JP4648802B2 - Electron beam irradiation device - Google Patents

Description

  The present invention relates to an electron beam irradiation apparatus that irradiates an electron beam toward an irradiation object that is transported in a direction intersecting the irradiation width direction, and more specifically, to prevent thermal deformation of an extraction electrode. The present invention relates to a means for dividing the extraction electrode into a plurality and preventing the uniformity of the electron dose distribution in the irradiation width direction caused by dividing the extraction electrode from deteriorating.

  A schematic cross-sectional view showing an example of a conventional electron beam irradiation apparatus is shown in FIG. Note that an electron beam irradiation apparatus having a structure similar to this is described in FIG. In FIG. 5, this electron beam irradiation apparatus is called a non-scanning type (or area type) that does not scan the electron beam 10, and is placed in a cylindrical vacuum container 2 that is long in the front and back direction (Y direction) of the paper surface. A long cylindrical shield electrode 4 is arranged in the Y direction, and a long electron source 6 is arranged in the Y direction. The vacuum vessel 2 and the shield electrode 4 are each formed with rectangular openings 3 and 5 that are long in the Y direction.

  The electron source 6 emits electrons and has a plurality of linear (also referred to as rod-shaped) filaments 8 extending in the X direction perpendicular to the Y direction. The structure is arranged in parallel to each other in the Y direction and on the same plane. The Y direction in which the filaments 8 are arranged is called the irradiation width direction of the electron beam 10. The X direction is called the irradiated object transport direction.

  The electron source 6 is further arranged in parallel to the surface on which the filaments 8 are arranged, and has one porous extraction electrode 12 that extracts the electrons emitted from the filaments 8 as electron beams 10. The extraction electrode 12 is formed in a rectangular plate shape and is disposed in the vicinity of the opening 5 of the shield electrode 4.

  The shield electrode 4 and the extraction electrode 12 are set to the same potential, and an extraction voltage Ve for extracting the electron beam 10 is applied between them and each filament 8 with the filament 8 side as a negative electrode. Further, a window foil 20 having the same potential as that of the vacuum vessel 2 is provided in the opening 3 of the vacuum vessel 2, and between these and the extraction electrode 12 or the like, the side of the extraction electrode 12 or the like is used as a negative electrode, An acceleration voltage Va for accelerating the electron beam 10 is applied.

  In this way, the electron beam 10 drawn and accelerated from the electron source 6 passes through the window foil 20 and is taken out of the vacuum vessel 2 and irradiated toward the irradiation object 22 conveyed in the X direction. Then, it is subjected to processing such as modification of the irradiated object 22.

  In addition, between the upper part of each filament 8 and the shield electrode 4, there may be provided a reflector 15 that acts to push back the electrons emitted from the filament 8 back to the extraction electrode 12 as in this example.

  However, in the electron beam irradiation apparatus having the single-electrode electron source 6 shown in FIG. 5, the elongation in the Y direction of the extraction electrode 12 is largely thermally deformed by heating by the radiant heat from the filament 8. As a result, the distortion of the electron accelerating electric field formed by the extraction electrode 12 increases, the convergence and divergence of the electron trajectory occur, the extraction electric field due to the extraction voltage Ve becomes non-uniform, and the extraction of the electron beam 10 becomes dense, The uniformity of the dose distribution in the Y direction of the electron beam 10 was deteriorated.

In order to solve such a problem, for example, FIG. 1 of Patent Document 2 discloses an electron beam irradiation apparatus that is divided into a plurality of extraction electrode pieces in the Y direction and has separated extraction electrodes. FIGS. 6 (a) and 6 (b) show an extraction electrode having substantially the same structure as the extraction electrode used in this electron beam irradiation apparatus. Here, FIG. 6A is a schematic plan view showing how the extraction electrode 14 is divided and separated, and FIG. 6B is a diagram showing a schematic example of the trajectory of the electron beam 10 in the irradiation width direction Y. . 6A, the end surfaces 141 of the extraction electrode pieces 14a, 14b... Constituting the extraction electrode 14 are substantially parallel to the X direction. Further, a gap σ ₀ is provided between the end surface 141 of one electrode piece 14a and the end surface 141 of another electrode piece 14b adjacent thereto.

In addition, as shown in FIG. 7, there is also an example of an electron beam irradiation apparatus provided with an electron source 6 having two extraction electrodes 16 and 18 arranged with a space between each other in the extraction direction Z of the electron beam 10. In this case, both extraction electrodes 16 and 18 have the same structure and are electrically coupled to the same potential. As described above, when the two extraction electrodes 16 and 18 are provided, the extraction electrode 18 on the downstream side in the Z direction is divided into a plurality of extraction electrode pieces in the Y direction and separated as described above. . At this time, the end surfaces 141 of the extraction electrode pieces 14a and 14b are substantially parallel to the X direction, and a gap σ is formed between the end surface 141 of one electrode piece 14a and the end surface 141 of another electrode piece 14b adjacent thereto. ₀ is formed (see FIG. 6A).

  Note that paragraph [0021] and FIG. 2 of Patent Document 1 disclose an electron source including two extraction electrodes that are divided into a plurality of pieces in the Y direction and separated.

JP 2003-4898 (paragraph 0021, FIG. 2, FIG. 3) Japanese Patent Laying-Open No. 2003-43197 (paragraph 0052, FIG. 1)

In the electron beam irradiation apparatus described in FIG. 1 of Patent Document 2 and FIG. 2 of Patent Document 1, since the distortion per extraction electrode is reduced, the unevenness of the electron dose distribution due to thermal deformation of the extraction electrode is eliminated. it can. However, as illustrated in FIG. 6B, in the vicinity of the gap σ ₀ between the end surface 141 of one electrode piece 14a and the end surface 141 of another electrode piece 14b adjacent to the one electrode piece 14a. The equipotential surface E of the accelerating electric field accelerated by the accelerating voltage Va is not flat, and the trajectory of the electron beam 10 is bent unevenly. As a result, as shown in FIG. 6C, the electron dose distribution is biased (uneven). Here, FIG. 6C is a diagram showing a schematic example of the electron dose in the irradiation width direction Y. FIG.

That is, the bias of the electron dose distribution occurs in the vicinity of the gap σ ₀ between the end surface 141 of one electrode piece 14a and the end surface 141 of another electrode piece 14b adjacent to the one electrode piece 14a. This is because the equipotential surface E enters from the gap σ ₀ to the upstream side in the electron beam extraction direction Z. As a result, there is a problem that this disturbs the acceleration electric field of the electron beam 10 and deteriorates the uniformity of the dose distribution in the Y direction of the electron beam 10.

  Therefore, the main object of the present invention is to prevent the bias of the electron dose distribution in the irradiation width direction while preventing thermal deformation of the extraction electrode.

  In the present invention, the following features are provided alone or in combination as appropriate. An electron beam irradiation apparatus according to the present invention for solving the above-mentioned problems is an electron beam irradiation apparatus that irradiates an electron beam toward an irradiation object conveyed in a direction X intersecting with an irradiation width direction Y. The electrons emitted from the filament are arranged in parallel to the plurality of filaments arranged on the same plane and arranged in the irradiation width direction Y, and the plurality of filaments arranged on the same plane. A plate-like extraction electrode for extracting the electron beam as an electron beam, and the extraction electrodes having the same potential are arranged in one or more stages in the electron beam extraction direction, and the extraction electrode on the most downstream side in the electron beam extraction direction is irradiated While being divided into a plurality of electrode pieces in the width direction Y, the irradiation width direction Y and the object to be irradiated are transported between one of the plurality of electrode pieces and another electrode piece adjacent thereto. Any direction It is characterized in that also the first gap in a direction crossing is formed.

  According to the above configuration, the first gap is formed in an oblique manner, so that the electron dose reaches a peak at the irradiated position substantially corresponding to the center in the Y direction of the first gap. Has been confirmed by experiments. Therefore, if the position in the X direction is different, the uneven position of the electron dose in the irradiation width direction Y irradiated to the irradiated object will be different.

  In the electron beam irradiation apparatus according to the present invention, the extraction electrode may be arranged in at least two stages, and the extraction electrode upstream of the most downstream extraction electrode may be divided into a plurality of electrode pieces in the irradiation width direction Y. . At this time, the irradiation width intersects both the irradiation width direction Y and the direction X in which the irradiated object is transported between one electrode piece of the plurality of electrode pieces and another electrode piece adjacent thereto. It is preferable that a second gap is formed at a position shifted in the direction from the first gap.

  According to the above configuration, the unevenness of the electron dose at the irradiated position corresponding to the first gap and the unevenness of the electron dose at the irradiated position corresponding to the second gap are shifted in the irradiation width direction Y.

  According to the first aspect of the present invention, the unevenness in which the electron dose reaches a peak occurs at the irradiated position corresponding substantially to the center in the Y direction of the first gap. Therefore, if the position in the X direction is different, the irradiation width The uneven position of the electron dose in the direction Y is different. Therefore, when the electron beam is irradiated to the irradiation object conveyed in the X direction, the uneven position of the electron dose in the irradiation width direction Y irradiated to the irradiation object is accompanied by the conveyance of the irradiation object. It moves corresponding to the first gap. As a result, after the irradiated object is transported, the electron dose distribution in the irradiation width direction Y irradiated to the irradiated object becomes substantially uniform. Furthermore, since the extraction electrode is divided and separated in the irradiation width direction Y, thermal deformation can be prevented.

  According to the invention described in claim 2, the unevenness of the electron dose at the irradiated position corresponding to the first gap and the unevenness of the electron dose at the irradiated position corresponding to the second gap are shifted in the irradiation width direction Y. . Therefore, even when two or more extraction electrodes are arranged, the electron dose distribution in the irradiation width direction Y irradiated to the irradiated object becomes substantially uniform after the irradiated object is transported.

  FIG. 1 is a schematic cross-sectional view showing an example of an electron beam irradiation apparatus according to the present invention, and includes a single extraction electrode (first extraction electrode) 24. FIG. 2 is a schematic plan view showing the positional relationship between the first extraction electrode 24 and the irradiated object 22 and a schematic example of the electron dose distribution at the irradiated position of the irradiated object. FIG. 3 is a schematic diagram showing the relationship between the position in the irradiation width direction Y and the electron dose irradiated to the non-irradiated object 22. FIG. 4 is a perspective view of the electron source 6b in the electron beam irradiation apparatus according to the present invention having two extraction electrodes (the first extraction electrode 24 and the second extraction electrode 26), and a partial electron dose distribution in this case. It is the schematic which showed these.

  In FIG. 1, the electron beam irradiation apparatus includes an electron source 6a in place of the electron source 6 in the conventional example.

  The electron source 6a includes one extraction electrode (first extraction electrode) 24 for extracting the electron beam 10, and the extraction voltage Ve and the acceleration voltage Va are applied to the first extraction electrode 24 in the same manner as described above. The

  In FIG. 2, the first extraction electrode 24 is divided into a plurality of (for example, three) electrode pieces and separated in the Y direction. The respective electrode pieces divided and separated into three in this way are denoted by reference numerals 24a to 24c. However, electrically, the three electrode pieces 24a to 24c are coupled to the same potential, and the first extraction electrode 24 functions as a single electrode as a whole. The first extraction electrode 24 has a large number of electron extraction holes 25 penetrating the first extraction electrode 24 in the Z direction. FIG. 2 shows an example in which four columns (rows A to D) of electron extraction holes 25 are formed vertically, but actually, a plurality of rows of electron extraction holes 25 are formed.

The first extraction electrode 24 includes an electrode piece 24a to 24c and another electrode piece 24a to 24c adjacent to the one electrode piece 24a to 24c, both in the X direction and the Y direction. A first gap σ ₁ is formed in the intersecting direction. That is, each of the electrode pieces 24a to 24c is obtained by dividing one extraction electrode 24 long in the Y direction obliquely with respect to the X direction so as to be a plurality of electrodes in the Y direction. The first gap σ ₁ is a gap formed between the adjacent electrode pieces 24a to 24c.

The electrode pieces 24 a to 24 c are divided at an angle θ counterclockwise with respect to the Y direction so as to avoid the electron extraction hole 25 formed in the first extraction electrode 24. In this specification, this angle θ is referred to as a division angle θ. As an example, the division angle θ is 30 degrees. However, the division angle θ is not limited to 30 degrees. For example, the division angle θ may be selected within the range of 0 <θ <90 ° so that a desired electron dose distribution can be obtained. Further, the division angle θ may be a clockwise angle with respect to the Y direction instead of a counterclockwise angle with respect to the Y direction. Here, in other words, the first gap σ ₁ is not parallel to the transport direction X of the non-irradiated object 22 as in the related art but is formed obliquely with an angle α. This angle α has a relationship of α = 90 ° −θ because the X direction and the Y direction are orthogonal to each other.

  Next, the electron dose distribution in the Y direction when the first extraction electrode 24 is obliquely divided will be described.

As shown in FIG. 2, the electron dose distribution in the Y direction irradiated on the irradiation object 22 has a peak at the irradiation position corresponding to approximately the center P in the Y direction of the first gap σ _1. It has been confirmed by experiments that unevenness is generated (this can also be understood from FIGS. 6B and 6C). Here, the “irradiated position corresponding to the center P” means a position where the virtual line L extending from the center P in the drawing direction Z of the electron beam 10 intersects the irradiated object 22. Thus, the unevenness | corrugation position of the electron dose in a Y direction differs for every row | line | column by forming _1st clearance gap (sigma) ₁ diagonally. More specifically, the A column is each of the B column to the D column, the B column is the A column, the C column and the D column, the C column is the A column, the B column and the D column, and the D column is Each of the A to C rows and the uneven position of the electron dose are different in the Y direction. Therefore, the electron dose distribution is obtained by superimposing the unevenness of the electron dose distribution of each column A to D on the irradiated object 22 that has passed through all the columns A to D in the X direction as indicated by the arrow F. Is offset. As a result, as shown in FIG. 3, the irradiation object 22 is irradiated with the electron beam 10 so as to be substantially uniform in the Y direction. Thereby, the subject of this invention that the uniformity of the electron dose distribution in a Y direction deteriorates can be solved. Strictly speaking, the irradiation of the electron beam 10 onto the object 22 is not performed with the electron beam 10 completely and uniformly in the Y direction as shown in FIG. The electron beam 10 is uniformly irradiated.

Further, since the first extraction electrode 24 is divided into a plurality of electrode pieces 24a to 24c in the Y direction, the elongation in the Y direction per electrode piece 24a to 24c is small. Further, since the extension of the first extraction electrode 24 due to the radiant heat from the filament 8 can be absorbed by the first gap σ ₁ , thermal deformation of the first extraction electrode 24 can also be suppressed.

  Next, an electron beam irradiation apparatus provided with two extraction electrodes will be described with reference to FIG.

  In the electron source 6b in this electron beam irradiation apparatus, the second extraction electrode 26 is disposed in parallel with the first extraction electrode 24 on the upstream side in the Z direction with a gap therebetween. Each of the extraction electrodes 24 and 26 has a number of electron extraction holes 25 and 27, respectively. The lead electrodes 24 and 26 are electrically coupled to each other at the same potential, and the lead voltage Ve and the acceleration voltage Va are applied to the lead electrodes 24 and 26 as described above.

The first extraction electrode 24 is the same as that shown in FIG. The second extraction electrode 26 is formed with a plurality of electron extraction holes 27 penetrating the second extraction electrode 26 in the Z direction, and is divided into a plurality of (for example, four) electrode pieces 26a to 26d in the Y direction. It is separated. In this case, the electrode pieces 26a to 26d are coupled to the same potential, and the second extraction electrode 26 functions as one electrode electrically as a whole, and the electrode pieces 26a to 26d are respectively in the X direction and the Y direction. The second gap σ ₂ is formed in a direction intersecting any of the directions, and the counterclockwise division angle θ with respect to the Y direction is 30 degrees as an example so as to avoid the electron extraction hole 27. Each of the divisions is the same as that of the first extraction electrode 24. That is, the second gap σ ₂ intersects both the X direction and the Y direction. However, the second lead-out electrode 26, (in other words, a position that does not correspond with the first gap sigma ₁ in the Z direction) at a position shifted to the first gap sigma ₁ and Y-direction second gap sigma ₂ is It differs from the first extraction electrode 24 in that it is formed.

As described above, when the first extraction electrode 24 and the second extraction electrode 26 are divided such that the first gap σ ₁ and the second gap σ ₂ are shifted from each other in the Y direction, the first gap The unevenness of the electron dose at the irradiated position corresponding to σ ₁ and the unevenness of the electron dose at the irradiated position corresponding to the second gap σ ₂ are shifted in the Y direction. Therefore, even when the extraction electrodes are arranged in two stages, when the irradiated object 22 is transported in the X direction, the electron dose in the irradiation width direction Y irradiated to the irradiated object 22 is substantially uniform. It becomes. Further, the effect of this equalization is greater than when both gaps σ ₁ and σ ₂ are not shifted in the Y direction. This is because the uneven positions corresponding to the first gap σ ₁ and the second gap σ ₂ are shifted from each other in the Y direction.

  In the present embodiment, the electron beam irradiation apparatus having one extraction electrode and two electron sources 6a and 6b has been described. However, the present invention is not limited to this. For example, the present invention can also be applied to an electron beam irradiation apparatus including an electron source including three extraction electrodes.

  In addition, the extraction electrode on the most downstream side in the electron beam extraction direction is not necessarily limited to an electron beam irradiation apparatus having an electron source having a plurality of extraction electrodes. The electrode becomes the extraction electrode on the most downstream side in the electron beam extraction direction.

  In the present embodiment, the division angle θ of the first extraction electrode 24 and the second extraction electrode 26 is the same angle with respect to the Y direction. However, the present invention is not limited to this, and the division angle θ of the first extraction electrode 24 The division angle of the second extraction electrode 26 may be different. Furthermore, the division angle of the first extraction electrode 24 may be a counterclockwise angle with respect to the Y direction, and the division angle of the second extraction electrode 26 may be a clockwise angle with respect to the Y direction, or vice versa. It may be.

It is a schematic sectional drawing which shows an example of the electron beam irradiation apparatus which concerns on this invention. It is a figure which shows the schematic plan view showing the positional relationship of a 1st extraction electrode, and a to-be-irradiated object, and the schematic example of the electron dose distribution in the to-be-irradiated position of a to-be-irradiated object. It is the schematic diagram which showed the relationship between the position of an irradiation width direction, and the electron dose irradiated to the non-irradiated object. It is the schematic which showed the perspective view of the electron source 6b in the electron beam irradiation apparatus which concerns on this invention provided with two extraction electrodes, and the one part electron dose distribution in this case. It is a schematic sectional drawing which shows an example of an electron beam irradiation apparatus provided with the conventional electron source. (A) is a schematic plan view showing how the extraction electrode is divided and separated, (b) is a diagram showing a schematic example of an electron beam trajectory in the irradiation width direction, and (c) is an electron dose in the irradiation width direction. It is a figure which shows a schematic example. It is a schematic sectional drawing which shows an example of the electron beam irradiation apparatus provided with the electron source which has two extraction electrodes.

Explanation of symbols

DESCRIPTION OF SYMBOLS 2 Vacuum container 3 Opening part 4 Shield electrode 5 Opening part 6 Electron source 6a-b Electron source 8 Filament 10 Electron beam 12 Extraction electrode 14 Extraction electrode 14a Electrode piece 14b Electrode piece 16 Extraction electrode 18 Extraction electrode 20 Window foil 22 Irradiation object 24 first extraction electrode 24a-24c electrode piece 25 electron extraction hole 26 second extraction electrode 26a-26c electrode piece 27 electron extraction hole Ve extraction voltage Va acceleration voltage σ ₀ gap σ ₁ first gap σ ₂ second gap θ Dividing angle

Claims (2)

An electron beam irradiation apparatus that irradiates an electron beam toward an object to be transported in a direction intersecting the irradiation width direction,
A plurality of filaments that emit electrons and are arranged on the same plane and arranged in the irradiation width direction are arranged in parallel to the plurality of filaments that are arranged on the same plane, and electrons emitted from the filaments are converted into electrons. It has a plate-like extraction electrode drawn out as a line,
The extraction electrodes having the same potential are arranged in one or more stages in the electron beam extraction direction,
The extraction electrode on the most downstream side in the electron beam extraction direction is divided into a plurality of electrode pieces in the irradiation width direction, and irradiation is performed between one electrode piece of the plurality of electrode pieces and another electrode piece adjacent thereto. An electron beam irradiation apparatus, wherein a first gap is formed in a direction intersecting both the width direction and the direction in which the irradiation object is conveyed. The extraction electrodes are arranged in at least two stages;
An extraction electrode on the upstream side of the extraction electrode on the most downstream side is divided into a plurality of electrode pieces in the irradiation width direction, and one electrode piece of the plurality of electrode pieces and another electrode piece adjacent thereto are provided. A second gap is formed at a position that intersects both the irradiation width direction and the direction in which the irradiation object is conveyed and is displaced from the first gap in the irradiation width direction. Item 2. The electron beam irradiation apparatus according to Item 1.

Images