JP2001324597A - Radiation image converting panel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve a problem of density nonuniformity when a moisture-proof protection film is used, and a problem of density nonuniformity caused by distribution in a characteristic of a phosphor sheet itself to allow usage in a satisfactory condition for a long period. SOLUTION: In this radiation image converting panel comprising the phosphor sheet provided with a stimulable phosphor layer on a polymer supporting body, and the moisture-proof protection films provided to cover a phosphor face of the phosphor sheet, the phosphor sheet is heat-treated for 12 hours or more at the temperature within a range from 40 deg.C to a glass transition temperature of the polymer supporting body, before the sheet is sealed with the moisture- proof protection film.

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 non-uniform adhesion between a phosphor sheet and a moisture-proof protective film and a luminance unevenness of the phosphor sheet. The present invention relates to a radiation image conversion panel which can be used in a good condition for a long time without causing image unevenness.

[0002]

2. Description of the Related Art Radiation images such as X-ray images are widely used for diagnosis of diseases. In order to obtain this X-ray image, the X-rays that have passed through the subject are applied to a phosphor layer (fluorescent screen)
Thus, a so-called radiograph is used, in which a visible light is generated by this, and this visible light is irradiated and developed on a film using a silver salt in the same manner as when a normal photograph is taken. 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.

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

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

In this method, a radiation image conversion panel containing a stimulable phosphor is used. Radiation transmitted through a subject is applied to the stimulable phosphor layer of the radiation image conversion panel to transmit radiation of each part of the subject. By accumulating radiation energy corresponding to the density, and subsequently exciting the stimulable phosphor with electromagnetic waves (excitation light) such as visible light and infrared light in a time series manner, the stimulable phosphor is accumulated in the stimulable phosphor. The emitted radiation energy is emitted as stimulated emission, and a signal based on the intensity of the light is photoelectrically converted, for example, to obtain an electric signal, and this signal is converted into a visible image on a recording material such as a photosensitive film or a display device such as a CRT. Is to be played as

According to the above radiation image recording / reproducing method,
Compared with the conventional radiographic method using a combination of a radiographic film and an intensifying screen, there is an advantage that a radiographic image rich in information can be obtained with a much smaller exposure dose.

As described above, the stimulable phosphor is a phosphor that emits stimulable light when irradiated with radiation and then with excitation light. However, in practice, excitation light having a wavelength in the range of 400 to 900 nm is used. In general, phosphors exhibiting stimulated emission in the wavelength range of 300 to 500 nm are used.

The following are examples of stimulable phosphors conventionally used in radiation image conversion panels.

(1) As described in JP-A-55-12145.
(Ba_1-X, M²⁺X) F_x: YA (however,
M²⁺Represents a small amount of 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, Pr, H
at least one of o, Nd, Yb, and Er;
And x is 0 ≦ x ≦ 0.6, y is 0 ≦ y ≦ 0.2
Rare earth element activated alkaline earth represented by the composition formula
Metal fluoride halide phosphor;
The following additives may be contained:
X ', BeX ", described in U.S. Pat.
M_ThreeX '"_Three(However, X ', X "and X'" are
Each of at least one of Cl, Br and I,
M_ThreeIs a trivalent metal); JP-A-55-160078
BeO, BgO, CaO, Sr described in the gazette
O, BaO, ZnO, Al_TwoO_Three, Y_TwoO_Three, La_TwoO_Three, I
n_TwoO_Three, SiO_Two, TiO_Two, ZrO_Two, GeO_Two, SnO
_Two, Nb_TwoO5, Ta_TwoO_FiveAnd ThO_TwoSuch as metal oxidation
Product: described in JP-A-56-116777
Zr, Sc; described in JP-A-57-23673.
B; described in JP-A-57-23675.
As, Si; described in JP-A-58-206678.
ML (where M is Li, Na, K, R
at least one selected from the group consisting of b and Cs
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
Described in JP-A-59-27980.
Calcined product of tetrafluoroboric acid compound;
Hexafluorosilicide described in No. 7289
Acid, hexafluorotitanic acid and hexafluorozil
Burned product of monovalent or divalent metal salt of conimic acid;
No. 59-56479 describes NaX '(
X 'is at least one of Cl, Br and I
Species); described in JP-A-59-56480.
Transition of V, Cr, Mn, Fe, Co and Ni
Metal transfer; described in JP-A-59-75200
M¹X ', M'^TwoX ", M^TwoX '", A (where M¹Is
Selected from the group consisting of Li, Na, K, Rb, and Cs
At least one alkali metal,^TwoIs B
at least one selected from the group consisting of e and Mg
A divalent metal; M^TwoAre Al, Ga, In, and Tl
At least one trivalent metal selected from the group consisting of
A is a metal oxide; X ', X ", and X"'
Is selected from the group consisting of F, Cl, Br and I
At least one type of halogen);
M described in Japanese Patent Publication No. 101173¹X '(just
Then M¹Is a small number selected from the group consisting of Rb and Cs
At least a kind of alkali metal; X 'is F, Cl, B
at least one member selected from the group consisting of r and I
Described in JP-A-61-23679.
M^Two'X'_Two・ M^Two'X'_Two(However, M^Two′
At least selected from the group consisting of Ba, Sr and Ca
Are also alkaline earth metals; X 'and X "are
Each selected from the group consisting of Cl, Br and I
At least one kind of halogen and X '≠ X "
Described in JP-A-61-264084.
LnX ″_Three(However, Ln is Sc, Y, L
a, Ce, Pr, Nd, Pm, Sm, Gd, Tb, D
from the group consisting of y, Ho, Er, Tm, Yb and Lu
At least one rare earth element selected; X ″ is
At least one selected from the group consisting of F, Cl, Br and I
(2) It is described in JP-A-60-84381.
M^TwoX_Two・ AM^TwoX '_Two: XEu²⁺(However, M^TwoIs Ba,
At least one selected from the group consisting of Sr and Ca
X and X 'are Cl, Br
At least one halo selected from the group consisting of
X and X ≠ X ′; and a is 0.1
≦ a ≦ 0.0, x is 0 <x ≦ 0.2)
Represented divalent europium activated alkaline earth metal halide
Phosphor; addition of the following to this phosphor
May be contained; Japanese Patent Application Laid-Open No. 60-166379.
M described in the gazette¹X '(where M¹Are Rb and
At least one kind of arc selected from the group consisting of
X 'is composed of F, Cl, Br and I
At least one halogen selected from the group);
K described in Japanese Unexamined Patent Publication No. 60-221483.
X ", MgX '"_Two, M^ThreeX ""_Three(However, M^ThreeIs Sc,
A small number selected from the group consisting of Y, La, Gd and Lu
At least a trivalent metal; X ", X '" and
X ″ is a group consisting of F, Cl, Br and I
Selected from at least one halogen);
B described in JP-A-60-228592;
SiO described in JP-A-60-228593_Two,
P_TwoO_FiveOxides such as those described in JP-A-61-120882
LiX ″ and NaX ″ described, where X ″ is
At least one selected from the group consisting of F, Cl, Br and I
Are also a kind of halogen);
No. 3 JP; JP-A-61-120
No. 885, SnX ″_Two(However,
X "is selected from the group consisting of F, Cl, Br and I
At least one halogen); JP-A-61-23
No. 5486, CsX ″ and SnX ′ ″
_Two(Where X ″ and X ′ ″ are F, Cl, B, respectively)
at least one member selected from the group consisting of r and I
And JP-A-61-235487.
CsX ″, Ln described in the report³⁺(However, X ″
At least one selected from the group consisting of F, Cl, Br and I
Ln is Sc, Y, Ce, P
r, Nd, Sm, Gd, Tb, Dy, Ho, Er, T
at least one selected from the group consisting of m, Yb and Lu
(3) It is described in JP-A-55-12144.
LnOX: xA (where Ln is La, Y, Gd, and
And Lu; X is Cl, Br, and
At least one of I; A is less of Ce and Tb
At least one; and x is 0 <x <0.1)
Rare earth element activated rare earth oxyhalai represented by the composition formula:
(4) described in JP-A-58-69281
M^TwoOX: xCe (where M^TwoIs Pr, Nd, Pm, S
m, Eu, Tb, Dy, Ho, Er, Tm, Yb, and
At least one type of gold oxide selected from the group consisting of
X is at least one of Cl, Br, and I
X is 0 <x <0.1).
Cerium-activated trivalent metal oxyhalide phosphor; (5) described in JP-A-62-25189.
M¹X: xBi (where M¹Is from Rb and Cs
At least one alkali metal selected from the group consisting of
X is a member selected from the group consisting of Cl, Br and I.
At least a halogen; and x is 0 <x ≦
Bismuth represented by a composition formula of 0.2)
(6) described in Japanese Patent Application Laid-Open No. 60-141783.
M^Two _Five(PO_Four)_ThreeX: xEu²⁺(However, M^TwoIs Ca,
At least one selected from the group consisting of Sr and Ba
X is F, Cl, Br and
At least one halogen selected from the group consisting of I
Yes; x is a numerical value in the range of 0 <x ≦ 0.2)
Bivalent europium-activated alkaline earth metal represented by the formula
Lophosphate phosphor; (7) described in JP-A-60-157,099
M^Two _TwoBO_ThreeX: xEu²⁺(However, M^TwoIs Ca, Sr
At least one type of al selected from the group consisting of
Is a potassium earth metal; X consists of Cl, Br and I
X is at least one halogen selected from the group;
0 <x ≦ 0.2).
Divalent europium activated alkaline earth metal haloborate
Phosphor; (8) described in JP-A-60-157100
M^Two _Two(PO_Four)_ThreeX: xEu²⁺(However, M^TwoIs Ca,
At least one selected from the group consisting of Sr and Ba
X is Cl, Br and I
At least one halogen selected from the group consisting of
X is a numerical value in the range of 0 <x ≦ 0.2)
Divalent europium-activated alkaline earth metal halo
Phosphate phosphor; (9) described in JP-A-60-217354
M^TwoHX: xEu²⁺(However, M^TwoAre Ca, Sr and
At least one alkali selected from the group consisting of Ba
X is an earth metal; X is a group consisting of Cl, Br and I
X is 0 <
x is a numerical value in the range of 0.2).
Valent europium activated alkaline earth metal hydride halogenation
(10) described in JP-A-61-21173.
LnX_Three・ ALn'X '_Three: XCe³⁺(However, Ln
And Ln 'consist of Y, La, Gd and Lu, respectively.
At least one rare earth element selected from the group consisting of
X and X 'each consist of F, Cl, Br and I
At least one halogen selected from the group consisting of
And X ≠ X ′; and a is 0.1 <a ≦ 10.0
X is a numerical value in the range of 0 <x ≦ 0.2
Cerium-activated rare earth composite represented by the composition formula
(11) described in JP-A-61-21182.
LnX_Three・ AM¹X ' _Three: XCe³⁺(However, Ln is
A small number selected from the group consisting of Y, La, Gd and Lu
At least a rare earth element; M¹Is Li, Na,
At least selected from the group consisting of K, Cs and Rb
X and X 'are each a C
at least one selected from the group consisting of l, Br and I
Is a species halogen; and a is in the range 0 <a ≦ 10.0.
X is a numerical value in the range of 0 <x ≦ 0.2.
Activated rare earth composite halide represented by the composition formula
(12) described in JP-A-61-40390.
LnPO_Four・ ALnX_Three: XCe³⁺(However, Ln is
A small number selected from the group consisting of Y, La, Gd and Lu
At least one kind of rare earth element; X is F, Cl, Br and
At least one halogen selected from the group consisting of
And a is a number in the range 0.1 ≦ a ≦ 10.0
X is a numerical value in the range of 0 <x ≦ 0.2)
Cerium-activated rare earth halophosphate fluorescence expressed by composition formula
(13) described in JP-A-61-236888.
CsX: aRbX ': xEu²⁺(However, X and
And X 'are selected from the group consisting of Cl, Br and I, respectively.
At least one halogen; and a is 0
<A ≦ 10.0 and x is 0 <x ≦ 0.
Divalent euro represented by the composition formula of 2)
Pium activated cesium rubidium halide phosphor;
And (14) described in JP-A-61-236890.
M^TwoX_Two・ AM¹X ': xEu²⁺(However, M^TwoIs B
a, at least selected from the group consisting of Sr and Ca
A kind of alkaline earth metal; M¹Are Li, Rb and
At least one kind of arc selected from the group consisting of
X and X 'are Cl, Br and
At least one halogen selected from the group consisting of
And a is a number in the range of 0.1 ≦ a ≦ 20.0
Where x is a numerical value in the range of 0 <x ≦ 0.2)
Bivalent europium activated complex halide represented by the formula
Phosphors;

Among the above stimulable phosphors, a divalent europium-activated alkaline earth metal fluorohalide-based phosphor containing iodine and a divalent europium-activated alkaline earth metal halide containing iodine The iodine-containing rare earth element-activated rare earth oxyhalide-based phosphor and the iodine-containing bismuth-activated alkali metal halide-based phosphor exhibit high luminance stimulable luminescence.

A radiation image conversion panel using these stimulable phosphors emits stored energy by scanning with excitation light after accumulating radiation image information. Therefore, the radiation image can be accumulated again after scanning. It can be used repeatedly. In other words, the conventional radiographic method consumes radiographic film for each photographing, whereas the radiographic image conversion method uses the radiographic image conversion panel repeatedly, which is advantageous in terms of resource conservation and economic efficiency. It is.

Therefore, it is desirable to provide the radiation image conversion panel with a performance that can be used for a long period of time without deteriorating the image quality of the obtained radiation image.

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 ordinary climatic conditions, absorbs the moisture in the air and deteriorates significantly with the passage of time. I do.

Specifically, for example, when a stimulable phosphor is placed under high humidity, the radiation sensitivity of the phosphor decreases with an increase in absorbed water. In general, since the latent image of a radiation image recorded on a stimulable phosphor regresses with the passage of time after irradiation, the intensity of the reproduced radiation image signal ranges from irradiation to scanning by excitation light. However, when the stimulable phosphor absorbs moisture, the latent image retreats faster. Therefore, when a radiation image conversion panel having a stimulable phosphor that has absorbed moisture is used, the reproducibility of a reproduction signal at the time of reading a radiation image is reduced.

Conventionally, in order to prevent the above-mentioned deterioration phenomenon due to moisture absorption of the stimulable phosphor, the stimulable phosphor layer is reached by covering the stimulable phosphor layer with a moisture-proof protective layer having low moisture permeability. A method of reducing moisture has been adopted.

As the moisture-proof protective layer having a low moisture permeability, a polyethylene terephthalate (PET) film formed by depositing a thin film of metal oxide, silicon nitride, or the like on a polyethylene terephthalate film may be used.
There is a method using a laminated film formed by laminating a plurality of sheets, but this method has a drawback that unevenness in adhesion between the phosphor sheet and the moisture-proof protective film appears in an output image as unevenness in image density.

Also, unevenness in image density due to uneven brightness due to the distribution of characteristics of the phosphor sheet itself was a serious problem.

[0018] The unevenness of image due to the unevenness of adhesion between the phosphor sheet and the moisture-proof protective film and the unevenness of luminance of the phosphor sheet are fatal defects for a radiation image conversion panel used for diagnosing a disease.

[0019]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of uneven density and uneven density due to the distribution of the characteristics of the phosphor sheet itself when a moisture-proof protective film is used, and to improve the long-term good performance. An object of the present invention is to provide a radiation image conversion panel that can be used in an appropriate state.

[0020]

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

1. In a radiation image conversion panel comprising a phosphor sheet having a stimulable phosphor layer provided on a polymer support and a moisture-proof protective film provided so as to cover the phosphor surface of the phosphor sheet, A radiation image conversion panel, wherein the sheet is heat-treated at 40 ° C. or more and the glass transition temperature of the polymer support for 12 hours or more before sealing with a moisture-proof protective film.

2. 2. The radiation image conversion panel according to the above item 1, wherein the panel is heat-treated in an environment having a dew point temperature of 30 ° C. or lower.

3. In a radiation image conversion panel comprising a phosphor sheet having a stimulable phosphor layer provided on a polymer support and a moisture-proof protective film provided so as to cover the phosphor surface of the phosphor sheet, A radiation image conversion panel, wherein the sheet is heat-treated at 40 ° C. or higher and the glass transition temperature of the polymer support for 12 hours or more after sealing with a moisture-proof protective film.

4. 4. The radiation image conversion panel according to the above item 3, wherein the panel is sealed in an environment having a dew point temperature of 30 ° C. or lower.

Hereinafter, the present invention will be described in more detail. When sealing the phosphor plate with the moisture-proof protective film, the outermost resin layer of the moisture-proof protective film on the side in contact with the phosphor sheet is made of a heat-fusible resin film, so that the moisture-proof protective film is melted. It is possible to attach the phosphor sheet, and the sealing work of the phosphor sheet is made efficient.

In the radiation image conversion panel of the present invention,
By providing a moisture-proof protective film above and below the phosphor sheet and forming a sealing structure in which the upper and lower moisture-proof protective films are fused to each other in a region where the periphery is outside the periphery of the phosphor sheet. It is also possible to prevent moisture from entering from the outer periphery of the body sheet. Furthermore, the infiltration of moisture can be reduced more reliably by forming a laminated moisture-proof film obtained by laminating one or more aluminum films as the moisture-proof protective film on the support surface side (see FIG. 1). Also, this sealing method is easy in operation.

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). ) Films, etc., but are not limited thereto.

The outermost heat-fusible resin layer on the side of the moisture-proof protective film of the radiation image conversion panel of the present invention which is in contact with the phosphor surface and the phosphor surface may or may not be adhered. The non-adhered state mentioned above means that the phosphor layer surface and the moisture-proof protective film are not optically integrated.

That is, 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 can be almost treated as a discontinuous body. It is.

In the present invention, the non-uniform contact refers to a non-uniform state of the phosphor in a bonded or point-contact state, and the dew-point temperature is defined as the time when water vapor in the air starts to change to dew. Temperature.

The glass transition temperature (T) of the support of the present invention
g) means that 10 mg of a sample is collected, set on a scanning calorimeter, and heated at a rate of 20 ° C./min under a nitrogen gas flow. It is the average value of the temperature returning to.

The sealing of the phosphor sheet causes image unevenness due to uneven adhesion between the resin film and the phosphor surface and uneven brightness of the phosphor sheet itself. This image is not acceptable as a reproduced image used for disease diagnosis.

This type of density unevenness occurs whether the phosphor surface and the laminated protective film are in an adhered state or not.

It is not clear why density unevenness occurs due to uneven adhesion of the moisture-proof protective film, but reflection or refraction of excitation laser light or photostimulated light at the interface between the phosphor surface and the moisture-proof protective film is not clear. It is presumed that the transmission pattern changes.

As a light source of the excitation light for the stimulable phosphor plate, a laser beam having a high beam convergence is generally used. When this laser beam is used, these image defects are particularly likely to appear.

In an effort to solve such problems, the inventors of the present invention have determined that the phosphor sheet should be kept at 40 ° C. or more and before the glass transition temperature of the polymer support before sealing with a moisture-proof protective film. It has been found that by performing the heat treatment for 12 hours or more, both the uneven adhesion between the moisture-proof protective film and the phosphor sheet and the uneven density due to the distribution of the characteristics of the phosphor sheet itself are eliminated. However, when the temperature is lower than 40 ° C., there is almost no effect, and when the temperature is higher than the glass transition temperature of the polymer support, new image unevenness appears due to deformation of the support, and in an environment where the dew point temperature during processing is 30 ° C. or higher. In some cases, it was found that the luminance was reduced due to moisture absorption of the phosphor.

After sealing with a moisture-proof protective film, 4
It has been found that a similar effect can be obtained by heat treatment at a temperature of 0 ° C. or more and the glass transition temperature of the polymer support for 12 hours or more. In this case, since the phosphor sheet is protected by the moisture-proof protective film, even if the dew point temperature during the treatment is 30 ° C. or higher, the luminance does not decrease due to the moisture absorption of the phosphor.

It is presumed that the heat treatment of the phosphor sheet under the conditions of the present invention stabilizes the physical properties of the surface and inside of the phosphor layer, and makes the state of adhesion to the moisture-proof protective film and the light emission characteristics of the phosphor layer uniform. You.

The moisture-proof protective film used in the present invention can have an optimum moisture-proof property by laminating a plurality of vapor-deposited films in accordance with the required moisture-proof property. As a lamination method in this case, any generally known method may be used as long as the conditions of the present invention are satisfied.

As the support used in the radiation image conversion panel of the present invention, various polymer materials are used.
In particular, those which can be processed into a flexible sheet or web in handling as an information recording material are preferable, and in this regard, a cellulose acetate film, a polyester film, a polyethylene terephthalate film,
Plastic films such as polyethylene naphthalate film, polyamide film, polyimide film, triacetate film, and polycarbonate film are preferred.

The thickness of the support varies depending on the material of the support to be used and the like.
The thickness is more preferably 80 μm to 500 μm from the viewpoint of handling.

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.

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 adhesion to the stimulable phosphor layer.

Examples of the binder used in the stimulable phosphor layer in the present invention include proteins such as gelatin, polysaccharides such as dextran, and natural polymer substances such as gum arabic; and polyvinyl butyral, Vinyl acetate, nitrocellulose, ethylcellulose,
A binder represented by a synthetic polymer such as vinylidene chloride-vinyl chloride copolymer, polyalkyl (meth) acrylate, vinyl chloride-vinyl acetate copolymer, polyurethane, cellulose acetate butyrate, polyvinyl alcohol, linear polyester, etc. Can be mentioned. Particularly preferred among such binders are nitrocellulose, linear polyesters, polyalkyl (meth) acrylates, mixtures of nitrocellulose and linear polyester, mixtures of nitrocellulose and polyalkyl (meth) acrylate and It is a mixture of polyurethane and polyvinyl butyral. In addition, these binders may be cross-linked by a cross-linking agent. The stimulable phosphor layer can be formed on the undercoat layer by the following method, for example.

First, a stimulable phosphor and a binder are added to an appropriate solvent, and these are sufficiently mixed to prepare a coating solution in which phosphor particles and particles of the compound are uniformly dispersed in a binder solution. I do.

Generally, the binder is used in an amount of 0.01 to 1 part by mass per 1 part by mass of the stimulable phosphor. However, from the viewpoint of the sensitivity and sharpness of the obtained radiation image conversion panel, it is preferable that the amount of the binder is small, and the range of 0.03 to 0.2 part by mass is more preferable in consideration of the ease of application.

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

The coating solution contains a dispersant for improving the dispersibility of the phosphor in the coating solution, 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 bonding strength 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 phosphoric esters such as triphenyl phosphate, tricresyl phosphate, and diphenyl phosphate; phthalic esters such as diethyl phthalate and dimethoxyethyl phthalate; ethylphthalylethyl glycolate, and butylphthalylbutyl 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 then uniformly applied to the surface of the undercoat layer to form a coating of the coating solution. This coating operation can be performed by using ordinary coating means, for example, a doctor blade, a roll coater, a knife coater, or the like.

Next, the formed coating film is dried by gradually heating to complete the formation of the stimulable phosphor layer on the undercoat layer. The thickness of the stimulable phosphor layer varies depending on the characteristics of the intended radiation image conversion panel, the type of the stimulable phosphor, the mixing ratio between the binder and the phosphor, and the like.
0 μm to 1 mm. However, this layer thickness is preferably 50 to 500 μm.

The preparation of the coating solution for the stimulable phosphor layer is performed using a dispersing apparatus 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. The prepared coating solution is coated on a support using a coating solution such as a doctor blade, a roll coater, or a knife coater, and dried to form a stimulable phosphor layer.

The thickness of the stimulable phosphor layer of the radiation image conversion panel of the present invention depends on the characteristics of the intended radiation image conversion panel, the type of stimulable phosphor, and the mixing of the binder with the stimulable phosphor. Although it depends on the ratio and the like, it is preferably selected from the range of 10 μm to 1000 μm, more preferably from the range of 10 μm to 500 μm.

A phosphor sheet having a phosphor layer provided on a support is cut into a predetermined size. Any general method can be used for cutting, but a cosmetic cutting machine, a punching machine, or the like is desirable in terms of workability and accuracy.

Any known method can be used to seal the phosphor sheet cut to a predetermined size with the moisture-proof protective film. For example, the phosphor sheet is placed between the upper and lower moisture-proof protective films. And a laminating method in which the peripheral portion is heated and fused with an impulse sealer, and a pressure heating is performed between two heated rollers.

In the method of heat-sealing with the impulse sealer, the heat-sealing under a reduced pressure environment means that the phosphor sheet is prevented from being displaced in the moisture-proof protective film and that moisture in the air is eliminated. More preferred.

[0056]

The present invention will now be illustrated by way of examples.

Example 1 In order to synthesize a stimulable phosphor precursor of europium-activated barium fluoroiodide, an aqueous BaI ₂ solution (3.6 mol) was used.
/ L) 2780 ml and EuI ₃ aqueous solution (0.2 mol /
L) 27 ml were placed in the reactor. The reaction mother liquor in the reactor was kept at 83 ° C. while stirring. 322 ml of an aqueous solution of ammonium fluoride (8 mol / L) was injected into the reaction mother liquor using a roller pump to generate a precipitate. After completion of the injection, the temperature and the stirring were continued for 2 hours to ripen the precipitate. Next, the precipitate was separated by filtration, washed with ethanol, and dried under vacuum to obtain europium-activated barium fluoroiodide 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 calcined at 850 ° C. for 2 hours in a hydrogen gas atmosphere using a tube furnace 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 Pa · s. Using a doctor blade, the coating liquid having a thickness of 1 shown in Table 1 was used.
After coating on a 00 μm support, it was dried at 100 ° C. for 15 minutes to form a phosphor layer having a thickness of 230 μm, heat-treated under the conditions shown in Table 1, and then sealed by the following method. The glass transition point (Tg) of the support used
Are PET: polyethylene terephthalate (Tg = 69 ° C.) PEN: polyethylene naphthalate (Tg = 119 ° C.)
Met.

(Encapsulation of Phosphor Sheet) The coated sample was cut into a square of 20 cm × 20 cm, and a laminated protective film including an alumina-deposited PET resin layer shown in (A) below was used. Was sealed by fusing using an impulse sealer. FIG. 1 shows a cross-sectional view of the radiation image conversion panel of the present invention.

The fusion was performed so that the distance from the fusion portion to the peripheral edge of the phosphor sheet was 1 mm. The heater of the impulse sealer used for fusion had a width of 3 mm. The protective film on the support surface side of the phosphor sheet is made of casting polypropylene (CPP) 30 μm / aluminum film 9 μm / polyethylene terephthalate (PET).
A dry laminated film having a structure of 188 μm was obtained.
Further, in this case, the thickness of the adhesive layer was 1.5 μm, and a two-component reaction type urethane-based adhesive was used.

[0061] In FIG.
ET (commercial product: manufactured by Toyo Metallizing Co., Ltd.) is shown.

(A) NY15 /// VMPET12 /
// VMPET12 /// PET12 /// CPP20 PET (polyethylene terephthalate) NY (nylon) CPP (casting polypropylene) The above “///” is a dry lamination adhesive layer and the thickness of the adhesive layer is 3.0 μm. Is shown. The number behind each resin layer indicates the thickness (μm) of the resin layer.

(Evaluation of radiation image conversion panel) Evaluation of sensitivity The sensitivity was measured by applying a tube voltage of 80 kVp to the radiation image conversion panel.
After irradiating the panel with X-rays, the panel is excited by operating with He-Ne laser light (633 nm), and the photostimulated emission emitted from the phosphor layer is received by a photodetector (photoelectron image tube with spectral sensitivity S-5). And the intensity was measured. The sensitivities in the table are average values of the entire phosphor surface, and are relative sensitivities when the sensitivity of sample 1 is set to 1.

Evaluation of Sharpness Regarding the sharpness, the radiation image conversion panel was made of lead MT.
After irradiating X-rays at a tube voltage of 80 kVp through the F chart, the panel is excited by operating with panel He-Ne laser light, and the stimulated emission emitted from the phosphor layer is received by the same receiver as described above and converted into an electric signal. Then, this was converted from analog to digital and recorded on a magnetic tape, and the magnetic tape was analyzed by a computer to examine the modulation transfer function (MTF) of the X-ray image recorded on the magnetic tape. Table 1 below shows the MTF value (%) at a spatial frequency of 2 cycles / mm. In this case, the higher the MTF value, the better the sharpness.

Evaluation of density unevenness After irradiating the radiation image conversion panel with X-rays having a tube voltage of 80 kVp, the panel was irradiated with He-Ne laser light (633 nm).
The photostimulated light 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, which is converted into an image by an image reproducing device. The image was reproduced and printed out by magnifying it five times from the output device, and the obtained printed image was visually observed to evaluate the appearance of density unevenness. For each of the density unevenness, the state where no occurrence occurred was evaluated as 0, and the case where the most severe occurrence occurred was evaluated as 5.

[0066]

[Table 1]

As is clear from Table 1, the samples of the present invention show excellent performance. Example 2 A coating solution prepared in the same manner as in Example 1 was applied to a 100 μm-thick support shown in Table 2 using a doctor blade, and dried at 100 ° C. for 15 minutes to obtain a 230 μm-thick fluorescent light. After the formation of the body layer, the sealing was immediately performed in the same manner as in Example 1 except that no heat treatment was performed, and after the sealing, heat treatment was performed under the conditions shown in Table 2.

[0068]

[Table 2]

As is clear from Table 2, the sample of the present invention shows excellent performance.

[0070]

According to the present invention, it is possible to solve the above-mentioned problems of uneven density and uneven density due to the distribution of the characteristics of the phosphor sheet itself when the moisture-proof protective film is used, and to use the film in a good condition for a long time. A radiation image conversion panel capable of performing the above can be provided.

[Brief description of the drawings]

FIG. 1 is a sectional view of a radiation image conversion panel of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 11 phosphor 12 support 13 laminated protective film 14 aluminum laminated film

Claims (4)

[Claims] 1. A radiation image conversion comprising a phosphor sheet having a stimulable phosphor layer provided on a polymer support and a moisture-proof protective film provided so as to cover the phosphor surface of the phosphor sheet. The radiation image conversion panel, wherein the phosphor sheet is heat-treated at 40 ° C. or higher and the glass transition temperature of the polymer support for 12 hours or more before sealing with the moisture-proof protective film. 2. The radiation image conversion panel according to claim 1, wherein the panel is heat-treated in an environment having a dew point temperature of 30 ° C. or lower. 3. A radiation image conversion comprising a phosphor sheet having a stimulable phosphor layer provided on a polymer support, and a moisture-proof protective film provided so as to cover the phosphor surface of the phosphor sheet. A radiation image conversion panel, wherein the panel is heat-treated at 40 ° C. or higher and a glass transition temperature of a polymer support for 12 hours or more after sealing with a moisture-proof protective film. 4. The radiation image conversion panel according to claim 3, wherein the panel is sealed in an environment having a dew point temperature of 30 ° C. or lower.