JP2002107498A - Panel for converting radiation image, and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing easily a radiation image converting panel, of which the surface of the phosphor layer comprising columnar crystals is flat. SOLUTION: This method for manufacturing this radiation image converting panel having the highly stimulable phosphor layer of a smoothed surface comprises a process for forming a stimulable phosphor film on the surface of a temporary support body having the smooth surface by a vapor deposition method, a process for separating the phosphor film from the support body, and a process for arranging on a support body to bring the stimulable phosphor film into contact with a surface in a side reverse to a surface in a side having been in contact with temporary support body, to be followed by bonding.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a radiation image conversion panel used in a radiation image recording / reproducing method utilizing the stimulable light emission of a stimulable phosphor.

[0002]

2. Description of the Related Art A radiation image recording / reproducing method using a stimulable phosphor is known as an alternative to the conventional radiographic method. This method uses a radiation image conversion panel (a stimulable phosphor sheet) containing a stimulable phosphor, and transmits radiation transmitted through a subject or emitted from a subject to the stimulable phosphor of the panel. The radiation energy stored in the stimulable phosphor is absorbed by the body in a time-series manner by exciting the stimulable phosphor with electromagnetic waves (excitation light) such as visible light and infrared rays. The fluorescent light is emitted as (stimulated emission light), the fluorescence is read photoelectrically to obtain an electric signal, and a radiation image of a subject or a subject is reproduced as a visible image based on the obtained electric signal. After the reading, the panel is prepared for the next photographing after the remaining image is erased. That is, the radiation image conversion panel is used repeatedly.

A radiation image conversion panel used in a radiation image recording / reproducing method has, as a basic structure, a support and a stimulable phosphor layer provided thereon. However, a protective layer is usually provided on the upper surface of the stimulable phosphor layer (the side not facing the support) to protect the phosphor layer from chemical deterioration or physical impact. ing.

[0004] The stimulable phosphor layer is usually formed by applying a binder solution in which the stimulable phosphor is dispersed on a support and drying. However, it is also known that the stimulable phosphor layer is formed by a vapor deposition method or a sintering method.

The radiation image recording / reproducing method (and the radiation image forming method) is a method having many excellent advantages.
Even in the radiation image conversion panel used for this method,
It is desired to provide an image that is as sensitive as possible and has good image quality (sharpness, granularity, etc.).

For the purpose of enhancing sensitivity and image quality, for example, Japanese Patent Application Laid-Open No. Sho 62-47600 discloses a radiation image conversion panel and a stimulable phosphor layer formed by an electron beam evaporation method which is a kind of vapor phase deposition method. Has been proposed. This method uses a stimulable phosphor or a stimulable phosphor material as an evaporation source, irradiates an electron beam with an electron gun to the evaporation source to evaporate and scatter the evaporation source, and forms a support for a support such as a metal sheet. By depositing the evaporated material on the surface, a phosphor layer composed of columnar crystals of the stimulable phosphor is formed. The phosphor layer formed by a vapor deposition method such as an electron beam evaporation method does not contain a binder, and is composed of only a stimulable phosphor, and between the columnar crystals of the stimulable phosphor. There are voids (cracks). Therefore, it has high sensitivity,
It is said that an image with high sharpness can be obtained.

However, in the stimulable phosphor layer formed by the vapor deposition method, each columnar crystal does not always grow at the same height, and the upper surface of each columnar crystal is also flat. It tends to be more convex. Therefore, when the surface of the stimulable phosphor layer (the surface opposite to the side in contact with the support) is irradiated with excitation light when reading an image, a part of the excitation light is scattered on the phosphor layer surface. As a result, the image quality is reduced.

Japanese Patent Application Laid-Open No. 6-230198 discloses a radiation image conversion panel manufactured by flattening the surface of a stimulable phosphor layer composed of columnar crystals by polishing or the like.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for easily producing a radiation image conversion panel having a flat phosphor layer made of columnar crystals. Another object of the present invention is to provide a method of manufacturing a radiation image conversion panel that provides high-sensitivity, high-quality radiation images.

[0010]

The present inventor studied a method of flattening the surface of a stimulable phosphor layer composed of columnar crystals. As a result, after forming the phosphor layer by a vapor deposition method, the phosphor was formed. The inventors have found that the surface of the phosphor layer on the excitation light incident side can be easily planarized by inverting the body layer upside down and adhering the phosphor layer onto the support, which has led to the present invention.

Accordingly, the present invention provides a step of forming a stimulable phosphor film on a surface of a temporary support having a smooth surface by a vapor deposition method, and drawing the stimulable phosphor film from the temporary support. Peeling off, and the stimulable phosphor film is arranged on the support such that the surface on the side in contact with the temporary support and the surface on the opposite side are in contact with each other, and a step of bonding. To manufacture a radiation image conversion panel.

The temporary support used in the present invention is preferably a metal plate such as an aluminum metal plate, and the support is preferably a quartz plate. The peeling of the stimulable phosphor film from the temporary support is realized by giving a sudden temperature change (heat shock) to the temporary support and causing the temporary support to expand or contract instantaneously. Preferably.

[0013] The present invention also resides in a radiation image storage panel manufactured using the above manufacturing method.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a method for manufacturing a radiation image storage panel of the present invention will be described in detail.

First, a stimulable phosphor layer is formed on a temporary support (temporary substrate) by a vapor deposition method. The temporary support may be arbitrarily selected from materials conventionally known as a substrate for a vapor deposition method such as an evaporation method. Particularly preferred substrate materials have a flat surface, high smoothness, and high heat resistance. It is an excellent metal sheet (plate) made of aluminum, iron, tin, chromium and the like, and a resin sheet made of aramid and the like.

The stimulable phosphor has a wavelength of 400 to 9
Irradiation with excitation light in the range of
A stimulable phosphor that emits stimulable light in the wavelength range of nm is preferred. An example of such a stimulable phosphor is described in JP-B-7-845.
No. 88, JP-A-2-193100 and JP-A-4-3
It is described in detail in each publication of No. 10900.

[0017] Among these, the basic formula ^{(I): M I X ·} aM II X '2 · bM III X "3: zA ‥‥ alkali metal halide stimulable phosphor represented by (I) Is particularly preferred, provided that M ^I is Li, Na, K, Rb
And represents at least one alkali metal selected from the group consisting of Cs, M ^II is Be, Mg, Ca, Sr, B
a, at least one kind of alkaline earth metal or divalent metal selected from the group consisting of Ni, Cu, Zn and Cd, and M ^III is Sc, Y, La, Ce, Pr, Nd, P
m, Sm, Eu, Gd, Tb, Dy, Ho, Er, T
m represents at least one rare earth element or trivalent metal selected from the group consisting of Lu, Al, Ga and In, and A represents Y, Ce, Pr, Nd, Sm, Eu, G
d, Tb, Dy, Ho, Er, Tm, Yb, Lu, N
a, at least one rare earth element or metal selected from the group consisting of Mg, Cu, Ag, Tl and Bi.
X, X ′ and X ″ are F, Cl, Br and I, respectively.
Represents at least one halogen selected from the group consisting of a, b and z are respectively 0 ≦ a <0.5, 0 ≦
b <0.5, 0 ≦ z <0.2.

It is preferable that M ^I in the basic composition formula (I) contains at least Cs. It is preferable that X contains at least Br. A is particularly preferably Eu or Bi. In addition, the basic composition formula (I) includes, if necessary, aluminum oxide,
A metal oxide such as silicon dioxide or zirconium oxide may be added as an additive in an amount of 0.5 mol or less based on 1 mol of M ^I.

Further, a rare earth activated alkaline earth metal fluorohalide-based stimulable phosphor represented by the basic composition formula (II): M ^II FX: zLn ‥‥ (II) is also preferable. However, M ^II is Ba,
Ln represents at least one kind of alkaline earth metal selected from the group consisting of Sr and Ca, and Ln represents Ce, Pr, Sm, E
represents at least one rare earth element selected from the group consisting of u, Tb, Dy, Ho, Nd, Er, Tm and Yb. X represents at least one halogen selected from the group consisting of Cl, Br and I. z is 0 <z ≦ 0.2
Represents a numerical value within the range.

In the above basic composition formula (II), M ^II represents:
Ba preferably accounts for more than half. Ln is particularly preferably Eu or Ce. In addition, in the basic composition formula (II), F: X = 1: 1 appears in the notation, which indicates that it has a BaFX type crystal structure, and the stoichiometry of the final composition It does not indicate the composition. In general, a state in which many F ⁺ (X ⁻ ) centers, which are vacancies of X ⁻ ions, are generated in the BaFX crystal is preferable from the viewpoint of increasing the photostimulation efficiency with respect to light of 600 to 700 nm. At this time, F is often slightly more than X.

Although omitted in the basic composition formula (II), one or more of the following additives may be added to the basic composition formula (II) as necessary. bA, wN ^I , xN ^II , yN ^III where A represents a metal oxide such as Al ₂ O ₃ , SiO ₂ and ZrO ₂ . In preventing sintering between M ^II FX particles, it is preferable to use an average particle size of the primary particles has low reactivity with M ^II FX in the following ultrafine particles 0.1 [mu] m. N ^I represents at least one kind of alkali metal compound selected from the group consisting of Li, Na, K, Rb and Cs; N ^II represents an alkaline earth metal compound consisting of Mg and / or Be; ^III is Al, Ga, In,
It represents a compound of at least one trivalent metal selected from the group consisting of Tl, Sc, Y, La, Gd and Lu. As these metal compounds, it is preferable to use halides as described in JP-A-59-75200, but it is not limited thereto.

B, w, x and y are each M ^II
This is the charged addition amount when the number of moles of FX is 1, and 0
≦ b ≦ 0.5, 0 ≦ w ≦ 2, 0 ≦ x ≦ 0.3, 0 ≦ y ≦
Represents a numerical value within each range of 0.3. These figures do not represent the element ratios contained in the final composition for additives that are reduced by baking or subsequent cleaning. Some of the above compounds may remain as added in the final composition.
^Some react with ^II FX or are incorporated.

In addition, the basic composition formula (II) may further include, if necessary, a Z compound described in JP-A-55-12145.
n and Cd compounds; TiO ₂ , BeO, MgO, C which are metal oxides described in JP-A-55-160078.
aO, SrO, BaO, ZnO, Y 2 O 3, La 2 O 3, I
n ₂ O ₃ , GeO ₂ , SnO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ , Th
O ₂ ; Zr and Sc compounds described in JP-A-56-116777; B compounds described in JP-A-57-23673; As described in JP-A-57-23675.
And Si compounds; tetrafluoroboric acid compounds described in JP-A-59-27980; JP-A-59-4728.
No. 9, hexafluorosilicic acid, hexafluorotitanic acid, and hexafluorozirconic acid, a hexafluoro compound comprising a monovalent or divalent salt of hexafluorozirconic acid; V, Cr, Mn, F
e, a compound of a transition metal such as Co and Ni, or the like may be added. Further, the present invention is not limited to the phosphor containing the above-described additive, and any phosphor having a composition which is basically regarded as a rare earth activated alkaline earth metal fluorinated halide-based stimulable phosphor can be used. It may be.

As the vapor deposition method, various known methods such as an evaporation method (an electron beam evaporation method, a resistance heating method, etc.) and a sputtering method can be used. Among them, the vapor deposition method, particularly the electron beam vapor deposition method, is preferable because a columnar crystal having a good shape and a well-arranged array can be obtained. In electron beam evaporation,
Since the evaporation source is locally heated and evaporated instantaneously, a substance having a high vapor pressure in the evaporation source evaporates preferentially (for example, the activator evaporates before the phosphor matrix), There is almost no discrepancy between the composition of the phosphor charged as the evaporation source and the composition of the phosphor in the formed phosphor layer.

As an example of the vapor deposition method, an electron beam evaporation method is used. First, a stimulable phosphor as an evaporation source and a substrate as an object to be deposited are placed in a deposition apparatus, and the inside of the apparatus is evacuated. Then, the degree of vacuum is set to about 3 × 10 ^{−7 to} 3 × 10 ⁻⁴ Pa. At this time, while maintaining the degree of vacuum at a level in this range, Ar
An inert gas such as a gas or a Ne gas may be introduced.

The stimulable phosphor is preferably processed into a tablet (pellet) shape by pressurizing and compression. The compression under pressure is generally performed by applying a pressure in the range of 800 to 1000 kg / cm ² . During compression, the tablet may be heated to a temperature in the range of 50 to 200 ° C., and after compression, the resulting tablet may be subjected to a degassing treatment. Thereby, the relative density of the evaporation source can be increased. If the relative density of the evaporation source is low,
If the phosphor does not evaporate uniformly, the film thickness of the deposited film becomes uneven, bumps adhere to the substrate, and the phosphor itself evaporates unevenly, and the phosphor is activated in the deposited film. Agents and additives are bent. Further, it is also possible to use the raw material or the raw material mixture instead of the stimulable phosphor.

Next, an electron beam is generated from the electron gun and irradiated to the evaporation source. At this time, the electron beam acceleration voltage is set to 1.5
It is desirable to set the voltage to not less than kV and not more than 5.0 kV. If the acceleration voltage is lower than 1.5 kV, the voltage becomes unstable, the beam position of the electron beam fluctuates, or the shape of the scanning surface by the electron beam of the evaporation source changes to keep the evaporation surface flat. It becomes difficult. On the other hand, when the acceleration voltage is higher than 5.0 kV, the columnar crystals of the phosphor that grows in vapor phase by evaporation become uneven.

The stimulable phosphor, which is the evaporation source, is heated by evaporation of the electron beam, evaporates and scatters, and is sequentially deposited on the substrate surface. The deposition rate of the phosphor, that is, the deposition rate, is generally in the range of 0.1 to 1000 μm / min, preferably in the range of 1 to 100 μm / min. Note that two or more phosphor layers may be formed by performing electron beam irradiation a plurality of times, or different phosphors may be co-evaporated using a plurality of electron guns. Further, it is also possible to synthesize a phosphor on a substrate using the phosphor raw material and simultaneously form the phosphor layer. Further, the object to be deposited (substrate) may be cooled or heated as necessary during the vapor deposition, or the phosphor layer may be subjected to a heat treatment (annealing treatment) after the vapor deposition.

Next, the stimulable phosphor film (deposited film) formed by vapor-phase growth of the stimulable phosphor is peeled off from the temporary support I. As a method of peeling off, a heat shock method is preferable.
The heat shock method is a method in which a substrate having a vapor-deposited film is heated and then rapidly cooled, so that the substrate is separated using a difference in thermal conductivity between the vapor-deposited film and the substrate. Although it varies depending on the material of the substrate and the type of the phosphor, it is generally 200 ° C to 60 ° C.
Immediately after heating to a temperature in the range of 0 ° C.,
A method of cooling to the range of 200 ° C (preferably 0 to 200 ° C) is suitably used. Alternatively, the phosphor layer may be peeled off from the substrate by mechanical means such as a tensile tester or etching from the substrate side.

Next, the peelable stimulable phosphor layer is turned upside down and bonded to the support using an adhesive or the like.

The support can be arbitrarily selected from materials known as supports for conventional radiation image conversion panels. In particular, in the present invention, the support material is selected in consideration of the mechanical properties and optical properties according to the purpose of use of the radiation conversion panel without considering the surface state and heat resistance required for vapor deposition. be able to. Preferred support materials are quartz glass sheets and resin sheets made of polyethylene terephthalate and the like.

In a known radiation image conversion panel, in order to improve the sensitivity or image quality (sharpness, granularity) of the radiation image conversion panel, a light reflecting layer made of a light reflecting material such as titanium dioxide or carbon black is used. It is known to provide a support such as a light absorbing layer made of a light absorbing material such as a light absorbing material. The support used in the radiation image storage panel of the present invention can also be provided with these various layers, and the configuration thereof can be arbitrarily selected according to the purpose of the desired radiation image storage panel, use, and the like. it can. Further, as described in JP-A-58-200200, the surface of the support on the phosphor layer side (the surface of the support on the phosphor layer side) When auxiliary layers such as a coating layer (adhesion-imparting layer), a light reflecting layer, and a light absorbing layer are provided, the surface of these auxiliary layers may be fine irregularities. You may.

In this way, a phosphor layer composed of the columnar crystals of the stimulable phosphor and having a flat upper surface as shown in FIG. 1 is obtained. The phosphor layer is composed of only the stimulable phosphor, and voids (cracks) exist between the columnar crystals of the stimulable phosphor. The thickness of the phosphor layer is usually in the range of 100 μm to 1 mm, preferably 200 μm.
m to 700 mm.

FIGS. 1A and 1B were obtained by photographing the surface of the stimulable phosphor layer according to the present invention (the side opposite to the support) with a scanning electron microscope (SEM). Photo
(1) was taken at a magnification of 2000 times and (2) was taken at a magnification of 10,000 times.

FIGS. 2 (1) and 2 (2) are obtained by photographing the back surface (the surface on the support side) of the stimulable phosphor layer according to the present invention, that is, the surface of the deposited film at the time of vapor deposition with a scanning electron microscope. (1) is 2000 times and (2) is 1
The photograph was taken at a magnification of 0000.

When the stimulable phosphor is vapor-phase grown, the shape of the upper surface of each columnar crystal is made to be a specific shape such as a hemisphere so that the surface of the phosphor layer on the support side can be formed. It is also possible to give directivity to emitted light (stimulated emission light).

It is desirable to provide a protective layer on the surface of the phosphor layer for the convenience of transportation and handling of the radiation image storage panel and to avoid a change in characteristics.

The protective layer is desirably transparent so as to hardly affect the incidence of excitation light and the emission of stimulated emission light. It is desirable that the panel be chemically stable, highly moisture-proof, and have high physical strength so that the panel can be sufficiently protected. As the protective layer, a solution prepared by dissolving a transparent organic polymer substance such as a cellulose derivative, polymethyl methacrylate, or an organic solvent-soluble fluororesin in an appropriate solvent is applied on the stimulable phosphor layer. Or a sheet for forming a protective layer such as an organic polymer film such as polyethylene terephthalate or a transparent glass plate, and provided on the surface of the phosphor layer using an appropriate adhesive. Alternatively, an inorganic compound formed on the phosphor layer by vapor deposition or the like is used. In the protective layer, various additives such as light scattering fine particles such as magnesium oxide, zinc oxide, titanium dioxide, and alumina, slip agents such as perfluoroolefin resin powder and silicone resin powder, and cross-linking agents such as polyisocyanate. May be dispersedly contained. The thickness of the protective layer is generally in the range of about 0.1 to 20 μm.

A fluorine resin coating layer may be further provided on the surface of the protective layer in order to increase the contamination 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 on the surface of the protective layer and drying.
The fluororesin may be used alone, but is usually used as a mixture of the fluororesin and a resin having a high film forming property. Further, an oligomer having a polysiloxane skeleton or an oligomer having a perfluoroalkyl group can be used in combination. The fluororesin coating layer may be filled with a particulate filler in order to reduce interference unevenness and further improve the quality of a radiographic image. The thickness of the fluororesin coating layer is usually in the range of 0.5 μm to 20 μm. In forming the fluororesin coating layer, additional components such as a crosslinking agent, a hardening agent, an anti-yellowing agent and the like can be used. In particular, the addition of a crosslinking agent is advantageous for improving the durability of the fluororesin coating layer.

Although the radiation image conversion panel of the present invention is obtained as described above, the configuration of the panel of the present invention may include various known variations. For example, for the purpose of improving the sharpness of the obtained image, at least one of the above-mentioned layers may be colored with a coloring agent that absorbs excitation light but does not absorb stimulating light (Japanese Patent Publication No. No. 59-23400).

[0041]

EXAMPLES Example 1 (1) Preparation of evaporation source 100 g of cesium bromide (CsBr, 0.47 mol) and 1.8404 g of europium bromide (EuBr ₃ , 4.7 ×)
10 ⁻³ mol) in a mortar, and then mixed by stirring with a stirring vibrator for 15 minutes. The resulting mixture was placed in a furnace, evacuated for 3 minutes, and then heated to 525 ° C. in a nitrogen atmosphere.
For 2 hours. After firing, the furnace was evacuated for 15 minutes to cool the fired product. Then, the obtained europium-activated cesium bromide (CsBr: 0.01 Eu) stimulable phosphor was pulverized in a mortar, and then press-compressed at a pressure of 800 kg / cm ² to prepare a tablet for vapor deposition. Tablets with an additional temperature of 15
Evacuation was performed at 0 ° C. for 2 hours to perform a degassing treatment.

(2) Formation of Vapor Deposition Film An aluminum plate (temporary support) was placed in a vapor deposition apparatus.
After placing the above evaporation source at a predetermined position in the apparatus, the inside of the apparatus was evacuated to a vacuum degree of 3.0 × 10 ⁻⁶ Pa. Then
The deposition source is irradiated with an electron beam having an accelerating voltage of 4.0 kV and 60 W using an electron gun, and a 25 μm stimulable phosphor is deposited on an aluminum plate.
Deposited at a rate of m / min. Thereafter, the irradiation of the electron beam was stopped, the inside of the apparatus was returned to the atmospheric pressure, and the aluminum plate was taken out of the apparatus. On an aluminum plate, the width is about 10 μm,
A stimulable phosphor deposited film (thickness: 4) having a structure in which columnar crystals of the phosphor having a length of about 450 μm densely stand almost vertically in a forest.
50 μm).

(3) Attaching Phosphor Layer The deposited film was peeled off from the aluminum plate by a heat shock method (heating to 300 ° C., then rapidly cooling to 100 ° C.). Next, the deposited film was turned upside down and bonded to a quartz sheet (support, thickness: 1.0 mm) using an adhesive.

In this way, a radiation image conversion panel comprising the support and the stimulable phosphor layer was manufactured. When the surface of the stimulable phosphor layer was photographed with an electron microscope, a photograph as shown in FIG. 1 was obtained.

Comparative Example 1 A radiation image conversion panel comprising an aluminum plate (support) and a phosphor layer was manufactured by performing the same operations as in (1) and (2) in Example 1. When the surface of the phosphor layer was photographed with an electron microscope, a photograph as shown in FIG. 2 was obtained.

As is apparent from FIG. 1, the surface of the phosphor layer was flat in the radiation image conversion panel (Example 1) of the present invention. On the other hand, as is apparent from FIG. 2, in the conventional radiation image conversion panel (Comparative Example 1), unevenness was generated on the phosphor layer surface.

[0047]

According to the method of manufacturing a radiation enhanced conversion panel of the present invention, a stimulable phosphor layer having a flat surface can be easily formed on a support without performing any special operation such as surface polishing. be able to. Thereby, the scattering of the excitation light on the phosphor layer surface can be significantly suppressed, and the image quality of the obtained radiation image can be further improved. In addition, the support can be arbitrarily selected in consideration of mechanical characteristics and optical characteristics according to the purpose of use of the radiation image conversion panel itself, without depending on the method and conditions of vapor deposition.

[Brief description of the drawings]

FIGS. 1 (1) and (2) are micrographs each showing an example of the surface of a phosphor layer formed according to the method of the present invention [(2) is enlarged than (1)]. .

FIGS. 2 (1) and 2 (2) are micrographs each showing an example of the surface of a phosphor layer formed according to a conventional method [(2) is enlarged than (1)].

Claims (7)

[Claims] A step of forming a stimulable phosphor film on the surface of the temporary support having a smooth surface by a vapor deposition method, a step of peeling off the stimulable phosphor film from the temporary support, and A step of arranging the stimulable phosphor film on a support so that the surface on the side in contact with the temporary support and the surface on the opposite side are in contact with each other, and adhering to the radiation image. Panel manufacturing method. 2. The method according to claim 1, wherein the temporary support is a metal plate. 3. The method according to claim 2, wherein the temporary support is an aluminum metal plate. 4. The radiation image conversion panel according to claim 1, wherein the stimulable phosphor film is peeled off from the temporary support by a heat shock method. Manufacturing method. 5. A radiation image conversion panel manufactured by the method according to claim 1, wherein the support is a quartz plate. 6. A radiation image conversion panel manufactured by the method according to claim 1. Description: 7. The radiation image conversion panel according to claim 6, wherein a protective layer is provided on the surface of the stimulable phosphor layer.