JP2004061172A - Radiation conversion sheet for digital x-ray imaging, and digital x-ray imaging equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a digital X-ray imaging radiation conversion sheet which is free from warpages and deformation of a photoelectric conversion imaging element and inclusion of foreign matters and has a small sensitivity distribution and a digital X-ray imaging equipment using the sheet. <P>SOLUTION: In the digital X-ray imaging radiation conversion sheet, a substrate/a phosphor layer/an adhesive layer/a transparent release film are laminated, in this sequence. The adhesive layer comprises at least (1) a main monomer imparting tackiness and (2) a polar group containing monomer imparting adhesiveness. As the polar group containing monomer, 2-hydroxyethyl(meta)acrylate is cited. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a radiation conversion sheet for digital radiography and a digital radiography apparatus. In particular, the present invention relates to a radiation conversion sheet for digital X-ray imaging, which has no warpage of a photoelectric conversion imaging device and has a small sensitivity distribution, and a digital X-ray imaging apparatus using the same.
[0002]
[Prior art]
2. Description of the Related Art In recent years, digital X-ray imaging apparatuses using a photoelectric conversion element and a X-ray light conversion material using a semiconductor have been commercialized for the purpose of abolishing the film of X-ray (radiation) imaging and digital X-ray imaging.
[0003]
The photoelectric conversion imaging device is formed by two-dimensionally arranging pixels (each side having a size of 50 to 300 μm) including a thin film transistor and an electric wiring on a glass substrate. Further, an IC for reading information is arranged around the photoelectric conversion image pickup device (Japanese Patent Laid-Open No. 10-41013).
[0004]
The X-ray light conversion material is a material called a scintillator or a phosphor. Digital X-ray photography in which a phosphor layer formed by mixing phosphor particles and a binder resin is formed on a sheet-like plastic substrate by an application method as an X-ray light conversion material used for a radiation conversion sheet for digital X-ray photography. Radiation conversion sheets (phosphor sheets) are disclosed in JP-A-11-305000 and JP-A-2000-155198. Gadolinium oxysulfide is mainly used as the phosphor particles. These phosphor sheets are obtained by continuously applying phosphor particles to a substrate material, drying a solvent, and then cutting into a predetermined size. It is possible to produce a phosphor sheet of several hundred m ² or more in one production.
[0005]
In order to manufacture a digital X-ray imaging apparatus, it is essential to stack a photoelectric conversion imaging device and a scintillator. In order to stack the scintillator with the photoelectric conversion imaging device, the scintillator is stacked on the photoelectric conversion imaging device via an adhesive.
[0006]
As a problem when the phosphor layer is laminated on the surface of the photoelectric conversion imaging element via an adhesive layer, the resolution is reduced unless the adhesive layer is thinned. Therefore, the thickness of the adhesive layer is usually 20 μm or less. is necessary.
[0007]
Apply a low-viscosity adhesive (adhesive) to the sensor substrate surface to make it thinner, apply pressure from the surface of the phosphor sheet with a laminator roll, etc., and stack the phosphor sheets. In order to protrude, it is necessary to clean the protruding adhesive (adhesive). Around the photoelectric conversion image sensor, there is a pad for connecting an IC for reading photoelectric conversion information. Further, it is necessary to apply and bond an adhesive (adhesive) for each photoelectric conversion imaging element, which increases the cost of the bonding process.
[0008]
Furthermore, in order to stabilize the low-viscosity pressure-sensitive adhesive layer, a heat-curing step is required, and a step of heating the photoelectric conversion imaging element / pressure-sensitive adhesive layer / phosphor sheet laminate to 60 to 100 ° C. is required. Become. Heating causes delamination and warpage of the laminate due to the difference in thermal expansion of the laminate of different materials.
[0009]
Solvent evaporation-curable pressure-sensitive adhesives, such as vinyl acetate resins, have a residual solvent remaining in the pressure-sensitive adhesive layer when pasting a surface with an area that is significantly larger than the thickness of the pressure-sensitive adhesive layer. This has an adverse effect on the durability of the device.
[0010]
The UV-curable pressure-sensitive adhesive layer cures quickly, but hardening of the pressure-sensitive adhesive layer is hindered because most of the photoelectric conversion imaging element, the radiation conversion sheet, and the conductive member do not sufficiently transmit ultraviolet light.
[0011]
During storage until the phosphor sheet produced in the continuous production is bonded to the surface of the photoelectric conversion imaging device, dust foreign matter adheres to the surface of the phosphor sheet, and it is necessary to remove the dust foreign matter before bonding. Alternatively, it is necessary to manage the surface of the phosphor sheet manufactured in advance so that no foreign matter adheres to the surface.
[0012]
Further, when a foreign substance enters between the photoelectric conversion imaging device and the phosphor layer, a defect occurs in the X-ray photographed image.
[0013]
It has been found that when an ion component is contained in the pressure-sensitive adhesive layer formed on the surface of the photoelectric conversion imaging device made of a semiconductor, a sensitivity distribution occurs in the photoelectric conversion imaging device. The sensitivity distribution of the photoelectric conversion imaging device was remarkable when the semiconductor material forming the photoelectric conversion imaging device was formed from amorphous silicon.
[0014]
[Problems to be solved by the invention]
An object of the present invention is to provide a radiation conversion sheet for digital X-ray imaging, which prevents foreign matter from being mixed, does not cause warpage of a photoelectric conversion imaging element, and has no sensitivity distribution, and a digital X-ray imaging apparatus using the same. is there.
[0015]
[Means for Solving the Problems]
Therefore, the radiation conversion sheet for digital radiography of the present invention is characterized in that at least a substrate, a phosphor layer, an adhesive layer, and a transparent release film are sequentially laminated.
[0016]
Preferred aspects of the invention are as follows.
[0017]
The pressure-sensitive adhesive layer is made of an acrylic pressure-sensitive adhesive.
[0018]
The acrylic pressure-sensitive adhesive is composed of 1) a main monomer for imparting tackiness, and 2) a polar group-containing monomer for imparting adhesiveness.
[0019]
The polar group of the polar group-containing monomer is a hydroxyl group.
[0020]
Further, the digital X-ray imaging apparatus of the present invention, after peeling the transparent release film of the above-mentioned radiation conversion sheet for digital X-ray imaging, laminates the sheet on the surface of the photoelectric conversion imaging element via the adhesive layer. It is characterized by having done.
[0021]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a cross-sectional view of the radiation conversion sheet for digital X-ray imaging of the present invention.
[0022]
The substrate 1 functions as a substrate sheet for forming a phosphor layer. As the substrate 1, a material that transmits X-rays is preferable. As a material of the base material 1, a plastic substrate, a silicon substrate, a carbon substrate, or the like can be used.
[0023]
As the plastic material, a resin material such as polyethylene terephthalate, polycarbonate, or polyethylene naphthalate, or a white resin material in which a pigment such as titanium oxide or aluminum oxide is mixed into the resin material can be used. The thickness of the substrate 1 is preferably 0.1 to 2 mm in order to ensure a sufficient amount of X-ray transmission.
[0024]
The phosphor layer 2 has a function of converting X-rays into visible light. A particulate phosphor layer composed of a phosphor material and a binder resin is used. As the phosphor material, particles such as Gd ₃ O ₂ S ₂ : Tb and Gd ₃ O ₂ S ₂ : Eu are used. Further, it can also be obtained by forming a columnar crystal layer such as CsI: Tl on the substrate 1 by an evaporation method.
[0025]
The pressure-sensitive adhesive layer 3 may be any of a rubber-based pressure-sensitive adhesive, an acrylic-based pressure-sensitive adhesive, a silicone-based pressure-sensitive adhesive, and among others, it is particularly preferable to mainly use an acrylic-based pressure-sensitive adhesive. The acrylic pressure-sensitive adhesive is composed of a polymer or copolymer mainly comprising a low Tg main monomer component for imparting tackiness, and a polar group-containing monomer component for crosslinking and improving adhesion.
[0026]
Examples of the main monomer component include alkyl acrylates such as ethyl acrylate, butyl acrylate, amyl acrylate, 2-ethylhexyl acrylate, octyl acrylate, cyclohexyl acrylate and benzyl acrylate, butyl methacrylate, and methacrylic acid. And alkyl methacrylates such as 2-ethylhexyl acid, cyclohexyl methacrylate, and benzyl methacrylate.
[0027]
Examples of the polar group-containing monomer component include carboxyl group-containing monomers such as acrylic acid, methacrylic acid, maleic acid, and itaconic acid, 2-hydroxyethyl (meth) acrylate, and 2-hydroxypropyl (meth) acrylate. And hydroxyl group-containing monomers such as N-methylolacrylamide, acrylamide, methacrylamide, glycidyl methacrylate and the like.
[0028]
The reason why such a material is preferable is that, in addition to being excellent in tackiness and cohesiveness, there is no unsaturated bond in the polymer, so the stability to light and oxygen is high, and the type and molecular weight of the monomer are selected to suit the application. This is because any quality and characteristics can be obtained.
[0029]
Particularly, as the polar group-containing monomer component, a hydroxyl group-containing monomer such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, or N-methylolacrylamide is preferable.
[0030]
A hydroxyl group (-OH) as a polar group is less likely to dissociate than a carboxyl group (-COOH). As a result, the possibility of affecting the potential of the photoelectric conversion imaging device using a semiconductor is reduced, and a change in the sensitivity of the photoelectric conversion imaging device hardly occurs. Therefore, an image captured by a large-screen digital X-ray imaging apparatus is clear, an image without ghost is obtained, and an X-ray image without misdiagnosis is obtained.
[0031]
Examples of the rubber-based pressure-sensitive adhesive include natural rubber-based, isoprene-based, styrene-butadiene-based, recycled rubber-based, and polyisobutylene-based adhesives, and blocks containing rubbers such as styrene-isoprene-styrene and styrene-butadiene-styrene. Those mainly comprising a copolymer are exemplified. Examples of the silicone-based pressure-sensitive adhesive include dimethylsiloxane-based and diphenylsiloxane-based adhesives.
[0032]
As the above-mentioned pressure-sensitive adhesive, any of a crosslinked type and a non-crosslinked type can be used. In the case of a cross-linking type, a method using various cross-linking agents such as an epoxy compound, an isocyanate compound, a metal chelate compound, a metal alkoxide, a metal salt, an amine compound, a hydrazine compound, and an aldehyde compound, or a method of irradiating radiation is used. These are appropriately selected according to the type of the functional group and the like.
[0033]
As the pressure-sensitive adhesive, one having a light-transmitting property at a wavelength at which light is exposed in a photoelectric conversion imaging device is essential. A plasticizer is added to such an adhesive as needed. Examples of the plasticizer include esters such as phthalic acid ester, trimellitic acid ester, pyromellitic acid ester, adipic acid ester, sebacic acid ester, phosphoric acid triester, and glycol ester, process oil, liquid polyether, and liquid polyterpene. And other liquid resins, and one or more of these can be used as a mixture.
[0034]
In addition to the plasticizer, various additives such as an ultraviolet absorber and an antioxidant can be added as necessary.
[0035]
As the release film 4, any one may be used. For example, a film composed of various resins such as polyethylene terephthalate, polycarbonate, polyarylate, and polypropylene is used as a base material, and the base material is bonded to the pressure-sensitive adhesive layer 3. One having a release coat layer (silicone layer) (not shown) formed on the surface can be used. It is desired that the adhesion of the release film 4 to the pressure-sensitive adhesive layer 3 be sufficiently lower than the adhesion of the pressure-sensitive adhesive layer 3 to the phosphor layer 2. Further, the release film 4 is desired to be optically transparent. It is desired that the phosphor layer is transparent at least in a wavelength region of the fluorescence generated by the phosphor layer. Before the radiation conversion sheet for digital X-ray imaging is laminated on the photoelectric conversion imaging device, the radiation conversion sheet is inspected for dust particles contained in the phosphor layer or the adhesive layer, or on the surface, and has a non-standard dust particle. The release film needs to be transparent in order to exclude the radiation conversion sheet for digital radiography as a defective product. For example, a polyester film (PET) is a preferable film.
[0036]
FIG. 2 shows a cross-sectional view of the pressure-sensitive adhesive sheet with a release film.
[0037]
After applying and curing an adhesive on the surface of the release film 41, the adhesive layer 3 having a thickness of 5 to 20 μm was formed, and then a release film 42 was laminated on the adhesive layer 3. There is a difference in the adhesive strength between the release films 41 and 42 to the pressure-sensitive adhesive layer 3, and it is designed so that either one of the release films can be easily peeled off.
[0038]
【Example】
Example 1
1) Release sheet 41
Constituent materials: polyester film, silicone treatment on one side (manufactured by Lintec, SP, PET25)
Thickness: 25 μm
On the other hand, the release sheet 42 is made of the same material as the release sheet 41 and has a thickness of 38 μm, but has not been subjected to silicone treatment.
[0039]
2) Pressure sensitive adhesive sheet Acrylic acid: 10 parts by mass to 90 parts by mass of acrylate: 90 parts by mass of acrylic acid ester polymer (pressure sensitive adhesive): 99.9 parts by mass of trimethylolpropane tolylene diisocyanate ( Crosslinking agent): 0.1 parts by mass was mixed to prepare an adhesive solution. This solution was applied on the silicone-treated surface of the release sheet 41, and was heat-cured and dried at 80 ° C. to form the pressure-sensitive adhesive layer 3. A release film 42 was further laminated thereon to obtain a pressure-sensitive adhesive sheet.
[0040]
3) Phosphor sheet with adhesive layer (radiation conversion sheet for digital radiography)
FIG. 3 is a diagram showing an outline of a method for producing a radiation conversion sheet for digital X-ray imaging according to the present invention.
[0041]
A 100-m scroll of a white PET material (E400, manufactured by Toray Industries, Ltd.) 11 having a thickness of 188 μm was prepared.
[0042]
A first phosphor layer 31 (thickness 30 μm) is applied to the surface of the white PET material 11, and then a second phosphor layer 32 (thickness 150 μm) is applied, and then the solvent is dried. Got. As the phosphor, a material in which Gd ₃ O ₂ S ₂ : Tb was dispersed in a binder resin was used. Next, the adhesive film was continuously adhered to the surface of the phosphor layer 32 while peeling off the release film 41 of the pressure-sensitive adhesive sheet prepared in 2).
[0043]
Next, it is cut into a predetermined size, and foreign substances on the base material, the phosphor layer, and the adhesive layer are detected by an X-ray inspection, and non-standard defective products are eliminated. Then, as shown in FIG. A radiation conversion sheet for digital radiography with an adhesive layer was obtained.
[0044]
Example 2
Butyl acrylate: 90 parts by mass of 2-hydroxyethyl (meth) acrylate: 10 parts by mass of acrylate ester-based polymer (adhesive): 99.9 parts by mass of trimethylolpropane tolylene diisocyanate (Crosslinking agent): The solution was changed to a solution in which 0.1 parts by mass was mixed, and an adhesive solution was prepared. This solution was applied onto the silicone-treated surface of the release sheet 41 of Comparative Example 1, dried by heat curing at 80 ° C., and a release film 42 was laminated thereon to obtain an adhesive sheet.
[0045]
Using the above-mentioned adhesive, a radiation conversion sheet for digital radiography with an adhesive layer using an adhesive material having an —OH group as a polar group was obtained. No foreign matter was mixed into the sheet.
[0046]
Example 3
Immediately after the release film 41 of the radiation conversion sheet for digital radiography obtained in Example 1 was peeled off, it was laminated on the surface of a semiconductor photoelectric conversion imaging device (sensor) made of amorphous silicon at room temperature using a roll laminator. 4 was obtained.
[0047]
Example 4
In Example 3, the radiation conversion sheet for digital radiography used there was replaced with the radiation conversion sheet for digital radiography obtained in Example 2 to obtain a digital radiography apparatus.
[0048]
The sensitivity distribution of the obtained digital X-ray imaging apparatus was smaller than that of the digital X-ray imaging apparatus obtained in Example 3. No foreign matter was mixed into the apparatus.
[0049]
【The invention's effect】
1. The cost of laminating the radiation conversion sheet for digital X-ray imaging on the surface of the photoelectric conversion imaging device has been reduced by half. For example, assuming that the cost of applying and forming the adhesive one by one on the photoelectric conversion imaging device is 100, the cost of Example 2 was 50.
[0050]
2. Lamination of the radiation conversion sheet for digital X-ray imaging on the surface of the photoelectric conversion imaging element becomes possible at room temperature, and the radiation conversion sheet for digital X-ray imaging / adhesive layer (adhesive layer) / photoelectric conversion imaging element / glass substrate The warpage of the element composed of is eliminated.
[0051]
3. By making the polar group of the acrylic pressure-sensitive adhesive a hydroxyl group (-OH), digital X-ray imaging having a small sensitivity distribution with a small influence of a weak potential change on a photoelectric conversion imaging device made of amorphous silicon The device was obtained.
[0052]
4. Since the release film was transparent, foreign substances were easily monitored, and a radiation conversion sheet for digital X-ray photography free of foreign substances was obtained.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a radiation conversion sheet for digital radiography with an adhesive layer of the present invention.
FIG. 2 is a sectional view of a pressure-sensitive adhesive sheet with a release film used in the present invention.
FIG. 3 is a view showing an outline of a manufacturing process of the radiation conversion sheet for digital X-ray photography with an adhesive of the present invention.
FIG. 4 is a schematic diagram of a digital X-ray imaging apparatus.
[Explanation of symbols]
Reference Signs List 1 base material 2 phosphor layer 3 adhesive layer 4 release film 31 first phosphor layer 32 second phosphor layers 41, 42 release film

Claims (5)

A radiation conversion sheet for digital radiography, wherein at least a substrate / phosphor layer / adhesive layer / transparent release film are sequentially laminated. 2. The radiation conversion sheet according to claim 1, wherein the pressure-sensitive adhesive layer is made of an acrylic pressure-sensitive adhesive. 3. The digital radiography according to claim 2, wherein the acrylic pressure-sensitive adhesive comprises at least 1) a main monomer for imparting tackiness, and 2) a copolymer polymer comprising a polar group-containing monomer for imparting adhesiveness. Radiation conversion sheet. The radiation conversion sheet according to claim 3, wherein the polar group of the polar group-containing monomer is a hydroxyl group. After peeling off the transparent release film of the radiation conversion sheet for digital radiography according to any one of claims 1 to 4, laminating the sheet on the surface of a photoelectric conversion imaging element via the adhesive layer of the sheet. A digital radiography apparatus characterized by the following.

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