JP2002131498A - Radiation image conversion panel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radiation image conversion panel with good image sharpness and capable of obtaining an image with high contrast. SOLUTION: The radiation image conversion panel has a fluorescent body sheet having a stimulable phosphor layer on a support body and a protection film arranged on the upside and downside of the fluorescent body sheet and provided to cover the whole surface of the fluorescent body sheet. The protection film has a function absorbing excited light.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a radiation image conversion panel.

[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 stored by the phosphor is absorbed by the phosphor. There is a method of detecting and imaging this fluorescence.

[0004] Specifically, for example, US Pat.
A radiation image conversion method using a stimulable phosphor as described in JP-A-9-527 and JP-A-55-12144 is known.

The above-mentioned method uses a radiation image conversion panel containing a stimulable phosphor, and the radiation transmitted through the object is applied to the stimulable phosphor layer of the radiation image conversion panel, and each part of the object is irradiated with the radiation. By accumulating radiation energy corresponding to the radiation transmission density, and then stimulating the stimulable phosphor with electromagnetic waves (excitation light) such as visible light and infrared light in a time series manner, The stored 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 the signal is applied to a recording material such as a photosensitive film or a display device such as a CRT. It is reproduced as a visual image.

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) (Ba _{1 -X} , M (II) _x ) FX: yA, described in JP-A-55-12145, wherein
M (II) is at least one of Mg, Ca, Sr, Zn and Cd, X is at least one of Cl, Br and I, A is Eu, Tb, Ce, Tm, Dy, P
at least one of r, Ho, Nd, Yb, and Er, and 0 ≦ x ≦ 0.6, and y is 0 ≦ y ≦ 0.
2) a rare earth element-activated alkaline earth metal fluorohalide phosphor represented by the following composition formula; and the phosphor may contain the following additives.

(A) X ', BeX ", M (III) X"" ₃ , wherein X', X" and X "" described in JP-A-56-74175 are Cl and Br respectively
And M (III) is a trivalent metal; and (b) B described in JP-A-55-160078.
eO, MgO, CaO, SrO, BaO, ZnO, Al
₂ O ₃ , Y ₂ O ₃ , La ₂ O ₃ , In ₂ O ₃ , SiO ₂ , Ti
O ₂ , ZrO ₂ , GeO ₂ , SnO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅
And metal oxides such as ThO ₂ ; (c) Z described in JP-A-56-116777.
r, Sc; (d) B described in JP-A-57-23667; (e) A described in JP-A-57-23675.
s, Si; (f) M described in JP-A-58-206678.
L, wherein M is at least one alkali metal selected from the group consisting of Li, Na, K, Rb, and Cs, and L is Sc, Y, La, Ce, Pr, Nd, Pm,
Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, L
at least one trivalent metal selected from the group consisting of u, Al, Ga, In and Tl; (g) a calcined product of a tetrafluoroborate compound described in JP-A-59-27980; 59-272
No. 89, a fired product of a salt of a monovalent or divalent metal of hexafluorosilicic acid, hexafluorotitanic acid and hexafluorozirconic acid;
No. 6479, wherein X 'is C
(h) V, as described in JP-A-59-56480,
Transition metals such as Cr, Mn, Fe, Co and Ni; M (I) described in JP-A-59-75200
X ', M' (II) X " ₂ , M (III) X"' ₃ , A, wherein M (I) is at least one selected from the group consisting of Li, Na, K, Rb and Cs M ′ (II) represents at least one divalent metal selected from the group consisting of Be and Mg, and M (III) represents A
at least one trivalent metal selected from the group consisting of l, Ga, In, and Tl; A is a metal oxide; X ', X ", and X"' are F, Cl,
At least one halogen selected from the group consisting of Br and I; (i) M described in JP-A-60-101173.
(I) X ′, wherein M (I) is at least one alkali metal selected from the group consisting of Rb and Cs,
X 'is at least one halogen selected from the group consisting of F, Cl, Br and I; (j) M described in JP-A-61-23679.
(II) ′ X ′ ₂ .M (II) ′ X ″ ₂ , wherein M (II) ′ is at least one alkaline earth metal selected from the group consisting of Ba, Sr and Ca; X "is at least one halogen selected from the group consisting of Cl, Br and I, and X '≠ X"; and LnX "described in JP-A-61-264084. ₃ , where Ln is Sc, Y, La, C
e, Pr, Nd, Pm, Sm, Gd, Tb, Dy, H
at least one rare earth element selected from the group consisting of o, Er, Tm, Yb and Lu;
It is at least one halogen selected from the group consisting of l, Br and I.

(2) JP-A-60-84381
M (II) X_Two・ AM (II) X '_Two: XEu²⁺(formula
Where M (II) is selected from the group consisting of Ba, Sr and Ca
At least one alkaline earth metal;
And X 'is selected from the group consisting of Cl, Br and I
At least one halogen and X ≠ X ′
And a is 0.1 ≦ a ≦ 10.0 and x is 0 <x ≦
0.2) with divalent europium represented by the composition formula
Active alkaline earth metal halide phosphor;
The light body may contain the following additives: (a) M described in JP-A-60-166379.
(I) X ′, wherein M (I) is composed of Rb and Cs
At least one alkali metal selected from the group;
X 'is selected from the group consisting of F, Cl, Br and I
(B) K described in JP-A-60-221483.
X ", MgX" "_Two, M (III) X ""_Three, Where M (I
II) is from the group consisting of Sc, Y, La, Gd and Lu
At least one trivalent metal selected; X ″,
X ′ ″ and X ″ ″ are both F, Cl, Br and
At least one halogen selected from the group consisting of I
(C) It is described in JP-A-60-228592.
B, Si described in JP-A-60-228593.
O_Two, P_TwoO_FiveOxides such as JP-A-61-208882
LiX ″, NaX ″, wherein X ″ is
At least one selected from the group consisting of F, Cl, Br and I
And (d) S described in JP-A-61-220883.
iO: S described in JP-A-61-120885
nX "_TwoWherein X ″ is F, Cl, Br and I.
At least one halogen selected from the group consisting of: (e) C described in JP-A-61-235486;
sX ", SnX" "" _TwoWhere X ″ and X ′ ″ are
Each selected from the group consisting of F, Cl, Br and I
At least one halogen;
CsX ″, Ln described in US Pat.³⁺,
Wherein 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) Ln described in JP-A-55-12144.
OX: xA (where Ln is La, Y, Gd, and Lu
X is Cl, Br, and I
A is at least one of Ce and Tb
And x is 0 <x <0.1).
Rare earth element activated rare earth oxyhalide phosphor; (4) M described in JP-A-58-69281
(II) OX: xCe (where M (II) is Pr, Nd, P
m, Sm, Eu, Tb, Dy, Ho, Er, Tm, Y
at least one selected from the group consisting of b and Bi
X is Cl, Br, and I
At least one; x is 0 <x <0.1) tuple
Cerium-activated trivalent metal oxyhalide fire represented by the formula
(5) described in JP-A-62-25189.
M (I) X: xBi (where M (I) is Rb and C
at least one alkali gold selected from the group consisting of
X is selected from the group consisting of Cl, Br and I
Is at least one halogen; and x is 0 <
x is a numerical value in the range of 0.2).
(6) M described in Japanese Patent Application Laid-Open No. 60-141783.
(II)_Five(PO_Four)_ThreeX: xEu²⁺(Where M (II) is C
at least one selected from the group consisting of a, Sr and Ba
X is a kind of alkaline earth metal; X is F, Cl, Br and
At least one halogen selected from the group consisting of
X is a number in the range of 0 <x ≦ 0.2)
Bivalent europium activated alkaline earth gold represented by the composition formula
(7) M described in JP-A-60-1557099
(II)_TwoBO_ThreeX: xEu²⁺(Where M (II) is Ca, S
at least one member selected from the group consisting of r and Ba
X is an alkaline earth metal; X is from 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 halobor
(8) M described in JP-A-60-157100
(II)_Two(PO_Four)_ThreeX: xEu²⁺(Where M (II) is C
at least one selected from the group consisting of a, 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) M described in JP-A-60-217354
(II) HX: xEu²⁺(Where M (II) is Ca, Sr and
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 hydride halide
(10) L described in JP-A-61-211173
nX_Three・ ALn'X '_Three: XCe³⁺, (Where Ln and
Ln 'is a group consisting of Y, La, Gd and Lu, respectively.
At least one rare earth element selected from
And X ′ are each a group consisting of F, Cl, Br and I
At least one halogen selected from the group consisting of
X ≠ X ′; and a is in the range of 0.1 <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
(11) L described in JP-A-61-21182
nX_ThreeAM (I) X'3: xCe³⁺, (Where Ln is
A small number selected from the group consisting of Y, La, Gd and Lu
At least a kind of rare earth element; M (I) is Li, N
a selected from the group consisting of a, K, Cs and Rb
X and X 'are each a kind of alkali metal.
At least selected from the group consisting of Cl, Br and I
Is also a kind of halogen; and a is 0 <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
(12) L described in JP-A-61-40390.
nPO_Four・ ALnX_Three: XCe³⁺, (Where Ln is Y, L
at least one selected from the group consisting of a, Gd and Lu
X is a rare earth element; X is F, Cl, Br and I
At least one halogen selected from the group consisting of
And a is a numerical value in the range of 0.1 ≦ a ≦ 10.0.
Where x is a numerical value in the range of 0 <x ≦ 0.2)
A cerium-activated rare earth halophosphate phosphor represented by the formula: (13) described in JP-A-61-236888.
CsX: aRbX ': xEu²⁺, (Where 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; (14) described in JP-A-61-236890
M (II) X_TwoAM (I) X ': xEu²⁺, (Where M
(II) is selected from the group consisting of Ba, Sr and Ca
At least one alkaline earth metal; M (I)
At least selected from the group consisting of Li, Rb and Cs
Is also a kind of alkali metal; X and X ′ are each
At least selected from the group consisting of Cl, Br and I
A is a kind of halogen; and a is 0.1 ≦ a ≦ 20.
X is a number in the range 0 <x ≦ 0.2
Activated bivalent europium represented by the composition formula
Compound halide phosphor; Among the above stimulable phosphors,
Divalent europium-activated alkaline earth gold containing iodine
Divalent halogen containing iodine
Activated alkaline earth metal halide fluorescence
Body, rare earth element activated rare earth oxyhalo containing iodine
With bismuth containing genide-based phosphor and iodine
Active alkali metal halide phosphor emits high brightness
Indicates light.

A radiation image conversion panel using these stimulable phosphors emits stored energy by scanning with excitation light after accumulating radiation image information, so that 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 withstand long-term use 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 normal climatic conditions, absorbs 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, a polyethylene terephthalate film, a polyethylene terephthalate (PET) film, a polyethylene terephthalate film, or a vapor-deposited film obtained by vapor-depositing a thin film of a metal oxide, silicon nitride, or the like is used.

As a light source of the excitation light of the stimulable phosphor plate, a laser beam having a high beam convergence is generally used. However, when the laser beam is scanned through a protective layer made of a polymer film such as PET, Due to the scattering of the excitation laser light inside the protective layer film, and the irregular reflection of the excitation laser light between the protective layer and the photodetector and peripheral members, the stimulable phosphor surface at a place away from the place where the excitation light was scanned is changed. The sharpness is reduced due to excitation and emission of stimulated emission. Further, even when the phosphor plate does not have a protective layer, there is a problem that 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 a large refractive index despite having excellent physical properties as a protective layer in terms of transparency, barrier properties and strength. Therefore, 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 and propagates to a place away from the scanned position, emits photostimulated light and reduces sharpness. .

Also, the excitation light reflected at the upper and lower interfaces of the protective layer in the opposite direction to the phosphor surface is also reflected between the photodetectors and the peripheral members, and the stimulable light is further reflected at a place farther from the scanned place. To excite the phosphor surface and emit photostimulated light,
This further reduces the sharpness. Since the excitation light is coherent light of long wavelength from red to infrared, the amount absorbed in the space inside the protective film and the reader is small unless it actively absorbs scattered light and reflected light. It propagates to the place and deteriorates sharpness.

When a film such as a polyethylene terephthalate film or a polyethylene naphthalate film is used as a protective layer, shading other than a radiographic image of a subject, that is, image unevenness, or a linear pattern which is considered to be caused during the manufacturing process of the protective layer. There is also a problem that noise and the like appear. With respect to these image unevenness and linear noise, JP-A-59-42,500 and Japanese Patent Publication No. 1-57759 show means for increasing the haze ratio of the protective layer to eliminate the image unevenness and linear noise. ing. However, there is a disadvantage that sharpness is reduced when the haze ratio of the protective layer is increased.

In order to prevent the sharpness from deteriorating, a method of thinning the protective film and shortening the propagation distance of the excitation light inside the protective film is conceivable. However, the effect is small. The problem is a decrease in moisture resistance and scratch resistance.
Regarding improvement of sharpness, Japanese Patent Publication No. 59-23400 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 that absorbs excitation light. Japanese Patent Application Laid-Open No. 60-200200 discloses a method of coloring an adhesive layer between a phosphor layer and a protective layer. However, when sharpness is enhanced by these methods, the above-mentioned image unevenness and linear noise become more remarkable. There is a problem that it becomes.

If the sharpness is deteriorated, or the image unevenness or the linear noise is severe, the radiation image conversion panel used for diagnosing a disease becomes a fatal defect.

Therefore, there has been a demand for solving the above-mentioned problems.

[0024]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a radiation image conversion panel having good image sharpness and capable of obtaining a high-contrast image.

[0025]

The above objects of the present invention have been attained by the following items 1 to 5.

1. A radiation image conversion panel comprising: a phosphor sheet having a stimulable phosphor layer on a support; and a protective film disposed above and below the phosphor sheet and provided to cover the entire surface of the phosphor sheet. 3. The radiation image conversion panel according to claim 1, wherein the protective film has an excitation light absorbing function.

2. Arranged above and below the phosphor sheet,
2. The radiation image conversion panel according to the item 1, wherein the protective film provided so as to cover the entire surface of the phosphor sheet is formed from a folded protective film.

3. 3. The radiation image conversion panel according to the above item 2, wherein the excited light absorbing function of the folded portion of the protective film is larger than the excited light absorbing function of the protective film disposed on the stimulable phosphor layer.

4. 4. The radiation image conversion panel according to any one of the above items 1 to 3, wherein the support has an excitation light absorbing function.

5. The excitation light absorbing function of the protective film A provided on the support surface opposite to the support having the stimulable phosphor layer is different from the excitation light of the protective film B provided on the stimulable phosphor layer side. The radiation image conversion panel according to any one of the above items 1 to 4, wherein the radiation image conversion panel has a larger absorption function.

Hereinafter, the present invention will be described in detail. In the present invention, a phosphor sheet having a stimulable phosphor layer on a support, and a protective film disposed above and below the phosphor sheet and provided so as to cover the entire surface of the phosphor sheet. In the radiation image conversion panel having, by adjusting the protective film to have the excitation light absorbing function, the sharpness degradation due to the excitation laser is eliminated,
In addition, a radiation image conversion panel capable of obtaining a high-contrast image can be provided.

The protective film according to the present invention will be described. As the material for producing the protective film according to the present invention, specifically, a polyester film, a polymethacrylate film, a nitrocellulose film, a cellulose acetate film and the like can be used, such as a polyethylene terephthalate film and a polyethylene naphthalate film. A stretched film is preferable as a protective film in terms of transparency and strength, and among them, a polyethylene terephthalate film is preferably used.

The excitation light absorbing functional layer of the protective film according to the present invention will be described. From the viewpoint of preventing sharpness deterioration due to the excitation laser, the protective film of the present invention is provided with an excitation light absorbing function. Here, having the function of absorbing the excitation light means a function of absorbing the excitation light of the stimulable phosphor, and is defined as having a light transmittance of 97% or less with respect to the excitation light. However, from the viewpoint of maintaining the luminance of the radiation image conversion panel at an appropriate level, the protective film provided on the stimulable phosphor layer side of the phosphor sheet has a preferable light transmittance of 97% to 30%. For the protective film provided on the support surface of the body sheet opposite to the stimulable phosphor layer side, the preferred light transmittance is 97% to 0%.

Here, the light transmittance is 97% of the light transmittance of the protective film having the excitation light absorbing layer when the light transmittance of the protective film having no excitation light absorbing layer is set to 100%. This means that adjustment is made as follows.

The light transmittance described above is obtained according to the following equation. Light transmittance (%) = (transmitted light / incident light) × 100 Further, from the viewpoint of preferably obtaining the effects described in the present invention, in the present invention, the support on the opposite side of the support having the stimulable phosphor layer is used. The protective film provided on the body surface preferably has an excitation light absorbing ability larger than that of the protective film B provided on the stimulable phosphor layer side.

In order to provide the protective film with the excitation light absorbing function as described above, for example, the protective film is excited by applying a layer containing a colorant that selectively absorbs the excitation light. A light absorbing function can be provided.
Further, as a means for imparting the excitation light absorbing function, the protective film itself may be colored with a coloring agent or the like.

The colorant used to impart the excitation light absorbing function to the protective film according to the present invention is determined by the type of the stimulable phosphor used in the radiation image storage panel. As a depleting phosphor,
Usually, 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 used.
A green organic or inorganic colorant is preferably used.

Examples of blue to green organic colorants 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 No1 (National Aniline Co., Ltd.), Spirit Blue (Hodogaya Chemical Co., Ltd.), Oil Blue No. 603 (Orient Co., Ltd.), Kitten Blue A
(Manufactured by Ciba-Geigy), Eisenkatilon Blue GL
H (made by Hodogaya Chemical Co., Ltd.), Lake Blue A, F, H
(Kyowa Sangyo Co., Ltd.), Rhodaline Blue 6GX (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.), Lionor 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 the invention is not limited thereto.

In the present invention, from the viewpoint of preventing the stimulable phosphor from absorbing and deteriorating due to moisture, the protective film according to the present invention is preferably provided with a moisture proof property. It is preferably at most 50 g / m ² · day, more preferably at most 10 g / m ² · day, particularly preferably at most 1 g / m ² · day.

The moisture permeability of the above protective film is determined according to JIS.
It can be measured with reference to the method defined by Z0208.

Further, from the viewpoint of more effectively preventing the stimulable phosphor from deteriorating due to moisture absorption, claim 2 and / or claim 3.
When the entire surface of the phosphor sheet is covered with the protective film as described in (1), the surface of the phosphor sheet (the surface having the stimulable phosphor layer) and the back surface (the surface of the support) as shown in FIG. ) Is preferably integrally folded so that the entire surface is covered with at least one folded protective film.

In FIG. 2, one protective film 15
Is folded in two, two sides (not shown) are thermocompression-bonded or heat-fused, and then the entire surface of the support 12 and the phosphor 11 formed on the support 12 is coated. The radiation image conversion panel 2 in which the remaining one side 15a is thermocompression bonded or thermally fused and the phosphor 11 is sealed by three sides of the protective film 15 is shown.

The "folded portion of the protective film" is defined as the folded portions 16a and 16b in FIG.
A portion covering from the end of the phosphor sheet 11 to the end of the support 12 is shown.

From the viewpoint of adjusting the moisture permeability of the protective film to the above-mentioned range and improving the moisture-proof property of the protective film,
It is preferable to use a polyethylene terephthalate film or a vapor-deposited film obtained by vapor-depositing a thin film such as a metal oxide or silicon nitride on a polyethylene terephthalate film.

The protective film according to the present invention is provided with an optimum moisture-proof property by laminating a plurality of resin films or a vapor-deposited film obtained by depositing a metal oxide or the like on the resin film in accordance with the required moisture-proof property. However, as a method of laminating the resin film, a conventionally known method can be applied.

In the present invention, by providing a layer having the above-described excitation light absorbing ability between the laminated resin films, the excitation light absorbing ability-imparting layer is protected from physical impact and chemical deterioration. , Stable plate performance can be maintained for a long period of time.

As described above, the excitation light absorbing layer may be provided at a plurality of locations between the laminated resin films, or the adhesive layer for laminating may contain a coloring agent and be used as the excitation light absorbing layer. .

The haze ratio of the protective film according to the present invention will be described. From the viewpoint of improving the effects described in the present invention, particularly sharpness, and obtaining a high-contrast image, it is preferable to adjust the haze ratio of the protective film to 5% or more and 60% or less, more preferably 5% or less. % To 50%, particularly preferably 5% to 30%.

The haze ratio of the protective film described above is A
It is measured using the method specified in STMD-1003. The haze ratio of the protective film can be adjusted with reference to the haze ratio of the resin film used. A resin film having an arbitrary haze ratio is industrially available.

For sealing the phosphor plate using the protective film according to the present invention, any conventionally known method can be applied, but the outermost layer of the protective film on the side in contact with the phosphor sheet is heat-sealed. A protective film can be fused by containing a resin having a hydrophilic property, the sealing work at the peripheral edge of the phosphor sheet is made more efficient, and the deterioration of the properties due to moisture absorption of the stimulable phosphor is extremely effectively prevented. Is preferred.

More preferably, a protective film is arranged above and below the phosphor sheet, and a sealing structure in which the upper and lower protective films are fused in a region where the periphery is outside the periphery of the phosphor sheet. This effectively prevents moisture from entering from the outer peripheral portion of the phosphor sheet. It is particularly preferable to provide the protective film with a layer containing the resin having the above-mentioned heat-fusing property only at the portions used for the above-mentioned sealing.

In this case, it is preferable that the outermost layer of the protective film on the side in contact with the stimulable phosphor layer and the phosphor surface are not substantially adhered.

The above-mentioned "the protective film and the stimulable phosphor layer are not substantially bonded" means that the stimulable phosphor layer and the protective film are not optically integrated. Means More specifically, even if the stimulable phosphor layer and the protective film are microscopically point-contacted, the stimulable phosphor layer and the protective film are optically and mechanically almost discontinuous. It means that it can be treated as a body.

In the above-described sealing structure, it is considered that the photostimulable phosphor layer and the moisture-proof protective layer are in contact at various places in a microscopic point. 10
% Or less is defined as not substantially adhered in the present invention.

The heat-fusible film described above is 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). Although a film etc. are mentioned, this invention is not limited to these.

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

From the viewpoint of obtaining a high-sharpness, high-contrast image, the support according to the present invention preferably has the above-described excitation light absorbing function. As a means for imparting the excitation light absorbing function to the support, it is preferable to include the colorant as described above in the support, or to provide a colorant-containing layer on the support.

In the present invention, the expression that the support has an excitation absorbing function is the same as that of the protective film described above, and is defined as having a light transmittance of 97% or less for excitation light. Here, the light transmittance of the support with respect to the excitation light is 97% or less of the light transmittance of the support having the same configuration except that it does not have the excitation light absorbing function when the light transmittance is set to 100%. Means to adjust.

The layer thickness of the support varies depending on the material of the support to be used and the like, but is generally from 80 μm to 1000 μm, and more preferably from 80 μm to 80 μm from the viewpoint of handling.
It is 500 μm. 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 according to the present invention include proteins such as gelatin, polysaccharides such as dextran, and natural polymer substances such as gum arabic; Polyvinyl butyral, polyvinyl acetate, nitrocellulose, ethyl cellulose, vinylidene chloride-vinyl chloride copolymer,
Examples thereof include binders represented by synthetic polymer substances such as polyalkyl (meth) acrylate, vinyl chloride / vinyl acetate copolymer, polyurethane, cellulose acetate butyrate, polyvinyl alcohol, and linear polyester.

Among the binders described above, particularly preferred 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. The stimulable phosphor layer can be formed on the undercoat layer by the following method, for example.

First, the stimulable phosphor and the binder are added to an appropriate solvent, and these are mixed well to prepare a coating solution in which the phosphor particles and the compound particles are uniformly dispersed in the 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 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 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,
Lipophilic surfactants and the like can be mentioned. 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, butylphthalylbutyl glycolate, and the like. And polyesters of polyethylene glycol and aliphatic dibasic acid, such as polyesters of triethylene glycol and adipic acid, and polyesters of diethylene glycol and succinic acid.

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. This layer thickness is 50 to 5
It is preferably set to 00 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 characteristics of the intended radiation image conversion panel, the type of stimulable phosphor, and the mixture of the binder and 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 protective film. For example, the phosphor sheet is sandwiched between the upper and lower protective films, and the peripheral portion is sealed. And a laminating method in which two heated rollers are pressurized and heated.

In the above-mentioned method of heat-sealing with an impulse sealer, heat-sealing under a reduced pressure environment is more preferable from the viewpoint of preventing displacement of the phosphor sheet in the protective film and eliminating moisture in the atmosphere. .

[0074]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited thereto.

Example 1 << Preparation of Radiation Image Conversion Panel Sample 7 >> (Preparation of Phosphor Sheet) In order to synthesize a stimulable phosphor precursor of europium-activated barium fluoroiodide, BaI was used.
2780 ml of ₂ aqueous solution (3.6 mol / L) and 27 ml of EuI ₃ aqueous solution (0.2 mol / L) were put in a reactor.
The reaction mother liquor in the reactor was kept at 83 ° C. while stirring. 322m of ammonium fluoride aqueous solution (8mol / L)
1 was injected into the reaction mother liquor using a roller pump to form 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 fusion between particles, alumina ultrafine powder is used in an amount of 0.1%.
2% by mass was added, and the mixture was sufficiently stirred with a mixer to uniformly adhere ultrafine alumina powder to the crystal 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 was applied on a 100-μm-thick black PET support using a doctor blade, and then dried at 100 ° C. for 15 minutes to prepare a phosphor sheet having a 270 μm-thick phosphor layer.

(Preparation of Protective Film) As the protective film on the phosphor surface side of the phosphor sheet obtained above, one having the following constitution (A) was used.

Configuration (A) VMPET12 // VMPET12 // PET12 //
Sealant film PET: Polyethylene terephthalate Sealant film: CPP (casting polyproprete) or LLDPE (low-density linear polyethylene) is used as a heat-sealable film. The number after is the film thickness (μm)
Is shown.

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-based adhesive.

At this time, by adding an organic blue colorant (Zavon Fast Blue 3G, manufactured by Hoechst) previously dispersed and dissolved in methyl ethyl ketone to the used adhesive solution, all of the adhesive layer is excited. A light absorbing layer was formed. The light transmittance of the excitation light absorbing layer was adjusted by adjusting the amount of addition at this time.

The light transmittance of the excitation light absorbing layer referred to here is
The light transmittance at the light wavelength of the semiconductor laser light (690 nm) was a value when compared with the light transmittance of an equivalent protective film having no excitation light absorbing layer.

The protective film on the support surface side of the phosphor sheet was a dry laminate film having a structure of sealant film / aluminum foil film 9 μm / polyethylene terephthalate (PET) 188 μm. 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.

(Sealing of Phosphor Sheet)
It was cut into a square of 0 cm × 20 cm, and using a protective film having the various haze and excitation light absorbing layers described above, the peripheral edge was fused under the reduced pressure using an impulse sealer, and the upper and lower edges were fused and four sides were sealed. . FIG. 1 is a cross-sectional view of a radiation image conversion panel having a configuration in which upper and lower edges are fused and four sides are sealed (two sides are not shown in FIG. 1). The distance from the fused portion to the peripheral edge of the phosphor sheet is 1
mm. The heater of the impulse sealer used for fusion had a width of 8 mm.

A radiation image conversion panel sample 7 was obtained as described above. In addition, except that the light transmittance of the protective layer and the light transmittance of the support were adjusted as shown in Table 1, radiation image conversion panels 8 to 11 and a comparative radiation image conversion panel sample 2 were produced in the same manner.

Next, except that the phosphor sheet was sealed in an integrally folded configuration as shown in FIG. 2 and the light transmittance of the protective layer and the light transmittance of the support were adjusted as shown in Table 1. Radiation image conversion panel samples 1 to 6 and comparative radiation image conversion panel sample 1 were prepared in the same manner as in the preparation of sample 7.

Further, in the preparation of the radiation image conversion panel sample 7, a PET film (thickness: about 12 μm) provided with a polyester-based adhesive on the phosphor sheet was laminated such that the adhesive came to the phosphor layer surface. In the same manner as above, except that the light transmittance of the protective layer and the light transmittance of the support were adjusted as shown in Table 1 by adjusting the light transmittance of the protective layer by heating and pressing using a heat roll at 80 to 100 ° C. to form an unsealed structure. Radiation image conversion panels 12 to 14, comparative radiation image conversion panel sample 3
Were each produced.

The obtained radiation image conversion panel samples were evaluated as described below. << Evaluation of Radiation Image Conversion Panel >> (Evaluation of Sharpness) Regarding sharpness, the radiation image conversion panel was irradiated with X-rays having a tube voltage of 80 kVp through a lead MTF chart.
The panel is scanned with a semiconductor laser beam (690 nm) to excite it, the stimulated emission emitted from the phosphor layer is received by the same photodetector as described above, and converted into an electric signal, which is converted from analog to digital to a hard disk. And analyze the record with a computer and record the X
The modulation transfer function (MTF) of the line image was examined. Spatial frequency 1
The MTF value (%) at the cycle / mm was measured. M
The higher the TF value, the better the sharpness can be obtained, which is preferable. Further, the sharpness for practical use as a radiation image conversion panel preferably exceeds 65%.

<< Evaluation of Contrast >> The contrast was measured by uniformly irradiating X-rays having a tube voltage of 80 kVp so that a lead disk having a thickness of 2 mm was projected onto the produced radiation image conversion panel. 690n
m), the excitation is performed by scanning, and the stimulated emission emitted from the phosphor layer is received by a photodetector (a photomultiplier tube having a spectral sensitivity of S-5), and the image is read. Output using a laser writing type film printer,
The black-and-white contrast level appearing in the lead disk portion and the peripheral portion of the image was visually evaluated by the following five-stage evaluation. The five-level evaluation by visual observation was based on the following criteria, and the evaluation of 3 or less was judged to be unsuitable for diagnosis in practice.

5: Peripheral edge of lead disk and brightness difference between black and white are clearly confirmed. 4: Peripheral edge of lead disk is slightly blurred, but brightness difference between black and white is almost clearly recognized. 3: Peripheral edge of lead disk. 2: The brightness difference between black and white is not clear. 2: The brightness difference between the lead disk and black and white is not clear, and the lead disk size is not reproduced. 1: The brightness difference between the shape of the lead disk and the brightness difference between black and white. The results are not clear, and the whiteness at the center is low. The obtained results are shown in Table 1.

[0090]

[Table 1]

From Table 1, it can be seen that the sample of the present invention shows better sharpness and a high-contrast image can be obtained as compared with the comparison.

[0092]

According to the present invention, a radiation image conversion panel having good image sharpness and obtaining a high-contrast image can be provided.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an example of a radiation image conversion panel of the present invention in which a protective film form has an upper and lower edge fused configuration.

FIG. 2 is a cross-sectional view showing an example of a radiation image conversion panel of the present invention in which a protective film form has an integrally folded configuration.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 radiation image conversion panel 11 phosphor 12 support 13 protective film 14 protective film 2 radiation image conversion panel 15 protective film 15 a

Claims (5)

[Claims] 1. A phosphor sheet having a stimulable phosphor layer on a support, and a protective film disposed above and below the phosphor sheet and provided so as to cover the entire surface of the phosphor sheet. A radiation image conversion panel, comprising the protective film having an excitation light absorbing function. 2. A protection film, which is disposed above and below a phosphor sheet and is provided so as to cover the entire surface of the phosphor sheet, is formed from a folded protection film. Item 2. A radiation image conversion panel according to Item 1. 3. The excitation light absorbing function of the folded portion of the protective film is larger than the excitation light absorbing function of the protective film disposed on the stimulable phosphor layer. Radiation image conversion panel. 4. The radiation image conversion panel according to claim 1, wherein the support has an excitation light absorbing function. 5. The protective film A provided on the support surface opposite to the support having the stimulable phosphor layer has an excitation light absorbing function provided by the protection film provided on the stimulable phosphor layer side. The radiation image conversion panel according to any one of claims 1 to 4, wherein the radiation image conversion panel has an excitation light absorption function larger than that of the film B.