WO2018110061A1

WO2018110061A1 - Scintillator plate, radiation detector and radiation detection system

Info

Publication number: WO2018110061A1
Application number: PCT/JP2017/037101
Authority: WO
Inventors: 小林　玉樹; 智之大池; 徹則尾島
Original assignee: キヤノン株式会社
Priority date: 2016-12-12
Filing date: 2017-10-13
Publication date: 2018-06-21
Also published as: JP2018096792A

Abstract

A scintillator plate which comprises: a scintillator that has a plurality of columnar crystals arranged on a substrate; and a protective film that covers the scintillator. The protective film comprises a first layer and a second layer that covers the first layer; the first layer contains a fluorine resin; and the second layer contains a metal alkoxide and a crosslinked body that is obtained by crosslinking some of the metal atoms contained in the metal alkoxide by means of oxygen.

Description

Scintillator plate, radiation detection apparatus and radiation detection system

The present invention relates to a scintillator plate, a radiation detection apparatus, and a radiation detection system.

Radiation detection apparatuses that combine a scintillator that converts radiation into light and a photoelectric conversion element that detects light converted by the scintillator are widely used. The scintillator is required to efficiently propagate light converted from radiation to the photoelectric conversion element. In order to propagate light efficiently, it is known to use a scintillator having a columnar crystal (which may also be referred to as a needle-like crystal) to propagate light within the columnar crystal. Alkali halide crystals typified by CsI are widely used as scintillators having columnar crystals, but alkali halide crystals exhibit deliquescence, and when exposed to the atmosphere, they are easily deliquescent and altered by water vapor contained in the atmosphere. Patent Document 1 discloses that the scintillator is covered with a polyparaxylylene film in order to prevent contact between the scintillator and water vapor in the atmosphere, thereby suppressing deliquescence of the scintillator.

Japanese Patent Laid-Open No. 2000-9845

When a thick polyparaxylylene film is used as a protective film for protecting the scintillator from water vapor in the atmosphere as shown in Patent Document 1, the effect of suppressing the deliquescence of the scintillator is improved. On the other hand, when the protective film is thickened, the spatial resolution of the radiation detection apparatus may be reduced. However, if the protective film using the polyparaxylylene film is thinned, the effect of suppressing the deliquescence of the scintillator is lowered.

The object of the present invention is to provide a technique advantageous for suppressing deterioration of the characteristics of the scintillator.

In view of the above problems, a scintillator plate according to an embodiment of the present invention is a scintillator plate that includes a scintillator having a plurality of columnar crystals arranged on a substrate, and a protective film that covers the scintillator. Includes a first layer and a second layer covering the first layer, the first layer includes a fluororesin, and the second layer is included in the metal alkoxide and the metal alkoxide. And a cross-linked product in which part of metal atoms are cross-linked with oxygen.

The above means provides a technique advantageous for suppressing deterioration of the characteristics of the scintillator.

Other features and advantages of the present invention will become apparent from the following description with reference to the accompanying drawings. In the accompanying drawings, the same or similar components are denoted by the same reference numerals.

The accompanying drawings are included in the specification, constitute a part thereof, show an embodiment of the present invention, and are used to explain the principle of the present invention together with the description.
Sectional drawing which shows the structural example of the scintillator plate which concerns on embodiment of this invention. Sectional drawing which shows the structural example of the radiation detection apparatus using the scintillator plate of FIG. The figure which shows the result of MTF evaluation of the scintillator plate of FIG. The figure which shows the result of MTF evaluation of the scintillator plate of FIG. The figure which shows the structural example of the radiation detection system using the radiation detection apparatus of FIG.

Hereinafter, specific embodiments of a scintillator plate, a radiation detection apparatus, and a radiation detection system according to the present invention will be described with reference to the accompanying drawings. The radiation in the present invention includes a beam having energy of the same degree or more, such as X-rays, β-rays, γ-rays, etc., which are beams formed by particles (including photons) emitted by radiation decay, such as X It can also include rays, particle rays, and cosmic rays.

With reference to FIG. 1, the structure of the scintillator plate according to the embodiment of the present invention will be described. FIG. 1 is a cross-sectional view showing a configuration of a scintillator plate 100 according to an embodiment of the present invention. The scintillator plate 100 includes a scintillator 110 that converts incident radiation into light, a substrate 120 that holds the scintillator 110, and a protective film 130 that covers the scintillator 110. In the present embodiment, the scintillator 110 is composed of a plurality of columnar crystals. The protective film 130 has a stacked structure of a first layer 131 and a second layer 132 that covers the first layer 131.

First, the protective film 130 will be described in detail. The protective film 130 is provided to protect the scintillator 110 that exhibits deliquescence such as cesium iodide (CsI). A fluororesin is used for the first layer 131 of the protective film 130 and can be in contact with a columnar crystal body (columnar crystal) of the scintillator 110. The second layer 132 of the protective film 130 includes a metal alkoxide and a crosslinked body in which some metal atoms included in the metal alkoxide are crosslinked with oxygen. The second layer 132 covers the side of the first layer 131 opposite to the scintillator 110 and can be in contact with the first layer 131. The second layer 132 does not necessarily cover the scintillator 110 via the first layer 131, and the second layer 132 may be in contact with the scintillator 110 depending on the portion.

As the fluororesin used for the first layer 131, polytetrafluoroethylene (PTFE), tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene / hexafluoropropylene copolymer (FEP), tetrafluoro Materials that contain fluorine in the constituent molecules such as ethylene / ethylene copolymer (ETFE), polyvinylidene fluoride (PVDF), polychlorotrifluoroethylene (PCTFE), chlorotrifluoroethylene / ethylene copolymer (ECTFE) are used May be. Further, as a method for forming the fluororesin used for the first layer 131, the first layer 131 may be formed by application using a spray using a fluorine-based coating agent used as a moisture-proof coating agent. The film thickness of the first layer 131 can be reduced by diluting the fluororesin with a solvent to reduce the solid concentration.

However, when the thickness of the first layer 131 using a fluororesin is reduced, the first layer 131 alone may be insufficient as a protective film for protecting the scintillator 110. This is because the film thickness of the first layer 131 is thin, so that intrusion of water molecules cannot be sufficiently suppressed, or there may be a site where the scintillator 110 cannot be covered. In order to prevent this, a second layer 132 described later is formed so as to cover the first layer 131. When the first layer 131 is formed by application using spray as described above, the first layer 131 can be formed relatively easily. For this reason, after forming the scintillator 110 using a vacuum deposition method or the like, the first layer 131 covering the scintillator 110 can be formed immediately when the substrate 120 on which the scintillator 110 is formed is taken out of the vacuum container. Thereafter, the second layer 132 is formed. After the formation of the first layer 131, until the formation of the second layer 132, the influence of water molecules can be substantially suppressed even if exposed to the atmosphere for about several hours. It became clear by experiment (Example).

The protective film 130 including the first layer 131 and the second layer 132 has a function of suppressing the influence of water molecules if the fluororesin constituting the first layer 131 is in a short time (about several hours). Have. Furthermore, since the second layer 132 contains a metal alkoxide and a cross-linked product thereof, the second layer 132 has an effect of capturing and consuming water molecules and an effect of not allowing water molecules to physically permeate. By these effects, the influence of water molecules on the scintillator 110 can be suppressed. Since the protective film using polyparaxylylene disclosed in Patent Document 1 only suppresses the permeation of water molecules, the water molecules that have once permeated the protective film remain inside the protective film, and the scintillator Degradation can proceed by contacting 110 with water molecules. On the other hand, in this embodiment, the metal alkoxide used for the second layer 132 consumes water molecules when contacted with water molecules, causes hydrolysis, and generates hydroxyl groups and alcohol molecules bonded to metal atoms. . For this reason, the protective film 130 can suppress the influence of the water molecules on the scintillator 110 by capturing and consuming the water again even when the water molecules permeate the protective film 130. For this reason, in the protective film 130, not only the thickness of the first layer 131 is reduced, but also the thickness of the second layer 132 is reduced and the thickness of the entire protective film 130 is reduced. 110 can be prevented from deteriorating.

Here, in the crosslinked body in which some metal atoms of the metal alkoxide included in the second layer 132 are crosslinked with oxygen, the stoichiometric ratio of the alkoxide atoms to the metal atoms is 0.02 or more and 1 or less. Also good. An alkoxide atom means atoms other than a metal among the atoms contained in a metal alkoxide. Further, the stoichiometric ratio of the alkoxide atom to the metal atom may be 0.02 or more and 1 or less in the entire second layer 132. The amount of the alkoxide can be controlled by adjusting the activation during the reaction for crosslinking the metal alkoxide. For example, when the activation amount of the metal alkoxide is increased, the amount of the alkoxide of the crosslinked product is reduced. . The alkoxide contained in the compound of the metal alkoxide constituting the second layer 132 and its cross-linked product may be Fourier transform infrared spectroscopy (FT-IR) or time-of-flight secondary ion mass spectrometry (TOF-SIMS). Qualitative analysis can be performed by law. The alkoxide contained in the compound can be quantitatively analyzed by FT-IR or X-ray photoelectron spectroscopy (XPS). However, when quantitative analysis is performed using the XPS method, the compound must contain carbon (C) other than alkoxide. In addition, when performing quantitative analysis using FT-IR, first, a compound in which C is contained only in alkoxide is prepared, and quantitative analysis is performed by XPS method. Subsequently, a calibration curve is prepared by measuring a compound in which C is contained only in the alkoxide by the FT-IR method. Thereafter, quantitative analysis can be performed by measuring a compound containing the desired metal alkoxide and its crosslinked product.

When the amount of the alkoxide in the crosslinked body increases with respect to the metal atoms, the crosslinked body of the second layer 132 constituting the protective film 130 decreases, and the strength of the entire protective film 130 may be weakened. In addition, the density of the protective film 130 may be reduced, and water molecules may be easily transmitted. On the other hand, when the amount of the alkoxide in the crosslinked body with respect to the metal atom is reduced, the effect of capturing and consuming water molecules is reduced, and the effect of suppressing the deterioration of the scintillator 110 can be reduced. For this reason, as described above, the amount of alkoxide atoms contained in the crosslinked product may be appropriately adjusted.

The film thickness of the protective film 130 may be 100 nm or less. The light converted from the radiation in the scintillator 110 is guided through the columnar crystal of the scintillator 110 due to the difference in refractive index between the scintillator 110 and air. On the other hand, the difference in refractive index between the scintillator 110 and the protective film 130 is smaller than the difference in refractive index between the scintillator 110 and air. When the protective film 130 fills the gap between the columnar crystals of the adjacent scintillators 110, light may diffuse between the adjacent columnar crystals through the protective film 130. Since the gap between the columnar crystals is 200 nm or more near the tip of the columnar crystal of the scintillator 110 to be described later, if the film thickness of the protective film 130 is 100 nm or less, the gap between the columnar crystals may remain. When air is present outside the protective film 130, the light guided through the columnar crystal of the scintillator 110 is reflected between the protective film 130 and the air, and passes through the structure that combines the columnar crystal and the protective film 130. Can be guided. As a result, light diffusion can be suppressed. Since the voids of the columnar crystals of the scintillator 110 are not uniform, the thickness of the protective film 130 may be as thin as possible in order to leave the voids even in a narrow place.

The film thickness of the first layer 131 in the protective film 130 may be, for example, 100 nm or less. When the protective film 130 is set to 100 nm or less as described above, the thickness of the first layer 131 may be, for example, 50 nm or less in consideration of the thickness of the second layer 132. Further, the second layer 132 can capture and consume water molecules and suppress permeation even when the film thickness is small. For this reason, the film thickness of the second layer 132 may be, for example, 100 nm or less. When the protective film 130 is set to 100 nm or less as described above, the thickness of the second layer 132 may be, for example, 50 nm or less in consideration of the thickness of the first layer 131. In the scintillator 110, since there is a portion where the gap between the columnar crystals is locally narrow, the thinner the protective film 130 may be as a waveguide as described above. On the other hand, when the protective film 130 is too thin, the effect of suppressing the permeation of water molecules and the effect of capturing and consuming water molecules can be reduced. In addition, when the thickness of the protective film 130 is too thin, the strength of the protective film 130 itself may be reduced. For this reason, the film thickness of the protective film 130 may be 0.3 nm or more. The film thicknesses of the first layer 131 and the second layer 132 can be appropriately set within a range in which deterioration of the scintillator 110 can be suppressed.

Further, as shown in FIG. 1, the protective film 130 may cover the columnar crystals of the scintillator 110 one by one from the tip to the side surface up to the substrate 120. Further, for example, the protective film 130 may cover at least 100 μm or more from the front end to the side surface of the scintillator 110 one by one. However, the portion where the adjacent columnar crystals of the scintillator 110 are in contact or close to each other may not be covered with the protective film 130.

In the radiation detection apparatus using the scintillator plate 100 shown in this embodiment, by thinning the protective film 130, most of the light generated in the scintillator 110 repeats total reflection or Fresnel reflection in the columnar crystal of the scintillator 110. As a result, much of the generated light can be guided through the scintillator 110 and the protective film 130 and incident on the light receiving surface. In this case, the light can be efficiently received in the vicinity of the position of the foot of the perpendicular line that is lowered from the light emitting point (where the light is generated) toward the light receiving surface. In other words, the light diffusion can be suppressed by the many optical interfaces guiding the light toward the light receiving surface. Further, since the thickness of the protective film 130 at the tip of the scintillator 110 is thin, the light emitted from the tip of the scintillator 110 is scattered and spreads in the protective film 130 between the tip of the scintillator 110 and the light receiving surface. Can also be suppressed. As a result, diffusion of light generated in the scintillator 110 is suppressed, and a radiation detection apparatus with high spatial resolution can be obtained.

In this embodiment, the protective film 130 has a two-layer structure of the first layer 131 and the second layer 132, but is not limited thereto. A three-layer structure in which a layer using a fluororesin is further formed so as to cover the first layer 131 and the second layer 132 may be used. Further, a metal alkoxide and a part of the metal may be oxygen. A four-layer structure in which a layer containing a crosslinked product is formed may be used.

As the metal alkoxide used for the second layer 132, a metal alkoxide represented by the following general formula (1) may be used.

M1 (OR) _n ... (1)

Here, M1 is at least one selected from silicon (Si), aluminum (Al), titanium (Ti), and zirconium (Zr). R is at least one selected from a methyl group, an ethyl group, a propyl group, an isopropyl group, and a butyl group. M1 may be phosphorus (P), boron (B), hafnium (Hf), or tantalum (Ta). Further, as the metal alkoxide, a metal-substituted derivative in which a halogen, an amino group and a hydrogen atom thereof are substituted, or acetylene may be used. These also react with water to cause hydrolysis and form a hydroxyl group on the metal atom.

For example, tetraethyl orthosilicate (TEOS: Si (OC ₂ H ₅ ) ₄ ) may be used as a precursor of a metal alkoxide when forming a second layer 132 described later. In the above general formula (1), the metal alkoxide precursor may be n when M1 is Si, Ti and Zr, and n may be 3 when M1 is Al.

Further, the second layer 132 constituting the protective film 130 may include a hydroxyl group bonded to a metal atom. Hydroxyl groups can hydrogen bond with water molecules and trap water molecules. However, at the same time, the affinity for water is increased, so that when there are excessive hydroxyl groups, the permeability of water molecules is increased. For this reason, in the second layer 132, the stoichiometric ratio of the hydroxyl group to the metal atoms contained in the second layer 132 may be 2.5 or less, and may be 2 or less.

Further, the second layer 132 constituting the protective film 130 may contain hydrogen atoms bonded to metal atoms. When the ratio of metal atoms having a structure in which all the bonds are bonded to other metal atoms through oxygen is increased, structural distortion may occur in the second layer 132, and cracks may occur. Therefore, the generation of cracks can be prevented by including a bond between a metal atom and a hydrogen atom. However, when the ratio of the bond between the metal atom and the hydrogen atom increases, a small gap increases in the structure of the second layer 132. Therefore, in the second layer 132, the stoichiometric ratio of hydrogen atoms to metal atoms contained in the second layer 132 may be 1 or less.

Next, a method for forming the protective film 130 in this embodiment will be described. The protective film 130 has a two-layer structure as described above. First, as a method of forming the fluororesin used for the first layer 131, as described above, the first layer 131 is formed by spraying using a fluorine-based coating agent used as a moisture-proof coating agent. Also good. For example, Novec 2702 (registered trademark) manufactured by 3M Japan Co., Ltd. can be used as the fluorine-based coating agent, and Novec 7200 (registered trademark) can be used as the solvent. By diluting with a solvent, the first layer 131 can be formed in a desired thickness. For example, the first layer 131 can be formed to have a thickness of 20 nm or less by diluting with a solvent 30 times and performing application by spraying. After the scintillator 110 is formed by a vacuum deposition method, the first layer 131 is quickly formed when the scintillator 110 is taken out of the vacuum vessel. It has been confirmed from the measurement of spatial resolution, which will be described later, that the moisture-proof effect of about several hours can be obtained by the first layer 131 made of a fluororesin formed using a fluorine-based coating agent. Therefore, the second layer 132 may be formed within a time during which the moistureproof effect can be maintained. In designing the formation process of the protective film 130, it is not necessary to store the substrate 120 on which the scintillator 110 is formed in a vacuum, and the inspection can be performed in the atmosphere. large.

Next, a method for forming the second layer 132 will be described. The second layer 132 can be formed by causing a reaction by bringing the metal alkoxide into contact with the scintillator 110 having a plurality of columnar crystals held on the substrate 120. By activating the metal alkoxide, the reaction for forming the second layer 132 is promoted. As an activation method, heat, plasma, chemical reaction, or the like can be used. By appropriately controlling the activation of the metal alkoxide, the scintillator 110 can be covered with the second layer 132 constituting the protective film 130 from each tip of the columnar structure of the scintillator 110 to a portion close to the back substrate 120. . By covering the back of the columnar crystal of the scintillator 110 with the second layer 132, it can be expected to suppress the deterioration of the scintillator 110 even with the protective film 130 having a thinner thickness.

Next, the scintillator 110 used for the scintillator plate 100 of this embodiment will be described. In this embodiment, the scintillator 110 is an aggregate of a plurality of columnar crystals that are formed on the substrate 120 and project from the surface of the substrate 120, and converts incident radiation into light. The scintillator 110 absorbs the energy of incident radiation and can emit light in the range from 300 nm to 800 nm, that is, light from ultraviolet light to infrared light centering on so-called visible light. The major axis of the columnar crystal of the scintillator 110 may intersect the substrate 120 perpendicularly, but does not have to be strictly perpendicular and may be inclined. The influence on the effect of the present embodiment, which is not strictly vertical, is small. The light emitted from the scintillator 110 needs to be guided to the light receiving surface while propagating through the scintillator 110. For this reason, the angle formed by the long axis of the columnar crystal of the scintillator 110 and the perpendicular of the surface of the substrate 120 on which the scintillator 110 is formed may be less than 45 degrees. Further, the inclination of each columnar crystal of the scintillator 110 may not be uniform. For this reason, the scintillator 110 can include a large number of optical interfaces having an angle of less than 45 degrees with respect to the normal to the surface of the substrate 120. In the present embodiment, as described above, since the protective film 130 may be thinned, the optical interface between the scintillator 110 and the protective film 130 is substantially equal to the optical interface between the scintillator 110 and air, and light diffusion is reduced. Can be suppressed.

As long as the scintillator 110 has a columnar crystal structure, the columnar crystal may be cylindrical or polygonal. Further, the scintillator 110 does not need to have a uniform columnar crystal, and the scintillator 110 may include, for example, a columnar crystal and a polygonal columnar crystal. Furthermore, the thickness of each columnar crystal of the scintillator 110 need not be uniform. Here, the thickness of the columnar crystal refers to the thickness in the direction orthogonal to the major axis of the columnar crystal that grows in the direction intersecting with the substrate 120 described above. In the scintillator 110, the thickness of each columnar crystal may be distributed. The thickness of each columnar crystal of the scintillator 110 may be not less than 0.1 μm and not more than 50 μm, and may be not less than 0.1 μm and not more than 15 μm. When the thickness of the columnar crystal of the scintillator 110 is less than 0.1 μm, the thickness of the columnar crystal is smaller than the wavelength of light generated in the scintillator 110, so that geometric light diffraction and optical scattering are reduced. It may be difficult to cause the light to be guided toward the light receiving surface. For this reason, light diffuses out of the columnar crystal of the scintillator 110, which can be a factor of reducing the spatial resolution in a radiation detector using such a scintillator 110. On the other hand, in theory, it is difficult to resolve the scintillator plate 100 that is smaller than the thickness of each columnar crystal of the scintillator 110. Therefore, when the thickness of each columnar crystal of the scintillator 110 is larger than 50 μm, for example, not only a high spatial frequency region such as 10 LP / mm but also a spatial resolution in a low spatial frequency region such as 1 LP / mm is reduced. It can be.

Further, in each columnar crystal of the scintillator 110, the thickness in the columnar crystal does not need to be uniform, and even if the change in thickness from one end to the other end is 50 μm or less, for example. Good. However, in the present embodiment, the columnar crystal includes a needle-like structure that is thick on the side of the substrate 120 and becomes tapered as the distance from the substrate 120 increases. When the columnar crystal of the scintillator 110 has a needle-like structure, the tip of the scintillator 110 (the end opposite to the side in contact with the substrate 120) is 50 μm or thinner than other portions such as the portion in contact with the substrate 120 of the scintillator 110. It may be. In addition, the cross-sectional shape of the columnar crystal of the scintillator 110 may not be uniform from one end to the other end. For example, a crystal that has a polygonal columnar shape in a portion close to the substrate 120 is As the distance increases, it may change to a cylindrical shape.

The length (height) of the scintillator 110 is the length of the major axis of the columnar crystal, and it is better that the variation in the length of each columnar crystal of the scintillator 110 is smaller, even if the length is uniform. Good. However, the length is not necessarily uniform, and the scintillator 110 may have a long columnar crystal and a short columnar crystal. Even when light leaks from the end of the short columnar crystal, the light can enter the adjacent columnar crystal and propagate through the columnar crystal of the scintillator 110 as it is toward the light receiving surface. Therefore, even the scintillator 110 in which long and short columnar crystals are mixed can suppress light diffusion and thus has optical waveguide properties.

The length of the long axis of each columnar crystal of the scintillator 110 does not greatly affect the effect of the present embodiment, and the effect of the present embodiment can be achieved regardless of whether the scintillator 110 is short or long. Therefore, the length of the scintillator 110 is not particularly limited, but may be 100 nm or more and 10 cm or less in consideration of a realistic manufacturing process. Furthermore, the length of the scintillator 110 may be 1 μm or more and 1 cm or less.

The columnar crystals adjacent to each other of the scintillator 110 may have independent columnar structures in which the distance between the side surfaces is 200 nm or more and 1 μm or less. However, the columnar crystals are not completely separated from each other, and the optical interface may exist intermittently in a direction intersecting the surface of the scintillator 110. Even when the optical interface is intermittently present, the scintillator 110 can have optical waveguide properties. A plurality of voids or light scatterers may exist in the scintillator 110. Light is scattered by the air gap or the light scatterer, but the scattered light can enter the columnar crystal of the nearby scintillator 110 and propagate toward the light receiving surface. For this reason, the scintillator 110 can have optical waveguide properties even if a plurality of voids or scatterers are included therein. Further, the scintillator 110 may have a flat end at each columnar crystal. In that case, the unevenness with the light receiving surface is reduced, and it can be expected that the light is efficiently received by the light receiving surface.

As a material for forming the scintillator 110, various known scintillator materials can be used. In this embodiment, since the scintillator 110 is covered with the thin protective film 130 and is not easily affected by water molecules, a material that deteriorates in contact with water molecules can be used as the scintillator 110. Specifically, the scintillator 110 includes a compound having deliquescence, and among them, a halide such as a metal halide can be used. When a metal halide is exposed to the atmosphere, it deliquesces and its structure changes. When the deliquescent structure changes, the light propagating in the scintillator 110 diffuses out of the scintillator 110, and the spatial resolution in the radiation detector can be reduced. Here, the present embodiment is not limited to deliquescence, but can be applied to the scintillator 110 using a material that degrades by contact with water molecules and can reduce the spatial resolution in the radiation detector.

As a representative material among metal halides, there is an alkali halide such as CsI. CsI has high conversion efficiency of X-rays into visible light in radiation. CsI can easily form the scintillator 110 having columnar crystals by vapor deposition, and can increase the length of the scintillator 110. Since CsI alone does not have sufficient luminous efficiency, an activator is added. For example, indium (In), thallium (Tl), lithium (Li), potassium (K), rubidium (Rb), sodium (Na), or the like is used as the activator.

For example, the scintillator 110 can be formed using an additive containing one or more Tl compounds and CsI as a raw material for forming a CsI scintillator containing Tl. CsI: Tl has a broad emission wavelength from 400 nm to 750 nm. As the Tl compound containing one or more types of Tl compounds, monovalent and trivalent oxidation number compounds can be used. For example, thallium iodide (TlI), thallium bromide (TlBr), thallium chloride (TlCl), thallium fluoride (TlF, TlF ₃ ), or the like can be used. The content of the activator may be appropriately adjusted according to the target performance. For example, it may be 0.01 mol% or more and 20 mol% or less with respect to CsI.

As the alkali halide used for the scintillator 110, an alkali halide represented by the following general formula (2) may be used.

M2X1, αM3X2, βM4X3: γA1 (2)

Here, M2 is at least one selected from lithium (Li), sodium (Na), potassium (K), rubidium (Rb), and cesium (Cs). M3 is from beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), zinc (Zn), cadmium (Cd), copper (Cu), and nickel (Ni) At least one selected. M4 is scandium (Sc), yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium ( Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), aluminum (Al), gallium (Ga), and At least one selected from indium (In). X1, X2, and X3 are each independently at least one selected from fluorine (F), chlorine, (Cl), bromine (Br), and iodine (I). A1 is Eu, Tb, In, bismuth (Bi), Ce, Tm, Dy, Pr, Ho, Nd, Yb, Er, Gd, Lu, Sm, Y, thallium (Tl), Na, silver (Ag), It is at least one selected from Cu and Mg. α, β, and γ represent numerical values in the ranges of 0 ≦ α <0.5, 0 ≦ β <0.5, and 0 <γ ≦ 0.2, respectively.

Further, as the scintillator 110, a halide compound can be used in addition to the above-mentioned alkali halide, and a rare earth activated alkaline earth metal fluoride halogen compound represented by the general formula (3) may also be used.

M5FX4: δA2 (3)

Here, M5 is at least one alkaline earth metal atom selected from Ba, Sr, and Ca. A2 is at least one rare earth atom selected from Ce, Pr, Sm, Eu, Tb, Dy, Ho, Nd, Er, Tm, and Yb. X4 is at least one halogen atom selected from Cl, Br, and I. δ represents a numerical value within a range of 0 <δ ≦ 0.2.

In the present embodiment, a compound other than the above-described halide compound may be used as the scintillator 110. Specifically, LnTaO ₄ : (Nb, Gd) system, Ln ₂ SiO ₅ : Ce system, LnO _X : Tm system (Ln represents a rare earth element), Gd ₂ O ₂ S: Tb, Gd ₂ O ₂ S: Pr, Ce, ZnWO ₄ , LuAlO ₃ : Ce, Gd ₃ Ga ₅ O ₁₂ : Cr, HfO ₂ and the like.

In this embodiment, the substrate 120 may be a solid that can hold the scintillator 110. A sensor panel in which a substrate formed of a material such as a metal and its oxide, a semiconductor and its oxide, glass, or resin, or a photoelectric conversion element for detecting light on these substrates is formed on the substrate 120. Can be used as

Next, the radiation detection apparatus 200 including the scintillator plate 100 according to the present embodiment will be described with reference to FIG. FIG. 2 is a cross-sectional view of a radiation detection apparatus 200 including the scintillator plate 100 of the present embodiment. The radiation detection apparatus 200 includes a sensor panel 201 in addition to the scintillator plate 100 described above. The sensor panel 201 includes a light detection unit 203 disposed on the substrate 202. The light detection unit 203 is provided with a plurality of photoelectric conversion elements 204 for detecting light converted from radiation by the scintillator 110. The radiation detection apparatus 200 detects radiation when light converted from radiation by the scintillator 110 enters the light receiving surface of the photoelectric conversion element 204. In the configuration shown in FIG. 2, the scintillator plate 100 is arranged such that the substrate 120 shown in FIG. 1 is outside the radiation detection apparatus 200, and the scintillator 110 and the photoelectric conversion element 204 are arranged to face each other.

Further, a bonding layer 205 using an adhesive or the like may be provided between the scintillator plate 100 and the sensor panel 201. The coupling layer 205 may have a function of protecting the scintillator plate 100 and the photoelectric conversion element 204 in addition to integrating the scintillator plate 100 and the sensor panel 201. Further, the coupling layer 205 may have a function of optically connecting the scintillator 110 and the light receiving surface of the photoelectric conversion element 204. The bonding layer 205 may have a stacked structure in which two or more different materials are stacked.

The radiation detection apparatus 200 shown in FIG. 2 can be manufactured by combining the scintillator plate 100 and the sensor panel 201. The scintillator plate 100 may have a reflective layer between the substrate 120 and the scintillator plate 100, the surface opposite to the surface of the scintillator plate 100 that contacts the sensor panel 201. About half of the light generated by the scintillator 110 proceeds to the surface in contact with the sensor panel 201, but the other half can travel to the substrate 120 side. This light can be advanced in the direction of the sensor panel 201 by the reflective layer, and the light reaching the photoelectric conversion element 204 can be increased. By using the reflective layer, the sensitivity of the radiation detection apparatus 200 to radiation can be increased.

In the present embodiment, the scintillator plate 100 and the sensor panel 201 are bonded via the bonding layer 205. However, the scintillator 110 and the protective film 130 may be formed on the sensor panel 201. In this case, the sensor panel 201 can also serve as the substrate 120.

Example Next, an example of the above-described embodiment will be described. First, the scintillator 110 was formed on the substrate 120 using Si by a heating vapor deposition method. In the heating vapor deposition, a heating boat in a vacuum vessel was filled with CsI raw material powder, and four substrates 120 were mounted on a rotating disk so as to face the heating boat. Further, a boat different from the boat filled with the CsI raw material powder was installed in the vacuum vessel, and this boat was filled with the TlI raw material powder as the light emission center. After the raw material and the substrate 120 were set, the inside of the vacuum vessel was put into a high vacuum state with a vacuum pump, and the scintillator 110 was formed on the substrate 120 while rotating the substrate 120 in the vacuum vessel.

Next, when the substrate 120 on which the scintillator 110 was formed was taken out from the vacuum vessel, the vacuum vessel containing the substrate was adjusted to atmospheric pressure using nitrogen gas. The door of the vacuum vessel was opened, and fluorine resin was formed as the first layer 131 by immediately spraying a fluorine-based coating agent on three of the four substrates 120 on which the scintillator 110 was formed. As the fluorine-based coating agent, 3M Japan Co., Ltd. Novec2702 (registered trademark) was diluted 30 times with Novec7200 (registered trademark) as a solvent. The remaining one of the four substrates 120 on which the scintillator 110 was formed did not form the protective film 130 including the first layer 131, and was used as the scintillator plate of Comparative Example 1.

Next, one of the substrates 120 on which the first layer 131 was formed was immediately brought into contact with appropriately activated ethyl silicate. As a result, a second layer 132 including a metal alkoxide and a crosslinked body in which some metal atoms of the metal alkoxide are crosslinked with oxygen is formed on the surface of the scintillator 110 on which the first layer 131 is formed. In this example, TEOS was used as a precursor of ethyl silicate. The formed second layer 132 includes Si and an ethyl group. Through the above steps, a protective film in which the first layer 131 containing a fluororesin and the second layer 132 containing a metal alkoxide and a crosslinked body in which some metal atoms of the metal alkoxide are crosslinked with oxygen are laminated. 130 was formed, and the scintillator plate 100 of Example 1 was obtained. In addition, another substrate 120 on which the first layer 131 is formed is exposed to the atmosphere (room temperature 25 ° C., humidity 45%) for 60 minutes, and then the second layer 132 is formed. The scintillator plate 100 of Example 2 was obtained. Further, among the substrates 120 on which the first layer 131 is formed, the other one of them is the scintillator plate of Comparative Example 2 in which only the first layer 131 is formed and the second layer 132 is not formed. It was.

The obtained samples of Examples 1 and 2 and Comparative Examples 1 and 2 were irradiated with X-rays, and resolution evaluation was performed by MTF (Modulation Transfer Function) evaluation. The method of MTF evaluation is described below. A general edge method was used as a method for evaluating the resolution. The quality of the X-ray used was RQA5 (radiation source: tungsten, tube voltage: 70 kV, tube current: 0.5 mA, filter: aluminum having a thickness of 21 mm). MTF measurement is performed by pressing the samples of Examples 1 and 2 and Comparative Examples 1 and 2 against a CCD (Charge-Coupled Device) with a FOP (Fiber Optic Plate) and irradiating an evaluation X-ray. Went.

The results of MTF evaluation will be described below. After the second layer 132 was formed, the scintillator plate 100 of Example 1 was exposed to the atmosphere (room temperature 25 ° C., humidity 45%) for 100 minutes, and then MTF evaluation was performed. Further, after being exposed to the air atmosphere (room temperature 25 ° C., humidity 45%) for one week (about 10,000 minutes), the scintillator plate 100 of Example 1 was evaluated for MTF. At each measurement timing, the scintillator plate of Comparative Example 2 in which only the first layer 131 was formed was also measured. The results are shown in FIG.

From the results shown in FIG. 3, the scintillator plate 100 of Example 1 has substantially the same MTF after being exposed to the atmosphere (room temperature 25 ° C., humidity 45%) for one week after the second layer 132 is formed. It was found to be extremely stable. Further, from the result of the scintillator plate of Comparative Example 2, even when the first layer 131 was formed and exposed to the air atmosphere for 100 minutes, the MTF was not significantly different from that of Example 1. On the other hand, it was found that the MTF of the scintillator plate of Comparative Example 2 was lowered by exposure to the air atmosphere for one week. This is because the first layer 131 alone cannot prevent water molecules from acting on the scintillator 110 in the long term and causing the scintillator 110 to deliquesce.

In addition, prior to the measurement whose results are shown in FIG. 3, in the scintillator plate 100 of Example 2, the results of the MTF evaluation performed after forming the first layer 131 and before forming the second layer 132 are shown in FIG. Show. From the results shown in FIG. 4, it was found that the MTF of the scintillator plate 100 of Example 2 was not different from the scintillator plate 100 of Example 1 described above. The scintillator plate 100 of Example 2 was exposed to the atmosphere (room temperature 25 ° C., humidity 45%) for 60 minutes after the first layer 131 was formed and before the second layer 132 was formed. From this result, it was found that by forming the first layer 131, it is possible to prevent a decrease in MTF for 60 minutes. As described above, in view of the result of Comparative Example 2, the MTF decreases even after being exposed to the atmosphere for about 100 minutes from the formation of the first layer 131 to the formation of the second layer 132. I found out that

Further, when the MTF was measured after the scintillator plate 100 of Example 2 was exposed to the air atmosphere (room temperature 25 ° C., humidity 45%) for one week after the second layer was formed, 0.422 (2 LP / mm )Met. Similar to the scintillator plate 100 of Example 1, no significant change with time was observed. From these results, after forming the first layer 131 using a fluororesin, the second layer 132 using a metal alkoxide and a crosslinked body in which some of the metal atoms are crosslinked with oxygen is formed. Thus, it has been found that the change in MTF can be substantially suppressed. From the above results, it is considered that the protective film 130 shown in the present embodiment can suppress the deliquescent of the scintillator 110.

Next, the scintillator plates of Examples 1 and 2 and Comparative Example 2 described above were subjected to the MTF evaluation described above, and then subjected to cross-sectional observation using a scanning electron microscope (SEM). As a result, none of the scintillator plates had a characteristic difference, and the thickness of the scintillator 110 was not substantially changed. In addition, the size of the gap between the columnar crystals of the scintillator 110 was about the same.

In the scintillator plate of Comparative Example 1, when the cross section was promptly observed after the completion of the deposition of the scintillator 110, no characteristic difference was observed as in the observation results of Examples 1 and 2 and Comparative Example 2 described above. However, as a result of observation after exposure to an air atmosphere (room temperature 25 ° C., humidity 45%) for one week, it was observed that adjacent columnar crystals were bonded to each other and dissolved. This is because the protective film 130 is not formed on the scintillator 110 of the first comparative example, so that the scintillator 110 is deliquescent, which is greatly different from the cross sections of the scintillators 110 of the first and second embodiments and the second comparative example. It was.

As described above, in the scintillator plate of Comparative Example 1, when the cross section was promptly observed after the completion of vapor deposition of the scintillator 110, no characteristic difference from the scintillator 110 of Examples 1 and 2 was found. For this reason, in Examples 1 and 2, it was found that the protective film 130 did not have a film thickness enough to fill the gap between the columnar crystals of the scintillator 110. Since the gap between the columnar crystals of the scintillator 110 is about 200 nm, the thickness of the protective film 130 is 100 nm or less, and is estimated to be 50 nm or less from cross-sectional observation by SEM. From the above results, it is considered that the scintillator plate 100 of the present embodiment can effectively suppress the deliquescence of the scintillator 110 even when the protective film 130 has a thin film thickness of 50 nm or less.

As mentioned above, although embodiment and the Example which concern on this invention were shown, it cannot be overemphasized that this invention is not limited to these Embodiment and Example, In the range which does not deviate from the summary of this invention, embodiment mentioned above The embodiments can be appropriately changed and combined.

Hereinafter, radiation detection in which a radiation detection apparatus 200 using the scintillator 110 covered with the protective film 130 described above with reference to FIG. 5 and a photoelectric conversion element 204 for detecting light generated by the scintillator 110 is incorporated. The system will be exemplarily described. X-rays 6060 generated by an X-ray tube 6050 serving as a radiation source pass through the chest 6062 of the patient or subject 6061 and enter the radiation detection apparatus 200 of the present invention. This incident X-ray includes information inside the body of the patient or subject 6061. In the radiation detection apparatus 200, the scintillator 110 emits light in response to the incidence of the X-ray 6060, and this is photoelectrically converted by the photoelectric conversion element 204 to obtain electrical information. This information is converted into digital data, image-processed by an image processor 6070 as a signal processing unit, and can be observed on a display 6080 as a display unit of a control room.

Further, this information can be transferred to a remote place by a transmission processing unit such as a network 6090 such as a telephone, a LAN, and the Internet. In this way, it can be displayed on a display 6081 which is a display unit such as a doctor room in another place, and a doctor in a remote place can make a diagnosis. In addition, this information can be recorded on a recording medium such as an optical disk, and can also be recorded on a film 6110 serving as a recording medium by the film processor 6100.

The present invention is not limited to the above embodiment, and various changes and modifications can be made without departing from the spirit and scope of the present invention. Therefore, in order to make the scope of the present invention public, the following claims are attached.

This application claims priority on the basis of Japanese Patent Application No. 2016-240569 filed on Dec. 12, 2016, the entire contents of which are incorporated herein by reference.

Claims

A scintillator plate including a scintillator having a plurality of columnar crystals disposed on a substrate, and a protective film covering the scintillator,
The protective film includes a first layer and a second layer covering the first layer,
The first layer includes a fluororesin,
The scintillator plate, wherein the second layer includes a metal alkoxide and a crosslinked body in which some metal atoms included in the metal alkoxide are crosslinked by oxygen.
2. The scintillator plate according to claim 1, wherein in the crosslinked body, a stoichiometric ratio of an alkoxide atom to a metal atom contained in the crosslinked body is 0.02 or more and 1 or less.
The scintillator plate according to claim 1 or 2, wherein the protective film has a thickness of 0.3 nm or more and 100 nm or less.
The scintillator plate according to any one of claims 1 to 3, wherein the first layer has a thickness of 50 nm or less.
The metal alkoxide is represented by the following general formula (1):
M1 (OR) n ... (1)
Here, M1 is at least one selected from silicon (Si), aluminum (Al), titanium (Ti), and zirconium (Zr),
The scintillator plate according to any one of claims 1 to 4, wherein R is at least one selected from a methyl group, an ethyl group, a propyl group, an isopropyl group, and a butyl group.
The scintillator plate according to claim 5, wherein the M1 is silicon and the R is an ethyl group.
The second layer further comprises a hydroxyl group bonded to a metal atom;
The scintillator plate according to any one of claims 1 to 6, wherein a stoichiometric ratio of a hydroxyl group to a metal atom contained in the second layer is 2.5 or less.
The second layer further comprises hydrogen atoms bonded to metal atoms;
The scintillator plate according to any one of claims 1 to 7, wherein a stoichiometric ratio of hydrogen atoms to metal atoms contained in the second layer is 1 or less.
The protective film covers each side surface of the plurality of columnar crystals,
9. The scintillator according to any one of claims 1 to 8, wherein the scintillator includes a gap between a side surface covered with the protective film of the columnar crystals adjacent to each other among the plurality of columnar crystals. The scintillator plate described.
10. The scintillator plate according to claim 9, wherein an interval between the side surfaces of the columnar crystals adjacent to each other among the plurality of columnar crystals is 200 nm or more and 1 μm or less.
The scintillator plate according to any one of claims 1 to 10, wherein a thickness of the plurality of columnar crystals is 0.1 µm or more and 50 µm or less.
The scintillator plate according to any one of claims 1 to 11, wherein the scintillator contains a halide.
The scintillator plate according to claim 12, wherein the halide contains an alkali halide.
The alkali halide is represented by the following general formula (2):
M2X1, αM3X2, βM4X3: γA1 (2)
Here, M2 is at least one selected from lithium (Li), sodium (Na), potassium (K), rubidium (Rb), and cesium (Cs),
M3 is from beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), zinc (Zn), cadmium (Cd), copper (Cu), and nickel (Ni) At least one selected,
M4 is scandium (Sc), yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium ( Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), aluminum (Al), gallium (Ga), and At least one selected from indium (In),
X1, X2 and X3 are each independently at least one selected from fluorine (F), chlorine, (Cl), bromine (Br) and iodine (I);
A1 is Eu, Tb, In, bismuth (Bi), Ce, Tm, Dy, Pr, Ho, Nd, Yb, Er, Gd, Lu, Sm, Y, thallium (Tl), Na, silver (Ag), At least one selected from Cu and Mg;
α, β, and γ are respectively
0 ≦ α <0.5
0 ≦ β <0.5
0 <γ ≦ 0.2
The scintillator plate according to claim 13, wherein
The scintillator plate according to any one of claims 1 to 14,
A photoelectric conversion element for detecting light converted from radiation by the scintillator;
A radiation detection apparatus comprising:
A radiation detection apparatus according to claim 15;
A signal processing unit for processing a signal from the radiation detection device;
A radiation detection system comprising: