JP2007271504A - Scintillator panel, planar detector and imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a scintillator panel 21 that prevents contrast from lowering at peripheral sections. <P>SOLUTION: A scintillator layer 26 is formed on a glass substrate 22. A reflecting film 24 is formed between the glass substrate 22 and the scintillator layer 26, and constitutes a reflecting plane 23 on the glass substrate 22. A protective film 25 is formed, in a region other than the peripheral section 26 of the scintillator layer 26 on the reflecting film 24. In the reflecting plane 23, the reflectivity in a region, corresponding to the peripheral section 26a of the scintillator layer 26, is lower than the reflectivity in regions other than the peripheral section 26a. Stray light that causes reduction in the contrast in sections with low reflectivity in the peripheral section on the reflection plane 23, is absorbed, and the contrast is inhibited from being lowered in the peripheral sections. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a scintillator panel, a flat panel detector, and an imaging device that convert radiation into visible light.

  Conventionally, a flat panel detector (hereinafter referred to as FPD) and an imaging apparatus are used for medical and industrial nondestructive inspection, and convert an X-ray image transmitted through a subject into a visible light image or an electrical image signal. Is used.

  FIG. 7 shows an example of a scintillator panel used for FPD. In this scintillator panel 1, a reflective film 4 and a protective film 5 having a function of a reflective surface 3 are formed on a radiation transmissive substrate 2 such as a glass substrate, and a Tl-doped CsI ( The scintillator layer 6 composed of columnar crystals (hereinafter simply referred to as CsI) is formed, and the scintillator layer 6 is further covered to form a moisture-proof layer 7.

  The processing method of the reflecting surface 3 is to form the reflecting film 4 formed by sputtering, for example, aluminum when the function of the reflecting surface 3 is low as it is, for example, glass or graphite. Depending on the surface condition of 2, the surface of the substrate 2 may be mirror-polished prior to the formation of the reflective film 4. Alternatively, when a metal material such as aluminum or beryllium is used as the substrate 2, a degreasing treatment, a chemistry is performed on the raw material after the rolling process of the material is completed by utilizing a reflection ability inherent to the material. The reflective surface 3 may be formed only by performing a normal cleaning method such as a polishing method or an ultrasonic cleaning method, or the reflective surface 3 may be formed by mirror polishing or applying a reflective film to those materials. is there.

  An FPD that uses the scintillator layer 6 as a radiation conversion film is called an indirect conversion FPD. In this indirect conversion type FPD, as shown in FIG. 8, a scintillator panel 1 is bonded to an image sensor 9 in which a plurality of light receiving elements 8 are arranged one-dimensionally or two-dimensionally; As shown in FIG. 9, there are two typical forms of direct vapor deposition type FPD in which the scintillator layer 6 is directly vapor deposited on the image sensor 9.

  The bonding type FPD has a structure in which the scintillator panel 1 is bonded to the image sensor 9.

  The direct vapor deposition type FPD typically has a structure in which a scintillator layer 6, a protective film 10, a reflective film 12 having a function of a reflective surface 11, and a moisture-proof film 13 are sequentially laminated on the image sensor 9. The surface of the scintillator layer 6 is subjected to surface polishing if necessary, and further, by selecting an organic film such as polyparaxylylene as the protective film 10, the surface smoothness is improved, thereby the reflectance of the reflective film 12 is improved. It is also possible to improve. As the reflective film 12, for example, a sputtered aluminum film is used as in the case of the scintillator panel 1.

  In addition to such a configuration, there is an imaging device (hereinafter referred to as CCD-DR) having a configuration in which the scintillator panel 1 and the CCD camera system are opposed to each other. Also in this case, the configuration of the scintillator panel 1 is basically the same as the configuration of the scintillator panel 1 used for the bonded FPD.

  A protective film 5, 10 is generally applied between the scintillator layer 6 and the reflective films 4, 12 on the scintillator panel 1 and the reflective films 4, 12 of the scintillator layer 6 used in the direct vapor deposition type FPD. It is. The protective films 5 and 10 have a function of increasing the chemical stability of the reflective films 4 and 12 and the reflectance of the reflective surfaces 3 and 11 (or the reflective films 4 and 12). Even for direct vapor deposition type FPD, if the moisture-proof film 13 is applied after the reflective film 12 in the order of lamination, the moisture-proof film 13 has a function of chemically stabilizing the reflective film 12, but the reflective film 12 In order to make it closer to a mirror surface, it is already known that the reflective film 12 is not directly formed on the scintillator layer 6 but is smoothed with a protective film 10 such as an organic film in between (for example, Patent Documents). 1).

  When the image sensor 9 or CCD camera system and the scintillator panel 1 are combined to create an FPD or CCD-DR, the size of the light emitting surface of the scintillator panel 1 is usually equivalent to the light receiving surface of the image sensor 9 or CCD camera. It is designed to be larger than the part to be. This is because the peripheral portion 6a of the scintillator layer 6 located in the vicinity of the end of the jig holding the substrate 2 or the image sensor 9 becomes slightly shaded against the incidence of CsI vapor when CsI is vacuum-deposited. This is because the film thickness is reduced, resulting in a taper shape. The tapered portion of the scintillator layer 6 causes a luminance distribution when radiation is incident due to the gradual change in film thickness, and as a result cannot be used as an image for imaging or diagnosis. .

Therefore, the effective area 14 of the FPD image sensor 9 and the effective area corresponding to the CCD light receiving portion on the scintillator panel 1 of the CCD-DR camera system (generally, the portion 15 in FIG. 7) have a tapered portion of the scintillator layer 6. As a result, the scintillator layer 6 is attached to the outside of the effective area of the photographing apparatus.
Japanese Patent No. 3126715 (page 3-4, Fig. 1-2)

  However, the peripheral portion 6a of the scintillator layer 6 causes unnecessary light emission when radiation transmitted through the subject is incident on the FPD or CCD-DR, and reduces the contrast of the peripheral portion of the effective area of the FPD or CCD-DR. There is a problem to make.

  The present invention has been made in view of these points, and an object of the present invention is to provide a scintillator panel, a flat panel detector, and an imaging device that can prevent a decrease in contrast at the peripheral portion.

  The scintillator panel of the present invention comprises a substrate having a reflecting surface and a scintillator layer formed on the reflecting surface of the substrate, and the reflecting surface has a reflectance in a region corresponding to a peripheral portion of the scintillator layer. The reflectance is lower than that of the corresponding region other than the peripheral portion.

  Further, the flat detector of the present invention includes an image sensor in which a plurality of light receiving elements are arranged, and the scintillator panel combined with the image sensor.

  The photographing apparatus of the present invention includes the scintillator panel and a camera facing the scintillator panel.

  Further, the flat detector of the present invention comprises an image sensor in which a plurality of light receiving elements are arranged, a scintillator layer formed on the image sensor, and a reflective surface formed on the scintillator layer, The reflection surface has a lower reflectance in a region corresponding to the peripheral portion of the scintillator layer than in a region corresponding to the portion other than the peripheral portion.

  According to the scintillator panel of the present invention, the reflectance of the reflecting surface in the region corresponding to the peripheral portion of the scintillator layer is made lower than the reflectance of the reflecting surface in the region corresponding to other than the peripheral portion. It is possible to absorb stray light that causes a decrease in contrast at a low portion and suppress a decrease in contrast at the peripheral portion.

  Further, according to the flat detector and the photographing apparatus of the present invention, the contrast characteristic can be improved by using the scintillator panel.

  Further, according to the flat detector of the present invention, the reflectance of the reflective surface in the region corresponding to the peripheral portion of the scintillator layer formed on the image sensor is determined from the reflectance of the reflective surface in the region corresponding to other than the peripheral portion. Since it is lowered, stray light that causes a decrease in contrast is absorbed in a portion having a low reflectance of the reflecting surface, and a decrease in contrast in the peripheral portion can be suppressed to improve contract characteristics.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  1 to 3 show a first embodiment, FIG. 1 is a cross-sectional view of a scintillator panel, FIG. 2 is a front view of the scintillator panel, and FIG. 3 is a cross-section of a bonded flat detector using the scintillator panel. FIG.

As shown in FIG. 1 and FIG. 2, a scintillator panel 21 includes a reflective film 24 made of an aluminum sputtered film having a function of a reflective surface 23 on a glass substrate 22 as a radiation transmissive substrate, A protective film 25 made of a sputtered film of silicon oxide (SiO ₂ ) is applied on the reflective film 24 in the central region other than the peripheral part of the reflective film 24, and Tl is doped on the reflective film 24 and the protective film 25. A scintillator layer 26 in which CsI (hereinafter simply referred to as CsI) is formed by vacuum deposition is formed, and polyparaxylylene is CVD-coated so as to cover the entire surface side of the glass substrate 22 including the reflective film 24 and the scintillator layer 26. A moisture-proof film 27 applied by the method is formed.

  The scintillator layer 26 has an effect of being shaded against the incidence of CsI vapor by the rising portion of the jig that holds the glass substrate 22 when the CsI is formed by vacuum vapor deposition. Tapered. In this example, the peripheral portion 26a of the scintillator layer 26, that is, the region of the tapered portion, and the region where the scintillator layer 26 is in direct contact with the reflective film 24 at the peripheral portion of the protective film 25 are substantially the same.

  By selecting an organic film such as polyparaxylylene as the protective film 25, the surface smoothness is improved, whereby the reflectance of the reflective film 24 can be improved. Therefore, in the part where the scintillator layer 26 is formed in direct contact with the reflective film 24, even if the film thickness of the scintillator layer 26 is the same as the part where the protective film 25 is sandwiched between the reflective film 24 of the scintillator layer 26, The amount of light emitted in the opposite direction is reduced by about 30%.

  Therefore, the scintillator panel 21 has a probability that the light emitted from the peripheral region 28 corresponding to the peripheral portion 26a of the scintillator layer 26 is absorbed by the reflective film 24, and the central region 29 inside the peripheral region 28. Thus, the probability is higher than the light emitted at, and as a result, stray light generated in the peripheral region 28 is absorbed.

  As described above, the reflectance of the reflecting surface 23 corresponding to the peripheral portion 26a of the scintillator layer 26 that does not contribute to the construction of the X-ray image transmitted through the subject is set to the reflecting surface 23 of the region corresponding to the portion other than the peripheral portion 26a. Therefore, stray light that causes a decrease in contrast can be absorbed by the low reflectance portion of the reflecting surface 23, and a decrease in contrast in the peripheral portion of the scintillator panel 21 can be suppressed.

  Of the reflecting surface 23, the reflectance of the portion where the protective film 25 is not applied is lower than that of the applied portion, and as a result, a desired reflectance can be obtained. Moreover, according to this method, the objective can be realized without adding a new process such as applying a light absorption film in order to reduce the reflectance of the peripheral portion of the reflecting surface 23, resulting in cost reduction. Leads to.

  Next, as shown in FIG. 3, the bonding type flat detector 31 is configured by bonding a scintillator panel 21 and an image sensor 32.

  The image sensor 32 is formed on a glass substrate 33 with a plurality of light receiving elements 34 such as photodiodes arranged in a matrix, and a switching element that selectively extracts an electric signal from the light receiving elements 34. A planarizing layer 35 is formed on the surface of the image sensor 32.

  The effective area 36 where the light receiving element 34 of the image sensor 32 is disposed and the central region 29 of the scintillator panel 21, that is, the region inside the peripheral portion 26a of the scintillator layer 26 are formed to coincide with each other.

  Thus, since the flat detector 31 uses the scintillator panel 21 in which the decrease in contrast in the peripheral portion is suppressed, the contrast characteristics in the peripheral portion of the effective area 36 can be improved.

  Next, FIG. 4 shows a second embodiment, and FIG. 4 is a sectional view of the scintillator panel.

  In the scintillator panel 21, a light absorption film 38 such as a sputtered graphite film is formed between the reflective film 24 and the scintillator layer 26 in the peripheral portion 26a of the scintillator layer 26, that is, in the tapered region.

  By forming the light absorbing film 38, stray light generated in the peripheral region 28 of the scintillator panel 21 can be more reliably absorbed, and a decrease in contrast can be further suppressed.

  Even if the protective film 25 is not necessarily provided, the effect of improving the contrast can be obtained, but it is more preferable to have the protective film 25 in consideration of the sensitivity of the effective area to the radiation.

  Next, FIG. 5 shows a third embodiment, and FIG. 5 is a sectional view of the scintillator panel.

  In the scintillator panel 21 of the second embodiment, a light absorption film 39 such as a sputtered graphite film is formed on the surface of the peripheral portion 26a of the scintillator layer 26, that is, the tapered portion region.

  By forming both the light absorption film 38 and the light absorption film 39, stray light generated in the peripheral region 28 of the scintillator panel 21 can be more reliably absorbed, and a decrease in contrast can be further suppressed. .

  The scintillator panel 21 described above can also be applied to a photographing device (CCD-DR) in which a scintillator panel 21 is opposed to a camera such as a CCD camera. Also in the case of this photographing apparatus, since the scintillator panel 21 that suppresses the decrease in contrast in the peripheral portion is used, the contrast characteristics in the peripheral portion of the effective area of the camera can be improved.

  Next, FIG. 6 shows a fourth embodiment, and FIG. 6 is a sectional view of a flat detector.

  The flat detector 41 is a direct vapor deposition type flat detector and includes an image sensor 42. In the image sensor 42, a plurality of light receiving elements 44 such as photodiodes arranged in a matrix and a switching element for selectively extracting an electric signal from the light receiving elements 44 are formed on a glass substrate 43. A planarizing layer 45 is formed on the surface of the image sensor 42.

  A scintillator layer 46 made of CsI is formed on the image sensor 42 by a vacuum deposition method. The scintillator layer 46 has the effect of being shaded against the incidence of CsI vapor by the rising portion of the jig that holds the image sensor 42 when the CsI is formed by vacuum deposition, and the peripheral portion 46a of the scintillator layer 46 is Tapered. In this example, the peripheral area 46a of the scintillator layer 46, that is, the area inside the area of the tapered portion, and the effective area 47 where the light receiving element 44 of the image sensor 42 is disposed are substantially the same.

A protection composed of a sputtered film of SiO ₂ in a region corresponding to the effective area 47 where the light receiving element 44 of the image sensor 42 is disposed, which is a region inside the peripheral portion 46a of the scintillator layer 46, that is, a region of the tapered portion. A film 48 is formed.

  Covering the entire surface of the image sensor 42 including the scintillator layer 46 and the protective film 48, a reflective film 50 made of an aluminum sputtered film constituting the reflective surface 49, and a moisture-proof film 51 in which polyparaxylylene is laminated by a CVD method Are sequentially stacked.

  In the case of such a flat detector 41, when an X-ray image transmitted through the subject is incident from above in FIG. 6, the light emitted from the peripheral portion 46a of the CsI of the scintillator layer 46 is reflected by the reflection film 50 of the peripheral portion 46a. Since the light is absorbed at the interface where the scintillator layer 46 is in contact, and the useless stray light is absorbed, the decrease in contrast can be suppressed.

  Of the reflecting surface 49, the reflectance of the portion where the protective film 48 is not applied is lower than that of the coated portion, and as a result, a desired reflectance can be obtained. Moreover, according to this method, the purpose can be realized without adding a new process such as applying a light absorption film in order to reduce the reflectance of the peripheral portion of the reflection surface 49, resulting in cost reduction. Leads to.

  In the case of the flat detector 41, a light absorption layer may be applied corresponding to the tapered portion of the scintillator layer 46.

  Further, in the scintillator panel 21, the reflecting surface 23 is not limited to the reflecting film 24 on the glass substrate 22, but may be in a state in which the rolling process of the substrate material mainly composed of a metal such as aluminum, beryllium, or titanium is finished. In addition, these substrate materials may be made into a reflective surface 23 only by performing a normal cleaning method such as a degreasing process, a chemical polishing method, or an ultrasonic cleaning method, or those substrate materials are mirror-polished. It is also included. In addition to the substrate mainly composed of metal, the reflecting surface 23 includes a substrate made of glass, carbon fiber, glassy carbon, or plastic and coated with a metal reflecting film.

  In the direct vapor deposition type flat panel detector 41, the reflective film 50 includes not only Al but also a thin film formed by sputtering or other processes such as Ag, Au, Pd, and Cr.

  In addition, the reflecting surfaces 23 and 49 defined in the present invention do not particularly define the reflecting ability of the surface, but comprehensively represent the surface of the material and the surface where the reflecting films 24 and 50 are applied to all materials. In addition, all surfaces that have a reflectance that is not completely zero are included. Therefore, the configuration in which the reflection films 24 and 50 are not applied to portions other than the effective area of the flat detector 31 or the imaging apparatus is also applied to the substrate having a low reflectance such as glassy carbon in the scintillator panel 21. The configuration is also included in the present invention.

  Further, the scintillator layers 26 and 46 include not only CsI but also those containing gadolinium sulfate (commonly called GOS), calcium tungstate, sodium iodide (NaI) or the like as main components.

Further, the protective film 25, 48 is, in addition to _{SiO 2, LiF, MgO, SiN} , SiNO, also included materials TiO _2, CaF _2, MgF ₂ or the like.

In addition to polyparaxylylene, the moisture-proof films 27 and 51 include polyimide, polyurea, polyamide, polyurethane, polyazomethine, nitrocellulose, cellulose acetate, polycarbonate, polyester, polyvinylidene chloride, polyamide synthetic fiber, and vinylidene chloride. - Enka vinyl copolymer, polyolefin, epoxy resins, polyacrylates, thin polymeric material such as a soft epoxy or a _thereof, such as _{SiO 2, SiNO, In 2 O} 3, Si 3 N 4, SiC, Al 2 O 3 And a multilayer film with an inorganic film transparent to visible light.

It is sectional drawing of the scintillator panel which shows the 1st Embodiment of this invention. It is a front view of a scintillator panel same as the above. It is sectional drawing of the bonding type | formula flat detector using a scintillator panel same as the above. It is sectional drawing of the scintillator panel which shows the 2nd Embodiment of this invention. It is sectional drawing of the scintillator panel which shows the 3rd Embodiment of this invention. It is sectional drawing of the direct vapor deposition type flat detector which shows the 4th Embodiment of this invention. It is sectional drawing of the conventional scintillator panel. It is sectional drawing of the conventional bonding type | formula flat detector. It is sectional drawing of the conventional direct vapor deposition type flat detector.

Explanation of symbols

21 Scintillator panel
22 Glass substrate as substrate
23 Reflective surface
24 Reflective film
25 Protective film
26 Scintillator layer
26a peripheral part
31 Flat detector
32 Image sensor
36 Effective area
41 Planar detector
42 Image sensor
46 Scintillator layer
46a peripheral
47 Effective area
48 Protective film
49 Reflecting surface
50 Reflective film

Claims (9)

A substrate having a reflective surface;
A scintillator layer formed on the reflective surface of the substrate,
The scintillator panel according to claim 1, wherein the reflective surface has a reflectance of a region corresponding to a peripheral portion of the scintillator layer lower than a reflectance of a region corresponding to a portion other than the peripheral portion. A reflective film constituting a reflective surface formed on the substrate;
The scintillator panel according to claim 1, further comprising: a protective film formed in a region other than a peripheral portion of the scintillator layer on the reflective film. An image sensor in which a plurality of light receiving elements are arranged;
A flat detector comprising: the scintillator panel according to claim 1 combined with the image sensor. The flat detector according to claim 3, wherein a region around the scintillator layer corresponds to an area outside the effective area of the image sensor. A scintillator panel according to claim 1 or 2,
And a camera facing the scintillator panel. The imaging device according to claim 5, wherein a region around the scintillator layer corresponds to an area outside the effective area of the camera. An image sensor in which a plurality of light receiving elements are arranged;
A scintillator layer formed on the image sensor;
A reflective surface formed on the scintillator layer,
The flat surface detector, wherein the reflective surface has a lower reflectance of a region corresponding to a peripheral portion of the scintillator layer than a reflectance of a region corresponding to a portion other than the peripheral portion. The protective film formed in a region other than the peripheral portion on the scintillator layer, and the reflective film constituting the reflective surface formed on the scintillator layer and the protective film. Scintillator panel. The flat detector according to claim 7 or 8, wherein a region in a peripheral portion of the scintillator layer corresponds to an area outside the effective area of the image sensor.

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