JP2010096616A - Radiographic image detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To eliminate degradation of sensitivity and blurring of an image and to prevent the effect of back scattered radiation, in a radiographic image detector which detects the light converted by a wavelength conversion layer and converts it into an image signal expressing a radiation image. <P>SOLUTION: The radiographic image detector 3 is constituted by stacking the wavelength conversion layer 32 which is irradiated with radiation and converts the radiation into the light of a longer wavelength and the detector 31 which detects the light converted by the wavelength conversion layer 32 and converts the light into the image signal expressing the radiation image. Herein a radiation absorbing layer 35 which absorbs the radiation is provided on the side opposite to the detector 31 side of the wavelength conversion layer 32. <P>COPYRIGHT: (C)2010,JPO&INPIT

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.

  The electric reading type radiological image detector may be a direct conversion type that directly converts radiation into a charge in a semiconductor layer and accumulates it, or the radiation is once converted into light by a phosphor, and the converted light An indirect conversion method has been proposed in which is converted into electric charge by a photodiode or the like and stored.

  For example, Patent Document 1 proposes 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. In the radiation image detector of Patent Document 1, radiation is irradiated from the phosphor layer side, and visible light converted by the phosphor layer by irradiation of the radiation is detected by a detection substrate. And in the radiation image detector of patent document 1, the radiation irradiated from the fluorescent substance layer side permeate | transmits a fluorescent substance layer and a detection board, reflects a housing | casing etc., and becomes a fluorescent substance layer again as a scattered ray from back. In order to prevent incidence of so-called backscattered rays that are incident, it has been proposed to provide a radiation absorbing member that absorbs radiation on the side of the detection substrate opposite to the phosphor layer.

  Also in Patent Document 2, an indirect conversion type radiation image detector is proposed, and in order to prevent the backscattered rays from entering, radiation absorption that absorbs radiation on the opposite side of the phosphor layer of the detection substrate is also proposed. It has been proposed to provide a member.

  On the other hand, in the radiation image detectors described in Patent Document 1 and Patent Document 2, since radiation is incident from the phosphor layer side, the light converted by the phosphor layer is absorbed by the phosphor layer itself, resulting in deterioration in sensitivity. Or the image is blurred due to light scattering in the phosphor layer.

Therefore, Patent Document 3 proposes a radiation image detector in which radiation is incident not from the phosphor layer side but from the detection substrate side.
JP 2006-91016 A JP 2000-65933 A Japanese Patent No. 3333278

  Here, in the radiation image detectors described in Patent Document 1 and Patent Document 2, if radiation is incident from the detection substrate side as in the radiation image detector described in Patent Document 3, radiation is incident on the radiation absorbing member. Since it is absorbed, the image quality is deteriorated.

  Further, in the radiation image detector described in Patent Document 1, a glass substrate, a detection substrate, and a space exist between the radiation absorbing member and the phosphor layer, that is, rearward between the radiation absorbing member and the phosphor layer. Since there is an interval at which scattered radiation can enter, it is not possible to completely prevent the back scattered radiation from entering the phosphor layer.

  Also in the radiographic image detector described in Patent Document 2, since an insulating substrate and a detection substrate exist between the radiation absorbing member and the phosphor layer, backscattering is again performed between the radiation absorbing member and the phosphor layer. There is an interval at which the lines can enter, and the backscattered lines cannot be completely prevented from entering the phosphor layer.

  An object of this invention is to provide the radiographic image detector which can prevent the influence of a backscattering ray, without producing sensitivity deterioration and a blur of an image in view of said situation.

  The radiation image detector of the present invention is a wavelength conversion layer that receives radiation and converts the radiation into light having a longer wavelength, and detects the light converted by the wavelength conversion layer into an image signal that represents a radiation image. In the radiation image detector in which the detector to be converted is laminated, a radiation absorbing layer that absorbs radiation is provided on the side opposite to the detector side of the wavelength conversion layer.

  Moreover, in the radiographic image detector of the said invention, a detector, a wavelength conversion layer, and a radiation absorption layer can be arrange | positioned in this order from the radiation irradiation side.

  Further, a reflection layer that reflects light converted by the wavelength conversion layer can be provided between the radiation absorbing layer and the wavelength conversion layer.

  The radiation absorbing layer can include at least one of lead, tungsten, and tantalum.

  Further, the thickness of the radiation absorbing layer can be 0.1 mm or more and 10 mm or less.

  Moreover, a radiation absorption layer shall support a wavelength conversion layer.

  Further, the radiation absorbing layer can absorb the radiation and reflect the light converted by the wavelength conversion layer.

  In addition, the radiation absorbing layer can be formed from a resin in which particles containing an element having an atomic number of 50 or more are dispersed.

  In addition, as particles containing an element having an atomic number of 50 or more, tin, antimony, rare earth elements (excluding promethium), barium, tantalum, lead, and oxides of elements of bismuth, barium sulfate, lead fluoride, and fluorine are used. Any of bismuth chloride can be used.

  Further, the thickness of the radiation absorbing layer can be set to 250 μm or more and 600 μm or less.

  Further, the thickness of the radiation absorbing layer can be set to 300 μm or more and 500 μm or less.

A wavelength conversion layer containing GOS (Gd ₂ O ₂ S: Tb) particles can be used.

  A wavelength conversion layer including at least one of CsI: Na and CsI: TI can be used.

  According to the radiation image detector of the present invention, a wavelength conversion layer that receives radiation and converts the radiation into light having a longer wavelength, and an image that represents the radiation image by detecting the light converted by the wavelength conversion layer In the radiation image detector in which the detector for converting to a signal is stacked, a radiation absorbing layer that absorbs radiation is provided on the side opposite to the detector side of the wavelength conversion layer. Can be prevented from being deteriorated without the radiation being absorbed by the radiation absorbing member as in the radiation image detectors described in Patent Document 1 and Patent Document 2. In addition, since it is possible to prevent an interval where the backscattered rays can enter between the wavelength conversion layer and the radiation absorbing layer, the influence of the backscattered rays can be further prevented.

  Moreover, in the radiographic image detector of the present invention, when a reflection layer that reflects light converted by the wavelength conversion layer is provided between the radiation absorption layer and the wavelength conversion layer, the wavelength conversion layer Of the converted light, the light directed to the opposite side to the detector side can also be reflected by the reflective layer and condensed on the detector side, so that the S / N is improved and the image quality is improved. Can do.

  For example, when a metal such as lead, tungsten, and tantalum is used as the material of the radiation absorbing layer, the backscattered radiation can be sufficiently obtained by setting the thickness of the radiation absorbing layer to 0.1 mm or more and 10 mm or less. In addition to being able to absorb, the thickness of the entire radiation image detector can be reduced, and handling becomes easy.

  In addition, when the radiation absorbing layer is also used as a support for supporting the wavelength conversion layer, it is not necessary to provide the radiation absorbing layer and the support separately, so that the manufacturing process can be further simplified. it can.

  In addition, when the radiation absorbing layer absorbs radiation and reflects the light converted by the wavelength conversion layer, it is not necessary to provide the radiation absorbing layer and the support separately, so that the manufacturing process is further improved. It can be simplified.

  In addition, when a material in which a radiation absorbing member is dispersed in a resin is used as the material of the radiation absorbing layer, for example, the thickness of the radiation absorbing layer is 250 μm or more and 600 μm or less, more preferably 300 μm or more and 500 μm or less. In addition to sufficiently absorbing backscattered rays, the weight of the entire radiation image detector can be reduced, handling becomes easy, and processing is also easy.

  Further, when the radiation absorbing layer is formed from a resin in which particles containing an element having an atomic number of 50 or more are dispersed, backscattered rays can be sufficiently absorbed by the particles.

  A radiographic imaging apparatus using a first 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 radiation image detector 3 according to the first embodiment.

  As shown in FIG. 2, the radiation image detector 3 according to the first embodiment includes a phosphor layer 32 that receives radiation irradiated through a subject and converts the radiation into light having a longer wavelength, and a phosphor layer. A solid state detector 31 that detects the light converted by the light source 32 and converts it into an image signal representing a radiation image; a reflective layer 33 that reflects the light converted by the fluorescent material layer 32; and the fluorescent material layer 32 and the reflective layer 33 And a radiation absorbing layer 35 that absorbs radiation that has passed through the phosphor layer 32 and backscattered rays that are irradiated from the side opposite to the radiation source 1 side of the radiation image detector 3. .

  The radiation image detector 3 according to the first embodiment includes a solid state detector 31, a phosphor layer 32, a reflective layer 33, a support 34, and a radiation absorbing layer 35 arranged in this order from the radiation source 1 side. It receives radiation from the solid detector 31 side.

  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 is provided for each pixel row arranged in the X direction and a plurality of pixels 31 a arranged two-dimensionally in the XY direction, and is input to each pixel 31 a of the pixel row. The scanning line 31b through which the scanning signal to be transmitted flows and the data line 31c provided for each pixel column arranged in the Y direction and from which the pixel signal detected by each pixel 31a of the pixel column flows out are provided.

  The scanning line 31b and the data line 31c are provided so as to be orthogonal to each other, and the pixel 31a is provided in a portion surrounded by 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 illustrating a schematic configuration of each pixel 31 a in the solid-state detector 31. As shown in FIG. 3 and FIG. 4, the pixel 31 a photoelectrically converts the light converted by the phosphor layer 32 and a charge signal photoelectrically converted by the photodiode unit 36 for reading out as a pixel signal. TFT switch 37 is provided.

  The pixel 31a is provided on an insulating substrate 31d made of alkali-free glass or the like. The photodiode portion 36 includes a transparent electrode 36a that transmits light converted by the phosphor layer 32, a semiconductor layer 36b that functions as a photodiode, and a lower electrode 36c. For example, a PIN structure photodiode can be used as the semiconductor layer 36b. The lower electrode 36c is connected to a drain electrode 37b of a TFT switch 37 described later.

  The TFT switch 37 includes a gate electrode 37a, a drain electrode 37b, a source electrode 37c, and a semiconductor layer 37d. 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.

  As described above, the phosphor layer 32 receives radiation and converts the radiation into light having a longer wavelength. As long-wave light after conversion, near ultraviolet, visible, and near infrared are preferable, and visible is particularly preferable. In the present embodiment, what is converted into visible light is used.

The phosphor layer 32 includes a phosphor that converts radiation into visible light. Examples of the phosphor include GOS (Gd ₂ O ₂ S: Tb) particles and CsI: Na and CsI made of columnar crystals. : At least one of the TIs can be used. In addition, the formation method of the fluorescent substance layer 32 is demonstrated in detail in the Example mentioned later.

  The reflection layer 33 reflects visible light converted from the phosphor layer 32 toward the solid detector 31 side. Any material may be used as the material of the reflective layer 33 as long as it reflects light having a wavelength emitted from the phosphor layer 32. In addition, the formation method of a reflection layer is demonstrated in detail in the Example mentioned later.

  The support 34 has a reflective layer 33 and a phosphor layer 32 formed thereon, and supports these layers. Then, a phosphor sheet in which the reflective layer 33 and the phosphor layer 32 are formed on the support 34 is attached to the solid detector 31. As a material for the support, for example, polyethylene terephthalate having a thickness of 200 μm can be used.

  The radiation absorbing layer 35 is scattered by radiation transmitted through the phosphor layer 32, the reflective layer 33, and the support 34, and other subjects 2, and the phosphor layer 32 from the side opposite to the radiation source 1 side of the radiation image detector 3. It absorbs backscattered rays incident on the. As a material of the radiation absorbing layer 35 of the present embodiment, for example, at least one of lead, tungsten, and tantalum can be used. The thickness of the radiation absorbing layer 35 is preferably 0.1 mm or more and 10 mm or less.

  Next, the operation of the radiographic imaging apparatus using the radiographic image detector of the first 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 phosphor layer 32. The phosphor layer 32 that has been irradiated with radiation converts the radiation into visible light. At this time, the radiation transmitted through the phosphor layer 32 and the backscattered rays described above are absorbed by the radiation absorbing layer 35 and are not incident on the phosphor layer 32.

  The visible light converted by the phosphor layer 32 is irradiated to the solid state detector 31 and is incident on the photodiode portion 36 of each pixel 31 a of the solid state detector 31. Of the visible light converted in the phosphor layer 32, the light emitted toward the side opposite to the solid detector 31 side is reflected by the reflective layer 33 and applied to the solid detector 31. Visible light incident on the photodiode portion 36 is applied to 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 pixel rows arranged in the X direction is sequentially selected in the Y direction by the gate driver 40, and each pixel 31a 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 the TFT switch 37 of each pixel 31a connected to the scanning line 31b, and between the drain electrode 37b and the source electrode 37c of the TFT switch 37. Is conducted through the semiconductor layer 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.

  Next, a radiographic imaging apparatus using a second embodiment of the radiographic image detector of the present invention will be described.

  The present radiographic image capturing apparatus is the same as the configuration of the radiographic image capturing apparatus of the first embodiment except for the configuration of the radiographic image detector. Therefore, only the configuration of the radiographic image detector of the second embodiment will be described below. To do.

  As shown in FIG. 5, the radiation image detector 6 according to the second embodiment includes a solid state detector 31, a phosphor layer 32, and a radiation absorption layer 60 arranged in this order from the radiation source 1 side. It receives radiation from the solid detector 31 side. The configurations of the solid state detector 31 and the phosphor layer 32 are the same as those of the radiation image detector 3 of the first embodiment.

  The radiation absorbing layer 60 of the radiation image detector 6 according to the second embodiment is similar to the radiation absorbing layer 35 in the radiation image detector 3 according to the first embodiment. The detector 6 absorbs backscattered rays incident on the phosphor layer 32 from the side opposite to the radiation source 1 side, and further functions as a support for the phosphor layer 32.

The radiation absorbing layer 60 can be formed from, for example, a resin such as polyethylene terephthalate in which a radiation absorbing member is dispersed. In addition, as the thickness of the radiation absorbing layer 60,
The thickness is preferably 250 μm or more and 600 μm or less, more preferably 300 μm or more and 500 μm or less. The method for forming the radiation absorbing layer 60 will be described in detail in the examples described later.

  The radiation image detector 6 of the second embodiment shown in FIG. 5 is not provided with the reflection layer 33 in the radiation image detector 3 of the first embodiment, but the phosphor layer 32 and the radiation absorption layer. You may make it provide a reflective layer between 60.

  The operation of the radiographic image capturing apparatus is the same as that of the radiographic image capturing apparatus using the radiographic image detector 3 of the first embodiment.

  Next, a radiographic imaging apparatus using a third embodiment of the radiographic image detector of the present invention will be described.

  The present radiographic imaging apparatus is the same as the configuration of the radiographic image capturing apparatus of the first and second embodiments except for the configuration of the radiographic image detector, and therefore only the configuration of the radiographic image detector of the third embodiment. This will be described below.

  As shown in FIG. 6, the radiation image detector 7 of the third embodiment includes a solid state detector 31, a phosphor layer 32, a radiation absorbing layer 70, and a support 34 arranged in this order from the radiation source 1 side. It is intended to receive radiation from the solid detector 31 side. The configuration of the solid state detector 31, the phosphor layer 32, and the support 34 is the same as that of the radiation image detector 3 of the first embodiment.

  The radiation absorbing layer 70 of the radiation image detector 7 of the third embodiment is similar to the radiation absorbing layer 35 in the radiation image detector 3 of the first embodiment, and the radiation or radiation image transmitted through the phosphor layer 32. While absorbing the backscattering ray which injects into the fluorescent substance layer 32 from the opposite side to the radiation source 1 side of the detector 7, it functions also as a reflection layer. That is, the visible light converted from the phosphor layer 32 is reflected toward the solid detector 31 side.

  The material of the radiation absorbing layer 70 may be any material that absorbs radiation and reflects light having a wavelength emitted from the phosphor layer 32. For example, particles containing an element having an atomic number of 50 or more are used. A dispersed resin can be used. Examples of the particles containing an element having an atomic number of 50 or more include tin, antimony, rare earth elements (excluding promethium), barium, tantalum, lead and oxides of elements of bismuth, barium sulfate, lead fluoride and Any of bismuth fluoride can be used.

  The particles contained in the radiation absorbing layer 70 preferably have an average particle size of 0.1 μm or more and 3 μm or less. The average particle size of the particles contained in the radiation absorbing layer 70 is desirably determined based on the wavelength of light emitted from the phosphor layer 32. The average particle diameter is preferably 1/4 to 2 times the emission wavelength. Since the emission wavelength used as fluorescence is 0.4 to 0.8 μm, the average particle diameter is 0.1 μm to 1.6 μm. It is more preferable.

  The radiation absorbing layer 70 desirably has a reflectance of 85% with respect to the main emission wavelength of visible light emitted from the phosphor layer 32. The reflectance is obtained by measuring the diffuse reflectance by installing a radiation absorbing layer in a device in which a 150φ integrating sphere (150-0901) is attached to a U-3210 self-recording spectrophotometer manufactured by Hitachi, Ltd. Can do.

  Moreover, it is desirable that the scattering length of the main emission wavelength of visible light emitted from the phosphor layer 32 is 5 μm or more and 20 μm or less. With such a scattering length, the blurring of the image can be improved. The scattering length can be obtained as follows. First, three or more samples having the same composition as the radiation absorbing layer of the radiation image detector to be measured and having different layer thicknesses are manufactured, and then the thickness (μm) of each sample and the diffuse transmittance ( %) (Measured by a device with a 150φ integrating sphere (150-0901) attached to a U-3210 self-recording spectrophotometer manufactured by Hitachi, Ltd.) and an expression derived from the theoretical formula of Kubelka-Munk It can be determined by introducing it. The measurement wavelength was matched with the emission wavelength of the phosphor layer of the target radiographic image detector (representing 545 nm as a representative value). The theoretical formula can be derived, for example, from formulas 5 · 1 · 12 to 5 · 1.15 on page 403 of “Phosphor Handbook” (Edited by Phosphor Handbook, Ohm Co., Ltd., published in 1987).

  In addition, the thickness of the radiation absorbing layer 70 is preferably 250 μm or more and 600 μm or less, and more preferably 300 μm or more and 500 μm or less.

  In addition, the formation method of the radiation absorption layer 70 is demonstrated in detail in the Example mentioned later.

  The operation of the radiographic image capturing apparatus is the same as that of the radiographic image capturing apparatus using the radiographic image detector 3 of the first embodiment.

  Examples of the radiation image detectors according to the first to third embodiments described above will be described below. [Example 1] to [Example 3] described below are examples of the radiation image detector of the first embodiment, and [Example 4] to [Example 6] are those of the second embodiment. It is an Example of a radiographic image detector, [Example 7]-[Example 17] are examples of the radiographic image detector of 3rd Embodiment.

[Example 1]
1) Preparation of phosphor sheet 20% by weight of a mixture of polyvinyl butyral resin, urethane resin fat and plasticizer is dissolved in 80% by weight of a mixed solvent of toluene, 2-butanol and xylene, and sufficiently stirred to prepare a binder. did.

Then, this binder and a Gd ₂ O ₂ S: Tb phosphor having an average particle diameter of 5 μm were mixed at a weight ratio of 15:85, and dispersed by a ball mill to prepare a phosphor coating solution.

  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. Peeling from the support gave a phosphor sheet (thickness: 300 μm).

2) Formation of Reflective Layer A material having the following composition was added to 5 g of MEK (methyl ethyl ketone) and mixed and dispersed to prepare a coating solution. This coating solution was applied to the surface of PET (polyethylene terephthalate) (support, thickness: 200 μm) using a doctor blade, dried and cured to form an adhesive layer (film thickness: 5 μm) on the reflective layer side.

Resin: MEK solution of saturated polyester resin (Byron 300, manufactured by Toyobo Co., Ltd.) “Solid content 30% by weight”
Curing agent: Polyisocyanate (Olestar NP38-70S “Solid content 70%”, manufactured by Mitsui Toatsu Co., Ltd.)
Conductive agent: MEO dispersion of SnO ₂ (Sb dope) needle-shaped fine particles “solid content 30% by weight”
Subsequently, a material having the following composition was added to 387 g of MEK and mixed and dispersed to prepare a coating solution. This coating solution was applied to the surface of the adhesive layer on the support made of PET using a doctor blade and dried to form a reflective layer (layer thickness, about 100 μm).

Light reflecting material: high purity alumina fine particles (average particle size: 0.4 μm)
Binder: Soft acrylic resin (Chriscoat P-1018GS “20% toluene solution”, manufactured by Dainippon Ink & Chemicals, Inc.)
3) Formation of phosphor layer The phosphor sheet prepared in 1) is overlapped with the surface of the reflective layer on the support so that the back surface (temporary support side) at the time of coating and formation is in contact with the surface, and this is used with a calendar machine. Thermal compression was performed 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 phosphor layer was completely fused to the reflective layer. The thickness of the phosphor layer after heat compression was 200 μm.

4) Formation of radiographic image detector After a double-sided adhesive tape (adhesive layer; thickness 25 μm, CS9621 manufactured by Nitto Denko Corporation) was applied to the surface of the phosphor layer, the surface of the solid detector was used using a laminator. The phosphor layer was bonded through a double-sided adhesive tape.

5) Formation of radiation absorbing layer After a double-sided adhesive tape (adhesive layer; thickness 25 μm, CS9621 manufactured by Nitto Denko Corporation) is applied to the phosphor layer support (PET), a lead plate (thickness: 0.2 mm) Was attached to a support via a double-sided adhesive tape to produce the radiation image detector of Example 1.

[Example 2]
The radiation image detector of Example 2 was prepared by using a Ta (tantalum) plate (thickness: 0.2 mm) as a radiation absorbing layer instead of the lead plate in the radiation image detector of Example 1.

[Example 3]
The radiation image detector of Example 3 was prepared by using a W (tungsten) plate (thickness: 0.2 mm) as a radiation absorbing layer instead of the lead plate in the radiation image detector of Example 1.

[Example 4]
1) Preparation of phosphor sheet 20% by weight of a mixture of polyvinyl butyral resin, urethane resin fat and plasticizer is dissolved in 80% by weight of a mixed solvent of toluene, 2-butanol and xylene, and sufficiently stirred to prepare a binder. did.

Then, this binder and a Gd ₂ O ₂ S: Tb phosphor having an average particle diameter of 5 μm were mixed at a weight ratio of 15:85 and dispersed by a ball mill to prepare a phosphor coating solution.

  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. Peeling from the support gave a phosphor sheet (thickness: 300 μm).

2) Formation of radiation absorbing layer and reflecting layer A material having the following composition was added to 5 g of MEK (methyl ethyl ketone), and mixed and dispersed to prepare a coating solution. PET (polyethylene terephthalate) in which Ta ₂ O ₅ particles, which are radiation absorbing members, are dispersed at high density in this coating solution (radiation absorbing layer having a support function, thickness: 500 μm, weight filling density of Ta ₂ O ₅ : 40% ) Using a doctor blade, dried and cured to form an adhesive layer (film thickness: 5 μm) on the reflective layer side.

Resin: MEK solution of saturated polyester resin (Byron 300, manufactured by Toyobo Co., Ltd.) “Solid content 30% by weight”
Curing agent: Polyisocyanate (Olestar NP38-70S “Solid content 70%”, manufactured by Mitsui Toatsu Co., Ltd.)
Conductive agent: MEO dispersion of SnO ₂ (Sb dope) needle-shaped fine particles “solid content 30% by weight”
Subsequently, a material having the following composition was added to 387 g of MEK and mixed and dispersed to prepare a coating solution. This coating solution was applied to the surface of the adhesive layer using a doctor blade and dried to form a reflective layer (layer thickness, about 100 μm).

Light reflecting material: high purity alumina fine particles (average particle size: 0.4 μm)
Binder: Soft acrylic resin (Chriscoat P-1018GS “20% toluene solution”, manufactured by Dainippon Ink & Chemicals, Inc.)
3) Formation of phosphor layer The phosphor sheet prepared in 1) is overlapped with the surface of the reflection layer on the radiation absorbing layer formed in 2) so that the back surface (temporary support side) at the time of coating and formation is in contact. Was calendered using a calender machine at a total load of 2300 kg, upper roll 45 ° C., lower roll 45 ° C., feed rate 0.3 m / min. As a result, the phosphor layer was completely fused to the reflective layer. The thickness of the phosphor layer after heat compression was 200 μm.

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 phosphor layer, and then both surfaces were applied to the surface of the solid detector using a laminator. A radiographic image detector was prepared by laminating phosphor layers through an adhesive tape.

[Example 5]
The radiation image detector of Example 5 is a PET (radiation-absorbing layer having a support function, thickness: 500 μm, volume of PbO) in which PbO particles are dispersed at a high density instead of Ta ₂ O ₅ in Example 4-2). (Packing density: 40%).

[Example 6]
The radiation image detector of Example 6 is a PET (radiation-absorbing layer having a support function, thickness: 500 μm) in which Bi ₂ O ₃ particles are dispersed at a high density instead of Ta ₂ O ₅ in Example 4-2). Bi ₂ O ₃ volume filling density: 40%).

[Example 7]
1) Preparation of phosphor sheet 20% by weight of a mixture of polyvinyl butyral resin, urethane resin fat and plasticizer is dissolved in 80% by weight of a mixed solvent of toluene, 2-butanol and xylene, and sufficiently stirred to prepare a binder. did.

Then, this binder and a Gd ₂ O ₂ S: Tb phosphor having an average particle diameter of 5 μm were mixed at a weight ratio of 15:85 and dispersed by a ball mill to prepare a phosphor coating solution.

  Then, this coating solution was applied to the surface of a polyethylene terephthalate sheet (temporary support, thickness: 190 μm) coated with a silicone release agent using a doctor blade in a width of 300 mm, and then dried. Was peeled off to obtain a phosphor sheet (thickness: 300 μm).

2) Formation of radiation absorbing layer having function of reflection layer A material having the following composition was added to 5 g of MEK (methyl ethyl ketone) and mixed and dispersed to prepare a coating solution. This coating solution was applied to the surface of PTE (polyethylene terephthalate) (support, thickness: 200 μm) using a doctor blade, dried and cured to form an adhesive layer (film thickness: 5 μm) on the radiation absorbing layer side. .

Resin: MEK solution of saturated polyester resin (Byron 300, manufactured by Toyobo Co., Ltd.) “Solid content 30% by weight”
Curing agent: Polyisocyanate (Olestar NP38-70S “Solid content 70%”, manufactured by Mitsui Toatsu Co., Ltd.)
Conductive agent: MEO dispersion of SnO ₂ (Sb dope) needle-shaped fine particles “solid content 30% by weight”
Subsequently, a material having the following composition was added to 387 g of MEK and mixed and dispersed to prepare a coating solution. This coating solution was applied to the surface of the adhesive layer using a doctor blade and dried to form a radiation absorbing layer having a function of a reflective layer (layer thickness, about 400 μm).

Light reflective / radioactive absorbing material: Bi ₂ O ₃ (average particle size: 1 μm)
Binder: Soft acrylic resin (Chriscoat P-1018GS “20% toluene solution”, manufactured by Dainippon Ink & Chemicals, Inc.)
3) Formation of phosphor layer The phosphor sheet prepared in 1) is superimposed on the surface of the radiation absorbing layer on the support so that the back surface (temporary support side) at the time of coating and formation is in contact, and this is used with a calendar machine The heat compression was performed 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 phosphor layer was completely fused to the radiation absorbing layer. The thickness of the phosphor layer after heat compression was 200 μm, the film thickness of the radiation absorbing layer was about 300 μm, and the volume packing density of Bi ₂ O ₃ particles in the radiation absorbing layer was about 70%.

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 phosphor layer, and then both surfaces were applied to the surface of the solid detector using a laminator. A radiographic image detector was prepared by laminating phosphor layers through an adhesive tape.

[Example 8]
The radiographic image detector of Example 8 was produced in the same manner as the radiographic image detector of Example 7 except that the thickness of the radiation absorbing layer formed in 2) of Example 7 was changed to about 500 μm. The thickness of the radiation absorbing layer after compression in 3) of Example 7 of the radiation image detector of Example 8 was about 400 μm [Example 9].
The radiographic image detector of Example 9 was produced in the same manner as the radiographic image detector of Example 7 except that the thickness of the radiation absorbing layer formed in 2) of Example 7 was changed to about 600 μm. In addition, the thickness of the radiation absorbing layer after compression in 3) of Example 7 of the radiation image detector of Example 9 was about 500 μm.

[Example 10]
The radiation image detector of Example 10 is the same as that of Example 7 except that the thickness of the radiation absorbing layer formed in 2) of Example 7 is changed to about 600 μm and the material of the radiation absorbing material is changed to PbF ₂ . It was created in the same way as the radiation image detector. In addition, the thickness of the radiation absorbing layer after compression in 3) of Example 7 of the radiographic image detector of Example 10 was about 500 μm.

[Example 11]
The radiation image detector of Example 11 is the same as that of Example 7 except that the thickness of the radiation absorbing layer formed in 2) of Example 7 is changed to about 600 μm and the material of the radiation absorbing material is changed to SnO ₂ . It was created in the same way as the radiation image detector. In addition, the thickness of the radiation absorbing layer after compression in 3) of Example 7 of the radiation image detector of Example 11 was about 500 μm.

[Example 12]
The radiation image detector of Example 12 is the same as Example 7 except that the thickness of the radiation absorbing layer formed in 2) of Example 7 is changed to about 600 μm and the material of the radiation absorbing material is changed to Sb ₂ O _3. It produced similarly to the radiographic image detector of No.7. In addition, the thickness of the radiation absorbing layer after compression in 3) of Example 7 of the radiographic image detector of Example 12 was about 500 μm.

[Example 13]
The radiation image detector of Example 13 is the same as that of Example 7 except that the thickness of the radiation absorbing layer formed in 2) of Example 7 is changed to about 600 μm and the material of the radiation absorbing material is changed to CeO ₂ . It was created in the same way as the radiation image detector. In addition, the thickness of the radiation absorbing layer after compression in 3) of Example 7 of the radiographic image detector of Example 13 was about 500 μm.

[Example 14]
The radiation image detector of Example 14 is the same as that of Example 7 except that the thickness of the radiation absorbing layer formed in 2) of Example 7 is changed to about 600 μm and the material of the radiation absorbing material is changed to Ta ₂ O _5. It produced similarly to the radiographic image detector of No.7. In addition, the thickness of the radiation absorbing layer after compression in 3) of Example 7 of the radiographic image detector of Example 14 was about 500 μm.

[Example 15]
The radiation image detector of Example 15 was the same as that of Example 7 except that the thickness of the radiation absorbing layer formed in 2) of Example 7 was changed to about 600 μm and the material of the radiation absorbing material was changed to PbO. It was made in the same way as the image detector. In addition, the thickness of the radiation absorbing layer after compression in 3) of Example 7 of the radiation image detector of Example 15 was about 500 μm.

[Example 16]
The radiation image detector of Example 16 is the same as that of Example 7 except that the thickness of the radiation absorbing layer formed in 2) of Example 7 is changed to about 600 μm and the material of the radiation absorbing material is changed to BaSO ₄ . It was created in the same way as the radiation image detector. The thickness of the radiation absorbing layer after compression in 3) of Example 7 of the radiation image detector of Example 16 was about 500 μm.

[Example 17]
The radiation image detector of Example 17 is the same as that of Example 7 except that the thickness of the radiation absorbing layer formed in 2) of Example 7 is changed to about 600 μm and the material of the radiation absorbing material is changed to BiF ₃ . It was created in the same way as the radiation image detector. In addition, the thickness of the radiation absorbing layer after compression in 3) of Example 7 of the radiographic image detector of Example 17 was about 500 μm.

  In addition, the above [Example 1] to [Example 17] are created, and [Comparative Example 1] to [Comparative Example 4] described below are created, and the deterioration of image quality due to backscattered rays is evaluated for each. The results are shown in Table 1 below.

  A method of creating [Comparative Example 1] to [Comparative Example 4] will be described.

[Comparative Example 1]
The radiographic image detector of Comparative Example 1 was prepared in the same manner as the radiographic image detector of Example 1 except that the radiation absorbing layer of 5) was not formed in the radiographic image detector of Example 1.

[Comparative Example 2]
The radiographic image detector of Comparative Example 2 was the same as the radiographic image detector of Example 4 except that PET (support, thickness: 500 μm) in which the particles of the radiation absorbing member were not dispersed was used as the PET of 4). It produced similarly to the radiographic image detector of Example 4.

[Comparative Example 3]
The radiographic image detector of Comparative Example 3 was prepared in the same manner as the radiographic image detector of Example 7 except that the thickness of the radiation absorbing layer formed in 2) of Example 7 was changed to about 300 μm. The thickness of the radiation absorbing layer after compression in 3) of Example 7 of the radiographic image detector of Comparative Example 3 was about 200 μm.

[Comparative Example 4]
The radiographic image detector of Comparative Example 4 was prepared in the same manner as the radiographic image detector of Example 9 except that the material of the radiation absorbing substance in Example 9 was changed to ZnO.

  The evaluation of the deterioration in image quality due to backscattered rays was performed as follows.

With the concrete (scatterer) placed behind the radiation image detector, the radiation image detector is placed so that X-rays pass through the solid detector and the phosphor layer in this order, and the X-ray incident on the radiation image detector Images were taken with a resolution (CTF) chart on the side. The photographed image was output to a film, and how clearly the 101p / mm line in the resolution (CTF) chart reflected in the image looks clear was visually evaluated using a magnifying glass with a magnification of 10 times. Then, when there is no decrease in contrast and the line can be clearly distinguished, a circle is given. When the contrast is slightly lowered and the line is slightly blurred, a triangle is given. The contrast is lowered and the line is blurred. The case was evaluated as x.

  As shown in Table 1, for the radiographic image detectors of Examples 1 to 17, the influence of backscattered rays could be prevented and good evaluation results could be obtained. On the other hand, since the radiation image detectors of Comparative Examples 1 and 2 are not provided with a radiation absorbing layer, the influence of backscattered rays cannot be prevented, and an inappropriate evaluation result is obtained as a diagnostic image. It was.

  In addition, the radiation image detector of Comparative Example 3 cannot sufficiently absorb backscattered rays because the thickness of the radiation absorbing layer is reduced compared to the radiation image detector of Example 7, and as a diagnostic image, Somewhat inappropriate evaluation results were obtained.

  Further, the radiation image detector of Comparative Example 3 uses Zn oxide having an atomic number of 30 as the material of the radiation absorbing material as compared with the radiation image detector of Example 9, so that the oxide of ZnO However, backscattered rays could not be absorbed sufficiently, and evaluation results that were somewhat inappropriate for diagnostic images were obtained.

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 1st 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 structure of the pixel in a solid state detector Sectional drawing which shows schematic structure of 2nd Embodiment of the radiographic image detector of this invention Sectional drawing which shows schematic structure of 3rd Embodiment of the radiographic image detector of this invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Radiation source 2 Subject 3 Radiation image detector 4 Signal processing unit 5 Reproduction unit 6 Radiation image detector 7 Radiation image detector 31 Solid state detector 31a Pixel 31b Scan line 31c Data line 31d Substrate 32 Phosphor layer 33 Reflective layer 34 Support Body 35 radiation absorbing layer 36 photodiode portion 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 60 radiation absorbing layer 70 radiation absorbing layer

Claims (13)

A wavelength conversion layer 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 are stacked. In the radiation image detector
A radiation image detector, wherein a radiation absorbing layer that absorbs radiation is provided on a side opposite to the detector side of the wavelength conversion layer.   The radiation image detector according to claim 1, wherein a detector, a wavelength conversion layer, and a radiation absorption layer are arranged in this order from the side irradiated with the radiation.   The radiation image detector according to claim 1, wherein a reflection layer that reflects light converted by the wavelength conversion layer is provided between the radiation absorption layer and the wavelength conversion layer.   The radiation image detector according to claim 1, wherein the radiation absorbing layer contains at least one of lead, tungsten, and tantalum.   The radiation image detector according to any one of claims 1 to 4, wherein the radiation absorbing layer has a thickness of 0.1 mm or more and 10 mm or less.   The radiation image detector according to claim 1, wherein the radiation absorption layer supports the wavelength conversion layer.   The radiation image detector according to claim 1, wherein the radiation absorption layer absorbs radiation and reflects light converted by the wavelength conversion layer.   8. The radiation image detector according to claim 6, wherein the radiation absorbing layer is formed from a resin in which particles containing an element having an atomic number of 50 or more are dispersed.   The particles are any one of tin, antimony, rare earth elements (excluding promethium), barium, tantalum, lead and bismuth oxides, or barium sulfate, lead fluoride and bismuth fluoride. 9. The radiation image detector according to claim 8, wherein   10. The radiation image detector according to claim 6, wherein a thickness of the radiation absorbing layer is 250 μm or more and 600 μm or less.   The radiation image detector according to claim 6, wherein a thickness of the radiation absorbing layer is not less than 300 μm and not more than 500 μm. The radiation image detector according to claim 1, wherein the wavelength conversion layer includes GOS (Gd ₂ O ₂ S: Tb) particles.   The radiation image detector according to any one of claims 1 to 11, wherein the wavelength conversion layer includes at least one of CsI: Na and CsI: TI.

Images