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 for example, to a technique that is effective when applied to a scintillator structure having a plurality of cells, each of which contains a resin and a phosphor. [Background technology]

[0002] Japanese Patent Laid-Open Publication 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 struck by the radiation. This scintillator is commercialized as a scintillator structure including 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, radiation leakage testing equipment, etc.

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

[0006] Also, when the scintillator is made of "GOS" alone, the "GOS" is made of ceramic. On the other hand, as described below, it is also being considered to make the scintillator out of a mixture of "GOS" and resin, in which case the "GOS" is made 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". In contrast, when it is necessary to specifically state the ceramic, it will be called "GOS" ceramic. On the other hand, when it is necessary to specifically state the powder, it will be called "GOS" powder.

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

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

[0009] In this regard, one of the high priority requirements for the scintillator structure is to improve its reliability. This is because if the reliability of the scintillator structure can be improved, the life of the radiation detector can be extended. Therefore, the scintillator is required to have high radiation resistance in order to improve its reliability. In particular, as described above, when the scintillator is made of a mixture of "GOS" powder and resin, it is desired that the resin is resistant to deterioration when exposed to radiation.

[0010] An object of the present invention is to improve the reliability of a 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, where each of the plurality of cells includes a resin and a phosphor, and the resin has 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. Effect of the Invention

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

[0013] [Figure 1] FIG. 2 is a diagram illustrating an X-ray detector. [Diagram 2] 4 is a flowchart illustrating a manufacturing process of the scintillator structure. [Diagram 3] 1A to 1C are diagrams illustrating steps from a dicing step to a reflective material coating step. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[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 a current from the visible light generated by the scintillator 11, and is composed of, for example, a photoelectric conversion element typified by 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 scintillator 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 upper surface and four side surfaces of the cells CL are covered with the reflective layer 12. On the other hand, the lower surface of the cell CL is not covered with the reflective layer 12 because it needs to be in contact with the light receiving element 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, the electrons in the phosphor 11a constituting 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] Then, a part of the visible light generated from the scintillator 11 directly enters the light receiving element 20, while another part of the visible light generated from the scintillator 11 is repeatedly reflected by the reflective layer 12 covering the scintillator 11 and is collected on the light receiving element 20. Next, when visible light is incident on the light receiving element 20 composed of, for example, a photodiode, the energy of the visible light excites electrons of the semiconductor material constituting the photodiode from the valence band to the conduction band. As a result, a current caused by the electrons excited to the conduction band flows in the photodiode. Then, an X-ray image is acquired based on the current output from the photodiode. In this way, 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-shaped scintillator 11 and a reflective layer 12 covering the scintillator 11. Here, the rectangular parallelepiped-shaped scintillator 11 is formed through processing steps such as a dicing step and a grinding step, 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 subjected to mechanical processing. Specifically, the "processed surface" includes a surface that has been ground with a grinding wheel when performing thickness adjustment of a workpiece, or a surface where the workpiece has been cut with a slicing blade to perform a dicing process.

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

[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 constituting 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 as the scintillator 11 in place of "CWO" which contains cadmium. 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 scintillator 11 made of epoxy resin or other resin mixed with 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 for the 11th insulator.

[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 emission output than "CWO". Furthermore, the "first resin GOS" 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 emission output but also good afterglow characteristics.

[0029] The afterglow characteristics will now be described. 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, the 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 transition to the ground state immediately. 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 becomes the afterglow. In other words, the afterglow is the visible light generated when the timing of the transition from the excited state to the ground state occurs after a certain amount of time has passed since the time of X-ray irradiation. And, this afterglow is large means that the intensity of the visible light generated is large 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 that the afterglow is small. In other words, good afterglow characteristics mean small afterglow. In this regard, the afterglow characteristics of the "first resin GOS" are equivalent to those of the "CWO".

[0032] Therefore, since "resin GOS" has the following advantages over "CWO", it is excellent as a scintillator 11 that can achieve both high performance and low manufacturing costs. (1) "Resin GOS" has a higher luminous output than "CWO." (2) The afterglow characteristics of the "First Resin GOS" are equivalent to those of "CWO." (3) "Resin GOS" does not contain cadmium. (4) "Resin GOS" has lower manufacturing costs than "CWO."

[0033] In addition, 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 persistence 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. That is, "resin GOS" and "GOS" ceramic contain heavy metals such as "Gd", "Ga" or "Bi". These heavy metals are relatively expensive and there is concern that they may have a negative impact on living organisms and the environment if they are leaked. Therefore, it is desirable that the amount of heavy metals contained in the scintillator 11 is as small as possible. In this regard, "resin GOS", which is composed of a mixture of "GOS" powder and resin, uses less "GOS" than "GOS" ceramic, which is bulk. This means that "resin GOS" can be used to configure a scintillator 11 with a lower heavy metal content than "GOS" ceramic. From this, it can be said that "resin GOS" is superior to "GOS" ceramic in that it can provide a scintillator 11 with a lower heavy metal content.

[0035] For these reasons, "resin GOS" is seen as a promising 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). On the other hand, "GGAG" is activated with at least one selected from cerium (Ce) and praseodymium (Pr) (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), however, the phosphor 11a 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 not easily altered or deteriorated when irradiated with radiation. The material of resin 11b and resin 12b is a characteristic feature of this embodiment, which will be described later.

[0039] <<Reflection particle 12a>> Examples of the constituent material of the reflective particles 12a include white particles such as "TiO2" (titanium oxide), "Al2O3" (aluminum oxide), and "ZrO2" (zirconium oxide). Here, the reflective particles 12a may be, for example, a mixture of bulk or powder and resin. In particular, the 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 receiving efficiency of the light receiving element 20, the light reflectance of the reflective particles 12a is desirably 80% or more, and further, 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 constituting the scintillator 11 and the 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 agent and a curing agent as constituent materials, and for example, bisphenol A type epoxy resin is often used as the base agent, and an amine-based curing agent is often used as the curing agent. However, the present inventor has newly discovered that when a general epoxy resin that uses bisphenol A type epoxy resin as the base agent and an amine-based curing agent as the curing agent is used as the resin constituting "Resin GOS," it deteriorates and discolors when repeatedly exposed to radiation (X-rays) for a long period of time.

[0042] And discoloration of the translucent resin means that light absorption increases, which ultimately means that light transmittance decreases. This makes it harder for the 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 study of the present inventor, it was found that if a general epoxy resin that uses a bisphenol A type epoxy resin as a main component and an amine-based curing agent as a curing agent is used as the resin constituting "resin GOS", it is difficult to ensure stable detection performance in the X-ray detector for a long period of time. In other words, the present inventor has newly discovered that if the above-mentioned general epoxy resin is used as the resin constituting "resin GOS", it is difficult to ensure the reliability of the X-ray detector for a long period of time.

[0044] Therefore, based on the above-mentioned new findings, it is found that in order to ensure the reliability of the X-ray detector 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 constituting the "Resin GOS" instead of the above-mentioned general epoxy resin. Therefore, the present inventor has found 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> The feature of this embodiment is that the epoxy resins shown below are used as the resins contained in the "Resin GOS" and the reflector as epoxy resins containing at least a base agent and a hardener. This ensures the long-term reliability of the X-ray detector having the scintillator structure of this embodiment as a component.

[0046] <<Main ingredient>> The base material is a triazine-derived epoxy resin. An example of the 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 an epoxy resin having an "isocyanurate ring" in its skeleton has excellent stability in terms of resistance to radiation and heat, and is resistant to discoloration.

[0047] In particular, from the viewpoint of suppressing discoloration, it is preferable that an epoxy resin having an "isocyanurate ring" in the skeleton has multiple epoxy groups per isocyanurate ring, for example, three epoxy groups per isocyanurate ring. This is because when multiple epoxy groups are bonded to an isocyanurate ring, the resin has high reactivity and strong stability, and as a result, the resin 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)isocyanurate ... 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]triplopanoate, 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 1,3,5-tris(2,3-epoxypropyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione products; Examples of such a compound 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] <<Hardening agent>> In order to suppress discoloration due to X-ray irradiation, it is desirable to use a material that does not have a carbon double bond as the curing agent. This is because the carbon double bond has a weaker bond strength than the carbon single bond, and the carbon double bond is easily cut by X-ray irradiation, which makes the material more likely to discolor. 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 suppressing discoloration due to X-ray irradiation, one type of polybasic acid carboxylic acid anhydride that is non-aromatic and does not chemically have a carbon double bond may be used, or two or more types may be used in combination.

[0051] Specific examples of the curing agent include tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, hexahydrophthalic anhydride, methylhexahydrophthalic anhydride, methylnadic anhydride, dodecenylsuccinic anhydride, etc. In particular, it is preferable to use methylhexahydrophthalic anhydride.

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

[0053] <<Curing catalyst>> Although the curing catalyst is not an essential component, it is desirable to add it from the viewpoint of promoting the curing reaction of the base material. As the curing catalyst, it is desirable to use an organic phosphorus compound that does not easily discolor even when irradiated with X-rays. Specifically, the curing catalyst may include tetrabutylphosphonium 0,0-diethyl phosphorodithioate (Hishikorin PX-4ET, manufactured by Nippon Chemical Industry Co., Ltd.), methyltributylphosphonium dimethylphosphate (Hishikorin PX-4MP, manufactured by Nippon Chemical Industry Co., Ltd.), etc.

[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 is scattered inside the scintillator and has a transmission direction that deviates from the incident direction as transmitted light. In other words, the term "total light transmittance" refers to the transmittance when it includes not only transmitted light that travels straight from the incident direction but also transmitted light that is scattered inside the scintillator and has a transmission direction that deviates from the straight direction. The reason for using this "total light transmittance" is that in the scintillator structure, the cell made of the scintillator is covered with a reflective layer, so that the light scattered inside the cell also repeats reflections and finally enters the light receiving element arranged on the bottom surface of the cell, and the light scattered inside the cell also contributes to the detection of radiation by the light receiving element. In other words, the term "total light transmittance" is used to evaluate the transmitted light that contributes to the detection of radiation by taking into account all transmitted light.

[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. In measuring the "light transmittance," samples with dimensions of 15 mm x 15 mm x 1.5 mm 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 indicates the "resin GOS" of this embodiment, which is a "resin GOS" that uses a triazine derivative epoxy resin as the base agent and "Me-HHPA" (material name: methylhexahydrophthalic anhydride, product name: "Rikacid MH-T" manufactured by New Japan Chemical Co., Ltd.) as the hardener. On the other hand, Sample B indicates the "resin GOS" of the related technology, which is a "resin GOS" that uses a bisphenol A type epoxy resin as the base agent and an amine compound as the hardener.

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

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

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

[0063] In particular, from the results of Table 1, the "resin GOS" of the present embodiment can achieve excellent performance, in which the initial total light transmittance for light having a wavelength of 542 nm is secured to be 90% or more before irradiation with X-rays, while the reduction rate of the total light transmittance for light having a wavelength of 542 nm is less than 8% after irradiation with X-rays at a dose of 100 kGy. Therefore, by using the "resin GOS" of the present embodiment, a scintillator structure having 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 for 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 the suppression of the decrease in the total light transmittance of the "resin GOS" containing a triazine derivative epoxy resin even after irradiation with a high dose of X-rays of 100 kGy.

[0065] For example, even if a material is known to have radiation resistance, if it is not known how much radiation radiation the material can withstand, it is impossible to say whether the reliability of an X-ray detector can be ensured for a long period of time. In other words, even if a material is merely qualitatively radiation resistant, it is not necessarily possible to guarantee the reliability of an X-ray detector using a high dose of X-rays for a long period of time. In this regard, in this embodiment, the verification results after irradiation with a high dose of X-rays of 100 kGy are shown, and based on this verification result, it is stated that the radiation resistance of the "resin GOS" containing a triazine derivative epoxy resin is excellent. Here, it is of great technical significance that it has been verified that the "resin GOS" containing a triazine derivative epoxy resin can suppress the decrease in "total light transmittance" even after irradiation with 100 kGy of X-rays. This is because the verification results are based on the assumption of a high dose of 100 kGy, and therefore provide highly reliable data as a basis for guaranteeing the reliability of an X-ray detector using a high dose of X-rays for a long period of time.

[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 a manufacturing process for the scintillator structure.

[0068] In FIG. 2, first, the raw powder and flux components are weighed and mixed in a predetermined amount (S101), and then the mixture is filled into a crucible and baked in an atmospheric furnace at 1300°C to 1400°C for 7 to 9 hours (S102) to produce "GOS" powder. Then, the flux components and impurities contained in the "GOS" powder are removed by washing with hydrochloric acid and hot water (S103). Next, epoxy resin is dripped onto the "GOS" powder to allow the "GOS" powder to be saturated with the epoxy resin (S104). Next, after the epoxy resin is hardened (S105), the epoxy resin that is not mixed with the "GOS" powder is removed (S106). This allows 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 coated with a reflective material so as to cover the plurality of cells (S109). Then, unnecessary parts of the scintillator structure 10A are cut off (S110), and the 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, the substrate WF on which the scintillator made of "resin GOS" is formed is diced to separate the substrate WF into a plurality of cells CL. The separated 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] In addition, in Figure 3, a line-shaped scintillator structure 10A using 1 x n cells is used as an example, 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 idea of ​​the present embodiment will be described below based on examples. Note that the technical idea 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 (Hishiko-rin PX-4ET)

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

[0079] The shape of this sample was 15 mm×15 mm×1.5 mm (length×width×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 is 90% or more in all of Examples 1 to 3 and the Comparative Example. On the other hand, looking at the "total light transmittance" after irradiation with X-rays at a dose of 100 kGy, Examples 1 to 3 have values ​​of 80% or more, whereas the Comparative Example does not reach 80%. When this result is converted into a "total light transmittance reduction rate," Examples 1 to 3 have a reduction rate of less than 5%, whereas the Comparative Example has a reduction rate of 14% or more.

[0083] From the above, it is evident that it is supported 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, in that the initial total light transmittance for light having a wavelength of 542 nm is maintained at 90% or more before X-ray irradiation, while the reduction rate of the total light transmittance for light having a wavelength of 542 nm is less than 5% after X-ray irradiation at a dose of 100 kGy. This shows 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. The use of this scintillator structure can provide an X-ray detector with excellent reliability that can maintain stable detection performance for a long period of time.

[0085] The invention made by the inventor has been specifically described above based on the embodiment thereof. However, it goes without saying that the present invention is not limited to the above embodiment, and various modifications can be made 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 detector 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, 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, prior to irradiation with X-rays, the resin has an initial total light transmittance of 90% or more for light having a wavelength of 542 nm.

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

4. 2. The scintillator structure of claim 1, A scintillator structure, wherein the resin contains an isocyanurate ring.

5. 5. The scintillator structure according to claim 4, A scintillator structure, wherein the resin has a plurality of epoxy groups per one isocyanurate ring.

6. 5. The scintillator structure according to claim 4, A scintillator structure, wherein the resin has three epoxy groups per one isocyanurate ring.

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

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