JP2010098102A - Radiological image detector - Google Patents

Abstract

In a radiation image detector in which an electrode end is covered with a dielectric, the dielectric covering the outer peripheral side of the outermost electrode is made difficult to peel off.
In a radiation image detector 10 in which an electrode end portion is covered with a dielectric 5c, a close contact member 5e is disposed on the outer peripheral portion of a second electrode layer, and the linear electrode 5b on the outermost periphery of the second electrode layer is provided. The end portion of the dielectric 5c is covered with a dielectric 5c so that the end portion facing the close contact member 5e and the end portion facing the outermost linear electrode 5b of the close contact member 5e are covered with the dielectric 5c. Instead of being in close contact with the weak substrate 6a, it is in close contact with the close contact member 5e having a strong adhesive force.
[Selection] Figure 1

Description

  The present invention relates to a radiological image detector that records a radiographic image by generating electric charge upon irradiation with radiation and accumulating the electric charge.

  Conventionally, in the medical field and the like, various radiological image detectors that record radiation images related to a subject by receiving radiation transmitted through the subject and output an electrical signal corresponding to the recorded radiation image have been proposed and put into practical use. ing.

The method of the radiation image detector, the direct conversion scheme for storing radiation is converted directly into charges charge, radiation once _{CsI: Tl, GOS (Gd 2} O 2 S: Tb) scintillator is converted into light such as There is an indirect conversion method in which the light is converted into charges by the photoconductive layer and stored. The reading method is roughly classified into an optical reading method using reading light and an electric reading method using a TFT (thin film transistor), a CCD (charge coupled device), a CMOS (complementary metal oxide semiconductor) sensor, and the like.

  As an optical reading type radiographic image detector, for example, the charge generated in the photoconductive layer for recording due to irradiation of radiation is accumulated and the charge having the opposite polarity to the accumulated charge is charged to the linear electrode. It is known to read the accumulated charge by combining each charge of the charge pair generated in the reading photoconductive layer with the accumulated charge and the charged charge.

  As an electric reading type radiographic image detector, for example, charges generated by radiation irradiation are collected by a pixel electrode for each pixel and accumulated in a storage capacitor connected to the pixel electrode. It is known to read by turning on and off the target switch one line at a time.

  The above-mentioned linear electrodes and pixel electrodes are detection electrodes for detecting signals corresponding to the charges generated by radiation irradiation, and electric fields are injected at the ends of such detection electrodes because electric fields tend to concentrate. Easy to be. When charges are injected into the detection electrode, an image defect occurs and the image quality deteriorates. In order to prevent charge injection, it is effective to cover with an insulating material.

  Patent Document 1 describes a configuration in which the pixel electrode is covered with an insulating film. However, since the entire pixel electrode including not only the end portion of the pixel electrode but also the flat electrode portion is covered, the charge transport property is low. As a result, sensitivity and afterimage characteristics are degraded. Note that Patent Document 1 proposes to cover the entire pixel electrode with a film containing particles having a charge transporting property in order to improve conductivity. However, in this configuration, it is easy to inject charges, and the image Defects are likely to occur.

Patent Document 2 describes a configuration in which the end portion of the pixel electrode is covered with a semiconductor. However, since the semiconductor has high conductivity, the sensitivity and the afterimage characteristics are good, but the amount of charge injection increases. It is not an effective method for image defects.
JP 2006-156555 A Japanese Patent Application No. 9-507038

  In order to solve the above problems, it is conceivable to cover only the ends of the linear electrodes and the pixel electrodes with a dielectric.

  When manufacturing such a radiation image detector, a linear electrode or a pixel electrode is formed on a substrate, and a gap between opposing ends of electrodes adjacent to each other is covered with a dielectric, and then photoconductive is applied from above them. Although a layer is formed, since there is no adjacent electrode on the outer peripheral side of the outermost electrode, the end portion of the dielectric is in direct contact with the substrate in this portion.

  Usually, the electrode is made of a transparent conductive material made of a metal oxide or a metal material, and is formed on a resin such as acrylic on the uppermost layer of the substrate immediately below the electrode. In addition, a resin such as novolac is used for the dielectric.

  When the end portions of the electrodes adjacent to each other are covered with a dielectric, the end portions of the dielectric are in intimate contact with an electrode made of a metal oxide or a metal material, but the adhesion between the dielectric and the electrode is Since it is relatively high, there is almost no risk of the dielectric peeling off.

  However, with respect to the outer peripheral side of the outermost electrode, one end of the dielectric covering this portion is in intimate contact with the substrate, but the adhesion between the dielectric and the substrate is relatively weak, and the dielectric Prone to peeling.

  And, when the photoconductive layer is formed in a state where the dielectric is peeled off, a protrusion is generated in that portion and the electrical characteristics are different from other portions, so that an artifact is generated in the detected image, etc. The image quality will deteriorate.

  In view of the above circumstances, the present invention provides a radiographic image detector in which an electrode end portion is covered with a dielectric, and the dielectric covering the outer peripheral side of the outermost electrode can be made difficult to peel off. The object is to provide a detector.

  The radiation image detector of the present invention includes a first electrode layer that is permeable to electromagnetic waves, a photoconductive layer that generates charges when irradiated with electromagnetic waves, and a second electrode that includes a plurality of divided electrodes. A radiation image detector in which layers are stacked on a substrate in order from a second electrode layer, and a space between opposing ends of adjacent divided electrodes is covered with a dielectric, and the second electrode An adhesion member is arranged on the outer periphery of the layer, and a dielectric is formed between an end portion of the second electrode layer facing the adhesion member of the outermost divided electrode and an end portion of the adhesion member facing the outermost division electrode. The adhesion force between the substrate surface and the adhesion member and the adhesion force between the adhesion member and the dielectric are higher than the adhesion force between the substrate surface and the dielectric.

  In the above, the “radiation image detector” is a detection that detects recording light (electromagnetic waves such as recording light or radiation) carrying image information of a subject, for example, radiation and outputs an image signal representing a radiation image related to the subject. An image signal representing a radiographic image relating to a subject can be obtained by converting incident radiation directly or once into light after being converted into electric charge and outputting the electric charge to the outside.

  There are various types of image detectors. For example, from the aspect of the charge generation process that converts radiation into electric charge, the photoelectric conversion element detects the fluorescence emitted from the phosphor when irradiated with radiation. The signal charge generated in this way is converted into an image signal (electrical signal) and output, or a radiographic image detector that converts the signal charge generated in the radiation conductor when irradiated with radiation is converted into an electrical signal. From the aspect of the direct-conversion radiation image detector that outputs and the charge reading process for reading out the charge to the outside, TFT (thin film transistor), CCD (charge coupled device), CMOS connected to the electricity storage unit (Complementary metal oxide semiconductor) Electric reading method using a sensor, etc., or optical reading method that reads the reading light (reading light or electromagnetic waves such as radiation) by irradiating the detector Ones such as news of, there is such an improved direct conversion type which is a combination of the direct conversion type and the optical readout type.

  Further, “the end portion of the divided electrode / contact member” means a side surface of the divided electrode / contact member and a part of a surface facing the photoconductive layer continuous to the side surface (an outer peripheral portion of the facing surface).

  Further, the “substrate” means a layer including all layers up to the second electrode layer, and may include not only the support but also other layers.

  In addition, it is sufficient that the dielectric covers at least the ends of the divided electrodes, and the areas between the divided electrodes other than the ends of the divided electrodes and between the divided electrodes and the contact member are not partially covered with the dielectric. There may be.

  When different kinds of materials are brought into contact with each other, the adhesion at the interface is derived from the surface free energy of each material. For example, when a thin film is formed on a substrate, adhesion is defined as the energy required to peel the thin film from the substrate. The adhesion energy Wad is expressed as in equation (1).

Wad = γ _f + γ _s -γ _fs (1)
Here, γ _f is the surface free energy of the thin film, γ _s is the surface free energy of the substrate, and γ _fs is the surface free energy between the thin film and the substrate. This γ _fs is approximately expressed by Fowkes as shown in equation (2).

γ _fs = γ _f + γ _s -2√ (γ _f · γ _s ) (2)
Further, when equation (2) is substituted into equation (1), equation (3) can be obtained.

Wad = 2√ (γ _f · γ _s ) (3)
From this formula, it can be seen that those having a large surface free energy have strong adhesion and those having a small surface free energy are easily peeled off.

In the present case, the substrate or adhesion member, the electrode is gamma _s, the insulating layer corresponds to the gamma _f. Table 1 shows the surface free energy of various materials.

  The insulating member is a novolak resin made of an organic hydrocarbon polymer, and has a surface free energy equivalent to that of similar nylon, PMMA, etc., and is 20-40 mN / m. The actual substrate surface is coated with another organic layer (PMMA), and has the same energy as the insulating member. On the other hand, the electrode and the adhesion member are classified into metal and inorganic, and have values that are orders of magnitude greater than> 200 mN / m. This is the same size as glass, silicon, and Au. Therefore, the insulating member is more strongly bonded to the inorganic metal material than to bond the same organic material. Based on this, if the surface free energy of the substrate and the insulating layer is 40 mN / m, the surface free energy of the adhesion member and the electrode is 1000 mN / m, the interface free energy (adhesion force) between the substrate and the adhesion member, the adhesion member-dielectric The interfacial free energy between the bodies and the interfacial free energy between the substrate and the dielectric are 400, 400, and 80, respectively, and the adhesion can be increased by inserting an adhesion member.

  These adhesions are evaluated by applying a scotch tape on the membrane surface, pulling one end in a direction almost parallel to the membrane surface, standing a hard needle with a small radius of curvature on the membrane surface, scratching the membrane, and gradually applying a load to the needle. There is a scratch method for determining whether the film is peeled off from the substrate.

  Furthermore, the contact member is preferably made of the same material as that of the divided electrodes.

  The radiographic image detector of the present invention is a radiographic image detector in which an electrode end portion is covered with a dielectric, and an adhesion member is disposed on the outer peripheral portion of the second electrode layer, and the outermost divided electrode of the second electrode layer. The end portion of the dielectric member is covered with a dielectric so that the end portion facing the close contact member and the end portion facing the outermost divided electrode of the close contact member are covered with a dielectric. Instead, since it is made to adhere to an adhesive member having a strong adhesion, it is possible to make it difficult for the dielectric covering the outer peripheral side of the outermost electrode to peel off.

  Further, if the close contact member is made of the same material as the divided electrode, the close contact member can be formed at the same time when the split electrode is formed, so that the manufacturing cost can be reduced.

  Hereinafter, a first embodiment of a radiation image detector of the present invention will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram of a radiographic image detector according to a first embodiment of the present invention, and FIG. 2 is a top view showing a configuration of a second electrode layer of the radiographic image detector. 1 and 2 schematically show the configuration of each layer, and do not accurately illustrate the thickness and width of each layer.

  The radiation image detector 10 is a light reading type radiation image detector, and includes a first electrode layer 1 that transmits a recording electromagnetic wave carrying image information such as X-rays transmitted through a subject, and a first electrode layer 1. A recording photoconductive layer 2 that generates conductivity by receiving irradiation of a recording electromagnetic wave transmitted through the electrode layer 1 and exhibits conductivity, and recording of image information out of the charges generated in the recording photoconductive layer 2. The charge transport layer 3 that acts as an insulator for the charge (accumulated charge) accumulated at that time and acts as a conductor for the transport charge of the opposite polarity to the stored charge, and irradiation of the reading light A plurality of first linear electrodes 5a (divided electrodes) serving as detection electrodes for detecting a signal corresponding to the charges generated in the photoconductive layer 4 for recording and the photoconductive layer 2 for recording that generates charges by receiving ) And a plurality of second linear electrodes 5b (divided) A second electrode layer made of an electrode), a transparent insulating layer 6a having insulating properties and transparency to reading light, and a support 7 having transparency to reading light are arranged in this order. .

  Further, at the interface between the recording photoconductive layer 2 and the charge transport layer 3, a two-dimensionally distributed power storage unit 8 that accumulates stored charges that carry the radiation image generated in the recording photoconductive layer 2 is formed. The Each of the above layers is formed in order from the second transparent insulating layer 6a on a support 7 such as a glass substrate that transmits reading light.

  As a characteristic configuration of the radiation image detector 10, an adhesion member 5 e is provided on the outer peripheral portion of the second electrode layer, and the first linear electrode 5 a, the second linear electrode 5 b, A dielectric 5c is provided so as to cover the end of the contact member 5e. As shown in FIG. 2, in the present embodiment, signal reading (not shown) is not provided on the side in the arrangement direction (vertical direction in FIG. 2) of the first linear electrode 5a and the second linear electrode 5b. Since a circuit or the like is to be connected, the contact member 5e is provided only on the outer peripheral portion of the side in the longitudinal direction (the left-right direction in FIG. 2) of the linear electrode.

  A crystallization preventing layer 5d is provided so as to cover the surfaces of the first linear electrode 5a, the second linear electrode 5b, the adhesion member 5e, and the dielectric 5c. The detailed configuration of the dielectric 5c, the crystallization preventing layer 5d, and the adhesion member 5e will be described later.

  The size (area) of the radiological image detector 10 is, for example, 18 × 18 cm or more, and in particular in the case of chest X-ray imaging, the effective size is about 43 × 43 cm.

  The first electrode layer 1 may be any material that transmits radiation, and for example, a metal thin film is preferably used. Materials include Au, Ni, Cr, Pt, Ti, Al, Cu, Pd, Ag, Mg, MgAg 3-20% alloy, Mg-Ag intermetallic compound, MgCu 3-20% alloy, Mg-Cu intermetallic It can be formed from a metal such as a compound.

  As the material of the first electrode layer 1, Au, Pt, or Mg—Ag intermetallic compound can be preferably used. For example, when Au is used, the thickness is preferably 15 nm or more and 200 nm or less, more preferably 30 nm or more and 100 nm or less. When, for example, MgAg 3 to 20% is used as the material of the first electrode layer 1, the thickness is preferably 100 nm or more and 400 nm or less. Although the preparation method is arbitrary, it can be formed by vapor deposition by a resistance heating method.

The recording photoconductive layer 2 is a photoconductive substance that generates charges when irradiated with radiation. Amorphous selenium _{compounds, Bi 2 MO 20 (M:} Ti, Si, Ge), Bi 4 M 3 O 12 (M: Ti, Si, Ge), Bi 2 O 3, BiMO 4 (M: Nb, Ta, V) , Bi ₂ WO ₆ , Bi ₂₄ B ₂ O ₃₉ , ZnO, ZnS, ZnSe, ZnTe, MNbO ₃ (M: Li, Na, K), PbO, HgI ₂ , PbI ₂ , CdS, CdSe, CdTe, BiI ₃ , It can be comprised by the compound which has at least 1 among GaAs etc. as a main component. Among these, an amorphous selenium compound that is excellent in terms of relatively high quantum efficiency with respect to radiation and high dark resistance is preferable.

  When an amorphous selenium compound is used for the recording photoconductive layer 2, the layer is doped with an alkali metal such as Li, Na, K, Cs, and Rb in a small amount between 0.001 ppm and 1 ppm, LiF, Fluoride such as NaF, KF, CsF, RbF and the like doped with a slight amount of 0.1 ppm to 1000 ppm, P, As, Sb, Ge doped between 50 ppm and 0.5%, As 10 ppm Those doped between ˜0.5% and those doped with a slight amount of Cl, Br, I between 1 ppm and 100 ppm can be used. In particular, amorphous selenium containing about 10 ppm to 200 ppm of As, amorphous selenium containing about 0.2% to 1% of As and further containing 5 ppm to 100 ppm of Cl, about 0.2% to 1% of As Furthermore, amorphous selenium containing about 0.001 ppm to 1 ppm of alkali metal is preferably used.

Also, Bi ₂ MO ₂₀ (M: Ti, Si, Ge), Bi ₄ M ₃ O ₁₂ (M: Ti, Si, Ge), Bi ₂ O ₃ , BiMO ₄ (M: Nb) having a size of several nm to several μm. , Ta, V), Bi ₂ WO ₆ , Bi ₂₄ B ₂ O ₃₉ , ZnO, ZnS, ZnSe, ZnTe, MNbO ₃ (M: Li, Na, K), PbO, HgI ₂ , PbI ₂ , CdS, CdSe, A thick film containing fine particles of a photoconductive substance such as CdTe, BiI ₃ , or GaAs can be used.

  The thickness of the recording photoconductive layer 2 is preferably 100 μm or more and 2000 μm or less when an amorphous selenium compound is used. In particular, it is particularly preferably in the range of 150 μm or more and 250 μm or less for mammography, and in the range of 500 μm or more and 1200 μm or less for general photographing applications.

The charge transport layer 3 may have an insulating property with respect to a charge having a polarity to be accumulated, and have a conductivity with respect to a charge having a polarity opposite to the charge. Those having a difference of 3 digits or more are preferable. As the charge transport layer 3, polymers such as acrylic organic resin, polyimide, BCB, PVA, acrylic, polyethylene, polycarbonate, polyetherimide, sulfides such as As ₂ S ₃ , Sb ₂ S ₃ , ZnS, etc. are oxidized. And fluoride. Preferred _compounds, those 500ppm~20000ppm doped Cl, Br, and I to _{As 2 Se 3, As 2 Se} 3, As 2 obtained by substituting Se in _As 2 Se ₃ to about 50% Te _(Se x Te _{1 -X} ) 3 (0.5 <x <1), As ₂ Se ₃ with Se replaced to about 50%, As ₂ Se ₃ As concentration changed about ± 15%, An amorphous Se-Te system with Te of 5 to 30 wt% can be mentioned.

  In the case of using a substance containing a chalcogenide element as described above, the thickness of the charge transport layer 3 is preferably 0.4 μm or more and 3.0 μm or less, more preferably 0.5 μm or more and 2 μm or less. Such a charge transport layer 3 may be formed by one film formation, or may be laminated in a plurality of times.

  As a preferable charge transport layer 3 using an organic film, a compound obtained by doping a charge transport material with respect to a polymer such as an acrylic organic resin, polyimide, BCB, PVA, acrylic, polyethylene, polycarbonate, or polyetherimide is preferably used. . Preferred charge transport materials include tris (8-quinolinolato) aluminum (Alq3), N, N′-diphenyl-N, N′-di (m-tolyl) benzine (TPD), polyparaphenylene vinylene (PPV), poly Alkylthiophene, polyvinylcarbazole (PVK), triphenylene (TNF), metal phthalocyanine, 4-dicyanomitylene) -2-methyl-6- (p-dimethylaminostyryl) -4H-pyran (DCM), liquid crystal molecule, hexapenti A molecule selected from the group consisting of loxytriphenylene, a discotic liquid crystal molecule whose central core contains a π-conjugated condensed ring or a transition metal, carbon nanotubes, and fullerenes. Dope amount is 0.1-50 wt. % Can be set.

  The reading photoconductive layer 4 is a photoconductive substance that generates charges when irradiated with reading light. A semiconductor material having an energy gap in the range of 0.7 to 2.5 eV such as an amorphous selenium compound or amorphous Si: H can be used. It is particularly preferable to use amorphous selenium.

  When an amorphous selenium compound is used, an alkali metal such as Li, Na, K, Cs, Rb or the like doped in a small amount between 0.001 ppm and 1 ppm in the layer, LiF, NaF, KF, CsF, RbF A small amount of fluoride such as 10 ppm to 10000 ppm, P, As, Sb, Ge doped between 50 ppm to 0.5%, As doped between 10 ppm to 0.5% Or a small amount of Cl, Br, or I doped between 1 ppm and 100 ppm can be used. In particular, amorphous selenium containing about 10 ppm to 200 ppm of As, amorphous selenium containing about 0.2% to 1% of As and further containing 5 ppm to 100 ppm of Cl, about 0.2% to 1% of As Furthermore, amorphous selenium containing about 0.001 ppm to 1 ppm of alkali metal is preferably used.

  The reading photoconductive layer 4 has a thickness of 1 μm as long as the reading light can be sufficiently absorbed, and the electric field generated by the charge accumulated in the power storage unit 8 can drift the charge generated in the reading photoconductive layer 4 by irradiation of the reading light. About 30 μm is preferable.

  The first linear electrodes 5a and the second linear electrodes 5b are periodically and alternately arranged substantially in parallel at a predetermined interval. The second linear electrode 5b is configured to be shielded from reading light by a color filter layer 6b described later, whereas the first linear electrode 5a is an electrode for generating a photocharge pair, The second linear electrode 5b is an electrode for generating no photocharge pairs. That is, no charge pair for signal extraction is generated in the reading photoconductive layer 4 corresponding to the second linear electrode 5b. Here, the purpose of configuring the electrodes of the second electrode layer with linear electrodes is to simplify the correction of structure noise, to improve the S / N of the image by reducing the capacity, or to perform parallel reading (mainly The main scanning direction) is performed to shorten the readout time.

  The first linear electrode 5a and the second linear electrode 5b may be any material as long as it is transmissive to the reading light and has conductivity, but is caused by electric field concentration when a high voltage is applied. In order to avoid destruction, it is necessary to ensure flatness. For example, ITO, IZO or the like can be used with a thickness of 0.1 to 1 μm. Further, it may be formed with a thickness (for example, about 10 nm) that allows reading light to pass through using a metal such as Al or Cr.

  The first linear electrode 5a and the second linear electrode 5b extend outside the laminated region of each layer and are connected to a signal detection wiring board. The first linear electrode 5a Used as a signal line, the second linear electrode 5b is shared outside the laminated region. For example, the widths of the first linear electrode 5a and the second linear electrode 5b are 10 μm and 20 μm, respectively, the distance between them is 10 μm, and the first linear electrode 5a and the second linear electrode 5b are 1 When considered as one set, the pitch of the set can be 50 μm.

  A dielectric 5c is provided along the longitudinal direction of the ends of the first linear electrode 5a and the second linear electrode 5b. As shown in FIGS. 1 and 2, the term “end” as used herein refers to the side surfaces of the first linear electrode 5a and the second linear electrode 5b and the recording photoconductive layer 2 continuous with the side surfaces. It is a part consisting of a part of the surface. By covering the end portion where the electric field tends to concentrate in this way with the dielectric 5c, charge injection from the end portion can be reduced, and image defects can be suppressed.

  The material of the dielectric 5c may be any material as long as it has an insulating property, and may be any material that transmits reading light or light shielding. For example, a novolac resin, an acrylic resin, a PVA (polyvinylcohol) film, PVP ( A polyvinyl pyrrolidone) film, a PAA (polyacrylic acid) film, or the like can be used. In addition, the thickness of the dielectric 5c can be set to 0.05 μm to 5 μm, and preferably has a sufficient thickness so that charge injection can be prevented.

  As the material of the adhesion member 5e, the adhesion force with the transparent insulating layer 6a, which is a layer immediately below the second electrode layer, and the adhesion force with the dielectric 5c are based on the adhesion force between the transparent insulation layer 6a and the dielectric 5c. Any material can be used as long as the first linear electrode 5a and the second linear electrode 5b are made of the same material as the first linear electrode 5a and the second linear electrode 5b. Since the linear electrode 5b and the close contact member 5e can be formed at the same time, the manufacturing cost can be reduced. The contact member 5e is electrically separated from the other linear electrodes, and is configured such that no voltage is applied when an electric field is formed during a recording operation described later.

  In the present embodiment, as shown in FIG. 1, the end portion of the outermost linear electrode 5b of the second electrode layer facing the adhesion member 5e and the outermost linear electrode 5b of the adhesion member 5e are opposed. The end of the dielectric 5c is covered with the dielectric 5c so that the end of the dielectric 5c is not brought into close contact with the substrate 6a with weak adhesion, but is brought into close contact with the adhesion member 5e with strong adhesion. Therefore, it is possible to make it difficult for the dielectric 5c covering the outer peripheral side of the outermost linear electrode 5b to peel off.

  A crystallization preventing layer 5d is provided so as to cover the surfaces of the first linear electrode 5a, the second linear electrode 5b, the adhesion member 5e, and the dielectric 5c. The crystallization preventing layer 5d is for preventing the reading photoconductive layer 4 from being crystallized, and can prevent deterioration of characteristics when the radiation image detector 10 is repeatedly used.

As the crystallization preventing layer 5d, for the purpose of preventing crystallization, As is added to amorphous selenium in a range of 5% to 15%, S, Te, P, Sb, Ge is added in an amount of 1% to 10%. Those added in a range or those added in combination with the above elements and other elements are preferred. Alternatively, As ₂ S ₃ or As ₂ Se ₃ having a higher crystallization temperature can also be preferably used. Furthermore, in order to prevent charge injection from the electrode layer, in addition to the above-mentioned additive elements, in particular, in order to prevent hole injection, alkali metals such as Li, Na, K, Rb, Cs, LiF, NaF, KF It is also preferable to dope molecules such as RbF, CsF, LiCl, NaCl, KCl, CsCl, and CsBr in the range of 10 ppm to 5000 ppm. Conversely, in order to prevent electron injection, it is also preferable to dope a halogen element such as Cl, I, or Br, or a molecule such as In 2 O 3 in the range of 10 ppm to 5000 ppm.

  If the thickness of the crystallization preventing layer 5d is too small, the above-mentioned purpose will not be sufficiently achieved, and if it is too thick, the electrical characteristics such as the sensitivity and afterimage of the detector will be lowered. It is preferable to be set in between.

  The transparent insulating layer 6a is insulative and transparent to reading light, and for example, an acrylic resin can be used, and the thickness is desirably about 5 μm or less.

A color filter layer 6b is provided in a portion corresponding to the second linear electrode 5b via the transparent insulating layer 6a. The color filter layer 6b has a light shielding property against reading light. For example, Al, Mo, Cr or the like can be used for a metal material, and MoS ₂ , WSi ₂ , TiN or the like can be used for an inorganic material. It is also possible to use a pigment dispersed in an organic material such as an acrylic resin. The width of the color filter layer 6b can be set to 30 μm, for example.

  Since the color filter layer 6b can block the incidence of the reading light on the second linear electrode 5b, in the reading photoconductive layer 4 corresponding to the second linear electrode 5b, a charge pair for signal extraction is obtained. Can be prevented.

  The support 7 may be transparent to the reading light, and for example, a glass substrate or an organic polymer material can be used.

  Next, an operation example of the radiation image detector 10 will be described. In the operation example described below, the first electrode layer 1 is charged with a negative charge and the second electrode layer is charged with a positive charge, so that an electric storage formed at the interface between the recording photoconductive layer 2 and the charge transport layer 3 is formed. The negative charge as the accumulated charge is accumulated in the portion 8 and the mobility of the positive charge as the transport charge having the opposite polarity to the charge transport layer 3 is larger than the mobility of the negative charge as the accumulated charge. The crystallization preventing layer 5d functions as a so-called hole transport layer, and is an example in which the anti-crystallization layer 5d functions so as to have conductivity with respect to negative charges and insulation with respect to positive charges. Each of these may have a reverse polarity charge. When the polarity is reversed in this way, the charge transport layer functioning as a hole transport layer is changed to a charge transport layer functioning as an electron transport layer. You only need to make changes.

  First, a negative bias voltage is applied to the first electrode layer 1 of the radiation image detector 10 by a high-voltage power source, and an electric field is formed between the first electrode layer 1 and the second electrode layer. When an electric field is formed, positive charges are charged in the first linear electrode 5a and the second linear electrode 5b of the second electrode layer. In this state, radiation is emitted toward the subject from a radiation source such as an X-ray source, and radiation carrying image information of the subject through the subject is emitted from the first electrode layer 1 side.

  The irradiated radiation passes through the first electrode layer 1 and is applied to the recording photoconductive layer 2. As a result, a charge pair consisting of positive and negative charges is generated in the recording photoconductive layer 2 (see FIG. 3A). A positive charge (hole) of the charge pair moves toward the first electrode layer 1 and is combined with the negative charge on the first electrode layer 1 induced by the high-voltage power source and disappears. On the other hand, the negative charge (electrons) of the charge pair moves toward the second electrode layer along the electric field distribution formed by the application of the voltage, and the recording photoconductive layer 2 and the charge transport layer 3 It is accumulated as accumulated charges in the power storage unit 8 as an interface (see FIG. 3B). The amount of accumulated charge is substantially proportional to the amount of irradiation radiation, and this amount of accumulated charge indicates a radiation image.

  Here, when the electric field is formed, if the end portions of the first linear electrode 5a and the second linear electrode 5b of the second electrode layer are not covered with the dielectric 5c, these end portions In the radiation image detector 10 according to the present embodiment, the dielectric 5c is provided, so that charge injection from the end can be reduced and image defects are suppressed. can do.

  When reading the radiation image recorded on the radiation image detector 10 as described above, the reading light is irradiated from the support 7 side in a state where the first electrode layer 1 is grounded. In this irradiation, linear reading light extending in a direction orthogonal to the longitudinal direction of the second electrode layer is moved in the longitudinal direction of the second electrode layer to scan the entire surface of the radiation image detector 10. As a result, a positive / negative charge pair is generated in the reading photoconductive layer 4 corresponding to the scanning position of the reading light (see FIG. 3C). The generation of the charge pair in the reading photoconductive layer 4 does not occur in the portion corresponding to the second linear electrode 5b shielded by the color filter layer 6b.

  3A and 3B, illustration of the transparent insulating layer 6a, the color filter layer 6b, and the support 7 is omitted. In FIG. 3C, the support 7 is not shown, and the reading light is irradiated from below the support 7.

  The positive charge of the charge pair moves toward the accumulated charge of the power storage unit 8, and is combined with the accumulated charge and disappears. On the other hand, the negative charge of the charge pair moves toward the positive charge charged in the first linear electrode 5a of the second electrode layer, and disappears by combining with the positive charge.

  Then, due to the combination of the negative charge and the positive charge as described above, the current i flows through the current detection amplifier, and this current is integrated and detected as an image signal, and the image signal corresponding to the radiation image is read.

  Next, a second embodiment of the radiation image detector of the present invention will be described. FIG. 4 is a schematic configuration diagram of a radiographic image detector according to a second embodiment of the present invention, and FIG. 5 is a top view showing a configuration of a second electrode layer of the radiographic image detector.

  The radiation image detector 30 according to the present embodiment is of an electric reading system, and as shown in FIG. 4, a first electrode layer 31 that transmits recording electromagnetic waves carrying image information, and an electrode layer 31. And a plurality of pixel electrodes 35 (divided as detection electrodes for detecting a signal corresponding to the charges generated in the photoconductive layer 32). The second electrode layer provided with the electrode) is laminated in this order. Each pixel electrode 35 is connected to a storage capacitor 36 for storing charges collected by the pixel electrode 35 and a switch element 37. The pixel electrode 35, the storage capacitor 36, and the switch element 37 are connected to the pixel portion 34. The charge detection layer 33 is configured by arranging a large number of pixel portions 34 two-dimensionally.

  The electrode layer 31 is made of a low resistance conductive material such as Au. The electrode layer 31 is connected to a high voltage power source (not shown) for applying a bias voltage.

  The photoconductive layer 32 has electromagnetic wave conductivity, and generates electric charges therein by irradiation with radiation. As the photoconductive layer 32, for example, an amorphous a-Se film having a film thickness of 100 to 1000 μm mainly composed of selenium can be used.

  The charge detection layer 33 is made of an active matrix substrate. In addition to the pixel electrode 35 and the like, the pixel unit 34 includes a large number of scanning lines 38 for turning on / off the switch elements 37 and a large number of data lines 39 for reading out the charges accumulated in the storage capacitor 36. It has.

  The pixel electrode 35 collects signal charges corresponding to the charges generated in the photoconductive layer 32, and uses a material such as Al, Au, Cr, ITO (Indium Tin Oxide), IZO (Indium Zinc Oxide), for example. The thickness is preferably in the range of 0.05 μm to 1 μm.

  The radiation image detector 30 of the present embodiment also has a characteristic configuration in which a close contact member 35e is provided on the outer periphery of the second electrode layer so as to cover the end portions of the pixel electrode 35 and the close contact member 35e. Is provided with a dielectric 35c. Further, a crystallization preventing layer 35d is provided so as to cover the surfaces of the pixel electrode 35, the close contact member 35e and the dielectric 35c. The detailed configuration of the dielectric 35c, the crystallization preventing layer 35d, and the adhesion member 35e will be described later.

  The dielectric 35 c covers the end of the pixel electrode 35. The term “end portion” as used herein refers to a portion formed of a part of a side surface of the pixel electrode 35 and a surface facing the photoconductive layer 32 continuous with the side surface. By providing the dielectric 35c at the end where the electric field tends to concentrate in this way, charge injection from the end can be reduced and image defects can be suppressed.

  The material of the dielectric 35c may be any material having an insulating property, and the same material as that of the dielectric 5c of the first embodiment can be used.

  As the material of the adhesion member 35e, the adhesion force with the charge detection layer 33 and the adhesion force with the dielectric 35c, which are layers immediately below the second electrode layer, are determined by the adhesion force between the charge detection layer 33 and the dielectric 35c. Any material can be used as long as it is higher, but by using the same material as the pixel electrode 35, the pixel electrode 35 and the contact member 35e can be formed at the same time, so that the manufacturing cost can be reduced. The contact member 35e is electrically separated from the pixel electrode 35, and is configured such that no voltage is applied when an electric field is formed during a recording operation described later.

  In the present embodiment, as shown in FIG. 5, the end of the second electrode layer facing the contact member 35e of the outermost pixel electrode 35 and the end of the contact member 35e facing the outermost pixel electrode 35 are arranged. The dielectric 35c is covered with a dielectric 35c so that the end of the dielectric 35c is not in close contact with the charge detection layer 33 with low adhesive strength, but is in close contact with the adhesive member 35e with strong adhesive strength. Therefore, it is possible to make it difficult for the dielectric 35c covering the outer peripheral side of the outermost pixel electrode 35 to peel off.

  As shown in FIG. 4, the crystallization preventing layer 35d in the present embodiment is provided so as to cover the surfaces of the pixel electrode 35, the adhesion member 35e, and the dielectric 35c. The crystallization preventing layer 35d is for preventing the crystallization of the photoconductive layer 32, and can prevent deterioration of characteristics when the radiation image detector 30 is repeatedly used.

  As the crystallization preventing layer 35d, the same material as that of the crystallization preventing layer 5d of the first embodiment can be used.

  Next, an operation example of the radiation image detector 30 will be described. First, a negative bias voltage is applied to the electrode layer 31 of the radiation image detector 30 by a high voltage power source, and an electric field is formed between the electrode layer 31 and the pixel electrode 35. In this state, radiation is emitted toward the subject from a radiation source such as an X-ray source, and radiation carrying image information of the subject through the subject is emitted from the electrode layer 31 side.

  The irradiated radiation passes through the electrode layer 31 and is irradiated to the photoconductive layer 32. As a result, a charge pair consisting of positive and negative charges is generated in the photoconductive layer 32. The positive charge (holes) of the charge pair moves toward the electrode layer 31 and disappears in combination with the negative charge on the electrode layer 31 induced by the high-voltage power source.

  On the other hand, negative charges (electrons) of the charge pair move toward the pixel electrode 35 along the electric field distribution formed by the application of the voltage, are collected by the pixel electrode 35, and are electrically connected to the pixel electrode 35. The accumulated storage capacity 36 is accumulated. Since the photoconductive layer 32 generates an amount of charge corresponding to the amount of irradiated radiation, the charge corresponding to the image information carried by the radiation is stored in the storage capacitor 36 of each pixel unit 34.

  Here, when the electric field is formed, if the end of the pixel electrode 35 is not covered with the dielectric 35c, the electric field concentrates on the end and charge injection occurs. In the detector 30, since the dielectric 35c is provided, charge injection from the end can be reduced, and image defects can be suppressed.

  When reading the radiographic image recorded in the radiographic image detector 30 as described above, a signal for sequentially turning on the switch element 37 via the scanning line 38 is added, and each storage capacitor via the data line 39 is added. The electric charge accumulated in 36 is taken out. Furthermore, image information can be read by detecting the charge amount of each pixel by the amplifier 40.

  The present invention is not limited to the above-described embodiment, and various modifications can be made without changing the gist of the invention. For example, in the optical reading radiation image detector described in the first embodiment, the second linear electrode 5b may be made of a material made of a light-shielding substance instead of providing the color filter layer 6b. . In the optical reading type radiographic image detector, all the linear electrodes may be configured to be charge generation electrodes. Further, the voltage application during driving may be reversed.

1 is a schematic configuration diagram of a radiation image detector according to a first embodiment of the present invention. The top view which shows the structure of the 2nd electrode layer of the said radiographic image detector. The figure for demonstrating the operation | movement of recording of the radiographic image to the said radiographic image detector The figure for demonstrating the operation | movement of recording of the radiographic image to the said radiographic image detector The figure for demonstrating the operation | movement of reading of the radiographic image to the said radiographic image detector. The schematic block diagram of the radiographic image detector concerning the 2nd Embodiment of this invention. The top view which shows the structure of the 2nd electrode layer of the said radiographic image detector.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 1st electrode layer 2 Recording photoconductive layer 3 Charge transport layer 4 Reading photoconductive layer 5a 1st linear electrode 5b 2nd linear electrode 5c, 35c Dielectric 5d, 35d Anti-crystallization layer 5e, 35e Adhesive member 6a Transparent insulating layer 6b Color filter layer 7 Support body 8 Power storage unit 10, 30 Radiation image detector 31 Electrode layer 32 Photoconductive layer 33 Charge detection layer 34 Pixel unit 35 Pixel electrode 36 Storage capacitor 37 Switch element

Claims (2)

A first electrode layer that is transparent to electromagnetic waves;
A photoconductive layer that generates electric charge upon irradiation with the electromagnetic wave;
A second electrode layer having a plurality of divided electrodes, and laminated on the substrate in order from the second electrode layer;
A radiation image detector in which a gap between mutually facing ends of the divided electrodes adjacent to each other is covered with a dielectric,
An adhesion member is disposed on the outer periphery of the second electrode layer,
A gap between an end portion of the outermost outer periphery of the second electrode layer facing the adhesion member and an end portion of the adhesion member facing the outermost division electrode is covered with the dielectric,
The radiation image detector, wherein an adhesion force between the substrate surface and the adhesion member and an adhesion force between the adhesion member and the dielectric are higher than an adhesion force between the substrate surface and the dielectric.   The radiation image detector according to claim 1, wherein the contact member is made of the same material as the divided electrode.

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