JP2003139896A - Radiation image conversion panel and its production method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radiation image conversion panel superior in brightness and sharpness and its production method. SOLUTION: The radiation image conversion panel has a stimulable phosphor layer dispersedly containing stimulable phosphor in bonding agent on a support body. The particle diameter ratio (A/B) of average particle diameter A of stimulable phosphor in the region of depth of 50 μm from the surface layer into the support surface side, and the average diameter B of stimulable phosphor in the region of depth of 50 μm from the support surface side into the surface layer is 2 to 10. The stimulable phosphor particle diameter varies with inclined particle diameter distribution without a boundary from the surface layer to the support surface side and the average particle diameter B of the stimulable phosphor in the radiation image conversion panel is 1 to 10 μm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiation image conversion panel using a stimulable phosphor and a manufacturing method thereof, and more particularly to a radiation image conversion panel excellent in brightness and sharpness and a manufacturing method thereof. is there.

[0002]

2. Description of the Related Art Radiation images such as X-ray images are widely used in the fields of disease diagnosis and the like. This X-ray image can be obtained by irradiating the phosphor layer (fluorescent screen) with X-rays that have passed through the subject to generate visible light, which is the same as when taking a normal photo. Then, a so-called radiographic method is widely used 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.

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

As this method, the radiation that has passed through the subject is absorbed by the phosphor, and then the phosphor is excited by, for example, light or thermal energy, so that the radiation energy accumulated by the phosphor is absorbed. Then, there is a method of detecting this fluorescence and imaging it.

Specifically, for example, US Pat. No. 3,85
A radiation image conversion method using a stimulable phosphor as described in JP-A No. 9,527 and JP-A No. 55-12144 is known.

This method uses a radiation image conversion panel containing a stimulable phosphor, and the radiation transmitted through the object is applied to the stimulable phosphor layer of the radiation image conversion panel to apply the radiation to each part of the object. Accumulates radiation energy corresponding to the radiation transmission density, and then accumulates in the stimulable phosphor by time-sequentially exciting the stimulable phosphor with electromagnetic waves (excitation light) such as visible light and infrared rays. The emitted radiation energy is emitted as stimulated emission, and the signal due to the intensity of this light is photoelectrically converted to obtain an electric signal, and this signal is recorded, such as a recording material such as a silver halide photographic light-sensitive material, a CRT, etc. Is reproduced as a visible image on the display device.

According to the above radiographic image reproducing method, compared with the conventional radiographic method using a combination of a radiographic film and an intensifying screen, the radiographic image has a much smaller exposure dose and a rich information content. Has the advantage that

As described above, the stimulable phosphor is a phosphor that exhibits stimulated emission when irradiated with excitation light after being irradiated with radiation, but in practice, excitation with a wavelength in the range of 400 to 900 nm is used. A phosphor that emits stimulated emission in the wavelength range of 300 to 500 nm by light is generally used.

A radiation image conversion panel using these stimulable phosphors releases radiation energy by scanning excitation light after storing radiation image information. Therefore, radiation images can be stored again after scanning. It can be used repeatedly. In other words, in the conventional radiographic method, the radiographic film is consumed for each photographing, whereas in the radiographic image conversion method, the radiographic image conversion panel is repeatedly used. It is advantageous.

The superiority or inferiority of the radiation image conversion system using the radiation image conversion panel is greatly influenced by the stimulable luminescence brightness (also referred to as sensitivity) of the panel and the sharpness of the obtained image,
In particular, it is said that the characteristics of the stimulable phosphor used have a great influence on the sharpness characteristics.

To solve the above problem, for example, Japanese Patent Publication No. 4-75
No. 480 discloses a method of improving sharpness by mainly mixing stimulable phosphors having two kinds of average particle diameters. However, only by mixing two kinds of stimulable phosphors having different average particle diameters, the characteristics of one of the stimulable phosphor particles are biased toward the obtained radiation image conversion panel, which results in a comprehensive It was found that the contribution to the improvement of the characteristics was reduced and the improvement effect was small. Further, although the above specification suggests the possibility of mixing two or more kinds of stimulable phosphors, it does not mention the distribution state thereof, and will be examined specifically. Then, it was found that there was a region where the effect was hardly exhibited depending on the selected mixing ratio. Further, if the difference in average particle size between the stimulable phosphor particles to be mixed is small, the degree of improvement in properties is reduced, and conversely, if the difference in average particle size is large, the sharpness of the obtained image, so-called sharpness This results in deterioration.

On the other hand, Japanese Examined Patent Publication No. 4-44720 discloses a method of improving sharpness and brightness by forming a plurality of layers containing phosphors having different particle diameters.
However, the use of a plurality of constituent layers causes the scattering of the excitation light at the interface between the layers, and thus has a problem that the sharpness is rather lowered.

The deterioration of the sharpness of the image as described above makes it difficult to detect and confirm a lesion or the like when applied to a medical image, and may cause a fatal problem. Immediate improvement is demanded. ing.

[0014]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object thereof is to provide a radiation image conversion panel excellent in brightness and sharpness and a manufacturing method thereof.

[0015]

The above objects of the present invention have been achieved by the following constitutions.

1. In a radiation image conversion panel having a stimulable phosphor layer containing a stimulable phosphor dispersed in a binder on a support, the stimulable phosphor layer is 50 μm from the surface side to the support side. Of the stimulable phosphor in the above region and the average particle size B of the stimulable phosphor in the region of 50 μm from the support surface side to the surface layer side (A /
B) is from 2 to 10, has a gradient particle size distribution in which the particle size of the stimulable phosphor changes from the surface layer side toward the support surface side without having an interface, and the average particle of the stimulable phosphor is Diameter B is 1
A radiation image conversion panel having a thickness of 10 μm.

2. The stimulable phosphor is Eu-activated BaF.
2. The radiation image conversion panel according to item 1, wherein the radiation image conversion panel is I.

3. The radiation image conversion panel according to 1 or 2, wherein at least two kinds of stimulable phosphors having different particle sizes are mixed, coated on a temporary support, dried, and then applied on another support. A method for manufacturing a radiation image conversion panel, which is manufactured by reattaching.

The inventors of the present invention have made earnest studies on a method capable of achieving both the brightness and the sharpness of the radiation image conversion panel, and as a result, in the stimulable phosphor layer consisting of a single layer, the particle diameter of the surface layer side is A large stimulable phosphor particle (hereinafter, also simply referred to as a phosphor particle) A is arranged, and a phosphor particle B having a small particle diameter is arranged on the side closer to the support by the contrary, and a particle diameter ratio of A / B is set. Is 2 to 10, and the stimulable phosphor (hereinafter, also simply referred to as phosphor) has a gradient particle size distribution in which the particle size changes without having an interface facing from the surface layer side to the support surface side, and the fluorescence By setting the average particle diameter B of the body to 1 to 10 μm,
It was found that a radiation image conversion panel having an excellent balance between brightness and sharpness could be obtained, and the present invention has been completed.

The details of the present invention will be described below. In the invention according to claim 1, in the stimulable phosphor layer, the average particle diameter A of the stimulable phosphor in the region of 50 μm from the surface layer side to the support surface side and 50 μm from the support surface side to the surface layer side. One of the characteristics is that the particle size ratio (A / B) to the average particle size B of the stimulable phosphor in the contained region is 2 to 10, and the particle size ratio (A / B) is preferably 2 ~ 8
Is. In addition, the stimulable phosphor having the average particle diameter A and the stimulable phosphor having the average particle diameter B change in the stimulable phosphor particle diameter without having an interface facing from the surface layer side to the support surface side. The feature is that it has a gradient particle size distribution.

First, a method of manufacturing the radiation image conversion panel of the present invention will be described. The following two types are mainly conceivable as the method of manufacturing the radiation image conversion panel of the present invention. As a first manufacturing method, a stimulable phosphor coating liquid composed of a binder and a plurality of stimulable phosphors having different particle diameters is applied onto a support to form a stimulable phosphor layer. Further, as a second production method, a stimulable phosphor coating composed of a binder and a plurality of stimulable phosphors having different particle diameters is first applied onto a temporary support to form a stimulable phosphor sheet. Form. Then
This stimulable phosphor sheet is placed on a support, and is manufactured by a step of adhering and transferring onto the support at a softening temperature or a temperature equal to or higher than the melting point of the binder. As the method for forming the stimulable phosphor layer on the support, the above-mentioned two types are mainly considered, but any method can be used as long as it is a method for uniformly forming the stimulable phosphor layer on the support. Well, it may be formed by spraying.

As the above-mentioned support and temporary support used in the radiation image conversion panel of the present invention, various polymer materials, glass, metal and the like are used. In particular, in terms of handling as an information recording material, a material that can be processed into a flexible sheet or web is preferable. From this point of view,
For example, a cellulose acetate film, a polyester film, a polyethylene terephthalate film, a polyamide film, a polyimide film, a plastic film such as a triacetate film, a polycarbonate film or the like, a metal sheet such as aluminum, iron, copper or chromium, or a coating layer of the hydrophilic fine particles is provided. Metal sheets are preferred.

The film thickness of the support and the temporary support varies depending on the materials of the support and the temporary support to be used, etc., but is generally 3 to 1000 μm, and from the viewpoint of easy handling, it is 80 It is preferably about 500 μm.

The surface of these supports may be a smooth surface, or may be a matte surface for the purpose of improving the adhesiveness with the stimulable phosphor layer.

Further, these supports may be provided with an undercoat layer on the surface on which the stimulable phosphor layer is provided for the purpose of improving the adhesiveness with the stimulable phosphor layer as described above.

In the present invention, examples of the binder used in the undercoat layer include proteins such as gelatin, polysaccharides such as dextran, and natural polymer substances such as gum arabic; and polyvinyl butyral and polyvinyl acetate. , Nitrocellulose, ethyl cellulose, vinylidene chloride / vinyl chloride copolymer, polyalkyl (meth) acrylate, vinyl chloride / vinyl acetate copolymer, polyurethane, cellulose acetate butyrate,
Examples thereof include binders represented by synthetic polymer substances such as polyvinyl alcohol and linear polyester. Further, these binders may be crosslinked with a crosslinking agent.

For the stimulable phosphor layer of the first production method, a support is coated with a coating liquid containing a phosphor having a small particle size,
After coating a coating solution containing a phosphor with a large particle size on top of that and laminating all layers, the coating film is allowed to evaporate while preventing solvent evaporation from the surface until the interface between layers disappears. Place. Then, after the interface disappears, it can be manufactured by drying the phosphor layer.

The sheet which becomes the stimulable phosphor layer in the second manufacturing method is prepared by temporarily supporting the stimulable phosphor coating solution on a temporary support for forming a stimulable phosphor sheet or as a protective film. It can be manufactured by applying it on the body, allowing it to stand for a certain period of time until the phosphor with a large particle size is settled, and then drying it, peeling it from the temporary support, or sticking the support to the surface thereof.

In one of the above methods, the stimulable phosphor coating is applied onto the temporary support or the temporary support as a protective film, allowed to stand and dried, and then peeled off from the temporary support. In the case of forming a sheet to be a luminescent phosphor layer, the surface of the temporary support is coated with a release agent in advance so that the formed stimulable phosphor sheet is easily peeled from the temporary support. Is preferred.

The stimulable phosphor layer of the present invention may be compressed. By compressing the stimulable phosphor layer, the packing density of the stimulable phosphor can be further improved and the sharpness can be further improved. Examples of the compression method include a press machine and a calendar roll. For example, in the case of the first manufacturing method, the stimulable phosphor layer and the support are compressed as they are. In the case of the second manufacturing method, the stimulable phosphor sheet is placed on the support and the sheet is adhered to the support while being compressed at the softening temperature or the temperature of the melting point or higher of the binder.

In the present invention, in the stimulable phosphor layer,
Any of the above methods is not particularly limited as a method for continuously providing the gradient particle size distribution of the phosphor particles, but the stimulable phosphor layer coating solution according to the invention of claim 3 is provided on a temporary support. It is preferable to use a method of manufacturing by coating and drying on, and then reattaching to another support, and a specific example thereof is shown below.

After mixing two or more kinds, preferably three or more kinds of phosphor particles having different particle diameters with a binder, a solvent is added so as to obtain a desired viscosity, and a stimulable phosphor layer coating solution is added. To prepare. This stimulable phosphor layer coating liquid is applied on a temporary support using a known coater, and after coating the stimulable phosphor layer, the coating film surface may be covered with a cover,
Alternatively, the inside of the chamber is set to a saturated vapor pressure atmosphere of the solvent and allowed to stand for a certain period of time while preventing the solvent from evaporating from the coating film. Let Then, it is dried according to a conventional method to obtain a stimulable phosphor layer in which phosphor particles of small particles are continuously distributed in the upper part and large particles are continuously distributed in the lower part. Then, the stimulable phosphor layer formed on the temporary support and a support having an adhesive layer on the surface are bonded by pressure or heating using a laminator or the like, and the stimulable phosphor layer is provided on the support side. The average particle size A of the stimulable phosphor in the region of 50 μm from the surface layer side defined in the present invention to the support surface side and the average particle diameter A from the support surface side to the surface layer side defined by 50
It is possible to obtain a radiation image conversion panel having a particle size ratio (A / B) of 2 to 10 with the average particle size B of the stimulable phosphor in the region of μm.

As a method for directly providing the stimulable phosphor layer on the support, for example, a stimulable phosphor layer coating solution containing a plurality of phosphor particles having different particle diameters and specific gravities is used, and A radiation image conversion panel having a desired particle size distribution can be obtained by applying, allowing to stand, and drying by the same method as above, and utilizing the difference in specific gravity.

In the present invention, in order to bring the ratio (A / B) of the surface layer side phosphor particle diameter A and the support side phosphor particle diameter B within the range specified in the present invention, for example, a plurality of phosphor particles used It can be achieved by appropriately selecting or combining the particle diameter ratio and the mixing ratio thereof, the type of binder, the addition amount of the solvent, the standing time, the standing temperature, and the like.

In the present invention, the average particle diameter A of the stimulable phosphor in the region of 50 μm from the surface side to the support surface side.
There is no particular limitation on the method for measuring the average particle diameter B of the stimulable phosphor in the region of 50 μm from the support surface side to the surface layer surface side, and an example of the measurement method is shown below.

First, 50 from the surface side to the support side.
The method of determining the average particle size A of the stimulable phosphor in the region containing μm is carried out by using a sample in which a stimulable phosphor layer containing a stimulable phosphor dispersed in a binder is coated on a support. 5 from the outermost surface
The solution is precisely dissolved to a depth of 0 μm with a solvent capable of eluting the stimulable phosphor layer such as methyl ethyl ketone, the eluted phosphor is filtered, washed with a solvent and the like, and then dried at 100 ° C. for 10 hours. Then, this dried product is subjected to a particle size measuring device, for example, a light scattering particle size measuring device LA-91 manufactured by Horiba Ltd.
It is possible to determine the average particle diameter A from the average value by measuring the particle diameter of 500 or more phosphor particles using 0 or the like.

Further, 50 μm from the support surface side to the surface layer side.
As a method for measuring the average particle size B of the stimulable phosphor in the area containing the sample, a sample in which a stimulable phosphor layer containing a stimulable phosphor dispersed in a binder is coated on a support is used. The solvent is precisely dissolved in a solvent capable of eluting the stimulable phosphor layer such as methyl ethyl ketone so that the phosphor layer on the support surface side from the surface layer of (1) remains 50 μm thick. Next, the remaining 50 μm-thick photostimulable phosphor layer is dissolved again with the same solvent, the eluate is filtered and washed with a solvent, and the phosphor is dried at 100 ° C. for 10 hours. Then, the particle size of 500 or more phosphor particles is measured in the same manner as above, and the average particle size B
Can be asked.

Next, each component of the radiation image conversion panel of the present invention will be described. The stimulable phosphor that can be used in the present invention has a wavelength of 400 to 900 nm.
Phosphors that exhibit stimulated emission in the wavelength range of 300 to 500 nm with excitation light in the range are generally used.

Examples of phosphors that can be preferably used in the radiation image conversion panel of the present invention will be given below, but the present invention is not limited to these.

(1) (Ba _1-X , M (II) _X ) FX: y
A, where M (II) is at least one of Mg, Ca, Sr, Zn and Cd, X is at least one of Cl, Br, and I, A is Eu, Tb, Ce, T
At least one of m, Dy, Pr, Ho, Nd, Yb, and Er, and 0 ≦ x ≦ 0.6, y is
0 ≦ y ≦ 0.2) and a rare earth element-activated alkaline earth metal fluorohalide phosphor represented by the composition formula;
This phosphor may contain the following additives.

A) X ', BeX ", M (III) X'"₃,
In the formula, X ′, X ″, and X ′ ″ are Cl and Br, respectively.
And at least one of I and M (III) is trivalent gold
Be a genus b) BeO, MgO, CaO, SrO, BaO, Zn
O, Al₂O₃, Y₂O₃, La₂O₃, In₂O₃, Si
O₂, TiO₂, ZrO₂, GeO₂, SnO₂, Nb
₂O _Five, Ta₂O_FiveAnd ThO₂Metal oxides such as c) Zr, Sc d) B e) As, Si f) M · L, where M is Li, Na, K, Rb, and
At least one alkali selected from the group consisting of Cs
Is a metal, L is Sc, Y, La, Ce, Pr, Nd,
Pm, Sm, Gd, Tb, Dy, Ho, Er, Tm, Y
b, Lu, Al, Ga, In, and Tl
At least one trivalent metal selected g) Calcined product of tetrafluoroboric acid compound; hexaflu
Orosilicic acid, hexafluorotitanic acid and hexaflu
Firing of monovalent or divalent metal salts of orozirconic acid
NaX ′, wherein X ′ is Cl, Br or I
Is at least one of h) transitions such as V, Cr, Mn, Fe, Co and Ni
Metal; M (I) X ', M' (II) X "₂, M (III)
X ′ ″₃, A, where M (I) is Li, Na, K, R
at least one selected from the group consisting of b and Cs
Is an alkali metal and M '(II) is Be and Mg.
At least one divalent metal selected from the group consisting of
However, M (III) is composed of Al, Ga, In, and Tl.
At least one trivalent metal selected from the group
Is a metal oxide, X ', X ", and X'" are
Each of which is selected from the group consisting of F, Cl, Br and I
At least a kind of halogen i) M (I) X ', where M (I) is Rb and Cs
At least one alkali metal selected from the group consisting of
X'is selected from the group consisting of F, Cl, Br and I.
Is at least one type of halogen j) M (II) 'X'₂・ M (II) 'X "₂, In the formula, M (I
I) ′ is selected from the group consisting of Ba, Sr and Ca
At least one alkaline earth metal; X ′ and
X ″ is selected from the group consisting of Cl, Br and I, respectively.
At least one halogen, and X ′ ≠
X ″; further, JP-A-61-264084
LnX ″ described in₃, Where Ln is Sc, Y,
La, Ce, Pr, Nd, Pm, Sm, Gd, Tb, D
From the group consisting of y, Ho, Er, Tm, Yb and Lu
Is at least one rare earth element selected; X ″ is
Less selected from the group consisting of F, Cl, Br and I
Both are a kind of halogen.

(2) M (II) X ₂ · aM (II) X ′ ₂ : x
Eu ²⁺ (wherein M (II) is at least one alkaline earth metal selected from the group consisting of Ba, Sr and Ca; X and X ′ are at least selected from the group consisting of Cl, Br and I) A kind of halogen, and X
≠ X ′; and a is 0.1 ≦ a ≦ 10.0 and x is 0 <x ≦ 0.2), and a divalent europium-activated alkaline earth metal halide fluorescence Further, the phosphor may contain the following additives.

A) M (I) X ', where M (I) is Rb
And at least one alkali metal selected from the group consisting of Cs; X'is at least one halogen selected from the group consisting of F, Cl, Br and I b) KX ", MgX '" ₂ , M ( III) X ″ ″ ₃ , in the formula,
M (III) is at least one trivalent metal selected from the group consisting of Sc, Y, La, Gd and Lu;
X ″, X ′ ″ and X ″ ″ are all at least one halogen selected from the group consisting of F, Cl, Br and I c) B, an oxide such as SiO ₂ , P ₂ O ₅ or LiX ″ , Na
X ″, where X ″ is at least one halogen selected from the group consisting of F, Cl, Br and I d) SiO; SnX ″ ₂ , where X ″ is F, Cl, Br
And e) CsX ″, SnX ″ ″ ₂ , wherein X ″ and X ′ ″ are at least one halogen selected from the group consisting of
Each is at least one halogen selected from the group consisting of F, Cl, Br and I;
CsX ″, L described in 1-235487
n ³⁺ , wherein X ″ is at least one halogen selected from the group consisting of F, Cl, Br and I; Ln is Sc, Y, Ce, Pr, Nd, Sm, Gd, Tb, D
It is at least one rare earth element selected from the group consisting of y, Ho, Er, Tm, Yb and Lu.

(3) LnOX: xA (where Ln is L
at least one of a, Y, Gd, and Lu; X at least one of Cl, Br, and I; A is Ce
And at least one of Tb; x is 0 <x <0.
1. The rare earth element-activated rare earth oxyhalide phosphor represented by the composition formula (1).

(4) M (II) OX: xCe (wherein M
(II) is Pr, Nd, Pm, Sm, Eu, Tb, Dy,
At least one metal oxide selected from the group consisting of Ho, Er, Tm, Yb, and Bi; X is Cl, B
at least one of r and I; x is 0 <x
A cerium-activated trivalent metal oxyhalide phosphor represented by the composition formula of <0.1).

(5) M (I) X: xBi (wherein M
(I) is at least one alkali metal selected from the group consisting of Rb and Cs; X is at least one halogen selected from the group consisting of Cl, Br and I; and x is 0 <x ≦ 0. It is a numerical value in the range of 2)
A bismuth-activated alkali metal halide phosphor represented by the following composition formula.

(6) M (II) ₅ (PO ₄ ) ₃ X: xEu ²⁺
(In the formula, M (II) is at least one alkaline earth metal selected from the group consisting of Ca, Sr, and Ba;
X is at least one halogen selected from the group consisting of F, Cl, Br and I; and x is a numerical value in the range of 0 <x ≦ 0.2). Alkaline earth metal halophosphate phosphor.

(7) M (II) ₂ BO ₃ X: xEu ²⁺ (wherein M (II) is at least one alkaline earth metal selected from the group consisting of Ca, Sr and Ba; X is A divalent europium-activated alkaline earth metal represented by the composition formula: at least one halogen selected from the group consisting of Cl, Br and I; x is a numerical value in the range of 0 <x ≦ 0.2. Haloborate phosphor.

(8) M (II) ₂ (PO ₄ ) ₃ X: xEu ²⁺
(In the formula, M (II) is at least one alkaline earth metal selected from the group consisting of Ca, Sr, and Ba;
X is at least one halogen selected from the group consisting of Cl, Br and I; x is a numerical value in the range of 0 <x ≦ 0.2), and the divalent europium-activated alkaline earth represented by the composition formula Metallohalophosphate phosphors.

(9) M (II) HX: xEu ²⁺ (wherein M
(II) is at least one alkaline earth metal selected from the group consisting of Ca, Sr and Ba; X is Cl,
At least one halogen selected from the group consisting of Br and I; x is a numerical value in the range of 0 <x ≦ 0.2) hydrogenated divalent europium-activated alkaline earth metal Halide phosphor.

(10) LnX ₃ · aLn'X ' ₃ : xCe
³⁺ , (wherein Ln and Ln ′ are Y, La, G
at least one rare earth element selected from the group consisting of d and Lu; X and X ′ are respectively F, Cl,
At least one halogen selected from the group consisting of Br and I, and X ≠ X ′; and a is a numerical value in the range of 0.1 <a ≦ 10.0, and x is 0 <x.
A cerium-activated rare earth composite halide phosphor represented by the composition formula: ≦ 0.2).

(11) LnX ₃ · aM (I) X′3: x
Ce ³⁺ , (wherein Ln is at least one rare earth element selected from the group consisting of Y, La, Gd and Lu; M (I) is selected from the group consisting of Li, Na, K, Cs and Rb. Is at least one alkali metal; X and X'are at least one halogen selected from the group consisting of Cl, Br and I respectively; and a is a numerical value in the range of 0 <a≤10.0. x is 0
A cerium-activated rare earth composite halide-based phosphor represented by the composition formula: <x ≦ 0.2).

(12) LnPO ₄ · aLnX ₃ : xC
e ³⁺ , (wherein Ln is at least one rare earth element selected from the group consisting of Y, La, Gd and Lu;
X is at least one halogen selected from the group consisting of F, Cl, Br and I; and a is 0.1 ≦ a
Cerium-activated rare earth halophosphate phosphor represented by the composition formula: ≦ 10.0, and x is 0 <x ≦ 0.2.

(13) CsX: aRbX ': xEu ²⁺ ,
(Wherein X and X ′ are at least one halogen selected from the group consisting of Cl, Br and I respectively; and a is a numerical value in the range of 0 <a ≦ 10.0,
x is a numerical value in the range of 0 <x ≦ 0.2), which is a divalent europium-activated cesium-rubidium halide phosphor.

(14) M (II) X ₂ · aM (I) X ′:
xEu ²⁺ , where M (II) is at least one alkaline earth metal selected from the group consisting of Ba, Sr and Ca; M (I) is selected from the group consisting of Li, Rb and Cs At least one alkali metal; X
And X'is at least one halogen selected from the group consisting of Cl, Br and I respectively; and a
Is a numerical value in the range of 0.1 ≦ a ≦ 20.0, and x is 0 <
A divalent europium-activated composite halide phosphor represented by the composition formula: x ≦ 0.2).

Among the above stimulable phosphors, it is preferable that the stimulable phosphor particles contain iodine, for example, a divalent europium-activated alkaline earth metal fluoride halide containing iodine. -Based phosphor, divalent europium-activated alkaline earth metal halide-based phosphor containing iodine, rare earth element-activated rare earth oxyhalide-based phosphor containing iodine, and bismuth-activated alkali metal halogen containing iodine The compound-based phosphor is preferable because it exhibits high-intensity stimulated emission, and in the invention according to claim 2,
The photostimulable phosphor is characterized in that it is a Eu-added BaFI compound.

In the present invention, as an example of the binder used in the stimulable phosphor layer, the compounds described in the above-mentioned undercoat layer can be similarly used, and these binders are crosslinked with a crosslinking agent. It can be a stuff.

In the stimulable phosphor layer coating solution, the mixing ratio of the binder and the stimulable phosphor varies depending on the characteristics of the intended radiation image conversion panel, the type of phosphor, etc. The ratio of the binder to 1 is preferably 1 to 20 parts by mass, but the amount of the binder is preferably small from the viewpoint of the brightness and sharpness of the obtained radiation image conversion panel, and it is 2 to 10 from the viewpoint of easy application. The range of parts by mass is more preferable.

Examples of the organic solvent used for preparing the stimulable phosphor layer coating solution include methanol, ethanol,
Lower alcohols such as isopropanol and n-butanol, acetone, methyl ethyl ketone, methyl isobutyl ketone, ketones such as cyclohexanone, esters of lower fatty acids and lower alcohols such as methyl acetate, ethyl acetate and n-butyl acetate, dioxane, ethylene glycol monoethyl Examples thereof include ethers, ethers such as ethylene glycol monomethyl ether, aromatic compounds such as triols and xylols, halogenated hydrocarbons such as methylene chloride and ethylene chloride, and mixtures thereof.

The coating liquid contains a dispersant for improving the dispersibility of the phosphor in the coating liquid, and a binder between the binder and the phosphor in the stimulable phosphor layer after formation. Various additives such as a plasticizer for improving the binding strength may be mixed. Examples of dispersants used for such purpose include phthalic acid, stearic acid, caproic acid, lipophilic surfactants and the like. Examples of plasticizers include phosphoric acid esters such as triphenyl phosphate, tricresyl phosphate, diphenyl phosphate; phthalic acid esters such as diethyl phthalate and dimethoxyethyl phthalate; ethyl phthalyl glycolate and butyl phthalyl butyl glycolate. And a glycolic acid ester such as; and a polyester of triethylene glycol and adipic acid, a polyester of polyethylene glycol and an aliphatic dibasic acid such as a polyester of diethylene glycol and succinic acid, and the like.

The coating liquid for the stimulable phosphor layer is prepared, for example, by a ball mill, a bead mill, a sand mill, an attritor, a three roll mill, a high speed impeller disperser, and Kady.
It is performed using a mill or a dispersing device such as an ultrasonic dispersing machine.

A coating film is formed by uniformly coating the surface of the undercoat layer with the coating liquid prepared as described above. As a coating method that can be used, a known coating means can be used, for example, a doctor blade,
A roll coater, a knife coater, a comma coater, a lip coater, etc. can be mentioned.

The film thickness of the stimulable phosphor layer varies depending on the characteristics of the intended radiation image conversion panel, the type of stimulable phosphor, the mixing ratio of the binder and the phosphor, etc., but is usually 10
To 1000 μm, more preferably 10 to 500 μm
m.

The phosphor sheet having the stimulable phosphor layer coated on the support is cut into a predetermined size. Although any general method can be used for cutting, a cosmetic cutting machine, a punching machine or the like is preferable in terms of workability and accuracy.

The radiation image conversion panel of the present invention is preferably provided with a protective film (also referred to as a protective film) for physically and chemically protecting the surface of the stimulable phosphor layer. It can be appropriately selected depending on the purpose, use and the like.

As the protective layer provided in the radiation image conversion panel of the present invention, a polyester film or polymethacrylate having an excitation light absorption layer having a haze ratio of 5% or more and less than 60% as measured by the method described in ASTM D-1003. A film, a nitrocellulose film, a cellulose acetate film or the like can be used, but a stretched film such as a polyethylene terephthalate film or a polyethylene naphthalate film is preferable as the protective layer in terms of transparency and strength, and further, these From the viewpoint of moisture resistance, a polyethylene terephthalate film or a vapor-deposited film obtained by vapor-depositing a thin film of a metal oxide, silicon nitride or the like on a polyethylene terephthalate film is more preferable.

The haze ratio of the film used in the protective layer can be easily adjusted by selecting the haze ratio of the resin film used, and a resin film having an arbitrary haze ratio can be easily obtained industrially. . As a protective film for a radiation image conversion panel, one having a very high optical transparency is supposed. As such a highly transparent protective film material, various plastic films having a haze value in the range of 2 to 3% are commercially available. The preferred haze ratio for obtaining the effect of the present invention is 5%.
Or more and less than 60%, more preferably 10% or more 5
It is less than 0%. If the haze ratio is less than 5%, the effect of eliminating image unevenness and linear noise is low, and if it is 60% or more, the effect of improving sharpness is impaired, which is not preferable.

In the present invention, the film used for the protective layer has an optimum moisture-proof property by laminating a plurality of resin films or vapor-deposited films obtained by vapor-depositing a metal oxide on the resin film, in accordance with the required moisture-proof property. Can be
The moisture permeability is preferably at least 50 g / m ² · day or less in consideration of prevention of moisture deterioration of the stimulable phosphor. The method for laminating the resin film is not particularly limited, and any known method may be used.

Further, by providing the excitation light absorption layer between the laminated resin films, the excitation light absorption layer is protected from physical impact and chemical alteration, and stable plate performance can be maintained for a long time, which is preferable. Further, the excitation light absorption layer may be provided at a plurality of positions, or the adhesive layer for laminating may contain a coloring agent to form the excitation light absorption layer.

The protective film may be adhered to the stimulable phosphor layer via an adhesive layer, but the structure is provided so as to cover the phosphor surface (hereinafter, also referred to as sealing or sealing structure). Is more preferable. In sealing the phosphor plate, any known method may be used, but the outermost resin layer on the side in contact with the phosphor sheet of the moisture-proof protective film is a resin film having heat-sealing property, and it is moisture-proof. This is one of the preferable modes in that the property protection film can be fused and the work of sealing the phosphor sheet can be made efficient.
Furthermore, the moisture-proof protective film is arranged on the upper and lower sides of the phosphor sheet, and the peripheral edge thereof is an area outside the peripheral edge of the phosphor sheet. The sealing structure is preferable because moisture can be prevented from entering from the outer peripheral portion of the phosphor sheet.
Further, the moisture-proof protective film on the support surface side is 1
By using a laminated moisture-proof film obtained by laminating aluminum films having more layers, it is possible to more reliably reduce the ingress of moisture, and this sealing method is also easy in terms of work, which is preferable. In the method of heat fusion with the impulse sealer, heat fusion in a reduced pressure environment is more preferable in terms of preventing displacement of the phosphor sheet in the moisture-proof protective film and eliminating moisture in the atmosphere.

It is preferable that the resin layer, which is the outermost layer having the heat-fusible property, on the side of the moisture-proof protective film in contact with the phosphor surface and the phosphor surface are not adhered. The term "non-adhesive" as used herein means that, even if the phosphor surface is microscopically in point contact with the moisture-proof protective film, the phosphor surface and the moisture-proof protective film are almost discontinuous optically and mechanically. It is a state that can be treated as a body. Further, the above-mentioned resin film having heat-fusible property is a resin film that can be fused by a commonly used impulse sealer, and for example, ethylene vinyl acetate copolymer (EVA), polypropylene (PP) film, polyethylene ( PE) film and the like can be mentioned, but the present invention is not limited thereto.

[0072]

[Preparation of europium-activated barium fluoroiodide phosphor]

(Preparation of Phosphor 1) To synthesize a europium-activated barium fluoroiodide stimulable phosphor precursor, 2780 ml of BaI ₂ aqueous solution (3.6 mol / L) and EuI ₃ aqueous solution (0.15 mol / L) were prepared. ) 27 ml was placed in the reactor.
The reaction mother liquor in this reactor was kept warm at 83 ° C. with stirring. Next, ammonium fluoride aqueous solution (8 mol / L)
322 ml was poured into the reaction mother liquor using a roller pump to form a precipitate. Keep warm and stir 2 after injection
The precipitate was aged for a period of time. Next, the precipitate was separated by filtration, washed with ethanol, and then vacuum dried to obtain europium-activated barium fluoroiodide crystals. In order to prevent changes in particle shape due to sintering during firing, and changes in particle size distribution due to fusion between particles, 0.2% by mass of ultrafine alumina powder was added, and the surface of the crystal was thoroughly stirred with a mixer. Ultra fine particles of alumina were uniformly adhered to the surface. This was packed in a quartz boat, and fired at 850 ° C. for 2 hours in a hydrogen gas atmosphere using a tube furnace, and then classified to be europium-activated barium fluoroiodide phosphor 1 having an average particle size of 3 μm. Was prepared.

(Preparation of Phosphors 2 to 7) In the preparation of the above-mentioned phosphor 1, the reaction conditions, the sintering conditions, the addition amount of the ultrafine alumina powder and the classification conditions are appropriately changed or combined to obtain an average particle size of After preparing a phosphor of 15 μm, it was classified in ethanol by a sedimentation method to obtain 1 μm, 8 μm, 10 μm, 15 μm, 20 μm, respectively.
50 μm phosphor particles 2 to 7 were prepared.

[Preparation of Radiation Image Conversion Panel 1] (Preparation of Phosphor Layer Coating Solution 1)
00g and polyester resin (Byron 30 manufactured by Toyobo Co., Ltd.)
0) as a solid content and 10.0 g were added to a mixed solvent of methyl ethyl ketone-toluene (1: 1), dispersed by a propeller mixer, and the viscosity was adjusted to 50 Pa · s,
A phosphor layer coating solution 1 was prepared.

(Preparation of phosphor sheet 1) Using the phosphor layer coating liquid 1 prepared above, a polyethylene terephthalate support having a thickness of 250 μm was coated with a doctor blade to give a coating width of 1000 mm and a film thickness of 230 μm. After coating in this manner, it was immediately dried at 60 ° C. for 30 minutes to form a phosphor layer 1, which was used as a phosphor sheet 1.

Next, a polyester adhesive is applied to one surface of a polyethylene terephthalate film having a thickness of 10 μm, the adhesive surface is brought into close contact with the phosphor layer surface of the phosphor sheet 1 prepared above, and pressure-bonding treatment is performed using a laminator. ,
The protective layer was attached.

(Production of Radiation Image Conversion Panel 1) The above-prepared phosphor sheet 1 was cut into squares each having a side of 20 cm to obtain a radiation image conversion panel 1.

[Production of Radiation Image Conversion Panels 2 and 3] In the production of the above radiation image conversion panel 1, instead of Phosphor 1 (average particle size: 3 μm), Phosphor 3 (average particle size: 8 μm) was used. ), Phosphor 5 (average particle size: 1
Radiation image conversion panels 2 and 3 were produced in the same manner except that the thickness was changed to 5 μm.

[Production of Radiation Image Conversion Panel 4] (Preparation of Phosphor Layer Coating Liquid 4) Phosphor 1 (Average Particle Diameter: 3)
25 g, and phosphor 3 (average particle size: 8 μm) 3
5 g, 40 g of phosphor 5 (average particle size: 15 μm) and 10.0 g of a polyester resin (Vylon 300 manufactured by Toyobo Co., Ltd.) as solid content were added to a methyl ethyl ketone-toluene (1: 1) mixed solvent, and a propeller mixer was added. And the viscosity was adjusted to 50 Pa · s to prepare a phosphor layer coating liquid 4.

(Production of Radiation Image Conversion Panel 4) In the same manner as in the production of the radiation image conversion panel 1, except that the phosphor layer coating liquid 1 was used in place of the phosphor layer coating liquid 1 prepared above. A radiation image conversion panel 4 was produced.

[Preparation of Radiation Image Conversion Panel 5] In the preparation of the radiation image conversion panel 4, the composition of the phosphor is 20 g of phosphor 2 (average particle diameter: 1 μm), 35 g of phosphor 4 (average particle diameter: 10 μm) and 45 g of phosphor 6
A radiation image conversion panel 5 was produced in the same manner except that the average particle diameter was changed to 20 μm.

[Preparation of Radiation Image Conversion Panel 6] (Preparation of Phosphor Layer Coating Liquid 6) Phosphor 1 (Average Particle Diameter: 3)
25 g, and phosphor 3 (average particle size: 8 μm) 3
5 g, 40 g of phosphor 5 (average particle size: 15 μm) and 10.0 g of a polyester resin (Vylon 300 manufactured by Toyobo Co., Ltd.) as solid content were added to a methyl ethyl ketone-toluene (1: 1) mixed solvent, and a propeller mixer was added. And the viscosity was adjusted to 20 Pa · s to prepare a phosphor layer coating liquid 6.

(Preparation of Phosphor Sheet 6) Using the above-prepared phosphor layer coating solution 6, a doctor blade was used to coat a polyethylene terephthalate support (protective layer) having a thickness of 10 μm with a coating width of 1000 mm. Is 230μ
It was applied so that it would be m. Then, in order to immediately prevent the solvent from evaporating from the surface of the phosphor layer, the surface of the phosphor layer is covered with a solvent-impermeable sheet and allowed to stand at room temperature for 10 hours. Was granted. Then, after leaving still, it was dried at 60 ° C. for 30 minutes to prepare a phosphor sheet 6.

Next, a polyester adhesive is applied to one surface of a polyethylene terephthalate film having a thickness of 250 μm, the adhesive surface is adhered to the phosphor layer surface of the phosphor sheet 6 prepared above, and pressure-bonding treatment is performed using a laminator. , The support was laminated. When used, the top and bottom were inverted and the 10 μm PET support surface (protective layer) was used as the front surface side.

(Preparation of Radiation Image Conversion Panel 6) Using the phosphor sheet 6 prepared above, the radiation image conversion panel 1
A radiation image conversion panel 6 was produced in the same manner as in the production method of 1.

[Production of Radiation Image Conversion Panels 7 and 8] In the production of the radiation image conversion panel 6, the phosphor sheet was similarly prepared except that the constitution of each phosphor particle in the phosphor layer was changed as follows. 7 and 8 and radiation image conversion panels 7 and 8 were produced.

(Fluorescent Particles of Radiation Image Conversion Panel 7)
20 g of phosphor 2 (average particle size: 1 μm), phosphor 4
35 g of (average particle diameter: 10 μm) and 45 g of phosphor 6 (average particle diameter: 20 μm) were used.

(Fluorescent Particles of Radiation Image Conversion Panel 8)
20 g of phosphor 2 (average particle size: 1 μm), phosphor 4
35 g of (average particle diameter: 10 μm) and 45 g of phosphor 7 (average particle diameter: 50 μm) were used.

<< Measurement of Average Particle Size A and Average Particle Size B of Each Phosphor Sheet >> The average particle of the stimulable phosphor in the region of 50 μm from the surface layer side to the support surface side according to the method described below. The diameter A and the average particle diameter B of the stimulable phosphor in the region of 50 μm from the support surface side to the surface layer surface side were measured.
Since the phosphor sheets 6 to 8 are used upside down when used, the average particle size of the 10 μm PET support surface side is the average particle size A, and the average particle size of the phosphor layer surface side is the average particle size. It was set to B.

The average particle diameter A of the stimulable phosphor in the region of 50 μm from the surface side of each phosphor sheet to the support surface side.
Is calculated from the surface of the phosphor layer of each phosphor sheet by
The solution was precisely dissolved to a depth of μm using methyl ethyl ketone, and the solution containing the eluted phosphor was filtered, washed with methyl ethyl ketone, and then dried at 100 ° C. for 10 hours.
Then, this dried product was used as a particle size measuring device using a light scattering particle size measuring device LA-910 manufactured by Horiba Ltd.
The particle size of 500 phosphor particles was measured, and the average particle size A (μm) was determined from the average value.

Next, the average particle diameter B was precisely dissolved using methyl ethyl ketone so that the phosphor layer on the support surface side remained 50 μm thick from the surface of each phosphor sheet. Then
The remaining 50 μm-thick photostimulable phosphor layer was dissolved with methyl ethyl ketone, the eluate was filtered and washed with methyl ethyl ketone, and the obtained phosphor was heated to 100 ° C.
Dry for 10 hours. Then, in the same manner as described above, the particle size of 500 phosphor particles was measured, and the average particle size B was determined from the average value.

Table 1 shows the measurement results obtained as described above. << Characteristic Evaluation of Radiation Image Conversion Panel >> The radiation image conversion panels 1 to 8 produced as described above were evaluated for brightness and sharpness according to the methods described below.

(Measurement of Luminance) With respect to each radiation image conversion panel, the luminance was measured according to the following method.

For the brightness measurement, for each radiation image conversion panel, X-rays with a tube voltage of 80 kVp were irradiated to the phosphor sheet support surface side, and then the panel was irradiated with He-Ne laser light (63
3 nm) for excitation, and stimulated emission emitted from the phosphor layer is received by a photodetector (photoelectron image multiplier with spectral sensitivity S-5), its intensity is measured, and this is referred to as luminance. It was defined and displayed as a relative value with the brightness of the radiation image conversion panel 1 as 100.

(Evaluation of Sharpness) Regarding the sharpness, X-rays with a tube voltage of 80 kVp were irradiated to the phosphor sheet support surface side of each radiation image conversion panel through a lead MTF chart, and then the panel was irradiated with a He-Ne laser. Light (633nm)
The stimulated emission emitted from the phosphor layer is received by a photodetector (photoelectron image multiplier with spectral sensitivity S-5) and converted into an electric signal, which is converted from analog to digital. Recorded on a magnetic tape, the magnetic tape was analyzed by a computer, and the modulation transfer function (MTF) at 1 cycle / mm of the X-ray image recorded on the magnetic tape was examined. The measurement was performed, and the average value (average MTF value) was defined as the sharpness, and displayed as a relative value with the sharpness of the radiation image conversion panel 1 being 100.

Table 1 shows the results obtained as described above.

[0097]

[Table 1]

As is clear from Table 1, the stimulable phosphor layer of the present invention has a particle size ratio (A / B) of the average particle size A and the average particle size B of the stimulable phosphor particles of 2 10 to 10, having a gradient particle size distribution in which the stimulable phosphor particle diameter changes without having an interface from the surface layer side to the support surface side, and the average particle diameter B of the stimulable phosphor is 1 It can be seen that the radiation image conversion panel having a thickness of 10 μm has higher brightness and superior sharpness as compared with the comparative example.

[0099]

According to the present invention, it is possible to provide a radiation image conversion panel excellent in brightness and sharpness and a manufacturing method thereof.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C09K 11/61 CPF C09K 11/61 CPF G01T 1/00 G01T 1/00 B G03B 42/02 G03B 42/02 BF term (reference) 2G083 AA03 BB01 CC02 CC04 DD02 DD11 DD12 DD16 EE02 EE03 2H013 AC01 4H001 CA02 CA04 CA08 XA09 XA53 XA56 YA63

Claims (3)

[Claims] 1. In a radiation image conversion panel having a stimulable phosphor layer containing a stimulable phosphor dispersed in a binder on a support, the stimulable phosphor layer is supported from the surface side. Particle size ratio of the average particle size A of the stimulable phosphor in the region of 50 μm on the body surface side and the average particle size B of the stimulable phosphor in the region of 50 μm from the support surface side to the surface layer side. (A /
B) is from 2 to 10, has a gradient particle size distribution in which the particle size of the stimulable phosphor changes from the surface layer side toward the support surface side without having an interface, and the average particle of the stimulable phosphor is Diameter B is 1
A radiation image conversion panel having a thickness of 10 μm. 2. The stimulable phosphor is Eu-activated BaFI.
The radiation image conversion panel according to claim 1, wherein 3. The radiation image conversion panel according to claim 1 or 2, wherein at least two kinds of stimulable phosphors having different particle sizes are mixed, coated on a temporary support and dried,
A method for manufacturing a radiation image conversion panel, which is manufactured by reattaching it on another support.