JP2007150278A - Radiation image taking panel and photoconductive layer forming the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photoconductive layer wherein an increase in image defect due to aging can be suppressed by improved electron transit, and to provide a radiation image taking panel provided with the photoconductive layer. <P>SOLUTION: The photoconductive layer forms a radiation image taking panel to record radiation image information as an electrostatic latent image, and it is formed by selenium alloy containing 0.1 to 1,000 molar ppm of monovalent metal and 0.1 to 4,000 molar ppm of a group V element. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a radiation imaging panel suitable for application to a radiation imaging apparatus such as an X-ray, and more particularly to a photoconductive layer constituting the radiation imaging panel.

  Conventionally, in medical X-ray photography, a photoconductive layer sensitive to X-rays has been used as a photoconductor to reduce the exposure dose received by a subject and improve diagnostic performance, and this photoconductive layer is formed by X-rays. An X-ray imaging panel that reads and records a recorded electrostatic latent image with light or multiple electrodes is known. These are superior in that the resolution is higher than the indirect photographing method using a TV image pickup tube which is a well-known photographing method.

The X-ray imaging panel described above generates charges corresponding to X-ray energy by irradiating the charge generation layer provided in the imaging panel with X-rays, and reads the generated charges as an electrical signal. The photoconductive layer functions as a charge generation layer. Conventionally, materials such as amorphous selenium (a-Se), PbO, PbI ₂ , HgI ₂ , BiI ₃ , and Cd (Zn) Te are used for the photoconductive layer.

  The amorphous selenium can easily cope with an increase in area by using a thin film forming technique such as a vacuum vapor deposition method, but sensitivity tends to deteriorate because it tends to include many structural defects due to amorphous. Therefore, in order to improve performance, it is generally performed to add (doping) an appropriate amount of impurities. For example, Patent Document 1 discloses a photoconductive layer using amorphous selenium doped with alkali metal. Are listed.

On the other hand, Non-Patent Document 1 describes that a group V element such as As is added for the purpose of preventing crystallization and improving electron transport properties. Patent Document 2 describes impurities in selenium.
JP 2003-315464 A JP 2001-284628 A Jounal Vacuum Science and Technology Vol. 9, 387-390 (1972)

  However, since amorphous selenium doped with an alkali metal as described in Patent Document 1 is locally crystallized, if it is used for a photoconductive layer, image defects are likely to occur over time.

  It should be noted that the content of As described in Non-Patent Document 1 is 0.3%, which is a level two orders of magnitude higher than the tens of mol ppm of the present invention, and holes due to the addition of As for preventing crystallization. This is a technique of using several tens of ppm by weight of chlorine for the purpose of improving the deterioration of running performance, and is different from the combined use with the monovalent metal of the present invention.

  The present invention has been made in view of the above circumstances, a photoconductive layer capable of solving the problem of crystallization, improving electron transit, and suppressing an increase in image defects over time, and the photoconductive An object of the present invention is to provide a radiation imaging panel having a layer.

  The photoconductive layer of the present invention is a photoconductive layer constituting a radiation imaging panel that records radiation image information as an electrostatic latent image, and the photoconductive layer contains 0.1 to 1000 mol ppm of monovalent metal and It is formed by using a selenium alloy containing 0.1 to 4000 mol ppm of group V element.

  Monovalent metals are alkali metals (Li, Na, K, Rb, Cs), Tl, Ag, Cu, etc., and group V elements are N, P, As, Sb, Bi. The selenium alloy means an alloy of selenium and other elements other than selenium.

  The monovalent metal is Na, and the content of Na is preferably 0.2 to 300 mol ppm. The group V element is Sb, and the Sb content is 0.15 to 20 mol ppm, or As, and the As content is 1.5 to 4000 mol ppm. Is preferred.

  The radiation imaging panel of the present invention is formed by using a selenium alloy containing 0.1 to 1000 mol ppm of a monovalent metal and 0.1 to 4000 mol ppm of a group V element that records radiation image information as an electrostatic latent image. The photoconductive layer is provided.

  In addition, the content of the monovalent metal in the actual photoconductive layer is about two orders of magnitude lower than the raw materials used, and the content of the V group element in the photoconductive layer is 1000 mol ppm in the V group. If it becomes about, it will drop about half to one digit by the fractional effect. Therefore, the photoconductive layer of the present invention comprises a selenium alloy containing 0.001 to 10 mol ppm of monovalent metal and 0.1 to 2000 mol ppm of group V element.

  Since the photoconductive layer of the present invention is formed using a selenium alloy containing 0.1 to 1000 mol ppm of monovalent metal and 0.1 to 4000 mol ppm of group V element, local crystallization occurs. It is difficult to improve the electron mobility, and it is possible to suppress an increase in image defects due to local crystallization progress over time.

  In particular, the monovalent metal is Na, the Na content is 0.2 to 300 mol ppm, or the V group element is Sb, the Sb content is 0.15 to 20 mol ppm, or the V group element is As, By setting the As content to 1.5 to 4000 mol ppm, it is possible to suppress an increase in image defects accompanying local crystallization progress with time.

  The photoconductive layer of the present invention is formed using a selenium alloy containing 0.1 to 1000 mol ppm of a monovalent metal and 0.1 to 4000 mol ppm of a group V element. When the monovalent metal is less than 0.1 mol ppm, the crystallization cannot be sufficiently suppressed when the group V element is less than 0.1 ppm. On the other hand, when the monovalent metal is 1000 mol ppm or more, it becomes easy to crystallize even if it contains a group V element, or dark current increases. On the other hand, when the group V element is 4000 mol ppm or more, it becomes difficult to form a reproducible photoconductive layer by fractional distillation or the like.

  In order to form a film containing a monovalent metal and a group V element in Se, a selenium alloy obtained by reacting a monovalent metal and a group V element with Se is deposited on a substrate by a known deposition apparatus. Can do.

The radiation imaging panel includes a direct conversion system that directly converts radiation into electric charge and accumulates the charge, and once converts the radiation into light by a scintillator such as CsI: Tl, Gd ₂ O ₂ S: Tb, and the light is a− Although there is an indirect conversion method in which charges are converted into charges by a Si photodiode, the photoconductive layer of the present invention can be used for the former direct conversion method or an indirect conversion type photo-electron conversion layer. In addition to X-rays, γ rays, α rays, etc. can be used as radiation.

  In addition, the photoconductive layer of the present invention is read by a radiation image detector using a semiconductor material that generates a charge by irradiation of light, so-called optical reading method, and also accumulates the charge generated by irradiation of radiation, The accumulated electric charge can be used in a method (hereinafter referred to as a TFT method) in which an electrical switch such as a thin film transistor (TFT) is turned on and off pixel by pixel.

  First, a radiation imaging panel used for the former optical reading method will be described as an example. FIG. 1 is a sectional view showing an embodiment of a radiation imaging panel having a photoconductive layer according to the present invention.

  The radiation imaging panel 10 includes a first conductive layer 1 that is transparent to a recording radiation L1, which will be described later, and a recording radiation that exhibits conductivity when irradiated with the radiation L1 transmitted through the conductive layer 1. The conductive layer 2 and the charge charged on the conductive layer 1 (latent image polar charge; for example, negative charge) act as an insulator and have a charge opposite to the charge (transport polar charge; in the above example) Is positively charged), a charge transport layer 3 that acts as a substantially conductive material, a read photoconductive layer 4 that exhibits conductivity when irradiated with read light L2 for reading, which will be described later, and is transparent to electromagnetic waves L2. The second conductive layer 5 having the above is laminated.

Here, as the conductive layers 1 and 5, for example, a transparent glass plate uniformly coated with a conductive material (nesa film or the like), more specifically, polycrystalline ITO (In ₂ O ₃ : Sn) ), Amorphous ITO (In ₂ O ₃ : Sn), amorphous IZO (In ₂ O ₃ : Zn), ATO (SnO ₂ : Sb), FTO (SnO ₂ : F), AZO (ZnO: Al), GZO (ZnO) : Ga), a thin film of gold, silver, platinum, aluminum, indium or the like, or a coating film of a dispersion of a noble metal (platinum, gold, silver) having a size of about 10 to 1000 nm.

As the charge transport layer 3, the larger the difference between the mobility of the negative charge charged in the conductive layer 1 and the mobility of the positive charge having the opposite polarity, the better, poly N-vinylcarbazole (PVK), N, N Organic compounds such as' -diphenyl-N, N'-bis (3-methylphenyl)-[1,1'-biphenyl] -4,4'-diamine (TPD) and discotic liquid crystals, or TPD polymers ( Polycarbonate, polystyrene, PVK, polyvinyl alcohol) dispersion, As ₂ Se ₃ , Sb ₂ S ₃ , silicon oil, semiconductor materials such as a-Se doped with 10 to 200 ppm of Cl, and polycarbonate are suitable. In particular, an organic compound (PVK, TPD, discotic liquid crystal, etc.) is preferable because it has light insensitivity, and since the dielectric constant is generally small, the capacitance of the charge transport layer 3 and the reading photoconductive layer 4 is reduced. The signal extraction efficiency can be increased.

The reading photoconductive layer 4 includes a-Se doped with 10-200 ppm of a-Se, Cl, a-Se doped with 5-200 ppm of As, Se-Te, Se-As-Te, As ₂ Se ₃ , Metal-free phthalocyanine, metal phthalocyanine, MgPc (Magnesium phtalocyanine), VoPc (phase II of Vanadyl phthalocyanine), CuPc (Cupper phtalocyanine), 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 and the} like, a photoconductive substance whose main component is at least one is preferable. A selenium alloy containing 0.1 to 1000 mol ppm of monovalent metal and 0.1 to 4000 mol ppm of group V element can also be preferably used.

For the recording radiation conductive layer 2, the photoconductive layer of the present invention is used. That is, the photoconductive layer of the present invention is a recording radiation conductive layer. The monovalent metal is preferably added as a chalcogenide compound of a monovalent metal. In the case of Na, it is preferably added as Na ₂ Se, but may be added as Na ₂ S or Na ₂ Te. Na ₂ SeO ₃ , NaOH, NaCl can also be used. As is preferably added as As ₂ Se ₃ , As alone, As doped selenium, Sb is added as Sb ₂ Se ₃ and Sb alone, and Bi is added as Bi ₂ Se ₃ and Bi alone. Each sulfide or telluride may be used.

  An electron injection blocking layer may be provided between the first conductive layer and the recording radiation conductive layer 2. As the electron injection blocking layer, antimony sulfide, N, N′-diphenyl-N, N′-bis (3-methylphenyl)-[1,1′-biphenyl] -4,4′-diamine (TPD) is used. It is done. Further, a hole injection blocking layer may be provided between the reading photoconductive layer 4 and the second conductive layer 5. As the hole injection blocking layer, cerium oxide, antimony sulfide, and zinc sulfide are used.

  Next, a system that uses light to read an electrostatic latent image will be briefly described. FIG. 2 is a schematic configuration diagram of a recording / reading system using the radiation imaging panel 10 (integrated electrostatic latent image recording device and electrostatic latent image reading device). This recording / reading system comprises a radiation imaging panel 10, a recording irradiation means 90, a power source 50, a current detection means 70, a reading exposure means 92, and connection means S1, S2. The panel 10, the power supply 50, the recording irradiation means 90, and the connection means S 1, and the electrostatic latent image reading device portion includes the radiation imaging panel 10, the current detection means 70, and the connection means S 2.

  The conductive layer 1 of the radiation imaging panel 10 is connected to the negative electrode of the power source 50 through the connection means S1, and is also connected to one end of the connection means S2. One end of the connection means S2 is connected to the current detection means 70, and the conductive layer 5 of the radiation imaging panel 10, the positive electrode of the power supply 50, and the other end of the connection means S2 are grounded. The current detection means 70 includes a detection amplifier 70a made of an operational amplifier and a feedback resistor 70b, and constitutes a so-called current-voltage conversion circuit.

  The conductive layer 5 may have a structure described in JP 2001-337171 A or JP 2001-160922 A.

  A subject 9 is disposed on the upper surface of the conductive layer 1, and the subject 9 has a portion 9a that is transparent to the radiation L1 and a blocking portion 9b that is not transparent. The recording irradiation means 90 uniformly exposes the radiation L1 to the subject 9, and the reading exposure means 92 emits the reading light L2 such as laser light, LED, organic EL, and inorganic EL in the direction of the arrow in FIG. It is desirable that the reading light L2 has a linearly converged shape.

  Hereinafter, an electrostatic latent image recording process in the recording / reading system having the above configuration will be described with reference to a charge model (FIG. 3). In FIG. 2, the connection means S2 is opened (not connected to either the ground or current detection means 70), the connection means S1 is turned on, and the DC voltage Ed from the power source 50 is applied between the conductive layer 1 and the conductive layer 5. Then, a negative charge is applied to the conductive layer 1 and a positive charge is applied to the conductive layer 5 from the power source 50 (see FIG. 3A). Thereby, a parallel electric field is formed between the conductive layers 1 and 5 in the radiation imaging panel 10.

  Next, the radiation L1 is uniformly irradiated toward the subject 9 from the recording irradiation means 90. The radiation L1 passes through the transmission part 9a of the subject 9, and further passes through the conductive layer 1. The radiation conductive layer 2 receives the transmitted radiation L1 and exhibits conductivity. This is understood by acting as a variable resistor that shows a variable resistance value according to the dose of radiation L1, and the resistance value is caused by the generation of a charge pair of electrons (negative charge) and holes (positive charge) by radiation L1. The resistance value is large if the dose of the radiation L1 transmitted through the subject 9 is small (see FIG. 3B). The negative charge (−) and the positive charge (+) generated by the radiation L1 are represented by enclosing − or + in circles in the drawing.

  The positive charge generated in the radiation conductive layer 2 moves at high speed in the radiation conductive layer 2 toward the conductive layer 1, and the negative charge is charged in the conductive layer 1 at the interface between the conductive layer 1 and the radiation conductive layer 2. And disappear due to charge recombination (see FIGS. 3C and 3D). On the other hand, the negative charges generated in the radiation conductive layer 2 move in the radiation conductive layer 2 toward the charge transport layer 3. Since the charge transport layer 3 acts as an insulator against a charge having the same polarity as the charge charged on the conductive layer 1 (in this example, a negative charge), the negative charge moving through the radiation conductive layer 2 is radiation. It stops at the interface between the conductive layer 2 and the charge transport layer 3 and accumulates at this interface (see FIGS. 3C and 3D). The amount of charge accumulated is determined by the amount of negative charge generated in the radiation conductive layer 2, that is, the dose of radiation L1 transmitted through the subject 9.

  On the other hand, since the radiation L1 does not pass through the blocking portion 9b of the subject 9, no change occurs in the portion corresponding to the lower portion of the blocking portion 9b of the radiation imaging panel 10 (see FIGS. 3B to 3D). In this way, by exposing the subject 9 to the radiation L1, charges corresponding to the subject image can be accumulated at the interface between the radiation conductive layer 2 and the charge transport layer 3. The subject image based on the accumulated charges is called an electrostatic latent image.

  Next, an electrostatic latent image reading process will be described with reference to a charge model (FIG. 4). The connection means S1 is opened to stop the power supply, and S2 is temporarily connected to the ground side, and the conductive layers 1 and 5 of the radiation imaging panel 10 on which the electrostatic latent image is recorded are charged to the same potential to recharge the charge. After the arrangement (see FIG. 4A), the connection means S2 is connected to the current detection means 70 side.

  When the reading light L2 is scanned and exposed to the conductive layer 5 side of the radiation imaging panel 10 by the reading exposure means 92, the reading light L2 passes through the conductive layer 5, and the photoconductive layer 4 irradiated with the transmitted reading light L2 is Conductivity is exhibited according to scanning exposure. This is dependent on the fact that the radiation conductive layer 2 is exposed to the radiation L1 to generate positive and negative charge pairs, and has a positive and negative charge pair upon receiving the reading light L2. (See FIG. 4B). As in the recording process, the negative charge (−) and the positive charge (+) generated by the reading light L2 are represented by enclosing − or + in circles in the drawing.

  Since the charge transport layer 3 acts as a conductor for the positive charge, the positive charge generated in the photoconductive layer 4 moves rapidly in the charge transport layer 3 so as to be attracted to the accumulated charge, The accumulated charges recombine and disappear at the interface between the radiation conductive layer 2 and the charge transport layer 3 (see FIG. 4C). On the other hand, the negative charge generated in the photoconductive layer 4 is recombined with the positive charge of the conductive layer 5 and disappears (see FIG. 4C). The photoconductive layer 4 is scanned and exposed with a sufficient amount of light by the reading light L2, and all accumulated charges accumulated at the interface between the radiation conductive layer 2 and the charge transport layer 3, that is, the electrostatic latent image, are recombined. Will be extinguished. Thus, the disappearance of the charges accumulated in the radiation imaging panel 10 means that the current I has flowed through the radiation imaging panel 10 due to the movement of charges, and this state is the radiation imaging panel 10. Can be expressed by an equivalent circuit as shown in FIG. 4D, in which the current amount is expressed by a current source whose amount depends on the accumulated charge amount.

  In this way, by detecting the current flowing out from the radiation imaging panel 10 while scanning and exposing the reading light L2, it is possible to sequentially read the accumulated charge amount of each scanning-exposed part (corresponding to the pixel). The electrostatic latent image can be read. The operation of the radiation detection unit is described in Japanese Patent Application Laid-Open No. 2000-105297.

  Next, the latter TFT type radiation imaging panel will be described. This radiation imaging panel has a structure in which a radiation detection unit 100 and an active matrix array substrate (hereinafter referred to as an AMA substrate) 200 are joined as shown in FIG. As shown in FIG. 6, the radiation detection unit 100 is roughly divided into a common electrode 103 for applying a bias voltage and light that generates carriers that are electron-hole pairs in response to the radiation to be detected in order from the radiation incident side. The conductive layer 104 and the detection electrode 107 for collecting carriers are stacked. The upper layer of the common electrode may have a radiation detection unit support.

  The photoconductive layer 104 is the photoconductive layer of the present invention. The common electrode 103 and the detection electrode 107 are made of a conductive material such as ITO (indium tin oxide), Au, or Pt, for example. Depending on the polarity of the bias voltage, a hole injection blocking layer and an electron injection blocking layer may be attached to the common electrode 103 and the detection electrode 107. As the hole injection blocking layer, cerium oxide, antimony sulfide, zinc sulfide, and as the electron injection blocking layer, antimony sulfide, N, N′-diphenyl-N, N′-bis (3-methylphenyl)-[1, 1'-biphenyl] -4,4'-diamine (TPD) is used.

  The configuration of each part of the AMA substrate 200 will be briefly described. As shown in FIG. 7, the AMA substrate 200 is provided with a capacitor 210 as a charge storage capacitor and a TFT 220 as a switching element for each of the radiation detection portions 105 corresponding to pixels. In the support 102, the radiation detection units 105 corresponding to the pixels are two-dimensionally arranged in a matrix configuration of about 1000 to 3000 × 1000 to 3000 in accordance with the required pixels, and the AMA substrate 200 also has pixels. The same number of capacitors 210 and TFTs 220 are two-dimensionally arranged in the same matrix configuration. The electric charge generated in the photoconductive layer is accumulated in the capacitor 210 and becomes an electrostatic latent image corresponding to the optical reading method. In the TFT method, an electrostatic latent image generated by radiation is held in a charge storage capacitor.

  Specific configurations of the capacitor 210 and the TFT 220 in the AMA substrate 200 are as shown in FIG. That is, the AMA substrate support 230 is an insulator, and the connection-side electrode 210b of the capacitor 210 and the TFT 220 are disposed on the ground electrode 210a of the capacitor 210 and the gate electrode 220a of the TFT 220 formed on the surface thereof via the insulating film 240. In addition to the source electrode 220b and the drain electrode 220c being stacked, the outermost surface side is covered with a protective insulating film 250. Further, the connection side electrode 210b and the source electrode 220b are connected to each other and are formed simultaneously. As the insulating film 240 constituting both the capacitor insulating film of the capacitor 210 and the gate insulating film of the TFT 220, for example, a plasma SiN film is used. The AMA substrate 200 is manufactured by using a thin film forming technique or a fine processing technique used for manufacturing a liquid crystal display substrate.

  Subsequently, the joining of the radiation detection unit 100 and the AMA substrate 200 will be described. With the detection electrode 107 and the connection side electrode 210b of the capacitor 210 aligned, both substrates 100 and 200 are made of anisotropic conductive film (ACF) containing conductive particles such as silver particles and having conductivity only in the thickness direction. The substrates 100 and 200 are mechanically combined by heating and pressurizing and bonding together, and at the same time, the detection electrode 107 and the connection side electrode 210b are electrically connected by the interposition conductor 140. .

  Further, the AMA substrate 200 is provided with a read drive circuit 260 and a gate drive circuit 270. As shown in FIG. 7, the read drive circuit 260 is connected to a read wiring (read address line) 280 in the vertical (Y) direction that connects the drain electrodes of the TFTs 220 having the same column, and the gate drive circuit 270 has a row. A horizontal (X) direction read line (gate address line) 290 connecting the gate electrodes of the same TFT 220 is connected. Although not shown, one preamplifier (charge-voltage converter) is connected to one readout wiring 280 in the readout drive circuit 260. As described above, the read driving circuit 260 and the gate driving circuit 270 are connected to the AMA substrate 200. However, an integrated circuit in which the read drive circuit 260 and the gate drive circuit 270 are integrally formed in the AMA substrate 200 is also used.

The radiation detection operation by the radiation imaging apparatus in which the radiation detector 100 and the AMA substrate 200 are joined and combined is described in, for example, Japanese Patent Application Laid-Open No. 11-287862.
Examples of the photoconductive layer constituting the radiation imaging panel of the present invention are shown below.

(Examples 1-10, Comparative Examples 2-6)
A comb-shaped electrode was prepared on a 5 cm square glass substrate provided with an amorphous IZO layer, and a high-purity selenium (6N Super: manufactured by Osaka Asahi Metal Factory) was applied at a crucible temperature of 300 ° C. and a degree of vacuum of 0. A Se film having a film thickness of 10 μm was deposited under the conditions of a substrate temperature of 65 ° C. and a deposition rate of 1 μm / min under the condition of 0001 Pa, and further, As ₂ Se ₃ (6N manufactured by Furuuchi Chemical Co.) was set to a crucible temperature of 460 ° C. 2 μm was laminated. Further, Sb ₂ Se ₃ and Na ₂ Se are added to the high-purity selenium, filled in a quartz tube, evacuated, sealed, reacted at 550 ° C., and an Se alloy having the composition shown in Table 1 is obtained. Produced. A substrate temperature of this selenium alloy was changed to 55 ° C. under a deposition rate of 1 μm / min, and a 200 μm deposited film was laminated. A device was fabricated by sputtering with a thickness of 60 nm using gold as the upper electrode.

(Examples 11 to 20, Comparative Examples 7 to 11)
A device using a selenium alloy having the composition shown in Table 1 was manufactured in the same manner as in Example 1 except that Sb ₂ Se ₃ described in Example 1 was replaced with As ₂ Se ₃ .

(Comparative Example 1)
A device was fabricated in the same manner as described in Example 1 without doping Na and Sb into the high-purity selenium.

(Charge collection amount and image defects)
The charge collection amount was measured using an image reading apparatus described in JP-A-2004-147255. For image defects, using the same reading device, the signal is output as a two-dimensional image under the condition of not irradiating radiation or light, the spots of 10 μm or more are counted, and after that, they are aged for 2 weeks under the condition of 40 ° C. dry. Spots were counted and the ratio of the number of image defects before and after aging was calculated.

(Analysis of device raw materials)
The raw materials were analyzed by glow discharge mass spectrometry (GDMS). As for the element concentration in selenium, the mole fraction relative to 1 mol of selenium was expressed in ppm. In addition, the 6N super selenium of Comparative Example 1 was below the measurement limit, and the Na concentration, Sb concentration, and As concentration were less than 0.03 mol ppm, less than 0.006 mol ppm, and less than 1 mol ppm, respectively. .
The results are shown in Table 1. The charge collection amount and the image defect number ratio are both shown as relative values in Comparative Example 1.

  As is apparent from Table 1, the devices of Examples 1 to 20 were formed using a selenium alloy containing 0.1 to 1000 mol ppm of monovalent metal and 0.1 to 4000 mol ppm of group V element as raw materials. Therefore, compared with the device of Comparative Example 1 that does not contain a monovalent metal and a group V element, the charge collection amount was high, and an increase in image defects over time could be suppressed. In addition, the charge collection amount is higher than that of Comparative Example 2 in which the content of monovalent metal is less than 0.1 mol ppm, and those of Comparative Examples 3, 4, and 7 in which the content of Group V element is less than 0.1 mol ppm. Compared with devices, the increase in image defects over time could be significantly suppressed. From Comparative Examples 5 and 6, when Na is 1000 mol ppm or more, even if the V group element Sb is added, the suppression of the increase in image defects over time does not work.

  A device manufactured using a selenium alloy containing As of 4000 mol ppm or less had a good charge collection amount, and there was no increase in image defects over time.

(Analysis of device deposition film)
In order to measure the element concentration in the deposited film in the device of Comparative Example 1 and the device of Example 2, a silicon wafer was prepared together with a 5 cm square glass substrate provided with an amorphous IZO layer and a comb-shaped electrode. Deposition was performed under the conditions of 1 and Example 6. The total amount of the selenium alloy film on the silicon substrate is dissolved with nitric acid, the amount of selenium in the solution is quantified by ICP emission, the amount of Na is quantified by graphite-type atomic absorption spectroscopy, and the amount of Sb and As is Quantified by ICP-MS method. The concentration of each element with respect to selenium was determined. At this time, in order to remove the influence of Na contamination on the surface layer, washing with water was performed twice to remove Na, K, etc. not incorporated in the selenium layer. Etching of 1 nm or less was performed twice.

  When an inorganic layer or organic layer other than selenium is attached on the selenium layer, peeling due to strain stress when the selenium layer is crystallized to change the volume, peeling due to a difference in expansion rate by cooling, etc. By performing this operation, a selenium layer adhering to the substrate or a single selenium layer can be obtained.

  The Na amount of the device of Comparative Example 1 was less than 0.02 mol ppm, and the Sb amount was less than the detection limit of less than 0.07 mol ppm. On the other hand, the Na amount of the device of Example 2 was 0.03 mol ppm, and the Sb amount was 0.2 mol ppm. It can be seen that Na is difficult to be incorporated into selenium during vapor deposition, and Sb also has a tendency that the concentration of the deposited film tends to be lower than the concentration of the raw material. Further, the Na concentration of the devices of Examples 14 and 20 was 0.03 mol ppm, and the As concentrations of Examples 14 and 20 were 45 ppm and 980 ppm. This shows that the concentration of the deposited film tends to be lower than the concentration of the raw material as the As concentration increases.

  As described above, since the photoconductive layer of the present invention is formed using a selenium alloy containing 0.1 to 1000 mol ppm of a monovalent metal and 0.1 to 4000 mol ppm of a group V element, Crystallization can be prevented, and therefore, the carrier running property can be improved, and an increase in image defects over time can be suppressed.

Sectional drawing which shows one Embodiment of the radiation imaging panel which has the photoconductive layer of this invention Schematic configuration diagram of a recording and reading system using a radiation imaging panel Diagram showing the electrostatic latent image recording process in a recording and reading system using a charge model Diagram showing the electrostatic latent image reading process in the recording and reading system using a charge model Schematic diagram showing the combined state of the radiation detector and the AMA substrate Schematic cross-sectional view showing the pixels of the radiation detector Electrical circuit diagram showing equivalent circuit of AMA substrate

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Conductive layer 2 Recording radiation conductive layer 3 Charge transport layer 4 Reading photoconductive layer 5 Conductive layer 10 Radiation imaging panel

Claims (6)

  A photoconductive layer constituting a radiation imaging panel for recording radiographic image information as an electrostatic latent image, the photoconductive layer comprising 0.1 to 1000 mol ppm of monovalent metal and 0.1 to V group element A photoconductive layer formed using a selenium alloy containing 4000 mol ppm.   2. The photoconductive layer according to claim 1, wherein the monovalent metal is Na and is formed using a selenium alloy having a Na content of 0.2 to 300 mol ppm.   3. The photoconductive layer according to claim 1, wherein the group V element is Sb, and is formed using a selenium alloy having a content of Sb of 0.15 to 20 mol ppm.   3. The photoconductive layer according to claim 1, wherein the group V element is As and is formed using a selenium alloy having an As content of 1.5 to 4000 mol ppm.   A photoconductive layer constituting a radiation imaging panel for recording radiographic image information as an electrostatic latent image, the photoconductive layer comprising 0.001 to 10 mol ppm of monovalent metal and 0.1 to V group element A photoconductive layer comprising a selenium alloy containing 2000 mol ppm.   6. A radiation imaging panel comprising the photoconductive layer according to claim 1, which records radiation image information as an electrostatic latent image.

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