Scintillator array, radiation detector, and radiation inspection device

Abstract

To provide a scintillator array of which size changes less due to heating or cooling and to control the size change amount.SOLUTION: A scintillator array 1 includes: a structure including at least one scintillator segment 2 containing a sinter and a first reflection layer 3 which reflects light; a second reflection layer 4 in a surface of the structure, the second reflection layer reflecting light; and an adhesive layer 5 between a surface of the structure and the second reflection layer 4, the adhesive layer containing resin and having a thickness in the range of 5 μm to 30 μm, both inclusive. The deflection of the scintillator array is 50 μm at a maximum.SELECTED DRAWING: Figure 2

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 technology]

[0002] In the fields of medical diagnosis and industrial non-destructive testing, inspections are performed using radiation inspection equipment such as X-ray computed tomography equipment (hereinafter referred to as X-ray CT equipment). X-ray CT equipment has an X-ray tube (X-ray source) that irradiates a fan-shaped fan beam of X-rays, and an X-ray detector equipped with many X-ray detection elements, which are arranged facing each other with the tomographic plane of the object being inspected in between.

[0003] X-ray CT scanners rotate while irradiating the test object with a fan beam of X-rays from an X-ray tube, and collect absorption data of the X-rays that pass through the test object with an X-ray detector. After this, the X-ray absorption data is analyzed by a computer to reconstruct a tomographic image.

[0004] The radiation detectors of X-ray CT scanners widely use detection elements that use solid scintillators. Radiation detectors equipped with detection elements that use solid scintillators can easily reduce the size of the detection elements and increase the number of channels, which can further improve the resolution of X-ray CT scanners and the like.

[0005] Radiation inspection devices such as X-ray CT scanners are used in various fields such as medical and industrial applications. Examples of X-ray CT scanners include multi-slice devices in which detection elements such as photodiodes are arranged two-dimensionally vertically and horizontally and a scintillator array is mounted on top of them. Multi-slice devices can overlap computed tomography (CT), which allows CT images to be displayed three-dimensionally.

[0006] A radiation detector mounted on a radiation inspection device has multiple detection elements arranged in multiple rows and columns, and each detection element has a scintillator segment. The radiation detector converts X-rays incident on the scintillator segments into visible light, and the detection elements convert the visible light into electrical signals to form an image. In recent years, the detection elements have been made smaller to obtain higher resolution, and the pitch between adjacent detection elements has been narrowed. Accordingly, the size of the scintillator segments has also been reduced.

[0007] Among the various scintillator materials used for the scintillator segments as described above, rare earth oxysulfide phosphor ceramics have high luminous efficiency and suitable properties for use in scintillator segments. For this reason, radiation detectors that combine scintillator segments processed by cutting or grooving a sintered body (ingot) of rare earth oxysulfide phosphor ceramics, which is the scintillator material, with a photodiode as a detection element are becoming more widespread.

[0008] An example of a scintillator using phosphor ceramics includes a scintillator made of 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, which is a scintillator material, is molded into an appropriate shape and sintered to form a sintered body (ingot). This sintered body is cut by cutting or grooving to form scintillator segments corresponding to a plurality of detection elements. Furthermore, a reflective layer that reflects light is formed between these scintillator segments to integrate them, thereby manufacturing a scintillator array.

[0009] When the above-mentioned scintillator array is used in a radiation detector, the dimensional accuracy of the scintillator array affects the resolution of the CT diagnostic image. Furthermore, the radiation detector mounted in the X-ray CT device is subjected to a maximum temperature of 50°C. In a scintillator array having a reflective layer containing resin, the reflective layer expands when heated and contracts when cooled, resulting in minute dimensional changes between adjacent scintillator segments, i.e., pitch deviations between the scintillator segments and variations in external dimensions mainly caused by warping of the scintillator array. These factors cause a deterioration in the resolution of diagnostic images obtained by the radiation inspection device.

[0010] As diagnostic images from radiological imaging devices become increasingly high resolution, there is a demand for scintillator arrays that undergo little dimensional change due to heating and cooling. Furthermore, as the detection area of ​​radiation detectors increases, the area of ​​the scintillator array also increases, making it important to control the amount of dimensional change due to heating and cooling. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] International Publication No. 2013 / 080565 [Patent Document 2] International Publication No. 2017 / 082337 [Patent Document 3] International Publication No. 2017 / 110850 Summary of the Invention

[0012] The scintillator array of the embodiment comprises a structure having at least one scintillator segment including a sintered body and a first reflective layer that reflects light, a second reflective layer that reflects light and is provided on the surface of the structure, and an adhesive layer that contains resin and has a thickness of 5 μm or more and 30 μm or less and is provided between the surface of the structure and the second reflective layer, and has a warp of 50 μm or less. [Brief description of the drawings]

[0013] [Figure 1] FIG. 2 is a plan view showing an example of the structure of a scintillator array. [Diagram 2] 1 is a cross-sectional view showing an example of the structure of a scintillator array. [Diagram 3] FIG. 13 is a diagram showing the relationship between adhesive layer thickness and warpage of a scintillator array. [Figure 4] FIG. 2 is a diagram illustrating a configuration example of a radiation inspection detector. [Diagram 5] FIG. 1 is a diagram illustrating an example of the configuration of a radiation inspection apparatus. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, the embodiments will be described with reference to the drawings. The relationship between the thickness and planar dimensions of each component, the thickness ratio of each component, etc. shown in the drawings may differ from the actual product. In addition, in the embodiments, substantially the same components are given the same reference numerals and the description will be omitted as appropriate.

[0015] A scintillator array, a radiation detector, and a radiation inspection apparatus according to the embodiments will be described below.

[0016] (Scintillator Array) Fig. 1 is a plan view showing an example of the structure of a scintillator array. Fig. 2 is a cross-sectional view showing an example of the structure of a scintillator array. Fig. 1 and Fig. 2 illustrate a scintillator array 1, a scintillator segment 2, a reflective layer 3, a reflective layer 4, and an adhesive layer 5. Note that the reflective layer 4 and the adhesive layer 5 are omitted in Fig. 1 for convenience.

[0017] 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 which is an X-ray incident surface, and a surface 20b opposite to surface 20a. It is sufficient that the scintillator array 1 includes at least one scintillator segment 2. The number of scintillator segments 2 is set appropriately depending on the structure, resolution, etc. of the radiation detector.

[0018] The scintillator segments 2 convert incident radiation (X-rays) into light (visible light). A plurality of scintillator segments 2 are integrated together by a reflective layer 3 that adheres to the scintillator segments 2 to form a structure 20.

[0019] The reflective layer 3 reflects light (visible light). The reflective layer 3 may transmit X-rays. The reflective layer 3 is provided between adjacent scintillator segments 2 and adheres to each of the scintillator segments 2.

[0020] The reflective layer 4 reflects light (visible light). The reflective layer 4 may transmit X-rays. As shown in FIG. 2, the reflective layer 4 is provided on the surface 20a via an adhesive layer 5 and covers the structure 20. The reflective layer 4 is formed by adhering a resin film formed by molding a resin containing reflective particles that reflect light into a sheet to the surface 20a via the adhesive layer 5.

[0021] The scintillator array 1 may have either a structure in which a plurality of scintillator segments 2 are arranged in a line, or a structure in which a predetermined number of a plurality of scintillator segments 2 are arranged two-dimensionally in the vertical and horizontal directions as shown in Fig. 1. 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 vertical direction and on the scintillator segments 2 arranged in the horizontal direction. The reflective layer 3 may surround the scintillator segments 2 along the surface 20a.

[0022] The scintillator segment 2 has a sintered body containing a rare earth oxysulfide phosphor. Examples of the rare earth oxysulfide phosphor include rare earth oxysulfide phosphors containing praseodymium (Pr) as an activator. Examples of the rare earth oxysulfides include oxysulfides of rare earth elements such as yttrium (Y), gadolinium (Gd), lanthanum (La), and lutetium (Lu).

[0023] Rare earth oxysulfide phosphors are General formula: RE2O2S:Pr…(1) (RE represents at least one element selected from the group consisting of Y, Gd, La, and Lu). It is preferable that the composition is represented by the following formula:

[0024] Among the rare earth elements described above, Gd has a particularly large X-ray absorption coefficient and contributes to improving the light output of the scintillator array 1. Therefore, it is more preferable that the scintillator segment 2 has a Gd2O2S:Pr phosphor. Note that a part of Gd may be replaced with another rare earth element. In this case, the amount of Gd replaced by the other rare earth element is preferably 10 mol % or less. That is, the rare earth oxysulfide phosphor is General formula: (Gd 1-x ,RE x )2O2S:Pr …(2) (In the formula, 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.) It is preferable that the composition is substantially as shown below.

[0025] The scintillator segment 2 contains praseodymium (Pr) as an activator that increases light output. Pr can reduce afterglow compared to other activators. Therefore, rare earth oxysulfide phosphor ceramics containing Pr as an activator are effective as fluorescent generators for radiation detectors.

[0026] The Pr content in the rare earth oxysulfide phosphor is preferably 0.001 mol % or more and 10 mol % or less with respect to the content of the phosphor host (e.g., RE2O2S such as Gd2O2S). If the Pr content exceeds 10 mol %, the light output decreases. If the Pr content is less than 0.001 mol %, the effect as a main activator cannot be sufficiently obtained. The Pr content is more preferably 0.01 mol % or more and 1 mol % or less.

[0027] The rare earth oxysulfide phosphor may contain, in addition to Pr as a main activator, a small 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 are effective in suppressing deterioration due to exposure and suppressing afterglow. The total content of these co-activators is preferably in the range of 0.00001 mol % to 0.1 mol % of the phosphor matrix.

[0028] The sintered body constituting the scintillator segment 2 is preferably made of high-purity rare earth oxysulfide phosphor ceramics (scintillator material). Since impurities can reduce the sensitivity of the scintillator, it is preferable to have as little impurity as possible. In particular, since phosphate radicals (PO4) cause a decrease in sensitivity, it is preferable that the content be 100 ppm or less. When fluorides or the like are used as sintering aids to increase the density of the sintered body, the sintering aids remain as impurities, resulting in a decrease in sensitivity.

[0029] The sintered body has a cubic or rectangular parallelepiped shape. The volume of the scintillator segment 2 is 1 mm 3 By miniaturizing the scintillator segment 2, the detected image can be made finer. The vertical (L), horizontal (S) and thickness (T) dimensions of the scintillator segment 2 are not necessarily limited, but each is preferably 1 mm or less. When the volume of the scintillator segment 2 is 1 mm 3 When it is equal to or less than this, the width (W) of the reflective layer 3 can be made thinner, to 100 μm or less, or even to 50 μm or less.

[0030] The reflective layer 3 contains a resin that transmits light (translucent resin) and reflective particles that are dispersed in the resin and reflect light. The resin contains at least one selected from the group consisting of epoxy resin, silicone resin, phenol resin, urea resin, melamine resin, polyester resin, polyurethane resin, and acrylic resin. The reflective particles contain 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. Note that air bubbles contained in the resin may also function as reflective particles.

[0031] The reflective layer 4 can use the same light-transmitting resin and reflective particles as the reflective layer 3. The reflective layer 4 is formed by forming a resin film by processing a material containing the above-mentioned light-transmitting resin and reflective particles into a sheet in advance, and attaching the resin film to the surface 20a of the structure 20 via an adhesive layer 5. A commercially available white film can also be used as the resin film.

[0032] The thickness of the reflective layer 4 is preferably 50 μm or more and 250 μm or less. If the thickness of the reflective layer 4 is less than 50 μm, the reflection efficiency cannot be sufficiently improved. If the thickness of the reflective layer 4 exceeds 250 μm, the amount of transmitted X-rays decreases, resulting in a decrease in detection sensitivity.

[0033] The translucent resin has a glass transition point (transition temperature) of 50°C or higher. The temperature during the manufacturing process of the X-ray CT device, the temperature during use of the X-ray CT device, and the temperature of the storage environment of the X-ray CT device are all about 18°C ​​or higher and 50°C or lower, so if the glass transition point of the translucent resin is 50°C or higher, dimensional changes during manufacturing, use, and storage (pitch deviation of the scintillator segments 2, warping of the scintillator array 1, and variation in the external dimensions of the scintillator array 1) can be suppressed. The glass transition point of the translucent resin is more preferably higher than 50°C, even more preferably 60°C or higher, and particularly preferably 85°C or higher. In addition, the glass transition point of the translucent resin is preferably 120°C or lower. If the glass transition point exceeds 120°C, the shrinkage of the resin during the manufacturing of the scintillator array 1 may become large, and warping of the scintillator array 1 and pitch deviation of the scintillator segments 2 may become large.

[0034] The thermal expansion coefficient (linear expansion coefficient) of the light-transmitting resin constituting the reflective layer 3 and the reflective layer 4 at a temperature exceeding the glass transition point is 2×10 -5 It is preferable that the thermal expansion coefficient is 2×10 -5 / °C, the temperature in the manufacturing process of the X-ray CT device is likely to cause changes in the finished dimensions of the scintillator array 1 (pitch deviation of the scintillator segments 2, warping of the scintillator array 1, and variation in external dimensions). -5 / °C or less is more preferable.

[0035] In order to satisfy the above glass transition temperature and thermal expansion coefficient, the light-transmitting resin preferably has a molecular structure including a cyclo structure that does not include a double structure (double bond). When the molecular structure of the light-transmitting resin includes a double structure, the glass transition temperature is likely to be less than 50°C.

[0036] 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 glass transition point and the above 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 cyclo structure. By using such an epoxy resin, it is easy to increase the glass transition point and to reduce the thermal expansion coefficient at a temperature above the glass transition point.

[0037] The ratio of the light-transmitting resin to the reflective particles in the reflective layers 3 and 4 is preferably such that the mass ratio of the light-transmitting resin is 15% or more and 60% or less, and the mass ratio of the reflective particles is 40% or more and 85% or less. The sum of the mass ratio of the light-transmitting resin and the mass ratio of the reflective particles is 100%. If the mass ratio of the reflective particles is less than 40%, the reflection efficiency of the reflective layer decreases, and the reflection efficiency of the reflective layer for light with a wavelength of 512 nm is likely to be lower than 90%. If the mass ratio of the reflective particles exceeds 85%, the reflection efficiency of the reflective layer remains unchanged, but the mass ratio of the light-transmitting resin decreases relatively, making it difficult to stably solidify the reflective layer.

[0038] The adhesive layer 5 contains 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 of light, heat, and moisture. The adhesive layer 5 may be a light-transmitting resin, but in order to reduce the intrusion of light from one scintillator segment 2 into another scintillator segment 2 through the adhesive layer 5, the adhesive layer 5 preferably contains at least one selected from the group consisting of titanium oxide, zirconium oxide, aluminum oxide, and silicon oxide.

[0039] Fig. 3 is a diagram showing the relationship between the thickness (adhesive layer thickness) of the adhesive layer 5 of the scintillator array 1 and the warpage of the scintillator array 1. Fig. 3 shows the degree of improvement in warpage in the scintillator array 1. An example of the scintillator array 1 is formed by integrating scintillator segments 2, each of which is 1 mm in length (L), width (S) and thickness (T), with 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 laminating a white polyethylene terephthalate (PET) film as the reflective layer 4 and an epoxy resin as the adhesive layer 5 to the structure 20. Fig. 3 shows the change in warpage of the scintillator array 1 with respect to the thickness of the adhesive layer 5.

[0040] The warping of the scintillator array 1 is measured as follows. A warped scintillator array 1 normally has a convex side and a concave side. To measure the warping, first place the scintillator array 1 with the convex side facing down on a flat surface. At this time, the scintillator array 1 is in a state where it rises upward, away from the installation surface, towards its ends. In this state, the vertical distance between the most raised point and the installation surface is measured, and this is defined as the warping. The warping of the scintillator array 1 is generally required to be 50 μm or less. A state with no warping refers to a state where the bottom surface of the scintillator array 1 is in contact with the installation surface at all points, and the warping at this point is 0 μm.

[0041] It can be seen from Fig. 3 that the warpage increases as the adhesive layer 5 becomes thicker. This is due to stress generated inside the adhesive layer 5 due to shrinkage during curing. The value of the warpage has a range of about ±5 µm, but if the thickness of the adhesive layer 5 exceeds 50 µm, the warpage also increases beyond 50 µm, which is undesirable. If the warpage exceeds 50 µm, pressurization or polishing is usually required to correct the warpage, making the process complicated.

[0042] In the scintillator array 1, a scintillator array 1 with a preferred range of warping can be formed in a single process by laminating a white film with an appropriate adhesive layer thickness as the reflective layer 4. This is thought to be because, compared to the conventional process in which the reflective layer 4 is formed by applying a thick layer and curing it, laminating a pre-formed flexible white film with a comparatively thin adhesive layer 5 can reduce the volume that hardens and shrinks, making it less likely to generate stress that causes warping.

[0043] If the thickness of the adhesive layer 5 is less than 2 μm, the adhesive strength is weak and the reflective layer 4 is likely to peel off. Therefore, the thickness of the adhesive layer 5 is preferably in the range of 2 μm to 40 μm, more preferably 5 μm to 30 μm. If the thickness exceeds 40 μm, the volume that shrinks during curing becomes large, which is undesirable because it increases the warping of the scintillator array 1. In addition, in the case of an adhesive layer 5 having optical transparency, it is undesirable because the light generated in the pixel (scintillator segment 2) passes through the adhesive layer 5 and enters the adjacent pixel, causing crosstalk. The thickness of the adhesive layer 5 can be measured from the observed image by observing the cross section in the thickness direction with an electron microscope or optical microscope. The reflective layer 4 and the adhesive layer 5 form a polymer network structure in each layer, so the interface between these layers is clear. In addition, when the pigment concentration is different, it is even clearer, making it easier to determine the thickness.

[0044] Scintillator arrays used in conventional X-ray CT devices need to confine the light generated by X-rays within the pixels and efficiently extract it to the photodiode side. Since high alignment accuracy is required when bonding to the photodiode, it is necessary that the pitch between the pixels is not easily affected by temperature, and that the warping of the scintillator itself is particularly small. If the scintillator warps significantly, the thickness of the adhesive layer between the scintillator array and the photodiode when it is bonded to the photodiode becomes uneven. In places where the adhesive layer is thick, light enters adjacent pixels, increasing crosstalk and resulting in uneven X-ray detection sensitivity. In addition, air bubbles are easily trapped in the adhesive layer, which scatters the light from the scintillator, reducing X-ray detection sensitivity.

[0045] In response to this, a technology is known in which the number of reflective particles per unit area (5 μm x 5 μm) in the reflective layer between scintillator segments and the ratio of reflective particle agglomerates per unit area (10 μm x 10 μm) are controlled to make the shrinkage rate of the reflective layer uniform when the translucent resin solidifies, thereby suppressing warping of the scintillator array during and after manufacture.

[0046] The glass transition point 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 point is 3.5×10 -5 / ° C. Generally, the thermal expansion coefficient of a transparent resin changes significantly at the glass transition point, and warping that occurs with this change is adjusted by setting the conditions.

[0047] Also, in order to reduce warping of the scintillator array, a scintillator array is known in which multiple scintillator segments are integrated by a reflective layer, the reflective layer has a translucent resin with a glass transition point of 50°C or higher, and a second reflective layer arranged on the side of the multiple scintillator segments where X-rays are incident has a glass transition point of 30°C or lower.

[0048] Although these scintillators can improve warping to some extent, the demand for improved image quality requires miniaturization of the scintillator array, and further measures are required to prevent degradation of image quality and detection sensitivity due to crosstalk that occurs with warping.

[0049] The scintillator array of the embodiment includes a first reflective layer that forms a structure 20 together with a plurality of scintillator segments, and a second reflective layer that is disposed on the surface side of the plurality of scintillator segments on which X-rays are incident.

[0050] In the scintillator array of the embodiment, the second reflective layer can be formed by attaching a preformed light-reflecting film via an adhesive layer, instead of applying a slurry in which reflective particles are dispersed in a light-transmitting resin to the X-ray incident surface side of the scintillator array and thermally curing the layer. A scintillator array having such a configuration is easier to fabricate than a conventional one. Furthermore, warping can be reduced by controlling the thickness of the adhesive layer to a predetermined range.

[0051] Next, an example of a method for manufacturing the scintillator array 1 will be described. The scintillator array 1 is manufactured, for example, as follows. First, reflective particles and an uncured resin composition (uncured translucent resin) constituting the translucent resin are prepared and mixed to prepare a mixture. Next, a plurality of scintillator segments 2 processed into a predetermined shape are arranged at regular intervals. The mixture of the reflective particles and the uncured resin composition described above is applied or filled between adjacent scintillator segments 2.

[0052] The uncured resin composition preferably has a viscosity of 0.2 Pa·s or more and 1.0 Pa·s or less (200 cps or more and 1000 cps or less). If the viscosity of the resin composition exceeds 1.0 Pa·s, the fluidity is poor, and the workability of applying or filling between the scintillator segments 2 is reduced. If the viscosity of the resin composition is less than 0.2 Pa·s, the fluidity becomes too high, and the application or filling property is reduced. In addition, the total light transmittance of the light-transmitting resin is preferably 85% or more. If the total light transmittance of the light-transmitting resin is less than 85%, the reflection efficiency of the reflective layer 3 is likely to decrease.

[0053] A mixture of reflective particles and an uncured resin composition is applied or filled between a plurality of scintillator segments 2, and the resin composition in the mixture is then cured to form a reflective layer 3, thereby bonding and integrating adjacent scintillator segments 2 to form a structure 20. The curing treatment of the mixture is appropriately set depending on the type of uncured resin composition and curing agent, etc. For example, in the case of a thermosetting resin composition, the curing reaction is advanced by heat treatment.

[0054] Next, the reflective layer 4 is formed on the surface 20a of the structure 20 via the adhesive layer 5. In the method of manufacturing the white film, a resin containing reflective particles that can be used to form the reflective layer 3 is processed into a sheet using a doctor blade or the like and cured. This is not limited to the above method, and a commercially available white film may be used. Such a commercially available white film is formed by kneading reflective particles such as titanium oxide, alumina, and silica into a light-transmitting resin such as an epoxy resin or a polyester resin and processing the resulting mixture into a sheet. The thickness of the white film is, for example, 50 μm or more and 250 μm or less.

[0055] A light-transmitting resin with a viscosity of 0.2 Pa·s to 1.0 Pa·s is applied onto the surface 20a of the structure 20 as the adhesive layer 5, and a white film of a predetermined size is placed on top of it, and cured while applying pressure. Curing while applying pressure is a process that is made possible by using a white film for the reflective layer 4, and is difficult in conventional processes. Therefore, it is believed that the process also contributes to reducing warpage.

[0056] (Radiation detector) The radiation detector of the embodiment includes the above-mentioned scintillator array 1 as a fluorescence generator that emits light in response to incident radiation, and further includes a photoelectric converter that receives light from the fluorescence generator and converts the optical output into an electrical output. Fig. 4 is a diagram showing an example of the configuration of a radiation detector, and shows an X-ray detector. The X-ray detector 6 shown in Fig. 4 includes the scintillator array 1 as a fluorescence generator and a photoelectric conversion element 7 as a photoelectric converter.

[0057] 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 segments 2. Examples of the photoelectric conversion element 7 include a photodiode and the like. The photoelectric conversion elements 7 are arranged to correspond to each of the multiple scintillator segments 2. These components form a radiation detector.

[0058] (Radiation Inspection Equipment) The radiation inspection apparatus of the embodiment includes a radiation source that irradiates radiation toward an object to be inspected, and a radiation detector that detects radiation that has passed through the object to be inspected. The radiation detector may be any of the radiation detectors of the above-described embodiments.

[0059] Fig. 5 is a diagram showing a configuration example of a radiation inspection device. Fig. 5 illustrates an X-ray CT device 10, a subject 11, an X-ray tube 12, a computer 13, a display 14, and a subject image 15. The X-ray CT device 10 includes an X-ray detector 6. The X-ray detector 6 is attached to, for example, the inner wall surface of a cylinder on which an imaging region of the subject 11 is disposed. An X-ray tube 12 that emits X-rays is disposed approximately at the center of the arc of the cylinder on which the X-ray detector 6 is attached. The subject 11 is disposed 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.

[0060] The X-ray detector 6 and the X-ray tube 12 are configured to rotate around the subject 11 while performing X-ray imaging. Image information of the subject 11 is collected three-dimensionally from different angles. Signals obtained by X-ray imaging (electrical signals converted by photoelectric conversion elements) are processed by a computer 13 and displayed as a subject image 15 on a display 14. The subject image 15 is, for example, a tomographic image of the subject 11. As shown in FIG. 1, it is also possible to configure a multi-tomographic image type X-ray CT device 10 by using a scintillator array 1 in which scintillator segments 2 are arranged two-dimensionally. In this case, multiple tomographic images of the subject 11 are simultaneously captured, and the imaging results can be depicted three-dimensionally, for example.

[0061] The X-ray CT device 10 shown in FIG. 5 includes 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 segments 2 based on the configuration of the reflective layers 3 and 4, and therefore has excellent light output. By using the X-ray detector 6 having such a scintillator array 1, the imaging time by the X-ray CT device 10 can be shortened. As a result, the exposure time of the subject 11 can be shortened, and low exposure can be achieved. The radiation inspection device (X-ray CT device 10) is not limited to X-ray inspection for medical diagnosis of the human body, but can also be applied to X-ray inspection of animals and X-ray inspection for industrial purposes. Furthermore, it also contributes to improving the inspection accuracy by the X-ray nondestructive inspection device. EXAMPLES

[0062] We will now describe specific examples and evaluation results of the scintillator array 1. In showing the examples and comparative examples, a structure 20 having the scintillator segments 2 and the reflective layer 3 before forming the reflective layer 4 on the X-ray entrance surface was prepared as follows.

[0063] A phosphor powder having a composition of Gd2O2S:Pr (Pr concentration = 0.05 mol%) was provisionally molded by a rubber press, and the provisionally molded body was degassed and sealed in a capsule made of tantalum (Ta), and then set in a hot isostatic pressing (HIP) processing device. Argon gas was filled into the HIP processing device as a pressurizing medium, and the HIP processing device was treated for 3 hours under 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 this 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 out in a matrix shape of 84 scintillator segments in the length direction and 31 scintillator segments in the width direction. Next, the above-mentioned multiple scintillator segments 2 were integrated via a reflective layer 3 made of a mixture of 65% reflective particles and 35% light-transmitting resin by mass ratio to produce a structure 20. A reflective layer 3 with a thickness of 0.1 mm was arranged in the vertical and horizontal directions of the structure 20. The reflective particles were a mixture of 80% titanium oxide particles and 20% alumina particles by mass ratio, and a structure 20 having a length of 76 mm, a width of 25 mm, and a thickness of 0.7 mm was fabricated.

[0064] Example 1 An adhesive containing titanium oxide and epoxy resin (glass transition point after curing: 85° C.) was applied to a thickness of 10 μm on the surface 20a of the fabricated structure 20 to form an adhesive layer 5, and a white PET film (manufactured by Mitsubishi Chemical, thickness: 100 μm) was placed on the adhesive layer 5 as a reflective layer 4, and the scintillator array 1 was completed by curing for 24 hours at room temperature while applying a load of 16 kg. After removing the load, the warpage was measured and found to be 15 μm. The results are shown in Table 1.

[0065] Example 2 An adhesive containing titanium oxide and epoxy resin (glass transition point after curing: 85° C.) was applied to a thickness of 15 μm on the surface 20a of the fabricated structure 20 to form an adhesive layer 5, and a white PET film (manufactured by Mitsubishi Chemical, thickness: 100 μm) was placed on the adhesive layer 5 as a reflective layer 4, and the scintillator array 1 was completed by curing for 24 hours at room temperature while applying a load of 10 kg. After removing the load, the warpage was measured and found to be 20 μm. The results are shown in Table 1.

[0066] Example 3 A white PET film (manufactured by Mitsubishi Chemical, thickness 100 μm) was bonded as the reflective layer 4 onto the surface 20a of the fabricated structure 20 via a prepreg epoxy adhesive sheet (thickness 25 μm) as the adhesive layer 5. When bonding, the structure 20, the epoxy adhesive sheet, and the white PET film were stacked, and a load of 16 kg was applied and heated to a temperature of 100° C. to bond them together. After cooling to room temperature, the load was removed to complete the scintillator array 1. The warpage was measured and found to be 20 μm. The results are shown in Table 1.

[0067] Example 4 A mixture of 65% titanium oxide particles and 35% epoxy resin (glass transition point after curing: 55°C) by mass ratio was formed on a fluororesin sheet using a doctor blade, and cured at room temperature for 24 hours to form a white film. The thickness of the obtained white film was 150 μm. Next, a white film was formed as a reflective layer 4 on the surface 20a of the fabricated structure 20 by sandwiching a prepreg epoxy adhesive sheet (thickness: 25 μm) as an adhesive layer 5, and a load of 20 kg was applied and heated at a temperature of 100°C to bond them. After cooling to room temperature, the load was removed to complete the scintillator array 1. The warpage was measured to be 30 μm. The results are shown in Table 1.

[0068] Example 5 A mixture of 65% titanium oxide particles and 35% epoxy resin (glass transition point after curing: 55°C) by mass ratio was formed on a fluororesin sheet using a doctor blade, and cured at room temperature for 24 hours to form a white film. The thickness of the obtained white film was 120 μm. Next, a white film was placed on the surface 20a of the fabricated structure 20, sandwiching a prepreg epoxy adhesive sheet (thickness: 25 μm) as an adhesive layer 5, and a load of 20 kg was applied and heated at a temperature of 100°C to bond them. After cooling to room temperature, the load was removed to complete the scintillator array 1. The warpage was measured to be 25 μm. The results are shown in Table 1.

[0069] Comparative Example 1 A mixture of titanium oxide and epoxy resin (glass transition point after curing: 85°C) was applied onto surface 20a of fabricated structure 20, and cured at 100°C for 3 hours. To achieve a thickness of 150 μm, the mixture was polished after curing to form reflective layer 4. Since the epoxy resin is a hard resin at room temperature, large internal stress was generated in the epoxy resin during the curing process, and the warpage was measured to be 140 μm. The results are shown in Table 1.

[0070] Comparative Example 2 A mixture of titanium oxide and epoxy resin (glass transition point after curing: 85°C) was applied onto the surface 20a of the fabricated structure 20, and cured at a temperature of 100°C for 3 hours. To make the thickness 130 µm, the cured layer was polished to form a reflective layer 4. Since the thickness of the reflective layer 4 was thinner than that of Comparative Example 1, the stress was relaxed, and the warpage was measured and found to be 132 µm. The results are shown in Table 1.

[0071] Comparative Example 3 A liquid in which titanium oxide and nitrocellulose were dispersed in a solvent was sprayed onto the surface 20a of the fabricated structure 20, and the solvent was evaporated by heating to form a coating film that would become the reflective layer 4. The thickness of the coating film after drying was 100 μm. The warpage due to drying shrinkage was measured and found to be 100 μm. The results are shown in Table 1.

[0072] [Table 1]

[0073] In the comparative example, the same light-transmitting resin as in the example is applied to the X-ray entrance surface side, but the reflective layer after curing is thick, so the internal stress generated during curing is large, and the warping is large. In the example, a white film is used and the adhesive layer is made thin, so the stress during curing can be reduced and the warping can be significantly reduced. In addition, while the example does not require correction of the warping, the comparative example requires further heat treatment and polishing processes to correct the warping, and the scintillator array 1 is significantly warped, so the thickness of the reflective layer 4 and the scintillator segments 2 on the X-ray entrance surface becomes non-uniform within the surface, and there is a tendency for the output characteristics to vary.

[0074] According to the scintillator array of the embodiment, warping can be significantly 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 process of heat treatment and polishing for correcting warping can be eliminated, which is an extremely advantageous industrial advantage.

[0075] Although some embodiments of the present invention have been described, 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 forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and spirit of the invention, and are included in the scope of the invention and its equivalents described in the claims.

Claims

1. A structure having at least one scintillator segment including a sintered body and a first reflective layer that reflects light; a second reflective layer provided on a surface of the structure and reflecting light; an adhesive layer containing a resin and having a thickness of 5 μm to 30 μm, the adhesive layer being provided between the surface of the structure and the second reflective layer; Equipped with A scintillator array having a warp of 50 μm or less.

2. The volume of the at least one scintillator segment is less than 1 mm ３ 2. The scintillator array of claim 1 , wherein:

3. 3. The scintillator array according to claim 1, wherein the second reflective layer has a thickness of 50 μm or more and 250 μm or less.

4. At least one reflective layer selected from the group consisting of the first and second reflective layers is a resin including at least one selected from the group consisting of an epoxy resin, a silicone resin, a phenolic resin, a urea resin, a melamine resin, a polyester resin, a polyurethane resin, and an acrylic resin; Reflective particles that reflect light and contain at least one selected from the group consisting of titanium oxide, aluminum oxide, silicon oxide, barium sulfate, zinc oxide, zirconium oxide, and gadolinium oxide; 4. The scintillator array of claim 1 , comprising:

5. the resin in the at least one reflective layer has a first mass ratio of 15% or more and 60% or less; the reflective particles in the at least one reflective layer have a second mass ratio of greater than or equal to 40% and less than or equal to 85%; The scintillator array of claim 4 , wherein the sum of the first mass ratio and the second mass ratio is 100%.

6. 6. The scintillator array of claim 1, wherein the adhesive layer contains 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 light, heat, or moisture.

7. The scintillator array of claim 6 , wherein the adhesive layer further comprises at least one selected from the group consisting of titanium oxide, zirconium oxide, aluminum oxide, and silicon oxide.

8. The scintillator array according to claim 1 , wherein the second reflective layer is a white PET film.

9. 9. 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 has a glass transition point higher than 50°C and lower than 120°C.

10. A radiation detector comprising a scintillator array according to any one of claims 1 to 9.

11. A radiation inspection device comprising the radiation detector according to claim 10.

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