JPWO2012137425A1 - X-ray detector - Google Patents

Abstract

As a light irradiation mechanism for irradiating the semiconductor thick film 7 with light, a scintillator film 11 for converting X-rays into visible light is provided on a surface opposite to the X-ray detection surface. Since the scintillator film 11 converts X-rays incident on the X-ray detector 1 into visible light, it is not necessary to provide a power source or a control unit required for light emission. In addition, the number of parts used is reduced, and cost reduction and assembly work can be reduced. Moreover, power consumption can be reduced by providing the scintillator film 11. In addition, the X-ray intensity reaching the scintillator film 11 is particularly strong between the divided electrodes (pixel electrodes) 3 and the fluorescence intensity is increased at a necessary place (especially between the pixel electrodes), thereby suppressing sensitivity fluctuations. A possible X-ray detector 1 can be realized.

Description

  The present invention relates to an X-ray detector used in the medical field, industrial field, nuclear power field, and the like, and more particularly, a direct conversion type X that directly converts X-rays into electric charges by a semiconductor sensitive to X-rays. It relates to the technology of line detectors.

  In the conventional X-ray detector, there is a phenomenon that charges generated by X-rays easily accumulate in a space area between the divided electrodes (pixel electrodes), an effective sensitive area changes, and sensitivity changes. Furthermore, there is a phenomenon that after the X-ray incidence is stopped, the electric charge accumulated in the space region between the divided electrodes is gradually swept away to generate a residual output. In order to prevent these phenomena, there is an X-ray detector provided with a light irradiation mechanism (surface emitting plate) that emits visible light during detection of X-rays (see, for example, Patent Document 1).

  When a surface emitting plate is provided, by irradiating a semiconductor thick film (a semiconductor sensitive to X-rays) with visible light from the surface emitting plate, out of charges generated by visible light even before the X-ray incidence. Since one side is already accumulated in the space area between the divided electrodes, the sensitive area does not change and the sensitivity does not change. Further, if the irradiation with visible light is continued until after the X-ray incidence is stopped, the charges accumulated in the space area between the divided electrodes are not gradually swept out, and no residual output is generated. The light emission from the surface light emitting plate is controlled by controlling the power supply with an on / off switch or a control unit.

JP 2004-146769 A (FIG. 1)

  However, in the case of a conventional X-ray detector having such a configuration, it is necessary to provide a power source and a control unit required for light emission as described above.

  The present invention has been made in view of such circumstances. An X-ray capable of reducing power consumption and suppressing sensitivity fluctuations without requiring a power source and a control unit required for light emission. An object is to provide a detector.

In order to achieve such an object, the present invention has the following configuration.
That is, the X-ray detector according to the present invention is an X-ray detector including a semiconductor sensitive to X-rays and a light irradiation mechanism that irradiates the semiconductor with visible light, and the light irradiation mechanism includes: A phosphor that converts X-rays into visible light is provided, and the phosphor is disposed on a surface opposite to the X-ray detection surface.

  [Operation / Effect] According to the X-ray detector of the present invention, since the phosphor converts the X-rays incident on the X-ray detector into visible light, it is not necessary to provide a power source or a control unit required for light emission. . In addition, the number of parts used is reduced, and cost reduction and assembly work can be reduced. Further, the phosphor can be provided as a light irradiation mechanism on the surface opposite to the X-ray detection surface to reduce power consumption. In addition, the X-ray intensity reaching the phosphor is particularly strong between the divided electrodes (pixel electrodes), and the fluorescence height is increased at a required place (especially between the pixel electrodes), so that the sensitivity variation can be suppressed. A line detector can be realized.

  According to the X-ray detector of the present invention, since the phosphor converts the X-rays incident on the X-ray detector into visible light, power consumption is reduced without requiring a power source and a control unit required for light emission. It is possible to realize an X-ray detector that can suppress sensitivity fluctuation while being able to.

It is a schematic sectional drawing of the X-ray detector which concerns on an Example. It is a circuit diagram around an X-ray detector. It is a schematic diagram when the scintillator film of an X-ray detector has converted X-rays into visible light. (A), (b) is a schematic sectional drawing of the X-ray detector of embodiment different from FIGS. 1-3.

Embodiments of the present invention will be described below with reference to the drawings.
1 is a schematic cross-sectional view of an X-ray detector according to an embodiment, FIG. 2 is a circuit diagram around the X-ray detector, and FIG. 3 is an X-ray detected by a scintillator film of the X-ray detector. FIGS. 4A and 4B are schematic cross-sectional views of an X-ray detector according to another embodiment different from FIGS. 1 to 3.

  As shown in FIG. 1, the X-ray detector 1 includes a thin film transistor (TFT) switch S (see FIG. 2), a charge storage capacitor Ca (see FIG. 2) and a division on a transparent insulating substrate such as a glass substrate. A semiconductor thick film 7 sensitive to X-rays is formed on a TFT substrate 5 on which an electrode (pixel electrode) 3 is formed. A common electrode 9 for voltage application is formed on the upper surface (detection surface) of the semiconductor thick film 7. Is formed. A scintillator film 11 is optically coupled to the back surface (that is, the surface opposite to the X-ray detection surface) of the TFT substrate 5 that is the divided electrode 3 side. In the case of “optically coupled”, the scintillator film 11 may be bonded to the back surface of the TFT substrate 5 with a transparent adhesive, or the scintillator film 11 is mechanically bonded to the back surface of the TFT substrate 5. It may be fixed. That is, as long as the visible light from the scintillator film 11 reaches the TFT substrate 5, the “optically coupled” connection method is not particularly limited. The scintillator film 11 is made of a phosphor such as CsI, NaI or GOS. The semiconductor thick film 7 corresponds to the semiconductor in the present invention, the scintillator film 11 corresponds to the phosphor in the present invention, and also corresponds to the light irradiation mechanism in the present invention.

  As shown in FIG. 2, a plurality of gate lines G and data lines D (only one is shown in FIG. 2) arranged two-dimensionally are formed on the TFT substrate 5, and around the X-ray detector 1 A gate drive circuit 13, a charge-voltage conversion amplifier 15, and an image processing unit 17 are provided. The gate drive circuit 13 is electrically connected to a gate line G, and each gate line G is electrically connected to a thin film transistor (TFT) switch S in the same row. Each data line D is electrically connected to a thin film transistor (TFT) switch S in the same column, and is electrically connected to the charge voltage conversion amplifier 15 on the downstream side.

  The semiconductor thick film 7 is not particularly limited as long as it is a semiconductor sensitive to X-rays, and is amorphous amorphous selenium (a-Se), CdTe (cadmium telluride), ZnTe (zinc telluride), or CdZnTe. (Cadmium zinc telluride) and the like.

  When a bias voltage is applied to the common electrode 9 and X-rays are incident, charges are generated in the semiconductor thick film 7 and the charges are accumulated in the charge storage capacitor Ca via the divided electrode 3. By applying a voltage from the gate drive circuit 13 to each gate line G, the thin film transistor (TFT) switch S is turned ON, and the carriers accumulated in the charge storage capacitor Ca are read out to the data line D. The read charge is amplified in a state converted into a voltage by the charge-voltage conversion amplifier 15, and the image processing unit 17 performs various signal processing on the voltage value to obtain a two-dimensional image.

  In the X-ray detector 1 configured as described above, when X-rays are incident, the X-rays are transmitted through the common electrode 9, the semiconductor thick film 7 and the TFT substrate 5 as shown in FIG. X-rays are incident on the scintillator film 11. In particular, since the substrate constituting the TFT substrate 5 is a transparent insulating substrate and is a glass substrate in this embodiment, the X-ray attenuation factor at the X-ray detector 1 for incident X-rays is 70%. Then, the remaining 30% of X-rays pass through the TFT substrate 5 and reach the scintillator film 11.

  When X-rays are incident (that is, during detection of X-rays), the scintillator film 11 converts the incident X-rays into visible light Opt (see FIG. 3) and emits light. Visible light is irradiated from the scintillator film 11 to the semiconductor thick film 7 by the light emission from the scintillator film 11.

  Since visible light from the scintillator film 11 may come out to the outside on the back surface (that is, the surface opposite to the X-ray detection surface), as shown in FIG. It is preferable to provide a reflecting member represented by the above. By providing a reflecting member typified by the light reflecting sheet 19 or the like on the back surface of the scintillator film 11 (the surface opposite to the X-ray detection surface), visible light is prevented from coming out to the outside, and the TFT Visible light can be guided toward the substrate 5 and the semiconductor thick film 7.

  In order to prevent visible light from being reflected by the TFT substrate 5, it is preferable to apply an antireflection coating 21 (see also FIG. 1 and FIG. 2) to the TFT substrate 5, as shown in FIG. By applying the antireflection coating 21 to the TFT substrate 5, visible light can be prevented from being reflected by the TFT substrate 5, and visible light can be guided toward the semiconductor thick film 7.

  Since the incident X-rays are blocked by the divided electrodes 3, the X-ray intensity reaching the scintillator film 11 is particularly strong between the divided electrodes 3. And since the visible light from the scintillator film 11 is also blocked by the divided electrodes 3, the fluorescence intensity between the divided electrodes 3 is increased.

  According to the X-ray detector 1 according to the present embodiment having the above-described configuration, since the scintillator film 11 converts X-rays incident on the X-ray detector 1 into visible light, a power source and a control unit required for light emission. There is no need to provide. In addition, the number of parts used is reduced, and cost reduction and assembly work can be reduced. Moreover, power consumption can be reduced by providing the scintillator film 11 on the surface opposite to the X-ray detection surface as a light irradiation mechanism. In addition, the X-ray intensity reaching the scintillator film 11 is particularly strong between the divided electrodes (pixel electrodes) 3 and the fluorescence intensity is increased at a necessary place (especially between the pixel electrodes), thereby suppressing sensitivity fluctuations. A possible X-ray detector 1 can be realized.

As described above, when the X-ray attenuation rate is 70%, the remaining 30% of X-rays pass through the TFT substrate 5 and reach the scintillator film 11. The fluorescence conversion rate (luminance) is a value around 10 [cd · m ⁻² / R · sec ⁻¹ ], and when the incident X-ray dose is 0.5 [R · sec ⁻¹ ], the scintillator The luminance of visible light from the film 11 is about 0.5 [R · sec ⁻¹ ] × 30% × 10 [cd · m ⁻² / R · sec ⁻¹ ] = 1.5 [cd · m ⁻² ]. become. If the luminance of visible light from the scintillator film 11 is small enough to suppress fluctuations in sensitivity, a light emitting means typified by a surface light emitting plate 23 or the like is used as an auxiliary material as shown in FIG. May be.

  For example, the light irradiation mechanism includes, in addition to the phosphor represented by the above scintillator film 11 and the like, as shown in FIG. Generate visible light. Then, the semiconductor thick film 7 is irradiated with visible light from the light emitting means represented by the surface light-emitting plate 23 and the like together with visible light from the phosphor represented by the scintillator film 11 and the like. In the case of the structure shown in FIG. 4A, it is necessary to provide a power source and a control unit required for light emission, but power consumption can be suppressed by the amount of visible light from the scintillator film 11.

  The X-rays become scattered X-rays at the semiconductor thick film 7 and the TFT substrate 5. Although this scattered X-ray is originally a noise component, it may be used effectively. That is, as shown in FIG. 4B, a scintillator film 25 for scattered X-rays that converts scattered X-rays (see dotted lines in the figure) into visible light is provided, and is a surface opposite to the X-ray detection surface. The scintillator film 25 for scattered X-rays may be disposed on another side surface. In FIG. 4B, the scattered X-rays transmitted to the outside of the semiconductor thick film 7 and the scattered X-rays transmitted to the outside of the TFT substrate 5 are effectively used to form the scattered X-rays on the side surface of the semiconductor thick film 7. A scintillator film 25 is provided, and a scattered X-ray scintillator film 25 is also provided on the side surface of the TFT substrate 5. The scattered X-ray scintillator film 25 corresponds to the scattered X-ray phosphor in this invention.

  By providing such a scintillator film 25 for scattered X-rays, the scattered X-ray scintillator film 25 converts the scattered X-rays into visible light so that the scattered X-rays can be used effectively. Similar to FIGS. 1 to 3, a reflection member typified by a scattered X-ray light reflection sheet 27 and the like is provided, and an antireflection coating 29 for scattered X-rays is applied to the TFT substrate 5 and the semiconductor thick film 7. preferable.

  The scattered X-ray scintillator film 25 may not be provided on the side surface of the semiconductor thick film 7, but the scattered X-ray scintillator film 25 may be provided on the side surface of the TFT substrate 5. By providing the scattered X-ray scintillator film 25 on at least the side surface of the TFT substrate 5, the fluorescent intensity at a required place (particularly between pixel electrodes) is enhanced. When the scattered X-ray scintillator film 25 is provided on the side surface of the semiconductor thick film 7, visible light from the scattered X-ray scintillator film 25 is reflected by the TFT substrate 5. The TFT substrate 5 does not necessarily need to be provided with an antireflection coating on this surface.

  The present invention is not limited to the above-described embodiment, and can be modified as follows.

  (1) In the above-described embodiments, the reflecting member is a light reflecting sheet, but the material and form are not particularly limited as long as it is a reflecting member that prevents visible light from going outside. For example, a paint made of a reflective agent may be applied.

  (2) In the above-described embodiments, the phosphor is a scintillator film formed of CsI, NaI, or GOS. However, as long as the phosphor converts X-rays into visible light, the substance and form are particularly limited. Not. For example, an element made of a phosphor may be used, or a paint made of a phosphor may be applied. The scattered X-ray phosphor is not limited to the scintillator film (scattered X-ray scintillator film 25), and may be an element made of a phosphor or a coating made of a phosphor.

  (3) In the above-described embodiment, the light emitting means is the surface light emitting plate shown in FIG. 4A. However, the light emitting means is composed of a cold cathode tube which is a white light source and a light guide plate obtained by finely processing the surface of the acrylic plate. It may be a structure.

  (4) You may combine both the structure of Fig.4 (a), and the structure of FIG.4 (b).

  (5) In the embodiment described above, the voltage application common electrode 9 has a structure as shown in FIGS. 1 and 2, but for example, includes a support substrate and a graphite substrate that serves both as a voltage application common electrode. The present invention can also be applied to other structures.

DESCRIPTION OF SYMBOLS 1 ... X-ray detector 7 ... Semiconductor thick film 11 ... Scintillator film 25 ... Scintillator film for scattered X-rays Opt ... Visible light

Claims (13)

A semiconductor sensitive to X-rays,
An X-ray detector comprising: a light irradiation mechanism for irradiating the semiconductor with visible light,
The light irradiation mechanism includes a phosphor that converts X-rays into visible light,
An X-ray detector, wherein the phosphor is disposed on a surface opposite to the X-ray detection surface. The X-ray detector according to claim 1,
The light irradiation mechanism includes a light emitting means for generating visible light,
An X-ray detector for irradiating the semiconductor with visible light from the light emitting means together with visible light from the phosphor. The X-ray detector according to claim 1 or 2,
A phosphor for scattered X-rays that converts scattered X-rays into visible light;
An X-ray detector, wherein the scattered X-ray phosphor is disposed on a side surface different from a surface opposite to the X-ray detection surface. In the X-ray detector in any one of Claims 1-3,
The X-ray detector, wherein the phosphor is a scintillator film. The X-ray detector according to claim 4,
The X-ray detector, wherein the scintillator film is CsI, NaI or GOS. The X-ray detector according to any one of claims 1 to 5,
An X-ray detector comprising a reflecting member on a surface opposite to the X-ray detection surface of the phosphor. The X-ray detector according to any one of claims 1 to 6,
With a common electrode for voltage application,
An X-ray detector, wherein a common electrode for applying voltage is formed on a detection surface of the semiconductor. The X-ray detector according to claim 7.
A TFT substrate having a thin film transistor switch, a charge storage capacitor, and a pixel electrode formed on a transparent insulating substrate,
An X-ray detector, wherein the semiconductor is formed on the TFT substrate, and the common electrode for voltage application is formed on the semiconductor. The X-ray detector according to claim 8.
An X-ray detector, wherein an antireflection coating is applied to the TFT substrate. The X-ray detector according to claim 8 or 9,
An X-ray detector, wherein the phosphor is optically coupled to a lower surface of the TFT substrate. The X-ray detector according to claim 10.
An X-ray detector, wherein the phosphor is bonded to a lower surface of the TFT substrate with a transparent adhesive. The X-ray detector according to claim 10 or 11,
An X-ray detector, wherein the phosphor is mechanically fixed to a lower surface of the TFT substrate. The X-ray detector according to any one of claims 8 to 12,
The X-ray detector, wherein the transparent insulating substrate is a glass substrate.

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