JP2007093545A - Radiation detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an X-ray detector suppressing the characteristics degradation due to thermal expansion. <P>SOLUTION: A metal plate 25, whose thermal expansion coefficient difference from an X-ray photoconductor layer 4 is smaller than that from the X-ray photoconductor layer 4 and a TFT circuit board 3, is jointed to the opposite side of the TFT circuit board 3 to the X-ray photoconductor layer 4. Stress by the thermal expansion coefficient difference on the interface between the X-ray photoconductor layer 4 and a TFT circuit board 3 side that is generated by temperature variations during use, after manufacturing, or during storage of the X-ray detector is suppressed, breakage of a retain substrate 11 constituting the TFT circuit board 3, the characteristics variations of the X-ray photoconductor layer 4, and breakage by crack occurrence can be suppressed, and the characteristics degradation due to thermal expansion can be suppressed. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a radiation detector including a signal conversion layer that converts incident radiation into a predetermined signal and a circuit board that detects a signal converted by the signal conversion layer.

  As a new generation image detector for X-ray diagnosis, an X-ray image detector using an active matrix has attracted much attention. Such an X-ray image detector is formed in a planar shape, and an X-ray image or a real-time X-ray image is output as a digital signal by applying X-rays. Since such an X-ray image detector is a solid state detector, it is extremely expected in terms of image quality performance or stability, and many researches and developments have been made.

  As the first application for practical use, it has been developed for the chest or general radiography for collecting still images with a relatively large dose, and has been commercialized in recent years. Commercialization is expected in the near future for applications in the fields of circulatory organs and digestive organs that require higher performance and real-time video at 30 frames per second under fluoroscopic dose. For such moving image applications, improvement of S / N and real-time processing technology of minute signals are important development items.

  By the way, there are two types of flat detectors, a direct method and an indirect method.

  The direct method is a method in which incident X-rays are directly converted into a charge signal using a photoconductive film such as a-Se, and the converted signal charge is stored in a charge storage capacitor (see, for example, Patent Document 1).

  On the other hand, the indirect method receives incident X-rays from the scintillator layer, temporarily converts it into visible light, converts this visible light into signal charge by an a-Si photodiode or CCD, and leads it to a charge storage capacitor. (For example, refer to Patent Document 2).

  In the X-ray image detectors, the indirect method currently occupies the majority, but the direct method is considered to have a higher possibility of the configuration in the future.

  The direct method requires an X-ray photoconductive material that directly converts incident X-rays into a charge signal, which is a kind of semiconductor. The main application of the flat panel detector is to transmit the human body and use the information for medical purposes in many cases, and it needs to be large enough to cover the human body. For this reason, detectors with a side of about 40 cm are often used as the size that is normally used. At this time, in order to realize a direct X-ray image detector, an X-ray photoconductive film must be uniformly formed on a TFT circuit substrate having a larger size.

  In order to sufficiently detect incident X-rays, an X-ray photoconductive film having a thickness of several hundred μm is required even if a material having a large specific gravity made of heavy metal is used. That is, it is necessary to form a semiconductor film having a size of 40 cm on one side on the TFT circuit substrate.

  Since the X-ray photoconductive material is a kind of semiconductor, there is a very high possibility that the characteristics will change greatly depending on its crystal structure and composition. Moreover, although the characteristic of a normal semiconductor material can obtain the highest characteristic in a single crystal, a semiconductor single crystal material that can cover the size of an X-ray image detector has not been realized. Therefore, in order to realize a direct X-ray image detector, it is necessary to form an X-ray photoconductive film directly on the TFT circuit substrate.

A TFT circuit board of a normal X-ray image detector is manufactured by diverting a manufacturing process of a liquid crystal display device. For this reason, aluminum or ITO is often used for the pixel electrode in direct contact with the X-ray photoconductive film, and the insulating film of silicon oxide (SiO ₂ ) is also in contact with the X-ray photoconductive film so as to surround the pixel electrode. It has a structure to do.

When an X-ray photoconductive film is formed on this TFT circuit substrate, the X-ray photoconductive film, which is usually several hundred μm, is formed by using vacuum evaporation to efficiently charge the X-ray photoconductive signal. After forming a material having characteristics that change into, for example, lead iodide (PbI ₂ ) or bismuth iodide (BiI ₃ ) into a film shape, an upper electrode having a role of supplying charges to the X-ray photoconductive film is formed. Thus, the basic configuration of the X-ray image detector is completed.

In addition, the indirect X-ray image detector, which is the other method, has a thickness of several hundreds μm made of a phosphor made of a material having a relatively large specific gravity and made of heavy metal in order to sufficiently detect incident X-rays. An X-ray input film having The TFT circuit substrate used in the indirect method is also manufactured by diverting the same liquid crystal display manufacturing process as that in the direct method. Therefore, an X-ray input phosphor film is formed on the TFT circuit substrate manufactured in this way, and the currently widely used phosphor material composed of cesium iodide (CsI) is used as a TFT circuit. A method of forming a thick film on a substrate by vacuum deposition and an intensifying screen having a structure in which gadolinium oxysulfide (Gd ₂ O ₂ S) or scheelite (CaWO ₄ ) is dispersed in a resin A method of bonding to the surface, or a method of bonding a cesium iodide film formed by vacuum deposition on another substrate to the surface of the TFT circuit substrate.
JP 2002-214351 A (page 3-4, FIG. 1) Japanese Patent No. 3034587 (page 2, Fig. 2)

  As described above, in the conventional X-ray image detector, there is a large difference in the coefficient of thermal expansion between the TFT circuit substrate formed mainly on the glass substrate and the X-ray photoconductive film or the X-ray input fluorescent film. .

  For example, in a glass substrate used for a general TFT circuit substrate, the coefficient of thermal expansion is set to about 5 ppm / ° C. so that the circuit is not damaged due to expansion. Along with this, the coefficient of thermal expansion is expected to be further reduced.

In contrast, selenium (Se), which is a typical X-ray photoconductive material, has a coefficient of thermal expansion of 44 ppm / ° C, lead iodide (PbI ₂ ) at 40 ppm / ° C, and mercury iodide (HgI ₂ ). At 54 ppm / ° C., thallium bromide (TlBr) reaches 51 ppm / ° C.

  Also, the thermal expansion coefficient of the input phosphor film used in the indirect X-ray image detector is 49 ppm / ° C. for cesium iodide. Furthermore, even when using an intensifying screen, the main component of the intensifying screen is a resin, so that the coefficient of thermal expansion is close to the value of this resin and is expected to take a value of about several tens to 100 ppm / ° C. .

  As shown above, when there is a large difference in thermal expansion coefficient between the X-ray photoconductive material or the X-ray input phosphor film that is in close contact with the TFT circuit substrate, the X-ray image detector is being used or stored. Due to a possible temperature change, a large stress is generated at the interface between the TFT circuit board and the X-ray photoconductor or the input fluorescent film. It is expected to become a “Yes” state.

  There is a risk that stress will be transmitted to the inside of the TFT circuit due to the stress generated on the surface of the TFT circuit substrate, and the characteristics of the TFT composed of semiconductors may change, or the internal wiring may be disconnected or short-circuited. It is done.

  It is also expected that the semiconductor characteristics inside the X-ray photoconductive film directly formed on the TFT circuit substrate surface will change.

  Further, the same applies to the X-ray input fluorescent film directly formed on the TFT circuit substrate, and the gap that greatly affects the resolution of the input fluorescent film changes to cause a characteristic change.

  In both cases, the stress is likely to cause the X-ray photoconductive film or the X-ray input phosphor film to be peeled off or cracked from the TFT circuit substrate, which may adversely affect the product characteristics.

  The present invention has been made in view of these points, and an object thereof is to provide a radiation detector that suppresses deterioration of characteristics due to thermal expansion.

  The present invention has a signal conversion layer for converting incident radiation into a predetermined signal, and a signal having a thermal expansion coefficient smaller than that of the signal conversion layer, joined to the signal conversion layer, and converted by the signal conversion layer. A circuit board provided with a detection body for detecting the signal and a main surface of the circuit board opposite to the signal conversion layer, and a difference in thermal expansion coefficient between the signal conversion layer and the signal conversion layer is determined between the signal conversion layer and the circuit board. And a coefficient of thermal expansion that is smaller than the difference in coefficient of thermal expansion.

  According to the present invention, the circuit board when the temperature rises by making the difference in thermal expansion coefficient between the signal conversion layer and the coefficient of thermal expansion adjustment body smaller than the difference in thermal expansion coefficient between the signal conversion layer and the circuit board. It is possible to suppress the stress at the interface due to the difference in thermal expansion coefficient between the signal conversion layer and the signal conversion layer, and to suppress the deterioration of characteristics.

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

  In FIG. 1, reference numeral 1 denotes an X-ray detector which is an X-ray image detector as a radiation detector, and the X-ray detector 1 shown in FIG. 1 is a direct X-ray planar image detector. As shown in FIGS. 2 and 3, the detector portion of the X-ray detector 1 is a TFT which is a photoelectric conversion substrate as a circuit substrate having a plurality of pixels 2 arranged in a two-dimensional matrix. A circuit board 3 is provided.

  An X-ray photoconductor that is a radiation photoconductor layer as a signal conversion layer that converts incident X-rays L as incident radiation into an electric signal is provided on the surface that is one main surface of the TFT circuit substrate 3. The layer 4 is provided by being laminated. This X-ray photoconductor layer 4 is in a PN junction state, for example, and is in a state of being completely adhered to the surface of the TFT circuit substrate 3. That is, the X-ray photoconductor layer 4 is directly formed on the TFT circuit substrate 3.

Here, the X-ray photoconductive layer 4 includes an X-ray photoconductive film 5 as a radiation photoconductive film, which is an important element for detecting an X-ray image, as shown in FIG. The X-ray photoconductive film 5 is, for example, a heavy metal and semiconducting X-ray photoconductive material, selenium (Se) having a coefficient of thermal expansion of 44 ppm / ° C., lead iodide (PbI) having a coefficient of thermal expansion of 40 ppm / ° C. ₂ ), mercury iodide (HgI ₂ ) having a thermal expansion coefficient of 54 ppm / ° C., or thallium bromide (TlBr) having a thermal expansion coefficient of 51 ppm / ° C. as a main component, and these X-ray photoconductive materials Is vacuum-deposited on the TFT circuit substrate 3 to a predetermined thickness. Further, a bias electrode layer 6 serving as an upper electrode is laminated on the surface which is one main surface of the X-ray photoconductive film 5, and the pixel electrodes 13 serving as detection bodies are opposed to each other. As a result, the X-ray photoconductor layer 4 has a higher thermal expansion coefficient than the TFT circuit substrate 3.

  As shown in FIG. 2, the TFT circuit substrate 3 includes a holding substrate 11 as an insulating substrate formed of a rectangular flat plate-shaped glass having translucency. Here, the holding substrate 11 is mainly composed of glass with a suppressed thermal expansion coefficient. For this reason, the holding substrate 11 is extremely weak against tensile stress, and generally, an elastic body such as rubber (not shown) is used to avoid breakage due to inadvertent tensile stress generated by a strong fixing means. It is loosely fixed at the periphery and is configured so that stress is not applied as much as possible.

  A TFT circuit layer 12 and a pixel electrode 13 are formed for each pixel 2 on the surface which is one main surface of the holding substrate 11. The pixel electrode 13 is disposed so as to cover most of the outermost surface of the TFT circuit substrate 3. The pixel electrode 13 is made of ITO (indium-tin mixed oxide) which is a metal oxide.

  Furthermore, as shown in FIG. 3, the TFT circuit layer 12 includes a thin film transistor (TFT) 14 as a switching element and a charge storage capacitor 15 as a capacitor. Each of the pixel electrode 13, the thin film transistor 14, and the charge storage capacitor 15 is formed for each pixel 2 on the holding substrate 11. That is, each of the pixel electrode 13, the thin film transistor 14 and the charge storage capacitor 15 has a grid-like arrangement in which these are one set, and each set corresponds to the pixel 2 of the X-ray image. Has been.

  On the holding substrate 11, control electrodes 16 are wired as a plurality of control lines along the row direction of the holding substrate 11. The plurality of control electrodes 16 are located between the respective pixels 2 on the holding substrate 11 and are separated from each other in the column direction of the holding substrate 11. These control electrodes 16 are electrically connected to the gate electrode 17 of the thin film transistor 14.

  Furthermore, a plurality of readout electrodes 18 are wired on the holding substrate 11 along the column direction of the holding substrate 11. The plurality of readout electrodes 18 are located between the respective pixels 2 on the holding substrate 11 and are separated from each other in the row direction of the holding substrate 11. A source electrode 19 of the thin film transistor 14 is electrically connected to the plurality of readout electrodes 18. The drain electrode 20 of the thin film transistor 14 is electrically connected to the charge storage capacitor 15 and the pixel electrode 13, respectively.

  On the other hand, as shown in FIGS. 1 and 2, island-like pixel electrodes 13 are stacked in a matrix so as to correspond to the respective pixels 2 on the TFT circuit layer 12 on the holding substrate 11. . Metal oxide (not shown) is formed on the entire surface of the TFT circuit layer 12 including the pixel electrode 13 and the interface between the X-ray photoconductive film 5 and the interface between the X-ray photoconductive film 5 and the bias electrode layer 6. A thin film layer is formed, and a PN junction state is realized inside the X-ray photoconductive film 5.

  Further, a metal plate 25 as a coefficient of thermal expansion adjustment body is bonded via an adhesive layer 26 to the back surface side which is the other main surface of the TFT circuit substrate 3, that is, the main surface opposite to the X-ray photoconductor layer 4. Has been.

  The metal plate 25 is a block formed of, for example, aluminum (Al), that is, an aluminum block, and the difference in thermal expansion coefficient between the X-ray photoconductor layer 4 and the TFT circuit substrate 3 and the X-ray photoconductive film 5 is It is formed so as to be smaller than the difference in thermal expansion coefficient.

  That is, the metal plate 25 has a thickness and a coefficient of thermal expansion larger than the holding substrate 11 of the TFT circuit substrate 3, for example, and is bonded to the holding substrate 11 so that the TFT circuit substrate 3 and the metal plate 25 are bonded. By making the overall thermal expansion coefficient close to the thermal expansion coefficient of the metal plate 25, it is configured to suppress the difference in thermal expansion coefficient with the X-ray photoconductor layer 4 having a thermal expansion coefficient larger than that of the holding substrate 11. ing. Note that the thickness, thermal expansion coefficient, and the like of the metal plate 25 are appropriately set according to characteristics such as the thermal expansion coefficient of the holding substrate 11.

  The metal plate 25 is bonded to the holding substrate 11 in the entire range of the pixel 2 as the arrangement range of the pixel electrode 13, that is, in the entire image acquisition range.

  As the adhesive layer 26, for example, a resin adhesive such as epoxy, acrylic, or silicone is used. The temperature when the X-ray detector 1 is used (for example, 0 ° C. to 40 ° C.) and the temperature during storage (for example, −20 In a temperature atmosphere above the maximum temperature in this temperature range, for example, a temperature atmosphere such as 100 ° C. so that a compressive stress is constantly applied to the holding substrate 11 of the TFT circuit substrate 3 Heat bonding is performed.

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

  First, when X-rays are incident on the X-ray photoconductive film 5 of the X-ray photoconductive layer 4 of the X-ray detector 1 from the outside, the incident X-rays L incident into the X-ray photoconductive film 5 are It is absorbed and excited in the X-ray photoconductive film 5.

  A large number of pairs of electrons e and holes h are generated inside the X-ray photoconductive film 5 by the energy of the incident X-ray L itself.

  At this time, a voltage of several hundred volts is applied between the bias electrode layer 6 and the pixel electrode 13 to form a bias electric field, so that the photoconductive charge Q generated in the X-ray photoconductive film 5 is biased. It moves by the electric field.

  Then, either the electron e or the hole h moves to the pixel electrode 13 as the photoconductive charge Q and reaches.

  Thereafter, the photoconductive charge Q that has flowed into and flowed into the respective pixel electrodes 13 flows into the respective pixels until the gate electrode 17 of the thin film transistor 14 connected to the respective pixel electrodes 13 is driven, that is, turned on. It moves to the charge storage capacitor 15 connected to the electrode 13 and is held and stored.

  At this time, when one of the control electrodes 16 is turned on, the horizontal row of thin film transistors 14 connected to the control electrode 16 in the on state is turned on.

  Then, the photoconductive charge Q stored in the charge storage capacitor 15 connected to each thin film transistor 14 in the on state is output to the readout electrode 18.

  As a result, since a signal corresponding to the pixel 2 in a specific row of the X-ray image is output, the control electrode 16 to be turned on is sequentially controlled to control all the X-ray image pixels. The image information can be output to the outside as a video signal, that is, an X-ray image by converting the output signal into a digital image signal.

  Here, due to the operation of the X-ray detector 1, a temperature rise occurs due to the heat generated by the surrounding electrical equipment, and when the X-ray detector 1 is stored or transported, a temperature change more than that during the operation is expected. Due to such temperature change, stress is generated in the TFT circuit substrate 3 and the X-ray photoconductor layer 4.

  At this time, since the thermal expansion coefficient of the X-ray photoconductor layer 4 is larger than the thermal expansion coefficient of the TFT circuit board 3 in particular, tensile stress is generated in the TFT circuit board 3 to constitute the TFT circuit board 3. The glass holding substrate 11 may be damaged.

  In addition, in the X-ray photoconductor layer 4 that needs to be formed directly on the TFT circuit substrate 3, the X-ray photoconductive material is generally X-rayed by a vacuum deposition method or the like while the TFT circuit substrate 3 is heated. When the photoconductive film 5 is required to be formed and returned to room temperature after such a manufacturing process, extremely large stress is generated due to the difference in thermal expansion coefficient.

  At this time, the stress concentrates on the mechanically weak X-ray photoconductor layer 4 and may cause a change in characteristics of the X-ray photoconductor layer 4 which is a semiconductor material or damage due to generation of cracks.

  Therefore, in the first embodiment, the metal plate 25 is smaller in the difference in thermal expansion coefficient from the X-ray photoconductor layer 4 than in the X-ray photoconductor layer 4 and the TFT circuit substrate 3. Is bonded to the opposite side of the holding substrate 11 constituting the TFT circuit substrate 3 from the X-ray photoconductor layer 4 to reduce the difference in thermal expansion coefficient between the X-ray photoconductor layer 4 and the TFT circuit substrate 3 side. That is, it was set as the structure which improves.

  Specifically, for example, the thickness of the holding substrate 11 is 0.7 mm, the thermal expansion coefficient is 3.8 ppm / ° C., and the Young's modulus is 84 GPa, whereas the thickness of the metal plate 25 is 10 mm and the thermal expansion coefficient is 23. By setting the Young's modulus to 1 ppm / ° C. and the Young's modulus of 73 GPa, etc., the overall thermal expansion coefficient of the TFT circuit board 3, that is, the holding substrate 11 and the metal plate 25 is 22.4 ppm / ° C. For example, with respect to the lateral thermal expansion coefficient (40 ppm / ° C.) of the X-ray photoconductor layer 4 when lead iodide is used as the material of the X-ray photoconductor layer 4, Although the holding substrate 11 has a coefficient of thermal expansion (3.8 ppm / ° C.) and an opening of 10 times or more, the structure of the present embodiment is improved to an opening of 2 or less.

  For this reason, the stress due to the difference in thermal expansion coefficient at the interface between the X-ray photoconductor layer 4 and the TFT circuit substrate 3 generated due to a temperature change during use, after manufacture, or during storage is used. It is possible to suppress the damage of the holding substrate 11 constituting the TFT circuit board 3, the change in characteristics of the X-ray photoconductor layer 4, the damage due to the occurrence of cracks, and the like, and the characteristic deterioration can be suppressed. The X-ray detector 1 can be easily handled, and the X-ray detector 1 can be a high-performance and highly reliable product.

  Furthermore, in the direct X-ray detector 1, since the X-ray photoconductor layer 4 is indispensable for electrical connection with the TFT circuit substrate 3, the X-ray photoconductor layer 4 and the TFT circuit substrate 3 Since it is important that is completely adhered, stress due to the difference in thermal expansion coefficient between the X-ray photoconductor layer 4 and the TFT circuit substrate 3 side tends to act on these interfaces. By configuring as described above, the stress due to the difference in thermal expansion coefficient at this interface can be reliably suppressed.

  In particular, the glass holding substrate 11 constituting the TFT circuit substrate 3 protects various circuits formed on the holding substrate 11 from thermal expansion of the holding substrate 11, and further increases the accuracy of this circuit in the future. Since it is necessary to suppress the thermal expansion coefficient as much as possible, the difference in thermal expansion coefficient from the X-ray photoconductor layer 4 made of heavy metal and generally having a higher thermal expansion coefficient than glass is large. Therefore, by improving the difference in thermal expansion coefficient between the X-ray photoconductor layer 4 and the TFT circuit substrate 3 as described above, it is easy to protect such a circuit and to improve the accuracy. It can correspond to.

  Further, in the above configuration, thermal stress is generated in the structurally weak glass holding substrate 11, but when the holding substrate 11 of the TFT circuit substrate 3 and the metal plate 25 are joined, the use is assumed thereafter. This holding is performed by heat-bonding at a temperature range of 60 ° C. or higher, for example, 100 ° C., which is a maximum temperature of −20 ° C. to 60 ° C., for example, during storage and in the manufacturing process of the TFT circuit board 3. After the bonding process between the substrate 11 and the metal plate 25, the holding substrate 11 can always be subjected to compressive stress. Generally, the glass holding substrate 11 that is strong against compressive stress and weak against tensile stress is damaged by thermal stress. It can suppress more reliably.

  Furthermore, the entire image acquisition range can be protected from thermal stress by setting the entire image acquisition range of the X-ray detector 1 as the bonding range between the TFT circuit board 3 and the metal plate 25.

  Furthermore, by using an aluminum block as the metal plate 25, the coefficient of thermal expansion of the metal plate 25 can be set high, the weight of the metal plate 25 can be reduced, and the metal plate 25 can be manufactured at low cost.

  Next, a second embodiment will be described with reference to FIGS. In addition, about the structure and effect | action similar to the said 1st Embodiment, the same code | symbol is attached | subjected and the description is abbreviate | omitted.

  In the second embodiment, an indirect X-ray detector 1 provided with an input fluorescent film 28 as a signal conversion layer is used instead of the X-ray photoconductor layer 4 of the first embodiment. Show.

The input fluorescent film 28 has a relatively large coefficient of thermal expansion, for example, cesium iodide (CsI), sodium iodide (NaI), gadolinium oxysulfide (Gd ₂ O ₂ S), or an organic material as a main material. It is directly formed on the surface of the circuit board 3.

  The metal plate 25 is set so that the difference in thermal expansion coefficient between the input fluorescent film 28 and the thermal expansion coefficient difference between the TFT circuit substrate 3 and the input fluorescent film 28 is smaller.

  The TFT circuit substrate 3 is provided with a photodiode 29 as a detector instead of the pixel electrode 13 of the first embodiment. That is, the parallel circuit of the photodiode 29 and the charge storage capacitor 15 is electrically connected to the drain electrode 20 of the thin film transistor 14 on the cathode side of the photodiode 29.

  The X-ray detector 1 is in a state in which a reverse bias voltage is applied to the photodiode 29 by the charge stored in the charge storage capacitor 15 in advance. In this state, the X-ray detector 1 is incident on the input phosphor film 28 from the outside. Fluorescence is generated by the incident X-ray L, and when this fluorescence enters the photodiode 29, carriers are generated inside the photodiode 29. A photocurrent corresponding to the intensity of the fluorescence flows and is stored in the charge storage capacitor 15. The generated charge is reduced, and the change in the charge changes the potential of the control electrode 16, whereby the thin film transistor 14 connected to the control electrode 16 is turned on and output to the outside through the readout electrode 18.

  Also in the second embodiment, the metal plate 25 having a smaller difference in thermal expansion coefficient from the input fluorescent film 28 than the difference in thermal expansion coefficient between the input fluorescent film 28 and the TFT circuit board 3 is used as the TFT circuit board. 3 is bonded to the opposite side of the input fluorescent film 28 and the difference in thermal expansion coefficient between the input fluorescent film 28 and the TFT circuit substrate 3 side is improved, so that the same effect as the first embodiment can be obtained. Therefore, the X-ray detector 1 of the indirect system can be easily handled.

  In particular, in the indirect type input fluorescent film 28, when the fluorescence having X-ray image information is incident on the TFT circuit board 3, it is required to reduce the image transmission loss to the limit. Since it is important that the TFT circuit substrate 3 is in close contact with each other, stress due to a difference in thermal expansion coefficient between the input fluorescent film 28 and the TFT circuit substrate 3 side easily acts on these interfaces. By comprising like this, the stress by the thermal expansion coefficient difference in this interface can be suppressed reliably.

  In the second embodiment, the input fluorescent film 28 is made of, for example, an X-ray photoconductive material, X-ray phosphor, or X-ray phosphor powder that is made of heavy metal and generally has a higher coefficient of thermal expansion than glass. It is also possible to adopt a configuration in which an intensifying screen formed in a plate shape with a resin is brought into close contact with the TFT circuit substrate 3, and the configuration in which the thermal expansion coefficient adjusting body is bonded to the TFT circuit substrate 3 is such an X This is an effective technology for general line detectors.

  In each of the above embodiments, instead of the aluminum block, the metal plate 25 has a relatively large thermal expansion coefficient, for example, zinc (Zn) having a thermal expansion coefficient of 30 ppm / ° C., a thermal expansion coefficient of 17 ppm / ° C. Copper (Cu), lead (Pb) with a coefficient of thermal expansion of 29 ppm / ° C., lithium (Li) with a coefficient of thermal expansion of 47 ppm / ° C., magnesium (Mg) with a coefficient of thermal expansion of 26 ppm / ° C., silver with a coefficient of thermal expansion of 19 ppm / ° C. Ag) or tin (Sn) having a coefficient of thermal expansion of 22 ppm / ° C. can also be used.

  Similarly, as the thermal expansion coefficient adjusting body, the difference in thermal expansion coefficient between the X-ray photoconductor layer 4 and the thermal expansion coefficient difference between the TFT circuit substrate 3 and the X-ray photoconductor layer 4 is made smaller. If selected, not only a metal plate but also a synthetic resin plate can be used as appropriate.

It is a longitudinal cross-sectional view which shows the radiation detector of the 1st Embodiment of this invention. It is a disassembled perspective view which shows a radiation detector same as the above. It is a top view which shows a radiation detector same as the above. It is a longitudinal cross-sectional view which shows the radiation detector of the 2nd Embodiment of this invention. It is a disassembled perspective view which shows a radiation detector same as the above. It is a top view which shows a radiation detector same as the above.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 X-ray detector as a radiation detector 3 TFT circuit board as a circuit board 4 X-ray photoconductor layer which is a radiation photoconductor layer as a signal conversion layer
13 Pixel electrode as detector
25 Metal plate as coefficient of thermal expansion adjustment
28 Input phosphor film as signal conversion layer
29 Photodiode as detector

Claims (9)

A signal conversion layer for converting incident radiation into a predetermined signal;
A circuit board having a thermal expansion coefficient smaller than that of the signal conversion layer, including a detection body which is bonded to the signal conversion layer and detects a signal converted by the signal conversion layer;
Bonded to the main surface of the circuit board opposite to the signal conversion layer, the thermal expansion coefficient difference between the signal conversion layer and the signal conversion layer is smaller than the thermal expansion coefficient difference between the signal conversion layer and the circuit board. A radiation detector comprising: an adjustment body. The radiation detector according to claim 1, wherein the signal conversion layer is a radiation photoconductor layer that converts incident radiation into an electrical signal. The radiation photoconductor layer is made of selenium (Se), lead iodide (PbI ₂ ), mercury iodide (HgI ₂ ), or thallium bromide (TlBr) as a main raw material. The radiation detector described. The radiation detector according to claim 1, wherein the signal conversion layer is an input phosphor film that converts incident radiation into light. 5. The radiation according to claim 4, wherein the input fluorescent film is mainly composed of cesium iodide (CsI), sodium iodide (NaI), gadolinium oxysulfide (Gd ₂ O ₂ S), or an organic substance. Detector. The radiation detector according to any one of claims 1 to 5, wherein the circuit board and the coefficient of thermal expansion adjustment body have the entire arrangement range of the detection body as a bonding range. The coefficient of thermal expansion adjuster is any one of aluminum (Al), zinc (Zn), copper (Cu), lead (Pb), lithium (Li), magnesium (Mg), silver (Ag) and tin (Sn). The radiation detector according to claim 1, wherein the radiation detector is a main component. The radiation detector according to any one of claims 1 to 7, wherein the circuit board is in a state in which compressive stress is applied to the circuit board in a predetermined temperature range during use and storage. The radiation detection according to any one of claims 1 to 8, wherein the circuit board and the coefficient of thermal expansion adjuster are bonded in a temperature atmosphere equal to or higher than a maximum temperature in a predetermined temperature range during use and storage. vessel.

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