JP2002139568A - Radiation detecting device, its manufacturing method, and radiation image pickup system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent cracks and film peeling or the like from occurring even when a reflecting layer is formed on a phosphor layer by devising the shape of the phosphor layer. SOLUTION: This radiation detecting device is provided with a wavelength converter 4 converting radioactive rays into light and a photodetector 10 detecting the light converted by the wavelength converter 4. A curved shape 5a is formed between the side face and the upper face of the cross section in the lamination direction of the wavelength converter 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiation detection apparatus used in the medical field and nondestructive inspection, a method for manufacturing the same, and a radiation imaging system.

[0002]

2. Description of the Related Art Conventionally, various types of radiation detecting devices using a phosphor layer for converting radiation including X-rays into light and a two-dimensional photodetector for detecting the converted light have been proposed.

As a radiation detector having high sensitivity and sharpness, for example, as disclosed in Japanese Patent Application Laid-Open No. 9-61536, a phosphor layer having a rectangular cross section is provided on the entire surface of a photodetector of the radiation detector. 2. Description of the Related Art There is known a radiation detection apparatus having phosphors separated for each pixel by removing a phosphor layer between pixels of a photodetector in a lattice shape by laser light after formation.

Further, there is known a radiation detecting apparatus in which a reflective film made of metal or the like is formed on a fluorescent material by vacuum deposition such as sputtering in order to efficiently make light generated by the fluorescent material incident on pixels of a photodetector. ing.

FIG. 7 is a sectional view of a conventional radiation detecting apparatus. In FIG. 7, reference numeral 1 denotes an insulating substrate made of a glass substrate or the like. On this, a pixel 2 having a sensor using a semiconductor thin film made of amorphous silicon or the like and a TFT is formed separately. A protective layer 3 made of SiN _X is formed on the surface to constitute the photodetector 10. Each pixel 2
A phosphor layer 4 having a corner 5c is laminated on the substrate. Then, a reflective layer 6 made of metal or the like is formed on the phosphor layer 4.

[0006]

However, since the phosphor layer of the radiation detecting device disclosed in the above publication has a corner, a reflective film is formed thereon by vacuum deposition such as sputtering. Then, the stress of the film is concentrated on the corner, and there is a problem that cracks and peeling of the film occur at the corner particularly when an environmental resistance test is performed.

Accordingly, it is an object of the present invention to prevent cracks and film peeling from occurring even when a reflective layer is formed on a phosphor layer by devising the shape of the phosphor layer.

[0008]

According to the present invention, there is provided a wavelength converter for converting radiation into light, and a photodetector for detecting the light converted by the wavelength converter. In the radiation detection apparatus described above, a curved portion is formed between a side surface and a top surface of a cross section of the wavelength converter in the stacking direction.

The present invention also relates to a method for manufacturing a radiation detecting apparatus comprising: a wavelength converter for converting radiation into light; and a photodetector for detecting the light converted by the wavelength converter. The space between the side surface and the upper surface of the cross section in the stacking direction of the body is formed into a curved shape by laser light irradiation or screen printing.

[0010] Further, the radiation imaging system of the present invention comprises:
The radiation detection device, signal processing means for processing a signal from the radiation imaging device, recording means for recording a signal from the signal processing means, and display for displaying a signal from the signal processing means Means, transmission processing means for transmitting a signal from the signal processing means, and a radiation source for generating the radiation.

[0011]

Embodiments of the present invention will be described below in detail with reference to the drawings.

(Embodiment 1) FIG. 1 is a sectional view of a radiation detecting apparatus according to an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes an insulating substrate made of a glass substrate or the like. A pixel 2 having a sensor using a semiconductor thin film made of amorphous silicon or the like and a TFT is formed thereon separately. A protective layer 3 made of SiNx is formed on the surface, and a photodetector 1 is formed.
0. On each pixel 2, a phosphor layer 4, which is a wavelength converter having a trapezoidal cross section and a corner formed by a curved surface 5a, is laminated. Then, a reflective layer 6 made of metal or the like is formed on the phosphor layer 4.

In order to efficiently absorb X-rays, the phosphor layer 4
The thickness varies depending on the type, particle size and filling state of the phosphor, but is generally in the range of 50 to 500 μm.

Next, a method of manufacturing the radiation detecting apparatus shown in FIG. 1 will be described. First, a-S is placed on the insulating substrate 1.
i: An individual pixel 2 of the photodetector is formed by a photodetection sensor composed of an H semiconductor thin film and a TFT, and a protective layer 3 of SiNx is formed thereon to produce a semiconductor photodetector 10.

Next, after a paste containing a phosphor is uniformly applied on the photodetector 10, the fluorescent organic substance is evaporated and scattered by the condensed laser light to form the phosphor layer 4, or by a printing method. The phosphor layer 4 is formed by selectively applying a phosphor paste to the pixels 2 of the photodetector 10.

Further, as shown in FIG. 1, in order to form a curved surface 5a between the side surface and the upper surface of the cross section in the laminating direction of the phosphor layer 4, it is necessary to use a laser beam. Can be obtained by changing the intensity distribution of the condensed laser light from a normal Gaussian curve to a skirt-spread shape.

When the paste is produced by a printing method, the viscosity of the paste is adjusted so that the applied paste is printed so as to be about 10% larger than the opening shape of the screen plate, so that the cross section of the phosphor layer 4 in the laminating direction is adjusted. Curved surface 5 between the side and top surfaces of
a can be formed.

The radiation detecting apparatus of the present embodiment can be prepared by either a method using laser light or a printing method. However, in the case of laser light, the resin on the outer peripheral portion of the phosphor layer 4 is deteriorated by the heat of the laser light. As a result, a part of the deteriorated resin is carbonized, so that light absorption occurs and hinders the light extraction efficiency of the phosphor. Further, by performing a temperature / humidity test, which is an accelerated durability test, the deteriorated portion and its vicinity are accelerated in the deteriorated portion more than the portion not irradiated with the laser beam, causing a decrease in the sensitivity as a phosphor, thereby lowering the durability. In some cases, formation by a printing method to which heat is not applied is desirable.

As a printing method, generally used printing, for example, letterpress printing, lithographic printing, intaglio (gravure) printing, screen printing, etc. can be used, but the printing position accuracy is good and the printing paste is applied thickly. Screen printing is the most suitable. As shown in FIG. 2, the cross-sectional shape of the phosphor layer 4 in the stacking direction is
b may be formed.

FIG. 3 is a plan view of a screen plate for screen printing for forming the phosphor layer of FIG. 1. Inside the screen 8, a photodetector 10 is formed as a printing pattern.
The opening 7 is formed at a position corresponding to the pixel 2.
A screen frame 9 is arranged outside the screen 8 to apply tension to the screen 8.

As the screen plate, a plate for screen printing which is usually used can be used. However, the accuracy of the printing pattern is determined by the pixel size and the pixel pitch, and when the pixel pitch is 200 μm or less, the accuracy of about ± 10 μm is used. Must be controlled at a strict value compared to the accuracy of a normal screen printing plate.

For this reason, the screen plate can be used for both a metal foil mask and a mesh screen plate. However, as a master for printing a pattern on a screen plate, a film master is inferior in accuracy, so that a glass master is used for printing. Is desirable.

FIG. 4 is a view for explaining a screen printing method for forming the phosphor layer 4 on the pixels 2 of the photodetector 10 using the screen plate of FIG. A screen plate is arranged on the photodetector 10 with a constant gap. A phosphor paste 12 made of a phosphor powder, a resin binder, a solvent, and the like is placed on the screen, and the squeegee 11 is slid at a constant printing pressure while contacting the screen in the direction of the arrow, so that the squeegee 11 slides through the opening 7 of the screen 8. A certain amount of paste is discharged, and a phosphor paste pattern having the same shape as the opening of the screen can be formed on the pixels 2 of the photodetector 10.

By drying the printed phosphor paste, a separated columnar phosphor pattern can be obtained.
Since the thickness of a pattern that can be formed by ordinary printing is about 5 to 30 μm, the phosphor layer 4 can be formed thick by performing overprinting. Overprint printing is a method in which after printing and drying, alignment is performed so that printing can be performed at the same position, printing is performed again, and drying is repeated to increase the print film thickness of the printed material at the same position. For example, if a film thickness of 200 μm is required, overprinting about 10 to 20 times is required.

The phosphor powder mixed with the phosphor paste includes CaWO ₄ , Gd ₂ O ₂ S: Tb, BaSO
₄ : A conventionally known phosphor material such as Pb can be used. As the organic material mixed in the phosphor paste, organic materials used in screen printing can be used, and as the binder resin, nitrocellulose, cellulose acetate, ethyl cellulose, polyvinyl butyral, polyester, vinyl chloride, vinyl acetate Conventionally known resins such as acrylic resin and polyurethane can be used.

As the organic solvent, for example, conventionally known organic solvents such as ethanol, methyl ethyl ketone, butyl acetate, ethyl acetate, xylene, butyl carbitol and terpineol can be used. Further, additives for imparting the phosphor powder dispersibility improving effect, defoaming effect, and thixotropic effect may be mixed.

The viscosity of the phosphor paste for producing the phosphor layer 4 having the curved surface 5a as in this embodiment is desirably in the range of 10 to 100 Pa · S.

The curved surface 5a does not necessarily have to be spherical, and its curvature varies depending on the size of the phosphor particles used. In the case of a spherical surface, the radius is approximately 10 μm or more. Further, FIG. 1 illustrates an example in which the phosphor layer 4 is formed such that the cross section in the stacking direction is trapezoidal. However, if the phosphor layer 4 has the curved surface 5a, the side surface has a slope. It is not necessary.

The phosphor layer 4 is formed by forming a reflective layer 6 of a reflective metal film on the phosphor layer 4 formed as described above by a conventionally known method such as sputtering or vapor deposition. The emitted light can be efficiently guided to the pixel 2.

As the material of the reflection layer 6, any metal such as nickel, titanium, chromium, gold, etc. which has a high reflectivity and is used in ordinary vacuum film formation can be used.

Further, a resin film, for example, a polyester film, a vinyl chloride film, a polycarbonate film or the like or an inorganic substrate such as glass or the like is adhered on the reflective layer 6 as a protective layer of the fluorescent substance by an adhesive, so that abrasion and mechanical properties are obtained. Properties such as strength, chemical resistance, and moisture resistance can be improved.

(Embodiment 2) FIGS. 5A and 5B
3A and 3B are a schematic configuration diagram and a schematic cross-sectional view of an X-ray imaging device equipped with the radiation imaging device described in the first embodiment. First, the configuration of the X-ray imaging device will be described. The photoelectric conversion element and the transistor are a-Si sensor substrate 601
A plurality is formed in one. The shift register SR1 and the flexible circuit board 6010 on which the integrated circuit IC for detection is mounted are connected.

On the other side of the flexible circuit board 6010,
It is connected to circuit boards PCB1 and PCB2. Said a
-A plurality of Si sensor substrates 6011 are bonded on the base 6012. In addition, a lead plate 6013 is mounted under the base 6012 which constitutes a large-sized photoelectric conversion device to protect the memory 6014 in the processing circuit 6018 from X-rays.

On the a-Si sensor substrate 6011, a phosphor 6030 for converting X-rays into visible light, for example,
CsI is applied or pasted. X-rays are detected using the photoelectric conversion device described with reference to FIG. In this embodiment, as shown in FIG. 5B, the whole is housed in a case 6020 made of carbon fiber.

FIG. 6 shows the X-ray image of the radiation imaging apparatus according to the first embodiment.
It shows an application example to a line diagnostic system. X-rays 6060 generated by the X-ray tube 6050 pass through the chest 6062 of the patient or subject 6061 and enter a photoelectric conversion device 6040 on which a phosphor is mounted. The incident X-ray includes information on the inside of the body of the patient 6061. The phosphor emits light in response to X-ray incidence, and photoelectrically converts the light to obtain electrical information. This information is converted into digital data, image-processed by an image processor 6070, and can be observed on a display 6080 in the control room.

This information can be transferred to a remote place by a transmission means such as a telephone line 6090, displayed on a display 6081 such as a doctor's room in another place, or stored in a storage means such as an optical disk. It is also possible to make a diagnosis. Also film processor 6
100 can also be recorded on the film 6110.

In this embodiment, the photoelectric conversion device is
Although the case of applying to an X-ray diagnostic system has been described,
The present invention can also be applied to a radiation imaging system such as a non-destructive inspection device using radiation other than X-rays such as α-rays, β-rays, and γ-rays.

[0038]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, a pixel 2 having an amorphous silicon sensor and a TFT is formed on a glass substrate 1, a protective film 3 made of SiNx is formed thereon, and a photodetector 10 is formed.
Was prepared.

As a phosphor paste, 100 parts by weight of Gd ₂ O ₂ S: Tb having an average particle diameter of about 9 μm, 10 parts by weight of ethyl cellulose, 55 parts by weight of terpineol, xylene 3
0 parts by weight were mixed and dispersed by a sand mill to prepare a phosphor paste. As a result of measuring the viscosity after rotating the spindle for 2 minutes by a viscometer (Brookfield HBT),
It was 40 Pa · S.

Next, as a screen plate for printing, for example, a mesh screen plate (SS325) having dimensions of a plate frame 550 mm square, a pattern area 230 mm square, a pattern pitch 200 μm, and a size of the pattern opening 7 150 μm.
-16; Sonocom Co., Ltd.).

Using this paste and the screen plate,
Printing was performed with a printing device (MT-550TV: manufactured by Microtec) to form a phosphor on the photodetector 10. The screen printing conditions were squeegee speed 60 mm
/ Sec, screen clearance 1.0 mm, printing pressure 2.0 kg / cm, drying conditions 80 ° C., 3 minutes. A single printing resulted in a film thickness of 13 μm,
A phosphor having a thickness of 200 μm was obtained by performing the overprinting twice.

Next, as a result of three-dimensional observation of the shape of the phosphor with a laser microscope, a phosphor layer 4 having a trapezoidal cross section shown in FIG. 1 and having a curved surface 5a having a radius of about 30 μm was formed. Finally, a radiation detecting device was manufactured by forming a titanium thin film having a thickness of about 3000 Å as a reflective layer 6 on the phosphor layer 4 by a sputtering method.

The amount of terpineol as a solvent of the paste was increased so that the viscosity of the phosphor paste became, for example, 30 Pa · S, and the size of the opening 7 of the screen plate for printing was set to about 130 μm. However, the spindle-shaped phosphor layer 4 shown in FIG. 2 was formed.

The external appearance of the reflection film was checked in detail with a microscope after initial storage of the radiation detector manufactured as described above and storage in a 60 ° C., 90% temperature / humidity test tank for 1000 hours. Was.

[0045]

As described above, according to the present invention, since the curved portion is formed between the side surface and the upper surface of the cross section in the laminating direction of the wavelength converter, even if the reflective layer is formed on the phosphor layer, Cracks and film peeling can be prevented.

[Brief description of the drawings]

FIG. 1 is a sectional view of a radiation detecting apparatus according to a first embodiment of the present invention.

FIG. 2 is a sectional view of the radiation detecting apparatus according to the first embodiment of the present invention.

FIG. 3 is a plan view of a screen plate for screen printing for forming the phosphor layer of FIG. 1;

4 is a diagram illustrating a screen printing method for forming a phosphor layer 4 on a pixel 2 of a photodetector 10 using the screen plate of FIG.

FIG. 5 is a schematic configuration diagram and a schematic cross-sectional view of an X-ray imaging apparatus according to a second embodiment of the present invention.

FIG. 6 is a configuration diagram of an X-ray diagnostic system according to Embodiment 2 of the present invention.

FIG. 7 is a cross-sectional view of a conventional radiation detection device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Insulating substrate 2 Pixel 3 Protective layer 4 Phosphor layer 5a Curved surface 5b Spindle type 6 Reflective layer 7 Opening 8 Screen 9 Screen frame 10 Photodetector 11 Squeegee 12 Phosphor paste

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04N 5/32 H04N 7/18 L 5/335 H01L 27/14 K 7/18 31/00 A (72) Inventor Mitsuho Hiraoka 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Yoshihiro Ogawa 3-30-2 Shimomaruko 3-chome, Ota-ku, Tokyo F-term (reference) 2G088 EE01 EE27 FF02 FF14 GG16 GG19 GG20 JJ05 JJ09 JJ37 4M118 AA10 AB01 AB10 BA14 CB06 CB11 GA10 5C024 AX14 AX17 CY47 CY50 EX21 GX09 GY00 HX55 HX60 5C054 AA01 CA02 CC04 DA08 EA01 EA05 EA05 EA05 EA05 EA05 EA05 EA05 EA05

Claims (9)

[Claims] 1. A radiation detecting apparatus comprising: a wavelength converter for converting radiation into light; and a photodetector for detecting light converted by the wavelength converter, wherein a cross section of the wavelength converter in a stacking direction is provided. A radiation detection device, wherein a curved portion is formed between a side surface and an upper surface. 2. The radiation detecting apparatus according to claim 1, wherein the wavelength converter has a spindle-shaped portion. 3. The wavelength converter according to claim 1, wherein the side surface is formed so as to be inclined with respect to the laminating direction, so that a curved portion is formed between the side surface and the upper surface. The radiation detection device according to claim 1. 4. The radiation detecting apparatus according to claim 1, wherein the curve shape of the wavelength converter is formed by irradiating a laser beam or screen printing. 5. The radiation detecting apparatus according to claim 1, wherein a reflection layer for guiding the light to the photodetector is formed on a surface of the wavelength converter. 6. The radiation detecting apparatus according to claim 1, wherein the wavelength converter is a scintillator or a phosphor. 7. The radiation detecting apparatus according to claim 6, wherein the phosphor has a different shape by changing the viscosity of the phosphor paste. 8. A method for manufacturing a radiation detection device comprising: a wavelength converter for converting radiation into light; and a photodetector for detecting light converted by the wavelength converter, wherein: a stacking direction of the wavelength converter. A method for manufacturing a radiation detecting apparatus, comprising: forming a curved shape between a side surface and an upper surface of a cross section by laser light irradiation or screen printing. 9. A radiation detecting apparatus according to claim 1, a signal processing means for processing a signal from said radiation imaging apparatus, and a recording means for recording a signal from said signal processing means. Display means for displaying a signal from the signal processing means; transmission processing means for transmitting a signal from the signal processing means; and a radiation generation source for generating the radiation. A radiation imaging system characterized by the above-mentioned.