JP4079073B2 - Radiation image conversion panel and method for manufacturing radiation image conversion panel - Google Patents

Description

  The present invention relates to a radiation image (hereinafter also simply referred to as a radiation image) conversion panel and a method for manufacturing a radiation image conversion panel (hereinafter also simply referred to as a manufacturing method).

  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 photostimulable phosphor layer on a support and using one or both of visible light and infrared light as excitation energy is known (for example, patents). Reference 1).

As a radiation image conversion method using a stimulable phosphor with higher brightness and higher sensitivity, for example, BaFX: Eu ²⁺ system (X: Cl, Br, I) described in JP-A-59-75200, etc. Radiation image conversion method using phosphor, Radiation image conversion method using alkali halide phosphor as described in JP-A-61-72087, etc., JP-A-61-73786, JP-A-61-73787, etc. As described above, alkali halide phosphors containing Tl ⁺ and Ce ³⁺ , Sm ³⁺ , Eu ³⁺ , Y ³⁺ , Ag ⁺ , Mg ²⁺ , Pb ²⁺ , and In ³⁺ metals as coactivators Has been developed.

  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.

  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.

  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 a photostimulable phosphor layer formed on a support described in JP-A-62-39737. And a stimulable phosphor layer having a cavity formed 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.

Furthermore, a radiation image conversion panel having a photostimulable phosphor layer in which elongated columnar crystals having a certain inclination with respect to the normal direction of the support are formed on the support by vapor deposition is described. (For example, see Patent Document 2)
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.

  Recently, a radiation image conversion panel using a stimulable phosphor in which Eu is activated with an alkali halide such as CsBr as a base has been proposed, and in particular, X-ray conversion efficiency that has been impossible in the past by using Eu as an activator. It became possible to improve.

  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.

  However, in order to form the CsBr: Eu phosphor layer, it is required to form a film by a vapor deposition method. In the formation of a deposited film, a highly accurate film thickness distribution is realized by arranging a highly accurate substrate-evaporation source in order to control the film thickness distribution and devising a physical position.

  In particular, in CsBr: Eu, diffusion of Eu due to heat is remarkable, and since the vapor pressure under vacuum is also high, there is a problem that the presence of Eu in the base material is ubiquitous. It is important to the uniformity of the.

In particular, it has a large area, and in order to increase the film thickness and improve the performance, the uniformity of adhesion between the base material and the phosphor layer is important. When a resin is present on the surface of the substrate, there are a large number of residual solvents and volatile components due to the resin production process, so that volatile components are generated during phosphor film formation, changing the degree of vacuum and causing film fluctuations.
US Pat. No. 3,859,527 JP-A-2-58000

  An object of the present invention is to provide a radiation image conversion panel having high uniformity, high brightness, and high sharpness, and a method for manufacturing the radiation image conversion panel.

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

1. 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). is formed as a protective layer having a thermoplastic resin at least one layer of the fluorescent body layer is, while controlling the temperature of the fluorescent material layer within a predetermined range, it is made form heat treatment and deposition A radiation image conversion panel characterized by that.

  2. 2. The radiation image conversion panel as described in 1 above, comprising a stimulable phosphor based on an alkali halide represented by the following general formula (1).

General formula (1)
M ¹ X · aM ² X ′ · bM ³ X ″: 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 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.].

  3. 3. The radiation image conversion panel according to 1 or 2, wherein the protective layer having the thermoplastic resin has a reflectance of 20% or less.

  4). 4. The radiation image conversion panel according to any one of 1 to 3, wherein the thermoplastic resin is a polyimide resin.

  The radiation image conversion panel and the method for producing the same according to the present invention are excellent in the uniformity of the activator in the phosphor, exhibit high brightness and high sharpness, and have an excellent effect.

  Hereinafter, the present invention will be described in more detail.

1) protective layer present invention having a thermoplastic resin, the stimulable phosphor (hereinafter, is characterized in that a protective layer having a thermoplastic resin to be referred) layer and the phosphor.

  The protective layer may be formed by directly applying a protective layer coating solution on the photostimulable phosphor layer, or a protective layer formed in advance may be adhered to the photostimulable phosphor layer. Although a means for forming a photostimulable phosphor layer may be taken on the formed protective layer, in the invention of claim 5 of the present application, a protective layer having a thermoplastic resin is deposited on the photostimulable phosphor layer. It is characterized by providing by the method or sputtering method. The thickness of the protective layer is preferably 0.1 to 2000 μm.

  As a heating temperature at the time of the said vapor deposition method or sputtering method, 100-300 degreeC is preferable. In addition, the vacuum degree at the time of a vapor deposition method or sputtering method is equivalent to the vapor deposition method or sputtering method which forms the fluorescent substance layer mentioned later.

  The reflectance of the protective layer is preferably 20% or less. The lower limit is unlimited and is preferably close to 0.

  Next, the thermoplastic resin of the present invention will be described.

  The thermoplastic resin of the present invention is, for example, polycarbonate, polyacrylonitrile, polystyrene, polyacrylate ester copolymer, polyvinyl alcohol, polymethacrylic acid, polyvinyl chloride-vinyl acetate copolymer, polyethylene, polyethylene-ethyl acetate copolymer. Polymer, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, polyester, polyamide, polyether, silicone, polybutadiene, styrene-butadiene copolymer, ABS rubber, acrylonitrile-butadiene copolymer, polyurethane, silicon-acrylic copolymer Examples include coalescence, acrylic-modified fluororesin, and polyimide resin.

  Also included are random copolymers, block copolymers, graft copolymers and the like obtained by copolymerizing these polymer compounds.

  In the present invention, a polyimide resin is preferable.

  The thermoplastic resin used in the present invention is preferably appropriately crosslinked.

  In order to produce a thermoplastic resin having a cross-linking agent, divinylbenzene, trimethanolpropane triacrylate, 1,6- What is necessary is just to superpose | polymerize, after adding a suitable quantity of crosslinking agents more than bifunctional, such as hexanediol diacrylate.

  In the case of a condensable polymer such as polyester and polyurethane, a condensation reaction may be performed using a trifunctional or higher alcohol such as trimethylolpropane and a trifunctional or higher isocyanate during the production of the polyester or polyurethane.

  It is desirable that the thermoplastic resin of the present invention has a configuration and material that has low reflectivity and is capable of extracting photostimulated luminescence and preventing the adsorption and removal of the deposited crystals.

  The CsBr phosphor film is formed by a vapor deposition process. It is important that the obtained CsBr phosphor forms columnar crystals as crystals having excellent brightness and sharpness.

  In order to increase the light guide effect, it is desirable to form a columnar crystal having good crystallinity and a tip diameter of 2 to 8 μm. When this columnar crystal is formed in a vacuum in a vapor deposition chamber, it has been found that there is a problem that moisture is adsorbed on the surface when taken out in the air after film formation, and the performance deteriorates. When the tip diameter of the columnar crystal is reduced, the adsorption due to the capillary phenomenon appears to be more affected.

  However, as a result of various studies, the present inventors have found that the formation of an anti-adsorption protective film by continuous film formation is effective in order to prevent this influence.

2) Production of protective layer by vapor deposition method or sputtering method In CsBr phosphor film formation, film formation is performed by a vapor deposition process. The point is to form columnar crystals as crystals with excellent brightness sharpness. In order to increase the light guide effect, it is desirable to form a columnar crystal having a good crystallinity and a tip diameter of several microns.

  It was found that when this columnar crystal was formed by vacuuming in a vapor deposition chamber, moisture was adsorbed on the surface when the film was taken out in the air after film formation, resulting in a decrease in performance. If the columnar crystal tip diameter is narrowed to enhance the performance, the adsorption effect due to the capillary effect appears.

  In order to prevent this influence, it was found that the formation of an anti-adsorption protective film by continuous film formation is effective.

  Next, the stimulable phosphor represented by the general formula (1) preferably used in the present invention will be described.

In the photostimulable phosphor represented by the general formula (1), M ¹ represents at least one alkali metal atom selected from each of atoms such as Li, Na, K, Rb, and Cs, among which Rb and At least one kind of alkaline earth metal atom selected from each atom of Cs is preferable, and Cs atom is more preferable.

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.

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.

  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.

  From the viewpoint of improving the photostimulable emission brightness of the photostimulable phosphor, X, X ′ and X ″ each represents an atom with at least one halogen selected from F, Cl, Br and I atoms. And at least one halogen atom selected from Br and I, and more preferably at least one halogen atom selected from Br and I atoms.

  The photostimulable phosphor represented by the general formula (1) is produced, for example, by the production 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 (I), a is 0 ≦ a <0.5, preferably 0 ≦ a <0.01, b is 0 ≦ b <0.5, preferably 0 ≦ b ≦ 10−. 2, e is 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 that the pH value C of the obtained aqueous solution is adjusted to 0 <C <7, and then water is evaporated.

  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 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 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.

  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.

  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 degree of vacuum of about 1.333 × 10 ⁻⁴ Pa.

  Next, at least one of the photostimulable phosphor is heated and evaporated by a resistance heating method, an electron beam method, or the like to grow the photostimulable phosphor on the surface of the support to a desired thickness.

  As a result, a photostimulable phosphor layer containing no binder is formed, but it is also possible to form the photostimulable phosphor layer in a plurality of times in the vapor deposition step.

  In the vapor deposition step, it is possible to co-evaporate using a plurality of resistance heaters or electron beams to synthesize the desired photostimulable phosphor on the support and simultaneously form the photostimulable phosphor layer. is there.

  After the 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.

  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.

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.

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.

  Various applied treatments can be used in the sputtering step as in the vapor deposition method.

  The third method is a CVD method, and the fourth method is an ion plating method.

  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 unfavorable. If the growth rate exceeds 300 μm / min, it is difficult to control the growth rate.

  When the radiation image conversion panel is obtained by the above-described vacuum deposition method, sputtering method, etc., since there is no binder, the packing density of the photostimulable phosphor can be increased, and preferable radiation image conversion in terms of sensitivity and resolution. A panel is obtained and preferred.

  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 50 μm to 1 mm, preferably 50 from the viewpoint of obtaining the effects of the present invention. It is -300 micrometers, More preferably, it is 100-300 micrometers, Most preferably, it is 150-300 micrometers.

  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.

  Further, from the viewpoint of obtaining a radiation image conversion panel exhibiting high sharpness, the reflectance of the stimulable phosphor layer of the present invention is preferably 20% or more, more preferably 30% or more, and still more preferably. 40% or more. The upper limit is 100%.

  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. In addition to providing a reinforcing effect, this is effective in reducing the lateral light diffusion of the stimulated excitation light incident on the stimulable phosphor layer.

  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.

  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.

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.

  Since these white pigments have a strong hiding power and a high refractive index, they can easily scatter photostimulated luminescence by reflecting or refracting light, thereby significantly improving the sensitivity of the resulting radiation image conversion panel. it can.

  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.

  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.

  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.

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.

  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 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 for detecting the stimulated emission emitted from the radiation image conversion panel 23, and 26 is a photoelectric conversion signal detected by the photoelectric conversion device 25. 27 is an image display device that displays the reconstructed image, and 28 is a device that cuts off the reflected light from the stimulating excitation light source 24 and transmits only the light emitted from the radiation image conversion panel 23. It is a filter to make it.

  FIG. 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 photostimulable phosphor layer of the radiation image conversion panel 23, so that a number of electrons and / or holes proportional to the amount of radiation absorbed in the photostimulable phosphor layer are generated. Occurs and accumulates at the trap level of the photostimulable phosphor.

  That is, a latent image in which the energy of the radiation transmission image is accumulated is formed. Next, this latent image is made visible by being excited with light energy.

  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.

  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.

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

  In addition, when excited by light energy, it is necessary to separate the reflected light of the stimulated excitation light from the stimulated emission emitted from the stimulable phosphor layer, and it is emitted from the stimulable phosphor layer. Photoelectric converters that receive light emission generally have high sensitivity to light energy with a short wavelength of 600 nm or less, so that the stimulated emission emitted from the stimulable phosphor layer has a spectral distribution in the short wavelength region as much as possible. What you have is desirable.

  The emission wavelength range of the photostimulable phosphor of the present invention is 300 to 500 nm, while the photostimulable excitation wavelength range is 500 to 900 nm, which satisfies the above-mentioned conditions at the same time. Recently, downsizing of diagnostic devices has progressed. A semiconductor laser that has a high output and is easy to be compacted is preferable for the excitation wavelength used for image reading of the radiation image conversion panel. 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.

  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.

  As the stimulated excitation light source 24, a light source including the stimulated 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.

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, this is the excitation of the stimulable phosphor contained in the radiation image conversion panel 23. It is determined by the combination of the emission wavelength and the wavelength of the stimulated excitation light source 24.

  For example, in the case of a practically preferable combination in which the 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.

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

Example 1
<< Production of Radiation Image Conversion Panel Samples (Samples) 1-8 >>
Under the conditions shown in Table 1, the vapor deposition apparatus shown in FIG. 2 (provided that θ1 = 5 degrees and θ2 = 5 degrees) is provided on the surface of a 1 mm thick crystallized glass (manufactured by Nippon Electric Glass Co., Ltd.) support. A stimulable phosphor layer having a stimulable phosphor (CsBr: Eu) was used.

  In the vapor deposition apparatus shown in FIG. 2, 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.

  In the vapor deposition, the support was placed in a vapor deposition device, and then, the phosphor raw material (CsBr: Eu) was pressed using a vapor deposition source and placed in a water-cooled crucible.

Thereafter, the inside of the vapor deposition device was once evacuated, then N ₂ gas was introduced and the degree of vacuum was adjusted to 0.133 Pa, and then vapor deposition was performed while maintaining the temperature of the support (also referred to as the substrate temperature) at about 350 ° C. Deposition was terminated when the thickness of the photostimulable phosphor layer reached 300 μm, and then this phosphor layer was heat-treated at a temperature of 400 ° C. In a dry air atmosphere, the periphery of the protective layer having a support and borosilicate glass was sealed with an adhesive to obtain a radiation image conversion panel sample 1 (Comparative Example 1) having a structure in which the phosphor layer was sealed. .

In the preparation of the radiation image conversion panel sample 1 (Comparative Example 1), on the phosphor layer on the support, the heat treatment at a temperature shown in Table 1, the protective layer having a polyimide resin with deposited (film thickness 10 [mu] m) Except having provided, it carried out similarly to the comparative example 1, and produced the radiation image conversion panel samples 2-6 (Example 1-5 in Table 1).

《Evaluation of sharpness》
The sharpness of the radiation image conversion panel sample was evaluated by obtaining a modulation transfer function (MTF).

  In the MTF, after attaching a CTF chart to the radiation image conversion panel sample, the radiation image conversion panel sample was 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 1.0 lp / mm.

  The obtained results are shown in Table 1.

  As is apparent from Table 1, it can be seen that the sample of the present invention is superior to the comparative sample.

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 stimulable fluorescent substance layer on a support body by vapor deposition.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Support body 12 Stimulable fluorescent substance layer 13 Columnar crystal 14 Space | gap formed between columnar crystals 15 Support body holder 21 Radiation generator 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 (4)

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). is formed as a protective layer having a thermoplastic resin at least one layer of the fluorescent body layer is, while controlling the temperature of the fluorescent material layer within a predetermined range, it is made form heat treatment and deposition A radiation image conversion panel characterized by that. 2. The radiation image conversion panel according to claim 1, comprising a stimulable phosphor having an alkali halide represented by the following general formula (1) as a base.
General formula (1)
M ¹ X · aM ² X ′ · bM ³ X ″: 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 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.]. The radiation image conversion panel according to claim 1, wherein a reflectance of the protective layer having the thermoplastic resin is 20% or less. The radiation image conversion panel according to claim 1, wherein the thermoplastic resin is a polyimide resin.

Images