Scintillator structure and x-ray detector

Abstract

To improve reliability of a scintillator structure.SOLUTION: A scintillator structure for X-ray detection forming an X-ray detector, includes a resin and a fluorescent substance. The fluorescent substance includes gadolinium oxysulfide. The resin is an epoxy resin including a main agent, a hardener, and a hardening catalyst. The hardener is a phthalic anhydride-based hardener. The resin has an isocyanurate ring in a skeleton, and after radiation of X-ray whose radiation dose is 100 kGy, the whole light transmittance of the resin to light having a wavelength of 542 nm is 80% or more.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a scintillator structure, and more particularly, to a technique effective when applied to a scintillator structure having a plurality of cells each containing a resin and a phosphor.

Background Art

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

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] A scintillator is a substance that absorbs the energy of radiation, such as X-rays and gamma rays, and generates visible light when irradiated. This scintillator is commercialized as a scintillator structure including a scintillator and a reflective layer, and an X-ray detector combining the scintillator structure and a photoelectric conversion element such as a photodiode is used in, for example, medical devices such as X-ray CT, analytical instruments, non-destructive inspection devices using radiation, radiation leakage inspection devices, and the like.

[0005] For example, for the scintillator, ceramics made of gadolinium oxysulfide (Gd2O2S) are used. Here, in this specification, gadolinium oxysulfide will be referred to as "GOS". Strictly speaking, gadolinium oxysulfide itself hardly emits light, and it emits light by containing praseodymium, terbium, etc. in gadolinium oxysulfide. Therefore, in this specification, the term "GOS" is used implicitly to mean a substance (phosphor) in which gadolinium oxysulfide itself contains praseodymium, terbium, etc. and emits light. 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 composed of "GOS" alone, "GOS" is composed of ceramics. On the other hand, as will be described later, it has also been considered to compose the scintillator from a mixture of "GOS" and resin, and in this case, "GOS" is composed of powder. Therefore, in this specification, when there is no need to specifically indicate ceramics and powder, it is simply expressed as "GOS". On the contrary, when it is necessary to explicitly indicate ceramics, it is called "GOS" ceramics. On the other hand, when it is necessary to explicitly indicate powder, it will be called "GOS" powder.

[0007] This "GOS" has the advantage that the light emission output of visible light is larger than that of cadmium tungstate (CdWO4), but the manufacturing cost is high.

[0008] Therefore, in order to reduce the manufacturing cost of the scintillator structure, it has been considered to use a mixture of "GOS" powder and resin as the scintillator.

[0009] Regarding this point, improving reliability is one of the high-priority items required for the scintillator structure. This is because if the reliability of the scintillator structure can be improved, the lifespan of the radiation detector can be extended. 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 desired that the resin is less likely to deteriorate due to radiation exposure.

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

Means for Solving the Problems

[0011] A scintillator structure according to an embodiment includes a plurality of cells and a reflective layer covering the plurality of cells. Here, each of the plurality of cells contains a resin and a phosphor, and the resin has a total light transmittance reduction rate of less than 8% for light having a wavelength of 542 nm after being irradiated with X-rays having a dose of 100 kGy.

Advantages 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

Figure 2

Figure 3

Embodiments for Carrying Out 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 easier 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. 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 the scintillator structure 10, the scintillator 11 is divided into a plurality of cells (CL). That is, from the viewpoint of improving the resolution of the X-ray image, the scintillator 11 is divided into a plurality of cells CL in accordance with each of the plurality of light receiving elements 20 (arraying of the scintillator 11). Thus, the scintillator structure 10 includes a plurality of cells CL and a reflective layer 12 covering the plurality of cells CL. Specifically, the upper surface and the four side surfaces of the cell CL are covered with the reflective layer 12. On the other hand, since the lower surface of the cell CL needs to be in contact with the light receiving element 20, it is not covered with the reflective layer 12.

[0019] The X-ray detector configured as described above operates as follows.

[0020] That is, when X-rays enter 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 the excited state. Then, the excited electrons 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. By such a 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, and another part of the visible light generated from the scintillator 11 is condensed on the light receiving element 20 while being repeatedly reflected by the reflective layer 12 covering the scintillator 11. Subsequently, for example, when visible light enters the light receiving element 20 composed of a photodiode, the electrons of the semiconductor material constituting the photodiode are excited from the valence band to the conduction band by the energy of this visible light. As a result, a current caused by the electrons excited to the conduction band flows through the photodiode. Then, an X-ray image is acquired based on the current output from the photodiode. In this way, according to the X-ray detector 100, an X-ray image can be acquired.

[0022] For example, as shown in FIG. 1, the scintillator structure 10 is composed of a cuboid-shaped scintillator 11 and a reflective layer 12 that covers the scintillator 11. Here, since the cuboid-shaped scintillator 11 is formed through processing steps such as a dicing process and a grinding process, a processed surface is formed on the surface of the cuboid shape. That is, the "processed surface" refers to a surface that has been mechanically processed. Specifically, the "processed surface" includes a surface ground with a grinding wheel or a surface of the workpiece cut with a slicing blade when performing workpiece thickness measurement.

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

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

[0025] For example, as the scintillator 11 constituting the scintillator structure 10, cadmium tungstate (hereinafter referred to as "CWO") is used, but this "CWO" contains cadmium, which is a substance subject to the RoHS Directive / REACH Regulation. Therefore, as the scintillator 11, "GOS" ceramic has been used instead of "CWO" containing cadmium. This "GOS" ceramic has the merit of having a higher visible light emission output compared to "CWO", but has the demerit of higher manufacturing cost.

[0026] Therefore, from the perspective of reducing manufacturing costs, as the scintillator 11, instead of the "GOS" ceramic, "resin GOS" which is a mixture of a resin made of epoxy resin or the like and "GOS" powder is considered to be adopted. That is, in order to suppress the increase in manufacturing costs due to the "GOS" ceramic, there is a move to use "resin GOS", which is cheaper than the "GOS" ceramic, for the scintillator 11.

[0027] Here, the "resin GOS" includes "first resin GOS" which is a mixture of "GOS" powder obtained by adding praseodymium (Pr) and cerium (Ce) to gadolinium oxysulfide and epoxy resin, and "second resin GOS" which is a mixture of "GOS" powder obtained by adding terbium (Tb) and cerium (Ce) to gadolinium oxysulfide and epoxy resin.

[0028] Both the "first resin GOS" and the "second resin GOS" have the advantage of having a higher emission output compared to "CWO". Furthermore, the afterglow characteristics of the "first resin GOS" are also equivalent to those of "CWO". That is, as the performance of the scintillator structure 10, not only a large emission output but also good afterglow characteristics are required.

[0029] Therefore, the afterglow characteristics will be described. The scintillator 11 constituting the scintillator structure 10 is a substance that generates visible light when irradiated with X-rays. In the scintillator 11, the mechanism for generating 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 the ground state with low energy to the excited state with high energy. Then, the electrons in the excited state transition to the ground state with low energy. 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 period of time.

[0031] The visible light generated by the transition of electrons from an excited state to a ground state that occurs after a certain amount of time has elapsed becomes afterglow. That is, the afterglow is 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 the fact that this afterglow is large means that the intensity of the visible light generated even after a certain amount of time has passed since X-ray irradiation is large. In this case, the afterglow generated by the previous X-ray irradiation will remain until the next X-ray irradiation, and the remaining afterglow will become noise. Therefore, it is desirable that the afterglow is small. That is, good afterglow characteristics mean that the afterglow is small. In this regard, the afterglow characteristics of "Resin GOS" are equivalent to those of "CWO".

[0032] Therefore, "Resin GOS" has the following advantages compared to "CWO", and is excellent as the scintillator 11 that can balance performance and manufacturing cost. (1) "Resin GOS" has a higher light emission output than "CWO". (2) The afterglow characteristics of "First Resin GOS" are equivalent to those of "CWO". (3) "Resin GOS" does not use cadmium. (4) "Resin GOS" has a lower manufacturing cost than "CWO".

[0033] Also, cesium iodide (CsI) is used as the scintillator 11, but "Resin GOS" also has the following advantages compared to "CsI". (1) "Second Resin GOS" has better X-ray stopping characteristics than "CsI". (2) The afterglow characteristics of "Second Resin GOS" are about 1 / 70 of those of "CsI". (3) "Resin GOS" is a stable substance without deliquescence.

[0034] Furthermore, "resin GOS" also has the following advantages compared to "GOS" ceramic. That is, both "resin GOS" and "GOS" ceramic contain heavy metals such as "Gd", "Ga", or "Bi". These heavy metals are relatively expensive and there are concerns about their adverse effects on living organisms and the environment due to leaching. Therefore, it is desirable that the heavy metals contained in the scintillator 11 be as few as possible. In this regard, "resin GOS" composed of a mixture of "GOS" powder and resin uses less "GOS" than bulk "GOS" ceramic. This means that according to "resin GOS", a scintillator 11 with a lower heavy metal content than "GOS" ceramic can be constructed. From this, it can be said that "resin GOS" is superior to "GOS" ceramic in terms of being able to provide a scintillator 11 with a low heavy metal content.

[0035] From the above, "resin GOS" is expected to be a promising scintillator 11 that can balance performance and manufacturing cost.

[0036] <Specific materials> Subsequently, the specific materials of the components constituting the scintillator structure 10 will be described.

[0037] <<Phosphor 11a>> The phosphor 11a used in this embodiment is composed of, for example, gadolinium oxysulfide or gadolinium-aluminum-gallium garnet (GGAG). Here , gadolinium oxysulfide has a composition of "Gd2O2S" activated with at least one selected from, for example, praseodymium (Pr), cerium (Ce), or terbium (Tb). On the other hand, "GGAG" is, for example, (Gd 1-x Lu x ) 3+a (Ga u Al 1-u ) 5-a O 12It 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] <<Resins 11b and 12b>> The resins 11b and 12b are composed of materials that are less likely to deteriorate due to alteration when irradiated with radiation. The materials of these resins 11b and 12b are the characteristic points in this embodiment, and this characteristic point will be described later.

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

[0040] <<Other additives>> In addition to the above-described components, other additives may be blended in the reflector constituting the scintillator 11 and the reflection layer 12. For example, it is desirable to blend a curing catalyst to shorten the curing time of the resin.

[0041] <Examination of improvement> For example, epoxy resin is used as the resin contained in "resin GOS". This epoxy resin contains at least a main agent and a curing agent as constituent materials. For example, bisphenol A type epoxy resin is often used as the main agent, and an amine-based curing agent is often used as the curing agent. However, when using a general epoxy resin with bisphenol A type epoxy resin as the main agent and an amine-based curing agent as the curing agent as the resin constituting "resin GOS", the inventor newly found that it deteriorates and discolors when irradiated with radiation (X-rays) repeatedly over a long period.

[0042] And the fact that the resin with translucency discolors means that the light absorption increases, and as a result, it means that the light transmittance decreases. From this, the light generated from the scintillator made of "resin GOS" becomes difficult to reach the light receiving element (photodiode), so the detection performance of the X-ray detector decreases.

[0043] That is, according to the study of the inventor, when using a general epoxy resin with bisphenol A type epoxy resin as the main agent and an amine-based curing agent as the curing agent as the resin constituting "resin GOS", it is found that it is difficult to exhibit stable detection performance over a long period in an X-ray detector. In other words, the inventor has newly obtained the knowledge that when using the above-mentioned general epoxy resin as the resin constituting "resin GOS", it is difficult to ensure the reliability of the X-ray detector over a long period.

[0044] Therefore, based on the above-mentioned new knowledge, in order to ensure the reliability of the X-ray detector over a long period, it can be seen that it is desirable to adopt a resin that is difficult to discolor even when irradiated with X-rays over a long period as the resin constituting "resin GOS" instead of the above-mentioned general epoxy resin. Therefore, since the inventor has found a resin with excellent radiation resistance that is difficult to discolor even when irradiated with X-rays over a long period, this point will be explained below.

[0045] <Features in the Embodiment> The feature point in this embodiment is that, as an epoxy resin containing at least a main agent and a curing agent, the epoxy resin shown below is used for the resin contained in "resin GOS" and the resin contained in the reflector. Thereby, the reliability of the X-ray detector having the scintillator structure in this embodiment as a component can be ensured over a long period.

[0046] <<Main Agent>> The main agent is a triazine derivative epoxy resin. Examples of the triazine derivative epoxy resin include 1,3,5-triazine derivative epoxy resin. And it is desirable that the 1,3,5-triazine derivative epoxy resin is an epoxy resin having an "isocyanurate ring". This is because an epoxy resin having an "isocyanurate ring" as a skeleton has excellent stability against radiation and heat and has the property of being difficult to discolor.

[0047] In particular, from the viewpoint of suppressing discoloration, it is desirable that the epoxy resin having an "isocyanurate ring" as a skeleton has a plurality of epoxy groups for one isocyanurate ring. For example, it is desirable to have three epoxy groups for one isocyanurate ring. This is because when a plurality of epoxy groups are bonded to the isocyanurate ring, the reactivity is high and it has a tough stability, so that it is difficult to discolor even when irradiated with X-rays.

[0048] Examples of the epoxy resin 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-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]tripropanoate, and the like.

[0049] Examples of commercially available products of triazine derivative epoxy resins (epoxy resins having an "isocyanurate ring") include "TEPIC-G", "TEPIC-S", "TEPIC-SS", "TEPIC-HP", "TEPIC-L", "TEPIC-PAS" manufactured by Nissan Chemical Industries, Ltd., which are commercially available products of 1,3,5-tris(2,3-epoxypropyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione; "TEPIC-VL" manufactured by Nissan Chemical Industries, Ltd., which is a commercially available product of 1,3,5-tris(3,4-epoxybutyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione; "TEPIC-FL" manufactured by Nissan Chemical Industries, Ltd., which is a commercially available product of 1,3,5-tris(5,6-epoxybutyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione; "TEPIC-UC" manufactured by Nissan Chemical Industries, Ltd., which is 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, and the like.

[0050] <<Hardener>> In order to suppress discoloration caused by X-ray irradiation, it is desirable to use a material without a carbon-carbon double bond. This is because the carbon-carbon double bond has a weaker bond strength than the carbon-carbon single bond, and as a result of the carbon-carbon double bond being easily cleaved by X-ray irradiation, discoloration of the material is likely to occur. For example, as the curing agent, an acid anhydride-based curing agent typified by a phthalic anhydride-based curing agent can be used. In particular, from the viewpoint of effectively suppressing discoloration due to X-ray irradiation, one type or two or more types of polybasic carboxylic acid anhydrides that are non-aromatic and chemically do not have a carbon-carbon double bond may be used in combination.

[0051] Specifically, examples of the curing agent include tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, hexahydrophthalic anhydride, methylhexahydrophthalic anhydride, methylnadic anhydride, dodecenyl succinic anhydride, and the like. In particular, it is desirable to use methylhexahydrophthalic anhydride.

[0052] Specific examples of the acid anhydride compound include "Ricacid TH", "TH-1A", "HH", "MH", "MH-700", "MH-700G" (all manufactured by Shin Nippon Rika Co., Ltd.).

[0053] <<Curing Catalyst>> The curing catalyst is not an essential constituent material, but it is desirable to add it from the viewpoint of promoting the curing reaction of the main agent. As the curing catalyst, it is desirable to use an organophosphorus compound that is less likely to discolor even when irradiated with X-rays. Specifically, examples of the curing catalyst include tetrabutylphosphonium 0,0-diethyl phosphorodithioate (Hisico-phosphine PX-4ET, manufactured by Nippon Chemical Industry Co., Ltd.), methyltributylphosphonium dimethyl phosphate (Hisico-phosphine PX-4MP, manufactured by Nippon Chemical Industry Co., Ltd.), and the like.

[0054] <Verification of Effects> According to the "resin GOS" containing the triazine derivative epoxy resin described above, verification results will be described that can suppress a decrease in the "total light transmittance" even after X-ray irradiation.

[0055] As used in this specification, the "total light transmittance" is intentionally used to include light that is transmitted through the scintillator with its transmission direction deviated from the incident direction due to scattering inside the scintillator. That is, the "total light transmittance" represents the transmittance including not only the transmitted light that travels straight through from the incident direction but also the transmitted light that is scattered inside the scintillator and whose transmission direction is deviated from the straight-through direction. The intention of 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, the light scattered inside the cell is repeatedly reflected and finally incident on the light-receiving element arranged on the bottom surface of the cell. Therefore, the light scattered inside the cell also contributes to the detection of radiation by the light-receiving element. That is, the "total light transmittance" is used to evaluate taking into account all the transmitted light that contributes to the detection of radiation.

[0056] Also, the "total light transmittance" in this specification means the total light transmittance measured using light having a wavelength of 542 nm for a sample with a thickness of 1.5 mm. Note that, for the measurement of the "total light transmittance", after preparing a sample with a length × width × thickness of 15 mm × 15 mm × 1.5 mm, a sample with its surface mirror-finished is used to measure the "total light transmittance" for each sample.

[0057]

Table 1

[0058] Table 1 is a table showing the verification results for Sample A and Sample B.

[0059] ​In Table 1, Sample A represents the "resin GOS" in the present embodiment, which is a "resin GOS" using a triazine derivative epoxy resin as the main agent and "Me-HHPA" (material name: methylhexahydrophthalic anhydride, product name: "Rikacid MH-T" manufactured by Shin Nippon Rika Co., Ltd.) as the curing agent. On the other hand, Sample B represents the "resin GOS" in the related art, which is a "resin GOS" using a bisphenol A type epoxy resin as the main agent and an amine compound as the curing agent.

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

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

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

[0063] In particular, from the results in Table 1, according to the "resin GOS" in the present embodiment, before irradiation with X-rays, while ensuring that the initial total light transmittance for light having a wavelength of 542 nm is 90% or more, after irradiation with X-rays having a dose of 100 kGy, an excellent performance can be realized in which the reduction rate of the total light transmittance for light having a wavelength of 542 nm is less than 8%. From this, by using the "resin GOS" in the present embodiment, a scintillator structure with high emission output and excellent radiation resistance can be provided. As a result, by using the scintillator structure in the present embodiment, an X-ray detector with excellent reliability that can maintain stable detection performance over a long period can be provided.

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

[0065] For example, even if a material is known to have radiation resistance, it is impossible to determine whether the reliability of an X-ray detector can actually be ensured over a long period of time without knowing how much X-ray irradiation dose it is resistant to. That is, just because a material has radiation resistance qualitatively, it does not necessarily guarantee the reliability of an X-ray detector that uses a high dose of X-rays over a long period of time. In this regard, this embodiment shows the verification results after irradiation with X-rays at a high dose of 100 kGy, and based on this verification result, it is stated that the radiation resistance of "resin GOS" containing a triazine derivative epoxy resin is excellent. Here, according to "resin GOS" containing a triazine derivative epoxy resin, it has great technical significance that it has been verified that the decrease in "total light transmittance" can be suppressed even after irradiation with 100 kGy of X-rays. Because this verification result is data based on a high dose of 100 kGy, it will provide highly reliable data as the basis for guaranteeing the reliability of an X-ray detector that uses a high dose of X-rays over a long period of time.

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

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

[0068] In FIG. 2, first, a predetermined amount of raw material powder and a flux component are weighed and mixed (S101). After that, this mixture is filled into a crucible and fired in an air 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 warm water (S103). Next, an epoxy resin is dropped onto the "GOS" powder to impregnate the "GOS" powder with the epoxy resin (S104). Next, after curing the epoxy resin (S105), the epoxy resin not mixed with the "GOS" powder is removed (S106). Thereby, a scintillator made of "resin GOS" can be formed.

[0069] Subsequently, the substrate on which the scintillator is formed is diced to individualize the substrate into a plurality of cells (S107). After the plurality of individualized cells are rearranged (S108), a reflective material is applied to cover the plurality of cells (S109). Then, after cutting off the unnecessary part as the scintillator structure 10A (S110), the scintillator structure that has passed the inspection is shipped (S111).

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

[0071] As shown in FIG. 3, by dicing the substrate WF on which a scintillator made of "resin GOS" is formed, the substrate WF is individualized into a plurality of cells CL. Then, the plurality of individualized cells CL are rearranged, for example, in a line. After that, an outer frame FR is 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 way, the scintillator structure 10A is manufactured.

[0072] In FIG. 3, a linear scintillator structure 10A using 1×n cells is described as an example. However, the technical idea in the present embodiment is not limited to this. For example, it is also applicable to an array-shaped (matrix-shaped) scintillator structure using n×n cells.

[0073] <Example> Hereinafter, based on examples, detailed verification results supporting the effects of the technical idea in the present embodiment will be described. Note that the technical idea in the present embodiment is not limited to these examples.

[0074]

Table 2

[0075] Table 2 is a table showing the evaluation results based on the samples.

[0076] First, the samples will be described.

[0077] <<Materials>> "GOS" powder: Gadolinium oxysulfide (Gd2O2S) Main agent: 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-based epoxy resin (Epiclon 840 (DIC)) Hardener: Acid anhydride (Ricacid MH-T) Hardening catalyst: Organophosphorus compound (Hisico-phosphorus PX-4ET)

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

[0079] The shape of this sample is 15 mm × 15 mm × 1.5 mm (length × width × thickness), and the surface of the sample is mirror-finished.

[0080] <<Evaluation Method>> After irradiating the sample with X-rays at 100 kGy, the "total light transmittance" with respect to the light having a wavelength of 542 nm was measured using a UV-visible-near-infrared spectrophotometer V-570 manufactured by JASCO Corporation.

[0081] Here, an integrating sphere device and a reflector were used, and the diffused transmitted light and the direct transmitted light were collected by 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 shows a value of 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 irradiating with X-rays at a dose of 100 kGy, in Examples 1 to 3, the value is 80% or more, while in the comparative example, it does not reach 80%. When this result is converted to the "total light transmittance reduction rate", in Examples 1 to 3, the reduction rate is less than 5%, while in the comparative example, the reduction rate is 14% or more.

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

[0084] In particular, from the results in Table 2, according to the "resin GOS" in Examples 1 to 3, before irradiating with X-rays, while ensuring that the initial total light transmittance with respect to light having a wavelength of 542 nm is 90% or more, after irradiating with X-rays having a dose of 100 kGy, it can be seen that an excellent performance can be achieved in which the reduction rate of the total light transmittance with respect to light having a wavelength of 542 nm is less than 5%. From this, by using the "resin GOS" in Examples 1 to 3, a scintillator structure with high emission output and excellent radiation resistance can be provided. And by using this scintillator structure, an X-ray detector with excellent reliability that can maintain stable detection performance over a long period can be provided.

[0085] As described above, the invention made by the present inventor has been specifically described based on its embodiments. However, it goes without saying that the present invention is not limited to the above embodiments and can be variously modified without departing from the gist thereof.

Explanation of reference numerals

[0086] 10 Scintillator structure 11 Scintillator 11a Phosphor 11b Resin 12 Reflective layer 12a Reflective particles 12b Resin 20 Light receiving element 30 Support 100 X-ray detector CL Cell

Claims

1. A scintillator structure for X-ray detection, wherein the scintillator structure includes a resin and a phosphor, the phosphor includes gadolinium oxysulfide, the resin is an epoxy resin including a main agent, a curing agent, and a curing catalyst, the curing agent is an anhydrous phthalic acid-based curing agent scintillator structure.

2. The scintillator structure according to Claim 1, wherein the curing catalyst is an organic phosphorus-based compound scintillator structure.

3. A scintillator structure for X-ray detection, wherein the scintillator structure includes a resin and a phosphor, the phosphor includes gadolinium oxysulfide, the resin is an epoxy resin including a main agent, a curing agent, and a curing catalyst, the resin has an isocyanurate ring as a backbone scintillator structure.

4. The scintillator structure according to Claim 3, wherein the resin is a triazine derivative epoxy resin scintillator structure.

5. The scintillator structure according to Claim 3, wherein the resin has a plurality of epoxy groups with respect to one isocyanurate ring scintillator structure.

6. A scintillator structure for X-ray detection, wherein the scintillator structure includes a resin and a phosphor, the phosphor includes gadolinium oxysulfide, the resin is an epoxy resin including a main agent, a curing agent, and a curing catalyst, the resin has an isocyanurate ring as a backbone, the total light transmittance of the resin with respect to light having a wavelength of 542 nm is 80% or more scintillator structure.

7. A scintillator structure for X-ray detection, wherein the scintillator structure includes a resin and a phosphor, the phosphor includes gadolinium oxysulfide, the resin is an epoxy resin including a main agent, a curing agent, and a curing catalyst, the resin has an isocyanurate ring as a backbone, after irradiating X-rays with a dose of 100 kGy, the total light transmittance of the resin with respect to light having a wavelength of 542 nm is 80% or more scintillator structure.

8. An X-ray detector having the scintillator structure of Claim 1 and a light receiving element.

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