JP2002131495A - Radiation image conversion panel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radiation image conversion panel capable of preventing lowering of sharpness caused by scattering and irregular reflection of laser light for excitation and improving brightness. SOLUTION: The radiation image conversion panel comprises a stimulable phosphor layer 4 consisting of material with Eu-activated BaFI as the main component by way of a reflection layer 2 and an underlaid layer 3, a protection layer 5 is formed so as to cover the stimulable phosphor layer 4 and the radiation energy absorbed by the stimulable phosphor layer 4 is discharged as stimulated light by excited light such as laser light. In each of the underlaid layer 3 and the protection layer 5, the specific coloring agent absorbing the excited light is included with a specific fraction. By setting the absorbance of the reflection of excited light in the reflection layer 2/underlaid layer 3 to be larger than the absorbance of transmission of excited light in the protection layer and setting the absorbance of the coloring agent in excited light average wavelength region larger than the absorbance in the absorbance in the stimulable luminescence average wavelength region, and setting the thickness of the stimulable phosphor layer 4 to be 230 nm or lower, both of sharpness and brightness are improved.

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 more particularly to a radiation image conversion panel excellent in the balance between the emission luminance and sharpness of a stimulable phosphor.

[0002]

2. Description of the Related Art Radiation images such as X-ray images are widely used for diagnosing diseases and the like. As a method for obtaining such X-ray images, X-rays passing through a subject are irradiated onto a phosphor layer (fluorescent screen). Developing by irradiating the visible light emitted from the phosphor layer to a film using a silver salt in the same manner as a normal photograph,
So-called radiography is used. However, in recent years, a method has been devised for directly taking out an image from the phosphor layer without using a film coated with a silver salt.

This method is disclosed, for example, in US Pat.
No. 527 and JP-A-55-12144, specifically, a radiation image conversion panel containing a stimulable phosphor is used. The body layer is irradiated with radiation transmitted through the subject to accumulate radiation energy corresponding to the radiation transmission density of each part of the subject, and then the stimulable phosphor layer is exposed to visible light,
By exciting the radiation energy accumulated in the stimulable phosphor layer as stimulable luminescence by exciting the electromagnetic wave (excitation light) such as infrared rays in a time series manner, a signal based on the intensity of the light is converted into, for example, a photoelectric signal. This is converted into an electric signal, and the electric signal is reproduced as a visible image on a recording material such as a photosensitive film or a display device such as a CRT.

A radiation image conversion panel using such a stimulable phosphor emits accumulated energy by scanning with excitation light after accumulating radiation image information. Therefore, the radiation image is accumulated again after scanning. Can be used repeatedly. Therefore, compared to the conventional radiographic method using a combination of a radiographic film and an intensifying screen, it is possible to obtain a radiographic image with a much smaller amount of information with a much smaller exposure dose. While the radiographic film is consumed for each photographing operation, the radiographic image conversion method can repeatedly use the radiographic image conversion panel, which is advantageous in terms of resource conservation and economic efficiency.

The stimulable phosphor used in the radiation image conversion panel emits stimulable light when irradiated with radiation and then with excitation light. However, in practice, the stimulable phosphor has a wavelength of 400 to 900 nm. 300 with excitation light in range
Phosphors that exhibit stimulated emission in the wavelength range of -500 nm are commonly used. Here, an example of a stimulable phosphor conventionally used in a radiation image conversion panel is described in the following (1).
To (14).

(1) (Ba _1-x , M ^{II +} _x ) FX: yA described in JP-A-55-12145 (where M ^{II +} is Mg, Ca, Sr, Zn and Cd) At least one, X is at least one of Cl, Br, and I, A is Eu, Tb, Ce, Tm, Dy, P
At least one of r, Ho, Nd, Yb and Er, x and y are respectively 0 ≦ x ≦ 0.6 and 0 ≦ y ≦
A rare earth element-activated alkaline earth metal fluorohalide phosphor represented by a composition formula:

Further, this phosphor has the following (a) to
An additive as shown in (n) may be contained.

(A) As described in JP-A-56-74175.
X ', BeX ", M^{II I}X '' '_Three(However,
X ', X "and X"' are Cl, Br and I, respectively.
At least one of M^IIIIs a trivalent metal), (b)
Be described in JP-A-55-160078.
O, BgO, CaO, SrO, BaO, ZnO, Al_Two
O_Three, Y_TwoO_Three, La_TwoO_Three, In_TwoO_Three, SiO_Two, Ti
O_Two, ZrO_Two, GeO_Two, SnO_Two, Nb_TwoO_Five, Ta_TwoO_Five
And ThO_TwoMetal oxides such as (c) JP-A-56-
No. 116777, Zr, Sc,
(D) It is described in JP-A-57-23673.
B, (e) described in JP-A-57-23675.
As, Si, (f) JP-A-58-206678
ML described in the report (where M is Li, Na,
At least selected from the group consisting of K, Rb, and Cs
Is also a kind of alkali metal, L is Sc, Y, La, Ce, P
r, Nd, Pm, Sm, Gd, Tb, Dy, Ho, E
r, Tm, Yb, Lu, Al, Ga, In, and Tl
At least one trivalent metal selected from the group consisting of
(G) It is described in JP-A-59-27980.
Calcined product of tetrafluoroborate compound, (h) JP-A-5
Hexafluoro described in JP-A-9-27289
Silicic acid, hexafluorotitanic acid and hexafluoro
Calcined product of monovalent or divalent metal salt of zirconate,
(I) It is described in JP-A-59-56479.
NaX '(where X' is a small number of Cl, Br and I)
At least one kind), (j) JP-A-59-56480.
V, Cr, Mn, Fe, Co and N described in
transition metal such as i, (k) JP-A-59-75200
M listed in the report^IX ', M'^IIX ", M ^IIX '' ', A
(However, M^IIs Li, Na, K, Rb, and Cs
At least one alkali metal selected from the group consisting of
M '^IIIs at least one selected from the group consisting of Be and Mg
A kind of divalent metal, M^IIAre Al, Ga, In, and
At least one trivalent selected from the group consisting of Tl
Genus, A is a metal oxide, X ', X "and X'" are each
Selected from the group consisting of F, Cl, Br and I
At least one type of halogen), (l) JP-A-60-1011
M described in No. 73^IX '(however, M ^IIs R
at least one member selected from the group consisting of b and Cs
The alkali metal, X ', consists of F, Cl, Br and I
At least one halogen selected from the group), (m)
M described in JP-A-61-23679.^II'X'
_Two・ M^II'X "_Two(However, M^II'Is Ba, Sr and Ca
At least one alkaline earth element selected from the group consisting of
Metals, X 'and X "are from Cl, Br and I respectively
At least one halogen selected from the group consisting of
X '≠ X "), (n) JP-A-61-26408
LnX "described in the specification of No. 4_Three(However, Ln is
Sc, Y, La, Ce, Pr, Nd, Pm, Sm, G
d, Tb, Dy, Ho, Er, Tm, Yb and Lu
At least one rare earth element selected from the group consisting of
X "is selected from the group consisting of F, Cl, Br and I
At least one halogen).

(2) M ^II X ₂ .a M ^II X ' ₂ : xEu ²⁺ described in JP-A-60-84381 (where M ^II is selected from the group consisting of Ba, Sr and Ca) At least one alkaline earth metal, X and X ′ are at least one halogen selected from the group consisting of Cl, Br and I, and X ≠ X ′, a is 0.1 ≦
a ≦ 0.0, x is a numerical value satisfying 0 <x ≦ 0.2) a divalent europium-activated alkaline earth metal halide phosphor represented by a composition formula:

Further, this phosphor has the following (a) to (c).
An additive such as (i) may be included.

(A) JP-A-60-166379
M described^IX '(however, M ^IIs Rb and Cs
At least one alkali gold selected from the group consisting of
The genus X 'is selected from the group consisting of F, Cl, Br and I
At least one type of halogen), (b)
KX ", MgX '' 'described in JP-A-221483
_Two, M^IIIX '' ''_Three(However, M^IIIIs Sc, Y, La, G
at least one member selected from the group consisting of d and Lu
Trivalent metals, X ″, X ″ ′ and X ″ ″ are all F, C
at least one selected from the group consisting of l, Br and I
Species halogen), (c) JP-A-60-228592
B, (d) JP-A-60-22859
SiO described in Japanese Patent Publication No. 3_Two, P_TwoO_FiveOxidation of etc.
(E) described in JP-A-61-120882.
LiX ", NaX" (where X "is F, Cl, B
at least one member selected from the group consisting of r and I
(F) described in JP-A-61-120883.
SiO, (g) JP-A-61-120885
SnX "described in Japanese Patent Publication_Two(However, X "is F,
At least selected from the group consisting of Cl, Br and I
A kind of halogen), (h) JP-A-61-235486.
CsX ", SnX '' 'described in the gazette _Two(However,
X ″ and X ′ ″ are each from F, Cl, Br and I
At least one halogen selected from the group consisting of
(I) It is described in JP-A-61-235487.
CsX ", Ln³⁺(However, X "represents F, Cl, Br and
At least one halogen selected from the group consisting of
And Ln are Sc, Y, Ce, Pr, Nd, Sm, Gd,
Tb, Dy, Ho, Er, Tm, Yb and Lu
At least one rare earth element selected from the group consisting of

(3) LnOX: xA described in JP-A-55-12144 (where Ln is La,
At least one of Y, Gd, and Lu, and X is C
1, at least one of Br and I, A is at least one of Ce and Tb, x is 0 <x <0.1
A rare earth element-activated rare earth oxyhalide phosphor represented by a composition formula:

(4) M ^II OX: xCe described in JP-A-58-69281 (where M ^II is Pr,
Nd, Pm, Sm, Eu, Tb, Dy, Ho, Er, T
at least one metal oxide selected from the group consisting of m, Yb, and Bi; X is at least one of Cl, Br, and I, and x is a numerical formula satisfying 0 <x <0.1). Activated trivalent metal oxyhalide phosphor.

[0014] (5) M is described in JP-A-62-25189 specification ^I X: xBi (However, M at least one alkali metal ^I is selected from the group consisting of Rb and Cs, X is Cl, At least one halogen selected from the group consisting of Br and I, x is a bismuth-activated alkali metal halide phosphor represented by a composition formula of 0 <x ≦ 0.2).

(6) M ^II ₅ (PO ₄ ) ₃ X: xEu ²⁺ described in JP-A-60-141783 (where M ^II is at least selected from the group consisting of Ca, Sr and Ba) A kind of alkaline earth metal, X is F, Cl,
A divalent europium-activated alkaline earth metal halophosphate phosphor represented by a composition formula of at least one halogen selected from the group consisting of Br and I, where x is a numerical value satisfying 0 <x ≦ 0.2).

(7) M ^II ₂ BO ₃ X: xEu ²⁺ described in JP-A-60-157099 (where M ^II
Is at least one alkaline earth metal selected from the group consisting of Ca, Sr and Ba, and X is Cl, Br and I
At least one halogen selected from the group consisting of
Is a divalent europium-activated alkaline earth metal haloborate phosphor represented by a composition formula of 0 <x ≦ 0.2).

(8) M ^II ₂ (PO ₄ ) ₃ X: xEu ²⁺ described in JP-A-60-157100 (where M ^II is at least selected from the group consisting of Ca, Sr and Ba) A kind of alkaline earth metal, X is Cl, Br
And at least one halogen selected from the group consisting of I and I, wherein x is a numerical value satisfying 0 <x ≦ 0.2), a divalent europium-activated alkaline earth metal halophosphate phosphor represented by a composition formula:

(9) M ^II HX: xEu ²⁺ described in JP-A-60-217354 (where M ^II is C
at least one alkaline earth metal selected from the group consisting of a, Sr and Ba; X is at least one halogen selected from the group consisting of Cl, Br and I;
A divalent europium-activated alkaline earth metal hydride halide phosphor represented by a composition formula of <x ≦ 0.2).

[0019] (10) JP-61-21173 Patent LnX disclosed in Japanese ^{_{3 · aLn'X '3: xCe 3+}} ( However, Ln and Ln', respectively Y, La, the group consisting of Gd and Lu X and X ′ are at least one halogen selected from the group consisting of F, Cl, Br and I, respectively, and X ≠ X ′, a is 0.1 <a ≦ 10.0, x is 0
A cerium-activated rare earth composite halide phosphor represented by a composition formula of <x ≦ 0.2).

[0020] (11) JP-61-21182 Patent LnX disclosed in Japanese ^{_{3 · aM I X '3:}} xCe 3+ ( provided that at least Ln is Y, La, selected from the group consisting of Gd and Lu A kind of rare earth element, M ^I is Li, N
at least one alkali metal selected from the group consisting of a, K, Cs and Rb;
at least one halogen selected from the group consisting of l, Br and I, a is 0 <a ≦ 10.0, x is 0 <x ≦
A cerium-activated rare earth composite halide phosphor represented by a composition formula of (a numerical value satisfying 0.2).

(12) LnPO ₄ .aLnX ₃ : xCe ³⁺ described in JP-A-61-40390 (where Ln is at least one rare earth element selected from the group consisting of Y, La, Gd and Lu) Element, X is F, Cl, B
at least one halogen selected from the group consisting of r and I, a is 0.1 ≦ a ≦ 10.0, and x is 0 <x ≦ 0.
A cerium-activated rare earth halophosphate phosphor represented by a composition formula:

(13) CsX: aRbX ': xEu ²⁺ described in JP-A-61-236888 (wherein X and X' are each at least one member selected from the group consisting of Cl, Br and I) A is 0
<A ≦ 10.0, x is a numerical value satisfying 0 <x ≦ 0.2) A divalent europium-activated cesium rubidium halide phosphor represented by a composition formula:

[0023] (14) JP 61-236890 Pat M ^II X ₂ · aM ^I X that are described in ': xEu ²⁺ (However, M ^II is selected from the group consisting of Ba, Sr and Ca at least one alkaline earth metal, M ^I is Li,
At least one alkali metal selected from the group consisting of Rb and Cs, X and X ′ are at least one halogen selected from the group consisting of Cl, Br and I, respectively, a is 0.1 ≦ a ≦ 20.0, x Is a divalent europium-activated composite halide phosphor represented by a composition formula of 0 <x ≦ 0.2).

Among the above-described stimulable phosphors, a divalent europium-activated alkaline earth metal fluorohalide phosphor containing iodine and a divalent europium-activated alkaline earth metal containing iodine are used. Halide-based phosphor,
Rare earth element-activated rare earth oxyhalide-based phosphors containing iodine and bismuth-activated alkali metal halide-based phosphors containing iodine are materials that exhibit stimulated emission with high luminance.

In the method using such a stimulable phosphor, it is desirable to provide a performance that can withstand long-term use without deteriorating the image quality of the radiation image obtained by the radiation image conversion panel. However, the stimulable phosphor used in the manufacture of the radiation image conversion panel generally has a large hygroscopic property, and when left in a room under normal climatic conditions, absorbs moisture in the air and deteriorates significantly with the passage of time.

Specifically, for example, when the stimulable phosphor layer is placed under high humidity, the radiation sensitivity of the phosphor decreases with an increase in absorbed water. Generally, since the latent image of the radiation image recorded on the stimulable phosphor layer retreats with the passage of time after irradiation, the intensity of the reproduced radiation image signal is scanned by the excitation light from the irradiation. However, if the stimulable phosphor layer absorbs moisture, the speed of this latent image regression is further increased, and the reproducibility of a reproduced signal is reduced when a radiation image is read.

Therefore, in order to prevent the stimulable phosphor layer from deteriorating due to moisture absorption, the stimulable phosphor layer is covered with a moisture-proof protective layer having low moisture permeability to reduce the amount of water reaching the phosphor layer. The method of making it take is taken. As the moisture-proof protective layer, a polyethylene terephthalate (PET) film or a polyethylene terephthalate film, or a vapor-deposited film in which a thin film of a metal oxide, silicon nitride, or the like is vapor-deposited on a polyethylene terephthalate (PET) film or a polyethylene terephthalate film is used.

[0028]

However, in the above-mentioned radiation image conversion panel, a laser beam having a high beam convergence is generally used as a light source of excitation light for the stimulable phosphor plate. When scanning with a laser beam through a protective layer made of a film, the excitation light is scattered due to scattering of the excitation laser beam inside the protective layer film, and irregular reflection of the excitation laser beam between the protective layer and the photodetector and peripheral members. Since the stimulable phosphor surface at a position distant from the area where the light is scanned is excited to emit stimulable light, the sharpness is reduced. In addition, even when the protective layer is not formed on the phosphor plate, high sharpness cannot be obtained due to irregular reflection of the excitation laser light between the phosphor plate surface and the photodetector or at a peripheral member. .

Particularly, a stretched film such as a polyethylene terephthalate film or a polyethylene naphthalate film has excellent physical properties as a protective layer in terms of transparency, barrier properties and strength, but has a large refractive index. Because of this, part of the excitation light incident on the inside of the protective film is repeatedly reflected at the upper and lower interfaces of the film, propagates to a place away from the scanned location and emits stimulated emission, and the sharpness is reduced . Also, the excitation light reflected in the opposite direction to the phosphor surface at the upper and lower interfaces of the protective layer is also reflected again between the photodetectors and peripheral members, and the stimulable phosphor at a location further away from the scanned location. This excites the layer and emits stimulated emission, which further reduces sharpness.

Since the excitation light is coherent light having a long wavelength from red to infrared, the amount of light absorbed in the space inside the protective film or in the reader unless the scattered light or reflected light is actively absorbed. Is small and propagates to distant places, causing a reduction in sharpness. Further, when the polyethylene terephthalate film or polyethylene naphthalate film or the like is used as the protective layer, shading other than the radiation image of the subject, that is, image unevenness, linear noise or the like that is considered to be caused during the manufacturing process of the protective layer, etc. There is also the problem of appearing.

For these image unevenness and linear noise,
JP-A-59-23400 and Japanese Patent Publication No. 1-57759
Japanese Patent Application Laid-Open Publication No. Hei 11 (1995) discloses a means for increasing the haze ratio of the protective layer to eliminate the above-mentioned image unevenness and linear noise. However, when the haze ratio of the protective layer is increased, the sharpness is disadvantageously reduced. In order to prevent such sharpness deterioration, the protective film is made thinner,
A method of shortening the propagation distance of the excitation light inside the protective film can be considered, but the effect of this method is small, and conversely, the reduction in moisture resistance and scratch resistance due to the thinning of the protective layer causes a problem.

Regarding improvement of sharpness, Japanese Patent Publication No.
Japanese Patent Application Laid-Open No. Sho 60-2400 discloses a method of coloring any one of a support, an undercoat layer, a phosphor layer, an intermediate layer, and a protective layer of a radiation image conversion panel with a color absorbing excitation light.
Japanese Patent Application Publication No. 20000 discloses a method of coloring the adhesive layer between the phosphor layer and the protective layer. However, when sharpness is increased by these methods, the above-described image unevenness and linear noise become more remarkable. There is a problem that it becomes. When the sharpness is reduced, the image unevenness or the linear noise is remarkable, it becomes a fatal defect as a radiation image conversion panel used for disease diagnosis.

The present invention has been made in view of the above-mentioned problems, and a main object of the present invention is to prevent sharpness from being reduced due to scattering and irregular reflection of excitation laser light and to improve luminance. It is an object of the present invention to provide a radiation image conversion panel capable of performing the above.

[0034]

In order to achieve the above object, the present invention comprises a stimulable phosphor layer provided on a support via a reflective layer and an undercoat layer. A protective layer is formed on the radiation image conversion panel that emits the energy of the radiation absorbed by the stimulable phosphor layer as stimulated emission by excitation light, wherein each of the undercoat layer and the protective layer And an excitation light absorption layer containing a colorant that absorbs the excitation light, and the reflection absorbance of the excitation light in the laminate including the reflective layer and the undercoat layer is an excitation light in the protective layer. The content of the coloring agent is adjusted so as to be equal to or higher than the transmission absorbance of the colorant.

The present invention also provides a stimulable phosphor layer provided with a subbing layer on a support having a reflective function comprising polyethylene terephthalate and containing a large number of air bubbles, with an undercoat layer interposed therebetween. A protective layer is formed on the radiation image conversion panel that emits the energy of the radiation absorbed by the stimulable phosphor layer as stimulated emission by excitation light, wherein each of the undercoat layer and the protective layer A excitation light absorbing layer containing a colorant that absorbs the excitation light at a predetermined ratio, and the reflection absorbance of the excitation light in the laminate including the support and the undercoat layer is such that the protective absorption is The content of the colorant is adjusted so as to be equal to or higher than the transmission absorbance of the excitation light in the layer.

In the present invention, the protective layer may include a structure including the excitation light absorbing layer therein, a structure in which the excitation light absorbing layer is coated on at least one surface of a base resin film, or It is preferable that the resin film is made of any one of the structures containing the coloring agent.

In the present invention, it is preferable that the colorant is selected such that the absorbance of the colorant in the average wavelength region of excitation light is greater than the absorbance in the average wavelength region of stimulated emission.

In the present invention, the stimulable phosphor layer has a thickness of about 250 μm or less, preferably about 230 μm.
m and the stimulable phosphor is Eu-activated BaF
It can be made of a material containing I as a main component.

As described above, according to the present invention, it is possible to balance the absorption of the excitation light and the stimulated emission in the undercoat layer and the protective film, and to improve both the luminance and the sharpness.

[0040]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A radiation image conversion panel according to one embodiment of the present invention will be described below with reference to FIG. FIG. 1 is a sectional view schematically showing the structure of the radiation image conversion panel according to one embodiment of the present invention.

As shown in FIG. 1, in the radiation image conversion panel of the present embodiment, a stimulable phosphor layer 4 is formed on a support 1 via a reflective layer 2 and an undercoat layer 3. The upper part is covered with a protective layer 5. Then, the excitation light from the laser or the like spreads due to scattering or irregular reflection, and is absorbed by the stimulable phosphor layer in an unintended location, and the stimulable phosphor from the stimulable phosphor layer is unnecessary for other structures. The undercoat layer 3 and the protective layer 5 are colored with a predetermined coloring agent so as to prevent a problem such as a reduction in luminance due to absorption,
The degree of coloring is adjusted so that the absorbance of each layer with respect to the excitation light satisfies a predetermined relationship. Hereinafter, each structure constituting the radiation image conversion panel of the present embodiment will be described.

First, various polymer materials are used as the support 1. In particular, in handling as information recording material,
Those which can be processed into a flexible sheet or web are suitable, and from this viewpoint, plastics such as cellulose acetate film, polyester film, polyethylene terephthalate film, polyethylene naphthalate film, polyamide film, polyimide film, triacetate film, polycarbonate film, etc. Films are preferred.

Although the thickness of the support varies depending on the material used, it is generally 80 μm to 1000 μm.
About 80 μm to 500 μm in terms of handling.
m is preferable. The surface of these supports may be a smooth surface or a mat surface for the purpose of improving the adhesion to the stimulable phosphor layer.

Next, the undercoat layer 3 may be a material obtained by laminating a colored film on the support 1 or a material coated with a colored resin, and is a colored resin film containing a colorant. It is desirable that the resin material is formed by applying a resin such as polyester, polyurethane, acrylic, polyvinyl butyral, or epoxy.

The stimulable phosphor layer 4 is formed on the undercoat layer 3. Examples of the binder used for the stimulable phosphor layer 4 include proteins such as gelatin and polydexames such as dextran. Natural polymer substances such as saccharides or gum arabic, and polyvinyl butyral, polyvinyl acetate, nitrocellulose, ethyl cellulose, vinylidene chloride-vinyl chloride copolymer, polyalkyl (meth) acrylate, vinyl chloride-vinyl acetate copolymer, polyurethane, There are binders typified by synthetic polymer substances such as cellulose acetate butyrate, polyvinyl alcohol, and linear polyester.

Particularly preferred among such binders are nitrocellulose, linear polyesters, polyalkyl (meth) acrylates, mixtures of nitrocellulose and linear polyesters, nitrocellulose and polyalkyl (meth) acrylates. And a mixture of polyurethane and polyvinyl butyral. In addition, these binders may be cross-linked by a cross-linking agent.

Next, the method for forming the stimulable phosphor layer 4 will be described. First, the stimulable phosphor and the above binder are added to an appropriate solvent, and these are mixed well to form a binder solution. First, a coating liquid in which phosphor particles and particles of the compound are uniformly dispersed is prepared. In general, the binder is used in an amount of 0.01 to 1 part by mass with respect to 1 part by mass of the stimulable phosphor, but from the viewpoint of sensitivity and sharpness of the obtained radiation image conversion panel, the binder is The amount is preferably as small as possible, and more preferably in the range of 0.03 to 0.2 parts by mass from the viewpoint of ease of application. The preparation of the coating solution for the stimulable phosphor layer is performed using a dispersing device such as a ball mill, a sand mill, an attritor, a three-roll mill, a high-speed impeller disperser, a Kady mill, and an ultrasonic disperser.

Examples of the solvent used for preparing the coating solution for the stimulable phosphor layer 4 include methanol, ethanol,
Lower alcohols such as isopropanol and n-butanol; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone; esters of lower fatty acids such as methyl acetate, ethyl acetate and n-butyl acetate with lower alcohols; dioxane; ethylene glycol monoethyl Examples thereof include ethers, ethers such as ethylene glycol monomethyl ether, aromatic compounds such as triol and xylol, halogenated hydrocarbons such as methylene chloride and ethylene chloride, and mixtures thereof.

The coating solution contains a dispersing agent for improving the dispersibility of the phosphor in the coating solution, and the dispersant between the binder and the phosphor in the stimulable phosphor layer 4 after formation. Various additives such as a plasticizer for improving the bonding strength of the rubber may be mixed. Examples of dispersants used for such purposes include phthalic acid, stearic acid, caproic acid, and lipophilic surfactants. Examples of the plasticizer include phosphates such as triphenyl phosphate, tricresyl phosphate, and diphenyl phosphate; phthalates such as diethyl phthalate and dimethoxyethyl phthalate; ethyl phthalyl ethyl glycolate; and butyl phthalyl butyl glycolate. Glycolic acid esters of
And polyester of polyethylene glycol and aliphatic dibasic acid, such as polyester of triethylene glycol and adipic acid, polyester of diethylene glycol and succinic acid, etc. can be mentioned.

The coating solution prepared as described above is uniformly applied to the surface of the undercoat layer to form a coating film of the coating solution. This coating operation is performed by a normal coating means, for example,
This is performed by using a doctor blade, a roll coater, a knife coater, or the like. Then, the formed coating film is dried by gradually heating to complete the formation of the stimulable phosphor layer 4 on the undercoat layer.

The thickness of the stimulable phosphor layer 4 depends on the characteristics of the target radiation image conversion panel, the type of the stimulable phosphor,
It depends on the mixing ratio of the binder and the stimulable phosphor, etc.
It is preferably selected from the range of about 10 μm to 1000 μm, and more preferably selected from the range of 10 μm to 250 μm.

Then, a protective layer 5 is formed so as to cover the stimulable phosphor layer 4. As the protective layer 5, ASTM D-10
The haze ratio measured by the method described in 03 is 5% or more and 60%
A polyester film, a polymethacrylate film, a nitrocellulose film, a cellulose acetate film, or the like, having less than an excitation light absorbing layer can be used. Among these, a stretched film such as a polyethylene terephthalate film or a polyethylene naphthalate film is preferable as a protective layer in terms of transparency and strength, and in particular,
These polyethylene terephthalate films and vapor-deposited films obtained by vapor-depositing thin films such as metal oxides and silicon nitride on the polyethylene terephthalate film are more preferable from the viewpoint of moisture resistance.

The protective layer 5 can be made to have an optimum moisture-proof property by laminating a plurality of resin films or vapor-deposited films obtained by depositing a metal oxide or the like on the resin film in accordance with the required moisture-proof property. However, in consideration of the moisture absorption deterioration of the stimulable phosphor, it is preferably at least 50 g / m ² · day or less. As a method for laminating the resin film, any generally known method may be used. In addition, in the case of laminating, by providing the excitation light absorbing layer between the laminated resin films, the excitation light absorbing layer is protected from physical impact and chemical deterioration, and maintains stable plate performance for a long time. be able to. Note that the excitation light absorbing layer may be provided at a plurality of locations, or an adhesive layer for lamination may contain a coloring agent to form an excitation light absorbing layer.

In sealing the phosphor plate with the protective film, the phosphor sheet is sandwiched between the upper and lower moisture-proof protective films, and the peripheral portion is heated and fused with an impulse sealer, or between the two heated rollers. Any known method such as a laminating method in which pressure and heat are applied may be used, but moisture proofing is performed by forming the outermost resin layer of the moisture-proof protective film on the side in contact with the phosphor sheet with a resin film having heat-fusibility. The protective film can be fused, and the sealing work of the phosphor sheet is made more efficient. Preferably, a moisture-proof protective film is arranged above and below the phosphor sheet, and a sealing structure is used in which the upper and lower moisture-proof protective films are fused in a region where the periphery is outside the periphery of the phosphor sheet. This can prevent water from entering from the outer peripheral portion of the phosphor sheet.
Furthermore, by making the moisture-proof protective film on the one side of the support a laminated moisture-proof film formed by laminating one or more layers of aluminum film, it is possible to more reliably reduce the ingress of moisture.

In the method of heat-sealing with the impulse sealer, the heat-sealing under a reduced-pressure environment prevents displacement of the phosphor sheet in the moisture-proof protective film and eliminates atmospheric moisture. More preferred in a sense. Also, the outermost layer of the moisture-proof protective film on the side in contact with the phosphor surface and the resin layer having heat-fusibility and the phosphor surface may or may not be adhered. The state of non-adhesion means that even if the phosphor surface and the moisture-proof protective film are microscopically point-contacted, optically and mechanically, the phosphor surface and the moisture-proof protective film are almost discontinuous. It can be handled. The term “heat-fusible film” as used herein refers to a resin film that can be fused with a generally used impulse sealer, such as an ethylene-vinyl acetate copolymer (EVA), a polypropylene (PP) film, or a polyethylene (PE). Examples include, but are not limited to, films.

The haze ratio of the protective film can be easily adjusted by selecting the haze ratio of the resin film to be used, and a resin film having an arbitrary haze ratio can be easily obtained industrially. It is assumed that the protective film of the radiation image conversion panel has a very high optical transparency, and the protective film material having such a high transparency is a plastic having a haze value in the range of 2 to 3%. Various films are commercially available.

In the present embodiment, the protective layer 5 is colored so as to absorb the excitation light. The structure of the colored protective layer 5 contains a coloring agent that selectively absorbs the excitation light. The structure is not limited to a structure having a layer inside, and a structure in which a colorant is applied to one or both surfaces of a resin film serving as a base of the protective layer 5 may be used. Structure.

As the colorant used for the protective film 5, a colorant having a characteristic of absorbing the excitation light in the wavelength region of the excitation light of the radiation image conversion panel is used. Preferably, the light transmittance of the protective layer in the excitation light wavelength region is 97% to 5% of the light transmittance of the equivalent protective layer having no excitation light absorbing layer.
It is desirable to provide the excitation light absorbing layer so as to have a light transmittance of 0%.
If it is less than 50%, the luminance of the radiation image conversion panel rapidly decreases. The reason that the luminance is not significantly reduced at the transmittance of 50% or more is presumed to be related to the fact that the information of the radiation image recorded on the radiation image conversion panel is unevenly distributed on the phosphor plate surface side. Is done.

What kind of coloring agent is used depends on the type of stimulable phosphor used in the radiation image storage panel.
As the stimulable phosphor for the radiation image conversion panel, for example, a phosphor that emits stimulable light in a wavelength range of 300 to 500 nm by excitation light having a wavelength in the range of 400 to 900 nm is usually used. As the agent, an organic or inorganic colorant of blue to green shown below is usually used.

Examples of the blue to green organic colorant include:
Pomelo Fast Blue 3G (manufactured by Hoechst), Estrol Brill Blue N-3RL (manufactured by Sumitomo Chemical Co., Ltd.),
Sumiacryl Blue F-GSL (Sumitomo Chemical Co., Ltd.),
D & C Blue No.1 (National Aniline Co., Ltd.), Spirit Blue (Hodogaya Chemical Co., Ltd.), Oil Blue No.
603 (manufactured by Orient Co., Ltd.), Kiton Blue A (manufactured by Ciba-Geigy), Eizenkatilon Blue GLH (manufactured by Hodogaya Chemical Co., Ltd.), Lake Blue A, F, H (manufactured by Kyowa Sangyo Co., Ltd.) , Rhodaline Blue 6GX (manufactured by Kyowa Sangyo Co., Ltd.), Brimocyanin 6GX (Inabata Sangyo Co., Ltd.)
Brill Acid Green 6BH (Hodogaya Chemical Co., Ltd.), Cyanine Blue BNRS (Toyo Ink Co., Ltd.), Lionol Blue SL (Toyo Ink Co., Ltd.)
Manufactured).

Examples of blue to green inorganic colorants include ultramarine blue, cobalt blue, cerulean blue, chromium oxide, and TiO ₂ —ZnO—CoO—NiO pigments, but are not limited thereto. And preferably copper phthalocyanine.

The absorbance of the colored undercoat layer 3 and the protective layer 5 at the excitation light peak wavelength is measured with a spectrophotometer (for example, U-3300 manufactured by Hitachi, Ltd.) exposing the colored portion. can do. In the measurement, the protective layer 5 may be peeled off and measured using an integrating sphere, and the undercoat layer 3 may be obtained by removing the stimulable phosphor layer 4,
The measurement may be performed by exposing the undercoat layer 3. The effect of the present embodiment can be confirmed by determining the absorbance (reflection absorbance and transmission absorbance) of the measured absorbance value at the excitation light peak wavelength and the absorbance ratio of the stimulated emission peak wavelength. When a phosphor having a plurality of peaks in the stimulated emission wavelength is used, the peak having the highest emission intensity is selected and the peak wavelength is used.

Here, as described in the prior art, JP-A-59-42500 and Japanese Patent Publication No. 1-577
No. 59 discloses a means for increasing the haze ratio of the protective layer 5 to eliminate image unevenness and linear noise. However, in this prior art, the sharpness is reduced. However, according to the present embodiment, image unevenness and linear noise can be eliminated, and the sharpness can be further improved. When the haze ratio is less than 5%, the effect of eliminating image unevenness and linear noise is small, and when the haze ratio is 60% or more, the effect of improving sharpness is reduced. Therefore, the haze ratio is 5% or more and less than 60%. And more preferably 10
% Or more and less than 50%.

Japanese Patent Publication No. 59-23400 discloses a method of coloring a radiation image conversion panel to improve sharpness.
Various embodiments in which each of the phosphor layer, the intermediate layer and the protective layer is colored are described, but the above publication does not describe or suggest specific protective films. Further, if the phosphor layer is merely colored, the sharpness is improved but the luminance is deteriorated, and the balance between the luminance and the sharpness is deteriorated.

On the other hand, as a result of various studies, the present inventors have found that the undercoat layer 3 and the protective layer 5 are colored so as to absorb the excitation light, and the excitation light transmission of the protection layer 5 is performed. When the absorbance and the excitation light reflection absorbance when the reflective layer 2 / undercoat layer 3 are combined are compared, the brightness and sharpness are set by setting the condition of the protective layer absorbance ≦ the lower reflective layer / undercoat layer absorbance. It was determined that the degree could be improved at the same time. Conversely, if the absorbance of the protective layer is greater than the absorbance of the undercoat layer, luminance unevenness tends to occur, making it difficult to obtain a uniform image.

[0066]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to explain the above-mentioned embodiment of the present invention in more detail, an embodiment of the present invention will be described with reference to FIG. FIG. 2 is a diagram showing experimental results for confirming the effect of the radiation image conversion panel of the present embodiment. In this embodiment, the structure of each component, its manufacturing method, and the effect of the radiation image conversion panel of this embodiment will be described.

(Pigment reflection layer) Titanium oxide C manufactured by Ishihara Sangyo Co., Ltd.
100 g of R-50 and 10 of Byron 630 manufactured by Toyobo
0 g of methyl ethyl ketone was added so that the coating viscosity became 20 Ps (poise), and the mixture was dispersed in a ball mill for 10 hours to obtain a reflective layer coating. X30-10 of carbon-containing black polyethylene terephthalate manufactured by Toray Co., Ltd.
The resulting mixture was coated with a doctor blade to a dry film thickness of 100 μm to obtain a support having a pigment reflection layer.

(Foamable support) Bubble is contained in polyethylene terephthalate by the method described in JP-A-3-76727 and JP-A-6-226894, and a 200 μm thick reflective layer is formed with the reflective layer dye. A combined support was made.

(Excitation light absorption layer A) Copper phthalocyanine manufactured by Sanyo Dyestuffs Co., Ltd. and Byron 630 manufactured by Toyobo Co., Ltd. were added to methyl ethyl ketone so that the paint viscosity became 20 Ps (poise), and dispersed by a ball mill for 10 hours. An absorbent paint was obtained. The above-mentioned excitation light absorbing paint was applied on the above-mentioned pigment reflection layer and the foamable support using a doctor blade.

(Preparation of Protective Film) As the protective layer on the phosphor surface side of the phosphor sheet, VMPET12 // VMP
ET12 // PET12 // Sealant film (PE
T: polyethylene terephthalate, sealant film: heat-fusible film using CPP (casting polyproprete) or LLDPE (low-density linear polyethylene), VMPET: alumina-deposited PET (commercial product: manufactured by Toyo Metallizing Co., Ltd.), each resin The number behind the film indicates the thickness (μm) of the film. )It was used.

The above “//” means that the dry lamination adhesive layer has a thickness of 2.5 μm. The adhesive used for dry lamination is a two-component reaction type urethane adhesive. In the adhesive solution used at this time, an organic blue colorant (Zabon Fast Blue 3G,
By adding Hoechst), all of the adhesive layers were used as the excitation light absorbing layer B. The light transmittance of the excitation light absorbing layer B was adjusted by adjusting the amount of addition at this time.

Here, the light transmittance of the excitation light absorbing layer means the light transmittance in the light wavelength region of the He—Ne laser beam (633 nm) as the light transmission of an equivalent protective film having no excitation light absorbing layer. The value was compared with the ratio. At the same time, by changing the dye concentration and the film thickness of the excitation light absorbing layer B, a laminated protective film having a different concentration and film thickness was prepared.

(Synthesis of Phosphor) In order to synthesize a stimulable phosphor precursor of europium-activated barium fluoroiodide,
2780 ml of BaI ₂ aqueous solution (3.6 mol / L) and E
27 ml of a uI ₃ aqueous solution (0.2 mol / L) was charged into the reactor. 83 ° C. while stirring the reaction mother liquor in this reactor
Was kept warm. Ammonium fluoride aqueous solution (8mol / L)
322 ml were injected into the reaction mother liquor using a roller pump to produce a precipitate. Keep warm and stir even after pouring
The sediment was aged continuously for an hour.

The precipitate was separated by filtration, washed with ethanol, and dried under vacuum to obtain europium-activated barium fluorinated barium iodide crystals. In order to prevent a change in particle shape due to sintering during firing and a change in particle size distribution due to inter-particle fusion, 0.2% by mass of ultrafine alumina powder is added, and the mixture is sufficiently stirred with a mixer. Ultrafine alumina powder was uniformly adhered to the surface. This was filled in a quartz boat and 850 in a hydrogen gas atmosphere using a tube furnace.
Calcination was carried out at 2 ° C. for 2 hours to obtain europium-activated barium fluoroiodide phosphor particles. Next, particles having an average particle diameter of 7 μm were obtained by classifying the phosphor particles.

As the phosphor layer forming material, 427 g of the europium-activated barium fluoroiodide phosphor obtained above, 15.8 g of polyurethane resin (Desmolac 4125, manufactured by Sumitomo Bayer Urethane Co., Ltd.), and bisphenol A type epoxy resin 0 g of methyl ethyl ketone-toluene (1:
1) The mixture was added to a mixed solvent and dispersed by a propeller mixer to prepare a coating solution having a viscosity of 25 to 30 Ps (poise). A phosphor layer was formed from the above coating solution using a doctor blade on a support or a support having a reflective layer so as to have a predetermined dry film thickness as shown in FIG.

(Sealing of Phosphor Sheet)
The sheet was cut into a square of 0 cm × 20 cm, and the peripheral edge portion was sealed using an impulse sealer under reduced pressure using a laminated protective film having the above-described various excitation light absorbing layers.
The distance from the fused portion to the peripheral edge of the phosphor sheet was 1 m.
m. The heater of the impulse sealer used for fusion had a width of 8 mm.

(Evaluation of Radiation Image Conversion Panel) The radiation image conversion panel formed by the above method was evaluated for sharpness, image unevenness, linear noise, and luminance. The result will be described with reference to FIG.

(Evaluation of Sharpness) Regarding the sharpness, the radiation image conversion panel was irradiated with X-rays having a tube voltage of 80 kVp through an MTF chart made of lead, and then operated with a panel He-Ne laser beam to excite the fluorescence. The stimulated emission radiated from the body layer is received by the same light receiver as described above, converted into an electric signal, converted into an analog / digital signal, recorded on a hard disk, analyzed by a computer, and analyzed by a computer. The modulation transfer function (MTF) of the line image was examined. The column of sharpness in FIG. 2 shows a spatial frequency of 1 cycle / mm.
Are shown, and the higher the MTF, the better the sharpness. In addition, the MTF here was 10 in Comparative Example 1.
The relative values are shown as 0.

(Evaluation of image unevenness and linear noise) After irradiating the radiation image conversion panel with X-rays having a tube voltage of 80 kVp,
The panel is excited by operating with a He-Ne laser beam (633 nm), and the stimulated emission emitted from the phosphor layer is received by a photodetector (photoelectron image multiplier with a spectral sensitivity of S-5) and converted into an electric signal. Then, this was reproduced as an image by an image reproducing apparatus, printed out by enlarging it twice as large as the output apparatus, and the obtained printed image was visually observed to evaluate the appearance of image unevenness and linear noise. The state where no image unevenness and linear noise were generated at all was evaluated as 0, and the state that generated the most severely was evaluated as 5 and shown in the image unevenness column of FIG.

(Evaluation of Luminance) Sensitivity was measured by irradiating a radiation image conversion panel with X-rays having a tube voltage of 80 kVp, operating the panel with a He-Ne laser beam (633 nm), exciting the panel, and radiating from the phosphor layer. The stimulated emission was received by a photodetector (photoelectron image multiplier with a spectral sensitivity of S-5) and the intensity was measured. The luminance in FIG. 2 is an average value of the entire surface of the radiation image conversion panel when the haze ratio of the protective layer is 40%, and is a relative luminance when the luminance when sealed with the protective film without the excitation light absorbing layer is 100. is there.

As can be seen from FIG. 2, judging based on the luminance and sharpness of Comparative Example 1 in which the reflective layer, the colored undercoat layer and the protective layer colored layer were not formed, the colored undercoat layer or the protective layer colored layer Comparative Examples 2, 3, 6, where no
In 7, 10, and 11, one of the luminance and the sharpness is larger than that of Comparative Example 1, but the other is smaller. Also,
Comparative Examples 4 and 5, in which a colored undercoat layer and a protective layer colored layer are formed, but the protective layer absorbance is greater than the undercoat absorbance.
8 and 9, similarly, one of the luminance and the sharpness is larger than that of the comparative example 1, but the other is conversely smaller. It can be seen that both the luminance and the sharpness cannot be improved under this condition. .

On the other hand, in Examples 1 to 7 in which a colored undercoat layer and a protective layer colored layer were formed and the relationship of the protective layer absorbance ≦ undercoat absorbance was satisfied, both the luminance and the sharpness were the same as those of Comparative Example 1.
It can be seen that both the luminance and the sharpness are improved. Therefore, it can be understood that it is important to adjust the degree of coloring of the undercoat layer and the protective layer so as to satisfy the relationship of absorbance of the protective layer ≦ absorbance of the undercoat in order to improve both the brightness and the sharpness.

Further, comparing Examples 4, 7, and 8 in which the thickness of the stimulable phosphor layer was changed, the excitation light spreads inside the stimulable phosphor layer for the sample having a large thickness of 280 nm. Therefore, the sharpness tends to be worse, and the thickness of the stimulable phosphor layer is preferably about 230 μm or less. In consideration of an error in the manufacturing process, the thickness of the stimulable phosphor layer is approximately Preferably it is 250 μm or less.

Regarding the structure of the support, foamable PET having the function of a reflective layer (Examples 4 to 6) can effectively reflect stimulated emission without providing a separate reflective layer. The luminance is improved as compared with the structure provided with the reflective layer (Examples 1 to 3), and it can be seen that the substrate has excellent characteristics.

Further, although not shown, according to an experiment conducted by the inventor of the present invention, the absorbance at the excitation light peak wavelength of the colorant used for coloring the undercoat layer and the protective layer is larger than the absorbance at the stimulated emission peak wavelength. It has been confirmed that when the ratio is 3 or more, the effect that the sharpness can be improved without lowering the luminance is more preferably exhibited.

[0086]

As described above, according to the radiation image conversion panel of the present invention, it is possible to prevent the sharpness from being reduced due to the diffusion of the excitation laser light and to improve the luminance.

The reason for this is that the undercoat layer and the protective layer are colored under a condition that satisfies the relationship of the undercoat layer absorbance ≧ protective layer absorbance, and the coloring agent is excited light average wavelength region absorbance> stimulated luminescence average wavelength region absorbance. Is selected under the condition that satisfies the relationship of
By setting the thickness of the stimulable phosphor to a predetermined value or less, the diffusion of the excitation light can be prevented, and the stimulable emission of the phosphor can be efficiently emitted to the outside.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically showing a structure of a radiation image conversion panel according to an embodiment of the present invention.

FIG. 2 is a list of experimental results showing the effects of the radiation image conversion panel according to one embodiment of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 support 2 reflection layer 3 undercoat layer 4 stimulable phosphor 5 protective layer

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2G083 AA03 CC01 CC04 CC05 CC06 CC08 DD01 DD02 DD06 DD11 EE02 EE03 2H013 AC01 4H001 CA02 CA08 XA09 XA53 XA56 YA63

Claims (8)

[Claims] 1. A stimulable phosphor comprising a stimulable phosphor layer provided on a support via a reflection layer and an undercoat layer, and a protective layer formed on the stimulable phosphor layer. A radiation image conversion panel that emits the energy of radiation absorbed by a layer as stimulated emission by excitation light, wherein the undercoat layer and the protective layer each include a colorant that absorbs the excitation light. It has an absorption layer,
A radiation image conversion panel, wherein a reflection absorbance of the excitation light in a laminate including the reflection layer and the undercoat layer is equal to or higher than a transmission absorbance of the excitation light in the protective layer. 2. A support comprising polyethylene terephthalate and having a plurality of air bubbles and having a reflection function, comprising a stimulable phosphor layer via an undercoat layer, and a protective layer provided on the stimulable phosphor layer. A radiation image conversion panel, wherein a layer is formed and the energy of the radiation absorbed by the stimulable phosphor layer is emitted as stimulated emission by the excitation light, wherein the undercoat layer and the protective layer each include the excitation light Having a predetermined ratio of a colorant absorbing the excitation light, and the reflection absorbance of the excitation light in the laminated body including the support and the undercoat layer, the excitation light in the protective layer A radiation image conversion panel, wherein the content of the coloring agent is adjusted so as to be equal to or higher than the transmission absorbance of the radiation image. 3. A structure in which the protective layer includes the excitation light absorbing layer therein, a structure in which the excitation light absorbing layer is provided on at least one surface of a base resin film, or 3. The structure having at least one of the structures containing the colorant.
3. A radiation image conversion panel according to item 1. 4. The colorant is selected so that the absorbance of the colorant in the average wavelength region of excitation light is greater than the absorbance in the average wavelength region of stimulated emission. 4. The radiation image conversion panel according to any one of 3. 5. The colorant is selected so that the ratio of the absorbance in the excitation light average wavelength region to the absorbance in the stimulated emission average wavelength region is 3 or more. Radiation image conversion panel. 6. The radiation image conversion panel according to claim 1, wherein the thickness of the stimulable phosphor layer is set to 250 μm or less. 7. The radiation image conversion panel according to claim 1, wherein the thickness of the stimulable phosphor layer is set to 230 μm or less. 8. The radiation image conversion panel according to claim 1, wherein the stimulable phosphor is made of a material containing Eu-activated BaFI as a main component.