JP2001324599A - Radiation image converting panel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve a problem of worsening in grainness caused by polarization- directional fluctuation of a laser beam for excitation to allow use in a satisfactory condition for a long period. SOLUTION: In this panel, a phosphor surface is coated by a moisture-proof protection film to make an angle fromed by a direction in the 0 degree of angle of rotation, by a cross nicol method, of the moisture-proof protection film for coating the phosphor surface of a phosphor sheet provided with a stimulable phosphor layer on a supporting body and an angle of a polarization direction of the laser beam come within 20 deg..

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 in which image unevenness due to the polarization of excitation laser light is eliminated. Things.

[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(Where X ', X ", and X"' are
Each of at least one of Cl, Br and I
M_ThreeIs a trivalent metal);
No. 8, BeO, BgO, CaO, S
rO, BaO, ZnO, Al_TwoO_Three, Y_TwoO_Three, La_TwoO_Three,
In_TwoO_Three, SiO_Two, TiO_Two, ZrO_Two, GeO_Two, Sn
O_Two, Nb_TwoO5, Ta_TwoO_FiveAnd ThO_TwoMetal acids such as
Compounds described in JP-A-56-116777
Zr, Sc; described in JP-A-57-23673.
B: described in JP-A-57-23675.
As and Si, which are described in JP-A-58-206678.
ML described (where M is Li, Na, K,
At least one selected from the group consisting of Rb and Cs
L is Sc, Y, La, Ce,
Pr, 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
Fired product of a salt of a monovalent or divalent metal of conic acid;
NaX 'described in JP-A-59-56479.
(Where X 'is at least one of Cl, Br and I)
Is also a kind); described in JP-A-59-56480.
V, Cr, Mn, Fe, Co and Ni etc.
Transition metals; described in JP-A-59-75200.
M¹X ', M'^TwoX ", M^TwoX '' ', A (just
Then M¹Consists of Li, Na, K, Rb, and Cs
At least one alkali metal selected from the group,
M '^TwoIs at least one selected from the group consisting of Be and Mg
Are both divalent metals; M^TwoAre Al, Ga, In,
At least one member selected from the group consisting of
A is a metal oxide; X ′, X ″, and
And X ′ ″ are each composed of F, Cl, Br and I.
At least one halogen selected from the group consisting of
M described in JP-A-60-101173¹
X '(where M¹Is selected from the group consisting of Rb and Cs
X 'is at least one alkali metal;
At least one selected from the group consisting of F, Cl, Br and I
Are also a kind of halogen);
M described in Japanese Patent Publication^Two'X'_Two・ M^Two'X'_Two(However
Then M^Two'Is selected from the group consisting of Ba, Sr and Ca
At least one alkaline earth metal;
And X ″ are from the group consisting of Cl, Br and I, respectively.
At least one halogen selected and X '
{X "); and JP-A-61-264084.
LnX ″ described in the detailed description_Three(However, Ln is S
c, Y, La, Ce, Pr, Nd, Pm, Sm, Gd,
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
(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^Three X ""_Three(However, M^ThreeIs S
selected from the group consisting of c, Y, La, Gd and Lu
At least one trivalent metal; X ", X" "and
And X ″ ″ are groups consisting of F, Cl, Br and I
At least one halogen selected from the group consisting of
B described in JP-A-60-228592;
Si described in JP-A-60-228593
O_Two, P_TwoO_FiveOxides such as JP-A-61-120882
LiX ″ and NaX ″ described in the gazette (however,
X "is selected from the group consisting of F, Cl, Br and I
At least one halogen); JP-A-61-12
SiO described in JP-A-08883;
SnX ″ described in 120885_Two(However
And X ″ is selected from the group consisting of F, Cl, Br and I
At least one type of halogen);
CsX ″ and Sn described in JP-A-235486.
X '' ''_Two(However, X ″ and X ′ ″ are respectively
At least one selected from the group consisting of F, Cl, Br and I
And a kind of halogen); and JP-A-61-23.
CsX ″, Ln described in US Pat.³⁺(T
Where X ″ is selected from the group consisting of F, Cl, Br and I.
At least one halogen; Ln is Sc;
Y, Ce, Pr, Nd, Sm, Gd, Tb, Dy, H
selected from the group consisting of o, Er, Tm, 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, a polyethylene terephthalate (PET) film or a film obtained by depositing a thin film such as a metal oxide or silicon nitride on a polyethylene terephthalate film is used.

A laser beam having a high beam convergence is generally used as a light source of the excitation light of the stimulable phosphor plate. The laser beam is applied through a moisture-proof protective layer made of a polymer film such as PET or a polymer transparent support. When scanning with laser light, the polarization state of the laser light changes due to the rotation due to the birefringence of the film due to the uneven thickness of the moisture-proof protective layer and the difference in the incident angle of the laser light, and the granularity of the output image deteriorates There was a problem of doing.

Particularly, a stretched film such as a polyethylene terephthalate film or a polyethylene naphthalate film has excellent physical properties as a protective layer and a support in terms of transparency, barrier properties, and strength, but has a high degree of transparency. The large refractivity degrades the granularity of the output image.

If the granularity is seriously deteriorated, it becomes a fatal defect for a radiation image conversion panel used for diagnosing a disease.

[0019]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a radiation image conversion panel which can solve the problem of deterioration in graininess due to a change in the polarization direction of an excitation laser beam and can be used in a good condition for a long time. To provide.

[0020]

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

1. The angle between the direction of the rotation angle of 0 ° by the crossed Nicols method and the polarization direction of the excitation laser light of the moisture-proof protective film covering the phosphor surface of the phosphor sheet having the stimulable phosphor layer provided on the support. The phosphor image surface is covered with the moisture-proof protective film so that the angle is within 20 °.

2. The angle between the direction of the rotation angle of 0 degree by the crossed Nicols method and the polarization direction of the excitation laser beam of the phosphor sheet in which the stimulable phosphor layer is provided on the transparent support is within 20 °. A radiation image conversion panel, wherein a phosphor layer is provided on the support.

3. A phosphor sheet in which a stimulable phosphor layer is provided on a support; and a phosphor sheet which is disposed above and below the phosphor sheet and which is not substantially adhered to the phosphor layer of the phosphor sheet and whose peripheral edge is the phosphor. 2. The radiation image conversion panel according to the above item 1, comprising a moisture-proof protective film provided outside the peripheral edge of the sheet and covering the entire surface of the phosphor sheet.

4. A moisture-proof protective film is a laminated film formed by laminating at least two or more resin films of at least two layers, and the outermost resin layer on the side in contact with the phosphor sheet is formed of a resin having a heat-fusing property. 4. The radiation image conversion panel according to the above 1 or 3, wherein:

[5] 3. The radiation image conversion panel according to the above 1 or 2, wherein the support is polyethylene terephthalate or polyethylene naphthalate.

Hereinafter, the present invention will be described in more detail. In sealing the phosphor plate with the moisture-proof protective film, any known method may be used, but the resin film of the outermost layer of the moisture-proof protective film on the side in contact with the phosphor sheet has a heat-fusible resin film. By doing so, the moisture-proof protective film can be fused and the sealing work of the phosphor sheet is made more efficient.

Preferably, sealing is provided in which moisture-proof protective films are arranged above and below the phosphor sheet, and the upper and lower moisture-proof protective films are fused in a region where the periphery is outside the periphery of the phosphor sheet. With this structure, it is possible to prevent moisture from entering from the outer peripheral portion of the phosphor 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). This sealing method is also easy in terms of work.

In this case, the outermost heat-fusible resin layer on the side in contact with the phosphor surface of the moisture-proof protective film may or may not be adhered to the phosphor surface.

The state of non-adhesion means that the phosphor surface and the moisture-proof protective film optically and mechanically hardly have a point contact even if the phosphor surface and the moisture-proof protective film are in microscopic contact. It can be treated as a continuum.

The term "heat-sealable film" as used herein refers to a resin film which can be fused by a generally used impulse sealer. For example, an ethylene-vinyl acetate copolymer (EVA), a polypropylene (PP) film, a polyethylene ( PE) film and the like, but are not limited thereto.

When a transparent support is used, the penetration of moisture can be reduced by fusing a barrier film to the phosphor surface side. In this case, since the laser beam for excitation can be scanned through the transparent support, an aluminum laminate film which is opaque on the phosphor surface side but has substantially zero moisture permeability can be used. Further, it is more preferable that an acrylic resin or the like having a high barrier property is applied to the outer peripheral portion of the phosphor sheet.

The direction of the optical rotation angle of 0 degree by the crossed Nicols method referred to in the present invention means that two polarizing plates are placed in a crossed Nicols (polarization axis is perpendicular), and a film (protective film, transparent support) is placed between the polarizing plates. This is the direction of the polarization axis when the amount of transmitted light becomes minimum when the film is sandwiched and the film is rotated.

The polarization direction of the excitation laser light referred to in the present invention means that a semiconductor laser light having a high beam convergence is generally used as a light source of the excitation light of the stimulable phosphor plate. The direction of the plane of polarization.

It is not clear why the change in the polarization state of the laser light due to the birefringence of the film deteriorates the granularity of the output image, but it is presumed that the light emission amount of the stimulable phosphor changes depending on the polarization. Is done.

In particular, when a stretched film such as a polyethylene terephthalate or polyethylene naphthalate film is used as the polymer film, the granularity is greatly deteriorated depending on the angle at which the film is used. It will not be acceptable.

In order to solve such a problem, the present inventors have found that the angle between the direction of the optical rotation angle of 0 ° by the crossed Nicols method and the polarization direction of the excitation laser light is within 20 °. By disposing the moisture-proof protective film and the transparent support as described above, it was found that the problem of graininess was solved.

It is considered that by arranging the transparent polymer film under the conditions of the present invention, fluctuations in the polarization state of laser light due to birefringence of the film are suppressed to a minimum and graininess is improved.

When a stretched film such as a polyethylene terephthalate or polyethylene naphthalate film is used as the transparent polymer film, the direction of the optical rotation angle of 0 ° changes in the width direction of the film. If the angle between the direction of the optical rotation angle of 0 degree by the Nicol method and the polarization direction of the excitation laser beam is within 20 °, the effect of the present invention can be obtained.

The moisture-proof protective film used in the present invention can have an optimum moisture-proof property by laminating a plurality of polymer films or vapor-deposited films according to the required moisture-proof property. In this case, as a lamination method, any generally known method may be used.

When the moisture-proof protective film is produced by laminating a plurality of polymer films or vapor-deposited films, it is assumed that the directions of the optical rotation angles of 0 degrees of each film constituting the moisture-proof protective film are the same. However, the transmitted light pattern by the crossed Nicols method of the film after lamination may be more complicated than that of a single-layer film, but in this case, the direction of the optical rotation angle of 0 degree is transmitted when the film is rotated. This is the direction in which the amount of light is minimized.

More preferably, when laminating a plurality of moisture-proof protective films, if the films constituting the moisture-proof protective film have the same optical rotation angle of 0 °, the optical rotation angle after lamination is 0 °. Can be predicted in advance, which is convenient.

Particularly, in a stretched film such as a polyethylene terephthalate or polyethylene naphthalate film,
At the center of the film forming width, the direction of the optical rotation angle of 0 ° coincides with the film forming direction (MD direction). By using this vicinity, the direction of the optical rotation angle of 0 ° corresponds to the film forming direction. A consistent moisture-proof protective film can be obtained.

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 layer 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, in these supports, an undercoat layer may be provided 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 high molecular 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 the phosphor particles and the compound particles are uniformly dispersed in a binder solution. I do.

In general, 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 dispersant 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.

Next, 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 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 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. 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 desired properties of the 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 coated 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 sandwiched between the upper and lower moisture-proof protective films. And a method in which the peripheral edge portion is heated and fused by an impulse sealer, or a laminating method in which pressure is applied 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 the moisture in the air is eliminated. More preferred.

[0059]

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. This coating solution is applied on a black PET support having a thickness of 100 μm using a doctor blade, and dried at 100 ° C. for 15 minutes to form a phosphor layer having a thickness of 230 μm. Sealing was performed so that the direction of the angle of 0 degree and the polarization direction of the excitation laser light were in the conditions shown in Table 1.

(Encapsulation of Phosphor Sheet) The coated sample was cut into a square of 20 cm × 20 cm, and a peripheral protective film containing an alumina-deposited PET resin layer shown in (A) below was used under reduced pressure. 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 /
A dry laminated film having a structure of aluminum film 9 μm / polyethylene terephthalate (PET) 188 μm was used. In this case, the thickness of the adhesive layer is 1.5 μm.
, A two-component urethane adhesive was used. VMPET in (A) indicates alumina-deposited PET (commercial product: manufactured by Toyo Metallizing Co., Ltd.).

(A) VMPET12 /// VMPET
12 /// PET /// CPP20 PET (polyethylene terephthalate) CPP (casting polypropylene) The above “///” indicates that the thickness of the dry lamination adhesive layer is 3.0 μm.

The number behind each resin film indicates the film thickness (μm). In the case of VMPET and PET, the direction of the optical rotation angle of 0 degree at the center of the width is the film forming direction (MD direction).
As for the direction of the optical rotation angle of 0 ° of the CPP film, the direction of the optical rotation angle of 0 ° was coincident with the film forming direction (MD direction) at any position regardless of the width direction.

The direction of the optical rotation angle of 0 ° in the laminated moisture-proof protective film (width 50 cm) produced in this manner coincides with the film forming direction (MD direction).
For the m width, there was no width direction distribution in the direction of the optical rotation angle of 0 degree in the width direction.

(Evaluation of Radiation Image Conversion Panel) Evaluation of Graininess The graininess was measured by uniformly irradiating the produced radiation image conversion panel sample with X-rays having a tube voltage of 80 kVp, and then applying the panel from the actual moisture-proof protective layer side. It is scanned and excited by a semiconductor laser beam (690 nm), stimulated emission emitted from the phosphor layer is received by a light receiver, converted into an electric signal, and the average value of the electric signal is set as S, and the average intensity S Assuming the deviation signal (structural signal noise) as the root mean square value N, 20 × log ₁₀ (S / N) dB is calculated, and the granularity is evaluated based on the calculated value. Noted.

The reference value of the graininess of Sample 2 was set to 0.
It is displayed as

[0070]

[Table 1]

As is clear from Table 1, the sample of the present invention shows excellent performance. Example 2 A coating solution prepared in the same manner as in Example 1 was applied on a transparent PET support having a thickness of 100 μm using a doctor blade,
After drying at 100 ° C. for 15 minutes to form a phosphor layer having a thickness of 230 μm, the direction of the rotation angle of the support film of the coated sample and the polarization direction of the excitation laser light are shown in Table 2. 20cm x 20c at an angle that meets the conditions
m, cut into squares of cast polypropylene (C
A dry laminated film having a structure of (PP) 30 μm / aluminum film 9 μm / polyethylene terephthalate (PET) 188 μm was heated and fused to the phosphor surface side.

The 100 μm transparent PET used at this time
The support is 40 cm wide, in which the optical rotation angle is 0
The direction of the degree was 30 ° with respect to the film forming direction (MD direction) at any position regardless of the width direction.

(Evaluation of Radiation Image Conversion Panel) Evaluation of Graininess The granularity was measured by uniformly irradiating the produced radiation image conversion panel sample with X-rays having a tube voltage of 80 kVp, and then applying a semiconductor laser from the transparent support side to the panel. Excitation is performed by scanning with light (690 nm), and stimulated emission emitted from the phosphor layer is received by a light receiver and converted into an electric signal. The average value of the electric signal is represented by S, and deviates from the average intensity S. Assuming that the signal (structural signal noise) is the root mean square value N, 20 × log ₁₀ (S / N) dB was calculated, and the granularity was evaluated based on the calculated value. Table 2 shows the results. . In addition, the reference value of the granularity of the sample 12 is displayed as 0.

[0074]

[Table 2]

As is evident from Table 2, the samples of the present invention show excellent performance.

[0076]

According to the present invention, it is possible to provide a radiation image conversion panel which can solve the problem of deterioration in graininess due to the fluctuation of the polarization direction of the excitation laser beam and can be used in a good condition for a long period of time.

[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

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2G083 AA03 CC01 CC04 CC07 DD01 DD16 DD18 EE01 EE02 EE07 EE08 2H013 AC01

Claims (5)

[Claims] 1. A method according to claim 1, wherein a direction of an optical rotation angle of 0 degree by a crossed Nicols method and a direction of an excitation laser beam of a moisture-proof protective film covering a phosphor surface of a phosphor sheet having a stimulable phosphor layer provided on a support. A radiation image conversion panel, wherein the phosphor surface is coated with the moisture-proof protective film so that the angle between the polarization directions is within 20 °. 2. An angle between a direction of an optical rotation angle of 0 degree by a crossed Nicols method and a polarization direction of excitation laser light of a phosphor sheet having a stimulable phosphor layer provided on a transparent support. A phosphor layer provided on the support so that the angle is within 20 °. 3. A phosphor sheet in which a stimulable phosphor layer is provided on a support, and are disposed substantially above and below the phosphor sheet and are not substantially adhered to the phosphor layer of the phosphor sheet. The radiation image conversion panel according to claim 1, wherein a peripheral edge is outside the peripheral edge of the phosphor sheet, and is made of a moisture-proof protective film provided so as to cover the entire surface of the phosphor sheet. 4. A laminated film in which the moisture-proof protective film is formed by laminating at least two or more resin films, wherein the outermost resin layer on the side in contact with the phosphor sheet has heat-fusibility. The radiation image conversion panel according to claim 1, wherein the radiation image conversion panel is made of a resin. 5. The radiation image conversion panel according to claim 1, wherein the support is polyethylene terephthalate or polyethylene naphthalate.