Radiation imaging panel, radiation imaging apparatus, and radiation imaging system

Abstract

To provide a technique advantageous for achieving both improvement of a MTF and improvement of DQE.SOLUTION: A radiation imaging panel includes: a substrate having a first principal surface and a second principal surface; a photoelectric conversion unit arranged on the first principal surface; a first scintillator arranged to cover the photoelectric conversion unit; and a second scintillator arranged to cover the second principal surface. The thickness of the substrate is 50 μm or less. The first scintillator is formed of columnar crystals and has a film thickness of 300 μm or more and 800 μm or less. The second scintillator is formed of granulated crystals and has a film thickness of 20% or more and 70% or less of the film thickness of the first scintillator.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a radiation imaging panel, a radiation imaging apparatus, and a radiation imaging system. [Background technology]

[0002] A radiation imaging device is known in which a scintillator that converts radiation into light detectable by a photoelectric conversion element is arranged on a sensor panel on which a photoelectric conversion element is arranged. In order to improve the detective quantum efficiency (DQE) of the radiation imaging device, it is conceivable to thicken the scintillator and increase the amount of radiation absorbed by the scintillator and converted into light. On the other hand, if the scintillator is made thicker, the optical path length until the light converted by the scintillator reaches the sensor panel becomes longer, and the optical transfer coefficient (Modulation Transfer Function: MTF) may decrease. Patent Document 1 shows a photoelectric detection structure in which scintillators are arranged on both sides of a sensor panel, and the scintillator arranged on the radiation incident side converts low-energy radiation into light, and the scintillator arranged on the opposite side to the radiation incident side converts high-energy radiation into light. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] US Patent Application Publication No. 2019 / 0361133 Summary of the Invention [Problem to be solved by the invention]

[0004] Patent Document 1 shows that the total thickness of the two scintillators is made to match the thickness of the scintillator when a single-layer scintillator is used. If the thickness of each scintillator is reduced, the MTF improves, but the DQE may decrease.

[0005] An object of the present invention is to provide a technique that is advantageous in achieving both an improvement in MTF and an improvement in DQE. [Means for solving the problem]

[0006] In view of the above problems, a radiation imaging panel according to an embodiment of the present invention is a radiation imaging panel including a substrate having a first main surface and a second main surface, a photoelectric conversion section arranged on the first main surface, a first scintillator arranged to cover the photoelectric conversion section, and a second scintillator arranged to cover the second main surface, wherein a thickness of the substrate is 50 μm or less, the first scintillator is composed of columnar crystals and has a film thickness of 300 μm or more and 800 μm or less, and the second scintillator is composed of granular crystals and has a film thickness of 20% or more and 70% or less of the film thickness of the first scintillator. Effect of the Invention

[0007] According to the present invention, it is possible to provide a technique that is advantageous in achieving both an improvement in MTF and an improvement in DQE. [Brief description of the drawings]

[0008] [Figure 1] FIG. 2 is a plan view showing an example of the configuration of a radiation imaging panel according to the present embodiment. [Diagram 2] FIG. 2 is a cross-sectional view showing an example of the configuration of the radiation imaging panel shown in FIG. [Diagram 3] FIG. 2 is a cross-sectional view showing an example of the configuration of the radiation imaging panel shown in FIG. [Figure 4] FIG. 11 is a cross-sectional view showing an example of the configuration of a radiation imaging panel of a comparative example. [Diagram 5] 2A to 2C are diagrams showing an example of a method for manufacturing the radiation imaging panel of FIG. 1; [Figure 6] 2A to 2C are diagrams showing an example of a method for manufacturing the radiation imaging panel of FIG. 1; [Figure 7] 2 is a diagram showing an example of the configuration of a radiation imaging apparatus and a radiation imaging system including the radiation imaging panel of FIG. 1; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, the embodiments will be described in detail with reference to the attached drawings. Note that the following embodiments do not limit the invention according to the claims. Although the embodiments describe a number of features, not all of these features are essential to the invention, and the features may be combined in any manner. Furthermore, in the attached drawings, the same reference numbers are used for the same or similar configurations, and duplicated descriptions are omitted.

[0010] Furthermore, radiation in this disclosure may include α-rays, β-rays, γ-rays, and the like, which are beams produced by particles (including photons) emitted by radioactive decay, as well as beams having the same or greater energy, such as X-rays, particle beams, and cosmic rays.

[0011] A radiation imaging panel according to an embodiment of the present disclosure will be described with reference to Fig. 1 to Fig. 7. Fig. 1 is a plan view of a radiation imaging panel 100 of the present embodiment, and Fig. 2 is a cross-sectional view taken along line AA' shown in Fig. 1.

[0012] The radiation imaging panel 100 may include a substrate 111 having a principal surface 161 and a principal surface 162, a photoelectric conversion unit 112 having a plurality of pixels arranged on the principal surface 161 of the substrate 111, a scintillator 121 arranged so as to cover the photoelectric conversion unit 112 arranged on the principal surface 161 of the substrate 111, and a scintillator 141 arranged so as to cover the principal surface 162 of the substrate 111. In orthogonal projection onto the principal surface 161 of the substrate 111, the scintillator 121 may be arranged so as to overlap with the photoelectric conversion unit 112. Similarly, in orthogonal projection onto the principal surface 161 of the substrate 111, the scintillator 141 may be arranged so as to overlap with the photoelectric conversion unit 112.

[0013] The radiation imaging panel 100 may include a sensor protection layer 113 disposed between the photoelectric conversion unit 112 and the scintillator 121 so as to cover the photoelectric conversion unit 112. The substrate 111, the photoelectric conversion unit 112, and the sensor protection layer 113 may constitute a sensor panel 110. The sensor panel 110 includes at least the substrate 111 and the photoelectric conversion unit 112.

[0014] The radiation imaging panel 100 may further include a reflective layer 122 arranged to cover the scintillator 121. The radiation imaging panel 100 may further include a protective layer 123 arranged to cover the reflective layer 122. A combination of the scintillator 121, the reflective layer 122, and the protective layer 123 may be referred to as a wavelength conversion section 120 hereinafter.

[0015] The radiation imaging panel 100 may include a bonding layer 142 disposed between the scintillator 141 and the main surface 162 of the substrate 111. The radiation imaging panel 100 may also include a reflective layer 143 disposed so as to cover the scintillator 141. The combination of the bonding layer 142, the scintillator 141, and the reflective layer 143 may be referred to as a wavelength conversion section 140 hereinafter.

[0016] A signal for controlling the radiation imaging panel 100 can be transmitted from the circuit board 132 to the radiation imaging panel 100 via the wiring board 131 or the like. A signal generated in the radiation imaging panel 100 can be transmitted from the radiation imaging panel 100 to the circuit board 132 via the wiring board 131 or the like. In order to transmit and receive these signals, for example, an anisotropic conductive film (ACF) 133 can be disposed between the radiation imaging panel 100 and the wiring board 131 and between the wiring board 131 and the circuit board 132. The radiation imaging panel 100 and the circuit board 132 constitute a radiation imaging device 200 (shown in FIG. 7 ) described later. The circuit board 132 can function as, for example, a control unit for controlling the radiation imaging panel 100. For example, the circuit board 132 can function as a signal processing unit for processing a signal output from the radiation imaging panel 100.

[0017] The substrate 111 can allow the scintillation light converted from radiation in the scintillator 121 or the scintillator 141 to reach the photoelectric conversion unit 112 with almost no attenuation. For example, glass, quartz, a light-transmitting plastic film, or the like can be used as the substrate 111. Examples of the plastic film used as the substrate 111 include polyimide, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyethersulfone (PES), polyetherimide, polyetheretherketone, polyphenylene sulfide, polyarylate, polycarbonate (PC), cellulose triacetate (TAC), cellulose acetate propionate (CAP), and the like.

[0018] The thickness of the substrate 111 may be 50 μm or less in order to suppress scattering of the scintillation light. From the viewpoint of cost and from the viewpoint of preventing damage such as cracking or chipping of the substrate 111 during the manufacture of the radiation imaging panel 100, the substrate 111 may be made of a flexible material such as a plastic film. Furthermore, the lower limit of the thickness of the substrate 111 may be 10 μm or more in consideration of the process during the manufacture of the radiation imaging panel 100. Furthermore, for example, the thickness of the substrate 111 may be 12 μm or more, 15 μm or more, or 20 μm or more.

[0019] The photoelectric conversion unit 112 converts the scintillation light converted from radiation by the scintillators 121, 141 into an electrical signal. The photoelectric conversion unit 112 has a plurality of pixels arranged, for example, in a matrix. Each of the pixels arranged in the photoelectric conversion unit 112 may include, for example, a photoelectric conversion element that converts incident light into an electric charge, and a switch element for reading out an electric signal corresponding to the electric charge generated by the photoelectric conversion element. A radiological image may be generated based on the electric signal output from the pixels arranged in the photoelectric conversion unit 112.

[0020] 2, a part of main surface 161 of substrate 111 is recessed, and photoelectric conversion section 112 is disposed in the recessed portion of main surface 161 of substrate 111, but this is not limited thereto. Main surface 161 of substrate 111 may be flat, and photoelectric conversion section 112 may be disposed on flat main surface 161.

[0021] In a radiation imaging system SYS (shown in FIG. 7) described later, the radiation imaging device 200 and the radiation source 210 may be arranged so that the photoelectric conversion unit 112 is arranged on the radiation incident side of the substrate 111. In other words, as shown in FIG. 2, the radiation imaging device 200 and the radiation source 210 may be arranged in the radiation imaging system SYS so that radiation is incident on the radiation imaging panel 100 from the side of the wavelength conversion unit 120. This suppresses scattering of scintillation light from the scintillator 121, which is arranged at a position closer to the photoelectric conversion unit 112 than the scintillator 141.

[0022] The sensor protection layer 113 is formed so as to cover the photoelectric conversion unit 112 and protects the photoelectric conversion unit 112. A thermosetting resin having heat resistance may be used as the sensor protection layer 113. Examples of the thermosetting resin include phenol resin, epoxy resin, silicone, polyurethane, and polyimide. When the thickness of the sensor protection layer 113 increases, the optical transparency and sharpness (related to MTF) are affected. On the other hand, since the method of forming the thin sensor protection layer 113 has difficulty (cost), the thickness of the sensor protection layer 113 may be, for example, 1 μm or more and 10 μm or less. The sensor protection layer 113 may be formed, for example, by applying the material of the sensor protection layer 113 in a liquid state by dissolving it in a solvent, and drying the solvent. In addition, for example, the sensor protection layer 113 may be a sheet that can be thermally bonded. In addition, the sensor protection layer 113 may be formed as the final layer in the process of forming the photoelectric conversion unit 112.

[0023] The scintillator 121 is made of a scintillator constituted by a collection of columnar crystals. By providing the scintillator 121 with a plurality of columnar crystals, it is possible to transmit information with high sharpness to the photoelectric conversion unit 112 due to the light guide effect caused by each columnar crystal. For example, an alkali metal halide compound is used as a material for the scintillator 121 constituted by columnar crystals. For example, cesium iodide (CsI:Tl) to which a small amount of thallium (Tl) is added as an activator may be used for the scintillator 121. Also, for example, sodium iodide (NaI:Tl) to which a small amount of thallium is added as an activator may be used for the scintillator 121.

[0024] It is considered that the film thickness of the scintillator 121 is increased from the viewpoint of improving the DQE. On the other hand, when the film thickness of the scintillator 121 is increased, the optical path length is increased, and even when the light guide effect of the columnar crystal is taken into consideration, the MTF may be decreased. Furthermore, the inventors' experiments have found that when the film thickness of the scintillator 121 exceeds 800 μm, the DQE is saturated. Therefore, the film thickness of the scintillator 121 may be 800 μm or less. Furthermore, when the film thickness of the scintillator 121 is reduced, the MTF is improved. However, it has been found that when the film thickness of the scintillator 121 is less than 200 μm, it is difficult to obtain sufficient performance as the radiation imaging panel 100. Therefore, the scintillator 121 may have a film thickness of, for example, 200 μm or more and 800 μm or less. Furthermore, for example, as the performance of the radiation imaging panel 100, from the viewpoint of the DQE, the scintillator 121 may have a film thickness of 300 μm or more. In other words, the scintillator 121 may have a film thickness of 300 μm or more and 800 μm or less. Furthermore, for example, the scintillator 121 may have a film thickness of 350 μm or more and 800 μm or less.

[0025] The scintillator 121 may be formed on the sensor panel 110 by, for example, a vapor deposition method so as to cover the photoelectric conversion unit 112. However, this is not limited thereto, and as shown in Fig. 3, the scintillator 121 formed on the reflective layer 125 may be bonded to the sensor panel 110 via a bonding layer 124. The configuration shown in Fig. 3 will be described later.

[0026] The reflective layer 122 may be made of a material having a high reflectance at the wavelength of the scintillation light so as to reflect the scintillation light converted from radiation by the scintillator 121. The reflective layer 122 may contain resin to which white dye or particles of metal oxides such as white lead, zinc oxide, or titanium oxide are added. The sensitivity of the photoelectric conversion unit 112 is improved by the reflection of light by the reflective layer 122. In addition, the optical path length of the distance (for example, twice the film thickness of the reflective layer) that the scintillation light emitted by the scintillator 121 travels through the reflective layer 122 is reduced compared to the case where the scintillation light is reflected by the protective layer 123. This improves the sharpness.

[0027] A hot melt resin such as a polyolefin-based, polyester-based, or polyamide-based resin may be used as the reflective layer 122. A highly moisture-proof material may be used for the reflective layer 122 in order to protect the scintillator 121 using an alkali metal halide compound exhibiting deliquescent properties. In addition, in the case of a configuration in which the protective layer 123 is capable of reflecting scintillation light as shown in Fig. 2, the light transmittance that transmits the scintillation light reflected by the protective layer 123 is also important.

[0028] An increase in the thickness of the reflective layer 122 affects the optical transparency and sharpness. On the other hand, since the method of forming the thin reflective layer 122 is difficult (cost), the thickness of the reflective layer 122 may be 10 μm or more and 30 μm or less.

[0029] The protective layer 123 is formed so as to cover the scintillator 121, and may have a function of reflecting, toward the photoelectric conversion unit 112, the light that travels in the opposite direction to the photoelectric conversion unit 112, among the scintillation light emitted by the scintillator 121. The sensitivity of the photoelectric conversion unit 112 is improved by the protective layer 123 reflecting the scintillation light. The protective layer 123 may also have a function of preventing light (external light) other than the scintillation light from being incident on the photoelectric conversion unit 112. Furthermore, the protective layer 123 may also function as a moisture-proof layer or an electromagnetic shield layer for the scintillator 121. The protective layer 123 may be formed of, for example, a metal sheet such as a metal foil or a metal thin film. Examples of materials for the protective layer 123 include metal materials such as aluminum, gold, silver, copper, and aluminum alloy. The protective layer 123 may be an aluminum sheet, which is a material with high radiation transparency.

[0030] In the configuration shown in FIG. 2, the wavelength conversion unit 120 includes a protective layer 123. Therefore, the reflective layer 122 can also function as a bonding layer between the scintillator 121 and the protective layer 123. As described above, the reflective layer 122 may be a resin to which dye or metal oxide particles are added in order to reflect the scintillation light emitted by the scintillator 121, but the dye or the like may not be added. Even in that case, a part of the scintillation light may be reflected at the interface between the scintillator 121 and the reflective layer 122. In addition, when the reflective layer 122 has a sufficient function as a protective layer such as moisture protection for the scintillator 121, the protective layer 123 may not be provided.

[0031] Here, the configuration of the wavelength conversion unit 120 shown in Fig. 3 will be described. In the configuration shown in Fig. 3, the scintillator 121 is formed on the reflective layer 125 by, for example, a vapor deposition method, and then is bonded to the sensor panel 110 via the bonding layer 124. Although not shown in Fig. 3, a protective layer 123 similar to the configuration shown in Fig. 2 may be arranged so as to cover the bonding layer 124, the scintillator 121, and the reflective layer 125.

[0032] The bonding layer 124 can allow the scintillation light emitted by the scintillator 121 to reach the substrate 111 with almost no attenuation. For example, an acrylic resin or the like can be used for the bonding layer 124. The bonding layer 124 is formed thin in order to suppress scattering of the scintillation light. On the other hand, in order to ensure the bonding force that bonds the sensor panel 110 and the scintillator 121, the film thickness of the bonding layer 124 may be about 10 μm.

[0033] For example, a polyester resin such as polyethylene terephthalate (PET) may be used for the reflective layer 125. For example, the reflective layer 125 may be a resin (for example, PET) molded in white. For the reflective layer 125, an appropriate material may be selected in consideration of heat resistance in the process of forming the scintillator 121, etc.

[0034] Next, a description will be given of the wavelength conversion section 140. The wavelength conversion section 140 can include a scintillator 141, a bonding layer 142, and a reflective layer 143.

[0035] The scintillator 141 is a scintillator formed by an assembly of granular crystals. The scintillator 141 formed by a plurality of granular crystals may be formed of a metal oxysulfide represented by the general formula Me2O2S:Re from the viewpoints of moisture resistance, luminous efficiency, thermal process resistance, and afterglow. Here, Me is any one of lanthanum (La), yttrium (Y), and gadolinium (Gd), and Re is at least one of terbium (Tb), samarium (Sm), europium (Eu), cerium (Ce), praseodymium (Pr), and thulium (Tm). For example, gadolinium oxysulfide (GOS:Tb) to which a small amount of terbium (Tr) is added, or gadolinium oxysulfide (GOS:Pr) to which a small amount of praseodymium (Pr) is added may be used as the scintillator 141. Furthermore, as the scintillator 141, not only metal oxysulfides but also gadolinium aluminum gallium oxide (GAGG:Ce) with a small amount of cerium added thereto may be used.

[0036] In this embodiment, the radiation imaging panel 100 includes not only the scintillator 121 covering the main surface 161 of the substrate 111, but also the scintillator 141 covering the main surface 162. As described above, in the radiation imaging system SYS, the scintillator 121 is disposed on the radiation incident side. As a result, radiation that passes through the scintillator 121 without being converted into scintillation light is absorbed by the scintillator 141, converted into scintillation light, and reaches the photoelectric conversion unit 112. Therefore, the sensitivity and DQE of the radiation imaging panel 100 are improved compared to a radiation imaging panel 199 not including the scintillator 141 as shown in FIG. 4.

[0037] In addition, since light is reflected at the interface between the granular crystals, a scintillator formed by an assembly of granular crystals is likely to reflect light. Therefore, of the scintillation light emitted by the scintillator 121, the scintillation light that has passed through the sensor panel 110 is reflected by the granular crystals of the scintillator 141, and is more likely to reach the photoelectric conversion unit 112 again, improving the sensitivity and DQE of the radiation imaging panel 100. For this reason, a scintillator made of granular crystals is used as the scintillator 141, instead of columnar crystals like the scintillator 121.

[0038] Since the substrate 111 is present between the scintillator 141 and the photoelectric conversion unit 112, the optical path length of the scintillation light emitted by the scintillator 141 may be long. Furthermore, in the radiation imaging system SYS, conversion from radiation to light is performed in the scintillator 121 disposed on the radiation incidence side. Therefore, the film thickness of the scintillator 141 may be thinner than the film thickness of the scintillator 121. The inventors have obtained the following findings regarding the film thickness of the scintillator 141 through experiments.

[0039] In order to obtain the effect of the scintillation light emitted by the scintillator 141 and the above-mentioned reflection effect by the granular crystals, the scintillator 141 needs to have a certain film thickness. Even when the scintillator 121 is thinned to about 300 μm, if the scintillator 141 has a film thickness of about 20% of the film thickness of the scintillator 121, the above-mentioned effect can be obtained, and the DQE can be improved while improving the MTF. In other words, by having the scintillator 141 have a film thickness of about 20% of the film thickness of the scintillator 121, it is possible to compensate for the decrease in DQE caused by thinning the scintillator 121, and the thin scintillator 121 can improve the MTF. In addition, even when the film thickness of the scintillator 121 is thickened to 800 μm, if the scintillator 141 has a film thickness of about 20% of the film thickness of the scintillator 121, it is possible to improve the DQE while maintaining the MTF. Furthermore, it was found that when the film thickness of the scintillator 141 was increased, the DQE was saturated in the combination of the scintillator 121 and the scintillator 141. Specifically, it was found that when the film thickness of the scintillator 141 exceeded 70% of the film thickness of the scintillator 121, the DQE did not improve even if the film thickness of the scintillator 141 was increased. In other words, when the film thickness of the scintillator 121 was between 300 μm and 800 μm and the film thickness of the scintillator 141 exceeded 70% of the film thickness of the scintillator 121, no improvement in the DQE was observed. Moreover, an unnecessary increase in the film thickness of the scintillator 141 may result in a decrease in the MTF. From these results, in order to improve both the MTF and the DQE, the scintillator 121 of columnar crystals may have a film thickness of, for example, 300 μm or more and 800 μm or less, and in that case, the scintillator 141 of granular crystals may have a film thickness of, for example, 20% or more and 70% or less of the film thickness of the scintillator 121. In addition, it was found that when the film thickness of the scintillator 141 is increased, the DQE is saturated at about 250 μm to 300 μm. As described above, an unnecessary increase in the film thickness of the scintillator 141 may not only saturate the DQE but also cause a decrease in the MTF. Therefore, the sum of the film thickness of the scintillator 121 and the film thickness of the scintillator 141 may be 1100 μm or less.That is, for example, the upper limit of the film thickness of scintillator 121 may be 800 μm, and the upper limit of the film thickness of scintillator 141 may be 300 μm. Furthermore, for example, the upper limit of the film thickness of scintillator 141 may be 250 μm. In that case, the sum of the film thicknesses of scintillator 121 and scintillator 141 may be 1050 μm or less.

[0040] A combination of the film thicknesses of the scintillator 121 and the scintillator 141 that achieves both improvements in MTF and DQE can be, for example, when the film thickness of the scintillator 121 is 300 μm, the film thickness of the scintillator 141 can be in a range of 60 μm or more, which is 20% of the film thickness of the scintillator 121 (300 μm), and 210 μm or less, which is 70%. Also, for example, when the film thickness of the scintillator 121 is 350 μm, the film thickness of the scintillator 141 can be in a range of 70 μm or more, which is 20% of the film thickness of the scintillator 121 (350 μm), and 245 μm or less, which is 70%. For example, when the film thickness of the scintillator 121 is 318 μm, the film thickness of the scintillator 141 can be 64 μm, 124 μm, 173 μm, 222 μm, etc. Furthermore, for example, when the film thickness of the scintillator 121 is 340 μm, the film thickness of the scintillator 141 can be 70 μm, 135 μm, 187 μm, 230 μm, etc. For example, when the film thickness of the scintillator 121 is 364 μm, the film thickness of the scintillator 141 can be 86 μm, 123 μm, 178 μm, 225 μm, etc. For example, when the film thickness of the scintillator 121 is 385 μm, the film thickness of the scintillator 141 can be 77 μm, 124 μm, 199 μm, 234 μm, etc.

[0041] For example, when the film thickness of the scintillator 121 is 400 μm, the film thickness of the scintillator 141 may be in the range of 80 μm or more, which is 20% of the film thickness of the scintillator 121, 400 μm, and 280 μm or less, which is 70%. For example, when the film thickness of the scintillator 121 is 450 μm, the film thickness of the scintillator 141 may be in the range of 90 μm or more, which is 20% of the film thickness of the scintillator 121, 450 μm, and 315 μm or less, which is 70%. However, as described above, when the film thickness of the scintillator 141 is about 250 μm to 300 μm, the DQE is saturated. Therefore, the film thickness of the scintillator 141 may be 300 μm or less, or may be 250 μm or less. For example, when the film thickness of the scintillator 121 is 412 μm, the film thickness of the scintillator 141 may be 93 μm, 151 μm, 205 μm, 248 μm, etc. Furthermore, when the film thickness of the scintillator 121 is 439 μm, the film thickness of the scintillator 141 may be 100 μm, 168 μm, 221 μm, 237 μm, etc. Furthermore, when the film thickness of the scintillator 121 is 456 μm, the film thickness of the scintillator 141 may be 109 μm, 183 μm, 214 μm, 241 μm, etc. Furthermore, when the film thickness of the scintillator 121 is 489 μm, the film thickness of the scintillator 141 may be 102 μm, 158 μm, 211 μm, 240 μm, etc.

[0042] For example, when the film thickness of the scintillator 121 is 500 μm, the film thickness of the scintillator 141 may be in the range of 100 μm or more, which is 20% of the film thickness of the scintillator 121 of 500 μm, and 350 μm or less, which is 70% of the film thickness of the scintillator 121 of 500 μm. Also, for example, when the film thickness of the scintillator 121 is 550 μm, the film thickness of the scintillator 141 may be in the range of 110 μm or more, which is 20% of the film thickness of the scintillator 121 of 550 μm, and 385 μm or less, which is 70% of the film thickness of the scintillator 121 of 550 μm. However, as described above, when the film thickness of the scintillator 141 is about 250 μm to 300 μm, the DQE is saturated. Therefore, the film thickness of the scintillator 141 may be 300 μm or less, or may be 250 μm or less. For example, when the film thickness of the scintillator 121 is 531 μm, the film thickness of the scintillator 141 may be 110 μm, 148 μm, 216 μm, 233 μm, etc. Furthermore, when the film thickness of the scintillator 121 is 545 μm, the film thickness of the scintillator 141 may be 135 μm, 151 μm, 222 μm, 246 μm, etc. Furthermore, when the film thickness of the scintillator 121 is 567 μm, the film thickness of the scintillator 141 may be 148 μm, 188 μm, 229 μm, 250 μm, etc. Furthermore, when the film thickness of the scintillator 121 is 578 μm, the film thickness of the scintillator 141 may be 126 μm, 149 μm, 183 μm, 236 μm, etc.

[0043] For example, when the film thickness of the scintillator 121 is 600 μm, the film thickness of the scintillator 141 may be in the range of 120 μm or more, which is 20% of the film thickness of the scintillator 121 of 600 μm, and 420 μm or less, which is 70% of the film thickness of the scintillator 121. Also, for example, when the film thickness of the scintillator 121 is 650 μm, the film thickness of the scintillator 141 may be in the range of 130 μm or more, which is 20% of the film thickness of the scintillator 121 of 650 μm, and 455 μm or less, which is 70% of the film thickness of the scintillator 121. However, as described above, when the film thickness of the scintillator 141 is about 250 μm to 300 μm, the DQE is saturated. Therefore, the film thickness of the scintillator 141 may be 300 μm or less, or may be 250 μm or less. For example, when the film thickness of the scintillator 121 is 619 μm, the film thickness of the scintillator 141 may be 136 μm, 192 μm, 225 μm, 240 μm, etc. Furthermore, when the film thickness of the scintillator 121 is 631 μm, the film thickness of the scintillator 141 may be 147 μm, 178 μm, 201 μm, 229 μm, etc. Furthermore, when the film thickness of the scintillator 121 is 675 μm, the film thickness of the scintillator 141 may be 140 μm, 174 μm, 215 μm, 243 μm, etc. Furthermore, when the film thickness of the scintillator 121 is 691 μm, the film thickness of the scintillator 141 may be 158 μm, 181 μm, 228 μm, 250 μm, etc.

[0044] For example, when the film thickness of the scintillator 121 is 700 μm, the film thickness of the scintillator 141 may be in a range of 140 μm or more, which is 20% of the film thickness of the scintillator 121 of 700 μm, and 490 μm or less, which is 70%. Also, when the film thickness of the scintillator 121 is 750 μm, the film thickness of the scintillator 141 may be in a range of 150 μm or more, which is 20% of the film thickness of the scintillator 121 of 750 μm, and 525 μm or less, which is 70%. Furthermore, when the film thickness of the scintillator 121 is 800 μm, the film thickness of the scintillator 141 may be in a range of 160 μm or more, which is 20% of the film thickness of the scintillator 121 of 800 μm, and 560 μm or less, which is 70%. However, as described above, when the film thickness of the scintillator 141 is about 250 μm to 300 μm, the DQE is saturated. Therefore, the film thickness of the scintillator 141 may be 300 μm or less, and may further be 250 μm or less. For example, when the film thickness of the scintillator 121 is 717 μm, the film thickness of the scintillator 141 may be 154 μm, 186 μm, 213 μm, 239 μm, etc. For example, when the film thickness of the scintillator 121 is 736 μm, the film thickness of the scintillator 141 may be 162 μm, 199 μm, 216 μm, 235 μm, etc. For example, when the film thickness of the scintillator 121 is 781 μm, the film thickness of the scintillator 141 may be 164 μm, 196 μm, 205 μm, 246 μm, etc. Furthermore, for example, when the film thickness of the scintillator 121 is 795 μm, the film thickness of the scintillator 141 may be 180 μm, 208 μm, 226 μm, 247 μm, or the like.

[0045] The above-mentioned combinations of the film thicknesses of the scintillator 121 and the scintillator 141 are merely examples, and the present invention is not limited to these combinations. The combination of the film thicknesses of the scintillator 121 and the scintillator 141 may be any appropriate combination within the above-mentioned range.

[0046] The scintillator 141 may be formed, for example, on the reflective layer 143 and bonded to the sensor panel 110 via the bonding layer 142. Alternatively, for example, the scintillator 141 may be formed directly on the substrate 111, and the reflective layer 143 may be bonded onto the scintillator 141. In this case, the bonding layer 142 may not be provided.

[0047] The bonding layer 142 is disposed between the substrate 111 and the scintillator 141, and allows the scintillation light to reach the substrate 111 with almost no attenuation. For example, an acrylic resin or the like may be used for the bonding layer 142. The bonding layer 142 is formed thin in order to suppress scattering of the scintillation light. On the other hand, in order to ensure the bonding force that bonds the sensor panel 110 and the scintillator 141, the film thickness of the bonding layer 142 may be about 10 μm.

[0048] The reflective layer 143 can be disposed to reflect the scintillation light emitted by the scintillator 141 and traveling in the opposite direction to the photoelectric conversion unit 112. This allows a large amount of the scintillation light emitted by the scintillator 141 to reach the photoelectric conversion unit 112. As a result, the sensitivity of the radiation imaging panel 100 is improved. For example, a polyester-based resin such as polyethylene terephthalate (PET) may be used for the reflective layer 143. For example, the reflective layer 143 may be a resin (for example, PET) molded in white.

[0049] Although not shown in Fig. 2 and Fig. 3, the wavelength conversion section 140 may be covered with a layer similar to the protective layer 123 of the wavelength conversion section 120. For example, the wavelength conversion section 140 may be covered with a metal sheet such as an aluminum sheet. This prevents light other than the scintillation light (external light) from entering the photoelectric conversion section 112. In addition, the metal sheet also functions as an electromagnetic shielding layer, and noise in the obtained radiation image can be reduced.

[0050] The radiation imaging panel 100 of this embodiment has the above-mentioned configuration, and while the photoelectric conversion unit 112 receives information of high sharpness, high luminance and high DQE from the wavelength conversion unit 120, the wavelength conversion unit 140 reflects the scintillation light emitted by the scintillator 121 that has passed through the sensor panel 110. Furthermore, light emitted by the scintillator 141 due to radiation not absorbed by the scintillator 121 is provided to the photoelectric conversion unit 112 while maintaining sharpness. This makes it possible for the radiation imaging panel 100 to improve the DQE while maintaining the MTF.

[0051] Next, a method for manufacturing the radiation imaging panel 100 will be described. First, as shown in Fig. 5(a), a substrate 111 having a photoelectric conversion section 112 formed on a main surface 161 is prepared. At this time, as shown in Fig. 5(a), the flexible substrate 111 may be supported by a support base 151. The support base 151 may be made of glass, for example. However, the present invention is not limited thereto, and a material other than glass may be used as the support base 151 as long as the material ensures the rigidity of the substrate 111 in the process of manufacturing the radiation imaging panel 100.

[0052] 5(b), the sensor protection layer 113 is formed so as to cover the photoelectric conversion part 112. For example, the sensor protection layer 113 is formed by applying a material of the sensor protection layer 113 in a liquid state in which the material is dissolved in a solvent, and then drying the solvent.

[0053] After forming the sensor protection layer 113, the scintillator 121 is formed by a vapor deposition method so as to cover the main surface 161 of the substrate 111 on which the photoelectric conversion part 112 is disposed. As described above, the scintillator 121 has a columnar crystal structure.

[0054] Next, protective layer 123 having reflective layer 122 functioning as a bonding layer formed on one surface thereof is disposed to cover scintillator 121 so that reflective layer 122 is in contact with scintillator 121. Thereafter, as shown in Fig. 5(d), protective layer 123 is bonded to scintillator 121 via reflective layer 122 by heating and pressurizing in a vacuum. Through the steps shown in Figs. 5(c) and 5(d), wavelength conversion section 120 is formed.

[0055] After the wavelength conversion section 140 is formed, the circuit board 132 may be connected via the wiring board 131 as shown in Fig. 6(a). Thermocompression bonding via the ACF 133 may be used for the connection between the sensor panel 110 and the wiring board 131 and the connection between the wiring board 131 and the circuit board 132. In this embodiment, the wiring board 131 is connected to the sensor panel 110 before the wavelength conversion section 140 including the scintillator 141 is formed, but this is not limiting. For example, the wiring board 131 may be connected to the radiation imaging panel 100 after the radiation imaging panel 100 including the wavelength conversion section 140 is completed.

[0056] 6(b), the support base 151 is peeled off from the substrate 111. Methods for peeling the support base 151 from the substrate 111 include, but are not limited to, a technique called Laser Lift-Off (LLO) processing, in which a laser is irradiated to melt and evaporate (laser ablation) the interface of an object to be processed, and the processed surface is used as a boundary for peeling. The support base 151 may also be peeled off from the substrate 111 by mechanical peeling (delamination) or the like.

[0057] After removing the support base 151 from the substrate 111, a granular crystal scintillator 141 using GOS:Tb formed on a reflective layer 143 using white PET is bonded to a main surface 162 of the substrate 111 via a bonding layer 142. This process forms a wavelength conversion section 140. By including these processes, a radiation imaging panel 100 as shown in FIG. 2 is manufactured.

[0058] Here, a radiation imaging device 200 including the above-mentioned radiation imaging panel 100 and an example in which the radiation imaging device 200 is applied to a radiation detection system SYS represented by a radiation inspection device will be described with reference to Fig. 7. Fig. 7 is a schematic diagram showing an example of the configuration of the radiation imaging system SYS.

[0059] The radiation imaging device 200 includes a radiation imaging panel 100 and a circuit board 132. The circuit board 132 may function as, for example, a control unit for controlling the radiation imaging panel 100. In this case, a control circuit for controlling the radiation imaging panel 100 may be disposed on the circuit board 132. In addition, for example, the circuit board 132 may function as a signal processing unit for processing signals output from the radiation imaging panel 100. In this case, a processing circuit for processing signals output from the radiation imaging panel 100, such as a digital-analog conversion circuit, may be disposed on the circuit board 132.

[0060] The radiation imaging system SYS includes, for example, a radiation imaging device 200 equipped with the above-mentioned radiation imaging panel 100, a signal processing device 230, a display device 240, and a radiation source 210. The signal processing device 230 may include an image processor or the like that processes signals output from the radiation imaging device 200. The display device 240 may include a display or the like. The radiation source 210 generates radiation for irradiating the radiation imaging device 200 with radiation.

[0061] In the radiation imaging system SYS shown in FIG. 7, radiation (e.g., X-rays) generated by a radiation source 210 passes through, for example, the chest of a subject 220 such as a patient and enters a radiation imaging device 200. The incident radiation contains information about the inside of the body of the subject 220. In the radiation imaging device 200, electrical information corresponding to the incident radiation is obtained. This information is then digitally converted by, for example, a circuit board 132, and image-processed by a signal processing device 230. The pixel-processed information can be displayed as an examination result by a display device 240 in a control room. This information can also be transferred to a remote location via a network such as a telephone, LAN, or the Internet. This allows this information to be displayed as an examination result on a display in another location such as a doctor's room, and a doctor in a remote location can make a diagnosis. This information and the examination result can also be stored in a storage medium such as a hard disk, an optical disk, or a flash memory, or can be recorded on a recording medium such as a film by a film processor.

[0062] As described above, the radiation imaging device 200 and the radiation source 210 are disposed so that the radiation irradiated from the radiation source 210 to the radiation imaging panel 100 travels from the main surface 161 to the main surface 162 of the substrate 111 of the radiation imaging panel 100. For this reason, the radiation emitted from the radiation source 210 first enters the scintillator 121 (the scintillator on the radiation incident side) of the scintillators 121, 141. The radiation not absorbed in the scintillator 121 then enters the scintillator 141. Since FIG. 7 focuses on the arrangement of the main surfaces 161, 162 of the substrate 111, the photoelectric conversion unit 112, and the scintillators 121, 141 relative to the radiation source 210, some of the configuration of the radiation imaging panel 100 described above is omitted.

[0063] 7, the tube voltage of the radiation source 210 may be set to about 60 kV to 130 kV. Therefore, the above-mentioned radiation imaging panel 100 may be suitable for radiation having a maximum incident energy value of 60 keV or more and 130 keV or less. For example, the radiation imaging panel 100 (radiation imaging system SYS) may be driven under the radiation quality condition of RQA5.

[0064] With the above configuration, the radiation imaging device 200 and the radiation imaging system SYS using the radiation imaging panel 100 that achieves both improved MTF and improved DQE are realized.

[0065] The disclosure of the present specification includes the following radiation imaging panel, radiation imaging device, and radiation imaging system.

[0066] (Item 1) A radiation imaging panel including a substrate having a first main surface and a second main surface, a photoelectric conversion unit disposed on the first main surface, a first scintillator disposed so as to cover the photoelectric conversion unit, and a second scintillator disposed so as to cover the second main surface, The thickness of the substrate is 50 μm or less, the first scintillator is composed of columnar crystals and has a film thickness of 300 μm or more and 800 μm or less; 2. A radiation imaging panel comprising: a second scintillator that is made of granular crystals and has a thickness that is 20% to 70% of the thickness of the first scintillator.

[0067] (Item 2) 2. The radiation imaging panel according to item 1, wherein the sum of the film thickness of the first scintillator and the film thickness of the second scintillator is 1100 μm or less.

[0068] (Item 3) the first scintillator includes an alkali metal halide compound; 3. The radiation imaging panel according to item 1 or 2, wherein the second scintillator contains a metal oxysulfide.

[0069] (Item 4) the first scintillator includes cesium iodide; 4. The radiation imaging panel according to claim 1, wherein the second scintillator contains gadolinium oxysulfide.

[0070] (Item 5) 5. The radiation imaging panel according to any one of items 1 to 4, further comprising a first reflective layer disposed so as to cover the first scintillator.

[0071] (Item 6) 6. The radiation imaging panel according to item 5, wherein the first reflective layer is a resin to which a dye or metal oxide particles are added.

[0072] (Item 7) 7. The radiation imaging panel according to item 5 or 6, further comprising a protective layer disposed so as to cover the first reflective layer.

[0073] (Item 8) 8. The radiation imaging panel of claim 7, wherein the protective layer comprises a metal sheet.

[0074] (Item 9) 9. The radiation imaging panel according to any one of items 1 to 8, further comprising a second reflective layer disposed so as to cover the second scintillator.

[0075] (Item 10) 10. The radiation imaging panel of item 9, wherein the second reflective layer contains a white resin.

[0076] (Item 11) 11. The radiation imaging panel according to any one of items 1 to 10, wherein the substrate is flexible.

[0077] (Item 12) 12. The radiation imaging panel according to any one of items 1 to 11, characterized in that the radiation imaging panel is adapted for radiation having a maximum incident energy value of 60 keV or more and 130 keV or less.

[0078] (Item 13) A radiation imaging panel according to any one of items 1 to 12, a control unit for controlling the radiation imaging panel; a signal processing unit for processing a signal output from the radiation imaging panel; 13. A radiation imaging apparatus comprising:

[0079] (Item 14) Item 14. The radiation imaging apparatus according to item 13, a radiation source for irradiating the radiation imaging device with radiation; 1. A radiation imaging system comprising:

[0080] (Item 15) Item 15. The radiation imaging system according to item 14, wherein the radiation imaging device and the radiation source are arranged so that radiation emitted from the radiation source travels from the first principal surface to the second principal surface.

[0081] The invention is not limited to the above-described embodiments, and various modifications and variations are possible without departing from the spirit and scope of the invention. Accordingly, the following claims are appended to apprise the public of the scope of the invention. [Explanation of symbols]

[0082] 100: radiation imaging panel, 111: substrate, 112: photoelectric conversion section, 121, 141: scintillator, 161, 162: main surface

Claims

1. A radiation imaging panel including a substrate having a first main surface and a second main surface, a photoelectric conversion unit disposed on the first main surface, a first scintillator disposed so as to cover the photoelectric conversion unit, and a second scintillator disposed so as to cover the second main surface, The thickness of the substrate is 50 μm or less, The first scintillator is composed of columnar crystals and has a film thickness of 300 μm or more and 800 μm or less, 13. A radiation imaging panel, comprising: said second scintillator being formed of granular crystals and having a thickness which is 20% or more and 70% or less of the thickness of said first scintillator.

2. 2. The radiation imaging panel according to claim 1, wherein the sum of the film thickness of said first scintillator and the film thickness of said second scintillator is 1100 [mu]m or less.

3. the first scintillator includes an alkali metal halide compound; 2. The radiation imaging panel according to claim 1, wherein the second scintillator contains a metal oxysulfide.

4. the first scintillator includes cesium iodide; 2. The radiation imaging panel according to claim 1, wherein the second scintillator contains gadolinium oxysulfide.

5. 2. The radiation imaging panel according to claim 1, further comprising a first reflective layer disposed so as to cover the first scintillator.

6. 6. The radiation imaging panel according to claim 5, wherein the first reflective layer is made of a resin to which a dye or metal oxide particles are added.

7. 6. The radiation imaging panel according to claim 5, further comprising a protective layer disposed to cover the first reflective layer.

8. The radiation imaging panel according to claim 7 , wherein the protective layer comprises a metal sheet.

9. 2. The radiation imaging panel according to claim 1, further comprising a second reflective layer disposed so as to cover the second scintillator.

10. 10. The radiation imaging panel according to claim 9, wherein the second reflective layer contains a white resin.

11. 2. The radiation imaging panel according to claim 1, wherein the substrate is flexible.

12. 2. The radiation imaging panel according to claim 1, wherein the radiation imaging panel is adapted for radiation having a maximum incident energy value of 60 keV or more and 130 keV or less.

13. A radiation imaging panel according to any one of claims 1 to 12, a control unit for controlling the radiation imaging panel; a signal processing unit for processing a signal output from the radiation imaging panel; 13. A radiation imaging apparatus comprising:

14. The radiation imaging apparatus according to claim 13 ; a radiation source for irradiating the radiation imaging device with radiation; 1. A radiation imaging system comprising:

15. 15. The radiation imaging system according to claim 14, wherein the radiation imaging device and the radiation source are arranged so that radiation emitted from the radiation source travels from the first principal surface toward the second principal surface.

Images