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.

4). Firing In order to produce a photostimulable phosphor using the phosphor precursor crystal obtained by the above method (hereinafter also referred to as “phosphor precursor”), the production of the present invention shown in FIG. By using the apparatus, a firing method through the following steps a) to e) is particularly employed.

  a) In the stimulable phosphor precursor filling portion 23 inside the furnace tube 21 before firing, the total mass m (kg) of the stimulable phosphor precursor crystal 51 and the internal volume l (L) of the core tube 21 are Filling the stimulable phosphor precursor 51 so that the ratio m / l (kg / L) is 0.03 or more and 1.0 or less; b) containing 0.1 to 10% hydrogen and the balance being nitrogen A step of heating the stimulable phosphor precursor crystal from 100 ° C. or lower to 600 ° C. or higher while flowing the atmospheric gas at a flow rate ratio of 0.01 to 2.0 (% / min) with respect to the core tube volume; c) Subsequent to the above b), the atmospheric gas containing 0.1 to 7% oxygen and 0.1 to 10% hydrogen and the remainder being nitrogen is supplied at a flow rate ratio of 0.01 to 2.0 with respect to the core tube volume. The step of heating the photostimulable phosphor precursor at 600 ° C. or higher for 30 minutes or longer while being distributed at (% / min) d) Subsequent to the above c), the ambient gas containing 0.1 to 10% hydrogen and the remainder being nitrogen was circulated at a flow rate of 0.01 to 10 (% / min) with respect to the reactor core volume. A step of heating the stimulable phosphor precursor at 600 ° C. or higher for 30 minutes or longer; e) Subsequent to d), an atmospheric gas containing 0.1 to 10% hydrogen and the remainder being nitrogen is supplied to the core tube volume. While flowing at a flow rate ratio of 2.0 to 10 (% / min), the firing furnace 11 is moved to each of the firing furnace upper partial retreat position 15 and the firing furnace lower partial retreat position 16, and the photostimulable phosphor is moved to 100. The process of rapidly cooling to below ℃ and taking out.

  Hereinafter, details of each process will be described. First, the ratio between the total mass m (kg) of the stimulable phosphor precursor 51 and the internal volume l (L) of the core tube 21 in the stimulable phosphor precursor filling portion 23 inside the core tube 21 before firing. The stimulable phosphor precursor 51 is filled so that m / l (kg / L) is 0.03 or more and 1.0 or less.

  Thereafter, an atmosphere gas containing 0.1 to 10% hydrogen and the remainder being nitrogen is circulated inside the core tube 21. At this time, it is preferable that the temperature of the stimulable phosphor precursor filling portion 23 be kept at 100 ° C. or lower until an atmosphere gas having a volume of at least 10% of the capacity inside the core tube 21 is injected.

  After replacing the inside of the furnace core tube 21 with the above atmospheric gas, heating is performed to 600 ° C. or higher. At this time, it is preferable for the mixed atmosphere in the core tube to flow the atmosphere gas at a flow rate ratio of 0.01 to 2.0 (% / min) with respect to the core tube volume. More preferably, it is 0.1-3.0 (% / min). Further, the rate of temperature rise varies depending on the specifications of the electric furnace, but is preferably 1 to 50 ° C./min.

  After reaching 600 ° C. or higher, an atmosphere gas containing at least 0.1 to 7% oxygen and 0.1 to 10% hydrogen and the remainder being nitrogen is introduced into the reactor core tube for at least 30 minutes, preferably 1 to A mixed atmosphere gas of nitrogen, hydrogen, and oxygen is circulated at 600 ° C. or higher for 5 hours. The flow rate is preferably circulated at a flow rate ratio of 0.01 to 2.0 (% / min) with respect to the core tube volume. More preferably, it is 0.1-3.0 (% / min). The temperature at this time is preferably 600 to 1300 ° C, more preferably 700 to 1000 ° C. By setting the temperature to 600 ° C. or higher, good photostimulated luminescence characteristics can be obtained, and when the temperature is 700 ° C. or higher, more preferable photostimulable luminescence properties for practical diagnosis of radiation images can be obtained. Further, if it is 1300 ° C. or lower, it is possible to prevent the particle size from being increased by sintering. it can. More preferably, it is around 820 ° C. As the newly introduced atmosphere, a mixed gas in which the hydrogen concentration is 0.1 to 10%, the oxygen concentration is less than 7% and less than the hydrogen concentration, and the remaining component is nitrogen is preferable. More preferably, it is a mixed gas in which the hydrogen concentration is 0.1 to 3%, the oxygen concentration is 40 to 150% with respect to the hydrogen concentration, and the remaining components are nitrogen. Particularly preferred is a mixed gas of 1% hydrogen, 1.1% oxygen, and the remaining components being nitrogen. When the hydrogen concentration is 0.1% or more, reducing power can be obtained and the light emission characteristics can be improved. It is preferable for handling when the hydrogen concentration is 5% or less, and the photostimulable phosphor crystal itself is reduced. Can be prevented. Further, the stimulated emission intensity can be remarkably improved with the oxygen concentration peaking at about 110% with respect to the hydrogen concentration.

  After the above operation, an atmosphere containing 0.1 to 10% hydrogen and the remainder being nitrogen is introduced again into the core tube 21. At this time, it is preferable to use the same atmospheric gas as that used to raise the temperature. The flow rate of the atmospheric gas is preferably a flow rate ratio of 0.01 to 10 (% / min) with respect to the core tube volume. Moreover, since the atmospheric gas inside the core tube 21 is replaced by this, reaction products other than the photostimulable phosphor generated inside the core tube 21 can be discharged. At least 30 minutes or more, preferably 30 minutes to 12 hours, an atmosphere is maintained at 600 ° C. or more and containing 0.1-10% hydrogen with the balance being nitrogen. By setting it to 30 minutes or more, a photostimulable phosphor exhibiting good photostimulable light emission characteristics can be obtained. Moreover, the fall of the photostimulable luminescent property by heating can be prevented by setting it as 12 hours or less. The temperature at this time is preferably 600 to 1300 ° C, more preferably 700 to 1000 ° C.

  Cooling is preferably performed while flowing an atmospheric gas containing 0.1 to 10% hydrogen and the remainder being nitrogen at a flow rate ratio of 2.0 to 10 (% / min) with respect to the core tube volume. In order to increase the efficiency of substitution, it is preferable to increase the flow rate of the atmospheric gas. By setting the flow rate ratio with respect to the core tube volume to 2.0 to 10 (% / min), reaction products other than the stimulable phosphor generated in the core can be discharged. The rate of temperature reduction is preferably 1 to 50 ° C./min.

  From the two viewpoints of improving productivity and phosphor characteristics, cooling is preferably performed at a speed as fast as possible. The manufacturing apparatus according to the present invention is advantageous because the cooling rate can be extremely increased by dividing the firing furnace.

Cooling is preferably performed to at least 100 ° C., and then the produced phosphor is preferably taken out, and a particularly preferred taking-out temperature is 50 ° C. or lower.
According to the present invention, the photostimulable phosphor can be fired uniformly and then rapidly cooled to prevent deterioration and contamination due to corrosion.

  Hereinafter, the present invention will be described in detail with reference to preferred embodiments.

  FIG. 1 is an external perspective view of a photostimulable phosphor manufacturing apparatus (hereinafter sometimes simply referred to as “manufacturing apparatus”) according to an embodiment of the present invention.

  In FIG. 1, reference numeral 11 denotes a firing furnace, in which a core tube 21 is disposed so as to pass through, and both ends are supported by a core tube rotation support device 13. The firing furnace 11 is divided into two parts, and a heat source disposed on the inner surface of the firing furnace outside the core tube can be moved to a position away from the core tube during cooling of the core tube.

  FIG. 2 is a cross-sectional view of the stimulable phosphor manufacturing apparatus of the present invention. In FIG. 2, 11 is a firing furnace, and a core tube 21 is disposed in a state where it penetrates. A heat source 12 is arranged on the inner surface of the firing furnace 11 and outside the core tube 21, and the inside of the firing furnace 11 is heated by the heat source 12, and the photostimulable phosphor precursor crystal that is directly put into the core tube 21. 51 is configured to be baked.

  As a shape of the core tube 21, as shown in FIG. 2, the structure which connected the cylinder with a smaller diameter to the both ends of a cylinder is preferable. The portion connecting the cylinders having different diameters may have a structure in which two large and small cylinders are directly connected via a donut-shaped plate in addition to the structure in which the cylinders are smoothly connected as shown in FIG.

  It is preferable to have a ring-shaped in-core tube projection 22 as shown in FIG. 2 at any position in the small-diameter portion inside the core tube. The height of the core tube projection 22 can be selected from about 5 to 50 mm. Due to the core tube protrusions 22, it is possible to prevent residues and dirt deposited and adhered to both ends of the tube from entering the photostimulable phosphor precursor 51.

  The size of the core tube 21 is appropriately set according to the purpose, but the diameter of the cross section of the portion having a large central diameter is generally selected from the range of about 50 to 1000 mm, and the range of about 100 to 400 mm is preferable. . A portion having a large central diameter is a portion filled with the photostimulable phosphor precursor, that is, a photostimulable phosphor precursor filling portion 23, which is indicated by hatching in the drawing. The length of the stimulable phosphor precursor filling portion 23 (left and right direction in the figure) is preferably 100 to 1000 mm. The diameter of the cross section of both end portions connected to the photostimulable phosphor precursor filling portion 23 is selected from the range of about 20 to 90% of the diameter of the photostimulable phosphor precursor filling portion 23, and about 50 to 80%. The range of is preferable. When the stimulable phosphor precursor 51 is introduced into the stimulable phosphor precursor filling portion 23, the stimulable phosphor precursor 51 is heated by the firing furnace 11 when the furnace core tube 21 is rotated. Can be stopped.

  Further, the length of the core tube 21 is about 300 to 2000 mm from the end of the firing furnace 11 in order to provide a portion for holding the core tube 21 and not to raise the temperature at both ends of the core tube 21 to about 200 ° C. or more. It is preferable to have the length.

  The material of the core tube 21 and the core tube projections 22 is preferably quartz glass. Quartz glass has strong corrosion resistance and is characterized by rapid temperature changes.

  In order to adjust the fluidity of the photostimulable phosphor precursor 51, the photostimulable phosphor precursor filling portion 23 may include a blade-like projection having a height of about 5 to 50 mm.

  In the core tube 21, the ratio m / l (kg / L) of the total mass m (kg) of the stimulable phosphor precursor 51 to the internal volume (L) of the core tube 21 is 0.03 or more and 1.0 or less. It is preferable that m / l is 0.04 or more and 0.7 or less. When the ratio m / l is 1.0 or more, the phosphor material mixture is densely packed in a narrow space, and it may be difficult to perform uniform firing as a whole, and is 0.03 or less. Then, the volatile halogen atmosphere is too low, and the photostimulable luminescence amount and erasing property of the resulting photostimulable phosphor may be deteriorated.

  The core tube 21 is held by a core tube rotation support device 13 disposed on the left side of the firing furnace 11 in the drawing and a core tube rotation drive device 14 disposed on the right side. The core tube 21 may be horizontal or slightly inclined in the axial direction. When the core tube 21 is filled with the photostimulable phosphor precursor 51 and the core tube 21 is rotated, the photostimulable phosphor is filled from the photostimulable phosphor precursor filling portion 23. It is necessary to suppress the inclination angle to such an extent that the precursor 51 does not spill out. The furnace core tube 21 preferably has a structure that does not substantially contact the firing furnace 11. The core tube rotation support device 13 and the core tube rotation drive device 14 are each composed of two rubber rollers arranged horizontally, and the core tube 21 is disposed so as to be in contact with the two rubber rollers. Further, the core tube rotation driving device 14 includes a motor for rotating the rubber roller, a chain for transmitting the rotation of the motor, and the like, and is used for rotating the core tube 21.

  It is preferable that the rotational speed of the core tube 21 can be adjusted in the range of 0.1 to 10 rpm. At a rotational speed of 0.1 rpm or less, there is little effect of supplying heat or atmospheric gas uniformly to the stimulable phosphor precursor 51, and at 10 rpm or more, the stimulable phosphor precursor 51 is damaged by excessive movement. May give.

  As shown on the left side in the figure, a gas introduction pipe 33 is connected to the core tube 21 through a gas introduction side lid 31 in order to introduce gas into the core tube. The gas introduction side lid 31 and the gas introduction side piping 33 are connected via a so-called gas introduction side rotary joint 32 installed at the center of the lid. The gas introduction side rotary joint 32 has an oil seal, a mechanical seal and the like inside, seals the rotating part, and keeps the atmosphere inside the core tube 21 constant. Similarly, a gas discharge pipe 43 is connected to the opposite end (right side in the figure) of the core tube 21 via a gas discharge side rotary joint 42 and a gas discharge side lid 41 in order to discharge gas. .

  As the atmospheric gas, at least three kinds including nitrogen, hydrogen, and oxygen are required. For safety reasons, it is preferable to use a mixed gas of 1 to 5% hydrogen and the remaining nitrogen instead of 100% hydrogen. Similarly, a mixed gas of oxygen and nitrogen may be used instead of 100% oxygen. In the drawing, an oxygen mixed gas flow rate control device 34 and a nitrogen gas flow rate control device 35 are supplied from three types of gas supply sources of an oxygen mixed gas cylinder 37, a nitrogen gas cylinder 38, and a hydrogen mixed gas cylinder 39 through a regulator, a valve and the like (not shown in the drawing). The hydrogen mixed gas flow rate control device 36 is connected to each other.

  The supply amounts of the three kinds of gases are controlled by the gas flow rate control devices 34 to 36. The gas flow rate control devices 34 to 36 can use a mass flow controller, a float type flow meter, etc., control the flow rates of the three types of gas independently, mix them, and introduce them into the core tube 21 through the gas introduction pipe 33. To do. It is preferable that the atmosphere gas is always circulated during firing to continuously replace the atmosphere inside the furnace tube 21.

  As the flow rate of the atmospheric gas, the oxygen mixed gas flow control device 34 is 1-1000 ml / min, the nitrogen gas flow control device 35 is 0.1-30 L / min, and the hydrogen mixed gas flow control device 36 is 0.01-10 L / min. It is preferable that adjustment is possible within the range of min.

  When firing a photostimulable phosphor of a rare earth element activated alkaline earth metal fluorohalide as shown in the general formula (EFS1), halogen gases such as iodine and bromine may be generated. The contacted portion preferably has corrosion resistance.

  The material of the gas inlet side lid 31, the gas outlet side lid 41, the gas inlet side rotary joint 32, and the gas outlet side rotary joint 42 is preferably a stainless alloy, aluminum, or the like. Further, the surface in contact with the atmospheric gas is preferably coated with fluorine. Examples of fluororesins include polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-ethylene copolymer ( ETFE), polychlorotrifluoroethylene (PCTFE), chlorotrifluoroethylene-ethylene copolymer (ECTFE), polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF) and the like can be selected, and PFA and ETFE are particularly preferable. .

  The material of the gas introduction pipe 33, the gas discharge pipe 43, and the gas trap 44 may be a fluororesin itself in addition to the fluorine-coated metal similar to the gas introduction side cover 31 and the like.

  Inside the gas trap 44, the exhaust gas is washed with a sodium thiosulfate aqueous solution 45 and then discharged into the atmosphere. The sodium thiosulfate aqueous solution 45 can efficiently remove halogen gas such as iodine from the exhaust gas.

  Gas contact portions of the gas introduction side lid 31, the gas discharge side lid 41, the gas introduction side rotary joint 32, the gas discharge side rotary joint 42, the gas supply pipe 33, the gas discharge pipe 43, the gas trap 44, and the core tube 21 described above. 80% or more of the total area is preferably coated with fluorine or quartz glass. Particularly preferably, it is 90% or more. By setting it to 80% or more, corrosion due to halogen gas during firing can be prevented, and generation of corrosion products can be suppressed. Moreover, it is preferable to use quartz glass for the portion where the temperature reaches 200 ° C. or higher during firing, and the portion lower than 200 ° C. is preferably a fluorine-coated metal.

  As the heat source 12, any conventionally known heat source can be used. For example, a known electric heater can be adopted. The heat source 12 needs to have an ability to keep at least the range of the stimulable phosphor precursor filling portion 53 at an arbitrary temperature between 600 to 900 ° C.

  When firing the photostimulable phosphor precursor crystal 51, first, the photostimulable phosphor precursor 51 is put into the photostimulable phosphor precursor filling portion 53. After that, the gas introduction side lid 31 and the gas discharge side lid 41 are fixed to the core tube 21, and the inside of the core tube 21 is sealed. Then, the atmosphere gas inside the core tube 21 is appropriately introduced and exhausted through the gas introduction pipe 33, the gas discharge pipe 43, and the like, and heat is applied from the heat source 12 while the atmosphere inside the core tube 21 is kept in a predetermined state. . Firing conditions (atmospheric gas flow rate, temperature, time, firing temperature, number of steps of atmosphere, etc.) may be set appropriately according to the purpose.

  After firing, the firing furnace 11 can be divided into two parts and moved to the firing furnace upper partial retreat position 15 and the firing furnace lower partial retreat position 16. The cooling rate can be increased by moving the heat source 12 away from the core tube 21. In addition, a cooling device such as a cooling fan can be installed in the divided space to further increase the cooling rate. The dividing method of the firing furnace is not limited to moving up and down, and may be divided into left and right or in the left and right direction in the figure. Moreover, you may divide | segment into three or more components. The moving distance can be selected from a range of about 100 to 1000 mm. The longer the moving distance, the higher the cooling rate.

  After the furnace tube 21 is sufficiently cooled, the gas introduction side cover 31 and the gas discharge side cover 41 are removed, and then the sintered stimulable phosphor precursor crystal 51, that is, the stimulable phosphor is taken out.

(Production of radiation image conversion panel)
As described above, the target oxygen-introduced rare earth-activated alkaline earth metal fluorohalide photostimulable phosphor is obtained, and a radiation image conversion panel having a phosphor layer formed using the phosphor is produced. Hereinafter, the production of the radiation image conversion panel will be described in detail.

[Support]
Various polymer materials are used as the support used in the radiation image conversion panel according to the present invention. In particular, a material that can be processed into a flexible sheet or web as an information recording material is suitable. In this respect, cellulose acetate film, polyester film, polyethylene terephthalate film, polyethylene naphthalate film, polyamide film, polyimide A plastic film such as a film, a triacetate film or a polycarbonate film is preferred.

  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. 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.

  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.

[Undercoat layer]
The undercoat layer according to the present invention preferably contains a polymer resin that can be crosslinked by a crosslinking agent and a crosslinking agent.

  The polymer resin that can be used in the undercoat layer is not particularly limited. For example, polyurethane, polyester, vinyl chloride copolymer, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinylidene chloride copolymer, Vinyl chloride-acrylonitrile copolymer, butadiene-acrylonitrile copolymer, polyamide resin, polyvinyl butyral, cellulose derivative (nitrocellulose, etc.), styrene-butadiene copolymer, various synthetic rubber resins, phenol resin, epoxy resin, urea Examples thereof include resins, melamine resins, phenoxy resins, silicon resins, acrylic resins, urea formamide resins, and the like. Among them, polyurethane, polyester, vinyl chloride copolymer, polyvinyl butyral, nitrocellulose and the like can be mentioned. In the invention according to claim 2, the average glass transition temperature (Tg) of the polymer resin used in the undercoat layer can be mentioned. ) Is 25 ° C. or higher, and preferably a polymer resin having a Tg of 25 to 200 ° C. is used.

  The crosslinking agent that can be used in the undercoat layer according to the present invention is not particularly limited, and examples thereof include polyfunctional isocyanates and derivatives thereof, melamine and derivatives thereof, amino resins and derivatives thereof, and the like. It is preferable to use a polyfunctional isocyanate compound as the agent, and examples thereof include Coronate HX and Coronate 3041 manufactured by Nippon Polyurethane.

  The undercoat layer according to the present invention can be formed on the support by, for example, the following method.

  First, the polymer resin and the crosslinking agent described above are added to an appropriate solvent, for example, a solvent used in the preparation of a stimulable phosphor layer coating liquid described later, and mixed sufficiently to prepare an undercoat layer coating liquid. .

  The amount of crosslinking agent used varies depending on the characteristics of the intended radiation image conversion panel, the type of materials used for the stimulable phosphor layer and the support, the type of polymer resin used in the undercoat layer, etc. Considering the maintenance of the adhesive strength of the phosphor layer to the support, it is preferably added at a ratio of 50% by mass or less, particularly preferably 15 to 50% by mass with respect to the polymer resin.

  The thickness of the undercoat layer varies depending on the characteristics of the intended radiation image conversion panel, the type of materials used for the stimulable phosphor layer and the support, the type of polymer resin and crosslinking agent used in the undercoat layer, etc. In general, the thickness is preferably 3 to 50 μm, and particularly preferably 5 to 40 μm.

[Stimulable phosphor layer]
Examples of the binder used in the 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, and nitrocellulose. , Represented by synthetic polymer materials such as ethyl cellulose, vinylidene chloride / vinyl chloride copolymer, polyalkyl (meth) acrylate, vinyl chloride / vinyl acetate copolymer, polyurethane, cellulose acetate butyrate, polyvinyl alcohol, linear polyester, etc. Examples of the binder include a resin mainly composed of a thermoplastic elastomer. Examples of the thermoplastic elastomer include polystyrene-based thermoplastic elastomers and polyolefins described above. Thermoplastic elastomers, polyurethane thermoplastic elastomers, polyester thermoplastic elastomers, polyamide thermoplastic elastomers, polybutadiene thermoplastic elastomers, ethylene vinyl acetate thermoplastic elastomers, polyvinyl chloride thermoplastic elastomers, natural rubber thermals Examples thereof include thermoplastic elastomers, fluororubber-based thermoplastic elastomers, polyisoprene-based thermoplastic elastomers, chlorinated polyethylene-based thermoplastic elastomers, styrene-butadiene rubber, and silicon rubber-based thermoplastic elastomers. Among these, polyurethane-based thermoplastic elastomers and polyester-based thermoplastic elastomers have good dispersibility due to their strong bonding strength with phosphors, and are also excellent in ductility, and have excellent flexibility against radiation intensifying screens. This is preferable. These binders may be crosslinked by a crosslinking agent.

  The mixing ratio of the binder and the stimulable phosphor in the coating solution varies depending on the set value of the haze ratio of the intended radiation image conversion panel, but is preferably 1 to 20 parts by mass with respect to the phosphor, and more preferably 2 to 2. 10 parts by mass is more preferable.

[Protective layer]
As a protective layer provided in a radiation image conversion panel having a coating-type phosphor layer, a polyester film provided with an excitation light absorption layer having a haze ratio measured by the method described in ASTM D-1003 of 5% or more and less than 60%, Polymethacrylate film, nitrocellulose film, cellulose acetate film and the like can be used, but stretched films such as polyethylene terephthalate film and polyethylene naphthalate film are preferable as a protective layer in terms of transparency and strength. A vapor deposition film obtained by depositing a thin film such as a metal oxide or silicon nitride on the polyethylene terephthalate film or the polyethylene terephthalate film is more preferable from the viewpoint of moisture resistance.

  The haze ratio of the film used in the protective layer can be easily adjusted by selecting the haze ratio of the resin film to be used, and a resin film having an arbitrary haze ratio can be easily obtained industrially. As a protective film for a radiation image conversion panel, an optically highly transparent film is assumed. As such a highly transparent protective film material, various plastic films having a haze value in the range of 2 to 3% are commercially available. In order to obtain the effect of the present invention, the preferred haze ratio is 5% or more and less than 60%, and more preferably 10% or more and less than 50%. If the haze ratio is less than 5%, the effect of eliminating image unevenness and linear noise is low, and if it is 60% or more, the effect of improving sharpness is impaired.

The film used in the protective layer according to the present invention is made to be optimal moisture-proof by laminating a plurality of vapor-deposited films obtained by depositing a metal oxide or the like on a resin film or resin film in accordance with the required moisture-proof property. In consideration of preventing moisture absorption deterioration of the stimulable phosphor, the moisture permeability is preferably at least 5.0 g / m ² · day or less. There is no restriction | limiting in particular as a lamination method of a resin film, You may use any well-known method.

  In addition, it is preferable to provide an excitation light absorption layer between the laminated resin films so that the excitation light absorption layer is protected from physical impact and chemical alteration and stable plate performance can be maintained for a long period of time. Further, the excitation light absorption layer may be provided at a plurality of locations, or a color material may be contained in the adhesive layer for stacking to form the excitation light absorption layer.

  The protective film may be in close contact with the photostimulable phosphor layer via an adhesive layer, but has a structure (hereinafter also referred to as a sealing or sealing structure) provided to cover the phosphor surface. Is more preferable. In sealing the phosphor plate, any known method may be used, but the outermost resin layer on the side in contact with the phosphor sheet of the moisture-proof protective film may be a moisture-proof resin film. This is one of the preferred forms in that the protective film can be fused and the phosphor sheet can be efficiently sealed. Furthermore, a moisture-proof protective film is arranged above and below the phosphor sheet, and the upper and lower moisture-proof protective films are heated and fused with an impulse sealer or the like in a region where the periphery is outside the periphery of the phosphor sheet. The sealing structure is preferable because it can prevent moisture from entering from the outer peripheral portion of the phosphor sheet. In addition, the moisture-proof protective film on the support surface side is a laminated moisture-proof film formed by laminating one or more aluminum films, so that moisture entry can be reduced more reliably. It is easy and preferable. In the method of heat-sealing with the impulse sealer, heat-sealing under a reduced pressure environment is more preferable in terms of preventing displacement of the phosphor sheet in the moisture-proof protective film and eliminating moisture in the atmosphere.

  The outermost resin layer and the phosphor surface having the heat-sealing property on the side where the phosphor surface of the moisture-proof protective film is in contact may or may not be adhered. Here, the state of non-adhesion means that the phosphor surface and the moisture-proof protective film are optically and mechanically discontinuous even if the phosphor surface and the moisture-proof protective film are in point contact. It is a state that can be treated as a body. The resin film having the above-mentioned heat-fusibility is a resin film that can be fused with a commonly used impulse sealer. For example, ethylene vinyl acetate copolymer (EVA), polypropylene (PP) film, polyethylene ( PE) film and the like can be mentioned, but the present invention is not limited to this.

  Examples of the organic solvent used for the preparation of the stimulable phosphor layer coating solution include lower alcohols such as methanol, ethanol, isopropanol and n-butanol, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone and 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.

  In the coating solution, a dispersing agent for improving the dispersibility of the phosphor in the coating solution, and the binding force between the binder and the phosphor in the photostimulable phosphor layer after formation are improved. Various additives such as a plasticizer 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 phosphoric esters such as triphenyl phosphate, tricresyl phosphate and diphenyl phosphate; phthalic esters such as diethyl phthalate and dimethoxyethyl phthalate; ethyl phthalyl ethyl glycolate and butyl phthalyl butyl glycolate 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. In addition, a dispersing agent such as stearic acid, phthalic acid, caproic acid or a lipophilic surfactant is mixed in the stimulable phosphor layer coating solution for the purpose of improving the dispersibility of the stimulable phosphor particles. Also good.

  The coating solution for the photostimulable phosphor layer is prepared using a dispersing device such as a ball mill, a bead mill, a sand mill, an attritor, a three-roll mill, a high-speed impeller disperser, a Kady mill, or an ultrasonic disperser. .

  A coating film is formed by uniformly coating the coating solution prepared as described above on the surface of a support described later. As a coating method that can be used, usual coating means such as a doctor blade, a roll coater, a knife coater, a comma coater, a lip coater and the like can be used.

  The coating film formed by the above means is then heated and dried to complete the formation of the photostimulable phosphor layer on the support. 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 10 to 1000 μm. More preferably, it is 10-500 micrometers.

  The following examples illustrate the invention.

Example 1
A photostimulable phosphor was manufactured using the manufacturing apparatus of the present invention shown in FIG. The specifications of each part of the manufacturing apparatus used are shown below.

Core tube 21: made of quartz glass, large diameter portion = 400 mm, small diameter portion = 200 mm, large diameter portion length = 500 mm, internal volume = 120 L, core tube protrusion 22 = 10 mm at the end of the small diameter portion (position in FIG. 2) The gas inlet side lid 31, the gas inlet side rotary joint 32, the gas outlet side lid 41, the gas outlet side rotary joint 42, and the gas outlet pipe 43 are made of aluminum with an ETFE coating on the surface. .
Oxygen mixed gas flow rate control device 34: CMQ9200 manufactured by Yamatake Corporation,
Nitrogen gas flow control device 35: CMQ0005 manufactured by Yamatake Corporation
Hydrogen mixed gas flow control device 36: CMQ0020 manufactured by Yamatake Corporation
Oxygen gas cylinder 37: 20% oxygen / 80% nitrogen gas mixture,
Hydrogen gas cylinder 39: 1% hydrogen / 99% nitrogen gas mixture.

In order to synthesize a stimulable phosphor precursor of europium-activated barium fluorobromide, 2500 ml of BaBr ₂ aqueous solution (1.5 mol / L) and EuBr ₃ aqueous solution (0.2 mol / L) were placed in a pressure vessel having _two holes. ) 50 ml was placed in the reactor. The reaction mother liquor in this reactor was kept at 60 ° C. with stirring. While ventilating dry air at a rate of 10 L / min, 300 ml of an aqueous ammonium fluoride solution (10 mol / L) was injected into the reaction mother liquor using a roller pump to precipitate crystals (precipitates). After completion of the reaction, the mass ratio of the solution before and after aeration was 0.94. The mixture was stirred for 90 minutes at the same temperature. The mixture was stirred for 90 minutes, filtered, washed with 2000 ml of ethanol, and dried at 80 ° C. To prevent changes in particle shape due to sintering during sintering and particle size distribution due to inter-particle fusion, 0.1% by mass of ultrafine powder of alumina was added, and the mixture was stirred sufficiently with a mixer. An ultrafine particle powder of alumina was uniformly attached to the surface.

  7 kg of a mixture of europium-activated barium fluorobromide crystal powder and alumina ultrafine particles is filled in the stimulable phosphor precursor crystal filling portion 23 inside the reactor core tube 21, and 99% nitrogen / 1% hydrogen mixed gas is charged. The atmosphere gas was replaced by flowing for 60 minutes at a flow rate of 10 L / min. Thereafter, the flow rate of the 99% nitrogen / 1% hydrogen mixed gas was reduced to 1.5 L / min, and the reactor core tube was rotated at a speed of 0.2 rpm, and heated to 820 ° C. at a temperature increase rate of 20 ° C./min. .

  Sixty minutes after the sample temperature reaches 820 ° C., the gas to be introduced is added to 99% nitrogen / 1% hydrogen mixed gas 1.5 L / min at a flow rate of 20% oxygen / 80% nitrogen mixed gas 90 ml / min. It was kept at 820 ° C. while flowing for 2 hours and 30 minutes.

  Thereafter, the gas to be introduced was changed again to 99% nitrogen / 1% hydrogen mixed gas, the flow rate was increased to 5 L / min, and the mixture was held at 820 ° C. for 1 hour 30 minutes.

  Then, it cooled to 600 degreeC with the temperature-fall rate of 6 degrees C / min, maintaining the flow volume of 99% nitrogen / 1% hydrogen mixed gas at 5 L / min. Furthermore, the firing furnace 11 was divided into two parts, moved to the firing furnace upper partial retreat position 15 and the firing furnace lower partial retreat position 16, and cooled to 50 ° C. at a cooling rate of 15 ° C./min. Thereafter, the firing furnace atmosphere was returned to the atmosphere, and the europium activated barium fluorobromide photostimulable phosphor particles produced by stopping the rotation of the furnace core tube were taken out. The extracted photostimulable phosphor particles were uniformly white.

  Next, the phosphor particles were classified by sieving to obtain particles having an average particle size of 2.2 μm.

  In addition, the mass of the collect | recovered precursor was measured and the yield was calculated | required. The crystal structure of the crystal obtained by the above operation was identified by X-ray diffraction measurement. X-rays were Cu-Kα rays. Moreover, while measuring the average particle diameter of the obtained crystal | crystallization, the ratio (%) of the crystal | crystallization with a particle size of 10 micrometers or more and 0.5 micrometers or less was calculated. The same measurement and evaluation were performed for the following comparative examples.

Comparative Example 1
Furnace tube 21: made of quartz glass, cylindrical portion with diameter portion = 400 mm, internal volume = 250 L, gas inlet side lid 31, gas inlet side rotary joint 32, gas outlet side lid 41, gas outlet side rotary joint 42, and gas The discharge pipe 43 is made of aluminum (no fluorine coating).

  A precursor crystal was prepared in the same manner as in the example. 7 kg of a mixture of europium-activated barium fluorobromide crystal powder and alumina ultrafine particles is filled near the center of the core tube 21 and a 99% nitrogen / 1% hydrogen mixed gas is circulated at a flow rate of 10 L / min for 60 minutes. The atmosphere gas was replaced.

  Thereafter, the flow rate of the 99% nitrogen / 1% hydrogen mixed gas was reduced to 1.5 L / min, and the reactor core tube was rotated at a speed of 0.2 rpm, and heated to 820 ° C. at a temperature increase rate of 20 ° C./min. .

  Sixty minutes after the sample temperature reaches 820 ° C., the gas to be introduced is added to 99% nitrogen / 1% hydrogen mixed gas 1.5 L / min at a flow rate of 20% oxygen / 80% nitrogen mixed gas 90 ml / min. It was kept at 820 ° C. while flowing for 2 hours and 30 minutes.

  Thereafter, the gas to be introduced was changed again to 99% nitrogen / 1% hydrogen mixed gas, the flow rate was increased to 5 L / min, and the mixture was held at 820 ° C. for 1 hour 30 minutes.

  Then, it cooled to 600 degreeC with the temperature-fall rate of 6 degrees C / min, maintaining the flow volume of 99% nitrogen / 1% hydrogen mixed gas at 5 L / min. Furthermore, the furnace body was naturally cooled without being divided. The firing furnace atmosphere was returned to the atmosphere, and the europium activated barium fluorobromide phosphor particles produced by stopping the rotation of the furnace core tube were taken out.

  After firing, corrosion and rust occurred in the gas contact portions of the gas introduction side cover 31, the gas introduction side rotary joint 32, the gas discharge side cover 41, the gas discharge side rotary joint 42, and the gas discharge pipe 43. The extracted photostimulable phosphor particles were mixed with many impurities that seemed to be rust.

Comparative Example 2
The same manufacturing apparatus as in the example was used. A precursor was prepared in the same manner as in the examples.

  7 kg of a mixture of europium-activated barium fluorobromide crystal powder and alumina ultrafine particles is filled into the stimulable phosphor precursor filling portion 23 inside the core tube 21, and 10 L of 99% nitrogen / 1% hydrogen mixed gas is filled. The atmosphere was replaced by flowing for 60 minutes at a flow rate of / min. Thereafter, the flow rate of the 99% nitrogen / 1% hydrogen mixed gas was reduced to 1.5 L / min, and the reactor core tube 21 was heated to 820 ° C. at a temperature increase rate of 20 ° C./min without rotating.

  Sixty minutes after the sample temperature reaches 820 ° C., the gas to be introduced is added to 99% nitrogen / 1% hydrogen mixed gas 1.5 L / min at a flow rate of 20% oxygen / 80% nitrogen mixed gas 90 ml / min. It was kept at 820 ° C. while flowing for 2 hours and 30 minutes.

  Thereafter, the gas to be introduced was changed again to 99% nitrogen / 1% hydrogen mixed gas, the flow rate was increased to 5 L / min, and the mixture was held at 820 ° C. for 1 hour 30 minutes.

  Then, it cooled to 600 degreeC with the temperature-fall rate of 6 degrees C / min, maintaining the flow volume of 99% nitrogen / 1% hydrogen mixed gas at 5 L / min. Furthermore, the furnace body was naturally cooled without being divided. The firing furnace atmosphere was returned to the atmosphere, and the produced europium-activated barium fluorobromide phosphor particles were taken out.

  The photostimulable phosphor particles that were taken out were found to be partially brownish brown.

Comparative Example 3
The same manufacturing apparatus as in Example 1 was used. A precursor was prepared in the same manner as in the examples.

  Except that the core tube 21 was not rotated, firing was performed in the same manner as in the example, and the produced europium-activated barium fluorobromide phosphor particles were taken out.

The photostimulable phosphor particles that were taken out were found to be partially brownish brown.
Comparative Example 4
In order to synthesize a stimulable phosphor precursor of europium-activated barium fluorobromide, 2500 ml of an aqueous solution of BaBr ₂ (2 mol / L) and 26.5 ml of an aqueous solution of EuBr ₃ (0.2 mol / L) were placed in a reactor. . The reaction mother liquor in this reactor was kept at 60 ° C. with stirring. 250 ml of an aqueous ammonium fluoride solution (10 mol / L) was injected into the reaction mother liquor using a roller pump to precipitate crystals (precipitates). After completion of the injection, the mixture was stirred at the same temperature for 90 minutes. The mixture was stirred for 90 minutes, filtered, washed with 2000 ml of ethanol, dried at 80 ° C., and europium-activated barium fluorobromide phosphor particles were taken out in the same manner as in Example 1 except that the precursor was prepared.

<Production of radiation image conversion panel>
(Formation of undercoat layer)
The undercoat layer coating solution described below was applied to a foamed polyethylene terephthalate film (188E60L manufactured by Toray Industries, Inc.) having a thickness of 188 μm using a doctor blade, and dried at 100 ° C. for 5 minutes. A subbing layer was applied.

(Undercoat layer coating solution)
Polyester resin-dissolved product (Toyobo Co., Ltd. Byron 55SS, solid content 35%) 288.2 g, β-copper phthalocyanine dispersion 0.34 g (solid content 35%, pigment content 30%) and polyisocyanate compound (Japan) 11.22 g of Coronate HX (Polyurethane Industry Co., Ltd.) was mixed and dispersed with a propeller mixer to prepare an undercoat layer coating solution.

[Formation of phosphor layer]
(Preparation of phosphor layer coating solution)
300 g of each of the photostimulable phosphor particles prepared above and 52.63 g of polyester resin (Byron 530 manufactured by Toyobo Co., Ltd., solid content: 30%, solvent: methyl ethyl ketone / toluene = 5/5), 0.13 g of methyl ethyl ketone, and 0 of toluene A phosphor layer coating solution was prepared by adding to a mixed solvent of .13 g and 41.84 g of cyclohexanone and dispersing with a propeller mixer. The solvent ratio of cyclohexane in the phosphor layer coating solution is 53% by mass.

(Formation of phosphor layer, production of phosphor sheet)
The prepared phosphor layer coating solution is applied onto the formed undercoat layer using a doctor blade so as to have a film thickness of 180 μm, and then dried at 100 ° C. for 15 minutes to form a phosphor layer. Thus, a phosphor sheet was produced.

[Production of moisture-proof protective film]
The thing of the following structure (A) was used as a protective film by the side of the fluorescent substance layer coating surface of the produced fluorescent substance sheet.
Configuration (A)
NY15 /// VMPET12 /// VMPET12 /// PET12 /// CPP20
NY: Nylon PET: Polyethylene terephthalate CPP: Casting polypropylene VMPET: Alumina-deposited PET (commercial product: manufactured by Toyo Metallizing Co., Ltd.)
The numbers described behind each resin film indicate the film thickness (μm) of the resin layer. The above “///” means a dry lamination adhesive layer, and the thickness of the adhesive layer is 3.0 μm. As the adhesive used for dry lamination, a two-component reaction type urethane adhesive was used. The protective film on the back side of the support of the phosphor sheet was a dry laminate film having a structure of CPP 30 μm // aluminum film 9 μm // polyethylene terephthalate 188 μm. In this case, “//” used a two-component reaction type urethane adhesive with an adhesive layer thickness of 1.5 μm.

[Production of radiation image conversion panel]
After cutting each of the produced phosphor sheets into squares each having a side of 20 cm, using the produced moisture-proof protective film, the peripheral edge is fused and sealed using an impulse sealer under reduced pressure, Each radiation image conversion panel was produced. In addition, it fused so that the distance from a fusion | melting part to a fluorescent substance sheet peripheral part might be set to 1 mm. The impulse sealer heater used for fusion was a 3 mm wide heater.

<Evaluation of radiation image conversion panel>
(Luminance evaluation)
After irradiating each radiation image conversion panel 6 with X-rays having a tube voltage of 80 kVp, the panel is operated with He-Ne laser light (633 nm) to excite the photostimulated luminescence emitted from the phosphor layer. (Photoelectron image multiplier of spectral sensitivity S-5), the intensity thereof is measured, this is defined as luminance, and the relative image is displayed with the luminance of the radiographic image conversion panel of Comparative Example 1 as 100. did.

(Evaluation of sharpness)
For sharpness, each radiation image conversion panel was irradiated with X-rays with a tube voltage of 80 kVp from the back side of the phosphor sheet support through a lead MTF chart, and then the panel was excited by operating with He-Ne laser light. The stimulated luminescence emitted from the phosphor layer is received by the same light receiver as above, converted into an electrical signal, converted to analog / digital, recorded on a magnetic tape, and analyzed by a computer. The modulation transfer function (MTF) at 1 cycle / mm of the X-ray image recorded on the magnetic tape is examined, and this is measured at 25 positions of the radiation image conversion panel, and the average value (average MTF value) is the sharpness. And the relative value with the sharpness of Comparative Example 1 as 100 was displayed.

  The evaluation results are shown in Table 1.

  From Table 1, according to the production method of the present invention, it is possible to obtain an oxygen-introduced rare earth-activated alkaline earth metal fluorohalide photostimulable phosphor having a uniform particle size distribution with high productivity and high yield. It can be seen that the radiation image conversion plate using the photostimulable phosphor produced by the above method has high brightness and good sharpness.

Stimulable phosphor manufacturing apparatus according to an embodiment of the present invention Sectional drawing of the photostimulable phosphor manufacturing apparatus according to the embodiment of the present invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Firing furnace 12 Heat source 13 Furnace tube rotation support device 14 Furnace tube rotation drive device 15 Firing furnace upper side partial retracted position 16 Firing furnace lower side partial retracted position 21 Furnace core tube 22 Protrusion in core tube 23 Stimulable phosphor precursor filling part 31 Gas introduction side lid 32 Gas introduction side rotary joint 33 Gas introduction piping 34 Oxygen mixed gas flow rate control device 35 Nitrogen gas flow rate control device 36 Hydrogen mixed gas flow rate control device 37 Oxygen mixed gas cylinder 38 Nitrogen gas cylinder 39 Hydrogen mixed gas cylinder 41 Gas discharge side lid 42 Gas discharge side rotary joint 43 Gas discharge pipe 44 Gas trap 45 Sodium thiosulfate aqueous solution 51 Stimulable phosphor precursor crystal

Claims (6)

In the method for producing a halide-based stimulable phosphor, a step of precipitating a halide-based stimulable phosphor precursor crystal from a mixed solution prepared by adding at least two inorganic solutions to a halide ion solution And a step of removing the solvent from the mixed solution tank for precipitating the crystals to obtain a halide-based stimulable phosphor precursor crystal and firing in a firing furnace satisfying the following requirements 1) to 4): And a method for producing a halide-based stimulable phosphor.
Requirements:
1) The firing furnace has a furnace core tube having a structure in which a quartz glass cylinder having a smaller diameter is connected to both ends of a quartz glass cylinder, and a stimulable phosphor is provided in a large diameter portion at the center of the furnace core tube. The precursor can be charged, and the inside of the core tube can be heated to 600 to 900 ° C. while rotating the core tube.
2) The reactor core tube can replace the atmosphere gas inside the reactor core tube, and at least three kinds of atmosphere gases, that is, an atmosphere gas containing at least hydrogen, an atmosphere gas containing at least oxygen, and a nitrogen gas are supplied at respective flow rates. It has a function that can be controlled and introduced into the core tube and discharged.
3) The member of the furnace core tube that occupies 80% or more of the total surface area of the surface portion in contact with the atmospheric gas is quartz glass or a metal covered with a fluororesin.
4) The firing furnace has a heat source disposed outside the core tube, and when the core tube is cooled, the heat source can be moved to a position away from the core tube. In the method for producing a halide-based stimulable phosphor, it takes a longer time to remove the solvent than the step of adding the inorganic solution, and the halide-based stimulable phosphor precursor crystal is obtained from the mixed solution. The method for producing a halide-based photostimulable phosphor according to claim 1, wherein the solvent is removed while being deposited. The method for producing a halide photostimulable phosphor according to claim 1 or 2, wherein the halide photostimulable phosphor is a rare earth activated alkaline earth metal fluorobromide stimulable phosphor. . The halogenated photostimulable phosphor is an oxygen-introduced rare earth-activated alkaline earth metal fluorobromide photostimulable phosphor represented by the following general formula (EFS1): 2. A method for producing a halide photostimulable phosphor according to item 1.
General formula (EFS1)
Ba _1-x M ² _x FX _1-y Br _y : aM ¹ , bLn, cO
[Wherein, M ¹ : at least one alkali metal selected from the group consisting of Li, Na, K, Rb and Cs, at least one halogen element selected from X: Cl or I, M ² : Be, Mg, Sr And at least one alkaline earth metal selected from the group consisting of Ca, at least one selected from the group consisting of Ln: Ce, Pr, Sm, Eu, Gd, Tb, Tm, Dy, Ho, Nd, Er, and Yb The rare earth elements x, y, a, b and c are 0 ≦ x ≦ 0.3, 0 ≦ y ≦ 1.0, 0 ≦ a ≦ 0.05, 0 <b ≦ 0.2, 0 <c, respectively. Represents ≦ 0.1. ] A halide photostimulable phosphor produced by the method for producing a halide photostimulable phosphor according to any one of claims 1 to 4. A radiation image conversion panel using the halide-based stimulable phosphor produced by the method for producing a halide-based stimulable phosphor according to any one of claims 1 to 4.

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