JP2008232781A - Scintillator panel and radiation image sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a scintillator panel and a radiation image sensor with improved optical transmission efficiency by improving the reflectivity of a reflective layer. <P>SOLUTION: In a scintillator panel 10 comprising: a scintillator layer 2 for converting radiation into light; a radiation transparent substrate 1 for supporting the scintillator layer 2; a reflective layer 3 for emitting light converted in the scintillator layer 2 outside; and a dielectric layer 6, the reflective layer 3, the dielectric layer 6, the radiation transparent substrate 1b and the scintillator layer 2 are disposed in this order, and, further, the radiation transparent substrate 1b has 5% or more transmittance of the light converted in the scintillator layer 2, and a refractive index of the dielectric layer 6 is smaller than that of the radiation transparent substrate 1b. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a scintillator panel and a radiation image sensor, and more particularly to a scintillator panel and a radiation image sensor in which the reflectance of a reflective layer is improved and the light transmission efficiency is improved.

  Conventionally, radiographic images such as X-ray images have been widely used for diagnosis of medical conditions in the medical field. In particular, radiographic images using intensifying screens and film systems have been developed as an imaging system that combines high reliability and excellent cost performance as a result of high sensitivity and high image quality in the long history. Used in the medical field. However, the image information is so-called analog image information, and free image processing and instantaneous electric transmission cannot be performed like the digital image information that has been developed in recent years.

  In recent years, digital radiographic image detection apparatuses represented by computed radiography (CR), flat panel type radiation detectors (FPD) and the like have appeared. In these, since a digital radiographic image is directly obtained and an image can be directly displayed on an image display device such as a cathode tube or a liquid crystal panel, image formation on a photographic film is not necessarily required. As a result, these digital X-ray image detection devices reduce the need for image formation by the silver halide photography method, and greatly improve the convenience of diagnosis work in hospitals and clinics.

  Computed radiography (CR) is currently accepted in the medical field as one of the digital technologies for X-ray images. However, the sharpness is insufficient and the spatial resolution is insufficient, and the image quality level of the screen / film system has not been reached. As a new digital X-ray imaging technique, for example, a flat plate X-ray detection device (FPD) using a thin film transistor (TFT) has been developed (for example, see Non-Patent Documents 1 and 2).

  In order to convert radiation into visible light, a scintillator panel made of an X-ray phosphor having a characteristic of emitting light by radiation is used. In order to improve the S / N ratio in low-dose imaging, luminous efficiency is used. It is necessary to use a high scintillator panel. In general, the light emission efficiency of a scintillator panel is determined by the thickness of the scintillator layer (phosphor layer) and the X-ray absorption coefficient of the phosphor. The thicker the phosphor layer, the light emission in the phosphor layer. Light scattering occurs and sharpness decreases. Therefore, when the sharpness necessary for the image quality is determined, the film thickness is determined.

  In particular, cesium iodide (CsI) has a relatively high rate of change from X-rays to visible light, and phosphors can be easily formed into a columnar crystal structure by vapor deposition. Therefore, it was possible to increase the thickness of the phosphor layer.

  However, since the luminous efficiency is low only with CsI, for example, a mixture of CsI and sodium iodide (NaI) at an arbitrary molar ratio is used as sodium-activated cesium iodide (CsI: Na) on the substrate by vapor deposition. Deposition, or in recent years, a mixture of CsI and thallium iodide (TlI) mixed in an arbitrary molar ratio deposited on a substrate as a thallium-activated cesium iodide (CsI: Tl) by vapor deposition. As a result of annealing, the visible conversion efficiency is improved and used as an X-ray phosphor.

  As another means for increasing the light output, a method for making the substrate on which the scintillator is formed reflective (for example, see Patent Document 1), a method for providing a reflective layer on the substrate (for example, see Patent Document 2), and a method for providing on the substrate. Although a method of forming a scintillator on a reflective metal thin film and a transparent organic film covering the metal thin film (see, for example, Patent Document 3) has been proposed, these methods increase the amount of light obtained, but still Insufficient.

For each scintillator element corresponding to a pixel, a method is proposed in which a dielectric layer is provided on all surfaces except the light extraction surface, and a reflective layer is provided between the scintillator elements (see, for example, Patent Document 4). Although this method increases the amount of light obtained, it is still not sufficient.
Japanese Patent Publication No. 7-21560 Japanese Patent Publication No. 1-240887 JP 2000-356679 A JP-A-5-203755 Physics Today, November 1997, page 24, John Laurans' paper "Amorphous Semiconductor User in Digital X-ray Imaging" SPIE, Vol. 32, 1997, E. Antonuk's paper “Development of a High Resolution, Active Matrix, Flat-Panel Imager with Enhanced Fill Factor”

  An object of the present invention is to provide a scintillator panel and a radiation image sensor in which the reflectance of a reflective layer is improved and the light transmission efficiency is improved.

  The above object of the present invention can be achieved by the following configuration.

  1. A scintillator comprising a scintillator layer for converting radiation into light, a radiation transmissive substrate for supporting the scintillator layer, a reflective layer for emitting light converted by the scintillator layer to the outside, and a dielectric layer In the panel, each of the layers is arranged in the order of a reflective layer, a dielectric layer, a radiation transmissive substrate, and a scintillator layer, and the radiation transmissive substrate has a transmittance of 5% or more of light converted by the scintillator layer. A scintillator panel, wherein the dielectric layer has a refractive index smaller than that of the radiation transmissive substrate.

  2. 2. The scintillator panel according to 1 above, wherein the dielectric layer is made of air.

  3. 3. The scintillator panel as described in 1 or 2 above, wherein the scintillator layer contains cesium iodide as a main component.

  4). 4. The scintillator panel according to any one of 1 to 3, wherein the radiation transmissive substrate has a thickness of 25 μm to 1000 μm.

  5. 5. The scintillator panel according to any one of 1 to 4, wherein the radiation transmissive substrate is mainly composed of any one of PI, PET, PEN, and polycarbonate.

  6). 6. The scintillator panel according to any one of 1 to 5, wherein the reflective layer has any one of Al, Ag, and Au as a main component.

  7. A radiation image sensor comprising a photodetector for the scintillator panel according to any one of 1 to 6 above.

  According to the present invention, it is possible to provide a scintillator panel and a radiation image sensor in which the reflectance of the reflective layer is improved and the light transmission efficiency is improved.

  The present invention will be described in more detail.

  The present invention will be described in more detail. Hereinafter, each constituent layer and constituent elements will be described.

(Scintillator layer)
As a material for forming the scintillator layer (also referred to as “phosphor layer”), various known phosphor materials can be used. However, the rate of change from X-ray to visible light is relatively high, and it is easy to perform by vapor deposition. In addition, since the phosphor can be formed into a columnar crystal structure, scattering of emitted light within the crystal can be suppressed by the light guide effect, and the thickness of the scintillator layer can be increased. Therefore, cesium iodide (CsI) Is preferred.

  However, since only CsI has low luminous efficiency, various activators are added. For example, as shown in Japanese Patent Publication No. 54-35060, a mixture of CsI and sodium iodide (NaI) at an arbitrary molar ratio can be mentioned. Further, for example, CsI as disclosed in Japanese Patent Application Laid-Open No. 2001-59899 is deposited, and thallium (Tl), europium (Eu), indium (In), lithium (Li), potassium (K), rubidium (Rb) ), CsI containing an activating substance such as sodium (Na) is preferred. In the present invention, thallium (Tl) and europium (Eu) are particularly preferable. Furthermore, thallium (Tl) is preferred.

  In the present invention, it is particularly preferable to use an additive containing one or more types of thallium compounds and cesium iodide as raw materials. That is, thallium activated cesium iodide (CsI: Tl) is preferable because it has a wide emission wavelength from 400 nm to 750 nm.

  As the thallium compound as an additive containing one or more types of thallium compounds according to the present invention, various thallium compounds (compounds having oxidation numbers of + I and + III) can be used.

In the present invention, preferred thallium compounds are thallium iodide (TlI), thallium bromide (TlBr), thallium chloride (TlCl), thallium fluoride (TlF, TlF ₃ ) and the like.

  The melting point of the thallium compound according to the present invention is preferably in the range of 400 to 700 ° C. If the temperature exceeds 700 ° C., the additives in the columnar crystals exist non-uniformly, resulting in a decrease in luminous efficiency. In the present invention, the melting point is a melting point at normal temperature and pressure.

  Moreover, it is preferable that the molecular weight of a thallium compound exists in the range of 206-350.

  In the scintillator layer of the present invention, the content of the additive is desirably an optimum amount according to the target performance and the like, but is 0.001 mol% to 50 mol% with respect to the content of cesium iodide, and further 0 It is preferable that it is 1-10.0 mol%.

  Here, when the additive is less than 0.001 mol% with respect to cesium iodide, the target light emission luminance cannot be obtained without much difference from the light emission luminance obtained by using cesium iodide alone. Moreover, when it exceeds 50 mol%, the property and function of cesium iodide cannot be maintained.

  In the present invention, after a scintillator layer is formed on the polymer film by vapor deposition of the raw material of the scintillator, it is one hour in an atmosphere in a temperature range of −50 ° C. to + 20 ° C. based on the glass transition temperature of the polymer film. The above heat treatment is required. Thereby, the deformation | transformation of a film and generation | occurrence | production of peeling of a fluorescent substance do not generate | occur | produce, and a scintillator panel with high luminous efficiency is realizable.

(Reflective layer)
The reflective layer according to the present invention is for reflecting light emitted from the scintillator to enhance light extraction efficiency. The reflective layer is preferably formed of a material containing any element selected from the element group consisting of Al, Ag, Cr, Cu, Ni, Ti, Mg, Rh, Pt, and Au. In particular, it is preferable to use a metal thin film made of the above elements, for example, an Ag film, an Al film, or the like. Two or more such metal thin films may be formed.

  In addition, it is preferable from a viewpoint of the emitted light extraction efficiency that the thickness of a reflection layer is 0.01-0.3 micrometer.

(Protective layer)
The protective layer according to the present invention focuses on protecting the scintillator layer, but covers the entire scintillator panel including the base material. Cesium iodide (CsI) absorbs water vapor in the air and deliquesces when it is exposed with high hygroscopicity, and its main purpose is to prevent this.

  The protective layer can be formed using various materials. For example, a polyparaxylylene film is formed by a CVD method. That is, a polyparaxylylene film can be formed on the entire surface of the scintillator and the substrate to form a protective layer.

  Moreover, a polymer protective film can also be provided on the whole scintillator panel as a protective layer of another aspect. In addition, as a material of a polymer protective film, the film similar to the polymer film as a substrate material mentioned later can be used.

  The thickness of the polymer protective film is preferably 12 μm or more and 200 μm or less, more preferably 20 μm or more and 150 μm or less, taking into consideration the formation of voids, scintillator layer protection, sharpness, moisture resistance, workability, and the like. Is preferred.

  The light transmittance of the protective film is preferably 70% or more at 550 nm in consideration of photoelectric conversion efficiency, scintillator emission wavelength, etc., but a film having a light transmittance of 99% or more is difficult to obtain industrially. Substantially 99% to 70% is preferable.

The moisture permeability of the protective film is preferably 50 g / m ² · day (40 ° C., 90% RH) (measured according to JIS Z0208) or less, more preferably 10 g / m, taking into account the protection and deliquescence properties of the scintillator layer. ² · day (40 ° C./90% RH) (measured according to JIS Z0208) or less is preferable, but a film with a water vapor transmission rate of 0.01 g / m ² · day (40 ° C./90% RH) or less is industrially used. Substantially 0.01 g / m ² · day (40 ° C, 90% RH) or more, 50 g / m ² · day (40 ° C, 90% RH) (measured according to JIS Z0208) The following are preferable, and more preferably 0.1 g / m ² · day (40 ° C. · 90% RH) or more and 10 g / m ² · day (40 ° C. · 90% RH) (measured according to JIS Z0208) or less.

  The average roughness (Ra) of the protective layer in the present invention is defined by JIS surface roughness (B0601-1994). As a method for measuring the surface roughness (Ra), the humidity was adjusted for 24 hours under a condition where the measurement samples were not overlapped in an environment of 25 ° C. and 65% RH, and then measured in the environment. The non-overlapping condition shown here is, for example, one of a method of stacking paper between the scintillator panel and the scintillator panel, or a method of producing a frame with cardboard and fixing its four corners. Examples of the measuring apparatus that can be used include a RSTPLUS non-contact three-dimensional micro surface shape measuring system manufactured by WYKO.

(substrate)
The scintillator panel of the present invention preferably uses a polymer film as the substrate. As the polymer film, polymer films (plastic film) such as cellulose acetate film, polyester film, polyethylene terephthalate film, polyamide film, polyimide film, triacetate film, polycarbonate film, and carbon fiber reinforced resin sheet can be used. In particular, a polymer film containing any one of polyimide, polyethylene terephthalate, polyethylene naphthalate, and polycarbonate is suitable when a columnar scintillator is formed by a vapor phase method using cesium iodide as a raw material.

  The polymer film as the substrate according to the present invention is preferably a polymer film having a thickness of 25 to 1000 μm and further having flexibility.

Here, “a substrate having flexibility” means a substrate having an elastic modulus (E120) at 120 ° C. of 1000 to 6000 N / mm ² , and a polymer film containing polyimide or polyethylene naphthalate as such a substrate. Is preferred.

  Note that the “elastic modulus” means the slope of the stress with respect to the strain amount in a region where the strain indicated by the standard line of the sample conforming to JIS-C2318 and the corresponding stress have a linear relationship using a tensile tester. Is what we asked for. This is a value called Young's modulus, and in the present invention, this Young's modulus is defined as an elastic modulus.

Substrate used in the present invention, the elastic modulus at the 120 ° C. as described above (E120) is preferably a ^{1000N / mm 2 ~6000N / mm 2} . More preferably ^{1200N / mm 2 ~5000N / mm 2} .

Specifically, polyethylene naphthalate ^{(E120 = 4100N / mm 2)} , polyethylene terephthalate ^{(E120 = 1500N / mm 2)} , polybutylene naphthalate ^{(E120 = 1600N / mm 2)} , polycarbonate (E120 = 1700N / mm ²⁾ , Syndiotactic polystyrene (E120 = 2200 N / mm ² ), polyetherimide (E120 = 1900 N / mm ² ), polyarylate (E120 = 1700 N / mm ² ), polysulfone (E120 = 1800 N / mm ² ), polyethersulfone Examples thereof include a polymer film made of (E120 = 1700 N / mm ² ).

  These may be used singly or may be laminated or mixed. Among them, as a particularly preferable polymer film, a polymer film containing polyimide or polyethylene naphthalate is preferable as described above.

  Note that when the scintillator panel and the planar light receiving element surface are bonded together, the image quality is not uniform within the light receiving surface of the flat panel detector due to the influence of deformation of the substrate and warpage during vapor deposition. By making the substrate a polymer film having a thickness of 50 μm or more and 500 μm or less, the scintillator panel is deformed into a shape that matches the shape of the planar light receiving element surface, and uniform sharpness is obtained over the entire light receiving surface of the flat panel detector.

(Production method of scintillator panel)
A typical example of a method for manufacturing a scintillator panel of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing a schematic configuration of a radiation image sensor.

  First, radiation is incident on the radiation image sensor 100 from the substrate 1 a side of the reflective layer 3 of the scintillator panel 10. Then, the radiation incident on the radiation scintillator panel 10 is absorbed by the scintillator layer 2 in the radiation scintillator panel 10 and emits electromagnetic waves corresponding to the intensity thereof. The emitted electromagnetic wave is converted into an electronic signal as it is or reflected by the reflection layer 3 and installed in the photodetector 20, for example, a combination of a photodiode and a TFT (thin film transistor).

  Since the surfaces of the substrates 1a and 1b of the scintillator panel 10 are not smooth and rough, the radiation-transmitting substrate 1b holding the scintillator layer 2 and the reflective layer 3 do not adhere to each other, and have the air layer 6 and the dielectric layer of the present invention. Become.

  FIG. 2 is a diagram showing a schematic configuration of the vapor deposition apparatus 61.

<Vapor deposition equipment>
As shown in FIG. 2, the vapor deposition apparatus 61 has a box-shaped vacuum vessel 62, and a resistance heating crucible 63 for vacuum vapor deposition is disposed inside the vacuum vessel 62. The resistance heating crucible 63 is a filling member of a vapor deposition source, and an electrode is connected to the resistance heating crucible 63. When a current flows through the electrode to the resistance heating crucible 63, the resistance heating crucible 63 generates heat due to Joule heat. At the time of manufacturing the radiation scintillator panel 10, a mixture containing cesium iodide and an activator compound is filled in the resistance heating crucible 63, and an electric current flows through the resistance heating crucible 63, thereby heating and evaporating the mixture. Be able to.

  As the member to be filled, an alumina crucible around which a heater is wound may be applied, or a refractory metal heater may be applied.

  A holder 64 for holding the substrate 1 b is disposed inside the vacuum vessel 62 and directly above the resistance heating crucible 63. The holder 64 is provided with a heater (not shown), and the substrate 1b mounted on the holder 64 can be heated by operating the heater. When the substrate 1b is heated, the adsorbate on the surface of the substrate 1b is removed and removed, or an impurity layer is formed between the substrate 1b and the scintillator layer (phosphor layer) 2 formed on the surface. The adhesion between the substrate 1b and the scintillator layer 2 formed on the surface of the substrate 1b can be strengthened, and the film quality of the scintillator layer 2 formed on the surface of the substrate 1b can be adjusted. It has become.

  The holder 64 is provided with a rotating mechanism 65 that rotates the holder 64. The rotating mechanism 65 includes a rotating shaft 65a connected to the holder 64 and a motor (not shown) as a driving source thereof. When the motor is driven, the rotating shaft 65a rotates to resist the holder 64. It can be rotated while facing the heating crucible 63.

  In the vapor deposition apparatus 61, in addition to the above configuration, a vacuum pump 66 is disposed in the vacuum container 62. The vacuum pump 66 exhausts the inside of the vacuum vessel 62 and introduces gas into the inside of the vacuum vessel 62. By operating the vacuum pump 66, the inside of the vacuum vessel 62 has a gas atmosphere at a constant pressure. Can be maintained below.

<Scintillator panel>
Next, a method for manufacturing the scintillator panel 10 according to the present invention will be described.

  In the manufacturing method of the said scintillator panel 10 for radiation, the evaporator 61 demonstrated above can be used suitably. A method for producing the radiation scintillator panel 10 using the evaporation device 61 will be described.

<Formation of reflective layer>
A metal thin film (Al film, Ag film, etc.) as a reflective layer is formed on one surface of the substrate 1a by sputtering. Moreover, various types of films in which an Al film is sputter-deposited on a polymer film are distributed in the market, and these can be used as the substrate of the present invention.

<Formation of scintillator layer>
While attaching the board | substrate 1b to the holder 64, the resistance heating crucible 63 is filled with the powdery mixture containing a cesium iodide and a thallium iodide (preparation process). In this case, it is preferable that the distance between the resistance heating crucible 63 and the substrate 1b is set to 100 to 1500 mm, and the vapor deposition process described later is performed while remaining within the set value range.

  When the preparation process is completed, the vacuum pump 66 is operated to evacuate the inside of the vacuum vessel 62, and the inside of the vacuum vessel 62 is brought to a vacuum atmosphere of 0.1 Pa or less (vacuum atmosphere forming step). Here, “under vacuum atmosphere” means under a pressure atmosphere of 100 Pa or less, and preferably under a pressure atmosphere of 0.1 Pa or less.

  Thereafter, an inert gas such as argon is introduced into the vacuum vessel 62, and the inside of the vacuum vessel 62 is maintained in a vacuum atmosphere of 0.1 Pa or less. Thereafter, the heater of the holder 64 and the motor of the rotating mechanism 65 are driven, and the substrate 1b attached to the holder 64 is rotated while being heated while facing the resistance heating crucible 63.

  In this state, a current is passed from the electrode to the resistance heating crucible 63, and a mixture containing cesium iodide and thallium iodide is heated at about 700 to 800 ° C. for a predetermined time to evaporate the mixture. As a result, innumerable columnar crystals are sequentially grown on the surface of the substrate 1b to form the scintillator layer 2 having a desired thickness (evaporation process). Thereby, the scintillator panel 10 for radiation which concerns on this invention can be manufactured.

(Photodetector)
As shown in FIG. 1, the scintillator panel 10 faces the photodetector 20 and constitutes a radiation image sensor 100.

  The photodetector 20 converts the radiographic image record stored in the scintillator panel 10 into an optical image, and further converts the obtained optical image into an electronic signal image and stores it.

  For example, a combination of a photodiode and a TFT (thin film transistor) is installed in the photodetector 20 and converted into an electronic signal. This TFT may be an inorganic semiconductor type used in a liquid crystal display or the like, or an organic semiconductor, and is preferably a TFT formed on a plastic film.

Example 1
<Production of radiation image sensor>
(Production of radiation image sensor 1-1)
(Radiation transparent substrate)
A PEN (polyethylene naphthalate) film (manufactured by Teijin Limited: Teonex Q65F) having a thickness of 100 μm was prepared as a radiation transmissive substrate. The surface roughness Ra of the radiation transmissive substrate has two surfaces: a surface with Ra = 0.8 nm and a surface with Ra = 10.0 nm.

(Formation of scintillator layer)
A scintillator (CsI: 0.003 Tl) was vapor-deposited on the surface of the radiation transparent substrate having a surface roughness Ra = 10.0 nm using the vapor deposition apparatus shown in FIG. 2 to form a scintillator layer.

  First, a resistance heating crucible was filled as the phosphor material as an evaporation material, and the support was placed on a rotating support holder, and the distance between the support and the evaporation source was adjusted to 700 mm.

  Subsequently, the inside of the vapor deposition apparatus was once evacuated, Ar gas was introduced and the degree of vacuum was adjusted to 0.5 Pa, and then the support was rotated at a speed of 6 rpm.

  Furthermore, the temperature of the radiation transparent substrate was kept at 200 ° C. using a heating device in the vapor deposition apparatus. Next, the resistance heating crucible was heated to deposit a scintillator. When the film thickness reached 500 μm, the deposition was terminated to obtain a scintillator layer.

(Production of reflective layer)
A reflective layer (0.01 μm) was formed by sputtering aluminum on a 50 μm thick PEN (polyethylene naphthalate) film (Teijin Corp .: Teonex Q51DW) as a reflective layer support to obtain a reflective film.

(Formation of dielectric layer)
Air having a refractive index of 1.0 was used for the dielectric layer. The dielectric layer is an air layer formed when the surface of the substrate 1b having a scintillator layer having a substantially surface roughness (surface of Ra = 0.8 nm) and the reflective layer having a substantially surface roughness are overlapped. did.

(Preparation of protective layer)
An adhesive (Byron 300: manufactured by Toyobo Co., Ltd.) was applied on one side of a 12 μm thick PET film and dried to form an adhesive layer (1 μm), thereby preparing a first protective film. A second protective film was produced in the same manner as the first protective film. The two protective films are arranged so that the respective adhesive layers face each other, and the scintillator layer / radiation transmissive substrate / dielectric layer / reflective film (reflective layer / reflective layer support) from the adhesive layer on the second protective film side between them. Each layer is arranged in the order of body) / first protective film. The second protective film and the first protective film are prepared so as to have ears around the scintillator layer / radiation transmissive substrate / dielectric layer / reflective film (reflective layer / reflective layer support). . The ears of the two protective films are thermally bonded at 100 ° C., and the scintillator layer / radiation transmissive substrate / dielectric layer / reflective film (reflective layer / reflective layer support) is bonded with the second protective film and the first protective film. Package to obtain a scintillator panel. The packaging is performed in an atmosphere of a pressure of 100 kPa, and air remains in the packaged interior. Therefore, an air layer exists between the second protective film and the scintillator layer, between the radiation transmissive substrate and the reflective layer, and between the reflective layer support and the first protective film. In particular, the air layer between the radiation transmissive substrate and the reflective layer functions as a dielectric layer. In this case, the 1st protective film 4 and the 2nd protective film 5 become a protective layer.

(Production of radiation image sensor)
The obtained scintillator panel was set to a CMOS flat panel (X-ray CMOS camera system Shad-o-Box 4KEV manufactured by Radicon Co., Ltd.) in such a manner that the CMOS surface side and the second protective film face each other. Further, a sponge sheet was disposed on the carbon plate of the radiation incident window and the radiation incident surface (first protective film side) of the scintillator panel, and both were fixed by lightly pressing the planar light receiving element surface and the protective film 1. A radiation image sensor 1-1 was obtained.

(Production of radiation image sensor 1-2)
(Radiation transparent substrate)
A PEN (polyethylene naphthalate) film (manufactured by Teijin Limited: Teonex Q65F) having a thickness of 100 μm was prepared as a radiation transmissive substrate. The surface roughness Ra of the radiation transmissive substrate has two surfaces: a surface with Ra = 0.8 nm and a surface with Ra = 10.0 nm.

(Formation of scintillator layer)
A scintillator (CsI: 0.003 Tl) was vapor-deposited on the surface of the radiation transparent substrate having a surface roughness Ra = 10.0 nm using the vapor deposition apparatus shown in FIG. 2 to form a scintillator layer.

  First, a resistance heating crucible was filled as the phosphor material as an evaporation material, and the support was placed on a rotating support holder, and the distance between the support and the evaporation source was adjusted to 700 mm.

  Subsequently, the inside of the vapor deposition apparatus was once evacuated, Ar gas was introduced and the degree of vacuum was adjusted to 0.5 Pa, and then the support was rotated at a speed of 6 rpm.

  Furthermore, the temperature of the radiation transparent substrate was kept at 200 ° C. using a heating device in the vapor deposition apparatus. Next, the resistance heating crucible was heated to deposit a scintillator. When the film thickness reached 500 μm, the deposition was terminated to obtain a scintillator layer.

(Production of reflective layer)
Aluminum was sputtered onto a PET film having a thickness of 12 μm, which was a support for the reflective layer, to form a reflective layer having a thickness of 0.01 μm. Further, an adhesive (Byron 300: manufactured by Toyobo Co., Ltd.) was applied to the aluminum sputter surface and dried to form an adhesive layer (1 μm), thereby producing a reflective film having a configuration of adhesive layer / reflective layer / reflective layer support.

(Formation of dielectric layer)
Air having a refractive index of 1.0 was used for the dielectric layer. The dielectric layer is an air layer formed when the surface of the substrate 1b having a scintillator layer having a substantially surface roughness (surface of Ra = 0.8 nm) and the reflective layer having a substantially surface roughness are overlapped. did.

(Preparation of protective layer)
An adhesive (Byron 300: manufactured by Toyobo Co., Ltd.) was coated on one side of a 12 μm thick PET film and dried to form an adhesive layer (1 μm), thereby preparing a second protective film. The adhesive layers of the second protective film and the reflective film are arranged so as to face each other, and the scintillator layer / radiation transmissive substrate / dielectric layer / reflective film (adhesive layer / reflective film) from the adhesive layer on the second protective film side therebetween. Each layer is arranged in the order of layer / reflective layer support). The second protective film and the reflective film are made so that the scintillator layer / radiation transmissive substrate / dielectric layer can be packaged with ears around the periphery. The ears of the second protective film and the reflective film are thermally bonded at 100 ° C., and the scintillator layer / radiation transmissive substrate / dielectric layer is wrapped with the second protective film and the reflective film to obtain a scintillator panel. The packaging is performed in an atmosphere of a pressure of 100 kPa, and air remains in the packaged interior. Therefore, an air layer exists between the second protective film and the scintillator layer, and between the radiation transmissive substrate and the reflective layer. In particular, the air layer between the radiation transmissive substrate and the reflective layer functions as a dielectric layer. In this case, the 2nd protective film 5 and the board | substrate 1a which has a reflection layer become a protective layer.

(Production of radiation image sensor)
The obtained scintillator panel was set to a CMOS flat panel (Radicon X-ray CMOS camera system Shad-o-Box 4KEV) in such a manner that the CMOS surface side and the protective film 1 face each other. Furthermore, a sponge sheet was placed on the carbon plate of the radiation incident window and the radiation incident surface (reflective film side) of the scintillator panel, and both were fixed by lightly pressing the planar light receiving element surface and the second protective film. A radiation image sensor 1-2 was obtained.

(Production of radiation image sensor 1-3)
A radiation image sensor 1-3 was produced in the same manner as the radiation image sensor 1-2 except that the adhesive layer of the reflective film was formed only on the ear.

(Preparation of radiation image sensor 1-4)
Radiation image except that a reflective layer (0.01 μm) is formed by sputtering aluminum on the surface of the radiation transparent substrate having a surface roughness Ra = 10.0 nm, and a scintillator layer is formed on the surface of the reflective layer. A radiation image sensor 1-4 was produced by the same method as the production of the sensor 1. This sample does not have a dielectric layer.

(Evaluation of radiation image sensor)
Using this radiation image sensor 1-1 to radiation image sensor 1-4, the output luminance was measured from 12-bit output data by the following method, and evaluated by the following method.

  X-rays having a tube voltage of 80 kVp were irradiated from the back surface (surface on which the scintillator layer was not formed) of each sample, and image data was detected by a CMOS flat panel on which the scintillator was arranged and recorded on a hard disk. Thereafter, the recording on the hard disk was analyzed by a computer, and the average count of the entire imaging region of the X-ray image recorded on the hard disk was calculated. A numerical value normalized by setting the average count of the radiation image sensor 1-4 to 1.0 for the average count of each sample was defined as the output luminance.

(Evaluation results of radiation image sensor)
The evaluation results are shown in Table 1. As shown in Table 1, it was confirmed that the radiation image sensors 1-1 to 1-3 according to the present invention are superior in output luminance compared to the radiation image sensor 1-4 as a comparative example.

  As is clear from the results shown in Table 1, it can be seen that the examples according to the present invention are superior in graininess compared to the comparative examples.

Example 2
(Production of radiation image sensor 2-1)
A radiation image sensor 2-1 was produced in the same manner as the radiation image sensor 1-1 except that the reflective layer was silver.

(Production of radiation image sensor 2-2)
A radiation image sensor 2-2 was produced by the same method as the radiation image sensor 1-2 except that the reflective layer was silver.

(Production of radiation image sensor 2-3)
A radiation image sensor 2-3 was produced in the same manner as the radiation image sensor 1-3 except that the reflective layer was silver.

(Production of radiation image sensor 2-4)
A radiation image sensor 2-4 was produced in the same manner as the radiation image sensor 1-4 except that the reflective layer was silver.

(Evaluation of radiation image sensor)
Evaluation was performed in the same manner as in Example 1. The average count of the radiation image sensor 2-4 was normalized to 1.0, and the output luminance of each sample was obtained (evaluation result of the radiation image sensor).
The evaluation results are shown in Table 2.

  As shown in Table 2, it was confirmed that the radiation image sensors 2-1 to 2-3 according to the present invention are superior in output luminance as compared with the radiation image sensor 2-4 as a comparative example.

It is sectional drawing which shows schematic structure of a radiation image sensor. It is a figure which shows schematic structure of a vapor deposition apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1a, 1b Board | substrate 2 Scintillator (phosphor) layer 3 Reflective layer 4 1st protective film 5 2nd protective film 6 Air layer 10 Scintillator panel 20 Photo detector 61 Deposition apparatus 62 Vacuum vessel 63 Resistance heating crucible (filled member)
64 Holder 65 Rotating mechanism 66 Vacuum pump 100 Radiation image sensor

Claims (7)

A scintillator comprising a scintillator layer for converting radiation into light, a radiation transmissive substrate for supporting the scintillator layer, a reflection layer for emitting light converted by the scintillator layer to the outside, and a dielectric layer In the panel, the layers are arranged in the order of a reflective layer, a dielectric layer, a radiation transmissive substrate, and a scintillator layer, and the radiation transmissive substrate has a transmittance of 5% or more of light converted by the scintillator layer. A scintillator panel, wherein the dielectric layer has a refractive index smaller than that of the radiation transmissive substrate. The scintillator panel according to claim 1, wherein the dielectric layer is made of air. The scintillator panel according to claim 1 or 2, wherein the scintillator layer contains cesium iodide as a main component. The scintillator panel according to any one of claims 1 to 3, wherein a thickness of the radiation transmissive substrate is from 25 µm to 1000 µm. The scintillator panel according to any one of claims 1 to 4, wherein the radiation transmissive substrate is mainly composed of any one of PI, PET, PEN, and polycarbonate. The scintillator panel according to any one of claims 1 to 5, wherein the reflective layer contains Al, Ag, or Au as a main component. A radiation image sensor comprising a photodetector for the scintillator panel according to claim 1.

Images