JP2006064383A - Radiation image conversion panel and method for manufacturing it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radiation image conversion panel which has high luminance and is excellent in workability and to provide a method for manufacturing the panel. <P>SOLUTION: The method for manufacturing the radiation image conversion panel is characterized in that a phosphor layer is formed on a support by filling an evaporation source crucible which has at least two or more cells inside it with vapor deposition materials of two or more kinds which are different in temperature characteristics and dissolving and vaporizing the materials by heating them. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

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

  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.

  As a specific method, a radiation image conversion method using a panel having a phosphor layer on a support and using one or both of visible light and infrared light as excitation energy (for example, see Patent Document 1) is known. ing.

A radiation image conversion method using a BaFX: Eu ²⁺ (X: Cl, Br, I) phosphor as a radiation image conversion method using a stimulable phosphor with higher brightness (high sensitivity) (for example, a patent) Reference 2), a radiation image conversion method using an alkali halide phosphor (see, for example, Patent Document 3), Tl ⁺ and Ce ³⁺ , Sm ³⁺ , Eu ³⁺ , Y ³⁺ as co-activators, Alkali halide phosphors containing metals such as Ag ⁺ , Mg ²⁺ , Pb ²⁺ and In ³⁺ have been developed (see, for example, Patent Documents 4 and 5).

  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.

  As one of these attempts, for example, a method using a phosphor layer composed of fine pseudo-columnar blocks formed by depositing a photostimulable phosphor on a support having a fine concavo-convex pattern (see, for example, Patent Document 6). .)

  In addition, a radiation image conversion panel having a phosphor layer further developed by shock-treating cracks between columnar blocks obtained by depositing a photostimulable phosphor on a support having a fine pattern (for example, a patent) And a radiation image conversion panel (see, for example, Patent Document 8) in which the phosphor layer formed on the surface of the support is cracked from the surface side to form a pseudo-columnar shape. In addition, a method of using a phosphor layer having a cavity by vapor deposition on the upper surface of a support, and then growing a cavity by heat treatment to provide a crack (see, for example, Patent Document 9) has been proposed. .

  Furthermore, a radiation image conversion panel having a 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 (see, for example, Patent Document 10). Has been proposed.

  Recently, a radiation image conversion panel using a stimulable phosphor obtained by activating Eu with an alkali halide such as CsBr as a base material has been proposed. It has become possible to derive a high X-ray conversion efficiency.

  However, Eu has a remarkable diffusion due to heat, and since the vapor pressure under vacuum is high, there is a problem that the existence of Eu in the matrix is ubiquitous due to, for example, dispersal, and the intended high X-ray conversion efficiency can be obtained. Because it is difficult, it has not been put to practical use in the market.

  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 uniform under vacuum due to vapor pressure characteristics. Also, in the manufacturing method, in the phosphor layer formed by vapor phase growth (deposition), raw material heating, substrate (support) heating during vacuum deposition, annealing after film formation (substrate) There is a problem in that the presence of the activator becomes non-uniform because a large amount of heat treatment is applied by the (strain relaxation) treatment.

  When two or more materials with different temperature characteristics are mixed and evaporated, there is a temperature deviation in the crucible (in many cases, both ends connected to the heating electrode tend to be hot and the central part tends to be cold). In addition, materials having different melting points are biased in the crucible, and the bias is also generated in evaporation. It is conceivable to install several crucibles for each material type and evaporate them individually, but it is difficult to evaporate multiple materials at the same time to form a vapor deposition film. There is a problem that the equipment burden increases.

For this reason, there has been a demand for a method for manufacturing a radiation image conversion panel that has improved brightness and sharpness required from the market as a radiation image conversion panel, and has reduced equipment burden and improved workability.
US Pat. No. 3,859,527 JP 59-75200 A JP-A-61-72087 JP-A-61-73786 JP 61-73787 A JP 61-142497 A JP-A-61-142500 JP 62-39737 A JP-A-62-110200 JP-A-2-58000

  An object of the present invention is to provide a radiation image conversion panel having high luminance and excellent workability, and a method for manufacturing the same.

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

(Claim 1)
Filling an evaporation source crucible having at least two cells inside with two or more kinds of vapor deposition materials having different temperature characteristics and dissolving and evaporating by heating to form a phosphor layer on the support. A method for producing a radiation image conversion panel.

(Claim 2)
2. The method for manufacturing a radiation image conversion panel according to claim 1, wherein at least two kinds of vapor deposition materials among the vapor deposition materials are mixed and then filled into the evaporation source crucible.

(Claim 3)
The method for manufacturing a radiation image conversion panel according to claim 1, wherein at least one of the vapor deposition materials is a phosphor material.

(Claim 4)
The method for manufacturing a radiation image conversion panel according to claim 3, wherein the phosphor material is a stimulable phosphor material.

(Claim 5)
The method for producing a radiation image conversion panel according to claim 4, wherein the photostimulable phosphor material is CsBr.

(Claim 6)
At least 1 sort (s) of the said vapor deposition material is an activator, The manufacturing method of the radiation image conversion panel of any one of Claims 1-5 characterized by the above-mentioned.

(Claim 7)
The method for producing a radiation image conversion panel according to claim 6, wherein the activator is Eu.

(Claim 8)
A radiation image conversion panel manufactured by the method for manufacturing a radiation image conversion panel according to claim 1.

  According to the present invention, it is possible to provide a radiation image conversion panel having high luminance and excellent workability, and a method for manufacturing the same.

  As a result of diligent research, the present inventor filled two or more kinds of vapor deposition materials having different temperature characteristics into an evaporation source crucible having at least two or more cells inside, and dissolved and evaporated by heating, and then on the support. It has been found that a radiation image conversion panel having high brightness and excellent workability can be obtained by the method for producing a radiation image conversion panel in which a phosphor layer is formed. In the present invention, the temperature characteristic means the melting point and the vapor pressure at the melting point.

  The present invention will be described in detail below.

[Support]
As the support used in the radiation image conversion panel of the present invention, various types of glass, polymer materials, carbon fiber reinforced resin (CFRP), metals, and the like are used. For example, flat glass such as quartz, borosilicate glass, chemically tempered glass, cellulose acetate film, polyester film, polyethylene terephthalate film, polyamide film, polyimide film, triacetate film, polycarbonate film and other plastic films, foamed polyimide or foamed polyacrylic resin Examples thereof include a composite resin film having both sides coated with a carbon fiber reinforced resin, a metal sheet such as an aluminum sheet, an iron sheet, and a copper sheet, or a metal sheet having a coating layer of the metal oxide. Among these, a metal substrate or glass mainly composed of aluminum is preferable. The surface of these supports may be a smooth surface or a matte surface for the purpose of improving the adhesion to the phosphor layer.

  Moreover, in order to improve the adhesiveness of a support body and a fluorescent substance 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 to be used, but is generally 80 to 4000 μm, and more preferably 80 to 1000 μm from the viewpoint of handling.

  Further, the spectral absorption characteristic of the support is such that the absorbance on the long wavelength side (600 to 700 nm) is 1.1 to 10.0 times that on the short wavelength side than the short wavelength side (370 to 500 nm). Preferably it is 1.5 to 5.0 times. Setting the spectral absorption characteristics of the support as described above can be achieved by adding a dye during the preparation of the support.

  Examples of the dye that can be used in preparing the support include, for example, perylene pigments described in JP-A-47-30330 and JP-A-56-5552, quinacridone pigments described in JP-A-47-30331, and the like. Bisbenzimidazole pigments described in JP-A-47-18543, aromatic polycondensed ring compounds described in JP-A-47-18544, JP-A-55-98754, JP-A-55-126254, JP-A-55-163543, Azo pigments described in JP-A-44-16373, JP-A-48-30513, JP-A-56-32465, etc., JP-B-50-7434, JP-A-47-37548, JP-A-55-11715, JP-A-56. No. 1944, No. 56-9752, No. 56-2352, No. 56-8050, etc., JP-A 44-1267 40-2780, 52-1667, 46-30035, 49-17535, JP-A-49-11136, 49-99142, 51-109841, 57-148745 Phthalocyanine pigments and the like described in Japanese Patent Publication No. Gazette and the like, and these can be used alone or in combination of two or more. Among these compounds, phthalocyanine compounds are preferable from the viewpoint of the wavelength range. In the present invention, examples of the pigment include zinc oxide, titanium oxide, and zirconium oxide.

[Protective layer]
The radiation image conversion panel of the present invention may have a protective layer on the phosphor layer.

The protective layer may be formed by directly applying a protective layer coating solution on the phosphor layer, or a protective layer separately formed in advance may be adhered on the phosphor layer. Or you may take the procedure of forming a fluorescent substance 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 the protective layer. 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. The thickness of these protective layers is generally preferably about 0.1 to 2000 μm.

[Vapor deposition material]
In the present invention, since the phosphor layer is formed by heating, melting, and evaporation of the vapor deposition material, the vapor deposition material used in the present invention is any material that imparts a necessary function to the phosphor layer. Specific examples of the vapor deposition material include a phosphor, a stimulable phosphor, an activator, a binder, a substance having a high light absorption rate, a substance having a high light reflectance, and the like.

(Phosphor)
The phosphor used in the present invention refers to a phosphor that is excited by X-rays and emits visible light immediately in the relaxation process or upon receiving a stimulus such as infrared light. Examples of phosphors that immediately emit visible light include ZnS: Ag and CaWO ₄ that have been used for medical diagnosis. A phosphor that emits visible light in response to a stimulus such as infrared light is a stimulable phosphor. In the present invention, a stimulable phosphor is preferable among the phosphors.

(Stimulable phosphor, activator)
Examples of the stimulable phosphor used in the vapor deposition type phosphor layer include a stimulable phosphor represented by BaSO ₄ : Ax described in JP-A-48-80487, and JP-A-48-80488. MgSO _4: stimulable phosphor represented by Ax, SrSO described in JP 48-80489 _4: stimulable phosphor represented by Ax, Na ₂ SO ₄ described in JP 51-29889 Stimulable phosphors obtained by adding at least one of Mn, Dy and Tb to CaSO ₄ and BaSO ₄ , and stimulants such as BeO, LiF, MgSO ₄ and CaF ₂ described in JP-A No. 52-30487 Phosphors, stimulable phosphors such as Li ₂ B ₄ O ₇ : Cu, Ag described in JP-A-53-39277, Li ₂ O. (Be ₂ O described in JP-A-54-47883) ₂₎ x: Cu, stimulable phosphor such as Ag, U.S. Patent No. 3,85 , Described in JP 527 SrS: Ce, Sm, SrS : Eu, Sm, La 2 O 2 S: Eu, Sm and (Zn, Cd) S: stimulable phosphor represented by Mnx the like. Further, a ZnS: Cu, Pb phosphor described in JP-A-55-12142, a barium aluminate phosphor whose general formula is BaO.xAl ₂ O ₃ : Eu, and a general formula of M (II) O XSiO ₂ : An alkaline earth metal silicate phosphor represented by A is mentioned. Here, the atom described after “:” is an activator.

Further, an alkaline earth fluorohalide phosphor represented by the general formula (Ba _1-xy Mg _x Ca _y ) F _x : Eu ²⁺ described in JP-A-55-12143, A stimulable phosphor in which the general formula described in No. 12144 is represented by LnOX: xA, and a general formula described in JP-A No. 55-12145 is (Ba _1-x M (II) _x ) F _x : yA A stimulable phosphor represented by the general formula described in JP-A-55-84389 is represented by BaFX: xCe, yA, and a general formula described in JP-A-55-160078 is represented by Rare earth element-activated divalent metal fluorohalide phosphor represented by M (II) FX.xA: yLn, general formula ZnS: A, CdS: A, (Zn, Cd) S: Stimulation represented by A, X Phosphor, any one of the following general formulas xM ₃ (PO ₄ ) ₂ · NX described in JP-A-59-38278 ₂ : yA
xM ₃ (PO ₄ ) ₂ : yA
A stimulable phosphor represented by any one of the following formulas described in JP-A-59-155487: nReX ₃ · mAX ′ ₂ : xEu
nReX ₃ · mAX ′ ₂ : xEu, ySm
A bismuth-activated alkali halide phosphor represented by the general formula M (I) X: xBi described in JP-A No. 61-228400, and JP-A No. 61-72087. The following general formula (1)
M ¹ X · aM ² X ′ · bM ³ X ″: eA
(In the formula, 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 1 type 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, and a, b, e each represent a number between 0 ≦ a <0.5,0 ≦ b <0.5,0 <e ≦ 0.2.)
An alkali halide phosphor represented by

  In particular, the alkali halide phosphor is preferable because a columnar phosphor layer is easily formed by vapor deposition.

  Among the alkali halide phosphors, RbBr and CsBr phosphors are preferable in terms of high brightness and high image quality, and CsBr phosphors are particularly preferable.

  The phosphor represented by the general formula (1) is manufactured by, for example, a manufacturing method described below.

  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 a neutralization point. Is evaporated to produce the following crystals.

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.

_{(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 compound selected from ₂ and NiI ₂ compounds is used.

  (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.

  (D) The activator A includes, for example, 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 atoms is used.

In the compound represented by the general formula (1), a is 0 ≦ a <0.5, preferably 0 ≦ a <0.01, b is 0 ≦ b <0.5, preferably 0 ≦ b ≦ 10 ^{−. 2} and e are 0 <e ≦ 0.2, preferably 0 <e ≦ 0.1.

  The phosphor materials (a) to (d) 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 to 0 to 7, and then water is evaporated and vaporized.

  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 preferably 500 to 1000 ° C. The firing time varies depending on the filling amount of the raw material mixture, the firing temperature and the like, but is preferably 0.5 to 6 hours.

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

  After firing once under the aforementioned firing conditions, the fired product is taken out from the electric furnace and pulverized, and then the fired product powder is again filled in a heat-resistant container and placed in the electric furnace, and again under the same firing conditions as described above. If the calcination is performed, the emission luminance of the phosphor can be further increased. When the baked product is cooled to the room temperature from the calcination temperature, the desired fluorescence can also be obtained by removing the baked 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.

(Material with high light absorption rate)
Further, a material having a high light absorptivity, a material having a high light reflectance, or the like may be filled in the gaps between the columnar crystals. In addition to providing a reinforcing effect, it is possible to almost completely prevent the lateral diffusion of the stimulated excitation light incident on the phosphor layer.

  As the substance having a high light absorption rate, for example, carbon, chromium oxide, nickel oxide, iron oxide or the like and a blue color material are used. Of these, carbon also absorbs stimulated luminescence.

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. Materials are also mentioned. Examples of inorganic color materials include ultramarine blue, cobalt blue, cerulean blue, chromium oxide, and TiO ₂ —ZnO—Co—NiO pigments.

(High light reflectance material)
A substance having high light reflectance means a material having a high reflectance with respect to stimulated excitation light (500 to 900 nm, particularly 600 to 800 nm), such as white pigment and green to red, such as aluminum, magnesium, silver, indium and other metals. Area colorants can be used.

White pigments can also reflect stimulated emission. As white pigments, 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 At least one of Ca, and X is at least one of Cl and Br.), CaCO ₃ , ZnO, Sb ₂ O ₃ , SiO ₂ , ZrO ₂ , lithopone (BaSO ₄ .ZnS) , Magnesium silicate, basic lead silicic acid sulfate, basic lead phosphate, aluminum silicate and the like. Since these white pigments have strong hiding power and a high refractive index, they can easily scatter stimulated luminescence by reflecting or refracting light, and can significantly improve the sensitivity of the resulting radiation image conversion panel.

[Formation of phosphor layer]
In the present invention, an evaporation source crucible (hereinafter also referred to as a crucible) having at least two cells inside is filled with two or more kinds of vapor deposition materials having different temperature characteristics and heated to be dissolved and evaporated to be supported. It is characterized by forming a phosphor layer on the body.

  Since the inside of the crucible is divided into cells, even if the crucible has a temperature unevenness, the unevenness of vapor deposition materials having different melting points can be suppressed, and vapor deposition can be performed while maintaining the initial mixing conditions. Therefore, it is possible to form a vapor deposition film in which the characteristics of the vapor deposition material function effectively as designed. Furthermore, as with a normal crucible, it is easy to fill the vapor deposition material, and there is no need for the troublesome work of changing the temperature of each boat by installing multiple boats for each vapor deposition material. No need for equipment.

  As a method for forming a phosphor layer on a support by vapor deposition, for example, a vapor of phosphor or the raw material is supplied on the support at a specific incident angle and vapor deposition (deposition) such as vapor deposition is performed. Thus, an independent phosphor layer composed of elongated columnar crystals can be obtained. The columnar crystal can be grown at a growth angle that is about half of the incident angle of the vapor flow of the phosphor during vapor deposition. Moreover, a molecular vapor deposition film can also be provided by vapor-depositing near normal temperature.

  In order to supply the vapor flow of the phosphor with a certain incident angle with respect to the support surface, the support is inclined with respect to the crucible charged with the evaporation source, or the support and the crucible are installed parallel to each other. Then, it is possible to take a method such as restricting only the oblique component from being vapor-deposited on the support by a slit or the like from the evaporation surface of the crucible charged with the vapor deposition material.

  In these cases, it is appropriate that the distance between the shortest part of the support and the crucible is set to approximately 10 to 60 cm in accordance with the average range of the phosphor. In addition, the thickness of the columnar crystal tends to become thinner as the temperature of the support decreases.

  The above vapor deposition material mainly composed of a phosphor as an evaporation source is uniformly dissolved or mixed and formed by pressing or hot pressing into a crucible having two or more cells. At this time, it is preferable to perform a degassing treatment. A method of evaporating the vapor deposition material from the evaporation source is performed by scanning an electron beam emitted from an electron gun, but it can also be evaporated by other methods, for example, a resistance heating method.

  The phosphor evaporation source is not necessarily a phosphor, and may be a mixture of phosphor materials.

  In order to reduce the haze ratio in the phosphor layer composed of these columnar crystals, the size of the columnar crystals (the diameter in terms of the circle of the cross-sectional area of each columnar crystal when the columnar crystal is observed from a plane parallel to the support) (Calculated from a microphotograph including at least 100 columnar crystals in the field of view) is preferably about 1 to 50 μm, more preferably 1 to 30 μm.

  Further, the size of the gap between the columnar crystals is preferably 30 μm or less, more preferably 5 μm or less. That is, when the gap exceeds 30 μm, the scattering of the laser light in the phosphor layer increases and the sharpness decreases.

  The growth angle of the oblique columnar crystal of the phosphor is not particularly limited as long as it is larger than 0 ° and smaller than 90 °, but is preferably 10 to 70 °, and preferably 20 ° to 55 °. To make the growth angle 10-70 °, the incident angle should be 20-80 °, and to make it 20-55 °, the incident angle should be 40-70 °. When the growth angle is large, the columnar crystal falls too much against the support, and the film becomes brittle.

  As a method for vapor-depositing (depositing) the phosphor, there are a vapor deposition method, a sputtering method, and a CVD method. In the present invention, the vapor deposition method is used. Hereinafter, the formation of the phosphor layer by the vapor deposition method will be described in detail. In the following, the case of growing columnar crystals will be described.

As a method of forming the phosphor layer by the vapor deposition method, the pressure inside the vapor phase deposition apparatus is 1.33 × 10 ⁻² to 1.33 Pa, and the pressure control gas is introduced, and the phosphor layer is on the support. A phosphor layer having an independent elongated columnar crystal structure can be obtained by a method in which a vapor or a raw material of a phosphor is supplied at an incident angle and a crystal is grown in a vapor phase (referred to as a vapor deposition method).

The flow rate of the pressure adjusting gas for adjusting the degree of vacuum to 1.33 × 10 ⁻² to 1.33 Pa is 0.001 to 1000 sccm (standard cc / min, 1 × 10 ⁻⁶ m ³ / min). This is true. When the flow rate of the regulated gas exceeds 1000 sccm, the vapor flow is disturbed by the gas flow, which adversely affects the growth of the phosphor. Further, if the flow rate of the pressure adjusting gas is less than 0.001 sccm, the adhesiveness is reduced.

  The pressure adjusting gas used for adjusting the degree of vacuum is preferably nitrogen or argon.

  In order to supply the vapor flow of the phosphor or the phosphor raw material at an angle of incidence with respect to the support surface, the support is inclined with respect to the crucible charged with the evaporation source, or the support and the crucible are arranged. Can be installed in parallel with each other, and a method can be adopted in which only an oblique component is regulated to be deposited on the support by a slit or the like from the evaporation surface of the crucible charged with the evaporation source. In these cases, it is preferable that the distance between the shortest portion of the support and the crucible is set to approximately 10 to 60 cm in accordance with the average range of the phosphor.

  In order to improve the modulation transfer function (MTF) in the phosphor layer composed of these columnar crystals, the size of the columnar crystals (the cross-sectional area of each columnar crystal when the columnar crystals are observed from a plane parallel to the support) is used. The average value of the diameter in terms of a circle and calculated from a micrograph including at least 100 columnar crystals in the visual field is preferably about 1 to 50 μm, more preferably 1 to 30 μm. That is, when the columnar crystal is thinner than 1 μm, the excitation excitation light is scattered by the columnar crystal, so that the MTF decreases. When the columnar crystal exceeds 50 μm, the directivity of the excitation excitation light decreases, and the MTF Will decline.

  Further, the size of the gap between the columnar crystals is preferably 30 μm or less, more preferably 5 μm or less. That is, when the gap exceeds 30 μm, the filling rate of the phosphor in the phosphor layer is lowered and the sensitivity is lowered.

  The film thickness of the phosphor layer formed by the above method varies depending on the sensitivity of the intended radiation image conversion panel to radiation, the type of phosphor, etc., but is preferably 50 μm to 20 mm, more preferably 100 to 1000 μm.

  Further, when the phosphor layer is produced using the vapor deposition method, the phosphor serving as an evaporation source is uniformly dissolved or molded by pressing or hot pressing and charged into a crucible. At this time, it is preferable to perform a degassing treatment. A method of evaporating the phosphor from the evaporation source is performed by scanning an electron beam emitted from an electron gun, but it can be evaporated by other methods.

  The evaporation source is not necessarily a phosphor, and may be a mixture of phosphor materials.

  FIG. 1 is a schematic view showing an example of the configuration of the radiation image conversion panel of the present invention.

  In FIG. 1, 21 is a radiation generator, 22 is a subject, 23 is a radiation image conversion panel having a phosphor layer containing a phosphor, and 24 is a radiation image for emitting a radiation latent image of the radiation image conversion panel 23 as stimulated emission. A stimulating excitation light source, 25 is a photoelectric conversion device that detects the stimulated emission emitted from the radiation image conversion panel 23, 26 is an image reproducing device that reproduces a photoelectric conversion signal detected by the photoelectric conversion device 25 as an image, and 27 is An image display device 28 that displays the reproduced image is a filter 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.

  FIG. 1 shows an example of obtaining a radiation transmission image of a subject. However, when the subject 22 itself emits radiation, the radiation generator 21 is not particularly necessary.

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

  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 of 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.

  The incident transmission image RI is absorbed by the phosphor layer of the radiation image conversion panel 23, thereby generating a number of electrons and / or holes proportional to the amount of radiation absorbed in the phosphor layer, which is the phosphor. Accumulated at the trap level.

  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.

  Further, the phosphor layer is irradiated with the stimulating excitation light source 24 to expel electrons and / or holes accumulated at the trap level, and the accumulated energy is emitted 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 phosphor layer of the radiation image conversion panel 23. For example, it is converted into an electric signal by a photoelectric conversion device 25 such as a photomultiplier tube, reproduced as an image by an image reproduction device 26, and this image is displayed by an image display device 27.

  The image reproduction device 26 is more effective not only for reproducing an electrical signal as an image signal but also using an apparatus that can perform so-called image processing, image calculation, image storage, storage, and the like.

  In addition, when excited by light energy, it is necessary to separate the reflected light of the stimulated excitation light from the stimulated light emitted from the phosphor layer, and photoelectric conversion that receives the light emitted from the phosphor layer In general, it is desirable that the stimulated luminescence emitted from the phosphor layer has a spectral distribution in the short wavelength region as much as possible because the sensitivity is generally high with respect to light energy having a short wavelength of 600 nm or less.

  The emission wavelength range of the phosphor used in the present invention is 300 to 500 nm, while the stimulated excitation wavelength range is 500 to 900 nm, which satisfies the above conditions at the same time. Recently, downsizing of diagnostic devices has progressed, The excitation wavelength used for image reading of the radiation image conversion panel is preferably a semiconductor laser that has a high output and can be easily made compact, and the wavelength of the laser light is preferably 680 nm. The radiation image conversion panel of the present invention The phosphor incorporated in shows a very good sharpness when using an excitation wavelength of 680 nm.

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

  As the excitation light source 24, a light source including the excitation wavelength of the 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.

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.

  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.

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

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

  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. When an interference filter is used, a filter having an arbitrary characteristic can be selected and used to some extent. The photoelectric conversion device 25 may be any device capable of converting a change in light quantity into a change in electronic signal, such as a photoelectric tube, a photomultiplier tube, a photodiode, a phototransistor, a solar cell, or a photoconductive element.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated concretely, the embodiment of this invention is not limited to these.

Example [Production of Radiation Image Conversion Panel 1]
(Preparation of vapor deposition material)
Cesium bromide (CsBr) 1 mol and europium bromide (EuBr ₃ ) 0.001 mol were pulverized and mixed in a mortar, and further stirred and mixed with a stirring vibrator for 15 minutes. The obtained mixture was placed in a furnace, evacuated for 3 minutes, and then baked at a temperature of 525 ° C. for 2 hours in a nitrogen atmosphere. After firing, the furnace was evacuated for 15 minutes to cool the fired product. Next, the obtained europium-activated cesium bromide (CsBr: 0.001Eu) stimulable phosphor was pulverized in a mortar and then compressed and compressed at a pressure of 80 MPa to produce a tablet for vapor deposition. The tablets were further evacuated for 2 hours at a temperature of 150 ° C. and subjected to degassing treatment to obtain a mixture of two vapor deposition materials CsBr and EuBr ₃ having different temperature characteristics.

(Formation of phosphor layer)
At the deposition angle shown in FIG. 2 (however, θ1 = 5 degrees and θ2 = 5 degrees are set), the above-prepared deposition material is filled in a crucible with six partitions and water-cooled, and a 1 mm thick crystallized glass ( (Nippon Electric Glass Co., Ltd.) After placing the support in a predetermined position, the inside of the vapor deposition apparatus was once evacuated, N ₂ gas was introduced again, the degree of vacuum was adjusted to 0.133 Pa, and the temperature of the support was about 150 While maintaining the temperature, the vapor deposition source was irradiated with an electron beam with an acceleration voltage of 4.0 kV and 60 W by an electron gun for vapor deposition. In the vapor deposition apparatus shown in FIG. 2, vapor deposition was performed using an aluminum slit and a distance d between the support and the slit of 60 cm while transporting the support in a direction parallel to the support. Deposition was terminated when the thickness of the phosphor layer reached 300 μm, and then this phosphor layer was heat-treated at 100 ° C.

  On the support, a phosphor layer (porosity: 2%) having a structure in which columnar crystal phosphors having a width of about 2.5 μm and a length of about 150 μm were densely planted in the vertical direction was formed.

(Formation of protective layer)
Using a two-component reaction type urethane adhesive, a polyethylene terephthalate film having a film thickness of 12 μm was attached to the phosphor layer to form a protective layer, and the radiation image conversion panel 1 was produced.

[Production of radiation image conversion panel 2]
In the production of the radiation image conversion panel 1, the radiation image conversion panel 2 was produced in the same manner except that the water-cooled crucible without partitioning was replaced with six water-cooled crucibles.

[Production of Radiation Image Conversion Panel 3]
In the production of the radiation image conversion panel 1, in the vapor deposition material production process, two vapor deposition materials are produced without mixing CsBr and EuBr ₃ , and in the phosphor layer formation process, two water-cooled crucibles without partitions are formed. The two crucible temperatures are controlled so that the two vapor deposition materials are individually filled and the deposition amount ratio of CsBr and EuBr ₃ is 1: 0.001. Produced.

[Evaluation of radiation image conversion panel]
About each radiation image conversion panel produced as mentioned above, the brightness | luminance and workability | operativity were evaluated according to the method shown below. The results are shown in Table 1.

(Luminance)
After irradiating the radiation image conversion panel with X-rays having a tube voltage of 80 kVp, the radiation image conversion panel is excited by scanning with a He—Ne laser beam (633 nm), and the stimulated emission emitted from the phosphor layer is received by a light receiver ( It is received by a photoelectron image multiplier tube having a spectral sensitivity of S-5, its intensity is measured, this is defined as sensitivity, and the relative value with the sensitivity of the radiation image conversion panel 1 being 100 is shown.

(Workability)
The workability (manufacturing man-hour and difficulty of work) of the process from filling of the vapor deposition material to formation of the phosphor layer was evaluated according to the following criteria.

○: The number of work steps is small and the work is easy. △: The number of work steps is large or the work is difficult. ×: The work time is large and the work is difficult.

  As can be seen from Table 1, the radiation image conversion panel of the present invention is superior in brightness and workability to the comparative product.

It is the schematic which shows an example of a structure of the radiation image conversion panel of this invention. It is the schematic which shows an example of the method of producing a fluorescent substance layer on a support body by vapor deposition.

Explanation of symbols

DESCRIPTION OF SYMBOLS 21 Radiation generator 22 Subject 23 Radiation image conversion panel 24 Excitation light source 25 Photoelectric conversion device 26 Image reproducing device 27 Image display device 28 Filter

Claims (8)

Filling an evaporation source crucible having at least two cells inside with two or more kinds of vapor deposition materials having different temperature characteristics and dissolving and evaporating by heating to form a phosphor layer on the support. A method for producing a radiation image conversion panel. 2. The method for manufacturing a radiation image conversion panel according to claim 1, wherein at least two kinds of vapor deposition materials among the vapor deposition materials are mixed and then filled into the evaporation source crucible. The method for manufacturing a radiation image conversion panel according to claim 1, wherein at least one of the vapor deposition materials is a phosphor material. The method for manufacturing a radiation image conversion panel according to claim 3, wherein the phosphor material is a stimulable phosphor material. The method for producing a radiation image conversion panel according to claim 4, wherein the photostimulable phosphor material is CsBr. At least 1 sort (s) of the said vapor deposition material is an activator, The manufacturing method of the radiation image conversion panel of any one of Claims 1-5 characterized by the above-mentioned. The method for producing a radiation image conversion panel according to claim 6, wherein the activator is Eu. A radiation image conversion panel manufactured by the method for manufacturing a radiation image conversion panel according to claim 1.

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