JP2002350596A - Radiation image conversion panel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the relation between the picture quality and sensitivity of a radiation image conversion panel using stimulable phosphors and specifically obtain a radiation image conversion panel that is excellent in the balance between luminance and sharpness. SOLUTION: The radiation image conversion panel which is formed by laminating a stimulable phosphor layer, a low-refractivity layer and a protective layer on a support in order of mention is characterized in that the stimulable phosphor layer is formed by a vapor growth method at least, the protective layer contains a color material which absorbs the excitation light exciting the stimulable phosphor layer and the transmissivity of the excitation light in the protective layer is between 60% and 95% inclusive.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiation image conversion panel using a stimulable phosphor, and more particularly to a radiation image conversion panel having improved brightness and sharpness.

[0002]

2. Description of the Related Art In recent years, a method of imaging a radiation image by a radiation image conversion panel using a stimulable phosphor has been used.

This is disclosed, for example, in US Pat. No. 3,859,52.
No. 7, JP-A-55-12144, and the like, a radiation image conversion panel having a stimulable phosphor layer formed on a support is used. The radiation transmitted through the subject is applied to the stimulable phosphor layer of the radiation image conversion panel, and radiation energy corresponding to the radiation transmittance of each part of the subject is accumulated in the stimulable phosphor layer to form a latent image (accumulated image). The stimulable phosphor layer is formed, and the stimulable phosphor layer is irradiated with stimulating light (laser light is used).
By scanning with, the radiation energy accumulated in each part is emitted and converted into light, and the intensity of the light is read to obtain an image. This image may be reproduced on various displays such as a CRT, or may be reproduced as a hard copy.

[0004] The stimulable phosphor layer of the radiation image conversion panel used in this radiation image conversion method must have a high radiation absorption rate and a high light conversion rate, good image graininess and high sharpness. Required.

In general, it is necessary to increase the thickness of the stimulable phosphor layer in order to increase the radiation sensitivity. However, if the thickness is too large, scattering of the stimulable luminescence between the stimulable phosphor particles may be caused. Therefore, there is a phenomenon that light emission does not come out to the outside, and there is a limit.

The sharpness is improved as the stimulable phosphor layer is made thinner. However, if it is too thin, the phenomenon of sensitivity increases.

Regarding the graininess, the graininess of the image is determined by the spatial fluctuation of the radiation quantum number (quantum mottle) or the structural disorder of the stimulable phosphor layer of the radiation image conversion panel (structural mottle).
When the thickness of the stimulable phosphor layer is reduced, the radiation quantum number absorbed by the stimulable phosphor layer decreases, the mottle increases, and structural disorder becomes apparent. For example, the mottle increases and the image quality deteriorates. Therefore, in order to improve the granularity of an image, the stimulable phosphor layer needs to be thick.

As described above, the image quality and sensitivity of the radiation image conversion method using the radiation image conversion panel are determined from various factors. Various studies have been made to improve sensitivity and image quality by adjusting a plurality of factors relating to the sensitivity and image quality.

As means for improving the sharpness of the internal radiographic image, for example, attempts have been made to control the shape of the stimulable phosphor to be formed to improve the sensitivity and sharpness.

As one of these attempts, for example, a fine stimulable phosphor formed by depositing a stimulable phosphor on a support having a fine concavo-convex pattern as disclosed in Japanese Patent Application Laid-Open No. Sho 61-142497. There is a method using a stimulable phosphor layer composed of pseudo columnar blocks.

Further, as described in JP-A-61-142500, cracks between columnar blocks obtained by depositing a stimulable phosphor on a support having a fine pattern are subjected to a shock treatment, and A method using a radiation image conversion panel having a developed stimulable phosphor layer,
JP-A-39737 describes a method of using a radiation image conversion panel in which a stimulable phosphor layer formed on the surface of a support is cracked from the surface side thereof and has a pseudo columnar shape, As described in JP-A-62-110200, there has been proposed a method of forming a stimulable phosphor layer having a cavity on the upper surface of a support by vapor deposition, and then growing the cavity by heat treatment to form a crack.

[0012] Also, in JP-A-2-58000,
There has been proposed a radiation image conversion panel having a stimulable phosphor layer in which elongated columnar crystals having a certain inclination with respect to the normal direction of the support are formed on the support by a vapor deposition method.

In any of these attempts to control the shape of the stimulable phosphor layer, the stimulable phosphor layer is formed in a columnar shape so that the stimulable excitation light (or the stimulable luminescence) is emitted in the lateral direction. Diffusion can be suppressed (it reaches the surface of the support while repeating reflection at the crack (columnar crystal) interface), so that sharpness of an image due to stimulated emission can be significantly increased.

However, these vapor phase growths (deposition)
Also in the radiation image conversion panel having the stimulable phosphor layer formed by the method described above, the relationship between the sensitivity and the sharpness cannot be said to have sufficient characteristics, and further improvement is required.

An attempt to further improve the image quality, particularly sharpness, of a radiation image conversion panel having a stimulable phosphor layer formed by the vapor phase growth (deposition) method has been made in JP-A-1-131498. Have been done. This is to suppress the reflection and refraction at the layer interface in the radiation image conversion panel and further improve the image quality by combining a phosphor layer composed of the pseudo columnar stimulable phosphor crystal and a low refractive index layer. .

However, by combining the low refractive index layer, reflection between the low refractive index layer and the protective layer is certainly reduced, and although there is a certain improvement effect on the improvement of sharpness such as image quality, the effect is limited. There are drawbacks.

[0017]

An object of the present invention is to improve the relationship between the image quality and the sensitivity of a radiation image conversion panel using a stimulable phosphor, and more particularly, to a radiation image having an excellent balance between brightness and sharpness. The object is to obtain an image conversion panel.

[0018]

The above object of the present invention is achieved by the following means.

1. In a radiation image conversion panel having a stimulable phosphor layer, a low refractive index layer, and a protective layer laminated in this order on a support, the stimulable phosphor layer is formed at least by a vapor phase growth method, and the protective layer A radiation image conversion panel comprising a coloring material that absorbs excitation light that excites the stimulable phosphor layer, and the protective layer has an excitation light transmittance of 60% or more and 95% or less.

2. 2. The radiation image conversion panel according to the above item 1, wherein the stimulable phosphor layer formed by the vapor phase growth method is composed of columnar crystals.

3. 3. The radiation image conversion panel according to the item 2, wherein the stimulable phosphor layer formed by the vapor phase growth method is composed of CsBr columnar crystals.

4. 4. The radiation image conversion panel according to any one of the above items 1 to 3, wherein the protective layer is a glass on which a colored film is laminated.

5. 4. The radiation image conversion panel according to any one of the above items 1 to 3, wherein the protective layer is a glass in which a colored layer is provided on one of the surfaces by coating.

6. The radiation image conversion panel according to any one of the above items 1 to 3, wherein the protective layer is a colored glass.

Hereinafter, the present invention will be described in detail. The present invention
Forming at least one stimulable phosphor layer composed of independent elongated columnar crystals having a certain inclination with respect to the normal direction of the support on the support by a vapor phase growth (deposition) method In this radiation image conversion panel, the stimulable phosphor layer is formed by laminating a support, a stimulable phosphor layer, a low refractive index layer, and a protective layer in this order, and the stimulable phosphor layer is formed on the protective layer. A dye that absorbs the excitation light for exciting the light in an amount such that the excitation light transmittance of the protective layer is 60% or more and 95% or less. It has been found that sharpness can be greatly improved and sensitivity (luminance of stimulated emission) can be significantly improved as compared with a radiation image conversion panel comprising a layer and a protective layer.

As described in JP-A-1-131498, a low-refractive-index layer is provided between a stimulable phosphor layer composed of a columnar crystal and a protective layer and is mainly combined with a stimulable phosphor layer. It is known that reflection at the interface between the substrate and the protective layer can be suppressed and the image quality of the radiation image conversion panel can be improved. However, by combining the low-refractive-index layer with a stimulable phosphor layer composed of columnar crystals, the reflection at the interface between the protective layer and the low-refractive-index layer is suppressed, and the diffusion of light in the plane direction is reduced. Can be improved,
On the other hand, regarding the reflection between the low refractive index layer and the stimulable phosphor layer due to the provision of the low refractive index layer, secondary light scattering occurs, and the reflected light travels a relatively long distance in the low refractive index layer. It is thought to be due to diffusion, but it was found that this caused a problem of deterioration in sharpness.

The present inventors can suppress this effect by including a coloring material (pigment or dye) that absorbs stimulating excitation light in the protective layer, and further enhance the effect of providing the low refractive index layer. I found something that could be improved. That is, by including a coloring material (pigment or dye) in the protective layer, reflection of stimulating excitation light at the interface between the low refractive index layer and the stimulable phosphor layer can be suppressed, and the low refractive index layer can be suppressed. The deterioration of the image quality due to light scattering in a relatively long range between the stimulable phosphor layers was able to be suppressed. In order to efficiently suppress the reflection of stimulating excitation light at the interface between the protective layer and the low refractive index layer, the concentration of the pigment (although it may be a dye) contained in the protective layer depends on the concentration of the stimulating excitation light of the protective layer. 6 light transmittance at wavelength
It must be 0% or more and 95% or less.

Before assembling the radiation image conversion panel, the transmittance of the protective layer alone can be measured using a usual spectrophotometer.

The balance between luminance and sharpness can be improved by allocating the improved image quality, particularly the sharpness, to the increase in the thickness of the phosphor layer according to the present invention.

As the stimulable phosphor, among the alkali halide stimulable phosphor columnar crystals formed by vapor phase growth (deposition) such as vapor deposition, RbBr and CsB are particularly preferable.
It has been found that the r-based phosphor has high luminance and high image quality and has a high effect of being combined with the above-mentioned absorption layer. Among them, CsBr-based phosphors have particularly high luminance and high image quality, and have a high effect of being combined with the above-mentioned absorption layer.

In the above-mentioned JP-A-1-131498,
A form in which a substance or a coloring agent having a high reflectivity or a high absorptivity is filled in the voids formed between the columnar crystals of a stimulable phosphor layer formed of columnar crystals formed on a support by a vapor phase growth (deposition) method. Although it is disclosed that it further has the effect of preventing light diffusion in the lateral direction in the stimulable phosphor layer,
As in the present invention, the effect of improving the image quality focusing on the reflection at the interface between the stimulable phosphor layer composed of the columnar crystal and each constituent layer has not been known so far.

In the present invention, an independent columnar crystal, that is, a crystal which grows in a columnar shape with a certain gap between each crystal, can be obtained by the method described in JP-A-2-58000.

That is, a photostimulable phosphor composed of independent elongated columnar crystals is provided by a method of supplying a vapor of the stimulable phosphor or the raw material at a specific incident angle onto a support and vapor-phase growing (depositing) such as vapor deposition. A phosphor layer can be obtained. It is known that the columnar crystal grows at a growth angle of about half the incident angle of the vapor flow of the stimulable phosphor during vapor deposition.

The method of supplying the vapor flow of the stimulable phosphor at a certain incident angle with respect to the surface of the support may be such that the support is arranged to be inclined with respect to the crucible charged with the evaporation source, or The crucible and the crucible are placed in parallel with each other, and only the oblique component is vapor-deposited on the support by a slit or the like from the evaporation surface of the crucible charged with the evaporation source.

In these cases, it is appropriate that the distance between the shortest part of the support and the crucible is approximately 10 cm to 60 cm in accordance with the average range of the stimulable phosphor. Incidentally, the thickness of the columnar crystals tends to become thinner as the temperature of the support becomes lower.

The stimulable phosphor serving as an evaporation source is charged into a crucible after being uniformly dissolved or formed by pressing or hot pressing. At this time, it is preferable to perform a degassing treatment. The method of evaporating the stimulable phosphor from the evaporation source is performed by scanning with an electron beam emitted from an electron gun, but may be performed by other methods.

The evaporation source does not necessarily need to be a stimulable phosphor, and may be a mixture of a stimulable phosphor material.

The activator is a base (basic sub).
activator to the stance
May be deposited, or only the base may be deposited and then an activator may be doped. For example, after depositing only RbBr as a base, for example, Tl as an activator may be doped. That is, since the crystals are independent, the doping can be sufficiently performed even if the film is thick, and the MTF does not decrease because crystal growth hardly occurs.

The doping can be performed by thermally diffusing a doping agent (activator) into the formed base layer of the phosphor and by ion implantation.

In order to improve the modulation transfer function (MTF) in the stimulable phosphor layer composed of these columnar crystals,
The size of the columnar crystal (the average value of the circle-converted diameter of the cross-sectional area of each columnar crystal when the columnar crystal is observed from a plane parallel to the support, and a microscope including at least 100 or more columnar crystals in the field of view. (Calculated from the photograph) is preferably about 1 to 50 μm, and more preferably 1 to 30 μm. That is,
When the columnar crystal is thinner than 1 μm, the MTF decreases because the stimulating excitation light is scattered by the columnar crystal, and when the columnar crystal is 50 μm or more, the directivity of the stimulating excitation light decreases,
MTF decreases.

The size of the gap between the columnar crystals is 30 μm.
The thickness is preferably 5 μm or less, more preferably 5 μm or less. That is,
If the gap exceeds 30 μm, the filling rate of the phosphor in the phosphor layer is reduced, and the sensitivity is reduced.

The growth angle of the oblique columnar crystal of the stimulable phosphor is not particularly limited as long as it is larger than 0 ° and smaller than 90 °, but it is preferably 10 to 70 °, preferably 20 to 55.
°. To make the growth angle 10 to 70 °, the incident angle should be 20 to 80 °, and to make it 20 to 55 °, the incident angle should be 40 to 70 °. If the growth angle is large, the columnar crystals will fall too much with respect to the support, and the film will become brittle.

As a method for vapor-phase growing (depositing) the stimulable phosphor, there are a vapor deposition method, a sputtering method and a CVD method.

In the vapor deposition method, after the support is placed in a vapor deposition apparatus, the interior of the apparatus is evacuated to a vacuum of about 1.333 × 10 ⁻⁴ Pa, and then at least one of the stimulable phosphors is heated by resistance. The stimulable phosphor is obliquely deposited to a desired thickness on the surface of the support by heating and evaporating it by a method such as an electron beam method or an electron beam method. As a result, a stimulable phosphor layer containing no binder is formed, but the stimulable phosphor layer may be formed in a plurality of times in the vapor deposition step. Further, in the vapor deposition step, vapor deposition can be performed using a plurality of resistance heaters or electron beams. In the vapor deposition method, a stimulable phosphor material is vapor-deposited using a plurality of resistance heaters or electron beams to synthesize a desired stimulable phosphor on a support and simultaneously form a stimulable phosphor layer. It is also possible to form. Further, in the vapor deposition method, an object to be deposited may be cooled or heated as needed during the vapor deposition. After the deposition, the stimulable phosphor layer may be subjected to a heat treatment.

In the sputtering method, a support is placed in a sputtering apparatus in the same manner as in the vapor deposition method, and the inside of the apparatus is once evacuated to a degree of vacuum of about 1.333 × 10 ⁻⁴ Pa, and then used as a gas for sputtering. An inert gas such as Ar or Ne is introduced into the apparatus to have a gas pressure of about 1.333 × 10 ^-1 Pa. Next, using the stimulable phosphor as a target, the stimulable phosphor is obliquely deposited on the surface of the support to a desired thickness by sputtering obliquely. In this sputtering step, the stimulable phosphor layer can be formed in a plurality of times in the same manner as the vapor deposition method, or the stimulable phosphor layer can be formed by sputtering the target simultaneously or sequentially using each of them. It is also possible to form In the sputtering method, a plurality of stimulable phosphor materials can be used as a target, and these can be simultaneously or sequentially sputtered to form a desired stimulable phosphor layer on a support. If necessary, reactive sputtering may be performed by introducing a gas such as O ₂ or H ₂ . Further, in the sputtering method, the object to be deposited may be cooled or heated as required during the sputtering. Further, the stimulable phosphor layer may be subjected to a heat treatment after the end of the sputtering.

In the CVD method, an organic metal compound containing a target stimulable phosphor or a stimulable phosphor material is decomposed by heat, high-frequency power, or other energy, so that a binder is contained on a support. It is possible to obtain a stimulable phosphor layer that does not have any specific stimulable phosphor layer, and to vapor-grow the stimulable phosphor layer into independent elongated columnar crystals with a specific inclination with respect to the normal direction of the support. .

The thickness of the stimulable phosphor layer formed by these methods varies depending on the sensitivity of the intended radiation image conversion panel to radiation, the type of stimulable phosphor, etc.
It is preferably selected from the range of 0 μm to 1000 μm, and more preferably selected from the range of 20 μm to 800 μm.

As the stimulable phosphor used in the radiation image conversion panel of the present invention, for example, JP-A-48-8048
A phosphor represented by BaSO ₄ : Ax described in JP-A No. 7; MgSO ₄ : Ax described in JP-A-48-80488;
A phosphor represented by SrSO ₄ : Ax described in JP-A-48-80489;
Na ₂ SO ₄ as described in JP 1-29889, CaS
A phosphor obtained by adding at least one of Mn, Dy and Tb to O ₄ and BaSO _4, etc .; BeO, LiF, MgSO ₄ and CaF ₂ described in JP-A-52-30487.
And phosphors such as Li ₂ B ₄ O ₇ : Cu and Ag described in JP-A-53-39277.
Li ₂ O. (Be ₂ O ₂ ) described in No. 47883
x: phosphor such as Cu, Ag, U.S. Pat. No. 3,859,5
SrS: Ce, Sm, SrS described in No. 27:
Eu, Sm, La ₂ O ₂ S: Eu, Sm and (Zn, C
d) S: Phosphor represented by Mnx. Also, ZnS: C described in JP-A-55-12142.
u, Pb phosphor general formula BaO · xAl ₂ O _3: barium aluminate phosphor cited by Eu, and the general formula _{M (II) O · xSiO 2} : alkaline earth metal silicate represented by A Salt-based phosphors;

An alkaline earth fluorohalide phosphor represented by the general formula (Ba _{1 -xy} Mg _x C a _y ) F _x : Eu ²⁺ described in JP-A-55-12143, The general formula described in JP-A-55-12144 is LnO
X: a phosphor represented by xA, and the general formula described in JP-A-55-12145 is represented by (Ba _1-x M (II) _x ) F _x :
The phosphor represented by yA, the general formula described in JP-A-55-84389, and the phosphor represented by BaFX: xCe, yA, the general formula described in JP-A-55-160078. M (II) FX · xA: a rare earth element-activated divalent metal fluorohalide phosphor represented by yLn, a general formula Z
a phosphor represented by nS: A, CdS: A, (Zn, Cd) S: A, X, and any one of the following general formulas xM ₃ (PO ₄ ) ₂ described in JP-A-59-38278. _{· NX 2: yA xM 3 (} PO 4) 2: phosphor represented by yA, following one of the general formulas described in _{JP-a-59-155487 nReX 3 · mAX '2:} xEu nReX 3 · MAX _'2: xEu, phosphor represented by the following general formula M (I) X · aM that is described in JP-a-61-72087 (II) X represented by _{ySm' 2 · bM (III)} X "3 : C
A. The alkali halide phosphor represented by A.
General formula M (I) X described in No. 228400: x
Bismuth-activated alkali halide phosphors represented by Bi and the like can be mentioned.

In particular, the alkali halide phosphor is deposited,
It is preferable because a columnar stimulable phosphor layer can be formed by a method such as sputtering.

As described above, among the alkali halide phosphors, RbBr and CsBr-based phosphors are preferred in terms of high luminance and high image quality, and among them, CsBr-based phosphors are particularly preferred.

However, the stimulable phosphor used in the radiation image conversion panel of the present invention is not limited to the above-described phosphor, and the stimulable phosphor is irradiated with a radiation and then irradiated with a stimulating excitation light. Any phosphor that emits light may be used.

FIG. 1 is a sectional view of a stimulable phosphor layer composed of columnar crystals formed on a support in this manner. Reference numeral 11 denotes a support, 12 denotes a stimulable phosphor layer, and 13 denotes a columnar crystal constituting the stimulable phosphor layer. Incidentally, reference numeral 14 denotes a gap formed between the columnar crystals.

FIG. 2 is a view showing a state in which a stimulable phosphor layer is formed on a support by vapor deposition. The incidence of the stimulable phosphor vapor flow V in the normal direction (P) of the support surface is shown. Assuming that the angle is θ ₂ (incident at 60 ° in the figure), the angle of the columnar crystal to be formed with respect to the normal direction (P) of the support surface is θ ₁ (about 30 ° in the figure, empirically approximately Halves)
And a columnar crystal is formed at this angle.

Since the stimulable phosphor layer formed on the support in this manner does not contain a binder, the stimulable phosphor layer has excellent directivity, and the directivity of stimulable excitation light and stimulable light emission is improved. The thickness is higher than that of a radiation image conversion panel having a dispersion type stimulable phosphor layer in which a stimulable phosphor is dispersed in a binder. Further, the sharpness of the image is improved by reducing the scattering of the stimulating light in the stimulable phosphor layer.

The gap between the columnar crystals may be filled with a filler such as a binder to reinforce the stimulable phosphor layer. Further, a substance having a high light absorption rate, a substance having a high light reflectance, or the like may be filled.
Thereby, in addition to having the reinforcing effect, it is possible to almost completely prevent the stimulable excitation light incident on the stimulable phosphor layer from being diffused in the lateral direction.

The substance having a high light reflectance is defined as stimulating excitation light (50
A material having a high reflectance with respect to 0 to 900 nm (particularly, 600 to 800 nm). For example, a white pigment and a coloring material in a green to red region such as aluminum, magnesium, silver, indium and other metals can be used.

The white pigment can also reflect stimulated emission.
You. TiO as a white pigment_Two(Anatase type, rutile
Type), MgO, PbCO_Three・ Pb (OH)_Two, BaS
O_Four, Al_TwoO_Three, M (II) FX (where M (II) is B
a is at least one of a, Sr and Ca, and X is C
1 and at least one of Br. ), Ca
CO _Three, ZnO, Sb_TwoO_Three, SiO_Two, ZrO_Two, Litopo
(BaSO_Four・ ZnS), magnesium silicate, basic
Examples include lead silicate sulfate, basic lead phosphate, and aluminum silicate.
Can be These white pigments have strong hiding power and high refractive index.
Irritating by reflecting or refracting light
The luminescence is easily scattered and the feeling of the radiation image conversion panel obtained
The degree can be significantly improved.

As the substance having a high light absorption rate, for example, carbon, chromium oxide, nickel oxide, iron oxide and the like and a blue coloring material are used. Of these, carbon also absorbs stimulated emission.

The coloring material may be an organic or inorganic coloring material. Examples of organic color materials include Pomelo Fast Blue 3G (manufactured by Hoechst), Estrol Brill Blue N-3RL (manufactured by Sumitomo Chemical), and D & C Blue No. 1
(Made by National Aniline), Spirit Blue (made by Hodogaya Chemical), Oil Blue No. 603 (manufactured by Orient), Kiton Blue A (manufactured by Ciba Geigy), Aizen Chillon Blue GLH (manufactured by Hodogaya Chemical), Lake Blue AFH (manufactured by Kyowa Sangyo), 6MX Primocyanin (manufactured by Inabata Sangyo), Brill Acid Green 6BH (manufactured by Hodogaya) Chemical Blue), Cyan Blue BNRCS (manufactured by Toyo Ink), Lionoyl Blue SL (manufactured by Toyo Ink) and the like are used.
Also, the color index No. 24411, 23160,
74180, 74200, 22800, 23154, 2
3155, 24401, 14830, 15050, 15
760, 15707, 17941, 74220, 134
25, 13361, 13420, 11836, 7414
And organic metal complex salt coloring materials such as 0, 74380, 74350, and 74460. Ultramarine, cobalt blue, cerulean blue, chromium oxide, TiO
Examples include _2- ZnO-Co-NiO-based pigments.

As the support used in the radiation image storage panel of the present invention, various types of glass, polymer materials, metals and the like are used. For example, plate glass such as quartz, borosilicate glass, chemically strengthened glass, cellulose, etc. A plastic film such as an acetate film, a polyester film, a polyethylene terephthalate film, a polyamide film, a polyimide film, a triacetate film, a polycarbonate film, a metal sheet such as an aluminum sheet, an iron sheet, a copper sheet, or a metal sheet having a coating layer of the metal oxide. Is preferred. The surface of the support may be a smooth surface or a mat surface for the purpose of improving the adhesion to the stimulable phosphor layer.

In the present invention, an adhesive layer may be provided in advance on the surface of the support, if necessary, in order to improve the adhesion between the support and the stimulable phosphor layer.

The thickness of the support varies depending on the material and the like of the support used, but is generally 80 μm to 2000 μm.
m, more preferably 8 from the viewpoint of handling.
It is 0 μm to 1000 μm.

As the protective layer of the present invention, a protective layer having good translucency and capable of forming a sheet can be used. For example, sheet glass such as quartz, borosilicate glass, and chemically strengthened glass, and organic polymers such as PET, OPP, and polyvinyl chloride can be given.

The protective layer of the present invention may be a single layer or a multilayer, and may be composed of two or more layers made of different materials. For example, a film in which two or more polymer films are combined can be used. Examples of a method for producing such a composite polymer film include methods such as dry lamination, extrusion lamination, and co-extrusion coating lamination. The combination of two or more protective layers is not limited to organic polymers, but may be glass sheets or an organic polymer. For example, as a method of combining a sheet glass and a polymer layer, there is a method in which a coating liquid for a protective layer is directly applied to the sheet glass to form, or a polymer protective layer formed separately in advance is bonded to the sheet glass. . The two or more protective layers may be in close contact with each other or may be separated from each other.

The thickness of the protective layer of the present invention is practically 10 μm.
m to 3 mm. In order to obtain good moisture resistance and impact resistance, the thickness of the protective layer is preferably 100 μm or more, especially when a protective layer of 500 μm or more is provided, a conversion panel excellent in durability and durability can be obtained, More preferred.

When a sheet glass is used as the protective layer, it is particularly preferable because of its extremely excellent moisture resistance.

The protective layer desirably has a high transmittance in a wide wavelength range in order to transmit the stimulated excitation light and the stimulated emission efficiently, and the transmittance is 60% or more, preferably 80%.
That is all. For example, quartz glass, borosilicate glass, and the like can be given as those satisfying this. Borosilicate glass shows a transmittance of 80% or more in a wavelength range of 330 nm to 2.6 μm, and quartz glass shows a high transmittance even at a shorter wavelength.

Further, it is preferable to provide an antireflection layer such as MgF _{2 on} the surface of the protective layer, because it has the effects of efficiently transmitting stimulating excitation light and stimulating luminescence and reducing a decrease in sharpness. Although the refractive index of the protective layer is not particularly limited, many of practically used materials have a refractive index between 1.4 and 2.0.

In the present invention, a sheet glass is preferable as a material of the protective layer. As a means for containing a coloring material in the glass and coloring the glass so as to have a function of absorbing the stimulating excitation light, the following method is available.

(1) A film colored with a coloring material (pigment or dye) is laminated on glass. As a method for producing a colored film, there is a method in which a layer containing a coloring material (pigment or dye) is formed by coating or the like on the surface of a plastic film or a plastic film into which a coloring material is kneaded.

The colored glass used as the protective layer can be obtained by uniformly bonding the colored plastic film produced by such a method to the glass surface using an adhesive or the like.

As a coloring material used for coloring, a pigment or dye absorbing stimulating light is suitable.

(2) A method in which a layer containing a dye or a pigment is provided on one side of the glass by coating.

This is a method of obtaining a colored glass by applying a pigment or dye dispersed or dissolved in a binder (such as water glass or an organic polymer such as polyvinyl butyral) having good adhesiveness directly to the glass.

(3) Next, there is a method in which the glass itself contains a dispersed pigment or colorant as a coloring material.

For example, at the time of manufacture, a colorant such as lead phosphate is mixed as a coloring material into glass to be colored. In this case, it is a condition that the coloring material has good thermal stability because it is mixed during glass production, and inorganic pigment-based heat-resistant pigments can be dispersed and used.

When a layer containing a dye or pigment is applied to glass or a glass to which a colored film is attached is used as a protective layer, the effect of the present invention can be obtained by providing a colored layer on either side. It is more preferable that the colored layer or film is in contact with the low refractive index layer side in that the effect of the present invention is exhibited.

The colorant used for the protective layer and capable of absorbing the excitation light may be either an organic or inorganic colorant. Examples of the organic colorant include Pomelo Fast Blue 3G (manufactured by Hoechst) and Estrol Brill. Blue N-3
RL (manufactured by Sumitomo Chemical), D & C Blue No. 1 (made by National Aniline), Spirit Blue (made by Hodogaya Chemical),
Oil Blue No. 603 (manufactured by Orient), Kiton Blue A (manufactured by Ciba Geigy), Eisenka Tiron Blue G
LH (Hodogaya Chemical), Lake Blue AFH (Kyowa Sangyo), Primocyanin 6GX (Inabatake Sangyo), Brill Acid Green 6BH (Hodogaya Chemical), Cyan Blue BNRCS (Toyo Ink), Lionoyl Blue S
L (manufactured by Toyo Ink) or the like is used. In addition, the color index No. 24411, 23160, 74180, 74
200, 22800, 23154, 23155, 244
01, 14830, 15050, 15760, 1570
7,17941,74220,13425,1336
1, 13420, 11836, 74140, 7438
Organic metal complex salt dyes or pigments such as 0, 74350, and 74460. Particularly, metal phthalocyanine pigments are preferred. Ultramarine, cobalt blue,
Cerulean blue, chromium oxide, TiO ₂ -ZnO-C
o-NiO-based pigments.

The low refractive index layer of the present invention 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 the sharpness deterioration even when the protective layer is thickened. For example, the following substances can be used, and they are preferably used in a state of a thin film formed by a vapor phase growth method such as vapor deposition.

[0081] Alternatively, the following liquid layer can be used.

[0082] Further, when a layer having a refractive index of substantially 1 such as a gas layer of air, nitrogen, argon or the like or a vacuum layer is used as the low refractive index layer of the present invention, the effect of preventing the sharpness from lowering is high, and it is particularly preferable. .

The thickness of the low refractive index layer of the present invention is 0.05 μm
To 3 mm is practical. The low refractive index layer of the present invention may be in close contact with the stimulable layer or may be separated therefrom. In order to make the low refractive index layer and the stimulable layer adhere to each other, one method is to use an adhesive. In this case, the refractive index of the adhesive is the refractive index of the stimulable layer or the refractive index of the low refractive index layer. Preferably, it is close to the rate.

FIG. 3 is a sectional view showing the structure of the radiation image conversion panel of the present invention. 16 is a protective layer, 15 is a low refractive index layer, 12 is a stimulable phosphor layer, and 11 is a support.

FIG. 4 is a sectional view showing an example of the configuration of the radiation image conversion panel of the present invention, in which an air layer is provided as a low refractive index layer. There is a method in which a spacer S1 is provided at the side edge of the panel to keep the air layer 15 at a constant thickness. FIG. 5 is a cross-sectional view showing another example of the configuration of the radiation image conversion panel of the present invention. An air layer is provided by dispersing spacers S2 between the protective layer and the stimulable phosphor layer. It is an example. As the spacer, for example, a fine glass fiber piece having a diameter of several μm used as a spacer material of a liquid crystal panel can be used.

FIG. 6 schematically shows a radiation image conversion method using the radiation image conversion panel of the present invention.

That is, in FIG. 6, 21 is a radiation generator, 22 is a subject, 23 is a conversion panel according to the present invention,
24 is a stimulating excitation light source (such as a laser), 25 is a photoelectric conversion device for detecting stimulating fluorescence emitted by the conversion panel,
26 is a device for reproducing the signal detected at 25 as an image, 27 is a device for displaying the reproduced image, 28 is a filter that separates stimulating excitation light and stimulating fluorescence and transmits only stimulating fluorescence. is there. In addition, after 25, it is sufficient that the optical information from 23 can be reproduced as an image in some form.
It is not limited to the above.

As shown in FIG. 6, the radiation generator 2
The radiation (R) from 1 enters the conversion panel 23 through the subject 22 (RI). The incident radiation is absorbed by the photostimulable layer of the panel 23, and its energy is stored.
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 24 and emitted as stimulating light.

Since the intensity of the emitted photostimulated light is proportional to the amount of accumulated radiation energy, this optical signal is photoelectrically converted by a photoelectric conversion device 25 such as a photomultiplier tube, and reproduced as an image by an image generation device 26. Image display device 2
By displaying by 7, the radiation transmission image of the subject can be observed.

[0091]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited thereto.

<Production of radiation image conversion panel> 500 μm
The surface of a thick crystallized glass (manufactured by NEC Corporation) support was heated to 100 ° C., and an alkali halide phosphor (RbBr: 0.0005 Tl or Cs) was deposited using the vapor deposition apparatus shown in FIG.
(2 kinds of phosphors of Br: 0.0005 Eu) were prepared) at an angle of 30 ° with respect to the normal direction of the surface, using an aluminum slit, and the distance between the support and the evaporation source from an oblique direction. Is set to 60 cm, vapor deposition is performed while transporting the support in a direction parallel to the support, and a stimulable phosphor layer (thickness of crystal) of 300 μm, 200 μm, and 100 μm thick for each stimulable phosphor. 10 μm, and the width of each crack was 1 μm).

The activation of the phosphor was carried out by uniformly mixing the activator in the evaporation source at the time of vapor deposition and vapor-depositing at the same time.

Next, a radiation image conversion panel having a structure as shown in FIG. 4 was produced using the glass support on which the stimulable phosphor layer produced above was formed by vapor deposition. That is, an air layer having a thickness of 300 μm is formed as a low refractive index layer between the stimulable phosphor layer and the glass used as a separate protective layer via a spacer at the glass-like side edge portion having the stimulable phosphor layer. Thus, a protective layer made of glass was provided. As a spacer, a glass spacer was set up so that an air layer was formed at the plate edge, and a glass protective layer was provided thereon. The glass spacer was bonded to the glass support and the side edge of the glass protective layer using an epoxy adhesive (manufactured by Three Bond).

The protective layer made of glass was prepared as follows. Glass A: transparent glass without coloring (thickness: 550 μm,
Refractive index 1.52, stimulated excitation light (semiconductor laser; 680n
m) The transmittance in m) is 98%) Glass B: The following pigment-dispersed coating solution is directly applied to the transparent glass surface without coloring, and the transmittance in one side of the glass to stimulating excitation light (semiconductor laser; 680 nm) is increased. Thickness was adjusted to 95%, 85%, 65%, and 40%, respectively, applied with a bar coater, and dried to obtain a colored glass of a protective layer. (Glass B ₉₅ , B ₈₅ , B ₆₅ , B ₄₀ ) (Pigment dispersion coating liquid) Copper phthalocyanine 1.0 g Polyvinyl butyral 1000 g Methyl ethyl ketone 10,000 g using a sand mill (Dino Mill KD-60 manufactured by Willie & Bacoffen) for 6 hours. It was dispersed to prepare a coating solution.

Glass C: A polyethylene terephthalate film (60 μm; T-6 manufactured by Toray Industries, Ltd.)
0) The colored film prepared by applying the pigment dispersion on one surface and drying the same (film thickness such that the transmittance for the stimulating excitation light is 85% together with the glass serving as the substrate). Was adjusted so that the pigment coating layer was on the outermost surface on one side of the glass to produce a protective layer glass C.

Glass D: another colored glass having a thickness of 550 μm and containing copper phosphate uniformly as a coloring agent (also having a transmittance of 8 at the emission wavelength of the stimulating excitation light).
5%) was used as a protective layer.

The transmittance of the protective layer was measured using a Hitachi spectrophotometer U-3300.

The kind of the phosphor was RbBr: 0.0005T.
1 and CsBr: 0.0005 Eu, the thickness of each phosphor layer, the type of colored glass used for the protective layer, and the transmittance of the protective layer were changed to produce a radiation image conversion panel with the configuration shown in Table 1. did. In the prepared radiation image conversion panel, the pigment layer of the colored glass having the pigment layer used for the protective layer glass, and the glass layer to which the film having the pigment layer is attached, the pigment layer becomes the low refractive index layer of the panel. It was configured to be on the side of the air layer.

The characteristics of each panel were evaluated by the following methods. <Evaluation of Radiation Image Conversion Panel> X-rays of 80 kVp were applied to each radiation image conversion panel by 10 mR (distance to subject; 1.
After irradiation, the panel was irradiated with a semiconductor laser beam (680 nm, power on the panel: 40 nW), and the luminance of the panel with respect to X-rays was determined from the magnitude of the obtained signal. The diameter of the laser is 100 μmφ. In addition, as a comparison, 1-1
The brightness of each panel was relatively determined with the brightness of the panel of 100 as 100.

Regarding the sharpness, the modulation transfer function (MT
F) was determined and evaluated. After sticking the CTF chart to the panel, the MTF was irradiated with X-rays in the same manner as the sensitivity measurement.
The CTF chart was obtained by scanning and reading with a semiconductor laser beam having a diameter of 100 μmφ. The values in Table 1 were obtained as relative values for each panel, with the MTF value at 0.5 lp / mm as 100.

[0102]

[Table 1]

In a stimulable phosphor panel using a colored protective layer having a transmittance for stimulating excitation light within the range of the present invention, sharpness is lower than that of a comparative panel having the same luminance without coloring. It can be seen that the brightness is considerably improved and the brightness is high when compared at the same sharpness.

[0104]

According to the present invention, a radiation image conversion panel excellent in balance between luminance and sharpness is obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a stimulable phosphor layer composed of columnar crystals formed on a support.

FIG. 2 is a view showing a state in which a stimulable phosphor layer is formed on a support by vapor deposition.

FIG. 3 is a cross-sectional view illustrating a configuration of the radiation image conversion panel of the present invention.

FIG. 4 is a sectional view showing an example of the configuration of the radiation image conversion panel of the present invention.

FIG. 5 is a cross-sectional view showing another example of the radiation image conversion panel having an air layer as the low refractive index layer of the present invention.

FIG. 6 is a schematic diagram showing a radiation image conversion method using the radiation image conversion panel of the present invention.

FIG. 7 is a schematic view showing an example of a method for producing a stimulable phosphor layer on a support by vapor deposition.

[Explanation of symbols]

Reference Signs List 11 support 12 stimulable phosphor layer 13 columnar crystal 14 gap formed between columnar crystals 15 low refractive index layer 16 protective layer 21 radiation generator 22 subject 23 radiation image conversion panel 24 stimulating excitation light source 25 conversion panel Device for detecting photostimulated fluorescence emitted by the device 26 Image reproducing device 27 Image display device 28 Filter S1, S2 Spacer

Claims (6)

[Claims] 1. A radiation image conversion panel having a stimulable phosphor layer, a low refractive index layer, and a protective layer laminated in this order on a support, wherein the stimulable phosphor layer is formed at least by a vapor phase growth method. A radiation image, wherein the protective layer contains a colorant that absorbs excitation light that excites the stimulable phosphor layer, and the protective layer has an excitation light transmittance of 60% or more and 95% or less. Conversion panel. 2. The radiation image conversion panel according to claim 1, wherein the stimulable phosphor layer formed by a vapor growth method is composed of columnar crystals. 3. The radiation image conversion panel according to claim 2, wherein the stimulable phosphor layer formed by the vapor growth method is composed of CsBr columnar crystals. 4. The radiation image conversion panel according to claim 1, wherein the protective layer is a glass on which a colored film is laminated. 5. The radiation image conversion panel according to claim 1, wherein the protective layer is a glass in which a colored layer is provided on one of the surfaces by coating. 6. The radiation image conversion panel according to claim 1, wherein the protective layer is a colored glass.