JPH0634118B2 - Radiation image conversion panel - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a radiation image conversion panel used in a radiation image conversion method using a stimulable phosphor.

[Technical Background of the Invention] As a method replacing the conventional radiographic method, for example, as described in JP-A-55-12145,
A radiation image conversion method using a stimulable phosphor is known. This method uses a radiation image conversion panel (stimulable phosphor sheet) containing a stimulable phosphor, and the radiation transmitted through the subject or the radiation emitted from the subject is stimulable to the panel. After being absorbed by the phosphor, the stimulable phosphor is then irradiated with electromagnetic waves (excitation light) such as visible light and infrared light.
The radiation energy accumulated in the stimulable phosphor is emitted as fluorescence (stimulated luminescence) by exciting it in a time series with. Recording signal such as photosensitive filter, CR
The image is reproduced as a visible image on a display device such as T.

This radiographic image conversion method has an advantage that a radiographic image having a large amount of information can be obtained with a much smaller exposure dose than in the case of the conventional radiographic method. Therefore, this method is especially useful for medical diagnosis.
It has a very high utility value in direct medical radiography such as radiography.

The radiation image conversion panel used in the radiation image conversion method is
The basic structure is composed of a support and a phosphor layer provided on one surface thereof. In addition, the surface of the phosphor layer opposite to the support (the surface not facing the support) is generally provided with a transparent protective film made of a polymer substance, and the phosphor layer is chemically protected. Protects against physical alteration or physical shock.

The phosphor layer is generally composed of a stimulable phosphor and a binder which contains and supports the stimulable phosphor in a dispersed state. The stimulable phosphor absorbs radiation such as X-ray and then visible light and infrared rays. When it is irradiated with electromagnetic waves (excitation light), it has a property of emitting light (stimulated light emission). Therefore, the radiation transmitted through the subject or emitted from the subject is absorbed by the phosphor layer of the radiation image conversion panel in proportion to the radiation amount, and the radiation image of the subject or the subject is displayed on the radiation image conversion panel. It is formed as an accumulated image of radiation energy. This accumulated image can be emitted as stimulated emission by being excited in time series by the electromagnetic wave, and the accumulated image of radiation energy can be imaged by photoelectrically reading this stimulated emission and converting it into an electric signal. Can be converted.

Although the radiation image conversion method is a very advantageous image forming method as described above, the radiation image conversion panel used in this method is also similar to the intensifying screen used in the conventional radiographic method,
It is desired to provide an image having high sensitivity and excellent image quality (sharpness, graininess, etc.). In particular, when applying the radiation image conversion method to medical radiation imaging, it is necessary to reduce the exposure dose to the human body and obtain more information. Therefore, the radiation image conversion panel used in the method should be as sensitive as possible. Is desirable.

The sensitivity of the radiation image conversion panel is basically determined by the stimulated emission amount of the stimulable phosphor contained in the panel, and this emission amount depends not only on the emission characteristics of the phosphor itself,
When the excitation light for generating stimulated emission does not have sufficient intensity, it also depends on the intensity.

In the radiation image conversion method, the radiation image conversion panel is read out by scanning the panel surface with, for example, laser light as excitation light. However, a part of the excitation light is stimulable in the phosphor layer. Since the phosphor passes through the panel without being excited and is emitted from the panel surface on the opposite side, the phosphor is not sufficiently excited, and therefore, it cannot be said that the utilization efficiency of the excitation light is necessarily high. In particular, when a laser having a small output is used as a light source of excitation light, it is desired to improve the utilization efficiency of the excitation light and improve the sensitivity of the panel.

The applicant has already applied for a radiation image conversion panel in which an antireflection film made of an inorganic substance or the like is provided on the panel surface (Japanese Patent Laid-Open No. 61-164200). The thin film is provided in order to prevent the excitation light applied to the panel from being reflected on the surface of the panel, and is merely a thin film having a characteristic that the light reflectance with respect to the excitation light is low.

Further, the present applicant has found that the light reflectance at the excitation wavelength of the stimulable phosphor is 60% or more on one surface of the phosphor layer made of a binder containing and supporting the stimulable phosphor in a dispersed state. And a patent has already been filed for a radiation image conversion panel provided with a multilayer film filter having a light transmittance of 60% or more at the stimulated emission wavelength of the stimulable phosphor (Japanese Patent Application No. 61- 11297).

SUMMARY OF THE INVENTION An object of the present invention is to provide a radiation image conversion panel with improved sensitivity.

The above-mentioned object is a radiation image conversion panel having a phosphor layer obtained by sintering a stimulable phosphor, on one surface of the phosphor layer, the light reflectance at the excitation wavelength of the stimulable phosphor. Of 60% or more and a light transmittance at the stimulated emission wavelength of 60% or more is provided in the multilayer film filter of the present invention.

That is, the present invention, the phosphor layer of the radiation image conversion panel is composed of only the sintered stimulable phosphor, and on one surface of the phosphor layer to the light of the excitation wavelength of the stimulable phosphor By providing the reflective multilayer film filter, the utilization efficiency of the excitation light is increased and the packing state of the phosphor is densified to realize a remarkable improvement in sensitivity.

In the radiation image storage panel of the present invention, a multilayer film filter such as a dichroic filter having a reflection characteristic for excitation light is provided on one surface of the phosphor layer.
When the panel is read out, by irradiating the excitation light from the side where the multilayer filter is not provided, the excitation light that tries to pass through the phosphor layer without exciting the phosphor is reflected by the multilayer filter and is again phosphor. It will proceed through the layers. If the multilayer filter is transmissive to the stimulated emission light, the stimulated emission light is transmitted through the multilayer filter by performing the detection from the opposite side where the multilayer filter is provided. Will be detected by a photodetector installed facing the panel.

As a result, it is possible to reduce the loss of the excitation light such that the excitation light in the phosphor layer deviates to the outside without contributing to the excitation of the stimulable phosphor, and accumulated in the excited stimulable phosphor. The rate at which the stored information (trapped electrons) is read can be increased. In other words, by confining the excitation light in the panel, the stimulated emission amount of the phosphor can be significantly increased, and the sensitivity of the panel can be remarkably enhanced as compared with the conventional case.

Further, since the phosphor layer itself does not contain a binder and is filled with the stimulable phosphor at a high density, the phosphor layer can be absorbed by the conventional binder as compared with the phosphor layer in which the phosphor particles are supported. The amount of radiation is large, which can also increase the sensitivity. There is no mixing of air that was apt to occur when the phosphor is dispersedly contained in the binder, and since there are few bubbles in the phosphor layer, it is possible to reduce scattering of excitation light and stimulated emission light. The sensitivity can be further increased.

Therefore, the amount of radiation absorbed per phosphor layer having the same film thickness is large, and the information can be efficiently read out, so that the quantum noise of radiation can be reduced and an image with excellent graininess can be obtained.

Further, the panel can be maintained at high sensitivity even when the excitation light with low intensity is irradiated. Particularly, when the light source of the excitation light has a small output or when the intensity of the excitation light cannot be increased due to the read setting conditions,
It can be said that the increase in utilization efficiency of the radiation image conversion panel for the excitation light is a great advantage.

Further, when the multilayer filter is transparent to the stimulated emission light, the excitation light does not pass and only the stimulated emission light passes and is detected, so that the excitation light wavelength and the emission light wavelength are Even if they are close to each other, it is not necessary to perform wavelength separation when detecting light, and it is not necessary to provide a special means therefor.

As described above, by using the panel of the present invention, restrictions on the excitation light source and the readout system can be relaxed, and the radiation image conversion device used for readout of the panel can be improved in size, speed, and the like. Easy,
Consequently, it becomes possible to widen the range of application of the radiation image conversion method.

[Structure of the Invention] FIG. 1 shows an aspect of the radiation image storage panel of the present invention.

FIG. 1 is a sectional view showing the layer structure of a radiation image storage panel according to the present invention.

In FIG. 1, the panel is composed of a multilayer filter 1, a sintered phosphor layer 2 and a protective film 3 in this order, and the multilayer filter 1 is reflective to the light of the excitation wavelength of the stimulable phosphor. Therefore, it is transparent to the light having the stimulated emission wavelength. The excitation light is irradiated from the protective film side (solid line arrow →), and the stimulated emission light is detected from the filter side (dotted line arrow). ).

However, the radiation image conversion panel of the present invention is not limited to the above-mentioned aspect, and it is sufficient that at least the multilayer filter is provided on one surface of the phosphor layer, for example, the side in contact with the phosphor layer of the multilayer filter. A support may be provided on the opposite side.

The radiation image storage panel of the present invention can be manufactured, for example, by the method described below.

The multilayer filter, which is a characteristic requirement of the present invention, has a light reflectance of 60% or more with respect to the excitation light for exciting the stimulable phosphor used in the radiation image conversion panel. Preferably, it has a light reflectance of 80% or more with respect to the excitation light. That is, the multilayer filter needs to have the reflectance for at least one wavelength included in the excitation wavelength region of the stimulable phosphor. It is preferable that the above reflectance is satisfied with respect to a wavelength near the peak of the excitation spectrum of the phosphor.

The multilayer filter also has a light transmittance of the stimulable phosphor for stimulated emission light of 60% or more, particularly preferably 80.
% Or more. Here, the transmittance may be shown at least for one wavelength included in the stimulated emission wavelength region of the stimulable phosphor, and preferably for a wavelength near the emission peak. .

As an example, a commercially available radiation image conversion panel usually uses a divalent europium-activated barium fluorobromide-based phosphor (emission peak wavelength: about 390 nm), and He-Ne laser light (wavelength: wavelength) as excitation light. : 633 nm) is used. When the panel contains this stimulable phosphor, the multilayer filter may have, for example, a light reflectance for the excitation wavelength of 633 nm that satisfies the above numerical range. Further, it is preferable that the light transmittance for the stimulated emission wavelength of 390 nm satisfies the above numerical range.

A dichroic filter is a typical multi-layer film filter having the above-described reflection characteristics and transmission characteristics.

FIG. 2 shows the reflection and transmission characteristics of the dichroic filter which is an example of the multilayer filter used in the present invention.

FIG. 2 shows the transmission and reflection spectra of the dichroic filter. A filter that is light-reflective with respect to the excitation wavelength of the stimulable phosphor and light-transmissive with respect to the stimulable emission wavelength is shown.

The multilayer filter is one in which two or more kinds of substances having different refractive indexes are sequentially laminated in a thickness of about 1/4 of the wavelength of light.
Various materials used for known optical thin films can be used for the multilayer filter, but specifically, Si
Low refractive index materials such as O ₂ and MgF ₂ and TiO ₂ and Z
High refractive index materials such as rO ₂ and ZnS can be mentioned.

The multilayer filter is provided by laminating several layers to several tens of layers on the surface of a transparent substrate such as a glass plate by a method such as vacuum deposition, sputtering, and ion plating. it can. The ion plating method is a preferable method in the case where the substrate is made of a polymer substance, because a filter having high adhesion to the substrate can be formed without raising the temperature of the substrate.

In manufacturing a multilayer filter, various filters having the above characteristics can be obtained according to the stimulable phosphor to be used by controlling the constituent substances (refractive index) and the film thickness of each layer. Generally, the total thickness of the multilayer filter is in the range of about 0.1 to 10 μm.

In addition, since the multilayer filter is usually formed on a substrate such as a glass plate, it is not necessary to provide a support in the radiation image storage panel of the present invention, but if desired, a plastic used in a known panel may be used. A transparent support made of a sheet or the like may be provided on one surface of the multilayer filter (the side not in contact with the phosphor layer) with an adhesive or the like.

Next, a phosphor layer is formed on the transparent substrate on which the multilayer filter is formed. The phosphor layer, which is the second characteristic requirement of the present invention, is a layer composed only of a sintered stimulable phosphor.

The stimulable phosphor is a phosphor that exhibits stimulated emission when irradiated with excitation light after being irradiated with radiation as described above, but from a practical viewpoint, the wavelength is in the range of 400 to 900 nm. A phosphor that exhibits stimulated emission in the wavelength range of 300 to 500 nm by excitation light is desirable. Examples of stimulable phosphors used in the radiation image storage panel of the present invention include SrS: Ce, Sm, SrS: Eu, Sm and Th described in US Pat. No. 3,859,527.
O ₂ : Er, and La ₂ O ₂ S: Eu, Sm, Zn described in JP-A-55-12142.
S; Cu, Pb, BaO.xA ₂ O ₃ : Eu (however, 0.8 ≦ x ≦ 10), and M ^II O.xSi
O ₂ : A (however, M ^II is Mg, Ca, Sr, Zn, C
d, or Ba, A is Ce, Tb, Eu, Tm,
Pb, T, Bi, or Mn, and x is 0.5 ≦
x ≦ 2.5), as described in JP-A-55-12143 (Ba).
_{1-xy, Mg x, Ca} y) FX: aEu 2+ ( However, X
Is at least one of C and Br, x and y are 0 <x + y ≦ 0.6, and xy ≠ 0,
a is 10 ⁻⁶ ≦ a ≦ 5 × 10 ⁻² ), LnO described in JP-A-55-12144.
X: xA (where Ln is La, Y, Gd, and Lu
, X is at least one of C and Br, A is at least one of Ce and Tb, and x is 0 <x <0.1). No. 12145 gazette (Ba
_1-x , M ²⁺ _x ) FX: yA (where M ²⁺ is Mg, C
at least one of a, Sr, Zn, and Cd,
X is at least one of C, Br, and I, A
Is Eu, Tb, Ce, Tm, Dy, Pr, Ho, Nd,
At least one of Yb and Er, and x
Is 0 ≦ x ≦ 0.6 and y is 0 ≦ y ≦ 0.2), M ^II described in JP-A-55-160078.
FX xA: yLn [However, M ^II is Ba, Ca, S
at least one of r, Mg, Zn, and Cd,
A is BeO, MgO, CaO, SrO, BaO, Zn
O, A ₂ O ₃ , Y ₂ O ₃ , La ₂ O ₃ , In ₂ O ₃ ,
SiO ₂ , TiO ₂ , ZrO ₂ , GeO ₂ , SnO ₂ ,
At least one of Nb ₂ O ₅ , Ta ₂ O ₅ , and ThO ₂ , and Ln is Eu, Tb, Ce, Tm, Dy, P.
At least one of r, Ho, Nd, Yb, Er, Sm, and Gd, X is at least one of C, Br, and I, and x and y are each 5 × 10 5.
^-5 ≦ x ≦ 0.5 and 0 <y ≦ 0.2], which is described in JP-A-56-116777 (B).
a _1-x , M ^II _x ) F ₂ · aBaX ₂ : yEu, zA [where M ^II is beryllium, magnesium, calcium,
At least one of strontium, zinc, and cadmium, X is at least one of chlorine, bromine, and iodine, A is at least one of zirconium and scandium, and a, x, y, and z are each 0. .5 ≦ a ≦ 1.25, 0 ≦ x ≦ 1, 10 ⁻⁶ ≦ y
≦ 2 × 10 ⁻¹ , and 0 <z ≦ 10 ⁻² ], which is described in JP-A-57-23673 (Ba).
_1-x , M ^II _x ) F ₂ · aBaX ₂ : yEu, zB [M ^II is at least one of beryllium, magnesium, calcium, strontium, zinc, and cadmium, and X is chlorine, bromine, and iodine. And at least one of a, x, y, and z is 0.
5 ≦ a ≦ 1.25, 0 ≦ x ≦ 1, 10 ⁻⁶ ≦ y ≦ 2 × 10
⁻¹ , and 0 <z ≦ 2 × 10 ⁻¹ ], the phosphor represented by the composition formula described in JP-A-57-23675 (Ba).
_1-x , M ^II _x ) F ₂ · aBaX ₂ : yEu, zA [where M ^II is beryllium, magnesium, calcium,
At least one of strontium, zinc, and cadmium, X is at least one of chlorine, bromine, and iodine, A is at least one of arsenic and silicon, and a, x, y, and z are each 0. .5 ≦ a
≦ 1.25, 0 ≦ x ≦ 1, 10 ⁻⁶ ≦ y ≦ 2 × 10 ⁻¹ , and 0 <z ≦ 5 × 10 ⁻¹ ]. M ^III described in Japanese Patent No. 69281
OX: xCe [However, M ^III is Pr, Nd, Pm, S
m, Eu, Tb, Dy, Ho, Er, Tm, Yb, and at least one trivalent metal selected from the group consisting of Bi, and X is one or both of C and Br, x is 0 <x <0.1], a phosphor represented by the composition formula: Ba described in JP-A-58-206678.
_1-x M _{x / 2} L _{x / 2} FX: _y Eu ²⁺ [where M is Li, N
a represents at least one alkali metal selected from the group consisting of K, Rb, and Cs; L represents Sc, Y,
La, Ce, Pr, Nd, Pm, Sm, Gd, Tb, D
y, Ho, Er, Tm, Yb, Lu, A, Ga, I
n and at least one trivalent metal selected from the group consisting of T; X represents at least one halogen selected from the group consisting of C, Br, and I; and x represents 10 ^-2 ≤x ≦ 0.5, y is 0 <y ≦
0.1]] and a BaF described in JP-A-59-27980.
X · xA: yEu ²⁺ [wherein X is at least one halogen selected from the group consisting of C, Br, and I; A is a calcined product of a tetrafluoroboric acid compound; and x is 10 ⁻⁶ ≦ x ≦ 0.1, y is 0 <y ≦
0.1]] and a BaF described in JP-A-59-47289.
X · xA: yEu ²⁺ [wherein X is at least one halogen selected from the group consisting of C, Br, and I; A is hexafluorosilicic acid, hexafluorotitanic acid, and hexafluorozirconic acid Is a calcined product of at least one compound selected from the group of hexafluoro compounds consisting of monovalent or divalent metal salts; and x is 10 ⁻⁶ ≦ x ≦ 0.1 and y is 0 <y ≦ 0. 1. The phosphor represented by the composition formula [1], BaF described in JP-A-59-56479.
X · xNaX ′: aEu ²⁺ [where X and X ′ are
At least one of C, Br, and I, and x and a are 0 <x ≦ 2 and 0 <, respectively.
a ≦ 0.2], the phosphor represented by the composition formula: M ^II F described in JP-A-59-56480.
X · xNaX ′: yEu ²⁺ : zA [where M ^II is B
a is at least one alkaline earth metal selected from the group consisting of Sr, and Ca; X and X ′ are at least one halogen selected from the group consisting of C, Br, and I; A is , V, Cr, M
at least one transition metal selected from n, Fe, Co, and Ni; and x is 0 <X ≦ 2, y is 0
<Y ≦ 0.2, and z is 0 <z ≦ 10 ⁻² ], the phosphor represented by the composition formula: M ^II F described in JP-A-59-75200.
X ・ aM ^I X '・ bM' ^II X " ₂・ cM ^III X ₃・ x
A: yEu ²⁺ [However, M ^II is Ba, Sr, and Ca
Is at least one alkaline earth metal selected from the group consisting of, M ^I is Li, Na, K, Rb, and Cs
Is at least one alkali metal selected from the group consisting of; M ^'II is at least one trivalent metal selected from the group consisting of Be and Mg; M ^II is A, G
at least one trivalent metal selected from the group consisting of a, In, and T; A is a metal oxide; X is at least one halogen selected from the group consisting of C, Br, and I; X ′, X ″, and X are
Is at least one halogen selected from the group consisting of F, C, Br, and I; and a is 0 ≦ a ≦
2, b is 0 ≦ b ≦ 10 ⁻² , c is 0 ≦ c ≦ 10 ⁻² , and a
+ B + c ≧ 10 ⁻⁶ ; x is 0 <x ≦ 0.5, y is 0
Phosphor represented by the composition formula of <y ≦ 0.2], M ^II X described in JP-A-60-84381.
₂ · aM ^II X ′ ₂ : xEu ²⁺ [where M ^II is Ba, S
at least one alkaline earth metal selected from the group consisting of r and Ca; X and X ′ are at least one halogen selected from the group consisting of C, Br and I, and X ≠ X ′. ; And a is 0.1 ≦
a ≦ 10.0, x is 0 <x ≦ 0.2], and a stimulable phosphor represented by the composition formula M ^II described in JP-A-60-101173.
^{FX · aM I X ': xEu} 2+ [ However, M ^II is Ba, S
at least one alkaline earth metal selected from the group consisting of r and Ca; M ^I is at least one alkali metal selected from the group consisting of Rb and Cs; X is from the group consisting of C, Br and I At least one halogen selected; X'is F, C, Br
And at least one halogen selected from the group consisting of I and I; and a and x are each 0 ≦ a ≦ 4.
0 and 0 <x ≦ 0.2 in which] stimulable phosphor represented by a composition formula of which is described in Japanese Patent Application No. Sho 60-70484 Pat of the applicant ^M I X: xBi [However, 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 C, Br and I; and x is 0.
A photostimulable phosphor represented by the composition formula <x ≦ 0.2], JP-A-61-72087 and JP-A-61-72.
Examples thereof include alkali metal halide phosphors described in Japanese Patent No. 088.

In addition, in the M ^II X ₂ · aM ^II X ′ ₂ : xEu ²⁺ stimulable phosphor described in JP-A-60-84381, the following additives are added to M ^II X _2. · aM ^II X _'2
It may be contained in the following ratio per mol.

BM described in JP-A-60-166379
^I X ″ (where 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, C, Br and I, and b is 0 <b ≦ 10.
BKX ″ · cMgX ₂ · dM ^III X ′ described in JP-A-60-221483.
₃ (however, M ^III is Sc, Y, La, Gd and Lu
At least one trivalent metal selected from the group consisting of X ″, X and X ′ are all F, C and Br.
And at least one halogen selected from the group consisting of I, and b, c and d are each 0 ≦
b ≦ 2.0, 0 ≦ c ≦ 2.0, 0 ≦ d ≦ 2.0, and 2 × 10 ⁻⁵ ≦ b + c + d);
YB described in JP-A-228592 (however,
y is 2 × 10 ⁻⁴ ≦ y ≦ 2 × 10 ⁻¹ );
BA described in Japanese Patent No. 228593 (however,
A is at least one oxide selected from the group consisting of SiO ₂ and P ₂ O ₅ , and b is 10 ⁻⁴ ≦ b ≦
10 ⁻¹ ); bSiO described in JP-A-61-1208883 (where b is 0 <b ≦ 3 × 10).
^-2 ); bSnX ″ ₂ (where X ″ is F, C, Br) described in JP-A-61-120885.
And at least one halogen selected from the group consisting of I and b, and b is 0 <b ≦ 10 ⁻³ ); bCs described in JP-A No. 61-235486.
X ″ · cSnX ₂ (wherein X ″ and X are at least one halogen selected from the group consisting of F, C, Br and I, and b and c are 0 <b ≦ 10.0 and 10 respectively. ^-6 ≤ c ≤ 2 x 10 ^-2
BCsX ″ · yLn ³⁺ described in JP-A-61-235487 (where X ″ is at least one halogen selected from the group consisting of F, C, Br and I, Ln is Sc, Y, Ce, P
r, Nd, Sm, Gd, Tb, Dy, Ho, Er, T
at least one rare earth element selected from the group consisting of m, Yb, and Lu, and b and y are 0 <b ≦ 10.0 and 10 ⁻⁶ ≦ y ≦ 1.8 × 10, respectively.
^-1 ).

Among the above-mentioned stimulable phosphors, the divalent europium-activated alkaline earth metal halide-based phosphor and the rare earth element-activated rare earth oxyhalide-based phosphor are particularly preferable because they exhibit high-intensity stimulated emission. However, the stimulable phosphor used in the present invention is not limited to the above-mentioned phosphor, and may be any phosphor that exhibits stimulated emission when irradiated with excitation light after irradiation with radiation. It may be.

In the radiation image storage panel of the present invention, the phosphor layer can be formed by the step of molding the phosphor layer forming material containing the stimulable phosphor into a sheet and the step of sintering the molded product.

First, in the molding step, a powdery material composed of particles of the above-described stimulable phosphor is used as the phosphor layer forming material.

Alternatively, a dispersion liquid containing stimulable phosphor particles and a binder can be used. In this case, the stimulable phosphor and the binder are added to a suitable solvent and then thoroughly mixed,
A dispersion liquid in which phosphor particles are uniformly dispersed in a binder solution is prepared.

As the binder, a substance excellent in dispersibility of the phosphor or divergence in the sintering step is preferable. An example of this is paraffin (for example, carbon number: 16
-40, melting point: 37.8-64.5 ° C); wax (example of natural wax: candelilla wax, carnauba wax, rice wax, plant wax such as wood wax, beeswax, lanolin, whale wax, etc.) Examples of animal waxes, mineral waxes such as montan wax, ozokerite, ceresin, synthetic waxes: synthetic waxes such as polyethylene wax, Fischer-Tropsch wax, coal-based waxes, hardened castor oil, fatty acid amides, ketones and other synthetic waxes ); Resin (eg, polyvinyl butyral, polyvinyl acetate, nitrocellulose,
Examples thereof include ethyl cellulose, vinylidene chloride / vinyl chloride copolymer, polyalkyl (meth) acrylate, vinyl chloride / vinyl acetate copolymer, polyurethane cellulose acetate butyrate, polyvinyl alcohol, and linear polyester. Further, proteins such as gelatin, polysaccharides such as dextran, gum arabic and the like can also be used.

Examples of the solvent include lower alcohols such as methanol, ethanol, n-propanol and n-butanol; hydrocarbons containing a chlorine atom such as methylene chloride and ethylene chloride; ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone; methyl acetate, acetic acid. Mention may be made of esters of lower fatty acids and lower alcohols such as ethyl and butyl acetate; ethers such as dioxane, ethylene glycol monoethyl ether, ethylene glycol monomethyl ether; and mixtures thereof.

The mixing ratio of the binder and the stimulable phosphor in the dispersion liquid varies depending on the kind of the phosphor or the molding conditions and sintering conditions described later, but generally the mixing ratio of the binder and the phosphor is 1 :. It is preferably selected in the range of 1 to 1: 300 (weight ratio), and particularly preferably in the range of 1:20 to 1: 150 (weight ratio).

The dispersion liquid may be mixed with an additive such as a dispersant for improving the dispersibility of the phosphor. Examples of dispersants include phthalic acid, stearic acid, caproic acid, lipophilic surfactants and the like.

When the material for forming the phosphor layer is a powdery material composed of phosphor particles, it can be molded into a sheet by, for example, pressing the powdery material into a molding die. A rectangular mold is usually used as the molding die. When the phosphor layer-forming material is a dispersion liquid containing phosphor particles and a binder, it is applied onto an appropriate substrate using a usual application method (for example, a doctor blade) and molded into a sheet. Alternatively, or in the same manner as the above powdery material, it is poured into a molding die to be molded into a sheet. As the substrate, for example, a sheet made of an inorganic material such as quartz, zirconia, alumina, or silicon carbide is used.

A compression treatment may be performed during molding, and it is particularly preferable to perform the compression treatment when the phosphor layer forming material is a powder. The compression process is performed by, for example, press molding, and 1 ×
It is preferable to apply a pressure in the range of 10 ² to 1 × 10 ⁴ kg / cm ² . This makes it possible to further increase the relative density of the phosphor layer obtained.

Next, the sheet-shaped molded product is subjected to a sintering process.

Sintering is performed in a firing furnace such as an electric furnace. The sintering temperature and the sintering time differ depending on the type of phosphor layer forming material, the shape and state of the sheet-shaped molded product, and the type of stimulable phosphor used for these. Generally, in the case where the sheet-shaped molded product is a powdered product made of a phosphor, the sintering temperature is in the range of 500 to 1000 ° C., preferably 70.
The sintering time is in the range of 0 to 950 ° C., and the sintering time is in the range of 0.5 to 6 hours, preferably 1 to 4 hours. As the sintering atmosphere, a neutral atmosphere such as a nitrogen gas atmosphere or an argon gas atmosphere, or a weakly reducing atmosphere such as a nitrogen gas atmosphere containing a small amount of hydrogen gas or a carbon dioxide atmosphere containing carbon monoxide is used. .

When the sheet-shaped molded product is a dispersion liquid containing a phosphor and a binder, the binder in the sheet-shaped molded product is previously subjected to a nitrogen gas atmosphere, a neutral atmosphere such as an argon gas atmosphere, an oxygen gas atmosphere, or an air atmosphere. It is preferable to evaporate the phosphor at a relatively low temperature (a temperature in the range of 100 to 450 ° C.) in an oxidizing atmosphere such as, and then sinter the phosphor under the above sintering conditions. By heating in this low temperature range, components other than the stimulable phosphor such as a binder evaporate or carbonize at around 300 to 400 ° C., and further become carbon dioxide gas to dissipate and can be easily removed. . As a result, the sintered phosphor layer is composed only of the phosphor. The time required for low temperature evaporation is preferably in the range of 0.5 to 6 hours.

The compression process may be performed before the sintering process as described above, but may be performed during the sintering process. That is,
You may sinter while giving a compression process. In particular, it is suitable when the sheet-shaped molded product is a powdery product composed of phosphor particles.

The layer thickness of the sintered phosphor layer varies depending on the intended characteristics of the radiation image conversion panel and the like, but is generally in the range of 20 μm to 1 mm, and preferably in the range of 50 to 500 μm. The grain boundary size of the phosphor is 1 to 100 μm.
It is preferably in the range of m.

Then, the phosphor layer can be provided on the multilayer filter by adhering it to the multilayer filter using an adhesive or the like. When the sheet-shaped molded product is provided on the substrate by coating, the phosphor layer is separated from the substrate. Alternatively, the sheet-shaped molded product obtained in the molding step can be directly formed on the filter by placing the molded product on a substrate provided with a multilayer film filter and performing sintering. In the case of coating, a substrate provided with a multilayer filter in advance may be used as the substrate.

Further, the multilayer filter can be provided directly or after performing a treatment such as polishing to increase the flatness of the phosphor layer formed by sintering.

The details of the method of forming the phosphor layer by the above-mentioned sintering and the effect thereof are described in Japanese Patent Application No. 61-61, filed by the applicant.
-163284.

The phosphor layer formed by the above method has a relative density of 7
It is preferably 0% or more. Here, the relative density means a value calculated by the following theoretical formula (I).

Vp / V = aA / (a + b) ρ _x V −−− (I) (where V: total volume of phosphor layer Vp: volume of phosphor A: total weight of phosphor layer ρ _x : density of phosphor) a: weight of phosphor b: weight of binder) However, since the binder is not present in the phosphor layer formed by sintering, b is almost 0.

A transparent protective film is preferably provided on the surface of the phosphor layer opposite to the side in contact with the multilayer filter for the purpose of physically and chemically protecting the phosphor layer.

The transparent protective film is, for example, a cellulose derivative such as cellulose acetate or nitrocellulose; or a transparent polymer material such as polymethyl methacrylate, polyvinyl butyral, polyvinyl formal, polycarbonate, polyvinyl acetate, vinyl chloride / vinyl acetate copolymer, or the like. It is possible to form a solution prepared by dissolving a high-molecular substance in a suitable solvent on the surface of the phosphor layer. Alternatively, a plastic sheet made of polyethylene terephthalate, polyethylene, polyvinylidene chloride, polyamide or the like; and a protective film forming sheet such as a transparent glass plate are separately formed and adhered to the surface of the phosphor layer with an appropriate adhesive. It can also be formed by the method of. The thickness of the transparent protective film thus formed is preferably about 0.1 to 20 μm.

Alternatively, the protective film may be formed by vapor-depositing an inorganic material such as an oxide such as SiO ₂ or A ₂ O _3, a fluoride such as MgF _2, a carbide such as SiC. Alternatively, the protective film can be formed using glass, ceramics, a coating agent, or the like.

Next, examples and comparative examples of the present invention will be described. However,
Each of these examples does not limit the invention.

Example 1 Methyl ethyl ketone was added to a mixture of powdery divalent europium-activated barium fluorobromide phosphor particles (BaFBr: 0.001Eu ²⁺ ) and an acrylic resin to contain phosphor particles in a dispersed state. A dispersion liquid was prepared. Next, this dispersion is thoroughly stirred and mixed using a propeller mixer,
The phosphor particles are uniformly dispersed, the mixing ratio of the binder and the phosphor particles is 1:20, and the viscosity is 35 to 50 PS (25 ° C.).
Was prepared.

This coating solution was applied uniformly on a Teflon sheet placed horizontally using a doctor blade. After the application, the Teflon sheet having the coating film formed thereon was placed in a dryer, and the temperature inside the dryer was gradually raised from 25 ° C. to 100 ° C. to dry the coating film. After drying, the coating film was peeled off from the Teflon sheet, placed on a quartz plate and placed in a high temperature electric furnace to evaporate the binder and sinter the phosphor. First, in order to evaporate the binder, the phosphor was sintered in an air atmosphere at a temperature of 400 ° C. for 4 hours, and then the phosphor was sintered in a nitrogen gas atmosphere at a temperature of 850 ° C. for 2 hours. The obtained sintered product was taken out of the electric furnace and cooled to obtain a layer thickness of 2
A phosphor layer consisting of only 50 μm phosphor was obtained.

Next, on one surface of the phosphor layer, a dichroic filter having a spectral characteristic shown in FIG. 2 (a multi-layer film provided on a transparent glass substrate, trade name: DF-C, Hoya Glass Co., Ltd.)
Was manufactured by using a polyester adhesive to attach a dichroic filter.

In addition, a transparent film of polyethylene terephthalate (thickness: 12 μm, with a polyester adhesive applied) is attached to the other surface of the phosphor layer with the adhesive layer side facing down, and the film is transparent. A protective film was formed.

In this way, a radiation image conversion panel composed of the dichroic filter, the sintered phosphor layer and the transparent protective film was manufactured [see FIG. 1].

[Comparative Example 1] A support, a sintered phosphor layer, and a transparent layer were prepared in the same manner as in Example 1 except that a transparent glass plate having the same thickness was used instead of the dichroic filter. A radiation image conversion panel composed of a protective film was manufactured.

[Comparative Example 2] On a transparent glass plate having the same thickness as the dichroic filter used in Example 1, powdery divalent europium-activated barium fluorobromide phosphor particles were coated with a binder resin (linear polyester and nitro ester) according to a conventional method. A phosphor layer having a layer thickness of 250 μm dispersed in a mixture with cellulose) is formed, and then a transparent film of polyethylene terephthalate (thickness: 12 μm) is provided on the phosphor layer to form a support, a phosphor layer and a transparent layer. A radiation image conversion panel composed of a protective film was manufactured.

Next, the radiation image conversion panels of Example 1 and Comparative Examples 1 and 2 were evaluated by performing the above-mentioned sensitivity test.

The results obtained are summarized in Table 1.

As is clear from the results shown in Table 1, the radiation image conversion panel of the present invention provided with the multilayer filter (Example 1) is a radiation image for comparison in which the multilayer filter is not provided. The sensitivity was significantly higher than that of the conversion panel (Comparative Example 1).

Further, the sensitivity of the radiation image storage panel of the present invention (Example 1) having the sintered phosphor layer and the multilayer filter is the same as that of the comparative example having the binder-containing phosphor layer and not including the multilayer filter. It was much higher than that of the radiation image conversion panel (Comparative Example 2).

[Brief description of drawings]

FIG. 1 is a sectional view showing an aspect of a radiation image storage panel according to the present invention. FIG. 2 is a diagram showing transmission and reflection spectra of a dichroic filter (light transmissive for stimulated emission wavelength), which is an example of the multilayer filter used in the present invention. 1: multilayer filter, 2: phosphor layer, 3: protective film, arrow →: excitation light, arrow : Stimulated emission light

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP 62-63929 (JP, A) JP 62-169095 (JP, A) JP 62-169096 (JP, A) JP 62- 169097 (JP, A) JP 62-169098 (JP, A) JP 62-169099 (JP, A) JP 62-169100 (JP, A) JP 62-182700 (JP, A) JP 63-167300 (JP, A)

Claims (9)

[Claims] 1. A radiation image conversion panel having a phosphor layer formed by sintering a stimulable phosphor, wherein one surface of the phosphor layer has a light reflectance at an excitation wavelength of the stimulable phosphor. Of 60% or more and a multilayer film filter having a light transmittance of 60% or more at the stimulated emission wavelength are provided. 2. The radiation image conversion panel according to claim 1, wherein the stimulable phosphor of the multilayer filter has a light reflectance of 80% or more at an excitation wavelength. 3. The radiation image storage panel according to claim 1, wherein the stimulable phosphor of the multilayer filter has a light transmittance of 80% or more at a stimulated emission wavelength. 4. The radiation image conversion panel according to claim 1, wherein the multilayer film filter is a dichroic filter. 5. The multilayer filter comprises SiO ₂ and M.
The radiation image according to claim 1, comprising at least one low refractive index substance selected from the group consisting of gF ₂ and at least one high refractive index substance selected from the group consisting of TiO ₂ , ZrO ₂ and ZnS. Conversion panel. 6. The radiation image storage panel according to claim 1, wherein the multilayer film filter is formed by vacuum vapor deposition. 7. The excitation wavelength of the stimulable phosphor is 400-9.
It is in the range of 00 nm and has a stimulated emission wavelength of 300 to 500.
The radiation image conversion panel according to claim 1, which is in the range of nm. 8. The radiation image storage panel according to claim 7, wherein the stimulable phosphor is a divalent europium-activated halide phosphor. 9. The radiation image conversion panel according to claim 8, wherein the divalent europium-activated halide phosphor is a divalent europium-activated fluorohalide phosphor.