JP7531737B2 - Radiation detector - Google Patents

Description

The present invention relates to a radiation detector.

Patent documents 1 to 3 are known as technologies in this field.

Patent Document 1 discloses a scintillator panel. The scintillator panel has a metal film provided between a resin substrate and a phosphor layer.

Patent Document 2 discloses a radiation detection device equipped with a scintillator panel. The scintillator panel has a scintillator layer whose main component is cesium iodide. This scintillator layer is doped with thallium. The concentration of thallium in the scintillator layer is high near the interface with the substrate. This thallium concentration distribution improves the light output.

Patent Document 3 discloses a radiation detector equipped with a phosphor layer. This radiation detector also has a scintillator layer whose main component is cesium iodide, and the scintillator layer is doped with thallium. The concentration of thallium in the scintillator layer is higher on the substrate side. This thallium concentration distribution improves the adhesion between the sensor substrate and the phosphor layer.

International Publication No. 2011/065302 JP 2008-51793 A JP 2012-98110 A

The growth substrate on which the scintillator layer is grown may have moisture permeability that allows moisture to pass through. Moisture that has permeated the growth substrate reaches the base of the scintillator layer. Scintillator layers formed from cesium iodide are known to be deliquescent. If this occurs, moisture supplied from the growth substrate will cause deliquescence at the base of the scintillator layer, ultimately degrading the characteristics of the scintillator panel. Therefore, in this field, there is a demand for improving the moisture resistance of scintillator panels having scintillator layers formed from cesium iodide.

For example, in Patent Document 1, a metal film is provided between the substrate and the phosphor layer, aiming to inhibit the movement of moisture from the resin substrate to the phosphor layer.

The present invention aims to provide a radiation detector that can improve moisture resistance.

The scintillator panel according to one embodiment of the present invention comprises a substrate made of an organic material, a barrier layer formed on the main surface of the substrate and containing thallium iodide as a main component, a scintillator layer formed on the barrier layer and composed of a plurality of columnar crystals containing cesium iodide doped with thallium as a main component, and a functional layer including a portion formed on the back surface side of the substrate. The scintillator panel according to one embodiment of the present invention comprises a substrate made of an organic material, a barrier layer formed on the substrate and containing thallium iodide as a main component, and a scintillator layer formed on the barrier layer and composed of a plurality of columnar crystals containing cesium iodide doped with thallium as a main component.

In this scintillator panel, a barrier layer is provided between the substrate and the scintillator layer. The barrier layer contains thallium iodide as its main component. Such a barrier layer has the property of being difficult for moisture to pass through. This makes it possible for the barrier layer to block moisture that attempts to move from the substrate to the scintillator layer. This suppresses deliquescence at the base of the scintillator layer, which in turn suppresses deterioration of the properties of the scintillator panel. This therefore improves the moisture resistance of the scintillator panel.

The organic material in the above scintillator panel may be polyethylene terephthalate. With this configuration, a substrate suitable for the scintillator panel can be easily prepared.

The organic material in the above scintillator panel may be polyethylene naphthalate. This configuration also makes it easy to prepare a substrate suitable for a scintillator panel.

Another aspect of the present invention is a radiation detector that includes a scintillator panel having a substrate made of an organic material, a barrier layer formed on the substrate and containing thallium iodide as a main component, and a scintillator layer formed on the barrier layer and composed of a plurality of columnar crystals containing cesium iodide doped with thallium as a main component, and a sensor substrate including a light detection surface provided with a photoelectric conversion element that receives light generated in the scintillator panel, and the light detection surface of the sensor substrate faces the scintillator layer.

A radiation detector according to yet another embodiment of the present invention includes a substrate made of an organic material, a barrier layer formed on the substrate and containing thallium iodide as a main component, and a scintillator layer formed on the barrier layer and composed of a plurality of columnar crystals containing cesium iodide doped with thallium as a main component, and the substrate has a light detection surface provided with a photoelectric conversion element that receives light generated in the scintillator layer.

In these radiation detectors, light is generated by radiation incident on the scintillator panel, and the light is detected by a photoelectric conversion element provided on the light detection surface. Here, the scintillator panel has a barrier layer containing thallium iodide as a main component between the substrate and the scintillator layer. This barrier layer makes it possible to prevent the movement of moisture from the substrate to the scintillator layer. Therefore, deliquescence at the base of the scintillator layer is suppressed, making it possible to suppress deterioration of the properties of the scintillator panel. As a result, deterioration of the radiation detection properties of the radiation detector is suppressed. Therefore, the moisture resistance of the radiation detector can be improved.

The present invention provides a radiation detector that can improve moisture resistance.

FIG. 1 is a cross-sectional view showing a scintillator panel according to the first embodiment. FIG. 2 is a cross-sectional view showing a radiation detector according to the second embodiment. FIG. 3A is a cross-sectional view showing a scintillator panel according to a first modified example, and FIG. 3B is a cross-sectional view showing a scintillator panel according to a second modified example. FIG. 4A is a cross-sectional view showing a scintillator panel according to Modification 3, and FIG. 4B is a cross-sectional view showing a scintillator panel according to Modification 4. As shown in FIG. Part (a) of Figure 5 is a cross-sectional view showing a scintillator panel relating to variant example 5, part (b) of Figure 5 is a cross-sectional view showing a scintillator panel relating to variant example 6, and part (c) of Figure 5 is a cross-sectional view showing a scintillator panel relating to variant example 7. FIG. 6A is a cross-sectional view showing a scintillator panel according to Modification 8, and FIG. 6B is a cross-sectional view showing a scintillator panel according to Modification 9. As shown in FIG. 7A is a cross-sectional view showing a radiation detector according to a tenth modification, and FIG. 7B is a cross-sectional view showing a radiation detector according to an eleventh modification. FIG. 8A is a cross-sectional view showing a radiation detector according to a twelfth modification, and FIG. 8B is a cross-sectional view showing a radiation detector according to a thirteenth modification. FIG. 9A is a cross-sectional view showing a radiation detector according to a fourteenth modification, and FIG. 9B is a cross-sectional view showing a radiation detector obtained by further modifying the fourteenth modification. Part (a) of Figure 10 is a cross-sectional view showing a radiation detector related to modified example 15, part (b) of Figure 10 is a cross-sectional view showing a radiation detector related to modified example 16, and part (c) of Figure 10 is a cross-sectional view showing a radiation detector related to modified example 17. FIG. 11A is a cross-sectional view showing a radiation detector according to Modification 18, and FIG. 11B is a cross-sectional view showing a radiation detector according to Modification 19. As shown in FIG. Part (a) of FIG. 12 is a cross-sectional view showing a radiation detector according to Modification 20. FIG. 13 is a graph showing the results of an experimental example.

Below, the embodiment of the present invention will be described in detail with reference to the attached drawings. In the description of the drawings, the same elements are given the same reference numerals, and duplicate explanations will be omitted.

First Embodiment
1, a scintillator panel 1 according to the first embodiment has a substrate 2, a barrier layer 3, a scintillator layer 4, and a protective film 6. The scintillator panel 1 having such a configuration is combined with a photoelectric conversion element (not shown) and used as a radiation image sensor.

The substrate 2, the barrier layer 3, and the scintillator layer 4 are laminated in this order along their respective thickness directions to form the laminate 7. Specifically, the barrier layer 3 is formed on the substrate 2. Then, the scintillator layer 4 is formed on the barrier layer 3. In other words, the substrate 2 and the scintillator layer 4 are not in direct contact with each other. The laminate 7 has a laminate front surface 7a, a laminate back surface 7b, and a laminate side surface 7c. The laminate 7 is covered with a protective film 6. Specifically, the laminate front surface 7a, the laminate back surface 7b, and the laminate side surface 7c are each covered with the protective film 6. In other words, the laminate front surface 7a, the laminate back surface 7b, and the laminate side surface 7c are not directly exposed to the atmosphere.

The substrate 2 forms the base of the scintillator panel 1. The substrate 2 has a rectangular, polygonal or circular shape in plan view, and its thickness is 10 micrometers to 5000 micrometers, for example 100 micrometers. The substrate 2 has a substrate front surface 2a, a substrate back surface 2b, and a substrate side surface 2c. The substrate back surface 2b constitutes the above-mentioned laminate back surface 7b. The substrate side surface 2c constitutes part of the above-mentioned laminate side surface 7c. The substrate 2 is made of an organic material. Examples of organic materials include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), and polyimide (PI).

The barrier layer 3 inhibits the movement of moisture from the substrate 2 to the scintillator layer 4. The barrier layer 3 is formed on the substrate surface 2a, and has a thickness of 0.001 micrometers to 1.0 micrometers, for example, 0.06 micrometers (600 angstroms). The barrier layer 3 has a barrier layer surface 3a, a barrier layer back surface 3b, and a barrier layer side surface 3c. The barrier layer side surface 3c constitutes a part of the above-mentioned laminate side surface 7c. The barrier layer 3 contains thallium iodide (TlI) as a main component. For example, the TlI content of the barrier layer 3 may be 90% or more and 100% or less. In other words, when the TlI content in the barrier layer 3 is 90% or more, it can be said that the barrier layer 3 is mainly composed of TlI. Such a barrier layer 3 can be formed, for example, by a two-source deposition method. Specifically, a first deposition source containing cesium iodide (CsI) and a second deposition source containing thallium iodide (TlI) are used. The barrier layer 3 is formed by depositing TlI on the substrate before CsI. The thickness of the barrier layer is, for example, about 600 angstroms. The thickness of the barrier layer can be measured by peeling the scintillator layer and the substrate with a strong adhesive tape or the like and analyzing the substrate interface with an X-ray fluorescence analysis (XRF) device. An example of the device is Rigaku's ZSX Primus.

The scintillator layer 4 receives radiation and generates light corresponding to the radiation. The scintillator layer 4 contains cesium iodide, which is a phosphor material, as a main component, and further contains thallium as a dopant (CsI:Tl). For example, the CsI content of the scintillator layer 4 may be 90% or more and 100% or less. In other words, when the CsI content of the scintillator layer 4 is 90% or more, it can be said that the scintillator layer 4 is mainly composed of CsI. Furthermore, since the scintillator layer 4 is made of a plurality of columnar crystals, each columnar crystal has a light guide effect, making it suitable for high-resolution imaging. Such a scintillator layer 4 can be formed, for example, by a vapor deposition method. The scintillator layer 4 has a thickness of 10 micrometers or more and 3000 micrometers or less, for example, 600 micrometers. The scintillator layer 4 has a scintillator layer surface 4a, a scintillator layer back surface 4b, and a scintillator layer side surface 4c. The scintillator layer surface 4a constitutes the laminate surface 7a described above. The scintillator layer side surface 4c constitutes part of the laminate side surface 7c described above.

The scintillator layer 4 includes a plurality of columnar crystals extending in the thickness direction. The roots of the plurality of columnar crystals form the back surface 4b of the scintillator layer and are in contact with the barrier layer surface 3a of the barrier layer 3. The tips of the plurality of columnar crystals form the scintillator layer surface 4a. Furthermore, the columnar crystals formed in the outer periphery of the scintillator layer 4 form the scintillator layer side surface 4c. Here, the laminate side surface 7c includes the substrate side surface 2c, the barrier layer side surface 3c, and the scintillator layer side surface 4c, and these substrate side surface 2c, barrier layer side surface 3c, and scintillator layer side surface 4c are flush. Here, "flush" means that when the substrate side surface 2c, the barrier layer side surface 3c, and the scintillator layer side surface 4c are viewed macroscopically, each surface is included in the same imaginary plane. In addition, when viewed microscopically, the substrate side surface 2c and the scintillator layer side surface 4c may have minute uneven structures such as sagging, rough surfaces, and burrs, but when defining "flush," these uneven structures are ignored.

The protective film 6 covers the laminate 7 to protect it from moisture. The protective film 6 covers the substrate back surface 2b, the substrate side surface 2c, the barrier layer side surface 3c, the scintillator layer side surface 4c, and the scintillator layer surface 4a. The thickness of the protective film 6 may be approximately the same at all locations where it is formed, or may vary from location to location. According to the protective film 6 shown in FIG. 1, for example, the film portion formed on the scintillator layer surface 4a is thicker than the film portions formed on the substrate back surface 2b, the substrate side surface 2c, the barrier layer side surface 3c, and the scintillator layer side surface 4c. The protective film 6 is mainly composed of polyparaxylylene. Such a protective film 6 can be formed, for example, by chemical vapor deposition (CVD).

In this scintillator panel 1, a barrier layer 3 is provided between the substrate 2 and the scintillator layer 4. The barrier layer 3 contains thallium iodide as its main component. Such a barrier layer 3 has the property of being difficult for moisture to pass through. This makes it possible for the barrier layer 3 to block moisture that attempts to move from the substrate 2 to the scintillator layer 4. This suppresses deliquescence at the base of the scintillator layer 4, thereby suppressing deterioration of the characteristics of the scintillator panel 1.

The organic material in the above scintillator panel 1 can be polyethylene terephthalate. With this configuration, a substrate 2 suitable for the scintillator panel 1 can be easily prepared. A substrate suitable for the scintillator panel 1 has the following characteristics: heat resistance during the formation of the scintillator layer, ease of handling during the formation of the scintillator panel, optical properties (reflectivity and absorbency) for scintillation light, radiation transparency, availability, price, etc.

The organic material in the above scintillator panel 1 can be polyethylene naphthalate, polyimide, or polyether ether ketone. With this configuration, the substrate 2 suitable for the scintillator panel 1 can be easily prepared.

Second Embodiment
Next, a description will be given of a radiation detector according to a second embodiment. Note that, in reality, an area (side) for establishing electrical continuity is provided on the sensor panel 11, but for convenience, this is not shown.

As shown in FIG. 2, the radiation detector 10 has a sensor panel 11 (sensor substrate), a barrier layer 3A, a scintillator layer 4A, and a sealing portion 12. Radiation received from the sealing plate 14 is incident on the scintillator layer 4A. The scintillator layer 4A generates light in response to the radiation. The light passes through the barrier layer 3A and is incident on the sensor panel 11. The sensor panel 11 generates an electrical signal in response to the incident light. The electrical signal is output through a specified electrical circuit. A radiation image is obtained based on this electrical signal.

The sensor panel 11 has a panel surface 11a, a panel back surface 11b, and a panel side surface 11c. The sensor panel 11 is a CCD sensor, a CMOS sensor, or a TFT panel having photoelectric conversion elements 16, and includes a substrate made of an organic material. The multiple photoelectric conversion elements 16 are arranged two-dimensionally on the panel surface 11a. The area on the panel surface 11a where the multiple photoelectric conversion elements 16 are arranged is a light detection area S1 (light detection surface). In addition to the light detection area S1, the panel surface 11a also includes a surrounding area S2 that surrounds the light detection area S1.

The barrier layer 3A is formed on the panel surface 11a. The barrier layer 3A has a barrier layer surface 3a, a barrier layer back surface 3b, and a barrier layer side surface 3c. More specifically, the barrier layer 3A is formed on the panel surface 11a so as to cover the light detection region S1. That is, the barrier layer surface 3a faces the panel surface 11a. In addition, when the barrier layer 3A is viewed in plan, the barrier layer 3A is smaller than the sensor panel 11. Therefore, the barrier layer side surface 3c is not flush with the panel side surface 11c. Except for the above configuration, the barrier layer 3A has the same configuration as the barrier layer 3 in the first embodiment. For example, the materials constituting the barrier layer 3A are the same as those of the barrier layer 3 in the first embodiment.

The scintillator layer 4A is formed on the barrier layer 3A. More specifically, the scintillator layer 4A is formed on the barrier layer back surface 3b. That is, like the barrier layer 3A, the scintillator layer 4A is also formed so as to cover the light detection region S1 via the barrier layer 3A. With this configuration, the photoelectric conversion element 16 can reliably capture light from the scintillator layer 4A. In addition, the scintillator layer side surface 4c is not flush with the panel side surface 11c.

Furthermore, the scintillator layer 4A has a truncated pyramid shape, and the side surface 4c of the scintillator layer is inclined with respect to the thickness direction. In other words, the side surface 4c of the scintillator layer has a slope. Specifically, when the scintillator layer 4A is viewed in cross section from a direction perpendicular to the thickness direction, the cross section has a trapezoidal shape. In other words, one side on the front surface 4a side of the scintillator layer is longer than one side on the back surface 4b side of the scintillator layer.

The sealing portion 12 covers a portion of the panel surface 11a of the sensor panel 11, the barrier layer 3A, and the scintillator layer 4A. The sealing portion 12 is fixed to the peripheral region S2 of the panel surface 11a. The sealing portion 12 and the sensor panel 11 keep the internal space formed by the sealing portion 12 and the sensor panel 11 airtight. This configuration protects the scintillator layer 4A from moisture.

The sealing portion 12 has a sealing frame 13 and a sealing plate 14. The sealing frame 13 has a frame surface 13a, a frame back surface 13b, and a frame wall portion 13c. The frame wall portion 13c connects the frame surface 13a and the frame back surface 13b. The height of the frame wall portion 13c (i.e., the length from the frame surface 13a to the frame back surface 13b) is higher than the height from the panel surface 11a to the scintillator layer back surface 4b. Therefore, a gap is formed between the scintillator layer back surface 4b and the sealing plate 14. The sealing frame 13 may be made of, for example, a resin material, a metal material, or a ceramic material. The sealing frame 13 may be solid or hollow. The frame surface 13a and the plate back surface 14b, and the frame back surface 13b and the panel surface 11a may be joined by an adhesive.

The sealing plate 14 is a rectangular plate material in a plan view. The sealing plate 14 has a plate surface 14a, a plate back surface 14b, and a plate side surface 14c. The plate back surface 14b is fixed to the frame surface 13a. The plate side surface 14c may be flush with the outer surface of the frame wall portion 13c. The sealing plate 14 may be made of, for example, a glass material, a metal material, a carbon material, or a barrier film. An example of the metal material is aluminum. An example of the carbon material is carbon fiber reinforced plastic (CFRP). An example of the barrier film is a laminate of an organic material layer (PET or PEN) and an inorganic material layer (SiN).

In the radiation detector 10, light is generated by radiation incident on the scintillator layer 4A, and the light is detected by the photoelectric conversion element 16 provided in the light detection region S1. Here, the radiation detector 10 has a barrier layer 3A containing thallium iodide as a main component between the sensor panel 11 and the scintillator layer 4A. This barrier layer 3A prevents the movement of moisture from the sensor panel 11 to the scintillator layer 4A. This suppresses deliquescence at the base of the scintillator layer 4A, thereby suppressing deterioration of the characteristics of the radiation detector 10.

The above describes the embodiments of the present invention, but the present invention may be embodied in various forms without being limited to the above embodiments. Modifications 1 to 14 are modifications of the first embodiment. Modifications 15 to 20 are modifications of the second embodiment.

<Modification 1>
Part (a) of FIG. 3 shows a scintillator panel 1A according to the first modification. The scintillator panel 1A may have another layer in addition to the substrate 2, the barrier layer 3, and the scintillator layer 4. The scintillator panel 1A has a functional layer 8 as the other layer. The functional layer 8 has a functional layer surface 8a facing the substrate back surface 2b. The functional layer 8 contains an inorganic material as a main component. The functional layer 8 may be, for example, a metal foil, a metal sheet, or a coating layer formed of an inorganic material. The laminate 7A including the functional layer 8 is covered with a protective film 6. That is, the protective film 6 covers the functional layer back surface 8b, the functional layer side surface 8c, the substrate side surface 2c, the barrier layer side surface 3c, the scintillator layer side surface 4c, and the scintillator layer surface 4a of the functional layer 8. According to the scintillator panel 1A, the barrier layer 3 and the functional layer 8 can protect the scintillator layer 4 from moisture penetrating through the substrate 2.

<Modification 2>
Part (b) of FIG. 3 shows a scintillator panel 1B according to the second modification. The scintillator panel 1B may have a functional layer 8A having a different configuration from that of the first modification. The functional layer 8A is formed on the substrate side surface 2c in addition to the substrate back surface 2b. That is, the functional layer 8A has a first portion formed on the substrate back surface 2b and a second portion formed on the substrate side surface 2c. The first portion has a functional layer surface 8a and a functional layer back surface 8b. The functional layer surface 8a faces the substrate back surface 2b. Then, the substrate 2 is covered on all sides by the barrier layer 3 and the functional layer 8A. The functional layer 8A contains an inorganic material as a main component. The functional layer 8A may be, for example, a coating layer formed of an inorganic material. The laminate 7B including the functional layer 8A is covered by a protective film 6. That is, the protective film 6 covers the first portion of the functional layer 8A, the second portion of the functional layer 8A, the barrier layer side surface 3c, the scintillator layer side surface 4c, and the scintillator layer surface 4a. According to the scintillator panel 1B, the barrier layer 3 and the functional layer 8A can protect the scintillator layer 4 from moisture penetrating through the substrate 2.

<Modification 3>
Part (a) of FIG. 4 shows a scintillator panel 1C according to the third modification. The scintillator panel 1C may have a functional layer 8B different from that of the first modification. The functional layer 8B is formed on the protective film 6. Specifically, the laminate 7 including the substrate 2, the barrier layer 3, and the scintillator layer 4 is covered by the protective film 6. That is, the protective film 6 covers the rear surface 2b of the substrate. The functional layer 8B is formed on the portion covering the rear surface 2b of the substrate. Therefore, the scintillator panel 1C has a laminated structure in which the functional layer 8B, the protective film 6, the substrate 2, the barrier layer 3, and the scintillator layer 4 are laminated in this order along the thickness direction. The functional layer 8B contains an inorganic material as a main component. The functional layer 8B may be, for example, a metal foil, a metal sheet, or a coating layer formed of an inorganic material. According to the scintillator panel 1C, the barrier layer 3 and the functional layer 8B can protect the scintillator layer 4 from moisture penetrating through the substrate 2.

<Modification 4>
Part (b) of FIG. 4 shows a scintillator panel 1D according to the fourth modification. The scintillator panel 1D according to the fourth modification may have a functional layer 8C different from that of the first modification. The functional layer 8C is formed on the protective film 6. The functional layer 8C covers at least a part of the laminate 7C. Specifically, the laminate 7 including the substrate 2, the barrier layer 3, and the scintillator layer 4 is covered by the protective film 6. That is, the protective film 6 has a portion covering the substrate back surface 2b and a portion covering the substrate side surface 2c. The functional layer 8C is formed on each of the portion covering the substrate back surface 2b and the portion covering the substrate side surface 2c. Therefore, the scintillator panel 1D has a laminated structure in which the functional layer 8C, the protective film 6, the substrate 2, the barrier layer 3, and the scintillator layer 4 are laminated in this order along the thickness direction. The scintillator panel 1D also has a laminated structure in which the functional layer 8C, the protective film 6, the substrate 2, the protective film 6, and the functional layer 8C are laminated in this order along a direction intersecting the thickness direction. The functional layer 8C contains an inorganic material as a main component. The functional layer 8C may be, for example, a metal foil, a metal sheet, or a coating layer formed of an inorganic material. According to the scintillator panel 1D, the barrier layer 3 and the functional layer 8C can protect the scintillator layer 4 from moisture penetrating through the substrate 2.

The scintillator panel 1 according to the first embodiment is obtained by forming a panel base in which a barrier layer 3 and a scintillator layer 4 are formed on a single large substrate 2, and then cutting the panel base. In other words, processing marks may be generated on the panel side surface 11c of the scintillator panel 1 according to the type of cutting. For example, laser light may be used to cut the panel base.

<Modification 5>
Part (a) of Fig. 5 shows a scintillator panel 1E according to variant 5. The scintillator panel 1E may have a molten region 5 formed on the laminate side surface 7c. The molten region 5 is a portion of the substrate 2, the barrier layer 3, and the scintillator layer 4 that has been melted by the laser light and then solidified again. In other words, the molten region 5 is formed on the entire surface of each of the substrate side surface 2c, the barrier layer side surface 3c, and the scintillator layer side surface 4c. The scintillator panel 1E allows cutting to be performed using laser light.

Such processing marks are formed by the following process. First, the laminate 7 is formed. Next, laser light is irradiated from the side of the scintillator layer 4 on the laminate 7. The laser light then cuts the scintillator layer 4, the barrier layer 3, and the substrate 2 in that order. The substrate 2 is less cleavable than the scintillator layer 4 and the barrier layer 3, which are made of multiple columnar crystals. Therefore, the laser light continues to be irradiated until it reaches the back surface 2b of the substrate. Therefore, the laser light continues to be irradiated from the scintillator layer surface 4a to the back surface 2b of the substrate, so that a melted region 5 is formed over the entire surface of the laminate side surface 7c, which is the cut surface.

<Modification 6>
Part (b) of Fig. 5 shows a scintillator panel 1F according to Modification 6. The scintillator panel 1F may have a molten region 5A formed in a portion of the laminate side surface 7c. The molten region 5A is formed on the entire surface of each of the substrate side surface 2c and the barrier layer side surface 3c, and in a portion of the scintillator layer side surface 4c. Specifically, the molten region 5A is formed in a portion of the scintillator layer side surface 4c that is continuous with the barrier layer side surface 3c.

Such processing marks are formed by the following process. First, the laminate 7 is formed. Next, the laminate 7 is irradiated with laser light from the side of the substrate 2. The laser light then cuts the substrate 2, the barrier layer 3, and the scintillator layer 4 in that order. The scintillator layer 4 is an aggregate of columnar crystals and has high cleavage properties. Therefore, when grooves or cracks are formed at the base of the scintillator layer 4, the cracks can be used as a trigger for cleavage. In other words, it is not necessary to continue irradiating the laser light from the back surface 2b of the substrate to the front surface 4a of the scintillator layer. The laser light stops irradiating when it slightly reaches the side surface 4c of the scintillator layer from the back surface 2b of the substrate. Then, the grooves and cracks formed in the scintillator layer 4 are used as a trigger for cleaving the scintillator layer 4. According to this cutting method, the irradiation of the laser light to the scintillator layer 4 can be kept to a minimum. Therefore, compared to the cutting method of the fifth modification, damage to the scintillator layer 4 can be reduced.

<Modification 7>
Part (c) of Fig. 5 shows a scintillator panel 1G according to the seventh modification. The scintillator panel 1G may have a molten region 5B formed in a part of the laminate side surface 7c. The molten region 5B has a molten portion 5a formed on the substrate side surface 2c and a molten portion 5b formed in a part of the scintillator layer side surface 4c. Specifically, the molten portion 5b is formed in a part of the scintillator layer side surface 4c on the scintillator layer surface 4a side. In other words, the molten region 5B is not formed in the base portion of the scintillator layer 4. Note that a molten region continuous with the molten portion 5a may be formed on the barrier layer side surface 3c.

Such processing marks are formed by the following process. First, the laminate 7 is formed. Next, the laminate 7 is irradiated with laser light from the side of the substrate 2. Then, when the laser light reaches the substrate surface 2a, the irradiation is stopped. This process forms a molten part 5a on the substrate side surface 2c. Next, the laser light is irradiated from the scintillator layer 4 side. Then, when the laser light reaches a predetermined depth from the scintillator layer surface 4a, the irradiation is stopped. In other words, the laser light does not continue to irradiate from the scintillator layer surface 4a to the scintillator layer back surface 4b. At this stage, the laminate 7 maintains its integrity by the root part of the scintillator layer 4 and the barrier layer 3. Then, the scintillator layer 4 is cleaved using grooves and cracks provided in the scintillator layer 4 as a trigger. According to this cutting method, the irradiation of the laser light to the scintillator layer 4 can be kept to a minimum. Therefore, compared to the cutting method of the modified example 5, damage to the scintillator layer 4 can be reduced.

<Modification 8>
Part (a) of FIG. 6 shows a scintillator panel 1H according to the eighth modified example. The scintillator panel 1H has a protective sheet 6A instead of the protective film 6. That is, the scintillator panel 1H has a laminate 7 and a protective sheet 6A. The protective sheet 6A is formed by bonding two sheet members 6a and 6b together. Specifically, the sheet member 6a is arranged so as to face the scintillator layer surface 4a, and the sheet member 6b is arranged so as to face the substrate back surface 2b. A gap may be provided between the sheet member 6a and the scintillator layer surface 4a, and between the sheet member 6b and the substrate back surface 2b. In addition, the sheet member 6a and the scintillator layer surface 4a may be in contact with each other, and the sheet member 6b and the substrate back surface 2b may be in contact with each other. The peripheral portion of the sheet member 6a is overlapped with the peripheral portion of the sheet member 6b and is adhered to each other. According to this configuration, the internal area in which the laminate 7 is housed can be kept airtight. Therefore, the scintillator layer 4 can be protected from moisture.

<Modification 9>
Part (b) of Fig. 6 shows a scintillator panel 1K according to a ninth modified example. The scintillator panel 1K may have a bag-shaped protective sheet 6B instead of the protective film 6. That is, the scintillator panel 1K has a laminate 7 and a protective sheet 6B. The protective sheet 6B has an opening through which the laminate 7 is housed. After the laminate 7 is housed, the opening is closed and fixed with an adhesive or the like. This configuration also makes it possible to keep the internal area housing the laminate 7 airtight. Therefore, the scintillator layer 4 can be protected from moisture.

<Modification 10>
Part (a) of Fig. 7 shows a radiation detector 10A according to Modification 10. The radiation detector 10A has the laminate 7 of the scintillator panel 1 according to the first embodiment, a sensor panel 11, and a sealing portion 12. The sensor panel 11 has a configuration substantially similar to that of the sensor panel 11 of the radiation detector 10 according to the second embodiment.

The sealing portion 12 has a configuration substantially similar to that of the sealing portion 12 of the radiation detector 10 according to the second embodiment. In the radiation detector 10A according to the modification 10, the height of the frame wall portion 13c of the sealing frame 13 is higher than the height from the panel surface 11a to the substrate back surface 2b. The sealing frame 13 may be made of, for example, a resin material, a metal material, or a ceramic material. When the sealing frame 13 is made of a metal material or a ceramic material, an adhesive layer (not shown) is formed between the frame surface 13a and the sealing plate 14, and an adhesive layer (not shown) is formed between the frame back surface 13b and the panel surface 11a. The sealing plate 14 may be made of, for example, a glass material, a metal material, a carbon material, or a barrier film. An example of the metal material is aluminum. An example of the carbon material is CFRP. An example of the barrier film is a laminate of an organic material layer (PET or PEN) and an inorganic material layer (SiN). The radiation detector 10A can protect the scintillator layer 4 from moisture by the sensor panel 11 and the sealing portion 12.

<Modification 11>
Part (b) of FIG. 7 shows a radiation detector 10B according to the modified example 11. The radiation detector 10B has a sealing portion 12A different from the radiation detector 10A of the modified example 10. The other configurations of the laminate 7 and the sensor panel 11 are the same as those of the modified example 10. The sealing portion 12A includes a sealing plate 14 and a sealing frame 13A, and the sealing frame 13A further includes an inner sealing frame 17 and an outer sealing frame 18. That is, the sealing frame 13 has a double structure. The inner sealing frame 17 may be made of, for example, a resin material. The outer sealing frame 18 may be made of, for example, a coating layer formed of an inorganic material or an inorganic solid material such as a glass rod. The radiation detector 10B can suitably protect the scintillator layer 4 from moisture by the sensor panel 11 and the sealing portion 12A.

<Modification 12>
Part (a) of Fig. 8 shows a radiation detector 10C according to Modification 12. The radiation detector 10C according to Modification 12 has a laminate 7C having a different configuration from the laminate 7 of the sensor panel 11 according to the first embodiment. The laminate 7C has a substrate 2A, a barrier layer 3A, and a scintillator layer 4A. The individual configuration of the barrier layer 3A according to Modification 12 is similar to that of the barrier layer 3A according to the second embodiment. Moreover, the individual configuration of the scintillator layer 4A according to Modification 12 is similar to that of the scintillator layer 4A according to the second embodiment. In other words, the scintillator layer side surface 4c is inclined with respect to the thickness direction.

On the other hand, the laminate 7C differs from the laminate 7 according to the first embodiment in that the substrate side 2c and the barrier layer side 3c are not flush with each other, and the substrate side 2c and the scintillator layer side 4c are not flush with each other. When viewed in a plan view from the thickness direction, the substrate 2A is larger than the barrier layer 3A and the scintillator layer 4A. Therefore, the substrate surface 2a has an exposed region S3 that is exposed from the barrier layer 3A and the scintillator layer 4A.

The laminate 7C is attached to the sensor panel 11 so that the scintillator layer surface 4a faces the panel surface 11a. With this configuration, the exposed area S3 on the substrate surface 2a also faces the peripheral area S2 of the panel surface 11a. The substrate surface 2a is spaced from the panel surface 11a by the height of the scintillator layer 4A and the barrier layer 3A. A sealing frame 13 is sandwiched between the substrate surface 2a and the panel surface 11a. The sealing frame 13 and the substrate 2A are fixed to each other by adhesion. Similarly, the sealing frame 13 and the sensor panel 11 are fixed to each other by adhesion. With this configuration, the substrate 2A can function as a growth substrate for the barrier layer 3A and the scintillator layer 4A, and as a sealing plate in the radiation detector 10C. Therefore, the number of parts constituting the radiation detector 10C can be reduced.

<Modification 13>
Part (b) of Fig. 8 shows a radiation detector 10D according to Modification 13. The radiation detector 10D has a sealing frame 13A different from that of the radiation detector 10C of Modification 12. The other configurations of the laminate 7C and the sensor panel 11 are similar to those of Modification 12. The sealing frame 13A has a configuration similar to that of the sealing frame 13A according to Modification 11. In other words, the sealing frame 13A has an inner sealing frame 17 and an outer sealing frame 18. In the radiation detector 10D, the substrate 2A, the sensor panel 11, and the sealing frame 13A can protect the scintillator layer 4A from moisture.

<Modification 14>
Part (a) of FIG. 9 shows a radiation detector 10E according to a modified example 14. The radiation detector 10E has a fiber optical plate (hereinafter referred to as "FOP 9") in addition to the laminate 7, the protective film 6C, and the sensor panel 11. The FOP 9 is disposed between the laminate 7 and the sensor panel 11. That is, the laminate 7 is joined to the sensor panel 11 via the FOP 9. Specifically, the FOP 9 is disposed between the scintillator layer 4 and the sensor panel 11. The FOP 9 has an FOP front surface 9a, an FOP back surface 9b, and an FOP side surface 9c. The FOP back surface 9b contacts the scintillator layer front surface 4a. The FOP front surface 9a contacts the panel front surface 11a. The FOP side surface 9c is flush with the laminate side surface 7c. The protective film 6C covers the substrate back surface 2b, the substrate side surface 2c, the barrier layer side surface 3c, the scintillator layer side surface 4c, and the FOP side surface 9c. Therefore, the protective film 6C is not formed between the scintillator layer 4 and the FOP 9, and between the FOP 9 and the sensor panel 11. The radiation detector 10E can protect the scintillator layer 4 from moisture, and can suitably optically connect the scintillator layer 4 to the sensor panel 11 by the FOP 9, and the absence of the protective film 6C between the scintillator layer 4 and the FOP 9, and between the FOP 9 and the sensor panel 11 can suppress a decrease in resolution.

As in the radiation detector 10S shown in part (b) of FIG. 9, the protective film 6C may cover the outer peripheral surface of the stack 7. In other words, the protective film 6C may be formed between the stack 7 and the FOP 9.

<Modification 15>
Part (a) of Fig. 10 shows a radiation detector 10F according to Modification 15. The radiation detector 10F has a sealing portion 12A different from the radiation detector 10 according to the second embodiment. The remaining configurations of the barrier layer 3A, the scintillator layer 4A, and the sensor panel 11 are similar to those of the radiation detector 10 according to the second embodiment. The sealing portion 12A has a similar configuration to the sealing portion 12A according to Modification 11. That is, the sealing portion 12A includes a sealing plate 14 and a sealing frame 13A, and the sealing frame 13A further includes an inner sealing frame 17 and an outer sealing frame 18. The radiation detector 10F can suitably protect the scintillator layer 4A from moisture.

<Modification 16>
Part (b) of Fig. 10 shows a radiation detector 10G according to Modification 16. The radiation detector 10G does not have the sealing portion 12 compared to the radiation detector 10 according to the second embodiment, and has a protective film 6D instead of the sealing portion 12. The remaining configurations of the barrier layer 3A, the scintillator layer 4A, and the sensor panel 11 are similar to those of the radiation detector 10 according to the second embodiment. The protective film 6D covers the panel front surface 11a, the barrier layer side surface 3c, the scintillator layer side surface 4c, and the scintillator layer back surface 4b. The radiation detector 10G can suitably protect the scintillator layer 4A from moisture. The protective film 6D is made of the same material as the protective film 6.

<Modification 17>
Part (c) of Fig. 10 shows a radiation detector 10H according to the modified example 17. The radiation detector 10H is obtained by further adding a sealing frame 13B to the radiation detector 10G according to the modified example 16. Therefore, the scintillator layer 4A, the barrier layer 3A, the sensor panel 11, and the protective film 6D are the same as those of the radiation detector 10G according to the modified example 16. The sealing frame 13B is formed so as to close the joint between the sensor panel 11 and the protective film 6D. Therefore, the sealing frame 13B is formed along the outer edge of the protective film 6D when viewed in a plan view from the thickness direction. The sealing frame 13B may be made of, for example, a UV curing resin. According to this configuration, the intrusion of moisture from the joint between the sensor panel 11 and the protective film 6D is suppressed, and therefore the moisture resistance can be further improved.

<Modification 18>
Part (a) of FIG. 11 shows a radiation detector 10K according to Modification 18. The radiation detector 10K does not have the sealing portion 12 of the radiation detector 10 according to the second embodiment, and has a sealing sheet 12B instead of the sealing portion 12. The other configurations of the barrier layer 3A, the scintillator layer 4A, and the sensor panel 11 are the same as those of the radiation detector 10 according to the second embodiment. The sealing sheet 12B has a rectangular, polygonal, or circular shape when viewed in a plan view in the thickness direction. The sealing sheet 12B may be composed of, for example, a metal sheet such as a metal foil or an aluminum sheet, or a barrier film. The sealing sheet 12B covers the scintillator layer 4A and the barrier layer 3A. Specifically, it covers the scintillator layer back surface 4b, the scintillator layer side surface 4c, the barrier layer side surface 3c, and a part of the panel surface 11a. That is, when viewed in a plan view, the sealing sheet 12B is larger than the scintillator layer 4A and the barrier layer 3A. The outer peripheral edge 12a of the sealing sheet 12B is adhered to the panel surface 11a by the adhesive 15. Thus, the sealing sheet 12B and the sensor panel 11 form an airtight region that houses the scintillator layer 4A and the barrier layer 3A. Thus, the scintillator layer 4A can be protected from moisture. The adhesive 15 may contain a filler material. The filler material has a particle size less than the thickness of the adhesive layer. The radiation detector 10K can suitably protect the scintillator layer 4A from moisture.

<Modification 19>
Part (b) of FIG. 11 shows a radiation detector 10L according to the modified example 19. The radiation detector 10L has a sealing frame 12C having a different configuration from the sealing sheet 12B according to the modified example 18. The sealing frame 12C has a box shape and has an opening on the bottom surface. That is, the sealing sheet 12B according to the modified example 18 has flexibility, but the sealing frame 12C according to the modified example 19 is different in that it maintains a predetermined shape and is hard. Therefore, the sealing frame 12C may be made of, for example, a glass material, a metal material, or a carbon material. The bottom surface of the sealing frame 12C is bonded to the panel surface 11a by an adhesive 15. According to this configuration, the scintillator layer 4A is disposed in an airtight region formed by the sealing frame 12C and the sensor panel 11, so that the scintillator layer 4A can be protected from moisture. Furthermore, since the sealing frame 12C is hard, the scintillator layer 4A can be mechanically protected.

<Modification 20>
12 shows a radiation detector 10M according to the modified example 20. The radiation detector 10M has a barrier layer 3B and a scintillator layer 4B different from those of the radiation detector 10 according to the second embodiment. The barrier layer 3B has a barrier layer front surface 3a, a barrier layer back surface 3b, and a barrier layer side surface 3c. The scintillator layer 4B has a scintillator layer front surface 4a, a scintillator layer back surface 4b, and a scintillator layer side surface 4c. The single structure of the sensor panel 11 is similar to that of the radiation detector 10 according to the second embodiment. The scintillator layer 4B is formed on one side surface of the sensor panel 11 so as to protrude from the light detection region S1. Specifically, first, the barrier layer 3B is formed on the light detection region S1, one panel side surface 11c, and a surrounding region S2a between the light detection region S1 and one panel side surface 11c. Then, the scintillator layer 4B is formed on the entire surface of the barrier layer 3B so as to cover the barrier layer 3B. The radiation detector 10M having this configuration can be suitably used as a radiation detector for mammography, for example, by arranging the side of the scintillator layer 4B that is formed so as to extend beyond the light detection region S1 on the chest wall side.

<Experimental Example>
In the experimental example, the effect of the barrier layer on improving moisture resistance was confirmed. In this experimental example, moisture resistance refers to the relationship between the time of exposure to an environment having a certain humidity and the degree of change in the resolution (CTF) exhibited by the scintillator panel. In other words, high moisture resistance refers to a small degree of decrease in the resolution exhibited by the scintillator panel even when exposed to a humid environment for a long period of time. Conversely, low moisture resistance refers to a large degree of decrease in the resolution exhibited by the scintillator panel when exposed to a humid environment for a long period of time.

In the experimental example, first, three test specimens (scintillator panels) were prepared. Each test specimen had a scintillator layer and a substrate. Each scintillator layer contained CsI as a main component and had a thickness of 600 micrometers. The first and second test specimens had a barrier layer containing TlI as a main component between the substrate and the scintillator layer. On the other hand, the third test specimen did not have a barrier layer. In other words, the third test specimen was a comparative example in which a scintillator layer was formed directly on a substrate. The substrate of the first test specimen was an organic substrate containing an organic material as a main component. In other words, the first test specimen corresponded to the scintillator panel 1 according to the first embodiment. The substrate of the second test specimen was a substrate in which a protective film containing an organic material as a main component was formed on an aluminum base. In other words, the second test specimen corresponded to the scintillator panel according to the reference example. The substrate of the third test specimen was the same as that of the second test specimen.

In short, the configurations of the first to third test specimens are as follows:
First specimen: a substrate made of an organic material, a barrier layer, and a scintillator layer.
Second specimen: a substrate having an organic layer, a barrier layer, and a scintillator layer.
Third specimen: substrate with organic layer, scintillator layer (without barrier layer).

Next, the resolution of each of the first to third test specimens was obtained. This resolution was used as the reference value. Next, the first to third test specimens were placed in an environmental test machine with a temperature of 40°C and a humidity of 90%. Next, the resolution of each test specimen was obtained at each predetermined time from the start of placement. Then, the percentage of the resolution obtained at each predetermined time relative to the reference value of the resolution was calculated. In other words, a relative value was obtained with respect to the resolution before placement in the environmental test machine. For example, a relative value of 100 percent indicates that the resolution obtained after the predetermined time has elapsed has not changed from the resolution before placement in the environmental test machine, and that the performance has not deteriorated. Therefore, as the relative value decreases, the characteristics of the scintillator panel deteriorate.

The graph shown in Figure 13 shows the relationship between the time (horizontal axis) exposed to the above environment and the relative value (vertical axis). The resolution of the first test specimen was measured 1 hour, 72 hours, and 405 hours after the start of installation. The respective results are shown as plots P1a, P1b, and P1c. The resolution of the second test specimen was measured 1 hour, 20.5 hours, 84 hours, and 253 hours after the start of installation. The respective results are shown as plots P2a, P2b, P2c, and P2d. The resolution of the third test specimen was measured 1 hour, 24 hours, 71 hours, and 311 hours after the start of installation. The respective results are shown as plots P3a, P3b, P3c, and P3d.

When each plot is checked, the performance of the third test body (plots P3a, P3b, P3c, P3d) without a barrier layer was the largest among the first to third test bodies. In other words, it is considered that the performance of the third test body was deteriorated because moisture penetrated from the organic layer into the scintillator layer and the deliquescence of the scintillator layer progressed over time. On the other hand, the first and second test bodies (plots P1a, P1b, P1c, plots P2a, P2b, P2c, P2d) also showed a tendency for the relative values to decrease over time. However, the degree of decrease in the relative values shown by the first and second test bodies was clearly suppressed compared to the degree of decrease in the relative values shown by the third test body. Therefore, it was found that the deterioration of the properties of the scintillator panel can be suppressed by providing a barrier layer containing TlI as a main component. In other words, it was found that a barrier layer containing TlI as a main component can contribute to improving the moisture resistance of the scintillator panel.

1, 1A, 1B, 1C, 1D, 1E, 1F, 1G, 1H, 1K...scintillator panel, 2, 2A...substrate, 2a...substrate surface, 2b...substrate back surface, 2c...substrate side surface, 3, 3A, 3B...barrier layer, 3a...barrier layer surface, 3b...barrier layer back surface, 3c...barrier layer side surface, 4, 4A, 4B...scintillator layer, 4a...scintillator layer surface, 4b...scintillator layer Back surface, 4c...side surface of scintillator layer, 5, 5A, 5B...molten region, 5a, 5b...molten portion, 6, 6C, 6D...protective film, 6A, 6B...protective sheet, 6a, 6b...sheet member, 7, 7A, 7B...laminar body, 7a...surface of laminate, 7b...back surface of laminate, 7c...side surface of laminate, 8, 8A, 8B, 8C...functional layer, 8a...surface of functional layer, 8b...back surface of functional layer, 8c...functional layer Side, 9...FOP, 9a...FOP surface, 9b...FOP back surface, 9c...FOP side, 10, 10A, 10B, 10C, 10D, 10E, 10F, 10G, 10H, 10L, 10K, 10M...Radiation detector, 11...Sensor panel, 11a...Panel surface, 11b...Panel back surface, 11c...Panel side, 12, 12A...Sealing portion, 12B...Sealing sheet, 12 a...outer periphery, 12C...sealing frame, 13, 13A, 13B...sealing frame, 13a...frame surface, 13b...frame back surface, 13c...frame wall portion, 14...sealing plate, 14a...plate surface, 14b...plate back surface, 14c...plate side surface, 16...photoelectric conversion element, 17...inner sealing frame, 18...outer sealing frame, 15...adhesive, S1...light detection region, S2...surrounding region, S3...exposed region, S2a...surrounding region.

Claims (4)

a sensor panel having a panel surface including a light detection region in which a photoelectric conversion element is provided;
a barrier layer formed on the panel surface and containing thallium iodide as a main component;
a scintillator layer formed on the barrier layer and composed of a plurality of columnar crystals containing cesium iodide doped with thallium as a main component;
a sealing sheet adhered to the panel surface to form an airtight region that contains the scintillator layer and the barrier layer. The radiation detector according to claim 1, wherein the sealing sheet is a metal sheet or a barrier film. The radiation detector according to claim 1, further comprising an adhesive portion that fixes the outer periphery of the sealing sheet to the sensor panel by adhesion. The adhesive portion includes a filler material,
The radiation detector according to claim 3 , wherein the filler material has a particle size less than a thickness of an adhesive layer formed between the panel surface and the sealing sheet.

Images