Radiation detector, radiography apparatus, and method for manufacturing radiation detector

A radiation detector includes a substrate having flexibility, a plurality of pixels which are provided on a surface of the substrate and each of which includes a photoelectric conversion element, and a scintillator that is stacked on the substrate and has a plurality of corners. An outer edge of each of the corners of the scintillator is disposed closer to the inside of the substrate than an extension line of each of sides sharing the corner.

BACKGROUND

Technical Field

The technology of the present disclosure relates to a radiation detector, a radiography apparatus, and a method for manufacturing a radiation detector.

Related Art

The following technology has been known as a technology related to a radiography apparatus. For example, JP2015-064284A (Patent Document 1) discloses a radiographic image detection device comprising: a scintillator that has a scintillator main body having a polygonal plate shape and a protruding portion protruding outward from at least one corner of the scintillator main body and converts radiation into visible light; a substrate that supports the scintillator; and a scintillator protective film that covers the surfaces of the scintillator main body and the protruding portion and has a peripheral portion closely attached to the substrate.

In contrast, JP2003-075594A (Patent Document 2) discloses a radiation image conversion panel characterized in that at least a phosphor layer is accommodated in an enclosed space formed by two sheet-shaped rigid bodies and a frame body provided between the two sheet-shaped rigid bodies and the inner corner of the frame body has a curved shape or a polygonal shape in which each angle is equal to or greater than 90 degrees.

As a radiation detector used in a radiography apparatus, a radiation detector has been known that includes a substrate, a plurality of pixels which are provided on a surface of the substrate and each of which includes a photoelectric conversion element, and a scintillator stacked on the substrate. In recent years, a flexible material, such as a resin film, has been used as a material of a substrate forming the radiation detector. In a case in which the substrate has flexibility, the corner of the scintillator has a smaller contact area with the substrate than other portions of the scintillator. Therefore, the corner is likely to peel off.

SUMMARY

An object of the technology of the present disclosure is to reduce the risk of a scintillator peeling off from a substrate, as compared to a case in which the outer edge of each corner of a scintillator is disposed on an extension line of each of sides sharing the corner or is disposed closer to the outside of the substrate than the extension line.

According to a first aspect of the technology of the present disclosure, there is provided a radiation detector comprising: a substrate having flexibility; a plurality of pixels which are provided on a surface of the substrate and each of which includes a photoelectric conversion element; and a scintillator that is stacked on the substrate and has a plurality of corners. An outer edge of each of the corners of the scintillator is disposed closer to an inside of the substrate than an extension line of each of sides sharing the corner.

According to a seventh aspect of the technology of the present disclosure, there is provided a method for manufacturing a radiation detector. The method comprises: a step of forming a plurality of pixels each of which includes a photoelectric conversion element on a surface of a substrate having flexibility; and a step of stacking a scintillator which has a plurality of corners and in which an outer edge of each of the corners is disposed closer to an inside of the substrate than an extension line of each of sides sharing the corner.

DETAILED DESCRIPTION

Hereinafter, an example of an embodiment of the technology of the present disclosure will be described with reference to the drawings. In the drawings, the same or equivalent components and portions are denoted by the same reference numerals.

FIG. 1is a perspective view illustrating an example of a configuration of a radiography apparatus10according to an embodiment of the technology of the present disclosure. The radiography apparatus10has the form of a portable electronic cassette. The radiography apparatus10includes a radiation detector30(flat panel detector (FPD)), a control unit12, a support plate16, and a housing14that accommodates the radiation detector30, the control unit12, and the support plate16.

For example, the housing14has a monocoque structure made of a carbon fiber reinforced resin (carbon fiber) that has high transparency to radiation, such as X-rays, a light weight, and high durability. An upper surface of the housing14is a radiation incident surface15on which radiation that has been emitted from a radiation source (not illustrated) and transmitted through a subject (not illustrated) is incident. In the housing14, the radiation detector30and the support plate16are disposed in order from the radiation incident surface15.

The support plate16supports a circuit substrate19(seeFIG. 2) on which an integrated circuit chip for performing, for example, signal processing is mounted and is fixed to the housing14. The control unit12is disposed at an end in the housing14. The control unit12includes a battery (not illustrated) and a controller29(seeFIG. 5).

FIG. 2is a cross-sectional view illustrating an example of the configuration of the radiography apparatus10. The radiation detector30includes a substrate34having flexibility, a plurality of pixels41which are provided on a surface of the substrate34and each of which includes a photoelectric conversion element36(seeFIG. 5), a scintillator32that is stacked on the substrate34, and a support member60that supports the substrate34.

The substrate34is a flexible substrate having flexibility. In the specification, the flexibility of the substrate34means that, in a case in which one of four sides of the substrate34having a rectangular shape is fixed, the height of a portion of the substrate34which is 10 cm away from the fixed side of the substrate34is less than the height of the fixed side by 2 mm or more. For example, a resin substrate, a metal foil substrate, or a thin glass having a thickness of about 0.1 mm can be used as the substrate34. In particular, it is preferable to use a resin film, such as Xenomax (registered trademark) which is a high heat-resistant polyimide film, as the substrate34. Each of the plurality of pixels41is provided on a first surface S1of the substrate34.

The scintillator32is stacked on the first surface S1of the substrate34. The scintillator32includes a phosphor that converts the emitted radiation into light. The scintillator32is configured by, for example, an aggregate of columnar crystals including thallium-activated cesium iodide (CsI:Tl). The columnar crystal of CsI:Tl can be directly formed on the substrate34by, for example, a vapor growth method. The columnar crystal of CsI:Tl formed on a substrate different from the substrate34may be attached to the substrate34. In addition, the scintillator32can be made of terbium-activated gadolinium oxysulfide (Gd2O2S:Tb). Each of the photoelectric conversion elements36(seeFIG. 5) forming the plurality of pixels41generates charge on the basis of light emitted from the scintillator32. In the specification, an area in which the plurality of pixels41are provided on the substrate34is referred to as an active area40.

A surface S3of the scintillator32which is opposite to a contact surface with the substrate34and a surface S4intersecting the surface S3are covered with a reflective film50. The reflective film50has a function of reflecting the light emitted from the scintillator32to the substrate34. The reflective film50can be made of, for example, Al2O3. The reflective film50covers the surfaces S3and S4of the scintillator32and also covers the substrate34in the periphery of the scintillator32. In a case in which the radiography apparatus10can obtain a radiographic image with desired quality without providing the reflective film50, the reflective film50can be omitted.

The surface of the reflective film50is covered with a sealing film51. The sealing film51covers the surfaces S3and S4of the scintillator32through the reflective film50and also covers the substrate34at the periphery of the scintillator32. The sealing film51has a moisture-proof function of sealing the scintillator32to prevent moisture from being penetrated into the scintillator32. The sealing film51can be made of a resin, such as polyethylene terephthalate, polyphenylene sulfide, or polyethylene naphthalate.

In this embodiment, the radiography apparatus10adopts an imaging method using irradiation side sampling (ISS) in which the substrate34is disposed on the radiation incident side. The adoption of the irradiation side sampling makes it possible to reduce the distance between a strong emission position of the scintillator32and the pixel41, as compared to a case in which penetration side sampling (PSS) in which the scintillator32is disposed on the radiation incident side is adopted. As a result, it is possible to increase the resolution of a radiographic image. The radiography apparatus10may adopt the penetration side sampling.

The support plate16is disposed on the side of the scintillator32which is opposite to the radiation incident side. A gap is provided between the support plate16and the scintillator32. The support plate16is fixed to the side of the housing14. The circuit substrate19is provided on a surface of the support plate16which is opposite to the scintillator32. For example, a signal processing unit26that generates image data and an image memory28that stores the image data generated by the signal processing unit26are mounted on the circuit substrate19.

The circuit substrate19and the substrate34are electrically connected to each other through wires printed on a flexible printed circuit (FPC), a tape carrier package (TCP), or a chip-on-film (COF)20. A charge amplifier24that converts charge read out from the pixel41into an electric signal is mounted on the COF20. A gate line driving unit22(seeFIG. 5) is mounted on another flexible printed circuit (not illustrated inFIG. 2) that electrically connects the circuit substrate19and the substrate34.

The support member60is stacked on a second surface S2of the substrate34which is opposite to the first surface S1. The support member60has a function of giving the substrate34rigidity necessary for the substrate34to support the scintillator32. That is, in a case in which the support member60is provided, the warpage of the substrate34caused by the weight of the scintillator32is suppressed, as compared to a case in which the support member60is not provided.

The support member60can be made of a resin, such as polyphenylene sulfide (PPS), polyarylate (PAR), polysulfone (PSF), polyether sulfone (PES), polyetherimide (PEI), polyamideimide (PAI), polyether ether ketone (PEEK), a phenol resin, polytetrafluoroethylene, polychlorotrifluoroethylene, a silicone resin, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), or polycarbonate. Further, the support member60may be made of metal such as aluminum, iron, or an alloy thereof. Furthermore, the support member60may be made of a stacked material obtained by stacking a resin and metal. A surface S5of the support member60which is opposite to a contact surface with the substrate34is attached to the inner wall of the housing14through an adhesive layer18.

FIG. 3is a plan view illustrating an example of the positional relationship among the housing14, the substrate34, the active area40, and the scintillator32, and the outer shapes thereof.

The outer shapes of the housing14and the substrate34are, for example, a rectangle. The substrate34is accommodated in the housing14with a clearance A1between the substrate34and the housing14. That is, a gap is provided between each side of the substrate34and the inner wall of the housing14. Therefore, for example, even in a case in which the radiography apparatus10is dropped, an impact is applied to the radiography apparatus10, and the housing14is deformed, it is possible to suppress the risk that the substrate34and each member mounted on the substrate34will be damaged.

The entire active area40of the substrate34is covered by the scintillator32. That is, the scintillator32covers each of the plurality of pixels41. The size of the scintillator32is smaller than the size of the substrate34. The entire scintillator32comes into contact with the substrate34. In this embodiment, the scintillator32has four corners32C1,32C2,32C3, and32C4and four sides32L1,32L2,32L3, and32L4. The sides32L1and32L2share the corner32C1. The sides32L2and32L3share the corner32C2. The sides32L3and32L4share the corner32C3. The sides32L4and32L1share the corner32C4. The sharing of the corner32C1by the side32L1and the side32L2means that the side32L1is connected to one end of the corner32C1and the side32L2is connected to the other end of the corner32C1. This holds for the other corners32C2to32C4.

Here,FIG. 4is an enlarged view illustrating an area R around the corner32C1that is surrounded by a one-dot chain line inFIG. 3. Hereinafter, the corner32C1will be described. However, this holds for the other corners32C2,32C3, and32C4. The corner32C1of the scintillator32is chamfered and an outer edge32E of the corner32C1of the scintillator32is disposed closer to the inside (center) of the substrate34than an extension line32bof the side32L1and the side32L2sharing the corner32C1. In other words, the outer edge32E of the corner32C1of the scintillator32is disposed at a position that is retracted from the extension line32bof the side32L1and the side32L2sharing the corner32C1. The outer edge32E of the corner32C1is an edge of the scintillator32which is connected to the side32L1and the side32L2sharing the corner32C1and is bent or curved with respect to the side32L1and the side32L2. This holds for the corners32C2,32C3, and32C4other than the corner32C1illustrated inFIG. 4.

The chamfering of the scintillator32means removing the apex of each of the corners32C1to32C4of the scintillator32to form an edged surface or a curved surface at each of the corners32C1to32C4. The angle φ of the chamfer at each of the corners32C1to32C4of the scintillator32(that is, the angle between the outer edge32E of each of the corners32C1to32C4and the extension line32b) is typically 45°. However, the present disclosure is not limited thereto. Each of the corners32C1to32C4of the scintillator32can be chamfered such that the angles θ1and θ2of bent portions at each of the corners32C1to32C4of the scintillator32are obtuse angles.

In a case in which the distance between the end of the active area40and the corresponding side of the scintillator32is B and the chamfer dimension of the scintillator32is C, it is preferable that the following Expression (1) is satisfied. In a case in which the following Expression (1) is satisfied, the entire active area40can be covered with the scintillator32even though the corners32C1to32C4of the scintillator are chamfered.
C<2B(1)

In a case in which the distance between each of the sides32L1to32L4of the scintillator32and the corresponding side of the substrate34is D and the distance between the end of the active area40and the housing14is L, it is preferable that the following Expression (2) is satisfied. The following Expression (2) means that the clearance between the substrate34and the housing14is greater than zero. In addition, Expression (3) can be derived from Expressions (1) and (2).
L−B−D>0  (2)
C<2B<2(L−D)  (3)

FIG. 5is a diagram illustrating an example of an electrical configuration of the radiography apparatus10. The plurality of pixels41are arranged in a matrix on the first surface S1of the substrate34. Each of the pixels41includes the photoelectric conversion element36that generates charge on the basis of light emitted from the scintillator32and a thin film transistor (TFT)42as a switching element that is turned on in a case in which the charge generated in the photoelectric conversion element36is read out. The photoelectric conversion element36may be, for example, a photodiode made of amorphous silicon.

Gate lines43that extend in one direction (row direction) along the arrangement of the pixels41, and signal lines44that extend in a direction (column direction) intersecting with the direction in which the gate lines43extend are provided on the first surface S1of the substrate34. Each of the pixels41is provided so as to correspond to each intersection portion of the gate line43and the signal line44.

Each of the gate lines43is connected to the gate line driving unit22. The gate line driving unit22reads out the charge accumulated in the pixels41on the basis of a control signal supplied from the controller29. Each of the signal lines44is connected to the charge amplifier24. The charge amplifier24is provided so as to correspond to each of the plurality of signal lines44. The charge amplifier24generates an electric signal on the basis of the charge read out from the pixel41. An output terminal of the charge amplifier24is connected to the signal processing unit26. The signal processing unit26performs a predetermined process for the electric signal supplied from the charge amplifier24on the basis of a control signal supplied from the controller29to generate image data. The image memory28is connected to the signal processing unit26. The image memory28stores the image data generated by the signal processing unit26on the basis of the control signal supplied from the controller29.

The controller29communicates with a console (not illustrated) connected to the radiation source through a wired or wireless communication unit (not illustrated) to control the gate line driving unit22, the signal processing unit26, and the image memory28, thereby controlling the operation of the radiography apparatus10. The controller29may be configured to include, for example, a microcomputer. The gate line driving unit22is an example of a reading unit in the technology of the present disclosure. The signal processing unit26is an example of a generation unit in the technology of the present disclosure.

Hereinafter, an example of the operation of the radiography apparatus10will be described. In a case in which radiation that has been emitted from the radiation source (not illustrated) and transmitted through the subject is incident on the radiation incident surface15of the radiography apparatus10, the scintillator32absorbs the radiation and emits visible light. The photoelectric conversion element36forming the pixel41converts the light emitted from the scintillator32into charge. The charge generated by the photoelectric conversion element36is accumulated in the corresponding pixel41. The amount of charge generated by the photoelectric conversion element36is reflected on the value of the corresponding pixel41.

In a case in which a radiographic image is generated, the gate line driving unit22supplies a gate signal to the TFT42through the gate line43on the basis of a control signal supplied from the controller29. Each row of the TFTs42is turned on by the gate signal. In a case in which the TFT42is turned on, the charge accumulated in the pixel41is read out to the signal line44and is then supplied to the charge amplifier24. The charge amplifier24generates an electric signal on the basis of the charge read out to the signal line44and supplies the electric signal to the signal processing unit26.

The signal processing unit26comprises a plurality of sample-and-hold circuits, a multiplexer, and an analog-to-digital converter (which are not illustrated). The plurality of sample-and-hold circuits are provided so as to correspond to the plurality of signal lines44, respectively. The electric signal supplied from the charge amplifier24is held by the sample-and-hold circuit. The electric signal held by each sample-and-hold circuit is input to the analog-to-digital converter through the multiplexer and is converted into a digital signal. The signal processing unit26generates data in which the digital signal generated by the analog-to-digital converter is associated with the positional information of the pixel41as image data and supplies the image data to the image memory28. The image memory28stores the image data generated by the signal processing unit26.

Hereinafter, a method for manufacturing the radiation detector30will be described.FIGS. 6A to 6Eare cross-sectional views illustrating an example of the method for manufacturing the radiation detector30.

First, the plurality of pixels41are formed on the first surface S1of the substrate34(FIG. 6A). The pixels41may be formed in a state in which the substrate34is supported by a support (not illustrated) for supporting the substrate34.

Then, the support member60is attached to the second surface S2of the substrate34which is opposite to the first surface S1(FIG. 6B).

Then, a mask70is formed on the first surface S1of the substrate34(FIG. 6C). Here,FIG. 7is a plan view illustrating an example of the configuration of the mask70. As illustrated inFIG. 7, the mask70has an opening portion71with a shape corresponding to the outer shape of the scintillator32that is formed in the subsequent process.

Then, the scintillator32is formed in a portion of the first surface S1of the substrate34which is exposed through the opening portion71of the mask70(FIG. 6D). The scintillator32can be formed by directly growing the columnar crystal of CsI doped with Tl on the substrate34using, for example, a vapor growth method. In a case in which the mask70is used to form the scintillator32, the outer shape of the scintillator32corresponds to the shape of the opening portion71of the mask70. That is, each of the corners32C1to32C4of the scintillator is chamfered. As illustrated inFIG. 4, for example, the outer edge32E of the corner32C1of the scintillator32is disposed closer to the inside (center) of the substrate34than the extension line32bof the side32L1and the side32L2sharing the corner32C1. After the scintillator32is formed, the mask70is removed.

Then, the reflective film50is formed so as to cover the surface S3of the scintillator32which is opposite to the contact surface with the substrate34and the surface S4intersecting the surface S3. Then, the sealing film51covering the reflective film50is formed (FIG. 6E). A stacked film including the reflective film50and the sealing film51is formed so as to cover the substrate34in the periphery of the scintillator32.

In a case in which the substrate has flexibility and is handled in, for example, the process of manufacturing the radiation detector, the substrate is likely to warp and the scintillator is likely to peel off from the substrate. In particular, since the corners of the scintillator have a smaller contact area with the substrate than the other portions of the scintillator, peeling is likely to occur at the corners. According to the radiation detector30and the radiography apparatus10of the embodiment of the technology of the present disclosure, each of the corners32C1to32C4of the scintillator32is chamfered and the outer edge32E of each of the corners32C1to32C4is disposed closer to the inside (center) of the substrate34than the extension line of each of the sides sharing the corners32C1to32C4. Therefore, it is possible to increase the contact area of the scintillator32with the substrate34at each of the corners32C1to32C4and to reduce the risk of the scintillator32peeling off from the substrate34, as compared to a case in which the outer edge of each of the corners32C1to32C4of the scintillator32is disposed on the extension line of each of the sides sharing the corners32C1to32C4or is disposed closer to the outside of the substrate than the extension line.

In addition, since each of the corners32C1to32C4of the scintillator32is chamfered, it is possible to suppress the occurrence of the breakage of the stacked film including the reflective film50and the sealing film51in a portion covering the corners32C1to32C4of the scintillator32as compared to a case in which the corners are not chamfered. Further, it is possible to increase the contact area of the stacked film including the reflective film50and the sealing film51with the substrate34in the vicinity of the corners32C1to32C4of the scintillator32. Therefore, it is possible to suppress the risk that the stacked film including the reflective film50and the sealing film51will peel off from the scintillator32and to suppress the occurrence of damage such as the breakage of the stacked film.

Here,FIG. 8is a diagram illustrating an outer edge E2of a substrate and an outer edge E4of a scintillator in a case in which a glass substrate without flexibility is used as the substrate, and the outer edge E1of the substrate34and the outer edge E3of the scintillator32according to the embodiment of the technology of the present disclosure. According to the radiography apparatus10of the embodiment of the technology of the present disclosure, since the substrate34is made of a flexible material, such as a resin film, the clearance A1between the substrate34and the housing14can be less than a clearance A2in the case in which the glass substrate is used. The size of the substrate34according to the embodiment of the technology of the present disclosure can be larger than the size of the glass substrate. Therefore, the size of the scintillator32according to the embodiment of the technology of the present disclosure can be larger than the size of the scintillator in the case in which the glass substrate is used. Therefore, according to the radiation detector30and the radiography apparatus10of the embodiment of the technology of the present disclosure, even in a case in which the corners32C1to32C4of the scintillator32are chamfered, the entire active area40can be covered with the scintillator32. As a result, it is possible to make each of the plurality of pixels41function effectively and all of the radiography images obtained by the radiography apparatus10can have high quality.

FIG. 9is a cross-sectional view illustrating the radiation detector30according to the embodiment of the technology of the present disclosure. In a case in which the scintillator32is formed by a vapor growth method, the surface S4of the end of the scintillator32is an inclined surface as illustrated inFIG. 9. As described above, according to the radiation detector30of the embodiment of the technology of the present disclosure, the size of the substrate34can be larger than that in the case in which the glass substrate is used. Therefore, an inclination angle α of the surface S4of the scintillator32can be less than that in the case in which the glass substrate is used. As a result, it is possible to reduce the accuracy of the alignment between the stacked film including the reflective film50and the sealing film51and the scintillator32in a case in which the stacked film is formed on the surface of the scintillator32, as compared to the case in which the glass substrate is used.

As illustrated inFIG. 9, the pixel41may be disposed at a position overlapping the inclined surface S4of the scintillator32. In this case, it is preferable that the thickness of an inclined portion of the scintillator32which covers the pixel41is equal to or greater than 70% of the thickness T of a flat portion of the scintillator32. As a result, it is possible to make each of the plurality of pixels41function effectively and all of the radiography images obtained by the radiography apparatus10can have high quality.

In the above-described embodiment, the case in which the scintillator32is directly grown on the substrate34by the vapor growth method has been described as an example. However, the present disclosure is not limited to this aspect. For example, the scintillator32formed on a substrate different from the substrate34by the vapor growth method may be attached to the substrate34. In this case, a mask that has an opening portion with a shape corresponding to the outer shape of the scintillator32is disposed on a substrate different from the substrate34and the columnar crystal of CsI:Tl is grown on a portion of the different substrate which is exposed through the opening portion of the mask to form the scintillator32on the substrate. Then, the scintillator32formed on the substrate is attached to the substrate34.

In general, a scintillator that is made of a material without having a columnar crystal structure, such as Gd2O2S:Tb, is provided in the state of a scintillator sheet. In a case in which a scintillator sheet is used as the material forming the scintillator32, as illustrated inFIG. 10A, a scintillator sheet32S is cut along a cutting line Lc corresponding to the outer shape of the scintillator32. As a result, as illustrated inFIG. 10B, the scintillator32with the chamfered corners32C1to32C4is cut out from the scintillator sheet32S. Then, the scintillator32cut out from the scintillator sheet32S is attached to the substrate34.

In the above-described embodiment, each of the corners32C1to32C4of the scintillator32is chamfered such that the outer edge32E of each of the corners32C1to32C4of the scintillator32includes one side which extends in a direction intersecting each of the sides sharing the corner. However, the present disclosure is not limited to this aspect. For example, as illustrated inFIG. 11A, the outer edge32E of each of the corners32C1to32C4of the scintillator32may have two sides which extend in directions intersecting each of the sides sharing the corner. Further, the outer edge32E of each of the corners32C1to32C4of the scintillator32may have three or more sides which extend in directions intersecting each of the sides sharing the corner. Since the outer edge32E of each of the corners32C1to32C4of the scintillator32has at least one side which intersects each of the sides sharing the corner, the scintillator32can come into contact with the substrate34on the at least one side and it is possible to promote the effect of reducing the risk of the scintillator32peeling off from the substrate34.

Further, as illustrated inFIG. 11B, the outer edges32E of the corners32C1to32C4of the scintillator32may have a rounded shape. In this case, the outer edge32E may have a shape corresponding to the arc of a circle or an ellipse or may have a curved shape other than a circle or an ellipse. In a case in which the outer edge32E of each of the corners32C1to32C4of the scintillator32is formed in a rounded shape, the scintillator32can come into contact with the substrate34at the rounded edge32E and it is possible to promote the effect of reducing the risk of the scintillator32peeling off from the substrate34.

Here, the distance between the end of the active area40and the corresponding side of the scintillator32is B, the distance between each of the sides32L1to32L4of the scintillator32and the corresponding side of the substrate34is D, and the distance between the end of the active area40and the housing14is L, it is preferable to that the following Expression (4) is satisfied. The following Expression (4) means that the clearance between the substrate34and the housing14is greater than zero.
L−B−D>0  (4)

Further, in a case in which the curvature radius of the outer edge32E of each of the corners32C1to32C4of the scintillator32is R, a distance F between an imaginary line Q that passes through the apex P of each of the corners32C1to32C4of the scintillator32and is parallel to the end of the active area40and each of the sides32L1to32L4of the scintillator is represented by the following Expression (5). In addition, since B>F is satisfied, Expression (6) can be derived. Furthermore, Expression (7) can be derived from Expressions (4) and (6).
F=R−R/√2  (5)
B>R−R/√2  (6)
R<(2+√2)B<(2+√2)×(L−D)  (7)

In each of the aspects illustrated inFIGS. 11A and 11B, the outer edge32E of each of the corners32C1to32C4of the scintillator32is disposed closer to the inside (center) of the substrate34than the extension line of each of the sides sharing the corner. Therefore, it is possible to reduce the risk of the scintillator peeling off from the substrate, as compared to a case in which the technology of the present disclosure is not applied.

All of the documents, patent applications, and technical standards described in the specification are incorporated in the specification by reference to the same extent as each document, patent application, and technical standard are specifically and individually noted to be incorporated by reference.

According to a second aspect of the technology of the present disclosure, in the radiation detector, each of the corners of the scintillator is chamfered.

According to a third aspect of the technology of the present disclosure, in the radiation detector, the outer edge of each of the corners of the scintillator has at least one side that intersects each of the sides sharing the corner.

According to a fourth aspect of the technology of the present disclosure, in the radiation detector, the outer edge of each of the corners of the scintillator has a rounded shape.

According to a fifth aspect of the technology of the present disclosure, in the radiation detector, the scintillator covers each of the plurality of pixels.

According to a sixth aspect of the technology of the present disclosure, there is provided a radiography apparatus comprising: the radiation detector according to any one of the first to fifth aspects; a reading unit that reads out charge which has been generated by each of the photoelectric conversion elements and accumulated in each of the plurality of pixels; and a generation unit that generates image data on the basis of the charge read out from each of the plurality of pixels.

According to an eighth aspect of the technology of the present disclosure, in the manufacturing method, the step of stacking the scintillator on the substrate comprises: a step of disposing a mask having an opening portion with a shape corresponding to an outer shape of the scintillator on the substrate; and a step of depositing a material forming the scintillator on a portion of the substrate which is exposed through the opening portion.

According to a ninth aspect of the technology of the present disclosure, in the manufacturing method, the step of stacking the scintillator on the substrate comprises: a step of disposing a mask having an opening portion with a shape corresponding to an outer shape of the scintillator on a substrate different from the substrate; a step of depositing a material forming the scintillator on a portion of the different substrate which is exposed through the opening portion to obtain the scintillator; and a step of attaching the scintillator formed on the different substrate to the substrate.

According to a tenth aspect of the technology of the present disclosure, in the manufacturing method, the step of stacking the scintillator on the substrate comprises: a step of processing a scintillator sheet into a shape corresponding to an outer shape of the scintillator to obtain the scintillator; and a step of attaching the scintillator obtained by processing the scintillator sheet to the substrate.

According to the first aspect of the technology of the present disclosure, it is possible to reduce the risk of the scintillator peeling off from the substrate, as compared to a case in which the outer edge of each of the corners of the scintillator is disposed on an extension line of each of the sides sharing the corner or is disposed closer to the outside of the substrate than the extension line.

According to the second aspect of the technology of the present disclosure, it is possible to promote the effect of reducing the risk of the scintillator peeling off from the substrate.

According to the third aspect of the technology of the present disclosure, it is possible to promote the effect of reducing the risk of the scintillator peeling off from the substrate.

According to the fourth aspect of the technology of the present disclosure, it is possible to promote the effect of reducing the risk of the scintillator peeling off from the substrate.

According to the fifth aspect of the technology of the present disclosure, it is possible to make each of the plurality of pixels function effectively.

According to the sixth aspect of the technology of the present disclosure, it is possible to reduce the risk of the scintillator peeling off from the substrate.

According to the seventh aspect of the technology of the present disclosure, it is possible to reduce the risk of the scintillator peeling off from the substrate, as compared to the case in which the outer edge of each of the corners of the scintillator is disposed on the extension line of each of the sides sharing the corner or is disposed closer to the outside of the substrate than the extension line.

The manufacturing method according to the eighth aspect of the technology of the present disclosure can be applied to, for example, a case in which a scintillator is directly formed on a substrate by a vapor growth method.

The manufacturing method according to the ninth aspect of the technology of the present disclosure can be applied to, for example, a case in which a scintillator formed on another substrate by the vapor growth method is used.

The manufacturing method according to the tenth aspect of the technology of the present disclosure can be applied to, for example, in a case in which a scintillator sheet is used.