JPH0634115B2 - 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 for obtaining a radiographic 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.

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 surface of the panel with, for example, laser light as excitation light, but a part of the excitation light is in the panel, especially in the phosphor layer. After being scattered by, the photostimulable phosphor is emitted from both surfaces of the panel without being excited, so that the phosphor is not sufficiently excited, and therefore the utilization efficiency of the excitation light is not 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 to prevent the excitation light applied to the panel from being reflected on the panel surface, and is merely a thin film having a characteristic that the reflectance for 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 support, a light reflection layer reflecting excitation light and stimulated emission and a phosphor layer containing a stimulable phosphor in this order, in which the light reflection layer is the phosphor layer. On the surface opposite to the contact side, the light transmittance at the excitation wavelength of the stimulable phosphor is 70% or more with respect to the incident angle of light in the range of 0 to 5 °, and the light at the excitation wavelength is 60% for incident angle of light with reflectance of 30 ° or more
This can be achieved by a radiation image conversion panel characterized in that the multilayer film filter as described above is provided.

In addition, in this specification, an incident angle means an angle from a perpendicular of an incident surface. Therefore, the incident angle can range from 0 to 90 °.

The present invention provides a multilayer film filter having a light transmittance and a light reflectance having an incident angle dependence on an excitation wavelength on a phosphor layer of a radiation image conversion panel, thereby improving the utilization efficiency of the excitation light of the panel. It realizes a marked improvement in sensitivity.

Usually, the reading of the radiation image conversion panel is performed on the panel surface (the surface of the phosphor layer on the side opposite to the side in contact with the light reflection layer, or the protective film if a protective film is provided on the phosphor layer). This is performed from the surface on the side opposite to the phosphor layer side), and the excitation light such as laser light is applied to the panel surface substantially perpendicularly during reading. On the other hand, most of the excitation light scattered in the panel goes to the panel surface in the direction opposite to the incident direction with an angle.

In the radiation image storage panel of the present invention, when the incident angle of the excitation light is small (close to the incident surface), the excitation light is transmitted, and conversely, when the incident angle is large (oblique incidence), the excitation light is transmitted. A multilayer film filter having transmission and reflection characteristics depending on the incident angle, such as reflection without transmission, is provided on the surface of the phosphor layer opposite to the side in contact with the light reflection layer. With this multilayer filter, the excitation light emitted to the panel surface is transmitted, but the excitation light scattered in the panel and having an angle is reflected by the filter surface without being transmitted, and is again transmitted to the phosphor layer. I will be heading. Therefore, the excitation light scattered in the panel can prevent the loss of the excitation light that deviates to the outside without contributing to the excitation of the stimulable phosphor, and the excited stimulable phosphor is 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.

Further, in the panel of the present invention, since the light reflection layer is provided between the support and the phosphor layer, the support of the stimulated emission light emitted from the stimulable phosphor is excited. The light scattered in the direction is reflected by the light reflecting layer without being absorbed by the support or transmitted through the support, and is emitted toward the panel surface. Therefore, these reflected lights also increase with an increase in the amount of stimulated emission light emitted from the efficiently excited stimulable phosphor, and can contribute to the improvement of the sensitivity of the panel.

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.

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.

Further, when the multilayer filter is provided on the surface of the phosphor layer by using a fluoride such as magnesium fluoride, the multilayer filter has a relatively high hardness and therefore also functions as a protective film. However, the scratch resistance can be improved. Usually, the detection of fluorescence emitted from the radiation image conversion panel (that is, the reading of image information) is performed from the same side as the irradiation of the excitation light. Therefore, the scratch resistance of the panel surface is improved due to the improvement of the scratch resistance of the panel surface. It is possible to prevent deterioration of image quality.

[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 support 1, a light reflection layer 2 and a phosphor layer 3 in this order, and the multilayer filter 4 is provided on the side of the phosphor layer not facing the light reflection layer (panel surface side). There is.

However, the radiation image storage panel of the present invention is not limited to the embodiment shown in FIG. 1, and the multilayer filter may be provided on the surface of the phosphor layer that does not face the light reflection layer. .

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

The support used in the present invention can be arbitrarily selected from various materials used as a support for intensifying screens in conventional radiography or various materials known as a support for radiographic image conversion panels. . Examples of such materials include glass plate, cellulose acetate, polyester, polyethylene terephthalate, polyamide,
Sizing films of plastic materials such as polyimide, triacetate and polycarbonate, metal sheets such as aluminum foil and aluminum alloy foil, ordinary paper, baryta paper, resin coated paper, pigment paper containing pigments such as titanium dioxide, polyvinyl alcohol, etc. You can cite the paper made. However, in consideration of the characteristics and handling of the radiation image storage panel as an information recording material, a particularly preferable material for the support in the present invention is a plastic film.

The surface of the support may be coated with a polymer substance such as gelatin to provide an adhesion-imparting layer for the purpose of strengthening the bond with the light-reflecting layer provided thereon.

Next, a light reflecting layer is provided on the support.

The light reflecting layer is provided in order to improve the sensitivity of the radiation image conversion panel, and is a layer containing a light reflecting substance.
The light-reflecting substance can be appropriately selected from the materials described in JP-A-56-12600 and Japanese Patent Application No. 58-37838. Examples of the light-reflecting substance include metals such as aluminum and aluminum alloys; white pigments such as titanium dioxide, lead white, zinc sulfide, aluminum oxide, and magnesium oxide; barium fluorobromide, barium fluorochloride, fluorochloride. Examples thereof include alkaline earth metal fluoride halides such as strontium, strontium fluoride chloride, calcium fluoride bromide and calcium fluoride chloride.

Further, polymer particles made of a styrene-based and / or acrylic polymer having a hollow structure can be used as the light-reflecting substance (see Japanese Patent Application No. 60-278665).

The light-reflecting layer may be formed by using the above-mentioned light-reflecting substance. For example, in the case of a metal, a vacuum deposition method or a method of laminating a metal foil. It can be formed on the support by a method such as applying a coating solution containing a binder dispersed therein and heating and drying.

The binder in the case of preparing the coating solution is appropriately selected from the binders used for forming the phosphor layer described below, in addition to the aqueous polymer substance such as an acrylic ester copolymer. Can be used.

The mixing ratio of the binder and the light-reflecting substance in the coating liquid is generally selected from the range of 1: 1 to 1:50 (weight ratio),
From the viewpoint of adhesion to the support, etc., it is preferably selected from the range of 1: 2 to 1:20 (weight ratio). The above light-reflecting substances may be used alone or in combination at an appropriate ratio.

The thickness of the light reflection layer is preferably 5 to 100 μm.

As described in JP-A-58-200200 by the applicant of the present invention, sandblasting is performed on the surface of the light reflecting layer on which the phosphor layer is provided for the purpose of improving the sharpness of the obtained image. Fine irregularities may be uniformly formed by treatment or the like.

Next, a phosphor layer is formed on the light reflection layer. The phosphor layer is basically a layer containing a 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. 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, and A is Eu, Tb, Ce, Tm, Dy, Pr, Ho, Nd, Y.
at least one of b and Er, and x is
0 ≦ x ≦ 0.6, 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 [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 either 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: yEu 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⁺ [wherein M ^II is Ba, Sr, and C
is at least one alkaline earth metal selected from the group consisting of a; ^{M I} is Li, Na, K, Rb, and C
is at least one alkali metal selected from the group consisting of s; M ^'II is at least one trivalent metal selected from the group consisting of Be and Mg; M ^III is A,
X is at least one trivalent metal selected from the group consisting of Ga, 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
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 <y ≦ 0. 2, which is represented by the composition formula of 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 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 ″ · ccSnX ₂ (however, described in Japanese Patent Application No. 60-78033).
X ″ 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 ⁻⁶ ≦ c ≦ 2 × 10 ⁻² respectively); and Japanese Patent Application No. 60-
BCsX ″ · yL described in the specification of 78035
n ³⁺ (where X ″ is at least one halogen selected from the group consisting of F, C, Br and I, and Ln
Is Sc, Y, Ce, Pr, Nd, Sm, Gd, Tb, D
at least one rare earth element selected from the group consisting of y, Ho, Er, Tm, Yb and Lu, and b
And y are 0 <b ≦ 10.0 and 10 ⁻⁶ ≦, respectively.
y ≦ 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 polymeric 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 of the binder include synthetic polymers such as copolymers, polyurethane, cellulose acetate butyrate, polyvinyl alcohol, and linear polyester. Particularly 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. is there. Note that these binders may be crosslinked with a crosslinking agent.

The phosphor layer can be formed on the light reflecting layer 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).

The coating liquid contains a dispersant for improving the dispersibility of the phosphor in the coating liquid, and also for improving the binding force between the binder and the phosphor in the formed phosphor layer. Various additives such as plasticizers may be mixed. Examples of dispersants used for such purpose include:
Examples thereof include phthalic acid, stearyl acid, caproic acid and lipophilic surfactants. Examples of plasticizers include phosphoric acid esters such as triphenyl phosphate, tricresyl phosphate, diphenyl phosphate; phthalic acid esters such as diethyl phthalate and dimethoxyethyl phthalate; ethyl phthalyl glycolate, butyl phthalyl butyl glycolate, etc. And a polyester of polyethylene glycol and an aliphatic dibasic acid, such as a polyester of triethylene glycol and adipic acid, a polyester of diethylene glycol and succinic acid, and the like.

The coating liquid containing the phosphor and the binder prepared as described above is then uniformly applied to the surface of the light reflecting layer 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 to be dried to complete the formation of the phosphor layer on the light reflection layer.

Note that the phosphor layer does not necessarily have to be formed by directly applying the coating liquid on the light reflecting layer as described above.For example, the coating liquid is separately applied on a sheet such as a glass plate, a metal plate, or a plastic sheet. Then, after the phosphor layer is formed by drying, the light reflection layer and the phosphor layer may be joined by pressing the phosphor layer on the light reflection layer or by using an adhesive.

Further, the phosphor layer may be formed by vapor deposition of a stimulable phosphor on the light reflection layer, etc., in addition to the method of coating and forming using a binder as described above. For example, when forming the phosphor layer, F. Calcia and Elle. Etch. Vacuum evaporation method (ELECTRONICS AND OPTICS, Thin Solid Fi) performed by PFCARCIA AND LHBRIXNER
lm, 115 (1984) 89-95).

The surface of the phosphor layer formed by this vapor deposition method (the surface on the side opposite to the light reflection layer) has excellent surface smoothness, which is extremely advantageous for forming a multilayer filter on the surface.

The layer thickness of the phosphor layer is the characteristics of the intended radiation image conversion panel, the type of phosphor, and when formed using a binder,
Although it depends on the mixing ratio of the binder and the phosphor, etc., it is usually 20 μm to 1 mm. However, this layer thickness (film thickness)
Is preferably 50 to 500 μm.

Next, a multilayer filter, which is a characteristic requirement of the present invention, is provided on the surface of the phosphor layer opposite to the side in contact with the light reflection layer.

In the present invention, the multilayer filter has an incident angle of the excitation light for exciting the stimulable phosphor contained in the phosphor layer of 0 to 0.
When it is in the range of 5 °, it has a light transmittance of 70% or more,
And 60% when the incident angle of excitation light is 30 ° or more
It has the above light reflectance. Preferably, it has a light transmittance of 80% or more when the incident angle of the excitation light is in the range of 0 to 5 ° and a light reflection of 70% or more when the incident angle of the excitation light is 30 ° or more. One that has a rate. That is, the multilayer filter needs to have such angle-dependent transmission and reflection characteristics for at least one wavelength included in the excitation wavelength region of the stimulable phosphor. Preferably, the above-mentioned transmission and reflection characteristics are satisfied for wavelengths near the peak of the excitation spectrum of the phosphor.

As an example, a commercially available radiographic image conversion panel usually uses a divalent europium-activated barium fluorobromide-based phosphor, and He-Ne laser light (wavelength: 6) as excitation light.
33 nm) is used. Therefore, when the phosphor layer contains this stimulable phosphor, the multilayer filter has 63
It is sufficient that the light transmittance with respect to the excitation wavelength of 3 nm has the angle dependency as described above.

In addition, usually, the stimulated emission light is also detected from the surface on the side of the phosphor layer (the surface opposite to the light reflection layer). Therefore, from the viewpoint of the sensitivity of the panel, the multilayer filter has a stimulated emission wavelength of the phosphor. It is preferable that the light transmittance at is high regardless of the angle.
In general, when the incident angle is in the range of 0 to 40, the transmittance at the peak wavelength of light emission is preferably 60% or more, more preferably 80% or more. Therefore, it is desirable that the above-mentioned divalent europium-activated barium fluorobromide-based phosphor has the above-mentioned transmittance for the peak wavelength of about 390 nm.

The multilayer filter may be a short pass filter having a wide transmission band in the transmission spectrum or a band pass filter having an extremely narrow transmission band.

The transmission spectrum of the multilayer filter used in the present invention,
Examples of the reflection spectrum and its angle dependence are shown in FIGS. 2 to 5, respectively.

FIG. 2 shows the incident angle of the short pass filter 0 °, 30 °
It is a transmission spectrum in each of ° and 45 °.

FIG. 3 is a graph showing the relationship between the incident angle and the transmittance and the relationship between the incident angle and the reflectance for the short pass filter. In FIG. 3, 633 nm corresponds to the excitation wavelength of the divalent europium-activated barium fluorobromide-based phosphor, and 390 nm corresponds to the peak wavelength of stimulated emission.

FIG. 4 is a transmission spectrum of the bandpass filter at an incident angle of 0 °.

FIG. 5 is a graph showing the relationship between the incident angle and the transmittance and the relationship between the incident angle and the reflectance at 390 nm and 633 nm for the bandpass 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 may be a protective film when a thin film made of the above substance is applied directly to the surface of the phosphor layer by a method such as vacuum deposition, sputtering, or ion plating, or when a protective film is provided on the multilayer filter. It can be provided by stacking several to several tens of layers on the surface of the forming sheet.

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.

Examples of the transparent sheet for forming a protective film include polyethylene terephthalate, polyethylene, polyvinylidene chloride,
Examples thereof include a plastic sheet made of polyamide or the like; and a glass plate. The surface of this transparent sheet may be previously subjected to various surface treatments and undercoating treatments for cleaning the surface.

The protective film and the multilayer filter are provided on the phosphor layer, for example, by forming the above-mentioned multilayer filter on the transparent sheet and then adhering it to the surface of the phosphor layer with an appropriate adhesive. be able to. When a multilayer filter is directly provided on the phosphor layer by a vacuum deposition method or the like and a protective film is provided thereon, the transparent sheet is bonded to the surface of the multilayer filter with an appropriate adhesive. In addition to being formed by, for example, cellulose derivatives such as cellulose acetate and nitrocellulose; or synthetic polymer substances such as polymethylmethacrylate, polyvinyl butyral, polyvinyl formal, polycarbonate, polyvinyl acetate, vinyl chloride / vinyl acetate copolymer, etc. It can also be formed by a method of applying a solution prepared by dissolving a transparent polymer substance as described above in a suitable solvent to the surface of the multilayer filter.

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 1] A transparent glass plate (protective film sheet, thickness: about 1 mm) heated to about 350 ° C was placed in a vacuum container and alternated while controlling the film thickness of each layer using TiO ₂ and SiO _2. By repeatedly vacuum-depositing on the glass plate, a multilayer film filter (short-pass filter) having the transmission and reflection characteristics shown in FIG. 3 is formed on the glass plate with a total film thickness of about 2 μm (a stack of about 20 layers). did.

Next, methyl ethyl ketone was added to a mixture of powdery divalent europium-activated barium fluorobromide phosphor (BaFBr: 0.001Eu ⁺² ) and a linear polyester resin, and nitrocellulose having a nitrification degree of 11.5% was further added. A dispersion liquid containing the phosphor in a dispersed state was prepared. After tricresyl phosphate, n-butanol and methyl ethyl ketone were added to this dispersion, the mixture was sufficiently stirred and mixed by using a propeller mixer to uniformly disperse the phosphor, and the mixing ratio of the binder and the phosphor was 1 :. 10, viscosity is 25 ~ 35PS
A coating liquid (25 ° C.) was prepared.

Next, the coating solution was uniformly applied onto a glass plate provided with a multilayer filter placed horizontally by using a doctor blade. After coating, the glass plate with the coating film was placed in a drier, and the temperature inside the drier was changed from 25 ° C to 1 ° C.
The coating film was dried by gradually raising the temperature to 00 ° C. In this way, a phosphor layer having a layer thickness of 250 μm was formed on the multilayer filter.

Separately, a polyethylene terephthalate sheet (support, thickness: 180 μm) was prepared, and aluminum was vapor-deposited using a vacuum vapor deposition method to form an aluminum vapor deposition film with a thickness of 2 μm on the support to form a light reflection layer.

Next, a polyester-based adhesive was used to adhere onto the phosphor layer such that the aluminum vapor deposition surface of the support was on the phosphor layer side.

Thus, a radiation image conversion panel composed of the support, the light reflection layer, the phosphor layer, the multilayer filter and the transparent protective film (glass plate) was manufactured.

Example 2 In Example 1, TiO ₂ and SiO were formed on the glass plate.
_{By 2} a vacuum deposition, except that the provision of multilayer filters having transmission and reflection characteristics respectively shown in FIG. 5 (the band-pass filter) with a thickness of about 2 [mu] m, the same operation as the method of Example 1 By performing the above, a radiation image conversion panel composed of a support, a light reflection layer, a phosphor layer, a multilayer filter and a transparent protective film was manufactured.

Comparative Example 1 A support, a light reflection layer, a phosphor layer and a transparent protective film were prepared in the same manner as in Example 1 except that the multilayer filter was not provided on the glass plate. A radiation image conversion panel composed of

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 storage panel provided with the multilayer filter according to the present invention (Examples 1 and 2) is a radiation image provided with no known multilayer filter. Compared with the conversion panel (Comparative Example 1),
The sensitivity is significantly improved.

[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: Support, 2: Light reflection layer, 3: Phosphor layer, 4: Multilayer film filter FIG. 2 shows an example of the short pass filter used in the present invention at incident angles of 0 °, 30 ° and 45 °, respectively. It is a figure which shows a transmission spectrum. Fig. 3 shows the above short pass filter at 390nm.
3 is a graph showing the transmittance at 633 nm and the angular dependence of the reflectance. FIG. 4 is a diagram showing a transmission spectrum at an incident angle of 0 ° for an example of a bandpass filter used in the present invention. FIG. 5 is a graph showing the angular dependence of the transmittance and reflectance at 390 nm and 633 nm for the bandpass filter.

 ─────────────────────────────────────────────────── ─── 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 62-169100 (JP, A) JP 62-182700 (JP, A)

Claims (11)

[Claims] 1. A radiation image conversion panel having a support, a light reflection layer reflecting excitation light and stimulated emission and a phosphor layer containing a stimulable phosphor in this order, in which the light reflection layer of the phosphor layer is formed. On the surface opposite to the contact side, the light transmittance at the excitation wavelength of the stimulable phosphor is 70% or more with respect to the incident angle of light in the range of 0 to 5 °, and the light at the excitation wavelength is A radiation image conversion panel comprising a multi-layer film filter having a reflectance of 60% or more with respect to an incident angle of light of 30 ° or more. 2. The multi-layer film filter has a photostimulable phosphor having a light transmittance at an excitation wavelength of 80% or more with respect to an incident angle of light in the range of 0 to 5 °, and light reflection at the excitation wavelength. The radiation image conversion panel according to claim 1, wherein the ratio is 70% or more for an incident angle of light of 30 ° or more. 3. The light transmittance of the stimulable phosphor of the multilayer filter at the stimulable emission wavelength is 60% or more with respect to the incident angle of light in the range of 0 to 40 °. The radiation image conversion panel according to the item. 4. The light transmittance of the stimulable phosphor of the multilayer filter at the stimulable emission wavelength is 80% or more with respect to the incident angle of light in the range of 0 to 40. The radiation image conversion panel according to the item. 5. The radiation image conversion panel according to claim 1, wherein the multilayer film filter is a short pass filter or a band pass filter. 6. 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. 7. The radiation image conversion panel according to claim 1, wherein the multilayer filter is formed by vacuum vapor deposition. 8. The radiation image storage panel has a structure in which a protective film is provided on a phosphor layer, the protective film is made of a polymer, and the multilayer filter is formed by ion plating to form the protective film. The radiation image conversion panel according to claim 1, which is formed on the surface. 9. The excitation wavelength of the stimulable phosphor is 400-9.
The radiation image conversion panel according to claim 1, which is in the range of 00 nm. 10. The radiation image storage panel according to claim 9, wherein the stimulable phosphor is a divalent europium-activated halide phosphor. 11. The radiation image storage panel according to claim 10, wherein the divalent europium-activated halide phosphor is a divalent europium-activated fluorohalide phosphor.