JPH0634113B2 - 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. The phosphor is not excited enough because the photostimulable phosphor is again emitted from the surface of the panel without being excited, and therefore the utilization efficiency of the excitation light is not necessarily high. In particular,
When a laser with a small output is used as a light source for excitation light, it is desired to improve the sensitivity of the panel by improving the utilization efficiency of the excitation light.

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 support, and a radiation image conversion panel having a phosphor layer made of a stimulable phosphor on the support (however, there is no protective layer on the phosphor layer), the phosphor On the surface of the layer opposite to the support, the light transmittance of the stimulable phosphor at the excitation wavelength is 70% or more with respect to the incident angle of light in the range of 0 to 5 °, and the excitation wavelength is Light reflectance of 60% against the incident angle of light of 30 ° or more
This can be achieved by the radiation image conversion panel of the present invention, which is provided with the above-described multilayer film filter.

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 radiation image conversion panel is read out on the panel surface (when the panel is composed of a support and a phosphor layer, the surface of the phosphor layer opposite to the side where the support is provided, and When a protective film is provided on the phosphor layer, it means the surface of the protective film), and the excitation light such as a laser beam is irradiated almost perpendicularly to the panel surface 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 filter having a transmission and reflection characteristic depending on an incident angle that is reflected without being transmitted is provided on the surface of the phosphor 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 the phosphor layer is again formed. Will be headed for. 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, this makes it possible to maintain a large amount of stimulated luminescence of the phosphor in the panel even when the excitation light with low intensity is irradiated, and the panel can be maintained at 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.

Furthermore, when the multilayer filter is provided on the surface of the phosphor layer using a fluoride such as magnesium fluoride, the multilayer filter has a relatively high hardness and thus also has a function as a protective film. Therefore, the multilayer filter can further improve the damage resistance of the radiation image conversion panel. 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 a specific embodiment of the radiation image storage 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 is a support 1
And the phosphor layer 2, and the multilayer filter 3 is provided on the surface of the phosphor layer (the surface opposite to the side where the support is provided).

However, the radiation image conversion 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 opposite to the support, For example, an undercoat layer, an intermediate layer or the like may be provided between the support and the phosphor 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,
Films of plastic materials such as polyimide, triacetate and polycarbonate, metal sheets such as aluminum foil and aluminum alloy foil, ordinary paper, baryta paper,
Examples thereof include resin-coated paper, pigment paper containing a pigment such as titanium dioxide, and paper sized with polyvinyl alcohol. However, in consideration of the characteristics of the radiation image conversion panel as an information recording material, handling, and the like, the particularly preferable material for the support in the present invention is a plastic film or a glass plate. This plastic film may be kneaded with a light absorbing substance such as carbon black, or may be kneaded with a light reflecting substance such as titanium dioxide. The former is a support suitable for a radiation image conversion panel of high sharpness type, and the latter is a support suitable for a radiation image conversion panel of high sensitivity type.

In a known radiation image conversion panel, a phosphor layer is provided in order to strengthen the bond between the support and the phosphor layer or to improve the sensitivity or image quality (sharpness, graininess) of the radiation image conversion panel. The surface of the support is coated with a polymeric substance such as gelatin to form an adhesion-imparting layer, or a light-reflecting layer made of a light-reflecting substance such as titanium dioxide, or a light-absorbing substance such as carbon black. Providing a light absorption layer is also performed. Also for the support used in the present invention, these various layers can be provided.

Further, as described in JP-A-58-200200, the surface of the support on the side of the phosphor layer (adhesiveness to the surface of the support on the side of the phosphor layer is used for the purpose of improving the sharpness of the image. When an imparting layer, a light reflecting layer, a light absorbing layer, or the like is provided, it means the surface thereof) and fine irregularities may be uniformly formed.

Next, a phosphor layer is formed on the support. The phosphor layer is a layer made of 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 the stimulable phosphor 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 ], the phosphor represented by the composition formula 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 × 1
0 ⁻¹ , and 0 <z ≦ 5 × 10 ⁻¹ ], the phosphor represented by the composition formula: M ^III described in JP-A-58-69281.
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: 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,
At least one trivalent metal selected from the group consisting of Ga, In, and T; A is a metal oxide; Z
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.

The phosphor layer can be formed, for example, on the support by a vapor deposition method such as vacuum vapor deposition of the above-described stimulable phosphor.

The vacuum vapor deposition method is performed using a vacuum vapor deposition apparatus as shown in FIG.

FIG. 2 is a configuration diagram showing a typical example of a vacuum vapor deposition device.

In FIG. 2, the vacuum vapor deposition apparatus 20 comprises a vacuum container 22 that has a vapor deposition system 21 that performs vacuum vapor deposition and that constitutes a main body of the apparatus, and an exhaust system 23 that evacuates the same. Further, the exhaust system 23 includes an oil diffusion pump 24, a liquid nitrogen cooling cold trap 25, and an oil rotary pump 26. The exhaust system 23, as shown in FIG. 2, has a main valve (MV) and a valve (V ₁ ,
V ₂ ) is connected to the main body of the apparatus. The vapor deposition system 21 includes an evaporation source 21a and a substrate heating device 21b.

First, the powder of the stimulable phosphor is introduced into a molybdenum boat which is an evaporation source 21 a provided in the vapor deposition system 21. In addition, a substrate (support) which is a material to be vapor-deposited is also mounted at a predetermined position of the vapor system 21 at the same time. Then, the exhaust system 23 is driven to set the inside of the vacuum container 22 to a predetermined vapor pressure (10 ⁻⁶ Torr or less) to deposit the phosphor.

The vapor deposition is performed by heating the substrate to a preset temperature (for example, a temperature range of about 25 to 400 ° C.), driving the exhaust system 23, and heating the molybdenum boat. The deposition rate of the phosphor powder is usually in the range of about 200 to 4400Å / min.

In this way, a vapor deposition film made of a stimulable phosphor is formed on the substrate.

When carrying out the above vapor deposition method, the substrate (support) is usually washed in advance. For cleaning the substrate, a generally used method can be used in the present invention. For example, an ultrasonic cleaning method, a steam cleaning method, or a combination thereof may be used. Moreover, you may use a detergent, a chemical | medical agent, a detergent etc. suitably in these methods.

In addition, specifically, the formation of the phosphor layer by the vacuum deposition method is described in F. Calcia and Elle. Etch. The method (ELECTR) performed by PFCARCIA AND LHBRIXNER
ONICS AND OPTICS, Thin Solid Film, 115 (1984) 89-95)
Can be performed by using.

The layer thickness of the phosphor layer (deposited film) varies depending on the desired characteristics of the radiation image conversion panel, the type of phosphor, etc., but is usually 10 μm to 500 μm. However, this layer thickness is preferably 20 to 250 μm.

Since the surface of the phosphor layer (the surface on the side opposite to the support) formed by the above vapor deposition method has excellent surface smoothness, it is extremely advantageous in forming a multilayer filter described later. Moreover, since the phosphor layer can be formed without using a binder as in the conventional case, it is possible to increase the amount of light emission per unit volume by the excitation light, and to reduce the thickness of the phosphor layer as a whole. There are advantages. Further, this also makes it possible to improve the image quality without lowering the sensitivity.

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 support.

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 radiation image conversion panel usually uses a divalent europium-activated barium fluorohalide-based phosphor, and He-Ne laser light (wavelength: 633 nm) as excitation light. Therefore, when the phosphor layer contains this stimulable phosphor, the multilayer filter may be such that the light transmittance with respect to the excitation wavelength of 633 nm has the above angle dependency.

Further, usually, the stimulated emission light is also detected from the surface on the side of the phosphor layer (the surface on the side opposite to the support). Therefore, from the viewpoint of the sensitivity of the panel, the multilayer filter has a wavelength of the stimulated emission of the phosphor. It is preferable that the light transmittance 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 divalent europium-activated barium fluorohalide-based phosphor has the above-described 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. 3 to 6, respectively.

FIG. 3 shows the incident angle of the short pass filter 0 °, 30 °
It is a transmission spectrum in each of ° and 45 °.

FIG. 4 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 short pass filter.

In FIG. 4, 633 nm corresponds to the excitation wavelength of the divalent europium-activated barium fluorohalide-based phosphor,
390 nm corresponds to the peak wavelength of stimulated emission.

FIG. 5 is a transmission spectrum at an incident angle of 0 ° of the bandpass filter.

FIG. 6 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 can be provided, for example, by forming a thin film made of the above substances by laminating several layers to several tens of layers on the surface of the phosphor layer by a method such as vacuum deposition, sputtering, and ion plating. In particular, in order to form the multilayer filter on the surface of the phosphor layer by the vacuum vapor deposition method, it is convenient that the phosphor layer is also formed by the vacuum vapor deposition method as described above. Since the phosphor layer is a vapor deposition layer, the smoothness of the phosphor layer surface can be improved. Further, since the phosphor layer and the multilayer filter can be continuously formed in the same vacuum system by the vapor deposition method, there is an advantage that the manufacturing process of the panel can be simplified.

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

Since the multilayer filter itself formed of the above substances has a relatively high hardness, it also has a function as a protective film for physically and chemically protecting the phosphor layer.

The radiation image conversion panel of the present invention is disclosed in JP-A-55-1464.
As described in Japanese Patent No. 47, white powder may be dispersed in the phosphor layer for the same purpose.

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

[Example 1] Aluminum was vacuum-deposited on a transparent glass plate (support, thickness: 1 mm) to form an aluminum vapor deposition layer with a layer thickness of about 2 µm.

Then, on the aluminum vapor-deposited layer of the glass plate, a powdery divalent europium-activated barium fluorochloride phosphor (Ba
FC: 0.001Eu ⁺² ) was vapor-deposited to form a vapor-deposited film of the phosphor layer. The vapor deposition operation was performed by first introducing the phosphor powder into a molybdenum boat in a vacuum container (vapor pressure of about 2 × 10 ⁻⁷ Torr) and heating. On the other hand, the glass plate, which is the material to be vapor-deposited, is also cleaned by subjecting its surface (the surface of the aluminum vapor-deposited layer) to ultrasonic cleaning in advance, and then mounted on the apparatus and heated using a single-color quartz lamp (heating temperature 250 ℃).

In this way, 3 on the aluminum vapor deposition layer of the glass plate.
A phosphor layer having a layer thickness of 0 μm was formed.

Next, a multilayer filter (short pass filter) was formed by vacuum vapor deposition on the phosphor layer.

The multilayer filter heats a glass plate provided with a phosphor layer in a vacuum container to about 350 ° C. to obtain TiO ₂ and SiO _2.
2 was alternately and repeatedly vacuum-deposited while controlling the film thickness to form a total film thickness of about 2 μm (total 20 layers) on the phosphor layer.

The obtained multilayer filter was a short-pass filter having the transmission and reflection characteristics shown in FIG. 4, respectively.

In this way, a radiation image conversion panel composed of the support, the aluminum vapor deposition layer, the phosphor layer and the multilayer filter was manufactured.

Example 2 In Example 1, a multilayer filter (bandpass filter) having the transmission and reflection characteristics shown in FIG.
By performing the same operation as in the method of Example 1 except that the film is formed to have a film thickness of
A radiation image conversion panel composed of a phosphor layer and a multilayer filter was manufactured.

[Comparative Example 1] In Example 1, a radiation image conversion composed of a support, an aluminum vapor deposition layer and a phosphor layer was performed by performing the same operation as in Example 1 except that the multilayer film filter was not provided. The panel was manufactured.

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

(1) Sensitivity test After irradiating the radiation image conversion panel with X-rays at a tube voltage of 80 KVp, the sensitivity of excitation with He-Ne laser light (wavelength: 633 nm) was measured.

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: Phosphor layer, 3: Multilayer film filter FIG. 2 is a configuration diagram of a vacuum vapor deposition apparatus used in the present invention. 20: Vacuum evaporation system, 21: Vapor deposition system, 21a: Evaporation source, 21b: Substrate heating device 22: Vacuum container 23: Exhaust system, 24: Oil diffusion pump, 25: Liquid nitrogen cooling cold trap, 26: Oil rotary pump, MV: main valve, V ₁ , V ₂ : valve, FIG. 3 is a diagram showing transmission spectra at an incident angle of 0 °, 30 ° and 45 ° for an example of the short pass filter used in the present invention. Fig. 4 shows the above short pass filter at 390nm.
2 is a graph showing the angular dependence of transmittance and reflectance at 633 nm and 633 nm. FIG. 5 is a diagram showing a transmission spectrum at an incident angle of 0 ° for an example of the bandpass filter used in the present invention. FIG. 6 is a graph showing the angular dependence of the transmittance and reflectance at 390 nm and 633 nm for the above bandpass filter.

Front Page Continuation (56) References JP 62-63929 (JP, A) JP 62-169095 (JP, A) JP 62-169096 (JP, A) JP 62-169098 (JP , A) JP 62-169099 (JP, A) JP 62-169100 (JP, A) JP 62-182700 (JP, A)

Claims (10)

[Claims] 1. A radiation image conversion panel having a support and a phosphor layer made of a stimulable phosphor on the support and having no protective film on the phosphor layer. On the surface opposite to the body, the light transmittance at the excitation wavelength of the stimulable phosphor is 7 with respect to the incident angle of light in the range of 0 to 5 °.
0% or more, and the light reflectance at the excitation wavelength is 3
A radiation image conversion panel comprising a multilayer film filter that is 60% or more with respect to an incident angle of light of 0 ° 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 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. 9. The radiation image storage panel according to claim 8, wherein the stimulable phosphor is a divalent europium-activated halide phosphor. 10. The radiation image storage panel according to claim 9, wherein the divalent europium-activated halide phosphor is a divalent europium-activated fluorohalide phosphor.