Abstract:
To provide a take up type vacuum vapor deposition apparatus capable of suppressing generation of a thermally-affected area on a film without lowering productivity. A take-up type vacuum vapor deposition apparatus according to the present invention includes: a payout roller configured to successively pay out a film ; a take-up roller configured to take up the film paid out from the payout roller; a cooling roller disposed between the payout roller and the take-up roller and configured to cool the film by coming into close contact with the film ; an evaporation source that faces the cooling roller and configured to deposit an evaporation material on the film; and an electron beam irradiator disposed between the payout roller and the evaporation source and configured to irradiate the film with an electron beam while the film is traveling. In the take-up type vacuum vapor deposition apparatus, the electron beam irradiator includes a filament configured to discharge electrons by electrical heating and DC generation means for supplying a direct current to the filament.

Description:
FIELD 
       [0001]    The present invention relates to a take-up type vacuum vapor deposition apparatus for depositing, while successively paying out an insulation film in a reduced-pressure atmosphere and cooling the film by bringing the film into close contact with a cooling roller, an evaporation material onto the film and taking up the film. 
       BACKGROUND 
       [0002]    In the related art, take-up type vacuum vapor deposition apparatus, each of which deposits an evaporation material from an evaporation source onto a long film successively paid out from a payout roller and takes up the film that has been subjected to the vapor deposition by a take-up roller, are widely used (see, for example, Patent Document 1 below). In the vacuum vapor deposition apparatus of this type, for preventing thermal deformations of a film during vapor deposition, film formation processing is carried out while the film is cooled by being brought into close contact with a circumferential surface of a cooling can roller. Therefore, how to secure an adhesion operation of the film with respect to the cooling can roller becomes important. 
         [0003]      FIG. 6  shows an exemplary structure of the take-up type vacuum vapor deposition apparatus of the related art. A film  52  paid out from a payout roller (not shown) is taken up by a take-up roller (not shown) via a guide roller  53 , a cooling can roller  54 , and a guide roller  55 . An evaporation material from an evaporation source  56  is deposited onto the film  52  on the can roller  54 . An electron beam irradiator  51  is disposed between the payout roller and the evaporation source  56 , and the film not yet subjected to the vapor deposition is negatively charged when irradiated with electron beams, whereby the film  52  is brought into close contact with the can roller  54  by an electrostatic force generated between the film  52  and the can roller  54  that is grounded. Accordingly, thermal deformations of the film  52  due to insufficient cooling can be prevented. 
         [0004]      FIG. 7  is an equivalent circuit diagram showing a structure of the electron beam irradiator  51 . The electron beam irradiator  51  includes a filament  61  for discharging thermal electrons, a heating power source  62  for energizing the filament  61 , and an extraction power source  63  for the electron beams. The heating power source  62  is an AC power source and is constituted of, for example, a commercial frequency supply. 
         [0005]    Patent Document 1: Japanese Patent Application Laid-open No. 2005-146401 
       SUMMARY 
       [0006]    Problems to be solved by the Invention 
         [0007]    However, the take-up type vacuum vapor deposition apparatus of the related art described above has had a problem in that thermally-affected areas  65  are generated periodically in a longitudinal direction of the film  52  as schematically shown in  FIG. 8A . The thermally-affected area  65  is an area of the film that is easily wrinkled or deformed by heat. When a traveling speed of the film  52  is increased, intervals with which the thermally-affected areas  65  are generated become longer as shown in  FIG. 8B . In contrast, when the traveling speed of the film  52  is decreased immoderately, the thermally-affected area  65  is not generated at all. However, a decrease in traveling speed of the film is unfavorable because productivity is lowered. 
         [0008]    The generation of the thermally-affected areas  65  is caused by insufficient irradiation of electron beams to the film  52 . A low irradiation amount of the electron beams leads to weakening of an adhesion force of the film  52  to the can roller  54 , resulting in a reduction of a cooling effect. The traveling speed of the film  52  is constant, and the thermally-affected areas are generated periodically. Therefore, it is considered that the thermally-affected areas  65  are generated because of variances in irradiation amount of the electron beams with respect to the film  52 . 
         [0009]    The present invention has been made in view of the above-mentioned problems, and it is therefore an object of the invention to provide a take-up type vacuum vapor deposition apparatus capable of suppressing generation of thermally-affected areas on a film without lowering productivity. 
         [0000]    Means for solving the Problems 
         [0010]    To solve the above-mentioned problems, the inventors of the present invention have conducted keen studies and found that generation of thermally-affected areas on a film is caused by an electrical heating mechanism of a filament constituting an electron beam irradiator as described below. Specifically, as shown in  FIGS. 9A and 9B , the electron beam irradiator of the related art has generated electron beams by applying an alternating current to the filament  61 . At this time, an induced alternating magnetic field corresponding to an alternating current frequency appears around the filament  61 , and the generated electron beams receive an electromagnetic force caused by the induced alternating magnetic field, thus oscillating in a direction perpendicular to the induced magnetic field. As a result, as shown in  FIG. 10 , areas to which an insufficient amount of electron beams are irradiated appear periodically on the film  52  in a traveling direction thereof, the areas being generated on the film  52  as the thermally-affected areas  65 . 
         [0011]    Thus, according to the present invention, there is provided a take-up type vacuum vapor deposition apparatus, characterized by including: a vacuum chamber; a payout roller disposed inside the vacuum chamber and configured to successively pay out a film having an insulation property; a take-up roller configured to take up the film paid out from the payout roller; a cooling roller disposed between the payout roller and the take-up roller and configured to cool the film by coming into close contact with the film; an evaporation source that faces the cooling roller and configured to deposit an evaporation material on the film; and an electron beam irradiator disposed between the payout roller and the evaporation source and configured to irradiate the film with an electron beam while the film is traveling, and in that the electron beam irradiator includes a filament configured to discharge electrons by electrical heating and DC generation means for supplying a direct current to the filament. 
         [0012]    In the present invention, by electrically heating the filament constituting the electron beam irradiator using a direct current, the oscillation of the electron beams caused by the induced alternating magnetic field generated around the filament is eliminated in principle, thus obtaining a uniform irradiation operation of the electron beams with respect to the film. Accordingly, it becomes possible to obtain an adhesion operation between an entire surface of the film and the cooling roller, and prevent generation of thermally-affected areas due to a decrease in cooling effect, without lowering productivity. 
         [0013]    An example of a specific structure of the DC generation means is a structure in which the heating power source of the filament is constituted of a DC power source. Further, a direct current can be supplied to the filament by constituting the heating power source by an AC power source and inserting a DC conversion circuit including a rectification device to the AC power source. 
       Effect of the Invention 
       [0014]    As described above, according to the take-up type vacuum vapor deposition apparatus of the present invention, it becomes possible to obtain an adhesion operation between an entire surface of the film and the cooling roller, and prevent generation of thermally-affected areas due to a decrease in cooling effect, without lowering productivity. 
     
    
     
       DRAWINGS 
         [0015]      FIG. 1  is a schematic structural diagram of a take-up type vacuum vapor deposition apparatus according to an embodiment of the present invention. 
           [0016]      FIG. 2  is a schematic cross-sectional diagram for illustrating a process of irradiating electron beams to a film. 
           [0017]      FIG. 3  is an equivalent circuit diagram for illustrating a structure of an electron beam irradiator used in the take-up type vacuum vapor deposition apparatus shown in  FIG. 1 . 
           [0018]      FIG. 4  is a schematic diagram for illustrating an operation of the electron beam irradiator shown in  FIG. 3 . 
           [0019]      FIGS. 5  are diagrams each showing a structural modification of the electron beam irradiator shown in  FIG. 3 . 
           [0020]      FIG. 6  is a schematic structural diagram showing main portions of a take-up type vacuum vapor deposition apparatus of the related art. 
           [0021]      FIG. 7  is an equivalent circuit diagram for illustrating a structure of an electron beam irradiator used in the take-up type vacuum vapor deposition apparatus of the related art. 
           [0022]      FIGS. 8  are diagrams for illustrating problems of the related art, each of which shows an example where thermally-affected areas are generated periodically on a film. 
           [0023]      FIGS. 9  are schematic diagrams each illustrating a state where an electron beam is oscillated when an alternating current is applied to a filament constituting the electron beam irradiator. 
           [0024]      FIG. 10  is a schematic diagram for illustrating a mechanism for generating thermally-affected areas shown in  FIGS. 8 . 
       
    
    
     DETAILED DESCRIPTION  
       [0025]    Hereinafter, an embodiment of the present invention will be described with reference to the drawings. 
         [0026]      FIG. 1  is a schematic structural diagram of a take-up type vacuum vapor deposition apparatus  10  according to the embodiment of the present invention. The take-up type vacuum vapor deposition apparatus  10  of this embodiment includes a vacuum chamber  11 , a payout roller  13  for a film  12 , a cooling can roller  14 , a take-up roller  15 , and an evaporation source  16  of an evaporation material. 
         [0027]    The vacuum chamber  11  is connected to a vacuum exhaust system such as a vacuum pump (not shown) via pipe connection portions  11   a  and  11   c , and is exhausted to reduce a pressure inside to a predetermined vacuum degree. An internal space of the vacuum chamber  11  is sectioned by a partition plate  11   b  into a room in which the payout roller  13 , the take-up roller  15 , and the like are disposed, and a room in which the evaporation source  16  is disposed. 
         [0028]    The film  12  is constituted of a long plastic film having an insulation property and cut at a predetermined width. In this embodiment, an OPP (drawn polypropylene) single-layer film is used for the film  12 . It should be noted that a plastic film such as a PET (polyethylene terephthalate) film and a PPS (polyphenylene sulfide) film, a paper sheet, and the like can be applied instead. 
         [0029]    The film  12  is successively paid out from the payout roller  13  and is taken up by the take-up roller  15  via a plurality of guide rollers  17 , the can roller  14 , an auxiliary roller  18 , and a plurality of guide rollers  19 . Although not shown, each of the payout roller  13  and the take-up roller  15  is provided with a rotary drive portion. 
         [0030]    The can roller  14  is tubular and made of metal such as iron. Inside, the can roller  14  has a cooling mechanism such as a cooling medium circulation system, a rotary drive mechanism for rotationally driving the can roller  14 , and the like. The film  12  is wound around a circumferential surface of the can roller  14  at a predetermined holding angle. The film  12  wound around the can roller  14  is deposited with, on a deposition surface on an outer surface side thereof, an evaporation material from the evaporation source  16  so as to form a deposited layer, and at the same time, is cooled by the can roller  14 . 
         [0031]    The evaporation source  16  accommodates the evaporation material and has a mechanism for causing the evaporation material to evaporate by heating using a well-known technique such as resistance heating, induction heating, and electron beam heating. The evaporation source  16  is disposed below the can roller  14 , and causes the vapor of the evaporation material to adhere onto the film  12  on the can roller  14  opposed to the evaporation source  16 , to thus form a deposited layer. 
         [0032]    As the evaporation material, in addition to a metal element single body such as Al, Co, Cu, Ni, and Ti, two or more metals such as Al-Zn, Cu—Zn, and Fe—Co, or a multi-component alloy can be used. In addition, the number of evaporation source is not limited to one, and a plurality of evaporation sources may be provided. 
         [0033]    The take-up type vacuum vapor deposition apparatus  10  of this embodiment additionally includes an electron beam irradiator  21 , a DC bias power source  22 , and a neutralization unit  23 . 
         [0034]    The electron beam irradiator  21 , which is disposed between the payout roller  13  and the evaporation source  16 , negatively charges the film  12  by irradiating electron beams onto the traveling film  12 .  FIG. 2  is a schematic cross-sectional diagram for illustrating a process of irradiating electron beams to the film  12 . The electron beam irradiator  21  is disposed so as to oppose the circumferential surface of the can roller  14 , and irradiates electron beams onto a deposition surface of the film  12  that is in contact with the can roller  14  at an irradiation width the same as or higher than a film width. 
         [0035]      FIG. 3  is an equivalent circuit diagram showing a structure of the electron beam irradiator  21 . The electron beam irradiator  21  includes a filament  31  for discharging thermal electrons, a heating power source  32  for energizing the filament  31 , and an extraction power source  33  for the electron beams. The heating power source  32  is constituted of a DC power source, thus constituting “DC generation means” of the present invention for supplying a direct current to the filament  31 . 
         [0036]    The DC bias power source  22  applies a predetermined DC voltage between the can roller  14  and the auxiliary roller  18 . The can roller  14  is connected to a positive electrode whereas the auxiliary roller  18  is connected to a negative electrode. The auxiliary roller  18  is made of metal and disposed at a position where the deposition surface of the film  12  comes into rotational contact with a circumferential surface thereof. When a metallic layer formed on the film  12  comes into contact with the auxiliary roller  18 , the film  12  sandwiched between the metallic layer and the can roller  14  is polarized, and electrostatic absorption power is generated between the film  12  and the can roller  14 . Accordingly, the film  12  and the can roller  14  are brought into close contact with each other. 
         [0037]    The neutralization unit  23  is disposed between the cooling can roller  14  and the take-up roller  15  and has a function of neutralizing the film  12  that has been charged by being irradiated with electron beams from the electron beam irradiator  21 . As an exemplary structure of the neutralization unit  23  in this embodiment, a mechanism for neutralizing the film  12  by carrying out bombard processing while causing the film  12  to pass through plasma is used. 
         [0038]    Next, descriptions will be given on an operation of the take-up type vacuum vapor deposition apparatus  10  of this embodiment structured as described above. 
         [0039]    Inside the vacuum chamber  11  that is pressure-reduced to a predetermined vacuum degree, the film  12  successively paid out from the payout roller  13  is subjected to an electron beam irradiation process, a vapor deposition process, and a neutralization process before being successively taken up by the take-up roller  15 . 
         [0040]    The film  12  paid out from the payout roller  13  is wound around the can roller  14 . The film  12  is irradiated with, in the vicinity of a position at which the film  12  starts to come into contact with the can roller  14 , the electron beams from the electron beam irradiator  21  to be negatively charged in potential. At this time, because the film  12  is irradiated with the electron beams at a position in contact with the can roller  14 , it is possible to effectively cool the film  12  while bringing the film  12  in close contact with the can roller  14 . 
         [0041]    Here, according to this embodiment, because the filament  31  constituting the electron beam irradiator  21  is electrically heated using a direct current, it is possible to eliminate, in principle, the oscillation of the electron beams due to an induced alternating magnetic field generated around the filament, which has been a problem in the system of the related art in which the filament is energized by an alternating current, and obtain a uniform irradiation operation of the electron beams with respect to the film  12  as schematically shown in  FIG. 4 . Thus, it becomes possible to obtain an adhesion operation between an entire surface of the film and the can roller  14 , and prevent generation of thermally-affected areas due to a decrease in cooling effect without lowering productivity. 
         [0042]    The film  12  negatively charged by being irradiated with the electron beams is brought into close contact with, through electrostatic attractive force, the can roller  14  that is biased to a positive electric potential by the DC bias power source  22 . Then, the evaporation material evaporated from the evaporation source  16  is deposited onto the deposition surface of the film  12  to thus form a metallic layer. 
         [0043]    The metallic layer formed on the film  12  is applied with a negative electric potential by the DC bias power source  22  via the auxiliary roller  18 . The metallic layer is formed successively in a longitudinal direction of the film  12 . Thus, the film  12  wound around the can roller  14  and deposited with the metallic layer is positively polarized on a surface on the metallic layer side and negatively polarized on the other surface on the can roller  14  side, and electrostatic absorption power is generated between the film  12  and the can roller  14 . As a result, the film  12  and the can roller  14  are brought into close contact with each other. 
         [0044]    As described above, in this embodiment, before the vapor deposition of the metallic layer, the film  12  is brought into close contact with the can roller  14  by being charged by irradiation of the electron beams, whereas after the vapor deposition of the metallic layer, the film  12  is brought into close contact with the can roller  14  by a bias voltage applied between the metallic layer and the can roller  14 . Thus, even if partial charge (electrons) charged with respect to the film  12  before the vapor deposition of the metallic layer is discharged to the metallic layer and lost in the vapor deposition process of the metallic layer thereafter, a part or all of the lost charge can be compensated for by applying a negative electric potential (supplying electrons) to the metallic layer from the auxiliary roller  18 . 
         [0045]    Therefore, according to this embodiment, lowering of the adhesion force between the film  12  and the can roller  14  is suppressed even after the vapor deposition process, and a stable cooling operation of the film  12  can be secured before and after the vapor deposition process. Accordingly, thermal deformations of the film  12  during the vapor deposition of the metallic layer can be prevented, and an increase in traveling speed of the film  12  and deposition operation speed is enabled to thus improve productivity. 
         [0046]    The film  12  onto which the metallic layer is deposited as described above is neutralized by the neutralization unit  23 , and is then taken up by the take-up roller  15 . Thus, it becomes possible to prevent wrinkles caused during winding due to the charge while securing a stable take up operation of the film  12 . 
         [0047]    Although the embodiment of the present invention has been described above, the present invention is of course not limited thereto, and can be variously modified based on the technical idea of the present invention. 
         [0048]    For example, in the above embodiment, the heating power source  32  constituted of a DC power source is used as the DC generation means for supplying a direct current to the filament  31  constituting the electron beam irradiator  21 . However, as shown in  FIGS. 5A and 5B , for example, the DC generation means may instead be constituted by an AC power source  35  and a DC conversion circuit including a rectification device. 
         [0049]      FIG. 5A  shows an equivalent circuit of an electron beam irradiator in which a DC conversion circuit constituted of a rectification device  36  and a capacitor  37  is inserted between the filament  31  for discharging thermal electrons and the AC power source  35 . The rectification device  36  converts an alternating current from the AC power source  35  into a direct current (half-wave rectification), and the capacitor  37  functions as a filter for smoothening the rectified waveform. 
         [0050]    Further,  FIG. 5B  shows an equivalent circuit of an electron beam irradiator in which a DC conversion circuit constituted of a diode bridge  38  and a capacitor  39  is inserted between the filament  31  for discharging thermal electrons and the AC power source  35 . The diode bridge  38  converts the alternating current from the AC power source  35  into a direct current (full-wave rectification), and the capacitor  39  functions as a filter for smoothening the rectified waveform.