JP4990084B2 - Radiation detector - Google Patents

Description

  The present invention relates to a radiation detector used in a medical X-ray imaging apparatus or the like.

As a radiation detector, the radiation detector disclosed in Patent Document 1 is known. In the radiation detector of Patent Document 1, an upper electrode portion is formed on a charge conversion layer formed of amorphous selenium or the like, and an insulating material is formed between the charge conversion layer and an edge portion of the upper electrode portion. As a result, the electric field concentration on the edge of the upper electrode portion is eliminated, and the pre-stage phenomenon of the through discharge and the discharge breakdown do not occur.
JP 2003-133575 A

  However, in the configuration of Patent Document 1, radiation detection cannot be performed at the portion of the charge conversion layer on which the insulating material is formed, and a useless region where radiation detection cannot be performed in the charge conversion layer is generated.

  In view of the above facts, the present invention aims to suppress the deterioration of the charge conversion layer due to the electric field concentration at the end of the upper electrode part, and to prevent a useless region where radiation detection cannot be performed in the charge conversion layer. To do.

A radiation detector according to claim 1 of the present invention includes a charge conversion layer that generates charges when radiation is incident thereon, and a lower part that is provided under the charge conversion layer and collects charges generated by the charge conversion layer. An electrode portion, a substrate provided with the lower electrode portion, and a layer stacked on the charge conversion layer, wherein one or more sides of the end portion are disposed outside the charge conversion layer, and a bias voltage is applied to the charge conversion layer. An upper electrode portion for applying the voltage, and a portion of the one side arranged outside the charge conversion layer, protrudes outside the charge conversion layer, and is electrically connected to a conducting wire for applying a bias voltage. And all of the one side other than the part are disposed outside the charge conversion layer at a position closer to the charge conversion layer than the tip of the extension electrode. It is characterized by that.

  According to this configuration, a bias voltage is applied from the upper electrode portion to the charge conversion layer. The charge conversion layer generates charges when radiation is incident thereon. The charges generated by the charge conversion layer are collected by the lower electrode part.

  The charge generated by the charge conversion layer includes not only the charge conversion layer directly generated but also the charge conversion layer indirectly generated, for example, corresponding to the charge directly generated by the charge conversion layer. It is a concept that includes generated charges.

  Here, in the configuration of claim 1, one or more sides of the end portion of the upper electrode portion are disposed outside the charge conversion layer, and the end portion does not cover the charge conversion layer. Leakage current increased due to electric field concentration in the portion does not flow to the charge conversion layer, and deterioration of the charge conversion layer can be suppressed.

  According to the first aspect of the present invention, the end of the upper electrode portion is arranged outside the charge conversion layer without forming an insulating material between the end of the upper electrode portion and the charge conversion layer. Since the deterioration of the conversion layer is suppressed, radiation detection is possible in the entire region of the charge conversion layer, and there is no useless region in the charge conversion layer where radiation detection is impossible.

  According to a second aspect of the present invention, there is provided a radiation detector according to the first aspect, wherein the radiation detector is provided between an end portion of the upper electrode portion and the substrate, and the end portion of the upper electrode portion is laminated. It is provided with.

  According to this configuration, since the insulating portion on which the end portion of the upper electrode portion is stacked is disposed between the end portion of the upper electrode portion and the substrate, the insulation between the upper electrode portion and the lower electrode portion is performed. Can be secured.

  According to a third aspect of the present invention, in the radiation detector according to the second aspect, the height of the laminated surface of the insulating portion where the end portion of the upper electrode portion is laminated is such that the upper electrode portion is laminated. It is substantially the same as the height of the stacked surface of the charge conversion layer.

  When the upper electrode portion is bent, the electric field concentration is likely to occur at the bending point as in the end portion. However, in the configuration of claim 3 of the present invention, the height of the laminated surface of the insulating portion where the end portion of the upper electrode portion is laminated is increased. Is substantially equal to the height of the layered surface of the charge conversion layer on which the upper electrode part is laminated, and it is difficult to form a bending point in the upper electrode part at the boundary between the charge conversion layer and the insulating part. Is less likely to occur, and deterioration of the charge conversion layer can be suppressed.

  According to a fourth aspect of the present invention, in the radiation detector according to the first or second aspect, the insulating portion is made of a resin.

  According to this configuration, since the insulating portion is formed of resin, it is easy to form the insulating portion.

  Since the present invention has the above-described configuration, it is possible to suppress the deterioration of the charge conversion layer due to the electric field concentration at the end of the upper electrode portion, and it is not possible to use a useless area where radiation detection cannot be performed in the charge conversion layer.

  Below, an example of an embodiment of a radiation detector concerning the present invention is explained based on a drawing.

  The radiation detector according to the present embodiment is used in an X-ray imaging apparatus or the like, and includes an electrostatic recording unit including a photoconductive layer that exhibits conductivity when irradiated with radiation. The image information is recorded upon receiving the irradiation of the radiation carrying the image, and the image signal representing the recorded image information is output.

  As the radiation detector, a so-called optical reading type radiation detection substrate 500 that reads using a semiconductor material that generates charges by light irradiation, and charges generated by radiation irradiation are accumulated, and the accumulated charges are stored in a thin film transistor. There is a radiation detector 400 or the like of a method of reading by turning on and off an electrical switch such as a TFT (thin film transistor) one pixel at a time (hereinafter referred to as TFT method).

(Configuration of optical reading radiation detection substrate 500)
First, a configuration of the optical reading type radiation detection substrate 500 will be described.

  FIG. 1 is a plan view showing a schematic configuration of a radiation detection substrate 500 according to the present embodiment. FIG. 2 is a side sectional view showing a schematic configuration of the radiation detection substrate 500 according to the present embodiment.

  As the radiation detection substrate 500 according to the present embodiment, for example, there is a mammography used for breast X-ray detection. In addition, when using for mammography, the A side in FIG. 1 becomes the chest wall side of the person who receives a medical examination.

  As shown in FIGS. 1 and 2, the radiation detection substrate 500 according to the present embodiment converts the incident X-rays into charges as a charge conversion layer that generates charges when the radiation is incident thereon. A radiation detection layer 522 is provided.

  Under the radiation detection layer 522, a lower electrode 520 is disposed as a lower electrode portion that collects charges corresponding to the charges generated by the radiation detection layer 522. The lower electrode 520 is provided on the glass substrate 536.

  The glass substrate 536 provided with the lower electrode 520 constitutes a radiation detection lower substrate 524. A readout device 512 is connected to the radiation detection lower substrate 524 via a TCP (Tape Carrier Package) 510.

  TCP510 is a flexible wiring board on which a signal detection IC (charge amplifier IC) 511 is mounted. The TCP 510 is connected to the radiation detection lower substrate 524 and the readout device 512 by thermocompression bonding using an ACF (Anisotropic Conductive Film).

  On the radiation detection layer 522, an upper electrode 518 formed in a rectangular shape is stacked as an example of an upper electrode portion for applying a bias voltage to the radiation detection layer 522.

  Further, the radiation detection substrate 500 according to the present embodiment includes a high voltage line 514 for applying a high voltage to the upper electrode 518.

  An extension electrode portion 519 for connecting the high voltage line 514 and the upper electrode 518 is formed on the upper electrode 518. The extension electrode portion 519 extends from the upper electrode 518 in the direction opposite to the A side (the chest wall side in mammography) in FIG. 1, and a high voltage line 514 is connected to the extension electrode portion 519.

  Here, at least one side of the end portion of the upper electrode 518 is disposed outside the radiation detection layer 522. That is, the end portion of the upper electrode 518 has a configuration in which at least one of the sides on the four sides around the upper electrode 518 is disposed outside the radiation detection layer 522.

  In the configuration of the present embodiment, both sides 518A adjacent to the side on the A side in FIG. 1 are arranged outside the radiation detection layer 522.

  When there is a portion protruding from the upper electrode 518 like the extended electrode portion 519, only the side 519A of the protruding portion is outside the radiation detection layer 522 as shown in FIG. As shown in FIG. 3A, the side 519A of the protruding portion and the side 518B of the upper electrode 518 are arranged outside the radiation detection layer 522, as shown in FIG. The part is disposed outside the radiation detection layer 522.

  As shown in FIGS. 1 and 2, an insulating portion 516 in which the end portion of the upper electrode 518 is laminated is provided between the end portion of the upper electrode 518 and the radiation detection lower substrate 524.

  The insulating portion 516 is formed such that the laminated surface on which the end portion of the upper electrode 518 is laminated is along the extension line of the laminated surface of the radiation detection layer 522 on which the upper electrode 518 is laminated. The height of the laminated surface of the insulating portion 516 on which is laminated is approximately equal to the height of the laminated surface of the radiation detection layer 522 on which the upper electrode 518 is laminated.

  As a result, the laminated surface of the insulating portion 516 is formed on substantially the same plane as the laminated surface of the radiation detection layer 522, and a bending point is formed in the upper electrode 518 at the boundary between the radiation detection layer 522 and the insulating portion 516. It becomes difficult.

  In addition, on the radiation detection lower substrate 524 and on the outside of the radiation detection layer 522 slightly away from the radiation detection layer 522, ribs 523 serving as walls for preventing the resin from flowing out as the insulating portion 516 are provided. Is provided.

  As the rib 523, for example, glass is used, but any material can be selected as long as the rib 523 is a material that can be sufficiently insulated from the lower electrode 520. Further, if the rib 523 is removed after the insulating portion 516 is formed, it may have conductivity.

  The insulating portion 516 is formed of, for example, an insulating resin, and is formed on the radiation detection lower substrate 524 so as to be filled between the rib 523 and the radiation detection layer 522. As the resin, for example, a curable resin is used. As the curable resin, for example, a room temperature curable resin such as epoxy or silicon is used. The curable resin preferably has a low viscosity from the viewpoint of moldability.

  The production of the radiation detection substrate 500 according to the present embodiment is roughly divided into the production of the radiation detection lower substrate 524 including the lower electrode 520, the formation of the radiation detection layer 522 and the upper electrode 518, and the connection of the high voltage line 514. .

  Hereinafter, the structure of the radiation detection lower substrate 524 will be described. FIG. 4 shows a schematic structure of the radiation detection lower substrate 524. In FIG. 4, TCP 510 is simplified to one channel on the left and three channels on each side, for a total of 6 channels. The radiation detection lower substrate 524 includes a radiation detection unit 526, a pitch conversion unit 528, and a TCP connection unit 530 as shown in FIG.

  In the radiation detection unit 526, lower electrodes 520 for extracting signals are arranged in a stripe shape (line shape). In addition, a color filter layer 534 that partially transmits only light having an arbitrary wavelength is formed under the transparent organic insulating layer 532.

  The layer above the color filter layer 534 is referred to as a common B line 520B, and the signal S line 520S in a portion without the color filter layer 534. The B line 520B is shared outside the radiation detection unit and has a comb electrode structure. The S line 520S is used as a signal line. The width of the B line 520B is, for example, 20 μm, the width of the S line 520S is, for example, 10 μm, and the interval between the B line 520B and the S line 520S is, for example, 10 μm.

  The width of the color filter layer 534 is, for example, 30 μm. The lower electrode 520 is transparent to irradiate light from the back surface, and needs flatness to avoid breakdown due to electric field concentration when a high voltage is applied. For example, IZO or ITO is used. When IZO is used, the thickness is 0.2 μm and the flatness is about Ra = 1 nm.

  The color filter layer 534 is a photosensitive resist in which a pigment is dispersed, for example, a red resist used for an LCD color filter. In order to eliminate the level difference of the color filter layer 534, a photosensitive organic transparent insulating layer 532 such as PMMA is used.

  Further, the substrate 536 serving as a support member is preferably transparent and rigid glass, and more preferably soda lime glass. As an example of the thickness of each layer, the lower electrode 520 is 0.2 μm, the color filter layer 534 is 1.2 μm, the organic transparent insulating layer 532 is 1.8 μm, and the glass substrate 536 is 1.8 mm. The color filter layer 534 and the organic insulating layer 532 are provided only in the radiation detection unit 526, and the boundary is in the radiation detection unit 526 and the pitch conversion unit 528. For this reason, the IZO wiring is formed on the glass substrate 536 in the TCP connection portion 530 via the boundary step portion of the organic insulating layer 532.

  In the radiation detection unit 526, wiring is taken out to the left and right TCPs 510 in units of a certain number. In FIG. 4, the unit is 3 lines. An example of the number of lines is 256 lines. The line width in the radiation detection unit 526 is different from the line width in the TCP connection unit 530 and is adjusted, and the line width is adjusted in the pitch conversion unit 528 in order to route the wiring to a predetermined TCP connection position. The B line 520B is made common and similarly drawn out to the TCP connection unit 530.

  In the TCP connection unit 530, the signal S line 520S and the common B line 520B shared by the outside of the radiation detection unit are arranged. The common B line 520B is disposed outside the signal S line 520S. As an example of the number, the signal line 256 and the common line are connected to the TCP using five lines above and below. The electrode line / space is 40/40 μm.

  In addition, an alignment mark for TCP is necessary to connect TCP with this TCP connection unit 530. Although it is desirable to form with a transparent electrode, it is difficult to recognize because it is transparent, and an alignment mark is formed using, for example, a color filter layer 534 that is a constituent member of this substrate as an opaque material.

  Next, the radiation detection layer 522 will be described. FIG. 5 is a schematic view schematically showing the configuration of the radiation detection substrate 500. As shown in FIG. 5, the radiation detection layer includes a recording photoconductive layer 542, a charge storage layer 544, a reading photoconductive layer 546, an electrode interface layer 548, an undercoat layer 550, and an overcoat layer 552. ing.

<Photoconductive layer for recording>
The recording photoconductive layer 542 is a photoconductive material that absorbs electromagnetic waves and generates charges, and is an amorphous selenium compound, Bi ₁₂ 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 , GaAs, and the like. Of these, an amorphous selenium compound is particularly preferable.

  In the case of an amorphous selenium compound, the layer is doped with a small amount of alkali metal such as Li, Na, K, Cs, Rb between 0.001 ppm and 1 ppm, LiF, NaF, KF, CsF, RbF, etc. A small amount of fluoride of 10ppm to 10000ppm, P, As, Sb, Ge added between 50ppm to 0.5%, As doped from 10ppm to 0.5%, Cl, Br , I doped in a slight amount 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, and alkali metals of about 0.001 ppm to 1 ppm were contained. Amorphous selenium is preferably used.

Also, Bi ₁₂ 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 Those containing fine particles of a photoconductive substance such as BiI ₃ or GaAs can also be used.

  The thickness of the recording photoconductive layer 542 is preferably 100 μm or more and 2000 μm or less in the case of amorphous selenium. 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.

<Charge storage layer>
The charge storage layer 544 may be any film that is insulative with respect to the polar charge to be stored, such as an acrylic organic resin, polyimide, BCB, PVA, acrylic, polyethylene, polycarbonate, polyetherimide, or a polymer such as As ₂ S. ₃ , sulfides such as Sb ₂ S ₃ and ZnS, oxides and fluorides. Furthermore, it is more preferable to be insulative with respect to the charge of the polarity to be accumulated, and to have conductivity with respect to the charge of the opposite polarity, and the product of mobility × lifetime is 3 digits or more depending on the polarity of the charge. Substances with differences are preferred.

Preferable compounds include As ₂ Se ₃ , As ₂ Se ₃ doped with Cl, Br, I from 500 ppm to 20000 ppm, and As ₂ Se ₃ Se ₂ substituted with Te to about 50% (Se _x Te _1-x ) ₃ (0.5 <x <1), As ₂ Se ₃ with Se replaced to about 50%, As _x Se _y with As concentration changed by ± 15% from As ₂ Se ₃ ( x + y = 100, 34 ≦ x ≦ 46), an amorphous Se—Te system containing 5-30 wt% Te.

  In the case of using such a substance containing a chalcogenide element, the thickness of the charge storage layer 544 is preferably 0.4 μm to 3.0 μm, more preferably 0.5 μm to 2 μm. Such a charge storage layer 544 may be formed by a single film formation or may be laminated in a plurality of times.

  As a preferable charge storage layer 544 using an organic film, a compound obtained by doping a charge transport agent with a polymer such as an acrylic organic resin, polyimide, BCB, PVA, acrylic, polyethylene, polycarbonate, or polyetherimide is preferably used. . Preferred charge transport agents include tris (8-quinolinolato) aluminum (Alq3), N, N-diphenyl-N, N-di (m-tolyl) benzidine (TPD), polyparaphenylene vinylene (PPV), polyalkylthiophene. , Polyvinylcarbazole (PVK), triphenylene (TNF), metal phthalocyanine, 4- (dicyanomethylene) -2-methyl-6- (p-dimethylaminostyryl) -4H-pyran (DCM), liquid crystal molecules, hexapentyloxytriphenylene And a molecule selected from the group consisting of a discotic liquid crystal molecule having a central core containing a π-conjugated condensed ring or a transition metal, a carbon nanotube, and fullerene. The doping amount is set between 0.1 and 50 wt.%.

<Reading photoconductive layer>
The photoconductive layer 546 for reading is a photoconductive material that absorbs electromagnetic waves, particularly visible light, and generates electric charge. The energy gap of amorphous selenium compound, amorphous Si: H, crystalline Si, GaAs, etc. is in the range of 0.7-2.5 eV. The semiconductor substance contained in the can be used. In particular, amorphous selenium is preferable.

In the case of an amorphous selenium compound, the layer is doped with a small amount of alkali metal such as Li, Na, K, Cs, Rb between 0.001 ppm and 1 ppm, LiF, NaF, KF, CsF, RbF, etc. A small amount of fluoride of 10ppm to 10000ppm, P, As, Sb, Ge added between 50ppm to 0.5%, As doped from 10ppm to 0.5%, Cl, Br , I doped in a slight amount 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, and alkali metals of about 0.001 ppm to 1 ppm were contained. Amorphous selenium is preferably used.

  The thickness of the reading photoconductive layer 546 is not limited as long as it can sufficiently absorb the reading light and the electric field generated by the charges accumulated in the charge storage layer 544 can drift the photoexcited charge, and is preferably about 1 μm to 30 μm.

<Electrode interface layer>
The electrode interface layer 548 is laid between the recording photoconductive layer 542 and the upper electrode 518 or between the reading photoconductive layer 546 and the lower electrode 520. For the purpose of preventing crystallization, amorphous selenium with As added in the range of 1% -20%, S, Te, P, Sb, Ge added in the range of 1% to 10%, the above What added the combination of an element and another element is preferable.

Alternatively, As ₂ S ₃ and As ₂ Se ₃ having a higher crystallization temperature can also be preferably used. Furthermore, in addition to the above-mentioned additive elements for the purpose of preventing charge injection from the electrode layer, in particular, alkali metals such as Li, Na, K, Rb, Cs, LiF, NaF, KF to prevent hole injection It is also preferable to dope a molecule such as RbF, CsF, LiCl, NaCl, KCl, RbF, CsF, CsCl, 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. The thickness of the interface layer is preferably set between 0.05 μm and 1 μm so as to sufficiently fulfill the above purpose.

The electrode interface layer 548, the reading photoconductive layer 546, the charge storage layer 544, and the recording photoconductive layer 542 have a substrate temperature of 25 ° C. or higher in a vacuum chamber having a degree of vacuum of 10 ⁻³ to 10 ⁻⁷ Torr. The boat or crucible containing each of the above alloys is kept at a temperature of 70 ° C. or lower and heated by resistance heating or electron beam to evaporate or sublimate the alloy or compound, and are laminated on the substrate.

When the evaporation temperatures of the alloy and the compound are greatly different, it is also preferable to control the addition concentration and the dope concentration by simultaneously heating and individually controlling a plurality of boats corresponding to a plurality of evaporation sources. For example, As ₂ Se ₃ / Amorphous selenium / LiF are put in a boat, As ₂ Se ₃ boat is 340 ° C, Amorphous selenium (a-Se) boat is 240 ° C, LiF boat is 800 ° C, and each boat By opening and closing the shutter, a layer of As10% doped amorphous selenium doped with 5000 ppm LiF can be formed.

<Underlayer>
An undercoat layer 550 can be provided between the reading photoconductive layer 546 and the lower electrode (charge collecting electrode) 520. When there is an electrode interface layer (crystallization prevention layer (A layer)) 548, it is preferably provided between the electrode interface layer 548 and the lower electrode 520. The undercoat layer 550 preferably has rectification characteristics from the viewpoint of reducing dark current and leakage current. It is preferable to have an electron blocking property when a positive bias is applied to the upper electrode 518 and a hole blocking property when a negative bias is applied.

The resistivity of the undercoat layer is preferably 10 ⁸ Ωcm or more, and the film thickness is preferably 0.01 μm to 10 μm. As a layer having an electron blocking property, that is, an electron injection blocking layer, a layer made of a composition such as Sb ₂ S ₃ , Sb ₂ Te ₃ , ZnTe, CdTe, As ₂ Se ₃ , As ₂ S ₃ , or an organic polymer layer Is preferred. As the organic polymer layer, a film in which NPD or TPD is mixed with a hole transporting polymer such as PVK or an insulating polymer such as polycarbonate, polystyrene, polyimide, or polycycloolefin can be preferably used.

As a layer having a hole blocking property, that is, a hole injection blocking layer, a film of CdS, CeO ₂ , or the like, or an organic polymer layer is preferable. The organic polymer layer, polycarbonate, polystyrene, polyimide, the insulating polymer polycycloolefin or the like, C _{60 (fullerene),} can be preferably used a film obtained by mixing carbon clusters such as C _70.

  On the other hand, a thin insulating polymer layer can also be preferably used. For example, parylene, polycarbonate, PVA, PVP, PVB, a polyester resin, an acrylic resin such as polymethyl methacrylate is preferable. The film thickness at this time is preferably 2 μm or less, and more preferably 0.5 μm or less.

<Upper layer>
An overcoat layer 552 can be provided between the recording photoconductive layer 542 and the upper electrode (voltage application electrode) 518. When there is an electrode interface layer (crystallization prevention layer (C layer)) 548, it is preferably provided between the electrode interface layer 548 and the upper electrode 518. The overcoat layer 552 preferably has a rectifying characteristic from the viewpoint of reducing dark current and leak current from the viewpoint of reducing dark current and leak current.

It is preferable to have a hole blocking property when a positive bias is applied to the upper electrode 518, and an electron blocking property when a negative bias is applied. The resistivity of the overcoat layer is preferably 10 ⁸ Ωcm or more, and the film thickness is preferably 0.01 μm to 10 μm.

As a layer having an electron blocking property, that is, an electron injection blocking layer, a layer made of a composition such as Sb ₂ S ₃ , SbTe, ZnTe, CdTe, SbS, AsSe, As ₂ S ₃ or an organic polymer layer is preferable. As the organic polymer layer, a film in which NPD or TPD is mixed with a hole transporting polymer such as PVK or an insulating polymer such as polycarbonate, polystyrene, polyimide, or polycycloolefin can be preferably used.

As a layer having a hole blocking property, that is, a hole injection blocking layer, a film of CdS, CeO ₂ , or the like, or an organic polymer layer is preferable. The organic polymer layer, polycarbonate, polystyrene, polyimide, the insulating polymer polycycloolefin or the like, C _{60 (fullerene),} can be preferably used a film obtained by mixing carbon clusters such as C _70.

  On the other hand, a thin insulating polymer layer can also be preferably used. For example, parylene, polycarbonate, PVA, PVP, PVB, a polyester resin, an acrylic resin such as polymethyl methacrylate is preferable. The film thickness at this time is preferably 2 μm or less, and more preferably 0.5 μm or less.

  Next, the upper electrode 518 and the surface protective layer 554 formed on the surface of the upper electrode 518 will be described.

<Upper electrode>
As the upper electrode 518 formed on the upper surface of the recording photoconductive layer 542, a metal thin film is preferably used. Materials include Au, Ni, Cr, Au, Pt, Ti, Al, Cu, Pd, Ag, Mg, MgAg3-20% alloy, Mg-Ag intermetallic compound, MgCu3-20% alloy, Mg-Cu metal What is necessary is just to make it form from metals, such as an intermetallic compound.

  In particular, Au, Pt, and Mg—Ag intermetallic compounds are preferably used. For example, when Au is used, the thickness is preferably 15 nm to 200 nm, more preferably 30 nm to 100 nm. For example, when an MgAg3-20% alloy is used, it is more preferable to use a thickness of 100 nm to 400 nm.

Although the preparation method is arbitrary, it is preferably formed by vapor deposition by a resistance heating method.
For example, after a metal lump is melted in a boat by a resistance heating method, the shutter is opened, vapor deposition is performed for 15 seconds, and cooling is performed once. It is formed by repeating a plurality of times until the resistance value becomes sufficiently low.

<Surface protective layer>
In order to form a latent image on the radiation detection device by irradiation, a high voltage of several kV is applied to the upper electrode 518. If the upper electrode 518 is open to the atmosphere, creeping discharge is generated, and there is a risk of electric shock of the subject. In order to prevent creeping discharge in the upper electrode 518, a surface protective layer 554 is formed on the upper surface of the electrode and subjected to insulation treatment.

  Insulation treatment requires a structure in which the electrode surface does not come into contact with the atmosphere at all, and a structure in which the electrode surface is tightly covered with an insulator. In addition, this insulator needs to have a dielectric breakdown strength exceeding the applied potential. Furthermore, it is necessary for the function of the radiation detection device to be a member that does not interfere with radiation transmission. As a material and manufacturing method of these required covering properties, high dielectric breakdown strength and high radiation transmittance, vapor deposition of insulating polymer or solvent coating is preferable.

  Specific examples include a room temperature curing type epoxy resin, a polycarbonate resin, a polyvinyl butyral resin, a polyvinyl alcohol resin, an acrylic resin, and a method of forming a polyparaxylylene derivative by a CVD method. Among these, a room temperature curing type epoxy resin and polyparaxylylene are preferably formed by a CVD method, and a method of forming a polyparaxylylene derivative by a CVD method is particularly preferable. A preferable film thickness is 10 μm or more and 1000 μm or less, and more preferably 20 μm or more and 100 μm or less.

  A polyparaxylylene film can be formed at room temperature, so that an insulating film with extremely high step coverage can be obtained without applying thermal stress to the adherend, but it is chemically very stable. In general, the adhesion is often not preferred. In order to increase the adhesion with the adherend, as a treatment to the adherend before the formation of polyparaxylylene, physical, such as a coupling agent, corona discharge, plasma treatment, ozone cleaning, acid treatment, surface treatment, Chemical treatment is generally known and can be used. In particular, a polyparaxylylene film is formed after applying a silane coupling agent or a solution obtained by diluting a silane coupling agent with an alcohol or the like if necessary to at least improve the adhesion to the adherend. A method of improving the adhesion with the adherend is preferable.

  Furthermore, it is preferable to perform a moisture-proof treatment to prevent the radiation detection device from aging. Specifically, the structure is covered with a moisture-proof member. As the moisture-proof member, a resin alone such as the insulating polymer is insufficient in function, and a configuration having at least an inorganic material layer such as glass or an aluminum laminate film is effective. However, since glass attenuates radiation transmission, the moisture-proof member is preferably a thin aluminum laminate film. For example, as an aluminum laminate film generally used as a moisture-proof packaging material, there is a laminate of PET 12 μm / rolled aluminum 9 μm / nylon 15 μm.

  The thickness of aluminum is preferably 5 μm or more and 30 μm or less, and the front and rear PET thicknesses and nylon thicknesses are each preferably 10 μm or more and 100 μm or less. The X-ray attenuation of this film is about 1%, which is optimal as a member that achieves both a moisture-proof effect and X-ray transmission.

  For example, as shown in FIG. 6, the entire surface of the radiation detection device subjected to insulation treatment with polyparaxylylene 554A is covered with a moisture-proof film 554B, and the periphery of the moisture-proof film 554B is adhered and fixed to the substrate with an adhesive outside the radiation detection device region. To do. Thus, the radiation detection device is sealed with the substrate and the moisture-proof film 554B.

  At the time of this adhesion and fixation, polyparaxylylene 554A is chemically very stable, and therefore generally has poor adhesion to other members by an adhesive, but light irradiation treatment with ultraviolet light prior to adhesion is performed. The adhesion can be improved by applying. The necessary irradiation time is appropriately adjusted to the optimum time depending on the wavelength and wattage of the ultraviolet light source to be used, but it is preferably 1 to 50 W with a low-pressure mercury lamp, and the light irradiation is preferably performed for 1 to 30 minutes.

  In addition, the radiation detection device according to the present embodiment uses amorphous selenium, and amorphous selenium may crystallize at a high temperature of 40 ° C. or higher, so that the function of forming a latent image may not be obtained. Heat treatment is not suitable. Therefore, a room temperature curable adhesive is desirable, and a two-component mixed room temperature curable epoxy adhesive having a high adhesive strength is optimal. This epoxy adhesive is applied to the outer periphery of the radiation detection device and covered with a moisture-proof film 554B. The adhesive portion is pressed and fixed uniformly from the upper surface of the moisture-proof film 554B, and is left in this state for 12 hours or more in a room temperature environment to be cured. After the adhesive is cured, the pressure is released to complete the sealing structure.

  It supplements about a sealing structure member. When a radiation detection device is used for mammography, imaging detection with a low dose is desired in order to suppress exposure in X-ray imaging. In order to detect a change in shadow caused by low-dose irradiation, it is desirable that members other than the subject (mammo) in the path from the radiation source to the device have a high X-ray transmittance, thereby obtaining a clear image.

  Although an example of a preferable protective layer / sealing structure is shown in FIG. 6, it is not limited to this. It is preferable to maintain the humidity environment of the device at 30% or less, more preferably 10% or less by forming the protective film.

  Hereinafter, although the example of a preferable layer structure is shown, this invention is not a thing limited to this. A model diagram of the cross section is shown in FIG.

<Configuration 1>
On the radiation detection lower substrate 524 as shown in FIG. 4, a layer structure was fabricated in the following order. As the lower electrode 520, a flat IZO electrode having a surface roughness Ra <1 nm was used.
Undercoat layer 550: CeO ₂ thickness 20 nm
Lower electrode interface layer 548: As10% doped amorphous selenium: LiF500ppm doped, thickness 0.1μm
Photoconductive layer for reading 546: amorphous selenium, thickness 7 μm
Charge storage layer 544: As ₂ Se ₃ , thickness 1 μm
Photoconductive layer 542 for recording: 0.001 ppm of amorphous selenium Na, thickness 200 μm
Upper electrode interface layer 548: As10% doped amorphous selenium, thickness 0.2 μm
Overcoat layer 552: Sb ₂ S ₃ , thickness 0.5 μm
Upper electrode 518: Au, thickness 70 nm
<Configuration 2>
On the radiation detection lower substrate 524 as shown in FIG. 4, a layer structure was fabricated in the following order. As the lower electrode 520, a flat IZO electrode having a surface roughness Ra <1 nm was used.
Undercoat layer 550: None Lower electrode interface layer 548: As3% doped amorphous selenium, thickness 0.15 μm
Photoconductive layer for reading 546: amorphous selenium, thickness 15 μm
Charge storage layer 544: As ₂ Se ₃ , thickness 2 μm
Photoconductive layer 542 for recording: containing 0.001 ppm of amorphous selenium Na, thickness 180 μm
Upper electrode interface layer 548: As10% doped amorphous selenium, thickness 0.1 μm
Overcoat layer 552: Sb ₂ S ₃ , thickness 0.2 μm
Upper electrode 518: Au, thickness 150 nm
<Configuration 3>
On the radiation detection lower substrate 524 as shown in FIG. 4, a layer structure was fabricated in the following order. As the lower electrode 520, a flat IZO electrode having a surface roughness Ra <1 nm was used.
Undercoat layer 550: CeO ₂ , thickness 30 nm
Lower electrode interface layer 548: As 6% doped amorphous selenium, thickness 0.25 μm
Photoconductive layer for reading 546: amorphous selenium, thickness 10 μm
Charge storage layer 544: As ₂ Se ₃ , thickness 0.6 μm
Photoconductive layer 542 for recording: 0.001 ppm of amorphous selenium Na, thickness 230 μm
Upper electrode interface layer 548: As10% doped amorphous selenium, thickness 0.3 μm
Overcoat layer 552: Sb ₂ S ₃ , thickness 0.3 μm
Upper electrode 518: Au, thickness 100 nm
<Charge extraction amplifier>
In the present embodiment, the charge is A / D converted after being amplified through an amplifier. FIG. 7 is a block diagram showing the configuration of the charge extraction amplifier and the connection mode between the charge extraction amplifier and the image processing apparatus 150 arranged outside the radiation detection substrate 500.

  The charge amplifier IC 511 as a charge extraction amplifier is a multiplexer that multiplexes a number of charge amplifiers 33a and sample hold (S / H) 33b connected to each element 15a of the radiation detection substrate 500, and a signal from each sample hold 33b. 33c.

  The current flowing out from the lower electrode is converted into a voltage by each charge amplifier 33a, the voltage is sampled and held at a predetermined timing by the sample hold 33b, and the voltage corresponding to each sampled and held element 15a is switched in the arrangement order of the elements 15a. Are sequentially output from the multiplexer 33c (corresponding to a part of main scanning).

  The signal sequentially output from the multiplexer 33c is input to the multiplexer 31c provided on the printed circuit board 31, and further, the voltage corresponding to each element 15a is sequentially output from the multiplexer 31c so as to be switched in the arrangement order of the elements 15a, thereby completing the main scanning. To do.

  The signals sequentially output from the multiplexer 31c are converted into digital signals by the A / D converter 31a, and the digital signals are stored in the memory 31b. The image signal once stored in the memory 31b is sent to an external image processing device 150 via a signal cable, and appropriate image processing is performed in the image processing device 150, and the image signal is uploaded to the network 151 together with the photographing information, and the server Or it is sent to a printer.

<Image acquisition sequence>
The image forming sequence of this image recording / reading system basically includes the process of irradiating recording light (for example, X-rays) while applying a high voltage and accumulating latent image charges, and irradiating the reading light after finishing the application of high voltage Then, it consists of a process of reading out the latent image charge. As the reading light L, a method of scanning the line light source 301 in the electrode direction (see FIG. 8) is optimal, but other methods are also possible.

  Furthermore, a process of sufficiently erasing the unread latent image charges can be combined as necessary. This erasing process is performed by irradiating the entire surface of the panel with erasing light. The entire surface may be irradiated at once, or line light or spot light may be scanned over the entire surface, after the reading process, and / or This is performed before the latent image accumulation process. When irradiating the erasing light, erasing efficiency can be increased by combining high voltage application. Further, by performing “pre-exposure” after applying a high voltage and before irradiating the recording light, it is possible to erase a charge (dark current charge) due to a dark current generated when a high voltage is applied.

  Furthermore, it is known that various charges are accumulated on the electrostatic recording medium before irradiation of recording light due to causes other than these. Since these residual signals affect the image information signal to be output next as an afterimage phenomenon, it is desirable to reduce them by correction.

  As a method of correcting the afterimage signal, a method of adding an afterimage reading process to the above-described image recording and reading process is effective. This afterimage recording process is performed by applying a high voltage without irradiating recording light and then reading an “afterimage image” with the reading light. The afterimage signal can be corrected by subtracting it from the signal. The afterimage reading process is performed before or after the image recording reading process. Further, an appropriate erasing process can be combined before or after the afterimage reading process.

(Effects of optical reading radiation detection substrate 500)
Next, functions and effects of the optical reading type radiation detection substrate 500 will be described.

  In the configuration of the present embodiment, one or more sides of the end portion of the upper electrode 518 are disposed outside the radiation detection layer 522, and the end portion does not cover the radiation detection layer 522. Leakage current increased due to the electric field concentration in the gas does not flow to the radiation detection layer 522, and deterioration of the radiation detection layer 522 can be suppressed.

  In the configuration of the present embodiment, the end of the upper electrode 518 is disposed outside the radiation detection layer 522 without forming an insulating material between the end of the upper electrode 518 and the radiation detection layer 522. Therefore, the radiation detection layer 522 is prevented from being deteriorated, so that radiation detection can be performed in the entire region of the radiation detection layer 522, and a useless region in the radiation detection layer 522 where radiation detection cannot be performed is not possible.

  Further, according to the configuration of the present embodiment, the insulating portion 516 on which the end portion of the upper electrode 518 is laminated is disposed between the end portion of the upper electrode 518 and the glass substrate 536, so that the upper electrode 518 Insulation with the lower electrode 520 can be ensured.

  Further, in the configuration of the present embodiment, the height of the laminated surface of the insulating portion 516 where the end portion of the upper electrode 518 is laminated substantially matches the height of the laminated surface of the radiation detection layer 522 where the upper electrode 518 is laminated. Therefore, a bending point is difficult to be formed in the upper electrode 518 at the boundary between the radiation detection layer 522 and the insulating portion 516, so that electric field concentration is unlikely to occur and deterioration of the radiation detection layer 522 can be suppressed.

(Comparative test between the radiation detection substrate 500 according to the present embodiment and the radiation detector 600 according to the comparative example)
A comparative test between the radiation detection substrate 500 according to the present embodiment and the radiation detector 600 according to the comparative example was performed.

  As shown in FIG. 9, the radiation detector 600 according to the comparative example has an upper electrode 518 laminated on the radiation detection layer 522, and the end of the upper electrode 518 is located inside the radiation detection layer 522 (the radiation detection layer 522 In the area). Other configurations are the same as those of the radiation detection substrate 500 described above.

  In the radiation detection substrate 500 according to the present embodiment and the radiation detector 600 according to the comparative example, a high voltage is applied to the upper electrode 518, and charge is generated by applying light to the surface of the radiation detection layer 522 during application of the high voltage. A durability test was conducted.

  As a result, in the radiation detector 600 according to the comparative example, a change is recognized in the end image of the upper electrode 518 after about 50,000 times of voltage application, and the end of the radiation detection layer 522 is visually observed after about 70,000 times. It was confirmed that crystallization occurred.

  On the other hand, in the radiation detection substrate 500 according to the present embodiment, no abnormality was observed in both 50,000 times of voltage application and 70,000 times of voltage application.

(Configuration of TFT radiation detector 400)
The present invention can also be applied to the TFT radiation detector 400. Here, a configuration of the TFT radiation detector 400 will be described.

  FIG. 10 is a side sectional view showing a schematic configuration of a TFT type radiation detector 400. 11 and 12 are plan views for explaining the positional relationship between the end portion of the bias electrode 401 and the photoconductive layer 404 in the TFT radiation detector 400. FIG. FIG. 13 shows the configuration of the main part of a TFT radiation detector 400 and shows each part laminated on a glass substrate.

  As shown in FIGS. 10 and 13, the TFT radiation detector 400 according to this embodiment has electromagnetic wave conductivity as a charge conversion layer that generates charges when X-rays as an example of radiation are incident. The photoconductive layer 404 shown is provided. As the photoconductive layer 404, an amorphous material having a high dark resistance, good electromagnetic wave conductivity with respect to X-ray irradiation, and capable of forming a large area film at a low temperature by a vacuum deposition method is preferred.

  For example, an amorphous Se (a-Se) film is used as the amorphous material. A material obtained by doping As, Sb, and Ge into amorphous Se is excellent in thermal stability and is a suitable material for the photoconductive layer 404.

  A plurality of charge collection electrodes 407a are formed under the photoconductive layer 404 as an example of the lower electrode portion. As shown in FIG. 13, the charge collection electrode 407a is connected to the charge storage capacitor 407c and the switch element 407b, respectively. The charge collection electrode 407a is provided on the glass substrate 408.

  On the photoconductive layer 404, a bias electrode 401 is formed as an example of an upper electrode portion for applying a bias voltage to the photoconductive layer 404. The bias electrode 401 is made of, for example, gold (Au).

  Here, as shown in FIGS. 10, 11, and 12, one or more sides of the end portion of the bias electrode 401 are disposed outside the photoconductive layer 404. That is, the end portion of the bias electrode 401 is configured such that at least one of the sides on the four sides around the bias electrode 401 is disposed outside the photoconductive layer 404.

  In the configuration of this embodiment, the side 401A on one side and the side 401B facing the side 401A are arranged outside the photoconductive layer 404.

  In the case where there is a portion protruding from the bias electrode 401 as in an extended electrode portion 431 described later, only the side 431A of the protruding portion is not arranged outside the photoconductive layer 404. 12, the side 431 A of the protruding portion and the side 401 B of the bias electrode 401 are arranged outside the photoconductive layer 404, so that the end of the bias electrode 401 is located outside the photoconductive layer 404. Be placed.

  As shown in FIG. 10, an insulating portion 456 on which the end portion of the bias electrode 401 is stacked is provided between the end portion of the bias electrode 401 and the glass substrate 408.

  The insulating portion 456 is formed such that the laminated surface on which the end portion of the bias electrode 401 is laminated is along the extension line of the laminated surface of the photoconductive layer 404 on which the bias electrode 401 is laminated. The height of the laminated surface of the insulating portion 456 on which is stacked substantially matches the height of the laminated surface of the photoconductive layer 404 on which the bias electrode 401 is laminated.

  Thereby, the laminated surface of the insulating portion 456 is formed on substantially the same plane as the laminated surface of the photoconductive layer 404, and a bending point is formed in the bias electrode 401 at the boundary between the photoconductive layer 404 and the insulating portion 456. It becomes difficult. In addition, the insulating portion 456 is formed of, for example, an insulating resin.

As shown in FIGS. 10 and 13, a hole injection blocking layer 402 is provided as an intermediate layer between the photoconductive layer 404 and the bias electrode 401. Here, the intermediate layer is a layer existing between the bias electrode 401 and the photoconductive layer 404, and may also serve as a charge injection blocking layer (including charge accumulation and diode formation). Although a resistance layer or an insulating layer may be used as the charge injection blocking layer, it is preferably a hole injection blocking layer that blocks hole injection while being a conductor for electrons, or for holes. For example, an electron injection blocking layer that blocks the injection of electrons while being a conductor is used. As the hole injection blocking layer, CeO ₂ , ZnS, Sb ₂ S ₃ can be used. Of these, ZnS is desirable because it can be formed at a low temperature. Examples of the electron injection blocking layer include Sb ₂ S ₃ , CdS, Te doped Se, CdTe, organic compounds, and the like. Note that Sb ₂ S ₃ becomes both a hole injection blocking layer and an electron injection blocking layer depending on the thickness provided. In this embodiment, since the bias electrode is a positive electrode, a hole injection blocking layer 402 is provided as an intermediate layer. Further, an electron injection blocking layer 406 is provided between the photoconductive layer 404 and the charge collection electrode 407a as shown in FIG.

Further, between the hole injection blocking layer 402 and the photoconductive layer 404 and between the electron injection blocking layer 406 and the photoconductive layer 404 as shown in FIG. Is provided. The crystallization preventing layer 403, 405 GeSe, can be used and _{GeSe 2, Sb 2 Se 3,} a-As 2 Se 3, Se-As, Se-Ge, a Se-Sb-based compounds.

  Note that an active matrix layer 407 is configured by the charge collection electrode 407a, the switch element 407b, and the charge storage capacitor 407c, and an active matrix substrate 450 is configured by the glass substrate 408 and the active matrix layer 407.

  FIG. 14 is a cross-sectional view showing the structure of one pixel unit of the radiation detector 400, and FIG. 15 is a plan view thereof. The size of one pixel shown in FIGS. 14 and 15 is about 0.1 mm × 0.1 mm to 0.3 mm × 0.3 mm, and this pixel is arranged in a matrix of about 500 × 500 to 3000 × 3000 pixels in the radiation detector as a whole. Has been.

  As shown in FIG. 14, the active matrix substrate 450 includes a glass substrate 408, a gate electrode 411, a charge storage capacitor electrode (hereinafter referred to as Cs electrode) 418, a gate insulating film 413, a drain electrode 412, a channel layer 415, a contact electrode. 416, a source electrode 410, an insulating protective film 417, an interlayer insulating film 420, and a charge collection electrode 407a.

  The gate electrode 411, the gate insulating film 413, the source electrode 410, the drain electrode 412, the channel layer 415, the contact electrode 416, and the like constitute a switch element 407b made of a thin film transistor (TFT), and a Cs electrode 418. Further, a charge storage capacitor 407c is configured by the gate insulating film 413, the drain electrode 412 and the like.

  The glass substrate 408 is a support substrate. As the glass substrate 408, for example, an alkali-free glass substrate (for example, # 1737 manufactured by Corning) can be used. As shown in FIG. 15, the gate electrode 411 and the source electrode 410 are electrode wirings arranged in a lattice pattern, and a switch element 407b made of a thin film transistor is formed at the intersection.

  The source / drain of the switch element 407b is connected to the source electrode 410 and the drain electrode 412 respectively. The source electrode 410 includes a linear portion as a signal line and an extended portion for configuring the switch element 407b, and the drain electrode 412 is provided to connect the switch element 407b and the charge storage capacitor 407c. Yes.

  The gate insulating film 413 is made of SiNx, SiOx, or the like. The gate insulating film 413 is provided so as to cover the gate electrode 411 and the Cs electrode 418, and a part located on the gate electrode 411 acts as a gate insulating film in the switch element 407b, and a part located on the Cs electrode 418. Acts as a dielectric layer in the charge storage capacitor 407c. That is, the charge storage capacitor 407c is formed by an overlapping region of the Cs electrode 418 and the drain electrode 412 formed in the same layer as the gate electrode 411. The gate insulating film 413 is not limited to SiNx or SiOx, and an anodic oxide film obtained by anodizing the gate electrode 411 and the Cs electrode 418 can be used in combination.

  A channel layer (i layer) 415 is a channel portion of the switch element 407 b and is a current path connecting the source electrode 410 and the drain electrode 412. A contact electrode (n + layer) 416 makes contact between the source electrode 410 and the drain electrode 412.

  The insulating protective film 417 is formed over almost the entire surface (substantially the entire region) on the source electrode 410 and the drain electrode 412, that is, on the glass substrate 408. Thus, the drain electrode 412 and the source electrode 410 are protected, and electrical insulation and separation are achieved. Further, the insulating protective film 417 has a contact hole 421 at a predetermined position thereof, that is, at a portion located on a portion of the drain electrode 412 facing the Cs electrode 418.

  The charge collection electrode 407a is made of an amorphous transparent conductive oxide film. The charge collection electrode 407a is formed so as to fill the contact hole 421, and is stacked on the source electrode 410 and the drain electrode 412. The charge collection electrode 407a and the photoconductive layer 404 are electrically connected to each other so that charges generated in the photoconductive layer 404 can be collected by the charge collection electrode 407a.

  Next, the charge collection electrode 407a will be described in detail. The charge collection electrode 407a used in this embodiment is composed of an amorphous transparent conductive oxide film. Examples of amorphous transparent conductive oxide film materials include oxides of indium and tin (ITO: Indium-Tin-Oxide), oxides of indium and zinc (IZO: Indium-Zinc-Oxide), indium and germanium. An oxide (IGO: Indium-Germanium-Oxide) or the like having a basic composition can be used.

  As the charge collection electrode 407a, various metal films and conductive oxide films are used, and transparent conductive oxide films such as ITO (Indium-Tin-Oxide) are often used for the following reasons. When the incident X-ray dose is large in the radiation detector 400, unnecessary charges may be trapped in the semiconductor film (or in the vicinity of the interface between the semiconductor film and an adjacent layer).

  Since such residual charges are stored for a long time or move while taking time, the X-ray detection characteristics are deteriorated during the subsequent image detection, and an afterimage (virtual image) appears. Therefore, in Japanese Patent Laid-Open No. 9-9153 (corresponding US Pat. No. 5,563,421), when residual charges are generated in the photoconductive layer 404, the residual charges are reduced by irradiating light from the outside of the photoconductive layer 404. A method of removing by excitation is disclosed. In this case, in order to irradiate light efficiently from the lower side of the photoconductive layer 404 (on the side of the charge collection electrode 407a), the charge collection electrode 407a needs to be transparent to the irradiation light.

  In addition, for the purpose of increasing the area filling factor (fill factor) of the charge collection electrode 407a or for shielding the switch element 407b, it is desirable to form the charge collection electrode 407a so as to cover the switch element 407b. If the collection electrode 407a is opaque, the switch element 407b cannot be observed after the charge collection electrode 407a is formed.

  For example, when the characteristic inspection of the switch element 407b is performed after the charge collection electrode 407a is formed, if the switch element 407b is covered with the opaque charge collection electrode 407a, the cause of the characteristic failure of the switch element 407b is found. Cannot be observed with an optical microscope. Therefore, it is desirable that the charge collection electrode 407a be transparent so that the switch element 407b can be easily observed even after the charge collection electrode 407a is formed.

  The interlayer insulating film 420 is made of a photosensitive acrylic resin, and serves to electrically isolate the switch element 407b. A contact hole 421 passes through the interlayer insulating film 420, and the charge collection electrode 407 a is connected to the drain electrode 412. The contact hole 421 is formed in a reverse taper shape as shown in FIG.

  A high voltage power supply (not shown) is connected between the bias electrode 401 and the Cs electrode 418. Here, a configuration in which the high voltage line 432 connected to the high voltage power source is electrically connected to the bias electrode 401 will be described.

  As shown in FIGS. 10 and 12, the TFT radiation detector 400 includes an extended electrode portion 431 that extends from the bias electrode 401 to a region without the photoconductive layer 404 on the glass substrate 408. As shown in FIG. 10, the extended electrode portion 431 is pulled down to the glass substrate 408 corresponding to the lowest portion of the radiation detector 400 along the downwardly inclined side surface inclined downward of the photoconductive layer 404.

  Further, as shown in FIGS. 10 and 12, the hole injection blocking layer 402 as an example of the intermediate layer is between the photoconductive layer 404 and the bias electrode 401 and between the extended electrode portion 431 and the glass substrate 408. It is formed over the glass substrate 408 and extends to a region without the photoconductive layer 404.

  The hole injection blocking layer 402 is directly formed on the glass substrate 408, and is also used as a base for bonding the extended electrode portion 431 to the glass substrate 408.

  The extension electrode portion 431 is electrically connected to the high voltage line 432 as a conducting wire for applying a bias voltage from the extension electrode portion 431 to the photoconductive layer 404 via the bias electrode 401 and the region on the glass substrate 408 where the photoconductive layer 404 is absent. Connected. The high voltage line 432 is drawn from the outside and is electrically connected to the distal end portion of the extended electrode portion 431 by the conductive paste 433.

  Next, a configuration for covering the photoconductive layer 404 will be described. As shown in FIG. 10, a cover glass 440 as an example of a cover member that covers the bias electrode 401 is provided above the bias electrode 401.

The glass substrate 408 is provided with a protective member 442 to which the cover glass 440 is bonded.
The protective member 442 surrounds the periphery of the photoconductive layer 404, and is formed in a box shape with the upper and lower portions opened as a whole.

  Further, the protective member 442 has a side wall 442a erected on the outer peripheral portion of the glass substrate 408, and a flange portion 442b protruding from the upper part of the side wall 442a to the upper side of the central portion of the glass substrate 408. It is formed in an L shape.

  The cover glass 440 has an upper surface of the outer peripheral portion bonded to the lower surface (inner wall) of the flange portion 442b and is supported by the protective member 442.

  The joint between the protective member 442 and the cover glass 440 is disposed outside the photoconductive layer 404. That is, the protective member 442 and the cover glass 440 are bonded to each other in a region where the photoconductive layer 404 on the glass substrate 408 is not present, but not above the photoconductive layer 404.

  Note that an insulating member having an insulating property is used for the protective member 442. As the insulating member, for example, polycarbonate, polyethylene terephthalate (PET), polymethyl methacrylate (acrylic), or polyvinyl chloride is used.

  Further, the protective member 442 has a lower opening closed by a glass substrate 408 and an upper opening closed by a cover glass 440, so that a closed space of a predetermined size is formed in the protective member 442. The photoconductive layer 404 is accommodated in the closed space, and the photoconductive layer 404 is covered with the cover glass 440, the glass substrate 408, and the protective member 442.

  In addition, a space surrounded by the cover glass 440, the protection member 442, and the glass substrate 408 is filled with a curable resin 444 as a filling member. As the curable resin 444, for example, a room temperature curable resin such as epoxy or silicon is used.

(Operation principle of TFT radiation detector)
Next, the operation principle of the above-described TFT radiation detector 400 will be described. When the photoconductive layer 404 is irradiated with X-rays, charges (electron-hole pairs) are generated in the photoconductive layer 404. In a state where a voltage is applied between the bias electrode 401 and the Cs electrode 418, that is, in a state where a voltage is applied to the photoconductive layer 404 via the bias electrode 401 and the Cs electrode 418, charge accumulation with the photoconductive layer 404 is performed. Since the capacitor 407c is electrically connected in series, the electrons generated in the photoconductive layer 404 move to the + electrode side, and the holes move to the-electrode side. As a result, the charge storage capacitor Charge is accumulated in 407c.

  The charge stored in the charge storage capacitor 407c can be taken out through the source electrode 410 by turning on the switch element 407b by an input signal to the gate electrode 411. Since the electrode wiring composed of the gate electrode 411 and the source electrode 410, the switch element 407b, and the charge storage capacitor 407c are all provided in a matrix, signals input to the gate electrode 411 are sequentially scanned to obtain the source electrode 410. By detecting the signal from each source electrode 410, X-ray image information can be obtained two-dimensionally.

(Effects of TFT radiation detector)
Next, operational effects of the above-described TFT radiation detector 400 will be described.

  In the configuration of the present embodiment, one or more sides of the end portion of the bias electrode 401 are arranged outside the photoconductive layer 404, and the end portion does not cover the photoconductive layer 404. The leakage current increased due to the electric field concentration at does not flow to the photoconductive layer 404, and deterioration of the photoconductive layer 404 can be suppressed.

  In the configuration of this embodiment, the end of the bias electrode 401 is disposed outside the photoconductive layer 404 without forming an insulating material between the end of the bias electrode 401 and the photoconductive layer 404. Therefore, since the deterioration of the photoconductive layer 404 is suppressed, radiation detection can be performed in the entire region of the photoconductive layer 404, and a useless region where radiation detection cannot be performed in the photoconductive layer 404 cannot be performed.

  Further, according to the configuration of the present embodiment, since the insulating portion 456 on which the end portion of the bias electrode 401 is laminated is disposed between the end portion of the bias electrode 401 and the glass substrate 536, the bias electrode 401 and Insulation with the lower electrode 520 can be ensured.

  In the configuration of the present embodiment, the height of the insulating surface 456 where the end of the bias electrode 401 is stacked substantially matches the height of the stacked surface of the photoconductive layer 404 where the bias electrode 401 is stacked. Therefore, since the bending point is difficult to be formed in the bias electrode 401 at the boundary between the photoconductive layer 404 and the insulating portion 456, electric field concentration hardly occurs and deterioration of the photoconductive layer 404 can be suppressed.

  The present invention is not limited to the above-described embodiment, and various modifications, changes, and improvements can be made.

FIG. 1 is a plan view showing a schematic configuration of a radiation detection substrate as an optical reading type radiation detector. FIG. 2 is a side sectional view showing a schematic configuration of a radiation detection substrate as an optical reading type radiation detector. FIG. 3 is a plan view for explaining the positional relationship between the end of the upper electrode and the radiation detection layer in the optical reading type radiation detection substrate. FIG. 4 is a diagram showing a schematic structure of the radiation detection lower substrate of the optical reading type radiation detection substrate. FIG. 5 is a schematic view schematically showing the configuration of an optical reading type radiation detection substrate. FIG. 6 is a view showing a sealing structure for sealing the upper electrode of the optical reading type radiation detection substrate. FIG. 7 is a block diagram showing a configuration of the charge extraction amplifier and a connection mode between the charge extraction amplifier and an image processing apparatus disposed outside the radiation detection substrate. FIG. 8 is a schematic diagram showing a state when line light is scanned as reading light in an optical reading type radiation detector. FIG. 9 is a side sectional view showing a schematic configuration of a radiation detector according to a comparative example. FIG. 10 is a side sectional view showing a schematic configuration of a TFT type radiation detector. FIG. 11 is a plan view for explaining the positional relationship between the end portion of the bias electrode and the photoconductive layer in the TFT radiation detector. FIG. 12 is a plan view for explaining the positional relationship between the end portion of the bias electrode on the side where the extension electrode portion is formed and the photoconductive layer in the TFT type radiation detector. FIG. 13 is a schematic configuration diagram showing a main part of a TFT radiation detector. FIG. 14 is a cross-sectional view showing the structure of one pixel unit of a TFT radiation detector. FIG. 15 is a plan view showing the structure of one pixel unit of a TFT radiation detector.

Explanation of symbols

400 radiation detector
401 Bias electrode (upper electrode)
404 Photoconductive layer (charge conversion layer)
407a Charge collection electrode (lower electrode)
408 Glass substrate (substrate)
456 insulation
500 Radiation detection board (radiation detector)
516 insulation
518 Upper electrode (upper electrode part)
522 Radiation detection layer (charge conversion layer)
520 Lower electrode (lower electrode part)
536 glass substrate

Claims (4)

A charge conversion layer that generates a charge upon incidence of radiation; and
A lower electrode part provided under the charge conversion layer and collecting charges generated by the charge conversion layer;
A substrate provided with the lower electrode part;
An upper electrode portion laminated on the charge conversion layer, wherein one or more sides of the end portion are disposed outside the charge conversion layer, and a bias voltage is applied to the charge conversion layer;
An extension electrode portion that protrudes outward from the charge conversion layer from a part of the one side disposed outside the charge conversion layer and is electrically connected to a conducting wire for applying a bias voltage;
With
The radiation detector according to claim 1, wherein all of the one side other than the part is disposed outside the charge conversion layer at a position closer to the charge conversion layer than a tip of the extension electrode portion .   The radiation detector according to claim 1, further comprising an insulating portion provided between an end portion of the upper electrode portion and the substrate, wherein the end portion of the upper electrode portion is laminated.   The height of the laminated surface of the insulating part on which the end of the upper electrode part is laminated is substantially equal to the height of the laminated surface of the charge conversion layer on which the upper electrode part is laminated. The radiation detector according to claim 2.   The radiation detector according to claim 2, wherein the insulating portion is made of resin.

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