JP2005114518A - Radiation detection device and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To uniformize in-plane distribution of sharpness caused by a film thickness distribution of a phosphor layer, and to prevent lamination deficiency between a scintillator and a photodetector. <P>SOLUTION: In this radiation detection device, constituted of the scintillator 11 wherein the phosphor layer 7 for converting a radiation into light is supported on a support substrate 9, and the photodetector 5, comprising a plurality of photoelectric conversion elements 2 for converting light into an electrical signal, the surface in contact with the phosphor layer 7 of the substrate 9 for supporting the phosphor layer 7 is a recessed surface. The recessed shape of the substrate 9, whose bottom part coincide approximately with the center part of the substrate 9 is a shape compensating the film thickness distribution of the phosphor layer 7, and the phosphor layer comprises an aggregate of fine columnar crystals of CsI. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a radiation detection apparatus, a manufacturing method thereof, and a radiation detection system, and more particularly, to a radiation detection apparatus used for X-ray imaging and the like and a manufacturing method thereof. In this specification, the description will be made assuming that electromagnetic waves such as X-rays and γ-rays are also included in the radiation.

  Conventionally, a radiation detection apparatus comprising a radiation intensifying screen having a phosphor layer for converting X-rays into light and a radiation film having a photosensitive layer has been generally used for X-ray photography.

  However, recently, a flat panel radiation detection apparatus having a scintillator made of a phosphor layer and a two-dimensional photodetector made of a photoelectric conversion element has been developed. This digital radiation detector can easily process images because the data obtained is digital data. Data can be shared by importing it into a networked computer system, and the image digital data can be stored on a magneto-optical disk or the like. For example, the storage space can be remarkably reduced as compared with the case of storing a film, and the past images can be easily retrieved. At this time, in order to reduce the exposure dose to the patient, a digital radiation detection apparatus having high sensitivity and high sharpness characteristics is required.

For example, in Patent Document 1 below, a scintillator in which a phosphor layer made of an aggregate of fine columnar crystals of cesium iodide (hereinafter referred to as CsI) formed by a vacuum deposition method on a parallel plate substrate and light detection are disclosed. A radiation detection apparatus having a combined device is disclosed. This radiation detection device was able to dramatically improve the sensitivity and sharpness compared to a conventional phosphor layer in which fine powders of particulate crystal were assembled.
Japanese Patent No. 3126715

  However, according to the conventional technology described above, the following problems occur. That is, the CsI phosphor layer produced on the parallel plate substrate by vacuum vapor deposition has a convex shape centered on the central portion of the substrate. For this reason, when the photodetector that is a parallel plate is joined to the scintillator through, for example, an adhesive layer, the thickness of the adhesive layer at the center of the photodetector is reduced and the peripheral portion is formed thicker. The distance between the scintillator and the photodetector increases from the center toward the periphery. When a distance is generated between the scintillator and the photodetector, the sharpness as a radiation detection apparatus has a negative correlation with the distance, and the sharpness decreases as the distance increases. Therefore, the sharpness of the radiation detection apparatus has a problem that the sharpness decreases as it goes from the central part to the peripheral part.

  In addition, if the scintillator is bent and joined along the plane of the photodetector through the adhesive layer, a stress that tends to return due to the rigidity of the scintillator is generated, and the adhesive layer is cured before the adhesive layer is cured. Defects such as delamination occur at the periphery of the adhesive layer due to defects that bubbles enter or long-term storage tests.

  Therefore, the present invention makes the substrate concave rather than flat so as to offset the film thickness distribution of the phosphor layer produced by vacuum deposition on the substrate, and flattenes the bonding surface of the scintillator with the photodetector. Accordingly, it is an object to make the in-plane distribution of sharpness uniform due to the film thickness distribution of the phosphor layer, and to prevent a problem of bonding of the scintillator and the photodetector.

  In order to solve the above-described problems, a radiation detection apparatus according to the present invention includes a scintillator that supports a phosphor layer that converts radiation into light on a support substrate, and a light that includes a plurality of photoelectric conversion elements that convert light into an electrical signal. In the radiation detection apparatus including the detector, the surface of the support substrate that contacts the phosphor layer is a concave surface.

  In particular, the phosphor layer is characterized by comprising an aggregate of fine columnar crystals of CsI.

  The concave bottom portion of the support substrate substantially coincides with the central portion of the support substrate.

  The concave shape of the support substrate is a shape that cancels out the film thickness distribution of the phosphor layer.

  The support substrate may have a vertical part around the concave surface.

  Furthermore, the manufacturing method of the radiation detection apparatus according to the present invention includes a scintillator configured by supporting a phosphor layer that converts radiation into light on a support substrate, and the plurality of photoelectric conversion elements that convert the scintillator into light into an electrical signal. In the manufacturing method of the radiation detection apparatus which adhere | attaches to the photodetector which consists of, the surface which contact | connects the fluorescent substance layer of the said support substrate is previously formed in a concave surface, The said fluorescent substance layer is formed by vacuum evaporation.

  According to the present invention, even if a convex film thickness distribution occurs in the phosphor layer, since the substrate has a concave shape, the in-plane distance of the joining surface of the scintillator and the photodetector can be made uniform, The sharpness distribution of the radiation detection apparatus can be reduced. In addition, since the scintillator and the photodetector can be joined without any stress remaining in the joining process of the scintillator and the photodetector, problems such as generation of bubbles and delamination at the junction between the scintillator and the photodetector of the radiation detection apparatus also occur. It is possible to provide a radiation detection apparatus that does not cause any problems.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1)
FIG. 1 is a cross-sectional view of a radiation detection apparatus according to Embodiment 1 of the present invention.

  In FIG. 1, a photodetector 5 consisting of 1 to 4 and a scintillator 11 consisting of 7 to 10 are joined via an adhesive layer 6.

  In FIG. 1, reference numeral 1 denotes a substrate for a photodetector having insulating properties such as a glass substrate, and 2 denotes a photoelectric conversion element using a semiconductor thin film made of amorphous silicon, for example. A semiconductor element such as a TFT for controlling the reading of electric charges and a wiring are arranged, and reference numeral 4 denotes a photodetector protective layer for protecting the semiconductor element inside the photodetector, which constitutes the photodetector 5.

  At this time, the photoelectric conversion elements 2 are arranged with a gap of about 20 to 60 μm each having a size of 100 to 200 μm square.

  Reference numeral 7 denotes a phosphor layer that converts radiation into light. Reference numeral 8 denotes a light reflecting layer that is provided as necessary. When high sensitivity is required, the light reflecting layer is used. . Reference numeral 9 denotes a support substrate that supports the phosphor layer 7 through the light reflecting layer 8, and 10 denotes a phosphor protective layer. These constitute the scintillator 11.

  FIG. 2 is a view schematically showing a cross section of the phosphor support substrate of the scintillator in Embodiment 1 of the present invention.

  The phosphor support substrate 9 has a concave bottom that is substantially coincident with the center.

  FIG. 3 is a diagram schematically showing a cross section of the scintillator according to Embodiment 1 of the present invention.

  In FIG. 3, a light reflection layer 8 is formed on the phosphor support substrate 9 shown in FIG. 2, and a phosphor layer 7 is further formed thereon. A protective layer can be formed on the scintillator as necessary. When the phosphor layer 7 made of CsI having high sensitivity and high sharpness is formed by vapor deposition, the thickness of the phosphor layer 7 becomes thicker as it goes to the peripheral portion. Therefore, by using the phosphor support substrate having the concave cross-sectional shape shown in FIG. 2, a flat scintillator in which the phosphor film thickness distribution shown in FIG. 3 is offset can be obtained.

  The radiation detection apparatus according to the present invention is formed by bonding a scintillator to a photodetector via an adhesive layer thereon, and the adhesive layer can obtain a uniform film thickness distribution. The in-plane distribution of the sharpness of the apparatus can be kept small.

  The distance between the bottom and the top of the concave substrate is set by the distribution of the deposited film thickness, but is usually a distance of about 20 to 100 μm.

  Examples of the phosphor material having a columnar structure include cesium iodide and cesium bromide. Moreover, sodium and thallium are mentioned as an activator of these fluorescent substances. The addition amount of the activator varies depending on the material, but is in the range of 0 to 0.5 mol%.

  The thickness of the phosphor layer 7 varies depending on the material of the phosphor, but is approximately 50 to 700 μm in order to efficiently absorb radiation.

  As the phosphor support substrate 9, a conventionally used material having high X-ray transparency, high heat resistance, and high rigidity can be used, and a light reflection layer is also conventionally used. A material having high heat resistance, high adhesion to the phosphor support substrate, and high light reflectivity can be used.

  As the adhesive 6, a known transparent adhesive can be used, but a hot-melt adhesive or pressure-sensitive adhesive is particularly preferable because the manufacturing process can be simplified.

  The phosphor support substrate 9 having a concave cross section according to the present invention is produced by a method by press molding, or a method in which a parallel plate is mechanically deleted by grinding, polishing, sandblasting or the like to form a concave shape.

  The phosphor layer can be formed by a conventionally known vacuum vapor deposition method, and the phosphor material is disposed in a vapor deposition port as a vapor deposition source of a vapor deposition apparatus, and a phosphor having a concave cross section in which a light reflecting layer is formed. The scintillator of the present invention can be manufactured by placing the support substrate on the substrate holder and performing vapor deposition.

  The scintillator thus obtained is subjected to a step of activating the activator by applying heat at 100 ° C. to 400 ° C. for 0.5 to 5 hours, and then passed through the adhesive layer 7 to the photodetector 5. The radiation detection apparatus of the present invention can be manufactured by pasting together.

  Hereinafter, a method for manufacturing the radiation detection apparatus of the present invention will be described.

  A photoelectric conversion gap 3 composed of an amorphous silicon photoelectric conversion element 2 and an electric element such as a TFT is formed on a non-alkali glass substrate which is a substrate for photodetectors 1 having a thickness of 1.0 mm and a size of 500 mm square, and a photoelectric conversion gap 3 formed on the non-alkali glass substrate. A photodetector protective layer 4 made of SiNx was formed to produce a photodetector 5.

  The phosphor support substrate 9 made of amorphous carbon having a thickness of 1.0 mm and a size of 500 mm is processed by grinding so that the cross section thereof becomes concave, and the curved surface is polished and finished to a predetermined surface roughness. A phosphor support substrate 9 having a continuous concave curved surface as shown in FIG. The distance between the bottom and the top of the concave substrate was 50 μm.

  On the phosphor support substrate 9, 1500 mm of aluminum thin film was formed as the light reflecting layer 8 by a sputtering method.

  FIG. 6 is a diagram schematically showing a vapor deposition apparatus used for manufacturing the radiation detection apparatus according to the first embodiment of the present invention.

  This vapor deposition apparatus is common to the case of Embodiment 2 described later.

  Next, the phosphor support substrate 9 with the light reflection layer 8 was placed on a substrate holder of a vapor deposition apparatus as shown in FIG. 6 used for manufacturing a radiation detection apparatus. Vacuum deposition was performed by placing CsI at three ports of the deposition source 24 and thallium iodide at the deposition source 25. The deposited CsI had a thickness of 500 μm at the central part of the substrate and 450 μm at the peripheral part, and the phosphor layer 7 having a shape that complemented the concave portion of the substrate and became a flat surface could be formed. After vapor deposition, the scintillator was heated uniformly at 250 ° C. for 2 hours to activate the activator, and the scintillator 11 shown in FIG. 3 was produced.

  Next, using a hot-melt adhesive made of an ethylene-acrylic acid copolymer, the photodetector 5 and the scintillator 11 were thermally laminated with a roll laminator to produce a radiation detection apparatus.

(Embodiment 2)
Hereinafter, a method for manufacturing the radiation detection apparatus according to the second embodiment of the present invention will be described.

  A photoelectric conversion gap 3 composed of an amorphous silicon photoelectric conversion element 2 and an electric element such as a TFT is formed on a non-alkali glass substrate, which is a substrate 1 for a photodetector having a thickness of 1.0 mm, and light detection made of SiNx is formed thereon. A detector protective layer 4 was formed to produce a photodetector 5.

  FIG. 4 is a view schematically showing a cross section of the phosphor support substrate of the scintillator according to Embodiment 2 of the present invention.

  A phosphor support substrate made of amorphous carbon having a thickness of 1.0 mm and a size of 500 mm is ground so that the cross section thereof becomes a concave shape having a vertical portion around it, and the concave curved surface is polished to obtain a predetermined surface roughness. Then, a phosphor supporting substrate 9 having a concave curved shape having a vertical portion around the periphery as shown in FIG. 4 was produced. The distance between the bottom and the top of the concave substrate was 50 μm.

  FIG. 5 is a diagram schematically showing a cross section of a scintillator according to Embodiment 2 of the present invention.

  On the phosphor support substrate 9, 1500 mm of an aluminum thin film was formed as a light reflecting layer by a sputtering method.

  Next, the phosphor support substrate 9 with the light reflection layer was placed on the substrate holder of the vapor deposition apparatus as shown in FIG. Vacuum deposition was performed by placing CsI at three ports of the deposition source 24 and thallium iodide at the deposition source 25. The deposited CsI had a thickness of 500 μm at the central part of the substrate and 450 μm at the peripheral part, and the phosphor layer 7 having a shape that complemented the concave portion of the substrate and became a flat surface could be formed. After vapor deposition, the scintillator 11 was uniformly heated at 250 ° C. for 2 hours to activate the activator, and the scintillator 11 shown in FIG. 5 was produced.

  The phosphor support substrate 9 having such a shape can be protected so that the phosphor layer 7 is sealed by the vertical portion.

  Next, a hot-melt adhesive made of an ethylene-acrylic acid copolymer, the photodetector 5 and the scintillator 11 were thermally laminated with a roll laminator to produce a radiation detection apparatus.

(Comparative example)
The photodetector 5 was produced in the same manner as in the first embodiment.
A parallel plane substrate made of amorphous carbon having a thickness of 1.0 mm and a size of 500 mm was used as a phosphor support substrate.

  On the phosphor support substrate 9, 1500 mm of aluminum thin film was formed as the light reflecting layer 8 by a sputtering method.

  The scintillator was manufactured by a conventional method.

  Next, the photodetector 5 and the scintillator 11 were thermally laminated with a roll laminator to produce a radiation detection apparatus.

  Table 1 shows the results of measuring MTF at 2 lp / mm in the outer peripheral part and the central part as the sharpness of the radiation detection apparatus produced as described above. Photographed with X-rays with a tube voltage of 80 kvp through a 10 cm water phantom. The first and second embodiments and the comparative example were compared by setting the sharpness of the central portion of the comparative example to 100.

（実施形態３）
図７は、本発明の実施形態３において放射線検出装置を放射線検出システムとして応用した例を示す図である。

(Embodiment 3)
FIG. 7 is a diagram showing an example in which the radiation detection apparatus is applied as a radiation detection system in Embodiment 3 of the present invention.

  The radiation detection apparatus is the radiation detection apparatus in the first and second embodiments.

  The X-ray 6060 generated by the X-ray tube 6050 passes through the chest 6062 of the patient or subject 6061 and enters the radiation detection device 6040 that captures a radiographic image. This incident X-ray includes information inside the body of the patient 6061. The scintillator (phosphor layer) of the radiation detection device 6040 emits light in response to the incidence of X-rays, and this is photoelectrically converted to obtain electrical information. This information can be digitally converted, image-processed by an image processor 6070, and observed on a display 6080 as display means in a control room.

  This information can be transferred to a remote place by transmission means such as a telephone line 6090, displayed on a display 6081 in a doctor room or the like in another place, or stored in a storage means such as an optical disk. Can also be diagnosed. It can also be recorded on the film 6110 by the film processor 6100.

Sectional drawing of the radiation detection apparatus in Embodiment 1 of this invention The figure which showed typically the cross section of the fluorescent substance support substrate of a scintillator similarly The figure which showed the section of a scintillator typically similarly The figure which showed typically the cross section of the fluorescent substance support substrate of the scintillator in Embodiment 2 of this invention. The figure which showed the section of a scintillator typically similarly The figure which showed typically the vapor deposition apparatus used for manufacture of the radiation detection apparatus in Embodiment 1, 2 of this invention. The figure which shows the example which applied the radiation detection apparatus as radiation detection system in Embodiment 3 of this invention

Explanation of symbols

1 Photodetector substrate 2 Photoelectric conversion element 3 Photoelectric conversion element gap 4 Photodetector protective layer 5 Photodetector 6 Adhesive layer 7 Phosphor layer 8 Light reflecting layer 9 Phosphor layer support substrate 10 Phosphor protective layer 11 Scintillator 20 Vacuum Vacuum tank of vapor deposition apparatus 21 CsI scattering direction 22 Thallium iodide scattering direction 23 Thallium iodide vapor deposition port 24 CsI vapor deposition port 25 Vapor deposition heating source

Claims (7)

  In the radiation detection apparatus, comprising: a scintillator that supports a phosphor layer that converts radiation into light on a support substrate; and a photodetector that includes a plurality of photoelectric conversion elements that convert light into an electrical signal. The radiation detection apparatus characterized in that the surface in contact with the phosphor layer is a concave surface.   The radiation detection apparatus according to claim 1, wherein the phosphor layer is made of an aggregate of fine columnar crystals of CsI.   The radiation detection apparatus according to claim 1, wherein a bottom portion of the concave shape of the support substrate substantially coincides with a central portion of the support substrate.   The radiation detection apparatus according to claim 1, wherein the concave shape of the support substrate is a shape that cancels out the film thickness distribution of the phosphor layer.   The radiation detection apparatus according to claim 1, wherein the support substrate has a shape having a vertical portion around a concave surface.   Production of a radiation detection apparatus for forming a scintillator by supporting a phosphor layer that converts radiation into light on a support substrate, and bonding the scintillator to a photodetector comprising a plurality of photoelectric conversion elements that convert light into electrical signals In the method, the surface of the support substrate that contacts the phosphor layer is formed in a concave surface in advance, and the phosphor layer is formed by vacuum vapor deposition.   From the radiation detection apparatus according to claim 1, a signal processing unit that processes a signal from the radiation detection apparatus as an image, a recording unit that records a signal from the processing unit, and the processing unit A radiation detection system comprising: display means for displaying a signal of the above; transmission means for transmitting a signal from the processing means; and a radiation source for generating the radiation.

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