JP2012108158A - Radiographic image detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve light conversion efficiency in a radiographic image detector that detects visible light converted by a wavelength conversion layer and converts it into an image signal representing a radiographic image.SOLUTION: In the radiographic image detector in which a detector 31 and a wavelength conversion layer 32 are disposed in an order from a side to which a radiation passing through a subject is applied, the wavelength conversion layer 32 is formed by superposing a first phosphor layer 32a and a second phosphor layer 32b. The first phosphor layer 32a and the second phosphor layer 32b are so formed that a total average particle size of phosphors contained in the second phosphor layer 32b becomes larger than the total average particle size of the phosphors contained in the first phosphor layer 32a; and, from the side to which the radiation passing through the subject is applied, the second phosphor layer 32b and the first phosphor layer 32a are disposed in this order.

Description

  The present invention relates to a radiation image detector that detects light converted by a wavelength conversion layer and converts it into an image signal representing a radiation image.

  2. Description of the Related Art Conventionally, in the medical field and the like, various radiological image detectors that record a radiographic image related to a subject by irradiation with radiation that has passed through the subject have been proposed and put into practical use.

  As the radiation image detector as described above, for example, a radiation image detector using a semiconductor that generates a charge upon irradiation of radiation has been proposed. An electric reading type using a thin film transistor (TFT), a charge coupled device (CCD), a complementary metal oxide semiconductor (CMOS) sensor, or the like has been proposed.

  In addition, the radiation image detector as described above may be a direct conversion type that converts radiation into direct charge in a semiconductor layer and stores it, or radiation is once converted into light by a phosphor and the converted light is converted into a photo. An indirect conversion method has been proposed in which the charge is converted and stored by a diode or the like.

  For example, Patent Document 1 to Patent Document 3 propose an indirect conversion radiation image detector in which a phosphor layer and a detection substrate on which a large number of detection elements are arranged are stacked.

  On the other hand, in the radiation image detectors described in Patent Document 1 to Patent Document 3, when radiation is incident from the phosphor layer side, the light converted by the phosphor layer is absorbed by the phosphor layer itself, and the sensitivity is deteriorated. There is a possibility that the image is blurred due to light scattering in the phosphor layer.

  Therefore, Patent Document 4 proposes a radiation image detector in which radiation is incident not from the phosphor layer side but from the detection substrate side.

JP 2003-215253 A JP 2004-239722 A JP 2006-258618 A Japanese Patent No. 3333278

  Here, in order to acquire a high-quality radiographic image in the indirect conversion type radiographic image detector as described above, it is necessary to increase the light conversion efficiency with respect to the radiation dose incident on the radiographic image detector. For this purpose, it is conceivable to use a high-sensitivity, large-sized particle phosphor, or to increase the thickness of the phosphor layer.

  However, when large-sized particles are dispersed over the entire phosphor layer, there is a problem that the liquid physical properties change and the liquid can easily drip. In addition, when the thickness of the phosphor layer is simply increased, there is a problem that the spread of light emission of the phosphor is increased and the image is blurred.

  Further, the radiation image detector in which radiation is incident from the detection substrate side like the radiation image detector described in Patent Document 4 has the same problem as described above, and the radiation image detector having such a structure. The structure of the phosphor layer adapted to the above has not been clarified so far.

  In view of the above circumstances, the present invention provides a radiation image detector capable of improving light conversion efficiency and obtaining a high-quality image in an indirect conversion type radiation image detector in which radiation is incident from the detection substrate side. The purpose is to provide.

  The radiological image detector of the present invention detects a radiographic image by detecting a wavelength conversion layer containing a phosphor that receives radiation and converting the radiation into light having a longer wavelength, and light converted by the wavelength conversion layer. A radiation image detector having a detector and a wavelength conversion layer arranged in this order from the side irradiated with radiation, wherein the wavelength conversion layer is a first phosphor. The first phosphor layer and the second phosphor layer have a total average particle diameter of phosphors contained in the second phosphor layer. The second phosphor layer and the first phosphor layer are formed so as to be larger than the total average particle diameter of the phosphors contained in the first phosphor layer, and from the side irradiated with radiation. Are arranged in this order.

  Here, the “wavelength conversion layer” converts radiation into light having a longer wavelength, but preferably converts near-infrared light, visible light, and near-infrared light. More preferably, the light is converted into visible light.

  In the radiation image detector of the present invention, the second phosphor layer may be a layer in which phosphors having different average particle diameters are mixed.

  Further, the second phosphor layer is mixed with the first phosphor having the first average particle diameter and the second phosphor having the second average particle diameter larger than the first average particle diameter. The weight ratio of the first phosphor: second phosphor can be 2: 8 to 4: 6.

  The first phosphor may have an average particle diameter of 1 μm or more and less than 5 μm, and the second phosphor may have an average particle diameter of 5 μm or more and 12 μm or less.

  Further, the first phosphor layer can be a layer in which phosphors having different average particle diameters are mixed.

  Further, the first phosphor layer is mixed with a third phosphor having a third average particle diameter and a fourth phosphor having a fourth average particle diameter larger than the third average particle diameter. The weight ratio of the third phosphor to the fourth phosphor can be 8: 2 to 6: 4.

  Moreover, the thing with an average particle diameter of 1 micrometer or more and less than 5 micrometers can be used as a 3rd fluorescent substance, and the thing with an average particle diameter of 5 micrometers or more and less than 12 micrometers can be used as a 4th fluorescent substance.

  In addition, the wavelength conversion layer has a phosphor dispersed in a binder, and the weight ratio of the binder / phosphor in the wavelength conversion layer is distributed so as to gradually decrease toward the center in the thickness direction of the wavelength conversion layer. Can be used.

  Moreover, the wavelength conversion layer can be a laminate of at least the first phosphor layer and the second phosphor layer.

  Moreover, the wavelength conversion layer can be obtained by bonding at least the first phosphor layer and the second phosphor layer by heat compression.

  In addition, the space filling factor of the phosphor in the wavelength conversion layer can be 63% or more.

Further, as the phosphor, particles represented by A ₂ O ₂ S: X (A is any of Y, La, Gd, and Lu, and X is any of Eu, Tb, and Pr) are used. be able to. The phosphor may contain Ce or Sm as a coactivator.

  Here, the above-mentioned “total average particle diameter of phosphors contained in the first phosphor layer” means an average value of the particle diameters of all phosphors contained in the first phosphor layer, “The total average particle diameter of the phosphors contained in the second phosphor layer” means the average value of the particle diameters of all the phosphors contained in the second phosphor layer. The “particle diameter” means a particle diameter measured with a Fisher Sub-Sieve Sizer.

  The “average particle diameter” means an average value of particle diameters measured with a Fisher Sub-Sieve Sizer.

  According to the radiation image detector of the present invention, the wavelength conversion layer is formed by laminating the first phosphor layer and the second phosphor layer, and the first phosphor layer, the second phosphor layer, Is formed such that the total average particle size of the phosphors included in the second phosphor layer is larger than the total average particle size of the phosphors included in the first phosphor layer, and is irradiated with radiation. From the above, the second phosphor layer and the first phosphor layer are arranged in this order, that is, the total average particle diameter of the phosphors contained in the second phosphor layer on which the radiation is incident first. In this case, the radiation is made larger than the total average particle diameter of the phosphors included in the first phosphor layer to which the radiation is incident later. Can be converted.

  Further, radiation that has passed through the second phosphor layer without being converted by the second phosphor layer can be received by the first phosphor layer and converted to light, and the light conversion efficiency can be further improved. Can do. In addition, since the first phosphor layer has a total average particle size of the phosphor smaller than that of the second phosphor layer, the scattering length, which is the average distance from the time the light is scattered to the next time it is scattered, is short. Therefore, it can also function as a reflective layer that reflects the light converted by the second phosphor layer toward the detector, and the light conversion efficiency can be further improved.

  In the radiographic image detector of the present invention, when the second phosphor layer is a layer in which phosphors having different average particle diameters are mixed, a large-sized particle phosphor and a small-sized particle are used. The phosphor space-filling ratio can be improved and the light conversion efficiency can be improved by increasing the ratio of the large-sized phosphor particles.

  In addition, when the first phosphor layer is a layer in which phosphors having different average particle diameters are mixed, a phosphor of a large size particle and a phosphor of a small size particle are mixed to obtain a small size. By increasing the ratio of the phosphor particles, the function as the reflective layer described above can be improved, and the light conversion efficiency can also be improved by the large-sized phosphor particles.

  In addition, the wavelength conversion layer has a phosphor dispersed in a binder, and the weight ratio of the binder / phosphor in the wavelength conversion layer is distributed so as to gradually decrease toward the center in the thickness direction of the wavelength conversion layer. Can be used, the binder ratio in the central portion of the wavelength conversion layer can be reduced, so that the spread of photons in the wavelength conversion layer due to scattering can be suppressed, thereby reducing image blurring. it can.

  Further, in the case where the wavelength conversion layer is bonded to at least the first phosphor layer and the second phosphor layer, the weight ratio of the binder / phosphor in the wavelength conversion layer described above can be simply manufactured. Can be realized. The reason will be described in detail later.

  In addition, when the wavelength conversion layer is bonded to at least the first phosphor layer and the second phosphor layer by heat compression, the space filling rate of the phosphor in the wavelength conversion layer is further improved by compression. And the light conversion efficiency can be further improved.

Schematic configuration diagram of a radiographic imaging apparatus using an embodiment of a radiographic image detector of the present invention Sectional drawing which shows schematic structure of one Embodiment of the radiographic image detector of this invention The figure which shows the top view of the solid state detector The figure which shows the composition of the photodiode section and TFT switch in the solid state detector Schematic diagram showing an example of binder weight distribution in the phosphor layer Schematic diagram showing an example of binder weight distribution in the wavelength conversion layer

  A radiographic imaging apparatus using an embodiment of the radiographic image detector of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram of the radiographic image capturing apparatus.

  The radiation imaging apparatus is a radiation source 1 that emits radiation toward a subject 2 and radiation that is irradiated with radiation that has passed through the subject 2 and that outputs an image signal representing a radiation image of the subject 2 carried by the radiation. An image detector 3, a signal processing unit 4 that performs predetermined signal processing on the image signal output from the radiation image detector 3, and a radiographic image is reproduced based on the image signal that has undergone signal processing in the signal processing unit 4 And a reproducing unit 5 for performing the above operation.

  FIG. 2 is a cross-sectional view showing a configuration of the radiographic image detector 3 in the radiographic image capturing apparatus.

  As shown in FIG. 2, the radiation image detector 3 detects the visible light converted by the wavelength conversion layer 32 and the wavelength conversion layer 32 that receives radiation irradiated through the subject and converts the radiation into visible light. Thus, a solid state detector 31 that converts the image signal into a radiographic image and a support 33 that supports the wavelength conversion layer 32 are provided.

  The radiation image detector 3 includes a solid detector 31, a wavelength conversion layer 32, and a support 33 arranged in this order from the radiation source 1 side, and receives radiation from the solid detector 31 side. It is.

  FIG. 3 is a plan view showing the configuration of the solid state detector 31. As shown in FIG. 3, the solid-state detector 31 includes a plurality of photodiode portions 36 and TFT switches 37 that are two-dimensionally arranged in the XY direction, and a row of photodiode portions 36 and TFT switches 37 that are aligned in the X direction. Provided for each column of the scanning line 31b to which the scanning signal input to each TFT switch 37 of the row is applied, and the photodiode portion 36 and the TFT switch 37 arranged in the Y direction. And a data line 31c from which a pixel signal detected by the photodiode portion 36 flows out.

  The scanning line 31b and the data line 31c are provided so as to be orthogonal to each other, and a photodiode portion 36 and a TFT switch 37 are provided corresponding to the intersection of the scanning line 31b and the data line 31c.

  A gate driver 40 that outputs a scanning signal to each scanning line 31b is connected to one end of each scanning line 31b, and an integrating amplifier 50 that detects a pixel signal flowing out to each signal line is connected to one end of each data line 31c. It is connected. 1 and 2, the gate driver 40 and the integrating amplifier 50 are not shown.

  FIG. 4 is a diagram showing a schematic configuration of each photodiode unit 36 and TFT switch 37 in the solid state detector 31. The photodiode unit 36 photoelectrically converts visible light converted by the wavelength conversion layer 32. The TFT switch 37 is for reading out a charge signal photoelectrically converted in the photodiode section 36 as a pixel signal.

  As shown in FIG. 4, the photodiode portion 36 and the TFT switch 37 are provided on an insulating substrate 31d made of non-alkali glass or the like. The photodiode portion 36 includes a transparent electrode 36a that transmits visible light converted by the wavelength conversion layer 32, a semiconductor layer 36b that functions as a photodiode, and a lower electrode 36c. As the semiconductor layer 36b, for example, a PIN structure can be used. Note that a MIS (Metal Insulator Semiconductor) structure may be used as the photodiode portion. The lower electrode 36c is connected to a drain electrode 37b of a TFT switch 37 described later. In FIG. 4, the photodiode portion 36 and the TFT switch 37 are arranged side by side. However, it is preferable that the photodiode area is increased by overlapping the photodiode portion 36 and the TFT switch 37.

  The TFT switch 37 includes a gate electrode 37a, a drain electrode 37b, a source electrode 37c, a semiconductor layer 37d, and a gate insulating film 37e. The gate electrode 37a is connected to the scanning line 31b, the drain electrode 37b is connected to the lower electrode 36c of the photodiode portion 36 as described above, and the source electrode 37c is connected to the data line 31c. Is. The semiconductor layer 37d is a channel portion of the TFT switch 37, and is a current path connecting the data line 31c and the drain electrode 37b which are turned ON / OFF by the gate voltage.

  As shown in FIG. 2, the wavelength conversion layer 32 is formed by laminating a first phosphor layer 32a and a second phosphor layer 32b. The first phosphor layer 32a and the second phosphor layer 32b both contain a phosphor that converts radiation into visible light, but the total average particle diameter of the phosphor contained in the second phosphor layer 32b. Is formed to be larger than the total average particle size of the phosphors included in the first phosphor layer 32a. Then, as shown in FIG. 2, the second phosphor layer 32b and the first phosphor layer 32a are arranged in this order from the side irradiated with the radiation that has passed through the subject 2.

  Here, the total average particle diameter of the phosphors included in the first phosphor layer 32a means the average value of the particle diameters of all the phosphors included in the first phosphor layer 32a. The total average particle diameter of the phosphors included in the second phosphor layer 32b means the average value of the particle diameters of all the phosphors included in the second phosphor layer 32b. The particle diameter of the phosphor contained in the first phosphor layer 32a and the particle diameter of the phosphor contained in the second phosphor layer 32b are the Fisher Sub-Sieve Sizer. It means the particle diameter measured by.

  More specifically, as the phosphor of the first phosphor layer 32a, for example, a phosphor having an average particle diameter of 1 μm to 5 μm is used, and as the phosphor of the second phosphor layer 32b, for example, an average A phosphor having a particle diameter of 5 μm to 12 μm may be used.

  Here, the average particle diameter means an average value of the particle diameters measured with a Fisher Sub-Sieve Sizer.

In addition, as the material of the phosphor, for example, GOS (Gd ₂ O ₂ S: Tb) particles can be used, and the first phosphor layer 32a and the phosphor are dispersed using a binder such as a resin. A second phosphor layer 32b can be formed. Note that the phosphor material of the first phosphor layer 32a and the second phosphor material may be the same, or phosphors of different materials may be used. In this case, for example, GOS (Gd ₂ O ₂ S: Tb) particles and LOS (Lu ₂ O ₂ S: Tb) particles can be used. In addition, as a phosphor, particles represented by A ₂ O ₂ S: X (where A is any one of Y, La, Gd, and Lu, and X is any one of Eu, Tb, and Pr) are used. Can be used. Further, as the _phosphor, A _{2 O 2} S: can be utilized that include Ce or Sm as a coactivator to X. Further, a mixed crystal phosphor may be used.

Further, the second phosphor layer 32b may be formed from a layer in which phosphors having different average particle diameters are mixed. Specifically, for example, the first phosphor having an average of 1 μm to 5 μm and the second phosphor having an average particle diameter of 5 μm to 12 μm are mixed and dispersed in a resin. The phosphor layer 32b may be formed. At this time, it is desirable that the ratio of the first phosphor to the second phosphor is 2: 8 to 4: 6 by weight. The first phosphor material and the second phosphor material may be the same or different from each other. Specifically, GOS (Gd ₂ O ₂ S: Tb) particles and LOS (Lu ₂ O ₂ S: Tb) particles can be used.

  The first phosphor: second phosphor ratio is derived, for example, by measuring the particle size distribution and assuming that there is a size species having a lognormal distribution corresponding to the number of peaks and fitting it. be able to.

Further, the first phosphor layer 32a may be formed from a layer in which phosphors having different average particle diameters are mixed. Specifically, for example, the first phosphor may be prepared by mixing and dispersing a third phosphor having an average particle diameter of 1 μm to 5 μm and a fourth phosphor having an average particle diameter of 5 μm to 12 μm in a resin. The phosphor layer 32a may be formed. At this time, it is desirable that the ratio of the third phosphor to the fourth phosphor is 8: 2 to 6: 4 by weight. The third phosphor material and the fourth phosphor material may be the same or different from each other. Specifically, GOS (Gd ₂ O ₂ S: Tb) particles and LOS (Lu ₂ O ₂ S: Tb) particles can be used.

  The method for obtaining the third phosphor: fourth phosphor ratio is as described above.

  The wavelength conversion layer 32 is desirably formed so that the weight ratio of the binder / phosphor in the wavelength conversion layer 32 is distributed so as to gradually decrease toward the center in the thickness direction of the wavelength conversion layer 32.

  Moreover, it is desirable that the space filling factor of the phosphor in the wavelength conversion layer 32 is 63% or more. The space filling factor of the phosphor can be obtained as follows. First, a part of the wavelength conversion layer is cut out and the volume is measured. Furthermore, the weight of the phosphor extracted from the wavelength conversion layer using a solvent or the like is measured, and the volume of the phosphor is calculated from the density of the phosphor. Each of the above volume ratios is expressed as the space filling factor of the phosphor. If the composition of the phosphor is unknown, composition analysis is performed and the density is calculated from the constituent elements and the crystal structure.

  In addition, the formation method of the wavelength conversion layer 32 is demonstrated in detail in the Example mentioned later.

  In the radiation image detector of the present embodiment, the wavelength conversion layer is composed of the first phosphor layer 32a and the second phosphor layer 32b as described above. Etc. may be further laminated in the wavelength conversion layer.

  The support 33 has a wavelength conversion layer 32 formed thereon and supports the wavelength conversion layer 32. And what formed the wavelength conversion layer 32 on the support body 33 will be affixed on the solid-state detector 31. FIG. As a material for the support, for example, polyethylene terephthalate having a thickness of 200 μm can be used.

  Next, the operation of the radiographic imaging apparatus using the radiographic image detector of this embodiment will be described.

  First, radiation is emitted from the radiation source 1 toward the subject 2. Then, radiation that passes through the subject 2 and carries a radiographic image of the subject is irradiated from the solid-state detector 31 side of the radiographic image detector 3.

  The radiation irradiated to the radiation image detector 3 passes through the solid detector 31 and is irradiated to the wavelength conversion layer 32. The wavelength conversion layer 32 that has received the radiation converts the radiation into visible light.

  Here, in the radiological image detector 3 of the present embodiment, the second phosphor layer 32b and the first phosphor layer 32a are arranged in this order from the side irradiated with the radiation transmitted through the subject 2 as described above. It is arranged. The total average particle diameter of the phosphor contained in the second phosphor layer 32b to which the radiation is first incident is that of the phosphor contained in the first phosphor layer 32a to which the radiation is incident later. Since it is made larger than the total average particle diameter, radiation can be efficiently converted by visible light in the second phosphor layer 32b.

  Further, the radiation transmitted through the second phosphor layer 32b without being converted by the second phosphor layer 32b can be received by the first phosphor layer 32a and converted into visible light. Further, the first phosphor layer 32a has a total average particle diameter of the phosphor smaller than that of the second phosphor layer 32b, that is, a scattering that is an average distance from the time the light is scattered to the next time it is scattered. Since the length is shortened, it can also function as a reflective layer that reflects visible light converted by the second phosphor layer 32b toward the solid state detector 31 side.

  The visible light converted by the first phosphor layer 32 a and the second phosphor layer 32 b of the wavelength conversion layer 32 is irradiated to the solid state detector 31 and is incident on each photodiode unit 36 of the solid state detector 31. The The visible light incident on the photodiode portion 36 is irradiated onto the semiconductor layer 36b of the photodiode portion 36, and charges are generated in the semiconductor layer 36b.

  At the time of image reading, each scanning line 31b connected to the row of TFT switches 37 arranged in the X direction is sequentially selected in the Y direction by the gate driver 40, and each scanning line 31b is selected from the gate driver 40 with respect to the selected scanning line 31b. An ON signal for turning on the TFT switch 37 is sequentially output.

  When an ON signal is supplied to the scanning line 31b, a gate voltage is applied to the gate electrode 37a of each TFT switch 37 connected to the scanning line 31b, and the region between the drain electrode 37b and the source electrode 37c of the TFT switch 37 is a semiconductor layer. Conduction occurs through 37d, and the TFT switch 37 is turned on.

  As a result, the charge signal generated in the photodiode portion 36 is read out via the TFT switch 37 and flows out to the data line 31c. The charge signal flowing out to each data line 31c is detected as an image signal by the integrating amplifier 50 connected to each data line 31c, and the image signal is output from the integrating amplifier 50 every time the scanning line 31b is selected.

  Then, the image signal output from the radiation image detector 3 is output to the signal processing unit 4, subjected to predetermined signal processing in the signal processing unit 4, and then the processed image signal is output to the reproduction unit 5. .

  Then, in the reproduction unit 5, for example, a radiographic image of the subject 2 is reproduced and displayed on a monitor or a radiographic image is reproduced and recorded on a predetermined recording medium based on the processed image signal.

  Hereinafter, examples of the radiation image detector of the above-described embodiment will be described.

1) Formation of first phosphor layer and second phosphor layer Polyurethane elastomer (Pandex (registered trademark) T-5265HM, manufactured by Dainippon Ink & Chemicals, Inc.) and epoxy resin (jER # 1001, oiled shell epoxy) 14.5% by weight of a mixture (manufactured by Kogyo Co., Ltd.) was dissolved in 85.5% by weight of methyl ethyl ketone (MEK) and sufficiently stirred to form a binder solution.

Then, this binder solution and Gd ₂ O ₂ S: Tb phosphor particles having an average particle diameter of 2.1 μm are mixed as a solid component at a weight ratio of 20:80, dispersed by a propeller mixer, and coated with a phosphor. A liquid was prepared.

  Then, this phosphor coating solution was applied to the surface of a polyethylene terephthalate sheet (temporary support, thickness: 190 μm) coated with a silicone mold release agent using a doctor blade in a width of 430 mm, and then dried. It peeled from the support body and obtained the 1st fluorescent substance layer (thickness: 300 micrometers).

Further, the binder and Gd ₂ O ₂ S: Tb phosphor particles having an average particle diameter of 6.3 μm are mixed as a solid component at a weight ratio of 20:80, and dispersed by a propeller mixer, and then a phosphor coating solution. Was prepared.

  Then, this phosphor coating solution was applied to the surface of a polyethylene terephthalate sheet (temporary support, thickness: 190 μm) coated with a silicone release agent with a doctor blade in a width of 300 mm and dried. It peeled from the support body and obtained the 2nd fluorescent substance layer (thickness: 300 micrometers).

  Here, when the first and second phosphor layers are formed on the temporary support as described above, the phosphor having a large specific gravity settles in the coating film, and the binder molecules are reversed. Move to the top. Since it is further promoted by drying, the distribution of the weight of the binder (binder) in the phosphor layer becomes a distribution that gradually increases from the lower side (temporary support) to the upper side, as shown in FIG. It was.

2) Formation of Support A material having the following composition was added to MEK and mixed and dispersed to prepare a coating solution having a viscosity of 0.02 to 0.05 Pa · s. This coating solution was applied to the surface of a polyethylene terephthalate (PET) sheet (support, thickness: 188 μm, haze: about 27, Lumirror (registered trademark) S-10, manufactured by Toray Industries, Inc.) using a doctor blade and dried. Thus, a conductive layer (layer thickness: 2 μm) was formed.

Conductive agent: SnO ₂ (Sb dope) needle-shaped fine particles (major axis: 0.2-2 μm, minor axis: 0.01
-0.02 μm, FS-10P, manufactured by Ishihara Sangyo Co., Ltd.) MEK dispersion (solid content 30)
500% by weight)
Resin: Saturated polyester resin (Byron 300, manufactured by Toyobo Co., Ltd.) 60 g
Curing agent: Polyisocyanate (Takenate D140N [solid content 75%], Takeshi Mitsui Chemi
6.6g
A material having the following composition was added to a MEK / butyl acetate mixed solvent, mixed and dispersed to prepare a coating solution having a viscosity of 2 to 3 Pa · s. This coating solution was applied to the surface of the conductive layer using a doctor blade and dried to form a light reflecting layer (layer thickness: about 70 μm).

Light reflecting material: high-purity alumina fine particles (average particle size: 0.4 μm, UA-5105,
Showa Denko) 500g
Binder: Soft acrylic resin (Chriscoat (registered trademark) P-1018GS [20% toluene solution], manufactured by Dainippon Ink & Chemicals, Inc.) 112 g
Colorant: Ultramarine (SM-03S, Daiichi Kasei Kogyo Co., Ltd.) 2.5g
Coupling agent: γ-aminopropyltriethoxysilane (KBE903, manufactured by Shin-Etsu Chemical Co., Ltd.) 5 g
3) Formation of wavelength conversion layer On the surface of the reflective layer on the support, the upper side of the first phosphor layer prepared in 1) (the side opposite to the temporary support side during coating formation) is in contact with the reflective layer. Further, the second phosphor layer produced in 1) is placed on the first phosphor layer so that the lower side (the temporary support side during coating formation) is in contact with the first phosphor layer. This was heated and compressed using a calender machine at a total load of 2300 kg, an upper roll of 45 ° C., a lower roll of 45 ° C., and a feed rate of 0.3 m / min. As a result, the first phosphor layer and the second phosphor layer were completely fused to the reflective layer on the support.

  Here, when the wavelength conversion layer is formed by superimposing the first and second phosphor layers on the support as described above, the distribution of the weight of the binder in the wavelength conversion layer is as shown in FIG. The distribution gradually decreased toward the center of the wavelength conversion layer 32 in the thickness direction. That is, the distribution of the weight ratio of the binder / phosphor in the wavelength conversion layer 32 is a distribution that gradually decreases toward the center of the wavelength conversion layer 32 in the thickness direction.

  In the present embodiment, the first phosphor layer and the second phosphor layer are bonded together as described above. However, the present invention is not limited to this, and in order to shorten the manufacturing time in the manufacturing process, 2 The phosphor layers may be formed by simultaneous multilayer coating.

4) Formation of radiation image detector A double-sided adhesive tape (adhesive layer; thickness 25 μm, CS9621 manufactured by Nitto Denko Corporation) was applied to the surface of the wavelength conversion layer on the support, and then a solid state detector using a laminator. A radiation image detector was prepared by laminating a wavelength conversion layer on the surface of the film with a double-sided adhesive tape.

  In the embodiments and examples described above, the radiation image detector using the electric reading type solid state detector has been described. However, the radiation image detector of the present invention uses an optical reading type solid state detector. Also good. Specifically, as an optical reading type solid state detector, for example, the first electrode layer that transmits visible light converted into the wavelength conversion layer, and the irradiation of visible light transmitted through the first electrode layer are received. Acts as an insulator for the charge of one polarity of the charges generated in the photoconductive layer for recording, and as a conductor for the charge of the other polarity. A second layer comprising an acting charge transport layer, a reading photoconductive layer that generates charges when irradiated with reading light, and a transparent linear electrode that transmits the reading light and a light shielding linear electrode that blocks the reading light. What laminated | stacked an electrode layer in this order can be used. Then, the above-described wavelength conversion layer may be provided on the first electrode layer of the radiation image detector so that the second phosphor layer is disposed on the first electrode layer side.

DESCRIPTION OF SYMBOLS 1 Radiation source 2 Subject 3 Radiation image detector 4 Signal processing part 5 Reproduction | regeneration part 31 Solid state detector 31b Scan line 31c Data line 31d Substrate 32 Wavelength conversion layer 32a 1st fluorescent substance layer 32b 2nd fluorescent substance layer 33 Support body 36 Photodiode section 36a Transparent electrode 36b Semiconductor layer 36c Lower electrode 37 TFT switch 37a Gate electrode 37b Drain electrode 37c Source electrode 37d Semiconductor layer 40 Gate driver 50 Integrating amplifier

Claims (6)

A wavelength conversion layer including a phosphor that receives radiation and converts the radiation into light having a longer wavelength, and a detector that detects the light converted by the wavelength conversion layer and converts the light into an image signal representing a radiation image A radiation image detector in which the detector and the wavelength conversion layer are arranged in this order from the side irradiated with the radiation,
A phosphor layer in which the wavelength conversion layer is mixed with a first phosphor having a first average particle size and a second phosphor having a second average particle size larger than the first average particle size. Have
The ratio of the first phosphor to the second phosphor is a weight ratio of 2: 8 to 4: 6, and the first average particle diameter is 1 μm or more and less than 5 μm, and the second average particle diameter is Is 5 μm or more and 12 μm or less,
The phosphor layer is obtained by dispersing the phosphor in a binder, and the weight ratio of the binder to the first and second phosphors is distributed so as to gradually decrease from the detector side. A radiation image detector characterized by.   The radiation image detector according to claim 1, wherein a space filling factor of the phosphor in the phosphor layer is 63% or more. The first and second phosphors are A ₂ O ₂ S: X (where A is any one of Y, La, Gd, and Lu, and X is any one of Eu, Tb, and Pr). The radiation image detector according to claim 1, wherein the radiation image detector is a represented particle.   The radiation image detector according to claim 2, wherein the first and second phosphors contain Ce or Sm as a coactivator.   The radiation image detector according to any one of claims 1 to 4, wherein the first and second phosphors are made of different materials.   The radiation image detector according to claim 1, wherein the first and second phosphors are made of the same material.

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