JP2007057306A - Radiation image conversion panel using stimulable phosphor and method for manufacturing it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radiation image conversion panel which uses stimulable phosphors and improves both in physical durability and in luminance and a method for manufacturing the panel. <P>SOLUTION: The radiation image conversion panel which has a stimulable phosphor layer on a support is characterized in that the stimulable phosphor layer is formed by a vapor phase epitaxial method and in that the stress intensity factor K<SB>Ic</SB>is between 0.3 (MPa m<SP>1/2</SP>) and 60 (MPa m<SP>1/2</SP>) inclusive. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

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

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

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

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

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

According to the above radiographic image reproduction method, it is possible to obtain a radiographic image with a large amount of information with a much smaller exposure dose as compared with a radiographic method using a combination of a conventional radiographic film and an intensifying screen. It has the advantage of being able to.
Radiation image conversion panels using these photostimulable phosphors, after accumulating radiation image information, release accumulated energy by scanning excitation light, so that radiation images can be accumulated again after scanning, and repeated Can be used. In other words, the conventional radiographic method consumes a radiographic film for each imaging, whereas this radiographic image conversion method repeatedly uses a radiographic image conversion panel, so from the viewpoint of resource protection and economic efficiency. Is also advantageous.

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

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

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

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

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

  By the way, as described above, radiation image conversion panels using photostimulable phosphors are used repeatedly, and depending on the method of use, the panels are stacked during use, or the panels are transported by rolls. It is required to be strong and durable.

As means to improve durability, methods such as providing a cured adhesive layer between the light reflecting layer and the support or laminating a protective sheet with a specified compression hardness on the phosphor layer have been proposed in the past. However, further improvement is necessary from the viewpoint of improving physical durability, and the method does not improve luminance unevenness (see Patent Documents 4 and 5).
JP 62-39737 A JP-A-62-110200 JP-A-2-58000 JP 2004-101386 A Japanese Patent Laid-Open No. 2005-62015

  The present invention has been made in view of the above circumstances, and an object thereof is a radiation image conversion panel using a photostimulable phosphor, which has improved physical durability and improved brightness. It is providing the conversion panel and its manufacturing method.

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

(1) In a radiation image conversion panel having a photostimulable phosphor layer on a support, the photostimulable phosphor layer is formed by a vapor phase growth method, and the stress intensity factor K _{Ic of the} support is 0.3 MPa. - a radiation image conversion panel, wherein m is ^1/2 or more 60 MPa · m ^1/2 or less.

(2) The radiation image conversion panel according to (1), wherein the stress intensity factor K _{Ic of the} support is 1 MPa · m ^1/2 or more and 20 MPa · m ^1/2 or less.

  (3) The radiation image conversion panel according to (1) or (2), wherein the support has a Young's modulus of 0.5 GPa or more and 60 GPa or less.

(4) Any of the above (1) to (3), wherein the photostimulable phosphor layer contains a photostimulable phosphor based on an alkali halide represented by the following general formula (1) The radiation image conversion panel of Claim 1.
The 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.].

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

  According to the above configuration of the present invention, it is possible to provide a radiation image conversion panel having improved physical durability and improved luminance and a method for manufacturing the same.

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

(Stress intensity factor and Young's modulus of support)
In the present invention, the stress intensity factor K _Ic means a resistance value indicated by a material when a crack progresses without an increase in load when a crack exists in a test piece.

Stress intensity factor of the support in the present invention is preferably 0.3 MPa · m ^1/2 or more 60 MPa · m ^1/2 or less, particularly preferably 1 MPa · m ^1/2 or more 20 MPa · m ^1/2 or less.

  If the stress intensity factor of the support is too low, the impact resistance of the radiation image conversion panel will be low. In addition, since a material having a high stress intensity factor is generally expensive, selecting a substrate having a stress intensity factor of the support that is too high increases the cost of the entire radiation image conversion panel, and the material has poor cutting properties. It is unsuitable for the poor handling.

Furthermore, the present inventors surprisingly not only improved the physical durability of the panel but also surprisingly the brightness when the stress intensity factor of the support is within the above range and the Young's modulus is within a specific range. It has been found that unevenness is suppressed. That is, the effect is significant when the Young's modulus of the support is 0.5 GPa or more and 60 GPa or less and the stress intensity factor of the support is 0.3 MPa · m ^1/2 or more and 60 MPa · m ^1/2 or less. The effect is more remarkable when the Young's modulus is 0.5 GPa or more and 60 GPa or less and the stress intensity factor of the support is 1 MPa · m ^1/2 or more and 20 MPa · m ^1/2 or less.

  It is a new discovery that the combination of the stress intensity factor and the Young's modulus of the support can achieve not only improvement in physical durability but also suppression of luminance unevenness. The reason why the luminance unevenness is suppressed is estimated as follows. In general, if there are fine cracks in the phosphor layer, it may affect the light reflectance and absorption rate of the phosphor layer and cause uneven brightness. However, the stress intensity factor of the support is within a specific range. When the Young's modulus is within a specific range, cracks are unlikely to occur on the surface of the support even when the panel is subjected to a physical impact. Will be done.

(Support)
The support used in the radiation image conversion panel of the present invention is not particularly limited as long as the stress intensity factor and Young's modulus are within the scope of the present invention.

  For example, flat glass such as quartz, borosilicate glass, chemically tempered glass, cellulose acetate film, polyester film, polyethylene terephthalate, polyamide, polyimide, triacetate, polycarbonate, polyphenylene sulfite, polyamideimide, and other plastics, aluminum sheet, iron Examples thereof include metal sheets such as sheets and copper sheets, metal sheets having a coating layer of the metal oxide, and ceramics of amorphous carbon.

(Stimulable phosphor layer)
FIG. 1 is a schematic view showing an example of a columnar crystal shape formed on a support according to the present invention. In FIG. 1 a) and b), reference numeral 2 denotes a stimulable phosphor columnar crystal formed on the support 1 by vapor deposition.

  FIG. 1 a) is an example having a cusp at substantially the center of the columnar crystal, and FIG. 1 b) is an example in which the tip of the columnar crystal has a certain inclination, and the columnar crystal has a side surface. It is an example which has a cusp part.

  In the present invention, the average crystal diameter of the columnar crystals is preferably 0.5 to 50 μm, more preferably 1 to 50 μm. Here, the average crystal diameter of the columnar crystal is an average value of the diameter in terms of a circle of the cross-sectional area of each columnar crystal when the columnar crystal is observed from a plane parallel to the support, and is at least 100 or more columnar crystals. Is calculated from the electron micrograph including

  By setting the average crystal diameter of the columnar crystal as defined above, the haze ratio of the photostimulable phosphor layer b can be reduced, and as a result, excellent sharpness can be realized.

The columnar crystal diameter is affected by the support temperature, the degree of vacuum, the vapor flow incident angle, and the like, and by controlling these, columnar crystals having a desired thickness can be formed. For example, the support temperature tends to become thinner as the temperature decreases, but if it is too low, it becomes difficult to maintain the columnar state. The temperature of the support is preferably 100 to 300 ° C, more preferably 150 to 270 ° C. The incident angle of the vapor flow is preferably 0 to 5 °. Further, the degree of vacuum is preferably 1.3 × 10 ⁻¹ Pa or less.

Next, the vapor deposition method will be described in detail. Examples of the stimulable phosphor that can be used in the stimulable phosphor layer formed by the vapor deposition method include, for example, a phosphor represented by BaSO ₄ : Ax described in Japanese Patent Application Laid-Open No. 48-80487. Phosphors represented by MgSO ₄ : Ax described in JP-A-48-80488, phosphors represented by SrSO ₄ : Ax described in JP-A-48-80489, JP-A-51-29889 Phosphors obtained by adding at least one of Mn, Dy, and Tb to Na ₂ SO ₄ , CaSO _4, BaSO _{4 and the} like described in No. 52, BeO, LiF described in JP-A-52-30487, Phosphors such as MgSO ₄ and CaF ₂ , phosphors such as Li ₂ B ₄ O ₇ : Cu, Ag described in JP-A-53-39277, Li described in JP-A-54-47883 _{2 O · (Be 2 O 2} ) x: u, phosphors such as Ag, U.S. Patent No. 3,859,527 is described in JP SrS: Ce, Sm, SrS: Eu, Sm, La 2 O 2 S: Eu, Sm and (Zn, Cd) S : A phosphor represented by Mnx.

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 _X SiO ₂ : An alkaline earth metal silicate phosphor represented by A can be used.

Further, an alkaline earth fluorohalide phosphor represented by the general formula (Ba _1-xy Mg _x Ca _y ) F _x : Eu ²⁺ described in Japanese Patent Laid-Open No. 55-12143, The phosphor represented by the general formula described in Japanese Patent No. 55-12144 is LnO _x : _x A, and the general formula described in Japanese Patent Laid-Open No. 55-12145 is (Ba _1-x M (II) _x ). A phosphor represented by F _x : _y A, a phosphor represented by BaFX: _x Ce, _y A having a general formula described in JP-A No. 55-84389, described in JP-A No. 55-160078 Rare earth element-activated divalent metal fluorohalide phosphors represented by the general formula M (II) FX · _x A: _y Ln, general formula ZnS: A, CdS: A, (Zn, Cd) S: A , X, a phosphor represented by any one of the following general formulas described in JP-A-59-38278 Phosphor represented,
General formula xM ³ (PO ₄ ) ₂ · NX ₂ : _y A
xM ³ (PO ₄ ) ₂ : _y A
A phosphor represented by any one of the following general formulas described in JP-A-59-155487.

General formula nReX ³ · _m AX ′ ₂ : _x Eu
nReX ³ · _m AX ′ ₂ : _x Eu, _y Sm
A phosphor represented by the following general formula described in JP-A-61-72087,
M (I) X · _a M (II) X ′ ₂ · bM (III) X ″ ₃ : _c A
In represented by an alkali halide phosphor and JP 61-228400 formula is described in JP M (I) X: Bismuth activated alkali halide phosphor, etc. represented by _x Bi and the like. In particular, the alkali halide phosphor is preferable because a columnar photostimulable phosphor layer can be easily formed by a method such as vapor deposition or sputtering.

(Stimulable phosphor represented by the general formula (1))
Next, the photostimulable phosphor represented by the general formula (1) according to the present invention will be described. In the photostimulable phosphor represented by the general formula (1) of the present invention, M ¹ represents at least one alkali metal atom selected from each atom such as Na, K, Rb and Cs, among which Rb And at least one alkaline earth metal atom selected from each atom of Cs, and more preferably a Cs atom.

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 selected from each atom of Eu, Tb, In, Ga, Ce, Tm, Dy, Pr, Ho, Nd, Yb, Er, Gd, Lu, Sm, Y, Tl, Na, Ag, Cu, and Mg. One kind of 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) of the present invention is produced, for example, by the production method described below.

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 or two or more compounds selected from ₂ and NiI ₂ compounds are 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.

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} and e are 0 <e ≦ 0.2, preferably 0 <e ≦ 0.1.

  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.

  Next, the obtained phosphor raw material mixture is filled in a heat-resistant container such as a quartz crucible or an alumina crucible and fired in an electric furnace. The firing temperature is suitably 300 to 1000 ° C. The firing time varies depending on the filling amount of the raw material mixture, the firing temperature, and the like, but generally 0.5 to 6 hours is appropriate. The firing atmosphere includes a nitrogen gas atmosphere containing a small amount of hydrogen gas, a weak reducing atmosphere such as a carbon dioxide gas atmosphere containing a small amount of carbon monoxide, a neutral atmosphere such as a nitrogen gas atmosphere and an argon gas atmosphere, or a small amount of oxygen gas. A weak oxidizing atmosphere is preferred.

  After firing once under the above firing conditions, the fired product is taken out from the electric furnace and pulverized, and then the fired product powder is again filled in a heat-resistant container and placed in the electric furnace, and again under the same firing conditions as described above. Firing is preferable because it can further increase the emission luminance of the phosphor.

  In addition, when the fired product is cooled to the room temperature from the firing temperature, the desired phosphor can be obtained by taking the fired product from the electric furnace and allowing it to cool in the air. You may cool in an atmosphere or neutral atmosphere.

  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.

  The photostimulable phosphor layer according to the present invention is formed by a vapor phase growth method.

  As a vapor phase growth method of the photostimulable phosphor, an evaporation method, a sputtering method, a CVD method, an ion plating method, and other methods can be used.

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. 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, it is preferable that 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 low, which is not preferable. If the growth rate exceeds 300 μm / min, it is difficult to control the growth rate.

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

  The film thickness of the photostimulable phosphor layer is preferably 50 μm to 1 mm from the viewpoint of obtaining the effects of the present invention, although it varies depending on the purpose of use of the radiation image conversion panel and the type of stimulable phosphor. More preferably, it is 100-600 micrometers, More preferably, it is 300-600 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.

  The stimulable phosphor layer of the radiation image conversion panel of the present invention is preferably formed by vapor-phase growth of the stimulable phosphor represented by the general formula (1) on the support. Sometimes it is more preferred that the photostimulable phosphor forms columnar crystals.

  In order to form a columnar photostimulable phosphor layer by a method such as vapor deposition or sputtering, the compound represented by the general formula (1) (stimulable phosphor) is used. Among them, a CsBr phosphor Is particularly preferably used.

  In the present invention, the columnar crystal preferably has a stimulable phosphor represented by the following general formula (2) as a main component.

General formula (2)
CsX: A
In the general formula (2), X represents Br or I, and A represents Eu, In, Tb, or Ce.

  As a method of forming a phosphor layer on a support by a vapor deposition method, an elongate columnar shape independent by a vapor deposition (deposition) method such as vapor deposition by supplying a vapor of the stimulable phosphor or the raw material. A photostimulable phosphor layer made of crystals can be obtained. In these cases, it is preferable that the distance between the shortest part of the support and the crucible is usually set to 10 to 60 cm in accordance with the average range of the stimulable phosphor.

The stimulable phosphor as an evaporation source is uniformly dissolved or formed by pressing or hot pressing and charged in a crucible. At this time, it is preferable to perform a degassing treatment. The method for evaporating the photostimulable phosphor from the evaporation source is performed by scanning the electron beam emitted from the electron gun, but it can also be evaporated by other methods.
The evaporation source is not necessarily a single stimulable phosphor, and may be a mixture of stimulable phosphor materials.

  Moreover, you may dope an activator afterwards with respect to the base material of fluorescent substance. For example, after depositing only RbBr as a base material, Tl as an activator may be doped. That is, since the crystals are independent, even if the film is thick, it can be sufficiently doped, and crystal growth hardly occurs, so the MTF does not decrease.

  Doping can be performed by thermal diffusion and ion implantation of a doping agent (activator) in the base layer of the formed phosphor.

  Further, the size of the gap between the columnar crystals is preferably 30 μm or less, and 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.

  Next, formation of the photostimulable phosphor layer according to the present invention will be described with reference to FIG. FIG. 2 is a diagram showing a state where a photostimulable phosphor layer is formed by vapor deposition on a support, and the photostimulable phosphor vapor flow 16 is 0 to 5 as an incident angle with respect to the normal direction of the support surface. A columnar crystal is formed by incidence in the range of °.

  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 thinner 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.

  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. Here, the high-reflectance substance means a substance having a high reflectivity to stimulated excitation light (500 to 900 nm, particularly 600 to 800 nm), for example, white pigment such as aluminum, magnesium, silver, indium and other metals. In addition, a color material in the green to red region can be used.

  From the viewpoint of obtaining a radiation image conversion panel having high sensitivity, the reflectance of the photostimulable phosphor layer according to the present invention is preferably 20% or more, more preferably 30% or more, and particularly preferably 40%. That's it. The upper limit is 100%.

  In the present invention, when a mirror surface treatment (for example, vapor deposition) that reflects light such as aluminum is performed on the substrate, the reflectance of the stimulable phosphor layer is measured.

Here, the reflectance can be measured under the same measurement conditions using the following measuring apparatus.
Equipment: HITACHI 557, Spectrophotometer
(Measurement condition)
Measurement light wavelength: 680 nm
Scan speed: 120 nm / min
Number of repetitions: 10 times Response: automatic setting The white pigment 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), silicic acid Examples include magnesium, basic silicic acid sulfate, basic lead phosphate, and aluminum silicate. Since these white pigments have a strong hiding power and a high refractive index, it is possible to easily scatter scattered light 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. 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 inorganic color materials include ultramarine, cobalt blue, cerulean blue, chromium oxide, and TiO ₂ —ZnO—Co—NiO pigments.

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

(Radiation image conversion panel and radiation image reading device)
FIG. 3 is a schematic diagram showing an example of the configuration of the radiation image conversion panel and the radiation image reading apparatus according to the present invention.

  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. FIG. 3 shows an example of obtaining a radiation transmission image of a subject. However, when the subject 22 itself emits radiation, the radiation generator 21 is not particularly necessary.

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

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

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

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

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

As the laser, the He-Ne laser, the He-Cd laser, Ar ion laser, Kr ion laser, N ₂ laser, YAG laser and its second harmonic, ruby laser, semiconductor lasers, various dye lasers, copper vapor laser, etc. There are metal vapor lasers. Normally, a continuous wave laser such as a He—Ne laser or an Ar ion laser is desirable, but a pulsed laser can also be used if the scanning time and pulse of one pixel of the panel are synchronized. Further, when using a method of separating light emission using a delay of light emission as shown in JP-A-59-22046 without using a filter 28, a pulsed laser is used rather than a continuous wave laser. It is preferable to use it.

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

  Since the filter 28 transmits the stimulated luminescence emitted from the radiation image conversion panel 23 and cuts the stimulated excitation light, this is the stimulation of the stimulable phosphor contained in the radiation image conversion panel 23. It is determined by the combination of the emission wavelength and the wavelength of the stimulated excitation light source 24. For example, in the case of a practically preferable combination in which the excitation wavelength is 500 to 900 nm and the emission wavelength is 300 to 500 nm, examples of the filter include C-39, C-40, and V- 40, V-42, V-44, Corning 7-54, 7-59, Spectrofilm BG-1, BG-3, BG-25, BG-37, BG-38, etc. A filter can be used. If an interference filter is used, a filter having an arbitrary characteristic can be selected and used to some extent. The photoelectric conversion device 25 may be any device capable of converting a change in light quantity into a change in electronic signal, such as a photoelectric tube, a photomultiplier tube, a photodiode, a phototransistor, a solar cell, or a photoconductive element.

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

Example << Preparation of Radiation Image Conversion Panel >>
(Preparation of radiation image conversion panel 1)
Using the vapor deposition apparatus 101 shown in FIG. 4 on one side of a support 111 made of a Ti alloy, a stimulable phosphor (CsBr: 0.0002Eu) is vapor-deposited according to the following method. Formed. First, a resistance heating crucible was filled with the phosphor raw material as a vapor deposition material, and the support 111 was placed on the rotating support holder 104, and the distance between the support 111 and the evaporation source 103 was adjusted to 800 mm. Subsequently, the inside of the vapor deposition apparatus 101 was once evacuated, Ar gas was introduced and the degree of vacuum was adjusted to 0.1 Pa, and then the temperature of the support 111 was maintained at 100 ° C. while rotating the support 111 at a speed of 10 rpm. .

  Next, the resistance heating crucible was heated to deposit the stimulable phosphor, and the deposition was terminated when the thickness of the stimulable phosphor layer reached 300 μm.

  Next, the stimulable phosphor layer was put in a protective layer bag in dry air to obtain a radiation image conversion panel 1 as Example 1 according to the present invention having a structure in which the stimulable phosphor layer was sealed.

(Production of radiation image conversion panels 2 to 13)
In the production of the radiation image conversion panel 1, radiation image conversion panels 2 to 13 were obtained in the same manner except that the support was changed to the support described in Table 1.

<Evaluation>
The following evaluation was performed using each radiographic image conversion panel produced as described above. The obtained results are shown in Table 1.

<Evaluation of stress intensity factor>
As shown in FIG. 5, the stress intensity factor K _Ic was cut to 10 mm × 900 mm, and a notched sample (support) was subjected to a tensile test at a tensile rate of 40 mm / min in an atmosphere of 23 ° C. and 55% RH. , Calculated from equation (1). In the formula (1), the critical stress value indicates a value at which the load is maximized.

Formula (1): K _Ic = σ (πa) ^1/2 · F (α)
here,
α = a / w = 0.2
F (α) = 1.12−0.231α + 10.55α ² −21.72α ³ + 30.39α ⁴
σ = critical stress value a is the length (mm) of the notch, and w is the sample width (ie 10 mm).

<< Evaluation of Young's modulus >>
A sample (support) cut to 10 mm × 900 mm was subjected to a tensile test at a tensile rate of 40 mm / min in an atmosphere of 23 ° C. and 55% RH, and the elastic modulus was obtained from the slope of the stress-strain curve.

<Evaluation of impact resistance>
A 500 g iron ball was dropped from a height of 20 cm on the radiation image conversion panel, and then visually evaluated. Further, after irradiating each radiation image conversion panel with X-rays having a tube voltage of 80 kVp, the panel is scanned with He-Ne laser light (633 nm) and excited, and the stimulated luminescence emitted from the phosphor layer is emitted as described above. The received light is received and converted into an electrical signal by the described light receiver, reproduced as an image by an image reproducing device, printed out from the output device, and the obtained printed image was visually evaluated for impact resistance. . The results are shown in Table 1.

  In Table 1, visual evaluation of impact resistance is shown according to the following criteria.

    (Double-circle): There is no crack and it is a uniform image.

    ○: There is no crack, and the image quality is hardly a concern.

    Δ: Cracks are observed, and image defects are confirmed, but at a practically acceptable level.

    X: A level at which cracks are observed, clear omissions are observed, and problems occur in practice.

<< Evaluation of brightness and brightness distribution (uneven brightness) >>
The luminance was evaluated using a Regius 350 manufactured by Konica Corporation. 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 image conversion panel, and then read by installing a radiation image conversion panel on the Regius 350. Evaluation was performed based on the electrical signal from the obtained photomal. The electrical signal distribution from the photographed in-plane photomultiplier was subjected to relative evaluation, and the standard deviation was obtained to obtain the luminance distribution (SD) of each sample. S. D. A smaller value indicates that luminance unevenness is suppressed.

As is clear from the results in Table 1, the impact resistance is excellent when the stress intensity factor K _Ic of the support is 0.3 MPa · m ^1/2 or more and 60 MPa · m ^1/2 or less (Sample Nos. 3 to 13). ).

Among them, when K _Ic of the support is 0.3 MPa · m ^1/2 or more and 60 MPa · m ^1/2 or less and the Young's modulus of the support is 0.5 GPa or more and 60 GPa or less, not only the impact resistance. There is an effect of suppressing luminance unevenness (Sample Nos. 5 and 7 to 13). Furthermore, when the Young's modulus of the support is 0.5 GPa or more and 60 GPa or less and the stress intensity factor of the support is 1 MPa · m ^1/2 or more and 20 MPa · m ^1/2 or less, the effect is remarkable in terms of impact resistance and luminance unevenness suppression. (Sample Nos. 8 to 13).

  The luminance distribution (SD) 10 to 20 is an excellent performance level, but it may be difficult to recognize light shadows such as peripheral blood vessels in the chest image. On the other hand, S.M. D. 4 and below are remarkably excellent levels, faint shadows can be easily recognized in chest images, and S.P. D. Is 10 to 20 and 4 or less, the difference is large.

Schematic showing an example of the columnar crystal shape formed on the support Schematic showing an example of how the photostimulable phosphor layer is formed on the support by vapor deposition Schematic showing an example of the configuration of a radiation image conversion panel and a radiation image reading device Sectional drawing which shows schematic structure of an example of vapor deposition apparatus Conceptual diagram of tensile test for evaluation of stress intensity factor

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Support body 2 Columnar crystal 3 Line passing the center of crystal growth direction 4 Tangent line of crystal | crystallization tip cross-section part 5 Crystal diameter of columnar crystal 15 Support body holder 16 Stimulable fluorescent substance vapor flow 21 Radiation generator 22 Subject 23 Radiation image conversion Panel 24 Photoexcitation light source 25 Photoelectric conversion device 26 Image reproduction device 27 Image display device 28 Filter 101 Vapor deposition device 102 Vacuum vessel 103 Evaporation source 104 Support holder 105 Support rotation mechanism 106 Vacuum pump 111 Support

Claims (5)

In a radiation image conversion panel having a photostimulable phosphor layer on a support, the photostimulable phosphor layer is formed by a vapor phase growth method, and the stress intensity factor K _{Ic of the} support is 0.3 MPa · m ^{1. / 2} or more radiographic image conversion panel, characterized in that 60 MPa · m is ^1/2 or less. The radiation image conversion panel according to claim 1, wherein the stress intensity factor K _{Ic of the} support is 1 MPa · m ^1/2 or more and 20 MPa · m ^1/2 or less. The radiation image conversion panel according to claim 1 or 2, wherein the Young's modulus of the support is 0.5 GPa or more and 60 GPa or less. The stimulable phosphor layer contains a stimulable phosphor based on an alkali halide represented by the following general formula (1). Radiation image conversion panel.
The 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 manufacturing method of the radiographic image conversion panel characterized by manufacturing the radiographic image conversion panel of any one of Claims 1-4.

Images