JP5522440B2 - Electron beam irradiation apparatus and electron beam irradiation method - Google Patents

Description

  The present invention relates to an electron beam irradiation apparatus and an electron beam irradiation method used for performing an electron beam irradiation treatment on an object to be processed.

  Conventionally, treatments such as cleaning, surface modification, sterilization, and sterilization have been performed by irradiating a resin workpiece with the electron beam. At that time, the workpiece is treated by electron beam irradiation. It is known that charging may occur.

  In order to prevent the resin workpiece from being charged by electron beam irradiation, for example, a static eliminator can be used. Generally, a static eliminator is an apparatus that has an ion generator that generates ions and neutralizes static electricity using the ions. An electron beam irradiation apparatus that neutralizes charges accumulated in a workpiece by disposing a PIG ion source in the electron beam irradiation section and ejecting ions generated from the PIG ion source toward the workpiece. Has been devised (see, for example, Patent Document 1).

JP 2002-25493 A

  The above-mentioned static eliminator such as the PIG ion source is provided in the electron beam irradiation device, and the charge generated in the resin processed material is neutralized by using the ions generated by this static eliminator, thereby making the resin processed It is also possible to prevent charging of objects. However, when such a static eliminator is provided in the electron beam irradiation apparatus, there is a problem that the electron beam irradiation apparatus becomes large and the manufacturing cost increases. For this reason, when an electron beam irradiation treatment is performed on a resin workpiece, it is desired to realize an electron beam irradiation apparatus that can prevent charging of the resin workpiece with a simple configuration.

  The present invention has been made based on the above circumstances, and an electron beam irradiation apparatus and electron beam irradiation capable of reducing the charging of the object to be processed with a simple configuration when the object to be processed is subjected to an electron beam irradiation process. It is intended to provide a method.

  The present invention for achieving the above object is an electron beam irradiation apparatus used for performing an electron beam irradiation treatment on a workpiece to be charged by irradiating an electron beam, wherein the electron beam is generated by the electron beam irradiation device. A radiation generator, an irradiation chamber in which the object to be processed is irradiated with the electron beam, and a vacuum atmosphere in the electron beam generator and an irradiation atmosphere in the irradiation chamber are partitioned and the electron beam is irradiated in the irradiation chamber. And a gas supply section for flowing a rare gas, nitrogen gas, or a mixed gas containing the rare gas or the nitrogen gas to the object to be processed, and the gas to the object to be processed The object is irradiated with the electron beam while flowing the rare gas, the nitrogen gas, or the mixed gas containing the rare gas or the nitrogen gas from the supply unit.

  In addition, the present invention for achieving the above object is an electron beam irradiation method used for performing an electron beam irradiation treatment on a workpiece to be charged by irradiating an electron beam, wherein a gas is applied to the workpiece. An object is irradiated with an electron beam while flowing a rare gas, nitrogen gas, or a mixed gas containing a rare gas or nitrogen gas from a supply unit.

  In the present invention, the rare gas or nitrogen gas receives energy from the electron beam by irradiating the electron beam while flowing a rare gas, nitrogen gas, or a mixed gas containing a rare gas or nitrogen gas over the surface of the object to be processed. As a result of being ionized, the electrons staying in the object to be processed diffuse into the ionized gas atmosphere, so that charging of the object to be processed by the electron beam irradiation process can be reduced. Here, the rare gas is preferably argon gas. Further, the surface of the object to be processed means, for example, when the object to be processed is in a sheet form, the surface on the front side or (and) the back side of the object to be processed, and the object to be processed is hollow. When it is a thing, it means the inner surface or (and) the outer surface of the workpiece.

  Further, it is desirable that the object to be processed is supported by a conductive support that is electrically grounded. As a result, the electrons staying in the object to be processed due to the electron beam irradiation can be diffused into the ionized gas atmosphere and can be released to the ground through the ionized gas atmosphere. The charged product can be prevented from being charged.

  When the object to be processed is a hollow resin container, the opening of the object to be processed is supported by a conductive support that is electrically grounded, and the object to be processed is conveyed. The transport direction is a direction perpendicular to the electron beam bundle of the electron beam irradiated into the irradiation chamber from the electron beam generator through the irradiation window, and the direction of the object to be processed is the belt shape. It is held in a posture so that it is parallel to the electron beam bundle, or in such a manner that the bottom of the object to be processed is in front and the mouth of the object to be grounded is in the rear in the transport direction. It is desirable to irradiate the object to be processed with an electron beam while flowing a gas, nitrogen gas, or a mixed gas containing a rare gas or nitrogen gas from the opening portion of the object to be processed into the object to be processed. Thereby, it can prevent reliably that the to-be-processed object which is a hollow resin container can be electrically charged by an electron beam irradiation process.

  The electron beam irradiation process may be a sterilization process, a sterilization process, or a surface modification process. Here, the surface modification treatment refers to a surface modification treatment in a broad sense including a crosslinking reaction, graft polymerization reaction, coating, hydrophilicity improvement, strength improvement, and the like.

  Further, an electron beam generated at an accelerating voltage in the range of 50 kV to 500 kV has a relatively shallow penetration depth into the object to be processed. Therefore, when the object is irradiated with such an electron beam, electrons are generated in the object to be processed. Tends to stay. Therefore, an electron beam irradiation apparatus that applies an electron beam irradiation treatment to an object to be processed using an electron beam generated at an acceleration voltage within a range of 50 kV to 500 kV is particularly preferable as an application target of the present invention.

  In the electron beam irradiation apparatus and the electron beam irradiation method of the present invention, when an electron beam irradiation treatment is performed on a workpiece, the workpiece is charged with a simple configuration without using a special device such as a static eliminator. Can be reduced.

FIG. 1A is a schematic configuration diagram of an electron beam irradiation apparatus according to an embodiment of the present invention, and FIGS. 1B and 1C are views for explaining the direction of an object to be processed when the object to be processed is conveyed. FIG. FIG. 2 is a schematic circuit diagram of an electron beam generator of an electron beam irradiation apparatus according to an embodiment of the present invention. FIG. 3 is a schematic view showing a state where an object to be processed is subjected to an electron beam irradiation process using an electron beam irradiation apparatus according to an embodiment of the present invention. FIG. 4 is a schematic perspective view for explaining an example of the positional relationship between the band-shaped electron beam bundle and the object to be processed during the electron beam irradiation process. FIG. 5 is a table showing the results of a first test when an electron beam irradiation treatment is performed on an object to be processed using a conventional electron beam irradiation apparatus. FIG. 6 is a table showing the result of the second test when the electron beam irradiation processing is performed while flowing argon gas into the hollow object to be processed by the electron beam irradiation apparatus of the present embodiment. FIG. 7 shows a third example in which an electron beam irradiation process is performed on an object to be processed in a state where the object to be processed is not held by a conductive support and is floated with respect to the ground using the electron beam irradiation apparatus of this embodiment. It is a table | surface which shows the result of a test. FIG. 8 is a table showing the results of the fourth test when the electron beam irradiation processing is performed while flowing the nitrogen gas into the hollow object to be processed by the electron beam irradiation apparatus of the present embodiment. FIG. 9 is a diagram showing an emission spectrum in the irradiation chamber when the irradiation chamber is in an air atmosphere and an electron beam is irradiated in a state where there is no object to be processed. FIG. 10 is a diagram showing an emission spectrum in the irradiation chamber when an object to be processed is placed in the irradiation chamber and an electron beam is irradiated while the irradiation chamber is kept in an air atmosphere. FIG. 11 is a diagram showing an emission spectrum in the irradiation chamber when an object to be processed is placed in the irradiation chamber and an electron beam is irradiated while flowing nitrogen gas in the irradiation chamber. FIG. 12 is a diagram showing an emission spectrum in the irradiation chamber when an object to be processed is placed in the irradiation chamber and an electron beam is irradiated while flowing argon gas in the irradiation chamber.

  The best mode for carrying out the present invention will be described below with reference to the drawings. FIG. 1A is a schematic configuration diagram of an electron beam irradiation apparatus according to an embodiment of the present invention, and FIGS. 1B and 1C are views for explaining the direction of an object to be processed when the object to be processed is conveyed. FIG. 2 is a schematic circuit diagram of an electron beam generator of the electron beam irradiation apparatus, and FIG. 3 is a schematic diagram showing a state in which an electron beam irradiation process is performed on an object to be processed using the electron beam irradiation apparatus. FIG.

  Generally, an electron beam irradiation apparatus is used to irradiate an object to be processed with an electron beam and perform a desired process on the object to be processed. For example, an electron beam is applied to a resin container to sterilize the object. Used to apply.

  As shown in FIGS. 1 and 2, the electron beam irradiation apparatus of the present embodiment includes an electron beam generation unit 10, an irradiation chamber 20, an irradiation window unit 30, a beam catcher (electron beam capturing unit) 24, and a gas. And a supply unit 40. Here, specifically, as the electron beam irradiation apparatus, a low energy electron beam irradiation apparatus having an acceleration voltage of 50 kV to 300 kV is used.

  The electron beam generator 10 includes a terminal 11 that generates an electron beam and an acceleration tube 12 that accelerates the electron beam generated at the terminal 11 in a vacuum space (acceleration space). The terminal 11 includes a linear filament 11a that emits thermoelectrons, a gun structure 11b that supports the filament 11a, and a grid 11c that controls thermoelectrons generated by the filament 11a.

The accelerating tube 12 is formed in a cylindrical shape, and is installed so that its central axis is substantially horizontal and perpendicular to the paper surface of FIG. A filament 11 a is disposed along the central axis of the acceleration tube 12. The accelerating tube 12 is shielded from lead so that X-rays generated secondarily during electron beam irradiation do not leak to the outside. Note that the inside of the acceleration tube 12 (electron beam generator 10) is 10 ⁻⁴ by a pump or the like (not shown) in order to prevent electrons from colliding with gas molecules and losing energy, and to prevent oxidation of the filament 11a. A vacuum of 10 ⁻⁵ Pa is maintained.

  The irradiation chamber 20 is provided below the electron beam generator 10. As shown in FIG. 1A, the object A to be processed, which is a hollow container, is conveyed from the left side to the right side in the irradiation chamber 20, for example. The workpiece to be conveyed is irradiated with the electron beam taken out from the irradiation window 30 below the irradiation window 30. The electron beam group forms a band-shaped electron beam bundle B extending perpendicularly to the paper surface of FIG. The conveying direction of the object to be processed is set in a direction orthogonal to the band-shaped electron beam bundle B. Specifically, for example, the workpiece A is arranged so that the mouth is held by the conductive holding means, and the longitudinal direction thereof is perpendicular to the paper surface of FIG. It is conveyed in the irradiation chamber 20. Hereinafter, a region near the irradiation window 30 in the irradiation chamber 20 is referred to as an irradiation space 21. That is, the irradiation space 21 is a space in which processing for irradiating the workpiece A with an electron beam is performed.

  In addition, the irradiation chamber 20 has a structure in which X-rays generated secondarily in the irradiation chamber 20 during electron beam irradiation do not leak to the outside. That is, the irradiation chamber 20 itself is an X-ray shielding structure. The irradiation chamber 20 is made of a material such as lead or stainless steel.

  The irradiation window portion 30 includes a window foil 31 made of a metal foil, a window frame portion 32, and a clamp plate 33. The window frame portion 32 cools the window foil 31 and supports the window foil 31. The clamp plate 33 presses the window foil 31 from the irradiation chamber 20 side. The window foil 31 separates the vacuum atmosphere in the electron beam generating unit 10 from the irradiation atmosphere in the irradiation space 21 and extracts an electron beam from the electron beam generating unit 10 to the irradiation space 21 through the window foil 31. It is. The metal used for the window foil 31 has a mechanical strength that can sufficiently maintain the vacuum atmosphere in the electron beam generator 10, has a small specific gravity and a small thickness so that the electron beam can be easily transmitted, and is heat resistant. It is desirable that it is excellent in

  The gas supply unit 40 is for supplying argon gas or nitrogen gas into the irradiation chamber or the workpiece A when the workpiece A is irradiated with an electron beam. For example, the argon gas or the nitrogen gas is ejected from the gas supply unit 40 through the resin supply pipe 41 and the nozzle unit 42 into the workpiece A as shown in FIG. That is, in this embodiment, when performing the electron beam irradiation treatment on the workpiece A, the workpiece is irradiated with the electron beam while flowing argon gas or nitrogen gas into the workpiece A which is a hollow container. . The present invention is not limited to argon gas or nitrogen gas, and may be helium, neon, krypton, or the like as long as it is a rare gas. Further, it may be a mixed gas of a rare gas and another gas such as nitrogen gas. Further, it may be a mixed gas containing nitrogen. Further, the supply pipe 41 of the present invention is not limited to resin, but may be made of metal.

  The electron beam irradiation apparatus includes a heating power source 71 for heating the filament 11a to generate thermoelectrons, a control DC power source 72 for applying a voltage between the filament 11a and the grid 11c, and the grid 11c. And an acceleration DC power source 73 for applying a voltage (acceleration voltage) between the window foil 31 and the window foil 31.

  When the filament 11a is heated with current by the heating power supply 71, the filament 11a emits thermoelectrons, and these thermoelectrons are scattered in all directions by the control voltage of the control DC power supply 72 applied between the filament 11a and the grid 11c. Gravitate. Of these, only those passing through the grid 11c are effectively extracted as electron beams. The electron beam taken out from the grid 11c is accelerated in the acceleration space in the accelerating tube 12 by the acceleration voltage of the acceleration DC power source 73 applied between the grid 11c and the window foil 31, and then the window foil. The workpiece A is irradiated in the irradiation space 21 in the irradiation chamber 20 through the 31. The current value due to the flow of the electron beam extracted from the grid 11c is referred to as a beam current. Therefore, the amount of electron beams increases as the beam current increases.

  In general, in an electron beam irradiation apparatus, an acceleration voltage, a beam current, a conveyance speed of an object to be processed are set to predetermined values, and a process for irradiating an object with an electron beam is performed. The energy given to the electron beam is determined by the acceleration voltage. That is, as the acceleration voltage is set higher, the kinetic energy obtained by the electron beam increases, and as a result, the electron beam can reach a deep position from the surface of the object to be processed. For this reason, the penetration depth of the electron beam into the workpiece can be adjusted by changing the set value of the acceleration voltage. Further, the amount of energy received by the object to be processed when the object is irradiated with an electron beam is represented by a value called absorbed dose. In order to give an appropriate absorbed dose to the object to be processed, the beam current is controlled. Normally, the beam current is adjusted by setting the heating power supply 71 and the acceleration DC power supply 73 to predetermined values and making the control DC power supply 72 variable. The absorbed dose received by the workpiece is proportional to the beam current and inversely proportional to the conveyance speed of the workpiece. For this reason, the absorbed dose of the electron beam can be adjusted by changing the beam current or the conveyance speed of the workpiece.

  By the way, normally, an electron beam generated at an accelerating voltage within a range from 50 kV to 300 kV is called a low energy electron beam. Here, if the acceleration voltage is made smaller than 50 kV, the amount of electron beam that can be extracted from the irradiation window 30 is too small, and it is not practical to set the acceleration voltage smaller than 50 kV. An electron beam generated at an acceleration voltage in the range of 300 kV to 1000 kV is called a medium energy electron beam, and an electron beam generated at an acceleration voltage higher than 1000 kV is called a high energy electron beam. In this embodiment, a low-energy electron beam irradiation apparatus that generates a low-energy electron beam is used. However, the low-energy electron beam cannot normally pass through the object to be processed, and part or all of the electrons are used. It stays in the workpiece. This is the cause of the workpiece A being charged during the electron beam irradiation treatment. On the other hand, since an electron beam generated at an acceleration voltage exceeding 500 kV and a high-energy electron beam can pass through a thin workpiece having a small thickness, the workpiece is charged by the electron beam irradiation treatment. There are few things.

  A beam catcher 24 is provided in the irradiation chamber 20. As shown in FIG. 1A, the beam catcher 24 is installed at a position facing the irradiation window 30 via the workpiece A. The beam catcher 24 captures an electron beam that has passed through the irradiation space 21. Here, the electron beam that has passed through the irradiation space 21 passes through the workpiece A and reaches the beam catcher 24 as well as the electron beam that has reached the beam catcher 24 without being irradiated on the workpiece A. Applicable to electron beams. The beam catcher 24 is made of, for example, stainless steel or aluminum.

  In the present embodiment, since an electron beam irradiation apparatus that irradiates a low energy electron beam is used, the penetration depth of the electron beam into the workpiece A is relatively shallow. For this reason, when the workpiece A is irradiated with a low-energy electron beam, a part of the electron beam remains on the workpiece A, and the workpiece A is charged. Therefore, in this embodiment, the electron beam irradiation treatment is performed on the workpiece while flowing argon gas or nitrogen gas into the hollow workpiece. Argon gas or nitrogen gas flowing into the object to be processed is ionized by receiving energy by electron beam irradiation. In this way, the inside of the object to be processed is an atmosphere of an ionized state of argon gas or nitrogen gas, and in this state, the object to be processed is irradiated with an electron beam. Then, as shown in FIG. 3, the electrons that are going to stay on the object to be processed diffuse into the ionized gas (atmosphere gas) 45 in an ionized state of argon gas or nitrogen gas, thereby charging the object to be processed. Is estimated to be reduced.

  Moreover, in this embodiment, the opening part of a hollow to-be-processed object is supported by the electroconductive support tool 50, and the electron beam irradiation process is performed to the to-be-processed object. This conductive support is connected to the ground via the housing of the electron beam irradiation device. For this reason, it is presumed that electrons that are going to stay on the object to be processed flow from the conductive support to the ground directly or via the atmospheric gas, thereby preventing the object to be processed from being charged.

  Next, based on the test result of the present embodiment, a method for reducing the charge of the object to be processed or preventing the charge will be described. In each of the following tests, an EC300 / 30/30 mA apparatus manufactured by Iwasaki Electric Co., Ltd. is used as the electron beam irradiation apparatus, and a resin container is used as the object to be processed. The object to be processed A was held so that the distance from the window foil 31 to the center of the object to be processed was about 100 mm, and in this state, the electron beam irradiation process was performed.

  In the test of the present embodiment, the charged amount was evaluated by putting filtered water into the object to be treated with the electron beam irradiation treatment and measuring the charge amount of the filtered water. In this measurement, an FDC 8031 (0.01 μF) Faraday cup was used, and the measurement was performed with an AD 8240 electrometer.

  First, a first test was performed in which an object to be processed was subjected to an electron beam irradiation process using a conventional electron beam irradiation apparatus, and the charge amount (water charge amount) of the object to be processed by the electron beam irradiation was measured. FIG. 5 is a table showing the results of a first test when an electron beam irradiation process is performed on an object to be processed using a conventional electron beam irradiation apparatus. The direction of the object to be processed when the object to be processed in this first test is conveyed (hereinafter also simply referred to as the direction of the object to be processed) is to be processed with respect to the band-shaped electron beam bundle as shown in FIG. The center axis of the object is made parallel. Moreover, the to-be-processed object's conveying method conveys to-be-processed object from the left side to the right side. The beam current of the workpiece was set to 5 mA, the conveyance speed was set to 6 m / min, and the acceleration voltages were set to 300 kV, 275 kV, and 250 kV. In the first test, the workpiece is irradiated with an electron beam in the atmosphere without flowing argon gas or nitrogen gas.

In the first test of the first test (acceleration voltage 300 kV), filtered water is put into the workpiece irradiated with the electron beam, and the amount of water in the workpiece is measured with a Faraday cup after 30 minutes. The value was -10745 to -12400 (10 ^-9 C). Moreover, when 24 hours passed, the value obtained by measuring the charge amount of water in the object to be processed with a Faraday cup was -3995 to -4640 (10 ^-9 C). The second and third tests, which have different acceleration voltages from the first test, showed almost the same results as the first test.

From the first to third test results of the first test, when an electron beam irradiation process is performed on the workpiece using a conventional electron beam irradiation apparatus, as shown in FIG. charge amount of the water contained in the object to be processed is -8600V a minimum (10 ^-9 C), also after 24 hours, -3995 that charge amount of the water contained in the object to be treated at a minimum (10 ^-9 C) high charge amount.

  Next, the electron beam irradiation apparatus according to the embodiment of the present invention is used to perform the electron beam irradiation treatment on the workpiece, and the charge amount (water charge amount) of the workpiece by the electron beam irradiation is measured. A test was conducted. FIG. 6 is a table showing the results of the second test when the electron beam irradiation processing is performed while flowing argon gas into the hollow object to be processed by the electron beam irradiation apparatus of the present embodiment. The second test is different from the first test described above. In the second test, as shown in FIG. 3, while argon gas is allowed to flow from the gas supply unit 40 into the hollow workpiece A, electrons are applied to the workpiece. The point which is performing the irradiation process of a line | wire, and the point which is hold | maintained with the electroconductive support which has electrically grounded the opening | mouth part of the to-be-processed object. The conveyance speed and beam current of the workpiece are the same as in the first test. The flowing argon gas has a gas pressure of 0.2 MPa and a gas flow rate of 15 L / min. This argon gas was allowed to flow for 5 minutes to sufficiently replace the object to be processed, and then the test was performed. The oxygen concentration in the workpiece, measured with an oxygen concentration meter of Toray LC-750, is 0.05 to 0.07%. Also in the second test, the method for conveying the object to be processed is set from the left side to the right side, and the object conveying direction is set in a direction orthogonal to the belt-like electron beam bundle B. Further, the direction of the object to be processed in the second test is set so that the central axis of the object to be processed and the band-shaped electron beam bundle are parallel to each other in the first test, as in the first test, that is, FIG. As shown in FIG. 1, the center axis of the object to be processed is perpendicular to the paper surface of FIG. In the second test, the direction of the object to be processed is such that the central axis of the object to be processed is perpendicular to the band-shaped electron beam bundle, and the bottom of the object to be processed is in front in the transport direction of the object to be processed. The mouth held by the sex supporter is located behind. That is, the direction of the object to be processed is as shown in FIG. In the third test, the direction of the object to be processed is such that the central axis of the object to be processed is perpendicular to the band-shaped electron beam bundle and is held by the conductive support of the object to be processed in the conveyance direction of the object to be processed. The mouth is made in front and the bottom is in the rear. That is, the direction of the object to be processed is as shown in FIG. 1 (c) and FIG. FIG. 4 is a perspective view for explaining an example of the positional relationship between the band-shaped electron beam bundle and the object to be processed during the electron beam irradiation process. Moreover, in said 1st test, although the acceleration voltage was changed and the test was performed 3 times, the result similar to the 3 times test was obtained. For this reason, in each test described below, only the test in which the acceleration voltage is set to 300 kV is performed.

In the first test of the second test, after performing electron beam irradiation treatment, filtered water is put into the object irradiated with the electron beam, and when 30 minutes have passed, the charge amount of water in the object to be processed is determined. The values measured with the Faraday cup were undetectable for all three objects. The fact that the value measured with the Faraday cup cannot be detected means that the measured value of the Faraday cup is -100 (10 ^-9 C) or less. This notation means the same in the following tests.

  In the second test of the second test, after the electron beam irradiation treatment is performed, filtered water is put into the object to be irradiated with the electron beam, and when 30 minutes have passed, the charge amount of the filtered water in the object to be processed The value measured with a Faraday cup was undetectable for all three workpieces.

In the third test of the second test, after performing the electron beam irradiation treatment, filtered water is put into the object to be treated which has been irradiated with the electron beam, and when 30 minutes have passed, the charge amount of water in the object to be treated is determined. The values measured with the Faraday cup were -1062 to -11517 (10 ^-9 C).

According to the first and second test results of the second test, filtered water was put into the workpiece irradiated with the electron beam, and after 30 minutes had passed, the charge amount of the water contained in the workpiece was not detected. It was possible. That is, according to the electron beam irradiation method of the first test and the second test of the second test, it is possible to prevent the workpiece from being charged by the electron beam irradiation process. Moreover, according to the test result of the 3rd time of a 2nd test, after putting filtered water into the to-be-processed object irradiated with the electron beam, and 30 minutes passed, the charge amount of the water accommodated in the to-be-processed object is the minimum, -10662 (10 ^-9 C). From the first to third test results of the second test, when irradiating a hollow workpiece with an electron beam, the orientation of the workpiece is important, and the orientation of the workpiece is the center of the workpiece. The axis and the band-shaped electron beam bundle are parallel to each other, or the center axis of the object to be processed is perpendicular to the band-shaped electron beam bundle, and the bottom of the object to be processed is in the conveyance direction of the object to be processed. In the front, it has been confirmed that the mouth (opening) held by the electrically conductive support that is electrically grounded needs to be the rear.

  Next, a test for verifying how the electrons that are going to stay on the object to be processed by the electron beam irradiation process using the electron beam irradiation apparatus of the present embodiment escape from the object to be processed. Went. FIG. 7 shows a state in which the object to be processed is not held by the conductive support using the electron beam irradiation apparatus according to the present embodiment, but is floated with respect to the ground by, for example, placing it in a resin basket 60 (see FIG. 7). And the result of the third test when the electron beam irradiation treatment is performed on the workpiece while flowing argon gas through the workpiece. The third test is different from the first test described above, in the third test, the electron beam irradiation treatment is performed on the workpiece while flowing argon gas into the workpiece as shown in FIG. In addition, the irradiation chamber has an argon gas atmosphere. The flowing argon gas has a gas pressure of 0.1 MPa and a gas flow rate of 15 L / min. The argon gas was allowed to flow for 5 minutes and the test was performed. The direction of the object to be processed in the third test is such that the central axis of the object to be processed and the band-shaped electron beam bundle are parallel to each other. The conveyance speed and beam current of the workpiece are the same as in the first test.

In the third test, filtered water was added to the object irradiated with the electron beam, and when 30 minutes passed, the charge amount of water in the object was -978 to -4306 (10 ^-9 C). .

  As a result of the third test, argon gas was allowed to flow into the object to be processed while the object to be processed was floated with respect to the ground without being held by the conductive support using the electron beam irradiation apparatus of the present embodiment. However, when an electron beam irradiation treatment is performed on the object to be processed, filtered water is put into the object to be processed which has been irradiated with the electron beam after the electron beam irradiation process, and is accommodated in the object to be processed after 30 minutes. It was confirmed that the water potential was less than half that of the first test. Therefore, the electron beam irradiation method of the third test can reduce charging of the object to be processed due to the electron beam irradiation treatment as compared with the conventional electron beam irradiation method. That is, according to the electron beam irradiation method of the third test, the object to be processed by the electron beam irradiation process is performed by performing the electron beam irradiation process while circulating the argon gas in the object to be processed. Can be reduced. From the third test, it is considered that the electrons that are going to stay on the object to be processed are diffused in the argon gas atmosphere in an ionized state.

  FIG. 8 is a table showing the results of a fourth test when the electron beam irradiation processing is performed while flowing nitrogen gas into the object to be processed by the electron beam irradiation apparatus of the present embodiment. The fourth test is different from the second test described above. In the fourth test, the object to be processed is irradiated with an electron beam while flowing nitrogen gas from the gas supply unit 40 as shown in FIG. It is the point which is given. The flowing nitrogen gas has a gas pressure of 0.2 MPa and a gas flow rate of 15 L / min. The oxygen concentration in the workpiece measured with an oxygen concentration meter (LC-750) manufactured by Toray Industries, Inc. is 920 to 931 ppm. In addition, the direction of the workpiece in the fourth test is such that the center axis of the workpiece is perpendicular to the band-shaped electron beam bundle, and the bottom of the workpiece is in front of the workpiece in the transport direction. The mouth held by the electrically conductive support that is grounded is placed behind. The conveyance speed and beam current of the workpiece are the same as in the first test.

  In the fourth test, after performing electron beam irradiation treatment, filtered water was put into the object irradiated with the electron beam, and when 30 minutes passed, the amount of water in the object to be processed was measured with a Faraday cup. The value was undetectable for all three objects. That is, according to the electron beam irradiation method of the fourth test, it is possible to prevent the workpiece from being charged by the electron beam irradiation treatment. Also in the case of the fourth test, the present inventors, as in the case of the second test in which the above-described argon gas was flowed, are in an ionized state where the electrons that are going to stay on the object to be processed by the electron beam irradiation treatment are ionized. It is considered that it diffuses into the nitrogen gas atmosphere and flows to the ground through the conductive support.

  Also, in the case of the fourth test, as in the case of the second test, the direction of the object to be processed depends on the electron beam irradiation treatment even if the central axis of the object to be processed and the belt-like electron beam bundle are parallel. Although it is possible to prevent the workpiece from being charged, the conductive support has a central axis perpendicular to the band-shaped electron beam bundle and is electrically grounded in the direction of the workpiece. If the mouth of the object to be processed held by the tool is in front and the bottom is in the rear, it is presumed that charging of the object to be processed cannot be prevented.

  Next, in order to confirm that the argon gas or nitrogen gas in the irradiation chamber was ionized by irradiation with an electron beam, a test for measuring an emission spectrum was performed. For comparison, first, the emission spectrum from the irradiation space was measured when the irradiation chamber was irradiated with an electron beam in an air atmosphere with no object to be processed. FIG. 9 is a diagram showing an emission spectrum in the irradiation chamber when the irradiation chamber is in an air atmosphere and an electron beam is irradiated in a state where there is no object to be processed. As can be seen from FIG. 9, when the irradiation chamber was in an air atmosphere and the electron beam was irradiated without any object to be processed, an emission spectrum indicating a specific excitation and ionization state was not detected.

  FIG. 10 is a diagram showing an emission spectrum in the irradiation chamber when an object to be processed is placed in the irradiation chamber and an electron beam is irradiated while the irradiation chamber is kept in an air atmosphere. As can be seen from FIG. 10, a specific spectrum was not detected even when the object to be processed was irradiated with an electron beam in an atmosphere in the irradiation chamber.

  FIG. 11 is a diagram showing an emission spectrum in the irradiation chamber when an object to be processed is placed in the irradiation chamber and an electron beam is irradiated while flowing nitrogen gas in the irradiation chamber. When an electron beam irradiation process is performed while flowing nitrogen gas into the irradiation chamber, the inner core electrons of the nitrogen molecule gain energy from the electron beam and enter an excited state, and electrons in the excited level transition to the lower level. The wavelength light corresponding to the energy between the energy levels is detected as a light spectrum. In FIG. 11, emission peaks attributed to excited nitrogen molecules are observed at about 342 nm, about 362 nm, about 386 nm, and the like. These emission spectra are consistent with those of a typical nitrogen plasma, and it was confirmed that the nitrogen gas is in an ionized gas state.

  FIG. 12 is a diagram showing an emission spectrum in the irradiation chamber when an object to be processed is placed in the irradiation chamber and an electron beam is irradiated while flowing argon gas in the irradiation chamber. When an electron beam irradiation process is performed while flowing argon gas into the irradiation chamber, as with nitrogen gas, the inner core electrons of the argon atoms gain energy from the electron beam and go up to an excited state, and electrons at the excited level are lowered. When transitioning to a level, light having a wavelength corresponding to the energy between the energy levels is emitted and observed as a spectrum. In FIG. 12, peaks were observed at about 700 nm, about 768 nm, about 778 nm, and the like. Since these are attributed to the excited state of argon and coincide with the peak of a typical argon plasma, it was confirmed that argon is in an ionized gas state. Especially in the excited state of rare gas such as argon, there is a level called metastable excitation where the probability of transition with light emission as described above is extremely low and loses its energy only by collision with other atomic molecules, It is expected that an ionized gas state can be easily obtained by electron beam irradiation. In FIG. 12, although a peak is also observed at 340 to 400 nm, this peak is an emission spectrum of nitrogen gas, indicating that the nitrogen gas is in an excited state. In this test, the irradiation chamber was not completely replaced with argon gas, and the electron beam irradiation treatment was performed with nitrogen remaining in the air, so the emission spectrum of nitrogen gas was also measured. In FIG. 9, although nitrogen is present in the irradiation chamber, nitrogen is not excited because the energy of the electron beam is taken up by oxygen molecules in the air, making it difficult to excite nitrogen. It is guessed.

  From the above test results, the present inventors have found that the argon gas or nitrogen gas supplied into the processing chamber is ionized, that is, a plasma state having conductivity, by electron beam irradiation, and the electron beam irradiation treatment causes the object to be processed. The accumulated electrons flow from the conductive support holding the workpiece directly or through an argon gas atmosphere or a nitrogen gas atmosphere to the ground, and it is presumed that this suppresses the charging of the workpiece. doing. In particular, according to the method of the present invention, the ionized gas that is a conductive medium is expected to diffuse not only to the surface layer of the object to be processed but also to the inner layer to some extent, and accumulates as charges on the surface layer and inner layer of the object to be processed. It is thought that the electron is effectively transported to the ground.

  In addition, based on the results of the first test and the second test described above, and the knowledge that argon gas or nitrogen gas obtained by emission spectrum measurement is ionized by electron beam irradiation, the object to be treated is a hollow resin container. When performing an electron beam irradiation process on an object, the object to be processed is held by an electrically grounded conductive support, and an electron beam irradiation process is performed while flowing argon gas or nitrogen gas into the object to be processed. Was found to be desirable. When performing an electron beam irradiation process, if an appropriate amount of argon gas or nitrogen gas is allowed to flow into the object to be processed, charging of the object to be processed due to the electron beam irradiation process can be prevented.

  According to the present embodiment, since an electron beam having a low energy is used, when the object A is irradiated with the electron beam, a part of the electron beam stays in the object A to be processed. Object A is charged. However, in a state where the object to be processed is held by an electrically grounded conductive support, the direction of the object to be processed is set so that the central axis of the object to be processed and the band-shaped electron beam bundle are parallel, or the object to be processed A mouth that is held by a conductive support that is electrically grounded so that the center axis of the object is perpendicular to the band-shaped electron beam bundle and the bottom of the object to be processed is in front in the conveyance direction of the object to be processed The electron that is going to stay on the workpiece by directing the electron beam irradiation treatment while flowing argon gas or nitrogen gas into the workpiece is directly or in an argon gas atmosphere or nitrogen. It is possible to prevent the object to be processed from being charged by the electron beam irradiation process by flowing from the conductive support holding the object to be processed through the gas atmosphere to the ground.

  Further, according to the second test and the fourth test of the present embodiment, as described above, while supplying argon gas or nitrogen gas from the gas supply unit 40 into the workpiece, the electron beam is applied to the workpiece. Irradiation treatment is applied. Thus, since the electron beam irradiation process is performed while supplying argon gas or nitrogen gas into the workpiece A, not the entire irradiation chamber 20, the electron beam irradiation apparatus of this embodiment is applied to the entire irradiation chamber 20. Compared to the case where the electron beam irradiation process is performed by supplying argon gas or nitrogen gas, the amount of expensive argon gas or nitrogen gas used can be reduced, and the cost for performing the electron beam irradiation process can be reduced. .

  In addition, this invention is not limited to said embodiment, A various deformation | transformation is possible within the range of the summary.

  For example, in the above-described embodiment, the direction of the object to be processed is set so that the central axis of the object to be processed and the band-shaped electron beam bundle are parallel, or the center axis of the object to be processed is perpendicular to the band-shaped electron beam bundle. The case has been described in which the bottom of the object to be processed is the front in the conveyance direction of the object to be processed and the mouth held by the electrically conductive support that is electrically grounded is the rear. However, the present invention is not limited to this, and the direction of the object to be processed is held by a conductive support that is electrically grounded in front of the bottom of the object to be processed in the conveyance direction of the object to be processed. What is necessary is just to make the made opening part back, and you may make it the central axis of a to-be-processed object become diagonal with respect to the conveyance direction of a to-be-processed object.

  In the above embodiment, the case where the object to be processed is a hollow resin container has been described. However, the present invention is not limited to this, and the object to be processed may be in the form of a film. Good. In this case, the object to be processed is subjected to electron beam irradiation while flowing argon gas, nitrogen gas, or the like on the front side surface, the back side surface, or both sides of the film to be processed. Further, in this case, as in the case of the hollow object to be processed, the conductive material that electrically grounds at least one end of the film and / or the film portion on which the electron beam irradiation treatment is performed. It is desirable to hold it with a support.

  In the above embodiment, the case where the electron beam irradiation process is a sterilization process has been described. However, the present invention is not limited to this, and the electron beam irradiation process may be a sterilization process. , Surface modification treatment in a broad sense including crosslinking reaction, graft polymerization reaction, coating, hydrophilicity improvement, strength improvement and the like.

  In the above embodiment, the case where the flow rate of argon gas or nitrogen gas is 15 L / min has been described. However, the flow rates of these atmospheric gases are not limited thereto. The flow rate of the atmospheric gas is set to an appropriate amount depending on the shape and size of the object to be processed.

  Furthermore, in the above-described embodiment, the case where the present invention is applied to a low energy electron beam irradiation apparatus has been described. However, as a matter of course, the present invention may be applied to a medium / high energy electron beam irradiation apparatus. For example, when the thickness of the workpiece is thick, even if a medium or high energy electron beam is irradiated on the electric wire, the electron beam cannot pass through the electric wire covering portion and stays in the covering portion. Sometimes. In such a case, the medium / high energy electron beam irradiation apparatus to which the present invention is applied is particularly effective, and the charging of the object to be processed by the electron beam irradiation process can be reduced with a simple configuration.

  As described above, the electron beam irradiation apparatus and the electron beam irradiation method of the present invention have a simple configuration without using a special device such as a static eliminator when performing an electron beam irradiation process on an object to be processed. The charge of the object to be processed can be reduced. Therefore, the present invention is suitable for use in, for example, an electron beam irradiation apparatus that irradiates a hollow resin container with an electron beam, particularly a low energy electron beam irradiation apparatus.

DESCRIPTION OF SYMBOLS 10 Electron beam generation part 11 Terminal 11a Filament 11b Gun structure 11c Grid 12 Acceleration tube 20 Irradiation chamber 21 Irradiation space 41 Supply tube 24 Beam catcher 42 Nozzle part 30 Irradiation window part 31 Window foil 32 Window frame part 40 Gas supply part 45 Ionization Gas 50 Conductive support 60 Resin cage 71 Heating power supply 72 Control DC power supply 73 Acceleration DC power supply A Processed object B Banded electron beam bundle

Claims (5)

An electron beam irradiation apparatus used for performing an electron beam irradiation treatment on a workpiece to be charged by irradiation with an electron beam,
An electron beam generator for generating the electron beam;
An irradiation chamber in which processing for irradiating the electron beam to the object to be processed is performed;
An irradiation window section that partitions the vacuum atmosphere in the electron beam generating section and the irradiation atmosphere in the irradiation chamber and takes out the electron beam into the irradiation chamber;
A gas supply unit for flowing a rare gas, nitrogen gas or a mixed gas containing the rare gas or the nitrogen gas to the object to be processed,
The object to be processed is a hollow resin container,
The opening of the workpiece is supported by a conductive support that is electrically grounded,
When the workpiece is transported, the transport direction is a direction orthogonal to the band-shaped electron beam bundle of the electron beam irradiated into the irradiation chamber from the electron beam generating section through the irradiation window section, and The direction of the object to be processed is substantially parallel to the band-shaped electron beam bundle, or the bottom part of the object to be processed is in front and the opening part of the object to be processed is behind in the transport direction. Held in a posture,
The object to be processed while flowing the noble gas, the nitrogen gas, or the mixed gas containing the noble gas or the nitrogen gas from the gas supply unit into the object to be processed through the opening of the object to be processed An electron beam irradiation apparatus for irradiating an object with the electron beam.   The electron beam irradiation apparatus according to claim 1, wherein the rare gas is an argon gas. The electron beam irradiation apparatus according to claim 1 , wherein the electron beam irradiation process is a sterilization process, a sterilization process, or a surface modification process. 4. The electron beam irradiation apparatus according to claim 1, wherein the electron beam generator generates the electron beam at an acceleration voltage within a range of 50 kV to 500 kV. An electron beam irradiation method used for performing an electron beam irradiation treatment on a workpiece to be charged by irradiation with an electron beam,
When the object to be processed is a hollow resin container, the opening of the object to be processed is supported by a conductive support that is electrically grounded, and the object to be processed is The transport direction of the object to be processed when transported is a direction orthogonal to the band-shaped electron beam bundle of the electron beam, and the direction of the object to be processed when the object to be processed is transported with respect to the band-shaped electron beam bundle Or in such a direction that the bottom of the object to be processed is in front and the mouth part of the object to be opened is in the rear in the transport direction,
A rare gas, nitrogen gas, or a mixed gas containing the rare gas or the nitrogen gas from a gas supply unit is allowed to flow into the object to be processed from the opening of the object to be processed. An electron beam irradiation method comprising irradiating the electron beam.

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