JP4099206B2 - Scintillator panel and radiation image sensor - Google Patents

Description

  The present invention relates to a scintillator panel and a radiation image sensor used for medical X-ray imaging and the like.

  Conventionally, X-ray photosensitive films have been used in medical and industrial X-ray imaging, but radiation imaging systems using radiation detectors have become widespread in terms of convenience and preservation of imaging results. In such a radiation imaging system, pixel data based on two-dimensional radiation is acquired as an electrical signal by a radiation detector, and this signal is processed by a processing device and displayed on a monitor.

  As a typical radiation detector, there is a radiation detector having a structure in which a scintillator panel is formed by forming a scintillator on a substrate made of aluminum, glass, fused silica, or the like, and this is bonded to an imaging device. In this radiation detector, radiation incident from the substrate side is converted into light by a scintillator and detected by an imaging device (see Japanese Patent Publication No. 7-21560).

  By the way, in order to obtain a clear image in the radiation detector, it is necessary to sufficiently increase the light output of the scintillator panel. However, in the above-described radiation detector, the light output is not sufficient. Therefore, the inventors of the present application have changed the quality based on moisture slightly contained in the scintillator by covering the reflective metal thin film provided on the substrate with a protective film as disclosed in JP-A-2000-356679. We have developed a technology to prevent the deterioration of the function of this metal thin film as a reflective film.

  The present invention is a further improvement of this technique, and it is an object of the present invention to provide a scintillator panel in which the stability of a metal thin film as a reflective film is further improved and a radiation image sensor using the scintillator panel.

  In order to solve the above problems, a scintillator panel according to the present invention is provided with a radiation transmissive substrate, a metal thin film that is provided on the substrate and reflects light of a predetermined wavelength, and is provided on the metal thin film. And a scintillator made of a large number of columnar crystals that are deposited on the protective film and convert radiation into light including a wavelength that can be reflected by the metal thin film, and a moisture-resistant protective film that covers the scintillator together with the substrate. In the scintillator panel in which the protective film prevents contact between the metal thin film and the scintillator, the substrate and the metal thin film are sealed by a protective film provided so as to enclose them, and the protective film and the scintillator are It is further sealed with a moisture-resistant protective film provided so as to wrap up the film.

  In the scintillator panel of the present invention, it is preferable that an intermediate film in close contact with the substrate and the metal thin film is disposed between the substrate and the metal thin film.

  Depending on the combination of the substrate and the metal thin film, the adhesion of the metal thin film to the substrate may not be good, and the thin film may peel off from the substrate during the subsequent manufacturing process or use. By disposing an intermediate film that is in close contact with the metal thin film and the substrate, peeling of the metal thin film is prevented, and the stability of the reflective film is enhanced.

  This substrate is preferably a glass substrate, an aluminum substrate, or a substrate mainly composed of carbon. In particular, in the case of a substrate mainly composed of carbon, for example, an amorphous carbon or graphite-based substrate, the adhesion of the metal thin film to the substrate is poor, but according to the present invention, the adhesion is caused by the intervening intermediate film. Will improve.

  When the substrate is a conductive substrate such as aluminum or amorphous carbon, the intermediate film preferably prevents contact between the substrate and the metal thin film.

  When the substrate is conductive and the substrate and the metal thin film are in contact with each other, the metal thin film may be corroded by electrochemical corrosion (galvanic corrosion). According to the present invention, since the intermediate film prevents the metal thin film and the substrate from coming into contact with each other, it is possible to suppress such corrosion caused by electrolytic corrosion and improve the stability of the metal thin film.

  This metal thin film is preferably a film made of a material containing a substance in the group consisting of Al, Ag, Cr, Cu, Ni, Ti, Mg, Rh, Pt and Au.

  The protective film is preferably a xylylene-based film. The moisture resistant protective film is preferably a xylylene film. The intermediate film is preferably made of an organic film.

  In addition, it is preferable that the metal film is in close contact with the intermediate film and the protective film and sealed with both because the stability is improved. Furthermore, it is preferable that the intermediate film wraps around the substrate because sealing properties are improved. The intermediate film is preferably a film formed on the substrate by a CVD method, and particularly preferably a xylylene-based film.

  The radiation image sensor according to the present invention is configured by combining these scintillator panels and an image sensor that captures an optical image obtained by converting radiation output from the surface of the scintillator panel opposite to the substrate. is there. It is preferable that the image sensor is disposed to face the scintillator side of the scintillator panel.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the accompanying drawings. In order to facilitate the understanding of the description, the same reference numerals are given to the same components in the drawings as much as possible, and duplicate descriptions are omitted. In addition, the dimension of each figure has the part exaggerated for description, and does not necessarily correspond with an actual dimension ratio.

  First, the first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a cross-sectional view of the scintillator panel 1, and FIG. 2 is a cross-sectional view of a radiation image sensor 2 using the scintillator panel 1.

  As shown in FIG. 1, an intermediate film 11 made of polyimide is disposed in close contact with one surface of a substrate 10 made of amorphous carbon (a-C) (glassy carbon or glassy carbon) of the scintillator panel 1. A metal thin film 12 that functions as a light reflecting film is formed on the surface of the intermediate film 11 in close contact. This metal thin film is made of, for example, Al. The surface of the metal thin film 12 is covered with a protective film 14 made of polyimide for protecting the metal thin film 12. As a result, the metal thin film 12 is sandwiched and sealed between the intermediate film 11 and the protective film 14 that are in close contact with each other. A columnar scintillator 16 that converts incident radiation into visible light is formed on the surface of the protective film 14. That is, the scintillator 16 has a configuration in which a large number of columnar crystals are erected in the shape of the protective film 14. The scintillator 16 uses Tl-doped CsI. The scintillator 16 is covered with a moisture-resistant protective film 18 made of polyparaxylylene together with the substrate 10.

  As shown in FIG. 2, the radiation image sensor 2 has a structure in which the light receiving surface of the image sensor 20 is attached to the side of the scintillator panel 1 where the scintillator 16 is formed.

  Next, the manufacturing process of the scintillator panel 1 will be described. First, polyimide resin is applied to one surface of a rectangular or circular aC substrate 10 (thickness 1 mm) with a certain thickness (10 μm) and cured, so that the substrate 10 is in close contact with the surface. A flat intermediate film 11 is formed.

  A metal thin film 12 as a light reflecting film is formed on the surface of the intermediate film 11 with a thickness of 150 nm by a vacuum deposition method. Since the polyimide constituting the intermediate film 11 has good affinity with the Al metal thin film 12, the metal thin film 12 adheres to the intermediate film 11. Further, since the intermediate film 11 itself is also in close contact with the substrate 10, it is possible to effectively prevent the metal thin film 12 from peeling off from the substrate 10.

  Next, a spin coat process is performed on the metal thin film 12 to form a polyimide protective film 14 with a thickness of 1000 nm to cover the entire metal thin film 12. As a result, the metal thin film 12 is sandwiched between the intermediate film 11 and the protective film 14 so as to be in close contact with and sealed, so that it can be effectively protected from peeling and damage in the subsequent manufacturing process.

  Next, a large number of CsI columnar crystals doped with Tl are grown on the surface of the protective film 14 by a vapor deposition method to stand, thereby forming the scintillator 16 with a thickness of 250 μm. The CsI forming the scintillator 16 absorbs water vapor in the air and is deliquescent if left exposed with high hygroscopicity. Therefore, in order to prevent this, the moisture resistance made of polyparaxylylene is prevented by the CVD method. A protective film 18 is formed. That is, the substrate 10 on which the scintillator 16 is formed is put in a CVD apparatus, and the moisture-resistant protective film 18 is formed to a thickness of 10 μm. The method for manufacturing the moisture-resistant protective film 18 is described in detail in WO99 / 66351 International Publication. As a result, the moisture-resistant protective film 18 made of polyparaxylylene is formed on substantially the entire surface of the scintillator 16 and the substrate 10, that is, substantially the entire surface of the substrate exposed without forming the scintillator or the like.

  Further, the radiation image sensor 2 is manufactured by attaching the light receiving portion of the imaging device (CCD) 20 so as to face the front end portion of the scintillator 16 of the completed scintillator panel 1 (see FIG. 2).

  According to the radiation image sensor 2 according to this embodiment, the radiation incident from the substrate 10 side is converted into light by the scintillator 16 and detected by the image sensor 20. Since the scintillator panel 1 constituting the radiation image sensor 2 is provided with the light-reflective metal thin film 12, the light incident on the light receiving portion of the image sensor 20 can be increased. The detected image can be made clear. Further, since the metal thin film 12 is sandwiched between the two by being in close contact with the intermediate film 11 and the protective film 14 made of polyimide, the metal thin film 12 is deteriorated such as corrosion, peeled off, or damaged. It is possible to prevent the function as the reflective film from being impaired due to the above, and the stability as the reflective film is improved.

  FIG. 3 is a cross-sectional view of a second embodiment of the scintillator panel according to the present invention. The scintillator panel 3 is different from the first embodiment in that the protective film 14 a does not cover the entire surface of the metal thin film 12 but covers only the central portion of the metal thin film 12. Also in this embodiment, since the scintillator 16 is formed only on the surface of the protective film 14a, the metal thin film 12 is completely prevented from contacting the scintillator 16 by the protective film 14a.

  Also in this embodiment, since the metal thin film 12 is sealed with at least a portion where the scintillator 16 is formed sandwiched between the intermediate film 11 and the protective film 14a, it is possible to effectively prevent damage, peeling, alteration, and the like. And the stability as a reflective film is improved.

  FIG. 4 is a cross-sectional view of a third embodiment of a scintillator panel according to the present invention. The scintillator panel 4 is different from the first and second embodiments shown in FIGS. 1 and 3 in that the same polyparaxylylene film as the moisture-resistant protective film 18 is used as the intermediate film 11b and the protective film 14b. To do. The intermediate film 11b covers the entire substrate 10, and the protective film 14b covers the metal thin film 12 and the intermediate film 11b exposed around the metal thin film 12.

  As in the case of the moisture-resistant protective film 18 described above, the intermediate film 11b and the protective film 14b are formed by the CVD method, thereby forming a good thin film that is uniform and free of pinholes. As a result, the metal thin film 12 can be sealed to completely prevent contact with the outside air and the scintillator 16 formed on the protective film 14b, so that the reaction between the scintillator component, moisture and the metal can be suppressed. In particular, when the scintillator 16 is formed, since the protective film 14b completely covers the substrate 10 and the metal thin film 12, the influence can be suppressed even when the scintillator component adheres to other places. Further, the intermediate film 11b which is a non-conductor is interposed between the conductive substrate 10 and the metal thin film 12, thereby preventing electrical contact between the substrate 19 and the metal thin film 12, and galvanic corrosion of the metal thin film 12. Can be effectively suppressed.

  It is preferable that the intermediate film 11b and the protective film 14b cover the entire substrate 10 as in the present embodiment because the sealing performance is improved and the film formation by the CVD method is easy.

  Here, a polyparaxylylene film was used, but in addition to this, polymonochloroparaxylylene, polydichloroparaxylylene, polytetrachloroparaxylylene, polyfluoroparaxylylene, polydimethylparaxylylene, polydiethylparaxylene. A xylylene-based organic film such as xylylene can be used.

  In each of the above-described embodiments, an aC substrate is used, but any substrate that transmits radiation may be used. Therefore, a graphite substrate, an Al substrate, a Be substrate, and a glass substrate may be used. A substrate or the like may be used.

In addition, as the protective film, a polyimide film or a xylylene-based organic film is used, but is not limited thereto, and includes substances in the group of LiF, MgF ₂ , SiO ₂ , Al ₂ O ₃ , TiO ₂ , MgO, and SiN. A transparent inorganic film made of a material may be used. Furthermore, a protective film formed by combining an inorganic film and an organic film may be used.

  Further, as the metal thin film, a film made of a material containing a substance in the group consisting of Ag, Cr, Cu, Ni, Ti, Mg, Rh, Pt and Au in addition to Al may be used. Further, two or more metal thin films may be formed, for example, an Au film is formed on the Cr film.

  It is also possible to form the oxide film on the metal thin film and use it as a protective film.

  Furthermore, the moisture resistance of the scintillator is made more complete by substantially covering the scintillator 16 and the entire surface of the substrate (the surface opposite to the surface on which the scintillator is formed, that is, the radiation incident surface) by the moisture resistant protective film 18. However, if the entire surface of the scintillator 16 and at least a part of the surface of the substrate 10 are covered with the moisture-resistant protective film 18, the moisture resistance of the scintillator can be increased as compared with the case where only the scintillator is covered.

  Further, as the scintillator 16, CsI (Na), NaI (Tl), LiI (Eu), KI (Tl) or the like may be used instead of CsI (Tl).

  Further, as the organic film covering the scintillator, a xylylene-based transparent organic film can be used.

Further, the intermediate film 11 must be made of a material having affinity for both the substrate 10 and the metal thin film 12, and in addition to polyimide and xylylene-based transparent organic films, organic films such as epoxy resins and acrylic resins can be used. In addition, an inorganic film such as SiO ₂ or SiN can be used. About an inorganic film, what is necessary is just to form it by baking, after apply | coating by dispersing CVD and an inorganic material in the organic solvent. However, when the substrate is conductive, it is preferable to use a non-conductive intermediate film because electric corrosion can be prevented by electrical shielding.

  The radiation image sensor according to the present invention is a combination of the scintillator panel and the image sensor described above, and as described above, the image sensor may be joined to face the scintillator side of the scintillator panel, and the interval You may arrange it. Or you may guide the optical image output from a scintillator panel to the image pick-up element arrange | positioned in an appropriate position with an optical system.

  The present invention is suitable for medical and industrial large-screen, high-sensitivity X-ray imaging systems.

It is sectional drawing of 1st Embodiment of the scintillator panel which concerns on this invention. It is sectional drawing of 1st Embodiment of the radiation image sensor which concerns on this invention using the scintillator panel which concerns on 1st Embodiment. It is sectional drawing of 2nd Embodiment of the scintillator panel which concerns on this invention. It is sectional drawing of 3rd Embodiment of the scintillator panel which concerns on this invention.

Claims (19)

A radiation transmissive substrate; a radiation transmissive metal thin film that reflects light of a predetermined wavelength; a protective film provided on the metal thin film; and a radiation deposited on the protective film. A scintillator composed of a number of columnar crystals that convert light into a wavelength that can be reflected by the metal thin film, and a moisture-resistant protective film that covers the scintillator together with the substrate, the protective film comprising the metal thin film and the scintillator In scintillator panels that prevent contact with
The substrate and the metal thin film are sealed by the protective film provided to enclose them,
The scintillator panel, wherein the protective film and the scintillator are further sealed by the moisture-resistant protective film provided so as to enclose them.   The scintillator panel according to claim 1, wherein an intermediate film that is in close contact with the substrate and the metal thin film is disposed between the substrate and the metal thin film.   The scintillator panel according to claim 2, wherein the intermediate film covers the entire substrate.   4. The scintillator panel according to claim 3, wherein the protective film is provided so as to enclose the substrate and the metal thin film that are entirely covered with the intermediate film.   The scintillator panel according to any one of claims 1 to 4, wherein the protective film is a xylylene-based film.   The scintillator panel according to claim 1, wherein the moisture-resistant protective film is a xylylene-based film.   The scintillator panel according to claim 2, wherein the intermediate film is an organic film.   The scintillator panel according to claim 2, wherein the intermediate film is a xylylene-based film.   The scintillator panel according to any one of claims 1 to 8, wherein the substrate is any one of a glass substrate, an aluminum substrate, and a substrate mainly composed of carbon.   The scintillator panel according to claim 2, wherein the substrate is a conductive substrate, and the intermediate film prevents contact between the substrate and the metal thin film.   The scintillator panel according to claim 10, wherein the conductive substrate is either an aluminum substrate or a substrate mainly composed of carbon.   The scintillator panel according to claim 11, wherein the substrate containing carbon as a main component is a substrate containing amorphous carbon.   The metal thin film is a film made of a material containing a substance in the group consisting of Al, Ag, Cr, Cu, Ni, Ti, Mg, Rh, Pt, and Au. A scintillator panel according to any one of the above.   The scintillator panel according to claim 2, wherein the metal thin film is in close contact with the intermediate film and the protective film and sealed with both.   The scintillator panel according to claim 1, wherein the protective film is a film formed on the substrate and the metal thin film by a CVD method.   The scintillator panel according to claim 1, wherein the moisture-resistant protective film is a film formed on the scintillator and the protective film by a CVD method.   The scintillator panel according to claim 2, wherein the intermediate film is a film formed on the substrate by a CVD method. A scintillator panel according to any one of claims 1 to 17,
An image sensor that captures an optical image obtained by converting radiation output from a surface opposite to the substrate of the scintillator panel;
A radiation image sensor comprising:   The radiation image sensor according to claim 18, wherein the imaging element is disposed to face the scintillator side of the scintillator panel.

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