JP2007322156A - Radiation image conversion panel and method for manufacturing it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a radiation conversion panel which eliminates the necessity of heat treatment by another device in a postprocess by cooling an accelerated phosphor layer properly after forming it and makes the radiation image conversion panel include an accelerated phosphor layer whose accelerated phosphorescence luminescence properties such as PSL sensitivity are good, and to provide an excellently efficient radiation image conversion panel manufactured by the method in the manufacture of the radiation image conversion panel. <P>SOLUTION: The method for manufacturing the radiation image conversion panel includes a process for changing the cooling rate of the accelerated phosphor layer in the range between 70 and 150°C of the temperature of the formed accelerated phosphor layer after finishing the formation of the accelerated phosphor layer by a gas phase lay-up method and is characterized in that the accelerated phosphor layer is cooled at the average cooling rate of 0.5 to 5°C/min. before changing the cooling rate and that it is cooled at the average cooling rate of 0.01 to 1°C/min. after changing the average cooling rate, and the conversion panel is manufactured by the method. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a radiation image conversion panel and a radiation image conversion panel in which a photostimulable phosphor layer is formed on a surface of a substrate in a vacuum vapor deposition tank by a vapor deposition method. The present invention relates to a manufacturing technique of a radiation image conversion panel capable of obtaining a radiation image conversion panel having good light emission characteristics.

  When irradiated with radiation (X-rays, α-rays, β-rays, γ-rays, electron beams, ultraviolet rays, etc.), a part of this radiation energy is accumulated and then irradiated with excitation light such as visible light. In addition, phosphors that exhibit stimulated emission according to the stored energy are known. This phosphor is called a stimulable phosphor (accumulating phosphor) and is used for various applications such as medical applications.

As an example, a radiation image conversion panel (hereinafter referred to as a conversion panel (also called a photostimulable phosphor panel (sheet)) having this photostimulable phosphor layer (stimulable phosphor layer). The radiation image information recording / reproducing system using the above-mentioned)) is known, and has been put into practical use, for example, as an FCR (Fuji Computed Radiography) manufactured by Fuji Photo Film Co., Ltd.
In this system, radiation image information of a subject is recorded on a conversion panel (phosphor layer) by irradiating X-rays or the like through a subject such as a human body. After recording, the conversion panel is scanned two-dimensionally with excitation light to generate stimulated emission, and this stimulated emission light is photoelectrically read to obtain an image signal, and an image reproduced based on this image signal is A radiographic image of a subject is output to a display device such as a CRT or LCD or a recording material such as a photographic photosensitive material.

A conversion panel is usually prepared by dispersing a stimulable phosphor powder in a solvent containing a binder and applying the paint to a glass or resin panel-like support and drying. Created by.
On the other hand, as disclosed in Patent Document 1 and Patent Document 2, a phosphor panel in which a phosphor layer is formed on a substrate by a vapor deposition method (vacuum film forming method) such as vacuum evaporation or sputtering is also known. It has been. Phosphor layers by vapor deposition are formed in a vacuum, so there are few impurities, and since there are almost no components such as binders other than stimulable phosphors, there is little variation in performance and luminous efficiency. Has excellent properties of being very good.

JP 2002-104946 A JP 2004-123968 A

By the way, when the phosphor layer is formed by the vapor deposition method, depending on the phosphor layer formation conditions (film formation conditions), the phosphor layer is about 200 ° C. when the phosphor layer formation is completed. It becomes high temperature. Therefore, in order to obtain an appropriate conversion panel free from cracks in the phosphor layer, it is necessary to properly cool the phosphor layer (and the substrate) after the phosphor layer is formed.
On the other hand, in Patent Document 1, a heater that heats the substrate during the formation (film formation) of the phosphor layer is used, and after the formation, the output of the heater is lowered step by step. The phosphor layer) is cooled slowly, preferably at a cooling rate of 1 to 20 ° C./min, so that the adhesion with the substrate is good and the conversion has a good phosphor layer without cracks. Manufacturing a panel is disclosed.

  However, the conversion panel is required not only to have good adhesion and properties of the phosphor layer but also to have stimulable light emission characteristics such as good PSL sensitivity. This is important for recording high-quality images with high sensitivity and uniformity of sensitivity, and for reducing the radiation dose of the subject.

  In addition, conventionally, for the purpose of improving photostimulated luminescence characteristics such as PSL sensitivity, the radiation image conversion panel having the formed phosphor layer is heat-treated (also called annealing) by a separate apparatus in a subsequent process. In addition, this process has a problem that the manufacturing process of the radiation image conversion panel is time-consuming.

  The object of the present invention has been made in view of the above circumstances, and the object of the present invention is to perform radiation image conversion in which a photostimulable phosphor layer is formed on a surface of a substrate by a vapor deposition method in a vacuum evaporation tank. In the manufacture of panels, by properly cooling after forming the photostimulable phosphor layer, the photostimulability with good photostimulable luminescence characteristics such as PSL sensitivity, etc., which eliminates the need for heat treatment by a separate device in the subsequent process. An object of the present invention is to provide a method for producing a radiation image conversion panel having a phosphor layer, and a radiation image conversion panel having excellent performance produced by this method.

  In order to achieve the above object, a method for producing a radiation image conversion panel according to the present invention is the method for producing a radiation image conversion panel in which a photostimulable phosphor layer is formed on a surface of a substrate by a vapor deposition method. After finishing the formation of the photostimulable phosphor layer by the deposition method, a process of changing the cooling rate of the photostimulable phosphor layer in the range of 70 to 150 ° C. In addition, the stimulable phosphor layer is cooled at an average cooling rate of 0.5 to 5 ° C./min before changing the cooling rate, and after changing the cooling rate, the average cooling rate of 0.01 to 1 ° C. / The photostimulable phosphor layer is cooled in min (claim 1).

Here, in the manufacturing method of the radiation image conversion panel which concerns on this invention, the storage atmosphere of the said photostimulable phosphor layer is 1.0 * 10 < ^-4 > -1.0 * 10 in the process of changing the said cooling rate. Preferably, the pressure is set to ² Pa (Claim 2), and the process of changing the cooling rate is preferably performed in a vacuum vapor deposition tank (Claim 3).
The step of changing the cooling rate is preferably performed by heating the formed photostimulable phosphor layer (Claim 4), and the step of changing the cooling rate is further performed. It is also preferable to carry out by heating from the back side of the support that supports the photostimulable phosphor layer.

It is also preferable to take out the radiation image conversion panel from the atmosphere system after the photostimulable phosphor layer has become 150 ° C. or lower (Claim 6), and further, formation of the photostimulable phosphor layer. Is preferably performed by vacuum deposition with a degree of vacuum of 0.1 to 3 Pa.
In the process of changing the cooling rate, at least before changing the cooling rate, the oxygen partial pressure is preferably 0% <O ₂ <30%, and the cooling rate is changed. Among the processes to be performed, it is also preferable that the relative humidity be 5 to 50% at least before the cooling rate is changed.

  The radiation image conversion panel according to the present invention is a radiation image conversion panel having excellent performance, characterized by being manufactured by any one of the above-described methods for manufacturing each radiation image conversion panel. ).

  According to the present invention having the above configuration, in the production of a radiation image conversion panel for forming a photostimulable phosphor layer by a vapor deposition method, the atmosphere during cooling after forming the photostimulable phosphor layer is appropriately set. By controlling, a radiation image conversion panel having a photostimulable phosphor layer having excellent photostimulable light emission characteristics such as PSL sensitivity can be manufactured without performing heat treatment by a separate apparatus in a subsequent process.

Hereinafter, an embodiment of a method for manufacturing a radiation image conversion panel according to the present invention will be described in detail.
In the present embodiment, a photostimulable phosphor layer (hereinafter also simply referred to as a phosphor layer), which is a layer (film) made of a photostimulable phosphor, is formed (film formation) on the surface of a substrate by a vapor deposition method. This is a method for manufacturing a radiation image conversion panel (hereinafter simply referred to as a conversion panel).

In the conversion panel manufacturing method of the present invention, the substrate on which the phosphor layer is formed is not particularly limited, and various types used in various conversion panels can be used.
Examples include plastic plates and plastic sheets (films) formed from cellulose acetate, polyester, polyethylene terephthalate, polyamide, polyimide, triacetate, polycarbonate, etc .; quartz glass, alkali-free glass, soda glass, heat-resistant glass (Pyrex (registered trademark)) Etc.) etc.) Metal plates and glass sheets formed from metals such as aluminum, iron, copper, chromium, etc .; coating such as metal oxide layers on the surface of such metal plates Examples thereof include plates and sheets formed with layers.
Further, the substrate used in the production method of the present invention has various layers (films) such as a reflective layer, a protective layer, an antioxidant layer, and an adhesion layer on the surface of such a plate material or sheet material. Furthermore, you may have more than one of these layers.

The size (area) and thickness of the substrate 12 are not particularly limited, and may be determined as appropriate according to the application of the conversion panel 10 or the like.
The conversion panel manufacturing method of the present invention forms a phosphor layer on the surface of such a substrate by vapor deposition.

  In the production method of the present invention, the photostimulable phosphor used as the phosphor layer is not particularly limited, and various known photostimulable phosphors can be used. The body is preferably exemplified.

“SrS: Ce, Sm”, “SrS: Eu, Sm”, “ThO ₂ : Er”, and “SrS: Ce, Sm”, which are described in US Pat. No. 3,859,527, _{La 2 O 2 S: Eu,} Sm ".

“ZnS: Cu, Pb”, “BaO.xAl ₂ O ₃ : Eu (provided that 0.8 ≦ x ≦ 10)” and the general formula “M ^II ” disclosed in JP-A-55-12142 Stimulable phosphor represented by “O.xSiO ₂ : A”.
In the above ^{formula, M II} is at least one of Mg, Ca, Sr, Zn, is selected from the group consisting of Cd and Ba, A is, Ce, Tb, Eu, Tm , Pb, Tl, Bi, and Mn Is at least one selected from the group consisting of Further, 0.5 ≦ x ≦ 2.5.

A stimulable phosphor represented by the general formula “LnOX: xA” disclosed in JP-A No. 55-12144.
In the above formula, Ln is at least one selected from the group consisting 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. Further, 0 ≦ x ≦ 0.1.

A stimulable phosphor represented by the general formula “(Ba _1-X , M ^II _X ) FX: yA” disclosed in JP-A-55-12145.
In the above formula, M ^II is at least one selected from the group consisting of Mg, Ca, Sr, Zn and Cd, X is at least one selected from the group consisting of Cl, Br and I, and A Is at least one selected from the group consisting of Eu, Tb, Ce, Tm, Dy, Pr, Ho, Nd, Yb and Er. Further, 0 ≦ x ≦ 0.6 and 0 ≦ y ≦ 0.2.

A stimulable phosphor represented by the general formula “xM ₃ (PO ₄ ) ₂ .NX ₂ : yA” or “M ₃ (PO ₄ ) ₂ .yA” disclosed in JP-A-59-38278.
In the above formula, M and N are each at least one selected from the group consisting of Mg, Ca, Sr, Ba, Zn and Cd, and X is selected from the group consisting of F, Cl, Br and I. A is at least one selected from the group consisting of Eu, Tb, Ce, Tm, Dy, Pr, Ho, Nd, Yb, Er, Sb, Tl, Mn, and Sn. Further, 0 ≦ x ≦ 6 and 0 ≦ y ≦ 1.

A photostimulable phosphor represented by the general formula “nReX ₃ · mAX ′ ₂ : xEu” or “nReX ₃ · mAX ′ ₂ : xEu, ySm”.
In the above formula, Re is at least one selected from the group consisting of La, Gd, Y and Lu, A is at least one selected from the group consisting of Ba, Sr and Ca, and X and X ′ Are at least one selected from the group consisting of F, Cl, and Br. Further, 1 × 10 ⁻⁴ <x <3 × 10 ⁻¹ , 1 × 10 ⁻⁴ <y <1 × 10 ⁻¹ , and 1 × 10 ⁻³ <n / m <7 × 10 ^{−. 1} .

Disclosed in JP-61-72087, JP-formula ^{"M I X · aM II X '} 2 · bM III X''3: cA " alkali halide-based stimulable phosphors represented by.
In the above formula, M ^I is at least one selected from the group consisting of Li, Na, K, Rb and Cs, and M ^II is Be, Mg, Ca, Sr, Ba, Zn, Cd, Cu and Ni. at least one trivalent metal selected from the group consisting ^{of, M III} is, Sc, Y, La, Ce , Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm , Yb, Lu, Al, Ga and In, at least one trivalent metal selected from the group consisting of F, Cl, Br and I. A is composed of Eu, Tb, Ce, Tm, Dy, Pr, Ho, Nd, Yb, Er, Gd, Lu, Sm, Y, Tl, Na, Ag, Cu, Bi, and Mg. At least one selected from the group A. Further, 0 ≦ a <0.5, 0 ≦ b <0.5, and 0 <c ≦ 0.2.

A stimulable phosphor represented by the general formula “(Ba _1-X , M ^II _X ) F ₂ .aBaX ₂ : yEu, zA” disclosed in JP-A-56-116777.
In the above ^{formula, M II} is, Be, at least one of Mg, Ca, Sr, selected from the group consisting of Zn and Cd, X is, Cl, is at least one selected from the group consisting of Br and I , A is at least one of Zr and Sc. Further, 0.5 ≦ a ≦ 1.25, 0 ≦ x ≦ 1, 1 × 10 ⁻⁶ ≦ y ≦ 2 × 10 ⁻¹ , and 0 <z ≦ 1 × 10 ⁻² .

A photostimulable phosphor represented by the general formula “M ^III OX: xCe” disclosed in JP-A-58-69281.
In the above formula, M ^III is at least one trivalent metal selected from the group consisting of Pr, Nd, Pm, Sm, Eu, Tb, Dy, Ho, Er, Tm, Yb and Bi, and X is , Cl and Br. Further, 0 ≦ x ≦ 0.1.

Disclosed in JP 58-206678 and JP-formula _{"Ba 1-x M a L a} FX: yEu 2+ " stimulable phosphors represented by.
In the above formula, M is at least one selected from the group consisting of Li, Na, K, Rb and Cs, and L is Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Gd, Tb. , Tb, Dy, Ho, Er, Tm, Yb, Lu, Al, Ga, In and Tl is at least one trivalent metal, and X is a group consisting of Cl, Br and I It is at least one kind selected. Further, 1 × 10 ⁻² ≦ x ≦ 0.5, 0 <y ≦ 0.1, and a is x / 2.

Stimulable fluorescence represented by the general formula “M ^II FX · aM ^I X ′ · bM ′ ^II X ″ ₂ · cM ^III X ₃ · xA: yEu ²⁺ ” disclosed in JP-A-59-75200 body.
In the above formula, M ^II is at least one selected from the group consisting of Ba, Sr and Ca, M ^I is at least one selected from the group consisting of Li, Na, K, Rb and Cs, M ′ ^II is at least one divalent metal of Be and Mg, M ^III is at least one trivalent metal selected from the group consisting of Al, Ga, In, and Tl, and A is And X, X ′ and X ″ are at least one selected from the group consisting of F, Cl, Br and I, respectively. Further, 0 ≦ a ≦ 2, 0 ≦ b ≦ 1 × 10 ⁻² , 0 ≦ c ≦ 1 × 10 ⁻² , a + b + c ≧ 10 ⁻⁶ , and 0 <x ≦ 0.5 and 0 <y ≦ 0.2.

Among them, the alkali halide photostimulable phosphor disclosed in JP-A-61-72087 is preferable in that it has excellent photostimulated luminescence properties and the effects of the present invention can be satisfactorily obtained. In particular, alkali halide photostimulable phosphors in which M ^I contains at least Cs, X contains at least Br, and A is Eu or Bi are preferable. A photostimulable phosphor represented by “CsBr: Eu” is preferable.

In the method for producing a conversion panel of the present invention, the phosphor layer composed of such a stimulable phosphor is formed on the surface of the substrate as described above on various gases such as vacuum deposition, sputtering, and CVD (Chemical Vapor Deposition). It is formed by a phase deposition method (vapor phase film formation method / vacuum film formation method).
Among these, vacuum deposition is preferably used in terms of productivity, formation speed, and the like. In particular, the phosphor layer is preferably formed by multi-source vacuum evaporation in which the phosphor component material and the activator (activator) component material are separately heated and evaporated. For example, in the case of a phosphor layer made of “CsBr: Eu”, cesium bromide (CsBr) is used as the material of the phosphor component, and europium bromide (EuBr _x (x is usually the same) as the material of the activator component. 2 to 3 but 2 is preferred)), and the phosphor layer is preferably formed by vacuum deposition in which each is heated and evaporated separately.
There is no particular limitation on the heating method in vacuum vapor deposition, and for example, it may be formed by electron beam heating using an electron gun or the like, or resistance heating. Furthermore, in the case of forming by multi-source vacuum deposition, all materials may be heated and evaporated by the same heating means (for example, electron beam heating), or the phosphor component material is heated by electron beam, A small amount of the activator component material may be formed by resistance heating and heat evaporation.

There are no particular limitations on the conditions for forming the phosphor layer (film formation conditions), and the conditions may be appropriately determined according to the type of vapor deposition method used, the film formation material used, the heating means, and the like.
Further, during the formation of the phosphor layer, the substrate and the formed phosphor layer may be heated at 300 ° C. or less, preferably 200 ° C. or less, by heating the substrate or the like. The substrate may be heated by a known method such as a means for providing a heating means on a substrate holder for holding the substrate in a phosphor layer forming apparatus such as a vacuum vapor deposition apparatus.

Here, in the method for producing a conversion panel of the present invention, the above-mentioned various photostimulable phosphors, particularly alkali halide photostimulable phosphors, in particular, a phosphor layer made of CsBr: Eu is formed by vacuum deposition. In this case, once the system is evacuated to a high degree of vacuum, argon gas, nitrogen gas or the like is introduced into the system to obtain a medium vacuum degree of about 0.01 to 3 Pa. It is preferable to perform vacuum vapor deposition with medium injection vacuum, in which the film forming material is heated by, for example.
Alkali halide phosphor layers such as CsBr: Eu have a columnar crystal structure, but such a phosphor layer obtained by vacuum deposition under medium vacuum has a particularly good columnar crystal structure, It is preferable in terms of exhaust light emission characteristics and image sharpness.
In addition, an alkali halide phosphor layer formed by vacuum deposition under such a medium vacuum, particularly a phosphor layer made of CsBr: Eu, has improved photostimulated luminescence characteristics by a cooling method unique to the present invention described later. The effect is great and this is also preferable.

The film forming speed of the phosphor layer is not particularly limited, and may be appropriately determined according to the type of stimulable phosphor, the film forming method, the performance of the film forming apparatus, and the like.
Furthermore, there is no particular limitation on the thickness of the phosphor layer, and the layer thickness capable of obtaining sufficient photostimulable luminescent properties is appropriately determined according to the use of the conversion panel, the type of stimulable phosphor, and the like. However, it is preferably 50 to 1500 μm, particularly about 200 to 1000 μm.

As described above, immediately after the phosphor layer is formed by such a vapor deposition method, the phosphor layer is at a high temperature of about 200 ° C.
In the method for producing the phosphor sheet of the present invention, after the phosphor layer is formed on the surface of the substrate by the vapor deposition method, the temperature of the photostimulable phosphor layer formed is 70 to 150 ° C. A process of changing the cooling rate of the photostimulable phosphor layer in a range, and before the cooling rate is changed, the photostimulable phosphor layer is cooled at an average cooling rate of 0.5 to 5 ° C./min. After the change, the photostimulable phosphor layer is cooled at an average cooling rate of 0.01 to 1 ° C./min.

In the above-mentioned Patent Document 1, after forming the phosphor layer, the substrate (that is, the phosphor layer) is gradually cooled to have a suitable phosphor layer having high adhesion to the substrate and free from cracks. Manufacturing a conversion panel is disclosed.
In addition, as a result of the study, the inventor has determined that cooling after forming the phosphor layer by vapor deposition is not limited to properties such as adhesion and cracking of the phosphor layer but also stimulated emission characteristics such as PSL sensitivity. I also found that it has an impact. As a result of further studies on this point, the inventor has further studied the photostimulated luminescence properties such as PSL sensitivity by cooling in the presence of oxygen because the atmosphere under cooling has a great influence on the photostimulated luminescence properties. Found that a conversion panel having a good phosphor layer can be obtained, and proposed a method for manufacturing a phosphor sheet based on this knowledge in Japanese Patent Application No. 2005-319666 “Method for manufacturing radiation image conversion panel”. ing.

  In addition, as a result of further examination of the cooling conditions after forming the phosphor layer by the vapor deposition method, the present inventor changed the cooling conditions to those having the two-stage cooling rate as described above. Thus, it has been found that a radiation image conversion panel having a photostimulable phosphor layer having excellent photostimulable luminescence properties such as PSL sensitivity can be produced without performing heat treatment by a separate apparatus in a subsequent process. It has also been found that the timing for switching the two-stage cooling rate described above is preferably in the range of 70 to 150 ° C. of the photostimulable phosphor layer formed as described above.

In addition, as a method of performing the above-described two-stage cooling speed switching (actually, the cooling speed is switched from a certain speed to a speed one step slower than this)
(1) The storage atmosphere of the phosphor layer should be set to atmospheric pressure before changing the cooling rate, and changed to 1.0 × 10 ^{−4 to} 1.0 × 10 ² Pa after changing the cooling rate. (2) Method of performing the above method in a vacuum vapor deposition tank (3) Method of performing heating by heating the phosphor layer (4) Heating from the back side of the support that supports the phosphor layer It has also been found that various methods can be used, such as a method of performing.

In particular, in the stage before switching the cooling rate (that is, the slightly faster speed of the two stages), the oxygen partial pressure in the vacuum deposition tank is set to 0% <O ₂ <30%. Furthermore, it has been found that the relative humidity is preferably 5 to 50%.
Note that these oxygen partial pressure and relative humidity conditions are effective in order to further enhance the effect on the main feature of the present invention of switching the cooling rate in two stages, and are not essential requirements. .

At the time of cooling, if the degree of vacuum is in the above range, more preferable photostimulable light emission characteristics can be obtained if even a small amount of oxygen is present as compared to a state where there is no oxygen such as an inert atmosphere. On the other hand, if the oxygen partial pressure during cooling is more than 30%, oxygen may adversely affect the phosphor layer, and a large amount of oxygen is introduced into the high-temperature film-forming system after film formation. That is, it is not preferable in terms of device durability and safety.
The oxygen partial pressure is preferably 10% ≦ O ₂ <25%, more preferably 15% <O ₂ ≦ 21%, in view of obtaining better stimulated emission characteristics.

For the same reason, the degree of vacuum is preferably 10 Pa to atmospheric pressure. If the degree of vacuum is 1 Pa or less, sufficient oxygen cannot be supplied to provide the phosphor layer with suitable stimulated emission characteristics, and conversely, the degree of vacuum (gas pressure) is not less than atmospheric pressure. Therefore, the degree of vacuum is preferably 1 Pa to atmospheric pressure.
Further, the relative humidity of the atmosphere is preferably set appropriately within the range of 30 to 80% as the relative humidity at the ambient temperature in order to obtain more suitable photostimulated luminescence characteristics. The reason why an appropriate humidity is preferable is considered that oxygen supplied from moisture in the atmosphere affects the crystal structure of the phosphor. If the relative humidity of the cooling atmosphere is less than 30%, the effect due to the influence of moisture may not be sufficiently obtained. If the relative humidity exceeds 80%, the phosphor layer may be deteriorated by moisture. . More preferably, the relative humidity of the atmosphere is set within a range of 50 to 60%.

  In addition, after forming the phosphor layer, as a method of bringing the system into such an atmosphere, air is introduced into the vacuum chamber in which the phosphor layer has been formed, and the target vacuum degree or even atmospheric pressure is restored. Examples include a method of (releasing to the atmosphere) and a method of introducing an air-fuel mixture in which an inert gas such as nitrogen or helium and oxygen is introduced into the vacuum chamber so as to achieve the oxygen partial pressure.

  In the production of the conversion panel of the present invention, in order to obtain more preferable photostimulated luminescence characteristics, a cooling process is performed at a two-stage cooling rate after the phosphor layer is formed. Here, when the cooling rate of the first stage is less than 0.5 ° C./min, the time during which the phosphor layer is at a high temperature is too long, and the heat treatment is inappropriately performed (overheated state). There is a possibility that the photostimulable light emission characteristics such as PSL sensitivity may be deteriorated. Further, the cooling time becomes redundant, which is disadvantageous in terms of productivity and workability. On the other hand, when the cooling rate exceeds 5 ° C./min, the cooling rate is too fast, and the adhesion force between the substrate and the phosphor layer decreases depending on the difference in the shrinkage rate between the thermally expanded phosphor layer and the substrate. The possibility of cracking in the phosphor layer is increased, which is not preferable.

Considering such points, the cooling rate in the first stage is preferably 0.5 to 5 ° C./min. The cooling rate in the second stage is preferably 0.01 to 1 ° C./min, which is slower than the cooling rate in the first stage. This second stage of cooling is considered to bring about the same effect (improvement of the photostimulable light emission characteristics such as PSL sensitivity) after the cooling (conventionally performed as a separate process).
The cooling rate can be controlled by a method using a cooling means / heating means, a method for selecting a heat capacity of a substrate holder for holding a substrate, or a substrate holder (or provided on the substrate holder when the substrate holder has a heating means). The heat conduction means to the substrate) and the method for adjusting the adhesion between the substrate (preferably after the formation of the phosphor layer), and the pressure in the chamber, etc. It is sufficient to do this.

Further, the temperature at which the conversion panel is taken out from the film forming system, that is, the temperature at which the cooling is finished is not particularly limited. It is preferable to take out the conversion panel from the film forming system.
When the phosphor layer is taken out in a state where the temperature of the phosphor layer exceeds 150 ° C., the cooling rate in the air after taking out from the system is high, and the same as when the previous cooling rate exceeds 10 ° C./min. It is not preferable for the reason, and it is disadvantageous in terms of safety and durability of the substrate.
Considering such points, it is more preferable to take out the conversion panel from the film forming system after the phosphor layer becomes 100 ° C. or lower.

In the present invention, the phosphor layer is cooled in such a manner that the phosphor layer is formed in the vacuum chamber of the vacuum vapor deposition apparatus without being taken out of the substrate (that is, the conversion panel) as it is after the phosphor layer is formed. It is preferable to carry out in the forming system (inside the film forming system).
However, the present invention is not limited to this, and after the phosphor layer, the conversion panel on which the phosphor layer is formed may be taken out from the system, and similar cooling may be performed in a separately provided cooling system.

  In the manufacturing method of the conversion panel of the present invention, after the phosphor layer is formed by the vapor deposition method in this way and cooling is completed, the phosphor layer is made moisture-proof in order to prevent moisture absorption of the phosphor layer. It may be covered with a protective film and sealed.

  As mentioned above, although the manufacturing method of the radiation image conversion panel of this invention was demonstrated in detail, this invention is not limited to the above-mentioned example, Even if various improvement and change are performed in the range which does not deviate from the meaning of this invention. It goes without saying that it is good.

  Hereinafter, the present invention will be described in more detail with reference to specific examples of the present invention. In addition, it cannot be overemphasized that this invention is not limited to a following example.

[Example 1]
By dual vacuum deposition using europium bromide as the activator component material (activator component film forming material) and cesium bromide as the phosphor component material (phosphor component film forming material), respectively. A phosphor layer made of CsBr: Eu (stimulable) was formed on the surface of the substrate. Both materials were heated by a resistance heating apparatus using a tantalum crucible and a 6 kW DC power source.
An aluminum substrate having an area of 450 × 450 mm was set on the substrate holder of the vacuum evaporation apparatus, and each material was set at a predetermined position. The substrate was masked so that the film formation region was a 430 × 430 mm region in the center of the substrate, was plasma-cleaned under conditions of 500 W / 60 seconds, and then set on the substrate holder. The substrate holder has a heater and a heat conductive sheet that conducts the heat of the heater, and the substrate has the back surface (the surface on which the phosphor layer is not formed) closely adhered (pressed) to the heat conductive sheet. ) And fixed.

After setting the substrate on the substrate holder, the vacuum chamber was closed and evacuation was started. For the exhaust, a diffusion pump and a cryocoil were used.
When the degree of vacuum reached 8 × 10 ⁻⁴ Pa, argon gas was introduced into the vacuum chamber while continuing evacuation, so that the degree of vacuum in the vacuum chamber was 1.5 Pa.
Next, the DC power source is driven, the crucible filled with cesium bromide is energized to heat the film forming material (cesium bromide), and after 60 minutes, the shutter corresponding to the crucible filled with cesium bromide is opened. Then, formation of the first layer (deposition of cesium bromide) was started. The vapor deposition rate was controlled at 10 μm / min.
When the thickness of the first layer (cesium bromide) reached 50 μm, the shutter was closed and the film formation was interrupted (the film formation for the first layer was completed).
Next, the heater was energized to heat the substrate, and the flow rate of argon gas was adjusted so that the degree of vacuum in the vacuum chamber was 1.0 Pa.
When the substrate temperature reaches 160 ° C., the crucible filled with europium bromide is energized in addition to the crucible filled with cesium bromide, and after 60 minutes, all the crucibles containing film-forming materials are supported. The shutter was opened, and formation of the second layer (film formation of photostimulable phosphor) was started. The evaporation amount of europium bromide was controlled so that the molar concentration ratio of Eu / Cs in the photostimulable phosphor layer was 0.003: 1.

When the total layer thickness of the first layer and the second layer reaches about 710 μm, the DC power supply is stopped, the energization to the crucible and the energization to the heater for heating the substrate are stopped, and the phosphor layer Finished formation. The temperature of the substrate, that is, the phosphor layer at the end of formation of the phosphor layer (at the end of vapor deposition) was about 200 ° C.
Next, dry air (oxygen partial pressure: 21%) was introduced until the pressure in the vacuum chamber reached atmospheric pressure, and the substrate was cooled to 130 ° C. The cooling rate was 1.7 ° C./min.
When the temperature of the substrate reached 130 ° C., the inside of the vacuum chamber was again evacuated and cooled to room temperature while maintaining the vacuum. The cooling rate was 0.2 ° C./min.

  Next, the cooled substrate was processed by the same method as the conventional method to produce a (radiation image) conversion panel.

[Example 2]
In the same manner as in Example 1, after forming the phosphor layer, dry air (oxygen partial pressure: 21%) was introduced until the substrate temperature was about 200 ° C. until the inside of the vacuum deposition tank reached atmospheric pressure. And cooled to 130 ° C. The cooling rate was 1.7 ° C./min.
When the temperature of the substrate reached 130 ° C., energization of the heater was started again at atmospheric pressure, and this energization was controlled to cool to room temperature at a cooling rate of 0.2 ° C./min.
Next, a (radiation image) conversion panel was produced in exactly the same manner as in Example 1.

[Comparative Example 1]
After forming the phosphor layer in the same manner as in Example 1, air (oxygen partial pressure: 21%) was introduced until the substrate temperature was about 200 ° C. until the inside of the vacuum deposition tank reached atmospheric pressure. And cooled to 100 ° C. The cooling rate was 1.7 ° C./min.
When the temperature reached 100 ° C., the substrate was removed from the substrate holder, removed from the vacuum chamber, placed on a stainless steel stitch rack, and cooled to room temperature in the atmosphere. The cooling rate was 1.2 ° C./min.
Next, a (radiation image) conversion panel was produced in exactly the same manner as in Example 1.

[Comparative Example 2]
The substrate obtained in Comparative Example 1 after the formation of the phosphor layer and cooled to room temperature was covered with an aluminum cover on a hot plate heated to a temperature of 180 ° C. in a nitrogen atmosphere, and heat-treated for 1 hour. went. After natural cooling, a (radiation image) conversion panel was produced in exactly the same manner as in Example 1.

  Each conversion panel produced as described above was evaluated for PSL sensitivity (Photostimulated Luminescence) and phosphor layer adhesion (film adhesion). The evaluation method is as follows.

[PSL sensitivity]
The conversion panel was housed in a light-shielding cassette and irradiated with about 1 mR of X-rays having a tube voltage of 80 kVp. After the X-ray irradiation, the conversion panel was taken out from the cassette in a dark room, and the phosphor layer was irradiated with He—Ne laser light (wavelength 633 nm: 10 mW) as excitation light, and stimulated emission light emitted from the phosphor layer was measured. The stimulated emission light is measured by separating the excitation light and the stimulated emission light through an excitation light cut filter (B410 manufactured by HOYA) and measuring the stimulated emission light using a photomultiplier tube. I went there.

The evaluation of PSL is based on the result of Example 1 being 100.
90 or more ◎;
80 or more and less than 90 ○;
60 or more and less than 80 △;
Less than 60 x:
The relative evaluation was as follows.

[Membrane adhesion]
X indicates that the formed phosphor layer is exfoliated;
Peeling is not observed in the phosphor layer, but Δ3 indicates that peeling occurs when a 3 cm square “well” is written on the phosphor layer.
Even if a 3 cm square “I” character is written on the phosphor layer, no peeling is observed, but when the “I” character is pasted with a gum tape and pulled in the vertical direction, ○
In all of the above, the phosphor layer does not peel off.
It was evaluated.

The above results are shown in Table 1 below. In Table 1, “before the change of the cooling rate” is abbreviated as “first half”, and after the change is abbreviated as “second half”.

As shown in Table 1, PSL sensitivity is low in Comparative Example 1 in which cooling is performed without sufficiently changing (not slowing) the cooling rate after the phosphor layer is formed, and it cannot be a suitable conversion panel.
On the other hand, according to the manufacturing method of the embodiment in which the cooling rate is clearly reduced, a conversion panel suitable for both PSL sensitivity and film adhesion can be obtained.
In addition, about the conversion panel of the comparative example 1, in the result (comparative example 2) which heat-processed as an additional process after cooling, the considerable PSL sensitivity rise was recognized, However, It reached the performance of the conversion panel of an Example. There wasn't.

  From the above results, the effects of the present invention are clear.

  It should be noted that the above-described embodiments and examples show examples of the present invention, and the present invention is not limited to these, and arbitrary modifications and improvements are made without departing from the spirit of the present invention. Needless to say, it is good.

Claims (8)

A method for producing a radiation image conversion panel, wherein a photostimulable phosphor layer is formed on a surface of a substrate by a vapor deposition method in a vacuum evaporation tank,
After completing the formation of the photostimulable phosphor layer by the vapor deposition method, the cooling rate of the photostimulable phosphor layer is changed within the temperature range of 70 to 150 ° C. Including the process of
Before changing the cooling rate, the stimulable phosphor layer is cooled at an average cooling rate of 0.5 to 5 ° C./min,
After the cooling rate is changed, the stimulable phosphor layer is cooled at an average cooling rate of 0.01 to 1 ° C / min. In the process of changing the cooling rate, the storage atmosphere of the photostimulable phosphor layer is set to atmospheric pressure before changing the cooling rate, and 1.0 × 10 ⁻⁴ to 1 after changing the cooling rate. The manufacturing method of the radiation image conversion panel of Claim 1 performed by changing to 0.0 * 10 < ² > Pa.   The manufacturing method of the radiation image conversion panel of Claim 1 or 2 which performs the process of changing the said cooling rate in a vacuum evaporation tank.   The method for producing a radiation image conversion panel according to claim 3, wherein the process of changing the cooling rate is performed by heating the formed photostimulable phosphor layer.   The manufacturing method of the radiation image conversion panel of Claim 4 which performs the process of changing the said cooling rate by the heating from the back side of the support body which supports the said photostimulable phosphor layer formed.   The manufacturing method of the radiation image conversion panel in any one of Claims 1-5 which take out a radiation image conversion panel from the inside of the system of the said atmosphere after the said stimulable fluorescent substance layer becomes 150 degrees C or less.   The method for producing a radiation image conversion panel according to any one of claims 1 to 6, wherein the photostimulable phosphor layer is formed by vacuum deposition with a vacuum degree of 0.01 to 3 Pa.   A radiation image conversion panel manufactured by the method for manufacturing a radiation image conversion panel according to claim 1.