JP2007161952A - Radiation image conversion panel and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a radiation image conversion panel that contains an activator (europium) in a phosphor layer, especially uniformly distributed in the layer thickness direction, has a phosphor layer with a uniform amount of emission and provides a high-quality radiation image and to provide a method for producing the same. <P>SOLUTION: In the radiation image conversion panel having a stimulable phosphor layer on a substrate, the stimulable phosphor layer has a europium-activated alkali halide phosphor deposition layer formed by a vapor growth method in which at least a europium oxide halide represented by general formula Eu<SB>x</SB>O<SB>y</SB>Br<SB>z</SB>(1<x≤4, 1≤y≤4 and 1<z≤6) and an alkali halide as vapor deposition sources are deposited from separate evaporators (crucibles), respectively, on a substrate and the amount of Eu in europium (II) oxide halide powder as the Eu deposition source is ≥50 mass%. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a radiation image conversion panel and a manufacturing method thereof.

  Radiation images such as X-ray images are often used in fields such as disease diagnosis. The X-ray image is obtained by irradiating the phosphor layer (phosphor screen) with X-rays that have passed through the subject, thereby generating visible light, and then using this visible light as when taking a normal photograph. Thus, a so-called radiographic method in which a silver halide photographic light-sensitive material (hereinafter also simply referred to as a light-sensitive material) is irradiated and then developed to obtain a visible silver image is widely used.

  However, in recent years, a new method for taking out an image directly from a phosphor layer has been developed instead of an image forming method using a photosensitive material having a silver halide salt.

  In this method, the radiation transmitted through the subject is absorbed by the phosphor, and then the phosphor is excited by light or thermal energy, for example, so that the radiation energy accumulated by the phosphor is absorbed as fluorescence. There is a method of emitting and detecting this fluorescence and imaging.

  Specifically, for example, a radiation image conversion method using a photostimulable phosphor as described in US Pat. No. 3,859,527 and Japanese Patent Application Laid-Open No. 55-12144 is known. This method uses a radiation image conversion panel using a stimulable phosphor layer containing a stimulable phosphor, and the radiation transmitted through the subject is applied to the stimulable phosphor layer of the radiation image conversion panel. The radiation energy corresponding to the radiation transmission density of each part of the subject is accumulated, and then the stimulable phosphor is excited in time series with electromagnetic waves (excitation light) such as visible light and infrared light. Radiation energy accumulated in the phosphor is emitted as stimulated emission, and a signal based on the intensity of this light is photoelectrically converted, for example, to obtain an electrical signal, which is then used as a recording material such as a photosensitive material, CRT The image is reproduced as a visible image on a display device.

  According to the above radiographic image reproduction method, it is possible to obtain a radiographic image with a large amount of information with a much smaller exposure dose as compared with a radiographic method using a combination of a conventional radiographic film and an intensifying screen. It has the advantage of being able to.

  Radiation image conversion panels using these photostimulable phosphors, after accumulating radiation image information, release accumulated energy by scanning excitation light, so that radiation images can be accumulated again after scanning, and repeated Can be used. In other words, the conventional radiographic method consumes a radiographic film for each imaging, whereas this radiographic image conversion method repeatedly uses a radiographic image conversion panel, so from the viewpoint of resource protection and economic efficiency. Is also advantageous.

  Furthermore, in recent years, a radiographic image conversion panel with higher sharpness has been required for analysis of diagnostic images. As means for improving the sharpness, for example, an attempt has been made to improve the sensitivity and sharpness by controlling the shape of the photostimulable phosphor itself.

  As one of these attempts, for example, it is composed of a fine pseudo-columnar block formed by depositing a photostimulable phosphor on a support having a fine concavo-convex pattern described in JP-A No. 61-142497. There is a method using a stimulable phosphor layer.

  Further, as described in JP-A-61-142500, a crack between columnar blocks obtained by depositing a photostimulable phosphor on a support having a fine pattern is subjected to shock treatment for further development. Method using a radiation image conversion panel having a photostimulable phosphor layer formed, and further, radiation image conversion in which a photostimulable phosphor layer formed on the surface of a support is cracked from the surface side to form a pseudo columnar shape A method using a panel (see Patent Document 1), a method of forming a stimulable phosphor layer having a cavity by vapor deposition on the upper surface of a support, and then growing a cavity by heat treatment to provide a crack are proposed. (See Patent Document 2).

  Furthermore, a radiation image conversion panel having a photostimulable phosphor layer in which elongated columnar crystals having a certain inclination with respect to the normal direction of the support are formed on the support by vapor phase epitaxy has been proposed ( (See Patent Document 3).

  Recently, a radiation image conversion panel using a stimulable phosphor activated with Eu based on an alkali halide such as CsBr has been proposed, and in particular, high X-rays that have not been obtained by using Eu as an activator. It became possible to derive the conversion efficiency.

  Europium halide is known as a raw material of a phosphor activated with europium. For example, WO 01/0356 A1 discloses two methods comprising a europium compound such as cesium halide and europium halide as a method for producing a phosphor screen comprising a europium activated cesium halide stimulable phosphor. A method of binary deposition on a substrate using an evaporation source is disclosed. According to this method, the cesium halide, which is the host component of the phosphor, and the europium compound, which is the activator component, are heated at the same time to evaporate and scatter, and react to form the phosphor and deposit on the substrate surface. Thus, a deposited film of phosphor is formed.

  In general, europium halides are in powder form, including commercial products, and when used for vapor deposition as they are, they are highly hygroscopic, so bumping is likely to occur due to contained moisture and halogens released by heating. It is difficult to form a vapor deposition film having a uniform composition and a good shape. Europium halide is also mixed with oxide halides such as odor oxides.

  It is known that when europium halide is heated in the presence of water or oxygen, it is difficult to obtain pure europium halide because europium oxide halide is easily formed. That is, it is difficult to obtain a pure europium halide melt solidified body simply by heating and melting and cooling the europium halide.

  When the phosphor layer of the radiation image conversion panel is formed by the vapor deposition method, if the europium halide containing a large amount of oxide is used as the evaporation source, the vapor deposition rate (evaporation flow rate) is not stable, and as a result It is known that a deposited film having a europium concentration and a uniform phosphor composition cannot be formed. In addition, a homogeneous vapor deposition film cannot be formed due to the mixing of impurities. Furthermore, a radiation image conversion panel having such a phosphor layer tends to give a radiation image with a lowered image quality.

  Also, if the moisture content of the evaporation source, europium halide, exceeds a certain value, troubles such as bumping of the evaporation source are likely to occur during deposition, and the moisture pressure in the deposition atmosphere increases and becomes unstable. . As a result, the shape of the columnar crystals of the obtained deposited film is impaired, or so-called “light emission unevenness” is generated in which the amount of emitted light is locally non-uniform when the entire phosphor layer is excited (for example, (See Patent Document 4).

In short, when forming the phosphor layer of the radiation image conversion panel by vapor deposition, if the vapor deposition source uses a hygroscopic or europium compound containing a large amount of oxide, the vapor deposition rate will not be stable, resulting in a non-uniform phosphor layer. This causes the problem of being formed.
JP 62-39737 A JP-A-62-110200 JP-A-2-58000 JP 2003-201119 A

  Therefore, the present invention has been made in view of the above problems, and the purpose thereof is to contain an activator (europium) uniformly distributed in the phosphor layer, particularly in the direction of the layer thickness. An object of the present invention is to provide a radiation image conversion panel that has a uniform phosphor layer and gives a high-quality radiation image, and a method for manufacturing the same.

  The above object of the present invention is achieved by the following configurations.

1. In the radiation image conversion panel having the photostimulable phosphor layer on the support, the photostimulable phosphor layer has at least a general formula: Eu _x O _y Br _z (1 <x ≦ 4, 1 ≦ y ≦ 4, Europium-activated alkali formed by vapor deposition using a europium oxide halide and an alkali halide represented by 1 <z ≦ 6) as vapor deposition sources, and vapor-deposited on a support from separate evaporators (crucibles). A radiation image conversion panel comprising a halogenated phosphor vapor-deposited layer and having an Eu content in a europium (II) oxide halide powder as an Eu vapor deposition source of 50% by mass or more.

2. The radiographic image according to 1 above, wherein the europium oxide halide as the Eu deposition source is Eu ₄ OBr ₆ powder, and the amount of Eu in the powder is 50% to 60% by mass. Conversion panel.

  3. 3. The radiation image conversion panel as described in 1 or 2 above, wherein the europium activated alkali halogenated phosphor vapor deposition layer has a layer thickness of 50 μm to 500 μm.

  4). The ratio of Eu concentration at any two points in the layer thickness direction of the europium-activated alkali halide phosphor vapor-deposited layer is 0.9 to 1.1. Radiation image conversion panel.

  5. 5. A method for manufacturing a radiation image conversion panel, wherein the radiation image conversion panel according to any one of 1 to 4 is manufactured.

  According to the present invention, the activator (europium) is contained in the phosphor layer in a uniform distribution, particularly in the direction of the layer thickness, and has a phosphor layer with a uniform amount of light emission and gives a high-quality radiation image. An image conversion panel and a manufacturing method thereof can be provided.

  Hereinafter, the present invention, components, and the like will be described in detail.

(Phosphor and its deposition source)
The photostimulable phosphor layer according to the present invention is characterized by containing at least a europium activated alkali halogenated phosphor. Further, the phosphor is a deposition source of europium oxide halide and alkali halide represented by the general formula: Eu _x O _y Br _z (1 <x ≦ 4, 1 ≦ y ≦ 4, 1 <z ≦ 6). A europium-activated alkali-halogenated phosphor film formed by vapor deposition method in which each is deposited on a support from a separate evaporator (resistance heating crucible), and europium oxide as an Eu deposition source The amount of Eu in the halide powder is 50% by mass or more.

As the europium oxide halide as the Eu evaporation source according to the present invention, powders having various compositions can be used. A preferable Eu vapor deposition source is Eu ₄ OBr ₆ powder, and the amount of Eu in the powder is 50% to 60% by mass.

  Various known alkali halides can be used as the alkali halide vapor deposition source according to the present invention. For example, at least one compound selected from NaF, NaCl, NaBr, NaI, KF, KCl, KBr, KI, RbF, RbCl, RbBr, RbI, CsF, CsCl, CsBr and CsI is used. In particular, a preferred vapor deposition source is cesium bromide (CsBr).

  Furthermore, the thickness of the europium-activated alkali halide phosphor deposited film is preferably 50 μm to 500 μm. More preferably, it is 200 micrometers-500 micrometers.

  In the present invention, when the above conditions are satisfied, the activator (europium) is contained uniformly in the phosphor layer, particularly in the thickness direction, and a phosphor layer having a uniform light emission amount can be obtained. .

As a preferable Eu vapor deposition source, Eu ₄ OBr ₆ powder can be produced in accordance with the following method.

Europium oxide is dissolved in hydrobromic acid. Evaporate to dryness with stirring to produce europium bromide powder. Europium bromide is a mixture of EuBr ₂ hydrate and EuBr ₃ hydrate. Europium bromide powder preferably has a bulk density of 1.0 × 10 ⁶ g / m ^{3 to} 2.0 × 10 ⁶ g / m ³ . If the surface area is 1.0 × 10 ⁶ g / m ³ or less, the surface area is large, so that it is oxidized to Eu ₂ O ₃ by introducing oxygen in the next step. If it is 2.0 × 10 ⁶ g / m ³ or more, oxygen cannot be uniformly introduced, and it is difficult to make Eu ₄ OBr ₆ uniform.

This is taken in a boat and fired in an oxygen atmosphere to produce Eu ₄ OBr ₆ . Firing may be performed in the air or in an oxygen-containing atmosphere, and is performed at 100 ° C to 700 ° C, preferably 100 ° C to 300 ° C. When the firing temperature is high, oxygen introduction is accelerated to Eu ₂ O ₃ . If the temperature is low, oxygen cannot be introduced, deliquescence increases, and handling is impossible.

  Further, in the present invention, as a vapor deposition condition, the CsBr vapor amount is adjusted by inserting a mesh filter in the upper part of the boat so that the Eu molar ratio is 5/10000 from the vapor amount of CsBr and the vapor amount of Eu. It is preferable.

  In addition, in this invention, conventionally well-known various photostimulable fluorescent substances can be used together with said europium activated alkali halogenated fluorescent substance.

(Method for manufacturing radiation image conversion panel)
Hereinafter, a typical manufacturing method of the radiation image conversion panel of the present invention will be described.

  FIG. 1 is a cross-sectional view of the radiation image conversion panel 1. As shown in FIG. 1, the radiation image conversion panel 1 includes a phosphor plate 4 having a photostimulable phosphor layer 3 formed on a predetermined support (substrate) 2.

  Further, the surface 2a (upper surface in FIG. 1) of the substrate 2 may be a smooth surface or a mat surface. The surface 2a (upper surface in FIG. 1) of the substrate 2 may be a matte surface for the purpose of improving the adhesion with the stimulable phosphor layer 3, and on the surface 2a, the stimulable phosphor layer 3 and An undercoat layer may be provided for the purpose of improving the adhesion of the light source, and light may be provided on the surface 2a for the purpose of preventing excitation light from entering the photostimulable phosphor layer 3 through the substrate 2. A reflective layer may be provided.

  The photostimulable phosphor layer 3 has a layered structure composed of at least one layer, and the layer thickness is 50 μm or more, preferably 200 to 500 μm, as described above. Further, the photostimulable phosphor layer 3 has a columnar structure in which a large number of columnar crystals 3 composed of the photostimulable phosphor are arranged at intervals.

[Support: Substrate]
As the support (substrate) used in the radiation image conversion panel according to the present invention, various glasses, polymer materials, metals, and the like are used. For example, plate glass such as quartz, borosilicate glass, chemically tempered glass, In addition, a plastic film such as cellulose acetate film, polyester film, polyethylene terephthalate film, polyamide film, polyimide film, triacetate film, polycarbonate film, metal sheet such as aluminum sheet, iron sheet, copper sheet, or coating layer of the metal oxide The metal sheet which has is preferable.

[Substrate support section]
In the present invention, since the substrate support part (substrate holder) is a metal block and the substrate and the metal block are in close contact with each other, deformation of the substrate is suppressed during vapor deposition, and heat conduction from the substrate support part to the substrate is within the substrate surface. Can be made uniform. Furthermore, in order to control the thermal conductivity from the substrate support portion to the substrate, a member having a heat insulation effect may be sandwiched between the adhesive material and the substrate.

  The metal block according to the present invention is not particularly limited as long as it has a high thermal conductivity and has a thickness that does not cause partial deformation due to gravity. Aluminum is preferable from the viewpoint of compatibility between cost and strength.

[Adhesive]
The pressure-sensitive adhesive material according to the present invention is effective in uniformly bringing the substrate surface into close contact with the metal block when the substrate is in close contact with the metal block. As the adhesive material, an adhesive sheet is preferable from the viewpoint of workability and environmental performance.

  After attaching the adhesive sheet to the metal block, as a means of attaching the substrate on it, touching and pressing the substrate directly by hand will cause irregularities in the substrate surface or cause foreign matter to adhere to the substrate surface, and as a result An image defect may occur in an image conversion panel obtained by vapor deposition. Therefore, as a means for suppressing adhesion of foreign matter, a means for placing a substrate on the adhesive sheet, placing a sheet-like material on the surface of the substrate, and pressing from above is preferable. Furthermore, it is more preferable to use means for bringing the substrate into close contact with the metal block without contacting the image area on the substrate. When this method is used, it is possible to suppress unevenness of the substrate surface that occurs during pasting. In addition, there is a method of pressing the outside of the image area on the substrate, that is, the peripheral portion of the substrate, as means for suppressing unevenness of the substrate surface that occurs during pasting. As a means for bringing the substrate into close contact with the metal block without being brought into contact with the image region on the substrate, it is more preferable to depressurize the region of the contact portion between the substrate and the adhesive material.

[Stimulable phosphor layer]
As described above, the photostimulable phosphor layer according to the present invention can be used in combination with various conventionally known photostimulable phosphors in addition to the europium activated alkali halogenated phosphor according to the present invention. In the following, first, a stimulable phosphor that can be used in combination will be described in detail.

  As the stimulable phosphor, those represented by the following general formula (1) can be used.

M ¹ X · aM ² X ′ ₂ · bM ³ X ″ ₃ : eA (1)
Here, M ¹ is at least one alkali metal atom selected from Li, Na, K, Rb and Cs, and preferably at least one alkali metal atom selected from K, Rb and Cs.

M ² is at least one divalent metal atom selected from Be, Mg, Ca, Sr, Ba, Zn, Cd, Cu and Ni, and in particular, at least selected from Be, Mg, Ca, Sr and Ba It is preferably a kind of divalent metal atom.

M ³ is at least one trivalent selected from Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Al, Ga, and In. In particular, at least one trivalent metal atom selected from Y, La, Ce, Sm, Eu, Gd, Lu, Al, Ga and In is preferable.

  X, X ′ and X ″ are at least one halogen atom selected from F, Cl, Br and I, and X is preferably at least one halogen atom selected from Br and I.

  A is at least one selected from Eu, Tb, In, Ga, Cs, Ce, Tm, Dy, Pr, Ho, Nd, Yb, Er, Gd, Lu, Sm, Y, Tl, Na, Ag, Cu, and Mg. In particular, at least one metal atom selected from Eu, Cs, Sm, Tl and Na is preferable.

a, b, and e are numerical values in the range of 0 ≦ a <0.5, 0 ≦ b <0.5, and 0 <e ≦ 0.2, respectively. In particular, b is in the range of 0 ≦ b ≦ 10 ⁻² . It is preferable to show a numerical value.

  Among these, it is particularly preferable to have a stimulable phosphor represented by the following general formula (2).

CsX: A (2)
Here, X represents F, Cl, Br or I, and A represents Eu, In, Ga or Ce. In particular, it is preferable to use Eu as an activator because X-ray conversion efficiency can be expected to improve.

The photostimulable phosphor is manufactured by the following manufacturing method using, for example, the following phosphor materials (a) to (d).
(A) At least one or two selected from LiF, LiCl, LiBr, LiI, NaF, NaCl, NaBr, NaI, KF, KCl, KBr, KI, RbF, RbCl, RbBr, RbI, CsF, CsCl, CsBr and CsI More than one compound.
_{(B) BeF 2, BeCl 2} , BeBr 2, BeI 2, MgF 2, MgCl 2, MgBr 2, MgI 2, CaF 2, CaCl 2, CaBr 2, CaI 2, SrF 2, SrCl 2, SrBr 2, SrI 2 , BaF ₂ , BaCl ₂ , BaBr ₂ , BaI ₂ , ZnF ₂ , ZnCl ₂ , ZnBr ₂ , ZnI ₂ , CdF ₂ , CdCl ₂ , CdBr ₂ , CdI ₂ , CuF ₂ , CuCl ₂ , CuBr ₂ , CuI ₂ , NiF ₂ , at least one compound selected from NiCl ₂ , NiBr ₂ and NiI ₂ or two or more compounds.
_{(C) ScF 3, ScCl 3} , ScBr 3, ScI 3, YF 3, YCl 3, YBr 3, YI 3, LaF 3, LaCl 3, LaBr 3, LaI 3, CeF 3, CeCl 3, CeBr 3, CeI 3 _{, PrF 3, PrCl 3, PrBr} 3, PrI 3, NdF 3, NdCl 3, NdBr 3, NdI 3, PmF 3, PmCl 3, PmBr 3, PmI 3, SmF 3, SmCl 3, SmBr 3, SmI 3, EuF _{3, EuCl 3, EuBr 3,} EuI 3, GdF 3, GdCl 3, GdBr 3, GdI 3, TbF 3, TbCl 3, TbBr 3, TbI 3, DyF 3, DyCl 3, DyBr 3, DyI 3, HoF 3, _{HoCl 3, HoBr 3, HoI 3} , ErF 3, ErCl 3, ErBr 3, ErI 3, TmF 3, TmCl 3, TmBr 3, TmI 3, YbF 3 _{YbCl 3, YbBr 3, YbI 3} , LuF 3, LuCl 3, LuBr 3, LuI 3, AlF 3, AlCl 3, AlBr 3, AlI 3, GaF 3, GaCl 3, GaBr 3, GaI 3, InF 3, InCl 3 At least one compound selected from InBr ₃ and InI _3, or two or more compounds.
(D) at least selected from Eu, Tb, In, Ga, Cs, Ce, Tm, Dy, Pr, Ho, Nd, Yb, Er, Gd, Lu, Sm, Y, Tl, Na, Ag, Cu and Mg One or more metal atoms.

  The phosphor materials of the above (a) to (d) are weighed so as to satisfy the ranges of a, b and e in the general formula (1) and mixed with pure water. At this time, the mixture may be sufficiently mixed using a mortar, ball mill, mixer mill or the like.

  Next, a predetermined acid is added so that the pH value C of the obtained mixed solution is adjusted to 0 <C <7, and then water is evaporated.

  Next, the obtained raw material mixture is filled in an evaporator (crucible), for example, a heat-resistant container such as a quartz crucible or an alumina crucible, and fired in an electric furnace. The firing temperature is preferably 500 to 1000 ° C. The firing time varies depending on the filling amount of the raw material mixture, the firing temperature and the like, but is preferably 0.5 to 6 hours.

  The europium-activated alkali halide phosphor according to the present invention is vapor phase growth in which europium oxide (II) halide and alkali halide are used as vapor deposition sources, and vapor deposition is performed on a support from separate evaporators (crucibles). It is formed by the method.

  The firing atmosphere includes a nitrogen gas atmosphere containing a small amount of hydrogen gas, a weak reducing atmosphere such as a carbon dioxide gas atmosphere containing a small amount of carbon monoxide, a neutral atmosphere such as a nitrogen gas atmosphere and an argon gas atmosphere, or a small amount of oxygen gas. A weak oxidizing atmosphere is preferred.

  After firing once under the aforementioned firing conditions, the fired product is taken out from the electric furnace and pulverized, and then the fired product powder is again filled in a heat-resistant container and placed in the electric furnace, and again under the same firing conditions as described above. If the firing is performed, the luminous brightness of the photostimulable phosphor can be further increased, and when the fired product is cooled to the room temperature from the firing temperature, the fired product is taken out of the electric furnace and allowed to cool in the air. Although a desired photostimulable phosphor can be obtained, it may be cooled in the same weakly reducing atmosphere, neutral atmosphere or weakly oxidizing atmosphere as at the time of firing.

  In addition, by moving the fired product from the heating part to the cooling part in an electric furnace and quenching in a weakly reducing atmosphere, neutral atmosphere or weakly oxidizing atmosphere, the resulting stimulable phosphor is excited. The light emission luminance can be further increased.

  As described above, the photostimulable phosphor layer 3 is formed from the photostimulable phosphor, and the photostimulable phosphor layer 3 and the substrate 2 constitute the phosphor plate 4.

  In the radiation image conversion panel 1, a protective layer for protecting the phosphor plate 4 is provided. As a protective layer, two moisture-proof protective films 10 and 20 are provided, and the phosphor plate 4 has a first moisture-proof property arranged on the upper side of the stimulable phosphor layer 3 as shown in FIG. The protective film 10 is interposed between the second moisture-proof protective film 20 disposed on the lower side of the substrate 2.

  The first moisture-proof protective film 10 has a slightly larger area than the phosphor plate 4, and the peripheral portion of the first moisture-proof protective film 10 is fluorescent in a state where it is not substantially adhered to the photostimulable phosphor layer 3 of the phosphor plate 4. It extends outward from the peripheral edge of the body plate 4. “The state in which the first moisture-proof protective film 10 is not substantially bonded to the photostimulable phosphor layer 3” means that the first moisture-proof protective film 10 and the photostimulable phosphor layer 3 are optical. Specifically, the contact area between the first moisture-proof protective film 10 and the photostimulable phosphor layer 3 is the surface of the photostimulable phosphor layer 3 (first moisture-proof property). The state which is 10% or less of the area of the surface facing the protective film 10).

  On the other hand, the second moisture-proof protective film 20 also has a slightly larger area than the phosphor plate 4, and its peripheral edge extends outward from the peripheral edge of the phosphor plate 4.

  In the radiation image conversion panel 1, the peripheral portions of the first and second moisture-proof protective films 10 and 20 are fused over the entire circumference, and the first and second moisture-proof protective films 10 and 20 are fluorescent. The body plate 4 is completely sealed. Each of the first and second moisture-proof protective films 10 and 20 protects the phosphor plate 4 by sealing the phosphor plate 4 to reliably prevent moisture from entering the phosphor plate 4. It is like that.

  As shown in the enlarged view at the top in FIG. 1, the first moisture-proof protective film 10 has a laminated structure in which three layers of a first layer 11, a second layer 12, and a third layer 13 are laminated. Yes.

  The first layer 11 is a layer facing the photostimulable phosphor layer 3 of the phosphor plate 4 with the air layer 14 interposed therebetween, and is made of a resin having a heat-fusibility. Examples of the “resin having heat-fusibility” include ethylene vinyl acetate copolymer (EVA), casting polypropylene (CPP), polyethylene (PE) and the like.

  The second layer 12 is a layer made of a metal oxide such as alumina or silica, and is deposited under the third layer 13 by a known vapor deposition method. Although the 2nd layer 12 strengthens the moisture-proof performance of the 1st moisture-proof protective film 10, it does not need to be.

  The third layer 13 is laminated on the second layer 12 and is made of a resin such as polyethylene terephthalate (PET).

  Thus, the 1st moisture-proof protective film 10 which has the 2nd layer 12 comprised with the metal oxide is excellent in workability and transparency, and is temperature in terms of a moisture-proof and oxygen-permeable property. Insensitive to humidity and humidity. Therefore, the first moisture-proof protective film 10 is suitable for the stimulable phosphor-based medical radiation image conversion panel 1 that requires stable image quality regardless of the environment.

  Note that on the third layer 13, a layer similar to the first layer 11, a layer similar to the second layer 12, a layer similar to the third layer 13, or the first layer 11, the third layer One layer or two or more layers made of a resin different from the layer 13 may be laminated.

  In particular, when a layer similar to the second layer 12 made of a metal oxide such as alumina or silica is laminated on the third layer 13, the first moisture-proof protective film 11 becomes the second layer. The optimum moisture-proof property according to the number of layers corresponding to 12 is exhibited. As a method for laminating the second layer 12 or a similar layer, any known method can be applied, but a method according to the dry laminating method is preferably used in terms of workability. .

  As shown in the enlarged view at the bottom in FIG. 1, the second moisture-proof protective film 20 has a laminated structure in which three layers of a first layer 21, a second layer 22, and a third layer 23 are laminated. Yes.

  The first layer 21 faces the substrate 2 of the phosphor plate 4 through the air layer 24. The first layer 21 is made of the same resin as the first layer 11 of the first moisture-proof protective film 10, and melts with the first layer 11 of the first moisture-proof protective film 10 at the peripheral portion thereof. I wear it.

  The second layer 22 is a layer laminated under the first layer 21 and is made of aluminum. Although the 2nd layer 22 improves the moisture-proof performance in the 2nd moisture-proof protective film 20, it does not need to be.

  The third layer 23 is laminated under the second layer 22 and is made of a resin such as PET.

  Note that, under the third layer 23, a layer similar to the first layer 21, a layer similar to the second layer 22, a layer similar to the third layer 23, or the first layer 11, the third layer One layer or two or more layers made of a resin different from the layer 13 may be laminated.

[Protective layer]
Moreover, the stimulable phosphor layer according to the present invention may have a protective layer as described above. The protective layer may be formed by directly applying a coating solution for the protective layer on the photostimulable phosphor layer, or a protective layer separately formed in advance may be adhered on the photostimulable phosphor layer. Or you may take the procedure of forming a photostimulable phosphor layer on the protective layer formed separately. Materials for the protective layer include cellulose acetate, nitrocellulose, polymethyl methacrylate, polyvinyl butyral, polyvinyl formal, polycarbonate, polyester, polyethylene terephthalate, polyethylene, polyvinylidene chloride, nylon, polytetrafluoroethylene, polytrifluoride-ethylene chloride Ordinary protective layer materials such as tetrafluoroethylene-hexafluoropropylene copolymer, vinylidene chloride-vinyl chloride copolymer, vinylidene chloride-acrylonitrile copolymer are used. In addition, a transparent glass substrate can be used as a protective layer. The protective layer may be formed by laminating inorganic materials such as SiC, SiO ₂ , SiN, Al ₂ O ₃ by vapor deposition, sputtering, or the like. The thickness of these protective layers is generally preferably about 0.1 to 2000 μm.

(Radiation image conversion panel and radiation image reading device)
FIG. 2 is a schematic diagram showing an example of the configuration of the radiation image conversion panel and the radiation image reading apparatus of the present invention.

  In FIG. 2, 21 is a radiation generator, 22 is a subject, 23 is a radiation image conversion panel having a visible or infrared photostimulable phosphor layer containing a stimulable phosphor, and 24 is a radiation of the radiation image conversion panel 23. A stimulated excitation light source for emitting a latent image as stimulated emission, 25 is a photoelectric conversion device that detects the stimulated emission emitted from the radiation image conversion panel 23, and 26 is a photoelectric conversion signal detected by the photoelectric conversion device 25. 27 is an image display device that displays the reconstructed image, and 28 is a device that cuts off the reflected light from the stimulating excitation light source 24 and transmits only the light emitted from the radiation image conversion panel 23. It is a filter to make it. FIG. 3 shows an example of obtaining a radiation transmission image of a subject. However, when the subject 22 itself emits radiation, the radiation generator 21 is not particularly necessary.

  The photoelectric conversion device 25 and the subsequent devices are not limited to the above as long as they can reproduce optical information from the radiation image conversion panel 23 as an image in some form.

  As shown in FIG. 3, when the subject 22 is placed between the radiation generator 21 and the radiation image conversion panel 23 and irradiated with the radiation R, the radiation R is transmitted according to the change in the radiation transmittance of each part of the subject 22, A transmission image RI (that is, an image of the intensity of radiation) enters the radiation image conversion panel 23. The incident transmitted image RI is absorbed by the photostimulable phosphor layer of the radiation image conversion panel 23, so that a number of electrons and / or holes proportional to the amount of radiation absorbed in the photostimulable phosphor layer are generated. Occurs and accumulates at the trap level of the photostimulable phosphor. That is, a latent image in which the energy of the radiation transmission image is accumulated is formed. Next, this latent image is made visible by being excited with light energy. That is, the photostimulable phosphor layer is irradiated with light in the visible or infrared region and the photostimulable phosphor layer is irradiated to expel electrons and / or holes accumulated at the trap level, and the accumulated energy is stimulated to emit light. Let it be released as. The intensity of the emitted stimulated emission is proportional to the number of accumulated electrons and / or holes, that is, the intensity of the radiation energy absorbed in the stimulable phosphor layer of the radiation image conversion panel 23. The optical signal is converted into an electric signal by a photoelectric conversion device 25 such as a photomultiplier tube, and reproduced as an image by an image reproduction device 26, and this image is displayed by an image display device 27. The image reproducing device 26 is more effective not only for reproducing an electrical signal as an image signal but also using what can perform so-called image processing, image calculation, image storage, storage, and the like.

  In addition, when excited by light energy, it is necessary to separate the reflected light of the stimulated excitation light from the stimulated emission emitted from the stimulable phosphor layer, and it is emitted from the stimulable phosphor layer. Photoelectric converters that receive light emission generally have high sensitivity to light energy with a short wavelength of 600 nm or less, so that the stimulated emission emitted from the stimulable phosphor layer has a spectral distribution in the short wavelength region as much as possible. What you have is desirable. The emission wavelength range of the photostimulable phosphor of the present invention is 300 to 500 nm, while the photostimulable excitation wavelength range is 500 to 900 nm, which satisfies the above-mentioned conditions at the same time. Recently, downsizing of diagnostic devices has progressed. A semiconductor laser that has a high output power and is easy to make compact is preferred for the image reading of the radiation image conversion panel, and the wavelength of the laser light is 680 nm, and is incorporated in the radiation image conversion panel of the present invention. The photostimulable phosphor exhibits extremely good sharpness when an excitation wavelength of 680 nm is used.

  That is, all of the photostimulable phosphors of the present invention emit light having a main peak at 500 nm or less, and the excitation excitation light can be easily separated and coincides well with the spectral sensitivity of the light receiver. The sensitivity of the image receiving system can be solidified.

  As the excitation light source 24, a light source including the excitation wavelength of the stimulable phosphor used in the radiation image conversion panel 23 is used. In particular, when laser light is used, the optical system is simplified, and the excitation light intensity can be increased, so that the photostimulative emission efficiency can be increased, and a more preferable result can be obtained.

  In the present invention, the laser diameter irradiated to the photostimulable phosphor layer is preferably 100 μm or less, more preferably 80 μm or less.

As the laser, the He-Ne laser, the He-Cd laser, Ar ion laser, Kr ion laser, N ₂ laser, YAG laser and its second harmonic, ruby laser, semiconductor lasers, various dye lasers, copper vapor laser, etc. There are metal vapor lasers. Normally, a continuous wave laser such as a He—Ne laser or an Ar ion laser is desirable, but a pulsed laser can also be used if the scanning time and pulse of one pixel of the panel are synchronized. Further, when using a method of separating light emission using a delay of light emission as shown in Japanese Patent Laid-Open No. 59-22046 without using the filter 28, a pulse oscillation laser is used rather than modulation using a continuous wave laser. Is preferred.

  Among the various laser light sources described above, the semiconductor laser is particularly preferably used because it is small and inexpensive and does not require a modulator.

  Since the filter 28 transmits the stimulated luminescence emitted from the radiation image conversion panel 23 and cuts the stimulated excitation light, this is the stimulation of the stimulable phosphor contained in the radiation image conversion panel 23. It is determined by the combination of the emission wavelength and the wavelength of the stimulated excitation light source 24.

  For example, in the case of a practically preferable combination in which the excitation wavelength is 500 to 900 nm and the emission wavelength is 300 to 500 nm, examples of the filter include C-39, C-40, and V- 40, V-42, V-44, Corning 7-54, 7-59, Spectrofilm BG-1, BG-3, BG-25, BG-37, BG-38, etc. A filter can be used. If an interference filter is used, a filter having an arbitrary characteristic can be selected and used to some extent. The photoelectric conversion device 25 may be any device capable of converting a change in light quantity into a change in electronic signal, such as a photoelectric tube, a photomultiplier tube, a photodiode, a phototransistor, a solar cell, or a photoconductive element.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited to these.

(Production of radiation image conversion panel)
A support made of an aluminum substrate having a size of 43 cm × 43 cm (17 inches × 17 inches) is placed in the vacuum chamber of the vapor deposition apparatus shown in FIG. 3, and a stimulable phosphor is formed on each aluminum substrate by the method described in the following examples. A photostimulable phosphor layer having (CsBr: 0.0002Eu) was formed.

[Preparation of phosphor layer]
Example 1
Eu ₂ O _{3 (} 40 g) was dissolved in a 48% HBr solution (40 g), and the pH was adjusted to 5 with an aqueous NaOH solution. The mixture was evaporated to dryness with stirring to prepare europium bromide powder. Then, it was fired at 100 ° C. for 1 hour in an air atmosphere to produce Eu ₄ OBr ₆ . The bulk density of the Eu ₄ OBr ₆ powder was 1.5 × 10 ⁶ g / m ³ .

CsBr and Eu ₄ OBr ₆ were put in separate crucibles and decompressed. By vacuum heating, the temperature inside the crucible of CsBr was 850 ° C. and the temperature inside the crucible of Eu ₄ OBr ₆ was 750 ° C. by resistance heating. The vapor pressure became constant by constant resistance current heating.

  The deposition was stopped by closing the shutter so that the target film thickness (300 μm) and 1/3 and 2/3 of the target film thickness were obtained, and a phosphor layer (deposition film) having three levels of thickness was produced.

Example 2
In the method of Example 1, pH adjustment with NaOH was not performed, and the same procedure as in Example 1 was performed except that the pH was adjusted to 1.

Example 3
In the method of Example 2, it was carried out similarly to Example 2 except having baked at 200 degreeC.

Example 4
In the method of Example 3, it was carried out similarly to Example 3 except having baked at 300 degreeC.

Comparative example a
In the method of Example 2, it was made to be the same as that of Example 2 except that baking was not performed.

In the vapor deposition, EuBr ₃ was fired like a meringue and the vapor pressure characteristics were not stable.

Comparative Example b
40 g of Eu ₂ O ₃ and 22.5 g of NH ₄ Br were melted in a platinum crucible at 800 ° C. for 2 hours.

  In the vapor deposition, the Eu source became scabbed, and the degree of vacuum varied depending on the reaction product.

(Eu measurement)
50 g of a sample was taken and dissolved in water to adjust the volume to 200 ml. Then, 0.1 g of ascorbic acid was added and adjusted with a pH meter while adding hexamine to a pH of 4.0 to 6.0 to obtain a measurement solution. . 0.05 g of XO indicator was added and titrated with 0.01M-EDTA, and the Eu amount was calculated from the EDTA concentration and the added amount.

  FIG. 4 shows the relationship (conceptual diagram) between the vapor deposition time and the vapor pressure in each of the above examples. Table 1 summarizes the Eu content and density of the europium (Eu) evaporation source.

  Next, the CPP layer of the first moisture-proof protective film is opposed to the stimulable phosphor layer of the various phosphor plates produced as described above, and the second moisture-proof protective film is placed on the substrate of the phosphor plate. The first and second moisture-proof protective films were superposed on each other in this state. Then, while decompressing the space surrounded by the first and second moisture-proof protective films, the peripheral portions of the first and second moisture-proof protective films are fused with an impulse sealer, and the first and second moisture-proof protections are obtained. The phosphor plate was sealed in the film to produce a radiation image conversion panel.

(Measurement of phosphor layer thickness)
A cross section of the sample is prepared, and the layer thickness (film thickness) can be obtained from a calibrated scanning electron micrograph. When measuring with a commercially available film thickness meter, such as a dial gauge or an eddy current film thickness meter, it is necessary to use a value calibrated with the scanning electron micrograph.

(Evaluation of luminous brightness)
The light emission luminance was evaluated according to the following method.

  Each sample was irradiated with X-rays having a tube voltage of 80 kV from the back surface (surface on which the photostimulable phosphor was not formed) of each sample. Thereafter, a semiconductor laser is scanned on the surface of each sample (the surface on which the photostimulable phosphor is formed) to excite the photostimulable phosphor layer, and stimulated emission emitted from the photostimulable phosphor layer. Was measured with a light receiver (photoelectron image intensifier tube with spectral sensitivity S-5) for each sample, and the measured value was defined as “sensitivity (light emission luminance)”. The measurement results are shown in Table 2. However, the relative luminance when the luminance of the target film thickness of Comparative Example a is 1 is shown in the table.

  As is apparent from Table 2, the brightness of the example according to the present invention is higher in various layer thicknesses (film thicknesses) than the comparative example.

Cross section of the radiation image conversion panel Schematic which shows an example of a structure of a radiographic image conversion panel and a radiographic image reading apparatus. Sectional drawing which shows schematic structure of an example of vapor deposition apparatus Conceptual diagram showing the relationship between deposition time and vapor pressure

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Radiation image conversion panel 2 Substrate 3 Stimulable phosphor layer 4 Stimulable phosphor plate 10, 20 Moisture-proof protective film 21 Radiation generation device 22 Subject 23 Radiation image conversion panel 24 Stimulation excitation light source 25 Photoelectric conversion device 26 Image Reproduction device 27 Image display device 28 Filter 30 Vapor deposition device 31 Vacuum vessel 32a, 32b Evaporation source 33 Support body holder 34 Support body rotation shaft 34a Support body rotation mechanism 35 Vacuum pump 36 Support body

Claims (5)

In the radiation image conversion panel having the photostimulable phosphor layer on the support, the photostimulable phosphor layer has at least a general formula: Eu _x O _y Br _z (1 <x ≦ 4, 1 ≦ y ≦ 4, Europium-activated alkali formed by vapor deposition using a europium oxide halide and an alkali halide represented by 1 <z ≦ 6) as vapor deposition sources, and vapor-deposited on a support from separate evaporators (crucibles). A radiation image conversion panel comprising a halogenated phosphor vapor-deposited layer and having an Eu content in a europium (II) oxide halide powder as an Eu vapor deposition source of 50% by mass or more. 2. The radiation according to claim 1, wherein the europium oxide halide as the Eu deposition source is Eu ₄ OBr ₆ powder, and the amount of Eu in the powder is 50% to 60% by mass. Image conversion panel. 3. The radiation image conversion panel according to claim 1, wherein a layer thickness of the europium-activated alkali halide phosphor vapor deposition layer is 50 μm to 500 μm. The ratio of Eu concentration is 0.9 to 1.1 at any two points in the layer thickness direction of the europium activated alkali halogenated phosphor vapor-deposited layer, according to any one of claims 1 to 3. The radiation image conversion panel described. The manufacturing method of the radiographic image conversion panel characterized by manufacturing the radiographic image conversion panel of any one of Claims 1-4.