JP2004340737A - Radiation detector and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radiation detector and its manufacturing method capable of improving a resolution characteristic, and having high manufacture yield and reliability. <P>SOLUTION: This radiation detector is equipped with a photoelectric conversion substrate 11 formed by arranging a plurality of a photoelectric conversion elements 13 of a pixel unit, a scintillator pixel 39 including a fluorescent material arranged on the photoelectric conversion substrate 11 for generating fluorescence by being excited by radiation and the first binder resin for bonding the fluorescent material, and a partition part 38 including a second binder resin formed on the photoelectric conversion substrate 11 for partitioning the scintillator element 39 into the pixel units. The detector has a characteristic wherein the difference of the solubility parameter between the first binder resin and the second binder resin in contact therewith is higher than 2(Mpa)<SP>1/2</SP>. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a radiation detector and a method of manufacturing the same, and more particularly, to an indirect radiation flat panel detector that detects a radiation image and a method of manufacturing the same.
[0002]
[Prior art]
For example, an active matrix type X-ray flat panel detector has attracted much attention as a new generation X-ray diagnostic detector. In this X-ray flat panel detector, an X-ray photographed image or a real-time X-ray image is output as a digital signal by detecting the irradiated X-ray. Since the X-ray flat panel detector is a solid-state detector, expectations are high in terms of image quality performance and stability. For this reason, many universities and manufacturers are engaged in R & D.
[0003]
As the first application for practical use, it has been developed for chest and general radiography of a human body for collecting a still image with a relatively large X-ray dose, and has been commercialized in recent years. Commercialization is expected in the near future for applications in the cardiovascular and gastrointestinal fields, where it is necessary to clear higher technical hurdles and realize real-time video of 30 frames per second or more under fluoroscopic dose. . For this moving image application, improvement of noise (S / N: signal / noise ratio) and real-time processing technology of minute signals are important development items.
[0004]
X-ray flat panel detectors are roughly classified into two types: a direct type and an indirect type. The direct method is a method in which X-rays are directly converted into signal charges using a photoconductive film such as a-Se, and the converted signal charges are stored in a charge storage capacitor. In this direct method, photoconductive charges generated by X-rays are directly led to a charge storage capacitor by a high electric field, so that a resolution characteristic substantially defined by a pixel pitch of an active matrix can be obtained.
[0005]
In the direct type X-ray flat panel detector, for example, an a-Se photoconductive film is formed with a thick film of about 1 mm in order to increase the absorptivity of X-rays and secure the signal intensity. Further, in order to increase the photoconductive charge generation rate per X-ray photon, to allow the generated photoconductive charge to reach the collecting electrode without being trapped by a defect level in the film, and to reduce the bias electric field. In order to minimize the diffusion of charges in the perpendicular direction, a strong bias electric field of, for example, 10 V / μm is applied and used.
[0006]
That is, in this example, a high voltage of 10 kV is applied to a-Se of the photoconductive film. For this reason, the direct method is more advantageous than the indirect method in terms of resolution characteristics. However, the reliability of protecting the thin film transistor having a low operating voltage, that is, the TFT, from the high voltage, the dark current and the sensitivity characteristic, There have been problems such as that a suitable photoconductive material having stability and the like cannot be found.
[0007]
On the other hand, the indirect method is a method in which X-rays are received by a scintillator layer, converted into visible light once, and the visible light is converted into signal charges by an a-Si photodiode or a CCD and guided to a charge storage capacitor. The problem of high voltage resistance that occurs in the direct method does not occur. In addition, it is advantageous that basic techniques have been established for scintillator materials and photodiodes.
[0008]
However, in the indirect method, the resolution is deteriorated by the optical diffusion and scattering until the visible light from the scintillator layer reaches the photodiode. In particular, as the thickness of the scintillator layer increases in order to secure the sensitivity characteristics, the spread of the fluorescent light until reaching the photoelectric conversion element such as a photodiode is increased, and the resolution is significantly deteriorated.
[0009]
As a method of securing the resolution by suppressing the spread of such fluorescence, in the indirect method, a scintillator layer is formed in a pixel unit according to a matrix of a photodiode and a TFT, and a partition portion for optically separating the scintillator pixels is provided. Provided X-ray detectors have been proposed. Thereby, the fluorescent light emitted in the scintillator pixel is suppressed from being scattered or diffused in the lateral direction by the partition walls. Therefore, the fluorescence can efficiently reach the photoelectric conversion element such as the photodiode by the optical guiding effect, and the resolution characteristic is improved (for example, see Patent Document 1).
[0010]
[Patent Document 1]
JP-A-11-166976
[0011]
[Problems to be solved by the invention]
However, in a radiation detector such as an X-ray detector having a scintillator pixel separated by a partition wall, the entire substrate is warped due to stress of the scintillator pixel and the flatness of the flat detector is reduced. Be impaired. For this reason, there arises a problem such as inconvenience in the manufacturing process and deterioration of quality. In addition, there is a possibility that the scintillator pixel or the partition wall and the photoelectric conversion substrate may be peeled off due to such stress of the scintillator pixel. For this reason, there arises a problem that the reliability of the radiation detector is significantly impaired.
[0012]
In particular, such a problem is more likely to occur as the size of the substrate is increased. For example, when a detector having a practical size of 9 inches or more is manufactured, the manufacture is caused by warpage of the substrate or peeling of the scintillator pixels. There are problems that the yield is reduced and the reliability of the device is impaired.
[0013]
The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a radiation detector capable of improving resolution characteristics and having a high production yield and high reliability, and a method of manufacturing the radiation detector. It is in.
[0014]
[Means for Solving the Problems]
The radiation detector according to the first aspect of the present invention includes:
A photoelectric conversion substrate in which photoelectric conversion elements in pixel units are arranged,
A scintillator pixel disposed on the photoelectric conversion substrate and containing a fluorescent material that is excited by radiation to generate fluorescence and a first binder resin that binds the fluorescent material, and a second binder resin that partitions the scintillator pixel into pixel units A partition part containing
With
The difference between the solubility parameters of the first binder resin and the second binder resin in contact with the first binder resin is 2 (Mpa).^1/2It is characterized by the above.
[0015]
The radiation detector according to the second aspect of the present invention includes:
A photoelectric conversion substrate in which photoelectric conversion elements in pixel units are arranged,
A scintillator pixel disposed on the photoelectric conversion substrate and containing a fluorescent material that is excited by radiation to generate fluorescence and a first binder resin that binds the fluorescent material, and a second binder resin that partitions the scintillator pixel into pixel units A partition part containing
An underlayer containing a third binder resin, which is interposed between the photoelectric conversion substrate and at least one of the scintillator pixel and the partition,
With
The difference in solubility parameter between the third binder resin and the first binder resin and the second binder resin in contact with the third binder resin is 2 (Mpa).^1/2It is characterized by the following.
[0016]
According to a third aspect of the present invention, there is provided a method of manufacturing a radiation detector.
Forming a scintillator layer containing a fluorescent material that emits fluorescence when excited by radiation and a first binder resin that binds the fluorescent material, on a photoelectric conversion substrate in which pixel-based photoelectric conversion elements are arranged;
Forming a scintillator pixel by patterning the scintillator layer into a shape that remains in accordance with each pixel;
Forming a partition containing the second binder resin between the scintillator pixels in pixel units;
With
The difference between the solubility parameters of the first binder resin and the second binder resin in contact with the first binder resin is 2 (Mpa).^1/2It is characterized by the above.
[0017]
According to a fourth aspect of the present invention, there is provided a method for manufacturing a radiation detector.
Forming a base layer containing a third binder resin on a photoelectric conversion substrate on which pixel-based photoelectric conversion elements are arranged;
Forming a scintillator layer containing a fluorescent material that is excited by radiation to generate fluorescence and a first binder resin that binds the fluorescent material, on the underlayer,
Forming a scintillator pixel by patterning the scintillator layer into a shape that remains in accordance with each pixel;
Forming a partition containing the second binder resin between the scintillator pixels in pixel units;
With
The difference in solubility parameter between the third binder resin and the first binder resin and the second binder resin in contact with the third binder resin is 2 (Mpa).^1/2It is characterized by the following.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a radiation detector and a method of manufacturing the radiation detector according to an embodiment of the present invention will be described with reference to the drawings. The present invention can be applied to the case of X-rays, γ-rays, and other various types of radiation. However, in the following embodiment, description will be made by taking the case of typical X-rays among the radiations as an example. I do. Therefore, by replacing “X-ray” in the embodiment with “radiation”, the present invention can be applied to other radiations targeted by the present invention.
[0019]
As shown in FIG. 1, an X-ray detector 1 that detects an X-ray and outputs an electric signal corresponding to the intensity distribution of the X-ray has an active matrix type photoelectric conversion substrate 11 having a plurality of pixels. I have. The photoelectric conversion substrates 11 are two-dimensionally arranged in a matrix at a predetermined pitch L in a row direction (for example, a horizontal direction in the drawing) and a column direction (for example, a vertical direction in the drawing) on an insulating substrate such as glass. A plurality of pixels 12 having the same structure. In the example shown in FIG. 1, nine pixels (12a to 12i) are illustrated.
[0020]
Each of the pixels 12 (a to i) includes a photodiode 13 functioning as a photoelectric conversion element that converts the signal charge into incident signal light intensity, a thin film transistor (hereinafter, referred to as a TFT) 14 functioning as a switching element, and a signal charge. It is composed of a storage capacitor 15 functioning as a charge storage unit for storing.
[0021]
Each TFT 14 has a gate electrode G, a source electrode S, and a drain electrode D. The drain electrode D is electrically connected to, for example, the photodiode 13 and the storage capacitor 15.
[0022]
A control circuit 16 is provided outside the photoelectric conversion substrate 11. The control circuit 16 controls the operation state of the TFT 14, for example, on / off. That is, a plurality of control lines 17 extending in the row direction on the photoelectric conversion substrate 11 are connected to the control circuit 16. Each control line 17 is connected to a gate electrode G of each TFT 14 constituting the pixels 12 in the same row. In the example shown in FIG. 1, first to fourth four control lines 171 to 174 are provided. For example, the first control line 171 is connected to the gate electrode G of each TFT 14 forming the pixels 12a to 12c.
[0023]
A plurality of data lines 18 are provided on the photoelectric conversion substrate 11 in the column direction. Each data line 18 is connected to the source electrode S of each TFT 14 constituting the pixels 12 in the same column. In the example shown in FIG. 1, first to fourth four data lines 181 to 184 are provided. For example, the first data line 181 is connected to the source electrode S of each TFT 14 forming the pixels 12a, 12d, and 12g.
[0024]
Each data line 17 is connected to a corresponding charge amplifier 19. Each charge amplifier 19 is composed of, for example, an operational amplifier. The data line 18 is connected to one input terminal a1, and the other input terminal a2 is grounded. A capacitor C is connected between one input terminal a1 and the output terminal b, and has an integrating function. Further, a switch SW is connected in parallel with the capacitor C. For example, the switch SW is closed to discharge the charge remaining in the capacitor C.
[0025]
Each charge amplifier 19 is connected to a parallel / serial converter or multiplexer 20 that converts a plurality of electric signals input in parallel to serial signals. The parallel / serial converter 20 is connected to an analog-to-digital converter or digitizer 21 that converts an analog signal to a digital signal.
[0026]
With such a configuration, the control circuit 16 outputs a control signal for simultaneously turning on / off the plurality of TFTs 14 in the same row connected to the same control line 17. The TFT 14 in the ON state under the control of the control circuit 16 transfers the image charge from the pixel 12 to the data line 18. Thereby, the potential of the pixel 12 is reset. The image charges transferred to the data line 18 are amplified by the charge amplifier 19, combined by the parallel / serial converter or the multiplexer 20, and then sent to the analog-digital converter or digitizer 21.
[0027]
Next, the structure of the pixel of the X-ray detector according to this embodiment will be described with reference to FIG. In FIG. 2, one pixel portion 12 is extracted and illustrated, and portions corresponding to FIG. 1 are denoted by the same reference numerals, and overlapping description is partially omitted.
[0028]
The photoelectric conversion substrate 11 includes a photodiode 13, a TFT 14, and a storage capacitor 15 formed on an insulating substrate 31 such as glass.
[0029]
The TFT 14 has three electrical connections, that is, a gate electrode G, a source electrode S, and a drain electrode D. The gate electrode G is formed on the insulating substrate 31. The gate electrode G is covered with the insulating film 32. The gate electrode G is connected to a common control line 17 together with the gate electrodes G of the other TFTs 14 located on the same row. For example, +10 V and −5 V are used to control turning on / off the TFT 14.
[0030]
The source electrode S is in contact with a semi-insulating film 33 formed on the insulating film 32. This source electrode S is connected to a common data line 18 together with the source electrodes S of the other TFTs 14 located in the same column. The drain electrode D is in contact with the semi-insulating film 33. The drain electrode D is connected to the photodiode 13 and the storage capacitor 15.
[0031]
The storage capacitor 15 includes a lower electrode 34 formed on the insulating substrate 31, an upper electrode 35 provided to face the lower electrode 34 with the insulating film 32 interposed therebetween, and the like. The upper electrode 35 is electrically connected to the drain electrode D of the TFT 14.
[0032]
The TFT 14 and the storage capacitor 15 are covered by the first insulating layer 361. The photodiode 13 is formed on the first insulating layer 361. On the first insulating layer 361 around the photodiode 13, a second insulating layer 362 is provided. The second insulating layer 362 is formed in a frame shape so as to surround the photodiode 13 having a substantially rectangular shape.
[0033]
The photodiode 13 is formed for each pixel in an a-Si pn diode structure, a pin diode structure, or the like. The photodiode 13 includes a first electrode 131 formed on the first insulating layer 361, a second electrode 132 disposed to face the first electrode 131, and the like.
[0034]
The first electrode 131 is electrically connected to the drain electrode D of the TFT 14 and the upper electrode 35 of the storage capacitor 15 via a through hole 37 formed in a part of the first insulating layer 361. The second electrode 132 is formed, for example, by forming a transparent conductive film such as ITO by a sputtering method. A bias voltage is applied between the first electrode 131 and the second electrode 132.
[0035]
In this embodiment, the photodiode 13 is formed in an area which does not overlap the storage capacitor 15 and the TFT 14 as shown in FIG. 2, but in order to secure a light receiving area, the photodiode 13 is formed on the TFT 14 and the storage capacitor 15. It is also possible to provide a structure in which an insulating layer is disposed on the substrate, a collecting electrode is formed on the entire area of the pixel including the insulating layer, and a photodiode corresponding to almost the entire surface of each pixel is formed thereon.
[0036]
On the photoelectric conversion substrate 11 having the above-described structure, a scintillator pixel 39 that converts X-rays incident from the outside into visible light (that is, emits fluorescence when excited by the X-rays) is arranged. Further, on the photoelectric conversion substrate 11, a partition wall section 38 that partitions the scintillator pixel 39 into pixel units is formed. A base layer 363 is interposed between the photoelectric conversion substrate 11 and at least one of the scintillator pixel and the partition 38.
[0037]
That is, as shown in FIG. 2, the photodiode 13 and the second insulating layer 362 are covered by the base layer 363. The underlayer 363 contains a binder resin, and has a function as a protective layer for protecting the photodiode 13 and a function as a base for at least one of the scintillator pixel and the partition. In the example shown in FIG. 2, the underlayer 363 is interposed between the photoelectric conversion substrate 11 and the scintillator pixels 39 and the partition 38.
[0038]
The scintillator pixel 39 is disposed on the base layer 363 on the photoelectric conversion substrate 11. The scintillator pixel 39 includes a fluorescent material and a binder resin that binds the fluorescent material.
[0039]
The fluorescent material that constitutes the scintillator pixel 39 generates fluorescence when excited by radiation such as X-rays, and phosphor particles having substantially the same average particle size, for example, GOS (Gd₂O₂S: Eu, Tb, PR⁺³, CE⁺³, F). In addition, as a phosphor applicable to the scintillator pixel 39, Gd₂O₂S: Other X-ray phosphor based on Tb, CsI: Tl, CsI: Na, CaWO₄, LaOBr: Tm or other X-ray phosphors.
[0040]
The partition 38 is configured to contain a binder resin. The partitioning portion 38 converts X-rays 40 incident on the scintillator pixel 39 from above into fluorescent light 41 in the scintillator pixel 39, and prevents the fluorescent light 41 from interfering with the area of the photodiode 13 of the adjacent pixel 12 as much as possible. It is formed along the boundary separating the pixels 12 on the base layer 363. As a result, the scintillator pixel 39 has an area mainly overlapping the photodiode 13 and is separated into pixels.
[0041]
The partition 38 has a light-reflecting property to reflect the fluorescence 411 scattered outward toward the adjacent pixel 12 from the fluorescence 41 generated in the scintillator pixel 39 toward the inside of the scintillator pixel 39. It may be formed of a material. Further, the partition 38 may be formed of an X-ray absorber that absorbs scattered X-rays scattered outward toward the adjacent pixel 12 among the X-rays incident on the pixel 12.
[0042]
Next, the binder resin included in the scintillator pixel 39, that is, the first binder resin, the binder resin included in the partition wall portion 38, that is, the second binder resin, and the binder resin included in the base layer 363, that is, the third binder resin are formed. The most suitable material will be described.
[0043]
That is, when the binder resin forming the partition wall portion 38 and the binder resin forming the scintillator pixel 39 are the same or the same material, the respective binder resins adhere to each other by intermixing, and the mutual adhesion strength is generally strong. . For this reason, the scintillator pixel 39 and the partition wall 38 are integrated over a wide area of the detection surface, and the intrinsic stress due to the material process and the stress due to the temperature change of the process cause the warpage of the photoelectric conversion substrate 11 and the scintillator pixel 39 and the like. The partition 38 is likely to be peeled off from the photoelectric conversion substrate 11.
[0044]
Therefore, in the present embodiment, the scintillator pixel 39 is improved in order to improve problems such as warpage of the photoelectric conversion substrate 11 due to stress of the scintillator pixel 39 and peeling of the scintillator pixel 39 and the partition 38 from the photoelectric conversion substrate 11. Attention is paid to the solubility parameter of each binder resin forming the partition wall portion 38 and the base layer 363.
[0045]
That is, in this embodiment, the optimal combination of materials constituting each of the first binder resin, the second binder resin, and the third binder resin is determined based on the solubility parameter of each material. .
[0046]
The solubility parameter δ used in this embodiment is a Hildebrand Solubility Parameter, which is represented by the same definition for both the organic solvent and the organic resin, and corresponds to the sum of Van der Waals forces per unit volume of the organic material. I do. The definition is as follows.
δ = (c)^1/2= ((ΔH-RT) / Vm)^1/2
Here, c is Cohesive energy density (intermolecular binding energy density), ΔH is Heat of evaporation (heat of evaporation), R is Gas constant (gas constant), T is Temperature (temperature), Vm is the molar volume (molar volume).
[0047]
Note that the unit system (cal / cm³)^1/2And SI unit system (MPa^1/2) Is as follows.
δ / cal^1/2cm^-3/2= 0.48888 × δ / MPa^1/2
δ / MPa^1/2= 2.0455 × δ / cal^1/2cm^-3/2
The solubility parameter (SP value) having such a definition is a value specific to each substance, and the solubility parameter of each organic solvent is obtained by measuring ΔH (heat of vaporization per mole) and Vm (molar volume) in the above formula. Can be measured. In addition, as for generally known materials, as shown in FIG. 6 described later, already known solubility parameters (SP values) can be used. FIG. 3 shows an example of a polymer that can be used as a binder resin and respective solubility parameters (SP values). FIG. 4 shows an example of a solvent that can be used for dissolving the binder resin and respective solubility parameters (SP values).
[0048]
FIG. 5 shows reference data for investigating a change in solubility between two substances due to a difference in solubility parameter. Here, the degree of swelling (Degree of swelling) of the oil film (linseed oil: solubility parameter; 19) in various solvents with respect to the solubility parameters of various solvents is graphed. The solubility parameter δ is expressed in SI units (MPa^1/2).
[0049]
The higher the swelling ratio, the better the oil film adapts to the solvent. In other words, from this reference material, it can be seen that the closer the solubility parameters of the two substances are, the higher the swelling ratio is, and the better the familiarity is. Conversely, it can be seen that the farther the solubility parameter of each of the two substances is, the lower the swelling ratio and the more difficult it is to adjust.
[0050]
Such a result is obtained in almost the same tendency between other organic materials (particularly, resin materials) and various solvents, and there is an invariable relationship between the organic materials. Therefore, it can be seen that, when the swelling ratio of each of the two organic materials is 0.4 (40%) or more, preferably 0.5 (50%) or more, the two materials are well compatible with each other and have high adhesion. That is, it can be seen that a borderline that causes intermixing is formed when the difference between the solubility parameter values of the two types of organic materials is about 2 (Mpa).
[0051]
Therefore, the difference between the solubility parameters of the two organic materials is 2 (Mpa).^1/2In the following case, the two firmly bond to each other. Conversely, the difference between the solubility parameters of the two organic materials is 2 (Mpa).^1/2If it is above, mutual mixing of both will be suppressed and it will be easy to isolate | separate.
[0052]
By the way, in the X-ray detector according to this embodiment, the difference in the solubility parameter between the first binder resin included in the scintillator pixel 39 and the second binder resin included in the partition 38 in contact with the scintillator pixel 39 is as follows. 2 (Mpa)^1/2It is desirable that this is the case.
[0053]
That is, the first binder resin is a kind of resin material having a relatively large solubility parameter such as a mylar type, an epoxy type, an acetyl cellulose type, a nitrocellulose type, a phenol type, a polyvinyl alcohol type, a nylon type, and a polyacrylonitrile type. Or it is composed of a mixture. The second binder resin that is optimally combined with the first binder resin is a polytetrafluoroethylene-based, polyethylene-based, polypropylene-based, polyisobutylene-based, natural rubber-based, styrene / butadiene-based, polystyrene-based, or silicone-based. It is composed of one or a mixture of resin materials having relatively small solubility parameters such as the above.
[0054]
The first binder resin is a resin having a relatively small solubility parameter such as polytetrafluoroethylene, polyethylene, polypropylene, polyisobutylene, natural rubber, styrene / butadiene, polystyrene, and silicone. It may be composed of one kind or a mixture of materials. The second binder resin that is optimally combined with the first binder resin is a mylar-based, epoxy-based, acetylcellulose-based, nitrocellulose-based, phenol-based, polyvinyl alcohol-based, nylon-based, or polyacrylonitrile-based one. It is composed of one or a mixture of resin materials having relatively large parameters.
[0055]
By appropriately selecting the first binder resin and the second binder resin according to the above-described combination, mutual intermixing is suppressed, and the individual scintillator pixels 39 and the partition wall portions 38 are unlikely to adhere independently. For this reason, it is possible to form a structure that easily disperses the film stress in which the stress over a wide area of the detection surface is integrated as in the case where the scintillator pixel 39 and the partition 38 are integrated.
[0056]
As a result, warpage of the photoelectric conversion substrate 11 can be prevented, and good flatness as a flat panel detector can be maintained. For this reason, defects in the manufacturing process and deterioration of quality are not caused. In addition, it is possible to prevent the scintillator pixels 39 and the partition 38 from peeling off from the photoelectric conversion substrate 11 due to the warpage of the photoelectric conversion substrate 11. For this reason, the reliability as a detector can be improved. Therefore, even if the size of the photoelectric conversion substrate 11 is increased, it is possible to provide a detector with high manufacturing yield and high reliability.
[0057]
Further, as in this embodiment, a base layer 363 may be arranged between the photoelectric conversion substrate 11 and the scintillator pixel 39 and the partition wall portion 38 in the X-ray detector. When such an underlayer 363 is disposed, the third binder resin included in the underlayer 363 and the first binder resin included in the scintillator pixel 39 in contact with the underlayer 363 and the second binder resin included in the partition 38 are formed. The difference in solubility parameter with the binder resin is 2 (Mpa)^1/2It is desirable that:
[0058]
That is, when the first binder resin and the second binder resin are made of the above-described materials, the third binder resin has a relatively intermediate solubility parameter of each of the first binder resin and the second binder resin. Such a resin material, for example, one or a mixture of NBR (neoptan butadiene rubber), chloride rubber, vinyl acetate resin, acrylic rubber, methyl methacrylate, vinyl chloride, and polyimide resin materials Be composed.
[0059]
By appropriately selecting the third binder resin, the first binder resin, and the second binder resin by the combination described above, each of the scintillator pixels 39 and the partition walls 38 (or any one of them) is intermixed. Strongly adheres to the base layer 363. For this reason, it is possible to prevent the scintillator pixels 39 and the partition 38 from peeling off from the base layer 363 on the photoelectric conversion substrate 11.
[0060]
As described above, since the adhesion between at least one of the scintillator pixel 39 and the partition wall portion 38 and the base layer 363 is kept good, the reliability as a detector can be improved even when used for a long time. Therefore, even if the size of the photoelectric conversion substrate 11 is increased, it is possible to provide a detector with high manufacturing yield and high reliability.
[0061]
The underlayer 363 is not necessarily provided, and the difference between the solubility parameters of the first binder resin of the scintillator pixel 39 and the second binder resin of the partition 38 described above is 2 (Mpa).^1/2With the above, the warpage of the photoelectric conversion substrate 11 can be prevented, and the object of the present invention can be achieved.
[0062]
Next, a method for manufacturing the X-ray detector will be described. Here, the case where the base layer 363 is provided as a base for the scintillator pixel 39 and the partition wall section 38 will be described. However, as described above, the base layer 363 is not necessarily provided. In this case, the scintillator layer 39 and the partition 38 may be directly formed.
[0063]
First, a base layer 363 containing a third binder resin is formed on the photoelectric conversion substrate 11 on which the photodiodes 13 and the like in pixel units are arranged. For example, a varnish obtained by dissolving a polyimide resin (solubility parameter: 23 to 24) as an example of a third binder resin in a solvent is applied to the entire surface of the photoelectric conversion substrate 11 by a spin coating method or the like, and then fired. Thereby, the underlayer 363 is formed.
[0064]
Subsequently, a scintillator layer containing a fluorescent material and a first binder resin is formed on the base layer 363. For example, an epoxy resin as an example of the first binder resin (solubility parameter: 22.3 (Mpa)^1/2) And Gd as an example of a fluorescent material₂O₂S: A mixed solution with Eu phosphor particles is applied to the entire surface of the underlayer 363 in a thickness of about 400 μm by a spin coating method or the like in the form of a solid film and solidified by firing. Thereby, a scintillator layer before being separated into scintillator pixels is formed. In addition, this mixed solution may be applied by a coating method such as a dispenser method, an inkjet method, or a spray method, in addition to the spin coating method.
[0065]
Subsequently, the scintillator pixel 39 is formed by patterning the scintillator layer into a shape that is left according to each pixel. For example, a groove is formed between the pixels 12 in the scintillator layer by a dicing method. In this embodiment, the groove is formed at a pitch of 150 μm and a groove width of about 25 μm in alignment with the underlying photodiode 13 and TFT 14 to separate the scintillator layer into pixels. Thus, a scintillator pixel 39 is formed.
[0066]
In addition, this groove is not limited to the dicing method, the scintillator layer is removed using photochemical decomposition by irradiating a laser beam having a main wavelength in the ultraviolet region, and a laser beam having a main wavelength in the infrared region is irradiated. It may be formed by removing the scintillator layer using thermal decomposition, or by a method of chemically dissolving the binder resin and etching away the groove. Further, the groove may be formed to a depth reaching the base 363, or may be formed to a depth such that the scintillator layer remains between the groove and the base layer 363.
[0067]
Subsequently, the partition 38 containing the second binder resin is formed between the scintillator pixels 39 in pixel units. For example, a polypropylene-based resin as an example of the second binder resin (solubility parameter: 16.2 (Mpa)^1/2) And Gd having a small particle diameter of about 1 μmφ₂O₂S: The mixture with the Eu phosphor powder is filled into a groove as a paste whose viscosity is reduced by a solvent, and dried. As a result, the partition 38 is formed.
[0068]
The partition 38 has a fine particle diameter of about 2 μmφ or less in TiO.₂Alternatively, the second binder resin may be formed by applying a mixture of a reflective material having a high transmittance and a high refractive index, such as fine powder of transparent ceramics or the like, and a second binder resin. Further, a metal film may be used as long as the film has high flatness.
[0069]
The control circuit 16 and the like connected to the outside of the photoelectric conversion substrate 11 may be manufactured as an integrated circuit connected to the photoelectric conversion substrate 11 by wire bonding. The charge amplifier 19, the multiplexer 20, the digitizer 21, and the like may also be manufactured as an integrated circuit connected to the photoelectric conversion substrate 11 by wire bonding.
[0070]
Further, in order to prevent deterioration of the scintillator pixel 39 due to moisture, the main part of the X-ray detector 1 may be covered with an envelope made of, for example, aluminum or plastic, and may be vacuum-sealed. You may enclose.
Through the above steps, an X-ray detector is manufactured.
[0071]
As described above, the difference in the solubility parameter between the first binder resin (epoxy resin) of the scintillator pixel 39 and the second binder resin (polypropylene resin) of the partition 38 in contact with the scintillator pixel 39 is 2 (Mpa). )^1/2More than a distance away. For this reason, the adhesion between the scintillator pixel 39 and the partition 38 can be reduced.
[0072]
In addition, the second binder resin is dissolved in a solvent to form the partition wall portion 38. The solvent used as the solvent is adjusted to the solubility parameter of the second binder resin so as to be well adapted to the second binder resin (to be well dissolved). The closest one is selected. Further, the solvent has a solubility parameter of 2 (Mpa) of the first binder resin.^1/2Those that are farther apart are selected.
[0073]
Thus, when the partition wall portion 38 is formed by filling the second binder resin dissolved in the solvent after forming the scintillator pixel 39 first, the first binder resin is not easily dissolved by the solvent, and the groove portion of the scintillator pixel 39 is formed. The flatness of the end face along the distance can also be suppressed. Naturally, the adhesion between the first binder resin and the second binder resin can be suppressed.
[0074]
Further, as described above, the solubility parameters of the third binder resin (polyimide resin) of the base layer 363, the first binder resin of the scintillator pixel 39 in contact with the base layer 363, and the second binder resin of the partition wall 38. Is 2 (Mpa)^1/2It is as follows. For this reason, when the scintillator layer is formed on the base layer 363, the first binder resin is well adapted to the third binder resin and can be firmly bonded to each other. Further, when the partition 38 is filled in the groove reaching the base layer 363, the second binder resin is well adapted to the third binder resin, and the two can be firmly bonded to each other.
[0075]
The method of manufacturing the X-ray detector is not limited to the above-described order, but can be changed in various ways. That is, even if all the applied materials are the same, the scintillator pixels 39 may be formed after forming the partition layer 38 after forming the base layer 363.
[0076]
For example, after a base layer 363 containing a polyimide resin as an example of a third binder resin is formed on the photoelectric conversion substrate 11 in which the photodiodes 13 and the like in pixel units are arranged, A partition layer containing two binder resins is formed. For example, a polypropylene-based resin as an example of the second binder resin and Gd₂O₂S: The mixture with the Eu phosphor powder is applied as a paste whose viscosity is reduced by a solvent to the entire surface of the underlayer 363 in the form of a solid film, and dried. Thereby, a partition layer is formed.
[0077]
Subsequently, the partition layer is formed by patterning the partition layer into a shape to be left between the pixels. For example, the partition layer located on the photodiode 13 in pixel units is removed by a photoetching process or the like. As a result, a grid-like partition 38 is formed.
[0078]
Subsequently, a scintillator pixel containing a fluorescent material and a first binder resin is formed in a region surrounded by the partition 38. For example, an epoxy resin as an example of a first binder resin and Gd as an example of a fluorescent material₂O₂S: The mixed solution with the Eu phosphor particles is filled in the region surrounded by the partition wall portion 38 and solidified by further firing. Thus, a scintillator pixel 39 is formed.
Hereinafter, an X-ray detector is manufactured by the same steps as those of the above-described manufacturing method.
[0079]
As described above, the difference in the solubility parameter between the first binder resin (epoxy resin) of the scintillator pixel 39 and the second binder resin (polypropylene resin) of the partition 38 in contact with the scintillator pixel 39 is 2 (Mpa). )^1/2More than a distance away. For this reason, the adhesion between the scintillator pixel 39 and the partition 38 can be reduced.
[0080]
Further, when the first binder resin is dissolved in a solvent to form the scintillator pixel 39, the solvent used as the solvent is adjusted to the solubility parameter of the first binder resin so as to be well adapted to the first binder resin (to be well dissolved). The closest one is selected. Further, the solvent has a solubility parameter of 2 (Mpa) of the second binder resin.^1/2Those that are farther apart are selected.
[0081]
Thereby, when the first binder resin dissolved in the solvent is filled and the scintillator pixel 39 is formed after the partition 38 is formed first, the second binder resin is less likely to be dissolved by the solvent, and the pixel of the partition 38 is not dissolved. The flatness of the end face along the gap can also be suppressed. Naturally, the adhesion between the first binder resin and the second binder resin can be suppressed.
[0082]
Further, as described above, the solubility parameters of the third binder resin (polyimide resin) of the base layer 363, the first binder resin of the scintillator pixel 39 in contact with the base layer 363, and the second binder resin of the partition wall 38. Is 2 (Mpa)^1/2It is as follows. For this reason, when the scintillator layer is formed on the base layer 363, the first binder resin is well adapted to the third binder resin and can be firmly bonded to each other. Further, when the partition 38 is filled in the groove reaching the base layer 363, the second binder resin is well adapted to the third binder resin, and the two can be firmly bonded to each other.
[0083]
As described above, according to the X-ray detector manufactured by these manufacturing methods, the scintillator layer that emits fluorescence when excited by X-rays is separated for each pixel by the partition wall. For this reason, although it is a highly reliable indirect method utilizing the advantage that the applied voltage to the device is as low as several tens of volts at the most, the diffusion of the fluorescence is suppressed, and it is possible to suppress the arrival at the photodiode of the adjacent pixel. In addition, it is possible to provide a flat panel detector having the same high resolution and high sensitivity as the direct system. Further, the adhesion between the scintillator pixel 39 and the partition 38 can be reduced, and the adhesion between the scintillator pixel 39 and the partition 38 and the base layer 363 can be improved.
[0084]
Next, the effect of a specific prototype was verified.
As a structure common to the comparative example and the first and second embodiments, the effective area of the detection surface is substantially a square of 9 inches × 9 inches, the pixel pitch in the effective area is 150 μm, the pixel size is 100 μm × 100 μm, and the photodiode Reference numeral 13 denotes an a-Si PIN structure formed by a plasma CVD method and a photolithography process, and the second electrode 132 of the photodiode 13 was formed by ITO using a sputtering method.
[0085]
In the comparative example, the scintillator pixel 39 and the partition wall portion 38 were prototyped for an X-ray detector using the same epoxy resin, and no underlayer was provided. In the first embodiment, the difference between the solubility parameters of the scintillator pixel 39 and the partition 38 is 2 (Mpa).^1/2Five types of X-ray detectors were prototyped using binder resins separated from each other. In the second embodiment, the difference between the solubility parameters of the scintillator pixel 39 and the partition 38 is 2 (Mpa).^1/2The solubility parameter is 2 (Mpa) with the binder resin of the scintillator pixel 39 or the binder resin of the partition wall portion 38.^1/2Five types of X-ray detectors using the binder resin existing as a base layer were manufactured.
[0086]
FIG. 6 summarizes the quality data of each prototype. As shown in FIG. 6, in the case of the comparative example in which the scintillator pixel and the partition wall are in close contact and integrated, the generated stress cannot be dispersed, and the warpage of the entire module is so large that it can be determined that the product is defective. To about 8 mm. In addition, regarding the presence or absence of a pixel defect due to peeling of a film constituting a scintillator pixel or a partition wall portion, about 1 to 3% of a pixel defect was visually observed immediately after the scintillator layer was formed into a structure for separating pixels. Was done. In the initial evaluation immediately after the completion of the prototype, about 2 to 5% of pixel defects were confirmed. Further, after being left for 500 hours in a high temperature environment of 60 ° C., about 12 to 19% of pixel defects were confirmed.
[0087]
On the other hand, in the case of the first embodiment, the adhesion between the scintillator pixel and the partition wall was reduced, and the generated stress could be dispersed, so that the warpage of the entire module could be suppressed to about 0 to 1 mm. Immediately after pixel separation, the rate of occurrence of pixel defects could be suppressed to less than 0.1%. In the initial evaluation immediately after the completion of the prototype, the rate of occurrence of pixel defects could be suppressed to less than 0.3%. Furthermore, after being left for 500 hours in a high-temperature environment of 60 ° C., the rate of occurrence of pixel defects could be suppressed to less than 0.5%. Here, the measured values are average values of five types of prototypes.
[0088]
In the case of the second embodiment, the adhesiveness between the scintillator pixel and the partition portion was reduced, and the generated stress was able to be dispersed, and at the same time, the adhesiveness between the scintillator pixel or the partition portion and the base layer was improved. The warpage of the entire module could be suppressed to about 0 to 1 mm. Immediately after pixel separation, the rate of occurrence of pixel defects could be suppressed to less than 0.1%. In the initial evaluation immediately after the completion of the prototype, the rate of occurrence of pixel defects could be suppressed to less than 0.1%. Furthermore, after being left for 500 hours in a high-temperature environment of 60 ° C., the rate of occurrence of pixel defects could be suppressed to less than 0.1%. The measured values here are also average values of five types of prototypes.
[0089]
As described above, it can be understood that the module configuration as in the first and second embodiments has a remarkable effect of reducing the pixel defects due to the warpage and film peeling of the entire module due to the relaxation of the scintillator film stress.
[0090]
As described above, according to the X-ray detector and the method of manufacturing the same according to this embodiment, it is possible to provide a high-quality product with extremely few pixel defects due to substrate warpage and film peeling and these defects. Can be. Therefore, the production yield can be improved.
[0091]
The present invention is not limited to the above embodiments, and various modifications and changes can be made at the stage of implementation without departing from the scope of the invention. In addition, the embodiments may be implemented in appropriate combinations as much as possible, and in that case, the effect of the combination is obtained.
[0092]
The X-ray detector according to the present invention has been described with respect to a configuration in which a plurality of pixels are arranged vertically and horizontally. However, at first glance, the ratio of the pixels vertically and horizontally is different (for example, when one of the pixels is one, etc.). It is also possible to apply to the X-ray detector comprised in the shape. In this case, the switching element can be implemented without using a TFT.
[0093]
In the example shown in FIG. 2, the partition 38 and the scintillator pixel 39 are arranged on the single underlayer 363, but the underlayer is not necessarily provided as described above.
[0094]
When the base layer 363 is provided, the difference between the solubility parameter of the second binder resin included in the partition 38 and the partition between the partition 38 and the photoelectric conversion substrate 11 is 2 (Mpa).^1/2A first underlayer containing the following binder resin is provided, and the difference between the solubility parameter of the first binder resin included in the scintillator pixel 39 and the scintillator pixel 39 between the scintillator pixel 39 and the photoelectric conversion substrate 11 is 2 (Mpa).^1/2A second underlayer containing the following binder resin may be provided. With such a configuration, the applicable range of the binder resin material included in each of the partition wall portion 38, the scintillator pixel 39, and the base layer 363 for achieving the object of the present invention is widened, and is adapted to the required characteristics. It is possible to select the binder resin material that has been used.
[0095]
【The invention's effect】
As described above, according to the present invention, it is possible to provide a radiation detector capable of improving the resolution characteristics and having a high production yield and high reliability, and a method of manufacturing the radiation detector.
[Brief description of the drawings]
FIG. 1 is a diagram schematically showing a circuit configuration of an X-ray detector according to one embodiment of the present invention.
FIG. 2 is a sectional view schematically showing a structure of one pixel portion of the X-ray detector shown in FIG.
FIG. 3 is a diagram showing an example of a polymer usable as a binder resin and respective solubility parameters.
FIG. 4 is a diagram showing an example of a solvent and respective solubility parameters.
FIG. 5 is a diagram for explaining a qualitative relationship between a solubility parameter between two substances and a swelling ratio.
FIG. 6 is a diagram summarizing effects of a comparative example and the present embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... X-ray detector, 11 ... Photoelectric conversion board, 12 ... Pixel, 13 ... Photodiode, 14 ... Thin film transistor (TFT), 15 ... Storage capacitor, 16 ... Control circuit, 17 ... Data line, 18 ... Control line, 38 ... partition wall, 39 ... scintillator layer, 41 ... fluorescence, 363 ... underlayer

Claims (9)

A photoelectric conversion substrate in which photoelectric conversion elements in pixel units are arranged,
A scintillator pixel disposed on the photoelectric conversion substrate and containing a fluorescent material that is excited by radiation to generate fluorescence and a first binder resin that binds the fluorescent material, and a second binder resin that partitions the scintillator pixel into pixel units A partition part containing
With
A radiation detector, wherein a difference in solubility parameter between the first binder resin and the second binder resin in contact with the first binder resin is 2 (Mpa) ^1/2 or more. A photoelectric conversion substrate in which photoelectric conversion elements in pixel units are arranged,
A scintillator pixel disposed on the photoelectric conversion substrate and containing a fluorescent material that is excited by radiation to generate fluorescence and a first binder resin that binds the fluorescent material, and a second binder resin that partitions the scintillator pixel into pixel units A partition part containing
An underlayer containing a third binder resin, which is interposed between the photoelectric conversion substrate and at least one of the scintillator pixel and the partition,
With
A radiation detector, wherein a difference in solubility parameter between the third binder resin and the first binder resin and the second binder resin in contact with the third binder resin is 2 (Mpa) ^1/2 or less. The first binder resin is one or a mixture of mylar, epoxy, acetylcellulose, nitrocellulose, phenol, polyvinyl alcohol, nylon, and polyacrylonitrile resin materials,
The second binder resin is one or a mixture of polytetrafluoroethylene-based, polyethylene-based, polypropylene-based, polyisobutylene-based, natural rubber-based, styrene-butadiene-based, polystyrene-based, and silicone-based resin materials. The radiation detector according to claim 1. The first binder resin is a polytetrafluoroethylene-based, polyethylene-based, polypropylene-based, polyisobutylene-based, natural rubber-based, styrene-butadiene-based, polystyrene-based, or silicone-based resin material or a mixture thereof; 3. The binder resin according to claim 1, wherein the binder resin is one or a mixture of a Mylar resin, an epoxy resin, an acetylcellulose resin, a nitrocellulose resin, a phenol resin, a polyvinyl alcohol resin, a nylon resin, and a polyacrylonitrile resin material. 3. A radiation detector according to claim 1. The third binder resin is one or a mixture of NBR (neoprene / butylene rubber), chloride rubber, vinyl acetate resin, acrylic rubber, methyl methacrylate, vinyl chloride, and polyimide resin resins. The radiation detector according to any one of claims 1 to 4, wherein: Forming a scintillator layer containing a fluorescent material that emits fluorescence when excited by radiation and a first binder resin that binds the fluorescent material, on a photoelectric conversion substrate in which pixel-based photoelectric conversion elements are arranged;
Forming a scintillator pixel by patterning the scintillator layer into a shape that remains in accordance with each pixel;
Forming a partition containing the second binder resin between the scintillator pixels in pixel units;
With
A method for manufacturing a radiation detector, wherein a difference in solubility parameter between the first binder resin and the second binder resin in contact with the first binder resin is 2 (Mpa) ^1/2 or more. Forming a base layer containing a third binder resin on a photoelectric conversion substrate on which pixel-based photoelectric conversion elements are arranged;
Forming a scintillator layer containing a fluorescent material that is excited by radiation to generate fluorescence and a first binder resin that binds the fluorescent material, on the underlayer,
Forming a scintillator pixel by patterning the scintillator layer into a shape that remains in accordance with each pixel;
Forming a partition containing the second binder resin between the scintillator pixels in pixel units;
With
The method of manufacturing a radiation detector, wherein a difference in solubility parameter between the third binder resin and the first binder resin and the second binder resin in contact with the third binder resin is 2 (Mpa) ^1/2 or less. Method. Forming a partition layer containing a second binder resin on a photoelectric conversion substrate on which pixel-based photoelectric conversion elements are arranged;
A step of patterning the partition layer in a shape to be left between pixels to form a partition portion,
Forming a scintillator pixel containing a fluorescent material that is excited by radiation to generate fluorescence and a first binder resin that binds the fluorescent material, in a region surrounded by the partition wall portion;
With
A method for manufacturing a radiation detector, wherein a difference in solubility parameter between the first binder resin and the second binder resin in contact with the first binder resin is 2 (Mpa) ^1/2 or more. Forming a base layer containing a third binder resin on a photoelectric conversion substrate on which pixel-based photoelectric conversion elements are arranged;
Forming a partition layer containing a second binder resin on the underlayer;
A step of patterning the partition layer in a shape to be left between pixels to form a partition portion,
Forming a scintillator pixel containing a fluorescent material that is excited by radiation to generate fluorescence and a first binder resin that binds the fluorescent material, in a region surrounded by the partition wall portion;
With
The method of manufacturing a radiation detector, wherein a difference in solubility parameter between the third binder resin and the first binder resin and the second binder resin in contact with the third binder resin is 2 (Mpa) ^1/2 or less. Method.

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