JP3915593B2 - Radiation image conversion panel and method for manufacturing radiation image conversion panel - Google Patents

Description

【０１２４】
【発明の効果】
実施例で実証した如く、本発明による放射線画像変換パネル及び該放射線画像変換パネルの製造方法は、賦活剤の均一性に優れ、且つ、高輝度、高鮮鋭性にも優れた効果を有する。
【図面の簡単な説明】
【図１】支持体上に形成した柱状結晶を有する輝尽性蛍光体層の一例を示す断面図である。
【図２】支持体上に輝尽性蛍光体層を蒸着法により形成される様子を示す図である。
【図３】本発明の放射線画像変換パネルの構成の一例を示す概略図である。
【図４】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である。
【符号の説明】
１１ 支持体
１２ 輝尽性蛍光体層
１３ 柱状結晶
１４ 柱状結晶間に形成された間隙
１５ 支持体ホルダ
２１ 放射線発生装置
２２ 被写体
２３ 放射線画像変換パネル
２４ 輝尽励起光源
２５ 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 the 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 (US Patent No. 1). 3,859,527).
[0004]
As a radiation image conversion method using a stimulable phosphor with higher brightness and sensitivity, for example, BaFX: Eu ²⁺ system (X: Cl, Br, I) described in JP-A-59-75200 and the like. Radiation image conversion method using phosphor, radiation image conversion method using alkali halide phosphor as described in JP-A-61-72087, etc., as described in JP-A-61-73786, 61-73787, etc. In addition, alkali halide phosphors containing Tl ⁺ and Ce ³⁺ , Sm ³⁺ , Eu ³⁺ , Y ³⁺ , Ag ⁺ , Mg ²⁺ , Pb ²⁺ , and In ³⁺ metals as co-activators were developed. Has been.
[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 to be formed.
[0006]
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, for example, JP-A No. 61-142497. There is a method using a stimulable phosphor layer.
[0007]
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 was further developed by applying a shock treatment. A method of using a radiation image conversion panel having a photostimulable phosphor layer, and further a crack from the surface side of the photostimulable phosphor layer formed on the support described in JP-A-62-39737 And a stimulable phosphor layer having a cavity by vapor deposition on a support as described in JP-A-62-110200. There has also been proposed a method in which a cavity is grown by heat treatment and a crack is formed after the formation.
[0008]
Furthermore, Japanese Patent Application Laid-Open No. 2-58000 discloses photostimulability 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 growth (vapor deposition). A radiation image conversion panel having a phosphor layer is described.
[0009]
In any of the methods for controlling the shape of the photostimulable phosphor layer, the stimulable phosphor layer is formed into a columnar shape, thereby suppressing the lateral diffusion of the photostimulated excitation light or the photostimulated luminescence (crack ( The columnar crystal) can reach the support surface while repeating reflection at the interface), and is therefore characterized in that the sharpness of the image due to stimulated emission can be remarkably increased.
[0010]
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. In particular, X-ray conversion efficiency, which has been impossible in the past by using Eu as an activator, has been proposed. It became possible to improve.
[0011]
However, 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 can be obtained. However, it has not been put to practical use in the market.
[0012]
In particular, in the activation of rare earth elements that are excellent in terms of X-ray conversion efficiency, the formation of a deposited film under vacuum is a problem that is difficult to make uniform from the vapor pressure characteristics. In particular, 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 vacuum deposition, 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 a later annealing (substrate strain relaxation) treatment.
[0013]
Accordingly, there has been a demand for further improvement and improvement in the brightness and sharpness of the radiation image conversion panel from the market.
[0014]
[Problems to be solved by the invention]
An object of the present invention is to provide a radiation image conversion panel excellent in uniformity of an activator, high brightness, and high sharpness, and a method for producing the radiation image conversion panel.
[0015]
[Means for Solving the Problems]
The above object of the present invention is achieved by the following configurations.
[0016]
1. In a radiation image conversion panel having a photostimulable phosphor layer on a support, at least one photostimulable phosphor layer is formed to a thickness of 50 μm to 1 mm by a vapor phase method (also referred to as a vapor deposition method). The radiation image is characterized in that vapor deposition is performed at a temperature difference between the endothermic start temperature and endothermic end temperature at the melting point of the rare earth compound of 14 ° C. or less, and the rare earth compound is uniformly contained inside the phosphor base crystal formed. Conversion panel.
[0017]
2. 2. The radiation image conversion according to 1 above, wherein the at least one photostimulable phosphor layer contains a photostimulable phosphor based on an alkali halide represented by the general formula (1). panel.
[0018]
3. In a radiation image conversion panel having a stimulable phosphor layer on a support, at least one of the stimulable phosphor layers has a thickness of 50 μm to 1 mm by a vapor phase method (also referred to as a vapor deposition method). In order to uniformly contain the rare earth compound inside the phosphor base crystal formed as described above, a double salt crystal is used as the phosphor compound raw material, and the phosphor compound raw material is 20 ° C. higher than the melting point of the rare earth compound. A method for producing a radiation image conversion panel, comprising heating at a temperature and vapor-depositing at a temperature difference of 14 ° C. or less between an endothermic start temperature and an endothermic end temperature at the melting point of the rare earth compound.
[0019]
Hereinafter, the present invention will be described in more detail.
In the radiation image conversion panel of the present invention, at least one photostimulable phosphor layer is formed to a film thickness of 50 μm to 1 mm by a vapor phase method, and the temperature difference between the endothermic start temperature and endothermic end temperature at the melting point of the rare earth compound. (T) is vapor-deposited at 0 <T ≦ 14 ° C., and the rare earth compound is uniformly contained in the inside of the phosphor base crystal formed.
[0020]
Here, uniformly containing means that the amount of activator present is the same on the support side and the phosphor surface side in the phosphor layer.
[0021]
Specifically, the activator abundance on the support side and the surface side of the phosphor layer is matched within ± 10%, and as a confirmation method, the activator abundance of the phosphor layer is about the phosphor layer. A sample in which the surface side of the phosphor layer formed with 500 microns is scraped about 100 microns and a sample in which the phosphor layer on the support side is made 100 microns are dissolved in pure water to form an aqueous solution. This aqueous solution can be analyzed by ICP to calculate and confirm the amount of activator.
[0022]
Conventionally, the melting point of a phosphor raw material is usually lowered by an impurity (an activator) added to the phosphor host crystal CsBr in vapor deposition by vapor deposition.
[0023]
In particular, when the melting point of the phosphor raw material (CsBr: Eu) in which the activator Eu is added to the phosphor base crystal CsBr is lowered and heat-deposited, it is gradually increased from CsBr (melting point around 645 ° C.) having a low melting point in the deposited film formation stage. It is volatilized, and the amount of Eu to be introduced into the deposited film as an activator decreases, and Eu is present in the crystal lattice (lattice defect) of the CsBr crystal, resulting in a crystal state in which the shape of the obtained columnar crystal has collapsed. In the columnar crystal, light scattering occurs, which causes a decrease in sharpness with respect to laser excitation.
[0024]
Accordingly, in the present invention, the temperature difference (T) between the endothermic start temperature and endothermic end temperature at the melting point of the rare earth compound is vapor-deposited in the range of 0 <T ≦ 14 ° C., and the rare earth compound is formed inside the phosphor base crystal formed. In order to introduce the activator Eu in CsBr vapor deposition, for example, the phosphor raw material that is a mixture of CsBr and EuBr ₂ is heated. By evaporating the above temperature difference in the melting point of EuBr ₂ at 14 ° C. or less, the rare phosphor layer of the present invention can be obtained.
[0025]
That is, when a rare earth compound is usually introduced, the phosphor base crystal collapses and the temperature difference exceeds 14 ° C., and this tendency becomes more prominent as the amount of the rare earth compound introduced is increased, and the phosphor base crystal and the rare earth compound have a melting point. Since the vapor pressure is different, the phosphor matrix crystal diffuses in the heated state, for example, radiant heat at the time of vapor deposition, and crystal formation by substrate heating, resulting in a difference in crystallinity of the phosphor matrix, and the rare earth compound It will exist ubiquitously.
[0026]
On the contrary, when vapor deposition is performed with the temperature difference being 14 ° C. or less, a uniform and highly crystalline phosphor base crystal is formed, and the place where the rare earth compound in the phosphor base can exist is determined. Therefore, it is estimated that a rare-earth compound can be uniformly contained inside the phosphor crystal matrix, and a radiation image conversion panel excellent in luminance and sharpness can be obtained.
[0027]
The temperature difference between the endothermic start temperature and the endothermic end temperature can be determined by TG-DTA measurement.
[0028]
The TG-DTA measurement of the phosphor material at the melting point of the rare earth compound (EuBr ₂ : about 638 ° C.) is that the endotherm begins when 10 mg of deposited film is put in a platinum sample holder and the temperature is raised from room temperature to 800 ° C. in an Ar atmosphere. The temperature is set as the endothermic start temperature, and the endothermic maximum peak point temperature is set as the endothermic end temperature. A temperature difference (T) is obtained in advance, and the heating and vapor deposition temperatures are set.
[0029]
Shimadzu Corporation was used for the TG-DTA measurement, but any other device from other companies may be used.
[0030]
When a double salt crystal of (Csa, Eu) Brx (a + b = x) is deposited as a phosphor compound material, the phosphor material is heated at a temperature higher by 20 ° C. than the melting point of EuBr ₂ to form a vapor. Moreover, the rare earth compound can be uniformly contained in the inside of the phosphor base crystal formed by vapor deposition at a temperature difference of 14 ° C. or less.
[0031]
In this case, the film formation rate during evaporation is preferably 20 μm / min or more, and most preferably 60 μm / min or more.
[0032]
In addition, in the vapor deposition of the present invention, it is preferable to perform annealing treatment together.
The crucible for vapor deposition differs depending on the heating method such as resistance heating method, halogen heating method EB (electron beam) method and the like.
[0033]
In the present invention, temperature control during heating of the vapor deposition source is extremely important, and heating is performed at a melting point of the rare earth compound in the phosphor raw material of the present invention + 20 ° C. or higher.
[0034]
For this purpose, in the resistance heating and halogen heating systems, the temperature of the vapor deposition boat (tungsten boat, molybdenum boat, tantalum boat, quartz boat) serving as a heating source is set so that the melting point of the rare earth compound + 20 ° C.
[0035]
Originally, in the heating method such as resistance heating, the volatilization amount is controlled by the applied current value, but in order to control the vapor deposition rate by heating at a temperature setting higher than the target range temperature, it depends on the opening area of the vapor deposition boat. Control the deposition rate.
[0036]
Specifically, when the deposition rate is slowed, a lid is provided on the vapor deposition boat that opens, and the volatilization amount can be adjusted by the number of holes in the opening and the opening area.
[0037]
The opening area of the vapor deposition boat when heated at a temperature 20 ° C. higher than the melting point of EuBr ₂ is preferably adjusted to 1/3 or less of the entire area of the lid of the vapor deposition boat, and the hole diameter is preferably 3 mm or less. More preferably, the diameter is 0.5 to 1 mm.
[0038]
In addition to the deposition rate, the size of the hole has the effect of preventing sudden boiling that occurs during vapor deposition, and needs to be adjusted depending on the area to be vapor deposited and the vapor deposition boat.
[0039]
Even when the vapor deposition scale is changed, it is possible to adjust the size up to a maximum of 14 × 17 inches as long as the hole and opening area of the boat lid are as described above. (However, 1 inch is 2.54 cm)
Next, the stimulable phosphor represented by the general formula (1) preferably used in the present invention will be described.
[0040]
In the photostimulable phosphor represented by the general formula (1), M ^I represents at least one alkali metal atom selected from each atom such as Na, K, Rb and Cs. At least one alkaline earth metal atom selected from each atom is preferred, and a Cs atom is more preferred.
[0041]
M ² represents at least one divalent metal atom selected from atoms such as Be, Mg, Ca, Sr, Ba, Zn, Cd, Cu, and Ni, and among them, Be, Mg are preferably used. , A divalent metal atom selected from atoms such as Ca, Sr and Ba.
[0042]
M ³ is at least selected from each atom such as Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Al, Ga and In. One kind of trivalent metal atom is represented, and among these, trivalent metal atoms selected from each atom such as Y, Ce, Sm, Eu, Al, La, Gd, Lu, Ga and In are preferred. is there.
[0043]
A is at least one selected from the atoms of Eu, Tb, In, Ce, Tm, Dy, Pr, Ho, Nd, Yb, Er, Gd, Lu, Sm, Y, Tl, Na, Ag, Cu, and Mg. Metal atom.
[0044]
From the viewpoint of improving the photostimulable emission brightness of the photostimulable phosphor, X, X ′, and X ″ each represent at least one halogen atom selected from F, Cl, Br, and I atoms. At least one halogen atom selected from Br is preferable, and at least one halogen atom selected from Br and I atoms is more preferable.
[0045]
In the general formula (1), the b value represents 0 ≦ b <0.5, and preferably 0 ≦ b ≦ 10 ⁻² .
[0046]
The photostimulable phosphor represented by the general formula (1) of the present invention is produced, for example, by the production method described below.
[0047]
As a phosphor material,
(A) 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.
[0048]
_{(B) MgF 2, MgCl 2} , MgBr 2, MgI 2, CaF 2, CaCl 2, CaBr 2, CaI 2, SrF 2, SrCI 2, SrBr 2, SrI 2, BaF 2, BaCl 2, BaBr 2, BaBr 2 2H ₂ O, 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, NiF ₂ , NiCl ₂ , NiBr _At least one or two or more compounds selected from ₂ and NiI ₂ compounds are used.
[0049]
(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 a compound having a metal atom selected from each atom such as Mg.
[0050]
The phosphor materials (a) to (c) are weighed so as to have a mixed composition in the above numerical range, and sufficiently mixed using a mortar, ball mill, mixer mill or the like.
[0051]
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.
[0052]
Further, the photostimulable phosphor layer of the present invention is formed by a vapor phase growth method.
Vapor deposition methods, sputtering methods, CVD methods, ion plating methods, and others can be used as the vapor phase growth method of the photostimulable phosphor.
[0053]
In the present invention, for example, the following methods can be mentioned.
In the vapor deposition method of the first method, first, after the support is installed in the vapor deposition apparatus, the inside of the apparatus is evacuated to a vacuum degree of about 1.333 × 10 ⁻⁴ Pa.
[0054]
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.
[0055]
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.
[0056]
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.
[0057]
After vapor deposition is completed, 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.
[0058]
Furthermore, in the vapor deposition method, the vapor deposition target (support, protective layer or intermediate layer) may be cooled or heated as necessary during vapor deposition.
[0059]
Further, the stimulable phosphor layer may be heat-treated after the vapor deposition. In the vapor deposition method, reactive vapor deposition may be performed in which vapor deposition is performed by introducing a gas such as O ₂ or H ₂ as necessary.
[0060]
In the sputtering method as the second method, like the vapor deposition method, after a support having a protective layer or an intermediate layer is placed in the sputtering apparatus, the inside of the apparatus is once evacuated to about 1.333 × 10 ⁻⁴ Pa. The degree of vacuum is set, and then an inert gas such as Ar or Ne is introduced into the sputtering apparatus as a sputtering gas to obtain a gas pressure of about 1.333 × 10 ⁻¹ Pa. Next, a stimulable phosphor layer is grown on the support to a desired thickness by sputtering using the stimulable phosphor as a target.
[0061]
Various applied treatments can be used in the sputtering step as in the vapor deposition method.
[0062]
The third method is a CVD method, and the fourth method is an ion plating method.
[0063]
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.
[0064]
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 photostimulable phosphor can be increased, which is preferable in terms of sensitivity and resolution. An image conversion panel is obtained and preferred.
[0065]
The film thickness of the photostimulable phosphor layer varies depending on the intended use of the radiation image conversion panel and the type of stimulable phosphor, but is preferably 50 μm to 1 mm from the viewpoint of obtaining the effects described in the present invention. Is 50 to 300 μm, more preferably 100 to 300 μm, and particularly preferably 150 to 300 μm.
[0066]
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 150-400 degreeC.
[0067]
Further, from the viewpoint of obtaining a radiation image conversion panel exhibiting high sharpness, the reflectivity of the stimulable phosphor layer of the present invention is 20% or more, preferably 30% or more, more preferably 40% or more. It is. The upper limit is 100%.
[0068]
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.
[0069]
Next, formation of the photostimulable phosphor layer of the present invention will be described with reference to FIGS.
FIG. 1 is a schematic cross-sectional view showing an example of a photostimulable phosphor layer having columnar crystals formed on a support using the vapor phase growth method described above. Reference numeral 11 denotes a support, 12 denotes a stimulable phosphor layer, and 13 denotes a columnar crystal constituting the stimulable phosphor layer. Reference numeral 14 denotes a gap formed between the columnar crystals.
[0070]
FIG. 2 is a diagram showing a state in which a photostimulable phosphor layer is formed on the support by vapor deposition. The incident angle of the photostimulable phosphor vapor flow 16 with respect to the normal direction (R) of the support surface is shown. Assuming θ ₂ (incident at 60 ° in the figure), the angle of the columnar crystal formed with respect to the normal direction (R) of the support surface is θ ₁ (about 30 ° in the figure, empirically about half) The columnar crystals are formed at this angle.
[0071]
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.
[0072]
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.
[0073]
A highly reflective substance refers to a substance having a high reflectivity with respect to stimulated excitation light (500 to 900 nm, particularly 600 to 800 nm). For example, white pigments such as aluminum, magnesium, silver, indium, and other metals In addition, a color material in the green to red region can be used. White pigments can also reflect stimulated emission.
[0074]
Examples of the white pigment include TiO ₂ (anatase type, rutile type), MgO, PbCO ₃ · Pb (OH) ₂ , BaSO ₄ , Al ₂ O ₃ , M (II) FX (where M (II) is Ba). , Sr, and Ca, and X is a Cl atom or a Br atom.), CaCO ₃ , ZnO, Sb ₂ O ₃ , SiO ₂ , ZrO ₂ , lithopone (BaSO ₄ ZnS), magnesium silicate, basic silicate, basic lead phosphate, aluminum silicate and the like.
[0075]
These white pigments have a strong hiding power and a high refractive index, so that it is possible to easily scatter scattered light by reflecting or refracting light, and to significantly improve the sensitivity of the resulting radiation image conversion panel. it can.
[0076]
In addition, as a material having a high light absorption rate, for example, carbon black, chromium oxide, nickel oxide, iron oxide, and the like and a blue color material are used. Among these, carbon black absorbs stimulated light emission.
[0077]
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.
[0078]
In addition, 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.
[0079]
Examples of the inorganic color material include inorganic pigments such as ultramarine, for example, cobalt blue, cerulean blue, chromium oxide, and TiO ₂ —ZnO—Co—NiO.
[0080]
As the support used in the radiation image conversion panel of the present invention, various types of glass, for example, polymer materials and metals are used. For example, plate glass such as quartz, borosilicate glass, chemically strengthened glass, or cellulose acetate. A metal sheet such as a film, a polyester film, a polyethylene terephthalate film, a polyamide film, a polyimide film, a triacetate film, 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. preferable.
[0081]
That is, the surface of the support may be a smooth surface, or the surface of the support may be a matte surface for the purpose of improving the adhesion to the stimulable phosphor layer.
[0082]
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.
[0083]
The thickness of the support varies depending on the material of the support used, but is generally 80 to 2000 μm, and more preferably 80 to 1000 μm from the viewpoint of handling.
[0084]
Moreover, the photostimulable phosphor layer of the present invention may have a protective layer.
The protective layer may be formed by directly applying a protective layer coating solution on the photostimulable phosphor layer, or a protective layer separately formed in advance may be adhered on the photostimulable phosphor layer. Alternatively, a means for forming a stimulable phosphor layer on a separately formed protective layer may be taken.
[0085]
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-chloride. Usual protective layer materials such as ethylene, 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.
[0086]
Further, this protective layer may be formed by laminating inorganic substances such as SiC, SiO ₂ , SiN, Al ₂ O ₃ by vapor deposition, sputtering, or the like.
[0087]
The thickness of these protective layers is preferably 0.1 to 2000 μm.
FIG. 3 is a schematic view showing an example of the configuration of the radiation image conversion panel of the present invention.
[0088]
In FIG. 3, 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.
[0089]
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.
[0090]
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.
[0091]
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, The transmission image RI (that is, an image of the intensity of radiation) enters the radiation image conversion panel 23.
[0092]
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.
[0093]
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.
[0094]
In addition, the stimulable 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. Release as luminescence.
[0095]
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 is reproduced as an image by an image reproduction device 26, and this image is displayed by an image display device 27.
[0096]
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.
[0097]
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.
[0098]
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 be compacted is preferably used for reading an image of the radiation image conversion panel, and the wavelength of the laser light is preferably 680 nm. The stimulable phosphor incorporated in the panel exhibits very good sharpness when using an excitation wavelength of 680 nm.
[0099]
That is, all of the photostimulable phosphors of the present invention emit light having a main peak at 500 nm or less, the photostimulated excitation light is easily separated, and coincides well with the spectral sensitivity of the light receiver, so that light can be received efficiently. The sensitivity of the image receiving system can be increased.
[0100]
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 intensity of the stimulated excitation light can be increased, so that the stimulated emission efficiency can be increased, and a more preferable result can be obtained.
[0101]
Examples of lasers include He-Ne laser, He-Cd laser, Ar ion laser, Kr ion laser, N ₂ laser, YAG laser and its second harmonic, ruby laser, semiconductor laser, various dye lasers, copper vapor There are metal vapor lasers such as 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.
[0102]
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 pulsed laser is used rather than modulation using a continuous wave laser. It is preferable to use it.
[0103]
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.
[0104]
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.
[0105]
For example, in the case of a practically preferable combination in which the photostimulation excitation wavelength is 500 to 900 nm and the photostimulation emission wavelength is 300 to 500 nm, examples of the filter include C-39, C-40, and 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.
[0106]
【Example】
EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated concretely, the embodiment of this invention is not limited to these.
[0107]
Example 1
<< Preparation of Radiation Image Conversion Panel Samples 1-8 >>
Under the conditions shown in Table 1, the deposition apparatus shown in FIG. 4 (however, θ1 = 5 degrees and θ2 = 5 degrees are set) 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 used.
[0108]
In the vapor deposition apparatus shown in FIG. 4, an aluminum slit is used, the distance d between the support and the slit is set to 60 cm, vapor deposition is performed while the support is transported in a direction parallel to the support, and photostimulable fluorescence is performed. The thickness of the body layer was adjusted to 300 μm.
[0109]
In the vapor deposition, the support was placed in a vapor deposition machine, and then press-molded using a phosphor material (CsBr: Eu) as a vapor deposition source and placed in a resistance heating vapor deposition tungsten boat.
[0110]
Thereafter, the inside of the vapor deposition machine is once evacuated, and after Ar gas is introduced and the degree of vacuum is adjusted to 0.133 Pa, the heating, endothermic start temperature and endothermic end temperature are maintained while maintaining the temperature of the support at 170 ° C. Vapor deposition was performed so that the temperature difference was 20 ° C.
[0111]
Deposition was terminated when the thickness of the photostimulable phosphor layer reached 300 μm, and then this phosphor layer was subjected to heat treatment (annealing treatment) at a temperature of 400 ° C.
[0112]
Next, a radiation image conversion panel sample 1 having a structure in which the periphery of the protective layer made of a support and borosilicate glass is sealed with an adhesive in an atmosphere of dry air so that the photostimulable phosphor layer is sealed ( Comparison) was obtained.
[0113]
Moreover, the heating temperature of the phosphor raw material which is a vapor deposition source in the crucible during vapor deposition was set to 660 ° C.
[0114]
The temperature difference between the endothermic start temperature and the endothermic end temperature of Sample 1 was 20 ° C. as a result of measurement by the method described in the detailed description.
[0115]
In preparation of the radiation image conversion panel sample 1 (comparison), the radiation image conversion panel samples 2, 3, 4, 5, 6, 7, and 8 were respectively prepared in the same manner except that the conditions described in Table 1 were used.
[0116]
The obtained radiation image conversion panel samples 1 to 8 were evaluated as follows.
[0117]
《Evaluation of sharpness》
The sharpness of each prepared radiographic image conversion panel sample was evaluated by obtaining a modulation transfer function (MTF).
[0118]
In the MTF, after attaching a CTF chart to a radiation image conversion panel sample, the radiation image conversion panel sample is irradiated 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 2.0 lp / mm. The obtained results are shown in Table 1.
[0119]
<Evaluation of luminance and luminance distribution>
The luminance was evaluated using a Regius 350 manufactured by Konica Corporation.
[0120]
As in the sharpness evaluation, 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 then a plate was set 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.
[0121]
The electrical signal distribution from the photographed in-plane photomultiplier was relatively evaluated, the standard deviation was obtained, and the luminance distribution (SD) of each sample was obtained.
[0122]
When each of the above evaluations is good, the activator is uniformly contained in the phosphor base crystal.
[0123]
[Table 1]

[0124]
【The invention's effect】
As demonstrated in the examples, the radiation image conversion panel and the method for producing the radiation image conversion panel according to the present invention are excellent in the uniformity of the activator, and also have excellent effects in high brightness and high sharpness.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an example of a photostimulable phosphor layer having columnar crystals formed on a support.
FIG. 2 is a view showing a state in which a photostimulable phosphor layer is formed on a support by a vapor deposition method.
FIG. 3 is a schematic diagram illustrating an example of a configuration of a radiation image conversion panel according to the present invention.
FIG. 4 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]
DESCRIPTION OF SYMBOLS 11 Support body 12 Photoluminescent phosphor layer 13 Columnar crystal 14 Space | gap 15 formed between columnar crystals Support body holder 21 Radiation generation device 22 Subject 23 Radiation image conversion panel 24 Photoexcitation light source 25 Photoelectric conversion device 26 Image reproducing device 27 Image display device 28 Filter

Claims (3)

In a radiation image conversion panel having a photostimulable phosphor layer on a support, at least one photostimulable phosphor layer is formed to a thickness of 50 μm to 1 mm by a vapor phase method (also referred to as a vapor deposition method). The radiation image is characterized in that vapor deposition is performed at a temperature difference between the endothermic start temperature and the endothermic end temperature at the melting point of the rare earth compound of 14 ° C. or less, and the rare earth compound is uniformly contained inside the phosphor base crystal. Conversion panel. The radiation image according to claim 1, wherein the at least one photostimulable phosphor layer contains a photostimulable phosphor based on an alkali halide represented by the following general formula (1). Conversion panel.
General formula (1)
M ¹ X · aM ² X ′ ₂ · bM ³ X ″ ₃ : eA
[Wherein, M ¹ is at least one alkali metal atom selected from Li, Na, K, Rb and Cs atoms, and M ² is Be, Mg, Ca, Sr, Ba, Zn, Cd, Cu. And at least one divalent metal atom selected from each atom of Ni, and M ³ is Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, At least one trivalent metal atom selected from each atom of Tm, Yb, Lu, Al, Ga and In, and X, X ′ and X ″ are at least selected from each atom of F, Cl, Br and I One kind of halogen atom, A is Eu, Tb, In, Ce, Tm, Dy, Pr, Ho, Nd, Yb, Er, Gd, Lu, Sm, Y, Tl, Na, Ag, Cu and Mg At least one metal atom selected from each atom of , A, b, e each represent a number between 0 ≦ a <0.5,0 ≦ b <0.5,0 <e ≦ 0.2.] A radiation image conversion panel having a photostimulable phosphor layer on a support, wherein at least one photostimulable phosphor layer is formed by a vapor phase method so as to have a film thickness of 50 μm to 1 mm. In order to uniformly contain a rare earth compound inside the crystal, a double salt crystal is used as a phosphor compound raw material, the phosphor compound raw material is heated at a temperature 20 ° C. higher than the melting point of the rare earth compound, A method for producing a radiation image conversion panel, wherein the temperature difference between an endothermic start temperature and an endothermic end temperature at a melting point of the compound is 14 ° C. or less.

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