JPH0634112B2 - 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 of obtaining a radiation image as an image, a so-called radiographic method has conventionally been used which uses a combination of a radiographic film having an emulsion layer made of a silver salt photosensitive material and an intensifying screen. There is. Recently, as one of the alternative methods to the radiographic method, a radiographic image conversion method using a stimulable phosphor as described in, for example, Japanese Patent Application Laid-Open No. 55-12145 has been attracting attention. became. The radiation image conversion method uses a radiation image conversion panel (a stimulable phosphor sheet) containing a stimulable phosphor, and the radiation transmitted through the subject or the radiation emitted from the subject is radiated to the panel. It is accumulated in the stimulable phosphor by absorbing it in the stimulable phosphor and then exciting the stimulable phosphor in time series with electromagnetic waves (excitation light) such as visible light and infrared rays. Radiation energy is emitted as fluorescence (stimulated luminescence), this fluorescence is photoelectrically read to obtain an electric signal, and the obtained electric signal is imaged.

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 composed of a stimulable phosphor and a binder which contains and supports the stimulable phosphor in a dispersed state.
After absorbing radiation such as rays, it has a property of emitting light (stimulated emission) when irradiated with electromagnetic waves (excitation light) such as visible light and infrared rays. 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 dose, and the radiation image of the subject or the subject is displayed on the radiation image conversion panel. Are 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.

The phosphor layer can also be formed by vapor deposition of a stimulable phosphor on a support instead of the method of coating by using a binder as described above. Specifically, for example, the formation of the phosphor layer is performed by the known PF CARCIA AND LH BR.
IXNER) vacuum deposition method (ELECTRONICS AND OPTICS, Th
in Solid Film, 115 (1984) 89-95).

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 surface of the panel on the opposite side, the phosphor is not sufficiently excited, so that 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 Application No. 60-5509). 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.

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 made of a stimulable phosphor, and one surface of the phosphor layer has a light reflectance of 60 at the excitation wavelength of the stimulable phosphor.
% Or more, and the radiation image conversion panel of the present invention, characterized in that a multilayer film filter having a light transmittance of 60% or more at the stimulated emission wavelength of the stimulable phosphor is provided. be able to.

The present invention provides, on one surface of a phosphor layer of a radiation image conversion panel, a multilayer filter which is light-reflecting with respect to the excitation wavelength of a stimulable phosphor and light-transmitting with respect to its stimulating emission wavelength. By providing the above, the utilization efficiency of the excitation light is increased and the sensitivity of the panel is significantly improved.

In the radiation image conversion panel of the present invention, a multilayer film filter such as a dichroic filter having a transmission and reflection characteristic that reflects excitation light and, conversely, transmits stimulated emission light, has one surface of the phosphor layer. It is provided in. When the panel is read out, the excitation light is emitted from the side where the multilayer filter is not provided, and the stimulated emission light is detected from the opposite side where the multilayer filter is provided to detect the phosphor. Excitation light that tries to pass through the phosphor layer without being excited is reflected by the multilayer filter and travels again in the phosphor layer. On the other hand, the stimulated emission light emitted from the stimulable phosphor passes through the multilayer filter and is detected by the photodetector installed facing the panel.

As a result, it is possible to prevent the loss of the excitation light such that the excitation light deviates to the outside without contributing to the excitation of the stimulable phosphor in the phosphor layer of the panel, and the excited stimulable phosphor is produced. The ratio of stored information (trapped electrons) 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.

This makes it possible to maintain a large amount of stimulated emission of the phosphor in the panel even with irradiation of excitation light of low intensity, and maintain the panel with high sensitivity. In particular, 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, the utilization efficiency of the radiation image conversion panel for the excitation light is greatly increased. It can be said to be an advantage.

Further, since the excitation light is not transmitted by the multilayer filter and only the stimulated emission light is transmitted and detected, even if the wavelength of the excitation light and the wavelength of the emission light are close to each other, the detection of the light is performed. At that time, it is not necessary to perform wavelength separation, and it is not necessary to provide a special means therefor.

Therefore, by using the panel of the present invention, it is possible to relax the restrictions on the excitation light source and the readout system, and thus it is easy to reduce the size and speed of the radiation image conversion device used to read the panel. Consequently, it becomes possible to widen the range of application of the radiation image conversion method.

[Structure of the Invention] FIG. 1 shows an embodiment of the radiation image conversion panel of the present invention having the preferable characteristics as described above.

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 comprises a multilayer filter 1, a phosphor layer 2 and a protective film 3 in this order.

However, the radiation image conversion panel of the present invention is not limited to the embodiment shown in FIG. 1, and at least the multilayer filter may be provided on one surface of the phosphor layer,
For example, a support may be further provided on the multilayer filter.

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, and It has a light transmittance of 60% or more for the stimulated emission light of the stimulable phosphor. Preferably 8 for excitation light
Has a light reflectance of 0% or more and 80% to the emitted light
It has the above light transmittance.

That is, the multilayer filter needs to have the above reflectance for at least one wavelength included in the excitation wavelength region of the stimulable phosphor. It is preferable that the reflectance be satisfied with respect to the wavelength near the peak of the excitation spectrum of the phosphor. At the same time, the multilayer filter needs to have the above-mentioned transmittance for at least one wavelength included in the stimulated emission wavelength region of the stimulable phosphor. Preferably, the above-mentioned transmittance is satisfied for wavelengths near the emission peak of the phosphor.

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. Therefore, when the panel contains this stimulable phosphor, the multilayer filter has, for example, a light reflectance for the excitation wavelength of 633 nm and a light transmittance for the stimulated emission wavelength of 390 nm that satisfy the above numerical ranges. I wish I had it.

A dichroic filter can be used as the multilayer filter having the transmission and reflection characteristics as described above.

FIG. 2 shows the transmission and reflection characteristics of a 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.

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.

By controlling the substance (refractive index) used and the film thickness of each layer in the production of the multilayer filter, various filters having the above characteristics can be obtained according to the stimulable phosphor used. 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 is basically a layer made of a binder which contains and supports stimulable phosphor particles in a dispersed state.

The phosphor layer may be a layer formed by vapor deposition of a stimulable phosphor on a support as described above.

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. It is desirable that the phosphor emits stimulated emission in the wavelength range of 300 to 500 nm by excitation light. 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
At least one of X, at least one of C and Br, A at least one of Ce and Tb, and x is 0 <x <0.1). 55-12145 (Pa (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 : yEn, 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 [wherein M ^II is at least one of beryllium, magnesium, calcium, strontium, zinc, and cadmium, and X is chlorine, bromine, or iodine. At least one of them, 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 ], the phosphor represented by the composition formula of JP-A-58-69281. M ^III described in Japanese Patent Publication
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; It is a calcined product of at least one compound selected from the group of hexafluoro compounds consisting of salts of monovalent or divalent metals; and x is 10 ⁻⁶ ≦ x ≦ 0.1 and y is 0 <y ≦ 0.1. And the 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 and 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 ^III 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 ≦ 0 ≦ 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. Stimulable phosphor represented by a composition formula of], are described in Japanese Patent Application No. Sho 60-70484 Pat of the applicant ^M I X: xBi [However, ^{M I} is 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 stimulable phosphor represented by the composition formula of <a value in the range of x ≦ 0.2].

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 and 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 Japanese Patent Application No. 59-84356 by the present applicant.
(However, y is 2 × 10 ⁻⁴ ≦ y ≦ 2 × 10 ⁻¹ );
BA described in Japanese Patent Application No. 59-84358
(However, A is at least one oxide selected from the group consisting of SiO ₂ and P ₂ O ₅ , and b is 1
0 ^-4 ≤ b ≤ 2 x 10 ^-1 ); Japanese Patent Application No. 59-2404
BSiO described in Japanese Patent No. 52 (where b is 0 <b ≦ 3 × 10 ⁻² ); Japanese Patent Application No. 59-24045.
BSnX ″ ₂ (provided that
X ″ is at least one halogen selected from the group consisting of F, C, Br and I, and b is 0 <b ≦
10 ^-3 ); bCsX ″ · cSnX ₂ (provided that X ″ is described in Japanese Patent Application No. 60-78033).
And X are each 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 ); and bCsX ″ · yLn ³⁺ described in Japanese Patent Application No. 60-78035 (where X ″ is F, C, Br and I). Is at least one halogen selected from the group, Ln is Sc,
Y, Ce, Pr, Nd, Sm, Gd, Tb, Dy, H
at least one rare earth element selected from the group consisting of o, Er, Tm, Yb and Lu, and b and y are 0 <b ≦ 10.0 and 10 ⁻⁶ ≦ y ≦, respectively.
1.8 × 10 ⁻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.

Examples of the binder for the phosphor layer include proteins such as gelatin,
Polysaccharides such as dextran or natural polymer substances such as gum arabic; and polyvinyl butyral, polyvinyl acetate, nitrocellulose, ethyl cellulose, vinylidene chloride / vinyl chloride copolymer, polyalkyl (meth) acrylate, vinyl chloride / vinyl acetate Examples thereof include binders represented by synthetic polymeric substances such as copolymers, polyurethane, cellulose acetate butyrate, polyvinyl alcohol, and linear polyester. Preferred among such binders are nitrocellulose, linear polyesters, polyalkyl (meth) acrylates, mixtures of nitrocellulose and linear polyesters and mixtures of nitrocellulose and polyalkyl (meth) acrylates. . Note that these binders may be crosslinked with a crosslinking agent.

The phosphor layer can be formed on the multilayer filter by the following method, for example.

First, the stimulable phosphor and the binder are added to a suitable solvent and mixed sufficiently to prepare a coating solution in which the phosphor particles are uniformly dispersed in the binder solution.

Examples of the solvent for preparing the coating solution include lower alcohols such as methanol, ethanol, n-propanol, and n-butanol; chlorine atom-containing hydrocarbons such as methylene chloride and ethylene chloride; ketones such as acetone, methyl ethyl ketone, and methyl isobutyl ketone. Ester of lower fatty acid and lower alcohol such as methyl acetate, ethyl acetate, butyl acetate; ether 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 coating solution varies depending on the characteristics of the intended radiation image conversion panel, the kind of the phosphor, etc., but generally the mixing ratio of the binder and the phosphor is 1 It is preferably selected from the range from 1 to 1: 100 (weight ratio), and particularly preferably from the range from 1: 8 to 1:40 (weight ratio).

In addition, in the coating liquid, in order to improve the dispersibility of the phosphor in the coating liquid, and to improve the binding force between the binder and the phosphor in the phosphor layer after formation. Various additives such as plasticizers may be mixed.
Examples of dispersants used for such purpose include phthalic acid, stearic acid, caproic acid, lipophilic surfactants and the like. And as an example of a plasticizer,
Phosphoric acid esters such as triphenyl phosphate, tricresyl phosphate and diphenyl phosphate; phthalic acid esters such as diethyl phthalate and dimethoxyethyl phthalate; glycolic acid esters such as ethyl phthalyl ethyl glycolate and butyl phthalyl butyl glycolate; and tri Examples thereof include polyesters of ethylene glycol and adipic acid, polyesters of polyethylene glycol such as diethylene glycol and succinic acid, and polyesters of aliphatic dibasic acid.

The coating liquid containing the phosphor and the binder prepared as described above is then uniformly applied to the surface of the multilayer filter to form a coating film of the coating liquid. This coating operation can be performed by using an ordinary coating means such as a doctor blade, a roll coater or a knife coater.

Then, the formed coating film is gradually heated and dried to complete the formation of the phosphor layer on the multilayer filter. The layer thickness of the phosphor layer varies depending on the characteristics of the intended radiation image conversion panel, the type of phosphor, the mixing ratio of the binder and the phosphor, etc., but is usually 20 μm to 1 mm. However, this layer thickness is preferably 50 to 500 μm.

The phosphor layer does not necessarily have to be formed by directly applying the coating liquid on the multilayer filter as described above.For example, the coating liquid may be separately applied on a sheet such as a glass plate, a metal plate or a plastic sheet. After forming the phosphor layer by drying, press this on the multilayer filter,
Alternatively, the multilayer filter and the phosphor layer may be joined by using an adhesive or the like.

Next, a transparent protective film may be 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 polymethylmethacrylate, polyvinyl butyral, polyvinyl formal, polycarbonate, polyvinyl acetate, vinyl chloride / vinyl acetate copolymer, or the like. It can be formed by a method in which a solution prepared by dissolving a high-molecular substance in a suitable solvent is applied to the surface of the phosphor layer. Alternatively, it can also be formed by a method of adhering a transparent thin film separately formed from polyethylene terephthalate, polyethylene, polyvinylidene chloride, polyamide or the like to the surface of the phosphor layer with an appropriate adhesive. The thickness of the transparent protective film thus formed is preferably about 0.1 to 20 μm.

The radiation image storage panel of the present invention manufactured in this manner has a high utilization efficiency of excitation light, and thus has a significantly higher sensitivity than conventional panels. Note that the decrease in the sharpness of the image due to the excitation of the photostimulable phosphor by the scattered and reflected excitation light can be easily eliminated by making the layer thickness of the phosphor layer slightly smaller. Is.

The radiation image conversion panel of the present invention is disclosed in JP-A-55-1.
63500, JP-A-57-96300 and the like, may be colored with a colorant,
By this coloring, the sharpness of the obtained image can be improved. Further, in the radiation image storage panel of the present invention, white powder may be dispersed in the phosphor layer for the same purpose as described in JP-A-55-146447.

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

[Example] Methyl ethyl ketone was added to a mixture of a stimulable divalent europium-activated barium fluorobromide phosphor (BaFBr: 0.001Eu ²⁺ ) and a linear polyester resin, and nitrous acid having a nitrification degree of 11.5% was added. Cellulose was added to prepare a dispersion liquid containing the phosphor in a dispersed state. After adding tricresyl phosphate, n-butanol and methyl ethyl ketone to this dispersion, the mixture is thoroughly stirred and mixed by using a propeller mixer to uniformly disperse the phosphor, and the mixing ratio of the binder and the phosphor is 1 :. 10, viscosity 25-35 PS (25
(° C) was prepared.

Next, the dichroic filter having the transmission and reflection characteristics shown in FIG. 2 (one in which a multilayer film is provided on a transparent glass substrate, trade name: DF-C, manufactured by Hoya Glass Co., Ltd.) is placed horizontally, The coating solution was applied uniformly using a doctor blade. After the coating, the filter on which the coating film was formed 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.
In this way, the layer thickness on the dichroic filter is 2
A 50 μm phosphor layer was formed.

A transparent protective film is formed by placing a transparent film of polyethylene terephthalate (thickness: 12 μm, with a polyester adhesive) on this phosphor layer with the adhesive layer side facing down did.

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

[Comparative Example] In the example, the same operation as in the method of the example was carried out except that the transparent glass plate having the same thickness was used instead of the dichroic filter, thereby forming a gas slab, a phosphor layer and a transparent protective film. A radiation image conversion panel was manufactured.

Next, each radiation image conversion panel was evaluated by performing the following sensitivity test.

The radiation image conversion panel was irradiated with X-rays having a tube voltage of 80 KVp, and then excited with He-Ne laser light (wavelength: 633 nm) to measure the sensitivity.

The results obtained are summarized in Table 1.

As is clear from the results shown in Table 1, the radiation image conversion panel provided with the multilayer filter according to the present invention (Example) is a radiation image conversion without a multilayer filter for comparison. The sensitivity was remarkably improved as compared with the panel (Comparative Example).

[Brief description of drawings]

FIG. 1 is a sectional view showing an aspect of a radiation image storage panel according to the present invention. 1: multilayer filter, 2: phosphor layer, 3: protective film, FIG. 2 is a diagram showing a transmission (reflection) spectrum of a dichroic filter which is an example of the multilayer filter used in the present invention.

Claims (9)

[Claims] 1. A radiation image conversion panel having a phosphor layer made of a stimulable phosphor, wherein one surface of the phosphor layer has a light reflectance of 60 at the excitation wavelength of the stimulable phosphor.
%, And a multilayer film filter having a light transmittance of 60% or more at the stimulated emission wavelength of the stimulable phosphor is provided. 2. The multilayer filter having a photostimulable phosphor having a light reflectance of 80% or more at an excitation wavelength, and the photostimulable phosphor having a light transmittance of 80% or more at a stimulated emission wavelength. A radiation image conversion panel according to claim 1. 3. The radiation image conversion panel according to claim 1, wherein the multilayer film filter is a dichroic filter. 4. 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. 5. The radiation image storage panel according to claim 1, wherein the multilayer filter is formed by vacuum vapor deposition. 6. The radiation image storage panel according to claim 1, wherein the radiation image storage panel comprises a multilayer filter, a phosphor layer and a protective film in this order. 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.