JP2005308582A - Radiation detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an X-ray detector which can prevent deterioration in the light emission efficiency and the resolution due to the deliquescence of a scintillator layer. <P>SOLUTION: A protective layer 44 for covering the scintillator layer 43 of the X-ray detector 1 is a transparent resin film having the water permeability of <1.2 g/m<SP>2</SP>day. The protective layer 44 can be made so that the pinhole defects are few and that the water permeability is small. The scintillator layer 43 is of columnar crystals of the material of sodium iodide or cesium iodide. The decrease in the brightness of the scintillator layer 43 caused by the deliquescence of the scintillator layer 43 can be securely prevented for a long period of time. The deterioration in the light emission efficiency and the resolution of the scintillator layer 43 can be securely prevented for a long period of time. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a radiation detector in which a scintillator layer is provided on a photoelectric conversion element or a support.

  2. Description of the Related Art In recent years, flat detectors using an active matrix have attracted a great deal of attention as radiation detectors that are new generation X-ray diagnostic detectors. This flat detector outputs an X-ray image or a real-time X-ray image as a digital signal by irradiating the flat detector with X-rays. Moreover, since this flat detector is a solid state detector, it is highly expected from the viewpoint of image quality performance and stability. Furthermore, as the first practical application of the flat panel detector, it has been developed and commercialized in recent years for chest / general imaging that collects still images with a relatively large dose.

  And there are two types of configurations of this flat detector, a direct method in which X-rays are directly converted into a charge signal by a photoconductive film such as amorphous selenium (a-Se) and led to a capacitor for charge storage, There is an indirect method in which X-rays are converted into visible light by a scintillator layer, and then the visible light is converted into a charge signal by a photodiode or CCD and led to a charge storage capacitor.

  Here, the scintillator layer of this indirect type flat panel detector includes those formed by applying a mixture of phosphor powder and binder and those formed by evaporating and depositing columnar crystals. In particular, when the scintillator layer is a columnar crystal, the diffusion of fluorescence is small due to the structure of the columnar crystal, and high resolution is exhibited.

  However, cesium iodide (CsI) or sodium iodide (NaI), which is the main material of this columnar crystal, is deliquescent, and if left in an air atmosphere, the luminous efficiency and resolution are degraded. In order to prevent the deterioration of the light emission efficiency and the resolution, it is necessary to form a protective layer having a shielding property against moisture and a permeability to X-rays. That is, a phosphor resistant to moisture has a problem in performance, and a phosphor having good performance is vulnerable to moisture.

And this protective layer is known by a method of forming an organic film such as a xylene-based resin or an inorganic film such as silicon oxynitride by an evaporation deposition method in a vacuum or an inert gas atmosphere (for example, (See Patent Documents 1 and 2.)
Japanese Examined Patent Publication No. 5-39558 (page 2-3, FIG. 1 and FIG. 3) Japanese Examined Patent Publication No. 6-58440 (page 2-5, Fig. 1)

  As described above, since the protective layer obtained by the evaporation deposition method has a thin film thickness and defects such as pinholes, the moisture permeability is large. In addition, the coating along the edge of the substrate of the protective layer increases the moisture permeability between the substrate and the resin interface. Therefore, it is insufficient to suppress deterioration of the luminous efficiency and resolution of the scintillator layer for a long time. Also, the formation of the protective layer by the evaporation deposition method deposits the protective layer in the gaps between the columnar crystals, and the refractive index ratio between these columnar crystals and the gaps is close to 1. Therefore, the reflection efficiency in the columnar crystals is high. There is a problem that the resolution and the light emission efficiency are reduced.

  The present invention has been made in view of these points, and an object of the present invention is to provide a radiation detector capable of suppressing deterioration in light emission efficiency and resolution due to deliquescence of the scintillator layer.

The present invention includes a photoelectric conversion element or support that converts incident light into a signal charge, a scintillator layer that is provided on the photoelectric conversion element or support and converts incident radiation into visible light, and at least the scintillator layer A side opposite to the side facing the photoelectric conversion element or the support is covered, and a protective layer which is a transparent resin film having a moisture permeability of less than 1.2 g / m ² · day is provided.

A protective layer that covers at least the side of the scintillator layer provided on the photoelectric conversion element or the support opposite to the side facing the photoelectric conversion element or the support is a transparent resin having a moisture permeability of less than 1.2 g / m ² · day. A film was obtained. As a result, this protective layer can suppress degradation of light emission efficiency and resolution caused by deliquescence of the scintillator layer over a long period of time, and can also suppress a decrease in resolution due to the deposition of the protective layer in the gap of the scintillator layer. .

According to the present invention, the protective layer covering at least the side of the scintillator layer facing the photoelectric conversion element or the support is a transparent resin film having a moisture permeability of less than 1.2 g / m ² · day, This protective layer can suppress degradation of light emission efficiency and resolution caused by the deliquescence of the scintillator layer over a long period of time, and can suppress a decrease in resolution due to the deposition of the protective layer in the gaps of the scintillator layer.

  The configuration of the first embodiment of the radiation detector of the present invention will be described below with reference to FIGS.

  1 and 2, reference numeral 1 denotes an X-ray detector. The X-ray detector 1 is an X-ray flat sensor as a flat detector that detects an X-ray image as radiation. The X-ray detector 1 is a radiation detector as a photodetector used in the X-ray detector system. And this X-ray detector 1 is provided with the photoelectric conversion board | substrate 2 as a photon detection part, as shown in FIG. This photoelectric conversion substrate 2 is an active matrix TFT array as an active matrix photoelectric conversion substrate. The photoelectric conversion substrate 2 has a glass substrate 3 which is an insulating substrate having translucency. On the surface which is one main surface of the glass substrate 3, a plurality of substantially rectangular photoelectric conversion portions 4 functioning as optical sensors are formed in a matrix.

  A plurality of pixels 5 each having the same structure are provided on the surface of the glass substrate 3 by each photoelectric conversion unit 4. These pixels 5 are two-dimensionally arranged at a predetermined pitch P in each of the row direction which is the horizontal direction in FIG. 2 and the column direction which is the vertical direction in FIG. In other words, the photoelectric conversion substrate 2 is configured by arranging a plurality of pixel-unit photoelectric conversion units 4.

  Each pixel 5 includes a photodiode 6 as a substantially L-shaped photoelectric conversion element that converts incident light into signal charges. These photodiodes 6 are formed for each pixel 5 as an amorphous silicon (a-Si) pn diode structure or a pin diode structure. Further, each of these photodiodes 6 is provided in a pixel unit, that is, in the central portion of each pixel 5 on the surface of the glass substrate 3. Further, a thin film transistor (TFT) 7 as a switching element is electrically connected to each of the photodiodes 6.

  Each of these thin film transistors 7 is at least partially composed of amorphous silicon as an amorphous semiconductor, which is a crystalline semiconductor material. Further, each of these thin film transistors 7 accumulates and emits charges generated by the incidence of light on the photodiode 6. Each thin film transistor 7 is provided in each pixel 5.

  Each pixel 5 is provided with a storage capacitor 8 on a rectangular flat plate, which is a charge storage capacitor as a charge storage unit for storing the signal charge converted by the photodiode 6. These storage capacitors 8 are provided under the photodiode 6 so as to face each other. Here, the thin film transistor 7 includes a gate electrode 11, a source electrode 12, and a drain electrode 13. The drain electrode 13 is electrically connected to each of the photodiode 6 and the storage capacitor 8.

  Further, the photodiode 6 is provided in an area that is a region that does not overlap the thin film transistor 7 and the storage capacitor 8. Here, in the photodiode 6, in order to secure a light receiving area, an insulating layer 35 is formed on the thin film transistor 7 and the storage capacitor 8, and a current collecting electrode 41 is formed over the entire area of the pixel 5 including the insulating layer 35. In addition, it is possible to adopt a structure in which the upper part of the collecting electrode 41 is formed so as to substantially correspond to the entire surface of each pixel 5.

  Each of these pixels 5 is provided with a rectangular flat pixel electrode 9. These pixel electrodes 9 are arranged to face the photodiode 6 and the storage capacitor 8 of each pixel 5. Each pixel electrode 9 is electrically connected to the drain electrode 13 of the thin film transistor 7 in the pixel 5 provided with each pixel electrode 9.

  Further, on one side edge along the row direction on the surface of the glass substrate 3, an operation control circuit 14 which is an elongated rectangular flat-plate driver circuit for controlling the operation state of each thin film transistor 7, for example, on and off of each thin film transistor 7. Has been implemented. The operation control circuit 14 has a longitudinal direction along the column direction on the surface of the glass substrate 3, and is provided along one side edge of the surface of the glass substrate 3. The operation control circuit 14 is provided outside each photoelectric conversion unit 4.

  The operation control circuit 14 is electrically connected to one end of a plurality of control lines 15 as gate lines. These control lines 15 are wired along the row direction of the glass substrate 3, and are provided between the respective pixels 5 on the glass substrate 3. Further, each control line 15 is electrically connected to each gate electrode 11 of the thin film transistor 7 constituting each pixel 5 in the same row, and is used for controlling on / off of the thin film transistor 7.

  A plurality of data lines 16 are wired on the surface of the glass substrate 3 along the column direction of the glass substrate 3. Each data line 16 is provided between each pixel 5 on the glass substrate 3. These data lines 16 are electrically connected to the source electrodes 12 of all the thin film transistors 7 constituting the pixels 5 in the same column. Further, one end of each data line 16 is electrically connected to a charge amplifier 17 which is a charge sensitive amplifier disposed corresponding to each data line 16.

  The charge amplifier 17 is mounted on one end edge in the column direction on the surface of the glass substrate 3, and is provided outside each pixel 5 on the glass substrate 3. Further, the charge amplifier 17 is constituted by an operational amplifier (not shown), for example, and includes a pair of input terminals 21 and 22 and an output terminal 23. Each of the negative input terminals 21 of the pair of input terminals 21 and 22 is electrically connected to one end of the data line 16. Further, the positive input terminal 22 which is the other of the pair of input terminals 21 and 22 is grounded.

  In addition, a series circuit of a capacitor 24 is connected in parallel between the input terminal 21 and the output terminal 23 on the negative electrode side, and the capacitor 24 is configured to have an integration function. Further, a series circuit of switches 25 is connected in parallel between the negative-side input terminal 21 and the output terminal 23. The switch 25 is connected in parallel to the capacitor 24, and is configured so that the charge remaining in the capacitor 24 can be discharged by closing the switch 25.

  Further, the output terminal 23 of each charge amplifier 17 is electrically connected to a multiplexer 26 as a parallel / serial converter in the shape of an elongated rectangular plate. The multiplexer 26 converts a plurality of electrical signals input in parallel from the charge amplifiers 17 to the multiplexer 26 into serial signals. The multiplexer 26 is provided at one end edge in the column direction on the glass substrate 3, and has a longitudinal direction along the row direction of the glass substrate 3. Further, the multiplexer 26 is provided outside each pixel 5 on the glass substrate 3.

  The multiplexer 26 is electrically connected to a digitizer 27 which is an elongated rectangular flat plate analog-digital converter that converts an analog signal into a digital signal. The digitizer 27 is provided on the other side edge along the row direction of the glass substrate 3, and is provided outside each pixel 5 on the glass substrate 3. The digitizer 27 is provided along one edge of the glass substrate 3 in the column direction, and has a longitudinal direction along the column direction of the glass substrate 3.

  Here, the operation control circuit 14 transfers the image charge from the pixel 5 to the plurality of data lines 16 and then sends the image charge to the respective charge amplifiers 17 through the plurality of control lines 15 to form a row of thin film transistors 7. Turn on at once. Further, the operation control circuit 14 resets the potential of each pixel electrode 9 by inputting the image charge to each charge amplifier 17. Then, the multiplexer 26 combines the amplified signal obtained for each row and sends it to the digitizer 27.

  On the other hand, as shown in FIG. 2, in each pixel 5 on the surface of the glass substrate 3, a thin film transistor 7, a storage capacitor 8, and a pixel electrode 9 are formed. Here, each thin film transistor 7 includes an island-like gate electrode 11 formed on the glass substrate 3. An insulating film 31 is laminated and formed on the glass substrate 3 including these gate electrodes 11. This insulating film 31 covers each gate electrode 11.

  Further, on the insulating film 31, a plurality of island-shaped semi-insulating films 32 are stacked. Each of these semi-insulating films 32 is arranged to face each gate electrode 11 and covers each gate electrode 11. That is, each of these semi-insulating films 32 is provided on each gate electrode 11 with the insulating film 31 interposed therebetween. Further, the source electrode 12 and the drain electrode 13 are formed on the insulating film 31 including the semi-insulating film 32. The source electrode 12 and the drain electrode 13 are insulated from each other and are not electrically connected. The source electrode 12 and the drain electrode 13 are provided on both sides of the gate electrode 11, and one end portions of the source electrode 12 and the drain electrode 13 are stacked on the semi-insulating film 32.

  As shown in FIG. 2, the gate electrode 11 of each thin film transistor 7 is electrically connected to a common control line 15 together with the gate electrodes 11 of other thin film transistors 7 located in the same row. Further, the source electrode 12 of each thin film transistor 7 is electrically connected to a common data line 16 together with the source electrodes 12 of other thin film transistors 7 located in the same column.

  On the other hand, the storage capacitor 8 includes an island-shaped lower electrode 33 formed on the glass substrate 3 as shown in FIG. An insulating film 31 is laminated and formed on the glass substrate 3 including the lower electrode 33. The insulating film 31 extends from the gate electrode 11 of each thin film transistor 7 to the lower electrode 33. Further, an island-shaped upper electrode 34 is laminated on the insulating film 31. The upper electrode 34 is disposed to face the lower electrode 33 and covers each lower electrode 33. That is, each upper electrode 34 is provided on each lower electrode 33 via the insulating film 31. A drain electrode 13 is laminated on the insulating film 31 including the upper electrode 34. The other end of the drain electrode 13 is laminated on the upper electrode 34 and is electrically connected to the upper electrode 34.

  Further, an insulating layer 35 is formed on the insulating film 31 including the semi-insulating film 32, the source electrode 12 and the drain electrode 13 of each thin film transistor 7, and the upper electrode 34 of each storage capacitor 8. Yes. A photodiode 6 is formed on the insulating layer 35.

  In addition, a through hole 36 serving as a contact hole communicating with the drain electrode 13 of the thin film transistor 7 is formed in a part of the insulating layer 35. On the insulating layer 35 including the through hole 36, a current collecting electrode 41 as a first electrode as a lower electrode positioned below the photodiode 6 is laminated and formed. Therefore, the collecting electrode 41 is electrically connected to the drain electrode 13 of the thin film transistor 7 and the upper electrode of the integrated capacitor 8 through the through hole 36. The thin film transistor 7 is provided in the lower layer of the photodiode 6.

  Further, a photodiode 6 is formed on the collecting electrode 41, and a bias electrode 42 as a second electrode is formed on the photodiode 6 as a top electrode. Yes. The bias electrode 42 is formed, for example, by depositing an ITO (Indium-Tin Oxide) transparent conductive film by sputtering. Therefore, a bias voltage is applied between the collecting electrode 41 and the bias electrode 42 to form a bias electric field.

  On the bias electrode 42, a scintillator layer 43 of a columnar crystal that changes incident X-rays by converting them into visible light is laminated. The scintillator layer 43 is provided on the photodiode 6 that is on the photoelectric conversion substrate 2. The scintillator layer 43 covers the periphery of the photodiode 6 over the entire circumferential direction. In other words, the scintillator layer 43 is provided around the photodiode 6. Further, the scintillator layer 43 is provided so as to overlap an area which is a region where the photodiode 6 is formed. Therefore, the scintillator layer 43 is optically coupled to the photoelectric conversion substrate 2.

  Further, the space between the columnar crystals of the scintillator layer 43 is configured by being filled with a vacuum or an inert gas and air. In other words, the scintillator layer 43 is formed of individual columnar crystal structures such as sodium iodide (NaI) or cesium iodide (CsI) by an evaporation method, an Electro Beam (EB) method, a sputtering method, or the like. This is a columnar crystal formed by depositing a phosphor that is not deposited. Therefore, the scintillator layer 43 has a low resolution with a small diffusion of light generated by the columnar crystals of the scintillator layer 43.

  On the scintillator layer 43, a protective layer 44 is formed and laminated. As shown in FIG. 1, the protective layer 44 covers at least the upper side of the scintillator layer 43 that is opposite to the side facing the photodiode 6. Here, the protective layer 44 is preferably a film having a low moisture permeability and a low shielding property that suppresses deliquescence of CsI or NaI of columnar crystals due to the influence of moisture entering the scintillator layer 43, and is generally used in the food packaging field. The transparent resin film currently used can be utilized.

  Here, as the protective layer 44, a transparent resin film having a transmittance of 85% or more for electromagnetic waves having a wavelength of 350 nm or more and 800 nm or less is preferable. Specifically, the transparent resin film constituting the protective layer 44 includes low density polyethylene, high density polyethylene, ethylene / vinyl acetate copolymer, ethylene / vinyl alcohol copolymer, polyvinyl alcohol / vinyl acetate polymer, polypropylene. , Polyvinylidene chloride, polyester resin, nylon, polyvinyl chloride, polyacrylonitrile, polystyrene and the like.

  Further, as the transparent resin film constituting the protective layer 44, an engineer plastic or the like can be used as the transparent resin film in consideration of heat resistance. Specifically, the transparent resin film constituting the protective layer 44 includes cyclic olefin, polyester carbonate, polymethylpentene, polyarylate, polyethersulfone, polyetheretherketone, polycarbonate, polysulfone, polymethylmethacrylate or polyvinylbutyral. Etc.

That is, as shown in FIG. 3, the protective layer 44 has a moisture permeability of less than 1.2 g / m ² · day, that is, 90% at 37 ° C. Also have low moisture permeability.

  Further, as the protective layer 44, it is possible to use a single layer of a transparent resin film or a layered type of laminated layers. Here, the protective layer 44 is formed by using a solution casting method, a spray printing method, an ink jet method, a thermocompression bonding method, or the like in a vacuum container (not shown) or a container under an inert gas atmosphere. It is formed by forming a transparent resin film made of at least one of the above resins by a method such as electrostatic coating.

On the protective layer 44, a reflection layer 45 is formed and laminated. That is, the reflective layer 45 is disposed on the protective film 44. In other words, the reflective layer 45 is provided on the upper side of the protective layer 44, which is the opposite side of the side facing the scintillator layer 43. Therefore, the reflective layer 45 is formed on the protective layer 44 so as to overlap the area of the scintillator layer 43. Here, the reflective layer 45 is made of a metal having high reflectivity such as gold (Au), silver (Ag), or aluminum (Al), or high reflectivity of titanium dioxide (TiO ₂ ) or gadolinium sulfate (GOS). It is comprised with the metal oxide etc. which are white pigments.

  Further, a support 46 on a rectangular flat plate is attached on the reflective layer 45. Here, when the reflective layer 45 is a metal, the reflective layer 45 is formed on the protective layer 44 or the support 46 by a method such as a silver salt method, a vacuum deposition method, or a sputtering method. Further, when the reflective layer 45 is a metal oxide, the reflective layer 45 is a coating liquid obtained by mixing a metal oxide and a resin that is a binder, and this coating liquid is used as a solution casting method, a spray printing method, an inkjet method. It is formed on the protective layer 44 or the support 46 by a method such as a method, a thermocompression bonding method or an electrostatic coating method.

  Next, the operation of the first embodiment will be described.

  First, the X-ray L sequentially passes through the support 46, the reflective layer 45, and the protective layer 44 and then enters the scintillator layer 43. The X-ray L incident on the scintillator layer 43 is converted into visible light. .

  The visible light converted by the scintillator layer 43 is converted by the photodiode 6 into a signal charge that is an electric signal. At this time, this signal charge is stored in the storage capacitor 8 via the drain electrode 13 by a bias electric field formed between the bias electrode 42 and the collecting electrode 41.

  On the other hand, the reading of the signal charges stored in the storage capacitor 8 is sequentially controlled by the operation control circuit 14 for each row of the pixel unit 12 (lateral direction in FIG. 2), for example.

  At this time, for example, an ON signal of 10 V is applied to each of the pixel-unit gate electrodes 11 located in the first row from the operation control circuit 14 through the first data line 16, so that the pixel unit of the first row Each thin film transistor 7 is turned on.

  At this time, the signal charge stored in the storage capacitor 8 of the pixel unit in the first row is output from the drain electrode 13 to the source electrode 12 as an electric signal. Each of the electric signals output to the source electrode 12 is amplified by a plurality of charge amplifiers 17.

  Further, this amplified electric signal is applied in parallel to the multiplexer 26 and converted into a serial signal. Thereafter, the digital signal is converted into a digital signal by the digitizer 27 and then sent to a signal processing circuit (not shown) in the next stage.

  When the readout of the charge of the pixel-based storage capacitor 8 located in the first row is completed, the operation control circuit 14 passes through the first data line 16 to the pixel-unit gate electrode 11 in the first row. For example, an off signal of −5 V is applied to turn off each of the thin film transistors 7 in the pixel unit in the first row.

  Thereafter, the above-described operation is sequentially performed for the pixel units in the second row and thereafter. Then, the signal charges stored in the storage capacitors 8 of all the pixels are read out, sequentially converted into digital signals and output, and an electrical signal corresponding to one X-ray screen is output from the digitizer 27.

  As described above, according to the first embodiment, the protective layer 44 that covers the scintillator layer 43 of the X-ray detector 1 is made of low-density polyethylene, high-density polyethylene, polypropylene, polyvinylidene chloride, polyester-based resin. , Polyvinyl chloride, polyacrylonitrile, polystyrene, nylon, ethylene / vinyl acetate copolymer, ethylene / vinyl alcohol copolymer, polyvinyl alcohol / vinyl acetate polymer, cyclic olefin, polyester carbonate, polymethylpentene, polyarylate, poly A transparent resin film made of at least one of ether sulfone, polyether ether ketone, polycarbonate, polysulfone, polymethyl methacrylate or polyvinyl butyral is applied to a solution casting method, a spray printing method, an ink jet method. It is formed by a method such as a spray method, a thermocompression bonding method, or an electrostatic coating method.

As a result, the protective layer 44 having fewer defects such as pinholes and lower moisture permeability than the conventional protective layer 44 can be obtained. That is, a protective layer 44 of a transparent resin film having a moisture permeability of less than 1.2 g / m ² · day was obtained. Therefore, as shown in FIG. 4 and FIG. 5, this protective layer 44 reduces the brightness of the scintillator layer 43 due to the deliquescent nature of sodium iodide or cesium iodide, which is the columnar crystal material of the scintillator layer 43. That is, it is possible to reliably suppress deterioration of the light emission efficiency and resolution over a long period of time.

  In addition, a solution casting method, spray printing method or ink jet method for forming a protective layer 44 by applying a coating liquid in which resin is diffused and then drying, or a heat for forming a protective layer 44 by pasting an existing transparent resin film By forming by the pressure bonding method or the electrostatic coating method, it is possible to prevent the protective film 44 from being deposited in the gaps between the columnar crystals of the scintillator layer 43 due to the surface tension of the coating liquid or the transparent resin film. Therefore, it is possible to suppress a decrease in resolution due to the protective layer 44 being deposited in the gaps between the columnar crystals of the scintillator layer 43.

  In other words, it is possible to provide the X-ray detector 1 having high sensitive characteristics that is stable for a long period of time by suppressing a decrease in resolution due to the protective layer 44 wrapping around the gaps between the columnar crystals of the scintillator layer 43. Therefore, the X-ray detector 1 that can form the protective layer 44 homogeneously and reliably, can manufacture the X-ray detector 1 having the scintillator layer 43 that is stable for a long time with high luminous efficiency, and can maintain high sensitivity characteristics for a long time. Can be manufactured.

  As in the second embodiment shown in FIG. 6, the protective layer 44 extends from the upper surface of the scintillator layer 43 to the peripheral surface of the support 46 via the peripheral surface and side surface of the photoelectric conversion substrate 2. It can also be configured to cover with. In this case, the photoelectric conversion substrate 2 is installed on the support 46, and a scintillator layer 43 is laminated and provided at the center in the width direction of the photoelectric conversion substrate 2. The scintillator layer 43 has a width dimension smaller than the width dimension of the photoelectric conversion substrate 2, and is formed only on each pixel 5 of the photoelectric conversion substrate 2. Further, on the photoelectric conversion substrate 2 including the scintillator layer 43, a protective layer 44 is laminated and formed. Further, a reflective layer 45 is formed on the protective layer 44 facing the upper surface of the scintillator layer 43.

  At this time, the protective layer 44 covers the upper surface of the scintillator layer 43 and each side surface of the outer peripheral portion of the scintillator layer 43. Further, the protective layer 44 covers each of the upper surface of the photoelectric conversion substrate 2 excluding the portion covered with the scintillator layer 43 and each side surface of the photoelectric conversion substrate 2. Furthermore, the protective layer 44 covers each side surface of the support 46 and the peripheral edge on the lower surface side of the support 46. That is, the protective layer 44 covers from the edge of the lower surface, which is the side surface of the support 46 opposite to the side facing the scintillator layer 43, to the inside. Therefore, the protective layer 44 covers from the upper side of the scintillator layer 43 to the periphery of the lower surface of the support 46.

As a result, since the scintillator layer 43 is covered with the protective layer 44 of the transparent resin film having a moisture permeability of less than 1.2 g / m ² · day, the same effects as the first embodiment can be achieved. it can. Further, the protective layer 44 covered the upper surface of the scintillator layer 43 and the side surfaces of the outer peripheral portion and the upper surface of the photoelectric conversion substrate 2 to the inner side of the lower surface of the support 46. Therefore, since moisture can be prevented from entering from the interface between the protective layer 44 and the photoelectric conversion substrate 2 or the support 46, the water permeability in the scintillator layer 43 can be further reduced.

  Further, a scintillator layer 43 may be formed on the support 46 as in the third embodiment shown in FIG. In this case, the scintillator layer 43 is laminated at the center in the width direction on the support 46. The scintillator layer 43 has a width dimension smaller than that of the support 46 and is formed only on each pixel 5 of the photoelectric conversion substrate 2. A protective layer 44 is laminated on the support 46 including the scintillator layer 43.

  Specifically, the protective layer 44 covers the upper surface of the scintillator layer 43 and each side surface of the outer peripheral portion. Further, the protective layer 44 includes an upper surface of the support 46 excluding a portion covered with the scintillator layer 43, each side surface of the outer periphery of the support 46, and a peripheral edge on the lower surface side of the support 46. Covering. That is, the protective layer 44 covers from the edge of the lower surface, which is the side surface of the support 46 opposite to the side facing the scintillator layer 43, to the inside. In other words, the protective layer 44 is formed from the edge of the end surface of the support 46 opposite to the side on which the scintillator layer 43 is attached to the inside. Here, the protective layer 44 exists between the scintillator layer 43 and the photodiode 6 of the photoelectric conversion substrate 2.

  Further, a reflective layer 45 is laminated on the lower surface of the support 46 so as to face the scintillator layer 43. That is, the reflective layer 45 is attached to the lower surface of the support 46 opposite to the side on which the scintillator layer 43 is attached. In other words, the reflective layer 45 is attached so as to overlap an area which is an area where the scintillator layer 43 is provided on the end surface of the support 46 opposite to the side where the scintillator layer 43 is attached. .

  The reflective layer 45 has a width dimension equal to that of the scintillator layer 43, and is provided on the lower surface of the support 46 corresponding to the scintillator layer 43. Here, each of the scintillator layer 43, the protective layer 44, the reflective layer 45, and the support 46 constitutes a support substrate 47. Then, on the protective layer 44 on the scintillator layer 43 of the support substrate 47, the photoelectric conversion substrate 2 is disposed to face each other with a gap. The photoelectric conversion substrate 2 is attached and bonded onto the scintillator layer 43 in a state optically corresponding to the scintillator layer 43. Further, in the photoelectric conversion substrate 2, each photodiode 6 of the photoelectric conversion substrate 2 is optically coupled on the scintillator layer 43.

As a result, in the protective layer 44 of the transparent resin film having a moisture permeability of less than 1.2 g / m ² · day, the upper surface of the scintillator layer 43 and the side surfaces of the outer peripheral portion, and the upper surface of the support 46 to the inner side of the lower surface edge. Since it was covered, the same effect as the second embodiment can be obtained.

  Further, the photodiode 6 and the thin film transistor 7 of the X-ray detector 1 are all made of an amorphous semiconductor, or at least a part of at least one of the photodiode 6 and the thin film transistor 7 is made of amorphous silicon or the like. A semiconductor, a crystalline semiconductor, or a polycrystalline semiconductor such as polysilicon (p-Si) can also be used.

It is explanatory sectional drawing which shows the radiation detector of the 1st Embodiment of this invention. It is explanatory top view which shows a radiation detector same as the above. It is a table | surface which shows the moisture permeability of the protective layer of a radiation detector same as the above. It is a graph which shows the time change of the resolution by the environmental test (60 degreeC, 90%) of a protective layer same as the above. It is a graph which shows the time change of the brightness | luminance by the environmental test (60 degreeC, 90%) of a protective layer same as the above. It is explanatory sectional drawing which shows 2nd Embodiment of the radiation detector of this invention. It is explanatory sectional drawing which shows 3rd Embodiment of the radiation detector of this invention.

Explanation of symbols

1 X-ray detector as a radiation detector 6 Photodiode as a photoelectric conversion element
43 Scintillator layer
44 Protective layer
45 Reflective layer
46 Support

Claims (7)

A photoelectric conversion element that converts incident light into a signal charge;
A scintillator layer that is provided in the photoelectric conversion element and converts incident radiation into visible light;
A radiation detection method comprising: a protective layer that covers at least the side of the scintillator layer opposite to the side facing the photoelectric conversion element and is a transparent resin film having a moisture permeability of less than 1.2 g / m ² · day. vessel. The scintillator layer is a columnar crystal,
The radiation detector according to claim 1, wherein the protective layer covers a side of the scintillator layer, a side of the photoelectric conversion element facing the scintillator layer, and a side surface. The radiation detector according to claim 1, further comprising a reflective layer provided on a side of the protective layer opposite to the side facing the scintillator layer. A support;
A scintillator layer that is provided on the support and converts incident radiation into visible light;
A radiation detector comprising: a protective layer that covers at least the opposite side of the scintillator layer opposite to the support and is a transparent resin film having a moisture permeability of less than 1.2 g / m ² · day. . The scintillator layer is a columnar crystal,
The radiation detector according to claim 4, wherein the protective layer covers a side portion of the scintillator layer, a side of the support that faces the scintillator layer, and a side surface. The radiation detector according to claim 4, further comprising a reflective layer provided on a side opposite to the side facing the scintillator layer of the support. The scintillator layer is a columnar crystal,
The radiation detector according to any one of claims 1 to 6, wherein a gap between the columnar crystals of the scintillator layer is filled with a vacuum or an inert gas and air.

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