X-ray fluorescent plate, X-ray detector, and X-ray inspection apparatus using same

Abstract

Provided is a fluorescent plate configured to convert X-rays into visible light, the fluorescent plate having: a first layer; a second layer; and a third layer that is provided between the first layer and the second layer and contains a phosphor, the phosphor being composed of europium-activated barium fluorochloride, the weight of the phosphor in the third layer being 300 mg / cm2 or more and 600 mg / cm2 or less, and the weight of the phosphor in the third layer being 100 mg / cm2 or less and 600 mg / cm2 or less. The total light transmittance of the first layer and the second layer with respect to the light emission wavelength of 380 nm of the phosphor is 70% or more, respectively.

Description

Technical Field

[0001] Embodiments of the present invention relate to an X-ray fluorescent plate, an X-ray detector, and an X-ray inspection apparatus using the same. Background Art

[0002] Transmission X-ray inspection devices using X-ray transmission and Compton scattering X-ray inspection devices using Compton scattering of X-rays are widely used in airports and the like to deal with terrorist incidents. Such X-ray inspection devices are generally configured to guide X-rays or Compton scattered X-rays that have transmitted the object to be inspected to an X-ray detector, convert the detected X-rays into visible light using a fluorescent substance, detect the intensity of the visible light using a photomultiplier tube, so-called a photomultiplier, and image the inside of the baggage based on the intensity, thereby performing inspection.

[0003] In order to improve the accuracy of baggage inspection, it is necessary to obtain a clearer image, and therefore, it is required to input visible light of sufficient intensity into the photomultiplier. In order to increase the intensity of visible light, it is important to increase the intensity of X-rays irradiated to baggage, etc., or maintain the characteristic of less afterglow, and to improve the conversion efficiency from X-rays to visible light. When converting X-rays to visible light, if a phosphor with high conversion efficiency is used, high-brightness visible light can be obtained, and visible light of sufficient intensity can be input to the photomultiplier. That is, if the fluorescent plate emits more visible light due to X-ray irradiation, a clear image can be obtained in the X-ray inspection device.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2013-851165

[0007] Patent Document 2: Japanese Utility Model Application Laid-Open No. 62-173100 Summary of the invention

[0008] Technical problem to be solved by the invention

[0009] The technical problem to be solved by the present invention is to provide a fluorescent plate which maintains the afterglow characteristics and has high light output.

[0010] Means for solving technical problems

[0011] According to the present embodiment, a fluorescent plate is provided, which is configured to convert X-rays into visible light, and the fluorescent plate comprises: a first layer; a second layer; and a third layer, which is disposed between the first layer and the second layer and contains a fluorescent body, wherein the fluorescent body is composed of europium-activated barium fluoride and has a weight of 300 mg / cm 2Above and 600mg / cm 2 Hereinafter, the total light transmittance of the first layer and the second layer with respect to the emission wavelength of 380 nm of the phosphor is respectively 70% or more. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a perspective view schematically showing the X-ray inspection apparatus according to the present embodiment.

[0013] Figure 2 It is a schematic cross-sectional view showing the structure of the scattered X-ray detector according to the present embodiment.

[0014] Figure 3 It is a schematic diagram showing the structure of the transmission X-ray detector according to this embodiment.

[0015] Figure 4 1 is a schematic cross-sectional view showing a fluorescent plate according to this embodiment.

[0016] Figure 5 This is a diagram showing the relationship between the concentration of europium in the phosphor and the relative light output of the phosphor plate according to the present embodiment.

[0017] Figure 6 This is a diagram showing the relationship between the europium concentration of the phosphor and the afterglow characteristics of the phosphor plate according to the present embodiment.

[0018] Figure 7 This is a graph showing the relationship between the phosphor weight and the relative light output of the phosphor layer according to the present embodiment.

[0019] Figure 8 This is a graph showing the relationship between the phosphor weight and the relative light output of the phosphor layer according to the present embodiment. DETAILED DESCRIPTION

[0020] Below, while referring to the attached Figure 1 The present embodiment is described while the same reference numerals are marked on the same parts in the drawings and their detailed description is appropriately omitted, and different parts are described. In addition, the drawings are schematic or conceptual diagrams, and the relationship between the thickness and width of each part, the ratio of the size between the parts, etc. may not be the same as the actual one. In addition, even when representing the same part, there is a case where the size and ratio of each other are represented differently depending on the drawings.

[0021] Figure 1 FIG. 1 is a perspective view schematically showing an X-ray inspection apparatus according to this embodiment. Figure 1In the X-ray inspection device, an X-ray tube 1 is provided as an X-ray irradiation unit. The X-ray tube 1 emits X-rays within a range of an X-ray tube voltage of 140 kV or more and 180 kV or less. A more preferred X-ray tube voltage is 160 kV. Conventionally, the X-ray tube voltage was used at 120 kV, but by using the fluorescent plate of the present embodiment described later, a value larger than the conventional X-ray tube voltage is used, thereby enabling a clearer image to be obtained. The emitted X-ray A is collimated by a slit having a predetermined width in a linear collimator 2. The collimated X-ray B is shaped into a pencil shape that repeatedly performs linear motion by a rotating collimator 3 having a plurality of slits in a radial direction. The pencil-beam-shaped X-ray C irradiates an object to be inspected, such as a baggage 5, which is moved by a conveyor 4, while scanning. The baggage 5 moves at a speed corresponding to the detection sensitivity of the X-rays.

[0022] The Compton scattered X-rays D, which are X-rays reflected by the baggage 5, are detected by the scattered X-ray detector 6. In addition, the X-rays E that have passed through the baggage 5 are detected by the transmission X-ray detector 7. The Compton scattered X-rays D detected by the scattered X-ray detector 6 and the transmission X-rays E detected by the transmission X-ray detector 7 are measured as continuous intensity values. Based on the X-ray intensity, the state of the interior of the baggage 5 is visualized and displayed on a display unit such as a liquid crystal display (not shown). The interior of the baggage 5 is inspected by the displayed image.

[0023] Figure 2 2 is a schematic cross-sectional view showing the structure of the scattered X-ray detector 6 according to the present embodiment. Figure 2 As shown, two scattered X-ray detectors 6 are arranged with a gap therebetween for passing pencil-beam X-rays C. The arrangement and number of scattered X-ray detectors 6 are not limited thereto, as long as they can pass X-rays C and allow scattered X-rays from baggage 5 to enter.

[0024] The scattered X-ray detector 6 has a shell-shaped detector body 8. The detector body 8 has an X-ray incident portion 8a for the Compton scattered X-ray D to be incident on the surface facing the luggage 5. The X-ray incident portion 8a is made of a material that transmits X-rays, such as resin. In order to maintain the strength of the detector body 8, the other part 8b of the detector body 8 other than the X-ray incident portion 8a is made of, for example, aluminum. The other part 8b has a surface that is inclined relative to the surface of the X-ray incident portion 8a. The one surfaces of the two scattered X-ray detectors 6 are arranged to face each other, and these surfaces constitute a gap for the passage of X-rays C. The outer surface of the other part 8b of the detector body 8 is covered with an X-ray shielding member 9 such as lead. This is to eliminate the influence of X-rays from the outside. A transmissive fluorescent plate 10 that directs the light emission direction toward the inside of the detector body 8 is provided inside the X-ray incident portion 8a. In addition, a reflective fluorescent plate 11 is provided inside the other part 8b of the detector body 8. A photomultiplier 12 is provided as a photoelectric conversion unit on another surface perpendicular to the surface of the X-ray incident portion 8a. The photomultiplier 12 has a peak of light sensitivity near 400 nm, and for example, R-1307 (trade name) manufactured by Hamamatsu Photonics Co., Ltd. is used. In addition, the structure and shape of the detector body 8, the type of the photomultiplier 12, etc. are not limited to these.

[0025] The Compton scattered X-ray D1 incident on the X-ray incident portion 8a of the detector body 8 is irradiated onto the transmission type fluorescent plate 10. The transmission type fluorescent plate 10 emits visible light a corresponding to the selected fluorescent substance by the irradiation of the Compton scattered X-ray D1. The visible light a is radiated toward the inside of the detector body 8. In addition, the reflective type fluorescent plate 11 emits visible light b corresponding to the selected fluorescent substance by the irradiation of the Compton scattered X-ray D2 that has passed through the X-ray incident portion 8a and the fluorescent plate 10. The visible light b is radiated toward the inside of the detector body 8. The visible lights a and b are detected by the photomultiplier 12, and the total intensity of the visible lights a and b is measured. In this way, the intensity of the Compton scattered X-ray incident on the scattered X-ray detector 6 is obtained. By detecting the Compton scattered X-ray, objects mainly composed of elements with small atomic numbers, such as plastic products, can be distinguished.

[0026] Figure 31 is a schematic diagram showing the structure of the transmission X-ray detector 7 of the present embodiment. The transmission X-ray detector 7 is configured so that the X-ray E that has passed through the object to be inspected enters the slit-shaped window 15 of the transmission X-ray detector 7. The transmission X-ray detector 7 has the window 15 of the elongated slit so that the X-ray E that has passed through the object to be inspected can be efficiently incident on the inside of the transmission X-ray detector 7. The window 15 is covered with a material 16 with little X-ray absorption, such as a plastic film or a carbon plate. The fluorescent plate 17 is provided on a setting plate 18 provided inside the transmission X-ray detector 7. The setting plate 18 is preferably transparent in order to efficiently extract the light emitted by the fluorescent plate 17 to the setting plate 18 side by the irradiation of the X-ray E. In order to emit light efficiently, the fluorescent plate 17 is provided to be inclined relative to the irradiation direction of the X-ray E to increase the irradiated area. In addition, the other parts of the transmission X-ray detector 7 except the window 15 are made of, for example, aluminum to maintain strength. The inner surface of the transmission X-ray detector 7 is white in order to reflect and focus the light on the photomultiplier 19, and is made of, for example, white paint or a white film. The outer surface of the detector body 8-1 other than the window 15 is covered with an X-ray shielding member 9-1 such as lead. This is to eliminate the influence of X-rays from the outside. A photomultiplier 19 as a photoelectric conversion mechanism is provided in the transmission X-ray detector. The photomultiplier 19 has a peak of light sensitivity near 400nm, for example, R-1307 (trade name) manufactured by Hamamatsu Photonics Co., Ltd. is used. In addition, the structure, shape, type of photomultiplier 19, etc. of the transmission X-ray detector 7 are not limited to this. As described above, the scattered X-ray detector 6 and the transmission X-ray detector 7 are provided with a fluorescent plate 10 and a fluorescent plate 17 that convert X-rays into visible light. The fluorescent plate 10 and the fluorescent plate 17 are described below.

[0027] Figure 4 1 is a schematic cross-sectional view showing the fluorescent plate 10 of this embodiment. In this embodiment, the transmissive fluorescent plate 10 used in the scattered X-ray detector 6 is described, but the fluorescent plate 17 of the transmissive X-ray detector 7 may also have the same structure and shape. Figure 4 As shown, the fluorescent plate 10 includes, for example, a support (first layer) 21, a protective layer (second layer) 22, and a fluorescent layer (third layer) 23. The fluorescent layer 23 contains, for example, fluorescent particles and a binder. The binder is generally a resin binder, and various organic resins are used. The fluorescent layer 23 is formed by applying a slurry mixed with fluorescent particles, a binder, and an organic solvent on the support 21.

[0028] The phosphor layer 23 includes phosphor particles composed of europium-activated barium fluoride chloride phosphor BaFCl:Eu. A portion of europium may be substituted with Ce, Yb, etc. In addition, a portion of fluorine and chlorine may be substituted with Br, I, etc. In the scattered X-ray detector 6, a photomultiplier 12 having a spectral sensitivity characteristic near 400nm is generally used. Therefore, as a phosphor that converts X-rays into visible light, a phosphor having a peak of a light emission wavelength near 400nm is preferred for combination with the photomultiplier 12. The light emission spectrum of the europium-activated barium fluoride chloride phosphor has a peak of a light emission wavelength near 380nm and is a wide waveform, so it has good compatibility with the photomultiplier 12. By using the europium-activated barium fluoride chloride phosphor, it is possible to provide an X-ray fluorescence plate with high conversion efficiency from X-rays to visible light and high output.

[0029] The weight per unit area of ​​the phosphor contained in the phosphor layer 23 is preferably 300 mg / cm 2 Above and 600mg / cm 2 If the weight of the phosphor is less than 300 mg / cm 2 , the element capability of the fluorescent plate 10 is poor with respect to the irradiation X-ray irradiated at the X-ray tube voltage of 160 kV, so a part of the irradiation X-ray that has not been wavelength-converted into visible light in the fluorescent layer 23 enters the photomultiplier 19, generating noise. As a result, the S / N ratio of the X-ray detector deteriorates. In addition, if the X-ray detector voltage exceeds 600 mg / cm 2 , the light output is reduced. This is believed to be because the thickness of the phosphor layer 23 increases and X-rays are difficult to transmit, or the visible light generated by X-ray irradiation is difficult to reach the photomultiplier 19 due to self-absorption of the phosphor layer 23. 2 Above and 600mg / cm 2 In the following range, the light output increases. When the light output when irradiating X-rays with an X-ray tube voltage of 120 kV using a conventional fluorescent plate with a small phosphor weight per unit area is set to 100%, the fluorescent plate 10 with a phosphor weight of the present embodiment is used to irradiate X-rays with an X-ray tube voltage of 160 kV, thereby obtaining a relative light output of more than 150%. That is, compared with the conventional fluorescent plate, more than 1.5 times the light output can be obtained. This is because the fluorescent plate 10 of the present embodiment can efficiently and effectively convert the wavelength of visible light with respect to the X-rays with a greater intensity than before. In addition, even in the range of X-ray tube voltage of 140 kV to 180 kV, by using the fluorescent plate 10 with a phosphor weight of the present embodiment, the same relative light output as the case of X-ray tube voltage of 160 kV can be obtained. Details are described in the embodiments described later.

[0030] As for the manufacturing method of the fluorescent plate 10, especially the manufacturing method of the fluorescent layer 23, various experiments and investigations such as the development of fluorescent solution and the strengthening of coating conditions were repeatedly conducted. As a result, the boiling point of the solvent of the fluorescent solution was set below 100°C, the amount of the solvent was set to 2 / 3 of the conventional amount, and the line speed was reduced to 1 / 3 of the coating conditions. As a result, even when the weight of the fluorescent material was 300 mg / cm 2 In the above case, a fully dried phosphor layer 23 can be formed on the support 21. In addition, in the conventional manufacturing method, if a phosphor layer 23 with a large phosphor weight, i.e., a large thickness, is to be formed, insufficient drying occurs in the drying step after the phosphor layer 23 is applied to the support, and the phosphor plate 10 cannot be manufactured.

[0031] The average particle size of the particles of the europium-activated barium fluoride phosphor of the phosphor layer 23 is preferably not less than 3 μm and not more than 6 μm. By increasing the average particle size of the phosphor particles, the phosphor layer 23 has transparency, so that the visible light converted from the X-rays can be taken out to the outside of the fluorescent plate 10 without being absorbed in the phosphor layer 23. Therefore, the light output of the fluorescent plate 10 can be increased. On the other hand, if the average particle size becomes larger, the disadvantage of poor yield in the manufacture of the phosphor occurs. Considering the above situation, the average particle size is preferably not more than 6 μm. If the average particle size becomes smaller, the visible light is attenuated in the phosphor layer 23 due to self-absorption of the phosphor layer 23, so the light output of the fluorescent plate 10 is reduced. Therefore, the average particle size is preferably not less than 3 μm.

[0032] The europium concentration of the europium-activated barium fluoride phosphor is preferably 0.3 wt% or more and 1.5 wt% or less. Within this concentration range, when irradiated with X-rays at an X-ray tube voltage of 140 kV to 180 kV, a relative light output exceeding 140% can be obtained. In addition, the relative light output is calculated by taking the light output when measured at an X-ray tube voltage of 160 kV using a conventional fluorescent plate as 100%. The details are described in the Examples described later.

[0033] Generally, the afterglow characteristics of the phosphor used in the X-ray inspection device are preferably such that the light output of the fluorescent plate 10 after 20ms after the X-ray irradiation is less than 0.06% of the light output at the time of irradiation. If this value is reached, a clear image without afterimage can be obtained in the X-ray inspection device. In this embodiment, the concentration of europium is greater than 0.3 wt % when the light output is less than 0.06%, and the afterglow characteristics are preferably obtained within this range. Based on the above, if the relative light output of the fluorescent plate 10 and the maintenance of the afterglow characteristics of the phosphor are considered, the europium concentration range of the phosphor is preferably greater than 0.3 wt % and less than 1.5 wt %.

[0034] The support 21 and the protective layer 22 of this embodiment are preferably light-transmitting. The total light transmittance of the support 21 and the protective layer 22 is preferably 70% or more, and more preferably 85% or more in order to obtain a greater light output. When the total light transmittance is less than 70%, the light output of the fluorescent plate 10 is reduced. Conventional fluorescent plates are provided with a support having light reflectivity, and the light emitted in the fluorescent layer is guided to the protective layer side provided on the opposite side of the support by the reflection of the support, so that the amount of light reaching the photomultiplier is increased. The material of the support uses a white film having a light reflectivity of 70% or more. However, the following problem arises: when the emitted light is reflected by the support and guided to the protective layer side, self-absorption occurs in the fluorescent layer, and a certain amount of light is lost. In this embodiment, the support 21 and the protective layer 22 are light-transmitting, thereby enabling the light emitted by the fluorescent layer 23 to be taken out to the outside of the fluorescent plate 10 through the support 21 and the protective layer 22. Therefore, the fluorescent plate 10 can obtain a high light output. A light-transmitting material such as a transparent plastic film can be used as the material of the support 21 and the protective layer 22. For example, transparent polyethylene terephthalate is preferably used.

[0035] The thickness of the support 21 and the protective layer 22 is preferably not less than 188 μm and not more than 350 μm. When the thickness of the support 21 and the protective layer 22 is less than 188 μm, the strength of the fluorescent plate 10 cannot be guaranteed and it is easy to break. In addition, from the viewpoint of strength, the thickness of the support 21 and the protective layer 22 is sufficient as long as 350 μm, and making them unnecessarily thick will increase the volume of the X-ray detector, which is not preferred.

[0036] Hereinafter, examples and comparative examples of the fluorescent plate 10 according to the present embodiment and their evaluation results will be described.

[0037] (Example A)

[0038] The fluorescent plate 10 is manufactured by coating a slurry obtained by mixing a fluorescent substance with a binder and an organic solvent on a transparent polyethylene terephthalate support 13 by a doctor blade coater or the like and drying the slurry to form a fluorescent substance layer 23, and laminating a transparent polyethylene terephthalate protective layer 22 on the fluorescent substance layer 23 by a punching machine or the like. The fluorescent substance uses europium-activated barium fluoride, the average particle size is set to 4 μm, and the europium concentration is set to 0.75% by weight. The fluorescent substance weight of the fluorescent substance layer 23 is 300 mg / cm 2 The total light transmittance of the support 21 and the protective layer 22 is 70%.

[0039] Figure 5The figure shows the relationship between the europium concentration of the europium-activated barium fluoride phosphor of the phosphor layer 23 and the relative light output of the phosphor plate 10. In the measurement of the relative light output, the phosphor plate 10 is irradiated with X-rays at an X-ray tube voltage of 160 kV. As a reference value for the relative light output, the average particle size of the europium-activated barium fluoride phosphor is about 4 μm, and the phosphor weight of the phosphor layer 23 is 250 mg / cm 2 The value of the light output measured by irradiating the existing fluorescent plate 10 with an X-ray tube voltage of 160 kV and a europium concentration of 0.75 wt % and a support 21 with a light reflectivity of 70% is set to 100%. The total light transmittance represents the transmittance relative to the main emission wavelength of 380 nm of the europium-activated barium fluoride chloride phosphor. Line 101 represents the measurement result. Figure 5 As shown in the table, when the europium concentration of the europium-activated barium fluorochloride phosphor is 0.3 wt% or more and 1.5 wt% or less, the relative light output exceeds 140%. Although not shown in the table, within this concentration range, even when the X-ray tube voltage is changed within the range of 140 kV to 180 kV to irradiate X-rays, a relative light output value exceeding 140% is also shown.

[0040] Figure 6 The figure shows the relationship between the europium concentration of the europium-activated barium fluoride phosphor of the phosphor layer 23 and the afterglow characteristics of the phosphor plate 10. In the measurement of afterglow, the light output of the phosphor plate 10 after 20ms after X-ray irradiation is measured and expressed as a relative value relative to the light output during X-ray irradiation as 100%. Line 102 shows the measurement result. Figure 6 As shown, the optical output power shows that the europium concentration is 0.06% or less and is 0.3% by weight or more.

[0041] (Example B)

[0042] Figure 7 The relationship between the phosphor weight of the phosphor layer 23 and the relative light output of the phosphor plate 10 is shown in comparison with the comparative example. Figure 7 Part of the data plotted in is divided into examples and comparative examples. Figure 7 In the determination of the reference values ​​shown in Table 1, the average particle size of the europium-activated barium fluoride phosphor used was about 4 μm, the europium concentration was 0.75 wt%, and the phosphor weight was 250 mg / cm 2, a conventional fluorescent plate having a light reflectivity of 70% for the support 21, and an X-ray irradiation voltage of 120 kV was used. The measured value of the light output of the X-ray detector in the measurement of the reference value was set to 100%, and the relative value of the light output of the X-ray detector of the embodiment and the comparative example was measured. In the phosphor layer 23 of the embodiment, the average particle size of the europium-activated barium fluoride chloride phosphor was about 4 μm, the concentration of europium was 0.75% by weight, and the total light transmittance of the support 21 and the protective layer 22 was 70% (Examples 1 to 4) or 85% (Examples 5 to 8). Line 103 shows the measurement result when the total light transmittance was 85%, and line 104 shows the measurement result when the total light transmittance was 60%. In addition, the measurement was performed using an X-ray irradiation voltage of 160 kV. Transparent polyethylene terephthalate was used for the support 21 and the protective layer 22, and the thickness of each was set to 250 μm. In the comparative example, the total light transmittance of the support 21 and the protective layer 22 was set to 60%, and the same fluorescent plate as in the example was used for measurement. In addition, the light reflectance of the support 21 was set to 70%, and the same fluorescent plate as in the example was used for measurement. Line 105 shows the measurement result when the light reflectance is 70%, and line 106 shows the measurement result when the total light transmittance is 60%.

[0043] [Table 1]

[0044] Table 1

[0045]

[0046] like Figure 7 As shown in Table 1, in Examples 1 to 8, the fluorescent plate with a total light transmittance of 85% for the support 21 and the protective layer 22 shows a higher value in relative light output than the fluorescent plate with a total light transmittance of 70%. In addition, the greater the weight of the fluorescent material in the fluorescent material layer 23, the greater the relative light output. If the weight of the fluorescent material is 300 mg / cm 2 If the weight of the phosphor is 500 to 600 mg / cm 2 The relative light output is the largest, exceeding 600mg / cm 2 , the relative light output decreases.

[0047] exist Figure 7 The less the phosphor weight is, the smaller the 2 , the smaller the relative light output is, and eventually it is less than 150%.

[0048] In the fluorescent plate of the comparative example, the total light transmittance of the support 21 and the protective layer 22 is 60%, and the light reflectance of the fluorescent plate and the support 21 are 70% and the weight of the fluorescent plate is approximately 300 mg / cm 2 , relative light output shows a maximum value, if it exceeds 300mg / cm 2 , the relative light output shows a constant value or decreases. In addition, the maximum value of the relative light output is about 130%, which is a value lower than that of Examples 1 to 8.

[0049] Regarding the method for manufacturing the phosphor layer 23 in Examples 1 to 8, the boiling point of the solvent of the phosphor solution is set to 100°C or less, and the amount of the solvent is reduced to 2 / 3 of the conventional amount. In addition, the line speed is reduced to 1 / 3 in the coating conditions. Thus, a phosphor weight of 300 mg / cm 2 The above-mentioned phosphor layer 23 is sufficiently dried.

[0050] In Examples 1 to 8, measurements were performed when the X-ray tube voltage was 160 kV, but the same experiment was performed when the X-ray tube voltage was greater than 140 kV and less than 180 kV. As a result, the relative light output of the fluorescent plate 10 showed the same value as when the X-ray tube voltage was 160 kV (not shown).

[0051] (Example C)

[0052] Figure 8 The relationship between the phosphor weight of the phosphor layer 23 and the relative light output of the phosphor plate 10 when the X-ray tube voltage is 120 kV and 160 kV is shown. The phosphor plate 10 is the same as in Examples 1 to 4, and the average particle size of the europium-activated barium fluoride phosphor is about 4 μm, the europium concentration is 0.75% by weight, and the total light transmittance of the support 21 and the protective layer 22 is 70%. In addition, the measurement is performed using X-rays irradiated at an X-ray tube voltage of 120 kV or 160 kV. In addition, regarding the reference value of the relative light output, the average particle size of the europium-activated barium fluoride phosphor is about 4 μm, the europium concentration is 0.75%, and the phosphor weight is 250 mg / cm 2 , the light reflectivity of the support 21 is 70%, and the measured value of the light output when the X-ray tube voltage is 120 kV is set to 100%. Line 107 shows the measurement result when the X-ray tube voltage is 160 kV, and line 108 shows the measurement result when the X-ray tube voltage is 120 kV. When the X-ray tube voltage is 120 kV, the phosphor weight is 300 mg / cm 2 ~400mg / cm 2, the relative light output is the maximum, and its value is about 130%. If the phosphor weight exceeds 400mg / cm 2 On the other hand, when the X-ray tube voltage is 160 kV and the phosphor weight is 300 mg / cm 2 Above and 600mg / cm 2 In the fluorescent plate 10 within the following range, the relative light output is 150% or more.

[0053] In this embodiment, the phosphor layer 23 of the phosphor plate 10 preferably includes europium-activated barium fluoride chloride, and the phosphor weight is 300 mg / cm 2 Above and 600mg / cm 2 The support 21 and the protective layer 22 preferably have a total light transmittance of 70% or more relative to the main emission wavelength of 380 nm of the phosphor. In this case, the relative light output of the fluorescent plate 10 becomes 1.5 times that of the conventional fluorescent plate as a reference value, and an X-ray detector with good afterglow characteristics and a small S / N ratio and an X-ray inspection device capable of obtaining a clear image can be obtained.

[0054] The embodiments of the present invention have been described, but these embodiments are presented as examples and are not intended to limit the scope of the invention. These new embodiments can be implemented in various other ways, and various omissions, substitutions, and changes can be made without departing from the scope of the main purpose of the invention. These embodiments and their variations are included in the scope and main purpose of the invention, and are included in the invention described in the claims and the scope of their equivalents.

[0055] [Explanation of Reference Numerals]

[0056] 1…X-ray tube; 2…linear collimator; 3…rotating collimator; 4…conveyor; 5…baggage; 6…scattered X-ray detector; 7…transmitted X-ray detector; 8…detector body; 8a…X-ray incident part; 8b…other parts; 9…X-ray shielding member; 10, 11, 17…fluorescent plate; 12, 19…photomultiplier; 15…window; 16…material; 18…setting plate; 21…support; 22…protective layer; 23…fluorescent layer.

Claims

1. A fluorescent plate configured to convert X-rays into visible light, The fluorescent plate has: First floor; Second level; and The third layer is disposed between the first layer and the second layer and includes a phosphor. The phosphor is composed of europium activated barium fluoride and chloride, and the weight of the phosphor in the third layer is 300 mg / cm 2 Above and 600mg / cm 2 Hereinafter, the total light transmittance of the first layer and the second layer with respect to the emission wavelength of 380 nm of the phosphor is respectively 70% or more.

2. The X-ray fluorescent plate according to claim 1, wherein The thickness of the first layer and the second layer are respectively 188 μm or more and 350 μm or less.

3. The X-ray fluorescent plate according to claim 1, wherein The average particle size of the phosphor is greater than or equal to 3 μm and less than or equal to 6 μm.

4. The X-ray fluorescent plate according to claim 1, wherein The europium concentration of the phosphor is greater than or equal to 0.3 wt % and less than or equal to 1.5 wt %.

5. The X-ray fluorescent plate according to claim 1, wherein The first layer and the second layer each include polyethylene terephthalate.

6. The X-ray fluorescent plate according to claim 1, wherein The first layer is a support, the second layer is a protective layer, and the third layer is a phosphor layer.

7. An X-ray detector comprising: A detector body having an incident portion for X-rays; a fluorescence generating mechanism, disposed at the incident portion, comprising a fluorescent plate as described in any one of claims 1 to 6; and The photoelectric conversion mechanism is arranged on the detector body.

8. An X-ray inspection device comprising: An X-ray irradiation mechanism irradiates the object to be inspected with X-rays; An X-ray detection mechanism, comprising the X-ray detector according to claim 7, detecting transmitted X-rays or Compton scattered X-rays from the object to be inspected; as well as A mechanism for imaging the interior of the inspection object based on the X-ray intensity measured by the X-ray detection mechanism.

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