JP4304998B2 - Radiation image conversion panel and method for manufacturing radiation image conversion panel - Google Patents

Description

【０１１６】
表１から、比較に比べて本発明の試料は、輝度、鮮鋭性に優れ、且つ、残光が極めて少ないことが判る。
【０１１７】
【発明の効果】
本発明により、コントラストが高く、且つ、高輝度低残光性を示す放射線画像変換パネル及び放射線画像変換パネルの製造方法を提供することが出来た。
【図面の簡単な説明】
【図１】本発明の放射線像変換パネルの構成の一例を示す概略図。
【図２】蒸着により支持体上に輝尽性蛍光体層を作製する方法の一例を示す概略図。
【符号の説明】
２１ 放射線発生装置
２２ 被写体
２３ 放射線像変換パネル
２４ 輝尽励起光源
２５ 該変換パネルにより放射された輝尽蛍光を検出する光電変換装置
２６ 画像再生装置
２７ 画像表示装置
２８ フィルタ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a radiation image conversion panel and a method for manufacturing a radiation image conversion panel.
[0002]
[Prior art]
Conventionally, so-called radiography using a silver salt has been used to obtain a radiographic image, but a method for imaging a radiographic image without using a silver salt has been developed. That is, the radiation transmitted through the subject is absorbed by the phosphor, and then the phosphor is excited with a certain energy to emit the radiation energy accumulated in the phosphor as fluorescence, and this fluorescence is detected. A method for imaging is disclosed.
[0003]
As a specific method, a radiation image conversion method using a panel having a photostimulable phosphor layer on a support and using one or both of visible light and infrared light as excitation energy is known (for example, patents). Reference 1).
[0004]
As a radiation image conversion method using a stimulable phosphor with higher brightness and sensitivity, BaFX: Eu²⁺Radiation image conversion method using a system (X: Cl, Br, I) phosphor (for example, see Patent Document 2), Radiation image conversion method using an alkali halide phosphor (for example, see Patent Document 3), Tl as a co-activator⁺And Ce³⁺, Sm³⁺, Eu³⁺, Y³⁺, Ag⁺, Mg²⁺, Pb²⁺, In³⁺Alkali halide phosphors containing these metals have been developed (see, for example, Patent Documents 4 and 5).
[0005]
In recent years, there has been a demand for a radiation image conversion panel with higher sharpness in analysis of diagnostic images. As means for improving the sharpness, for example, attempts have been made to improve the sensitivity and sharpness by controlling the shape of the photostimulable phosphor itself.
[0006]
As one of these attempts, for example, a method using a stimulable phosphor layer composed of fine pseudo-columnar blocks formed by depositing a stimulable phosphor on a support having a fine uneven pattern (for example, patent Reference 6).
[0007]
In addition, a radiation image conversion panel having a stimulable phosphor layer that is further developed by shock-treating cracks between columnar blocks obtained by depositing a stimulable phosphor on a support having a fine pattern ( For example, see Patent Document 7), and further, a radiation image conversion panel (for example, patent) 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. And a method in which a stimulable phosphor layer having a cavity is formed on the upper surface of a support by vapor deposition, and then a cavity is grown by heat treatment to provide a crack (for example, Patent Document 9). See also).
[0008]
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 deposition (for example, Patent Document 10). See) has been proposed.
[0009]
Recently, a radiation image conversion panel using a stimulable phosphor in which Eu is activated with an alkali halide such as CsBr as a base has been proposed, and it has not been obtained with a conventional phosphor by using Eu as an activator. It has become possible to derive a high X-ray conversion efficiency.
[0010]
However, on the other hand, Eu has a remarkable diffusion due to heat, and since there is a high vapor pressure under vacuum, there is a problem of ubiquitous existence of Eu in the matrix, and the intended high X-ray conversion efficiency is achieved. Since it is difficult to obtain, it has not been put to practical use in the market.
[0011]
In particular, in the activation of rare earth elements that can obtain high X-ray conversion efficiency, it has been difficult to make the film formation under vacuum more uniform than the vapor pressure characteristics. In addition, in the manufacturing method, in the stimulable phosphor layer formed by vapor phase growth (deposition), the raw material is heated when the stimulable phosphor layer is produced, the substrate (support) is heated during the vacuum evaporation, and the film is formed. There is a problem that the presence state of the activator becomes non-uniform because a large amount of heat treatment is performed by the annealing (substrate strain relaxation) treatment after the formation.
[0012]
For this reason, there has been a demand for improvement in manufacturing uniformity commensurate with improvements in brightness and sharpness required by the market as a radiation image conversion panel.
[0013]
In particular, the influence of the thermal expansion of the base material during heating / cooling due to the non-uniformity of the evaporating raw material has a large surface area of the phosphor layer, and as the film thickness increases, the adhesiveness decreases, and cracks are likely to occur. In particular, there is a problem that it is recognized remarkably in the fine structure.
[0014]
[Patent Document 1]
US Pat. No. 3,859,527
[0015]
[Patent Document 2]
JP 59-75200 A
[0016]
[Patent Document 3]
JP-A-61-72087
[0017]
[Patent Document 4]
JP-A-61-73786
[0018]
[Patent Document 5]
JP 61-73787 A
[0019]
[Patent Document 6]
JP 61-142497 A
[0020]
[Patent Document 7]
JP-A-61-142500
[0021]
[Patent Document 8]
JP 62-39737 A
[0022]
[Patent Document 9]
JP-A-62-110200
[0023]
[Patent Document 10]
JP-A-2-58000
[0024]
[Problems to be solved by the invention]
An object of the present invention is to provide a radiation image conversion panel having a high contrast and exhibiting high luminance and low afterglow, and a method for manufacturing the radiation image conversion panel.
[0025]
[Means for Solving the Problems]
The above object of the present invention has been achieved by the following configurations 1 to 3.
[0026]
  1. In a radiation image conversion panel having at least one photostimulable phosphor layer on a support,
  At least one layer is a stimulable phosphor layer made of CsBr: Eu stimulable phosphor, and the photostimulable phosphor layer includes:The support is formed to have a film thickness of 50 μm or more by a vapor phase method (also referred to as a vapor deposition method) at a temperature of 100 ° C. to 170 ° C. and a degree of vacuum of 10 mPa to 700 mPa.CsBr: EuA radiation image conversion panel, wherein the photostimulable phosphor has a crystallite size of 90 nm to 109 nm.
[0027]
  2.2. The radiation image conversion panel according to 1 above, wherein Eu, which is an activator of the CsBr: Eu stimulable phosphor, is introduced with an activator by a wet method.
[0028]
  3.In producing the radiation image conversion panel according to 1 or 2, at least one photostimulable phosphor layer has a temperature of 100 to 170 ° C. and a vacuum degree of 10 to 700 mPa. A method for manufacturing a radiation image conversion panel, which is manufactured through a step of forming a film having a thickness of 50 μm or more by a vapor deposition method.
[0029]
  Hereinafter, the present invention will be described in detail.
  As a result of various studies on the above problems, the present inventors have found that in a radiation image conversion panel having at least one stimulable phosphor layer on a support, at least one of the stimulable phosphor layers is ,The temperature of the support is 100 ° C. to 170 ° C., the degree of vacuum is 10 mPa to 700 mPa,By adjusting the crystallite size of the photostimulable phosphor in the layer to be 90 nm or more by forming the film with a film thickness of 50 μm or more by a vapor phase method (also referred to as a vapor deposition method). It was found that a radiation image conversion panel having high contrast and high brightness and low afterglow can be obtained.
[0030]
《Stimulable phosphor》
The photostimulable phosphor according to the present invention will be described.
[0031]
As the photostimulable phosphor according to the radiation image conversion panel of the present invention, a conventionally known photostimulable phosphor can be used by those skilled in the art, but preferably the photostimulability represented by the general formula (1). It is a phosphor.
[0032]
Examples of the stimulable phosphor represented by the general formula (1) include M¹, M²Each represents at least one alkali metal selected from the group consisting of Li, Na, K, Rb and Cs, preferably an alkali metal represented by Rb or Cs, and more preferably Cs.
[0033]
M^ThreeIs at least one selected from the group consisting of Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Al, Ga and In. Of these, trivalent metals are represented by at least one trivalent metal selected from the group consisting of Y, Ce, Sm, Eu, Al, La, Gd, Lu, Ga and In.
[0034]
A in the general formula (1) is preferably at least one metal selected from the group consisting of Eu, Ce, Sm, Tl, and Na, and particularly preferably Eu.
[0035]
From the viewpoint of improving the photostimulable emission brightness of the photostimulable phosphor, X, X ′ and X ″ are at least one halogen selected from the group consisting of F, Cl, Br and I. F, Cl and Br At least one halogen selected from is preferable, more preferably a halogen selected from the group consisting of Br and I, and a particularly preferable group is Br.
[0036]
In the general formula (1), the b value is 0 ≦ b <0.5, preferably 0 ≦ b ≦ 10.^-2It is.
[0037]
<< Method for producing photostimulable phosphor >>
The photostimulable phosphor represented by the general formula (1) according to the present invention is produced by, for example, the production method described below.
[0038]
First, as a phosphor material, an acid (HI, HBr, HCl, HF) is added to a carbonate so as to have the following composition, mixed and stirred, and then filtered at the neutralization point to obtain a furnace solution The following crystals are produced by evaporating the water.
[0039]
(A) one or more of NaF, NaCl, NaBr, NaI, KF, KCl, KBr, KI, RbF, RbCl, RbBr, RbI, CsF, CsCl, CsBr, CsI,
(B) MgF₂MgCl₂, MgBr₂, MgI₂, CaF₂, CaCl₂, CaBr₂, CaI₂, SrF₂, SrCI₂, SrBr₂, SrI₂, BaF₂, BaCl₂, BaBr₂, BaBr₂・ 2H₂O, BaI₂ZnF₂ZnCl₂ZnBr₂, ZnI₂, CdF₂, CdCl₂, CdBr₂, CdI₂, CuF₂, CuCl₂, CuBr₂, CuI, NiF₂NiCl₂, NiBr₂, NiI₂One or more of them, and
(C) In the general formula (1), Eu, Tb, In, Cs, Ce, Tm, Dy, Pr, Ho, Nd, Yb, Er, Gd, Lu, Sm, Y, Tl, Na, Ag, Cu And an activator raw material having a metal selected from the group consisting of Mg.
[0040]
In the photostimulable phosphor of the general formula (I) stoichiometrically,
a is preferably 0 ≦ a <0.5, more preferably 0 ≦ a <0.01,
b is preferably 0 ≦ b <0.5, more preferably 0 ≦ b ≦ 10.^-2,
e is preferably 0 <e ≦ 0.2, and more preferably 0 <e ≦ 0.1.
[0041]
The phosphor materials (a) to (c) are weighed so as to have a mixed composition in the above numerical range, and dissolved in 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 as to adjust the pH value of the obtained aqueous solution, and then water is evaporated.
[0042]
Next, the obtained raw material mixture is filled in a heat-resistant container such as a quartz crucible or an alumina crucible and fired in an electric furnace. The firing temperature is suitably 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 generally 0.5 to 6 hours is appropriate. 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 above 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 emission luminance of the phosphor can be further increased. When the fired product is cooled to the room temperature from the firing temperature, the desired fluorescence can also be obtained by removing the fired product from the electric furnace and allowing it to cool in the air. The body can be obtained, but it may be cooled in the same weakly reducing atmosphere or neutral atmosphere as at the time of firing. In addition, by moving the fired product from the heating unit to the cooling unit in an electric furnace and quenching in a weak reducing atmosphere, neutral atmosphere or weak oxidizing atmosphere, the emission luminance due to the phosphor phosphors obtained can be increased. It can be further increased.
[0043]
(Activator introduction method)
As a method for introducing the activator raw material into the stimulable phosphor, there are a dry introduction method and a wet introduction method.
[0044]
In the dry introduction method, powder is mixed, heated and baked and introduced into the base material (also referred to as phosphor raw material) by thermal diffusion and the activator to be introduced is used as steam, while heating the base material There is a way to introduce.
[0045]
What is carried out by powder mixing is simple and easy to put into practical use in a large area, but the heating temperature at the time of introduction is high, and when used, it is preferable to control the temperature distribution.
[0046]
In addition, the latter method of vaporizing the activator can be introduced by heating the base material at a relatively low temperature, but in order to uniformly introduce the activator to make the activator vapor, It is preferable to accommodate the facility for containing the activator vapor in the container or introducing the gas into the heating unit having a path for introducing the activator vapor while performing heating constantly, and a complicated response is required.
[0047]
Therefore, for the purpose of large area and stable introduction, the following wet introduction method is preferably used in which a solvent (for example, water) -soluble material is homogenized in the wet and introduced uniformly. .
[0048]
In the wet introduction method, a material to be a base material is added to a mother liquor, and an activator to be an additive is added to the solution. After the addition, the solution may be dried and solidified, or coprecipitation is performed by using an appropriate additive and the resulting precipitate is dried to obtain a base material into which the activator is introduced. You can also.
[0049]
For introducing the activator into the photostimulable phosphor according to the present invention, either the dry introduction method or the wet introduction method may be used.
[0050]
<Formation of photostimulable phosphor layer>
The formation of the photostimulable phosphor layer according to the present invention will be described.
[0051]
In the radiation image conversion panel of the present invention, it is essential that at least one photostimulable phosphor layer is formed by a vapor phase method (also referred to as a vapor phase deposition method or a vapor phase growth method). As a method, an evaporation method, a sputtering method, an ion plating method, or the like can be used.
[0052]
In the vapor deposition method as the first method, the support is first installed in the vapor deposition apparatus, and then the apparatus is evacuated to 1.333 × 10 6.^-FourThe degree of vacuum is about Pa. Next, at least one of the photostimulable phosphor is heated and evaporated by a resistance heating method, an electron beam method, or the like to grow the photostimulable phosphor on the surface of the support to a desired thickness.
[0053]
As a result, a photostimulable phosphor layer containing no binder is formed, but it is also possible to form the photostimulable phosphor layer in a plurality of times in the vapor deposition step. In the vapor deposition step, it is possible to co-evaporate using a plurality of resistance heaters or electron beams to synthesize the desired photostimulable phosphor on the support and simultaneously form the photostimulable phosphor layer. is there.
[0054]
After the vapor deposition, the radiation image conversion panel of the present invention is manufactured by providing a protective layer on the side opposite to the support side of the photostimulable phosphor layer as necessary. In addition, after forming a photostimulable phosphor layer on a protective layer, a procedure for providing a support may be taken.
[0055]
Further, in the vapor deposition method, during the vapor deposition, the deposition target (support or protective layer) may be cooled or heated as necessary. Further, the stimulable phosphor layer may be heat-treated after the vapor deposition. In the vapor deposition method, O may be added as necessary.₂, H₂Reactive vapor deposition may be performed by introducing a gas such as the above.
[0056]
In the sputtering method as the second method, as in the vapor deposition method, the support is placed in the sputtering apparatus, and then the inside of the apparatus is temporarily evacuated to 1.333 × 10 6.^-FourThe degree of vacuum was set to about Pa, and then an inert gas such as Ar or Ne was introduced into the sputtering apparatus as a sputtering gas to obtain 1.333 × 10 6.^-1The gas pressure is about Pa. Next, the stimulable phosphor layer is grown on the surface of the support to a desired thickness by sputtering using the stimulable phosphor as a target.
[0057]
Various applied treatments can be used in the sputtering step as in the vapor deposition method.
[0058]
There is a CVD method as a third method. A fourth method is an ion plating method.
[0059]
The growth rate of the stimulable phosphor layer in the vapor phase growth is preferably 0.05 μm / min to 300 μm / min. When the growth rate is less than 0.05 μm / min, the productivity of the radiation image conversion panel of the present invention is low, which is not preferable. If the growth rate exceeds 300 μm / min, it is difficult to control the growth rate. When the radiation image conversion panel is obtained by the above-described vacuum deposition method, sputtering method, etc., since there is no binder, the packing density of the stimulable phosphor can be increased, and radiation that is preferable in terms of sensitivity and resolution. An image conversion panel is obtained.
[0060]
(Thickness of photostimulable phosphor layer)
The dry thickness of the photostimulable phosphor layer varies depending on the intended use of the radiation image conversion panel and the type of the photostimulable phosphor, but from the viewpoint of obtaining the effects described in the present invention, the thickness is 50 μm or more. It is necessary, preferably 50 μm to 300 mm, more preferably 100 μm to 500 μm, and particularly preferably 400 μm to 500 μm.
[0061]
In producing the photostimulable phosphor layer by the vapor phase growth method described above, the temperature of the support on which the photostimulable phosphor layer is formed is preferably set to 100 ° C. or higher, more preferably 150 ° C. or higher. Especially preferably, it is 150 to 400 degreeC.
[0062]
The photostimulable phosphor layer according to the radiation image conversion panel of the present invention is formed by vapor-phase growth of the photostimulable phosphor represented by the general formula (1) on the support. The photostimulable phosphor preferably forms a columnar crystal.
[0063]
In order to form a columnar photostimulable phosphor layer by a method such as vapor deposition or sputtering, the photostimulable phosphor represented by the general formula (1) is preferably used. Among them, a CsBr phosphor is particularly preferable. Preferably used.
[0064]
Since the photostimulable phosphor layer formed on the support in this manner does not contain a binder, it has excellent directivity, high directivity of stimulated excitation light and stimulated emission, and high brightness. The layer thickness can be made thicker than that of a radiation image conversion panel having a dispersive stimulable phosphor layer in which a stimulable phosphor is dispersed in a binder. Furthermore, the sharpness of the image is improved by reducing the scattering of the stimulating light in the stimulable phosphor layer.
[0065]
《Phosphor crystal size in photostimulable phosphor layer》
The crystal size of the photostimulable phosphor according to the present invention will be described.
[0066]
At least one of the photostimulable phosphor layers according to the present invention is formed by a vapor phase method (also called a vapor phase deposition method or a vapor phase growth method), and the crystal size of the photostimulable phosphor in the layer is 90 nm. That is essential.
[0067]
In the present invention, there are various modes for producing a photostimulable phosphor having a crystallite size of 90 nm or more. For example, control of the substrate temperature of the deposited film and the degree of vacuum during evaporation are important adjustment factors. Specifically, it is preferably achieved by adjusting the substrate temperature to 170 ° C. or lower, the vacuum degree to 0.7 Pa (700 mPa) or lower, and introducing a rare earth element into the evaporation raw material. .
[0068]
(Rare earth element content)
In the present invention, the addition of rare earth elements (also called activators) improves the luminous brightness of the photostimulable phosphor, suppresses a decrease in crystallinity to a minimum, prevents a decrease in contrast, and sharpens an image. From the standpoint of maintaining good, rare earth elements (rare earth elements are also called activators) in the deposited film in an amount of 1/100 to 1 / 100,000 (in the formula of the general formula (1), M¹, M²It was found that a phosphor layer excellent in contrast and afterglow characteristics can be formed by setting the phosphor crystallite size in the film to 90 nm or more.
[0069]
Examples of rare earth elements according to the present invention include Eu, Tb, In, Cs, Ce, Tm, Dy, Pr, Ho, Nd, Yb, Er, Gd, Lu, Sm, and Y, but are particularly preferably used. Is at least one metal selected from the group consisting of Eu, Ce, Cs, and Sm, and Eu is particularly preferable.
[0070]
(Other additives in the photostimulable phosphor layer)
The additive in the photostimulable phosphor layer according to the present invention will be described.
[0071]
In addition, the gap between the columnar crystals may be filled with a filler or the like, and in addition to reinforcing the stimulable phosphor layer, it may be filled with a high light absorption substance, a high light reflectance substance, or the like. Thus, in addition to providing the above-mentioned reinforcing effect, it is effective for reducing the light diffusion in the lateral direction of the stimulated excitation light incident on the stimulable phosphor layer.
[0072]
A highly reflective material means a material having high reflectivity to stimulated excitation light (500 nm to 900 nm, particularly 600 nm to 800 nm), such as aluminum, magnesium, silver, indium and other metals, white pigments, and green to red regions. The coloring material can be used.
[0073]
White pigments can also reflect stimulated emission. TiO as white pigment₂(Anatase type, rutile type), MgO, PbCO_Three・ Pb (OH)₂, BaSO_Four, Al₂O_Three, M (II) FX (where M (II) is at least one of Ba, Sr and Ca, and X is at least one of Cl and Br), CaCO_Three, ZnO, Sb₂O_Three, SiO₂, ZrO₂, Lithopone (BaSO_FourZnS), magnesium silicate, basic silicate, basic lead phosphate, aluminum silicate and the like. Since these white pigments have a strong hiding power and a high refractive index, they can easily scatter scattered light by reflecting or refracting light, and can significantly improve the sensitivity of the resulting radiation image conversion panel.
[0074]
Moreover, as a substance having a high light absorption rate, for example, carbon, chromium oxide, nickel oxide, iron oxide and the like and a blue color material are used. Of these, carbon also absorbs stimulated luminescence.
[0075]
The color material may be either an organic or inorganic color material. Examples of organic colorants include Zavon First Blue 3G (Hoechst), Estrol Brill Blue N-3RL (Sumitomo Chemical), D & C Blue No. 1 (made by National Aniline), Spirit Blue (made by Hodogaya Chemical), Oil Blue No. 1 603 (made by Orient), Kitten Blue A (made by Ciba Geigy), Eisen Katyron Blue GLH (made by Hodogaya Chemical), Lake Blue AFH (made by Kyowa Sangyo), Primocyanin 6GX (made by Inabata Sangyo), Brill Acid Green 6BH (Hodogaya) Chemical Blue), Cyan Blue BNRCS (Toyo Ink), Lionoyl Blue SL (Toyo Ink), etc. are used. The color index No. 24411, 23160, 74180, 74200, 22800, 23154, 23155, 24401, 14830, 15050, 15760, 15707, 17941, 74220, 13425, 13361, 13420, 11836, 74140, 74380, 74350, 74460, etc. There are also materials. Inorganic color materials include ultramarine, cobalt blue, cerulean blue, chromium oxide, TiO₂-ZnO-Co-NiO pigments.
[0076]
<Support>
The support according to the present invention will be described.
[0077]
As the support used in the radiation image conversion panel of 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, cellulose acetate film, A metal film such as a polyester film, a polyethylene terephthalate film, a polyamide film, a polyimide film, a triacetate film, or a polycarbonate film, a metal sheet such as an aluminum sheet, an iron sheet, or a copper sheet, or a metal sheet having a coating layer of the metal oxide is preferable.
[0078]
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 stimulable phosphor layer.
[0079]
Moreover, in this invention, in order to improve the adhesiveness of a support body and a photostimulable phosphor layer, you may provide an adhesive layer in advance on the surface of a support body as needed. The thickness of these supports varies depending on the material of the support used, but is generally 80 μm to 2000 μm, and more preferably 80 μm to 1000 μm from the viewpoint of handling.
[0080]
(Protective layer)
Moreover, the photostimulable phosphor layer according to the present invention may have a protective layer.
[0081]
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. In addition, this protective layer is made of SiC, SiO, etc. by vapor deposition or sputtering.₂, SiN, Al₂O_ThreeIt may be formed by laminating inorganic substances such as. In general, the thickness of these protective layers is preferably about 0.1 μm to 2000 μm.
[0082]
Hereinafter, an example of a utilization system (also referred to as a diagnostic system) in which the radiation image conversion panel of the present invention is used will be described with reference to FIG.
[0083]
FIG. 1 is a schematic diagram showing an aspect of a system for using a radiation image conversion panel of the present invention.
[0084]
In FIG. 1, 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. Is a device for displaying the reproduced image, and 28 is a filter for cutting off the reflected light from the light source 24 and transmitting only the light emitted from the radiation image conversion panel 23. FIG. 1 shows an example of obtaining a radiation transmission image of a subject. However, when the subject 12 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.
[0085]
As shown in FIG. 1, 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 transmission 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 by the light source 24 that emits light in the visible or infrared region to expel electrons and / or holes accumulated at the trap level, and the accumulated energy is released as stimulated emission. . 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 electrical signal by a photoelectric conversion device 25 such as a photomultiplier tube, and reproduced as an image by an image processing device 26, and this image is displayed by an image display device 27. It is more effective to use an image processing device 26 that can not only reproduce an electrical signal as an image signal but also so-called image processing, image calculation, image storage, storage, and the like.
[0086]
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 according to the present invention is 300 to 500 nm, while the photostimulable excitation wavelength range is 500 to 900 nm, which satisfies the above conditions at the same time. A semiconductor laser that has a high output power and is easy to be compacted is preferably used for reading an image of the radiation image conversion panel. 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.
[0087]
That is, all of the photostimulable phosphors according to the present invention emit light having a main peak at 500 nm or less, and the excitation light can be easily separated and coincides well with the spectral sensitivity of the light receiver, so that light can be received efficiently. As a result, the sensitivity of the image receiving system can be solidified.
[0088]
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 a laser beam is used, the optical system becomes simple, and since the intensity of the stimulated excitation light can be increased, the photostimulated emission efficiency can be increased, and a more preferable result can be obtained.
[0089]
As the laser, He-Ne laser, He-Cd laser, Ar ion laser, Kr ion laser, N₂There are lasers, YAG lasers and second harmonics thereof, ruby lasers, semiconductor lasers, various dye lasers, metal vapor lasers such as copper vapor lasers, and the like. 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. In addition, when using a method of separating light emission using a delay of light emission as shown in JP-A-59-22046 without using a filter 28, a pulsed laser is used rather than a continuous wave laser. It is preferable to use it.
[0090]
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.
[0091]
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.
[0092]
For example, in the case of a practically preferable combination in which the photostimulation excitation wavelength is 500 nm to 900 nm and the photostimulation emission wavelength is 300 to 500 nm, examples of the filter include C-39, C-40, V-40, manufactured by Toshiba Corporation. Purple-blue glass filters such as V-42, V-44, Corning 7-54, 7-59, Spectrofilm BG-1, BG-3, BG-25, BG-37, BG-38, etc. 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.
[0093]
【Example】
EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited to these.
[0094]
Example 1
<< Preparation of radiation image conversion panel sample 1 >>
As described below, a stimulable phosphor into which an activator has been introduced, a stimulable phosphor plate having a stimulable phosphor layer containing the stimulable phosphor, and then the stimulator The radiation image conversion panel 1 was produced using the fluorescent phosphor plate.
[0095]
(Preparation of photostimulable phosphor plate 1): Introducing activator by dry method
Under the conditions shown in Table 1, the vapor deposition apparatus shown in FIG. 2 (provided that θ1 = 5 degrees and θ2 = 5 degrees) is provided on the surface of a 1 mm thick crystallized glass (manufactured by Nippon Electric Glass Co., Ltd.) support. A stimulable phosphor layer having a stimulable phosphor (CsBr: Eu) was formed on the support to produce a stimulable phosphor plate 1.
[0096]
In addition, the dry method shown below was used for the introduction method of the activator (Eu) to the evaporation source material used at the time of vapor deposition.
[0097]
(Introduction of activator by dry method)
Cesium bromide and europium bromide as evaporation source materials are weighed in advance so as to have a blending ratio blended in the deposited film (CsBr: Eu), and collected. The fractionated cesium bromide is put in a metal crucible made of Ta (tantalum), which is a dedicated vapor source for cesium bromide, and the other europium bromide is put in another metal crucible made of Ta (tantalum).
[0098]
As the deposition conditions, after reaching the degree of vacuum described in Table 1 below, evaporation is performed as follows.
[0099]
After reaching the vacuum, the Ta metal crucible containing cesium bromide is degassed by increasing the temperature at a rate of 10 ° C./min until the crucible temperature reaches 650 ° C. Thereafter, after confirming that the inside of the crucible has been completely melted at 650 ° C., the installed shutter is opened to start film formation.
[0100]
In addition, the Ta metal crucible containing the other europium bromide is heated until the crucible temperature reaches 750 ° C. However, it is preferable to adjust the rate of temperature increase to 750 ° C. so that the time and timing until the temperature of the crucible containing the cesium bromide reaches 650 ° C. are matched.
[0101]
Here, the deposition conditions of the europium bromide and the cesium bromide are adjusted so that the compounding ratio is CsBr: Eu.
[0102]
Moreover, in the vapor deposition apparatus shown in FIG. 2, the distance d between the support and the slit is adjusted to 60 cm using an aluminum slit, and vapor deposition is performed while transporting the support in a direction parallel to the support. The thickness of the photostimulable phosphor layer was adjusted to 300 μm.
[0103]
The radiation image conversion panel 1 was produced using the stimulable phosphor plate 1 produced above. Specifically, an air layer as a low refractive index layer is 100 μm between each stimulable phosphor layer and glass used as a protective layer via a spacer on the glass-like side edge portion having the stimulable phosphor layer. A protective layer made of glass was provided so as to have a thickness of. In addition, the spacer is made of glass ceramics, and the thickness is adjusted so that the stimulable phosphor layer and the low refractive index layer (air layer) have a predetermined thickness between the support and the protective layer glass, The side edges of the glass support and the protective layer made of glass were bonded using an epoxy adhesive to produce the radiation image conversion panel 1.
[0104]
<< Production of Radiation Image Conversion Panels 2-8 >>
In the production of the radiation image conversion panel 1, when the stimulable phosphor plate 1 is produced, the method of introducing the activator is changed from the dry method to the wet method as shown below, and the stimulable phosphor layer is produced. Radiation image conversion panels 2 to 8 were produced in the same manner except that the conditions (deposition conditions) were set as described in Table 1.
[0105]
(Introduction of activator by wet method)
Cesium bromide and europium bromide as evaporation raw materials are mixed so as to have a predetermined blending ratio and dissolved in water to obtain an aqueous solution. The obtained aqueous solution is heated and dried and solidified to obtain particles having a diameter of 50 μm to 200 μm. The particles were dehydrated by heating under vacuum at 120 ° C. for 2 hours to obtain an evaporation source material.
[0106]
The obtained evaporation source was put into a crucible, and it was confirmed that the degree of vacuum in the vapor deposition chamber reached the target degree of vacuum described in Table 1, the applied current was increased, and the temperature of the crucible ranged from 750 ° C to 950 ° C. The evaporation source was evaporated while adjusting.
[0107]
The cesium bromide formed as described above contains Eu.
The obtained radiation image conversion panels 1 to 8 were each evaluated for luminance, sharpness, and bright afterglow ratio (also simply referred to as luminance afterglow), as described below.
[0108]
"Luminance"
The luminance was evaluated using a Regius 350 manufactured by Konica Corporation.
[0109]
X-rays were irradiated with a tungsten tube at 80 kVp and 10 mAs at a distance of 2 m between the bombardment source and the plate, and a plate was placed on the Regius 350 and read. Relative evaluation was performed based on the electrical signal from the obtained photomultiplier. The luminance of sample 2 was set to 1.0, and the subsequent values were expressed as relative values.
[0110]
《Sharpness》
The sharpness of the radiation image conversion panel sample was evaluated by obtaining a modulation transfer function (MTF).
[0111]
The MTF applies a CTF chart to a radiation image conversion panel sample, irradiates the radiation image conversion panel sample with 80 kVp X-rays at a distance of 10 mR (distance to the subject: 1.5 m), and then a semiconductor laser having a diameter of 100 μmφ (680 nm). : The CTF chart image was scanned and read using a power of 40 mW on the panel). The values in the table are shown as values obtained by adding MTF values of 1.0 lp / mm.
[0112]
《Sparkling afterglow ratio》
In the case of stimulating light emission, signal values are read and measured in the same manner as in luminance evaluation.
[0113]
For the measurement of the afterglow ratio, half of the laser is scanned at the time of laser scanning, the brightness value (a) after scanning is obtained, the half is set to laser off, and the value after 300 msec of X-ray explosion after the laser off (b). Was measured, and the ratio of brightness was determined as the ratio of brightness afterglow.
[0114]
Afterglow ratio (%) = (a / b) × 100
The obtained results are shown in Table 1.
[0115]
[Table 1]

[0116]
From Table 1, it can be seen that the sample of the present invention is excellent in luminance and sharpness and has little afterglow compared to the comparison.
[0117]
【The invention's effect】
According to the present invention, it was possible to provide a radiographic image conversion panel having high contrast and high brightness and low afterglow, and a method for manufacturing the radiographic image conversion panel.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing an example of the configuration of a radiation image conversion panel according to the present invention.
FIG. 2 is a schematic view showing an example of a method for producing a photostimulable phosphor layer on a support by vapor deposition.
[Explanation of symbols]
21 Radiation generator
22 Subject
23 Radiation image conversion panel
24 Excited light source
25 Photoelectric conversion device for detecting photostimulated fluorescence emitted by the conversion panel
26 Image playback device
27 Image display device
28 Filter

Claims (3)

In a radiation image conversion panel having at least one photostimulable phosphor layer on a support,
At least one layer is a stimulable phosphor layer made of a CsBr: Eu stimulable phosphor, and the stimulable phosphor layer has a temperature of the support of 100 ° C. to 170 ° C. and a degree of vacuum of 10 mPa to 700 mPa. The film is formed to have a film thickness of 50 μm or more by a vapor phase method (also referred to as a vapor deposition method), and the crystallite size of the CsBr: Eu stimulable phosphor in the layer is 90 nm to 109 nm. Radiation image conversion panel characterized by. The radiation image conversion panel according to claim 1, wherein Eu, which is an activator of the CsBr: Eu stimulable phosphor, has been introduced with an activator by a wet method. In producing the radiation image conversion panel according to claim 1, at least one stimulable phosphor layer has a temperature of 100 ° C. to 170 ° C. and a vacuum degree of 10 mPa to 700 mPa. A method for manufacturing a radiation image conversion panel, which is manufactured through a step of forming a film having a thickness of 50 μm or more by a vapor deposition method (also referred to as a vapor phase deposition method).

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