Scintillator array, method for manufacturing scintillator array, radiation detector, and radiation inspection device

Abstract

The scintillator array of the present invention comprises a structure and a second reflecting layer, wherein the structure comprises at least one scintillator segment and a first reflecting layer for reflecting light, wherein at least one scintillator segment and the first reflecting layer have a first surface and a second surface, and at least one scintillator segment comprises a sintered body comprising a rare earth oxysulfide phosphor, and the second reflecting layer is arranged on the first surface via an adhesive layer having a thickness of 2 μm to 40 μm and comprises a film for reflecting light.

Description

Technical Field

[0001] The present embodiment relates to a scintillator array, a method for manufacturing a scintillator array, a radiation detector, and a radiation inspection apparatus. Background Art

[0002] In the fields of medical diagnosis, industrial non-destructive inspection, etc., inspection is performed using a radiation inspection device such as an X-ray tomography device (hereinafter referred to as an X-ray CT (Computed Tomography: CT) device). The X-ray CT device is configured such that an X-ray tube (X-ray source) that irradiates fan-shaped fan beam X-rays and an X-ray detector having a large number of X-ray detection elements are arranged facing each other with a cross-sectional plane of the object to be inspected sandwiched therebetween.

[0003] The X-ray CT apparatus irradiates fan beam X-rays from an X-ray tube while rotating relative to the subject, collects X-ray absorption data after passing through the subject with an X-ray detector, and then reconstructs a tomographic image by analyzing the X-ray absorption data with a computer.

[0004] The radiation detector of the X-ray CT apparatus widely uses a detection element using a solid scintillator. Since the radiation detector having a detection element using a solid scintillator can easily increase the number of channels by miniaturizing the detection element, the resolution of the X-ray CT apparatus can be further improved.

[0005] Radiological inspection devices such as X-ray CT devices are used in various fields such as medical and industrial use. Examples of X-ray CT devices include multi-slice devices in which detection elements such as photodiodes are arranged vertically and horizontally in two dimensions and a scintillator array is mounted thereon. Multi-slice devices can overlap computed tomography (CT) to display CT images in three dimensions.

[0006] The radiation detector carried in the radiation inspection device has a plurality of detection elements arranged in multiple rows and columns, and each detection element has a scintillator segment. The radiation detector converts the X-rays incident on the scintillator segment into visible light, and converts the visible light into an electrical signal by the detection element to form an image. In recent years, in order to obtain high resolution, the detection element has been miniaturized, and the spacing between adjacent detection elements has been further narrowed. With this, the size of the scintillator segment has also become smaller.

[0007] Among various scintillator materials used in the above-mentioned scintillator segments, rare earth oxysulfide-based phosphor ceramics have high luminous efficiency and have characteristics suitable for use in scintillator segments. Therefore, radiation detectors that combine scintillator segments processed by cutting or grooving a sintered body (ingot) of rare earth oxysulfide-based phosphor ceramics as a scintillator material with photodiodes as detection elements are becoming popular.

[0008] Examples of scintillators using phosphor ceramics include scintillators formed from a sintered body of a gadolinium oxysulfide phosphor. A scintillator array using the above scintillator is manufactured, for example, as follows. First, a rare earth oxysulfide phosphor powder as a scintillator material is molded into an appropriate shape and sintered to form a sintered body (ingot). The sintered body is subjected to cutting processing such as cutting or grooving to form scintillator segments corresponding to a plurality of detection elements. Furthermore, a reflective layer for reflecting light is formed between these scintillator segments and integrated to manufacture a scintillator array.

[0009] When a scintillator array such as the one described above is used in a radiation detector, the dimensional accuracy of the scintillator array will affect the resolution of the CT diagnostic image. Furthermore, a maximum temperature of 50°C is applied to the radiation detector mounted in the X-ray CT device. In a scintillator array having a reflective layer containing resin, expansion of the reflective layer due to heating and contraction due to temperature reduction will occur, resulting in slight dimensional changes between adjacent scintillator segments, i.e., unevenness of the outer dimensions mainly caused by the offset of the spacing between the scintillator segments and the warping of the scintillator array. These will cause the resolution of the diagnostic image of the radiation inspection device to deteriorate.

[0010] As the resolution of diagnostic images in radiological examination devices increases, scintillator arrays with less dimensional change due to heating and cooling are required. Furthermore, since the area of ​​the scintillator array increases with the increase in the detection area of ​​the radiation detector, it is important to control the dimensional change due to heating and cooling.

[0011] Prior art literature

[0012] Patent Literature

[0013] Patent Document 1: International Publication No. 2013 / 080565

[0014] Patent Document 2: International Publication No. 2017 / 082337

[0015] Patent Document 3: International Publication No. 2017 / 110850 Summary of the invention

[0016] The scintillator array of the embodiment comprises a structure and a second reflecting layer, the structure comprising at least one scintillator node and a first reflecting layer that reflects light, at least one scintillator node and the first reflecting layer having a first surface and a second surface, at least one scintillator node having a sintered body containing a rare earth oxysulfide phosphor, the second reflecting layer being arranged on the first surface via an adhesive layer having a thickness of 2 μm to 40 μm and comprising a film that reflects light. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a plan view showing a structural example of a scintillator array.

[0018] Figure 2 It is a cross-sectional view showing a structural example of a scintillator array.

[0019] Figure 3 This is a diagram showing the relationship between the adhesive layer thickness and the warpage of the scintillator array.

[0020] Figure 4 It is a diagram showing a configuration example of a radiation inspection detector.

[0021] Figure 5 It is a diagram showing a configuration example of a radiation inspection apparatus. DETAILED DESCRIPTION

[0022] Hereinafter, the embodiments are described with reference to the accompanying drawings. The relationship between the thickness and the plane size of each component element and the ratio of the thickness of each component element recorded in the accompanying drawings may be different from the actual object. In addition, in the embodiments, the same symbols are sometimes marked on substantially the same components and the description is appropriately omitted.

[0023] Hereinafter, a scintillator array, a radiation detector, and a radiation inspection apparatus according to the embodiment will be described.

[0024] (Scintillator Array)

[0025] Figure 1 It is a plan view showing a structural example of a scintillator array. Figure 2 It is a cross-sectional view showing a structural example of a scintillator array. Figure 1 and Figure 2 The figure shows a scintillator array 1, a scintillator segment 2, a reflective layer 3, a reflective layer 4 and an adhesive layer 5. It should be noted that the reflective layer 4 and the adhesive layer 5 are Figure 1 Omitted for convenience.

[0026] The scintillator array 1 includes a plurality of scintillator segments 2, a reflective layer 3, a reflective layer 4, and an adhesive layer 5. The scintillator segments 2 and the reflective layer 3 form a structure 20 having a surface 20a as an X-ray incident surface and a surface 20b on the opposite side of the surface 20a. It should be noted that the scintillator array 1 only needs to have at least one scintillator segment 2. The number of scintillator segments 2 is appropriately set according to the structure, resolution, etc. of the radiation detector.

[0027] The scintillator segments 2 convert incident radiation (X-rays) into light (visible light). The plurality of scintillator segments 2 are integrated with the reflective layer 3 bonded thereto to form a structure 20 .

[0028] The reflective layer 3 reflects light (visible light). The reflective layer 3 may also transmit X-rays. The reflective layer 3 is provided between adjacent scintillator segments 2 and is bonded to each scintillator segment 2 .

[0029] The reflective layer 4 reflects light (visible light). The reflective layer 4 may also transmit X-rays. Figure 2 As shown in , it is provided on the surface 20a via the adhesive layer 5 and covers the structure 20. The reflective layer 4 is formed by bonding a resin film formed by molding a resin containing reflective particles that reflect light into a sheet shape to the surface 20a via the adhesive layer 5.

[0030] The scintillator array 1 may also have a structure in which a plurality of scintillator segments 2 are arranged in a row, or Figure 1 As shown in , a plurality of scintillator segments 2 are arranged two-dimensionally in a predetermined number in the longitudinal and transverse directions. When a plurality of scintillator segments 2 are arranged two-dimensionally, the reflective layer 3 is provided between the scintillator segments 2 arranged in the longitudinal direction and in the scintillator segments 2 arranged in the transverse direction. The reflective layer 3 may also surround the scintillator segments 2 along the surface 20a.

[0031] The scintillator segment 2 has a sintered body containing a rare earth oxysulfide phosphor. Examples of the rare earth oxysulfide phosphor include a rare earth oxysulfide phosphor containing praseodymium (Pr) as an activator. Examples of the rare earth oxysulfide include oxysulfides of rare earth elements such as yttrium (Y), gadolinium (Gd), lanthanum (La), and lutetium (Lu).

[0032] The rare earth oxysulfide phosphor preferably has a composition represented by the following general formula:

[0033] General formula: RE2O2S:Pr (1)

[0034] (RE represents at least one element selected from the group consisting of Y, Gd, La and Lu).

[0035] Among the above-mentioned rare earth elements, Gd has a large X-ray absorption coefficient, which helps to improve the light output power of the scintillator array 1. Therefore, the scintillator segment 2 preferably has a Gd2O2S:Pr phosphor. It should be noted that a part of Gd can also be replaced by other rare earth elements. In this case, the replacement amount of Gd with other rare earth elements is preferably less than 10 mol%.

[0036] That is, the rare earth oxysulfide phosphor preferably has a composition substantially represented by the following general formula:

[0037] General formula: (Gd 1-x , R.E. x )2O2S:Pr (2)

[0038] (wherein RE represents at least one element selected from the group consisting of Y, La and Lu, and x is a number (atomic ratio) satisfying 0≤x≤0.1).

[0039] The scintillator segment 2 has praseodymium (Pr) as an activator for increasing the light output. Pr can reduce afterglow compared with other activators. Therefore, rare earth oxysulfide phosphor ceramics containing Pr as an activator are effective as a fluorescence generator of a radiation detector.

[0040] The content of Pr in the rare earth oxysulfide phosphor is preferably 0.001 mol% to 10 mol% relative to the content of the phosphor matrix (e.g., RE2O2S such as Gd2O2S). If the content of Pr exceeds 10 mol%, the light output power will be reduced. When the content of Pr is less than 0.001 mol%, the effect as a main activator cannot be fully obtained. The content of Pr is more preferably 0.01 mol% to 1 mol%.

[0041] In addition to Pr as a main activator, the rare earth oxysulfide phosphor may contain a trace amount of at least one element selected from the group consisting of cerium (Ce), zirconium (Zr) and phosphorus (P) as a co-activator. These elements show effects on the suppression of exposure degradation, the suppression of afterglow, etc. The content of these co-activators is preferably in the range of 0.00001 mol% to 0.1 mol% based on the total amount of the phosphor matrix.

[0042] The sintered body constituting the scintillator segment 2 is preferably formed of a high-purity rare earth oxysulfide phosphor ceramic (scintillator material). Since impurities may reduce the sensitivity of the scintillator, the amount of impurities is preferably as small as possible. In particular, since phosphate (PO4) may cause a decrease in sensitivity, its content is preferably less than 100 ppm. When fluoride or the like is used as a sintering aid to increase the density of the sintered body, the sintering aid will remain as an impurity, thereby causing a decrease in sensitivity.

[0043] The sintered body has a cubic shape or a rectangular parallelepiped shape. The volume of the scintillator segment 2 is preferably 1 mm 3 By miniaturizing the scintillator segment 2, the detected image can be highly refined. The dimensions of the scintillator segment 2, i.e., the length (L), width (S), and thickness (T), are not necessarily limited, but are preferably 1 mm or less. 3 In the case of 0.5 μm or less, the width (W) of the reflective layer 3 can be reduced to 100 μm or less, and further to 50 μm or less.

[0044] The reflective layer 3 contains a resin that transmits light (translucent resin) and reflective particles dispersed in the resin and reflecting light. The resin includes at least one selected from the group consisting of epoxy resin, silicone resin, phenolic resin, urea-formaldehyde resin, melamine resin, polyester resin, polyurethane resin and acrylic resin. The reflective particles include at least one selected from the group consisting of titanium oxide, aluminum oxide (alumina), silicon oxide, barium sulfate, zinc oxide, zirconium oxide and gadolinium oxide. It should be noted that the bubbles contained in the resin sometimes also play a role as reflective particles.

[0045] The reflective layer 4 may use the same translucent resin and reflective particles as the reflective layer 3. The reflective layer 4 is formed by pre-processing a material containing the translucent resin and reflective particles into a sheet to form a resin film, and attaching the resin film to the surface 20a of the structure 20 via the adhesive layer 5. As the resin film, a commercially available white film may also be used.

[0046] The thickness of the reflective layer 4 is preferably 50 μm to 250 μm. If the thickness of the reflective layer 4 is less than 50 μm, the effect of improving the reflection efficiency cannot be fully obtained. If the thickness of the reflective layer 4 exceeds 250 μm, the amount of transmitted X-rays decreases and the detection sensitivity decreases.

[0047] The light-transmitting resin has a glass transition temperature (transition temperature) of 50°C or more. Since the temperature during the manufacturing process of the X-ray CT apparatus, the temperature during use of the X-ray CT apparatus, and the temperature of the storage environment of the X-ray CT apparatus are all about 18°C ​​to 50°C, if the glass transition temperature of the light-transmitting resin is 50°C or more, it is possible to suppress dimensional changes during manufacturing, use, and storage (spacing deviation of the scintillator segments 2, warping of the scintillator array 1, and unevenness of the outer dimensions of the scintillator array 1). The glass transition temperature of the light-transmitting resin is more preferably higher than 50°C, further preferably higher than 60°C, and particularly preferably higher than 85°C. In addition, the glass transition temperature of the light-transmitting resin is preferably lower than 120°C. In the case of exceeding 120°C, there is a possibility that the shrinkage of the resin during the manufacturing of the scintillator array 1 becomes larger, and the warping of the scintillator array 1 and the spacing deviation of the scintillator segments 2 become larger.

[0048] The light-transmitting resin constituting the reflective layer 3 and the reflective layer 4 preferably has a thermal expansion coefficient (linear expansion coefficient) of 2×10 -5 / ℃ or less. If the above thermal expansion coefficient exceeds 2×10 -5 / °C, the finished dimensions of the scintillator array 1 are likely to change (the pitch of the scintillator segments 2 is offset, the scintillator array 1 is warped, and the outer dimensions are uneven) depending on the temperature in the manufacturing process of the X-ray CT apparatus. The thermal expansion coefficient is more preferably 1.5×10 -5 / ℃ below.

[0049] In order to satisfy the glass transition temperature and the thermal expansion coefficient, the light-transmitting resin preferably has a molecular structure including a ring structure without a double structure (double bond). When the molecular structure of the light-transmitting resin includes a double structure, the glass transition temperature tends to be lower than 50°C.

[0050] The light-transmitting resin constituting the reflective layer 3 and the reflective layer 4 is preferably an epoxy resin having an aliphatic skeleton. By using an epoxy resin having an aliphatic skeleton, the above-mentioned glass transition temperature and the above-mentioned thermal expansion coefficient can be easily achieved. Furthermore, the epoxy resin as the light-transmitting resin preferably has a molecular structure including the above-mentioned ring structure. By using such an epoxy resin, it becomes easy to increase the glass transition temperature and it becomes easy to reduce the thermal expansion coefficient at a temperature exceeding the glass transition temperature.

[0051] The ratio of the translucent resin to the reflective particles in the reflective layer 3 and the reflective layer 4 is preferably 15% to 60% by mass of the translucent resin and 40% to 85% by mass of the reflective particles. The total of the mass ratio of the translucent resin and the mass ratio of the reflective particles is 100%. When the mass ratio of the reflective particles is less than 40%, the reflective efficiency of the reflective layer decreases, and the reflective efficiency of the reflective layer with respect to light of a wavelength of 512 nm tends to become less than 90%. If the mass ratio of the reflective particles exceeds 85%, although the reflective efficiency of the reflective layer does not change, the stable solidification of the reflective layer becomes difficult because the mass ratio of the translucent resin is relatively reduced.

[0052] The adhesive layer 5 includes at least one resin selected from the group consisting of epoxy resin, silicone resin, acrylic resin, urethane resin, polyester resin and polyolefin resin, and cured by any one of light, heat and moisture. The adhesive layer 5 may also be a light-transmitting resin, but in order to reduce the light from one scintillator segment 2 entering another scintillator segment 2 through the adhesive layer 5, the adhesive layer 5 preferably includes at least one selected from the group consisting of titanium oxide, zirconium oxide, aluminum oxide and silicon oxide.

[0053] Figure 3It is a diagram showing the relationship between the thickness of the adhesive layer 5 of the scintillator array 1 (adhesive layer thickness) and the warpage of the scintillator array 1 . Figure 3 Indicates the improvement degree of the warpage in the scintillator array 1. An example of the scintillator array 1 is formed by integrating the scintillator segments 2 having a length (L), a width (S), and a thickness (T) of 1 mm through a reflective layer 3 having a width of 100 μm to form a structure 20 having a length of 76 mm and a width of 25 mm, and bonding a white polyethylene terephthalate (PET) film as the reflective layer 4 to the structure 20 using an epoxy resin as an adhesive layer 5. Figure 3 FIG. 5 shows the change in the warpage of the scintillator array 1 with respect to the thickness of the adhesive layer 5 .

[0054] The warping of the scintillator array 1 is measured as follows. The warped scintillator array 1 generally has a convex side and a concave side. In the measurement of the warping, first, the scintillator array 1 is placed on a plane with the convex side facing downward. At this time, the scintillator array 1 is in a state of being away from the setting surface toward the end and arched upward. In this state, the vertical distance between the uppermost arched point and the setting surface is measured, and it is defined as the warping. The warping of the scintillator array 1 is generally required to be less than 50μm. The so-called state without warping means a state in which the bottom surface of the scintillator array 1 is in contact with the setting surface at all points, and the warping at this time is 0μm.

[0055] Depend on Figure 3 It is known that as the thickness of the adhesive layer 5 increases, the warpage increases. This is due to the stress generated inside the adhesive layer 5 due to shrinkage during curing. The warpage value has a range of about ±5 μm, but if the thickness of the adhesive layer 5 exceeds 50 μm, the warpage also exceeds 50 μm and becomes larger, which is not preferred. If the warpage exceeds 50 μm and becomes larger, it is usually necessary to correct it by pressing or grinding, and the process becomes complicated.

[0056] In the case of the scintillator array 1, by bonding the white film as the reflective layer 4 with an appropriate adhesive layer thickness, the scintillator array 1 can be formed in a preferred range of warping through a single treatment. This is considered to be because, for example, compared to the conventional process of forming the reflective layer 4 by coating and curing the film thickly, bonding the pre-formed flexible white film with a relatively thin adhesive layer 5 can reduce the volume of the curing shrinkage, and thus, it is less likely to generate stress that causes warping.

[0057] If the thickness of the adhesive layer 5 is less than 2 μm, the adhesive force becomes weak, which easily causes the peeling of the reflective layer 4. Therefore, the thickness of the adhesive layer 5 is preferably in the range of 2 μm to 40 μm, and more preferably in the range of 5 μm to 30 μm. In the case of exceeding 40 μm, the volume of curing shrinkage becomes larger, and the warping of the scintillator array 1 becomes larger, so it is not preferred. In addition, in the case of a light-transmitting adhesive layer 5, the light generated in the pixel (scintillator node 2) is incident on the adjacent pixel through the adhesive layer 5, causing crosstalk, so it is not preferred. The thickness of the adhesive layer 5 can be measured by observing the cross section in the thickness direction through an electron microscope or an optical microscope, and the observed image is used for measurement. Since the reflective layer 4 and the adhesive layer 5 form a network structure of the polymer by each layer, the interface of these layers is clear. In addition, in the case of different pigment concentrations, it is further clear and therefore easy to judge the thickness.

[0058] The scintillator array used in the previous X-ray CT apparatus needs to confine the light generated by the X-rays within the pixel and effectively extract it to the photodiode side. Since the alignment accuracy is required when bonding with the photodiode, it is necessary to make the spacing between the pixels not easy to change with the temperature, especially the warping of the scintillator itself is small. In the case of large warping of the scintillator, the thickness of the adhesive layer filled between the scintillator array and the photodiode becomes uneven when attached to the photodiode. In the place where the adhesive layer is thick, the light enters the adjacent pixels, the crosstalk becomes larger, and the detection sensitivity of the X-rays becomes uneven. In addition, since bubbles are easily introduced into the adhesive layer, the light from the scintillator is scattered, so the detection sensitivity of the X-rays is reduced.

[0059] In contrast, the following technology is known: by controlling the ratio of the number of reflective particles per unit area (5μm×5μm) to the agglomerates of reflective particles per unit area (10μm×10μm) in the reflective layer between the scintillator nodes, the shrinkage ratio of the reflective layer portion when the translucent resin is cured is made uniform, thereby suppressing the warping of the scintillator array during and after manufacturing.

[0060] It is also known that the glass transition temperature of the light-transmitting resin constituting the reflective layer is 50° C. or higher, and the thermal expansion coefficient of the light-transmitting resin at a temperature higher than the glass transition temperature is 3.5×10 -5 / °C or less. Generally, the thermal expansion coefficient of a light-transmitting resin changes greatly around the glass transition temperature, and the warpage caused by the change is adjusted by setting the conditions.

[0061] In addition, there is known a scintillator array with the following structure: in order to reduce the warping of the scintillator array, a plurality of scintillator segments are integrated through a reflective layer, the glass transition temperature of the translucent resin of the reflective layer is above 50°C, and the glass transition temperature of the translucent resin of the second reflective layer arranged on the surface side of the plurality of scintillator segments on which X-rays are incident is below 30°C.

[0062] Although the warping of these scintillators has been improved to some extent, there is a demand for miniaturization of scintillator arrays in accordance with the demand for improved image quality, and further there is a demand for countermeasures against degradation of image quality or degradation of detection sensitivity due to crosstalk caused by the warping.

[0063] The scintillator array of the embodiment includes a first reflection layer forming the structure 20 together with a plurality of scintillator segments, and a second reflection layer arranged on the surface side of the plurality of scintillator segments on which X-rays are incident.

[0064] In the scintillator array of the embodiment, the second reflective layer can be formed by attaching a pre-formed light-reflecting film via an adhesive layer, instead of applying a slurry obtained by dispersing reflective particles in a light-transmitting resin to the X-ray incident surface side of the scintillator array and thermally curing it. The scintillator array thus constructed is easier to manufacture than the conventional scintillator array. Furthermore, by controlling the thickness of the adhesive layer within a specified range, warping can be reduced.

[0065] Next, an example of a method for manufacturing the scintillator array 1 is described. The scintillator array 1 is manufactured, for example, as follows. First, reflective particles and an uncured resin composition (uncured material of the light-transmitting resin) constituting a light-transmitting resin are prepared, and they are mixed to prepare a mixture. Next, a plurality of scintillator segments 2 processed into a prescribed shape are arranged at a certain interval. The mixture of the reflective particles and the uncured resin composition is applied or filled between adjacent scintillator segments 2.

[0066] The resin composition in the uncured state preferably has a viscosity of 0.2Pa·s to 1.0Pa·s (200cps to 1000cps). If the viscosity of the resin composition exceeds 1.0Pa·s, the fluidity is poor, and the workability of coating or filling between the scintillator sections 2 is reduced. When the viscosity of the resin composition is lower than 0.2Pa·s, the fluidity becomes too high and the coating or filling properties are reduced. In addition, the total light transmittance of the translucent resin is preferably 85% or more. If the total light transmittance of the translucent resin is lower than 85%, the reflection efficiency of the reflective layer 3 becomes easy to reduce.

[0067] After a mixture of reflective particles and an uncured resin composition is applied or filled between a plurality of scintillator sections 2, a reflective layer 3 is formed by curing the resin composition in the mixture, thereby combining and integrating adjacent scintillator sections 2 to form a structure 20. The curing treatment of the mixture is appropriately set according to the type of the uncured resin composition or curing agent, etc. For example, in the case of a thermosetting resin composition, a curing reaction is carried out by heat treatment.

[0068] Next, a reflective layer 4 is formed on the surface 20a of the structure 20 via an adhesive layer 5. As a method for manufacturing a white film, a resin containing reflective particles that can be used to form the reflective layer 3 is processed into a sheet using a scraper or the like and cured. Not limited to this, a commercially available white film may also be used. Such a commercially available white film is formed by mixing reflective particles such as titanium oxide, aluminum oxide, and silicon dioxide into a translucent resin such as an epoxy resin or a polyester resin and processing the resultant into a sheet. The thickness of the white film is, for example, 50 μm to 250 μm.

[0069] A light-transmitting resin with a viscosity of 0.2 Pa·s to 1.0 Pa·s as the adhesive layer 5 is applied to the surface 20a of the structure 20, and a white film of a predetermined size is arranged thereon, and the resin is cured while being pressed. The curing by simultaneous pressing is a process made possible by using a white film in the reflective layer 4, which is difficult in conventional processes. Therefore, it is believed that the process also contributes to the reduction of warpage.

[0070] (Radiation Detector)

[0071] The radiation detector of the embodiment includes the above-mentioned scintillator array 1 as a fluorescence generator that radiates light in response to incident radiation, and further includes a photoelectric converter that receives light from the fluorescence generator and converts the light output into an electrical output. Figure 4 This is a diagram showing a configuration example of a radiation detector, showing an X-ray detector. Figure 4 The X-ray detector 6 shown in FIG. 1 includes a scintillator array 1 as a fluorescence generator and a photoelectric conversion element 7 as a photoelectric converter.

[0072] The X-ray detector 6 includes a photoelectric conversion element 7 integrally provided on the surface 20b of the structure 20. The photoelectric conversion element 7 detects light (visible light) formed by converting X-rays in the scintillator segment 2. Examples of the photoelectric conversion element 7 include photodiodes and the like. The photoelectric conversion element 7 is arranged so as to correspond to each of the plurality of scintillator segments 2. These components constitute a radiation detector.

[0073] (Radiological inspection equipment)

[0074] The radiation inspection apparatus of the embodiment includes a radiation source that irradiates radiation toward a subject and a radiation detector that detects the radiation that has passed through the subject. The radiation detector can be the radiation detector of the above-described embodiment.

[0075] Figure 5 It is a diagram showing a configuration example of a radiation inspection apparatus. Figure 5 The figure shows an X-ray CT apparatus 10, a subject 11, an X-ray tube 12, a computer 13, a display 14, and a subject image 15. The X-ray CT apparatus 10 includes an X-ray detector 6. The X-ray detector 6 is attached to, for example, the inner wall surface of a cylinder arranged at the imaging site of the subject 11. An X-ray tube 12 for emitting X-rays is provided at the approximate center of the arc of the cylinder to which the X-ray detector 6 is attached. The subject 11 is arranged between the X-ray detector 6 and the X-ray tube 12. A collimator (not shown) is provided on the X-ray incident surface side of the X-ray detector 6.

[0076] The X-ray detector 6 and the X-ray tube 12 are configured to rotate while performing X-ray photography with the subject 11 as the center. Image information of the subject 11 is collected three-dimensionally from different angles. The signal obtained by X-ray photography (electrical signal converted by the photoelectric conversion element) is processed by the computer 13 and displayed on the display 14 as a subject image 15. The subject image 15 is, for example, a cross-sectional image of the subject 11. Figure 1 As shown in FIG. 1 , a multi-slice X-ray CT apparatus 10 can be configured by using a scintillator array 1 in which scintillator segments 2 are two-dimensionally arranged. In this case, a plurality of slice images of the subject 11 are simultaneously captured, and the imaging results can be described three-dimensionally, for example.

[0077] Figure 5 The X-ray CT device 10 shown in the figure has an X-ray detector 6 having a scintillator array 1. As described above, the scintillator array 1 has a high reflection efficiency of visible light emitted from the scintillator node 2 due to the structure based on the reflection layer 3 and the reflection layer 4, and therefore has excellent light output power. By using the X-ray detector 6 having such a scintillator array 1, the imaging time using the X-ray CT device 10 can be shortened. As a result, the radiation time of the subject 11 can be shortened, and low radiation exposure can be achieved. The radiation inspection device (X-ray CT device 10) is not limited to X-ray inspection for medical diagnosis of human bodies, but can also be applied to X-ray inspection of animals, X-ray inspection for industrial purposes, etc. Furthermore, it also helps to improve the inspection accuracy using X-ray non-destructive inspection devices.

[0078] Example

[0079] Specific examples and evaluation results of the scintillator array 1 will be described. In describing the examples and comparative examples, the structure 20 including the scintillator segments 2 and the reflection layer 3 before forming the reflection layer 4 on the X-ray incident surface is produced as follows.

[0080] The phosphor powder having the composition of Gd2O2S:Pr (Pr concentration = 0.05 mol%) was temporarily molded by rubber pressing, and the temporary molded body was degassed and sealed in a tantalum (Ta) capsule, and then placed in a hot isostatic pressing (HIP) treatment device. Argon gas was sealed in the HIP treatment device as a pressurizing medium, and the treatment was carried out for 3 hours under the conditions of a pressure of 147 MPa and a temperature of 1425°C. In this way, a cylindrical sintered body with a diameter of about 80 mm and a height of about 120 mm was produced. From the sintered body, scintillator segments 2 with a length of 0.8 mm, a width of 0.7 mm, and a thickness of 0.7 mm were cut into a matrix of 84 in the length direction and 31 in the width direction. Next, the above-mentioned plurality of scintillator segments 2 were integrated through a reflective layer 3 formed by a mixture of 65% of reflective particles and 35% of a translucent resin by mass ratio to produce a structure 20. Reflective layers 3 with a thickness of 0.1 mm were arranged in the longitudinal and transverse directions of the structure 20. A mixture of 80% titanium oxide particles and 20% aluminum oxide particles was used as the reflective particles. Thus, a structure 20 with a length of 76 mm, a width of 25 mm, and a thickness of 0.7 mm was prepared.

[0081] (Example 1)

[0082] On the surface 20a of the structure 20 thus produced, an adhesive containing titanium oxide and epoxy resin (glass transition temperature after curing 85°C) was applied to form an adhesive layer 5 with a thickness of 10 μm, and a white PET film (manufactured by Mitsubishi Chemical, with a thickness of 100 μm) was provided as a reflective layer 4 on the adhesive layer 5. The scintillator array 1 was completed by curing at room temperature for 24 hours while applying a load of 16 kg. After the load was removed, the warpage was measured and found to be 15 μm. The results are shown in Table 1.

[0083] (Example 2)

[0084] On the surface 20a of the structure 20 thus produced, an adhesive containing titanium oxide and epoxy resin (glass transition temperature after curing 85°C) was applied to form an adhesive layer 5 with a thickness of 15 μm, and a white PET film (manufactured by Mitsubishi Chemical, with a thickness of 100 μm) was provided as a reflective layer 4 on the adhesive layer 5, and the scintillator array 1 was completed by curing for 24 hours at room temperature while applying a load of 10 kg. After the load was removed, the warpage was measured and the result was 20 μm. The results are shown in Table 1.

[0085] (Example 3)

[0086] On the surface 20a of the structure 20 thus produced, a white PET film (manufactured by Mitsubishi Chemical, with a thickness of 100 μm) as the reflective layer 4 was bonded via an epoxy adhesive sheet (with a thickness of 25 μm) as a prepreg of the adhesive layer 5. When bonding, the structure 20, the epoxy adhesive sheet, and the white PET film were overlapped, a load of 16 kg was applied, and they were heated at a temperature of 100°C to bond them. After cooling to room temperature, the load was removed, and the scintillator array 1 was completed. The warpage was measured and the result was 20 μm. The results are shown in Table 1.

[0087] (Example 4)

[0088] A mixture of 65% titanium oxide particles and 35% epoxy resin (glass transition temperature after curing 55°C) by mass ratio is formed on a fluororesin sheet using a scraper, and cured at room temperature for 24 hours to form a white film. The thickness of the obtained white film is 150μm. Next, an epoxy adhesive sheet (thickness 25μm) of a prepreg as an adhesive layer 5 is clamped on the surface 20a of the manufactured structure 20 to form a white film as a reflective layer 4, a load of 20kg is applied, and the film is heated and bonded at a temperature of 100°C. After cooling to room temperature, the load is removed to complete the scintillator array 1. The warping was measured and the result was 30μm. The results are shown in Table 1.

[0089] (Example 5)

[0090] A mixture of 65% titanium oxide particles and 35% epoxy resin (glass transition temperature after curing 55°C) in a mass ratio is formed on a fluororesin sheet using a scraper, and cured at room temperature for 24 hours to form a white film. The thickness of the obtained white film is 120μm. Next, a white film is arranged on the surface 20a of the manufactured structure 20 by clamping an epoxy adhesive sheet (thickness 25μm) as a prepreg of the adhesive layer 5, applying a load of 20kg, and heating and bonding at a temperature of 100°C. After cooling to room temperature, the load is removed to complete the scintillator array 1. The warping was measured and the result was 25μm. The results are shown in Table 1.

[0091] (Comparative Example 1)

[0092] A mixture of titanium oxide and epoxy resin (glass transition temperature after curing 85°C) was applied to the surface 20a of the fabricated structure 20, and cured at 100°C for 3 hours. In order to set the thickness to 150 μm, polishing was performed after curing to form a reflective layer 4. Since the epoxy resin is a hard resin at room temperature, the internal stress generated in the epoxy resin during the curing process is large, and the warpage was measured to be 140 μm. The results are shown in Table 1.

[0093] (Comparative Example 2)

[0094] A mixture of titanium oxide and epoxy resin (glass transition temperature after curing 85°C) was applied to the surface 20a of the fabricated structure 20, and cured at 100°C for 3 hours. In order to set the thickness to 130 μm, polishing was performed after curing to form a reflective layer 4. Compared with Comparative Example 1, since the thickness of the reflective layer 4 was thin, the stress was relaxed, and the warpage was measured to be 132 μm. The results are shown in Table 1.

[0095] (Comparative Example 3)

[0096] On the surface 20a of the structure 20 thus produced, a solution in which titanium oxide and nitrocellulose were dispersed in a solvent was sprayed, and the solvent was evaporated by heating to form a coating film to be the reflective layer 4. The coating film had a thickness of 100 μm after drying. The warpage was measured along with the drying shrinkage, and the result was 100 μm. The results are shown in Table 1.

[0097] [Table 1]

[0098] Warping Warp Correction Example 1 15μm unnecessary Example 2 20μm unnecessary Example 3 20μm unnecessary Example 4 30μm unnecessary Example 5 25μm unnecessary Comparative Example 1 140μm need Comparative Example 2 132μm need Comparative Example 3 100μm need

[0099] In the comparative example, although the same light-transmitting resin as in the embodiment is applied to the X-ray incident surface side, the internal stress generated during curing is large and the warping is large because the reflective layer after curing is thick. In the embodiment, by using a white film and thinning the adhesive layer, the stress during curing can be reduced and the warping can be greatly reduced. In addition, in the embodiment, no correction of the warping is required, but in the comparative example, in order to correct the warping, a heat treatment process and a grinding process are further required, and the scintillator array 1 is greatly warped, so the thickness of the reflective layer 4 and the scintillator node 2 on the X-ray incident surface becomes uneven in the plane, and there is a tendency to easily produce uneven output characteristics.

[0100] According to the scintillator array of the embodiment, warping can be greatly reduced, and the thickness of the bonding surface with the photoelectric conversion element can be made uniform, thereby reducing the variation in output characteristics. In addition, the steps such as heat treatment and polishing for correcting warping can be reduced, which has great industrial advantages.

[0101] Several embodiments of the present invention have been described, but these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other ways, and various omissions, substitutions, and changes can be made without departing from the scope of the subject matter of the invention. These embodiments and their variations are included in the scope and subject matter of the invention, and are also included in the invention described in the claims and their equivalents.

Claims

1. A scintillator array, comprising: A structure comprising a plurality of scintillator segments and a first reflection layer disposed between adjacent scintillator segments and reflecting light, wherein the plurality of scintillator segments and the first reflection layer have a first surface and a second surface, and the plurality of scintillator segments have a sintered body containing a rare earth oxysulfide phosphor; and a second reflecting layer, which is provided on the first surface via an adhesive layer containing a resin and having a thickness of 2 μm to 40 μm, and is formed of a resin film that reflects light, The thickness of the second reflective layer is 50 μm to 250 μm. The warping of the scintillator array is 50 μm or less.

2. The scintillator array according to claim 1, wherein: The thickness of the adhesive layer is 5 μm to 30 μm.

3. The scintillator array according to claim 1, wherein: At least one reflective layer selected from the group consisting of the first and second reflective layers comprises: A resin containing at least one selected from the group consisting of epoxy resins, silicone resins, phenolic resins, urea-formaldehyde resins, melamine resins, polyester resins, polyurethane resins, and acrylic resins; and The reflective particles include at least one selected from the group consisting of titanium oxide, aluminum oxide, silicon oxide, barium sulfate, zinc oxide, zirconium oxide, and gadolinium oxide, and reflect light.

4. The scintillator array according to claim 3, wherein: The resin in the at least one reflective layer has a first mass ratio of 15% to 60%, The reflective particles in the at least one reflective layer have a second mass ratio of 40% to 85%, The total of the first mass ratio and the second mass ratio is 100%.

5. The scintillator array according to claim 1, wherein: The adhesive layer includes at least one resin selected from the group consisting of epoxy resin, silicone resin, acrylic resin, urethane resin, polyester resin, and polyolefin resin that is cured by light, heat, or moisture.

6. The scintillator array according to claim 5, wherein: The adhesive layer further includes at least one selected from the group consisting of titanium oxide, zirconium oxide, aluminum oxide, and silicon oxide.

7. The scintillator array according to claim 1, wherein: The rare earth oxysulfide phosphor has the following composition: Represented by the general formula: RE2O2S:Pr, RE is at least one element selected from the group consisting of Y, Gd, La and Lu, Furthermore, the content of Pr is 0.001 mol % to 10 mol % relative to the content of RE2O2S. 8 . A radiation detector comprising the scintillator array according to claim 1 . 9 . A radiation inspection apparatus comprising the radiation detector according to claim 8 .

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