JP2005315786A - Radiation image conversion panel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high-definition radiation image conversion panel which is free from the deterioration of a stimulable phosphor layer caused by moisture and the like. <P>SOLUTION: This radiation image conversion panel is so constituted that the stimulable phosphor layer can be sealed by a moisture-proof protective film made by using a substrate whose surface roughness Ra is 20 nm or less and forming a moisture-proof layer where an inorganic material layer and an organic/inorganic composite layer are formed alternately in at least two layers on the surface of the substrate. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention belongs to the technical field of a radiation image conversion panel that records / reproduces a radiation image with a stimulable phosphor layer, and more specifically, high-quality radiation with extremely little deterioration in characteristics of the stimulable phosphor layer due to moisture absorption. The present invention relates to an image conversion panel.

  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, Phosphors that exhibit photostimulated luminescence 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 (stimulable phosphor panel (sheet)) having this stimulable phosphor film (stimulable phosphor layer). Radiation image information recording / reproducing system using the above-mentioned)) is known, and is put into practical use as, for example, 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 the subject is output to a display device such as a CRT 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.

However, phosphor layers obtained by such a vapor deposition method, in particular, alkali halide photostimulable phosphor layers having good characteristics, have high hygroscopicity and are in a normal (normal temperature / normal humidity) environment. Even if it is, it absorbs moisture easily.
As a result, the photostimulable light emission characteristics, that is, the sensitivity, and the crystallinity of the photostimulable phosphor are degraded (for example, if the alkali halide photostimulable phosphor having a columnar structure is collapsed) As a result, the sharpness of the reproduced image is reduced.

For this reason, in the conversion panel, the phosphor layer is covered with a moisture-proof protective film and sealed to prevent deterioration of the phosphor layer due to moisture absorption.
For example, in Patent Document 3, in a (radiation image) conversion panel having a phosphor layer made of a stimulable phosphor, at least four or more transparent inorganic layers and organic layers are alternately laminated on a transparent support. A conversion panel is disclosed in which the phosphor layer is covered with a protective film (transparent protective layer) having a thickness of 50 μm or less and sealed to prevent deterioration of the phosphor layer due to moisture absorption.

Japanese Patent No. 2789194 JP-A-5-249299 JP-A-5-249299

According to the conversion panel disclosed in Patent Document 3, it is possible to prevent characteristic deterioration caused by moisture absorption of the phosphor layer. However, for example, when exposed to severe conditions such as high temperature / humidity, or for applications that require long-term reproduction of high-quality radiographic images, sufficient moisture-proof performance is still obtained. Has not reached.
In order to improve the moisture-proof performance of the conversion sheet (phosphor layer), it is effective to increase the thickness of the protective film, but on the other hand, if the protective film is thickened, the optical characteristics are also deteriorated. In many cases, the image quality deteriorates, such as a decrease in sharpness and density unevenness. That is, there is a demand for an application for a conversion panel having a protective film that is thin and has excellent moisture-proof performance.

  An object of the present invention is to solve the above-mentioned problems of the prior art, and in a radiation image conversion panel having a photostimulable phosphor layer formed by a vapor deposition method, under a severe environment such as high temperature / humidity, Even for applications that require long-term reproduction of high-quality radiological images, it has sufficient moisture-proof performance, and it has reduced image sharpness and uneven image density due to the moisture-proof protective film. It is an object of the present invention to provide a high-quality radiation image conversion panel capable of stably obtaining a high-quality radiation image over a long period of time without any deterioration in image quality.

  To achieve the above object, the present invention provides a substrate, a photostimulable phosphor layer formed by a vapor deposition method, and a moisture-proof property that seals the photostimulable phosphor layer to prevent moisture absorption. A radiation image conversion panel having a protective film, wherein the moisture-proof protective film is formed on a base material having an arithmetic average surface roughness Ra of 20 nm or less on one surface and the one surface of the base material. Provided is a radiation image conversion panel comprising a moisture-proof layer, and the moisture-proof layer has at least two layers in which an inorganic compound layer and a composite layer of an organic compound and an inorganic compound are alternately formed. .

In such a radiation image conversion panel of the present invention, in the moisture-proof layer, the lowermost layer formed on the surface of the base material is preferably the inorganic compound layer, and the uppermost layer of the moisture-proof layer is an inorganic compound. And the moisture-proof protective film preferably seals the photostimulable phosphor layer with the uppermost inorganic compound layer facing the photostimulable phosphor layer, and the moisture-proof layer. The lowermost inorganic compound layer formed on the surface of the substrate, the composite layer formed on the surface of the inorganic compound layer, and the inorganic compound layer formed on the surface of the composite layer. It is preferable to have at least.
Further, in the radiation image conversion panel of the present invention, the substrate is formed by forming an organic polymer layer on the surface of the substrate body, and the bottom layer of the moisture-proof layer is formed on the surface of the organic polymer layer. Preferably, the arithmetic average surface roughness Ra of the surface opposite to the moisture-proof layer forming surface of the substrate is preferably 20 nm or more, and the thickness of the substrate is preferably 10 μm or less. Moreover, it is preferable that the thickness of the moisture-proof layer is 1 μm or less, and it is preferable that the stimulable phosphor layer is made of CsBr: Eu.

According to the present invention having the above configuration, in the radiation image conversion panel formed with the stimulable phosphor layer by a vapor deposition method, the surface is used as a moisture-proof protective film for preventing moisture absorption of the stimulable phosphor layer. Using a low-roughness base material, the lowermost inorganic compound layer formed on the surface of the base material, the organic compound / inorganic compound composite layer formed on the surface, and the inorganic formed on the surface By having a moisture-proof protective film having a moisture-proof layer formed by forming at least three layers of the compound layer, it is very excellent due to the synergistic effect of the substrate having a low surface roughness and the excellent moisture-proof effect of the moisture-proof layer. The moisture-proof effect can be obtained, and deterioration of the photostimulable phosphor due to moisture absorption can be prevented over a long period of time.
In addition, since the moisture-proof protective film exhibits a very excellent moisture-proof performance even when it is thin, it is possible to prevent a reduction in the sharpness of the radiation image and the occurrence of image unevenness due to the thick moisture-proof protective film. Therefore, according to the present invention, it is possible to obtain a high-quality radiation image conversion panel that can stably obtain a high-quality radiation image with no image unevenness and the like and excellent image sharpness over a long period of time.

  Hereinafter, the radiation image conversion panel of the present invention will be described in detail based on preferred embodiments shown in the accompanying drawings.

In FIG. 1, the conceptual diagram of an example of the radiation image conversion panel of this invention is shown.
In the illustrated radiation image conversion panel 10 (hereinafter referred to as conversion panel 10), a stimulable phosphor layer 14 is formed on the surface of a substrate 12, and the stimulable phosphor layer 14 is formed into a moisture-proof protective film 16. It is covered and sealed.
In the present invention, the photostimulable phosphor layer 14 is not limited to be formed on the surface of the substrate 12, and for example, the surface of the substrate 12 has a reflective layer of stimulated emission light, or further, A protective layer for the reflective layer may be formed, and the photostimulable phosphor layer 14 may be formed thereon.

In the conversion panel 10 of the present invention, the substrate 12 is not particularly limited, and various types used in the conversion panel 10 (stimulable phosphor panel) 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 ^™, etc.), etc. Glass plates and glass sheets formed from: metal plates and metal sheets formed from metals such as aluminum, iron, copper, and chromium; a coating layer such as a metal oxide layer is formed on the surface of such metal plates Examples of such a plate or sheet are as follows.
Further, the size (area) and thickness of the substrate 12 are not particularly limited, and may be appropriately determined according to the use of the conversion panel 10 or the like.

  In the conversion panel 10 of the present invention, the photostimulable phosphor layer 14 (hereinafter referred to as phosphor layer 14) is formed (film formation) on such a substrate 12 by a vapor deposition method.

  In the conversion panel 10, the stimulable phosphor (accumulative phosphor) forming the phosphor layer 14 is not particularly limited, and various known stimulable phosphors can be used. The following stimulable phosphors are 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 ".

As disclosed in JP-A-55-12142, “ZnS: Cu, Pb”, “BaO.xAl ₂ O ₃ : Eu (provided that 0.8 ≦ x ≦ 10)”, and the general formula “M ^II ” Stimulable phosphor represented by “O.xSiO ₂ : A”.
(In the above formula, M ^II is at least one selected from the group consisting of Mg, Ca, Sr, Zn, Cd and Ba, and A is Ce, Tb, Eu, Tm, Pb, Tl, Bi and Mn. And at least one selected from the group consisting of 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. Also, 0 ≦ x ≦ 0.1.)

A stimulable phosphor represented by the general formula “(Ba ^1-x , M ^{2 + x} ) FX: yA” disclosed in JP-A No. 55-12145.
(In the above formula, M ²⁺ is at least one selected from the group consisting of Mg, Ca, Sr, Zn and Cd, and X is at least one selected from the group consisting of Cl, Br and I. , A is at least one selected from the group consisting of Eu, Tb, Ce, Tm, Dy, Pr, Ho, Nd, Yb, and Er, 0 ≦ x ≦ 0.6, and 0 ≦ y. ≦ 0.2.)

One of the following photostimulable phosphors disclosed in JP-A-57-148285.
That is, the photostimulable phosphor represented by the general formula “xM ₃ (PO ₄ ) ₂ .NX ₂ : yA” or “M ₃ (PO ₄ ) ₂ .yA”;
(In the above formula, M and N are at least one selected from the group consisting of Mg, Ca, Sr, Ba, Zn and Cd, respectively, 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. 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 'Is at least one selected from the group consisting of F, Cl, and Br. Also, 1 × 10 ⁻⁴ <x <3 × 10 ⁻¹ and 1 × 10 ⁻⁴ <y <1 × 10 ⁻¹ , and further 1 × 10 ⁻³ <n / m <7 × 10 ⁻¹ .)

And an alkali halide photostimulable phosphor represented by the general formula “M ^I X · aM ^II X ′ ₂ .bM ^III X ″ ₃ : cA”.
(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 at least one trivalent metal selected from the group consisting of Ni, M ^III is, Sc, Y, La, Ce , Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, At least one trivalent metal selected from the group consisting of Tm, Yb, Lu, Al, Ga and In, and X, X ′ and X ″ are selected from the group consisting of F, Cl, Br and I A is from 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 consisting of . Also, a 0 ≦ a <0.5, a 0 ≦ b <0.5, a 0 ≦ c <0.2.)

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

A stimulable 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; Is at least one of Cl and Br, and 0 ≦ x ≦ 0.1.)

A stimulable phosphor represented by the general formula “Ba ^1-x Ma La FX: yEu ²⁺ ” disclosed in JP ^-A- 58-206678.
(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, It is at least one trivalent metal selected from the group consisting of Tb, Tb, Dy, Ho, Er, Tm, Yb, Lu, Al, Ga, In and Tl, and X is composed of Cl, Br and I. And at least one selected from the group, 1 × 10 ⁻² ≦ x ≦ 0.5, 0 ≦ y ≦ 0.1, and a is x / 2.)

The stimuli 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 Phosphor. (In the above formula, M ^II is at least one selected from the group consisting of Ba, Sr and Ca, and 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, and M ^III is at least one trivalent metal selected from the group consisting of Al, Ga, In, and Tl, and A Is a metal oxide, and X, X ′ and X ″ are at least one selected from the group consisting of F, Cl, Br, and I. Also, 0 ≦ a ≦ 2, 0 ≦ b ≦ 1 × 10 ⁻² , 0 ≦ c ≦ 1 × 10 ⁻² , a + b + c ≧ 10 ⁻⁶ , 0 <x ≦ 0.5, and 0 <y ≦ 0.2.)

In particular, the alkali halide photostimulable phosphor disclosed in Japanese Patent Application Laid-Open No. 57-148285 is preferable in that it has excellent photostimulated luminescence properties and the effects of the present invention can be obtained satisfactorily. 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 conversion panel 10 of the present invention, the phosphor layer 14 made of such a stimulable phosphor is formed by various vapor deposition methods (vacuum film forming methods) such as vacuum deposition, sputtering, and CVD (Chemical Vapor Deposition). It is formed.
Among them, the phosphor layer 14 formed by vacuum deposition is preferable in terms of productivity and the like, and in particular, the material of the phosphor component and the material of the activator (activator) component are separately heated and evaporated. The phosphor layer 14 formed by multi-source vacuum deposition is preferable. For example, in the case of the phosphor layer 14 of “CsBr: Eu”, cesium bromide (CsBr) is used as a material of the phosphor component, and europium bromide (EuBr _x (x is usually 2) to 3)) and 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. Further, when formed 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 may be heated by electron beam heating. The material of the activator component that is a trace amount may be formed by resistance heating and heating and evaporation.

  Further, the formation conditions (film formation conditions) of the phosphor layer 14 are not particularly limited and may be appropriately determined according to the type of vapor deposition method used, the film formation material used, the heating means, and the like. The formed phosphor layer 14 may be heated at 300 ° C. or lower, preferably 200 ° C. or lower during film formation by heating the substrate 12 or the like.

Here, in the conversion panel 10 of the present invention, the above-described various photostimulable phosphors, especially alkali halide photostimulable phosphors, especially the phosphor layer 14 made of CsBr: Eu is formed by vacuum deposition. First, after evacuating the system to a high degree of vacuum, argon gas or nitrogen gas or the like is introduced into the system to obtain a medium vacuum degree of about 0.01 to 3 Pa, and resistance heating or the like under this medium vacuum. The film forming material is preferably heated by vacuum evaporation.
An alkali halide phosphor layer such as CsBr: Eu has a columnar crystal structure, but the phosphor layer 14 obtained by forming a film under such a medium vacuum has a particularly good columnar crystal structure. From the viewpoints of photostimulated luminescence characteristics and image sharpness.

  There is no particular limitation on the thickness of the phosphor layer 14, and the layer thickness capable of obtaining sufficient photostimulable light emission characteristics is appropriately determined according to the application of the conversion panel 10 and the type of stimulable phosphor. However, it is preferably 50 to 1500 μm, particularly about 200 to 1000 μm.

When the phosphor layer 14 is formed by the vapor deposition method in this manner, it is preferable to perform a heat treatment (annealing) in order to develop good stimulated emission characteristics.
The heat treatment conditions for the phosphor layer 14 are not particularly limited, but as an example, under an inert atmosphere such as a nitrogen atmosphere, at 50 to 600 ° C., particularly 100 ° C. to 300 ° C., 10 minutes to 10 hours, particularly It is preferable to perform a heat treatment for 30 minutes to 3 hours. The heat treatment may be performed by a known method such as a method using a baking furnace, and the heat treatment may be performed by using a vacuum deposition apparatus having a heating means for the substrate 12.

In the conversion panel 10 of the present invention, the moisture-proof protective film 16 covers and seals the phosphor layer 14 in order to prevent the phosphor layer 14 from absorbing moisture.
In the conversion panel 10 of the present invention, the moisture-proof protective film 16 (hereinafter referred to as the protective film 16) is formed by forming a moisture-proof layer 22 on the surface of the substrate 20 having a predetermined arithmetic average surface roughness Ra. It is. In addition, the moisture-proof layer 22 has at least two layers in which an inorganic compound layer and a composite layer of an inorganic material and an organic material are alternately laminated. The lowermost inorganic material layer 24 formed on the surface, the composite layer 26 of the organic material and the inorganic material formed on the surface of the inorganic material layer 24, and the inorganic material layer 28 formed on the surface of the composite layer 26 3 layers.

In the conversion panel 10 of the present invention, the base material 20 has an arithmetic average surface roughness Ra (hereinafter referred to as surface roughness Ra) of 20 nm at least on the surface on which the moisture-proof layer 22 is formed (hereinafter referred to as this surface). It is as follows.
In the present invention, the moisture permeability of 0.1 [g / (m ² · day)] or less is obtained by combining the base material 20 having a very high surface smoothness with a moisture-proof layer 30 described later. Therefore, the conversion panel 10 having the excellent moisture-proof property of the phosphor layer 14 can be realized.
When the roughness Ra exceeds 20 nm, the high moisture permeability as described above cannot be realized, and therefore, a high-quality conversion panel 10 is obtained that prevents deterioration of the phosphor layer 14 due to moisture absorption over a long period of time. It is not possible.

In the present invention, the surface roughness Ra of the surface of the base material 20 is preferably 10 nm or less in that the conversion panel 10 having more excellent moisture resistance of the phosphor layer 14 can be obtained.
In terms of moisture resistance and the like, the smaller the surface roughness Ra, the more advantageous, but generally, the smaller the surface roughness Ra, the higher the cost of the base material 20, so that the required moisture-proof performance and cost. What is necessary is just to select the base material 20 to be used suitably according to etc.

  In the present invention, the substrate 20 is not limited as long as it can transmit radiation and stimulated emission light, and the surface roughness Ra of at least one surface is 20 nm or less, and various materials can be used. It is. Examples include various plastic sheets (resin films) made of polyethylene terephthalate (PET), polyurethane, polyethylene naphthalate, polyethylene, polypropylene, polyvinylidene chloride, polyamide, and the like.

Further, in the present invention, by providing an organic polymer layer or the like as a smooth layer on the surface of a substrate body such as a resin film having a surface roughness Ra of more than 20 nm, the surface roughness Ra of at least one surface is 20 nm or less. The base material 20 which has been used can also be suitably used.
Furthermore, if the surface roughness Ra is 20 nm, the smooth layer may have a moisture-proof function, and an auxiliary moisture-proof layer is provided on the surface of the substrate body such as a resin film (or on the smooth layer). A substrate having the following may be used as the substrate 20.
That is, in the conversion panel 10 of the present invention, the base material 20 is such that the lowermost layer of a laminated structure in which an inorganic material layer and a composite layer are laminated is formed on the surface. Accordingly, when the inorganic material layer 24 / composite layer 26 / inorganic material layer 28 is provided as in the illustrated example, the inorganic material layer 24 serving as the lowermost part of the configuration in which the inorganic material layers and the composite layers are alternately stacked is provided. What has the surface formed becomes a base material of the moisture-proof film 16 in the present invention. Preferably, as shown in the figure, the substrate having the surface on which the lowermost part of the sandwich structure of the inorganic material layer 24 / composite layer 26 / inorganic material layer 28, which will be described later, is formed is the substrate of the moisture-proof film 16 in the present invention. Become.

In the conversion panel 10 of the present invention, it is preferable that the back surface of the substrate 20 (the surface opposite to the surface on which the moisture-proof layer 22 is formed) has a surface roughness Ra of 20 nm or more.
As a method for efficiently manufacturing the protective film 16, a method of forming the moisture-proof layer 22 by forming each layer while conveying the long base material 20 using a roller or the like is exemplified. Here, in the conversion panel 10 of the present invention, since the surface roughness Ra of the surface of the substrate 20 of the protective film 16 is low, if the surface roughness Ra of the back surface is also low, the substrate 20 is conveyed (handled) by slipping or the like. May not be stable. If the conveyance of the base material 20 is unstable, the moisture-proof layer 22 is not properly formed, and the target moisture-proof property may not be obtained.
On the other hand, when the surface roughness Ra of the back surface of the base material 20 is 20 nm or more, the base material 20 can be stably transported even when the moisture-proof layer 22 is formed while being transported by a roller or the like. That is, it is possible to stably manufacture the high-quality conversion panel 10 excellent in moisture resistance of the phosphor layer 14 with high productivity.
The upper limit of the surface roughness Ra on the back surface of the substrate 20 is not particularly limited, but is preferably 200 nm or less.

In the conversion panel 10 of the present invention, the thickness of the base material 20 of the protective film 16 is not particularly limited. A thicker substrate 20 is more advantageous in terms of moisture resistance of the phosphor layer 14, but a decrease in the transmission or scattering of radiation or stimulated emission light increases, resulting in image density unevenness or sharpness. This causes a decrease in the degree of image quality, which is disadvantageous in terms of image quality, and particularly in medical applications such as the aforementioned FCR.
Considering the above points, the thickness of the substrate 20 is preferably 10 μm or less, particularly preferably 6 μm or less.

In the conversion panel 10 in the illustrated example, the protective film 16 is formed on the surface of the base material 20 having such a surface roughness Ra of 20 nm or less (as described above, the surface having the surface roughness Ra of 20 nm or less). The lowermost inorganic material layer (hereinafter referred to as “inorganic layer”) 24 formed on the surface of the inorganic layer 24, the composite layer 26 of the organic material and the inorganic material formed on the surface of the inorganic layer 24, and the composite layer 26 It has a moisture-proof layer 22 composed of three layers of an inorganic layer 28 formed on the surface.
In FIG. 1, the lowermost inorganic layer 24 is on the upper side, but in the moisture-proof layer 22 of the present invention, the direction close to the base material 20 is referred to as the lower side. Therefore, the inorganic layer 24 formed on the surface of the substrate 20 is the lowermost layer, and the inorganic layer 28 farthest from the substrate 20 (that is, the outermost layer of the moisture-proof layer 22 with respect to the substrate 20) is the uppermost layer. .

The inorganic layer 24 and the inorganic layer 28 are films made of various inorganic materials, and greatly contribute to moisture-proof performance (reduction in moisture permeability of the protective film 16).
As the inorganic layer 24 and the inorganic layer 28, layers made of various inorganic materials can be used as long as they can transmit radiation and stimulated emission light.
As an example, silicon oxide (SiO ₂ ), silicon nitride (Si ₃ N ₄ ), aluminum oxide (Al ₂ O ₃ ), aluminum nitride (AlN), zirconium oxide (ZrO ₂ ), tin oxide (SnO ₂ ), magnesium oxide A film made of an inorganic material such as (MgO) is exemplified.
The formation method of the inorganic layer 24 and the inorganic layer 28 is not particularly limited, and various film forming means such as sputtering, CVD, vacuum deposition, PVD (Physical Vapor Deposition), ion plating method, etc. can be used as long as the target thin film can be formed. Is available.

The film thickness of the inorganic layer 24 and the inorganic layer 28 is not particularly limited, but good moisture-proof performance can be obtained, cracking of the inorganic layer 24 and inorganic layer 28 can be prevented, and the total thickness of the moisture-proof layer 22 can be avoided. In view of the above, it is preferably 50 to 100 nm.
In addition, the inorganic layer 24 and the inorganic layer 28 may be layers made of the same material or layers made of different materials, and may have the same or different thickness.

The composite layer 26 is a film made of a composite material of various inorganic materials and various organic materials.
By having such a composite layer 26, defects in the inorganic layer 24 and the inorganic layer 28 can be filled, and the moisture-proof performance of both inorganic layers can be maximized. That is, in the conversion panel 10 of the present invention, the moisture-proof layer 22 has at least two layers obtained by alternately laminating inorganic layers and composite layers, and the surface of the substrate 20 having a roughness Ra of 20 nm or less. In addition, by forming the moisture-proof layer 22 in contact with this alternately laminated structure, the moisture permeability of the protective film 16 is 0.1 [g / (m ² · day)] or less due to the synergistic effect of both. The high-quality conversion panel 10 can prevent deterioration of the phosphor layer 14 due to moisture absorption over a long period of time by sealing the phosphor layer 14 with such a protective film 16. Can be realized. In particular, as shown in the drawing, a moisture-proof layer 22 having a sandwich structure in which the composite layer 26 is sandwiched between at least the inorganic layer 24 and the inorganic layer 28 and the sandwich structure is formed on the surface of the substrate 20 is provided. This effect can be obtained more suitably.

As the composite layer 26, a layer made of a composite material of various inorganic materials and organic materials can be used as long as it can transmit radiation and stimulated emission light.
As an inorganic material, for example, (a) a substance that forms the above-described inorganic layer such as silicon oxide and powdered, (b) one or more metal alkoxides and hydrolysates thereof, and ( c) One consisting of at least one of tin chlorides is used. On the other hand, as the organic material, water-soluble polymer substances such as polyvinyl alcohol (PVA) and methyl cellulose are used.
The composite layer 26 is formed by applying, for example, a coating agent containing the inorganic material and the organic material as an aqueous solution or a water / alcohol mixed solution and using the mixture as a main component. The specific forming method is not particularly limited, and various coating methods such as sol-gel method, gravure coating, roll coating, doctor blade coating, dip coating, slide coating and extrusion coating, screen printing method, spraying method, etc. Various film forming means can be used.

The thickness of the composite layer 26 is not particularly limited, but is preferably 0.3 to 1 μm from the viewpoint of obtaining a good moisture-proof performance and avoiding the total thickness of the moisture-proof layer 22.
In the composite layer 26, the ratio between the inorganic material and the organic material is not particularly limited, but the defect filling effect of the inorganic layer can be suitably obtained. In view of the fact that the composite layer 26 can exhibit a barricade effect, the amount of the organic material is preferably 10 to 50% by weight, particularly 20 to 40% by weight.

In the conversion panel 10 of the present invention, if the moisture-proof layer 22 of the protective film 16 has at least two layers formed by alternately laminating inorganic layers and composite layers, the layer configuration is as shown in the illustrated example. The three-layer structure is not limited.
For example, a two-layer structure having only the inorganic layer 24 and the composite layer 26 may be used, or a protective layer having a five-layer structure in which a composite layer and an inorganic layer are formed on the inorganic layer 28 may be used. A film other than the inorganic layer or the composite layer may be provided as long as the exhaust light can be transmitted.

In the conversion panel of the present invention, the lowermost layer of the moisture-proof layer 22 is preferably an inorganic layer as shown in the illustrated example. By setting it as such a structure, the interlayer adhesiveness of the base material 20 and the moisture-proof layer 22 can fully be ensured, and it is preferable at points, such as intensity | strength.
Further, in the conversion panel of the present invention, as shown in the illustrated example, the uppermost layer (surface opposite to the base material 20) of the moisture-proof layer 22 is an inorganic layer, and the protective layer 16 is formed with this inorganic layer facing the phosphor layer 14 side. It is preferable to seal the phosphor layer 14. By adopting such a configuration, the adhesion of the protective film 16 can be secured, which is preferable in terms of strength and the like. In addition, as will be described later, in the present invention, not only the substrate 12 and the protective film 16 but also the phosphor layer 14 and the protective film 16 are bonded in terms of strength and the like, and the phosphor layer 14 is sealed with the protective film 16. In this case, it is preferable to ensure sufficient interlayer adhesion between the phosphor layer 14 and the protective film 14 by using the inorganic material layer as the uppermost layer and facing the phosphor layer 14. It is more preferable in terms of strength and the like.
In particular, as shown in the drawing, it has a sandwich structure in which the composite layer 26 is sandwiched between at least the inorganic layer 24 and the inorganic layer 28, the sandwich structure is formed on the surface of the substrate 20, and the moisture-proof layer 22. By using the inorganic material layer as the uppermost layer, it is possible to ensure sufficient interlayer adhesion between the base material 20 and the phosphor layer 14 in addition to extremely excellent moisture proofing properties, thereby realizing a more preferable conversion panel. .

Here, the thicker the moisture-proof layer 22 is, the more advantageous in terms of moisture-proofness. However, the image quality is disadvantageous in terms of image quality due to a decrease in image quality such as density unevenness and a decrease in sharpness. It is the same. Further, when the number of moisture-proof layers 22 is increased, there is a high possibility that foreign matters such as dust are mixed in the moisture-proof layer 22 when each layer is formed. If foreign matter is mixed in the moisture-proof layer 22, this becomes an image defect. As described above, such deterioration of image quality and image defects are serious problems in medical applications such as the aforementioned FCR.
Considering the above points, there is no particular limitation, but the number of moisture-proof layers 22 is preferably 9 layers or less, particularly 5 layers or less. Similarly, although there is no particular limitation, the thickness of the moisture-proof layer 22 is preferably 1 μm or less, and particularly preferably 0.8 μm or less.

When manufacturing such a conversion panel 10 of the present invention, as an example, the phosphor layer 14 is formed on the surface of the substrate 12 by vacuum deposition.
On the other hand, the inorganic layer 24 is formed by, for example, sputtering on the surface of the base material 20 having the surface roughness Ra of 20 nm or less and the surface roughness Ra of the back surface of 20 nm or more, and then the composite layer 26 is formed by the sol-gel method. Furthermore, the inorganic layer 28 is formed by sputtering, and the protective film 16 having the three moisture-proof layers 22 on the surface of the substrate 20 is formed. In forming the moisture-proof layer 22, it is preferable to form each layer as a slack-free state by applying tension to the four sides of the substrate 20. Thereby, it can prevent that a wrinkle enters into the base material 20, and can produce the conversion panel 10 excellent in sharpness, an image quality, and moisture-proof property.
Next, an adhesive is applied to the surface of the moisture-proof layer 22 (that is, the surface of the inorganic layer 28 in this example), and the phosphor layer 14 is entirely covered with the adhesive application surface facing the substrate 12 side. A protective film 16 is laminated on the substrate 12 and bonded together by thermal lamination, whereby the phosphor layer 14 is sealed with the protective film 16 to manufacture the conversion panel 10 as shown in FIG. In addition, it is also preferable to heat the bonding surface by heating the substrate 12 or the like prior to bonding of both by thermal lamination.

In the above example, the moisture-proof layer 22 was formed using only the base material 20 as a support to produce the conversion panel 10, but the present invention is not limited to this.
For example, a peeling film made of polyethylene or the like having a thickness of about 10 to 500 μm is bonded to the substrate 20 to form a bonded film, and a moisture-proof layer 22 is formed on the surface of the substrate 20 of the bonded film to form a protective film. 16 is applied, and then the phosphor layer 14 is sealed with the protective film 16 (laminated film) by applying an adhesive to the moisture-proof layer 22 and laminating / adhering the protective film 16 in the same manner as before. Moreover, the method of producing the conversion panel 10 by peeling the film for peeling from a bonding film is also suitable.
According to this method, wrinkles can be prevented from entering the base material 20 depending on the thickness of the peeling film (this wrinkle is macro and is an attribute different from the surface roughness Ra). The conversion panel 10 excellent in sharpness, image quality, and moisture resistance can be produced.

Here, the protective film 16 may be adhered to the substrate 12 only on the entire circumference surrounding the phosphor layer 14, but the phosphor can be prevented from being lifted and is advantageous in terms of strength. The surface of the layer 14 is also preferably bonded to the protective film 16.
In addition, a frame that surrounds the phosphor layer 14 in the substrate surface direction is fixed to the substrate 12, and the phosphor layer is adhered to the protective film 16 by adhering the frame and the protective film 16 (or the phosphor layer 14). A configuration in which 14 is sealed is also more preferable. By having such a frame body, damage to the phosphor layer 14 due to external impact or the like can be prevented, and a step between the upper surface of the phosphor layer 14 and the adhesive surface when sealed with the protective film 16. This can improve productivity and workability. In this case, the phosphor layer 14 is preferably formed after the frame body is fixed to the substrate 12.

  Although the radiation image conversion panel of the present invention has been described in detail above, the present invention is not limited to the above-described embodiment, and various improvements and modifications may be made without departing from the gist of the present invention. Of course.

Hereinafter, the present invention will be described in more detail with reference to specific examples of the present invention. Needless to say, the present invention is not limited to the following examples.
Further, in the following examples and comparative examples, the surface roughness Ra of the base material 20 is determined by a contact method using a surface roughness measuring machine (Micro shape measuring machine ET4000A manufactured by Kosaka Laboratory Ltd.). It is measured.

[Example 1]
The phosphor layer 14 made of CsBr: Eu is formed on the surface of the substrate 12 by binary vacuum vapor deposition using europium bromide as the film forming material for the activator and cesium bromide as the film forming material for the phosphor. did. In addition, both film-forming materials were heated with a resistance heating apparatus using a tantalum crucible and a 6 kW DC power source.
An aluminum substrate 12 having an area of 450 × 450 mm is set on the substrate holder of the vacuum evaporation apparatus, and each film forming material is set at each predetermined position. Further, the film forming region is 430 × 430 mm at the center of the substrate 12. The surface of the substrate 12 was masked so that Thereafter, 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 reaches 8 × 10 ⁻⁴ Pa, argon gas is introduced into the vacuum chamber to set the degree of vacuum to 0.5 Pa, and then the DC power source is driven to energize the crucible, The phosphor layer 14 was formed on the surface. Note that the outputs of the DC power supplies of both crucibles were adjusted so that the Eu / Cs molar concentration ratio in the phosphor layer 14 was 0.01: 1 and the film formation rate was 8 μm / min. During film formation, the surface of the substrate 12 was heated using a halogen lamp.
When the thickness of the phosphor layer 14 reached about 710 μm, the film formation was completed, and the substrate 12 was taken out from the vacuum chamber. The film thickness was controlled by an experiment conducted in advance.
Next, the substrate 12 on which film formation was completed was heat-treated at a temperature of 200 ° C. for 2 hours in a nitrogen atmosphere.

On the other hand, a PET film having a thickness of 6 μm, a surface roughness Ra of one surface (front surface) of 3 nm, and a surface roughness Ra of the other surface (back surface) of 20 nm is used as the substrate 20, and tension is applied to the four sides of the substrate 20. An SiO ₂ film as the inorganic layer 24 was formed to a thickness of 100 nm on the surface (surface roughness Ra 3 nm surface) by sputtering, with no looseness.
Subsequently, the coating material containing PVA and SiO ₂ is adjusted so that the ratio (weight ratio) between PVA and SiO ₂ is 1: 4, and the inorganic layer 24 (SiO ₂ film) is formed using this coating material. A 0.6 μm-thick composite layer 26 (PVA 20% by weight) made of PVA and SiO ₂ was formed on the inorganic layer 24 by a sol-gel method on the surface.
Further, an SiO ₂ film having a thickness of 100 nm as the inorganic layer 28 is formed on the surface of the composite layer 26 in the same manner as the inorganic layer 24, and the inorganic layer is formed on the surface of the substrate 20 having a surface roughness Ra of 3 nm. A protective film 16 having a moisture-proof layer 22 composed of three layers of 24 / composite layer 26 / inorganic layer 28 was produced.

  Using a dispenser, an adhesive is applied to the surface of the inorganic layer 28, the entire surface of the phosphor layer 14 is covered with the protective film 16, the protective film 16 and the substrate 14 are laminated, and the protective film is formed by thermal lamination. 16 and the substrate 14 were adhered, and the phosphor layer 14 was entirely sealed with the protective film 16 to produce the conversion panel 10 shown in FIG.

[Example 2]
A PET film having a thickness of 6 μm and a surface roughness Ra of 30 nm on one surface and a surface roughness Ra of 20 nm on the other surface was prepared. An acrylate polymer (a mixture of triethylene glycol diacrylate and methacrylic acid adduct of ethylene glycol diglycidyl ether in a molar ratio of 8: 2) was applied to the surface of this PET film having a roughness Ra of 30 nm, an acceleration voltage of 120 kV, and an irradiation dose of 0 An organic polymer layer having a thickness of 2 μm was formed by curing by irradiation with an electron beam of .1 kGy. The surface roughness Ra of the polymer layer was 5 nm.
A conversion panel 10 was produced in the same manner as in Example 1 except that the PET film on which the organic polymer layer was formed was used as the base material 20 and the moisture-proof layer 22 was formed on the surface with the organic polymer layer side as the surface. .

[Comparative Example 1]
As the substrate 20, a PET film having a surface roughness Ra of 30 nm on one side and a thickness of 6 μm on the other side having a surface roughness Ra of 20 nm is used, and a surface having a surface roughness Ra of 30 nm is used as a surface. A conversion panel 10 was produced in the same manner as in Example 1 except that 22 was formed.

[Example 3]
A composite layer is formed in the same manner as the composite layer 26 except that the thickness of the composite layer 26 is 0.3 μm, and the thickness is 0.3 μm on the inorganic layer 28. A radiation image conversion panel was produced in exactly the same manner as in Example 1 except that a SiO ₂ film having a thickness of 100 nm was formed as an inorganic layer in exactly the same manner as in Example 24.
That is, the protective layer of the moisture-proof protective film of this radiation image conversion panel has a five-layer structure of inorganic layer / composite layer / inorganic layer / composite layer / inorganic layer and a thickness of 0.9 μm.

[Example 4]
Except for using the same base material 20 as in Example 2 (base material in which an organic polymer layer was formed on the surface roughness Ra 30 nm surface and the surface roughness Ra was 5 nm), it was exactly the same as Example 3. Thus, a radiation image conversion panel was produced.
That is, this radiation image conversion panel also has a moisture-proof protective film having a five-layer protective layer having a thickness of 0.9 μm, as in Example 3.

[Comparative Example 2]
A PET film having a surface roughness Ra of 30 nm on one side and a thickness of 6 μm on the other side having a surface roughness Ra of 20 nm is used as the substrate 20, and a surface having a surface roughness Ra of 30 nm is used as a surface, and a protective layer is provided on this surface. A radiation image conversion panel was produced in the same manner as in Example 3 except that it was formed.
That is, this radiation image conversion panel also has a moisture-proof protective film having a five-layer protective layer having a thickness of 0.9 μm, as in Example 3.

[Comparative Example 3]
A radiation image conversion panel was produced in the same manner as in Example 1 except that the moisture-proof layer was only an inorganic layer (thickness: 100 nm).

[Measurement of moisture permeability]
Calcium chloride was put into a container having an opening of 10 × 10 cm, and the opening was sealed using the (moisture-proof) protective film of each example and comparative example.
Using a thermostat, each container was allowed to stand in an environment of 90% RH at 40 ° C. for 2 weeks, and then the moisture absorption of calcium chloride in each container was measured with an electronic balance (AB304-S manufactured by METTLER TOLEDO). Humidity ([g / (m ² · day)]) was calculated.

The thickness [μm] of the substrate 20, the surface / back surface roughness Ra [nm] of the substrate 20, the presence or absence of the (organic) polymer layer, the layer structure of the moisture-proof layer, and the transparency of each example and comparative example Humidity [g / (m ² · day)] is shown in Table 1 below.

[Sharpness evaluation]
A chart for MTF measurement is placed on the surface of the prepared (radiation image) conversion panel, and the entire surface is irradiated with X-rays of 80 kvp (equivalent to 10 mR), and then read with a radiation image information reading device (VELOCITY manufactured by Fujifilm). , MTF (1 cycle / mm) was calculated.
The MTF of each conversion panel was evaluated by a relative value where the MTF of the radiation image conversion panel having no protective film was 100. The MTF was evaluated before and after being left for 30 days in an environment of 90% RH at 30 ° C. using a thermostatic bath.
The results are shown in Table 2 below. In Table 2, the evaluation of the MTF is “before / after leaving”.

[Image quality evaluation]
The entire surface of the produced (radiation image) conversion panel was irradiated with X-rays of 80 kvp (equivalent to 10 mR), and then read with a radiation image information reading device (VELOCITY manufactured by FUJIFILM Corporation).
The read image was output as a visible image, and the image quality was evaluated visually.
Evaluation is “A” when no unevenness or defect is observed in the image, “B” when slight unevenness or defect is observed in the image but not a problem in diagnosis, and unevenness or The case where defects were observed was designated as “C”. This image quality evaluation was also performed before and after being left in an environment of 90% RH at 30 ° C. for 30 days using a thermostatic bath.
The results are also shown in Table 2. In Table 2, the evaluation of image quality is “before / after leaving”.

[Light intensity]
After irradiating the produced (radiation image) conversion panel with 80 kvp (equivalent to 10 mR) of X-rays, reading is performed by irradiating with excitation light of 660 nm using a radiation image information reading device (VELOCITY manufactured by Fujifilm). Then, the light emission amount of the stimulated emission light was measured.
This light emission amount measurement was performed before and after being left for 30 days in an environment of 90% RH at 30 ° C. using a thermostat, and the change in the light emission amount was observed. “O” indicates that the decrease in the amount of light emission is not particularly problematic in medical diagnosis, and “X” indicates that the problem is more than 10%.
The results are also shown in Table 2.

[Comprehensive judgment]
Relative MTFs in sharpness evaluation are 90 or more, image evaluations are both A or B, and the amount of light emission is all evaluated as “◯”. Evaluated as “x”.
The results are also shown in Table 2.

As shown in Tables 1 and 2, Comparative Examples 1 and 2 in which the surface roughness Ra of the base material of the protective film is large and Comparative Example 3 in which the moisture-proof layer of the protective film is only an inorganic layer are not moisture-proof. It is sufficient, and after leaving it under high temperature / humidity, the sharpness, image quality, and the amount of light emitted by stimulating light emission are all lowered, and there is a high possibility that a problem in diagnosis occurs.
On the other hand, the conversion panel of the present invention having the roughness Ra of the base material 20 of the protective film 16 and 20 nm or less and the moisture-proof layer 22 having a sandwich structure of the inorganic layer 24 / composite layer 26 / inorganic layer 28, In any case, a high-quality radiographic image that has excellent sharpness, image quality, and stimulated light emission and can be accurately diagnosed can be obtained even after being left under high temperature and high humidity.
Further, Examples 1 and 2 in which the protective film 16 has the three moisture-proof layers 22 are particularly excellent in sharpness and image quality, and Examples 3 and 4 in which the protective film 16 has five moisture-proof layers. Is particularly excellent in the moisture resistance of the phosphor layer 14. That is, according to the present invention, it is possible to obtain a high-quality radiation image conversion panel corresponding to the characteristics required for the conversion panel by selecting the number of moisture-proof layers.
From the above results, the effects of the present invention are clear.

It is a schematic sectional drawing of an example of the radiation image conversion panel of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 (Radiation image) conversion panel 12 Substrate 14 (Stimulable) phosphor layer 16 Moisture-proof protective film 20 Base material 22 Moisture-proof layer 24, 28 Inorganic (material) layer 26 Composite layer

Claims (9)

A radiation image conversion panel comprising a substrate, a photostimulable phosphor layer formed by a vapor deposition method, and a moisture-proof protective film that seals the photostimulable phosphor layer to prevent moisture absorption. ,
The moisture-proof protective film has a substrate having an arithmetic average surface roughness Ra of 20 nm or less on one surface, and a moisture-proof layer formed on the one surface of the substrate, and the moisture-proof layer is A radiation image conversion panel comprising at least two layers in which an inorganic compound layer and a composite layer of an organic compound and an inorganic compound are alternately formed.   The radiation image conversion panel according to claim 1, wherein in the moisture-proof layer, a lowermost layer formed on the surface of the base material is the inorganic compound layer.   The uppermost layer of the moisture-proof layer is an inorganic compound layer, and the moisture-proof protective film seals the photostimulable phosphor layer with the uppermost inorganic compound layer facing the photostimulable phosphor layer. The radiation image conversion panel according to claim 1.   The moisture-proof layer is the lowermost inorganic compound layer formed on the surface of the substrate, the composite layer formed on the surface of the inorganic compound layer, and the inorganic compound formed on the surface of the composite layer. The radiation image conversion panel according to claim 1, comprising at least a layer.   The said base material forms an organic polymer layer in the surface of a base-material main body, The lowest layer of the said moisture-proof layer is formed in the surface of this organic polymer layer in any one of Claims 1-4. Radiation image conversion panel.   The radiation image conversion panel according to any one of claims 1 to 5, wherein an arithmetic average surface roughness Ra of the surface opposite to the moisture-proof layer forming surface of the substrate is 20 nm or more.   The radiation image conversion panel according to claim 1, wherein the base material has a thickness of 10 μm or less.   The radiation image conversion panel according to claim 1, wherein the moisture-proof layer has a thickness of 1 μm or less.   The radiation image conversion panel according to claim 1, wherein the photostimulable phosphor layer is made of CsBr: Eu.

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