JP5294792B2 - Radiation solid state detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To eliminate possibility of peeling off in an end edge part of a photoconductive layer in a radiation solid-state detector including a protective film. <P>SOLUTION: The radiation solid-state detector 10 is configured such that a first electrode layer 11 having transmittance for an electromagnetic wave, a photoconductive layer 12 which is irradiated with an electromagnetic wave to generate electric charges, and a second electrode layer 13 provided with a plurality of split electrodes, are laminated on a glass substrate 14 in order from the second electrode layer 13 and a protective film 21 is stuck to seal the first electrode layer 11 and the photoconductive layer 12, wherein a low-adhesion film 30 of which the adhesion force on the side of the photoconductive layer 12 is smaller than that on the side of the protective film 21 is disposed in an end edge part of the photoconductive layer 12. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a radiation solid state detector provided with a photoconductive layer that directly generates a charge when irradiated with electromagnetic waves, and more particularly to protection of the photoconductive layer.

  Conventionally, in the medical field and the like, various radiation solid state detectors that record radiation images related to a subject by receiving radiation transmitted through the subject and output an electrical signal corresponding to the recorded radiation image have been proposed and put into practical use. ing.

As a radiation solid-state detector system, a direct conversion system that directly converts radiation into electric charge and accumulates the charge, and radiation is once converted into light by a scintillator such as CsI: Tl or GOS (Gd ₂ O ₂ S: Tb). There is an indirect conversion method in which the light is converted into charges by the photoconductive layer and stored. The reading method is roughly divided into an optical reading method using reading light and an electric reading method using a TFT (thin film transistor), a CCD (charge coupled device), a CMOS (complementary metal oxide semiconductor) sensor, and the like.

  As an optical solid-state detector of the optical reading system, for example, the charge generated in the photoconductive layer for recording due to the irradiation of radiation is accumulated and the charge having the opposite polarity to the accumulated charge is charged to the linear electrode. It is known to read the accumulated charge by combining each charge of the charge pair generated in the reading photoconductive layer with the accumulated charge and the charged charge.

  As an electrical reading type radiation solid state detector, for example, charges generated by irradiation of radiation are collected by a pixel electrode for each pixel, stored in a storage capacitor connected to the pixel electrode, and the stored charge is stored in an electrical device such as a TFT. A device that reads a target switch by turning it on and off pixel by pixel is known.

In the direct conversion radiation solid-state detector, various materials such as CdTe and HgI are used for the photoconductive layer, but most commonly, an amorphous material that is highly sensitive to radiation such as X-rays. Selenium (a-Se) is used. Se is easily affected by the temperature and humidity of the outside world, and when used for a long time without a protective film, there is a problem that deterioration such as a decrease in sensitivity and a decrease in image quality proceeds. Moreover, since Se has a low X-ray absorption rate, a relatively thick film is required. As a result, a high bias voltage needs to be applied in order to function as a photoconductive layer. When such a high electric field is applied, a fine defect generated in Se may lead to a large image defect. For this reason, as described in Patent Document 1, a photoconductive layer is usually protected by attaching a protective film to a radiation solid detector with an adhesive or a pressure-sensitive adhesive.
JP 2007-147596 A JP 2004-317167 A International Publication No. 01/075478 Pamphlet

  Here, the structure of the radiation solid detector which protected the a-Se layer using the protective film will be described with reference to FIGS. 5 is a top view of a conventional radiation solid state detector, FIG. 6 is a sectional view taken along line VI-VI in FIG. 5, and FIG. 6 is a sectional view taken along line VII-VII in FIG.

  A conventional radiation solid-state detector 110 includes a first conductive layer 111 on a glass substrate 114, a photoconductive layer 112 that generates electric charges directly upon receiving X-ray irradiation, and a reading circuit including TFTs. And a second conductive layer 113 made up of pixel electrodes are laminated in this order, and the first conductive layer 111 and the photoconductive layer 112 are sealed with a polymer 120 formed by chemical vapor deposition. Further, the radiation solid detector 110 described here is for mammography, and glass ribs 122 are arranged on three sides excluding the chest wall side (A arrow portion in FIG. 5) of the detection unit, A protective film 121 is attached so as to cover the detection region of the radiation solid detector 110 and the rib 122.

  In general, since the photoconductive layer 112 is formed by vapor deposition, an inclination is formed at the edge as shown in FIGS. 6 and 7, so that the side where the rib 122 is arranged is shown in FIG. A space is generated between the rib 122 and the first conductive layer 111, and an edge between the end of the glass substrate 114 and the first conductive layer 111 is also formed on the side where the rib 122 is not disposed as shown in FIG. 7. There will be a space between them, but since the protective film 121 is applied with an adhesive or a pressure-sensitive adhesive, the pressure-sensitive adhesive portion of the protective film 121 is exposed in the space portion (the T-arrow portion in FIGS. 6 and 7). Become.

  And when the protective film 121 of this part (T arrow part in FIG. 6, 7) is pressed, the protective film 121 will contact and adhere to the edge part of the photoconductive layer 112 in the lower part, and will be protected. When the film 121 is restored to its original shape by elastic force, the photoconductive layer 112 may be peeled off from the glass substrate 114.

In order to solve such a problem, as described in Patent Documents 2 and 3, it is conceivable to seal the end edge portion with resin. In view of the above circumstances, the present invention is not suitable for the case where it is desired to secure the detection region as far as possible to the edge of the detector, such as a radiation solid state detector for mammography. An object of the present invention is to provide a radiation solid detector including a film, which eliminates the possibility of peeling at the edge portion of the photoconductive layer.

  A first radiation solid detector of the present invention includes a first electrode layer, a photoconductive layer that generates an electric charge when irradiated with an electromagnetic wave, and a second electrode layer including a plurality of divided electrodes. A radiation solid-state detector, which is laminated on a substrate in order from two electrode layers, and has a protective film attached so as to protect at least the first electrode layer and the photoconductive layer. A low adhesive film having an adhesive force on the photoconductive layer side smaller than that of the protective film is disposed on the edge of the conductive layer.

  Here, the photoconductive layer side of the low adhesive strength film may be non-adhesive.

  The second radiation solid detector of the present invention includes a first electrode layer, a photoconductive layer that generates an electric charge upon irradiation with an electromagnetic wave, and a second electrode layer having a plurality of divided electrodes. A radiation solid state detector, which is laminated on the substrate in order from the second electrode layer, and has a protective film attached so as to protect at least the first electrode layer and the photoconductive layer, On the affixing side, at least a part of the photoconductive layer has an adhesive force at a portion corresponding to the edge of the photoconductive layer, which is smaller than that of the other part.

  Here, on the sticking side of the protective film, at least a portion corresponding to the edge portion of the photoconductive layer may be non-adhesive.

  The “radiation solid state detector” in the above is a detector that detects radiation carrying image information of a subject and outputs an image signal representing a radiation image related to the subject, and converts incident radiation directly into electric charges. By storing this charge once in the power storage unit and then outputting this charge to the outside, an image signal representing a radiographic image related to the subject can be obtained.

  According to the first radiation solid-state detector of the present invention, the first electrode layer, the photoconductive layer that generates an electric charge when irradiated with electromagnetic waves, and the second electrode layer including a plurality of divided electrodes are provided. In the radiation solid state detector, which is laminated on the substrate in order from the second electrode layer and has a protective film attached so as to protect at least the first electrode layer and the photoconductive layer, at least a part of the light Even if the protective film adheres to the substrate side by placing a low-adhesion film having an adhesive force on the photoconductive layer side smaller than that of the protective film on the edge of the conductive layer. Since the protective film adheres to the low adhesion film and does not contact the photoconductive layer, the photoconductive layer can be prevented from peeling off due to the adhesive force of the protective film.

  In addition, according to the second radiation solid detector of the present invention, the first electrode layer, the photoconductive layer that generates an electric charge when irradiated with electromagnetic waves, and the second electrode layer including a plurality of divided electrodes In a radiation solid state detector in which a protective film is applied so as to protect at least the first electrode layer and the photoconductive layer. On the affixing side, the adhesion force of the part corresponding to the edge part of at least a part of the photoconductive layer is made smaller than the adhesion force of the other part. Even when closely adhered to the photoconductive layer, the photoconductive layer can be prevented from peeling off due to the adhesive force of the protective film.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. 1 is a top view of a radiation solid state detector according to an embodiment of the present invention, FIG. 2 is a sectional view taken along line II-II in FIG. 1, and FIG. 3 is a sectional view taken along line III-III in FIG.

  The radiation solid state detector 10 includes a first conductive layer 11 on a glass substrate 14, a photoconductive layer 12 that exhibits direct conductivity by being irradiated with X-rays, and a reading circuit and pixels including TFTs. A second conductive layer 13 composed of an electrode is laminated in this order, and the first conductive layer 11 and the photoconductive layer 12 are sealed with a polymer 20 formed by chemical vapor deposition. Further, the radiation solid detector 10 described here is for mammography, and glass ribs 22 are arranged on three sides excluding the chest wall side (A arrow portion in FIG. 1) of the detection unit, A protective film 21 is attached so as to cover the detection region of the radiation solid detector 10 and the rib 22.

  The first conductive layer 11 only needs to be transparent to X-rays, and for example, a gold thin film can be used. In the present embodiment, a gold film having a thickness of 100 nm is used.

  The photoconductive layer 12 is made of amorphous selenium having high quantum efficiency and low dark current. In the present embodiment, the thickness of the photoconductive layer 12 is 200 μm.

  The second conductive layer 13 is provided with a TFT corresponding to each pixel, and the output line of each TFT is connected to a signal detection means (not shown). The control line of each TFT is connected to a TFT control means (not shown).

  Various polymers can be used as the polymer 20 for sealing the first conductive layer 11 and the photoconductive layer 12 as long as they have low moisture permeability and do not alter amorphous selenium. For example, poly-paraxylylenes Is mentioned.

  The thickness of the polymer 20 formed by chemical vapor deposition is preferably 1 to 100 μm, and more preferably 10 to 50 μm. In the present embodiment, poly-paraxylylene is deposited as the polymer 20 with a thickness of 15 μm by a CVD method.

  As a result, the radiation solid state detector 10 can be sealed without generating a gap, and since no adhesive is used, the adhesive does not permeate the photoconductive layer 12 containing amorphous selenium as a main component. It is possible to protect the photoconductive layer 12 without causing problems such as discharge breakdown.

  Further, a low-adhesion film 30 described later is disposed on the edge of the photoconductive layer 12 on the polymer 20, and then a protective film 21 with an adhesive is pasted on the polymer 20. The protective film 21 is a gas barrier film, and any film can be used as long as this characteristic is satisfied. Specifically, a film in which a film layer made of a polymer material and a metal thin film layer are laminated, a film in which a film layer made of a polymer material and an oxide thin film layer are laminated, and the like can be mentioned. Aluminum is preferably used as the metal thin film layer in the former, and silicon oxide and aluminum oxide are preferably used as the oxide in the latter. A more specific example of the latter is a letterpress printing GX film. Moreover, it is preferable that the thickness of the protective film 21 shall be 5-50 micrometers. In the present embodiment, a GX film made by relief printing is used as the protective film 21.

  The poly-paraxylylenes used as the polymer 20 generally have poor adhesion to other members using an adhesive, but the adhesion can be improved by performing light irradiation treatment with ultraviolet light prior to adhesion. . The necessary irradiation time is appropriately adjusted to the optimum time depending on the wavelength and wattage of the ultraviolet light source to be used, but it is preferably 1 to 50 W with a low-pressure mercury lamp, and the light irradiation is preferably performed for 1 to 30 minutes.

  In general, since the photoconductive layer 12 is formed by vapor deposition, as shown in FIGS. 2 and 3, an inclination is formed at the edge of the photoconductive layer 12. As shown in FIG. 2, a space is generated between the rib 22 and the first conductive layer 11, and even on the side where the rib 22 is not disposed, as shown in FIG. A space is formed between the conductive layer 11 and the conductive layer 11.

  In the present embodiment, a low-adhesion film 30 having an adhesive force on the photoconductive layer 12 side smaller than that of the protective film 21 is disposed on the space portion, that is, the edge of the photoconductive layer 12 on the polymer 20. doing.

  Usually, when the protective film 21 in the space portion (T arrow portion in FIGS. 2 and 3) is pressed, the protective film 21 comes into close contact with the edge portion of the photoconductive layer 12 below the protective film 21. The photoconductive layer 12 may be peeled off from the glass substrate 14 when it is restored to its original shape by the elastic force of the above, but by arranging the low adhesive film 30 on this part as described above, the space part Is pressed and the protective film 21 adheres to the glass substrate 14 side, as shown in FIGS. 2B and 3B, the protective film 21 adheres to the low-adhesive film 30 and the photoconductive layer. Therefore, the photoconductive layer 12 can be prevented from peeling off due to the adhesive force of the protective film 21.

  This low adhesive strength film 30 has insulating properties, and is preferably a PET material. The adhesive applied to the film is preferably an acrylic adhesive or an epoxy adhesive. Specific examples include LE952 manufactured by Toyo Ink Manufacturing Co., Ltd. Moreover, although it is preferable to make the thickness of the film main body of the low adhesive force film 30 thinner than the photoconductive layer 12, it is more preferable to set it as 10-50 micrometers. Moreover, it is preferable that the thickness of the part of the adhesion layer shall be 10 micrometers-50 micrometers. Furthermore, it is preferable to use the low-adhesion film 30 in which the four sides are integrated, rather than individually providing each side of the photoconductive layer 12, because positional deviation is less likely to occur. In the present embodiment, LE952 (PET film body thickness: 25 μm, adhesive layer thickness: 35 μm) manufactured by Toyo Ink Manufacturing Co., Ltd. is used as the low adhesion film 30.

  A polycarbonate resin of 3 mm × 10 mm is installed as a buffer material on the chest wall side (A arrow portion in FIG. 1) of the radiation solid detector 10 formed as described above, and is perpendicular to the inclination of the photoconductive layer 12. When pressure was applied with a force of 5N, 20N, 30N, or 40N, it was confirmed that peeling of the photoconductive layer 12 did not occur in any case.

  In addition, when the same confirmation as described above is performed on the same radiation solid state detector as in the present embodiment except that a low adhesive film is not provided, the photoconductive layer may be peeled off even at a pressure of 5N. It could be confirmed.

  The radiation solid detector 10 formed as described above irradiates the photoconductive layer 12 with X-rays when an electric field is formed between the first conductive layer 11 and the second conductive layer 13. Then, charge pairs are generated in the photoconductive layer 12 and latent image charges corresponding to the amount of the charge pairs are accumulated in the second conductive layer 13. When reading the accumulated latent image charge, the TFTs of the second conductive layer 13 are sequentially driven to output an image signal based on the latent image charge corresponding to each pixel from the output line. By detecting by the signal detecting means, the electrostatic latent image carried by the latent image charge can be read.

  As mentioned above, although preferable embodiment of this invention was described, this invention is not limited above, For example, after arrange | positioning the low adhesive force film 30 on the edge part of the photoconductive layer 12, it protects Rather than affixing the film 21, the low adhesion film 30 is affixed in advance to a position corresponding to the edge of the photoconductive layer 12 on the affixing side surface of the protective film 21, and then the protective film 21 is affixed. You may do it.

  Further, as shown in FIG. 4, an adhesive is applied only to the position 21 a except for the position 21 b corresponding to the edge of the photoconductive layer 12 on the surface on the sticking side of the protective film 21. You may make it affix the protective film 21 made non-adhesive in the position 21b corresponded to an edge.

  In addition, the low adhesive film 30 preferably has a slight adhesive force so as not to cause a positional shift at the time of manufacture, but a non-adhesive film may be used.

  Moreover, although the low-adhesion film 30 is a PET material in the above embodiment, it may be another resin film as long as it has insulating properties, or a thin glass plate having the same thickness may be used.

  Further, the present invention is not limited to the above-described radiation solid-state detector of the electric reading system, and any radiation solid-state detector provided with a photoconductive layer that directly generates an electric charge when irradiated with electromagnetic waves. It can also be applied to things.

The top view of the radiation solid detector by one embodiment of the present invention II-II line sectional view in FIG. Sectional view along line III-III in Fig. 1 Bottom view of protective film of radiation solid state detector of other embodiment Top view of conventional radiation solid state detector VI-VI line sectional view in FIG. VII-VII line sectional view in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Radiation solid state detector 11 1st conductive layer 12 Photoconductive layer 13 2nd conductive layer 14 Glass substrate 20 Polymer 21 Protective film 22 Rib 30 Low adhesive force film

Claims (4)

A first electrode layer;
A photoconductive layer that generates electric charges when irradiated with electromagnetic waves;
A second electrode layer having a plurality of divided electrodes, and laminated on the substrate in order from the second electrode layer;
A radiation solid state detector having a protective film attached so as to protect at least the first electrode layer and the photoconductive layer,
A radiation solid state detector, wherein a low-adhesion film having an adhesive force on the photoconductive layer side smaller than an adhesive force of the protective film is disposed on at least a part of the edge of the photoconductive layer.   The radiation solid state detector according to claim 1, wherein the photoconductive layer side of the low adhesive film is non-adhesive. A first electrode layer;
A photoconductive layer that generates electric charges when irradiated with electromagnetic waves;
A second electrode layer having a plurality of divided electrodes, and laminated on the substrate in order from the second electrode layer;
A bias voltage is applied to the photoconductive layer by forming an electric field between the first conductive layer and the second conductive layer;
A radiation solid state detector having a protective film attached so as to protect at least the first electrode layer and the photoconductive layer,
A radiation solid state detector, wherein, on the side to which the protective film is applied, at least a part of the photoconductive layer has an adhesive force corresponding to an edge of the photoconductive layer that is smaller than an adhesive force of another part.   The radiation solid state detector according to claim 3, wherein a portion corresponding to at least a part of the edge of the photoconductive layer is non-adhesive on the side where the protective film is applied.

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