JP2003279695A - Radiological image conversion panel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radiological image conversion panel which has high sensitivity to radiation and with which an image quality of high sharpness can be obtained. <P>SOLUTION: A metallic layer 12 is laminated on a base 11, and a low refractive index layer 13 having lower refractive index is formed on the metallic layer 12. A high refractive index layer 14 of higher refractive index is formed on the low refractive index layer 13, and a photostimulable phosphor layer 16 is formed on the high refractive index layer 14. The reflectivity to photostimulable emission light on a surface at the photostimulable phosphor layer 16 side, of the high refractive index layer 14 is 90% or more. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a radiation image conversion panel used in a radiation image conversion method using a stimulable phosphor.

[0002]

2. Description of the Related Art As a method replacing the conventional radiographic method, for example, a radiation image conversion method using a stimulable phosphor as described in JP-A-55-12145 is known. This method uses a radiation image conversion panel (stimulable phosphor sheet) containing a stimulable phosphor. The stimulable phosphor of the panel emits the radiation transmitted through the subject or emitted from the subject. Radiation, and then the stimulable phosphor is excited in time series by electromagnetic waves (excitation light) such as visible light and infrared rays to radiate the radiation energy accumulated in the stimulable phosphor ( (Stimulated emission light), this fluorescence is photoelectrically read to obtain an electric signal, and then a radiation image of a subject or a subject is reproduced as a visible image based on the obtained electric signal. The read panel is prepared for the next shooting after the remaining image is erased. That is, the radiation image conversion panel is repeatedly used.

According to this radiographic image conversion method, a radiographic image with a large amount of information can be obtained with a much smaller exposure dose than in the conventional radiographic method using a combination of a radiographic film and an intensifying screen. There is an advantage that it can be obtained. Further, in the conventional radiographic method, the radiographic film is consumed for each photographing, whereas in the radiographic image conversion method, the radiographic image conversion panel is repeatedly used, which is advantageous in terms of resource conservation and economic efficiency. Is. As described above, the radiation image conversion method is a very advantageous image forming method, but the radiation image conversion panel used in this method has a high sensitivity as well as the intensifying screen used in the conventional radiographic method, and It is desired to provide good image quality (sharpness, graininess, etc.).

As a technique for improving the sensitivity of the radiation image conversion panel, a light reflecting layer is provided on the support by applying a coating solution containing a white pigment dispersed in a suitable binder to the support. It is known to provide a phosphor layer on it. For example, a radiation image conversion panel provided with a light reflection layer made of a white pigment is disclosed in JP-A-56-126.
No. 00, titanium dioxide, lead white, zinc sulfide, aluminum oxide and magnesium oxide are exemplified as the white pigment.

However, even if a light reflecting layer made of a white pigment as exemplified in JP-A-56-12600 is provided between the support and the phosphor layer, the white pigment has a high reflectance in the visible region. However, the reflectance in the near-ultraviolet region is extremely low. Therefore, as in the case of the stimulated emission spectrum of a divalent europium-activated alkaline earth metal fluorohalide-based phosphor, which has hitherto been known as a very preferable phosphor in terms of stimulated emission luminance, etc. 390n is a band spectrum extending from the region to the blue region.
When the emission peak is around m, the light reflection characteristics of the light reflection layer cannot be said to be sufficiently high, and the improvement of the sensitivity of the radiation image conversion panel by providing the light reflection layer made of the white pigment is not always satisfactory. I couldn't say it was possible.

Further, the reflectance at the emission wavelength depends on the layer thickness of the light reflecting layer. Therefore, if the layer thickness of the light reflecting layer is increased,
The reflectance also increases in proportion to this, but even if the layer thickness is increased to obtain a high reflectance, the improvement in image quality cannot be expected so much. This is because as the thickness of the light reflecting layer becomes thicker, the proportion of excitation light diffused in the thicker light reflecting layer increases, and the thickness of the light reflecting layer does not directly improve the image quality. It is due.

On the other hand, Japanese Patent No. 2514321 describes a radiation image conversion panel in which a support, a light reflection layer, and a stimulable phosphor layer are laminated in this order, and the reflection surface of the light reflection layer is a metal surface. . According to this technique, since the stimulated excitation light does not pass through the light reflection layer, there is no scattering of light due to the thickness of the light reflection layer as in the conventional light reflection white pigment layer, and the support Since the light does not pass through to and is not scattered in the support, the sharpness of the read image is not reduced. However, since the metal surface of the light-reflecting layer is in direct contact with the phosphor layer, the support may be formed during the phosphor layer formation step, the subsequent heat treatment step (annealing step), or the time course after formation. There is a problem that the metal on the surface of the phosphor and the phosphor layer cause a chemical reaction to deteriorate the phosphor layer, the radiation sensitivity is lowered, and the light transmittance and reflectance characteristics on the metal surface fluctuate.

[0008]

In view of the above problems, Japanese Patent No. 3034587 discloses a radiation image conversion panel described in the above Japanese Patent No. 2514321, in which light with a wavelength of 350 to 800 nm is irradiated on a metal surface of a support. A technique for preventing the deterioration of the metal surface of the support and the phosphor layer by interposing a transparent thin film layer having a transmittance of 70% or more is described.

However, the light transmittance of the transparent thin film layer has a wavelength of 35
Although it is 70% or more for the light of 0 to 800 nm, the transparency of the stimulated excitation light and the stimulated emission light is secured,
It is said that simply interposing a transparent thin film layer on the metal surface does not ensure the reflectivity of the stimulated emission light, so that the emission amount of the stimulated emission light is reduced and a sufficiently satisfactory sharpness cannot be obtained. There's a problem.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a radiation image conversion panel which is highly sensitive to radiation and which can provide an image with high sharpness. Is.

[0011]

A radiation image storage panel of the present invention is a radiation image storage panel comprising a substrate, a metal layer, a transparent thin film layer and a stimulable phosphor layer laminated in this order,
It is characterized in that the transparent thin film layer is composed of a multilayer film of two or more layers having different refractive indexes.

The transparent thin film layer is preferably a multilayer film in which a layer in contact with the metal layer is a low refractive index layer and a layer in contact with the stimulable phosphor layer is a high refractive index layer. in this case,
In the transparent thin film layer, if the layer in contact with the metal layer is a low refractive index layer and the layer in contact with the stimulable phosphor layer is a high refractive index layer, a low refractive index layer and a high refractive index layer are provided. It may be composed of layers, or the low refractive index layer and the high refractive index layer may be repeatedly laminated in this order. Here, the low refractive index layer means a layer having a relatively low refractive index when comparing the refractive index of other transparent thin film layers adjacent to each other, and the high refractive index layer means another transparent thin film adjacent to the high refractive index layer. It means a layer having a relatively high refractive index when the refractive indexes of the layers are compared. The refractive index here is
The refractive index for air.

The transparent thin film layer in contact with the stimulable phosphor layer has a reflectance of 90% or more at a wavelength at which the spectrum of stimulated emission light on the surface of the stimulable phosphor layer side is maximized. It is preferable.

The metal layer is a layer made of aluminum,
The low refractive index layer of the transparent thin film layer is MgF ₂ , and the high refractive index layer is CeO ₂ , or the metal layer is a layer made of aluminum, and the low refractive index layer of the transparent thin film layer is Is SiO ₂ , and the high refractive index layer is preferably TiO ₂ .

[0015]

The radiation image conversion panel of the present invention is a radiation image conversion panel in which a metal layer, a transparent thin film layer and a stimulable phosphor layer are laminated in this order on a substrate, and the transparent thin film layer has a refractive index. Since it is made up of two or more different multilayer films, the stimulated emission light reflectance on the surface of the layer in contact with the stimulable phosphor layer on the side of the stimulable phosphor layer is increased, and the amount of emitted light is high,
It is possible to provide a radiation image conversion panel that has high sensitivity to radiation and can obtain image quality with high sharpness.

Particularly, the stimulable phosphor layer is formed by forming the transparent thin film layer into a multilayer film in which the layer in contact with the metal layer is a low refractive index layer and the layer in contact with the stimulable phosphor layer is a high refractive index layer. On the surface of the stimulable phosphor layer side of the transparent thin film layer in contact with, since it is possible to further increase the reflectance at the wavelength at which the spectrum of the stimulated emission light is maximum, higher luminescence amount, favorable sensitivity, It is possible to obtain a high quality radiation image conversion panel.

Further, the protective effect of the transparent thin film layer composed of the multilayer film of the low refractive index layer and the high refractive index layer makes it possible to secure the temporal stability of the amount of light emitted from the stimulable phosphor layer. .

When the phosphor layer is formed by a method of generating heat such as vapor deposition, the phosphor layer is irregular at intervals of several millimeters due to the difference in coefficient of thermal expansion between the phosphor layer and the substrate. Although a crack is likely to occur, the radiation image storage panel of the present invention has the metal layer and the transparent thin film layer between the substrate and the phosphor layer, and the ductility of the metal and the thermal expansion of the transparent thin film layer. The relaxation effect can effectively suppress the occurrence of cracks.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic cross-sectional view of a radiation image conversion panel showing a first embodiment of the present invention.
The radiation image storage panel 10 of the present invention is formed by laminating a metal layer 12, a transparent thin film layer 15 and a stimulable phosphor layer 16 on a substrate 11 in this order, and the transparent thin film layer 15 is in contact with the metal layer 12. The surface of the high refractive index layer 14 in contact with the stimulable phosphor layer 16 on the side of the stimulable phosphor layer 16 is composed of the refractive index layer 13 and the high refractive index layer 14 in contact with the stimulable phosphor layer 16. Has a stimulated emission light reflectance of 90% or more.

The low refractive index layer 13 is a layer having a lower refractive index than the high refractive index layer 14 constituting the transparent thin film layer 15,
The high refractive index layer 14 is a layer having a higher refractive index than the low refractive index layer 13 that constitutes the transparent thin film layer 15.

In FIG. 1, the transparent thin film layer 15 is the low refractive index layer 1
3 and the high-refractive index layer 14 are shown, the layer in contact with the metal layer is a low-refractive index layer and the layer in contact with the stimulable phosphor layer is a high-refractive index layer. It may be a multilayer film layer in which a refractive index layer, a high refractive index layer, a low refractive index layer and a high refractive index layer are alternately and repeatedly laminated. By forming such a multilayer film, it becomes easy to adjust the stimulated emission light reflectance on the surface of the high refractive index layer in contact with the stimulable phosphor layer on the side of the stimulable phosphor layer to 90% or more. It is possible to further suppress the occurrence of irregular cracks in the body layer.

The transparent thin film layer needs to be chemically stable so as not to deteriorate the metal layer and the stimulable phosphor layer. As a constituent material of such a transparent thin film layer, oxide or nitride is used. Thing, fluoride, carbide, or polymer,
Gelatin and the like are preferable. Specifically, SiO ₂ , Al
₂ O ₃ , TiO ₂ , CeO ₂ , ZrO _{2 and} other oxides, M
Fluoride such as gF ₂ , CaF ₂ , carbide such as SiC, S
Nitride such as iN, PET, polymer such as vinyl alcohol film, gelatin and the like are preferable.

From the viewpoint of the effect of relaxing the thermal expansion, M
gF ₂ , CeO ₂ (coefficient of thermal expansion at 200 ° C. (hereinafter the same): 7.9 × 10 ⁻⁶ / K), SiO ₂ (about 14 × 10
^-6 / K), TiO ₂ (about 9 × 10 ^-6 / K), ZrO ₂ (1
4 × 10 ⁻⁶ / K) and the like are more preferable. The layer thickness of each of the low refractive index layer and the high refractive index layer constituting the transparent thin film layer differs depending on the constituent material selected, so it cannot be generally stated,
The thickness is preferably 0.005 to 10 μm, more preferably 0.01 to 1 μm.

Low refractive index layer and high refractive index in transparent thin film layer
As an example of the combination of layers, SiO ₂(Refractive index: about 1.
4) and TiO₂(Refractive index: about 2.6), MgF₂(refraction
Ratio: about 1.4) and CeO₂Etc. (refractive index: about 2.4) etc.
Can be given. You can stack these layers repeatedly and
The surface of the high refractive index layer can be adjusted by adjusting the thickness of the
To have a stimulated emission light reflectance of 90% or more
can do. The stimulated emission light reflectance is
Is the reflectance at the wavelength where the spectrum of stimulated emission light is maximum
It means that it can be measured by an integrating sphere type spectrophotometer.
Wear.

The means for forming the transparent thin film layer is not particularly limited, and various thin film forming methods can be used. Specifically, a vacuum vapor deposition method, a sputtering method, an ion plating method, a coating method and the like can be mentioned.

The metal layer functions as a light-reflecting layer and a light-shielding layer, and it is necessary that the metal layer has a different optical density, that is, a reflectance, at the interface with an adjacent layer. As the metal constituting the metal layer,
Aluminum, gold, silver, copper, chromium, nickel, platinum,
Examples thereof include rhodium and tin. In order to suppress the occurrence of cracks in the phosphor layer, it is preferable to select a metal having a large ductility and a high reflectance, and aluminum is more preferable. The layer thickness of the metal layer varies depending on the metal selected, but is preferably 0.01 to 100 μm,
More preferably, it is from 05 to 10 μm.

This metal layer may be formed by a vapor deposition method, a sputtering method, an ion plating method, a plating method, or may be formed by laminating a metal foil. In particular, a vapor deposition method such as a vapor deposition method facilitates the formation of a metal layer.

A known substrate can be used as the substrate, and glass, ceramics, various polymer materials or the like can be used. Specifically, quartz glass, glass such as chemically strengthened glass, crystallized glass, ceramics such as a sintered plate of alumina or zirconia, or cellulose acetate film, polyester film, polyethylene terephthalate film, polyamide film, polyimide film, triacetate film. And a plastic film such as a polycarbonate film.

Although the case where the metal layer is provided on the substrate has been described here, a metal support may be provided instead of forming the metal layer on the substrate. In this case, a metal sheet of aluminum, aluminum-magnesium alloy, iron, stainless steel, copper, chromium, lead or the like can be used.

The thickness of the substrate or metal support varies depending on the material and the like, but is generally 100 μm to 5 m.
m is preferable, and from the viewpoint of convenience of handling, especially from 200 μm
2 mm is preferable. Note that the surface of the substrate may have minute irregularities.

Examples of the photostimulable phosphor used in the radiation image storage panel of the present invention include, for example, US Pat. No. 3,859,527.
SrS: Ce, Sm, SrS: Eu, Sm, Th
O ₂ : Er, and La ₂ O ₂ S: Eu, Sm,

ZnS: C described in JP-A-55-12142
u, Pb, BaO · xAl ₂ O ₃ : Eu (however, 0.8 ≦ x ≦ 10), and M ^II O · xSiO ₂ : A (however, M ^II is Mg, Ca, Sr, Zn, C)
d, or Ba, A is Ce, Tb, Eu, Tm, Pb, Tl, Bi
Or Mn and x is 0.5 ≦ x ≦ 2.5),

LnOX described in JP-A-55-12144:
xA (where Ln is at least one of La, Y, Gd, and Lu, X is at least one of Cl and Br, and A is
At least one of Ce and Tb, and x is 0
<X <0.1),

As described in JP-A-55-12145 (B
a _1-X , M ²⁺ _X ) FX: yA (where M ²⁺ is at least one of Mg, Ca, Sr, Zn and Cd, X is at least one of Cl, Br and I, A Is Eu, Tb, Ce, Tm, Dy, Pr, H
at least one of o, Nd, Yb and Er, and x
Is 0 ≦ x ≦ 0.6, y is 0 ≦ y ≦ 0.2),

One of the following general formulas xM ₃ (PO ₄ ) ₂ · NX ₂ : yA or general formula M ₃ described in JP-A-57-148285.
(PO ₄ ) ₂・ yA (In the formula, M and N are Mg, Ca, Sr, Ba, Z respectively.
At least one of n and Cd, X is at least one of F, Cl, Br and I, A is Eu, Tb, Ce, Tm, Dy, Pr, Ho, Nd, Yb, E
It represents at least one of r, Sb, Tl, Mn and Sn. Further, x and y are numbers satisfying the conditions of 0 <x ≦ 6 and 0 ≦ y ≦ 1. ), A phosphor represented by the general formula nReX ₃ · mAX ′ ₂ : xEu, a general formula nReX ₃ · mAX ′ ₂ : xEu, ySm
(In the formula, Re is at least one of La, Gd, Y, and Lu, A is an alkaline earth metal, at least one of Ba, Sr, and Ca, X
And X'represents at least one of F, Cl and Br.
Further, x and y are 1 × 10 ⁻⁴ <x <3 × 10 ⁻¹ , 1 × 10 ^−4.
<Y <1 × 10 ^-1 is a number satisfying the condition, and n / m is 1 × 1
The condition of 0 ^-3 <n / m <7 × 10 ^{-1 is} satisfied. Phosphor represented by), and the general formula ^{M I X · aM II X '} 2 · bM III X "3: cA
(However, M ^I is at least one alkali metal selected from Li, Na, K, Rb and Cs, and M ^{I I} is Be, Mg, Ca, Sr, Ba, Zn, C
It is at least one divalent metal selected from d, Cu and Ni. M ^III is Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, E
It is at least one trivalent metal selected from r, Tm, Yb, Lu, Al, Ga and In. X, X'and X "are at least one halogen selected from F, Cl, Br and I. A is Eu, Tb, C
It is at least one metal selected from e, Tm, Dy, Pr, Ho, Nd, Yb, Er, Gd, Lu, Sm, Y, Tl, Na, Ag, Cu, Bi and Mg. Also a
Is a numerical value in the range of 0 ≦ a <0.5, and b is 0 ≦ b <0.5.
Is a numerical value in the range of 0, and c is a numerical value in the range of 0 <c ≦ 0.2. ) Alkali halide phosphor represented by

As described in JP-A-56-116777 (Ba
_1-X , M ^II _X ) F ₂ · aBaX ₂ : yEu, zA (where M ^II is at least one of beryllium, magnesium, calcium, strontium, zinc and cadmium, X is chlorine,
At least one of 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
A phosphor represented by the composition formula

M ^III O described in JP-A-58-69281
X: xCe (However, M ^III is Pr, Nd, Pm, Sm, Eu, Tb, Dy, H
is at least one trivalent metal selected from the group consisting of o, Er, Tm, Yb and Bi, X is either one or both of Cl and Br, and x is 0 <x <0.1.
A phosphor represented by the composition formula

Ba _1-X described in JP-A-58-206678
M _{X / 2} L _{X / 2} FX: yEu ²⁺ (wherein M represents at least one alkali metal selected from the group consisting of Li, Na, K, Rb and Cs; L represents Sc, Y, La, Ce, Pr, Nd, Pm, S
represents at least one trivalent metal selected from the group consisting of m, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Al, Ga, In and Tl; X is Cl, Br and I Represents at least one halogen selected from the group; and x is 10
^-2 ≤ x ≤ 0.5, and y is 0 <y ≤ 0.1), the phosphor represented by the composition formula,

M ^II FX described in JP-A-59-75200
・ AM ^I X ′ ・ bM ′ ^II X ″ ₂・ cM ^III X ₃・ xA: yEu ²⁺ (However, M ^II
Is at least one alkaline earth metal selected from the group consisting of Ba, Sr and Ca; M ^I is at least one alkali metal selected from the group consisting of Li, Na, K, Rb and Cs; M ′ ^II is at least one divalent metal selected from the group consisting of Be and Mg; M ^III is Al, Ga, In
And at least one trivalent metal selected from the group consisting of Tl; A is a metal oxide; X is Cl, Br and I
At least one halogen selected from the group consisting of; X ', X "and X are at least one halogen selected from the group consisting of F, Cl, 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 a phosphor represented by a composition formula of 0 <y ≦ 0.2,
And so on.

Alkali halide phosphors are particularly preferable because they facilitate the formation of a stimulable phosphor layer by a method such as vapor deposition and sputtering. However, the stimulable phosphor used in the radiation image conversion panel of the present invention is not limited to the above-mentioned phosphor, and it exhibits stimulated emission when irradiated with radiation and then irradiated with excitation light. Any phosphor may be used as long as it is a phosphor. The stimulable phosphor layer may use the above-mentioned stimulable phosphors alone or in an appropriate combination.

As the vapor-phase deposition method of the stimulable phosphor, known methods such as a vapor deposition method, a resistance heating method, a sputtering method and a chemical vapor deposition (CVD) method can be used. Here, a case of forming by the electron vapor deposition method will be described as an example.

Compared to the resistance heating method and the like, the electron vapor deposition method locally heats the evaporation source to instantly evaporate it.
There is an advantage that the evaporation rate can be easily controlled, and a mismatch between the composition of the phosphor charged as an evaporation source or its raw material and the composition of the phosphor in the formed phosphor layer can be reduced.

[0043] When the phosphor layer is formed by multi-source deposition (co-deposition) as first evaporation source, those containing the stimulable phosphor maternal (M ^I X) component and activator component (A) And at least two evaporation sources including
Multi-source vapor deposition is preferable because the vapor deposition rates of the matrix component of the phosphor and the activator component can be controlled when the vapor pressures thereof are largely different. Each evaporation source, depending on the desired composition of the stimulable phosphor, may be composed only of the respective base component and activator component of the phosphor, or a mixture with additive components and the like. Good. The evaporation source is 2
The number is not limited to one, and may be three or more, for example, by separately adding an evaporation source including an additive component.

The matrix component of the phosphor may be the compound itself constituting the matrix or a mixture of two or more raw materials capable of reacting to form a matrix compound.
The activator component is generally a compound containing an activator element, and for example, a halide of the activator element is used.

When the activator A is Eu, the molar ratio of the Eu ²⁺ compound to the Eu compound as the activator component is 70%.
The above is preferable. In general, Eu compounds include E
This is because u ²⁺ and Eu ³⁺ are mixed and contained, but the desired stimulated emission (or even instantaneous emission) is emitted from the phosphor having Eu ²⁺ as an activator. . The Eu compound is preferably EuBr _x , in which case x
Is preferably a numerical value within the range of 2.0 ≦ x ≦ 2.3. It is desirable that x be 2.0, but if it is made to approach 2.0, oxygen will be easily mixed. Therefore, in reality, a state in which the ratio of Br is relatively high is stable when x is around 2.2.

The evaporation source preferably has a water content of 0.5% by weight or less from the viewpoint of preventing bumping. For dehydration of the evaporation source, 100 to 300 of the above phosphor components are decompressed.
It can be carried out by heat treatment in the temperature range of ° C or by heating at a temperature not lower than the melting point of the phosphor component for several tens of minutes to several hours in a moisture-free atmosphere such as a nitrogen atmosphere.

The relative density of the evaporation source is preferably 80% or more and 98% or less, and more preferably 90% or more and 96% or less. If the evaporation source is in a powder state with a low relative density, it may cause inconveniences such as powder scattering during vapor deposition, or the film thickness of the vapor deposition film may not be uniform because it does not evaporate uniformly from the surface of the evaporation source. Or Therefore, in order to realize stable vapor deposition, it is desirable that the density of the evaporation source is high to some extent. To obtain the above-mentioned relative density, powder is generally 20
It is pressed under a pressure of MPa or higher, or is heated and melted at a temperature of a melting point or higher to form a tablet. However, the evaporation source does not necessarily have to be tablet-shaped.

Further, the evaporation source, particularly the evaporation source containing the phosphor matrix component, has a content of alkali metal impurities (alkali metals other than the constituent elements of the phosphor) of 10 ppm or less, and alkaline earth metal impurities (phosphor). It is desirable that the content of the alkaline earth metal other than the constituent elements of 1) be 1 ppm or less. Such an evaporation source can be adjusted by using a raw material having a low content of impurities such as an alkali metal or an alkaline earth metal. This makes it possible to form a vapor-deposited film with less impurities mixed therein, and such a vapor-deposited film can increase the amount of light emission.

The above evaporation source and substrate are installed in the vapor deposition apparatus.
Place it, evacuate the inside of the device, and 1 x 10 ^-FivePa ~ 1 x 10^-2
The degree of vacuum is about Pa. At this time, the degree of vacuum
Inert gas such as Ar gas, Ne gas, etc.
May be introduced. Also, if necessary O₂, H₂Etc.
A reactive gas may be introduced. In the atmosphere inside the device
The water pressure of the diffusion pump and cold trap.
7.0 x 10
^-3It is preferable that the pressure is not more than Pa.

Next, an electron beam is generated from each of the two electron guns to irradiate each evaporation source. At this time, the acceleration voltage of the electron beam is preferably set to 1.5 kV or more and 5.0 kV or less. Upon irradiation with an electron beam, the matrix component and activator component of the stimulable phosphor, which is the evaporation source, are heated to evaporate and scatter, and react to form a phosphor and deposit it on the substrate surface. At this time, the evaporation rate of each evaporation source can be controlled by adjusting the acceleration voltage of each electron beam. The phosphor deposition rate, that is, the vapor deposition rate is preferably 0.05 μm / min to 300 μm / min. When the deposition rate is less than 0.05 μm / min, the productivity of the radiation image conversion panel of the present invention is low, which is not preferable. Further, if the deposition rate exceeds 300 μm / min, it becomes difficult to control the deposition rate. Note that the electron beam irradiation may be performed plural times to form two or more vapor deposition films. Furthermore, the object to be vapor-deposited (substrate) may be cooled or heated during vapor deposition, if necessary.

After completion of vapor deposition, the vapor deposition film obtained is subjected to heat treatment (annealing treatment). The heat treatment is, for example, 50 ° C to 6 ° C.
It is carried out at a temperature in the range of 00 ° C. under a nitrogen atmosphere (which may contain a small amount of oxygen or hydrogen) for several hours.

In the case of one-source vapor deposition (pseudo-one-source vapor deposition), one vaporization source containing the phosphor matrix component and the activator component separated in the direction perpendicular to the vaporization flow (direction parallel to the substrate). Is preferably prepared. During vapor deposition, one electron beam is used to control the time (residence time) for irradiating each of the matrix component region and the activator component region of the evaporation source with an electron beam, so that the stimulability of the composition is uniform. A vapor deposition film made of a phosphor can be formed.

Alternatively, the unitary vapor deposition using the stimulable phosphor itself as an evaporation source may be used, and in that case, the one whose water content is adjusted to 0.5% by weight or less as described above is used. Further, it is preferable that the phosphor of the evaporation source has an alkali metal impurity content of 10 ppm or less and an alkaline earth metal impurity content of 1 ppm or less.

Further, prior to the formation of the vapor-deposited film made of the stimulable phosphor, the vapor-deposited film made of only the matrix of the phosphor may be formed. This makes it possible to obtain a vapor deposition film having a better columnar structure. Additives such as an activator in the vapor-deposited film made of the phosphor are diffused in the vapor-deposited film made of the phosphor matrix, especially by heating during the vapor deposition and / or heat treatment after the vapor deposition. The boundaries are not always clear.

In this way, a phosphor layer in which the columnar structure of the desired alkali metal halide stimulable phosphor is grown in the thickness direction is obtained.

The phosphor layer does not contain a binder and is composed only of the above alkali metal halide stimulable phosphor, and voids exist between the columnar structures of the stimulable phosphor.

The layer thickness of the stimulable phosphor layer varies depending on the desired characteristics of the radiation image conversion panel, the means for implementing the vapor phase deposition layer, the conditions, etc., but is preferably in the range of 10 to 1000 μm, 20 It is more preferably in the range of ˜800 μm. When the layer thickness of the stimulable phosphor layer is less than 10 μm, the radiation absorptivity is extremely reduced, the radiation sensitivity is deteriorated, the granularity of the image is deteriorated, and the stimulable phosphor layer is transparent. This is not preferred, because it tends to occur and the lateral spread of the stimulable excitation light in the stimulable phosphor layer is significantly increased, and the sharpness of the image tends to deteriorate.

In the radiation image conversion panel of the present invention,
A protective layer for physically or chemically protecting the stimulable phosphor layer may be provided on the surface of the stimulable phosphor layer opposite to the surface on which the reflective layer is provided. This protective layer may be formed by directly coating the protective layer coating solution on the stimulable phosphor layer, or by forming a protective layer separately formed in advance on the stimulable phosphor layer. Good. As the material for the protective layer, usual materials for the protective layer such as cellulose acetate, nitrocellulose, polymethylmethacrylate, polyvinyl butyral, polyvinyl formal, polycarbonate, polyester, polyethylene terephthalate, polyethylene, vinylidene chloride and nylon are used. In addition, this protective layer is made of SiC, S
It may be formed by stacking inorganic substances such as iO ₂ , SiN, and Al ₂ O ₃ .

In the protective layer, magnesium oxide,
Various additives such as light-scattering fine particles such as zinc oxide, titanium dioxide, and alumina, a slip agent such as perfluoroolefin resin powder and silicone resin powder, and a crosslinking agent such as polyisocyanate may be dispersed and contained.

In general, the thickness of these protective layers is preferably in the range of about 0.1 μm to 20 μm when it is made of a polymeric substance, and in the range of 100 to 1000 μm when it is an inorganic compound such as glass.

The surface of the protective layer may be further provided with a fluororesin coating layer for enhancing the stain resistance of the protective layer.
The fluororesin coating layer can be formed by applying a fluororesin solution prepared by dissolving (or dispersing) a fluororesin in an organic solvent onto the surface of the protective layer and drying. Although the fluororesin may be used alone, it is usually used as a mixture of the fluororesin and a resin having high film forming property. Further, an oligomer having a polysiloxane skeleton or an oligomer having a perfluoroalkyl group can be used together. The fluororesin coating layer may be filled with a fine particle filler to reduce interference unevenness and further improve the quality of a radiation image. The layer thickness of the fluororesin coating layer is usually preferably in the range of 0.5 μm to 20 μm. Upon forming the fluororesin coating layer, an additive component such as a cross-linking agent, a hardener and an anti-yellowing agent can be appropriately used. In particular, the addition of the crosslinking agent is advantageous for improving the durability of the fluororesin coating layer.

Although the radiation image conversion panel of the present invention can be obtained as described above, the panel configuration may include known variations. For example, for the purpose of improving the sharpness of the obtained image, at least one of the above layers may be colored with a coloring agent that absorbs excitation light and does not absorb stimulated emission light. The present invention will be specifically described below with reference to examples.

[0063]

Example 1 (Preparation of CsBr evaporation source) 75 g of CsBr powder was put into a powder molding die (internal diameter: 35 mm) made of zirconia, and a powder mold press molding machine (table press TB-5 type, NPA). Pressed at a pressure of 50 MPa with System Co., Ltd., and tablets (diameter: 35 mm, thickness: 20 mm)
Molded into. At this time, the pressure applied to the CsBr powder was about 40 MPa. Next, this tablet was subjected to vacuum drying treatment at a temperature of 200 ° C. for 2 hours with a vacuum dryer. The obtained tablet had a density of 3.9 g / cm ³ and a water content of 0.3% by weight.

(EuBr_xPreparation of evaporation source) EuBr
_x(X = 2.2) 25g powder for zirconia powder molding
Put into a die (inner diameter: 25 mm) and press mold powder powder
Pressurized with a machine at a pressure of 50 MPa, and tablets (diameter:
25 mm, thickness: 10 mm). At this time, E
uBr _xThe pressure applied to the powder was about 80 MPa.
Next, apply a vacuum dryer to this tablet at a temperature of 200 ° C.
A vacuum drying process was performed for 2 hours. Of the obtained tablets
Density is 5.1g / cm³, The water content is 0.5% by weight
It was

(Preparation of Radiation Image Conversion Panel) 100 n was formed on the surface of a glass substrate (thickness 0.7 mm) by EB vapor deposition.
An Al layer having a thickness of m is provided, and a MgF ₂ (refractive index: about 1.4) layer is formed as a low refractive index layer on the Al layer by EB vapor deposition.
The layer was formed with a layer thickness of 0 nm, and a CeO ₂ (refractive index: about 2.4) layer as a high refractive index layer was further formed thereon with a layer thickness of 100 nm.

Next, the glass substrate provided with the metal layer and the transparent thin film layer was placed in the vapor deposition device, the EuBr _x tablet and the CsBr tablet were placed at predetermined positions in the vapor deposition device, and the vapor deposition device was evacuated. The degree of vacuum was 1 × 10 ⁻³ Pa.
Then, the substrate was heated to 200 ° C. with a heating source composed of a sheathed heater located on the opposite side of the vapor deposition surface of the substrate. Each of the vapor deposition sources is irradiated with an electron beam by an electron gun, and CsB
r: Eu stimulable phosphor (layer thickness 400 μm, area 10 cm)
X 10 cm) was deposited. At this time, the emission current of each electron gun was adjusted so that the Eu / Cs molar concentration ratio in the stimulable phosphor was 0.003 / 1.

Next, this substrate was put into a vacuum heating device capable of introducing gas, and a rotary pump was evacuated to about 1 Pa to remove water and the like adsorbed on the deposited film.
The vapor deposition film was heat-treated at a temperature of 200 ° C. for 2 hours in a nitrogen gas atmosphere. The substrate was cooled under vacuum, and the substrate was taken out from the apparatus while the temperature was sufficiently lowered. In this way
A radiation image conversion panel was produced in which a phosphor layer having a structure in which columnar structures of CsBr: Eu stimulable phosphor were densely forested was formed on a substrate.

(Example 2) Four low refractive index layers and four high refractive index layers were alternately laminated, and the thickness of each layer was as shown in Table 1, and the metal layer, the low refractive index layer and the high refractive index layer were used. A radiation image conversion panel was produced in the same manner as in Example 1 except that the rate layer was provided by sputtering.

Comparative Example 1 A radiation image conversion panel was produced in the same manner as in Example 1 except that the metal layer, the low refractive index layer and the high refractive index layer were not formed on the substrate.

Comparative Example 2 A radiation image conversion panel was produced in the same manner as in Example 1 except that the transparent thin film layer was only the CeO ₂ layer.

Comparative Example 3 A radiation image conversion panel was produced in the same manner as in Example 1 except that the transparent thin film layer was only the TiO ₂ layer.

With respect to the above radiation image conversion panel, the stimulated emission light reflectance was measured with an integrating sphere type spectrophotometer. The stimulated emission light reflectance is the reflectance at the wavelength where the spectrum of the stimulated emission light is maximum, and in Examples and Comparative Examples,
The peak (maximum) wavelength of the spectrum of stimulated emission light is 440.
Since it was nm, the reflectance at that wavelength was measured. Further, the degree of cracking of the phosphor layer was evaluated by visual observation, and the degree of adhesion was evaluated using an adhesive tape. Regarding the sensitivity, after irradiating 100 mR of X-rays with a tube voltage of 80 kVp, a semiconductor laser with a wavelength of 660 nm was irradiated with an intensity of excitation light of 20 J / m ² for a time, and the light emission at that time was passed through a hand pass filter (B-410). It was converted into an electric signal with a photomultiplier tube and their intensities were compared. Examples 1-2, Comparative Examples 1-
Table 1 shows the configuration of the radiation image conversion panel of No. 3 and the evaluation results from the above viewpoints.

[0073]

[Table 1] Since the radiation image conversion panel of the present invention is provided with the metal layer and the low reflectance layer and the high reflectance layer as the transparent thin film layer on the substrate, a comparison is made only by providing the metal layer and one transparent thin film layer on the substrate. Compared to Example 1 and Comparative Example 2, the stimulated emission light reflectance was high, sufficient sensitivity was obtained, and the stimulable phosphor layer had no cracks and was excellent in adhesion.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a radiation image conversion panel showing a first embodiment of the present invention.

[Explanation of symbols]

10 Radiation image conversion panel 11 board 12 metal layers 13 Low refractive index layer 14 High refractive index layer 15 Photostimulable phosphor layer

Claims (5)

[Claims] 1. A radiation image conversion panel comprising a metal layer, a transparent thin film layer and a stimulable phosphor layer laminated in this order on a substrate, wherein the transparent thin film layer is a multilayer having two or more layers having different refractive indexes. A radiation image conversion panel comprising a film. 2. The transparent thin film layer is a multilayer film in which a layer in contact with the metal layer is a low refractive index layer and a layer in contact with the stimulable phosphor layer is a high refractive index layer. The radiation image conversion panel according to 1. 3. The reflectance of the transparent thin film layer in contact with the stimulable phosphor layer is 90% or more at a wavelength at which the spectrum of stimulated emission light on the surface of the stimulable phosphor layer side is maximized. The radiation image conversion panel according to claim 1 or 2, wherein 4. The low refractive index layer of the transparent thin film layer is MgF ₂ and the high refractive index layer is CeO ₂ , wherein the metal layer is a layer made of aluminum.
The described radiation image conversion panel. 5. The low refractive index layer of the transparent thin film layer is SiO ₂ , and the high refractive index layer is TiO ₂ , wherein the metal layer is a layer made of aluminum.
The described radiation image conversion panel.