JPH077116B2 - Method for manufacturing radiation image conversion panel having vitreous protective layer - Google Patents

Description

TECHNICAL FIELD The present invention relates to a radiation image conversion panel using a stimulable phosphor, and more particularly to a radiation image conversion panel that can withstand long-term use. Is.

[Background of the Invention]

Radiation images such as X-ray images are often used for disease diagnosis.

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

According to this method, the radiation (generally X-rays) transmitted through the subject is absorbed by the phosphor, and thereafter, the phosphor is excited by, for example, light or thermal energy, and the radiation accumulated by the phosphor is absorbed. In this method, energy is emitted as fluorescence, and this fluorescence is detected and imaged.

Specifically, for example, U.S. Pat.
No. 5-12144 discloses a radiation image conversion method using a stimulable phosphor and using visible light or infrared light as stimulated excitation light.

This method uses a radiation image conversion panel (hereinafter abbreviated as a conversion panel) having a stimulable phosphor layer (hereinafter abbreviated as abbreviated layer) formed on a support. The latent energy is formed by irradiating the radiation that has passed through the subject and accumulating the radiation energy corresponding to the radiation transmittance of each part of the subject, and then the photostimulable layer is scanned with the stimulated excitation light to accumulate the respective parts. Radiation energy is emitted and converted into light, and an image is obtained by an optical signal depending on the intensity of the light.

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

The conversion panel used in this radiation image conversion method releases the stored energy by scanning the stimulated excitation light after storing the radiation image information, so that the radiation image can be stored again after the scanning and repeated use is possible. It is possible.

Therefore, it is desirable that the conversion panel has a performance that can be used for a long time or repeated many times without deteriorating the image quality of the obtained radiation image. For that purpose, the photostimulable layer in the conversion panel must be sufficiently protected from external physical or chemical irritation.

In the conventional conversion panel, in order to solve the above problems, a method of providing a protective layer for covering the photostimulable layer surface on the support of the conversion panel has been adopted.

This protective layer is formed, for example, as described in JP-A-59-42500, by directly coating a protective layer coating solution on the photostimulable layer, or by forming a protective layer separately formed in advance. It is formed by a method of adhering on the exhaust layer.

However, a protective layer made of a commonly used organic polymer is permeable to a certain amount of moisture and / or moisture, and the stimulating layer absorbs moisture, resulting in a decrease in the radiation sensitivity of the conversion panel or the stimulating effect. Accumulation of accumulated energy until receiving the irradiation of excitation light is large, resulting in variation and / or deterioration of image quality of the obtained radiation image.

Further, in the conventional conversion panel having the protective layer as described above, since the surface hardness of the protective layer is small, the protective layer surface may be scratched or buffered due to contact with a mechanical part such as a transport roller during transportation. Cracks in the stimulating layer due to insufficientness,
Folding is likely to occur, and the image quality of the obtained radiation image deteriorates with the increase in the number of times of repeated use, and improvement in moisture resistance, strength, and cushioning properties without impairing transparency is desired. It was

[Object of the Invention]

In line with the above requirements in a conversion panel using a stimulable phosphor, the object of the present invention is to provide a stimulable layer with a chemical stimulus from the outside,
Particularly, a conversion panel with high durability and durability that can be sufficiently protected against moisture, maintains high sensitivity, high sharpness and high graininess for a long period of time and can be used in good condition. To provide.

Another object of the present invention is to provide a conversion panel in which the photostimulable layer is protected from external physical stimuli to improve durability and durability for long-term and repeated use.

[Structure of Invention]

The object of the present invention is a conversion panel having a photostimulable layer and at least one protective layer as a constituent layer on a support, wherein the at least one protective layer is a glass powder layered and fired. It is achieved by a method for producing a conversion panel having a glassy protective layer, which is characterized in that it is a glassy layer.

Next, the present invention will be described in detail.

As the glassy material used for the protective layer according to the present invention, a substance having excellent moisture resistance is preferable in order to prevent deterioration of properties due to water absorption of the photostimulable layer.

Further, the conversion panel is liable to be scratched on the surface of the protective layer due to contact with a mechanical part such as a conveying roller during conveyance, and the image quality of a radiation image deteriorates as the number of times of repeated use increases. In order to prevent this, the strength of the protective layer is desired to be hard.

Further, it is preferable to have high transmittance for both stimulated emission light and stimulated emission light. This is because the energy of the stimulated excitation light is used as effectively as possible to generate the stimulated emission of the stimulable phosphor, and the stimulated emission is detected with the highest possible sensitivity.

As a glass material that can meet the requirements for the protective layer described above, an oxide glass material can be used.

That is, silicate glass, phosphate glass, borate glass and the like can be mentioned, and silicate glass is particularly preferable. Quartz glass (SiO ₂ ), lead silicate glass (PbO ・ SiO ₂ ), lead borosilicate glass (PbO ・ B ₂ O ₃・ SiO ₂ ), zinc borosilicate glass (Z
nO ・ B ₂ O ₃・ SiO ₂ ), aluminosilicate glass (Al ₂ O ₃・ Si
O ₂ ), alumino-lime silicate glass (CaO ・ Al ₂ O ₃・ SiO ₂ ),
Examples thereof include calcium borosilicate glass (CaO.B ₂ O ₃ .SiO ₂ ).

In addition, the melting point of the glass may be lowered by increasing the CaO composition and adding Na ₂ O within a range that does not impair the moisture resistance of the glassy protective layer, chemical durability such as acid resistance, or transparency stability.

The glass powder particle size is preferably 1 to 100 μm. FIG. 1 is a sectional view showing an example of the aspect of the conversion panel according to the present invention.

In FIG. 1 (1), 11 is a support, 12 is a photostimulating layer, and 13a is a vitreous protective layer provided by the method of the present invention.

Although FIG. 1 (1) shows the case where the glassy protective layer is one layer,
As shown in FIG. 1 (2), a two-layer structure or a multilayer protective layer structure of more than two layers may be used.

Further, as shown in FIG.
A multilayer protective layer may be formed by directly coating the protective layer coating solution proposed in JP-A-59-42500, and as a material for the protective layer, a radiation layer proposed in JP-A-61-176900 may be used. Resins that are cured by heat and / or heat may be used.

The protective layer made of these organic polymers and the vitreous protective layer according to the present invention may be used in any combination of the composition and the order of the layers.

Examples of the material for the protective layer of the organic polymer include cellulose acetate, nitrocellulose, cellulose derivatives such as ethyl cellulose, or polymethylmethacrylate, polyvinyl butyral, polyvinyl formal,
Polycarbonate, polyvinyl acetate, polyacrylonitrilonitrile, polymethylallyl alcohol, polymethyl vinyl ketone, cellulose diacetate, cellulose triacetate, polyvinyl alcohol, polyacrylic acid, polymethacrylic acid, polyglycine, polyacrylamide, polyvinylpyrrolidone, polyvinylamine , Polyethylene terephthalate, polyethylene, polyvinylidene chloride, polyvinyl chloride, polyamide (nylon), polytetrafluoroethylene, polytrifluoro-ethylene chloride, polypropylene, tetrafluoroethylene-hexafluoropropylene copolymer, polyvinyl isobutyl Examples include ether and polystyrene.

The radiation curable resin may be a compound having an unsaturated double bond or a composition containing the same, and such a compound is preferably a prepolymer and / or an oligomer having two or more unsaturated double bonds. Further, a monomer having an unsaturated double bond (vinyl monomer) can be contained therein as a reactive diluent.

Next, a method for forming the vitreous protective layer according to the present invention will be described.

A glassy layer is obtained by sprinkling the above-mentioned glass powder on the stimulable layer and firing. Alternatively, the glass powder may be sufficiently kneaded with a suitable vehicle to form a paste, which is applied onto the stimulable layer by the method shown in Table 1, dried and baked to form a glassy layer.

The glassy layer preferably has a thickness of about 1 to 100 μm.

Further, the protective layer using a polymer is the method described in JP-A-59-42500, and when a curable resin is used, it is JP-A-61.
It can be provided using the method described in -176900.

Moreover, the layer thickness of the protective layer formed using a polymer is 1
μm to 1000 μm, more preferably 2 μm to 50 μm
It is preferably in the range of a degree.

The stimulable phosphor used in the present invention is, after being irradiated with the first light or high-energy radiation, optical, thermal,
It is a phosphor that shows stimulated emission corresponding to the dose of initial light or high-energy radiation by mechanical, chemical, or electrical stimulation (stimulated excitation), but it is preferably 500 nm from a practical viewpoint. It is a phosphor that exhibits stimulated emission by the above stimulated excitation light. The stimulable phosphor, for example, described in JP-A-48-80487 BaSO _4: AX, JP 48
SrSO ₄ : AX described in JP-80489, JP-A-53-39277
No. of _{Li 2 B 4 O 7 Cu,} : Ag or the like, Li ₂ O · of JP 54-47883 (B ₂
O ₂ ) x: Cu and Li ₂ O. (B ₂ O ₂ ) x: Cu, Ag, etc., U.S. Pat.
No.9,527 SrS: Ce, Sm, SrS: Eu, Sm, La ₂ O ₂ S: Eu, Sm and (Zn,
Cd) The fluorescent substance represented by S: Mn, X is mentioned.

Further, the ZnS: Cu, Pb phosphor described in JP-A-55-12142, the barium aluminate phosphor represented by the general formula BaO.xAl ₂ O ₃ : Eu, and the general formula M An alkaline earth metal silicate-based phosphor represented by Further, the general formulas described in _{JP-A-55-12143 (Ba 1 -x-yMgxCay)} FX: eEu alkaline earth fluoride halide phosphor represented by ^2+, JP 55-12144 The phosphor represented by the general formula LnOX: xA described in JP-A-55-12145, the phosphor represented by the general formula (Ba ₁ -xMII) FX: yA described in JP-A-55-12145, JP-A-55 -84389, a phosphor represented by the general formula BaFX: xCe, yA, and a rare earth element represented by the general formula M ^II FXxA: yLn described in JP-A-55-160078. Active divalent metal fluorohalide phosphor, general formula ZnS: A, CdS: A, (Zn, Cd) S: A, ZnS: A, X and CdS:
Phosphors represented by A and X, represented by the general formula xM ₃ (PO ₄ ) ₂ · NX ₂ : yA M ₃ (PO ₄ ) ₂ : yA described in JP-A-59-38278. phosphors, the following Izure one of formulas _{nReX 3 · mAX '2: xEu} nReX 3 · mAX' 2: xEu, phosphor represented by ySm Osamu, the following general formula ^{M I X · aM II X '} 2 · Examples thereof include alkali halide phosphors represented by bM ^III X ″ ₃ : cA. Alkali halide phosphors are particularly preferred because they facilitate the formation of a stimulating layer by a method such as vapor deposition and sputtering.

However, the stimulable phosphor used in the conversion panel according to the present invention is not limited to the above-mentioned phosphor, and a phosphor that exhibits stimulated emission when irradiated with stimulated excitation light after being irradiated with radiation. Any phosphor may be used as long as it is a phosphor.

The conversion panel according to the present invention may be a stimulating layer group composed of one or more stimulating layers containing at least one kind of the stimulable phosphor described above. The stimulable phosphors contained in the respective stimulable layers may be the same or different.

The photostimulable layer of the present invention may be applied by either a coating method or a vapor phase growth method, but a panel having a vapor phase growth type photostimulable layer is more excellent in sharpness than the coating type and is preferable.

A vapor deposition method is a first method for vapor-phase growing the stimulable phosphor. FIG. 2 shows a schematic diagram of the vapor deposition device.

In this method, first, the support is placed in the vapor deposition apparatus and then the apparatus is evacuated to a vacuum degree of about 10 ^-6 Torr. Then, at least one of the stimulable layers is heated and evaporated by a method such as a resistance heating method or an electron beam method to deposit a stimulable phosphor on the surface of the support to a desired thickness.

As a result, a stimulable layer containing no binder is formed,
In the vapor deposition process, the photostimulable layer can be formed in multiple times. Further, in the vapor deposition step, co-evaporation can be performed using a plurality of resistance heaters or electron beams. In the vapor deposition method, the stimulable phosphor raw material is co-evaporated using a plurality of resistance heaters or electron beams to synthesize a target stimulable phosphor on a support and simultaneously form a stimulable layer. It is also possible to form.

Further, in the vapor deposition method, the vapor deposition target may be cooled or heated during vapor deposition, if necessary. In addition, the stimulable phosphor layer may be heat-treated after completion of vapor deposition.

The second method is the sputtering method, and the third method is the CV method.
Method D is as useful as the vapor deposition method described above.

The layer thickness of the stimulable layer of the panel according to the present invention varies depending on the sensitivity of the intended exchange panel to radiation, the type of stimulable phosphor, etc., but when the binder is not contained, it is 1 μm to 1000 μm.
It is preferably selected from the range of μm, more preferably from 20 μm to 800 μm, and 10 μm when a binder is included.
m-1000 μm range, more preferably 20 μm-500 μm
It is preferably selected from the range of m.

As the support used in the conversion panel according to the present invention, for example, a ceramic plate such as alumina, a glass plate such as chemically strengthened glass, a metal plate such as aluminum, iron, copper or chromium, or a coating layer of the metal oxide is used. A metal plate having is preferable.

The layer thickness of these supports varies depending on the material of the support used and the like, but is generally 80 μm to 3000 μm, and from the viewpoint of handling, more preferably 80 μm to 1000 μm.
m.

The surface of these supports may be a smooth surface or may be a matte surface for the purpose of improving the adhesiveness with the photostimulable layer. The surface of the support is an uneven surface 31 as shown in FIG.
Alternatively, as shown in (b), a structure in which tile-shaped plates 33 separated from each other are spread may be used.

In the case of FIG. 3 (a), the photostimulable layer is subdivided by the uneven surface 31 as shown in the sectional view of FIG. 3 (c), so that the sharpness of the image is further improved.

In the case of FIG. 3 (b), the stimulating layer is the tile-shaped plate 33 of the support.
As a result, the photostimulable layer is composed of columnar blocks 35 of photostimulable phosphors separated by cracks 36 as shown in the sectional view of FIG. 3 (d).
The sharpness of the image is further improved.

Also, in order to protect the photostimulable layer at the edge of the conversion panel, a third
As shown in FIG. (E), the folding frame 37 is provided at the peripheral edge of the support 32.
Alternatively, the photostimulable layer 38 may be formed in the central recess, and the protective layer 39 may be provided so as to cover the photostimulable layer.

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

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

That is, in FIG. 4, 41 is a radiation generator, 42 is a subject, 43 is a conversion panel according to the present invention, 44 is a stimulated excitation light source, and 45 is photoelectric conversion for detecting stimulated fluorescence emitted from the conversion panel. A device, 46 is a device for reproducing the signal detected by 45 as an image, 47 is a device for displaying the reproduced image, 48
Is a filter that separates stimulated excitation light and stimulated fluorescence and transmits only stimulated fluorescence. It should be noted that after 45, any light information from 43 can be reproduced as an image in some form,
It is not limited to the above.

As shown in FIG. 4, the radiation from the radiation generator 41 enters the conversion panel 43 through the subject 42. The incident radiation is absorbed by the photostimulable layer of the panel 43, its energy is accumulated, and an accumulated image of a radiation transmission image is formed.

Next, this accumulated image is excited by stimulated excitation light from the stimulated excitation light source 44 and emitted as stimulated emission.

Since the intensity of the stimulated emission emitted is proportional to the amount of accumulated radiation energy, this optical signal is photoelectrically converted by the photoelectric conversion device 45 such as a photomultiplier tube and reproduced as an image by the image reproduction device 46. By displaying with the display device 47, a radiation transmission image of the subject can be observed.

〔Example〕

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

Example 1 An alkali halide phosphor (RbBr; 0.0006Tl) was added to a quartz glass support having a thickness of 500 μm in an amount of 300 by using the vapor deposition apparatus shown in FIG.
μm vapor-deposited (panel P).

Next, a paste having the following composition was sufficiently kneaded with a three-roll mill to be prepared, and printed on the panel P with a stainless screen (150 mesh, 40 μm thickness).

Lead borosilicate glass powder (GA-1 made by Nippon Electric Glass): 75
Parts by weight Ethyl cellulose: 2.5 parts by weight Butyl carbitol: 22.5 parts by weight After that, it was dried at 120 ° C. for 10 minutes and baked at 600 ° C. for 60 minutes to obtain a panel A having a glassy protective layer thickness of 20 μm.

Example 2 Zinc borosilicate glass (GA-12 manufactured by Nippon Electric Glass Co., Ltd.) was used as the glass powder, and firing was carried out at 600 ° C. for 10 minutes, except that
A panel B was obtained in the same manner as in Example 1.

Example 3 The conversion panel A obtained in Example 1 was adhered with a polyethylene film having a thickness of 5 μm and a polyester adhesive applied thereto to form a second protective layer to obtain a conversion panel C.

Comparative Example 1 A protective film was formed by adhering a polyethylene film having a thickness of 5 μm with a polyester adhesive to the protective layer of the conversion panel P used in Example 1 as in Example 3 to form a protective layer. Panel E was obtained.

Comparative Example 2 The conversion panel P used in Example 1 had a thickness of 10 μm on the stimulating layer surface.
The vinylidene chloride-vinyl chloride copolymer film (1) was adhered with an epoxy-modified polyolefin adhesive on one side to form a protective layer, and a comparative exchange panel F was obtained.

With respect to the conversion panels A, B, C of the present invention and the conversion panels E, F of the comparison thus obtained, the moisture resistance of their protective layers was evaluated as follows.

The panels A, B, C and E, F are left for 350 hours in a thermo-hygrostat at a temperature of 50 ° C. and a relative humidity of 50%, and the sensitivity to radiation before and after the treatment is measured to determine the radiation sensitivity after the exposure. Then, the ratio to the radiation sensitivity before standing was obtained, and the moisture resistance was evaluated by the value of the ratio.

The results are shown in Table-2.

As is clear from the table, each of the panels A, B, and C of the present invention obtained a radiation angle ratio almost twice that of the comparative panels E and F. This indicates that the vitreous protective layer provided in this panel has a significant effect on moisture resistance.

Furthermore, when the above-mentioned panel was checked for scratch resistance by sandblasting, no "fogging" occurred on Panels A and B having a glassy layer on the surface.

There was no problem with transparency.

〔The invention's effect〕

The conversion panel of the present invention, since at least a part of the protective layer is formed of glass, it has excellent strength, and also prevents the sensitivity and the sharpness from decreasing due to the provision of the protective layer,
In addition, since the moisture resistance is particularly excellent, it is possible to prevent deterioration of the photostimulable layer due to moisture absorption, and it can be used in a good state for a long period of time.

[Brief description of drawings]

FIG. 1 is a sectional view showing a basic structure of a conversion panel according to the present invention. FIG. 2 is a schematic sectional view of an electron beam heating vapor deposition apparatus which is an example of the vapor deposition method used in the embodiment of the present invention. FIG. 3 is a diagram illustrating the shape of the surface of the vapor deposition substrate of the support. FIG. 4 is a diagram illustrating a radiation image conversion method. 11 ... Support 12 ... Photostimulable phosphor layer 13a, 13b and 14 ... Protective layer

Claims (1)

[Claims] 1. A radiation image conversion panel comprising a stimulable phosphor layer and at least one protective layer as a constituent layer on a support, wherein the at least one protective layer is formed by layering glass powder. A method for producing a radiation image conversion panel having a vitreous protective layer, which comprises laying and firing to form a vitreous layer.