JP2010101640A - Radiation detector - Google Patents

Abstract

An X-ray detector (11) that has excellent moisture-proof performance and suppresses stress exerted on an array substrate (12) by a moisture-proof structure (15).
A scintillator layer for converting X-rays into fluorescence is formed on a photodiode on an array substrate. A moisture-proof structure 15 that protects the scintillator layer 13 from external moisture is formed so as to cover the scintillator layer 13. The moisture-proof structure 15 includes a moisture-proof layer 29 formed on the scintillator layer 13, and a soft adhesive layer 28 that joins the moisture-proof layer 29 and the array substrate 12. Sufficient moisture-proof performance can be ensured for the scintillator layer 13, and the stress exerted on the array substrate 12 by the moisture-proof structure 15 can be suppressed by the manufacturing process and temperature change after manufacturing.
[Selection] Figure 1

Description

  The present invention relates to a radiation detector for detecting radiation.

  A planar X-ray detector using an active matrix has been developed as a new generation diagnostic X-ray detector. By detecting the X-rays irradiated to the X-ray detector, an X-ray image or a real-time X-ray image is output as a digital signal. In this X-ray detector, X-rays are converted into visible light, that is, fluorescence by a scintillator layer, and this fluorescence is signaled by a photoelectric conversion element such as an amorphous silicon (a-Si) photodiode or a CCD (Charge Coupled Device). Images are acquired by converting them into electric charges.

The scintillator layer is generally made of cesium iodide (CsI): sodium (Na), cesium iodide (CsI): thallium (Tl), sodium iodide (NaI), or gadolinium oxysulfide (Gd ₂ O _2). S) or the like is used, and the resolution characteristics can be improved by forming grooves by dicing or the like, or by depositing by a vapor deposition method so that a columnar structure is formed. There are various materials for the scintillator layer as described above.

  There is a method of forming a reflection film on the scintillator layer in order to improve the use efficiency of fluorescence and improve sensitivity characteristics. That is, of the fluorescence emitted from the scintillator layer, the fluorescence directed to the opposite side with respect to the photoelectric conversion element side is reflected by the reflection film to increase the fluorescence reaching the photoelectric conversion element side.

Examples of the reflective film include a method of forming a metal layer with high fluorescence reflectance such as silver alloy or aluminum on the scintillator layer, or light scattering composed of a light scattering material such as titanium oxide (TiO ₂ ) and a binder resin. A method of coating and forming a reflective film is known. In addition, a method of reflecting scintillator light by bringing a reflector having a metal surface such as aluminum into close contact with the scintillator layer instead of forming on the scintillator layer has been put into practical use.

  A moisture-proof structure for protecting a scintillator layer and a reflective layer (or a reflective plate, etc.) from the external atmosphere to suppress deterioration of characteristics due to humidity is an important component for making a detector a practical product. In particular, when a CsI: Tl film or a CsI: Na film, which is a material having a large deterioration with respect to humidity, is used as a scintillator layer, high moisture-proof performance is required.

As such a moisture-proof structure, for example, as illustrated in Patent Document 1 and related patent documents, a method using a CVD film of polyparaxylylene (hereinafter referred to as Parylene (registered trademark)), or Patent Document 2 As exemplified in the above, there is known a structure in which the periphery of the scintillator layer is surrounded by a surrounding member and sealed in combination with a moisture-proof layer.
Japanese Patent No. 3077741 (page 3-4, Fig. 2) JP-A-5-242841 (page 3-5, FIG. 1)

  However, the conventional moisture-proof structure has the following problems.

  For example, in the case of a method using a parylene CVD film, the moisture permeability barrier property is often insufficient at least in a practical film thickness range (for example, 20 μm). As a specific example, a spl using a CsI: Tl film (film thickness 600 μm) as a scintillator film and a parylene CVD film (20 μm) as a scintillator film on a glass substrate for confirmation of the moisture resistance performance was made in a high temperature and high humidity test. The results of investigating changes in brightness and resolution are outlined below.

  As a method for measuring luminance and resolution, X-rays were irradiated from the scintillator film side, and measurement was performed by focusing on the interface between the glass substrate and the CsI: Tl film by a CCD camera from the glass substrate side. The luminance was used as an index relative to the intensifying screen (HG-H2 Back (manufactured by Fuji Film Co., Ltd.)), and the resolution was used as an index by measuring 2 Lp / mm CTF (Contrast Transfer Function) from the resolution chart image.

  In the spl prepared in this manner, the relative luminance change is small as shown in the table of FIG. 9 in the high-temperature and high-humidity test of 60 ° C.-90% RH, but it is shown in the table of FIG. 10 and the graph of FIG. As described above, the resolution is greatly deteriorated, and the CTF value decreases to about 80% of the initial value in 24 hours. As a result of morphological observation with a scanning electron microscope (SEM) as an analysis of the phenomenon of resolution reduction, as shown in the micrographs of FIGS. 12 (a) and 12 (b), the CsI: Tl film, which was strongly independent at the beginning, was obtained. It was found that in the case of the spl whose resolution was degraded in the high-temperature and high-humidity test, the pillar structure was fused between the pillars. It is considered that the light guide effect is reduced by the fusion between the pillars, leading to a decrease in resolution.

  Next, in the case of a structure in which the periphery of the scintillator layer is enclosed by a surrounding member and sealed by a combination with a moisture-proof layer, the surrounding member is generally a material having mechanical strength such as metal, and between the substrate and the surrounding member, or the moisture-proof layer. Due to the difference in coefficient of thermal expansion between the sealing member and the surrounding member, cracks and peeling of the seal portion are likely to occur in reliability tests such as a cooling cycle and thermal shock, and in that case, the moisture-proof performance is fatally lowered. Also, due to the stress generated when the adhesive layer solidifies, the substrate warps or bends, resulting in lower manufacturability in subsequent processes, or the weak part of the seal breaks down due to long-term stress on the adhesive surface. There is also a risk of being

  This invention is made | formed in view of such a point, and it aims at providing the radiation detector which was excellent in moisture-proof performance and suppressed the stress which a moisture-proof structure exerts with respect to a board | substrate.

  The radiation detector of the present invention includes a substrate provided with a photoelectric conversion element, a scintillator layer that is formed on the photoelectric conversion element and converts radiation into fluorescence, and covers the scintillator layer. A moisture-proof structure that protects against moisture, and the moisture-proof structure includes at least a moisture-proof layer formed on the scintillator layer and a soft adhesive layer that joins the moisture-proof layer and the substrate. is there.

  According to the present invention, the moisture-proof structure that protects the scintillator layer from external moisture is constituted by a combination of the moisture-proof layer and the soft adhesive layer that joins the moisture-proof layer and the substrate, so that the scintillator layer is sufficient. It is possible to secure a sufficient moisture-proof performance and to suppress the stress exerted on the substrate by the moisture-proof structure due to a manufacturing process and a temperature change after the manufacturing.

  The configuration of the radiation detector according to the first embodiment of the present invention will be described below with reference to FIGS.

  FIG. 1 is a cross-sectional view of an X-ray detector 11 as a radiation detector, FIG. 2 is an explanatory cross-sectional view of the X-ray detector 11, and FIG. 3 is a perspective view of the X-ray detector 11. The X-ray detector 11 is an X-ray plane sensor that detects an X-ray image that is a radiation image, and is used, for example, for general medical purposes. The X-ray detector 11 includes an array substrate 12 that converts fluorescence into an electric signal, and radiation (X-rays) that is formed on the surface that is one main surface of the array substrate 12 and that converts incident X-rays into fluorescence. A scintillator layer 13 as a conversion unit, a reflection film 14 formed on the scintillator layer 13 to reflect fluorescence from the scintillator layer 13 toward the array substrate 12, and the scintillator layer 13 and the reflection film 14 formed to cover the scintillator layer 13 and the reflection film 14 A moisture-proof structure 15 that protects the layer 13 and the reflective film 14 from the outside air and humidity is provided.

  The array substrate 12 converts fluorescence converted from X-rays into visible light by the scintillator layer 13 into an electric signal. The glass substrate 16 is provided on the glass substrate 16 and has a substantially rectangular shape that functions as an optical sensor. A plurality of photoelectric conversion units 17, a plurality of control lines (or gate lines) 18 arranged along the row direction, a plurality of data lines (or signal lines) 19 arranged along the column direction, and each control line A control circuit (not shown) to which 18 is electrically connected and an amplification / conversion unit (not shown) to which each data line 19 is electrically connected are provided.

  In the array substrate 12, pixels 20 having the same structure are formed in a matrix corresponding to the intersection positions of the control line 18 and the data line 19, and photoelectric conversion is performed in each pixel 20. A photodiode 21 as an element is provided. These photodiodes 21 are disposed below the scintillator layer 13.

  Each pixel 20 includes a thin film transistor (TFT) 22 as a switching element electrically connected to the photodiode 21, and a storage capacitor (not shown) as a charge storage unit for storing the signal charge converted by the photodiode 21. I have. However, the storage capacitor may also serve as the capacitance of the photodiode 21, and is not necessarily required.

  Each thin film transistor 22 has a switching function for accumulating and releasing charges generated by the incidence of fluorescence on the photodiode 21, and amorphous silicon (a-Si) as an amorphous semiconductor which is a crystalline semiconductor material. ) Or a semiconductor material such as polysilicon (p-Si) which is a polycrystalline semiconductor. The thin film transistor 22 includes a gate electrode 23, a source electrode 24, and a drain electrode 25. The drain electrode 25 is electrically connected to the photodiode 21 and the storage capacitor.

  The storage capacitor is formed in a rectangular flat plate shape and is provided opposite to the lower part of each photodiode 21.

  The control line 18 is disposed between the pixels 20 along the row direction, and is electrically connected to the gate electrode 23 of the thin film transistor 22 of each pixel 20 in the same row.

  The data line 19 is disposed between the pixels 20 along the column direction, and is electrically connected to the source electrode 24 of the thin film transistor 22 of each pixel 20 in the same column. Each data line 19 receives an image data signal from the thin film transistor 22 constituting the pixel 20 in the same column. In addition, one end of each data line 19 is electrically connected to the high-speed signal processing unit 26. Further, a digital image transmission unit 27 is electrically connected to the high-speed signal processing unit 26. The digital image transmission unit 27 is attached in a state of being led out of the array substrate 12.

  The control circuit controls the operating state of each thin film transistor 22, that is, on and off, and is mounted on the side edge along the row direction on the surface of the glass substrate 16.

  The amplifying / converting unit includes, for example, a plurality of charge amplifiers arranged corresponding to each data line 19, a parallel / serial converter to which these charge amplifiers are electrically connected, and the parallel / serial converter is electrically connected And an analog-to-digital converter connected to the.

The scintillator layer 13 converts incident X-rays into visible light, that is, fluorescence. For example, cesium iodide (CsI): thallium (Tl) or sodium iodide (NaI): thallium (Tl) is used for vacuum deposition. The groove portion is formed by, for example, forming a columnar structure or gadolinium oxysulfide (Gd ₂ O ₂ S) phosphor particles with a binder material, coating on the array substrate 12, firing and curing, and dicing with a dicer. It is formed into a quadrangular prism shape. Between these columns, an atmosphere or an inert gas such as nitrogen (N ₂ ) for preventing oxidation can be sealed, or a vacuum state can be set.

The reflection film 14 reflects the light converted by the scintillator layer 13 toward the array substrate 12 side. For example, a coating liquid in which a submicron powder of titanium oxide (TiO ₂ ) is mixed with a binder resin and a solvent is used as a scintillator. It is formed by applying and drying on the layer 13.

  The moisture-proof structure 15 has a structure in which a moisture-proof layer 29 is bonded onto the reflective film 14 via a soft adhesive layer 28, and the soft adhesive layer 28 is in close contact with the array substrate 12 at the outer peripheral portion of the scintillator layer 13. ing.

  Further, this soft adhesive layer 28 is formed over the entire scintillator layer 13 side of the moisture-proof layer 29, and even if it is in close contact with the reflective film 14, it is interposed through a gap as shown in FIG. May be separated.

  The soft adhesive layer 28 can be applied as long as it is a flexible material such as a resin material containing a porous resin or a plasticizer, but has a low moisture permeability required by the moisture-proof structure 15. In order to ensure, for example, a resin material to which an inorganic filler material having a size of several to several tens of μm is added is preferable. The soft adhesive layer 28 preferably has a structure in which the core 35 of the resin foam and both ends thereof are sandwiched between the resin adhesive layers 36 from the viewpoint of ensuring adhesion to the moisture-proof layer 29 and the array substrate 12. . In particular, as the type of resin foam core 35 or resin adhesive layer 36, an acrylic resin is used to form a flexible adhesive layer 28 that is flexible and strong against deformation, thermal expansion and contraction due to external forces. can do.

As the inorganic filler material, for example, alumina or silicon dioxide (SiO ₂ ) is used.

  The moisture-proof layer 29 is formed so as to cover the entire upper part of the scintillator layer 13. For this moisture-proof layer 29, various metal foil materials and sheet materials can be used. For example, by using a foil mainly composed of aluminum, X-ray absorption loss can be suppressed, and the mechanical strength is appropriate. There is an advantage that can be maintained. Further, the moisture-proof layer 29 is easy to process according to the thickness and shape of the scintillator layer 13 and the like which are inexpensive and have moldability. The moisture-proof layer 29 is preferably thin in consideration of the absorption of X-rays. On the other hand, it is desirable that the moisture-proof layer 29 is thick in consideration of mechanical strength and pinhole risk. Therefore, in general, about 30 μm to 150 μm is preferable. It is considered to be thick.

The moisture-proof layer 29 can have a water vapor barrier property at the same level as the aluminum alloy foil by using an aluminum laminate film as a material other than the aluminum alloy foil. In addition, the development of a moisture-proof film that is a laminate (generally multilayer) of inorganic films such as Al ₂ O ₃ , SiO ₂ , and SiON and organic films that are resin films made of organic materials such as PET has progressed to several tens of μm Such a film material can be used as the moisture-proof layer 29 because a film having a film thickness of about a low water vapor transmission rate as low as that of an aluminum alloy foil has been put into practical use. In this case, as the inorganic film material, not only the Si-based or Al-based inorganic film described above but also a Zr-based, Mg-based, Y-based oxide film, nitride film, oxynitride film, or the like can be applied. In addition, various resin film materials other than PET can be applied to the organic film. Since such a film material is generally transparent, use as the moisture-proof layer 29 is suitable for detecting internal alteration and abnormality at the manufacturing stage.

  Here, the moisture permeability of the moisture-proof structure 15 will be described using an approximate expression. The moisture permeability Q of the entire moisture-proof structure 15 including the soft adhesive layer 28 and the moisture-proof layer 29 can be roughly expressed by the following expression (1).

Q = Q ₁ + Q ₂ + Q ₃ (1)

Here, in the structure of the present embodiment, Q ₁ of the first item of the formula (1) indicates the moisture permeability from the moisture-proof layer 29 occupying most of the moisture-proof structure 15, and this moisture permeability Q ₁ Can be suppressed to a level at which the influence on the scintillator layer 13 can be substantially ignored by using the foil material or the moisture-proof film. In addition, the value of Q ₃ of the third item of Equation (1) is the value of Q ₂ of the second item, which is the moisture permeability of the soft adhesive layer 28 by properly optimizing the interface cleaning and adhesion process. The value is suppressed to a sufficiently low value. Therefore, in the structure of the present embodiment, if the process is optimized, the value of Q _{2 in} the second item of the equation (1) is dominant with respect to the overall moisture permeability Q, which becomes a problem.

In the following formula (2) in which Q ₂ of the second item of formula (1) is written, if the moisture permeability coefficient P of the soft adhesive layer 28 is the same, the soft adhesive layer 28 is bonded to the array substrate 12 If the relationship between the sealing width W, which is the effective adhesion width, and the thickness T of the portion that is in close contact with the array substrate 12 is T / W << 1, that is, W >> T, the penetration from the soft adhesive layer 28 The humidity effect can be kept low.

Q ₂ = P · S / W
= P ・ L ・ T / W ...... (2)

  Further, as can be seen from the above equation (2), when the effective surface area S of the scintillator layer 13 increases, when the circumferential length of the soft adhesive layer 28 covering the periphery thereof is L, the moisture permeable cross-sectional area of the soft adhesive layer 28 Although the value of L · T also increases, the increase in the surface area of the scintillator layer 13 increases in proportion to the square of one side of the X-ray detector 11, whereas the moisture permeability cross-sectional area of the soft adhesive layer 28 Increases in proportion to approximately the first power of one side of the X-ray detector 11. Therefore, as shown in the following formula (3), when the effective surface area S of the scintillator layer 13 is increased, the humidity load q per unit area of the scintillator layer 13 is reduced.

  q = Q / S (3)

  From the results of various prototype evaluations using a CsI: Tl film as the scintillator layer 13 and the calculation results of the humidity load per unit area of the CsI: Tl film, when the relationship of the following formula (4) is satisfied, It was found that the reliability of the level (for example, 60 ° C.−90% RH × 500H and the characteristic maintenance rate of 80% or more) can be secured.

q <0.1 (mg / cm ² / day) (4)

The moisture permeability coefficient of the soft adhesive layer 28 is, for example, in the range of approximately 50 to 200 mg / m ² / day under the test conditions of 60 ° C.-90% RH. When the standard thickness T = 1.0 mm and the adhesion width W to the array substrate 12 is 5.0 mm, the CsI: Tl film is used in the case of the soft adhesive layer 28 having a moisture permeability coefficient of 100 mg / m ² / day. If the area size of the scintillator layer 13 is about 100 mm ² or more, the above level of moisture-proof performance can be secured.

  On the glass substrate 16, a resin layer 38 is formed between the thin film transistor 22, the scintillator layer 13, and the like.

  Next, the operation of the first embodiment will be described.

  When the X-ray detector 11 is manufactured, the photoelectric conversion unit 17 and the lines 18 and 19 are formed on the glass substrate 16 by repeating the normal film forming process and patterning process on the surface of the glass substrate 16. The array substrate 12 is used.

  Next, a scintillator layer 13 containing, for example, CsI as a base material and added with thallium (Tl) element is formed on the array substrate 12 by vapor deposition or the like.

Further, a coating liquid in which, for example, a titanium oxide (TiO ₂ ) submicron powder, a binder resin, and a solvent are mixed is applied onto the scintillator layer 13 and dried, thereby covering the scintillator layer 13 as a whole and reflecting film 14. Form.

  Then, covering the entire reflective film 14, and sticking the lower resin adhesive layer 36 of the soft adhesive layer 28, to the upper resin adhesive layer 36 of the soft adhesive layer 28, aluminum foil, aluminum alloy foil, Alternatively, the moisture-proof structure 15 is configured by attaching a moisture-proof layer 29 such as a film material having a laminated structure of an inorganic film such as an oxide film, a nitride film, and an oxynitride film and a resin film. The lower resin adhesive layer 36 is adhered to the array substrate 12 outside the scintillator layer 13.

  Thus, the moisture-proof structure 15 that protects the scintillator layer 13 from external moisture, such as an aluminum alloy foil, or a film material having a laminated structure of an inorganic film such as an oxide film, a nitride film, and an oxynitride film and a resin film, etc. By combining the moisture-proof layer 29 and the soft adhesive layer 28 that tightly bonds the moisture-proof layer 29 and the periphery of the array substrate 12 with each other, sufficient moisture-proof performance is provided for the scintillator layer 13 such as CsI. In addition, the stress exerted on the array substrate 12 by the moisture-proof structure 15 due to a temperature change or the like during the manufacturing process and after manufacturing can be minimized. By reducing this stress, it is possible to avoid risks such as deformation of the array substrate 12 caused by the moisture-proof structure 15 and damage to the scintillator layer 13 resulting from the deformation (there is a possibility of breakage if the degree is large) It becomes.

  As a result, the moisture-proof reliability for protecting the scintillator layer 13 from moisture is high, and the thermal expansion due to the stress between the array substrate 12 and the moisture-proof structure 15 generated by the manufacturing process of the moisture-proof structure 15 and the temperature change after commercialization A highly reliable X-ray detector 11 with low stress due to the stress can be obtained.

  In addition, the stress in the manufacturing process is, for example, a stress generated due to a difference in thermal expansion coefficient between members due to heating during manufacturing, a stress generated due to volume shrinkage or the like when solidified like a normal adhesive, etc. It is.

  Further, the post-manufacture stress is, for example, a stress generated due to a difference in thermal expansion coefficient between the moisture-proof structure 15 and the array substrate 12 (glass substrate 16) due to a change in environmental temperature, and the X-ray detector 11 This is a shift stress generated between the moisture-proof structure 15 and the array substrate 12 when an external force is applied and the whole is deformed.

  Next, a second embodiment will be described with reference to FIG. In addition, about the structure and effect | action similar to the said 1st Embodiment, the same code | symbol is attached | subjected and the description is abbreviate | omitted.

  In the second embodiment, the moisture-proof structure 15 of the first embodiment surrounds the scintillator layer 13 with a soft adhesive layer 28, and the resin adhesive layer 36 below the soft adhesive layer 28 is disposed on the array substrate 12. And the upper resin adhesive layer 36 is bonded to the moisture-proof layer 29, so that the soft adhesive layer 28 does not substantially cover the upper part of the scintillator layer 13.

  And by configuring in this way, it is possible to ensure sufficient moisture-proof performance for the scintillator layer 13, and to suppress the stress that the moisture-proof structure 15 exerts on the array substrate 12 after the manufacturing process and manufacturing, etc. The same effects as those of the first embodiment can be obtained.

  In addition, the soft adhesive layer 28 surrounds the scintillator layer 13, and the soft adhesive layer 28 does not substantially cover the scintillator layer 13, thereby joining the moisture-proof layer 29 with the minimum soft adhesive layer 28. In addition, the stress applied to the array substrate 12 due to the difference in thermal expansion of the core material 35 itself of the resin foam can be suppressed, and the change in the amount of warpage of the array substrate 12 with respect to the temperature change can be further suppressed.

  In addition, since the scintillator layer 13 is not substantially covered by the soft adhesive layer 28, the maximum thickness of the X-ray detector 11 can be suppressed, and the design of the X-ray detector 11 is advantageous.

  And each characteristic, such as a moisture resistance and the curvature of the array board | substrate 12, was measured about each of the Example corresponding to said each embodiment, and the comparative example corresponding to a prior art example, respectively. This comparison was performed with a dummy structure in which a scintillator layer, a reflective film, and a moisture-proof structure were formed on a glass substrate. A method for evaluating the luminance and resolution of these dummy structures will be described later.

As the size of the example, a # 1737 glass made by Corning having a thickness of 0.7 mm and a thickness of 400 mm ² was used as the glass substrate 16, and a CsI: Tl film was formed on the glass substrate 16 as a scintillator layer 13 by 380 mm □ (380 mm × An array substrate 12 deposited with an area size of 380 mm was used. On the scintillator layer 13, a reflective film 14 made of submicron TiO ₂ powder and a resin binder was formed to a thickness of about 100 μm and dried after coating. The moisture-proof layer 29 is an aluminum alloy A3004-H0 foil (80 μm thick), and the soft adhesive layer 28 is S-1079 (1.0 mm thickness) manufactured by Soken Chemical Co., Ltd. or J-7710 (manufactured by Soken Chemical Co., Ltd.). 1.0 mm thickness) was used. The soft adhesive layer 28 is laminated in the same size as the moisture-proof layer 29, and the form of the first embodiment (Example 1) and only the peripheral part that adheres to the glass substrate 16 are cut into a frame shape and the moisture-proof layer. Both 29 and the type of the above-described second embodiment (Example 2) were prototyped.

  In each of the above embodiments, the scintillator layer 13 has a film thickness of about 600 μm, and the columnar structure crystal pillar of CsI: Tl has a thickness of about 8 to 12 μm on the outermost surface.

  The type of the soft adhesive layer 28 used in each example and the results of measuring the water vapor transmission rate at 60 ° C.-90% RH by the cup method are shown in the table of FIG. Even in the same soft adhesive layer 28, there is a difference in moisture permeability, which is considered to be a difference due to the pore density of the core material 35 of the resin foam or the filler material of the added inorganic material.

Moreover, the table | surface of FIG. 6 shows the result of having measured the moisture permeability of 60 degreeC-90% RH with the cup method with respect to the kind of moisture-proof layer 29 used in each Example. As shown in the table of FIG. 6, all showed low moisture permeability almost close to the measurement limit (0.1 g / m ² / day).

  On the other hand, as the X-ray detector 11a of the comparative example, as shown in FIG. 7, a CVD film (20 μm thick) of polyparaxylylene (hereinafter referred to as Parylene (registered trademark)) having the same size as each of the above-described examples. As a moisture-proof layer 29a (Comparative Example 1) and as shown in FIG. 8, an aluminum frame 40a (1.0 mm thick) surrounds the periphery of the scintillator layer 13, and the lower surface is arrayed by an adhesive portion 41a. A prototype (Comparative Example 2) was prepared by bonding to the substrate 12 and bonding the upper surface to the aluminum plate 29b as a moisture-proof layer by the bonding portion 41a. The material and the process before the moisture-proof structure were the same as those in the above examples in any of the comparative examples sp1.

  The parylene moisture-proof layer 29a of Comparative Example 1 was a parylene film formed by thermally decomposing a raw material dimer through a vaporization chamber and a decomposition chamber and covering the entire spl in a room temperature film formation chamber.

  The production method of Comparative Example 2 is as follows. First, an aluminum material is processed into a frame shape surrounding the periphery of the scintillator layer 13 to form an aluminum frame 40a, and an aluminum alloy foil of A3004-H0 (80 μm thickness) is attached to the upper surface side of the aluminum frame 40a with an adhesive portion 41a. First of all, I made it. This moisture-proof structure is placed on the array substrate 12 on which a CsI: Tl film is formed as the scintillator layer 13, and the lower surface side of the aluminum frame 40a is attached to the peripheral portion of the array substrate 12 where the scintillator layer 13 is not provided, and the bonding portion 41a is provided. Bonded with the constituent adhesive. As this adhesive, an epoxy-based heat-curable adhesive was used and cured at a low temperature of about 60 ° C. in order to suppress the influence of thermal expansion. Further, in order to suppress moisture permeation from the bonding portion 41a, the thickness of the bonding portion 41a was suppressed to about 200 μm or less.

  In each of the above embodiments, as the final X-ray detector 11, a scintillator layer 13 and a reflective film 14 are sequentially formed on the array substrate 12. However, changes in brightness and resolution in a high temperature and high humidity test can be simplified. For evaluation, a CsI: Tl scintillator layer 13 is formed on a glass substrate 16, a reflective film 14 is formed on the scintillator layer 13, and a moisture-proof structure 15 is formed to obtain luminance and resolution (CTF) characteristics. The method of measuring was used as appropriate. The brightness and resolution characteristics of this method are as follows. X-rays are incident from the moisture-proof structure 15 side, and an X-ray image is taken with a CCD camera by focusing on the interface between the array substrate 12 and the scintillator layer 13 from the array substrate 12 side. The method to do was adopted. The X-ray quality condition is 70 KVp and RQA-5 equivalent condition, the brightness is relative brightness to the standard intensifying screen (HG-H2 Back (manufactured by Fujifilm Corporation)), and the resolution is 2 Lp / mm of the resolution chart image. The CTF (Contrast Transfer Function) value = CTF (2 Lp / mm)% was obtained by image processing.

  As shown in the table of FIG. 9, in the high-temperature and high-humidity test of 60 ° C.-90% RH × 500H, each example and comparative example 1 have a small change in relative luminance. On the other hand, as shown in the table of FIG. 10 and the graph of FIG. 11, in each example, the CTF maintenance ratio has a margin of 80% or more, while the spl of Comparative Example 1 is 100 hours. At the time, the maintenance rate has already decreased to 80% or less.

  In comparison between Example 1 and Example 2, the spl of Example 1 is slightly higher in terms of moisture resistance. This is presumably because the permeation resistance of water vapor that passes through the soft adhesive layer 28 and reaches the scintillator layer 13 can be ensured more when the soft adhesive layer 28 is laminated on the entire surface.

  As another characteristic comparison, with respect to the warpage of the array substrate 12, the spl of each example and the spl of the comparative example 1 had almost no warp at the end portions (the surface floated on the surface plate was 0). .. 2 mm or less). On the other hand, the spl of Comparative Example 2 suppressed the curing temperature of the adhesive to a low temperature of 60 ° C., but the amount of warpage reached about 1 mm as measured at the peripheral portion while being placed on a surface plate.

  Further, when 2spl of each example and each comparative example were subjected to a thermal cycle test at −20 ° C. and 50 ° C., both the spl of each example and the spl of Comparative Example 1 were particularly abnormal after 50 cycles. Although not, the spl of Comparative Example 2 was partially broken at the end of 50 cycles. This is presumably because stress was generated at the bonding interface for each temperature change of the cooling / heating cycle due to the difference in thermal expansion coefficient (thermal expansion coefficient) between the aluminum frame 40a and the glass substrate 16. In the temperature range around the test conditions, Corning # 1737 glass used as the glass substrate 16 has a thermal expansion coefficient of about 3 to 4 ppm / deg, and a general aluminum material has a thermal expansion coefficient of about 24 ppm / deg. large. As a countermeasure for the coefficient of thermal expansion, a method of creating a portion of the aluminum frame 40a with the same # 1737 glass (manufactured by Corning) as the glass substrate 16 can be considered, but it is difficult to process compared to metal processing such as aluminum and is an expensive member. End up. In addition, when a frame-shaped part is made of glass, the reliability is remarkably low in terms of mechanical strength.

  As described above, in each of the above embodiments, the moisture-proof reliability for protecting the scintillator layer 13 from moisture is high, and the stress between the array substrate 12 and the moisture-proof structure 15 generated by the manufacturing process of the moisture-proof structure, Thus, a highly reliable X-ray detector 11 with less stress due to thermal expansion due to the temperature change is obtained.

  Further, Example 1 which is spl in which the soft adhesive layer 28 is laminated on the entire surface, and the soft adhesive layer 28 are punched into a peripheral frame shape surrounding the scintillator layer 13 so that substantially only the adhesion portion with the array substrate 12 is a moisture-proof layer. In comparison with Example 2, which is 29 and laminated spl, Example 2 has a smaller change in warpage with respect to temperature change. This is presumably because the resin foam core 35 itself gives stress to the array substrate 12 due to a difference in thermal expansion, but this influence is small due to the minimum soft adhesive layer 28. Further, in the second embodiment, the maximum thickness of the X-ray detector 11 can be suppressed as compared with the first embodiment, and the design of the X-ray detector 11 is advantageous.

It is sectional drawing of the radiation detector which shows the 1st Embodiment of this invention. It is explanatory sectional drawing of a radiation detector same as the above. It is a perspective view of a radiation detector same as the above. It is explanatory drawing sectional drawing of the radiation detector which shows the 2nd Embodiment of this invention. It is a table | surface which shows the kind and material of a soft contact bonding layer used for the present Example 1 and this Example 2, thickness, and moisture permeability. It is a table | surface which shows the kind and thickness of a moisture-proof layer used for Example 1 and Example 2 same as the above, and water vapor transmission rate. It is explanatory sectional drawing which shows the comparative example 1 same as the above. It is explanatory sectional drawing which shows the comparative example 2 same as the above. It is a table | surface which shows the time change of each relative luminance of Example 1 and Example 2 and the comparative example 1 same as the above. It is a table | surface which shows the time change of each resolution of Example 1 and Example 2 and the comparative example 1 same as the above. It is a graph which shows the time change of each resolution of Example 1 and Example 2 and the comparative example 1 same as the above. It is a microscope picture which shows the lower layer part of the scintillator layer of the radiation detector of a prior art example, (a) shows the state before a high temperature, high humidity test, (b) shows the state after a high temperature, high humidity test.

Explanation of symbols

11 X-ray detectors as radiation detectors
12 Array substrate as substrate
13 Scintillator layer
15 Moisture-proof structure
21 Photodiodes as photoelectric conversion elements
28 Soft adhesive layer
29 Moisture barrier
35 core material
36 Resin adhesive layer

Claims (9)

A substrate provided with a photoelectric conversion element;
A scintillator layer formed on the photoelectric conversion element for converting radiation into fluorescence;
The scintillator layer is formed so as to cover the scintillator layer, and the scintillator layer is protected from external moisture.
The moisture-proof structure is
A moisture barrier layer formed on at least the scintillator layer;
A radiation detector comprising a moisture-proof layer and a soft adhesive layer that joins the substrate. The radiation detector according to claim 1, wherein the soft adhesive layer includes an inorganic filler material. Soft adhesive layer
Resin core material,
The radiation detector according to claim 1, further comprising a resin adhesive layer laminated with the core material. The radiation detector according to claim 3, wherein the core material of the resin foam and the main material of the resin adhesive layer are acrylic resins. The radiation detector according to any one of claims 1 to 4, wherein the moisture-proof layer is made of a foil material of aluminum or an aluminum alloy. The moisture-proof layer is a film material having a laminated structure of one of an oxide film, a nitride film, and an oxynitride film mainly containing at least one of Si, Al, Zr, Y, and Mg, and a resin film. The radiation detector according to any one of claims 1 to 4. The soft adhesive layer is formed so as to cover an adhesion surface between the moisture-proof layer and the substrate and at least a part between the upper surface of the scintillator layer and the moisture-proof layer. The radiation detector in any one. The radiation detector according to any one of claims 1 to 6, wherein the soft adhesive layer surrounds the scintillator layer and does not substantially cover an upper portion of the scintillator layer. . The soft adhesive layer satisfies a relationship of W >> T, where T is a thickness of a portion in close contact with the substrate and W is an effective adhesion width. Radiation detector.