JP2003262675A - Scintillator panel and radiation detection apparatus using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve moisture resistance and noise resistance of a scintillator. <P>SOLUTION: A conductive material, fixed to a constant potential, covers a conductive member (a metal reflection film, etc.), necessary for constituting the scintillator, and a conductive material between sensor panels for transmitting a light is transparent. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a medical X-ray diagnostic apparatus and a nondestructive inspection apparatus.

[0002]

2. Description of the Related Art In recent years, digitalization of X-ray imaging has accelerated, and various companies have announced X-ray area sensors. The method is also a direct method (a type that directly converts X-rays into electrical signals and reads them) and an indirect method (X
Lines are once converted into visible light and visible light is converted into an electric signal to be read).

FIG. 12 is a sectional view of general X-ray digital radiography. In the figure, 21 is a substrate, and a plurality of photoelectric conversion units 2 using amorphous silicon are provided on the substrate.
2. The TFT section 23 is formed, and the photoelectric conversion section 22 and the TFT section 23 are protected by the protective layer 25-a made of silicon nitride or the like and the protective layer 25-b made of PI. Reference numeral 24 denotes an electrode lead-out pad portion, to which TAB is connected via an ACF (not shown) to connect to an external circuit portion. Also,
The photoelectric conversion section 22, the TFT section 23, and the electrode lead-out pad section 24 are connected according to a circuit by wiring (not shown). The upper part 1 is a base material made of glass, 3 is a protective layer made of polyimide, and separates a reflective layer 2 made of an Al thin film from a phosphor layer described later. The phosphor layer 4 made of a columnar phosphor is protected against moisture from the outside by a protective layer 5 made of an organic resin or the like. Reflective layer 2 made of Al thin film
Is a reflection layer provided to reflect the light traveling from the phosphor layer 4 to the side opposite to the photoelectric conversion part and guide it to the photoelectric conversion part. Since it is insulated by the surrounding protective layer 3, it is electrically Is in a floating state. The sensor panel 200 composed of these 21 to 26 and the scintillator composed of 1 to 5 are bonded together by the transparent adhesive 26, and are moisture-resistant sealed by the sealing portion 27. As described above, the structure in which the sensor panel 200 and the scintillator 100 are bonded to each other via the adhesive 26 is not limited by the element structure of the sensor panel 200 or the phosphor structure of the scintillator 100, and various structures can be used depending on the application. It is possible to combine.

X-rays incident from the upper part of the drawing pass through the protective layer 5, the base material 1, the protective layer 3 and the reflective layer 2 and are absorbed by the phosphor layer 4 and then absorbed by the phosphor layer 4 to emit fluorescence. Body layer 4
Emits visible light. The emitted light reaches the photoelectric conversion unit 22, the photoelectric conversion unit converts it into an electric signal, switches it by the TFT unit 23, and reads it by an external circuit connected through a wiring, so that the incident X-ray information is two-dimensional digitally. It is converted into an image.

[0005]

When such a structure is adopted, the potential of the aluminum thin film provided as the reflection layer changes due to the influence of static electricity or an external electromagnetic field, and the photoelectric conversion section 22 and the TFT section are changed. 23, and further, the electric potential of the electrode of the wiring portion was changed, which turned out to be noise and deteriorated the image quality. Proposal (reference number 42
82037) discloses a method of solving this problem, in which a part of the protective layer 5 on the aluminum layer 2 is broken, and an electrode is connected to the electrode to drop it to a constant potential.
It was also found that the moisture resistance was lowered due to the breaking.

In view of the above, the object of the present invention is to
The purpose of the present invention is to provide a structure that does not impair the moisture resistance of the scintillator even if an electrically floating electrode is present and does not affect the sensor panel, that is, a structure resistant to noise.

[0007]

In order to solve the above-mentioned problems, the present invention provides a wavelength converter containing a conductive material 1, wherein an inorganic conductive material is provided on the side opposite to the conductive material 1 on the wavelength converter side. 2. A scintillator panel in which the inorganic conductive material 3 is placed on the side opposite to the wavelength converter side of the conductive material 1 side and the inorganic conductive material 2 and the inorganic conductive material 3 are electrically connected. Further, the inorganic conductive material 2 needs to be transparent and has a band gap (eV) wider than the peak value of the photon energy (eV) of electromagnetic waves generated after conversion by the wavelength converter. . Conductive material 1 is 1
It is a layer or more and includes a metal reflection film. The wavelength converter is a phosphor that converts radiation into visible light, and is a material having an alkali halide material as a base material.

The present invention also provides a radiation detecting device in which the above scintillator panel is attached to a photoelectric conversion panel, and the conductive material 3 or the conductive material 2 is connected to a constant potential of the device. The photoelectric conversion panel has a plurality of photoelectric conversion elements arranged on its surface, and the photoelectric conversion element is a MIS type or PIN.
It is a type structure.

As a result, the inorganic conductive materials 2 and 3 existing on the front and back of the scintillator panel can improve the humidity resistance and noise resistance.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The basic idea of this structure is to cover the circumference of a conductive member (such as a metal reflection layer) necessary for forming a scintillator with an inorganic conductive material fixed at a constant potential. The conductive material between the light-transmitting sensor panel and the sensor panel is transparent.

FIG. 1 shows a schematic sectional view thereof. In this configuration, an inorganic transparent electrode 6 is added around the scintillator in addition to the conventional configuration of FIG. 12, and it is connected to GND. Although the aluminum thin film 2 is not connected to GND, it has a structure in which it is difficult to cause a potential change due to static electricity because it is covered with electrodes. Even if the potential changes due to static electricity, the effect can be suppressed by the transparent electrode. Further, even if the potential of the aluminum thin film vibrates due to the influence of the external electromagnetic field, it is possible to suppress the influence.

FIG. 2 shows a detailed cross section of this structure, and FIG. 3 shows an equivalent circuit.

Generally, M using amorphous silicon
The IS type photo sensor section 3 and the TFT section 4 using the same material. 31 is a lower electrode made of chromium or the like 31-
Reference numeral a is a sensor lower electrode and 31-b is a TFT gate electrode. 32 is an insulating film made of a nitride film or the like and 32-a is MI.
An insulating film of the S sensor, 32-b is a gate insulating film for TFT. 33 is an active layer made of amorphous silicon or the like, 33-a is an active layer for a sensor, and 33-b is an active layer for a TFT. 34 is an n-type ohmic contact layer made of microcrystalline silicon or the like, 34-a functions as an upper electrode for a sensor, and 34-b functions as an ohmic contact layer. Reference numeral 35 is an upper electrode made of aluminum or the like, 35-a is a bias electrode, 35-b is a drain electrode, and 35-C is a source electrode (signal electrode). Three
The drain electrode 5-b and the sensor lower electrode 31-a are in contact with each other. Sensor panel 2 with these and substrate 1
00 is configured. The upper part is the scintillator 200
In the constituent part of -a, the aluminum thin film 2 is sandwiched by the transparent electrode 6 with the insulator (the substrate 1, the protective layer 5, the protective layer 3, and the phosphor 4) interposed therebetween. As shown in FIG. 1, the upper and lower transparent electrodes 6 are continuous bodies at portions not shown, and are connected to GND by a configuration not shown. The GND connection method will be described later. The GND electrode and the upper electrodes 35-a, 35-b, 35-C are capacitively coupled. Reference numerals 71 and 72 intentionally show the capacities of 35-b and 35-c coupling with the transparent electrode 6, respectively.

Light from the scintillator 200-b which is incident on the sensor panel 100 from the upper part of the drawing is absorbed by the sensor active layer 33-a, where carriers corresponding to the number of photons are generated. The potential change of the sensor lower electrode 31-a due to the accumulation of the carriers is switched by the TFT 4 so that the source electrode (signal electrode)
The signal is read by an amplifier connected to and is used as an optical signal. The switching of the TFT is performed by changing the bias of the gate electrode 31-b. Normal,
Vth of the TFT in this structure is 1.0 to 2.0
Since it is about V, the gate electrode 32-
B is biased with 0V, and when it is turned on, about 10V is biased. Two-dimensional analog information is converted into a digital image by arranging the photoelectric conversion unit 3 and the TFT unit 4 in such a two-dimensional manner.

The equivalent circuit is shown in FIG. 51 is a capacitor portion formed by the sensor active layer 33-a, 5
Reference numeral 2 denotes a capacitor portion formed by the sensor insulating film 32-a, and 51 and 52 form a MIS type photo sensor portion, which corresponds to 22. Reference numeral 61 is a signal line A corresponding to 35-b, and 53 is a TFT portion corresponding to 23. 54 is a bias line corresponding to 35-a, 57 is a power source for bias, 55 is a signal line B corresponding to 35-c, 58 is an amplifier, 56
Is a gate line, 60 is a signal reading device, and 59 is a gate drive device. 71 and 72 are respectively
The capacitance that the signal lines A and B couple with the transparent electrode 6 is intentionally illustrated. In this figure, the fluorescent plate is not shown. Here, the driving will be briefly described. First, a refresh voltage is applied from the bias power source 57 to refresh the capacitors 51 and 52 through the bias line 54. After that, when the bias voltage is switched to the bias voltage from the bias power source 57, X-rays are radiated and visible light from the phosphor is applied to the 51 part, and an amount of electron-hole pairs (carriers) corresponding to the light is generated. Occur. When a constant voltage is applied from the gate line 56 with the carriers stored in the capacitors 51 and 52, the TFT 53 becomes conductive and a considerable charge (weak)
Flows to the signal line 55. The signal output can be taken out by amplifying this by the amplifier 58 and performing the signal processing by the signal reading device 60. Since this sensor is a circuit that handles extremely weak signals, it can be said that it is easily affected by external noise. In the drawing, 3 × 3 pixels are shown for convenience, but in reality, N × M pixels can be used in both the vertical and horizontal directions.

At this time, since there are capacitive coupling components 71 and 72, if a temporal potential change occurs on the transparent electrode side, it will be redundant in the signal, but the transparent electrode falls to stable GND. Therefore, such noise is suppressed. Incidentally, in the conventional example, it can be said that the capacitive coupling components 71 and 72 exist between the electrically floating aluminum thin film.

In terms of structure, the periphery may be covered only with a transparent conductive material, and other conductive materials may be used for portions that do not require transparency, and the structure of the present invention may be combined with the transparent conductive material. It does not hurt.

The purpose of covering both surfaces with an inorganic conductor is to improve the moisture resistance and to suppress the influence of static electricity and electromagnetic waves from the surroundings as much as possible. Experimental data have shown that the presence of conductors on both sides enhances the electromagnetic wave shielding effect. In addition, since the moisture permeability of inorganic materials is lower than that of organic materials, the path to the outside (external →
It is also effective for narrowing the opening of (organic material → phosphor). For example, the effect is remarkable when an organic material or the like is used for the substrate. More preferably, the entire circumference is completely covered with the inorganic conductive material. Such a moisture resistant structure is particularly effective when an alkali halide phosphor having a high deliquescent property is used.

As a transparent electrode, In ₂ is used as a matrix component.
O ₃ (Eg = 3.5 to 4.0 eV), ZnO (Eg =
3.3 eV), SnO ₂ (Eg = 3.4 to 3.8 eV)
As typical materials, ITO in which In ₂ O ₃ is doped with Sn and AZO in which ZnO is doped with Al are included.
(Some books are written as ZAO). Besides this, Cd ₂ SnO ₄ (Eg = 2.1 to 2.9 eV), AgS
bO ₃ (Eg = 3.1 eV), CdGeO ₄ (Eg =
Materials such as 3.2 eV) are also applicable. In particular, the sensitivity region in the photoelectric conversion part using amorphous silicon is 500 nm (E = 2.60 eV) to 700 nm.
Since it is in the wavelength region of (E = 1.86 eV), a phosphor having a peak wavelength in this range is used.
The transparent conductive material has a band gap energy equal to or higher than photon energy. These can be formed by a method such as a sputtering method, an ion plating method, a CVD method (chemical vapor deposition method), a spray pyrolysis method, a laser ablation method, or a dip coating method. FIG. 7 shows a sectional view and a plan view of forming ITO on the scintillator by a sputtering method. In this example, it is shown that ITO is simultaneously formed on both surfaces of the scintillator. As shown in FIG. 7-b, the edge of the scintillator substrate 1 is supported by the chuck 44, ITO targets are arranged on both sides as shown in FIG. 7-a, and plasmas 43-1 and 43 are formed.
-2 is generated and sputtering is performed. At this time, the ITO film is not formed on the contact portion of the chuck 44, but since the film is formed around other portions even at the edges, the ITO films on the front and back sides are connected. FIG. 8 shows a method of completely covering the entire circumference with an ITO film. As shown in FIG. 8A, the phosphor layer 4 side is first directed to the ITO target 42 side, and plasma 43 is generated to perform sputtering. Then, the scintillator is inverted and the back side is similarly sputtered. This makes it possible to completely cover the entire circumference with the transparent conductive film.

4 to 6 are cross-sectional views showing how to drop to a constant potential. As the wiring for connection, there are materials such as a laminated sheet of metal foil (including a flexible cable), a conductive tape, and a spring. As a method of connecting the wiring material for connection and the conductor, there are methods such as pressure bonding with ACF, fixing with a conductive adhesive, fixing with a conductive adhesive, and fixing with a screw. FIG. 4-a shows a laminated sheet of metal foil (PET film 9 and aluminum foil 8) as a wiring for connection, and a conductive adhesive (7-a, 7-b) as a connection method.
Shows an example using. The chassis 15 is made of a lightweight alloy material such as magnesium alloy. FIG. 4B shows an example in which the chassis side 15 is connected by screws. FIG. 5 shows a conductive tape (conductive base 11 and conductive adhesive 1
0), and FIG. 6 shows an example of connection by the leaf spring 12. When using a leaf spring, it is necessary to adjust the pressure so as not to destroy the transparent conductive film.

[0021]

[Embodiment 1] FIG. 1 shows a preferred embodiment. In this example, an amorphous carbon material is used for the substrate 1, and protective layers 3-a and 3-b are provided on the front and back sides of the Al thin film for reflection. As the transparent conductive film, ITO is vapor-deposited all around, and the path between the outside and the phosphor (external → organic material 5 → phosphor 4) is completely blocked by the inorganic material 6. Inside the transparent conductive film, two layers of an Al thin film 2 and amorphous carbon 1 exist as conductive materials. Chassis 15
An Al laminate film was used for connection with the scintillator side, a conductive adhesive was used for the scintillator side, and a screw was used for the chassis side. It is connected to ITO from the chassis that fell to GND through an Al laminate film.

With this structure, the moisture resistance of the phosphor 4 is enhanced and the noise resistance of the sensor panel 200 is improved.

[0023]

[Embodiment 2] FIG. 2 shows a preferred embodiment. Also in this example, an amorphous carbon material is used for the substrate 1, and protective layers 3-a and 3-b are provided on the front and back surfaces of the Al thin film for reflection. As the transparent conductive film, ITO is vapor-deposited from the phosphor surface side, and the end surface of the substrate 1 is connected to the substrate 1. In this example as well, the ITO is in contact with the end face of the substrate 1 and a slight exposed portion around the substrate, and the path between the outside and the phosphor (external → organic material 5 → phosphor 4) is completely formed by the inorganic materials 6 and 1. Has been cut off.
An Al thin film exists as a conductive material inside the transparent conductive film. A leaf spring is used to connect with the chassis 15, and the scintillator side is pressed and fixed, and the chassis side is connected with a screw. It is connected to ITO via a leaf spring from the chassis that fell to GND.

With this structure, the moisture resistance of the phosphor 4 is enhanced and the noise resistance of the sensor panel 200 is improved.

It is possible to simplify the step of forming the ITO film as compared with the first embodiment.

[0026]

Third Embodiment FIG. 3 shows a preferred embodiment. Also in this example, an amorphous carbon material is used for the substrate 1, and protective layers 3-a and 3-b are provided on the front and back surfaces of the Al thin film for reflection. As the transparent conductive film, ITO was vapor-deposited from the phosphor surface side and the end face of the substrate 1 was connected to the substrate 1. However, unlike Example 2, ITO 6 was formed before forming the organic protective layer 5. In this example as well, the ITO is in contact with the end face of the substrate 1 and a slight exposed portion around the substrate, and the path between the outside and the phosphor (external → organic material 5 → phosphor 4) is completely formed by the inorganic materials 6 and 1. Has been cut off. As a conductive material inside the transparent conductive film,
The structure is such that an Al thin film exists. The conductive tapes 8 and 9 are used for the connection with the chassis 15, and the scintillator side is pressed and fixed, and the chassis side is connected with a screw. From the chassis 15 that fell to GND, the conductive tape 8,
It is connected to the substrate 1 made of amorphous carbon via 9.

With this structure, the moisture resistance of the phosphor 4 is enhanced and the noise resistance of the sensor panel 200 is improved.

Compared with the second embodiment, the ITO is less likely to be broken when the scintillator is bonded.

[0029]

According to the present invention, it is possible to provide a scintillator structure and a radiation detection device that are resistant to noise without impairing the moisture resistance of the scintillator.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an embodiment.

FIG. 2 is a detailed cross-sectional view of the embodiment.

FIG. 3 is an equivalent circuit diagram of the embodiment.

FIG. 4 is a cross-sectional view of the GND connection method according to the embodiment.

FIG. 5 is a cross-sectional view of the GND connection method according to the embodiment.

FIG. 6 is a cross-sectional view of the GND connection method according to the embodiment.

FIG. 7 is a cross-sectional view of the transparent conductive film forming method of the embodiment.

FIG. 8 is a cross-sectional view of the transparent conductive film forming method of the embodiment.

FIG. 9 is a cross-sectional view of the first embodiment.

FIG. 10 is a sectional view of a second embodiment.

FIG. 11 is a sectional view of a third embodiment.

FIG. 12 is a sectional view of a conventional example.

[Explanation of symbols]

1 substrate 2 Metal reflective layer 3 protective layer 4 Phosphor layer 5 Organic protective layer 6 Transparent conductive film 7 Conductive adhesive layer 8 metal foil 9 Organic film for laminating 10 Conductive adhesive material 11 Conductive film 12 spring 15 chassis 16 screws 21 board 22 Photoelectric converter 23 TFT section 24 Wiring pad 25 Protective layer 26 Adhesive layer 27 Sealing part 100 scintillator 200 sensor panel 31 Lower electrode 32 insulating layer 33 Active layer 34 Ohmic contact layer 35 Upper electrode 41 holder 42 ITO target 43 Plasma region 44 chuck 51 Capacitor part 52 Capacitor section 53 TFT section 54 Bias line 55 Signal line B 56 gate lines 57 Bias power supply 58 amplifier 59 Gate drive device 60 signal readout device 61 Signal line A 71 Coupling capacitance between drain electrode and ITO 72 Coupling capacitance between source electrode and ITO door

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Katsuro Takenaka             3-30-2 Shimomaruko, Ota-ku, Tokyo             Non non corporation (72) Inventor Tomoyuki Tamura             3-30-2 Shimomaruko, Ota-ku, Tokyo             Non non corporation F term (reference) 2G088 EE01 EE29 FF02 GG16 GG19                       JJ05 JJ09                 5F088 AA03 AA04 AB05 BB03 BB07                       HA15 LA08

Claims (9)

[Claims] 1. A wavelength converter including a conductive material 1, wherein an inorganic conductive material 2 is provided on a side of the wavelength converter opposite to the conductive material 1, and an inorganic material is provided on a side of the conductive material 1 opposite to the wavelength converter. A scintillator panel on which a conductive material 3 is placed, and the inorganic conductive material 2 and the inorganic conductive material 3 are electrically connected. 2. Photon energy (eV) of an electromagnetic wave generated after the inorganic conductive material 2 is converted by the wavelength converter.
The scintillator according to claim 1, which has a bandgap (eV) wider than the peak value of. 3. The scintillator panel according to claim 1, wherein the conductive material 1 is one or more layers. 4. The scintillator panel according to claim 1, wherein the conductive material 1 includes a metal reflective film. 5. The scintillator panel according to claim 1, wherein the wavelength converter is a phosphor that converts radiation into visible light. 6. The scintillator panel according to claim 1 or 5, wherein the wavelength converter is a material having an alkali halide material as a base material. 7. A radiation detection device comprising the scintillator panel according to any one of claims 1 to 6 bonded to a photoelectric conversion panel, and the conductive material 3 or the conductive material 2 connected to a constant potential of the device. 8. The radiation detection device according to claim 7, wherein the photoelectric conversion panel has a plurality of photoelectric conversion elements arranged on the surface thereof. 9. The radiation detection device according to claim 7, wherein the photoelectric conversion element has a MIS type or PIN type structure.