Radiation detector and method for manufacturing radiation detector

Abstract

To provide a radiation detector having a long product life, and a method for manufacturing the radiation detector.SOLUTION: A radiation detector is provided, comprising: an array substrate having a plurality of photoelectric conversion elements arranged in lattice form on one side; a scintillator provided on one side of the array substrate; an adhesive layer surrounding the scintillator and provided with an adhesive in frame shape on one side of the array substrate; and a moisture-proof body provided on one side of the scintillator, adhered to the adhesive layer and covering the scintillator together with the array substrate and the adhesive layer. The radiation detector further comprises a reflection layer provided between the scintillator and the moisture-proof body, and reflecting, toward the scintillator, the radiation having entered the scintillator. In the radiation detector, the reflection layer fixes the moisture-proof body and the scintillator.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] FIELD OF THE INVENTION Embodiments of the present invention relate to a radiation detector and a method for manufacturing a radiation detector. [Background technology]

[0002] X-ray detectors are becoming increasingly popular as radiation detectors, replacing X-ray film in diagnostic imaging equipment. Compared to X-ray film, X-ray detectors have the advantages of a very short time from taking an X-ray to confirming the image, a wide dynamic range of the image, and no need for chemicals for film development. Most X-ray detectors currently in practical use convert the X-ray image that has passed through the human body, etc., into visible light, called fluorescence, using phosphors inside the X-ray detector. The converted fluorescent image is then converted into an electrical signal by photodetectors arranged in a grid pattern on an array substrate, and image information created based on the converted electrical signal is output to the outside.

[0003] In general, this type of radiation detector comprises an array substrate having a plurality of photoelectric conversion elements arranged in a grid pattern, a scintillator provided on one side of the plurality of photoelectric conversion elements, an adhesive layer surrounding the scintillator and provided with adhesive in a frame shape on one side of the array substrate, a moisture-proof body provided on one side of the scintillator, and a reflective layer provided between the scintillator and the moisture-proof body. The array substrate, scintillator, reflective layer, and moisture-proof body are stacked one on top of the other. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-105591 Summary of the Invention [Problem to be solved by the invention]

[0005] However, due to manufacturing defects, etc., leak paths may occur between the array substrate and the moisture-proof body, or the adhesion between the scintillator and reflective layer, which are stacked together, or between the reflective layer and the moisture-proof body may decrease. If the leak path or the adhesion between the scintillator and the reflective layer or between the reflective layer and the moisture-proof body is reduced, the product will deteriorate and its lifespan will be shortened.

[0006] An object of the present embodiment is to provide a radiation detector with a long product life and a method for manufacturing the radiation detector. [Means for solving the problem]

[0007] One embodiment of the present invention relates to a radiation detector including an array substrate having a plurality of photoelectric conversion elements arranged in a grid pattern on one side thereof, a scintillator provided on one side of the array substrate, an adhesive layer surrounding the scintillator and having an adhesive provided in a frame shape on one side of the array substrate, and a moisture-proof body provided on one side of the scintillator, the moisture-proof body being adhered to the adhesive layer and covering the scintillator layer together with the array substrate and the adhesive layer, The radiation detector is provided with a reflective layer disposed between the scintillator and the moisture-proof body, which reflects radiation incident on the scintillator toward the scintillator, and the reflective layer fixes the moisture-proof body and the scintillator.

[0008] Another embodiment is a method for manufacturing a radiation detector according to the above embodiment, wherein the reflective layer includes a molten resin-based binder, and the reflective layer is formed on one side of the scintillator, a moisture-proof body is placed on one side of the reflective layer, and the resin-based binder of the reflective layer is solidified. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is an exploded perspective view showing a schematic configuration of a radiation detector according to an embodiment. [Figure 2] FIG. 2 is a vertical cross-sectional view showing a schematic configuration of the radiation detector shown in FIG. [Figure 3] FIG. 3 is a vertical cross-sectional view showing an example of a method for manufacturing the radiation detector shown in FIG. 2, illustrating a state before a moisture-proof body is attached. [Figure 4] FIG. 4 is a vertical cross-sectional view illustrating the operation of the radiation detector shown in FIG. [Figure 5] FIG. 5 is a comparative example, and is a longitudinal sectional view showing an example of a state in which leakage occurs in the radiation detector shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0010] The present embodiment will be described below with reference to the drawings. The disclosure is merely an example, and appropriate modifications that a person skilled in the art can easily make while maintaining the gist of the invention are naturally included within the scope of the present invention. Furthermore, the drawings may be schematic in terms of the width, thickness, shape, etc. of each part compared to the actual embodiment for clarity of explanation, but these are merely examples and are not intended to limit the interpretation of the present invention. Furthermore, in this specification and each drawing, components that perform the same or similar functions as those described above with reference to the previous drawings are designated by the same reference numerals, and redundant detailed descriptions may be omitted as appropriate.

[0011] In this embodiment, an X-ray detector will be described as an example of a radiation detector. Note that the main components disclosed in this embodiment can also be applied to radiation detectors for detecting various types of radiation, such as gamma rays, in addition to X-rays. Here, as an example, a case related to X-rays, which are representative of radiation, will be described. Therefore, by replacing "X-rays" in the following embodiments with "other radiation," the invention can also be applied to other radiations.

[0012] The radiation detector can be used in, for example, general medical care, etc. However, the use of the radiation detector is not limited to general medical care.

[0013] As shown in FIGS. 1 and 2, the radiation detector 1 includes a photoelectric conversion unit 3, an array substrate 5, and a circuit board . The photoelectric conversion section 3 converts the incident radiation (X-rays) received into fluorescent light. The array substrate 5 is formed on one surface (X-ray incident side) of the circuit board 7, and is provided with a plurality of photoelectric conversion elements 8 to convert the fluorescence into an electrical signal. The circuit board 7 is electrically connected to the array board 5, and electrically processes the output signal from the array board 5 and converts it into an image signal.

[0014] As shown in Figure 2, the photoelectric conversion unit 3 includes a scintillator 9 provided on one side of the array substrate 5, a reflective layer 11, and a moisture-proof body 13, and the moisture-proof body 13 is adhered to the array substrate 5 at its periphery by an adhesive layer 15. The scintillator 9 is made of thallium-activated cesium iodide (CsI:Tl), which is formed in a columnar shape on the array substrate 5 by using vacuum deposition. The scintillator 9 made of thallium-activated cesium iodide is formed in the shape of columnar crystals with an extremely elongated structure by vacuum deposition.

[0015] The photoelectric conversion unit 3 has a reduced pressure inside, which is covered with the scintillator 9, the reflective layer 11, the moisture-proof body 13, the adhesive layer 15, and the array substrate 5. Therefore, the space 17 shown in Fig. 2 is a reduced-pressure space. The reflective layer 11 is formed by applying and drying a white pigment, and contains a plurality of light-scattering particles and a resin-based binder. By forming the reflective layer 11 on one side (upper side) of the scintillator 9, adhering the moisture-proof body 13 to the reflective layer 11, and drying the reflective layer 11, the moisture-proof body 13 and the scintillator 9 can be bonded and fixed by the reflective layer 11. The light-scattering particles are a metal oxide such as titanium oxide.

[0016] The moisture-proof body 13 is a metal foil having moisture permeability, for example, a metal film such as an Al (aluminum) laminate film. The periphery of the moisture-proof body 13 is adhered to the adhesive layer 15 of the array substrate 5 to seal the periphery of the scintillator 9 . It is desirable that the moisture-proof body 13 contains a material with a low moisture permeability coefficient, such as polypropylene (PP) or polyethylene (PE), in order to minimize moisture permeation through the space 17 surrounded by the moisture-proof body 13, adhesive layer 15, and array substrate 5. The adhesive layer 15 surrounds the scintillator 9 with an adhesive and is arranged in a frame shape on one side of the array substrate 5. The adhesive of the adhesive layer 15 is a thermoplastic resin whose main components are polyethylene and polypropylene.

[0017] Next, the array substrate 5 will be described. The array substrate 5 is formed with a glass substrate 21 and photoelectric conversion elements 8 having pixels arranged in a grid pattern on the glass substrate 21. The photoelectric conversion element 8 includes a plurality of photodetection sections formed two-dimensionally on the glass substrate 21, and signal lines formed along the row and column directions of the photodetection sections. The photodetection sections include switching elements and photosensors as photoelectric conversion elements. The switching elements are formed of, for example, thin film transistors. The photosensors are formed of, for example, photodiodes. The switching elements and photosensors are formed using, for example, a-Si (amorphous silicon) as a base material. In FIG. 2, reference numeral 25 denotes a protective film. The photoelectric conversion elements 8 convert the received fluorescence into an electric signal, and a plurality of them are formed two-dimensionally in the row and column directions on the glass substrate 21. The photoelectric conversion element 8 can be an a-Si (amorphous silicon) photodiode (PD: Photo-diode).

[0018] Next, the effects of the radiation detector 1 according to the first embodiment will be described. 1, in the radiation detector according to the first embodiment, incident radiation (X-rays) is converted into fluorescent light, which is visible light, by the photoelectric conversion elements 8. The fluorescent light converted by the photoelectric conversion elements 8 is received by the photoelectric conversion elements 8 of the array substrate 5 and converted into an electrical signal as an image signal.

[0019] 4, the incident radiation will be explained in more detail. The incident X-rays that reach the scintillator 9 are converted into fluorescence 18a that propagates toward the array substrate and fluorescence 18b that propagates toward the reflective layer 1 inside the scintillator 9. The fluorescence 18a propagates along the columnar structure of the scintillator 9 and reaches the photoelectric conversion element 8. The fluorescent light 18 b is reflected by the reflective layer 11 toward the array substrate 5 and propagates along the columnar structure of the scintillator 9 , and reaches the photoelectric conversion element 8 . In this way, the fluorescent light 18a, 18b that reaches the photoelectric conversion element 8 is converted into an electric signal, which is output to the outside as an image signal.

[0020] Next, the relationship between the scintillator 9, the reflective layer 11, and the moisture-proof body 13 will be described. In this embodiment, the reflective layer 11 fixes the moisture-proof body 13 and the scintillator 9 . The reflective layer 11 contains a molten resin binder, and after forming the reflective layer 11 on one side of the scintillator 9, a moisture-proof body 13 is placed on one side of the reflective layer 11, and then the resin binder contained in the reflective layer 11 is solidified. Examples of this type of resin binder include butyral resin, but resin binders that use acetone or alcohol as a solvent are preferred. Other binders that solidify upon solvent evaporation include vinyl acetate resin emulsion adhesives. Furthermore, the resin binder is one that melts when heated and hardens when cooled, and polyester adhesives or olefin adhesives can be used. Furthermore, an epoxy adhesive that hardens when heated may be used, or an acrylic adhesive or epoxy adhesive that hardens when exposed to ultraviolet light may be used.

[0021] Another manufacturing method will be described with reference to FIG. 3, after forming the scintillator 9, the reflective layer 11 is formed on one side thereof, and the various binders (adhesives) described above are applied to the moisture-proof body 13-side (one side) surface of the reflective layer 11, after which the moisture-proof body 13 is placed on the binder-coated surface. Thereafter, depending on the type of binder, the entire assembly is heated, cooled, or irradiated with ultraviolet light to fix the reflective layer 11 and the moisture-proof body 13 together. Note that the reflective layer 11 itself contains, for example, a molten resin-based binder, and is already solidified together with the scintillator 9 when the reflective layer 11 is placed on the scintillator 9 to form the reflective layer 11. However, the present invention is not limited to this, and the various binders (adhesives) described above may be applied to the moisture-proof body-side surface of the reflective layer 11, and then the applied binder and the binder may be solidified between the reflective layer 11 and the scintillator 9.

[0022] Here, a case where a problem occurs in a manufactured product due to a manufacturing trouble will be described with reference to a comparative example shown in FIG. FIG. 5 shows a case where an abnormality exists in adhesive layer 15 due to a manufacturing problem, and a leak path 27 occurs inside adhesive layer 15 when the product is in use. Due to the occurrence of the leak path 27, outside air enters the internal space 17, which is in a reduced pressure state, through the leak path 27.

[0023] In the comparative example shown in Figure 5, a manufacturing problem occurs and outside air enters, causing the air pressure near the scintillator 9 inside the moisture-proof body 13 to rise, reducing the pressure exerted by the moisture-proof body 13 in the direction of the scintillator 9 due to atmospheric pressure, causing the moisture-proof body 13 and the scintillator 9 to lose their tight contact and separate, resulting in the creation of a gap 29 between the moisture-proof body 13 and the scintillator 9. If the above state is left as it is, moisture contained in the outside air will enter the scintillator 9 through the leak path 27 due to moisture permeation of the reflective layer 11, causing deterioration of the scintillator 9. In contrast to this, in this embodiment, the moisture-proof body 13 and the scintillator 9 are adhered to the reflective layer 11, so that even if a leak path 27 occurs and the reduced pressure is released, no gap 29 is created between the moisture-proof body 13 and the reflective layer 11, and the outside air does not cover the top surface of the scintillator 9, thereby minimizing moisture permeation through the reflective layer 11 and minimizing deterioration of the scintillator 9.

[0024] Therefore, in this embodiment, by preventing deterioration of the scintillator 9, it is possible to provide a radiation detector characterized by a long product life.

[0025] Furthermore, in this embodiment, the reflective layer 11 can be solidified into the scintillator 9 and the moisture-proof body 13 by adding a simple process such as heating.

[0026] The reflective layer 11 is formed of a mixture of white pigment and resin as its main component, and by reflecting the fluorescence 18a generated inside the scintillator 9 and escaping to the opposite side of the array substrate 5 back into the scintillator 9, the amount of fluorescence 18b that reaches the photoelectric conversion element 8 formed on the surface of the array substrate 5 increases, thereby obtaining a highly sensitive X-ray detector 1.

[0027] It is also known that if the scintillator 9 absorbs moisture in the atmosphere, the efficiency of converting X-rays into light decreases, and the absorption of moisture causes the columnar crystals to collapse, reducing the light trapping effect, resulting in a decrease in resolution and a decrease in the quality of the output X-ray image.However, by covering one side of the scintillator 9 with a moisture-proof body 13 and bonding the moisture-proof body 13 to the surface of the array substrate 5 at the edges of the scintillator 9 with an adhesive layer 15, the scintillator 9 is protected from moisture in the external atmosphere and deterioration of the quality of the X-ray image is prevented. In addition, by reducing the pressure inside the space sealed by the moisture-proof body 13, array substrate 5, and adhesive layer 15, it is possible to remove even small amounts of moisture that may have been mixed in during moisture-proof manufacturing.The reduced pressure inside the sealed space allows the moisture-proof body 13 and reflective layer 11 to adhere tightly to each other, preventing deterioration of the scintillator 9 due to moisture permeating through the adhesive layer 15 and making it possible to prevent deterioration in the image quality of X-ray images.

[0028] It should be noted that the present invention is not limited to the above-described embodiment itself, and that the components can be modified and embodied in practice without departing from the spirit of the invention. Furthermore, various inventions can be formed by appropriately combining multiple components disclosed in the above-described embodiment. For example, some components may be omitted from all the components shown in the embodiment. Furthermore, components from different embodiments may be appropriately combined. [Explanation of symbols]

[0029] 1...radiation detector, 3...photoelectric conversion section, 5...array substrate, 7...circuit board, 8...photoelectric conversion element, 9...scintillator, 11...reflective layer, 13...moisture-proof body, 15...adhesive layer

Claims

1. an array substrate having a plurality of photoelectric conversion elements arranged in a grid pattern on one side; a scintillator provided on one side of the array substrate; an adhesive layer surrounding the scintillator and having an adhesive provided in a frame shape on one side of the array substrate; a moisture-proof body provided on one side of the scintillator; the moisture-proof body is adhered to the adhesive layer and covers the scintillator layer together with the array substrate and the adhesive layer; A radiation detector comprising a reflective layer provided between the scintillator and the moisture-proof body, which reflects radiation incident on the scintillator toward the scintillator, the reflective layer fixing the moisture-proof body and the scintillator together.

2. 2. The radiation detector according to claim 1, wherein the moisture-proof body, together with the array substrate and the adhesive layer, forms a space that seals the scintillator layer, and the space is a space that is decompressed below atmospheric pressure.

3. A method for manufacturing a radiation detector according to claim 1, comprising the steps of: The reflective layer includes a molten resin-based binder, and the reflective layer is formed on one side of the scintillator, and then a moisture-proof body is placed on one side of the reflective layer, and the resin-based binder of the reflective layer is solidified.

4. A method for manufacturing a radiation detector according to claim 1, comprising the steps of: After forming a scintillator on one side of the array substrate, a reflective layer is formed on one side of the scintillator, and after the reflective layer solidifies the scintillator, An adhesive is applied to one side of the reflective layer, and then a moisture-proof body is placed on the adhesive; The moisture-proof body is fixed to the reflective layer by solidifying an adhesive applied to one side of the reflective layer.

5. A method for manufacturing a radiation detector according to claim 1, comprising the steps of: After forming the scintillator and the adhesive layer on one side of the array substrate, and drying the scintillator, A method for manufacturing a radiation detector, comprising forming a reflective layer containing an adhesive on one side of a scintillator, placing the moisture-proof body on one side of the reflective layer, and then using the reflective layer to fix the moisture-proof body and the scintillator.

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