JP2006125854A - Radiation image conversion panel, and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radiation image conversion panel excellent in sharpness, excellent in stability with the lapse of time of a characteristic, and excellent in an adhesive property of a stimulable phosphor layer, and a manufacturing method therefor. <P>SOLUTION: This radiation image conversion panel having the stimulable phosphor layer on a support is provided with an under coating resin layer having 0.01-0.05μm of average surface roughness Ra, and 0.5-10μm of film thickness, between the support and the stimulable phosphor layer. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a radiation image conversion panel using a photostimulable phosphor and a method for producing the same, and more particularly to a radiation image conversion panel excellent in sharpness, stability of characteristics over time and adhesiveness of the photostimulable phosphor layer, and It relates to the manufacturing method.

  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 proposed 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, for example, light or heat energy, 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, radiation using stimulable phosphors (hereinafter also simply referred to as phosphors) as described in US Pat. No. 3,859,527 and JP-A-55-12144. An image conversion method is known.

  This method uses a radiation image conversion panel containing a photostimulable phosphor. The radiation transmission density of each part of the subject is obtained by applying radiation transmitted through the subject to the photostimulable phosphor layer of the radiation image conversion panel. Is stored in the stimulable phosphor by chronologically exciting the stimulable phosphor with electromagnetic waves (excitation light) such as visible light and infrared light. Radiation energy is emitted as stimulated emission, and a signal based on the intensity of the light is photoelectrically converted to obtain an electrical signal, which is then used as a recording material such as a silver halide photographic material, or a display device such as a CRT. It is reproduced as a visible image on the top.

  According to the above radiographic image reproduction method, it is possible to obtain a radiographic image with a much smaller exposure dose and abundant information as compared with the radiographic method using a combination of a conventional radiographic film and an intensifying screen. Has the advantage of being able to

  Radiation image conversion panels using these photostimulable phosphors release accumulated energy by scanning excitation light after accumulating radiation image information, so that radiation images can be accumulated again after scanning. Can be used. In other words, the conventional radiographic method consumes a radiographic film for each photographing, whereas this radiographic image conversion method repeatedly uses a radiographic image conversion panel, so that also from the viewpoint of resource protection and economic efficiency. It is advantageous.

  Further, in recent years, a higher-definition radiation image conversion panel is 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 to be formed.

  As one of these attempts, for example, Japanese Patent Application Laid-Open No. 61-142497 discloses a stimulating property comprising a fine pseudo-columnar block formed by depositing a stimulable phosphor on a support having a fine uneven pattern. There is a method using a phosphor layer.

  Japanese Patent Application Laid-Open No. 61-142500 discloses a photostimulation in which cracks between columnar blocks obtained by depositing photostimulable phosphors on a support having a fine pattern are further developed by shock treatment. Using a radiation image conversion panel having a phosphor layer, and a method using a pseudo-columnar radiation image conversion panel in which a photostimulable phosphor layer formed on the surface of a support is cracked from its surface (patent) Reference 1), a method in which a stimulable phosphor layer having a cavity is formed on the upper surface of a support by vapor deposition, and then a cavity is grown by heat treatment (see Patent Document 2). A method using 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 a phase deposition method (see Patent Document 3) ) Etc. It is.

  Recently, a radiation image conversion panel using a stimulable phosphor using Eu as an activator with an alkali halide such as CsBr as a base has been proposed, and it is possible to derive a high X-ray conversion efficiency that has not been obtained so far. It became.

  However, even in the radiation image conversion panel having the photostimulable phosphor layer formed by vapor phase growth (deposition), the sharpness required from the market is not sufficiently improved, and further improvement has been demanded.

  In radiation image conversion panels used under various conditions, the adhesion between the support and the phosphor layer is one of the important characteristics, and an undercoat resin containing a cross-linking agent between the support and the phosphor layer. Although a method of providing a layer is disclosed (see Patent Document 4), by simply providing an undercoat resin layer, when forming a stimulable phosphor layer by the vapor phase growth method on the undercoat resin layer, When the surface of the undercoat resin layer is uneven, the adhesion to the support is poor and the crystal structure in the phosphor layer becomes non-uniform, resulting in variations in sharpness and irregularities in the radiation image conversion panel. It sometimes occurred. In addition, the film thickness of the undercoat resin layer may be too large, and the temporal stability of characteristics may be reduced.

Thus, in the radiation image conversion panel, development of a radiation image conversion panel excellent in sharpness, stability of characteristics over time, and adhesion to the support of the stimulable phosphor layer is desired.
JP 62-39737 A JP-A-62-110200 JP-A-2-58000 Japanese Patent Publication No. 4-44959

  The present invention has been made in view of the above problems, and its object is to provide a radiation image conversion panel excellent in sharpness, stability of characteristics over time, and adhesiveness of a stimulable phosphor layer, and a method for producing the same. That is.

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

(Claim 1)
In a radiation image conversion panel having a photostimulable phosphor layer on a support, an average surface roughness Ra is 0.01 to 0.05 μm and a film between the support and the photostimulable phosphor layer. A radiation image conversion panel comprising an undercoat resin layer having a thickness of 0.5 to 10 μm.

(Claim 2)
The radiation image conversion panel according to claim 1, wherein the undercoat resin layer has a thickness of 1 to 5 μm.

(Claim 3)
The radiation image conversion panel according to claim 1 or 2, wherein the stimulable phosphor layer contains a stimulable phosphor represented by the following general formula (1).

General formula (1)
M ¹ X · aM ² X ′ ₂ : eA, A ″
(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 X and X ′ are at least one halogen atom selected from each atom of F, Cl, Br and I, and A and A ″ Is at least one rare earth atom selected from each atom of Eu, Tb, In, Ce, Tm, Dy, Pr, Ho, Nd, Yb, Er, Gd, Lu, Sm and Y, and a and e are respectively (Numerical values in the range of 0 ≦ a <0.5 and 0 <e ≦ 0.2)
(Claim 4)
The radiation image conversion panel according to any one of claims 1 to 3, wherein at least one of the photostimulable phosphor layers has a thickness of 50 to 1 mm by a vapor deposition method (also referred to as a vapor deposition method). The manufacturing method of the radiographic image conversion panel characterized by forming like this.

  INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a radiation image conversion panel excellent in sharpness, temporal stability of characteristics, and adhesiveness of a stimulable phosphor layer, and a method for producing the same.

  As a result of diligent research, the present inventor has found that in a radiation image conversion panel having a stimulable phosphor layer on a support, the average surface roughness Ra is 0. 0 between the support and the stimulable phosphor layer. By providing an undercoat resin layer having a thickness of 01 to 0.05 μm and a film thickness of 0.5 to 10 μm, the radiation image is excellent in sharpness, stability of characteristics over time and adhesiveness of the stimulable phosphor layer. We found that a conversion panel was obtained.

  Moreover, in order to express this effect more, the film thickness of the said undercoat resin layer is 1-5 micrometers, and the said stimulable fluorescent substance layer is the stimulable fluorescence represented by the said General formula (1). It is preferable to contain a body.

  Hereinafter, the present invention will be described in detail.

[Support]
The support for the radiation image conversion panel used in the present invention will be described.

  As the support used in the radiation image conversion panel of the present invention, various glasses, polymer materials, metals, and the like are used. For example, plate glass such as quartz, borosilicate glass, chemically tempered glass, cellulose acetate film, Examples include polyester films, polyethylene terephthalate films, polyamide films, polyimide films, triacetate films, polycarbonate films and other metal films such as aluminum sheets, iron sheets and copper sheets, or metal sheets having a coating layer of the metal oxide. . Among these, a metal substrate or glass mainly composed of aluminum is preferable.

[Undercoat resin layer]
In the present invention, the average surface roughness Ra is 0.01 to 0.05 μm and the film thickness is 0.5 to 10 μm, more preferably 1 to 5 μm between the support and the photostimulable phosphor layer. It is characterized by providing a certain undercoat resin layer.

  The resin that can be used in the undercoat resin layer is not particularly limited. For example, polyvinyl alcohol, polyvinyl butyral, polyvinyl formal, polycarbonate, polyester resin, polyethylene terephthalate, polyethylene, nylon, (meth) acrylic acid or ( (Meth) acrylic acid esters, vinyl esters, vinyl ketones, styrenes, diolefins, (meth) acrylamides, vinyl chlorides, vinylidene chloride, cellulose derivatives such as nitrocellulose, acetylcellulose, diacetylcellulose, silicone resins, Examples include polyurethane resins, polyamide resins, various synthetic rubber resins, phenol resins, epoxy resins, urea resins, melamine resins, and phenoxy resins. Of these, hydrophobic resins such as polyester resins and polyurethane resins are preferable from the viewpoint of adhesion between the support and the stimulable phosphor layer and corrosion resistance of the support.

  The film thickness of the undercoat resin layer in the present invention is 0.5 to 10 μm, more preferably 1 to 5 μm. If the thickness of the undercoat resin layer is less than 0.5 μm, the adhesive force between the support and the photostimulable phosphor layer may be weak, and if it exceeds 10 μm, the temporal stability of quality such as sharpness may decrease. The

  The average surface roughness Ra as used in the present invention is defined by JIS-B-0601. That is, Ra is a portion of the measurement length L from the roughness curve in the direction of the center line, with a cut-off value of 0.8 mm, the center line of the extracted portion is the X axis, the direction of the vertical magnification is the Y axis, When the roughness curve is represented by Y = f (X), the value obtained by the following equation is represented by micrometers (μm).

  As a measuring apparatus, for example, it can be measured by a known surface roughness measuring method such as a stylus method or laser interferometry.

  The roughness Ra of the undercoat resin layer in the present invention is 0.01 to 0.05. When the roughness Ra of the undercoat resin layer is less than 0.01, there is a problem that the adhesive strength between the undercoat resin layer and the stimulable phosphor layer is weak and the stimulable phosphor layer is easily peeled off. If the roughness Ra of the undercoat resin layer exceeds 0.05, the crystal structure in the photostimulable phosphor layer becomes non-uniform when the photostimulable phosphor is formed by the vapor phase growth method, and the radiation image is converted. There is a problem that sharpness variation and granular unevenness occur in the panel.

  In addition to the resin, the undercoat resin layer according to the present invention may contain a crosslinking agent in order to impart film strength. There is no restriction | limiting in particular as a crosslinking agent which can be used, For example, a polyfunctional isocyanate and its derivative (s), a melamine and its derivative (s), an amino resin, and its derivative (s) etc. can be mentioned, A polyfunctional isocyanate compound is preferable. Examples of the polyfunctional isocyanate compound include Coronate HX and Coronate 3041 manufactured by Nippon Polyurethane.

  The amount of the crosslinking agent used varies depending on the characteristics of the intended radiation image conversion panel, the type of materials used for the stimulable phosphor layer and the support, the type of resin used for the undercoat resin layer, etc. Considering the maintenance of the adhesive strength between the body layer and the support, it is preferably 50% by mass or less, more preferably 5 to 30% by mass with respect to the undercoat resin. If it is less than 5% by mass, the crosslinking density is low, and both heat resistance and strength are insufficient. When it exceeds 30% by mass, the crosslink density is high, the toughness with the undercoat resin layer is lowered (becomes brittle), and the undercoat resin layer is cracked.

  In the present invention, in order to complete the reaction between the resin in the undercoat resin layer and the cross-linking agent after coating the undercoat resin layer on the support and before coating the stimulable phosphor layer, 40 to Heat treatment is performed at 150 ° C. for 1 to 100 hours.

  The undercoat resin layer can be obtained by applying and drying an undercoat resin layer coating liquid on a support. The coating method is not particularly limited, and a known coating coater such as a doctor blade, a roll coater, a knife coater, or an extrusion coater may be used, or a spin coater may be used.

[Stimulable phosphor layer]
Next, the photostimulable phosphor layer of the present invention will be described.

  FIG. 1 is a schematic view showing an example of a columnar crystal shape formed on the support of the present invention. 1A and 1B, reference numeral 2 denotes a stimulable phosphor columnar crystal formed on the support 1 by vapor deposition, and passes through the center of the crystal growth direction at the crystal tip. The angle (θ) formed between the perpendicular 3 and the tangent 4 of the crystal tip cross section is preferably 20 to 80 °, more preferably 40 to 80 °.

  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.

  Moreover, in this invention, it is preferable that the average crystal diameter of a columnar crystal is 0.5-50 micrometers, More preferably, it is 1-50 micrometers. By setting the average crystal diameter of the columnar crystals in this range, the haze ratio of the photostimulable phosphor layer b can be lowered, and as a result, excellent sharpness can be realized.

  The average crystal diameter of the columnar crystals is an average value of the diameters in terms of circles of the cross-sectional areas of the columnar crystals when the columnar crystals are observed from a plane parallel to the support, and at least 100 columnar crystals are being viewed. It is calculated from the electron micrographs included.

  The columnar crystal diameter is influenced 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 JP-A-48-80487, Phosphors represented by MgSO ₄ : Ax described in Kaikai 48-80488, phosphors represented by SrSO ₄ : Ax described in JP-A 48-80489, described in 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, etc., and BeO, LiF, MgSO _4, CaF _2, etc. described in JP-A-52-30487 Phosphors, phosphors such as Li ₂ B ₄ O ₇ : Cu, Ag described in JP-A-53-39277, Li ₂ O. (Be ₂ O ₂ ) x described in JP-A-54-47883 Phosphors such as Cu and Ag, US Pat. No. 3,859,5 7 described in JP SrS: Ce, Sm, SrS: Eu, Sm, La 2 O 2 S: Eu, Sm and (Zn, Cd) S: phosphor can be cited represented by Mnx.

Further, a ZnS: Cu, Pb phosphor described in JP-A-55-12142, a barium aluminate phosphor represented by the general formula BaO.xAl ₂ O ₃ : Eu, and a general formula represented by M (II) O. An alkaline earth metal silicate phosphor represented by xSiO ₂ : A is exemplified.

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, The phosphor represented by the general formula described in No. 12144 is represented by LnOX: xA, and the general formula described in JP-A-55-12145 is represented by (Ba _1-x M (II) _x ) F _x : yA. Phosphor, a phosphor represented by the general formula described in JP-A-55-84389 as BaFX: xCe, yA, and a general formula described in JP-A-55-160078 as M (II) FX.xA: yLn Rare earth element activated divalent metal fluorohalide phosphors represented by general formulas ZnS: A, CdS: A, phosphors represented by (Zn, Cd) S: A, X, JP-A-59-38278 A phosphor represented by any one of the following general formulas:
General formula xM ₃ (PO ₄ ) ₂ · NX ₂ : yA
xM ₃ (PO ₄ ) ₂ : yA
A phosphor represented by any one of the following general formulas described in JP-A-59-155487,
General formula nReX ₃ · mAX ′ ₂ : xEu
nReX ₃ · mAX ′ ₂ : xEu, ySm
JP 61-72087 general formulas described in JP-M (I) X · aM ( II) X '2 · bM (III) X "3: alkali halide phosphor and JP represented by cA 61-228400 Bismuth-activated alkali halide phosphors represented by the general formula M (I) X: xBi described in No. 1. In particular, alkali halide phosphors are columnar photostimulable phosphors by a method such as vapor deposition or sputtering. It is preferable because a layer is easily formed.

  Next, the photostimulable phosphor represented by the general formula (1) of the present invention will be described.

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

M ² represents at least one divalent metal atom selected from the atoms of Be, Mg, Ca, Sr, Ba, Zn, Cd, Cu, and Ni. Among these, Be, Mg, It is a divalent metal atom selected from each atom such as Ca, Sr and Ba.

M ³ is at least one selected from each atom of Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Al, Ga, and In. This represents a trivalent metal atom, but among them, a trivalent metal atom selected from each atom such as Y, Ce, Sm, Eu, Al, La, Gd, Lu, Ga, and In is preferable. .

  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 represent at least one halogen atom selected from F, Cl, Br, and I atoms. At least one halogen atom selected from Br is preferable, and at least one halogen atom selected from Br and I atoms is more preferable.

In the general formula (1), b represents 0 ≦ b <0.5, and preferably 0 ≦ b ≦ 10 ⁻² .

  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 (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 (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 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. Firing is preferable because it can further increase the light 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.

  In addition, the photostimulable phosphor layer of 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 degree of vacuum of about 1.333 × 10 ⁻⁴ Pa. Next, at least one of the photostimulable phosphors 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.

  It is preferable to manufacture the radiation image conversion panel of the present invention by providing a protective layer on the side opposite to the support side of the photostimulable phosphor layer, if necessary, after completion of the vapor deposition. 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 to 300 μm / min. When the growth rate is less than 0.05 μm / min, the productivity of the radiation image conversion panel of the present invention is low, which is not preferable. If the growth rate exceeds 300 μm / min, it is difficult to control the growth rate.

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

  The film thickness of the photostimulable phosphor layer is preferably 50 to 1000 μm 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 the production of 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 more, more preferably 150 ° C. or more. Yes, particularly preferably 150 to 400 ° C.

  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 for forming a phosphor layer on a glass support (hereinafter also simply referred to as a support) by vapor deposition, vapor of a stimulable phosphor or the raw material is supplied, and vapor deposition such as vapor deposition is performed. A photostimulable phosphor layer composed of independent long and narrow columnar crystals can be obtained by a method of (deposition). 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 stimulable phosphor, and may be a mixture of a stimulable phosphor material.

  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, 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 of 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 way 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. Further, 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.

  A highly reflective substance refers to a substance having a high reflectivity for 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.

  From the viewpoint of obtaining a radiation image conversion panel having high sensitivity, the reflectance of the photostimulable phosphor layer of the present invention is preferably 20% or more, more preferably 30% or more, and particularly preferably 40% or more. It is. 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 following measurement conditions using the following measuring apparatus.

(measuring device)
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. These white pigments have a strong hiding power and a high refractive index, so that it is possible to easily scatter scattered light by reflecting or refracting light, and to significantly improve the sensitivity of the resulting radiation image conversion panel. it can.

  Moreover, as a substance 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. 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.

  Moreover, the photostimulable phosphor layer of 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 the protective layer. In addition, 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.

  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 transmission image RI is absorbed by the photostimulable phosphor layer of the radiation image conversion panel 23, so that a number of electrons and / or holes proportional to the amount of radiation absorbed in the photostimulable phosphor layer are generated. Occurs and accumulates at the trap level of the photostimulable phosphor. That is, a latent image in which the energy of the radiation transmission image is accumulated is formed. Next, this latent image is made visible by being excited with light energy. That is, the stimulable phosphor layer is irradiated with light in the visible or infrared region to irradiate the photostimulable phosphor layer, expelling electrons and / or holes accumulated at the trap level and stimulating the accumulated energy. 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 is 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 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 make compact is preferred as the excitation wavelength used for 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 becomes simple, and the intensity of the stimulated excitation light can be increased, so that the photostimulated 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. Usually, 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 the pulse of one pixel of the panel are synchronized. In addition, when using a method of separating light emission using a delay of light emission as shown in JP-A-59-22046 without using 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 luminescence emitted from the radiation image conversion panel 23 and cuts the stimulated excitation light, the filter 28 emits the luminescent phosphor of the stimulable phosphor contained in the radiation image conversion panel 23. It is determined by the combination of the exhaust 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. 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 in detail, this invention is not limited to these.

Example [Production of Radiation Image Conversion Panel]
(Preparation of undercoat resin layer coating solution 1)
A polyester resin (Toyobo Co., Ltd., Byron 63SS) and a polyfunctional isocyanate compound, Coronate 3041 (manufactured by Nippon Polyeletan Kogyo Co., Ltd.), are mixed as a crosslinking agent, and this mixture is mixed with methyl ethyl ketone / toluene 1/1 Was added to and dispersed by a propeller mixer to prepare an undercoat resin layer coating solution 1.

(Preparation of undercoat resin layer coating solutions 2 to 5)
In the preparation of the undercoat resin layer coating solution 1, the amount of the mixed solvent is adjusted so that the average surface roughness Ra and the film thickness are the values shown in Table 1, and the others are similarly applied. Was prepared.

(Coating of undercoat resin layer)
On the aluminum plate support having a thickness of 500 μm and a 10 cm square, the above-prepared undercoat resin layer coating solutions 1 to 5 were applied using a knife coater so that the dry film thickness was a value shown in Table 1, respectively. It dried at 150 degreeC for 2 hours, and obtained the support body with an undercoat resin layer.

(Production of radiation image conversion panels 1 to 5)
A stimulable phosphor layer having a stimulable phosphor (CsBr: Eu) was formed on the prepared support with an undercoat resin layer using the vapor deposition apparatus shown in FIG.

  Using the vapor deposition apparatus shown in FIG. 4, using an aluminum slit and setting the distance d between the support and the slit to 60 cm, the phosphor raw material (CsBr: Eu) is parallel to the aluminum plate support. Vapor deposition was performed while the crucible contained therein was conveyed, and the thickness of the stimulable phosphor 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 press-molded 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 240 ° C. When the thickness of the photostimulable phosphor layer reached 300 μm, the vapor deposition was terminated, and radiation image conversion panel samples 1 to 5 were obtained.

[Evaluation of radiation image conversion panel]
About the radiographic image conversion panel produced as mentioned above, according to the following method, peelability, sharpness, and the temporal stability of sharpness were evaluated.

(Peelability)
When the stimulable phosphor layer was formed by growing a downward crystal by vapor deposition, the presence or absence of the crystal was visually examined.

(Sharpness)
Sharpness was evaluated by obtaining a modulation transfer function (MTF). After attaching a CTF chart to the radiation image conversion panel, the MTF is irradiated with 80 kVp X-rays at a distance of 10 mR (distance to the subject; 1.5 m), and then the semiconductor laser light (from the side having the stimulable phosphor layer) The CTF chart image was scanned and read by irradiating with 680 nm, a power of 40 mW on the panel, and a diameter of 100 μmφ. The values in Table 1 indicate MTF values at 2.0 lp / mm. In this case, the higher the MTF value, the better the sharpness.

(Sharpness stability over time)
The prepared radiation image conversion panel was stored for 240 hours in an atmosphere of 30 ° C. and 80% RH, and then the sharpness was measured by the same method as described above, and the sharpness (after time) / sharpness (before time) It was defined as stability over time. The closer this value is to 1, the higher the stability over time.

  From the table, it can be seen that the radiation image conversion panel of the present invention is superior in peelability, sharpness, and sharpness over time as compared with the comparative example.

It is the schematic which shows an example of the columnar crystal shape formed on the support body. It is the schematic which shows an example of a mode that a photostimulable phosphor layer is formed by vapor deposition on a support body. It is the schematic which shows one example of a structure of the radiographic image conversion panel and radiographic image reading apparatus of this invention. It is the schematic which shows an example of the method of forming a photostimulable fluorescent substance layer on a support body by vapor deposition.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Support body 2 Columnar crystal 3 Perpendicular through 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 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

Claims (4)

In a radiation image conversion panel having a photostimulable phosphor layer on a support, an average surface roughness Ra is 0.01 to 0.05 μm and a film between the support and the photostimulable phosphor layer. A radiation image conversion panel comprising an undercoat resin layer having a thickness of 0.5 to 10 μm. The radiation image conversion panel according to claim 1, wherein the thickness of the undercoat resin layer is 1 to 5 μm. The radiation image conversion panel according to claim 1 or 2, wherein the stimulable phosphor layer contains a stimulable phosphor represented by the following general formula (1).
General formula (1)
M ¹ X · aM ² X ′ ₂ : eA, A ″
(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 X and X ′ are at least one halogen atom selected from each atom of F, Cl, Br and I, and A and A ″ Is at least one rare earth atom selected from each atom of Eu, Tb, In, Ce, Tm, Dy, Pr, Ho, Nd, Yb, Er, Gd, Lu, Sm and Y, and a and e are respectively (Numerical values in the range of 0 ≦ a <0.5 and 0 <e ≦ 0.2) The radiation image conversion panel according to any one of claims 1 to 3, wherein at least one of the photostimulable phosphor layers has a thickness of 50 to 1 mm by a vapor deposition method (also referred to as a vapor deposition method). The manufacturing method of the radiographic image conversion panel characterized by forming like this.

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