Scintillator array, x-ray detector, and x-ray inspection apparatus

Abstract

The purpose of the present invention is to suppress reduction in dimensional accuracy and variation in dimensional accuracy due to deformation. A scintillator array according to an embodiment includes a plurality of scintillator segments formed of a sintered body of a rare earth oxysulfide phosphor, a first reflective layer interposed between adjacent scintillator segments so as to integrate the plurality of scintillator segments, and a second reflective layer disposed on a surface side of the plurality of scintillator segments on which X-rays are incident. The amount of deformation of the corners of the second reflective layer is 20 [mu] m or less.

Description

TECHNICAL FIELD

[0001] Embodiments of the present application relate to a scintillator array, an X-ray detector, and an X-ray inspection apparatus. BACKGROUND

[0002] In the fields of medical diagnosis, industrial non-destructive inspection, and the like, an X-ray inspection apparatus such as an X-ray tomography apparatus (hereinafter referred to as an X-ray CT apparatus) is used for inspection. The X-ray CT apparatus is configured such that an X-ray tube (X-ray source) that irradiates a fan-shaped beam X-ray and an X-ray detector that has a plurality of X-ray detecting elements are disposed facing each other with a tomographic plane of an object to be inspected as a center. In the X-ray CT apparatus, the fan-shaped beam X-ray is irradiated from the X-ray tube while rotating with respect to the object to be inspected, and X-ray absorption data after the X-ray has passed through the object to be inspected is collected with the X-ray detector. Thereafter, a tomographic image is reproduced by analyzing the X-ray absorption data with a computer. In the radiation detector of the X-ray CT apparatus, a detecting element using a solid scintillator is widely used. In the X-ray detector having the detecting element using the solid scintillator, since the detecting element can be easily miniaturized to increase the number of channels, the resolution of the X-ray CT apparatus and the like can be further improved.

[0003] The X-ray inspection apparatus such as the X-ray CT apparatus is used in various fields such as medical use and industrial use. As the X-ray CT apparatus, for example, a multi-slice type apparatus is known in which detecting elements such as photodiodes are arranged two-dimensionally in a vertical and horizontal direction, and a scintillator array is mounted thereon. By being made into the multi-slice type, slice images can be overlapped, and thus a CT image can be displayed stereoscopically. The X-ray detector mounted in the X-ray inspection apparatus has detecting elements arranged in a plurality of columns in a vertical and horizontal direction, and a scintillator segment is provided for each of the detecting elements. X-rays incident into the scintillator segment are converted into visible light, and the visible light is converted into an electric signal with the detecting element to be imaged. In recent years, in order to obtain high resolution, the detecting elements are miniaturized, and the pitch between adjacent detecting elements is further narrowed. Along with this, the size of the scintillator segment is also reduced.

[0004] Among various scintillator materials used in the scintillator segment as described above, a rare earth oxysulfide-based phosphor ceramic has high luminous efficiency, and has suitable characteristics for use in the scintillator segment. Therefore, an X-ray detector in which a scintillator segment processed by cutting or grooving from a sintered body (ingot) of a rare earth oxysulfide-based phosphor ceramic as a scintillator material is combined with a photodiode as a detecting element is being popularized.

[0005] As a scintillator using a phosphor ceramic, there is known, for example, a scintillator formed of a sintered body of gadolinium oxysulfide phosphor. A scintillator array is produced, for example, as follows. First, a rare earth oxysulfide phosphor powder as a scintillator material is shaped into an appropriate shape, and sintered to produce a sintered body (ingot). The sintered body of the scintillator material is subjected to cutting processing or slitting processing or the like to cut off, and scintillator segments corresponding to a plurality of detection elements are formed. A reflective layer is formed between the scintillator segments and integrated to produce a scintillator array. Further, for the scintillator array, a structure is required in which light generated by incident X-rays is enclosed in the scintillator segments in such a manner as not to penetrate from the X-ray incident surface, and is effectively extracted to the photodiode side, and therefore a reflective layer is also formed on the X-ray incident surface of the scintillator array.

[0006] When the scintillator array as described above is used as an X-ray detector, the dimensional accuracy of the scintillator array affects the alignment accuracy when the scintillator array is attached to the photodiode, and further affects the resolution of an X-ray CT diagnostic image. Furthermore, as the detection area of the X-ray detector increases, the area of the scintillator array also increases, and therefore the dimensional accuracy becomes important.

[0007] Prior Art Documents

[0008] Patent Documents

[0009] Patent Document 1: Japanese Patent Application Publication No. 2012-187137

[0010] Patent Document 2: Japanese Patent No. 4959877 SUMMARY

[0011] PROBLEMS TO BE SOLVED BY THE INVENTION

[0012] The present application provides a scintillator array capable of suppressing a decrease in dimensional accuracy and a variation in dimensional accuracy caused by deformation. Further, the present application provides a detector and an X-ray inspection apparatus that achieve an improvement in medical diagnostic ability and non-destructive inspection accuracy by using such a scintillator array.

[0013] MEANS FOR SOLVING THE PROBLEMS

[0014] The scintillator array of the embodiment includes a plurality of scintillator segments formed of sintered bodies of phosphors, a first reflective layer interposed between adjacent scintillator segments in a manner of integrating the plurality of scintillator segments, and a second reflective layer disposed on a side of a surface on which X-rays are incident on the plurality of scintillator segments. In the scintillator array of the embodiment, a deformation amount of a corner portion of the second reflective layer is 20 μm or less. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1is a cross-sectional view of a scintillator array representing an embodiment.

[0016] Figure 2 is a plan view of a scintillator array representing an embodiment.

[0017] Figure 3 is a perspective view of a scintillator segment used in a scintillator array representing an embodiment.

[0018] Figure 4 is a view of a second reflective layer viewed from an X-ray incident side.

[0019] Figure 5 is a view for explaining a deformation amount.

[0020] Figure 6 is a view of a manufacturing process of a scintillator array representing an embodiment.

[0021] Figure 7 is a view of a manufacturing process of a scintillator array representing an embodiment.

[0022] Figure 8 is a view of a manufacturing process of a scintillator array representing an embodiment.

[0023] Figure 9 is a view of a manufacturing process of a scintillator array representing an embodiment.

[0024] Figure 10 is a view of an appearance of a scintillator array representing an embodiment.

[0025] Figure 11 is a view of a part of a side surface of a scintillator array representing an embodiment.

[0026] Figure 12 is a view of an X-ray detector representing an embodiment.

[0027] Figure 13 is a view of an X-ray inspection apparatus representing an embodiment.

[0028] Figure 14 is a view of a relationship between a surface roughness of a side surface of a scintillator array and a deformation amount of a second reflective layer. DETAILED DESCRIPTION

[0029] Hereinafter, a mode of a scintillator array, an X-ray detector, and an X-ray inspection apparatus for carrying out the present application will be described. (Scintillator array)

[0030] Figure 1 is a cross-sectional view of a scintillator array representing an embodiment, Figure 2is a plan view of a scintillator array of an embodiment. In these drawings, 1 is a scintillator array, 2 is a scintillator segment, 3 is a first reflecting layer, and 4 is a second reflecting layer. Figure 2 In FIG. 2, the illustration of the second reflecting layer 4 is omitted. The scintillator array 1 has a plurality of scintillator segments 2. Between adjacent scintillator segments 2, there is the first reflecting layer 3. The first reflecting layer 3 is respectively bonded with respect to the adjacent scintillator segments 2. The plurality of scintillator segments 2 are integrated by the first reflecting layer 3 with which they are bonded. That is, the scintillator array 1 has a structure that integrates the plurality of scintillator segments 2 by the first reflecting layer 3. Further, on the surface of the plurality of scintillator segments 2 on which X-rays are incident, the second reflecting layer 4 is provided.

[0031] The scintillator array 1 can also have either of a structure that arranges the plurality of scintillator segments 2 in a row, or a structure that arranges the plurality of scintillator segments 2 in a prescribed number in two dimensions in the longitudinal direction and the lateral direction as shown in FIG. 3. Figure 2 When the plurality of scintillator segments 2 are arranged in two dimensions, the first reflecting layer 3 is provided between the scintillator segments 2 in the longitudinal direction and the lateral direction. Further, the second reflecting layer 4 is provided on the surface of the plurality of scintillator segments 2 integrated by the first reflecting layer 3 on which X-rays are incident. That is, the second reflecting layer 4 is provided on the first surface of the scintillator segments 2 and the first surface of the first reflecting layer 3. The first surface of the scintillator segments 2 and the first surface of the first reflecting layer 3 are the surfaces on the side on which X-rays are incident with respect to the scintillator array 1, and are on the same surface. A part of the first reflecting layer 3 can also protrude more toward the second reflecting layer 4 side than the first surface of the scintillator segments 2. In this case, the first surface of the first reflecting layer 3 is on the side on which X-rays are incident with respect to the scintillator array 1, compared to the first surface of the scintillator segments 2. The second reflecting layer 4 is provided on the entire upper surface of the first surface of the scintillator segments 2 and the first surface of the first reflecting layer 3. The second reflecting layer 4 constitutes the entire upper portion of the scintillator array 1. The number of scintillator segments 2 is appropriately set according to the structure or resolution of the X-ray detector.

[0032] The scintillator segment 2 is formed of a sintered body of a phosphor. As the phosphor, a rare earth oxysulfide phosphor, a rare earth garnet oxide phosphor, and a rare earth oxide phosphor, or the like can be used. As an example of a rare earth oxysulfide phosphor ceramic, a rare earth oxysulfide phosphor containing praseodymium (Pr) as an activator can be exemplified. As a rare earth oxysulfide that constitutes the phosphor ceramic, for example, oxysulfides of rare earth elements such as yttrium (Y), gadolinium (Gd), lanthanum (La), lutetium (Lu), or the like can be listed. Further, the scintillator segment 2 can also be formed of a resin containing a phosphor in an epoxy resin, for example.

[0033] In the scintillator array 1 of the embodiment, the scintillator segment 2 is preferably composed of a rare earth oxysulfide fluorescent ceramic (scintillator material) having a composition represented by the general formula: RE2O2S:Pr (1) (where RE represents at least one element selected from Y, Gd, La, and Lu).

[0034] Among the above-mentioned rare earth elements, Gd has a large X-ray absorption coefficient and contributes to an increase in the light output power of the scintillator array 1. Therefore, it is further preferable in the scintillator segment 2 of the embodiment to use a Gd2O2S:Pr fluorescent material. In addition, a part of Gd can also be substituted with other rare earth elements. In this case, the substitution amount of Gd with other rare earth elements is preferably set to 10 mol% or less.

[0035] That is, in the scintillator array 1 of the embodiment, it is preferable to use a rare earth oxysulfide fluorescent ceramic represented by the general formula: (Gd 1-x , RE’ x )2O2S:Pr (2) (where RE' represents at least one element selected from Y, La, and Lu, and x is a number (atomic ratio) satisfying 0≤x≤0.1) for the scintillator segment 2.

[0036] In the scintillator array 1 of the embodiment, praseodymium (Pr) is used as an activator for increasing the light output power of the rare earth oxysulfide fluorescent ceramic (scintillator material). Pr can further achieve a reduction in afterglow and the like compared to other activators. Therefore, the rare earth oxysulfide fluorescent ceramic (scintillator material) containing Pr as an activator is effective as a fluorescent generation mechanism of a radiation detector.

[0037] The content of Pr in the rare earth oxysulfide fluorescent ceramic is preferably set to a range of 0.001 mol% or more and 10 mol% or less with respect to the fluorescent body base (RE2O2S such as Gd2O2S). If the content of Pr exceeds 10 mol%, it conversely becomes a cause of a reduction in the light output power. If the content of Pr is less than 0.001 mol%, the effect as a main activator cannot be sufficiently obtained. The content of Pr is more preferably set to a range of 0.01 mol% or more and 1 mol% or less.

[0038] In the rare earth oxysulfide fluorescent ceramic used in the embodiment, in addition to Pr as a main activator, a trace amount of at least one element selected from the group consisting of Ce, Zr, and P can also be contained as a co-activator. These elements exhibit effects on the suppression of exposure deterioration, the suppression of afterglow, and the like. The content of these co-activators is preferably set to a range of 0.00001 mol% or more and 0.1 mol% or less in total with respect to the fluorescent body base.

[0039] Furthermore, the scintillator sintered body of the scintillator section 2 in the embodiment is preferably formed from high-purity rare-earth oxysulfide-based phosphor ceramic (scintillator material). Since impurities can reduce the sensitivity of the scintillator, the amount of impurities is preferably minimized. In particular, phosphate (PO4) content is preferably set to 150 ppm or less, as it can reduce sensitivity. When using fluorides or the like as sintering aids for high-density formation, the sintering aids remain as impurities, leading to a decrease in sensitivity.

[0040] like Figure 3 As shown, the scintillator section 2 is formed from a sintered body in the shape of a cube or cuboid. The volume of the scintillator section 2 is preferably 1 mm. 3 The following describes how miniaturizing the scintillator section 2 enables high-resolution imaging. While the dimensions of the scintillator section 2—vertical (L), horizontal (S), and thickness (T)—are not necessarily limited, they are preferably 1 mm or less. Miniaturizing the volume of the scintillator section 2 to 1 mm... 3 In the following cases, the width (W) of the first reflective layer 3 can also be thinned to less than 100 μm, and further to less than 50 μm.

[0041] In the scintillator array 1 of this embodiment, a plurality of scintillator segments 2 are integrated via a first reflective layer 3, and a second reflective layer 4 is provided on the X-ray incident surface of the integrated plurality of scintillator segments 2. The deformation amount of the corner of the second reflective layer 4 in the scintillator array 1 of this embodiment is 20 μm or less. The deformation amount of the corner of the second reflective layer 4 refers to the difference between the actual corner shape and the shape of the corner having two ideal sides estimated from the measured corner sides.

[0042] Figure 4 This diagram shows the second reflective layer as observed from the X-ray incident side.

[0043] Figure 5 This represents a diagram used to illustrate the amount of deformation.

[0044] like Figure 4 As shown, by observing the reflective layer on the X-ray incident surface from the X-ray incident side, the deformation can be measured at the four corners 4a, 4b, 4c, and 4d. Figure 5 One example of representing deformation is the deformation P of corner 4a, which is the difference between the actual shape of corner 4a and the shape of corner 4a' having ideal sides S1' and L1' estimated based on the measured sides S1 and L1 of corner 4a. The deformation is measured on both sides separately, but the smaller value is used as the deformation. As shown in the figure, here, the difference between the shorter sides S1 and S1' can be set as the deformation P. This is because... Figure 5Such deformation affects the recognition of the position of the long side L1 when the scintillator is combined with the diode, the degree of the effect being related to the deformation amount P, and as a result, the effect on the alignment accuracy. In addition, by suppressing the deformation amount P, the difference between the long sides L1 and L1' can also be suppressed, and therefore, in order to reduce the effect of the deformation of the corner portion 4a, it is sufficient to reduce the deformation amount P. The deformation amount P can be measured using an optical microscope having a length measuring function, such as the VHF series manufactured by KEYENCE Co., Ltd., at a magnification of, for example, 200 times.

[0045] By setting the deformation amount of the corner portion of the second reflecting layer 4 of the scintillator array 1 to 20 μm or less, the reduction in the dimensional accuracy and the deviation in the dimensional accuracy caused by the deformation of the outer dimensions of the scintillator array 1 can be suppressed, and as a result, the resolution of the diagnostic image of the X-ray detector can be improved. If the deformation amount of the corner portion of the second reflecting layer 4 of the scintillator array 1 is 20 μm or less, the reduction in the dimensional accuracy and the deviation in the dimensional accuracy caused by the deformation of the outer dimensions can be suppressed.

[0046] In addition, the thickness of the second reflecting layer 4 can be in the range of 0.05 mm or more and 0.5 mm or less. When the thickness of the second reflecting layer 4 is less than 0.05 mm, it can be difficult to sufficiently obtain the effect of improving the reflection efficiency. When the thickness of the second reflecting layer 4 exceeds 0.5 mm, the amount of transmitted X-rays decreases, and there is a tendency for the detection sensitivity to decrease. The size of the long side of the scintillator array 1 can be 10 mm or more and 100 mm or less, and the size of the short side can be 1 mm or more and 100 mm or less.

[0047] The thickness of the scintillator segment 2 can be in the range of 0.2 mm or more and 10 mm or less. When the thickness of the scintillator segment 2 is less than 0.2 mm, there is a tendency for the absorption of X-rays to be small and for the sensitivity to decrease. When the thickness of the scintillator segment 2 exceeds 10 mm, there is a tendency for the visible light within the scintillator segment to be unable to reach the detection element and for the sensitivity to decrease.

[0048] In the scintillator array 1 of the embodiment, the first reflecting layer 3 that integrates a plurality of scintillator segments 2, and the second reflecting layer 4 that is provided on the X-ray incident surface of the integrated plurality of scintillator segments 2 each contain a transparent resin and reflecting particles dispersed in the transparent resin. The reflecting particles dispersed in the transparent resin in the first reflecting layer 3 and the reflecting particles dispersed in the transparent resin in the second reflecting layer 4 are preferably the same inorganic substance particles. As the reflecting particles, at least one kind of inorganic substance particles selected from among titanium oxide (TiO2), aluminum oxide (Al2O3), barium sulfide (BaSO4), and zinc oxide (ZnO) is preferably used. By using such reflecting particles, it becomes possible to improve the reflectance of the visible light emitted from the scintillator segment 2 using the reflecting layers 3 and 4, and further, it becomes possible to improve the light output power of the scintillator array 1.

[0049] The reflective particles preferably have a bimodal particle size distribution. That is, the reflective particles preferably have a particle size distribution having a first particle diameter peak and a second particle diameter peak. Furthermore, in the particle size distribution of the reflective particles, the first particle diameter peak is preferably present in a range of 200 nm or more and 350 nm or less, and the second particle diameter peak is preferably present in a range of 750 nm or more and 1000 nm or less. When the particle size distribution of the reflective particles is unimodal, the reflectance of the reflective layers 3, 4 with respect to light having a wavelength of 512 nm tends to decrease. In contrast, by using reflective particles having a bimodal particle size distribution, the reflectance of the reflective layers 3, 4 can be improved. Specifically, the reflectance of the reflective layers 3, 4 with respect to light having a wavelength of 512 nm is preferably 90% or more, whereby the variation in the light output power of the scintillator array 1 can be reduced.

[0050] For the transparent resin constituting the second reflective layer 4, a resin having a glass transition temperature (transition temperature) of 30°C or less is preferably used. Since the temperature at the time of manufacturing the X-ray CT device, the temperature at the time of use of the X-ray CT device, and the temperature of the storage environment of the X-ray CT device are all in a range of 18°C or more and 50°C or less, if the glass transition temperature of the transparent resin constituting the second reflective layer 4 is 30°C or less, the expansion or contraction of the second reflective layer 4 at the time of manufacturing, at the time of use, and at the time of storage becomes easy, and warping and dimensional changes (shift in the pitch of the segments, variation in the outer dimensions) based thereon, and peeling of the second reflective layer 4 caused by the difference in the coefficient of thermal expansion between the second reflective layer 4 and the scintillator segments 2, and the like can be suppressed. The glass transition temperature of the transparent resin constituting the second reflective layer 4 is more preferably 20°C or less.

[0051] For the transparent resin constituting the second reflective layer 4, a resin satisfying the above glass transition temperature of 30°C or less and having a molecular structure including a double bond structure (double bond) is preferably used. When the molecular structure of the transparent resin constituting the second reflective layer 4 does not include a double bond structure, the glass transition temperature tends to exceed 30°C. The transparent resin constituting the second reflective layer 4 preferably includes at least one selected from the group consisting of an epoxy resin, a silicone resin, a phenol-aldehyde resin, a urea-aldehyde resin, a melamine resin, an unsaturated polyester, a polyurethane, an acrylic resin, and a polyethylene terephthalate, and the molecular structure of the selected resin includes a double bond structure.

[0052] For the transparent resin constituting the first reflective layer 3, a resin having a glass transition temperature of 50°C or higher is preferably used. Since the temperature at the time of manufacturing process of the X-ray CT device, the temperature at the time of use of the X-ray CT device, and the temperature of the storage environment of the X-ray CT device are all in the range of 18°C or higher and 50°C or lower, if the glass transition temperature of the transparent resin is 50°C or higher, the dimensional change (pitch shift, warping of the scintillator array, deviation of the outer dimensions) caused by the expansion and contraction of the first reflective layer 3 at the time of manufacturing process, at the time of use, and at the time of storage can be suppressed. The glass transition temperature of the transparent resin constituting the first reflective layer 3 is more preferably 60°C or higher, and further preferably 85°C or higher.

[0053] For the transparent resin constituting the first reflective layer 3, a resin satisfying the above glass transition temperature of 50°C or higher and having a molecular structure including a ring structure not including a double bond structure (double bond) is preferably used. When the molecular structure of the transparent resin constituting the first reflective layer 3 includes a double bond structure, the glass transition temperature tends to be lower than 50°C. The transparent resin constituting the first reflective layer 3 preferably includes at least one selected from the group consisting of an epoxy resin, a silicone resin, a phenol resin, a urea resin, a melamine resin, an unsaturated polyester, a polyurethane, an acrylic resin, and a polyethylene terephthalate, and the molecular structure of the selected resin includes a ring structure not including a double bond structure.

[0054] Regarding the ratio of the transparent resin and the reflective particles forming the first reflective layer 3 and the second reflective layer 4, the mass ratio of the transparent resin is preferably 15% or more and 60% or less, and the mass ratio of the reflective particles is 40% or more and 85% or less (assuming that the mass ratio of the transparent resin + the mass ratio of the reflective particles = 100%). When the mass ratio of the reflective particles is less than 40%, the reflectance of the reflective layers 3, 4 decreases, and the reflectance of the reflective layers 3, 4 with respect to light having a wavelength of 512 nm tends to be lower than 90%. If the mass ratio of the reflective particles exceeds 85%, although the reflectance of the reflective layers 3, 4 does not change, since the mass ratio of the transparent resin relatively decreases, the stable solidification of the reflective layers 3, 4 can become difficult.

[0055] According to the scintillator array 1 using the first reflective layer 3 and the second reflective layer 4 described above, the amount of dimensional change caused by the change in the pitch of the segments, warping, and the change in the outer dimensions can be suppressed. Therefore, a scintillator array 1 having a small deviation in the light output power can be provided. Furthermore, the decrease in the light output power of the scintillator array 1 can be suppressed.

[0056] The scintillator array 1 of the embodiment is manufactured, for example, in the following manner.

[0057] Figures 6 to 10 A drawing showing an example of the manufacturing process of the scintillator array 1 of the embodiment.

[0058] First, as a forming material of the first reflective layer 3, a mixture (first mixture) of reflective particles and a resin composition in an uncured state (uncured product of a transparent resin) constituting a transparent resin is prepared.

[0059] Next, the sintered body of the scintillator material is subjected to cutting processing or slot processing or the like, such as Figure 6 as shown, to obtain a sintered body 2' provided with slots 7 in a manner that a plurality of scintillator segments processed into a prescribed shape are arranged at a certain interval. The first mixture of the reflective particles and the resin composition in an uncured state described above is applied or filled in the slots 7 between adjacent scintillator segments. The resin composition in an uncured state preferably has a viscosity of 0.2 Pa-s or more and 1 Pa-s or less. When the viscosity of the resin composition is less than 0.2 Pa-s, the flowability is poor, and the application or filling workability to the slots between the scintillator segments is reduced. When the viscosity of the resin composition exceeds 1 Pa-s, the flowability becomes excessively high, and the application or filling properties are reduced.

[0060] After the first mixture is applied or filled between the plurality of scintillator segments 2, the resin composition in the first mixture is cured, as shown in Figure 7 to form the first reflective layer 3.

[0061] Next, as shown in Figure 8 , the bottoms of the slots 7 in which the first reflective layer 3 is formed are removed by polishing or the like, to obtain an array-like object 8 of a plurality of scintillator segments 2 integrated via the first reflective layer 3.

[0062] Next, as a forming material of the second reflective layer 4, a mixture (second mixture) of reflective particles and a resin composition in an uncured state (uncured product of a transparent resin) constituting a transparent resin is prepared. The second mixture is applied to the X-ray incident surface of the array-like object 8 of a plurality of scintillator segments 2 integrated via the first reflective layer 3. Thereafter, the second reflective layer 4 is formed by curing the resin composition in the second mixture, so that the adjacent scintillator segments 2 of the array-like object 8 are integrated by the first reflective layer 3, and the second reflective layer 4 is formed on the X-ray incident surface of the array-like object 8. At this time, a plurality of array-like objects 8 can be arranged to apply and form the second reflective layer 4, for example.

[0063] Figure 9 A case in which the plurality of array-like objects 8 in which the second reflective layer 4 is formed are cut to manufacture individual scintillator arrays 1 is shown in Figure 9In the middle, the plurality of array shapes 8 formed with the second reflective layer 4 are reversed. The cutting blade 21 capable of being used in the direction b is cut, and the array shape 8 is moved in the direction of, for example, an arrow d, and is cut along the first reflective layer 3, for example, along a dotted line C. When the four sides of the array shape 8 are thus cut, the first reflective layer 3 is exposed as a side surface.

[0064] Figure 10 The appearance of the obtained scintillator array is shown in the middle.

[0065] In addition, Figure 11 A part of the side surface of the scintillator array 1 is shown in the middle.

[0066] As shown, the obtained scintillator array 1 is provided with the second reflective layer 4 at the X-ray incidence surface la and with the end of the second reflective layer 4 and the first reflective layer 3 at the side surface lb.

[0067] The deformation amount of the corner of the second reflective layer 4 of the scintillator array 1 has a tendency to be affected by the surface roughness of the side surface lb, mainly the surface roughness of the first reflective layer 3. The surface roughness of the first reflective layer 3 and the deformation amount of the corner of the second reflective layer 4 can be adjusted by various changes in the cutting conditions at the time of cutting, such as the moving speed of the array shape 8, the rotation speed of the cutting blade 21, and the size of the abrasive grains capable of being used by the cutting blade 21. As the surface roughness, the arithmetic average surface roughness Ra can be used. The arithmetic average surface roughness Ra of the first reflective layer 3 can be, for example, 0.6 μm or less. When it exceeds 0.6 μm, there is a tendency that the deformation amount is greater than 20 μm.

[0068] Further, the curing treatment of the first and second mixtures is appropriately set depending on the kind of the resin composition in the uncured state, the kind of the curing agent, and the like. For example, in the case of a thermally curable resin composition, the curing reaction is performed by performing a heat treatment. The curing treatment of the first and second mixtures can be performed respectively or simultaneously.

[0069] The X-ray detector of the embodiment has the scintillator array 1 of the above-described embodiment as a fluorescence generation mechanism that radiates light according to the incident radiation, and further has a photoelectric conversion mechanism that receives the light from the fluorescence generation mechanism and converts the output of the light into an electric output. Figure 12 One example of the X-ray detector of the embodiment is shown. Figure 12 The X-ray detector 6 shown in the middle has the scintillator array 1 as a fluorescence generation mechanism and the photoelectric conversion element 5 like a photodiode as a photoelectric conversion mechanism. In addition, in the middle Figure 12 The illustration of the reflective layers 3, 4 of the scintillator array 1 is omitted in the middle.

[0070] The scintillator array 1 has an X-ray incident surface la, and the photoelectric conversion element 5 is integrally provided on a surface lc on the opposite side of the X-ray incident surface la. As the photoelectric conversion element 5, a photodiode is used, for example. The photoelectric conversion element 5 is arranged in correspondence with each of the plurality of scintillator segments 2 that constitute the scintillator array 1. By these, the X-ray detector 6 is constituted.

[0071] (X-ray inspection apparatus)

[0072] The X-ray inspection apparatus of the embodiment has an X-ray source that irradiates an X-ray toward an object to be inspected and an X-ray detector that detects an X-ray that has passed through the object to be inspected. As the X-ray detector, the X-ray detector of the above-described embodiment is used. Figure 13 An X-ray CT apparatus 10 is shown as one example of the X-ray inspection apparatus of the embodiment. In Figure 13 , 10 is an X-ray CT apparatus, 11 is an object to be inspected, 12 is an X-ray tube, 13 is a computer, 14 is a display, and 15 is an object to be inspected image. The X-ray CT apparatus 10 has the X-ray detector 6 of the embodiment. The X-ray detector 6 is attached to, for example, an inner wall surface of a cylinder that is arranged at a photographing site of the object to be inspected 11. In the vicinity of the center of the arc of the cylinder to which the X-ray detector 6 is attached, the X-ray tube 12 that emits an X-ray is provided. The object to be inspected 11 is arranged between the X-ray detector 6 and the X-ray tube 12. On the X-ray incident surface side of the X-ray detector 6, a collimator that is not shown is provided.

[0073] The X-ray detector 6 and the X-ray tube 12 are constituted in such a manner that they rotate while photographing the object to be inspected 11 using an X-ray. Image information of the object to be inspected 11 is collected stereoscopically from different angles. Signals (electric signals converted by the photoelectric conversion element) obtained by X-ray photographing are processed by the computer 13, and an object to be inspected image 15 is displayed on the display 14. The object to be inspected image 15 is, for example, a tomographic image of the object to be inspected 11. As shown in Figure 12 , by using the scintillator array 1 in which the scintillator segments 2 are arranged two-dimensionally, an X-ray CT apparatus 10 of a multi-tomographic image type can also be constituted. In this case, a plurality of tomographic images of the object to be inspected 11 are simultaneously photographed, and the photographing results can also be stereoscopically depicted, for example.

[0074] Figure 13The illustrated X-ray CT apparatus 10 is provided with the X-ray detector 6 having the scintillator array 1 of the embodiment. As described above, the scintillator array 1 of the embodiment has excellent light output power because of the high reflection efficiency of the visible light emitted from the scintillator segments 2 based on the constitution of the reflection layers 3, 4 and the like. By using the X-ray detector 6 having such a scintillator array 1, it is possible to shorten the imaging time with the X-ray CT apparatus 10. As a result, it is possible to shorten the irradiation time of the subject 11 and to achieve low irradiation. The X-ray inspection apparatus (X-ray CT apparatus 10) of the embodiment is not limited to the X-ray inspection for medical diagnosis of the human body, but can also be applied to X-ray inspection of animals, X-ray inspection for industrial use, and the like. Furthermore, it is also helpful to improve the inspection accuracy with the X-ray non-destructive inspection apparatus and the like.

[0075] Embodiment

[0076] Next, a specific embodiment of the present application and evaluation results thereof will be described. (Example 1, Comparative Examples 1 to 7)

[0077] A phosphor powder having a composition of Gd2O2S:Pr (Pr concentration = 0.05 mol%) was temporarily molded by rubber pressing, and after degassing and sealing in a capsule made of Ta, it was placed on a HIP processing apparatus. In the HIP processing apparatus, argon was enclosed as a pressurizing medium, and processing was performed at a pressure of 147 MPa and a temperature of 1425°C for 3 hours. By such an operation, a sintered body in the shape of a cylinder having a diameter of about 80 mm x height of about 120 mm was produced.

[0078] The sintered body was cut to a size of width 35 mm x length 95 mm and processed. Furthermore, groove processing was performed in the same manner, and the scintillator segments 2' having a thickness of 1.2 mm x width of 0.9 mm x length of 1.0 mm were cut into a matrix shape of 100 segments in the length direction x 30 segments in the width direction with the groove 7 interposed. Figure 6 The groove processing was performed in the same manner, and the scintillator segments 2' having a thickness of 1.2 mm x width of 0.9 mm x length of 1.0 mm were cut into a matrix shape of 100 segments in the length direction x 30 segments in the width direction with the groove 7 interposed.

[0079] The groove processing can be performed by a blade called a cutting blade in the shape of a disc. The cutting blade can be processed so as to protrude with respect to the edge portion of the sintered body on which the groove processing is performed. By processing so as to protrude with respect to the edge portion, the generation of burrs and the like can be suppressed. In addition, in the groove processing, the feed speed of the cutting blade can be controlled. The feed speed can be set to 0.2 mm / sec or more and 10 mm / sec or less.

[0080] In addition, in order to perform the groove processing, the cut sintered body can be fixed to a processing table. The cut sintered body can be fixed with wax or the like. As the wax, for example, paraffin wax or the like can be mentioned. The melting point of the wax can be 45°C or more and 80°C or less.

[0081] Furthermore, the abrasive grain size of the cutting blade can be controlled. The abrasive grain size can be #200 or higher and #2000 or lower. The larger the abrasive grain size, the larger the grain diameter. If an abrasive grain smaller than #200 is used, the grain diameter becomes too large, tending to result in a rough surface. On the other hand, if an abrasive grain larger than #2000 is used, the amount of material that can be processed in one pass becomes smaller, tending to result in longer processing times. Additionally, the cutting blade rotation speed can be set to 1000 rpm or higher and 25000 rpm or lower. If the rotation speed is lower than 1000 rpm, there is a tendency for longer processing times. On the other hand, if the rotation speed exceeds 25000 rpm, the amount of frictional heat generated is large, tending to increase the rate of defects such as chip formation due to the generated frictional heat.

[0082] In addition, during machining using cutting blades, cooling water can be sprayed onto the machining area. The spray pressure of the cooling water can be further adjusted. The spray pressure can be adjusted by adjusting the water flow rate. The water flow rate can be 0.2 to 2.0 liters / minute, for example, about 1.0 liter / minute. The cooling water temperature can be set to below 28°C.

[0083] The water used for cooling may contain cutting fluid components. Cutting fluids can be water-soluble or oil-soluble, and water-soluble cutting fluids are preferred. Examples of water-soluble cutting fluids include soluble, emulsion, and chemical solution types. Oil-soluble cutting fluids, on the other hand, tend to be difficult to rinse thoroughly with the water used for cleaning, as described later.

[0084] After processing, the material can be immersed in water or sprayed with water for cleaning. Water cleaning removes powder generated during grooving and cutting fluid residue remaining on the surface of the sintered body. Furthermore, immersion can be combined with ultrasonic cleaning.

[0085] Alternatively, when wax is used in the method of fixing the sintered body, the wax can be removed from the sintered body after cleaning by heating with a heating plate or similar means. To remove any adhering wax components, the removed, processed sintered body can be further cleaned. This cleaning can be done using an organic solvent. Examples of organic solvents include alcohols such as isopropanol, butanol, 2-butanol, ethanol, and propanol, or ketones such as acetone. Using alcohols or ketones can remove water and wax components remaining on the surface of the sintered body, making it easier to dry.

[0086] like Figure 7 As shown, a first reflective layer 3, formed of a mixture of 65% by mass of reflective particles and 35% by mass of transparent resin, is coated onto the substrate of the aforementioned plurality of scintillator sections 2' and then cured.

[0087] Furthermore, such as Figure 8As shown, the bottom of the groove is removed by grinding, thereby creating an array 8 composed of multiple scintillator sections 2 integrated together. A first reflective layer with a thickness of 0.1 mm is disposed in both the longitudinal and transverse directions of the scintillator array. For the reflective particles, a mixture of 80% by mass titanium oxide particles and 20% by mass aluminum oxide particles is used. In Examples 1 and Comparative Examples 1-7, a rigid epoxy resin A1 with a molecular structure containing ring structures but not double bonds was used as the transparent resin forming the first reflective layer. The glass transition temperature of the rigid epoxy resin A1 was adjusted by its molecular structure and set to 85°C.

[0088] Next, as Figure 9 As shown, multiple scintillator segments 3 are arranged at certain intervals in an array 8 integrally formed by a first reflective layer, and a second reflective layer 4 is formed on its X-ray incident surface. The thickness of the second reflective layer 4 is set to 0.3 mm. For the reflective particles, a mixture of 80% by mass titanium oxide particles and 20% by mass aluminum oxide particles is used, similar to the first reflective layer 3. In Examples 1 and Comparative Examples 1-7, a soft epoxy resin B1 having a molecular structure including a double bond structure was used in the transparent resin forming the second reflective layer 4. The glass transition temperature of the soft epoxy resin B1 is adjusted by the molecular structure and set to 10°C.

[0089] Next, the array of multiple array-shaped objects 8 on which the second reflective layer 4 is formed is cut to manufacture scintillator arrays 1 with various surface roughnesses as in Examples 1 and Comparative Examples 1 to 7.

[0090] In Examples 1 and Comparative Examples 1-7, the arithmetic mean surface roughness Ra was measured as the surface roughness of the scintillator array 1. The measurement was performed using a surface roughness measuring machine (Mitutoyo SJ-210). The measurement conditions were set as follows: measurement speed was 0.5 mm / s, reference length was 0.25 mm, and cutoff value λs was 2.5 μm. The arithmetic mean surface roughness Ra was then calculated.

[0091] The results are shown in Table 1 below.

[0092] In addition, the deformation of the scintillator arrays of Example 1 and Comparative Examples 1-7 was measured. The measurements were performed using an optical microscope with a length measuring function, at a magnification of 200x.

[0093] First, such as Figure 4 As shown, the second reflective layer was observed from the X-ray incident surface, and the shapes of the four corners 4a, 4b, 4c, and 4d were measured respectively. Next, as... Figure 5 As shown, calculate the difference between the two sides S1' and L1' of the ideal corner 4a' estimated based on the measured corner, for example, the two sides S1 and L1 of corner 4a. Then, calculate the deformation for each side separately, as shown... Figure 5As shown, the side with the smaller value is used as the deformation amount P.

[0094] The results obtained are shown in Table 1 below.

[0095] Figure 14 A graph showing the relationship between the surface roughness of the side surface representing the scintillator array and the deformation amount of the second reflective layer is shown.

[0096] Figure 14 is a graph in which the results of Table 1 are plotted.

[0097] As shown in Table 1 and Figure 14 As shown, if the arithmetic average surface roughness Ra is 0.06 μm or less, the deformation amount can be made 20 μm or less.

[0098] Table 1

[0099] Amount of deformation P (pm) Arithmetic average surface roughness Ra (pm) Example 1 8 0.04 Comparative Example 1 40 0.16 Comparative Example 2 43 0.13 Comparative Example 3 42 0.17 Comparative Example 4 38 0.16 Comparative Example 5 36 0.13 Comparative Example 6 34 0.13 Comparative Example 7 28 0.08

[0100] As shown in Table 1, it was confirmed that the scintillator array of Example 1 had a small deformation amount of 20 μm or less compared to Comparative Examples 1 to 7. In addition, as shown in Figure 14 and Table 1, it was found that the smaller the arithmetic average surface roughness Ra, the smaller the deformation amount P.

[0101] According to the scintillator array having such a deformation amount, it is possible to improve the dimensional accuracy in a manner that can cope with the miniaturization of the detector and the like, while maintaining excellent light output power. In addition, it is possible to maintain the alignment accuracy when the photodiode is attached and the dimensional accuracy when the area of the scintillator array is large. Therefore, it is possible to provide a scintillator array having optimal dimensional accuracy and reliability. By using such a scintillator array, it is possible to improve the resolution and the image accuracy, and thus it is possible to provide an X-ray detector and an X-ray inspection apparatus that achieve an improvement in the medical diagnostic ability and the non-destructive inspection accuracy.

[0102] In addition, several embodiments of the present application were described, but these embodiments are presented as examples and are not intended to limit the scope of the application. These novel embodiments can be implemented in other various forms, and various omissions, substitutions, and changes can be made within the scope of the gist of the application. These embodiments or modifications thereof are included in the scope and gist of the application, and are included in the scope of the application and equivalents thereof recited in the claims.

Claims

1. A scintillator array comprising: a plurality of scintillator segments formed of sintered bodies of phosphor; a first reflective layer provided between adjacent scintillator segments; and a second reflective layer provided on a side of the plurality of scintillator segments on which an X-ray is incident, wherein a deformation amount of a corner portion of the second reflective layer is 20 μm or less, wherein an arithmetic mean surface roughness of a side surface of the side on which the X-ray is incident is 0.06 μm or less, wherein the first reflective layer and the second reflective layer each contain a transparent resin and reflective particles dispersed in the transparent resin, wherein the reflective particles of the second reflective layer are the same particles as the reflective particles of the first reflective layer, wherein a glass transition temperature of the transparent resin of the first reflective layer is 50°C or higher, and a glass transition temperature of the transparent resin of the second reflective layer is 30°C or lower, wherein a molecular structure of the transparent resin of the first reflective layer has a ring structure that does not include a double bond structure, and a molecular structure of the transparent resin of the second reflective layer has a double bond structure, wherein the reflective particles include at least one inorganic substance particle selected from the group consisting of titanium oxide, aluminum oxide, barium sulfate, and zinc oxide, wherein the transparent resin of the first reflective layer and the transparent resin of the second reflective layer each include at least one selected from the group consisting of an epoxy resin, a silicone resin, a phenol resin, a urea resin, a melamine resin, an unsaturated polyester, a polyurethane, an acrylic resin, and a polyethylene terephthalate, wherein the first reflective layer and the second reflective layer each contain the transparent resin in a mass ratio of 15% or more and 60% or less, and the reflective particles in a mass ratio of 40% or more and 85% or less, wherein the phosphor is a rare earth oxysulfide phosphor represented by the general formula: RE2O2S:Pr, wherein RE is at least one selected from the group consisting of Y, Gd, La, and Lu, and has a composition in which the content of Pr with respect to RE2O2S is 0.001 mol% or more and 10 mol% or less, and wherein the rare earth oxysulfide phosphor includes a gadolinium oxysulfide phosphor containing Pr as an activator.

10. An X-ray detector comprising the scintillator array according to any one of claims 1 to 9.

11. An X-ray inspection apparatus comprising the X-ray detector according to claim 10. ​ wherein ​ 2. The scintillator array of claim 1, wherein, ​ 3. The scintillator array of claim 1, wherein, ​ ​ ​ 4. The scintillator array of claim 3, wherein, ​ 5. The scintillator array of claim 3, wherein, ​ 6. The scintillator array of claim 3, wherein, ​ 7. The scintillator array of claim 3, wherein, ​ 8. The scintillator array of any one of claims 1-7, wherein, ​ 9. The scintillator array of claim 8, wherein, ​ ​ ​

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