JP2656795B2 - Radiation image conversion panel - Google Patents

Description

The present invention relates to a radiation image conversion panel having a stimulable phosphor layer. More specifically, the present invention relates to a radiation image conversion panel having excellent moisture resistance. The present invention relates to a radiation image conversion panel having excellent durability and durability and excellent sharpness.

(Prior Art) Radiation images such as X-ray images are widely used for diagnosis of diseases and the like.

In order to obtain this X-ray image, an X-ray image conversion method has been devised in which an image is taken directly from the phosphor layer instead of the silver halide photosensitive material.

This method uses radiation transmitted through the subject (generally X-rays)
Is absorbed by the phosphor, and then the phosphor is excited by, for example, light or heat energy to cause the phosphor to emit the radiation energy accumulated due to the radiation absorption, thereby detecting the fluorescence. This is a method of imaging.

Specifically, for example, U.S. Pat.No. 3,859,527 and JP-A-55-12144 disclose a radiation image conversion method using stimulable phosphor and using visible light or infrared light as stimulating excitation light. .

This method uses a radiation image conversion panel (hereinafter abbreviated as a "conversion panel") having a stimulable phosphor layer (hereinafter abbreviated as "stimulation layer") formed on a support. The radiation transmitted through the subject is applied to the stimulable layer to accumulate the corresponding radiation energy after the radiation of each part of the subject is formed to form a latent image, and then the stimulable layer is scanned with the stimulating excitation light to form a latent image. The stored radiation energy is emitted and converted into light, and an image is obtained by an optical signal based on the intensity of the light.

This final image may be reproduced as a hard copy or reproduced on a CRT.

The conversion panel used in this radiation image conversion method accumulates the radiation image information and then emits the stored energy by scanning with the stimulating excitation light, so that the radiation image can be stored again after the scanning and can be used repeatedly. It is possible.

Therefore, it is desirable that the conversion panel has a performance that can withstand long-time or repeated use many times without deteriorating the image quality of the obtained radiation image. For this purpose, the photostimulable layer of the conversion panel needs to be sufficiently protected from external physical and chemical stimuli, in particular, from the ingress of moisture.

As a method for preventing the invasion of moisture from the outside in a conventional conversion panel, a method of providing a protective layer covering a photostimulable layer surface on a support of the conversion panel has been adopted. This protective layer may be formed by directly applying a protective layer coating solution on the photostimulable layer, as described in, for example, JP-A-59-42500, or by forming a separately formed protective layer in advance. It is formed by a method of bonding on the exhausted layer.

As the protective layer, a thin protective layer (about 10 μm thick) made of an organic polymer is generally used.

However, thin protective layers of commonly used organic polymers are permeable to a certain amount of moisture and / or moisture, so that the stimulable layer absorbs moisture, resulting in reduced radiation sensitivity or radiation exposure of the conversion panel. The stored energy is greatly attenuated (fading) until irradiation with stimulating excitation light is performed later, resulting in variation and / or deterioration in the image quality of the obtained radiation image.

For example, the moisture permeability of the thickness of 10 [mu] m PET is about 60g / m ² · 24hr
And permeate as much as 60 g of water per unit area per day. It is 15 g / m ² · 24 hr for a 10 μm-thick stretched polypropylene.

In the conventional conversion panel having a thin protective layer as described above, the surface hardness of the protective layer is small, so that the protective layer surface is damaged by contact with a mechanical part such as a transport roller during transport, or A thin protective layer is insufficient in impact resistance, so that cracks and breaks are apt to occur in the stimulable layer, and the quality of the obtained radiation image deteriorates with repeated use.

Such a conversion panel is manufactured by sealing a peripheral portion of a laminate including a support, a photostimulable layer, and a protective layer in order to further improve moisture resistance. As a sealing method,
For example, a method in which only the periphery of the conversion panel is immersed in an organic polymer solution, or a method in which an organic polymer solution is applied to the periphery to form a polymer film and sealed, and the periphery is sealed with a sealant. A method of fixing the sealant from the outside with a fixing component (Japanese Patent Application Laid-Open No. 237099/1986), and a method of sealing with the peripheral portion covered with an extension of the protective layer (Japanese Patent Application Laid-Open No. 61-237100) Gazette).

Such a conventional conversion panel can sufficiently prevent the invasion of moisture from the outside when used in a normal atmosphere, but when used under severe temperature and humidity conditions or when exposed to moisture. When a weak phosphor is used, there is still a problem that the phosphor is deteriorated due to invasion of moisture from the outside.

Also, in the conversion panel sealed with the sealing material,
The problem that the phosphor deteriorates due to the moisture entering through the protective layer has not been solved.

(Problems to be Solved by the Invention) In the conventional conversion panel, the deterioration of the phosphor is caused by the invasion of moisture from the outside, and as a result, the sensitivity to radiation or the deterioration of the latent image is deteriorated. This problem is particularly noticeable when the conversion panel is used in a high-temperature, high-humidity atmosphere.

Therefore, an object of the present invention is to provide a conversion panel which prevents invasion of moisture from the outside, has excellent durability and durability, and has excellent sharpness.

[Constitution of the invention] (Means for solving the problems) The conversion panel of the present invention is a radiation image conversion panel having a stimulable phosphor layer between a support and a protective layer, Between the phosphor layer and the protective layer, a layer having a lower refractive index than the protective layer, surrounding the stimulable phosphor layer, the thickness of the stimulable phosphor layer and It has a first moisture-proof member of equal or greater thickness, and further has a second moisture-proof member surrounding the outer periphery of the first moisture-proof member.

Hereinafter, the configuration of the conversion panel of the present invention will be described with reference to the accompanying drawings. 1 and 3 are schematic sectional views showing an example of the conversion panel of the present invention, and FIG. 2 is a schematic plan view of the conversion panel shown in FIG. Omitted). In FIGS. 1 to 3,
1 is a protective layer, 2 is a photostimulable layer, 3 is a support, 4 is a first moistureproof member, 5 is a second moistureproof member, and 6 in FIG. 3 is a low refractive index layer.

The configuration of the conversion panel of the present invention will be described with reference to the accompanying drawings.

As shown in FIGS. 1 and 2, the conversion panel of the present invention has a photostimulable layer 2 and a protective layer 1 on a support 3 in this order. It includes a moisture-proof member 4 and a second moisture-proof member 5. The first moisture-proof member is provided on the periphery of the photostimulable layer 2, and one end of the first moisture-proof member 4 is in close contact with the support 3, and the other end is in close contact with the protective layer 1. . Also,
The peripheral portion of the photostimulable layer 2 and the first moisture-proof member 4 may be in contact with or apart from each other. The space around the periphery of the first moisture-proof member, that is, the space formed by the protective layer 1, the first moisture-proof member 4 and the support 3, is filled with the second moisture-proof member. The conversion panel of the present invention may have a low refractive index layer 6 between the protective layer 1 and the photostimulable layer 2 as shown in FIG. Those having the low refractive index layer 6 are preferable because the sharpness of an image is not deteriorated even when the thick protective layer 1 is used, and because the thick protective layer 1 is used, there is no decrease due to invasion of moisture through the protective layer 1. .

In the conversion panel of the present invention, as a material for forming the protective layer, a material which has good light transmission and can be formed into a sheet shape can be used. Further, the protective layer preferably has a high light transmittance in a wide wavelength range in order to efficiently transmit stimulated excitation light and stimulated emission, and more preferably has a transmittance of 80% or more.

Examples of such a material include plate glass such as quartz, borosilicate glass, and chemically strengthened glass, and organic polymer compounds such as PET, OPP, and polyvinyl chloride. Here, for example, borosilicate glass shows a light transmittance of 80% or more in a wavelength range of 330 nm to 2.6 μm, and quartz glass shows a high light transmittance even at a shorter wavelength.

As a material for forming the protective layer, a sheet glass is preferable because of its excellent light transmittance and moisture resistance.

The thickness of the protective layer is practically 10 μm to 3 mm, and is preferably 100 μm or more in order to obtain good moisture proofness. When the thickness of the protective layer is 200 μm or more, a conversion panel excellent in durability and durability can be obtained, which is preferable. The thickness of the protective layer is such that the moisture permeability of the protective layer is 10 g / m ² from the viewpoint of moisture resistance.
· 24 hr or less, more preferably made to be 5.0g / m ² · 24hr. The moisture permeability was measured by a cup method (JIS Z0208).

Further, it is preferable to provide an antireflection layer such as MgF _{2 on} the surface of the protective layer, because it has an effect of efficiently transmitting the stimulating excitation light and the stimulating light emission and reducing a decrease in sharpness.

The refractive index of the protective layer is not particularly limited, but is practically 1.4.
A range of ~ 20 is common.

Two or more protective layers can be provided as necessary.

The stimulable phosphor constituting the stimulable layer in the conversion panel of the present invention is, after being irradiated with the first light or high-energy radiation, optically, thermally, mechanically, chemically or electrically. It is a phosphor that shows stimulated emission corresponding to the dose of initial light or high-energy radiation when stimulated (stimulated excitation), but from a practical point of view, a phosphor that emits stimulated emission by excitation light of 500 nm or more. The body is the preferred one. As such a stimulable phosphor, for example, JP-A-48-8048
BaSo described in 7 No. _4: Ax, SrSo are described in JP _{48-80489 4: Ax, Li 2 B} 4 O 7 as described in JP-A-53-39277 : Cu, Ag, etc., JP-A-54-47883
Li ₂ O. (B ₂ O ₂ ) x: Cu and Li ₂ O.
_{(B 2 O 2) x:} Cu, Ag , etc., in US Patent 3,859,527 SrS: C
e, Sm, SrS: Eu, Sm, La ₂ O ₂ S: Eu, Sm and (Zn, Cd) S: Mn, X
And a phosphor represented by

Further, ZnS: C described in JP-A-55-12142
u, Pb phosphor general formula BaO · xAl ₂ O _3: barium aluminate phosphor represented by Eu, and the general formula, M ^II O · xSiO _2: alkaline earth metal silicate phosphor represented by A No. Also, alkaline earth fluoride halide phosphor represented by the general formula (Ba _1-xy Mg _x Ca _y ) FX: Eu ²⁺ described in JP-A-55-12143, A phosphor represented by LnOX: xA, a general formula described in JP-A-55-12145, and (Ba _1-x M ^II _x ) FX: yA A phosphor represented by the general formula described in JP-A-55-84389, a phosphor represented by BaFX: xCe, yA, a general formula described in JP-A-55-160078, M ^II Rare earth element activated divalent metal fluorohalide phosphor represented by FX · xA: yLn, general formula, ZnS: A, CdS: A, (Zn, Cd) S: A, ZnS: A, X
And a phosphor represented by CdS: A, X, any one of the following general formulas described in JP-A-59-38278: xM ₃ (PO ₄ ) ₂ .NX ₂ : yAM ₃ (PO ₄ ) _2: phosphor represented by yA, either general _{formula, nReX 3 · mAX 2 · xEu} nReX 3 · mAX 2: xEu, phosphor, and described in JP 61-72087 discloses represented by ySm the following general formula which ^{is, M I X · aM II X} 2 '· bM III X 3 ": alkali halide phosphor and JP represented by cA 61-22
The general formulas described in 8400 JP, M ^I X: xBi, bismuth inactivated alkali halide phosphor, etc., shown in the like. In particular, an alkali halide phosphor is preferable since a stimulable layer can be easily formed by a method such as vapor deposition or sputtering.

However, the stimulable phosphor used in the conversion panel of the present invention is not limited to the above-described phosphor, and is a phosphor that shows stimulable luminescence when irradiated with stimulating excitation light after being irradiated with radiation. Any fluorescent material may be used. Since the conversion panel of the present invention can prevent the invasion of moisture from the outside, it is possible to use, for example, an alkaline earth fluorohalide phosphor, an alkali halide phosphor or the like which is easily deteriorated by moisture as a phosphor.

The stimulable layer in the conversion panel of the present invention may be a stimulable layer group composed of one or more stimulable layers containing at least one kind of the stimulable phosphor described above. Further, the stimulable phosphor contained in each stimulable layer may be the same or different.

As a method for forming the photostimulable layer, a coating method described in JP-A-56-12600 can be applied, and a vapor deposition method such as vapor deposition can be applied.

The stimulable layer formed by the vapor deposition method has a higher packing density of the phosphor and higher radiation sensitivity than the stimulable layer formed by the coating method.

The thickness of the stimulable layer of the conversion panel varies depending on the intended sensitivity of the conversion panel to radiation, the type of stimulable phosphor, etc., but when the binder is not contained, the thickness is in the range of 10 to 1000 μm, and more preferably 30. It is preferably selected from the range of from 800 to 800 µm, and in the case of containing a binder, is preferably selected from the range of from 20 to 1000 µm, more preferably from the range of from 50 to 500 µm.

Examples of the support used in the present invention include various polymer materials, glass, ceramics, and metals.

Examples of the polymer material include films such as cellulose acetate, polyester, polyethylene terephthalate, polyamide, polyimide, triacetate, and polycarbonate. Examples of the metal include a metal sheet or metal plate of aluminum, iron, copper, chromium, or the like, and a metal sheet or metal plate having a coating layer of the metal oxide. Examples of the glass include chemically strengthened glass and crystallized glass. Examples of the ceramic include a sintered plate of alumina and zirconia.

Further, the layer thickness of these supports varies depending on the material of the support to be used and the like, but is generally 80 μm to 55 mm, and is preferably 200 μm to 3 μm from the viewpoint of easy handling.
mm. The thickness of the support is preferably that the moisture permeability in terms of moisture resistance is such a thickness equal to or less than 10g / m ² · 24hr, such as more becomes below 5.0g / m ² · 24hr Preferably, it is a thickness.

The surface of these supports may be a smooth surface or a mat surface for the purpose of improving the adhesion to the photostimulable layer.
The surface of the support may be an uneven surface, or may have a surface structure in which minute tile plates independent of each other are densely arranged.

Further, on these supports, an undercoat layer may be provided on the surface on which the stimulable layer is provided for the purpose of improving the adhesiveness with the stimulable layer, and if necessary, a light reflecting layer and a light absorbing layer may be provided. May be provided.

The greatest feature of the conversion panel of the present invention is that a first moisture-proof member and a second moisture-proof member are provided between the support and the protective layer. Here, the second moisture-proof member contributes to preventing intrusion of moisture from the outside atmosphere into the inside of the conversion panel, and the first moisture-proof member serves to remove a small amount of moisture passing through the second moisture-proof member. This contributes to preventing intrusion into the photostimulated layer side.

The first moisture-proof member and the second moisture-proof member are not particularly limited as long as they are moisture-proof, but the first moisture-proof member holds the protective layer and keeps the support and the protective layer at a constant interval, and simultaneously performs the second moisture-proof. The second moisture-proof member is intended to prevent the intrusion of the trace amount of moisture that has passed through the member into the photostimulated layer side, and the second moisture-proof member is intended to prevent the invasion of moisture from the external atmosphere. The moisture permeability of the first moisture-proof member is preferably lower than the moisture permeability of the second moisture-proof member.

Therefore, from such a difference in purpose, it is preferable that the moisture permeability of both moisture-proof members is defined as follows. That is, the first moisture-proof member has a moisture permeability of 10 kg / m ² · 24h
It is preferably one that is not more than r, and more preferably one that is not more than 5 kg / m ² · 24 hr. Further, the moisture permeability of the second moisture-proof member is preferably 20 kg / m ² · 24 hr or less, and 10 g / m 2
² · 24 hr or less of what is more preferred. Here, the moisture permeability was measured by a cup method (JIS Z0208). It is preferable that the moisture permeability of the contact portion between the moisture-proof member, the protective layer, and the support is approximately equal to or less than the moisture permeability of the moisture-proof member.

Further, the second moisture-proof member needs to be able to adhere to the support and the protective layer for the purpose.

As the first moisture-proof member, a member obtained by processing a sheet of, for example, glass, ceramics, metal, or a polymer material is preferably used.

Here, as a material using glass, chemically strengthened glass, crystallized glass, and the like can be given. As a material using ceramics, a sintered plate of alumina, zirconia or the like can be used. Examples of a material using a metal include a metal sheet or a metal plate of aluminum, iron, copper, chromium, or the like, or a metal sheet or a metal plate whose surface is coated with an oxide of the metal. Films using a polymer material include films of cellulose acetate, polyester, polyethylene terephthalate, polyamide, polyimide, triacetate, polycarbonate and the like.

Examples of the second moisture-proof member include those similar to the first moisture-proof member, but in addition, a two-component urethane-based adhesive, a two-component modified acrylate-based adhesive, and a two-component modified Acrylic adhesives, resins that cure by polycondensation or cross-linking reaction by mixing two components such as two-component epoxy adhesives, X-rays, α-rays, β-rays, γ-rays, high-energy neutrons, Radiation-curable resins that irradiate electromagnetic waves or particle beams such as electron beams or ultraviolet rays and absorb the energy of the electromagnetic waves or particle beams and cure.

When a sheet-shaped member is used, the first moisture-proof member is processed so as to have a shape as shown in FIG. 5, and then disposed so as to surround the photostimulable layer. FIG. 5 is a diagram showing an example of a processed shape of the first moisture-proof member. FIG. 5 (a) is hollowed out in a circumferential shape and has particularly excellent moisture proofness because there is no seam. FIG. 5 (b) is a combination of two L-shaped moisture proof members, and FIG. Is a combination of four bar-shaped sheets. When the first moisture-proof member is brought into close contact with the support or the protective layer, the adhesive used as the second moisture-proof member can be preferably used. If the second moisture-proof member has a high moisture-proof property and the moisture permeability is 5.0 g / m ² · 24 hr or less, the first moisture-proof member may be substantially only for the purpose of holding the protective layer. . In this case, the first moisture-proof member does not need to be in close contact with the support and the protective layer.

When a sheet-shaped member is used as the second moisture-proof member, it is necessary to adhere the sheet-like member to the support and the protective layer, and the adhesive used for this purpose is used as the second moisture-proof member. An adhesive can be used.

The thickness of each of the first and second moisture-proof members is not particularly limited as long as the thickness is equal to or greater than the thickness of the photostimulable layer.

It is preferable that the width of the first and second moisture-proof members is wider because the moisture-proof property is higher, but practically it is 1 to 30 mm, preferably 2 to 10 mm. If the width is too small, not only does the moisture-proof property deteriorate, but also the moisture-proof property may be significantly reduced due to defects such as pinholes. If the width is too large, the effective use area of the conversion panel decreases, which is not preferable.

In the conversion panel of the present invention, a low refractive index layer is further provided between the stimulating layer and the protective layer as shown in FIG.

The low-refractive-index layer is made of a material having a lower refractive index than the protective layer, and the presence of this layer makes it possible to reduce a decrease in sharpness even when the protective layer is thickened. What constitutes a low refractive index layer is not particularly limited as long as it has a lower refractive index than the protective layer.

When the low refractive index layer is provided as described above, the first
And whether the thickness of the second moisture-proof member is the same as the thickness of the photostimulable layer,
It is necessary to make it thicker. First and second
Even if the thickness of the moisture-proof member is the same as the thickness of the photostimulable layer, a low refractive index layer must be interposed between the protective layer and the photostimulable layer unless the photostimulable layer and the protective layer are brought into close contact with an adhesive or the like. Can be provided.

This low refractive index layer is made of, for example, CaF ₂ (refractive index 1.23 to 1.2
6), Na ₃ AlF ₆ (refractive index 1.35), MaF ₂ (refractive index 1.38), Si
Layer composed of O ₂ (refractive index 1.46), etc .; ethanol (refractive index)
1.36), a layer composed of a liquid such as methanol (refractive index 1.33) and diethyl ether (refractive index 1.35); or a layer composed of a gas such as air, nitrogen, argon or the like and a vacuum layer having a refractive index of substantially 1. A certain layer;

As the low refractive index layer of the conversion panel, a gas layer or a vacuum layer is preferable because it has a high effect of preventing sharpness from lowering.

The thickness of the low refractive index layer is practically from 0.5 μm to 3 mm.

In the conversion panel of the present invention, it is preferable that the low refractive index layer be in close contact with the stimulable layer in order to sufficiently impart the effect of reducing sharpness reduction to the low refractive index layer. Therefore, when the low refractive index layer is a liquid layer, a gas layer and a vacuum layer, it may be left as it is,
When the protective layer is made of CaF ₂ , Na ₃ AlF ₆ , MaF ₂ , SiO ₂ or the like on the surface of the protective layer, the stimulable layer and the low refractive index layer are brought into close contact with each other by, for example, an adhesive. In this case, the refractive index of the adhesive is preferably close to the refractive index of the photostimulable layer.

In the conversion panel of the present invention, the protective layer can also function as a support. In that case, the support referred to in the present invention may not substantially exhibit the function of supporting the photostimulable layer.

Next, a method for manufacturing a conversion panel according to the present invention will be described with reference to an example.

First, after forming a photostimulable layer on a support by a vapor deposition method such as a vapor deposition method, a first moisture-proof member is adhered to the support so as to surround the photostimulable layer as shown in FIG. Adhere with the agent. Next, the other end of the first moisture-proof member (the portion opposite to the adhesive portion of the support) is similarly adhered to the protective layer. Thereafter, the conversion panel is obtained by filling the second moisture-proof member as shown in FIG.

As another manufacturing method, after the first moisture-proof member is brought into close contact with the support (or the protective layer) with an adhesive, a second moisture-proof member is provided outside the first moisture-proof member, and the protective layer ( Alternatively, a method of covering and adhering with a support is also applicable.

The conversion panel of the present invention is used in a radiation image conversion method schematically shown in FIG.

That is, the radiation from the radiation generator 41
The light enters the conversion panel 43 through 42.

This incident radiation is absorbed by the photostimulable layer of panel 43,
The energy is accumulated, and an accumulation image of the radiation transmission image is formed.

Next, the accumulated image is excited by the stimulating light from the stimulating light source 44, and the intensity of the stimulating light is proportional to the amount of accumulated radiation energy. By performing the photoelectric conversion by the conversion device 45, reproducing the image by the image reproduction device 46, and displaying the image by the image display device 47, the radiation transmission image of the subject can be observed.

(Examples) Next, the present invention will be described with reference to examples.

Examples 1 to 6 An alkali halide phosphor (RbBr; 0.0006 Tl) was vapor-deposited on a crystallized glass support having a thickness of 500 μm by a vapor deposition apparatus to a thickness of 300 μm to form a photostimulable layer. Then
As shown in FIGS. 1 and 2, a first moisture-proof member shown in Table 1 and having the same thickness as the photostimulable layer was bonded with an epoxy resin adhesive. Thereafter, the protective layer was similarly adhered to the first moisture-proof member. Next, FIG. 1 and FIG.
As shown in the figure, the conversion panel of the present invention was obtained by filling the second moisture proof member shown in Table 1.

Next, the conversion panel was evaluated for its moisture-proof property and sharpness. Table 1 shows the results of the moisture resistance.

The moisture resistance was evaluated from the rate of decrease in sensitivity and the rate of decrease in fading after the conversion panel was left for 80 days under conditions of 40 ° C. and 97% relative humidity for forced deterioration. The test method is as follows.

Sensitivity reduction rate P After irradiating the conversion panel before the forced deterioration test with 10 mR of X-rays at a tube voltage of 80 kVp, the semiconductor laser light (780 nm, 2
0 nW), and stimulated emission was photoelectrically converted by a photomultiplier tube, and the sensitivity S _{st (5 sec)} of the conversion panel before the deterioration test was _determined from the magnitude of the obtained electric signal. Similarly, the conversion panel sensitivity _{S80 (5 sec)} after the deterioration test was determined.

From each of the obtained sensitivities, the following equation: To determine the sensitivity reduction rate.

Fading drop rate Q Fading of conversion panel before forced deterioration test: F
_ST (decay rate of stored energy from irradiation of X-ray to reading of signal with laser light) was determined by the following method. First, after irradiating X-rays with a tube voltage of 80 kVp for 10 mR, stimulated with semiconductor laser light (780 nm, 20 mW) for 5 seconds, and stimulated photostimulation with a photomultiplier tube. The sensitivity S _{st (5 sec)} was obtained from the magnitude. Similarly, the sensitivity S _{st (120 sec)} was obtained from the magnitude of the electric signal obtained by stimulating excitation for 120 seconds after X-ray irradiation. From each of the obtained sensitivities, the following equation: From the result, the fading F _St before the deterioration test was obtained.

Following equation fading F ₈₀ of the conversion panel after forced degradation test in the same manner; Determined by

From the obtained _FST and _F80 , the following equation is obtained: To determine the fading reduction rate.

Sharpness Sharpness was evaluated by obtaining a modulation transfer function (MTF) of the conversion panel before the forced deterioration test.

Example 7 A conversion panel was obtained in the same manner as in Example 1 except that the stimulable layer was formed by the following method.

The method for forming the photostimulable layer is as follows. First, 8 parts by weight of a BaFBr: Eu phosphor having an average particle diameter of 2 μm and 1 part by weight of polyvinyl butyral (binder) were mixed and dispersed using a solvent (cyclohexanone) to obtain a coating solution. Next, this coating solution was uniformly applied on the same support as in Example 1 placed horizontally, and left standing all day long to form a photostimulable layer.

The same test as in Examples 1 to 6 was performed on the obtained conversion panel. The results are shown in Table 1.

Example 8 A conversion panel was obtained in the same manner as in Example 2, except that the thickness of the first moisture-proof member was larger than the thickness of the photostimulable layer as shown in Table 1 Table 1. Examples 1 to 3 of this conversion panel
The same test as in No. 6 was performed. The results are shown in Table 1.

Example 9 A conversion panel was obtained in the same manner as in Example 6, except that the thickness of the first moisture-proof member was larger than the thickness of the stimulable layer as shown in Table 1. The same test as in Examples 1 to 6 was performed on this conversion panel. The results are shown in Table 1.

Comparative Examples 1 and 2 Conversion panels were obtained in the same manner as in Examples 1 and 6, except that only the second moisture-proof member was used as the moisture-proof member. The same test as in Examples 1 to 6 was performed on this conversion panel. The results are shown in Table 1.

Comparative Example 3 The same except that a stimulable layer was formed by a coating method using BaFBr: Eu as a phosphor, a 10 μm-thick polyethylene terephthalate was further used as a protective layer, and the first and second moisture-proof members were not used. To obtain a conversion panel. The same test as in Examples 1 to 6 was performed on this conversion panel.
The results are shown in Table 1.

Comparative Example 4 A conversion panel was obtained in the same manner as in Example 1 except that the protective layer and the photostimulable layer were bonded using a polyurethane adhesive. The same test as in Examples 1 to 6 was performed on this conversion panel. The results are shown in Table 1.

As can be seen from Table 1, the conversion panels of Examples 1 to 9 of the present invention showed little initial characteristic deterioration and were excellent in durability even when kept under high temperature and high humidity for a long period of time. On the other hand, in the conversion panels of Comparative Examples 1 to 3, the phosphor deteriorated due to the intrusion of moisture, and the initial characteristics of the conversion panel were significantly deteriorated. Comparative Example 4
In the conversion panel, the photostimulable layer and the protective layer were adhered with an adhesive, so that the sharpness of the image was reduced due to the use of the thick protective layer. In the conversion panels of Examples 1 to 6, although the photostimulable layer and the protective layer were in contact with each other, the sharpness was not reduced because an optically discontinuous surface was present.

[Effect of the Invention] The image conversion panel of the present invention has excellent moisture-proof properties and sharpness, and maintains its initial performance even when used in a high-temperature, high-humidity atmosphere for a long period of time. It shows durability and durability.

[Brief description of the drawings]

1 and 3 are schematic sectional views of the conversion panel of the present invention, FIG. 2 is a schematic plan view of the conversion panel shown in FIG. 1, and FIG. 4 is a radiation image using the conversion panel. FIG. 5 is a diagram illustrating a conversion method, and FIG. 5 is a diagram illustrating an example of a processed shape of a first moisture-proof member.

Claims (1)

(57) [Claims] 1. A radiation image conversion panel having a stimulable phosphor layer between a support and a protective layer, wherein the stimulable phosphor layer is disposed between the support and the protective layer. Having a layer having a low refractive index, surrounding the stimulable phosphor layer, having a first moisture-proof member having a thickness equal to or greater than the thickness of the stimulable phosphor layer, A radiation image conversion panel, further comprising a second moisture-proof member surrounding the outer periphery of the first moisture-proof member.