Scintillator structure and X-ray detector

Abstract

To improve reliability of a scintillator structure.SOLUTION: A scintillator structure for detecting an X-ray forming an X-ray detector includes: a plurality of cells; and a reflection layer covering the cell layers. Each cell includes a resin and a phosphor. The resin is an epoxy resin which has an isocyanurate ring in a bone structure. Also, a drop rate of total light transmittance for light with a wavelength of 542 nm after an X-ray with a dosage of 100 kGy is radiated is less than 8%. The resin contains a hardening agent as a non-aromatic group which does not chemically comprise a carbon double bond.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a scintillator structure, and relates to a technique that is effective when applied to, for example, a scintillator structure having a plurality of cells each containing a resin and a phosphor. [Background technology]

[0002] Japanese Patent Application Laid-Open No. 63-100391 (Patent Document 1) describes a technique relating to a phosphor molded body containing a bisphenol A type epoxy resin. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-open No. 63-100391 Summary of the Invention [Problem to be solved by the invention]

[0004] A scintillator is a material that absorbs the energy of radiation, such as X-rays or gamma rays, and generates visible light when it is exposed to the radiation. This scintillator is commercialized as a scintillator structure that includes a scintillator and a reflective layer, and X-ray detectors that combine a scintillator structure with a photoelectric conversion element such as a photodiode are used in, for example, medical equipment such as X-ray CT, analytical equipment, non-destructive testing equipment using radiation, and radiation leakage testing equipment.

[0005] For example, ceramics made of gadolinium oxysulfide (Gd2O2S) are used in scintillators. Herein, gadolinium oxysulfide will be referred to as "GOS." Strictly speaking, gadolinium oxysulfide itself barely emits light; it emits light when gadolinium oxysulfide contains praseodymium, terbium, or the like. For this reason, the term "GOS" used in this specification implicitly refers to a substance (phosphor) that emits light when gadolinium oxysulfide itself contains praseodymium, terbium, or the like. However, when it is necessary to explicitly indicate that gadolinium oxysulfide itself contains praseodymium, terbium, or the like, it may be referred to as "GOS containing praseodymium" or "GOS containing terbium."

[0006] Furthermore, when the scintillator is constructed from "GOS" alone, the "GOS" is composed of ceramic. On the other hand, as will be described later, it is also being considered to construct the scintillator from a mixture of "GOS" and resin, in which case the "GOS" is composed of powder. Therefore, in this specification, when there is no need to specifically distinguish between ceramic and powder, it will simply be referred to as "GOS." On the other hand, when it is necessary to specifically specify the ceramic, it will be referred to as "GOS" ceramic. On the other hand, when it is necessary to specifically specify the powder, it will be referred to as "GOS" powder.

[0007] This "GOS" has the advantage of having a higher visible light output than cadmium tungstate (CdWO4), but its manufacturing costs are high.

[0008] For this reason, in order to reduce the manufacturing cost of the scintillator structure, the use of a mixture of "GOS" powder and resin as the scintillator is being considered.

[0009] In this regard, improving reliability is a high priority requirement for scintillator structures, because improving the reliability of the scintillator structure can extend the life of the radiation detector. Therefore, the scintillator is required to have high radiation resistance in order to improve reliability. In particular, as described above, when the scintillator is composed of a mixture of "GOS" powder and resin, it is desirable that the resin is resistant to deterioration when irradiated with radiation.

[0010] An object of the present invention is to improve the reliability of the scintillator structure. [Means for solving the problem]

[0011] In one embodiment, the scintillator structure includes a plurality of cells and a reflective layer covering the plurality of cells, wherein each of the plurality of cells includes a resin and a phosphor, and the resin exhibits a decrease in total light transmittance for light having a wavelength of 542 nm of less than 8% after irradiation with X-rays at a dose of 100 kGy. [Effects of the Invention]

[0012] According to one embodiment, the reliability of the scintillator structure can be improved. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a diagram schematically illustrating an X-ray detector. [Figure 2] 10 is a flowchart illustrating the flow of a manufacturing process of the scintillator structure. [Figure 3] 1A to 1C are diagrams schematically illustrating steps from a dicing step to a reflective material application step. DETAILED DESCRIPTION OF THE INVENTION

[0014] In all the drawings for explaining the embodiments, the same members are generally denoted by the same reference numerals, and repeated explanations thereof are omitted. Note that, in order to make the drawings easy to understand, hatching may be added even to a plan view.

[0015] <Overview of X-ray Detector> FIG. 1 is a diagram schematically showing an X-ray detector.

[0016] In FIG. 1, the X-ray detector 100 has a scintillator structure 10 and a light receiving element 20. The scintillator structure 10 is composed of a plurality of scintillators 11 that generate visible light from the X-rays incident on the X-ray detector 100, and a reflective layer 12 that covers each of these plurality of scintillators 11. On the other hand, the light receiving element 20 has a function of generating an electric current from the visible light generated by the scintillator 11, and is composed of a photoelectric conversion element typified by, for example, a photodiode. This light receiving element 20 is provided, for example, on a support 30 and is provided corresponding to each of the plurality of scintillators 11.

[0017] The scintillator 11 has a function of absorbing X-rays and generating visible light, and is composed of a phosphor 11a and a resin 11b. Here, in this specification, a material obtained by mixing the "GOS" powder constituting the phosphor 11a and the resin 11b may also be referred to as "resin GOS". That is, the scintillator 11 in the present embodiment is composed of "resin GOS". The phosphor 11a is a gadolinium oxysulfide containing praseodymium, terbium, etc., and the resin 11b is, for example, an epoxy resin. Further, the reflective layer 12 is composed of a resin 12b containing reflective particles 12a made of titanium oxide.

[0018] In recent years, as shown in Fig. 1, in a scintillator structure 10, a scintillator 11 is divided into a plurality of cells (CL). That is, from the viewpoint of improving the resolution of an X-ray image, the scintillator 11 is divided into a plurality of cells CL in accordance with each of a plurality of light receiving elements 20 (arraying the scintillators 11). In this manner, the scintillator structure 10 includes a plurality of cells CL and a reflective layer 12 that covers the plurality of cells CL. Specifically, the top surface and four side surfaces of the cells CL are covered with the reflective layer 12. On the other hand, the bottom surface of the cells CL is not covered with the reflective layer 12 because it needs to be in contact with the light receiving elements 20.

[0019] The X-ray detector configured in this manner operates as follows.

[0020] That is, when X-rays are incident on the scintillator 11 of the scintillator structure 10, electrons in the phosphor 11a that constitutes the scintillator 11 receive the energy of the X-rays and transition from the ground state to an excited state. The excited state electrons then transition to the ground state. At this time, visible light corresponding to the energy difference between the excited state and the ground state is emitted. Through this mechanism, the scintillator 11 absorbs X-rays and generates visible light.

[0021] Some of the visible light emitted from the scintillator 11 is directly incident on the light receiving element 20, while other visible light is repeatedly reflected by the reflective layer 12 covering the scintillator 11 and collected on the light receiving element 20. When visible light is incident on the light receiving element 20, which may be a photodiode, the energy of the visible light excites electrons in the semiconductor material that makes up the photodiode from the valence band to the conduction band. This causes a current to flow through the photodiode due to the electrons excited to the conduction band. An X-ray image is then acquired based on the current output from the photodiode. In this manner, the X-ray detector 100 can acquire an X-ray image.

[0022] For example, as shown in FIG. 1, a scintillator structure 10 is composed of a rectangular parallelepiped scintillator 11 and a reflective layer 12 covering the scintillator 11. Here, the rectangular parallelepiped scintillator 11 is formed through processing steps such as a dicing process and a grinding process, and therefore a processed surface is formed on the surface of the rectangular parallelepiped shape. In other words, the "processed surface" refers to a surface that has been mechanically processed. Specifically, the "processed surface" includes a surface that has been ground with a grinding wheel when thickening a workpiece, or a surface that has been cut from a workpiece with a slicing blade for dicing.

[0023] For example, in a scintillator 11 using "resin GOS," the "processed surface" is defined as a surface where the surface where the resin is exposed and the surface where the "GOS" powder is broken are mixed. For example, FIG. 1 shows a schematic representation of a scintillator 11 using "resin GOS" where the interface between the scintillator 11 and the reflective layer 12 is the "processed surface." In this case, it can be seen that the "processed surface" is a mixture of an area where the resin 11b is cut and an area where the phosphor 11a ("GOS" powder) is broken. In this way, the X-ray detector 100 is configured.

[0024] <Reasons for using "Resin GOS"> As described above, in this embodiment, "resin GOS" is used as the scintillator 11. The reason for this will be explained below.

[0025] For example, cadmium tungstate (hereinafter referred to as "CWO") is used as the scintillator 11 that constitutes the scintillator structure 10, but this "CWO" contains cadmium, which is a substance subject to the RoHS Directive / REACH Regulation. For this reason, "GOS" ceramic has been used instead of "CWO" that contains cadmium as the scintillator 11. This "GOS" ceramic has the advantage of having a higher visible light emission output than "CWO," but has the disadvantage of higher manufacturing costs.

[0026] Therefore, in order to reduce manufacturing costs, we decided to use a "resin GO" scintillator 11, which is a mixture of resin such as epoxy resin and "GOS" powder, instead of "GOS" ceramic. In other words, in order to suppress the increase in manufacturing costs due to "GOS" ceramic, "resin GOS" which is cheaper than "GOS" ceramic is being considered. There is a move to use on the Entrilator 11.

[0027] Here, "resin GOS" includes "first resin GOS," which is a mixture of "GOS" powder, in which praseodymium (Pr) and cerium (Ce) have been added to gadolinium oxysulfide, and epoxy resin, and "second resin GOS," which is a mixture of "GOS" powder, in which terbium (Tb) and cerium (Ce) have been added to gadolinium oxysulfide, and epoxy resin.

[0028] Both the "first resin GOS" and the "second resin GOS" have the advantage of having higher light output than "CWO." Furthermore, the "first resin GOS" also has the advantage of having the same afterglow characteristics as "CWO." In other words, the performance of the scintillator structure 10 requires not only high light output but also good afterglow characteristics.

[0029] Therefore, the afterglow characteristics will be explained. The scintillator 11 constituting the scintillator structure 10 is a material that generates visible light when irradiated with X-rays. The mechanism by which the scintillator 11 generates visible light when irradiated with X-rays is as follows.

[0030] That is, when the scintillator 11 is irradiated with X-rays, electrons in the scintillator 11 receive energy from the X-rays and transition from a low-energy ground state to a high-energy excited state. Then, the electrons in the excited state transition to a low-energy ground state. At this time, most of the excited electrons immediately transition to the ground state. On the other hand, some of the excited electrons transition to the ground state after a certain amount of time has passed.

[0031] The visible light generated by the transition of electrons from the excited state to the ground state after a certain amount of time has passed is called afterglow. In other words, afterglow is visible light generated when the transition from the excited state to the ground state occurs a certain amount of time after the X-ray irradiation. A high level of afterglow means that the intensity of the visible light generated is high even after a certain amount of time has passed since the X-ray irradiation. In this case, the afterglow generated by the previous X-ray irradiation remains until the next X-ray irradiation, and the remaining afterglow becomes noise. For this reason, it is desirable to have a small afterglow. In other words, good afterglow characteristics mean small afterglow. In this respect, the afterglow characteristics of the "First Resin GOS" are equivalent to those of "CWO."

[0032] Therefore, "resin GOS" has the following advantages over "CWO" and is therefore superior as a scintillator 11 that can achieve both high performance and low manufacturing costs. (1) "Resin GOS" has a higher light output than "CWO." (2) The afterglow characteristics of the "First Resin GOS" are equivalent to those of the "CWO." (3) Cadmium is not used in "Resin GOS." (4) "Resin GOS" has lower manufacturing costs than "CWO."

[0033] Furthermore, cesium iodide (CsI) is used as the scintillator 11, but "resin GOS" has the following advantages over "CsI". (1) "Second Resin GOS" has better X-ray stopping properties than "CsI." (2) The afterglow characteristics of the "Second Resin GOS" are approximately 1 / 70 of that of "CsI." (3) "Resin GOS" is a stable substance that does not deliquesce.

[0034] Furthermore, "resin GOS" has the following advantages over "GOS" ceramic. Specifically, "resin GOS" and "GOS" ceramic contain heavy metals such as Gd, Ga, and Bi. These heavy metals are relatively expensive, and there are concerns that their leakage could have adverse effects on living organisms and the environment. Therefore, it is desirable for the scintillator 11 to contain as few heavy metals as possible. In this regard, "resin GOS," which is composed of a mixture of "GOS" powder and resin, uses less "GOS" than bulk "GOS" ceramic. This means that "resin GOS" can be used to construct a scintillator 11 with a lower heavy metal content than "GOS" ceramic. Therefore, "resin GOS" can be said to be superior to "GOS" ceramic in that it can provide a scintillator 11 with a lower heavy metal content.

[0035] From the above, "resin GOS" is considered promising as a scintillator 11 that can achieve both high performance and low manufacturing costs.

[0036] <Specific materials> Next, specific materials of the components that make up the scintillator structure 10 will be described.

[0037] <<Phosphor 11a>> The phosphor 11a used in this embodiment is made of, for example, gadolinium oxysulfide or gadolinium-aluminum-gallium garnet (GGAG). Gadolinium oxysulfide has a composition of "Gd2O2S" activated with at least one element selected from praseodymium (Pr), cerium (Ce) or terbium (Tb), for example. On the other hand, "GGAG" is activated with at least one element selected from cerium (Ce) and praseodymium (Pr), for example (Gd 1-x Lu x ) 3+a (Ga u Al 1-u ) 5-a O 12The phosphor 11a has a main composition of (x=0 to 0.5, u=0.2 to 0.6, a=−0.05 to 0.15), but is not limited to a specific composition.

[0038] <<Resin 11b and Resin 12b>> Resin 11b and resin 12b are made of a material that is resistant to deterioration when irradiated with radiation. The materials of resin 11b and resin 12b are a feature of this embodiment, which will be described later.

[0039] <<Reflective particle 12a>> Examples of materials constituting the reflective particles 12a include white particles such as "TiO2" (titanium oxide), "Al2O3" (aluminum oxide), and "ZrO2" (zirconium oxide). Here, the reflective particles 12a can be, for example, in bulk or a mixture of powder and resin. In particular, reflective particles 12a made of "rutile-type TiO2" are desirable particles because they have excellent light reflection efficiency. From the viewpoint of improving the light reception efficiency of the light receiving element 20, the light reflectance of the reflective particles 12a is desirably 80% or more, and further desirably, the light reflectance of the reflective particles 12a is desirably 90% or more.

[0040] <<Other additives>> In addition to the above-mentioned components, other additives may be blended into the reflective material that constitutes scintillator 11 and reflective layer 12. For example, it is desirable to blend a curing catalyst in order to shorten the curing time of the resin.

[0041] <Consideration of improvements> For example, the resin contained in "Resin GOS" is an epoxy resin. This epoxy resin contains at least a base resin and a curing agent as constituent materials; for example, bisphenol A epoxy resin is often used as the base resin, and an amine-based curing agent is often used as the curing agent. However, the present inventors have newly discovered that when a typical epoxy resin that uses bisphenol A epoxy resin as the base resin and an amine-based curing agent as the curing agent is used as the resin constituting "Resin GOS," repeated exposure to radiation (X-rays) over a long period of time causes deterioration and discoloration.

[0042] Discoloration of the translucent resin means that light absorption increases, which ultimately means that light transmittance decreases. This makes it difficult for light generated from the scintillator made of "resin GOS" to reach the light-receiving element (photodiode), resulting in a decrease in the detection performance of the X-ray detector.

[0043] That is, according to the investigations of the present inventors, it has been found that if a general epoxy resin that uses a bisphenol A type epoxy resin as the main component and an amine-based curing agent as the curing agent is used as the resin that constitutes "Resin GOS," it is difficult to ensure stable detection performance in an X-ray detector over a long period of time. In other words, the present inventors have newly discovered that if the above-mentioned general epoxy resin is used as the resin that constitutes "Resin GOS," it is difficult to ensure the reliability of the X-ray detector over a long period of time.

[0044] Therefore, based on the above-mentioned new findings, it is clear that in order to ensure the reliability of X-ray detectors over a long period of time, it is desirable to use a resin that is resistant to discoloration even when irradiated with X-rays over a long period of time as the resin that constitutes "Resin GOS," instead of the general epoxy resin described above. The present inventors have therefore discovered a resin that has excellent radiation resistance and is resistant to discoloration even when irradiated with X-rays over a long period of time, and this point will be explained below.

[0045] <Features of the embodiment> A feature of this embodiment is that the epoxy resins shown below, which contain at least a base resin and a curing agent, are used for the resin contained in "Resin GOS" and the resin contained in the reflector. This ensures the long-term reliability of the X-ray detector that includes the scintillator structure of this embodiment as a component.

[0046] <<Main ingredient>> The base resin is a triazine-derived epoxy resin. An example of a triazine-derived epoxy resin is a 1,3,5-triazine-derived epoxy resin. The 1,3,5-triazine-derived epoxy resin is preferably an epoxy resin having an isocyanurate ring. This is because epoxy resins having an isocyanurate ring in their skeleton have excellent stability, resistance to radiation and heat, and are resistant to discoloration.

[0047] In particular, from the viewpoint of suppressing discoloration, epoxy resins having an "isocyanurate ring" in the skeleton preferably have multiple epoxy groups per isocyanurate ring, for example, three epoxy groups per isocyanurate ring, because when multiple epoxy groups are bonded to an isocyanurate ring, the resin has high reactivity and strong stability, and as a result, is less likely to discolor even when irradiated with X-rays.

[0048] Examples of epoxy resins having an "isocyanurate ring" include 1,3,5-triglycidyl isocyanurate, tris(2,3-epoxypropyl) isocyanurate, tris(α-methylglycidyl) isocyanurate, tris(1-methyl-2,3-epoxypropyl) isocyanurate, 1,3,5-tris(2,3-epoxypropyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, 1,3,5-tris(3,4-epoxypropyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, and 1,3,5-tris(3,4-epoxypropyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione. 1,3,5-tris(5,6-epoxybutyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, 1,3,5-tris(5,6-epoxybutyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, tris{2,2-bis[(oxiran-2-ylmethoxy)methyl]butyl}-3,3′,3″-[1,3,5-triazine-2,4,6(1H,3H,5H)-trione-1,3,5-triyl]trippropanoate, and the like can be mentioned.

[0049] Commercially available triazine derivative epoxy resins (epoxy resins having an isocyanurate ring) include, for example, Nissan Chemical Industries' "TEPIC-G", "TEPIC-S", "TEPIC-SS", "TEPIC-HP", "TEPIC-L", and "TEPIC-PAS", which are commercially available products of 1,3,5-tris(2,3-epoxypropyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione; and Nissan Chemical Industries' "TEPIC-G", "TEPIC-S", "TEPIC-SS", "TEPIC-HP", "TEPIC-L", and "TEPIC-PAS", which are commercially available products of 1,3,5-tris(3,4-epoxybutyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione. Examples of such compounds include "TEPIC-VL" manufactured by Nissan Chemical Industries, Ltd., a commercially available product of 1,3,5-tris(5,6-epoxybutyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, "TEPIC-FL" manufactured by Nissan Chemical Industries, Ltd., a commercially available product of 1,3,5-tris(5,6-epoxybutyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, and "TEPIC-UC" manufactured by Nissan Chemical Industries, Ltd., a commercially available product of tris{2,2-bis[(oxiran-2-ylmethoxy)methyl]butyl}-3,3',3"-[1,3,5-triazine-2,4,6(1H,3H,5H)-trione-1,3,5-triyl]tripropanoate.

[0050] <<Curing agent>> To prevent discoloration due to X-ray irradiation, it is desirable to use a curing agent that does not have a carbon-carbon double bond. This is because carbon-carbon double bonds have weaker bond strength than carbon-carbon single bonds, and carbon-carbon double bonds are easily cleaved by X-ray irradiation, resulting in discoloration of the material. For example, an acid anhydride curing agent, such as a phthalic anhydride curing agent, can be used as the curing agent. In particular, from the viewpoint of effectively preventing discoloration due to X-ray irradiation, one or more types of non-aromatic polybasic carboxylic acid anhydrides that do not chemically have a carbon-carbon double bond may be used.

[0051] Specific examples of the curing agent include tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, hexahydrophthalic anhydride, methylhexahydrophthalic anhydride, methylnadic anhydride, dodecenylsuccinic anhydride, etc. It is particularly desirable to use methylhexahydrophthalic anhydride.

[0052] Specific examples of acid anhydride compounds include "Rikacid TH," "TH-1A," "HH," "MH," "MH-700," and "MH-700G" (all manufactured by New Japan Chemical Co., Ltd.).

[0053] <<Curing catalyst>> Although a curing catalyst is not an essential component, it is desirable to add it in order to accelerate the curing reaction of the base resin. It is desirable to use an organophosphorus compound as the curing catalyst, as it is resistant to discoloration when irradiated with X-rays. Specific examples of the curing catalyst include tetrabutylphosphonium 0,0-diethylphosphorodithioate (Hishicolin PX-4ET, manufactured by Nippon Chemical Industry Co., Ltd.) and methyltributylphosphonium dimethylphosphate (Hishicolin PX-4MP, manufactured by Nippon Chemical Industry Co., Ltd.).

[0054] <Verification of effectiveness> The following describes the verification results showing that the "resin GOS" containing the above-mentioned triazine derivative epoxy resin can suppress the decrease in "total light transmittance" even after X-ray irradiation.

[0055] The term "total light transmittance" used in this specification is intended to include light that has been scattered inside the scintillator and has its transmission direction deviated from the incident direction. In other words, "total light transmittance" represents the transmittance when it includes not only transmitted light that travels straight from the incident direction but also transmitted light that has been scattered inside the scintillator and has its transmission direction deviated from the straight direction. The reason for using this "total light transmittance" is that in a scintillator structure, the cell made of the scintillator is covered with a reflective layer, and as a result, light scattered inside the cell is also reflected repeatedly and finally enters the light-receiving element arranged on the bottom surface of the cell, and therefore light scattered inside the cell also contributes to radiation detection by the light-receiving element. In other words, "total light transmittance" is used to evaluate the radiation detection by taking into account all transmitted light that contributes to radiation detection.

[0056] In addition, the term "total light transmittance" in this specification means the total light transmittance measured using light having a wavelength of 542 nm for a sample having a thickness of 1.5 mm. When measuring the "light transmittance," samples measuring 15mm x 15mm x 1.5mm in length x width x thickness were prepared, and the surfaces of the samples were mirror-finished. The "total light transmittance" is measured.

[0057] [Table 1]

[0058] Table 1 shows the verification results for Sample A and Sample B.

[0059] In Table 1, Sample A represents the "resin GOS" of the present embodiment, which uses a triazine derivative epoxy resin as the base material and "Me-HHPA" (material name: methylhexahydrophthalic anhydride, product name: "Rikacid MH-T" manufactured by New Japan Chemical Co., Ltd.) as the curing agent. On the other hand, Sample B represents the "resin GOS" of the related art, which uses a bisphenol A type epoxy resin as the base material and an amine compound as the curing agent.

[0060] As shown in Table 1, for Sample A, the initial "total luminous transmittance (0 kGy)" before X-ray irradiation was "91.358", while the "total luminous transmittance (100 kGy)" after X-ray irradiation with a dose of 100 kGy was "87.425", and the "total luminous transmittance difference" was "3.933".

[0061] In contrast, for sample B, the initial "total luminous transmittance (0 kGy)" before X-ray irradiation was "90.902", while the "total luminous transmittance (100 kGy)" after X-ray irradiation with a dose of 100 kGy was "78.361", and the "total luminous transmittance difference" was "12.541".

[0062] As a result, the "reduction rate of total light transmittance" of Sample A was "4.5%", while the "reduction rate of total light transmittance" of Sample B was "16%". Therefore, the results in Table 1 prove that the "resin GOS" of this embodiment can suppress the decrease in "total light transmittance" even after X-ray irradiation.

[0063] In particular, the results in Table 1 show that the "resin GOS" of the present embodiment ensures an initial total light transmittance of 90% or more for light having a wavelength of 542 nm before X-ray irradiation, while achieving excellent performance in that the decrease in total light transmittance for light having a wavelength of 542 nm after irradiation with an X-ray dose of 100 kGy is less than 8%. Therefore, by using the "resin GOS" of the present embodiment, a scintillator structure with high light emission output and excellent radiation resistance can be provided. As a result, by using the scintillator structure of the present embodiment, a highly reliable X-ray detector that can maintain stable detection performance over a long period of time can be provided.

[0064] In particular, the verification results in this embodiment have great technical significance in that they prove that the decrease in total light transmittance of "resin GOS" containing triazine derivative epoxy resin is suppressed even after irradiation with a high dose of X-rays of 100 kGy.

[0065] For example, even if a material is known to be radiation-resistant, it is impossible to determine whether it can actually ensure the long-term reliability of an X-ray detector without knowing the X-ray dose it can withstand. In other words, simply having a material that is qualitatively radiation-resistant does not necessarily guarantee the long-term reliability of an X-ray detector that uses high doses of X-rays. In this regard, this embodiment presents verification results after exposure to a high dose of X-rays (100 kGy). Based on these verification results, it is stated that the "GOS resin" containing a triazine derivative epoxy resin has excellent radiation resistance. Here, it is of great technical significance that the "GOS resin" containing a triazine derivative epoxy resin can suppress a decrease in "total light transmittance" even after exposure to 100 kGy of X-rays. This verification result is based on the assumption of a high dose of 100 kGy, and therefore provides reliable data that can serve as a basis for ensuring the long-term reliability of X-ray detectors that use high doses of X-rays.

[0066] <Method of manufacturing scintillator structure> Next, a method for manufacturing the scintillator structure will be described.

[0067] FIG. 2 is a flowchart illustrating the flow of the manufacturing process of the scintillator structure.

[0068] In Figure 2, first, predetermined amounts of raw material powder and flux components are weighed and mixed (S101). This mixture is then filled into a crucible and fired in an atmospheric furnace at 1300-1400°C for 7-9 hours (S102) to produce "GOS" powder. Flux components and impurities contained in the "GOS" powder are then removed by washing with hydrochloric acid and hot water (S103). Next, epoxy resin is dripped onto the "GOS" powder, allowing it to soak into the powder (S104). After the epoxy resin is cured (S105), any epoxy resin not mixed with the "GOS" powder is removed (S106). This completes the formation of a scintillator made of "resin GOS."

[0069] Next, the substrate on which the scintillator is formed is diced to separate the substrate into a plurality of cells (S107). The separated cells are rearranged (S108), and then a reflective material is applied to cover the plurality of cells (S109). Then, unnecessary portions of the scintillator structure 10A are cut off (S110), and scintillator structures that have passed inspection are shipped (S111).

[0070] FIG. 3 is a diagram showing the steps from the dicing step to the reflective material application step.

[0071] As shown in FIG. 3, a substrate WF on which a scintillator made of "resin GOS" is formed is diced, thereby dividing the substrate WF into a plurality of cells CL. The divided cells CL are then rearranged, for example, in a line. An outer frame FR is then arranged so as to enclose the plurality of cells CL rearranged in a line. Next, a reflective material made of, for example, an epoxy resin containing titanium oxide is applied so as to cover the plurality of cells CL arranged within the outer frame FR. Then, the outer frame FR is removed. In this manner, the scintillator structure 10A is manufactured.

[0072] Note that Figure 3 illustrates an example of a linear scintillator structure 10A using 1 x n cells, but the technical idea of ​​this embodiment is not limited to this and can also be applied to, for example, an array-shaped (matrix-shaped) scintillator structure using n x n cells.

[0073] <Example> Detailed verification results that support the effects of the technical concept of the present embodiment will be described below based on examples. Note that the technical concept of the present embodiment is not limited to these examples.

[0074] [Table 2]

[0075] Table 2 shows the evaluation results based on the samples.

[0076] First, the sample will be described.

[0077] <<Materials>> "GOS" powder: Gadolinium oxysulfide (Gd2O2S) Base resin: Example 1 Triazine derivative epoxy resin (TEPIC-PAS B22) Example 2 Triazine derivative epoxy resin (TEPIC-VL) Example 3 Triazine derivative epoxy resin (TEPIC-FL) Comparative Example: Hydrogenated bisphenol A diglycidyl ether epoxy resin (Epicron 840 (DIC)) Hardener: Acid anhydride (Rikacid MH-T) Curing catalyst: organic phosphorus compound (Hishico-rin PX-4ET)

[0078] <<Sample production>> Using the blend amounts (stoichiometric amount: equivalent ratio) shown in Table 2, samples were prepared under primary curing conditions (90°C, 15 hours) and secondary curing conditions (120°C, 2.5 hours).

[0079] The sample had a size of 15 mm x 15 mm x 1.5 mm (length x width x thickness), and the surface of the sample was mirror-finished.

[0080] <<Evaluation method>> After irradiating the sample with 100 kGy of X-rays, the "total light transmittance" for light having a wavelength of 542 nm was measured using a JASCO V-570 ultraviolet-visible-near-infrared spectrophotometer.

[0081] Here, an integrating sphere device and a reflector were used to collect diffuse transmitted light and straight transmitted light into a detector to measure the total light transmittance.

[0082] <<Evaluation Results>> As shown in Table 2, the initial "total light transmittance" before X-ray irradiation was 90% or more in all of Examples 1 to 3 and the Comparative Example. On the other hand, when looking at the "total light transmittance" after irradiation with X-rays at a dose of 100 kGy, Examples 1 to 3 had values ​​of 80% or more, while the Comparative Example did not reach 80%. When this result was converted into a "total light transmittance reduction rate," Examples 1 to 3 had a reduction rate of less than 5%, while the Comparative Example had a reduction rate of 14% or more.

[0083] From the above, it is evident that the "resin GOS" in Examples 1 to 3 can suppress the decrease in "total light transmittance" even after X-ray irradiation.

[0084] In particular, the results in Table 2 show that the "resin GOS" in Examples 1 to 3 can achieve excellent performance, ensuring an initial total light transmittance of 90% or more for light having a wavelength of 542 nm before X-ray irradiation, while reducing the total light transmittance for light having a wavelength of 542 nm by less than 5% after X-ray irradiation at a dose of 100 kGy. This indicates that the use of the "resin GOS" in Examples 1 to 3 can provide a scintillator structure with high light emission output and excellent radiation resistance. Furthermore, the use of this scintillator structure can provide a highly reliable X-ray detector that can maintain stable detection performance over a long period of time.

[0085] The invention made by the inventor has been specifically described above based on the embodiments thereof, but it goes without saying that the present invention is not limited to the above-described embodiments and can be modified in various ways without departing from the spirit of the invention. [Explanation of symbols]

[0086] 10 Scintillator structure 11 Scintillator 11a Phosphor 11b Resin 12 Reflective layer 12a reflective particles 12b Resin 20 Photodetector 30 Support 100 X-ray detectors CL Cell

Claims

1. A plurality of cells; a reflective layer covering the plurality of cells; A scintillator structure comprising: each of the plurality of cells includes a resin and a phosphor; the reflective layer includes the resin and reflective particles, The resin contains an isocyanurate ring, A scintillator structure, wherein the resin exhibits a decrease in total light transmittance for light having a wavelength of 542 nm of less than 8% after irradiation with X-rays at a dose of 100 kGy.

2. 2. The scintillator structure of claim 1, A scintillator structure, wherein the resin has an initial total light transmittance of 90% or more for light having a wavelength of 542 nm before irradiation with X-rays.

3. 2. The scintillator structure of claim 1, A scintillator structure, wherein the resin has a total light transmittance of 80% or more for light having a wavelength of 542 nm after irradiation with X-rays at a dose of 100 kGy.

4. 2. The scintillator structure of claim 1, A scintillator structure, wherein the resin has a plurality of epoxy groups per isocyanurate ring.

5. 2. The scintillator structure of claim 1, A scintillator structure, wherein the resin has three epoxy groups per one isocyanurate ring.

6. A scintillator structure according to claim 1; and a light receiving element.

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