JP2008244410A - Image detector - Google Patents

Abstract

There are provided a charge generation layer that generates charges upon receiving irradiation of an electromagnetic wave for recording, a storage capacitor that stores charges generated in the charge generation layer, and a TFT switch that reads out the charges stored in the storage capacitor. Detector in which a plurality of scanning wirings for turning on / off the TFT switches and a plurality of data wirings for reading out charges accumulated in a storage capacitor orthogonal to the scanning lines are stacked The resolution is improved.
An interval Pss between data lines 16 is made wider than an interval Pgg between scanning lines 15.
[Selection] Figure 2

Description

  The present invention relates to an image detector in which a large number of pixels having thin film transistors are two-dimensionally arranged.

  In recent years, flat panel detectors (FPDs) have been put into practical use in which an X-ray sensitive layer is disposed on a TFT active matrix substrate and X-ray information can be directly converted into digital data. Compared to the conventional imaging plate, there is an advantage that an image can be confirmed immediately and a moving image can be confirmed, and it is rapidly spreading.

  In the radiation image detector, a semiconductor film having electromagnetic conductivity is formed on an active matrix substrate on which charge collection electrodes are arranged in an array, and a bias electrode is sequentially formed thereon. The bias electrode is connected to a high voltage power source.

  The semiconductor film is an amorphous a-Se film having a film thickness of 100 to 1000 μm containing selenium as a main component, and generates charges inside the film when irradiated with X-rays. A TFT switch and a storage capacitor are provided in the vicinity of the charge collection electrodes arranged in an array on the active matrix substrate, and the drain electrode of the TFT switch and one electrode of the storage capacitor are connected. A scan wiring is connected to the gate electrode of the TFT switch, a data wiring is connected to the source electrode, and a signal detector (amplifier) is connected to the end of the data wiring (for example, a patent) Reference 1 and Patent Reference 2).

  Next, the operation principle of the conventional radiation image detector will be described.

  When X-rays are irradiated from the bias electrode side, the semiconductor film generates charges inside. Of the generated charges, holes are collected on the charge collection electrode by a bias between the bias electrode and the charge collection electrode, and accumulated in a storage capacitor electrically connected to the charge collection electrode. Since the semiconductor film generates different amounts of charge according to the X-ray dose, charges according to the image information carried by the X-rays are accumulated in the storage capacitors of the respective pixels. Thereafter, a signal for turning on the TFT switch is sequentially applied via the scan wiring, and the charges accumulated in the respective storage capacitors are taken out via the data wiring. Furthermore, image information can be read by detecting the charge amount of each pixel with a signal detector.

  Next, details of the active matrix substrate of the radiation image detector as described above will be described.

As shown in FIG. 9, in the active matrix substrate, the scanning wiring 15 and the data wiring 16 are arranged orthogonally. A TFT switch 13 is disposed in the vicinity of the intersection between the scanning wiring 15 and the data wiring 16. The source electrode 17 of the TFT switch 13 is connected to the data line 16, and the drain electrode 18 is connected to the storage capacitor upper electrode 20. The storage capacitor upper electrode 20 is connected to the collecting electrode 11 through a contact hole. A storage capacitor lower electrode 21 is disposed below the storage capacitor upper electrode 20, and the storage capacitor 12 is configured by the storage capacitor lower electrode 21 and the storage capacitor upper electrode 20. Further, the scanning wiring 15 and the data wiring 16 are arranged so that the scanning line wiring interval and the data wiring interval are the same.
Japanese Patent Laid-Open No. 11-190774 JP 2001-135809 A

  Here, resolution is one of the important detection capability indexes of the radiation image detector. In general, the smaller the pixel size, the higher the resolution and the better the image quality. Here, the pixel size refers to the size of the pixel region, that is, the scanning wiring interval × the data wiring interval.

  Accordingly, the reduction in pixel size leads to a reduction in the distance between the scanning wiring and the data wiring, and the connection terminals with the external IC circuit connected to these wirings are also narrowed. However, the radiation image detector generally employs the TAB method in which the pitch between terminals is limited to 70 μm for connection of the external IC circuit, and the resolution of the radiation image detector is limited to 70 μm. It was. For example, if the terminal pitch of the external IC circuit is increased with respect to the pixel pitch, the substrate size of the terminal portion is increased with respect to the radiation image detector main body, the outer shape of the radiation image detector is increased, and the manufacturing cost is increased. Problems arise and are not realistic.

  On the other hand, in a liquid crystal display that similarly employs an active matrix substrate, a package that directly mounts an IC chip on a glass substrate called COG (Chip on Glass) is employed in order to realize terminal mounting with a narrow pitch. In COG, the pitch between terminals can be reduced to about 35 μm.

  Therefore, although it is easiest to adopt COG in the radiation image detector, the charge amplifier IC is a circuit dedicated to the radiation image detector, and the charge amplifier IC is the main element that determines the performance of the radiation image detector. The COG type charge amplifier IC has not been developed for three reasons, because it is a component, the circuit configuration is complicated, and the market size of the radiation image detector is small.

  In view of the above circumstances, an object of the present invention is to provide an image detector capable of improving the resolution as much as possible.

  The radiation image detector according to the present invention includes a charge generation layer that generates a charge upon irradiation of a recording electromagnetic wave, a number of pixels and a TFT switch having a TFT switch for reading out the charge generated in the charge generation layer. In an image detector having a large number of scanning wirings for turning on and off and a large number of data wirings for reading out the charges, the interval between the data wirings is wider than the interval between the scanning wirings.

  In the radiation image detector of the present invention, the interval Pss between the data lines and the interval Pgg between the scanning lines can be set to a size satisfying the relationship of the following expression.

Pss = N × Pgg
However, N is an integer greater than or equal to 2. Moreover, ratio Pgg: Pss of the space | interval Pgg between data wirings and the space | interval Pss between scanning wirings may be set to 1: 2, 2: 3, 1: 3, or 3: 4. it can.

  In addition, the data wiring pixel array in which the pixels are arranged in the direction in which the data wiring extends can be shifted by a predetermined amount in the direction in which the data wiring extends in a certain cycle with respect to the direction in which the scanning wiring extends.

  Further, the data wiring pixel array can be shifted every other column by 1/2 of the scanning wiring interval.

  According to the radiation image detector of the present invention, a number of pixels and TFTs having a charge generation layer that generates charges upon irradiation of a recording electromagnetic wave, and a TFT switch for reading out the charges generated in the charge generation layer In an image detector having a large number of scanning lines for turning on / off the switches and a large number of data lines for reading out the charges, the interval between the data lines is made wider than the interval between the scanning lines. The resolution in the data wiring direction can be improved.

  In the radiological image detector of the present invention, when the interval Pss between the data lines and the interval Pgg between the scan lines are set to satisfy the following relationship, the pixel density in the data line direction and the scan line Conversion to image data having the same pixel density in the direction can be easily performed.

Pss = N × Pgg
However, N is an integer greater than or equal to 2. Also, image data detected by image detectors with different vertical and horizontal resolutions must be matched to either the vertical or horizontal resolution in order to be output to an external device. The combination Pgg / Pss of the interval Pgg between the data lines and the interval Pss between the scanning lines is 50 μm / 100 μm, 50 μm / 75 μm, 50 μm / 150 μm, 75 μm / 100 μm, 75 μm / 150 μm, or 100 μm / 150 μm. In other words, when the ratio Pgg: Pss of the two is 1: 2, 2: 3, 1: 3, or 3: 4, the above interpolation process can be simplified. In addition, even when repetitive noise or the like occurs during interpolation processing, it can be difficult to recognize.

  In addition, when the data wiring pixel array in which the pixels are arranged in the direction in which the data wiring extends is shifted by a predetermined amount in the direction in which the data wiring extends in a certain period with respect to the direction in which the scanning wiring extends, the resolution in the scanning wiring direction also increases. Can be improved.

  A radiation image detector using the first embodiment of the image detector of the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic configuration diagram of a radiation image detector 100 of the first embodiment.

  As shown in FIG. 1, the radiation image detector 100 of the present embodiment is provided on an active matrix substrate 10, a semiconductor film 20 formed on substantially the entire surface of the active matrix substrate 10, and the semiconductor film 20. The upper electrode 21 is constituted.

  The semiconductor film 20 has electromagnetic wave conductivity, and generates charges inside the film when irradiated with X-rays. As the semiconductor film 20, for example, an amorphous a-Se film having a film thickness of 100 to 1000 μm mainly composed of selenium can be used. The semiconductor film 20 is formed with a thickness of, for example, 100 to 1000 μm by a vacuum deposition method.

  The upper electrode 22 is made of a low-resistance conductive material such as Au or Al.

  The active matrix substrate 10 includes a collection electrode 11 that collects the charges generated in the semiconductor film 20, a storage capacitor 12 that stores the charges collected by the collection electrode 11, and a TFT switch 13 that reads the charges stored in the storage capacitor 12. And a plurality of scanning wirings 15 for turning on / off the TFT switch 13 and a number of data wirings 16 for reading out charges accumulated in the storage capacitor 12. The pixels 14 are arranged in an array.

  As the TFT switch 13, an a-Si TFT using amorphous silicon as an active layer is generally used.

  An amplifier 23 is connected to the end of the data line 5.

  FIG. 2 shows a layout diagram of the active matrix substrate 10.

  As shown in FIG. 2, a scanning line 15 and a data line 16 orthogonal to the scanning line 15 are arranged around each pixel 14. A TFT switch 13 is disposed in the vicinity of the intersection between the scanning wiring 15 and the data wiring 16. The source electrode 17 of the TFT switch 13 is connected to the data line 16, the drain electrode 18 is connected to the storage capacitor upper electrode 20, and the gate electrode 19 is connected to the scanning line 15. The storage capacitor upper electrode 20 is connected to the collecting electrode 11 through a contact hole. A storage capacitor lower electrode 21 is disposed below the storage capacitor upper electrode 20, and the storage capacitor 12 is configured by the storage capacitor lower electrode 21 and the storage capacitor upper electrode 20.

  In the active matrix substrate 10 of the radiation image detector according to the present embodiment, as shown in FIG. 2, each wiring is arranged such that the wiring interval Pss of the data wiring 16 is wider than the wiring interval Pgg of the scanning wiring 15. Is arranged. For example, in this embodiment, Pss = 75 μm and Pgg = 50 μm.

  Further, it is more desirable to set Pss and Pgg so as to satisfy the following expressions.

Pss = N × Pgg
However, N is an integer of 2 or more.

  When processing image data detected by radiation image detectors with different pixel densities in the horizontal and vertical directions, the image is once converted into image data in which the horizontal and vertical pixel densities are the same. It is necessary to perform processing. This is because the pixel density in the horizontal direction and the vertical direction of many output devices (display, printer, etc.) is the same. Generally, setting one pixel density to be an integer multiple of the other pixel density facilitates image conversion, so it is effective to set so that the above equation is satisfied. For example, when the pixel pitch of the radiation image detector is Pgg = 50 μm and Pss = 100 μm, Pss has a double length, so there is no pixel at the middle 50 μm. Therefore, by performing image conversion for generating interpolation data of the pixels, the image data is converted into image data of Pgg = Pss = 50 μm, and thereafter image correction is performed. As a result, it is possible to suppress the occurrence of artifacts associated with the correction and shorten the image conversion processing time.

  Further, the least common multiple of the interval Pss between the data lines 15 and the interval Pgg between the scanning lines 16 may be 6 times or less of Pgg. For example, therefore, Pgg and Pss can be set to the following ratio, for example.

Pgg: Pss = 50 μm: 100 μm (1: 2), 50 μm: 75 μm (2: 3), 50 μm: 150 μm (1: 3), 75 μm: 100 μm (3: 4), 75 μm: 150 μm (1: 2), 100 μm : 150 μm (2: 3)
For example, when one is not a simple integer multiple of the other, such as Pgg = 100 μm and Pss = 150 μm (pixel ratio 2: 3), the image detection apparatus outputs a pixel pitch (= Pgg = Pss) of 100 μm as the output image. Image processing. Therefore, since the scanning wiring direction is Pgg = 100 μm, image processing is performed as it is. However, since the data wiring direction is Pss 150 μm, it is necessary to generate data from two pixels to three pixels. That is, the data value of 2 pixels is distributed to 3 pixels from the mutual relationship of adjacent pixels in the data wiring direction.

  On the other hand, when the ratio of Pss to Pgg is 50 μm: 65 μm, the least common multiple is 650 μm, which is larger than 6 times Pgg. If the ratio is as described above, the interpolation algorithm when performing pixel interpolation becomes complicated, and as a result, it is difficult to obtain the effect of high definition.

  The least common multiple is preferably an integer multiple of the minimum pitch of pixels of an external device (printer, display, etc.) to which image data detected by the radiation image detector is output, or a fraction of an integer. For example, in a 20-inch QXGA (2048 × 1536), if the pixel pitch is 198 μm, an integer multiple of 198 μm, or a fraction of an integer, image processing at the actual size display becomes easy. In particular, printers often output in actual size, and when this relationship is not satisfied, the image quality (definition) decreases due to resolution conversion.

  FIG. 3 shows an equivalent circuit diagram of the radiation image detector of the present embodiment.

  As shown in FIG. 3, an amplifier 23 is connected to each data wiring 16. A gate driver 40 that outputs a control signal for turning on / off the TFT switch 13 is connected to each gate line 15.

  An amplifier IC is used as the amplifier 23, and a gate driver IC is used as the gate driver 40.

  FIG. 4 is a plan view of a radiation image detector in which the radiation image detector main body, the amplifier IC 31 and the gate driver IC 41 are mounted.

  In this embodiment, a radiographic image detector having a radiographic image detector main body of 90 mm × 90 mm will be described. In the radiological image detector of the present embodiment, as described above, the interval between the data lines is wider than the interval between the scan lines, and the interval between the scan lines with respect to the interval Pss = 75 μm between the data lines. Pgg = 50 μm. Therefore, the number of scanning lines is 1800 and the number of data lines is 1200. If a TCP package having a terminal pitch of 70 μm and 256 outputs (240 gate outputs) is employed as the gate driver IC 41, a substrate size of at least 150 mm or more is required. Therefore, in this embodiment, the gate driver IC 41 of the COG package is employed. Since the specification of the gate driver required for the radiation image detector is the same as that of the liquid crystal display, a COG gate driver IC for liquid crystal display can be easily obtained. The gate driver IC of the COG package has a terminal pitch of 36 μm, 256 outputs (240 gate outputs), and the installation area of the gate driver IC can be 80 mm or less.

  On the other hand, the amplifier IC 31 is a dedicated IC for a radiation image detector, and there is no COG package product in the world. In addition, the production amount of the radiation image detector is very small, and the development of a dedicated COG chip greatly increases the manufacturing cost. Further, since Se used for the semiconductor film is vulnerable to heat, in order to avoid heat generation of the amplifier IC, a TCP package in which an amplifier is disposed outside a glass substrate through a film is preferable.

  Therefore, in this embodiment, the interval between the data lines is set to 75 μm with respect to the interval between the scan lines of 50 μm. Therefore, even when a TCP package with a terminal pitch of 70 μm and 256 outputs (240 amplifier inputs) is used, the connection area of the amplifier IC 31 can be realized with 94 mm. For this reason, there is no difference between the size and the outer size of the radiation image detector main body, and a package that does not deteriorate the commerciality as a radiation image detector can be realized.

  On the other hand, in terms of image quality, the resolution of the scanning wiring can be made 1.5 times the resolution of the data wiring, and the image quality can be remarkably improved.

  As shown in FIG. 4, the gate driver IC 41 and the amplifier IC 31 are formed of a silicon substrate different from the substrate on which the scanning wiring 15 and the data wiring 16 of the radiation image detector main body are provided.

  Next, the operation principle of the radiation image detector of this embodiment will be described.

  When X-rays transmitted through the subject are irradiated from above in FIG. 1, the semiconductor film 20 generates electric charges therein. Then, of the charges generated in the semiconductor film 20, holes are collected on the collection electrode 11 by the bias between the upper electrode 21 and the collection electrode 11, and accumulated in the storage capacitor 12 electrically connected to the collection electrode 11. The Since the semiconductor film 20 generates different charge amounts depending on the X-ray dose, an amount of charge depending on the image information carried by the X-rays is stored in the storage capacitor 12 of each pixel 14.

  Thereafter, a signal for sequentially turning on the TFT switch 13 is applied via the scanning wiring 15, and the charge accumulated in the storage capacitor 12 is read via the data wiring 16. Further, the image information can be read by detecting the charge amount of each pixel 14 by the amplifier 30.

  Next, a radiation image detector using the second embodiment of the image detector of the present invention will be described. The radiation image detector using the second embodiment of the present invention is different from the radiation image detector using the first embodiment of the present invention in the manner of pixel arrangement.

  As shown in FIG. 5, in the radiographic image detector using the second embodiment of the present invention, the data wiring pixel array in which the pixels 14 are arrayed in the direction in which the data wiring 16 extends has the data wiring direction every other column. Are arranged so as to be shifted by a half of the interval of the scanning wiring 15.

  For example, in the case of the pixel arrangement as shown in FIG. 6, the pixel density in the range enclosed by the square is 3 pixels for the pixel density X in the scanning wiring direction and 4 pixels for the pixel density Y in the data wiring direction. However, the pixel density Y in the scanning wiring direction can be set to four pixels by arranging the data wiring pixel array by shifting the data wiring pixel array by ½ of the interval of the scanning wiring 15 every other column as described above. Therefore, not only the data wiring direction but also the resolution in the scanning wiring direction can be improved.

  In the second embodiment, every other column is shifted by half of the interval between the scanning lines 15. However, the interval is not necessarily 1/2. Further, the data wiring pixel array may be shifted in the data wiring direction every other column, not every other column.

  The radiation image detectors of the first and second embodiments are so-called direct conversion type radiation image detectors that directly receive radiation and generate electric charges. It can be applied not only to direct conversion type radiological image detectors but also to so-called indirect conversion type radiographic image detectors that convert radiation into light once by a phosphor and generate electric charges upon irradiation of the light. is there.

  FIG. 7 is a cross-sectional view showing a schematic configuration of the indirect conversion type radiation image detector. As shown in FIG. 7, the indirect conversion type radiation image detector 200 includes an active matrix substrate 30, a semiconductor film 31 formed on substantially the entire surface of the active matrix substrate 30, and a semiconductor as shown in FIG. 7. An upper electrode 32 provided on the film 31 and a wavelength conversion layer 33 provided on the upper electrode 32 are configured.

  The wavelength conversion layer 33 converts radiation into visible light.

  The semiconductor film 31 is made of, for example, a-Si that detects visible light, and has a thickness of 1 to 2 μm, which is thinner than a direct conversion type radiation image detector. As a result, a large capacity can be secured and an auxiliary capacity becomes unnecessary. That is, the semiconductor film 31 also has a function of a storage capacitor.

  The upper electrode 32 is formed of a material and a thickness that transmit visible light emitted from the wavelength conversion layer 33.

  The active matrix substrate 30 turns on / off a number of pixels 36 and TFT switches 35 each having a collection electrode 34 for collecting charges generated in the semiconductor film 31 and a TFT switch 35 for reading out the charges collected by the collection electrode 34. A large number of scanning wirings 37 for turning off and a large number of data wirings 38 for reading out the charges collected by the collecting electrodes 34 are provided.

  FIG. 8 shows a layout diagram of the active matrix substrate 30. As shown in FIG. 8, the indirect conversion type radiographic image detector does not include a storage capacitor unlike the direct conversion type radiographic image detector, and therefore the storage capacitor upper electrode and the storage capacitor lower electrode are not provided. . About another structure, it is the same as that of the direct conversion type radiographic image detector. In the indirect conversion type radiation image detector, the interval between the data lines 38 is wider than the interval between the scanning lines 37.

Sectional drawing of the radiographic image detector using 1st Embodiment of the image detector of this invention Layout diagram of active matrix substrate of radiation image detector shown in FIG. Equivalent circuit diagram of the radiation image detector shown in FIG. Plan view of a radiation image detector mounted with a radiation image detector body, an amplifier IC, and a gate driver IC Layout diagram of radiation image detector according to second embodiment of the present invention Layout diagram of the radiation image detector according to the first embodiment of the present invention. Sectional drawing which shows schematic structure of an indirect conversion type radiographic image detector Layout diagram of active matrix substrate of indirect conversion type radiation image detector Layout diagram of active matrix substrate of conventional radiation image detector

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Active matrix board | substrate 11 Charge collection electrode 12 Storage capacity 13 TFT switch 14 Pixel 15 Scanning wiring 16 Data wiring 17 Source electrode 18 Drain electrode 19 Gate electrode 20 Storage capacity upper electrode 21 Storage capacity lower electrode 23 Amplifier 31 Amplifier IC
41 Gate driver IC
100 Radiation image detector

Claims (5)

A charge generation layer that generates a charge upon irradiation of a recording electromagnetic wave, a large number of pixels having a TFT switch for reading out the charge generated in the charge generation layer, and a large number for turning on / off the TFT switch In an image detector having a scanning wiring and a number of data wirings from which the charges are read out,
An image detector, wherein an interval between the data lines is wider than an interval between the scanning lines. 2. The image detector according to claim 1, wherein the interval Pss between the data lines and the interval Pgg between the scanning lines satisfy a relationship of the following expression.
Pss = N × Pgg
N is an integer greater than or equal to 2   The ratio Pgg: Pss between the interval Pgg between the data lines and the interval Pss between the scan lines is 1: 2, 2: 3, 1: 3, or 3: 4. Image detector.   2. The data line pixel array in which the pixels are arranged in the direction in which the data lines extend extends from the direction in which the scanning lines extend by a predetermined amount in the direction in which the data lines extend in a predetermined period. 3. The image detector according to any one of 3 above.   5. The image detector according to claim 4, wherein the data wiring pixel array is shifted by half of the scanning wiring interval every other column.

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