JP2009212162A - Radiation detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress a discharge breakdown at an end of a bias electrode when a radiation detector is repeatedly used. <P>SOLUTION: In an area where wiring 440 is disposed, an outer peripheral end of an upper charge selective transmission layer 402 is disposed inside an outer peripheral end of a bias electrode 440, so that the outer peripheral end of the bias electrode 401 comes in direct contact with a photoconductive layer 404 not through the upper charge selective transmission layer 402. Consequently, charge accumulation at the outer peripheral end of the bias electrode 401 and an increase in electric field intensity resulting therefrom are suppressed to suppress the discharge breakdown at the end of the bias electrode 401. <P>COPYRIGHT: (C)2009,JPO&INPIT

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, a bias electrode is formed on a photoconductive layer made of amorphous selenium or the like, and an insulating material is formed between the photoconductive layer and the edge of the bias electrode. As a result, the electric field concentration on the edge of the bias electrode 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, when the radiation detector is repeatedly used for a long time, a part of the charge induced by repeatedly applying a voltage to the bias electrode is accumulated at the end of the bias electrode, It has been found that the electric field formed by this charge accumulation triggers the discharge breakdown.

  The present invention has been made in consideration of the above facts, and it is an object of the present invention to suppress discharge breakdown at the end of the bias electrode even when the radiation detector is repeatedly used.

  A radiation detector according to claim 1 of the present invention includes a photoconductive layer that generates charges when radiation is incident thereon, and a charge that is provided under the photoconductive layer and collects charges generated by the photoconductive layer. A collector electrode, a substrate provided with the charge collection electrode, a wiring connected to the charge collection electrode and drawn from the charge collection electrode, and laminated on the photoconductive layer, and bias voltage to the photoconductive layer And a charge that is provided between the photoconductive layer and the bias electrode and that transmits charges having a polarity opposite to that of the bias electrode and blocks charges having the same polarity as that of the bias electrode. A selective transmission layer, and an outer peripheral end of the charge selective transmission layer is located inside an outer peripheral end of the bias electrode in a region where the wiring is disposed.

  According to this configuration, a bias voltage is applied to the photoconductive layer by the bias electrode. The photoconductive layer generates charges when radiation is incident thereon. The charge generated by the photoconductive layer is collected by the charge collection electrode.

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

  Here, in the radiation detector configured as described in claim 1, a part of the electric charge induced by applying a voltage to the bias electrode repeatedly for a long time is accumulated at the end of the bias electrode, It has been found that the electric field formed by the charge accumulation triggers the discharge breakdown. This phenomenon is particularly remarkable in the configuration in which the charge selective transmission layer is disposed between the photoconductive layer and the bias electrode as described in claim 1.

  On the other hand, in the configuration of claim 1, the outer peripheral edge of the charge selective transmission layer is located inside the outer peripheral edge of the bias electrode in the region where the wiring is arranged. The outer peripheral edge of the bias electrode is brought into direct contact with the photoconductive layer.

  As a result, charge accumulation at the outer peripheral end of the bias electrode and an increase in electric field strength due to this are suppressed, and discharge breakdown at the end of the bias electrode can be suppressed.

  It should be noted that the discharge breakdown does not occur in the region where the wiring is not arranged immediately below the bias electrode, and the necessity of adopting a configuration in which the outer peripheral edge of the charge selective transmission layer is located inside the outer peripheral edge of the bias electrode is not necessary. Low.

  The radiation detector according to a second aspect of the present invention is characterized in that, in the configuration of the first aspect, the photoconductive layer includes amorphous selenium.

  When the photoconductive layer is configured to contain amorphous selenium as described in claim 2, the photoconductive layer is easily crystallized even in a micro discharge that does not cause destruction. It has been found that this induces the generation of nuclei, and this causes a destructive discharge breakdown.

  On the other hand, in the present invention, the outer peripheral edge of the charge selective transmission layer is positioned inside the outer peripheral edge of the bias electrode in the region where the wiring is arranged, thereby preventing charge accumulation at the outer peripheral edge of the bias electrode. Since the increase in the electric field strength due to this is suppressed, the effect of suppressing the discharge breakdown at the end of the bias electrode is remarkably exhibited.

  A radiation detector according to claim 3 of the present invention is characterized in that, in the configuration of claim 1 or 2, the charge selective transmission layer is made of antimony sulfide.

  According to the third aspect of the present invention, when the charge selective transmission layer is made of antimony sulfide, charges are likely to be accumulated by applying a voltage to the bias electrode repeatedly over a long period of time.

  On the other hand, in the present invention, the outer peripheral edge of the charge selective transmission layer is positioned inside the outer peripheral edge of the bias electrode in the region where the wiring is arranged, thereby preventing charge accumulation at the outer peripheral edge of the bias electrode. Since the increase in the electric field strength due to this is suppressed, the effect of suppressing the discharge breakdown at the end of the bias electrode is remarkably exhibited.

  Since the present invention has the above-described configuration, even when the radiation detector is used repeatedly, the discharge breakdown at the end of the bias electrode can be suppressed.

  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.

  The radiation detector includes a so-called optical reading type radiation detector 500 that reads using a semiconductor material that generates charges by light irradiation, and stores the charges generated by the irradiation of the radiation. 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 TFT radiation detector 400)
First, the configuration of the TFT radiation detector 400 will be described. FIG. 1 is a schematic cross-sectional view showing the overall configuration of a TFT radiation detector 400. FIG. 2 is a diagram showing a main configuration of a TFT radiation detector 400, and shows a glass substrate 408 and each portion laminated on the glass substrate 408. As shown in FIG.

  As shown in FIGS. 1 and 2, the TFT radiation detector 400 according to the present embodiment includes a photoconductive layer 404 that generates charges when X-rays as an example of radiation are incident thereon. As the photoconductive layer 404, an amorphous material having a high dark resistance and good photoconductivity against X-ray irradiation and capable of forming a large area 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 bias electrode 401 for applying a bias voltage to the photoconductive layer 404 is formed on the photoconductive layer 404. For example, gold (Au) or platinum is used for the bias electrode 401 and an extension electrode 431 described later.

  A plurality of charge collection electrodes 407a are formed under the photoconductive layer 404. As shown in FIG. 2, 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.

  An active matrix layer 407 is composed of the charge collection electrode 407a, the switch element 407b, and the charge storage capacitor 407c, and an active matrix substrate 450 is composed of the glass substrate 408 and the active matrix layer 407.

  Between the photoconductive layer 404 and the bias electrode 401, as shown in FIGS. 1 and 2, a charge that transmits charges having the opposite polarity to that of the bias electrode 401 and that blocks charges having the same polarity as that of the bias electrode 401 is transmitted. A selective transmission layer 402 is provided. On the other hand, as shown in FIG. 2, a charge selective transmission layer 406 having a polarity opposite to that of the charge selective transmission layer 402 is preferably provided between the photoconductive layer 404 and the charge collection electrode 407a (hereinafter referred to as charge selective transmission). In order to distinguish between the layer 402 and the charge selective transmission layer 406, the charge selective transmission layer 402 is referred to as an upper charge selective transmission layer 402, and the charge selective transmission layer 406 is referred to as a lower charge selective transmission layer 406).

  When the bias electrode 401 is a positive electrode, the upper charge selective transmission layer 402 is configured by a layer (hole injection blocking layer) that blocks holes while being a conductor for electrons. When 401 is a negative electrode, it is composed of a layer (electron injection blocking layer) that blocks electrons while being a conductor for holes.

  When the upper charge selective transmission layer 402 is a hole injection blocking layer, an electron injection blocking layer is used for the lower charge selective transmission layer 406, and when the upper charge selective transmission layer 402 is an electron injection blocking layer. In the lower charge selective transmission layer 406, a hole injection blocking layer 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.

Further, as shown in FIG. 2, the anti-crystallization layers 403 and 405 are interposed between the upper charge selective transmission layer 402 and the photoconductive layer 404 and between the lower charge selective transmission layer 406 and the photoconductive layer 404, respectively. 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.

  Even when an anti-crystallization layer is formed for the purpose of preventing the crystallization of the photoconductive layer 404, the anti-crystallization layer transmits charges having a polarity opposite to that of the bias electrode 401 and is biased. In the case where it has a function of blocking the transmission of charges having the same polarity as the electrode 401, it is included in the charge selective transmission layer of the present invention.

  3 is a cross-sectional view showing the structure of one pixel unit of the radiation detector 400, and FIG. 4 is a plan view thereof. The size of one pixel shown in FIGS. 3 and 4 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. 3, 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. 4, 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 constituting the switch element 407b, and the drain electrode 412 is provided so as 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).

  Such residual charges are stored in memory for a long time or move while taking time, so that X-ray detection characteristics deteriorate during subsequent image detection, and afterimages (virtual images) appear. 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.

  In the radiation detector 400 according to the present embodiment, the bias electrode 401 and the high voltage line 432 are electrically connected, and a high voltage power supply (not shown) is connected between the bias electrode 401 and the Cs electrode 418. The

  Specifically, the extension electrode 431 is extended from the bias electrode 401 to a region without the photoconductive layer 404 on the glass substrate 408, and the high voltage line 432 is connected to the extension electrode 431, so that The voltage line 432 is electrically connected.

  The photoconductive layer 404 is covered with an insulating member having an insulating property (not shown). As the insulating member, for example, glass, polycarbonate, polyethylene terephthalate (PET), polymethyl methacrylate (acrylic), or polyvinyl chloride is used.

  Furthermore, as shown in FIGS. 1 and 5, the radiation detector 400 according to the present embodiment includes a wiring 440 that is connected to the charge collection electrode 407a and led out from the charge collection electrode 407a.

  The wiring 440 includes a wiring for driving the switch element 407b and is used for reading a pixel signal, and is a wiring that is at or near a ground potential.

  Specifically, the wiring 440 is configured by an address wiring and a charge storage capacitor wiring including a scanning wiring and a signal wiring.

  In the present embodiment, the radiation detector 400 includes a Cs electrode 418 as a charge storage capacitor wiring, a gate electrode 411 as a scanning wiring, and a source electrode 410 and a drain electrode that are extraction electrodes for extracting signals as signal wirings. 412 is provided.

(Positional relationship of the outer peripheral ends of the photoconductive layer 404, the upper charge selective transmission layer 402, and the bias electrode 401)
Here, the positional relationship between the outer peripheral ends of the photoconductive layer 404, the upper charge selective transmission layer 402, and the bias electrode 401 will be described.

  As shown in FIGS. 1 and 5, the photoconductive layer 404 is in a wider area than the area where the charge collection electrode 407a as the image element is disposed in a plan view, that is, as viewed from the direction of the arrow X in FIG. It arrange | positions so that the electric charge collection electrode 407a may be covered.

  Further, the photoconductive layer 404 is installed in a wider area than the bias electrode 401, and the bias electrode 401 is located inside the outer peripheral end of the photoconductive layer 404 at all outer peripheral ends thereof, and creeping discharge does not occur. Are arranged as follows.

  The distance between the outer peripheral end of the photoconductive layer 404 and the outer peripheral end of the bias electrode 401 is preferably 5 times or more the thickness of the photoconductive layer 404 and 10 times or more (see distance C in FIG. 1).

  The upper charge selective transmission layer 402 disposed on the photoconductive layer 404 has an outer peripheral end located inside the outer peripheral end of the bias electrode 401 in a plan view in the region where the wiring 440 is disposed. The outer peripheral end portion of 401 is arranged so as to be in direct contact with the photoconductive layer 404 without passing through the upper charge selective transmission layer 402.

  Here, the area where the wiring 440 is disposed specifically corresponds to two sides (upper and left sides in FIG. 5) of the glass substrate 408 having a square shape, as shown in FIG. To do. On these two sides, the outer peripheral edge of the upper charge selective transmission layer 402 is located inside the outer peripheral edge of the bias electrode 401.

  Further, as shown in FIG. 6, when the wiring 440 is drawn from the charge collection electrode 407a on the two opposing sides (the right side and the left side in FIG. 6) of the glass substrate 408 having a square shape, These two sides are regions where the wirings 440 are arranged, and on these two sides, the outer peripheral edge of the upper charge selective transmission layer 402 is positioned inside the outer peripheral edge of the bias electrode 401.

  As shown in FIG. 7, the radiation detector 400 has a wiring 440 on at least one side (the left side in FIG. 7) of the glass substrate 408 having a rectangular shape, and the wiring 440 is arranged. In such a region, it is only necessary that the outer peripheral edge of the upper charge selective transmission layer 402 is positioned inside the outer peripheral edge of the bias electrode 401. When the wiring 440 is drawn out on the three sides and four sides of the glass substrate 408 having a rectangular shape, the outer peripheral edge of the upper charge selective transmission layer 402 on that side, as in the case of the two sides described above. Is located inside the outer peripheral edge of the bias electrode 401.

  Since the side where the wiring 440 is not disposed does not cause discharge breakdown, it is not necessary to adopt the above-mentioned configuration, and as shown in FIGS. The outer peripheral end of the layer 402 may be located outside the outer peripheral end of the bias electrode 401 pole.

  Further, it is preferable that the outer peripheral edge of the upper charge selective transmission layer 402 is located outside at least twice the thickness of the photoconductive layer 404 from the outer peripheral edge of the charge collecting electrode 407a (see distance A in FIG. 1). .

  Further, the outer peripheral end of the bias electrode 401 needs to be at least equal to or greater than the thickness of the photoconductive layer 404 with respect to the outer peripheral end of the charge collection electrode 407a, and preferably twice or more. Is 5 times or more (see distance B in FIG. 1).

(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.

  As described above, in the radiation detector 400, a voltage is applied to the bias electrode 401, but a part of the charge induced by repeatedly applying the voltage to the bias electrode 401 over a long period of time is applied to the end of the bias electrode 401. Accumulated in the department.

  The electric field formed by this charge accumulation triggers the discharge breakdown. In addition, since the locally formed high electric field is added by the electric field applied by the external electrode, the electric field is further increased and charge injection from the electrode is likely to occur. This is remarkable in a configuration in which the upper charge selective transmission layer 402 is disposed between the photoconductive layer 404 and the bias electrode 401 as in the radiation detector 400.

  The upper charge selective transmission layer 402 typified by antimony sulfide has the property of transmitting photo-induced charges of the opposite polarity to the bias electrode 401 and has little charge accumulation, but when operated continuously for a long time, the upper charge selective transmission layer 402 also gradually increases. Charge accumulation occurs via the charge selective transmission layer 402. As a result, an increase in the frequency of microdischarge in the portion is observed.

  Such progress of deterioration is likely to occur in a device using amorphous Se (a-Se) as the photoconductive layer 404. Even micro discharges that do not cause breakdown may induce crystal nuclei in an amorphous Se (a-Se) layer that is easily crystallized, and this may cause destructive discharge breakdown.

  In this case, providing an insulating layer between the electrodes has an adverse effect because it causes charge accumulation in the portion and an increase in the electric field strength.

  On the other hand, in the configuration of the present embodiment, the outer peripheral edge of the upper charge selective transmission layer 402 is located inside the outer peripheral edge of the bias electrode 401 in the region where the wiring 440 is disposed. Directly contact the photoconductive layer 404 without passing through the upper charge selective transmission layer 402.

  As a result, charge accumulation at the outer peripheral end of the bias electrode 401 and an increase in electric field intensity due to this are suppressed, and discharge breakdown at the end of the bias electrode 401 can be suppressed.

  Leakage in the image area leads to degradation of image quality, but leakage at the end of the bias electrode 401 outside the image area has no effect on the image, and charge in the upper charge selective transmission layer 402 in continuous use. The present embodiment has been made by discovering that accumulation causes discharge breakdown, and that the induced charge flows at the edge without passing through the upper charge selective transmission layer 402 leads to a significant improvement in durability. is there.

(Comparative test)
A comparative test between the radiation detector according to the example and the radiation detector according to the comparative example was performed.

In the radiation detector according to the present embodiment, a photoconductive layer 404 made of amorphous Se (a-Se) is deposited on the active matrix substrate 450 on the active matrix substrate 450 using a deposition mask to a thickness of 200 μm by vapor deposition. Formed. Next, the mask is changed, and in the region where the wiring 440 is disposed, the upper charge selective transmission layer 402 made of Sb ₂ S ₃ is zeroed by vacuum deposition into a region whose outer peripheral edge is 3 mm inside from the photoconductive layer 404. .Installed with a thickness of 3 μm.

  Next, by replacing the mask again, the region where the wiring 440 is disposed is a region that protrudes 1 mm from the outer peripheral edge of the upper charge selective transmission layer 402, and the other region is the upper charge selective transmission layer 402. A radiation detector was manufactured by evaporating a bias electrode 401 made of gold to a thickness of 3000 mm so as to be a region 2 mm inside from the outer peripheral edge of the electrode.

  In the radiation detector of the comparative example, the upper charge selective transmission layer 402 made of antimony sulfide is formed on the photoconductive layer 404 made of amorphous Se (a-Se) by vapor deposition using the same vapor deposition mask. The bias electrode 401 made of gold was formed in a region 2 mm inside the upper charge selective transmission layer 402 (photoconductive layer 404) so that the end and the outer peripheral edge of the upper charge selective transmission layer 402 were the same.

  The radiation detector according to the example and the radiation detector according to the comparative example were set in the durability test apparatus, and the application of a negative bias of 2 kV to the bias electrode with a rectangular wave was repeated until the discharge breakdown.

  In the radiation detector according to the comparative example, the discharge was destroyed at 80,000 times, whereas in the radiation detector according to the example, the radiation detector according to the example passed without being destroyed by the discharge until 350,000 times. It was confirmed that the operation was stable.

(Configuration of optical reading radiation detector)
The present invention can also be applied to an optical reading type radiation detector, and is applied according to the configuration of the radiation detector 400 described above. Here, the optical reading type radiation detector 500 will be described. FIG. 8 is a schematic diagram showing the overall configuration of the radiation detector 500.

  As shown in FIG. 8B, the radiation detector 500 includes an electrode substrate 502, a radiation detection layer 504, and a surface protective layer 506 from the bottom. A TCP (Tape Carrier Package) 508 for signal extraction is connected to the outer periphery. The charges generated in the detection area by the TCP 508 are read, converted into a voltage, and transferred to the reading device 510. The reading device 510 amplifies the signal through an amplifier, performs A / D conversion, and outputs it as image data. A high voltage application wiring 513 for radiation detection is connected at the upper left in FIG. A reading line light source 512 for mechanical scanning and an erasing surface light source 514 for erasing residual charges are provided below the electrode substrate 502.

<Electrode substrate>
Next, the electrode substrate 502 will be described. FIG. 9 is a schematic view of the electrode substrate 502. In this figure, TCP508 is simplified as one channel on the left and one on the left and three on each channel, for a total of 6 channels. As a general example, the number of channels is 266 each (5 channels at both ends are common). The electrode line / space is 45/25 μm, for example. The lower electrodes 516 in the detection area are alternately arranged on the stripe, and the common electrode has a comb structure.

  FIG. 10 shows the cross-sectional structure. The substrate 518 serving as a support member is preferably glass that is transparent and rigid with respect to reading light and erasing light, and more preferably soda lime glass. The thickness is about 0.5 mm to 2.5 mm, and preferably 1.8 mm.

  A color filter layer 520 is formed on the substrate 518. This layer cuts the light having the wavelength of the reading light, but is transparent to the wavelength of the erasing light. For example, when the reading light wavelength is 470 nm and the erasing light wavelength is 630 nm, a photosensitive resist in which a red pigment is dispersed, for example, a red color resist used for an LCD color filter is desirable. For example, the width is 25 μm, the pitch is 50 μm, and the thickness is 1.4 μm.

  A transparent organic insulating layer 522 is formed in order to eliminate the unevenness due to the pattern formation of the color filter layer 520 and make it flat. This layer is preferably transparent to both reading and erasing light. For example, PMMA, novolak resin, polyimide and the like are preferable. The thickness is, for example, 2.0 μm, and a photosensitive resin capable of forming a pattern is desirable. It is desirable that the color filter layer 520 and the organic insulating layer 522 are not formed on the end portion of the surface protective layer 506 and the TCP connection portion 533. This is to ensure adhesion of the surface protective layer 506 and to facilitate repair in the TCP connection process.

  An electrode pattern of the lower electrode 516 is formed on the organic insulating layer 522. The electrode on the color filter layer 520 is called a common B line 516B, and the electrode on the portion without the color filter layer 520 is called a signal S line 516S. The B line 516B is shared outside the radiation detection unit. The width of the B line 516B / S line 516S is, for example, 17 μm / 17 μm, the space between the lines is 8 μm, the pitch is 50 μm, and the thickness is 0.2 μm. The lower electrode 516 is also preferably transparent to reading light and erasing light, and is preferably a transparent electrode such as IZO or ITO. The lower electrode layer preferably has a flat surface, for example, Ra <2 nm, in order to suppress the destruction of the radiation detection layer 504 due to electric field concentration on the surface with fine protrusions. Ra is the centerline average roughness.

  In addition, an insulating layer (hereinafter referred to as an edge cover layer) 524 for protecting the end portion of the lower electrode 516 is provided. When an electric field is applied, electric field concentration occurs at the electrode end, and an electric field higher than that at the center is generated. An edge cover layer 524 is provided to prevent the electrode end of the high electric field from coming into contact with the radiation detection layer 504. The edge cover layer 524 has insulating properties and is preferably as transparent as possible with respect to reading light and erasing light. For example, novolak resin, PMMA, polyimide, or the like is desirable. The thickness and the width covering the electrode end are about 0.8 μm and 4 μm, for example. It is desirable that the space width between the lower electrode layers has the same space width not only in the detection area but also in the extraction portion to which an electric field is applied. When the space width is partially widened, the electric field concentration becomes strong and the deterioration starts from there.

  FIG. 11 shows a detailed pattern of the lower electrode at the boundary between the detection area and the extraction portion. Note that FIG. 11 is an enlarged view of the portion of the chain double-dashed line 11 in FIG.

  It is desirable to increase the width of the extraction line so that the space width is the same. For the same reason, it is desirable to provide the edge cover layer 524 with the same width as the detection area at the electrode end of the extraction portion for the same reason.

  FIG. 12 shows a schematic configuration of the detection area (top view). In the detection area, line light position correction units 532A and 532B and an offset correction unit 534 are provided in addition to the detection unit 530 that detects radiation. The line light position correction unit 532A is provided to correct the positional relationship between the reading line light source 512 and the electrode substrate 502, and corrects the positional deviation, inclination, etc. of the reading line light source 512 from the signal detected at this portion. . The pattern of this part has substantially the same configuration as that of the detection unit 530, and the number of channels is, for example, 6 channels. The offset correction unit 534 detects the background value when there is no radiation irradiation and is used for the image correction acquired by the detection unit 530. The pattern of this part is also substantially the same as that of the detection unit 530, and the left and right TCPs 508 and one block are used to correct the machine difference between the left and right reading devices 510.

  FIG. 13 shows a cross-sectional structure of one end of the electrode substrate 502 (end A shown in FIGS. 8 and 9). The end 504A of the radiation detection layer 504 is preferably inside the end 536A of the organic insulating layer 536. This is because, in the opposite case, the step at the end 536A of the organic insulating layer 536 causes a crack in the radiation detection layer 504.

  For mammography applications, it is necessary to bring the detection area to the edge of the electrode substrate 502. The distance from the end of the electrode substrate 502 to the end of the detection area is, for example, 2.4 mm. Along with this, the end portion A cannot be provided with a spacer for connecting the end portion of the surface protective layer 506, so the end portion of the surface protective layer 506 is connected to the side surface of the glass end portion 518A. For this reason, it is desirable that the end portion of the glass has a chamfering width as small as possible (for example, 0.25 mm or less), and the break end is not chamfered except for the corner portion.

<Bias electrode>
Next, the bias electrode 540 formed on the upper surface of the recording photoconductive layer 542 described later will be described.

  A metal thin film is preferably used as the bias electrode 540. Materials include Au, Ni, Cr, Pt, Ti, Al, Cu, Pd, Ag, Mg, MgAg3% to 20% alloy, Mg-Ag intermetallic compound, MgCu3% to 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, and more preferably 30 nm to 100 nm. For example, when an MgAg 3% to 20% alloy is used, the thickness is preferably 100 nm or more and 400 nm or less.

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

  Next, the radiation detection layer 504 will be described. FIG. 14 is a schematic diagram schematically showing the configuration of the radiation detector 500 including the radiation detection layer 504. As shown in FIG. As shown in FIG. 14, the radiation detection layer 504 includes a recording photoconductive layer 542, a charge storage layer 544, a reading photoconductive layer 546, an electrode interface layer 548, a charge storage layer interface layer 549, and a lower charge selective transmission layer 550. The upper charge selective transmission layer 552 is provided.

<Photoconductive layer for recording>
The recording photoconductive layer 542 is made of a photoconductive material that absorbs electromagnetic waves and generates charges, and includes amorphous Se, 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 are used as a main component.

  When a photoconductive material mainly composed of amorphous Se is used, amorphous Se doped with a small amount of alkali metal such as Li, Na, K, Cs, and Rb between 0.0001 ppm and 10 ppm, or LiF, NaF, KF , CsF, RbF and other fluorides doped in small amounts between 0.01 ppm and 1000 ppm, or Ge, P, As, Sb and other IV and V elements in amounts between 10 ppm and 1% It is possible to use amorphous Se doped with, or amorphous Se doped with a trace amount of halogen elements such as Cl, Br, and I between 1 ppm and 100 ppm.

  In particular, amorphous Se containing about 10 ppm to 200 ppm of As, or about 0.2% to 1% of As and amorphous Se containing about 5 ppm to 100 ppm of Cl, or Na of about 0.0001 ppm to 0.01 ppm. Amorphous Se, amorphous Se containing about 0.0001 ppm to 0.01 ppm Na and 0.1 to 0.5% As, or amorphous Se having a coordination number of 1.95 ± 0.02 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 Organic polymer layers containing photoconductive substance fine particles such as BiI ₃ and GaAs can also be used.

  The thickness of the recording photoconductive layer 542 is preferably 100 μm or more and 2000 μm or less, for example, in the case of a photoconductive material containing amorphous Se as a main component. In use, it is preferably in the range of 500 μm or more and 1200 μm or less.

<Charge storage layer>
The charge storage layer 544 is made of a material having an insulating property against the polar charge to be stored, such as chalcogenide compounds such as As ₂ S ₃ , Sb ₂ S ₃ , ZnS, As ₂ Se ₃ , Sb ₂ Se ₃ , It is composed of organic polymers such as acrylic organic resin, polyimide, BCB, PVA, acrylic, polystyrene, polycarbonate, polyetherimide, and other oxides and fluorides. Furthermore, it is more preferable to be insulative with respect to the charge of the polarity to be accumulated, and to be conductive with respect to the charge with the opposite polarity, and the product of mobility × lifetime is 3 digits depending on the polarity of the charge. It is preferable that there is a difference.

As the charge storage layer 544 using a chalcogenide-based compound, in particular, As ₂ Se ₃ or AsxSe ₁ -x (15 <x <55), As ₂ Se ₃ and halogen elements such as Cl, Br, and I are 500 ppm to Doped to 20000ppm, As ₂ Se ₃ Se substituted to about 50% with Te, As ₂ Se ₃ Se substituted to about 50% with S, or amorphous Se-Te system Te A material doped with 5% to 30% is preferably used. When such a substance containing a chalcogenide element is used, the thickness of the charge storage layer 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 storage layer may be formed by a single film formation, or may be laminated in a plurality of times.

As the charge storage layer 544 using an organic polymer, a compound obtained by doping an organic polymer such as acrylic organic resin, polyimide, BCB, PVA, acrylic, polystyrene, polycarbonate, or polyetherimide with a charge transport agent 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 C ₆₀ (fullerene). The doping amount is set between 0.1% and 50%. When such an organic polymer is used, the thickness of the charge storage layer is not less than 0.1 μm and not more than 1.5 μm.

<Reading photoconductive layer>
The photoconductive layer for reading 546 is composed of a photoconductive material that absorbs electromagnetic waves, particularly visible light, and generates charges, and includes amorphous Se, amorphous Si, crystalline Si, ZnO, ZnS, ZnSe, ZnTe, PbO, CdS, CdSe, It is a compound mainly composed of at least one of CdTe, GaAs, etc., and is composed of a semiconductor material having an energy gap in the range of 0.7 eV to 2.5 eV.

  When a photoconductive material mainly composed of amorphous Se is used, amorphous Se or LiF, NaF, KF, Amorphous Se doped with a small amount of fluoride such as CsF and RbF between 0.01 ppm and 1000 ppm, or a small amount of Group IV and V elements such as Ge, P, As, and Sb between 10 ppm and 1% Doped amorphous Se or amorphous Se doped with a trace amount of halogen elements such as Cl, Br, and I between 1 ppm and 100 ppm can be used. In particular, amorphous Se containing about 10 ppm to 200 ppm of As, or amorphous Se containing about 0.2% to 1% of As and further containing 5 ppm to 100 ppm of Cl, or Na of about 0.0001 ppm to 0.01 ppm was contained. Amorphous Se, amorphous Se containing about 0.0001 ppm to 0.01 ppm Na and 0.1% to 0.5% As, or amorphous Se having a coordination number of 1.95 ± 0.02 is preferably used.

  The thickness of the reading photoconductive layer 546 is preferably about 1 μm to 30 μm as long as the reading photoconductive layer 546 can sufficiently absorb the reading light and the electric field generated by the charges accumulated in the charge accumulation layer can drift.

<Electrode interface layer>
The electrode interface layer 548 includes an upper electrode interface layer 548A laid between the recording photoconductive layer 542 and the bias electrode 540, and a lower electrode interface layer 548B laid between the read photoconductive layer 546 and the lower electrode 516. There is.

As the electrode interface layer 548, for the purpose of preventing crystallization, amorphous Se doped with As in the range of 1% to 20%, or S, Te, P, Sb, Ge in the range of 1% to 10%. Doped amorphous Se, amorphous Se doped with a combination of the above elements and other elements, As ₂ S ₃ or As ₂ Se ₃ having a higher crystallization temperature can be preferably used. Furthermore, in addition to the above doping element for the purpose of preventing charge injection from the electrode layer, in order to prevent hole injection, in particular, alkali metals such as Li, Na, K, Rb, Cs, or LiF, NaF, KF, 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 In2O3 in the range of 10 ppm to 5000 ppm.

  The thickness of the electrode interface layer 548 is preferably about 0.05 μm to 1 μm so as to sufficiently fulfill the above purpose.

<Charge storage layer interface layer>
The charge storage layer interface layer 549 is provided between the charge storage layer 544A and the recording photoconductive layer 542, and between the charge storage layer upper interface layer 549A and the charge storage layer 544 and the reading photoconductive layer 546. There is a lower charge storage layer interface layer 549B.

  As the charge storage layer interface layer 549, for the purpose of suppressing crystallization of hole electron recombination sites, amorphous Se doped with As in a range of 0.1% to 40% is preferable. Further, in addition to the above doping elements, it is also preferable to dope with alkali metals such as Li, Na, K, Rb and Cs or halogen elements such as Cl, I and Br. Further, the thickness of the interface layer is preferably set between 0.5 μm and 50 μm so as to sufficiently fulfill the above purpose.

The lower electrode interface layer 548B, the reading photoconductive layer 546, the charge storage layer 544, the charge storage layer interface layer 549, the recording photoconductive layer 542, and the upper electrode interface layer 548A can be formed by any method. In a vacuum chamber between 10 ⁻³ and 10 ⁻⁷ Torr, the substrate is held between 25 ° C. and 70 ° C., and the boat or crucible containing the above alloys is heated by resistance heating, lamp heating or electron beam. The temperature is raised by, for example, and the alloy or compound is evaporated or sublimated to be laminated on the substrate.

  Further, a mesh or punching metal made of stainless steel, for example, can be installed on the upper part of the boat or crucible, and the amount of vapor deposition molecules and doping elements can be adjusted appropriately. Furthermore, the temperature of the mesh and punching metal can be controlled independently.

When the evaporation temperatures of the alloy and the compound are greatly different, it is also preferable to control the dope concentration by simultaneously heating and individually controlling a plurality of boats or crucibles corresponding to a plurality of vapor deposition sources. For example, As ₂ Se ₃ and amorphous Se and LiF are put in a boat, the As ₂ Se ₃ boat is set to 340 ° C, the amorphous Se boat is set to 240 ° C, and the LiF boat is set to 800 ° C, and the shutter of each boat is opened and closed. This makes it possible to form a layer in which AsF is doped with 5000 ppm of LiF on As10% -doped amorphous Se.

  In the case of an organic polymer layer, it can also be formed by coating using a solvent.

<Lower charge selective transmission layer>
A lower charge selective transmission layer 550 can be laid between the recording photoconductive layer 542 and the charge collection electrode (lower electrode) 516. When the electrode interface layer 548 is present, it is preferably laid between the electrode interface layer 548 and the lower electrode 516. The lower charge selective transmission layer 550 preferably has a rectification characteristic from the viewpoint of reducing dark current and leakage current. When the bias electrode 540 is a positive electrode, the lower charge selective transmission layer 550 is composed of a layer (electron injection blocking layer) that prevents the injection of electrons while being a conductor for holes. In the case of the negative electrode, the lower charge selective transmission layer 550 is configured by a layer that blocks the injection of holes while being a conductor for electrons (a hole injection blocking layer). The resistivity of the lower charge selective transmission layer 550 is preferably 10 ⁸ Ωcm or more, and the film thickness is preferably 0.01 μm to 10 μm.

As the electron injection blocking layer, an inorganic material having a composition such as Sb ₂ S ₃ , SbTe, ZnTe, CdTe, SbS, AsSe, AsS, or an organic polymer can be used. The layer made of an inorganic material is preferably used by adjusting the carrier selectivity by changing the composition from the stoichiometric composition or by using a multi-component composition with two or more kinds of homologous elements. The layer made of an organic polymer may use a polymer hole transport material including a pendant part having a charge transport group such as PVK, or an insulating polymer such as polycarbonate, polystyrene, polyimide, or polycycloolefin. Also, a low molecular hole transport material can be mixed and used. As such a hole transport material, an oxazole derivative, a triphenylmethane derivative, a hydrazone derivative, a triphenylamine derivative, or the like is preferable. Specifically, NPD (N, N′-di (1-naphthyl) -N, N′-diphenyl-1,1′-diphenyl-4,4′-diamine), TPD (N—N′-diphenyl-N, N′-bis (m-tolyl) benzidine), PDA (N, N, N′N′-tetrakis (m-methylphenyl) -1,3-diaminobenzene), m-MTDATA (4,4 ′, 4 ″) -Tris [3-methylphenyl (phenyl) amino] triphenylamine), 2-TNATA (4,4 ′, 4 ″ -tris (N- (2-naphthyl) -N-phenyl-amino) -triphenylamine ), TPAC (1,1-bis [4- {N, N-di (p-tolyl) amino} phenyl] cyclohexane).

The hole injection blocking layer is preferably an inorganic material such as CdS, CeO ₂ , Ta ₂ O ₅ , or SiO, or an organic polymer. As a layer made of an organic polymer, an insulating polymer such as polycarbonate, polystyrene, polyimide, polycycloolefin, and the like can be used by mixing a low molecular electron transport material. As such an electron transport material, trinitrofluorene and a derivative thereof, a diphenoquinone derivative, a bisnaphthylquinone derivative, an oxazole derivative, a triazole derivative, a mixture of carbon clusters such as C ₆₀ (fullerene), C ₇₀ and the like are preferable.

  Specifically, TNF (2,4,7-trinitrofluorene), DMDB (3,3′-dimethyl-5,5′-di-tert-butyl-4,4′-diphenoquinone), PBD (2- (4-biphenyl) ) -5- (4-tert-butylphenyl) -1,3,4-oxadiazole), TAZ (2- (4-tert-butylphenyl) -5- (4-biphenyl) -1,3,4 -Triazole).

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

Note that Sb ₂ S ₃ has a strong property of having many localized levels for capturing electrons, and thus has an electron injection blocking property. However, the interface between the Sb ₂ S ₃ layer and the adjacent a-Se layer serves as an electrical barrier. Therefore, it may be used as a hole injection blocking layer.

  When the lower charge selective transmission layer 550 is laid using an inorganic material, the production method is arbitrary. For example, a vacuum deposition method, a sputtering method, a plasma CVD method, an electron beam deposition method, or the like is preferably used.

  When the lower charge selective transmission layer 550 is laid using an organic polymer, the preparation method is arbitrary, but the material is dissolved in an organic solvent and applied by a known method. For example, a dip method, a spray method, an ink jet method, and the like can be mentioned, and an ink jet method that can easily control the ground contact region is preferably used.

<Upper charge selective transmission layer>
An upper charge selective transmission layer 552 can be laid between the recording photoconductive layer 542 and the bias electrode 540. In the case where the electrode interface layer 548 is present, it is preferably laid between the electrode interface layer 548 and the bias electrode 540. The upper charge selective transmission layer 552 preferably has rectification characteristics from the viewpoint of reducing dark current and leakage current. When the bias electrode 540 is a positive electrode, the upper charge selective transmission layer 522 is formed of a layer (hole injection blocking layer) that prevents holes from being injected while being a conductor for electrons. When 540 is a negative electrode, the upper charge selective transmission layer 522 is formed of a layer (electron injection blocking layer) that blocks electrons while being a conductor for holes. The resistivity of the upper charge selective transmission layer 552 is preferably 10 ⁸ Ωcm or more, and the film thickness is preferably 0.01 μm to 10 μm.

As the electron injection blocking layer, an inorganic material having a composition such as Sb ₂ S ₃ , SbTe, ZnTe, CdTe, SbS, AsSe, AsS, or an organic polymer can be used. The layer made of an inorganic material is preferably used by adjusting the carrier selectivity by changing the composition from the stoichiometric composition or by using a multi-component composition with two or more kinds of homologous elements. The layer made of an organic polymer may use a hole transport material of a polymer including a pendant part having a charge transport group such as PVK, or an insulating polymer such as polycarbonate, polystyrene, polyimide, polycycloolefin, etc. In addition, low molecular weight hole transport materials may be mixed and used at a weight ratio of 5% to 80%. As such a hole transporting material, an oxazole derivative, a triphenylmethane derivative, a hydrazone derivative, a triphenylamine derivative, or the like is used. Specifically, NPD, TPD, PDA, m-MTDATA2-TNATA, and TPAC.

The hole injection blocking layer is preferably an inorganic material such as CdS, CeO ₂ , Ta ₂ O ₅ , or SiO, or an organic polymer. The layer made of an inorganic material is preferably used by adjusting the carrier selectivity by changing the composition from the stoichiometric composition or by using a multi-component composition with two or more kinds of homologous elements. As the layer made of an organic polymer, an insulating polymer such as polycarbonate, polystyrene, polyimide, polycycloolefin, and the like can be used by mixing a low molecular weight electron transport material in a weight ratio of 5% to 80%. As such an electron transport material, trinitrofluorene and a derivative thereof, a diphenoquinone derivative, a bisnaphthylquinone derivative, an oxazole derivative, a triazole derivative, a mixture of carbon clusters such as C ₆₀ (fullerene), C ₇₀ and the like are preferable. Specifically, TNF, DMDB, PBD, and TAZ.

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

Note that Sb ₂ S ₃ has a strong property of having many localized levels for capturing electrons, and thus has an electron injection blocking property. However, the interface between the Sb ₂ S ₃ layer and the adjacent a-Se layer serves as an electrical barrier. Therefore, it may be used as a hole injection blocking layer.

  When the upper charge selective transmission layer 552 is laid using an inorganic material, the production method is arbitrary. For example, a vacuum deposition method, a sputtering method, a plasma CVD method, an electron beam deposition method, or the like is preferably used.

  When the upper charge selective transmission layer 552 is laid using an organic polymer, the preparation method is arbitrary, but the material is dissolved in an organic solvent and applied by a known method. For example, a dip method, a spray method, an ink jet method and the like can be mentioned, and an ink jet method in which the laying area is easily controlled is preferably used.

<Surface protective layer>
The following surface protective layer 506 is laminated on the surface of the radiation detection device.
(1) Polyparaxylylene film 506A for the purpose of improving the durability of the photoconductive layer
(2) Protective film 506B for securing insulation from high bias voltage
In addition, a spacer member 558 for protecting the bias electrode 540 when the polyparaxylylene film 506A is cut and securing the attachment surface of the protective film 506B includes a polyparaxylylene film 506A and a protective film 506B. It is adhered to the surface of the radiation detection device before application. Each of the following features is described.

(1) Polyparaxylylene (parylene) film It is preferable to provide a surface protective layer in order to protect the device comprising the photoconductive layer from the external environment. In particular, the photoconductive layer made of Se can effectively prevent the occurrence of cracks by the close-contact surface protective layer. In order to prevent device deterioration due to harmful gas components from the outside, the surface protective layer 506 needs to have a chemically stable composition with low gas permeability. 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 adhesion and high radiation transmittance, vapor deposition of an 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 polyparaxylene derivative by a CVD method.

  Among these, when the radiation detection device is composed of a material that is weak against heat, it is preferable to form a room temperature curing type epoxy resin and polyparaxylylene by a CVD method, and in particular, a polyparaxylylene derivative is formed by a CVD method. A filming method is preferred. The preferred film thickness is 10 μm or more and 1000 μm or less, and more preferably 20 μm or more and 100 μm or less.

  Since the polyparaxylylene film 506A can be formed at room temperature, an insulating film having a very high step coverage can be obtained without applying thermal stress to the adherend, but it is chemically very stable, so the adherend In general, there are many unfavorable cases. In the part where the polyparaxylylene film 506A is adhered, there is an Au vapor deposition surface and a glass surface. In order to improve the adhesion to the glass surface, coupling is performed as a treatment on the adherend before forming the polyparaxylylene film. Physical and chemical treatments such as an agent, corona discharge, plasma treatment, ozone cleaning, acid treatment, and surface roughening are generally known and can be used.

  In particular, a silane coupling agent or a solution obtained by diluting a silane coupling agent with alcohol or the like if necessary is applied to at least a portion where adhesion to the adherend is to be improved, or after acting as a gas, A method of improving the adhesion to the adherend by forming the len film 506A is preferable.

In addition, after deposition, a protective film, which will be described later, is laminated and bonded over a wider area than the polyparaxylylene film 506A, and further clamped mechanically from above to improve the peeling durability of the polyparaxylylene film 506A. You may plan.
(2) Insulating protective film A high voltage of several kV is applied to the bias electrode 540 in order to form a latent image on the radiation detection device by irradiation. When the bias electrode 540 approaches an external conductor, a discharge is generated and there is a risk that the subject will be electrocuted. In order to prevent discharge from the upper electrode, an insulating protective film 506B is attached to the upper surface of the electrode.

  This insulation protective film 506B needs to have a dielectric breakdown strength exceeding the applied potential, and further needs to be a member that does not interfere with radiation transmission in terms of the function of the radiation detection device. In addition, in order to ensure insulation over a long period of time, it is necessary to ensure adhesion durability to the device.

  Materials that satisfy these functions include PET film, or aluminum laminate film with a resin film such as PET or nylon formed on the aluminum surface. However, it is desirable to use a PET film because grounding treatment is not necessary.

  The voltage applied to this device is used in the range of 2 kV to 10 kV depending on the thickness of the photoconductive layer, but the dielectric breakdown strength of the insulating protective film is required to ensure insulation with a margin even in high humidity environments. Is preferably 10 kV or more. Moreover, this device has a chest wall as a structure peculiar to mammography, and a high voltage electrode exists to the end of the device. To insulate at this part, the insulating protective film is bent 90 ° on the chest wall and pasted. An acrylic adhesive or an epoxy adhesive can be applied to the PET film, but it is desirable to use an adhesive that does not require curing time. As an example of an adhesive, when this PET film is bonded using an acrylic adhesive with a 90 ° peel force and a 10N / 20mm adhesive strength to the glass surface, the thickness of the PET film can be reduced to 30 μm or less. It has been experimentally confirmed that the bending reaction force of the chest wall with respect to the agent can be set sufficiently low and the peeling durability against 90 ° bending can be obtained. However, the dielectric breakdown strength of PET film is about 7.8 kV for a thickness of 25 μm as an example, and a dielectric breakdown strength of 10 kV cannot be secured at a thickness of 30 μm. In order to obtain a dielectric breakdown strength of 10 kV or more with a margin, it is desirable that the PET film thickness is 50 μm or more. To cope with this, it is possible to achieve both a chest wall adhesion and a dielectric breakdown strength by stacking two or more PET films having a thickness of 30 μm or less to a thickness of 50 μm or more.

  In addition, in order to secure the adhesion of the insulating protective film on the chest wall surface, the chest wall section is a glass scribe surface. The edge is chamfered to prevent the occurrence of glass cullet. In a general glass polished surface, dirt such as an oil component that has entered a rough surface cannot be removed, and thus the adhesive strength is lowered. However, with such a structure, the cleaning property is improved and the adhesive strength stability can be secured.

  Note that the chamfering of the glass cut surface edge can be made unnecessary by using a laser scriber as the scribe device.

  In addition, when using a radiation detection device for mammography, in order to suppress the exposure in X-ray imaging, imaging | photography detection with a low dose is desired. In order to detect changes in shadow due to low-dose irradiation, it is desirable that members other than the subject (breast) in the path from the radiation source to the device have an X-ray transmittance of 98% or higher, so that a clear image can be obtained. can get. When the PET film is bonded with an acrylic pressure-sensitive adhesive, the X-ray transmittance can be secured by making the total thickness of the PET film and the acrylic pressure-sensitive adhesive 160 μm or less.

  Considering the above dielectric breakdown strength, chest wall adhesion durability, and X-ray transmission, it is necessary to satisfy the PET film thickness of 30 μm or less and the total thickness of PET film and acrylic adhesive material of 160 μm or less.

As an example, FIG. 15 shows a cross-sectional structure diagram of the chest wall portion of the radiation detector 500. Note that the present invention is not limited to this. It is possible to apply a configuration in which two adhesive PET films with a PET film thickness of 29 μm and an acrylic adhesive thickness of 30 μm are stacked and pasted to a total thickness of 118 μm.
(3) Spacer member On the outer periphery of the photoconductive layer region of the device, there is an electrode pattern for signal extraction and a terminal portion for high voltage application. In order to expose these electrode surfaces during polyparaxylene (parylene) film deposition It is necessary to perform masking. When this masking material is peeled off after vapor deposition, it is necessary to cut the polyparaxylene (parylene) film around the masking tape edge, but it is difficult to cut only the film without damaging the electrode surface. Therefore, a structure is adopted in which spacer members are bonded along the three sides excluding the chest wall on the outer periphery of the amorphous Se deposition region. The spacer material needs to have a certain degree of hardness in order to cut the polyparaxylylene (parylene) film on its upper surface, and glass, PET film, etc. are applicable. In addition, an acrylic pressure-sensitive adhesive, a two-component mixed epoxy adhesive, a UV curable adhesive, or the like can be applied to these adhesions.

  As a measure to prevent peeling of the end of the polyparaxylylene (parylene) film cut on such a spacer, the polyparaxylylene (parylene) film after the cut is wider than the vapor deposition range and within the range of the spacer member. On the other hand, end portions can be protected by adhering the above-described insulating protective film.

The spacer member can be realized by bonding three rectangular members, or by bonding three members that are integrated in a U shape. A spacer integrated with a U-shape is a more desirable shape because there is a concern of intrusion of polyparaxylylene or a decrease in the accuracy of spacer attachment. 16 and 17 show the sealing structure of the radiation detector 500. FIG. Note that the present invention is not limited to this.
(4) Other Features As shown in FIG. 18, the structure of the high voltage application terminal to which the high voltage application wiring 513 and the bias electrode 540 are connected is such that a plate-like terminal 560 is connected to the bias electrode terminal 540A on the device surface as a conductive adhesive. In this structure, the entire upper part is covered with a resin cover 564.

The resin cover 564 is formed of a highly insulating resin member (Zylon 300V or the like), and its minimum thickness is a thickness that can ensure a dielectric breakdown voltage. In the case of XYLON 300V, a minimum thickness of 0.9mm ensures a breakdown voltage of 22kV or higher. In addition, the resin cover 564 has a two-part structure, the Au electrode side cover is made of silicone adhesive 566 to ensure insulation in high-humidity environments and the accuracy of the cover attachment position, and the other has a high-voltage application cable 568. The double-sided adhesive tape 570 is used in consideration of workability when bending and attaching in a right angle direction.
<Preferred layer structure of radiation detector 500>
A preferred layer configuration of the radiation detector 500 according to the present embodiment will be described. Note that the present invention is not limited to the layer configuration described below.

<Configuration 1>
On the electrode substrate 502 as shown in FIGS. 8 to 13, layers were formed in the following order.
Lower charge selective transmission layer 550: CeO ₂ , thickness 20 nm
Lower electrode interface layer 548B: As 10% doped amorphous Se: LiF 500 ppm doped, thickness 0.1 μm
Photoconductive layer for reading 546: As40ppm doped amorphous Se, thickness 7μm
Charge storage layer lower interface layer 549B: None Charge storage layer 544: As ₂ Se ₃ , thickness 1 μm
Charge storage layer upper interface layer 549A: None Recording photoconductive layer 542: Na0.001 ppm doped amorphous Se, thickness 200 μm
Upper electrode interface layer 548A: As10% doped amorphous Se, thickness 0.2 μm
Upper charge selective transmission layer 552: Sb ₂ S ₃ , thickness 0.5 μm
Bias electrode 540: Au, thickness 70nm
<Configuration 2>
On the electrode substrate 502 as shown in FIGS. 8 to 13, layers were formed in the following order.
Lower charge selective transmission layer 550: None Lower electrode interface layer 548B: As3% doped amorphous Se, thickness 0.15 μm
Photoconductive layer for reading 546: As40ppm doped amorphous Se, thickness 15 μm
Charge storage layer lower interface layer 549B: None Charge storage layer 544: As ₂ Se ₃ , thickness 2 μm
Charge storage layer upper interface layer 549A: None Recording photoconductive layer 542: Na 0.001 ppm doped amorphous Se, thickness 180 μm
Upper electrode interface layer 548A: As10% doped amorphous Se, thickness 0.1 μm
Upper charge selective transmission layer 552: Sb ₂ S ₃ , thickness 0.2 μm
Bias electrode 540: Au, thickness 150 nm
<Configuration 3>
On the electrode substrate 502 as shown in FIGS. 8 to 13, layers were formed in the following order.
Lower charge selective transmission layer 550: CeO ₂ , thickness 30 nm
Lower electrode interface layer 548B: As6% doped amorphous Se, thickness 0.25 μm
Photoconductive layer for reading 546: As40ppm doped amorphous Se, thickness 10 μm
Charge storage layer lower interface layer 549B: None Charge storage layer 544: As ₂ Se ₃ , thickness 0.6 μm
Charge storage layer upper interface layer 549A: None Recording photoconductive layer 542: Na0.001 ppm doped amorphous Se, thickness 230 μm
Upper electrode interface layer 548A: As10% doped amorphous Se, thickness 0.3 μm
Upper charge selective transmission layer 552: Sb ₂ S ₃ , thickness 0.3 μm
Bias electrode 540: Au, thickness 100 nm
<Configuration 4>
On the electrode substrate 502 as shown in FIGS. 8 to 13, layers were formed in the following order.
Lower charge selective transmission layer 550: None Lower electrode interface layer 548B: As10% doped amorphous Se, thickness 0.15 μm
Photoconductive layer for reading 546: As40ppm doped amorphous Se, 14 μm thick
Charge storage layer lower interface layer 549B: As3% to 15% graded doped amorphous Se, thickness 0.5 μm
Charge storage layer 544: As ₂ Se ₃ , thickness 1.15 μm
Charge storage layer upper interface layer 549A: None Recording photoconductive layer 542: Na 0.001 ppm doped amorphous Se, thickness 150 μm
Upper electrode interface layer 548A: As4.5% doped amorphous Se, thickness 0.56 μm
Upper charge selective transmission layer 552: Sb _43.5 S _56.5 , thickness 0.4 μm
Bias electrode 540: Au, thickness 70nm
<Configuration 5>
On the electrode substrate 502 as shown in FIGS. 8 to 13, layers were formed in the following order.
Lower charge selective transmission layer 550: None Lower electrode interface layer 548B: As5% doped amorphous Se, thickness 0.3 μm
Photoconductive layer for reading 546: As40ppm doped amorphous Se, thickness 19 μm
Lower charge storage interface layer 549B: No charge storage layer 544: As ₂ Se ₃ , thickness 1 μm
Charge accumulation upper interface layer 549A: As3% doped amorphous Se, thickness 0.5μm
Photoconductive layer 542 for recording: Na 0.001 ppm doped amorphous Se, thickness 210 μm
Upper electrode interface layer 548A: As3% doped amorphous Se, thickness 0.6 μm
Upper charge selective transmission layer 552: Sb ₄₄ S ₅₆ , thickness 0.5 μm
Bias electrode 540: Au, thickness 70nm
<Image acquisition sequence>
The image forming sequence of this image recording / reading system basically includes a process of irradiating recording light (for example, X-rays) during application of a high voltage and accumulating the generated charge as a latent image, and applying a high voltage. After the completion, the process consists of a process of reading the accumulated charge by irradiating the reading light with the bias electrode 540 and the lower electrode B line 516B grounded (short circuited) from the S line 516S of the lower electrode. As the reading light, the method of scanning the line light in the electrode direction is optimal, but other methods are also possible. As the reading light source, a light source that can be controlled by a control circuit such as a laser or an LED is desirable, and a blue wavelength region is desirable. Furthermore, a process of sufficiently erasing unread 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. As the erasing light source, a fluorescent lamp, a cold cathode fluorescent lamp, an LED, or the like that is used for general illumination is desirable, and a wavelength range is desirably a visible light range. When irradiating 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 the charge (dark current charge) caused by the dark current generated when the 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 only applying a high voltage without irradiating recording light, and then reading the “afterimage” with the reading light. By subtracting from the “image” signal, the afterimage signal can be corrected. 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.

  If the non-operating state of the reading system continues for a certain period of time, such as when the apparatus is started up or between examinations, unevenness (image stability) of images recorded thereafter may deteriorate. In order to maintain image stability, a certain number of idle readings (execution of the image forming sequence without irradiating the recording light) are performed when the apparatus is started up, and every interval of time between examinations. You can perform idle reading. In order to shorten the time for this operation, instead of idle reading, a fixed amount of erasing light irradiation, or a stabilizing sequence appropriately combining erasing light irradiation and high voltage application may be performed. Furthermore, it is also effective for maintaining image stability to perform idle reading or a stabilization sequence for a certain time before imaging (for example, timing when a patient ID is input, etc.).

(Positional relationship of outer peripheral edges of the recording photoconductive layer 542, the upper charge selective transmission layer 552, and the bias electrode 540)
Here, the positional relationship between the outer peripheral ends of the recording photoconductive layer 542 as the photoconductive layer, the upper charge selective transmission layer 552 as the charge selective transmission layer, and the bias electrode 540 as the bias electrode will be described. FIG. 19 is a schematic diagram showing the positional relationship among the recording photoconductive layer 542, the upper charge selective transmission layer 552, and the bias electrode 540. Note that FIG. 19 illustrates the recording photoconductive layer 542 and the upper charge selective transmission layer 552 in the radiation detection layer 504.

  As shown in FIGS. 8 and 19, the recording photoconductive layer 542 is disposed in a wider area than the bias electrode 540 in a plan view, that is, as viewed from the direction of the arrow X in FIG. All of the outer peripheral ends are located inside the outer peripheral end of the recording photoconductive layer 542 so as to prevent creeping discharge.

  The distance between the outer peripheral edge of the recording photoconductive layer 542 and the outer peripheral edge of the bias electrode 540 is 5 times or more the thickness of the recording photoconductive layer 542 and preferably 10 times or more (see distance C in FIG. 19). .

  The upper charge selective transmission layer 552 disposed on the recording photoconductive layer 542 has an outer peripheral end located inside the outer peripheral end of the bias electrode 540 in a plan view in the region where the wiring 580 is disposed. The outer peripheral end of the bias electrode 540 is disposed so as to be in direct contact with the recording photoconductive layer 542 without passing through the upper charge selective transmission layer 552.

  Here, the wiring 580 is a wiring used for reading a pixel signal, and is a wiring that is at or near the ground potential. In the radiation detector 500, the wiring 580 is a lower electrode 516 portion outside the detection area. As shown in FIG. 9, TCP508A (right side in FIG. 9) is seen from the side (viewed from the direction of arrow Y in FIG. 9). In the part of the B line 516B and the S line 516S (the part on the TCP connection part 533 side) other than the part where the S line 516S extending from the TCP508) and the S line 516S extending from the TCP508B (TCP508 on the left side in FIG. 9) overlap. is there.

  Specifically, the region in which the wiring 580 is disposed corresponds to two sides (right and left sides in FIG. 8) of the electrode substrate 502 having a rectangular shape, as shown in FIG. On these two sides, the outer peripheral edge of the upper charge selective transmission layer 552 is located inside the outer peripheral edge of the bias electrode 540.

  The radiation detector 500 has a wiring 580 on at least one side of a rectangular electrode substrate 502. In the region where the wiring 580 is arranged, the outer peripheral edge of the upper charge selective transmission layer 552 is It only needs to be located inside the outer peripheral end of the bias electrode 540. When the wiring 580 is drawn out on the three sides and four sides of the electrode substrate 502 having a rectangular shape, the outer peripheral edge of the upper charge selective transmission layer 552 is formed on that side, as in the case of the two sides. Is located inside the outer peripheral edge of the bias electrode 540.

  The side where the wiring 580 is not disposed does not cause discharge breakdown, so there is no need to adopt the above-described configuration, and the outer peripheral edge of the upper charge selective transmission layer 552 is the outer peripheral edge of the bias electrode 540 pole as usual. It may be located outside.

  Further, it is preferable that the outer peripheral edge of the upper charge selective transmission layer 552 is located on the outer side at least twice the thickness of the recording photoconductive layer 542 from the outer peripheral edge of the detection area (see distance A in FIG. 19). .

  Furthermore, the outer peripheral edge of the bias electrode 540 needs to be at least equal to or greater than the thickness of the recording photoconductive layer 542 with respect to the outer peripheral edge of the detection area, and is preferably twice or more. Is 5 times or more (see distance B in FIG. 19).

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

  As described above, in the radiation detector 500, a voltage is applied to the bias electrode 540, but a part of the charge induced by repeatedly applying the voltage to the bias electrode 540 for a long period is the end of the bias electrode 540. Accumulated in the department.

  The electric field formed by this charge accumulation triggers the discharge breakdown. In addition, since the locally formed high electric field is added by the electric field applied by the external electrode, the electric field is further increased and charge injection from the electrode is likely to occur. This is remarkable in the configuration in which the upper charge selective transmission layer 552 is disposed between the recording photoconductive layer 542 and the bias electrode 540 like the radiation detector 500.

  The upper charge selective transmission layer 552 typified by antimony sulfide has a characteristic of transmitting photo-induced charges having the opposite polarity to the bias electrode 540 and has little charge accumulation. Charge accumulation occurs via the charge selective transmission layer 552. As a result, an increase in the frequency of microdischarge in the portion is observed.

  Such progress of deterioration is likely to occur in a device using amorphous Se (a-Se) as the recording photoconductive layer 542. Even micro discharges that do not cause breakdown may induce crystal nuclei in an amorphous Se (a-Se) layer that is easily crystallized, and this may cause destructive discharge breakdown.

  In this case, providing an insulating layer between the electrodes has an adverse effect because it causes charge accumulation in the portion and an increase in the electric field strength.

  On the other hand, in the configuration of the present embodiment, the outer peripheral edge of the upper charge selective transmission layer 552 is located inside the outer peripheral edge of the bias electrode 540 in the region where the wiring 580 is disposed. Directly contacts the recording photoconductive layer 542 without passing through the upper charge selective transmission layer 552.

  As a result, charge accumulation at the outer peripheral end of the bias electrode 540 and an increase in electric field strength due to this are suppressed, and discharge breakdown at the end of the bias electrode 540 can be suppressed.

  Leakage in the image area leads to degradation of image quality, but leakage at the end of the bias electrode 540 outside the image area has no effect on the image, and the charge in the upper charge selective transmission layer 552 is continuously used in continuous use. This embodiment has been made by discovering that accumulation causes discharge breakdown, and that the induced charge flows at the edge without passing through the upper charge selective transmission layer 552 leads to a significant improvement in durability. is there.

(Comparative test)
A comparative test between the radiation detector according to the example and the radiation detector according to the comparative example was performed.

In the radiation detector according to this example, in accordance with the description in Japanese Patent Application Laid-Open No. 2000-105297, the reading photoconductive layer 546 made of Se on the electrode substrate 502, the charge storage layer 544 made of As ₂ Se ₃ , A recording photoconductive layer 542 made of Se having a thickness of 200 μm, which generates charges by irradiation, and an upper electrode interface layer 548A made of an Se layer containing 10% As were deposited in a thickness of 0.2 μm. Next, by changing the mask, an evaporation material having a thickness of 0.3 μm and a composition of Sb ₂ S ₃ was deposited as the upper charge selective transmission layer 552.

  Here, on the two sides of the device where the wiring 580 is disposed, the end of the antimony sulfide deposition region is 3 mm inside the end of the recording photoconductive layer 542, and the recording on the other two sides Aligned with the end of the photoconductive layer 542. Further, by exchanging the mask, a bias electrode 540 made of gold was deposited thereon to a thickness of 3000 mm. This bias electrode 540 has an end at a position where the end of the antimony sulfide is receded by 2 mm from the end of the antimony sulfide on the other two sides up to a region extending 1 mm from the end of the antimony sulfide. Came to come.

  In the radiation detector according to the comparative example, a comparative detector was prepared in which the outer peripheral edge of the recording photoconductive layer 542 and the outer peripheral edge of the upper charge selective transmission layer 552 were aligned on all sides.

  The durability was examined by repeating the X-ray imaging operation continuously at an applied voltage of −1.6 kV to the bias electrodes of these detectors. The radiation detector according to the comparative example caused discharge at 60,000 times, whereas the radiation detector according to the example did not cause discharge breakdown even after repeated application at 330,000 times.

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

FIG. 1 is a schematic cross-sectional view showing the overall configuration of a TFT radiation detector. FIG. 2 is a schematic configuration diagram showing a main part of a TFT radiation detector. FIG. 3 is a cross-sectional view showing the structure of one pixel unit of a TFT radiation detector. FIG. 4 is a plan view showing the structure of one pixel unit of a TFT radiation detector. FIG. 5 is a schematic plan view showing the overall configuration of a TFT radiation detector. FIG. 6 is a schematic plan view showing a configuration in which wirings are arranged on two opposing sides of a glass substrate in a TFT radiation detector. FIG. 7 is a schematic plan view showing a configuration in which wiring is arranged on one side of a glass substrate in a TFT radiation detector. FIG. 8 is a schematic plan view showing the configuration of an optical reading type radiation detector. FIG. 9 is a schematic view showing the configuration of the electrode substrate. FIG. 10 is a schematic view showing a cross-sectional structure in the detection area of the electrode substrate. FIG. 11 is a schematic diagram showing the boundary between the detection area and the wiring in the electrode substrate. FIG. 12 is a diagram illustrating the configuration of the detection area. FIG. 13 is a schematic diagram illustrating a configuration of an end portion of the electrode substrate. FIG. 14 is a schematic view schematically showing a layer structure of an optical reading type radiation detector. FIG. 15 is a cross-sectional structure diagram of a chest wall portion of an optical reading type radiation detector. FIG. 16 is a schematic perspective view showing a sealing configuration in an optical reading type radiation detector. FIG. 17 is a schematic cross-sectional view showing a sealing configuration in an optical reading type radiation detector. FIG. 18 is a schematic diagram illustrating a configuration of a high voltage application terminal in an optical reading type radiation detector. FIG. 19 is a schematic cross-sectional view showing the overall configuration of an optical reading type radiation detector.

Explanation of symbols

400 radiation detector
401 Bias electrode
402 Upper charge selective transmission layer (charge selective transmission layer)
404 Photoconductive layer (Photoconductive layer)
407a Charge collection electrode
408 glass substrate
440 Wiring
500 Radiation detector
516 Lower electrode (charge collection electrode)
518 substrate
540 Upper electrode (bias electrode)
542 Photoconductive layer for recording (photoconductive layer)
552 Upper charge selective transmission layer (charge selective transmission layer)
580 wiring

Claims (3)

A photoconductive layer that generates an electric charge upon incidence of radiation;
A charge collecting electrode provided under the photoconductive layer and collecting the charge generated by the photoconductive layer;
A substrate provided with the charge collection electrode;
A wiring connected to the charge collection electrode and drawn from the charge collection electrode;
A bias electrode stacked on the photoconductive layer, for applying a bias voltage to the photoconductive layer;
A charge selective transmission layer provided between the photoconductive layer and the bias electrode, which transmits charges having a polarity opposite to that of the bias electrode and blocks charges having the same polarity as the bias electrode;
With
The radiation detector according to claim 1, wherein an outer peripheral end of the charge selective transmission layer is located inside an outer peripheral end of the bias electrode in a region where the wiring is disposed.   The radiation detector according to claim 1, wherein the photoconductive layer includes amorphous selenium.   3. The radiation detector according to claim 1, wherein the charge selective transmission layer is made of antimony sulfide.

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