JP2007095543A - Electron tube and method of manufacturing same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance image quality of an output image by improving an insulation characteristic of a high voltage generation part of an output part of an X-ray image tube to prevent occurrence of dielectric breakdown. <P>SOLUTION: The X-ray image tube 1 is characterized in that a high voltage part 16 set at a potential equivalent to that of a positive electrode 14 is insulated by a first insulation part 17 for insulating a vacuum envelope 11 and an output image formation part 13 and a second insulation part 18 covering the first insulation part so as to prevent micro discharge from reaching the outside even if the micro discharge is generated in the first insulation part. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an X-ray image tube that detects an X-ray image and outputs it as a visible light image, and more particularly to an electron tube capable of improving the image quality of an output image and a method for manufacturing the same.

  An X-ray detector, for example, an X-ray image tube 101 outputs a density distribution of X-rays transmitted through an inspection object as a visible light image, and an X-ray image corresponding to a difference in X-ray absorption rate of the inspection object. Can be obtained as a moving image or a still image.

  As shown in FIG. 4, the X-ray image tube has a vacuum envelope 111 whose inside is maintained in a vacuum, and an outer housing (not shown) that covers the periphery of the vacuum envelope 111.

  An input window 112 for converting X-rays incident from the outside into photoelectrons is provided at one end portion inside the vacuum envelope 111. An output image forming window 113 for converting photoelectrons amplified in the vacuum envelope 111 into visible light is provided at the other end facing the input window along the tube axis in the vacuum envelope 111. .

  Between the input window 112 and the output window 113, the photoelectrons converted by the input window 112 are accelerated toward the output window 113 and the photoelectrons accelerated toward the output window 113 are directed toward the output window 113. A focusing electrode 115 for focusing is provided. The anode 114 is fixed at a predetermined position of the vacuum envelope 111 by an output portion high voltage generator (anode holding portion) 116 fixed to the vacuum envelope 111 together with the output window 113.

  The output window 113 is fixed at a predetermined position of the vacuum envelope 111 together with the output portion high voltage generator 116 by an insulating portion 117 formed by potting a resin material, that is, an insulating material.

  However, when the insulating material 117 is potted, if bubbles 121 are generated inside the insulating material 117 as shown in FIG. 5, the surface of the insulating material 117 to the output high voltage generator 116 or the insulating material 117 There is a problem that the distance to the surface is reduced and the dielectric strength characteristics are deteriorated. Further, when a micro discharge is generated from the bubble 121, a discharge path 117a is formed in the insulating material 117, and the discharge path 117a reaches the surface of the output part high voltage generation part 116 or the insulating material 117 with time, thereby insulating. There is a problem that causes destruction.

  When dielectric breakdown occurs in the output high voltage generator 116, the voltage of the anode 114 decreases, and the voltage distribution of the electron lens changes, resulting in a deterioration in the image quality of the output image of the X-ray image tube. There is.

  In addition, due to the occurrence of discharge due to dielectric breakdown, a load is applied to a driving power supply (not shown) that supplies a voltage to the electronic lens, causing power supply failure.

  However, even when the insulating material 117 is sufficiently degassed and potted, when the X-ray image tube 101 is taken out from the vacuum to the atmosphere (1 atm), minute bubbles enter the insulating material. Is difficult to completely prevent. Further, since the bubbles cannot be confirmed from the surface of the insulating material, they cannot be removed by other processes or techniques, and it is inevitable that dielectric breakdown will occur over time.

  In addition, there is a problem that dielectric breakdown similarly occurs when moisture penetrates from the surface of the insulating material due to water droplets adhering to the surface of the insulating material due to the humidity of the use environment.

  An object of the present invention is to improve the insulation characteristics of the output high voltage generator of the X-ray image tube to suppress dielectric breakdown and to improve the image quality of the output image.

  The present invention includes an input unit that converts an X-ray image into an electronic image, an output image forming unit that converts the electronic image output from the input unit into a visible light image, and the electronic image output from the input unit. And a focusing electrode and an anode for focusing toward the output image forming unit, and a vacuum envelope for holding the input unit, the output image forming unit, the focusing electrode and the anode in a vacuum. In the X-ray image tube, the output image forming unit includes a high voltage unit having the same potential as the anode, a first insulating unit that insulates the vacuum envelope and the output image forming unit, and the first An X-ray image tube is provided that is insulated by a second insulating portion that covers the insulating portion.

  Further, according to the present invention, an accelerating electrode and a focusing electrode are arranged in a vacuum envelope including an input window, at least the accelerating electrode is fixed to an electrode holding portion provided in the vacuum envelope, and an output image is displayed on the electrode holding portion. Obtained by fixing the forming window, forming a first insulating part by potting in a predetermined region of the vacuum envelope, electrode holding part and output image forming window, and molding a resin material formed into a plate shape by stretching The X-ray image tube manufacturing method is characterized in that the second insulating portion is provided integrally with the first insulating portion.

  The present invention also provides a vacuum envelope, an input unit provided in the vacuum envelope for converting an X-ray image into an electronic image, and provided in the vacuum envelope and output from the input unit. An output image forming unit for converting the electron image into a visible light image, and an anode provided in the vacuum envelope and accelerating the electronic image output from the input unit toward the output image forming unit A focusing electrode that is provided in the vacuum envelope and focuses the electron image output from the input unit toward the output image forming unit; and an end of the vacuum envelope that is the input A first insulator covering at least the output image forming portion and the electrode holding portion held by the anode, and covering at least the electrode holding portion so as not to be exposed to the outside. And a plate-like body formed by stretching, wherein the inside of the first insulator An X-ray image tube comprising: a second insulator covering at least a part of the first insulator in order to prevent a generated micro discharge from reaching the outside. is there.

  According to the present invention, the high voltage generating portion of the output image forming portion is insulated by the first and second insulating materials provided by different manufacturing methods capable of preventing the minute discharge generated inside from reaching the outside. Therefore, in the X-ray image tube, it is possible to prevent the image quality from being deteriorated due to a decrease in insulation characteristics.

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

  FIG. 1 shows an example of an X-ray image tube to which the embodiment of the present invention can be applied.

  As shown in FIG. 1, the X-ray image tube 1 has a vacuum envelope 11 in which the inside is maintained in a vacuum and an exterior housing (not shown) that covers the periphery of the vacuum envelope 11.

  An input window (input screen) 12 for converting X-rays incident from the outside into photoelectrons is provided at one end inside the vacuum envelope 11. At the other end facing the input window 12 along the tube axis in the vacuum envelope 11, an output image forming window (output screen) 13 that converts photoelectrons amplified in the vacuum envelope 11 into visible light. Is provided.

  Between the input window 12 and the output image forming window 13, an anode 14 that accelerates photoelectrons converted by the input window 12 toward the output image forming window 13 and photoelectrons accelerated toward the output image forming window 13. A focusing electrode 15 for focusing toward the output image forming window 13 is provided (in this example, the first to third focusing electrodes are used, so that they are referred to as 15a to 15c for convenience). The anode 14 is fixed at a predetermined position of the vacuum envelope 11 by an output unit high voltage generation unit (anode holding unit) 16 fixed to the vacuum envelope 11 together with the output image forming window 13.

  The input window 12 is made of, for example, a substrate made of Al (aluminum) or Be (beryllium), and has a fluorescent screen (not shown) that converts incident X-rays into fluorescence on the inner surface, and fluorescence converted by the fluorescent screen. A photoelectric conversion surface (not shown) that converts to photoelectrons is sequentially stacked.

  The output image forming window 13, which will be described in detail below with reference to FIG. 2, is a glass plate having a predetermined thickness capable of transmitting visible light, and is located inside the vacuum envelope 11, that is, on the side facing the input window 12. In addition, a phosphor screen 131 is provided for converting photoelectrons emitted from the input window 12 into visible light. Accordingly, a visible light image corresponding to the X-ray density distribution (X-ray transmission image) input to the input window 12 is output outside the output image forming window 13, that is, the vacuum envelope 11.

  As shown in FIG. 2, the output image forming window 13, together with the output portion high voltage generating portion 16, is formed by a first insulating portion 17 formed by potting a sufficiently defoamed resin material. It is fixed at a predetermined position. The first insulating portion 17 is a thermosetting resin, for example, a silicone resin.

  The first insulating portion 17 is formed by a second insulating portion 18 having a manufacturing method different from that of a first insulating portion formed of a resin material previously formed into a plate shape (processed by stretching), for example, a polycarbonate material having a predetermined thickness, for example. Covered. The second insulating portion 18 formed in a plate shape in advance is disposed in a predetermined positional relationship with respect to the vacuum envelope 11 and the output image forming window 13, and the first insulating portion 18 is cured between the first insulating portion 18 and the second insulating portion 18. A resin material that becomes the insulating portion 17 may be potted.

  As shown in FIG. 2, by providing a second insulating portion 18 formed of a resin material formed into a plate shape by stretching on the outside of the first insulating portion 17, bubbles are formed in the first insulating portion 17. Even if the discharge path 17a is formed up to the surface of the first insulating part 17 by the micro discharge inside the bubble 21, the discharge path 17a is at the interface between the second insulating part 18 and the first insulating part 17. It can be stopped.

  Further, even when water droplets 31 adhere to the surface of the second insulating portion 18, it is difficult for water droplets or the like to penetrate from the surface of the second insulating portion 18 into the second insulating portion 18 and the first insulating portion 17. Insulation breakdown due to water droplets is also difficult to occur. In addition, by providing the 2nd insulating part 18 formed with the resin material formed in plate shape by extending | stretching process as shown in FIG. 2, the time to a dielectric breakdown is the front using FIG. X and FIG. It has been confirmed that it is about four times longer than the conventional structure described in (1). Therefore, it is possible to obtain the X-ray image tube 1 in which the image quality is hardly deteriorated due to the dielectric breakdown.

  FIG. 3 shows another embodiment of the output unit high voltage generator shown in FIG. The same components as those shown in FIG. 2 are denoted by the same reference numerals, and detailed description thereof is omitted.

  As shown in FIG. 3, the output image forming window 13, together with the output part high voltage generation part 16, is formed by a first insulating part 17 formed by potting a sufficiently defoamed resin material. It is fixed at a predetermined position. The first insulating portion 17 is a thermosetting resin, for example, a silicone resin.

  The 1st insulating part 17 is covered with the 2nd insulating part 18 formed with the resin material formed in plate shape by extending | stretching process.

  The second insulating portion 18 is further covered with a third insulating portion 31 formed of the same resin material as that of the first insulating portion 17. Note that the second insulating portion 18 may be embedded in the first insulating portion 17.

  As described above, the first insulating portion is configured such that the second insulating portion 18 is sandwiched between the first insulating portion 17 and the third insulating portion 31 formed of the same resin material as the first insulating portion 17. 17 or the third insulating portion 31, or when water droplets 22 are generated outside the vacuum envelope 11 and the output image forming window 13, discharge occurs from the bubbles 21 or water droplets 22, Even if the discharge path 17a or 31a is generated inside the first or third insulating portion 17 or 31, the discharge path 17a or 31a reaches the outside of the vacuum envelope 11 and the output window 13 to cause dielectric breakdown. Is prevented.

  Note that the present invention is not limited to the above-described embodiments as they are, and can be embodied by variously modifying the constituent elements without departing from the scope of the invention in the implementation stage. Various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the above-described embodiments. For example, some components may be deleted from all the components shown in the embodiment.

Schematic explaining an example of an X-ray image tube to which an embodiment of the present invention can be applied. Schematic explaining an example of the structure of the vicinity of the output window of the X-ray image tube shown in FIG. Schematic explaining another example of the configuration in the vicinity of the output window shown in FIG. Schematic explaining an example of a known X-ray image tube. Schematic explaining an example of a configuration in the vicinity of the output window of the X-ray image tube shown in FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... X-ray image tube, 11 ... Vacuum envelope, 12 ... Input window, 13 ... Output image formation window, 14 ... Anode, 15 (15a-15c) ... Focusing electrode, 16 ... Output part high voltage generation part, 17 ... 1st insulation part, 17a ... Discharge path, 18 ... 2nd insulation part, 21 ... Bubble, 22 ... Water droplet, 31 ... 3rd insulation part.

Claims (9)

An input unit for converting an X-ray image into an electronic image, an output image forming unit for converting the electronic image output from the input unit into a visible light image, and accelerating the electronic image output from the input unit, An X-ray image tube comprising a focusing electrode and an anode focused toward the output image forming unit, and a vacuum envelope for holding the input unit, the output image forming unit, the focusing electrode and the anode in a vacuum In
The output image forming unit includes a high voltage unit having the same potential as the anode, a first insulating unit that insulates the vacuum envelope and the output image forming unit, and a second covering the first insulating unit. An X-ray image tube characterized by being insulated by an insulating part.   2. The X-ray image tube according to claim 1, wherein the second insulating portion is formed by a manufacturing method different from that of the first insulating portion, and is made of a member capable of suppressing the expansion of a discharge path due to discharge.   The X-ray image tube according to claim 2, wherein the second insulating portion is obtained by molding a resin material manufactured in a plate shape by stretching.   The first insulating part is potted between the second insulating part provided in advance between the vacuum envelope and the output image forming part, and the vacuum envelope and the output image forming window. The X-ray image tube according to claim 2 or 3, characterized in that   5. The X-ray image tube according to claim 2, further comprising a third insulating portion formed of the same material as that of the first insulating portion outside the second insulating portion. Arrange the acceleration electrode and focusing electrode in the vacuum envelope including the input window,
At least the acceleration electrode is fixed to the electrode holding part provided in the vacuum envelope,
Fix the output image forming window to the electrode holder,
A first insulating portion is provided by potting in a predetermined region of the vacuum envelope, the electrode holding portion, and the output image forming window, and a second insulating portion obtained by molding a resin material formed into a plate shape by stretching is provided. Provided integrally with the first insulating portion;
A method for manufacturing an X-ray image tube.   The first insulating portion is potted between a second insulating portion previously provided at a predetermined position with respect to the vacuum envelope and the output image forming window, and the vacuum envelope and the output image forming window. A method for manufacturing an X-ray image tube according to claim 6.   8. The method of manufacturing an X-ray image tube according to claim 6, wherein a third insulating part is further formed outside the second insulating part with the same material as the first insulating part. A vacuum envelope,
An input unit provided in the vacuum envelope for converting an X-ray image into an electronic image;
An output image forming unit provided in the vacuum envelope and converting the electronic image output from the input unit into a visible light image;
An anode provided in the vacuum envelope and accelerating the electronic image output from the input unit toward the output image forming unit;
A focusing electrode that is provided in the vacuum envelope and focuses the electron image output from the input unit toward the output image forming unit;
An electrode holding part that is provided at an end of the vacuum envelope and that faces the input part, and holds at least the output image forming part and the anode;
A first insulator covering at least the electrode holder so as not to be exposed to the outside;
A plate-like body formed by stretching, a second body covering at least a part of the first insulator in order to prevent a micro discharge generated inside the first insulator from reaching the outside. An insulator;
An X-ray image tube comprising:

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