JP2010286447A - Radiation detector, and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a highly-reliable X-ray detector capable of improving adhesion between a moisture-proof layer and a substrate, and to provide a method for manufacturing the X-ray detector. <P>SOLUTION: A photoelectric conversion part 17 for converting fluorescence into an electrical signal is formed on a glass substrate 16; and a scintillator layer 13 for converting a radiation into fluorescence is arranged on the photoelectric conversion part 17; and the moisture-proof layer 31 is formed so as to cover the scintillator layer 13, and the moisture-proof layer 31 and an array substrate 12 are sealed by an adhesive layer 35, to thereby form a moisture-proof structure 15 that protects the scintillator layer 13 from external moisture. Here, a surface processing layer 34 comprising a silane coupling agent or a metal chelate agent is formed, in advance, on a section which is in contact with a bonding layer 35 of the moisture-proof layer 31. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a radiation detector for detecting radiation and a method for manufacturing the same.

  A planar X-ray detector using an active matrix has been developed as a new generation X-ray diagnostic 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 converted into signal charges by an amorphous silicon (a-Si) photodiode or a photoelectric conversion element such as a CCD (Charge Coupled Device). The image is acquired by converting.

As a material of the scintillator layer, cesium iodide (CsI): sodium (Na), cesium iodide (CsI): thallium (Tl), sodium iodide (NaI), or gadolinium oxysulfide (Gd ₂ O ₂₎ There are various types such as S), which are properly used depending on applications and necessary characteristics.

  The scintillator layer can improve resolution characteristics by forming grooves by dicing or the like, or by depositing by a vapor deposition method so that a columnar structure is formed.

  A reflective film may be formed on the scintillator layer for the purpose of improving the use efficiency of fluorescence and improving sensitivity characteristics. The reflection film reflects the fluorescence emitted from the scintillator layer toward the side opposite to the photoelectric conversion element side by the reflection film, and increases the fluorescence reaching the photoelectric conversion element side.

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

  In addition, a moisture-proof structure that protects the scintillator layer and the reflective layer (or reflective plate, etc.) from the outside atmosphere and suppresses the deterioration of characteristics due to humidity is an important component for making the detector a practical product. Become. 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 a conventional moisture-proof structure, a moisture-proof layer such as an AL foil is adhered and sealed to the substrate at the peripheral portion to maintain moisture-proof performance (for example, refer to Patent Document 1). There is a structure (for example, refer to Patent Document 2) in which adhesion and sealing are performed through a surrounding ring-shaped structure.

JP 2009-128023 A JP-A-5-242841

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

  In the moisture-proof structure mentioned above, an ultraviolet-curing or thermosetting resin adhesive is used for bonding the moisture-proof layer and the substrate, but it is difficult to ensure sufficient adhesion with only the adhesive. In particular, under high-temperature and high-humidity conditions, the elastic modulus of the resin itself decreases due to moisture absorption of the adhesive resin, and the mechanical strength decreases. Therefore, the adhesive force decreases until the moisture absorption amount is saturated. When a leak path to the inside of the moisture-proof structure occurs due to a decrease in the adhesion of the moisture-proof layer adhesion portion, a serious problem such as a reduction in resolution due to moisture absorption of the scintillator layer may be caused.

  This invention is made | formed in view of such a subject, and it aims at improving the contact | adhesion power of a moisture-proof layer and a board | substrate, and providing a highly reliable radiation detector and its manufacturing method.

  In order to achieve the above object, a radiation detector of the present invention includes a substrate having a photoelectric conversion unit that converts fluorescence into an electrical signal, and a scintillator layer that is formed on the photoelectric conversion unit and converts radiation into the fluorescence. A radiation detector having a moisture-proof structure in which a metal moisture-proof layer formed so as to cover the scintillator layer is bonded to the substrate with a bonding layer made of a resin adhesive, and protects the scintillator layer from external moisture. The moisture-proof layer has a surface treatment layer with a silane coupling agent or a metal chelating agent at least in a portion in contact with the bonding layer.

  Moreover, in order to achieve the above-mentioned object, a method for manufacturing a radiation detector according to the present invention includes a first step of forming a photoelectric conversion unit that converts fluorescence into an electric signal on a substrate, and the photoelectric conversion unit. A second step of disposing a scintillator layer that converts radiation into the fluorescence, a metal moisture barrier layer is formed so as to cover the scintillator layer, and the moisture barrier layer and the substrate are sealed with an adhesive layer And a third step of forming a moisture-proof structure that protects the scintillator layer from external moisture. In the method of manufacturing a radiation detector, a portion in contact with at least the bonding layer of the moisture-proof layer in the third step In addition, a surface treatment layer with a silane coupling agent or a metal chelating agent is previously formed.

  According to the present invention, sufficient adhesion can be secured in the adhesion between the moisture-proof layer and the substrate, and even under high temperature and high humidity, it is possible to suppress a decrease in adhesion due to moisture absorption of the adhesive. It is possible to provide a radiation detector that realizes the above.

It is a perspective view which shows the radiation detector which concerns on one embodiment of this invention. It is sectional drawing of the radiation detector of FIG. It is a figure which shows AL hat shape and the formation area of a surface treating agent of the radiation detector which concerns on one embodiment of this invention, (a) is a top view, (b) is a side view. It is a graph which shows the result of having measured the adhesive force of AL and glass which are not surface-treating. It is a schematic diagram of the adhesion strength evaluation sample of AL / adhesive.

  Hereinafter, a radiation detector according to an embodiment of the present invention will be described with reference to FIGS. 1 and 2.

(Overall structure of radiation detector)
FIG. 1 is a perspective view of a radiation detector according to the present embodiment, and FIG. 2 is a sectional view of the radiation detector.

  An X-ray detector denoted by reference numeral 11 as a radiation detector is an X-ray plane sensor that detects an X-ray image that is a radiation image, and is used for general medical applications, for example.

  As shown in FIGS. 1 and 2, the X-ray detector 11 is provided on an array substrate 12 as a photoelectric conversion substrate that converts fluorescence into an electrical signal, and is incident on a surface that is one main surface of the array substrate 12. A scintillator layer 13 which is an X-ray conversion unit for converting X-rays to fluorescence, a reflection film 14 provided on the scintillator layer 13 to reflect fluorescence from the scintillator layer 13 toward the array substrate 12, the scintillator layer 13 and the reflection film 14 is provided with a moisture-proof structure 15 that is provided on 14 and protects from outside air and humidity.

(Array substrate 12)
The array substrate 12 converts fluorescence converted from X-rays into visible light by the scintillator layer 13 into an electric signal. A glass substrate 16 and a plurality of substantially rectangular shapes functioning as optical sensors provided on the glass substrate 16. Photoelectric conversion unit 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 the control lines 18 Are electrically connected and a control circuit (not shown) is connected to each data line 19 (not shown).

  Pixels 20 having the same structure are formed in a matrix on the array substrate 12, and photodiodes 21 as photoelectric conversion elements are disposed in the pixels 20. 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 that stores the signal charge converted by the photodiode 21. Yes. However, the storage capacitor may also serve as the capacitance of the photodiode 21 and is not always necessary.

  Each thin film transistor 22 has a switching function for accumulating and discharging charges generated by the incidence of fluorescence on the photodiode 21. The thin film transistor 22 is at least partially composed of a semiconductor material such as amorphous silicon (a-Si) as an amorphous semiconductor or polysilicon (P-Si) as a polycrystalline semiconductor.

  The thin film transistor 22 includes a gate electrode 23, a source electrode 24, and a drain electrode 25, as shown in FIG. The drain electrode 25 is electrically connected to the photoelectric conversion element (photodiode) 21 and the storage capacitor.

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

  The control line 18 shown in FIG. 1 is arranged along the row direction between the pixels 20, and is electrically connected to the gate electrode 23 of the thin film transistor 22 of each pixel 20 in the same row as shown in FIG. Yes.

  A data line (signal line) 19 shown in FIG. 1 is arranged 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, as shown in FIG. It is connected to the.

  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.

  As shown in FIG. 2, a protective layer 26 made of resin is formed on the uppermost portion of the array substrate 12 to protect the photoelectric conversion element (photodiode) 21, the thin film transistor 22, and the like.

(Scintillator layer 13)
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) or the like is used as a vacuum deposition method. 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, applying the mixture on the array substrate 12, firing and curing, and dicing with a dicer. Some of them are formed into a square shape.

Between these columns, it is possible to enclose air or an inert gas such as nitrogen (N ₂ ) for preventing oxidation, or to make a vacuum state.

  In the following embodiment, a CsI: Tl vapor deposition film is used for the scintillator layer 13, the film thickness is about 600 μm, and the columnar structure crystal pillar (pillar) thickness is about 8 to 12 μm on the outermost surface. Things are used.

(Reflection layer 14)
The reflection layer 14 formed on the scintillator layer 13 reflects the fluorescence emitted on the side opposite to the photodiode, and increases the amount of fluorescence that reaches the photodiode.

As the reflective layer 14, a metal having a high fluorescence reflectance such as silver alloy or aluminum is formed on the scintillator layer 13, a reflector having a metal surface such as aluminum is adhered to the scintillator layer 13, TiO ₂ or the like. And a reflective layer having a diffuse reflection property made of a light scattering material and a binder resin.

  The reflective layer 14 is not necessarily required due to characteristics such as resolution and luminance required for the radiation detector 11.

(Dampproof structure 15)
The moisture-proof structure 15 is for protecting the scintillator layer 13 and the reflective layer 14 from the external atmosphere and suppressing characteristic deterioration due to humidity or the like. As shown in FIG. 2, the moisture-proof layer 31 having the flange 33 formed thereon, It consists of a surface treatment layer 34 and an adhesive layer 35.

  As shown in FIG. 3, the moisture-proof layer 31 is formed in a hat shape by press-molding a 0.1 mm-thick AL alloy foil (A1N30-O material) into a structure having a flange portion 33 having a width of 5 mm in the peripheral portion. The Next, after forming the surface treatment layer 34 by treating the flange portion 33 of the moisture-proof layer 31 with a silane coupling agent (epoxy-based or amine-based) or a metal chelating agent (organic zirconium chelate compound, organic titanium chelate compound). Then, an adhesive is applied to the surface-treated flange portion 33 by a dispenser to form an adhesive layer 35, which is bonded to the array substrate 12 on which the scintillator layer 13 and the reflective film 14 are formed (see FIG. 2).

  As the adhesive, a commercially available heat curable or ultraviolet curable epoxy adhesive can be used.

  The surface treatment of the flange portion 33 of the moisture-proof layer 31 is performed by immersing the AL hat in a surface treatment solution or by applying and forming a surface treatment liquid only on the flange portion 33 of the AL hat using a brush or the like. It can be performed by heat treatment under dry conditions suitable for the agent.

  Further, by adhering the moisture-proof structure 15 to the array substrate 12 with an AL hat in a reduced-pressure atmosphere, it is possible to form a moisture-proof structure with excellent mechanical strength under reduced pressure assuming airplane transportation. The AL hat surface treatment with a silane coupling agent or metal chelating agent can also be applied in this reduced pressure sealing, and a moisture-proof structure with high adhesion and high reliability can be provided.

  The moisture-proof structure 15 is formed, and the panel of the X-ray detector 11 is completed. Further, wiring is connected to each electrode pad portion of the control line and the signal line by TAB connection, connected to a circuit after the amplifier, and further incorporated into a housing structure to complete the X-ray detector 11.

(Evaluation of adhesion between AL hat and array substrate)
First, in order to simply evaluate the adhesion between the AL hat and the substrate, a strip-shaped AL foil is bonded to a glass substrate, the peel strength is measured by a peel tester, and data is collected at regular time intervals. It was used as an index of adhesion.

  Also, the thermal shock test required for the reliability of the radiation detector ((−20 ° C. × 1 h / RT. × 30 minutes / 50 ° C. × 1 h / RT. × 30 minutes) × 30 times), high temperature and high temperature The peel strength was also measured after the humidity test (60 ° C.-90% RH × 500 H) to confirm the reliability.

  The result of having measured the peel strength of AL foil and glass which have not performed surface treatment in FIG. 4 is shown.

  After initial and cold shock, a peel strength of 6 to 8 N is obtained and there is sufficient adhesion, but it can be seen that the adhesion decreases sharply when a high temperature and high humidity test is performed.

  There is also a difference in the peeling mode. In the state of good adhesion before the high-temperature and high-humidity test, the adhesive cohesive failure, whereas after the high-temperature and high-humidity test, the interface peeling at the interface between the AL and the adhesive It has become. In a high temperature and high humidity environment, it is expected that the mechanical strength of the adhesive itself is reduced due to moisture absorption by the adhesive, and the adhesive strength at the interface with AL is reduced.

  Next, in order to improve the adhesion between the AL and the adhesive, (1) a silane coupling agent effective for improving the adhesion between organic and inorganic materials, and (2) a functional group such as a hydroxyl group, a carboxyl group, and an epoxy group It is known as a cross-linking agent that reacts with -O-Ti-O-bonding and -O-Zr-O-bonding, and is coated with an organic titanium / zirconium chelate compound that is effective in improving water resistance and adhesion. It was dried and the adhesion between the adhesive and AL was confirmed.

In order to simply evaluate the adhesive strength of the AL / adhesive, as shown in FIG. 5, the AL alloy substrate 41 is treated with the above surface treatment agent, and an ultraviolet curable epoxy resin adhesive 43 is dropped thereon. A cured product was used. The diameter of the epoxy resin adhesive 43 was 5 mm in all cases. The evaluation of the adhesion force was performed based on whether or not the adhesive 43 was added with a finger and peeled off from the AL alloy substrate 41. The results are shown in the table below.

  From this result, in the untreated substrate, after 10 hours of high temperature and high humidity (121 ° C.-100% RH), all the dropped 10 adhesives were peeled off, but in the AL substrate treated with aminosilane and Zr chelating agent, It was found that there was no peeling and the adhesion was improved.

(Effect of X-ray detector 11 according to the present embodiment)
As described above, by treating the flange portion 33 of the moisture-proof layer 31 serving as a contact surface with the array substrate 12 with a silane coupling agent or a metal chelating agent, the moisture-proof layer 31 made of a metal foil or a metal thin plate and the TFT A sufficient adhesion can be secured in the adhesion of the array substrate 12 including the photodiode and the photodiode, and a decrease in the adhesion due to moisture absorption of the adhesive layer 35 can be suppressed even under high temperature and high humidity, realizing high moisture-proof performance and long-term reliability. A line detector 11 can be provided.

  Further, when the material of the moisture-proof layer 31 is AL or an AL alloy foil material, since the X-ray absorption coefficient is small as a metal material, the merit is great in that the X-ray absorption loss in the moisture-proof layer can be suppressed. Also, when processed into a hat shape, it is excellent in workability.

  11: X-ray detector, 12: array substrate, 13: scintillator layer, 14: reflective film, 15: moisture-proof structure, 17: photoelectric conversion part, 31: moisture-proof layer, 33: collar part, 34: surface treatment layer, 35 : Adhesive layer

Claims (6)

A substrate having a photoelectric conversion unit that converts fluorescence into an electric signal, a scintillator layer that is formed on the photoelectric conversion unit and converts radiation into the fluorescence, and a metal moisture-proof layer formed so as to cover the scintillator layer In a radiation detector having a moisture-proof structure that is bonded to the substrate and a bonding layer made of a resin adhesive and protects the scintillator layer from external moisture,
The moisture detector has a surface treatment layer with a silane coupling agent or a metal chelating agent at least in a portion in contact with the bonding layer.   The radiation detector according to claim 1, wherein the moisture-proof layer is made of a foil or a thin plate of aluminum or an aluminum alloy.   3. The radiation detector according to claim 1, wherein the moisture-proof layer has a depth including at least the scintillator layer and is formed in a hat shape including a collar portion around the moisture-proof layer. A first step of forming a photoelectric conversion unit for converting fluorescence into an electrical signal on a substrate;
A second step of disposing a scintillator layer for converting radiation into the fluorescence on the photoelectric conversion unit;
A metal moisture-proof layer is formed so as to cover the scintillator layer, and the moisture-proof layer and the substrate are sealed with an adhesive layer to form a moisture-proof structure that protects the scintillator layer from external moisture. In a method of manufacturing a radiation detector comprising:
A method for producing a radiation detector, comprising forming a surface treatment layer with a silane coupling agent or a metal chelating agent in advance in at least a portion of the moisture-proof layer in the third step that comes into contact with the bonding layer.   5. The method of manufacturing a radiation detector according to claim 4, wherein the surface treatment layer is formed by immersing the moisture-proof layer in a liquid of a silane coupling agent or a metal chelating agent and then heat-treating the surface.   The radiation detector according to claim 4, wherein the surface treatment layer is formed by directly applying a liquid of the silane coupling agent or metal chelating agent to the adhesion portion of the moisture-proof layer and then performing a heat treatment. Manufacturing method.

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