JP2005147889A - Radiation detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To increase detection capacity for a radiation image to reduce an exposure amount onto the human body in image diagnosis, in an indirect type radiation detector. <P>SOLUTION: In this radiation detector having a circuit board part 10 having a plurality of picture elements arranged matrixlikely with photoelectric transfer elements 19 of a picture element unit, and a fluorescence conversion film 1 formed on the circuit board part, the fluorescence conversion film has a reflection preventive film 24 formed of a material having a refractive index satisfying n<SB>P</SB><n<SB>R</SB><n<SB>F</SB>among the refractive index n<SB>P</SB>of a filler, the refractive index n<SB>R</SB>of the reflection preventive film and the the refractive index n<SB>F</SB>of a fluorescent particle. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a radiation detector that detects a radiographic image taken with radiation.

  As a new generation of radiation detectors, an active matrix system that can two-dimensionally arrange a plurality of radiation detection elements for detecting radiation and connect a switching element to each detection element to obtain an output signal selectively A planar detector that takes out the output of a pixel at an arbitrary position has attracted attention. According to the planar detector, an X-ray transmission image or an X-ray image corresponding to the X-ray absorption amount of the object is output as a digital signal. In addition, since the flat detector is a solid detector, it is expected to improve image quality performance and stability.

  Planar detectors for general radiography and chest radiography that collect still images with relatively large doses have already been developed and commercialized.

  In the near future, with higher performance, for example, real-time X-ray movie detection of 30 screens or more per second under fluoroscopic dose will be realized, and commercialization of products applied to fields such as circulatory organs and digestive organs. Expected. For detection of such an X-ray moving image, development of improvement of S / N, real-time processing technology of minute signals, and the like is required.

  There are two types of planar detectors: a direct method and an indirect method.

  The direct method is a method in which an X-ray is directly converted into a signal charge using an X-ray photoconductive material such as a-Se, and the obtained signal charge is stored in a charge storage capacitor.

  In the direct method, a pixel unit, a charge storage unit, a TFT (readout switch), and a Zener diode are provided for each pixel two-dimensionally arranged on the detection surface, and the voltage input to the TFT input side by the Zener diode is There has already been proposed a detector that prevents the breakdown of the TFT by outputting a charge to the charge storage portion when the voltage reaches a predetermined voltage lower than the voltage that destroys (see, for example, Patent Document 1).

  On the other hand, the indirect method converts X-rays into visible light using a scintillator material, converts the converted visible light into signal charges with an a-Si photodiode or CCD, and converts the signal charges into a charge storage capacitor. This is an accumulation method.

  In the indirect system, a plurality of switching elements are provided in a matrix, pixel electrodes are connected to the individual switching elements, and a scanning line and a row are connected to each row of switching elements connected to the pixel electrodes. Proposed is a detector in which a signal line connected to a switching element is disposed and an X-ray charge conversion film made of a photosensitive material containing inorganic semiconductor particles and a carrier transport material containing an organic semiconductor is provided on each pixel electrode. (For example, refer to Patent Document 2).

  In addition, as an example related to Patent Document 2, an example in which an X-ray charge conversion film is formed of a phosphor, a photoreceptor, and a carrier transport material has been proposed (see, for example, Patent Document 3).

There is a radiation detector having an optical fiber plate that guides light converted by a scintillator to a photoelectric conversion element without dispersing the light (for example, see Patent Document 4).
Japanese Patent Laid-Open No. 10-10237 (abstract, FIG. 1, paragraphs [0038] to [0048]). JP 2001-264443 A (Abstract, FIGS. 1 and 4, paragraphs [0033] to [0049]). JP 2002-90460 A (Abstract, FIG. 1, paragraphs [0023] to [0048]). JP 2000-241551 (FIG. 1, paragraph [0022], abstract).

  In an indirect X-ray detector, the amount of output light is reduced due to the effects of optical absorption and scattering until the visible light converted from incident X-rays in the fluorescence conversion layer reaches a photoelectric conversion element such as a photodiode. It is known to do. Note that when the thickness of the fluorescence conversion layer is increased for the purpose of increasing the efficiency of converting incident X-rays into visible light, in actuality, due to the influence of fluorescence absorption until visible light reaches the photoelectric conversion element. There is a problem that the amount of visible light does not always increase.

For example, when using a fluorescent powder film made of a material such as GdO ₂ S: Tb or CaWO ₄ as a phosphor and using a fluorescent conversion film formed in a film shape using a filler made of a transparent resin, When the thickness of the fluorescent conversion film is increased and the amount of the phosphor particle powder per unit area is increased, the absorption of fluorescence in the phosphor itself increases.

  For this reason, a fluorescence conversion film having a certain thickness or more has a problem that the fluorescence output does not necessarily increase in accordance with the increase in the film thickness.

  In order to increase the resolution, it has been proposed to divide the fluorescence conversion film in units of photoelectric conversion elements, and to form a light reflection layer composed of powder particles in the voids formed at that time. However, the light reflecting layer has such a size that the influence of absorption cannot be ignored.

  For this reason, the X-ray dose irradiated to the human body for image diagnosis, that is, the amount of exposure to the human body, is not small.

  An object of the present invention is to increase the radiation image detection capability in an indirect radiation detector and reduce the amount of exposure to the human body during image diagnosis.

  The present invention has been made on the basis of the above-described problems, and a plurality of photoelectric conversion elements are arranged in a plane in electrical connection with readout electrodes wired in a direction orthogonal to the control electrode and the selection electrode. In the radiation detector, a fluorescence conversion film for converting incident radiation into light is laminated so as to cover each photoelectric conversion element. The fluorescence conversion film converts X-rays into fluorescence. The fluorescent particles are transparent to the fluorescence generated by the fluorescent particles, and are filled with a filling material interposed in the space between the fluorescent particles. The refractive index of the fluorescent particles is formed on the surface of the fluorescent particles. And an antireflection film having a refractive index between the refractive index of the filler and the filler.

  Further, according to the present invention, a plurality of photoelectric conversion elements are arranged in a plane so as to be electrically connected to readout electrodes wired in a direction orthogonal to the control electrode and the selection electrode so as to cover the respective photoelectric conversion elements. In addition, in the radiation detector characterized in that a fluorescence conversion film for converting incident radiation into light is laminated, the fluorescence conversion film is generated by fluorescent particles that convert X-rays into fluorescence, and these fluorescent particles. Than the amount of light that is internally reflected by the fluorescent material generated by the fluorescent particles at the interface between the fluorescent material and the filler, And a material having a refractive index set so as to increase the amount of light emitted to the outside of the fluorescent particles.

  Furthermore, the present invention has a plurality of pixels in which photoelectric conversion elements in pixel units are arranged in a matrix, and generates a signal charge corresponding to the intensity of the visible light by photoelectrically converting visible light incident on each pixel. And a photoelectric conversion part having an antireflection material layer having a thickness defined by a predetermined magnification with respect to the wavelength of visible light obtained by converting radiation incident at a predetermined refractive index on the surface, Phosphor particles that convert incident radiation into visible light having a predetermined wavelength, a filler made of a material having a refractive index lower than the refractive index of the phosphor particles and the refractive index of the antireflection material layer, and the phosphor particles And a fluorescent conversion film having a reflective material layer that partitions the mixture of the fillers in units of individual pixels of the photoelectric conversion unit.

  As described above in detail, according to the present invention, the fluorescence generated by the phosphor particles is reflected on the surface of the phosphor particles by the antireflection film on the surface of the phosphor particles used in the fluorescence conversion film of the radiation detector. Absorption is deterred.

  Thereby, the radiation dose irradiated to the human body at the time of image diagnosis, that is, the exposure dose to the human body is reduced.

  In addition, the burden on the radiation generator is reduced.

  Hereinafter, an example of an embodiment of the present invention will be described in detail with reference to the drawings.

  In the present invention, the present invention can be applied to X-rays, γ-rays, and other various radiations. However, in the following embodiment, a case of representative X-rays in radiation will be described as an example. Therefore, by replacing “X-ray” in the embodiment with “radiation”, the present invention can be applied to other radiation targeted by the present invention.

  As shown in FIG. 1A, a radiation flat panel detector 101 that detects an X-ray and outputs an electric signal corresponding to the intensity of the X-ray has a plurality of pixels (photoelectric conversion elements) of m rows × n columns. A matrix photoelectric conversion substrate (hereinafter abbreviated as a circuit board portion) 10 arranged in a matrix, a fluorescence conversion film (radiation-fluorescence conversion layer) 1 deposited on the circuit substrate portion 10 to a predetermined thickness, and Have

  The circuit board 10 includes an insulating holding substrate (insulating substrate) 11 made of, for example, glass, a TFT (thin film transistor) 12 provided on the holding substrate 11, as shown in FIG. 1B, and a storage capacitor. 13 and a photodiode (pixel electrode) 19 described below with reference to FIG.

  The TFT 12 will be described in a state where one pixel is enlarged with reference to FIG. 2. The gate electrode G formed on the insulating substrate 11, the insulating film 14 covering the gate electrode G, the semi-insulating film 15 formed on the insulating film 14, And a source electrode S and a drain electrode D provided on the semi-insulating film 15. The TFT 12 can be formed by a process similar to the manufacturing process of a liquid crystal display panel or the like, and thus detailed description thereof is omitted.

  The storage capacitor 13 includes a lower electrode 16 formed on the insulating substrate 11, an insulating film 14 extending from the gate electrode G to the lower electrode 16, an upper electrode 17 provided on the insulating film 14, and the like.

  The upper electrode 17 is electrically connected to the drain electrode D. The upper electrode 17, the drain electrode D, and the source electrode S are covered with an insulating film 18.

  A photodiode (pixel electrode) 19 which is an a-Si pn diode or PIN diode is formed on the insulating film 18.

  The photodiode 19 is electrically connected to the drain electrode D of the TFT 12 through the through hole 20.

  Above the photodiode 19, incident X-rays (radiation) are converted into light (visible light or near-infrared light, rarely ultraviolet light) having a high efficiency when photoelectrically converted by the photodiode 19. For this purpose, a fluorescence conversion film 1 schematically shown in FIG. 1 is provided.

  The photoelectric conversion layer 1 includes detection particles defined by phosphor particles 21 having a predetermined diameter or volume, a filler (resin) 22 filled around the phosphor particles 21, and photodiodes or pixel electrodes 19. It includes a reflector layer 23 that can be separated independently. The reflector layer 23 is made of a material that is optically transparent to light (visible light, particularly fluorescence) generated by the phosphor particles 21, and is a particle having a smaller particle diameter than the phosphor particles 21. Are filled and formed. Further, the refractive index of the particles used for the reflector layer 23 is preferably higher (larger) than the refractive index of the phosphor particles 21.

The phosphor particles 21 include, for example, a heavy metal oxide as a main component. In this example, the phosphor particles 21 include Gd ₂ O ₂ S: Tb (gadolinium sulfate activated by terbium) or Ya ₂ O ₂ S: Tb (attached by terbium). Particles in which activated yttrium sulfate is used as a powder are used. As the material of the filler provided around the phosphor particles 21, the refractive index n _P as compared with the refractive index n _F of the phosphor particles 21 is significantly different materials used. As an example, the refractive index n _F of the phosphor particles 21 is n _F ≈2.2, and the refractive index n _P of the filler (resin) 22 is n _P ≈1.5.

  Moreover, the outer periphery of the phosphor particles 21 can reduce the occurrence of internal reflection of the fluorescence F in the phosphor particles 21 due to the difference in the refractive index at the interface between the phosphor particles 21 and the filler 22. It is covered with an antireflection film 24. The thickness of the antireflection film 24 is set to 1/4 of the wavelength of the fluorescence F generated in the phosphor particles 21 and an odd multiple thereof, as will be described below.

  In the circuit board unit 10 shown in FIG. 2, the X-ray E incident on the fluorescence conversion film 1 from the side opposite to the circuit board unit 10 is converted into fluorescence F by the fluorescent particles 14 of the fluorescence conversion film 1, and photo Guided by the diode 19.

  The fluorescence F guided to the photodiode 19 is converted into an electric signal having a strength corresponding to the light intensity of the fluorescence F. In addition, since the fluorescent material guided to each photodiode 19 is divided by the photodiode 19 by the reflecting material layer 23, the interference with the adjacent pixel and light leakage (crosstalk) are reduced. .

  FIG. 3 is a schematic diagram showing an equivalent circuit of the circuit board unit 10.

  The TFT 12, the storage capacitor 13, and the photodiode 19 are arranged at positions where the control electrode 31 and the readout electrode 32 arranged in a lattice pattern on the circuit board unit 10 intersect each other. The control electrode 31 is connected to the gate electrode G of the TFT 12, and the readout electrode 32 is connected to the drain electrode D (and the pixel electrode (photodiode) 19) of the TFT 12.

  Therefore, the electric charges generated by the photodiodes 19 of the respective pixels are held in the capacitors 13 connected to the respective gate electrodes G until the gate electrodes G connected thereto are turned on. In this state, when an arbitrary control electrode 31 is turned on for only one line, one line of TFTs 12 connected to the control electrode 31 is turned on, and charges accumulated in the individual capacitors 13 are applied to the readout electrodes 32. Flowing. Thereby, image information corresponding to one specific line is output. Hereinafter, the image information of m rows × n columns is obtained by turning on the control electrodes 31 in a predetermined order.

  Thus, the X-ray detector 101 is configured by configuring the circuit board portion 10 with the control electrodes 31 and the readout electrodes 32 arranged in a matrix and the switching elements (TFTs) 12 provided at positions where they intersect each other. As for the image information of the incident X-rays incident on the light, an electric signal (signal charge) having a magnitude corresponding to the intensity (light quantity) of visible light converted into visible light image information by the fluorescence conversion film 1 is obtained by the photodiode 19. Generated. The signal charge generated by the photodiode 19 is output to the outside through the readout electrode 32. Therefore, a planar image output using the photodiode 19 as a detection pixel can be easily obtained.

  FIG. 4 is a schematic diagram for explaining a process of forming the antireflection film 24 having a predetermined thickness on the phosphor particles 21 of the fluorescence conversion film 1 shown in FIG.

  As shown in FIG. 4A, a tray 202 in which a predetermined amount of phosphor particles 21 is set is set in the vacuum chamber 201, and the inside of the chamber 201 is brought to a predetermined degree of vacuum. In the tray 202, an antireflection film 24 is formed in a substantially uniform thickness over the entire surface of the set phosphor particles 21 by a well-known vibration generating mechanism, that is, a stirring device 203 provided in advance. It can vibrate at a predetermined frequency or rotational frequency.

Next, as shown in FIG. 4B, for example, La ₂ O ₃ is set as a sputtering source 205 at a predetermined position in the chamber 201, and a discharge voltage with a predetermined frequency is supplied from the power supply device 204. As a result, La ₂ O _{3 serving} as an antireflection film is sputtered onto the phosphor particles 21 set on the tray 202.

  Thereafter, the phosphor particles 21 having the antireflection film 24 with a predetermined thickness formed on the surface are formed by sputtering for a predetermined time while vibrating the tray 202 by the stirring device 203.

  FIG. 5 is a schematic diagram for explaining the behavior of X-rays incident on the phosphor 21 in the fluorescence conversion film 1 described above with reference to FIGS. 1 to 3.

For example, when the antireflection film 24 having a thickness of 70 nm is formed on the surface of the phosphor particles 21 by La ₂ O ₃ having a refractive index n _R of n _R ≈1.95, for example, by a sputtering vapor deposition method, the phosphor The internal reflection of the fluorescence F in the particles 21 can be substantially suppressed to “0” compared to the internal reflection in the phosphor particles without an antireflection film, which will be described later with reference to FIG. 6 (FIGS. 5 and 5). 6, the arrow indicates a light trace (propagation) of the fluorescence F, and the number of arrows corresponds to the intensity of the fluorescence F).

  As apparent from FIG. 5, the fluorescence F generated when the incident X-rays E are incident on the phosphor particles 21 provided with the antireflection film 24 having a predetermined thickness on the outer periphery (surface) is the surface of the phosphor particles 21. Or it is radiate | emitted outside the fluorescent substance particle 21 by the refraction in the vicinity. At this time, the degree of internal reflection (the degree of occurrence) generated in the phosphor particles 21 is reduced to a level that can be almost ignored compared to the internal reflection generated in the phosphor particles without an antireflection film, which will be described below with reference to FIG. Is done.

That is, assuming that the incident X-rays incident on the phosphor particles 21 are combined light of two planes orthogonal to each other, the refractive index of the phosphor particles 21 is N ₂ , and the filler 22 around the phosphor particles 21 If the refractive index is N ₁ and a well-known reflectance law is applied, a component parallel to the incident surface including the normal is a “p” component, a component orthogonal to the incident surface is an “s” component, and “i” is When the incident angle of the light ray with respect to the normal line and “i ′” is the emission angle of the light ray with respect to the normal line, the respective reflectances Rp and Rs are:
_{Rp = (N 2 cosi-N} 1 cosi') / (N 2 cosi + N 1 cosi'),
_{Rs = (N 1 cosi-N} 2 cosi') / (N 1 cosi + N 2 cosi')
Indicated by.

Therefore, the total reflection amount R in the phosphor particles 21 is
R = Rp · Rs = {(N ₁ −N ₂ ) / (N ₁ + N ₂ )} ²
As required.

Therefore, the larger the difference between the refractive index n _F of the phosphor particles 21 and the refractive index n _P of the filler 22, the larger the difference is caused at the interface between the phosphor particles 21 and the filler 22, that is, the surface of the phosphor particles 21. The degree of reflection is reduced.

Therefore, for example, when Gd ₂ O ₂ S: Tb is used as the phosphor particles 21, easily available glass (refractive index n _R is n _R ≈1.5 to 1.8) is used for the antireflection film 24. You can also In this case, the coating on the surface of the phosphor particles 21 is easy although the accuracy of the thickness is reduced. However, since the difference from the refractive index of the filler (resin) is expected to be small depending on the material of the glass, when the antireflection film 24 is formed, the refractive index n _P of the filler, the reflection Between the refractive index n _R of the prevention film and the refractive index n _F of the phosphor particles,
n _P <n _R <n _F
It is preferable to be formed of a material having a refractive index satisfying

The material that can be used for the antireflection film 24 is, for example, a material mainly composed of SnO ₂ , PbF ₂ , MgO, In ₂ O ₃ , Nd ₂ O ₃ , HfO ₂ , or Sb ₂ O _3. Is preferred.

Note that these from, in the case of the phosphor refractive index n antireflection film 24 the material is provided by the thickness d ₁ of _R on the surface of the particles 21 having a refractive index n _F, when the λ the wavelength of the fluorescence F From the known phase and amplitude conditions,
N _R = d ₁ (1/4) λ,
N _R = √n _F
Thus, it is explained that the internal reflection in the phosphor particles 21 can be significantly reduced as compared with the case where there is no internal reflection.

Accordingly, the thickness d ₁ of the antireflection film 24 is preferably ¼ of the wavelength λ of the fluorescence F or an odd multiple thereof.

  Further, as the antireflection film 24, an antireflection film having a first refractive index formed to have a thickness of ½ of the wavelength of the spectrum having the highest intensity among the spectra of the fluorescence F generated by the phosphor particles 21. A second antireflective film (usually a low refractive index) formed to a thickness of ¼ of the wavelength of the spectrum having the second highest intensity of the spectrum (usually a high refractive index); Needless to say, a multilayer film or a known multilayer coat (multilayer antireflection film) can be used.

  Instead of the example of forming the antireflection film 24 on the surface of the phosphor particles 21, the resin used for the filler 22 and the material used for the antireflection film 24 are each smaller than the average particle diameter of the phosphor particles 22. The phosphor particles 21 may be filled with an antireflection filler 25 in which the powder has an average particle diameter and the respective particles are mixed at a predetermined ratio.

  FIG. 6 is well known in order to compare the X-rays incident on the phosphor particles provided with the antireflection film of the present invention described above with reference to FIG. 5 and the behavior of the fluorescence generated from the incident X-rays. It is the schematic explaining the behavior of the fluorescence produced | generated from the X-ray which injected into the fluorescent substance particle (without an antireflection film) and the incident X-ray.

  As shown in FIG. 6, incident X-rays E incident on the phosphor particles 1021 are converted into fluorescence F, depending on the difference in refractive index between the phosphor particles 1021 and the resin 1022 filled in the surroundings. Then, reflection and diffusion are repeated on the surface of the phosphor particle 1021 (interface between the phosphor particle 1021 and the resin (filler) 1022), or incident again into the phosphor particle 1021 by the reflector layer 23 that separates the pixels. The

  Accordingly, the incident X-ray E passes through the plurality of resins (fillers) 1022 and the plurality of phosphor particles 1021 before reaching the outside, that is, the photodiode 19 as the fluorescence F. Note that the influence of internal reflection reflected on the inside of the phosphor particles 1021 (inside the phosphor particles 1021) cannot be ignored.

  For example, in FIG. 6, an arrow indicates a light trace (propagation) of the fluorescence F, and if the number of arrows corresponds to the intensity of the fluorescence F, the reflection described above with reference to FIG. In the phosphor particle 21 of the present invention provided with the anti-reflection film 24, the internal reflection is substantially “0”. However, as is apparent from FIG. It is recognized that the internal reflection is performed twice or more in the phosphor particle 1021.

  For this reason, the distance by which the incident X-ray E is propagated in the fluorescence conversion film 1 before reaching the photodiode 19 is several times to several tens of times the thickness of the fluorescence conversion film 1. Reach.

  This indicates that the fluorescence F generated in the fluorescence conversion film 1 is attenuated by the above-described absorption of fluorescence before reaching the photodiode 19.

  That is, even if the thickness of the fluorescence conversion film 1 is increased in order to increase the conversion efficiency for converting incident X-rays into fluorescence, the total amount of fluorescence F propagated to the photodiode 19 is the thickness of the fluorescence conversion film. There is no increase corresponding to the increased amount. On the contrary, it has been reported that the output signal charge is not small due to the influence of absorption by the phosphor particles 1021.

As described above, the outer periphery of the phosphor particles 21 (surface) has a refractive index lower than the refractive index n _F of the phosphor particles 21, formed of a material having a refractive index higher than the refractive index n _P of the filler 22 By covering with the antireflection film 24, absorption of the fluorescence generated inside the phosphor particles 21 and the filler 22 is suppressed, and the amount of fluorescence F that can be taken out is increased.

  As a result, the X-ray dose irradiated to the human body during image diagnosis, that is, the amount of exposure to the human body is reduced.

  The present invention is not limited to the above-described embodiments, and various modifications and changes can be made without departing from the scope of the invention when it is implemented. Moreover, each embodiment may be implemented in combination as appropriate as possible, and in that case, the effect of the combination can be obtained.

  In the above-described embodiment, the X-ray detector in which a plurality of vertical and horizontal pixels are arranged has been described. However, the ratio of the vertical and horizontal pixels is different (for example, when one pixel is one). The present invention is also applicable to an X-ray detector configured in a shape. In this case, the switching element can be implemented without using a TFT.

Schematic which shows an example of the structure of the radiation detector to which embodiment of this invention is applied. Schematic explaining an example of a section of a pixel of a circuit board part used for the radiation detector shown in FIG. FIG. 3 is an equivalent circuit diagram of the radiation detector shown in FIGS. 1 and 2. Schematic explaining the process of forming an antireflection film on the phosphor particles of the fluorescence conversion film of the radiation detector shown in FIGS. Schematic explaining the behavior of X-rays incident on the phosphor in the fluorescence conversion film described with reference to FIGS. In order to compare with the behavior of the fluorescence generated from the incident X-ray described with reference to FIG. 5, an outline explaining the behavior of the fluorescence generated from the X-ray incident on the well-known (without antireflection film) phosphor particles. Figure.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Circuit board, 12 ... TFT (thin film transistor), 13 ... Storage capacitor, 19 ... Photodiode (pixel electrode), 16 ... Circuit layer, 17 ... Holding substrate, 18 ... Fluorescence conversion film, 19 ... TFT circuit board, 21 ... Phosphor particles, 22 ... filler (resin), 23 ... reflector layer, 24 ... antireflection film, 31 ... control electrode, 32 ... readout electrode, 101 ... radiation detector, E ... incident X-ray, F ... fluorescence.

Claims (13)

A plurality of photoelectric conversion elements are arranged in a plane in electrical connection with readout electrodes wired in a direction orthogonal to the control electrode and the selection electrode, and incident radiation is applied so as to cover each photoelectric conversion element. In the radiation detector, wherein a fluorescent conversion film that converts light is laminated,
The fluorescence conversion film includes fluorescent particles that convert X-rays into fluorescence, and a filling material that is transparent to the fluorescence generated by the fluorescent particles and is interposed in the gap between the fluorescent particles, A radiation detector, wherein the surface of the fluorescent particle is coated with an antireflection film having a refractive index between the refractive index of the fluorescent particle and the refractive index of the filler.   The fluorescence conversion film is divided into grids in sections with the photoelectric conversion element as a unit, and optically with respect to the light generated by the fluorescent particles in the gaps between the divided fluorescence conversion films. The radiation detector according to claim 1, wherein the radiation detector is filled with particles made of a transparent material and having a diameter smaller than that of the fluorescent particles.   The fluorescence conversion film is divided into grids in sections with the photoelectric conversion element as a unit, and optically with respect to the light generated by the fluorescent particles in the gaps between the divided fluorescence conversion films. The radiation detector according to claim 1, wherein the radiation detector is filled with particles having a refractive index larger than that of the fluorescent particles. In the fluorescent conversion film, Gd ₂ O ₂ S or Ya ₂ O ₂ S: Tb is used as the phosphor particles, and La ₂ O ₃ , SnO ₂ , PbF ₂ , MgO, In ₂ O ₃ , Nd is used as the antireflection film substance. The radiation detector according to any one of claims 1 to 3, wherein any one of ₂ O ₃ , HfO ₂ , and Sb ₂ O ₃ is a main component.   5. The film thickness of the antireflection film is set to ¼ or several times the wavelength of the light generated by the fluorescent particles. 6. Radiation detector.   6. The radiation detector according to claim 5, wherein the film thickness of the antireflection film is set to an odd multiple of 1/4 of the wavelength of light generated by the fluorescent particles. A plurality of photoelectric conversion elements are arranged in a plane in electrical connection with readout electrodes wired in a direction orthogonal to the control electrode and the selection electrode, and incident radiation is applied so as to cover each photoelectric conversion element. In the radiation detector, wherein a fluorescent conversion film that converts light is laminated,
The fluorescent conversion film includes fluorescent particles that convert X-rays into fluorescent light, a filling material that is transparent to the fluorescence generated by the fluorescent particles and is interposed in a space between the fluorescent particles, and the fluorescent particles And a material having a refractive index that is set such that the amount of light emitted outside the fluorescent particles is larger than the amount of light internally reflected by the fluorescent particles at the interface with the filler. Characteristic radiation detector.   The fluorescence conversion film is divided into grids in sections with the photoelectric conversion element as a unit, and optically with respect to the light generated by the fluorescent particles in the gaps between the divided fluorescence conversion films. The radiation detector according to claim 7, wherein the radiation detector is filled with particles having a diameter smaller than that of the fluorescent particles.   The fluorescence conversion film is divided into grids in sections with the photoelectric conversion element as a unit, and optically with respect to the light generated by the fluorescent particles in the gaps between the divided fluorescence conversion films. 8. The radiation detector according to claim 7, wherein the radiation detector is filled with particles having a refractive index larger than that of the fluorescent particles. In the fluorescent conversion film, Gd ₂ O ₂ S or Ya ₂ O ₂ S: Tb is used as the phosphor particles, and La ₂ O ₃ , SnO ₂ , PbF ₂ , MgO, In ₂ O ₃ , Nd is used as the antireflection film substance. ₂ O _3, the radiation detector according to any one of _HfO 2, _Sb 2 to claims 7, characterized in that it is mainly composed of one any of the _{O 3} 9. A photoelectric conversion unit that has a plurality of pixels in which photoelectric conversion elements in pixel units are arranged in a matrix, and photoelectrically converts visible light incident on each pixel to generate a signal charge corresponding to the intensity of the visible light; ,
The surface has an anti-reflective material layer with a thickness defined by a predetermined magnification with respect to the wavelength of visible light obtained by converting the incident radiation with a predetermined refractive index, and the incident radiation has a predetermined wavelength. The phosphor particles that convert to visible light, a filler made of a material having a refractive index lower than the refractive index of the phosphor particles and the refractive index of the antireflection material layer, and a mixture of the phosphor particles and the filler A fluorescent conversion film having a reflector layer that divides the body in units of individual pixels of the photoelectric conversion unit;
A radiation detector comprising:   The reflective material layer is made of a material that is optically transparent with respect to light generated by the fluorescent particles in a gap between the fluorescent conversion films between the sections in units of the photoelectric conversion element, and the fluorescent particles The radiation detector according to claim 11, wherein particles having a smaller diameter are packed.   The reflective material layer is made of a material that is optically transparent with respect to light generated by the fluorescent particles in a gap between the fluorescent conversion films between the sections in units of the photoelectric conversion element, and the fluorescent particles The radiation detector according to claim 11, wherein particles having a higher refractive index are filled.

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